Riva, F.; Steiner, O.
Methodology for estimating the magnetic Prandtl number and application to solar surface small-scale dynamo simulations Journal Article
In: Astronomy and Astrophysics, vol. 660, pp. A115, 2022.
@article{refId0k,
title = {Methodology for estimating the magnetic Prandtl number and application to solar surface small-scale dynamo simulations},
author = {F. Riva and O. Steiner},
url = {https://doi.org/10.1051/0004-6361/202142644},
doi = {10.1051/0004-6361/202142644},
year = {2022},
date = {2022-04-23},
urldate = {2022-04-23},
journal = {Astronomy and Astrophysics},
volume = {660},
pages = {A115},
abstract = {Context. A crucial step in the numerical investigation of small-scale dynamos in the solar atmosphere consists of an accurate determination of the magnetic Prandtl number, Prm, stemming from radiative magneto-hydrodynamic (MHD) simulations.
Aims. The aims are to provide a reliable methodology for estimating the effective Reynolds and magnetic Reynolds numbers, Re and Rem, and their ratio Prm = Rem/Re (the magnetic Prandlt number), that characterise MHD simulations and to categorise small-scale dynamo simulations in terms of these dimensionless parameters.
Methods. The methodology proposed for computing Re and Rem is based on the method of projection on proper elements and it relies on a post-processing step carried out using higher order accurate numerical operators than the ones in the simulation code. A number of radiative MHD simulations with different effective viscosities and plasma resistivities were carried out with the CO5BOLD code, and the resulting growth rate of the magnetic energy and saturated magnetic field strengths were characterised in terms of Re and Rem.
Results. Overall, the proposed methodology provides a solid estimate of the dissipation coefficients affecting the momentum and induction equations of MHD simulation codes, and consequently also a reliable evaluation of the magnetic Prandtl number characterising the numerical results. Additionally, it is found that small-scale dynamos are active and can amplify a small seed magnetic field up to significant values in CO5BOLD simulations with a grid spacing smaller than h = 12 km, even at Prm ≃ 0.65. However, it is also evident that it is difficult to categorise dynamo simulations in terms of Prm alone, because it is not only important to estimate the amplitude of the dissipation coefficients, but also at which scales energy dissipation takes place.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Context. A crucial step in the numerical investigation of small-scale dynamos in the solar atmosphere consists of an accurate determination of the magnetic Prandtl number, Prm, stemming from radiative magneto-hydrodynamic (MHD) simulations.
Aims. The aims are to provide a reliable methodology for estimating the effective Reynolds and magnetic Reynolds numbers, Re and Rem, and their ratio Prm = Rem/Re (the magnetic Prandlt number), that characterise MHD simulations and to categorise small-scale dynamo simulations in terms of these dimensionless parameters.
Methods. The methodology proposed for computing Re and Rem is based on the method of projection on proper elements and it relies on a post-processing step carried out using higher order accurate numerical operators than the ones in the simulation code. A number of radiative MHD simulations with different effective viscosities and plasma resistivities were carried out with the CO5BOLD code, and the resulting growth rate of the magnetic energy and saturated magnetic field strengths were characterised in terms of Re and Rem.
Results. Overall, the proposed methodology provides a solid estimate of the dissipation coefficients affecting the momentum and induction equations of MHD simulation codes, and consequently also a reliable evaluation of the magnetic Prandtl number characterising the numerical results. Additionally, it is found that small-scale dynamos are active and can amplify a small seed magnetic field up to significant values in CO5BOLD simulations with a grid spacing smaller than h = 12 km, even at Prm ≃ 0.65. However, it is also evident that it is difficult to categorise dynamo simulations in terms of Prm alone, because it is not only important to estimate the amplitude of the dissipation coefficients, but also at which scales energy dissipation takes place.
Aims. The aims are to provide a reliable methodology for estimating the effective Reynolds and magnetic Reynolds numbers, Re and Rem, and their ratio Prm = Rem/Re (the magnetic Prandlt number), that characterise MHD simulations and to categorise small-scale dynamo simulations in terms of these dimensionless parameters.
Methods. The methodology proposed for computing Re and Rem is based on the method of projection on proper elements and it relies on a post-processing step carried out using higher order accurate numerical operators than the ones in the simulation code. A number of radiative MHD simulations with different effective viscosities and plasma resistivities were carried out with the CO5BOLD code, and the resulting growth rate of the magnetic energy and saturated magnetic field strengths were characterised in terms of Re and Rem.
Results. Overall, the proposed methodology provides a solid estimate of the dissipation coefficients affecting the momentum and induction equations of MHD simulation codes, and consequently also a reliable evaluation of the magnetic Prandtl number characterising the numerical results. Additionally, it is found that small-scale dynamos are active and can amplify a small seed magnetic field up to significant values in CO5BOLD simulations with a grid spacing smaller than h = 12 km, even at Prm ≃ 0.65. However, it is also evident that it is difficult to categorise dynamo simulations in terms of Prm alone, because it is not only important to estimate the amplitude of the dissipation coefficients, but also at which scales energy dissipation takes place.
Marassi, Alessandro; Monstein, Christian
Trieste CALLISTO Station Setup and Observations of Solar Radio Bursts Journal Article
In: Advances in Space Research, 2021, ISSN: 0273-1177.
@article{MARASSI2021,
title = {Trieste CALLISTO Station Setup and Observations of Solar Radio Bursts},
author = {Alessandro Marassi and Christian Monstein},
url = {https://www.sciencedirect.com/science/article/pii/S0273117721009704},
doi = {10.1016/j.asr.2021.12.043},
issn = {0273-1177},
year = {2021},
date = {2021-12-31},
urldate = {2021-01-01},
journal = {Advances in Space Research},
abstract = {The Trieste CALLISTO station (http://radiosun.oats.inaf.it) was established in 2012 at the Basovizza Observing Station (45°38'37” N, 13°52'34 E”, 398m above MSL) operated by the Italian National Institute for Astrophysics (INAF) - Astronomical Observatory of Trieste (Italy) to study solar radio bursts and the response of the Earth’s ionosphere and geomagnetic field. To date, three ‘Compound Astronomical Low-cost Low frequency Instrument for Spectroscopy and Transportable Observatory’ (CALLISTO) spectrometers have been installed, with the capability of observing in the frequency ranges 45-80 MHz (from 30 December 2014), 220-420 MHz (from 1 June 2012 to 23 October 2012 and from 05 October 2013), 905-1730 MHz (from 30 December 2019). The three receivers are fed respectively by a dipole, log-periodic and cross-dipole antenna. Nominally, frequency spectra are obtained with 4 sweeps per second over in total 600 channels. Here, we describe the Trieste CALLISTO station set-up, the local e-Callisto network digital archive, Trieste CALLISTO Radio Bursts Detection and Visualization System available via web and present dynamic spectra of a sample of Type I, II, III, IV and V radio bursts. As an additional feature, we show also its capability to record lightning strikes.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The Trieste CALLISTO station (http://radiosun.oats.inaf.it) was established in 2012 at the Basovizza Observing Station (45°38'37” N, 13°52'34 E”, 398m above MSL) operated by the Italian National Institute for Astrophysics (INAF) - Astronomical Observatory of Trieste (Italy) to study solar radio bursts and the response of the Earth’s ionosphere and geomagnetic field. To date, three ‘Compound Astronomical Low-cost Low frequency Instrument for Spectroscopy and Transportable Observatory’ (CALLISTO) spectrometers have been installed, with the capability of observing in the frequency ranges 45-80 MHz (from 30 December 2014), 220-420 MHz (from 1 June 2012 to 23 October 2012 and from 05 October 2013), 905-1730 MHz (from 30 December 2019). The three receivers are fed respectively by a dipole, log-periodic and cross-dipole antenna. Nominally, frequency spectra are obtained with 4 sweeps per second over in total 600 channels. Here, we describe the Trieste CALLISTO station set-up, the local e-Callisto network digital archive, Trieste CALLISTO Radio Bursts Detection and Visualization System available via web and present dynamic spectra of a sample of Type I, II, III, IV and V radio bursts. As an additional feature, we show also its capability to record lightning strikes.
Ndacyayisenga, T.; Umuhire, A. C.; Uwamahoro, J.; Monstein, C.
Space weather study through analysis of solar radio bursts detected by a single-station CALLISTO spectrometer Journal Article
In: Annales Geophysicae, vol. 39, no. 5, pp. 945–959, 2021.
@article{angeo-39-945-2021,
title = {Space weather study through analysis of solar radio bursts detected by a single-station CALLISTO spectrometer},
author = {T. Ndacyayisenga and A. C. Umuhire and J. Uwamahoro and C. Monstein},
url = {https://angeo.copernicus.org/articles/39/945/2021/},
doi = {10.5194/angeo-39-945-2021},
year = {2021},
date = {2021-10-29},
urldate = {2021-01-01},
journal = {Annales Geophysicae},
volume = {39},
number = {5},
pages = {945–959},
abstract = {This article summarises the results of an analysis of solar radio bursts (SRBs) detected by the Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Observatory (CALLISTO) spectrometer hosted by the University of Rwanda. The data analysed were detected during the first year (2014–2015) of the instrument operation. Using quick plots provided by the e-CALLISTO website, a total of 201 intense and well-separated solar radio bursts detected by the CALLISTO station located in Rwanda, are found consisting of 4 type II, 175 type III and 22 type IV radio bursts. It is found that all analysed type II and ∼ 37 % of type III bursts are associated with impulsive solar flares, while the minority (∼ 13 %) of type IV radio bursts are associated with solar flares. Furthermore, all type II radio bursts are associated with coronal mass ejections (CMEs), ∼ 44 % of type III bursts are associated with CMEs, and the majority (∼ 82 %) of type IV bursts were accompanied by CMEs. With aid of the atmospheric imaging assembly (AIA) images on board the Solar Dynamics Observatory (SDO), the location of open magnetic field lines of non-flare-associated type III radio bursts are shown. The same images are used to show the magnetic loops in the solar corona for type IV radio bursts observed in the absence of solar flares and/or CMEs. Findings from this study indicate that analysis of SRBs that are observed from the ground can provide a significant contribution to the early diagnosis of solar transients phenomena, such as solar flares and CMEs, which are major drivers of potential space weather hazards.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
This article summarises the results of an analysis of solar radio bursts (SRBs) detected by the Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Observatory (CALLISTO) spectrometer hosted by the University of Rwanda. The data analysed were detected during the first year (2014–2015) of the instrument operation. Using quick plots provided by the e-CALLISTO website, a total of 201 intense and well-separated solar radio bursts detected by the CALLISTO station located in Rwanda, are found consisting of 4 type II, 175 type III and 22 type IV radio bursts. It is found that all analysed type II and ∼ 37 % of type III bursts are associated with impulsive solar flares, while the minority (∼ 13 %) of type IV radio bursts are associated with solar flares. Furthermore, all type II radio bursts are associated with coronal mass ejections (CMEs), ∼ 44 % of type III bursts are associated with CMEs, and the majority (∼ 82 %) of type IV bursts were accompanied by CMEs. With aid of the atmospheric imaging assembly (AIA) images on board the Solar Dynamics Observatory (SDO), the location of open magnetic field lines of non-flare-associated type III radio bursts are shown. The same images are used to show the magnetic loops in the solar corona for type IV radio bursts observed in the absence of solar flares and/or CMEs. Findings from this study indicate that analysis of SRBs that are observed from the ground can provide a significant contribution to the early diagnosis of solar transients phenomena, such as solar flares and CMEs, which are major drivers of potential space weather hazards.
Clette, Frédéric; Lefèvre, Laure; Bechet, Sabrina; Ramelli, Renzo; Cagnotti, Marco
Reconstruction of the Sunspot Number Source Database and the 1947 Zurich Discontinuity Journal Article
In: Solar Physics, vol. 296, pp. 137, 2021.
@article{article,
title = {Reconstruction of the Sunspot Number Source Database and the 1947 Zurich Discontinuity},
author = {Frédéric Clette and Laure Lefèvre and Sabrina Bechet and Renzo Ramelli and Marco Cagnotti},
doi = {10.1007/s11207-021-01882-6},
year = {2021},
date = {2021-09-15},
urldate = {2021-01-01},
journal = {Solar Physics},
volume = {296},
pages = {137},
abstract = {The recalibration of the sunspot number series, the primary long-term record of the solar cycle, requires the recovery of the entire collection of raw sunspot counts collected by the Zurich Observatory for the production of this index between 1849 and 1980.
Here, we report about the major progresses accomplished recently in the construction of this global digital sunspot number database, and we derive global statistics of all the individual observers and professional observatories who provided sunspot data over more than 130 years.
First, we can announce the full recovery of long-lost source-data tables covering the last 34 years between 1945 and 1979, and we describe the unique information available in those tables. We then also retrace the evolution of the core observing team in Zurich and of the auxiliary stations. In 1947, we find a major disruption in the composition of both the Zurich team and the international network of auxiliary stations.
This sharp transition is unique in the history of the Zurich Observatory and coincides with the main scale-jump found in the original Zurich sunspot number series, the so-called “Waldmeier” jump. This adds key historical evidence explaining why methodological changes introduced progressively in the early 20th century could play a role precisely at that time. We conclude on the remaining steps needed to fully complete this new sunspot data resource.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The recalibration of the sunspot number series, the primary long-term record of the solar cycle, requires the recovery of the entire collection of raw sunspot counts collected by the Zurich Observatory for the production of this index between 1849 and 1980.
Here, we report about the major progresses accomplished recently in the construction of this global digital sunspot number database, and we derive global statistics of all the individual observers and professional observatories who provided sunspot data over more than 130 years.
First, we can announce the full recovery of long-lost source-data tables covering the last 34 years between 1945 and 1979, and we describe the unique information available in those tables. We then also retrace the evolution of the core observing team in Zurich and of the auxiliary stations. In 1947, we find a major disruption in the composition of both the Zurich team and the international network of auxiliary stations.
This sharp transition is unique in the history of the Zurich Observatory and coincides with the main scale-jump found in the original Zurich sunspot number series, the so-called “Waldmeier” jump. This adds key historical evidence explaining why methodological changes introduced progressively in the early 20th century could play a role precisely at that time. We conclude on the remaining steps needed to fully complete this new sunspot data resource.
Here, we report about the major progresses accomplished recently in the construction of this global digital sunspot number database, and we derive global statistics of all the individual observers and professional observatories who provided sunspot data over more than 130 years.
First, we can announce the full recovery of long-lost source-data tables covering the last 34 years between 1945 and 1979, and we describe the unique information available in those tables. We then also retrace the evolution of the core observing team in Zurich and of the auxiliary stations. In 1947, we find a major disruption in the composition of both the Zurich team and the international network of auxiliary stations.
This sharp transition is unique in the history of the Zurich Observatory and coincides with the main scale-jump found in the original Zurich sunspot number series, the so-called “Waldmeier” jump. This adds key historical evidence explaining why methodological changes introduced progressively in the early 20th century could play a role precisely at that time. We conclude on the remaining steps needed to fully complete this new sunspot data resource.
Riva, F.; Steiner, O.
16th European Solar Physics Meeting (ESPM-16), 2021.
@conference{riva2021_ESPM16,
title = {Methodology for estimating the magnetic Prandtl number and application to solar surface small-scale dynamo simulations},
author = {F. Riva and O. Steiner},
url = {http://www.irsol.usi.ch/wp-content/uploads/2022/02/Riva_ESPM16.pdf},
year = {2021},
date = {2021-09-06},
urldate = {2021-09-06},
booktitle = {16th European Solar Physics Meeting (ESPM-16)},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
Lightner, Carin R.; Gisler, Daniel; Meyer, Stefan A.; Niese, Hannah; Keitel, Robert C.; Norris, David J.
Measurement of Raman Optical Activity with High-Frequency Polarization Modulation Journal Article
In: Journal of Physical Chemistry A, vol. 125, no. 36, pp. 8132-8139, 2021.
@article{2021JPCA..125.8132L,
title = {Measurement of Raman Optical Activity with High-Frequency Polarization Modulation},
author = {Carin R. Lightner and Daniel Gisler and Stefan A. Meyer and Hannah Niese and Robert C. Keitel and David J. Norris},
doi = {10.1021/acs.jpca.1c06132},
year = {2021},
date = {2021-09-01},
urldate = {2021-09-01},
journal = {Journal of Physical Chemistry A},
volume = {125},
number = {36},
pages = {8132-8139},
abstract = {Many chiroptical spectroscopic techniques have been developed to detect chirality in molecular species and probe its role in biological processes. Raman optical activity (ROA) should be one of the most powerful methods, as ROA yields vibrational and chirality information simultaneously and can measure analytes in aqueous and biologically relevant solvents. However, despite its promise, the use of ROA has been limited, largely due to challenges in instrumentation. Here, we report a new approach to ROA that exploits high-frequency polarization modulation. High-frequency polarization modulation, usually implemented with a photoelastic modulator (PEM), has long been the standard technique in other chiroptical spectroscopies. Unfortunately, the need for simultaneous spectral and polarization resolution has precluded the use of PEMs in ROA instruments. We combine a specialized camera system (the Zurich imaging polarimeter, or ZIMPOL) with PEM modulation to perform ROA measurements. We demonstrate performance similar to the current standard in ROA instrumentation while reducing complexity and polarization artifacts. This development should aid researchers in exploiting the full potential of ROA for chemical and biological analysis.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Many chiroptical spectroscopic techniques have been developed to detect chirality in molecular species and probe its role in biological processes. Raman optical activity (ROA) should be one of the most powerful methods, as ROA yields vibrational and chirality information simultaneously and can measure analytes in aqueous and biologically relevant solvents. However, despite its promise, the use of ROA has been limited, largely due to challenges in instrumentation. Here, we report a new approach to ROA that exploits high-frequency polarization modulation. High-frequency polarization modulation, usually implemented with a photoelastic modulator (PEM), has long been the standard technique in other chiroptical spectroscopies. Unfortunately, the need for simultaneous spectral and polarization resolution has precluded the use of PEMs in ROA instruments. We combine a specialized camera system (the Zurich imaging polarimeter, or ZIMPOL) with PEM modulation to perform ROA measurements. We demonstrate performance similar to the current standard in ROA instrumentation while reducing complexity and polarization artifacts. This development should aid researchers in exploiting the full potential of ROA for chemical and biological analysis.
Ernest, Alsina Ballester; Belluzzi, Luca; Javier, Trujillo Bueno
Solving the Paradox of the Solar Sodium D$_1$ Line Polarization Journal Article
In: Physical Review Letters, vol. 127, no. 8, pp. 081101, 2021.
@article{2021PhRvL.127h1101A,
title = {Solving the Paradox of the Solar Sodium D$_1$ Line Polarization},
author = {Ernest, Alsina Ballester and Luca Belluzzi and Javier, Trujillo Bueno},
doi = {10.1103/PhysRevLett.127.081101},
year = {2021},
date = {2021-08-01},
urldate = {2021-08-01},
journal = {Physical Review Letters},
volume = {127},
number = {8},
pages = {081101},
abstract = {Twenty-five years ago, enigmatic linear polarization signals were
discovered in the core of the sodium D$_1$ line. The only
explanation that could be found implied that the solar
chromosphere is practically unmagnetized, in contradiction with
other evidences. This opened a paradox that has challenged
physicists for many years. Here we present its solution,
demonstrating that these polarization signals can be properly
explained in the presence of magnetic fields in the gauss range.
This result opens a novel diagnostic window for exploring the
elusive magnetism of the solar chromosphere.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Twenty-five years ago, enigmatic linear polarization signals were
discovered in the core of the sodium D$_1$ line. The only
explanation that could be found implied that the solar
chromosphere is practically unmagnetized, in contradiction with
other evidences. This opened a paradox that has challenged
physicists for many years. Here we present its solution,
demonstrating that these polarization signals can be properly
explained in the presence of magnetic fields in the gauss range.
This result opens a novel diagnostic window for exploring the
elusive magnetism of the solar chromosphere.
discovered in the core of the sodium D$_1$ line. The only
explanation that could be found implied that the solar
chromosphere is practically unmagnetized, in contradiction with
other evidences. This opened a paradox that has challenged
physicists for many years. Here we present its solution,
demonstrating that these polarization signals can be properly
explained in the presence of magnetic fields in the gauss range.
This result opens a novel diagnostic window for exploring the
elusive magnetism of the solar chromosphere.
Peter, H.; E., Alsina Ballester; Andretta, V.; Auch`ere, F.; Belluzzi, L.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Calcines, A.; Chitta, L. P.; Dalmasse, K.; del Pino Alemán, T.; Feller, A.; Froment, C.; Harrison, R.; Janvier, M.; Matthews, S.; Parenti, S.; Przybylski, D.; Solanki, S. K.; Štěpán, J.; Teriaca, L.; Bueno, J. Trujillo
Magnetic imaging of the outer solar atmosphere (MImOSA) Journal Article
In: Experimental Astronomy, 2021.
@article{2021ExA...tmp...95P,
title = {Magnetic imaging of the outer solar atmosphere (MImOSA)},
author = {H. Peter and E., Alsina Ballester and V. Andretta and F. Auch`ere and L. Belluzzi and A. Bemporad and D. Berghmans and E. Buchlin and A. Calcines and L. P. Chitta and K. Dalmasse and T. del Pino Alemán and A. Feller and C. Froment and R. Harrison and M. Janvier and S. Matthews and S. Parenti and D. Przybylski and S. K. Solanki and J. Štěpán and L. Teriaca and J. Trujillo Bueno},
doi = {10.1007/s10686-021-09774-0},
year = {2021},
date = {2021-08-01},
urldate = {2021-08-01},
journal = {Experimental Astronomy},
abstract = {The magnetic activity of the Sun directly impacts the Earth and human
life. Likewise, other stars will have an impact on the
habitability of planets orbiting these host stars. Although the
magnetic field at the surface of the Sun is reasonably well
characterised by observations, the information on the magnetic
field in the higher atmospheric layers is mainly indirect. This
lack of information hampers our progress in understanding solar
magnetic activity. Overcoming this limitation would allow us to
address four paramount long-standing questions: (1) How does the
magnetic field couple the different layers of the atmosphere,
and how does it transport energy? (2) How does the magnetic
field structure, drive and interact with the plasma in the
chromosphere and upper atmosphere? (3) How does the magnetic
field destabilise the outer solar atmosphere and thus affect the
interplanetary environment? (4) How do magnetic processes
accelerate particles to high energies? New ground-breaking
observations are needed to address these science questions. We
suggest a suite of three instruments that far exceed current
capabilities in terms of spatial resolution, light-gathering
power, and polarimetric performance: (a) A large-aperture UV-to-
IR telescope of the 1-3 m class aimed mainly to measure the
magnetic field in the chromosphere by combining high spatial
resolution and high sensitivity. (b) An extreme-UV-to-IR
coronagraph that is designed to measure the large-scale magnetic
field in the corona with an aperture of about 40 cm. (c) An
extreme-UV imaging polarimeter based on a 30 cm telescope that
combines high throughput in the extreme UV with polarimetry to
connect the magnetic measurements of the other two instruments.
Placed in a near-Earth orbit, the data downlink would be
maximised, while a location at L4 or L5 would provide
stereoscopic observations of the Sun in combination with Earth-
based observatories. This mission to measure the magnetic field
will finally unlock the driver of the dynamics in the outer
solar atmosphere and thereby will greatly advance our
understanding of the Sun and the heliosphere.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The magnetic activity of the Sun directly impacts the Earth and human
life. Likewise, other stars will have an impact on the
habitability of planets orbiting these host stars. Although the
magnetic field at the surface of the Sun is reasonably well
characterised by observations, the information on the magnetic
field in the higher atmospheric layers is mainly indirect. This
lack of information hampers our progress in understanding solar
magnetic activity. Overcoming this limitation would allow us to
address four paramount long-standing questions: (1) How does the
magnetic field couple the different layers of the atmosphere,
and how does it transport energy? (2) How does the magnetic
field structure, drive and interact with the plasma in the
chromosphere and upper atmosphere? (3) How does the magnetic
field destabilise the outer solar atmosphere and thus affect the
interplanetary environment? (4) How do magnetic processes
accelerate particles to high energies? New ground-breaking
observations are needed to address these science questions. We
suggest a suite of three instruments that far exceed current
capabilities in terms of spatial resolution, light-gathering
power, and polarimetric performance: (a) A large-aperture UV-to-
IR telescope of the 1-3 m class aimed mainly to measure the
magnetic field in the chromosphere by combining high spatial
resolution and high sensitivity. (b) An extreme-UV-to-IR
coronagraph that is designed to measure the large-scale magnetic
field in the corona with an aperture of about 40 cm. (c) An
extreme-UV imaging polarimeter based on a 30 cm telescope that
combines high throughput in the extreme UV with polarimetry to
connect the magnetic measurements of the other two instruments.
Placed in a near-Earth orbit, the data downlink would be
maximised, while a location at L4 or L5 would provide
stereoscopic observations of the Sun in combination with Earth-
based observatories. This mission to measure the magnetic field
will finally unlock the driver of the dynamics in the outer
solar atmosphere and thereby will greatly advance our
understanding of the Sun and the heliosphere.
life. Likewise, other stars will have an impact on the
habitability of planets orbiting these host stars. Although the
magnetic field at the surface of the Sun is reasonably well
characterised by observations, the information on the magnetic
field in the higher atmospheric layers is mainly indirect. This
lack of information hampers our progress in understanding solar
magnetic activity. Overcoming this limitation would allow us to
address four paramount long-standing questions: (1) How does the
magnetic field couple the different layers of the atmosphere,
and how does it transport energy? (2) How does the magnetic
field structure, drive and interact with the plasma in the
chromosphere and upper atmosphere? (3) How does the magnetic
field destabilise the outer solar atmosphere and thus affect the
interplanetary environment? (4) How do magnetic processes
accelerate particles to high energies? New ground-breaking
observations are needed to address these science questions. We
suggest a suite of three instruments that far exceed current
capabilities in terms of spatial resolution, light-gathering
power, and polarimetric performance: (a) A large-aperture UV-to-
IR telescope of the 1-3 m class aimed mainly to measure the
magnetic field in the chromosphere by combining high spatial
resolution and high sensitivity. (b) An extreme-UV-to-IR
coronagraph that is designed to measure the large-scale magnetic
field in the corona with an aperture of about 40 cm. (c) An
extreme-UV imaging polarimeter based on a 30 cm telescope that
combines high throughput in the extreme UV with polarimetry to
connect the magnetic measurements of the other two instruments.
Placed in a near-Earth orbit, the data downlink would be
maximised, while a location at L4 or L5 would provide
stereoscopic observations of the Sun in combination with Earth-
based observatories. This mission to measure the magnetic field
will finally unlock the driver of the dynamics in the outer
solar atmosphere and thereby will greatly advance our
understanding of the Sun and the heliosphere.
Kharayat, Hema; Joshi, Bhuwan; Mitra, Prabir K; Manoharan, P K; Monstein, Christian
A Transient Coronal Sigmoid in Active Region NOAA 11909: Build-up Phase, M-class Eruptive Flare, and Associated Fast Coronal Mass Ejection Journal Article
In: Solar Physics, vol. 296, pp. 99, 2021.
@article{2021arXiv210500411K,
title = {A Transient Coronal Sigmoid in Active Region NOAA 11909: Build-up Phase, M-class Eruptive Flare, and Associated Fast Coronal Mass Ejection},
author = {Hema {Kharayat} and Bhuwan {Joshi} and Prabir K {Mitra} and P ~K {Manoharan} and Christian {Monstein}},
url = {https://ui.adsabs.harvard.edu/link_gateway/2021arXiv210500411K/EPRINT_PDF},
doi = {10.1007/s11207-021-01830-4},
year = {2021},
date = {2021-06-22},
journal = {Solar Physics},
volume = {296},
pages = {99},
abstract = {In this article, we investigate the formation and disruption of a
coronal sigmoid from the active region (AR) NOAA 11909 on 07
December 2013, by analyzing multi-wavelength and multi-
instrument observations. Our analysis suggests that the
formation of `transient' sigmoid initiated $approx$1 hour
before its eruption through a coupling between two twisted
coronal loop systems. A comparison between coronal and
photospheric images suggests that the coronal sigmoid was formed
over a simple $beta$-type AR which also possessed dispersed
magnetic field structure in the photosphere. The line-of-sight
photospheric magnetograms also reveal moving magnetic features,
small-scale flux cancellation events near the PIL, and overall
flux cancellation during the extended pre-eruption phase which
suggest the role of tether-cutting reconnection toward the
build-up of the flux rope. The disruption of the sigmoid
proceeded with a two-ribbon eruptive M1.2 flare
(SOL2013-12-07T07:29). In radio frequencies, we observe type III
and type II bursts in meter wavelengths during the impulsive
phase of the flare. The successful eruption of the flux rope
leads to a fast coronal mass ejection (with a linear speed of
$approx$1085 km s -1 ) in SOHO/LASCO field-of-view. During the
evolution of the flare, we clearly observe typical ``sigmoid-to-
arcade'' transformation. Prior to the onset of the impulsive
phase of the flare, flux rope undergoes a slow rise ($approx$15
km s -1 ) which subsequently transitions into a fast eruption
($approx$110 km s -1 ). The two-phase evolution of the flux
rope shows temporal associations with the soft X-ray precursor
and impulsive phase emissions of the M-class flare,
respectively, thus pointing toward a feedback relationship
between magnetic reconnection and early CME dynamics.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In this article, we investigate the formation and disruption of a
coronal sigmoid from the active region (AR) NOAA 11909 on 07
December 2013, by analyzing multi-wavelength and multi-
instrument observations. Our analysis suggests that the
formation of `transient' sigmoid initiated $approx$1 hour
before its eruption through a coupling between two twisted
coronal loop systems. A comparison between coronal and
photospheric images suggests that the coronal sigmoid was formed
over a simple $beta$-type AR which also possessed dispersed
magnetic field structure in the photosphere. The line-of-sight
photospheric magnetograms also reveal moving magnetic features,
small-scale flux cancellation events near the PIL, and overall
flux cancellation during the extended pre-eruption phase which
suggest the role of tether-cutting reconnection toward the
build-up of the flux rope. The disruption of the sigmoid
proceeded with a two-ribbon eruptive M1.2 flare
(SOL2013-12-07T07:29). In radio frequencies, we observe type III
and type II bursts in meter wavelengths during the impulsive
phase of the flare. The successful eruption of the flux rope
leads to a fast coronal mass ejection (with a linear speed of
$approx$1085 km s -1 ) in SOHO/LASCO field-of-view. During the
evolution of the flare, we clearly observe typical ``sigmoid-to-
arcade'' transformation. Prior to the onset of the impulsive
phase of the flare, flux rope undergoes a slow rise ($approx$15
km s -1 ) which subsequently transitions into a fast eruption
($approx$110 km s -1 ). The two-phase evolution of the flux
rope shows temporal associations with the soft X-ray precursor
and impulsive phase emissions of the M-class flare,
respectively, thus pointing toward a feedback relationship
between magnetic reconnection and early CME dynamics.
coronal sigmoid from the active region (AR) NOAA 11909 on 07
December 2013, by analyzing multi-wavelength and multi-
instrument observations. Our analysis suggests that the
formation of `transient' sigmoid initiated $approx$1 hour
before its eruption through a coupling between two twisted
coronal loop systems. A comparison between coronal and
photospheric images suggests that the coronal sigmoid was formed
over a simple $beta$-type AR which also possessed dispersed
magnetic field structure in the photosphere. The line-of-sight
photospheric magnetograms also reveal moving magnetic features,
small-scale flux cancellation events near the PIL, and overall
flux cancellation during the extended pre-eruption phase which
suggest the role of tether-cutting reconnection toward the
build-up of the flux rope. The disruption of the sigmoid
proceeded with a two-ribbon eruptive M1.2 flare
(SOL2013-12-07T07:29). In radio frequencies, we observe type III
and type II bursts in meter wavelengths during the impulsive
phase of the flare. The successful eruption of the flux rope
leads to a fast coronal mass ejection (with a linear speed of
$approx$1085 km s -1 ) in SOHO/LASCO field-of-view. During the
evolution of the flare, we clearly observe typical ``sigmoid-to-
arcade'' transformation. Prior to the onset of the impulsive
phase of the flare, flux rope undergoes a slow rise ($approx$15
km s -1 ) which subsequently transitions into a fast eruption
($approx$110 km s -1 ). The two-phase evolution of the flux
rope shows temporal associations with the soft X-ray precursor
and impulsive phase emissions of the M-class flare,
respectively, thus pointing toward a feedback relationship
between magnetic reconnection and early CME dynamics.
Joshi, Bhuwan; Mitra, Prabir K; Bhattacharyya, R; Upadhyay, Kushagra; Oberoi, Divya; Raja, K Sasikumar; Monstein, Christian
In: Solar Physics, vol. 296, no. 6, pp. 85, 2021.
@article{2021SoPh..296...85J,
title = {Two-Stage Evolution of an Extended C-Class Eruptive Flaring Activity from Sigmoid Active Region NOAA 12734: SDO and Udaipur-CALLISTO Observations},
author = {Bhuwan {Joshi} and Prabir K {Mitra} and R {Bhattacharyya} and Kushagra {Upadhyay} and Divya {Oberoi} and K {Sasikumar Raja} and Christian {Monstein}},
doi = {10.1007/s11207-021-01820-6},
year = {2021},
date = {2021-06-03},
journal = {Solar Physics},
volume = {296},
number = {6},
pages = {85},
abstract = {In this article, we present a multi-wavelength investigation of a
C-class flaring activity that occurred in the active region NOAA
12734 on 8 March 2019. The investigation utilizes data from the
Atmospheric Imaging Assembly (AIA) and the Helioseismic Magnetic
Imager (HMI) on board the Solar Dynamics Observatory (SDO) and
the Udaipur-CALLISTO solar radio spectrograph of the Physical
Research Laboratory. This low intensity C1.3 event is
characterized by typical features of a long-duration event
(LDE), viz. extended flare arcade, large-scale two-ribbon
structures and twin coronal dimmings. The eruptive event
occurred in a coronal sigmoid and displayed two distinct stages
of energy release, manifested in terms of temporal and spatial
evolution. The formation of twin-dimming regions are consistent
with the eruption of a large flux rope with footpoints lying in
the western and eastern edges of the coronal sigmoid. The metric
radio observations obtained from Udaipur-CALLISTO reveals a
broad-band (ensuremathapprox50 -180 MHz), stationary
plasma emission for ensuremathapprox7 min during the
second stage of the flaring activity that resemble a type IV
radio burst. A type III decametre-hectometre radio bursts with
starting frequency of ensuremathapprox2.5 MHz precedes the
stationary type IV burst observed by Udaipur-CALLISTO by
ensuremathapprox5 min. The synthesis of multi-wavelength
observations and non-linear force-free field (NLFFF) coronal
modeling together with magnetic decay index analysis suggest
that the sigmoid flux rope underwent a zipping-like uprooting
from its western to eastern footpoints in response to the
overlying asymmetric magnetic field confinement. The
asymmetrical eruption of the flux rope also accounts for the
observed large-scale structures viz. apparent eastward shift of
flare ribbons and post-flare loops along the polarity inversion
line (PIL), and provides evidence for lateral progression of
magnetic reconnection site as the eruption proceeds.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In this article, we present a multi-wavelength investigation of a
C-class flaring activity that occurred in the active region NOAA
12734 on 8 March 2019. The investigation utilizes data from the
Atmospheric Imaging Assembly (AIA) and the Helioseismic Magnetic
Imager (HMI) on board the Solar Dynamics Observatory (SDO) and
the Udaipur-CALLISTO solar radio spectrograph of the Physical
Research Laboratory. This low intensity C1.3 event is
characterized by typical features of a long-duration event
(LDE), viz. extended flare arcade, large-scale two-ribbon
structures and twin coronal dimmings. The eruptive event
occurred in a coronal sigmoid and displayed two distinct stages
of energy release, manifested in terms of temporal and spatial
evolution. The formation of twin-dimming regions are consistent
with the eruption of a large flux rope with footpoints lying in
the western and eastern edges of the coronal sigmoid. The metric
radio observations obtained from Udaipur-CALLISTO reveals a
broad-band (ensuremathapprox50 -180 MHz), stationary
plasma emission for ensuremathapprox7 min during the
second stage of the flaring activity that resemble a type IV
radio burst. A type III decametre-hectometre radio bursts with
starting frequency of ensuremathapprox2.5 MHz precedes the
stationary type IV burst observed by Udaipur-CALLISTO by
ensuremathapprox5 min. The synthesis of multi-wavelength
observations and non-linear force-free field (NLFFF) coronal
modeling together with magnetic decay index analysis suggest
that the sigmoid flux rope underwent a zipping-like uprooting
from its western to eastern footpoints in response to the
overlying asymmetric magnetic field confinement. The
asymmetrical eruption of the flux rope also accounts for the
observed large-scale structures viz. apparent eastward shift of
flare ribbons and post-flare loops along the polarity inversion
line (PIL), and provides evidence for lateral progression of
magnetic reconnection site as the eruption proceeds.
C-class flaring activity that occurred in the active region NOAA
12734 on 8 March 2019. The investigation utilizes data from the
Atmospheric Imaging Assembly (AIA) and the Helioseismic Magnetic
Imager (HMI) on board the Solar Dynamics Observatory (SDO) and
the Udaipur-CALLISTO solar radio spectrograph of the Physical
Research Laboratory. This low intensity C1.3 event is
characterized by typical features of a long-duration event
(LDE), viz. extended flare arcade, large-scale two-ribbon
structures and twin coronal dimmings. The eruptive event
occurred in a coronal sigmoid and displayed two distinct stages
of energy release, manifested in terms of temporal and spatial
evolution. The formation of twin-dimming regions are consistent
with the eruption of a large flux rope with footpoints lying in
the western and eastern edges of the coronal sigmoid. The metric
radio observations obtained from Udaipur-CALLISTO reveals a
broad-band (ensuremathapprox50 -180 MHz), stationary
plasma emission for ensuremathapprox7 min during the
second stage of the flaring activity that resemble a type IV
radio burst. A type III decametre-hectometre radio bursts with
starting frequency of ensuremathapprox2.5 MHz precedes the
stationary type IV burst observed by Udaipur-CALLISTO by
ensuremathapprox5 min. The synthesis of multi-wavelength
observations and non-linear force-free field (NLFFF) coronal
modeling together with magnetic decay index analysis suggest
that the sigmoid flux rope underwent a zipping-like uprooting
from its western to eastern footpoints in response to the
overlying asymmetric magnetic field confinement. The
asymmetrical eruption of the flux rope also accounts for the
observed large-scale structures viz. apparent eastward shift of
flare ribbons and post-flare loops along the polarity inversion
line (PIL), and provides evidence for lateral progression of
magnetic reconnection site as the eruption proceeds.
McKenzie, D.; Ishikawa, R.; J., Trujillo Bueno; Auchere, F.; Aleman, T. Pino; Okamoto, T.; Kano, R.; Song, D.; Yoshida, M.; Rachmeler, L.; Kobayashi, K.; Narukage, N.; Kubo, M.; Ishikawa, S.; Hara, H.; Suematsu, Y.; Sakao, T.; Bethge, C.; B., De Pontieu; Vigil, G.; Winebarger, A.; E., Alsina Ballester; Belluzzi, L.; Stepan, J.; A., Asensio Ramos; Carlsson, M.; Leenaarts, J.
Mapping of Solar Magnetic Fields from the Photosphere to the Top of the Chromosphere with CLASP2 Inproceedings
In: American Astronomical Society Meeting Abstracts, pp. 106.03, 2021.
@inproceedings{2021AAS...23810603M,
title = {Mapping of Solar Magnetic Fields from the Photosphere to the Top of the Chromosphere with CLASP2},
author = {D. McKenzie and R. Ishikawa and J., Trujillo Bueno and F. Auchere and T. Pino Aleman and T. Okamoto and R. Kano and D. Song and M. Yoshida and L. Rachmeler and K. Kobayashi and N. Narukage and M. Kubo and S. Ishikawa and H. Hara and Y. Suematsu and T. Sakao and C. Bethge and B., De Pontieu and G. Vigil and A. Winebarger and E., Alsina Ballester and L. Belluzzi and J. Stepan and A., Asensio Ramos and M. Carlsson and J. Leenaarts},
year = {2021},
date = {2021-06-01},
urldate = {2021-06-01},
booktitle = {American Astronomical Society Meeting Abstracts},
volume = {53},
pages = {106.03},
series = {American Astronomical Society Meeting Abstracts},
abstract = {Coronal heating, chromospheric heating, and the heating & acceleration
of the solar wind, are well-known problems in solar physics.
Additionally, knowledge of the magnetic energy that powers solar
flares and coronal mass ejections, important drivers of space
weather, is handicapped by imperfect determination of the
magnetic field in the sun's atmosphere. Extrapolation of
photospheric magnetic measurements into the corona is fraught
with difficulties and uncertainties, partly due to the vastly
different plasma beta between the photosphere and the corona.
Better results in understanding the coronal magnetic field
should be derived from measurements of the magnetic field in the
chromosphere. To that end, we are pursuing quantitative
determination of the magnetic field in the chromosphere, where
plasma beta transitions from greater than unity to less than
unity, via ultraviolet spectropolarimetry. The CLASP2 mission,
flown on a sounding rocket in April 2019, succeeded in measuring
all four Stokes polarization parameters in UV spectral lines
formed by singly ionized Magnesium and neutral Manganese.
Because these ions produce spectral lines under different
conditions, CLASP2 thus was able to quantify the magnetic field
properties at multiple heights in the chromosphere
simultaneously, as shown in the recent paper by Ishikawa et al.
In this presentation we will report the findings of CLASP2,
demonstrating the variation of magnetic fields along a track on
the solar surface and as a function of height in the
chromosphere; and we will illustrate what is next for the CLASP
missions and the demonstration of UV spectropolarimetry in the
solar chromosphere.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Coronal heating, chromospheric heating, and the heating & acceleration
of the solar wind, are well-known problems in solar physics.
Additionally, knowledge of the magnetic energy that powers solar
flares and coronal mass ejections, important drivers of space
weather, is handicapped by imperfect determination of the
magnetic field in the sun's atmosphere. Extrapolation of
photospheric magnetic measurements into the corona is fraught
with difficulties and uncertainties, partly due to the vastly
different plasma beta between the photosphere and the corona.
Better results in understanding the coronal magnetic field
should be derived from measurements of the magnetic field in the
chromosphere. To that end, we are pursuing quantitative
determination of the magnetic field in the chromosphere, where
plasma beta transitions from greater than unity to less than
unity, via ultraviolet spectropolarimetry. The CLASP2 mission,
flown on a sounding rocket in April 2019, succeeded in measuring
all four Stokes polarization parameters in UV spectral lines
formed by singly ionized Magnesium and neutral Manganese.
Because these ions produce spectral lines under different
conditions, CLASP2 thus was able to quantify the magnetic field
properties at multiple heights in the chromosphere
simultaneously, as shown in the recent paper by Ishikawa et al.
In this presentation we will report the findings of CLASP2,
demonstrating the variation of magnetic fields along a track on
the solar surface and as a function of height in the
chromosphere; and we will illustrate what is next for the CLASP
missions and the demonstration of UV spectropolarimetry in the
solar chromosphere.
of the solar wind, are well-known problems in solar physics.
Additionally, knowledge of the magnetic energy that powers solar
flares and coronal mass ejections, important drivers of space
weather, is handicapped by imperfect determination of the
magnetic field in the sun's atmosphere. Extrapolation of
photospheric magnetic measurements into the corona is fraught
with difficulties and uncertainties, partly due to the vastly
different plasma beta between the photosphere and the corona.
Better results in understanding the coronal magnetic field
should be derived from measurements of the magnetic field in the
chromosphere. To that end, we are pursuing quantitative
determination of the magnetic field in the chromosphere, where
plasma beta transitions from greater than unity to less than
unity, via ultraviolet spectropolarimetry. The CLASP2 mission,
flown on a sounding rocket in April 2019, succeeded in measuring
all four Stokes polarization parameters in UV spectral lines
formed by singly ionized Magnesium and neutral Manganese.
Because these ions produce spectral lines under different
conditions, CLASP2 thus was able to quantify the magnetic field
properties at multiple heights in the chromosphere
simultaneously, as shown in the recent paper by Ishikawa et al.
In this presentation we will report the findings of CLASP2,
demonstrating the variation of magnetic fields along a track on
the solar surface and as a function of height in the
chromosphere; and we will illustrate what is next for the CLASP
missions and the demonstration of UV spectropolarimetry in the
solar chromosphere.
Kouloumvakos, Athanasios; Rouillard, Alexis; Warmuth, Alexander; Magdalenic, Jasmina; Jebaraj, Immanuel. C; Mann, Gottfried; Vainio, Rami; Monstein, Christian
Coronal Conditions for the Occurrence of Type II Radio Bursts Journal Article
In: Astrophysical Journal, vol. 913, no. 2, pp. 99, 2021.
@article{2021ApJ...913...99K,
title = {Coronal Conditions for the Occurrence of Type II Radio Bursts},
author = {Athanasios {Kouloumvakos} and Alexis {Rouillard} and Alexander {Warmuth} and Jasmina {Magdalenic} and Immanuel. C {Jebaraj} and Gottfried {Mann} and Rami {Vainio} and Christian {Monstein}},
doi = {10.3847/1538-4357/abf435},
year = {2021},
date = {2021-05-28},
journal = {Astrophysical Journal},
volume = {913},
number = {2},
pages = {99},
abstract = {Type II radio bursts are generally observed in association with flare-
generated or coronal-mass-ejection-driven shock waves. The exact
shock and coronal conditions necessary for the production of
type II radio emission are still under debate. Shock waves are
important for the acceleration of electrons necessary for the
generation of the radio emission. Additionally, the shock
geometry and closed field line topology, e.g., quasi-
perpendicular shock regions or shocks interacting with
streamers, play an important role for the production of the
emission. In this study we perform a 3D reconstruction and
modeling of a shock wave observed during the 2014 November 5
solar event. We determine the spatial and temporal evolution of
the shock properties and examine the conditions responsible for
the generation and evolution of type II radio emission. Our
results suggest that the formation and evolution of a strong,
supercritical, quasi-perpendicular shock wave interacting with a
coronal streamer were responsible for producing type II radio
emission. We find that the shock wave is subcritical before and
supercritical after the start of the type II emission. The shock
geometry is mostly quasi-perpendicular throughout the event. Our
analysis shows that the radio emission is produced in regions
where the supercritical shock develops with an oblique to quasi-
perpendicular geometry.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Type II radio bursts are generally observed in association with flare-
generated or coronal-mass-ejection-driven shock waves. The exact
shock and coronal conditions necessary for the production of
type II radio emission are still under debate. Shock waves are
important for the acceleration of electrons necessary for the
generation of the radio emission. Additionally, the shock
geometry and closed field line topology, e.g., quasi-
perpendicular shock regions or shocks interacting with
streamers, play an important role for the production of the
emission. In this study we perform a 3D reconstruction and
modeling of a shock wave observed during the 2014 November 5
solar event. We determine the spatial and temporal evolution of
the shock properties and examine the conditions responsible for
the generation and evolution of type II radio emission. Our
results suggest that the formation and evolution of a strong,
supercritical, quasi-perpendicular shock wave interacting with a
coronal streamer were responsible for producing type II radio
emission. We find that the shock wave is subcritical before and
supercritical after the start of the type II emission. The shock
geometry is mostly quasi-perpendicular throughout the event. Our
analysis shows that the radio emission is produced in regions
where the supercritical shock develops with an oblique to quasi-
perpendicular geometry.
generated or coronal-mass-ejection-driven shock waves. The exact
shock and coronal conditions necessary for the production of
type II radio emission are still under debate. Shock waves are
important for the acceleration of electrons necessary for the
generation of the radio emission. Additionally, the shock
geometry and closed field line topology, e.g., quasi-
perpendicular shock regions or shocks interacting with
streamers, play an important role for the production of the
emission. In this study we perform a 3D reconstruction and
modeling of a shock wave observed during the 2014 November 5
solar event. We determine the spatial and temporal evolution of
the shock properties and examine the conditions responsible for
the generation and evolution of type II radio emission. Our
results suggest that the formation and evolution of a strong,
supercritical, quasi-perpendicular shock wave interacting with a
coronal streamer were responsible for producing type II radio
emission. We find that the shock wave is subcritical before and
supercritical after the start of the type II emission. The shock
geometry is mostly quasi-perpendicular throughout the event. Our
analysis shows that the radio emission is produced in regions
where the supercritical shock develops with an oblique to quasi-
perpendicular geometry.
Battaglia, Andrea Francesco; Cuissa, José Roberto Canivete; Calvo, Flavio; Bossart, Aleksi Antoine; Steiner, Oskar
The Alfvénic nature of chromospheric swirls Journal Article
In: A&A, vol. 649, pp. A121, 2021.
@article{refId0j,
title = {The Alfvénic nature of chromospheric swirls},
author = {Andrea Francesco {Battaglia} and José Roberto {Canivete Cuissa} and Flavio {Calvo} and Aleksi Antoine {Bossart} and Oskar {Steiner}},
url = {https://doi.org/10.1051/0004-6361/202040110
https://arxiv.org/abs/2103.07366},
doi = {10.1051/0004-6361/202040110},
year = {2021},
date = {2021-05-26},
journal = {A&A},
volume = {649},
pages = {A121},
abstract = {Context. Observations show that small-scale vortical plasma motions are ubiquitous in the quiet solar atmosphere. They have received increasing attention in recent years because they are a viable candidate mechanism for the heating of the outer solar atmospheric layers. However, the true nature and the origin of these swirls, and their effective role in the energy transport, are still unclear.
Aims. We investigate the evolution and origin of chromospheric swirls by analyzing numerical simulations of the quiet solar atmosphere. In particular, we are interested in finding their relation with magnetic field perturbations and in the processes driving their evolution.
Methods. The radiative magnetohydrodynamic code CO5BOLD is used to perform realistic numerical simulations of a small portion of the solar atmosphere, ranging from the top layers of the convection zone to the middle chromosphere. For the analysis, the swirling strength criterion and its evolution equation are applied in order to identify vortical motions and to study their dynamics. As a new criterion, we introduce the magnetic swirling strength, which allows us to recognize torsional perturbations in the magnetic field.
Results. We find a strong correlation between swirling strength and magnetic swirling strength, in particular in intense magnetic flux concentrations, which suggests a tight relation between vortical motions and torsional magnetic field perturbations. Furthermore, we find that swirls propagate upward with the local Alfvén speed as unidirectional swirls driven by magnetic tension forces alone. In the photosphere and low chromosphere, the rotation of the plasma co-occurs with a twist in the upwardly directed magnetic field that is in the opposite direction of the plasma flow. All together, these are clear characteristics of torsional Alfvén waves. Yet, the Alfvén wave is not oscillatory but takes the form of a unidirectional pulse. The novelty of the present work is that these Alfvén pulses naturally emerge from realistic numerical simulations of the solar atmosphere. We also find indications of an imbalance between the hydrodynamic and magnetohydrodynamic baroclinic effects being at the origin of the swirls. At the base of the chromosphere, we find a mean net upwardly directed Poynting flux of 12.8 ± 6.5 kW m−2, which is mainly due to swirling motions. This energy flux is mostly associated with large and complex swirling structures, which we interpret as the superposition of various small-scale vortices.
Conclusions. We conclude that the ubiquitous swirling events observed in numerical simulations are tightly correlated with perturbations of the magnetic field. At photospheric and chromospheric levels, they form Alfvén pulses that propagate upward and may contribute to chromospheric heating.
},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Context. Observations show that small-scale vortical plasma motions are ubiquitous in the quiet solar atmosphere. They have received increasing attention in recent years because they are a viable candidate mechanism for the heating of the outer solar atmospheric layers. However, the true nature and the origin of these swirls, and their effective role in the energy transport, are still unclear.
Aims. We investigate the evolution and origin of chromospheric swirls by analyzing numerical simulations of the quiet solar atmosphere. In particular, we are interested in finding their relation with magnetic field perturbations and in the processes driving their evolution.
Methods. The radiative magnetohydrodynamic code CO5BOLD is used to perform realistic numerical simulations of a small portion of the solar atmosphere, ranging from the top layers of the convection zone to the middle chromosphere. For the analysis, the swirling strength criterion and its evolution equation are applied in order to identify vortical motions and to study their dynamics. As a new criterion, we introduce the magnetic swirling strength, which allows us to recognize torsional perturbations in the magnetic field.
Results. We find a strong correlation between swirling strength and magnetic swirling strength, in particular in intense magnetic flux concentrations, which suggests a tight relation between vortical motions and torsional magnetic field perturbations. Furthermore, we find that swirls propagate upward with the local Alfvén speed as unidirectional swirls driven by magnetic tension forces alone. In the photosphere and low chromosphere, the rotation of the plasma co-occurs with a twist in the upwardly directed magnetic field that is in the opposite direction of the plasma flow. All together, these are clear characteristics of torsional Alfvén waves. Yet, the Alfvén wave is not oscillatory but takes the form of a unidirectional pulse. The novelty of the present work is that these Alfvén pulses naturally emerge from realistic numerical simulations of the solar atmosphere. We also find indications of an imbalance between the hydrodynamic and magnetohydrodynamic baroclinic effects being at the origin of the swirls. At the base of the chromosphere, we find a mean net upwardly directed Poynting flux of 12.8 ± 6.5 kW m−2, which is mainly due to swirling motions. This energy flux is mostly associated with large and complex swirling structures, which we interpret as the superposition of various small-scale vortices.
Conclusions. We conclude that the ubiquitous swirling events observed in numerical simulations are tightly correlated with perturbations of the magnetic field. At photospheric and chromospheric levels, they form Alfvén pulses that propagate upward and may contribute to chromospheric heating.
Aims. We investigate the evolution and origin of chromospheric swirls by analyzing numerical simulations of the quiet solar atmosphere. In particular, we are interested in finding their relation with magnetic field perturbations and in the processes driving their evolution.
Methods. The radiative magnetohydrodynamic code CO5BOLD is used to perform realistic numerical simulations of a small portion of the solar atmosphere, ranging from the top layers of the convection zone to the middle chromosphere. For the analysis, the swirling strength criterion and its evolution equation are applied in order to identify vortical motions and to study their dynamics. As a new criterion, we introduce the magnetic swirling strength, which allows us to recognize torsional perturbations in the magnetic field.
Results. We find a strong correlation between swirling strength and magnetic swirling strength, in particular in intense magnetic flux concentrations, which suggests a tight relation between vortical motions and torsional magnetic field perturbations. Furthermore, we find that swirls propagate upward with the local Alfvén speed as unidirectional swirls driven by magnetic tension forces alone. In the photosphere and low chromosphere, the rotation of the plasma co-occurs with a twist in the upwardly directed magnetic field that is in the opposite direction of the plasma flow. All together, these are clear characteristics of torsional Alfvén waves. Yet, the Alfvén wave is not oscillatory but takes the form of a unidirectional pulse. The novelty of the present work is that these Alfvén pulses naturally emerge from realistic numerical simulations of the solar atmosphere. We also find indications of an imbalance between the hydrodynamic and magnetohydrodynamic baroclinic effects being at the origin of the swirls. At the base of the chromosphere, we find a mean net upwardly directed Poynting flux of 12.8 ± 6.5 kW m−2, which is mainly due to swirling motions. This energy flux is mostly associated with large and complex swirling structures, which we interpret as the superposition of various small-scale vortices.
Conclusions. We conclude that the ubiquitous swirling events observed in numerical simulations are tightly correlated with perturbations of the magnetic field. At photospheric and chromospheric levels, they form Alfvén pulses that propagate upward and may contribute to chromospheric heating.
Vigeesh, G; Roth, M; Steiner, O; Fleck, B
On the influence of magnetic topology on the propagation of internal gravity waves in the solar atmosphere Journal Article
In: Philosophical Transactions of the Royal Society of London Series A, vol. 379, no. 2190, pp. 20200177, 2021.
@article{2021RSPTA.37900177V,
title = {On the influence of magnetic topology on the propagation of internal gravity waves in the solar atmosphere},
author = {G {Vigeesh} and M {Roth} and O {Steiner} and B {Fleck}},
url = {https://arxiv.org/abs/2010.06926},
doi = {10.1098/rsta.2020.0177},
year = {2021},
date = {2021-02-01},
journal = {Philosophical Transactions of the Royal Society of London Series A},
volume = {379},
number = {2190},
pages = {20200177},
abstract = {The solar surface is a continuous source of internal gravity waves
(IGWs). IGWs are believed to supply the bulk of the wave energy
for the lower solar atmosphere, but their existence and role for
the energy balance of the upper layers is still unclear, largely
due to the lack of knowledge about the influence of the Sun's
magnetic fields on their propagation. In this work, we look at
naturally excited IGWs in realistic models of the solar
atmosphere and study the effect of different magnetic field
topographies on their propagation. We carry out radiation-
magnetohydrodynamic simulations of a magnetic field free and two
magnetic models-one with an initial, homogeneous, vertical field
of 100 G magnetic flux density and one with an initial
horizontal field of 100 G flux density. The propagation
properties of IGWs are studied by examining the phase-difference
and coherence spectra in the k$_ħ$ - ensuremathømega
diagnostic diagram. We find that IGWs in the upper solar
atmosphere show upward propagation in the model with
predominantly horizontal field similar to the model without
magnetic field. In contrast to that the model with predominantly
vertical fields show downward propagation. This crucial
difference in the propagation direction is also revealed in the
difference in energy transported by waves for heights below 0.8
Mm. Higher up, the propagation properties show a peculiar
behaviour, which require further study. Our analysis suggests
that IGWs may play a significant role in the heating of the
chromospheric layers of the internetwork region where horizontal
fields are thought to be prevalent.
textbackslashtextbackslashThis article is part of the Theo
Murphy meeting issue `High-resolution wave dynamics in the lower
solar atmosphere'.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The solar surface is a continuous source of internal gravity waves
(IGWs). IGWs are believed to supply the bulk of the wave energy
for the lower solar atmosphere, but their existence and role for
the energy balance of the upper layers is still unclear, largely
due to the lack of knowledge about the influence of the Sun's
magnetic fields on their propagation. In this work, we look at
naturally excited IGWs in realistic models of the solar
atmosphere and study the effect of different magnetic field
topographies on their propagation. We carry out radiation-
magnetohydrodynamic simulations of a magnetic field free and two
magnetic models-one with an initial, homogeneous, vertical field
of 100 G magnetic flux density and one with an initial
horizontal field of 100 G flux density. The propagation
properties of IGWs are studied by examining the phase-difference
and coherence spectra in the k$_ħ$ - ensuremathømega
diagnostic diagram. We find that IGWs in the upper solar
atmosphere show upward propagation in the model with
predominantly horizontal field similar to the model without
magnetic field. In contrast to that the model with predominantly
vertical fields show downward propagation. This crucial
difference in the propagation direction is also revealed in the
difference in energy transported by waves for heights below 0.8
Mm. Higher up, the propagation properties show a peculiar
behaviour, which require further study. Our analysis suggests
that IGWs may play a significant role in the heating of the
chromospheric layers of the internetwork region where horizontal
fields are thought to be prevalent.
textbackslashtextbackslashThis article is part of the Theo
Murphy meeting issue `High-resolution wave dynamics in the lower
solar atmosphere'.
(IGWs). IGWs are believed to supply the bulk of the wave energy
for the lower solar atmosphere, but their existence and role for
the energy balance of the upper layers is still unclear, largely
due to the lack of knowledge about the influence of the Sun's
magnetic fields on their propagation. In this work, we look at
naturally excited IGWs in realistic models of the solar
atmosphere and study the effect of different magnetic field
topographies on their propagation. We carry out radiation-
magnetohydrodynamic simulations of a magnetic field free and two
magnetic models-one with an initial, homogeneous, vertical field
of 100 G magnetic flux density and one with an initial
horizontal field of 100 G flux density. The propagation
properties of IGWs are studied by examining the phase-difference
and coherence spectra in the k$_ħ$ - ensuremathømega
diagnostic diagram. We find that IGWs in the upper solar
atmosphere show upward propagation in the model with
predominantly horizontal field similar to the model without
magnetic field. In contrast to that the model with predominantly
vertical fields show downward propagation. This crucial
difference in the propagation direction is also revealed in the
difference in energy transported by waves for heights below 0.8
Mm. Higher up, the propagation properties show a peculiar
behaviour, which require further study. Our analysis suggests
that IGWs may play a significant role in the heating of the
chromospheric layers of the internetwork region where horizontal
fields are thought to be prevalent.
textbackslashtextbackslashThis article is part of the Theo
Murphy meeting issue `High-resolution wave dynamics in the lower
solar atmosphere'.
Fleck, B; Carlsson, M; Khomenko, E; Rempel, M; Steiner, O; Vigeesh, G
Acoustic-gravity wave propagation characteristics in three-dimensional radiation hydrodynamic simulations of the solar atmosphere Journal Article
In: Philosophical Transactions of the Royal Society of London Series A, vol. 379, no. 2190, pp. 20200170, 2021.
@article{2021RSPTA.37900170F,
title = {Acoustic-gravity wave propagation characteristics in three-dimensional radiation hydrodynamic simulations of the solar atmosphere},
author = {B {Fleck} and M {Carlsson} and E {Khomenko} and M {Rempel} and O {Steiner} and G {Vigeesh}},
url = {https://arxiv.org/abs/2007.05847},
doi = {10.1098/rsta.2020.0170},
year = {2021},
date = {2021-02-01},
journal = {Philosophical Transactions of the Royal Society of London Series A},
volume = {379},
number = {2190},
pages = {20200170},
abstract = {There has been tremendous progress in the degree of realism of three-
dimensional radiation magneto-hydrodynamic simulations of the
solar atmosphere in the past decades. Four of the most
frequently used numerical codes are Bifrost, CO5BOLD, MANCHA3D
and MURaM. Here we test and compare the wave propagation
characteristics in model runs from these four codes by measuring
the dispersion relation of acoustic-gravity waves at various
heights. We find considerable differences between the various
models. The height dependence of wave power, in particular of
high-frequency waves, varies by up to two orders of magnitude
between the models, and the phase difference spectra of several
models show unexpected features, including
ensuremathpm180textdegree phase jumps.
textbackslashtextbackslashThis article is part of the Theo
Murphy meeting issue `High-resolution wave dynamics in the lower
solar atmosphere'.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
There has been tremendous progress in the degree of realism of three-
dimensional radiation magneto-hydrodynamic simulations of the
solar atmosphere in the past decades. Four of the most
frequently used numerical codes are Bifrost, CO5BOLD, MANCHA3D
and MURaM. Here we test and compare the wave propagation
characteristics in model runs from these four codes by measuring
the dispersion relation of acoustic-gravity waves at various
heights. We find considerable differences between the various
models. The height dependence of wave power, in particular of
high-frequency waves, varies by up to two orders of magnitude
between the models, and the phase difference spectra of several
models show unexpected features, including
ensuremathpm180textdegree phase jumps.
textbackslashtextbackslashThis article is part of the Theo
Murphy meeting issue `High-resolution wave dynamics in the lower
solar atmosphere'.
dimensional radiation magneto-hydrodynamic simulations of the
solar atmosphere in the past decades. Four of the most
frequently used numerical codes are Bifrost, CO5BOLD, MANCHA3D
and MURaM. Here we test and compare the wave propagation
characteristics in model runs from these four codes by measuring
the dispersion relation of acoustic-gravity waves at various
heights. We find considerable differences between the various
models. The height dependence of wave power, in particular of
high-frequency waves, varies by up to two orders of magnitude
between the models, and the phase difference spectra of several
models show unexpected features, including
ensuremathpm180textdegree phase jumps.
textbackslashtextbackslashThis article is part of the Theo
Murphy meeting issue `High-resolution wave dynamics in the lower
solar atmosphere'.
Ndacyayisenga, Theogene; Uwamahoro, Jean; Raja, K Sasikumar; Monstein, Christian
A statistical study of solar radio Type III bursts and space weather implication Journal Article
In: Advances in Space Research, vol. 67, no. 4, pp. 1425-1435, 2021.
@article{2021AdSpR..67.1425N,
title = {A statistical study of solar radio Type III bursts and space weather implication},
author = {Theogene {Ndacyayisenga} and Jean {Uwamahoro} and K {Sasikumar Raja} and Christian {Monstein}},
url = {https://arxiv.org/abs/2012.01210},
doi = {10.1016/j.asr.2020.11.022},
year = {2021},
date = {2021-02-01},
journal = {Advances in Space Research},
volume = {67},
number = {4},
pages = {1425-1435},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Ishikawa, Ryohko; Javier, Trujillo Bueno; Tanausu, Pino Alemán; Okamoto, Takenori J.; McKenzie, David E.; Auch`ere, Frédéric; Kano, Ryouhei; Song, Donguk; Yoshida, Masaki; Rachmeler, Laurel A.; Kobayashi, Ken; Hara, Hirohisa; Kubo, Masahito; Narukage, Noriyuki; Sakao, Taro; Shimizu, Toshifumi; Suematsu, Yoshinori; Bethge, Christian; Pontieu, Bart De; Dalda, Alberto Sainz; Vigil, Genevieve D.; Winebarger, Amy; Ernest, Alsina Ballester; Belluzzi, Luca; Štěpán, Jiř'i; Andrés, Asensio Ramos; Carlsson, Mats; Leenaarts, Jorrit
Mapping solar magnetic fields from the photosphere to the base of the corona Journal Article
In: Science Advances, vol. 7, no. 8, pp. eabe8406, 2021.
@article{2021SciA....7.8406I,
title = {Mapping solar magnetic fields from the photosphere to the base of the corona},
author = {Ryohko Ishikawa and Javier, Trujillo Bueno and Tanausu, Pino Alemán and Takenori J. Okamoto and David E. McKenzie and Frédéric Auch`ere and Ryouhei Kano and Donguk Song and Masaki Yoshida and Laurel A. Rachmeler and Ken Kobayashi and Hirohisa Hara and Masahito Kubo and Noriyuki Narukage and Taro Sakao and Toshifumi Shimizu and Yoshinori Suematsu and Christian Bethge and Bart De Pontieu and Alberto Sainz Dalda and Genevieve D. Vigil and Amy Winebarger and Ernest, Alsina Ballester and Luca Belluzzi and Jiř'i Štěpán and Andrés, Asensio Ramos and Mats Carlsson and Jorrit Leenaarts},
doi = {10.1126/sciadv.abe8406},
year = {2021},
date = {2021-02-01},
urldate = {2021-02-01},
journal = {Science Advances},
volume = {7},
number = {8},
pages = {eabe8406},
abstract = {Routine ultraviolet imaging of the Sun's upper atmosphere shows the
spectacular manifestation of solar activity; yet we remain blind
to its main driver, the magnetic field. Here we report
unprecedented spectropolarimetric observations of an active
region plage and its surrounding enhanced network, showing
circular polarization in ultraviolet (Mg II $h$ & $k$ and Mn I)
and visible (Fe I) lines. We infer the longitudinal magnetic
field from the photosphere to the very upper chromosphere. At
the top of the plage chromosphere the field strengths reach more
than 300 gauss, strongly correlated with the Mg II $k$ line core
intensity and the electron pressure. This unique mapping shows
how the magnetic field couples the different atmospheric layers
and reveals the magnetic origin of the heating in the plage
chromosphere.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Routine ultraviolet imaging of the Sun's upper atmosphere shows the
spectacular manifestation of solar activity; yet we remain blind
to its main driver, the magnetic field. Here we report
unprecedented spectropolarimetric observations of an active
region plage and its surrounding enhanced network, showing
circular polarization in ultraviolet (Mg II $h$ & $k$ and Mn I)
and visible (Fe I) lines. We infer the longitudinal magnetic
field from the photosphere to the very upper chromosphere. At
the top of the plage chromosphere the field strengths reach more
than 300 gauss, strongly correlated with the Mg II $k$ line core
intensity and the electron pressure. This unique mapping shows
how the magnetic field couples the different atmospheric layers
and reveals the magnetic origin of the heating in the plage
chromosphere.
spectacular manifestation of solar activity; yet we remain blind
to its main driver, the magnetic field. Here we report
unprecedented spectropolarimetric observations of an active
region plage and its surrounding enhanced network, showing
circular polarization in ultraviolet (Mg II $h$ & $k$ and Mn I)
and visible (Fe I) lines. We infer the longitudinal magnetic
field from the photosphere to the very upper chromosphere. At
the top of the plage chromosphere the field strengths reach more
than 300 gauss, strongly correlated with the Mg II $k$ line core
intensity and the electron pressure. This unique mapping shows
how the magnetic field couples the different atmospheric layers
and reveals the magnetic origin of the heating in the plage
chromosphere.
Keys, P H; Steiner, O; Vigeesh, G
On the effect of oscillatory phenomena on Stokes inversion results Journal Article
In: Philosophical Transactions of the Royal Society of London Series A, vol. 379, no. 2190, pp. 20200182, 2021.
@article{2021RSPTA.37900182K,
title = {On the effect of oscillatory phenomena on Stokes inversion results},
author = {P H {Keys} and O {Steiner} and G {Vigeesh}},
url = {https://arxiv.org/abs/2008.05539},
doi = {10.1098/rsta.2020.0182},
year = {2021},
date = {2021-02-01},
journal = {Philosophical Transactions of the Royal Society of London Series A},
volume = {379},
number = {2190},
pages = {20200182},
abstract = {Stokes inversion codes are crucial in returning properties of the solar
atmosphere, such as temperature and magnetic field strength.
However, the success of such algorithms to return reliable
values can be hindered by the presence of oscillatory phenomena
within magnetic wave guides. Returning accurate parameters is
crucial to both magnetohydrodynamics (MHD) studies and solar
physics in general. Here, we employ a simulation featuring
propagating MHD waves within a flux tube with a known driver and
atmospheric parameters. We invert the Stokes profiles for the
6301 Å and 6302 Å line pair emergent from the
simulations using the well-known Stokes Inversions from Response
functions code to see if the atmospheric parameters can be
returned for typical spatial resolutions at ground-based
observatories. The inversions return synthetic spectra
comparable to the original input spectra, even with asymmetries
introduced in the spectra from wave propagation in the
atmosphere. The output models from the inversions match closely
to the simulations in temperature, line-of-sight magnetic field
and line-of-sight velocity within typical formation heights of
the inverted lines. Deviations from the simulations are seen
away from these height regions. The inversions results are less
accurate during passage of the waves within the line formation
region. The original wave period could be recovered from the
atmosphere output by the inversions, with empirical mode
decomposition performing better than the wavelet approach in
this task. textbackslashtextbackslashThis article is part of
the Theo Murphy meeting issue `High-resolution wave dynamics in
the lower solar atmosphere'.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Stokes inversion codes are crucial in returning properties of the solar
atmosphere, such as temperature and magnetic field strength.
However, the success of such algorithms to return reliable
values can be hindered by the presence of oscillatory phenomena
within magnetic wave guides. Returning accurate parameters is
crucial to both magnetohydrodynamics (MHD) studies and solar
physics in general. Here, we employ a simulation featuring
propagating MHD waves within a flux tube with a known driver and
atmospheric parameters. We invert the Stokes profiles for the
6301 Å and 6302 Å line pair emergent from the
simulations using the well-known Stokes Inversions from Response
functions code to see if the atmospheric parameters can be
returned for typical spatial resolutions at ground-based
observatories. The inversions return synthetic spectra
comparable to the original input spectra, even with asymmetries
introduced in the spectra from wave propagation in the
atmosphere. The output models from the inversions match closely
to the simulations in temperature, line-of-sight magnetic field
and line-of-sight velocity within typical formation heights of
the inverted lines. Deviations from the simulations are seen
away from these height regions. The inversions results are less
accurate during passage of the waves within the line formation
region. The original wave period could be recovered from the
atmosphere output by the inversions, with empirical mode
decomposition performing better than the wavelet approach in
this task. textbackslashtextbackslashThis article is part of
the Theo Murphy meeting issue `High-resolution wave dynamics in
the lower solar atmosphere'.
atmosphere, such as temperature and magnetic field strength.
However, the success of such algorithms to return reliable
values can be hindered by the presence of oscillatory phenomena
within magnetic wave guides. Returning accurate parameters is
crucial to both magnetohydrodynamics (MHD) studies and solar
physics in general. Here, we employ a simulation featuring
propagating MHD waves within a flux tube with a known driver and
atmospheric parameters. We invert the Stokes profiles for the
6301 Å and 6302 Å line pair emergent from the
simulations using the well-known Stokes Inversions from Response
functions code to see if the atmospheric parameters can be
returned for typical spatial resolutions at ground-based
observatories. The inversions return synthetic spectra
comparable to the original input spectra, even with asymmetries
introduced in the spectra from wave propagation in the
atmosphere. The output models from the inversions match closely
to the simulations in temperature, line-of-sight magnetic field
and line-of-sight velocity within typical formation heights of
the inverted lines. Deviations from the simulations are seen
away from these height regions. The inversions results are less
accurate during passage of the waves within the line formation
region. The original wave period could be recovered from the
atmosphere output by the inversions, with empirical mode
decomposition performing better than the wavelet approach in
this task. textbackslashtextbackslashThis article is part of
the Theo Murphy meeting issue `High-resolution wave dynamics in
the lower solar atmosphere'.
Battaglia, Andrea Francesco; Cuissa, José Roberto Canivete; Calvo, Flavio; Bossart, Aleksi Antoine; Steiner, Oskar
The Alfvénic nature of chromospheric swirls Journal Article
In: A&A, vol. 649, 2021.
@article{refId0d,
title = {The Alfvénic nature of chromospheric swirls},
author = {Andrea Francesco} {Battaglia and José Roberto} {Canivete Cuissa and Flavio} {Calvo and Aleksi Antoine} {Bossart and Oskar} {Steiner},
url = {https://doi.org/10.1051/0004-6361/202040110},
doi = {10.1051/0004-6361/202040110},
year = {2021},
date = {2021-01-01},
journal = {A&A},
volume = {649},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Battaglia, Andrea Francesco; Cuissa, José Roberto Canivete; Calvo, Flavio; Bossart, Aleksi Antoine; Steiner, Oskar
The Alfvénic nature of chromospheric swirls Journal Article
In: A&A, vol. 649, 2021.
@article{refId0e,
title = {The Alfvénic nature of chromospheric swirls},
author = { Andrea Francesco} {Battaglia and José Roberto} {Canivete Cuissa and Flavio} {Calvo and Aleksi Antoine} {Bossart and Oskar} {Steiner},
url = {https://doi.org/10.1051/0004-6361/202040110},
doi = {10.1051/0004-6361/202040110},
year = {2021},
date = {2021-01-01},
journal = {A&A},
volume = {649},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
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