SWR1 – Understanding the solar lower magnetism and the drivers of space weather phenomena
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Talks
SWR1.1 Thu 7/11 17:30-18:30, room C2B – Sofia
Author(s): Maria D. Kazachenko
University of Colorado – Boulder / National Solar Observatory
Abstract: Space weather is largely caused by the activity of our Sun. Invisible yet powerful magnetic fields, created within the Sun, determine when and where the next solar eruption will happen. In this talk, I will review how advances in solar observations and data-driven models allowed scientists to understand flare magnetism in a lot more detail than ever before. I will specifically focus on results of statistical analyses of SDO/HMI datasets and will show some new results from DKIST observations.
Author(s): Dale Weigt, Andi Korpi-Lagg, Maarit Korpi-Lagg
Aalto University; Max Planck Institute for Solar System Research; Aalto University
Abstract: Helioseismology allows us to probe the turbulent and dynamic solar interior, utilising Doppler velocity measurements to determine the properties of pressure waves (p-modes) and surface gravity waves (f-modes). The potential of the f-modes to predict magnetic flux emergence has only very recently been recognized with recent reports of the f-mode to be enhanced 1-2 days prior to the appearance of concentrated magnetic fields which in turn form active regions. The f-mode was then observed to be continuously quenched once the flux was fully emerged. However the technique relied on various normalisations that introduce bias to the f-mode computation (e.g., using a selected ‘quiet’ patch). Here, we eliminate such biases using a data-driven flat-fielding technique at the selected location. This is more sensitive to fluctuations and obtains the f-mode power at any location on the solar disk and is independent of any normalisation from ‘quiet’ regions, making it more robust and accurate than current techniques. Here, we demonstrate that our novel technique reproduces f-mode behaviour observed from previous studies, with the addition of error bars and additional science information (e.g., geometry). We note that the chosen time of emergence is a key factor in determining the context of f-mode behaviour. Finally, we present a catalogue and associated statistics demonstrating the potential usefulness of this novel technique for space weather forecasting, predicting solar flux emergences leading to formation of active regions.
Author(s): Ioannis Kontogiannis
Leibniz Institute for Astrophysics Potsdam (AIP)
Abstract: The magnetic field of active regions deviates from a minimum potential-field energy state and carries electric currents. Specifically in the most complex regions, which are the sources of the strongest flares and coronal mass ejections (CMEs), the buildup of the magnetic energy and helicity which power these eruptions, requires the presence of significant amounts of volume electric currents. Notwithstanding the limitations posed by the routinely available photospheric magnetograms, a method based on morphological image processing and strict error analysis can lead to an estimation of the total amount of non-neutralized (net) photospheric electric currents present in active regions. In this talk I will summarize the results of a large statistical study of emerging active regions, which aims to improve our understanding of how some active regions evolve into extremely complex configurations and to advance flare and CME prediction by putting forward better complexity parameterizations. The temporal evolution of non-neutralized electric currents in emerging active regions exhibits a structure that reflects individual incidents of magnetic flux emergence and magnetic polarity interactions. In the most complex regions, those with δ-spots, the net electric current increases 2.6 times faster and reaches more than 3 times higher values in comparison to other regions, while their individual electric current injection events are stronger and more persistent. These results indicate the injection of net electric currents during flux emergence and also due to the incurred photospheric evolution. Furthermore, non neutralized electric currents exhibit strong correlation with flaring index, are potentially good indicators of future flaring activity and they are strongly associated with CME characteristics. In this context I will also present ongoing work for the development of improved flare and CME predictors based on the electric current as well as the prospects of including multi-wavelength ground-based magnetic field observations.
Author(s): Fabiana Ferrente, Carlos Quintero Noda, Francesca Zuccarello, Salvatore Luigi Guglielmino
University of Catania; Instituto de Astrofísica de Canarias; University of Catania; INAF – Catania Astrophysical Observatory
Abstract: The recent exploitation of spectropolarimetric data has significantly enhanced our understanding of the dynamical and magnetic responses of the photospheric and chromospheric layers during the rapid energy release associated with solar flares. In this study, we analyzed high-resolution observations from October 22, 2014, during an X1.6 confined flare, using the Interferometric Bidimensional Spectropolarimeter (IBIS) instrument, which measures the full Stokes parameters for the Fe I 6173 Å and Ca II 8542 Å transitions.
We applied the newly developed Departure Coefficient Aided Stokes Inversion based on Response Functions (DeSIRe) code to deduce the spatial distribution and vertical stratification of atmospheric parameters in the photospheric and chromospheric layers. Our results reveal significant temperature increases and pronounced upflows within the chromospheric flare ribbon, indicating the upward movement of hot material produced by the flare. In contrast, the photosphere shows no significant temperature rise or strong velocities, suggesting that the flare’s impact is primarily confined to the middle and upper layers.
Analysis of the magnetic field vector reveals relatively smooth stratifications in both magnetic field strength and inclination with height. Additionally, we find that the flare ribbon regions exhibit a notable depression in the height of formation (or sensitivity) for the chromospheric line, whereas this effect is not evident for the Fe I transition. These findings confirm that the main impact of flaring activity in the lower atmospheric layers occurs at chromospheric levels.
SWR1.2 Fri 4/11 09:00-10:15, room C2B – Sofia
Author(s): David Afonso Delgado, Rebecca Centeno, Roberto Casini
High Altitude Observatory; High Altitude Observatory; High Altitude Observatory
Abstract: The study of ultraviolet line polarization signals is one of the primary windows to study the magnetism of the upper layers of the chromosphere. The unprecedented results from the two Chromospheric LAyer Spectropolarimeter missions (CLASP2 and CLASP2.1) have demonstrated the suitability of the spectral region around the Mg II h & k resonant doublet to infer the magnetic field configuration in the solar chromosphere. Furthermore, several studies have advocated for the inclusion of the Fe II lines within the 250-270 nm spectral range as an optimal complement to the Mg II h and k spectral window lines for a comprehensive examination of the solar magnetic fields. Currently, the Chromospheric Magnetism Explorer (CMEx) mission is being developed with the purpose of exploiting the full potential of this ultraviolet region of the solar spectrum to quantify the magnetic field vector throughout the solar atmosphere.
Magneto-hydrodynamic (MHD) simulations predict that certain types of solar eruptions require the prior formation of a magnetic flux rope (MFR). The MFR develops from a simpler sheared magnetic arcade (SMA) some time before the eruption occurs. The stratification of the magnetic field from the photosphere to the chromosphere is very different between these two plasma structures. While the simulations predict a strong gradient in the magnetic field in the SMA, we expect an approximately constant magnetic field in the MFR case. In this work, we performed complex radiative transfer calculations in MHD simulations representative of both scenarios to model synthetic observations of the Mg II and Fe II polarization profiles in the 255 – 281 nm spectral window. Analyzing these synthetic observations, we demonstrate that a space mission like CMEx can infer the stratification of the magnetic field in active regions of the solar atmosphere. This approach will allow us to determine the precise process by which an SMA evolves into an MFR, confirming the validity of existing models of solar eruption formation.
Author(s): Clementina Sasso, Christoph Kuckein, Sergio Javier González Manrique, Maurizio Oliviero, Luciano Terranegra, Giuliana Russano, Alberto Paolo Pellizzoni
INAF-Astronomical Observatory of Capodimonte, Napoli, Italy; Instituto de Astrofísica de Canarias (IAC), Tenerife, Spain – Max Planck Institute for Solar System Research (MPS), Göttingen, Germany; Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain – Instituto de Astrofísica de Canarias (IAC), Tenerife, Spain – Institut für Sonnenphysik (KIS), Freiburg, Germany; INAF-Astronomical Observatory of Capodimonte, Napoli, Italy; INAF-Astronomical Observatory of Capodimonte, Napoli, Italy; INAF-Astronomical Observatory of Capodimonte, Napoli, Italy; INAF-Astronomical Observatory of Cagliari, Italy
Abstract: We analyze spectropolarimetric data of solar active filaments collected during the last observational campaigns (2022-2023) performed at the GREGOR telescope in Tenerife. We observed several filaments in the chromospheric He I 10830 Å triplet and the photospheric Si I 10827 Å line, triggered by solar flares. We focus on one observation obtained in September 2022, which, in a preliminary analysis, shows at least three independent magnetic components of the unresolved He lines. Thanks to this behavior, it is possible to attempt to discriminate between different theoretical models describing the magnetic support of these structures in the corona.
We present results from the analysis of the Stokes profiles obtained through inversions, showing maps of the velocity and magnetic field in such a filament, in both the photosphere and the chromosphere. There are also pixels where the He I 10830 Å profiles are seen in emission at the location of the flare.
In addition to these results related to the analysis of this specific case, we will also provide a small statistic on the several eruptive filaments we were able to observe. In order to get some hints on the activity of the active region hosting the filament and predict which one was most probably going to flare, we were observing with the support of the INAF-OACN coelostat equipped with a 0.5 Å FWHM Hα filter, acquiring full-disk images at a 2-second time maximum cadence.
Furthermore, the observations were coordinated with other Italian instruments that are part of the newly formed Space Weather INAF group. The importance of such an observation network will be addressed to improve the understanding of the conditions triggering eruptive filaments, which is of paramount importance to predict and characterize disruptive space weather events.
Author(s): Michiel van Noort, Christoph Kuckein
Max Planck Inst. for solar system research; Max Planck Inst. for solar system research
Abstract: While most of the magnetic activity of the upper solar atmosphere and corona is concentrated in active regions, that vast majority of the solar surface consists of quiet Sun and magnetic network regions. Although the magnetic activity of these parts of the solar surface is much lower than that of active regions, the fraction of the surface covered by them is much larger. The magnetic field in these regions is highly dynamic, and allows magneto-acoustic waves excited by convective motions to carry energy into the chromosphere and the corona. We present an analysis of high spatial, spectral and temporal resolution integral field observations of the quiet Sun in the FeI lines at 6301.5A and 6302.5A, containing several bright points. The spectral properties of these quiet Sun bright points show a persistent high degree of asymmetry, and a time variability on time scales down to only a few seconds. Inversion results cannot reproduce some of these spectra with a simple vertically stratified atmosphere, indicating that quiet Sun bright points experience highly dynamic events resulting in a complex vertical stratification.
Author(s): Gregory Fleishman
Institute for Solar Physics (KIS)
Abstract: Release of free magnetic energy in the solar corona is believed to fuel such transient solar drivers of the space weather as solar flares, eruptions, and jets. Quantitative measurements of the coronal magnetic field strength in the active regions (ARs) and solar flares are required to find out where exactly and at which rate this release takes place. The coronal magnetic field is very difficult to directly measure. The only available methodology capable of providing such measurements employs microwave imaging and spectroscopy of thermal gyroresonant (GR in ARs) or nonthermal gyrosynchrotron (GS in flares) emission from electrons accelerated in flares. Here, we review the magnetic field measurement techniques utilizing microwave observations of GR and GS emission in several ARs and solar flares. We present the record-braking coronal magnetic field in ARs and their association with extreme space weather drivers. In addition, we report the spatial and temporal changes in the coronal magnetic field in the flare volume including flaring loops and the cusp region; all located well below the nominal reconnection X point. The typical decay rate of the magnetic field in large flares is several Gauss per second, which continues at a given location for several minutes until reaches steady-state levels. The measured decrease of the stored magnetic energy is found sufficient to power the solar flare, including the associated eruption, particle acceleration, and plasma heating. We discuss how these novel magnetic measurements can be integrated in 3D modeling of solar phenomena.
Author(s): Alberto Pellizzoni, Sara Mulas, Marco Marongiu, Adriana Marcucci
INAF-Osservatorio Astronomico di Cagliari; INAF-Osservatorio Astronomico di Cagliari; INAF-Osservatorio Astronomico di Cagliari; AM-CNMCA
Abstract: High-frequency radio observations with large single-dish radio telescopes of the INAF network provide solar imaging since 2018 (SunDish project), useful to investigate the vertical structure and physical conditions of the solar chromosphere both for quiet and active regions, during their evolution at different phases of the solar cycle. After early science campaigns, the system is regularly monitoring the Sun to provide: (1) accurate measurement of the brightness temperature of the radio quiet Sun component, that has been poorly explored in the 20-26 GHz range to date, and representing a significant constraint for atmospheric models; (2) characterisation of the flux density, spectral properties and long-term evolution of dynamical features (active regions, coronal holes, loop systems, streamers and the coronal plateau); (3) prediction of powerful flares through the detection of peculiar spectral variations in the active regions, as a valuable forecasting probe for the Space Weather hazard network.
In particular, solar radio mapping in radio K-band (18-26 GHz) can probe the chromospheric magnetic field of the active regions through the detection of gyro-resonance spectral components anticipating flare events. Enhanced AR magnetic fields (up to 1500-2000 Gauss) determine a spectral flattening compared to pure free-free emission due to the addition of a steeper gyro-resonance component.
When this sporadic anomalous AR spectrum is detected, the probability of a strong flare occurrence within 1-2 days is >80%, further rising at >90% also requiring that AR brightness temperature exceeds about 50% the quiet Sun level.
We present several examples of 18-26 GHz radio images showing peculiar AR spectral and polarisation configurations anticipating or following flare events, and through correlation statistics analysis, we discuss the sensitivity and robustness of this flare forecast method and the perspective of coupling it with other multi-messenger Space Weather proxies.
Posters
Posters II Display Thu 7/11 – Fri 8/11, room C1A – Aeminium
Authors in attendance: Thu 7/11 10:15–11:30, 15:15-16:15; Fri 8/11 10:15–11:30
Author(s): Michele Berretti, Marco Stangalini, Gary Verth, Shahin Jafarzadeh, David B. Jess, Francesco Berrilli, Samuel D. T. Grant, Timothy Duckenfield, Viktor Fedun
University of Trento / University of Rome Tor Vergata, Department of Physics; ASI Italian Space Agency; Plasma Dynamics Group, School of Mathematics and Statistics, The University of Sheffield; Max Planck Institute for Solar System Research / Niels Bohr International Academy, Niels Bohr Institute; Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast / Department of Physics and Astronomy, California State University Northridge; University of Rome Tor Vergata, Department of Physics; Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast; Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast; Plasma Dynamics Group, Department of Automatic Control and Systems Engineering, The University of Sheffield
Abstract: It is well known that the dominant frequency of oscillations in the solar photosphere is at ≈3 mHz, which is the result of global resonant modes pertaining to the whole stellar structure. However, analyses of the horizontal motions of nearly 1 million photospheric magnetic elements spanning the entirety of solar cycle 24 has revealed an unexpected dominant frequency ≈5 mHz, i.e., a frequency typically synonymous with the chromosphere. Given the distinctly different physical properties of the magnetic elements examined in our statistical sample, when compared to largely quiescent solar plasma where ≈3 mHz frequencies are omnipresent, we argue that the dominant ≈5 mHz frequency is not caused by the buffeting of magnetic elements, but instead is due to the nature of the underlying oscillatory driver itself. This novel result was obtained by exploiting the unmatched spatial and temporal coverage of magnetograms acquired by the Helioseismic and Magnetic Imager (HMI), onboard NASA’s Solar Dynamics Observatory (SDO). Our findings provide a timely avenue for future exploration to better understand the magnetic connectivity between sub-photospheric, photospheric, and chromospheric layers of the Sun’s dynamic atmosphere.
Author(s): George Cherry, Boris Gudiksen, Adam Finley
Rosseland Centre for Solar Physics, Universititet i Oslo; Rosseland Centre for Solar Physics, Universitetet i Oslo; Département d’Astrophysique du CEA Paris-Saclay
Abstract: The dynamics of the lower solar atmosphere lay the foundation for important high-energy processes that occur in the upper atmosphere, thus influencing the energy and evolution of the solar wind. Although much groundwork has been done to analyse the behaviour of linear and non-linear waves alike, there is still a large gap between reality and theory. The busy and chaotic nature of the lower solar atmosphere, where the plasma beta is close to one, can distort the characteristics of waves through interference, instability, and mode-conversion. Any idealised waves are short lived, if they live at all, and so detecting any kind of recognizable wave activity becomes a challenging task.
The realistic rMHD-solver code, Bifrost, provides self-driving simulations from the upper convection zone to the lower corona at scales similar to and beyond what is capable by modern telescopes. By analysing a small, highly resolved Quiet-sun region, we aim to develop a method that detects signatures for the emergence, conversion and eventual decay of waves across significant atmospheric levels, such as the β = 1 layer, and transition region. Detections of such a kind give insight into the heating and energisation of the solar plasma, contributions to the coronal heating problem, and acceleration of the solar wind.
Author(s): Filip Matković, Roman Brajša, Manuela Temmer, Stephan G. Heinemann, Hans -G. Ludwig, Steven H. Saar, Caius L. Selhorst, Davor Sudar, Ivica Skokić
Hvar Observatory, Faculty of Geodesy, University of Zagreb, Kačićeva 26, 10000 Zagreb, Croatia; Hvar Observatory, Faculty of Geodesy, University of Zagreb, Kačićeva 26, 10000 Zagreb, Croatia; Institute of Physics, University of Graz, Universitätsplatz 5, 8010 Graz, Austria; Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany; Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany; Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; NAT – Núcleo de Astrofísica, Universidade Cruzeiro do Sul/Universidade de São Paulo, R. Galvão Bueno, 868, São Paulo, SP 01506-000, Brazil; Hvar Observatory, Faculty of Geodesy, University of Zagreb, Kačićeva 26, 10000 Zagreb, Croatia; Hvar Observatory, Faculty of Geodesy, University of Zagreb, Kačićeva 26, 10000 Zagreb, Croatia
Abstract: Coronal bright points (CBPs) are a fundamental class of solar activity phenomena. They represent a set of low-corona small-scale loops with an enhanced extreme-ultraviolet (EUV), X-ray, and radio emissions. There are many similarities between CBPs and active regions (ARs), including emission, morphology, magnetic properties, topology, and eruptive phenomena (e.g., flares, coronal mass ejections, and filament eruptions). Thus, studying CBP properties and their evolution is of great importance to understand both small- and large-scale solar activity. We report a first analysis of evolution of four different CBPs captured by Atacama Large Millimeter/submillimeter Array (ALMA) in the interferometric observing mode. We use the high-resolution ALMA interferometric data at 3 mm (Band 3), together with the concurrent EUV observations through multiple passbands obtained by Atmospheric Imaging Assembly (AIA) and magnetograms obtained by Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). Evolution of emission intensity, morphology, and magnetic properties of the four CBPs at different atmospheric layers from the photosphere (SDO/HMI), through the chromosphere (ALMA Band 3 and SDO/AIA 304 Å), and corona (SDO/AIA 94 Å, 131 Å, 171 Å, and 193 Å) is followed. The aim of this study is to find relationships between the different layers of the CBP atmosphere, to see how changes in CBP activity/energetics are communicated between different layers of the CBP structure. Understanding these CBP features and their interaction on a small scale might promote better understanding of AR properties and activity observed on much larger scales.
Author(s): Rayhaneh Sadeghi, Ehsan Tavabi
PNU; PNU
Abstract: The relationship between chromospheric height (CH) and lag times in Doppler velocity (DV) has been extensively researched in the field of solar physics. Researchers have observed that the motion of the chromosphere is nearly synchronized across a wide range of heights, with the infrared brightness lagging behind the DV measurements. This lag is attributed to the nonadiabatic response of the chromospheric to compression. Further investigations have revealed that regions of high amplitude oscillations are often confined to specific areas on the solar surface, and these oscillations are typically associated with narrow chromospheric structures. It has been suggested that mechanical energy from these oscillations may potentially escape into the corona, leading to various dynamic phenomena observed in the outer layers of the Sun’s atmosphere (Sadeghi & Tavabi, 2022b).
The main focus was placed on investigating the relationship between CH and lag times in DV. To accomplish this, the polar spectra obtained from the Interface Region Imaging Spectrograph (IRIS) were utilized (Sadeghi & Tavabi, 2022a). Specifically, data from the Mg II k line core were extracted to calculate the DV. In the analysis, several Doppler velocities were explored to gain a comprehensive understanding of the observed phenomena. The lag times in relation to two well-known periods of oscillation, namely 180 seconds and 300 seconds, were specifically observed and analyzed. By examining the relationship between CH and lag times in DV for these specific oscillation periods, the aim was to uncover any potential correlations or patterns that could provide insights into the underlying physical processes occurring in the chromosphere. These findings contribute to the understanding of the dynamic behavior of the chromosphere and provide valuable information regarding the relationship between CH and lag times in DV measurements (Sadeghi & Tavabi, 2022a; Sadeghi & Tavabi, 2024).
The current understanding of solar physics is significantly advanced by our investigation, as it sheds light on the intricate relationship between CH, DV, and oscillation periods. It is revealed by our study that clear and strong lag times related to CH are exhibited by the 300-second oscillations (Sadeghi & Tavabi, 2022a). However, beyond a certain point in the chromosphere, the 180-second oscillations become more prominent and exhibit stronger amplitudes compared to the 300-second oscillations. Valuable insights into the nature of intensity oscillations and their variation with height in the chromosphere are provided by these findings. The demonstration of the transition from dominant 300-second oscillations to stronger 180-second oscillations at a specific height contributes to the understanding of the energy dynamics within the chromosphere. The hypothesis that mechanical energy from these oscillations may escape into the corona, contributing to dynamic phenomena observed in the Sun’s outer atmosphere, is further supported by the localized energy deposition and release within narrow structures. The importance of considering both oscillation periods and their variation with height is highlighted by our conclusions when analyzing the dynamic behavior of the chromosphere. These findings carry implications for future studies that aim to unravel the mechanisms driving energy transport and dynamics in the atmosphere (Tavabi & Sadeghi, a, b,c,2024).
Author(s): Slava Bourgeois, Simone Chierichini, Szabolcs Soós, Robertus Erdélyi, Jiajia Liu, Marianna Korsós, Ricardo Gafeira, Teresa Barata
University of Coimbra, University of Sheffield; University of Rome Tor Vergata, University of Sheffield; Eötvös Loránd University Budapest, Hungarian Solar Physics Foundation; University of Sheffield, Eötvös Loránd University Budapest, Hungarian Solar Physics Foundation; University of Science and Technology of China; University of Sheffield, Eötvös Loránd University Budapest; University of Coimbra; University of Coimbra
Abstract: Investigating coronal structures, such as prominences, solar jets, coronal loops, etc. is essential for understanding their characteristics and how they reveal the magnetic field dynamics within the corona, potentially leading to space weather events. Thus, our goal is to detect these coronal structures and conduct a statistical analysis of their properties, focusing specifically on their density and intensity variations across time, latitude, and longitude throughout Solar Cycle (SC) 24.
In this study, we identify coronal off-limb structures using mathematical morphology algorithms. The original data acquired by the Atmospheric Imaging Assembly (AIA) instrument in the 304 Å channel aboard the Solar Dynamics Observatory (SDO), was pre-processed by Liu et al. (2023, ApJS 266 17) to highlight coronal features. Spanning nearly an entire solar cycle from June 2010 to December 2021 with a 3-hour cadence, the dataset was refined by eliminating noisy or misaligned images, resulting in 32,985 retained images and uncovering a total of 877,843 coronal off-limb structures.
With this extensive dataset, we observed different trends in the distribution of coronal structures between high intensity and lower intensity (corrections were made for the CCD degradation’s impact on the AIA instrument). Specifically, we found that only high-intensity structures follow distinctly the butterfly diagram, whereas lower-intensity structures are more prevalent around the poles and during the declining phase of SC 24. The latitudinal distribution of coronal off-limb structures also shows a North-South asymmetry that varies over years and months. This asymmetry is pronounced in the “rush-to-the-poles” phenomenon, where high-latitude coronal structures from both hemispheres migrate towards the poles before the polar field reversal near the solar cycle maximum. Furthermore, the longitudinal distribution of coronal off-limb structures reveals the presence of active longitudes—longitudinal zones characterized by increased activity. Our analysis also suggests that the positioning of these active longitudes is influenced by latitude and differential rotation.
Author(s): Mariarita Murabito, Marco Stangalini, Martin Laming, Deborah Baker
INAF-OAR, SSDC; ASI; NRL; UCL
Abstract: The chemical properties of the solar plasma remain unchanged as it travels unadulterated along open fields from the chromosphere/corona into the heliosphere and can be used as a tracer for the sources of the solar wind.
The solar corona should have the same chemical composition as the solar photosphere. However, It has been found that in the corona, some solar regions exhibit a different chemical composition compared to the lower atmosphere, known as the FIP effect.
For the first time, using spectropolarimetric data from the chromosphere we were able to detect wave reflection, linked with a strong coronal FIP bias, as predicted by the theory.
Unveiling solar wave characteristics from polarimetric measurements still represents a challenge. This detection has been accomplished using phase lag analysis on ground-based chromospheric Stokes V parameters. Using the same theoretical model proposed in 2004 and modified over these 20 years, we found good agreement with the observed results.
Author(s): Valentina Zharkva
Northumbria University, MPEE, NE1 8ST UK
Abstract: The eigen vectors of magnetic oscillations obtained with Principal Component Analysis from full disk synoptic maps of solar background magnetic field (SBMF) from the Wilcox Solar Observatory are shown to come in pairs assigned to magnetic waves produced by dipole, quadruple, sextuple and octuple magnetic sources. The first pair is linked to dipole magnetic waves with their summary curve revealing a reasonable fit to the averaged sunspot numbers in cycles 21-24. This verifies the previous results and confirms the summary curve as additional proxy of solar activity decreasing towards grand solar minimum in cycles 25-27, or grand solar minimum. There is also a noticeable asymmetry in latitudinal distributions of these PCs showing an increased activity in northern hemisphere in odd cycles and in south- ern hemisphere in even ones similar to the N-S asymmetries observed in sunspots. The second pair of PCs linked to quadruple magnetic sources, has 50% smaller amplitudes than the first, while their summary curve correlate closely with SXR fluxes in solar flares. Flare occurrences are also linked to variations of the next two pairs of eigen vectors, quadruple and sextuple components, revealing additional periodicity of about 2.75-3.1 years similar to observed oscillations in flares. Strong latitudinal asymmetries in quadruple and sextuple components are correlating with the N-S asymmetries of flare occurrences skewed to southern hemisphere in even cycles and to northern hemisphere in odd ones. PCA of solar magnetic field raises perspectives for simultaneous prediction of general and flaring solar activity.
Author(s): Ilaria Ermolli, FAbrizio Giorgi, Mariarita Murabito
INAF- OAR; INAF-OAR; INAF-OAR, SSDC
Abstract: The IBIS data Archive, aka IBIS-A, stores data acquired with the Interferometric BIdimensional Spectropolarimeter (IBIS), which was operated at the Dunn Solar Telescope of the US National Solar Observatory from June 2003 to June 2019. The instrument provided series of high-resolution narrowband spectropolarimetric imaging observations of the photosphere and chromosphere in the range 5800-8600 Å and co-temporal broadband observations in the same spectral range and with the same field of view as for the polarimetric data.
IBIS-A currently consists of 30 TB of data taken with IBIS during 28 observing campaigns performed in 2008 and from 2012 to 2019 on 159 days. It includes raw and calibrated observations, as well as science-ready data. Furthermore, it also contains links to observations complementary to the IBIS data, such as co-temporal high-resolution observations of the solar atmosphere available from the instruments onboard the Hinode and IRIS satellites, and full-disk multi-band images from INAF solar telescopes.
IBIS-A has been part of the virtual access program of H2020 SOLARNET. We present the data currently stored in IBIS-A, and theinterface utilized to explore them for their scientific exploitation. We also describe the planned IBIS-A upgrade in light of its utilization for the archiving of new data that will be acquired with IBIS 2.0. We also summarize information about the accesses to IBIS-A since the start of the H2020 SOLARNET project.
Author(s): Aneta Wisniewska
Astronomical Institute Slovak Academy of Science
Abstract: Active regions play a significant role in solar events, including solar flares and coronal mass ejections (CME). This work aims to scrutinise, in a more systematic manner, the presence of long-period oscillations in an active region within the lower solar atmosphere, both before and after the flare event. To investigate those long oscillations prior to a series of C-class flares we were using a 3D-wavelet analysis. We compared the findings with the 3-8 minute oscillations and shorter, that were previously studied in the different active region.
The objective of this work is to identify various periods of magnetic helicity and detect the plasma oscillation with long periods in the lower solar atmosphere. This case study suggest that varying oscillation properties of plasma in a solar active region are linked to the magnetic helicity oscillation and could be indicative of future flaring activity.
Author(s): Salvo Guglielmino, Fabiana Ferrente, Serena Lezzi, Mariarita Murabito, Paolo Romano, Vincenzo Andretta, Daniele Spadaro, Francesca Zuccarello, Ilaria Ermolli
INAF – Catania Astrophysical Observatory; University of Catania; University of Naples “Federico II”; INAF – Rome Astronomical Observatory; INAF – Catania Astrophysical Observatory; INAF – Capodimonte Astronomical Observatory; INAF – Catania Astrophysical Observatory; University of Catania; INAF – Rome Astronomical Observatory
Abstract: We present observations of small- to intermediate-scale energy release events occurring in the solar atmosphere, acquired during a 10-day observing campaign conducted in August 2023 at GREGOR telescope (1.5 m diameter, located on Tenerife island), using the High-resolution Fast Imager (HiFI) and GREGOR Infrared Spectrograph (GRIS) in spectropolarimetric mode. This campaign was also coordinated with IRIS and Hinode observations. IRIS carried out observations during the early morning hours (local time at GREGOR), acquiring medium dense rasters (0″.32 slit) and simultaneous slit-jaw images. Continuous coverage by SDO data complement these observations.
Data analysis has been limited to specific dates so far. On August 5th, IRIS captured a footpoint of a C-class flare within the leading sunspot of the active region. The following day, August 6th, IRIS detected a small-scale reconnection event (consisting of a UV burst and surge ejection) within the moat region surrounding the leading sunspot.
We have conducted an initial examination of the evolution of these events, using photospheric and chromospheric spectropolarimetric GRIS data, which have been investigated using the HAZEL inversion code to derive the magnetic configuration in the lower atmosphere.
Our analysis suggests that the interplay between emerging flux and other flux systems triggers small- and intermediate-scale energetic events. These can serve as a showcase for models of large-scale eruptive events, using a synergistic approach to assess their ultimate effect on Space Weather.
Author(s): Ruoyu Wang, David Fouhey, Richard Higgins, Spiro Antiochos, Graham Barnes, J. Todd Hoeksema, KD Leka, Yang Liu, Peter W. Schuck, Tamas Gombosi
New York University; New York University; University of Michigan; University of Michigan; NorthWest Research Associates; Stanford University; NorthWest Research Associates; Stanford University; NASA / GSFC; University of Michigan
Abstract: The magnetic field of the Sun’s photosphere is a primary information source for understanding and predicting everything from the solar cycle to heliospheric-impacting energetic events. With the long-duration data acquisition of two very different space-borne facilities, we have endeavored to create a new dataset that uses the best of each, based on a deep-learning model called SuperSynthia (Wang+2024, Fouhey+2023, Higgins+2022, 2021).
Specifically, the Solar Optical Telescope – Spectro-Polarimeter (SOT-SP) instrument onboard the JAXA/US/UK/ESA Hinode mission and its associated analysis pipeline provide highly accurate information about the vector magnetic field of the Sun’s photosphere. SOT-SP’s accuracy, however, comes at the price of a very limited field of view and long acquisition times. Complementing the 18-year Hinode/SP dataset is the 14-year run of the Helioseismic and Magnetic Imager on the Solar Dynamics Observatory (SDO/HMI), which provides fast full-disk acquisition at the cost of some spatial resolution, spectral sampling, and presents artifacts that can hinder analysis and modeling.
We use deep learning to obtain full-solar-disk vector magnetograms at the cadence and spatial sampling of SDO/HMI with characteristics closer to Hinode/SOT-SP. As input, our SuperSynthIA model accepts SDO/HMI Stokes images [I, Q, U, V] sampled at the 6 pass-bands across the 617.3nm FeI line (hmi.S_720 series data); as output, SuperSynthIA is trained to produce Hinode/SOT-SP-like vector magnetograms, including the Level 2.1 disambiguated data that provide heliographic components (the “physical” Br, Bphi, Btheta). We train and evaluate SuperSynthIA on a dataset of over 13.4K co-aligned scans spanning all latitudes. The resulting SuperSynthIA data products are accurate across the full disk, including the poles.
Key developments for both the model and its evaluation were crucial for success. Alignment between the datasets was critical (Fouhey+2023), and required two algorithms, one specifically adapted for polar Hinode/SP targets. Vector magnetograms are angle-based data, and in low-signal areas deep networks can impart a bias and a tendency to predict toward most-likely values; we mitigate both problems using a procedure akin to dithering in signal processing. Most importantly, we subjected the output to a battery of quantitative evaluations based on the requirement of data use-ability for physics-based investigations, including temporal consistency over hours, days, and years.
SuperSynthIA produces disambiguated heliographic magnetic fields and their vector direction directly from the Stokes image data, effectively performing a spectropolarimetric inversion and global disambiguation simultaneously. Due to the high quality of SOT-SP data and the learning algorithm used, SuperSynthIA shows a substantial reduction in key artifacts compared to the HMI pipeline. Specifically, we find large reductions in short-term temporal inconsistencies of the magnetic vector directions, and a strong reduction in a viewing-angle artifact in low-signal regions that limits data assimilation. SuperSynthia-produced data are intended to be used by the broad research community (details in Wang+2024 and SolarNews).
This research is enabled by from NASA/LWS-SC 80NSSC22K0892, NASA contract NAS5-02139 (HMI), Lockheed- Martin Space Systems contract #4103056734 for Solar-B FPP Phase E, NASA award 80NSSC22K064, and the University of Michigan CSE Division and Advanced Research Computing for HPC support.
Author(s): Djordje Mijovic, Ivan Milic, Gaojian Liu, Rebecca Centeno, Xudong Sun
Faculty of Mathematics, University of Belgrade; Institute for Solar Physics, Freiburg, Germany; Institute for Solar Physics, Freiburg, German; High Altitude Observatory, Boulder, USA; University of Hawai’i, USA
Abstract: The tension between the in-situ measurements of the magnetic field in the heliosphere and the field extrapolated from photospheric measurements has been referred to as the “Open flux problem”. A possible cause of the open flux problem is an inaccurate estimation of the photospheric magnetic field vector. In this contribution, we explore systematic errors in the magnetic field measurement caused by the finite angular resolution of our telescopes. We calculate synthetic observables (i.e. Stokes spectra) from the state-of-the-art 3D models of the solar atmosphere, apply instrumental PSF, and then use an inversion code to retrieve the magnetic field. By comparing the inferred field with the original one, we can assess the importance of the instrumental effects. We conclude that telescopes smaller than 1m underestimate the open flux in the quiet Sun at the disk center. We also discuss different observing geometries and active region cases and compare in more detail the differences in statistical properties between the original and inferred fields. Our results point toward the necessity of using high-resolution observations and spatially-coupled inversion techniques.
Author(s): Giulia M. Ronca, Galina Chikunova, Karin Dissauer, Tatiana Podladchikova, Astrid M. Veronig
Politecnico di Milano, Milano, Italy; [1] University of Zagreb, Faculty of Geodesy, Hvar Observatory, Croatia [2] Skolkovo Institute of Science and Technology, Mosсow Russia; NorthWest Research Associates, Boulder, CO, USA; Skolkovo Institute of Science and Technology, Mosсow Russia; [1] University of Graz, Institute of Physics, Graz, Austria [2] University of Graz, Kanzelhöhe Observatory for Solar and Environmental Research, Austria
Abstract: Coronal dimmings are regions of reduced emission in the lower corona, observed in the wake of CMEs, and therefore represent the footprints of these eruptions. Using SDO/AIA and STEREO/EUVI observations, we study the long-term evolution of coronal dimmings and their recovery to enhance our understanding of the replenishment and dynamics of the corona after large-scale eruptions. We propose two approaches to better understand the ongoing dynamics: analyzing the total dimming area and brightness within a fixed mask and studying the behavior of small subregions of 3×3 pixels in the dimming area to compare recovery across different parts of the dimming. We present four case studies (September 6, 2011; March 7, 2012; June 14, 2012; and March 8, 2019), where coronal dimmings are associated with a flare/CME eruption. Three of the four cases show complete recovery within 24 hours. The primary mechanism for recovery appears to be the expansion of the coronal loops into the dimming region. The recovery of brightness follows a two-step trend, with an initial steeper and faster phase followed by a slower one. Additionally, some portions of the dimming, which may be core dimmings, remain at the end of the analysis period and do not recover within three days, whereas the peripheral regions (secondary dimmings) show full recovery. The two proposed approaches have been tested and validated in this study and appear promising for analyzing the recovery phase of coronal dimmings. The fixed mask method effectively minimizes the contributions of artifacts and derotation, allowing us to track the full development of the dimming regions throughout the recovery process. Furthermore, the pixel box approach may support existing studies and help investigate different behaviors between core and secondary dimmings and the complexity of solar eruptions.
Author(s): Markus Roth, Hans-Peter Doerr, Sebastian Podleska, Hemanth Pruthvi, Michael Sigwarth
Thüringer Landessternwarte Tautenburg
Abstract: Real-time information about the variation of the surface velocity, magnetic field, and intensity in different layers of the solar atmosphere is an essential input to fundamental solar physics and space weather prediction. There is consensus that a worldwide distributed network of small, dedicated telescopes that observe the entire solar disk is needed to obtain these data continuously.
This contribution will report on the current status of designing the Solar Physics Research Integrated Network Group (SPRING). The key scientific products of this facility will be arc-second resolution images of the Sun in various wavelengths, synoptic vector magnetic fields, synoptic surface velocity fields with high time cadence, and observations of transient events such as flares. As a development platform towards SPRING, we present the Tautenburg Solar Laboraty (TauSoL), which is a new installation in Germany.
Author(s): Neal Hurlburt, Clem Tillier, Georgios Chintzoglou
Lockheed Martin ATC; Lockheed Martin ATC; Lockheed Martin ATC
Abstract: The emergence of ultra compact and inexpensive magnetographs, such as the Imaging Photonic Spectropolarimeter for Observing the Sun (IPSOS), offers the possibility of re-imagining how they might be used and distributed. In this talk, we review the current and expected future state of the IPSOS instrument and discuss its role in measuring the full vector field of the Sun at unprecedented accuracy.
The resulting observations could finally resolve questions on how the solar magnetic field is generated by the solar dynamo and the major space weather it drives: from the 22-year magnetic cycle that modulates total solar irradiance, to global coronal magnetic fields that structure the solar wind, to magnetic eruptions from sunspot active regions that power coronal mass ejections triggering major geomagnetic storms.
Author(s): Eka Gurgenashvili
Ilia State University
Abstract: This study investigates the influence of mid-range periodicities in solar activity indices on Total Solar Irradiance during solar cycles 23 and 24, focusing on Rieger-type periodicities. Utilizing SATIRE-S and SOHO/VIRGO data, we conducted a wavelet analysis of TSI, identifying significant periodic variations at 180 and 115 days during cycle 23, and at 170 and 145 days during cycle 24. We compared these findings with sunspot and faculae data, revealing that certain periods observed in these solar features do not manifest in TSI, likely due to the cancellation effect of simultaneous brightening and darkening. The presence of Rieger-type periodicity is attributed to magneto-Rossby waves in the solar dynamo layer, where the solar magnetic field is generated. The wave dispersion relation corresponding to the observed periods enables us to estimate the dynamo magnetic field strength at 10-15 kG. This method offers a promising approach for estimating the magnetic field strength in the dynamo layers of solar-like stars using light curves from space missions, providing insights into stellar magnetic activity.
Author(s): Iulia Chifu
Institute for Astrophysics and Geophysics, University of Goettingen
Abstract: The magnetic field is the key to understanding the Sun’s most important manifestations because it drives most solar structures such as sunspots, granulation, prominences, flares, coronal loops, coronal mass ejections (CMEs), magnetic cloud and the strongest solar eruptions.
The Solar magnetic field is routinely observed in the photosphere. To obtain information on the magnetic field at higher levels of the atmosphere one needs to extrapolate itallowing to estimate the magnetic field from the low to high corona like the NLFFF.
Many of the NLFFF methods use as input the photospheric vector magnetic field. For the global extrapolations applied to the full Sun, there is higher-temporal cadence of the radial magnetic field than for the vector-magnetic field. To be able to have a model of the full Sun magnetic field performed with NLFFF, we modified the NLFFF-optimization method (in spherical geometry) to accept only the radial component of the magnetic field. We apply the new NLFFF method to the HMI synchronic maps during PSP encounter 19.
Author(s): Iulia Chifu, K.D. Leka, Xiaoshuai Zhu, Ruoyu Wang, David Fouhey
University of Goettingen; NorthWest Research Associates; National Space Science Center, Chinese Academy of Sciences; New York University; New York University
Abstract: In May 2024, NOAA AR 13664 was the source of intensive space weather events, including the largest flare of the current solar cycle. We study here the inferred coronal magnetic fields of this active region using nonlinear force free field and magnetohydrostatic methods. Specifically, we have applied these models to both HARP HMI data and to SuperSynthIA HARP-based cutouts during 7th of May for AR13664 (HARP 11149). SuperSynthIA is a machine learning-based method that produces vector magnetograms from HMI Stokes vector data (see SuperSynthIA poster by Wang et al. in SWR1). As this is an early application of SuperSynthIA to solar physics research, the first goal is to quantify the differences in results between extrapolations from these two different boundary datasets, with a focus on the evolution of the AR 13664 shortly before it started to produce the strong X-class flares.
Author(s): D. Shukhobodskaia, D.-C. Talpeanu, L. Rodriguez, E. D’Huys, M. Mierla, B. D. Dorsch, M. West, D. Berghmans, A. Zhukov, C. Verbeeck
Solar-Terrestrial Centre of Excellence – SIDC, Royal Observatory of Belgium, Brussels, Belgium; Solar-Terrestrial Centre of Excellence – SIDC, Royal Observatory of Belgium, Brussels, Belgium; Solar-Terrestrial Centre of Excellence – SIDC, Royal Observatory of Belgium, Brussels, Belgium; Solar-Terrestrial Centre of Excellence – SIDC, Royal Observatory of Belgium, Brussels, Belgium; Solar-Terrestrial Centre of Excellence – SIDC, Royal Observatory of Belgium, Brussels, Belgium ; Institute of Geodynamics of the Romanian Academy, Bucharest, Romania; Solar-Terrestrial Centre of Excellence – SIDC, Royal Observatory of Belgium, Brussels, Belgium; KU Leuven, Leuven, Belgium; Southwest Research Institute, Boulder, USA; Solar-Terrestrial Centre of Excellence – SIDC, Royal Observatory of Belgium, Brussels, Belgium; Solar-Terrestrial Centre of Excellence – SIDC, Royal Observatory of Belgium, Brussels, Belgium; Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow, Russia; Solar-Terrestrial Centre of Excellence – SIDC, Royal Observatory of Belgium, Brussels, Belgium
Abstract: This study deals with prominence eruptions captured by the Extreme Ultraviolet Imager/Full Sun Imager (EUI/FSI) on board Solar Orbiter. We analyse a selection of 230 eruptions from the detailed catalogue, focusing on events where prominences reach projected heights beyond 2 solar radii.
The large field of view (up to fourteen solar radii) allows FSI to observe solar eruptions from the solar disc up to heights never before observed in EUV passbands. This makes the instrument uniquely suited for tracing the early phases of eruptions through the middle corona.
The large set of investigated events offers a wide perspective on the inherent variability within these phenomena. This ongoing statistical analysis aims at uncovering the various properties of these eruptions, such as speed and deflection, morphological features, 3D characteristics, and their interaction with neighbouring magnetic field structures. We present here the status of this statistical study with an overview of the observed prominence eruptions and their properties.