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Spatially-resolved X-ray observations are the key to understanding electron acceleration in solar flares. Currently, the underlying processes that efficiently energize solar flare particles are poorly constrained. Abundant flare…

Solar and Stellar Astrophysics · Physics 2026-03-09 Morgan Stores , Natasha Jeffrey , Ewan Dickson , James McLaughlin , Eduard Kontar

Until now, how the magnetic fields in M/X-class flaring active regions (ARs) differ from C-class flaring ARs remains unclear. Here, we calculate the key magnetic field parameters within the area of high photospheric free energy density (HED…

Solar and Stellar Astrophysics · Physics 2024-03-01 Ting Li , Yanfang Zheng , Xuefeng Li , Yijun Hou , Xuebao Li , Yining Zhang , Anqin Chen

Context. Velocity or intensity swirls have now been shown to be widely present throughout the photosphere and chromosphere. It has been suggested that these events could contribute to the heating of the upper solar atmosphere, via exciting…

Solar and Stellar Astrophysics · Physics 2019-12-11 Jiajia Liu , Mats Carlsson , Chris J Nelson , Robert Erdélyi

Violent solar flares and coronal mass ejections (CMEs) are magnetic phenomena. However, how magnetic fields reconnecting in the flare differ from non-flaring magnetic fields remains unclear owing to the lack of studies of the flare magnetic…

Solar and Stellar Astrophysics · Physics 2022-02-23 Maria D. Kazachenko , Benjamin J. Lynch , Antonia Savcheva , Xudong Sun , Brian T. Welsch

Long-lived rotational and meridional flows are important ingredients of the solar cycle. Magnetic field images have typically been used to measure these flows on the solar surface by cross-correlating thin longitudinal strips or square…

Solar and Stellar Astrophysics · Physics 2017-02-15 Derek A. Lamb

Abrupt and permanent changes of photospheric magnetic fields have been observed during solar flares. The changes seem to be linked to the reconfiguration of magnetic fields, but their origin is still unclear. We carried out a statistical…

Solar and Stellar Astrophysics · Physics 2018-01-17 J. S. Castellanos Durán , L. Kleint , B. Calvo-Mozo

The light curves of solar-type stars present both periodic fluctuation and flare spikes. The gradual periodic fluctuation is interpreted as the rotational modulation of magnetic features on the stellar surface and is used to deduce magnetic…

Solar and Stellar Astrophysics · Physics 2018-05-15 Han He , Huaning Wang , Mei Zhang , Ahmad Mehrabi , Yan Yan , Duo Yun

We used magnetograms acquired with the {\it Helioseismic and Magnetic Imager} (HMI) on board the {\it Solar Dynamics Observatory} (SDO) to calculate and analyze spatial correlation functions and the multi-fractal spectra in solar active…

Solar and Stellar Astrophysics · Physics 2024-04-11 Valentina Abramenko , Regina Suleymanova

The energy released during solar flares is believed to be stored in non-potential magnetic fields associated with electric currents flowing in the corona. While no measurements of coronal electric currents are presently available, maps of…

Solar and Stellar Astrophysics · Physics 2015-08-19 Sophie Musset , Nicole Vilmer , Véronique Bommier

Solar active regions (ARs) are thought to be formed by magnetic fields from the convection zone. Our flux emergence simulations revealed that a strong horizontal divergent flow (HDF) of unmagnetized plasma appears at the photosphere before…

Solar and Stellar Astrophysics · Physics 2015-06-22 Shin Toriumi , Keiji Hayashi , Takaaki Yokoyama

The power spectra of the fluctuation noise of the solar active region (AR) areas and magnetic fluxes sequentially observed in time contain information about their geometrical features and the related fundamental physical processes. These…

Solar and Stellar Astrophysics · Physics 2024-03-14 G. Dumbadze , B. M. Shergelashvili , M. L. Khodachenko , S. Poedts

Within the framework of a two-fluid description possible pathways for the generation of fast flows (dynamical as well as steady) in the lower solar atmosphere is established. It is shown that a primary plasma flow (locally sub-Alfv\'enic)…

Spectra of the cellular photospheric flows are determined from full-disk Doppler velocity observations acquired by the Helioseismic and Magnetic Imager (HMI) instrument on the Solar Dynamics Observatory (SDO) spacecraft. Three different…

Solar and Stellar Astrophysics · Physics 2015-10-01 David H. Hathaway , Thibaud Teil , Aimee A. Norton , Irina Kitiashvili

We use high spatial resolution observations and numerical simulations to study the velocity distribution of solar photospheric magnetic bright points. The observations were obtained with the Rapid Oscillations in the Solar Atmosphere…

Aims: Changes of the magnetic field and the line-of-sight velocities in the photosphere are being reported for an M-class flare that originated at a $\delta$-spot belonging to active region NOAA 11865. Methods: High-resolution ground-based…

We present the result of comparison between magnetic field parameters and the intensity of X-ray emission for solar microflares with Geosynchronous Operational Environmental Satellites (GOES) classes from A0.02 to B5.1. For our study, we…

Solar and Stellar Astrophysics · Physics 2017-08-30 A. S. Kirichenko , S. A. Bogachev

We present a database of 3137 solar flare ribbon events corresponding to every flare of GOES class C1.0 and greater within 45 degrees from the central meridian, from April 2010 until April 2016, observed by the \emph{Solar Dynamics…

Solar and Stellar Astrophysics · Physics 2017-08-23 Maria D. Kazachenko , Benjamin J. Lynch , Brian T. Welsch , Xudong Sun

Photospheric vortex flows are thought to play a key role in the evolution of magnetic fields. Recent studies show that these swirling motions are ubiquitous in the solar surface convection and occur in a wide range of temporal and spatial…

Solar and Stellar Astrophysics · Physics 2018-03-07 Iker S. Requerey , Basilio Ruiz Cobo , Milan Gošić , Luis R. Bellot Rubio

The magnetic non-potentiality is important for understanding flares and other solar activities in active regions (ARs). Five non-potential parameters, i.e., electric current, current helicity, source field, photospheric free energy, and…

Solar and Stellar Astrophysics · Physics 2015-06-11 Qiao Song , Jun Zhang , Shuhong Yang , Yang Liu

Temporal and spectral characteristics of X-ray emission from 60 flares of intensity $\ge$C class observed by Solar X-ray Spectrometer (SOXS) during 2003-2011 are presented. We analyse the X-ray emission observed in four and three energy…

Solar and Stellar Astrophysics · Physics 2018-10-17 Veena Choithani , Rajmal Jain , Arun Kumar Awasthi , Geetanjali Singh , Sneha Chaudhari , Som Kumar Sharma