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Sunspots or active regions (ARs) with a delta-magnetic configuration are known to be associated with strong eruptions such as flares and mass ejections. This article investigates the relationship between delta-ARs and flares over the course…

Solar and Stellar Astrophysics · Physics 2025-10-28 Rohan E. Louis

The aim of the present investigation is to study the spatio-temporal distribution of precursor flares during the 24-hour interval preceding M- and X-class major flares and the evolution of follower flares. Information on associated…

Solar and Stellar Astrophysics · Physics 2016-10-18 N. Gyenge , I. Ballai , T. Baranyi

Sunquakes are helioseismic power enhancements initiated by solar flares, but not all flares generate sunquakes. It is curious why some flares cause sunquakes while others do not. Here we propose a hypothesis to explain the disproportionate…

Solar and Stellar Astrophysics · Physics 2021-03-16 Ruizhu Chen , Junwei Zhao

Solar flares commonly have a hot onset precursor event" (HOPE), detectable from soft X-ray observations. Detecting this requires subtraction of pre-flare fluxes from the non-flaring Sun prior to the event, fitting an isothermal emission…

Solar and Stellar Astrophysics · Physics 2024-07-08 Hugh S. Hudson

There are relatively few observations of UV emission during the impulsive phases of solar flares, so the nature of that emission is poorly known. Photons produced by solar flares can resonantly scatter off atoms and ions in the corona.…

Solar and Stellar Astrophysics · Physics 2015-05-28 H. Johnson , J. C. Raymond , N. A. Murphy , S. Giordano , Y. -K. Ko , A. Ciaravella , R. Suleiman

The spot evolution on the Sun and solar-type stars is important for understanding the nature of consequential flaring activity. This study statistically investigates the variance of flare occurrence rate through the time evolution of spots…

Solar and Stellar Astrophysics · Physics 2025-05-23 Takato Tokuno , Kosuke Namekata , Hiroyuki Maehara , Shin Toriumi

We study flare processes in the lower solar atmosphere using observational data for a M1-class flare of June 12, 2014, obtained by New Solar Telescope (NST/BBSO) and Helioseismic Magnetic Imager (HMI/SDO). The main goal is to understand…

Solar and Stellar Astrophysics · Physics 2016-04-20 I. N. Sharykin , V. M. Sadykov , A. G. Kosovichev , S. Vargas-Dominguez , I. V. Zimovets

We report multi-wavelength observations of four solar flares on 2014 July 07. We firstly select these flares according to the soft X-ray (SXR) and extreme ultraviolet (EUV) emissions recorded by the Extreme Ultraviolet Variability…

Solar and Stellar Astrophysics · Physics 2021-05-05 Dong Li , Alexander Warmuth , Lei Lu , Zongjun Ning

Solar flares are large-scale releases of energy in the solar atmosphere, which are characterised by rapid changes in the hydrodynamic properties of plasma from the photosphere to the corona. Solar physicists have typically attempted to…

Solar and Stellar Astrophysics · Physics 2012-06-26 S. Adamakis , C. L. Raftery , R. W. Walsh , P. T. Gallagher

Superflares on solar-type stars has been a rapidly developing field ever since the launch of $\it Kepler$. Over the years, there have been several studies investigating the statistics of these explosive events. In this study, we present a…

Solar and Stellar Astrophysics · Physics 2020-04-22 Lauren Doyle , Gavin Ramsay , J. Gerard Doyle

Stellar flares cannot be spatially resolved, which complicates ascertaining the physical processes behind particular spectral signatures. Due to their proximity to Earth, solar flares can serve as a stepping stone for understanding their…

We present a study of multi-wavelength observations, of a C 2.3 solar flare in Active Region NOAA 12353, observed on 2015 May 23, which reveal new properties of acoustic waves in the flaring region. The space-, and ground-based data…

Solar and Stellar Astrophysics · Physics 2022-03-07 A. Wisniewska , E. Chmielewska , K. Radziszewski , M. Roth , J. Staiger

This article discusses statistical models for solar flare interval distribution in individual active regions. We analyzed solar flare data in 55 active regions that are listed in the GOES soft X-ray flare catalog. We discuss some problems…

Astrophysics · Physics 2009-11-13 Yuki Kubo

Three phases are typically observed during solar flares: the preflare, impulsive, and decay phases. During the impulsive phase, it is believed that the electrons and other particles are accelerated after the stored energy in the magnetic…

Solar and Stellar Astrophysics · Physics 2016-02-15 W. G. Fajardo-Mendieta , J. C. Martínez-Oliveros , J. D. Alvarado-Gómez , B. Calvo-Mozo

Solar flares are 3D phenomenon but modelling a flare in 3D, including many of the important processes in the chromosphere, is a computational challenge. Accurately modelling the chromosphere is important, even if the transition region and…

Solar and Stellar Astrophysics · Physics 2020-09-02 Graham S. Kerr , Joel C. Allred , Vanessa Polito

Quasi-periodic pulsations (QPPs) are a common feature of solar flares, but previously there has been a lack of observational evidence to support any of the theoretical models that might explain the origin of QPPs. We aimed to determine if…

Solar and Stellar Astrophysics · Physics 2019-04-17 C. E. Pugh , A. -M. Broomhall , V. M. Nakariakov

Magnetic reconnection is believed to be the dominant energy release mechanism in solar flares. The standard flare model predicts both downward and upward outflow plasmas with speeds close to the coronal Alfv\'{e}n speed. Yet, spectroscopic…

Solar and Stellar Astrophysics · Physics 2014-12-02 Hui Tian , Gang Li , Katharine K. Reeves , John C. Raymond , Fan Guo , Wei Liu , Bin Chen , Nicholas A. Murphy

During solar flares, a considerable portion of the flare atmosphere becomes heated; however, the energy deposition process is still unclear, especially in the lower solar atmosphere. Here, we present spectroscopic and imaging observations…

Solar and Stellar Astrophysics · Physics 2026-03-24 Girjesh Gupta , Ananya Rawat , Helen Mason , Robertus Erdélyi

We performed statistical and event studies of linear polarization in the H$\alpha$ line during solar flares. The statistical study revealed that, among 71 H$\alpha$ flares analyzed, including 64 GOES flares, only one event shows significant…

Solar and Stellar Astrophysics · Physics 2019-02-20 Tomoko Kawate , Yoichiro Hanaoka

Intermittent magnetohydrodynamical turbulence is most likely at work in the magnetized solar atmosphere. As a result, an array of scaling and multi-scaling image-processing techniques can be used to measure the expected self-organization of…

Astrophysics · Physics 2007-05-23 Manolis K. Georgoulis