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The impulsive phase of a solar flare is known to generate strong turbulence and to transfer magnetic energy into accelerated electrons. Recognizing the importance of angular diffusion on the dynamics of the accelerated electrons, we extend…

Solar and Stellar Astrophysics · Physics 2026-03-30 A. Gordon Emslie , Eduard P. Kontar

We analyzed the occurrence rates of flares on stars of spectral types K, G, F, and A, observed by Kepler. We found that the histogram of occurrence frequencies of stellar flares is systematically shifted towards a high-energy tail for…

Solar and Stellar Astrophysics · Physics 2017-03-15 M. Svanda , M. Karlicky

We present the statistical analysis of 33 flare-related coronal jets, and discuss the link between the jet and the flare properties in these events. We selected jets that were observed between 2010 and 2016 by the Atmospheric Imaging…

Solar and Stellar Astrophysics · Physics 2020-02-12 Sophie Musset , Mariana Jeunon , Lindsay Glesener

We advocate the idea that the nanoflares conjectured by Parker long ago to resolve the corona heating problem, may also trigger the larger solar flares. The arguments are based on the model where emission of extreme ultra violet (EUV)…

Solar and Stellar Astrophysics · Physics 2018-08-17 Ariel Zhitnitsky

All theories that attempt to explain the heating of the high temperature plasma observed in the solar corona are based on short bursts of energy. The intensities and velocities measured in the cores of quiescent active regions, however, can…

Solar and Stellar Astrophysics · Physics 2015-06-05 Fana M. Mulu-Moore , Amy R. Winebarger , Harry P. Warren

Coronal heating has puzzled solar physicists for decades. The question of why the Sun's upper atmosphere is significantly hotter than its lower atmosphere remains a key mystery. It is commonly believed that the source of coronal heating…

Solar and Stellar Astrophysics · Physics 2025-05-01 Hanlin Yang , Jingxiu Wang , Chunlan Jin

Recent observations of Krucker & Benz (1998) give strong support to Parker's hypothesis (Parker 1988) that small scale dissipative events make the main contribution to quiet Sun coronal heating. They also showed that these small scale…

Astrophysics · Physics 2009-11-06 V. Krasnoselskikh , O. Podladchikova , B. Lefebvre , N. Vilmer

Investigate particle acceleration and heating in a solar microflare. In a microflare with non-thermal emission to remarkably high energies ($>50$ keV), we investigate the hard X-rays with RHESSI imaging and spectroscopy and the resulting…

Astrophysics · Physics 2010-09-17 I. G. Hannah , S. Krucker , H. S. Hudson , S. Christe , R. P. Lin

Extending previous studies of nonthermal electron transport in solar flares which include the effects of collisional energy diffusion and thermalization of fast electrons, we present an analytic method to infer more accurate estimates of…

Solar and Stellar Astrophysics · Physics 2015-08-19 E. P. Kontar , N. L. S. Jeffrey , A. G. Emslie , N. H. Bian

Parker's initial insights from 1958 provided a key causal link between the heating of the solar corona and the acceleration of the solar wind. However, we still do not know what fraction of the solar wind's mass, momentum, and energy flux…

Astrophysics · Physics 2007-05-23 Steven R. Cranmer

Particle acceleration is one of the most significant features that are ubiquitous among space and cosmic plasmas. It is most prominent during flares in the case of the Sun, with which huge amount of electromagnetic radiation and high-energy…

Solar and Stellar Astrophysics · Physics 2014-05-15 Noriyuki Narukage , Masumi Shimojo , Taro Sakao

This paper reports on the re-analysis of solar flares in which the hard X-rays (HXRs) come predominantly from the corona rather than from the more usual chromospheric footpoints. All of the 26 previously analyzed event time intervals, over…

Solar and Stellar Astrophysics · Physics 2018-11-07 Brian R. Dennis , Miguel A. Duval-Poo , Michele Piana , Andrew R. Inglis , A. Gordon Emslie , Jingnan Guo , Yan Xu

Solar flares are explosive releases of magnetic energy stored in the solar corona, driven by magnetic reconnection. These events accelerate electrons, generating hard X-ray emissions and often display Quasi Periodic Pulsations (QPPs) across…

Solar and Stellar Astrophysics · Physics 2025-11-25 Luiz A. C. A. Schiavo , Natasha L. S. Jeffrey , Gert J. J. Botha , James A. McLaughlin

The time-dependence of heating in solar active regions can be studied by analyzing the slope of the emission measure distribution cool-ward of the peak. In a previous study we showed that low-frequency heating can account for 0% to 77% of…

Solar and Stellar Astrophysics · Physics 2013-03-20 Jeffrey W. Reep , Stephen J. Bradshaw , James A. Klimchuk

The transport of the energy contained in electrons, both thermal and suprathermal, in solar flares plays a key role in our understanding of many aspects of the flare phenomenon, from the spatial distribution of hard X-ray emission to global…

Solar and Stellar Astrophysics · Physics 2016-06-22 Nicolas H. Bian , Eduard P. Kontar , A. Gordon Emslie

Coronal heating through the explosive release of magnetic energy remains an open problem in solar physics. Recent hydrodynamical models attempt an investigation by placing swarms of 'nanoflares' at random sites and times in modeled…

Solar and Stellar Astrophysics · Physics 2016-11-30 K. Moraitis , A. Toutountzi , H. Isliker , M. Georgoulis , L. Vlahos , G. Chintzoglou

The acceleration and transport of energetic electrons during solar flares is one of the outstanding topics in solar physics. Recent X-ray and radio imaging and spectroscopy observations have provided diagnostics of the distribution of…

Solar and Stellar Astrophysics · Physics 2022-12-21 Xiangliang Kong , Bin Chen , Fan Guo , Chengcai Shen , Xiaocan Li , Jing Ye , Lulu Zhao , Zelong Jiang , Sijie Yu , Yao Chen , Joe Giacalone

To explain the high temperature of the corona, much attention has been paid to the distribution of energy in dissipation events. Indeed, if the event energy distribution is steep enough, the smallest, unobservable events could be the…

Solar and Stellar Astrophysics · Physics 2016-07-06 Vincent Joulin , Éric Buchlin , Jacques Solomon , Chloé Guennou

Observational evidence for gentle chromospheric evaporation during the impulsive phase of a C9.1 solar flare is presented using data from the Reuven Ramaty High-Energy Solar Spectroscopic Imager and the Coronal Diagnostic Spectrometer on…

Plasma with a temperature close to the chromospheric one is ejected in solar eruptions. Such plasma can occult some part of emission of compact sources in active regions as well as quiet solar areas. Absorption phenomena can be observed in…

Solar and Stellar Astrophysics · Physics 2015-05-20 V. V. Grechnev , I. V. Kuzmenko , I. M. Chertok , A. M. Uralov