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Solar flares are efficient particle accelerators with a large fraction of released magnetic energy (10-50%) converted into energetic particles such as hard X-ray producing electrons. This energy transfer process is not well constrained,…

Solar and Stellar Astrophysics · Physics 2023-04-12 Morgan Stores , Natasha L. S. Jeffrey , James A. McLaughlin

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

Driven by recent RHESSI observations of confined loop-top hard X-ray sources in solar flares, we consider stochastic acceleration of electrons in the presence of Coulomb collisions. If electron escape from the acceleration region can be…

Solar and Stellar Astrophysics · Physics 2015-06-23 Nicolas H. Bian , A. Gordon Emslie , Duncan J. Stackhouse , Eduard P. Kontar

This study explores the impact of a turbulent scattering mechanism, akin to those influencing solar and galactic cosmic rays propagating in the interplanetary medium, on the population of suprathermal electrons in the solar wind. We employ…

Based on quantum theory, we investigate the distribution of the electrons scattered in nonlinear Compton effect by an electromagnetic plane wave. Deviations of the final electron momentum from its initial value are solely due to quantum…

Atomic Physics · Physics 2015-06-05 Madalina Boca , Victor Dinu , Viorica Florescu

The aim of this paper is to investigate the spatial structure of the impulsive phase hard X-ray emission from solar flares. This work is motivated by the YOHKOH and the forthcoming HESSI observations. Summarizing past results, it is shown…

Astrophysics · Physics 2009-10-31 Vahe Petrosian , Timothy Q. Donaghy

We conduct two-dimensional particle-in-cell simulations to investigate the scattering of electron heat flux by self-generated oblique electromagnetic waves. The heat flux is modeled as a bi-kappa distribution with a T_parallel > T_perp…

Solar and Stellar Astrophysics · Physics 2023-07-12 Hanqing Ma , James F. Drake , Marc Swisdak

The standard flare model, despite its success, is limited in comprehensively explaining the various processes involving nonthermal particles. One such missing ingredient is a detailed understanding of the various processes involved during…

Solar and Stellar Astrophysics · Physics 2024-04-23 Surajit Mondal , Andrea F. Battaglia , Bin Chen , Sijie Yu

Context: Solar flare hard X-rays (HXRs) are thought to be produced by nonthermal coronal electrons stopping in the chromosphere, or remaining trapped in the corona. The collisional thick target model (CTTM) predicts that sources produced by…

Solar and Stellar Astrophysics · Physics 2015-06-15 A. O'Flannagain , P. Gallagher , J. Brown , R. Milligan , G. Holman

Aims: We investigate the electron acceleration in convective electric fields of cascading magnetic reconnection in a flaring solar corona and show the resulting hard X-ray (HXR) radiation spectra caused by Bremsstrahlung for the coronal…

Solar and Stellar Astrophysics · Physics 2015-12-09 X. Zhou , J. Büchner , M. Barta , W. Gan , S. Liu

The angular distribution of electrons accelerated in solar flares is a key parameter in the understanding of the acceleration and propagation mechanisms that occur there. However, the anisotropy of energetic electrons is still a poorly…

Solar and Stellar Astrophysics · Physics 2012-12-24 Ewan Cameron Mackenzie Dickson , Eduard Kontar

Solar flares effectively accelerate particles to non-thermal energies. These accelerated electrons are responsible for energy transport and subsequent emissions in HXR, radio, and UV/EUV radiation. Due to the steeply decreasing electron…

Solar and Stellar Astrophysics · Physics 2026-01-01 Yingjie Luo , Eduard P. Kontar , Debesh Bhattacharjee

Suprathermal tails are a common feature of solar wind electron velocity distributions, and are expected in the solar corona. From the corona, suprathermal electrons can propagate through the steep temperature gradient of the transition…

Solar and Stellar Astrophysics · Physics 2016-10-13 C. Vocks , E. Dzifcakova , G. Mann

We examine effects on the charge states of energetic ions associated with gradual solar flares due to shock heating and stripping at high ion velocities. Recent measurements of the mean charges of various elements after the flares of 1992…

Astrophysics · Physics 2009-10-30 D. Ruffolo

A number of double coronal X-ray sources have been observed during solar flares by RHESSI, where the two sources reside at different sides of the inferred reconnection site. However, where and how are these X-ray-emitting electrons…

Solar and Stellar Astrophysics · Physics 2022-07-20 Xiangliang Kong , Jing Ye , Bin Chen , Fan Guo , Chengcai Shen , Xiaocan Li , Sijie Yu , Yao Chen , Joe Giacalone

Solar flare hard X-ray spectroscopy serves as a key diagnostic of the accelerated electron spectrum. However, the standard approach using the collisional cold thick-target model poorly constrains the lower-energy part of the accelerated…

Solar and Stellar Astrophysics · Physics 2019-02-05 Eduard P. Kontar , Natasha L. S. Jeffrey , A. Gordon Emslie

The hard X-ray (HXR) emission in solar flares comes almost exclusively from a very small part of the flaring region, the footpoints of magnetic loops. Using RHESSI observations of solar flare footpoints, we determine the radial positions…

Solar and Stellar Astrophysics · Physics 2015-05-27 Marina Battaglia , Eduard P. Kontar

Nonthermal loop-top sources in solar flares are the most prominent observational signature that suggests energy release and particle acceleration in the solar corona. Although several scenarios for particle acceleration have been proposed,…

Solar and Stellar Astrophysics · Physics 2020-01-08 Xiangliang Kong , Fan Guo , Chengcai Shen , Bin Chen , Yao Chen , Sophie Musset , Lindsay Glesener , Peera Pongkitiwanichakul , Joe Giacalone

We carried out detailed analysis of X-ray and radio observations of a simple flare loop that occurred on 12th August 2002, with the impulsive hard X-ray (HXR) light curves dominated by a single pulse. The emission spectra of the early…

Solar and Stellar Astrophysics · Physics 2015-06-22 I. N. Sharykin , S. Liu , L. Fletcher

Plasma turbulence is thought to be associated with various physical processes involved in solar flares, including magnetic reconnection, particle acceleration and transport. Using Ramaty High Energy Solar Spectroscopic Imager ({\it RHESSI})…

Solar and Stellar Astrophysics · Physics 2015-05-27 E. P. Kontar , I. G. Hannah , N. H. Bian