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Microflares are energetically smaller versions of solar flares, demonstrating the same processes of plasma heating and particle acceleration. However, it remains unclear down to what energy scales this impulsive energy release continues,…

太阳与恒星天体物理 · 物理学 2024-02-09 Kristopher Cooper , Iain G. Hannah , Lindsay Glesener , Brian W. Grefenstette

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…

天体物理学 · 物理学 2010-09-17 I. G. Hannah , S. Krucker , H. S. Hudson , S. Christe , R. P. Lin

In some flares the thermal component appears much earlier than the nonthermal component in X-ray range. Using sensitive microwave observations we revisit this finding made by Battaglia et al. (2009) based on RHESSI data analysis. We have…

太阳与恒星天体物理 · 物理学 2015-06-11 Alexander A. Altyntsev , Gregory D. Fleishman , Sergey V. Lesovoi , Natalia S. Meshalkina

Flares close to the solar limb, where the footpoints are occulted, can reveal the spectrum and structure of the coronal loop-top source in X-rays. We aim at studying the properties of the corresponding energetic electrons near their…

We focus on the non-thermal components of the electron distribution in the keV range and analyse high-energy resolution X-ray spectra detected by RESIK and RHESSI for three solar flares.In the 2-4 keV range we assume that the electron…

太阳与恒星天体物理 · 物理学 2011-09-07 A. Kulinova , J. Kasparova , E. Dzifcakova , J. Sylwester , B. Sylwester , M. Karlicky

We report a NuSTAR observation of a solar microflare, SOL2015-09-01T04. Although it was too faint to be observed by the GOES X-ray Sensor, we estimate the event to be an A0.1 class flare in brightness. This microflare, with only 5 counts…

A popular scenario for electron acceleration in solar flares is transit-time damping of low-frequency MHD waves excited by reconnection and its outflows. The scenario requires several processes in sequence to yield energetic electrons of…

天体物理学 · 物理学 2015-06-24 Arnold O. Benz , Pascal Saint-Hilaire

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…

太阳与恒星天体物理 · 物理学 2026-01-01 Yingjie Luo , Eduard P. Kontar , Debesh Bhattacharjee

Nonthermal sources located above bright flare arcades, referred to as the "above-the-loop-top" sources, have been often suggested as the primary electron acceleration site in major solar flares. The X8.2 limb flare on 2017 September 10…

太阳与恒星天体物理 · 物理学 2021-03-03 Bin Chen , Marina Battaglia , Säm Krucker , Katharine K. Reeves , Lindsay Glesener

Solar flares are known to be prolific electron accelerators, yet identifying the mechanism(s) for such efficient electron acceleration in solar flare (and similar astrophysical settings) presents a major challenge. This is due in part to a…

太阳与恒星天体物理 · 物理学 2023-04-18 Eduard P. Kontar , A. Gordon Emslie , Galina G. Motorina , Brian R. Dennis

High-energy X-rays and gamma-rays from solar flares were discovered just over fifty years ago. Since that time, the standard for the interpretation of spatially integrated flare X-ray spectra at energies above several tens of keV has been…

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…

太阳与恒星天体物理 · 物理学 2015-08-19 E. P. Kontar , N. L. S. Jeffrey , A. G. Emslie , N. H. Bian

We present a detailed examination on the coronal nonthermal emissions during the preflare phase of the X4.8 flare that occurred on 2002 July 23. The microwave (17 GHz and 34 GHz) data obtained with Nobeyama Radioheliograph, at Nobeyama…

太阳与恒星天体物理 · 物理学 2011-02-11 Ayumi Asai , Hiroshi Nakajima , Masumi Shimojo , Takaaki Yokoyama , Satoshi Masuda , Sam Krucker

Nonthermal electrons accelerated in solar flares produce electromagnetic emission in two distinct, highly complementary domains - hard X-rays (HXRs) and microwaves (MWs). This paper reports MW imaging spectroscopy observations from the…

太阳与恒星天体物理 · 物理学 2020-04-29 Natsuha Kuroda , Gregory D. Fleishman , Dale E. Gary , Gelu M. Nita , Bin Chen , Sijie Yu

We investigate the spatial, temporal, and spectral properties of 10 microflares from AR12721 on 2018 September 9 and 10 observed in X-rays using the Nuclear Spectroscopic Telescope ARray (NuSTAR) and the Solar Dynamic Observatory's…

We investigate accelerated electron energy spectra for different sources in a large flare using simultaneous observations obtained with two instruments, the Nobeyama Radio Heliograph (NoRH) at 17 and 34 GHz, and the Reuven Ramaty High…

太阳与恒星天体物理 · 物理学 2015-05-13 M. R. Kundu , V. V. Grechnev , S. M. White , E. J. Schmahl , N. S. Meshalkina , L. K. Kashapova

We report the observation of an unusual cold, tenuous solar flare, which reveals itself via numerous and prominent non-thermal manifestations, while lacking any noticeable thermal emission signature. RHESSI hard X-rays and 0.1-18 GHz radio…

太阳与恒星天体物理 · 物理学 2015-05-27 Gregory D. Fleishman , Eduard P. Kontar , Gelu M. Nita , Dale E. Gary

In this paper, we use a highly sensitive telescope to characterize solar X-ray transients ranging from microflares in active regions down to weakly energetic brightenings in the quiet Sun. X-rays are closely linked to the initial energy…

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…

太阳与恒星天体物理 · 物理学 2019-02-05 Eduard P. Kontar , Natasha L. S. Jeffrey , A. Gordon Emslie

A primary characteristic of solar flares is the efficient acceleration of electrons to nonthermal deka-keV energies. While hard X-Ray (HXR) observation of bremsstrahlung emission serves as the key diagnostic of these electrons. In this…

太阳与恒星天体物理 · 物理学 2025-06-11 Debesh Bhattacharjee , Eduard P. Kontar , Yingjie Luo
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