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Particle acceleration consequences from fluctuating electric fields superposed on an X-type magnetic field in collisionless solar plasma are studied. Such a system is chosen to mimic generic features of dynamic reconnection, or the…

Astrophysics · Physics 2009-11-13 P. Petkaki , A. L. MacKinnon

Non-thermal particle acceleration in the solar corona is evident from both remote hard X-ray (HXR) sources in the chromosphere and direct in-situ detection in the heliosphere. Correlation of spectral indices between remote and in-situ…

Solar and Stellar Astrophysics · Physics 2025-02-27 Ross Pallister , Natasha L. S. Jeffrey , Morgan Stores

A new mechanism for acceleration and enrichment of 3He during impulsive solar flares is presented. Low-frequency electromagnetic plasma waves excited by the Electron Firehose Instability (EFI) can account for the acceleration of ions up to…

Astrophysics · Physics 2009-11-07 G. Paesold , R. Kallenbach , A. O. Benz

The excess broadening of high-temperature spectral lines, long observed near the tops of flare arcades, is widely considered to result from magnetohydrodynamic (MHD) turbulence. According to different theories, plasma turbulence is also…

Solar and Stellar Astrophysics · Physics 2024-07-18 William Ashfield , Vanessa Polito , Sijie Yu , Hannah Collier , Laura Hayes

One of the most important products of solar flares are nonthermal energetic particles which may carry up to 50\% energy releasing in the flaring processes. In radio observations, nonthermal particles generally manifest as spectral fine…

Solar and Stellar Astrophysics · Physics 2020-01-08 Baolin Tan , Nai-hwa Chen , Ya-hui Yang , Chengming Tan , Satoshi Masuda , Xingyao Chen , H. Misawa

In order to study the acceleration and propagation of bremsstrahlung-producing electrons in solar flares, we analyze the evolution of the flare loop size with respect to energy at a variety of times. A GOES M3.7 loop-structured flare…

Solar and Stellar Astrophysics · Physics 2015-06-05 Jingnan Guo , A. Gordon Emslie , Eduard P. Kontar , Federico Benvenuto , Anna Maria Massone , Michele Piana

High-energy particles may be accelerated widely in stellar coronae; probably by the same processes we find in the Sun. Here, we have learned of two physical mechanisms that dominate the acceleration of solar energetic particles (SEPs). The…

Solar and Stellar Astrophysics · Physics 2025-03-20 Donald V. Reames

We study the evolution of the spectral index and the normalization (flux) of the non-thermal component of the electron spectra observed by RHESSI during 24 solar hard X-ray flares. The quantitative evolution is confronted with the…

Astrophysics · Physics 2007-05-23 Paolo C. Grigis , Arnold O. Benz

X-ray observations are a direct diagnostic of fast electrons produced in solar flares, energized during the energy release process and directed towards the Sun. Since the properties of accelerated electrons can be substantially changed…

Solar and Stellar Astrophysics · Physics 2015-10-28 Natasha Jeffrey , Eduard Kontar , Gordon Emslie , Nicolas Bian

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

We study the acceleration in solar flares of $^3$He and $^4$He from a thermal background by parallel propagating plasma waves with a general broken power-law spectrum that takes into account the turbulence generation processes at large…

Astrophysics · Physics 2016-08-16 Siming Liu , Vahé Petrosian , Glenn M. Mason

Non-thermal and thermal parameters of 85 solar flares of GOES class B1 to M6 (background subtracted classes A1 to M6) have been compared to each other. The hard X-ray flux has been measured by RHESSI and a spectral fitting provided flux and…

Astrophysics · Physics 2009-11-11 Marina Battaglia , Paolo C. Grigis , Arnold O. Benz

We present a multi-wavelength observation of a solar flare occurring on 2006 December 13 with Hinode, RHESSI, and the Nobeyama Radio Observatory, to study the electron acceleration site and mechanism. The Solar Optical Telescope (SOT) on…

Solar and Stellar Astrophysics · Physics 2010-01-15 T. Minoshima , S. Imada , T. Morimoto , T. Kawate , H. Koshiishi , M. Kubo , S. Inoue , H. Isobe , S. Masuda , S. Krucker , T. Yokoyama

Quantifying the energy content of accelerated electron beams during solar eruptive events is a key outstanding objective that must be constrained to refine particle acceleration models and understand the electron component of space weather.…

Solar and Stellar Astrophysics · Physics 2024-09-24 Alexander W. James , Hamish A. S. Reid

Recent results of a mixed shell model heated asymmetrically by transient increases in nuclear burning indicate the transient generation of small hot spots inside the Sun somewhere between 0.1 and 0.2 solar radii. These hot bubbles are…

Solar and Stellar Astrophysics · Physics 2015-05-18 Attila Grandpierre

We investigate two microflares of GOES classes A9 and C1 (after background subtraction) observed by STIX onboard Solar Orbiter with exceptionally strong nonthermal emission. We complement the hard X-ray imaging and spectral analysis by STIX…

Solar and Stellar Astrophysics · Physics 2024-03-12 Jonas Saqri , Astrid M. Veronig , Andrea Francesco Battaglia , Ewan C. M. Dickson , Dale E. Gary , Säm Krucker

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)…

A common feature of electromagnetic emission from solar flares is the presence of intensity pulsations that vary as a function of time. Known as quasi-periodic pulsations (QPPs), these variations in flux appear to include periodic…

Solar and Stellar Astrophysics · Physics 2021-04-14 Brendan P. Clarke , Laura A. Hayes , Peter T. Gallagher , Shane A. Maloney , Eoin P. Carley

Sudden jets of collimated plasma arise from many locations on the Sun, including active regions. The magnetic field along which a jet emerges is often open to interplanetary space, offering a clear "escape route" for any flare-accelerated…

Solar and Stellar Astrophysics · Physics 2018-11-07 Lindsay Glesener , Gregory D. Fleishman

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
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