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Twisted magnetic fields should be ubiquitous in flare-producing active regions where the magnetic fields are strongly non-potential. It has been shown that reconnection in helical magnetic coronal loops results in plasma heating and…

Solar and Stellar Astrophysics · Physics 2016-01-20 R. F. Pinto , M. Gordovskyy , P. K. Browning , N. Vilmer

Context. High energy electrons accelerated during solar flare are abundant in the solar corona and in the interplanetary space. Commonly, the number and the energy of non-thermal electrons at the Sun is estimated using hard X-ray (HXR)…

Solar and Stellar Astrophysics · Physics 2015-06-03 E. P. Kontar , H. Ratcliffe , N. H. Bian

With the elementary energy release events introduced in a previous paper (Liu & Fletcher 2009) we model the chromospheric evaporation in flaring loops. The thick-target hard X-ray (HXR) emission produced by electrons escaping from the…

Solar and Stellar Astrophysics · Physics 2014-11-20 Siming Liu , Feiran Han , Lyndsay Fletcher

The hard X-ray flux ratio R of the footpoint sources to the loop-top source has been used to investigate non-thermal electron trapping and precipitation in solar flares. Considering the mission-long Yohkoh Hard X-ray Telescope database,…

Astrophysics · Physics 2009-11-11 M. Tomczak , T. Ciborski

We compare time variations of the H$\alpha$ and X-ray emissions observed during the pre-impulsive and impulsive phases of the C1.1-class solar flare on 21 June 2013 with those of plasma parameters and synthesized X-ray emission from a…

Solar and Stellar Astrophysics · Physics 2017-10-04 R. Falewicz , K. Radziszewski , P. Rudawy , A. Berlicki

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…

Solar and Stellar Astrophysics · Physics 2011-09-07 A. Kulinova , J. Kasparova , E. Dzifcakova , J. Sylwester , B. Sylwester , M. Karlicky

The interrelation of hard X-ray (HXR) emitting sources and the underlying physics of electron acceleration and transport presents one of the major questions in high-energy solar flare physics. Spatially resolved observations of solar flares…

Solar and Stellar Astrophysics · Physics 2015-06-12 Paulo J. A. Simões , Eduard P. Kontar

We explore the temporal relationship between microwave/HXR emission and Doppler velocity during the impulsive phase of a solar flare on 2014 October 27 (SOL2014-10-27), which displays a pulse on the light curves in microwave (34 GHz) and…

Solar and Stellar Astrophysics · Physics 2017-05-24 Dong Li , Zongjun Ning , Yu Huang , Qingmin Zhang

The impulsive phase of solar flares is a time of rapid energy deposition and heating in the lower solar atmosphere, leading to changes in the temperature and density structure of the region. We use an O V density diagnostic formed of the…

Solar and Stellar Astrophysics · Physics 2015-11-18 David R. Graham , Lyndsay Fletcher , Nicolas Labrosse

Recent measurements of vertical extents and positions of the chromospheric hard X-ray (HXR) flare sources based on Ramaty High-Energy Spectroscopic Imager (RHESSI) observations show a significant inconsistency with the theoretical…

Solar and Stellar Astrophysics · Physics 2016-12-07 Z. Moravec , M. Varady , J. Kasparova , D. Kramolis

We present high spatial resolution observations of chromospheric evaporation in the flare SOL2014-03-29T17:48. Interface Region Imaging Spectrograph (IRIS) observations of the FeXXI 1354.1 A line indicate evaporating plasma at a temperature…

Solar and Stellar Astrophysics · Physics 2015-11-11 Marina Battaglia , Lucia Kleint , Säm Krucker , David Graham

We present a multi-wavelength analysis of two flare-related jets on November 13, 2014, using data from SDO/AIA, RHESSI, Hinode/XRT, and IRIS. Unlike most coronal jets where hard X-ray (HXR) emissions are usually observed near the jet base,…

Solar and Stellar Astrophysics · Physics 2022-07-13 Yixian Zhang , Sophie Musset , Lindsay Glesener , Navdeep Panesar , Gregory Fleishman

The disparate nature of thermal-nonthermal energy partition during flares, particularly during weak flares, is still an open issue. Following the Neupert effect, quantifying the relative yield of X-ray emission in different energy bands can…

Solar and Stellar Astrophysics · Physics 2024-02-06 Arun Kumar Awasthi , Tomasz Mrozek , Sylwester Kołomański , Michalina Litwicka , Marek Stęślicki , Karol Kułaga

Observations with {\em RHESSI} have enabled the detailed study of the structure of dense hard X-ray coronal sources in solar flares. The variation of source extent with electron energy has been discussed in the context of streaming of…

Solar and Stellar Astrophysics · Physics 2015-06-19 Natasha L. S. Jeffrey , Eduard P. Kontar , Nicolas H. Bian , A. Gordon Emslie

This Research Note is in response to the recent paper by S. M. Perriyil et al. (2026). They provide measurements of the time delay (delta t) between the hard X-ray and soft X-ray peak times for 96 flares observed with RHESSI and GOES. These…

Solar and Stellar Astrophysics · Physics 2026-04-07 Brian R. Dennis , Hugh Hudson , Joel Allred

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

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

Simultaneous observations of explosive chromospheric evaporation are presented using data from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Coronal Diagnostic Spectrometer (CDS) onboard SOHO. For the first time,…

In this work, we use HyLoop (Winter et al. 2011), a loop model that can incorporate the effects of both MHD and non-thermal particle populations, to simulate soft X-ray emissions in various situations. First of all, we test the effect of…

Solar and Stellar Astrophysics · Physics 2012-01-30 Katharine K. Reeves , Henry D. Winter , Natalie L. Larson

We present new constraints on the high-temperature emission measure of a non-flaring solar active region using observations from the recently flown Focusing Optics X-ray Solar Imager sounding rocket payload. FOXSI has performed the first…