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A circular ribbon flare SOL2014-12-17T04:51 is studied using the 17/34 GHz maps from the Nobeyama Radioheliograph (NoRH) along with (E)UV and magnetic data from the Solar Dynamics Observatory (SDO). We report the following three findings as…

Solar and Stellar Astrophysics · Physics 2020-09-28 Jeongwoo Lee , Stephen M. White , Xingyao Chen , Yao Chen , Hao Ning , Bo Li , Satoshi Masuda

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

The Neupert effect refers to the strong correlation between the soft X-ray (SXR) light curve and the time-integrated hard X-rays (HXR) or microwave flux, which is frequently observed in solar flares. In this article, we therefore utilized…

Solar and Stellar Astrophysics · Physics 2024-04-04 Dong Li , Hanyang Dong , Wei Chen , Yang Su , Yu Huang , Zongjun Ning

The spectrum of gyrosynchrotron emission from solar flares generally peaks in the microwave range. Its optically-thin, high-frequency component, above the spectral peak, is often used for diagnostics of the nonthermal electrons and the…

Solar and Stellar Astrophysics · Physics 2018-11-07 Gregory D. Fleishman , Maria A. Loukitcheva , Varvara Yu. Kopnina , Gelu M. Nita , Dale E. Gary

Quasi-periodic pulsations (QPPs) are frequently detected in solar and stellar flares, but the underlying physical mechanisms are still to be ascertained. Here, we show microwave QPPs during a solar flare originating from quasi-periodic…

Solar and Stellar Astrophysics · Physics 2022-12-19 Yuankun Kou , Xin Cheng , Yulei Wang , Sijie Yu , Bin Chen , Eduard P. Kontar , Mingde Ding

We investigate the thermal, kinematic and magnetic structure of small-scale heating events in an emerging flux region (EFR). We use high-resolution multi-line observations (including Ca II 8542~\AA, Ca II K, and Fe I 6301~\AA line pair) of…

Solar and Stellar Astrophysics · Physics 2023-09-14 Rahul Yadav , Maria D. Kazachenko , Andrey N. Afanasyev , Jaime de la Cruz Rodríguez , Jorrit Leenaarts

Observational measurements of active region emission measures contain clues to the time-dependence of the underlying heating mechanism. A strongly non-linear scaling of the emission measure with temperature indicates a large amount of hot…

Solar and Stellar Astrophysics · Physics 2015-06-11 Stephen J. Bradshaw , James A. Klimchuk , Jeffrey W. Reep

Spectral line widths are often observed to be larger than can be accounted for by thermal and instrumental broadening alone. This excess broadening is a key observational constraint for both nanoflare and wave dissipation models of coronal…

Solar and Stellar Astrophysics · Physics 2016-03-23 David H. Brooks , Harry P. Warren

We report high-resolution observations at mid-infrared wavelengths of a minor solar flare, SOL2014-09-24T17T17:50 (C7.0), using Quantum Well Infrared Photodetector (QWIP) cameras at an auxiliary of the McMath-Pierce telescope. The flare…

Solar and Stellar Astrophysics · Physics 2016-03-23 M Penn , S Krucker , H Hudson , M Jhabvala , D Jennings , A Lunsford , P Kaufmann

We present the first in-depth statistical survey of flare source heights observed by RHESSI. Flares were found using a flare-finding algorithm designed to search the 6-10 keV count-rate when RHESSI's full sensitivity was available in order…

Solar and Stellar Astrophysics · Physics 2015-05-27 Steven Christe , S Krucker , Pascal Saint-Hilaire

A complete understanding of the onset and subsequent evolution of confined flares has not been achieved. Earlier studies mainly analyzed disk events so as to reveal their magnetic topology and cause of confinement. In this study, taking…

Solar and Stellar Astrophysics · Physics 2018-03-14 Hao Ning , Yao Chen , Zhao Wu , Yang Su , Hui Tian , Gang Li , Guohui Du , Hongqiang Song

In the classical flare picture, hard X-ray emission from the chromosphere is succeeded by soft-X-ray emission from hot plasma in the flare loop, the soft X-ray emission being a direct consequence of the impact of the non-thermal particle…

Solar and Stellar Astrophysics · Physics 2015-05-13 M. Battaglia , L. Fletcher , A. O. Benz

Aims. The H-alpha emission of solar flare kernels and associated hard X-ray (HXR) emission often show similar time variations but their light curves are shifted in time by energy transfer mechanisms. We searched for fast radiative response…

Solar and Stellar Astrophysics · Physics 2015-05-30 K. Radziszewski , P. Rudawy , K. J. H. Phillips

We analyze and model a C5.7 two-ribbon solar flare observed by SDO, Hinode and GOES on 2011 December 26. The flare is made of many loops formed and heated successively over one and half hours, and their footpoints are brightened in the UV…

Solar and Stellar Astrophysics · Physics 2018-04-04 Chunming Zhu , Jiong Qiu , Dana W. Longcope

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

Short timescale flux variations are closely related to the energy release process of magnetic reconnection during solar flares. Radio light curves at 1, 2, 3.75, 9.4, and 17 GHz of 209 flares observed by the Nobeyama Radio Polarimeter from…

Solar and Stellar Astrophysics · Physics 2020-06-04 Wang Lu , Liu Si-ming , Ning Zong-jun

Understanding the relationship among different emission components plays an essential role in the study of particle acceleration and energy conversion in solar flares. In flares where gradual and impulsive emission components can be readily…

Solar and Stellar Astrophysics · Physics 2015-06-15 Siming Liu , Youping Li , Lyndsay Fletcher

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

Solar flares form and release energy across a large number of magnetic loops. The global parameters of flares, such as the total energy released, duration, physical size, etc., are routinely measured, and the hydrodynamics of a coronal loop…

Solar and Stellar Astrophysics · Physics 2018-04-18 Jeffrey W. Reep , Vanessa Polito , Harry P. Warren , Nicholas A. Crump

Transition-region loops are a type of critical magnetic structure in the solar atmosphere, yet their physical properties and evolutionary characteristics remain statistically poorly constrained. We aim to statistically characterize the…

Solar and Stellar Astrophysics · Physics 2026-03-31 Xiuhui Zuo , Zhenghua Huang , Maria S. Madjarska , Hui Fu , Hengyuan Wei , Xinzheng Shi , Lidong Xia