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Radio and optical observations of the evolution of flare-associated phenomena have shown an initial and rapid burst at 0.4 THz only followed subsequently by a localized chromospheric heating producing an H{\alpha} brightening with later…

Even small solar flares can display a surprising level of complexity regarding their morphology and temporal evolution. Many of their properties, such as energy release and electron acceleration can be studied using highly complementary…

Solar and Stellar Astrophysics · Physics 2021-12-08 Marina Battaglia , Rohit Sharma , Yingjie Luo , Bin Chen , Sijie Yu , Säm Krucker

The GOES M2-class solar flare, SOL2010-06-12T00:57, was modest in many respects yet exhibited remarkable acceleration of energetic particles. The flare produced an ~50 s impulsive burst of hard X- and \gamma-ray emission up to at least 400…

High Energy Astrophysical Phenomena · Physics 2017-02-22 Fermi GBM Collaboration , Fermi LAT Collaboration , B. R. Dennis , R. A. Schwartz , A. K. Tolbert

The evolution of an X2.7 solar flare, that occurred in a complex $\beta\gamma\delta$ magnetic configuration region on 2003 November 3 is discussed utilizing a multi-wavelength data set. The very first signature of pre-flare coronal activity…

Astrophysics · Physics 2009-11-13 Bhuwan Joshi , P. K. Manoharan , Astrid M. Veronig , P. Pant , Kavita Pandey

Chromospheric activities prior to solar flares provide important clues to solar flare initiation, but are as yet poorly understood. We report a significant and rapid H$\alpha$ line broadening before the solar flare SOL2011-09-29T18:08, that…

Solar and Stellar Astrophysics · Physics 2020-05-14 Kyuhyoun Cho , Jeongwoo Lee , Jongchul Chae , Haimin Wang , Kwangsu Ahn , Heesu Yang , Eun-kyung Lim , Ram Ajor Maurya

We investigate how the magnetic loop length of solar flares relates to the timing between their thermal and nonthermal emission signatures. Our study analyzes a sample of 96 C-, M-, and X-class flares observed between 2013 and 2015 with…

Solar and Stellar Astrophysics · Physics 2026-02-24 S. M. Perriyil , S. S. Sadangaya , C. G. Giménez de Castro , P. J. A. Simões

Flares are powerful events ignited by a sudden release of magnetic energy. With the aim of studying flares in the 125-Myr-old stars in the Pleiades observed simultaneously in optical and X-ray light, we obtained new XMM-Newton observations…

Recent irradiance measurements from numerous heliophysics and astrophysics missions including SDO, GOES, Kepler, TESS, Chandra, XMM-Newton, and NICER have provided critical input in understanding the physics of the most powerful transient…

Solar and Stellar Astrophysics · Physics 2023-09-11 Jeffrey W. Reep , Vladimir S. Airapetian

Solar flare ribbons are features in the lower atmosphere that show enhanced emission intensity, particularly noticeable in H$\alpha$ and EUV images of the transition region and upper chromosphere. In this study, we provide observational…

Using the multi-wavelength images and the photospheric magnetograms from the \emph{Solar Dynamics Observatory}, we study the flare which was associated by the only one coronal mass ejection (CME) in active region (AR) 12192. The eruption of…

Solar and Stellar Astrophysics · Physics 2015-11-06 Xiaohong Li , Shuhong Yang , Huadong Chen , Ting Li , Jun Zhang

Several redback and black widow millisecond pulsar binaries have episodes of flaring in X-rays and optical. We initially detected such behavior from the Fermi selected redback candidate 1FGL J0523.5$-$2529 during optical time-series…

High Energy Astrophysical Phenomena · Physics 2022-08-31 Jules P. Halpern , Karen I. Perez , Slavko Bogdanov

(abridged) We describe highlights of the results of two observing campaigns in 2004 to investigate the correlation of flare activity in Sgr A* in different wavelength regimes, using a total of nine ground and space-based telescopes. We…

Recently, many superflares on solar-type stars were discovered as white-light flares (WLFs). A correlation between the energies (E) and durations (t) of superflares is derived as $t\propto E^{0.39}$, and this can be theoretically explained…

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

A solar active region (AR) that produces at least one M- or X-class major flare tends to produce multiple flares during its passage across the solar disk. It will be interesting if we can estimate how flare-productive a given major flaring…

Solar and Stellar Astrophysics · Physics 2018-12-12 Eo-Jin Lee , Sung-Hong Park , Yong-Jae Moon

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…

Solar and Stellar Astrophysics · Physics 2020-04-29 Natsuha Kuroda , Gregory D. Fleishman , Dale E. Gary , Gelu M. Nita , Bin Chen , Sijie Yu

We present multi-wavelength observations of an M-class flare (M3.9) that occurred on 2014 June 11. Our observations were conducted with the Dunn Solar Telescope (DST), adaptive optics, the multi-camera system ROSA (Rapid Oscillations in…

Solar and Stellar Astrophysics · Physics 2019-07-24 Damian J. Christian , David Kuridze , David B. Jess , Menoa Yousefi , Mihalis Mathioudakis

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…

The bulk of solar flare emission originates from very compact sources located in the lower solar atmosphere and seen in various wavelength ranges: near optical, UV, EUV, soft and hard X-rays, and gamma-ray emission, yet very few spatially…

Solar and Stellar Astrophysics · Physics 2015-05-28 Marina Battaglia , Eduard P. Kontar