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High-energy solar flares have shown to have at least two distinct phases: prompt-impulsive and delayed-gradual. Identifying the mechanism responsible for accelerating the electrons and ions and the site at which it occurs during these two…

Solar and Stellar Astrophysics · Physics 2021-09-29 Melissa Pesce-Rollins , Nicola Omodei , Vahe' Petrosian , Francesco Longo

The Sun is one of the most luminous $\gamma$-ray sources in the sky and continues to challenge our understanding of its high-energy emission mechanisms. This study provides an in-depth investigation of the solar disk $\gamma$-ray emission,…

High Energy Astrophysical Phenomena · Physics 2024-02-28 Bruno Arsioli , Elena Orlando

The sustained gamma-ray emission (SGRE) events from the Sun are associated with an ultrafast (2000 km/s or greater) halo coronal mass ejection (CME) and a type II radio burst in the decameter-hectometric (DH) wavelengths. The SGRE duration…

High Energy Astrophysical Phenomena · Physics 2021-08-26 Nat Gopalswamy , Pertti Mäkelä , Seiji Yashiro

Solar flares and X-ray plasma ejections (XPEs) occur simultaneously but usually are separated spatially. We present two exceptional events observed by {\sl Yohkoh} in 2001 October 2 (event 1) and 2000 October 16 (event 2), in which features…

Solar and Stellar Astrophysics · Physics 2013-03-11 Michal Tomczak

Gamma-ray emitting solar flares observed with Yohkoh were analyzed from a statistical viewpoint. The four-band hard X-ray (15--95 keV) photometric data, taken with the Hard X-ray Telescope onboard Yohkoh, were utilized in combination with…

The solar disk is a bright gamma-ray source. Surprisingly, its flux is about one order of magnitude higher than predicted. As a first step toward understanding the physical origin of this discrepancy, we perform a new analysis in 1-100 GeV…

High Energy Astrophysical Phenomena · Physics 2016-07-13 Kenny C. Y. Ng , John F. Beacom , Annika H. G. Peter , Carsten Rott

We report on the Fermi-LAT detection of high-energy emission from the behind-the-limb (BTL) solar flares that occurred on 2013 October 11, and 2014 January 6 and September 1. The Fermi-LAT observations are associated with flares from active…

We report on the linear relationship between the durations of two types of electromagnetic emissions associated with shocks driven by coronal mass ejections: sustained gamma-ray emission (SGRE) and interplanetary type II radio bursts. The…

Solar and Stellar Astrophysics · Physics 2018-10-23 N. Gopalswamy , P. Makela , S. Yashiro , A. Lara , H. Xie , S. Akiyama , R. J. MacDowall

Context: Solar flares release a large fraction of their energy into non-thermal electrons, but it is not clear where and how. Bremsstrahlung X-rays are observed from the corona and chromosphere. Aims: We aim to characterize the acceleration…

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

Solar flares are highly energetic events that happen in the solar atmosphere. They are mostly observed as X-ray or gamma-ray bursts located on the Sun's surface. While they are known to be sites of particle acceleration, the acceleration…

Solar and Stellar Astrophysics · Physics 2023-10-25 Jonathan Mauro , Gwenhaël de Wasseige

We compare the gamma-ray photon flux variability of northern blazars in the Fermi/LAT First Source Catalog with 37 GHz radio flux density curves from the Metsahovi quasar monitoring program. We find that the relationship between…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-27 J. Leon-Tavares , E. Valtaoja , M. Tornikoski , A. Lahteenmaki , E. Nieppola

This review discusses the complementary relationship between radio and hard X-ray observations of the Sun using primarily results from the era of the Reuven Ramaty High Energy Solar Spectroscopic Imager satellite. A primary focus of joint…

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

Explosive transient events occur throughout the solar atmosphere. The differing manifestations range from coronal mass ejections to Ellerman bombs. The former may have negligible signatures in the lower atmosphere, and the latter may have…

Solar and Stellar Astrophysics · Physics 2024-08-06 L. P. Chitta , I. G. Hannah , L. Fletcher , H. S. Hudson , P. R. Young , S. Krucker , H. Peter

We investigate the X-ray and UV emission detected by RHESSI and TRACE in the context of a solar flare on the 16th November 2002 with the goal of better understanding the evolution of the flare. We analysed the characteristics of the X-ray…

Solar and Stellar Astrophysics · Physics 2015-06-11 Hamish A. S. Reid , Nicole Vilmer , Guillaume Aulanier , Etienne Pariat

X-ray observations of solar flares routinely reveal an impulsive high-energy and a gradual low-energy emission component, whose relationship is one of the key issues of solar flare study. The gradual and impulsive emission components are…

Solar and Stellar Astrophysics · Physics 2015-05-20 Jingnan Guo , Siming Liu , Lyndsay Fletcher , Eduard P. Kontar

We compare the gamma-ray photon flux variability of northern blazars in the Fermi/LAT First Source Catalog with 37 GHz radio flux density curves from the Metsahovi quasar monitoring program. We find that the relationship between…

High Energy Astrophysical Phenomena · Physics 2011-10-25 J. Leon-Tavares , E. Valtaoja , M. Tornikoski , A. Lahteenmaki , E. Nieppola

A time series of soft X-ray emission observed on 1974-2007 years (GOES) is analyzed. We show that in the periods of high solar activity 1977-1981, 1988-1992, 1999-2003 the energy statistics of soft X-ray solar flares for class M and C is…

Astrophysics · Physics 2011-11-15 A. A. Stanislavsky , K. Burnecki , M. Magdziarz , A. Weron , K. Weron

The hard X-ray emission in a solar flare is typically characterized by a number of discrete sources, each with its own spectral, temporal, and spatial variability. Establishing the relationship amongst these sources is critical to determine…

Solar and Stellar Astrophysics · Physics 2018-08-08 Federica Sciacchitano , Alberto Sorrentino , A Gordon Emslie , Anna Maria Massone , Michele Piana