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The 'standard solar' flare model collects all physical ingredients identified by multi-wavelength observations of our Sun: magnetic reconnection, fast particle acceleration and the resulting emission at various wavelengths, especially in…

Solar and Stellar Astrophysics · Physics 2020-06-24 Wenzhi Ruan , Chun Xia , Rony Keppens

The angular distribution of electrons accelerated in solar flares is a key parameter in the understanding of the acceleration and propagation mechanisms that occur there. However, the anisotropy of energetic electrons is still a poorly…

Solar and Stellar Astrophysics · Physics 2012-12-24 Ewan Cameron Mackenzie Dickson , Eduard Kontar

Electron acceleration in the solar corona is often associated with flares and the eruption of twisted magnetic structures known as flux ropes. However, the locations and mechanisms of such particle acceleration during the flare and eruption…

Solar and Stellar Astrophysics · Physics 2016-12-14 Eoin P. Carley , Nicole Vilmer , Peter T. Gallagher

Electrons accelerated by solar flares and observed as type III solar radio bursts are not only a crucial diagnostic tool for understanding electron transport in the inner heliosphere but also a possible early indication of potentially…

Solar and Stellar Astrophysics · Physics 2024-10-16 Eduard P. Kontar , Francesco Azzollini , Olena Lyubchyk

We compare the characteristics of flare-accelerated energetic electrons at the Sun with those injected into interplanetary space. We have identified 17 energetic electron events well-observed with the SEPT instrument aboard STEREO which…

Solar and Stellar Astrophysics · Physics 2021-10-20 Nina Dresing , A. Warmuth , F. Effenberger , K. -L. Klein , S. Musset , L. Glesener , M. Brüdern

Using 2D particle-in-cell (PIC) plasma simulations we study electron acceleration by temperature anisotropy instabilities, assuming conditions typical of above-the-loop-top (ALT) sources in solar flares. We focus on the long-term effect of…

Solar and Stellar Astrophysics · Physics 2022-01-19 Mario Riquelme , Alvaro Osorio , Daniel Verscharen , Lorenzo Sironi

In large gradual solar energetic particle (SEP) events, especially the ground-level enhancement (GLE) events, where and how energetic particles are accelerated is still a problem. By using imaging data from TRACE, Yohkoh/HXT, SOHO/MDI and…

Astrophysics · Physics 2008-11-26 C. Li , Y. H. Tang , Y. Dai , W. G. Zong , C. Fang

We investigated the response of the solar atmosphere to non-thermal electron beam heating using the radiative transfer and hydrodynamics modelling code RADYN. The temporal evolution of the parameters that describe the non-thermal electron…

Solar and Stellar Astrophysics · Physics 2015-06-10 Michael B. Kennedy , Ryan O. Milligan , Joel C. Allred , Mihalis Mathioudakis , Francis P. Keenan

In general, large solar flares are more efficient at accelerating high-energy electrons than microflares. Nonetheless, we sometimes observe microflares that accelerate electrons to high energies. We statistically characterize 39 microflares…

Acceleration of particles and plasma heating is one of the fundamental problems in solar flare physics. An accurate determination of the spectrum of flare energized electrons over a broad energy range is crucial for our understanding of…

Solar and Stellar Astrophysics · Physics 2015-12-16 Marina Battaglia , Galina Motorina , Eduard P. Kontar

We report the observation of non-stationary Quasi-Periodic Pulsations (QPPs) in high-energy particles during the impulsive phase of an X4.8 flare on 2002 July 23 (SOL2002-07-23T00:35). The X4.8 flare was simultaneously measured by the…

Solar and Stellar Astrophysics · Physics 2022-06-08 Dong Li , Wei Chen

We identify a set of ~100 "cold" solar flares and perform a statistical analysis of them in the microwave range. Cold flares are characterized by a weak thermal response relative to nonthermal emission. This work is a follow up of a…

High-energy particles were recorded by near-Earth spacecraft and ground-based neutron monitors (NMs) on 2012 May 17. This event was the first ground level enhancement (GLE) of solar cycle 24. In this study, we try to identify the…

Solar and Stellar Astrophysics · Physics 2013-05-27 C. Li , Kazi A. Firoz , L. P. Sun , L. I. Miroshnichenko

We present an analysis of the plasma parameters during the initial phase of the 12 June 2010 flare (SOL2010-06-12T00:57). A peculiarity of the flare was the detection of $\gamma$--emission that is unusual for such weak and short event. The…

Solar and Stellar Astrophysics · Physics 2012-07-26 L. K. Kashapova , N. S. Meshalkina , M. S. Kisil

This work reports a peculiar and interesting train of microwave type III pair bursts in the impulsive rising phase of a solar flare on 2011 September 26. The observations include radio spectrometers at frequency of 0.80 - 2.00 GHz, hard…

Solar and Stellar Astrophysics · Physics 2016-09-28 Baolin Tan , Marian Karlicky , Hana Meszarosova , Larisa Kashapova , Jing Huang , Yan Yan , Eduard P. Kontar

The transport of the energy contained in electrons, both thermal and suprathermal, in solar flares plays a key role in our understanding of many aspects of the flare phenomenon, from the spatial distribution of hard X-ray emission to global…

Solar and Stellar Astrophysics · Physics 2016-06-22 Nicolas H. Bian , Eduard P. Kontar , A. Gordon Emslie

Recently, in a few case studies we demonstrated that gyrosynchrotron microwave emission can be detected directly from the acceleration region when the trapped electron component is insignificant. For the statistical study reported here, we…

Solar and Stellar Astrophysics · Physics 2016-07-27 Gregory D. Fleishman , Gelu M. Nita , Eduard P. Kontar , Dale E. Gary

Temporal and spectral characteristics of X-ray emission from 60 flares of intensity $\ge$C class observed by Solar X-ray Spectrometer (SOXS) during 2003-2011 are presented. We analyse the X-ray emission observed in four and three energy…

Solar and Stellar Astrophysics · Physics 2018-10-17 Veena Choithani , Rajmal Jain , Arun Kumar Awasthi , Geetanjali Singh , Sneha Chaudhari , Som Kumar Sharma

Blazars are known to emit a broad band emission from radio to gamma-rays with rapid time variations, particularly, in X- and gamma-rays. Synchrotron radiation and inverse Compton scattering are thought to play an important role in emission…

Astrophysics · Physics 2009-10-31 M. Kusunose , F. Takahara , H. Li

We report multi-wavelength observations of four solar flares on 2014 July 07. We firstly select these flares according to the soft X-ray (SXR) and extreme ultraviolet (EUV) emissions recorded by the Extreme Ultraviolet Variability…

Solar and Stellar Astrophysics · Physics 2021-05-05 Dong Li , Alexander Warmuth , Lei Lu , Zongjun Ning