Statistics of 'Cold' Early Impulsive Solar Flares in X-Ray and Microwave Domains
| Autor: | N. S. Meshalkina, Gregory D. Fleishman, Alexander T. Altyntsev, D. A. Zhdanov, A. Lysenko |
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| Rok vydání: | 2018 |
| Předmět: |
010504 meteorology & atmospheric sciences
Astrophysics::High Energy Astrophysical Phenomena Phase (waves) FOS: Physical sciences Astrophysics 01 natural sciences law.invention law 0103 physical sciences Thermal Astrophysics::Solar and Stellar Astrophysics 010303 astronomy & astrophysics Solar and Stellar Astrophysics (astro-ph.SR) 0105 earth and related environmental sciences Physics Solar flare Gamma ray X-ray Astronomy and Astrophysics Astrophysics - Solar and Stellar Astrophysics 13. Climate action Space and Planetary Science Physics::Space Physics Microwave Systematic search Flare |
| Zdroj: | The Astrophysical Journal. 856:111 |
| ISSN: | 1538-4357 |
| DOI: | 10.3847/1538-4357/aab271 |
| Popis: | Solar flares often happen after a preflare / preheating phase, which is almost or entirely thermal. In contrast, there are the so-called early impulsive flares that do not show a (significant) preflare heating but instead often show the Neupert effect--a relationship where the impulsive phase is followed by a gradual, cumulative-like, thermal response. This has been interpreted as a dominance of nonthermal energy release at the impulsive phase, even though a similar phenomenology is expected if the thermal and nonthermal energies are released in comparable amounts at the impulsive phase. Nevertheless, some flares do show a good quantitative correspondence between the nonthermal electron energy input and plasma heating, in such cases the thermal response was weak, which results in calling them "cold" flares. We undertook a systematic search of such events among early impulsive flares registered by Konus-Wind instrument in the triggered mode from 11/1994 to 04/2017 and selected 27 cold flares based on relationships between HXR (Konus-Wind) and SXR (GOES) emission. For these events we put together all available microwave data from different instruments. We obtained temporal and spectral parameters of HXR and microwave emissions of the events and examined correlations between them. We found that, compared with a `mean' flare, the cold flares: (i) are weaker, shorter, and harder in the X-ray domain, (ii) are harder and shorter, but not weaker in the microwaves, (iii) have a significantly higher spectral peak frequencies in the microwaves. We discuss the possible physical reasons for these distinctions and implication of the finding. Accepted for publication in ApJ |
| Databáze: | OpenAIRE |
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