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Journals / Volume 6 Issue 3 / Low-power solar flares of optical and X-ray wavelengths for solar cycles 21–24
UDC 52 UDC 55

LOW-POWER SOLAR FLARES OF OPTICAL AND X-RAY WAVELENGTHS FOR SOLAR CYCLES 21–24 Low-power solar flares of optical and X-ray wavelengths for solar cycles 21–24

Published in Untitled · Volume 6, Issue 3 · Pages 18–25 · Rubric: Results of current research
DOI: https://doi.org/10.12737/szf-63202002
Received: 20.01.2020 Accepted: 16.03.2026 Language of publication: RUS
Authors
AL
Aleksandr Borovik
ORCID
AN
Anton Zhdanov
ORCID
ABSTRACT
Using data obtained in optical and X-ray wavelengths, we have analyzed solar flare activity for cycles 21–24. Over the last three cycles, solar activity is shown to decrease significantly. As compared to solar cycle 21 (the most active over the last 50 years), in cycle 24 2–4-class large optical flares are 4.4 times rarer; 1-class flares, 8.2 times; and S-class small flares, 4.1 times. The number of X-class flares decreased 3.7 times; M-class flares, 3.2 times. This confirms that secular solar activity trends affect peak values of 11-year cycles. It is shown that optical low-power flares can be accompanied by proton fluxes and X-ray bursts of different intensity, including X-class ones. Ranges of small flare emission in soft X-rays largely overlap with emission ranges of flares of high optical classes. We have confirmed that X-ray emission from solar flares appears on average 2 min before the optical emission. The X-ray maximum for small optical flares and 1-class flares occurs approximately 1 min later; for 2–4-class flares, 2 min.
KEYWORDS
solar activity, solar flares
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