Solar-Terrestrial Physics Solar-Terrestrial Physics Solar-Terrestrial Physics 2500-0535 65064 10.12737/stp-94202302 Results of current research Results of current research Results of current research Bright ultraviolet knots as possible sources of coherent microwave radiation Bright ultraviolet knots as possible sources of coherent microwave radiation https://orcid.org/0000-0002-6873-6394 Мешалкина Наталия Сергеевна Meshalkina Nataliya Sergeevna nata@iszf.irk.ru

кандидат физико-математических наук;

candidate of physical and mathematical sciences;

 https://orcid.org/0000-0002-1589-556X Алтынцев Александр Тимофеевич Altyntsev Alexander Timofeevich

доктор физико-математических наук;

doctor of physical and mathematical sciences;

 Институт солнечно-земной физики СО РАН Иркутск Россия Institute of Solar Terrestrial Physics SB RAS Irkutsk Russian Federation Институт солнечно-земной физики СО РАН Иркутск Россия Institute of Solar Terrestrial Physics SB RAS Irkutsk Russian Federation 28 12 2023 28 12 2023 9 4 17 24 14 06 2023 14 09 2023 https://naukaru.ru/en/nauka/article/65064/view

A distinctive feature of the September 6, 2012 event was that sources of narrow-band (2–4 GHz) sub-second pulses (SSP) were observed in small areas of flare loops with so-called bright ultraviolet knots with high plasma density up to 10¹¹ cm⁻³. Time profiles of hard X-rays of the flare, although similar to microwave light curves, do not have structures corresponding to SSP. Analysis of microwave, X-ray, and ultraviolet data has shown that the observable pulses of microwave radiation with a narrow spectral band are coherent in nature and are generated by electrons with energies of several tens of kiloelectronvolt in bright knots at a double plasma frequency. The results of the observations suggest that the appearance of bright knots is associated with local processes of energy release due to interaction of flare loops.

A distinctive feature of the September 6, 2012 event was that sources of narrow-band (2–4 GHz) sub-second pulses (SSP) were observed in small areas of flare loops with so-called bright ultraviolet knots with high plasma density up to 1011 10¹¹ cm⁻³. Time profiles of hard X-rays of the flare, although similar to microwave light curves, do not have structures corresponding to SSP. Analysis of microwave, X-ray, and ultraviolet data has shown that the observable pulses of microwave radiation with a narrow spectral band are coherent in nature and are generated by electrons with energies of several tens of kiloelectronvolt in bright knots at a double plasma frequency. The results of the observations suggest that the appearance of bright knots is associated with local processes of energy release due to interaction of flare loops.

 Sun fine temporal structure UV bright knots microwave bursts coherent emission Sun fine temporal structure UV bright knots microwave bursts coherent emission The work was financially supported by the Ministry of Science and Higher Education of the Russian Federation The work was financially supported by the Ministry of Science and Higher Education of the Russian Federation

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