Solar-Terrestrial Physics Solar-Terrestrial Physics Solar-Terrestrial Physics 2500-0535 69840 10.12737/stp-94202305 Results of current research Results of current research Results of current research Dynamics of small-scale magnetic fields before small and large solar flares Dynamics of small-scale magnetic fields before small and large solar flares https://orcid.org/0000-0001-5725-8262 Боровик Александр Васильевич Borovik Aleksandr Vasil'evich aborovik@iszf.irk.ru

кандидат физико-математических наук;

candidate of physical and mathematical sciences;

 https://orcid.org/0000-0002-9563-1360 Жданов Антон Андреевич Zhdanov Anton Andreevich kick.out@mail.ru 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 37 45 02 09 2023 09 11 2023 https://zh-szf.ru/en/nauka/article/69840/view

We have examined the dynamics of the longitudinal magnetic field of active region NOAA 12673, using data from the Solar Dynamics Observatory (SDO). During the passage of the active region (AR) across the solar disk, its spots and background fields showed complex motion trajectories, and numerous small-scale short-lived local polarity inversion lines (LPILs) were formed when new magnetic fluxes appeared in the AR and came closer to fields of opposite polarity. The length of LPILs was less than 15.000 km (~20 arcsec); their lifetime was several hours. Study of the flare activity of NOAA 12673 has shown that low-power flares (optical class S, area ˂2 sq. degrees) generally occur near LPILs. Before small flares and the September 06, 2017 large flare (optical importance 3B, X-ray class X9.3), in limited sites of local and main polarity inversion lines there were shear stresses and an increase in the magnetic field gradient: in the region of low-power flares, to 1.3–1.5 G/km; in the region of the large flare, 3–3.5 G/km. The results obtained suggest that the longitudinal magnetic field behaves similarly before both small and large flares.

We have examined the dynamics of the longitudinal magnetic field of active region NOAA 12673, using data from the Solar Dynamics Observatory (SDO). During the passage of the active region (AR) across the solar disk, its spots and background fields showed complex motion trajectories, and numerous small-scale short-lived local polarity inversion lines (LPILs) were formed when new magnetic fluxes appeared in the AR and came closer to fields of opposite polarity. The length of LPILs was less than 15.000 km (~20 arcsec); their lifetime was several hours. Study of the flare activity of NOAA 12673 has shown that low-power flares (optical class S, area ˂2 sq. degrees) generally occur near LPILs. Before small flares and the September 06, 2017 large flare (optical importance 3B, X-ray class X9.3), in limited sites of local and main polarity inversion lines there were shear stresses and an increase in the magnetic field gradient: in the region of low-power flares, to 1.3–1.5 G/km; in the region of the large flare, 3–3.5 G/km. The results obtained suggest that the longitudinal magnetic field behaves similarly before both small and large flares.

 flares magnetic fields polarity inversion lines flares magnetic fields polarity inversion lines The work was financially supported by Basic Research Program II.16 The work was financially supported by Basic Research Program II.16

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