Solar-Terrestrial Physics Solar-Terrestrial Physics Solar-Terrestrial Physics 2500-0535 103599 10.12737/stp-113202513 The 15th Russian-Chinese Workshop on Space Weather, September 9–13, 2024, Institute of Solar-Terrestrial Physics SB RAS, Irkutsk, Russia The 15th Russian-Chinese Workshop on Space Weather, September 9–13, 2024, Institute of Solar-Terrestrial Physics SB RAS, Irkutsk, Russia The 15th Russian-Chinese Workshop on Space Weather, September 9–13, 2024, Institute of Solar-Terrestrial Physics SB RAS, Irkutsk, Russia The Rayleigh—Taylor instability as a trigger of solar flares The Rayleigh—Taylor instability as a trigger of solar flares Степанов Александр Владимирович Stepanov Aleksandr Vladimirovich stepanov@gaoran.ru

доктор физико-математических наук;

doctor of physical and mathematical sciences;

 Зайцев Валерий Васильевич Zaitsev Valeriy Vasilyevich za130@ipfran.ru

доктор физико-математических наук;

doctor of physical and mathematical sciences;

 Главная (Пулковская) астрономическая обсерватория РАН Санкт-Петербург Россия Central Astronomical Observatory at Pulkovo St. Petersburg Russian Federation Физико-технический институт им. А.Ф. Иоффе Санкт-Петербург Россия Ioffe Institute St. Petersburg Russian Federation Институт прикладной физики им. А.В. Гапонова-Грехова РАН Нижний Новгород Россия Institute of Applied Physics RAS Nizhny Novgorod Russian Federation 22 09 2025 22 09 2025 11 3 114 119 04 03 2025 03 04 2025 https://zh-szf.ru/en/nauka/article/103599/view

The review of authors’ papers is devoted to the essential role of the Rayleigh—Taylor instability (RTI) as a trigger of flare energy release. We have analyzed two cases of RTI: near coronal loop footpoints and at the loop top. RTI near loop footpoints requires pre-heating of chromospheric plasma. This pre-heating can be realized due to Joule dissipation in partially ionized plasma under condition of the Cowling resistivity. RTI at the loop top arises in current-carrying coronal loop loaded by prominence. We have determined the conditions of RTI as a flare trigger in both cases. It is shown that RTI generates super-Dreicer electric field in the chromospheric parts of a loop. This is the promising solution of longstanding “number problem” of particle acceleration. RTI can be also a cause of prompt (~10 s) hot onset precursor events (HOPE).

The review of authors’ papers is devoted to the essential role of the Rayleigh—Taylor instability (RTI) as a trigger of flare energy release. We have analyzed two cases of RTI: near coronal loop footpoints and at the loop top. RTI near loop footpoints requires pre-heating of chromospheric plasma. This pre-heating can be realized due to Joule dissipation in partially ionized plasma under condition of the Cowling resistivity. RTI at the loop top arises in current-carrying coronal loop loaded by prominence. We have determined the conditions of RTI as a flare trigger in both cases. It is shown that RTI generates super-Dreicer electric field in the chromospheric parts of a loop. This is the promising solution of longstanding “number problem” of particle acceleration. RTI can be also a cause of prompt (~10 s) hot onset precursor events (HOPE).

 Sun flare trigger Joule dissipation particle acceleration Sun flare trigger Joule dissipation particle acceleration The work was financially supported by RSF (Grant No. 22-12-00308-P) The work was financially supported by RSF (Grant No. 22-12-00308-P)

Alfvén H., Carlqvist P. Currents in the solar atmosphere and a theory of solar flares. Solar Phys. 1967, vol. 1, p. 220–228. DOI: 10.1007/BF00150857. Alfvén H., Carlqvist P. Currents in the solar atmosphere and a theory of solar flares. Solar Phys. 1967, vol. 1, p. 220–228. DOI: 10.1007/BF00150857. Andreev G.V. Calculation of ionization cross-section by electron shock for hydrogen and nitrogen atoms. Physical-Chemical Kinetics in Gas Dynamics. 2010, vol. 9, pp. 1–2. (In Russian). Andreev G.V. Calculation of ionization cross-section by electron shock for hydrogen and nitrogen atoms. Physical-Chemical Kinetics in Gas Dynamics. 2010, vol. 9, pp. 1–2. (In Russian). Awasthi A.K., Jain R. Multi-wavelength diagnostics of precursor phase in solar flares. First Asia-Pacific Solar Physics Meeting. Astron. Soc. India Conf. 2011, vol. 2, pp. 297–305. Awasthi A.K., Jain R. Multi-wavelength diagnostics of precursor phase in solar flares. First Asia-Pacific Solar Physics Meeting. Astron. Soc. India Conf. 2011, vol. 2, pp. 297–305. Battaglia A.F., Hudson H., Warmuth A., et al. The existence of hot X-ray onsets in solar flares. Astron. Astrophys. 2023, vol. 679, article number A139. DOI: 10.1051/0004-6361/202347706. Battaglia A.F., Hudson H., Warmuth A., et al. The existence of hot X-ray onsets in solar flares. Astron. Astrophys. 2023, vol. 679, article number A139. DOI: 10.1051/0004-6361/202347706. Brown J.C. On the ionization of hydrogen in optical flares. Solar Phys. 1973, vol. 29, pp. 421–427. DOI: 10.1007/BF00150822. Brown J.C. On the ionization of hydrogen in optical flares. Solar Phys. 1973, vol. 29, pp. 421–427. DOI: 10.1007/BF00150822. da Silva D. F., Hui L., Simoes P.J.A., et al. Statistical analysis of the onset temperature of solar flares in 2010–2011. Monthly Notices of the Royal Astronomical Society. 2023, vol. 525, iss. 3, pp. 4143–4148. DOI: 10.1093/mnras/stad2244. da Silva D. F., Hui L., Simoes P.J.A., et al. Statistical analysis of the onset temperature of solar flares in 2010–2011. Monthly Notices of the Royal Astronomical Society. 2023, vol. 525, iss. 3, pp. 4143–4148. DOI: 10.1093/mnras/stad2244. Emslie A.G., Henoux J.-C. The electrical current structure associated with solar flare electrons accelerated by large-scale electric fields. Astrophys. J. 1995, vol. 446, p. 371. DOI: 10.1086/175796. Emslie A.G., Henoux J.-C. The electrical current structure associated with solar flare electrons accelerated by large-scale electric fields. Astrophys. J. 1995, vol. 446, p. 371. DOI: 10.1086/175796. Fritzová-Švestková L., Švestka Z. Electron density in flares. II Results of measurement. Solar Phys. 1967, vol. 2, pp. 87–97. DOI: 10.1007/BF00155894. Fritzová-Švestková L., Švestka Z. Electron density in flares. II Results of measurement. Solar Phys. 1967, vol. 2, pp. 87–97. DOI: 10.1007/BF00155894. Giovanelli R.G. A theory of chromospheric flares. Nature. 1946, vol. 158, pp. 81–82. DOI: 10.1038/158081a0. Giovanelli R.G. A theory of chromospheric flares. Nature. 1946, vol. 158, pp. 81–82. DOI: 10.1038/158081a0. Hoyng P., Brown J.C., van Beek H.F. High time resolution analysis of solar hard X-ray flares observed on board the ESRO TD-1A satellite, Solar Phys. 1976, vol. 48, P.197–254. DOI: 10.1007/BF00151992. Hoyng P., Brown J.C., van Beek H.F. High time resolution analysis of solar hard X-ray flares observed on board the ESRO TD-1A satellite, Solar Phys. 1976, vol. 48, P.197–254. DOI: 10.1007/BF00151992. Hudson H., Simoes P.J.A., Fletcher L., et al. Hot X-ray onsets of solar flares. Monthly Notices of the Royal Astronomical Society. 2021, vol. 501, iss. 1, pp. 1273–1281. DOI: 10.1093/mnras/staa3664. Hudson H., Simoes P.J.A., Fletcher L., et al. Hot X-ray onsets of solar flares. Monthly Notices of the Royal Astronomical Society. 2021, vol. 501, iss. 1, pp. 1273–1281. DOI: 10.1093/mnras/staa3664. Kane S.R., Hurley K., McTiernan J.M., et al. Energy release and dissipation during giant solar flares. Astrophys. J. Lett. 1995, vol. 446, p. L47. DOI: 10.1086/187927. Kane S.R., Hurley K., McTiernan J.M., et al. Energy release and dissipation during giant solar flares. Astrophys. J. Lett. 1995, vol. 446, p. L47. DOI: 10.1086/187927. Kumar P., Srivastava A.K., Somov, B.V., et al. Evidence of solar flare triggering due to loop-loop interaction caused by footpoint shear motion. Astrophys. J. 2010, vol. 723, pp. 1651–1664. DOI: 10.1088/0004-637X/723/2/1651. Kumar P., Srivastava A.K., Somov, B.V., et al. Evidence of solar flare triggering due to loop-loop interaction caused by footpoint shear motion. Astrophys. J. 2010, vol. 723, pp. 1651–1664. DOI: 10.1088/0004-637X/723/2/1651. Kusano K., Bamba Y., Yamamoto T.T. Magnetic field structures triggering solar flares and coronal mass ejections. Astrophys. J. 2012, vol. 760, no. 1, p. 31. DOI: 10.1088/0004-637X/760/1/31. Kusano K., Bamba Y., Yamamoto T.T. Magnetic field structures triggering solar flares and coronal mass ejections. Astrophys. J. 2012, vol. 760, no. 1, p. 31. DOI: 10.1088/0004-637X/760/1/31. Ledentsov L. Thermal trigger for solar flares I: Fragmentation of the preflare current layer. Solar Phys. 2021, vol. 296, article number 74. DOI: 10.1007/s11207-021-01817-1. Ledentsov L. Thermal trigger for solar flares I: Fragmentation of the preflare current layer. Solar Phys. 2021, vol. 296, article number 74. DOI: 10.1007/s11207-021-01817-1. Masuda S., Kosugi T., Hara H., et al. A loop-top hard X-ray source in a compact solar flare as evidence for magnetic reconnection. Nature. 1994, vol. 371, pp. 495–497. DOI: 10.1038/371495a0. Masuda S., Kosugi T., Hara H., et al. A loop-top hard X-ray source in a compact solar flare as evidence for magnetic reconnection. Nature. 1994, vol. 371, pp. 495–497. DOI: 10.1038/371495a0. Meshalkina N.S., Altyntsev A.T. Heating manifestations at the onset of the 29 June 2012 flare. Solar-Terrestrial Physics. 2024, vol. 10, iss. 3, pp/ 1–17. DOI: 10.12737/stp-103202402. Meshalkina N.S., Altyntsev A.T. Heating manifestations at the onset of the 29 June 2012 flare. Solar-Terrestrial Physics. 2024, vol. 10, iss. 3, pp/ 1–17. DOI: 10.12737/stp-103202402. Melrose D.B. Neutralized and unneutralized current patterns in the solar corona. Astrophys. J. 1991, vol. 381, p. 306. DOI: 10.1086/170652. Melrose D.B. Neutralized and unneutralized current patterns in the solar corona. Astrophys. J. 1991, vol. 381, p. 306. DOI: 10.1086/170652. Miller J.A., Cargill P.J., Emslie A.G., et al. Critical issues for understanding particle acceleration in impulsive solar flares. J. Geophys. Res. 1997, vol. 102, pp. 14631–14659. DOI: 10.1029/97JA00976. Miller J.A., Cargill P.J., Emslie A.G., et al. Critical issues for understanding particle acceleration in impulsive solar flares. J. Geophys. Res. 1997, vol. 102, pp. 14631–14659. DOI: 10.1029/97JA00976. Pustil’nik L.A. Instability of quiescent prominences and the origin of solar flares. Soviet Astronomy. 1974, vol. 17, p. 763. Pustil’nik L.A. Instability of quiescent prominences and the origin of solar flares. Soviet Astronomy. 1974, vol. 17, p. 763. Sharykin I.N., Kosovichev A.G. Dynamics of electric currents, magnetic field topology, and helioseismic response of a solar flare. Astrophys. J. 2015, vol. 808, no.1. DOI: 10.1088/0004-637X/808/1/72. Sharykin I.N., Kosovichev A.G. Dynamics of electric currents, magnetic field topology, and helioseismic response of a solar flare. Astrophys. J. 2015, vol. 808, no.1. DOI: 10.1088/0004-637X/808/1/72. Somov B.V. Magnetic reconnection and topological trigger in physics of large solar flares. ?2008, vol. 17, no. 2-3, pp. 421–454. DOI: 10.48550/arXiv.0901.4697. Somov B.V. Magnetic reconnection and topological trigger in physics of large solar flares. ?2008, vol. 17, no. 2-3, pp. 421–454. DOI: 10.48550/arXiv.0901.4697. Stepanov A.V., Zaitsev V.V. Magnetospheres of Active Regions of the Sun and Stars. Moscow, Fizmatlit Publ., 2018, 387 p. (In Russian). Stepanov A.V., Zaitsev V.V. Magnetospheres of Active Regions of the Sun and Stars. Moscow, Fizmatlit Publ., 2018, 387 p. (In Russian). Stepanov A.V., Zaitsev V.V., Kupriyanova E.G. Features of electric current dissipation in the solar atmosphere. Geomagnetism and Aeronomy. 2024, vol. 64, pp. 1203–1214. DOI: 10.1134/S001679322470030. Stepanov A.V., Zaitsev V.V., Kupriyanova E.G. Features of electric current dissipation in the solar atmosphere. Geomagnetism and Aeronomy. 2024, vol. 64, pp. 1203–1214. DOI: 10.1134/S001679322470030. Struminsky A.B. Sadovsky A.M., Grogoryeva I.Yu. Criteria for forecasting proton events from real time solar observations. Geomagnetism and Aeronomy. 2024, vol. 64, no. 2, pp. 139–149. DOI: 10.1134/S0016793223600984. Struminsky A.B. Sadovsky A.M., Grogoryeva I.Yu. Criteria for forecasting proton events from real time solar observations. Geomagnetism and Aeronomy. 2024, vol. 64, no. 2, pp. 139–149. DOI: 10.1134/S0016793223600984. Syrovatskii S.I. Current sheet characteristics and thermal trigger of solar flares. Soviet Astronomy Letters. 1976, vol. 2, p. 13. Syrovatskii S.I. Current sheet characteristics and thermal trigger of solar flares. Soviet Astronomy Letters. 1976, vol. 2, p. 13. Verner D.A., Ferland C.J. Atomic data for astrophysics. I. Radiative recombination rates for H-like, He-like, Li-like, and Na-like ions over a broad range of temperature. Astrophys. J. Suppl. Ser. 1996, vol. 103, no. 2, pp. 467–473. DOI: 10.1086/192284. Verner D.A., Ferland C.J. Atomic data for astrophysics. I. Radiative recombination rates for H-like, He-like, Li-like, and Na-like ions over a broad range of temperature. Astrophys. J. Suppl. Ser. 1996, vol. 103, no. 2, pp. 467–473. DOI: 10.1086/192284. Veronig A., Vršnak B., Dennis B.R., et al. Investigation of the Neupert effect in solar flares. I. Statistical properties and the evaporation model. Astron. Astrophys. 2002, vol. 392, no. 2, pp. 699–712. DOI: 10.1051/0004-6361:20020947. Veronig A., Vršnak B., Dennis B.R., et al. Investigation of the Neupert effect in solar flares. I. Statistical properties and the evaporation model. Astron. Astrophys. 2002, vol. 392, no. 2, pp. 699–712. DOI: 10.1051/0004-6361:20020947. Wang H., Liu Ch., Ahn K., et al. High-resolution observations of flare precursors in the low solar atmosphere. Nature Astronomy. 2017, vol. 1, article number 0085. DOI: 10.1038/s41550-017-0085. Wang H., Liu Ch., Ahn K., et al. High-resolution observations of flare precursors in the low solar atmosphere. Nature Astronomy. 2017, vol. 1, article number 0085. DOI: 10.1038/s41550-017-0085. Zaitsev V.V. Ultrafine magnetic structures in the chromosphere. Geomagnetism and Aeronomy. 2015, vol. 55, pp. 846–849. DOI: 10.1134/S0016793215070294. Zaitsev V.V. Ultrafine magnetic structures in the chromosphere. Geomagnetism and Aeronomy. 2015, vol. 55, pp. 846–849. DOI: 10.1134/S0016793215070294. Zaitsev V.V., Stepanov A.V. Towards the circuit theory of solar flares. Solar Phys. 1992, vol. 139, pp. 343–356. DOI: 10.1007/BF00159158. Zaitsev V.V., Stepanov A.V. Towards the circuit theory of solar flares. Solar Phys. 1992, vol. 139, pp. 343–356. DOI: 10.1007/BF00159158. Zaitsev V.V., Urpo S., Stepanov A.V. Temporal dynamics of Joule heating and DC-electric field acceleration in single flare loop. Astron. Astrophys. 2000, vol. 357, pp. 1105–1114. Zaitsev V.V., Urpo S., Stepanov A.V. Temporal dynamics of Joule heating and DC-electric field acceleration in single flare loop. Astron. Astrophys. 2000, vol. 357, pp. 1105–1114. Zaitsev V.V., Stepanov A.V. Particle acceleration and plasma heating in the chromosphere. Solar Phys. 2015, vol. 290, pp. 3559–3572. DOI: 10.1007/s11207-015-0731-y. Zaitsev V.V., Stepanov A.V. Particle acceleration and plasma heating in the chromosphere. Solar Phys. 2015, vol. 290, pp. 3559–3572. DOI: 10.1007/s11207-015-0731-y. Zaitsev V.V., Stepanov A.V. On the nature of fast X-ray precursors of solar flares. Astronomy Lett. 2025, vol. 51, no. 1. (In print). Zaitsev V.V., Stepanov A.V. On the nature of fast X-ray precursors of solar flares. Astronomy Lett. 2025, vol. 51, no. 1. (In print). Zaitsev V.V., Kronshtadtov P.V., Stepanov A.V. Rayleigh — Taylor instability and excitation of super-Dreicer electric fields in the solar chromosphere. Solar Phys. 2016, vol. 291, pp. 3451–3459. DOI: 10.1007/s11207-016-0983-1. Zaitsev V.V., Kronshtadtov P.V., Stepanov A.V. Rayleigh — Taylor instability and excitation of super-Dreicer electric fields in the solar chromosphere. Solar Phys. 2016, vol. 291, pp. 3451–3459. DOI: 10.1007/s11207-016-0983-1. Zaitsev V.V., Stepanov A.V., Kronshtadtov P.V. On the possibility of heating the solar corona by heat fluxes from coronal magnetic structures. Solar Phys. 2020, vol. 295, article number 166. DOI: 10.1007/s11207-020-01732-x. Zaitsev V.V., Stepanov A.V., Kronshtadtov P.V. On the possibility of heating the solar corona by heat fluxes from coronal magnetic structures. Solar Phys. 2020, vol. 295, article number 166. DOI: 10.1007/s11207-020-01732-x. Zimovets I.V., Sharykin I.N., Gan W.Q. Relationships between photospheric vertical electric currents and hard X-ray sources in solar flares: Statistical study. Astrophys. J. 2020, vol. 891, no. 2. DOI: 10.3847/1538-4357/ab75be. Zimovets I.V., Sharykin I.N., Gan W.Q. Relationships between photospheric vertical electric currents and hard X-ray sources in solar flares: Statistical study. Astrophys. J. 2020, vol. 891, no. 2. DOI: 10.3847/1538-4357/ab75be.