Главная (Пулковская) астрономическая обсерватория РАН
Нижний Новгород, Россия
Санкт-Петербург, Россия
In this paper, we analyze images and the frequency spectrum of microwave emission in the maximum of brightness distribution in the January 20, 2022 and July 16, 2023 flares recorded by the Siberian Radioheliograph in the 3–6 GHz and 6–12 GHz ranges. We use the obtained spectrum data for radio diagnostics of magnetic field strength and orientation, plasma density, and parameters of accelerated particles in a radio source. The radio diagnostics is carried out by a method based on minimizing the functional containing the intensities of theoretically calculated and observed frequency spectra of left-polarized and right-polarized emission. Since the form of such a multidimensional functional is quite complex, and it is not possible to minimize it by standard approaches, we employ a genetic minimization method. The radio diagnostics allows us to determine features of the dynamics of the magnetic field intensity and orientation, as well as the density and the energy spectral index of non-thermal electrons in the region of maximum brightness of the radio source. We have found that during the growth phase of the main radiation peaks the magnetic field decreases, whereas during the decay phase, on the contrary, it increases. The rate of these changes varies from a few G/s to 11 G/s for the January 20, 2022 flare and is about 1 G/s for the July 16, 2023 flare.
solar flares, radioheliograph, radio diagnostics, magnetic field
1. Altyntsev A.T., Lesovoi S.V., Globa M.V., Gubin A.V., Kochanov A.A., Grechnev V.V., et al. Multiwave Siberian Radioheliograph. Solar-Terr. Phys. 2020, vol. 6, no. 2, pp. 30–40. DOI:https://doi.org/10.12737/stp-62202003.
2. Bogachev S.A., Somov B.V. Comparison of the Fermi and betatron acceleration efficiencies in collapsing magnetic traps. Astrophys. J. Lett. 2005, vol. 31, no. 8, pp. 537–545. DOI:https://doi.org/10.1134/1.2007030.
3. Christiansen U., Högbom I. Radioteleskopy [Radio telescopes]. Moscow, Mir Publ., 1988, p. 294. (In Russian).
4. Condon J.J. Errors in Elliptical Gaussian Fits. Publications of the Astronomical Society of the Pacific. 1997, vol. 109, pp. 166–172. DOI:https://doi.org/10.1086/133871.
5. Dulk G. Radio emission from the Sun and stars. Ann. Rev. Astron. Astrophys. 1985, vol. 23, pp. 169–224. DOI: 10.1146/ annurev.aa.23.090185.001125.
6. Fleishman G.D., Melnikov V.F. Gyrosynchrotron emission from anisotropic electron distributions. Astrophys. J. 2003, vol. 587, no. 2, pp. 823–835. DOI:https://doi.org/10.1086/368252.
7. Fleishman G.D., Kuznetsov A.A. Fast gyrosynchrotron codes. Astrophys. J. 2010, vol. 721, no. 2, pp. 1127–1141. DOI:https://doi.org/10.1088/0004-637X/721/2/1127.
8. Fleishman G.D., Nita G.M., Gary D.E. Dynamic magnetography of solar flaring loops. Astrophys. J. Lett. 2009, vol. 698, no. 2, pp. 183–187. DOI:https://doi.org/10.1088/0004-637X/698/2/L183.
9. Fleishman G.D., Gary D.E., Chen B., Kuroda N., Yu S., Nita G.M. Decay of the coronal magnetic field can release sufficient energy to power a solar flare. Science. 2020, vol. 367, no. 6475, pp. 278–280. DOI:https://doi.org/10.1126/science.aax6874.
10. Fleishman G.D., Nita G.M., Chen B., Yu S., Gary D.E. Solar flare accelerates nearly all electrons in a large coronal volume. Nature. 2022, vol. 606, pp. 674–677. DOI:https://doi.org/10.1038/s41586-022-04728-8.
11. Gary D.E., Fleishman G.D., Nita G.M. Magnetography of solar flaring loops with microwave imaging spectropolarimetry. Solar Phys. 2013, vol. 288, no. 2, pp. 549–565. DOI: 10.1007/ s11207-013-0299-3.
12. Gary D.E., Chen B., Dennis B.R., Fleishman G.D., Hurford G.J., Krucker S., et al. Microwave and hard X-ray observations of the 2017 September 10 solar limb flare. Astrophys. J. 2018, vol. 863, no. 1, 9 p. DOI:https://doi.org/10.3847/1538-4357/aad0ef.
13. Kuznetsov S.A., Melnikov V.F. Modeling the effect of dense plasma on the dynamics of the microwave spectrum of solar flaring loops. Geomagnetism and Aeronomy. 2012, vol. 52, no. 7, pp. 883–891.
14. Morgachev A.S., Kuznetsov S.A., Melnikov V.F. Radio diagnostics of the solar flaring loop parameters by direct fitting method. Geomagnetism and Aeronomy. 2014, vol. 54, no. 7, pp. 933–942. DOI:https://doi.org/10.1134/S0016793214070081.
15. Parker E.N. Cosmical Magnetic Fields. Part 1. Clarendon Press, Oxford, 1979.
16. Razin V.A. To the Theory of radio emission spectra caused by discrete sources at frequencies lower than 30 MHz. Izvestiya vysshih uchebnyh zavedenij. Radiofizika [News of higher educational institutions. Radiophysics]. 1960, vol. 3, no. 4, pp. 584–594. (In Russian).
17. Reznikova V.E., Melnikov V.F., Shibasaki K., Gorbikov S.P., Pyatakov N.P., Myagkova I.N., Ji H. 2002 August 24 limb flare loop: dynamics of microwave brightness distribution. Astrophys. J. 2009, vol. 697, pp. 735–746.
18. Solov’ev A.A., Kirichek E.A. Properties of the flare energy release in force-free magnetic flux ropes. Astron. Lett. 2023, vol. 49, no. 5, pp. 257–269. DOI:https://doi.org/10.1134/S1063773723050055.
19. Somov B.V., Kosugi T. Collisionless reconnection and high-energy particle acceleration in solar flares. Astrophys. J. 1997, vol. 485, no. 2, pp. 859−868. DOI:https://doi.org/10.1086/304449.
20. Wu Zh., Kuznetsov A., Anfinogentov S., Melnikov V., Sych R., et al. A multipeak solar flare with a high turnover frequency of the gyrosynchrotron spectra from the loop-top source. Astrophys. J. 2024, vol. 968, no. 1, 11 p. DOI: 10.3847/ 1538-4357/ad46ff.
21. Yan Y., Chen Z., Wang W., Liu F., Geng L., Chen L., et al. Mingantu spectral radioheliograph for solar and space weather studies. Frontiers in Astronomy and Space Sciences. 2021, vol. 8:584043. DOI:https://doi.org/10.3389/fspas.2021.584043.
22. Zirin H., Baumert B.M., Hurford G.J. The microwave brightness temperature spectrum of the quiet Sun. Astrophys. J. 1991, vol. 370, pp. 779–783. DOI:https://doi.org/10.1086/169861
