Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, no. 61, p. 6-14 (2020)
Magnetic fields in limb solar flares on heights 2–14 Mm
V. Lozitsky, Dr Hab.
I. Yakovkin, Lab. Assist., Student
E. Kravchenko, Student
Taras Shevchenko National University of Kyiv
Abstract
We present the results of observations of two powerful limb solar flares which occured on 17 July 1981 and 14 July 2005. Spectral observations of these flares were carried out with the Echelle spectrograph of the Horizontal Solar Telescope of the Astronomical Observatory of Taras Shevchenko National University of Kyiv. In order to measure the magnetic fields in these flares, I ± V profiles of К СаІІ, HeI 4471.5 and Нα lines were studied. It was found that effective (averaged) magnetic field Вeff in the flares reached 1100–3000 G on heights 2–14 Mm. However, the spectral evidences to yet stronger fields of ~ 104 G range were found. In particular, the weak spectral evidences of large Zeeman splitting were found in first flare by HeI 4471.5 line; this evidences corresponds to superstrong magnetic field of 15.5 kG. In the second flare, Нα line has non-parallelism of bisectors of I ± V profiles which can reflect existence of 1550–3000 G fields in the flare. However, in frame of simple two-component model these observed values can correspond to true local (amplitude) magnetic fields Вmax in range 4.65–18 kG. Apparently, such superstrong magnetic fields arise in structures of a force-free type, with strong twisting of the field lines. It is precisely such field values that are necessary in solar flares for energy reasons. Indeed, solar flares emit energy in the range of 1027-1032 erg in a volume of the order of 1027 cm3. Elementary calculations show that in order to provide such energy in such a volume, the magnetic field strength should be at least 103 G. In addition, if we take into account that solar magnetic fields have the sub-telescopic (spatially unresolved) structure, then the local magnetic field intensities in the flares at the coronal level can be expected even higher.
Key words
Sun, solar activity, limb solar flares, spectral-polarization observations, Zeeman effect, strong and superstrong magnetic fields.
References
Babcock, H. W. 1953, Astrophys. Journ., 118, 387
Babin, A. N., Koval’, A. N. 2011, Bulletin of the Crimean
Astrophysical Observatory, 107, 1, 36
Babin, A. N., Koval’, A. N. 1999, Kinematika Fiz. Nebesn. Tel., 15, 1, 51
Byull. Solnech. Dannye Akad. Nauk USSR. 1981, 7
Kirichek, E. A., Solov’ev, A. A., Lozitskaya, N. I., Lozitskii, V. G. 2013, Geomagn.and Aeronomy, 53, 7, 831
Koval, A. N. Krymskaia Astrofizicheskaia Observatoriia, Izvestiia, 1977, 5, 133
Kuridze, D., Mathioudakis, М., Morgan Н. et al. 2019, The Astrophys. Journ. 874, 2, article id. 126, 12
Kurucz, R. L., Bell, В. 1995, CD-ROM No. 23. Cambridge, Mass.: Smithsonian Astrophys. Obs., https://www.cfa.harvard.edu/amp/ampdata/kurucz23/sekur.html
Livingston, W., Harvey, J. W., Malanushenko, O. V. 2006, Solar Phys., 239, 41
Lozitsky, V., Botygina, О., Masliukh, V. 2014, Bulletin of National Taras Shevchenko University of Kyiv. Astronomy, 51, 31
Lozitsky, V., Masliukh, V., Botygina, О. 2015, Bulletin of National Taras Shevchenko University of Kyiv. Astronomy, 52, 7
Lozitsky, V., Botygina, О., Masliukh, V. 2014, Bulletin of National Taras Shevchenko University of Kyiv. Astronomy, 51, 31
Lozitsky, V.G. 2016, Advances in Space Research,57, 398
Lozitsky, V. G. 1998, Kinematics and Physics of Celestial Bodies, 14, 5, 401
Lozitsky, V. G. 2015, Advances in Space Research, 55, 3, 958
Lozitsky, V. G., Baranovsky, E. A., Lozitska, N. I., Tarashchuk, V. P. 2018, Monthly Notices of the Royal Astronomical Society, 477, 2, 2796
Lozitsky, V. G., Statsenko, М. М. 2006, Elista, Kalmyk Univ., 29 May – 2 June, 43
Lozitsky, V. G., Yakovkin, І. І., Lozitska, N. I. 2020, Journ. of Physical Studies, 24, 2, 2901
Martínez González, M. J., Manso Sainz, R., Ramos, A. Asensio, Belluzzi, L. 2012, Monthly Notices of the Royal Astron. Society, 419, 1, 153
Moore, C. E. 1945, Contributions from the Princeton University Observatory, 20, 110
Scherrer, Р. Н., Bogart, R. S., Bush, R. I. et al. 1995, Solar Phys., 162, 129
Tsuneta, S., Ichimoto, K., Tatsukawa, Y. et al. 2008, Solar. Phys., 249, 2, 167