We continue to study the physical processes occurring during the August 17, 2001 magnetospheric storm by analyzing the dynamics of the intensity of field-aligned currents (FACs) in Iijima—Potemra Region 1 in the polar ionospheres of the two hemispheres, using the modernized magnetogram inversion technique. The results obtained on the dynamics of two types of FAC asymmetry (dawn-dusk and interhemispheric), as well as the previously obtained regularities in the behavior of Hall currents and the polar cap boundaries depending on the large azimuthal component of the interplanetary magnetic field (IMF), observed during the storm, and the seasonal behavior of the conductivity are consistent with the open magnetosphere model and with satellite observations of auroras in two hemispheres. We have shown that the weakening of the asymmetry of two types in the FAC distribution during substorms in the storm under study occurs almost completely in the winter hemisphere and is much weaker in the summer one. We associate this phenomenon with the predominance of the effect of long-term exposure to the azimuthal IMF component in the sunlit polar ionosphere of the summer hemisphere over the substorm symmetrization effect of the night magnetosphere. A symmetrization effect of the polar cap and FACs, created by the solar wind pressure pulse at the end of the storm, is observed. We propose a qualitative explanation of this effect.
polar cap, field-aligned currents, magnetospheric storms and substorms, azimuthal component of the interplanetary magnetic field, dawn–dusk and interhemispheric asymmetries
1. Cowley S.W.H. Magnetospheric asymmetries associated with the y-component of the IMF. Planet. Space Sci. 1981, vol. 29, no. 1, pp. 79–96. DOI: 10.1016/0032-0633(81)90141-0.
2. Cowley S.W.H., Lockwood M. Excitation and decay of solar-wind driven flows in the magnetosphere-ionosphere system. Ann. Geophys. 1992, vol. 10, pp. 103–115.
3. Kurikalova M.A., Mishin V.M., Mishin V.V., Lunyushkin S.B., Penskikh Y.V. Relative role of the azimuthal Pedersen current component in the substorm global electric circuit. J. Atmos. Solar-Terr. Phys. 2018, vol. 179, pp. 562–568. DOI: 10.1016/j.jastp.2018.09.014.
4. Laundal K.M., Gjerloev J.W., Østgaard N., Reistad J.P., Haaland S., Snekvik K., Tenfjord P., Ohtani S., Milan S.E. The impact of sunlight on high-latitude equivalent currents. J. Geophys. Res.: Space Phys. 2016, vol. 121, no. 3, pp. 2715–2726. DOI: 10.1002/2015ja022236.
5. Lunyushkin S.B., Mishin V.V., Karavaev Y.A., Penskikh Y.V., Kapustin V.E. Studying the dynamics of electric currents and polar caps in ionospheres of two hemispheres during the August 17, 2001 geomagnetic storm. Solar-Terr. Phys. 2019, vol. 5, no. 2, pp. 15–27. DOI: 10.12737/stp-52201903.
6. Lunyushkin S.B., Penskikh Y.V. Diagnostics of the auroral oval boundaries on the basis of the magnetogram inversion technique. Solar-Terr. Phys. 2019, vol. 5, no. 2, pp. 88–100. DOI: 10.12737/stp-52201913.
7. Mishin V.M. The magnetogram inversion technique and some applications. Space Sci. Rev. 1990, vol. 53, no. 1-2, pp. 83–163. DOI: 10.1007/bf00217429.
8. Mishin V.M., Förster M., Kurikalova M.A., Mishin V.V. The generator system of field-aligned currents during the April 06, 2000, superstorm. Adv. Space Res. 2011, vol. 48, no. 7, pp. 1172–1183. DOI: 10.1016/j.asr.2011.05.029.
9. Mishin V.M., Mishin V.V., Kurikalova M.A., Sapronova L.A., Karavaev Y.A. Positive and negative feedbacks in the magnetosphere-ionosphere coupling. J. Atmos. Solar-Terr. Phys. 2019, vol. 187, pp. 10–21. DOI: 10.1016/j.jastp.2019.03.002.
10. Parkhomov V.A., Riazantseva M.O., Zastenker G.N. Local amplification of auroral electrojet as a response to a sharp solar wind pressure pulse. Planet. Space Sci. 2005, vol. 53, no. 1, pp. 265–274. DOI: 10.1016/j.pss.2004.09.052.
11. Østgaard N., Reistad J.P., Tenfjord P., et al. The asymmetric geospace as displayed during the geomagnetic storm on August 17, 2001 // Ann. Geophys. 2018, vol. 36, no. 6, pp. 1577–1596. DOI: 10.5194/angeo-36-1577-2018.
12. URL: http://supermag.jhuapl.edu (accessed November 18, 2020).
13. URL: https://ckp-angara.iszf.irk.ru (accessed November 18, 2020).