Convection and field-aligned currents, related to polar cap arcs, during strongly northward IMF (11 January 1983) |
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| Authors: | PL Israelevich IM Podgorny AK Kuzmin NS Nikolaeva EM Dubinin |
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| Institution: | Space Research Institute, Academy of Sciences U.S.S.R., 117810, Moscow, Profsoyuznaya 84/32, U.S.S.R. |
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| Abstract: | Electric and magnetic fields and auroral emissions have been measured by the Intercosmos-Bulgaria-1300 satellite on 10–11 January 1983. The measured distributions of the plasma drift velocity show that viscous convection is diminished in the evening sector under IMF By < 0 and in the morning sector if IMF By > 0. A number of sun-aligned polar cap arcs were observed at the beginning of the period of strongly northward IMF and after a few hours a θ-aurora appeared. The intensity of ionized oxygen emission O+(2P), 7320 Å] increased significantly reaching up to several kilo-Rayleighs in the polar cap arc. A complicated pattern of convection and field-aligned currents existed in the nightside polar cap which differed from the four-cell model of convection and NBZ field-aligned current system. This pattern was observed during 12 h and could be interpreted as six large scale field-aligned current sheets and three convective vortices inside the polar cap. Sun-aligned polar cap arcs may be located in regions both of sunward and anti-sunward convection. Structures of smaller spatial scale correspond to the boundaries of hot plasma regions related to polar cap arcs. Obviously these structures are due to S-shaped distributions of electric potential. Parallel electric fields in these S-structures provide electron acceleration up to 1 keV at the boundaries of polar cap arcs. The pairs of field-aligned currents correspond to those S-structures: a downward current at the external side of the boundary and an upward current at the internal side of it. |
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