| Popis: |
We report on field-aligned currents (FAC) ob- tained from precise magnetic field measurements made on- board the Orsted and Magsat satellites when the interplan- etary magnetic field (IMF) was near zero. We found that Region 1/Region 2 currents persist through southward IMF, IMF - 0, and northward IMF; also the central area of both the northern and southern polar caps is always filled with FACs, even during slightly southward IMF. A statis- tical distribution of the latter currents resembles the day- side NBZ system with the downward/upward currents at post-noon/pre-noon hours, discovered earlier from Magsat observations. We hypothesize that the quasi-viscous inter- action of the solar wind with the magnetospheric lobes may cause a sunward convection of the lobes' field lines through the bunch's core, effectively mapping the FACs of NBZ-type down to the near-pole area. |
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