Field-aligned currents during IMF similar to 0

We report on field-aligned currents (FAC) obtained from precise magnetic fi eld measurements made onboard the Orsted and Magsat satellites when the int erplanetary magnetic field (IMF) was near zero. We found that Region 1/Regi on 2 currents persist through southward IMF, IMF similar to 0, and northwar d IMF; also the central area of both the northern and southern polar caps i s always filled with FACs, even during slightly southward IMF. A statistica l distribution of the latter currents resembles the dayside NBZ system with the downward/upward currents at post-noon/pre-noon hours, discovered earli er from Magsat observations. We hypothesize that the quasi-viscous interact ion of the solar wind with the magnetospheric lobes may cause a sunward con vection of the lobes' field lines through the bunch's core, effectively map ping the FACs of NBZ-type down to the near-pole area.