The warped neutral sheet and plasma sheet in the near‐Earth geomagnetic tail

Abstract

An analysis of ISEE 2 plasma and magnetic field data indicates that the plasma sheet and neutral sheet in the near‐earth (X > −19 RE) magnetotail are warped in such a manner that in summer (winter) the neutral sheet rises above (dips below) the solar magnetospheric equatorial plane near the center of the tail but dips below (rises above) the equatorial plane along the tail flanks. In the near tail the neutral sheet crosses the equatorial plane ∼12 RE from the aberrated X axis, considerably closer to the center of the tail than has been inferred from data obtained farther (−16 > X > −40 RE) downstream. This increase in the warp with decreasing distance from the earth is consistent with theoretical predictions. In the near tail the warp is sufficiently strong when the dipole tilt angle is large that even in quiet times the upper or lower edge of the plasma sheet can be found close to the solar magnetospheric equatorial plane along the tail flanks. The seasonal dependence of the warp can produce certain dawn‐dusk asymmetries in satellite data which are more apparent than real.