Reverse draping of magnetic field lines in the boundary layer

ISEE satellite measurements of magnetic fields in the boundary layer of the earth's magnetosphere have revealed an unexpected orientation of the field lines there that may be indicative of a ‘reverse draping.’ In many crossings of the north dawn boundary of the magnetosphere the direction of the boundary layer field lines was such as to suggest that northern high latitude segments of those field lines were being pulled tailward by the boundary layer plasma faster than were their equatorial segments. The observations are compatible with the view that plasma entry occurs at high latitudes (around the cusps) and that the field aligned current source is at high, rather than near‐equatorial, latitudes. Three‐dimensional plasma flow measurements made with the ISEE satellites showed the tailward flow in the boundary layer to have an equatorward component and this also suggests high latitude entry of plasma. Simultaneous magnetic field measurements with ISEE‐1 and 2 during a sequence of boundary crossings provided determinations of the electric currents in the boundary layer and at its interfaces with the plasma sheet and the magnetosheath. these currents were found to be largely field‐aligned and to have intensities in the range 3‐6 × 10−2 μA/m².