Vortices in magnetospheric plasma flow

Vortical motion in the early morning sector of the plasma sheet was detected by means of two-dimensional and three-dimensional plasma measurements obtained by the LASL/MPI analyzers on the ISEE 1 and 2 satellites. The vortices, when present, are manifested as a recurrent or continuing rotation of the bulk flow vector in a plane sometimes moderately inclined with respect to the ecliptic plane. The preferred sense of the rotation is clockwise when viewed from above the ecliptic plane. The vortex rotation period ranges from 5 to 20 min., and several rotations can occur in a relatively uninterrupted sequence. The plasma vortices are estimated to be several earth radii in size. The possibility of a 'vortex street' convecting earthward along the axis of the magnetotail is considered.