Outlying dense plasma Plots of plasmaspheric ion (right) and
electron (below) density show significant density structure in
the plasma trough region outside the plasmapause. In both
panels, the y axis gives the particle density, while the x axis
indicates the position in L. The top panel shows a well-defined
plasmapause at L ~ 4.2, with structure extending out to the
magnetopause. In the bottom panel, high density structures can
be seen at L ~ 5.5-6 and from L = 7-9. The structuring in the
middle and outer magnetosphere evident in these data indicates
the presence of dense plasma regions beyond the plasmapause.
These regions consist of material that has been eroded from the
plasmasphere by enhanced convection and that may be in the form
either of detached plasma patches or of plasma plumes or tails
extending from the main body of the plasmasphere. The data in
the top panel were acquired with the ion mass spectrometer on
the Ogo 5 spacecraft; those in the bottom panel, with the sweep
frequency receiver on the