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
ISEE 1 satellite. As indicated by the trajectory plot in the
upper righthand corner of the bottom panel, the ISEE
measurements were made in the afternoon-evening sector
of the magnetosphere; the
Ogo data were taken in the morning-noon sector.
Sources: Chappell, C. R., Detached plasma regions in the
magnetosphere, J. Geophys. Res., 79, 1861, 1974 (Ogo plot);
Carpenter, D. L., et al., Plasmasphere dynamics in the
duskside bulge region: a new look at an old topic, J.
Geophys. Res., 98, 19243, 1993 (ISEE plot).