Return to "The Structure of the Magnetosphere" by
C. T. Russell.
"The Thickness of the Magnetopause Current Layer: ISEE 1 and 2
Observations"
This is a brief summary of
"The Thickness of the Magnetopause Current Layer: ISEE 1 and 2
Observations"
by J. Berchem and C. T. Russell.
This paper was one of the references in C. T. Russell's "The
Structure of the Magnetopause," which I am attempting to
summarize.
A study based on 30 magnetopause crossings by the
ISEE satellites gives values and approximate variations in
current sheet thickness and magnetopause velocity.
The measurements of magnetopause thickness ranged from
200 to 1800
km, with most (70%) of the observations occurring between 400 and
1000 km (1000 km ~ 10 ion gyroradii).
The velocity of the magnetopause was found to vary between
10 and 80 km/sec, slightly larger than previous predictions.
Crossings with ISEE-2 within 1000 km of ISEE-1 were considered in
the survey. Along with measurements of thickness and velocity,
variations along the magnetopause were also detected. The data seems
to indicate that the thickness of the magnetopause is more strongly
correlateded with the magnetic latitude of the earth's dipole than
with the GSM latitude. The statistics
did not support the hypothesis that magnetopause thickness
depends on the orientation of the magnetosheath magnetic field,
although previous data [Elphic and Russell, 1979] imply
otherwise. Furthermore, no evidence for a correlation between
geomagnetic activity and magnetopause was found, although the majority
of the crossings occurred during relatively quiet periods.
The current sheet is thinnest (around 500 km) near the magnetic
equator, which is consistent with reconnection in the equatorial
regions. They claim that this is evidence that magnetic reconnection
does not occur in the polar cusps.
However, observations of plasma mixing in the low latitude boundary
layer seems to imply that reconnection is occurring in
the polar cusps (see Figure 5 in Russell's paper, taken from
Song and Russell [1992]).
Return to "The Structure of the Magnetosphere" by
C. T. Russell.