5
tions of the hyperbola and the ellipse define a “trapped” region; ordinarily, no electrons should
occupy this space unless some form of scattering or possibly a time varying field-aligned potential
has occurred. The region within the loss cone hyperbolas and the ellipse is then left to electrons of
ionospheric origin. Several features are immediately apparent in the electron distribution. There is a
clear loss cone feature in the upward component, an enhancement in the electrons at 90° pitch angles
with a negative gradient along v⊥, and a small, beam-like feature at v⊥ = 0 near v|| ~ 5 × 104 km/sec.
All of these features appear to be resting on a broad plateau outlined by the green contour lines and
encompassed by the acceleration ellipse about the origin.
A second example of an AKR source crossing is shown in Figure 2 for orbit 1843. The plasma
FAST Orbit 1843 Plasma Wave Tracker & fce
UT
ALT
MLT
ILAT
10log10((mV/m)2/Hz)
15
365
Mon Oct 13 11:36:50 1997
Frequency (kHz)
370
360
355
350
49:50
3953.7
22.8
65.8
49:52
49:54
49:56
49:58
3952.6
3951.5
3950.3
3949.2
22.8
22.8
22.8
22.8
65.8
65.9
65.9
65.9
Minutes from 1997-02-07/20:49:50
-60
50:00
3948.0
22.8
66.0
FAST Eesa Survey df
1997-02-07/20:49:54.946 - :58.111
-15.0
6•104
-15.7
2•104
0
-16.4
-2•104
Tue Oct 14 14:13:26 1997
-4•104
-6•104
-6•104 -4•104 -2•104
0
2•104 4•104 6•104
Para. Velocity (km/s)
Log10(#/(cm3-(km/sec)3))
Perp. Velocity (km/s)
4•104
-17.2
-17.9
Figure 2. (a) Plasma wave tracker data and (b) electron contour
plot for orbit 1843.
wave tracker instrument shows emissions generated at just above and below the local Ωe. The electron
contour plot is similar to the source region electrons during orbit 1907, except the enhancements in