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10 2
10 1
10 0
0.60
0.40
0.20
1
10
0.00
5 50 km
2
20.20
10
3
20.40
10
20.60
4
10
5
2
0.80
10
2
1.00
6
10
50
100
150
2
1
10 0
10 1
10 2
10 3
10 4
10
10
Distance perpendicular to B (km)
1 )
Wave number (km
Figure 10.20 Horizontal variations in electron density relative to an exponential depen-
dence with altitude (top) and power spectrum of the data (bottom). [After Kelley et al.
(1980). Reproduced with permission of the American Geophysical Union.]
altitude dependence of the plasma density has been removed from the data by a
detrending technique, and the quantity
n has been plotted as a function
of distance perpendicular to B . The Fourier transform of these data is also
shown and indicates a power spectral index n of about 1.6, which is con-
sistent with a Kolmogorov ( n
n
/
=
/
3) spectrum (the straight line has a 5/3
slope). These auroral rocket data were obtained within minutes of the poleward
surge of a magnetospheric substorm. The signal level was above the noise for
λ
5
60m.
This unexplained difference between the “q-machine” plasma at low latitudes
and the violent high-latitude ionosphere is perplexing. Our instincts suggest that
field-aligned currents matter at high latitudes and break the transition to damped
diffusion waves. Perhaps the current convective instability dominates the cascade
process. Bohm diffusion always seems to occur in the laboratory and perhaps
this is the answer here as well. The latter is thought to be related to field-aligned
currents and ion cyclotron waves. Some evidence for the latter exists in very high
J
cases.
Information on even shorter-wavelength waves (
||
10m) comes almost entirely
from rocket measurements, due to the high data rates required. Three distinct
types of irregularities were observed during a rocket flight into the recovery
phase of a magnetospheric substorm on April 2, 1970 (Bering et al., 1975;
Kelley et al., 1975; Kelley and Carlson, 1977). At the edge of an auroral arc,
as detected by onboard particle detectors, intense (5mV/m) oxygen electrostatic
ion cyclotron waves were observed in data from the electric field wave receiver.
A spectrum from the rocket results is presented in Fig. 10.21. Existence of such
waves is consistent with auroral backscatter measurements of cyclotron waves
in the ionosphere. Both data sets indicate that the waves occur in a very local-
ized area. The waves detected on the rocket were observed in conjunction with
 
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