Geoscience Reference
In-Depth Information
Computed
March 1965
Peru
Mean observed
140
N/A [1
UNH-5
14.70
14.171
14.174
14.176
130
120
110
100
90
80
0
5
10
(10
26
amp m
22
)
J
(a)
Figure 3.17a
Observed and computed eastward current density profiles near noon at
the dip equator off the coast of Peru in March 1965, normalized to a magnetic field
perturbation of 100 nT at Huancayo. Measured profiles are from Shuman (1970) (flight
N/A #1), Maynard (1967) (flight UNH-5), and Davis et al. (1967) (flights 14.170, 14.171,
14.174, and 14.176). The theoretical profile is from Richmond's (1973a) theory. [After
Richmond (1973b). Reproduced with permission of Pergamon Press.]
field. In a steady state in this slab model, no vertical current may flow, and the
vertical Pedersen current must exactly cancel the Hall current. This implies that
σ
H
E
x
=
σ
P
E
z
and hence that
E
z
=
(σ
H
/σ
P
)
E
x
(3.13)
Since
σ
H
>σ
P
, the vertical electric field component considerably exceeds the
zonal electric field component. In addition,
E
z
(
z
)
has the same
z
dependence as
the function
σ
P
(
z
)/σ
H
(
z
)
. The zonal current is now given by
=
σ
H
E
z
+
σ
P
E
x
J
x
(3.14a)
(σ
H
/σ
P
)
1
2
=
+
σ
P
E
x
=
σ
J
x
c
E
x
(3.14b)
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