High-Latitude Electrodynamics - The Earth's Ionosphere: Plasma Physics and Electrodynamics - page 389

S3-2 REV 4460/N 15 October, 1976

60

2330 2336 2340 2346

E x

30 700

500
300

B y

0 100

2 100

2300

230 2500

2

700

260

10 9
10 8
10 7

180°

90°

0°

UT
MLT
ALT

2330.0
60
18.0
249

2332.7
70
17.5
238

2335.5
80
15.4
245

2340.5
80
9.0
296

2342.9
70
7.9
354

2346.0
60
7.5
430

Figure 8.3b S3-2 observations from a north polar pass on October 15, 1976. The dashed
line is the baseline for B y . [After Smiddy et al. (1980). Reproduced with permission of
the American Geophysical Union.]

Now consider the ionospheric load. In this resistive medium the horizontal
current from dawn to dusk is J E x h . In a steady state the current entering

the ionosphere in current sheet 1, J z dx , must be equal to the total horizontal
current in the vertical extent h of the ionosphere. Thus, making use of

= σ p δ

δ B y =

μ 0 J z dx and the fact that p = σ p h , we have

δ B y = μ 0 δ E x (8.17a)

p

This equation may be rewritten in the equivalent forms

δ E x = δ B y /μ 0 p (8.17b)

δ B y /δ E x = μ 0 p (8.17c)