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4000
4000
(b)
(c)(h)
(a)
(d) (g)(f)(e)
(h) (g) (f) (e)
(d)
(c)
(b)
(a)
3000
3000
2000
2000
1000
1000
O 1
H 1
0
10 1
0
800
1400
2600
Temperature (deg.K)
2000
3200
3800
10 2
10 3
10 4
10 5
10 6
Density (cm 23 )
(a)
(c)
4000
4000
(g)
(f)
(e)
(a)
(b)
(c)
(d) (e)
(f)
(g)
(h)
(c)
(b)
(a)
(h)
(d)
3000
3000
2000
2000
1000
1000
0
2
0
800
2
2
6
10
14
18
1200
1600
2000
2400
2800
3200
Velocity (km, sec 21 )
Temperature (deg.K)
(b)
(d)
Figure 9.3 Attitude distribution of (a) O + and H + densities, (b) H + velocity, (c) H +
temperature, and (d) O + temperature from models of the polar wind. The curves labeled
(a)-(h) correspond to assumed H + outflow velocities at 3000 km ranging from 0 to about
20 km/s. [After Raitt et al. (1975). Reproduced with permission of Pergamon Press.]
Figure 9.3 shows some typical results of calculations performed assuming dif-
ferent outflow velocities for H + at 3000 km. Notice in Fig. 9.3b that the H +
velocity increases rapidly in the region between 600 and 1400 km where O +
is the dominant ion (see Fig. 9.3a). This flow is induced by the O + -electron
polarization field. The flow of H + through O + produces frictional heating of
the H + gas to temperatures above that of the O + ions in this region. At higher
altitudes the distribution of the species is controlled by the specified H + outflow
velocity, that is, by the boundary condition placed on the solution. It shows that,
at 3000 km, the predicted H + polar wind can be supersonic since velocities in
excess of 10 km/s are associated with temperatures less than 4000K.
Two important considerations should be kept in mind when considering the
usefulness of this hydrodynamic description of the polar wind. First, the polar
wind does not simply result from an open field-line geometry of field tubes with
very large volumes. The minor ions H + and He + , for example, receive very little
 
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