Propagation of MHD-Beams - Hydromagnetic Waves in the Magnetosphere and the Ionosphere - page 262

10 0

Daytime ionosphere

σ g = 1 × 10 6 s −1
Σ P = 1.16

600 s

10 8 km/s
Σ H = 1.36 × 10 8 km/s

×

10 −1

3600 s

100 s

10 −2

20 s

60 s

10 −3

0 500 1000 1500 2000 2500 3000

Distance, km

Fig. 8.9. Spatial variations of the ground magnetic component b ( g x ( x ) for various
periods and for the day time ionospheric conditions. The source as in the Fig. 8.8
is a beam with a Gaussian spatial distribution of the magnetic field in the incident
beam. The half-width of the beam l = 200 km

at night are about three times smaller than dayside currents. The same corre-
lation must exist between the magnitudes of horizontal magnetic fields as well.
Note also the availability of smaller spatial gradients at night in comparison
to the dayside model.

Nighttime ionosphere

σ g = 1 × 10 6 s −1
Σ P = 0.17 × 10 7 km/s
Σ H = 0.23 × 10 7 km/s

10 −1

600 s

3600 s

10 −2

100 s

20 s

60 s

0 500 1000 1500 2000 2500 3000

Distance, km

Fig. 8.10. The same as in Fig. 8.9 but for the nightside ionosphere