ULF-Sounding of Magnetosphere and Earth - Hydromagnetic Waves in the Magnetosphere and the Ionosphere - page 335

0.7

0.6

T=100 s

0.5

ρ g = 10 6 Ohm⋅ m, day
ρ g = 10 5 Ohm ⋅ m, day
ρ g = 10 5 Ohm ⋅ m, night

0.4

0.3

0.2

0.1

0

0 500 1000 1500 2000 2500 3000

Distance, km

Fig. 11.10. The estimated spatial distribution of the vertical component in the
reflected FMS-wave for two values of the ground resistivity. The ionospheric models
respect the dayside and midnight conditions. The incident wave is the Alfven beam
of T = 100 s

in the figure. Maximum of the b is shifted with respect to the beam axis.
The far regions, beginning at distances of 1000 km, are the most sensitive

to variations of ground resistivity (compare the solid and dashed lines). An
order of magnitude change in the ground resistivity, changes the b some 1.5-2
times.
Suppose now that the field above the ionosphere is due to the FLR. In the
calculations the resonance period is 100 s, the geomagnetic dip is I =60 ◦ .The
height integrated Pedersen and Hall conductivities are Σ P =1 . 2

∼

×

10 8 km/s,

Σ H =1 . 4

10 8 km/s. This corresponds to dayside ionospheric conditions.
The curves are computed for two geoelectric cross-sections (see Table 11.2).
For simplicity the wave is independent on longitude, k y =0.
Figure 11.11 shows the magnetic components b x ( x ) ,b y ( x ) ,b z ( x ) (left
frame) above the ionosphere in the vicinity of the FLR-line for two differ-
ent geoelectric models (see Table 11.2). b y represents a sum of the incident

×

Table 11.2. Two models of the geoelectrical cross-sections

1 Model 2 Model

Resistivity, Ohm · m Thickness, km Resistivity, Ohm · m Thickness, km

ρ 1 =3 × 10 3 ρ 1 =30 h 1 =3 h 1 =3

ρ 2 =3 × 10 3 ρ 2 =3 × 10 4

h 2 =50 h 2 =50

ρ 3 =3 × 10 2 ρ 3 =3 × 10 3 h 3 =50 h 3 =50

ρ basement =3 × 10 − 2