Electrodynamic Properties of Space - Hydromagnetic Waves in the Magnetosphere and the Ionosphere - page 34

200

180

160

140

120

β e

β i

100

80

60

40

20
0

10 −5 10 −4 10 −3 10 −2 10 −1 10 0 10 1 10 2 10 3 10 4 10 5

Magnetization parameters β e , β i

Fig. 2.5. Height dependencies of the electron β e = ω ce /ν e and ion β i = ω ci /ν i
parameters

σ Pe . Above the 100 km level, in the E -layer the atmospheric concentration
decreases so that the ion-neutral collisions become less frequent, β i is small
but finite, β e β i > 1 , and σ P ≈ σ Pi . Here, ions move along the applied electric

field, electrons are magnetized so that they drift just perpendicular to both
the applied electric field and the geomagnetic field. In the F -layer, β e ,β i →∞
and σ P vanishes.

Layered Conductivity

It can be seen from Fig. 2.4 that σ exceeds σ P and σ H by about 4 or-
ders of magnitude. Due to this fact the ionosphere and the magnetosphere
are effectively short-circuited, as the electric field E excited by large-scale
perturbations in both media is transferred with practically no damping from
the magnetosphere to the conjugate ionospheres or from the ionosphere of one
hemisphere to the other.
Equipotentiality of the magnetic field-lines enables us in many cases to
approximate the ionosphere by a thin conductive shell surrounding the Earth.
Let us place the origin of the Cartesian coordinates at some point on the shell,
the axis x and y point southward and eastward respectively, the z axis points
upward. If the magnetic inclination (angle between geomagnetic field B 0 and
the horizontal plane) is I , then the current density produced by E can be
written as

j x =( σ cos 2 I + σ P sin 2 I ) E x + σ H E y sin I +( σ −

σ P ) E z cos I sin I,

(2.4)