Electrodynamic Properties of Space - Hydromagnetic Waves in the Magnetosphere and the Ionosphere - page 37

eastward along the equator. The electric field E y creates a Pedersen current
σ P E y along the equator.
The Hall current σ H E y must in this case flow in the vertical direction. The
Hall current is trapped between the atmosphere, the lower boundary of the
Hall layer, and the F 1-layer as its upper boundary. Electric charges appear on
the boundaries together with a vertical polarization field E p , which in its turn
produces a vertical Pedersen current. The latter compensates for the vertical
Hall current. Hence

E y σ H E P = −

σ P .

The horizontal Hall current from the vertical polarization field has the same
direction as the initial Pedersen current. The total horizontal current j y is
j y = σ P + σ 2 H
σ P

E y .

The quantity σ C

σ C = σ P + σ 2 H
σ P

that determines the horizontal electric conductivity of the near-equator
ionosphere, is called the Cowling conductivity. The altitude dependencies of
σ P and σ H are different, their extremes are removed from each other, therefore
the ratio σ 2 H /σ P can be quite large.
The global distributions of the layered integral ionospheric conductivity
with components Σ xx ,Σ xy ,Σ yy (see (2.9)) calculated for the summer in the
northern hemisphere are shown in Figs. 2.6-2.8. The calculations are per-
formed for the simplest case when the electron concentration is governed only
by the solar UV radiation. Recombination and other chemical processes taking
place in the upper atmosphere are ignored. One can see that Σ yy increases
in the equatorial region. Here Σ yy exceeds its value in the middle-latitude
ionosphere by 1

−

2 orders of magnitude. In the longitudinal dependence of the
conductivities, two anomalies appear in the terminator zone on the bound-
aries of the dayside and nightside ionospheres. The conductivities here change
by an order of magnitude.

2.3 Atmosphere

The atmosphere is a mixture of diverse gases, primarily oxygen O 2 , nitrogen
N 2 , carbon dioxide CO 2 and water vapor H 2 O. Other gases are contained in
the atmosphere in negligible amounts. Atmospheric air always contains tiny
particles of various substances in the solid and liquid states. Their radii do