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Fig. 12.2. Comparison between numerical (broken line) [14] and analytical calcu-
lations (solid line). L is the north-south scale length, and V 2 and V 3 are given by
(12.40) and (12.41)
Analytical estimates by (12.40)-(12.41) and the numerical results by Poole
et al. [14] are shown in Fig. 12.2, respectively, by the solid and the dashed
lines. The curves as for V 2 as for V 3 are close to each other. Both theory and
numerical experiment predict that, for almost all the interesting scales L
velocity,
V 2 ( L ) <V 3 ( L ) .
It also follows from (12.40) and (12.41) that the effects of both convection and
compressibility are proportional to the MHD-wave frequency.
Sutcliffe and Poole [17] calculated the height profiles of the pulsation elec-
tric E and magnetic b fields of an MHD-wave propagating in a real ionosphere
and the electron and ion velocities caused by the wave. It was shown that the
Jacobs and Watanabe theory [9] has to be modified. Specifically, it is neces-
sary to take into account, besides simple electron drift in crossed electric and
magnetic fields, both the longitudinal current transported by the Alfven wave
and the plasma compression effect in the reflected FMS-wave.
When a localized Alfven wave beam is incident on the ionosphere, a con-
tribution to the radio-wave frequency displacement will, as before, come from
plasma compression in the reflected FMS-wave and from the total longitudinal
current of the incident and reflected Alfven waves. Far from the beam axis,
the Alfven wave intensity falls rapidly. The contribution from plasma com-
pression by the FMS-wave generated by spread-out Hall currents becomes
predominant.
In contrast to localized beams, the longitudinal current amplitude in FLR-
oscillations decreases more slowly than the amplitude of spread-out Hall
currents generated by them. Consequently, the contribution to the Doppler
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