MHD-Wave Exposure on the Ionosphere - Hydromagnetic Waves in the Magnetosphere and the Ionosphere - page 357

Fig. 12.3. N T ( k x ) modulation dependence on the transverse wavenumber of
the MHD-wave, reflected from the dayside ionosphere: ( a ) amplitude relation for
δN T /N T (the solid line) and b ( m ) /B 0 (the dashed line) for the ground signal

y

b ( g )

x =1nT;( b ) the phase difference between the N T variations and b ( g x ; panels
( c )and( d )arethesameas( a )and( b ) but for the nighttime ionosphere

10 − 6 b ( g x . 2 π/ (300) km − 1 the modulation rate is δN T /N T ≈ that at k x ≈ 2 ×

For the nighttime pulsations Pi 2 at the typical amplitudes of b ( g )

≈

10 nT ,

x

the magnitude of the expected effect is δN T /N T ≈ 10 − 5 . Thus, according

to the numerical model, the modulation effects will be more clearly manifested
for daytime than for nighttime pulsations [4].

×

2

FMS-Wave

There is an additional possibility of a more effective coupling between an
MHD-wave and TEC-perturbations. FMS-wave incident on the ionosphere
produces, contrary to the transversal Alfven wave, compression and rarefac-
tion of the charged components. The expected modulation effects can be es-
timated as

b B 0
The observed perturbations of electron concentration δN T /N T ≈

δN T
N T ≈

10 − 4
can be caused by FMS-waves in the magnetosphere with amplitudes of

2 ×