Magnetospheric MHD Resonances and ULF Pulsations - Ultra and Extremely Low Frequency Electromagnetic Fields - page 258

Under fog conditions the amplitude of electric pulsation was found to increase
more than one order of magnitude whereas the spectral index of the fog aeroelectric
field pulsations does not differ drastically from the fair-weather spectrum index
(Anisimov et al. 2002 ).

6.4.10 Monitoring of Near-Earth Plasma

The measurements of the global electromagnetic resonances and ULF fields is
extremely important in the study of both the magnetospheric plasma dynamics
and the Earth's magnetosphere status as a whole. There exists a close analogy
with seismology, in which seismic waves are used to study the Earth's interior
structure. The fundamental difference between the two areas is that the position
and spectrum of the seismic sources are usually known with assurance whereas
we have only a rough measure of the source properties of the MHD waves
incident to the ionosphere. The monitoring of near-earth plasma density and the
study of the ionosphere conductivity have their basis in separating the resonance
effects from the ULF natural and man-made noises. The idea of hydromagnetic
diagnostics of the magnetosphere based on the resonance spectrum of a field line
was originally suggested by Obayashi ( 1958 ) and Dungey ( 1963 ). The problem
of the diagnostics can be split into two basic tasks; that is, the measurement of
the FLR-frequencies and solution of the inverse problems to determine plasma
parameters in the magnetosphere (Guglielmi 1974 , 1989 ; Baransky et al. 1985 ,
1990 ). Plausibility of this technique is restricted by an instability of the solution
of the inverse problem since this solution is rather sensitive to small perturbations
of the initial data. In practice, such perturbations are present not only due to the
measurement inaccuracy but also because of the variability of the magnetosphere
itself.
Much progress toward better understanding of the global ULF electromagnetic
resonances and noises has been achieved in the past decades, that results in the
appearance of “hydromagnetic seismology” of the near-earth space.

6.4.11 Space Weather

Overall the space weather describes today's status of the space environment includ-
ing the conditions on the Sun and in the solar wind, magnetosphere, ionosphere, and
thermosphere. When the space environment is disturbed by the variable output of
particles and radiation from the Sun, it can influence the performance and reliability
of space-borne equipment including computer memories. The geomagnetic storms,
substorms, cosmic and solar rays give rise to degradation of spacecraft material,
primarily solar battery. The interrelation between the fluxes of high energy particles
and onboard anomalies has been well documented. The failure quota due to