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Ann. Geophys., 19, 147-157, 2001
www.ann-geophys.net/19/147/2001/
© European Geosciences Union 2001
LHR effects in nonducted whistler propagation – new observations and numerical modelling
F. Jiřiček1, D. R. Shklyar2, and P. Třiska1
1Institute of Atmospheric Physics, Acad. Sci. Czech Republic, Boční II, 141 31 Prague 4, Czech Republic
2IZMIRAN, Troitsk, Moscow Region, 142190, Russia
Correspondence to: F. Jiřiček (fji@ufa.cas.cz)
Abstract. VLF-ELF broadband
measurements onboard the MAGION 4 and 5 satellites at heights above 1 Re in
plasmasphere provide new data on various known phenomena related to ducted and
nonducted whistler wave propagation. Two examples are discussed:
magnetospherically reflected (MR) whistlers and lower hybrid resonance (LHR)
noise band. We present examples of rather complicated MR whistler spectrograms
not reported previously and argue the conditions for their generation.
Analytical consideration, together with numerical modelling, yield understanding
of the main features of those spectrograms. LHR noise band, as well as MR
whistlers, is a phenomenon whose source is the energy propagating in the
nonducted way. At the plasmaspheric heights, where hydrogen (H+) is
the prevailing ion, and electron plasma frequency is much larger than
gyrofrequency, the LHR frequency is close to its maximumvalue in a given
magnetic field. This frequency is well followed by the observed noise bands. The
lower cutoff frequency of this band is somewhat below that maximum value. The
reason for this, as well as the possibility of using the LHR noise bands for
locating the plasma through position, are discussed.
Key words. Magnetospheric physics (plasmasphere; wave
propagation)
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