ANGEO

Annales Geophysicae

ANGEO

Ann. Geophys.

1432-0576

Copernicus Publications

Göttingen, Germany

10.5194/angeo-19-147-2001

LHR effects in nonducted whistler propagation – new observations and numerical modelling

Jiřiček

¹ ³ Shklyar

D. R.

² Třiska

Institute of Atmospheric Physics, Acad. Sci. Czech Republic, Boční II, 141 31 Prague 4, Czech Republic

IZMIRAN, Troitsk, Moscow Region, 142190, Russia

Correspondence to: F. Jiřiček (fji@ufa.cas.cz)

28 02 2001

19 2 147 157

2001

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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)