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Ann. Geophys., 19, 159-170, 2001
www.ann-geophys.net/19/159/2001/
© European Geosciences Union 2001
ULF waves with drift resonance and drift-bounce resonance energy sources as observed in artificially-induced HF radar backscatter
T. K. Yeoman and D. M. Wright
Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
Correspondence to: T. K. Yeomann, (tim.yeoman@ion.le.ac.uk)
Abstract. HF radar backscatter which
has been artificially-induced by a high power RF facility such as the EISCAT
heater at Tromsø has been demonstrated to provide ionospheric electric field
data of unprecedented temporal resolution and accuracy. Here such data are used
to investigate ULF wave processes observed by the CUTLASS HF radars. Within a
short period of time during a single four hour experiment three distinct wave
types are observed with differing periods, and latitudinal and longitudinal
phase evolution. Combining information from the three waves allows them to be
divided into those with a large-scale nature, driven externally to the
magnetosphere, and those with small azimuthal scale lengths, driven by
wave-particle interactions. Furthermore, the nature of the wave-particle
interactions for two distinct small-scale waves is revealed, with one wave
interpreted as being driven by a drift resonance process and the other by a
drift-bounce resonance interaction. Both of these mechanisms with m ≈ -35 and proton energies of 35–45 keV appear to be viable wave energy
sources in the postnoon sector.
Key words. Ionosphere (active experiments;
wave-particle interactions) – Magnetospheric physics (MHD waves and
in-stabilities).
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