Abstract
Abstract. Multi-point wave observations on Cluster spacecraft are used to infer the dispersion relation of electromagnetic ion cyclotron (EMIC) waves. In this study we use a phase differencing method and observations from STAFF and WHISPER during a well-studied event of 30 March 2002. The phase differencing method requires the knowledge of the direction of the wave vector, which was obtained using minimum variance analysis. Wave vector amplitudes were calculated for a number of frequencies to infer the dispersion relation experimentally. The obtained dispersion relation is largely consistent with the cold plasma dispersion relation. The presented method allows inferring the dispersion relation experimentally. It can be also used in the future to analyse the hot plasma dispersion relation of waves near the local gyrofrequency that can occur under high plasma beta conditions.
Highlights
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The STAFF and WHISPER instruments form part of the Wave Experiment Consortium (WEC) complex that is controlled by Digital Wave Processing experiment (DWP) (Woolliscroft et al, 1997)
In practice collecting data near this point may be difficult: as the wavenumber approaches infinity, the phase velocity approaches zero and so the same wave packet may be seen on two satellites with a significant delay, making matching and phase difference calculations inaccurate
Summary
EMIC waves propagate and grow around the dense plasmasphere region near the plasmapause (Fraser and Nguyen, 2001), cyclotron-resonate with radiation belt ions and Landau-resonate with outer radiation belt electrons (Horne and Thorne, 1990, 1994) scattering both species into the loss cone. This paper uses the cospectral/phase differencing method of k vector determination (Balikhin and Gedalin, 1993; Dudok de Wit et al, 1995; Balikhin et al, 1997a) to calculate the frequency–wavenumber relation directly and compare it to existing EMIC wave dispersion theory This method assumes that in the plasma rest frame (PF) a wave field can be represented as B(r, t) =. The phase differencing techniques have been exploited and enabled identification of wave modes in various regions of geospace such as foreshock, shock front and the magnetosheath (Balikhin et al, 1997b; Chisham et al, 1999; Walker et al, 2004)
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