Multi-point wave observations on Cluster spacecraft are used toinfer the dispersion relation of electromagnetic ion cyclotron (EMIC) waves.In this study we use a phase differencing method and observations from STAFFand WHISPER during a well-studied event of 30 March 2002. The phasedifferencing method requires the knowledge of the direction of the wavevector, which was obtained using minimum variance analysis. Wave vectoramplitudes were calculated for a number of frequencies toinfer the dispersion relation experimentally. The obtained dispersion relation is largelyconsistent with the cold plasma dispersion relation. The presented methodallows inferring the dispersion relation experimentally. It can be also usedin the future to analyse the hot plasma dispersion relation of waves near thelocal gyrofrequency that can occur under high plasma beta conditions.
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