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Ann. Geophys., 26, 185-199, 2008
www.ann-geophys.net/26/185/2008/
© European Geosciences Union 2008
Multi-instrument observations of a large scale Pc4 pulsation
L. B. N. Clausen1, T. K. Yeoman1, R. Behlke2, and E. A. Lucek3
1Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK
2Department of Physics, University of Tromsø, N-9037 Tromsø, Norway
3Department of Physics, Imperial College London, London SW7 2AZ, UK
Abstract. On 7 November 2005 various ground based and spaced based instruments
registered five wave packets with frequencies in the Pc4 range. The most
prominent of the five wave packets was observed in ground based magnetometer
data spanning almost all latitudes on the dayside magnetosphere. The
propagation from the dayside into the tail is deduced from Poynting flux
calculations of Cluster data and an onset time analysis of the ground based
magnetometer data. This suggests an upstream source. Backstreaming ions are
identified to be the most probable source mechanism for this event. Due to
the fortunate configuration of the Cluster satellites, the harmonic structure
of the wave is analysed and compared with cross-phase spectra from ground
data. We present evidence that the driving wave resonantly interacted with
geomagnetic field lines. The data suggests that resonant driving occurred at
stations where the driving frequency was harmonically related to the local
fundamental frequency, creating FLR-like signatures.
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