No abstract

Abstract. A 16 mHz Pc4 pulsation was recorded on March 17, 1998, in the prenoon sector of the Earth's magnetosphere by the Equator-S satellite. The event is strongly localized in radial direction at approximately L 5 and exhibits properties of a ®eld line resonance such as an ellipticity change as seen by applying the method of the analytical signal to the magnetic ®eld data. The azimuthal wave number was estimated as m % 150. We discuss whether this event can be explained by the FLR mechanism and ®nd out that the change in ellipticity is more a general feature of a localized Alfve n wave than indicative of a resonant process.

No abstract