Locations of Auroral Kilometric Radiation Bursts Inferred From Multi-Spacecraft Wideband Cluster VLBI Observations i: Description of Technique and Initial Results

摘要

The Cluster Wideband Data instrument has been used to determine the locationsof auroral kilometric radiation (AKR) using very long baseline interferometry.The technique involves cross-correlating individual AKR bursts from all sixCluster baselines using time and frequency filtered waveforms. We report thelocations of over 1,700 individual AKR bursts during six observing epochsbetween 10 July 2002 and 22 January 2003 when the Cluster constellation washigh above the southern or northern hemisphere. In general we find that the AKRburst locations lie along magnetic field lines which map onto the nighttimeauroral zone as expected from previous AKR studies. The distribution of AKRauroral footprint locations at each epoch had a overall spatial scale between1000 - 2000 km, much larger than the positional uncertainty of an individualAKR burst location magnetic footprint, but a small fraction of the auroraloval. For two of the six epochs, there was a significant drift in the meanlocation of AKR activity over a period of 1-2 hours. The drift waspredominantly in latitude at one epoch and in longitude at the other, withaverage drift speed V ~ 80-90 m s-1 at the AKR emission location.