Spatial and temporal properties of AKR burst emission derived from Cluster WBD VLBI studies

Abstract : We have determined the locations of over 6000 individual auroral kilometric radiation (AKR) bursts between July 2002 and May 2003 using a very long baseline interferometer (VLBI) array. Burst locations were determined by triangulation using differential delays from cross-correlated Cluster WBD waveforms. Typical position uncertainties are 200-400km in the plane normal to the source-spacecraft line, but much larger along this line. The AKR bursts are generally located above the auroral zone with a strong preference for the evening sector (22:00 MLT±2h). However, a few epochs imaged during the austral summer have loci in the daytime sector, especially near 15:00 MLT. There is marginal evidence for a small N-S hemispheric asymmetry in mean MLT and invariant latitude.