Abstract
Quasiperiodic emissions are electromagnetic waves observed in the inner magnetosphere at frequencies betweenabout 0.5 and 4 kHz both by ground-based instruments and satellites, which exhibit a nearly periodic temporalmodulation of the wave intensity (typical periods on the order of minutes). We present an analysis of 26 eventsobserved simultaneously by the Kannuslehto station in Finland (L~5.46) and Van Allen Probes spacecraft.
We usethe multipoint observations to estimate the spatial extent of the events, finding out that they typically expand lessthan 3 hours in magnetic local time. The events appear to be systematically confined to within the plasmasphere,with maximum event intensities occurring at about 2 Earth radii inward from the plasmapause location.
Thisindicates a probable position of their source region. Finally, we analyze the event propagation parameters as afunction of relevant controlling factors, most importantly the distance from the plasmapause.