Latitudinal extension of the sources of continuum radiations
Résumé
The electromagnetic radio emissions known as 'continuum radiation' are widely
observed for decades in planetary magnetospheres. Although their main source
location is well identified for Earth in the vicinity of the equatorial plasmapause and
its generation mechanism generally associated with electrostatic emissions arising
between half harmonics of the electron gyro harmonics, many details of their
characteristics and source are still missing. Recent observations had suggested new
features in their description. For example, studies based on the Whisper
instruments have shown that continuum sources can also be located at mid latitudes
and can be generated at exact harmonics of the electron frequency. The higher
perigee of the present phase of the Cluster extended mission allows the spacecraft
to skim the sources regions close to the plasmapause and to explore their latitudinal
extension thanks to its polar orbit. This higher perigee also allows to get Peace data,
seldom available at the lower perigees earlier in the mission, to characterize the
electrons populations at the origin of these emissions. We present here the first
analysis of the best events observed so far.