Polarization measurements of Saturn Electrostatic Discharges with Cassini/RPWS below a frequency of 2 MHz
Résumé
Early in 2006 the RPWS (Radio and Plasma Wave Science) instrument and the ISS (Imaging Science Subsystem) onboard the Cassini spacecraft detected a lightning storm on Saturn that lasted for about one month. The RPWS measured the so-called SEDs (Saturn Electrostatic Discharges), which are high frequency radio signals produced by lightning discharges. The ISS imaged a remarkable cloud system associated with these SEDs at a latitude of 35° South. Below the frequency of 1825 kHz the RPWS was in a mode capable of measuring the polarization of the SEDs. A surprising result was gained; SEDs appeared to be highly polarized (80%) and were exclusively right-handed polarized with a high degree of circular polarization. We will present an explanation for this diagnosis involving magneto-ionic modes and their differential absorption in the magnetoplasma of Saturn's ionosphere.
Domaines
Astrophysique [astro-ph]
Fichier principal
Journal of Geophysical Research Space Physics - 2007 - Fischer - Polarization measurements of Saturn Electrostatic.pdf (625.78 Ko)
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