Day/night asymmetry of ion density and velocity in Saturn's inner magnetosphere - Cassini RPWS/LP observations
Abstract
We present Radio and Plasma Wave Science (RPWS) Langmuir probe (LP) data that show a day/night asymmetry in the ion density and velocity in the inner plasma disk of Saturn. We use data from 131 Cassini orbits, recorded between the years 2005 to 2010, to map the structure and dynamics of the inner plasma disk of Saturn, from magnetic L shell 2.5 to 10. The derived ion densities shows a clear minimum on the day side close to LT noon, of around 35 cm-3, and higher values on the night side close to midnight, of around 80 cm-3. The estimated ion velocities also shows a minimum on the day side with velocities of around 28-32 km/s around noon and a maximum on the night side with 36-40 km/s close to midnight. The asymmetry is largest in the region 4 and 6 RS from the planet. The detected day/night asymmetry could be explained by a noon to midnight electric field of the strength 0.1-1 mV/m previously suggested by Andriopoulou et al., 2012. Such an electric field would give the ions an extra ExB drift component adding to the ion drift in the region around midnight and slowing the ions down in the region around noon. This would alter the particle orbits and cause the density to be lower on the dayside and higher on the night side for the same radial distance. Our results can be interpreted as an additional evidence for the existence of the previously suggested electric field.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMSM21A2169H
- Keywords:
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- 2740 MAGNETOSPHERIC PHYSICS Magnetospheric configuration and dynamics