A study of low-energy plasma in the inner magnetosphere of Saturn

Abstract

In this thesis the inner magnetosphere of Saturn has been studied using data from the Langmuir probe on the spacecraft Cassini. A program has been developed to analyze data from the Langmuir probe. Using this program, three topics have been investigated.

The first topic is the effect of photoelectrons on Langmuir probe measurements. Photoelectron current from the probe is found to depend on spacecraft attitude. It is found that a leakage current from the stub is a likely cause of this. Because the probe is relatively close to Cassini, photoelectrons emitted from Cassini can dominate over plasma electrons under certain conditions.

The second topic is the analysis of Langmuir probe data from Saturn orbit insertion, from 20 R$_S$ to closest approach and back out to 15 R$_S$. The results reveal a diverse plasma environment showing signs of interaction with the rings and moons of Saturn.

The last topic concerns velocity measurements by the Langmuir probe, which in certain areas differ from the velocity measured by other instruments. A combination of ions moving at corotation velocities and ions moving at Keplerian velocities can produce the results and explain why other instruments did not get the same results as the Langmuir probe.