IRF logo Project work in Space Plasma Physics
Examensarbete (20 p), spring 2005
Analysis of Cassini RPWS LP measurement profiles in Titan's ionosphere

Student: Erik Wikström
Supervisor: Jan-Erik Wahlund

Swedish Institute of Space Physics, Uppsala
Department of Astronomy and Space Physics, Uppsala University


This thesis comprises a study of the ionosphere at the Saturnian moon Titan. What has been analysed is its heat conduction and cooling for the lower parts (1000-2000 km). Furthermore possible lost terms for electrons have been studied. The results were examined and compared with the theory.

The proposal for the thesis was that from raw data make profiles for different parameters for the lower parts of ionosphere. These profiles and data were compiled to a theory that was compared to existing theories, conductive or thermal conductive atmosphere. All this was done to answer the question if thermal conduction, i.e. energy flux, can explain resulting electron temperatures.

The largest part of the work was done with MATLAB and consisted in creating different parameters like temperatures, densities, frequencies, cooling rates and conduction for a set of flybys, visualize them and compare them with each other. Also a few results that don't come directly from this analysis are shown.

The main results are mainly that all parametric curves are fairly to very "noisy" most likely due to external influence, mainly from the spacecraft itself. For temperatures and densities one can observe distinct patterns, they increase respectively decrease with increasing altitude. Frequencies and cooling rates that both depend on temperature and density also show distinct patterns, they decrease rapidly with higher altitude. Frequencies, i.e. collision frequencies, are much less dependant on nitrogen than on electrons except for low altitudes. For cooling rates the influence of nitrogen is much greater than the influence of methane except for low altitudes. Conduction shows a distinct pattern, it increases for low strata of air but shows only "noise" for higher.

The conclusions are that the atmosphere on Titan is heat conductive. This can partly be linked to thermal conduction for the magnetotail. This conclusion is due to the fact that the conduction does not correspond to the cooling rates, which means that there is a heat flow, and therefore energy flux, in the ionosphere. This is assuming that all other heat transport is very small. However,this is not the case at all times because then the cooling rates would be equivalent to conduction.



Jan-Erik Wahlund,

Example of a calculated cooling rate profile, based on Cassini RPWS LP observations.
last modified onMonday, 01-Oct-2007 11:49:37 CEST