Deciphering the Solar Wind at Saturn

The effects of the solar wind on Saturn’s magnetosphere are poorly constrained as there are no consistent solar wind monitors upstream of the planet. This has limited previous studies of the solar wind’s influence on the Saturnian magnetosphere to case studies and time dependant analyses of intervals of the Cassini data. While useful and enlightening, these methods assume a priori, a relationship between the solar wind and magnetospheric driving or are biased due to their selection based on particular events detected within the magnetosphere.  

 

Mutual information is a measure of information gain and is measured by the change in uncertainty, after the reception of an input variable in relation to a related output variable. The more mutual information in a system between two variables, the stronger the relationship between the two. We apply Mutual Information Theory to investigate the statistical relationship between solar wind parameters e.g. density, magnetic field strength, velocity, and magnetospheric driving. We consider the entire Cassini dataset, identifying intervals where the Tao et al. [2005] solar wind propagation model is valid. This robust statistical analysis determines magnetospheric proxies for the solar wind and, crucially, how much information these proxies provide about the state of the solar wind. Finding and confirming the relation of these indirect proxies to solar wind propagation models presents the opportunity to open long time scale data to interpretation with respect to the solar wind’s behaviour at the outer planets, using data from past missions. Initial results indicate that the direction of the IMF plays a stronger role in driving Saturn’s magnetosphere than previously thought and identifies potentially new solar wind parameters that effect Saturn’s magnetosphere.