The Role of Electron Density on the Interchange Instability at Saturn

Friday, 19 December 2014
Timothy Kennelly1, George B Hospodarsky1, Michelle F Thomsen2, Ann M Persoon1, William S Kurth1, Donald A Gurnett1, Nicholas A Achilleos3, Maria Andriopoulou4, Sarah Victoria Badman5, Caitriona M Jackman3, Xianzhe Jia6, Krishan K Khurana7, Norbert Krupp4, Philippe Louarn8, Chris Paranicas9, Elias Roussos4 and Nick Sergis10, (1)University of Iowa, Iowa City, IA, United States, (2)Planetary Science Institute, Los Alamos, NM, United States, (3)University College London, London, United Kingdom, (4)Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, (5)University of Lancaster, Lancaster, LA1, United Kingdom, (6)University of Michigan, Ann Arbor, MI, United States, (7)University of California Los Angeles, Los Angeles, CA, United States, (8)CNRS/IRAP, Toulouse, France, (9)Applied Physics Laboratory Johns Hopkins, Laurel, MD, United States, (10)National and Kapodistrian University of Athens, Athens, Greece
Interchange events, where “injections” of hotter, less dense plasma moves inward to return the magnetic flux carried outward by the colder, more dense plasma in rapidly rotating magnetospheres, are detected at Saturn by Cassini on almost every orbit that encounters the inner and middle (<15 Rs) magnetosphere. Significant changes can occur in the number of injection events and their location (L shell) between inbound and outbound passes on a given orbit (over a several hour time span). Furthermore, changes are observed between orbits for the same local time sampling (over tens of days). Similar changes between inbound and outbound passes, and between orbits have been observed in the electron density values measured by Cassini. We examine the period in 2010 when Cassini was in near equatorial orbits with the inbound period between L of 4.5 and 10 primarily in the midnight sector and the outbound period was near noon. Using Cassini Plasma Spectrometer (CAPS) and Magnetospheric Imaging Instrument (MIMI) data we determine the occurrence of injection events, their signature in a wide range of energies (eV to MeV), and examine their relationship with the electron density determined from the upper hybrid resonance emission measured by the Radio and Plasma Wave Science instrument.