Magnetospheric Storms at Saturn and Jupiter and Their Relation to Rotational Periodicities

Details Magnetospheric Storms at Saturn and Jupiter and Their Relation to Rotational Periodicities Magnetospheric Storms at Saturn and Jupiter and Their Relation to Rotational Periodicities

Dec 2008

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.p21b..08b&link_type=abstract

American Geophysical Union, Fall Meeting 2008, abstract #P21B-08

Physics

2740 Magnetospheric Configuration And Dynamics, 2756 Planetary Magnetospheres (5443, 5737, 6033), 2778 Ring Current, 2784 Solar Wind/Magnetosphere Interactions, 2788 Magnetic Storms And Substorms (7954)

Scientific paper

A magnetospheric storm is a well-known phenomenon in the terrestrial magnetosphere and leads to intensified plasma pressure, electrical currents and magnetic field perturbations. While terrestrial magnetospheric storms are externally driven predominantly by dayside reconnection with the interplanetary magnetic field (IMF), imaging of Saturn's magnetospheric energetic plasma distribution by Cassini/INCA reveals that storms occur during enhanced solar wind dynamic pressure. Galileo measurements in Jupiter's magnetosphere strongly suggest a similar scenario for Jovian magnetospheric storms. We discuss the possible mechanisms behind the stormy behaviors and the consequences for rotational periodicities that appear to become more pronounced during storms. One such periodic phenomenon is the periodic magnetic field perturbations seen in Saturn's magnetosphere. We show that these can be explained by the currents driven by the injected and energized plasma pressure distribution drifting around Saturn. We use a magnetic field model based on the Tsyganenko et al. [2000, 2002] formulation, with a magnetodisc like configuration, seasonal tilt, and a rotating partial ring current (PRC) distribution. The asymmetric PRC pressure is retrieved from Cassini/MIMI and CAPS observations of hot and cold plasma. Our preliminary findings show that the magnetic field perturbations are consistent with the hot plasma pressure distributions observed by the Cassini/MIMI/INCA. However, there appears to be a need for a component of cold plasma, not observed by MIMI, to fully match the magnetic field measurements. With a seasonal tilt of the plasmasheet, the PRC causes perturbations that expand the plasmasheet asymmetrically in the north-south direction, resulting in a periodic oscillation of the plasmasheet tilt southward in winter and northward in summer. This is consistent with the idea discussed by Khurana et al. [2008]. We seek direct evidence in the INCA images for this periodic oscillation.

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