HR: 15:25h
AN: P23C-08 INVITED    [Abstracts]
TI: Rotational Modulations of Saturn's Magnetosphere and Synchronous Regeneration of its Asymmetry
AU: * Khurana, K K
EM: kkhurana@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, Slichter Hall, UCLA, Los Angeles, CA 90095, United States
AU: Dougherty, M K
AF: Imperial College, Department of Physics, London, SW7 2AZ, United Kingdom
AU: Russell, C T
AF: Institute of Geophysics and Planetary Physics, Slichter Hall, UCLA, Los Angeles, CA 90095, United States
AU: Paranicas, C
AF: Applied Physics Laboratory, Laurel MD, Laurel, MD 20723,
AU: Mitchell, D G
AF: Applied Physics Laboratory, Laurel MD, Laurel, MD 20723,
AU: Arridge, C S
AF: MSSL, Mullard Space Science Laboratory, Surrey, RH5 6NT, United Kingdom
AU: Krupp, N
AF: MPAE, D-37191, Katlenburg-Lindau, Gemany, Germany
AB: We show that Saturn's magnetosphere displays two types of rotational modulations in the fluxes of energetic charged particles and field strength. In the "in-phase" modulations which are observed outside of the current sheet, the magnetic field strength and charged particle fluxes are observed to vary in phase. In the second type of rotational modulations, which are observed during current sheet crossings, the particle fluxes and the field strength are seen to be anti-correlated. In this work we will show that Saturn's magnetosphere contains semi-permanent azimuthal variations in fluxes of energetic particles and plasma density. Using arguments based on stress balance, we show that such plasma variations would create the observed in-phase magnetic field variations above the current sheet. Next, we demonstrate that when the solar elevation angle is large, the solar wind dynamic pressure generates a tilt in the current sheet of Saturn because of magnetosphere's asymmetric "rigidity". In this process, the "light" azimuthal sectors of the current sheet are pushed further away from the rotational equator than are the "heavy" sectors which remain close to the rotational equator. This current sheet tilt is the source of "out-of-phase" periodicities observed at low latitudes in Saturn's magnetosphere. Finally, we present a heuristic model of synchronous regeneration of azimuthal asymmetry in Saturn's magnetosphere by a process which maintains and reinforces the existing azimuthal variations in the charged particle fluxes. We postulate that when the heavy and distended portions of the m = 1 semi-permanent azimuthal structure face the magnetotail, field reconfiguration and reconnection events are maximized. The resulting bursty bulk flows and plasma injections into the middle and inner magnetosphere then reinforce the existing azimuthal enhancement of particle fluxes, perpetuating the azimuthal asymmetries of the magnetosphere.
DE: 2740 Magnetospheric configuration and dynamics
DE: 2756 Planetary magnetospheres (5443, 5737, 6033)
DE: 5734 Magnetic fields and magnetism
DE: 6275 Saturn
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting