HR: 1340h
AN: P43A-1026    [Abstracts]
TI: Phase Space Density of Energetic Electron in Saturn's Inner Magnetosphere From Cassini Observation
AU: * Tadokoro, H
EM: syougun@pparc.geophys.tohoku.ac.jp
AF: Planetary Plasma and Atmospheric Research Center, 6-3, Aramaki Aza Aoba, Aoba-ku, Sendai, 980-8578, Japan
AU: Misawa, H
EM: misawa@pparc.geophys.tohoku.ac.jp
AF: Planetary Plasma and Atmospheric Research Center, 6-3, Aramaki Aza Aoba, Aoba-ku, Sendai, 980-8578, Japan
AU: Tsuchiya, F
EM: tsuchiya@pparc.geophys.tohoku.ac.jp
AF: Planetary Plasma and Atmospheric Research Center, 6-3, Aramaki Aza Aoba, Aoba-ku, Sendai, 980-8578, Japan
AU: Katoh, Y
EM: yuto@pparc.geophys.tohoku.ac.jp
AF: Planetary Plasma and Atmospheric Research Center, 6-3, Aramaki Aza Aoba, Aoba-ku, Sendai, 980-8578, Japan
AU: Morioka, A
EM: morioka@pparc.geophys.tohoku.ac.jp
AF: Planetary Plasma and Atmospheric Research Center, 6-3, Aramaki Aza Aoba, Aoba-ku, Sendai, 980-8578, Japan
AU: Miyoshi, Y
EM: miyoshi@stelab.nagoya-u.ac.jp
AF: Solar Terrestrial Environment Laboratory, Furou cho, Chikusa-ku, Nagoya, 464-8601, Japan
AB: Energetic particles in magnetized planet have been studied to understand particle acceleration and loss processes. Phase space density (PSD) gives a clue to determine internal or external source of energetic particles. We investigate source of energetic electrons (20 keV - a few MeV) in Saturnfs inner magnetosphere (2<L<10 Rs) by performing phase space density analyses for the Saturn orbit insertion (SOI) of Cassini. The analyses show that there is a difference of characteristics of electron PSD between inbound and outbound in 6 - 8 Rs as follows. 1. Electron PSD of outbound is greater than that of inbound in 6 - 8 Rs. 2. Electron PSD of inbound decreases with decreasing of radial distance. 3.Electron PSD of outbound has a local peak in 6 - 8 Rs. The results of 1 and 2 are consistent with PSD analyses from the Voyager data of Armstrong et al., [1983] although they did not calculate PSD for the region more than 8 Rs. The local peak in 6 - 8 Rs is a newly confirmed result and shows an evidence of the internal source region such as a local acceleration due to wave-particle interactions. Pancake or flat pitch angle distribution is observed in the internal source region. One of possible mechanisms explaining these distributions would be pitch angle scattering due to wave-particle interactions. On the other hand, butterfly distribution appears in inbound. Possible mechanism explaining the butterfly distribution would be a ring absorption. In this presentation, we will discuss causes of the difference of electron PSD between inbound and outbound by comparing observed pitch angle distribution and performing numerical calculations about the ring absorption, possibility of wave-particle interactions, and diffusion equation. Acknowledgments We grateful thank for the Magnetospheric Imaging Instrument (MIMI) group and the Radio and Plasma Wave Science (RPWS) group.
DE: 2720 Energetic particles: trapped
DE: 2730 Magnetosphere: inner
DE: 2732 Magnetosphere interactions with satellites and rings
DE: 2774 Radiation belts
DE: 6275 Saturn
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting