HR: 0800h
AN: SH41A-0297    [Abstracts]
TI: Computational Study of Particle Cross-Field Diffusion Caused by Interaction With Interplanetary Magnetic Decreases
AU: * Costa Junior, E d
EM: junior@plasma.inpe.br
AF: Instituto Nacional de Pesquisas Espaciais, Av. dos Astronautas, 1758, Sao Jose dos Campos, SP 12227010, Brazil
AU: Alves, M V
EM: virginia@plasma.inpe.br
AF: Instituto Nacional de Pesquisas Espaciais, Av. dos Astronautas, 1758, Sao Jose dos Campos, SP 12227010, Brazil
AU: Echer, E
EM: eecher@dge.inpe.br
AF: Instituto Nacional de Pesquisas Espaciais, Av. dos Astronautas, 1758, Sao Jose dos Campos, SP 12227010, Brazil
AU: Tsurutani, B
EM: bruce.t.tsurutani@jpl.nasa.gov
AF: Jet Propulsion Laboratory, Calif. Inst. Tech., 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AU: Guarnieri, F L
EM: guarnieri@univap.br
AF: UNIVAP, Av. Shishima Hifumi, 2911, Urbanova, Sao Jose dos Campos, SP 12244000, Brazil
AB: In the last ~ 3 decades, magnetic field observations have shown the existence of isolated regions in interplanetary space and even into the Earth's magnetosphere where the magnitude of the magnetic field drops to few tenths, or less, of its ambient values. These regions are now called magnetic decreases (MDs). Particles within MDs are heated preferentially perpendicular to B₀, the ambient magnetic field. MDs are believed to be caused by a diamagnetic effect from these perpendicularly accelerated protons. The decrease of the magnetic field is accompanied by an increase of particle density in such a way that the balance pressure (magnetic plus plasma thermal) is sustained. The proton acceleration is associated with the dissipation of phase-steepened Alfvén waves, presumably through the ponderomotive force. In this paper we are interested in investigating the non-resonant particles cross-field diffusion due to their interactions with MDs at large heliospheric latitudes. To do such a study, we start from distribution functions obtained from analytical fits to experimental distributions, for an ensemble of high heliospheric latitude MDs observed by Ulysses. The distribution functions are dependent on the ratio between the magnitude values of the magnetic field inside the MD and around it, and on the space dimension of the MD. These distribution functions are them statistically represented by points, obtained using Monte Carlo method. The particle diffusion is analyzed using a theoretical model presented by Tsurutani et al. (Nonlinear Processes in Geophys., 6, 235, 1999). For the simulations, we let a particle with specific energy interacts with an MD of a field decrease and thickness given by the selected random points from the distribution functions. This process can be continued until all particles have been scattered. This computational simulation has other applications besides the high heliospheric latitude, such as interplanetary/magnetospheric diffusion of energetic particles, cosmic rays and other astrophysical problems
DE: 7524 Magnetic fields
DE: 7807 Charged particle motion and acceleration
DE: 7899 General or miscellaneous
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Fall Meeting