HR: 0800h
AN: SM51A-0355    [Abstracts]
TI: Electrostatic Fields in Density Cavities and Nonlinear Energization of Ions
AU: * Ram, A K
EM: abhay@mit.edu
AF: Plasma Science and Fusion Center, Massachusetts Institute of Technology, NW16-260, 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AU: Strozzi, D J
EM: dstrozzi@mit.edu
AF: Plasma Science and Fusion Center, Massachusetts Institute of Technology, NW16-260, 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AB: In auroral ionospheric plasmas, intense electrostatic fields in density depleted regions and associated transverse energization of ions are observed [1]. We have been studying, theoretically and computationally, the characteristic features of fields in density cavities and the energization of ions by electrostatic fields. Intense localized electric fields can be generated in regions where plasma resonances exist. An appropriate description of the fields is obtained from Maxwell's equations for a cold plasma with a spatial profile. We will discuss the characteristic features of the fields obtained from such a description. We further study the interactions of ionospheric ions with electrostatic fields to understand the observed transverse energization of ions. The electrostatic fields are assumed to be represented either by a set of plane waves propagating obliquely to the geomagnetic field or localized field structures whose spatial dimensions are small compared to the thermal Larmor radii of the ionospheric ions. We find that for obliquely propagating waves, nonlinear, coherent, transverse energization of low energy ions can occur [2,3], while for localized field structures the phase space of the energized ions is chaotic. The ion dynamics will be compared and contrasted in the two cases using detailed analytical and numerical studies. \noindent This work is supported by NSF Grant No. ATM-98-06328. \noindent [1] K.A.\ Lynch et al., {\it J.\ Geophys.\ Res.} {\bf 104}, 28,515 (1999). \noindent [2] A.K. Ram, A. Bers, and D. Benisti, {\it J.\ Geophys.\ Res.} {\bf 103}, 9431 (1998). \noindent [3] D.J.\ Strozzi, A.K.\ Ram, and A.\ Bers, {\it Physics of Plasmas} {\bf 10}, 2722 (2003).
DE: 7839 Nonlinear phenomena
DE: 2407 Auroral ionosphere (2704)
DE: 2451 Particle acceleration
DE: 2471 Plasma waves and instabilities
DE: 2483 Wave/particle interactions
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting