HR: 0800h
AN: SM51A-0281    [Abstracts]
TI: Ion Distribution Functions in Response to Cylindrically Symmetric Electric Fields That Change Linearly With Radius
AU: * Ma, J Z
EM: jzhm2006@hotmail.com
AF: ISAS, University of Saskatchewan, 116 Science Place, Saskatoon, SK S7N 5E2, Canada
AU: St.-Maurice, J
EM: jp.stmaurice@usask.ca
AF: ISAS, University of Saskatchewan, 116 Science Place, Saskatoon, SK S7N 5E2, Canada
AB: It is important to study the response of ambient ions to spatially inhomogeneous electric fields for a better understanding of ion velocity distribution data obtained in space, as well as for a clearer understanding of transport properties under such conditions. We have undertaken a kinetic study of the ion response in cylindrically symmetric cases. As a first step, we have determined the response of the ion distribution function and associated transport properties under the idealized case of an ambient cylindrical, radially-inward, inhomogeneous, but otherwise linearly varying electric field as a function of radial distance. We have found that in this particular case we can describe the results with closed-form analytical expressions. For this geometry, we have studied the ion response to the sudden introduction the cylindrically symmetric electric field by solving the attendant Boltzmann equation. In this case, individual ions gyrate in phase, though at a frequency that differs from the conventional gyro-frequency. The phase lock causes the associated velocity distribution to pulsate at a non- steady rate at a frequency roughly comparable to the cyclotron frequency. Nevertheless, for an initial uniform Maxwellian velocity distribution, the distribution remains Maxwellian at all times, although the drift, density and temperature of that distribution oscillate with time (but not with position). In a second phase of our linearly increasing electric fields study, we have also determined the response of the ions after a few collision times, for application to ionospheric F region situations. In this case the distribution no longer pulsates, as the collisions randomize the phases of the various ions. The ion velocity distribution then evolves towards a horseshoe shape in velocity space
DE: 2437 Ionospheric dynamics
DE: 2451 Particle acceleration
DE: 2704 Auroral phenomena (2407)
DE: 2736 Magnetosphere/ionosphere interactions (2431)
DE: 2752 MHD waves and instabilities (2149, 6050, 7836)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting