HR: 0800h
AN: SM51B-0371    [Abstracts]
TI: Dispersion Characteristics for Plasma Resonances of Maxwellian and Kappa Distribution Plasmas and their Comparisons to the IMAGE/RPI Observations
AU: * Vi\~{n}as, A F
EM: Adolfo.Vinas@gsfc.nasa.gov
AF: NASA, Goddard Space Flight Center, Greenbelt, MD 20771 United States
AU: Benson, R F
EM: Robert.F.Benson@nasa.gov
AF: NASA, Goddard Space Flight Center, Greenbelt, MD 20771 United States
AU: Mace, R L
EM: macer@ukzn.ac.za
AF: University of KwaZulu-Natal, South Africa, Pietermaritzburg, . 11111 South Africa
AB: The Radio Plasma Imager (RPI) on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite stimulates short-range plasma wave echoes and plasma emissions, known as plasma resonances, detected on plasmagrams. These resonances are used to provide measurements of the local electron density n$_{e}$ and magnetic field strength $|B|$. The RPI-stimulated resonances are the magnetospheric analog of plasma resonances stimulated by topside ionospheric sounders. These resonances are stimulated at the harmonic of the electron cyclotron frequency f$_{ce}$, the electron plasma frequency f$_{pe}$ and the upper-hybrid frequency f$_{uh}$ (where f$_{uh}$$^{2}$ = f$_{pe}$$^{2}$ + f$_{ce}$$^{2}$). They are also observed between the harmonics of f$_{ce}$ (i.e., n f$_{ce}$) both above and below f$_{pe}$ and are known as the Qn and Dn resonances, respectively. In this work we solely focus on the Qn resonances. Calculations of these resonances in the ionospheric environment, based upon a thermal Maxwellian plasma model provided confidence in the resonance identification. There is an apparent difference however, between the ob-served Qn resonances and calculations based on a Maxwellian plasma model in the magnetosphere environment. For example, the Qn's are often (and perhaps consistently) observed at frequencies slightly lower than expected for a Maxwellian plasma. We present a new set of resonance calculations based upon the non-thermal kappa distribution that provides dispersion characteristics of these resonances. Comparisons of these calculations to the IMAGE/RPI observations seems to resolve the frequency discrepancy. The results also provide insight into the nature of the electron distribution function in the magnetosphere.
DE: 7800 SPACE PLASMA PHYSICS
DE: 6984 Waves in plasma
DE: 2471 Plasma waves and instabilities
DE: 2772 Plasma waves and instabilities
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting