HR: 0830h
AN: SM51C-0544    [PDF]
TI: Intensity Distribution of Plasmaspheric Hiss in the Plasmasphere
AU: * Boardsen, S A
EM: boardsen@mail630.gsfc.nasa.gov
AF: L3-EER, NASA Goddard SFC Code 632, Greenbelt, Md 20771-0001 United States
AU: Green, J L
EM: James.L.Green.1@gsfc.nasa.gov
AF: NASA/GSFC, NASA Goddard SFC Code 632, Greenbelt, Md 20771-0001 United States
AU: Fung, S F
EM: Shing.F.Fung.1@gsfc.nasa.gov
AF: NASA/GSFC, NASA Goddard SFC Code 632, Greenbelt, Md 20771-0001 United States
AU: Garcia, L N
EM: Leonard.N.Garcia.1@gsfc.nasa.gov
AF: QSS Group, Inc., NASA Goddard SFC Code 632, Greenbelt, Md 20771-0001 United States
AU: Reinisch, B
AF: Center for Atmospheric Research, University of Mass. Lowell, Lowell, Ma 01854 United States
AB: Plasmaspheric hiss is an electromagnetic emission in the $10$s Hz to ~$10$ kHz frequency range propagating in the whistler mode that is typically confined within the plasmasphere. Two of the most important aspects about plasmaspheric hiss are its source location and generation mechanism. Generation mechanisms have been proposed both inside and outside the plasmasphere and are still controversial. To investigate the source location, plasma wave intensity maps have been constructed by using three years of plasma wave observations from the Dynamics Explorer and three years from the Imager for Magnetopause$-$to$-$Aurora Global Exploration (IMAGE) spacecraft. These intensity maps show the potential source locations or sites where waves are amplified due to particle$-$ wave interactions. In this presentation, we show that the plasmaspheric hiss spectrum can be viewed as having low ($10$ to $300$ Hz), mid ($300$ Hz to $3.3$ kHz), and high frequency ($> 3.3$ kHz) components. Observations of low$-$frequency plasmaspheric hiss show that the most intense region is in or near the magnetic equator in the afternoon sector and that the maximum intensity region tends to move from L value of $3$ to less than $2$ during times of negative Bz. These observations are consistent with particle$-$ wave interactions in or near the magnetic equator. The mid$-$ frequency portion of the hiss spectrum shows the peak$-$ intensity region moves from high latitudes at L$= 4$ toward the magnetic equator over L $= 2$ to $3$. The longitudinal distribution of the hiss intensity in this frequency range is similar to that of lightning intensity with the peak near late afternoon and the minimum near early morning local times. The near$-$ equatorial minimum at L$= 2 - 3$ is also consistent with particle$-$ wave interactions in the magnetic equator. At frequencies above $3.3$ kHz the maximum intensity shifts to the local evening$-$post midnight with enhancements along all L shells from $1.8$ to $3$. Indications are that the cyclotron resonance also operates in this frequency range.
DE: 2720 Energetic particles, trapped
DE: 2768 Plasmasphere
DE: 2772 Plasma waves and instabilities
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting