Intensity Distribution of Whistler Mode Emissions in the Plasmasphere:
Comparisons with the Radiation Belts

J. Green (1), S. Boardsen (2), S. Fung (1), L. Garcia (3), and Bodo Reinisch (4)

(1) NASA Goddard Space Flight Center, Greenbelt, MD
(2) L3 Communications, Largo, MD
(3) Raytheon, ITSS, Landover, MD
(4) Center for Atmospheric Research, University of Mass. Lowell, Lowell, MA


Five years of plasma wave observations from the Dynamics Explorer-1 spacecraft
and three years from the Imager for Magnetopause-to-Aurora Global Exploration
(IMAGE) spacecraft are used to construct plasma wave intensity maps. These
intensity maps show the potential source locations or sites of wave
amplification due to particle-wave interactions of whistler mode emissions in
the plasmasphere. The plasmaspheric hiss spectrum can be viewed as having low
(10 Ð 300 Hz) and high (300 Hz Ð 3.3 kHz) components.  Observations of
plasmaspheric hiss in the low frequency portion of the spectrum show that the
most intense region is in or near the magnetic equator in the afternoon sector
and that during times of negative Bz that maximum intensity moves from L values
of 3 to less than 2. These observations are consistent with particle-wave
interactions in or near the magnetic equator in the slot region of the electron
radiation belts. The high-frequency portion of the hiss spectrum shows
intensity enhancements at high latitudes (L= 4) and in the magnetic equator
near over L values from 2 to 3.  The longitudinal distribution of the hiss
intensity is similar to the distribution of lightning with the peak intensity
near late afternoon and the minimum near early morning local times in addition
to particle-wave interactions in the magnetic equator.  At frequencies above
3.3 kHz whistler mode emissions from ground-based transmitters are observed. 
For these emissions the maximum intensity shifts almost exclusively to the
local evening with enhancements all along L shells from 1.8 to 3.   Indications
are that the cyclotron resonance also operates in this frequency range.  

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Presentation at URSI National Radio Science meeting, 
Boulder, Colorado, USA, 4-8 January 2004