dc.description.abstract |
Intense ~300-Hz to 1.0-kHz plasmaspheric hiss was studied using Polar plasma wave data. It is
found that the waves are coherent in all local time sectors with the wave coherency occurring in
approximately three- to five-wave cycle packets. The plasmaspheric hiss in the dawn and local noon time
sector are found to be substorm (AE*) and storm (SYM-H*) dependent. The local noon sector is also solar wind
pressure dependent. It is suggested that coherent chorus monochromatic subelements enter the
plasmasphere (as previously suggested by ray tracing models) to explain these plasmaspheric hiss features.
The presence of intense, coherent plasmaspheric hiss in the local dusk and local midnight time sectors is
surprising and more difficult to explain. For the dusk sector waves, either local in situ plasmaspheric wave
generation or propagation from the dayside plasmasphere is possible. There is little evidence to support
substorm generation of the midnight sector plasmaspheric hiss found in this study. One possible
explanation is propagation from the local noon sector. The combination of high wave intensity and
coherency at all local times strengthens the suggestion that the electron slot is formed during substorm
intervals instead of during geomagnetic quiet (by incoherent waves). Plasmaspheric hiss is found to
propagate at all angles relative to the ambient magnetic field, θkB. Circular, elliptical, and linear polarized
plasmaspheric hiss have been detected. No obvious, strong relationship between the wave polarization and
θkB was found. This information of hiss properties should be useful in modeling wave-particle interactions
within the plasmasphere. |
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