Statistics of Plasmaspheric Hiss Poynting Flux

Abstract:

The measured wave properties of plasmaspheric hiss are important to constrain models
of the generation of hiss as well as its propagation and amplification. For example,
the generation mechanism for plasmaspheric hiss has been suggested
to come from one of three possible mechanisms: 1) local generation
and amplification, 2) whistlers from lightning, and 3) chorus emissions
which have refracted into the plasmasphere. The latter two mechanisms
are external sources which produce an incoherent hiss signature as the
original waves mix in a stochastic manner, propagating in both directions
along the background magnetic field. In contrast, local generation of
plasmaspheric hiss within the plasmasphere should produce a signature
of waves propagating away from the source region. For all three mechanisms
scattering of energetic particles into the loss cone transfers some energy
from the particles to the waves. By examining the statistical characteristics of
the Poynting flux of plasmaspheric hiss, we can determine the properties
of wave energy flow in the plasmasphere. We report on the statistics
of observations from the Electric and Magnetic Field Instrument Suite and
Integrated Science (EMFISIS) Waves instrument on the Van Allen Probes
for periods when the spacecraft is inside the plasmasphere. We find that
the Poynting flux associated with plasmaspheric hiss has distinct and unexpected
structure in the Poynting flux which shows significant, organized variation
in the properties of these waves as a function of position and and frequency.