Testing the Organization of Whistler-mode Chorus Wave Properties by
Plasmapause Location
Abstract
Lower-band whistler-mode chorus waves are important to the dynamics of
Earth’s radiation belts, playing a key role in accelerating seed
population electrons (100’s of keV) to relativistic ($>$
1 MeV) energies, and in scattering electrons such that they precipitate
into the atmosphere. When constructing and using statistical models of
lower-band whistler-mode chorus wave power, it is commonly assumed that
wave power is spatially distributed with respect to magnetic L-shell. At
the same time, these waves are known to drop in power at the
plasmapause, a cold plasma boundary which is dynamic in time and space
relative to L-shell. This study organizes wave power and propagation
direction data with respect to distance from the plasmapause location to
evaluate what role the location of the plasmapause may play in defining
the spatial distribution of lower band whistler-mode chorus wave power.
It is found that characteristics of the statistical spatial distribution
of equatorial lower band whistler mode chorus are determined by L-shell,
and are largely independent of plasmapause location. The primary
physical importance of the plasmapause is to act as an Earthward
boundary to lower band whistler mode chorus wave activity. This behavior
is consistent with an equatorial lower band whistler mode chorus wave
power spatial distribution that follows the L-shell organization of the
particles driving wave growth.