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 (hundreds 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.
Bibliographical noteFunding Information:
The authors thank the Van Allen Probes team, especially the EFW and EMFISIS teams for their support. This work was funded by NASA award NNX17AI51G. The authors acknowledge the International Space Sciences Institute (ISSI) and the participants in a 2020 ISSI workshop in Bern.
© 2020. The Authors.
- chorus waves
- radiation belts
- spatial distribution
- wave particle interactions