The Effect of Equatorial noise on the Proton Density Structure of the
Inner Van Allen Belt
Abstract
We present evidence of damping of equatorial noise due to
Finite-Larmor-radius (FLR) effect in the inner Van Allen belt. Detail
observation of the FLR phenomenon in the inner belt region has not been
reported until now. Waves primarily damped by the FLR mechanism can
influence the energy dependent proton density structure. We analyze a
typical case recorded by the Van Allen probe that involves FLR damping
of equatorial noise, which was propagating radially towards the Earth,
at L-shell ~1.7. As a result of this damping, protons in
the energy range of ~18 – 21 MeV at L-shell
~1.7 – 2 get energized. This kind of wave-particle
interaction should be included in the future models of the inner Van
Allen belt. This phenomenon may also account for the unknown proton loss
mechanism reported in Selesnick and Albert (2019).