Observational Evidence for Whistler Mode Waves Guided/Ducted by the Inner and Outer Edges of the Plasmapause

Abstract

AbstractWe present observational support for whistler mode waves guidance by the plasmapause gradients based on a case study and statistical analyses. Due to the combined effects of inhomogeneous magnetic fields and plasma densities, whistler mode waves near the inner edge of plasmapause (plasmasphere side) will be guided by a high density duct‐like (HDD) gradient, and tend to have very small wave normal angles (WNAs ≤ 20°) relative to the ambient magnetic field,B0. In contrast, whistler mode waves near the outer edge of the plasmapause (plasmatrough side) guided by a low density duct‐like (LDD) gradient, tend to have quite large WNAs (≥∼60°). Statistical analyses emphasize these remarkably different properties of waves in the plasmapause gradients. The results indicate that the wave ducting effects at the plasmapause may lead to unusual and anomalous energetic pitch angle scattering.