Relativistic electron precipitations in association with diffuse aurora: Conjugate observation of SAMPEX and the all-sky TV camera at Syowa Station

Abstract

It has been believed that whistler mode waves can cause relativistic electron precipitations. It has been also pointed out that pitch angle scattering of ∼keV electrons by whistler mode waves results in diffuse auroras. Thus, it is natural to expect relativistic electron precipitations associated with diffuse auroras. Based on a conjugate observation between the SAMPEX spacecraft and the all-sky TV camera at Syowa Station, we report, for the first time, a case in which relativistic electron precipitations are associated with diffuse aurora. The SAMPEX observation shows that the precipitations of > 1 MeV electrons are well accompanied with those of > 150 and > 400 keV electrons. This indicates that electrons in the energy range from several keV to > 1 MeV precipitate into the atmosphere simultaneously. Our result supports the idea that whistler mode waves contribute to both generation of diffuse auroras and relativistic electron precipitations.