Chorus wave scattering responsible for the Earth's dayside diffuse auroral precipitation: A detailed case study

Abstract

AbstractThe diffuse aurora is an almost permanent feature in the Earth's upper polar atmosphere, providing the major source of ionizing energy input into the high‐latitude region. Previous theoretical and observational studies have demonstrated that whistler mode chorus scattering primarily accounts for intense nightside diffuse auroral precipitation within ~ 8 RE, but what causes the dayside diffuse aurora remains poorly understood. Using conjugate satellite wave and particle observations on 13 August 2009 from the Time History of Events and Macroscale Interactions during Substorms spacecraft and ground‐based all‐sky imager measurements at the South Pole on the dayside, we perform a quantitative analysis of wave‐driven diffusion and electron precipitation. Our results demonstrate that the dayside chorus scattering was the dominant contributor to the observed dayside diffuse auroral precipitation and that the chorus wave intensity primarily controlled its brightness, indicating that dayside chorus can be the major driver of the Earth's dayside diffuse aurora. While further investigations are required to bring closure to the origin of the dayside diffuse aurora under differing solar wind conditions and geomagnetic situations, our finding is an important complement to recent work on the formation mechanism of the diffuse aurora and provides improved understanding of the roles of resonant wave‐particle interactions in diffuse auroral precipitation pattern on a global scale.