Modulated electron‐acoustic waves in auroral density cavities: FAST observations

TLDR

The auroral density cavity edges contain a hot (~keV) electron population and a minority cold (<60 eV) component, with ion acoustic waves modulating the environment. The nonlinear waves are recorded when the spacecraft passes the base of the parallel auroral acceleration region. FAST observations reveal large‑amplitude envelope solitary waves at the AKR source edges that form intense electrostatic electron‑acoustic packets propagating along the magnetic field at a few hundred km s⁻¹ and may significantly influence auroral acceleration processes.

Abstract

We report on FAST observations of large amplitude (up to 500 mV m −1 ) envelope solitary waves at the edges of the AKR source region. These edges are characterized by the presence of two electron populations: a dominant hot (∼keV) component and a minority cold (&lt;60 eV) component. The nonlinear waves are recorded when the spacecraft passes the base of the parallel auroral acceleration region. They form intense packets of electron acoustic waves. The modulation is due to ion acoustic waves. These structures are electrostatic and propagate along the magnetic field at speeds of a few 100 km s −1 . They may play a crucial role in the acceleration processes taking place in these regions.