Evidence for surprathermal electron burst intensification due to
inverted-V precipitation
Abstract
The ACES-II sounding rocket mission launched two payloads from Andøya
Rocket Range into a post-dusk discrete auroral arc and observed
field-aligned electron dispersions near inverted-V precipitation. Five
repetitive suprathermal electron bursts (STEBs) associated with low
frequency (< 8 Hz) Earth-ward traveling Alfvén waves are
observed at 400 km altitude. The electron bursts occur both coincident
and outside inverted-V electrons, with those nearest to inverted-V
precipitation displaying higher peak energy and differential flux values
than events further away. We interpret the events as wave-particle
acceleration via inertial Alfvén waves along near-Earth field lines and
employ time-of-flight methods to gauge source altitudes. We show the
differences in STEB behavior are better explained by changes in the
resonant source population and not from significant variation in Alfvén
wave parameters, a result that agrees with previous simulated
predictions.