Persistent quasiperiodic precipitation of suprathermal ambient electrons in decaying auroral arcs

An analysis of ground-based images and rocket-borne electron data from the Physics of Auroral Zone Electrons II rocket experiment suggests that suprathermal ambient electrons, precipitating in field-aligned bursts, may play an active role in regulating the decay of auroral potential structures. A set of discrete arcs were observed to form in quasiperiodic succession behind a passing westward traveling surge. The nascent arcs faded rapidly, losing 90% of their luminosity within 15 s, The fading then abruptly stopped at a brightness consistent with a peak electron energy of similar to1.5 keV. Rocket-borne measurements of energetic electrons over the residual arcs 2 min later revealed a superposition of hot isotropic and cold ionospheric electrons, the latter precipitated in dispersive periodic (3-5 Hz) bursts from a source altitude of 3000-6000 km. A combined analysis of the optical the FAB component (1) was present for at least 1 min, (2) precipitated in spatial scales of similar to 10 km and (3) carried a number flux comparable to that of the overlying isotropic population. Bulk plasma parameters calculated in the vicinity of the fading arcs revealed an inverse relationship between parallel potential drop and number flux carried by the field-aligned population.