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 suprat hermal ambient electrons, precipitating in field-aligned bursts, may play a n active role in regulating the decay of auroral potential structures. A se t 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. Ro cket-borne measurements of energetic electrons over the residual arcs 2 min later revealed a superposition of hot isotropic and cold ionospheric elect rons, 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 FA B 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 tha t 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 popul ation.