Drifting black aurorae?

Abstract

Characteristics of eastward drifting forms, previously described in the literature as black aurorae, have been identified in low‐light level TV camera data. The TV field of view was within the field of view of STARE and that of an all‐sky camera. On the basis of these observations we propose that these euroral forms are a manifestation of folds or waves on the borders of auroral bands propagating along the dark regions between neighboring auroral bands. Conditions under which the folds or waves occur are compatible with their formation by the Kelvin‐Helmholtz electrostatic instability.