High latitude pulsating aurorae revisited

Abstract

Dayside auroral pulsations (10–40 s periods) have been studied for different levels of geomagnetic disturbance with N2+ 427.8 nm emission data obtained at South Pole station, Antarctica (−74.2° MLAT). The occurrence distribution exhibits a single peak at magnetic noon under geomagnetically quiet conditions (0 ≤ Kp < 1). With increased Kp, the distribution shifts to earlier times, the peak occurring at 1000–1030 MLT for 1 ≤, Kp < 4. At these higher Kp levels a secondary occurrence peak is evident in the afternoon sector between 1400 and 1600 MLT, occurring earlier as Kp increases. These results are compared with those obtained separately for pre‐noon pulsations observed at Ny Alesund and post‐noon pulsations observed at Davis, northern and southern hemisphere sites at approximately the same magnetic latitude as South Pole. South Pole and Ny Alesund observe morning peaks at the same time and with a similar lack of Kp dependence; South Pole and Davis observe afternoon peaks with similar Kp dependence, though the peak occurs earlier at Davis. In contrast to the results from the earlier studies, the South Pole observations show larger pulsation amplitudes in the morning sector and significantly higher occurrence rates overall.