Recurrent fast motions of pulsating auroral patches: 1. A case study on optical and quantitative characteristics during a slightly active period

Observations of pulsating auroras with all‐sky TV cameras during the Canadian pulsating aurora campaign (January–February 1980) have revealed that fast motions occurring within auroral patches with direction predominantly parallel to the long axis of elongated auroral structures (termed streaming pulsations) are one of the most prevalent conditions in the pulsating auroral displays. An example of a typical period on a slightly active day, February 15, 1980, is described in detail by analyzing the fast motion of and within auroral forms. Some initial results of studies on their motional characteristics, derived from studying the spatial coherence of luminosity fluctuations, are presented. The dominant direction of the streaming pulsations within E‐W elongated structures was westward with speeds in the range of 10–100 km/s. The extent of movement was normally between 10 and 150 km, but sometimes longer than 1000 km. These characteristics are briefly discussed in relation to wave‐particle interactions, by referring to the previously proposed models.