Observation of isolated high-speed auroral streamers and their interpretation as optical signatures of Alfven waves generated by bursty bulk flows

摘要

The THEMIS All-Sky Imager at Fort Smith, Canada observed a sudden appearance and subsequent evolution of auroral streamers on April 15, 2006. The event took place in an oval that was optically dark, and evolved into a 20-minute period of intense equatorward streaming of red aurora. We characterize the incipient event as isolated streamers, a phenomenon previously linked with bursty bulk flows in the plasma sheet. Thanks to the high time and spatial resolution of THEMIS ASI, the observed streamer reveals some detailed features hitherto not reported. Aside from their exceptionally high speed and fine transient structures, the streamers are found to exhibit an unusual convergent motion (equatorward from high latitudes and poleward from low latitudes) to form a complete flow channel. Our analysis shows that this observation is best explained with a new theory on the origin of auroral streamers.