On the role of pre-onset streamers in substorm onset and development

Abstract:

A large body of THEMIS-era research has made significant progress in studying both the morphology and the impact on substorm development of pre-onset auroral streamers. Specifically, beginning in 2010, a series of papers by Nishimura, Lyons, and others has laid out a scenario in which pre-onset white light streamers that appear to move from hight to low latitude represent low entropy flux tubes propagating to the near-Earth transition region. These entropy depleted flux tubes trigger an instability which then grows exponentially, rapidly leading to substorm onset. In the context of previously established terminology, this is considered a hybrid triggered inside-out scenario. More recent work has also challenged the traditional interpretation that Pi2 pulsations, the initiation of the substorm current wedge, and auroral onset are nearly simultaneous, as predicted by a model of onset driven by magnetotail flow bursts. Instead, it has been argued that auroral onset occurs many minutes earlier, and that further development is fed by post-onset auroral streamer activity. In this talk, I assess the role of of pre-onset auroral streamers in substorm onset and development, and review how the observations and interpretations relate to our current understanding of magnetotail processes.