Alternative Paradigms Regarding Auroral Arc Currents, Substorms, Reconnection and Solar Flares

As the THEMIS mission approaches with its central theme of solving the substorm problem, it seems appropriate to review current paradigms regarding the visual aurora associated with substorms and the connections to reconnection. In particular this talk will focus on the underlying assumptions on which substorm paradigms are founded, demonstrate that these assumptions are not necessarily justified, and discuss alternate paradigms with implications to solar flares. Below are listed 5 paradigms that will be challenged. 1) Magnetospheric driver and ionospheric load paradigm: This paradigm is often applied to closed flux tubes where the magnetosphere acts as the driver and the ionosphere is the load. Pictorial descriptions of this relationship include examples where closed flux tubes evolve to more stressed configurations under some unknown force, driving field aligned currents to the ionosphere. An alternate paradigm is one where closed flux tubes only relax, and the system is driven only when flux tubes are open. 2) Large scale region I/II upward current systems and the current wedge produce most visual aurora paradigm: There are correlations between the magnitude of these current systems and visual aurora, with AE correlated with oval brightening and the current wedge correlated with substorm aurora. This leads many to assume that active or bright auroras are primarily due to these large scale upward currents. However, actual arcs have rather limited east-west extent and often form as a series of arcs. In addition, substorm aurora are not localized at one edge of the current wedge. An alternate paradigm is that bright arcs are primarily caused by localized flow vortices not large scale vortices. A source of these localized vortices will be discussed. 3) Reconnection accelerates the plasma resulting in bursty bulk flows paradigm: This paradigm is often pictured with the fields already determined rather than as a cause and effect. An alternate paradigm is that bulk motion results from the interchange instability associated with the decrease in flux tube content associated with plasmoid formation. 4) X-line motion paradigm: This paradigm generally has the near-Earth X-line forming in the Earth frame and remaining stationary until pressure builds up in the tail forcing it tailward. Since reconnection is a local instability, the X- line doesn't know about the Earth-frame. The only relevant reference frame is the plasma in-flow frame and the X-line should be stationary in this frame. 5) Reconnection diffusion regions are the primary energization regions for magnetospheric plasma paradigm. In particular this paradigm is applied to electrons, with reconnection energization assumed to produce the hot plasma sheet electrons. Related phenomena include observations of energetic electrons associated with flares, and the assumption that solar reconnection diffusion regions produce these energizations. FAST and Cluster observations suggest electron energization in the diffusion regions is negligible and point to another source for the production of the hot electrons. These observations suggest that the current "solar flare reconnection paradigm" may also be wrong and suggest an alternate paradigm.