Solar Wind Driving of Magnetospheric Convection and Plasma Sheet Content

For some time now energetic neutral atom (ENA) measurements have been used to quantitatively track the behavior of the ring current, predominantly during storm times. More recently it has been shown that ENA observations may also provide a good measure of convection in the magnetosphere via tracking the position of the plasma sheet and the amount of plasma contained in it. We present long-duration (days to weeks), near- continuous time series of ENA observations of the near-tail plasma sheet that show just how sensitive these observations are to large-scale convection. We can track convection over a large range of geomagnetic activity levels (including major storms) on time scales better than, for example, Kp. We compare ENA convection observations to established geomagnetic activity indices and discuss the correlation with the solar wind, including crucial pre-storm intervals. We will also explore the limits of this technique as we currently see it. This includes a discussion of the shortest sensible integration time for our measurements, and the possibility to derive an absolute measurement of convection and/or plasma sheet content based on near-Earth tail observations.