Global ENA observations of the storm mainphase ring current: Implications for skewed electric fields in the inner magnetosphere P. C:son Brandt (1), S. Ohtani (1), D. G. Mitchell (1), M. -C. Fok (2), E. C. Roelof (1), R. Demajistre (1) 1 - The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 2 - NASA Goddard Space Flight Center The ring current in the 27-39 keV range during 19 geomagnetic storm main phases is investigated. The data is obtained by the high energy neutral atom (HENA) imager on board IMAGE. Global ion distributions are derived from the observed energetic neutral atom (ENA) images using a constrained linear inversion technique. The peak of the ion distribution is skewed to the midnight to dawn sector, whereas in the classical picture the fluxes peak at dusk. The skewing angle is increasing with the total solar wind electric field across the magnetosphere. We discuss how this morphology implies the existence of strong and skewed equatorial electric fields in the inner magnetosphere. These observations are consistent with observations and kinetic models that self-consistently calculate the electric field produced by the closure of the partial ring current. These observations point to a new understanding of the main phase ring current. _______________ Submitted to Geophysical Research Letters, 2002