Ion equatorial pitch angle distributions from energetic neutral atom images obtained by IMAGE during geomagnetic storms

The purpose of this investigation is to study the global structure of the ring current based on ion equatorial distributions of the ring current extracted from energetic neutral atom (ENA) images obtained by the IMAGE satellite during geomagnetic storm/substorm times.; Deconvolution technique has been proven to be an effective image inversion method that can be used to extract the ion pitch angle distribution from the ENA image. Exploring the effectiveness of the deconvolution technique with the actual ENA image data from the IMAGE satellite, we have found the deconvolved ion fluxes contain the main features of the parent, ion sources which are capable of reflecting the global structure of the ring current during stormtime.; Deconvolved ion equatorial fluxes for two major storms are used to study the global structure and drift patterns of the ring current. We have shown that these two storms have similar observed features that the peaks of the energetic ion fluxes persist in the post-midnight instead of being in the pre-midnight during the time period of interest. However, one storm shows the peak ion flux slowly drifting eastward, whereas another shows the flux peak slowly drifting westward. We found there are two different mechanisms to explain these observed features. For the first storm, the strong electric field in the storm mainly takes responsibility in bringing the ion flux more eastward; whereas for the second storm, the repeated ion injections refill refresh ions from the plasma sheet into the nightside ring current after the ion fluxes drift away from that region due to the dominant energy-dependent magnetic drift. From the detailed comparisons and discussions for these two different storms, we also found the electric field of the inner magnetosphere is an important feature in understanding the drift patterns of the ion flux in the stormtime ring current. The study of the ion flux drift patterns under different storm conditions can help us to understand the electric field structures in the inner magnetosphere.; Correlation studies between characteristics of the Far Ultraviolet/Spectrographic Imager (FUV/SI12) images in the polar region and properties of mapped ion fluxes from the equatorial plane show that (1) the ring current is one of most important sources for proton precipitation in the polar region and the trapped ions in the ring current can precipitate into the night side auroral oval region; (2) the intense ion flux on the equatorial plane results in more poleward proton precipitation, whereas the weaker ion flux results in more equatorward proton precipitation, and (3) the proton precipitation from the ring current can not only intensify the proton auroras but also destroy the symmetry structure of the ring current.