Energetic Neutral Atom (ENA) Pitch Angle Distribution as a Function of Storm Phase - Precursor to Future Work in Mapping ENA/Ion Albedo with Storm Phase

Charge exchange between ring current ions spiraling into the upper atmosphere and terrestrial neutral constituents produces a non-isotropic distribution of escaping Energetic Neutral Atoms (ENA). These ENA’s are no longer tied to the magnetic field, and can therefore be observed remotely from orbiting platforms. In this study we build on previous work described in Pollock et al., 2009 in which IMAGE/MENA data was used to compute the pitch angle distribution of ENA’s observed in the 29 October 2003 storm. The algorithm used in Pollock et al., 2009 is used to compute the pitch angle distribution for additional storms at different phases of the solar cycle. The pitch angles are then used to characterize the velocity-space distribution of ENA’s emanating from the source point as well as the configuration-space distribution of ENA fluxes from a point in the upper atmosphere. This work is the foundation for a further study to model the ENA/ion precipitation albedo over storm phase. The albedo maps will be used in conjunction with in-situ ion precipitation data to study the energy input as a function of storm phase.