Energetic Neutral Atom (ENA) Low Altitude Emission (LAE) Pitch Angle Distribution obtained from IMAGE/MENA over the span of the mission

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. Particularly of interest is Low Altitude Emissions (LAE) of ENA's. These ENA emissions occur near the oxygen exobase and constitute the brightest ENA signatures during geomagnetic storms. 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 algorithms used in Pollock et al. [2009] are used to compute the pitch angle distribution for 80 identified storms at different phases of the solar cycle. The pitch angles are a function of invariant latitude, magnetic local time, and universal time. This allows them to be 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.