Using X-ray Occultation Sounding to Detect Dynamic Atmospheric Features in the Upper Mesosphere and Lower Thermosphere

X-ray Occultation Sounding (XOS) is a new technique for measuring total atmospheric density in the lower thermosphere and mesopause region (70-150 km) . As bright celestial X-ray sources are occulted by the Earth's atmosphere, extinction arising from inner-shell photoionization provides density information which is independent the chemistry, ionization, and thermal states of atmospheric gases. Simplistic density retrievals using XOS have demonstrated densities roughly consistent with the NRLMSISE-00 empirical climatological atmospheric model. We present results from a more detailed retrieval algorithm that enables us to examine the differences between observed density profiles and climatological predictions. An ensemble of X-ray occultations observed with the Pulse Counter Array aboard the Rossi X-ray Timing Explorer satellite are presented. We search for heating effects caused by solar X-ray flares by correlating XOS-based densities against solar X-ray fluxes measured by the GOES satellite. We also consider how other dynamical and space weather effects might account for deviations of measured densities from climatological predictions.