The Causes of Changes in Hydrogen Distribution

Neutral hydrogen plays an important role in determining the state of the plasmasphere and its response to forcing from geomagnetic storms. In this presentation we consider the distribution of hydrogen above the exobase and how it changes with time of day, season and in response to geomagnetic forcing. NCAR-TIMEGCM hydrogen densities are compared with those from MSIS to determine the fidelity of the GCM runs and a postprocessor term analysis is performed to determine the physicalprocesses for quiet times. Results from a geomagnetic storm simulation run with the NCAR-TIMEGCM are then analyzed to determine how this hydrogen distribution is changed and what processes cause the changes