The proposal is to investigate the DMSP satellite database of particle precipitation during a series of magnetospheric state transitions. State transitions will include the magnetospheric response to changes in IMF By and Bz components, precursors and responses to substorm onset, and states of flux tube refilling. These state changes will be investigated using state variables determines from DMSP particle data. Such state variables include the ion isotropy boundary and polar cap boundary - from which can be estimated the polar cap area. The database includes over 356,000 nightside crossings which will be investigated statistically, sorted according to substorm phase.
