LOW-ALTITUDE OBSERVATIONS AND MODELING OF QUASI-STEADY MAGNETOPAUSE RECONNECTION

Data from two near-conjugate passes of DE 1 and DE 2 through the cusp/ cleft region of the Earth's magnetosphere are presented and compared w ith model calculations of particle transport from the solar wind to sp acecraft locations in the magnetosphere. Comparison of the observed an d calculated particle spectra shows that the model can successfully ma tch the spectra at both spacecraft using the same model parameters. Th is demonstrates that the modeling technique is applicable at both high and low altitudes. We are also able to conclude that the particles or iginate from a fairly narrow spatial region on the magnetopause even t hough magnetosheath plasma has access to the magnetosphere over the en tire magnetopause in the model. The success of the model in reproducin g key features of the observed spectra and the fact that the two satel lites in near magnetic conjunction but at different altitudes observed similar, distinctive features at times separated by 10 - 20 min demon strates that there are quasi-stationary, spatial features in the cusp/ cleft region of the Earth's magnetosphere.