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 with model calculations of particle transport from the solar wind to spacecraft locations in the magnetosphere. Comparison of the observed and calculated particle spectra shows that the model can successfully match the spectra at both spacecraft using the same model parameters. This demonstrates that the modeling technique is applicable at both high and low altitudes. We are also able to conclude that the particles originate from a fairly narrow spatial region on the magnetopause even though magnetosheath plasma has access to the magnetosphere over the entire magnetopause in the model. The success of the model in reproducing key features of the observed spectra and the fact that the two satellites in near magnetic conjunction but at different altitudes observed similar, distinctive features at times separated by 10 - 20 min demonstrates that there are quasi-stationary, spatial features in the cusp/cleft region of the Earth's magnetosphere.