ELECTRON-DENSITY AT THE SUBSOLAR MAGNETOPAUSE FOR HIGH MAGNETIC SHEAR- ISEE-1 AND ISEE-2 OBSERVATIONS

The ISEE radio wave propagation electron density experiment allowed th e determination of the integrated electron density between the ISEE 1 and ISEE 2 satellites at the relatively high rate of 8 or 32 Hz. When the component of the spacecraft separation vector in the direction of the normal to the magnetopause is significantly smaller than the thick ness of the current layer, this data set allows the internal structure of the magnetopause to be studied and compared with theoretical predi ctions. For a particular triple subsolar magnetopause crossing with hi gh magnetic shear, an electron density overshoot is observed in the cu rrent layer adjacent to the magnetosheath. The similarity of the three crossings indicates that the internal structure of the magnetopause d oes not change dramatically during the time interval considered. A sup erposed epoch analysis of these crossings is consistent with the densi ty profile obtained from kinetic simulations. The general relationship between magnetic field asymmetry, magnetic field rotation angle and e lectron density overshoot is discussed. It is concluded that a density overshoot could be a typical feature of the subsolar magnetopause wit h high magnetic shear. This conclusion is supported by two other daysi de magneto;pause crossings for which high time resolution electron den sity data are available.