Plasma transfer processes at the magnetopause

Abstract

With the possible exception of a small area at each of the two magnetic cusps, classical theory of interaction between the solar wind and the magnetosphere predicts the magnetopause to be an impenetrable boundary separating cold (~ 100 eV) dense (~ 30 cm−3) plasmas on magnetosheath magnetic field lines from hot (~ 1 keV) tenuous (~ 0.3 cm−3) plasmas on magnetospheric magnetic field lines. But in fact, observations indicate that a boundary layer of magnetosheath-like plasmas can be found just inside all regions of the magnetopause, including the nightside equatorial magnetopause (Hones et al., 1972), the low-latitude dayside magnetopause (Eastman et al., 1976; Haerendel et al., 1978), and the high-latitude magnetopause (Rosenbauer et al., 1975; Paschmann et al., 1976). A recent statistical survey indicates that this layer is present on over 90% of all equatorial and mid-latitude magnetopause crossings (Eastman et al.,1996). The boundary layer is often divided into the low-latitude boundary layer (LLBL), the entry layer near the polar cusps, and the plasma mantle (PM) along the high-latitude magnetotail. Some reports suggest that such plasmas can be observed deep inside the magnetosphere during periods of strongly northward IMF orientation (Mitchell et al., 1987; Sauvaud et al., 1997; Fujimoto et al., 1997).