The dawn polar cap boundary at high altitude     

T.E. Moore  R.L. Arnoldy  B. Hultqvist  R. Aparicio 《Planetary and Space Science》1980,28(11):1019-1026

Comparison of hot plasma data from ATS-6 and GEOS-1 when the satellites were near dawn L.T. conjunction reveals the presence of strong gradients separating plasmas differing by more than two orders of magnitude in keV particle fluxes. These gradients are observed at off-equatorial geomagnetic latitudes of 25–30° on field lines outside the synchronous orbit. They are associated with magnetic storms and are distinct from magnetopause crossings. Interpretation of these events in terms of a boundary between magnetospheric and polar-cap plasma leads to the following conclusions: (1) the polar cap/lobe region is essentially devoid of keV plasma at these times; (2) the field lines defining this boundary are significantly distorted from a dipolar to a more stretched form consistent with the presence of a storm-ring current, (3) smaller substorm-scale motions are superposed on the gross motion of the boundary with some evidence present for structure in the plasma spatial profile, and (4) magnetosheath-like plasma finds access to the inner magnetosphere at dawn L.T., much as it does near noon, along polar-cap boundary-layer field lines which close through the low latitude magnetospheric boundary layer.  相似文献   

Quiet-time convection electric field properties derived from keV electron measurements at the inner edge of the plasma sheet by means of GEOS-2     

B. Hultqvist  H. Borg  L.-Ă. Holmgren  H. Reme  A. Bahnsen  M. Jespersen  G. Kremser 《Planetary and Space Science》1982,30(3):261-283

From an analysis of the local time distribution of the electron upper energy limit reached by the geostationary satellite GEOS-2 in cutting through the innermost part of the electron plasma sheet during fairly quiet conditions the following results have been obtained, among others. An electric field model given by $\text{E}\text{= ?▽{AR}{}^4\text{sin}\text{(φ+}\text{π}\text{4}\text{)}}$, with the dusk singular point of the forbidden region boundary at 1500, instead of at 1800 M.L.T., is in quite good agreement with the observations. This means that effects due to the shielding by the hot plasma of the inner magnetosphere from the convection electric field are quite strong in situations of low disturbance level. The quiet-time convection electric field strength at 2100 M.L.T. in the geostationary orbit obtained from this analysis varies in the range 0.15–0.3 kV/R_e. Six hours earlier or later in the satellite orbit the convection field is four times stronger. Also when the convection field varies, some information about its magnitude can be obtained from the keV electron measurements.  相似文献