Plasma sheet Pv5/3 and nV and associated plasma and energy transport for different convection strengths and AE levels

摘要

To understand the large-scale plasma sheet thermodynamics, we have used Geotail data and a formula for estimating flux tube volume V to investigate statistically the equatorial distributions of PV5/3 and nV for slow flowing plasma in the nightside plasma sheet and compare them with the physical bases of ideal MHD and the Rice Convection Model (RCM). We have examined the distributions under three conditions: (1) weak convection and low AE, (2) enhanced convection and low AE, and (3) enhanced convection and high AE. The overall nV decreases significantly with increasing convection or AE, while the overall PV513 remains similar. We found that PV5 drops significantly earthward along the estimated electric drift paths near midnight, inconsistent with ideal MHD. Examination of PkV5/3 and the electric and magnetic drift paths of different energy invariants, where Pk is the partial pressure of a specific energy invariant, shows that the strong duskward drift of the above thermal-energy particles due to magnetic drift, together with there being significantly fewer higher-energy particles from the dawn flank than from the tail, results in the strong earthward decrease of PV 5/3 . We also found that d(PkV5/3)/dt = 0 and d(nkV)/dt = 0 along the electric and magnetic drift paths used in the RCM are good approximations for slow flowing pressure-bearing plasma sheet ions. The distributions of nV indicate that low-energy plasma becomes dominant when convection and AE are low, and their transport from the flanks may be affected by nonadiabatic processes not included in ideal MHD or the RCM.