Modeling the quiet time inner plasma sheet protons

In order to understand the characteristics of the quiet time inner plasma s heet protons, we use a modified version of the Magnetospheric Specification Model to simulate the bounce averaged electric and magnetic drift of isotr opic plasma sheet protons in an approximately self-consistent magnetic fiel d. Proton differential fluxes are assigned to the model boundary to mimic a mixed tail source consisting of hot plasma from the distant tail and coole r plasma from the low latitude boundary layer (LLBL). The source is local t ime dependent and is based on Geotail observations and the results of the f inite tail width convection model, For the purpose of self-consistently sim ulating plasma motion and a magnetic field, the Tsyganenko 96 magnetic fiel d model is incorporated with additional adjustable ring-current shaped curr ent loops. We obtain equatorial proton flow and midnight and equatorial pro files of proton pressure, number density, and temperature. We find that our results agree well with observations. This indicates that the drift motion dominates the plasma transport in the quiet time inner plasma sheet. Our s imulations show that cold plasma from the LLBL enhances the number density and the proton pressure in the inner plasma sheet and decreases the dawn-du sk asymmetry of the equatorial proton pressure. From our approximately forc e-balanced simulations the magnetic field responds to the increase of press ure gradient force in the inner plasma sheet by changing its configuration to give a stronger magnetic force. At the same time, the plasma dynamics is affected by the changing field configuration and its associated pressure g radient force becomes smaller. Our model predicts a quiet time magnetic fie ld configuration with a local depression in the equatorial magnetic field s trength at the inner edge of the plasma sheet and a cross-tail current sepa rated from the ring current, results that are supported by observations. A scale analysis of our results shows that in the inner plasma sheet the magn itude of the Hall term in the generalized Ohm's law is not small compared w ith the quiet time electric field. This suggests that the frozen-in conditi on E = -v x B is not valid in the inner plasma sheet and that the Hall term needs to be included to obtain an appropriate approximation of the general ized Ohm's law in that region.