Self-Consistent Calculation of the Magnetic Field Reversal

We present a test particle numerical method to self-consistently calculating equilibrium profiles for the magnetotail current sheet that incorporates the full nonlinear/chaotic charged particle dynamics of the plasma ions. The ions are modeled using a drifting Maxwellian source in the asymptotic region. The ions are them numerically pushed through a model magnetic field, all the while calculating their density, current and pressure. Initially, the electrons are taken to be a neutralizing back ground that does not contribute to the net current. Once all of the ions have been pushed through the field, a new magnetic field is calculated and compared to the input field. The process is iterated until the input and calculated field converge. The results are in agreement with other similar models. We have focused on the effects of bound vs free currents in the field reversal. We find that as the drift velocity becomes smaller (as compared to the thermal velocity) the current sheet becomes thicker and the field due to the bound current becomes much larger (and in the opposite direction) to the net magnetic field (due to the sum of the bound and the free currents). For very small drift velocities, the convergence begins to fail. We believe this is due to the bound current becoming sufficient large that the free current cannot contribute a sufficient amount to create the assumed field reversal.