SELF-CONSISTENT EQUILIBRIA IN THE EARTH’S MAGNETOTAIL CURRENT SHEET
Due to the non-linear/chaotic dynamics of charged particles in the Earth’s magnetotail, the equilibria structure of the current sheet is notoriously difficult to calculate. Simple analytic models can reproduce qualitatively correct magnetic fields (B-field), but for completely incorrect reasons. Additionally, the simple models cannot determine realistic densities and pressures. In this presentation, we self-consistently determine the equilibrium structure of the current sheet including the full non-linear ion dynamics. Using a test particle simulation, an input source distribution of protons is pushed through a model B-field. As each particle moves through the B-field, its contributions to the overall particle density, current, and pressure are calculated. Appropriate weightings are then used to calculate the total density, current, and pressure. Updated magnetic fields are determined from the calculated currents and compared with the input B-field. The calculated and input B-fields are mixed to produce an updated input field. This process is iterated until the calculated and input fields converge. Once the fields are convergence, the solution exhibits pressure balance in both the diagonal and off-diagonal elements of the momentum equations. We will show serval examples varying both the drift velocity and temperature of the source distribution. It is found that adding low levels of noise into the system does not significantly alter the results. Finally, we allow for Boltzmann electrons, which results in an electric field near the center of the current sheet that acts to attract electrons and repel ions. This tends to increase the current sheet thickness.
Sullivan-Woods, Jonathan, "SELF-CONSISTENT EQUILIBRIA IN THE EARTH’S MAGNETOTAIL CURRENT SHEET" (2019). University Research Symposium. 344.