Effects of Diamagnetism onMagnetotail Current Sheet Equilibrium

Magnetic fields are ubiquitous in nature, with currents sheets found on numerous stellar bodies. Here, we model plasma diamagnetism’s affects in the current sheet in a Earth-like magnetotail. A commonly used analytic model for magnetic field reversals is the Harris equilibrium. In this model, the particle motion is completely integrable, and is characterized by a strongly peaked (in z) density profile that asymptoticly approaches zero, and a magnetic field that varies in z, but points in the x direction. When we allow for normal component to the current sheet of the magnetic field, the particle dynamics are nonintegrable, and frequently chaotic.We have developed a test-particle simulation method for calculating the self-consistent equilibrium of the earth's magnetotail that fully incorporates the nonlinear/chaotic charged particle dynamics of the ions. The equilibrium of the magnetic field is qualitatively similar to the Harris model, but the density is asymptoticly constant and the current is created by a completely different mechanism. We show that the current density can be broken into a free current density and a bound current density. The free current is formed by the meandering motion of ions in the vicinity of the field reversal, and the bound current is caused by plasma diamagnetism. Furthermore, the more field aligned the ion sources are in the asymptotic region, the thinner the current sheet, the more peaked the density profile, and the smaller the effects of diamagnetism.