Kinetic dissipation in magnetotail dipolarizations

Understanding kinetic mechanisms of dissipation in collisionless plasmas is one of the most compelling unsolved problems of magnetospheric physics. In the absence of collisions, dissipation is enabled by the Landau resonance for ions and electrons. In the magnetotail, the magnetic field, stretched in the antisunward direction because of its interaction with the solar wind, undergoes rapid contractions making it more dipolar. The Landau dissipation makes these dipolarizations irreversible and it controls the time scales of plasma instabilities that lead to their formation during substorms, pseudobreakups, bursty bulk flows and dipolarization fronts. However, studies of collisionless dissipation encounter two problems. First, conventional single-fluid measures of dissipation cannot resolve between ion and electron dissipative processes. Second, simple 1D current sheet models cannot properly describe dipolarizations, because they ignore the finite magnetic field component B_z normal to the current sheet plane. 2D models with finite B_z values require either an external driving or special tail features to make dipolarization plasma eigenmodes unstable: X-lines, thin current sheets with the thickness comparable to the thermal ion gyroradius, and tailward B_z gradient regions. In this study we perform a set of PIC simulations of magnetotail current sheets. The simulation setups are based on 2D models of the tail current sheet, taking its observations into account. This is implemented through the empirical reconstruction of the magnetotail and its dipolarizations by mining historical spaceborne magnetometer data on substorm scales. The results of PIC simulations are analyzed using new kinetic measures of collisionless dissipation, which have been recently proposed in studies of collisionless turbulence and dipolarization fronts. Simulation-based kinetic dissipation parameters are compared with similar parameters inferred from MMS observations. They are also used to determine the observational regimes that are necessary to evaluate the new kinetic dissipation parameters.