The Inertialized Rice Convection Model

摘要

The Rice Convection Model (RCM) is an established first-principles physics model in which the field-aligned current density is computed by the Vasyliunas equation. Its slow-flow assumption neglects the inertial term in the MHD momentum equation, which is a major obstacle to using the RCM to model some of the fluid dynamics of bursty bulk flows in the plasma sheet. This paper describes the RCM-I, which represents an effort to approximately add inertial effects in the RCM by correcting the expression for field-aligned currents. That inertial current is calculated under the assumption that the mass on each field line is concentrated near the equatorial plane. RCM-I results are presented with magnetic fields calculated in two different ways: A static statistics-based model and an MHD code. In both cases, the bubble flow velocities are much smaller and more realistic than those calculated from the traditional RCM. An additional promising feature is that the injection of a low-entropy bubble produces interchange (braking) oscillations and buoyancy waves that radiate away from the original bubble, forming multiple flow vortices. None of these features could be produced by traditional RCM simulations. Comparison simulations also suggest that gradient and curvature drifts have substantial effect on oscillation of bubbles and tend to damp buoyancy waves. We also note that substantial work will be needed in the future to further improve the pressure distribution by inertializing an anisotropic version of the RCM and to understand the effects of neglecting the magnetosphere-ionosphere communication time.