Physics
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufmsm14b..02z&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #SM14B-02
Physics
[2740] Magnetospheric Physics / Magnetospheric Configuration And Dynamics, [2753] Magnetospheric Physics / Numerical Modeling, [2760] Magnetospheric Physics / Plasma Convection, [2778] Magnetospheric Physics / Ring Current
Scientific paper
Conservation of entropy of a fluid element along its flow path is an assumption made in all global ideal magnetohydrodynamics (MHD) models of the magnetosphere. While appropriate in the farther plasma sheet, closer to Earth this assumption is inaccurate: the energy-dependent gradient/curvature drifts (or, equivalently in a fluid picture, the diamagnetic drift) cannot be neglected anymore; the separation of particles with different energies onto different trajectories leads to the entropy of any given plasma parcel not being conserved along any path. We investigate the effect of the full kinetic motion (conserving the first and second adiabatic invariants) on the entropy behavior and more generally the whole near-Earth magnetosphere dynamics under sustained solar wind driving (southward IMF) and strong convection typical of geomagnetic storm conditions. The main tool in the investigation is our self-consistent kinetic inner magnetosphere model RAM-SCB, a 2-way coupling of the kinetic ring current-atmosphere interactions model (RAM) with an Euler potential-based 3D anisotropic plasma equilibrium code. To fully capture the region where the kinetic drifts are important, the model boundary has been expanded from the geosynchronous location to 9 RE from Earth. This presentation analyzes, using simulation results with the expanded RAM-SCB of both an idealized event and a real storm, the following effects: 1). the changes in 2D entropy profile in the near-Earth magnetosphere under sustained convection, and their dependence on magnetic self-consistency (pressure feedback on the field); 2). the strength of energy injection (as portrayed by plasma pressure and the Dst index) as a function of plasma sheet conditions (density, temperature, entropy and their local time structure); and 3). the importance of the gradient and curvature drifts and entropy non-conservation on ring current development and pressure increase in the near-Earth magnetosphere during strong convection.
Jordanova Vania K.
Welling Dan T.
Zaharia Sorin G.
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