Physics
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufmsm33a1107z&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #SM33A-1107
Physics
2730 Magnetosphere: Inner, 2753 Numerical Modeling, 2778 Ring Current, 2788 Magnetic Storms And Substorms (7954), 7959 Models
Scientific paper
For accurate physical understanding and modeling of inner magnetosphere dynamics one needs to take into account the coupling between particles and fields. Indeed, observations consistently show the magnetic field in the inner magnetosphere to be significantly depressed during active times such as geomagnetic storms. The field changes are caused by large amounts of injected plasma into the region, and they in turn strongly influence the dynamic evolution of both the plasma and the outer radiation belts. We have developed a self-consistent inner magnetosphere code that includes the field/plasma interaction, by coupling a kinetic ring current model with an Euler potential-based 3D plasma equilibrium code; in our approach, the magnetic field is computed in force balance with the kinetic model anisotropic pressures and then fed back into the kinetic code to drive its evolution. Here we report results from recent improvements to our approach that allow us to compute the self-consistent magnetic field at geostationary orbit and thus validate model output vs. geosynchronous (e.g. GOES) field measurements. This is now possible through the expansion of the model boundary into the plasma sheet (at 10 Earth radii), achieved through a new Euler potential technique in the 3D equilibrium code, coupled with the use of a statistical pressure model to expand geosynchronous pressure observations to larger distances. The new Euler potential choice also allows much more freedom in imposing the model magnetic boundary; for example, realistic storm-time empirical models such as T04S, which were difficult to use previously due to their strong asymmetry, can now be easily employed. We present output from our improved self-consistent model during both quiet times and geomagnetic storms, focusing on the computed 3D magnetic field and how it compares with both empirical model fields and in situ measurements (including from geosynchronous GOES satellites, but also from POLAR and CLUSTER when available). Finally, we compare model-computed with observed Dst during selected storms, and analyze how much of the Dst depression is due to the tail current, i.e. current systems outside geosynchronous orbit.
Friedel Reiner
Jordanova Vania K.
Reeves Geoff D.
Roeder Jens
Zaharia Sorin G.
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