HR: 14:40h
AN: GP33A-05    [Abstracts]
TI: Using the TIEGCM to Examine the Effects of Gravity and Plasma Pressure on Magnetic Perturbations at low Latitudes
AU: * Maute, A I
EM: maute@ucar.edu
AF: High Altitude Observatory NCAR, 3450 Mitchell Lane, Boulder, CO 80301 United States
AU: Richmond, A D
EM: richmond@ucar.edu
AF: High Altitude Observatory NCAR, 3450 Mitchell Lane, Boulder, CO 80301 United States
AB: We use the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General-Circulation Model (TIEGCM) to calculate the electric currents driven by gravity and plasma pressure gradients. Using spherical-harmonic analysis of the three-dimensional current system we determine the magnetic perturbations at the ground, within and above the ionosphere. In regions of enhanced plasma density like the equatorial anomaly the influence of currents driven by gravity and plasma pressure gradients on the magnetic perturbations is most pronounced. Using measurements from the CHAMP satellite L\"uhr et al. [2003] were able to quantify for the first time the size of the diamagnetic effect associated with plasma pressure on the magnetic perturbations, which can be up to 5 nanoteslas We find that the gravity driven current can cause magnetic perturbations comparable in size with those from the diamagnetic effect. Depending on the altitude and location the magnetic perturbations due to plasma pressure gradients and gravity can sometimes tend to cancel. We will examine the strength of the two contributions with altitude but also study the longitudinal and local time variability. In addition we expect changes over the solar cycle in the magnetic perturbations due the two current sources.
DE: 2409 Current systems (2708)
DE: 2415 Equatorial ionosphere
DE: 2443 Midlatitude ionosphere
DE: 1555 Time variations--diurnal to secular
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting