Physics
Scientific paper
Dec 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agufmsm11a0801l&link_type=abstract
American Geophysical Union, Fall Meeting 2001, abstract #SM11A-0801
Physics
2400 Ionosphere, 2409 Current Systems (2708), 2427 Ionosphere/Atmosphere Interactions (0335), 2437 Ionospheric Dynamics, 2443 Midlatitude Ionosphere
Scientific paper
Ground magnetic perturbations due to ionospheric and Birkeland currents are computed with an ionosphere-magnetosphere coupling model, which is built in a realistic geomagnetic field coordinate system. These magnetic coordinates are based on Euler potentials and have been computed for the International Geomagnetic Reference Field. The coupling is reduced to the ionospheric dynamo by assuming an empty magnetosphere. The ionosphere composition is modeled with realistic conductances and a diurnal tidal wind, which is recognized as the main driver of the dynamo. Magnetospheric currents are not taken into account except Birkeland currents that flow along equipotential magnetic field lines to maintain the divergence-free of the current system, formed in the two hemispheres. Usage of a realistic geomagnetic field allows for direct comparison with local observations and for longitudinal variation studies. The magnetic perturbations for 15 locations in three longitudinal sectors are investigated. The locations are chosen to correspond with geomagnetic observatories within the [-50°, +50°] dip latitude range. Quiet days around equinoxes are considered for observations. Our simple model is able to reproduce the general features but not all the details observed. Nevertheless, the coupling along realistic field lines allows for the simulation of some longitudinal differences. For example, the following observed features are reproduced: the dissimilar behavior of the magnetic declination at -50° dip latitude in the three longitudinal sectors, the difference between the horizontal component at 30° dip latitude in Asian and Europe sectors, and the difference in declination and horizontal component at -30° dip latitude in the American and African sectors. These first comparisons emphasize the importance of the magnetic field model to simulate the interhemispheric coupling along field lines and ionospheric electrodynamics in general.
Huang Tao
Le Sager Philippe
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