Other
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmsm51a1311w&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #SM51A-1311
Other
[2409] Ionosphere / Current Systems, [7904] Space Weather / Geomagnetically Induced Currents, [7924] Space Weather / Forecasting, [7959] Space Weather / Models
Scientific paper
Prior methods for calculating geomagnetic perturbations as a function of the solar wind/interplanetary magnetic field (IMF) are often based on simulation or empirical calculations of the electric fields and currents in the ionosphere. The geomagnetic perturbations at ground level are calculated from the ionospheric parameters without having a complete knowledge of the ionospheric conductance as well as the effects of induced, underground currents. A new empirical model for geomagnetic predictions is under development, based on global measurements of the ground level geomagnetic field, along with the simultaneous measurements of the IMF. This model uses measurements from over 100 stations in the Northern hemisphere, presently from a four-year interval. This new model will be able to more accurately reproduce the geomagnetic fluctuations for a given set of IMF conditions, since it bypasses the need for ionospheric models and also implicitly includes conductivity variations. Comparisons of IMF-derived model “predictions” with measurements at different locations show very good results, even for stations location near the South pole. Variations on long temporal scales have very good agreement, particularly in the polar cap. Within the auroral zone there are often higher frequency variations from the prediction level, due to the storage and release substorm cycle, as well as the random motions of the aurora. Due to their chaotic nature, the most rapid variations may never be predictable other than by an estimation of probabilities, much like present day forecasts of atmospheric thunderstorms. The latitude-MLT maps of the Northward and Eastward components of the magnetic perturbations that are produced from this model as a function of the IMF are very consistent with the corresponding maps of the ionospheric electric potentials. Interestingly, the maps of the Vertical component very much resemble the maps of ionospheric field-aligned currents.
Clauer Robert C.
Weimer Daniel R.
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