Physics
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufmsm23b1718l&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #SM23B-1718
Physics
2409 Current Systems (2721), 2431 Ionosphere/Magnetosphere Interactions (2736), 2721 Field-Aligned Currents And Current Systems (2409), 2788 Magnetic Storms And Substorms (7954), 2790 Substorms
Scientific paper
The seasonal variation in geomagnetic activity and related events in the Earth's magnetosphere and ionosphere is well known for many years. One of important effects related to seasonal variation is the variation in the correlation between geomagnetic activity indices and solar wind data: The geomagnetic activity indices show good correlation with solar wind data for winter and equinoxes but the correlation is strongly reduced in summer months when polar cap is predominantly sunlit. This reduces significantly the reliability of forecasting of geomagnetic activity and related events in summer months. We investigated the correlation between the AL index (showing substorm activity in Northern hemisphere) and two geomagnetic activity indices, the Polar Cap (PC) index and the recently developed Polar Magnetic (PM) index [Lyatsky and Khazanov (2008), Space Weather, 6, S06002, doi:10.1029/2007SW000382] showing the magnetic disturbances in two polar caps. For the analysis, we used the data for four years. We obtained an unexpected yet important result: Substorm activity in summer months correlates much better with geomagnetic activity not in the nearby polar cap but in the opposite polar cap. A possible cause for this effect may be the interhemispheric field-aligned currents flowing from the summer high-latitude ionosphere and close the ionospheric currents in the opposite auroral zone. These interhemispheric currents are directed opposite to substorm field-aligned currents in the summer hemisphere providing a significant decrease in the total substorm field-aligned currents, which may be the cause for the strong seasonal variations in geomagnetic activity and related events.
Khazanov George V.
Lyatskaya Sonya
Lyatsky Wladislav
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