| Summary: | This study reports the longitudinal dependence of the field-aligned Poynting flux in the Northern Hemisphere (NH) based on 11 years' (1999-2009) observations at similar to 800 km altitude by the Defense Meteorological Satellite Program (DMSP) F13 satellite. Seasonal variations of the longitudinal distributions of the Poynting flux in both geographic and geomagnetic coordinates were statistically investigated. The net Poynting flux, which is the sum of downward and upward fluxes, is downward and peaks in the magnetic local time pre-noon sector and near the geomagnetic pole. In geographic coordinates there is a longitudinal peak of the net Poynting flux that occurs between similar to 130 degrees and 160 degrees W. The net Poynting flux is, in general, stronger in the western hemisphere than in the eastern hemisphere and larger in summer than in winter. These results indicate that the magnetospheric energy deposition into the northern polar upper atmosphere has obvious longitudinal and seasonal variations.
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