Berlin 2005 – wissenschaftliches Programm

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EP: Extraterrestrische Physik

EP 18: Poster-Session I: CAWSES, Atmosph
äre und erdnaher Weltraum

EP 18.5: Poster

Freitag, 4. März 2005, 09:00–19:00, Poster TU BH

SOLAR ZENITH ANGLE AND MERGING ELECTRIC FIELD CONTROL OF FIELD-ALIGNED CURRENTS: A STATISTICAL STUDY OF THE SOUTHERN HEMISPHERE — •Hui Wang1,2, Hermann Luehr1, and ShuYing Ma21GeoForschungsZentrum, Potsdam, Germany — 2Dept.of Space Physics, College of Electric Information, Wuhan Univeristy, P. R. China

Two years’ high-resolution CHAMP FGM measurements are used to study the statistical features of the field-aligned currents (FACs) in the southern polar ionosphere, which provide a double coverage of the seasons and about a six-fold coverage of all local times. Special attention is paid to the influence of the solar illumination induced conductivity on the morphology features of FACs on normal conditions when merging electric field is not exceeding 2 mV/m. It shows that the solar influence on the conductivity strongly controls the FAC densities at the dayside. A linear relation between the conductivity and the peak FAC density exists. Solar elevation does not affect the nightside FAC density, the conductivity is dominated by the precipitation of energetic particles carrying the field-aligned current. On the dayside a systematic difference of the footprint latitude between sun-lit and dark conditions emerges. Based on the above results, we may suggest that the sources of Birkeland currents on the dayside behave like a voltage source, while on the nightside possibly like a current source.

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