Interannual consistency of bi‐monthly differences in diurnal variations of the ground‐level, vertical electric field
2005; American Geophysical Union; Volume: 110; Issue: D10 Linguagem: Inglês
10.1029/2004jd005469
ISSN2156-2202
AutoresG.B. Burns, A. V. Frank‐Kamenetsky, О. А. Troshichev, E. A. Bering, Brandon Reddell,
Tópico(s)Geomagnetism and Paleomagnetism Studies
ResumoInteryear consistency is demonstrated in the bi‐monthly average diurnal vertical electric field measured over ∼720 “fair‐weather” days collected during a 5‐year interval (1998 to 2002) at Vostok (78.5°S, 107°E; magnetic latitude 83.6°S), Antarctica. After correcting for the influence of polar‐cap convection, seasonal peaks in the average electric field values occur around July‐August with a diurnal maximum at ∼ 2050 UT while lowest average magnitudes are measured near November‐December when the associated diurnal maximum occurs at ∼1830 UT. These variations are consistent with expected seasonal changes in global thunderstorm activity. Comparisons of ground‐level vertical electric field measurements (Vm −1 ) with Weimer‐1996 model cross‐polar cap potentials above Vostok (kV) for individual UT hours yield significant correlations over all hours but with reduced standard errors around local magnetic noon (∼1300 UT). This implies a more direct linkage between solar wind parameters and the cross‐polar cap potential near magnetic noon, for this site (magnetic latitude: 83.6°S). An all hours–all seasons linkage factor of 0.76 ± 0.06 Vm −1 per kV is determined, broadly consistent with an average ionosphere‐ground potential difference of ∼250 kV and a measured average vertical electric field of 185 Vm −1 . Evidence is presented supporting a seasonal variation in this linkage factor, with generally lower magnitudes in the austral winter (May to August).
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