Interannual consistency of bi‐monthly differences in diurnal variations of the ground‐level, vertical electric field

Abstract

[1] Interyear 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 À1 ) 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 À1 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 À1 . Evidence is presented supporting a seasonal variation in this linkage factor, with generally lower magnitudes in the austral winter (May to August).Citation: Burns, G. B., A. V. Frank-Kamenetsky, O. A. Troshichev, E. A. Bering, and B. D. Reddell (2005), Interannual consistency of bi-monthly differences in diurnal variations of the ground-level, vertical electric field,

The Global Circuit Intensity: Its Measurement and Variation over the Last 50 Years

“…A rapid increase in electric field intensity near the surface of the ice field initiated at varying wind velocities has been reported at Vostok where a diurnal variation in wind velocity commonly occurs (Burns et al 2005). A diurnal wind speed variation is observed nine months a year (data available online from Station Vostok, surface wind and air pressure field, atwww.aari.ru/south/statioris/vostok/ vostok_en.html).…”

“…Earlier measurements (Bering et al 1998) showed a maximum in the diurnal variation in the 0800-1600 UTC interval for spring/summer and in the 1200-1600 UTC range for autumn/winter, which is different than the maximum in the 1800-2000 UTC period for the Carnegie curve at all times of the year (Israel 1973, p. 353). More recent analysis (Burns et al 2005) shows the Carnegie curve when two-month daily averages are compiled. This improvement is due to careful selection of fair-weather days (39% of the days in a 5-yr period) and correction for the polar-cap ionospheric generator.…”

“…An additional problem in trying to study the global circuit in the polar-cap region is that ionospheric electric fields map downward to the Earth s surface (Richmond 1986;Roble and Tzur 1986;Burns et al 2005) and are superimposed on the fields of the global convective cloud generator. Considerable progress has been made in removing global electric fields from Antarctic data.…”

Characteristics of the atmospheric electric field and correlation with CO2 at a rural site in southern Balkans

“…Such is the case for the Xanthi site. Applications of that method are found for Marsta Observatory (Israelsson and Tammet 2001), Nagycenk Geophysical Observatory (Märcz and Harrison 2003), and elsewhere (O'Connor 1976; Burns et al 2005) with criteria customized for each site.…”

Surface fair-weather potential gradient measurements from a small tropical island station Suva, Fiji

“…Harrison, 2003). At Vostok station, fair-weather data were selected on the basis of electric field values alone, and spikes (change of 50 V m −1 within 5 mins) were rejected (Burns et al, 2005). On most days, the overhead atmosphere at Suva was covered in full or part with cirrus/cirrostratus clouds and a mean solar radiation of 850 W m −2 was recorded near the solar zenith.…”