Abstract
Abstract Observations of atmospheric Maxwell current from the low-latitude continental station, Tirunelveli (8.7°N, 77.8°E), over a period of 8 years are presented in this study. The horizontal long-wire antenna is used as a sensor for picking up charges from the atmosphere. The objectives of the present work have been to understand the antenna system in response to different meteorological conditions and on fairweather days. We define a fairweather day as a day when there is no snowfall/rainfall at the measuring site, when there are high clouds less than 3 octas throughout the day, and when the wind speed is less than 10 m s−1. A sunrise effect is observed in the measured Maxwell current during fairweather days in all seasons. The measured current exhibits an increase that commences about 30 min before sunrise and lasts for nearly 1.5 h. The sunrise effect is found to be inhibited on days when there is pre-dawn convection and during the presence of rain, haze, or cloud cover. Barring the sunrise effect, the rest of the variations on fairweather day appear to follow a trend typical of the Carnegie curve. On clear cloudless conditions, reasonably good data are obtained during equinox and winter months but not in summer when strong winds associated with the onset of the southwest monsoon make the measurement of Maxwell current difficult and limited data are available.
Highlights
Continuous measurements of atmospheric electrical parameters, namely, the vertical electric field, the conductivity, and the air-Earth current, that characterize the global electric circuit (GEC) are considered useful in any study with the aim of understanding fully the electrical environment of the Earth
We have explored the possibility of identifying the signature of the DC global circuit in our Maxwell current data
In this paper we report observations of the atmospheric Maxwell current and electric field made at Maitri during fairweather days for the period 2001–2004 Fig. 2(a)
Summary
Continuous measurements of atmospheric electrical parameters, namely, the vertical electric field, the conductivity, and the air-Earth current, that characterize the global electric circuit (GEC) are considered useful in any study with the aim of understanding fully the electrical environment of the Earth. Since the global circuit links the lower troposphere, the ionosphere, and the magnetosphere, the measurements of atmospheric electrical parameters will be useful in any integrated approach that involves all these regions (Bering, 1995; Rycroft et al, 2000). Wilson by identifying global signatures in measured atmospheric electrical parameters (Adlerman and Williams, 1996). The measurement sites need to be free of atmospheric aerosols and convective activity that otherwise would obscure the weak signatures representing global thunderstorm activity (Israel, 1970, 1973). Ruling out earlier measurements from different stations as possibly due to local processes, Adlerman and Williams (1996) were able to de-
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