Measurements of positive ions and air-Earth current density at Maitri,

[1] Simultaneous measurements of the small, intermediate and large positive ions and air-Earth current density made at a coastal station, Maitri (704552S, 114403E, 130 m above sea level), at Antarctica during JanuaryFebruary 2005, are reported. Although small and large positive ion concentrations do not show any systematic diurnal variations, variations in them are almost similar to each other. On the other hand, variations in intermediate positive ion concentrations are independent of variations in the small/large positive ions and exhibit a diurnal variation which is similar to that in atmospheric temperature on fair weather days with a maximum during the day and minimum during the night hours. No such diurnal variation in intermediate positive ion concentration is observed on cloudy days when variations in them are also similar to those in small/large positive ion concentrations. Magnitude of diurnal variation in intermediate positive ion concentration on fair weather days increases with the lowering of atmospheric temperature in this season. Scavenging of ions by snowfall and trapping of a-rays from the ground radioactivity by a thin layer of snow on ground is demonstrated from observations. Variations in intermediate positive ion concentration are explained on the basis of the formation of new particles by the photolytic nucleation process