Simultaneous measurements of the small-, intermediate- and large- positiveions and air earth current density made at a coastal station, Maitri atAntarctica during January to February 2005, are reported. Although, small andlarge positive ion concentrations do not show any systematic diurnalvariations, variations in them are almost similar to each other. On the otherhand, variations in intermediate positive ion concentrations are independent ofvariations in the small/large positive ions and exhibit a diurnal variationwhich is similar to that in atmospheric temperature on fair weather days with amaximum during the day and minimum during the night hours. No such diurnalvariation in intermediate positive ion concentration is observed on cloudy dayswhen variations in them are also similar to those insmall/large positive ionconcentrations. Magnitude of diurnal variation in intermediate positive ionconcentration on fair weather days increases with the lowering of atmospherictemperature in this season. Scavenging of ions by snowfall and trapping of Alha- rays from the ground radioactivity by a thin layer of snow on ground, isdemonstrated from observations. Variations in intermediate positive ionconcentration are explained on the basis of the formation of new particles bythe photolytic nucleation process.
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