Using ground magnetometer data from several stations near the dip equator, the magnetically quiet-time characteristics of the daytime normal electrojet and the morning and afternoon counter-electrojets are established and illustrated. In particular, the solar cycle, seasonal, longitudinal and day-to-day variations of counterelectrojets as well as their dependence on lunar phase are studied. In order to investigate the influence of solar tidal winds in the production of counter-electrojets, the equatorial electric fields generated by such winds through the dynamo mechanism are calculated, using a numerical dynamo simulation model developed earlier at UCLA. From these calculations it is found that westward electric fields responsible for the afternoon counter-electrojets can be produced in the local summer solstice (when these events are most common) by a combination of the solar semidiurnal (2, 2) tide and the diurnal (1, -2) tide. An example from January 1964 is discussed to illustrate that afternoon counter-electrojet events occurring at all longitudes on the same day are likely to be associated with abnormalities in the global Sq or SR current system. It is suggested that the lunar semi-diurnal tide is a more important causative agent for the morning rather than the afternoon counterelectrojets.

It is shown that time‐structure analysis of geomagnetic crochets can be useful in the ground‐based detection of XUV radiation from solar flares. The crochets often manifest a composite structure that consists of a ‘fast’ component presumably produced by EUV radiation (100–1000Å) and a ‘slow’ component produced by soft X rays (1–100Å). This composite structure is taken into account in the proposed method of analysis for crochet current systems. Some preliminary results are given from the simulation studies of Sq and crochet current systems. These studies are intended to probe into the nature of the atmospheric winds that drive the ionospheric dynamo and that generate both the Sq and crochet currents.

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An attempt has been made to assess the groundwater recharge potential zones in Upper Manimuktha sub basin, Vellar river, Tamil Nadu. Groundwater recharge denotes to the entry of water from the unsaturated zone into the saturated zone below the water table surface, together with the associated movement away from the water table within the saturated zone. This study mainly focus the many factors that control the occurrence and movement of groundwater in a hardrock region including topography, Geology, lineament, drainage patterns, land use/land cover, slope and soil. Using remote sensing and Geographic Information System it is possible to take number of different thematic maps of the area and overlay form a new integrated layer. The integrated map reveals about the groundwater recharge potential zones of the area and classified into five categories which represents very low to Very good Groundwater Recharge Potential Zones (GWRPZ). Downstream areas as well as waterbodies fall in the very high GWRPZ (12.4 km 2 ) indicates high infiltration and low runoff. Then followed by high GWRPZ (115.74 km 2 ) indicate these area maximum covered by agricultural land (57.99 km 2 ) as well as fallow land (85.41 km 2 ), so the infiltration high. In the poor (125.28 km 2 ) and very low GWRPZ (82.61 km 2 ) mainly fall in the hilly terrain as well as in the waste, barren and buildup land of the study area. Based on the GWRPZ study indicate 34.4 % of the rainwater infiltrate in the ground of the entire study area.

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