The intrinsic dipole model of the magnetosphere of Mercury is combined with statistics on the solar wind dynamic pressure from Explorers 33 and 35 to obtain histograms of the solar wind stand‐off distance for aphelion, perihelion and median distance of Mercury from the sun. The results show that even at perihelion the stand‐off distance lies above the surface the great majority of the time. On rare occasions, direct impact of the solar wind onto the surface will occur.

The purpose of this note is to point out: 1) that during geomagnetic reversals and excursion, the zones of frequent auroral occurrence will be located at very different geographical positions than at present; and 2) that two of the most recent excursions that have been suggested, the Laschamp-Gothenburg and the Lake Mungo events, are dated in upper paleolithic period (ca. 12,000 yr BP and 30,000yr BP respectively (NOEL and TARLING, 1975;MoRNER and LANSER, 1975;BARBETTI and MCELHINNY, 1972;FREED and HEALY, 1974)), and could have produced frequent auroral displays to major populations of stone age people. The second point might be important because it opens the possibility that some of the previously uninterpreted artifacts and drawings from this period could be representations of auroral forms.At present the aurora are seen most frequently in fairly narrow, approximately latitudinal bands around 70 north and south. In these so-called auroral zones, the aurora is a nightly occurrence.The location of the auroral zones is determined by the present values of the strength and orientation of the magnetic dipole of the earth and by average solar wind parameters.Statistics of auroral occurrence at low latitudes are governed by the statistics of variations of certain solar wind parameters.We assume for this discussion that solar wind averages and statistics have remained constant in time, and look at the changes in the location of the auroral zones that result from changes in the geomagnetic field that occur during reversals and excursions.In particular we concentrate in this note on the effect of decreasing the strength of the dipole, and on excursions of the dipole axis.There is not complete agreement among paleomagnetists about whether the dipole axis actually moves much during one of these events or whether the ap-*On leave from the

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Five water samples were collected from tap and hand pump of various area of tonk city. The physical chemical parameters such as fluoride, iron, calcium, magnesium, sulphate and nitrate were analyzed in the water samples, to characterize the ground water quality and suitability for drinking purpose. All the water samples were compared with Indian standard of drinking water prescribed by bureau of Indian standard BIS 10500:2012. The physical chemical analysis of water samples of Tonk city showed that Fluoride varied from 0.0 to 0.3 mg/l, Iron from 0.1 to 22.22 mg/l, Calcium from 45.29 to 252.50 mg/l, magnesium from 6.65 to 37.84 mg/l, Sulphate from 25.74 to 94.65 mg/l and Nitrate from 2.25 to 22.00 mg/l. The result of physical chemical analysis of water samples of Tonk city indicated that tap water of Jawahar Bazar Area (S1), Taj colony Area (S2) and hand pump of Mehandi Bagh Area (S4) were suitable for drinking purpose but hand pump water of Takhata Area (S3) and Civil line Area (S5) were unsuitable for drinking purpose on the basis of calcium and iron concentration. This study thus concludes that hand pump water in study area is chemically unsuitable for drinking and it is recommended to carry out a proper water quality program in study area.