Time variation analysis of the daily Forbush decrease indices

In the present paper we have analyzed the daily Forbush decrease indices from January 1, 1967 to December 31, 2003. First filtering the time series by Simple Exponential Smoothing, we have applied Scargle Method of Periodogram on the processed time series in order to search for its time variation. Study exhibits periodicities around 174, 245, 261, 321, 452, 510, 571, 584, 662, 703, 735, 741, 767, 774, 820, 970, 1062, 1082, 1489, 1715, 2317, 2577, 2768, 3241 and 10630 days with confidence levels higher than 90%. Some of these periods are significantly similar to the observed periodicities of other solar activities, like solar filament activity, solar electron flare occurrence, solar-flare rate, solar proton events, solar neutrino flux, solar irradiance, cosmic ray intensity and flare, spectrum of the sunspot, solar wind, southern coronal hole area and solar cycle, which may suggest that the Forbush decrease behaves similarly to these solar activities and these activities may have a common origin.     

Neoproterozoic age based on microbiotas from the Raipur Group of Baradwar sub-basin,Chhattisgarh

An assemblage of structurally preserved organic-walled microfossils (OWMs) from the macerated residue of black carbonaceous shale belonging to Saradih Formation, the youngest carbonate horizon of the Raipur Group, Chhattisgarh Supergroup exposed at on the right bank of Mahanadi River, NE of Sarangarh township in Raigarh district, Chhattisgarh is being reported for the first time. The assemblage is comprised of 19 taxa of 13 genera belong to eukaryotes and prokaryotes viz. Leiosphaeridia, Stictosphaeridium, Dictyotidium, Synsphaeridium, Symplassosphaeridium, Satka, Trachysphaeridium, Goniosphaeridium, Trachyhystrichosphaera, Vandalosphaeridium, Siphonophycus, Oscillatoriopsis and Polythrichoides. The comprehensive account of recovered microbiotic assemblage can be correlated with globally known Neoproterozoic (early Cryogenian) assemblages, deposited in tidal complexes of shallow sea.     

Interspecific association of heavy minerals in late Paleozoic Gondwana sandstones of Singrauli sub-basin,central India: Implications for provenance

Heavy mineral analysis of the late Paleozoic Barakar and Raniganj sandstones from the Singrauli Gondwana sub-basin shows relative abundance of garnet, epidote, zircon, tourmaline and muscovite in the Raniganj Sandstone and epidote, garnet, rutile and tourmaline in the Barakar sandstones. Stratigraphically, the heavy mineral crops donot exhibit marked variation in their relative abundance, though garnet, epidote and muscovite form the bulk of the heavy minerals. Significant interspecific association among heavy minerals and provenance of the Barakar and Raniganj sandstones are evaluated by using σ-M multivariate model. Quantitative result suggests that the Barakar Sandstone are characterized by the basic pair match significantly more than expected due to chance alone (p value <<0.05) are garnet-tourmaline and epidote-rutile, whereas, the succeeding Raniganj sandstone are characterized by zircon-rutile and epidote-garnet. These basic pairs may be regarded as interspecific association among the heavy minerals. The basic pairs deduced from heavy mineral suites suggest that the source rocks of late Paleozoic Barakar and Raniganj sandstones have been principally derived from the acid plutonic rocks and low to high grade metasediments lying to the south and southeast of the Singrauli Gondwana sub-basin.     

Hydrochemistry deducing basaltic trap thickness for groundwater resource mapping along the Deccan Volcanic Province (DVP) margin in India

It is hypothesized that hydrochemical parameters can be employed to deduce the basaltic trap thickness and that there exist diverse hydrochemical processes within the existing host rocks along the Deccan Volcanic Province (DVP) margin. Chemical imprints of aquifers, in various flows of flood basalt and fissured zones of granites, had been appraised using major ion chemistry of groundwater in a test site of 623 km² at the southern margin of the DVP in India. The wide ranging hydrochemical processes, obtained from empirical data, describe the predominance of carbonate, dolomite, calcite and anorthite weathering in basalts, and alkali feldspar (albite and orthoclase) in granites. Results showed that the elevated concentrations of alkaline earth elements in basaltic aquifers and alkali rich elements in granitic aquifers were useful in tracing the sources of host rock for dissolved mineral reactants. Further, a digital elevation model using Shuttle Radar Topography Mission (90 m) elevation satellite data aided in deciphering trap thickness, vertical transition zone of trap and granitic basement comprising the well depths and hydrochemistry. The mapping of trap thickness is useful to explore the groundwater resources at the vertical transition zone between the basaltic trap and granitic base. The estimated thickness of the basaltic trap is varied from 4 to 98 m at the DVP southern margin, which is further verified with the help of exploratory well lithologs matched closely.     

North–south asymmetry of different solar activity features during solar cycle 23

A study on north–south (N–S) asymmetry of different solar activity features (DSAF) such as solar proton events, solar active prominences [total, low (?40°) and high (?50°) latitudes], Hα flare indices, soft X-ray flares, monthly mean sunspot areas and monthly mean sunspot numbers carried out from May 1996 to October 2008. Study shows a southern dominance of DSAF during this period. During the rising phase of the cycle 23 the number of DSAF approximately equals on both, the northern and the southern hemispheres. But these activities tend to shift from northern to southern hemisphere during the period 1998–1999. The statistical significance of the asymmetry time series using a χ²-test of goodness of fit indicates that in most of the cases the asymmetry is highly significant, meaning thereby that the asymmetry is a real feature in the N–S distribution of DSAF.     

Landslide susceptibility maps comparing frequency ratio and artificial neural networks: a case study from the Nepal Himalaya

This study considers landslide susceptibility mapping by means of frequency ratio and artificial neural network approaches using geographic information system (GIS) techniques as a basic analysis tool. The selected study area was that of the Panchthar district, Nepal. GIS was used for the management and manipulation of spatial data. Landslide locations were identified from field survey and aerial photographic interpretation was used for location of lineaments. Ten factors in total are related to the occurrence of landslides. Based on the same set of factors, landslide susceptibility maps were produced from frequency ratio and neural network models, and were then compared and evaluated. The weights of each factor were determined using the back-propagation training method. Landslide susceptibility maps were produced from frequency ratio and neural network models, and they were then compared by means of their checking. The landslide location data were used for checking the results with the landslide susceptibility maps. The accuracy of the landslide susceptibility maps produced by the frequency ratio and neural networks is 82.21 and 78.25%, respectively.     

Discovery of Gondwana plant fossils and palynomorphs of Late Asselian (Early Permian) age in the Karakoram Block

We report the discovery of Early Permian (late Asselian, ∼280–275 Ma) plant fossils and associated palynomorphs from a marine sedimentary sequence of the eastern Karakoram plate, in northern India. These specimens show affinities with those found in marine Lower Gondwana sediments of the Indian subcontinent. This supports the contention that during the Early Permian Period, the Karakoram plate was Peri-Gondwanan. It is suggested to have had an intermediate position between the Indian plate and the Qiangtang–Lhasa microcontinents, at a latitude of about 35° south.     

Effect of oblateness on the non-linear stability of the triangular liberation points of the restricted three-body problem in the presence of resonances

The non-linear stability of the triangular libration points of the restricted three-body problem is studied under the presence of third and fourth order resonance's, when the more massive primary is an oblate spheroid. In this study Markeev's theorem are utilised with the help of KAM theorem. It is found that the stability of the triangular libration points are unstable in the third order resonance case and stable in the fourth order resonance case, for all the values of oblateness factor A₁. This revised version was published online in August 2006 with corrections to the Cover Date.     

Projecting impacts of climate change on surface water temperatures of a large subalpine lake: Lake Tahoe, USA

Predicted increases in atmospheric CO₂ concentration are expected to cause increases in air temperatures in many regions around the world, and this will likely lead to increases in the surface water temperatures of aquatic ecosystems in these regions. Using daily air and littoral water temperature data collected from Lake Tahoe, a large sub-alpine lake located in the Sierra Nevada mountains (USA), we developed and tested an empirical approach for constructing models designed to estimate site-specific daily surface water temperatures from daily air temperature projections generated from a regional climate model. We used cluster analysis to identify thermally distinct groups among sampled sites within the lake and then developed and independently validated a set of linked regression models designed to estimate daily water temperatures for each spatially distinct thermal group using daily air temperature data. When daily air temperatures projections, generated for 2080–2099 by a regional climate model, were used as input to these group models, projected increases in summer surface water temperatures of as much as 3 °C were projected. This study demonstrates an empirical approach for generating models capable of using daily air temperature projections from established climate models to project site specific impacts on littoral surface waters within large limnetic ecosystems.