A study on precursors leading to geomagnetic storms using artificial neural network

Space weather prediction involves advance forecasting of the magnitude and onset time of major geomagnetic storms on Earth. In this paper, we discuss the development of an artificial neural network-based model to study the precursor leading to intense and moderate geomagnetic storms, following halo coronal mass ejection (CME) and related interplanetary (IP) events. IP inputs were considered within a 5-day time window after the commencement of storm. The artificial neural network (ANN) model training, testing and validation datasets were constructed based on 110 halo CMEs (both full and partial halo and their properties) observed during the ascending phase of the 24th solar cycle between 2009 and 2014. The geomagnetic storm occurrence rate from halo CMEs is estimated at a probability of 79%, by this model.     

Controls on synorogenic alluvial-fan architecture, Beartooth Conglomerate (Palaeocene), Wyoming and Montana

Late Palaeocene uplift of the Beartooth Range in northwestern Wyoming and southwestern Montana generated the Beartooth Conglomerate along the eastern and northeastern flanks of the range. Systematic unroofing sequences and intraformational unconformities, folds, and faults in the conglomerate attest to deposition during uplift. Along the eastern flank, at least three ancient alluvial-fan systems and a braidplain system can be distinguished on the bases of petrofacies and lithofacies. The two southern fans consist of 700+ m of sedimentary-clast conglomerate and subordinate sandstone, dominated by hyperconcentrated-flow and stream-flow facies. The next fan to the north is dominated by plutonic and metamorphic clasts and contains abundant mud-matrix-supported debris-flow facies, as well as stream-flow facies. The northernmost depositional system consists of arkosic, channellized fluvial conglomerate and sandstone, overbank mudstone, and crevasse-splay sandstone units. Palaeocurrent data indicate eastward dispersal, away from the Beartooth Range. Outstanding exposure of the Beartooth Conglomerate allows facies to be mapped on lateral photographic mosaics. A seven-fold hierarchy of bounding surfaces and enclosed lithosomes exists in the Beartooth Conglomerate. First- through fourth-order surfaces are analogous to first- through fourth-order surfaces that recently have been documented in sandy fluvial facies, with one exception: sediment gravity flows are bounded by first-order surfaces. Fifth-order surfaces are either erosional (e.g. lateral migration of fanhead trench) or accretionary (e.g. aggradation of fan surface during backfilling of trench, and construction of lobes on lower fan during entrenchment on upper fan). Some fifth-order surfaces coincide with intraformational angular unconformities and are thus the result of long-term fanhead entrenchment following uplift of the upper part of the fan. Sixth-order surfaces bound individual fan packages that are several hundred metres thick and ～ 10 km² in area. The enclosed sixth-order lithosomes are distinguishable in terms of petrofacies and lithofacies. A single seventh-order surface bounds the entire Beartooth Conglomerate. Lower-order lithosomes are produced by intrinsic processes of fan construction. Fifth-order lithosomes can be attributed to both extrinsic and intrinsic controls. Sixth- and seventh-order lithosomes are generated by extrinsic controls.     

Has influence of extratropical waves in modulating Indian summer monsoon rainfall (ISMR) increased?

In the paper, influence of extratropical circulation features on Indian Summer Monsoon Rainfall (ISMR) is examined. Energetics of extratropics, north of Indian subcontinent for deficient and non-deficient ISMR years, during two periods 1951–1978 and 1979–2005, are calculated and critically analyzed. It is observed that for the period 1951–1978, only two out of the 10 energetics parameters, viz., the zonal available potential energy (high) and conversion of zonal kinetic energy to eddy kinetic energy (low) differed significantly in JJA months of the deficient years from that of the non-deficient years. However, during the 1979–2005 period, as many as six out of the 10 energetics parameters, viz., eddy available potential energy, zonal available potential energy, eddy kinetic energy, generation of zonal available potential energy, conversion of zonal available potential energy to zonal kinetic energy and conversion of zonal kinetic energy to eddy kinetic energy differed significantly in JJA months of the deficient years from that of the non-deficient years. These results confirm growing influence of the transient stationary waves in deficient years after the climate shift year, 1979. Analysis of energetics parameters of the pre-monsoon season of the two periods also reveals similar results. This suggests that forcings apparently responsible for energetics in JJA months of the deficient years of the later period were present even before the advent of Indian summer monsoon season.     

Palynology and clay mineralogy of the Deccan volcanic associated sediments of Saurashtra,Gujarat: Age and paleoenvironments

The intertrappean sediments associated with Deccan Continental Flood Basalt (DCFB) sequence at Ninama in Saurashtra, Gujarat yielded palynoassemblage comprising at least 12 genera and 14 species including Paleocene taxa such as Intrareticulites brevis, Neocouperipollis spp., Striacolporites striatus, Retitricolpites crassimarginatus and Rhombipollis sp. The lava flows of Saurashtra represent the northwestern most DCFB sequence in India. It is considered that the Saurashtra lava flows represent the earliest volcanic activity in the Late Cretaceous of the Reunion Mantle Plume on the northward migrating Indian Plate. The present finding of the Paleocene palynoflora from Ninama sediments indicate Paleocene age for the associated lava flows occurring above the intertrappean bed which suggests that the Saurashtra plateau witnessed eruption of Deccan lava flows even during Paleocene. The clay mineral investigation of the Ninama sediments which are carbonate dominated shows dominance of low charge smectite (LCS) along with the presence of mica and vermiculite. Based on the clay mineral assemblage it is interpreted that arid climatic conditions prevailed during the sedimentation. The smectite dominance recorded within these sediments is in agreement with global record of smectite peak close to the Maastrichtian–Paleocene transition and climatic aridity.     

Decision Support System integrated with Geographic Information System to target restoration actions in watersheds of arid environment: A case study of Hathmati watershed,Sabarkantha district,Gujarat

Journal of Earth System Science - Watershed morphometric analysis is important for controlling floods and planning restoration actions. The present study is focused on the identification of...