Features of discrete VLF emissions observed at Gulmarg, India during the magnetic storm of 6-7 March, 1986

During the analysis of archived VLF data from Indian low latitude ground stations, some discrete VLF emissions recorded at the low latitude ground station Gulmarg (geomagnetic latitude 24°26′N; geomagnetic longitude 147°09′E, L = 1.28) during moderate magnetic storm activity (Σ K P − = 32, K P index varies from 4 to 6 during the observation period) on 6/7 March, 1986 are presented in this paper. The dynamic spectra of these discrete VLF emissions were observed along with tweeks and its harmonics, which is interesting and complex to explain. In most of the events the harmonic frequency of tweeks correlates with the starting frequency of harmonics of discrete emissions. In order to explain the observed features of discrete VLF emissions, we propose cyclotron resonance interaction between whistler mode wave and energetic electrons of inner radiation belt as possible generation mechanism. An attempt is also made to determine parallel energy, anisotropy and wave growth relevant to the generation process of VLF emission

Thermal effects on parallel resonance energy of whistler mode wave

In this short communication, we have evaluated the effect of thermal velocity of the plasma, particles on the energy of resonantly interacting energetic electrons with the propagating whistler mode waves as a function of wave frequency and L-value for the normal and disturbed magnetospheric conditions. During the disturbed conditions when the magnetosphere is depleted in electron density, the resonance energy of the electron enhances by an order of magnitude at higher latitudes, whereas the effect is small at low latitudes. An attempt is made to explain the enhanced wave activity observed during magnetic storm periods. © Indian Academy of Sciences

Thunderstorms, lightning, sprites and magnetospheric whistler-mode radio waves

Thunderstorms and the lightning that they produce are inherently interesting phenomena that have intrigued scientists and mankind in general for many years. The study of thunderstorms has rapidly advanced during the past century and many efforts have been made towards understanding lightning, thunderstorms and their consequences. Recent observations of optical phenomena above an active lightning discharge along with the availability of modern technology both for data collection and data analysis have renewed interest in the field of thunderstorms and their consequences in the biosphere. In this paper, we review the electrification processes of a thunderstorm, lightning processes and their association with global electric circuit and climate. The upward lightning discharge can cause sprites, elves, jets, etc. which are together called transient luminous events. Their morphological features and effects in the mesosphere are reviewed. The wide spectrum of electromagnetic waves generated during lightning discharges couple the lower atmosphere with the ionosphere/ magnetosphere. Hence various features of these waves from ULF to VHF are reviewed with reference to recent results and their consequences are also briefly discussed. © Springer Science+Business Media B.V. 2009

Weathered basalt application for management of Vertisols: A traditional knowledge of groundnut (Arachis hypogaea) growers of Gujarat, India

793-799Gujarat tops with 27.87% of total groundnut production. The basaltic shrink-swell soils are generally evaluated as unsuitable for groundnut production in Saurtashtra region of Gujarat. They have untapped source of traditional knowledge for managing heavy shrink-swell soils of basaltic terrain. Groundnut growers of the region are applying weathered basalt (WB, Vēraḍēḍa bēsālṭanuṁ in Gujarati) in pure form which is naturally available or sometimes treated by mixing the farmyard manures (FYM) or groundnut husk, and/or fortified with nitrogenous and phosphatic fertilizers. A study was planned to find out the reason for higher production of groundnut with the application of WB before sowing the seed. For this study the farmers were divided in to 05 groups on the basis of forms and combinations of WB application in groundnut fields. The participatory approaches and personal interviews were combined to collect the data from 25 farmers of each group. After interviewing the farmers, we came to know that this practice is being followed since 40 years. The study revealed that the practice significantly reduces the contracting and expanding phenomenon in black Vertisols and improve physico-chemical properties of soils like hydraulic characteristics (infiltration, permeability, percolation and drainage), aeration, bulk density, porosity, thermal conductivity and also improve availability of secondary (Ca, Mg & S) and micronutrients (Fe, Mn, Zn & Cu). The present study forms the basis for upgrading the traditional management packages for sustainable groundnut production in black soil region of India

Photoprotective and biotechnological potentials of cyanobacterial sheath pigment, scytonemin

Cyanobacteria are the main component of microbial populations fixing atmospheric nitrogen in aquatic as well as terrestrial ecosystems, especially in wetland rice-fields, where they significantly contribute to fertility as natural biofertilizers. Cyanobacteria require solar radiation as their primary source of energy to carry out both photosynthesis and nitrogen fixation. The stratospheric ozone depletion which has resulted in an increase in ultraviolet-B (UV-B; 280 - 315 nm) radiation on earth’s surface has been reported to inhibit a number of photochemical and photobiological processes in cyanobacteria. However, certain cyanobacteria have evolved mechanisms such as synthesis of photoprotective compound scytonemin and their derivatives to counteract the damaging effects of UV-B. In addition this compound has anti-inflammatory and anti-proliferative potentials. This review deals with the role of scytonemin as photoprotective compound and its pharmacological as well as biotechnological potentials

Potential of Mimulas glabratus in removal of Fe and Cu from the aqueous solutions containing Nitrate and Phosphate and its growth responses

The metal bioabsorption potential and survival efficiency of aquatic macrophyte M. glabratus was examined for the removal of Fe and Cu in presence of nitrate and Phosphates. M.glabratus removes Fe 10% more than Cu in  case of bio-chemical and physical responses the increment in fresh weight found 0.74% more in Fe treated plants than Cu treated plants and in photosynthetic pigments there was 10% more increment was noted in the plants treated with Fe. Bioabsorption of Fe was noted 18.9% more than Cu by M. glabratus. The results demonstrate that M.glabratus can be utilized in the remediation operations of aquatic systems Keywords: Bioabsorption, M. glabratus, Photosynthetic pigments, Biomas

Tidal and gravity waves study from the airglow measurements at Kolhapur(India)

Simultaneous photometric measurements of the OI 557.7 nm and OH (7, 2) band from a low latitude station, Kolhapur (16.8° N, 74.2° E) during the period 2004-2007 are analyzed to study the dominant waves present in the 80-100 km altitude region of the atmosphere. The nocturnal intensity variations of different airglow emissions are observed using scanning temperature controlled filter photometers. Waves having period lying between 2 and 12 hours have been recorded. Some of these waves having subharmonic tidal oscillation periods 4, 6, 8 and 12 hours propagate upward with velocity lying in the range 1.6-11.3 m/s and the vertical wave length lying between 28.6 and 163 kms. The other waves may be the upward propagating gravity waves or waves resulting from the interaction of inter-mode tidal oscillations, interaction of tidal waves with planetary waves and gravity waves. Some times, the second harmonic wave has higher vertical velocity than the corresponding fundamental wave. Application of these waves in studying the thermal structure of the region is discussed