Kalyan Bhuyan

Diurnal, seasonal and latitudinal variation of electron density in the topside F-region of the Indian zone ionosphere at solar minimum and comparison with the IRI

Abstract The diurnal, seasonal and latitudinal variation of electron density (Ne) measured by the Indian SROSS C2 satellite from December 1994 to January 1997 at low and equatorial latitudes along 75°E meridian are investigated. The satellite covered the latitude belt of 31°S to 34°N and longitude range of 40°E to 100°E at an average altitude of ∼500 km . Electron density is minimum before sunrise and reaches the diurnal maximum in the afternoon hours. A secondary enhancement is observed in the sunset hours of June solstice. The well-known equatorial ionization anomaly is found to be asymmetric at the altitude tracked by the satellite in this period of low solar activity (mean sunspot number=13.9). The location of the crest of the anomaly varies with season. There are seasonal and latitudinal variations of Ne. Further, electron density is found to be positively correlated with the strength of the equatorial electrojet. Comparison of measured density with that predicted by the International Reference Ionosphere (IRI) reveals that the IRI overestimates Ne at about all local times and in all seasons. The IRI also fails to produce the secondary enhancement of electron density.

Bianchi III Cosmologies for the Form \(f(R)=R-\beta /R^n\) Using the Palatini Formalism

We derive the exact solutions for Palatini version of f(R) gravity for the anisotropic Bianchi type-III cosmological model using Dynamical System Approach. For f(R) of the form \(f(R)=R-\beta /R^n\), we have found the fixed points describing the radiation (\(P_r\)), matter (\(P_m\)), de-Sitter (\(P_d\)), shear (\(P_s\)) and spatial curvature (\(P_k\)). Moreover, we also analyse the phase space of the system to observe the evolution of the spatial curvature.

Phase Portraits of Higher Dimensional FRW Cosmology in \(R^pexp(\lambda R)\) Gravity Filled with Non-perfect Fluid

In this work we investigate the higher dimensional FRW model in the presence of a non-perfect fluid in case of \(R^pexp(\lambda R)\) gravity. We use the dynamical system approach to find the set of fixed points for the cosmological system. The analysis of the phase space of this model has been extended with the aim of finding the stability of the universe, particularly whether the anisotropy in the model isotropizes in the future and a late times the universe evolves towards accelerated expansion.

Impact of zonal wind on latitudinal variation of total columnar ozone over the Indian Peninsula

Latitudinal and seasonal variability of total columnar ozone from September 2007 to August 2008 across the Indian longitude sector within 10.5° N to 34.5° N and 70.5° E to 94.5° E using satellite data obtained from Aura Ozone Monitoring Instrument (OMI) of National Aeronautics and Space Administration (NASA) Earth Observing System (EOS) is presented. The total column ozone (TCO) over the area of study shows a gradually varying pattern throughout the year. In the post-monsoon (autumn) and winter months, maximum TCO is observed in the north-western part of the subcontinent while the minimum is often observed towards the east at about the same latitudes. A west–east spatial gradient is clearly observed in autumn months. As winter approaches, a north–south spatial gradient becomes more prominent than the east–west gradient. It has been further observed that TCO does not vary significantly over the entire subcontinent in monsoon.