S. S. De

On Schlomilch's Integral Equation for the Ionospheric Plasma

The analytical form of the absorption index appropriate to the D- and E-region of the ionospheric plasma is derived. It has been utilised to build up Schlomilchs integral equation. The corresponding solution is obtained in terms of certain ionospheric parameters. The variation of effective collision frequency with height has been computed numerically from the derived solution. The results are presented graphically along with an earlier work.

Schumann resonance: A latest wonder for climate forecast!

Enhanced tropical convection is associated with increased upper-tropospheric relative humidity. The positive co-relationship between deep convection and upper-tropospheric humidity is observed for both regional and temporal variations over a wide range of space and time scales. The regions of increased upper-tropospheric moisture are found to be strongly correlated with an enhanced greenhouse trapping, although the effects of lower-tropospheric moisture and temperature lapse rate are also observed to be important. The greenhouse effect of water vapour increases sharply when temperature increases, leading to a positive feed back for climate change. Upper-tropospheric water-vapour (UTWV) variability and global lightning activity are closely linked suggesting that upper-tropospheric water-vapour changes can be inferred from the records of global lightning activity. The continental deep-convective thunderstorms could transport large amount of water vapour into the upper troposphere, which would dominate the variations of global UTWV while producing most of the lightning on Earth. Global lightning produces Schumann resonance modes, which are trapped in the Earth-ionospheric waveguide. As there are approximately 50–100 lightning flashes per second around the globe, the variability of the intensity of the Schumann resonances represents a continuous measure of the variability of global lightning activity which is dependent on UTWV. Thus monitoring of SR would provide a tool for time-tracking UTWV changes which will contribute to a better understanding of the processes affecting climate change. The correlation between troposheric water content and Schumann Resonance field can be explored using data of several years, which is still lacking to the world researchers. From the observed nature of correlation of time series data, a model will be built which will be made useful to forecast the water vapour content from the observed value of Schumann Resonance data. Climatic condition would be forecasted using SR data with the sequence below: SR data ⇒ Water vapour content ⇒ climate forecasting

Thermal Anomalies Around the Time of Nepal Earthquakes M 7.8 April 25, 2015 And M 7.3 May 12, 2015

TwoconsecutivelargeearthquakeshavingMvalues7.8and7.3occurredonApril25andMay12, 2015,respectivelyatNepal.Duringtheiroccurrences,abruptincreaseingreenhousegases(likeCO2, CH4,H2etc.)andenhancementofradonemanationsarefound.Theseattainhighmomentumthat introduceanomalyinthefluidexpulsionfromseismicallyactivefaultswhichproduceairionization beforetheselargeearthquakes.Theprocessmaybeverymuchrelatedtothelatentheatreleasedue tocondensationofionizedaerosols,producedbyenergeticalphaparticlesfromradonjustbeforethe earthquake.Thisprobablyintroduceschangesintheobservedmeteorologicalparametersintheregion. Suchvariationsmaybeduetosiesmotectonicallyinducedradonanomalybeforetheearthquake.

Time series modelling of maximum tsunami wave heights recorded in Sibolga (Sumatra)

This study reports univariate modeling methodologies applied to the maximum tsunami wave height over Sibolga, Sumatra. The univariate time series models fitted are autoregressive model (AR), autoregressive integrated moving average (ARIMA) and autoregressive neural network (AR-NN). Goodness of fit of the models to the time series of maximum tsunami wave height has been assessed using percentage of prediction error, Pearson correlation coefficient, and Willmotts indices. After rigorous skill assessment using the above three models, the AR-NN model with seven previous values as predictor has been identified as the best predictive model for the time series under study.

Field solution in an anisotropic plasma imbedded in a moving dielectric medium

Wave equations in an anisotropic plasma imbedded in a moving dielectric medium have been derived through Maxwell-Minkowski relations. These are solved for longitudinal and transverse cases of propagation. The dispersion relation within the medium has been deduced through which the nature of splitting may be understood.

Field solution for a dipole in an anisotropic medium containing time-varying irregularities

Field solutions for a dipole in an anisotropic plasma medium are obtained in the presence of an infinitesimally small electric current source and time-varying irregularities through the use of inverse Fourier-transform technique. The derived solutions can be utilized for the evaluation of the field at an arbitrary distance and are also useful to lossy medium.

Dynamical evolution of Schumann resonance frequency spectra during some strong Q-bursts

Schumann resonances (SR) observations from a tropical region near Kolkata at the estuary of the river Ganges merging into the Bay-of-Bengal (21.48° N, 88.61° E) are being made frequently. Several Q-bursts spectra are observed. Strong ELF transients are detected in the recorded data of SR. The dynamic evolution of electric and magnetic field components of the Q-bursts will be presented in this paper. Time series evolutions of signals of several Q-bursts are analyzed in the present study. It is observed that, the Q-burst amplitudes from 1 to 300 Hz of Q-bursts spectra for 1 sec FFT reaches about −47 dB near the first mode of SR frequency. This shows that Q-burst has the tendency to dominate within 1 to 300 Hz.

Studies on the effects of AILA-2009 on VLF Integrated Field Intensity of Atmospherics

Remarkable effects on the records on Integrated Field Intensity of Atmospherics (IFIA) over Kolkata (latitude: 22.56° N, longitude: 88.5° E) at 3 kHz and 9 kHz are observed due to severe electrical activity in a thunderstorm, AILA, followed by severe thundershowers and lightning. The analyses and evaluation of the recorded data have been presented here.

A Markov chain approach in the prediction of severe pre-monsoon thunderstorms through artificial neural network with daily total ozone as predictor: XXXth URSI general assembly and scientific symposium to be held in Istanbul, Turkey, August 13–20, 2011

Purpose of the present paper is to examine the predictability of the occurrence of the severe pre-monsoon thunderstorm over Gangetic West Bengal. Instead of considering various meteorological predictors, the daily total ozone concentration is chosen as the predictor because of the influence of tropospheric as well as stratospheric ozone on the genesis of meteorological phenomena. Considering the occurrence/non-occurrence of thunderstorm in the pre-monsoon season (March-May) of the year 2005 as the dichotomous time series{Xt} that realizes 0 and 1 for non-occurrence and occurrence of TS respectively, a first order two state (FOTS) Markov dependence is revealed within this time series.

Studies on the short-range pressure pulse generation within the auroral ionosphere

Auroral electric field is a probable source of Atmospheric Gravity Waves (AGW) in the thermospheric region of Auroral zone of the ionosphere and associated Traveling Ionospheric Disturbances (TID). This field is considered to be active through Lorentz force and Joule dissipation that influence the neutral gas of the medium through collision. The process introduces the short-range gravity waves. The expressions for the low frequency part of the fractional pressure variations have been derived within the auroral region of the ionosphere. The results of numerical analyses are presented graphically.