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Welcome to the Institutional Repository of Indian Institute of Geomagnetism! This repository contains re-prints, working papers, presentations, project reports, Ph.D. Thesis, posters, conference proceedings, annual reports and all the publications by the institute scientists, staff and students. Care has been taken to adhere to the copyright of materials contained in the repository. In case of any complains please do not hesitate to contact us at (iig.library@iigm.res.in).
Recent Submissions
We introduce a new framework called Machine Learning (ML) based Auroral Ionospheric electrodynamics Model (ML‐AIM). ML‐AIM solves a current continuity equation by utilizing the ML model of Field Aligned Currents of Kunduri et al. (2020, https://doi.org/10.1029/2020JA027908), the FAC‐derived auroral conductance model of Robinson et al. (2020, https://doi.org/10.1029/2020JA028008), and the solar irradiance conductance model of Moen and Brekke (1993, https://doi.org/10.1029/92gl02109). The M...
The Asian summer monsoon is one of the active synoptic scale weather phenomena, and has significant socioeconomic implications. A vast population relies on the associated precipitation, mostly dominating the agricultural practices of the region. Therefore, it is essential to assess past behavior to understand the present, including future projections. We used palaeomonsoon precipitation synthesis and Coupled Model Intercomparison Project Phase 6 (CMIP6) data to interactively show the dynamics...
The boundary layer plays a vital role in governing the local atmospheric dynamics and meteorology, including the vertical transport of moisture, momentum, energy, and air pollutants. Hence, accurate parameterization of the boundary layer processes is essential in atmospheric models such as the regional climate models (RCMs). However, evaluations of different boundary layer schemes within the Weather Research and Forecasting (WRF) model remain nearly non-existing over complex terrains of the H...
To investigate the transient strain rate of postseismic deformation associated with the highly devastating December 26, 2004 Andaman–Sumatra earthquake (Mw 9.3), a combined analysis have been done using GPS data and Seismic Moment Tensors (SMT) acquired from Andaman–Nicobar–Sumatra regions during 2005–2007. The displacement estimated during postseismic periods 2005–2006 and 2006–2007with respect to ITRF2008 and Indian Reference Frame, display dominating arc-normal active deformation in t...
Lightning generated radio atmospheric that propagates over long distances via multiple reflections through the boundaries of the Earth‐ionosphere waveguide (EIWG), shows sharp dispersion near the cut‐off frequency ∼1.8 kHz of the EIWG. These dispersed atmospherics at lower frequency end are called as ‘tweek’ radio atmospherics. In order to estimate D‐region electron densities at the ionospheric reflection heights we have utilized the dispersive property of tweeks observed at low latitude Indi...
206Alfvénic turbulence has been detected by Comet Halley at spacecrafts Giotto and Vega and by Comet Giacobini-Zinner at International Cometary Explorer (ICE). We have studied the KAW instability driven by field aligned drifts of solar wind electrons (se), and protons (H) in a cometary pair-ion plasma consisting of cometary electrons (ce), positively and negatively charged oxygen ions, with each species being modeled by a drifting ring distribution [with Vdce = VdO+ = VdO– = 0 and VdH = Vdse]...
This paper presents the results of a magnetovariational study undertaken over a basalt-covered region of western India which has been experiencing a swarm of seismic activity since early 1986. The most striking feature of the transient variations is the anomalous enhancement of the east-west (Y) component at stations bounding the seismically active belt. From the nature of the horizontal transfer functions and the anomalous induction arrows, it is inferred that this behaviour is related to th...
Bernstein, Greene, and Kruskal (BGK) have developed the theory for one-dimensional stationary nonlinear electrostatic waves in a collisionless plasma [2]. It is a nonlinear kinetic theory formulated in the one-dimensional Vlasov-Poisson framework of equations. If the solution obtained after the BGK analysis is positive, it is a model of a one-dimensional electrostatic coherent structure, usually called a BGK wave. There are certain structures called a phase space holes that develop because of...
Effects of space weather on the performance of satellite-based communication/ navigation systems have been studied for several decades. A major concern is the predictability of these effects. Apart from the effects produced by changes in the large-scale distribution of plasma in the ionosphere, it is the sub-kilometer structures that appear in the ionosphere that are of great concern as they give rise to scintillations on transionospheric radio signals. The current status of various aspects o...
A generation mechanism for kinetic Alfvén waves (KAWs) by ion-beam and velocity shear is discussed. For this, a three-component plasma model, consisting of cold background ions, hot electrons, and hot ion beams is considered. The model is very general in the sense that all of the three species have drifting Maxwellian distributions, nonuniform streaming, and velocity shear, and can be applied to magnetospheric regions where velocity shear is present. The eff ects of the ion beam alone...
Satellite observations in the magnetosphere have shown that Pc 1, 2 waves with frequencies (0.1-5Hz) below the hydrogen gyrofrequency have left-handed to linear polarization and are related to electromagnetic ion cyclotron (EMIC) waves. The parallel propagating EMIC waves are left circularly polarized wave (L-mode) and at oblique propagation, they are coupled to the right hand circularly polarized waves (R-mode). These waves exist in three distinct wave bands, e.g., H+ - band, He+ - band and ...
One of the natural laboratory for the study of solitary waves is the Earth's magnetosphere. The large gradient in particle properites at the magnetospheric boundary layers initiate the perturbation which leads to the generation of solitary waves. These structures propagate either parallel or perpendicular to the local magnetic field. The E-field bipolar structures moving parallel to the background magnetic field (Electrostatic Solitary Waves (ESWs)) are observed ubiquitously in different magn...
The effect of a non-thermal ion velocity distribution is studied on linear and nonlinear dust-acoustic waves in an unmagnetized three component dusty plasma. For the linear theory, electrons are Boltzmann distributed, ions are treated kinetically with a non-thermal ion velocity distribution and the dust particles are considered to be streaming with respect to ions. It is found that growth of the waves is possible when streaming velocity of the dust particles is larger than the phase velocity ...
Magnetic Field Satellite (MAGSAT) data contains contribution from the earth's core, external currents and the crust; the data has been successfully utilised to derive information about each of these sources. Magsat provided the first main magnetic field model based on global vector survey, determining the core radius and mapping fluid motions at the core mantle boundary. It studied the external meridional currents and field aligned currents at high latitudes. But above all Magsat's contributi...
Disturbed time prompt penetration electric fields are observed to transmit instantaneously from high to low latitudes and are believed to effect the global ionosphere similarly. However, some new observations claim that during disturbed times the F region responses are not uniform and the top side F region can respond differently in comparison to the bottom side. Such observations, which are critical to understating of ionospheric electrodynamics in 3-dimensions, are extremely difficult to ma...
Geomagnetic variations, recorded through a two-phase magnetovariational study carried out along the Ganga-Yamuna valley of the Garhwal Himalaya, northwest India, are reduced to a set of induction arrows spanning a period range of 12-128 minutes. The spatial behaviour of induction response indicates that the Main Frontal Thrust is a major electrical discontinuity with enhanced conductivity to the south, beneath the Indo-Gangetic plains. Simple two-dimensional (2-D) geoelectrical models with ge...
Some of the linear macroinstabilities which can play important roles in space plasmas like the Earth's ionosphere and magnetosphere are discussed. Starting from the basic concept of plasma instabilities, we proceed to discuss the mathematical tools available for investigating macroinstabilities in plasma. Using equations for the magnetohydrodynamics (MHD), and also two fluids equations where ever necessary, we derive the evolution equations for some macroscopic instabilities and, then, discus...
The mesosphere/lower thermosphere (MLT) wind data from the 46 ground-based (GB) MF and meteor radar (MR) stations, located at the different latitudes over the globe, and the space-based (SB) HRDI data were used for constructing of the empirical global climatic 2-D prevailing wind model at 80–100 km heights for all months of the year. The main data set is obtained during 1990–2001 period. It is shown that the three datasets (MF, MR, HRDI) are mainly well correlated. However, a certain systemat...
We present the results of a study of Electrostatic Solitary Waves (ESWs) in which propagation of a series of noncyclical ESWs is observed from one Cluster spacecraft to another over distances as great as tens of km and time lags as great as a few tens of ms. This propagation study was conducted for locations near the magnetopause on the magnetosheath side. Propagation was found primarily toward the earth with speeds on the order of 1500 to 2400 km/s. The sizes of the ESWs obtained from these ...
We report on recent measurements of solitary waves made by the Wideband Plasma Wave Receiver located on each of the four Cluster spacecraft at 4.5-6.5RE (well above the auroral acceleration region) as they cross field lines that map to the auroral zones. These solitary waves are observed in the Wideband data as isolated bipolar and tripolar waveforms. Examples of the two types of pulses are provided. The time durations of the majority of both types of solitary waves observed in this region ra...
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