A5035946718- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Earthquake Detection and Analysis
- Lightning and Electromagnetic Phenomena
- Geomagnetism and Paleomagnetism Studies
- Electromagnetic Compatibility and Noise Suppression
- Impact of Light on Environment and Health
- Meteorological Phenomena and Simulations
- GNSS positioning and interference
- Electrostatic Discharge in Electronics
- Tropical and Extratropical Cyclones Research
- Climate variability and models
- Low-power high-performance VLSI design
- Electromagnetic Compatibility and Measurements
- Cryospheric studies and observations
- Electric Motor Design and Analysis
- Plant responses to elevated CO2
- Induction Heating and Inverter Technology
- Atmospheric Ozone and Climate
- Underwater Acoustics Research
- Fire effects on ecosystems
- Multilevel Inverters and Converters
- Remote Sensing and LiDAR Applications
- Atmospheric aerosols and clouds
- Radio Wave Propagation Studies
State Key Laboratory of Marine Geology
2019-2022
Vikram Sarabhai Space Centre
2022
Tongji University
2019-2022
Geological Survey of India
2014-2019
University of Nottingham
1998
Stray components distributed in a pulsewidth modulation (PWM) drive system form parts of resonant circuits which can be excited to produce radio frequency (RF) noise driven by the pulsed switching action power devices. The dynamic response such is complex. It essential identify dominant oscillation modes so that electromagnetic interference (EMI) reduction techniques effectively implemented. This paper (Part I) investigates mechanisms conducted EMI emissions associated with typical PWM...
For pt.I see ibid., vol.13, no.4, p.757-67 (1998). Predicting conducted emissions in pulsewidth modulation (PWM) inverter induction motor drive systems requires various frequency-dependent effects to be considered. A frequency domain method has advantages such cases compared a time approach. Based on the modal analysis presented Part I, this paper develops models evaluate spectra of directly. The common and differential mode excitation sources are modeled related switching functions PWM...
Dispersive atmospherics (tweeks) observed during 2010 simultaneously at two low‐latitude stations, Allahabad (geomagnetic latitude, 16.05°N) and Nainital 20.48°N), have been used to estimate the nighttime D region electron density ionospheric reflection height under local propagation (21:00–02:00 LT or 15:30–20:30 UT). The analysis of recorded tweeks both stations on five international quiet days one month each from summer (June), winter (January), equinox (March) seasons shows that varies...
Abstract. The devastating flood episode (16–17 June 2013) at Kedarnath (Uttrakhand, India), caused a huge loss of lives and physical/material wealth. To understand this catastrophic event, rainfall/convective data associated climate meteorological parameters are investigated. A low-pressure zone with very high cloud cover (60–90 %) relative humidity (70–100 %), low (< 4 m s−1) wind velocity, observed over the region during 15–17 June. cause disaster seems to be heavy continuous rainfall,...
Abstract We present analysis of more than 2000 lightning‐generated whistlers recorded at a low‐latitude station, located Allahabad (geographic latitude, 25.40°N; geographic longitude, 81.93°E; L = 1.081), India, during December 2010 to November 2011. The main focus this work is on the correlation between observed and lightning activity detected by World‐Wide Lightning Location Network near conjugate point (geography 9.87°S, 83.59°E) Allahabad. Whistler occurrence higher in postmidnight...
Abstract Observations of relativistic energetic electron fluxes in the outer radiation belt can show dropouts, that is, sudden flux depletions during main phase a geomagnetic storm. Many recent studies these dropouts typically involve true loss particles, nonadiabatic losses nature. Precipitation into atmosphere electrons driven bounce cone, through wave‐particle interactions, is envisaged as one primary mechanisms. Such precipitation be studied using ground‐based observations such VLF...
The loss of electron flux the outer radiation belt has been widely studied in terms mechanism that brings these losses. There are a few studies which have attempted to explain interplanetary conditions favor depletions. As Sun is prime cause any change happening magnetosphere, it important look at solar drivers bring such changes. In this study, we attempt understand effect structures and substructures on high-energy electrons during intense geomagnetic storms. superposed epoch analysis used...
Abstract. The devastating episode (17–18 June 2013) at Kedarnath (Uttrakhand, India) caused huge loss of lives and physical/material wealth. To understand this catastrophic event, rainfall/convective data associated climate meteorological parameters are investigated. Low pressure zone with very high cloud cover (60–90%), relative humidity (70–100%) low (< 4 m s−1) wind velocity over region during 15–17 observed. cause disaster seems to be the heavy continuous rainfall snow melting...
Experiments are carried out to investigate conducted EMC phenomena in a PWM induction motor drive system. Time domain simulation models which take into account the high frequency characteristics proposed. Good agreement between measured and simulated results is obtained for well defined laboratory test system, thus validating numerical models. Digital can be used predict general performance of evaluate compare effectiveness various EMI reduction techniques during design stage. Three dominant...
Abstract Throat aurora is a special discrete auroral form often observed at the ionospheric convection throat region near magnetic local noon. Some observational properties of have been established, but geomagnetic response not yet explored. Using observations from chain stations in Norwegian sector and an all‐sky imager DMSP satellites, for first time, we identify responses associated with occurrence aurora. These variations are well explained by combining models flux transfer events The...
Abstract Throat aurora is believed to be associated with magnetopause indentations and has direct implications on reconnection. In this study, for the first time, we use Defense Meteorological Satellite Program/Special Sensor Ultraviolet Spectrographic Imager observations over ∼14 years characterize throat occurrence, latitudinal extent, seasonal, its solar cycle dependence. We identified 386 cases during different passes of satellite northern hemisphere. The extent these aurorae are...
The impulse-induced super substorm of 21st January 2005 has been reported by Hajra and Tsurutani (2018) they have discussed the abnormal morphology auroral dynamics mainly examining images currents. This event is revisited here with additional datasets global Cosmic Noise Absorption (CNA) Riometers, a space-based Imager, plasma flux data from geostationary satellites magnetic field measurements ground stations covering almost all latitudinal local time sectors. We observed some peculiar...
Since last four decades and more generation propagation mechanism of very low latitude (L < 1.4) whistlers has been studied by many workers in lowlatitude regions especially India. The key questions that remain unanswered include: (1) Where are the lightning discharges, source located? (2) Do whistler waves at latitudes propagate along magnetic field lines ionosphere? We reported discharges have generated located conjugate region Indian Ocean suggested these stations ionosphere. In this...