A5063001005- Ionosphere and magnetosphere dynamics
- Earthquake Detection and Analysis
- Solar and Space Plasma Dynamics
- Lightning and Electromagnetic Phenomena
- Seismic Waves and Analysis
- Tropical and Extratropical Cyclones Research
- GNSS positioning and interference
- Geomagnetism and Paleomagnetism Studies
- Meteorological Phenomena and Simulations
- Climate variability and models
- Atmospheric aerosols and clouds
- Radio Wave Propagation Studies
- Fire effects on ecosystems
- Geophysics and Sensor Technology
- Precipitation Measurement and Analysis
- Ocean Waves and Remote Sensing
- earthquake and tectonic studies
- Atmospheric Ozone and Climate
- Astro and Planetary Science
- Underwater Acoustics Research
- Geophysics and Gravity Measurements
- Magneto-Optical Properties and Applications
- Hydrological Forecasting Using AI
- High voltage insulation and dielectric phenomena
- Advanced Chemical Physics Studies
University of the South Pacific
2015-2024
University of Hertfordshire
2024
Gautam Buddha University
2018-2023
University of Delhi
2020
Dr. Bhim Rao Ambedkar University
2005
Barkatullah University
1993-2000
Abstract The technique of radio occultation (RO) is demonstrated to be a powerful tool for studying equatorial F‐region irregularities (EFIs) associated with plasma bubbles. extensive 4.9 year RO dataset the Constellation Observing System Meteorology, Ionosphere and Climate (COSMIC) satellites was employed in this study contains EFI observations under wide variety solar geomagnetic conditions. From an analysis occurrence dependence on season/longitude, it found that statistics largely match...
Worldwide lightning location (WWLL) using only 30 sensors has been successfully achieved by VLF propagation in the Earth-ionosphere waveguide (EIWG). Ground or mixed "sky" and ground is avoided requiring evidence of dispersion. A further requirement that strike must be inside perimeter defined sensor sites detecting stroke. Under these conditions, time stroke can determined, along with rms errors. Lightning strokes errors exceeding Ps To assist identifying impulses from same stroke,...
The effects of solar flares on the propagation subionospheric VLF signals from NWC and NLK transmitter stations monitored at a low-latitude station, Suva (18.2°S, 178.4°E), Fiji, between December 2006 2010 (an unprecedented minimum cycles 23 24) January 2012 2013 (moderate activity peak cycle have been analyzed to find flare time D-region changes. amplitude phase enhancements associated with were observed in both which are due an increase electron density as result extra ionization caused by...
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 response of the D region low‐latitude ionosphere has been examined for extreme space weather event 14–16 December 2006 associated with a X1.5 solar flare and an intense geomagnetic storm ( Dst = −146 nT) using VLF signals from Northwest Cape, Australia (NWC) (19.8 kHz) Lualualei, Hawaii (callsign NPM) (21.4 transmitters monitored at Suva (Geographic Coordinates, 18.10°S, 178.40°E), Fiji. Modeling amplitude phase enhancements NWC (3.6 dB, 223°) NPM (5 153°) Long‐Wave Propagation...
The effects of the solar flares and geomagnetic storms (disturbance storm time (Dst) < −50 nT) during December 2006 to 2008, a period unprecedented minimum cycles 23 24, have been examined on sub-ionospheric very low frequency (VLF) signals from NWC (19.8 kHz), NPM (21.4 VTX (18.2 NLK (24.8 kHz) transmitters monitored at Suva (18.2° S, 178.4° E), Fiji. Apart higher class (C X), flare B8.5 also produced enhancements both amplitude phase. in NLK, NPM, as function peak X-ray flux decibel (dB;...
[1] Observations of tweeks with higher harmonics (n > 1) at low latitude stations Allahabad and Nainital, in the Indian sector, during total solar eclipse on 22 July 2009, are presented. Nainital were 100% 85% totality paths. suggest that about 30–40% obscuration disc can lead to occurrence which otherwise occur only nighttime. A 148 20 recorded some them up 3rd harmonics. The World Wide Lightning Location Network data indicated observed generated by lightning's located partial area...
Abstract Two seasons of Darwin, Australia, C-band polarimetric (CPOL) research radar, radiosoundings, and lightning data are examined to study the relative influence large-scale atmospheric regimes underlying surface types on tropical convective cloud properties their diurnal evolution. The authors find that in “deep westerly” regime, which corresponds monsoon period, occurrence rate is highest, consistent with its highest humidity. However, these clouds have relatively low cloud-top...
Abstract We present first report on the periodic wave‐like signatures (WLS) in D region ionosphere during 22 July 2009 total solar eclipse using JJI, Japan, very low frequency (VLF) navigational transmitter signal (22.2 kHz) observations at stations, Allahabad, Varanasi and Nainital Indian Sector, Busan Korea, Suva Fiji. The amplitude increased by about 6 7 dB Allahabad decreased 2.7, 3.5, 0.5 Nainital, Busan, Suva, respectively, as compared to 24 (normal day). increase/decrease can be...
Abstract D region effects of the 17–19 March 2015, a St Patrick's Day super geomagnetic storm ( Dst = −223 nT), using navigational transmitter very low frequency (VLF) signal (NWC, 19.8 kHz) recorded at low‐latitude Indian station, Allahabad (geomag. lat., 16.45°N), have been analyzed and compared with similar strength 22–25 June 2015 −204 nT). During storm, NWC amplitude decreased on 17 (main phase storm) recovered 27 March, which is 1 day after recovery whereas for VLF 2 days only during...
Abstract Very low frequency (VLF) electromagnetic signals from navigational transmitters propagate worldwide in the Earth‐ionosphere waveguide formed by Earth and electrically conducting lower ionosphere. Changes signal properties are signatures of variations conductivity reflecting boundary ionosphere which is located mesosphere thermosphere, their analysis is, therefore, a way to study processes these remote regions. Here we present on amplitude perturbations local origin VLF transmitter...
Abstract The changes in critical frequency of the F 2 layer ( f o ) and deviation (Δ have been determined for three geomagnetic storms March years 2012, 2013, 2015 at low‐latitude stations, Darwin (geomag. lat. 21.96°S) Townsville (28.95°S), midlatitude Brisbane (36.73°S), Canberra (45.65°S), Hobart (54.17°S). moderate storm during 15–16 2012 Dst = −87 nT) showed a decrease no effect stations. For intense 17–18 2013 −132 super −222 nT), some middle‐ to stations short‐duration increase , but...
Lightning strokes are known to cause direct heating and ionization of the D region, some which detected via scattering VLF transmitter signals as Early events. The disturbed ionosphere typically recovers in many tens seconds. New experimental evidence is presented demonstrating that pattern onset amplitude events strongly related both magnitude polarity causative lightning peak current. Observations at nine Stanford receiver sites across continental United States combined with geolocation...
Abstract We estimate D region changes due to 22 July 2009 total solar eclipse (SE), 13–14 November 2012 SE, and 9–10 May 2013 annular using VLF navigational transmitters signal observations at Suva, Fiji. The North West Cape (NWC) (19.8 kHz) showed an amplitude phase decrease of 0.70 dB 23° during SE 2.0 90° SE. modeling Long Wave Propagation Capability code for NWC‐Suva path SEs increase in average reflection height ( H ′) sharpness factor β ) by 0.6 0.5 km 0.012 0.015 −1 , respectively....
First observations of early Very Low Frequency (VLF) perturbations on signals from NWC (19.8 kHz) and NPM (21.4 monitored at Suva, in the month November 2006, are presented. The early/fast, early/slow, early/short (RORD), step‐like VLF observed both transmitters. early/fast events found to occur more often nighttime than daytime whereas predominantly daytime. Most associated with amplitude changes between 0.2–0.8 dB only a few cases > 0.8 dB. In general, recovery time is less when...
Abstract Atmospherics or sferics that originate from lightning discharges on propagating large distances in the Earthionosphere waveguide, particularly at night, form dispersed called tweeks. Tweeks are novel diagnostic tool to monitor nighttime D -region ionosphere. Mean equivalent electron density n em mean tweek reflection heights h m and profile have been estimated using higher harmonic tweeks recorded time between 21–03 hrs LT Suva (18.2°S, 178.3°E), Fiji, during a period March–December...
Long D‐region ionospheric recovery perturbations are a recently discovered and poorly understood subcategory of early VLF events, distinguished by exceptionally long times up to 20 min (compared more typical ∼1 times). Characteristics occurrence rates events on the NWC transmitter signal recorded at Malaysia presented. 48 were observed. The location causative lightning discharge for each event is determined from GLD360 WWLLN data, categorized as being over land or sea. Results provide strong...
Abstract. A simple technique to estimate the distance of lightning strikes d with a single VLF electromagnetic wave receiver at station is described. The based on recording oscillatory waveforms electric fields sferics. Even though process estimating using waveform rather classical one, novel and procedure for finding proposed in this paper. adopted provides two independent estimates stroke. accuracy measurements has been improved by employing high speed (333 ns sampling rate) signal...
Abstract In this paper we present ionospheric disturbances during the simultaneous presence of two to three Large Meteorological Systems, classified as hurricanes and tropical storms, in Atlantic Ocean from August November 2016. The were detected by very low frequency (3–30 kHz) signals North American transmitters observed Algiers (36.75°N, 03.47°E). results show clear anomalies amplitude both at nighttime daytime. At nighttime, association with all Systems even stage storm intensity...
The ionospheric effects of six intense geomagnetic storms with Dst index ≤ −100 nT that occurred in 2012 were studied at a low-latitude station, Darwin (Geomagnetic coordinates, 21.96° S, 202.84° E), low-mid-latitude Townsville (28.95° 220.72° and mid-latitude Canberra (45.65° 226.30° the Australian Region, by analyzing storm–time variations critical frequency F2-region (foF2). Out storms, storm 23–24 April did not produce any effect. 30 September–3 October (minimum = −122 nT) 7–10 −109 are...