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Singh, Rajesh
- First Observations of Transient Luminous Events In Indian Sub-Continent
Abstract Views :255 |
PDF Views:97
Authors
Rajesh Singh
1,
Ajeet K. Maurya
1,
B. Veenadhari
2,
Sneha A. Gokani
2,
R. Selvakumaran
2,
Morris B. Cohen
3,
Olivier Chanrion
3,
Torsten Neubert
3
Affiliations
1 KSK Geomagnetic Research Laboratory, IIG, Chamanganj, Allahabad 221 505, IN
2 Indian Institute of Geomagnetism, New Panvel, Navi Mumbai 410 218, IN
3 School of Electrical and Computer Engineering, Georgia Institute of Technology, IN
1 KSK Geomagnetic Research Laboratory, IIG, Chamanganj, Allahabad 221 505, IN
2 Indian Institute of Geomagnetism, New Panvel, Navi Mumbai 410 218, IN
3 School of Electrical and Computer Engineering, Georgia Institute of Technology, IN
Source
Current Science, Vol 107, No 7 (2014), Pagination: 1107-1108Abstract
No Abstract.Full Text
- Very Low Latitude Whistlers (L = 1.08):Arrival Azimuth Determination
Abstract Views :225 |
PDF Views:101
Authors
Affiliations
1 Indian Institute of Geomagnetism, New Panvel, Navi Mumbai 410 218, IN
2 KSK Geomagnetic Research Laboratory, Indian Institute of Geomagnetism, Chamanganj, Allahabad 221 505, IN
1 Indian Institute of Geomagnetism, New Panvel, Navi Mumbai 410 218, IN
2 KSK Geomagnetic Research Laboratory, Indian Institute of Geomagnetism, Chamanganj, Allahabad 221 505, IN
Source
Current Science, Vol 111, No 1 (2016), Pagination: 198-201Abstract
Since last four decades and more generation and propagation mechanism of very low latitude (L < 1.4) whistlers has been studied by many workers in lowlatitude regions and especially in India. The key questions that remain unanswered include: (1) Where are the lightning discharges, the source of whistlers located? (2) Do the whistler waves at low latitudes propagate along the magnetic field lines in low latitude ionosphere? We reported that the lightning discharges that have generated whistlers are located in the conjugate region in the Indian Ocean and suggested the whistlers at these stations propagate along the magnetic field lines in the low latitude ionosphere. In this communication, we present the arrival azimuth determination technique adopted to confirm the location of the lightning discharges which generated the observed whistlers and the technique is validated with real-time lightning data. The technique adopted to determine the arrival azimuths of low latitude whistler causative lightning discharges is of significance and will help in resolving the unanswered questions of low latitude whistler phenomena.Keywords
Arrival Azimuth, Ionosphere, Lightning, Low Latitude, Whistlers.Full Text
- Extreme Space-Weather Effect on D-Region Ionosphere in Indian Low Latitude Region
Abstract Views :244 |
PDF Views:82
Authors
Affiliations
1 K.S.K. Geomagnetic Research Laboratory, Indian Institute of Geomagnetism, Allahabad 221 505, IN
1 K.S.K. Geomagnetic Research Laboratory, Indian Institute of Geomagnetism, Allahabad 221 505, IN
Source
Current Science, Vol 114, No 09 (2018), Pagination: 1923-1926Abstract
The present study delineates on the observations and modelling of low latitude D-region ionosphere perturbations caused by strongest solar flare (X6.9) of solar cycle 24. An extreme space weather event occurred on 9 August 2011. To understand the severity of X-class flare on ionosphere, a comparative study was made with a low intensity C-class flare of 6 August 2011. Both flares originated from the same sunspot AR#1263. Very low frequency (VLF) waves propagating in the Earth’s ionosphere wave guide (EIWG) measured from VLF transmitter NWC (19.8 kHz) located in Australia, and recorded at Allahabad (India) were used. The recorded VLF amplitude and phase were modelled with long wavelength propagation capability code to understand solar flare-induced ionospheric variation. Modelling results revealed that the lower boundary of D-region ionosphere is lowered by 10 km during X-class and 1.0 km for C-class flare. This implies change in the properties of EIWG, and hence becomes important to observe our ionosphere on continuous basis for space weather events since ionosphere is the key medium of propagation for radio waves.Keywords
Low Latitude, D-Region Ionosphere, Solar Flare, Solar Cycle 24, Very Low Frequency Waves.Full Text
References
- Mitra, A. P., Ionospheric Effects of Solar Flares, D. Reidel, Dordrecht-Holland, 1974.
- Hargreaves, J. K., The Solar-Terrestrial Environment, Cambridge University Press, New York, 2003.
- Thomson, N. R., Rodger, C. J. and Clilverd, M. A., Large solar flares and their ionospheric D-region enhancements. J. Geophys. Res., 2005; doi:10.1029/2005JA011008.
- Maurya, A. K. et al., Morphological features of tweeks and nighttime D region ionosphere at tweek reflection height from the observations in the low-latitude Indian sector. J. Geophys. Res., 2012; doi:10.1029/2011JA016976.
- Rajesh, S. et al., Very low latitude (L = 1.08) whistlers. J. Geophys. Res., 2012; doi:10.1029/2012GL054122.
- Thomson, N. R. and Clilverd, M. A., Solar flare induced ionospheric D-region enhancements from VLF amplitude observations. J. Atmos. Solar Terr. Phys., 2001, 63(7), 1729–1737.
- McRae, W. M. and Thomson, N. R., Solar flare induced ionospheric D-region enhancement from VLF phase and amplitude observations. J. Atmos. Solar Terr. Phys., 2004, 66, 77–87.
- Ferguson, J. A. and Snyder, F. P., Computer programs for assessment of long wavelength radio communications, version 1.0: Full FORTRAN code user’s guide. Nav. Ocean Syst. Cent., Tech. Doc. 1773, DTIC AD-B144 839, Def. Tech. Inf. Cent, Alexandria, Va, 1990.
- Wait, J. R. and Spies, K. P., Characteristics of the earth-ionosphere waveguide for VLF radio waves. Tech. Note 300, Natl. Bur. of Stand., Boulder, Colorado, 164.
- Kumar, S. et al., Response of the low-latitude D region ionosphere to extreme space weather event of 14–16 December 2006. J. Geo-phys. Res., 2015; doi:10.1002/2014JA020751.
- Electrical Signature of the October 2013 Very Severe Cyclonic Storm Phailin
Abstract Views :265 |
PDF Views:87
Authors
Affiliations
1 Dr K. S. Krishnan Geomagnetic Research Laboratory, Indian Institute of Geomagnetism, Allahabad 221 505, IN
2 Department of Physics, Doon University, Dehradun 248 001, IN
1 Dr K. S. Krishnan Geomagnetic Research Laboratory, Indian Institute of Geomagnetism, Allahabad 221 505, IN
2 Department of Physics, Doon University, Dehradun 248 001, IN
Source
Current Science, Vol 118, No 3 (2020), Pagination: 421-427Abstract
In this study we examine first of its kind from Indian sub-continent which concentrates the electrical signatures of lightning discharges associated with a very severe cyclonic storm (VSCS). Phailin cyclone during 8–14 October 2013 has been selected for the study. We have primarily used ground-based GLD360 network lightning data to understand the distribution, polarity and radiated peak current of lightning discharge associated with the inner core (~100 km radius) of Phailin. In the initial development stage of Phailin as a deep depression on 8–9 October, there were very few lightning discharged (>50) in the inner core, but when Phailin developed into a VSCS on 10 October, ~2300 lightning discharges were recorded in inner core. There was near-even distribution of positive cloud to ground and negative cloud to ground discharges in the core, and with strong opposite peak currents of ±150 kA prior to the cyclone landfall. The observations show that monitoring of lightning discharges in eye of the cyclone is helpful in tracking its intensity changes and hence can serve as early warning systems.Keywords
Electrical Signature, Lightning Discharges, Peak Current, Tropical Cyclone.Full Text
References
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- IMD, A report on very severe cyclonic storm PHAILIN. Cyclone Warning Division, India Meteorological Department, Ministry of Earth Sciences, Government of India, 2013.
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- Cheng, Z., Cummer, S. A., Su, H.-T. and Hsu, R.-R., Broadband VLF measurement of Dregion ionospheric perturbations caused by lightning electromagnetic pulses. J. Geophys. Res., 2007; doi: 10.1029/2006JA011840.
- Extreme space weather events of solar cycle 24: X-class solar flares and their impact on the low-latitude D-region ionosphere
Abstract Views :143 |
PDF Views:73
Authors
Affiliations
1 KSK Geomagnetic Research Laboratory, Indian Institute of Geomagnetism, Prayagraj 211 506, India., IN
2 Department of Physics, Babasaheb Bhimrao Ambedkar University, Lucknow 226 025, India., IN
3 K. Banerjee Centre of Atmospheric and Ocean Studies, University of Allahabad, Prayagraj 221 002, India., IN
1 KSK Geomagnetic Research Laboratory, Indian Institute of Geomagnetism, Prayagraj 211 506, India., IN
2 Department of Physics, Babasaheb Bhimrao Ambedkar University, Lucknow 226 025, India., IN
3 K. Banerjee Centre of Atmospheric and Ocean Studies, University of Allahabad, Prayagraj 221 002, India., IN
Source
Current Science, Vol 124, No 7 (2023), Pagination: 812-819Abstract
X-class solar flares, which occurred in the daytime from 2008 to 2016 during solar cycle 24, were studied for their influence on the lower ionosphere over the low-equatorial Indian region. To understand the D-region behaviour during flare events, we used the very low frequency (VLF) navigational transmitter NWC (19.8 kHz) signal recorded at Pryagraj, Uttar Pradesh, India. A total of seven parameters were estimated: (i) the magnitude of X-ray flux, (ii) VLF signal rising amplitude perturbation (SRAP), (iii) X-ray flux and NWC signal start time difference (STD), (iv) peak time difference (PTD), (v) Wait’s ionospheric parameters h′ (reference height), (vi) β (sharpness factor) and (vii) D-region electron density difference (EDD) to determine the overall effect of solar flares on the D-region. The results suggest that three parameters (X-ray flux, SRAP and h′) show a decreasing trend through the linear fit line, two parameters (β and EDD) show an increasing trend, while the remaining two parameters show a mixed trend (decrease during low activity and increase during high activity). Further, the trend line during the diurnal variation shows an increasing trend for X-ray flux, PTD and h′, and a decreasing trend for SRAP, STD, β and EDD. Deviation in the case of individual events may indicate the dependence of these parameters on the seasons as well. The present study will provide the base for more robust analysis and modelling work in the future to understand the complexity of ionospheric change during flare events, and to develop a predictive model for space weather mitigation.Keywords
D-Region Ionosphere, Space Weather, Solar Cycle, Solar Flares, Trend Line, Vlf Waves.Full Text
References
- Hargreaves, J. K., The Solar–Terrestrial Environment, Cambridge University Press, New York, USA, 2003, p. 420.
- Maurya, A. K., Singh, R., Kumar, S., Kumar, D. V. and Veenadhari, B., Wave-like signatures in the D-region ionosphere generated by solar flares. In Proceedings of the IEEE General Assembly and Scientific Symposium, XXXI URSI, 2014, pp. 1–4; 10.1109/URSIGASS. 2014.6929796.
- Maurya, A. K. et al., Low–mid latitude D region ionospheric perturbations associated with 22 July 2009 total solar eclipse: wave-like signatures inferred from VLF observations. J. Geophys. Res.: Space Phys., 2014, 119, 8512–8523; doi:10.1002/2013JA019521.
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