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PublicationArticle Simulation of nose whistlers: An application to low latitude whistlers(2006) Kalpana Singh; R.P. Singh; Abhay Kumar Singh; R.N. SinghSimulation technique for whistler mode signal propagating through inhomogeneous plasma using WKB approximation has been developed (Singh, K., Singh, R.P., Ferencz, O.E., 2004. Simulation of whistler mode propagation for low latitude stations. Earth Planet Space 56, 979-987). In the present paper, we have used it for the analysis of recorded signals at low latitudes and estimated the nose frequency, which is not observed on the dynamic spectra. At low latitudes nose frequency is ∼100 kHz or more and therefore it is absent in the dynamic spectra due to attenuation of the signal at higher frequencies. The importance of nose frequency is in determining the exact path of propagation, which is required in probing of ambient medium. It is shown that the method permits to study the nose frequency variation, it can be used to deduce physical parameters as the global electric field. A case study permits to get a reasonable value of the electric field, which up to now could not be done at very low latitude. © 2006 Elsevier Ltd. All rights reserved.PublicationArticle Characteristics of modulating VLF hiss observed at Indian Antarctic Station, Maitri (L = 4.5)(2010) A.K. Singh; S.B. Singh; R.P. Patel; R.P. SinghVery low frequency (VLF) hiss emissions were observed for the first time at the Indian Antarctic Station, Maitri (geographic lat. 70°46′S, long. 11°50′E, geomagnetic lat. 66°.03′S, long. 53°.21′E) with the modulating intensity variations. Various spectrograms of modulating VLF hiss emissions clearly show band limited spectra regularly modulating its intensity with almost equal period of the order of few seconds in the frequency range of 9-12.8 kHz. To explain these modulating characteristics of VLF hiss, we propose that the hiss emissions are generated through Doppler-shifted cyclotron interactions near the geomagnetic equator and propagate towards the Earth in the whistlermode. Further, the micropulsations propagating along the geomagnetic field lines could modulate the growth rate of the wave. The growth rates of the waves are also computed.PublicationArticle Review of electromagnetic coupling between the Earth's atmosphere and the space environment(Elsevier Ltd, 2005) Devendraa Siingh; R.P. Singh; A.K. Kamra; P.N. Gupta; V. Gopalakrishnan; A.K. SinghWe review our understanding of the electrical properties of the lower and upper atmosphere along with various possible sources of the electromagnetic energy near and far above the Earth's surface. The transport of electromagnetic energy from the atmosphere to the ionosphere and then to the magnetosphere and back to the Earth's surface via ionosphere and lower atmosphere is discussed. The electromagnetic coupling of various regions is also discussed. © 2005 Elsevier Ltd. All rights reserved.PublicationArticle Hiss emissions during quiet and disturbed periods(Indian Academy of Sciences, 2002) D.K. Singh; R.P. SinghThe characteristic features of VLF hiss emissions during quiet and disturbed conditions observed at ground stations and on-board satellites are summarized. The increased intensity of the hiss emissions during magnetic storm period is explained by considering the enhanced flux of energetic electrons during magnetic storm period. The generation and propagation mechanism of VLF hiss are also briefly discussed.PublicationArticle Space Weather: Physics, Effects and Predictability(2010) A.K. Singh; Devendraa Siingh; R.P. SinghThe time varying conditions in the near-Earth space environment that may affect space-borne or ground-based technological systems and may endanger human health or life are referred to as space weather. Space weather effects arise from the dynamic and highly variable conditions in the geospace environment starting from explosive events on the Sun (solar flares), Coronal Mass Ejections near the Sun in the interplanetary medium, and various energetic effects in the magnetosphere-ionosphere-atmosphere system. As the utilization of space has become part of our everyday lives, and as our lives have become increasingly dependent on technological systems vulnerable to the space weather influences, the understanding and prediction of hazards posed by these active solar events have grown in importance. In this paper, we review the processes of the Sun-Earth interactions, the dynamic conditions within the magnetosphere, and the predictability of space weather effects on radio waves, satellites and ground-based technological systems today. © 2010 Springer Science+Business Media B.V.PublicationArticle Study of wave-particle interaction in the disturbed magnetosphere(2005) Devendraa Siingh; Shubha Singh; R.P. SinghDoppler-shifted cyclotron resonance interaction between whistler mode wave and counter streaming energetic electrons has been invoked to explain whistler triggered emissions recorded at low latitude station Varanasi (Geomagnetic latitude 14°55′, L = 1.07) during moderate magnetic storm activity (ΣKP= 28-, KP index varies from 4 - to 4+ during the observation period) on 28 Feb. 1993. The mechanism of generation of triggered emissions is briefly discussed. Parallel resonance energy of participating electrons under normal and disturbed magnetospheric conditions have been evaluated, which is found to decrease with increase in L-value and wave frequency. Applying a simplified approach we have estimated the interaction length, wave magnetic field and transverse resonant current, which are found to increase during the disturbed magnetospheric conditions. However, the number of energetic electrons participating in resonance process under normal and disturbed magnetosphere remains approximately the same.PublicationArticle VLF Emissions observed at the low latitude Indian station Varanasi(Elsevier Ltd, 2008) R.P. Patel; A.K. Singh; S. Singh; R. Singh; K. Singh; R.P. SinghVLF emissions such as hiss, chorus, pulsing hiss, triggered emissions observed at Varanasi (geom. lat. = 14° 55′ N, long. = 153° 55′ E) are reported. An attempt has been made to explain the dynamic spectra in terms of the generation mechanism and propagation through the inhomogeneous magnetoplasma. It is noted that the reported events have propagated along different L-values in the magnetosphere, although they have been recorded at the same station. The ULF waves propagating along geomagnetic field lines modulate the growth rate of VLF waves, which results in the pulsation of VLF hiss intensity. The pulsating growth rate has been computed. © 2007 COSPAR.