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PublicationArticle Propagation characteristics and generation mechanism of ELF/VLF hiss observed at low-latitude ground station (L = 1.17)(2007) Kalpana Singh; Rajesh Singh; A.K. Singh; R.P. SinghExtremely low frequency (ELF)/Very low frequency (VLF) hiss is whistler mode wave that interacts with energetic electrons in the magnetosphere. The characteristics features of ELF/VLF hiss observed at low latitude ground station Jammu (Geomag. lat. 22°16′ N, L = 1.17) are reported. It is observed that most of hiss events first propagate in ducted mode along higher L-values (L = 4-5), after reaching lower edge of ionosphere excite the Earth-ionosphere waveguide and propagate towards equator to be received at low-latitude station Jammu. To understand the generation mechanism of ELF/VLF hiss, incoherent Cerenkov radiated power from the low-latitude and mid-latitude plasmasphere are evaluated. Considering this estimated power as an input for wave amplification through wave-particle interaction, the growth rate and amplification factor is evaluated which is too small to explain the observed wave intensity. It is suggested that some non-linear mechanism is responsible for the generation of ELF/VLF hiss. © Springer Science+Business Media, Inc. 2006.PublicationArticle Triggered emissions observed at Varanasi (India)(Elsevier Ltd, 2003) R.P. Singh; R.P. Patel; D.K. SinghWhistler triggered emissions recorded at a low latitude station e.g. Varanasi are described. The study covers various aspects of these emissions including riser, riser followed by constant frequency emissions, hiss and oscillating tones. Analysis shows that the whistlers have propagated along paths with L-values lying between L = 1.9 and 2.4, suggesting that these whistlers are to be regarded as mid-latitude whistlers. These waves could have propagated along the geomagnetic field lines either in a ducted mode or in a pro-longitudinal mode. The measured intensity of the triggered emissions is either equal to or more than that of the source wave and also varies from one event to another. It is proposed that these emissions are generated through a process of resonant interaction of the whistler waves with energetic electrons. Parameters related to this interaction are computed for different values of L and wave amplitude. The proposed mechanism explains some aspects of the dynamic spectra. © 2003 Elsevier Science Ltd. All rights reserved.PublicationArticle VLF emissions from ionospheric/magnetospheric plasma(Indian Academy of Sciences, 2001) R.P. Patel; R.P. SinghVLF emissions such as hiss, chorus, oscillating tones, hiss-triggered chorus and whistler triggered emissions have been observed at low latitude Indian stations. In this paper we present dynamic spectra of these emissions and discuss their various observed features. It is argued that most of the emissions are generated during Doppler shifted cyclotron resonance interaction between the whistler mode wave and counter streaming energetic electrons. Resonance energy of the participating electron and interaction length are evaluated to explain the generation mechanism of some of these emissions observed at Indian stations.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 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 Observation of pulsing hiss at low latitudes(2005) R.P. Singh; R.P. Patel; Kalpana Singh; Ashok K. SinghIn this paper we report pulsing hiss emissions observed at low latitude Indian station Varanasi (geomag. Lat. = 14°55′N, Long. = 153°55′E) in which intensity seems to decrease with increase in frequency. The bandwidth of the pulsing hiss also decreases with increase in frequency. The entire dynamic spectra has irregular structure and varied from pulse to pulse. It is proposed that pulsing hiss is generated through wave particle interaction near the geomagnetic equator and propagated to the earth in the whistler mode. Further, the micropulsations propagating along the geomagnetic field lines could modulate the growth rate of the wave resulting in the modulation of hiss intensity. © 2005 Elsevier Ltd. All rights reserved.