Observations of Rising Tone Chorus Emissions at Indian Low Latitude Ground Station and Their Generation Mechanism
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In this article, the spectral analysis of recorded chorus emissions shows that each chorus element originates from the upper edge of the underlying hiss band, which is the most common form of very low frequency (VLF) emissions in the Earth's magnetosphere.Abstract:
Chorus emissions are the most common form of very low frequency (VLF) emissions in the Earth’s magnetosphere which typically consist of a series of rising tones generated near the magnetic equator, excited by energetic electrons injected into the inner magnetosphere. In the present study, observation of chorus emissions recorded at Indian low latitude ground station Jammu (geomag. lat., 19 26 N; L = 1.17) during a geomagnetic quiet period on 24 February, 1999 is reported. The spectral analysis of recorded chorus emissions shows that each chorus element originates from the upper edge of the underlying hiss band. The observed mean chorus element parameters are as follows: lower band frequency fmin = 1.2 kHz, upper band frequency fUB = 1.96 kHz, frequency sweep rate df/dt = 1.14 kHz/s and repetition period T = 2.5 s. To explain the observed dynamic spectra of these chorus emissions, a possible generation mechanism is presented based on the recent nonlinear theory. It is observed that the seeds of chorus emissions grow from the saturation level of the whistler-mode instability at the equator and then propagate away from the equator as a result of a nonlinear growth mechanism that depends on the wave amplitude. On the basis of this theory, frequency sweep rate of chorus emission is computed and compared with that of our experimentally observed values, which shows, in general, a good agreement.read more
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Magnetospherically reflected (MR) whistlers observed in DEMETER satellite and on the ground observation of normal whistlers at low latitudes
TL;DR: In this paper, the DEMETER (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions) satellite data have been analyzed for a period of three and half months from 01 September to 16 December 2010 in search of whistlers and VLF emissions and their ground observations at low latitudes.
References
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Waves in plasmas
TL;DR: In this paper, the straight-trajectory approximation quasilinear diffusion in a magnetized plasma bounce-averaged quasilevel diffusion was proposed. But this diffusion is not suitable for a hot plasma in a magnetic field.
Journal ArticleDOI
An ISEE/Whistler model of equatorial electron density in the magnetosphere
TL;DR: In this paper, an empirical model of equatorial electron density in the magnetosphere covering the L range 2.25-8.9043 was presented for application to the local time interval 00-15 MLT, and a way to extend the model to the 15-24 MLT period is presented.
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Postmidnight chorus: A substorm phenomenon
TL;DR: In this paper, the post-midnight chorus was detected in the midnight sector of the magnetosphere in conjunction with magnetospheric substorms and the characteristics of these emissions such as their frequency time structure, emission frequency with respect to the local equatorial electron gyrofrequency, intensity-time variation, and the average intensity were investigated.
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Theory and simulation of the generation of whistler-mode chorus
TL;DR: In this article, the authors derived the relativistic second-order resonance condition for a whistler-mode wave with a varying frequency and found that the seeds of chorus emissions with a rising frequency are generated near the magnetic equator as a result of a nonlinear growth mechanism that depends on the wave amplitude.
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