Characteristics of discrete VLF falling-tone chorus emissions observed at low latitude ground station Jammu

doi:10.1186/BF03352969

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Characteristics of discrete VLF falling-tone chorus emissions observed at low latitude ground station Jammu

Journal Article•DOI•

Characteristics of discrete VLF falling-tone chorus emissions observed at low latitude ground station Jammu

Ashutosh K. Singh¹, R. P. Patel², R. P. Patel¹, R. P. Singh, K. K. Singh¹, A. K. Singh¹ - Show less +2 more•Institutions (2)

Banaras Hindu University¹, P.G. College²

30 Nov 2009-Earth, Planets and Space (Springer Berlin Heidelberg)-Vol. 61, Iss: 10, pp 1179-1183

TL;DR: The discrete VLF chorus emissions recorded at low latitude ground station Jammu (geomag. lat. = 22 ◦ 26 � N, L = 1.17) are reported and their characteristics based on spectral analysis have been carried out as discussed by the authors.

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Abstract: The discrete VLF chorus emissions recorded at low latitude ground station Jammu (geomag. lat. = 22 ◦ 26 � N, L = 1.17) are reported and their characteristics based on spectral analysis have been carried out. These discrete chorus emissions are falling tone emissions which are rarely observed at low latitude ground stations. These discrete chorus emissions are generated during a strong geomagnetic storm period of 2–7 May, 1998. We have computed the frequency sweep rate, repetition period and source region of the individual chorus elements. It is observed that the sweep rate increases with time.

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Journal Article•DOI•

Multiflash whistlers in ELF-band observed at low latitude

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Ashutosh K. Singh¹, K. K. Singh¹, S. B. Singh¹, A. K. Singh¹, Lalmani² - Show less +1 more•Institutions (2)

Banaras Hindu University¹, National Institute of Technology, Srinagar²

10 Jan 2011-Annales Geophysicae

TL;DR: In this paper, a multiflash whistler-like event in the ELF-band, observed during March 1998 at low latitude station Jammu, is reported, and the most prominent feature of these events is the multiflash nature along with the decrease in frequency within a very short span of time resembling similar to terrestrial whistlers.

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Abstract: . Multiflash whistler-like event in the ELF-band, observed during March 1998 at low latitude station Jammu, is reported. The most prominent feature of these events is the multiflash nature along with the decrease in frequency within a very short span of time resembling similar to terrestrial whistlers. The events have a significantly smaller time duration (0.5–3.5 s) than those reported earlier from high, mid and low latitudes and also display a diurnal maximum occurring around 09:30 h (IST). There have been similar reportings from other latitudes, but whistlers in the ELF-band with a multiflash nature along with a precursor emission have never been reported. Lightning seems to be the dominant source for the ELF whistlers reported here.

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4 citations

Journal Article•DOI•

Observation of discrete VLF emissions at Indian low-latitude ground station Srinagar (L = 1.28)

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S. B. Singh¹, Mehraj ud Din Rather², Prince A. Ganai², Ashutosh K. Singh¹•Institutions (2)

Banaras Hindu University¹, National Institute of Technology, Srinagar²

01 Apr 2015-Indian Journal of Physics

TL;DR: In this article, the spectral analysis of the observed discrete very low-frequency emissions consisting of risers, fallers, hooks and oscillating tones has been presented to explain the observed dynamic spectra of the discrete chorus emissions.

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Abstract: During the routine analysis of recorded very low-frequency data during the period November, 2012 to February, 2013, at an Indian low-latitude ground station Srinagar (geomag. lat., 24°10′N; L = 1.28), we observed some interesting discrete emissions during quiet period on February 5, 2013, which has been presented in the present study. The spectral analysis of the observed discrete very low-frequency emissions consisting of risers, fallers, hooks and oscillating tones has been presented. To explain the observed dynamic spectra of the discrete chorus emissions, a possible generation mechanism has been presented based on the recent nonlinear theory. On the basis of this theory, frequency sweep rate of discrete chorus emissions has been computed and compared with those of our experimentally observed values.

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Journal Article•DOI•

Limit on stably trapped particle fluxes

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Charles F. Kennel, H. E. Petschek

01 Jan 1966-Journal of Geophysical Research

TL;DR: The limit on stably trapped particle fluxes determined theoretically and compared with data from Explorer satellites was first established in this paper, and the limit was later confirmed by the International Journal of Astronautics.

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Abstract: Limit on stably trapped particle fluxes determined theoretically and compared with data from Explorer satellites

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2,706 citations

"Characteristics of discrete VLF fal..." refers background in this paper

...The generation of chorus emissions is derived by the injection of substorm electrons (Tsurutani and Smith, 1974) that interact with whistler mode waves through the cyclotron resonance (Andronov and Trakhtengerts, 1964; Kennel and Petschek, 1966)....
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Journal Article•DOI•

Postmidnight chorus: A substorm phenomenon

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Bruce T. Tsurutani, Edward J. Smith¹•Institutions (1)

California Institute of Technology¹

01 Jan 1974-Journal of Geophysical Research

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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Abstract: The ELF emissions were detected in the midnight sector of the magnetosphere in conjunction with magnetospheric substorms. The emissions were observed at local midnight and early morning hours and are accordingly called 'post-midnight chorus.' 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. The occurrence of the chorus in the nightside magnetosphere was investigated as a function of local time, L shell, magnetic latitude, and substorm activity, and the results of this analysis are presented. Specific features of postmidnight chorus are discussed in the context of possible wave-particle interactions occurring during magnetospheric substorms.

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626 citations

"Characteristics of discrete VLF fal..." refers background in this paper

...The most frequent observations of chorus events by satellites near the geomagnetic equator (Tsurutani and Smith, 1974; Burtis and Helliwell, 1976) support the idea that the source of chorus emissions are mostly localized near equatorial region....
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...The generation of chorus emissions is derived by the injection of substorm electrons (Tsurutani and Smith, 1974) that interact with whistler mode waves through the cyclotron resonance (Andronov and Trakhtengerts, 1964; Kennel and Petschek, 1966)....
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Journal Article•DOI•

Theory and simulation of the generation of whistler-mode chorus

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Yoshiharu Omura¹, Yuto Katoh¹, Yuto Katoh², Danny Summers¹, Danny Summers³ - Show less +1 more•Institutions (3)

Kyoto University¹, Tohoku University², Memorial University of Newfoundland³

01 Apr 2008-Journal of Geophysical Research

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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Abstract: [1] The generation process of whistler-mode chorus emissions is analyzed by both theory and simulation. Driven by an assumed strong temperature anisotropy of energetic electrons, the initial wave growth of chorus is linear. After the linear growth phase, the wave amplitude grows nonlinearly. It is found that the seeds of chorus emissions with rising frequency are generated near the magnetic equator as a result of a nonlinear growth mechanism that depends on the wave amplitude. We derive the relativistic second-order resonance condition for a whistler-mode wave with a varying frequency. Wave trapping of resonant electrons near the equator results in the formation of an electromagnetic electron hole in the wave phase space. For a specific wave phase variation, corresponding to a rising frequency, the electron hole can form a resonant current that causes growth of a wave with a rising frequency. Seeds of chorus elements grow from the saturation level of the whistler-mode instability at the equator and then propagate away from the equator. In the frame of reference moving with the group velocity, the wave frequency is constant. The wave amplitude is amplified by the nonlinear resonant current, which is sustained by the increasing inhomogeneity of the dipole magnetic field over some distance from the equator. Chorus elements are generated successively at the equator so long as a sufficient flux of energetic electrons with a strong temperature anisotropy is present.

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485 citations

Journal Article•DOI•

A theory of discrete VLF emissions from the magnetosphere

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R. A. Helliwell

01 Oct 1967-Journal of Geophysical Research

TL;DR: Magnetospheric discrete VLF emissions, discussing gyroresonance extension, resonant electron and emission frequency are discussed in this article, where the authors also discuss the effect of gyroreance extension.

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Abstract: Magnetospheric discrete VLF emissions, discussing gyroresonance extension, resonant electron and emission frequency

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463 citations

"Characteristics of discrete VLF fal..." refers background in this paper

...…that the generation mechanism of these emissions is connected with the cyclotron instability of whistler-mode waves and radiation belt electrons (Helliwell, 1967), the generation mechanism of these emissions and formation of spectrum of separate elements are still a subject of active…...
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...Helliwell (1967) was the first to suggest the idea of chorus emission and explained how the frequency spectrum of discrete elements is formed....
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...Although it is generally accepted that the generation mechanism of these emissions is connected with the cyclotron instability of whistler-mode waves and radiation belt electrons (Helliwell, 1967), the generation mechanism of these emissions and formation of spectrum of separate elements are still a subject of active experimental and theoretical research (Smith et al....
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...The chorus emissions are generally generated in the near equatorial region by the cyclotron instability of radiation belt electrons (Helliwell, 1967; Sazhin and Hayakawa, 1992)....
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Journal Article•DOI•

The unexpected origin of plasmaspheric hiss from discrete chorus emissions.

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Jacob Bortnik¹, Richard M. Thorne¹, Nigel P. Meredith²•Institutions (2)

University of California, Los Angeles¹, Natural Environment Research Council²

06 Mar 2008-Nature

TL;DR: It is shown that a different wave type called chorus, previously thought to be unrelated to hiss, can propagate into the plasmasphere from tens of thousands of kilometres away, and evolve into hiss.

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Abstract: Plasmaspheric hiss is a type of electromagnetic wave found ubiquitously in the dense plasma region that encircles the Earth, known as the plasmasphere. This important wave is known to remove the high-energy electrons that are trapped along the Earth's magnetic field lines, and therefore helps to reduce the radiation hazards to satellites and humans in space. Numerous theories to explain the origin of hiss have been proposed over the past four decades, but none have been able to account fully for its observed properties. Here we show that a different wave type called chorus, previously thought to be unrelated to hiss, can propagate into the plasmasphere from tens of thousands of kilometres away, and evolve into hiss. Our new model naturally accounts for the observed frequency band of hiss, its incoherent nature, its day-night asymmetry in intensity, its association with solar activity and its spatial distribution. The connection between chorus and hiss is very interesting because chorus is instrumental in the formation of high-energy electrons outside the plasmasphere, whereas hiss depletes these electrons at lower equatorial altitudes.

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337 citations

"Characteristics of discrete VLF fal..." refers background in this paper

...…and theoretical research (Smith et al., 1996; Trakhtengerts, 1999; Singh et al., 2000; Lauben et al., 2002; Santolik and Gurnett, 2003; Titova et al., 2003; Singh and Singh, 2004; Singh and Ronnmark, 2004; Santolik, 2008; Bortnik et al., 2008; Omura et al., 2008 and references there in)....
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