Polarization properties of Gendrin mode waves observed in the Earth's magnetosphere: observations and theory

Verkhoglyadova, O. P.; Tsurutani, B. T.

doi:10.5194/angeo-27-4429-2009

Cited by 14 publications

(15 citation statements)

References 28 publications

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“…As discussed in a recent paper by Sauer and Sydora (2010), a similar process happens during beam excitation of obliquely propagating whistler modes. The importance of whistler Gendrin modes has also been pointed out recently by Verkhoglyadova and Tsurutani (2009) showing that the measured propagation direction of a chorus event in the Earth's magnetosphere agrees well with the calculated Gendrin angle. In this respect it is remarkable that Gendrin mode radiation in the same whistler wave branch has been verified experimentally by Stenzel et al (2008) in a large laboratory plasma.…”

Section: Introductionsupporting

confidence: 68%

“…An important lesson we have learned is that the predictions of linear instability theory say very little about the wave characteristics under the conditions of nonlinear saturation and may even be misleading. Our main finding is that Gendrin modes and related oscillitons seem to play an essential role in characterizing the final nonlinear state of the system (Sydora et al, 2007;Dubinin et al, 2007;Stenzel et al, 2008;Verkhoglyadova and Tsurutani, 2009;Sauer and Sydora, 2010). In this respect many further applications (such as electron and ion cyclotron harmonic waves, multi-ion waves etc.)…”

Section: Discussion and Summarymentioning

confidence: 99%

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Whistler-Langmuir oscillitons and their relation to auroral hiss

Sauer

Sydora

2011

Ann. Geophys.

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Abstract.A new type of oscilliton (soliton with superimposed spatial oscillations) is described which arises in plasmas if the electron cyclotron frequency e is larger than the electron plasma frequency ω e , which is a typical situation for auroral regions in planetary magnetospheres. Both highfrequency modes of concern, the Langmuir and the whistler wave, are completely decoupled if they propagate parallel to the magnetic field. However, for oblique propagation two mixed modes are created with longitudinal and transverse electric field components. The lower mode (in the literature commonly called the whistler mode, e.g. Gurnett et al., 1983) has whistler wave characteristics at small wave numbers and asymptotically transforms into the Langmuir mode. As a consequence of the coupling between these two modes, with different phase velocity dependence, a maximum in phase velocity appears at finite wave number. The occurrence of such a particular point where phase and group velocity coincide creates the condition for the existence of a new type of oscillating nonlinear stationary structure, which we call the whistler-Langmuir (WL) oscilliton. After determining, by means of stationary dispersion theory, the parameter regime in which WL oscillitons exist, their spatial profiles are calculated within the framework of cold (non-relativistic) fluid theory. Particle-in-cell (PIC) simulations are used to demonstrate the formation of WL oscillitons which seem to play an important role in understanding electron beam-excited plasma radiation that is observed as auroral hiss in planetary magnetospheres far away from the source region.

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Section: Introductionsupporting

confidence: 68%

Section: Discussion and Summarymentioning

confidence: 99%

Whistler-Langmuir oscillitons and their relation to auroral hiss

Sauer

Sydora

2011

Ann. Geophys.

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“…(11). A comparable polarization is obtained in the paper by Verkhoglyadova and Tsurutani (2009) in the context of the Gendrin mode analysis.…”

Section: Whistler Oscillitons (Nonlinear Gendrin Modes)supporting

confidence: 61%

“…2.1, the corresponding waves are also called Gendrin modes (Gendrin, 1961). Their physical relevance has recently been discussed in a paper by Verkhoglyadova and Tsurutani (2009). Several indications brought us to the conclusion that the nonlinear saturation of beam-excited whistlers at oblique propagation may be directly associated with the formation of whistler oscillitons (a kind of nonlinear Gendrin mode wave).…”

Section: Whistler Oscillitons (Nonlinear Gendrin Modes)mentioning

confidence: 99%

“…Our numerical studies of beam-excited whistlers are completed by the addition of some useful analytical expressions that are related to the specific whistler wave mode with kc/ω e = 1, which has been called the Gendrin mode (Gendrin, 1961;Verkhoglyadova and Tsurutani, 2009). If we start from the whistler dispersion relation, assuming ω e e , the real frequency is expressed as…”

Section: Fluid Approachmentioning

confidence: 99%

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Beam-excited whistler waves at oblique propagation with relation to STEREO radiation belt observations

Sauer

Sydora

2010

Ann. Geophys.

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Abstract. Isotropic electron beams are considered to explain the excitation of whistler waves which have been observed by the STEREO satellite in the Earth's radiation belt. Aside from their large amplitudes (∼240 mV/m), another main signature is the strongly inclined propagation direction relative to the ambient magnetic field. Electron temperature anisotropy with T e⊥ > T e , which preferentially generates parallel propagating whistler waves, can be excluded as a free energy source. The instability arises due to the interaction of the Doppler-shifted cyclotron mode ω = − e + kV b cosθ with the whistler mode in the wave number range of kc/ω e ≤ 1 (θ is the propagation angle with respect to the background magnetic field direction, ω e is the electron plasma frequency and e the electron cyclotron frequency). Fluid and kinetic dispersion analysis have been used to calculate the growth rate of the beam-excited whistlers including the most important parameter dependencies. One is the beam velocity (V b ) which, for instability, has to be larger than about 2V Ae , where V Ae is the electron Alfvén speed. With increasing V Ae the propagation angle (θ) of the fastest growing whistler waves shifts from θ ∼ 20 • for V b = 2V Ae to θ ∼ 80 • for V b = 5V Ae . The growth rate is reduced by finite electron temperatures and disappears if the electron plasma beta (β e ) exceeds β e ∼ 0.2. In addition, Gendrin modes (kc/ω e ≈ 1) are analyzed to determine the conditions under which stationary nonlinear waves (whistler oscillitons) can exist. The corresponding spatial wave profiles are calculated using the full nonlinear fluid approach. The results are compared with the STEREO satellite observations.

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Theoretical analysis of Poynting flux and polarization for ELF‐VLF electromagnetic waves in the Earth's magnetosphere

Verkhoglyadova

Tsurutani

Lakhina³

2013

JGR Space Physics

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[1] We discuss properties of extremely low-frequency (ELF) and very low-frequency (VLF) electromagnetic waves in the Earth's magnetosphere. General expressions for wave magnetic field polarization and for the angle Â P between the direction of the Poynting flux vector and the ambient magnetic field are derived for low-amplitude (linear) waves taking into account first-order finite gyroradius effects. The wave magnetic field is always in a plane perpendicular to the direction of the wave propagation, and the polarization depends on wave frequency (or wavelength), dispersion, and plasma parameters. In a warm plasma, the Poynting flux is not aligned with the group velocity and generally deviates from the wave propagation direction, except for parallel propagation. Numerical estimates for Â P and wave polarization are made for plasmaspheric hiss (at L = 2, 4, and 6) for typical plasma parameters and for the case of elevated electron temperature (5 keV). The plasmaspheric hiss wave magnetic field is right-hand circularly polarized, except for highly oblique hiss waves which are elliptically polarized. We note a possible transition to the magnetosonic wave regime at short wavelengths. The maximum Poynting flux angle is 20 ı . Estimates for daytime outer zone chorus (L = 6) show two regions of oblique Poynting flux corresponding to a low-frequency band (! < ! ce /2) and to a high-frequency band (! ce /2 < ! < ! ce ) where ! and ! ce are the wave frequency and the electron cyclotron frequency, respectively. The wave magnetic field polarization varies from circular to elliptical at shorter wavelengths. In a hot plasma, chorus is elliptically polarized. The maximum Â P in the low-frequency band is 20 ı . Â P can reach 60 ı in the high-frequency band. Our results are consistent with the Poynting flux statistics of Polar measurements.Citation: Verkhoglyadova, O. P., B. T. Tsurutani, and G. S. Lakhina (2013), Theoretical analysis of Poynting flux and polarization for ELF-VLF electromagnetic waves in the Earth's magnetosphere,

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Polarization properties of Gendrin mode waves observed in the Earth's magnetosphere: observations and theory

Cited by 14 publications

References 28 publications

Whistler-Langmuir oscillitons and their relation to auroral hiss

Whistler-Langmuir oscillitons and their relation to auroral hiss

Beam-excited whistler waves at oblique propagation with relation to STEREO radiation belt observations

Theoretical analysis of Poynting flux and polarization for ELF‐VLF electromagnetic waves in the Earth's magnetosphere

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