Effects of Ions on Whistler‐Mode Ray Tracing

Kimura, Ikuo

doi:10.1002/rds196613269

Cited by 258 publications

(212 citation statements)

References 12 publications

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“…We will mention only some work that is directly related to − or especially important for − the present study. An unexpected possibility for whistler-wave reflection when the ions are taken into account in the dispersion relation, and the visualisation of this effect by ray tracing, were first demonstrated by Kimura (1966). In a sense, this finding predicted magnetospherically reflected (MR) whistlers, which were found in the spectrograms of wave data from OGO 1 and 3 (Smith and Angerami, 1968).…”

Section: Introductionmentioning

confidence: 93%

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Characteristic properties of Nu whistlers as inferred from observations and numerical modelling

2004

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Abstract. The properties of Nu whistlers are discussed in the light of observations by the MAGION 5 satellite, and of numerically simulated spectrograms of lightning-induced VLF emissions. The method of simulation is described in full. With the information from this numerical modelling, we distinguish the characteristics of the spectrograms that depend on the site of the lightning strokes from those that are determined mainly by the position of the satellite. Also, we identify the region in the magnetosphere where Nu whistlers are observed most often, and the geomagnetic conditions favouring their appearance. The relation between magnetospherically reflected (MR) whistlers and Nu whistlers is demonstrated by the gradual transformation of MR whistlers into Nu whistlers as the satellite moves from the high-altitude equatorial region to lower altitudes and higher latitudes. The magnetospheric reflection of nonducted whistler-mode waves, which is of decisive importance in the formation of Nu whistlers, is discussed in detail.

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Section: Introductionmentioning

confidence: 93%

“…The possibility that whistler waves might be reflected within the magnetosphere was suggested and studied by Kimura (1966). In the one-dimensional case, wave reflection corresponds to a change in sign of the group velocity.…”

Section: Magnetospheric Reflection Of Whistler-mode Wavesmentioning

confidence: 99%

Characteristic properties of Nu whistlers as inferred from observations and numerical modelling

2004

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“…If the wave encounters a region where f -foeHR, the wave is reflected by the LHR reflection mechanism [Kimura, 1966]. Figure 10 is an electromagnetic wave that has a small/• and is also the wave that will eventually fall in the transmission cone for our model.…”

Section: Reflection Of Ah At Low Altitudesmentioning

confidence: 99%

“…VLF wave propagation theory in a smooth magnetosphere predicts that a whistler mode wave propagating at large 0 will undergo reflection within the magnetosphere at an altitude where the wave frequency f = f•.u•t, where fi;HS is the lower hybrid resonance frequency [Kimura, 1966]. For a typical auroral magnetosphere the maximum value of fLHft ranges from 2-15 kHz depending on the density model.…”

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confidence: 99%

An explanation of ground observations of auroral hiss: Role of density depletions and meter‐scale irregularities

Sonwalkar¹,

Harikumar²

2000

J. Geophys. Res.

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Abstract. Auroral hiss is one of the most intense whistler mode plasma wave phenomena observed both on the ground at high latitudes and on spacecraft in the auroral zone. Propagation of auroral hiss from its source region to the ground is poorly understood. The standard whistler mode propagation in a smooth magnetosphere predicts that auroral hiss generated at large wave-normal angles along the auroral field lines by Cerenkov resonance cannot penetrate to the ground. We show that the presence of density depletions along the field lines in the auroral zone and meter-scale density irregularities at altitudes < 5000 km at high latitude permits the auroral hiss propagation to the ground. In our mechanism the auroral hiss generated at high altitudes (> 5000-20,000 km) propagates to lower altitudes (< 3000-5000 km) in two modes: (1) a ducted mode guided by field-aligned density depletions and (2) a nonducted mode. The hiss with large wave-normal angle arriving at < 5000 km altitude is scattered by meter-scale irregularities, and about 0.1% to 10% of the scattered hiss has small wave-normal angles which can penetrate to the ground. Our mechanism explains the following features of auroral hiss observed on the ground: (1) the characteristic spectra of continuous and impulsive auroral hiss, (2) the upper and lower frequency cutoffs, (3) the dispersion of impulsive auroral hiss, (4) the location of ionospheric exit points of auroral hiss with respect to visible aurora, and (5) the 2-5 order of magnitude intensity decrease of auroral hiss observed on the ground relative to that observed on spacecraft. Based on the model presented here, we provide methods to infer parameters of density depletions and intensity of lower hybrid waves stimulated by auroral hiss from the ground measurements of auroral hiss together with optical and radar measurements.

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“…However, when propagating along the curved magnetic field in a homogeneous plasma, the angle q of the wave vector to B 0 will change and become so large that the whistler will reflect off the conjugate ionosphere, and thus never reach the ground. Furthermore, the effect of ions may cause whistlers to reflect at still higher altitudes and drift radially to higher L shells between bounces, in a manner reminiscent of the azimuthal drift of charged particles bouncing between hemispheres [Kimura, 1966]. These are two of several reasons [Smith, 1961] why ducting by some plasma density structure is needed to explain the whistlers routinely detected by ground stations.…”

Section: Introductionmentioning

confidence: 99%

Precession of the whistler polarisation plane normal observed on Freja

Karlsson

Carozzi

Bergman

et al. 2005

Geophysical Research Letters

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[1] We have observed that the normal to the polarisation plane of a whistler precesses around the geomagnetic field. Magnetic field observations by the Freja spacecraft have been used. These results were made possible by the use of an analysis which estimates the instantaneous polarisation properties of waves. During one event, the instantaneous normal of the polarisation plane precesses around the direction antiparallel to the geomagnetic field with an average deviation of 6°. In total, the normal precesses four times around this direction as the whistler frequency decreases from 2 to 0.4 kHz in about 0.2 s. Available theoretical understanding can not unambiguously explain the precession. We show that the precession of whistler wave vectors can be observed, and suggest to use this new observable parameter to put new constraints on the theories of whistler propagation. Citation: Karlsson, R. L., T.

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Effects of Ions on Whistler‐Mode Ray Tracing

Cited by 258 publications

References 12 publications

Characteristic properties of Nu whistlers as inferred from observations and numerical modelling

Characteristic properties of Nu whistlers as inferred from observations and numerical modelling

An explanation of ground observations of auroral hiss: Role of density depletions and meter‐scale irregularities

Precession of the whistler polarisation plane normal observed on Freja

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