Whistler waves in plasmas with magnetic field irregularities: Experiment and theory

Gushchin, M. E.; Zaboronkova, T. M.; Koldanov, V. A.; Korobkov, S. V.; Костров, А. В.; Krafft, C.; Strikovsky, A. V.

doi:10.1063/1.2837892

Cited by 8 publications

(14 citation statements)

References 29 publications

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“…Gushchin et al [2008] have shown with a controlled laboratory plasma experiment that a local magnetic field enhancement can act as a lens, focusing whistler waves and increasing their amplitudes. Magnetic field perturbations of this sort in the magnetosphere can come from MHD oscillations or diamagnetic currents formed at nearby plasma or field gradients.…”

Section: Wave Observationsmentioning

confidence: 99%

Large-amplitude transmitter-associated and lightning-associated whistler waves in the Earth's inner plasmasphere atL< 2

et al. 2011

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[1] We report observations of very large amplitude whistler mode waves in the Earth's nightside inner radiation belt enabled by the STEREO Time Domain Sampler. Amplitudes range from 30-110 mV/m (zero-peak), 2 to 3 orders of magnitude larger than previously observed in this region. Measurements from the peak electric field detector (TDSMax) indicate that these large-amplitude waves are prevalent throughout the plasmasphere. A detailed examination of high time resolution electric field waveforms is undertaken on a subset of these whistlers at L < 2, associated with pump waves from lightning flashes and the naval transmitter NPM in Hawaii, that become unstable after propagation through the ionosphere and grow to large amplitudes. Many of the waveforms undergo periodic polarization reversals near the lower hybrid and NPM naval transmitter frequencies. The reversals may be related to finite plasma temperature and gradients in density induced by ion cyclotron heating of the plasma at 200 Hz, the modulation frequency of the continuous-mode NPM naval transmitter signal. Test particle simulations using the amplitudes and durations of the waves observed herein suggest that they can interact strongly with high-energy (>100 keV) electrons on a time scale of <1 s and thus may be an important previously unaccounted for source of energization or pitch-angle scattering in the inner radiation belt.

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Section: Wave Observationsmentioning

confidence: 99%

Large-amplitude transmitter-associated and lightning-associated whistler waves in the Earth's inner plasmasphere atL< 2

et al. 2011

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“…The possibility of formation of magnetic field disturbances by electrostatic fields from thunderstorm sources penetrating into the ionosphere has been estimated in [27]. On the other hand, the properties of whistler waves propagating in a large laboratory magnetoplasma with artificially created magnetic field irregularities have been studied in [29][30][31]. Cylindrical magnetic field irregularities were generated by DC-carrying coils in a quasi-uniform plasma.…”

Section: Introductionmentioning

confidence: 99%

“…Cylindrical magnetic field irregularities were generated by DC-carrying coils in a quasi-uniform plasma. It was shown that the non-uniformities of the ambient magnetic field can strongly influence the whistler propagation [29,30] and the VLF antennas' radiation efficiencies [31]. Even a comparatively weak relative magnetic field disturbance of the order of 10% can lead under certain conditions to significant modifications of the whistler waves' pattern.…”

Section: Introductionmentioning

confidence: 99%

“…The theoretical analysis of axisymmetric whistler waves radiated by a loop antenna immersed in a magnetoplasma with ambient magnetic field perturbations has been performed in [30,31]. In the present paper we consider several types of dipole sources oriented both parallel and perpendicular with respect to the ambient magnetic field in a plasma containing comparatively weak and short (of the order of the whistler longitudinal wavelength) cylindrical magnetic field perturbations.…”

Section: Introductionmentioning

confidence: 99%

“…Two types of inhomogeneities are investigated in our theoretical model: magnetic field enhancements and depletions. Related computations are performed for conditions typical of recent laboratory studies [29,30]; the results are successfully compared with those provided by experimental observations and with theoretical analyses performed for electric ring currents oriented across the ambient magnetic field [30].…”

Section: Introductionmentioning

confidence: 99%

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Whistler radiation in plasmas with cylindrical magnetic field irregularities

Krafft¹,

Zaboronkova²

2009

J. Plasma Phys.

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International audienceThe radiation of whistler waves by linear dipole sources immersed in magnetoplasmas with cylindrical magnetic field inhomogeneities are studied. Two types of irregularities are investigated: magnetic field enhancements and depletions. A theoretical analysis is developed for comparatively weak local perturbations of the ambient magnetic field. Results are provided by numerical calculations performed for physical conditions typical of laboratory experiments involving artificially created magnetic field irregularities. It is shown that plasma regions with locally enhanced (depleted) magnetic field intensities can increase (decrease) the amplitudes of whistler waves radiated by dipole sources, regardless of their orientation with respect to the ambient magnetic field. Results are relevant to space and laboratory experiments on very low-frequency wave radiation

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Whistler modes in highly nonuniform magnetic fields. II. Propagation in three dimensions

Stenzel

Urrutia

2018

Physics of Plasmas

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In a large laboratory plasma, the properties of whistler modes are investigated in highly nonuniform magnetic fields. In an extension to previous measurements in two dimensions (2D), the present work shows new phenomena such as wave splitting in the third dimension and shedding of cross-field helicon-like modes. Three-dimensional (3D) data also permit the correct calculations of the field derivatives (∇⋅, ∇×), helicity density (J ⋅ B), Hall electric fields, phase and energy flow, and out-of-plane field structures, which are not visible from 2D data. Novel findings are the loss of the angular momentum of an m = 1 helicon mode, the splitting of a single wave packet into two wave packets in the direction of the loop axis, and the shedding of perpendicular whistler modes with angular momentum. The 3D effects cannot be explained by nonuniformities in the density and the 2D ambient magnetic field B0. They may arise from the conservation of orbital angular momentum whose direction changes along a curved magnetic field. It results in a precessional motion which creates asymmetries in the third dimension. Further effects are the interference of oppositely propagating helicon modes on circular field lines which creates linear polarization near the conjugate point of the antenna. Detached whistler modes are excited in the oscillating near-zone field. The waves propagate nearly perpendicular to the ambient field. The field polarization is right-hand circular around the oblique wave vector k but not around B0. Since the wave field is force-free the wave magnetic field lines form twisted field lines or writhed flux tubes. From streamlines of hodogram normals, it is shown that the wave exhibits a helical phase flow similar to helicon modes. These observations show the complexity of whistler modes in nonuniform magnetic fields, even under the simplest conditions of a uniform, unbounded plasma and linear waves. The results may be of interest to other laboratory plasmas and space plasmas in nonuniform magnetic fields. Meaningful comparisons require 3D field data which are rarely available.

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Whistler waves in plasmas with magnetic field irregularities: Experiment and theory

Cited by 8 publications

References 29 publications

Large-amplitude transmitter-associated and lightning-associated whistler waves in the Earth's inner plasmasphere atL< 2

Large-amplitude transmitter-associated and lightning-associated whistler waves in the Earth's inner plasmasphere atL< 2

Whistler radiation in plasmas with cylindrical magnetic field irregularities

Whistler modes in highly nonuniform magnetic fields. II. Propagation in three dimensions

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