Whistler waves in plasmas with time-varying magnetic field: Laboratory investigation

Gushchin, M. E.; Korobkov, S. V.; Костров, А. В.; Starodubtsev, M.; Strikovsky, A. V.

doi:10.1016/j.asr.2007.06.027

Cited by 10 publications

(5 citation statements)

References 18 publications

(17 reference statements)

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“…Wave propagation in nonuniform and time-varying magnetic fields has also been studied in a large laboratory device. [43][44][45] In the present laboratory experiment, we establish controlled nonuniform magnetic fields of known topology and strength and measure the wave propagation under various conditions.…”

Section: Introductionmentioning

confidence: 99%

Whistler modes in highly nonuniform magnetic fields. III. Propagation near mirror and cusp fields

Stenzel

Urrutia

2018

Physics of Plasmas

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The properties of helicon modes in highly nonuniform magnetic fields are studied experimentally. The waves propagate in an essentially unbounded uniform laboratory plasma. Helicons with mode number m ¼ 1 are excited with a magnetic loop with dipole moment across the dc magnetic field. The wave fields are measured with a three-component magnetic probe movable in three orthogonal directions so as to resolve the spatial and temporal wave properties. The ambient magnetic field has the topology of a mirror or a cusp, produced by the superposition of a uniform axial field B 0 and the field of a current-carrying loop with the axis along B 0. The novel finding is the reflection of whistlers by a strong mirror magnetic field. The reflection arises when the magnetic field changes on a scale length shorter than the whistler wavelength. The simplest explanation for the reflection mechanism is the strong gradient of the refractive index which depends on the density and magnetic field. More detailed observations show that the incident wave splits when the k vector makes an angle larger than 90 with respect to B 0 which produces a parallel phase velocity component opposite to that of the incident wave. The reflection coefficient has been estimated to be close to unity. Interference between reflected and incident waves creates nodes in which the whistler mode becomes linearly polarized. When the magnetic field topology is that of a reversed field configuration (FRC), the incident wave is absorbed near the three-dimensional (3D) magnetic null point which prevents wave reflections. However, waves outside the separatrix are not absorbed and continue to propagate around the null point. When waves are excited inside the FRC, their polarization and helicon mode are reversed. Implications of these observations on research in space plasmas and helicon sources are pointed out.

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Section: Introductionmentioning

confidence: 99%

Whistler modes in highly nonuniform magnetic fields. III. Propagation near mirror and cusp fields

Stenzel

Urrutia

2018

Physics of Plasmas

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“…The experimental setup represented a vacuum chamber of 10 m in length and 3 m in width, in which a plasma column of 4 m in length and 1.5 m in diameter was created. Detailed description of the experimental setup can be found by, e.g., Gushchin et al [2008]. In a dense magnetized plasma with f Be 2 ≪ f pe 2 ( f pe = 2.8 GHz and f Be = 225 MHz are the plasma frequency of electrons and the electron gyrofrequency, respectively), whose magnetic field is modulated with the frequency Ω = 1 MHz and amplitude δB ≃ 2 × 10 −2 B , a quasi‐monochromatic wave of the whistler range f 0 < f Be , where f 0 is the wave frequency in the source region, was generated.…”

Section: Nonresonant Parametric Transformation Of the Radiation Frequmentioning

confidence: 99%

“…Dynamic spectra of the initially continuous quasi‐monochromatic wave of the whistler range after the passage across the region with periodic disturbance of the magnetic field for (a) f = 140 MHz, (b) f = 150 MHz, and (c) f = 160 MHz (adapted from Gushchin et al [2008]). …”

Section: Nonresonant Parametric Transformation Of the Radiation Frequmentioning

confidence: 99%

“…The amplitude‐frequency modulation of the initially quasi‐monochromatic signal is stipulated by two effects: the nonresonant parametric modulation of the signal frequency due to a time variation in the refractive index, whose instability is stipulated by a harmonic variation in the magnetic field, and strong frequency dispersion of the medium, i.e., the dependence of the refractive index and group velocity of the propagating electromagnetic radiation on frequency [ Gushchin et al , 2008]. Depending on the phase of the variable magnetic field, the signal frequency is shifted toward larger or smaller frequencies.…”

Section: Nonresonant Parametric Transformation Of the Radiation Frequmentioning

confidence: 99%

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Parametric mechanism for the formation of Jovian millisecond radio bursts

et al. 2011

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[1] We develop a theory of formation of a fine structure in the dynamic spectra of the Jovian decametric radio emission. Main attention is paid to the formation of narrowband (NB) emission and quasiperiodic trains of short (S) bursts. Our model is based on the effects of occurrence of the amplitude-frequency modulation and extension of the frequency spectrum of a signal during propagation of radiation in a medium with timevaried parameters. It is shown that nonstationary disturbances of the planetary magnetic field and strong frequency dispersion of the plasma at frequencies close to the cutoff frequency of the extraordinary wave in the Jovian ionosphere play a crucial role in the formation of NB emission and quasiperiodic trains of S bursts. As a result of the numerical experiments, it was concluded that the amplitude-frequency characteristics of an initially continuous signal can drastically vary as a functions of the form of the magnetic field disturbance in the Jovian ionosphere. Structures similar to those observed in the real experiments, ranging from NB emission and quasiperiodic trains of S bursts to more complex structures, arise in the dynamic spectrum. Time variation in the conditions of generation and propagation of decametric radiation in the Jovian ionosphere is reflected in the dynamic spectrum as a time variation in the fine structure of the radiation. For example, a structure of the NB emission type is replaced by a quasiperiodic train of S bursts and vice versa.Citation: Shaposhnikov, V. E., S. V. Korobkov, H. O. Rucker, A. V. Kostrov, M. E. Gushchin, and G. V. Litvinenko (2011), Parametric mechanism for the formation of Jovian millisecond radio bursts,

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“…5 Some of the more recent laboratory experiments dealing with more complex nonlinear effects are from Refs. [6][7][8][9]. Laboratory experiments such as these isolate particular effects under controlled and repeatable conditions, which are difficult to achieve with in situ experiments using ground based antennas, sounding rockets, and satellites.…”

Section: Introductionmentioning

confidence: 97%

Whistler wave propagation in the antenna near and far fields in the Naval Research Laboratory Space Physics Simulation Chamber

2010

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In previous papers, early whistler propagation measurements were presented [W. E. Amatucci et al., IEEE Trans. Plasma Sci. 33, 637 (2005)] as well as antenna impedance measurements [D. D. Blackwell et al., Phys. Plasmas 14, 092106 (2007)] performed in the Naval Research Laboratory Space Physics Simulation Chamber (SPSC). Since that time there have been major upgrades in the experimental capabilities of the laboratory in the form of improvement of both the plasma source and antennas. This has allowed access to plasma parameter space that was previously unattainable, and has resulted in measurements that provide a significantly clearer picture of whistler propagation in the laboratory environment. This paper presents some of the first whistler experimental results from the upgraded SPSC. Whereas previously measurements were limited to measuring the cyclotron resonance cutoff and elliptical polarization indicative of the whistler mode, now it is possible to experimentally plot the dispersion relation itself. The waves are driven and detected using balanced dipole and loop antennas connected to a network analyzer, which measures the amplitude and phase of the wave in two dimensions (r and z). In addition the frequency of the signals is also swept over a range of several hundreds of megahertz, providing a comprehensive picture of the near and far field antenna radiation patterns over a variety of plasma conditions. The magnetic field is varied from a few gauss to 200 G, with the density variable over at least 3 decades from 107 to 1010 cm−3. The waves are shown to lie on the dispersion surface for whistler waves, with observation of resonance cones in agreement with theoretical predictions. The waves are also observed to propagate without loss of amplitude at higher power, a result in agreement with previous experiments and the notion of ducted whistlers.

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Whistler waves in plasmas with time-varying magnetic field: Laboratory investigation

Cited by 10 publications

References 18 publications

Whistler modes in highly nonuniform magnetic fields. III. Propagation near mirror and cusp fields

Whistler modes in highly nonuniform magnetic fields. III. Propagation near mirror and cusp fields

Parametric mechanism for the formation of Jovian millisecond radio bursts

Whistler wave propagation in the antenna near and far fields in the Naval Research Laboratory Space Physics Simulation Chamber

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