Occurrence distributions of the auroral kilometric radiation ordinary and extraordinary wave modes

Hanasz, J.; Panchenko, M.; Féraudy, H. de; Schreiber, R.; Mogilevsky, M. M.

doi:10.1029/2002ja009579

Cited by 37 publications

(34 citation statements)

References 40 publications

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“…Internal Z mode is also detected in the source region [ Gurnett et al , 1983], but may result from conversion of RX mode radiation propagating normal to the auroral cavity [ Pritchett et al , 2002]. Although the RX mode almost always dominates observed AKR emission, there is often significant power in the LO mode, usually in the range 1%–10% of the RX power [ Mellott et al , 1984; Benson et al , 1988; Hanasz et al , 2003]. When LO and RX mode are seen together, their observed fluxes are often highly correlated, with LO mode flux densities about 2% of RX mode [ Mellott et al , 1984].…”

Section: Introductionmentioning

confidence: 99%

Dependence of cyclotron maser instability growth rates on electron velocity distributions and perturbation by solitary waves

et al. 2007

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[1] We calculate growth rates and corresponding gains for right-hand circularly polarized extraordinary (RX) and left-hand ordinary circularly polarized (LO) mode radiation associated with the cyclotron maser instability (CMI) for parameterized horseshoe electron velocity distributions. The velocity distribution function was modeled to closely fit the electron distribution functions observed in the auroral cavity. We systematically varied the model parameters as well as the propagation direction to study the dependence of growth rates on model parameters. The growth rate depends strongly on loss cone opening angle, which must be less than 90°for significant CMI growth. The growth rate is sharply peaked for perpendicular radiation (k k = 0), with a full width at half maximum 1.7°, in good agreement with observed k-vector orientations and numerical simulations. The fractional bandwidth varied between 10 À4 and 10 À2 , depending most strongly on propagation direction. This range encompasses nearly all observed fractional auroral kilometric radiation (AKR) burst bandwidths. We find excellent agreement between the computed RX mode emergent intensities and observed AKR intensities assuming convective growth length L c % 20-40 km and group speed 0.15c. The only computed LO mode growth rates compatible observed LO mode radiation levels occurred for number densities more than 100 times the average energetic electron densities measured in auroral cavities. This implies that LO mode radiation is not produced directly by the CMI mechanism but more likely results from mode conversion of RX mode radiation. We find that perturbation of the model velocity distribution by large ion solitary waves (ion holes) can enhance the growth rate by a factor of 2-4. This will result in a gain enhancement more than 40 dB depending on the convective growth length within the structure. Similar enhancements may be caused by strong electromagnetic ion cyclotron waves.

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Section: Introductionmentioning

confidence: 99%

Dependence of cyclotron maser instability growth rates on electron velocity distributions and perturbation by solitary waves

et al. 2007

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“…Satellites that investigated these auroral regions have observed that the radiation is emitted in the extraordinary (X) plasma mode , Ergun et al 2000, polarized and propagating perpendicular to the static magnetic field. More distant observations indicate some small fraction is also polarized in the ordinary (O) mode (Hanasz et al 2003). In the magnetosphere a parallel electric field, E , is necessary to constantly accelerate the electrons into the converging magnetic field to obtain the AKR distribution (Wu andLee 1979, Pritchett andWinglee 1989) and reduce the plasma density.…”

Section: Introductionmentioning

confidence: 99%

Demonstration of auroral radio emission mechanisms by laboratory experiment

McConville

Speirs

Ronald

et al. 2008

Plasma Phys. Control. Fusion

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This version is available at https://strathprints.strath.ac.uk/63095/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. AbstractAuroral kilometric radiation occurs in regions of depleted plasma density in the polar magnetosphere. These emissions are close to the electron cyclotron frequency and appear to be connected to the formation of high pitch angle electron populations due to the conservation of the magnetic moment. This results in a horseshoe type distribution function being formed in velocity space where electrons are magnetically compressed as they descend towards the Earth's atmosphere. Satellites have observed that radio emissions occur in conjunction with the formation of this distribution and show the radiation to have propagation and polarization characteristics of the extraordinary (X-mode) plasma mode with emission efficiency observed at ∼1-2%. To investigate this phenomenon a laboratory experiment, scaled to microwave frequencies and lab dimensions by increasing the cyclotron frequency, was constructed whereby an electron beam propagated through a region of increasing magnetic field created by five independently variable solenoids. Results are presented for two experimental regimes of resonant coupling, 11.7 and 4.42 GHz, achieved by varying the peak magnetic field. Measurements of the experimental radiation frequency, power and efficiency were undertaken as a function of the magnetic compression. Results showed the radiation to be polarized in the near cut-off transverse electric radiation modes, with efficiency of emission ∼1-2%, peak power outputs of ∼19-30 kW and frequency close to the cyclotron frequency. This represented close correlation between the laboratory radiation efficiency, spectra, polarization and propagation with that of numerical predictions and the magnetospheric observations.

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“…In general, the occurrence distribution of L-O mode is less than that of R-mode [30] and L-X mode lies in a very limited frequency range. Since the diffusion coefficients depend on the wave occurrence distribution and the resonant frequency also depends on the wave frequency range, the acceleration produced by L-O and L-X modes should be less efficient than by R-X mode.…”

Section: Resultsmentioning

confidence: 92%

Dynamic evolution of outer radiation belt electrons driven by superluminous R-X mode waves

Xiao

Chen

Yang

et al. 2010

Sci. China Technol. Sci.

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We present initial results on the temporal evolution of the phase space density (PSD) of the outer radiation belt energetic electrons driven by the superluminous R-X mode waves. We calculate diffusion rates in pitch angle and momentum assuming the standard Gaussian distributions in both wave frequency and wave normal angle at the location L=6.5. We solve a 2D momentum-pitch-angle Fokker-Planck equation using those diffusion rates as inputs. Numerical results show that R-X mode can produce significant acceleration of relativistic electrons around geostationary orbit, supporting previous findings that superluminous waves potentially contribute to dramatic variation in the outer radiation belt electron dynamics. wave-particle interaction, superluminous R-X waves, phase space density evolution, radiation belt electrons Citation:Xiao F L, Chen L X, He Y H, et al. Dynamic evolution of outer radiation belt electrons driven by superluminous R-X mode waves.

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Occurrence distributions of the auroral kilometric radiation ordinary and extraordinary wave modes

Cited by 37 publications

References 40 publications

Dependence of cyclotron maser instability growth rates on electron velocity distributions and perturbation by solitary waves

Dependence of cyclotron maser instability growth rates on electron velocity distributions and perturbation by solitary waves

Demonstration of auroral radio emission mechanisms by laboratory experiment

Dynamic evolution of outer radiation belt electrons driven by superluminous R-X mode waves

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