Laboratory astrophysics: Investigation of planetary and astrophysical maser emission

Bingham, R.; Speirs, D. C.; Kellett, B. J.; Vorgul, I.; McConville, S. L.; Cairns, R. A.; Cross, A. W.; Phelps, A. D. R.; Ronald, K.

doi:10.1007/s11214-013-9963-z

Cited by 42 publications

(34 citation statements)

References 61 publications

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“…This trend is reflected in the results of unbounded PiC simulations of cyclotron-wave coupling, where radiation propagation has been observed with a distinctive backward-wave character to it, typically directed in a slightly backward direction, only a few degrees away from the perpendicular to the magnetostatic field. The corresponding rf conversion efficiencies are comparable with estimates for the astrophysical phenomena (Gurnett 1974;Treumann 2006;Bingham et al 2013). …”

Section: Discussionsupporting

confidence: 79%

Numerical simulations of unbounded cyclotron-maser emissions

Speirs¹,

McConville²,

Gillespie³

et al. 2013

J. Plasma Phys.

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Abstract. Numerical simulations have been conducted to study the spatial growth rate and emission topology of the cyclotron-maser instability responsible for stellar/planetary auroral magnetospheric radio emission and intense non-thermal radio emission in other astrophysical contexts. These simulations were carried out in an unconstrained geometry, so that the conditions existing within the source region of some natural electron cyclotron masers could be more closely modelled. The results have significant bearing on the radiation propagation and coupling characteristics within the source region of such non-thermal radio emissions.

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Section: Discussionsupporting

confidence: 79%

Numerical simulations of unbounded cyclotron-maser emissions

Speirs¹,

McConville²,

Gillespie³

et al. 2013

J. Plasma Phys.

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“…More recently, this radiation model has been extended to a variety of astrophysical environments including Blazar jets, collisionless shocks, and brown dwarfs [3][4][5][6][7]. Planetary auroral radio emission has been a topic of interest for many years with several mechanisms having been proposed [8][9][10][11][12][13][14][15].…”

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confidence: 99%

Backward Wave Cyclotron-Maser Emission in the Auroral Magnetosphere

et al. 2014

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In this Letter, we present theory and particle-in-cell simulations describing cyclotron radio emission from Earth's auroral region and similar phenomena in other astrophysical environments. In particular, we find that the radiation, generated by a down-going electron horseshoe distribution is due to a backwardwave cyclotron-maser emission process. The backward wave nature of the radiation contributes to upward refraction of the radiation that is also enhanced by a density inhomogeneity. We also show that the radiation is preferentially amplified along the auroral oval rather than transversely. The results are in agreement with recent Cluster observations. DOI: 10.1103/PhysRevLett.113.155002 PACS numbers: 94.05.Dd, 94.30.Aa, 96.12.Wx, 98.62.Nx The electron cyclotron-maser instability plays a significant role in the generation of highly nonthermal, polarized radio emission from the auroral region of planets and stars having a dipolelike magnetic field [1,2]. More recently, this radiation model has been extended to a variety of astrophysical environments including Blazar jets, collisionless shocks, and brown dwarfs [3][4][5][6][7]. Planetary auroral radio emission has been a topic of interest for many years with several mechanisms having been proposed [8][9][10][11][12][13][14][15]. As the dispersion relation describing the electromagnetic wave growth only depends on the factor by which the magnetic field increases and on the ratio of plasma and cyclotron frequencies, the mechanism can scale effectively over many orders of magnitude both in wavelength and spatial scale. Blazar jets, in particular, represent a prime example of this scalability [3]. Generated perpendicular to the accretion disk of super massive black holes, they can extend over many thousands of light years and have been observed to generate highly nonthermal radio emission at frequencies in the hundreds of GHz range. It has been suggested that small scale magnetic mirrors or convergent flux tubes may be formed within the jet via hydrodynamic instabilities or shocks, providing the means of generating the required electron velocity distribution Bing2003, Begel2005. In Earth's auroral region, observations by the Viking spacecraft [11,16] and the Fast Auroral Snapshot (FAST) satellite [14] led to the suggestion that the free energy source for AKR is a population of downward accelerated electrons having a large perpendicular velocity produced by a combination of parallel accelerating electric fields and converging magnetic field lines. The electron distribution takes the form of a horseshoe or crescent shape due to the first adiabatic invariance as the electrons move into the stronger magnetic field. The FAST satellite [13,14,17] clearly demonstrates a strong correlation between the electromagnetic wave emission and the occurrence of the horseshoe distribution [13].Further observations by FAST of localized double-layer structures within the auroral density cavity have combined our understanding of auroral particle acceleration with the auroral kilome...

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“…In general, maser instabilities due to loss-cone or ring-like electron distributions give rise to excitations in the Z (slow X) mode or upper hybrid mode branch for pe ce ω ω [13], while radiation in the fast X mode branch near ce ω dominates in the opposite limit. The latter has been studied extensively in the framework of auroral kilometric radiation [21], solar and stellar radio bursts [22], etc, and via simulations and laboratory experiments [23][24][25]. There are also anisotropydriven electromagnetic and electrostatic waves for different sets of parameters [26].…”

Section: Introductionmentioning

confidence: 99%

Electrostatic electron cyclotron instabilities near the upper hybrid layer due to electron ring distributions

Eliasson

Speirs

Daldorff

2016

Plasma Phys. Control. Fusion

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A theoretical study is presented of the electrostatic electron cyclotron instability involving Bernstein modes in a magnetized plasma. The presence of a tenuous thermal ring distribution in a Maxwellian plasma decreases the frequency of the upper hybrid branch of the electron Bernstein mode until it merges with the nearest lower branch with a resulting instability. The instability occurs when the upper hybrid frequency is somewhat above the third, fourth, and higher electron cyclotron harmonics, and gives rise to a narrow spectrum of waves around the electron cyclotron harmonic nearest to the upper hybrid frequency. For a tenuous cold ring distribution together with a Maxwellian distribution an instability can take place also near the second electron cyclotron harmonic. Noise-free Vlasov simulations are used to assess the theoretical linear growth-rates and frequency spectra, and to study the nonlinear evolution of the instability. The relevance of the results to laboratory and ionospheric heating experiments is discussed.

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Laboratory astrophysics: Investigation of planetary and astrophysical maser emission

Cited by 42 publications

References 61 publications

Numerical simulations of unbounded cyclotron-maser emissions

Numerical simulations of unbounded cyclotron-maser emissions

Backward Wave Cyclotron-Maser Emission in the Auroral Magnetosphere

Electrostatic electron cyclotron instabilities near the upper hybrid layer due to electron ring distributions

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