<i>Z</i>‐mode maser instability

Yi, So Jeong; Lee, Sang-Yun; Kim, Hee‐Eun; Lim, Daye; Seough, Jungjoon; Yoon, Peter H.; Broughton, M.; LaBelle, J.

doi:10.1002/2013ja019376

Cited by 9 publications

(7 citation statements)

References 56 publications

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“…Lee et al (2013) conducted a parameter study on the electron cyclotron maser instability which directly excites the escaping X and ordinary (O) modes (Wu & Lee 1979) and checked the variation of both parameters for the regime of ω pe Ω ce ≤ 5. Yi et al (2013) extends the study to investigate the variations of the two parameters of Z-mode instability. Both studies are based on cold plasma approximation.…”

Section: Introductionmentioning

confidence: 93%

Effect of the Temperature of Background Plasma and the Energy of Energetic Electrons on Z-mode Excitation

Chen

Kong

et al. 2019

ApJ

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It has been suggested that the Z-mode instability driven by energetic electrons with a loss-cone type velocity distribution is one candidate process behind the continuum and zebra pattern of solar type-IV radio bursts. Both the temperature of background plasma (T 0 ) and the energy of energetic electrons (v e ) are considered to be important to the variation of the maximum growth rate (γ max ). Here we present a detailed parameter study on the effect of T 0 and v e , within a regime of the frequency ratio (10 ≤ ω pe Ω ce ≤ 30). In addition to γ max , we also analyze the effect on the corresponding wave frequency (ω r max ) and propagation angle (θ max ). We find that (1) γ max in-general decreases with increasing v e , while its variation with T 0 is more complex depending on the exact value of v e ; (2) with increasing T 0 and v e , ω r max presents step-wise profiles with jumps separated by gradual or very-weak variations, and due to the warm-plasma effect on the wave dispersion relation ω r max can vary within the hybrid band (the harmonic band containing the upper hybrid frequency) and the band higher; (3) the propagation is either perpendicular or quasi-perpendicular, and θ max presents variations in line with those of ω r max , as constrained by the resonance condition. We also examine the profiles of γ max with ω pe Ω ce for different combinations of T 0 and v e to clarify some earlier calculations which show inconsistent results.

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Section: Introductionmentioning

confidence: 93%

Effect of the Temperature of Background Plasma and the Energy of Energetic Electrons on Z-mode Excitation

Chen

Kong

et al. 2019

ApJ

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“…As a matter of fact, the local absorption coefficient turns negative, and the whole plasma region becomes an emitter of radiation, mainly in the X mode and weaker in the O mode. There is, of course, also excitation of the Z mode below the upper hybrid frequency (see, e.g., Yi et al, 2013), but this is basically electrostatic and cannot leave the plasma without invoking other wave transformation processes.…”

Section: Review and Justificationmentioning

confidence: 99%

Electron cyclotron maser instability (ECMI) in strong magnetic guide field reconnection

Treumann

Baumjohann

2017

Ann. Geophys.

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Abstract. The ECMI model of electromagnetic radiation from electron holes is shown to be applicable to spontaneous magnetic reconnection. We apply it to reconnection in strong current-aligned magnetic guide fields. Such guide fields participate only passively in reconnection, which occurs in the antiparallel components to both sides of the guidefield-aligned current sheets with current carried by kinetic Alfvén waves. Reconnection generates long (the order of hundreds of electron inertial scales) electron exhaust regions at the reconnection site X point, which are extended perpendicular to the current and the guide fields. Exhausts contain a strongly density-depleted hot electron component and have properties similar to electron holes. Exhaust electron momentum space distributions are highly deformed, exhibiting steep gradients transverse to both the reconnecting and guide fields. Such properties suggest application of the ECMI mechanism with the fundamental ECMI X-mode emission beneath the nonrelativistic guide field cyclotron frequency in localized source regions. An outline of the mechanism and its prospects is given. Potential applications are the kilometric radiation (AKR) in auroral physics, solar radio emissions during flares, planetary emissions and astrophysical scenarios (radiation from stars and compact objects) involving the presence of strong magnetic fields and field-aligned currents. Drift of the exhausts along the guide field maps the local field and plasma properties. Escape of radiation from the exhaust and radiation source region still poses a problem. The mechanism can be studied in 2-D particle simulations of strong guide field reconnection which favours 2-D, mapping the deformation of the electron distribution perpendicular to the guide field, and using it in the numerical calculation of the ECMI growth rate. The mechanism suggests also that reconnection in general may become a source of the ECMI with or without guide fields. This is of particular interest in extended turbulent plasmas where reconnection serves as an integral dissipation mechanism of turbulent energy in myriads of small-scale current filaments.

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“…Recently, Yi et al [] found that the Z mode actually consists of broadband and narrowband modes, each with a distinct polarization. The broadband mode can have a significant O mode polarization and may mode convert and propagate out of the plasma.…”

Section: Discussionmentioning

confidence: 99%

A new natural radio emission observed at South Pole Station

2014

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[1] Continuous waveform data taken at South Pole Station in 2011-2012 within a few hours of magnetic midnight revealed 12 observations of a new natural radio emission. The waves had frequencies ranging from 1320 to 2160 kHz, bandwidths ranging from 94 to 272 kHz, and durations ranging from 16 to 355 s. Spectral analysis of the waveform data revealed that the emission has a complex combination of at least three kinds of fine structures: broad, banded structures; short-lived, narrowband structures; and striated features that occur predominantly near the lower frequency boundary of the emission. For model auroral electron distributions, positive growth rates for the cyclotron maser instability occurred near the electron cyclotron frequency (f ce ), which is inconsistent with the observed wave frequencies. On the other hand, Langmuir wave growth could be excited at frequencies consistent with observations. Spatial Langmuir wave growth is more favorable for electron beam energies of hundreds of eV than for those at higher energies.

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Z‐mode maser instability

Cited by 9 publications

References 56 publications

Effect of the Temperature of Background Plasma and the Energy of Energetic Electrons on Z-mode Excitation

Effect of the Temperature of Background Plasma and the Energy of Energetic Electrons on Z-mode Excitation

Electron cyclotron maser instability (ECMI) in strong magnetic guide field reconnection

A new natural radio emission observed at South Pole Station

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