Simulations of coronal type III solar radio bursts: 2. Dynamic spectrum for typical parameters

Li, Bo; Cairns, Iver H.; Robinson, P. A.

doi:10.1029/2007ja012958

Cited by 31 publications

(41 citation statements)

References 43 publications

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“…We see from Figures a and b that both bursts are weak yet are observable for typical instruments with thresholds ≈1 sfu (solar flux unit) (=10 −22 Wm −2 Hz −1 ). This result of weak f p emission is consistent with our previous simulations that have Maxwellian spectra for the injected electrons [e.g., Li et al , , ]. Figures a and b show that at a given f , the burst in S1 has a much earlier onset and slightly earlier termination than in S2.…”

Section: Representative Simulationssupporting

confidence: 90%

Type III bursts produced by power law injected electrons in Maxwellian background coronal plasmas

Cairns

2013

JGR Space Physics

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[1] Simulations are presented for coronal type III bursts produced by injection of energetic electrons with power law speed spectra onto open magnetic field lines embedded in an otherwise unmagnetized Maxwellian background coronal plasma, including quasi-linear wave-particle interactions and nonlinear wave-wave processes. The simulations show that although fast electrons with speeds > 0.3c are injected, they are important only to the onset and not to the peak of f p emission, where f p is the local electron plasma frequency. Instead, slower beam electrons are the major drivers of the peak f p emission. Therefore, the type III beam speeds derived from the drift rates of peak f p emission are less than the typical speeds of c/3 observed for coronal type III bursts. This occurs mainly because the number of fast beam electrons with speeds > 0.3c is much less than the slower ones, causing weaker f p emission from these fast beam electrons. Comparisons are made with injected electrons having Maxwellian spectra. We find that type III beams are faster when the injection has power law spectra, since there are more fast electrons injected than for Maxwellian spectra. These results suggest that type III beams produced in the corona with Maxwellian background particle distributions and either power law or Maxwellian spectra can account only for the lower half of the observed range 0.1-0.6c of type III beam speeds but not for the upper half.Citation: Li, B., and I. H. Cairns (2013), Type III bursts produced by power law injected electrons in Maxwellian background coronal plasmas,

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Section: Representative Simulationssupporting

confidence: 90%

Type III bursts produced by power law injected electrons in Maxwellian background coronal plasmas

Cairns

2013

JGR Space Physics

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“…The values of v b in Figure 3f are quantitatively consistent with the beam speeds V obtained directly from the simulated electron distribution function f e [ Li et al , 2008b]. Here v b characterizes the region in phase space where f e is unstable (∂ f e /∂ V > 0).…”

Section: Effects Of Varying Coronal Conditionssupporting

confidence: 79%

“…The model is based on quasilinear electron‐Langmuir wave equations augmented with nonlinear terms for Langmuir electrostatic (ES) decay, and with nonlinear wave‐wave processes that produce electromagnetic (EM) waves at f p and 2 f p . In the second paper (paper 2) [ Li et al , 2008b] we presented the simulation results for a coronal type III burst observed at Earth using a set of realistic parameters for the beam acceleration and coronal conditions. Our detailed comparisons between the simulations and typical observations showed quantitative or semiquantitative agreement in the spectral characteristics.…”

Section: Introductionmentioning

confidence: 99%

Simulations of coronal type III solar radio bursts: 3. Effects of beam and coronal parameters

Cairns

Robinson

2009

J. Geophys. Res.

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[1] A recently developed simulation model is used to investigate the effects of varying the coronal and electron heating conditions on the dynamic spectra of coronal type III bursts (70-370 MHz) observed at Earth. The flux of 2f p emission is significantly higher than that of f p emission, which is unlikely to be observable except under very favorable propagation conditions. Moreover, the 2f p emission is unlikely to continue into the solar wind, although some bursts are very strong and will extend into the upper corona with lower frequencies than simulated, consistent qualitatively with observations. The flux and brightness temperature of 2f p emission are affected significantly by variations in the parameters, while the frequency drift rate and half-power duration are affected only weakly. Further, the simulations confirm the standard interpretation of the drift rate of 2f p emission in terms of the plasma density profile and a characteristic beam speed that agrees quantitatively with the simulated beam dynamics for wide ranges of coronal and heating conditions. For weak heating events or events with high coronal electron temperature, the remote radiation shows characteristics that agree quantitatively with microbursts. When the heating is even weaker and/or the electron temperature is even higher, the heating events are radio quiet, consistent qualitatively with hard X-ray observations. For similar heating originating in similar frequency ranges, different density models yield quantitatively similar results except for the drift rate. Variations of the levels of a given density profile, corresponding to background corona or coronal streamers, can also cause significant changes in spectral characteristics.

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“…In this work for a first time we are concerned with the investigation of the generation of Langmuir waves, its spectra and total energy density, and also the gas-dynamical parameters of the beam such as the height of the plateau in the beam distribution function, its upper velocity boundary, the beam width in velocity space, and its local and average velocity of propagation in the solar wind plasma by considering a Lorentzian background distribution function. Gas-dynamical parameters are helpful in understanding the dynamic spectra of type III radio bursts (Li et al 2008a(Li et al , 2008b.…”

Section: Introductionmentioning

confidence: 99%

Beam propagation and Langmuir wave generation in a plasma with κ distribution function

Khalilpour

Foroutan

2011

Astrophys Space Sci

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Using a kappa velocity distribution function for the electrons of the background plasma, the dynamics of a beam of hot electrons streaming through the plasma and the generation of Langmuir waves are investigated in the frame work of quasilinear theory. It is shown that the Langmuir waves are strongly damped by high energy tail of the Kappa distribution function. The spatial expansion of the beam is reduced and the spectral density of Langmuir waves becomes narrower. The height of the plateau in the beam distribution function increases at small velocities and the average velocity of beam is larger than that of a Maxwellian distribution. The influence of Kappa velocity distribution function on the gasdynamical parameters is investigated. It is found that, the height of plateau in the beam distribution function, and its lower velocity boundary are enhanced while, the local beam width in velocity space decreases.

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Simulations of coronal type III solar radio bursts: 2. Dynamic spectrum for typical parameters

Cited by 31 publications

References 43 publications

Type III bursts produced by power law injected electrons in Maxwellian background coronal plasmas

Type III bursts produced by power law injected electrons in Maxwellian background coronal plasmas

Simulations of coronal type III solar radio bursts: 3. Effects of beam and coronal parameters

Beam propagation and Langmuir wave generation in a plasma with κ distribution function

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