Double plasma resonance instability as a source of solar zebra emission

Benáček, Jan; Karlický, M.

doi:10.1051/0004-6361/201731424

Cited by 16 publications

(12 citation statements)

References 14 publications

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“…We found that due to an error in the growth-rate normalization in our previous paper the growth rate in this paper was overestimated 20 times. Considering this correction the maximal growth rate Γ from the present paper agrees to that in the paper by Benáček & Karlický (2018).…”

Section: Discussionsupporting

confidence: 90%

“…We make simulations using a 3D Particle-in-Cell (PIC) relativistic model (Buneman & Storey 1985;Matsumoto & Omura 1993;Karlický & Bárta 2008;Benáček & Karlický 2018) with multi-core Message Passing Interface (MPI) parallelization. Further details can be found in Matsumoto & Omura (1993, p.67-84) and on the link below.…”

Section: Numerical Growth Rates In the Pic Modelmentioning

confidence: 99%

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Growth Rates of the Electrostatic Waves in Radio Zebra Models

Benáček

Karlický

2019

ApJ

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Zebras were observed not only in the solar radio emission but also in radio emissions of Jupiter and Crab Nebula pulsar. In their models, growth rates of the electrostatic waves play an important role. Considering the plasma composed from the thermal background plasma and hot and rare component with the Dory-Guest-Harris distribution, we compute the growth rates γ and dispersion branches of the electrostatic waves in the ω − k ⊥ domain. We show complexity of the electrostatic wave branches in the upper-hybrid band. In order to compare the results, which we obtained using the kinetic theory and Particle-in-cell (PIC) simulations, we define and compute the integrated growth rate Γ, where the "characteristic width" of dispersion branches was considered. We found a very good agreement between the integrated growth rates and those from PIC simulations. For maximal and minimal Γ we showed locations of dispersion branches in the ω −k ⊥ domain. We found that Γ has a maximum when the dispersion branches not only cross the region with high growth rates γ, but when the dispersion branches in this region are sufficiently long and wide. We also mentioned the effects of changes in the background plasma and hot component temperatures.

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Section: Discussionsupporting

confidence: 90%

Section: Numerical Growth Rates In the Pic Modelmentioning

confidence: 99%

Growth Rates of the Electrostatic Waves in Radio Zebra Models

Benáček

Karlický

2019

ApJ

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“…Therefore our gyro-harmonic number agrees to that determined by Chen et al (2011). We note that the gyroharmonic number need not be necessarily an integer number; see the paper by Benáček & Karlický (2018). The plasma density and magnetic field in the zebra-stripe source with s 1 = 12.7 are n = 1.97 × 10 10 cm −3 and B = 35.58 G, respectively (Table 1).…”

Section: Zebra-stripe Sources Moving In Fan Of Magnetic Field Linessupporting

confidence: 81%

“…Another process that can influence the zebra-stripe frequency is a fast change of the "temperature" of the hot anisotropic electrons, which can change the ratio of the upper-hybrid and electron-cyclotron frequency for the maximum of the growth rate of the upper-hybrid waves (see Fig. 7 in Benáček & Karlický 2018).…”

Section: Zebra-stripe Sources Moving In Fan Of Magnetic Field Linesmentioning

confidence: 99%

Zebra-stripe sources in the double-plasma resonance model of solar radio zebras

Karlický

Yasnov²

2019

A&A

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Context. Radio bursts with fine structures are used in diagnostics of solar flare plasmas, of which zebra structures are the most important. However, there is still a debate about their origin. Aims. The most probable model of zebras is that based on double-plasma resonance (DPR) instability. The paper wants to contribute to a verification of this model. Methods. We used analytical methods. Results. We studied the DPR model in two scenarios: a model with the zebra-stripe sources in a single loop and a model with the zebra-stripe sources moving through a fan of magnetic field lines. In the first case, we found several new relations among the parameters of zebra stripes and their sources, which can be used to analyze observed zebras and thus to verify if the zebra is generated according to the DPR model. These relations were derived for the zebra-stripe sources distributed along the loop and also for those having some extent in the loop radius. In the scenario with the moving zebra-stripe sources, we determined the parameters of the 14 December 2006 zebra and estimated a change of the ratio of magnetic field and density scales causing the change of zebra-stripe frequencies. In this case we found that this zebra can be also explained in the model with the zebra-stripe sources in a single loop. Both the interpretations are discussed.

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“…For ECME, a positive gradient in the EVDF is needed in the direction perpendicular to the magnetic field, , e.g. in loss-cone (Benáček & Karlický 2017), ring (Pritchett 1984; Lee, Omura & Lee 2011), horseshoe (Bingham & Cairns 2000; Melrose & Wheatland 2016), cup-like (Büchner & Kuska 1996) or shell-shaped distribution functions. The corresponding ‘inverted’ population in the velocity space led to the early authors calling this cyclotron-resonance-related mechanism a ‘maser’ mechanism.…”

Section: Introductionmentioning

confidence: 99%

The effects of density inhomogeneities on the radio wave emission in electron beam plasmas

et al. 2021

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Type III radio bursts are radio emissions associated with solar flares. They are considered to be caused by electron beams travelling from the solar corona to the solar wind. Magnetic reconnection is a possible accelerator of electron beams in the course of solar flares since it causes unstable distribution functions and density inhomogeneities (cavities). The properties of radio emission by electron beams in an inhomogeneous environment are still poorly understood. We capture the nonlinear kinetic plasma processes of the generation of beam-related radio emissions in inhomogeneous plasmas by utilizing fully kinetic particle-in-cell code numerical simulations. Our model takes into account initial electron velocity distribution functions (EVDFs) as they are supposed to be created by magnetic reconnection. We focus our analysis on low-density regions with strong magnetic fields. The assumed EVDFs allow two distinct mechanisms of radio wave emissions: plasma emission due to wave–wave interactions and so-called electron cyclotron maser emission (ECME) due to direct wave–particle interactions. We investigate the effects of density inhomogeneities on the conversion of free energy from the electron beams into the energy of electrostatic and electromagnetic waves via plasma emission and ECME, as well as the frequency shift of electron resonances caused by perpendicular gradients in the beam EVDFs. Our most important finding is that the number of harmonics of Langmuir waves increases due to the presence of density inhomogeneities. The additional harmonics of Langmuir waves are generated by a coalescence of beam-generated Langmuir waves and their harmonics.

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Double plasma resonance instability as a source of solar zebra emission

Cited by 16 publications

References 14 publications

Growth Rates of the Electrostatic Waves in Radio Zebra Models

Growth Rates of the Electrostatic Waves in Radio Zebra Models

Zebra-stripe sources in the double-plasma resonance model of solar radio zebras

The effects of density inhomogeneities on the radio wave emission in electron beam plasmas

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