Growth Rates of the Electrostatic Waves in Radio Zebra Models

Benáček, Jan; Karlický, M.

doi:10.3847/1538-4357/ab2bfc

Cited by 12 publications

(5 citation statements)

References 28 publications

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“…We use the zebra model based on the double-plasma resonance (DPR) instability (Zheleznyakov & Zlotnik 1975;Winglee & Dulk 1986;Kuznetsov & Tsap 2007;Tan 2010;Zlotnik 2013;Tan et al 2014;Karlický & Yasnov 2015;Benáček & Karlický 2019). In this model, each zebra-stripe source is located at a different place.…”

Section: Introductionmentioning

confidence: 99%

Estimating density and magnetic field turbulence in solar flares using radio zebra observations

Karlický

Yasnov

2020

A&A

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Context. In solar flares the presence of magnetohydrodynamic turbulence is highly probable. However, information about this turbulence, especially the magnetic field turbulence, is still very limited. Aims. In this paper we present a new method for estimating levels of the density and magnetic field turbulence in time and space during solar flares at positions of radio zebra sources. Methods. First, considering the double-plasma resonance model of zebras, we describe a new method for determining the gyro-harmonic numbers of zebra stripes based on the assumption that the ratio R = Lb/Ln (Ln and Lb are the density and magnetic field scales) is constant in the whole zebra source. Results. Applying both the method proposed in this work and one from a previous paper for comparison, in the 14 February 1999 zebra event we determined the gyro-harmonic numbers of zebra stripes. Then, using the zebra-stripe frequencies with these gyro-harmonic numbers, we estimated the density and magnetic field in the zebra-stripe sources as n = (2.95−4.35) × 1010 cm−3 and B = 17.2−31.9 G, respectively. Subsequently, assuming that the time variation of the zebra-stripe frequencies is caused by the plasma turbulence, we determined the level of the time varying density and magnetic field turbulence in zebra-stripe sources as |Δn/n|t = 0.0112–0.0149 and |ΔB/B|t = 0.0056–0.0074, respectively. The new method also shows deviations in the observed zebra-stripe frequencies from those in the model. We interpret these deviations as being caused by the spatially varying turbulence among zebra-stripe sources; i.e., they depend on their gyro-harmonic numbers. Comparing the observed and model zebra-stripe frequencies at a given time, we estimated the level of this turbulence in the density and magnetic field as |Δn/n|s = 0.0047 and |ΔB/B|s = 0.0024. We found that the turbulence levels depending on time and space in the 14 February 1999 zebra event are different. This indicates some anisotropy of the turbulence, probably caused by the magnetic field structure in the zebra source.

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Section: Introductionmentioning

confidence: 99%

Estimating density and magnetic field turbulence in solar flares using radio zebra observations

Karlický

Yasnov

2020

A&A

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“…To confirm a similarity between SZ and SBN of the 13 June 2012 flare given by auto-correlations (Figure 7) and SBN observed in 7 November 2013 with the Bernstein modes, we fitted the mean SZ band frequencies by the same way as in the SBN 7 November 2013 case (Karlický, Benáček, and Rybák, 2021), see also Benáček and Karlický (2019). Firstly, we searched for the time where the bandwidth of SZ spike bands is the narrowest.…”

Section: Modelling Of Sz Frequencies By Bernstein Modesmentioning

confidence: 94%

Narrowband spikes observed during the 13 June 2012 flare in the 800-2000 MHz range

Karlicky,

Rybak,

Benacek

et al. 2022

Preprint

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Narrowband (∼5 MHz) and short-lived (∼0.01 s) spikes with three different distributions on the 800-2000 MHz radio spectrum of the 13 June 2012 flare are detected and analyzed. We designate them as SB (spikes distributed in broad band or bands), SZ (spikes distributed in zebra-like bands) and SBN (spikes distributed in broad and narrow bands). Analyzing AIA/SDO images of the active region NOAA 11504, a rough correspondence between groups of the spikes observed on 1000 MHz and peaks in the time profiles of AIA channels taken from the flare sub-area close to the leading sunspot is found. Among types of spikes the SZ type is the most interesting because it resembles to zebras. Therefore, using auto-correlation and cross-correlation methods we compare SZ and SBN spikes with the typical zebra observed in the same frequency range. While the ratio of SZ band frequencies with their frequency separation (220 MHz) is about 4, 5 and 6, in the zebra the frequency stripe separation is about 24 MHz and the ratio is around 50. Moreover, the bandwidth of SZ bands, which consists of clouds of narrowband spikes, is much broader than that of zebra stripes. This comparison indicates that SZ spikes are generated different way than the zebra, but similar way as SBN spikes. We successfully fit the SZ band frequencies by the Bernstein modes. Based on this fitting we interpret SZ and SBN spikes as those generated in the model with Bernstein modes. Thus, the magnetic field and plasma density in the SZ spike source is estimated as about 79 G and 8.4 × 10 9 cm −3 , respectively.

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“…ECMI could be caused by EVDFs including, e.g., cup-like distribution functions (Büchner & Kuska 1996), horseshoe-like EVDFs (Bingham & Cairns 2000;Melrose & Wheatland 2016), ring-(Pritchett 1984Lee et al 2011;Yao et al 2021) and crescent-shaped EVDFs in the velocity space perpendicular to magnetic field (Burch et al 2016b;Chen et al 2016b;Egedal et al 2016). The ECMI produces electromagnetic waves at the local electron cyclotron frequency and its harmonics as well as UH waves (Benáček & Karlický 2019;Ni et al 2020). The electron cyclotron maser emission (ECME) mechanism predicts the electromagnetic emission amplified by a quasi-linear wave-particle interaction in the magnetic field (Twiss 1958;Melrose et al 1984;Melrose 2017).…”

Section: Introductionmentioning

confidence: 99%

Wave Emission of Nonthermal Electron Beams Generated by Magnetic Reconnection

Yao

Muñoz²,

Büchner³

et al. 2022

ApJ

Self Cite

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Magnetic reconnection in solar flares can efficiently generate nonthermal electron beams. The energetic electrons can, in turn, cause radio waves through microscopic plasma instabilities as they propagate through the ambient plasma along the magnetic field lines. We aim at investigating the wave emission caused by fast-moving electron beams with characteristic nonthermal electron velocity distribution functions (EVDFs) generated by kinetic magnetic reconnection: two-stream EVDFs along the separatrices and in the diffusion region, and perpendicular crescent-shaped EVDFs closer to the diffusion region. For this purpose, we utilized 2.5D fully kinetic Particle-In-Cell code simulations in this study. We found the following: (1) the two-stream EVDFs plus the background ions are unstable to electron/ion (streaming) instabilities, which cause ion-acoustic waves and Langmuir waves due to the net current. This can lead to multiple-harmonic plasma emission in the diffusion region and the separatrices of reconnection. (2) The perpendicular crescent-shaped EVDFs can cause multiple-harmonic electromagnetic electron cyclotron waves through the electron cyclotron maser instabilities in the diffusion region of reconnection. Our results are applicable to diagnose the plasma parameters, which are associated to magnetic reconnection in solar flares by means of radio wave observations.

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Growth Rates of the Electrostatic Waves in Radio Zebra Models

Cited by 12 publications

References 28 publications

Estimating density and magnetic field turbulence in solar flares using radio zebra observations

Estimating density and magnetic field turbulence in solar flares using radio zebra observations

Narrowband spikes observed during the 13 June 2012 flare in the 800-2000 MHz range

Wave Emission of Nonthermal Electron Beams Generated by Magnetic Reconnection

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