Radiotechnologies in the Service of Human Health

Chernova, T. M.; Timchenko, V. N.; Чернов, А. В.

doi:10.21518/2079-701x-2017-20-210-215

Cited by 6 publications

(6 citation statements)

References 1 publication

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“…Zebra patterns (ZPs), appearing as regular stripes in emission and absorption in the dynamic spectra of solar radio bursts, are commonly known, and their observed characteristics and their models have been described in many papers (Slottje 1972;Kuijpers 1975;Zheleznyakov & Zlotnik 1975;Chernov 1976Chernov , 1990LaBelle et al 2003;Kuznetsov 2005;Bárta & Karlický 2006;Ledenev et al 2006;Tan 2010;Karlický 2013;Zlotnik 2013;Tan et al 2014;Chernov et al 2018), see also the reviews by Chernov (2011Chernov ( , 2014. The most frequently discussed mechanism in the literature is that based on the double plasma-resonance (DPR) instability (Kuijpers 1975(Kuijpers , 1980Zheleznyakov & Zlotnik 1975;Mollwo 1983Mollwo , 1988Winglee & Dulk 1986;Yasnov & Karlický 2004;Kuznetsov & Tsap 2007;Chen et al 2011;Karlický & Yasnov 2015;Yasnov et al 2016Yasnov et al , 2017Benáček et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Double plasma-resonance surfaces in flare loops and radio zebra emission

Karlický

Yasnov

2018

A&A

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Aims. The zebra structures observed in radio waves during solar flares are some of the most important structures used as diagnostics of solar flare plasmas. We here not only analyze the so-called double plasma-resonance (DPR) surfaces, but also estimate the effects of their form on the size of the zebra sources and brightness temperature. Methods. To compute the DPR surfaces, we used numerical and analytical methods. Results. We found that except for the case of a constant magnetic field across the loop, the DPR surfaces deviate from the constant plasma density surfaces. We found that the regime with a finite height scale has three forms of resonance surfaces depending on the magnetic field variation across the loop. This magnetic field variation also determines if in the generated zebra structure, an increase in gyro-harmonic number leads to an increase or decrease of the zebra stripe frequency. In the case with an infinite height scale, the resonance surfaces are parallel to the loop axis. Furthermore, we found that for highly polarized zebra structures that are generated at DPR surfaces close to the plasma frequency, the zebra emission is limited to the narrow escaping cone and the emitting source area increases with increasing viewing angle compared to the loop axis. Moreover, with increasing deviation of the DPR surfaces from those of constant density surfaces, the frequency bandwidth of the DPR emission increases and can cause the zebra stripes to overlap, which limits the zebra generation. For the zebra structures observed on 14 February 1999, 6 June 2000, and 1 August 2010 and the observed view perpendicular to the loop axis, we estimated that the brightness temperature is 3.67 × 1014 K, 6.58 × 1013 K, and 7.35 × 1015 K, respectively. These brightness temperatures are much lower than those derived for the view along the loop axis (up to 1017 K), and thus are more realistic. The area of the emitting source for coronal loops in the view perpendicular to the loop axis can be larger by several orders of magnitude than that in the view along the loop axis.

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Section: Introductionmentioning

confidence: 99%

Double plasma-resonance surfaces in flare loops and radio zebra emission

Karlický

Yasnov

2018

A&A

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“…The most commonly discussed mechanism in the literature is the mechanism based on the double plasma resonance (DPR), in which the radiation is at the upper hybrid frequency and simultaneously at the electron cyclotron harmonics with the integer gyroharmonic number s (Kuijpers 1975(Kuijpers , 1980Zheleznyakov & Zlotnik 1975;Mollwo 1983Mollwo , 1988Winglee & Dulk 1986). A number of works have also been devoted to other mechanisms of ZP generation, see, for example, Chernov (1976Chernov ( , 1990, Karlický et al (2001), LaBelle et al (2003), Bárta & Karlický (2006), Ledenev et al (2006), Kuznetsov & Tsap (2007) and Laptukhov & Chernov (2009). Karlický (2014) interpreted the frequency variations of the zebra stripes as being caused by the plasma turbulence.…”

Section: Introductionmentioning

confidence: 99%

Spatial quasi-periodic variations of the plasma density and magnetic field in zebra radio sources

Karlický

Yasnov

2021

A&A

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Context. Radio bursts and their fine structures are an integral part of solar flares. Fine structures in particular are used for diagnostics of solar flare processes. The so-called zebras belong to the most important of such fine structures. Aims. We analyze seven zebra events in order to search for spatial variations in the plasma density and magnetic field in zebra-stripe sources. Methods. We used an improved method for estimating the gyroharmonic numbers of zebra-stripe frequencies. We compared observed zebra-stripe frequencies with those calculated in the zebra model. The differences in these frequencies vary and thus show spatial variations in the plasma density and magnetic field. Results. In six out of seven analyzed zebras, we found a rather high correlation coefficient (about 0.7 and higher) between spatial variations in the density and magnetic field and a strictly periodic function. These density and magnetic field variations are explained by the torsional or sausage magnetoacoustic waves in the loop in which zebra-stripe sources are located. We present the wavelengths of these waves in dependence on the zebra frequency and estimate their periods.

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“…In most of these works, the appearance of ZS is associated with the generation mechanism features. In the solar radio emission case, preference is given to plasma generation mechanisms, whereby plasma (electrostatic) waves are first excited and then these waves are transformed into electromagnetic radiation (see, e.g., Chernov 1976;Zheleznyakov et al 2016). In a number of works, the appearance of ZS is explained by the interference of waves during their propagation in plasma with a regular non-uniform density (Barta & Karlicky 2006;Ledenev et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Origin of the zebra structure in the Jovian decameter radio emission

Шапошников

Litvinenko

Зайцев

et al. 2020

A&A

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Context. We discuss the origin of quasi-harmonic emission bands that have been observed in the dynamic spectra of the Jovian decameter emission. Aims. We aim to show that the interpretation of the observed structure can be based on the effect of double plasma resonance (DPR) at ion cyclotron harmonics. Methods. According to the proposed model, in the extended source in the upper ionosphere of Jupiter, where the DPR condition is satisfied for one of the ion cyclotron frequency harmonics, the ion cyclotron waves are effectively excited at the frequency of the lower hybrid resonance. The observed electromagnetic radiation with a quasi-harmonic structure arises due to scattering of ion cyclotron waves by supra-thermal electrons. Results. Based on the VIP4 magnetic field model, we determine the longitudes at which the source of the considered radiation can be located. The obtained estimates of the plasma density and its height distribution in the source, as well as the energies of emitting ions and scattering electrons provide information about the plasma parameters in the upper ionosphere of Jupiter. Furthermore, these estimates are in good agreement with the observational data.

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Radiotechnologies in the Service of Human Health

Cited by 6 publications

References 1 publication

Double plasma-resonance surfaces in flare loops and radio zebra emission

Double plasma-resonance surfaces in flare loops and radio zebra emission

Spatial quasi-periodic variations of the plasma density and magnetic field in zebra radio sources

Origin of the zebra structure in the Jovian decameter radio emission

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