Pulsations of microwave emission and flare plasma diagnostics

Stepanov, A. V.; Kopylova, Yu. G.; Tsap, Yu. T.; Shibasaki, Κ.; Melnikov, V. F.; Goldvarg, T. B.

doi:10.1134/1.1774400

Cited by 30 publications

(24 citation statements)

References 19 publications

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“…Quasi-periodic pulsations with shorter periods, comparable with the transverse Alfvén transit time (e.g., with the periods of about a second, often reported in literature, see e.g. Stepanov et al 2004) can possibly be explained in terms of higher spatial harmonics of this mode. However, it is not clear what is the mechanism responsible for the selection of those particular harmonics only.…”

Section: Discussionmentioning

confidence: 55%

Sausage oscillations of coronal loops

Pascoe

Nakariakov

Arber

2006

A&A

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Aims. Analytical theory predicts the existence of trapped global (or fundamental) sausage fast magnetoacoustic modes in thick and dense coronal loops only, with the periods estimated as the ratio of double the loop length and the Alfvén speed outside the loop. We extend this study to the leaking regime, considering global sausage modes of long loops with small density contrasts. Methods. Anti-symmetric fast magnetoacoustic perturbations (sausage, or m = 0 modes) of a low β plasma slab with the symmetric Epstein profile of plasma density are modelled numerically. Results. It was found that long loops with sufficiently small density contrast can support global sausage leaky modes of detectable quality. The periods of the leaky modes are found to be approximately determined by the loop length and the external Alfvén speed. If the loop length can be estimated from imaging observations, the observed period of this mode provides us with the information about the Alfvén speed outside the loop. For typical flaring coronal loops, the estimated periods of the global sausage modes are about 5−60 s.

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Section: Discussionmentioning

confidence: 55%

Sausage oscillations of coronal loops

Pascoe

Nakariakov

Arber

2006

A&A

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“…Typically, these QPPs have rapidly varying amplitudes, variable periods, and narrow bandwidths δf/f 1 (e.g., Young et al 1961;Zlobec et al 1987;Stepanov & Yurovsky 1990;Kurths et al 1991;Yurovsky 1991;Fleishman et al 1994;Aschwanden et al 1995;Fleishman et al 2002aFleishman et al , 2002bMagdalenić et al 2002;Benz et al 2005;Mészárosová et al 2005;Chen & Yan 2007;Benz et al 2011;Chen et al 2011). Longer-period QPPs, with periods τ 10 s, are observed in microwaves; such QPPs are often accompanied by QPPs in hard X-rays (HXRs; e.g., Parks & Winckler 1969;Janssens et al 1973;Zaitsev & Stepanov 1982a;Kane et al 1983;Nakajima et al 1983;Asai et al 2001;Grechnev et al 2003;Nakariakov et al 2003;Stepanov et al 2004;Melnikov et al 2005;Fleishman et al 2008). …”

Section: Introductionmentioning

confidence: 99%

Modeling of Gyrosynchrotron Radio Emission Pulsations Produced by Magnetohydrodynamic Loop Oscillations in Solar Flares

Mossessian

Fleishman

2012

ApJ

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A quantitative study of the observable radio signatures of the sausage, kink, and torsional magnetohydrodynamic (MHD) oscillation modes in flaring coronal loops is performed. Considering first non-zero order effect of these various MHD oscillation modes on the radio source parameters such as magnetic field, line of sight, plasma density and temperature, electron distribution function, and the source dimensions, we compute time-dependent radio emission (spectra and light curves). The radio light curves (of both flux density and degree of polarization) at all considered radio frequencies are then quantified in both time domain (via computation of the full modulation amplitude as a function of frequency) and in Fourier domain (oscillation spectra, phases, and partial modulation amplitude) to form the signatures specific to a particular oscillation mode and/or source parameter regime. We found that the parameter regime and the involved MHD mode can indeed be distinguished using the quantitative measures derived in the modeling. We apply the developed approach to analyze radio burst recorded by Owens Valley Solar Array and report possible detection of the sausage mode oscillation in one (partly occulted) flare and kink or torsional oscillations in another flare.

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“…QPPs are found to be a common feature of solar flaring lightcurves associated with both thermal (Simões et al 2015) and non-thermal emission (Kupriyanova et al 2010). In the impulsive phase, QPPs might be explained by a repetitive regime of spontaneous magnetic reconnection ('magnetic dripping', see , such as periodic shedding of plasmoids (e.g., Kliem et al 2000;Bárta et al 2008;Kumar & Cho 2013); or by an effect of magnetohydrodynamic (MHD) oscillations: variation of the plasma and magnetic field parameters, which changes the efficiency of the gyrosynchrotron emission (e.g., Stepanov et al 2004;Khodachenko et al 2006;Kuznetsov et al 2015); periodically change the non-thermal particle kinematics (e.g., Zaitsev & Stepanov 1982), or periodically trigger magnetic reconnection by MHD oscillations (Chen & Priest 2006;Nakariakov et al 2006). The modulating MHD oscillations could be confined to the flaring site, or could occur in plasma structures situated nearby.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Damped Oscillations in Solar and Stellar X-Ray Flares

Cho

Nakariakov

Kim

et al. 2016

ApJ

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We explore the similarity and difference of the quasi-periodic pulsations (QPPs) observed in the decay phase of solar and stellar flares at X-rays. We identified 42 solar flares with pronounced QPPs, observed with the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) and 36 stellar flares with QPPs, observed with X-ray Multi Mirror Newton observatory (XMM-Newton). The Empirical Mode Decomposition (EMD) method and least-square fit by a damped sine function were applied to obtain the periods (P ) and damping times (τ ) of the QPPs. We found that (1) the periods and damping times of the stellar QPPs are 16.21±15.86 min and 27.21±28.73 min, while those of the solar QPPs are 0.90±0.56 and 1.53±1.10 min, respectively. (2) The ratio of the damping times to the periods (τ /P ) observed in the stellar QPPs (1.69±0.56) are statistically identical to those of solar QPPs (1.74±0.77). (3) The scalings of the QPP damping time with the period are well described by the power law in both solar and stellar cases. The power indices of the solar and stellar QPPs are 0.96±0.10 and 0.98±0.05, respectively. This scaling is consistent with the scalings found for standing slow magnetoacoustic and kink modes in solar coronal loops. Thus, we propose that the underlying mechanism responsible for the stellar QPPs is the natural magnetohydrodynamic oscillations in the flaring or adjacent coronal loops, as in the case of solar flares.

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Pulsations of microwave emission and flare plasma diagnostics

Cited by 30 publications

References 19 publications

Sausage oscillations of coronal loops

Sausage oscillations of coronal loops

Modeling of Gyrosynchrotron Radio Emission Pulsations Produced by Magnetohydrodynamic Loop Oscillations in Solar Flares

Comparison of Damped Oscillations in Solar and Stellar X-Ray Flares

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