Very Long-Period Pulsations Before the Onset of Solar Flares

Tan, Baolin; Yu, Zhiqiang; Huang, Jing; Zhang, Y.

doi:10.3847/1538-4357/833/2/206

Cited by 43 publications

(42 citation statements)

References 36 publications

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“…Moreover, the developed theory could also address a more exotic case of an apparently non-decaying SUMER type oscillation detected by Mariska et al (2008), by choosing the values of τ 1 and τ 2 which give ω I ≈ 0. In addition, acoustic over-stability could be considered as a mechanism for the excitation of 8-30 min oscillations of the soft X-ray emission generated in pre-flaring active region (Tan et al 2016).…”

Section: Discussionmentioning

confidence: 99%

Damping of slow magnetoacoustic oscillations by the misbalance between heating and cooling processes in the solar corona

Kolotkov

Nakariakov

Zavershinskii

2019

A&A

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Context. Rapidly decaying slow magnetoacoustic waves are regularly observed in the solar coronal structures, offering a promising tool for a seismological diagnostics of the coronal plasma, including its thermodynamical properties. Aims. The effect of damping of standing slow magnetoacoustic oscillations in the solar coronal loops is investigated accounting for the field-aligned thermal conductivity and a wave-induced misbalance between radiative cooling and some unspecified heating rates. Methods. The non-adiabatic terms were allowed to be arbitrarily large, corresponding to the observed values. The thermal conductivity was taken in its classical form, and a power-law dependence of the heating function on the density and temperature was assumed. The analysis was conducted in the linear regime and in the infinite magnetic field approximation. Results. The wave dynamics is found to be highly sensitive to the characteristic time scales of the thermal misbalance. Depending on certain values of the misbalance time scales three regimes of the wave evolution were identified, namely the regime of a suppressed damping, enhanced damping where the damping rate drops down to the observational values, and acoustic over-stability. The specific regime is determined by the dependences of the radiative cooling and heating functions on thermodynamical parameters of the plasma in the vicinity of the perturbed thermal equilibrium.Conclusions. The comparison of the observed and theoretically derived decay times and oscillation periods allows us to constrain the coronal heating function. For typical coronal parameters, the observed properties of standing slow magnetoacoustic oscillations could be readily reproduced with a reasonable choice of the heating function.

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Section: Discussionmentioning

confidence: 99%

Damping of slow magnetoacoustic oscillations by the misbalance between heating and cooling processes in the solar corona

Kolotkov

Nakariakov

Zavershinskii

2019

A&A

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“…overstability ( Figure 6, mechanism 10). Modulation of plasma parameters and possibly of the magnetic field by this overstability can produce QPPs (see, e.g., observations in [Tan et al, 2016]).…”

Section: Thermal Overstabilitymentioning

confidence: 99%

Quasi-Periodic Pulsations in Solar and Stellar Flares. Review

Kupriyanova

Kolotkov

Nakariakov

et al. 2020

Solar-Terrestrial Physics

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This paper provides an overview of the state-of-the-art studies of oscillatory processes in solar and stellar flares, based on modern observational data from ground-based and space-borne instruments with high temporal, spatial, and spectral resolution in different bands of the electromagnetic spectrum. We examine the mecha-nisms that generate flare emission and its quasi-periodic modulation. We discuss similarities and differences be-tween solar and stellar flares, and address associated problems of superflares on the Sun and space weather. Quasi-periodic pulsations (QPPs) of flare emission are shown to be an effective tool for diagnosing both the flare processes themselves and the parameters of flaring plasmas and accelerated particles. We consider types of QPPs, their statistical properties, and methods of analysis, taking into account the non-stationarity of the QPPs’ parameters. We review the proposed mechanisms of QPPs and summarize open questions.

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“…) where ρ 0 , I 0 and B ||0 are the mass density, and the electric current and parallel magnetic field in the loop in the equilibrium, respectively; c is the speed of light; and Λ = ln 4L πrmin − 7/4, with L being the loop length (see, e.g., Khodachenko et al 2009;Tan et al 2016). For L = 700 Mm, r min = 30 Mm, ρ 0 = 3 × 10 −12 g cm −3 , B ||0 = 30 G, typical for stellar coronae (see e.g.…”

Section: Discussionmentioning

confidence: 99%

Multi-wavelength quasi-periodic pulsations in a stellar superflare

Kolotkov,

Nakariakov,

Holt

et al. 2021

Preprint

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We present the first multi-wavelength simultaneous detection of QPP in a superflare (more than a thousand times stronger than known solar flares) on a cool star, in soft X-rays (SXR, with XMM-Newton) and white light (WL, with Kepler). It allowed for the first-ever analysis of oscillatory processes in a stellar flare simultaneously in thermal and non-thermal emissions, conventionally considered to come from the corona and chromosphere of the star, respectively. The observed QPP have periods 1.5 ± 0.15 hours (SXR) and 3 ± 0.6 hours (WL), and correlate well with each other. The unique relationship between the observed parameters of QPP in SXR and WL allowed us to link them with oscillations of the electric current in the flare loop, which directly affect the dynamics of non-thermal electrons and indirectly (via Ohmic heating) the thermal plasma. These findings could be considered in favour of the equivalent LCR-contour model of a flare loop, at least in the extreme conditions of a stellar superflare.

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Very Long-Period Pulsations Before the Onset of Solar Flares

Cited by 43 publications

References 36 publications

Damping of slow magnetoacoustic oscillations by the misbalance between heating and cooling processes in the solar corona

Damping of slow magnetoacoustic oscillations by the misbalance between heating and cooling processes in the solar corona

Quasi-Periodic Pulsations in Solar and Stellar Flares. Review

Multi-wavelength quasi-periodic pulsations in a stellar superflare

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