Footpoint excitation of standing acoustic waves   in 
 coronal loops

Taroyan, Y.; Erdélyi, R.; Doyle, J. G.; Bradshaw, S. J.

doi:10.1051/0004-6361:20052794

Cited by 65 publications

(65 citation statements)

References 30 publications

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“…Recently, the high-resolution observation with the Atmospheric Imaging Assembly (AIA Lemen et al 2012) onboard the Solar Dynamics Observatory (SDO, Pesnell et al 2012), evidenced that oscillations in the hot coronal loops are excited by an energy release at one of the footpoints of the arcade loops (Kumar et al 2013(Kumar et al , 2015. These observational findings are consistent with the interpretation of SUMER oscillations in terms of slow magnetoacoustic waves (Ofman & Wang 2002;Nakariakov et al 2004;Taroyan et al 2005).…”

Section: Introductionsupporting

confidence: 91%

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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Section: Introductionsupporting

confidence: 91%

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

Cho

Nakariakov

Kim

et al. 2016

ApJ

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“…Tirry & Poedts (1998) studied the heating of 2D coronal arcades by linear resonant Alfvén waves that are excited directly by photospheric toroidally polarised footpoint motions. Taroyan et al (2005) studied the excitation of slow standing waves in a 1D loop by footpoint heat deposition. They found that the time profile of the longlasting pulse determines whether a standing or propagating wave is excited.…”

Section: Introductionmentioning

confidence: 99%

Excitation of vertical kink waves in a solar coronal arcade loop by a periodic driver

Selwa

Murawski

Solanki

et al. 2010

A&A

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Aims. We study an oscillatory driver as a possible excitation mechanism of vertical kink loop oscillations in the ideal MHD regime. Methods. We consider a solar coronal magnetic arcade with a dense photospheric layer. The two-dimensional numerical model that we implement includes the effects of nonlinearity and line curvature on the excitation and attenuation of fast magnetosonic kink waves. We investigate the effects of a driven sinusoidal pressure pulse and compare it with the impulsive excitation by a pressure pulse that impacts the overlying loop. Results. Our numerical simulations reveal wave signatures that are reminiscent of vertical loop oscillations seen in TRACE observational data. Conclusions. We conclude that attenuation of vertical kink oscillations can be reduced to the value observed by adopting an oscillatory instead of an impulsive excitation. An oscillatory driver also naturally explains why only a small subset of all loops is excited to oscillate transversally in an active region.

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“…These oscillations have a phase shift of about one-quarter period between velocity and intensity. The periods and damping times of the standing slow waves are in the ranges of 8.6-32.3 min and 3.1-42.3 min, respectively Wang et al, 2002aWang et al, , 2002bWang et al, , 2003Wang et al, , 2005Banerjee et al, 2007;Erdélyi et al, 2008). The effect of energy dissipation on the slow waves through thermal conduction, compressive viscosity, radiative cooling, and heating on the periods, period ratio, and damping times has formed the focus of recent studies.…”

Section: Introductionmentioning

confidence: 99%

“…Only with the combined effect of thermal conduction and viscosity the results are consistent with the observations. Moreover, Taroyan et al (2005) investigated the effect of temperature inhomogeneity on the dissipation of standing slow waves through considering thermal conduction and optically thin radiative losses. They found that the damping time of the isothermal loops is proportional to the wave period and the oscillations are rapidly damped mainly by thermal conduction.…”

Section: Introductionmentioning

confidence: 99%

Slow-Mode Oscillations and Damping of Hot Solar Coronal Loops

2012

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The effect of temperature inhomogeneity on the periods, their ratios (fundamental vs. first overtone), and the damping times of the standing slow modes in gravitationally stratified solar coronal loops are studied. The effects of optically thin radiation, compressive viscosity, and thermal conduction are considered. The linearized one-dimensional magnetohydrodynamic (MHD) equations (under low-β condition) were reduced to a fourth-order ordinary differential equation for the perturbed velocity. The numerical results indicate that the periods of non-isothermal loops (i.e. temperature increases from the loop base to apex) are smaller compared to those of isothermal loops. In the presence of radiation, viscosity, and thermal conduction, an increase in the temperature gradient is followed by a monotonic decrease in the periods (compared with the isothermal case), while the period ratio turns out to be a sensitive function of the gradient of the temperature and the loop lengths. We verify that radiative dissipation is not a main cooling mechanism of both isothermal and non-isothermal hot coronal loops and has a small effect on the periods. Thermal conduction and compressive viscosity are primary mechanisms in the damping of slow modes of the hot coronal loops. The periods and damping times in the presence of compressive viscosity and/or thermal conduction dissipation are consistent with the observed data in specific cases. By tuning the dissipation parameters, the periods and the damping times could be made consistent with the observations in more general cases.

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Footpoint excitation of standing acoustic waves in coronal loops

Cited by 65 publications

References 30 publications

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

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

Excitation of vertical kink waves in a solar coronal arcade loop by a periodic driver

Slow-Mode Oscillations and Damping of Hot Solar Coronal Loops

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