Coexisting fast and slow propagating waves of the extreme-UV intensity in solar coronal plasma structures

Zhang, Yuzong; Zhang, Jun; Wang, Jingxiu; Nakariakov, V. M.

doi:10.1051/0004-6361/201525621

Cited by 31 publications

(25 citation statements)

References 42 publications

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“…Rather, it is based on the relationship to other periodicities and comparison with those expected for known wave modes when realistic loop and plasma properties are assumed. Zhang et al (2015) reported an observation of a coronal funnel with SDO/AIA which demonstrates fast and slow waves propagating along the same field-aligned path, consistent with numerical simulations of Pascoe et al (2013b; Nisticò et al (2014). Measurement of the propagation speeds allowed the plasma-β to be estimated as approximately 0.01.…”

Section: Introductionsupporting

confidence: 59%

Spatially resolved observation of the fundamental and second harmonic standing kink modes using SDO/AIA

Pascoe

Goddard

Nakariakov

2016

A&A

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Aims. We consider a coronal loop kink oscillation observed by the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO) which demonstrates two strong spectral components. The period of the lower frequency component being approximately twice that of the shorter frequency component suggests the presence of harmonics. Methods. We examine the presence of two longitudinal harmonics by investigating the spatial dependence of the loop oscillation. The time-dependent displacement of the loop is measured at 15 locations along the loop axis. For each position the detrended displacement is fitted as the sum of two damped sinusoids, having periods P 1 and P 2 , and a damping time τ. The shorter period component exhibits anti-phase oscillations in the loop legs. Results. We interpret the observation in terms of the first (global or fundamental) and second longitudinal harmonics of the standing kink mode. The strong excitation of the second harmonic appears connected to the preceding coronal mass ejection (CME) which displaced one of the loop legs. The oscillation parameters found are P 1 " 5.00˘0.62 minutes, P 2 " 2.20˘0.23 minutes, P 1 {2P 2 " 1.15˘0.22, and τ{P " 3.35˘1.45.

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Section: Introductionsupporting

confidence: 59%

Spatially resolved observation of the fundamental and second harmonic standing kink modes using SDO/AIA

Pascoe

Goddard

Nakariakov

2016

A&A

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“…Thus, for low values of β, which are also observed in solar coronal plasma structures (e.g. β ≈ 0.01 [22]), for the electron plasma frequencies of about 0.4 GHz, typical periods of current sheet oscillations are a few microseconds. …”

Section: Discussionmentioning

confidence: 83%

Nonlinear oscillations of coalescing magnetic flux ropes

2016

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An analytical model of highly nonlinear oscillations occurring during a coalescence of two magnetic flux ropes, based upon two-fluid hydrodynamics, is developed. The model accounts for the effect of electric charge separation, and describes perpendicular oscillations of the current sheet formed by the coalescence. The oscillation period is determined by the current sheet thickness, the plasma parameter β, and the oscillation amplitude. The oscillation periods are typically greater or about the ion plasma oscillation period. In the nonlinear regime, the oscillations of the ion and electron concentrations have a shape of a narrow symmetric spikes.PACS numbers: 52.35.

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“…Andries et al 2005;Srivastava et al 2013) or wave modes (e.g. Zhang et al 2015), spatial seismology using time series from different locations (e.g. Verth et al 2007;Pascoe et al 2009b), temperature data from multiple bandpasses (e.g.…”

Section: Discussionmentioning

confidence: 99%

Coronal loop seismology using damping of standing kink oscillations by mode coupling

Pascoe

Goddard

Nisticò

et al. 2016

A&A

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Context. Kink oscillations of solar coronal loops are frequently observed to be strongly damped. The damping can be explained by mode coupling on the condition that loops have a finite inhomogeneous layer between the higher density core and lower density background. The damping rate depends on the loop density contrast ratio and inhomogeneous layer width. Aims. The theoretical description for mode coupling of kink waves has been extended to include the initial Gaussian damping regime in addition to the exponential asymptotic state. Observation of these damping regimes would provide information about the structuring of the coronal loop and so provide a seismological tool. Methods. We consider three examples of standing kink oscillations observed by the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO) for which the general damping profile (Gaussian and exponential regimes) can be fitted. Determining the Gaussian and exponential damping times allows us to perform seismological inversions for the loop density contrast ratio and the inhomogeneous layer width normalised to the loop radius. The layer width and loop minor radius are found separately by comparing the observed loop intensity profile with forward modelling based on our seismological results. Results. The seismological method which allows the density contrast ratio and inhomogeneous layer width to be simultaneously determined from the kink mode damping profile has been applied to observational data for the first time. This allows the internal and external Alfvén speeds to be calculated, and estimates for the magnetic field strength can be dramatically improved using the given plasma density. Conclusions. The kink mode damping rate can be used as a powerful diagnostic tool to determine the coronal loop density profile. This information can be used for further calculations such as the magnetic field strength or phase mixing rate.

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Coexisting fast and slow propagating waves of the extreme-UV intensity in solar coronal plasma structures

Cited by 31 publications

References 42 publications

Spatially resolved observation of the fundamental and second harmonic standing kink modes using SDO/AIA

Spatially resolved observation of the fundamental and second harmonic standing kink modes using SDO/AIA

Nonlinear oscillations of coalescing magnetic flux ropes

Coronal loop seismology using damping of standing kink oscillations by mode coupling

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