GROWING TRANSVERSE OSCILLATIONS OF A MULTISTRANDED LOOP OBSERVED BY
                    <i>SDO</i>
                    /AIA

Wang, Tongjiang; Ofman, L.; Davila, J. M.; Su, Yang

doi:10.1088/2041-8205/751/2/l27

Cited by 138 publications

(130 citation statements)

References 37 publications

(62 reference statements)

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“…Tomczyk et al (2007) used ground-based spectral measurements with the Coronal Multichannel Polarimeter (CoMP) ) to demonstrate that small-amplitude propagating transverse waves are ubiquitous in the solar corona. This result seems to be supported by the recent report of running transverse waves in coronal loops by AIA/SDO (McIntosh et al 2011;Wang et al 2012).…”

Section: Introductionsupporting

confidence: 83%

Statistical seismology of transverse waves in the solar corona

Verwichte

Doorsselaere

White

et al. 2013

A&A

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Context. Observations show that transverse oscillations commonly occur in solar coronal loops. The rapid damping of these waves has been attributed to resonant absorption. The oscillation characteristics carries information of the structuring of the corona. However, self-consistent seismological methods that extract information from individual oscillations are limited because there are fewer observables than unknown parameters in the model, and the problem is underdetermined. Furthermore, it has been shown that one-to-one comparisons of the observed scaling of period and damping times with wave damping theories are misleading. Aims. We aim to investigate whether seismological information can be gained from the observed scaling laws in a statistical sense. Methods. A statistical approach is used whereby scaling laws are produced by forward modelling using distributions of values for key loop cross-sectional structuring parameters. We study two types of observations: 1) transverse loops oscillations as seen mainly with TRACE and SDO and 2) running transverse waves seen with the Coronal Multichannel Polarimeter (CoMP). Results. We demonstrate that the observed period-damping time scaling law does provide information about the physical damping mechanism, if observations are collected from as wide range of periods as possible and a comparison with theory is performed in a statistical sense. The distribution of the ratio of damping time over period, i.e. the quality factor, has been derived analytically and fitted to the observations. A minimum value for the quality factor of 0.65 has been found. From this, a constraint linking the ranges of possible values for the density contrast and inhomogeneity layer thickness is obtained for transverse loop oscillations. If the layer thickness is not constrained, then the density contrast is at most equal to 3. For transverse waves seen by CoMP, it is found that the ratio of maximum to minimum values for these two parameters has to be less than 2.06; i.e., the sampled values for the layer thickness and Alfvén travel time come from a relatively narrow distribution. Conclusions. Now that more and more transverse loop oscillations have been analysed, a statistical approach to coronal seismology becomes possible. Using the observed data cloud, we have found restrictions to the loop's density contrast and inhomogeneity layer thickness. Surprisingly, for running waves, narrow distributions for loop parameters have been found.

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Section: Introductionsupporting

confidence: 83%

Statistical seismology of transverse waves in the solar corona

Verwichte

Doorsselaere

White

et al. 2013

A&A

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“…1 we show an example of such a process that is detected at 171 Å with the Atmospheric Imaging Assembly on the Solar Dynamics Observatory (SDO/AIA). This oscillation was first analysed by Wang et al (2012). During the oscillation, its amplitude experiences some variation, however it is typically much weaker and at much longer timescale than in the rapidly decaying regime.…”

Section: Observational Resultsmentioning

confidence: 99%

“…Sometimes up to 10-20 cycles of oscillations with almost constant amplitude are observed (e.g. Wang et al 2012;Nisticò et al 2013). Using the observations of undamped oscillations in 21 non-flaring active regions (NOAA 11637-11657) observed in January 2013 in the 171 Å channel of SDO/AIA (Anfinogentov et al 2015), we constructed scalings of the oscillation amplitudes with the period and loop length (Fig.…”

Section: Observational Resultsmentioning

confidence: 99%

“…Kink oscillations of loops are detected to appear in two different regimes: large-amplitude rapidly decaying oscillations and small-amplitude undamped oscillations (Wang et al 2012;Nisticò et al 2013). In the former regime the loop displacement reaches several minor radii of the loop and, typically, the oscillation decays in a few oscillation cycles.…”

Section: Introductionmentioning

confidence: 99%

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Undamped transverse oscillations of coronal loops as a self-oscillatory process

Nakariakov

Anfinogentov

Nisticò

et al. 2016

A&A

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Context. Standing transverse oscillations of coronal loops are observed to operate in two regimes: rapidly decaying, large amplitude oscillations and undamped small amplitude oscillations. In the latter regime the damping should be compensated by energy supply, which allows the loop to perform almost monochromatic oscillations with almost constant amplitude and phase. Different loops oscillate with different periods. The oscillation amplitude does not show dependence on the loop length or the oscillation period. Aims. We aim to develop a low-dimensional model explaining the undamped kink oscillations as a self-oscillatory process caused by the effect of negative friction. The source of energy is an external quasi-steady flow, for example, supergranulation motions near the loop footpoints or external flows in the corona. Methods. We demonstrate that the interaction of a quasi-steady flow with a loop can be described by a Rayleigh oscillator equation that is a non-linear ordinary differential equation, with the damping and resonant terms determined empirically. Results. Small-amplitude self-oscillatory solutions to the Rayleigh oscillator equation are harmonic signals of constant amplitude, which is consistent with the observed properties of undamped kink oscillations. The period of self-oscillations is determined by the frequency of the kink mode. The damping by dissipation and mode conversion is compensated by the continuous energy deposition at the frequency of the natural oscillation. Conclusions. We propose that undamped kink oscillations of coronal loops may be caused by the interaction of the loops with quasi-steady flows, and hence are self-oscillations, which is analogous to producing a tune by moving a bow across a violin string.

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“…The Atmospheric Imaging Assembly (AIA) on board NASA's Solar Dynamics Observatory (SDO) satellite (Lemen et al 2012;Pesnell et al 2012) continues the stream of reported oscillation Appendices are available in electronic form at http://www.aanda.org events and further stimulates interest in these phenomena (e.g. Aschwanden & Schrijver 2011;Wang et al 2012;Gosain 2012;Verwichte et al 2013). Oscillations of this type are normally interpreted as fast kink magnetohydrodynamic (MHD) modes of cylinder-like structures (Edwin & Roberts 1983), and on this basis, procedures have been developed to deduce coronal parameters from wave properties (e.g.…”

Section: Introductionmentioning

confidence: 99%

A unified view of coronal loop contraction and oscillation in flares

Russell

Simões

Fletcher

2015

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Context. Transverse loop oscillations and loop contractions are commonly associated with solar flares, but the two types of motion have traditionally been regarded as separate phenomena. Aims. We present an observation of coronal loops that contract and oscillate following the onset of a flare. We aim to explain why both behaviours are seen together and why only some of the loops oscillate. Methods. A time sequence of SDO/AIA 171 Å images is analysed to identify the positions of coronal loops following the onset of the M6.4 flare SOL2012-03-09T03:53. We focus on five loops in particular, all of which contract during the flare, with three of them oscillating as well. A simple model is then developed for the contraction and oscillation of a coronal loop. Results. We propose that coronal loop contractions and oscillations can occur in a single response to removal of magnetic energy from the corona. Our model reproduces the various types of loop motion observed and explains why the highest loops oscillate during their contraction, while no oscillation is detected for the shortest contracting loops. The proposed framework suggests that loop motions can be used as a diagnostic for the removal of coronal magnetic energy by flares, while rapid decrease in coronal magnetic energy is a newly identified excitation mechanism for transverse loop oscillations.

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GROWING TRANSVERSE OSCILLATIONS OF A MULTISTRANDED LOOP OBSERVED BY SDO /AIA

Cited by 138 publications

References 37 publications

Statistical seismology of transverse waves in the solar corona

Statistical seismology of transverse waves in the solar corona

Undamped transverse oscillations of coronal loops as a self-oscillatory process

A unified view of coronal loop contraction and oscillation in flares

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