The Impact of a Filament Eruption on Nearby High-Lying Cool Loops

Context. Solar flares are often accompanied by kink (transverse) oscillations of coronal loops. Despite intensive study of these oscillations in recent years, the mechanisms that excite them are still not known. Aims. We aim to clarify the excitation mechanisms for these kink oscillations of coronal loops. Methods. We analysed 58 kink-oscillation events observed by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) during its first four years (2010)(2011)(2012)(2013)(2014) with the use of the JHelioviewer. Association of these oscillation events with flares, lower coronal (r 1.4 R ) eruptions and plasma ejections, coronal mass ejections (CMEs), and coronal Type-II radio bursts is studied. Results. We find that 44 of these 58 oscillation events (76%) were associated with CMEs observed in the white light emission. Moreover, 57 events (98%) were accompanied by lower coronal eruptions/ejections (LCEs) observed in the extreme-ultraviolet band in the parental active regions. In the remaining event an LCE was not clearly seen, but it was definitely associated with a CME too. The main observational finding is that the kink oscillations were excited by the deviation of loops from their equilibria by a nearby LCE in 55 events (95%). In three remaining events, it was difficult to reliably determine the cause of the oscillations because of limitations in the observational data. We also found that 53 events (91%) were associated with flares. In five remaining events, the parental active regions were behind the limb and we could not directly see flare sites. It indicates that there is a close relationship between these two kinds of solar activity. However, the estimated speeds of a hypothetical driver of kink oscillations by flares were found to be lower than 500 km s −1 in 80% of the cases. Such low speeds do not favour the association of the oscillation excitation with a shock wave, as usually assumed. That only 23 (40%) of the oscillation events were found to be associated with coronal Type-II radio bursts also goes against the shock wave mechanism for the excitation of kink oscillations.Conclusions. The statistical analysis shows that the most probable mechanism for exciting the kink oscillations of coronal loops is the deviation of loops from their equilibrium by nearby eruptions or plasma ejections rather than a blast shock wave ignited by a flare.

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“…Recent observational results (e.g. Harra et al 2014, for an individual event) are consistent with this conclusion.…”

Section: Resultssupporting

confidence: 71%

Excitation of kink oscillations of coronal loops: statistical study

Zimovets

Nakariakov

2015

A&A

121

128

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“…Other mechanisms for populating the resonance line upper levels might complicate matters further, removing this sensitivity to density. Absorption of radiation was ruled out by the intensity ratio (Harra et al 2014 note that the k/h intensity ratio would be closer to 4:1 if radiation is an important process) A high lying level of Mg ii can be excited by Lyβ pumping, leading to cascades down to the h and k line upper levels. This process was found to be negligible in the quiet chromosphere by Lemaire & Gouttebroze (1983) and preliminary results suggest it is also negligible in flares (Leenaarts 2015, priv.…”

Section: Discussionmentioning

confidence: 99%

“…The only times at which these pixels show higher intensity ratios is when filament expands over the field of view (the filament material has a much higher ratio of between R kh ∼ 1.4-1.7). Harra et al (2014) report an increase in the ratio following a filament eruption, for off-limb observations.…”

Section: K/h Intensity Ratiomentioning

confidence: 95%

IRIS observations of the Mg ii h and k lines during a solar flare

Kerr¹,

Simões²,

Qiu³

et al. 2015

A&A

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The bulk of the radiative output of a solar flare is emitted from the chromosphere, which produces enhancements in the optical and UV continuum, and in many lines, both optically thick and thin. We have, until very recently, lacked observations of two of the strongest of these lines: the Mg ii h and k resonance lines. We present a detailed study of the response of these lines to a solar flare. The spatial and temporal behaviour of the integrated intensities, k/h line ratios, line of sight velocities, line widths and line asymmetries were investigated during an M class flare (SOL2014-02-13T01:40). Very intense, spatially localised energy input at the outer edge of the ribbon is observed, resulting in redshifts equivalent to velocities of ∼15-26 km s −1 , line broadenings, and a blue asymmetry in the most intense sources. The characteristic central reversal feature that is ubiquitous in quiet Sun observations is absent in flaring profiles, indicating that the source function increases with height during the flare. Despite the absence of the central reversal feature, the k/h line ratio indicates that the lines remain optically thick during the flare. Subordinate lines in the Mg ii passband are observed to be in emission in flaring sources, brightening and cooling with similar timescales to the resonance lines. This work represents a first analysis of potential diagnostic information of the flaring atmosphere using these lines, and provides observations to which synthetic spectra from advanced radiative transfer codes can be compared.

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“…In fact, there are two such larger regions of loops and the eruptions are located in between them such that they oscillate in anti-phase with each other. This event was also investigated Harra et al (2014) using the Interface Region Imaging Spectrograph (IRIS) in addition to SDO. Analysis of the spectral lines measured with IRIS demonstrated the existence of flows in the loops before the eruption which were affected by the subsequent impact of the filament and indicate plasma motions parallel to the line of sight preceding the transverse oscillations.…”

Section: Loop #1mentioning

confidence: 99%

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

Pascoe

Anfinogentov

Nisticò

et al. 2017

A&A

101

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(2017) Coronal loop seismology using damping of standing kink oscillations by mode coupling II. additional physical effects and Bayesian analysis. Astronomy and Astrophysics, 600 . A78. Permanent WRAP URL:http://wrap.warwick.ac.uk/85278 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher's statement:Reproduced with permission from Astronomy & Astrophysics, © ESO A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP URL' above for details on accessing the published version and note that access may require a subscription. ABSTRACTContext. The strong damping of kink oscillations of coronal loops can be explained by mode coupling. The damping envelope depends on the transverse density profile of the loop. Observational measurements of the damping envelope have been used to determine the transverse loop structure which is important for understanding other physical processes such as heating.Aims. The general damping envelope describing the mode coupling of kink waves consists of a Gaussian damping regime followed by an exponential damping regime. Recent observational detection of these damping regimes has been employed as a seismological tool. We extend the description of the damping behaviour to account for additional physical effects, namely a time-dependent period of oscillation, the presence of additional longitudinal harmonics, and the decayless regime of standing kink oscillations. Methods. We examine four examples of standing kink oscillations observed by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). We use forward modelling of the loop position and investigate the dependence on the model parameters using Bayesian inference and Markov Chain Monte Carlo (MCMC) sampling. Results. Our improvements to the physical model combined with the use of Bayesian inference and MCMC produce improved estimates of model parameters and their uncertainties. Calculation of the Bayes factor also allows us to compare the suitability of different physical models. We also use a new method based on spline interpolation of the zeroes of the oscillation to accurately describe the background trend of the osci...

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The Impact of a Filament Eruption on Nearby High-Lying Cool Loops

Cited by 11 publications

References 13 publications

Excitation of kink oscillations of coronal loops: statistical study

Excitation of kink oscillations of coronal loops: statistical study

IRIS observations of the Mg ii h and k lines during a solar flare

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

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