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Multi-instrument observations of a failed flare eruption associated with MHD waves in a loop bundle
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Nisticò, Giuseppe, Polito, V., Nakariakov, V. M. (Valery M.) and Del Zanna, G. (2016) Multi-instrument observations of a failed flare eruption associated with MHD waves in a loop bundle. Astronomy & Astrophysics . ISSN 0004-6361.
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Abstract
Context. We present observations of a B7.9 class flare that occurred on January 24th, 2015, using SDO/AIA, Hinode/EIS and XRT.
The flare triggers an eruption of a dense cool plasma blob as seen in AIA 171Å which is unable to completely break out and remains
confined within a local bundle of active region loops. During this process, transverse oscillations of the threads are observed. The cool
plasma is then observed to descend back to the chromosphere along each loop strand. At the same time, a larger diffuse co-spatial
loop observed in the hot wavebands of SDO/AIA and Hinode/XRT is formed, exhibiting periodic intensity variations along its lenght.
Aims. The formation and evolution of magnetohydrodynamic (MHD) waves depend upon the values of the local plasma parameters
(e.g., density, temperature, magnetic field) which can hence be inferred by coronal seismology. In this study we aim to assess how the
observed MHD modes are affected by the variation of density and temperature.
Methods. We combine analysis of EUV/X-ray imaging and spectroscopy using SDO/AIA, Hinode/EIS and XRT.
Results. The transverse oscillations of the cool loop threads are interpreted in terms of vertically polarised kink oscillations. The
fitting procedure provides estimates for the period of about 3.5–4 min, and the amplitude of ∼ 5 Mm. The oscillations are strongly
damped showing very low quality factor (1.5–2), which is defined as the ratio of the damping time and the oscillation period. The
weak variation of the period of the kink wave, which is estimated from the fitting analysis, is in agreement with the density variations
due to the presence of the plasma blob inferred from the intensity light curve at 171Å. The coexisting intensity oscillations along the
hot loop are interpreted as a slow MHD wave with the period of 10 min and phase speed of about 436 km s−1
. Comparison between
the fast and slow modes allows for the determination of the Alfvén speed, and consequently magnetic field values. The plasma-β
inferred from the analysis is estimated to be around 0.1–0.3.
Conclusions. We show that the evolution of the detected waves is determined by the temporal variations of the local plasma parameters,
caused by the flare heating and the consequent cooling. We apply coronal seismology to both waves obtaining estimations of the
background plasma parameters
Item Type: | Journal Article | ||||||
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Subjects: | Q Science > QB Astronomy | ||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||
Library of Congress Subject Headings (LCSH): | Sun -- Corona , Solar flares , Magnetohydrodynamic waves | ||||||
Journal or Publication Title: | Astronomy & Astrophysics | ||||||
Publisher: | EDP Sciences | ||||||
ISSN: | 0004-6361 | ||||||
Official Date: | 24 November 2016 | ||||||
Dates: |
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Status: | Peer Reviewed | ||||||
Publication Status: | Published | ||||||
Access rights to Published version: | Restricted or Subscription Access | ||||||
Date of first compliant deposit: | 25 November 2016 | ||||||
Date of first compliant Open Access: | 28 November 2016 | ||||||
Funder: | Science and Technology Facilities Council (Great Britain) (STFC), Isaac Newton Trust, Gates Cambridge Trust | ||||||
Grant number: | ST/L000733/1 (STFC) |
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