High-frequency oscillations in a solar active region coronal loop

Williams, David R.; Phillips, K. J. H.; Rudawy, P.; Mathioudakis, M.; Gallagher, Peter T.; O’Shea, E.; Keenan, F. P.; Read, P. D.; Rompolt, B.

doi:10.1046/j.1365-8711.2001.04491.x

Cited by 126 publications

(114 citation statements)

References 17 publications

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“…For observational investigations on quasi-periodic fast-mode waves, Williams et al (2002) first reported a quasi-periodic fast wave that travels through the apex of an active-region coronal loop with a speed of 2100 km s −1 and a dominant period of six seconds. This event was observed during the total solar eclipse on 11 August 1999, with the Solar Eclipse Corona Imaging System (SECIS) instrument, which has a rapid cadence of 2.25 × 10 −2 seconds and a pixel size of 4.07 ′′ (Williams et al, 2001). This temporal resolution is sufficient to detect the short-period fast waves.…”

Section: Introductionmentioning

confidence: 99%

Observations of a Quasi-periodic, Fast-Propagating Magnetosonic Wave in Multiple Wavelengths and Its Interaction with Other Magnetic Structures

Shen

Liu

et al. 2013

Sol Phys

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We present observations of a quasi-periodic fast-propagating (QFP) magnetosonic wave on 23 April 2012, with high-resolution observations taken by the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. Three minutes after the start of a C2.0 flare, wave trains were first observed along an open divergent loop system in 171Å observations at a distance of 150 Mm from the footpoint of the guiding loop system and with a speed of 689 km s −1 , then they appeared in 193Å observations after their interaction with a perpendicular, underlaying loop system on the path; in the meantime; their speed decelerated to 343 km s −1 within a short time. The sudden deceleration of the wave trains and their appearance in 193Å observations are interpreted through a geometric effect and the density increase of the guiding loop system, respectively. We find that the wave trains have a common period of 80 seconds with the flare. In addition, a few low frequencies are also identified in the QFP wave. We propose that the generation of the period of 80 seconds was caused by the periodic releasing of energy bursts through some nonlinear processes in magnetic reconnection, while the low frequencies were possibly the leakage of pressure-driven oscillations from the photosphere or chromosphere, which could be an important source for driving coronal QFP waves. Our results also indicate that the properties of the guiding magnetic structure, such as the distributions of magnetic field and density as well as geometry, are crucial for modulating the propagation behaviors of QFP waves.

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Section: Introductionmentioning

confidence: 99%

Observations of a Quasi-periodic, Fast-Propagating Magnetosonic Wave in Multiple Wavelengths and Its Interaction with Other Magnetic Structures

Shen

Liu

et al. 2013

Sol Phys

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“…However, application of rigorous statistical tests showed that none of these was significant. An earlier wavelet analysis (Williams et al, 2001) of the same data shows evidence of a travelling wave moving down the leg of a small loop, with periodicities of six seconds (0.16 Hz).…”

Section: Introductionmentioning

confidence: 84%

Search for Rapid Changes in the Visible-Light Corona during the 21 June 2001 Total Solar Eclipse

et al. 2010

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Some 8000 images obtained with the Solar Eclipse Coronal Imaging System (SECIS) fast-frame CCD camera instrument located at Lusaka, Zambia, during the total eclipse of 21 June 2001 have been analysed to search for short-period oscillations in intensity that could be a signature of solar coronal heating mechanisms by MHD wave dissipation. Images were taken in white-light and Fe XIV green-line (5303 Å) channels over 205 seconds (frame rate 39 s −1 ), approximately the length of eclipse totality at this location, with a pixel size of four arcseconds square. The data are of considerably better quality than those that we obtained during the 11 August 1999 total eclipse (Rudawy et al.: Astron. Astrophys. 416, 1179, in that the images are much better exposed and enhancements in the drive system of the heliostat used gave a much improved image stability. Classical Fourier and wavelet techniques have been used to analyse the emission at 29 518 locations, of which 10 714 had emission at reasonably high levels, searching for periodic fluctuations with periods in the range 0.1 -17 seconds (frequencies 0.06 -10 Hz). While a number of possible periodicities were apparent in the wavelet analysis, none of the spatially and time-

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“…In the case of ground-based observations, when the loop is observed in the green line bandpass, the observability is limited by the spatial resolution of the telescope, which is usually over a few arcsec, as the time resolution of such observations is usually less then 1 s (e.g., the cadence time of SECIS is 2.25 × 10 −2 s and the pixel size is 4.07 arcsec, Williams et al 2001). In particular, this effect can be responsible for propagating 6 s disturbances of the Fe  green line, discovered by the stroboscopic method in a solar eclipse data and interpreted as fast magnetoacoustic waves (Williams et al 2002, see also Williams et al 2001.…”

Section: Discussionmentioning

confidence: 99%

Line-of-sight effects on observability of kink and sausage modes in coronal structures with imaging telescopes

Cooper

Nakariakov

Tsiklauri

2002

A&A

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Abstract. Kink modes of solar coronal structures, perturbing the loop in the direction along the line-of-sight (LOS), can be observed as emission intensity disturbances propagating along the loop provided the angle between the LOS and the structure is not ninety degrees. The effect is based upon the change of the column depth of the loop (along the LOS) by the wave. The observed amplitude of the emission intensity variations can be larger than the actual amplitude of the wave by a factor of two and there is an optimal angle maximizing the observed amplitude. For other angles this effect can also attenuate the observed wave amplitude. The observed amplitude depends upon the ratio of the wave length of kink perturbations to the width of the structure and on the angle between the LOS and the axis of the structure. Sausage modes are always affected negatively from the observational point of view, as the observed amplitude is always less than the actual one. This effect should be taken into account in the interpretation of wave phenomena observed in the corona with space-borne and ground-based imaging telescopes.

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High-frequency oscillations in a solar active region coronal loop

Cited by 126 publications

References 17 publications

Observations of a Quasi-periodic, Fast-Propagating Magnetosonic Wave in Multiple Wavelengths and Its Interaction with Other Magnetic Structures

Observations of a Quasi-periodic, Fast-Propagating Magnetosonic Wave in Multiple Wavelengths and Its Interaction with Other Magnetic Structures

Search for Rapid Changes in the Visible-Light Corona during the 21 June 2001 Total Solar Eclipse

Line-of-sight effects on observability of kink and sausage modes in coronal structures with imaging telescopes

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