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Anti-phase signature of flare generated transverse loop oscillations  

Rebecca White   Submitted: 2013-06-24 02:46

Transverse loop oscillations observed by the Atmospheric Imaging Assembly (AIA) instrument on the Solar Dynamics Observatory (SDO) spacecraft are studied after an impulsive solar flare eruption on 2012 May 8. We have found that a transversely oscillating coronal loop seen in the 171 Å bandpass oscillates in anti-phase with respect to adjacent larger loops seen in the 193 Å and 211 Å bandpasses. These unusual oscillations are analysed to investigate the excitation mechanism responsible for their initial inwardly directed anti-phase behaviour. The transverse oscillations are analysed by constructing space-time diagrams from cuts made parallel to the projected loop displacements. The displacement time oscillation profiles are background subtracted and fitted with a damped cosine curve that includes a linear change in the period with time. The local magnetic topology of the active region is modelled using potential field source surface (PFSS) extrapolation. It reveals that the loops are anchored in different topological regions with foot point locations identified either side of the EUV flare peak emission source. In this context, the oscillation characteristics indicate that the excitation mechanism is closely linked to the local magnetic field topology and the reconnection generated wave dynamics in the active region rather than following an external flare blast wave. We discuss how observations such as these may serve to identify reconnection processes in similar quadrupolar active regions.

Authors: R.S. White, E. Verwichte and C. Foullon
Projects: SDO-AIA

Publication Status: ApJ (in press)
Last Modified: 2013-06-24 12:39
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First observation of a transverse vertical oscillation during the formation of a hot post flare loop  

Rebecca White   Submitted: 2012-07-25 02:39

Aims. We report and analyse the first observation of a transverse oscillation in a hot coronal loop with the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO), following a C4.9 GOES-class flare and Coronal Mass Ejection on the 3rd November 2010. The oscillating coronal loop is observed off the East solar limb and exclusively in the 131AA and 94AA bandpasses, indicating a loop plasma in the range of 9 - 11 MK. Furthermore the loop is not observed to cool into the other AIA channels, but just disappears from all bandpasses at the end of the oscillation. Methods. Time series analysis of the loop oscillation is conducted by taking several cuts at different positions along the loop, estimating the transverse displacements over time for two strands in the loop and fitting those with a damped cosine curve. Intensity time variations, both along the loop and for a series of cut cross-sections, are investigated. Using a 3D loop geometry obtained from a comparison of STEREO-B/EUVI and AIA images, we model different modes of transverse oscillations in the uniformly-filled loop. Results. Time series analysis revealed a period of 302 pm 14 s (291 pm 9 s) and a damping time of 306 pm 43 s (487 pm 125 s) for the first (second) loop strand. A spatial phase shift along the loop of approximately 180degr suggests we observe a higher order harmonic. Intensity oscillations are consistent with the interpretation in terms of a vertically polarised mode. Our forward modelling suggests that the loop oscillates as either a second or third order harmonic of this mode. Conclusions. This is the first observation of a transverse loop oscillation observed exclusively in the hot coronal lines. The loop oscillation is vertically polarised and is dominated by a higher order harmonic mode. It is concluded that the excitation mechanism of this 5 min period oscillation is directly connected with the reconnection processes that form the post flare loop, which differs to the blast wave excitation mechanism often concluded for cooler transverse loop oscillations.

Authors: R. White, E. Verwichte & C. Foullon
Projects: SDO-AIA,STEREO

Publication Status: A&A (accepted)
Last Modified: 2012-07-25 14:20
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Transverse coronal loop oscillations seen in unprecedented detail by AIA/SDO  

Rebecca White   Submitted: 2011-10-28 08:37

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: R.S. White, E. Verwichte
Projects: SDO-AIA,STEREO

Publication Status: A&A (Accepted)
Last Modified: 2011-10-31 16:25
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Abstracts by Author
Anti-phase signature of flare generated transverse loop oscillations
First observation of a transverse vertical oscillation during the formation of a hot post flare loop
Transverse coronal loop oscillations seen in unprecedented detail by AIA/SDO

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