Coronal Loop Oscillations Seen in Unprecedented Detail by SDO/AIA

1. Coronal Loop Oscillations Seen in Unprecedented Detail by SDO/AIA Rebecca White andErwin Verwichte University of Warwick, Centre for Fusion, Space and Astrophysics, Coventry, CV4 7AL R.S.White@warwick.ac.uk BUKS 2011 28th June 2011

2. Introduction • Coronal loop oscillations are interpreted as the fast kink mode. • Observations of coronal loop oscillations since 1998, majority with TRACE e.g. • - Nakariakov et al 1999 • - Aschwanden et al 1999 • - Verwichte et al 2004, 2010 • - Van Doorsselaere et al 2007 • Launch of SDO in 2010 carrying the Atmospheric Imaging Assembly (AIA) instrument. • - 7 EUV band passes (94Å - 335 Å) • - Continuous full disk images • - Spatial resolution 1.5″, time cadence ~ 12s

3. Introduction • Motivation: • Study multiple loops in the same event. • Combine AIA/SDO data with EUVI/STEREO data to obtain the 3D loop geometry. • The short time cadence of AIA may allow shorter period oscillations to be observed. • Application of seismology techniques to the fast kink mode: • - Used to probe local properties of the coronal plasma such as the magnetic field.

4. Observations • 3 events studied in the 171Å bandpass • Oscillations triggered by a flare/CME event. M1.0 GOES flare C4.9 GOES flare • 11 loops studied • 3D information using STEREO obtained for 6 loops

5. 13 June 2010

6. 02 August 2010

7. 03 November 2010

8. Time Series Analysis • Cuts made perpendicular to the loops. • Loop features enhanced by applying a 2D wavelet transform. • Gaussian plus background profile fitted to the flux at each time to attempt to automatically locate the loop position. • Damped cosine function fitted to the resulting time series after background subtraction:

9. Time Series Analysis

10. Intensity Oscillations 2 3 4 5 • Intensity obtained from the cuts using the time series points. • Reliably observed for 6 loops. • Possible explanation of intensity variations: • Variations of line of sight column depth. Verwichte et al. (2009) • Vertically polarised mode. Wang and Solanki (2004) • Non linear coupling of the kink mode to a slow magnetoacoustic mode. Terradas and Ofman (2004) • Linear coupling of the kink mode to a slow magnetoacoustic mode. Terradas et al. (2011)

11. Intensity Oscillations 2 3 5 4 Intensity amplitude increases with displacement amplitude for this loop. → Consistent with l.o.s variations.

12. 3D Loop Geometry from STEREO Azimuth = 68.8° Inclination = 26.0°

13. Results Event 1 (13 June 2010): Intensity oscillations: • Periods between 3.55 minutes and 3.75 minutes for displacement time series. • Periods of 3.58 minutes and 4.12 minutes for intensity oscillations.

14. Results Event 2 (02 August 2010): Intensity oscillations: • Periods of 8.67 minutes and 9.93 minutes for displacement time series. • Periods of 9.17 minutes and 10.2 minutes for intensity oscillations.

15. Results Event 3 (03 November 2010): • Period scales with loop length and possibly footpoint distance from the event. • Periods of less than 2 minutes found for loops 4 and 5. Intensity oscillations:

16. Results

17. DEM Analysis • Differential emission measure distribution analysis technique. Aschwanden, (2011) • First estimate of the average magnetic field strength made by estimating the density contrast in the 171Å bandpass: • B = 16.72 ± 3.34 G

18. Conclusions and Future Work • Performed the analysis of 11 coronal loop oscillations, determining periods, damping times and phases. • - 3D geometry obtained for 6 loops using EUVI/STEREO. • - DEM analysis to be applied to suitable loops. • Oscillations with periods of less than 2 minutes observed. • Intensity oscillations reliably observed in 6 of the loops. • - Most likely due to line of sight effect but other possibilities cannot be ruled out. • Seismology techniques are to be applied to the kink mode e.g Goossens et al 2008, Nakariakov and Ofman 2001.