1. Quasi-periodic upflows in the solar active region Hui Tian High Altitude Observatory, National Center for Atmospheric Research ASP research review 2010/10/27

2. Outline  The solar corona  Propagating disturbances interpreted as waves  Combination of imaging and spectroscopic observations  Oscillations driven by repetitive upflows  Conclusion

3. The solar corona  Extremely hot corona Heating problem EUV & X-Ray emission AIA/SDO 193 Å Image Credit: SDO Peter, 2004, Reviews in Modern Astronomy  Highly inhomogeneous corona

4. Propagating disturbances interpreted as waves De Moortel, 2002, Astronomy & Astrophysics  Propagating disturbances in imaging observation Period: 3-30 minutes Speed: 50-200 km/s Interpreted as magneto-acoustic waves

5. Combination of imaging and spectroscopic observations (I)  XRT observation 3-min cadence image sequence Relentless upflows at the boundary of the AR

6. Combination of imaging and spectroscopic observations (II)  EIS observation 32-s cadence SAS spectra Several emission lines  Fe XII 195.12 Å  Fe XIII 202.04 Å  Single Gaussian fit Intensity Doppler shift Line width  R-B

7. Combination of imaging and spectroscopic observations (III)

8. Oscillations driven by repetitive upflows (I)

9. Oscillations driven by repetitive upflows (II)

10. Oscillations driven by repetitive upflows (III) black: intensity red: Doppler shift (inverted) green: line width purple: R-B (inverted) blue: relative intensity of the 2 nd component cyan: relative Doppler shift of the two components

11. Oscillations driven by repetitive upflows (IV) Doppler shift & R-B are inverted in time series

12. Conclusion  Coronal oscillations could be signatures of Waves Repetitive upflows  Spectroscopic observations could distinguish between the two phenomena Waves: double frequency of line width; excess blueward and redward emission alternatively Upflows: same frequency of intensity, Doppler shift, and line width; repetitive excess blueward emission  The upflows could be the result of impulsive heating at the lower layers and may be an efficient way to provide the corona with hot plasma Reference: Tian et al., ApJ, 727, L37, 2011

13. Thank you!