quasi-periodic upflows in the solar active region hui tian high altitude observatory, national...

Quasi-periodic upflows in the solar active region

Hui Tian High Altitude

Observatory, National Center for Atmospheric Research

ASP research review

2010/10/27

Outline

The solar coronaPropagating disturbances interpreted as

wavesCombination of imaging and

spectroscopic observationsOscillations driven by repetitive upflowsConclusion

The solar corona

Extremely hot corona• Heating problem• EUV & X-Ray emission

AIA/SDO 193 Å

Image Credit: SDOPeter, 2004, Reviews in Modern Astronomy

Highly inhomogeneous corona

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

Combination of imaging and spectroscopic observations (I)

XRT observation• 3-min cadence image

sequence• Relentless upflows at

the boundary of the AR

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

Combination of imaging and spectroscopic observations (III)

Oscillations driven by repetitive upflows (I)

Oscillations driven by repetitive upflows (II)

Oscillations driven by repetitive upflows (III)

black: intensity red: Doppler shift (inverted) green: line width purple: R-B (inverted) blue: relative intensity of the 2nd component cyan: relative Doppler shift of the two components

Oscillations driven by repetitive upflows (IV)

Doppler shift & R-B are inverted in time series

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

Thank you!