Quasi-periodic upflows in the solar active region

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 emissionThe 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!