Quasi-periodic upflows in the solar active region Hui Tian High Altitude Observatory, National Center for Atmospheric Research ASP research review 2010/10/ 27
Jan 14, 2016
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!