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Quasi-periodic upflows in the solar active region Hui Tian High Altitude Observatory, National Center for Atmospheric Research ASP research review 2010/10/27
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Outline The solar corona Propagating disturbances interpreted as waves Combination of imaging and spectroscopic observations Oscillations driven by repetitive upflows Conclusion
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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
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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
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Combination of imaging and spectroscopic observations (I) XRT observation 3-min cadence image sequence Relentless upflows at the boundary of the AR
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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
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Combination of imaging and spectroscopic observations (III)
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Oscillations driven by repetitive upflows (I)
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Oscillations driven by repetitive upflows (II)
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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
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Oscillations driven by repetitive upflows (IV) Doppler shift & R-B are inverted in time series
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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
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Thank you!
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