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Understanding Coronal Mass Ejections Through Spectroscopic Observations

This research review explores insights gained from spectroscopic observations of coronal mass ejections (CMEs) at the HuiTian High Altitude Observatory and the National Center for Atmospheric Research. By combining imaging and spectroscopy, we analyze the kinematics of CMEs, including their frequency, mass, speed, and impact on high-tech systems on Earth. Notably, spectroscopic data reveals critical details about outflow speeds and the dynamics of dimming regions, providing a comprehensive understanding of CMEs' behaviors and potential dangers to technology and astronauts.

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Understanding Coronal Mass Ejections Through Spectroscopic Observations

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  1. HuiTian High Altitude Observatory, National Center for Atmospheric Research What can we learn about coronal mass ejections through spectroscopic observations ASP research review 2011/10/5

  2. Observation of the corona Habbal et al. 2010,ApJ Fe X 174 Å, imager Fe X 6374 Å, solar eclipse • White light • Ground & space • Eclipse • Coronagraph • UV & X-ray • Space • Imager • Coronagraph • Spectrograph/spectrometer SOHO LASCO-2 Lower corona, coronagraph Extended corona, coronagraph

  3. Coronal mass ejections (CMEs) • Occurring frequency • Solar maximum: 3-5 per day • Solar minimum: 1 every 3-5 days • Mass: 2 × 1014-16g • Speed: 200-2000 km/s • Sometimes dimmings in EUV & X-ray Credit: STEREO Science Center

  4. Space weather • Earth-directed CMEs are potentially dangerous to our high-tech systems • Satellite anomalies, orbit changes, health of astronauts • Disruption of GPS & other spacecraft signals, radio signals • Damage of electric power grids & pipelines • Imaging observations at the Earth orbit can not observe the evolution of Earth-directed CMEs Credit: SwRI Credit: SOHO Daily MPEG Credit: STEREO Science Center

  5. EUV spectroscopy Curdt et al. 2001, A&A

  6. Combine imaging & spectroscopic observations

  7. Line profiles in the ejecta • Two well-separated components • A nearly stationary background • A high-speed components (~200 km/s) representing the emission of the ejecta • Calculate the real speed: v=Sqrt(vpos2+vlos2)

  8. Spectroscopic observations of coronal dimmings Attrill et al. 2010, Sol. Phys. McIntosh,ApJ, 2009 • ~20 km/s Blue shift: outflows refilling the corona • Enhanced line width: growth of wave amplitude

  9. Blueward asymmetry of line profiles in dimming regions

  10. Two emission components in dimming regions • Two emission components • A nearly stationary background • A weak high-speed (~100 km/s) components representing outflows • Blue shift of ~ 20 km/s and enhanced line width are caused by the superposition of the two components • Only a small portion of the materials in the dimming region are flowing outward • The outflow speed is around 100 km/s

  11. Conclusion • Spectroscopic observations can provide valuable information on the kinematics of CMEs • 3-D CME evolutions can be obtained by simultaneous imaging and spectroscopic observations • The outflow speed in the dimming region is of the order of 100 km/s, not ~20 km/s

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