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Hui Tian 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 . Observation of the corona. Habbal et al. 2010, ApJ. Fe X 174 Å, imager.

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hui tian high altitude observatory national center for atmospheric research
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

observation of the corona
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

coronal mass ejections cmes
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

slide4

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

euv spectroscopy
EUV spectroscopy

Curdt et al. 2001, A&A

line profiles in the ejecta
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)
spectroscopic observations of coronal dimmings
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
two emission components in dimming regions
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
conclusion
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