Download presentation
Presentation is loading. Please wait.
Published byBritton Fitzgerald Modified over 8 years ago
1
What can we learn about coronal mass ejections through spectroscopic observations Hui Tian High Altitude Observatory, National Center for Atmospheric Research 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 Lower corona, coronagraphExtended corona, coronagraph SOHO LASCO-2 White light Ground & space Eclipse Coronagraph UV & X-ray Space Imager Coronagraph Spectrograph/sp ectrometer
3
Coronal mass ejections (CMEs) Credit: STEREO Science Center Occurring frequency Solar maximum: 3-5 per day Solar minimum: 1 every 3-5 days Mass: 2 × 10 14-16 g Speed: 200-2000 km/s Sometimes dimmings in EUV & X-ray
4
Credit: STEREO Science Center Space weather Credit: SwRI Credit: SOHO Daily MPEG 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
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(v pos 2 +v los 2 )
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
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.