Upload
reese
View
34
Download
0
Tags:
Embed Size (px)
DESCRIPTION
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. - PowerPoint PPT Presentation
Citation preview
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
Observation of the coronaHabbal et al. 2010, ApJ
Fe X 174 Å, imager Fe X 6374 Å, solar eclipse
Lower corona, coronagraph Extended corona, coronagraph
SOHO LASCO-2 White lightGround &
spaceEclipseCoronagraph
UV & X-raySpace ImagerCoronagraphSpectrograph/
spectrometer
Coronal mass ejections (CMEs)
Credit: STEREO Science Center
Occurring frequencySolar maximum: 3-5 per daySolar minimum: 1 every 3-5
days Mass: 2 × 1014-16 g Speed: 200-2000 km/s Sometimes dimmings in EUV & X-ray
Credit: STEREO Science Center
Space weather
Credit: SwRICredit: 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
EUV spectroscopy
Curdt et al. 2001, A&A
Combine imaging & spectroscopic observations
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(vpos
2+vlos2)
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
Blueward asymmetry of line profiles 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
ConclusionSpectroscopic 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