what can we learn about coronal mass ejections through spectroscopic observations
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 PresentationTRANSCRIPT
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