Corona
Above chromosphere is Corona
- very hot -- 1 million K and hotter
- Puzzle -- what heats the Corona?
- photosphere is only 6000 K
- probably due to solar magnetic activity
- flares, etc. -- treated later
- Characteristic features are x-rays and highly ionized atoms
- high energy photons from high temperatures
- Fe+13 (13 electrons removed from Fe)
- cf. photosphere Fe+1 (once ionized)
- Clearly seen during a solar eclipse
- at other times can be studied using a coronagraph
- place occulting disk over photosphere w-21
- shown in “Solar Activity” video