2. SUN COURSE - SLIDE SHOW 8 Today: Solar flares & coronal mass ejections (CME’s)

3. 1. Introduction - Sunspot Numbers

4. Corona Changes with Solar Cycle

5. Coronal Mass Ejections (see talk 3) SOHO Coronagraph -- Artificial eclipse Can reach Earth - communications / satellites Discovered huge ejections of plasma

6. 2.Northern Lights (Aurora)

7. The Magnetic Field of the Earth The Earth’s magnetic field is like that of a bar magnet close to the Earth The solar wind distorts the magnetic field into a comet like shape on the nightside (the magnetotail).

8. Astronaut safety: Enhanced radiation levels Telecommunication and power lines Indirect effects of CME impact

9. What causes the aurora ? Distortion of Earth’s magnetic field by CME energizes particles in the magnetotail. These particles hit the molecules of the upper atmosphere and make them glow Different colours: different molecules (oxygen, nitrogen), also the level of excitation of the molecules

10. What accelerates the particles ? The Earth’s magnetic field shields us from any direct effects of CME’s ! Reconnection in the tail Energetic particles move along the magnetic field, and hit the atmosphere close to the north and south poles !

11. Aurora pictures taken from the Space Shuttle Height of auroral emission: 100-400 km (60 - 200 miles) Space shuttle orbit has similar height, so the Space shuttle can go directly through the aurora !

12. Photo sphere from SOHO 3. On October 28, 2003

13. Magnetic field from SOHO

14. X-ray Intensity(t) -3rd largest

15. Outer Corona from SOHO CME 2000 km/s (5 times faster than normal) Snow -- rel c particles

16. 1 Week Later - Fireworks Continued SOHO Site (Nov 6): Just as solar scientists were ready to start breathing normally again, active region 10486 blasted off yet another mega-flare. This one saturated the X-ray detectors on the NOAA's GOES satellites; the jury was therefore out for a while on the definitive classification of the flare -- speculations ranged from simply well above X20, to X40 or even X50. Today word came from the SEC that their best estimate was X28. It is now official: We have a new number 1 X-ray flare for the record books.

17. The biggest solar flare ever recorded ! X-ray intensity(t)

18. Conjuring trick -- plasma appearing by magic ? Close-up of plasma motions

19. Solar Flare  Very sudden brightening in corona  -- due to appearance of heat  Occurs above complex sunspots  The only possible source of vast amount of energy - B  Heating is ohmic ( )  How do large currents appear ??  How is magnetic energy converted into heat (reconnection) ?

20. 4. Overall Picture of Solar Flare In core - magnetic tube twisted (energy stored in fff) - erupts (catastrophe) - drives reconnection

21. Reconnection heats loops/ribbons

22. Reconnection proceeds -- loops rise Chromosphere Reconnection heats loops/ribbons

23. Reconn. Accelerate p’cles --> hard X

24. (Priest and Schrijver 1999) Reconnection heats loops Continues: new loops form & evaporate. Old loops cool & drain Feet move apart

25. Ex of Loops Rising

26. Same process for eruptions outside a.r. Ex of rising cusp

27. Before: twisted, force- free --> energy stored

28. Example from SOHO

29. TRACE - 1st image of j sheet

30. RHESSI Overlay of TRACE Blue contours: X- rays from very high energy particles Red contours: X-rays from high energy pcls Reconnection accelerates particles - -> hard X

31. Effects: (i) creates wave

32. (ii) Wave --Movie from TRACE

33. Cause of Eruption ? Magnetic Catastrophe 2.5 D Model

34. Numerical Model Suggestive of Catastrophe

35. Cause of energy release -- reconnection When an X-point collapses

36. Reconnection converts energy

37. Future Space Observatories STEREO (NASA) * Two satellites * Stereoscopic images of corona Solar Orbiter (ESA) * 3 times closer than Mercury Solar Dynamics Observatory Successor to SOHO (super - MDI + Trace)