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SUN COURSE - SLIDE SHOW 8

SUN COURSE - SLIDE SHOW 8. Today: Solar flares & coronal mass ejections (CME’s). 1. Introduction - Sunspot Numbers. Corona Changes with Solar Cycle. Coronal Mass Ejections (see talk 3). SOHO Coronagraph -- Artificial eclipse. Discovered huge ejections of plasma.

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SUN COURSE - SLIDE SHOW 8

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

  2. 1. Introduction - Sunspot Numbers

  3. Corona Changes with Solar Cycle

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

  5. Northern Lights(Aurora)

  6. 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).

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

  8. 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

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

  10. 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 !

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

  12. Magnetic field from SOHO

  13. X-ray Intensity(t) -3rdlargest

  14. Outer Coronafrom SOHO CME 2000 km/s (5 times faster than normal) Snow -- relc particles

  15. 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.

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

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

  18. 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) ?

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

  20. Reconnection heats loops/ribbons

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

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

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

  24. Ex of Loops Rising

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

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

  27. Example from SOHO

  28. TRACE - 1st image of j sheet

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

  30. Effects: (i) creates wave

  31. (ii) Wave --Movie from TRACE

  32. Cause of Eruption ? Magnetic Catastrophe 2.5 D Model

  33. Numerical Model Suggestive of Catastrophe

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

  35. Reconnection converts energy

  36. 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)

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