1. R. P. Lin Physics Dept & Space Sciences Laboratory University of California, Berkeley The Solar System: A Laboratory for the Study of the Physics of Particle Acceleration October 2008, Krakow, Poland

2. The Sun is the most energetic particle accelerator in the solar system: - Ions up to ~ 1-10 GeV - Electrons up to ~100s of MeV Acceleration to these energies occurs in transient energy releases, in two (!) processes: - Large Solar Flares, in the lower corona - Fast Coronal Mass Ejections (CMEs), in the inner heliosphere, ~2-40 solar radii

3. Bastille Day Flare

5. 23 July 2002 X4.8 Flare ( Lin et al 2003) Thermal Plasma ~3x10 7 K Accelerated Electrons ~10 keV to >10s MeV Accelerated Ions ~1 to >100s of MeV

6. Π 0 Decay Nonthermal Bremsstrahlung Thermal Bremsstrahlung Solar Flare Spectrum Positron and Nuclear Gamma-Ray lines T = 2 x 10 7 K T = 4 x 10 7 K hot loop HXR footpoints soft X-rays hard X-rays g -rays  photosphere

8. Krucker & Lin 2003

9. RHESSI – Hα movie

10. Krucker & Lin 2004

11. e-e- e-e- HXR v in v fp e-e- e-e- HXR v in t1t1 t2t2 v fp ? ? HXR source motions in magnetic reconnection models photosphere B fp BcBc v in = coronal inflow velocity B c = coronal magnetic field strength v fp = HXR footpoint velocity B fp = magnetic field strength in HXR footpoint ~ photospheric value v in B c = v fp B fp

12. HXR footpoint motion movie, all

13. Velocity-HXR flux correlation Rough correlation between v and HXR flux d F = B v a dt Reconnection rate d F /dt= B v a ~ 2x10 18 Mx/s E = vB ~ 5 kV/m v= velocity B= magnetic field strength a=footpoint diameter

14. Mean Electron Flux Fit 2002 July 23 Flare 00:30:00 – 00:30:20 UT, Isothermal component + double power-law T = 37 MK EM = 4.1 × 10 49 cm -3 nVF = 6.9 × 10 55 cm -2 s -1 E c = 34 keV δ L = 1.5 E B = 129 keV δ U = 2.5 _ _

15. Spectral Components 511 keV- positron annihilation Neutron-capture2.2 MeV power law - electron bremsstrahlung De-excitation lines -narrow broad total model

16. Energetics – 23 July 2002 Flare Accelerated Electrons: > ~2 x 10 31 ergs ~3 x 10 28 ergs/s = ~3 x 10 35 (~50 keV) electrons/s for ~600s Accelerated Ions (>2.5 MeV) : ~ 10 31 ergs ~ 10 28 ergs/s = ~10 33 (~10 MeV) protons/s for ~1000s Thermal Plasma: ~ 10 31 ergs + losses

17. Multi-island reconnection (Drake, et al., 2006) Large energy gains require interaction with multiple magnetic islands - energy gain linked to geometrical change of island aspect ratio Consider a reconnection region with multiple islands in 3-D with a stochastic magnetic field - Electrons can wander from island to island Stochastic region assumed to be macroscopic u up C Ax xx yy

18. Protons vs Electrons >~30 MeV p (2.223 MeV n-capture line) > 0.2 MeV e (0.2-0.3 MeV bremsstrahlung X-rays) e & p separated by ~10 4 km, but close to flare ribbons

19. Electrons >0.3 MeV (Bremsstrahlung Fluence >0.3 MeV) Protons >30 MeV (2.223 MeV Line Fluence, corrected for limb darkening) (Shih et al 2008)

20. Mason et al., 2000

21. Electron - 3 He-rich SEP events - ~1000s/year at solar maximum - dominated by: - electrons of ~0.1 (!) to ~100 keV energy - 3 He ~10s keV/nuc to ~MeV/nuc energy x10-x10 4 (!) enhancements - heavy nuclei: Fe, Mg, Si, S enhancements - high charge states, e.g., Fe +20 - associated with: - small flares/coronal microflares - Type III radio bursts - Impulsive soft X-ray bursts (so also called Impulsive SEP events )

23. A series of He3 rich impulsive electron Krucker & Weidenbeck, private comm 2003

24. Reconstruct event geometry

25. Adapted from Gloeckler et al 2006

26. Mewaldt et al 2004

28. Large (L)SEP events - tens/year at solar maximum - >10 MeV protons (small e/p ratio) - Normal coronal composition (but sometimes 3 He & Fe/O enhanced) - Normal coronal charge states, Fe +10 (but sometimes enhanced ) - SEPs seen over >~100º of solar longitude - associated with: - Fast Coronal Mass Ejections (CMEs) - Large flares (but sometimes missing) - Gradual (hours) soft X-ray bursts (also called Gradual SEP events ) * Acceleration by fast CME driven shock wave in inner heliosphere, 2-40 solar radii

30. (Mewaldt et al. 2004)

31. Mewaldt et al, 2005 If these SEPs are accelerated by CME-driven shocks, they use a significant fraction of the CME kinetic energy (up to 20%) (see also Emslie et al. 2004).

32. Tylka & Lee, 2006

35. Tylka & Lee 2006

38. Cliver & Ling, 2007 Gradual SEP events

39. Zurbuchen 2004

40. Ng et al 2003

41. Solar Probe +

42. Oct-Nov 2003 Simulation

43. Thanks to the RHESSI team, and many colleagues