R. P. Lin Physics Dept & Space Sciences Laboratory University of California, Berkeley

1. R. P. LinPhysics Dept & Space Sciences LaboratoryUniversity 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 MeVAcceleration 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 ~3x107 K Accelerated Electrons ~10 keV to >10s MeV Accelerated Ions ~1 to >100s of MeV

6. <----- RHESSI coverage -----> Solar Flare Spectrum hot loop Thermal Bremsstrahlung T = 2 x 107 K HXR footpoints T = 4 x 107 K photosphere Nonthermal Bremsstrahlung Π0Decay Positron and Nuclear Gamma-Ray lines soft X-rays hard X-rays g-rays 

8. Krucker & Lin 2003

9. RHESSI –Hα movie

10. Krucker & Lin 2004

11. Bc t1 vin vin HXR source motions in magnetic reconnection models ? vin = coronal inflow velocity Bc = coronal magnetic field strength vfp = HXR footpoint velocity Bfp = magnetic field strength in HXR footpoint ~ photospheric value vin Bc = vfpBfp e- e- Bfp HXR HXR photosphere t2 vin vin ? e- e- HXR HXR vfp vfp

12. HXR footpoint motion movie, all

13. Velocity-HXR flux correlation Rough correlation between v and HXR flux dF = B v a dt Reconnection rate dF/dt= B v a ~ 2x1018 Mx/s E = vB ~ 5 kV/m v= velocity B= magnetic field strength a=footpoint diameter

14. Mean Electron Flux Fit2002 July 23 Flare • 00:30:00 – 00:30:20 UT, • Isothermal component + double power-law • T = 37 MK • EM = 4.1 × 1049 cm-3 • nVF = 6.9 × 1055 cm-2 s-1 • Ec = 34 keV • δL = 1.5 • EB = 129 keV • δU = 2.5 _ _

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

16. Energetics – 23 July 2002 Flare • Accelerated Electrons: > ~2 x 1031 ergs ~3 x 1028 ergs/s = ~3 x 1035 (~50 keV) electrons/s for ~600s • Accelerated Ions (>2.5 MeV) : ~ 1031 ergs ~ 1028 ergs/s = ~1033 (~10 MeV) protons/s for ~1000s • Thermal Plasma: ~ 1031 ergs + losses

17. uup CAx y x 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

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 ~104 km, but close to flare ribbons

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

20. Mason et al., 2000

21. Electron -3He-rich SEP events • - ~1000s/year at solar maximum • - dominated by: • - electrons of ~0.1 (!) to ~100 keV energy • - 3He ~10s keV/nuc to ~MeV/nuc energy • x10-x104 (!) 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 3He & 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, 2005If 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

33. Tylka & Lee, 2006

35. Tylka & Lee 2006

36. 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