1. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Suprathermal Tails in Coronal Proton Velocity Distributions J. L. Kohl, A. Panasyuk, S. Cranmer, S. Fineschi, L. D. Gardner, D.H. Phillips, J. C. Raymond, and M. Uzzo

2. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Theory of shock acceleration of SEPs M. A. Lee (1983, 2005) developed a theory of coupled turbulent wave excitation and proton acceleration at shocks.

3. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Theory of shock acceleration of SEPs  In this theory, in order to produce large SEP events, it is necessary for a suprathermal seed particle population to exist after the first encounter of the coronal plasma with a CME shock. The theory requires that.001 to.01 of this proton velocity distribution have an injection speed higher than 2 times the difference between the shock speed and the wave phase speed (~V A in corona).  Alternatively, there could be a pre-existing suprathermal population in the corona that would help to satisfy this requirement. Gopalswamy et al. (2004) found higher SEP intensities when there was a preceding CME within ~24 hours that perhaps left behind suprathermals.

4. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Theory of shock acceleration of SEPs  The threshold velocity for particle injection is extremely uncertain. There are several lines of evidence that particles of 1000 to 2000 km/s (i.e., 5.2 – 20.7 keV) are preferentially accelerated. From the experimental side, that includes creation of anomalous cosmic rays from pick-up ions. Theories such as the transparency function of Gieseler et al. give similar results.

5. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Density of Suprathermal Seed Particles Preshock  fi (v): Resonantly scattered Ly  constrains the seed particle distribution  fe(v): Thomson-scattered Ly 

6. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions kappa needed to provide various population fractions with velocities above the injection velocity  Injection speeds of 940 – 1460 km/s, are 6.1 to 9.7 in units of V 1/e  A kappa distribution where.01 -.001 of the population has speeds beyond 6.1 to 9.7 V 1/e has a kappa between 4 and 2.  Hence, proton velocity distributions resembling kappa distributions with kappa values in this range and lower are of interest.

7. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Proton velocity distribution in a diffuse coronal region Kappa = 21.8 ± 7.0

8. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Observation of a proton velocity distribution with kappa = 3.5 Kappa = 3.5 ± 0.34

9. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

10. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Pseudo-kappa function –Data clearly show asymmetrical wings. –Kappa-function cannot model asymmetrical line profiles. –Idea is to create a function that is close to a kappa-function when the line is symmetrical but allows for a shift of the wings relative to the core. –Some theoreticians use a power-law, so a sum of Gaussian and power-law function seems natural. –For example the plot on the right shows that a kappa- function does not fit the observation. +

11. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions We empirically determine the dependency of all parameters (G,A,δ,ρ and σ) of the k- value of approximated function. The only additional parameter (vs kappa-function) is the Δ – shift which allow us to fit asymmetrical profiles. Pseudo-kappa function

12. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Best fit to data

13. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

14. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

15. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Effect of Stray Light

16. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 10 Feb 2006

17. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 10 Feb 2006

18. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Conclusions  UVCS/SOHO is able to measure proton velocity distributions including departures from Maxwellians.  These observations may lead to testing and refining theories of SEP production.  Work is in progress: line of sight, more observations and archival data analyses to be done.

19. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Simulation of observation for kappa = 4  Simulation includes coronal emission assuming kappa = 4, Poisson noise, Binning to UVCS sampling, Random flat field uncertainty, Detector background, Fitting with and without error in instrument profile  Fit with no profile error yields kappa = 3.92 +/- 0.66  Fit with profile error yields kappa = 3.66 +/- 0.59

20. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

21. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

22. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event  Kappa is large  19 Jan 2005, 22:01 + 2:00

23. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

24. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event  Kappa = 3.43 ± 1.0  19 Jan 2005, 22:01 + 3:30

25. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

26. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event 19 Jan 05, 22:01 + 5:30 19 Jan 05, 22:01 + 6:00

27. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Interpretation  Phil Isenberg suggested that the non-Maxwellian tails might be associated with heat flux along the magnetic field.  He speculates that the appearance and disappearance of these tails could be due to rotations of the field direction into and out of the line of sight.  He points out that this interpretation probably would not be consistent with a symmetric LOS velocity distribution.

28. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Interpretation  Next week Gang Li of UC, Riverside will give an SSP seminar describing his recent theoretical finding that a predecessor CME can greatly enhance turbulence upstream of a second shock. This decreases the acceleration time scale at the second shock allowing fast particle acceleration to occur.  To explain the result of Gopalswamy et al., the turbulence would need to be present for several hours after the first shock.  It is not clear if our observations indicate any increase in turbulence following a predecessor shock.

29. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions LASCO C2 image of CME region on 23 & 24 Dec 1996

30. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Simulation of observation for kappa = 4

31. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions UVCS Determinations of Pre-CME Corona  UVCS routinely obtains the densities, temperatures, outflow speeds, ionization states and elemental abundances in the pre-CME corona  Densities obtained by UVCS can be combined with Type II radio burst drift rates to obtain shock speeds  The angle between the shock front and the magnetic field requires the pre-shock field direction, which can be determined from the streamer morphology

32. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Testing and Guiding Theoretical Models of SEP Acceleration  The measured and derived parameters allow shock acceleration and current sheet models to be tailored to a specific event.  The theoretical models can then predict SEP acceleration, transport and energy spectra for those events.  In situ measurements of SEP energy spectra near the Sun (e.g., by Inner Heliospheric Sentinels) can then be used to test and guide the theoretical models.

33. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Key Parameters in Theories of SEP Acceleration by shocks  Pre-shock plasma conditions (including the supra-thermal seed particle population)  The shock speed  The compression ratio (which yields the Mach number)  The angle between the magnetic field and the shock motion

34. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

35. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

36. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

37. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

38. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

39. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

40. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

41. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

42. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

43. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

44. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

45. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

46. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

47. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

48. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions 20 Jan 2005 Event

49. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Density of Suprathermal Seed Particles Preshock  fe(v): Thomson-scattered Ly   fi (v): Resonantly scattered Ly  constrains the seed particle distribution

50. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions Lin and Forbes Unified Model of a Flare and CME In the Lin and Forbes model, a stressed magnetic arcade begins to rise. A current sheet develops as external pressure forces oppositely directed magnetic field lines to reconnect. The liberated energy heats and drives the CME and drives energetic particles downward producing the flare.

51. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions SEP source regions  The source regions of solar energetic particles (SEPs) are not well established and the physical processes associated with their acceleration are not well understood.  Gradual phase SEPs are believed to be produced by CME shocks, while impulsive phase SEPs are believed to be produced in the current sheet or other sites closely associated with the solar flare.

52. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions UVCS observations of CME shocks  Broad lines appear when shock forms  Shock speeds can be determined from detection of shock arrival at different heights  At onset radius, Mach number = 1, so V shock gives V Alfven. Unshocked foreground/ background shocked O +5 (T > 10 8 K)

53. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions The required insertion speed for producing observed SEP events  UVCS observations of CME shocks yielded an upper limit for the Alfven speed V A = 540 km/s at 2.3 R sun  Assuming a shock speed of 1000 km/s and 270 < V A < 540 km/s at 3.5 R sun, we derive an injection speed of 920 to 1460 km/s (4.4 – 10.1 keV).  Proton V 1/e in a streamer at 3.5 R sun is 150 km/s. Unshocked foreground/ background shocked O +5 (T > 10 8 K)

54. NESSC 5 April 2006 Suprathermal Tails in Coronal Proton Velocity Distributions UVCS Instrument Profile Left: UVCS instrument profile. Right: High spectral resolution scan of Ne-Pt hollow cathode spectrum convolved with UVCS instrument profile (black) and UVCS scan of lamp spectrum (red).