Review of CIR-related Particle Composition, Charge States, & Energy Spectra

1. Review of CIR-related Particle Composition, Charge States, & Energy Spectra Joe Mazur The Aerospace Corporation Glenn Mason Johns Hopkins/APL Joe Dwyer Florida Institute of Technology Mihir Desai Southwest Research Institute 1

2. Processes for 1 AU observations of solar material After Stone et al., Space Sci Rev., 86, 1, 2000 2

3. 5 AU 1 AU Desai et al., JGR, 104, 6705, 1999 Mason et al., ApJ Letters, 486, L149, 1997 3

4. Stream interface 4

5. Abundances Mason et al., ApJ Letters, 486, L149, 1997 see also Richardson et al., JGR 98, 13, 1993 5

6. Ratios vs. solar wind speed 6

7. Abundance summary • similar to solar system except for factor of 2-3 enhancement of He and C/O • increase of He/O, C/O, and Ne/O with solar wind speed • He abundance increases from 1 to 5 AU Mason & von Steiger et al. Space Sci. Rev. 89, 1999 (ISSI CIR Workshop held in 1998) 7

8. Ulysses 4.5 AU Pick up ion He+ increases its contribution to CIRs at greater radial distances Suggested that other pickup ions (such as inner source) at 1 AU might account for some puzzling composition observations Gloeckler et al., JGR, 99, 17637, 1994. 8

9. Acceleration of suprathermal He+ in CIRs: enhanced 103 - 104 over solar wind Chotoo et al., JGR, 105, 23107, 2000. 9

10. Mazur et al. ApJ 566, 2002 Mobius et al. Geophysical Research Letters, 29, 2001 10

11. Averaged CIR charge states: ~0.5 MeV/n Mobius et al. Geophysical Research Letters, 29, 2001 Mazur et al. ApJ 566, 2002 11

12. Möbius et al., AIP Conf. Proc. 598, 201, 2001 12

13. Charge state summary • More pickup He at 4.5 AU than 1 AI (at 1 AU the pickup He is ~15% He++, while at 4.5 AU it is twice as abundant) • Heavy ions at 1 AU show little evidence of pickup species 13

14. 14 Mason et al., ApJ Letters, 486, L149, 1997

15. Summary Abundances Ion composition similar to solar system but with some differences Still puzzling dependence of some ratios on solar wind speed Charge states Little evidence of Z>2 pickup ions at 1 AU Large abundance of pickup helium at 5 AU Energy spectra Power law from tens of keV/n to ~1 MeV/n Steepening above ~1 MeV/n Spectral forms do not change out to 10’s of AU The source population is coming from the suprathermal region, but that population is not just heated solar wind; other constituents are important Most often the 1 AU particles are not accelerated at shocks requiring another mechanism (Jokipii et al. 2003) As we approach solar minimum we have the opportunity to revisit some of these observables with ACE 15

16. Essential new work needed: • Complete ACE surveys with much larger number of species identified • fully characterize properties of suprathermal / pick-up ion distributions • detailed theoretical models to probe injection issues 16

17. 17 C. Chotoo, Ph.D. thesis, U of Maryland 1998

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19. 19

20. Energy spectra summary • power law from tens of keV/n to ~1 MeV/n • steepening above ~1 MeV/n • spectral forms do not change out to 10’s of AU See also Mason & von Steiger et al. Space Sci. Rev. 89, 1999 (ISSI CIR Workshop held in 1998) 20

21. 21

22. Energy spectra summary • More pickup He at 4.5 AU than 1 AI (at 1 AU the pickup He is ~15% He++, while at 4.5 AU it is twice as abundant) • Heavy ions at 1 AU show little evidence of pickup species 22

23. 23 Möbius et al., AIP Conf. Proc. 598, 201, 2001

24. 24 Möbius et al., AIP Conf. Proc. 598, 201, 2001

25. 25 Richardson et al., JGR, 98, 13, 1993

26. Dwyer et al, in preparation, 2002 26

27. Fisk & Lee acceleration model-- • particles in CIRs accelerated by compression at forward and reverse shocks at several AU: propagate in to 1 AU • adiabatic deceleration in solar wind included • yields distribution function spectra and gradients similar to observations above ~100 keV/n • injection energy > 5 keV required, ie from postulated suprathermal tail of the solar wind • composition similar to source material (assumed to be solar wind suprathermal tail) -- (note: no systematic measurements of solar wind comp. available at that time) L. A. Fisk and M. A. Lee, Astrophys. J., 237, 620, 1980 27

28. Suprathermals as a seed population-- • SEP related events • “super events” in the inner solar-system (Dröge et al. 1992.) • Peak intensities in August 1972 (Smart et al. 1990) • Interplanetary shocks • Aug 1978 shock (Gosling et al. 1981) • IP shock survey (Tsurutani & Lin 1985) • Sources? • long lived remnants of solar flares • planetary bow shocks • corotating interaction regions 28

29. Fisk & Lee CIR spectral form-- CIR spectral form: where: v = particle speed; r = radius of observer; rs = shock radius; = shock strength; diffusion coefficient V = solar wind speed 29

30. CIR model status 1970s-80s • Successful: • spectra above ~100 keV/n • composition “similar” to (unmeasured) solar wind • origin at several AU, and gradients • Not successful / unaddressed: • C/O ratio • spectral forms vs. compression ratios • intensities 30

31. New CIR energetic particle observations & challenges to standard model-- • Particle spectra continue to rise down to ~10 keV/nucleon at 1 AU • C/O ratio dependence on solar wind speed • Mg/O shows no FIP effect • large abundance of He+ at 1 and several AU • 3He abundance enhanced compared to solar wind 31

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34. Hilchenbach et al., Trnas. Am.Geophys. U., 78, F554, 1997 34

35. Interstellar Gas Flow in Inner Solar System From: University of New Hampshire group WWW page http://www-ssg.sr.unh.edu/tof/Missions/Ace/aceset.html 35

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37. 3He is enriched in CIRs -- about 4 times the solar wind value compared to 4He Dwyer et al, in preparation, 2002 37

38. Role of pick up ions -- • consistent with He+ abundance • tempting explanation for C/O ratio, but • no seasonal variation of heavy ion abundances detected, but data is sparse • at 1 AU C+ is a small fraction of CIR carbon 38

39. CY 1994, <r> = 2.8AU; <latitude> = -65° <vsw>=784 km/s 39 Gloeckler & Geiss, Space Sci. Rev, 86, 127, 1998

40. SAMPEX: geomagnetic latitude cutoffs of: (a) 14 CIRs (1992- 95), and (b) all 1998 SEP events Mazur, Mason & Mewaldt, 2002, ApJ, in press 40

41. SAMPEX: Calibration of adjusted magnetic invariant latitude cutoffs for CIRs and SEP events Mazur, Mason & Mewaldt, 2002, ApJ, in press 41

42. SAMPEX: Observed magnetic cutoffs for CIR events, vs inferred cutoff if ions were singly ionized. Singly stripped ions must be no more than a few percent of total. Mazur, Mason & Mewaldt, 2002, ApJ, in press 42

43. CIR abundance details show that bulk solar wind source does not fit the new observations-- • Source population is coming from suprathermal region, but that population is not just heated solar wind -- other constituents important • Do other shock-associated energetic particle observations show evidence for suprathermal seed ions? YES: SEPs, ESPs -- tracer ion is 3He 43

44. 3He and 4He time intensity profiles in large June 4, 1999 solar particle event 44 Mason et al., Ap.J. Letters, 525, L133, 1999

45. Enhanceed abundances of 3He in large SEP events ACE/ULEIS 0.5-2 MeV/n ACE/SIS 8-13 MeV/n Wiedenbeck et al., AIP Conf Proc 528, 107, 2000 Mason et al., Ap.J. Letters, 525, L133, 1999 45

46. Suprathermals show 10-100 times more variation in intensity than solar wind -- likely critical issue in energetic particle intensities 46

47. Conclusions: 1 AU CIRs • CIR source is not bulk solar wind, but rather the suprathermal region (v/vsw >~ 1.5) • time dependent, multiple ingredients: • solar wind suprathermal tail • pick up ions (interstellar) • pick up ions (inner source) • other remnants (large SEP events, impulsive SEP events) • at < few hundred keV/n, CIR ions are “locally accelerated” 47

48. CIRs observed in early 2000 on ACE • typical appearance • note change in C/O ratio in CIRs vs. solar events 48

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