1. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary George C. Ho and Glenn M. Mason The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723 June 26th, 2008 Energetic Electrons in 3 He Enhanced Solar Energetic Particle Events

2. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Key: proton = neutron = electron = Helium-3 Helium-4 Relative Abundance 1 2500 Introduction –First Discovery –Classification Paradigm Energetic Electron –Timing –Occurrence Fluence Analysis –Observations –Implication Discussion Outline

3. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Introduction

4. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Anglin, 1975 Discovery that small solar particle events sometimes showed enormous enrichments of 3 He, without any accompanying 3 H or 2 H enrichments (Garrard, Stone & Vogt, NASA SP- 342, 1973; Anglin et al. 1974; Serlemitsos & Balasubrahmanyan 1975)

5. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Kilometric Type III Association Reames and Stone, 1986

6. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Overall Picture as of Mid 1990s

7. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Gradual and Impulsive SEP Events Mason et al., 1989

8. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary     keV/n      MeV/n ACE He Mass Resolution

9. Event onsets often show almost pure velocity dispersion -- but multiple events can overlap in time. These are separated in constructing fluence spectra

10. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Solar Cycle Dependence ACE launched in August ‘97

11. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Fraction of time with 3 He present. Points are shown for individual Bartels rotations; lines show running average over 6 rotations. Unfilled circles and dotted line: unambiguous 3 He (categories 2–4); filled circles and solid line: probable 3 He (categories 1 and 5) also included. Wiedenbeck et al., Solar Wind 10 3 He-rich Population

12. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Ultra-Heavy Particles Mason et al., 2004 Ultra-heavy ions ~200 times SW value Acceleration depends on M/Q ratio No satisfactory theory Mason et al. (2004)

13. Coordinated Observations

14. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Ionization States Mean Q-states of Fe increase with Energy At low-E - ionic charge states correspond to equilibrium Temperature At high-E, stripping due to acceleration and transport Klecker et al. (2005)

15. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Energetic Electrons in 3 He-rich Events

16. UT Time Flux SUN ? e - beam Earth Injection study of impulsive electrons 10 7 10 6 10 5 10 4 05:00 07:00 09:00 11:00 type III radio burst Freq (Hz) Linghua Wang et al. 2006 SPD

17. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Casual Relationship Ho et al., 2001

18. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Timing Analysis Ho et al., 2003

19. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Scatter-free Transport Ho et al., 2003

20. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Lack of Correlation Ho et al., 2001

21. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Association with all Impulsive Events Ho et al., 2001

22. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Fluence Analysis

23. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary “Apparent” Anti-correlation

24. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Upper Limit on 3 He Fluence Measurements above instrument thresholds 4 He fluences range over a factor of 10,000 while the 3 He fluences in the same SEP range over only a factor of 100 3 He/ 4 He does not order the data A strict upper limit on the 3 He fluence

25. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Fluence Distributions Ho, Roelof, Mason., 2005

26. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary 20 Ne vs. 4 He Fluences Ho, Roelof, Mason., 2005

27. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Class-1 Events: power law or double power law form above ~1 MeV/n all spectra similar 3 He is power law or double power law Mason et al., 2002 Spectral Form-Class I

28. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Class-1 Events: single power law for all species except 3 He 3 He harder than others below ~1 MeV/n 3 He: 4 He peaks from 1-few MeV/n Mason et al., 2002 Spectral Form-Class I

29. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Class-2 Events: 4 He is power law 3 He and Fe flatten notably at low energies (other heavy ion species not clear) 3 He and Fe curve at different energies highest 3 He: 4 He Mason et al., 2002 Spectral Form-Class II

30. Possible synthesis:  initial 3 He enrichment mechanism (Cascade MHD?)  further acceleration results in power law spectra  still further acceleration results in similar spectra for all species

31. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Fluence Distributions Ho, Roelof, Mason., 2005

32. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Discussions New observations from advanced instrumentations give us new insight into this class of SEP events As we learned more about this class of events, we find there is more outstanding questions (personal views): –What enhancement/acceleration mechanism operate in this remarkable class of SEP event? (Ultra-heavy ion?) –Why is the 3 He presented continuously in the interplanetary space? –What are the causal relationship between the energetic electrons, flare, and 3 He enrichment? –Why is there an apparent upper limit on the 3 He fluence in the interplanetary space? What is its implications? –Why the 3 He spectral shape different from other ions?

33. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Discussions Current observations at 1 AU are hampered by transport effects as we are far from the source Require high resolution in-suite observation close to the source of the enrichment/acceleration Solar Orbiter:Solar Probe + :

34. SHINE 2008 Introduction Energetic ElectronsFluence AnalysisSummary Fluence Analysis The remarkable enrichment of the isotope 3 He in solar energetic particle (SEP) events is usually described in terms of the ratio of the fluences of the two isotopes ( 3 He/ 4 He) However, only weak correlations between 3 He/ 4 He and flare properties have been found [Reames, Dennis, and Stone, ApJ., 1988] Strong correlation is found between the occurrence of 3 He-rich SEP with energetic electrons [Reames, von Rosenvinge, and Lin, ApJ., 1985] However, Ho et al. [ApJ., 2001] found same association in all impulsive SEP events with energetic electrons Ho, Roelof, & Mason [ApJL., 2005] found during the peak of solar activity, there is an upper limited on the 3 He flunence of 0.2 to 2.0 MeV/nuc.