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Heavy Ion Abundances in Large Solar Energetic Particle Events Spring AGU 2006, SH43B-04 Heavy Ion Abundances in Large Solar Energetic Particle Events Spring.

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Presentation on theme: "Heavy Ion Abundances in Large Solar Energetic Particle Events Spring AGU 2006, SH43B-04 Heavy Ion Abundances in Large Solar Energetic Particle Events Spring."— Presentation transcript:

1 Heavy Ion Abundances in Large Solar Energetic Particle Events Spring AGU 2006, SH43B-04 Heavy Ion Abundances in Large Solar Energetic Particle Events Spring AGU 2006, SH43B-04 Mihir I. Desai Southwest Research Institute San Antonio, Texas Co-authors: G. M. Mason, R. E. Gold, S. M. Krimigis, C. M. S. Cohen, R. A. Mewaldt, J. E. Mazur & J. R. Dwyer Mihir I. Desai Southwest Research Institute San Antonio, Texas Co-authors: G. M. Mason, R. E. Gold, S. M. Krimigis, C. M. S. Cohen, R. A. Mewaldt, J. E. Mazur & J. R. Dwyer

2 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Event Selection & Data Analysis 85 solar proton events that affected the Earth environment between Nov Jan (source: NOAA SPE event list; criteria: 10 PFU’s for >10 MeV protons) Removed 21 events where: ULEIS intensities were dominated by IP shock-accelerated ions ULEIS was completely saturated Little or no intensity increases at ~1 MeV/n. and/or at ~100 keV/n. Events with complex time-histories with multiple CMEs, flares, and IP shock contributions

3 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Nov. 24, 2001 SEP Sampling Interval with shock passage masked STEP 1 Start time - Flare/CME onset Stop Time - End of SEP decay STEP 2 Mask ESP intervals STEP 3 Select energy- dependent start intervals using smoosh plots.

4 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue 29 of the 64 events have finite 3He Enhancements ~4-150 times SW value August 20, MeV/n 3 He/ 4 He = /-0.99 (x10 -3 ) Correlation is not statistically significant

5 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Must encounter 3He- and heavy ion-rich flare material in the corona and the IP medium 486 CME shocks

6 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Fe/O decreases with increasing energy - due to shock acceleration Fe/O is enhanced relative to SW value (unknown mechanism) Energy-dependent Fe/O in large SEP events Fe/O Enhanced Fe/O Depleted

7 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue LSEP abundances vs. Slow Solar wind Not well organized by any simple physical quantity (e.g., M/Q ratio, FIP, etc.) ACE/ULEIS MeV/n Ulysses/SWICS solar wind

8 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue This survey vs. SEP events Enhanced relative to gradual SEPs at ~5-12 MeV/n Depleted relative to 3He-rich events ACE/ULEIS MeV/n

9 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue M/Q-dependent event-to-event variations LSEP events ACE/ULEIS MeV/n

10 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue ACE/ULEIS MeV/n M/Q-dependent event-to-event variations in IP shocks + LSEP events

11 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue ACE/ULEIS MeV/n M/Q-dependent variations - IP shocks, LSEP events, 3He-rich SEP events

12 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Same fit works for LSEP events, 3He-rich events, and IP shocks ACE/ULEIS MeV/n

13 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Fe/O decreases with increasing energy - due to shock acceleration Fe/O is enhanced relative to SW value - due to the seed population Fe/O in the seed population must be larger than LSEPs Two distinct M/Q-dependent mechanisms Fe/O EnhancedFe/O Depleted

14 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue M/Q-dependent depletion relative to “seed” population Desai et al., 2004 IP shock vs. ambient Apply this function to infer source abundances from measured LSEP values

15 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Comprises ~75% impulsive SEP-like material Inferred Source Abundances

16 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Summary Fe/O decreases with energy up to ~60 MeV/n - signature of shock acceleration 3He and heavy ions show large, variable, and unsystematic enhancements relative to SW values - Heavy ion abundances are not organized by a simple quantity wrt. SW values Same M/Q-dependent enhancements are seen in IP shocks, LSEP events, and 3He-rich events

17 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Conclusion The event-to-event variability in the ion composition in large SEP events at ULEIS energies can be attributed primarily to that of suprathermal seed population, most of which originates from processes similar to those occurring during 3He-rich SEP events.

18 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Large SEP events at ACE 64 large SEP events (NOAA’s SPE list) between 1997-Jan 2005

19 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Aug. 24, 2002

20 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Energy-dependence of C/O and Fe/O C/O ratios remain constant with energy; Fe/O decreases by a factor of 2

21 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Same situation For 9 events with Fe/O <0.1 and upper limit 3He/4He

22 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Comparison with prior surveys Fe/O at ULEIS energies are greater than prior surveys at higher energies

23 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Fe/O exhibits no clear solar cycle dependence 50% of events have finite 3He during Occ. freq. drops below ~25% in 2004 Solar activity

24 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Fe/O ratio is poorly correlated with CME speed & flare longitude

25 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Event-integrated Fe/O vs. Mean Fe/O from 1 hr. averages

26 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Unlike for IP shocks, the Fe/O in LSEPs is not correlated with pre- event Fe/O on a case- by-case basis Fe/O LSEPs vs. Pre-event

27 Desai et al. 2006; To appear in ApJ vol. 648 n1, Sep. 1, issue Perhaps STEREO will help sample the seed population for some LSEP events


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