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A twin CME scenario?

Why “similar” eruptions which lead to similar shocks behave very differently in terms of accelerating energetic particles? Perhaps seed population? What makes a large SEP events --- presence of seed population – how to get these seed population?. A twin CME scenario?.

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A twin CME scenario?

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  1. Why “similar” eruptions which lead to similar shocks behave very differently in terms of accelerating energetic particles? Perhaps seed population? What makes a large SEP events --- presence of seed population – how to get these seed population?

  2. A twin CME scenario? Pseudo-streamer configuration Reconnection between open and closed field lines Stronger turbulence, higher seed population

  3. Some questions: 1) what about Large SEP events? Do they agree with twin-CME scenario? (Group I) 70% of them have preceding CMEs. 2) Do “twin-CMEs” always lead to large SEPs? (Group II) No, but almost al of them (90%) show enhancement in ACE/SIS measurements. 3) Are fast single CMEs (from western hemisphere) capable of leading to large SEPs? (Group III) 60% of them DO NOT lead to large SEPs.

  4. Problems with DSA 1) How thermal particles are extracted from the thermal pool? What is the injection efficiency? 2) DSA assumes the particles are test particle and ignores the effects of energetic particles on the shock structure. Numerical study of particle acceleration at shocks Test particle approach Hybrid code PIC approach Other approaches based on particle-wave interaction. Galinsky & Shevchenko, 2007

  5. Drury (1983)‏ Define p0 If Acceleration time scale The highest energy is decided by the available acceleration time scale. p0 is the highest accelerated momentum when the injection momentum is small. p0 is decided by the acceleration time scale.

  6. Wave amplification at a parallel shock Gordon et. al. (1999)‏ Doppler condition:

  7. – NLGC theory At a quasi-perp. shock, Alfven wave intensity goes to zero, so contribution of || cos() can be ignored. The major contribution comes from . Need a good theory of   = || /[1 + (|| / rl)2] Jokippi 1987 Simple QLT: Non-linear-Guiding-center: Matthaeus et al 2003 Zank, Li, et al 2004

  8. the Injection problem

  9. Anisotropy and the injection threshold diffusive shock acceleration assumes isotropic distribution f   = s / f v Diffusion tensor: Since , the anisotropy becomes For a nearly perpendicular shock

  10. Injection as a function of BN Zank, Li, et al, 2006 Evaluate injection threshold as a function of angle by assuming  =1 Although have a smaller acceleration time scale, quasi-perpendicular shocks require higher injection energies Remark: Isotropic assumption for diffusive shock acceleration may not be necessary.

  11. – NLGC theory At a quasi-perp. shock, Alfven wave intensity goes to zero, so contribution of || cos() can be ignored. The major contribution comes from . Need a good theory of   = || /[1 + (|| / rl)2] Simple QLT: Jokipii 1987 Non-linear-Guiding-center: Matthaeus et al 2003 Zank, et al 2004

  12. Maximum energy as function of time for an oblique shock

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