Stochastic Electron Acceleration in Shell-Type Supernova Remnants

1. Stochastic Electron Acceleration in Shell-Type Supernova Remnants Siming Liu Los Alamos National Laboratory In Collaboration with Zhonghui Fan, Christopher L. Fryer, Jianmin Wang, and Hui Li

2. Challenges to the Leptonic Models 1 TeV spectrum too narrow: Background photon? Porter et al. Tanaka et al.

3. Uchiyama et al. 2007 2 Weak B field: Variability Challenges to the Leptonic Models Tanaka et al.

4. A New Paradigm for Collisionless Shocks Lee et al. 1994

5. Speed Profiles in the Downstream vA<<U

6. Turbulence spectrum

7. Electron Acceleration by Fast Mode Waves

8. Spectral Fit to SNR RX J1713.7-3946

9. Kelvin-Helmholtz Instability? No Thermal X-rays The Nature of the SNR Shock

10. Nonthermal Electron Energy Thermal Energy Acceleration Efficiency Energy equipartition between B and nonthermal electrons

11. X-ray Variability Scattering Mean Free path Filament Width Diffusion Time: 0.93 yr Uchiyama et al. 2007

12. Conclusions Hadronic model faces several challenges in accounting for the broadband spectrum of shell-type supernova remnants Leptonic models need a gradual high energy cutoff Stochastic electron acceleration by fast mode waves in the downstream of collisionless shocks can produce the required electron distribution with reasonable model parameters. Hard X-ray and gamma-ray observations can distinguish these models

13. Observations HESS

14. No thermal X-rays Egret upper limit 1 Suppression of Electron Acceleration 4 Hard Spectrum with p<2.0 2 High Energy & 3 Density Requirement Challenges to the Hadronic Models SNR RX J1713.7-3946 Tanaka et al.

15. 5 B Field Amplification Challenges to the Hadronic Models Tanaka et al.

16. Challenges to the Hadronic Models 6 Lack of Correlation between TeV and Cloud Distribution: Plaga

17. Acceleration Time

18. SNR RX J0852.0-4622 and Cas A (Preliminary)