1. Cosmic-ray acceleration by forward and reverse shocks in young SNR
Martin Pohl
U-Potsdam and DESY Zeuthen
with Igor Telezhinsky and Vikram Dwarkadas

2. Modelling methods Gas hydro with semi-analytical acceleration
Gas hydro + CR acceleration and transport
Full account of gas, CRs, and MF
only plane-parallel shock, no transport
can include CR feedback
accurate CR transport
multiple shocks possible
CR feedback difficult
maybe at ICRC

3. Hydrodynamical profiles
Often assumed: Sedov phase Late time only!

4. Reality: dynamical evolution
Typically at least 2 shocks!
Acceleration everywhere, because

5. The method 1. Use flow profiles from hydrodynamical simulations
2. Solve CR transport equation for these flow profiles.
Advantage:
Accurate treatment of acceleration and transport
Consistent account of escape possible
Disadvantage:
No account for CR feedback (works for low CR pressure)

6. The method Transformation of spatial coordinate required
Diffusion coefficient can be coupled to MF profile
2 MF profiles used thus far
D: density scaling
P: pressure scaling
4. Multiple shocks can be accounted for
5. Self-consistent calculation of emission

7. Magnetic-field profiles
Examples of MF profiles for Type 1a
Magnetic-field amplification at shocks
M1: Caprioli et al. 2009
M2: constant amplification factor
More accurate MF transport forthcoming

8. Particle spectra Note the bumps in the spectra! Electrons Protons
Here density scaling of MF with 75 mG at forward shock
Note the bumps in the spectra!

9. It is critical to know where gas and MF sits
Emission (Type 1a)
It is critical to know where gas and MF sits

10. With more MF amplification
Electrons
Protons
Again density scaling, but relative to Caprioli model at forward shock

11. Emission (Type 1a)

12. Surface Brightness Maps
M M2
RADIO 1.4GHz
SY 3 keV
PD 1 TeV
IC 1 TeV

13. Conclusions Realistic fluid profiles are important for modeling
Reverse shock can dominate for young SNR
Adiabatic cooling/heating throughout the system
Complicated particle / emission spectra
Hard gamma-ray spectra don‘t always imply CR modification