1. Roger Blandford KIPAC, Stanford with Paul Simeon and Noemie Globus
Acceleration of Cosmic Rays by Interstellar and Intergalactic Shock Fronts
Roger Blandford
KIPAC, Stanford
with Paul Simeon and Noemie Globus
14 viii 2018
VHEPU

2. Radio detection of UHECR Piotrowski PS4.4 JEM-EUSO
Haungs PS4.4
Radio detection of UHECR
Piotrowski PS4.4
JEM-EUSO
14 viii 2018
VHEPU
GeV TeV PeV EeV ZeV

3. Mixed Composition Model
CREAM
Seo et al
Allard PS2.3
Mixed Composition Model
ACE
Mewaldt et al
AMS
Kaskade
Grande
14 viii 2018
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4. UHECR Spectrum and Composition
Globus PS2.3
Dipole
GZK cutoff observed
Heavier nuclei at highest energies
14 viii 2018
VHEPU

5. Refutable Comprehensive Model Mostly Diffusive Shock Acceleration
Heliosphere to rich cluster accretion shocks
Scaling laws
Reflection as well as transmission
Injection of pre-existing population
Magnetic bootstrap
Propagation
Rigidity
Charge?
Background spectrum and CR-generated
Refutable
14 viii 2018
VHEPU

6. Schematic of Shock Acceleration Sites
Cluster Accretion Shock M~ 30
Filament/Circumgalactic
Shock M~3
Galactic Wind
Termination Shock M~10
SNR/OB M~100
Not to Scale!
14 viii 2018
VHEPU

7. Tycho SNR Magnetic amplification X-ray striations Currents or fields?
X-ray synchrotron emission at shock front by ~50TeV electrons
rL ~ 2x1015cm ~ 50 mas
Thermal emission by shocked gas
Magnetic amplification
X-ray striations
Currents or fields?
Lasagna or spaghetti?
Hughes
14 viii 2018
VHEPU

8. Cosmic Ray Protons Accelerated in SNR?
Pion decay signature of cosmic ray proton acceleration in the presence of molecular gas
Only observe in high density environments
W44
Yang PS3.1
CR from Star Clusters
George Miley
ECR ~1043J
Protons may escape
14 viii 2018
VHEPU

9. Galactic Wind Termination Shock
Driven by hot SNR and Cosmic Rays
Escape through buouyancy, Parker instabilities
Lwind ~ 10-3 Lgal
Shocks when momentum flux ~ PCGM
M uncertain
Highest energy particles escape upstream
Recchia PS3.1
CR-Driven Wind
14 viii 2018
VHEPU

10. Cluster Observations and Simulations
Perseus Cluster
14 viii 2018
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11. Intergalactic Shocks Cluster Accretion Shocks Filament Shocks
Skillman
2008
Cluster Accretion Shocks
10<M<100
Filament Shocks
3<M<10
Interior shocks
1<M<3
14 viii 2018
VHEPU

12. Cluster Accretion Shocks
Sgas/k
Measured entropy in outer parts of clusters is much greater than gas entropy after reionization
DS > 10 k?
Requires strong accretion shock
Arise in simulations
M can be as large as 100
A candidate site for UHECR acceleration
Adequate power
M-H nuclei 18 17 16 15
Simionescu et al
Perseus cluster 14 13 r r
Werner et al
14 viii 2018
VHEPU

13. DiffusiveShock Acceleration
Statistical (kinetic) approach
Distribution function – f(p,x,t)
Energy in bulk motion
Clouds, waves, shocks…
Stochastic energy gain
Fokker-Planck equation
Diffusion in momentum space
Wave scattering
l ~ rL, D ~ rL v/3
Self-excited by particles
L~D/u~Ea
CR pressure
Decelerates flow
Changes g
14 viii 2018
VHEPU

14. Magnetic Bootstrap Shocks also amplify B
SNR
P(E) / u2
GeV
TeV
PeV
0.1
Shock X E
GeV TeV PeV
Shocks also amplify B
Increases EMAX
Cosmic rays create their scatterers
Weibel B<<Bshock
Bell l<rL(PeV)
Resonant l~rL(PeV)
Firehose l>rL(PeV) …
X increases with E
14 viii 2018
VHEPU

15. In or out? Dimensionality Energy Escape Do not escape planar shock
Can escape cylindrical or spherical shock
Energy
mfp ~ E0.5-1
Only highest energy particles escape upstream
Most, lower energy particles held downstream
Expansion loss in SNR
Escape
Limited by instability?
eg Blasi
14 viii 2018
VHEPU

16. Scaling Laws Compromise average spectrum for M>>1
S(R) ~ R-0.3
Maximum Rigidity ~ u B R/c
Field coherent on scale of largest Larmor radius
rL ~p/ZeB
Transmitted Pressures
PCR ~ Pmag ~ r u2 /4
Rmax ~ 30 (Lshock/1034W)1/2 u81/2PV/c
14 viii 2018
VHEPU

17. Propagation Galactic propagation SNR accelerate to ~ 30 TV/c
MHD turbulence, wandering fields at higher energy
Alfven-limited propagation at lower energy
UCR(R) ~R-0.3 R-.35 ~ R-0.65
SNR accelerate to ~ 30 TV/c
GWTSR to ~ 1 PV/c
Anisotropy
Weak filaments accelerate GCR
to ~ ankle
Rich clusters re-accelerate GCR
to ~toenails
Propagation uninhibited at highest energies until Galaxy
Merten PS3.1
CR transport
Vittino PS3.1
Interstellar electrons
and positrons
Johannesson PS2.3
CR and Interstellar
Emission
14 viii 2018
VHEPU

18. Range and Luminosity Density
Allard
lIGM ~ 0.1 g cm-2
t ~ 100EeV(p,Fe)
Pairs>pions < 10EeV
Eternal < 1EeV
Acceleration depends on E/Z
Luminosity Density
L(GV/c)~10L(PV/c) ~ 100L (10EeV) ~ Lgal
14 viii 2018
VHEPU

19. Summary UHECR are energetic and luminous GCR from SNR etc to ~ 10 TeV
~0.1ZeV=1020eV; L~0.03 LGeVCR
GCR from SNR etc to ~ 10 TeV
Higher energy from G, CG, filamentary shocks
Acceleration faster than propagation
UHECR from cluster accretion shocks
Reacceleration of galactic cosmic rays?
10<M<100
Highest energy are M-H nuclei escaping upstream
Propagation faster than acceleration
14 viii 2018
VHEPU