Cosmic ray accelerationand transport from MeVenergies to the knee

Vladimir Ptuskin

IZMIRAN, RussiaUniversity of Maryland, USA

Paris, November 13 – 14, 2014

E-2.7

direct measurements of interstellarCR spectra at low energies

Voyager 1 at the edge of interstellar space

after E. Stone 2013

energy, MeV/nuc100 101 102 103 104 105

parti

cle

/(m2 s

ec s

r MeV

/nuc

)10-5

10-4

10-3

10-2

10-1

100

101

102

103

low energies:Voyager 1Stone et al. 2013

high energies:BESSPamelaSparvoli et al 2012

HHe

launched in 1977, 70 kb, 22 w

M51

Jcr(E) = Qcr(E)×Te(E)

sourcepower

confinement time of CR in the Galaxy;~ 108 yr at 1 GeV

~ 15% of SN kinetic energy transfer to cosmic raysGinzburg & Syrovatsky 1964

-1snν = (30 yr)

cosmic ray intensity

traversed matter thickness ~ 12 g/cm2 at 1 GeV/nuc(surface gas density of galactic disk ~ 2.5 10-3 g/cm2)

E-2.7 E-2.2 E-0.5

basic empirical diffusion modelGinzburg & Ptuskin 1976, Berezinskii et al. 1990, Strong & Moskalenko 1998 (GALPROP),Donato et al 2002, Ptuskin et al. 2006, Strong et al. 2007, Vladimirov et al. 2010, Bernardo et al. 2010,Maurin et al 2010, Putze et al 2010, Trotta et al 2011

28 2 at~ 3 10 cm / s 1 GeV/n

1 pc

D

l

empirical diffusion coefficient

H = 4 kpc, R = 20 kpc

diffusion mean free path

NGC4631

Jones et al 2001

rg = 1/k - resonance condition2

2

v3

g tot

res

r BDB

cosmic ray particles are strongly magnetized but large-scale random magnetic field (Lmax ~ 100 pc) makes diffusion close to isotropic

mechanism of cosmic ray diffusion

spectrum of turbulence:

2 ( )reskres

B w k dk

Jokipii 1966, …

spectrum of turbulence

regimes of cosmic ray diffusion

Kolmogorov spectrum: D ~ vR1/3 + reacceleration- may be valid up to 1017Z eV- source spectrum R-2.4 – too soft to be produced in SNRs

(but dispersion of SNR parameters may help)- anisotropy – acceptable- peak of B/C ratio at 1 GeV/n – explained by distributed reacceleration- underpredicts antiproton flux below few GeV- in contradiction with theory of MHD turbulence (wave distribution in k-space)- contradiction to radio-astronomical data ? (too many secondary leptons)

Kraichnan spectrum: D ~ vR1/2 +wave damping- may be valid up to 1016Z eV only- source spectrum R-2.2 – consistent with shock acceleration in SNRs- anisotropy – too high- peak of B/C ratio at 1 GeV/n – explained by turbulence dissipation on CR- B/C ratio at V1 energies is too high- not in contradiction with theory of MHD turbulence –

1 1.1

27 2

10.552

v~ 10 cm / ,

(3 1) / 2 2.7, at 2.1

~ ~ ~

s

s

cr p p

s s

ef

p

B p pD sq Zm c Zm c

H p pXD Zm c Z

diffusion-convection model: galactic wind driven by CR

Zirakashvili et al. 1996, 2002, 2005, VP et al. 1997, 2000,

uinf = 500km/sRsh = 300 kpc

Ipavich 1975, Breitschwerdt et al. 1991, 1993, Everett et al.2008, 2010

+ cosmic ray streaming instabilitywith nonlinear saturation

CR scale height is larger then thescale height of thermal gas. CR pressuregradient drives the wind.Hef(p/Z)

sh shu R> 10

D(p)

, s-γs

σ + 2J ~ p γ = = 2σ -1

shmax sh

uE 0.3 Ze B R

c

- D(р) should be anomalously small both upstream and downstream; CR streaming creates turbulence in shock precursor

Bell 1978; Lagage & Cesarsky 1983; McKenzie & Vőlk 1982 …

diffusive shock accelerationFermi 1949, Krymsky 1977, Bell 1978, …

“Bohm” limit DB=vrg/3:

Emax,ism = 1013…1014 Z eV

compression ratio = 4

-condition of CRaccelerationand confinement

for Bism = 5 10-6 G

for testparticles !

~ Bsht-1/5 at Sedov stage

- strong cosmic-ray streaming instability givesin young SNR Bell & Lucek 2000, Bell 2004

Pelletier et al 2006; Amato & Blasi 2006; Zirkashvili & VP 2008; Vladimirov et al 2009; Gargate & Spitkovsky 2011

- wave dissipation in shock precursor leads torapid decrease of and Emax with time

VP & Zirakashvili 2003- finate Va leads to steeper CR spectrum

abandonment of interstellar Bohm limit hypotheses;D = DB,ism

δB

ismδB B

t = 103 yrAlfv. driftdownstream

Jxp2

under extreme conditions (SN Ib/c, e.g. SN1998 bw)

Emax ~ 1017Z (ush/3×104 km/s)2 Mej1/3n1/6 eV

Bmax ~ 10-3 (ush/3×104 km/s)n1/2 Gconfirmed by X-ray observations of young SNRsSN 1006, Cas A, Tycho, RCW 86, Kepler, RX J1713.7-3946, Vela Jr., G1.9+0.3

B2/8π = 0.035 ρu2 /2 Voelk et al. 2005

1 ,1

2 ,2

a

a

u Vu V

SN 1006

numerical simulationsof particle accelerationand radiation in SNR

radio polarization in red (VLA),X-rays in green (CHANDRA),optical in blue (HST)

Cas A

Zirakashvili et al 2014

Zirakashvili & VP 2012

Berezhko et al. 1994-2006, Kang & Jones 2006Zirakashvili & VP 2012,semianalytic models Blasi et al.(2005), Ellison et al. (2010) )

calculated spectrum ofGalactic cosmic rays: acceleration in SNRs,transport in interstellarmagnetic fields, D~R0.54

data from HEAO 3, AMS, BESS TeV, ATIC 2,TRACER experiments

data from ATIC 1/2, Sokol, JACEE, Tibet, HEGRA,Tunka, KASCADE, HiRes and Auger experiments

interstellar spectrum ofall particles

solar modulation

extragalacticcomponent

«knee» is formed atthe beginning of Sedov stage

VP, Zirakashvili, Seo 2010

JxE2.75

source spectra produced by SNRs

15 1/6 -2/3knee sn,51 ej

•15 -1

knee sn,51 -5 w,6 ej

E Z = 1.1×10 W n M eV,

E c Z = 8.4×10 W M u M eV

44 ( ) /sn sncp p

protons

Berezhnev et al. 2012

structure above the knee

different types of nuclei, Eknee ~ Zdifferent types of SNtransition to extragalactic component

knee and beyond p,He knee 2nd knee

JxE3

p

He

Fe

Kampert 2013

JxE2.7

spectra of p and He are different

hardening above 200 GeV/nucleonconcave source spectrumsuperposition of sourcesnew source Zatsepin & Sokolskaya 2006reacceleration in local bubble Erlykin & Wolfendale 2011streeming instability below 200 GV Blasi et al. 2012

shock goes through material enriched in He:- helium wind VP et al. 2010, - bubble Ohira & Ioka 2011effect of injection Malkov et al 2011

features to explain:

both featurescontribution of reversed SNR shock VP et al 2013

p He

BUT !preliminaryAMS-02data do notshow spectralfeatures

positrons in cosmic rays

GALPROP calculations Cholis, Hooper 2014H = 4 kpcD = 2.95 1028v(R/3 GV)0.43 cm2/sVa = 10 km/s

pulasar origin Harding, Ramaty 1987, Aharonian et al. 1995, Hooper et al. 2008, Malyshev et al. 2009e+ production and acceleration in shell SNRs Blasi 2009, Berezhko, Ksenofontov 2013reverse shock in radioactive ejecta Ellison et al 1990, Zirakashvili, Aharonian 2011

annihilation and decay of dark matter Tylka 1989, Fan et al 2011

AMS-02 upto 500 GeV now

data:

Lallerment et al 2003

large-scale anisotropy

Conclusions

Cosmic ray origin scenario where supernova remnants serve as principle accelerators of cosmic rays in the Galaxy is strongly confirmed by recent numerical simulations.

Diffusion model provides reasonably good description of cosmic ray propagation in the Galaxy even under simplified assumptions on cosmic ray transport coefficients and geometry of propagation region (e.g. as included in GALPROP code). Energy dependence of diffusion is still uncertain.

High-accuracy measurements indicate deviations of cosmic ray spectra from plain power laws below the knee. If confirmed, it requires refining models of cosmic ray acceleration and propagation.