Cosmic Rays, Photons and Neutrinos

Cosmic Rays, Photons and Neutrinos Michael Kachelrieß NTNU, Trondheim []

Introduction Outline Plan of the lectures: Cosmic rays Galactic cosmic rays Basic observations Acceleration Supernova remnants Problems Extragalactic cosmic rays Transition Anisotropies and sources Nuclear composition CR secondaries: photons and neutrinos Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 2 / 30

Introduction Outline Milky Way globular clusters disc h = 300pc Sun 8 kpc gas/cr halo Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 3 / 30

Introduction Outline Milky Way globular clusters disc h = 300pc Sun 8 kpc gas/cr halo Larmor radius 1 pc = 3.1 10 18 cm R L = cp ZeB 100 pc 3µG B E Z 10 18 ev pp interaction: σ pp 50 mbarn mbarn = 10 27 cm 2 Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 3 / 30

Introduction Outline Milky Way globular clusters disc h = 300pc Sun 8 kpc gas/cr halo Larmor radius 1 pc = 3.1 10 18 cm R L = cp ZeB 100 pc 3µG B E Z 10 18 ev pp interaction: σ pp 50 mbarn mbarn = 10 27 cm 2 extragalactic scales: distance to Virgo: 18 Ṁpc observable universe: c/h0 4 Gpc Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 3 / 30

1910: Father Wulf measures ionizing radiation in Paris 80m: flux/2

300m: flux/2 80m: flux/2

Introduction History 1912: Victor Hess discovers cosmic rays The results are most easily explained by the assumption that radiation with very high penetrating power enters the atmosphere from above; the Sun can hardly be considered as the source. Hess and Kolhoerster s results: 80 excess ionization 60 40 20 0-10 1 2 3 4 5 6 7 8 9 altitude/1000m Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 5 / 30

Introduction Observational techniques What do we know 100 years later? solar modulation LHC Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 6 / 30

Introduction Observational techniques What do we know 100 years later? solar modulation only few bits of information? energy density ρ cr 0.8eV/cm 3 exponent α of dn/de 1/E α nuclear composition for E < 10 17 ev isotropic flux for E < 10 18 ev LHC Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 6 / 30

Introduction Observational techniques Observing gamma-rays or cosmic rays: GeV-TeV Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 7 / 30

Introduction Observational techniques Observing gamma-rays or cosmic rays: around TeV Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 7 / 30

Introduction Observational techniques Pierre Auger Observatory: Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 8 / 30

Introduction Observational techniques Three options for HE astronomy: High-energy photons: IACT s (HESS, MAGIC, Veritas) extremely successful new sources, extragal. backgrounds, evidence for hadronic accelerators, M87,... synergy with Fermi-LAT next generation experiment CTA on the way Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 9 / 30

Introduction Observational techniques Three options for HE astronomy: VHE photons: successful, but restricted to few Mpc 22 radio 20 18 log10(e/ev) 16 photon horizon γγ e + e CMB 14 IR 12 10 kpc 10kpc 100kpc Mpc 10Mpc 100Mpc Gpc Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 10 / 30

Introduction Observational techniques Three options for HE astronomy: VHE photons: successful, but restricted to few Mpc hadronic photons vs. synchrotron/compton photons Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 10 / 30

Introduction Observational techniques Three options for HE astronomy: astronomy with VHE photons restricted to few Mpc astronomy with HE neutrinos: smoking gun for hadrons but challenging large λν, but also large uncertainty δϑ > 1 small event numbers: < few/yr for PAO or ICECUBE identification of steady sources challenging without additional input Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 11 / 30

Introduction Observational techniques Three options for HE astronomy: astronomy with VHE photons restricted to few Mpc astronomy with HE neutrinos: Alternative: smoking gun for hadrons but challenging large λν, but also large uncertainty δϑ > 1 small event numbers: < few/yr for PAO or ICECUBE identification of steady sources challenging without additional input Astronomy with neutrinos possible? Astronomy with charged particles possible? Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 11 / 30

Introduction Observational techniques Three options for HE astronomy: 22 proton horizon 20 18 log10(e/ev) 16 photon horizon γγ e + e CMB 14 IR 12 10 kpc 10kpc 100kpc Mpc Virgo 10Mpc 100Mpc Gpc Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 12 / 30

Introduction Observational techniques Three options for HE astronomy: 22 proton horizon 20 18 log10(e/ev) 16 if UHECRs 14 are protons: deflections may be small photon horizon γγ e + e use 12 larger statistics of UHECRs well-suited horizon scale 10 kpc 10kpc 100kpc Mpc Virgo 10Mpc 100Mpc CMB IR Gpc Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 12 / 30

Introduction Basic observations Basic observations: Solar modulations Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 13 / 30

Introduction Basic observations Basic observations: Solar modulations Solar wind carries plasma solar rest frame: electric potential Φ Fish (t) low-energy particles cannot penetrate solar sytem Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 13 / 30

Introduction Basic observations Basic observations: Abundances at E/n = 5 GeV Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 14 / 30

Introduction Basic observations Basic observations: Abundances at E/n = 5 GeV Li, B and Ti groups strongly enriched Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 14 / 30

Introduction Basic observations Basic observations: Abundances at E/n = 5 GeV Li, B and Ti groups strongly enriched spallation product of CRs on gas B/C fixes residence time τ 10 7 yr Low energy CR make random walk Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 14 / 30

Introduction Basic observations Basic observations: Abundances at E/n = 5 GeV Li, B and Ti groups strongly enriched spallation product of CRs on gas B/C fixes residence time τ 10 7 yr Low energy CR make random walk diffuse in Galactic magnetic field constrains combination of D0 and h Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 14 / 30

Introduction Basic observations Diffusion in turbulent magnetic fields Galactic magnetic field: regular + turbulent component turbulent: fluctuations on scales l min AU to l max 150 pc CRs scatter mainly on field fluctuations B(k) with kr L 1. Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 15 / 30

Introduction Basic observations Diffusion in turbulent magnetic fields Galactic magnetic field: regular + turbulent component turbulent: fluctuations on scales l min AU to l max 150 pc CRs scatter mainly on field fluctuations B(k) with kr L 1. slope of power spectrum P(k) k α determines energy dependence of diffusion coefficient D(E) E β as β = 2 α: Kolmogorov α = 5/3 β = 1/3 Kraichnan α = 3/2 β = 1/2 Bohm α = 1 β = 1 Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 15 / 30

Introduction Basic observations Diffusion in turbulent magnetic fields Galactic magnetic field: regular + turbulent component turbulent: fluctuations on scales l min AU to l max 150 pc CRs scatter mainly on field fluctuations B(k) with kr L 1. slope of power spectrum P(k) k α determines energy dependence of diffusion coefficient D(E) E β as β = 2 α: Kolmogorov α = 5/3 β = 1/3 Kraichnan α = 3/2 β = 1/2 Bohm α = 1 β = 1 observed energy spectrum of primaries: injection: dn/de E α observed: dn/de E α β α = 3/2 and β = 1/2 simplest combination Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 15 / 30

Sources and acceleration Acceleration Fermi acceleration 1.order, diffusive shock acceleration: SNR, GRB 2.order: superbubbles, continuously? Electromagnetic induction: Pulsar, Kerr BH Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 16 / 30

Sources and acceleration Acceleration Electromagnetic induction: Pulsar, Kerr BH millisecond pulsar: E max ZB 0R 3 ω 2 c 2 8 10 20 ev Z B ( Ω 10 13 G 3000 s 1 ) 2 Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 17 / 30

Sources and acceleration Acceleration Electromagnetic induction: Pulsar, Kerr BH millisecond pulsar: E max ZB 0R 3 ω 2 c 2 8 10 20 ev Z B ( Ω 10 13 G 3000 s 1 but: gap, curvature radiation, plasma, Lmin : minimal power P dissipated by such an accelerator up to 10 20 ev? L min = U 2 /R > 10 37 W = 10 44 erg/s ) 2 Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 17 / 30

Sources and acceleration Acceleration Electromagnetic induction: Pulsar, Kerr BH millisecond pulsar: E max ZB 0R 3 ω 2 c 2 8 10 20 ev Z B ( Ω 10 13 G 3000 s 1 but: gap, curvature radiation, plasma, Lmin : minimal power P dissipated by such an accelerator up to 10 20 ev? L min = U 2 /R > 10 37 W = 10 44 erg/s [density of stationary UHECR sources n s < L/L 10 5 /Mpc 3 ] ) 2 Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 17 / 30

Sources and acceleration Acceleration Electromagnetic induction: Pulsar, Kerr BH millisecond pulsar: E max ZB 0R 3 ω 2 c 2 8 10 20 ev Z B ( Ω 10 13 G 3000 s 1 but: gap, curvature radiation, plasma, Lmin : minimal power P dissipated by such an accelerator up to 10 20 ev? L min = U 2 /R > 10 37 W = 10 44 erg/s [density of stationary UHECR sources n s < L/L 10 5 /Mpc 3 ] SMBH may be UHECR sources, pulsars mainly local e + e source ) 2 Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 17 / 30

Sources and acceleration Possible sources and the Hillas plot: log(b/g) 13 11 9 7 5 3 1 1 3 5 7 9 pulsars AU pc AGN cores GRB SNR kpc Galactic halo Mpc radio galaxies cluster 0 2 4 6 8 10 12 14 16 18 20 22 log(r/km) Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 18 / 30

Sources and acceleration Possible sources and the Hillas plot: log(b/g) 13 11 9 7 5 3 1 1 3 5 7 9 pulsars AU pc AGN cores GRB SNR kpc Galactic halo Mpc radio galaxies cluster 0 2 4 6 8 10 12 14 16 18 20 22 log(r/km) contains only size constraint; additionally age limitation: SNR, galaxy clusters energy losses: pulsars, AGN Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 18 / 30

Sources and acceleration Standard Galactic source: SNRs energetics: sources are SNRs: kinetic energy output of SNe: 10M ejected with v 5 10 8 cm/s every 30 yr L SN,kin 3 10 42 erg/s explains local energy density of CR ǫcr 1 ev/cm 3 for a escape time from disc τ esc 6 10 6 yr and efficiency 1% 1.order Fermi shock acceleration dn/de E γ with γ = 2.0 2.2 diffusion in GMF with D(E) τ 1 esc(e) E δ and δ 0.5 explains observed spectrum E 2.6 Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 19 / 30

Sources and acceleration Standard Galactic source: SNRs energetics: sources are SNRs: kinetic energy output of SNe: 10M ejected with v 5 10 8 cm/s every 30 yr L SN,kin 3 10 42 erg/s explains local energy density of CR ǫcr 1 ev/cm 3 for a escape time from disc τ esc 6 10 6 yr and efficiency 1% 1.order Fermi shock acceleration dn/de E γ with γ = 2.0 2.2 diffusion in GMF with D(E) τ 1 esc(e) E δ and δ 0.5 explains observed spectrum E 2.6 Problems: maximal energy E max too low anisotropy too large (?) Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 19 / 30

Sources and acceleration 1.order Fermi acceleration 2.nd order Fermi acceleration consider CR with initial energy E 1 scattering at a cloud moving with velocity V : E p 2 2 θ θ 1 2 V E p 1 1 Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 20 / 30

Sources and acceleration 1.order Fermi acceleration Energy gain ξ (E 2 E 1 )/E 1? Lorentz transformation 1: lab (unprimed) cloud (primed) E 1 = γe 1 (1 β cos ϑ 1 ) where β = V/c and γ = 1/ 1 β 2 Lorentz transformation 2: cloud lab E 2 = γe 2(1 + β cos ϑ 2) scattering off magnetic irregularities is collisionless, the cloud is very massive E 2 = E 1 Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 21 / 30

Sources and acceleration 1.order Fermi acceleration Energy gain ξ (E 2 E 1 )/E 1? E 2 = E 1 : Lorentz transformation 1: lab cloud E 1 = γe 1 (1 β cos ϑ 1 ) }{{} where β = V/c and γ = 1/ 1 β 2 Lorentz transformation 2: cloud lab E 2 = γe 2(1 + β cos ϑ 2) ξ = E 2 E 1 E 1 = 1 β cos ϑ 1 + β cos ϑ 2 β2 cos ϑ 1 cos ϑ 2 1 β 2 1. we need average values of cos ϑ 1 and cos ϑ 2 : Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 22 / 30

Sources and acceleration 1.order Fermi acceleration Assume: CR scatters off magnetic irregularities many times in cloud its direction is randomized, cos ϑ 2 = 0. collision rate CR cloud: proportional to their relative velocity (v V cos ϑ 1 ): for ultrarelativistic particles, v = c, dn dω 1 (1 β cos ϑ 1 ), and we obtain cos ϑ 1 = dn dn cos ϑ 1 dω 1 / dω 1 = β dω 1 dω 1 3 Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 23 / 30

Sources and acceleration 1.order Fermi acceleration Energy gain ξ for 2.nd order Fermi: Plugging cos ϑ 2 = 0 and cos ϑ 1 = β 3 since β 1. ξ β 2 > 0 energy gain ξ = 1 + β2 /3 1 β 2 1 4 3 β2 into formula for ξ gives O(ξ) = β 2, because β 1: average energy gain is very small ξ depends on drift velocity of clouds Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 24 / 30

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Sources and acceleration Diffusive shock acceleration Diffusive shock acceleration consider CR with initial energy E 1 scattering at a shock moving with velocity V s : E 1 V p θ 1 E 1 V s E 1 E 1 V p E 2 shock E 2 θ 2 E 2 E 2 Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 26 / 30

Sources and acceleration Diffusive shock acceleration same discussion, but now different angular averages: projection of istropic flux on planar shock: dn d cos ϑ 1 = thus cos ϑ 1 = 2 3 and cos ϑ 2 = 2 3 { 2 cos ϑ1 cos ϑ 1 < 0 0 cos ϑ 1 > 0 ξ 4 3 β = 4 3 (u 1 u 2 ) + ξ β: efficient + test particle approximation + strong shock: universal spectrum dn/de E 2 Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 27 / 30

Sources and acceleration Diffusive shock acceleration Maximal energy of SNR: Lagage-Cesarsky limit acceleration rate β acc = de dt = 3Ev2 sh acc ζd(e), ζ 8 20 Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 28 / 30

Sources and acceleration Diffusive shock acceleration Maximal energy of SNR: Lagage-Cesarsky limit acceleration rate β acc = de dt = 3Ev2 sh acc ζd(e), ζ 8 20 assume Bohm diffusion D(E) = cr L /3 E and B µg Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 28 / 30

Sources and acceleration Diffusive shock acceleration Maximal energy of SNR: Lagage-Cesarsky limit acceleration rate β acc = de dt = 3Ev2 sh acc ζd(e), ζ 8 20 assume Bohm diffusion D(E) = cr L /3 E and B µg E max 10 13 10 14 ev Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 28 / 30

Sources and acceleration Diffusive shock acceleration Maximal energy of SNR: [Bell, Luzcek 02, Bell 04 ] (resonant) coupling CR Alfven waves Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 29 / 30

Sources and acceleration Diffusive shock acceleration Maximal energy of SNR: [Bell, Luzcek 02, Bell 04 ] (resonant) coupling CR Alfven waves non-linear non-resonant magnetic field amplification Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 29 / 30

Sources and acceleration Diffusive shock acceleration Maximal energy of SNR: [Bell, Luzcek 02, Bell 04 ] (resonant) coupling CR Alfven waves non-linear non-resonant magnetic field amplification observational evidence for B 0.1 1 mg in young SNR rims Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 29 / 30

Sources and acceleration Diffusive shock acceleration SNR RX J1713.7-3946 changes on δt 1 yr imply B 1mG Michael Kachelrieß (NTNU Trondheim) Cosmic Rays NORDITA School 2013 30 / 30