Anomalies in Cosmic Ray Composition: Explanation Based on Mass to - PowerPoint PPT Presentation

Anomalies in Cosmic Ray Composition: Explanation Based on Mass to Charge Ratio Adrian Hanusch , Tatyana Liseykina, Mikhail Malkov Universität Rostock Institut für Physik 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 1 / 12

Hypothesis of CR origin acceleration by a 1 st order Fermi mechanism diffusive shock acceleration (DSA) • particles gain energy by crossing the shock front • scattering by magnetic perturbations • power-law spectrum f ( p ) ∼ p − q 3 r 4 with q = r − 1 = 1 − M − 2 supernova SN 1006 remnant X-ray Chandra image 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 2 / 12

Anomalies in CR composition Measurements M. Aguilar et al., PRL , 115(21):211101, (2015). � ∆ q ≈ 0 . 1 is in conflict with the DSA � EOM in terms of rigidity R = p c/Z e 1 d R dt = E ( r , t ) + R × B ( r , t ) 1 d r R dt = c � R 2 c � R 2 0 + R 2 0 + R 2 ◮ same phase-space trajectories for R ≫ R 0 = A m p c 2 /Z e 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 3 / 12

Content Anomalies in cosmic ray composition Scenarios Hybrid simulation Basics Simulation set-up Results Particle spectra Injection efficiency Proton-to-helium ratio Summary and Outlook 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 4 / 12

Anomalies in CR composition Scenarios 1. contribution from several SNRs with different p -He mixtures V. I. Zatsepin and N. V. Sokolskaya, Astron. Astrophys. 458, 5 (2006). 2. CR spallation in the ISM P. Blasi and E. Amato, J. Cosmol. Astropart. Phys. 01 (2012). 3. time-dependence of the shock evolution 3.1 effect of SNR environment Y. Ohira and K. Ioka, Astrophys. J. Lett. 729, L13+ (2011). 3.2 time-dependence of shock strength M. A. Malkov, P. H. Diamond, and R. Z. Sagdeev, PRL 108(8), 081104 (2012). 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 5 / 12

Anomalies in CR composition Scenarios 1. contribution from several SNRs with different p -He mixtures V. I. Zatsepin and N. V. Sokolskaya, Astron. Astrophys. 458, 5 (2006). → not testable 2. CR spallation in the ISM P. Blasi and E. Amato, J. Cosmol. Astropart. Phys. 01 (2012). 3. time-dependence of the shock evolution 3.1 effect of SNR environment Y. Ohira and K. Ioka, Astrophys. J. Lett. 729, L13+ (2011). 3.2 time-dependence of shock strength M. A. Malkov, P. H. Diamond, and R. Z. Sagdeev, PRL 108(8), 081104 (2012). 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 5 / 12

Anomalies in CR composition Scenarios 1. contribution from several SNRs with different p -He mixtures V. I. Zatsepin and N. V. Sokolskaya, Astron. Astrophys. 458, 5 (2006). → not testable 2. CR spallation in the ISM P. Blasi and E. Amato, J. Cosmol. Astropart. Phys. 01 (2012). → not sufficient for explaining the p /He ratio A. E. Vladimirov, G. Jóhannesson, I. V. Moskalenko, and T. A. Porter, Astrophys. J. 752, 68 (2012). 3. time-dependence of the shock evolution 3.1 effect of SNR environment Y. Ohira and K. Ioka, Astrophys. J. Lett. 729, L13+ (2011). 3.2 time-dependence of shock strength M. A. Malkov, P. H. Diamond, and R. Z. Sagdeev, PRL 108(8), 081104 (2012). 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 5 / 12

Anomalies in CR composition Scenarios 1. contribution from several SNRs with different p -He mixtures V. I. Zatsepin and N. V. Sokolskaya, Astron. Astrophys. 458, 5 (2006). → not testable 2. CR spallation in the ISM P. Blasi and E. Amato, J. Cosmol. Astropart. Phys. 01 (2012). → not sufficient for explaining the p /He ratio A. E. Vladimirov, G. Jóhannesson, I. V. Moskalenko, and T. A. Porter, Astrophys. J. 752, 68 (2012). 3. time-dependence of the shock evolution 3.1 effect of SNR environment Y. Ohira and K. Ioka, Astrophys. J. Lett. 729, L13+ (2011). → C/He and O/He ratios are independent of R 3.2 time-dependence of shock strength M. A. Malkov, P. H. Diamond, and R. Z. Sagdeev, PRL 108(8), 081104 (2012). 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 5 / 12

Anomalies in CR composition Mass-to-charge ratio assumption mass-to-charge dependence of • injection power law exponent: • 4 q ( M ) = 1 − M − 2 shock strength decreases with • time M. Aguilar et al., PRL , 115(21):211101, (2015). if He 2+ is injected more readily • C/He and O/He ratios are independent of R • at earlier times AMS-02 Collaboration, harder integrated spectra http://www.ams02.org/wp-content/uploads/2016/12/Final.pdf. (2016). ◮ ◮ fractions of different species can probe properties of CR accelerators 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 6 / 12

Hybrid simulation Basics ions determine the relevant scales electrons are treated as a massless fluid � � n e m d v e E + 1 dt = 0 = − e n e − ∇ p e + e n e η J c v e × B ions are treated kinetically (PIC) � � m i d v E + 1 d x dt = q i c v × B − η J dt = v non-relativistic • ∇ × B = 4 π low-frequency magnetostatic model: c J • 1 c ∂ t B = ∇ × E p e ∼ n γ e with γ e = 5 adiabatic relation for electron pressure: • 3 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 7 / 12

Hybrid simulation Simulation set-up 1D spatially, 3D velocity • super-alfvénic plasma flow • enters from the right B 0 = B 0 x • realistic composition: 10% • He 2+ in number density units: t inverse proton gyrofrequency 1 /ω c n upstream density n 0 − − x proton inertial length c/ω p B upstream magnetic − − v Alfvén velocity v A field B 0 − L x up to 17 · 10 3 c/ω p N α ∆ x = 0 . 2 c/ω p , ∆ t = 0 . 01 /v 0 , ppc = 100 , 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 8 / 12

Hybrid simulation Simulation set-up 1D spatially, 3D velocity • super-alfvénic plasma flow • enters from the right B 0 = B 0 x • realistic composition: 10% • He 2+ in number density units: t inverse proton gyrofrequency 1 /ω c n upstream density n 0 − − x proton inertial length c/ω p B upstream magnetic − − v Alfvén velocity v A field B 0 − L x up to 17 · 10 3 c/ω p N α ∆ x = 0 . 2 c/ω p , ∆ t = 0 . 01 /v 0 , ppc = 100 , 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 8 / 12

Results Particle spectra Energy distribution: v 0 = 15 v A , t = 1000 1/ ω c 10 1 f p (E) 10 0 f He (E) 10 -1 f(E) / arb. units 10 -2 10 -3 E 0 = 1 2 m p v 2 A 10 -4 10 -5 10 -6 10 -7 10 0 10 1 10 2 10 3 10 4 10 5 10 6 E / E 0 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 9 / 12

Results Particle spectra Energy distribution: v 0 = 15 v A , t = 1000 1/ ω c 10 1 f p (E) 10 0 f th (E) 10 -1 f(E) / arb. units f He (E) 10 -2 f th (E) 10 -3 E 0 = 1 2 m p v 2 A 10 -4 10 -5 T p = 39.26 T He = 170.08 10 -6 10 -7 10 0 10 1 10 2 10 3 10 4 10 5 10 6 E / E 0 thermal distribution • f th ( E ) ∝ E 1 / 2 exp( − E/T ) 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 9 / 12

Results Particle spectra Energy distribution: v 0 = 15 v A , t = 1000 1/ ω c 10 1 f p (E) 10 0 f th (E) 10 -1 f(E) / arb. units f pow (E) 10 -2 f He (E) f th (E) 10 -3 E 0 = 1 2 m p v 2 A f pow (E) 10 -4 10 -5 T p = 39.26 T He = 170.08 10 -6 10 -7 10 0 10 1 10 2 10 3 10 4 10 5 10 6 E / E 0 power-law with cut-off thermal distribution • • f pow ( E ) ∼ E − q exp( − E/E cut ) f th ( E ) ∝ E 1 / 2 exp( − E/T ) supra-thermal particles • 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 9 / 12

Results Injection efficiency definition of the injection efficiency f ( E inj ) η inj = with E inj from f pow ( E inj ) = f th ( E inj ) � ∞ f th ( E ) d E 0 Energy distribution: v 0 = 15 v A , t = 1000 1/ ω c 10 1 f p (E) 10 0 f th (E) 10 -1 f(E) / arb. units f pow (E) 10 -2 f He (E) 10 -3 f th (E) f pow (E) 10 -4 10 -5 T p = 39.26 T He = 170.08 10 -6 10 -7 10 0 10 1 10 2 10 3 10 4 10 5 10 6 E / E 0 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 10 / 12

Results Injection efficiency definition of the injection efficiency f ( E inj ) η inj = with E inj from f pow ( E inj ) = f th ( E inj ) � ∞ f th ( E ) d E 0 0.05 p + He 2+ agreement with theoretical injection e ffi ciency / % 0.04 • fi t prediction fi t 0.03 η inj ∼ M − 1 ln( M/M ∗ ) 0.02 at high M 0.01 M. A. Malkov, Phys. Rev. E 58, 4911, (1998). fit η ( M ) = a · ( M − b ) · M − c 0 • 0 10 20 30 40 50 M 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 10 / 12

Results Injection efficiency definition of the injection efficiency f ( E inj ) η inj = with E inj from f pow ( E inj ) = f th ( E inj ) � ∞ f th ( E ) d E 0 0.05 p + He 2+ agreement with theoretical injection e ffi ciency / % 0.04 • fi t prediction fi t 0.03 η inj ∼ M − 1 ln( M/M ∗ ) 0.02 at high M 0.01 M. A. Malkov, Phys. Rev. E 58, 4911, (1998). fit η ( M ) = a · ( M − b ) · M − c 0 • 0 10 20 30 40 50 M ◮ slight prevalence of He 2+ injection at high M ◮ proton injection dominant at low M shocks 15. 07. 2017 Anomalies in Cosmic Ray Composition | ICRC 2017 10 / 12