TeV-PeV CR ANISOTROPY AS TeV-PeV CR ANISOTROPY AS A PROBE OF LOCAL A PROBE OF LOCAL INTERSTELLAR TURBULENCE INTERSTELLAR TURBULENCE Gwenael Giacinti (MPIK Heidelberg) (MPIK Heidelberg) Gwenael Giacinti & John G. Kirk (MPIK Heidelberg) & John G. Kirk (MPIK Heidelberg) ApJ 835, 258 (2017) [arXiv:1610.06134] Summary: arXiv:1702.01001 G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)
Origin of the CR anisotropy Origin of the CR anisotropy B B grad f f 0 ξ grad ξ 0 ~ 10 pc Schwadron et al., Science (2014) ---> … and δΒ/Β << 1 G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)
Cosmic-Ray Anisotropy Cosmic-Ray Anisotropy large-scale small-scales + + (« small » amplitude) e.g. GG & Sigl (2012), → In the direction of field lines Ahlers (2014), → Amplitude Malkov et al. (2010), Drury (2013), → SHAPE Desiati et al. (2013), Zhang et al. (2014), … G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)
LARGE-SCALE Cosmic-Ray Anisotropy Cosmic-Ray Anisotropy LARGE-SCALE Dipole only ??? … or could it look like this : G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)
Observations (IceCube, IceTop) Observations (IceCube, IceTop) Aartsen et al. (2013) ~ 30 o IceTop (400 TeV) ~ 40 o IceTop (2 PeV) G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)
CR Anisotropy : Probe of turbulence CR Anisotropy : Probe of turbulence θ θ (gyrophase-averaged) δΒ/Β<<1 δΒ/Β<<1 0 0 Pitch-angle diffusion G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)
CR Anisotropy : Probe of turbulence CR Anisotropy : Probe of turbulence 0 α α => + f 0 NOT 1 – µ 2 in general ! G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)
Pitch-angle diffusion coefficient Pitch-angle diffusion coefficient => G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)
Alfven (and Slow) modes Alfven (and Slow) modes k k CR CR B 0 B 0 < (1) (1) (2) MHD simulations of Cho & Lazarian (2002) : (2) Fast magnetosonic modes Fast magnetosonic modes MHD simulations of Cho & Lazarian (2002) : Isotropic with G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)
Resonance functions (RF) Resonance functions (RF) (1) NARROW : NARROW : RF dominated by Lagrangian correlation time : (1) Chandran (2000) Chandran (2000) (2) BROAD : BROAD : Conservation of the adiabatic invariant (2) Yan & Lazarian Yan & Lazarian (2008) (2008) B 0 B 0 G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)
Case 1 : Fast modes & Narrow RF Case 1 : Fast modes & Narrow RF No visible dependence of the shape on CR energy RULED OUT ! G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)
Case 2 : GS – Heaviside & Broad RF Case 2 : GS – Heaviside & Broad RF G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)
Case 3 : GS – Exponential & Broad RF Case 3 : GS – Exponential & Broad RF Can fit well the 400 TeV and the 2 PeV data ! Energy-dependence reproduced for fixed turbulence parameters G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)
Case 4 : Fast modes & Broad RF Case 4 : Fast modes & Broad RF Can fit the 2 PeV data ! → OK (But cannot fit well the 400 TeV data) G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)
Conclusions and perspectives Conclusions and perspectives (A) Explanation for the data (IceCube/Top) (A) Explanation for the data (IceCube/Top) (B) Large-scale CR Anisotropy = NEW Probe of (i) local ISMFs (Modes and their anisotropy in k-space) (ii) local CR transport properties The existing data already places constraints ! The existing data already places constraints ! → Flattening in directions perpendicular to field lines, → Can fit the 2 PeV data with GS turbulence or fast modes with a moderately broad RF, → Constraints on RF : Narrow ones disfavoured, → Change in anisotropy shape with CR energy ? - - -> | k |-dependent anisotropy in power spectrum ?? G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)
First Eigenvalue and « Boundary layer » First Eigenvalue and « Boundary layer » C C A A B B D D E E F F G. Giacinti CR Anisotropy as a Probe of Local Interstellar Turbulence ISSI, May 10 (2017)
Half-width of the anisotropy Half-width of the anisotropy B B E E F F D D A A C C Within the allowed parameter-space, the anisotropy is too wide with the narrow RF . G. Giacinti CR Anisotropy as a Probe of Local Interstellar Turbulence ISSI, May 10 (2017)
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