TeV-PeV CR ANISOTROPY AS TeV-PeV CR ANISOTROPY AS A PROBE OF LOCAL - - PowerPoint PPT Presentation

• G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)

Gwenael Giacinti Gwenael Giacinti (MPIK Heidelberg) (MPIK Heidelberg) & John G. Kirk (MPIK Heidelberg) & John G. Kirk (MPIK Heidelberg)

TeV-PeV CR ANISOTROPY AS TeV-PeV CR ANISOTROPY AS A PROBE OF LOCAL A PROBE OF LOCAL INTERSTELLAR TURBULENCE INTERSTELLAR TURBULENCE

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)

~ 10 pc

B B

ξ ξ

grad grad f f0

Schwadron et al., Science (2014) --->

Origin of the CR anisotropy Origin of the CR anisotropy

… 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

→ In the direction of field lines → Amplitude

→ SHAPE

e.g. GG & Sigl (2012), Ahlers (2014), Malkov et al. (2010), Drury (2013), Desiati et al. (2013), Zhang et al. (2014), … (« small » amplitude)

• G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)

Dipole only ???

LARGE-SCALE LARGE-SCALE Cosmic-Ray Anisotropy Cosmic-Ray Anisotropy

… 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)

IceTop (400 TeV) IceTop (2 PeV) ~ 40o ~ 30o

Aartsen et al. (2013)

• 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

(gyrophase-averaged) θ θ

δΒ/Β<<1 δΒ/Β<<1

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

=>

α α

+ f0

NOT 1 – µ2 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

B B0 k k

<

CR CR (1) (1) (2) (2) MHD simulations of Cho & Lazarian (2002) :

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) (1) NARROW : NARROW : RF dominated by Lagrangian correlation time : (2) (2) BROAD : BROAD : Conservation of the adiabatic invariant

B B0

Chandran (2000) Chandran (2000) Yan & Lazarian Yan & Lazarian (2008) (2008)

• 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)

Can fit well the 400 TeV and the 2 PeV data ! Energy-dependence reproduced for fixed turbulence parameters

Case 3 : GS – Exponential & Broad RF Case 3 : GS – Exponential & Broad RF

• G. Giacinti et al. CR Anisotropy as a Probe of Interstellar Turbulence ICRC, Jul 14 (2017)

Can fit the 2 PeV data ! →

OK

Case 4 : Fast modes & Broad RF Case 4 : Fast modes & Broad RF

(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

(B) Large-scale CR Anisotropy = NEW Probe of (i) local ISMFs (Modes and their anisotropy in k-space) (ii) local CR transport properties

→ 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 ??

(A) Explanation for the data (IceCube/Top) (A) Explanation for the data (IceCube/Top)

The existing data already places constraints ! The existing data already places constraints !

• G. Giacinti CR Anisotropy as a Probe of Local Interstellar Turbulence ISSI, May 10 (2017)

First Eigenvalue and « Boundary layer » First Eigenvalue and « Boundary layer » A A B B E E F F D D C C

• 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 E E B B A A F F C C D D

Within the allowed parameter-space, the anisotropy is too wide with the narrow RF.