Nicola Tomassetti

Origin of the Spectral Hardeningin Galactic Cosmic Rays

ECRS July 2012 Moscow

INFN Perugia

1. Hardening effectRemarkable change in slope above ~100 GeV/n

2. Discrepant hardeningDifferent elements (p, He…) exibith different spectral slopes

3. Another PAMELA anomaly?Sharp structures in p and He spectra at 100 GV (the dip & the break).

Spectral Features in Primary Cosmic Rays

CR data on primary nuclei indicate three remarkable features

NL-DSA concavity?Multi-source?

Could be a signature of DSA/SNRMalkov et al 2012 – Ohira et Ioka 2011

Likely “extrinsic”, e.g. from local source(Erlykin &Wolfendale Aph 2012)

To be confirmed experimentally

N. Tomassetti - INFN Perugia ECRS 2012 - Moscow [ 01 / 14 ]

“These data challenge the current paradigm of cosmic-ray acceleration in supernova remnants followed by diffusive propagation in the Galaxy”.

Adriani et al. Science 2011

“…We rather think that the SNR paradigm is in fact more complex than usually assumed in doing these claims, and that its consequences are not yet so well understood as sometimes people would like to believe”.

Blasi & Amato JCAP 2012

Spectral Features in Primary Cosmic Rays

N. Tomassetti - INFN Perugia ECRS 2012 - Moscow [ 02 / 14 ]

Pion decayInverse comptonBremsstrahlung

DGE

Isotropic EGB+ RIBPoint sources

Total

Fermi/GALPROP resultsInner Galaxy Halo

High-energy gamma-ray data are under(over)-predicted in the inner Galaxy (outer halo)

Cosmic-ray spectral variations??

Ackermann et al ApJ april 2012 [1202.4039]

N. Tomassetti - INFN Perugia ECRS 2012 - Moscow [ 03 / 14 ]

The CR/SNR Paradigm (and problems)

N. Tomassetti - INFN Perugia ECRS 2012 - Moscow 

EEk )(

DSA@SNRs: power-law source spectra (α~ 2.0 – 2.2)

QLT: power-law diffusion regime (δ~ 0.3 - 0.7)

Expected CR spectra at Earth (E>>GeV/n)

• Primary CR data: α+δ = 2.7 (Depending on the element)• Anisotropy data: δ < 0.3 α > 2.4? (Small diffusivity. Steep source spectra?)• Gamma-ray data: α < 2.3 δ > 0.4 ? (Still too hard for anisotropy)• Sec/Pri ratios: δ = 0.2 - 0.8 (Need of data at high energy)

Data say

Basic predictions

• Stocasticity (Blasi & Amato JCAP 2012)• Non-linear DSA acceleration (e.g. Caprioli JCAP 2012)• …

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The Magnetic Halo

HaloPropagation region

L ~

5 k

pc

2h ~ 200 pc

SNRsCosmic ray sources

CRsErratic motion in turbulent B-field

Free escape boundary

DiskContains SNRs and ISM matter

All CR propagation models assume the same turbulence spectrum in the whole halo same rigidity dependence for K(R) everywhere!

BUT…WHERE THE TURBULENCE COME FROM?

N. Tomassetti - INFN Perugia ECRS 2012 - Moscow 

The Magnetic Halo

The Magnetic Halo

INNER HALOSNRs are the source of turbulent motion

OUTER HALONo SNRs! Turbulence is driven by CRs themselves.

Large irregularitiessmall wave numberssoft turbulence spectrumhard diffusivity (small δ)

steeper diffusivity (large δ)

Erlykin & Wolfendale J.Phys.G 2002

A Two-Halo Model of CR Diffusion

NOT separable into space and energy terms!

N. Tomassetti - INFN Perugia ECRS 2012 - Moscow [ 08 / 14 ]

NT ApJ 715 L13 [astro-ph/1204.4492]

diffusion interactions sources0/ tN0)( LzN

A Two-Halo Model of CR Diffusion

NOT separable into space and energy terms!

Non-separability deviation from power-law

N. Tomassetti - INFN Perugia ECRS 2012 - Moscow [ 08 / 14 ]

NT ApJ 715 L13 [astro-ph/1204.4492]

Results for primary CR spectra

TeV hardening predicted in all CR nuclei spectra

N. Tomassetti - INFN Perugia ECRS 2012 - Moscow [ 09 / 14 ]

NT ApJ 715 L13 [astro-ph/1204.4492]

Results for secondary/primary ratios

Hardening effect for sec/pri ratios.Barely suggested by data.

Detecting a spectral hardening in the B/C ratio would be a signature for its diffusive origin.

B/C ratio

N. Tomassetti - INFN Perugia ECRS 2012 - Moscow [ 10 / 14 ]

Model implications in open problems of CR physics

This model: Anisotropy must flatten at high energyHigh energy anisotropy weakly E-dependent above E=TeV

This model: Sec/pri ratio must flatten at high energyB/C and pbar/p ratios seem to flatten at high energy

This model: CR spectra must harden CR spectral hardening observed at > 100 GeV/n

This model: spectra must be steeper in the outer haloDiffuse γ-ray spectra appear steeper in the outer halo

N. Tomassetti - INFN Perugia ECRS 2012 - Moscow [ 11 / 14 ]

Alpha Magnetic Spectrometer

AMS Hadronic TomographyAMS on orbit - from STS-134 to ISS

• H/He ratio VS rigidity up 1 TV.• Confirm or disprove the PAMELA structures (dip/ankles)• Give spectral indices, break rigidities, sharpness parameters.

• Spectral structures search in Z>2 nuclei (C, O, Si, Fe)• Sec/Pri ratio up to TeV/n energies (Li/C, B/C, F/Ne, pbar/p)• Other channels: e- / isotopes / gamma

N. Tomassetti - INFN Perugia ECRS 2012 - Moscow 

p/He ratio

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A simple discrimination scheme is as follows:(see also Vladimirov et al 2012 ApJ astro-ph/1108.1023)

need of precision

data:AMS

origin of theCR hardening

Prispectr

a

Secspectr

a

Pri/Sec

ratios

from nearby sources

Yes No No

from acceleration Yes Yes No

from propagation Yes Yes Yes

need of high energy

data:AMS

ThisModel

Thoudam et al 2012Zatsepin et al 2012Erlykin & W. 2011Yuan et al 2011Ptuskin et al 2011Biermann et al 2010…

Alpha Magnetic Spectrometer AMSAMS

AMS AMS

N. Tomassetti - INFN Perugia ECRS 2012 - Moscow [ 13 / 14 ]

Conclusions

if everybody does their job…

…new results and new understanding will soon arrive

N. Tomassetti - INFN Perugia ECRS 2012 - Moscow 

Physicists provide:

AMS provide

s:

Universe provides

:

data analysisand theory

rawdata

cosmic rays

Thank you

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