Transcript Diapositiva 1

Origin of the Spectral Hardening
in Galactic Cosmic Rays
Nicola Tomassetti
INFN Perugia
ECRS July 2012 Moscow
Spectral Features in Primary Cosmic Rays
CR data on primary nuclei indicate three remarkable features
1. Hardening effect
Remarkable change in slope above ~100 GeV/n
NL-DSA concavity?
Multi-source?
2. Discrepant hardening
Different elements (p, He…) exibith different spectral slopes
Could be a signature of DSA/SNR
Malkov et al 2012 – Ohira et Ioka 2011
3. Another PAMELA anomaly?
Sharp structures in p and He spectra
at 100 GV (the dip & the break).
Likely “extrinsic”, e.g. from local source
(Erlykin &Wolfendale Aph 2012)
To be confirmed experimentally
N. Tomassetti - INFN Perugia
[ 01 / 14 ]
ECRS 2012 - Moscow
Spectral Features in Primary Cosmic Rays
“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
N. Tomassetti - INFN Perugia
[ 02 / 14 ]
ECRS 2012 - Moscow
Fermi/GALPROP results
Ackermann et al ApJ april 2012 [1202.4039]
Inner Galaxy
Pion decay
Inverse compton
Bremsstrahlung
Halo
DGE
Total
Isotropic EGB+ RIB
Point sources
N. Tomassetti - INFN Perugia
High-energy gamma-ray data are
under(over)-predicted in the inner
Galaxy (outer halo)
Cosmic-ray spectral variations??
[ 03 / 14 ]
ECRS 2012 - Moscow
The CR/SNR Paradigm (and problems)
Basic predictions
Q(E) » E
-a
k ( E)  E
f (E) » E
DSA@SNRs: power-law source spectra (α~ 2.0 – 2.2)
QLT: power-law diffusion regime (δ~ 0.3 - 0.7)
-(n +d )
Expected CR spectra at Earth (E>>GeV/n)
Data say
•
•
•
•
Primary CR data: α+δ = 2.7
Anisotropy data: δ < 0.3  α > 2.4?
Gamma-ray data: α < 2.3  δ > 0.4 ?
Sec/Pri ratios: δ = 0.2 - 0.8
(Depending on the element)
(Small diffusivity. Steep source spectra?)
(Still too hard for anisotropy)
(Need of data at high energy)
• Stocasticity (Blasi & Amato JCAP 2012)
• Non-linear DSA acceleration (e.g. Caprioli JCAP 2012)
• …
N. Tomassetti - INFN Perugia
[ 04 / 14 ]
ECRS 2012 - Moscow
The Magnetic Halo
Halo
Propagation region
L ~ 5 kpc
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?
Disk
Contains SNRs and ISM matter
2h ~ 200 pc
SNRs
Cosmic ray sources
K(R)µ Rd
CRs
Erratic motion in turbulent B-field
Free escape boundary
N. Tomassetti - INFN Perugia
ECRS 2012 - Moscow
The Magnetic Halo
The Magnetic Halo
Erlykin & Wolfendale J.Phys.G 2002
 Large irregularities
small wave numbers
soft turbulence spectrum
INNER HALO
SNRs are the source of turbulent motion hard diffusivity (small δ)
OUTER HALO
No SNRs! Turbulence is driven by CRs themselves.
 steeper diffusivity (large δ)
A Two-Halo Model of CR Diffusion
NT ApJ 715 L13 [astro-ph/1204.4492]
ì
ï k0 b Rd
K(z, R) = í
d +D
ïî k0 b R
d » 1/ 3
D » 0.55
(inner - halo)
(outer - halo)
NOT separable into space and energy terms!
diffusion
interactions
sources
K(z, R) ¹ f (z)× k(R)
N / t  0
N ( z   L)  0
N. Tomassetti - INFN Perugia
[ 08 / 14 ]
ECRS 2012 - Moscow
A Two-Halo Model of CR Diffusion
NT ApJ 715 L13 [astro-ph/1204.4492]
ì
ï k0 b Rd
K(z, R) = í
d +D
ïî k0 b R
(inner - halo)
(outer - halo)
NOT separable into space and energy terms!
d » 1/ 3
D » 0.55
K(z, R) ¹ f (z)× k(R)
Non-separability  deviation from power-law
N. Tomassetti - INFN Perugia
[ 08 / 14 ]
ECRS 2012 - Moscow
Results for primary CR spectra
NT ApJ 715 L13 [astro-ph/1204.4492]
TeV hardening predicted in all CR nuclei spectra
N. Tomassetti - INFN Perugia
[ 09 / 14 ]
ECRS 2012 - Moscow
Results for secondary/primary ratios
B/C ratio
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.
N. Tomassetti - INFN Perugia
[ 10 / 14 ]
ECRS 2012 - Moscow
Model implications in open problems of CR physics
CR spectral hardening observed at > 100 GeV/n
This model: CR spectra must harden
High energy anisotropy weakly E-dependent above E=TeV
This model: Anisotropy must flatten at high energy
B/C and pbar/p ratios seem to flatten at high energy
This model: Sec/pri ratio must flatten at high energy
Diffuse γ-ray spectra appear steeper in the outer halo
This model: spectra must be steeper in the outer halo
N. Tomassetti - INFN Perugia
[ 11 / 14 ]
ECRS 2012 - Moscow
Alpha Magnetic Spectrometer
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•
•
H/He ratio VS rigidity up 1 TV.
Confirm or disprove the PAMELA structures (dip/ankles)
Give spectral indices, break rigidities, sharpness parameters.
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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
AMS on orbit - from STS-134 to ISS
AMS Hadronic Tomography
p/He ratio
N. Tomassetti - INFN Perugia
[ 12 / 14 ]
ECRS 2012 - Moscow
Alpha Magnetic Spectrometer
AMS
A simple discrimination scheme is as follows:
AMS
(see also Vladimirov et al 2012 ApJ astro-ph/1108.1023)
Thoudam et al 2012
Zatsepin et al 2012
Erlykin & W. 2011
Yuan et al 2011
Ptuskin et al 2011
Biermann et al 2010
…
origin of the
CR hardening
Pri
Sec
Pri/Sec
spectra spectra ratios
from nearby sources
Yes
No
No
from acceleration
Yes
Yes
No
from propagation
Yes
Yes
Yes
This
Model
need of
precision
data:
AMS
N. Tomassetti - INFN Perugia
[ 13 / 14 ]
need of
high energy
data:
AMS
ECRS 2012 - Moscow
Conclusions
if everybody does their job…
Physicists
provide:
AMS
provides:
Universe
provides:
data analysis
and theory
raw
data
cosmic
rays
…new results and new understanding will soon arrive
Thank you
N. Tomassetti - INFN Perugia
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ECRS 2012 - Moscow