... and a few words about Cosmic Rays and Climate CRs and Climate - PowerPoint PPT Presentation

Vulcano 2010 Inhomogeneity in the SN Remnant Distribution as the Origin of the PAMELA Anomaly, and the B/C ratio (i.e., a mundane solution to PAMELA, while abiding to stringent CR constraints) Nir J. Shaviv (Hebrew U.) with Tsvi Piran (Hebrew U.), Ehud Nakar (TAU) & David Binyamin (Hebrew U.) ... and a few words about Cosmic Rays and Climate

• CRs and Climate • Solar activity and Climate

Forbush decreases • Carefully select Forbush decreases which large atmospheric ionization effect AERONET SSM/I MODIS ISCCP 1.35 0.365 0.335 5 0.092 0.330 0.360 1.30 0 Aangstroem 340-440nm 0.090 0.325 Liquid Water CF 0.355 CWC (kg/m 2 ) 1.25 CLIMAX (%) Low IR CF -5 0.320 0.088 0.350 1.20 0.315 -10 0.345 0.086 1.15 0.310 -15 0.340 1.10 0.084 -15 -10 -5 0 5 10 15 20 -15 -10 -5 0 5 10 15 20 -15 -10 -5 0 5 10 15 20 -15 -10 -5 0 5 10 15 20 days days days days 5 strongest forbush decreases (1987-2007) Svensmark et al. GRL 2009

Experimental Results

Cloud Experiment @ CERN • Positive Results soon to come! scintillation counter roof (GCR monitor) gas & aerosol systems cooling /temperature control liquid FC cryogenics synthetic air/ argon cooling UV illumination water vapour video camera mixing inspection chamber field cage voltage aerosols in situ analysers trace gases CCD cameras Mie scattering detector ice particle lasers beam detector retractable telescope aerosol /trace probe gas analysers refractive index gas thermometer temperature condensation particle & pressure counters (CPC) differential mobility particle sizers (DMPS) trace gas analysers mass piston control piston vacuum spectrometers system actuator system ion mobility spectrometers expansion system Kirkby et al. external analysers Fig. 6: The CLOUD experiment, showing the 0.5m cloud

Sea Level Variations Solar Sea Level Flux change rate Shaviv, JGR 2008

Synopsis ❖ The Standard Picture of CR Acceleration & Diffusion ❖ The PAMELA anomaly ❖ New Type of sources?? ❖ A SN Remnant Solution: ✴ Distribution of SNe ✴ Implications (e.g., B/C)

Standard View • Electrons and Protons are mostly accelerated by supernova/ C, p, e- spectrum at source interstellar medium faster diffusion (ISM) shocks. • C, p, e- spectrum in galaxy Pairs are produced by the protons interacting with the ISM B, e+ e- spectrum in galaxy • Positron / Electron ratio should decrease with energy! EVEN faster diffusion

These models fit the data well Typical parameter values D(E>E 0 ) = D 0 (E/E 0 ) ! " D 0 = 3-5 ! 10 28 cm 2 /s E 0 ~ 3 GeV ! = 0.3-0.6 l H =2-4 kpc

PAMELA results:

1 st Type of Solutions: Astrophysical Sources of Pairs: Pulsars

2 nd Type of Solutions: Decay of exotic particles (WIMPs)

Source distribution: Most SNe occur in the spiral arms • In the Milky Way: Almost all SNe are non-Type Ia, and occur where almost all star formation takes place: In the Spiral Arms • Meteorites: Show that density changes by a factor of > 2.5 • Deconvolved Synchrotron: Shows arm to inter-arm ratio of ~ 3

3rd Type of Solution: Source Distribution 0.5 1.0 1.5 2.0 60 03 02 01 00 DECLINATION (B1950) 59 59 58 57 56 55 NGC6946 54 20 34 15 00 33 45 30 RIGHT ASCENSION (B1950) Lacey & Duric 2003

Meteoritic and Terrestrial Evidence Shaviv & Veizer 2003

So? • If CRs primarily come from the spiral arms, it takes them time! • Along the way, electrons cool though Synchrotron & Compton (on CMB, IR background and starlight). • Above some energy, they don’t have enough time to reach us.

So?

This means that... • Above E b ~ 20 GeV, the electrons will start cooling. • Positrons however, form along the way from proton-ISM interactions, therefore the positron/electron ratio will increase

• Primary electrons cool and disappear before reaching earth • Secondary electrons/positrons form nearer and can reach earth before cooling

What does it mean? • p, e- spectrum at source Electrons from Sprial faster diffusion arms above ~ 20 GeV out of the galaxy! cool (synchrotron and inverse-Compton) p spectrum in galaxy before reaching the solar system! e+ e- spectrum in galaxy • Protons do not cool, so positron production near us does not care (too much) about cooling. e - s p e c t r u m i n g a l a x y

What does it mean? • p, e- spectrum at source Electrons from Sprial faster diffusion arms above ~ 20 GeV out of the galaxy! cool (synchrotron and inverse-Compton) p spectrum in galaxy before reaching the solar system! e+ e- spectrum in galaxy • Protons do not cool, so positron production near us does not care (too much) about cooling. e - s p e c t r u m i n g a l a x y

Monte Carlo Model

Results

e + /(e + +e - ) ratio and e - spectrum

e + /(e + +e - ) ratio and e - spectrum A comaprison with Pamela/Fermi/ HESS data ? Contribution from nearby KNOWN young SNRs: Geminga, Monogem, Vela LoopI and Cygnus Loop

e + /(e + +e - ) ratio and e - spectrum Exact CR diffusivity effects high E behavior (effect of singular SNRs) Contribution from nearby KNOWN young SNRs: Geminga, Monogem, Vela LoopI and Cygnus Loop

e + /(e + +e - ) ratio and e - spectrum Break Preliminary results (Bruno, here) are consistent with a spectral break at ~50 GeV This is naturally interpreted as the contribution from disk +local SNR

Does this disturbe the protons? Break due to the solar wind • Arm + non-truncated disk - dotted line • Arm + truncated disk - dashed line • Arm + truncated disk + nearby sources - full line • Nearby sources - dot-dashed line

More detailed modeling • All the galaxy. • Allowing arm dynamics (important for B/C): ★ CR age at high energy: Diffusion time (smaller for larger E) ★ CR age at low energies: Time from last arm passage (t p ~ few 10^7 yr)

More detailed modeling • All the galaxy. • Allowing arm dynamics (important for B/C): ★ CR age at high energy: Diffusion time second./prim. ~ d 2 / κ c ~ E -1/3 (smaller for larger E) ★ CR age at low energies: Time from last arm passage (t p ~ few 10^7 yr) d

More detailed modeling • All the galaxy. • Allowing arm dynamics (important for B/C): ★ CR age at high energy: Diffusion time (smaller for larger E) second./prim. ~ t p v ~ E +1/2 ★ CR age at low energies: Time from last arm passage (t p ~ few 10^7 yr) t p

Results for B/C

Conclusions Taking the real distribution of SNRs gives the ➡ correct positron/electron energy behavior. NO Free parameters give the correct break ➡ energy (constrained by cosmic ray age). Nearby young known SNRs dominate around 800 ➡ GeV. e + /e - @ high E depends on exact κ . Predictions: ➡ e + /e tot ratio should saturate < 50% ❖ At higher energies the ratio should decrease! ❖ (due to fresh electrons) B/C ratio naturally explained once including the ➡ arm dynamics. No need for ad hoc assumptions (break in diffusivity, wind, reacceleration)

That’s it!