# Presentation: 911407

## THE ORIGIN OF COSMIC RAYS

**Pasquale Blasi**
**Fermilab/Center for Particle Astrophysics**
**INAF/Arcetri Astrophysical Observatory, Italy**

## Slide 2

## Early History of Cosmic Rays

## Ionized by what?

- 1895:  X-rays (Roengten)
- 1896: Radioactivity (Becquerel)
- But ionization remained, though to a lesser extent, when the electroscope was inserted in a lead or water cavity

## Victor F. Hess: the 1912 flight 

**Wulf Electroscope**
**(1909)**

**+**

**+     +**

**6am August 7, 1912 **
**Aussig, Austria**

## COSMIC Rays

## Millikan Theory

- Cosmic Rays (as Millikan named them) are gamma rays
- as the birth cry of elements heavier than hydrogen
**Millikan fit:    **300     1250      2500 g/cm2
-                            26        110        220 MeV

- 4 p → He       ΔM=27 MeV       **OK**
- 14 p → N       ΔM=108 MeV     **OK**
**12 p → C****	****Δ****M=85 MeV****        ?**
- 16 p → O       ΔM=129 MeV     **OK**
- 28 p →Si	ΔM=150 MeV      **May be**

## But birth cries do not go through lead!

- Bruno Rossi had performed several experiments with his
- coincidence Geiger counters and found that CR could
- penetrate even 1m of lead

**G**

**G**

**G**

- Lead
- Lead

- COSMIC RAYS
- Must have
- ENERGY > GeV

## Definitely charged...

**D. Skobeltsyn: ****picture of cosmic ray**
**event in cloud chamber with B-field (1927)**

## 1930: B. Rossi in Arcetri predicts the East-West effect

1932: Carl Anderson discovers the positron in CR

1934: Bruno Rossi detects coincidences even at large distance from the center...first evidence of extensive showers!

1937: Seth Neddermeyer and Carl Anderson discover the muon 

1938-39: Auger detects first extensive air showers with energy up to 1013-14 eV

1940’s: Boom of particle physics discoveries in CR

1962: UHECRs by Linsley & Scarsi

**1932:**** ****Carl Anderson**** discovers the positron in CR**
**1934:**** Bruno Rossi ****detects coincidences even at large distance from the center...first evidence of extensive showers****!**
**1937:**** Seth Neddermeyer ****and**** Carl Anderson** **discover the muon **
**1938-39:**** Auger detects first extensive air showers with energy up to 10****13-14**** eV**
**1940’s****: Boom of particle physics discoveries in CR**
**1962:**** UHECRs by Linsley & Scarsi**

## The Spectrum of Cosmic Rays

-     **Knee****	****      2****nd**** knee?  Dip/Ankle    GZK?**

**140 GeV       ****2.5 TeV****     20 TeV   ****100 TeV****  450 TeV**

## Spectra of different species

- Protons

**Hörandel‘s model (2003)**

## COSMIC

**COSMIC**
**ACCELERATORS**

## Supernovae and CR

- RATE OF SUPERNOVAE: 1/100 years
- Typically **E****kin**** ~ 10****51**** erg** goes to KINETIC ENERGY OF
- EJECTA**.**
- This corresponds to:

**Efficiency of conversion to CR ~  10-20 %**

- BUT HOW DOES THE CONVERSION OCCUR?

## Shocks

**MASS OF THE EJECTA****: M****ej **

**FREE EXPANSION VELOCITY: **

**SEDOV PHASE: **

**The sound speed in the ISM is about 10****6**** cm/s **

**STRONG**
**SHOCK**

## Collisional vs Collisionless

## First order Fermi Acceleration:TEST PARTICLE THEORY

**U****2****	****   U****1**

**Downstream****	**** Upstream**

**In a few interaction lengths**
**particles are isotropized**
**namely the plasma is heated **

- T2

- T1

- U2

- U1

- WHAT HAPPENS TO
- A TEST PARTICLE
- THROWN IN THE
- SHOCKED REGION?

## 1st order Fermi Acceleration(Krimsky 1977, Bell 1978)

**P return probab.**
**G energy gain**

## Return Probability and energy gain

**Return Probability and energy gain**

*THE SPECTRUM OF ACCELERATED PARTICLES **IS A POWER LAW  WITH  UNIVERSAL SLOPE*

- RETURN PROBABILITY FROM DOWN

- ENERGY GAIN PER
- CYCLE

- ONLY DEPENDS UPON THECOMPRESSION FACTOR!!!!!

## Problems with test particle theory

- Efficiency requested 10-20% and yet no dynamical reaction???
- Why do particles go back to the shock anyway ?
- Maximum energy exceedingly low!
- Injection problem and connection to the total energy/heating

## Why do particles return to the shock?

- B0

- Bx

- By

- Bx,y<<B0

- z

**Clearly the mean displacement vanishes:**

## Diffusion

**Resonant k**

**Power in the **
**modes with k**

**Diffusion in angle**

**Charged particles propagate diffusively in a **
**background of Alfven waves**

## The Maximum Energy problem

**If the background of Alfven waves is the same**
**responsible for diffusion of CR in the Galaxy**
**then**
** ****MAX ENERGY OF ORDER ****1 GeV or LESS !!!**

**ACCELERATION WORKS ONLY IF SOMETHING ELSE PROVIDES A BACKGROUND OF STRONGER WAVES**

## Non-Linear Theory of Particle Acceleration aims at:

- Determining the dynamical reaction of accelerated particles
- Determining the background of Alfven waves due to accelerated particles

## Dynamical Reaction of Accelerated Particles

- PRECURSOR

**Undisturbed Medium**

**Shock Front**

- v

**subshock       Precursor**

**Conservation of Momentum**

**Transport equation**
**for cosmic rays**

**SUBSHOCK**

- Velocity Profile

## Cosmic Ray self-induced scattering: a primer

**Small perturbations in a magnetized medium made of **
**electrons and protons simply give ****ALFVEN WAVES**
**WHAT HAPPENS WHEN THERE IS A SHOCK AND **
**IT IS ACCELERATING COSMIC RAYS?**

## Non Resonant Instability of Vlasov modes

**Vs=10****9**** cm/s**

**Vs=5 10****8**** cm/s**

**Vs=2 10****8**** cm/s**

**Vs=10****8**** cm/s**

- PB and Amato 2007
- Bell 2004

## Exciting News! 

**Exciting News! **

**CAS-A****	****	****	****	****SN1006**

**First detection of amplified **
**magnetic field in SNR**

## Rim A

**240****μ****G**

**360****μ****G**

**240****μ****G**

**360****μ****G**

- Rim B

- Berezhko, Voelk and ksenofontov 2005

- upstream and further
- compressed at the
- subshock by ~3

## Implications of B-field amplification

- pmax/mc

**10****7**
**10****6**
**10****5**
**10****4**

- M0

-  50               100	         150              200

- M0

**MAXIMUM MOMENTUM**

- PROTON
- KNEE

- PB, Amato & Caprioli, 2007

- Bohm Diff without
- B-amplification

## The case of RXJ1713

**HESS Collaboration**

## Multifrequency Modeling

**RADIO****	****	****	****  X-RAYS**

*Berezhko & Völk (2006)*

**Morlino, Amato & PB 2008**

**RXJ1713**

- Emax

- Eπ

- νsyn

- νICS

- B-Fields

- Compress.

## The End of Galactic CR

** ****The levels of B-field observed allow for **
**    ****proton acceleration in a SNR up to ****~3 10****6**** GeV**
** ****A nucleus with charge Z would acquire **
**   ****~3 Z 10****6**** GeV**
** ****For an Iron nucleus this would lead to**** **
**   ****~10****8**** GeV=10****17**** eV**
** ****END OF THE GALACTIC SPECTRUM**
** ****AROUND   10****17 ****eV  and  Fe  Dominated!**

## Anisotropies and chemicals

- Getting
- Heavier

- ?

## THE TRANSITION FROM GALACTIC TO ULTRA HIGH ENERGY COSMIC RAYS

## An ankle or a twisted ankle?

**Gal-CR extend to >10****19**** eV and are Fe-dominated**
**The ankle is due to a steep Gal-CR spectrum crossing the flat Extra-Gal Spectrum**
**The chemical composition should be heavy up to about 10****19**** eV **

**Ankle**

## PROPAGATION OF EXTRAGALACTIC COSMIC RAYS

## Cosmic Ray Energy Losses

- UNIVERSE
-  EXPANDS

- BETHE-HEITLER
- PAIR PRODUCTION

- PHOTO-PION
- PRODUCTION

## Transition through the Pair Production Dip 

## Pair-Production Dip

- Aloisio, Berezinsky, PB, Gazizov, Grigorieva, Hnatyk, 2007
- Berezinsky et al 2005

## The Dip

- Aloisio, Berezinsky, PB, Gazizov, Grigorieva, Hnatyk 2007
- Berezinsky et al 2005

## The effect of chemicals

- No more than ~15% of Helium is allowed at the source...still
- compatible with primordial abundances

**Helium****	****	****	****	****	****Iron**

## Mixed Composition at the source

- Allard, Parizot and Olinto, 2005-2007

## Penetration Depth

- Aloisio, Berezinsky, PB, Ostapchenko, 2007

- D

- DIP				ANKLE

## Penetration depths

- Kampert 2008

## Ultra-High Energy Cosmic Rays

**HiRes****	****	****	****	****	****PAO**

- The GZK feature seems to be present and it’s at the “right” place

## The Spectrum

**Solid: ****γ****=2.6  m=0  Emax=10****21****eV**
**Dashed: ****γ****=2.6  m=0 Emax=10****20****eV**
**Dotted: ****γ****=2.4  m=4 Emax=10****21****eV**

- Q(E,z)~E-γ (1+z)m exp(-E/Emax)

- A flux suppression is
- present at the same
- energy but for
- different reasons

## CR Astronomy with PAO

- CORRELATION OF THE ARRIVAL DIRECTIONS
- WITH THE *LOCAL DISTRIBUTION OF MATTER*
***FIRST DETECTION OF ANISOTROPIES !!!***
*UHECR are extragalactic after all !*

## Anisotropy and Chemical Composition

- Xmax compatible with anisotropies?
- May be there is something new to learn on cross section/multiplicity at ~300 TeV c.m.
- A proton dominated composition at the highest energies is common to all models of UHECR, but...

## Limits on the local B-field

- Galactic Magnetic Field
- Intergalactic Magnetic Field

- (1-3) Z deg in the halo
- 30 Z deg in the disc

- THE LOCAL UNIVERSE IS NOT STRONGLY MAGNETIZED

## AGN as sources?

- Image courtesy of NRAO/AUI

## Let’s do the numbers

**A simple estimate of the conditions in the knots**
**The Poynting flux would be**

## Particle Acceleration at Relativistic Shocks?

**c/3   c**

- At the lowest level there
- is no acceleration, BUT...
- If there is strong turbulence:
- Spectrum with γ~2.2-2.3
**BUT NOT UNIVERSAL!**

- In general steep spectra come out...but there are
- exceptions...

## Auger North 

- The UHE cosmic ray sky may be anisotropic on a large scale: FULL SKY COVERAGE
- DISCOVER THE SOURCES requires even larger exposures: 7 times Auger South is the plan
- Measuring the spectrum of one source is a breakthrough to look forward to
- UHE Neutrinos

## A New Type of Astronomy 

**PB & De Marco 2003**

**E>10****20**** eV**

**CRITICAL EXPOSURE...**

*Source*
*Spectrum*

## Summary

- Direct measurements are reaching the knee!
- Spectra of different chemical species!
- Discovery of B-field amplification → acceleration in SNR
- A new standard model with end of galactic CR at 1017 eV
- Transition GALACTIC→EXTRA-GALACTIC
- PAO Anisotropies and Spectrum
- Auger North as a UHECR telescope and as a tool to test interactions at 300 TeV c.m.