Introduction toHigh Energy Astrophysics

Paolo Lipari: INFN Roma “La Sapienza”

XXVI SNFNSN OTRANTO 5-6 giugno 2014

Sources of High Energy Particles in the universe

1. Cosmic Rays 2. Gamma Rays 3. Neutrinos

Viktor HESS (1912)

The beginning of “High Energy Astrophysics” the discovery of Cosmic Rays

First “hint”of the “high energy universe” (beginning of '900)

Existence of “Ionizing Radiation”

Discharge of an electroscope

Effect grows with altitude(and has a maximum soon discovered by Kolhorster )

Source of ionizationis “extraterrrestrial”

Primary Particle

Ground

“Secondaries”

(many absorbed in the atmosphere)

Some secondariesreach the ground

Birth of

Particle Physics

Carl Anderson “Wilson chamber”

march 15, 1933 Discovery of the “positron”

Carl Anderson and Viktor Hess share Nobel prize in 1936

6 mmLead plate

63 MeV

23 MeV

Cosmic Rays are charged particles

Most particles have POSITIVE electric charge:

Protons +ionized nuclei

LATITUDE effect

EAST-WEST effect

LATITUDE EFFECT

East-West effectMost Cosmic Rays havepositive electric charge

Relativistic charged particles. [Latitude effect]

Mostly protons (+ ionized nuclei) [East-West effect]

Extraordinary energy (!) [Extensive Air Showers (electrodynamics) ](1015, 1016 eV) now: 1020eV

Pierre Auger Phys.Rev. 1939

Relativistic charged particles. [Latitude effect]

Mostly protons (+ ionized nuclei) [East-West effect]

Extraordinary energy (!) [Extensive Air Showers (electrodynamics) ]

Power Law energy spectrum(nearly featureless)

(1015, 1016 eV) now: 1020eV

● Where are these relativistic particles coming from ? ● How are they produced ? ● Are they filling the universe (or are more “local”) ?

Relativistic charged particles. [Latitude effect]

Mostly protons (+ ionized nuclei) [East-West effect]

99% nuclei

1% electrons

89% protons

10% Helium

1% Nuclei Z > 2

small quantities : positrons + anti-protons

Power-Law

Energy spectra

Particle Flux: [cm2 s sr GeV]-1

[cm2 s sr GeV/nucleon]-1

Number of particles per [ unit of surface unit of time unit of solid angle unit of energy]

Esponent :

from Tom Gaisser

from Tom Gaisser

Flux *E2Knee

High Energy suppresionor “cutoff”

Ankle

from Tom Gaisser

Knee

High Energy suppresionor “cutoff”

Ankle

electrons

positrons

anti-p

Direct Measurementsof Cosmic Rays

Detectors on satellitesor stratospheric balloons

Kinetic energy

PAMELA

Proton/HeliumCR fluxes1 GV – 1.2 TV

Science in press(march 2011)

Surprising and important result.

Broken power law fits to spectra. Break at same rigidity p/Z

p He

Surprising and important result.

Broken power law fits to spectra. “Ankle” at same rigidity p/Z

p He

Structure

CREAM (calorimeter on balloon) (5 flights in Antartica. Total of 156 days)

Cream 5 trajectory37 days 12/2009-01/2010

SUNSPOTS: signals of solar activity.

Visible lightX-rays

Solar Modulations

NeutronMonitors

Measure the flux of neutronsproduced by the evaporation of Air nuclei by primary cosmic rays

Sunspotnumber

Neutron MonitorCounts

Time of BESS flights:

BESS proton flux MEASUREMENTS

p

e

PAMELA

The SUN as a “laboratory” for CR Acceleration and Transport

PAMELA: Solar Flare 13/dec/2006Ap.J 742 2 2011.

AMS Launch May 16th 2011

ExtragalacticParticle

Particle accelerated in the Milky Way

“Bubble” of cosmic rays generated in the Milky Way and contained by the Galaxy magnetic field

Space extension and properties of this “CR bubble” remain very uncertain

Extragalacticcontribution

GALACTICMAGNETIC FIELDS

“Regular Field”

“Random Field”(turbulent motions)

“Regular Field”(along the spiral Arms) + “Random” (Turbulent) Field

EnergyDensity

25-35 Kpc

0.5 Kpc

8 Kpc

B

Diffusion approximation

Maximum energy for containment

Piece of extragalactic space: Non MilkyWay-like sources

Galaxy

Milky Way

AGN

Injection of cosmic rays

Containment time

Different particles

Galactic Cosmic Rays

Determination of the “confinement time” T(p/Z)

“Cosmic clock” (Beryllium-10)

Nuclear Fragmentation (collisions with the Inter Stellar Medium)

Solar system

v

v

v

proton at rest

(extended halo)

Column density

Escape faster at higher E

Injection of cosmic rays

Containment time

LARGE PowerRequirement

Spectral Shape [Dynamics of acceleration process]

Source Identification

Power Provided by SN is sufficient with a conversion efficiency of 15-20 % in relativistic particles

The cosmic ray acceleratorsinject particles witha power law spectrumof approximately this form

11th june 2008: Launch of GLAST

Gamma rayLargeAreaSpaceTelescope.

NASA press release: 26th august 2008

Enrico Fermi

ELECTRO-WEAK MASS SCALE

The Idea of FERMI acceleration

Why a power law spectrum ?

Origin of the power law spectrum:

Stochastic Process

Gradual acceleration madein many steps

= probability of stopping the iteration

The iterative process results in apopulation of particles with a power law spectrumwith exponent:

Particles that come out of the accelerator

Collision with Moving Plasma Cloudsin the Galaxy

Ei

Ef

MODIFICATION of the original FERMI Model(2nd order Fermi acceleration)

ACCELERATION at SHOCK FRONTS(1st order Fermi acceleration)

Trinity Test (1945)

CAS A(1667)

“Fireball” of an Supernova explosion

Interstellar Gas

Strong Shock

Fermi 1st orderacceleration

SNR

Unshocked material at restPiston

ShockFront

Unshocked material at restPiston

ShockFront

STRONG SHOCK

Unshocked material shocked material

Unshocked material at rest

Compression factor r

For Strong Shocks

Universal exponent for the spectra of acceleration at strong shocks