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PARTICLE ACCELERATION IN ASTROPHYSICAL SOURCES Elena Amato INAF-Osservatorio Astrofisico di Arcetri.

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Presentation on theme: "PARTICLE ACCELERATION IN ASTROPHYSICAL SOURCES Elena Amato INAF-Osservatorio Astrofisico di Arcetri."— Presentation transcript:

1 PARTICLE ACCELERATION IN ASTROPHYSICAL SOURCES Elena Amato INAF-Osservatorio Astrofisico di Arcetri

2 ACCELERATED PARTICLES IN THE COSMOS Sub-GeV GALACTIC EXTRA GALACTIC ~EeV CERN LHC (14 TeV) FINAL TEVATRON (2TeV) E -2.7/3

3 ENERGETIC REQUIREMENTS 1 eV/cm 3 CERN LHC (14 TeV) FINAL TEVATRON (2TeV) E -2.7/3 LARGE ENERGY DENSITY: EQUIPARTITION WITH B-FIELD AND THERMAL GAS L CR ~3x10 40 erg s -1 ~0.1 x erg x 3x s -1 E SN R SN SUPERNOVA REMNANT PARADIGM (Baade & Zwicky 1934)

4 SUPERNOVA REMNANTS Tycho RX J SN 1006 Cas A RELATIVISTIC ELECTRONS SEEN THROUGH X-RAY EMISSION

5 RELATIVISTIC PROTONS IN SNRS? RX J TeV EMISSION DETECTED! SN 1006 NEUTRAL PION-DECAY OR INVERSE COMPTON SCATTERING OF ELECTRONS? DETAILED SPECTRAL MODELING REQUIRED! CONCLUSION UNCERTAIN IN MOST CASES BUT….

6 EVIDENCE FOR RELATIVISTIC PROTONS W44 “PION BUMP” IN MIDDLE AGED SNRs INTERACTING WITH MOLECULAR CLOUDS Fermi (Abdo+ 09,10; Ackerman+ 13) & Agile (Giuliani+ 10,11; Cardillo+ 14) Cardillo+ 14 IC443 NOT VERY ENERGETIC PROTONS THOUGH….

7 SUPERNOVA REMNANTS PARADIGM CERN LHC (14 TeV) FINAL TEVATRON (2TeV) E -2.7/3 Cas A Tycho MUST BE PEVATRONS

8 FERMI ACCELERATION MECHANISM PARTICLE GAINS ENERGY EACH TIME IT CROSSES THE SHOCK PARTICLE GAINS ENERGY SOMETIMES LOSES ENERGY SOME OTHERS AVERAGE ENERGY GAIN ENERGY GAIN PER CYCLE V UPSTREAMDOWNSTREAM V-v 2 FROM UPSTREAMFROM DOWNSTREAM V-v 2 RETURN PROBABILITY INDEPENDENT OF E POWER LAW ENERGY SPECTRA ONLY DEPENDENT ON COMPRESSION RATIO STRONG SHOCKS: u 1 /u 2 =4   p =4   e =2

9 PARTICLE ISOTROPIZATION IF  B SAME RESPONSIBLE FOR CR CONFINEMENT IN THE GALAXY: E max ~GeV IF  B ~B 0, E max ~ GeV (Lagage & Cesarsky 83) AMPLIFIED B IS REQUIRED TO REACH THE KNEE COLLISIONLESS PLASMA… WAVE-PARTICLE INTERACTIONS!!! INTERACTIONS MOST EFFICIENT AT RESONANCE ACCELERATION TIME DEPENDS ON TURBULENCE LEVEL MAXIMUM ACHIEVABLE ENERGY DEPENDS ON TURBULENCE LEVEL ->SPATIAL DIFFUSION PITCH ANGLE DIFFUSION:

10 PARTICLE DIFFUSION AND WAVE GROWTH IF CR ARE ISOTROPIZED BY THE WAVES… MOMENTUM HAS GONE TO THE WAVES BEFORE SCATTERING : P CR =n CR m  CR v d AFTER SCATTERING : P CR =n CR m  CR v A FOR RESONANT ALFVÉN WAVES with SUPERALFVÉNIC STREAMING OF CRs  WAVE GROWTH IN ADDITION 10% EFFICIENCY  SHOCK MODIFICATION!!!!

11 EFFICIENT ACCELERATION AT SNR SHOCKS  CR STREAMING INDUCES PRESSURE GRADIENT UPSTREAM  A PRECURSOR IS FORMED: FLUID PROGRESSIVELY SLOWS DOWN  CR ESCAPE MAKES SHOCK RADIATIVE R TOT >4 WHILE R SUB <4 CR PRECURSOR SUBSHOCK DENSITY OF ACCELERATED PARTICLES DIFFERENT ENERGY PARTICLES HAVE DIFFERENT DIFFUSION LENGTHS  EXPERIENCE DIFFERENT R ( 4 AT HIGH EN)  SPECTRUM BECOMES CONCAVE (STEEP AT LOW EN. FLAT AT HIGH)

12 BASIC PREDICTIONS OF NL-DSA  COMPRESSION RATIO > 4: CD VS SHOCK IN TYCHO (Warren+ 05) AND SN1006 (Cassam-Chenaii+ 08) AND EMISSION PROFILES ( Morlino+ 10)  T 2 IS LOWER THAN EXPECTED: IN RCW86 T 2 ~ 1/10 T RH (Helder+ 09, Morlino+ 13)  CONCAVE SPECTRA: RADIO SNRs ( Reynolds & Ellison 92) AND SED FITTING OF SN1006 AND RCW86 (Vink 12)  B-FIELD LARGELY AMPLIFIED Blasi, Gabici, Vannoni 05  BACK-REACTION OF CRs  MAGNETIC FIELD AMPLIFICATION  BACK-REACTION OF AMPLIFIED FIELD TWO-FLUIDS : Drury & co. MONTECARLO : Ellison & co. FINITE DIFFERENCE : Berezhko, Volk & co. KINETIC: Amato & Blasi 05,06; Blasi+ 08 Caprioli+ 08,09,10,11 HINTS OF EFFICIENT ACCELERATION:

13 AMPLIFIED MAGNETIC FIELDS B~  G IN THE SIMPLEST PICTURE EFFICIENT PARTICLE ACCELERATION BECAUSE OF HIGH B-FIELD HIGH B-FIELD BECAUSE OF EFFICIENT PARTICLE ACCELERATION CAVEAT: LARGE MAGNETIC FIELDS MIGHT HAVE DIFFERENT ORIGIN AND DO NOT IMPLY EFFICIENT SCATTERING… Cas A Tycho

14 CR AMPLIFIED FIELDS “STANDARD” GROWTH RATE ONLY APPLIES WHEN OTHERWISE GROWTH OF RESONANT MODES IS SUPPRESSED NON RESONANT MODES (Bell 04, Amato & Blasi 09) BECOME DOMINANT  CR CURRENT INDUCES COMPENSATING CURRENT IN PLASMA  INDUCES TRANSVERSE PLASMA MOTION  RESULTING CURRENT ACTS AS A SOURCE OF B  FOR RIGHT-HAND POLARIZED WAVES, FIELD LINES ARE STRETCHED: FIELD IS AMPLIFIED VERY LARGE FIELD ON VERY SMALL SCALES EFFICIENT FOR SCATTERING?

15 SATURATION & SCATTERING B-FIELD EASILY AMPLIFIED TO FEW X 100  G (Riquelme & Spitkovsky 09, Caprioli & Spitkovsky 14) BUT SCATTERING IN SMALL SCALE TURBULENCE -> D(p)  p 2  ONLY EXTREME SNRS REACH THE KNEE (Zirakashvili & Ptuskin 08) BUT BELL’S TURBULENCE MIGHT SEED A DYNAMO (Bykov+13) NUMERICAL WORK (Caprioli & Spitkovsky 14): SCALE INDEED GROWS QUICKLY AND SCATTERING IS IN BOHM REGIME EFFICIENT FIELD AMPLIFICATION ALSO HELPS RECONCILING OBSERVED SPECTRA WITH OBSERVATIONS (Zirakashvili & Ptuskin 08, Caprioli 11) SELF-REGULATING ACCELERATION AND ESCAPE LITTLE TURBULENCE LARGE CURRENT LARGE ESCAPE FRACTION TURBULENCE INCREASES CURRENT DECREASES EFFICIENT ACCELERATION

16 STEEPENING THE SOURCE SPECTRA… Caprioli 11 Morlino & Caprioli 11 TYCHO THEORY PREDICTS FLATTER THAN 2 GAMMA RAYS SHOW STEEPER THAN 2 CAVEAT: DEPENDS ON DETAILS OF THE TURBULENCE PROPERTIES MIGHT EVEN FLATTEN THE SPECTRA FOR SLOW SHOCK PARTIAL IONIZATION STEEPENS SPECTRA (Morlino+ 13, 14)

17 SEEING A PEVATRON HOWEVER ONE COULD SEE ESCAPED PeV PARTICLES FOR MUCH LONGER (Gabici & Aharonian 07) HARD TO SEE Gallant, Amato, Lavalle in prep. WITH UPCOMING TELESCOPES POSSIBLE TO CHECK ON CAS A PEVATRONS: EXTREME TYPE II FOR FEW X10 YR Schure & Bell 13

18 A PEVATRON WE SEE… SYNCHROTRON AND ICS RADIATION BY RELATIVISTIC PARTICLES IN INTENSE (>few x 100 B ISM ) ORDERED (HIGH POLARIZATION, IN RADIO, OPTICAL AND EVEN  - RAYS, Dean et al 08 ) MAGNETIC FIELD SOURCE OF B FIELD AND PARTICLES: NS SUGGESTED BEFORE PSR DISCOVERY ( Pacini 67 ) Atoyan & Aharonian 96 PeV ELECTRONS

19 A PULSARS AND THEIR WINDS PRIMARY CHARGES EMIT Υ-RAYS AND PAIR PRODUCE: LARGE MULTIPLICTY ~ ROTATING CONDUCTING MAGNET SURFACE ELECTRIC FIELD EXTRACTS CHARGES A DENSE RELATIVISTIC WIND MAINLY MADE OF PAIRS (THOUGH MAYBE PeV IONS…) AND A TOROIDAL B-FIELD LEAVES THE STAR: LORENTZ FACTOR ~ FEW X 10 6 THE MOST RELATIVISTIC OUTFLOW IN NATURE AND THE MOST EFFICIENT ACCELERATOR KNOWN!!!

20 PULSAR WIND NEBULAE WIND IS CONFINED BY SURROUNDING SNR (OR ISM IN OLDER SYSTEM) WIND MUST SLOW DOWN TO MATCH SNR EXPANSION SPEED THIS HAPPENS THROUGH A SHOCK TRANSITION Kes 75 ( Chandra ) (Gavriil et al., 2008) Gaensler & Slane 2006

21 RELATIVISTIC SHOCKS IN ASTROPHYSICS Cyg A SS433 Crab Nebula AGNs  ~a few tens MQSs  ~a few PWNe  ~ GRBs  ~10 2

22 PARTICLE ACCELERATION THE PW TERMINATION SHOCK IS COLLISIONLESS MECHANIMSMS FOR DISSIPATION AND ACCELERATION DEPEND ON FLOW COMPOSITION (e - -e + -p?) MAGNETIZATION (  =B 2 /4  n  mc 2 ) GEOMETRY (   ( B·n )) COMPOSITION: MOSTLY PAIRS BY NUMBER BUT…. MAGNETIZATION:DYNAMICS ->  >10 -2 FOR MOST OF THE FLOW GEOMETRY: TRANSVERSE PROPOSED MECHANISMS:  FERMI MECHANISM IF/WHERE MAGNETIZATION IS LOW ENOUGH  DRIVEN MAGNETIC RECONNECTION AT THE SHOCK (Lyubarsky 03, Lyubarsky & Liverts 08, Sironi & Spitkovsky 11 )  RESONANT CYCLOTRON ABSORPTION IN ION DOPED PLASMA ( Hoshino et Al 92, Amato & Arons 06 )

23 FERMI PROCESS AT RELATIVISTIC PAIR SHOCKS EFFICIENT ACCELERATION AT UNMAGNETIZED SHOCKS NO ACCELERATION AT SUPERLUMINAL SHOCKS NOT EVEN FERMI PROCESS AT LARGE OBLIQUITIES… SAME CONCLUSIONS FOR ELECTRON-ION SHOCKS…. RESULTS FROM PIC SIMULATIONS BY Spitkovsky 08, Sironi & Spitkovsky 09, 11

24 DRIVEN MAGNETIC RECONNECTION ( Sironi & Spitkovsky 11) REQUIRED K>10 7 BROAD PARTICLE SPECTRA WITH  =-(1-1.5) JUST RIGHT FOR PWN RADIO EMISSION BUT RECONNECTION BEFORE THE SHOCK? (Kirk & Skjaeraasen 03)

25 Drifting e + -e - -p plasma Plasma starts gyrating B increases Configuration at the leading edge ~ cold ring in momentum space Coherent gyration leads to collective emission of cyclotron waves Pairs thermalize to kT~m e  c 2 over  (1/  ce ) Ions take their time: m i /m e times longer RESONANT CYCLOTRON ABSORPTION IN ION DOPED PLASMA Magnetic reflection mediates the transition

26 ACCELERATION EFFICIENCY: ~few% for U i /U tot ~60% ~30% for U i /U tot ~80% SPECTRAL SLOPE: >3 for U i /U tot ~60% <2 for U i /U tot ~80% MAXIMUM ENERGY: ~20% m i c 2  for U i /U tot ~60% ~80% m i c 2  for U i /U tot ~80% PARTICLE SPECTRA AND ACCELERATION EFFICIENCY IONS CARRY MOST OF THE ENERGY:  { "@context": "http://schema.org", "@type": "ImageObject", "contentUrl": "http://images.slideplayer.com/4207772/14/slides/slide_25.jpg", "name": "ACCELERATION EFFICIENCY: ~few% for U i /U tot ~60% ~30% for U i /U tot ~80% SPECTRAL SLOPE: >3 for U i /U tot ~60% <2 for U i /U tot ~80% MAXIMUM ENERGY: ~20% m i c 2  for U i /U tot ~60% ~80% m i c 2  for U i /U tot ~80% PARTICLE SPECTRA AND ACCELERATION EFFICIENCY IONS CARRY MOST OF THE ENERGY: 

27 SUMMARY PARTICLE ACCELERATION AT SNR SHOCKS IS A SELF- REGULATING PROCESS WELL DESCRIBED BY NLDSA THEORY ACCELERATION UP TO THE “KNEE” LIKELY POSSIBLE FOR A SHORT TIME AFTER THE SN EXPLOSION NO EVIDENCE YET FOR PEVATRONS AMONG SNRs BUT HOPES FOR THE NEAR FUTURE PeV ELECTRONS ARE SEEN IN PWNe: THE CRAB NEBULA IS THE MOST EFFICIENT ACCELERATOR DIRECTLY OBSERVED IN NATURE! THE MAIN ACCELERATION PROCESS IS NOT FULLY UNDERSTOOD THE PRESENCE OF PEV IONS COULD PROVIDE A POSSIBLE SOLUTION TO THIS PUZZLE

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