1. PULSAR WINDS AND NEBULAE Elena Amato INAF-Osservatorio Astrofisico di Arcetri Collaborators: Jonathan Arons, Niccolo’ Bucciantini, Luca Del Zanna, Delia Volpi, Barbara Olmi

2. OUTLINE  INTRODUCTION  CURRENT STATUS OF OUR UNDERSTANDING OF PULSAR WINDS AND NEBULAE  HOW TO USE PWNe TO LEARN ABOUT PULSAR ELECTRODYNAMICS AND THE PHYSICS OF RELATIVISTIC OUTFLOWS

3. WHY PWNe ARE INTERESTING  PULSAR PHYSICS: THEY ENCLOSE MOST OF THE PULSAR SPIN-DOWN ENERGY  CLOSE AND BRIGHT: BEST-SUITED LABORATORIES FOR THE PHYSICS OF RELATIVISTIC ASTROPHYSICAL PLASMAS  PARTICLE ACCELERATION AT THE HIGHEST SPEED SHOCKS IN NATURE (10 4 <  <10 7 )  COSMIC RAYS: ONLY SOURCES SHOWING DIRECT EVIDENCE FOR PEV PARTICLES  ANTIMATTER STORAGE ROOMS: AS MANY POSITRONS AS ELECTRONS (PAMELA AND AMS02 EXCESS?)

4. PULSAR WIND NEBULAE AT A GLANCE PLERIONS: SUPERNOVA REMNANTS WITH A CENTER FILLED MORPHOLOGY FLAT RADIO SPECTRUM (  R <0.5) VERY BROAD NON-THERMAL EMISSION SPECTRUM (FROM RADIO TO MULTI-TEV  - RAYS ) Kes 75 ( Chandra ) (Gavriil et al., 2008)

5. THE CRAB NEBULA (WHERE WE HAVE LEARNT MOST OF WHAT WE KNOW) PRIMARY EMISSION MECHANISM: SYNCHROTRON RADIATION BY RELATIVISTIC PARTICLES IN INTENSE (>few x 100 B ISM ) ORDERED (HIGH DEGREE OF 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 )

6. RADIO INFRARED OPTICAL X-RAYS THE BASIC PICTURE E.M. BRAKING OF FAST-SPINNING MAGNETIZED NS MAGNETIZED RELATIVISTIC WIND IF WIND EFFICIENTLY CONFINED STAR ROTATIONAL ENERGY VISIBLE AS NON-THERMAL EMISSION OF THE MAGNETIZED RELATIVISTIC PLASMA Gaensler & Slane 2006 ON THE OTHER HAND:

7. THE PULSAR WIND AT LARGER DISTANCES FIELD LINES ARE OPEN: B P MONOPOLE LIKE TOROIDAL FIELD BECOMES DOMINANT ACTS AS SOURCE OF TOROIDAL FIELD: B T COMPARABLE TO B P AT THE LIGHT CYLINDER ~SAME AS FOR OBLIQUE DIPOLE IN VACUUM Spitkovsky 06

8. THE WIND ENERGY WE MEASURE IT DEPENDS ONLY ON MEASURED PSR PARAMETERS CAN BE EVALUATED FROM PWN SYNC. EMISSION KNOWING B MUST BE LARGE AT LC:  10 4 -10 6 PROBABLY SMALL IN THE PWN BASED ON MHD MODELING FURTHER OUT THE FORCE-FREE APPROXIMATION BREAKS:

9. OPEN QUESTIONS WHAT IS  ? WHAT IS  ? IS IT IONS THAT CARRY THE RETURN CURRENT? WHAT IS  wind ? DETAILED MODELING OF PWNE REQUIRED FOR QUANTITATIVE ANSWERS NOTES ON IONS: FOR  wind =10 6 THESE WOULD BE PeV PROTONS OR 30PeV Fe IF  <m i /m  IONS MAY CARRY MORE ENERGY THAN PAIRS

10. THE TERMINATION SHOCK IN CRAB R TS ~0.1 pc~10 9 R LC BOUNDARY OF DARK REGION “WISPS” R TS ~R N (V N /c) 1/2 PRESSURE BALANCE ( e.g. Rees & Gunn 74 ) pulsar wind Synchrotron bubble R TS RNRN MOST LIKELY PARTICLE ACCELERATION SITE

11. WIND MAGNETIZATION AT THE SHOCK:  ~ V N /c ~3 x 10 -3 FROM BASIC DYNAMICS WITHIN STEADY STATE 1D MHD (Kennel & Coroniti 84; Emmering & Chevalier 90; Begelman & Li 92) At r~R LC :  ~10 4 ( PULSAR AND PULSAR WIND THEORIES ) At R TS :  «1(!?!) ( PWN THEORY AND OBSERVATIONS )  -paradox! MAGNETIC RECONNECTION IN THE WIND (Coroniti 90) ? SHOCK DRIVEN MAGNETIC RECONNECTION (Petri & Lyubarsky 07) ? OR MAGNETIC FLUX DESTROYED BY KINKS IN THE NEBULA (Begelman 99) ? WITHIN IDEAL MHD  STAYS LARGE

12. WIND LORENTZ FACTOR & PULSAR MULTIPLICITY  ~3x10 6 k~10 4 FROM OPTICAL/X-RAY EMISSION (e.g. Kennel & Coroniti 84)  ~2.2 JUST RIGHT FOR FERMI I NOTE: A GJ DENSITY OF IONS, IF PRESENT, WOULD DOMINATE THE WIND ENERGY FLOW  ~10 4 k~10 6 FROM RADIO EMISSION (e.g. Bucciantini et al 12)  ~1.5 DRIVEN MAGNETIC RECONNECTION? ALTERNATIVELY: RADIO ELECTRONS FOSSILE (Atoyan 99) OR ACCELERATED ELSEWHERE NOTE: NO WAY FOR IONS TO BE ENERGETICALLY IMPORTANT EVEN IF THEY WERE THERE

13. JETS AND TORII G11.2 B1509 3C 58 Crab G21.5 Vela

14. THE ANISOTROPIC PULSAR WIND AT LARGER DISTANCES FIELD LINES ARE OPEN: B P MONOPOLE LIKE TOROIDAL FIELD BECOMES DOMINANT ACTS AS SOURCE OF TOROIDAL FIELD: B T COMPARABLE TO B P AT THE LIGHT CYLINDER ~SAME AS FOR OBLIQUE DIPOLE IN VACUUM Spitkovsky 06 ANALYTIC SPLIT MONOPOLE SOLUTIONS ( Michel 73; Bogovalov 99 ) CONFIRMED BY NUMERICAL STUDIES IN THE FORCE FREE ( Contopoulos et al 99, Gruzinov 04, Spitkovsky 06 ) AND RMHD REGIME ( Bogovalov 01, Komissarov 06, Bucciantini et al 06 ) STREAMLINES BECOME ASYMPTOTICALLY RADIAL BEYOND R LC MOST ENERGY FLOWS AT LOW LATITUDES: F  sin 2 (  ) MAGNETIC FIELD COMPONENTS: B r  1/r 2 B   sin(  )/r CURRENT SHEET IN EQUATORIAL PLANE: OSCILLATING AROUND EQUATOR IN OBLIQUE CASE ANGULAR EXTENT DEPENDS ON OBLIQUITY

15. THE WIND MAGNETIZATION LOWERING  THROUGH DISSIPATION IN THE STRIPED WIND ( Coroniti 90 ) (Kirk & Lyubarsky 01) RECENT STUDIES:  RECONNECTION NOT FAST ENOUGH AT MINIMUM RATE ( Lyubarsky & Kirk 01 )  dN/dt~10 40 s -1 REQUIRED FOR CRAB ( Kirk & Skjaeraasen 03 )  THIS CONTRASTS WITH PSR THEORY (e.g. Hibschman & Arons 01 :  ~10 3 -10 4  dN/dt~10 38 for Crab) BUT JUST RIGHT FOR RADIO EMITTING PARTICLES IN 2-D MHD SIMULATIONS B  sin(  ) G(  ) with G(  ) accounting for decreasing magnetization toward equator DIRECT EVIDENCE OF STRIPED WIND IN BINARY PSR 0737 (McLaughlin et al. 04) PULSED  - RAYS FROM RECONNECTION? (Kirk et al. 02)

16. AXISYMMETRIC RMHD SIMULATIONS OF PWNE Komissarov & Lyubarsky 03, 04 Del Zanna et al 04, 06 Bogovalov et al 05 TERMINATION SHOCK STRUCTURE F  sin 2 (  )  sin 2 (  ) B   sin(  )G(  ) A: ULTRARELATIVISTIC PSR WIND B: SUBSONIC EQUATORIAL OUTFLOW C: SUPERSONIC EQUATORIAL FUNNEL A: TERMINATION SHOCK FRONT B: RIM SHOCK C: FMS SURFACE

17.  FOR SUFFICIENTLY HIGH , EQUIPARTITION IS REACHED IN EQUATORIAL REGION  EQUATORIAL FLOW IS DIVERTED TOWARDS HIGHER LATITUDES  A FAST CHANNEL MAY THEN FORM ALONG THE AXIS VelocityMagnetization  =0.03 FLOW PATTERN

18.  =0.003  =0.01  =0.03 DEPENDENCE ON  OF FLOW VELOCITY (Del Zanna et al 04) LOWER LIMIT ON  :  >0.01 REQUIRED FOR JET FORMATION BEST FIT  : 10 X LARGER THAN WITHIN 1D MHD MODELS BUT STILL <<1

19.  =0.03 DEPENDENCE ON FIELD STRUCTURE b=10 b=100 (Del Zanna et al 04,06; Volpi et al 08) B(  ) POLE-EQUATOR SIMULATIONS

20. SYNCHROTRON EMISSION MAPS  =0.025, b=10  =0.1, b=1 optical X-rays (Hester et al 95) E max IS EVOLVED WITH THE FLOW f(E)  E - , E<E max ( Del Zanna et al 06 ) BETWEEN 3 AND 15 % OF THE WIND ENERGY FLOWS WITH  <0.001 (Pavlov et al 01) (Weisskopf et al 00)

21. HIGHER  REQUIRED? COMPUTED ICS FLUX EXCEEDS THE DATA BY A FACTOR ~2 THE CRAB NEBULA INTEGRATED EMISSION SPECTRUM Quantitative fit of the spectral properties of the Crab Nebula requires injection spectrum with  =2.7!!!! But…. Volpi et al 08  Optical spectral index maps ( Veron-Cetty & Woltjer 92 ) suggest flatter injection spectrum:  ~2.2 ( but see also Kargaltsev & Pavlov 09)  Suspicion that particles are loosing too little: average B too low?  In order to recover total flux number of particles artificially large  Synchrotron only offers combined information on n e and B: L syn  n e B 2  But computation of ICS offers additional constraints: L ICS  n e U ph

22. RECENT ADVANCES PREJUDICE TOWARDS VERY LOW  MAINLY BASED ON 1D MHD MODELING  MOST MODELS OF DISSIPATION PREDICT LOW  AROUND EQUATOR, BUT HIGH  AT HIGH LATITUDE UNLESS ORTHOGONAL ROTATOR CHECK THE EFFECT OF INCREASING  ON BOTH MORPHOLOGY AND SPECTRUM  POLE-POLE SET-UP SO THAT DIFFUSION OF MAGNETIC FIELD LINES IS ALLOWED DECREASING THE TENSION ORIGIN OF RADIO EMITTING PARTICLES  CHECK RADIO EMISSION MORPHOLOGY AND NEED FOR SPECTRAL CONTINUITY  IMPORTANT CONSTRAINTS ON ACCELERATION MECHANISM LOOK FOR QUANTITATIVE AGREEMENT OF HIGH ENERGY MORPHOLOGY

23. INCREASING   =0.025  =1.5 (Olmi et al in prep)

24. BUT…  =0.025  =1.5

25. X-RAY EMISSION INNER RING:ENTIRETY, SIZE AND LATITUDE (Weisskopf et al 12) OK! TORUS TOO WEAK: MISSING TURBULENCE? FIELD PROGRESSIVELY MESSED UP?  =0.025 ISOTROPIC B FOR SYNC

26. OPTICAL EMISSION OPTICAL AND X-RAY EMITTING PARTICLES FROM THE WIND (ACCELERATED AT TS) L PART /L PSR =40%  WIND  10 6  10 4 NOTICE: NO SPECTRAL CONTINUITY WITH RADIO PARTICLES VERY STEEP INJECTION SPECTRUM: N(E)  E -2.9 INTEGRATED EMISSION

27. RADIO EMISSION Bandiera et al 02 EMISSION TRACES B-FIELD DISTRIBUTION TOO CONCENTRATED ALONG THE AXIS SLIGHTLY BETTER FOR DIFFUSE ELECTRON INJECTION INJECTED AT SHOCK UNIFORM IN THE NEBULA Olmi et al in prep

28. HOW TO MAKE PROGRESS (Porth et al 13) DIMENSIONALITY OF SIMULATIONS: IN 3D SAME  LOOKS VERY DIFFERENT! KINKS MAY MESS UP AND DISSIPATE FIELD IN THE PWN (Begelman 98) CONSEQUENCES ON SPECTRUM AND POLARIZATION???

29. LESSONS TO LEARN (and to remember when wondering about particle acceleration) CONTINUITY OF PARTICLE SPECTRUM NOT NEEDED DISTRIBUTED ACCELERATION IN PRINCIPLE COULD DO THE JOB FOR RADIO EMITTING PARTICLES  ACCELERATION OF RADIO EMITTING PARTICLES COULD BE UNRELATED TO WIND AND SHOCK X-RAY EMITTING PARTICLES NEEDED AT HIGH LATITUDES ALONG THE SHOCK FRONT  ACCELERATION IN MAGNETIZED FLOW HOW ARE PARTICLES ACCELERATED AT THE MOST RELATIVISTIC SHOCKS IN NATURE?