UHECR from Pulsars/Magnetars based on An Auroral Accelerator Model for Gamma Ray Pulsars

Transcription

1 UHECR from Pulsars/Magnetars based on An Auroral Accelerator Model for Gamma Ray Pulsars Jonathan Arons University of California, Berkeley Bai & Spitkovsky 2010 Collaborators: N. Bucciantini, A. Spitkovsky 05/09/ 1

2 Heavy UHECR: a neutron star source? Energy Spectrum GZK cutoff or source Ends above ev Composition; or hadronic interactions in air shower model not understood Pulsars/Nebulae can accelerate (e ± ) to PeV; have (Fe) crust/ocean 05/09/ 2

3 Magnetospheric Current System Requires Ion Extraction from Star (Atmosphere? Ocean? Crust?) Aligned/Oblique Rotators structurally similar, J cond + J disp (=0 in aligned) Spitkovsky s (2006) oblique force free rotator Polar Gap Slot Gap Field Lines (with real open flux) Total Current Outer Gap Gaps = local quasi-vacuum E zones inserted by hand into vacuum B to model gamma ray emission and pair creation by construction, gaps carry small fraction of total current I L gap small; Accelerate test particles along B rotation è lighthouse beamed photons (lighthouse) =IΦ, Φ=Ω 2 µ/c 2 Force Free model has no accelerator: pure MHD (Alfven s ghost angry): Gap Models J. Arons: with UHECR vacuum from Auroral PSR have too little energy 05/09/ E 3

4 rb φ /Β * Wind PIC aligned rotator simulation e ± pairs, low altitude pair creation (Cerutti+2015) - ~force-free + active current sheet (dynamics, particle acceleration) Poloidal field lines r 2 J r /J GJ* - radial positive current = positive charge outflow (return current in equatorial current sheet) radial volume current = electrons e - precipitation net ion outflow E /B B outside current sheet, B=0 inside 05/09/ 4

5 Heavy Ions Source (14-17) δ r J r J Unmagnetized Diffusion region & CS center: fed by reconnection inflow from wind thermal evaporation forms precipitation beam Reconnection inflow Polar Outflow v = c J r 2δ 2l D E,J Field Aligned Return Current B φ Electron precipitation density * = I/r cap δ GJ attracts upward ion beam from upper atmosphere (p +,He +,CNO +?) Or ocean (Fe +many?) Electron precipitation current I =cφ I ion Magnetic Y-line Diffusion Region Acceleration along radial (r R L ) X-lines of reconnecting current sheet ~ linear accelerator Electric return current channel Ω i µ > 0 Downward electron beam, 05/09/ upward ion beam J. Arons: UHECR from Auroral Ω i µ PSR < 0 Downward positron beam, upward electron beam 5 R L

6 3D PIC e± (Sironi2014+) Density Spectrum (whole box radial, height, width ~ 6000 rl rwind ~109RL) Energy Histories dn/dγ γ ~ monoenergetic, highest energy particles have most energy 05/09/ 6

7 Linear Accelerator = current sheet in wind; carries electric return current Particle rate: N i (t) = I return(t) Ze = Ω2 (t)µ Zec Decays as star spins down (EM after initial 10s, neutrino heated wind gone): t EM = I c 3 M 10 yr " P % = 2Ω $ ' µ # 1msec & µ Ω i 2 t t EM ( Ω i ) Maximum Energy: radial electric field Ε r = reconnection = (v rec /c)b φ B φ = Φ/r, Φ=µΩ 2 /c 2 =1.3x10 19 µ 30 /P msec 2 Volts (magnetar: µ 30 ~10 3 ) V rec (simulations; simple 2 fluid theory) =0.8±0.2v A, v A = c after initial 10s 05/09/ ε = γmc 2 = Ze r max r min E r! dr = Ze v $ rec # " c & % r max r min Φ! dr = Ze v $! rec r # " c & Φ ln r $ max # & % " % r min 7

8 Oblique Rotators: Inner Wind Magnetically Striped Equatorial cross-section Ω µ Meridional cross-section Wavelength = R L = cp/2π Current Sheet Dissipated in Wind Zone if σ 0 = Γ wind 10 6 for Crab Nebula, σ 0 ~ Suggests stripes gone outside! E R Mc! 2 r=r diss = r min ~ R L = 10 -(3-2) R TWS R TWS = wind termination radius = r max Mass loading of millisecond PSR =? Outside R diss, current sheet flat = linear accelerator to R TWS ε max (t) = γmc 2 = Ze r max r min E r! dr = Ze v $ rec # " c & % r max r min Φ! dr = Ze v $! rec r # " c & Φ(t) ln r $ max # & % " % r min 05/09/ 8

9 R diss = stripe dissipation radius 10 7 R L based on fast reconnection of striped current sheet Site of Crab gamma ray flares? recurrence time time to restore current sheet after tearing flow time from LC = R diss /c ~ (Crab) πcP/c = 0.9 months observed: 4 months 1 year Aharonian+ suggested dissipation at 30 R L, without mechanism R TWS ~10 9 R L (Crab) Particle Spectrum E -1.3 from one star too hard for UHECR Heavy ion source appealing, so Superpose many stars/galaxies with a spectrum of voltages? (Kotera) Process heavy ions (Fe?) in SNe ejecta shell? (Fang+) 05/09/ 9

10 possible relation to hypernova models of GRBs - fast rotating magnetic core forms in core collapse supernova; magnetic pressure explodes stellar envelope, Compton upscatter of radiation field as wind escapes creates (slow) GRB? Pre SN star likely compact, with fairly short dynamical time Wheeler et al 2000 model: 05/09/ BLOWOUT Rare compact objects: ν m = 10 4 ν m4 yr 1 Suggests unusual core collapse SNe - Ib/c? Newly formed magnetic core dumps EM energy (B fields, ) in a few minutes - initial spin down by GW emission, ΔE EM (t < t GR ) µ 33 2 ε /10 2 t d ~ 20 (R * / km) 3 / 2 (M / M sun ) 1/ 2 sec 30 t GR (Ω i ) Ω 4 4 ε /10 2 ergs = IΩ i 2 ( ) 2 sec, ( Ω i ~ 10 4 s 1 ) 10 10

11 Injected EM Energy disrupts pre SN envelope in the dynamical time Rayleigh-Taylor of light EM energy shreds envelope in time t dyn, short compared to standard SN, Wind then expands freely, blows bubble in ISM, expansion nonrelativistic after 1 year deposits ~2-5 x ergs/neutron * in the ISM, limited by gravitational wave loss Crab filaments - RT shredded ejecta (Sankrit Hester et al); also Gamma ray leakage from 87a 05/09/ 11

12 Adverisement: Special Collection (a.k.a. Special Issue) of the Journal of Plasma Physics look under Special Collections Plasma Physics of Gamma Ray Pulsars and their Nebulae Arons & Uzdensky, eds multiple invited authors, most in this room at Purdue THE END 05/09/ 12