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Multiple Sheet Beam Instability of Current Sheets in Striped Relativistic Winds

Multiple Sheet Beam Instability of Current Sheets in Striped Relativistic Winds

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## Multiple Sheet Beam Instability of Current Sheets in Striped Relativistic Winds

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**Multiple Sheet Beam Instability of**Current Sheets in Striped Relativistic Winds Inertial Parallel E in Neutron Star Magnetospheres: Return Cuurent Sheets and Pulsed Gammas Jonathan Arons University of California, Berkeley 1**latitude sector**As if energy flux in a narrow Crab Vela G54.1 J2229 B1706 J0538 Rings and Torii Ng & Romani Torii in rotational equator - small aspect ratio - /r ~ 0.1(Crab), smaller in others 2**, nebular response ~ images**Magic: If Poynting Flux dominated wind strongest toward equator “Unmagnetized” equatorial channel (Komisssarov & Lyubarsky 2003; del Zanna et al 2004; Bogovalov et al 2005)**Outer Wind Properties,**: Like Split Monopole of Aligned Rotator Without Dissipation: Current Sheet, carries return current Relativistic Beam: “protons” (i=0), e- (i=p) Sheet Opening Angle: 4**Frozen-in wave,**Striped wind Equatorial Current Sheet Observed PSR = oblique rotators Gamma Ray PSR, i from Romani and Yadigarglou outer gap model Striped Jets: Spruit, Konigl 5**i=9o**i=60o Inner Wind: Magnetically Striped Force Free Simulation of i=60o Rotator (Spitkovsky) Current Sheet Separating Stripes (Bogovalov) 6**Stripe Dissipation**If wrinkled current dissipates, striped field dissipates, magnetic energy coverts to flow kinetic energy, “heat” & high frequency radiation, strong waves - partition? Sheet Dissipation: Tearing of one locally ~ plane sheet? (Coroniti; too slow? - Kirk & co.) Cause: Current starvation? (everybody) sheet strong waves? - Melatos-vacuum) 7**Stream Instability of Multiple Sheets**Current sheets = transmission lines Current = charged particle beam injected by source - Y or X line at LC | |=IGJ=Goldreich-Julian Current In absence of dissipation, beams flow adiabatically in narrow channel 8**Simplified Sheet Structure**2H (adiabatic EOS) Sheets swallow stripes (H > RL): (Crab) only if (protons) - sheets survive? 9**Sheets Interact - Two Stream (Weibel-like) instability**x0=RL<< r Thin Sheet (krL<<1) dynamics as if each sheet is unmagnetized although intersheet medium MHD x0 10**Imagine Magnetic**disturbance at each sheet - Alfven pol Two Symmetric Sheet Instability j0 x force compresses each sheet’s surface density into filaments parallel to j0 Surface current filaments reinforce - Weibel instability in flatland RL Growth Rate 2 symmetric sheets = purely growing in proper frame 11**Proper Growth Rate (vA=c, vbeam=c, sheet thickness =**) Growth rate > expansion rate for 12**Saturation - Magnetic Trapping**beam particles scattered by self fields Growth & Trapping Saturation of Spatially Distributed Weibel (Spitkovsky & JA) shock - transient growth and decay; current sheet is driven but end result will “always” be magnetic turbulence that scatters particles 13**Anomalous Resistivity in Sheets - rapid expansion**of sheets, destruction of intersheet field? (Coroniti’s model) Resistive electric field in sheet - equilibrium beam energy (?) Anomalous resistance, scattering: radiation (synchroton), sheets radiate - pulsed emission? (Kirk et al; historically, JA) Many sheets, sheet strength j0 declines with r: radiation of long wavelength EM waves (fast modes shocks) of relativistic amplitude?**X**X Experiments Computational: 3D PIC, must be MHD between sheets (frozen-in pairs) resolve current layer: Larmor and c/p scales of beam particles could use rectangular geometry Lab Experiment? Use laser on dense slab to launch relativistic electron-positron plasma onto field lines of reversed B (RFP?) Launch beams into field reversal region? Charged particle beam currents Laser generated MHD electron-positron plasma Perp E to give cross field plasma flow? Expt improves on simulation? Strong Background B 15**Parallel E in Pulsar return currents**Pulsed Gamma Rays: Acceleration in Boundary layer along open field lines**Return Current Sheet**: thickness ~ rl(RL)(r/RL)3/2 Y-line at r = RY ~ RL Gamma rays radiated by some sort of sheet at or near the boundary layer Return current, precipitating plasma formed by reconnection at RY Return current density huge: Jret ~ J[RL/rl(RL)] ~ J (e/mc2) >>>1 magnetospheric potential = B*R*(R*/RL)2: 1012-1017 V Particle inertia in the current channel: ret = pair multiplicity, precipitating from Y-line, < 104 Romani’s “outer gap” surface: quasi-vacuum E accelerator Simulations? Experiments (Earth’s auroral currents, magnetotail reconnection informative)