Particle Acceleration and Pair Production in Pulsar Winds John Kirk - PowerPoint PPT Presentation

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Particle Acceleration and Pair Production in Pulsar Winds John Kirk Max-Planck-Institut für Kernphysik Heidelberg, Germany Kinetic modelling of astrophysical plasmas, Krakow, 5th - 9th October 2008

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Outline Pair production in pulsars 1 Pair production in laser light 2 Particle trajectories in an E-M wave 3 Counter-propagating laser beams 4 Pair production in pulsar winds 5

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Surface field B ∼ B crit = 4 . 4 × 10 13 G -10 -12 -14 -16 -18 -20 -3 -2 -1 0 1

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Surface field B ∼ B crit = 4 . 4 × 10 13 G E · B � = 0 acceleration → -10 curvature radiation -12 → single-photon pair production -14 -16 -18 -20 -3 -2 -1 0 1

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Surface field B ∼ B crit = 4 . 4 × 10 13 G E · B � = 0 acceleration → -10 curvature radiation -12 → single-photon pair production -14 Screening by pair-production front -16 -18 -20 -3 -2 -1 0 1

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Surface field B ∼ B crit = 4 . 4 × 10 13 G E · B � = 0 acceleration → -10 curvature radiation -12 → single-photon pair production -14 Screening by pair-production front -16 Multiplicity � 10 4 -18 -20 -3 -2 -1 0 1

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Surface field B ∼ B crit = 4 . 4 × 10 13 G E · B � = 0 acceleration → -10 curvature radiation -12 → single-photon pair production -14 Screening by pair-production front -16 Multiplicity � 10 4 Conflicts with PWN -18 obs.(de Jager 2007) -20 Time-dependent -3 -2 -1 0 1 cascade models? (e.g., Timokhin, this workshop)

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Accessible to Lab. experiment? Extraction from vacuum requires E > E Schwinger = 1 . 3 × 10 18 V/cm Reached at laser intensity 2 . 3 × 10 29 W/cm 2 (Hope for 10 23 –10 24 W/cm 2 in 2009/2010)

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Accessible to Lab. experiment? Extraction from vacuum requires E > E Schwinger = 1 . 3 × 10 18 V/cm Reached at laser intensity 2 . 3 × 10 29 W/cm 2 (Hope for 10 23 –10 24 W/cm 2 in 2009/2010) But not possible in a single plane-wave

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Accessible to Lab. experiment? Extraction from vacuum requires E > E Schwinger = 1 . 3 × 10 18 V/cm Reached at laser intensity 2 . 3 × 10 29 W/cm 2 (Hope for 10 23 –10 24 W/cm 2 in 2009/2010) But not possible in a single plane-wave Pair production by electron requires γ B ′ ⊥ η = ∼ 1 B crit or, equivalently γ E ′ ⊥ / E Schwinger ∼ 1 (component of acceleration perp. to v important)

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Figure-of-eight trajectory in linearly polarised wave Strictly periodic in a special reference frame (ZMF)

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Figure-of-eight trajectory in linearly polarised wave Strictly periodic in a special reference frame (ZMF) If picked up at rest in lab. frame, particle recoils ZMF reached by boost in direction of wave, with Lorentz factor equal to (invariant) strength parameter: eB / mc a = 2 πν

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Figure-of-eight trajectory in linearly polarised wave Strictly periodic in a special reference frame (ZMF) If picked up at rest in lab. frame, particle recoils ZMF reached by boost in direction of wave, with Lorentz factor equal to (invariant) strength parameter: eB / mc a = 2 πν � Laser: a = 840 I 24 λ µ m , � ˙ Pulsar: a = 2 . 6 × 10 7 P 15 / P 3 r L / r

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai E-M wave in ˆ z direction E along ˆ x E = − ˆ z × B Lorentz force vanishes for v → c ˆ z No cancellation for periodic orbit, but B ′ = B / a , so threshold is γ B ′ / B crit η ≈ = ( γ/ a ) B / B crit

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Counter-propagating beams Pair production at node B = 0 Hot spot size ≈ λ laser Production via virtual photon dominates at η � 0 . 5 For η > 0 . 8, cascade via real (curvature) photon Radiation reaction important for η > 0 . 5 Bell & Kirk arXiv:0808.2107

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Current starvation in -10 striped wind B ∝ 1 / r , -12 n ∝ 1 / r 2 Complete dissipation of -14 Poynting flux impossible if -16 κ < 2 × 10 3 ˙ P 1 / 4 15 P − 9 / 4 -18 E-M wave in outer wind “Reflection” at termination -20 “shock”? -3 -2 -1 0 1

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai -10 Assume presence of a reflected wave -12 Threshold -14 ∝ γ B ∝ 1 / r 2 Very rapid rise in -16 production rate inside r threshold -18 Pair production possible if -20 r threshold > r L . -3 -2 -1 0 1

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai -10 Assume presence of a reflected wave -12 Threshold ∝ γ B ∝ 1 / r 2 -14 Very rapid rise in production rate -16 inside r threshold -18 Pair production possible if -20 r threshold > r L . -3 -2 -1 0 1

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai -10 Assume presence of a reflected wave -12 Threshold ∝ γ B ∝ 1 / r 2 -14 Very rapid rise in production rate -16 inside r threshold -18 Pair production possible if -20 r threshold > r L . -3 -2 -1 0 1

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Conclusions Kinetic modelling of laser plasmas closely related to kinetic modelling of astrophysical plasmas

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Conclusions Kinetic modelling of laser plasmas closely related to kinetic modelling of astrophysical plasmas Colliding laser beams expected to produce pairs in lab.

Pair production in pulsars Pair production in laser light Particle trajectories in an E-M wave Counter-propagating laser beams Pai Conclusions Kinetic modelling of laser plasmas closely related to kinetic modelling of astrophysical plasmas Colliding laser beams expected to produce pairs in lab. Pair production in pulsar wind/wave cavity may be possible