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Pulsars: the Magnetosphere and the γ -ray emission

Pulsars: the Magnetosphere and the γ -ray emission. Gabriele Brambilla. Supervisors : P. M. Pizzochero ( Unimi ), A. K. Harding (NASA GSFC). The pulsar radio emission lead to the conclusion they are fast rotating compact objects. www.cv.nrao.edu. C. Kalapotharakos.

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Pulsars: the Magnetosphere and the γ -ray emission

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  1. Pulsars: the Magnetosphere and the γ-ray emission Gabriele Brambilla Supervisors: P. M. Pizzochero (Unimi), A. K. Harding (NASA GSFC)

  2. The pulsar radio emission lead to the conclusion they are fast rotating compact objects www.cv.nrao.edu C. Kalapotharakos

  3. Pulsars are formed in supernovae explosions, and they accelerate particles that emit in X and γ rays Supernova shell Jet Neutron star and Pulsar wind Pulsar wind nebula Pulsar Credit: NASA/CXC/ISDC/L. Pavan et al Credit: NASA/CXC/Eureka Scientific/M. Roberts et al.

  4. Measuring the pulsar period and its deceleration, we get a lot of information about the pulsar For a spinning magnetic dipole: Harding from ATNF data Harding 2013

  5. Pulsars behaves like a dynamo; currents dissipate, emitting light when particles are accelerated www.physicsforums.com Google images Particle’s acceleration produces light -> dissipation

  6. Pulsars cannot be surrounded by vacuum. The opposite limit is called force-free plasma Ω J = σ ( E + v x B) E magnetosphere =0 (force free) PULSAR B E·B=0

  7. The magnetosphere can get close to the force-free condition by electron-positron pair cascades e± e- e± e± A. K. Harding QED: g+ B  e Pair Formation Front e+ e-

  8. Finite conductivity implies particles’ acceleration and emission along the magnetic field lines E·B≠0 B A. A. Abdo et al. The second Fermi Large Area Telescope catalog of gamma-ray pulsars. The Astrophysical Journal Supplement Series, 2013. ρ

  9. The geometry of the emission depends on the location of particles’ acceleration and on relativistic effects ζ ϕ C. Kalapotharakos

  10. The global magnetosphere structure was explored with MHD models, which matched up well with the data Gruzinov 1999 A. Spitkovsky 2006 I. Contopoulos et al 1999 Bai & Spitkovsky 2010 b C. Kalapotharakos et al 2014

  11. PIC codes allow for the exploration of feedback mechanisms in the magnetosphere including both e+ and e- Philippov et al 2015 A. Marocchino

  12. ^3)

  13. RETARDATION Ω B µ CAUSTIC ABERRATION µ LEADING EDGE TRAILING EDGE ●

  14. Particle-in-cell simulations: Spitkovsky & Arons 2002 Torus develops diocotron instability Petri, Heyvaerts & Bonazzola 2002b

  15. Time scale (limit cycle): µs Timokhin & Arons, 2013 Pair multiplicity: 103 ÷ 105 Timokhin & Harding, 2015 g+ g  e

  16. The magnetospheric gaps models are not self-consistent but they partly describe the Fermi data Radio beam from the polarcap Slot gap Striped wind Outer gap J. G. Kirk et al 2009 A. K. Harding

  17. C. Kalapotharakos et al, 2014

  18. Observed Model: a = 600, z = 500, s = 10W DeCesar 2013 Brambilla et al. 2015

  19. Observed Model: a = 600, z = 500, s = 10W Fermi 2nd Pulsar Catalog, Abdo et al. 2013 Brambilla et al. 2015

  20. Agevsσ Brambilla et al. 2015

  21. Non-uniform conductivity C. Kalapotharakos et al, 2015 (in prep.) a = 150450750 s finite The first results show a significant dependence of Lγ on α This dependence together with the fΩvariability with ζ may be able to explain the Lγ scattering

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