TY - JOUR
T1 - Particle acceleration in axisymmetric pulsar current sheets
AU - Cerutti, Benoît
AU - Philippov, Alexander
AU - Parfrey, Kyle
AU - Spitkovsky, Anatoly
N1 - Funding Information:
We thank J. Arons, A. Beloborodov, A. Chen, D. Caprioli, L. Sironi, A. Tchekhovskoy, and D. A. Uzdensky for discussions, and the referee Ioannis Contopoulos for his valuable comments on the manuscript. BC acknowledges support from the Lyman Spitzer Jr Fellowship awarded by the Department of Astrophysical Sciences at Princeton University. This work was partially supported by the Max-Planck/Princeton Center for Plasma Physics, by NASA grants NNX12AD01G and NNX13AO80G, and by the Simons Foundation (grant 291817 to AS). Computing resources were provided by the PICSciE-OIT TIGRESS High Performance Computing Center and Visualization Laboratory at Princeton University.
Publisher Copyright:
© 2015 The Authors.
PY - 2015/3/21
Y1 - 2015/3/21
N2 - The equatorial current sheet in pulsar magnetospheres is often regarded as an ideal site for particle acceleration via relativistic reconnection. Using 2D spherical particle-in-cell simulations, we investigate particle acceleration in the axisymmetric pulsar magnetosphere as a function of the injected plasma multiplicity and magnetization. We observe a clear transition from a highly charge-separated magnetosphere for low plasma injection with little current and spin-down power, to a nearly force-free solution for high plasma multiplicity characterized by a prominent equatorial current sheet and high spin-down power. We find significant magnetic dissipation in the current sheet, up to 30 per cent within 5 light-cylinder radii in the high-multiplicity regime. The simulations unambiguously demonstrate that the dissipated Poynting flux is efficiently channelled to the particles in the sheet, close to the Y-point within about 1-2 light-cylinder radii from the star. The mean particle energy in the sheet is given by the upstream plasma magnetization at the light cylinder. The study of particle orbits shows that all energetic particles originate from the boundary layer between the open and the closed field lines. Energetic positrons always stream outwards, while high-energy electrons precipitate back towards the star through the sheet and along the separatrices, which may result in auroral-like emission. Our results suggest that the current sheet and the separatrices may be the main source of high-energy radiation in young pulsars.
AB - The equatorial current sheet in pulsar magnetospheres is often regarded as an ideal site for particle acceleration via relativistic reconnection. Using 2D spherical particle-in-cell simulations, we investigate particle acceleration in the axisymmetric pulsar magnetosphere as a function of the injected plasma multiplicity and magnetization. We observe a clear transition from a highly charge-separated magnetosphere for low plasma injection with little current and spin-down power, to a nearly force-free solution for high plasma multiplicity characterized by a prominent equatorial current sheet and high spin-down power. We find significant magnetic dissipation in the current sheet, up to 30 per cent within 5 light-cylinder radii in the high-multiplicity regime. The simulations unambiguously demonstrate that the dissipated Poynting flux is efficiently channelled to the particles in the sheet, close to the Y-point within about 1-2 light-cylinder radii from the star. The mean particle energy in the sheet is given by the upstream plasma magnetization at the light cylinder. The study of particle orbits shows that all energetic particles originate from the boundary layer between the open and the closed field lines. Energetic positrons always stream outwards, while high-energy electrons precipitate back towards the star through the sheet and along the separatrices, which may result in auroral-like emission. Our results suggest that the current sheet and the separatrices may be the main source of high-energy radiation in young pulsars.
KW - Acceleration of particles
KW - Magnetic reconnection
KW - Methods: numerical
KW - Outflows
KW - Pulsars: general
KW - Stars: winds
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U2 - 10.1093/mnras/stv042
DO - 10.1093/mnras/stv042
M3 - Article
AN - SCOPUS:85019586897
SN - 0035-8711
VL - 448
SP - 606
EP - 619
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 1
ER -