Pair Production Multiplicities in Rotation-powered Pulsars

By Johann A. Hibschman, J. Arons. 2001

135 citations recorded by the source corpus.

We discuss the creation of electron-positron cascades in the context of pulsar polar cap acceleration models and derive several useful analytic and semianalytic results for the spatial extent and energy response of the cascade. Instead of Monte Carlo simulations, we use an integrodifferential equation that describes the development of the cascade energy spectrum in one space dimension quite well, when it is compared to existing Monte Carlo models. We reduce this full equation to a single integral equation, from which we can derive useful results, such as the energy loss between successive generations of photons and the spectral index of the response. We find that a simple analytic formula represents the pair cascade multiplicity quite well, provided that the magnetic field is below 1012 G and that an only slightly more complex formula matches the numerically calculated cascade at all other field strengths. Using these results, we find that cascades triggered by γ-rays emitted through inverse Compton scattering of thermal photons from the neutron star's surface, both resonant and nonresonant, are important for the dynamics of the polar cap region in many pulsars. In these objects, the expected multiplicity of pairs generated by a single input particle is lower than previously found in cascades initiated by curvature emission, frequently being on the order of 10 rather than ~1000 as usually quoted. Such pulsars also are expected to be less luminous in polar cap γ-rays than when curvature emission triggers the cascade, a topic that will be the subject of a subsequent paper.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Ocean Engineering

View Paper: https://www.semanticscholar.org/paper/0d659794c019a435b33d79c3d5e1e4848ee3c05f

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Citations in the corpus

EFFICIENCY OF MAGNETIC TO KINETIC ENERGY CONVERSION IN A MONOPOLE MAGNETOSPHERE (2009, background): “…near the surface of the neutron star in polar gaps (Sturrock 1971; Ruderman & Sutherland 1975; Scharlemann et al. 1978; Daugherty & Harding 1982; Hibschman & Arons 2001a,b) and farther from the neutron star in slot gaps (Arons 1983) and outer gaps (Cheng et al. 1976, 1986; Romani & Yadigaroglu…”
Chandra Imaging of the X-Ray Nebula Powered by Pulsar B1509–58 (2001, background): “Gallant, Y. A., Hoshino, M., Langdon, A. B., Arons, J., & Max,C. E. 1992, ApJ, 391, 73.”
The Termination Shock in a Striped Pulsar Wind (2003, background): “The available theoretical models (Hibschman & Arons 2001a,b), give κ from a few to thousands.”
Coherent emission mechanisms in astrophysical plasmas (2017, methodology): “Numerical models suggest Lorentz factors in the range tens to hundreds (Zhang and Harding, 2000; Hibschman and Arons, 2001; Arendt and Eilek, 2002).”
Time-dependent pair cascades in magnetospheres of neutron stars - I. Dynamics of the polar cap cascade with no particle supply from the neutron star surface (2010, background): “For young pulsars the dominant emission process in terms of the number of pair-production capable photons is the curvature radiation (e.g. Hibschman & Arons 2001a).”
The Proto-Magnetar Model for Gamma-Ray Bursts (2010, background): “Once neutrino heating decreases sufficiently, other processes (e.g. γ−B or γ−γ pair production) likely take over as the dominant source of mass-loading (Hibschman & Arons 2001; Thompson 2008) and the wind composition may change from baryon- to pair-dominated. c© ????”