Extended Acceleration in Slot Gaps and Pulsar High-Energy Emission

By A. Muslimov, A. Harding. 2003

195 citations recorded by the source corpus.

We revise the physics of primary electron acceleration in the "slot gap" (SG) above the pulsar polar caps (PCs), a regime originally proposed by Arons & Scharlemann in their electrodynamic model of pulsar PCs. We employ the standard definition of the SG as a pair-free space between the last open field lines and the boundary of the pair plasma column that is expected to develop above the bulk of the PC. The rationale for our revision is that the proper treatment of primary acceleration within the pulsar SGs should take into account the effect of the narrow geometry of the gap on the electrodynamics within the gap and also include the effect of inertial frame dragging on the particle acceleration. We show that the accelerating electric field within the gap, being significantly boosted by the effect of frame dragging, becomes reduced because of the gap geometry by a factor proportional to the square of the SG width. The combination of the effects of frame dragging and geometrical screening in the gap region naturally gives rise to a regime of extended acceleration, which is not limited to "favorably curved" field lines as in earlier models, and the possibility of multiple-pair production by curvature photons at very high altitudes, up to several stellar radii. We present our estimates of the characteristic SG thickness across the PC, energetics of primaries accelerated within the gap, high-energy bolometric luminosities emitted from the high altitudes in the gaps, and maximum heating luminosities produced by positrons returning from the elevated pair fronts. The estimated theoretical high-energy luminosities are in good agreement with the corresponding empirical relationships for γ-ray pulsars. We illustrate the results of our modeling of the pair cascades and γ-ray emission from the high altitudes in the SG for the Crab pulsar. The combination of the frame-dragging field and high-altitude SG emission enables both acceleration at the smaller inclination angles and a larger emission beam, both necessary to produce widely spaced double-peaked profiles.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/219998854b1a02cec99999411109d56895c05e93

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Citations in the corpus

THE LARGE AREA TELESCOPE ON THE FERMI GAMMA-RAY SPACE TELESCOPE MISSION (2009, background): “Some also predict emission between the polar cap and outer magnetosphere extremes (Muslimov & Harding 2003; Dyks & Rudak 2003).”
VHE γ-Ray Observation of the Crab Nebula and its Pulsar with the MAGIC Telescope (2007, background): “We should not omit the slot-gap model, which places the acceleration zone at the outer rim of the polar cap (Arons 1983; Muslimov & Harding 2003).”
MODELING OF GAMMA-RAY PULSAR LIGHT CURVES USING THE FORCE-FREE MAGNETIC FIELD (2009, background): “…al. 1978; Daugherty & Harding 1982, 1996), the slot gap model (SG, or two-pole caustic model, TPC for short; Arons & Scharlemann 1979; Arons 1983; Muslimov & Harding 2003, 2004; Dyks & Rudak 2003; Dyks et al. 2004), the outer gap model(OG, Cheng et al. 1986a,b; Romani & Yadigaroglu 1995;…”
High-Altitude Emission from Pulsar Slot Gaps: The Crab Pulsar (2008, background): “The width of the slot gap, SG, is a function of pulsar period and surface magnetic field, and can be expressed as a fraction in colatitude / 0 of the polar cap opening angle, 0 ’ ( R /c)1/2 (Muslimov & Harding 2003, hereafter MH03), SG 2P(kB12) 4=7I 3=745 ; ð1Þ where we will take k ¼ 0:1.”
THE FIRST FERMI LARGE AREA TELESCOPE CATALOG OF GAMMA-RAY PULSARS (2009, background): “In slot gap models (Muslimov & Harding 2003), the break occurs at about 1035 erg s−1, when the gap is limited by screening of the accelerating field by pairs.”
Modelling high-energy pulsar light curves from first principles (2015, background): “…and open field lines, extending from the stellar surface up to the light-cylinder in some cases (slot-gap Arons & Scharlemann 1979; Arons 1983; Muslimov & Harding 2003, 2004, two-pole caustics Dyks & Rudak 2003 models), but the Fermi-LAT data currently favor emission from the outer…”
Two-Pole Caustic Model for High-Energy Light Curves of Pulsars (2003, background): “…may provide physical grounds for the geometry of the two-pole caustic model: the slot-gap model of Arons & Scharlemann (1979), in the modern version of Muslimov & Harding (2003); and the model of Hirotani et al. (2003) of an outer gap extended on either side of the null surface due to the currents.”
Three-dimensional numerical simulations of the pulsar magnetosphere: preliminary results (2008, background): “3 above, allow for a nonzero parallel component as current emission models imply (e.g. Arons 1983; Daugherty & Harding 1982; Muslimov & Harding 2003; Cheng et al. 1986; Romani 1996).”
AN ATLAS FOR INTERPRETING γ-RAY PULSAR LIGHT CURVES (2008, background): “A physical TPC model should also have a finite gap thickness; the " slot gap " model of Muslimov & Harding (2003) provides a possible physical foundation for the TPC picture.”
Particle acceleration in axisymmetric pulsar current sheets (2014, background): “…rays are often associated with curvature radiation, emitted by relativistic electron-positron pairs accelerated in tiny regions where the electric field is not perfectly screened by the plasma (the so-called “gap” models, e.g., Arons 1983; Cheng et al. 1986; Romani 1996; Muslimov & Harding 2003).”
High-Altitude Particle Acceleration and Radiation in Pulsar Slot Gaps (2004, background): “In our previous paper (Muslimov & Harding 2003 [MH03]) we began discussing the regime of acceleration of particles and production of high-energy emission within the pulsar slot gap (SG), a narrow region on the boundary of the open field lines, where the electric field drops to zero.”
High-Energy Emission from Millisecond Pulsars (2004, background): “…young pulsars produce sufficient electron-positron pairs to screen the accelerating electric field, thereby limiting acceleration to low altitudes over nearly the entire PC (except in a narrow slot gap; Muslimov & Harding 2003), many older pulsars and nearly all MSPs are marginally producing pairs.”