Potential drops above pulsar polar caps: acceleration of nonneutral beams from the stellar surface
We develop a self-consistent, three-dimensional method for the calculation of the steady-state acceleration of nonneutral plasma at the surface of a rotating, magnetized, isolated neutron star. When the effects of surface work functions are negligible, there is a unique monotonic electrostatic potential and associated current profile. We obtain explicit solutions in the monopole and polar-cap geometries. In the latter, we neglect field-line curvature and consider only the aligned rotator. The maximum asymptotic particle energy in the polar-cap case, achieved along the central field line, is found to be E/sub max/=2.8 x 10/sup 9/ eV x (P/1 s)/sup -1/(B/10/sup 12/ gauss)/sup 1/2/(R/sub asterisk6/ cm)/sup 1/2/(Zm/m/sub e/)/sup 1/2/. This result is in good accord with previous estimates made by Michel. The total luminosity of the pulsar in the form of each charged-particle beam from a polar cap is L/sub cap/=4 x 10/sup 27/(P/1 s)/sup -3/(B/10/sup 12/ gauss)/sup 3/2/ (R/sub asterisk6/ cm)/sup 9/2/(m/Zm/sub e/)/sup 1/2/ ergs s/sup -1/. This luminosity is sufficient to explain radio pulsars if the beam energy can be converted to radio radiation with reasonably high efficiency, but is insufficient to explain pulsed ..gamma..-ray emission from the Crab and other pulsars. In these numerical estimates, we assume that the closed magnetosphere extends to the light cylinder. We also investigate the rotation rate of the plasma, and show that on the open-field lines of the aligned rotator, the beam current induces a twist to the field lines such that an observer at infinity sees the plasma as nonrotating. We apply these results and point out the necessity of including the effects of field-line curvature in a realistic model.
- Research Organization:
- Department of Astronomy, University of California, Berkeley
- OSTI ID:
- 7281948
- Journal Information:
- Astrophys. J.; (United States), Vol. 217:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
NEUTRON STARS
MAGNETOHYDRODYNAMICS
STAR MODELS
PULSARS
ACCELERATION
CHARGED PARTICLES
ELECTRIC FIELDS
FLUID FLOW
MAGNETIC FIELDS
MAXWELL EQUATIONS
PLASMA
ROTATION
COSMIC RADIO SOURCES
DIFFERENTIAL EQUATIONS
EQUATIONS
FLUID MECHANICS
HYDRODYNAMICS
MATHEMATICAL MODELS
MECHANICS
MOTION
STARS
640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
Radio & X-Ray Sources