Light Cylinder Radius Research Articles

A model of unpulsed gamma rays from the Crab pulsar

view Abstract Citations (5) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Model of Unpulsed Gamma Rays from the Crab Pulsar Cheung, W. M. ; Cheng, K. S. Abstract We study the possibility that the unpulsed gamma rays in the energy range of 100 MeV-10 GeV from the direction of the Crab Nebula and pulsar are actually emitted from a region extending to a couple of light cylinder radii from the pulsar instead of from the extensive nebula. In our model, two pulsed photon beams from two different outer gaps cross each other beyond the light cylinder and result in pair production. Since the pitch angles of these pairs do not correlate with the local magnetic field, and the typical mean free path for pair production is comparable to the local radius of curvature, the subsequent synchrotron radiation and inverse Compton scattering produce unpulsed X-rays and gamma rays, respectively. Publication: The Astrophysical Journal Pub Date: August 1993 DOI: 10.1086/173037 Bibcode: 1993ApJ...413..694C Keywords: Crab Nebula; Gamma Ray Spectra; Pair Production; Photons; Pulsars; Astronomical Models; Compton Effect; Gamma Ray Astronomy; Astrophysics; GAMMA RAYS: THEORY; STARS: PULSARS: INDIVIDUAL NAME: CRAB NEBULA; RADIATION MECHANISMS: MISCELLANEOUS; ISM: SUPERNOVA REMNANTS full text sources ADS | data products SIMBAD (2)

Electromagnetically driven relativistic jets - A class of self-similar solutions

view Abstract Citations (204) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Electromagnetically Driven Relativistic Jets: A Class of Self-similar Solutions Li, Zhi-Yun ; Chiueh, Tzihong ; Begelman, Mitchell C. Abstract We have constructed a class of self-similar solutions for relativistic winds driven by rotating magnetic fields. These winds are collimated to cylindrical jet flows of finite radii and may attain supermagnetosonic speeds with high Lorentz factors. Most of the flow acceleration results from the "magnetic nozzle" effect and occurs beyond the fast magnetosonic point, which is typically located a few light cylinder radii from the rotation axis. Approximate equipartition between the electromagnetic and flow kinetic energies is generally achieved for these jets, in contrast to the radial wind case in which the flow is magnetically dominated at all radii. Publication: The Astrophysical Journal Pub Date: August 1992 DOI: 10.1086/171597 Bibcode: 1992ApJ...394..459L Keywords: Computational Astrophysics; Electromagnetic Fields; Interstellar Magnetic Fields; Jet Flow; Magnetohydrodynamic Flow; Relativistic Particles; Active Galactic Nuclei; Kinetic Energy; Magnetic Field Configurations; Magnetic Flux; Numerical Integration; Astrophysics; GALAXIES: JETS; GALAXIES: QUASARS: GENERAL; MAGNETOHYDRODYNAMICS: MHD; STARS: PULSARS: GENERAL full text sources ADS |

Pulsar Polarization Limiting Radii and the Evolution of Pulsar Beams

We estimate the polarization limiting radius, rp1, as a function of rotation period P, magnetic field strength B, and radio frequency v, in radio pulsars assuming plasma parameters that are typical of polar-cap pair-creation models of pulsars. We find that rpl ⋍ 9 × 108(P/1s)0.4 cm, for a surface magnetic field strength of 1012 G, and radio frequency of 109 Hz. For short rotation periods, rpl approaches the light cylinder radius, rlc. Here the magnetic field becomes more azimuthal, and the excursion in position angle over a pulse is less, on average, than when rpl ≪ rlc. With the assumption of a vacuum magnetic field we calculate the polarization position angle as a function of pulse longitude, and the angles i (the angle between the magnetic moment and the rotation axis) and α (the angle between the line of sight and the rotation axis). We calculate the average change in polarization angle as a function of pulsar period, assuming a circular beam, and find consistency with the polarization data summarized by Narayan and Vivekand (1983). We conclude that the evidence is consistent with beams that are roughly constant in shape, providing an alternative to the evolving elliptical beam model of Narayan and Vivekand (1983). This interpretation is further supported by the frequency dependence of the polarization angle in the Crab Pulsar, the frequency of pulsars with double and multiple pulse components, the frequency of pulsars with interpulses, and the absence of pulsars in plerions. See Barnard (1986) for further details.

Probing the magnetic field of radio pulsars - A reexamination of polarization position angle swings

The author calculates the polarization position angle as a function of pulse longitude and polarization limiting radius in radio pulsars assuming a vacuum magnetic field. He also estimates the polarization radius r<SUB>pl</SUB>, based on the calculations of Cheng and Ruderman and Stinebring. It is found that for rotation periods P &lt; 0.06 s this radius is r<SUB>pl</SUB> ≈ 2×10<SUP>5</SUP>(P/1 s)<SUP>-2</SUP>cm and for P &gt; 0.06 s it is r<SUB>pl</SUB> ≈ 9×10<SUP>8</SUP>(P/1 s)<SUP>0.4</SUP>cm for a surface magnetic field strength of 10<SUP>12</SUP>G and radio frequency of 10<SUP>9</SUP>Hz. For short rotation periods, r<SUB>pl</SUB> approaches the light cylinder radius r<SUB>lc</SUB>.

X-ray emission from radio pulsar winds

view Abstract Citations (20) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X-ray emission from radio pulsar winds. Cheng, A. F. Abstract Synchrotron radiation from a pulsar wind is considered as a possible basis for unpulsed X-ray emission from radio pulsars. In a simple spherical model for a hot, relativistic plasma wind from a pulsar, the magnetic field is essentially toroidal and the flow mostly radial, and it is assumed that the wind model applies beyond a radius that is several times the light cylinder radius. If the pulsar wind is unconfined, most of the X-ray synchrotron radiation would be emitted from the vicinity of the radius, and the angular diameter of such a source would be too small to be resolvable. If the pulsar wind is confined, then unpulsed, spatially extended X-ray emission may be detectable in addition to the point source emission from near the radius. A ram pressure-confined pulsar wind would be observable as a spatially extended emission region located in front of the pulsar. These models are applied to Einstein observatory observations. Publication: The Astrophysical Journal Pub Date: December 1983 DOI: 10.1086/161574 Bibcode: 1983ApJ...275..790C Keywords: Pulsars; Stellar Models; Stellar Spectrophotometry; Stellar Winds; Synchrotron Radiation; X Ray Sources; Magnetic Field Configurations; Point Sources; Radiant Flux Density; Radiation Distribution; Relativistic Particles; Astrophysics full text sources ADS | data products SIMBAD (2)

The Electric Fields in Nonneutral Beam Models of Pulsar Magnetospheres

The electric fields in the polar cap region of the magnetosphere of a pairless orthogonal rotator are being calculated using a modified Poisson's equation which takes explicit account of the effect of the displacement current on the potential Φ. This is the first step in a program to determine how return currents are formed in these models and the resulting global current flow patterns. The potential is being calculated from 0.1 RL to 3 RL, where RL is the light cylinder radius, using known results for ⊘ at 0.1 RL with an inner last closed magnetic field line corresponding to that of a point dipole. Considerable difficulty is being encountered because of the mixed nature of the equation and the irregular boundaries. Possible methods of overcoming these difficulties are indicated.

The Axially Symmetric Wind Magnetosphere

A central question in magnetospheric theory of pulsars is: how does a rapidly rotating magnetized neutron star manage to short-circuit its huge unipolar induction voltage? This problem is best studied in an idealized geometry like the parallel rotator. The theory must at least include basic plasma physics with relativistic particle inertia. Even the simplest model will require a global self-consistent solution of both Maxwell's equations and relativistic MHD-equations of motion. Assuming time independence, axial symmetry and charge separation, we reduce this problem to three coupled, quasilinear second order partial differential equations for three dimensionless scalar quantities Φ, f and Γ (see Schmalz et al., 1980): Here x and z are cylindrical coordinates measured in units of the light cylinder radius. Φ is the stream function which is constant on stream lines, f = x · vφ/C is connected with the angular momentum (vφ = toroidal velocity), and Γ = 2∊γ = 2∊/(1 - v2/c2)1/2 where ∊ = mc2/(eBoa2ω) is a dimensionless parameter. Taking electrons (mass m, charge e) and typical neutron star parameters (radius a = 10 km, angular velocity ω = 30/s, polar field strength Bo = 108 T), we have ∊ ≈ −10−12.