scholarly journals The Origin of the Magnetic Field and Relativistic Particles in the Crab Nebula

1974 ◽  
Vol 167 (1) ◽  
pp. 1-12 ◽  
Author(s):  
M. J. Rees ◽  
J. E. Gunn
Keyword(s):  
Magnetic Field ◽  
Crab Nebula ◽  
The Crab Nebula ◽  
The Magnetic Field ◽  
Relativistic Particles

scholarly journals Relativistic Particle Acceleration in Plerions

1994 ◽  
Vol 142 ◽  
pp. 797-806
Author(s):  
Jonathan Arons ◽  
Marco Tavani
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Shock Waves ◽  
Shock Front ◽  
Heavy Ions ◽  
Surface Brightness ◽  
Crab Nebula ◽  
Electrons And Positrons ◽  
The Crab Nebula ◽  
The Magnetic Field

AbstractWe discuss recent research on the structure and particle acceleration properties of relativistic shock waves in which the magnetic field is transverse to the flow direction in the upstream medium, and whose composition is either pure electrons and positrons or primarily electrons and positrons with an admixture of heavy ions. Particle-in-cell simulation techniques as well as analytic theory have been used to show that such shocks in pure pair plasmas are fully thermalized—the downstream particle spectra are relativistic Maxwellians at the temperature expected from the jump conditions. On the other hand, shocks containing heavy ions which are a minority constituent by number but which carry most of the energy density in the upstream medium do put ~20% of the flow energy into a nonthermal population of pairs downstream, whose distribution in energy space is N(E) ∝ E−2, where N(E)dE is the number of particles with energy between E and E + dE.The mechanism of thermalization and particle acceleration is found to be synchrotron maser activity in the shock front, stimulated by the quasi-coherent gyration of the whole particle population as the plasma flowing into the shock reflects from the magnetic field in the shock front. The synchrotron maser modes radiated by the heavy ions are absorbed by the pairs at their (relativistic) cyclotron frequencies, allowing the maximum energy achievable by the pairs to be γ±m±c2 = mic2γ1/Zi, where γ1 is the Lorentz factor of the upstream flow and Zi, is the atomic number of the ions. The shock’s spatial structure is shown to contain a series of “overshoots” in the magnetic field, regions where the gyrating heavy ions compress the magnetic field to levels in excess of the eventual downstream value.This shock model is applied to an interpretation of the structure of the inner regions of the Crab Nebula, in particular to the “wisps,” surface brightness enhancements near the pulsar. We argue that these surface brightness enhancements are the regions of magnetic overshoot, which appear brighter because the small Larmor radius pairs are compressed and radiate more efficiently in the regions of more intense magnetic field. This interpretation suggests that the structure of the shock terminating the pulsar’s wind in the Crab Nebula is spatially resolved, and allows one to measure γ1, and a number of other properties of the pulsar’s wind. We also discuss applications of the shock theory to the termination shocks of the winds from rotation-powered pulsars embedded in compact binaries. We show that this model adequately accounts for (and indeed predicted) the recently discovered X-ray flux from PSR 1957+20, and we discuss several other applications to other examples of these systems.Subject headings: acceleration of particles — ISM: individual (Crab Nebula) — relativity — shock waves

scholarly journals The Magnetic Field of the Crab as Revealed by New, High Resolution, Multi-Band Radio Images

1990 ◽  
Vol 140 ◽  
pp. 79-80
Author(s):  
M. F. Bietenholz ◽  
P. P. Kronberg
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Crab Nebula ◽  
Radio Observations ◽  
Field Orientation ◽  
Magnetic Field Orientation ◽  
The Crab Nebula ◽  
The Magnetic Field ◽  
Made In ◽  
Multi Band

We present and describe recent radio observations of the Crab Nebula, which allow us to determine the magnetic field orientation and depolarization at unprecedented resolution. The observations were made in 1987-1988 using all four configurations of the VLA, at 1410,1515,4625, and 4885 MHz. The resulting maps were all convolved with a clean beam of 1.8″ × 2.0″, elongated in P.A. 80°, and the residuals added back in.

scholarly journals Relationship Between Pulsar and Nebula

1971 ◽  
Vol 46 ◽  
pp. 389-391
Author(s):  
L. Woltjer
Keyword(s):  
Magnetic Field ◽  
Energy Density ◽  
Energy Supply ◽  
Crab Nebula ◽  
Supernova Explosion ◽  
Relativistic Electrons ◽  
The Crab Nebula ◽  
The Magnetic Field

The magnetic field and the relativistic electrons in the Crab Nebula cannot have originated at the time of the supernova explosion. The energy density in the magnetic field is so large that it must have been generated using the energy supply in the pulsar. The energies of the electrons are so high, and their lifetimes correspondingly are so short, that they must have been accelerated, again using the pulsar energy. The efficiency of these processes must be high, but there is an adequate energy supply.

Production of the magnetic field of the Crab Nebula

1959 ◽  
Vol 12 (5) ◽  
pp. 477-482
Author(s):  
L. Marshall
Keyword(s):  
Magnetic Field ◽  
Crab Nebula ◽  
The Crab Nebula ◽  
The Magnetic Field

The magnetic field of the Crab Nebula and the nature of its 'jet'

1990 ◽  
Vol 357 ◽  
pp. L13 ◽  
Author(s):  
M. F. Bietenholz ◽  
P. P. Kronberg
Keyword(s):  
Magnetic Field ◽  
Crab Nebula ◽  
The Crab Nebula ◽  
The Magnetic Field

scholarly journals Synchrotron Thermal Instabilities and Radio Filaments in the Lobes of Cygnus A

1989 ◽  
Vol 8 ◽  
pp. 417-422
Author(s):  
G. Bodo ◽  
A. Ferrari ◽  
S. Massaglia ◽  
E. Trussoni
Keyword(s):  
Magnetic Field ◽  
Thermal Instability ◽  
Crab Nebula ◽  
Relativistic Electrons ◽  
Synchrotron Emission ◽  
Cygnus A ◽  
The Crab Nebula ◽  
The Magnetic Field

Recent VLA observations of the lobes of Cygnus A exhibit complex “filamentary” structures, with typical scale width ~ 1 arcsec (Dreher, Carilli and Perley, 1987, Perley, 1987). The filaments appear aligned with the magnetic field, as results from polarization measures, suggesting that the field may play a fundamental role in the process of their formation.We propose a mechanism for the possible formation of these filaments based upon a thermal instability connected with synchrotron emission from relativistic electrons. This type of instability was studied by Simon and Axford (1967), who discussed it in connection with the Crab Nebula filaments, and by Eilek and Caroff (1979), who generalized the previous study for application to quasar atmospheres.

scholarly journals Reconnection in Pulsar Winds

2001 ◽  
Vol 18 (4) ◽  
pp. 415-420 ◽  
Author(s):  
J. G. Kirk ◽  
Y. Lyubarsky
Keyword(s):  
Magnetic Field ◽  
Energy Transport ◽  
Crab Nebula ◽  
Low Frequency ◽  
Frequency Wave ◽  
Poynting Flux ◽  
High Particle ◽  
The Crab Nebula ◽  
Pulsar Winds ◽  
The Magnetic Field

AbstractThe spin-down power of a pulsar is thought to be carried away in an MHD wind in which, at least close to the star, the energy transport is dominated by Poynting flux. The pulsar drives a low frequency wave in this wind, consisting of stripes of toroidal magnetic field of alternating polarity, propagating in a region around the equatorial plane. The current implied by this configuration falls off more slowly with radius than the number of charged particles available to carry it, so that the MHD picture must, at some point, fail. Recently, magnetic reconnection in such a structure has been shown to accelerate the wind significantly. This reduces the magnetic field in the comoving frame and, consequently, the required current, enabling the solution to extend to much larger radius. This scenario is discussed and, for the Crab Nebula, the range of validity of the MHD solution is compared with the radius at which the flow appears to terminate. For sufficiently high particle densities, it is shown that a low frequency entropy wave can propagate out to the termination point. In this case, the ‘termination shock’ itself must be responsible for dissipating the wave.This paper is dedicated to Don Melrose on his 60th birthday.

scholarly journals Radio Polarization of the Crab Nebula

1971 ◽  
Vol 46 ◽  
pp. 292-295
Author(s):  
R. G. Conway
Keyword(s):  
Magnetic Field ◽  
Crab Nebula ◽  
Line Of Sight ◽  
Rotation Measure ◽  
Radio Measurements ◽  
The Crab Nebula ◽  
The Magnetic Field ◽  
Concentration Of Electrons

Optical and radio measurements of polarization can be combined to find the configuration of the magnetic field throughout the Crab Nebula. The component in the line of sight is found from the radio rotation measure.New measurements of polarisation at 11 cm with a resolution of 7′ x 14′ are combined with previous results to show that the rotation measure is fairly uniform and near −25 rad m−2 near the centre, but that it becomes irregular near the edges. It rises to 300 rad m−2 in the filaments, possibly indicating a concentration of electrons about 10–100 cm−3.

scholarly journals A lower limit to the magnetic field in the Crab Nebula from cosmic γ-ray experiments at 1011 eV

1970 ◽  
Vol 37 ◽  
pp. 250-256
Author(s):  
G. G. Fazio ◽  
H. F. Helmken ◽  
G. H. Rieke ◽  
T. C. Weekes
Keyword(s):  
Magnetic Field ◽  
Lower Limit ◽  
Crab Nebula ◽  
High Energy ◽  
Secondary Products ◽  
High Energy Electrons ◽  
Γ Rays ◽  
Γ Ray ◽  
The Crab Nebula ◽  
The Magnetic Field

The 10-m optical reflector at Mt. Hopkins, Arizona, has been used to search for cosmic γ-Rays by the detection of atmospheric Čerenkov radiation from energetic particle showers. Approximately 100 drift scans of the Crab Nebula during 1968–69 have yielded no positive evidence of a γ-Ray flux. The upper limit to the flux at 1.7 × 1011 eV is 2.0 × 10−10 photons/cm2 sec. Assuming γ-Rays of this energy are produced by Compton scattering, a lower limit on the average magnetic field in the Crab Nebula is 1.5 × 10−4 gauss. This experiment also verifies previous evidence that the high-energy electrons in the Crab Nebula are not the secondary products of high-energy proton interactions but must have been accelerated from lower energies.

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