Position of the Low Frequency Radio Source in the Crab Nebula

Nature ◽  
1967 ◽  
Vol 213 (5082) ◽  
pp. 1213-1214 ◽  
Author(s):  
J. F. R. GOWER
Keyword(s):  
Radio Source ◽  
Crab Nebula ◽  
Low Frequency ◽  
The Crab Nebula

scholarly journals Strong Waves from Pulsars and Morphologies in SNRs

1983 ◽  
Vol 101 ◽  
pp. 499-501
Author(s):  
Gregory Benford ◽  
Attilio Ferrari ◽  
Silvano Massaglia
Keyword(s):  
Large Amplitude ◽  
Crab Nebula ◽  
Surrounding Medium ◽  
Low Frequency ◽  
Optical Emission ◽  
Amplitude Wave ◽  
Surface Magnetic Field ◽  
Plasma Absorption ◽  
The Crab Nebula ◽  
Large Amplitude Wave

Canonical models for pulsars predict the emission of low–frequency waves of large amplitudes, produced by the rotation of a neutron star possessing a strong surface magnetic field. Pacini (1968) proposed this as the basic drain which yields to the pulsar slowing–down rate. The main relevance of the large amplitude wave (LAW) is the energetic link it provides between the pulsar and the surrounding medium. This role has been differently emphasized (Rees and Gunn, 1974; Ferrari, 1974), referring to absorption effects by relativistic particle acceleration and thermal heating, either close to the pulsar magnetosphere or in the nebula. It has been analyzed in the special case of the Crab Nebula, where observations are especially rich (Rees, 1971). As the Crab Nebula displays a cavity around the pulsar of dimension ∼1017cm, the function of the wave in sweeping dense gas away from the circumpulsar region is widely accepted. Absorption probably occurs at the inner edges of the nebula; i.e., where the wave pressure and the nebular pressure come into balance. Ferrari (1974) interpreted the wisps of the Crab Nebula as the region where plasma absorption occurs, damping the large amplitude wave and driving “parametric” plasma turbulence, thus trasferring energy to optical radiation powering the nebula. The mechanism has been extended to interpret the specific features of the “wisps” emission (Benford et al., 1978). Possibly the wave fills the nebula completely, permeating the space outside filaments with electromagnetic energy, continuously accelerating electrons for the extended radio and optical emission (Rees, 1971).

Preferential acceleration of heavy ions from thermal velocities

1968 ◽  
Vol 46 (10) ◽  
pp. S638-S641 ◽  
Author(s):  
D. B. Melrose
Keyword(s):  
Frequency Spectrum ◽  
High Frequency ◽  
Heavy Ions ◽  
Crab Nebula ◽  
Low Frequency ◽  
High Frequency Waves ◽  
Hydromagnetic Waves ◽  
The Crab Nebula ◽  
Low Frequency Waves

The acceleration of ions from thermal velocities is analyzed to determine conditions under which heavy ions can be preferentially accelerated. Two accelerating mechanisms involving high-and low-frequency hydromagnetic waves respectively are considered. Preferential acceleration of heavy ions occurs for high-frequency waves if the frequency spectrum falls off faster than (frequency)−1. For the low-frequency waves heavy ions are less effectively accelerated than lighter ions. However, very heavy ions can be preferentially accelerated, the abundances of the very heavy ions being enhanced by a factor Ai over the thermal abundances. Acceleration of ions in the envelope of the Crab nebula is considered as an example.

The Crab Nebula as a Radio Source.

1953 ◽  
Vol 118 ◽  
pp. 1 ◽  
Author(s):  
Jesse L. Greenstein ◽  
Rudolph Minkowski
Keyword(s):  
Radio Source ◽  
Crab Nebula ◽  
The Crab Nebula

scholarly journals 58. Results of observations of the scattering of radio waves by the electronic inhomogeneities of the solar corona

1957 ◽  
Vol 4 ◽  
pp. 313-317
Author(s):  
V. V. Vitkevitch
Keyword(s):  
Solar Corona ◽  
Radio Source ◽  
Crab Nebula ◽  
New Method ◽  
Radio Waves ◽  
The Crab Nebula

A new method for the investigation of the solar corona, suggested by us (Vitkevitch, 1951) [1], consists of observing the radio source identified with the Crab nebula (NGC 1952; α = 05h 31m 40s, δ = 22° 10′) when it is covered by the solar corona. This occurs every year on 14–15 June.

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.

The Fortieth Anniversary of Extragalactic Radio Astronomy: Radiophysics in Exile

1990 ◽  
Vol 8 (04) ◽  
pp. 381-383 ◽  
Author(s):  
J. G. Bolton
Keyword(s):  
Radio Astronomy ◽  
Crab Nebula ◽  
Low Frequency ◽  
Early Years ◽  
Owens Valley ◽  
Detection Range ◽  
Staff Members ◽  
Cygnus A ◽  
The Galaxy ◽  
The Crab Nebula

In 1931 Karl Jansky established that radio noise was associated with our own galaxy–the Milky Way. For a decade and a half there was little follow-up; those of us who were associated with low frequency radar during the war regarded it as a nuisance which could limit the detection range of enemy aircraft. Grote Reber was the first to make a detailed but fairly low resolution map of the radiation from the galaxy showing, for the first time, some detailed structure. The event which we celebrate today occurred when Gordon Stanley, Bruce Slee and I showed that three of the discrete sources that we had discovered could be identified with visual objects. One was with the Crab Nebula, a supernova remnant within our own galaxy and the other two with galaxies, far beyond our own system, in the constellations of Virgo and Centaurus. Thus began extragalactic radio astronomy. In 1982 at the Noosa meeting of the ASA, I gave an account of those early years, later to be published in the ASA Proceedings. As I don’t wish to repeat myself, I propose to speak on my involvement in a later development which was to extend the observable scale of the universe to look-back times as great as the age of the oldest stars in our own system. The first important step was Graham Smith’s identification of Cygnus A with a galaxy that was much fainter than our two. The spectrum by Minkowski revealed an instrinsically highly-luminous galaxy with strong emission lines and opened up the possibility of discovering similar objects at significantly greater distance. This was achieved nine years later with the building of the Owens Valley Observatory and my title of ‘Radiophysics in Exile’ comes from the fact the observatory owed its existence and early successes very largely to past and future staff members of Radiophysics. They were, in order of appearance, J. G. Bolton, G. J. Stanley, K. C. Westfold, J. A. Roberts, V. Radhakrishnan, D. Morris and K. I. Kellermann. Some still bear . the scars–Westfold left the tip of one index finger in the Owens Valley!

scholarly journals Radio observations of the lunar atmosphere

1959 ◽  
Vol 9 ◽  
pp. 47-49
Author(s):  
B. Elsmore
Keyword(s):  
Radio Source ◽  
Crab Nebula ◽  
Large Diameter ◽  
Radio Observations ◽  
Radio Brightness ◽  
Lunar Occultation ◽  
Terrestrial Atmosphere ◽  
Accurate Position ◽  
The Crab Nebula

Observations of a lunar occultation of a radio source may provide information concerning both the distribution of radio “brightness” across the source and its accurate position. For sources of which these results are already fairly well known, observations at long wavelengths may be used to derive the density of the lunar atmosphere [1]. During recent years two such occultations have been observed at Cambridge: one, the occultation of IC 443, the large-diameter radio source in the constellation of Gemini, from which the density of the lunar atmosphere was estimated to be less than 10–12 of that of the density of the terrestrial atmosphere [2] and [3]; and two, the occultation of the Crab nebula on 1956 January 24 [4].

Low-frequency Spectrum of the Crab Nebula

Nature ◽  
1970 ◽  
Vol 225 (5237) ◽  
pp. 1035-1037 ◽  
Author(s):  
A. H. BRIDLE
Keyword(s):  
Frequency Spectrum ◽  
Crab Nebula ◽  
Low Frequency ◽  
The Crab Nebula

Observation of Polarization for the Crab Nebula with PHENEX Polarimeter

2010 ◽  
Vol 8 (ists27) ◽  
pp. Tm_35-Tm_40 ◽  
Author(s):  
Yuji KISHIMOTO ◽  
Shuichi GUNJI ◽  
Yushi ISHIKAWA ◽  
Makoto TAKADA ◽  
Tatehiro MIHARA ◽  
...  
Keyword(s):  
Crab Nebula ◽  
The Crab Nebula
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