scholarly journals Occultations of the Crab Nebula by the Solar Corona in June 1957 and 1958

1959 ◽  
Vol 12 (2) ◽  
pp. 134 ◽  
Author(s):  
OB Slee
Keyword(s):  
Solar Corona ◽  
Large Scale ◽  
Crab Nebula ◽  
Angular Separation ◽  
Pencil Beam ◽  
Scattering Process ◽  
Short Term ◽  
Transmission Properties ◽  
The Crab Nebula ◽  
Comparable Magnitude

A description is given of some observations of the occultations of the Crab nebula by the solar corona in June 1957 and 1958, obtained with pencil-beam, fan-beam, and interferometer-type instruments. It is shown that the distribution of 85� 5 Mc/s radiation on days when the angular separation is less than 10 solar radii is not consistent with a symmetrical scattering process. Better agreement is obtained by postulating the existence of scattering and regular refraction of comparable magnitude. Certain unexplained features of the pencil-beam distributions indicate that large-scale electron irregularities may be important in the scattering and refraction process. Additional evidence is presented for very short-term changes in the transmission properties of the corona.

scholarly journals Occupation of the Crab Nebula by the Solar Corona in June 1963

Nature ◽  
1963 ◽  
Vol 200 (4908) ◽  
pp. 766-766 ◽  
Author(s):  
J. D. WYNDHAM ◽  
B. G. CLARK
Keyword(s):  
Solar Corona ◽  
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.

Coronal Broadening of the Crab Nebula 1969-71: Interpretation

1972 ◽  
Vol 2 (2) ◽  
pp. 86-88 ◽  
Author(s):  
P. A. Dennison ◽  
R. G. Blesing
Keyword(s):  
Power Spectrum ◽  
Crab Nebula ◽  
Preceding Paper ◽  
Theoretical Models ◽  
Brightness Distribution ◽  
Two Dimensional ◽  
Scattering Process ◽  
Angular Power Spectrum ◽  
Basic Parameters ◽  
The Crab Nebula

In the preceding paper, observations of the coronal broadening of the Crab Nebula during 1969-71 were described. The basic parameters, radial and tangential broadening, and their relation to previous work were discussed. Whereas previous observations have utilized two or three interferometers only, so that the degree of broadening along any particular axis could only be obtained under the assumption of a particular form (e.g. Gaussian) for the angular power spectrum, the present work has enabled complete sampling of the two-dimensional brightness distribution of the broadened source. It is therefore possible, and of considerable interest, to compare the observed distributions to those computed on the basis of various theoretical models for the scattering process.

Coronal Broadening of the Crab Nebula 1969-71: Observations

1972 ◽  
Vol 2 (2) ◽  
pp. 84-86 ◽  
Author(s):  
R. G. Blesing ◽  
P. A. Dennison
Keyword(s):  
Solar Cycle ◽  
Solar Corona ◽  
Crab Nebula ◽  
Two Dimensional ◽  
Dimensional Image ◽  
Two Dimensional Image ◽  
The Crab Nebula

A description was given in a previous paper of the first observations of the two-dimensional image of the Crab Nebula as it became broadened by the solar corona in June 1969. In this paper we describe further observations at 80 MHz during 1970 and 1971, again using the CSIRO Radioheliograph at Culgoora, N.S.W., and we discuss the derived values for radial and tangential broadening in relation to previous work at various phases of the solar cycle. Other methods of observing angular broadening have generally employed two or three interferometers at different position angles, and only the simplest model for the image could be assumed in interpreting the results. The radioheliograph, however, has the advantage of recording the complete two-dimensional image and also, simultaneously, the surrounding background.

scholarly journals Search for Plerions in the Direction of Two Young Pulsars

1987 ◽  
Vol 125 ◽  
pp. 124-124
Author(s):  
S. Krishnamohan ◽  
D.K. Mohanty ◽  
A.R. Patnaik ◽  
T. Velusamy
Keyword(s):  
Supernova Remnants ◽  
Large Scale ◽  
Galactic Plane ◽  
Crab Nebula ◽  
Dispersion Measure ◽  
Positional Error ◽  
Continuum Source ◽  
Interesting Possibility ◽  
Average Flux ◽  
The Crab Nebula

Two of the recently discovered pulsars PSR 1800-21 and 1823-13 have characteristics ages of 17,000 and 22,000 yr respectively and all the three known pulsars that are younger than these two lie within the known supernova remnants (Clifton and Lyne, 1986). These two pulsars are expected to have, by scaling from the Crab nebula, plerions of ∼1 Jy each associated with them at 327 MHz. We mapped a field of 1.˚95 × 1.˚5 around both the pulsars with the Ooty Synthesis Radio Telescope (Swarup, 1984). As the fields are on the galactic plane having complex large scale emission and as the plerions are expected to be compact, we have made maps by excluding baselines less than 500 λ. This would make our maps insensitive to emission regions larger than ∼7 arc min. The synthesised beam is 96 × 36 arc sec in PA 0°. No source with a surface brightness greater than 60 mJy/beam was detected in the direction of PSR 1823-13. An unresolved source of ∼150 mJy was detected, in the positional error box of PSR 1800-21, as is shown in the figure. No pulsed emission with an average flux density greater than 10 mJy was detected from this continuum source. It is possible that the pulse is so highly scatter broadened that it becomes undetectable at 327 MHz and the detected source is the scatter broadened pulsar. But, such a possibility seems unlikely as the pulsar's dispersion measure is only 230 cm−3 pc, leaving the interesting possibility that the detected source is a plerion associated with the pulsar.

Occultation of the Crab Nebula by the Solar Corona in June 1962

Nature ◽  
1963 ◽  
Vol 197 (4870) ◽  
pp. 885-886 ◽  
Author(s):  
SANTIMAY BASU ◽  
JOHN CASTELLI
Keyword(s):  
Solar Corona ◽  
Crab Nebula ◽  
The Crab Nebula
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