Solar Radio Observations at 843 MHz

1989 ◽  
Vol 8 (2) ◽  
pp. 142-144 ◽  
Author(s):  
A. D. Gray ◽  
D. Campbell-Wilson ◽  
M. I. Large
Keyword(s):  
Solar Radio ◽  
Coronal Holes ◽  
Total Power ◽  
The Sun ◽  
Two Dimensional ◽  
Radio Observations ◽  
Radio Brightness ◽  
Partial Synthesis ◽  
One Dimensional ◽  
Exact Relationship

AbstractThe Molonglo Observatory Synthesis Telescope (MOST) has been used to observe the Sun with total-power fan-beams having a one-dimensional resolution of 41 arcsec at 843 MHz. The scans reveal clearly the rotation and evolution of the slowly-varying component as well as some burst activity. Low radio brightness features have also been identified, but the exact relationship between these features and coronal holes is, as yet, unclear. Several partial synthesis observations have been used to generate two-dimensional radioheliograms.

scholarly journals Solar Brightness Distribution at a Wavelength of 60 Centimetres. I. The Quiet Sun

1955 ◽  
Vol 8 (4) ◽  
pp. 487 ◽  
Author(s):  
G Swarup ◽  
R Parthasarathy
Keyword(s):  
Solar Cycle ◽  
Brightness Distribution ◽  
Central Meridian ◽  
The Sun ◽  
Two Dimensional ◽  
Radio Brightness ◽  
One Dimensional ◽  
Quiet Sun ◽  
Solar Brightness

A multiple-element interferometer has been employed to determine one-dimensional distributions of radio brightness over the quiet Sun at a wavelength of 60 cm for scanning directions varying from 90� to 60� with respect to the central meridian of the Sun. These observations have been compared with measurements by other workers at the same, or nearly the same, wavelength. The present observations are reasonably consistent with the two-dimensional brightness distribution derived recently by O'Brien and Tandberg-Hanssen with a two-aerial interferometer, but do not agree with the earlier results of Stanier at the same wavelength. The disagreement, largely the absence of the theoretically predicted limb-brightening in Stanier's results, may reflect actual changes in the Sun over the solar cycle. However, the possibility of localized disturbed regions affecting Stanier's results for the quiet Sun cannot be eliminated.

Correlations of solar-flare electron events with radio and X-ray emission from the sun

1968 ◽  
Vol 46 (10) ◽  
pp. S757-S760 ◽  
Author(s):  
R. P. Lin
Keyword(s):  
Solar Flare ◽  
Solar Radio ◽  
Interplanetary Space ◽  
The Sun ◽  
Radio Bursts ◽  
Radio Observations ◽  
X Ray ◽  
Type Iii ◽  
Electron Event ◽  
Burst Emission

The > 40-keV solar-flare electrons observed by the IMP III and Mariner IV satellites are shown to be closely correlated with solar radio and X-ray burst emission. In particular, intense type III radio bursts are observed to accompany solar electron-event flares. The energies of the electrons, the total number of electrons, and the size of the electron source at the sun can be inferred from radio observations. The characteristics of the electrons observed in interplanetary space are consistent with these radio observations. Therefore these electrons are identified as the exciting agents of the type III emission. It has been noted that the radio and X-ray bursts are part of the flash phase of flares. The observations indicate that a striking feature of the flash phase is the production of electrons of 10–100 keV energies.

Measurements of Solar Radiation at a Wavelength of 50 Centimetres during the Eclipse of November 1, 1948

1949 ◽  
Vol 2 (4) ◽  
pp. 506 ◽  
Author(s):  
WN Christiansen ◽  
DE Yabsley ◽  
BY Mills
Keyword(s):  
Magnetic Field ◽  
Solar Radiation ◽  
Total Power ◽  
The Sun ◽  
Radio Brightness ◽  
Circularly Polarized ◽  
Small Areas ◽  
Abrupt Changes ◽  
Frequency Power ◽  
Visible Disk

Radio-frequency power received from the sun at a wavelength of 50 cm. was measured at three well-separated places during the solar eclipse of November 1, 1948. Abrupt changes in slope on the records of received flux density were interpreted as being the result of the covering and uncovering on the sun of small areas of great radio brightness. These areas were found to be associated with some visible sunspots, with positions previously occupied by sunspots, and with one prominence. The average effective temperature of the bright areas was about 5 X 106 �K., and the are= contributed a total power of roughly one-fifth of that from the entire sun. After the effects of active areas had been taken into account, the remaining four- fifths of the power received from the sun was found to originate from a source larger than the visible disk. About 40 per cent. of the power from this source originated outside the edge of the visible disk. The results were consistent with a theoretical distribution of brightness on the source, which involved limb-brightening. The relative magnitudes of the two circularly-polarized components of the solar radiation showed small differences as the bright areas were eclipsed. No predominance of one component was seen when one hemisphere of the sun was eclipsed ; hence no effects of any general magnetic field on the sun were detected.

Techniques for Decimetre Wavelength Observations of Radio Plages and Bursts

1967 ◽  
Vol 1 (2) ◽  
pp. 55-55
Author(s):  
W. N. Christiansen
Keyword(s):  
Brightness Distribution ◽  
Resolving Power ◽  
The Sun ◽  
Two Dimensional ◽  
Radio Brightness ◽  
Field Station ◽  
Radio Brightness Distribution ◽  
The University

The first daily maps showing the two-dimensional radio brightness distribution over the Sun were produced at Fleurs ten years ago when the 64-antenna grating cross was completed. The maps had a resolution of 3′ arc at λ = 21 cm.When the Fleurs field station was given to the University by CSIRO in 1963 it was decided to use the antennas of the grating cross and add to them four or more larger antennas (45 ft diameter) to produce a pair of high resolving-power compound interferometers.

scholarly journals The Distribution of Radio Brightness over the Solar Disk at a Wavelength of 21 Centimetres. III. The Quiet Sun ? Two-Dimensional Observations

1955 ◽  
Vol 8 (4) ◽  
pp. 474 ◽  
Author(s):  
WN Christiansen ◽  
JA Warburton
Keyword(s):  
Solar Disk ◽  
Fourier Method ◽  
Brightness Distribution ◽  
Sunspot Activity ◽  
Polar Regions ◽  
Two Dimensional ◽  
Radio Brightness ◽  
One Dimensional ◽  
Quiet Sun ◽  
Coronal Electron

A distribution of solar radio brightness at a wavelength of 21 cm has been derived from observations made during the period of low sunspot activity from 1952 to 1954. The observations were made using two multiple interferometers arranged at right angles; this enabled the solar disk to be scanned in many different directions. The derived one-dimensional profiles of the quiet Sun for these various scanning directions were combined and a Fourier method adopted to derive a two-dimensional brightness distribution. The distribution shows marked limb-brightening in the equatorial zones but none in the polar regions. The contours of brightness are in general conformity with those expected from a solar atmosphere having a coronal electron density distribution of the kind proposed by van de Hulst for the period of minimum sunspot activity.

Ranging Technique Based on Conically Scanned Single Pixel Millimeter Wave Radiometer

2014 ◽  
Vol 12 ◽  
pp. 43-52 ◽  
Author(s):  
Xuan Lu ◽  
Li Wu ◽  
Ze Long Xiao ◽  
Jian Zhong Xu
Keyword(s):  
Millimeter Wave ◽  
Pulse Width ◽  
Solid Angle ◽  
Total Power ◽  
Two Dimensional ◽  
Threshold Method ◽  
One Dimensional ◽  
Concealed Weapon Detection ◽  
Millimeter Wave Radiometer ◽  
Single Pixel

Passive millimeter wave detection offers great advantages of covertness and anti-interference in surveillance and concealed weapon detection but suffers from disabilities of distance measurement. Based on the conically scanned single pixel millimeter wave radiometer, this paper presents a ranging method via dual-measurement utilizing the relation between the solid angle of the object and its distance from antenna. Both one-dimensional and two-dimensional detections are considered. For one-dimensional detection, the relation between the solid angle of the object and the range is reflected by the pulse width of the radiometer output, and the pulse widths of the radiometer output in two measurements could be extracted by derivative or threshold method. Then the range is calculated since it is inversely proportional to the pulse width, which is demonstrated in simulation. For two-dimensional imaging, a scale extracting algorithm is developed to search the scale between the object sizes of bi-measured images. Experiments are performed using a 94.5GHz total-power radiometer mounted on conically scanning platform. The obtained radiometric images are processed by the developed algorithm and the results indicated that both the scale extracting algorithm and the ranging method are effective and practical.

Position Measurements of a Harmonic Type II Solar Burst

1970 ◽  
Vol 1 (7) ◽  
pp. 310-312 ◽  
Author(s):  
A. C. Riddle
Keyword(s):  
Shock Front ◽  
The Sun ◽  
Type Ii ◽  
Two Dimensional ◽  
One Dimensional ◽  
Harmonic Emission ◽  
Solar Burst ◽  
Coronal Streamer ◽  
Conflicting Evidence ◽  
Solar Bursts

Prior to the advent of the Culgoora 80 MHz radioheliograph position measurements on type II solar bursts were restricted to those made with one-dimensional interferometers. These measurements yielded conflicting evidence on the apparent positions of fundamental and harmonic emission observed at a given frequency; different observers reported the fundamental to be closer to and further from the centre of the Sun than the harmonic. Here we report on two-dimensional observations at 80 MHz made on both fundamental and harmonic emission of a type II event that occurred on 1969 March 2. The observations are shown to be consistent with the hypothesis that the emission is produced as the result of a disturbance moving out from the site of a flare and forming a shock front within an overlying coronal streamer. Both fundamental and harmonic are explained by ‘forward’ emission from the shock front. Observations of the harmonic emission at 158 MHz are also consistent with this model.

scholarly journals 51. Interpretation of solar radio-frequency disk brightness distributions derived from observations with aerials extended in one dimension

1957 ◽  
Vol 4 ◽  
pp. 290-293 ◽  
Author(s):  
S. F. Smerd ◽  
J. P. Wild
Keyword(s):  
Solar Radio ◽  
Synthesis Method ◽  
One Dimension ◽  
Solar Model ◽  
Two Dimensional ◽  
Fourier Synthesis ◽  
One Dimensional ◽  
Finite Resolution ◽  
Dimensional Distribution ◽  
The Individual

Several recent papers have dealt with observations of brightness distributions over the solar disk, which were derived either from two-aerial interferometer observations at various spacings and orientations (e.g. O'Brien, 1953) [1], or from multiple-element interferometer fan-beam observations at various orientations (e.g. Christiansen and Warburton, 1954) [2], In each a two-dimensional distribution is derived from a number of essentially one-dimensional observations by a Fourier synthesis method described by O'Brien. The detail given by these methods must be limited by the finite resolution of the individual observations (limited by the maximum aperture of the aerial system), but the form of the limitation is not obvious, though its knowledge is required when relating the observations to a solar model.

scholarly journals VI. Solar Radiophysics

1985 ◽  
Vol 19 (1) ◽  
pp. 78-84
Author(s):  
R. T. Stewart
Keyword(s):  
Time Resolution ◽  
Solar Maximum ◽  
Research Effort ◽  
Solar Spectrum ◽  
Low Frequency ◽  
High Time Resolution ◽  
Two Dimensional ◽  
Radio Observations ◽  
One Dimensional ◽  
X Ray

The past 3 years since the last solar maximum have witnessed an unprecedented number (>200) of published scientific papers on many aspects of solar radiophysics. These contributions are the result of an intense research effort mounted during the first Solar Maximum Mission of 1980 and continued until the present. Excellent x-ray, EUV, and visible light observations of the disturbed corona and transition region have been obtained from the SMM, Hinotori, P78-1, and ISEE-3 spacecraft. ISEE-3 also has provided very low-frequency radio observations of solar bursts in the interplanetary medium. Ground-based radio support for space experiments has been provided by many observatories throughout the world. In particular, many collaborative studies using x-ray and radio observations of solar flares have been reported. The outstanding radio instrument during this period has been the VLA, operating at 2, 6, and 20 cm with a time resolution of 10 s and both modes of circular polarization. The two-dimensional spatial resolution of the radio images is a few seconds of arc, almost as good as the best resolution obtained so far at any wavelength in the solar spectrum. To complement the rather poor time resolution of the VLA one-dimensional arrays such as the WSRT at 6 cm wavelength and the Nobeyama interferometer at 17 GHz have been used successfully. In addition, a number of very-high-time resolution radiometers have been built at different locations. At meter wavelengths two-dimensional arrays at Clark Lake, Culgoora, and Nancay and a one-dimensional array at Nobeyama have been employed. The little known region of the solar spectrum at decimeter wavelengths is being investigated by the Zurich spectrograph. It is pleasing to see Chinese participation in solar radiophysics.

A one-dimensional self-gravitating stellar gas

1966 ◽  
Vol 25 ◽  
pp. 46-48 ◽  
Author(s):  
M. Lecar
Keyword(s):  
Gravitational Field ◽  
Phase Space ◽  
Motion Picture ◽  
Space Distribution ◽  
Two Dimensional ◽  
One Dimensional ◽  
Phase Space Distribution ◽  
Dimensional Phase Space ◽  
The Mean

“Dynamical mixing”, i.e. relaxation of a stellar phase space distribution through interaction with the mean gravitational field, is numerically investigated for a one-dimensional self-gravitating stellar gas. Qualitative results are presented in the form of a motion picture of the flow of phase points (representing homogeneous slabs of stars) in two-dimensional phase space.

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