Observations of the Spectrum of High-Intensity Solar Radiation at Metre Wavelength. II. Outbursts

1950 ◽  
Vol 3 (3) ◽  
pp. 399 ◽  
Author(s):  
JP Wild
Keyword(s):  
Solar Radiation ◽  
Magnetic Storm ◽  
Solar Flares ◽  
High Intensity ◽  
Solar Radio ◽  
Dynamic Spectrum ◽  
Spectral Features ◽  
Frequency Range ◽  
Radio Frequency Radiation ◽  
Frequency Radiation

Observations are described of the spectrum of outbursts of solar radio-frequency radiation in the frequency range 70-130 Mc/s. In accordance with Part I of this series, an " outburst " is defined as a burst having a particular type of " dynamic " spectrum, characterized by a drift of spectral features, with time, towards the lower frequencies at a rate of the order of � Mc/s. per second. The observed outbursts are shown to have a close connexion with solar flares and their geophysical accompaniments. �� The spectra are tentatively interpreted in terms of the motion of a physical agency in the solar atmosphere. The possible identification of the agency with " surge " prominences and the corpuscular streams that cause a type of terrestrial magnetic storm is discussed. It is shown that the evidence is quite consistent with the hypothesis that the agency corresponds to the magnetic storm particles.

Observations of the Spectrum of High-Intensity Solar Radiation at Metre Wavelengths. IV. Enhanced Radiation

1951 ◽  
Vol 4 (1) ◽  
pp. 36 ◽  
Author(s):  
JP Wild
Keyword(s):  
Solar Radiation ◽  
High Intensity ◽  
Narrow Band ◽  
The Sun ◽  
Frequency Range ◽  
Radio Frequency Radiation ◽  
Variable Level ◽  
Background Continuum ◽  
High Level ◽  
Frequency Radiation

Observations are described of the spectrum of " enhanced radiation" from the Sun (i.e. the radio-frequency radiation which maintains a high but variable level for periods of hours' or days' duration) in the frequency range 70-130 Mc/s. This radiation is known to be received from the direction of sunspots and to show circular polarization. For the purpose of presenting results, two components are recognized, viz. a background continuum which varies gradually with time and frequency, and short-lived, narrow-band bursts (" storm bursts "). The behaviour of the two components, and the relation between them during periods of high level (" noise storms ") are described. A detailed analysis is given of the properties of recorded storm bursts. The distribution of recorded bursts with frequency was found to be markedly non- uniform, e.g. a pronounced minimum at 89 Mc/s. was present. The possibility that the background continuum is due to the resultant of a large number of bursts is discussed.

scholarly journals An Estimate of the Density and Motion of Solar Material from Observed Characteristics of Solar Radio Outbursts

1953 ◽  
Vol 6 (1) ◽  
pp. 67 ◽  
Author(s):  
Hari K Sen
Keyword(s):  
Radio Frequency ◽  
Radio Wave ◽  
Dispersion Equation ◽  
Solar Radio ◽  
Particle Density ◽  
Frequency Range ◽  
Radio Frequency Radiation ◽  
Charge Interaction ◽  
Solar Material ◽  
Frequency Radiation

The theory of radio wave generation by multistream charge interaction (Feinstein and Sen 1951) is extended and applied to the observations made by Australian workers (Wild 1950) of the spectrum of outbursts of solar radio-frequency radiation in the frequency range 70?130 Mc/s. The dispersion equation is derived as a function of the velocity of solar material erupting into a static corona and of the temperatures and densities of the material and the corona. The application of the dispersion equation to the Australian data (loc. cit.) enables an estimate to be made of the velocity (?500 km./s.) and the particle density (?108 cm.?3) of the moving solar material.

scholarly journals An investigation of radio-frequency radiation from the sun

1948 ◽  
Vol 193 (1032) ◽  
pp. 98-120 ◽  
Keyword(s):  
Solar Radiation ◽  
Radio Frequency ◽  
Random Noise ◽  
Internal Noise ◽  
Black Body ◽  
Local Source ◽  
The Sun ◽  
Radio Frequency Radiation ◽  
Absolute Measurements ◽  
Frequency Radiation

It has been known for some time that the sun emits radio-frequency radiation whose intensity greatly exceeds the value expected from a black-body at 6000°K. In the present paper, experiments are described in which measurements have been made of the solar radiation at frequencies of 175 and 80 Mcyc. /sec. Measurement of the small powers which can be abstracted from practical aerial systems requires special types of receiving equipment if absolute measurements are to be recorded automatically over long periods of time. An apparatus has been developed in which the output power of a local source of random ‘noise’ is automatically and continuously adjusted so as to be equal to the aerial power; in this way the receiver is used only as an indicator of balance, and errors due to variation of its gain or internal noise are eliminated. A special type of aerial has been devised which enables the solar radiation to be recorded separately from the galactic radiation, and so enables continuous observation of the sun to be made with aerials of comparatively low directivity. The results obtained on these two frequencies show that the sun normally emits radiation whose intensity corresponds to a surface temperature of the order of 10 6 °K. Large fluctuations in the intensity occur, however, and during the passage of large sunspots, equivalent temperatures as high as 10 8 to 10 9 °K have been observed. In addition to these day-to-day variations the radiation is subject to sudden brief increases of intensity lasting only for a few seconds. Measurements of the diameter of the source, by a method analogous to Michelson’s stellar interferometer, have shown that during periods of very great intensity the radiation originates in an area of the sun of the same order of size as a sunspot. This result means that equivalent temperatures of 10 9 to 10 10 °K must exist. Measurements of the polarization of the radiation have shown that during periods of increased activity the radiation is mainly circularly polarized. The present account covers the experimental methods and the results obtained up to the present time. It is hoped to consider these results theoretically in a future paper.

scholarly journals 60. Relation between optical solar features and solar radio emission

1957 ◽  
Vol 4 ◽  
pp. 327-333
Author(s):  
H. W. Dodson
Keyword(s):  
Radio Emission ◽  
Radio Frequency ◽  
Research Council ◽  
Solar Radio ◽  
National Research Council ◽  
Solar Radio Emission ◽  
Radio Frequency Radiation ◽  
Cornell University ◽  
Frequency Radiation

During the last five years, we at the McMath-Hulbert Observatory have been attempting to determine the characteristics of radio-frequency radiation associated with certain of the transient solar features that we normally observe on monochromatic spectroheliograms or in integrated light. We have had the privilege of using the original 200 Mc./s. records at Cornell University and the 2800 Mc./s. records at the National Research Council in Ottawa.

Solar Radio-Frequency Emission from Localized Regions at Very High Temperatures

1951 ◽  
Vol 4 (2) ◽  
pp. 131
Author(s):  
JH Piddington ◽  
HC Minnett
Keyword(s):  
Radio Frequency ◽  
Solar Radio ◽  
Thermal Emission ◽  
Thermionic Emission ◽  
Magnetic Data ◽  
Radio Frequency Radiation ◽  
Sunspot Data ◽  
Polarization Characteristics ◽  
Frequency Radiation ◽  
Three Components

Solar radio-frequency radiation is analysed into three components ; a basic steady component B, a slowly varying component S, and various forms of more or less rapid fluctuations called the X component. The spectra of all three components are drawn between 600 and 24,000 Mc/s., and suggested extensions to lower frequencies are discussed. The properties of the S component are described in some detail ; these include correlation with sunspot data, polarization, and the location of the sources of origin. Evidence is presented in favour of generation by thermal processes. It is suggested that the S component is due to thermal emission from localized regions at temperatures of about 107 �K., often in the vicinity of sunspots. The radiation from a model hot region is examined in detail and the emission spectrum and polarization characteristics are derived. The results are found to compare reasonably with observation. Thermionic emission of electrons and protons would probably occur from the hot regions. These particles would travel to the Earth with average velocities of a few hundred kilometres per second and may be identical with the slow corpuscular radiation whose presence is deduced from terrestrial magnetic data.

Observations of the Spectrum of High-Intensity Solar Radiation at Metre Wavelengths. III. Isolated Bursts

1950 ◽  
Vol 3 (4) ◽  
pp. 541 ◽  
Author(s):  
JP Wild
Keyword(s):  
Solar Atmosphere ◽  
Small Groups ◽  
Distinct Type ◽  
Maximum Intensity ◽  
Frequency Drift ◽  
Frequency Range ◽  
Radio Frequency Radiation ◽  
Type Iii ◽  
Or Groups ◽  
Frequency Radiation

Observations are described of the spectrum of " isolated bursts" of solar radio-frequency radiation in the frequency range 70-130 Mc/s. These bursts last for a few seconds and have a bandwidth of the order of tens of megacycles per second. Prior observations indicate that they are not circularly polarized. They occur sporadically, often in small groups ; many hours sometimes elapse between successive bursts or groups. Although, in general, their spectra show diverse features, some of them (referred to as " type III " bursts) are of a distinct type characterized by a rapid drift, with time, of the frequency of maximum intensity towards the lower frequencies, at a rate of the order of 20 Mc/s. per second. Characteristics of the spectra of type III bursts are described in detail. The results are discussed and hypotheses of origin examined. It is shown in particular that the frequency drift of type III bursts cannot be attributed to the selective group retardation of waves in the solar atmosphere emanating from a fixed source. The frequency drift may, however, be associated with the rapid motion of a source travelling outwards through the solar atmosphere.

Galactic Radiation at Radio Frequencies. II. The Discrete Sources

1950 ◽  
Vol 3 (2) ◽  
pp. 234 ◽  
Author(s):  
GJ Stanley ◽  
OB Slee
Keyword(s):  
Radio Frequency ◽  
Crab Nebula ◽  
Wave Length ◽  
Frequency Range ◽  
Radio Frequency Radiation ◽  
Short Period ◽  
Background Continuum ◽  
The Crab Nebula ◽  
Observational Techniques ◽  
Frequency Radiation

An account is given of observations on a number of discrete sources of radio- frequency radiation, together with a brief description of the observational techniques used in their detection, and of the methods employed to determine their positions and angular extent.Noise spectra of four of the more intense sources have been measured over a frequency range of 40-160 Mc/s. : in three cases the change of intensity with wave- length is found to be greater than that of the background continuum, and in one case less. Two of the sources have been provisionally identified with astronomically rare objects, the Crab Nebula and N.G.C. 5128.Finally, the short period fluctuations in the intensity of some of the sources, notably that in Cygnus, are discussed. Evidence is presented which, contrary to previous views, suggests that these fluctuations are of terrestrial rather than of extra-terrestrial origin.

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