Solar Radiation at a Wavelength of 3.18 Centimetres

1950 ◽  
Vol 3 (1) ◽  
pp. 60 ◽  
Author(s):  
HC Minnett ◽  
NR Labrum
Keyword(s):  
Body Temperature ◽  
Solar Radiation ◽  
Black Body ◽  
Sunspot Area ◽  
Probable Error ◽  
The Sun ◽  
Solar Origin ◽  
Unit Increase ◽  
Uniform Disk ◽  
Visible Disk

Solar radiation at a wavelength of 3.18 cm. has been measured over a period of three months. The received intensity was found to vary from day to day and the changes are shown to be closely associated with sunspots. The equivalent black-body temperature of the sun over this period, in the absence of sunspots, was 19,300 �K., with a probable error of �7 per cent. The temperature increased by 8 �K. per unit increase of sunspot area (one unit equals 10-5 times the area of the sun's visible disk). This increase is much less than that at longer microwavelengths. Sudden increases of radiation at 3.18 cm., caused by disturbed conditions in the sun, were found to be rare. A number of bursts were observed and a comparison is made with records of longer wave solar radiation and other phenomena of solar origin. Observations were made during the solar eclipse of November 1, 1948 and the results are consistent with either of two simple brightness distributions on the sun's disk. In the first of these, 74 per cent. of the energy is emitted uniformly by the sun's visible disk and the remaining 26 per cent. by a bright ring around the circumference ; in the second, the whole of the radiation comes from a uniform disk of diameter 1.1 times that of the visible sun.

Solar Radiation at 1200 MC/S., 600 MC/S., and 200 MC/S

1949 ◽  
Vol 2 (1) ◽  
pp. 48 ◽  
Author(s):  
FJ Lehany ◽  
DE Yabsley
Keyword(s):  
Magnetic Field ◽  
Body Temperature ◽  
Solar Radiation ◽  
Thermal Emission ◽  
Black Body ◽  
Sunspot Area ◽  
The Sun ◽  
Long Period ◽  
Period Variations ◽  
The Magnetic Field

Daily observations of solar radiation at frequencies of 1200 Mc/s., 600 Mc/s., and 200 Mc/s. taken between August 18 and November 30, 1947, are described. The characteristics of the radiation at 200 Mc/s. were in general agreement with those observed by earlier workers. At 600 Mc/s. and 1200 Mc/s., the received intensity was normally steady on any one day but underwent long-period variations over a range of about two to one. The radiation received when the sun was almost free of sunspots corresponded to an effective black-body temperature of 0.5 million �K. at 600 Mc/s. and 0.1 million �K. at 1200 Mc/s. As sunspots appeared, the temperature rose and showed marked oar- relation with sunspot area. It is considered that radiation at these frequencies is entirely thermal in origin and that the long-period variations are at least partly due to the influence of the magnetic field of sunspots on the mechanism of thermal emission from a magneto-ionic medium. On a few occasions, isolated disturbances were observed on 600 Mc/s. and 1200 Mc/s. some of which were associated with chromospheric flares and radio fade-outs. The difficulties arising in the calibration of the apparatus and the steps taken to overcome them are discussed in detail.

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.

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.

Solar Radiation of Wavelength 1.25 Centimetres

1949 ◽  
Vol 2 (4) ◽  
pp. 539
Author(s):  
U Radok
Keyword(s):  
Solar Activity ◽  
Solar Radiation ◽  
Michelson Interferometer ◽  
Black Body ◽  
Maximum Error ◽  
Average Intensity ◽  
Observational Accuracy ◽  
Short Period ◽  
Uniform Disk ◽  
Narrow Ring

Observations of solar radiation at a wavelength of 1.25 cm. and covering a period of about six months are described. The average intensity of radiation corresponded to a black-body temperature of 1.00 x 104 �K. with a maximum error of about � 5 per cent. Day-to-day variations in intensity were less than � 3 per cent., which was the limit of observational accuracy. Short-period fluctuations were observed on a few occasions ; even during periods of intense solar activity they were not greater than � 5 per cent. The distribution of intensity over the solar disk was measured by a method analogous to the Michelson interferometer technique and found to be consistent with 84 per cent. of the radiation coming from a uniform disk and 16 per cent. from a narrow ring around the circumference.

The ecology of the island-lizard Podarcis sicula salfii

1981 ◽  
Vol 2 (3) ◽  
pp. 243-257 ◽  
Author(s):  
P.E. Ouboter
Keyword(s):  
Body Temperature ◽  
Interspecific Competition ◽  
The Sun ◽  
Podarcis Sicula ◽  
Dense Vegetation ◽  
Food Size ◽  
Preferred Body Temperature ◽  
Erica Arborea ◽  
Sufficient Food ◽  
Excursion Time

AbstractIn the summers of 1974 till 1979 microdistribution of Podarcis sicula saffti was examined. Areas without much vegetation and areas with dense vegetation have low densities. Horizontal space, predators, parasites, interspecific competition, shelter and dew appear to be non important factors in the microdistribution of P. s. safii. From 9 a. m. until 6 p. m. temperature in the sun is above PBT (preferred-body-temperature) in all zones. Shade temperature is different from one zone to another. In the most rocky zone without much vegetation, shade is provided by crevices. Shade temperature is under PBT. Food is mainly available outside crevices, in vegetation of Statice sinuatum. Food-size is small, so excursion-time will be long. Lizards are able to collect sufficient food if Statice-plants are close to crevices. The zone with vegetation of Erica arborea, on top of the island, is shaded all day. Shade temperature is under PBT. Only clearings are inhabited by lizards. All other zones have bushes and open areas. During the hot hours bushes provide shade, with shade temperature close to PBT. Food is mainly available in these bushes.

Evolution of Comets into Asteroids?

1971 ◽  
Vol 12 ◽  
pp. 413-421 ◽  
Author(s):  
B.G. Marsden
Keyword(s):  
Solar Radiation ◽  
Solar Nebula ◽  
Oort Cloud ◽  
Original Version ◽  
Terrestrial Planets ◽  
Minor Planets ◽  
The Sun ◽  
Physical Difference ◽  
Short Period ◽  
The One

There has long been speculation as to whether comets evolve into asteroidal objects. On the one hand, in the original version of the Oort (1950) hypothesis, the cometary cloud was supposed to have formed initially from the same material that produced the minor planets; and an obvious corollary was that the main physical difference between comets and minor planets would be that the latter had long since lost their icy surfaces on account of persistent exposure to strong solar radiation (Öpik, 1963). However, following a suggestion by Kuiper (1951), it is now quite widely believed that, whereas the terrestrial planets and minor planets condensed in the inner regions of the primordial solar nebula, icy objects such as comets would have formed more naturally in the outer parts, perhaps even beyond the orbit of Neptune (Cameron, 1962; Whipple, 1964a). Furthermore, recent studies of the evolution of the short-period comets indicate that it is not possible to produce the observed orbital distribution from the Oort cloud, even when multiple encounters with Jupiter are considered (Havnes, 1970). We must now seriously entertain the possibility that most of the short-period orbits evolved directly from low-inclination, low-eccentricity orbits with perihelia initially in the region between, say, the orbits of Saturn and Neptune, and that these comets have never been in the traditional cloud at great distances from the Sun.

3. Note on Solar Radiation

1888 ◽  
Vol 14 ◽  
pp. 118-121
Author(s):  
John Aitken
Keyword(s):  
Solar Radiation ◽  
The Sun ◽  
Geological History ◽  
Conservation Of Energy ◽  
Vast Amount ◽  
Chemical Theory ◽  
Energy Theory ◽  
The Many ◽  
Different Sources

In the many theories that have been advanced to explain the comparative constancy of solar radiation in long past ages as evidenced by geological history, it has been generally assumed that the temperature of the sun has not varied much, and to account for its not falling in temperature a number of theories have been advanced, all suggesting different sources from which it may have received the energy which it radiates as heat. Since the chemical theory was shown to be insufficient to account for the vast amount of heat radiated, other theories, such as the meteoric theory and the conservation of energy theory, have been advanced.

scholarly journals ON THE EFFECTS OF SOLAR RADIATION PRESSURE ON THE DEVIATION OF ASTEROIDS

2021 ◽  
Vol 57 (2) ◽  
pp. 279-295
Author(s):  
L. O. Marchi ◽  
D. M. Sanchez ◽  
F. C. F. Venditti ◽  
A. F. B. A. Prado ◽  
A. K. Misra
Keyword(s):  
Solar Radiation ◽  
Radiation Pressure ◽  
Scientific Research ◽  
Orbital Plane ◽  
Solar Radiation Pressure ◽  
The Sun ◽  
Mass Ratio ◽  
High Area ◽  
Planetary Defense

In this work, we study the effects of solar radiation pressure (SRP) on the problem of changing the orbit of an asteroid to support planetary defense, scientific research, or exploitation of materials. This alternative considers a tethered reflective balloon (or a set of reflective balloons) attached to the asteroid, with a high area-to-mass ratio, to use the SRP to deflect a potentially hazardous asteroid (PHA) or to approximate the target asteroid to Earth. The tether is assumed to be inextensible and massless, and the motion is described only in the orbital plane of the asteroid around the Sun. The model is then used to study the effects that the tether length, the reflectivity coefficient, and the area-to-mass ratio have on the deviation of the trajectory of the asteroid.

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