Solar Radiation at 3.2 MM during the July 20, 1963, Eclipse.

Tolbert, C. W.; Krause, L.; Straiton, A. W.

doi:10.1086/147919

Cited by 10 publications

(5 citation statements)

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“…The limitation of single dish measurements is always spatial resolution: a typical telescope with a diameter of 10 m has a spatial resolution of λ mm 30 , where λ mm is the observing wavelength in mm, and thus, e.g., a 10 m telescope operating at 90 GHz cannot resolve features smaller than about 100 . This problem has been circumvented in two ways: by observing eclipses, when the Moon's limb acts as a knife edge crossing the field of view, and the time dependence of the millimeter flux can be converted into (onedimensional) spatial resolution much finer than the telescope beam (e.g., Tolbert et al 1964;Hagen et al 1971;Beckman et al 1975;Swanson & Hagen 1975;Shimabukuro et al 1975;Roellig et al 1991;Ewell, Jr. et al 1993); and by going to submillimeter wavelengths (smaller λ), which is possible with the James Clerk Maxwell Telescope (JCMT) and Caltech Submillimeter Telescope (CSO) on Mauna Kea, Hawaii. These telescopes have been able to make images of the solar disk at submillimeter wavelengths with a spatial resolution as small as 20 (Horne et al 1981;Lindsey & Jefferies 1991;Bastian et al 1993a,b;.…”

Section: Introductionmentioning

confidence: 99%

High-resolution millimeter-interferometer observations of the solar chromosphere

White¹,

Loukitcheva

Solanki

2006

A&A

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The use of millimeter-interferometer data for the study of chromospheric structure and dynamics is tested using 85 GHz observations with the 10-element Berkeley-Illinois-Maryland Array (BIMA). Interferometer data have the advantage over single-dish data that they allow both high spatial resolution and dense temporal sampling simultaneously. However, snapshot imaging of the quiet solar atmosphere with a small number of dishes is challenging. We demonstrate that techniques are available to carry out this task successfully using maximum entropy deconvolution from a default image constructed from the entire observation: one of our results is that the solar chromosphere at millimeter wavelengths exhibits features that are long-lasting and the map of the entire observation is significant provided that atmospheric phase errors do not prevent deconvolution. We compare observations of quiet Sun, active region and coronal hole targets. The interferometer is not sensitive to the disk emission and the positivity constraint of the maximum entropy algorithm used forces the zero level in the images to be at the temperature of the coolest feature in each field. The brightest features in the images are typically 1000-1500 K above the zero level, with a snapshot noise level of order 100 K. We use extensive tests to determine whether oscillation power can be recovered from sequences of snapshot images and show that individual sources can be down to quite weak levels at locations in the image where significant flux is present; oscillation power located in cool regions of the image is not well recovered due to the deconvolution method used and may be redistributed to brighter regions of the millimeter image. We then investigate whether the data do show oscillation power using uninterrupted 30-min scans of the target regions. Intensity oscillations with significant power in the frequency range 1.5-8.0 mHz are found in the quiet-Sun and active region targets. For the quiet-Sun region we compare the oscillation properties of network boundaries and cell interiors (internetwork) in the spatially-resolved time series. In agreement with investigations at other wavelengths, in the millimeter data the power in the network tends to be at periods of 5 min and longer while power in the internetwork is present also at shorter (3-min) periods.

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Section: Introductionmentioning

confidence: 99%

High-resolution millimeter-interferometer observations of the solar chromosphere

White¹,

Loukitcheva

Solanki

2006

A&A

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“…Absorption measurements by the University of Texas [Tolbert, Krause, and Straiton, 1964] have provided greater detail on the shape and intensity of the oxygen absorption lines in the complex from 5 to 6 mm, the oxygen line at 2.5 mm, and the water-vapor line at 1.65 mm. These studies were made point-topoint through the atmosphere, by using extraterrestrial sources and by transmission through a 500-ft low-pressure absorption cell.…”

Section: Transmission Measurementsmentioning

confidence: 99%

“…As part of a detailed inv.estigation of the oxygen-line complex between 58 and 62 MHz, Tolbert and Straiton !1964] report on observations of atmospheric radiation using a balloon-borne Dicke radiometer with the antenna pointed toward the earth. Emission temperatures into space from 100,000 ft were found to be 200 °K between the oxygen lines and 225 °K at line centers.…”

Section: Atmospheric Radiationmentioning

confidence: 99%

“…The University of Texas observed during the 1963 solar eclipse that there was no significant limb brightening but there was enhanced radiation in the region of an observed prominence [Tolbert, Krause, and Straiton, 1964]. Observation of Venus suggested that a strong ionospheric model might explain the observed decrease in apparent temperature at the millimeter wavelength [Tolbert and Straiton, 1964].…”

Section: Extraterrestrial Sourcesmentioning

confidence: 99%

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U.S.A. National Committee Report, Fifteenth URSI General Assembly, Munich, September 1966: Commission 2, Radio Propagation in Nonionized Media; Progress in Radio Propagation in Nonionized Media

Katz¹,

Ament²,

Atlas³

et al. 1966

Radio Science

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In 1965 there was a strong reawakening of interest in “angel” or clear‐air radar echoes. Atlas [1965] postulated that "dot" or point‐like angles were reflections from smooth, sharp boundaries at the apex of convective thermals. Focusing from the curved surface reduced the requirement on the index gradient to 1 N unit through 1 em; however, the requirement of smoothness to a fraction of a em over the first Fresnel zone is still severe and lacks experimental confirmation. Dot angel activity at night requires another explanation. Hardy, Atlas, and Glover [1966] and Deam and LaGrone [1965] conclude that dot angel characteristics are explainable only if the targets are insects. These conclusions stem from considerations of absolute cross section and wavelength dependence.

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“…All Rights Reserved Copyright 9 1970 by D. Reidel Publishing Company, Dordrecht-Holland over a period of several years. Subsequently, Tolbert et al (1964) have made observations at 3.2 mm at the time of a solar eclipse to detect limb brightening. Their antenna had a beamwidth of 9' but observation at eclipse yielded very good resolution at the limb.…”

Section: Introductionmentioning

confidence: 99%

Variations in solar emission at 3.3 mm wavelength and their relation to flares

1970

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An investigation of variations in solar radio emission at 3.3 mm wavelength as observed with an antenna of half-power beamwidth of 2.8 arc-min indicates the existence of hot stable regions associated with sunspots. These regions are enhanced from 240 K (4~) to more than 3200K (50~) over the quiet center of the disk temperature of 6 600K. Positions of maximum enhancement occur near the neutral lines of primarily bipolar magnetic fields as determined from magnetograms of the longitudinal component of the field. Fourteen of the 113 regions studied were observed to produce flares reported as importance class 2 or greater during the period from mid-February through mid-August 1967. Eleven of the regions which flared had an enhancement of 8.5~ or greater and a temperature gradient of 0.5~/deg or greater.

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Solar Radiation at 3.2 MM during the July 20, 1963, Eclipse.

Cited by 10 publications

References 0 publications

High-resolution millimeter-interferometer observations of the solar chromosphere

High-resolution millimeter-interferometer observations of the solar chromosphere

U.S.A. National Committee Report, Fifteenth URSI General Assembly, Munich, September 1966: Commission 2, Radio Propagation in Nonionized Media; Progress in Radio Propagation in Nonionized Media

Variations in solar emission at 3.3 mm wavelength and their relation to flares

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