A coronal hole observed at 10.7 GHz with a large single dish

Fuerst, E.; Hirth, W.

doi:10.1007/bf00153292

Cited by 21 publications

(5 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Note , however , that the displ acement is also present near the central meridian . It also appears to be nearly wavelength independent, i.e., the displacements at 2.0 cm, appears to be present in the 2.8 cm observations by F~irst and Hirth (1975) . Dulk et al .…”

Section: Summary and Discussionmentioning

confidence: 80%

The Radio Spectrum of Coronal Hole 1,

Wefer¹,

Papagiannis²

1977

View full text Add to dashboard Cite

Section: Summary and Discussionmentioning

confidence: 80%

The Radio Spectrum of Coronal Hole 1,

Wefer¹,

Papagiannis²

1977

View full text Add to dashboard Cite

“…From the NanCay E-W interferometer records, Lantos and Avignon (1975) were able to observe coronal holes at 169 MHz. At about the same time, Fiirst and Hirth (1975) provided excellent evidence for coronal holes at 10.7 GHz. The high-frequency range was extended still further, to 85 GHz, by Kundu and Liu (1976).…”

Section: Radio Observations Of Coronal Holesmentioning

confidence: 82%

“…Using their own measured diameter, Lantos and Avignon (1975) derived a central brightness temperature of the truly quiet Sun at 169MHz as Tb=750 000K*l5%. This value is valid both during the The numbers on the radio contours give the deviation (unit 1 K) from the level of the quiet Sun, which is assumed to be 12 000 K. The optical limb is approximately given by the isophote 6000 K. The dark black line indicates a strong depression zone, which partly corresponds to a coronal hole (Fiirst and Hirth 1975).…”

Section: Radio Observations Of Coronal Holesmentioning

confidence: 99%

Advances in solar radio astronomy

Kundu

1982

Rep. Prog. Phys.

View full text Add to dashboard Cite

In this review article we provide an account of the present status of the observations and interpretations of the Sun's radio emission covering the entire radio spectrum from millimetre wavelengths to hectometre and kilometre wavelengths. We deal with the radio emissions originating from different solar atmospheric regions-the quiet solar atmosphere, active regions and flares. We emphasise the progress made in solar radio physics because of the recent advances in plasma and radiation theory combined with the capability of observing the Sun with a spatial resolution of about a second of arc and temporal resolution of about a millisecond at centimetre wavelengths and of obtaining fast multifrequency two-dimensional pictures of the Sun at metre and decametre wavelengths.We review the observations of the quiet Sun at millimetre, centimetre and metredecametre wavelengths. We discuss the quiet Sun brightness distributions at millimetre wavelengths in relation to chromospheric models-in particular the spicular and interspicular models below 3000 km above the photosphere. We review the highresolution (a few arcsec) observations of the quiet Sun at centimetre wavelengths and provide evidence that there is a radio analogue of the supergranulation network. We discuss the radio searches for solar oscillations similar to the five-minute oscillations at optical wavelengths. In the range of wavelengths 1.2 mm to 11.1 cm, there appears to be no evidence for the presence of periodic radio fluctuations. The observations of coronal holes at metre and centimetre wavelengths are reviewed. The coronal holes which appear as regions of emission much fainter than the nearby background in x-rays and extreme untraviolet usually appear dark at 2.8 cm and shorter wavelengths; however, at metre wavelengths the situation is more complex, appearing dark at 160 MHz but often bright at 80 MHz. Simultaneous observations of coronal holes at radio and EUV wavelengths permit the determination of temperature and density in the hole in the corona and in the transition region.The properties of non-flaring active regions at millimetre, centimetre and metredecametre wavelengths are summarised. The polarisation maps of mm and cm active regions can clearly be used as chromospheric and coronal magnetograms, thus complementing the photospheric magnetograms obtained at optical wavelengths. The strength of the magnetic fields at these levels can be estimated, assuming that the 0034-4885/82/121435

show abstract

“…Observations at 87 GHz show the presence of enhanced compact regions surrounded by depressed diffuse emission in CH's at a resolution of 1 Pohjolainen 2000). At 10.7 GHz, observations made with a resolution of 1.25 show the mean polar CH levels are depressed relative to the quiet sun (Furst & Hirth 1975), but small unresolved enhanced emission sources might be present. Observations at 98 GHz made with a resolution of 17 show no polar CH diffuse or compact enhancements (Kosugi et al 1986).…”

Section: Introductionmentioning

confidence: 97%

A multi-wavelength study of solar coronal-hole regions showing radio enhancements

Moran

Gopalswamy

Dammasch

et al. 2001

A&A

View full text Add to dashboard Cite

Abstract. We observed 17 GHz microwave-enhanced regions in equatorial coronal holes (ECH) together with extreme-ultraviolet (EUV), far-ultraviolet (FUV) and visible emissions in a search for temperature increases which might explain the bright spots in radio wavelengths. The ultraviolet (UV) observations span a wide range of formation temperatures (8000 K to 630 000 K). Increased UV emission was observed at the approximate location of the radio enhancements, but unlike the radio brightening, the UV emission did not exceed the mean quiet sun level. However, there were two observations showing increased Hα brightness in radio enhancements above mean quiet sun levels. No Hα bright spots were detected in ECHs outside of radio enhancement regions. The ECH Hα bright spots were caused by bright fibrils, bright points and a lack of dark fibrils. Since the 17 GHz and Hα enhancements are co-spatial, have equal integrated normalized enhanced emission and brightness temperatures, the observations suggest that the radio enhancements are caused by increased fibril radio emission. In addition, increased Fe xii EUV emission was recorded at the location of some well-defined radio enhancements, which were the bases of coronal plumes. Since the radio brightness temperature is much lower than the Fe xii formation temperature, the radio and EUV enhancements are likely both related to the presence of concentrated magnetic flux, but do not arise from the same physical layer.

show abstract

A coronal hole observed at 10.7 GHz with a large single dish

Cited by 21 publications

References 9 publications

The Radio Spectrum of Coronal Hole 1,

The Radio Spectrum of Coronal Hole 1,

Advances in solar radio astronomy

A multi-wavelength study of solar coronal-hole regions showing radio enhancements

Contact Info

Product

Resources

About