Solar Noise Observations on 10.7 Centimeters

Covington, A. E.

doi:10.1109/jrproc.1948.234598

Cited by 58 publications

(30 citation statements)

References 12 publications

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“…The most common proxy of solar EUV irradiance is the F10.7 which was previously called the Covington index. The 27-day variability in this solar radiometric emission, coincident with the appearance of sunspots, was first described from ground-based daily measurement during the late 1940s [Covington, 1948] In an effort to address the weaknesses of SERF2 and in order to assist the evaluation of the solar data from the San Marco Airglow Solar Spectrometer Instrument (ASSI) [Tobiska et al, 1993], the SERF2 model was substantially revised [Tobiska, 1991] There are a number of weaknesses still remaining in the models. 251.95 1.46E+08 403.26 1.44E+08 500 252.19 1.03E+08 417.24 2.38E+07 501 253.78 1.06E+08 430.47 2.22E+08 502 256.32 5.92E+08 436.7 3.31E+08 503 256.38 2.33E+08 453 9.67E+06 504 256.64 9.61E+07 454 9.67E+06 507.93 256.92 1.60E+07 vides generally greater intensities at short wavelengths compared to SERF1, the modeled electron densities using EUV91 were in better agreement with the data in and above the E-F 1 region.…”

Section: E Uv Irradiance Proxiesmentioning

confidence: 99%

Recent solar extreme ultraviolet irradiance observations and modeling: A review

Tobiska¹

1993

J. Geophys. Res.

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For more than 90 years, solar extreme ultraviolet (EUV) irradiance modeling has progressed from empirical blackbody radiation formulations, through fudge factors, to typically measured irradiances and reference spectra as well as time‐dependent empirical models representing continua and line emissions. A summary of recent EUV measurements by five rockets and three satellites during the 1980s is presented along with the major modeling efforts. The most significant reference spectra are reviewed and three independently derived empirical models are described. These include Hinteregger's 1981 SERF1, Nusinov's 1984 two‐component, and Tobiska's 1990/1991 SERF2/EUV91 flux models. They each provide daily full‐disk broad spectrum flux values from 2 to 105 nm at 1 AU. All the models depend to one degree or another on the long time series of the Atmosphere Explorer E (AE‐E) EUV database. Each model uses ground‐ and/or space‐based proxies to create emissions from solar atmospheric regions. Future challenges in EUV modeling are summarized including the basic requirements of models, the task of incorporating new observations and theory into the models, the task of comparing models with solar‐terrestrial data sets, and long‐term goals and modeling objectives. By the late 1990s, empirical models will potentially be improved through the use of proposed solar EUV irradiance measurements and images at selected wavelengths that will greatly enhance modeling and predictive capabilities.

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Section: E Uv Irradiance Proxiesmentioning

confidence: 99%

Recent solar extreme ultraviolet irradiance observations and modeling: A review

Tobiska¹

1993

J. Geophys. Res.

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“…Pawsey and Yabsley·(1949) found it to be superimposed upon a basic steady level attributed to thermal radiation from the " quiet Sun". The component was found by Covington (1948) and Lehany and Yabsley (1949) to have good correlation with the sunspot area. Eclipse observations made by Covington (1947) at a wavelength of 10 cm, and by Christiansen, Yabsley, and Mills (1949) at 50 cm showed that the component originated in localized regions on the solar disk.…”

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confidence: 85%

Solar Brightness Distribution at a Wavelength of 60 Centimetres. II. Localized Radio Bright Regions

Swarup¹,

Parthasarathy²

1958

Aust. J. Phys.

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SummaryThe localized radio bright regions on the Sun which give rise to a slowly varying component of the solar radiation were studied at a wavelength of 60 cm, using a 32·aerial interferometer with a beamwidth of 8·7 min of arc. The observations were undertaken during July 1954 to March 1955 and were limited in number due to this being a minimum period of the solar cycle. The low activity, however, provided the advantage of simple i:I;tterpretation as often only one r!)gion was present on the solar disk.The characteristics of the observed bright regions are described; their occurrence is closely correlated with regions of chromospheric faculae, the emission polar diagram has a half· power width of 6 days, the estimated size of the sources varied from less than 3 to 6 min of are, the largest value of the derived brightness temperature was 107 oK, and for two groups of localized regions the height of the source was derived to be 35,000±15,000 km above the photosphere. Sometimes the slowly varying component showed marked intensity fluctuations in periods of nearly half an hour. The presence of apparently associated fluctuations suggests that at least a part of the slowly varying component at 60 em has a non· thermal origin.I. INTRODUOTION Measurements of solar radiation at decimetre wavelengths by several workers identified a component which has been called the slowly varying component. It varies slowly from day to day, and was distinguished from the rapid variations that were observed occasionally for a duration of seconds or minutes. Pawsey and Yabsley·(1949) found it to be superimposed upon a basic steady level attributed to thermal radiation from the " quiet Sun". The component was found by Covington (1948) and Lehany and Yabsley (1949) to have good correlation with the sunspot area. Eclipse observations made by Covington (1947) at a wavelength of 10 cm, and by Christiansen, Yabsley, and Mills (1949) at 50 cm showed that the component originated in localized regions on the solar disk. These radio bright regions were observed close to positions where sunspots were visible or had occurred during previous rotations. One was found close to a stable prominence well off the limb.

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“…where m is the month representing the seasonal variation, and F 10.7 index is a proxy most commonly used to represent the solar activity levels which was originally called the Covington index (Covington, 1948). It is the solar radio flux density measured at a wavelength of 10.7 cm and expressed in units of 10 −22 Watts/m 2 /Hertz.…”

Section: Modelling the Associated Eof Coefficientsmentioning

confidence: 99%

A global model of the ionospheric F2 peak height based on EOF analysis

et al. 2009

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Abstract. The ionospheric F2 peak height hmF2 is an important parameter that is much needed in ionospheric research and practical applications. In this paper, an attempt is made to develop a global model of hmF2. The hmF2 data, used to construct the global model, are converted from the monthly median hourly values of the ionospheric propagation factor M(3000)F2 observed by ionosondes/digisondes distributed globally, based on the strong anti-correlation existed between hmF2 and M(3000)F2. The empirical orthogonal function (EOF) analysis method, combined with harmonic function and regression analysis, is used to construct the model. The technique used in the global modelling involves two layers of EOF analysis of the dataset. The first layer EOF analysis is applied to the hmF2 dataset which decomposed the dataset into a series of orthogonal functions (EOF base functions) E k and their associated EOF coefficients P k . The base functions E k represent the intrinsic characteristic variations of the dataset with the modified dip latitude and local time, the coefficients P k represents the variations of the dataset with the universal time, season as well as solar cycle activity levels. The second layer EOF analysis is applied to the EOF coefficients P k obtained in the first layer EOF analysis. The coefficients A k , obtained in the second layer EOF analysis, are then modelled with the harmonic functions representing the seasonal (annual and semi-annual) and solar cycle variations, with their amplitudes changing with the F 10.7 index, a proxy of the solar activity level. Thus, the constructed global model incorporates the geographical location, diurnal, seasonal as well as solar cycle variations of hmF2 through the combination of EOF analysis and the harmonic function expressions of the associated EOF coefficients. Comparisons between the model results and observational data were consistent, indicating that the modelling Zhang (zhangml@mail.iggcas.ac.cn) technique used is very promising when used to construct the global model of hmF2 and it has the potential of being used for the global modelling/mapping of other ionospheric parameters. Statistical analysis on model-data comparison showed that our constructed model of hmF2, based on the EOF expansion method, compares better with the observational data than the model currently used in the International Reference Ionosphere (IRI) model.

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Solar Noise Observations on 10.7 Centimeters

Cited by 58 publications

References 12 publications

Recent solar extreme ultraviolet irradiance observations and modeling: A review

Recent solar extreme ultraviolet irradiance observations and modeling: A review

Solar Brightness Distribution at a Wavelength of 60 Centimetres. II. Localized Radio Bright Regions

A global model of the ionospheric F2 peak height based on EOF analysis

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