Showing papers on "Solar constant published in 1997"

Solar constant temporal and frequency characteristics

Abstract: The Sun's total irradiance at the mean Sun-Earth distance decreased from mid-1979 to mid-1987 during the descending part of solar cycle 21. After the minimum had been reached it increased with the onset of cycle 22 and came to a maximum at mid-1991 during the highest solar activity of cycle 22. From the modelized shape of the time signal of the solar constant based on the Space Absolute Radiometric Reference (SARR), temporal, amplitude and behaviour characteristics are derived. It is suggested that the variation observed over a period of more than 14 years is the response of the outer solar layers, the photosphere in particular, to some excitation originating somewhere near the bottom of the solar convection zone also responsible for the solar spots and the correlated photospheric features. Wavelet analysis and periodiograms are shown for the solar constant and the sunspot index. Their non-stationarity is well illustrated as well as strong recurrent periods.

Estimations of Maunder Minimum Solar Irradiance and Ca II H and K Fluxes Using Rotation Rates and Diameters

Abstract: The total solar irradiance and Ca H and K fluxes (HK) for the Maunder minimum are estimated from scaling laws for solar-type stars using historical solar rotation rates and solar diameters. We found that the irradiance may be lower than modern solar minimum values by 1.23% in 1683 and by 0.37% in 1715. The estimate for 1683 is substantially lower than previously reported. Analysis of cosmogenic isotope records in ice cores and tree rings shows continuation of the Sun's magnetic cycle through the Maunder minimum; therefore, we find the HK fluxes to be 0.161 for 1683 and 0.163 for 1715, compared with the modern solar minimum flux value of ~0.164. This suggests that the Sun never reached a noncycling state.

Solar cell calibration and measurement techniques

Abstract: The increasing complexity of space power solar cells and the increasing international markets for both cells and arrays has resulted in workshops jointly sponsored by NASDA, ESA and NASA. These workshops are designed to obtain international agreement on standardized values for the AM0 spectrum and constant, recommend laboratory measurement practices and establish a set of protocols for international comparison of laboratory measurements. A working draft of an ISO standard, WD15387, "Requirements for Measurement and Calibration Procedures for Space Solar Cells" was discussed with a focus on the scope of the document, a definition of primary standard cell, and required error analysis for all measurement techniques. Working groups addressed the issues of Air Mass Zero (AM0) solar constant and spectrum, laboratory measurement techniques, and the international round robin methodology. A summary is presented of the current state of each area and the formulation of the ISO document.

Correlations of solar cycle 22 UV irradiance

Abstract: The solar ultraviolet spectral irradiance monitor (SUSIM) onboard the upper atmosphere research satellite (UARS) is an absolutely calibrated UV spectrometer which has measured the solar spectral irradiance over the wavelengths 115 nm to 410 nm since October 1991. This data set now extends for about six years from near the peak of solar cycle 22, through its minimum, to the initial rise associated with solar cycle 23. Generally, the time series of UV spectral irradiances obtained shows behavior similar to that of other solar activity indices. The conditions on the sun, which can in result in dominant 13.5-day periodicity, are analyzed and illustrated. It is found that any combination of presence or absence of dominant 13.5-day in UV irradiance and solar wind velocity is possible depending entirely on the particular surface distribution and orientation of solar active regions.

Long-term variations in total solar and UV irradiances

Abstract: The variations of total solar and UV irradiances during solar cycles 21 and 22 are compared. The total solar irradiance data used were obtained by the SMM/active cavity radiometer irradiance monitoring (ACRIM) 1, upper atmosphere research satellite (UARS)/ACRIM 2 and ERBS experiments. The space-based irradiance observations are compared to the Mount Wilson Magnetic Plage and Photometric Sunspot Index, which is derived from the area and position of sunspots published by the NOAA World Data Center Solar Geophysical Data Catalog. It is found that the variations in solar UV irradiance were similar during the maximum and minimum of solar cycles 21 and 22. The possible reasons for the differences in the irradiance values during the minima of the two solar cylces are discussed.

A cause of evolution of solar magnetic field - solar gyromagnetic effect.

Abstract: In this paper, the close correlation between the time rate of change of angular momentum of the Sun rotating around the center of mass of the solar system and the annual mean values of sunspot numbers has been demonstrated, and the coefficient of correlation reached as high as 0.81 during A.D. 1900 1980 with confidence far higher than 99.9% when time lag τ～ 2 yrs. It appears that the Solar Gyromagnetic Effect which may determine the basic magnetic dipole moment of the Sun by its rotation around the center of mass of the solar system is the key to affirm the cause of evolution of solar magnetic field (or solar activity) in the solar system. By inference, we think that the most part of matter in the solar interior should have very small velocity of rotation, as well as the solar differential rotation observed directly is only a phenomenon in the surface layer of the Sun. For the analysis of the magnetism of the Earth and other planets as well as various rotational celestial bodies or galaxies, the basic theory in the paper should be valid too.

Automated recognition and characterization of solar active regions based on the SOHO/MDI images

Abstract: The first results of a new method to identify and characterize the various surface structures on the sun, which may contribute to the changes in solar total and spectral irradiance, are shown. The full disk magnetograms (1024 x 1024 pixels) of the Michelson Doppler Imager (MDI) experiment onboard SOHO are analyzed. Use of a Bayesian inference scheme allows objective, uniform, automated processing of a long sequence of images. The main goal is to identify the solar magnetic features causing irradiance changes. The results presented are based on a pilot time interval of August 1996.

Solar-Radius Variations over a Solar Cycle Observed with the Tokyo Photoelectric Meridian Circle

Abstract: As the Sun shows the well-known magnetic activity of eleven-year period, many other interesting observational features of the Sun have been examined in connection with the solar cycle. The diameter of the Sun is one of these interesting observable quantities. The apparent radius of the Sun has been observed regularly since 1985 with the Tokyo Photoelectric Meridian Circle (Tokyo PMC) at Mitaka. Here, we show the average value of the solar radii observed by us. We also show that the annual-mean values of the observed radii take the smallest value near the solar-cycle maximum, in 1989 and 1990, and the largest ones around the solar-cycle minimum, in 1986 and 1994. The average peak-to-peak shift of the annual-mean solar radius for the solar cycle is ΔR⊙/R⊙ ∼ 1.2 × 10-4, which is close to the relative change of the frequency of the 5-minute p-mode solar oscillation within one solar cycle.

The solar continuum in the 0.33–2.45 μm range from the results of observation

Abstract: The solar continuum absolute intensity obtained by means of averages is the most reliable of the observational data from different authors Measurements of the solar constant, the spectral energy distribution, limb darkening, and the blanketing effect are used The continuum intensity is obtained for the centre disk and the entire disk The centre brightness temperature is compared with the similar temperature for the model by Maltby et al (1986)