Contribution of chromospheric features to UV irradiance variability from spatially-resolved Ca II K spectroheliograms

We have digitized the Ca ii K spectroheliograms, observed at the National Solar Observatory at Sacramento Peak, for the period 1980 (maximum of solar cycle 21), 1985 (minimum of solar cycle 21), 1987 (beginning of the ascending phase of solar cycle 22), 1988 and 1989 (ascending phase and maximum of solar cycle 22), and 1992 (declining phase of solar cycle 22). A new method for analyzing the K spectroheliograms has been developed and applied to the K images for the time interval of 1992. Using histograms of intensity, we have segregated and measured the cumulative intensity and area of various chromospheric features like the plages, magnetic network and intranetwork elements. Also, the full width at half maximum (FWHM) derived from the histograms has been introduced as a new index for describing the chromospheric activity in the K-line. The full-disk intensity (spatial K index) has been derived from spatially-resolved K images and compared to the spectral K index derived from the line profiles for the full disk. Both the spatial K index and FWHM have been compared to the UV irradiance measured in the Mg ii h and k lines by the NOAA9 satellite and found that they are highly correlated with the Mg ii h and k c/w ratio.NRC Resident Research Associate, on leave from Indian Institute of Astrophysics, Bangalore 560034, India.     

Correlation of atmospheric occurences over the United States with some physical and chemical parameters. Part III: Frequencies of precipitation

Summary Correlation between some physical and chemical variables, measured at 28 stations of the United States Weather Bureau Network, and seasonal and annual frequencies of precipitation, has been attempted with the aim of gaining insight into the bearing of such variables, on occurrence of precipitation. — Concurrent trends of frequencies with local temperature functions, altitude parameters, precipitable water vapour increments, and some chemical species have been found.Contribution of the «Centro Nucleazione Aerosoli» of the National Research Council of Italy, Via Vettore 4 (Monte Sacro),Roma.     

Sunspot photometry and the total solar irradiance deficit measured in 1980 by ACRIM

Until now a simple Photometric Sunspot Index (PSI) model was used (e.g. Willsonet al., 1981) to describe the contribution of sunspots to the solar irradiance deficit measurement by ACRIM. In this work we replace this model by a photometry of sunspot pictures for the period of 19 August to 4 September, 1980 taking into account the individual features, like lightbridges or umbral dots, of each spot. The main results of this preliminary analysis are: (1) theA _u/A _p ratios and alsos the values vary in a wide range and are by no means constant as in the PSI model; (2) the general trend of the irradiance deficit from our analysis agrees well with the ACRIM measurements; (3) on some days there are differences of more than 50% between the deficits derived from our measurements and from the PSI model.Paper presented at the 11th Eurpean Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain     

Long-term change in precipitation in southern Italy

Summary Annual average precipitation values obtained at 765 Italian raingauge stations south of the Rome parallel and in the Italian Isles, are analyzed. The analysis is extended over 18 years and marked variations in precipitation with the Zürich annual relative sunspot numbers are found. It is found furthermore that the magnitude of change appears to depend also on the average altitude of the 5 categories of stations considered.

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Riassunto In questo articolo viene fatta un'analisi sulle variazioni delle precipitazioni medie annue in base ai dati forniti da 765 stazioni pluviometriche dell'Italia meridionale, Sicilia e Sardegna, negli anni dal 1926 al 1943 incluso. Tali variazioni sembrano essere legate al numero medio annuo di macchie solari e dipendono anche dall'altezza delle stazioni.

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Contribution of the Centro Nucleazione Aerosoli of the National Research Council of Italy; Via Vettore 4 (Monte Sacro)     

On the chemical composition of atmospheric aerosols — Part III: Trends of the total annual precipitation with respect to the chemical content of rainwater over the United States

Summary Following a recent hypothesis on the role of activated sodium chloride particles as potential nuclei of atmospheric precipitation, further analysis is made of average annual data due toC. Junge on the chemical composition of rainwater salts, and correlation of some parameters with the total amount of rainfall is attempted. It is found that the results obtained are in agreement with the proposed role of activated sodium chloride as a nucleus of a substantial part of the atmospheric precipitation.     

Effect of some co-dissolved inorganic groups on the photodecomposition of aqueous nitrates

Summary The rate of nitrite formation, in UV-irradiated aqueous solutions of alkali metals, is found to depend on co-dissolved chemical compounds and on their reactivities. The effect of some common and simple components of the atmospheric aerosol is investigated in the laboratory.     

Statistical Feature Recognition for Multidimensional Solar Imagery

A maximum a posteriori (MAP) technique is developed to identify solar features in cotemporal and cospatial images of line-of-sight magnetic flux, continuum intensity, and equivalent width observed with the NASA/National Solar Observatory (NSO) Spectromagnetograph (SPM). The technique facilitates human understanding of patterns in large data sets and enables systematic studies of feature characteristics for comparison with models and observations of long-term solar activity and variability. The method uses Bayes’ rule to compute the posterior probability of any feature segmentation of a trio of observed images from per-pixel, class-conditional probabilities derived from independently-segmented training images. Simulated annealing is used to find the most likely segmentation. New algorithms for computing class-conditional probabilities from three-dimensional Gaussian mixture models and interpolated histogram densities are described and compared. A new extension to the spatial smoothing in the Bayesian prior model is introduced, which can incorporate a spatial dependence such as center-to-limb variation. How the spatial scale of training segmentations affects the results is discussed, and a new method for statistical separation of quiet Sun and quiet network is presented.     

Estimating Long-Term Solar Irradiance Variability: A New Approach

The detection of solar irradiance variations (both bolometric and at various wavelengths) by satellite-based experiments during the last one-and-a-half decades stimulated modeling efforts to help identify their causes and to provide estimates of irradiance data for those time intervals when no satellite observations exist. In this paper we present estimates of the long-term irradiance changes developed with Fourier and wavelet transforms. The month-to-month irradiance variations, after removing the solar cycle related long-term changes, are studied with the cross-correlation technique. Results of the analysis reveal a significant phase shift at 3 months between the full-disk magnetic field strength and total solar and UV irradiance, with irradiance leading the magnetic field variability. In addition to this time delay between the changes in solar irradiance and the magnetic field, a 10-month phase shift has been found between the UV flux at 280 nm and total solar irradiance corrected for sunspot darkening. The existence of these phase shifts suggests the possibility of a coupling between the physical processes taking place below, in, and above the photosphere.     

The first experience of solar eclipse observations with a miniature torsion balance

We observed the behavior of the pointer of an asymmetric torsion balance (TB) at solar eclipse dates and on other off-eclipse days. A peculiar reaction of the miniature TB different from its reaction at off-eclipse time was recorded for some solar eclipses. The relative positions of the Earth, Moon, and Sun are among the possible factors affecting the position of the TB pointer. A time shift between the maximum phase of a solar eclipse and the maximum TB reaction was detected. We conclude that base observations of such phenomena from different points of the terrestrial globe are necessary.     

Comparison of two different solutions to Molodensky’s G1 term

The main purpose of this paper is comparison of two different approaches of solution to the Simple Molodensky’s Problem, the Molodensky’s Approach and the Analytical Continuation Approach, based on numerical computation. Although these approaches have been described theoretically by several authors, e.g. Molodensky et al. (1960), Heiskanen and Moritz (1967), Vaníček (1974), Moritz (1980) and Holota (1991, unpublished results) and theoretical proof of equivalence was given by Heiskanen and Moritz (1967), Moritz (1971), Ecker (1971) and Pellinen (1972, unpublished results), only very few practical experiences about the differences between particular solutions and computational efficiency exist. In this paper we compare the above two mentioned approaches in terms of the G₁-effect on quasigeoid. Both quasigeoid solutions are tested by the independent GPS/levelling approach and are also compared with the previous quasigeoid model of Slovakia where the G₁-term has been approximated using the classical terrain correction. The effect of the G₂-term is also numerically estimated, revealing that it might be significant for the precise quasigeoid determination. Some practical comments and recommendations are given at the end of the paper.