Limb-darkening and solar cycle variation of sunspot intensities

New observations of the umbral limb-darkening are presented. We find a real and significant decrease in the umbra/photosphere intensity ratio towards the limb. This result contrasts the findings of previous authors and we believe this to be the first time such a decrease is reported. Our conclusion is based on broad band pinhole photometer intensity observations of 22 large sunspots covering the spectral region 0.387–2.35 m. The data are selected from measurements on approximately 600 days during the last 15.5 yr. The application of the limb-darkening data to the study of the temperature stratification in the umbra is briefly discussed. The observations confirm the suggestion that the umbra/photosphere intensity ratio seems to be a linear function of the phase in the solar cycle.     

On the discrepancy between the magnetic D-component and the overhead horizontal current at high-latitudes

The discrepancy between the overhead E-region current and the magnetic D-component is studied using data obtained by the Chatanika incoherent scatter radar (L = 5.6). The F-region horizontal current is estimated to be too small to cause the observed D-deflection. Also, the assumption that the magnetic effects of the Pedersen and field-aligned currents cancel each other on the ground is shown to be inadequate to solve the problem. The significance of the inclination angle in the data analysis and the importance of the field-aligned current sheets are discussed.     

Motions in the solar atmosphere associated with the white light flare of 11 July 1978

Series of white light heliograms and oft- and on-band H filtergrams have been obtained, with an average spatial resolution of 1, to study the flare active McMath region 15403 on 11 July, 1978. A great number of accurate heliographic positions were determined for the umbrae, the white light flare patches and several bright H flare knots, as well as along the principal zero filament and an arch prominence. Using the measured heliographic coordinates of these objects their motions could be analyzed in some detail. The velocities of several different objects could be deduced from the coordinates. Since the heliocentric angle of the region was about 45°, the variation in apparent heliographic coordinates also enabled some variations in heights to be determined.It is pointed out that the flare when fully developed, consisted almost entirely of loops. The zero filament which was activated prior to the flare ran between two umbrae of common penumbra and opposite polarity, one belonging to an old, the other to a new spot group. The white light flare developed on both sides of the filament where it passed between these two umbrae; it was also the place where the flare started. Observational evidence appears to indicate that the erupted filament re-formed from below.An indication has been found that there was a link between the motion of some umbrae and the major flare occurrence.     

A relation in families of periodic solutions

We show the existence of a general relation between the parameters of periodic solutions in dynamical systems with ignorable coordinates. In particular, for time-independent systems with an axis of symmetry, the relation takes the form T/A=–/E, whereT is the period,A is the angular momentum, is the angle through which the system has rotated after one period, andE is the energy.     

The north-south distribution of major solar flare events,sunspot magnetic classes and sunspot areas (1955–1974)

The north-south incidence has been studied of 31 white-light flares observed since 1859 and of 1669 events meeting the criteria for major flares of Dodson and Hedeman (1971) for the period 1955–1974. The asymmetry in favor of the northern hemisphere increases strikingly with the importance of the events. Similarly, magnetically complex sunspot groups (Mt. Wilson classes, and) display a more pronounced asymmetry in favor of the north than non-complex groups for 1962–1970. Contrary to the flare asymmetry, the spottedness asymmetry is independent of the size of sunspots.     

Thermoluminescence of the lunar surface

Observations of the lunar luminescence are reported for a dozen of specific Moon features using the line-depth method with a high resolution spectroscopic technique. The data indicate a variation of the Moon proper emission as a function of the phase angle which is interpreted as a proof of the thermoluminescent origin of this emission.     

Window technique for climate trend analysis

Climatic characteristics are affected by various systematic and occasional impacts: besides the changes in the observing system (locations of the stations of the meteorological network, instruments, observing procedures), the possible local-scale and global natural and antropogenic impacts on climatic conditions should be taken into account. Apart from the predictability problems, the phenomenological analysis of the climatic variability and the determination of past persistent climatic anomalies are significant problems, among other aspects, as evidence of the possible anomalous behavior of climate or for climate impact studies. In this paper, a special technique for the identification of such shifts in the observational series is presented. The existence of these significant shorter or longer term changes in the mean characteristics for the properly selected adjoining periods of time is the necessary condition for the formation of any more or less unidirectional climatic trends. Actually, the window technique is based on a complete set of orthogonal functions. The sensitivity of the proposed model on its main parameters is also investigated. This method is applied for hemispheric and Hungarian data series of the mean annual surface temperature.Contribution to Clima Locarno — Past and Present Climate Dynamics; Conference September 1990, Swiss Academy of Sciences — National Climate Program     

Les gisements d'or des tonalites archéennes (Abitibi,Québec)

Résumé De nombreux gisements ont été mis en exploitation depuis une dizaine d'années dans des plutons granitiques de la ceinture de roches vertes archéennes de l'Abitibi. La plupart d'entre eux sont encaissés par des faciès sodiques. Dans la zone sud-est de cette ceintúre, il existe deux types de concentrations, des zones filoniennes et des disséminations à caractère porphyrique.Les gisements filoniens sont encaissés dans des sills ou des dykes de tonalite-trondhjemite. Deux associations minéralogiques sont distinguées, l'une avec tourmaline et scheelite, l'autre avec hématite et métaux de base, spécifiques de chacun des blocs lithotectoniques qui composent la ceinture. Les variations paragénétiques peuvent être mise en relation avec la profondeur de mise en place des systèmes hydrothermaux. A l'échelle d'un bloc, on observe des variations de la structure des minéralisations controlées par les variations de la pression de fluide, plus importante au coeur des massifs et conduisant à des structures plus régulières empruntant des zones de faiblesse préexistantes.Les disséminations sont associées à un granite tardif issu de la refusion de tonalites. Dans la région de Launay, près d'Amos, l'or est associé à des zones d'épisyénites avec pyrite et molybdénite, ou avec des zones de cisaillement. Elles pourraient correspondre à des concentrations plus précoces.

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Several deposits have been developped since 10 years in granitics plutons of the Archean greenstone belt of Abitibi. Most of them are hosted by Na-rich granitoids. In the south-eastern part of Abitibi, two main type of deposit may be distinguished:The lode type is hosted in pre-tectonic dykes or sills of tonalite-trondhjemite. Two mineralogical association are caracterised, one with tourmaline, scheelite, the other with hematite, and seems specific of lithotectonic blocs. Paragenetic variations may be related to vertical variations of deposition. On a bloc scale, high fluid pressure predominate in the center of pluton and may be responsible for more regular structure.The disseminated type is hosted in late granodioritic intrusions associated with tonalite. The only occurrence of that type is the Launay deposit, near Amos. Gold is associated either with abite-rich episyenite, with pyrite and Mo, or with shear-zone cross-cutting the granitic intrusions.

     

Synchronous aperture synthesis observations of pulsars

By modifying the online software of the Westerbork Synthesis Radio Telescope it is possible to sample the radio emission from a field containing a pulsar synchronously with the pulsed signal. Recording the emission from eight separate temporal windows, we can simultaneously observe both the on-pulse and off-pulse signals. We are using this technique for three different kinds of pulsar investigation: (a) to check and improve the positions of some pulsars; (b) to look for unpulsed components; and (c) to search for weak extended emission around pulsars. Observations have been carried out at 6, 21, 49, and 92 cm. Examples of results from all three types of investigation are given.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.