Structure of the 5-minute solar oscillations 1976–1980

The discrete structure in the 5 min velocity oscillations of the solar surface has been confirmed by a re-analysis of data obtained between 1976 and 1979, and in addition a preliminary analysis of 1980 data show excellent consistency of the determined frequencies over the five year period. It is further shown that atmospheric transparency, as measured by the power in the solar intensity fluctuations, shows no correlation with the measured amplitude of the velocity fluctuations, over 2 orders of magnitude.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands.     

The stability of coronal loops: Finite-length and pressure-profile limits

Solar Physics - Vertically propagating traveling waves have been observed in the solar photosphere. These waves have a period of 278 ± 41 seconds and a vertical phase velocity of about 2 km...     

The onset of coronal transients

A model for the motion of transients in the high corona, recently given by Anzer (1978), is extended to include also the onset of a transient, associated with prominence destabilization. A comparison is made with flare instabilities, and some relevant observations are considered.     

An evaluation of the use of halogen and water abundances in efforts to distinguish mineralized and barren intrusive rocks

Analysis of the chlorine, fluorine and water content of approximately 200 samples from a total of fourteen mineralized and ten barren intrusive rocks from the Caribbean and Central America indicates that abundances of these constituents fail to distinguish mineralized rocks from barren rocks. Variations in background abundances arise from the increase in halogen content of potassium-rich rocks and from the depletion of halogens in altered and porphyritic rocks. A particularly well developed potassium-fluorine covariance is observed in tin-bearing granites, but such a covariance cannot be used to distinguish intrusive rocks associated with porphyry copper mineralization.     

Dark matter influence on velocity dispersion profiles of clusters of galaxies

We have performed a series ofN-body experiments including the effects of a massive dominant background which follows Schuster's density law in order to simulate clusters of galaxies in which a smoothly distributed dark component is present. The existence of this background is inferred from the weak luminosity segregation observed in clusters which, however, show several characteristics of well-relaxed systems. The comparison of the velocity dispersion profiles of three clusters of galaxies (Coma, Perseus, and Virgo) with those obtained in the numerical experiments allows us to place some constraints on both the distribution and amount of distributed dark material in these clusters. The profiles are rather insensitive to variations in the ratio of the background mass to the mass attached to galaxies (M _b/M_g), but exhibit a strong dependence on their relative concentration. We conclude that highly concentrated background models are not consistent with observations. We find a maximum value for the ratio of the gravitational radius of the galaxies and the background (R _g/R_b) (approximately 0.6) and using previous results (Navarroet al., 1986) we conclude that virial theorem masses underestimate the total mass (M _b+M _g) of the clusters. As a final result, we derive a minimum value for theM _b/M_g ratio. All these conclusions could apply in general if Coma, Perseus, and Virgo constitute a fair sample of the rich clusters of galaxies in the Universe.     

Case B of mass exchange in systems 4+3.2m ⊙ and 4+1.6m ⊙

Two examples of case B of mass exchange are computed to estimate the effect of basic initial parameters on the course and the results of mass exchange.It seems that the resulting mass of original primary is independent of the initial mass ratio, the resulting orbital period is independent of initial mass of primary and surface hydrogen content is independent of both of these parameters.     

Relative sea-level rise and climate change over the last 1500 years

We constructed a detailed relative sea-level rise curve for the last 1500 years using a novel approach, i.e. charting the rate of relative sea-level rise using microfaunal and geochemical data from a coastal salt marsh sequence (Clinton, CT, USA). The composition of benthic foraminiferal assemblages and the iron abundance in peats were used to describe shifts in marsh environment through time quantitatively. The resulting sea-level rise curve, with age control from ¹⁴C dating and the onset of anthropogenic metal pollution, shows strong increases in the rate of relative sea-level rise during modern global warming (since the late nineteenth century), but not during the Little Climate Optimum (ad 1000–1300). There was virtually no rise in sea-level during the Little Ice Age (ad 1400–1700). Most of the relative sea-level rise over the last 1200 years in Clinton appears to have occurred during two warm episodes that jointly lasted less than 600 years. Changes from slow to fast rates of relative sea-level rise apparently occurred over periods of only a few decades. We suggest that changes in ocean circulation could contribute to the sudden increases in the rate of relative sea-level rise along the northeastern USA seaboard. Relative sea-level rise in that area is currently faster than the worldwide average, which may result partially from an ocean surface effect caused by hydrodynamics. Our data show no unequivocal correlation between warm periods (on a decaal to centennial time-scale) and accelerated sea-level rise. One period of acclerated sea-level rise may have occurred between about ad 1200 and 1450, which was the transition for the Little Climate Optimum to the Little Ice Age, i.e. a period of cooling (at least in northwestern Europe). Local changes in tidal range might also have contributed to this apparent increase in the rate of relative sea-level, however. The second period of accelerated sea-level rise occurred during the period of modern global warming that started at the end of the last century.