Meteorological microseisms and stratospheric warmings

Summary The meteorological microseisms recorded at Prague are found to be essentially independent of the occurrence of the major midwinter stratospheric warmings. This finding contributes to studying the downward propagation mechanism of some extraterrestrial influences.     

Sudden ionospheric disturbances and flare activity in the course of the solar cycle no 20

a¶rt;a ma nu an u u (SID) u nu n a (a n¶rt; au) mu 1965–1975 . u u SID na¶rt;am nau, mum u nm R.     

The response of the total electron content to the interplanetary magnetic sector boundary crossing

¶rt;m uu n ¶rt;au m uu nu mau nam aum n. mu uu auam mmmuu uuu ¶rt;u u naam. a¶rt;am auu ¶rt; uuu n ¶rt;au m u u. a auu a¶rt;am nuu amm 245 . ¶rt;aam umnmau m a¶rt;a uu.     

Relation between the monthly sums of sunshine and global radiation

Summary The statistical treatment of the dependence of monthly sums of global radiation on the monthly sums of sunshine at the stations of Hradec Králové, Bratislava — Koliba and Hurbanovo is presented. The parameters of linear and quadratic regression are derived for the said stations and for the individual months of the year. Drawing on the statistical analysis of the initial data sets, the accuracy and reliability of the mentioned regression relations are critically evaluated.     

A model for the emplacement of the eastern compartment of the bushveld complex

The stratigraphy and geological position of the eastern compartment of the Bushveld Complex are described. A mechanical model for the initiation and growth of the eastern compartment of the Bushveld intrusion has been developed using thin elastic plate theory, assuming linked conical magma chambers. It is shown that the contribution to the pressure at the base of a cell by the restitutional force exerted by the roof of Rooiberg felsites is 10⁴ times as great as that of the layers of host in the cone. Both are minimal compared to the lithostatic pressure exerted by the magma pile. Roof deformation is therefore seen to be a more important process than sagging of the floor during intrusion—a feature which probably occurred during cooling, solidification and isostatic readjustment of the area.A stratigraphie model is proposed in which the intrusion of basic rocks into the Transvaal sequence is discussed in the light of continuous basin subsidence. Early submarine sedimentation in an irregularly-floored basin some 620 km in diameter situated on the Archaean craton gave rise to a 7.7 km thick sedimentary pile, to which was added some 7 km of subaerial basalts and felsites. Depression of the floor of the basin into the regime of maximum horizontal compression induced favourable conditions for the intrusion of a total of 2.5 km of diabase sills which further assisted the subsidence. The 9 km thick Bushveld Complex was intruded into the basal sections at points along a 010° trend in a regime characterised by shear failure. Early magma influxes gave rise to a laminated marginal zone forming a shallow cone, with associated sill activity, whilst continued later influxes filled the conical cell, transgressed the floor and uparched the roof. Partial melting in the regions beneath the Complex, exacerbated by continued crustal depression, gave rise to the late Bushveld granites.     

Day-time ionospheric disturbances of corpuscular origin in the midlatitudeD-region

¶rt;m uu nau mu m a nu a¶rt;u ¶rt; D-amu u. a¶rt; m nu u u. u¶rt;a a a mu nma u nma mu m (20 ¶rt; 150 ).     

5-alkylsalicylaldoximes as collectors in flotation of sphalerite,smithsonite and dolomite in a Hallimond tube

Flotation tests for sphalerite, smithsonite and dolomite were carried out in a Hallimond tube at various pH values and two concentrations of collector.Adsorption of 5-alkylsalicylaldoximes on the surface of minerals was examined and isotherms for 5-butylsalicylaldoxime plotted.It was shown that sorption intensity of 5-alkylsalicylaldoximes on the surface of minerals decreased in the order: smithsonite, sphalerite and dolomite.Relationship between length of aliphatic chain and collecting activity of 5-alkylsalicylaldoximes was investigated in microflotation tests in a Hallimond tube.5-Propylsalicylaldoxime proved to have the best selectivity in flotation for the range of parameters studied, taking the difference in flotation rates of smithsonite and dolomite as a criterion.It was found that modifications of pH value resulted in changes in both adsorption and flotation.     

Present-day strain rates at the northern end of the ethiopian rift valley

Five successive geodimeter surveys during a five-year period yield hints as to the manner and rate of crustal extension in the Ethiopian rift valley. The northern geodimeter network traverses an en-echelon offset in the Wonji fault belt at latitude 8°30′N; this belt comprises the youngest volcanism and faulting of the rift floor. The northern network surveys reveal progressive rift extension at mean rates of 3–5 mm/year and strain rates of 6–16 · 10⁻⁷/yr, essentially confined within the Wonji fault belt segments. Small longitudinal motions of persistent dextral sense have occurred in the intervening zone between the offset segments. It is too early to say whether these deformations are local, regional or plate-tectonic phenomena, but the present aseismicity of the rift suggests the buildup of regional strain.