Mauna loa coronagraph observations around the 7 March 1970 eclipse

The locations of seven principal coronal features observed in projection at the 7 March 1970 eclipse are established from synoptic coronagraphic measurements.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Flow-induced transverse motions of a flexible cable aligned with the flow direction

Experimental studies of the transverse motions induced in a long flexible cable by axial flows have been conducted in a large blowdown water channel. A cable with a diameter of 1.59 cm and a length of 9 m was employed. Experiments were conducted over a fluid velocity range of 4.6-9.1 m/s. Both free and fixed downstream terminations of the cable were utilized, the former simulating a towed cable and the latter a mooring cable. Measurements of the drag coefficient of the cable with the free end were also made. These results were compared with those obtained previously for a flexible cylinder with a smooth exterior surface, and the following conclusions were drawn. 1) The amplitudes of the flow-induced transverse motions in a flexible cable or cylinder with a free downstream end in general decrease with increasing distance from this end, but they exhibit weak dependence on flow velocity and surface roughness near this end. 2) The amplitudes of the flow-induced motions are in general smaller when the cable is fixed at both ends than when the downstream end is free. 3) The drag coefficient of the flexible cylinder or cable increases with increasing surface roughness.     

Simultaneous estimation of terrestrial eigenvibrations

Summary. Recently, time domain methods have been shown to be advantageous in determining the quality of observations of terrestrial eigenvibrations. Complex demodulation has been used in estimating amplitude, period, decay constant Q and phase. Non-linear regression in the frequency domain yields formal uncertainties in each estimate. A crucial problem arises in isolating neighbouring modes of nearly the same frequency and comparable amplitude. Complex demodulation displays can be used to identify interferences such as beating. In such cases, the assumption of stationarity is violated in the regression analysis yielding biased results. Improved resolution has now been obtained by formulating the regression scheme to estimate simultaneously small sets of neighbouring spectral peaks so that stationarity is not violated. Under the assumption of stationarity this procedure becomes optimal in a statistical sense. A general analysis of variance serves to indicate the amount of correlation that exists between estimated parameters of neighbouring modes as well as the relative information that is supplied by each Fourier transform point to the overall system of equations. The covariance matrix indicates that there is no linear correlation between spectral peaks when their frequencies are separated by 5 per cent. There are, however, significant correlations when two frequencies differ by 0.5 per cent. The result is that overtone modes very near in frequency to fundamental modes can, under certain conditions, be resolved with a non-linear regression technique, although parameter uncertainties are underestimated in general.     

Reorientation of global coronal magnetic fields due to differential rotation

Because of the progressive decrease in rotation rate of the solar plasma at increasing latitudes, the photospheric foot-points of large-scale closed magnetic structures in the corona, which are originally widely separated in longitude, may ultimately be brought into proximity. Magnetic mergers and reconnections between magnetic fields of opposite polarity are presumed to occur, producing major structural changes in the corona and in the locations of underlying filaments. Thus we believe that the differential rotation phenomenon is essential to understanding both gradual (evolutionary) and sudden (transient) changes in the corona, and that they can occur without any observable change in the photospheric magnetic flux. A process is suggested for the splitting or bifurcation of a high-latitude magnetic structure, producing two separate components at the same latitude, whose rotation rates are influenced by their respective magnetic linkages to other regions on the Sun.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Coronal rotation during solar cycle 20

Using K-coronameter observations made by the High Altitude Observatory at Haleakala and Mauna Loa, Hawaii during 1964–1976, we determine the apparent recurrence period of white-light solar coronal features as a function of latitude, height, and time. A technique based on maximum entropy spectral analysis is used to produce rotational period estimates from daily K-coronal brightness observations at 1.125R _S and 1.5R _S from disk center and at angular intervals of 5° around the Sun's limb. Our analysis reaffirms the existence of differential rotation in the corona and describes both its average behavior and its large year-to-year variations. On the average, there is less differential rotation at the greater height. After 1966–1967 we observe a general increase in coronal rotation rate which may relate to similar behavior reported for the equatorial photospheric Doppler rate. However, the coronal rate increase is significantly greater than the photospheric. If K-coronal features reflect the rotation at depth in the Sun, the long-term rate increase and the variable differential rotation may be evidence for dynamically important exchanges of energy and momentum in the upper convection zone.     

Relationships of soil,plant, and microbial characteristics in silt-clay and sand,tall-formSpartina alterniflora marshes

The relationships between soil texture, plant growth, and anaerobic microbial activity in two tall-formSpartina alterniflora marshes on Sapelo Island, Georgia, were compared. The soil of one marsh was composed of typical silt-clay-sized particles; the soil of the other marsh consisted of >90% sand-sized particles. The two soils supported similar biomasses ofS. alterniflora, however, plants were taller and more robust in the silt-clay-soil than in the sand soil. Total microbial adenosine triphosphate concentrations in the silt-clay and sand soils averaged 5.71 and 1.64 μg per cm³, respectively. Seawater slurries of both soils exhibited potential for microbial sulfate reduction, methanogenesis, and glucose fermentation; rates for the processes averaged 2.03 and 0.33 nmol S-cm³ per h; 1.20 and 0.87 μmol CH₄ per cm³ per h; and 0.04 and 0.12 per min (rate constant) for the sand and silt-clay soils, respectively.     

Ein einfaches Modell der Zirkulation im Meere

Zusammenfassung In einem geschichteten Meer einfacher Form werden aus den vorgegebenen Randbedingungen und Randwerten, unter denen die Dichte an der Meeresoberfläche die Hauptrolle spielt, die Bewegungsvorgänge und die Massenverteilung im Innern des Meeres ermittelt. Es existiert eine Tiefe, in der die Horizontalkomponente der Geschwindigkeit Null ist. Diese Tiefe hängt in dem einfachen Modell außer von dem Verhältnis Gesamttiefe durch Länge von dem Verhältnis des horizontalen zu dem vertikalen Austausch ab. Je größer der erste ist, desto näher rückt die Tiefe mit verschwindender Horizontalkomponente der Strömung an die Oberfläche.

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A simple model of oceanic circulation

Summary The processes of motion and mass distribution in the depths of the ocean are derived from given boundary conditions (Randbedingungen) and bonudary values (Randwerte) in a stratified ocean of simple form, and especially from the density at the sea surface of such ocean. In pursuance of these assumptions one arrives at a level at which the horizontal component of velocity equals zero. In the simple model this level depends upon the ratio of the total depth to the length as well as upon the ratio of the horizontal to the vertical eddy viscosity. With intensifying eddy viscosity the zero level approaches the sea surface.

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Un modèle simple de la circulation océanique

Résumé Les processus de mouvement et de distribution de masses dans les profondeurs de l'océan sont dérivés des grandeurs supposées desRandbedingungen (conditions au-contour) et desRandwerte (valeurs au contour) dans un océan stratifié de forme simple et, surtout, de la densité superficielle d'un tel océan. Ces suppositions conduisent à un niveau où la composante horizontale de la vitesse devient égale à zéro. Dans le modèle simple, ce niveau de zéro dépend de la proportion entre la profondeur totale et la longueur d'une part et entre la viscosité virtuelle horizontale et la viscosité virtuelle verticale d'autre part. Avec l'intensification de la viscosité virtuelle le niveau de zéro s'approche de la surface de la mer.

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Herrn Professor Dr. Gerhard Schott zum 90. Geburtstag gewidmet.