Suspended matter in surface waters of the eastern Gulf of Guinea

Suspended matter in the surface waters of the eastern Gulf of Guinea was studied in relation to the prevailing oceanic currents and the sediment composition and source. A confused current system arises from the confluence of the Guinea Current and the South Equatorial Current in this area. Sediment-laden water is transported to the south of Fernando Póo into the Gulf in a south-westerly direction. The southeasterly flowing Guinea Current along the western edge of the Niger delta and the enormous sediment loads of the distributaries in this area contribute to a major lobe of suspended matter off the southwestern nose of the delta. Sediment concentration is inversely related to salinity in the northeastern Gulf. Sediment is also swept northwestward from the continental shelf of Gabon and the Congo Republic into the Gulf. Diatoms are the most abundant constituents with lesser amounts of organic aggregates and two varieties of fecal pellets.     

On the width distribution of penumbral filaments in sunspots

The mean width and distribution of penumbral filaments of a sunspot have been estimated, using white light photographs obtained with a vacuum, Newtonian type, telescope. Three areas corresponding to the penumbra of a sunspot have been analysed. Data were collected during the solar eclipse of June 1973. The photometric profiles of the Moon limb over the photosphere have been analysed to obtain useful information on both, atmospheric and instrumental perturbation on each exposure. The mean value of the width of penumbral filaments is 0.37 arc sec.Now at INTA-Villafranca, S.T.S., P.O. Box 54065, Madrid, Spain.     

How can α 2-dynamos generate axisymmetric magnetic fields?

Inspired by a recently observed axisymmetric field in a fully convective star we investigate the influence of an anisotropic diffusivity on the dynamo. We find that with reasonable assumptions for the anisotropy of the diffusivity and the α -effect the preference of axisymmetric modes is achieved. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Axial rotation of near-earth asteroids: The influence of the YORP effect

The distribution of axial rotation velocities of near-Earth asteroids (NEAs) substantially differs from that of the Main-Belt asteroids by an excess of both quickly and slowly rotating objects. Among the possible causes of this difference is the influence of the solar radiation—the so-called YORP effect—that arises from the absorption of solar energy and its reemission in the thermal range by a rotating body of irregular shape. It is known that the magnitude of this effect depends on the asteroid size and the quantity of received solar energy (the insolation). Analysis of the observational data showed that the mean diameter of NEAs decreases from the middle of the distribution to the edges, i.e., the excess of both slowly (ω ≤ 2 rev/day) and quickly (ω = 8–11 rev/day) rotating objects is formed due to the asteroids with sizes smaller than those in the middle of the distribution, which agrees well with the influence of the YORP effect. Moreover, the dependence of the axial rotation velocity of NEAs on the relative insolation shows that, for the NEAs referred to, both excesses are found in orbits where, on average, they receive 8–10% more solar energy than the NEAs in the middle of the distribution. This result also agrees with the character of the influence of the YORP effect and can be considered as an additional argument in its support. Thus, the study showed that one can infer that the currently available observational data suggest the possible influence of the YORP effect on the axial rotation of the near-Earth asteroids having sizes of D ～ 2 km and less. This is the first attempt to find the influence of the YORP effect on the axial rotation of the NEA family as a whole.     

Integrated Research of the Southeastern Baltic Sea during the Cruise 47 of the R/V Akademik Nikolaj Strakhov

Oceanology - New data on the geological structure and genesis of relict bottom relief forms, objects of underwater cultural heritage, and the structure of bottom sediments in the Baltic Sea were...