Observations of sunspot transition region oscillations

Oscillations with a period of 3 minutes are observed in the transition region of six sunspots with the Solar and Heliospheric Observatory - SOHO joint observing programme for velocity fields in sunspot regions. Observations of the transition region lines Ov 629 and Nv 1238, 1242 with the SUMER instrument show significant differences in the amplitude of the 3-minute oscillations from one sunspot to another, both in intensity and line-of-sight velocity. In four sunspots the central part of the umbra is observed. Two of these sunspots show coincidence between the maxima in peak line intensity and velocity directed towards the observer, as is expected for an upward-propagating acoustic wave. The two other sunspots show large oscillation amplitudes and a difference of 25° between maxima in intensity and blue shift. The possible effect of partial wave reflection on the observed phase relation is discussed. For one sunspot only a part of the umbra, close to the penumbra, was observed and the observations show a difference of 50° between maxima in intensity and blueshift. For the smallest sunspot the observations are found to be contaminated by contributions from an area without oscillations. Observed oscillations in line width are small, but probably significant in two sunspots. The observations of NOAA 8378 allow us to compare simultaneous recordings of the oscillations in the chromospheric Siii 1260 line with the oscillations in the transition region lines. We question the suggestion by Fludra (1999) that the sunspot transition region oscillations are a typical feature of the sunspot plumes.     

SUMER - Solar Ultraviolet Measurements of Emitted Radiation

The instrument SUMER - Solar Ultraviolet Measurements of Emitted Radiation is designed to investigate structures and associated dynamical processes occurring in the solar atmosphere, from the chromosphere through the transition region to the inner corona, over a temperature range from 10⁴ to 2 × 10⁶ K and above. These observations will permit detailed spectroscopic diagnostics of plasma densities and temperatures in many solar features, and will support penetrating studies of underlying physical processes, including plasma flows, turbulence and wave motions, diffusion transport processes, events associated with solar magnetic activity, atmospheric heating, and solar wind acceleration in the inner corona. Specifically, SUMER will measure profiles and intensities of EUV lines; determine Doppler shifts and line broadenings with high accuracy; provide stigmatic images of the Sun in the EUV with high spatial, spectral, and temporal resolution; and obtain monochromatic maps of the full Sun and the inner corona or selected areas thereof. SUMER will be flown on the Solar and Heliospheric Observatory (SOHO), scheduled for launch in November, 1995. This paper has been written to familiarize solar physicists with SUMER and to demonstrate some command procedures for achieving certain scientific observations.     

Gesteinsbildung im Flachseebecken,am Beispiel der Jade

Zusammenfassung Die grundberührenden, durch Winde erzeugten Seegangswellen verhindern, wie das Studium der rezenten Jade (südliche Nordsee) zeigt, für große Teile eines Flachseebeckens die sofortige endgültige Ablagerung der von Gezeiten und Süßwasserzuflüssen gelieferten Sedimente. Sie unterliegen einer ständigen Umlagerung; Schichtaufbau wechselt mit Schichtabbau. Diese Umlagerungen führen zur Ausspülung der in den eben gebildeten Schichten lebenden Organismen und ihrer kalkigen Hartteile. Seegangswirkung bis zum Meeresgrund zeigt sich daher in Schillausspülungen an. So läßt Schillreichtum im fossilen Sediment auf Flachwasserablagerung schließen.Die Jade, eine noch junge Meeresbucht der südlichen Nordseeküste, verdankt ihre Entstehung mehreren Sturmfluten im Mittelalter, die nach und nach eine tiefgründige Küstenmarsch und weite Alluvialmoore ausräumten (Schütte 1939). Im 15. Jahrhundert hatte sie ihre größte Ausdehnung erreicht; seit dieser Zeit haben großräumige Verlandungen, vor allem im S und W der Jade, unterstützt durch Deichbauten und künstliche Auflandungen, die in Abb. 1 gegebene Umrißform entstehen lassen.     

Joint interpretation of earthquake travel-time residuals and seismic measurements along the ‘Blue Norma’ profile in northern Scandinavia

The deep seismic sounding project Blue Norma was carried out in the summer of 1977 in northern Scandinavia in order to investigate the deep structure of the Norwegian continental margin and the Caledonian mountain chain. During the measurements, by chance the core phase PKIKP of an earthquake at the New Hebrides was recorded with 30 seismic field stations along a profile through the central Caledonides. The results of the refraction seismic data, as obtained by a ray-tracing method, are presented and compared to the interpretation of the relative residuals of the PKIKP travel times. From both data sets a continentward down-dipping crust-mantle boundary is evaluated. From the interpretation of the refraction seismic measurements a crustal thickness of 32 km below the coastline and 42 km below the central mountain chain is obtained. The increase of the crustal thickness derived by the inversion of the travel-time residuals along this line amounts only to 6 km. This considerable discrepancy can only be explained by an eastward increasing seismic velocity in the mantle.     

Sediments of Lake Vens (SW European Alps,France) record large-magnitude earthquake events

We studied sediment cores from Lake Vens (2,327 m asl), in the Tinée Valley of the SW Alps, to test the paleoseismic archive potential of the lake sediments in this particularly earthquake-sensitive area. The historical earthquake catalogue shows that moderate to strong earthquakes, with intensities of IX–X, have impacted the Southern Alps during the last millennium. Sedimentological (X-ray images, grain size distribution) and geochemical (major elements and organic matter) analyses show that Lake Vens sediments consist of a terrigenous, silty material (minerals and organic matter) sourced from the watershed and diatom frustules. A combination of X-ray images, grain-size distribution, major elements and magnetic properties shows the presence of six homogenite-type deposits interbedded in the sedimentary background. These sedimentological features are ascribed to sediment reworking and grain sorting caused by earthquake-generated seiches. The presence of microfaults that cross-cut the sediment supports the hypothesis of seismic deposits in this system. A preliminary sediment chronology is provided by ²¹⁰Pb measurement and AMS ¹⁴C ages. According to the chronology, the most recent homogenite events are attributable to damaging historic earthquakes in AD 1887 (Ligure) and 1564 (Roquebillière). Hence, the Lake Vens sediment recorded large-magnitude earthquakes in the region and permits a preliminary estimate of recurrence time for such events of ~400 years.     

A 4D sedimentological approach to reconstructing the flood frequency and intensity of the Rhône River (Lake Bourget,NW European Alps)

A high-resolution sedimentological study of Lake Bourget was conducted to reconstruct the flood frequency and intensity (or magnitude) in the area over the last 350 years. Particular emphasis was placed on investigating the spatio-temporal distribution of flood deposits in this large lake basin. The thicknesses of deposits resulting from 30 flood events of the Rhône River were collected over a set of 24 short sediment cores. Deposit thicknesses were compared with instrumental data for the Rhône River discharge for the period from 1853 to 2010. The results show that flood frequency and intensity cannot be reliably reconstructed from a single core because of the inhomogeneous flood-deposit geometry in such a large lake. From all documented flood-deposit thicknesses, volumes of sediment brought into the lake during each flood event were computed through a Kriging procedure and compared with the historical instrumental data. The results show, in this study, that reconstructed sediment volumes are well correlated to maximal flood discharges. This significant correlation suggests that the increase of embankment and dam settlements on the Rhône River during the last 150 years has not significantly affected the transport of the smallest sediment fraction during major flood events. Hence, assessment of the flood-sediment volumes deposited in the large Lake Bourget is the only way to reliably reconstruct the flood frequency and intensity.     

The Santa Filomena meteorite shower: Trajectory,classification, and opaque phases as indicators of metamorphic conditions

On August 19, 2020, at 13:18—UTC, a meteor event ended as a meteorite shower in Santa Filomena, a city in the Pernambuco State, northeast Brazil. The heliocentric orbital parameters resulting from images by cameras of the weather broadcasting system were semimajor axis a = 2.1 ± 0.1 au, eccentricity e = 0.55 ± 0.03, and inclination i = 0.15^o ± 0.05. The data identified the body as an Apollo object, an Earth-crossing object with a pericenter interior to the Earth's orbit. The chemical, mineralogical, and petrological evaluations, as well as the physical analysis, followed several traditional techniques. The meteorite was identified as a H5-6 S4 W0 ordinary chondrite genomict breccia. The large amount of metal in the meteorite made a metallographic evaluation based on the opaque phases possible. The monocrystalline kamacite crystals suggest a higher petrological type and the distorted Neumann lines imply at least two different shock events. The absence of the plessite phase shows that the meteorite did not reach the highest shock levels S5 and S6. The well-defined polycrystalline taenite is indicative of petrologic types 4 and 5 due to the conserved internal tetrataenite rim at the boundaries. The presence of polycrystalline taenites and the characteristics of the Agrell Effect suggest that the Santa Filomena meteorite did not reheat above 700°C. The absence of martensite confirms reheating temperatures <800°C and a slow cooling rate. The Ni contents and sizes of the zoned taenite particles indicate a slow cooling rate ranging from 1 to 10 K Myr⁻¹.     

Morphology and geology of the continental shelf and upper slope of southern Central Chile (33°S–43°S)

The continental shelf and slope of southern Central Chile have been subject to a number of international as well as Chilean research campaigns over the last 30 years. This work summarizes the geologic setting of the southern Central Chilean Continental shelf (33°S–43°S) using recently published geophysical, seismological, sedimentological and bio-geochemical data. Additionally, unpublished data such as reflection seismic profiles, swath bathymetry and observations on biota that allow further insights into the evolution of this continental platform are integrated. The outcome is an overview of the current knowledge about the geology of the southern Central Chilean shelf and upper slope. We observe both patches of reduced as well as high recent sedimentation on the shelf and upper slope, due to local redistribution of fluvial input, mainly governed by bottom currents and submarine canyons and highly productive upwelling zones. Shelf basins show highly variable thickness of Oligocene-Quaternary sedimentary units that are dissected by the marine continuations of upper plate faults known from land. Seismic velocity studies indicate that a paleo-accretionary complex that is sandwiched between the present, relatively small active accretionary prism and the continental crust forms the bulk of the continental margin of southern Central Chile.     

Phase equilibria and compositions of Fe-Mg-Al minerals and melts in water-saturated peraluminous granitic systems

Phase assemblages and phase compositions were studied experimentally in water-saturated, biotite-bearing peraluminous granitic melts as a function of alumina excess and temperature. The runs were performed at 2 and 5 kbars under NNO buffer. Biotite was stable only in composition containing 5% of normative corundum; it coexisted with cordierite and hercynite at 2 kbars and with hercynite at 5 kbars. In composition containing 10% of normative corundum biotite was not observed; abundant cordierite and hercynite were the only Fe-Mg-Al minerals. These relationships show that, at constant pressure, the amount of cordierite increases with increasing excess of alumina. Simultaneously the stability of biotite decreases due to preferential partitioning of Mg into cordierite and Fe into biotite. Besides the distribution of Fe, Mg and Al among the coexisting solid phases, solubility of these elements in the melts is given. Below 900° C melts are poor in iron and magnesium and correspond, in terms of these elements, to leucogranites. It is suggested that the leucogranitic magmas, such as parental magmas of European Hercynian and Himalayan leucogranites, must have been formed through highly efficient separation of partial melt from restite, in which ferromagnesian components are concentrated. Peraluminous granites rich in ferromagnesian minerals originate supposedly from restite-bearing magmas.