Latitudinal Flow Research Articles

Pragian conodont biostratigraphy of the western slope of the Southern Urals (Mindigulovo section)

Research subject. Pragian conodonts from the Mindigulovo section on the western slope of the South Urals. Aim. Conodont-based biostratigraphy of the Pragian deposits. Materials and methods. This study is based on the biostratigraphic method: identification of conodonts using conventional techniques, recognition of Pragian conodont associations, zonal scale proposal and correlation. Results. The Pragian beds in the Mindigulovo Section in the latitudinal flow of the Belaya River are characterized using conodonts for the first time. The following conodont-based subdivisions at the rank of beds with fauna are recognized (from bottom to top): Beds with Gondwania irregularis, Latericriodus steinachensis, Beds with Pelekysgnathus serratus, Beds with Gondwania profunda, Pseudogondwania kindlei and Beds with Polygnathus cf. pireneae. Conclusions. The recognized conodont-based units can be directly correlated with the standard zonal scale of the Pragian. The conodont assemblage studied contains taxa characterizing the Gondwania irregularis–Gondwania profunda, Pseudogondwania kindlei–Eognathodus zeravshanicus, Polygnathus pireneae lineage, also known in the Pragian successions of Australia and the South Tien Shan. The co-occurrence of the deep-water family Eognathodidae and the shallow-water Icriodontidae in the Mindigulovo Section enables the correlation of different facies sections.

Shoreline deformation of the Konda river: Trends and threats

The study of the hydrological hazards in the north of Western Siberia is important because settlements in this territory are generally located on the banks of rivers and are therefore subject to the negative effects of water. The purpose of this study is to identify the dynamics of hydrological hazards in the settlements of the Konda river basin. The objectives of the study are aimed at identifying hazardous areas, which is necessary to make informed decisions related to rational bank reinforcement. The research object was the settlements of the Khanty-Mansi Autonomous district–Yugra (Kama village, Altay village, Vykatnoy settlement) within the latitudinal flow of the Konda river between 59 and 61 N and between 66 and 70 E, where the manifestation of hydrological hazards is active in nature. Research methods are based on field surveys using satellite geodetic surveying, remote probing, and bed mapping analysis. The data obtained during the study show that the most significant bank line deformations occur within the Vykatnoy, Kama, and Altay areas. The results showed the need for engineering solutions to bank reinforcement and protection of these settlements from the negative impact of river.

Hydrodynamic Properties of the Sun’s Giant Cellular Flows

Abstract Measurements of the large cellular flows on the Sun were made by local correlation tracking of features (supergranules) seen in full-disk Doppler images obtained by the Helioseismic and Magnetic Imager (HMI) instrument on the NASA Solar Dynamics Observatory (SDO) satellite. Several improvements made to the local correlation tracking method allowed for more precise measurements of these flows. Measurements were made hourly over the nearly ten years of the mission-to-date. A four-hour time-lag between images was determined to give the best results as a compromise between increased feature displacement and decreased feature evolution. The hourly measurements were averaged over the 34 days that it takes to observe all longitudes at all latitudes to produce daily maps of the latitudinal and longitudinal velocities. Analyses of these flow maps reveal many interesting characteristics of these large cellular flows. While flows at all latitudes are largely in the form of vortices with left-handed helicity in the north and right-handed helicity in the south, there are key distinctions between the low-latitude and high-latitude cells. The low-latitude cells have roughly circular shapes, lifetimes of about one month, rotate nearly rigidly, do not drift in latitude, and do not exhibit any correlation between longitudinal and latitudinal flow. The high-latitude cells have long extensions that spiral inward toward the poles and can wrap nearly completely around the Sun. They have lifetimes of several months, rotate differentially with latitude, drift poleward at speeds approaching 2 m s−1, and have a strong correlation between prograde and equatorward flows. Spherical harmonic spectral analyses of maps of the divergence and curl of the flows confirm that the flows are dominated by the curl component with rms velocities of about 12 m s−1 at wavenumber ℓ = 10. Fourier transforms in time over 1024 daily records of the spherical harmonic spectra indicate two notable components—an m = ±ℓ feature representing the low-latitude component and an m = ±1 feature representing the high-latitude component. The dispersion relation for the low-latitude component is well represented by that derived for Rossby waves or r-modes. The high-latitude component has a constant temporal frequency for all ℓ indicating features advected by differential rotation at rates representative of the base of the convection zone high latitudes. The poleward motions of these features further suggest that the high-latitude meridional flow at the base of the convection zone is poleward—not equatorward.

Biostratigraphy and foraminiferal Assemblages of the West Siberian Albian

New data of the Biostratigraphy and Albian foraminiferal assemblages from the sections of newly drilled wells in the Yamal peninsula have been obtained. This territory is assigned by the author to the Northern palaeobiogeographical district, the southern border of which goes along the latitudinal flow of the Ob River. The most diverse Albian foraminiferal assemblages have been discovered in the section of borehole 50 of the Malyginskaya area as well as in the sections of borehole 124 of the West-Tambeiskaya, boreholes, 201, 205 of the North-Tambeiskaya areas. Somewhat similar Albian foraminiferal assemblages were earlier studied by the author in 10 sections of the boreholes of the Samatlor area in the latitudinal Ob River Region. The Middle Albian assemblage is the most stable and diverse in its specific respect. It was discovered not only in the identified sections in the Yamal wells but also southwards in the earlier explored areas. The Albian foraminiferal species of the Yamal peninsula are illustrated in 5 photos and 1 drawing.

Are the strengths of solar cycles determined by converging flows towards the activity belts?

It is proposed that the observed near-surface inflows towards the active regions and sunspot zones provide a nonlinear feedback mechanism that limits the amplitude of a Babcock-Leighton-type solar dynamo and determines the variation of the cycle strength. This hypothesis is tested with surface flux transport simulations including converging latitudinal flows that depend on the surface distribution of magnetic flux. The inflows modulate the build-up of polar fields (represented by the axial dipole) by reducing the tilt angles of bipolar magnetic regions and by affecting the cross-equator transport of leading-polarity magnetic flux. With flux input derived from the observed record of sunspot groups, the simulations cover the period between 1874 and 1980 (corresponding to solar cycles 11 to 20). The inclusion of the inflows leads to a strong correlation of the simulated axial dipole strength during activity minimum with the observed amplitude of the subsequent cycle. This in agreement with empirical correlations and in line with what is expected from a Babcock-Leighton-type dynamo. The results provide evidence that the latitudinal inflows are a key ingredient in determining the amplitude of solar cycles.

COSMIC-RAY DIFFUSION IN A SECTORED MAGNETIC FIELD IN THE DISTANT HELIOSHEATH

Very high intensities of galactic cosmic rays measured by Voyager 1 in the heliosheath appear to be incompatible with the presence of a modulation "wall" near the heliopause produced by a pile up of the heliospheric magnetic field. We propose that the modulation wall is a structure permeable to cosmic rays as a result of a sectored magnetic field topology compressed by plasma slowdown on approach to the heliopause and stretched to high latitudes by latitudinal flows in the heliosheath. The tightly folded warped current sheet permits efficient cosmic-ray transport in the radial direction via a drift-like mechanism. We show that when stochastic variations in the sector widths are taken into account, particle transport becomes predominantly diffusive both along and across the magnetic sectors. Using a test-particle model for cosmic rays in the heliosheath we investigate the dependence of the diffusion coefficients on the properties of the sector structure and on particle energy.

THE EFFECT OF ACTIVITY-RELATED MERIDIONAL FLOW MODULATION ON THE STRENGTH OF THE SOLAR POLAR MAGNETIC FIELD

We studied the effect of the perturbation of the meridional flow in the activity belts detected by local helioseismology on the development and strength of the surface magnetic field at the polar caps. We carried out simulations of synthetic solar cycles with a flux transport model, which follows the cyclic evolution of the surface field determined by flux emergence and advective transport by near-surface flows. In each hemisphere, an axisymmetric band of latitudinal flows converging towards the central latitude of the activity belt was superposed onto the background poleward meridional flow. The overall effect of the flow perturbation is to reduce the latitude separation of the magnetic polarities of a bipolar magnetic region and thus diminish its contribution to the polar field. As a result, the polar field maximum reached around cycle activity minimum is weakened by the presence of the meridional flow perturbation. For a flow perturbation consistent with helioseismic observations, the polar field is reduced by about 18% compared to the case without inflows. If the amplitude of the flow perturbation depends on the cycle strength, its effect on the polar field provides a nonlinearity that could contribute to limiting the amplitude of a Babcock-Leighton type dynamo.

GENERATION OF MAGNETIC FIELDS BY THE STATIONARY ACCRETION SHOCK INSTABILITY

We begin an exploration of the capacity of the stationary accretion shock instability (SASI) to generate magnetic fields by adding a weak, stationary, and radial (but bipolar) magnetic field, and in some cases rotation, to an initially spherically symmetric fluid configuration that models a stalled shock in the post-bounce supernova environment. In axisymmetric simulations we find that cycles of latitudinal flows into and radial flows out of the polar regions amplify the field parallel to the symmetry axis, typically increasing the total magnetic energy by about two orders of magnitude. Nonaxisymmetric calculations result in fundamentally different flows and a larger magnetic energy increase: shearing associated with the SASI spiral mode contributes to a widespread and turbulent field amplification mechanism, boosting the magnetic energy by almost four orders of magnitude (a result which remains very sensitive to the spatial resolution of the numerical simulations). While the SASI may contribute to neutron star magnetization, these simulations do not show qualitatively new features in the global evolution of the shock as a result of SASI-induced magnetic field amplification.

Long-term variations of the flow direction and angular momentum of the solar wind observed by Helios

The flow directions of solar wind protons were measured in situ by the Helios spacecraft. A long-term average of the velocity shows a systematic drift in the latitudinal flow angle of about +1 north observed with Helios 1 and 1 south observed onboard of Helios 2. The longitudinal flow angle migrates about +1 west over a period of almost 10 years for Helios 1 and 6 years for Helios 2. This systematic change with time of the plasma flow direction may be caused by solar-cycle variations of the orientation of the Sun's magnetic eld which partially corotates with the Sun inside the Alfv en surface (varying in distance between 10 R over the poles and 30 R near the equator). These variations must have been imprinted on the solar wind flow when it detached from corotation with the Sun near the Alfv en point. The angular momentum of the wind is intimately connected with the flow and eld directions. The gain of total angular momentum of the wind equals the loss of angular momentum of the Sun, which is caused by the torque exerted on the rotating Sun through the magnetic eld of the expanding corona. Implications of the Helios observations for models of the magnetic elds of the Sun as well as the solar wind are discussed. We show evidence, that changes of the solar magnetic eld inside the Alfv en surface are responsible for systematic drifts in the solar wind flow direction.

A map of the horizontal flows in the solar convection zone

The first map of the horizontal flows as a function of depth and heliocentric position in the solar convection zone is presented. The map is inferred from a least-squares smoothness-constrained inversion of velocities measured from ring diagrams of the solar p-mode oscillations. The data provide information in four longitude regions at a latitude just south of the solar equator. The presence of several features is suggested by the results: (1) A prograde directed longitudinal jet between the hydrogen and first helium ionization zone, reversing direction to retrograde below the second helium ionization zone. (2) A equatorward directed latitudinal flow above the second helium ionization zone. (3) A poleward latitudinal flow below the second helium ionization zone, but only in one of the four longitude bands. A large active region was present in this band, but not in two of the other bands, suggesting a possible relationship between the activity and the different flow pattern.

Paleoceanographic and biogeographic evolution of the Southern Ocean during the Cenozoic, and Cenozoic microfossil datums

The paleoclimatic history of Antarctica is intimately linked with the evolution of the Circum-Antarctic paleocirculation system and hence with Cenozoic plate tectonism. The development of the Circum-Antarctic circulation system occurred as southern land masses moved away, creating unrestricted latitudinal flow. Changing boundary conditions in this region included the opening of the Australian—Antarctic seaway as Australia moved northwards, the opening of Drake Passage and the development of the Kerguelen Plateau. The formation, and later development, of the Circum-Antarctic Current thermally isolated Antarctica by decoupling the warmer subtropical gyres from the colder Subantarctic—Antarctic gyres. The climatic history of the Southern Ocean is, in general, one of decreasing temperatures, including the development of increased antarctic glaciation and later ice sheet formation, a climatic regime which itself had a profound effect on environmental evolution, and thus the biogeography at high southern latitudes. Environmental characteristics resulting from the development of this climatic regime included extensive seasonal sea-ice production, the cooling of waters surrounding the continent, and meteorologically forced upwelling of nutrient-rich intermediate waters which increase biogenic productivity in the Southern Ocean. The thermal barriers in high southern latitudes represented by the Antarctic Convergence and the Subtropical Convergence also became major biogeographic barriers strongly affecting the distribution of planktonic organisms. The development of the Circum-Antarctic Current also removed biogeographic provinciality previously occurring within different sectors of the Southern Ocean as a result of previous land barriers. As a result, cool-water planktonic assemblages of the Southern Hemisphere show little interoceanic difference. During the Cenozoic, major changes have occurred in planktonic microfossil biogeography in the Southern Ocean as reflected in the biostratigraphic sequences. Datum levels representing the first or last appearances of microfossil species (planktonic foraminifera, calcareous nannofossils, radiolaria, diatoms and silicoflagellates) have been compiled for Antarctic and Subantarctic sections. This compilation provides a series of integrated datums and hence a historical sequence of microfossil events through the Cenozoic. The datum levels of Quaternary and Pliocene age, their nature, relative position and age are now well known mainly because of integration with magnetostratigraphy because of superior sediment records. In contrast, the relative position of Miocene and older datum levels is much less firmly established. There are several reasons for this, including poorer stratigraphic control because of a lack of magnetostratigraphic framework; few section that contain siliceous and calcareous microfossil assemblages in association to establish detailed relation; and poor stratigraphic representation especially in the Early Cenozoic. In general, most datum levels do not extend over both the Antarctic and Subantarctic regions. Instead, microfossil events, if they occur in both regions, can be highly diachronous between the two water-mass regimes. This is most strongly developed in the calcareous Cenozoic microfossil groups which, as in the present-day, show major differences across the water-mass boundaries.

First order latitude effects in the solar wind

The Weber-Davis model of the solar wind is generalized to include the effects of latitude. The principal assumptions of perfect electrical conductivity, rotational symmetry, a polytropic relation between pressure and density, and a flow aligned magnetic field in a system rotating with the Sun, are retained. A flow aligned magnetic field in the rotating system may be expressed in terms of the flow velocity and density. Rotational symmetry fixes the longitudinal flow velocity V φ in terms of the flow in the r− θ plane. Thus, the original three dimensional magnetohydrodynamic flow problem is reduced to a two dimensional hydrodynamic flow problem in the r− θ plane. There are three critical surfaces associated with the equations which supply conditions to determine three of six required boundary conditions. The specified boundary conditions at the base of the corona are the temperature, density, and magnitude of the magnetic field. The equations are then expanded about the radial, nonrotating Parker solution and an analytic solution is obtained for the resulting first order equations. The results show that for constant coronal boundary conditions there is a latitudinal flow toward the solar poles, as a result of magnetic stresses, which persists out to large distances for the Sun. Associated with this flow is a latitudinal component of the magnetic field. The radial flow parameters are, to within small first order differences, in agreement with those of the Parker and the Weber-Davis models of the solar wind. The equations are further generalized to permit first order latitudinal variations in the specified coronal boundary conditions. Results at 1 a.u. are presented for 5 per cent latitudinal differences between the equatorial and polar values. These results show that the solution at 1 a.u. is most sensitive to a latitudinal dependence in the boundary temperature and least sensitive to a latitudinal dependence in the magnetic field magnitude. A solution is then obtained for an approximate dipolar variation in the coronal magnetic field magnitude. This solution predicts that the latitudinal flow is initially toward the Equator due to magnetic channeling; however, this effect is rapidly overcome and the latitudinal flow at 1 a.u. is toward the pole and not significantly different from the solution for constant boundary conditions.

OROGRAPHICAL AND CLIMATOLOGICAL INFLUENCES ON DEPOSITION OF NUCLEAR-BOMB DEBRIS

Abstract The behavior of nuclear bomb debris in the atmosphere is reviewed in order to see how far such debris might be used as a tracer in atmospheric physics. Much debris seems to be captured by orographic precipitation, and information about the development of orographic clouds might be found by measurements of radioactivity in precipitation. Deposition of bomb debris from the stratosphere is examined by available world-wide measurements of long-lived radioactive isotopes. The simple assumption that Sr90 is more rapidly brought down to earth by precipitation than is Cs137 is shown to be reasonable. This might explain Norwegian, Danish, and British measurements of the Cs137/Sr90 ratio in precipitation, provided that various climatic factors are taken into account. This interpretation of the Cs137/Sr90 ratio together with measured total Sr90 deposition is in agreement with accepted latitudinal flow models for low and medium latitudes.