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Sample records for equatorial current nec

  1. Niger - NECS

    Data.gov (United States)

    Millennium Challenge Corporation — This impact evaluation uses random assignment at the village level to estimate impacts of the NECS and IMAGINE projects on enrollment, attendance, learning and other...

  2. VM-ADCP measured upper ocean currents in the southeastern Arabian Sea and Equatorial Indian Ocean during December, 2000

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, V.S.N.; Suryanarayana, A.; Somayajulu, Y.K.; Raikar, V.; Tilvi, V.

    west wind forcing through December and retroflection of NEC. The transport of the NECC in the upper 100 m varies from 4x10@u6@@ m@u3@@ /s at 83 degrees E to 7x10@u6@@ m@u3@@ /s at 93 degrees E. The data details the structure of the South Equatorial...

  3. Surface currents in the equatorial Indian Ocean during spring and fall - An altimetry based analysis

    Digital Repository Service at National Institute of Oceanography (India)

    Antony, M.K.; Somayajulu, Y.K.

    This communication presents the results of a study aimed at investigating the nature and variability of surface currents in the equatorial Indian Ocean between 5 degrees N and 5 degrees S during spring and fall seasons. Geostrophic surface currents...

  4. Role of interannual Kelvin wave propagations in the equatorial Atlantic on the Angola Benguela Current system

    Science.gov (United States)

    Imbol Koungue, Rodrigue Anicet; Illig, Serena; Rouault, Mathieu

    2017-06-01

    The link between equatorial Atlantic Ocean variability and the coastal region of Angola-Namibia is investigated at interannual time scales from 1998 to 2012. An index of equatorial Kelvin wave activity is defined based on Prediction and Research Moored Array in the Tropical Atlantic (PIRATA). Along the equator, results show a significant correlation between interannual PIRATA monthly dynamic height anomalies, altimetric monthly Sea Surface Height Anomalies (SSHA), and SSHA calculated with an Ocean Linear Model. This allows us to interpret PIRATA records in terms of equatorial Kelvin waves. Estimated phase speed of eastward propagations from PIRATA equatorial mooring remains in agreement with the linear theory, emphasizing the dominance of the second baroclinic mode. Systematic analysis of all strong interannual equatorial SSHA shows that they precede by 1-2 months extreme interannual Sea Surface Temperature Anomalies along the African coast, which confirms the hypothesis that major warm and cold events in the Angola-Benguela current system are remotely forced by ocean atmosphere interactions in the equatorial Atlantic. Equatorial wave dynamics is at the origin of their developments. Wind anomalies in the Western Equatorial Atlantic force equatorial downwelling and upwelling Kelvin waves that propagate eastward along the equator and then poleward along the African coast triggering extreme warm and cold events, respectively. A proxy index based on linear ocean dynamics appears to be significantly more correlated with coastal variability than an index based on wind variability. Results show a seasonal phasing, with significantly higher correlations between our equatorial index and coastal SSTA in October-April season.

  5. Recent development on pelletron systems at NEC

    International Nuclear Information System (INIS)

    Yan Shengqing

    1992-01-01

    Some of the most recent developments at NEC are presented. They are: the high current pelletron systems; a variety of small machines for different special purpose; some of the improvements on the accelerating tube and the terminal potential stabilizer; the large horizontal pelletron 8 UDH; the electron cooling technique

  6. Necrotizing enterocolitis (NEC: what’s going on

    Directory of Open Access Journals (Sweden)

    Mario De Curtis

    2013-06-01

    Full Text Available Necrotizing enterocolitis (NEC is among the most common and devastating diseases in neonates and, despite the significant advances in neonatal care and clinical and basic science investigations, its etiology remains incompletely understood, specific treatment strategies are lacking, and morbidity and mortality from this disease remain high. Recent improvements in the pathophysiology of NEC may have therapeutic consequences. Toll-like receptors and intestinal microflora play an increasing role in the pathogenesis of NEC. Pharmacologic inhibition of TLR signaling, the use of novel nutritional strategies, and microflora modulation may represent novel promising approaches to the prevention and treatment of NEC. This review focuses on current and future therapeutic perspectives, starting from the recent acquisitions in the pathogenic mechanisms of NEC. Proceedings of the 9th International Workshop on Neonatology · Cagliari (Italy · October 23rd-26th, 2013 · Learned lessons, changing practice and cutting-edge research

  7. Detection of radiation from a heated and modulated equatorial electrojet current system

    International Nuclear Information System (INIS)

    Lunnen, R.J.; Lee, H.S.; Ferraro, A.J.; Collins, T.W.

    1984-01-01

    In May 1983, ionospheric heating experiments were conducted using the very high frequency radar facility at Lima, Peru. Experiments involving high frequency heating of the ionosphere were successfully conducted during 1982 at Islote, Puerto Rico. These local experiments had characterized the signal radiated from a heated and modulated ionospheric current system near the mid-latitudes. A long-path signal had also been received in September 1982 at Salinas, Puerto Rico from a mid-day equatorial electrojet, heated and modulated by the Jicamarca facility. The authors have investigated the characteristics of the local signal that would be radiated from a strong equatorial electrojet when heated and modulated, and report here that at the geomagnetic equator they were similar to, but less intense than, those observed at Arecibo, Puerto Rico due to parameter differences. This radiation is believed to be the first detected from a heated and modulated equatorial electrojet current system in the Western Hemisphere. (author)

  8. Quantifying the Benefits of NEC

    National Research Council Canada - National Science Library

    Court, Georgia; Sharp, Lynda C

    2005-01-01

    ...). The white paper notes that NEC, through enabling "the ability to respond more quickly and precisely, will act as a force multiplier enabling our forces to achieve the desired effect through a smaller...

  9. NEC-2020 emission reduction scenarios

    DEFF Research Database (Denmark)

    Slentø, Erik; Nielsen, Ole-Kenneth; Hoffmann, Leif

    The upcoming NEC-2020 EU directive sets up emission ceilings for NOX, SO2, NH3, NMVOC and PM in order to meet the environmental exposure targets of the Thematic Strategy. This report contains an assessment of intermediary emission reduction scenarios for Denmark, computed by the GAINS model 2007,......, which serves as the basis for the pending negotiations in EU. The assessment is brought up to date by including a brief evaluation of the new reduction scenarios published in 2008, founding the European Commission NEC-2020 directive proposal....

  10. Penetration of ELF currents and electromagnetic fields into the Earth's equatorial ionosphere

    Science.gov (United States)

    Eliasson, B.; Papadopoulos, K.

    2009-10-01

    The penetration of extremely low frequency (ELF) transient electromagnetic fields and associated currents in the Earth's equatorial E-region plasma is studied theoretically and numerically. In the low-frequency regime, the plasma dynamics of the E-region is characterized by helicon waves since the ions are viscously coupled to neutrals while the electrons remain mobile. For typical equatorial E-region parameters, the plasma is magnetically insulated from penetration of very long timescale magnetic fields by a thin diffusive sheath. Wave penetration driven by a vertically incident pulse localized in space and time leads to both vertical penetration and the triggering of ELF helicon/whistler waves that carry currents obliquely to the magnetic field lines. The study presented here may have relevance for ELF wave generation by lightning discharges and seismic activity and can lead to new concepts in ELF/ULF injection in the earth-ionosphere waveguide.

  11. Equatorial Indian Ocean subsurface current variability in an Ocean General Circulation Model

    Science.gov (United States)

    Gnanaseelan, C.; Deshpande, Aditi

    2018-03-01

    The variability of subsurface currents in the equatorial Indian Ocean is studied using high resolution Ocean General Circulation Model (OGCM) simulations during 1958-2009. February-March eastward equatorial subsurface current (ESC) shows weak variability whereas strong variability is observed in northern summer and fall ESC. An eastward subsurface current with maximum amplitude in the pycnocline is prominent right from summer to winter during strong Indian Ocean Dipole (IOD) years when air-sea coupling is significant. On the other hand during weak IOD years, both the air-sea coupling and the ESC are weak. This strongly suggests the role of ESC on the strength of IOD. The extension of the ESC to the summer months during the strong IOD years strengthens the oceanic response and supports intensification and maintenance of IODs through modulation of air sea coupling. Although the ESC is triggered by equatorial winds, the coupled air-sea interaction associated with IODs strengthens the ESC to persist for several seasons thereby establishing a positive feedback cycle with the surface. This suggests that the ESC plays a significant role in the coupled processes associated with the evolution and intensification of IOD events by cooling the eastern basin and strengthening thermocline-SST (sea surface temperature) interaction. As the impact of IOD events on Indian summer monsoon is significant only during strong IOD years, understanding and monitoring the evolution of ESC during these years is important for summer monsoon forecasting purposes. There is a westward phase propagation of anomalous subsurface currents which persists for a year during strong IOD years, whereas such persistence or phase propagation is not seen during weak IOD years, supporting the close association between ESC and strength of air sea coupling during strong IOD years. In this study we report the processes which strengthen the IOD events and the air sea coupling associated with IOD. It also unravels

  12. Evidence and effects of a wave-driven nonlinear current in the equatorial electrojet

    Directory of Open Access Journals (Sweden)

    M. Oppenheim

    1997-07-01

    Full Text Available Ionospheric two-stream waves and gradient-drift waves nonlinearly drive a large-scale (D.C. current in the E-region ionosphere. This current flows parallel to, and with a comparable magnitude to, the fundamental Pedersen current. Evidence for the existence and magnitude of wave-driven currents derives from a theoretical understanding of E-region waves, supported by a series of nonlinear 2D simulations of two-stream waves and by data collected by rocket instruments in the equatorial electrojet. Wave-driven currents will modify the large-scale dynamics of the equatorial electrojet during highly active periods. A simple model shows how a wave-driven current appreciably reduces the horizontally flowing electron current of the electrojet. This reduction may account for the observation that type-I radar echoes almost always have a Doppler velocity close to the acoustic speed, and also for the rocket observation that electrojet regions containing gradient-drift waves do not appear also to contain horizontally propagating two-stream waves. Additionally, a simple model of a gradient-drift instability shows that wave-driven currents can cause nonsinusoidal electric fields similar to those measured in situ.

  13. NEC3 - Managing change - 16380

    International Nuclear Information System (INIS)

    Wilsoncroft, Charles

    2009-01-01

    The Office of Government Commerce (OGC) has endorsed the use of NEC for all public sector contracts. The reason being is that it stimulates effective project management and enables the parties to manage risk and change more efficiently, which in turn serves to mitigate the cost and time effects of any risk event should it arise under the contract. In essence it facilitates a more collaborative working culture between the parties. The NEC3 contract is gaining in popularity and has been adopted for use in the decommissioning of nuclear power stations and the London Olympics, it also recently received support in the Tenth Special Report on Construction Matters by the House of Commons. It has strict time limits for the notification of compensation events as set out in the core clause 61.3 whereby the Contractor's contract administration team needs to notify the project manager within an eight week period of becoming aware of the event. The contract also provides for an early warning procedure whereby the Contractor and the project manager will cooperate and pro-actively discuss how issues can be overcome in a collaborative manner. This NEC3 contract requires both the Contractor and the Employer to act positively and is welcomed as a possible solution to the entrenched disputes which have regularly occurred on major energy projects and if properly administered will hopefully result in an earlier and less fraught final account settlement process for both parties. (authors)

  14. Electromagnetic analysis of ITER generic equatorial port plug designs during three plasma current disruption cases

    International Nuclear Information System (INIS)

    Guirao, J.; Rodríguez, E.; Ordieres, J.; Cabanas, M.F.; García, C.H. Rojas

    2012-01-01

    Highlights: ► Electromagnetic transient performance evaluation of the GEPP structure. ► Three different plasma current disruption cases: MD UP LIN36, VDE UP LIN36 and VDE DW LIN36 were analyzed. ► Three DSM-First Wall (FW) designs (horizontal and vertical drawers and monoblock) were compared. - Abstract: Electromagnetic phenomena due to plasma current disruptions are the cause for the main mechanical operation loads over the ITER equatorial level port plug structures. This paper presents a detailed finite element simulation and analysis of the transient electromagnetic effects of three different plasma current disruption cases over three designs of diagnostic shielding module (DSM) structure. The DSMs are contained into and supported by the generic equatorial port plug (GEPP) analyzed structure. The three plasma disruption cases studied were: major disruption upwards linear decay in 36 ms (MD UP LIN36), vertical displacements events, upwards and downwards linear decay in 36 ms (VDE UP LIN36 and VDE DW LIN36). A detailed analysis for GEPP structure and three DSM-first wall (FW) designs (horizontal and vertical drawers and monoblock) is also presented in order to extract the Eddy current distribution on these devices and thus the resultant electromagnetic forces and moments acting on them.

  15. Off-equatorial current-driven instabilities ahead of approaching dipolarization fronts

    Science.gov (United States)

    Zhang, Xu; Angelopoulos, V.; Pritchett, P. L.; Liu, Jiang

    2017-05-01

    Recent kinetic simulations have revealed that electromagnetic instabilities near the ion gyrofrequency and slightly away from the equatorial plane can be driven by a current parallel to the magnetic field prior to the arrival of dipolarization fronts. Such instabilities are important because of their potential contribution to global electromagnetic energy conversion near dipolarization fronts. Of the several instabilities that may be consistent with such waves, the most notable are the current-driven electromagnetic ion cyclotron instability and the current-driven kink-like instability. To confirm the existence and characteristics of these instabilities, we used observations by two Time History of Events and Macroscale Interactions during Substorms satellites, one near the neutral sheet observing dipolarization fronts and the other at the boundary layer observing precursor waves and currents. We found that such instabilities with monochromatic signatures are rare, but one of the few cases was selected for further study. Two different instabilities, one at about 0.3 Hz and the other at a much lower frequency, 0.02 Hz, were seen in the data from the off-equatorial spacecraft. A parallel current attributed to an electron beam coexisted with the waves. Our instability analysis attributes the higher-frequency instability to a current-driven ion cyclotron instability and the lower frequency instability to a kink-like instability. The current-driven kink-like instability we observed is consistent with the instabilities observed in the simulation. We suggest that the currents needed to excite these low-frequency instabilities are so intense that the associated electron beams are easily thermalized and hence difficult to observe.

  16. Comparison of dayside current layers in Venus' ionosphere and earth's equatorial electrojet

    Science.gov (United States)

    Cole, Keith D.

    1993-01-01

    The major physical aspects of the equatorial electrojet of Earth and the dayside ionospheric current layers of Venus are compared, viz., the electric current intensity and total current, roles of electric field, pressure and gravity, diffusion time scales, and the Bernouille effect. The largest potential differences, of the order of 10 volts, horizontally across the dayside ionosphere of Venus, have important implications for possible dynamo action in the Venus ionosphere and the application of an electric field from the lower atmosphere or from the solar wind. An upper limit to the horizontal scale of vertical magnetic fields in the Venus ionosphere is estimated thereby for the first time. New upper limits on the velocity in, and thickness of, a possible S layer at Venus are presented. If an S layer exists, it is only for extreme conditions of the solar wind. A mechanism for formation of magnetic ropes in the Venus ionosphere is also proposed.

  17. Role of the magnetospheric and ionospheric currents in the generation of the equatorial scintillations during geomagnetic storms

    Directory of Open Access Journals (Sweden)

    L. Z. Biktash

    2004-09-01

    Full Text Available The equatorial ionosphere parameters, Kp, Dst, AU and AL indices characterized contribution of different magnetospheric and ionospheric currents to the H-component of geomagnetic field are examined to test the geomagnetic activity effect on the generation of ionospheric irregularities producing VLF scintillations. According to the results of the current statistical studies, one can predict near 70% of scintillations from Aarons' criteria using the Dst index, which mainly depicts the magnetospheric ring current field. To amplify Aarons' criteria or to propose new criteria for predicting scintillation characteristics is the question. In the present phase of the experimental investigations of electron density irregularities in the ionosphere new ways are opened up because observations in the interaction between the solar wind - magnetosphere - ionosphere during magnetic storms have progressed greatly. According to present view, the intensity of the electric fields and currents at the polar regions, as well as the magnetospheric ring current intensity, are strongly dependent on the variations of the interplanetary magnetic field. The magnetospheric ring current cannot directly penetrate the equatorial ionosphere and because of this difficulties emerge in explaining its relation to scintillation activity. On the other hand, the equatorial scintillations can be observed in the absence of the magnetospheric ring current. It is shown that in addition to Aarons' criteria for the prediction of the ionospheric scintillations, models can be used to explain the relationship between the equatorial ionospheric parameters, h'F, foF2, and the equatorial geomagnetic variations with the polar ionosphere currents and the solar wind.

  18. The Sidebands of the Equatorial Electrojet: General Characteristic of the Westward Currents, as Deduced From CHAMP

    Science.gov (United States)

    Zhou, Yun-Liang; Lühr, Hermann; Alken, Patrick

    2018-02-01

    Based on 5 years (2001-2005) of magnetic field measurements made by the CHAMP satellite, latitudinal profiles of the equatorial electrojet (EEJ) have been derived. This study provides a comprehensive characterization of the reverse current EEJ sidebands. These westward currents peak at ±5° quasi-dipole latitude with typical amplitudes of 35% of the main EEJ. The diurnal amplitude variation is quite comparable with that of the EEJ. Similarly to the EEJ, the intensity is increasing with solar EUV flux, but with a steeper slope, indicating that not only the conductivity plays a role. For the longitude distribution we find, in general, larger amplitudes in the Western than in the Eastern Hemisphere. It is presently a common understanding that the reverse current EEJ sidebands are generated by eastward zonal winds at altitudes above about 120 km. In particular, a positive vertical gradient of wind speed generates westward currents at magnetic latitudes outside of 2° dip latitude. Interesting information about these features can be deduced from the sidebands' tidal characteristics. The longitudinal variation of the amplitude is dominated by a wave-1 pattern, which can primarily be attributed to the tidal components SPW1 and SW3. In case of the hemispheric amplitude differences these same two wave-1 components dominate. The ratio between sideband amplitude and main EEJ is largely controlled by the tidal features of the EEJ. The longitudinal patterns of the latitude, where the sidebands peak, resemble to some extent those of the amplitude. Current densities become larger when the peaks move closer to the magnetic equator.

  19. The rôle of the complete Coriolis force in cross-equatorial flow of abyssal ocean currents

    Science.gov (United States)

    Stewart, A. L.; Dellar, P. J.

    Ocean currents flowing close to or across the equator are strongly constrained by the change in sign of f, the locally vertical component of the Earth's rotation vector, across the equator. We investigate these currents using a shallow water model that includes both the locally vertical and locally horizontal components of the Earth's rotation vector, thus accounting for the complete Coriolis force. We therefore avoid making the so-called "traditional approximation" that retains only the part of the Coriolis force associated with the locally vertical component of the rotation vector. Including the complete Coriolis force contributes an additional term to the fluid's potential vorticity, which may partially balance the change in sign of f as fluid crosses the equator over suitably shaped bathymetry. We focus on the Antarctic Bottom Water, which crosses the equator northwards in the western Atlantic ocean where the local bathymetry forms an almost-zonal channel. We show that this bathymetry facilitates the current's equatorial crossing via the action of the "non-traditional" component of the Coriolis force. We illustrate this process using both analytical and numerical solutions for flow of an abyssal current over idealised equatorial topography. We also consider the one-dimensional geostrophic adjustment of a body of fluid across the equator, and show that the "non-traditional" contribution to the fluid's angular momentum permits a larger cross-equatorial transport. These results underline the importance of including the complete Coriolis force in studies of the equatorial ocean, particularly in the weakly-stratified abyssal ocean where the non-traditional component is most pronounced.

  20. Latitude-dependent delay in the responses of the equatorial electrojet and Sq currents to X-class solar flares

    Science.gov (United States)

    Nogueira, Paulo A. B.; Abdu, Mangalathayil A.; Souza, Jonas R.; Denardini, Clezio M.; Barbosa Neto, Paulo F.; Serra de Souza da Costa, João P.; Silva, Ana P. M.

    2018-01-01

    We have analyzed low-latitude ionospheric current responses to two intense (X-class) solar flares that occurred on 13 May 2013 and 11 March 2015. Sudden intensifications, in response to solar flare radiation impulses, in the Sq and equatorial electrojet (EEJ) currents, as detected by magnetometers over equatorial and low-latitude sites in South America, are studied. In particular we show for the first time that a 5 to 8 min time delay is present in the peak effect in the EEJ, with respect that of Sq current outside the magnetic equator, in response to the flare radiation enhancement. The Sq current intensification peaks close to the flare X-ray peak, while the EEJ peak occurs 5 to 8 min later. We have used the Sheffield University Plasmasphere-Ionosphere Model at National Institute for Space Research (SUPIM-INPE) to simulate the E-region conductivity enhancement as caused by the flare enhanced solar extreme ultraviolet (EUV) and soft X-rays flux. We propose that the flare-induced enhancement in neutral wind occurring with a time delay (with respect to the flare radiation) could be responsible for a delayed zonal electric field disturbance driving the EEJ, in which the Cowling conductivity offers enhanced sensitivity to the driving zonal electric field.

  1. NEC violation in mimetic cosmology revisited

    Directory of Open Access Journals (Sweden)

    Anna Ijjas

    2016-09-01

    Full Text Available In the context of Einstein gravity, if the null energy condition (NEC is satisfied, the energy density in expanding space–times always decreases while in contracting space–times the energy density grows and the universe eventually collapses into a singularity. In particular, no non-singular bounce is possible. It is, though, an open question if this energy condition can be violated in a controlled way, i.e., without introducing pathologies, such as unstable negative-energy states or an imaginary speed of sound. In this letter, we will re-examine the claim that the recently proposed mimetic scenario can violate the NEC without pathologies. We show that mimetic cosmology is prone to gradient instabilities even in cases when the NEC is satisfied (except for trivial examples. Most interestingly, the source of the instability is always the Einstein–Hilbert term in the action. The matter stress-energy component does not contribute spatial gradient terms but instead makes the problematic curvature modes dynamical. We also show that mimetic cosmology can be understood as a singular limit of known, well-behaved theories involving higher-derivative kinetic terms and discuss ways of removing the instability.

  2. The influence of Pacific Equatorial Water on fish diversity in the southern California Current System

    Science.gov (United States)

    McClatchie, Sam; Thompson, Andrew R.; Alin, Simone R.; Siedlecki, Samantha; Watson, William; Bograd, Steven J.

    2016-08-01

    The California Undercurrent transports Pacific Equatorial Water (PEW) into the Southern California Bight from the eastern tropical Pacific Ocean. PEW is characterized by higher temperatures and salinities, with lower pH, representing a source of potentially corrosive (aragonite,Ωaragonite saturation with depth. Although there is substantial variability in PEW presence as measured by spice on the 26.25-26.75 isopycnal layer, as well as in pH and aragonite saturation, we found fish diversity to be stable over the decades 1985-1996 and 1999-2011. We detected significant difference in species structure during the 1998 La Niña period, due to reduced species evenness. Species richness due to rare species was higher during the 1997/1998 El Niño compared to the La Niña but the effect on species structure was undetectable. Lack of difference in the species abundance structure in the decade before and after the 1997/1999 ENSO event showed that the assemblage reverted to its former structure following the ENSO perturbation, indicating resilience. While the interdecadal species structure remained stable, the long tail of the distributions shows that species richness increased between the decades consistent with intrusion of warm water with more diverse assemblages into the southern California region.

  3. Tests of compressed geometry NEC acceleration tubes

    International Nuclear Information System (INIS)

    Raatz, J.E.; Rathmell, R.D.; Stelson, P.H.; Ziegler, N.F.

    1985-01-01

    Tests have been performed in the 3 MV Pelletron test machine at NEC on a compressed geometry tube which increases the insulating length of the tube by eliminating the heated electrode assemblies (approx.2.5 cm thick) at the end of each tube section. Some insert electrodes are changed to provide some trapping of secondary ions. The geometry tested provided an 18% increase in live ceramic in the tube. The compressed geometry tube allowed a terminal voltage of 3.55 MV on the 3 MV column at normal gradients of 30.3 kv/tube gap. The tube was also conditioned to more than 4 MV and remained stable in voltage with few sparks and with low x-ray levels for days at about 4 MV. This same performance could be achieved with or without arc discharge cleaning. 4 refs., 4 figs

  4. Secure Service Oriented Architectures (SOA) Supporting NEC [Architecture orientée service (SOA) gérant la NEC

    NARCIS (Netherlands)

    Meiler, P.P.; Schmeing, M.

    2009-01-01

    Combined scenario ; Data management ; Data processing ; Demonstrator ; Information systems ; Integrated systems ; Interoperability ; Joint scenario ; Network Enabled Capability (NEC) ; Operational effectiveness ; Operations research ; Scenarios ; Secure communication ; Service Oriented Architecture

  5. Watermass structure and current system in the equatorial western Indian Ocean during August, 1985

    Digital Repository Service at National Institute of Oceanography (India)

    Suryanarayana, A.; Reddy, G.V.; Pankajakshan, T.

    . At the equator, currents were computed using Montgomery's method. Westerly flows near Equator and easterly flows on either side of the equator are deduced. The presence of the Arabian Sea surface water, the Red Sea water, and Pacific low salinity water is noticed...

  6. Numerical simulation of dipolar magnetic field inflation due to equatorial ring-current

    International Nuclear Information System (INIS)

    Kajimura, Yoshihiro; Funaki, Ikkoh; Shinohara, Iku; Usui, Hideyuki; Matsumoto, Masaharu; Yamakawa, Hiroshi

    2014-01-01

    Magneto Plasma Sail (MPS) is one of the next generation space propulsion systems which generates a propulsive force using the interaction between the solar wind plasma and an artificial inflated magnetosphere generated by a superconductive coil. In the MPS system, the magnetosphere as a sail must be inflated by the plasma injection from the spacecraft in order to obtain the thrust gain. In the present study, the magnetic inflation concept is numerically tested by so-called ion one-component plasma model. As a simulation result, the magnetic moment of the system is drastically increased up to 45 times that of the coil current at plasma-β = 20 and r Li /L (radius of gyro motion / characteristics length of the magnetic field) = 0.01, and this is the first successful magnetosphere inflation obtained by numerical simulation. Corresponding maximum thrust gain is also estimated to be about 45. (author)

  7. Equatorial Guinea.

    Science.gov (United States)

    1989-03-01

    Equatorial Guinea is situated on the Gulf of Guinea along the west African coast between Cameroon and Gabon. The people are predominantly of Bantu origin. The country's ties with Spain are significant; in 1959, it became the Spanish Equatorial region ruled by Spain's commissioner general. Recent political developments in Equatorial Guinea include the formation of the Democratic Party for Equatorial Guinea in July of 1987 and the formation of a 60-member unicameral Chamber of Representatives of the People in 1983. Concerning the population, 83% of the people are Catholic and the official language is Spanish. Poverty and serious health, education and sanitary problems exist. There is no adequate hospital and few trained physicians, no dentists, and no opticians. Malaria is endemic and immunization for yellow fever is required for entrance into the country. The water is not potable and many visitors to the country bring bottled water. The tropical climate of Equatorial Guinea provides the climate for the country's largest exports and source of economy; cacao, wood and coffee. Although the country, as a whole, has progressed towards developing a participatory political system, there are still problems of governmental corruption in the face of grave health and welfare conditions. In recent years, the country has received assistance from the World Bank and the United States to aid in its development.

  8. An animal model of necrotizing enterocolitis (NEC) in preterm rabbits.

    Science.gov (United States)

    Bozeman, Andrew P; Dassinger, Melvin S; Birusingh, Rhea J; Burford, Jeffrey M; Smith, Samuel D

    2013-04-01

    Creation of an animal model of necrotizing enterocolitis (NEC) allowing adjustment of severity and potential recoverability is needed to study effectiveness of prevention and treatment strategies. This study describes a novel model in preterm rabbits capable of adjusting severity of NEC-like histologic changes. Rabbit pups (n = 151) were delivered by cesarean section 2 days preterm. In the treatment groups, tissue adhesive was applied to anal openings to simulate the poor intestinal function and dysmotility of preterm neonates. Pups were placed into five groups: 3INT (3 day intermittent block), 4INT (4 day intermittent block), 3COM (3 day complete block), 4COM (4 day complete block), based on differences in type of anal blockage and day of life sacrificed. The fifth group, 4CON, was comprised of a control arm (n = 28) without anal block, with sacrifice of subjects on day 4. All pups were gavage fed with formula contaminated with Enterobacter cloacae, ranitidine, and indomethacin. Following sacrifice, the intestines were harvested for pathologic evidence of NEC. A blinded pathologist graded histologic changes consistent with NEC using a grading scale 0-4 with 4 being most severe. Fifty-seven pups (57/123) (46%) in the research arm survived to sacrifice, compared to 26/28 (93%) in the control arm of the investigation, p < 0.0001. The incidence and severity of NEC-like damage increased with the duration and completeness of the anal blockage. 44/57 (77%) of survivors revealed various degrees of NEC-like damage to large and small bowel, and 3/26 (12%) exhibited early NEC-like mucosal injury in the research and control arms, respectively. This animal model produces NEC-like pathologic changes in both small and large intestine in preterm rabbits. Because incidence and severity of damage increases with duration and completeness of intestinal dysmotility, this allows future effectiveness studies for nonsurgical treatment and prevention of NEC.

  9. PENERAPAN ASAS PACTA TERTIIS NEC NOCENT NEC PROSUNT BERKAITAN DENGAN STATUS HUKUM DAERAH DASAR LAUT SAMUDERA DALAM (SEA BED

    Directory of Open Access Journals (Sweden)

    Aryuni Yuliatiningsih

    2010-01-01

    Full Text Available International ocean seabed area out of national jurisdiction recognized as a common heritage of mankind. Its regulations under International authority based on UNCLOS 1982. UNCLOS 1982 didn’t universal acceptance because there are several states unwilling consent to be bound by a treaty. In the law of treaty there is pacta tertiis nec nocent nec prosunt principle, means a treaty does not either obligations or rights for a third State without its consent. Nevertheless, rules in a treaty becoming binding upon on third states through international custom and there is a principle has character erga omnes Key Words: pacta tertiis nec nocent nec prosunt principle, legal status, ocean seabed, erga omnes

  10. SimNEC : research platform for studying human functioning in NCW

    NARCIS (Netherlands)

    Veen, H.A.H.C. van; Graaf, B. de; Essens, P.

    2006-01-01

    SimNEC is TNOÆs grand scheme for experimentally studying human factors issues related to NEC/NCW. The research platform SimNEC consists of multidisciplinary expert teams, long-term research programmes, and a local network of state-of-the-art simulator modules. SimNEC does not focus on technology,

  11. Signatures of moderate (M-class) and low (C and B class) intensity solar flares on the equatorial electrojet current: Case studies

    Science.gov (United States)

    Chakrabarty, D.; Bagiya, Mala S.; Thampi, Smitha V.; Pathan, B. M.; Sekar, R.

    2013-12-01

    The present investigation brings out, in contrast to the earlier works, the changes in the equatorial electrojet (EEJ) current in response to a few moderate (M-class) and low (C and B class) intensity solar flares during 2005-2010. Special care is taken to pick these flare events in the absence of prompt electric field perturbations associated with geomagnetic storms and substorms that also affect the electrojet current. Interestingly, only the normalized (with respect to the pre-flare level) deviations of daytime EEJ (and not the deviations alone) change linearly with the increases in the EUV and X-ray fluxes. These linear relationships break down during local morning hours when the E-region electric field approaches zero before reversal of polarity. This elicits that the response of EEJ strength corresponding to less-intense flares can be appropriately gauged only when the local time variation of the quiet time E-region zonal electric field is taken into account. The flare events enhanced the EEJ strength irrespective of normal or counter electrojet (CEJ) conditions that shows that solar flares change the E-region ionization density and not the electric field. In addition, the enhancements in the X-ray and EUV fluxes, for these flares occurring during this solar minimum period, are found to be significantly correlated as opposed to the solar maximum period, indicating the differences in the solar processes in different solar epochs.

  12. Anomalous current structure in the eastern equatorial Indian Indian Ocean during the south-west monsoon of 1994

    Digital Repository Service at National Institute of Oceanography (India)

    Unnikrishnan, A.S.; Murty, V.S.N.; Babu, M.T.; Gopinathan, C.K.; Charyulu, R.J.K.

    ., and Mcphaden M. J. (1989). Use of the geostrophic approximation to estimate time-varying zonal currents at the equator. Journal of Geophysical Research 94(C3), 3228–36. Pond, S., and Pickard, G. L. (1983). ‘Introductory Dynamic Oceanography.’ (Pergamon Press...

  13. Geometry of duskside equatorial current during magnetic storm main phase as deduced from magnetospheric and low-altitude observations

    Directory of Open Access Journals (Sweden)

    S. Dubyagin

    2013-03-01

    Full Text Available We present the results of a coordinated study of the moderate magnetic storm on 22 July 2009. The THEMIS and GOES observations of magnetic field in the inner magnetosphere were complemented by energetic particle observations at low altitude by the six NOAA POES satellites. Observations in the vicinity of geosynchronous orbit revealed a relatively thin (half-thickness of less than 1 RE and intense current sheet in the dusk MLT sector during the main phase of the storm. The total westward current (integrated along the z-direction on the duskside at r ~ 6.6 RE was comparable to that in the midnight sector. Such a configuration cannot be adequately described by existing magnetic field models with predefined current systems (error in B > 60 nT. At the same time, low-altitude isotropic boundaries (IB of > 80 keV protons in the dusk sector were shifted ~ 4° equatorward relative to the IBs in the midnight sector. Both the equatorward IB shift and the current strength on the duskside correlate with the Sym-H* index. These findings imply a close relation between the current intensification and equatorward IB shift in the dusk sector. The analysis of IB dispersion revealed that high-energy IBs (E > 100 keV always exhibit normal dispersion (i.e., that for pitch angle scattering on curved field lines. Anomalous dispersion is sometimes observed in the low-energy channels (~ 30–100 keV. The maximum occurrence rate of anomalous dispersion was observed during the main phase of the storm in the dusk sector.

  14. Differential disease resistance response in the barley necrotic mutant nec1

    Directory of Open Access Journals (Sweden)

    Kunga Laura

    2011-04-01

    Full Text Available Abstract Background Although ion fluxes are considered to be an integral part of signal transduction during responses to pathogens, only a few ion channels are known to participate in the plant response to infection. CNGC4 is a disease resistance-related cyclic nucleotide-gated ion channel. Arabidopsis thaliana CNGC4 mutants hlm1 and dnd2 display an impaired hypersensitive response (HR, retarded growth, a constitutively active salicylic acid (SA-mediated pathogenesis-related response and elevated resistance against bacterial pathogens. Barley CNGC4 shares 67% aa identity with AtCNGC4. The barley mutant nec1 comprising of a frame-shift mutation of CNGC4 displays a necrotic phenotype and constitutively over-expresses PR-1, yet it is not known what effect the nec1 mutation has on barley resistance against different types of pathogens. Results nec1 mutant accumulated high amount of SA and hydrogen peroxide compared to parental cv. Parkland. Experiments investigating nec1 disease resistance demonstrated positive effect of nec1 mutation on non-host resistance against Pseudomonas syringae pv. tomato (Pst at high inoculum density, whereas at normal Pst inoculum concentration nec1 resistance did not differ from wt. In contrast to augmented P. syringae resistance, penetration resistance against biotrophic fungus Blumeria graminis f. sp. hordei (Bgh, the causal agent of powdery mildew, was not altered in nec1. The nec1 mutant significantly over-expressed race non-specific Bgh resistance-related genes BI-1 and MLO. Induction of BI-1 and MLO suggested putative involvement of nec1 in race non-specific Bgh resistance, therefore the effect of nec1on mlo-5-mediated Bgh resistance was assessed. The nec1/mlo-5 double mutant was as resistant to Bgh as Nec1/mlo-5 plants, suggesting that nec1 did not impair mlo-5 race non-specific Bgh resistance. Conclusions Together, the results suggest that nec1 mutation alters activation of systemic acquired resistance

  15. NEC1, a regulator of nectary development and nectar production in Petunia hybrida

    NARCIS (Netherlands)

    Ge, Ya-Xin

    2001-01-01

    This thesis describes an efficient cloning, characterization and functional analysis of a nectary-specific gene in Petunia hybrida. NEC1, a novel gene, is highly expressed in nectaries. NEC1 is involved in nectar production and nectar secretion. Nectar secreted from floral nectaries is the main

  16. Water masses in the Humboldt Current System: Properties, distribution, and the nitrate deficit as a chemical water mass tracer for Equatorial Subsurface Water off Chile

    Science.gov (United States)

    Silva, Nelson; Rojas, Nora; Fedele, Aldo

    2009-07-01

    Three sections are used to analyze the physical and chemical characteristics of the water masses in the eastern South Pacific and their distributions. Oceanographic data were taken from the SCORPIO (May-June 1967), PIQUERO (May-June 1969), and KRILL (June 1974) cruises. Vertical sections of temperature, salinity, σ θ, dissolved oxygen, nitrate, nitrite, phosphate, and silicate were used to analyze the water column structure. Five water masses were identified in the zone through T- S diagrams: Subantarctic Water, Subtropical Water, Equatorial Subsurface Water, Antarctic Intermediate Water, and Pacific Deep Water. Their proportions in the sea water mixture are calculated using the mixing triangle method. Vertical sections were used to describe the geographical distributions of the water mass cores in the upper 1500 m. Several characteristic oceanographic features in the study area were analyzed: the shallow salinity minimum displacement towards the equator, the equatorial subsurface salinity maximum associated with a dissolved oxygen minimum zone and a high nutrient content displacement towards the south, and the equatorward intermediate Antarctic salinity minimum associated with a dissolved oxygen maximum. The nitrate deficit generated in the denitrification area off Peru and northern Chile is proposed as a conservative chemical tracer for the Equatorial Subsurface Waters off the coast of Chile, south of 25°S.

  17. Upper ocean circulation modulation by phytoplankton concentration in the Equatorial Pacific and the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Nakamoto, S.; PrasannaKumar, S.; Oberhuber, J.M.; Sammarco, P.; Muneyama, K.; Sato, T.; AjoyKumar, A.; Frouin, R.

    gradient in the upper ocean. This strengthens the geostrophically balanced westward currents in both side of the equatorial wave-guide (within 5 degree bands). Once these currents reach the western Pacific coast, they feed the Equatorial undercurrent (EUC...

  18. Intermonsoonal equatorial jets

    Digital Repository Service at National Institute of Oceanography (India)

    Muraleedharan, P.M.

    , respectively. Hydrographic features and transport computations favour a well developed equatorial jet during both seasons. The net surface eastward and subsurface westward flows are well balanced during the premonsoon transition period and appear...

  19. Physical activity and gastric residuals as biomarkers for region-specific NEC lesions in preterm neonates

    DEFF Research Database (Denmark)

    Cao, Muqing; Andersen, Anders Daniel; Li, Yanqi

    2016-01-01

    onset of NEC can be predicted by decreased physical activity during the first few days after birth. Methods: Cesarean-delivered preterm pigs were fed parenteral nutrition and increasing amounts of formula for 5 days after birth (n = 120). Their physical activity was quantified by a continuous camera....... Results: Half of the pigs (48%) showed clear NEC-like lesions on day 5, and these individuals had more adverse clinical symptoms from day 3 but decreased physical activity already from day 2 relative to the unaffected pigs (both p ... physical activity on days 2 and 3, and the increased volume of gastric residuals was specifically related to colon lesions (both p physical activity precedes the clinical symptoms of NEC in the small intestine of preterm pigs, and increased gastric residuals predict NEC...

  20. Geomagnetic storms and electric fields in the equatorial ionosphere

    International Nuclear Information System (INIS)

    Rastogi, R.G.

    1977-01-01

    Using direct measurements of equatorial electric field during a geomagnetic storm it is shown that the large decrease in the field observed near the dip equator is due to the reversal of the equatorial electrojet current. This is caused by the imposition of an additional westward electric field on the equatorial ionosphere which was originated by the interaction of solar wind with the interplanetary magnetic field. (author)

  1. Equatorial electrojet and its response to external electromagnetic effects

    Science.gov (United States)

    Bespalov, P. A.; Savina, O. N.

    2012-09-01

    In the quiet low-latitude Earth's ionosphere, a sufficiently developed current system that is responsible for the Sq magnetic-field variations is formed in quiet Sun days under the action of tidal streams. The density of the corresponding currents is maximum in the midday hours at the equatorial latitudes, where the so-called equatorial electrojet is formed. In this work, we discuss the nature of the equatorial electrojet. This paper studies the value of its response to external effects. First of all, it is concerned with estimating the possibility of using the equatorial electrojet for generating low-frequency electromagnetic signals during periodic heating of the ionosphere by the heating-facility radiation. The equatorial electrojet can also produce electrodynamic response to the natural atmospheric processes, e.g., an acoustic-gravity wave.

  2. Pacific Equatorial Transect

    OpenAIRE

    Pälike, Heiko; Nishi, Hiroshi; Lyle, Mitch; Raffi, Isabella; Klaus, Adam; Gamage, Kusali

    2009-01-01

    Integrated Ocean Drilling Program Expedition 320/321, "Pacific Equatorial Age Transect" (Sites U1331–U1338), was designed to recover a continuous Cenozoic record of the paleoequatorial Pacific by coring above the paleoposition of the Equator at successive crustal ages on the Pacific plate. These sediments record the evolution of the paleoequatorial climate system throughout the Cenozoic. As we gained more information about the past movement of plates and when in Earth's history "critical" cli...

  3. A convenient way to double the capacity of a NEC type foil stripper

    International Nuclear Information System (INIS)

    Chapman, K.R.

    1988-01-01

    A convenient method is described to increase the capacity of a NEC type terminal stripper. This renders the necessity for tank entry to renew foils less frequent. This is especially useful when the use of heavy ion beams renders foil lifetimes very short. (orig.)

  4. Nec-1 Enhances Shikonin-Induced Apoptosis in Leukemia Cells by Inhibition of RIP-1 and ERK1/2

    Directory of Open Access Journals (Sweden)

    Hongming Pan

    2012-06-01

    Full Text Available Necrostatin-1 (Nec-1 inhibits necroptosis by allosterically inhibiting the kinase activity of receptor-interacting protein 1 (RIP1, which plays a critical role in necroptosis. RIP1 is a crucial adaptor kinase involved in the activation of NF-κB, production of reactive oxygen species (ROS and the phosphorylation of mitogen activated protein kinases (MAPKs. NF-κB, ROS and MAPKs all play important roles in apoptotic signaling. Nec-1 was regarded as having no effect on apoptosis. Here, we report that Nec-1 increased the rate of nuclear condensation and caspases activation induced by a low concentration of shikonin (SHK in HL60, K562 and primary leukemia cells. siRNA-mediated knockdown of RIP1 significantly enhanced shikonin-induced apoptosis in K562 and HL60 cells. Shikonin treatment alone could slightly inhibit the phosphorylation of ERK1/2 in leukemia cells, and the inhibitory effect on ERK1/2 was significantly augmented by Nec-1. We also found that Nec-1 could inhibit NF-κB p65 translocation to the nucleus at a later stage of SHK treatment. In conclusion, we found that Nec-1 can promote shikonin-induced apoptosis in leukemia cells. The mechanism by which Nec-1 sensitizes shikonin-induced apoptosis appears to be the inhibition of RIP1 kinase-dependent phosphorylation of ERK1/2. To our knowledge, this is the first study to document Nec-1 sensitizes cancer cells to apoptosis.

  5. OGCM Simulations of Equatorial Pacific Current and Temperature to ERS-1, FSU and NMC Surface Winds and to Assimilation of Subsurface Temperature Data

    Science.gov (United States)

    Halpern, David

    1995-01-01

    The relative accuracies of three surface wind data products for the tropical Pacific Ocean during April 1992 to March 1994 were examined by analyzing temperature and current fields along the equator, which were simulated with an ocean general circulation model. Simulations were made with and without assimilation of surface and subsurface temperature data. Simulated currents were compared with observations at three sites (170oW, 140oW, 110oW) at the equator. Model-generated currents and temperatures indicated that the ERS-1 westward wind speeds were low compared to the FSU and NMC winds. With data assimilation, the agreement between simulated and observed currents was highest at 170oW and lowest at 110oW.

  6. Equatorial westward electrojet impacting equatorial ionization anomaly development during the 6 April 2000 superstorm

    Science.gov (United States)

    Horvath, Ildiko; Lovell, Brian C.

    2013-11-01

    investigate the forward plasma fountain and the equatorial ionosphere in the topside region during the 6 April 2000 superstorm in the Australian sector at ~0900 LT. Space- and ground-based multi-instrument measurements, Coupled Thermosphere-Ionosphere-Plasmasphere Electrodynamics (CTIPe) simulations, and field-aligned observations comprise our results. These reveal an unusual storm development during which the eastward prompt penetration electric (E) field (PPEF) developed and operated under the continuous effects of the westward disturbance dynamo E-field (DDEF) while large-scale traveling ionospheric disturbances (TIDs) traveled equatorward and generated strong equatorward wind surges. We have identified the eastward PPEF by the superfountain effect causing the equatorial ionization anomaly (EIA)'s development with crests situated at ~±28°N (geomagnetic) in the topside ionosphere at ~840 km altitude. The westward DDEF's occurrence is confirmed by mapping the "anti-Sq" current system wherein the equatorial westward current created a weak long-lasting westward electrojet event. Line plots of vertical drift data tracked large-scale TIDs. Four scenarios, covering ~3.5 h in universal time, demonstrate that the westward DDEF became superimposed on the eastward PPEF. As these E-fields of different origins became mapped into the F region, they could interact. Consequently, the eastward PPEF-related equatorial upward E × B drift became locally reduced by up to 75 m/s near the dip equator by the westward DDEF-related equatorial downward E × B drift. Meanwhile, the EIA displayed a better development as equatorial wind surges, reproduced by CTIPe, increased from 501 to 629 m/s, demonstrating the crucial role of mechanical wind effects keeping plasma density high.

  7. Proton flux under radiation belts: near-equatorial zone

    International Nuclear Information System (INIS)

    Grigoryan, O.R.; Panasyuk, M.I.; Petrov, A.N.; Kudela, K.

    2005-01-01

    In this work the features of low-energy proton flux increases in near-equatorial region (McIlvein parameter L th the proton flux (with energy from tens keV up to several MeV) increases are registering regularly. However modern proton flux models (for example AP8 model) works at L>1.15 only and does not take into account near-equatorial protons. These fluxes are not too big, but the investigation of this phenomenon is important in scope of atmosphere-ionosphere connections and mechanisms of particles transport in magnetosphere. In according to double charge-exchange model the proton flux in near-equatorial region does not depend on geomagnetic local time (MLT) and longitude. However the Azur satellite data and Kosmos-484, MIR station and Active satellite data revealed the proton flux dependence on longitude. The other feature of near-equatorial proton flux is the dependence on geomagnetic local time revealed in the Sampex satellite experiment and other experiments listed above. In this work the dependences on MLT and longitude are investigated using the Active satellite (30-500 keV) and Sampex satellite (>800 keV). This data confirms that main sources of near-equatorial protons are radiation belts and ring current. The other result is that near-equatorial protons are quasi-trapped. The empirical proton flux dependences on L, B at near-equatorial longitudes are presented. (author)

  8. Storm-associated variations of equatorially mirroring ring current protons, 1--800 keV, at constant first adiabatic invariant

    International Nuclear Information System (INIS)

    Lyons, L.R.; Williams, D.J.

    1976-01-01

    Explorer 45 observations of ring current protons mirroring near the equator, 1--800 keV, are presented at constant first adiabatic invariant μ throughout the period of the December 17, 1971, geomagnetic storm. To obtain μ, simultaneous magnetic field and particle observations are used. Particle deceleration in response to the storm time magnetic field decrease causes ring current measurements viewed at constant energy to underestimate the storm time increase in proton intensities at energies approximately-less-than200 keV. This adiabatic deceleration also accounts for the large flux decreases observed at energies approximately-greater-than200 keV during the storm, in contradiction with previous results (Soraas and Davis, 1968) obtained using a model for the storm time magnetic field

  9. Present capabilities and new developments in antenna modeling with the numerical electromagnetics code NEC

    Energy Technology Data Exchange (ETDEWEB)

    Burke, G.J.

    1988-04-08

    Computer modeling of antennas, since its start in the late 1960's, has become a powerful and widely used tool for antenna design. Computer codes have been developed based on the Method-of-Moments, Geometrical Theory of Diffraction, or integration of Maxwell's equations. Of such tools, the Numerical Electromagnetics Code-Method of Moments (NEC) has become one of the most widely used codes for modeling resonant sized antennas. There are several reasons for this including the systematic updating and extension of its capabilities, extensive user-oriented documentation and accessibility of its developers for user assistance. The result is that there are estimated to be several hundred users of various versions of NEC world wide. 23 refs., 10 figs.

  10. [FACTORS RELATED TO MORTALITY IN NECROTIZINGENTEROCOLITIS(NEC) IN NEONATES AND OLDER INFANTS

    Science.gov (United States)

    Ríos D , Hugo; Rivera M , Juan

    1997-01-01

    In order to determine the factors related to mortality in Necrotizing enterocolitis (NEC), medical records of neonates and older infants diagnosed of NEC in the Instituto de Salud del Niño between 1984 and 1993 were retrospectively reviewed. Only the cases with a reliable roentgenologic, surgical or pathologic diagnosis were included. Sixty cases (46 infants and 14 neonates) were found, with a higher incidence in males (37 males vs 23 females). Twenty six cases required surgical treatment. Overall mortality was 77%, with no significant differences between neonates and infants, nor between those who were operated or not. Moderate or severe malnutrition, diarrhea as an early clinical manifestations, bronchopneumonia, shock and poor nutricional management were found as factors related to mortality.

  11. Equatorial ionospheric electric fields during the November 2004 magnetic storm

    OpenAIRE

    Fejer, Bela G.; Jensen, J. W.; Kikuchi, T.; Abdu, M. A.; Chau, J. L.

    2007-01-01

    [1] We use radar measurements from the Jicamarca Radio Observatory, magnetometer observations from the Pacific sector and ionosonde data from Brazil to study equatorial ionospheric electric fields during the November 2004 geomagnetic storm. Our data show very large eastward and westward daytime electrojet current perturbations with lifetimes of about an hour (indicative of undershielding and overshielding prompt penetration electric fields) in the Pacific equatorial region during the November...

  12. Porting the 3D Gyrokinetic Particle-in-cell Code GTC to the CRAY/NEC SX-6 Vector Architecture: Perspectives and Challenges

    International Nuclear Information System (INIS)

    Ethier, S.; Lin, Z.

    2003-01-01

    Several years of optimization on the super-scalar architecture has made it more difficult to port the current version of the 3D particle-in-cell code GTC to the CRAY/NEC SX-6 vector architecture. This paper explains the initial work that has been done to port this code to the SX-6 computer and to optimize the most time consuming parts. Early performance results are shown and compared to the same test done on the IBM SP Power 3 and Power 4 machines

  13. Modelling the development of mixing height in near equatorial region

    Energy Technology Data Exchange (ETDEWEB)

    Samah, A.A. [Univ. of Malaya, Air Pollution Research Unit, Kuala Lumpur (Malaysia)

    1997-10-01

    Most current air pollution models were developed for mid-latitude conditions and as such many of the empirical parameters used were based on observations taken in the mid-latitude boundary layer which is physically different from that of the equatorial boundary layer. In the equatorial boundary layer the Coriolis parameter f is small or zero and moisture plays a more important role in the control of stability and the surface energy balance. Therefore air pollution models such as the OMLMULTI or the ADMS which were basically developed for mid-latitude conditions must be applied with some caution and would need some adaptation to properly simulate the properties of equatorial boundary layer. This work elucidates some of the problems of modelling the evolution of mixing height in the equatorial region. The mixing height estimates were compared with routine observations taken during a severe air pollution episodes in Malaysia. (au)

  14. Equatorial electrojet in east Brazil longitudes

    Indian Academy of Sciences (India)

    dip latitude as the electrons/ions can move vertically along the inclined magnetic field lines. Equatorial electrojet has been extensively studied from ground, rocket ... Keywords. Equatorial electrojet; Brazilian anomaly in equatorial electrojet; asymmetries in equatorial electrojet. J. Earth Syst. Sci. 119, No. 4, August 2010, pp.

  15. Delayed initiation but not gradual advancement of enteral formula feeding reduces the incidence of necrotizing enterocolitis (NEC in preterm pigs.

    Directory of Open Access Journals (Sweden)

    Nada Ghoneim

    Full Text Available Enteral formula feeding is a risk factor for necrotizing enterocolitis (NEC in premature infants, yet studies are conflicting regarding the safest timing for introduction and advancement of feeds. Our aim was to test the effects of early vs. late initiation and abrupt vs. gradual advancement of enteral feeding of an intact vs. hydrolyzed protein formula on NEC incidence and severity in preterm pigs. In Experiment 1, preterm pigs received total parenteral nutrition (TPN at birth with abrupt initiation of enteral formula feeds (50% full intake on d of life (DOL 2 (EA or 5 (LA while PN continued. Pigs were also fed formula containing either intact or hydrolyzed protein. In Experiment 2, preterm pigs received TPN at birth with enteral, hydrolyzed-protein formula feeds introduced on DOL 2 either abruptly (EA; 50% full feeds or gradually (EG; 10-50% full feeds over 5 d while PN continued. NEC incidence and severity were assessed based on macroscopic and histological scoring. In Experiment 1, NEC incidence (41% vs. 70%, P<0.05 and severity were reduced in LA vs. EA groups and LA was associated with a higher survival rate, daily weight gain and jejunum villus height. Piglets fed hydrolyzed vs. intact protein formula had lower stomach content weights and similar NEC incidence. In Experiment 2, NEC incidence and severity were not different between pigs the EG vs. EA group. Proinflammatory gene expression (IL-1β, IL-6 and S100A9 in the ileum was lower in both LA and EG vs. EA groups. In conclusion, delayed initiation but not gradual advancement of enteral feeding is protective against NEC in preterm pigs. Feeding hydrolyzed vs. intact protein formula improved gastric transit without affecting the NEC incidence.

  16. Current meter data from moored current meter casts in the Pacific Ocean as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1979-01-20 to 1984-04-26 (NODC Accession 8500007)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the Pacific Ocean from January 20, 1979 to April 26, 1984. Data were submitted by Pacific...

  17. Current meter data from moored current meter casts in the Pacific Ocean as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1986-05-28 to 1987-05-11 (NODC Accession 8900168)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the Pacific Ocean from 28 May 1986 to 01 May 1983. Data were submitted by Pacific Marine...

  18. Current meter data from moored current meter casts in the Pacific Ocean as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1979-01-20 to 1984-04-01 (NODC Accession 8700077)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the Pacific Ocean from January 20, 1979 to April 1, 1984. Data were submitted by Pacific Marine...

  19. Current meter data from moored current meter casts in the South Pacific Ocean as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1981-11-21 to 1983-11-20 (NODC Accession 8500258)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the South Pacific Ocean from November 21, 1981 to November 20, 1983. Data were submitted by...

  20. Current meter data from moored current meter casts in the Pacific Ocean as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1990-04-30 to 1991-05-15 (NODC Accession 9400005)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the Pacific Ocean from April 30, 1990 to May 15, 1991. Data were submitted by Pacific Marine...

  1. Investigation of beam transmission in A 9SDH-2 3.0 MV NEC pelletron tandem accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Deoli, Naresh T.; Kummari, Venkata C.; Pacheco, Jose L.; Duggan, Jerome L.; Glass, Gary A.; McDaniel, Floyd D.; Reinert, Tilo; Rout, Bibhudutta; Weathers, Duncan L. [Ion Beam Modification And Analysis Laboratory, Department of Physics, University of North Texas, Denton, Texas 76203 (United States)

    2013-04-19

    Electrostatic tandem accelerators are widely used to accelerate ions for experiments in materials science such as high energy ion implantation, materials modification, and analyses. Many applications require high beam current as well as high beam brightness at the target; thus, maximizing the beam transmission through such electrostatic accelerators becomes important. The Ion Beam Modification and Analysis Laboratory (IBMAL) at University of North Texas is equipped with four accelerators, one of which is a 9SDH-2 3.0 MV National Electrostatic Corporation (NEC) Pelletron Registered-Sign tandem accelerator. The tandem accelerator is equipped with three ion sources: one radio frequency-He ion source (Alphatross) and two ion sources of Cs-sputter type, the SNICS II (Source of Negative Ions by Cesium Sputtering) and a Cs-sputter source for trace-element accelerator based mass spectrometry. This work presents a detailed study of the beam transmission of hydrogen, silicon, and silver ions through the accelerator using the SNICS ion source with injection energies ranging from 20 keV to 70 keV. The beam transmission is quantified for three different terminal voltages: 1.5 MV, 2.0 MV and 2.5 MV. For a given terminal voltage, it has been found that beam transmission is strongly dependent on the ion source injector potential. Details of experiments and data analysis are presented.

  2. Instability of equatorial protons in Jupiter's mid-magnetosphere

    International Nuclear Information System (INIS)

    Northrop, T.G.; Schardt, A.W.

    1980-01-01

    Two different models for the distribution function are fit to the Jovian protons seen by Pioneer 10 inbound. The models reproduce the observed energy and angular distributions. These models are then used to assess the collisionless mirror instability. Because of the pancake proton angular distributions in the equatorial ring current region, the ring current particle population appears to be mirror unstable at times, with instability growth rates of approx.10 min. Such a time is consistent with observed proton flux autocorrelation times. An instability such as this (there are other candidates) may be responsible for the previously established proton flux flowing parallel to the magnetic field away from the equatorial region

  3. Observational evidence of lower-frequency Yanai waves in the central equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    David, D.T.; PrasannaKumar, S.; Byju, P.; Sarma, M.S.S.; Suryanarayana, A.; Murty, V.S.N.

    created by the northward shifting and strengthening of the westward flowing south equatorial current associated with positive IOD and the eastward flowing southwest monsoon current provides energy for the generation of lower-frequency Yanai waves. Vertical...

  4. The growth and decay of equatorial backscatter plumes

    Science.gov (United States)

    Tsunoda, R. T.

    1980-02-01

    During the past three years, a series of rocket experiments from the Kwajalein Atoll, Marshall Islands, were conducted to investigate the character of intense, scintillation-producing irregularities that occur in the nighttime equatorial ionosphere. Because the source mechanism of equatorial irregularities, believed to be the Rayleigh-Taylor instability, is analogous to that which generates plasma-density striations in a nuclear-induced environment, there is considerable interest in the underlying physics that controls the characteristics of these irregularities. A primary objective of ALTAIR investigations of equatorial irregularities is to seek an understanding of the underlying physics by establishing the relationship between meter-scale irregularities (detected by ALTAIR), and the large-scale plasma-density depletions (or 'bubbles') that contain the kilometer-scale, scintillation-producing irregularities. We describe the time evolution of backscatter 'plumes' produced by one meter equatorial field-aligned irregularities. Using ALTAIR, a fully steerable backscatter radar, to repeatedly map selected plumes, we characterize the dynamic behavior of plumes in terms of growth and a decay phase. Most of the observed characteristics are found to be consistent with equatorial-irregularity generation predicted by current theories of Rayleigh-Taylor and gradient-drift instabilities. However, other characteristics have been found that suggest key roles played by the eastward neutral wind and by altitude-modulation of the bottomside F layer in establishing the initial conditions for plume growth.

  5. Radar observation of the equatorial counter-electrojet

    International Nuclear Information System (INIS)

    Hanuise, C.; Crochet, M.; Gouin, P.; Ogubazghi, Ghebrebrhan

    1979-01-01

    Electron drift velocity in the equatorial electrojet has been measured for a few years by coherent radar techniques in Africa. For the first time such measurements were performed during a strong reversal of the ionospheric current dubbed 'counter-electrojet'. These observations agree with the theories of the plasma instabilities at the origin of the electron density irregularities giving the radar echoes

  6. Midday reversal of equatorial ionospheric electric field

    Directory of Open Access Journals (Sweden)

    R. G. Rastogi

    1997-10-01

    Full Text Available A comparative study of the geomagnetic and ionospheric data at equatorial and low-latitude stations in India over the 20 year period 1956–1975 is described. The reversal of the electric field in the ionosphere over the magnetic equator during the midday hours indicated by the disappearance of the equatorial sporadic E region echoes on the ionograms is a rare phenomenon occurring on about 1% of time. Most of these events are associated with geomagnetically active periods. By comparing the simultaneous geomagnetic H field at Kodaikanal and at Alibag during the geomagnetic storms it is shown that ring current decreases are observed at both stations. However, an additional westward electric field is superimposed in the ionosphere during the main phase of the storm which can be strong enough to temporarily reverse the normally eastward electric field in the dayside ionosphere. It is suggested that these electric fields associated with the V×Bz electric fields originate at the magnetopause due to the interaction of the solar wind and the interplanetary magnetic field.

  7. Midday reversal of equatorial ionospheric electric field

    Directory of Open Access Journals (Sweden)

    R. G. Rastogi

    Full Text Available A comparative study of the geomagnetic and ionospheric data at equatorial and low-latitude stations in India over the 20 year period 1956–1975 is described. The reversal of the electric field in the ionosphere over the magnetic equator during the midday hours indicated by the disappearance of the equatorial sporadic E region echoes on the ionograms is a rare phenomenon occurring on about 1% of time. Most of these events are associated with geomagnetically active periods. By comparing the simultaneous geomagnetic H field at Kodaikanal and at Alibag during the geomagnetic storms it is shown that ring current decreases are observed at both stations. However, an additional westward electric field is superimposed in the ionosphere during the main phase of the storm which can be strong enough to temporarily reverse the normally eastward electric field in the dayside ionosphere. It is suggested that these electric fields associated with the V×Bz electric fields originate at the magnetopause due to the interaction of the solar wind and the interplanetary magnetic field.

  8. Intraseasonal vertical velocity variation caused by the equatorial wave in the central equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Horii, T.; Masumoto, Y.; Ueki, I.; PrasannaKumar, S.; Mizuno, K.

    to the theoretical solution of the equatorial waves [Matsuno, 1966] and the phase speed of the baroclinic mode, the wave that has meridional current on the equator with a quasi-biweekly period is the anti-symmetric mixed Rossby-gravity wave. In the wave... and conclusions are given in section 5. 2. Field Experiment, Data, and Methods 2.1. MISMO Ocean Observation [8] The goal of MISMO was to observe atmospheric conditions and variability associated with intraseasonal disturbances and resulting ocean responses...

  9. Aerosol Transport Over Equatorial Africa

    Science.gov (United States)

    Gatebe, C. K.; Tyson, P. D.; Annegarn, H. J.; Kinyua, A. M.; Piketh, S.; King, M.; Helas, G.

    1999-01-01

    Long-range and inter-hemispheric transport of atmospheric aerosols over equatorial Africa has received little attention so far. Most aerosol studies in the region have focussed on emissions from rain forest and savanna (both natural and biomass burning) and were carried out in the framework of programs such as DECAFE (Dynamique et Chimie Atmospherique en Foret Equatoriale) and FOS (Fires of Savanna). Considering the importance of this topic, aerosols samples were measured in different seasons at 4420 meters on Mt Kenya and on the equator. The study is based on continuous aerosol sampling on a two stage (fine and coarse) streaker sampler and elemental analysis by Particle Induced X-ray Emission. Continuous samples were collected for two seasons coinciding with late austral winter and early austral spring of 1997 and austral summer of 1998. Source area identification is by trajectory analysis and sources types by statistical techniques. Major meridional transports of material are observed with fine-fraction silicon (31 to 68 %) in aeolian dust and anthropogenic sulfur (9 to 18 %) being the major constituents of the total aerosol loading for the two seasons. Marine aerosol chlorine (4 to 6 %), potassium (3 to 5 %) and iron (1 to 2 %) make up the important components of the total material transport over Kenya. Minimum sulfur fluxes are associated with recirculation of sulfur-free air over equatorial Africa, while maximum sulfur concentrations are observed following passage over the industrial heartland of South Africa or transport over the Zambian/Congo Copperbelt. Chlorine is advected from the ocean and is accompanied by aeolian dust recirculating back to land from mid-oceanic regions. Biomass burning products are transported from the horn of Africa. Mineral dust from the Sahara is transported towards the Far East and then transported back within equatorial easterlies to Mt Kenya. This was observed during austral summer and coincided with the dying phase of 1997/98 El

  10. Central Equatorial Pacific Experiment (CEPEX)

    Energy Technology Data Exchange (ETDEWEB)

    1993-01-01

    The Earth's climate has varied significantly in the past, yet climate records reveal that in the tropics, sea surface temperatures seem to have been remarkably stable, varying by less than a few degrees Celsius over geologic time. Today, the large warm pool of the western Pacific shows similar characteristics. Its surface temperature always exceeds 27[degree]C, but never 31[degree]C. Heightened interest in this observation has been stimulated by questions of global climate change and the exploration of stabilizing climate feedback processes. Efforts to understand the observed weak sensitivity of tropical sea surface temperatures to climate forcing has led to a number of competing ideas about the nature of this apparent thermostat. Although there remains disagreement on the processes that regulate tropical sea surface temperature, most agree that further progress in resolving these differences requires comprehensive field observations of three-dimensional water vapor concentrations, solar and infrared radiative fluxes, surface fluxes of heat and water vapor, and cloud microphysical properties. This document describes the Central Equatorial Pacific Experiment (CEPEX) plan to collect such observations over the central equatorial Pacific Ocean during March of 1993.

  11. Quantum cloning machines for equatorial qubits

    International Nuclear Information System (INIS)

    Fan Heng; Matsumoto, Keiji; Wang Xiangbin; Wadati, Miki

    2002-01-01

    Quantum cloning machines for equatorial qubits are studied. For the case of a one to two phase-covariant quantum cloning machine, we present the networks consisting of quantum gates to realize the quantum cloning transformations. The copied equatorial qubits are shown to be separable by using Peres-Horodecki criterion. The optimal one to M phase-covariant quantum cloning transformations are given

  12. Diagnostic usefulness of CT attenuation coefficients of urine after enteral administration of iodinated water (iohexol) in neonates with NEC

    International Nuclear Information System (INIS)

    Moon, Jeung Hee; Yun, Eun Joo; Yoon, Dae Young

    2006-01-01

    We wanted to evaluate the clinical efficacy of an increased computed tomography attenuation coefficient (CTAC) of urine after the oral administration of iohexol in neonates who are suspected of suffering with neonatal necrotizing enterocolitis (NEC). During a recent 1 year-period, seventeen neonates were admitted for suspected NEC, and they were divided into the suspected and definite groups based on their clinical signs and radiographic findings; we also included ten normal neonates as the control group. Diluted iohexol was administered and the CTACs of collected urine samples at 8-12 hour intervals were measured. Comparative analysis of the three groups was done and statistical significance was determined by the Scheffe test. Among 17 neonates, there were 13 neonates in the suspect group and 4 neonates in the definite group. The mean CTACs of urine in each group were 2711 HU (control group), 3411 HU (suspected group), and 7625 HU (definite group), respectively. There was a significant difference between the mean CTAC of the definite group and that of the control or suspected groups (Scheffe t >2.65). However, no statistically significant difference was seen between the suspected and control groups (Scheffe t=1.14). Although measurements of the CTAC of urine showed no significant diagnostic efficacy in the suspected group, the CTAC of urine, which reflects the correlated degree of bowel mucosal injury, can be a useful aid for determining the severity and progression of NEC

  13. Comparative evaluation of antimicrobial activity of three cements: new endodontic cement (NEC), mineral trioxide aggregate (MTA) and Portland.

    Science.gov (United States)

    Hasan Zarrabi, Mohammad; Javidi, Maryam; Naderinasab, Mahboube; Gharechahi, Maryam

    2009-09-01

    Using the agar diffusion method, we conducted an in vitro study to evaluate the antimicrobial activity of mineral trioxide aggregate (MTA), new endodontic cement (NEC) and Portland cement at different concentrations against five different microorganisms. A base layer was made using Muller-Hinton agar for Escherichia coli (ATCC 10538) and Candida (ATCC 10231). For Actinomyces viscosus (ATCC 15987), Enterococcus faecalis (ATCC 10541) and Streptococcus mutans (ATCC 25175) blood agar medium was used. Wells were formed by removing the agar, and the materials were placed in the well immediately after manipulation. The plates were kept at room temperature for 2 h for prediffusion, and then incubated at 37 degrees C for 72 h. The inhibition zones were then measured. The data were analyzed using ANOVA and the Tukey test to compare the differences among the three cements at different concentrations. The positive controls showed bacterial growth, while the negative controls showed no bacterial growth. All materials showed antimicrobial activity against the tested strains except for Enterococcus faecalis. NEC created larger inhibition zones than MTA and Portland cement. This difference was significant for Portland cement (P 0.05). Among the examined microorganisms, the largest inhibition zone was observed for Actinomyces group (P < 0.05). The antimicrobial activity of the materials increased with time and concentration (P < 0.05). It was concluded that NEC is a potent inhibitor of microorganism growth.

  14. Physical, chemical, current profile, water pressure, sea surface temperature, meteorological, and other data from current meters, bottle casts, pressure gauges, meteorological sensors, current meters, and other instruments from the ANDRE NIZERY and other platforms from the TOGA Area - Atlantic as part of the Seasonal Response of the Equatorial Atlantic Experiment/Francais Ocean Et Climat Dans L'Atlantique Equatorial (SEQUAL/FOCAL) project from 1964-01-01 to 1985-12-31 (NODC Accession 8700150)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Physical, chemical, current profile, water pressure, sea surface temperature, meteorological, and other data were collected from the ANDRE NIZERY and other platforms...

  15. Lagrangian mixed layer modeling of the western equatorial Pacific

    Science.gov (United States)

    Shinoda, Toshiaki; Lukas, Roger

    1995-01-01

    Processes that control the upper ocean thermohaline structure in the western equatorial Pacific are examined using a Lagrangian mixed layer model. The one-dimensional bulk mixed layer model of Garwood (1977) is integrated along the trajectories derived from a nonlinear 1 1/2 layer reduced gravity model forced with actual wind fields. The Global Precipitation Climatology Project (GPCP) data are used to estimate surface freshwater fluxes for the mixed layer model. The wind stress data which forced the 1 1/2 layer model are used for the mixed layer model. The model was run for the period 1987-1988. This simple model is able to simulate the isothermal layer below the mixed layer in the western Pacific warm pool and its variation. The subduction mechanism hypothesized by Lukas and Lindstrom (1991) is evident in the model results. During periods of strong South Equatorial Current, the warm and salty mixed layer waters in the central Pacific are subducted below the fresh shallow mixed layer in the western Pacific. However, this subduction mechanism is not evident when upwelling Rossby waves reach the western equatorial Pacific or when a prominent deepening of the mixed layer occurs in the western equatorial Pacific or when a prominent deepening of the mixed layer occurs in the western equatorial Pacific due to episodes of strong wind and light precipitation associated with the El Nino-Southern Oscillation. Comparison of the results between the Lagrangian mixed layer model and a locally forced Eulerian mixed layer model indicated that horizontal advection of salty waters from the central Pacific strongly affects the upper ocean salinity variation in the western Pacific, and that this advection is necessary to maintain the upper ocean thermohaline structure in this region.

  16. Nonlinearly coupled dynamics of irregularities in the equatorial electrojet

    Energy Technology Data Exchange (ETDEWEB)

    Atul, J.K., E-mail: jkatulphysics@gmail.com [Department of Physics, College of Commerce under Magadh University, Patna 800020 (India); Sarkar, S. [FCIPT, Institute for Plasma Research, Gandhinagar 382428 (India); Singh, S.K. [Department of Physics, College of Commerce under Magadh University, Patna 800020 (India)

    2016-04-01

    Kinetic wave description is used to study the nonlinear influence of background Farley Buneman (FB) modes on the Gradient Drift (GD) modes in the equatorial electrojet ionosphere. The dominant nonlinearity is mediated through the electron flux term in the governing fluid equation which further invokes a turbulent current into the system. Electron dynamics reveals the modification in electron collision frequency and inhomogeneity scale length. It is seen that the propagation and growth rate of GD modes get modified by the background FB modes. Also, a new quasimode gets excited through the quadratic dispersion relation. Physical significance of coupled dynamics between the participating modes is also discussed. - Highlights: • Nonlinear influence of Farley Buneman mode on the Gradient drift mode, is investigated. • Electron collision frequency and density gradient scale length get modified. • A new quasimode gets excited due to the competition between these modes. • It seems to be important for modelling of Equatorial Electrojet current system.

  17. Nonlinearly coupled dynamics of irregularities in the equatorial electrojet

    International Nuclear Information System (INIS)

    Atul, J.K.; Sarkar, S.; Singh, S.K.

    2016-01-01

    Kinetic wave description is used to study the nonlinear influence of background Farley Buneman (FB) modes on the Gradient Drift (GD) modes in the equatorial electrojet ionosphere. The dominant nonlinearity is mediated through the electron flux term in the governing fluid equation which further invokes a turbulent current into the system. Electron dynamics reveals the modification in electron collision frequency and inhomogeneity scale length. It is seen that the propagation and growth rate of GD modes get modified by the background FB modes. Also, a new quasimode gets excited through the quadratic dispersion relation. Physical significance of coupled dynamics between the participating modes is also discussed. - Highlights: • Nonlinear influence of Farley Buneman mode on the Gradient drift mode, is investigated. • Electron collision frequency and density gradient scale length get modified. • A new quasimode gets excited due to the competition between these modes. • It seems to be important for modelling of Equatorial Electrojet current system.

  18. Modeling an HF NVIS Towel-Bar Antenna on a Coast Guard Patrol Boat. A Comparison of WIPL-D and the Numerical Electromagnetics Code (NEC)

    National Research Council Canada - National Science Library

    Mora, Darla; Weiser, Christopher; McKaughan, Michael

    2005-01-01

    A Coast Guard patrol boat high-frequency (HF) near-vertical incident skywave (NVIS) antenna is selected as a test case to compare the electromagnetic modeling programs Numerical Electromagnetics Code, NEC and WIPL-D code...

  19. Inventory of atmospheric pollutant emissions in France under the Convention on long-distance transfrontier atmospheric pollution and the European directive on national emission ceilings (NEC) - CEE-NU/NFR and NEC, March 2011

    International Nuclear Information System (INIS)

    Mathias, Etienne; Chang, Jean-Pierre; Fontelle, Jean-Pierre; Allemand, Nadine; Jacquier, Guillaume; Andre, Jean-Marc; Joya, Romain; Deflorenne, Emmanuel; Martinet, Yann; Druart, Ariane; Nicco, Laetitia; Gavel, Antoine; Prouteau, Emilie; Gueguen, Celine; Serveau, Laetitia; Jabot, Julien; Vincent, Julien

    2011-03-01

    %), cadmium (88%), mercury (84%), carbon monoxide (74%), nickel (69%), polychloro-biphenyls (68%), non-methane volatile organic compounds (67%), arsenic (61%), and polycyclic aromatic hydrocarbons (51%) (BaP 54%, BbF 53% IndPy 49% and BkF 48%), - a sharp decline (between 25 and 50%) for nitrogen oxides (41%) and fine particles (36% for PM 10 and 44% for the PM 2.5 ). - a significant decline (between 5 and 25%) for total suspended particles (23%), selenium (21%), copper (8%) and ammonia (6%). As a whole, these trends are encouraging since they show that most of the targets to which France committed itself under the protocols have been reached, up to now, and give an indication of measures already taken to reduce emissions in anticipation of future targets (the detailed targets are presented within the table 26 of this report). Future reviews of these data are always possible, if not probable, to take into account both changes in methodology and work underway at international level in order to improve knowledge and rules on compiling and presenting emissions. Review of methods and emission factors: The revision of emission factors for particulate matter from power plants has significantly impacted all emissions of Heavy metals for the whole period in particular for As. The emissions of Hg for electric furnace steel plants and Se blast furnaces were also changed for the entire period. Incorporation of specific emission data from declaration s: the process of incorporation of the emission data, at the level of the installations, continues with a great improvement in the treatment of chemical plants for this submission again. Activity update: the main changes are related to NMVOC and NO x . These emissions from agriculture were transferred and excluded from the national total to ensure the consistency with the scopes of the NEC and the protocols. HCB were also significantly modified with the update of the amount of sludge incinerated. Currently the main expected improvement are

  20. EQUATORIAL SUPERROTATION ON TIDALLY LOCKED EXOPLANETS

    International Nuclear Information System (INIS)

    Showman, Adam P.; Polvani, Lorenzo M.

    2011-01-01

    The increasing richness of exoplanet observations has motivated a variety of three-dimensional (3D) atmospheric circulation models of these planets. Under strongly irradiated conditions, models of tidally locked, short-period planets (both hot Jupiters and terrestrial planets) tend to exhibit a circulation dominated by a fast eastward, or 'superrotating', jet stream at the equator. When the radiative and advection timescales are comparable, this phenomenon can cause the hottest regions to be displaced eastward from the substellar point by tens of degrees longitude. Such an offset has been subsequently observed on HD 189733b, supporting the possibility of equatorial jets on short-period exoplanets. Despite its relevance, however, the dynamical mechanisms responsible for generating the equatorial superrotation in such models have not been identified. Here, we show that the equatorial jet results from the interaction of the mean flow with standing Rossby waves induced by the day-night thermal forcing. The strong longitudinal variations in radiative heating-namely intense dayside heating and nightside cooling-trigger the formation of standing, planetary-scale equatorial Rossby and Kelvin waves. The Rossby waves develop phase tilts that pump eastward momentum from high latitudes to the equator, thereby inducing equatorial superrotation. We present an analytic theory demonstrating this mechanism and explore its properties in a hierarchy of one-layer (shallow-water) calculations and fully 3D models. The wave-mean-flow interaction produces an equatorial jet whose latitudinal width is comparable to that of the Rossby waves, namely the equatorial Rossby deformation radius modified by radiative and frictional effects. For conditions typical of synchronously rotating hot Jupiters, this length is comparable to a planetary radius, explaining the broad scale of the equatorial jet obtained in most hot-Jupiter models. Our theory illuminates the dependence of the equatorial jet

  1. Photoelectric panel with equatorial mounting of drive

    Science.gov (United States)

    Kukhta, M. S.; Krauinsh, P. Y.; Krauinsh, D. P.; Sokolov, A. P.; Mainy, S. B.

    2018-03-01

    The relevance of the work is determined by the need to create effective models for sunny energy. The article considers a photoelectric panel equipped with a system for tracking the sun. Efficiency of the system is provided by equatorial mounting, which compensates for the rotation of the Earth by rotating the sunny panel in the plane of the celestial equator. The specificity of climatic and geographical conditions of Tomsk is estimated. The dynamics of power variations of photoelectric panels with equatorial mounting during seasonal fluctuations in Tomsk is calculated. A mobile photovoltaic panel with equatorial mounting of the drive has been developed. The methods of design strategy for placing photovoltaic panels in the architectural environment of the city are presented. Key words: sunny energy, photovoltaics, equatorial mounting, mechatronic model, wave reducer, electric drive.

  2. Equatorial electrojet as part of the global circuit: a case-study from the IEEY

    Directory of Open Access Journals (Sweden)

    A. T. Kobea

    1998-06-01

    Full Text Available Geomagnetic storm-time variations often occur coherently at high latitude and the day-side dip equator where they affect the normal eastward Sq field. This paper presents an analysis of ground magnetic field and ionospheric electrodynamic data related to the geomagnetic storm which occured on 27 May 1993 during the International Equatorial Electrojet Year (IEEY experiment. This storm-signature analysis on the auroral, mid-latitude and equatorial ground field and ionospheric electrodynamic data leads to the identification of a sensitive response of the equatorial electrojet (EEJ to large-scale auroral return current: this response consists in a change of the eastward electric field during the pre-sunrise hours (0400-0600 UT coherently to the high-, mid-, and equatorial-latitude H decrease and the disappearance of the EEJ irregularities between the time-interval 0800-0950 UT. Subsequent to the change in h'F during pre-sunrise hours, the observed foF2 increase revealed an enhancement of the equatorial ionization anomaly (EIA caused by the high-latitude penetrating electric field. The strengthening of these irregularities attested by the Doppler frequency increase tracks the H component at the equator which undergoes a rapid increase around 0800 UT. The ∆H variations observed at the equator are the sum of the following components: SR, DP, DR, DCF and DT.Keywords. Equatorial electrojet · Magnetosphere-ionosphere interactions · Electric fields and currents · Auroral ionosphere · Ionospheric disturbances

  3. The Role of Reversed Equatorial Zonal Transport in Terminating an ENSO Event

    Science.gov (United States)

    Chen, H. C.; Hu, Z. Z.; Huang, B.; Sui, C. H.

    2016-02-01

    In this study, we demonstrate that a sudden reversal of anomalous equatorial zonal current at the peaking ENSO phase triggers the rapid termination of an ENSO event. Throughout an ENSO cycle, the anomalous equatorial zonal current is strongly controlled by the concavity of the anomalous thermocline meridional structure near the equator. During the ENSO developing phase, the anomalous zonal current in the central and eastern Pacific generally enhances the ENSO growth through its zonal SST advection. In the mature phase of ENSO, however, the equatorial thermocline depth anomalies are reflected in the eastern Pacific and slowly propagate westward off the equator in both hemispheres. As a result, the concavity of the thermocline anomalies near the equator is reversed, i.e., the off-equatorial thermocline depth anomalies become higher than that on the equator for El Niño events and lower for La Niño events. This meridional change of thermocline structure reverses zonal transport rapidly in the central-to-eastern equatorial Pacific, which weakens the ENSO SST anomalies by reversed advection. More importantly, the reversed zonal mass transport weakens the existing zonal tilting of equatorial thermocline and suppresses the thermocline feedback. Both processes are concentrated in the eastern equatorial Pacific and can be effective on subseasonal time scales. These current reversal effects are built-in to the ENSO peak phase and independent of the zonal wind effect on thermocline slope. It functions as an oceanic control on ENSO evolution during both El Niño and La Niña events.

  4. Protective Effects of Bifidobacterium on Intestinal Barrier Function in LPS-Induced Enterocyte Barrier Injury of Caco-2 Monolayers and in a Rat NEC Model.

    Directory of Open Access Journals (Sweden)

    Xiang Ling

    Full Text Available Zonulin protein is a newly discovered modulator which modulates the permeability of the intestinal epithelial barrier by disassembling intercellular tight junctions (TJ. Disruption of TJ is associated with neonatal necrotizing enterocolitis (NEC. It has been shown bifidobacterium could protect the intestinal barrier function and prophylactical administration of bifidobacterium has beneficial effects in NEC patients and animals. However, it is still unknown whether the zonulin is involved in the gut barrier dysfunction of NEC, and the protective mechanisms of bifidobacterium on intestinal barrier function are also not well understood. The present study aims to investigate the effects of bifidobacterium on intestinal barrier function, zonulin regulation, and TJ integrity both in LPS-induced enterocyte barrier injury of Caco-2 monolayers and in a rat NEC model. Our results showed bifidobacterium markedly attenuated the decrease in transepithelial electrical resistance and the increase in paracellular permeability in the Caco-2 monolayers treated with LPS (P < 0.01. Compared with the LPS group, bifidobacterium significantly decreased the production of IL-6 and TNF-α (P < 0.01 and suppressed zonulin release (P < 0.05. In addition, bifidobacterium pretreatment up-regulated occludin, claudin-3 and ZO-1 expression (P < 0.01 and also preserved these proteins localization at TJ compared with the LPS group. In the in vivo study, bifidobacterium decreased the incidence of NEC from 88 to 47% (P < 0.05 and reduced the severity in the NEC model. Increased levels of IL-6 and TNF-α in the ileum of NEC rats were normalized in bifidobacterium treated rats (P < 0.05. Moreover, administration of bifidobacterium attenuated the increase in intestinal permeability (P < 0.01, decreased the levels of serum zonulin (P < 0.05, normalized the expression and localization of TJ proteins in the ileum compared with animals with NEC. We concluded that bifidobacterium may

  5. Modeling Global Ocean Biogeochemistry With Physical Data Assimilation: A Pragmatic Solution to the Equatorial Instability

    Science.gov (United States)

    Park, Jong-Yeon; Stock, Charles A.; Yang, Xiaosong; Dunne, John P.; Rosati, Anthony; John, Jasmin; Zhang, Shaoqing

    2018-03-01

    Reliable estimates of historical and current biogeochemistry are essential for understanding past ecosystem variability and predicting future changes. Efforts to translate improved physical ocean state estimates into improved biogeochemical estimates, however, are hindered by high biogeochemical sensitivity to transient momentum imbalances that arise during physical data assimilation. Most notably, the breakdown of geostrophic constraints on data assimilation in equatorial regions can lead to spurious upwelling, resulting in excessive equatorial productivity and biogeochemical fluxes. This hampers efforts to understand and predict the biogeochemical consequences of El Niño and La Niña. We develop a strategy to robustly integrate an ocean biogeochemical model with an ensemble coupled-climate data assimilation system used for seasonal to decadal global climate prediction. Addressing spurious vertical velocities requires two steps. First, we find that tightening constraints on atmospheric data assimilation maintains a better equatorial wind stress and pressure gradient balance. This reduces spurious vertical velocities, but those remaining still produce substantial biogeochemical biases. The remainder is addressed by imposing stricter fidelity to model dynamics over data constraints near the equator. We determine an optimal choice of model-data weights that removed spurious biogeochemical signals while benefitting from off-equatorial constraints that still substantially improve equatorial physical ocean simulations. Compared to the unconstrained control run, the optimally constrained model reduces equatorial biogeochemical biases and markedly improves the equatorial subsurface nitrate concentrations and hypoxic area. The pragmatic approach described herein offers a means of advancing earth system prediction in parallel with continued data assimilation advances aimed at fully considering equatorial data constraints.

  6. Understanding the Longitudinal Variability of Equatorial Electrodynamics using integrated Ground- and Space-based Observations

    Science.gov (United States)

    Yizengaw, E.; Moldwin, M.; Zesta, E.

    2015-12-01

    The currently funded African Meridian B-Field Education and Research (AMBER) magnetometer array comprises more than thirteen magnetometers stationed globally in the vicinity of geomagnetic equator. One of the main objectives of AMBER network is to understand the longitudinal variability of equatorial electrodynamics as function of local time, magnetic activity, and season. While providing complete meridian observation in the region and filling the largest land-based gap in global magnetometer coverage, the AMBER array addresses two fundamental areas of space physics: first, the processes governing electrodynamics of the equatorial ionosphere as a function of latitude (or L-shell), local time, longitude, magnetic activity, and season, and second, ULF pulsation strength at low/mid-latitude regions and its connection with equatorial electrojet and density fluctuation. The global AMBER network can also be used to augment observations from space-based instruments, such us the triplet SWARM mission and the upcoming ICON missions. Thus, in coordination with space-based and other ground-based observations, the AMBER magnetometer network provides a great opportunity to understand the electrodynamics that governs equatorial ionosphere motions. In this paper we present the longitudinal variability of the equatorial electrodynamics using the combination of instruments onboard SWARM and C/NOFS satellites and ground-based AMBER network. Both ground- and pace-based observations show stronger dayside and evening sector equatorial electrodynamics in the American and Asian sectors compared to the African sector. On the other hand, the African sector is home to stronger and year-round ionospheric bubbles/irregularities compared to the American and Asian sectors. This raises the question if the evening sector equatorial electrodynamics (vertical drift), which is believed to be the main cause for the enhancement of Rayleigh-Taylor (RT) instability growth rate, is stronger in the

  7. Current meter components and other data from FIXED PLATFORMS from Gulf of Guinea and other locations as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) and other projects from 08 July 1976 to 01 April 1982 (NODC Accession 9000067)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter components data were collected from FIXED PLATFORMS in the Gulf of Guinea and other locations from 08 July 1976 to 01 April 1982. Data were collected...

  8. Wind and temperature data from current meter in the TOGA - Pacific Ocean (30 N to 30 S) as part of the Equatorial Pacific Ocean Climate Studies (EPOCS), 28 May 1994 to 21 March 1995 (NODC Accession 9800041)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Wind and temperature data were collected using current meter in the TOGA Area - Pacific Ocean (30 N to 30 S) from May 28, 1994 to March 21, 1995. Data were submitted...

  9. Therapeutic Use of Prebiotics, Probiotics, and Postbiotics to Prevent Necrotizing Enterocolitis: What is the Current Evidence?

    Science.gov (United States)

    Patel, Ravi Mangal; Denning, Patricia Wei

    2013-01-01

    Synopsis Necrotizing enterocolitis (NEC) is a leading cause of neonatal morbidity and mortality and preventative therapies that are both effective and safe are urgently needed. Current evidence from therapeutic trials suggests that probiotics are effective in decreasing NEC in preterm infants and probiotics are currently the most promising therapy on the horizon for this devastating disease. However, concerns regarding safety and optimal dosing have limited the widespread adoption of routine clinical use of probiotics in preterm infants. In addition, prebiotics and postbiotics may be potential alternatives or adjunctive therapies to the administration of live microorganisms, although studies demonstrating their clinical efficacy in preventing NEC are lacking. This review summarizes the current evidence regarding the use of probiotics, prebiotics and postbiotics in the preterm infant, including its therapeutic role in preventing NEC. PMID:23415261

  10. The oil boom in Equatorial Guinea

    International Nuclear Information System (INIS)

    Frynas, J.G.

    2004-01-01

    In less than a decade, Equatorial Guinea has transformed itself from an African backwater into one of the world's fastest growing economies and a sought-after political partner in the Gulf of Guinea. The sole reason for this transformation has been the discovery of oil and gas. This article outlines the rise of Equatorial Guinea as one of Africa's leading oil-producing countries and investigates the political, economic and social effects of becoming a petro-state. The article is based on the author's field research in Equatorial Guinea in the autumn of 2003 and interviews with senior oil company staff, government officials and staff of international organizations as well as secondary sources. This research demonstrates how reliance on oil and gas exports can lead to profound changes in a country's political economy. (author)

  11. Equatorial waves in the stratosphere of Uranus

    Science.gov (United States)

    Hinson, David P.; Magalhaes, Julio A.

    1991-01-01

    Analyses of radio occultation data from Voyager 2 have led to the discovery and characterization of an equatorial wave in the Uranus stratosphere. The observed quasi-periodic vertical atmospheric density variations are in close agreement with theoretical predictions for a wave that propagates vertically through the observed background structure of the stratosphere. Quantitative comparisons between measurements obtained at immersion and at emersion yielded constraints on the meridional and zonal structure of the wave; the fact that the two sets of measurements are correlated suggests a wave of planetary scale. Two equatorial wave models are proposed for the wave.

  12. A concurrent visualization system for large-scale unsteady simulations. Parallel vector performance on an NEC SX-4

    International Nuclear Information System (INIS)

    Takei, Toshifumi; Doi, Shun; Matsumoto, Hideki; Muramatsu, Kazuhiro

    2000-01-01

    We have developed a concurrent visualization system RVSLIB (Real-time Visual Simulation Library). This paper shows the effectiveness of the system when it is applied to large-scale unsteady simulations, for which the conventional post-processing approach may no longer work, on high-performance parallel vector supercomputers. The system performs almost all of the visualization tasks on a computation server and uses compressed visualized image data for efficient communication between the server and the user terminal. We have introduced several techniques, including vectorization and parallelization, into the system to minimize the computational costs of the visualization tools. The performance of RVSLIB was evaluated by using an actual CFD code on an NEC SX-4. The computational time increase due to the concurrent visualization was at most 3% for a smaller (1.6 million) grid and less than 1% for a larger (6.2 million) one. (author)

  13. Early gradual feeding with bovine colostrum improves gut function and NEC resistance relative to infant formula in preterm pigs

    DEFF Research Database (Denmark)

    Shen, René L.; Thymann, Thomas; Østergaard, Mette V.

    2015-01-01

    It is unclear when and how to start enteral feeding for preterm infants when mother’s milk is not available. We hypothesized that early and slow advancement with either formula or bovine colostrum stimulates gut maturation and prevents necrotizing enterocolitis (NEC) in preterm pigs, used as models...... for preterm infants. Pigs were given either total parenteral nutrition (TPN, n = 14) or slowly advancing volumes (16–64 ml·kg-1·day-1) of preterm infant formula (IF, n = 15) or bovine colostrum (BC, n = 13), both given as adjunct to parenteral nutrition. On day 5, both enteral diets increased intestinal mass...... intestinal permeability, compared with BC pigs (all P colostrum supports gut maturation when mother’s milk is absent during the first week after preterm birth...

  14. Early gradual feeding with bovine colostrum improves gut function and NEC resistance relative to infant formula in preterm pigs

    DEFF Research Database (Denmark)

    Shen, Rene L; Thymann, Thomas; Østergaard, Mette V

    2015-01-01

    It is unclear when and how to start enteral feeding for preterm infants when mother's milk is not available. We hypothesized that early and slow advancement with either formula or bovine colostrum stimulates gut maturation and prevents necrotizing enterocolitis (NEC) in preterm pigs, used as models...... for preterm infants. Pigs were given either total parenteral nutrition (TPN, n = 14) or slowly advancing volumes (16–64 ml·kg−1·day−1) of preterm infant formula (IF, n = 15) or bovine colostrum (BC, n = 13), both given as adjunct to parenteral nutrition. On day 5, both enteral diets increased intestinal mass......), and higher intestinal permeability, compared with BC pigs (all P colostrum supports gut maturation when mother's milk is absent during the first week after...

  15. Anthropogenic 236U recorded in annually banded coral skeleton at Majuro atoll, the equatorial Pacific

    International Nuclear Information System (INIS)

    Sakaguchi, Aya; Eto, Asuka; Takahashi, Yoshio; Steier, Peter; Yamazaki, Atsuko; Watanabe, Tsuyoshi; Sasaki, Keiichi; Yamano, Hiroya

    2013-01-01

    Historical 236 U/ 238 U atom ratio and concentration of 236 U were determined by Accelerator Mass Spectrometry (AMS) in skeletons of dated modern coral core sample collected from Majuro atoll, equatorial Pacific, to reconstruct anthropogenic 236 U inputs to the Equatorial Pacific. The maximum hydrogen bomb-pulses of 236 U/ 238 U and 236 U concentration, 2.83x10 -9 and 1.85x10 7 atom/g, in an annually resolved coral core were captured in 1954 (Operation Castle at Bikini and Enewetok atolls). The values were abruptly decreased in a few years, and they have been gradually decreased over time. Our results allow studies of not only the present distribution pattern, but gives access to the temporal evolution of 236 U in surface seawater of North Equatorial Current which is introduced to the Japan Sea and the North West Pacific Ocean as Kuroshio and Tsushima currents over the past decades. (author)

  16. Coccolithophores in the equatorial Atlantic Ocean

    DEFF Research Database (Denmark)

    Kinkel, Hanno; Baumann, K.-H.; Cepek, M.

    2000-01-01

    with each other. In general, the living coccolithophores in the surface and subsurface waters show considerable variation in cell numbers and distribution patterns. Cell densities reached a maximum of up to 300 x 10 coccospheres/l in the upwelling area of the equatorial Atlantic. Here, Emiliania huxleyi...

  17. A Secure NEC-enabling Architecture : Disentangling Infrastructure, Information and Security

    NARCIS (Netherlands)

    Boonstra, D.; Hartog, T.; Schotanus, H.A.; Verkoelen, C.A.A.

    2011-01-01

    The NATO Network-Enabled Capability (NNEC) study envisions effective and efficient cooperation among the coalition partners in missions. This requires information sharing and efficient deployment of IT assets. Current military communication infrastructures are mostly deployed as stand-alone

  18. Protective Effects of Bifidobacterium on Intestinal Barrier Function in LPS-Induced Enterocyte Barrier Injury of Caco-2 Monolayers and in a Rat NEC Model.

    Science.gov (United States)

    Ling, Xiang; Linglong, Peng; Weixia, Du; Hong, Wei

    2016-01-01

    Zonulin protein is a newly discovered modulator which modulates the permeability of the intestinal epithelial barrier by disassembling intercellular tight junctions (TJ). Disruption of TJ is associated with neonatal necrotizing enterocolitis (NEC). It has been shown bifidobacterium could protect the intestinal barrier function and prophylactical administration of bifidobacterium has beneficial effects in NEC patients and animals. However, it is still unknown whether the zonulin is involved in the gut barrier dysfunction of NEC, and the protective mechanisms of bifidobacterium on intestinal barrier function are also not well understood. The present study aims to investigate the effects of bifidobacterium on intestinal barrier function, zonulin regulation, and TJ integrity both in LPS-induced enterocyte barrier injury of Caco-2 monolayers and in a rat NEC model. Our results showed bifidobacterium markedly attenuated the decrease in transepithelial electrical resistance and the increase in paracellular permeability in the Caco-2 monolayers treated with LPS (P zonulin release (P zonulin (P zonulin protein release and improvement of intestinal TJ integrity.

  19. Reflection of equatorial Kelvin waves at eastern ocean boundaries Part I: hypothetical boundaries

    Directory of Open Access Journals (Sweden)

    J. Soares

    1999-06-01

    Full Text Available A baroclinic shallow-water model is developed to investigate the effect of the orientation of the eastern ocean boundary on the behavior of equatorial Kelvin waves. The model is formulated in a spherical polar coordinate system and includes dissipation and non-linear terms, effects which have not been previously included in analytical approaches to the problem. Both equatorial and middle latitude response are considered given the large latitudinal extent used in the model. Baroclinic equatorial Kelvin waves of intraseasonal, seasonal and annual periods are introduced into the domain as pulses of finite width. Their subsequent reflection, transmission and dissipation are investigated. It is found that dissipation is very important for the transmission of wave energy along the boundary and for reflections from the boundary. The dissipation was found to be dependent not only on the presence of the coastal Kelvin waves in the domain, but also on the period of these coastal waves. In particular the dissipation increases with wave period. It is also shown that the equatorial β-plane approximation can allow an anomalous generation of Rossby waves at higher latitudes. Nonlinearities generally have a small effect on the solutions, within the confines of this model.Key words. Oceanography: general (equatorial oceanography; numerical modeling · Oceanography: physical (eastern boundary currents

  20. Interannual variability of the Equatorial Jets in the Indian Ocean from the merged altimetry data

    Digital Repository Service at National Institute of Oceanography (India)

    Somayajulu, Y.K.; Murty, V.S.N.; Neelima, C.; Jagadeesh, P.S.V.

    The merged ERS-1/2, TOPEX/Poseidon and Jason-1 altimeter weekly sea level anomalies (SLAs) for the period 1997- 2005 were analyzed to study the variability of sea level and computed geostrophic currents in relation to the equatorial jets...

  1. Effect of solar flare on the equatorial electrojet in eastern Brazil region

    Indian Academy of Sciences (India)

    The effect of solar flare, sudden commencement of magnetic storm and of the disturbances ring current on the equatorial electrojet in the Eastern Brazil region, where the ground magnetic declination is as large as 20∘W is studied based on geomagnetic data with one minute resolution from Bacabal during ...

  2. Equatorial electrojet as part of the global circuit: a case-study from the IEEY

    Directory of Open Access Journals (Sweden)

    A. T. Kobea

    Full Text Available Geomagnetic storm-time variations often occur coherently at high latitude and the day-side dip equator where they affect the normal eastward Sq field. This paper presents an analysis of ground magnetic field and ionospheric electrodynamic data related to the geomagnetic storm which occured on 27 May 1993 during the International Equatorial Electrojet Year (IEEY experiment. This storm-signature analysis on the auroral, mid-latitude and equatorial ground field and ionospheric electrodynamic data leads to the identification of a sensitive response of the equatorial electrojet (EEJ to large-scale auroral return current: this response consists in a change of the eastward electric field during the pre-sunrise hours (0400-0600 UT coherently to the high-, mid-, and equatorial-latitude H decrease and the disappearance of the EEJ irregularities between the time-interval 0800-0950 UT. Subsequent to the change in h'F during pre-sunrise hours, the observed foF2 increase revealed an enhancement of the equatorial ionization anomaly (EIA caused by the high-latitude penetrating electric field. The strengthening of these irregularities attested by the Doppler frequency increase tracks the H component at the equator which undergoes a rapid increase around 0800 UT. The ∆H variations observed at the equator are the sum of the following components: SR, DP, DR, DCF and DT.

    Keywords. Equatorial electrojet · Magnetosphere-ionosphere interactions · Electric fields and currents · Auroral ionosphere · Ionospheric disturbances

  3. Long wavelength irregularities in the equatorial electrojet

    OpenAIRE

    Kudeki, E.; Farley, D. T.; Fejer, Bela G.

    1982-01-01

    We have used the radar interferometer technique at Jicamarca to study in detail irregularities with wavelengths of a few kilometers generated in the unstable equatorial electrojet plasma during strong type 1 conditions. In-situ rocket observations of the same instability process are discussed in a companion paper. These large scale primary waves travel essentially horizontally and have large amplitudes. The vertical electron drift velocities driven by the horizontal wave electric fields reach...

  4. Intraseasonal meridional current variability in the eastern equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Ogata, T.; Sasaki, H.; Murty, V.S.N.; Sarma, M.S.S.; Masumoto, Y.

    . [2007] demonstrate the possibility of the air-sea interac- tion in the eastern Indian Ocean at the intraseasonal time- scale by analyzing observed and simulated data. Recent studies also reveal that multiscale air-sea interactions be- tween intraseasonal...

  5. Probability Distribution Function of the Upper Equatorial Pacific Current Speeds

    National Research Council Canada - National Science Library

    Chu, Peter C

    2005-01-01

    ...), constructed from hourly ADCP data (1990-2007) at six stations for the Tropical Atmosphere Ocean project satisfies the two-parameter Weibull distribution reasonably well with different characteristics between El Nino and La Nina events...

  6. High altitude flights in equatorial regions

    Science.gov (United States)

    Redkar, R. T.

    A thorough analysis of balloon flights made from Hyderabad, India (Latitude 17°28'N, Longitude 78°35'E), and other equatorial sites has been made. It has been shown that limited success is expected for flights made from equatorial latitudes with balloons made out of natural colour polyethylene film, since the best known balloon film in the world today viz. Winzen Stratofilm is tested for low temperature brittleness only at -80°C., whereas the tropopause temperatures over equatorial latitudes vary between -80°C and -90°C. The success becomes even more critical when flights are made with heavy payloads and larger balloons particularly at night when in the absence of solar radiation the balloon film becomes more susceptible to low temperature brittle failure. It is recommended that in case of capped balloons longer caps should be used to fully cover the inflated protion of the balloon at the higher level equatorial tropopause. It is also advised that the conditions such as wind shears in the tropopause should be critically studied before launching and a day with the tropopause temperature nearer to -80°C should be chosen. Special care also should be taken while handling the balloon on ground and during launching phase. Properties of Winzen Stratofilm have been critically studied and fresh mandates have been recommended on the basis of limiting values of film stresses which caused balloon failures in the equatorial tropopause. It is also emphasized that the data on such flights is still meagre especially for flights with heavy payloads and larger balloons. It has been also shown that it is safest to use balloons made out of grey coloured film which retains its flexibility with the absorption of solar radiation, the success obtained with such balloons so far being 100%. The drawback, however, is that these balloons cannot be used for night flights. Stratospheric wind regimes over Hyderabad are also discussed with a view to determine the period over which long

  7. Nuclear Energy Center: upper St. Lawrence region. Part I. Siting. Part II. Fort Drum surrogate site, description and impact assessment. Part III. Dispersed sites impact assessment and comparison with the NEC

    Energy Technology Data Exchange (ETDEWEB)

    Merry, P.A.; Luner, C.; Hong, S.W.; Canham, H.O.; Boggs, J.F.; McCool, T.P.

    1976-12-01

    This report is one of many supporting documents used by the Nuclear Regulatory commission in the preparation of the Nuclear Energy Center Site Survey (NECSS) mandated by Congress. While the overall study focuses on the feasibility and practicability of nuclear energy centers (NECs), this report is directed towards choosing a suitable surrogate site in the upper St. Lawrence region of New York State, assessing the probable impacts associated with construction and operation of the NEC, and comparing these impacts with those associated with small dispersed nuclear power stations. The upper St. Lawrence region is surveyed to identify a specific site that might be suitable for a surrogate NEC. Several assumptions about the basic design of an NEC are delineated, and a general overview of the characteristics of the region is given. The Fort Drum Military Reservation is chosen as a suitable surrogate site. Fort Drum and the surrounding area are described in terms of land use and population patterns, terrestrial and aquatic ecology, water use and quality, meteorology, institutional framework, and socioeconomic structure. The impacts associated with NEC development are assessed. Then the impacts associated with smaller dispersed nuclear power stations located throughout New York State are assessed and compared with the impacts associated with the NEC. Finally, the impacts due to development of the transmission line networks associated with the NEC and with the dispersed power stations are assessed and compared.

  8. Continuous day-time time series of E-region equatorial electric fields derived from ground magnetic observatory data

    Science.gov (United States)

    Alken, P.; Chulliat, A.; Maus, S.

    2012-12-01

    The day-time eastward equatorial electric field (EEF) in the ionospheric E-region plays an important role in equatorial ionospheric dynamics. It is responsible for driving the equatorial electrojet (EEJ) current system, equatorial vertical ion drifts, and the equatorial ionization anomaly (EIA). Due to its importance, there is much interest in accurately measuring and modeling the EEF. However, there are limited sources of direct EEF measurements with full temporal and spatial coverage of the equatorial ionosphere. In this work, we propose a method of estimating a continuous day-time time series of the EEF at any longitude, provided there is a pair of ground magnetic observatories in the region which can accurately track changes in the strength of the EEJ. First, we derive a climatological unit latitudinal current profile from direct overflights of the CHAMP satellite and use delta H measurements from the ground observatory pair to determine the magnitude of the current. The time series of current profiles is then inverted for the EEF by solving the governing electrodynamic equations. While this method has previously been applied and validated in the Peruvian sector, in this work we demonstrate the method using a pair of magnetometers in Africa (Samogossoni, SAM, 0.18 degrees magnetic latitude and Tamanrasset, TAM, 11.5 degrees magnetic latitude) and validate the resulting EEF values against the CINDI ion velocity meter (IVM) instrument on the C/NOFS satellite. We find a very good 80% correlation with C/NOFS IVM measurements and a root-mean-square difference of 9 m/s in vertical drift velocity. This technique can be extended to any pair of ground observatories which can capture the day-time strength of the EEJ. We plan to apply this work to more observatory pairs around the globe and distribute real-time equatorial electric field values to the community.

  9. Westward equatorial electrojet during daytime hours. [relation to geomagnetic horizontal field depression

    Science.gov (United States)

    Rastogi, R. G.

    1974-01-01

    The phenomenon of the depression of the geomagnetic horizontal field during the daytime hours of magnetically quiet days at equatorial stations is described. These events are generally seen around 0700 and 1600 LT, being more frequent during the evening than the morning hours. The evening events are more frequent during periods of low solar activity and in the longitude region of weak equatorial electrojet currents. The latitudinal extent of the phenomenon is limited to the normal equatorial electrojet region, and on some occasions the phenomenon is not seen at both stations, separated by only a few hours in longitude. During such an event, the latitudinal profile of the geomagnetic vertical field across the equator is reversed, the ionospheric drift near the equator is reversed toward the east, the q type of sporadic E layer is completely absent, and the height of the peak ionization in the F2 region is decreased. It is suggested that these effects are caused by a narrow band of current flowing westward in the E region of the ionosphere and within the latitude region of the normal equatorial electrojet, due to the reversal of the east-west electrostatic field at low latitudes.

  10. MACSAT - A Near Equatorial Earth Observation Mission

    Science.gov (United States)

    Kim, B. J.; Park, S.; Kim, E.-E.; Park, W.; Chang, H.; Seon, J.

    MACSAT mission was initiated by Malaysia to launch a high-resolution remote sensing satellite into Near Equatorial Orbit (NEO). Due to its geographical location, Malaysia can have large benefits from NEO satellite operation. From the baseline circular orbit of 685 km altitude with 7 degrees of inclination, the neighboring regions around Malaysian territory can be frequently monitored. The equatorial environment around the globe can also be regularly observed with unique revisit characteristics. The primary mission objective of MACSAT program is to develop and validate technologies for a near equatorial orbit remote sensing satellite system. MACSAT is optimally designed to accommodate an electro-optic Earth observation payload, Medium-sized Aperture Camera (MAC). Malaysian and Korean joint engineering teams are formed for the effective implementation of the satellite system. An integrated team approach is adopted for the joint development for MACSAT. MAC is a pushbroom type camera with 2.5 m of Ground Sampling Distance (GSD) in panchromatic band and 5 m of GSD in four multi-spectral bands. The satellite platform is a mini-class satellite. Including MAC payload, the satellite weighs under 200 kg. Spacecraft bus is designed optimally to support payload operations during 3 years of mission life. The payload has 20 km of swath width with +/- 30 o of tilting capability. 32 Gbits of solid state recorder is implemented as the mass image storage. The ground element is an integrated ground station for mission control and payload operation. It is equipped with S- band up/down link for commanding and telemetry reception as well as 30 Mbps class X-band down link for image reception and processing. The MACSAT system is capable of generating 1:25,000-scale image maps. It is also anticipated to have capability for cross-track stereo imaging for Digital elevation Model (DEM) generation.

  11. The equatorial F-layer: progress and puzzles

    Directory of Open Access Journals (Sweden)

    H. Rishbeth

    Full Text Available This work reviews some aspects of the ionospheric F-layer in the vicinity of the geomagnetic equator. Starting with a historical introduction, brief summaries are given of the physics that makes the equatorial ionosphere so interesting, concentrating on the large-scale structure rather than the smaller-scale instability phenomena. Several individual topics are then discussed, including eclipse effects, the asymmetries of the `equatorial trough', variations with longitude, the semiannual variation, the effects of the global thermospheric circulation, and finally the equatorial neutral thermosphere, including `superrotation' and possible topographic influences.

    Keyword: Ionosphere (equatorial ionosphere

  12. An equatorial coronal hole at solar minimum

    Science.gov (United States)

    Bromage, B. J. I.; DelZanna, G.; DeForest, C.; Thompson, B.; Clegg, J. R.

    1997-01-01

    The large transequatorial coronal hole that was observed in the solar corona at the end of August 1996 is presented. It consists of a north polar coronal hole called the 'elephant's trunk or tusk'. The observations of this coronal hole were carried out with the coronal diagnostic spectrometer onboard the Solar and Heliospheric Observatory (SOHO). The magnetic field associated with the equatorial coronal hole is strongly connected to that of the active region at its base, resulting in the two features rotating at almost the same rate.

  13. Priority areas for large mammal conservation in Equatorial Guinea.

    Science.gov (United States)

    Murai, Mizuki; Ruffler, Heidi; Berlemont, Antoine; Campbell, Genevieve; Esono, Fidel; Agbor, Anthony; Mbomio, Domingo; Ebana, Agustín; Nze, Antonio; Kühl, Hjalmar S

    2013-01-01

    Hunting is one of the main driving forces behind large mammal density distribution in many regions of the world. In tropical Africa, urban demand for bushmeat has been shown to dominate over subsistence hunting and its impact often overrides spatial-ecological species characteristics. To effectively protect remaining mammal populations the main factors that influence their distribution need to be integrated into conservation area prioritisation and management plans. This information has been lacking for Río Muni, Equatorial Guinea, as prior studies have been outdated or have not systematically covered the continental region of the country. In this study we evaluated: 1) the relative importance of local vs. commercial hunting; 2) wildlife density of protected vs. non-protected areas; and 3) the importance of ecological factors vs. human influence in driving mammal density distribution in Río Muni. We adopted a systematic countrywide line transect approach with particular focus on apes and elephants, but also including other mammal species. For analysis of field data we used generalised linear models with a set of predictor variables representing ecological conditions, anthropogenic pressure and protected areas. We estimate that there are currently 884 (437-1,789) elephants and 11,097 (8,719-13,592) chimpanzees and gorillas remaining in Río Muni. The results indicate strong hunting pressures on both local and commercial levels, with roads demonstrating a negative impact on elephants and overall mammal body mass. Protected areas played no role in determining any of the mammal species distributions and significant human hunting signs were found inside these protected areas, illustrating the lack of environmental law enforcement throughout the country. Río Muni is currently under-represented in conservation efforts in Western Equatorial Africa, and we recommend a focus on cross-boundary conservation, in particular in the Monte Alén-Monts de Cristal and Río Campo

  14. Necrotizing Enterocolitis (NEC)

    Science.gov (United States)

    ... YouTube follow us on Flickr follow us on Instagram Español NICHD Theme Browse AZTopics Browse A-Z ... Publications Sitemap Español facebook twitter pinterest youtube flickr Instagram NEWSROOM NICHD News Videos OUTREACH Safe to Sleep® ...

  15. Improving NEC Fit

    Science.gov (United States)

    2015-09-01

    TAD Temporary Additional Duty TFMMS Total Force Manpower Management System UIC Unit Identification Code USFFC United States Fleet Forces Command...not include sailors on temporary additional duty ( TAD ). In addition, for class average Fit, we excluded units that had billets but no onboard

  16. Preliminary report: STOIC CGCM intercomparison - equatorial sections

    International Nuclear Information System (INIS)

    Davey, M; Huddleston, M; Sperber, K R.

    1999-01-01

    An intercomparison and assessment of the tropical behaviour of coupled general circulation models (CGCMs) is being carried out, to identify common strengths and weaknesses and thus guide future CGCM development. The work is being carried out as part of the CLIVAR climate research programme, as a WG-SIP (Working Group on Seasonal to Interannual Prediction) project called STOIC (Study of Tropical Oceans In CGCMs), organised by Michael Davey. This project complements a companion sub-project called ENSIP (El Ni no Simulation Intercomparison Project) organised by Mojib Latif (Max- Planck-Institute for Meteorology) that focusses on equatorial Pacific CGCM behaviour (Latif et al. 1999). Previous coupled model assessments (Mechoso et al. 1995, Neelin et al. 1992, and ENSIP) have focussed on tropical Pacific behaviour. The aim of STOIC is to look at model performance in all tropical ocean regions. This status report contains a sample of the STOIC assessment work, highlighting mean and inter- annual equatorial sea surface temperatures and zonal windstresses. The intention is to submit STOIC and ENSIP papers in mid-1999 for publication together in a refereed journal

  17. Nighttime ionospheric D region: Equatorial and nonequatorial

    Science.gov (United States)

    Thomson, Neil R.; McRae, Wayne M.

    2009-08-01

    Nighttime ionospheric D region parameters are found to be generally well modeled by the traditional H‧ and β as used by Wait and by the U.S. Navy in their Earth-ionosphere VLF radio waveguide programs. New comparisons with nonequatorial, mainly all-sea VLF path observations reported over several decades are shown to be consistent with the previously determined height H‧ ˜ 85.0 km and sharpness β ˜ 0.63 km-1. These paths include NPM (Hawaii) to Washington, D. C., Omega Hawaii and NLK (Seattle) to Japan, NWC (N.W. Australia) to Madagascar, and NBA (Panama) to Colorado. In marked contrast, transequatorial path observations (even when nearly all-sea) are found to be often not well modeled: for example, for Omega Japan and JJI (Japan) to Dunedin, New Zealand, the observed amplitudes are markedly lower than those which would be expected from H‧ ˜ 85.0 km and β ˜ 0.63 km-1, or any other realistic values of H‧ and β. Other transequatorial observations compared with modeling include NWC to Japan, Omega Hawaii to Dunedin, and NPM (Hawaii) to Dunedin. It is suggested that the effects of irregularities in the equatorial electrojet may extend down into the nighttime D region and so account for the observed equatorial VLF perturbations through scattering or mode conversion.

  18. Central Equatorial Pacific Experiment (CEPEX). Design document

    Energy Technology Data Exchange (ETDEWEB)

    1993-04-01

    The Earth`s climate has varied significantly in the past, yet climate records reveal that in the tropics, sea surface temperatures seem to have been remarkably stable, varying by less than a few degrees Celsius over geologic time. Today, the large warm pool of the western Pacific shows similar characteristics. Its surface temperature always exceeds 27{degree}C, but never 31{degree}C. Heightened interest in this observation has been stimulated by questions of global climate change and the exploration of stabilizing climate feedback processes. Efforts to understand the observed weak sensitivity of tropical sea surface temperatures to climate forcing has led to a number of competing ideas about the nature of this apparent thermostat. Although there remains disagreement on the processes that regulate tropical sea surface temperature, most agree that further progress in resolving these differences requires comprehensive field observations of three-dimensional water vapor concentrations, solar and infrared radiative fluxes, surface fluxes of heat and water vapor, and cloud microphysical properties. This document describes the Central Equatorial Pacific Experiment (CEPEX) plan to collect such observations over the central equatorial Pacific Ocean during March of 1993.

  19. Spread F – an old equatorial aeronomy problem finally resolved?

    Directory of Open Access Journals (Sweden)

    R. F. Woodman

    2009-05-01

    Full Text Available One of the oldest scientific topics in Equatorial Aeronomy is related to Spread-F. It includes all our efforts to understand the physical mechanisms responsible for the existence of ionospheric F-region irregularities, the spread of the traces in a night-time equatorial ionogram – hence its name – and all other manifestations of the same. It was observed for the first time as an abnormal ionogram in Huancayo, about 70 years ago. But only recently are we coming to understand the physical mechanisms responsible for its occurrence and its capricious day to day variability. Several additional techniques have been used to reveal the spatial and temporal characteristics of the F-region irregularities responsible for the phenomenon. Among them we have, in chronological order, radio star scintillations, trans-equatorial radio propagation, satellite scintillations, radar backscatter, satellite and rocket in situ measurements, airglow, total electron content techniques using the propagation of satellite radio signals and, recently, radar imaging techniques. Theoretical efforts are as old as the observations. Nevertheless, 32 years after their discovery, Jicamarca radar observations showed that none of the theories that had been put forward could explain them completely. The observations showed that irregularities were detected at altitudes that were stable according to the mechanisms proposed. A breakthrough came a few years later, again from Jicamarca, by showing that some of the "stable" regions had become unstable by the non-linear propagation of the irregularities from the unstable to the stable region of the ionosphere in the form of bubbles of low density plasma. A problem remained, however; the primary instability mechanism proposed, an extended (generalized Rayleigh-Taylor instability, was too slow to explain the rapid development seen by the observations. Gravity waves in the neutral background have been proposed as a seeding mechanism to

  20. The D1 parameter for the equatorial F1 region

    International Nuclear Information System (INIS)

    Adeniyi, J.O.; Radicella, S.M.

    2002-01-01

    This work is a contribution to the effort at improving the representation of the F1 equatorial ionospheric region in the International Reference Ionosphere (IRI) model. The D1 parameter has been proposed for describing the F1 layer. We have therefore produced a maiden table of D1 parameter for an equatorial station. Diurnal and seasonal effects were considered. (author)

  1. Current meter data from moored current meter casts in the TOGA Area - Pacific (30 N to 30 S) as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1984-04-16 to 1985-10-01 (NODC Accession 8700147)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the TOGA Area - Pacific (30 N to 30 S) from April 16, 1984 to October 1, 1985. Data were...

  2. Current meter data from moored current meter casts in the TOGA Area - Pacific (30 N to 30 S) as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1987-05-01 to 1987-05-05 (NODC Accession 9000211)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the TOGA Area - Pacific (30 N to 30 S) from 01 May 1987 to 06 August 1988. Data were submitted...

  3. Current meter data from moored current meter casts in the SW Pacific (limit-147 E to 140 W) as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1985-09-29 to 1986-04-01 (NODC Accession 8800136)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the SW Pacific (limit-147 E to 140 W) from September 29, 1985 to June 1, 1986. Data were...

  4. Long wavelength irregularities in the equatorial electrojet

    International Nuclear Information System (INIS)

    Kudeki, E.; Farley, D.T.; Fejer, B.G.

    1982-01-01

    We have used the radar interferometer technique at Jicamarca to study in detail irregularities with wavelengths of a few kilometers generated in the unstable equatorial electrojet plasma during strong type 1 conditions. In-situ rocket observations of the same instability process are discussed in a companion paper. These large scale primary waves travel essentially horizontally and have large amplitudes. The vertical electron drift velocities driven by the horizontal wave electric fields reach or exceed the ion-acoustic velocity even though the horizontal phase velocity of the wave is considerably smaller. A straightforward extension to the long wavelength regime of the usual linear theory of the electrojet instability explains this and several other observed features of these dominant primary waves

  5. Linear theory of equatorial spread F

    International Nuclear Information System (INIS)

    Hudson, M.K.; Kennel, C.F.

    1975-01-01

    A fluid dispersion relation for the drift and interchange (Rayleigh-Taylor) modes in a collisional plasma forms the basis for a linear theory of equatorial spread F. The collisional drift mode growth rate will exceed the growth rate of the Rayleigh-Taylor mode at short perpendicular wavelengths and density gradient scale lengths, and the drift mode can grow on top side as well as on bottom side density gradients. However, below the F peak, where spread F predominates, it is concluded that both the drift and the Rayleigh-Taylor modes contribute to the total spread F spectrum, the Rayleigh-Taylor mode dominating at long and the drift mode at short perpendicular wavelengths above the ion Larmor radius

  6. Equatorial circular motion in Kerr spacetime

    International Nuclear Information System (INIS)

    Pugliese, Daniela; Quevedo, Hernando; Ruffini, Remo

    2011-01-01

    We analyze the properties of circular orbits of test particles on the equatorial plane of a rotating central mass whose gravitational field is described by the Kerr spacetime. For rotating black holes and naked singularities we explore all the spatial regions where circular orbits can exist and analyze the behavior of the energy and the angular momentum of the corresponding test particles. In particular, we find all the radii at which a test particle can have zero angular momentum due to the repulsive gravity effects generated by naked singularities. We classify all the stability zones of circular orbits. It is shown that the geometric structure of the stability zones of black holes is completely different from that of naked singularities.

  7. Dynamical variability in Saturn Equatorial Atmosphere

    Science.gov (United States)

    Sánchez-Lavega, A.; Pérez-Hoyos, S.; Hueso, R.; Rojas, J. F.; French, R. G.; Grupo Ciencias Planetarias Team

    2003-05-01

    Historical ground-based and recent HST observations show that Saturn's Equatorial Atmosphere is the region where the most intense large-scale dynamical variability took place at cloud level in the planet. Large-scale convective storms (nicknamed the ``Great White Spots") occurred in 1876, 1933 and 1990. The best studied case (the 1990 storm), produced a dramatic change in the cloud aspect in the years following the outburst of September 1990. Subsequently, a new large storm formed in 1994 and from 1996 to 2002 our HST observations showed periods of unusual cloud activity in the southern part of the Equator. This contrast with the aspect observed during the Voyager 1 and 2 encounters in 1980 and 1981 when the Equator was calm, except for some mid-scale plume-like features seen in 1981. Cloud-tracking of the features have revealed a dramatic slow down in the equatorial winds from maximum velocities of ˜ 475 m/s in 1980-1981 to ˜ 275 m/s during 1996-2002, as we have recently reported in Nature, Vol. 423, 623 (2003). We discuss the possibility that seasonal and ring-shadowing effects are involved in generating this activity and variability. Acknowledgements: This work was supported by the Spanish MCYT PNAYA 2000-0932. SPH acknowledges a PhD fellowship from the Spanish MECD and RH a post-doc fellowship from Gobierno Vasco. RGF was supported in part by NASA's Planetary Geology and Geophysics Program NAG5-10197 and STSCI Grant GO-08660.01A.

  8. Solar flare effect in equatorial magnetic field during morning counter electrojet

    International Nuclear Information System (INIS)

    Rangarajan, G.K.; Rastogi, R.G.

    1981-01-01

    Surface geomagnetic signatures of intense solar radio noise bursts are studied from the magnetograms of several equatorial and low latitude observatories. It is shown that for the even on 21 June 1980, the solar flare effect recorded was during a period of counter electrojet currents in the morning hours in the Indian region, and hence it reverses direction between Alibag and Trivandrum. The longitudinal extent of this event has been estimated to be less than three hours (45). (author)

  9. Current meter data from moored current meter casts in the TOGA Area - Pacific (30 N to 30 S) as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1988-05-24 to 1989-05-26 (NODC Accession 9100207)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the TOGA Area - Pacific (30 N to 30 S) from 24 May 1988 to 26 May 1989. Data were submitted by...

  10. Current components, physical, ocean circulation, wind circulation, and other data from moored buoys, CTD casts, drifting buoys, and in situ wind recorders from AIRCRAFT and other platforms from the North Atlantic Ocean and other locations as part of the Seasonal Response of the Equatorial Atlantic Experiment/Français Océan et Climat dans l'Atlantique Equatorial (SEQUAL/FOCAL) project from 1980-01-25 to 1985-12-18 (NODC Accession 8700111)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current components, physical, ocean circulation, wind circulation, and other data were collected from moored buoys, CTD casts, drifting buoys, and in situ wind...

  11. Theoretical evaluation of the biological shielding sufficiency for the Pelletron NEC Particle Accelerator at the Ghana Atomic Energy Commission

    International Nuclear Information System (INIS)

    Amoah, P. A.

    2012-01-01

    Theoretical evaluation of the biological shielding sufficiency provided for 1.7MV Pelletron NEC Particle Accelerator yet to be installed at the Accelerator Research Centre of the Ghana Atomic Energy Commission (GAEC) has been done. Using the Beer Lambert law attenuation of radiation dose outside the walls of the facility was made for protons of energy 1.7MeV. Simulation of charged particle-matter interactions leading to bremsstrahlung radiation using Monte Carlo code (MCNP5) have been carried out. Neutron Activation Analysis (NAA) technique has also been used to identify the composition of the concrete material used during the construction of the Accelerator Research Centre (ARC) building. The NAA analysis revealed that the elemental constituents of the ordinary concrete of density 2.3g/cm 3 used for the construction of the walls included Na, Al, and Ca. Background radiation levels within and outside the facility was measured with the aid of a Sodium Iodide (NaI) identifinder and a Rados detector so as to have a practical reference datum. The weekly background radiation measurements yielded an average dose rate value of 0.05μSv/hr from recorded value range of 0.01μSv/hr to 0.07μSv/hr for an eight month period. Modeling and simulation of charged particle-matter interactions at different beam energies using Monte Carlo code (MCNP5) have yielded the dose rate of 1.58E-07μSv/hr, 1.98E-07μSv/h and 2.20E-05μSv/h outside the 22.86cm (9.0 inch) thick wall of the accelerator facility, for the beam energy range of 0.5-3.0MeV for Titanium, iron and Zirconium target samples respectively. From the Beer-Lambert law, the operational energy of 1.7MeV was used to evaluate theoretically the radiation dose rate of 1.178E-05μSv/hr, 2.656E-05μSv/hr and 4.787E-05μSv/hr outside the 22.86cm thick wall of the accelerator facility for Titanium, Iron and Zirconium targets respectively. At the operational energy energy of 3.0 MeV, the dose rate values obtained were 4.382E-05μSv/h, 9

  12. Longitudinal, seasonal and solar cycle variation in lunar tide influence on the equatorial electrojet

    Directory of Open Access Journals (Sweden)

    E. Yizengaw

    2017-04-01

    Full Text Available It has been well documented that the lunar tidal waves can modulate the ionospheric electrodynamics and create a visible influence on the equatorial electrojet (EEJ. The lunar tide influence gets intensified around noon, primarily during new and full Moon periods. However, the longitudinal, seasonal and solar cycle variability in the lunar tide influence on ionospheric current systems is not well understood yet. In order to investigate this, 17 years (1998–2014 of extensive magnetometer observations at four longitudinal sectors (western American, western and eastern African, and Asian have been analyzed. All observations performed during magnetically active periods (Kp>3 have been excluded for this study to eliminate storm contributions to the geomagnetic field variation at the geomagnetic equator. This study's quantitative analysis revealed significant longitudinal, seasonal and solar cycle dependence of the lunar tide influence on the equatorial electrojet.

  13. Longitudinal, seasonal and solar cycle variation in lunar tide influence on the equatorial electrojet

    Energy Technology Data Exchange (ETDEWEB)

    Yizengaw, Endawoke [Boston College, Chestnut Hill, MA (United States). Inst. for Scientific Research; Carter, Brett A. [RMIT Univ., Melbourne, VIC (Australia). SPACE Research Centre

    2017-07-01

    It has been well documented that the lunar tidal waves can modulate the ionospheric electrodynamics and create a visible influence on the equatorial electrojet (EEJ). The lunar tide influence gets intensified around noon, primarily during new and full Moon periods. However, the longitudinal, seasonal and solar cycle variability in the lunar tide influence on ionospheric current systems is not well understood yet. In order to investigate this, 17 years (1998-2014) of extensive magnetometer observations at four longitudinal sectors (western American, western and eastern African, and Asian) have been analyzed. All observations performed during magnetically active periods (K{sub p}>3) have been excluded for this study to eliminate storm contributions to the geomagnetic field variation at the geomagnetic equator. This study's quantitative analysis revealed significant longitudinal, seasonal and solar cycle dependence of the lunar tide influence on the equatorial electrojet.

  14. Longitudinal, seasonal and solar cycle variation in lunar tide influence on the equatorial electrojet

    International Nuclear Information System (INIS)

    Yizengaw, Endawoke; Carter, Brett A.

    2017-01-01

    It has been well documented that the lunar tidal waves can modulate the ionospheric electrodynamics and create a visible influence on the equatorial electrojet (EEJ). The lunar tide influence gets intensified around noon, primarily during new and full Moon periods. However, the longitudinal, seasonal and solar cycle variability in the lunar tide influence on ionospheric current systems is not well understood yet. In order to investigate this, 17 years (1998-2014) of extensive magnetometer observations at four longitudinal sectors (western American, western and eastern African, and Asian) have been analyzed. All observations performed during magnetically active periods (K p >3) have been excluded for this study to eliminate storm contributions to the geomagnetic field variation at the geomagnetic equator. This study's quantitative analysis revealed significant longitudinal, seasonal and solar cycle dependence of the lunar tide influence on the equatorial electrojet.

  15. Equatorial ozone profile comparisons using OSO-8 UVMCS and Nimbus 4 BUV data

    Science.gov (United States)

    Aikin, A. C.; Millier, F.; Emery, B.

    1981-01-01

    A comparison is made of equatorial ozone altitude profiles derived from data taken during near-coincident passes of the French solar occultation experiment on OSO-8 and the BUV instrument on Nimbus 4. The period of observation is August through October 1975. OSO-8 data are confined to sunset and the BUV measures ozone during the day for a range of solar zenith angles. Good agreement is found between ozone concentrations from OSO-8 and Nimbus 4 in the region of near overlap, 0.7 mb (52 km). Data indicate that the diurnal variation in ozone below 55 km is less than 20 percent in agreement with current models. The equatorial ozone profile can be described frequently by a single scale height from 34 to 60 km.

  16. Priority areas for large mammal conservation in Equatorial Guinea.

    Directory of Open Access Journals (Sweden)

    Mizuki Murai

    Full Text Available Hunting is one of the main driving forces behind large mammal density distribution in many regions of the world. In tropical Africa, urban demand for bushmeat has been shown to dominate over subsistence hunting and its impact often overrides spatial-ecological species characteristics. To effectively protect remaining mammal populations the main factors that influence their distribution need to be integrated into conservation area prioritisation and management plans. This information has been lacking for Río Muni, Equatorial Guinea, as prior studies have been outdated or have not systematically covered the continental region of the country. In this study we evaluated: 1 the relative importance of local vs. commercial hunting; 2 wildlife density of protected vs. non-protected areas; and 3 the importance of ecological factors vs. human influence in driving mammal density distribution in Río Muni. We adopted a systematic countrywide line transect approach with particular focus on apes and elephants, but also including other mammal species. For analysis of field data we used generalised linear models with a set of predictor variables representing ecological conditions, anthropogenic pressure and protected areas. We estimate that there are currently 884 (437-1,789 elephants and 11,097 (8,719-13,592 chimpanzees and gorillas remaining in Río Muni. The results indicate strong hunting pressures on both local and commercial levels, with roads demonstrating a negative impact on elephants and overall mammal body mass. Protected areas played no role in determining any of the mammal species distributions and significant human hunting signs were found inside these protected areas, illustrating the lack of environmental law enforcement throughout the country. Río Muni is currently under-represented in conservation efforts in Western Equatorial Africa, and we recommend a focus on cross-boundary conservation, in particular in the Monte Alén-Monts de Cristal

  17. Quiet Time Depression of the Equatorial Electrojet and Dynamics of the F-layer Ionosphere

    Science.gov (United States)

    Khadka, S.; Valladares, C. E.; Doherty, P.

    2017-12-01

    The depression of the equatorial electrojet (EEJ) is marked by a westward current due to streaming movement of laterally limited (±3°) charged particles in the ionospheric E region during the day along the magnetic equator. It is a complex low-latitude phenomenon and driven by various sources of electric fields associated with global neutral wind, solar tidal force, Interplanetary magnetic Field (IMF), etc. This unique physical property of the equatorial ionosphere holds a great promise for sorting out the governing mechanism of the dayside ionospheric electrodynamics and the onset of the enigmatic plasma structures in the ionospheric layers. Present study provides an overview of the special sequence of the longitudinal, seasonal, and occurrence rate variability of the depression of the EEJ, including its temporal variation, using data from an excellent chain of magnetic and ionospheric observatories along the low-latitude regions. A case and statistical study of the geomagnetically quiet time depression of EEJ strengths is presented using a pair of magnetometers, one located at the dip equator and another off the dip equator (±6° to ±9° away) in the American low-latitude regions. The significance of the variability of the depression of the EEJ current observed in the scenario of vertical drifts, sporadic E-layer, the equatorial F region plasma fountain, and height of the peak ionization in the F-layer, as well as GPS-TEC distributions, will be investigated.

  18. Electron correlation in molecules: concurrent computation Many-Body Perturbation Theory (ccMBPT) calculations using macrotasking on the NEC SX-3/44 computer

    International Nuclear Information System (INIS)

    Moncrieff, D.; Wilson, S.

    1992-06-01

    The ab initio determination of the electronic structure of molecules is a many-fermion problem involving the approximate description of the motion of the electrons in the field of fixed nuclei. It is an area of research which demands considerable computational resources but having enormous potential in fields as diverse as interstellar chemistry and drug design, catalysis and solid state chemistry, molecular biology and environmental chemistry. Electronic structure calculations almost invariably divide into two main stages: the approximate solution of an independent electron model, in which each electron moves in the average field created by the other electrons in the system, and then, the more computationally demanding determination of a series of corrections to this model, the electron correlation effects. The many-body perturbation theory expansion affords a systematic description of correlation effects, which leads directly to algorithms which are suitable for concurrent computation. We term this concurrent computation Many-Body Perturbation Theory (ccMBPT). The use of a dynamic load balancing technique on the NEC SX-3/44 computer in electron correlation calculations is investigated for the calculation of the most demanding energy component in the most accurate of contemporary ab initio studies. An application to the ground state of the nitrogen molecule is described. We also briefly discuss the extent to which the calculation of the dominant corrections to such studies can be rendered computationally tractable by exploiting both the vector processing and parallel processor capabilities of the NEC SX-3/44 computer. (author)

  19. Seasonal cycle of cross-equatorial flow in the central Indian Ocean

    Science.gov (United States)

    Wang, Yi; McPhaden, Michael J.

    2017-05-01

    This study investigates the seasonal cycle of meridional currents in the upper layers of central equatorial Indian Ocean using acoustic Doppler current profiler (ADCP) and other data over the period 2004-2013. The ADCP data set collected along 80.5°E is the most comprehensive collection of direct velocity measurements in the central Indian Ocean to date, providing new insights into the meridional circulation in this region. We find that mean volume transport is southward across the equator in the central Indian Ocean in approximate Sverdrup balance with the wind stress curl. In addition, mean westerly wind stress near the equator drives convergent Ekman flow in the surface layer and subsurface divergent geostrophic flow in the thermocline at 50-150 m depths. In response to a mean northward component of the surface wind stress, the maximum surface layer convergence is shifted off the equator to between 0.5° and 1°N. Evidence is also presented for the existence of a shallow equatorial roll consisting of a northward wind-driven surface drift overlaying the southward directed subsurface Sverdrup transport. Seasonal variations are characterized by cross-equatorial transports flowing from the summer to the winter hemisphere in quasi-steady Sverdrup balance with the wind stress curl. In addition, semiannually varying westerly monsoon transition winds lead to semiannual enhancements of surface layer Ekman convergence and geostrophic divergence in the thermocline. These results quantify expectations from ocean circulation theories for equatorial Indian Ocean meridional circulation patterns with a high degree of confidence given the length of the data records.

  20. Equatorial wave activity during 2007 over Gadanki, a tropical station

    Indian Academy of Sciences (India)

    been used to investigate the wave activity in the troposphere and lower stratosphere. Waves in the ...... Oltmans S J 2001 Water vapor control at the tropopause by equatorial Kelvin .... observed in UARS microwave limb sounder temperature.

  1. An overview on the equatorial electrojet theoretical grounds

    International Nuclear Information System (INIS)

    Zamlutti, C.J.; Sobral, J.H.A.; Abdu, M.A.

    1988-01-01

    The grounds on which the equatorial electrojet theory is based are reexamined in a way as to suggest specific additional implementations in the existing electrodynamical modeling of this phenomena, making use of now existing improved computer processing speeds. (author) [pt

  2. ITER L 6 equatorial maintenance duct remote handling study

    International Nuclear Information System (INIS)

    Millard, J.

    1996-09-01

    The status and conclusions of a preliminary study of equatorial maintenance duct remote handling is reported. Due to issues with the original duct design a significant portion of the study had to be refocused on equatorial duct layout studies. The study gives an overview of some of the options for design of these ducts and the impact of the design on the equipment to work in the duct. To develop a remote handling concept for creating access through the ducts the following design tasks should be performed: define the operations sequences for equatorial maintenance duct opening and closing; review the remote handling requirements for equatorial maintenance duct opening and closing; design concept for door and pipe handling equipment and to propose preliminary procedures for material handling outsides the duct. 35 figs

  3. Onset conditions for equatorial spread F

    International Nuclear Information System (INIS)

    Mendillo, M.; Baumgardner, J.; Xiaoqing Pi; Sultan, P.J.; Tsunoda, R.

    1992-01-01

    The problem of day-to-day variability in the occurrence of equatorial spread F (ESF) is addressed using multidiagnostic observations and semiempirical modeling. The observational results are derived from a two-night case study of ESF onset conditions observed at Kwajalein Atoll (Marshall Islands) using the ALTAIR incoherent scatter radar and all-sky optical imaging techniques. The major difference between nights when ESF instabilities did not occur (August 14, 1988) and did occur (August 15, 1988) in the Kwajalein sector was that the northern meridional gradient of 6300-angstrom airglow was reduced on the night of limited ESF activity. Modeling results suggest that this unusual airglow pattern is due to equatorward neutral winds. Previous researchers have shown that transequatorial thermospheric winds can exert a control over ESF seasonal and longitudinal occurrence patterns by inhibiting Rayleigh-Taylor instability growth rates. They present evidence to suggest that this picture can be extended to far shorter time scales, namely, that 'surges' in transequatoral winds acting over characteristic times of a few hours to a day can result in a stabilizing influence upon irregularity growth rates. The seemingly capricious nature of ESF onset may thus be controlled, in part, by the inherent variability of low-latitude thermospheric winds

  4. An equatorial temperature and wind anomaly (ETWA)

    International Nuclear Information System (INIS)

    Raghavarao, R.; Wharton, L.E.; Mayr, H.G.; Brace, L.H.; Spencer, N.W.

    1991-01-01

    Data obtained from the WATS (Wind and Temperature Spectrometer) and LP (Langmuir Probe) experiments on board DE-2 (Dynamic Explorer) during high solar activity show evidence of anomalous latitudinal variations in the zonal winds and temperature at low latitudes. The zonal winds exhibit a broad maximum centered around the dip equator, flanked by minima on either side around 25 degrees; while the temperature exhibits a pronounced bowl-shaped minimum at the dip equator which is flanked by maxima. The two minima in the zonal winds and the corresponding maxima in the temperature are nearly collocated with the crests of the well known Equatorial Ionization Anomaly (EIA). The maximum in the zonal winds and the minimum in the gas temperature are collected with the trough of the EIA. The differences between the maxima and minima in temperature and zonal winds, on many occasions, are observed to exceed 100 K and 100 m/s, respectively. The characteristics of this new phenomenon have eluded present day empirical models of thermospheric temperature and winds. The connection among these variables can be understood from the ion-neutral drag effect on the motions of the neutrals that in turn affect their energy balance

  5. Plasma instabilities multifrequency study in equatorial electrojet

    International Nuclear Information System (INIS)

    Hanuise, C.

    1983-01-01

    In this thesis, multifrequential HF coherent radar results are presented, in the field plasma instabilities in equatorial electrojet. In a first part, characteristics of the irregularities observed either at the 3 meter wavelength by VHF radars, either at other wavelengths during pinpoint experiments, or in-situ by probe rockets are recalled. Theoretical studies progressed and are presented, at the same time with these experimental observations: instability linear theory, non linear theories, HF radar specificity, and problems associated to HF waves propagation and refraction in ionosphere. Original experimental results from Ethiopia are gathered in the second part. Plasma instability has been studied in different geophysical conditions and Doppler spectra characteristics are presented for each one of them. These characteristics are completely different according to the various cases; they are also different according to wether observations are made during the day in normal conditions (electric field pointed to the east at the equator) or in counter-electrojet conditions (electric field pointed to the west). The last part is concerned with theoretical interpretation of the previous results. A comprehensive view of the instability physical mechanisms, according to the geophysical conditions encountered, has been allowed by our results, VHF radar measurements at Jicamarca, or in situ probe measurements on the whole. Irregularities study has been limited to the E region [fr

  6. Condor equatorial electrojet campaign: Radar results

    International Nuclear Information System (INIS)

    Kudeki, E.; Fejer, B.G.; Farley, D.T.; Hanuise, C.

    1987-01-01

    A review of the experimental and theoretical background to the Condor equatorial electrojet compaign is followed by the presentation and discussion of VHF radar interferometer and HF radar backscatter data taken concurrently with two rocket in situ experiments reported in companion papers (Pfaff et al., this issue (a, b). Both experiments were conducted in strongly driven periods with the on-line radar interferometer displaying signatures of what has been interpreted in earlier radar work (Kudeki et al., 1982) as kilometer scale gradient drift waves. Low-frequency density fluctuations detected by in situ rocket sensors confirm the earlier interpretation. VHF radar/rocket data comparisons also indicate the existence of a turbulent layer in the upper portion of the daytime electrojet at about 108 km altitude driven purely by the two-stream instability. Nonlinear mode coupling of linearly growing two-stream waves to linearly damped 3-m vertical modes could account for the radar echoes scattered from this layer, which showed no indication of large-scale gradient drift waves. Nonlinear mode coupling may therefore compete with the wave-induced anomalous diffusion mechanism proposed recently by Sudan (1983) for the saturation of directly excited two-stream waves. Nighttime radar data show a bifurcated layer with the two parts having comparable echo strength but oppositely directed zonal drift velocities. The lower layer shows narrow backscatter spectra; the upper layer is characterized by kilometer scale waves and vertically propagating type 1 waves

  7. Radiation protection in hospitals of Equatorial Guinea

    International Nuclear Information System (INIS)

    Rabat Macambo, P.

    2001-01-01

    With a population of four hundred thousand (400.000) inhabitants and distributed in a territory of 28 thousand (28.000) km 2 , the use of ionizing radiations for medical practice in Equatorial Guinea is few and decreasing. It is used for diagnostic practices in the main hospitals of the country, where the work burden is not over 20 patients per day. The political, social and economical embryonic development of the country until recently had a negative influence on indicators and health organisations, so that even now the country does not have any radiological protection law, this shortness, in addition with the old architectural structure that x ray tools is lodging, as well as dosimetrical lack of employed staff, put this staff under risk of electromagnetic energy. This is to show the present survey of medical activities with ionizing radiation and to request technical support for implementing suitably the basic standards of radiation protection which will help us as basis for the elaboration outline law, on radiological protection in accordance with the new guidelines of the International Atomic Energy Agency. (author)

  8. Time dependent response of equatorial ionospheric electric fieldsto magnetospheric disturbances

    OpenAIRE

    Fejer, Bela G.; Scherliess, L.

    1995-01-01

    We use extensive radar measurements of F region vertical plasma drifts and auroral electrojet indices to determine the storm time dependence of equatorial zonal electric fields. These disturbance drifts result from the prompt penetration of high latitude electric fields and from the dynamo action of storm time winds which produce largest perturbations a few hours after the onset of magnetic activity. The signatures of the equatorial disturbance electric fields change significantly depending o...

  9. Filamentary Alfvénic structures excited at the edges of equatorial plasma bubbles

    Directory of Open Access Journals (Sweden)

    R. Pottelette

    2007-11-01

    Full Text Available Recent observations performed by the French DEMETER satellite at altitudes of about 710 km suggest that the generation of equatorial plasma bubbles correlates with the presence of filamentary structures of field aligned currents carried by Alfvén waves. These localized structures are located at the bubble edges. We study the dynamics of the equatorial plasma bubbles, taking into account that their motion is dictated by gravity driven and displacement currents. Ion-polarization currents appear to be crucial for the accurate description of the evolution of plasma bubbles in the high altitude ionosphere. During their eastward/westward motion the bubbles intersect gravity driven currents flowing transversely with respect to the background magnetic field. The circulation of these currents is prohibited by large density depressions located at the bubble edges acting as perfect insulators. As a result, in these localized regions the transverse currents have to be locally closed by field aligned currents. Such a physical process generates kinetic Alfvén waves which appear to be stationary in the plasma bubble reference frame. Using a two-dimensional model and "in situ" wave measurements on board the DEMETER spacecraft, we give estimates for the magnitude of the field aligned currents and the associated Alfvén fields.

  10. Performance evaluation of GPS receiver under equatorial scintillation

    Directory of Open Access Journals (Sweden)

    Alison de Oliveira Moraes

    2009-06-01

    Full Text Available Equatorial scintillation is a phenomenon that occurs daily in the equatorial region after the sunset and affects radio signals that propagate through the ionosphere. Depending on the temporal and spatial situation, equatorial scintillation can represent a problem in the availability and precision of the Global Positioning System (GPS. This work is concerned with evaluating the impact of equatorial scintillation on the performance of GPS receivers. First, the morphology and statistical model of equatorial scintillation is briefly presented. A numerical model that generates synthetic scintillation data to simulate the effects of equatorial scintillation is presented. An overview of the main theoretical principles on GPS receivers is presented. The analytical models that describe the effects of scintillation at receiver level are presented and compared with numerical simulations using a radio software receiver and synthetic data. The results achieved by simulation agreed quite well with those predicted by the analytical models. The only exception is for links with extreme levels of scintillation and when weak signals are received.

  11. Possible ionospheric preconditioning by shear flow leading to equatorial spread F

    Directory of Open Access Journals (Sweden)

    D. L. Hysell

    2005-10-01

    Full Text Available Vertical shear in the zonal plasma drift speed is apparent in incoherent and coherent scatter radar observations of the bottomside F region ionosphere made at Jicamarca from about 1600–2200 LT. The relative importance of the factors controlling the shear, which include competition between the E and F region dynamos as well as vertical currents driven in the E and F regions at the dip equator, is presently unknown. Bottom-type scattering layers arise in strata where the neutral and plasma drifts differ widely, and periodic structuring of irregularities within the layers is telltale of intermediate-scale waves in the bottomside. These precursor waves appear to be able to seed ionospheric interchange instabilities and initiate full-blown equatorial spread F. The seed or precursor waves may be generated by a collisional shear instability. However, assessing the viability of shear instability requires measurements of the same parameters needed to understand shear flow quantitatively - thermospheric neutral wind and off-equatorial conductivity profiles. Keywords. Ionosphere (Equatorial ionosphere; ionospheric irregularities – Space plasma physics (Waves and instabilities

  12. Healthcare in Equatorial Guinea, West Africa: obstacles and barriers to care.

    Science.gov (United States)

    Reuter, Kim Eleanor; Geysimonyan, Aurora; Molina, Gabriela; Reuter, Peter Robert

    2014-01-01

    The provision of healthcare services in developing countries has received increasing attention, but inequalities persist. One nation with potential inequalities in healthcare services is Equatorial Guinea (Central-West Africa). Mitigating these inequalities is difficult, as the Equatoguinean healthcare system remains relatively understudied. In this study, we interviewed members of the healthcare community in order to: 1) learn which diseases are most common and the most common cause of death from the perspective of healthcare workers; and 2) gain an understanding of the healthcare community in Equatorial Guinea by describing how: a) healthcare workers gain their professional knowledge; b) summarizing ongoing healthcare programs aimed at the general public; c) discussing conflicts within the healthcare community and between the public and healthcare providers; d) and addressing opportunities to improve healthcare delivery. We found that some causes of death, such as serious injuries, may not be currently treatable in country, potentially due to a lack of resources and trauma care facilities. In addition, training and informational programs for both healthcare workers and the general public may not be effectively transmitting information to the intended recipients. This presents hurdles to the healthcare community, both in terms of having professional competence in healthcare delivery and in having a community that is receptive to medical care. Our data also highlight government-facility communication as an opportunity for improvement. Our research is an important first step in understanding the context of healthcare delivery in Equatorial Guinea, a country that is relatively data poor.

  13. Authigenic Uranium in Eastern Equatorial Pacific Sediments

    Science.gov (United States)

    Marcantonio, F.; Lyle, M. W.; Loveley, M. R.; Ibrahim, R.

    2014-12-01

    Authigenic U concentrations have been used as an indicator of redox state in marine sediments. Soluble U(VI) in porewaters is reduced to insoluble U(IV) under suboxic conditions setting up a diffusion gradient through which U in bottom waters is supplied to reducing sediments. Researchers have used sedimentary redox enrichment of U as a tool to identify past redox changes, which may be caused by changes in organic carbon rain rates and/or bottom water oxygen levels. Differentiating between these two explanations is important, as the former is tied to the use of authigenic U as a paleoproductivity proxy. We examined sediments from 4 sediment cores retrieved from two different localities in the Panama Basin in the eastern equatorial Pacific. Two cores were retrieved from the northern Panama basin at the Cocos Ridge, (4JC at 5° 44.7'N 85° 45.5' W, 1730 m depth; 8JC at 6° 14.0'N 86° 2.6' W, 1993 m depth), and two were retrieved from the south at the Carnegie Ridge, (11JC at 0° 41.6'S 85° 20.0' W, 2452 m depth; 17JC at 0° 10.8'S 85° 52.0' W, 2846 m depth). Using 230Th systematics and seismic profiling at each of the sites, we've identified significant sediment winnowing (4JC and 11JC) and focusing (8JC and 17JC). At all sites, we believe that changes in age-model-derived sand (i.e., >63µm) mass accumulation rates (MAR) best represent changes in rain rates. Glacial rain rates are higher than those in the Holocene by a factor of 2-3 at both sites. Peak Mn levels (>1%), the brown-to-green color transition (which likely represents the oxic/post-oxic boundary), and peak U concentrations all appear in the same order with increasing depth down core. At the Carnegie sites, where MARs are greater than those at the Cocos sites, increases in authigenic U (up to 4 ppm) occur during the mid- to late Holocene at depths of 10-15 cm. At the Cocos sites, increases in authigenic U (up to 12 ppm) occur lower in the sediment column (25-30 cm) during the late glacial. The decrease

  14. Deciphering Equatorial Pacific Deep Sea Sediment Transport Regimes by Core-Log-Seismic Integration

    Science.gov (United States)

    Ortiz, E.; Tominaga, M.; Marcantonio, F.

    2017-12-01

    Investigating deep-sea sediment transportation and deposition regimes is a key to accurately understand implications from geological information recorded by pelagic sediments, e.g. climate signals. However, except for physical oceanographic particle trap experiments, geochemical analyses of in situsediments, and theoretical modeling of the relation between the bottom currents and sediment particle flux, it has remained a challenging task to document the movement of deep sea sediments, that takes place over time. We utilized high-resolution, multichannel reflection seismic data from the eastern equatorial Pacific region with drilling and logging results from two Integrated Ocean Drilling Program (IODP) sites, the Pacific Equatorial Age Transect (PEAT) 7 (Site U1337) and 8 (Site U1338), to characterize sediment transportation regimes on 18-24 Ma oceanic crust. Site U1337, constructed by a series of distinct abyssal hills and abyssal basins; Site U1338, located 570 km SE from Site U1337 site and constructed by a series of ridges, seamounts, and abyssal hills. These sites are of particular interest due to their proximity to the equatorial productivity zone, areas with high sedimentation rates and preservation of carbonate-bearing sediment that provide invaluable insights on equatorial Pacific ecosystems and carbon cycle. We integrate downhole geophysical logging data as well as geochemistry and physical properties measurements on recovered cores from IODP Sites U1337 and U1338 to comprehensively examine the mobility of deep-sea sediments and sediment diagenesis over times in a quasi-3D manner. We also examine 1100 km of high resolution underway seismic surveys from site survey lines in between PEAT 7 and 8 in order to investigate changes in sediment transportation between both sites. Integrating detailed seismic interpretations, high resolution core data, and 230Th flux measurements we aim to create a detailed chronological sedimentation and sediment diagenesis history

  15. High current pelletron for ion implantation

    International Nuclear Information System (INIS)

    Schroeder, J.B.

    1989-01-01

    Since 1984, when the first production MeV ion implanter (an NEC model MV-T30) went on-line, interest in versatile electrostatic accelerator systems for MeV ion implantation has grown. The systems use a negative ion source to inject a tandem megavolt accelerator. In early systems the 0.4 mA of charging current from the two Pelletron charging chains in the accelerator was sufficient for the low intensity of beams from the ion source. This 2-chain system, however, is no longer adequate for the much higher beam intensities from today's improved ion sources. A 4-chain charging system, which delivers 1.3 mA to the high voltage terminal, was developed and is in operation in new models of NEC S Series Pelletron accelerators. This paper describes the latest beam performance of 1 MV and 1.7 MW Pelletron accelerators with this new 4-chain charging system. (orig.)

  16. Nonlinear bounce resonances between magnetosonic waves and equatorially mirroring electrons

    Science.gov (United States)

    Chen, Lunjin; Maldonado, Armando; Bortnik, Jacob; Thorne, Richard M.; Li, Jinxing; Dai, Lei; Zhan, Xiaoya

    2015-08-01

    Equatorially mirroring energetic electrons pose an interesting scientific problem, since they generally cannot resonate with any known plasma waves and hence cannot be scattered down to lower pitch angles. Observationally it is well known that the flux of these equatorial particles does not simply continue to build up indefinitely, and so a mechanism must necessarily exist that transports these particles from an equatorial pitch angle of 90° down to lower values. However, this mechanism has not been uniquely identified yet. Here we investigate the mechanism of bounce resonance with equatorial noise (or fast magnetosonic waves). A test particle simulation is used to examine the effects of monochromatic magnetosonic waves on the equatorially mirroring energetic electrons, with a special interest in characterizing the effectiveness of bounce resonances. Our analysis shows that bounce resonances can occur at the first three harmonics of the bounce frequency (nωb, n = 1, 2, and 3) and can effectively reduce the equatorial pitch angle to values where resonant scattering by whistler mode waves becomes possible. We demonstrate that the nature of bounce resonance is nonlinear, and we propose a nonlinear oscillation model for characterizing bounce resonances using two key parameters, effective wave amplitude à and normalized wave number k~z. The threshold for higher harmonic resonance is more strict, favoring higher à and k~z, and the change in equatorial pitch angle is strongly controlled by k~z. We also investigate the dependence of bounce resonance effects on various physical parameters, including wave amplitude, frequency, wave normal angle and initial phase, plasma density, and electron energy. It is found that the effect of bounce resonance is sensitive to the wave normal angle. We suggest that the bounce resonant interaction might lead to an observed pitch angle distribution with a minimum at 90°.

  17. Ocean Color and the Equatorial Annual Cycle in the Pacific

    Science.gov (United States)

    Hammann, A. C.; Gnanadesikan, A.

    2012-12-01

    The presence of chlorophyll, colored dissolved organic matter (CDOM) and other scatterers in ocean surface waters affect the flux divergence of solar radiation and thus the vertical distribution of radiant heating of the ocean. While this may directly alter the local mixed-layer depth and temperature (Martin 1985; Strutton & Chavez 2004), non-local changes are propagated through advection (Manizza et al. 2005; Murtugudde et al. 2002; Nakamoto et al. 2001; Sweeny et al. 2005). In and coupled feedbacks (Lengaigne et al. 2007; Marzeion & Timmermann 2005). Anderson et al. (2007), Anderson et al. (2009) and Gnanadesikan & Anderson (2009) have performed a series of experiments with a fully coupled climate model which parameterizes the e-folding depth of solar irradiance in terms of surface chlorophyll-a concentration. The results have so far been discussed with respect to the climatic mean state and ENSO variability in the tropical Pacific. We extend the discussion here to the Pacific equatorial annual cycle. The focus of the coupled experiments has been the sensitivity of the coupled system to regional differences in chlorophyll concentration. While runs have been completed with realistic SeaWiFS-derived monthly composite chlorophyll ('green') and with a globally chlorophyll-free ocean ('blue'), the concentrations in two additional runs have been selectively set to zero in specific regions: the oligotrophic subtropical gyres ('gyre') in one case and the mesotrophic gyre margins ('margin') in the other. The annual cycle of ocean temperatures exhibits distinctly reduced amplitudes in the 'blue' and 'margin' experiments, and a slight reduction in 'gyre' (while ENSO variability almost vanishes in 'blue' and 'gyre', but amplifies in 'margin' - thus the frequently quoted inverse correlation between ENSO and annual amplitudes holds only for the 'green' / 'margin' comparison). It is well-known that on annual time scales, the anomalous divergence of surface currents and vertical

  18. Seasonal influence of ENSO on the Atlantic ITCZ and equatorial South America

    Science.gov (United States)

    Münnich, M.; Neelin, J. D.

    2005-11-01

    In late boreal spring, especially May, a strong relationship exists in observations among precipitation anomalies over equatorial South America and the Atlantic intertropical convergence zone (ITCZ), and eastern equatorial Pacific and central equatorial Atlantic sea surface temperature anomalies (SSTA). A chain of correlations of equatorial Pacific SSTA, western equatorial Atlantic wind stress (WEA), equatorial Atlantic SSTA, sea surface height, and precipitation supports a causal chain in which El Niño/Southern Oscillation (ENSO) induces WEA stress anomalies, which in turn affect Atlantic equatorial ocean dynamics. These correlations show strong seasonality, apparently arising within the atmospheric links of the chain. This pathway and the influence of equatorial Atlantic SSTA on South American rainfall in May appear independent of that of the northern tropical Atlantic. Brazil's Nordeste is affected by the northern tropical Atlantic. The equatorial influence lies further to the north over the eastern Amazon and the Guiana Highlands.

  19. Magnetospheric conditions near the equatorial footpoints of proton isotropy boundaries

    Directory of Open Access Journals (Sweden)

    V. A. Sergeev

    2015-12-01

    Full Text Available Data from a cluster of three THEMIS (Time History of Events and Macroscale Interactions during Substorms spacecraft during February–March 2009 frequently provide an opportunity to construct local data-adaptive magnetospheric models, which are suitable for the accurate mapping along the magnetic field lines at distances of 6–9 Re in the nightside magnetosphere. This allows us to map the isotropy boundaries (IBs of 30 and 80 keV protons observed by low-altitude NOAA POES (Polar Orbiting Environmental Satellites to the equatorial magnetosphere (to find the projected isotropy boundary, PIB and study the magnetospheric conditions, particularly to evaluate the ratio KIB (Rc/rc; the magnetic field curvature radius to the particle gyroradius in the neutral sheet at that point. Special care is taken to control the factors which influence the accuracy of the adaptive models and mapping. Data indicate that better accuracy of an adaptive model is achieved when the PIB distance from the closest spacecraft is as small as 1–2 Re. For this group of most accurate predictions, the spread of KIB values is still large (from 4 to 32, with the median value KIB ~13 being larger than the critical value Kcr ~ 8 expected at the inner boundary of nonadiabatic angular scattering in the current sheet. It appears that two different mechanisms may contribute to form the isotropy boundary. The group with K ~ [4,12] is most likely formed by current sheet scattering, whereas the group having KIB ~ [12,32] could be formed by the resonant scattering of low-energy protons by the electromagnetic ion-cyclotron (EMIC waves. The energy dependence of the upper K limit and close proximity of the latter event to the plasmapause locations support this conclusion. We also discuss other reasons why the K ~ 8 criterion for isotropization may fail to work, as well as a possible relationship between the two scattering mechanisms.

  20. Effect of geomagnetic storm conditions on the equatorial ionization anomaly and equatorial temperature anomaly

    Science.gov (United States)

    Bharti, Gaurav; Bag, T.; Sunil Krishna, M. V.

    2018-03-01

    The effect of the geomagnetic storm on the equatorial ionization anomaly (EIA) and equatorial temperature anomaly (ETA) has been studied using the atomic oxygen dayglow emissions at 577.7 nm (OI 557.7 nm) and 732.0 nm (OII 732.0 nm). For the purpose of this study, four intense geomagnetic storms during the ascending phase of solar cycle 24 have been considered. This study is primarily based on the results obtained using photochemical models with necessary inputs from theoretical studies and experimental observations. The latest reaction rate coefficients, quantum yields and the corresponding cross-sections have also been incorporated in these models. The volume emission rate of airglow emissions has been calculated using the neutral densities from NRLMSISE-00 and charged densities from IRI-2012 model. The modeled volume emission rate (VER) for OI 557.7 nm shows a positive correlation with the Dst index at 150 km and negative correlation with Dst at 250 and 280 km altitudes. Latitudinal profile of the greenline emission rate at different altitudes show a distinct behaviour similar to what has been observed in EIA with crests on either sides of the equator. The EIA crests are found to show poleward movement in the higher altitude regions. The volume emission rate of 732.0 nm emission shows a strong enhancement during the main phase of the storm. The changes observed in the airglow emission rates are explained with the help of variations induced in neutral densities and parameters related to EIA and ETA. The latitudinal variation of 732.0 nm emission rate is correlated to the variability in EIA during the storm period.

  1. High-current beam transport in electrostatic accelerator tubes

    International Nuclear Information System (INIS)

    Ramian, G.; Elais, L.

    1987-01-01

    The UCSB Free Electron Laser (FEL) has successfully demonstrated the use of a commercial 6 megavolt electrostatic accelerator as a high current beam source in a recirculating configuration. The accelerator, manufactured by National Electrostatics Corp. (NEC), Middleton WI, uses two standard high gradient accelerator tubes. Suppression of ion multiplication was accomplished by NEC with apertures and a shaped electrostatic field. This field shaping has fortuitously provided a periodically reversing radial field component with sufficient focusing strength to transport electron beams of up to 3 Amps current. Present two-stage FEL work requires a 20 Amp beam and proposed very high voltage FEL designs require currents as high as 100 Amps. A plan to permit transport of such high current beams by the addition of solenoidal focussing elements is described

  2. Trophic Diversity of Plankton in the Epipelagic and Mesopelagic Layers of the Tropical and Equatorial Atlantic Determined with Stable Isotopes

    Directory of Open Access Journals (Sweden)

    Antonio Bode

    2018-06-01

    Full Text Available Plankton living in the deep ocean either migrate to the surface to feed or feed in situ on other organisms and detritus. Planktonic communities in the upper 800 m of the tropical and equatorial Atlantic were studied using the natural abundance of stable carbon and nitrogen isotopes to identify their food sources and trophic diversity. Seston and zooplankton (>200 µm samples were collected with Niskin bottles and MOCNESS nets, respectively, in the epipelagic (0–200 m, upper mesopelagic (200–500 m, and lower mesopelagic layers (500–800 m at 11 stations. Food sources for plankton in the productive zone influenced by the NW African upwelling and the Canary Current were different from those in the oligotrophic tropical and equatorial zones. In the latter, zooplankton collected during the night in the mesopelagic layers was enriched in heavy nitrogen isotopes relative to day samples, supporting the active migration of organisms from deep layers. Isotopic niches showed also zonal differences in size (largest in the north, mean trophic diversity (largest in the tropical zone, food sources, and the number of trophic levels (largest in the equatorial zone. The observed changes in niche size and overlap (up to 71% between the mesopelagic layers but <50% between the epipelagic and upper mesopelagic layers support the prevalence of in situ feeding at deep layers in tropical and equatorial zooplankton.

  3. Space Weather Research in the Equatorial Region: A Philosophical Reinforcement

    Science.gov (United States)

    Chukwuma, Victor; Odunaike, Rasaki; Laoye, John

    Investigations using radio waves reflected from the ionosphere, at high-and mid-latitudes indicate that ionospheric absorption can strongly increase following geomagnetic storms; which appears to suggest some definite relationship between ionospheric radio wave absorption and geomagnetic storms at these latitudes. However, corresponding earlier studies in the equatorial region did not appear to show any explicit relationship between ionospheric radio wave absorption and geomagnetic storm activity. This position appeared acceptable to the existing scientific paradigm, until in an act of paradigm shift, by a change of storm selection criteria, some more recent space weather investigations in the low latitudes showed that ionospheric radio wave absorption in the equatorial region clearly increases after intense storms. Given that these results in the equatorial region stood against the earlier results, this paper presently attempts to highlight their philosophical underpinning and posit that they constitute a scientific statement.

  4. Occurrence of Equatorial Plasma Bubbles during Intense Magnetic Storms

    Directory of Open Access Journals (Sweden)

    Chao-Song Huang

    2011-01-01

    Full Text Available An important issue in low-latitude ionospheric space weather is how magnetic storms affect the generation of equatorial plasma bubbles. In this study, we present the measurements of the ion density and velocity in the evening equatorial ionosphere by the Defense Meteorological Satellite Program (DMSP satellites during 22 intense magnetic storms. The DMSP measurements show that deep ion density depletions (plasma bubbles are generated after the interplanetary magnetic field (IMF turns southward. The time delay between the IMF southward turning and the first DMSP detection of plasma depletions decreases with the minimum value of the IMF Bz, the maximum value of the interplanetary electric field (IEF Ey, and the magnitude of the Dst index. The results of this study provide strong evidence that penetration electric field associated with southward IMF during the main phase of magnetic storms increases the generation of equatorial plasma bubbles in the evening sector.

  5. Molecular characterization of Cryptosporidium isolates from humans in Equatorial Guinea.

    Science.gov (United States)

    Blanco, María Alejandra; Iborra, Asunción; Vargas, Antonio; Nsie, Eugenia; Mbá, Luciano; Fuentes, Isabel

    2009-12-01

    The aim of the study was to perform a molecular characterization of clinical isolates of Cryptosporidium species from Equatorial Guinea. Standard laboratory methods were used to identify 35 cryptosporidiosis cases among 185 patients. PCR-RFLP successfully identified 34 Cryptosporidium species from these 35 cases, comprising C. parvum (52.9%), C. hominis (44.1%) and C. meleagridis (2.9%); over 90% of the species were isolated from HIV-positive patients. This is the first report of the molecular characterization of Cryptosporidium species isolated from humans in Equatorial Guinea and shows that zoonotic and anthroponotic transmission is present in this country.

  6. Longitudinal Variation and Waves in Jupiter's South Equatorial Wind Jet

    Science.gov (United States)

    Simon-Miller, A. A.; Rogers, John H.; Gierasch, Peter J.; Choi, David; Allison, Michael; Adamoli, Gianluigi; Mettig, Hans-Joerg

    2012-01-01

    We have conducted a detailed study of the cloud features in the strong southern equatorial wind jet near 7.5 S planetographic latitude. To understand the apparent variations in average zonal wind jet velocity at this latitude [e.g.. 1,2,3], we have searched for variations iIi both feature latitude and velocity with longitude and time. In particular, we focused on the repetitive chevron-shaped dark spots visible on most dates and the more transient large anticyclonic system known as the South Equatorial Disturbance (SED). These small dark spots are interpreted as cloud holes, and are often used as material tracers of the wind field.

  7. Blow-up of solutions to the rotation b-family system modeling equatorial water waves

    Directory of Open Access Journals (Sweden)

    Min Zhu

    2018-03-01

    Full Text Available We consider the blow-up mechanism to the periodic generalized rotation b-family system (R-b-family system. This model can be derived from the f-plane governing equations for the geographical water waves with a constant underlying current in the equatorial water waves with effect of the Coriolis force. When b=2, it is a rotation two-component Camassa-Holm (R2CH system. We consider the periodic R2CH system when linear dispersion is absent (which model is called r2CH system and derive two finite-time blow-up results.

  8. Coral settlement on a highly disturbed equatorial reef system.

    Science.gov (United States)

    Bauman, Andrew G; Guest, James R; Dunshea, Glenn; Low, Jeffery; Todd, Peter A; Steinberg, Peter D

    2015-01-01

    Processes occurring early in the life stages of corals can greatly influence the demography of coral populations, and successful settlement of coral larvae that leads to recruitment is a critical life history stage for coral reef ecosystems. Although corals in Singapore persist in one the world's most anthropogenically impacted reef systems, our understanding of the role of coral settlement in the persistence of coral communities in Singapore remains limited. Spatial and temporal patterns of coral settlement were examined at 7 sites in the southern islands of Singapore, using settlement tiles deployed and collected every 3 months from 2011 to 2013. Settlement occurred year round, but varied significantly across time and space. Annual coral settlement was low (~54.72 spat m(-2) yr(-1)) relative to other equatorial regions, but there was evidence of temporal variation in settlement rates. Peak settlement occurred between March-May and September-November, coinciding with annual coral spawning periods (March-April and October), while the lowest settlement occurred from December-February during the northeast monsoon. A period of high settlement was also observed between June and August in the first year (2011/12), possibly due to some species spawning outside predicted spawning periods, larvae settling from other locations or extended larval settlement competency periods. Settlement rates varied significantly among sites, but spatial variation was relatively consistent between years, suggesting the strong effects of local coral assemblages or environmental conditions. Pocilloporidae were the most abundant coral spat (83.6%), while Poritidae comprised only 6% of the spat, and Acroporidae coral spat. These results indicate that current settlement patterns are reinforcing the local adult assemblage structure ('others'; i.e. sediment-tolerant coral taxa) in Singapore, but that the replenishment capacity of Singapore's reefs appears relatively constrained, which could lead

  9. An estimate of equatorial wave energy flux at 9- to 90-day periods in the Central Pacific

    Science.gov (United States)

    Eriksen, Charles C.; Richman, James G.

    1988-01-01

    Deep fluctuations in current along the equator in the Central Pacific are dominated by coherent structures which correspond closely to narrow-band propagating equatorial waves. Currents were measured roughly at 1500 and 3000 m depths at five moorings between 144 and 148 deg W from January 1981 to March 1983, as part of the Pacific Equatorial Ocean Dynamics program. In each frequency band resolved, a single complex empirical orthogonal function accounts for half to three quarters of the observed variance in either zonal or meridional current. Dispersion for equatorial first meridional Rossby and Rossby gravity waves is consistent with the observed vertical-zonal coherence structure. The observations indicate that energy flux is westward and downward in long first meridional mode Rossby waves at periods 45 days and longer, and eastward and downward in short first meridional mode Rossby waves and Rossby-gravity waves at periods 30 days and shorter. A local minimum in energy flux occurs at periods corresponding to a maximum in upper-ocean meridional current energy contributed by tropical instability waves. Total vertical flux across the 9- to 90-day period range is 2.5 kW/m.

  10. Ocean dynamics, not dust, have controlled equatorial Pacific productivity over the past 500,000 years

    OpenAIRE

    Winckler, Gisela; Anderson, Robert F.; Jaccard, Samuel L.; Marcantonio, Franco

    2016-01-01

    Biological productivity in the equatorial Pacific is relatively high compared with other low latitude regimes especially east of the dateline where divergence driven by the trade winds brings nutrient rich waters of the Equatorial Undercurrent to the surface. The equatorial Pacific is one of the three principal high nutrient low chlorophyll ocean regimes where biological utilization of nitrate and phosphate is limited in part by the availability of iron. Throughout most of the equatorial Paci...

  11. Iron sources and pathways into the Pacific Equatorial Undercurrent

    NARCIS (Netherlands)

    Qin, Xuerong; Menviel, Laurie; Sen Gupta, Alex; van Sebille, Erik

    2016-01-01

    Using a novel observationally constrained Lagrangian iron model forced by outputs from an eddy-resolving biogeochemical ocean model, we examine the sensitivity of the Equatorial Undercurrent (EUC) iron distribution to EUC source region iron concentrations. We find that elevated iron concentrations

  12. Equatorial electrojet in the Indian region during the geomagnetic ...

    Indian Academy of Sciences (India)

    1998-11-14

    Nov 14, 1998 ... In the recovery phase of the storm, the electric field due to shielding layer penetrates to equatorial latitudes as an overshielding electric field with opposite polarity, westward during day- side and eastward during night side (Kelley et al. 1979). In addition to the prompt penetration elec- tric fields, there are ...

  13. Climate regulation of fire emissions and deforestation in equatorial Asia

    NARCIS (Netherlands)

    van der Werf, G. R.; Dempewolf, J.; Trigg, S. N.; Randerson, J. T.; Kasibhatla, P. S.; Giglio, L.; Murdiyarso, D.; Peters, W.; Morton, D. C.; Collatz, G. J.; Dolman, A. J.; Defries, R. S.

    2008-01-01

    Drainage of peatlands and deforestation have led to large-scale fires in equatorial Asia, affecting regional air quality and global concentrations of greenhouse gases. Here we used several sources of satellite data with biogeochemical and atmospheric modeling to better understand and constrain fire

  14. Backscatter measurements of 11-cm equatorial spread-F irregularities

    International Nuclear Information System (INIS)

    Tsunoda, R.T.

    1980-01-01

    In the equatorial F-region ionosphere, a turbulent cascade process has been found to exist that extends from irregularity spatial wavelengths longer than tens of kilometers down to wavelengths as short as 36 cm. To investigate the small-scale regime of wavelengths less than 36 cm, an equatorial radar experiment was conducted using a frequency of 1320 MHz that corresponds to an irregularity wavelength of 11 cm. The first observations of radar backscatter from 11-cm field-aligned irregularities (FAI) are described. These measurements extend the spatial wavelength regime of F-region FAI to lengths that approach both electron gyroradius and the Debye length. Agreement of these results with the theory of high-frequency drift waves suggests that these observations may be unique to the equatorial ionosphere. That is, the requirement of low electron densities for which the theroy calls may preclude the existence of 11-cm FAI elsewhere in the F-region ionosphere, except in equatorial plasma bubbles

  15. Characterisation of tectonic lineaments in the Central Equatorial ...

    African Journals Online (AJOL)

    Characterisation of tectonic lineaments in the Central Equatorial Atlantic region of Africa using Bouguer anomaly gravity data. ... Ife Journal of Science ... 3-D standard Euler deconvolution analysis was carried out on Bouguer anomaly gravity data for configuration definition and approximate depth estimate of tectonic ...

  16. Planktonic foraminifera from core tops of western equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.; Guptha, M.V.S.

    distributional pattern showing upward trend in its abundance from 38 per cent at 21 degrees S latitude to 0.8 per cent at 6 degrees N latitude. Sub-tropical fauna is sparsely distributed in the Equatorial Indian Ocean. Based on these studies it is interpreted...

  17. equatorial electrojet strength in the african sector during high

    African Journals Online (AJOL)

    Preferred Customer

    shown to be consistent with the earlier similar work carried out for the American and ... reference to the quiet day night time level of H, ... February and July, and shifts equator ward to 27°N ... effect of the equatorial electrojet along this line is.

  18. Post-midnight occurrence of equatorial plasma bubbles

    Science.gov (United States)

    Ajith, K. K.; Otsuka, Yuichi; Yamamoto, Mamoru; Yokoyama, Tatsuhiro; Tulasiram, S.

    2016-07-01

    The equatorial plasma bubbles (EPBs)/equatorial spread F (ESF) irregularities are an important topic of space weather interest because of their impact on transionospheric radio communications, satellite-based navigation and augmentation systems. This local plasma depleted structures develop at the bottom side F layer through Rayleigh-Taylor instability and rapidly grow to topside ionosphere via polarization electric fields within them. The steep vertical gradients due to quick loss of bottom side ionization and rapid uplift of equatorial F layer via prereversal enhancement (PRE) of zonal electric field makes the post-sunset hours as the most preferred local time for the formation of EPBs. However, there is a different class of irregularities that occurs during the post-midnight hours of June solstice reported by the previous studies. The occurrence of these post-midnight EPBs maximize during the low solar activity periods. The growth characteristics and the responsible mechanism for the formation of these post-midnight EPBs are not yet understood. Using the rapid beam steering ability of 47 MHz Equatorial Atmosphere Radar (EAR) at Kototabang (0.2°S geographic latitude, 100.3°E geographic longitude, and 10.4°S geomagnetic latitude), Indonesia, the spatial and temporal evolution of equatorial plasma bubbles (EPBs) were examined to classify the evolutionary-type EPBs from those which formed elsewhere and drifted into the field of view of radar. The responsible mechanism for the genesis of summer time post-midnight EPBs were discussed in light of growth rate of Rayleigh-Taylor instability using SAMI2 model.

  19. The response of the equatorial Pacific Ocean to a westerly wind burst in May 1986

    Science.gov (United States)

    McPhaden, Michael J.; Freitag, H. Paul; Hayes, Stanley P.; Taft, Bruce A.; Chen, Zeshi; Wyrtki, Klaus

    1988-09-01

    Western Pacific westerly wind bursts of 1- to 3-week duration are potentially important in triggering and sustaining El Niño-Southern Oscillation events. One such burst of 10-day duration and maximum speeds of greater than 10 m s-1 occurred in May 1986 west of the date line. The response to this westerly wind burst is documented from equatorial current meter moorings, thermistor chain moorings, and sea level and hydrographic data. At 0°, 165°E in the western Pacific the thermocline was depressed by 25 m, sea surface temperature dropped by 0.3°-0.4°C, and sea level rose by 10-15 cm a few days after the maximum in westerly wind speed. Likewise, the South Equatorial Current rapidly accelerated eastward and attained speeds in excess of 100 cm s-1. Vertical shear in an approximately 100 m deep surface layer reversed within a few days of the winds, consistent with a simple model of equatorial mixed layer dynamics in which vertical eddy viscosities are inferred to be O(100 cm2 s-1). A sharp Kelvin wavelike pulse in sea level propagated out of the directly forced region into the central and eastern Pacific. The pulse took 45 days to travel from Tarawa (1°N, 173°E) to La Libertad (2°S, 81°W) on the South American coast, at an average phase speed of about 300 cm s-1. This is of the same order of magnitude as, but significantly higher than, the phase speed of a first baroclinic mode Kelvin wave and is probably the result of Doppler shifting by the Equatorial Undercurrent. A rise in sea surface temperature of about 1°C in 2 days occurred at 0°N, 110°W with the passage of the pulse. However, coincidental meridional advection of a sharp sea surface temperature front, rather than zonal advection of downwelling associated with the pulse, appears to be responsible for this warming. The relevance of this wind-forced pulse to the subsequent evolution of the 1986-1987 El Niño-Southern Oscillation event is discussed in the light of these observations.

  20. Rocket studies of plasma turbulence in the equatorial and auroral electrojets

    International Nuclear Information System (INIS)

    Pfaff, R.F. Jr.

    1986-01-01

    Rocket observations of plasma turbulence in the equatorial and auroral electrojets have been studied in detail. Intense electric field and plasma density fluctuations characterize the collisional two-stream and gradient drift instabilities, showing a marked spectral differentiation with respect to height consistent with changes in the local sources of free energy. The interpretation of the frequencies and amplitudes of irregularities detected by in-situ probes travelling at comparable speeds to the waves is discussed in detail. Observations from three rockets in the daytime equatorial electrojet during strong, mild, and weak currents show that the linear theory accounts for the general height and wavelength domains of the irregularities. In the strong case, laminar two-stream waves were observed where the current was strongest and the density gradient was stable. The data suggest phase velocities that were comparable to the electron drift velocity (∼500 m/s) and peak wavelengths (2-3 m) that agree with kinetic theory. Vertically propagating waves observed here may have been generated by mode coupling. Where the gradient was unstable, large amplitude, kilometer scale waves dominated, although the linear gradient drift growth rate peaks at a few hundred meters. The amplitudes (10-15 mV/m) of these horizontal waves were strong enough to drive vertical two-stream waves

  1. Variabilities of mesospheric tides and equatorial electrojet strength during major stratospheric warming events

    Directory of Open Access Journals (Sweden)

    S. Sridharan

    2009-11-01

    Full Text Available The present study demonstrates the relationship between the high latitude northern hemispheric major sudden stratospheric warming (SSW events and the reversal in the afternoon equatorial electrojet (EEJ, often called the counter-electrojet (CEJ, during the winter months of 1998–1999, 2001–2002, 2003–2004 and 2005–2006. As the EEJ current system is driven by tidal winds, an investigation of tidal variabilities in the MF radar observed zonal winds during the winters of 1998–1999 and 2005–2006 at 88 km over Tirunelveli, a site close to the magnetic equator, shows that there is an enhancement of semi-diurnal tidal amplitude during the days of a major SSW event and a suppression of the same immediately after the event. The significance of the present results lies in demonstrating the latitudinal coupling between the high latitude SSW phenomenon and the equatorial ionospheric current system with clear evidence for major SSW events influencing the day-to-day variability of the CEJ.

  2. Instabilities of continuously stratified zonal equatorial jets in a periodic channel model

    Directory of Open Access Journals (Sweden)

    S. Masina

    2002-05-01

    Full Text Available Several numerical experiments are performed in a nonlinear, multi-level periodic channel model centered on the equator with different zonally uniform background flows which resemble the South Equatorial Current (SEC. Analysis of the simulations focuses on identifying stability criteria for a continuously stratified fluid near the equator. A 90 m deep frontal layer is required to destabilize a zonally uniform, 10° wide, westward surface jet that is symmetric about the equator and has a maximum velocity of 100 cm/s. In this case, the phase velocity of the excited unstable waves is very similar to the phase speed of the Tropical Instability Waves (TIWs observed in the eastern Pacific Ocean. The vertical scale of the baroclinic waves corresponds to the frontal layer depth and their phase speed increases as the vertical shear of the jet is doubled. When the westward surface parabolic jet is made asymmetric about the equator, in order to simulate more realistically the structure of the SEC in the eastern Pacific, two kinds of instability are generated. The oscillations that grow north of the equator have a baroclinic nature, while those generated on and very close to the equator have a barotropic nature.  This study shows that the potential for baroclinic instability in the equatorial region can be as large as at mid-latitudes, if the tendency of isotherms to have a smaller slope for a given zonal velocity, when the Coriolis parameter vanishes, is compensated for by the wind effect.Key words. Oceanography: general (equatorial oceanography; numerical modeling – Oceanography: physics (fronts and jets

  3. Self-reported adherence to antiretroviral therapy in HIV+ population from Bata, Equatorial Guinea.

    Science.gov (United States)

    Salmanton-García, Jon; Herrador, Zaida; Ruiz-Seco, Pilar; Nzang-Esono, Jesús; Bendomo, Veronica; Bashmakovic, Emma; Nseng-Nchama, Gloria; Benito, Agustín; Aparicio, Pilar

    2016-01-01

    The human immunodeficiency virus (HIV) and the acquired immune deficiency syndrome (AIDS) represent a serious public health problem in Equatorial Guinea, with a prevalence of 6.2% among adults. the high-activity antiretroviral treatment (HAART) coverage data is 10 points below the overall estimate for Sub-Saharan Africa, and only 61% patients continue with HAART 12 months after it started. This study aims to assess HAART adherence and related factors in Litoral Province of Equatorial Guinea. In this cross-sectional study, socio-demographic and clinical data were collected at Regional Hospital of Bata, during June-July 2014. Adherence to treatment was assessed by using the Spanish version of CEAT-VIH. Bivariate and linear regression analyses were employed to assess HAART adherence-related factors. We interviewed 50 men (35.5%) and 91 women (64.5%), with a mean age of 47.7 ± 8.9 and 36.2 ± 11.2, respectively (p VIH score varied by ethnic group (p = .005). There was a positive correlation between CEAT-VIH score and current CD4 T-cells count (p = .013). The Cronbach's α value was 0.52. To our knowledge, this is the first study to assess HAART adherence in Equatorial Guinea. Internal reliability for CEAT-VIH was low, nonetheless the positive correlation between the CEAT-VIH score and the immunological status of patients add value to our findings. Our results serve as baseline for future research and will also assist stakeholders in planning and undertaking contextual and evidence-based policy initiatives.

  4. Instabilities of continuously stratified zonal equatorial jets in a periodic channel model

    Directory of Open Access Journals (Sweden)

    S. Masina

    Full Text Available Several numerical experiments are performed in a nonlinear, multi-level periodic channel model centered on the equator with different zonally uniform background flows which resemble the South Equatorial Current (SEC. Analysis of the simulations focuses on identifying stability criteria for a continuously stratified fluid near the equator. A 90 m deep frontal layer is required to destabilize a zonally uniform, 10° wide, westward surface jet that is symmetric about the equator and has a maximum velocity of 100 cm/s. In this case, the phase velocity of the excited unstable waves is very similar to the phase speed of the Tropical Instability Waves (TIWs observed in the eastern Pacific Ocean. The vertical scale of the baroclinic waves corresponds to the frontal layer depth and their phase speed increases as the vertical shear of the jet is doubled. When the westward surface parabolic jet is made asymmetric about the equator, in order to simulate more realistically the structure of the SEC in the eastern Pacific, two kinds of instability are generated. The oscillations that grow north of the equator have a baroclinic nature, while those generated on and very close to the equator have a barotropic nature. 

    This study shows that the potential for baroclinic instability in the equatorial region can be as large as at mid-latitudes, if the tendency of isotherms to have a smaller slope for a given zonal velocity, when the Coriolis parameter vanishes, is compensated for by the wind effect.

    Key words. Oceanography: general (equatorial oceanography; numerical modeling – Oceanography: physics (fronts and jets

  5. Particle reduction strategies - PAREST. Gridded European emission data for projection years 2010, 2015 and 2020 based on the IIASA GAINS NEC scenarios. Teilbericht

    Energy Technology Data Exchange (ETDEWEB)

    Gon, Hugo Denier van der; Visschedijk, Antoon; Brugh, Hans van den [TNO Earth, Environment and Life Sciences, Utrecht (Netherlands)

    2013-06-15

    Projected emissions for selected scenarios for the years 2010, 2015 and 2020 were obtained from the GAINS NEC scenario reports and distributed on a high resolution over Europe using the TNO gridding tools. These emission maps are available as model input in the PAREST project to model the contribution of Europe to air quality in Germany in 2010, 2015 and 2020 (see note Rainer Stern, May 2009). The scenarios have a significant influence on absolute emission levels for the countries that were covered by IIASA GAINS. This suggests that emission changes in countries were no scenarios were available (Armenia, Azerbaijan, Georgia) or where only a projection year baseline is available (all non-EU) may be subject to significant changes as well (but these are quite far from Germany). For future projects it is recommended to make simple and transparent scenarios for these other countries, as well as for International Shipping. The change in emissions from the base year 2005 to the projection year 2010 needs to be interpreted with care. This because some methodology differences between 2005 official emission data as used in the PAREST base year 2005 emission set and GAINS 2010 data exist. It is expected that the emission reduction steps towards 2020 are more realistic.

  6. On the origin of pre-reversal enhancement of the zonal equatorial electric field

    Directory of Open Access Journals (Sweden)

    M. C. Kelley

    2009-05-01

    Full Text Available In November 2004, a large and variable interplanetary electric field (IEF was felt in the reference frame of the Earth. This electric field penetrated to the magnetic equator and, when the Jicamarca Radio Observatory (JRO was in the dusk sector, resulted in a reversal of the normal zonal component of the field. In turn, this caused a counter-electrojet (CEJ, a westward current rather than the usual eastward current. At the time of the normal pre-reversal enhancement (PRE of the eastward field, the Jicamarca incoherent scatter radar (ISR observed that the westward component became even more westward. Two of the three current explanations for the PRE depend on the neutral wind patterns. However, this unique event was such that the neutral wind-driven dynamos could not have changed. The implication is that the Haerendel-Eccles mechanism, which involves partial closure of the equatorial electrojet (EEJ after sunset, must be the dominant mechanism for the PRE.

  7. The Equatorial Scintillations and Space Weather Effects on its Generation during Geomagnetic Storms

    Science.gov (United States)

    Biktash, Lilia

    Great diversity of the ionospheric phenomena leads to a variety of irregularity types with spatial size from many thousands of kilometers to few centimeters and lifetimes from days to fractions of second. Since the ionosphere strongly influences the propagation of radio waves, signal distortions caused by these irregularities affect short-wave transmissions on Earth, transiono-spheric satellite communications and navigation. In this work the solar wind and the equatorial ionosphere parameters, Kp, Dst, AU, AL indices characterized contribution of different mag-netospheric and ionospheric currents to the H-component of geomagnetic field are examined to test the space weather effect on the generation of ionospheric irregularities producing VLF scintillations. According to the results of the current statistical studies, one can predict scintil-lations from Aarons' criteria using the Dst index, which mainly depicts the magnetospheric ring current field. To amplify Aarons' criteria or to propose new criteria for predicting scintillation characteristics is the question. In the present phase of the experimental investigations of elec-tron density irregularities in the ionosphere new ways are opened up because observations in the interaction between the solar wind -magnetosphere -ionosphere during magnetic storms have progressed greatly. We have examined scintillation relation to magnetospheric and ionospheric currents and show that the factor, which presents during magnetic storms to fully inhibit scin-tillation, is the positive Bz-component of the IMF. During the positive Bz IMF F layer cannot raise altitude where scintillations are formed. The auroral indices and Kp do better for the prediction of the ionospheric scintillations at the equator. The interplanetary magnetic field data and models can be used to explain the relationship between the equatorial ionospheric parameters, h'F, foF2, and the equatorial geomagnetic variations with the polar ionosphere cur-rents and

  8. Global mode of Pi2 waves in the equatorial region

    International Nuclear Information System (INIS)

    Kitamura, Tai-ichi; Saka, Ousuke; Shimoizumi, Masashi

    1988-01-01

    Fluxgate magnetometers with accurate timing data logger were set up at two equatorial stations (Garous-Marous and Huancayo), and also at a middle latitude station (Kuju). The phase of Pi2 waves is compared among these stations. It is found that 1) Pi2 pulsations in low and equatorial latitudes are linearly polarized approximately along the magnetic meridian, 2) phase difference of the H component of Pi2 waves at different stations is much less than 1 - 10 of the pulsation period despite a large longitudinal separation (∼ 90 deg) of the stations, showing the so-called azimuthal wave number, m, to be much less than unity and 3) phase difference of the D component at different stations is variable. (author)

  9. Ongoing Analysis of Jupiter's Equatorial Hotspots and Plumes from Cassini

    Science.gov (United States)

    Choi, D. S.; Showmwn, A. P.; Vasavada, A. R.; Simon-Miller, A. A.

    2012-01-01

    We present updated results from our ongoing analysis of Cassini observations of Jupiter's equatorial meteorology. For two months preceding the spacecraft's closest approach of the planet, the ISS instrument onboard Cassini regularly imaged the atmosphere of Jupiter. We created time-lapse movies from this period that show the complex activity and interactions of the equatorial atmosphere. During this period, hot spots exhibited significant variations in size and shape over timescales of days and weeks. Some of these changes appear to be a result of interactions with passing vortex systems in adjacent latitudes. Strong anticyclonic gyres to the southeast of the dark areas converge with flow from the west and appear to circulate into a hot spot at its southwestern corner.

  10. Bottomside sinusoidal irregularities in the equatorial F region

    Science.gov (United States)

    Valladares, C. E.; Hanson, W. B.; Mcclure, J. P.; Cragin, B. L.

    1983-01-01

    By using the Ogo 6 satellite, McClure and Hanson (1973) have discovered sinusoidal irregularities in the equatorial F region ion number density. In the present investigation, a description is provided of the properties of a distinct category of sinusoidal irregularities found in equatorial data from the AE-C and AE-E satellites. The observed scale sizes vary from about 300 m to 3 km in the direction perpendicular to B, overlapping with and extending the range observed by using Ogo 6. Attention is given to low and high resolution data, a comparison with Huancayo ionograms, the confinement of 'bottomside sinusoidal' (BSS) irregularities essentially to the bottomside of the F layer, spectral characteristics, and BSS, scintillation, and ionosonde observations.

  11. Equatorial enhancement of the nighttime OH mesospheric infrared airglow

    International Nuclear Information System (INIS)

    Baker, D J; Thurgood, B K; Harrison, W K; Mlynczak, M G; Russell, J M

    2007-01-01

    Global measurements of the hydroxyl mesospheric airglow over an extended period of time have been made possible by the NASA SABER infrared sensor aboard the TIMED satellite which has been functioning since December of 2001. The orbital mission has continued over a significant portion of a solar cycle. Experimental data from SABER for several years have exhibited equatorial enhancements of the nighttime mesospheric OH (Δv=2) airglow layer consistent with the high average diurnal solar flux. The brightening of the OH airglow typically means more H+O 3 is being reacted. At both the spring and autumn seasonal equinoxes when the equatorial solar UV irradiance mean is greatest, the peak volume emission rate (VER) of the nighttime Meinel infrared airglow typically appears to be both significantly brighter plus lower in altitude by several kilometres at low latitudes compared with midlatitude findings

  12. Saturn's equatorial jet structure from Cassini/ISS

    Science.gov (United States)

    García-Melendo, Enrique; Legarreta, Jon; Sánchez-Lavega, Agustín.; Pérez-Hoyos, Santiago; Hueso, Ricardo

    2010-05-01

    Detailed wind observations of the equatorial regions of the gaseous giant planets, Jupiter and Saturn, are crucial for understanding the basic problem of the global circulation and obtaining new detailed information on atmospheric phenomena. In this work we present high resolution data of Saturn's equatorial region wind profile from Cassini/ISS images. To retrieve wind measurements we applied an automatic cross correlator to image pairs taken by Cassini/ISS with the MT1, MT2, MT3 filters centred at the respective three methane absorbing bands of 619nm, 727nm, and 889nm, and with the adjacent continuum CB1, CB2, and CB3 filters. We obtained a complete high resolution coverage of Saturn's wind profile in the equatorial region. The equatorial jet displays an overall symmetric structure similar to that shown the by same region in Jupiter. This result suggests that, in accordance to some of the latest compressible atmosphere computer models, probably global winds in gaseous giants are deeply rooted in the molecular hydrogen layer. Wind profiles in the methane absorbing bands show the effect of strong vertical shear, ~40m/s per scale height, confirming previous results and an important decay in the wind intensity since the Voyager era (~100 m/s in the continuum and ~200 m/s in the methane absorbing band). We also report the discovery of a new feature, a very strong and narrow jet on the equator, about only 5 degrees wide, that despite the vertical shear maintains its intensity (~420 m/s) in both, the continuum and methane absorbing band filters. Acknowledgements: Work supported by the Spanish MICIIN AYA2009-10701 with FEDER and Grupos Gobierno Vasco IT-464-07.

  13. Meteorology of Jupiter's Equatorial Hot Spots and Plumes from Cassini

    Science.gov (United States)

    Choi, David Sanghun; Showman, Adam P.; Vasavada, Ashwin R.; Simon-Miller, Amy A.

    2013-01-01

    We present an updated analysis of Jupiter's equatorial meteorology from Cassini observations. For two months preceding the spacecraft's closest approach, the Imaging Science Subsystem (ISS) onboard regularly imaged the atmosphere. We created time-lapse movies from this period in order to analyze the dynamics of equatorial hot spots and their interactions with adjacent latitudes. Hot spots are relatively cloud-free regions that emit strongly at 5 lm; improved knowledge of these features is crucial for fully understanding Galileo probe measurements taken during its descent through one. Hot spots are quasistable, rectangular dark areas on visible-wavelength images, with defined eastern edges that sharply contrast with surrounding clouds, but diffuse western edges serving as nebulous boundaries with adjacent equatorial plumes. Hot spots exhibit significant variations in size and shape over timescales of days and weeks. Some of these changes correspond with passing vortex systems from adjacent latitudes interacting with hot spots. Strong anticyclonic gyres present to the south and southeast of the dark areas appear to circulate into hot spots. Impressive, bright white plumes occupy spaces in between hot spots. Compact cirrus-like 'scooter' clouds flow rapidly through the plumes before disappearing within the dark areas. These clouds travel at 150-200 m/s, much faster than the 100 m/s hot spot and plume drift speed. This raises the possibility that the scooter clouds may be more illustrative of the actual jet stream speed at these latitudes. Most previously published zonal wind profiles represent the drift speed of the hot spots at their latitude from pattern matching of the entire longitudinal image strip. If a downward branch of an equatorially-trapped Rossby wave controls the overall appearance of hot spots, however, the westward phase velocity of the wave leads to underestimates of the true jet stream speed.

  14. Equatorial noise emissions with quasiperiodic modulation of wave intensity

    Czech Academy of Sciences Publication Activity Database

    Němec, F.; Santolík, Ondřej; Hrbáčková, Zuzana; Pickett, J. S.; Cornilleau-Wehrlin, N.

    2015-01-01

    Roč. 120, č. 4 (2015), s. 2649-2661 ISSN 2169-9380 R&D Projects: GA MŠk(CZ) LH11122 Institutional support: RVO:68378289 Keywords : equatorial noise * magnetosonic waves * quasiperiodic modulation Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.318, year: 2015 http://onlinelibrary.wiley.com/doi/10.1002/2014JA020816/full

  15. Increases of equatorial total electron content (TEC) during magnetic storms

    International Nuclear Information System (INIS)

    Yeboah-Amankwah, D.

    1976-01-01

    This paper is a report on the analysis of equatorial electron content, TEC, during magnetic storms. Storms between 1969 and 1972 have been examined as part of an on-going study of TEC morphology during magnetically disturbed days. The published magnetic Ksup(p) indices and TEC data from the Legon abservatory have been employed. The general picture arising from the analysis is that the total electron content of the ionosphere is significantly enhanced during magnetic storms. (author)

  16. Electromagnetic analysis of ITER diagnostic equatorial port plugs during plasma disruptions

    International Nuclear Information System (INIS)

    Zhai, Y.; Feder, R.; Brooks, A.; Ulrickson, M.; Pitcher, C.S.; Loesser, G.D.

    2013-01-01

    Highlights: ► Disruption loads on ITER diagnostic equatorial port plugs are extracted. ► Upward major disruption produces the largest radial moment and radial force on diagnostic first walls and diagnostic shield modules. ► Large eddy currents on supporting rails, keys and water pipes are observed during disruption. -- Abstract: ITER diagnostic port plugs perform many functions including structural support of diagnostic systems under high electromagnetic loads while allowing for diagnostic access to the plasma. The design of diagnostic equatorial port plugs (EPP) are largely driven by electromagnetic loads and associate responses of EPP structure during plasma disruptions and VDEs. This paper summarizes results of transient electromagnetic analysis using Opera 3d in support of the design activities for ITER diagnostic EPP. A complete distribution of disruption loads on the diagnostic first walls (DFWs), diagnostic shield modules (DSMs) and the EPP structure, as well as impact on the system design integration due to electrical contact among various EPP structural components are discussed

  17. Reflection of equatorial Kelvin waves at eastern ocean boundaries Part II: Pacific and Atlantic Oceans

    Directory of Open Access Journals (Sweden)

    J. Soares

    1999-06-01

    Full Text Available The effect of viscosity, non linearities, incident wave period and realistic eastern coastline geometry on energy fluxes are investigated using a shallow water model with a spatial resolution of 1/4 degree in both meridional and zonal directions. Equatorial and mid-latitude responses are considered. It is found that (1 the influence of the coastline geometry and the incident wave period is more important for the westward energy flux than for the poleward flux, and (2 the effect of the inclination of the eastern ocean boundary on the poleward energy flux, for the Pacific and Atlantic Oceans, decline as the period of the incident wave increases. Furthermore, the model simulations suggest that the poleward energy fluxes from meridional boundaries give plausible results for motions of seasonal and annual periods. For comparatively shorter periods, a realistic coastline geometry has to be included for more accurate results. It is recommended that any numerical model involving the reflection of baroclinic Rossby waves (of intraseasonal, seasonal or annual periods on the eastern Pacific or Atlantic Oceans, should consider the effect of the coastline geometry in order to improve the accuracy of the results.Key words. Oceanography: general (climate and interannual variability; equatorial oceanography. Oceanography: physical (eastern boundary currents.

  18. Equatorial F region neutral winds and shears near sunset measured with chemical release techniques

    Science.gov (United States)

    Kiene, A.; Larsen, M. F.; Kudeki, E.

    2015-10-01

    The period near sunset is a dynamic and critical time for the daily development of the equatorial nighttime ionosphere and the instabilities that occur there. It is during these hours that the preconditions necessary for the later development of Equatorial Spread F (ESF) plasma instabilities occur. The neutral dynamics of the sunset ionosphere are also of critical importance to the generation of currents and electric fields; however, the behavior of the neutrals is experimentally understood primarily through very limited single-altitude measurements or measurements that provide weighted altitude means of the winds as a function of time. To date, there have been very few vertically resolved neutral wind measurements in the F region at sunset. We present two sets of sounding rocket chemical release measurements, one from a launch in the Marshall Islands on Kwajalein atoll and one from Alcantara, Brazil. Analysis of the release motions has yielded vertically resolved neutral wind profiles that show both the mean horizontal winds and the vertical shears in the winds. In both experiments, we observe significant vertical gradients in the zonal wind that are unexpected by classical assumptions about the behavior of the neutral wind at these altitudes at sunset near the geomagnetic equator.

  19. Letter to the editor: Electric field fluctuations (25-35 min in the midnight dip equatorial ionosphere

    Directory of Open Access Journals (Sweden)

    J. Hanumath Sastri

    2000-02-01

    Full Text Available Measurements with a HF Doppler sounder at Kodaikanal (10.2°N, 77.5°E, geomagnetic latitude 0.8°N showed conspicuous quasi-periodic fluctuations (period 25-35 min in F region vertical plasma drift, Vz in the interval 0047-0210 IST on the night of 23/24 December, 1991 (Ap = 14, Kp < 4-. The fluctuations in F region vertical drift are found to be coherent with variations in Bz (north-south component of interplanetary magnetic field (IMF, in geomagnetic H/X components at high-mid latitude locations both in the sunlit and dark hemispheres and near the dayside dip equator, suggestive of DP2 origin. But the polarity of the electric field fluctuations at the midnight dip equator (eastward is the same as the dayside equator inferred from magnetic variations, contrary to what is expected of equatorial DP2. The origin of the coherent occurrence of equatorial electric field fluctuations in the DP2 range of the same sign in the day and night hemispheres is unclear and merits further investigations.Key words: Ionosphere (electric fields and currents; equatorial ionosphere; ionosphere-magnetosphere interactions

  20. The magnetic field of the equatorial magnetotail - AMPTE/CCE observations at R less than 8.8 earth radii

    Science.gov (United States)

    Fairfield, D. H.; Acuna, M. H.; Zanetti, L. J.; Potemra, T. A.

    1987-01-01

    The MPTE/CCE magnetic field experiment has been used to obtain a quantitative evaluation of the frequency and extent of magnetic field distortion in the near-tail region at less than 8.8 earth radii. The variation of this distortion with Kp, radial distance, longitude, and near-equatorial latitude is reported. It has been found that taillike distortions from the dipole field direction may reach 80 deg near the MPTE/CE apogee of 8.8 earth radii. The Bz field component in dipole coordinates was always positive within 0.5 earth radii of the equatorial current sheet, indicating the neutral lines were never seen inside of 8.8 earth radii. Fields were most taillike near midnight and during times of high Kp. At 8.5 earth radii the equatorial field magnitude depressions were roughly half the dipole field strength of 51 nT. These depressions are larger at lesser distances, reaching -40 nT at 3.4 earth radii for Kp of 2- or less and -80 nT and Kp of 3+ and greater.

  1. Current meter components and other data from fixed platforms from TOGA Area - Pacific (30 N to 30 S) and other locations in support of the Tropical Ocean Global Atmosphere (TOGA) and the Equatorial Pacific Ocean Climate Studies (EPOCS) projects from 1989-04-16 to 1990-05-14 (NODC Accession 9200266)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter components data were collected from fixed platforms from the TOGA Area - Pacific (30 N to 30 S) and other locations from 16 April 1989 to 14 May 1990....

  2. Longitudinal Variation of the Lunar Tide in the Equatorial Electrojet

    Science.gov (United States)

    Yamazaki, Yosuke; Stolle, Claudia; Matzka, Jürgen; Siddiqui, Tarique A.; Lühr, Hermann; Alken, Patrick

    2017-12-01

    The atmospheric lunar tide is one known source of ionospheric variability. The subject received renewed attention as recent studies found a link between stratospheric sudden warmings and amplified lunar tidal perturbations in the equatorial ionosphere. There is increasing evidence from ground observations that the lunar tidal influence on the ionosphere depends on longitude. We use magnetic field measurements from the CHAMP satellite during July 2000 to September 2010 and from the two Swarm satellites during November 2013 to February 2017 to determine, for the first time, the complete seasonal-longitudinal climatology of the semidiurnal lunar tidal variation in the equatorial electrojet intensity. Significant longitudinal variability is found in the amplitude of the lunar tidal variation, while the longitudinal variability in the phase is small. The amplitude peaks in the Peruvian sector (˜285°E) during the Northern Hemisphere winter and equinoxes, and in the Brazilian sector (˜325°E) during the Northern Hemisphere summer. There are also local amplitude maxima at ˜55°E and ˜120°E. The longitudinal variation is partly due to the modulation of ionospheric conductivities by the inhomogeneous geomagnetic field. Another possible cause of the longitudinal variability is neutral wind forcing by nonmigrating lunar tides. A tidal spectrum analysis of the semidiurnal lunar tidal variation in the equatorial electrojet reveals the dominance of the westward propagating mode with zonal wave number 2 (SW2), with secondary contributions by westward propagating modes with zonal wave numbers 3 (SW3) and 4 (SW4). Eastward propagating waves are largely absent from the tidal spectrum. Further study will be required for the relative importance of ionospheric conductivities and nonmigrating lunar tides.

  3. New Measurements Of Jupiter's Equatorial Region In Visible Wavelengths

    Science.gov (United States)

    Rojas, Jose; Arregi, J.; García-Melendo, E.; Barrado-Izagirre, N.; Hueso, R.; Gómez-Forrellad, J. M.; Pérez-Hoyos, S.; Sanz-Requena, J. F.; Sánchez-Lavega, A.

    2010-10-01

    We have studied the equatorial region of Jupiter, between 15ºS and 15ºN, on Cassini ISS images obtained during the Jupiter flyby at the end of 2000 and on HST images acquired in May and July 2008. We have found significant longitudinal variations in the intensity of the 6ºN eastward jet, up to 60 m s-1 in Cassini and HST observations. In the HST case we found that these longitudinal variations are associated to different cloud morphology. Photometric and radiative transfer analysis of the cloud features used as tracers in HST images shows that there is only a small height difference, no larger than 0.5 - 1 scale heights at most, between the slow ( 100 m s-1) and fast ( 150 m s-1) moving features. This suggests that speed variability at 6ºN is not dominated by vertical wind shears and we propose that Rossby wave activity is the responsible for the zonal variability. After removing this variability we found that Jupiter's equatorial jet is actually symmetric relative to the equator with two peaks of 140 - 150 m s-1 located at latitudes 6ºN and 6ºS and at a similar pressure level. We also studied a large, long-lived feature called the White Spot (WS) located at 6ºS that turns to form and desapear. The internal flow field in the White Spot indicates that it is a weakly rotating quasi-equatorial anticyclone relative to the ambient meridionally sheared flow. Acknowledgements: This work was supported by the Spanish MICIIN AYA2009-10701 with FEDER and Grupos Gobierno Vasco IT-464-07.

  4. Discovery Of A Rossby Wave In Jupiter's South Equatorial Region

    Science.gov (United States)

    Simon-Miller, Amy A.; Choi, D. S.; Rogers, J. H.; Gierasch, P. J.

    2012-01-01

    A detailed study of the chevron-shaped dark spots on the strong southern equatorial wind jet near 7.5 deg S planetographic latitude shows variations in velocity with longitude and time. The chevrons move with velocities near the maximum wind jet velocity of approx.140 m/s, as deduced by the history of velocities at this latitude and the magnitude of the symmetric wind jet near 7 deg N latitude. Their repetitive nature is consistent with an inertia-gravity wave (n = 75-100) with phase speed up to 25 m/s, relative to the local flow, but the identity of this wave mode is not well constrained. However, high spatial resolution movies from Cassini images show that the chevrons oscillate in latitude with a approx.7-day period. This oscillating motion has a wavelength of approx.20 deg and a speed of approx.100 m/s, following a pattern similar to that seen in the Rossby wave plumes of the North Equatorial Zone, and possibly reinforced by it, though they are not perfectly in phase. The transient anticyclonic South Equatorial Disturbance (SED) may be a similar wave feature, but moves at slower velocity. All data show chevron latitude variability, but it is unclear if this Rossby wave is present during other epochs, without time series movies that fully delineate it. In the presence of multiple wave modes, the difference in dominant cloud appearance between 7 deg N and 7.5 deg S may be due to the presence of the Great Red Spot, either through changes in stratification and stability or by acting as a wave boundary.

  5. Regulation of primary productivity rate in the equatorial Pacific

    International Nuclear Information System (INIS)

    Barber, R.T.; Chavez, F.P.

    1991-01-01

    Analysis of the Chl-specific rate of primary productivity (P B ) as a function of subsurface nutrient concentration at >300 equatorial stations provides an answer to the question: What processes regulate primary productivity rate in the high-nutrient, low-chlorophyll waters of the equatorial Pacific? In the western Pacific where there is a gradient in 60-m [NO 3 ] from 0 to ∼12 μM, the productivity rate is a linear function of nutrient concentration; in the eastern Pacific where the gradient is from 12 to 28 μM, the productivity rate is independent of nutrient concentration and limited to ∼36 mg C(mg Chl) -1 d -1 , or a mean euphotic zone C-specific growth rate (μ) of 0.47 d -1 . However, rates downstream of the Galapagos Islands are not limited; they are 46.4 mg C(mg Chl) -1 d -1 and μ = 0.57 d -1 , very close to the predicted nutrient-regulated rates in the absence of other limitation. This pattern of rate regulation can be accounted for by a combination of eolian Fe, subsurface nutrients, and sedimentary Fe derived from the Galapagos platform. In the low-nutrient western Pacific the eolian supply of Fe is adequate to allow productivity rate to be set by subsurface nutrient concentration. In the nutrient-rich easter equatorial region eolian Fe is inadequate to support productivity rates proportional to the higher nutrient concentrations, so in this region eolian Fe is rate limiting. Around the Galapagos Islands productivity rates reach levels consistent with nutrient concentrations; sedimentary Fe from the Galapagos platform seems adequate to support increased nutrient-regulated productivity rates in this region

  6. Propagation of EMIC triggered emissions toward the magnetic equatorial plane

    Science.gov (United States)

    Grison, B.; Santolik, O.; Pickett, J. S.; Omura, Y.; Engebretson, M. J.; Dandouras, I. S.; Masson, A.; Decreau, P.; Cornilleau-Wehrlin, N.

    2011-12-01

    EMIC triggered emissions are observed close to the equatorial plane of the magnetosphere at locations where EMIC waves are commonly observed: close to the plasmapause region and in the dayside magnetosphere close to the magnetopause. Their overall characteristics (frequency with time dispersion, generation mechanism) make those waves the EMIC analogue of rising frequency whistler-mode chorus emissions. In our observations the Poynting flux of these emissions is usually clearly arriving from the equatorial region direction, especially when observations take place at more than 5 degrees of magnetic latitude. Simulations have also confirmed that the conditions of generation by interaction with energetic ions are at a maximum at the magnetic equator (lowest value of the background magnetic field along the field line). However in the Cluster case study presented here the Poynting flux of EMIC triggered emissions is propagating toward the equatorial region. The large angle between the wave vector and the background magnetic field is also unusual for this kind of emission. The rising tone starts just above half of the He+ gyrofrequency (Fhe+) and it disappears close to Fhe+. At the time of detection, the spacecraft magnetic latitude is larger than 10 degrees and L shell is about 4. The propagation sense of the emissions has been established using two independent methods: 1) sense of the parallel component of the Poynting flux for a single spacecraft and 2) timing of the emission detections at each of the four Cluster spacecraft which were in a relatively close configuration. We propose here to discuss this unexpected result considering a reflection of this emission at higher latitude.

  7. Equatorial storm sudden commencements and interplanetary magnetic field

    International Nuclear Information System (INIS)

    Rastogi, R.G.

    1980-01-01

    A comparison is made of the signatures of interplanetary (IP) shocks in the B and theta plots of interplanetary magnetic field (IMF) data of satellites Explorer 33, 34 and 35 and in the H magnetograms at ground observatories within the equatorial electrojet belt, Huancayo, Addis Ababa and Trivandrum associated with major storm sudden commencements during 1967-70. The IP shocks showing sudden increase of the scalar value of IMF, i.e. B without any change of the latitude theta or with the southward turning of theta, were followed by a purely positive sudden increase of H, at any of the magnetic observatories, either on the dayside or the nightside of the earth. The IP shocks identified by a sudden increase of B and with the northward turning of the latitude theta (positive ΔBsub(z)) were associated with purely positive sudden commencement (SC) at the observatories in the nightside, but at the equatorial observatories in the dayside of the earth the signature of the shock was a SC in H with a preliminary negative impulse followed by the main positive excursion (SC-+). It is suggested that the SCs in H at low latitudes are composed of two effects, viz. (i) one due to hydromagnetic pressure on the magnetosphere by the solar plasma and (ii) the other due to the induced electric field associated with the solar wind velocity, V and the Z-component of the IP magnetic field (E = - V x Bsub(z)). The effect of magnetosphere electric field is faster than the effect due to the compression of the magnetosphere by the impinging solar plasma. The negative impulse of SC-+ at low latitude is seen at stations close to the dip equator and only during daytime due to the existence of high ionospheric conductivities in the equatorial electrojet region. (author)

  8. PLUMEX II: A second set of coincident radar and rocket observations of equatorial spread-F

    International Nuclear Information System (INIS)

    Szuszczewicz, E.P.; Tsunoda, R.T.; Narcisi, R.; Holmes, J.C.

    1981-01-01

    PLUMEX II, the second rocket in a two-rocket operation that successfully executed coincident rocket and radar measurements of backscatter plumes and plasma depletions, was launched into the mid-phase of well-developed equatorial spread-F. In contrast with the first operation, the PLUMEX II results show large scale F-region irregularities only on the bottomside gradient with smaller scale irregularities (i.e., small scale structure imbedded in larger scale features) less intense than corresponding observations in PLUMEX I. The latter result could support current interpretations of east-west plume asymmetry which suggests that during initial upwelling the western wall of a plume (the PLUMEX I case) is more unstable than its eastern counterpart (the PLUMEX II case). In addition, ion mass spectrometer results are found to provide further support for an ion transport model which ''captures'' bottomside ions in an upwelling bubble and transports them to high altitudes

  9. Variability in equatorial B0 and B1

    International Nuclear Information System (INIS)

    Adeniyi, J.O.; Radicella, S.M.

    2002-01-01

    Variability of ionospheric profile parameters B0 and B1, below the F2 peak is investigated for an equatorial station at two levels of solar activities. The whole 24 hours of the day and the four seasons of the year are covered. Absolute and relative variability indices were utilized in the study. Some evidences of correlations of variability index and profiles parameters were observed. Daytime values of relative variability in B1 at solar minimum were found to be greater than those of solar maximum. (author)

  10. Vertical Rise Velocity of Equatorial Plasma Bubbles Estimated from Equatorial Atmosphere Radar Observations and High-Resolution Bubble Model Simulations

    Science.gov (United States)

    Yokoyama, T.; Ajith, K. K.; Yamamoto, M.; Niranjan, K.

    2017-12-01

    Equatorial plasma bubble (EPB) is a well-known phenomenon in the equatorial ionospheric F region. As it causes severe scintillation in the amplitude and phase of radio signals, it is important to understand and forecast the occurrence of EPBs from a space weather point of view. The development of EPBs is presently believed as an evolution of the generalized Rayleigh-Taylor instability. We have already developed a 3D high-resolution bubble (HIRB) model with a grid spacing of as small as 1 km and presented nonlinear growth of EPBs which shows very turbulent internal structures such as bifurcation and pinching. As EPBs have field-aligned structures, the latitude range that is affected by EPBs depends on the apex altitude of EPBs over the dip equator. However, it was not easy to observe the apex altitude and vertical rise velocity of EPBs. Equatorial Atmosphere Radar (EAR) in Indonesia is capable of steering radar beams quickly so that the growth phase of EPBs can be captured clearly. The vertical rise velocities of the EPBs observed around the midnight hours are significantly smaller compared to those observed in postsunset hours. Further, the vertical growth of the EPBs around midnight hours ceases at relatively lower altitudes, whereas the majority of EPBs at postsunset hours found to have grown beyond the maximum detectable altitude of the EAR. The HIRB model with varying background conditions are employed to investigate the possible factors that control the vertical rise velocity and maximum attainable altitudes of EPBs. The estimated rise velocities from EAR observations at both postsunset and midnight hours are, in general, consistent with the nonlinear evolution of EPBs from the HIRB model.

  11. Electric field mapping and auroral Birkeland currents

    International Nuclear Information System (INIS)

    Kaufmann, R.L.; Larson, D.J.

    1989-01-01

    Magnetic field lines, electric fields and equipotentials have been mapped throughout the magnetosphere in the vicinity of strong Birkeland currents. It was found that a uniform electric field at either the ionospheric or the equatorial end of a field line can map to a highly structured field at the other end if strong Birkeland currents are located nearby. The initiation of sheet currents of the region 1 - region 2 scale size and intensity resulted in magnetic field line displacements of about 1/2 hour in local time between equatorial and ionospheric end points. As a result, a uniform dawn to dusk electric field at the equator mapped to an ionospheric electric field with strong inward pointing components in the dusk hemisphere. Similar distortions were produced by Birkeland currents associated with narrow east-west-aligned auroral arcs. A specific model for the auroral current system, based on ionospheric measurements during a large substorm, was used to study effects seen during disturbed periods. An iterative procedure was developed to generate a self-consistent current system even in the presence of highly twisted field lines. The measured ionospheric electric field was projected tot he equatorial plane in the presence of the model Birkeland current system. Several physical processes were seen to influence ionospheric and equatorial electric fields, and the associated plasma convection, during a substorm

  12. Acquisition of an Underway CTD System for the Flow Encountering Abrupt Topography DRI

    Science.gov (United States)

    2015-09-30

    Acquisition of an Underway CTD System for the Flow Encountering Abrupt Topography DRI T. M. Shaun Johnston Scripps Institution of Oceanography...westward flow in the North Equatorial Current (NEC) encounters tall, steep, submarine topography and islands. During the Flow Encountering Abrupt... Topography (FLEAT) DRI, investigators will determine: • Whether appreciable energy/momentum is lost from the large-scale NEC flow to smaller scales and

  13. Preface: The International Reference Ionosphere (IRI) at equatorial latitudes

    Science.gov (United States)

    Reinisch, Bodo; Bilitza, Dieter

    2017-07-01

    This issue of Advances in Space Research includes papers that report and discuss improvements of the International Reference Ionosphere (IRI). IRI is the international standard for the representation of the plasma in Earth's ionosphere and recognized as such by the Committee on Space Research (COSPAR), the International Union of Radio Science (URSI), the International Telecommunication Union (ITU), and the International Standardization Organization (ISO). As requested, particularly by COSPAR and URSI, IRI is an empirical model relying on most of the available and reliable ground and space observations of the ionosphere. As new data become available and as older data sources are fully exploited the IRI model undergoes improvement cycles to stay as close to the existing data record as possible. The latest episode of this process is documented in the papers included in this issue using data from the worldwide network of ionosondes, from a few of the incoherent scatter radars, from the Alouette and ISIS topside sounders, and from the Global Navigation Satellite Systems (GNSS). The focus of this issue is on the equatorial and low latitude region that is of special importance for ionospheric physics because it includes the largest densities and steep density gradients in the double hump latitudinal structure, the Equatorial Ionization Anomaly (EIA), which is characteristic for this region.

  14. The Plasma Environment Associated With Equatorial Ionospheric Irregularities

    Science.gov (United States)

    Smith, Jonathon M.; Heelis, R. A.

    2018-02-01

    We examine the density structure of equatorial depletions referred to here as equatorial plasma bubbles (EPBs). Data recorded by the Ion Velocity Meter as part of the Coupled Ion Neutral Dynamics Investigation (CINDI) aboard the Communication/Navigation Outage Forecasting System (C/NOFS) satellite are used to study EPBs from 1600 to 0600 h local time at altitudes from 350 to 850 km. The data are taken during the 7 years from 2008 to 2014, more than one half of a magnetic solar cycle, that include solar minimum and a moderate solar maximum. Using a rolling ball algorithm, EPBs are identified by profiles in the plasma density, each having a depth measured as the percent change between the background and minimum density (ΔN/N). During solar moderate activity bubbles observed in the topside postsunset sector are more likely to have large depths compared to those observed in the topside postmidnight sector. Large bubble depths can be observed near 350 km in the bottomside F region in the postsunset period. Conversely at solar minimum the distribution of depths is similar in the postsunset and postmidnight sectors in all longitude sectors. Deep bubbles are rarely observed in the topside postsunset sector and never in the bottomside above 400 km in altitude. We suggest that these features result from the vertical drift of the plasma for these two solar activity levels. These drift conditions affect both the background density in which bubbles are embedded and the growth rate of perturbations in the bottomside where bubbles originate.

  15. Evidence for a continuous spectrum of equatorial waves in the Indian Ocean

    Science.gov (United States)

    Eriksen, Charles C.

    1980-06-01

    Seven-month records of current and temperature measurements from a moored array centered at 53°E on the equator in the Indian Ocean are consistent with a continuous spectrum of equatorially trapped internal inertial-gravity, mixed Rossby-gravity, and Kelvin waves. A model spectrum of free linear waves analogous to those for mid-latitude internal gravity waves is used to compute spectra of observed quantities at depths greater than about 2000 m. Model parameters are adjusted to fit general patterns in the observed spectra over periods from roughly 2 days to 1 month. Measurements at shallower depths presumably include forced motions which we have not attempted to model. This `straw-person' spectrum is consistent with the limited data available. The model spectru Ē (n, m, ω) = K · B(m) · C(n, ω), where Ē is an average local energy density in the equatorial wave guide which has amplitude K, wave number shape B(m) ∝ (1 + m/m*)-3, where m is vertical mode number and the bandwidth parameter m* is between 4 and 8, and frequency shape C(n, ω) ∝ [(2n + 1 + s2)½ · σ3]-1 where n is meridional mode number, and s and σ are dimensionless zonal wave number and frequency related by the usual dispersion relation. The scales are (β/cm)½ and (β · cm)½ for horizontal wave number and frequency, where cm is the Kelvin wave speed of the vertical mode m. At each frequency and vertical wave number, energy is partitioned equally among the available inertial gravity modes so that the field tends toward horizontal isotropy at high frequency. The transition between Kelvin and mixed Rossby-gravity motion at low frequency and inertial-gravity motion at high frequency occurs at a period of roughly 1 week. At periods in the range 1-3 weeks, the model spectrum which fits the observations suggests that mixed Rossby-gravity motion dominates; at shorter periods gravity motion dominates. The model results are consistent with the low vertical coherence lengths observed (roughly 80 m

  16. Quasi-biennial variation of equatorial waves as seen in satellite remote sensing data

    Science.gov (United States)

    Chen, Zeyu

    The quasi-biennial oscillation (QBO) in zonal winds in the lower stratosphere at the Equator is the most prominent inter-annual variation signal in the middle atmosphere. Theoretically, it is driven by the drag from the damping of equatorial waves including the equatorially trapped planetary scale waves, such as Kelvin waves propagating eastward and Rossby-gravity waves propagating westward, inertio-gravity waves and gravity waves. In current research, the tem-perature data collected by the SABER/TIMED mission in 2002-2009 are used to investigate the equatorial waves activities. The Fast Fourier Synoptic Mapping (FFSM) method is applied to delineate planetary wave components with the zonal wavenumber spanning over -6 to +6, hereby, positive (negative) wavenumber is assigned to westward (eastward) propagating waves. Limited by the SABER/TIMED sampling scheme, only the waves with periods longer than one day can be resolved. Focusing on the height region 70-10 hPa where the QBO signal is most significant, it is clearly observed that the composite activity of all the eastward waves exhibit QBO like variation. Specifically, for each QBO cycle, the activity at 50 hPa level is characterized by the occurrence of a substantially clear minimum that coincides to the fast downward propagation of the westerly phase, the typical pattern of the QBO phenomenon. Phase speed spectra are derived by using the FFSM analysis results. And vertical shear of the zonal wind is derived by using the rawinsonde data at Singapore. Comparison of the phase speed spectra and the wind shear indicates that the minimum is due to the westerly shear below 30 hPa. Between the minimum, significant wave activities emerge, thus the property for the components are investigated. Results show that in height range 70-10 hPa, both wave 1 to wave 3 are prominent during the inter-minimum period for each QBO cycle. At 50 hPa level, wave 1 component exhibits amplitude spectral peak at three kinds of period, 8, 11

  17. Variability in the origins and pathways of Pacific Equatorial Undercurrent water

    NARCIS (Netherlands)

    Qin, Xuerong; Sen Gupta, Alex; Van Sebille, Erik

    2015-01-01

    The Pacific Equatorial Undercurrent (EUC) transports water originating from a number of distinct source regions, eastward across the Pacific Ocean. It is responsible for supplying nutrients to the productive eastern Equatorial Pacific Ocean. Of particular importance is the transport of iron by the

  18. A study on ionospheric scintillation near the EIA crest in relation to equatorial electrodynamics

    Science.gov (United States)

    Chatterjee, S.; Chakraborty, S. K.; Veenadhari, B.; Banola, S.

    2014-02-01

    Equatorial electrojet (EEJ) data, which are considered as a proxy index of equatorial electric field, are analyzed in conjunction with equatorial ionosonde, total electron content (TEC) and scintillation data near the equatorial ionization anomaly (EIA) crest for the equinoctial months of high solar activity years (2011-2012) to identify any precursor index of postsunset evolution of equatorial electron density irregularities and subsequent occurrence of scintillation near the northern EIA crest. Only geomagnetically quiet and normal electrojet days are considered. The diurnal profiles of EEJ on the scintillation days exhibit a secondary enhancement in the afternoon to presunset hours following diurnal peaks. A series of electrodynamical processes conducive for generation of irregularities emerge following secondary enhancement of EEJ. Latitudinal profile of TEC exhibits resurgence in EIA structure around the postsunset period. Diurnal TEC profile near the EIA crest resembles postsunset secondary enhancement on the days with afternoon enhancement in EEJ. Occurrence of equatorial spread F and postsunset scintillation near the EIA crest seems to follow the secondary enhancement events in EEJ. Both the magnitude and duration of enhanced EEJ are found to be important for postsunset intensification of EIA structure and subsequent occurrence of equatorial irregularities. A critical value combining the two may be considered an important precursor for postsunset occurrence of scintillation near the EIA crest. The results are validated using archived data for the years 1989-1990 and explained in terms of modulation effects of enhanced equatorial fountain.

  19. Influence of biomass burning emissions on precipitation chemistry in the equatorial forests of Africa

    International Nuclear Information System (INIS)

    Lacaux, J.P.; Lefeivre, B.; Delmas, R.A.; Cros, B.; Andreae, M.O.

    1991-01-01

    As part of the DESCAFE program (Dynamics and Chemistry of the Atmosphere in Equatorial Forest), measurements of precipitation chemistry were made at two sampling sites of the equatorial forest in the Republic of Congo. The measurements were made in order to identify and compare atmospheric sources of gases and particles (mainly biogenic sources and emissions from burning vegetation)

  20. Main Ionospheric Trough and Equatorial Ionization Anomaly During Substorms With the Different UT Onset Moments

    Science.gov (United States)

    Klimenko, M. V.; Klimenko, V. V.; Bryukhanov, V. V.

    2007-05-01

    In the given work the numerical calculation results of ionospheric effects of four modeling substorms which have begun in 00, 06, 12 and 18 UT are presented. Calculations are executed on the basis of Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP), developed in WD IZMIRAN, added by the new block of calculation of electric fields in the ionosphere of the Earth for vernal equinox conditions in the minimum of solar activity. In calculations we considered superposition of magnetospheric convection electric field (at set potential differences through polar caps and field aligned currents of the second zone with taking into account of particle precipitation) and dynamo field generated by thermospheric winds without taking into account the tides. It is shown, that in the given statement of problem the substorms cause strong positive disturbances in F-region of ionosphere in night sector. Negative disturbances are much less and arise, mainly, at night in the middle and low latitudes. During substorms longitudinal extent of main ionospheric trough increases. The substorm beginning in 18 UT, causes negative disturbances in high latitudes except for a southern polar cap. Besides there is "stratification" of the main ionospheric trough. As a result in southern hemisphere the additional high-latitude trough which is absent in quiet conditions is formed. "Stratification" of the main ionospheric trough occurs in northern hemisphere at 6 hours after the beginning of the substorm. These "stratifications" are consequence non-stationary magnetospheric convection. Distinction between these events consists that "stratification" in a southern hemisphere occurs in active phase of substorm, and in northern hemisphere in recovery phase. During a substorm beginning in 00 UT, foF2 increases in all northern polar cap. Positive disturbances of foF2 in the equatorial anomaly region cause all presented substorms, except for a substorm beginning in 18 UT

  1. Seasonal-longitudinal variability of equatorial plasma bubbles

    Directory of Open Access Journals (Sweden)

    W. J. Burke

    2004-09-01

    Full Text Available We compare seasonal and longitudinal distributions of more than 8300 equatorial plasma bubbles (EPBs observed during a full solar cycle from 1989-2000 with predictions of two simple models. Both models are based on considerations of parameters that influence the linear growth rate, γRT, of the generalized Rayleigh-Taylor instability in the context of finite windows of opportunity available during the prereversal enhancement near sunset. These parameters are the strength of the equatorial magnetic field, Beq, and the angle, α, it makes with the dusk terminator line. The independence of α and Beq from the solar cycle phase justifies our comparisons.

    We have sorted data acquired during more than 75000 equatorial evening-sector passes of polar-orbiting Defense Meteorological Satellite Program (DMSP satellites into 24 longitude and 12 one-month bins, each containing ~250 samples. We show that: (1 in 44 out of 48 month-longitude bins EPB rates are largest within 30 days of when α=0°; (2 unpredicted phase shifts and asymmetries appear in occurrence rates at the two times per year when α≈0°; (3 While EPB occurrence rates vary inversely with Beq, the relationships are very different in regions where Beq is increasing and decreasing with longitude. Results (2 and (3 indicate that systematic forces not considered by the two models can become important. Damping by interhemispheric winds appears to be responsible for phase shifts in maximum rates of EPB occurrence from days when α=0°. Low EPB occurrence rates found at eastern Pacific longitudes suggest that radiation belt electrons in the drift loss cone reduce γRT by enhancing E-layer Pedersen conductances. Finally, we analyze an EPB event observed during a magnetic storm at a time and place where α≈-27°, to illustrate how electric-field penetration from

  2. Relation of zonal plasma drift and wind in the equatorial F region as derived from CHAMP observations

    Directory of Open Access Journals (Sweden)

    J. Park

    2013-06-01

    Full Text Available In this paper we estimate zonal plasma drift in the equatorial ionospheric F region without counting on ion drift meters. From June 2001 to June 2004 zonal plasma drift velocity is estimated from electron, neutral, and magnetic field observations of Challenging Mini-satellite Payload (CHAMP in the 09:00–20:00 LT sector. The estimated velocities are validated against ion drift measurements by the Republic of China Satellite-1/Ionospheric Plasma and Electrodynamics Instrument (ROCSAT-1/IPEI during the same period. The correlation between the CHAMP (altitude ~ 400 km estimates and ROCSAT-1 (altitude ~ 600 km observations is reasonably high (R ≈ 0.8. The slope of the linear regression is close to unity. However, the maximum westward drift and the westward-to-eastward reversal occur earlier for CHAMP estimates than for ROCSAT-1 measurements. In the equatorial F region both zonal wind and plasma drift have the same direction. Both generate vertical currents but with opposite signs. The wind effect (F region wind dynamo is generally larger in magnitude than the plasma drift effect (Pedersen current generated by vertical E field, thus determining the direction of the F region vertical current.

  3. Neodymium isotope ratios in fish debris as a tracer for a low oxygen water mass in the equatorial Pacific across the last glacial termination.

    Science.gov (United States)

    Reimi Sipala, M. A.; Marcantonio, F.

    2017-12-01

    The deep ocean has long been suggested as a potential sink of carbon during the LGM, providing storage for the drawdown of atmospheric CO2 observed in the climate record. However, the exact location, origin and pathway of this respired carbon pool remains largely unconstrained. The equatorial Pacific is an important player in the ocean biogeochemical cycling of carbon, with many researchers focusing on the changes in iron-limited systems and potential micronutrient supply changes throughout the Pleistocene glaciation. Here we attempt to isolate the role of deep water circulation changes that may be associated with changing bottom water oxygen conditions in the Central Equatorial Pacific during the last deglaciation. We measure the variability of the Nd isotopic composition of fish debris from three sites in the Central Equatorial Pacific (CEP) along a meridional transect at approximately 160° W -- 0° 28' N (ML1208-17PC), 4° 41' N (ML1208-31BB), and 7 ° 2'N (ML1208-31BB). Nd isotopic values in fish debris reflect the Nd isotopic composition of bottom water at the time of deposition and are insensitive to moderate changes in redox conditions or pore water oxygen levels. Nd isotope ratios can, therefore, be used as an effective deep-ocean water mass tracer. This work attempts to illuminate our current understanding of changes in bottom water oxygenation conditions throughout the Equatorial Pacific over the past 25 kyr. High authigenic U concentrations during peak glacial conditions have been attributed to deep-water suboxic conditions potentially associated with increased respired carbon storage. However, it is still unclear if these changes originate in the Southern Ocean, and propagate to the equatorial Pacific through an increased in penetration of Southern Ocean Intermediate water, or if they represent a change in the efficiency of the biological pump, permitting a drawdown of oxygen in bottom water without increased nutrient availability.

  4. Optimum launching of electron-cyclotron power for localized current drive in a hot tokamak

    International Nuclear Information System (INIS)

    Smith, G.R.

    1989-05-01

    Optimum launch parameters are determined for localized electron-cyclotron current drive near the magnetic axis and the q=2 surface by solving several minimization problems. For central current drive, equatorial and bottom launch are compared. Localized current drive near q=2 is studied for equatorial launch and for an alternative outside launch geometry that may be better for suppressing tearing modes and controlling disruptions. 6 refs., 2 figs

  5. Multistation digisonde observations of equatorial spread F in South America

    Directory of Open Access Journals (Sweden)

    B. W. Reinisch

    2004-09-01

    Full Text Available Directional ionogram and F-region drift observations were conducted at seven digisonde stations in South America during the COPEX campaign from October to December 2002. Five stations in Brazil, one in Argentina, and one in Peru, monitored the ionosphere across the continent to study the onset and development of F-region density depletions that cause equatorial spread F (ESF. New ionosonde techniques quantitatively describe the prereversal uplifting of the F layer at the magnetic equator and the eastward motion of the depletions over the stations. Three of the Brazilian stations were located along a field line with a 350-km apex over the equator to investigate the relation of the occurrence of ESF and the presence of sporadic E-layers at the two E-region intersections of the field line. No simple correlation was found.

  6. Observers in Kerr spacetimes. The ergoregion on the equatorial plane

    Energy Technology Data Exchange (ETDEWEB)

    Pugliese, D. [Silesian University in Opava, Faculty of Philosophy and Science, Institute of Physics, Opava (Czech Republic); Quevedo, H. [Universita di Roma ' ' La Sapienza' ' , Dipartimento di Fisica, Rome (Italy); Universidad Nacional Autonoma de Mexico, Instituto de Ciencias Nucleares, Mexico, DF (Mexico); Kazakh National University, Department of Theoretical and Nuclear Physics, Almaty (Kazakhstan)

    2018-01-15

    We perform a detailed analysis of the properties of stationary observers located on the equatorial plane of the ergosphere in a Kerr spacetime, including light-surfaces. This study highlights crucial differences between black hole and the super-spinner sources. In the case of Kerr naked singularities, the results allow us to distinguish between ''weak'' and ''strong'' singularities, corresponding to spin values close to or distant from the limiting case of extreme black holes, respectively. We derive important limiting angular frequencies for naked singularities. We especially study very weak singularities as resulting from the spin variation of black holes. We also explore the main properties of zero angular momentum observers for different classes of black hole and naked singularity spacetimes. (orig.)

  7. Seeding and layering of equatorial spread F by gravity waves

    International Nuclear Information System (INIS)

    Hysell, D.L.; Kelley, M.C.; Swartz, W.E.; Woodman, R.F.

    1990-01-01

    Studies dating back more than 15 years have presented evidence that atmospheric gravity waves play a role in initiating nighttime equatorial F region instabilities. This paper analyzes a spectabular spread F event that for the first time demonstrates a layering which, the authors argue, is controlled by a gravity wave effect. The 50-km vertical wavelength of a gravity wave which they have found is related theoretically to a plasma layering irregularity that originated at low altitudes and then was convected, intact, to higher altitudes. Gravity waves also seem to have determined bottomside intermediate scale undulations, although this fact is not as clear in the data. The neutral wind dynamo effect yields wave number conditions on the gravity wave's ability to modulate the Rayleigh-Taylor instaiblity process. Finally, after evaluating the gravity wave dispersion relation and spatial resonance conditions, we estimate the properties of the seeding wave

  8. Solar cycle signatures in the NCEP equatorial annual oscillation

    Science.gov (United States)

    Mayr, H. G.; Mengel, J. G.; Huang, F. T.; Nash, E. R.

    2009-08-01

    Our analysis of temperature and zonal wind data (1958 to 2006) from the National Center for Atmospheric Research (NCAR) reanalysis (Re-1), supplied by the National Centers for Environmental Prediction (NCEP), shows that the hemispherically symmetric 12-month equatorial annual oscillation (EAO) contains spectral signatures with periods around 11 years. Moving windows of 44 years show that, below 20 km, the 11-year modulation of the EAO is phase locked to the solar cycle (SC). The spectral features from the 48-year data record reveal modulation signatures of 9.6 and 12 years, which produce EAO variations that mimic in limited altitude regimes the varying maxima and minima of the 10.7 cm flux solar index. Above 20 km, the spectra also contain modulation signatures with periods around 11 years, but the filtered variations are too irregular to suggest that systematic SC forcing is the principal agent.

  9. Is there a hole in the topside, equatorial ionosphere?

    Directory of Open Access Journals (Sweden)

    D. Gallagher

    Full Text Available A paper in 2000 (Huba, 2000 found a depression in electron density in the topside ionosphere near the magnetic equator, based on the SAMI-2 physical ionospheric model. The model showed, for the first time, the formation of a hole in electron density in the altitude range 1500–2500 km at geomagnetic equatorial latitudes. The model produced the hole because of transhemispheric O+ flows that collisionally couple to H+, transporting it to lower altitudes, and thereby reducing the electron density at high altitudes. At that time and until now, no published observations have been reported to confirm or refute this numerical result. Recent, new analysis of Dynamics Explorer 1 Retarding Ion Mass Spectrometer measurements provides the first tentative experimental support for this model result. Keywords: Ionosphere, Topside, Magnetic equator, Plasmasphere

  10. Solar cycle signatures in the NCEP equatorial annual oscillation

    Directory of Open Access Journals (Sweden)

    H. G. Mayr

    2009-08-01

    Full Text Available Our analysis of temperature and zonal wind data (1958 to 2006 from the National Center for Atmospheric Research (NCAR reanalysis (Re-1, supplied by the National Centers for Environmental Prediction (NCEP, shows that the hemispherically symmetric 12-month equatorial annual oscillation (EAO contains spectral signatures with periods around 11 years. Moving windows of 44 years show that, below 20 km, the 11-year modulation of the EAO is phase locked to the solar cycle (SC. The spectral features from the 48-year data record reveal modulation signatures of 9.6 and 12 years, which produce EAO variations that mimic in limited altitude regimes the varying maxima and minima of the 10.7 cm flux solar index. Above 20 km, the spectra also contain modulation signatures with periods around 11 years, but the filtered variations are too irregular to suggest that systematic SC forcing is the principal agent.

  11. Combined radar observations of equatorial electrojet irregularities at Jicamarca

    Directory of Open Access Journals (Sweden)

    D. L. Hysell

    2007-03-01

    Full Text Available Daytime equatorial electrojet plasma irregularities were investigated using five distinct radar diagnostics at Jicamarca including range-time-intensity (RTI mapping, Faraday rotation, radar imaging, oblique scattering, and multiple-frequency scattering using the new AMISR prototype UHF radar. Data suggest the existence of plasma density striations separated by 3–5 km and propagating slowly downward. The striations may be caused by neutral atmospheric turbulence, and a possible scenario for their formation is discussed. The Doppler shifts of type 1 echoes observed at VHF and UHF frequencies are compared and interpreted in light of a model of Farley Buneman waves based on kinetic ions and fluid electrons with thermal effects included. Finally, the up-down and east-west asymmetries evident in the radar observations are described and quantified.

  12. The earth's equatorial principal axes and moments of inertia

    Science.gov (United States)

    Liu, H. S.; Chao, B. F.

    1991-01-01

    The earth's equatorial principal moments of inertia are given as A and B, where A is less than B, and the corresponding principal axes are given as a and b. Explicit formulas are derived for determining the orientation of a and b axes and the difference B - A using C(22) and S(22), the two gravitational harmonic coefficients of degree 2 and order 2. For the earth, the a axis lies along the (14.93 deg W, 165.07 deg E) diameter, and the b axis lies perpendicular to it along the (75.07 deg E, 104.93 deg W) diameter. The difference B - A is 7.260 x 10 to the -6th MR2. These quantities for other planets are contrasted, and geophysical implications are discussed.

  13. A Generalized Equatorial Model for the Accelerating Solar Wind

    Science.gov (United States)

    Tasnim, S.; Cairns, Iver H.; Wheatland, M. S.

    2018-02-01

    A new theoretical model for the solar wind is developed that includes the wind's acceleration, conservation of angular momentum, deviations from corotation, and nonradial velocity and magnetic field components from an inner boundary (corresponding to the onset of the solar wind) to beyond 1 AU. The model uses a solution of the time-steady isothermal equation of motion to describe the acceleration and analytically predicts the Alfvénic critical radius. We fit the model to near-Earth observations of the Wind spacecraft during the solar rotation period of 1-27 August 2010. The resulting data-driven model demonstrates the existence of noncorotating, nonradial flows and fields from the inner boundary (r = rs) outward and predicts the magnetic field B = (Br,Bϕ), velocity v = (vr,vϕ), and density n(r,ϕ,t), which vary with heliocentric distance r, heliolatitude ϕ, and time t in a Sun-centered standard inertial plane. The description applies formally only in the equatorial plane. In a frame corotating with the Sun, the transformed velocity v' and a field B' are not parallel, resulting in an electric field with a component Ez' along the z axis. The resulting E'×B'=E'×B drift lies in the equatorial plane, while the ∇B and curvature drifts are out of the plane. Together these may lead to enhanced scattering/heating of sufficiently energetic particles. The model predicts that deviations δvϕ from corotation at the inner boundary are common, with δvϕ(rs,ϕs,ts) comparable to the transverse velocities due to granulation and supergranulation motions. Abrupt changes in δvϕ(rs,ϕs,ts) are interpreted in terms of converging and diverging flows at the cell boundaries and centers, respectively. Large-scale variations in the predicted angular momentum demonstrate that the solar wind can drive vorticity and turbulence from near the Sun to 1 AU and beyond.

  14. A tropospheric ozone maximum over the equatorial Southern Indian Ocean

    Directory of Open Access Journals (Sweden)

    L. Zhang

    2012-05-01

    Full Text Available We examine the distribution of tropical tropospheric ozone (O3 from the Microwave Limb Sounder (MLS and the Tropospheric Emission Spectrometer (TES by using a global three-dimensional model of tropospheric chemistry (GEOS-Chem. MLS and TES observations of tropospheric O3 during 2005 to 2009 reveal a distinct, persistent O3 maximum, both in mixing ratio and tropospheric column, in May over the Equatorial Southern Indian Ocean (ESIO. The maximum is most pronounced in 2006 and 2008 and less evident in the other three years. This feature is also consistent with the total column O3 observations from the Ozone Mapping Instrument (OMI and the Atmospheric Infrared Sounder (AIRS. Model results reproduce the observed May O3 maximum and the associated interannual variability. The origin of the maximum reflects a complex interplay of chemical and dynamic factors. The O3 maximum is dominated by the O3 production driven by lightning nitrogen oxides (NOx emissions, which accounts for 62% of the tropospheric column O3 in May 2006. We find the contribution from biomass burning, soil, anthropogenic and biogenic sources to the O3 maximum are rather small. The O3 productions in the lightning outflow from Central Africa and South America both peak in May and are directly responsible for the O3 maximum over the western ESIO. The lightning outflow from Equatorial Asia dominates over the eastern ESIO. The interannual variability of the O3 maximum is driven largely by the anomalous anti-cyclones over the southern Indian Ocean in May 2006 and 2008. The lightning outflow from Central Africa and South America is effectively entrained by the anti-cyclones followed by northward transport to the ESIO.

  15. Observations of EMIC Triggered Emissions off the Magnetic Equatorial Plane

    Science.gov (United States)

    Grison, B.; Breuillard, H.; Santolik, O.; Cornilleau-Wehrlin, N.

    2016-12-01

    On 19/08/2005 Cluster spacecraft had their perigee close to the dayside of the Earth magnetic equatorial plane, at about 14 hours Magnetic Local Time. The spacecraft crossed the equator from the southern hemisphere toward the northern hemisphere. In the Southern hemisphere, at about -23° magnetic latitude (MLAT) and at distance of 5.25 Earth Radii from Earth, Cluster 3 observes an EMIC triggered emission between the He+ and the proton local gyrofrequencies. The magnetic waveform (STAFF instrument data) is transformed into the Fourier space for a study based on single value decomposition (SVD) analysis. The emission lasts about 30s. The emission frequency rises from 1Hz up to 1.9Hz. The emission polarization is left-hand, its coherence value is high and the propagation angle is field aligned (lower than 30º). The Poynting flux orientation could not be established. Based on previous study results, these properties are indicative of an observation in vicinity of the source region of the triggered emission. From our knowledge this is the first time that EMIC triggered emission are observed off the magnetic equator. In order to identify the source region we study two possibilities: a source region at higher latitudes than the observations (and particles orbiting in "Shabansky" orbits) and a source region close to the magnetic equatorial plane, as reported in previous studies. We propose to identify the source region from ray tracing analysis and to compare the observed propagation angle in several frequency ranges to the ray tracing results.

  16. Characteristics of Volcanic Stratospheric Aerosol Layer Observed by CALIOP and Ground Based Lidar at Equatorial Atmosphere Radar Site

    Science.gov (United States)

    Abo, Makoto; Shibata, Yasukuni; Nagasawa, Chikao

    2018-04-01

    We investigated the relation between major tropical volcanic eruptions in the equatorial region and the stratospheric aerosol data, which have been collected by the ground based lidar observations at at Equatorial Atmosphere Radar site between 2004 and 2015 and the CALIOP observations in low latitude between 2006 and 2015. We found characteristic dynamic behavior of volcanic stratospheric aerosol layers over equatorial region.

  17. F2 layer characteristics and electrojet strength over an equatorial station

    Science.gov (United States)

    Adebesin, B. O.; Adeniyi, J. O.; Adimula, I. A.; Reinisch, B. W.; Yumoto, K.

    2013-09-01

    The data presented in this work describes the diurnal and seasonal variation in hmF2, NmF2, and the electrojet current strength over an African equatorial station during a period of low solar activity. The F2 region horizontal magnetic element H revealed that the Solar quiet Sq(H) daily variation rises from early morning period to maximum around local noon and falls to lower values towards evening. The F2 ionospheric current responsible for the magnetic field variations is inferred to build up at the early morning hours, attaining maximum strength around 1200 LT. The Sq variation across the entire months was higher during the daytime than nighttime. This is ascribed to the variability of the ionospheric parameters like conductivity and winds structure in this region. Seasonal daytime electrojet (EEJ) current strength for June solstice, March and September equinoxes, respectively had peak values ranging within 27-35 nT (at 1400 LT) , 30-40 nT (at 1200 LT) and 35-45 nT (at 1500 LT). The different peak periods of the EEJ strength were attributed to the combined effects of the peak electron density and electric field. Lastly, the EEJ strength was observed to be higher during the equinoxes than the solstice period.

  18. Nanosatellites constellation as an IoT communication platform for near equatorial countries

    Science.gov (United States)

    Narayanasamy, A.; Ahmad, Y. A.; Othman, M.

    2017-11-01

    Anytime, anywhere access for real-time intelligence by Internet of Things (IoT) is changing the way that the whole world will operate as it moves toward data driven technologies. Over the next five years, IoT related devices going to have a dramatic breakthrough in current and new applications, not just on increased efficiency and cost reduction on current system, but it also will make trillion-dollar revenue generation and improve customer satisfaction. IoT communications is the networking of intelligent devices which enables data collection from remote assets. It covers a broad range of technologies and applications which connect to the physical world while allowing key information to be transferred automatically. The current terrestrial wireless communications technologies used to enable this connectivity include GSM, GPRS, 3G, LTE, WIFI, WiMAX and LoRa. These connections occur short to medium range distance however, none of them can cover a whole country or continent and the networks are getting congested with the multiplication of IoT devices. In this study, we discuss a conceptual design of a nanosatellite constellation those can provide a space-based communication platform for IoT devices for near Equatorial countries. The constellation design i.e. the orbital plane and number of satellites and launch deployment concepts are presented.

  19. The role of the complete Coriolis force in cross-equatorial transport of the Antarctic Bottom Water

    Science.gov (United States)

    Stewart, Andrew; Dellar, Paul

    2010-05-01

    We investigate the equatorial crossing of the Antarctic Bottom Water using a shallow water model that includes the complete Coriolis force. Most theoretical models of the atmosphere and ocean neglect the component of the Coriolis force associated with the horizontal component of the Earth's rotation vector, the so-called traditional approximation. This approximation is typically justified on the basis that ratio of the ocean depth to the Rossby radius of deformation is negligibly small, H-Rd ≪ 1. However, the steep topography and weak stratification in the abyssal ocean magnify the role of the non-traditional component of the Coriolis force. This is most pronounced in equatorial regions, where the traditional component of the Coriolis force is weakest and the non-traditional component is strongest. The inclusion of the complete Coriolis force gives rise to a range of very long sub-inertial waves, whose frequencies lie below the inertial frequency, in the two-layer shallow water equations. These waves have a dramatically different structure to their traditional counterparts, particularly when the stratification is weak. We focus on the flow of the Antarctic Bottom Water from the Brazil Basin in the western South Atlantic to the Guiana Basin in the western North Atlantic. In this region, the current traverses a deep channel directed westwards and very slightly northwards across the equator. Previous attempts to model this flow have struggled to explain why the cross-equatorial transport is so high, with around 2.0-2.2 Sv exiting at the northern end of the channel. We present analytical and numerical solutions of the non-traditional shallow water equations for the cross-equatorial flow of the Antarctic Bottom Water. We obtain analytical solutions by considering the steady-state flow of a single layer of shallow water through a northwesterly channel with a simple geometry. We assume zero potential vorticity, as it may be shown that fluid whose potential vorticity q

  20. CONVECTIVE BURSTS AND THE COUPLING OF SATURN'S EQUATORIAL STORMS AND INTERIOR ROTATION

    International Nuclear Information System (INIS)

    Heimpel, Moritz; Aurnou, Jonathan M.

    2012-01-01

    Temporal variations of Saturn's equatorial jet and magnetic field hint at rich dynamics coupling the atmosphere and the deep interior. However, it has been assumed that rotation of the interior dynamo must be steady over tens of years of modern observations. Here we use a numerical convection model and scaling estimates to show how equatorial convective bursts can transfer angular momentum to the deeper interior. The numerical model allows angular momentum transfer between a fluid outer spherical shell and a rigid inner sphere. Convection drives a prograde equatorial jet exhibiting quasiperiodic bursts that fill the equatorial volume outside the tangent cylinder. For each burst strong changes in the equatorial surface velocity are associated with retrograde torque on the inner sphere. Our results suggest that Saturn's Great White Spot, a giant storm that was observed to fill the equatorial region in 1990, could mobilize a volume of fluid carrying roughly 15% of Saturn's moment of inertia. Conservation of angular momentum then implies that a 20% change in the equatorial jet angular velocity could change the average interior rotation rate by about 0.1%—roughly an order of magnitude less than the apparent rotation rate changes associated with Saturn's kilometric radio (SKR) signal. However, if the SKR signal originates outside the liquid metal core in a 'planetary tachocline' that separates the layer of fast zonal flow from the magnetically controlled and slowly convecting deep interior, then convective bursts can provide a possible mechanism for the observed ∼1% SKR changes.

  1. The streaming-trapped ion interface in the equatorial inner magnetosphere

    Science.gov (United States)

    Lin, J.; Horwitz, J. L.; Gallagher, D.; Pollock, C. J.

    1994-01-01

    Spacecraft measurements of core ions on L=4-7 field-lines typically show trapped ion distributions near the magnetic equator, and frequently indicate field-aligned ion streams at higher latitudes. The nature of the transition between them may indicate both the microphysics of hot-cold plasma interactions and overall consequences for core plasma evolution. We have undertaken a statistical analysis and characterization of this interface and its relation to the equatorial region of the inner magnetosphere. In this analysis, we have characterized such features as the equatorial ion flux anisotropy, the penetration of field-aligned ionospheric streams into the equatorial region, the scale of the transition into trapped ion populations, and the transition latitude. We found that most transition latitudes occur within 13 deg of the equator. The typical values of equatorial ion anisotropies are consistent with bi-Maxwellian temperature ratios of T(sub perpendicular)/T(sub parallel) in the range of 3-5. The latitudinal scales for the edges of the trapped ion populations display a rather strong peak in the 2-3 deg range. We also found that there is a trend for the penetration ratio, the anisotropy half width, and the transition scale length to decrease with a higher equatorial ion anisotropy. We may interpret these features in terms of Liouville mapping of equatorially trapped ions and the reflection of the incoming ionospheric ion streams from the equatorial potential peaks associated with such trapped ions.

  2. Optimization of Saturn paraboloid magnetospheric field model parameters using Cassini equatorial magnetic field data

    Directory of Open Access Journals (Sweden)

    E. S. Belenkaya

    2016-07-01

    Full Text Available The paraboloid model of Saturn's magnetosphere describes the magnetic field as being due to the sum of contributions from the internal field of the planet, the ring current, and the tail current, all contained by surface currents inside a magnetopause boundary which is taken to be a paraboloid of revolution about the planet-Sun line. The parameters of the model have previously been determined by comparison with data from a few passes through Saturn's magnetosphere in compressed and expanded states, depending on the prevailing dynamic pressure of the solar wind. Here we significantly expand such comparisons through examination of Cassini magnetic field data from 18 near-equatorial passes that span wide ranges of local time, focusing on modelling the co-latitudinal field component that defines the magnetic flux passing through the equatorial plane. For 12 of these passes, spanning pre-dawn, via noon, to post-midnight, the spacecraft crossed the magnetopause during the pass, thus allowing an estimate of the concurrent subsolar radial distance of the magnetopause R1 to be made, considered to be the primary parameter defining the scale size of the system. The best-fit model parameters from these passes are then employed to determine how the parameters vary with R1, using least-squares linear fits, thus providing predictive model parameters for any value of R1 within the range. We show that the fits obtained using the linear approximation parameters are of the same order as those for the individually selected parameters. We also show that the magnetic flux mapping to the tail lobes in these models is generally in good accord with observations of the location of the open-closed field line boundary in Saturn's ionosphere, and the related position of the auroral oval. We then investigate the field data on six passes through the nightside magnetosphere, for which the spacecraft did not cross the magnetopause, such that in this case we compare the

  3. Spatial relationship of 1-meter equatorial spread-F irregularities and depletions in total electron content

    International Nuclear Information System (INIS)

    Tsunoda, R.T.; Towle, D.M.

    1979-01-01

    An experiment was conducted at Kwajalein Atoll, Marshall Islands to investigate the spatial relationship of 1-m equatorial spread-F irregularities to total electron content (TEC) depletions. A high-power radar was operated (1) in a backscatter scan mode to spatially map the distribution of 1-m irregularities, and (2) in a dual-frequency, satellite-track mode to obtain the longitudinal TEC variations. We show that radar backscatter ''plumes'' found in the disturbed, nighttime equatorial ionosphere are longitudinally coincident with TEC depletions. We suggest that the TEC depletions are probably due to the presence of plasma ''bubbles'' in the equatorial F layer

  4. The physical and theoretical basis of solar-terrestrial relationships 1. Equatorial locations

    International Nuclear Information System (INIS)

    Njau, E.C.

    1988-07-01

    The theory of solar-terrestrial relationships developed earlier by the author is extended to incorporate expressions that represent the non-linear responses of the earth-atmosphere system to incoming solar radiation in a more detailed manner. Application of the extended theory to equatorial locations leads to new and interesting features that are consistent with past observations. It also predicts the existence of new oscillations in the equatorial atmosphere whose causative physical processes are given and explained. Non-equatorial locations are treated along similar lines in Part 2 of the series. (author). 44 refs

  5. DEMETER Observations of Equatorial Plasma Depletions and Related Ionospheric Phenomena

    Science.gov (United States)

    Berthelier, J.; Malingre, M.; Pfaff, R.; Jasperse, J.; Parrot, M.

    2008-12-01

    DEMETER, the first micro-satellite of the CNES MYRIAD program, was launched from Baikonour on June 29, 2004 on a nearly circular, quasi helio-synchronous polar orbit at ~ 715 km altitude. The DEMETER mission focuses primarily on the search for a possible coupling between seismic activity and ionospheric disturbances as well as on the effects of natural phenomena such as tropospheric thunderstorms and man-made activities on the ionosphere. The scientific payload provides fairly complete measurements of the ionospheric plasma, energetic particles above ~ 70 keV, and plasma waves, up to 20 kHz for the magnetic and 3.3 MHz for the electric components. Several studies related to space weather and ionospheric physics have been conducted over the past years. Following a brief description of the payload and the satellite modes of operation, this presentation will focus on a set of results that provide a new insight into the physics of instabilities in the night-time equatorial ionosphere. The observations were performed during the major magnetic storm of November 2004. Deep plasma depletions were observed on several night-time passes at low latitudes characterized by the decrease of the plasma density by nearly 3 orders of magnitude relative to the undisturbed plasma, and a significant abundance of molecular ions. These features can be best interpreted as resulting from the rise of the F-layer above the satellite altitude over an extended region of the ionosphere. In one of the passes, DEMETER was operated in the Burst mode and the corresponding high resolution data allowed for the discovery of two unexpected phenomena. The first one is the existence of high intensity monochromatic wave packets at the LH frequency that develop during the decay phase of intense bursts of broadband LH turbulence. The broadband LH turbulence is triggered by whistlers emitted by lightning from atmospheric thunderstorms beneath the satellite. The second unexpected feature is the detection of a

  6. The equatorial E-region and its plasma instabilities: a tutorial

    Directory of Open Access Journals (Sweden)

    D. T. Farley

    2009-04-01

    Full Text Available In this short tutorial we first briefly review the basic physics of the E-region of the equatorial ionosphere, with emphasis on the strong electrojet current system that drives plasma instabilities and generates strong plasma waves that are easily detected by radars and rocket probes. We then discuss the instabilities themselves, both the theory and some examples of the observational data. These instabilities have now been studied for about half a century (!, beginning with the IGY, particularly at the Jicamarca Radio Observatory in Peru. The linear fluid theory of the important processes is now well understood, but there are still questions about some kinetic effects, not to mention the considerable amount of work to be done before we have a full quantitative understanding of the limiting nonlinear processes that determine the details of what we actually observe. As our observational techniques, especially the radar techniques, improve, we find some answers, but also more and more questions. One difficulty with studying natural phenomena, such as these instabilities, is that we cannot perform active cause-and-effect experiments; we are limited to the inputs and responses that nature provides. The one hope here is the steadily growing capability of numerical plasma simulations. If we can accurately simulate the relevant plasma physics, we can control the inputs and measure the responses in great detail. Unfortunately, the problem is inherently three-dimensional, and we still need somewhat more computer power than is currently available, although we have come a long way.

  7. Recent global-warming hiatus tied to equatorial Pacific surface cooling.

    Science.gov (United States)

    Kosaka, Yu; Xie, Shang-Ping

    2013-09-19

    Despite the continued increase in atmospheric greenhouse gas concentrations, the annual-mean global temperature has not risen in the twenty-first century, challenging the prevailing view that anthropogenic forcing causes climate warming. Various mechanisms have been proposed for this hiatus in global warming, but their relative importance has not been quantified, hampering observational estimates of climate sensitivity. Here we show that accounting for recent cooling in the eastern equatorial Pacific reconciles climate simulations and observations. We present a novel method of uncovering mechanisms for global temperature change by prescribing, in addition to radiative forcing, the observed history of sea surface temperature over the central to eastern tropical Pacific in a climate model. Although the surface temperature prescription is limited to only 8.2% of the global surface, our model reproduces the annual-mean global temperature remarkably well with correlation coefficient r = 0.97 for 1970-2012 (which includes the current hiatus and a period of accelerated global warming). Moreover, our simulation captures major seasonal and regional characteristics of the hiatus, including the intensified Walker circulation, the winter cooling in northwestern North America and the prolonged drought in the southern USA. Our results show that the current hiatus is part of natural climate variability, tied specifically to a La-Niña-like decadal cooling. Although similar decadal hiatus events may occur in the future, the multi-decadal warming trend is very likely to continue with greenhouse gas increase.

  8. Energy efficiency and comfort conditions in passive solar buildings: Effect of thermal mass at equatorial high altitudes

    Science.gov (United States)

    Ogoli, David Mwale

    This dissertation is based on the philosophy that architectural design should not just be a function of aesthetics, but also of energy-efficiency, advanced technologies and passive solar strategies. A lot of published literature is silent regarding buildings in equatorial highland regions. This dissertation is part of the body of knowledge that attempts to provide a study of energy in buildings using thermal mass. The objectives were to establish (1) effect of equatorial high-altitude climate on thermal mass, (2) effect of thermal mass on moderating indoor temperatures, (3) effect of thermal mass in reducing heating and cooling energy, and (4) the amount of time lag and decrement factor of thermal mass. Evidence to analyze the effect of thermal mass issues came from three sources. First, experimental physical models involving four houses were parametrically conducted in Nairobi, Kenya. Second, energy computations were made using variations in thermal mass for determining annual energy usage and costs. Third, the data gathered were observed, evaluated, and compared with currently published research. The findings showed that: (1) Equatorial high-altitude climates that have diurnal temperature ranging about 10--15°C allow thermal mass to moderate indoor temperatures; (2) Several equations were established that indicate that indoor mean radiant temperatures can be predicted from outdoor temperatures; (3) Thermal mass can reduce annual energy for heating and cooling by about 71%; (4) Time lag and decrement of 200mm thick stone and concrete thermal mass can be predicted by a new formula; (5) All windows on a building should be shaded. East and west windows when shaded save 51% of the cooling energy. North and south windows when fully shaded account for a further 26% of the cooling energy; (6) Insulation on the outside of a wall reduces energy use by about 19.6% below the levels with insulation on the inside. The basic premise of this dissertation is that decisions that

  9. Indian Moorings: Deep-sea current meter moorings in the Eastern Equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, V.S.N.; Sarma, M.S.S.; Suryanarayana, A.; Sengupta, D.; Unnikrishnan, A.S.; Fernando, V.; Almeida, A.; Khalap, S.; Sardar, A.; Somasundar, K.; Ravichandran, M.

    understanding and ability to predict the monsoons and related climate phenomena in much the same way as TAO/TRITON and PIRATA have advanced studies of ENSO and Tropical Atlantic climate variability. Acknowledgments The authors would like to thank the CLIVAR..., for assistance with logistic support; NOAA’s Office of Climate Observation for financial support; and JAMSTEC for its support of the TRITON mooring program. References Duval, J.P. and J. vialard, 2006: The VASCO-CIRENE experiment. Proc 27th AMS Conference...

  10. Satellite-tracked drifting buoy observations in the south equatorial current in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Shetye, S.R.; Michael, G.S.

    two buoys moved north and the third moved south. Over the open sea regime the buoys moved with a speed of approximately 30 cm/s at an angle of about 35 degrees to the left of the wind. The overall tendencies seen in the buoy drift are similar to those...

  11. An Analysis of Unseasonal Equatorial Plasma Bubbles in July 2014

    Science.gov (United States)

    Carter, B. A.; Currie, J. L.; Pradipta, R.; Groves, K. M.; Caton, R. G.; Yokoyama, T.

    2017-12-01

    In the equatorial ionosphere, the Raleigh-Taylor (RT) plasma instability in the post sunset region is known to cause plasma depletions, known as equatorial plasma bubbles (EPBs). These EPBs can have adverse effects on satellite-reliant technologies by causing scintillations in the phase and amplitude of Global Navigation Satellite System (GNSS) signals. The effect of EPBs on satellite-reliant technologies highlights a need for reliable forecasting of EPBs in the low-latitude regions, which requires a solid understanding of their climatology and daily variability. The climatology of EPB occurrence is known to correlate with the angle between the magnetic field and solar terminator. This angle controls the longitudinal E-region conductivity gradient across the day-night terminator, which influences the strength of the pre-reversal enhancement in the upward plasma drift, a dominant term in the linear RT growth rate. This relationship is well established from ground-based GNSS and satellite-based studies. However, reliable forecasts have not been developed by space weather forecasting agencies due to the lack of understanding of EPB daily variability. During July, EPB occurrence is small in the South-East Asia longitude sector due to the relatively large angle between the magnetic field and solar terminator. As a result, the pre-reversal enhancement in the upward plasma drift is typically low during this period, creating less favourable conditions for EPB growth. However, despite the typically low pre-reversal enhancement strength, this analysis reveals that July 2014 is not devoid of EPB events above South-East Asia. These unseasonal EPB events during July 2014 are studied in the context of the prevalently low solar and geomagnetic activity conditions. Given the lack of solar and geomagnetic control, the influence of the lower atmosphere on EPB generation (e.g., via atmospheric gravity wave seeding) is explored. These events provide a unique opportunity to investigate

  12. Snowball Earth termination by destabilization of equatorial permafrost methane clathrate.

    Science.gov (United States)

    Kennedy, Martin; Mrofka, David; von der Borch, Chris

    2008-05-29

    The start of the Ediacaran period is defined by one of the most severe climate change events recorded in Earth history--the recovery from the Marinoan 'snowball' ice age, approximately 635 Myr ago (ref. 1). Marinoan glacial-marine deposits occur at equatorial palaeolatitudes, and are sharply overlain by a thin interval of carbonate that preserves marine carbon and sulphur isotopic excursions of about -5 and +15 parts per thousand, respectively; these deposits are thought to record widespread oceanic carbonate precipitation during postglacial sea level rise. This abrupt transition records a climate system in profound disequilibrium and contrasts sharply with the cyclical stratigraphic signal imparted by the balanced feedbacks modulating Phanerozoic deglaciation. Hypotheses accounting for the abruptness of deglaciation include ice albedo feedback, deep-ocean out-gassing during post-glacial oceanic overturn or methane hydrate destabilization. Here we report the broadest range of oxygen isotope values yet measured in marine sediments (-25 per thousand to +12 per thousand) in methane seeps in Marinoan deglacial sediments underlying the cap carbonate. This range of values is likely to be the result of mixing between ice-sheet-derived meteoric waters and clathrate-derived fluids during the flushing and destabilization of a clathrate field by glacial meltwater. The equatorial palaeolatitude implies a highly volatile shelf permafrost pool that is an order of magnitude larger than that of the present day. A pool of this size could have provided a massive biogeochemical feedback capable of triggering deglaciation and accounting for the global postglacial marine carbon and sulphur isotopic excursions, abrupt unidirectional warming, cap carbonate deposition, and a marine oxygen crisis. Our findings suggest that methane released from low-latitude permafrost clathrates therefore acted as a trigger and/or strong positive feedback for deglaciation and warming. Methane hydrate

  13. 10Be/230Th ratios as proxy for particle flux in the equatorial Pacific ocean

    International Nuclear Information System (INIS)

    Anderson, R.F.; Fleisher, M.Q.; Kubik, P.W.; Suter, M.

    1997-01-01

    Particulate 10 Be/ 230 Th ratios collected by sediment traps in the central equatorial Pacific Ocean exhibit a positive correlation with particle flux, but little or no correlation with particle composition. (author) 1 fig., 4 refs

  14. Determination of vertical velocities in the equatorial part of the western Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Bahulayan, N.; Varadachari, V.V.R.

    Using steady state two-dimensional turbulent diffusion equations of salt and heat some important characteristics of vertical circulation in the equatorial part of the Indian Ocean have been evaluated and discussed. Upwelling and sinking velocities...

  15. Bacterial Diversity in Deep-Sea Sediments from Afanasy Nikitin Seamount, Equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Khandeparker, R.; Meena, R.M.; Deobagkar, D.D.

    Deep-sea sediments can reveal much about the last 200 million years of Earth history, including the history of ocean life and climate. Microbial diversity in Afanasy Nikitin seamount located at Equatorial East Indian Ocean (EEIO) was investigated...

  16. Weight Percentage of Calcium Carbonate for 17 Equatorial Pacific Cores from Brown University

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Weight percentages of calcium carbonate in this file were compiled by J. Farrell and W. L. Prell of Brown University for 17 equatorial Pacific Ocean sediment cores....

  17. Detection and Characterization of Equatorial Scintillation for Real-Time Operational Support

    National Research Council Canada - National Science Library

    McNeil, W

    1997-01-01

    The Phillips Laboratory Scintillation Network Decision Aid (PL-SCINDA) is a software tool which uses real-time data from remote sites to model ionospheric plasma depletions in the equatorial region...

  18. Investigations of equatorial ionosphere nighttime mode conversion at VLF

    Science.gov (United States)

    Hildebrand, Verne

    1993-05-01

    VLF Radiowave propagation provides one of the few viable tools for exploring the properties of the lower D-region ionosphere. Conversely, VLF communications coverage analysis and prediction is directly dependent on the quality of models for the D-region ionosphere. The VLF Omega navigation signals are an excellent and under-utilized resource for conducting D-region research in direct support of VLF communications. Stations are well placed for investigating polar, mid latitude, and equatorial phenomena. Much can be learned by fully utilizing the very stable signals radiated at five frequencies, available from each of the eight transmitters, and taking full advantage of modal structure. While the Omega signals, 10.2 to 13.6 kHz, are well below the VLF communications band, we contend that much of the knowledge gained on D-region characteristics can be directly applied at the higher frequencies. The opportunity offered by Omega needs to be exploited. With the Global Positioning System (GPS) coming onboard as the prime means for global navigation, pressure is mounting to phase out Omega. In this paper we describe how we are using Omega along with computer codes of full wave VLF propagation, provided to us by the U.S. Naval Ocean Systems Center (NOSC), for ionosphere research and by example illustrate the potential for other investigations.

  19. Equatorial segment of the mid-atlantic ridge

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-12-31

    The Equatorial Segment of the Mid-Atlantic Ridge is a part of this mid-oceanic ridge limited by a cluster of fracture zones - Cape Verde, Marathon, Mercury, Vema, Doldrums, Vernadsky and Sierra Leone - in the North, and a similar cluster of fracture zones - St Paul, Romanche and Chain - in the South. During recent decades, following the publication of the 5. edition of the General Bathymetric Chart of the Oceans (GEBCO), there has been a great deal of geological-geophysical research and mapping of the World Ocean. The results have led to the development of a number of theories concerning the essential heterogeneity of the structure of the ocean floor and, in particular, the heterogeneity of the structure and segmentation of mid-oceanic ridges. Research on the nature of such segmentation is of great importance for an understanding of the processes of development of such ridges and oceanic basins as a whole. Chapter 20 is dedicated to the study of the atlantic ocean mantle by using (Th.U)Th, (Th/U)pb and K/Ti systematics 380 refs.

  20. Equatorial segment of the mid-atlantic ridge

    International Nuclear Information System (INIS)

    1996-01-01

    The Equatorial Segment of the Mid-Atlantic Ridge is a part of this mid-oceanic ridge limited by a cluster of fracture zones - Cape Verde, Marathon, Mercury, Vema, Doldrums, Vernadsky and Sierra Leone - in the North, and a similar cluster of fracture zones - St Paul, Romanche and Chain - in the South. During recent decades, following the publication of the 5. edition of the General Bathymetric Chart of the Oceans (GEBCO), there has been a great deal of geological-geophysical research and mapping of the World Ocean. The results have led to the development of a number of theories concerning the essential heterogeneity of the structure of the ocean floor and, in particular, the heterogeneity of the structure and segmentation of mid-oceanic ridges. Research on the nature of such segmentation is of great importance for an understanding of the processes of development of such ridges and oceanic basins as a whole. Chapter 20 is dedicated to the study of the atlantic ocean mantle by using (Th.U)Th, (Th/U)pb and K/Ti systematics

  1. A Cenozoic record of the equatorial Pacific carbonate compensation depth.

    Science.gov (United States)

    Pälike, Heiko; Lyle, Mitchell W; Nishi, Hiroshi; Raffi, Isabella; Ridgwell, Andy; Gamage, Kusali; Klaus, Adam; Acton, Gary; Anderson, Louise; Backman, Jan; Baldauf, Jack; Beltran, Catherine; Bohaty, Steven M; Bown, Paul; Busch, William; Channell, Jim E T; Chun, Cecily O J; Delaney, Margaret; Dewangan, Pawan; Dunkley Jones, Tom; Edgar, Kirsty M; Evans, Helen; Fitch, Peter; Foster, Gavin L; Gussone, Nikolaus; Hasegawa, Hitoshi; Hathorne, Ed C; Hayashi, Hiroki; Herrle, Jens O; Holbourn, Ann; Hovan, Steve; Hyeong, Kiseong; Iijima, Koichi; Ito, Takashi; Kamikuri, Shin-ichi; Kimoto, Katsunori; Kuroda, Junichiro; Leon-Rodriguez, Lizette; Malinverno, Alberto; Moore, Ted C; Murphy, Brandon H; Murphy, Daniel P; Nakamura, Hideto; Ogane, Kaoru; Ohneiser, Christian; Richter, Carl; Robinson, Rebecca; Rohling, Eelco J; Romero, Oscar; Sawada, Ken; Scher, Howie; Schneider, Leah; Sluijs, Appy; Takata, Hiroyuki; Tian, Jun; Tsujimoto, Akira; Wade, Bridget S; Westerhold, Thomas; Wilkens, Roy; Williams, Trevor; Wilson, Paul A; Yamamoto, Yuhji; Yamamoto, Shinya; Yamazaki, Toshitsugu; Zeebe, Richard E

    2012-08-30

    Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0-3.5 kilometres during the early Cenozoic (approximately 55 million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth.

  2. A mantle plume model for the Equatorial Highlands of Venus

    Science.gov (United States)

    Kiefer, Walter S.; Hager, Bradford H.

    1991-01-01

    The possibility that the Equatorial Highlands are the surface expressions of hot upwelling mantle plumes is considered via a series of mantle plume models developed using a cylindrical axisymmetric finite element code and depth-dependent Newtonian rheology. The results are scaled by assuming whole mantle convection and that Venus and the earth have similar mantle heat flows. The best model fits are for Beta and Atla. The common feature of the allowed viscosity models is that they lack a pronounced low-viscosity zone in the upper mantle. The shape of Venus's long-wavelength admittance spectrum and the slope of its geoid spectrum are also consistent with the lack of a low-viscosity zone. It is argued that the lack of an asthenosphere on Venus is due to the mantle of Venus being drier than the earth's mantle. Mantle plumes may also have contributed to the formation of some smaller highland swells, such as the Bell and Eistla regions and the Hathor/Innini/Ushas region.

  3. Improved design of an ITER equatorial EC launcher

    International Nuclear Information System (INIS)

    Takahashi, K.; Kajiwara, K.; Kobayashi, N.; Kasugai, A.; Sakamoto, K.

    2008-01-01

    New design improvements for an ITER equatorial EC launcher are described. A design of the front shield modules was evaluated analytically. The results indicate that these modules can withstand the electromagnetic forces induced by plasma disruption and vertical plasma motion. The steering mirror mock-up including the spiral cooling tubes was fabricated based on the present design with application of the hot isostatic pressing technique to bond the copper alloy mirror body and the embedded stainless steel cooling tubes. The test of water flow was carried out and the expected flow rate was successfully obtained. A quasi-optical (QO) transmission layout has been proposed instead of the waveguide lines. The advantage of this option is possibly to increase the reliability in terms of fabrication and refurbishment. According to the beam propagation analysis, it is verified that transmission loss at the QO region is 1.1%-2.2%, which is comparable to the reference design. The peak heat load on the steering mirror surface could be reduced by 55%, which relaxes the mirror design

  4. Mismo field experiment in the equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Masumoto, Y.; Kuroda, Y.; Katsumata, M.; Mizuno, K.; Takayabu, Y.N.; Yoshizaki, M.; Shareef, A.; Fujiyoshi, Y.; McPhaden, M.J.; Murty, V.S.N.; Shirooka, R; Yasunaga, K.; Yamada, H.; Sato, N.; Ushiyama, T.; Moteki, Q.; Seiki, A.; Fujita, M.; Ando, K.; Hase, H.; Ueki, I; Horii, T.; Yokoyama, C.; Miyakawa, T.

    MISMO FIELD EXPERIMENT IN THE EQUATORIAL INDIAN OCEAN * b y Ku n i o yo n e y a m a , yu K i o ma s u m o t o , yo s h i f u m i Ku r o d a , ma s a K i Ka t s u m a t a , Ke i s u K e mi z u n o , yu K a r i n. ta K a y a b u , ma s a n o r i... yo s h i z a K i , al i sh a r e e f, ya s u s h i fu j i y o s h i , mi c h a e l j. mcPh a d e n , V. s. n. mu r t y , ry u i c h i sh i r o o K a , Ka z u a K i ya s u n a g a , hi r o y u K i ya m a d a , na o K i sa t o , to m o K i us...

  5. Bottom-type scattering layers and equatorial spread F

    Directory of Open Access Journals (Sweden)

    D. L. Hysell

    2004-12-01

    Full Text Available Jicamarca radar observations of bottom-type coherent scattering layers in the post-sunset bottomside F-region ionosphere are presented and analyzed. The morphology of the primary waves seen in radar images of the layers supports the hypothesis of kudeki+bhattacharyya-1999 that wind-driven gradient drift instabilities are operating. In one layer event when topside spread F did not occur, irregularities were distributed uniformly in space throughout the layers. In another event when topside spread F did eventually occur, the irregularities within the pre-existing bottom-type layers were horizontally clustered, with clusters separated by about 30km. The same horizontal periodicity was evident in the radar plumes and large-scale irregularities that emerged later in the event. We surmise that horizontal periodicity in bottom-type layer irregularity distribution is indicative of large-scale horizontal waves in the bottomside F-region that may serve as seed waves for large-scale Rayleigh Taylor instabilities. Key words. Ionosphere (equatorial ionosphere; ionospheric irregularties; plasma waves and instabilities

  6. Asymptotic approach for the nonlinear equatorial long wave interactions

    International Nuclear Information System (INIS)

    Ramirez Gutierrez, Enver; Silva Dias, Pedro L; Raupp, Carlos

    2011-01-01

    In the present work we use an asymptotic approach to obtain the long wave equations. The shallow water equation is put as a function of an external parameter that is a measure of both the spatial scales anisotropy and the fast to slow time ratio. The values given to the external parameters are consistent with those computed using typical values of the perturbations in tropical dynamics. Asymptotically, the model converge toward the long wave model. Thus, it is possible to go toward the long wave approximation through intermediate realizable states. With this approach, the resonant nonlinear wave interactions are studied. To simplify, the reduced dynamics of a single resonant triad is used for some selected equatorial trios. It was verified by both theoretical and numerical results that the nonlinear energy exchange period increases smoothly as we move toward the long wave approach. The magnitude of the energy exchanges is also modified, but in this case depends on the particular triad used and also on the initial energy partition among the triad components. Some implications of the results for the tropical dynamics are discussed. In particular, we discuss the implications of the results for El Nino and the Madden-Julian in connection with other scales of time and spatial variability.

  7. Equatorial spread F: a review of recent experimental results

    International Nuclear Information System (INIS)

    Kelley, M.C.

    1979-01-01

    In this paper the authors review an intense research effort aimed at understanding the large scale disruption of the equatorial F layer which often commences just after sunset, and lasts for most of the night. A very attractive explanation for the phenomena, although one not universally accepted, is that the F layer is unstable to the classic Rayleigh-Taylor condition in which a heavy fluid, the plasma, is supported against gravity by a light 'fluid', the Earth's magnetic field. It is concluded that a reasonable case has been made for this explanation provided that the concept is extended to include nonlinear Rayleigh-Taylor like buoyancy effects above the F peak where linear process is stable. Internal gravity waves in neutral atmosphere seem to play an important role in seeding the Rayleigh-Taylor process with large scale finite amplitude perturbations. One of the remarkable features of this phenomena is the nearly simultaneous generation of structure with scale sizes spanning five orders of magnitude. These results may have applications in astrophysical processes where the Rayleigh-Taylor instability is thought to play a role. (Auth.)

  8. Equatorial insolation: from precession harmonics to eccentricity frequencies

    Directory of Open Access Journals (Sweden)

    A. Berger

    2006-01-01

    Full Text Available Since the paper by Hays et al. (1976, spectral analyses of climate proxy records provide substantial evidence that a fraction of the climatic variance is driven by insolation changes in the frequency ranges of obliquity and precession variations. However, it is the variance components centered near 100 kyr which dominate most Upper Pleistocene climatic records, although the amount of insolation perturbation at the eccentricity driven periods close to 100-kyr (mainly the 95 kyr- and 123 kyr-periods is much too small to cause directly a climate change of ice-age amplitude. Many attempts to find an explanation to this 100-kyr cycle in climatic records have been made over the last decades. Here we show that the double maximum which characterizes the daily irradiation received in tropical latitudes over the course of the year is at the origin in equatorial insolation of not only strong 95 kyr and 123 kyr periods related to eccentricity, but also of a 11-kyr and a 5.5-kyr periods related to precession.

  9. Equatorial circular orbits in the Kerr-de Sitter spacetimes

    International Nuclear Information System (INIS)

    Stuchlik, Zdenek; Slany, Petr

    2004-01-01

    Equatorial motion of test particles in Kerr-de Sitter spacetimes is considered. Circular orbits are determined, their properties are discussed for both black-hole and naked-singularity spacetimes, and their relevance for thin accretion disks is established. The circular orbits constitute two families that coalesce at the so-called static radius. The orientation of the motion along the circular orbits is, in accordance with case of asymptotically flat Kerr spacetimes, defined by relating the motion to the locally nonrotating frames. The minus-family orbits are all counterrotating, while the plus-family orbits are usually corotating relative to these frames. However, the plus-family orbits become counterrotating in the vicinity of the static radius in all Kerr-de Sitter spacetimes, and they become counterrotating in the vicinity of the ring singularity in Kerr-de Sitter naked-singularity spacetimes with a low enough rotational parameter. In such spacetimes, the efficiency of the conversion of the rest energy into heat energy in the geometrically thin plus-family accretion disks can reach extremely high values exceeding the efficiency of the annihilation process. The transformation of a Kerr-de Sitter naked singularity into an extreme black hole due to accretion in the thin disks is briefly discussed for both the plus-family and minus-family disks. It is shown that such a conversion leads to an abrupt instability of the innermost parts of the plus-family accretion disks that can have strong observational consequences

  10. Equatorial segment of the mid-atlantic ridge

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-12-31

    The Equatorial Segment of the Mid-Atlantic Ridge is a part of this mid-oceanic ridge limited by a cluster of fracture zones - Cape Verde, Marathon, Mercury, Vema, Doldrums, Vernadsky and Sierra Leone - in the North, and a similar cluster of fracture zones - St Paul, Romanche and Chain - in the South. During recent decades, following the publication of the 5. edition of the General Bathymetric Chart of the Oceans (GEBCO), there has been a great deal of geological-geophysical research and mapping of the World Ocean. The results have led to the development of a number of theories concerning the essential heterogeneity of the structure of the ocean floor and, in particular, the heterogeneity of the structure and segmentation of mid-oceanic ridges. Research on the nature of such segmentation is of great importance for an understanding of the processes of development of such ridges and oceanic basins as a whole. Chapter 20 is dedicated to the study of the atlantic ocean mantle by using (Th.U)Th, (Th/U)pb and K/Ti systematics 380 refs.

  11. Tree rings and rainfall in the equatorial Amazon

    Science.gov (United States)

    Granato-Souza, Daniela; Stahle, David W.; Barbosa, Ana Carolina; Feng, Song; Torbenson, Max C. A.; de Assis Pereira, Gabriel; Schöngart, Jochen; Barbosa, Joao Paulo; Griffin, Daniel

    2018-05-01

    The Amazon basin is a global center of hydroclimatic variability and biodiversity, but there are only eight instrumental rainfall stations with continuous records longer than 80 years in the entire basin, an area nearly the size of the coterminous US. The first long moisture-sensitive tree-ring chronology has been developed in the eastern equatorial Amazon of Brazil based on dendrochronological analysis of Cedrela cross sections cut during sustainable logging operations near the Rio Paru. The Rio Paru chronology dates from 1786 to 2016 and is significantly correlated with instrumental precipitation observations from 1939 to 2016. The strength and spatial scale of the precipitation signal vary during the instrumental period, but the Rio Paru chronology has been used to develop a preliminary reconstruction of February to November rainfall totals from 1786 to 2016. The reconstruction is related to SSTs in the Atlantic and especially the tropical Pacific, similar to the stronger pattern of association computed for the instrumental rainfall data from the eastern Amazon. The tree-ring data estimate extended drought and wet episodes in the mid- to late-nineteenth century, providing a valuable, long-term perspective on the moisture changes expected to emerge over the Amazon in the coming century due to deforestation and anthropogenic climate change.

  12. Oligocene-Miocene magnetic stratigraphy carried by biogenic magnetite at sites U1334 and U1335 (equatorial Pacific Ocean)

    Science.gov (United States)

    Channell, J. E. T.; Ohneiser, C.; Yamamoto, Y.; Kesler, M. S.

    2013-02-01

    AbstractSediments from the equatorial Pacific Ocean, at the Integrated Ocean Drilling Program sites U1334 and U1335, record reliable magnetic polarity stratigraphies back to ~26.5 Ma (late Oligocene) at sedimentation rates usually in the 5-20 m/Myr range. Putative polarity subchrons that do not appear in current polarity timescales occur within Chrons C5ACr, C5ADn, and C5Bn.1r at Site U1335; and within Chrons C6AAr.2r, C6Br, C7Ar, and C8n.1n at Site U1334. Subchron C5Dr.1n (~17.5 Ma) is recorded at both sites, supporting its apparent recording in the South Atlantic Ocean, and has an estimated duration of ~40 kyr. The Oligocene-Miocene calcareous oozes have magnetizations carried by submicron magnetite, as indicated by thermal demagnetization of magnetic remanences, the anhysteretic remanence to susceptibility ratio, and magnetic hysteresis parameters. Transmission electron microscopy of magnetic separates indicates the presence of low-titanium iron oxide (magnetite) grains with size (50-100 nm) and shape similar to modern and fossil bacterial magnetite, supporting other evidence that biogenic submicron magnetite is the principal remanence carrier in these sediments. In the equatorial Pacific Ocean, low organic-carbon burial arrests microbial pore-water sulfate reduction, thereby aiding preservation of bacterial magnetite.

  13. On the Nocturnal Downward and Westward Equatorial Ionospheric Plasma Drifts During the 17 March 2015 Geomagnetic Storm

    Science.gov (United States)

    Bagiya, Mala S.; Vichare, Geeta; Sinha, A. K.; Sripathi, S.

    2018-02-01

    During quiet period, the nocturnal equatorial ionospheric plasma drifts eastward in the zonal direction and downward in the vertical direction. This quiet time drift pattern could be understood through dynamo processes in the nighttime equatorial ionosphere. The present case study reports the nocturnal simultaneous occurrence of the vertically downward and zonally westward plasma drifts over the Indian latitudes during the geomagnetic storm of 17 March 2015. After 17:00 UT ( 22:10 local time), the vertical plasma drift became downward and coincided with the westward zonal drift, a rarely observed feature of low latitude plasma drifts. The vertical drift turned upward after 18:00 UT, while the zonal drift became eastward. We mainly emphasize here the distinct bipolar type variations of vertical and zonal plasma drifts observed around 18:00 UT. We explain the vertical plasma drift in terms of the competing effects between the storm time prompt penetration and disturbance dynamo electric fields. Whereas, the westward drift is attributed to the storm time local electrodynamical changes mainly through the disturbance dynamo field in addition to the vertical Pedersen current arising from the spatial (longitudinal) gradient of the field aligned Pedersen conductivity.

  14. Biogeochemical impact of a model western iron source in the Pacific Equatorial Undercurrent

    OpenAIRE

    Slemons, L.; Gorgues, T.; Aumont, Olivier; Menkès, Christophe; Murray, J. W.

    2009-01-01

    Trace element distributions in the source waters of the Pacific Equatorial Undercurrent (EUC) show the existence of elevated total acid-soluble iron concentrations. This region has been suggested to contribute enough bioavailable iron to regulate interannual and interglacial variability in biological productivity downstream in the high-nitrate low-chlorophyll upwelling zone of the eastern equatorial Pacific. We investigated the advection and first-order biogeochemical impact of an imposed, da...

  15. The effect of J2 on equatorial and halo orbits around a magnetic planet

    International Nuclear Information System (INIS)

    Inarrea, Manuel; Lanchares, Victor; Palacian, Jesus F.; Pascual, Ana I.; Pablo Salas, J.; Yanguas, Patricia

    2009-01-01

    We calculate equatorial and halo orbits around a non-spherical (both oblate and prolate) magnetic planet. It is known that circular equatorial and halo orbits exist for a dust grain orbiting a spherical magnetic planet. However, the frequency of the orbit is constrained by the charge-mass ratio of the particle. If the non-sphericity of the planet is taken into account this constraint is modified or, in some cases, it disappears.

  16. Impact of convection over the equatorial trough on the summer monsoon activity over India

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Shenoi, S.S.C.; Schulz, J.

    . There have been studies (Cadet and Olory Togbe, 1981; Sadhuram and Sastry, 1987) on the role of Equatorial Trough (ET) as well as Southern Hemispheric Equatorial Trough (SHET) on the rainfall over central India. Most of these studies are related... the ET, WET and EET behave in a similar fashion during different monsoon and El Nino conditions ? c) What role do the synoptic systems play during the BM over the Indian subcontinent? 2. Data and Methodology The pentad precipitation data used...

  17. The effect of J{sub 2} on equatorial and halo orbits around a magnetic planet

    Energy Technology Data Exchange (ETDEWEB)

    Inarrea, Manuel [Universidad de la Rioja, Area de Fisica, 26006 Logrono (Spain); Lanchares, Victor [Dpto. de Matematicas y Computacion, CIEMUR: Centro de Investigacion en Informatica, Estadistica y Matematicas, Universidad de la Rioja, 26004 Logrono (Spain)], E-mail: vlancha@unirioja.es; Palacian, Jesus F. [Universidad Publica de Navarra, Departamento de Ingenieria Matematica e Informatica, 31006 Pamplona (Spain); Pascual, Ana I. [Dpto. de Matematicas y Computacion, CIEMUR: Centro de Investigacion en Informatica, Estadistica y Matematicas, Universidad de la Rioja, 26004 Logrono (Spain); Pablo Salas, J. [Universidad de la Rioja, Area de Fisica, 26006 Logrono (Spain); Yanguas, Patricia [Universidad Publica de Navarra, Departamento de Ingenieria Matematica e Informatica, 31006 Pamplona (Spain)

    2009-10-15

    We calculate equatorial and halo orbits around a non-spherical (both oblate and prolate) magnetic planet. It is known that circular equatorial and halo orbits exist for a dust grain orbiting a spherical magnetic planet. However, the frequency of the orbit is constrained by the charge-mass ratio of the particle. If the non-sphericity of the planet is taken into account this constraint is modified or, in some cases, it disappears.

  18. The MMS observation of an off-equatorial dipolarization front and associated wave characteristics in the near-Earth magnetotail

    Science.gov (United States)

    Li, H.; Guo, L.; Zhou, M.; Cheng, Q.; Yu, X.; Huang, S.; Pang, Y.

    2017-12-01

    In this paper, we report the observation of the off-equatorial depolarization front structures by Magnetospheric Multiscale (MMS) mission at around X -8Re in the Earth's magnetotail. The dipolarization front was located at the flow rebounce region associated with a parallel electron beam. A large lower frequency electromagnetic wave fluctuation at the depolarization front is observed with the frequency near the ion gyrofrequency, left-handed polarization and a parallel propagation. A parallel current attributed to an electron beam coexist with the wave. The wave is believed to be generated by the current-driven ion cyclotron instability. Such instability is important because of its potential contribution to global electromagnetic energy conversion at the dipolarization front.

  19. Day-to-day correlation of equatorial electrojet at two stations separated by 2000 km

    Directory of Open Access Journals (Sweden)

    R. G. Rastogi

    2007-05-01

    Full Text Available Day-to-day fluctuations of the daily range of the geomagnetic field H at the equatorial electrojet stations Ancon (ANC, 77.0° W and Sao Luis (SLZ, 44.2° W are described for the period January–June 1993. The H field started increasing between midnight and sunrise, reaching a peak shortly before noon. The daily range of H was maximum during March and April and minimum during June. Regardless of the month, the range in H was significantly larger at ANC than at SLZ. The 27-day running mean of the range of H varied from 80 nT to 125 nT at SLZ and from 105 nT to 180 nT at ANC. The day-to-day values of the range of H showed very faithful variations at the two stations. The deviations of the daily range of H from its 27-day running mean values showed good correlation between the two stations. Some large storm-time effects were seen at both stations. The correlation was still significant, when data were corrected for Dst index values. It is suggested that the range in H at the two electrojet stations, separated by more than 2000 km, are affected by some common sources other than the ring current, which need to be identified. Spectral analysis of the range of H shows remarkable similarity at the two stations, with a dominant period of 15 days at both stations.

  20. Conservation strategies for understanding and combating the primate bushmeat trade on Bioko Island, Equatorial Guinea.

    Science.gov (United States)

    Cronin, Drew T; Sesink Clee, Paul R; Mitchell, Matthew W; Bocuma Meñe, Demetrio; Fernández, David; Riaco, Cirilo; Fero Meñe, Maximiliano; Esara Echube, Jose Manuel; Hearn, Gail W; Gonder, Mary Katherine

    2017-11-01

    Bioko Island, Equatorial Guinea is among the important places in Africa for the conservation of primates, but a cultural preference for bushmeat and a lack of effective law enforcement has encouraged commercial bushmeat hunting, threatening the survival of the remaining primate population. For over 13 years, we collected bushmeat market data in the Malabo market, recording over 35,000 primate carcasses, documenting "mardi gras" consumption patterns, seasonal carcass availability, and negative effects resulting from government intervention. We also conducted forest surveys throughout Bioko's two protected areas in order to localize and quantify primate populations and hunting pressure. Using these data, we were able to document the significant negative impact bushmeat hunting had on monkey populations, estimate which species are most vulnerable to hunting, and develop ecological niche models to approximate the distribution of each of Bioko's diurnal primate species. These results also have allowed for the identification of primate hotspots, such as the critically important southwest region of the Gran Caldera Scientific Reserve, and thus, priority areas for conservation on Bioko, leading to more comprehensive conservation recommendations. Current and future efforts now focus on bridging the gap between investigators and legislators in order to develop and effectively implement a management plan for Bioko's Gran Caldera Scientific Reserve and to develop a targeted educational campaign to reduce demand by changing consumer attitudes toward bushmeat. Using this multidisciplinary approach, informed by biological, socioeconomic, and cultural research, there may yet be a positive future for the primates of Bioko. © 2017 Wiley Periodicals, Inc.

  1. Examining the Electric Fields of the Evening Equatorial Ionosphere When the Solar Terminator is Aligned and Not Aligned with the Magnetic Meridian

    Science.gov (United States)

    Eccles, J. V.

    2014-12-01

    The electric field structure of the equatorial ionosphere near sunset has implications on the development of plasma irregularities. The details of the development of the electric fields are examined using a global ionosphere-electrodynamics model. The results of simulations of simplified conditions show the influence of the arrangement of the solar terminator with the magnetic meridian. The relationships of the Curl-Free mechanism, the Hall Current Divergence mechanism, and the role of the Equatorial Electorjet region control the magnitude and timing of the Prereversal Enhancement of the zonal electric field as well as its altitude profile above the F region bottomside. Realistic conditions for 'equinox' and 'solstice' solar terminator arrangments are presented. The stability of the low-latitude ionosphere has a demonstrated relationship with the solar terminator alignment [Tsunoda, JGR, 1981]. The profile of the vertical and zonal electric field below the bottomside is then examined using the global model to explore the controlling elements of the electric field structure and the growth rates of the Rayleigh-Taylor instability and Collisional Shear instability.Tsunoda, R. T. (1985), Control of the seasonal and longitudinal occurrence of equatorial scintillations by the longitudinal gradient in integrated E region Pedersen conductivity, J. Geophys. Res., 90(A1),447-456, doi:10.1029/JA090iA01p00447.

  2. Role of the meridional dipole of SSTA and associated cross-equatorial flow in the tropical eastern Pacific in terminating the 2014 El Niño development

    Science.gov (United States)

    Wu, Yi-Kai; Chen, Lin; Hong, Chi-Cherng; Li, Tim; Chen, Cheng-Ta; Wang, Lu

    2018-03-01

    In the boreal spring of 2014, the oceanic and atmospheric conditions were favorable for an El Niño's development. It was predicted that in 2014, a super El Niño or at least a regular El Niño with normal magnitude, would initiate. However, the growth rate of the sea surface temperature anomaly (SSTA) in the equatorial eastern Pacific suddenly declined in the boreal summer. The physical processes responsible for the termination of the 2014 El Niño were addressed in this study. We hypothesized that a meridional dipole of SSTA, characterized by a pronounced warm SSTA over the eastern North Pacific (ENP) and cold SSTA over the eastern South Pacific (ESP), played a crucial role in blocking the 2014 El Niño's development. The observational analysis revealed that the meridional dipole of SSTA and the relevant anomalous cross-equatorial flow in the tropical eastern Pacific, induced anomalous westward ({u^' }0) currents in the equatorial eastern Pacific, leading to negative anomalous zonal advection term (- {u^' }partial \\overline T /partial xpartial \\overline T /partial znegative SSTA tendency in the boreal summer, and thus killed off the budding 2014 El Niño. The idealized numerical experiments further confirmed that the 2014 El Niño's development could be suppressed by the meridional dipole of SSTA, and both the ENP pole and ESP pole make a contribution.

  3. Modeling Tides, Planetary Waves, and Equatorial Oscillations in the MLT

    Science.gov (United States)

    Mengel, J. G.; Mayr, H. G.; Drob, D. P.; Porter, H. S.; Bhartia, P. K. (Technical Monitor)

    2001-01-01

    Applying Hines Doppler Spread Parameterization for gravity waves (GW), our 3D model reproduces some essential features that characterize the observed seasonal variations of tides and planetary waves in the upper mesosphere. In 2D, our model also reproduces the large Semi-Annual Oscillation (SAO) and Quasi Biennial Oscillation (QBO) observed in this region at low latitudes. It is more challenging to describe these features combined in a more comprehensive self consistent model, and we give a progress report that outlines the difficulties and reports some success. In 3D, the GW's are partially absorbed by tides and planetary waves to amplify them. Thus the waves are less efficient in generating the QBO and SAO at equatorial latitudes. Some of this deficiency is compensated by the fact that the GW activity is observed to be enhanced at low latitudes. Increasing the GW source has the desired effect to boost the QBO, but the effect is confined primarily to the stratosphere. With increasing altitude, the meridional circulation becomes more important in redistributing the momentum deposited in the background flow by the GW's. Another factor involved is the altitude at which the GW's originate, which we had originally chosen to be the surface. Numerical experiments show that moving this source altitude to the top of the troposphere significantly increases the efficiency for generating the QBO without affecting much the tides and planetary waves in the model. Attention to the details in which the GW source comes into play thus appears to be of critical importance in modeling the phenomenology of the MLT. Among the suite of numerical experiments reported, we present a simulation that produced significant variations of tides and planetary waves in the upper mesosphere. The effect is related to the QBO generated in the model, and GW filtering is the likely cause.

  4. Engineering activities on the ITER representative diagnostic equatorial port plug

    International Nuclear Information System (INIS)

    Meunier, L.; Doceul, L.; Salasca, S.; Martins, J.-P.; Jullien, F.; Dechelle, Christian; Bidaud, Pierre; Pilard, Vincent; Terra, Alexis; Ogea, Mathieu; Ciattaglia, Emanuela; Walker, Christopher

    2009-01-01

    Most of ITER diagnostic systems are integrated in port plugs, which are water cooled stainless steel structures inserted into the vacuum vessel ports. The port plug must provide basic functions such as neutron and gamma shielding, supporting the first wall armour (BSM), closing the vacuum vessel ports, while supporting the diagnostic equipments. ITER diagnostic port plug must resist a severe environment like high temperature due to neutron interaction with the structures and high electromechanical loading during disruptions events. CEA has contributed to the design and integration tasks in the frame of the representative equatorial port plug EQ no. 01, in particular on the engineering, structural and thermal finite element analysis. These detailed analyses have highlighted some design issues which were worked out through different solutions. This paper contains a description of the engineering activities performed such as: -The static mechanical calculations of the top plate closure system under disruption load. -The static mechanical calculations of the BSM attachment to the port plug. These two first studies led to design changes proposals which significantly improved the behaviour of the structures but also showed that the safety margin with respect to design limits is quite low. -The design of a Diagnostic Shield Module (DSM) integrated inside the port plug and a proposition of attachment scheme, with respect to disruption loads. The manufacturing of the DSM has been taken into account, as well as diagnostic integration inside the structure and maintenance aspects. -The thermal assessment of the port plug under neutronic load during normal operation, with the optimization of the cooling system. The maximum temperature calculated in normal operation has been reduced from 900 deg. C to less than 400 deg. C in the front plate; and the cooling arrangement at the back of the port plug has been simplified without important temperature increase.

  5. Engineering activities on the ITER representative diagnostic equatorial port plug

    Energy Technology Data Exchange (ETDEWEB)

    Meunier, L. [Association Euratom CEA, CEA/DSM/IRFM (France)], E-mail: lmeunier@cea.fr; Doceul, L.; Salasca, S.; Martins, J.-P.; Jullien, F.; Dechelle, Christian; Bidaud, Pierre; Pilard, Vincent; Terra, Alexis; Ogea, Mathieu [Association Euratom CEA, CEA/DSM/IRFM (France); Ciattaglia, Emanuela [EFDA CSU, Garching (Germany); Walker, Christopher [ITER International Organisation (France)

    2009-06-15

    Most of ITER diagnostic systems are integrated in port plugs, which are water cooled stainless steel structures inserted into the vacuum vessel ports. The port plug must provide basic functions such as neutron and gamma shielding, supporting the first wall armour (BSM), closing the vacuum vessel ports, while supporting the diagnostic equipments. ITER diagnostic port plug must resist a severe environment like high temperature due to neutron interaction with the structures and high electromechanical loading during disruptions events. CEA has contributed to the design and integration tasks in the frame of the representative equatorial port plug EQ no. 01, in particular on the engineering, structural and thermal finite element analysis. These detailed analyses have highlighted some design issues which were worked out through different solutions. This paper contains a description of the engineering activities performed such as: -The static mechanical calculations of the top plate closure system under disruption load. -The static mechanical calculations of the BSM attachment to the port plug. These two first studies led to design changes proposals which significantly improved the behaviour of the structures but also showed that the safety margin with respect to design limits is quite low. -The design of a Diagnostic Shield Module (DSM) integrated inside the port plug and a proposition of attachment scheme, with respect to disruption loads. The manufacturing of the DSM has been taken into account, as well as diagnostic integration inside the structure and maintenance aspects. -The thermal assessment of the port plug under neutronic load during normal operation, with the optimization of the cooling system. The maximum temperature calculated in normal operation has been reduced from 900 deg. C to less than 400 deg. C in the front plate; and the cooling arrangement at the back of the port plug has been simplified without important temperature increase.

  6. Duffy Negative Antigen Is No Longer a Barrier to Plasmodium vivax – Molecular Evidences from the African West Coast (Angola and Equatorial Guinea)

    Science.gov (United States)

    Mendes, Cristina; Dias, Fernanda; Figueiredo, Joana; Mora, Vicenta Gonzalez; Cano, Jorge; de Sousa, Bruno; do Rosário, Virgílio E.; Benito, Agustin; Berzosa, Pedro; Arez, Ana Paula

    2011-01-01

    Background Plasmodium vivax shows a small prevalence in West and Central Africa due to the high prevalence of Duffy negative people. However, Duffy negative individuals infected with P. vivax have been reported in areas of high prevalence of Duffy positive people who may serve as supply of P. vivax strains able to invade Duffy negative erythrocytes. We investigated the presence of P. vivax in two West African countries, using blood samples and mosquitoes collected during two on-going studies. Methodology/Findings Blood samples from a total of 995 individuals were collected in seven villages in Angola and Equatorial Guinea, and 820 Anopheles mosquitoes were collected in Equatorial Guinea. Identification of the Plasmodium species was achieved by nested PCR amplification of the small-subunit rRNA genes; P. vivax was further characterized by csp gene analysis. Positive P. vivax-human isolates were genotyped for the Duffy blood group through the analysis of the DARC gene. Fifteen Duffy-negative individuals, 8 from Equatorial Guinea (out of 97) and 7 from Angola (out of 898), were infected with two different strains of P. vivax (VK210 and VK247). Conclusions In this study we demonstrated that P. vivax infections were found both in humans and mosquitoes, which means that active transmission is occurring. Given the high prevalence of infection in mosquitoes, we may speculate that this hypnozoite-forming species at liver may not be detected by the peripheral blood samples analysis. Also, this is the first report of Duffy negative individuals infected with two different strains of P. vivax (VK247 and classic strains) in Angola and Equatorial Guinea. This finding reinforces the idea that this parasite is able to use receptors other than Duffy to invade erythrocytes, which may have an enormous impact in P. vivax current distribution. PMID:21713024

  7. Geomagnetic field variations at the equatorial electrojet station in Sri Lanka, Peredinia

    Directory of Open Access Journals (Sweden)

    R. G. Rastogi

    2004-09-01

    Full Text Available The paper discusses the variations of the horizontal (H, vertical (Z and eastward (Y components of the geomagnetic field at Peredinia (PRD, an electrojet station in Sri Lanka, with the time of the day, season, sudden commencement (SSC and during geomagnetic storms. The daily variation of H showed a large peak around midday. The daily variation of Z appeared to be almost a time gradient curve of the daily variation of H, showing a maximum around 09:00 LT (75° EMT when the H field was increasing fastest and not at noon when Δ H was the maximum. Storm time variation of H resembled the variation of the Dst index but that of Z showed a large minimum about 2-3h before the time of minimum Dst or at the time of maximum time gradient of Dst variation. These features are compared with corresponding variations at the equatorial stations Trivandrum (TRD in India, and remarkable similarity in all observations is noticed at PRD and TRD. It is suggested that the observed abnormal features of Z variations at electrojet stations in India-Sri Lanka are due to (i direct effect of the ionospheric electrojet current (ii the induction effect of the image current by the average spatially extended conductivity region and (iii the induction current in the local subsurface conductor. It is suggested that the conductor responsible for the observed features in Z in India and Sri Lanka has to have extended spatial domain to latitudes well south of India, rather than confined to narrow Palk Strait.

  8. Westward ionospheric currents over the dip equator during geomagnetic disturbances

    International Nuclear Information System (INIS)

    Rastogi, R.G.

    1975-01-01

    During geomagnetic disturbed periods, the q type of sporadic E layer near the dip equator is shown to disappear with maximum error of five minutes during the period when the difference of the geomagnetic H field between the equatorial and non-equatorial station decreases below the night level. These periods are identified with the reversal to westward direction of the electrojet currents at the base of the E region around 100 km level irrespective of the changes in the S/subq/ current system which might be produced by the disturbance

  9. The role of the Indonesian Throughflow in equatorial Pacific thermocline ventilation

    Science.gov (United States)

    Rodgers, Keith B.; Cane, Mark A.; Naik, Naomi H.; Schrag, Daniel P.

    1999-09-01

    The role of the Indonesian Throughflow (ITF) in the thermocline circulation of the low-latitude Pacific Ocean is explored using a high-resolution primitive equation ocean circulation model. Seasonally forced runs for a domain with an open Indonesian passage are compared with seasonally forced runs for a closed Pacific domain. Three cases are considered: one with no throughflow, one with 10 Sv of imposed ITF transport, and one with 20 Sv of ITF transport. Two idealized tracers, one that tags northern component subtropical water and another that tags southern component subtropical water, are used to diagnose the mixing ratio of northern and southern component waters in the equatorial thermocline. It is found that the mixing ratio of north/south component waters in the equatorial thermocline is highly sensitive to whether the model accounts for an ITF. Without an ITF, the source of equatorial undercurrent water is primarily of North Pacific origin, with the ratio of northern to southern component water being approximately 2.75 to 1. The ratio of northern to southern component water in the Equatorial Undercurrent with 10 Sv of ITF is approximately 1.4 to 1, and the ratio with 20 Sv of imposed ITF is 1 to 1.25. Estimates from data suggest a mean mixing ratio of northern to southern component water of less than 1 to 1. Assuming that the mixing ratio changes approximately linearly as the ITF transport varies between 10 and 20 Sv, an approximate balance between northern and southern component water is reached when the ITF transport is approximately 16 Sv. It is also shown that for the isopycnal surfaces within the core of the equatorial undercurrent, a 2°C temperature front exists across the equator in the western equatorial Pacific, beneath the warm pool. The implications of the model results and the temperature data for the heat budget of the equatorial Pacific are considered.

  10. Multiple embryos, multiple nepionts and multiple equatorial layers in Cycloclypeus carpenteri.

    Science.gov (United States)

    Briguglio, Antonino; Kinoshita, Shunichi; Wolfgring, Erik; Hohenegger, Johann

    2016-04-01

    In this study, 17 specimens of Cycloclypeus carpenteri have been analyzed by means of microCT scanning. We used CT scanning technique as it enables the visualization and the quantifications of internal structures of hollow specimens without their destruction. It has been observed that many specimens possessing the natural morphology of this taxon, actually contain multiple embryos (up to 16 in one single specimen) and, in some few cases, multiple nepionts each with its own heterosteginid chambers (up to three separated nepionts). The diameter of each proloculus has been measured, and as a result, they are very variable even within the same specimen, therefore questioning the long known theory that schizonts have smaller proloculi than gamonts and also questioning the fact that proloculi in the same species should all have comparable size. Furthermore, we have observed the presence of additional equatorial planes on several specimens. Such additional planes are always connected to what seems to be the main equatorial plane. Such connections are T-shaped and are located at the junction between two equatorial layers; these junctions are made by a chamberlet, which possesses an unusually higher number of apertures. The connections between equatorial planes are always perfectly synchronized with the relative growth step and the same chamber can be therefore followed along the multiple equatorial planes. Apparently there is a perfect geometric relationship between the creation of additional equatorial planes and the position of the nepionts. Whenever the nepionts are positioned on different planes, additional planes are created and the angle of the nepionts is related to the banding angle of the equatorial planes. The presence of additional planes do not hamper the life of the cell, on the contrary, it seems that the cell is still able to build nicely shaped chamberlets and, after volumetric calculations, it seems all specimens managed to keep their logistic growth

  11. Cross-equatorial flow through an abyssal channel under the complete Coriolis force: Two-dimensional solutions

    Science.gov (United States)

    Stewart, A. L.; Dellar, P. J.

    The component of the Coriolis force due to the locally horizontal component of the Earth's rotation vector is commonly neglected, under the so-called traditional approximation. We investigate the role of this "non-traditional" component of the Coriolis force in cross-equatorial flow of abyssal ocean currents. We focus on the Antarctic Bottom Water (AABW), which crosses from the southern to the northern hemisphere through the Ceara abyssal plain in the western Atlantic ocean. The bathymetry in this region resembles a northwestward channel, connecting the Brazil Basin in the south to the Guyana Basin in the north. South of the equator, the AABW leans against the western continental rise, consistent with a northward flow in approximate geostrophic balance. The AABW then crosses to the other side of the abyssal channel as it crosses the equator, and flows into the northern hemisphere leaning towards the east against the Mid-Atlantic Ridge. The non-traditional component of the Coriolis force is strongest close to the equator. The traditional component vanishes at the equator, being proportional to the locally vertical component of the Earth's rotation vector. The weak stratification of the abyssal ocean, and subsequent small internal deformation radius, defines a relatively short characteristic horizontal lengthscale that tends to make non-traditional effects more prominent. Additionally, the steep gradients of the channel bathymetry induce large vertical velocities, which are linked to zonal accelerations by the non-traditional components of the Coriolis force. We therefore expect non-traditional effects to play a substantial role in cross-equatorial transport of the AABW. We present asymptotic steady solutions for non-traditional shallow water flow through an idealised abyssal channel, oriented at an oblique angle to the equator. The current enters from the south, leaning up against the western side of the channel in approximate geostrophic balance, and crosses the

  12. No iron fertilization in the equatorial Pacific Ocean during the last ice age.

    Science.gov (United States)

    Costa, K M; McManus, J F; Anderson, R F; Ren, H; Sigman, D M; Winckler, G; Fleisher, M Q; Marcantonio, F; Ravelo, A C

    2016-01-28

    The equatorial Pacific Ocean is one of the major high-nutrient, low-chlorophyll regions in the global ocean. In such regions, the consumption of the available macro-nutrients such as nitrate and phosphate is thought to be limited in part by the low abundance of the critical micro-nutrient iron. Greater atmospheric dust deposition could have fertilized the equatorial Pacific with iron during the last ice age--the Last Glacial Period (LGP)--but the effect of increased ice-age dust fluxes on primary productivity in the equatorial Pacific remains uncertain. Here we present meridional transects of dust (derived from the (232)Th proxy), phytoplankton productivity (using opal, (231)Pa/(230)Th and excess Ba), and the degree of nitrate consumption (using foraminifera-bound δ(15)N) from six cores in the central equatorial Pacific for the Holocene (0-10,000 years ago) and the LGP (17,000-27,000 years ago). We find that, although dust deposition in the central equatorial Pacific was two to three times greater in the LGP than in the Holocene, productivity was the same or lower, and the degree of nitrate consumption was the same. These biogeochemical findings suggest that the relatively greater ice-age dust fluxes were not large enough to provide substantial iron fertilization to the central equatorial Pacific. This may have been because the absolute rate of dust deposition in the LGP (although greater than the Holocene rate) was very low. The lower productivity coupled with unchanged nitrate consumption suggests that the subsurface major nutrient concentrations were lower in the central equatorial Pacific during the LGP. As these nutrients are today dominantly sourced from the Subantarctic Zone of the Southern Ocean, we propose that the central equatorial Pacific data are consistent with more nutrient consumption in the Subantarctic Zone, possibly owing to iron fertilization as a result of higher absolute dust fluxes in this region. Thus, ice-age iron fertilization in the

  13. Role of amino acid supplementation in the prevention of necrotizing enterocolitis in preterm neonates - a review of current evidences.

    Science.gov (United States)

    Garg, Bhawan Deep; Kabra, Nandkishor S

    2018-09-01

    Necrotizing enterocolitis (NEC) is one of the most common acute and fatal gastrointestinal emergency in very low birth weight (VLBW) preterm neonates with mortality range from 15 to 30%. NEC is likely due to multifactorial process such as oxidative injury, ischemic necrosis, and over-reactive inflammatory response to intestinal microbes. To evaluate the role of amino acid supplementation for reduction of neonatal NEC in preterm neonates. The literature search was done for various randomized control trial (RCT) by searching the Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, EMBASE, Web of Science, Scopus, Index Copernicus, African Index Medicus (AIM), Thomson Reuters (ESCI), Chemical Abstracts Service (CAS) and other database. This review included 15 RCTs that fulfilled inclusion criteria. The total neonates enrolled in these different RCT are 3424 (amino acid group 1711 and control 1713). Almost all participating neonates were of VLBW or extremely low birth weight (ELBW). In two trials, birth weight was between 1500-2000 grams. The intervention was started within first few days after birth and continued up to 30th day of postnatal age in most of the trials. In two trials, intervention was continued up to 120th day of postnatal age. Arginine, glutamine and N-acetyl cysteine (NAC) were used at the dose of 1.5 mol/kg/day (261 mg/kg/day), 0.3 grams/kg/day and 16-32 mg/kg/day, respectively. Role of amino acid in the prevention of neonatal NEC is not exclusively supported by the current evidence. Only three studies were able to show reduction in the incidence of NEC with amino acid supplementation (arginine, glutamine), and the remaining studies did not report any positive effect. Amino acid supplementation was not associated with significant reduction in mortality due to any causes. However, arginine supplementation was associated with significant reduction in mortality due to NEC. Two studies on glutamine were reported significant reduction in

  14. Guest investigator program study: Physics of equatorial plasma bubbles

    Science.gov (United States)

    Tsunoda, Roland T.

    1994-01-01

    Plasma bubbles are large-scale (10 to 100 km) depletions in plasma density found in the night-time equatorial ionosphere. Their formation has been found to entail the upward transport of plasma over hundreds of kilometers in altitude, suggesting that bubbles play significant roles in the physics of many of the diverse and unique features found in the low-latitude ionosphere. In the simplest scenario, plasma bubbles appear first as perturbations in the bottomside F layer, which is linearly unstable to the gravitationally driven Rayleigh-Taylor instability. Once initiated, bubbles develop upward through the peak of the F layer into its topside (sometimes to altitudes in excess of 1000 km), a behavior predicted by the nonlinear form of the same instability. While good general agreement has been found between theory and observations, little is known about the detailed physics associated with plasma bubbles. Our research activity centered around two topics: the shape of plasma bubbles and associated electric fields, and the day-to-day variability in the occurrence of plasma bubbles. The first topic was pursued because of a divergence in view regarding the nonlinear physics associated with plasma bubble development. While the development of perturbations in isodensity contours in the bottomside F layer into plasma bubbles is well accepted, some believed bubbles to be cylinder-like closed regions of depleted plasma density that floated upward leaving a turbulent wake behind them (e.g., Woodman and LaHoz, 1976; Ott, 1978; Kelley and Ott, 1978). Our results, summarized in a paper submitted to the Journal of Geophysical Research, consisted of incoherent scatter radar measurements that showed unambiguously that the depleted region is wedgelike and not cylinderlike, and a case study and modeling of SM-D electric field instrument (EFI) measurements that showed that the absence of electric-field perturbations outside the plasma-depleted region is a distinct signature of wedge

  15. Nonlinear Rayleigh-Taylor instability in partially ionized plasma and the equatorial spread - F

    International Nuclear Information System (INIS)

    Jain, R.K.; Das, A.C.

    1978-01-01

    The nonlinear evolution of the collisional gravitation induced Rayleigh-Taylor (R-T) instability in the equatorial F region is investigated taking into account the finite Larmor radius (FLR) effects and the complete ion inertial term in ion equation of motion. A special class of coherent weakly nonlinear modes as solutions to the wave equation describing R-T instability driven modes is obtained. The leading nonlinear effects in the wave equation are found to appear through Vsub(L), the ion diamagnetic drift which essentially gives the FLR corrections. It is shown that the R-T modes in the equatorial F region can evolve into coherent, nonlinear, almost sinusoidal, stationary wave structures. These structures are found to travel with a constant phase velocity and to have slightly distorted sinusoidal shapes. These results seem to have a good agreement with many of the recent rocket and satellite observations of the equatorial spread F irregularities. (author)

  16. Typical disturbances of the daytime equatorial F region observed with a high-resolution HF radar

    Directory of Open Access Journals (Sweden)

    E. Blanc

    1998-06-01

    Full Text Available HF radar measurements were performed near the magnetic equator in Africa (Korhogo 9°24'63''N–5°37'38''W during the International Equatorial Electrojet Year (1993–1994. The HF radar is a high-resolution zenithal radar. It gives ionograms, Doppler spectra and echo parameters at several frequencies simultaneously. This paper presents a comparative study of the daytime ionospheric structures observed during 3 days selected as representative of different magnetic conditions, given by magnetometer measurements. Broad Doppler spectra, large echo width, and amplitude fluctuations revealed small-scale instability processes up to the F-region peak. The height variations measured at different altitudes showed gravity waves and larger-scale disturbances related to solar daytime influence and equatorial electric fields. The possibility of retrieving the ionospheric electric fields from these Doppler or height variation measurements in the presence of the other possible equatorial ionospheric disturbances is discussed.

  17. Effects of the equatorial ionosphere on L-band Earth-space transmissions

    Science.gov (United States)

    Smith, Ernest K.; Flock, Warren L.

    1993-01-01

    Ionosphere scintillation can effect satellite telecommunication up to Ku-band. Nighttime scintillation can be attributed to large-scale inhomogeneity in the F-region of the ionosphere predominantly between heights of 200 and 600 km. Daytime scintillation has been attributed to sporadic E. It can be thought of as occurring in three belts: equatorial, high-latitude, and mid-latitude, in order of severity. Equatorial scintillation occurs between magnetic latitudes +/- 25 degrees, peaking near +/- 10 degrees. It commonly starts abruptly near 2000 local time and dies out shortly after midnight. There is a strong solar cycle dependence and a seasonal preference for the equinoxes, particularly the vernal one. Equatorial scintillation occurs more frequently on magnetically quiet than on magnetically disturbed days in most longitudes. At the peak of the sunspot cycle scintillation depths as great as 20 dB were observed at L-band.

  18. Larger CO2 source at the equatorial Pacific during the last deglaciation

    Science.gov (United States)

    Kubota, Kaoru; Yokoyama, Yusuke; Ishikawa, Tsuyoshi; Obrochta, Stephen; Suzuki, Atsushi

    2014-01-01

    While biogeochemical and physical processes in the Southern Ocean are thought to be central to atmospheric CO2 rise during the last deglaciation, the role of the equatorial Pacific, where the largest CO2 source exists at present, remains largely unconstrained. Here we present seawater pH and pCO2 variations from fossil Porites corals in the mid equatorial Pacific offshore Tahiti based on a newly calibrated boron isotope paleo-pH proxy. Our new data, together with recalibrated existing data, indicate that a significant pCO2 increase (pH decrease), accompanied by anomalously large marine 14C reservoir ages, occurred following not only the Younger Dryas, but also Heinrich Stadial 1. These findings indicate an expanded zone of equatorial upwelling and resultant CO2 emission, which may be derived from higher subsurface dissolved inorganic carbon concentration. PMID:24918354

  19. Geology of the Venus equatorial region from Pioneer Venus radar imaging

    International Nuclear Information System (INIS)

    Senske, D.A.; Head, J.W.

    1989-01-01

    The surface characteristics and morphology of the equatorial region of Venus were first described by Masursky et al. who showed this part of the planet to be characterized by two topographic provinces, rolling plains and highlands, and more recently by Schaber who described and interpreted tectonic zones in the highlands. Using Pioneer Venus (PV) radar image data (15 deg S to 45 deg N), Senske and Head examined the distribution, characteristics, and deposits of individual volcanic features in the equatorial region, and in addition classified major equatorial physiographic and tectonic units on the basis of morphology, topographic signature, and radar properties derived from the PV data. Included in this classification are: plains (undivided), inter-highland tectonic zones, tectonically segmented linear highlands, upland rises, tectonic junctions, dark halo plains, and upland plateaus. In addition to the physiographic units, features interpreted as coronae and volcanic mountains have also been mapped. The latter four of the physiographic units along with features interpreted to be coronae

  20. Sensitivity of equatorial Pacific and Indian Ocean watermasses to the position of the Indonesian Throughflow

    Science.gov (United States)

    Rodgers, Keith B.; Latif, Mojib; Legutke, Stephanie

    2000-09-01

    The sensitivity of the thermal structure of the equatorial Pacific and Indian Ocean pycnoclines to a model's representation of the Indonesian Straits connecting the two basins is investigated. Two integrations are performed using the global HOPE ocean model. The initial conditions and surface forcing for both cases are identical; the only difference between the runs is that one has an opening for the Indonesian Straits which spans the equator on the Pacific side, and the other has an opening which lies fully north of the equator. The resulting sensitivity throughout much of the upper ocean is greater than 0.5°C for both the equatorial Indian and Pacific. A realistic simulation of net Indonesian Throughflow (ITF) transport (measured in Sverdrups) is not sufficient for an adequate simulation of equatorial watermasses. The ITF must also contain a realistic admixture of northern and southern Pacific source water.

  1. Prevalence of anemia and associated factors in children living in urban and rural settings from Bata District, Equatorial Guinea, 2013.

    Science.gov (United States)

    Ncogo, Policarpo; Romay-Barja, Maria; Benito, Agustin; Aparicio, Pilar; Nseng, Gloria; Berzosa, Pedro; Santana-Morales, Maria A; Riloha, Matilde; Valladares, Basilio; Herrador, Zaida

    2017-01-01

    Anemia in children under 5 years of age is a global public health problem. According to the World Health Organization the current rate of anemia among preschool aged children in Equatorial Guinea is 66%. No information is available above this age. The cross-sectional Prevamal Survey was conducted in 2013 aimed at providing baseline data on malaria prevalence in children aged 2 months-15 years old. Sampling was carried out with the use of a multistage, stratified cluster strategy in the district of Bata, Equatorial Guinea. The χ2 test and adjusted Poisson regression models were applied to assess the association between social-demographic and economic factors, malaria and anemia. A total of 1436 children were tested, out of which 1,421 children (99%) were tested for anemia. Over 85% were anemic; out of them, 284 (24%), 815 (67%) and 111 (9%) children had mild, moderate and severe anemia, respectively. Severe anemia was more frequent among children aged 2-12 months old and those living in rural sites. About 47% tested positive for malaria via a rapid diagnostic test (RDT). This rate was significantly higher in rural villages (66%; panemia and malaria was higher in rural settings (panemia in urban areas displayed a heterogeneity and complexity that differed from the rural environment: in urban neighbourhoods, children with concomitant malaria infection were more likely to be anemic (adjusted prevalence rate (aPR):1.19; CI 95%: 1.12-1.28). Moreover, the prevalence of anemia was higher in children aged above 13 months compared to younger children (pchildren' parents being employees (aPR: 0.86, 95% CI: 0.76-0.96) or self-employed (aPR: 0.86, 95% CI: 0.76-0.97) vs. working in agriculture and/or fishing negatively associated with anemia among urban children. This marked urban-rural variation indicates the importance of targeting specific areas or districts. Strategies aimed at reducing malaria are clearly paramount in this country. Prevention and treatment of other factors

  2. The ITER Equatorial Visible/Infra-Red Wide Angle Viewing System: Status of design and R&D

    Energy Technology Data Exchange (ETDEWEB)

    Salasca, Sophie, E-mail: sophie.salasca@cea.fr [CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France); Aumeunier, Marie-Helene; Benoit, Fabrice; Cantone, Bruno; Corre, Yann; Delchambre, Elise; Ferlet, Marc; Gauthier, Eric; Guillon, Christophe; Houtte, Didier van; Keller, Delphine; Labasse, Florence; Larroque, Sebastien; Loarer, Thierry; Micolon, Frederic; Peluso, Bertrand; Proust, Maxime [CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France); Blanchet, David; Peneliau, Yannick [CEA, DEN/DER, F-13108 Saint-Paul-lez-Durance (France); Alonso, Javier [CIEMAT, Avda. Complutense, 40, Madrid 28040 (Spain); and others

    2015-10-15

    Highlights: • The status of Equatorial Visible/Infra-Red Wide Angle Viewing System is presented. • An assessment of measurement parameters relevant for machine protection has been done. • Remaining uncertainties will be clarified during the System Level Design (SLD). • WAVS design is not considered mature enough to launch prototypes of subcomponents. • Mandatory prototypes and qualification tests are already identified. • Next stage (SLD) will enable to do trade-offs and address pending design issues. - Abstract: The Equatorial Visible/Infra-Red Wide Angle Viewing System (WAVS) is one of the ITER key diagnostics owing to its role in machine investment protection through the monitoring of Plasma Facing Components (PFCs) by Infra-Red thermography and visible imaging. Foreseen to be installed in 4 equatorial port plugs to maximize the coverage of divertor, first wall, heating antennas and upper strike zone, the WAVS will likely be composed of 15 lines of sight and 15 optical systems transferring the light along several meters from the PFCs through the port plug and interspace up to detectors located in the port cell. After a conceptual design phase led by ITER Organization, the design is being further developed through a Framework Partnership Agreement signed between the European Domestic Agency, Fusion for Energy, and a consortium gathering CEA, CIEMAT (with INTA as third party) and Bertin Technologies company. The next design step is the System Level Design (SLD) which will enable to consolidate the WAVS specifications as well as the performance realistically achievable (taking into account ITER and project constraints). The SLD has been preceded by a preparatory phase aiming at clarifying the WAVS functions and identifying critical prototyping. The outcomes of this preparatory phase are reported in this paper. First a review by the consortium of the WAVS measurement specifications is presented, for the purpose of a clearer separation of measurement

  3. Prevalence of anemia and associated factors in children living in urban and rural settings from Bata District, Equatorial Guinea, 2013.

    Directory of Open Access Journals (Sweden)

    Policarpo Ncogo

    Full Text Available Anemia in children under 5 years of age is a global public health problem. According to the World Health Organization the current rate of anemia among preschool aged children in Equatorial Guinea is 66%. No information is available above this age. The cross-sectional Prevamal Survey was conducted in 2013 aimed at providing baseline data on malaria prevalence in children aged 2 months-15 years old. Sampling was carried out with the use of a multistage, stratified cluster strategy in the district of Bata, Equatorial Guinea. The χ2 test and adjusted Poisson regression models were applied to assess the association between social-demographic and economic factors, malaria and anemia. A total of 1436 children were tested, out of which 1,421 children (99% were tested for anemia. Over 85% were anemic; out of them, 284 (24%, 815 (67% and 111 (9% children had mild, moderate and severe anemia, respectively. Severe anemia was more frequent among children aged 2-12 months old and those living in rural sites. About 47% tested positive for malaria via a rapid diagnostic test (RDT. This rate was significantly higher in rural villages (66%; p<0.001. The prevalence of anemia and malaria was higher in rural settings (p<0.001. On the other hand, anemia in urban areas displayed a heterogeneity and complexity that differed from the rural environment: in urban neighbourhoods, children with concomitant malaria infection were more likely to be anemic (adjusted prevalence rate (aPR:1.19; CI 95%: 1.12-1.28. Moreover, the prevalence of anemia was higher in children aged above 13 months compared to younger children (p<0.005. Belonging to the poorest wealth tertile were positively (aPR: 1.14, 95% CI: 1.05-1.24 and children' parents being employees (aPR: 0.86, 95% CI: 0.76-0.96 or self-employed (aPR: 0.86, 95% CI: 0.76-0.97 vs. working in agriculture and/or fishing negatively associated with anemia among urban children. This marked urban-rural variation indicates the

  4. Equatorial atmospheric Kelvin waves during El Niño episodes and their effect on stratospheric QBO

    International Nuclear Information System (INIS)

    Das, Uma; Pan, C.J.

    2016-01-01

    Equatorial atmospheric Kelvin waves are investigated during a positive El Niño Southern Oscillation (ENSO) episode using temperature data retrieved from GPS Radio Occultation (RO) observations of FORMOSAT-3/COSMIC during the period from August 2006 to December 2013. Enhanced Kelvin wave amplitudes are observed during the El Niño episode of 2009–2010 and it is also observed that these amplitudes correlate with the Niño 3.4 index and also with outgoing longwave radiation and trade wind index. This study indicates that the enhanced equatorial atmospheric Kelvin wave amplitudes might be produced by geophysical processes that were involved in the onset and development of the El Niño episode. Further, easterly winds above the tropopause during this period favored the vertically upward propagation of these waves that induced a fast descending westerly regime by the end of 2010, where the zero-wind line is observed to take only 5 months to descend from 10 to 50 hPa. The current study presents observational evidence of enhanced Kelvin wave amplitudes during El Niño that has affected the stratospheric quasi-biennial oscillation (QBO) through wave–mean flow interactions. Earlier El Niño episodes of 1987 and 1998 are also qualitatively investigated, using reanalysis data. It is found that there might have been an enhancement in the equatorial Kelvin wave amplitudes during almost all El Niño episodes, however, an effect of a fast descending westerly is observed in the QBO only when the ambient zonal winds in the lower stratosphere favor the upward propagation of the Kelvin waves and consequently they interact with the mean flow. This study indicates that the El Niño and QBO are not linearly related and wave mean flow interactions play a very important role in connecting these two geophysical phenomena. - Highlights: • Enhanced atmospheric Kelvin Wave amplitudes observed during El Nino of 2010. • The waves are probably produced by processes generating El Nino.

  5. Equatorial atmospheric Kelvin waves during El Niño episodes and their effect on stratospheric QBO

    Energy Technology Data Exchange (ETDEWEB)

    Das, Uma [Department of Physics, University of New Brunswick, Fredericton (Canada); Pan, C.J., E-mail: cjpan@jupiter.ss.ncu.edu.tw [Institute of Space Science, National Central University, Jhongli, Taiwan (China)

    2016-02-15

    Equatorial atmospheric Kelvin waves are investigated during a positive El Niño Southern Oscillation (ENSO) episode using temperature data retrieved from GPS Radio Occultation (RO) observations of FORMOSAT-3/COSMIC during the period from August 2006 to December 2013. Enhanced Kelvin wave amplitudes are observed during the El Niño episode of 2009–2010 and it is also observed that these amplitudes correlate with the Niño 3.4 index and also with outgoing longwave radiation and trade wind index. This study indicates that the enhanced equatorial atmospheric Kelvin wave amplitudes might be produced by geophysical processes that were involved in the onset and development of the El Niño episode. Further, easterly winds above the tropopause during this period favored the vertically upward propagation of these waves that induced a fast descending westerly regime by the end of 2010, where the zero-wind line is observed to take only 5 months to descend from 10 to 50 hPa. The current study presents observational evidence of enhanced Kelvin wave amplitudes during El Niño that has affected the stratospheric quasi-biennial oscillation (QBO) through wave–mean flow interactions. Earlier El Niño episodes of 1987 and 1998 are also qualitatively investigated, using reanalysis data. It is found that there might have been an enhancement in the equatorial Kelvin wave amplitudes during almost all El Niño episodes, however, an effect of a fast descending westerly is observed in the QBO only when the ambient zonal winds in the lower stratosphere favor the upward propagation of the Kelvin waves and consequently they interact with the mean flow. This study indicates that the El Niño and QBO are not linearly related and wave mean flow interactions play a very important role in connecting these two geophysical phenomena. - Highlights: • Enhanced atmospheric Kelvin Wave amplitudes observed during El Nino of 2010. • The waves are probably produced by processes generating El Nino.

  6. Observation of low energy particle precipitation at low altitude in the equatorial zone

    Science.gov (United States)

    Miah, M. A.

    1989-01-01

    Precipitation of protons in the equatorial zone was investigated by the Phoenix-1 experiment on the S81-1 mission from May to November, 1982. The protons show a precipitation peak along the line of minimum magnetic field strength with a FWHM of 13 deg. The index of equatorial pitch angle distribution is about 19. The peak proton flux shows a fifth-power altitude dependence, and the proton flux shows approximately a factor of 3 times increase in 1982 compared to that in 1969 due, possibly, to the stronger solar maximum conditions of 10.7-cm radiation in 1982.

  7. Concept development for the ITER equatorial port visible/infrared wide angle viewing system

    International Nuclear Information System (INIS)

    Reichle, R.; Beaumont, B.; Boilson, D.; Bouhamou, R.; Direz, M.-F.; Encheva, A.; Henderson, M.; Kazarian, F.; Lamalle, Ph.; Lisgo, S.; Mitteau, R.; Patel, K. M.; Pitcher, C. S.; Pitts, R. A.; Prakash, A.; Raffray, R.; Schunke, B.; Snipes, J.; Diaz, A. Suarez; Udintsev, V. S.

    2012-01-01

    The ITER equatorial port visible/infrared wide angle viewing system concept is developed from the measurement requirements. The proposed solution situates 4 viewing systems in the equatorial ports 3, 9, 12, and 17 with 4 views each (looking at the upper target, the inner divertor, and tangentially left and right). This gives sufficient coverage. The spatial resolution of the divertor system is 2 times higher than the other views. For compensation of vacuum-vessel movements, an optical hinge concept is proposed. Compactness and low neutron streaming is achieved by orienting port plug doglegs horizontally. Calibration methods, risks, and R and D topics are outlined.

  8. Instabilities associated with the equatorial spread-F phenomenon and their north-south asymmetry

    International Nuclear Information System (INIS)

    Beghin, C.; Pandey, R.; Roux, D.

    1985-01-01

    Six North to South passes of AUREOL/ARCAD 3 satellite through the equatorial electron density depletion at variable altitude between 400 and 550 km, at night, during a two weeks period, exhibit a similar feature in plasma density irregularities which are thought to be associated with spread F phenomenon. The irregularities are found to be quasi-sinusoidal with a scale size of about 2 km along the satellite trajectory and occur only on the Northern edge of the equatorial electron density depletion. This implies a violation of the generally believed principle of conjugate mapping for those wavelengths. These observations are analysed and discussed in terms of different known generation mechanisms

  9. Collisional Rayleigh-Taylor instability and shear-flow in equatorial Spread-F plasma

    Directory of Open Access Journals (Sweden)

    N. Chakrabarti

    2003-05-01

    Full Text Available Collisional Rayleigh-Taylor (RT instability is considered in the bottom side of the equatorial F-region. By a novel nonmodal calculation it is shown that for an applied shear flow in equilibrium, the growth of the instability is considerably reduced. Finite but small amounts of diffusion enhances the stabilization process. The results may be relevant to the observations of long-lived irregularities at the bottom-side of the F-layer.Key words. Ionosphere (ionospheric irregularities, equatorial ionosphere, plasma waves and instabilities

  10. The physical and theoretical basis of solar-terrestrial relationships 2. Non-equatorial locations

    International Nuclear Information System (INIS)

    Njau, E.C.

    1988-07-01

    The basic formulations presented in Part 1 of this series (hereinafter simply referred to as ''Paper 1'') are modified in order to mathematically represent the expected solar-terrestrial influences in non-equatorial regions. Analysis and interpretation of these formulations lead to the establishment of several new periodicities as well as other features associated with the non-equatorial atmosphere. Besides, we show through suitable examples that the physical processes that cause and influence some previously observed climatic and upper atmospheric variations in temperate and polar regions are easily deduced from our formulations. (author). 35 refs

  11. Observations of Pc5 micropulsation-related electric field oscillations in the equatorial ionosphere

    Directory of Open Access Journals (Sweden)

    C. A. Reddy

    1994-05-01

    Full Text Available A 54.95-MHz coherent backscatter radar, an ionosonde and the magnetometer located at Trivandrum in India (8.5°N, 77°E, 0.5°N dip angle recorded large-amplitude ionospheric fluctuations and magnetic field fluctuations associated with a Pc5 micropulsation event, which occurred during an intense magnetic storm on 24 March 1991 (Ap=161. Simultaneous 100-nT-level fluctuations are also observed in the H-component at Brorfelde, Denmark (55.6°N gm and at Narsarsuaq, Greenland (70.6°N gm. Our study of the above observations shows that the E-W electric field fluctuations in the E- and F-regions and the magnetic field fluctuations at Thumba are dominated by a near-sinusoidal oscillation of 10 min during 1730-1900 IST (1200-1330 UT, the amplitude of the electric field oscillation in the equatorial electrojet (EEJ is 0.1-0.25 mV m-1 and it increases with height, while it is about 1.0 mV m-1 in the F-region, the ground-level H-component oscillation can be accounted for by the ionospheric current oscillation generated by the observed electric field oscillation in the EEJ and the H-component oscillations at Trivandrum and Brorfelde are in phase with each other. The observations are interpreted in terms of a compressional cavity mode resonance in the inner magnetosphere and the associated ionospheric electric field penetrating from high latitudes to the magnetic equator.

  12. Development of a global education environment to study the Equatorial Ionosphere with Cognitive Radars

    Science.gov (United States)

    Urbina, J. V.

    2011-12-01

    The author has recently been awarded the NSF Career award to develop a radar with cognitive sensing capabilities to study Equatorial plasma instabilities in the Peruvian Andes. Educational research has shown that a rich learning environment contributes tremendously toward improvement in learning achievements and also attitudes toward studies. One of the benefits of this project is that it provides such an environment and a global platform to involve several students at both graduate and undergraduate levels from the US, Puerto Rico, and Peru, and who will benefit from designing, installing, and deploying a radar in multi-instrument science campaigns. In addition to working in the laboratories, students will gain invaluable real world experience building this complex instrument and making it work under challenging conditions at remote sites. The PI will describe how these components are being developed in a Freshman Seminar course and Graduate courses in the Department of Electrical Engineering at Penn State University, and how they are aligned well with the department's and university's strategy for greater global engagement through a network of Global Engagement Nodes in South America (GENSA). The issues of mentoring, recruitment, and retention become particularly important in consideration of the educational objective of this career project to involve underrepresented students with diverse backgrounds and interest them in research projects. The author is working very closely with the Office of Engineering Diversity to leverage existing programs at Penn State designed to increase the participation of women and minority students in science and engineering research: (a) WISER (Women In Science and Engineering Research), and (b) MURE (Minority Undergraduate Research Experience). The Electrical Engineering Department at Penn State is also currently an NSF REU (Research Experience for Undergraduates) site. The PI will also present his efforts in connecting his career

  13. Changes in Eastern Equatorial Pacific Thermocline Structure across the Last Deglaciation: Evidence from the Carnegie Ridge

    Science.gov (United States)

    Glaubke, R.; Schmidt, M. W.; Warner, L.; Hertzberg, J. E.; Marcantonio, F.; Bianchi, T. S.

    2017-12-01

    The eastern equatorial Pacific (EEP) is an important climatological region given its influence in the modulation of the El Niño - Southern Oscillation (ENSO). The current climatic mean state of the EEP is characterized by cool sea surface temperatures (SST) and a strong, shallow thermocline. Nevertheless, there remains significant uncertainty about past changes in tropical Pacific climate and how ENSO variability relates to the millennial-scale climate events of the last deglaciation. Here, we will present 21 kyrs of Mg/Ca paleotemperature data from the surface-dwelling foraminifera Globigerinoides ruber and the thermocline-dwelling foraminifera Neogloboquadrina dutertrei collected from piston core MV1014-02-17JC (00° 10.83'S, 85° 52.00'W; 2846 m depth) on the Carnegie Ridge. Initial results reveal a 1.3°C warming of the surface ocean from the early-Holocene until 6 kyrs, a trend present in other EEP SST reconstructions (Pena et al., 2008; Timmerman et al., 2014; Lea et al., 2000). The surface ocean subsequently cools from 6 kyrs and reaches present-day temperatures by 3.5 kyrs. The subsurface reveals a nearly monotonic cooling of 1.8°C from 10.8 kyrs to the present day, which suggest a gradual shoaling of the thermocline across the Holocene. Furthermore, an increase in the vertical temperature gradient occurs from the late- to mid-Holocene, with the sharpest temperature difference centered at 6 kyrs, coincident with the mid-Holocene peak in SSTs. Taken together, these data suggest a gradual shoaling of the thermocline across the Holocene, with the variations in SST primarily governing the intensity of the vertical temperature gradient. Future work includes extending this record back to the last glacial maximum (LGM) to assess tropical Pacific mean state change across the abrupt climate events that characterized the last deglaciation.

  14. Observations of Pc5 micropulsation-related electric field oscillations in equatorial ionosphere

    Science.gov (United States)

    Reddy, C. A.; Ravindran, Sudha; Viswanathan, K. S.; Murthy, B. V. Krishna; Rao, D. R. K.; Araki, T.

    1994-01-01

    A 54.95-MHz coherent backscatter radar, an ionosonde and the magnetometer located at Trivandrum in India (8.5 deg N, 77 deg E, 0.5 deg N dip angle) recorded large-amplitude ionospheric fluctuations and magnetic field fluctuations associated with a Pc5 micropulsation event, which occurred during an intense magnetic storm on 24 March 1991 (A(sub p) = 161). Simultaneous 100-n T-level fluctuations are also observed in the H-component at Brorfelde, Denmark (55.6 deg N gm) and at Narsarsuaq, Greenland (70.6 deg N gm). Our study of the above observations shows that the E-W electric field fluctuations in the E- and F-regions and the magnetic field fluctuations at Thumba are dominated by a near-sinusoidal oscillation of 10 min during 1730-1900 IST (1200-1330 UT), the amplitude of the electric field oscillation in the equatorial electrojet (EEJ) is 0.1-0.25 mV/m and it increases with height, while it is about 1.0 mV/m in the F-region, the ground-level H-component oscillation can be accounted for by the ionospheric current oscillation generated by the observed electric field oscillation in the EEJ and the H-component oscillations at Trivandrum and Brofelde are in phase with each other. The observations are interpreted in terms of a compressional cavity mode resonance in the inner magnetosphere and the assoicated ionospheric electric field penetrating from high latitudes to the magnetic equator.

  15. Observations of Pc5 micropulsation-related electric field oscillations in the equatorial ionosphere

    Directory of Open Access Journals (Sweden)

    C. A. Reddy

    Full Text Available A 54.95-MHz coherent backscatter radar, an ionosonde and the magnetometer located at Trivandrum in India (8.5°N, 77°E, 0.5°N dip angle recorded large-amplitude ionospheric fluctuations and magnetic field fluctuations associated with a Pc5 micropulsation event, which occurred during an intense magnetic storm on 24 March 1991 (Ap=161. Simultaneous 100-nT-level fluctuations are also observed in the H-component at Brorfelde, Denmark (55.6°N gm and at Narsarsuaq, Greenland (70.6°N gm. Our study of the above observations shows that the E-W electric field fluctuations in the E- and F-regions and the magnetic field fluctuations at Thumba are dominated by a near-sinusoidal oscillation of 10 min during 1730-1900 IST (1200-1330 UT, the amplitude of the electric field oscillation in the equatorial electrojet (EEJ is 0.1-0.25 mV m-1 and it increases with height, while it is about 1.0 mV m-1 in the F-region, the ground-level H-component oscillation can be accounted for by the ionospheric current oscillation generated by the observed electric field oscillation in the EEJ and the H-component oscillations at Trivandrum and Brorfelde are in phase with each other. The observations are interpreted in terms of a compressional cavity mode resonance in the inner magnetosphere and the associated ionospheric electric field penetrating from high latitudes to the magnetic equator.

  16. Global characteristics of the lunar tidal modulation of the equatorial electrojet derived from CHAMP observations

    Directory of Open Access Journals (Sweden)

    H. Lühr

    2012-03-01

    Full Text Available It has been known since many decades that lunar tide has an influence on the strength of the equatorial electrojet (EEJ. There has, however, never been a comprehensive study of the tidal effect on a global scale. Based on the continuous magnetic field measurements by the CHAMP satellite over 10 years it is possible to investigate the various aspects of lunar effects on the EEJ. The EEJ intensity is enhanced around times when the moon is overhead or at the antipode. This effect is particularly strong around noon, shortly after new and full moon. The lunar tide manifests itself as a semi-diurnal wave that precesses through all local times within one lunar month. The largest tidal amplitudes are observed around December solstice and smallest around June solstice. The tidal wave crest lags behind the moon phase. During December this amounts to about 4 days while it is around 2 days during other times of the year. We have not found significant longitudinal variations of the lunar influence on the EEJ. When comparing the average EEJ amplitude at high solar activity with that during periods of solar minimum conditions a solar cycle dependence can be found, but the ratio between tidal amplitude and EEJ intensity stays the same. Actually, tidal signatures standout clearer during times of low solar activity. We suggest that the tidal variations are caused by a current system added to the EEJ rather than by modulating the EEJ. Gravitational forcing of the lower atmosphere by the moon and the sun is assumed to be the driver of an upward propagating tidal wave. The larger tidal amplitudes around December solstice can be related to stratospheric warming events which seem to improve the conditions for upward propagation. The results described here have to large extent been presented as a Julius-Bartels Medal Lecture during the General Assembly 2011 of the European Geosciences Union.

  17. Association between mean and interannual equatorial Indian Ocean subsurface temperature bias in a coupled model

    Science.gov (United States)

    Srinivas, G.; Chowdary, Jasti S.; Gnanaseelan, C.; Prasad, K. V. S. R.; Karmakar, Ananya; Parekh, Anant

    2018-03-01

    In the present study the association between mean and interannual subsurface temperature bias over the equatorial Indian Ocean (EIO) is investigated during boreal summer (June through September; JJAS) in the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFSv2) hindcast. Anomalously high subsurface warm bias (greater than 3 °C) over the eastern EIO (EEIO) region is noted in CFSv2 during summer, which is higher compared to other parts of the tropical Indian Ocean. Prominent eastward current bias in the upper 100 m over the EIO region induced by anomalous westerly winds is primarily responsible for subsurface temperature bias. The eastward currents transport warm water to the EEIO and is pushed down to subsurface due to downwelling. Thus biases in both horizontal and vertical currents over the EIO region support subsurface warm bias. The evolution of systematic subsurface warm bias in the model shows strong interannual variability. These maximum subsurface warming episodes over the EEIO are mainly associated with La Niña like forcing. Strong convergence of low level winds over the EEIO and Maritime continent enhanced the westerly wind bias over the EIO during maximum warming years. This low level convergence of wind is induced by the bias in the gradient in the mean sea level pressure with positive bias over western EIO and negative bias over EEIO and parts of western Pacific. Consequently, changes in the atmospheric circulation associated with La Niña like conditions affected the ocean dynamics by modulating the current bias thereby enhancing the subsurface warm bias over the EEIO. It is identified that EEIO subsurface warming is stronger when La Niña co-occurred with negative Indian Ocean Dipole events as compared to La Niña only years in the model. Ocean general circulation model (OGCM) experiments forced with CFSv2 winds clearly support our hypothesis that ocean dynamics influenced by westerly winds bias is primarily

  18. Global equatorial sea-surface temperatures over the last 150,000 years: An update from foraminiferal elemental analysis

    Digital Repository Service at National Institute of Oceanography (India)

    Saraswat, R.

    for the warmest waters. However, how the equatorial SST affects global climate, is still not clear. Long-term past seawater temperature records are required to understand the effect of temporal changes in equatorial SST on the global climate. Various techniques...

  19. A Nonequilibrium Figure of Saturn's Satellite Iapetus and the Origin of the Equatorial Ridge on Its Surface

    Science.gov (United States)

    Kondratyev, B. P.

    2018-03-01

    The structure, dynamical equilibrium, and evolution of Saturn's moon Iapetus are studied. It has been shown that, in the current epoch, the oblateness of the satellite ɛ2 ≈ 0.046 does not correspond to its angular velocity of rotation, which causes the secular spherization behavior of the ice shell of Iapetus. To study this evolution, we apply a spheroidal model, containing a rock core and an ice shell with an external surface ɛ2, to Iapetus. The model is based on the equilibrium finite-difference equation of the Clairaut theory, while the model parameters are taken from observations. The mean radius of the rock core and the oblateness of its level surface, ɛ1 ≈ 0.028, were determined. It was found that Iapetus is covered with a thick ice shell, which is 56.6% of the mean radius of the figure. We analyze a role of the core in the evolution of the shape of a gravitating figure. It was determined that the rock core plays a key part in the settling of the ice masses of the equatorial bulge, which finally results in the formation of a large circular equatorial ridge on the surface of the satellite. From the known mean altitude of this ice ridge, it was found that, in the epoch of its formation, the rotation period of Iapetus was 166 times shorter than that at present, as little as T ≈ 11h27m. This is consistent with the fact that a driving force of the evolution of the satellite in our model was its substantial despinning. The model also predicts that the ice ridge should be formed more intensively in the leading (dark and, consequently, warmer) hemisphere of the satellite, where the ice is softer. This inference agrees with the observations: in the leading hemisphere of Iapetus, the ridge is actually high and continuous everywhere, while it degenerates into individual ice peaks in the opposite colder hemisphere.

  20. Study of alkylphenols, indol and pyridinic nucleus of HPAN compounds by SPE/SI and SPE/C{sub 18}/NEC: application of SPE/Si phase to oils from the Alagoas sub-basin

    Energy Technology Data Exchange (ETDEWEB)

    Reboucas, L.M.C.; Nogueira, F.A.R.; Sabino, A.R.; Araujo, O.R.P.; Sant' Ana, A.E.G. [Universidade Federal de Alagoas (LABIS/UFAL), Maceio, AL (Brazil). Inst. de Quimica e Biotecnologia. Lab. de Analise de Biomarcadores e Semioquimicos], E-mail: lmcr@qui.ufal.br

    2008-10-15

    Alkylphenols (AP) and hydrocarbon polycyclic aromatic nitrogen (HPAN) compounds are important to study secondary migrations of petroleum. The behavior of AP and HPAN standards was investigated by solid phase extraction (SPE) on silica gel (SPE/Si) and C{sub 18}/NEC (SPE/C{sub 18}) stationary phases. The AP standards were eluted with dichloromethane (DCM) in the F2 fraction, on both SPE/Si and SPE/C{sub 18} phases. The basic and neutral HPAN compounds were eluted together with DCM, in F2 fraction, when a SPE/C18 column was used. However in the SPE/Si column the HPAN compounds were separated by their basic and neutral character in two different fractions. The neutral HPAN compounds were eluted with DCM, F2 fraction, and the HPAN basic compounds were eluted with the mixture DCM:isopropanol 5%, F3 fraction. In general, the quantity of recovered AP and HPAN compounds was higher with SPE/Si than SPE/C{sub 18}. The nine oil samples were analyzed by SPE/Si and the saturated and aromatic hydrocarbon were separated from the polar AP and HPAN. (author)

  1. Numerical modeling of the equatorial ionization anomaly (EIA), equatorial temperature and wind anomaly (ETWA) and equatorial electron temperature anomaly (EETA) on the basis of the GSM TIP

    Science.gov (United States)

    Klimenko, M. V.; Klimenko, V. V.; Bryukhanov, V. V.

    On the basis of Global Self-consistent Model of Thermosphere Ionosphere and Protonosphere GSM TIP developed in WD IZMIRAN the calculations of the behavior of thermosphere F-region and upper ionosphere parameters at middle and low geomagnetic latitudes are carried out The calculations were carried out with use the new block of the calculation of electric fields in the ionosphere in which the decision of the three-dimensional equation describing the law of the conservation of the full current density in the ionosphere of the Earth is realized by adduction it to the two-dimensional by integration on the thickness of the current conductive layer of the ionosphere along equipotential geomagnetic field lines The calculations of the neutral atmosphere composition and temperature were executed with use of the MSIS model The quite geomagnetic conditions of the equinox were considered in the minimum of the solar activity There are presented the calculated global distributions of the critical frequency of the F2-layer of ionosphere for the different moments UT the latitudinal course of the N e and T e in the F-region and upper ionosphere in the vicinity of geomagnetic equator and unrolling on UT of the calculated velocities of zonal component of the thermospheric wind and ion temperature in the F-region of ionosphere as well as critical frequency and height of the F2-layer maximum of the ionosphere at three longitude chains of the stations Brazilian -- Fortaleza 4 0 r S 38 0 r W Jicamarca 11 9 r S 76 0 r W Cachoeira

  2. Surface temperature of the equatorial Pacific Ocean and the Indian rainfall

    Digital Repository Service at National Institute of Oceanography (India)

    Gopinathan, C.K.

    The time variation of the monthly mean surface temperature of the equatorial Pacific Ocean during 1982-1987 has been studied in relation to summer monsoon rainfall over India The ENSO events of 1982 and 1987 were related to a significant reduction...

  3. A study of Sq(H) variations over equatorial electrojet regions | Okeke ...

    African Journals Online (AJOL)

    The newly established geomagnetic field observations in Japan, have enabled us to analyse the 1998 data of Huancayo, Kiritimati (Christmas Island) and Pohnpei where the geomagnetic Sq(H) variations of equatorial electrojet have been studied. The diurnal variation of the monthly means of Sq(H) on the five international ...

  4. Equatorial Indian Ocean productivity during the last 33 kyr and possible linkage to Westerly Jet variability

    Digital Repository Service at National Institute of Oceanography (India)

    Punyu, V.R.; Banakar, V.K.; Garg, A.

    The top 1 m radiocarbon dated section of a 5.6 m long sediment core retrieved from the Equatorial Indian Ocean is studied for productivity changes in response to climate variability that have taken place during the last ~33 kyr. The robust...

  5. Seasonal Variation of Diurnal Cycle of Rainfall in the Eastern Equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Pednekar, S.; Katsumata, M.; Antony, M.K.; Kuroda, Y.; Unnikrishnan, A.S.

    The diurnal cycle of rainfall over the eastern equatorial Indian Ocean is studied for the period 23rd October 2001 to 31st October 2003 using the hourly data from the Triton buoy positioned at 1.5°S and 90°E. An analysis of the active and weak...

  6. A study of evolution/suppression parameters of equatorial postsunset plasma instability

    Directory of Open Access Journals (Sweden)

    O. S. Oyekola

    2009-01-01

    Full Text Available Evening equatorial pre-reversal vertical ion E×B drift (VZP and the peak of the ionospheric F2 maximum altitude (hmF2P of the postsunset equatorial F-layer, which are the essential parameters requisite for the generation or inhibition of postsunset bottomside equatorial irregularities were deduced from ionosonde observations made in the Africa region (Ouagadougou: ~3° N dip latitude between January 1987 and December 1990 for solar activity minimum, medium, and maxima (F10.7=85, 141, 214, and 190, respectively for quiet geomagnetic conditions. We investigate variations of evening equatorial pre-reversal drift and the corresponding altitude at four levels of solar activity. Our observations show strong variations with solar variability. Correlation analysis between these parameters indicates that the correlation coefficient value between hmF2P versus VZP decreases considerably with increasing solar flux value. There seems to be no significant link between these parameters under high solar activity, especially for solar intensity F10.7>200 units. We conclude that meridional neutral wind in the F-region contributes substantially to the variations of the pre-reversal vertical plasma drifts enhancement and the peak hmF2, particularly the electrodynamics during twilight high solar flux conditions.

  7. The heat and moisture budgets of the atmosphere over central equatorial Indian Ocean during summer monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Sadhuram, Y.; Gopalakrishna, V.V.; RameshBabu, V.; Sastry, J.S.

    The heat and moisture budgets of the atmosphere (surface to 100 mb) over the central equatorial Indian Ocean (2 degrees N to 2 degrees S; 76 degrees E to 80 degrees E) have been investigated utilising the surface and upper air data collected...

  8. Post sunset equatorial spread-F at Kwajalein and interplanetary magnetic field

    Science.gov (United States)

    Rastogi, R. G.; Chandra, H.; Janardhan, P.; Reinisch, B. W.; Bisoi, Susanta Kumar

    2017-10-01

    We connect the time sequence of changes in the IMF-Bz to the development of spread-F at an equatorial station Kwajalein on three different nights in November 2004, one during a geomagnetic quiet period and other two during geomagnetic disturbed periods. The chosen days show clear and smooth variations of IMF-Bz without any large fluctuations thereby enabling one to correlate changes in equatorial spread-F with corresponding changes in IMF-Bz. It is shown that a slow and continuous increase in the IMF-Bz over a duration of few hours has a similar effect on the equatorial ionosphere as of a sudden northward turning of the IMF-Bz in causing an electric field through the polar region and then to the equator. We conclude that the Spread-F at equatorial and low latitudes are due to echoes from ionization irregularities that arise due to the plasma instabilities generated by an eastward electric field on the large plasma density gradient in or below the base of the F-layer during any period of the night time along with the gravity driven Rayleigh-Taylor instability.

  9. Nonlinear theory of the collisional Rayleigh-Taylor instability in equatorial spread F

    International Nuclear Information System (INIS)

    Chaturvedi, P.K.; Ossakow, S.L.

    1977-01-01

    The nonlinear behavior of the collisional Rayleigh-Taylor instability is studied in equatorial Spread F by including a dominant two-dimensional nonlinearity. It is found that on account of this nonlinearity the instability saturates by generating damped higher spatial harmonics. The saturated power spectrum for the density fluctuations is discussed. A comparison between experimental observations and theory is presented

  10. Targeting Aurora B to the equatorial cortex by MKlp2 is required for cytokinesis.

    Directory of Open Access Journals (Sweden)

    Mayumi Kitagawa

    Full Text Available Although Aurora B is important in cleavage furrow ingression and completion during cytokinesis, the mechanism by which kinase activity is targeted to the cleavage furrow and the molecule(s responsible for this process have remained elusive. Here, we demonstrate that an essential mitotic kinesin MKlp2 requires myosin-II for its localization to the equatorial cortex, and this event is required to recruit Aurora B to the equatorial cortex in mammalian cells. This recruitment event is also required to promote the highly focused accumulation of active RhoA at the equatorial cortex and stable ingression of the cleavage furrow in bipolar cytokinesis. Specifically, in drug-induced monopolar cytokinesis, targeting Aurora B to the cell cortex by MKlp2 is essential for cell polarization and furrow formation. Once the furrow has formed, MKlp2 further recruits Aurora B to the growing furrow. This process together with continuous Aurora B kinase activity at the growing furrow is essential for stable furrow propagation and completion. In contrast, a MKlp2 mutant defective in binding myosin-II does not recruit Aurora B to the cell cortex and does not promote furrow formation during monopolar cytokinesis. This mutant is also defective in maintaining the ingressing furrow during bipolar cytokinesis. Together, these findings reveal that targeting Aurora B to the cell cortex (or the equatorial cortex by MKlp2 is essential for the maintenance of the ingressing furrow for successful cytokinesis.

  11. Intensities and spatiotemporal variability of equatorial noise emissions observed by the Cluster spacecraft

    Czech Academy of Sciences Publication Activity Database

    Němec, F.; Santolík, Ondřej; Hrbáčková, Zuzana; Cornilleau-Wehrlin, N.

    2015-01-01

    Roč. 120, č. 3 (2015), s. 1620-1632 ISSN 2169-9380 R&D Projects: GA MŠk(CZ) LH11122 Institutional support: RVO:68378289 Keywords : equatorial noise * magnetosonic waves Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.318, year: 2015 http://onlinelibrary.wiley.com/doi/10.1002/2014JA020814/full

  12. Estimation of eddy diffusivity coefficient of heat in the upper layers of equatorial Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Zavialov, P.O.; Murty, V.S.N.

    in the Central Equatorial Arabian Sea (CEAS). A comparison of the model computed K sub(h) values with those estimated from the heat balance of the upper layer (50 m) of the sea shows good agreement in the region of weak winds (CEAS) or low turbulent mixing regime...

  13. Effective potential for equatorial motion in the Tomimatsu-Sato space-times

    Energy Technology Data Exchange (ETDEWEB)

    Calvani, M [Padua Univ. (Italy). Ist. di Astronomia

    1978-01-28

    We give general rules to draw the effective potential curves for equatorial motion in the T-S space-times either with am. Some general properties of the potentials are pointed out and few examples shown.

  14. Variability in foF2 at an equatorial station and the influence of magnetic activity

    International Nuclear Information System (INIS)

    Adeniyi, J.O.; Radicella, S.M.

    2003-01-01

    Variability in foF2 is investigated for an equatorial station in the African region. Variability during the day time at high solar activity varies between 10 and 30 percent. It varies between 10 and 20 percent at high solar activity. Magnetic storms increase the variability at both solar activity periods. (author)

  15. An Enduring Rapidly Moving Storm as a Guide to Saturn's Equatorial Jet's Complex Structure

    Science.gov (United States)

    Sanchez-Lavega, A.; Garcia-Melendo, E.; Perez-Hoyos, S.; Hueso, R.; Wong, M. H.; Simon, A.; Sanz-Requena, J. F.; Antunano, A.; Barrado-Izagirre, N.; Garate-Lopez, I.; hide

    2016-01-01

    Saturn has an intense and broad eastward equatorial jet with a complex three-dimensional structure mixed with time variability. The equatorial region experiences strong seasonal insolation variations enhanced by ring shadowing, and three of the six known giant planetary-scale storms have developed in it. These factors make Saturn's equator a natural laboratory to test models of jets in giant planets. Here we report on a bright equatorial atmospheric feature imaged in 2015 that moved steadily at a high speed of 450/ms not measured since 1980-1981 with other equatorial clouds moving within an ample range of velocities. Radiative transfer models show that these motions occur at three altitude levels within the upper haze and clouds. We find that the peak of the jet (latitudes 10degN to 10degS) suffers intense vertical shears reaching + 2.5/ms/km, two orders of magnitude higher than meridional shears, and temporal variability above 1 bar altitude level.

  16. Disruption of Saturn's quasi-periodic equatorial oscillation by the great northern storm

    Science.gov (United States)

    Fletcher, Leigh N.; Guerlet, Sandrine; Orton, Glenn S.; Cosentino, Richard G.; Fouchet, Thierry; Irwin, Patrick G. J.; Li, Liming; Flasar, F. Michael; Gorius, Nicolas; Morales-Juberías, Raúl

    2017-11-01

    The equatorial middle atmospheres of the Earth1, Jupiter2 and Saturn3,4 all exhibit a remarkably similar phenomenon—a vertical, cyclic pattern of alternating temperatures and zonal (east-west) wind regimes that propagate slowly downwards with a well-defined multi-year period. Earth's quasi-biennial oscillation (QBO) (observed in the lower stratospheric winds with an average period of 28 months) is one of the most regular, repeatable cycles exhibited by our climate system1,5,6, and yet recent work has shown that this regularity can be disrupted by events occurring far away from the equatorial region, an example of a phenomenon known as atmospheric teleconnection7,8. Here, we reveal that Saturn's equatorial quasi-periodic oscillation (QPO) (with an 15-year period3,9) can also be dramatically perturbed. An intense springtime storm erupted at Saturn's northern mid-latitudes in December 201010-12, spawning a gigantic hot vortex in the stratosphere at 40° N that persisted for three years13. Far from the storm, the Cassini temperature measurements showed a dramatic 10 K cooling in the 0.5-5 mbar range across the entire equatorial region, disrupting the regular QPO pattern and significantly altering the middle-atmospheric wind structure, suggesting an injection of westward momentum into the equatorial wind system from waves generated by the northern storm. Hence, as on Earth, meteorological activity at mid-latitudes can have a profound effect on the regular atmospheric cycles in Saturn's tropics, demonstrating that waves can provide horizontal teleconnections between the phenomena shaping the middle atmospheres of giant planets.

  17. Effects of solar eclipse on the electrodynamical processes of the equatorial ionosphere: a case study during 11 August 1999 dusk time total solar eclipse over India

    Directory of Open Access Journals (Sweden)

    R. Sridharan

    Full Text Available The effects on the electrodynamics of the equatorial E- and F-regions of the ionosphere, due to the occurrence of the solar eclipse during sunset hours on 11 August 1999, were investigated in a unique observational campaign involving ground based ionosondes, VHF and HF radars from the equatorial location of Trivandrum (8.5° N; 77° E; dip lat. 0.5° N, India. The study revealed the nature of changes brought about by the eclipse in the evening time E- and F-regions in terms of (i the sudden intensification of a weak blanketing ES-layer and the associated large enhancement of the VHF backscattered returns, (ii significant increase in h' F immediately following the eclipse and (iii distinctly different spatial and temporal structures in the spread-F irregularity drift velocities as observed by the HF radar. The significantly large enhancement of the backscattered returns from the E-region coincident with the onset of the eclipse is attributed to the generation of steep electron density gradients associated with the blanketing ES , possibly triggered by the eclipse phenomena. The increase in F-region base height immediately after the eclipse is explained as due to the reduction in the conductivity of the conjugate E-region in the path of totality connected to the F-region over the equator along the magnetic field lines, and this, with the peculiar local and regional conditions, seems to have reduced the E-region loading of the F-region dynamo, resulting in a larger post sunset F-region height (h' F rise. These aspects of E-and F-region behaviour on the eclipse day are discussed in relation to those observed on the control day.

    Key words. Ionosphere (electric fields and currents; equatorial ionosphere; ionospheric irregularities

  18. Effects of solar eclipse on the electrodynamical processes of the equatorial ionosphere: a case study during 11 August 1999 dusk time total solar eclipse over India

    Directory of Open Access Journals (Sweden)

    R. Sridharan

    2002-12-01

    Full Text Available The effects on the electrodynamics of the equatorial E- and F-regions of the ionosphere, due to the occurrence of the solar eclipse during sunset hours on 11 August 1999, were investigated in a unique observational campaign involving ground based ionosondes, VHF and HF radars from the equatorial location of Trivandrum (8.5° N; 77° E; dip lat. 0.5° N, India. The study revealed the nature of changes brought about by the eclipse in the evening time E- and F-regions in terms of (i the sudden intensification of a weak blanketing ES-layer and the associated large enhancement of the VHF backscattered returns, (ii significant increase in h' F immediately following the eclipse and (iii distinctly different spatial and temporal structures in the spread-F irregularity drift velocities as observed by the HF radar. The significantly large enhancement of the backscattered returns from the E-region coincident with the onset of the eclipse is attributed to the generation of steep electron density gradients associated with the blanketing ES , possibly triggered by the eclipse phenomena. The increase in F-region base height immediately after the eclipse is explained as due to the reduction in the conductivity of the conjugate E-region in the path of totality connected to the F-region over the equator along the magnetic field lines, and this, with the peculiar local and regional conditions, seems to have reduced the E-region loading of the F-region dynamo, resulting in a larger post sunset F-region height (h' F rise. These aspects of E-and F-region behaviour on the eclipse day are discussed in relation to those observed on the control day.Key words. Ionosphere (electric fields and currents; equatorial ionosphere; ionospheric irregularities

  19. Study of the Equatorial and Low-Latitude Electrodynamic and Ionospheric Disturbances During the 22-23 June 2015 Geomagnetic Storm Using Ground-Based and Spaceborne Techniques

    Science.gov (United States)

    Astafyeva, E.; Zakharenkova, I.; Hozumi, K.; Alken, P.; Coïsson, P.; Hairston, M. R.; Coley, W. R.

    2018-03-01

    We use a set of ground-based instruments (Global Positioning System receivers, ionosondes, magnetometers) along with data of multiple satellite missions (Swarm, C/NOFS, DMSP, GUVI) to analyze the equatorial and low-latitude electrodynamic and ionospheric disturbances caused by the geomagnetic storm of 22-23 June 2015, which is the second largest storm in the current solar cycle. Our results show that at the beginning of the storm, the equatorial electrojet (EEJ) and the equatorial zonal electric fields were largely impacted by the prompt penetration electric fields (PPEF). The PPEF were first directed eastward and caused significant ionospheric uplift and positive ionospheric storm on the dayside, and downward drift on the nightside. Furthermore, about 45 min after the storm commencement, the interplanetary magnetic field (IMF) Bz component turned northward, leading to the EEJ changing sign to westward, and to overall decrease of the vertical total electron content (VTEC) and electron density on the dayside. At the end of the main phase of the storm, and with the second long-term IMF Bz southward turn, we observed several oscillations of the EEJ, which led us to conclude that at this stage of the storm, the disturbance dynamo effect was already in effect, competing with the PPEF and reducing it. Our analysis showed no significant upward or downward plasma motion during this period of time; however, the electron density and the VTEC drastically increased on the dayside (over the Asian region). We show that this second positive storm was largely influenced by the disturbed thermospheric conditions.

  20. A biweekly mode in the equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Sengupta, D.; Senan, R.; Murty, V.S.N.; Fernando, V.

    at these depths. [14] To determine the space-time characteristics of the biweekly wave, wave number-frequency spectra of currents at 50 m and 500 m from the QuikSCAT simulation are computed following the method of Wheeler and Kiladis [1999]. The symmetric...

  1. Pneumoperitoneum in a Micropremie: Not Always NEC

    Directory of Open Access Journals (Sweden)

    Ahmed Khan

    2012-01-01

    Full Text Available Pneumoperitoneum in the newborn is an acute surgical emergency requiring immediate surgical intervention to ensure survival. It refers to radiological evidence of rupture of an air-containing viscus with resultant soiling of the peritoneal cavity. A female baby was born preterm at 29 weeks with birth weight of 650 grams. She developed abdominal distension on day 6, and abdominal radiography revealed presence of free air in the peritoneum. She proceeded for a laparotomy, and intraoperative findings revealed blood in the peritoneum with an area of inflammation and a small perforation. About 5 cm of the inflamed bowel was resected, and an end to end anastomosis performed. The histopathology of the specimen was consistent with Meckel's diverticulum. Symptomatic Meckel's diverticulum is usually seen in the first two years of life, and perforation is a rare presentation. Perforated Meckel's diverticulum in a premature newborn is very rare, and a review of literature reveals only one other reported case. Newborn Meckel's perforation cases often mimic necrotizing enterocolitis, although many present without any feature of peritonitis. Establishing a preoperative diagnosis of perforated Meckel's is difficult and may not be essential as the treatment remains the same. However, prompt surgical intervention confers a good prognosis in neonates with isolated perforated Meckel's diverticulum.

  2. Evidence for Suppression of Onchocerciasis Transmission in Bioko Island, Equatorial Guinea.

    Directory of Open Access Journals (Sweden)

    Laura Moya

    2016-07-01

    Full Text Available Onchocerciasis or "river blindness" is a chronic parasitic neglected tropical disease which is endemic both in mainland and insular Equatorial Guinea. We aim to estimate the current epidemiological situation of onchocerciasis in Bioko Island after vector elimination in 2005 and more than sixteen years of Community Directed Treatment with Ivermectin (CDTI by using molecular and serological approaches for onchocerciasis diagnosis. A community-based cross-sectional study was carried out in Bioko Island from mid-January to mid-February 2014. A total of 544 study participants were recruited. A complete dermatological examination was performed and three skin snips were performed in every participant for parasitological and molecular assessments. Blood spots were also taken for determination of Ov16 IgG4 antibodies trough an "in-house" ELISA assay. Overall, we found 15 out of 522 individuals suffering any onchocerciasis specific cutaneous lesions and 16 out of 528 (3.0% with onchocercal nodules in the skin. Nodules were significantly associated with age, being more common in subjects older than 10 years than in younger people (3.9% vs. 0%, p = 0.029. Regarding the onchocerciasis laboratory assessment, no positive parasitological test for microfilaria detection was found in the skin snips. The calculated seroprevalence through IgG4 serology was 7.9%. No children less than 10 years old were found to be positive for this test. Only one case was positive for Onchocerca volvulus (O. volvulus after skin PCR. The present study points out that the on-going mass ivermectin treatment has been effective in reducing the prevalence of onchocerciasis and corroborates the interruption of transmission in Bioko Island. To our knowledge, this is the first time that accurate information through molecular and serological techniques is generated to estimate the onchocerciasis prevalence in this zone. Sustained support from the national program and appropriate communication

  3. The complete spectrum of the equatorial electrojet related to solar tides: CHAMP observations

    Directory of Open Access Journals (Sweden)

    H. Lühr

    2013-08-01

    Full Text Available Based on 10 yr of magnetic field measurements by the CHAMP satellite we draw a detailed picture of the equatorial electrojet (EEJ tidal variations. For the first time the complete EEJ spectrum related to average solar tides has been compiled. A large fraction of the resulting spectrum is related to the switch on/off of the EEJ between day and night. This effect has carefully been considered when interpreting the results. As expected, largest amplitudes are caused by the migrating tides representing the mean diurnal variation. Higher harmonics of the daily variations show a 1/f fall-off in amplitude. Such a spectrum is required to represent the vanishing of the EEJ current at night. The migrating tidal signal exhibits a distinct annual variation with large amplitudes during December solstice and equinox seasons but a depression by a factor of 1.7 around June–July. A rich spectrum of non-migrating tidal effects is deduced. Most prominent is the four-peaked longitudinal pattern around August. Almost 90% of the structure can be attributed to the diurnal eastward-propagating tide DE3. In addition the westward-propagating DW5 is contributing to wave-4. The second-largest non-migrating tide is the semi-diurnal SW4 around December solstice. It causes a wave-2 feature in satellite observations. The three-peaked longitudinal pattern, often quoted as typical for the December season, is significantly weaker. During the months around May–June a prominent wave-1 feature appears. To first order it represents a stationary planetary wave SPW1 which causes an intensification of the EEJ at western longitudes beyond 60° W and a weakening over Africa/India. In addition, a prominent ter-diurnal non-migrating tide TW4 causes the EEJ to peak later, at hours past 14:00 local time in the western sector. A particularly interesting non-migrating tide is the semi-diurnal SW3. It causes largest EEJ amplitudes from October through December. This tidal component shows a

  4. Phanerozoic burial, uplift and denudation of the Equatorial Atlantic margin of South America

    Science.gov (United States)

    Japsen, Peter; Bonow, Johan M.; Green, Paul F.; dall'Asta, Massimo; Roig, Jean-Yves; Theveniaut, Hervé

    2017-04-01

    We have initiated a study aimed at understanding the history of burial, uplift and denudation of the South American Equatorial Atlantic Margin (SAEAM Uplift) including the Guiana Shield to provide a framework for investigating the hydrocarbon prospectivity of the offshore region. We report first results including observations from fieldwork at the northern and southern flank of the Guiana Shield. The study combines apatite fission-track analysis (AFTA) and vitrinite reflectance data from samples of outcrops and drillcores, sonic velocity data from drill holes and stratigraphic landscape analysis (mapping of peneplains) - all constrained by geological evidence, following the methods of Green et al. (2013). The study will thus combine the thermal history from AFTA data with the denudation history from stratigraphic landscape analysis to provide magnitudes and timing of vertical movements (Japsen et al. 2012, 2016). Along the Atlantic margin of Suriname and French Guiana, tilted and truncated Lower Cretaceous strata rest on Precambrian basement (Sapin et al. 2016). Our AFTA data show that the basement underwent Mesozoic exhumation prior to deposition of the Lower Cretaceous cover. Sub-horizontal peneplains define the landscape of the Guiana Shield at elevations up to 500 m a.s.l. As these sub-horizontal peneplains truncate the tilted, sub-Cretaceous surface along the Atlantic margin, these peneplains were therefore formed and uplifted in post-Cretaceous time. This interpretation is in good agreement with our AFTA data that define Paleogene exhumation along the margin and with the results of Theveniaut and Freyssinet (2002) who used palaeomagnetic data to conclude that bauxitic surfaces across basement at up to 400 m a.s.l. on the Guiana Shield formed during the Palaeogene. Integration of the results from AFTA with stratigraphic landscape analysis (currently in progress) and geological evidence will provide a robust reconstruction of the tectonic development of the

  5. The Pacific Equatorial Age Transect, IODP Expeditions 320 and 321: Building a 50-Million-Year-Long Environmental Record of the Equatorial Pacific Ocean

    Directory of Open Access Journals (Sweden)

    Kusali Gamage

    2010-04-01

    Full Text Available In March 2009, the R/V JOIDES Resolution returned to operations after its extended refit and began with a drilling program ideally suited to its drilling strengths, the Pacific Equatorial Age Transect (PEAT, IODP Exp 320/321; Fig. 1A. The PEAT drilling program was developed to understand how a major oceanic region evolved over the Cenozoic Era(65–0 Ma and how it interacted with global climate. It specifically targeted the interval between 52 Ma and 0 Ma and drilled a series of sites that originated on the paleoequator. These sites have since been moved to the northwest by plate tectonics.The equatorial Pacific is an important target for paleocean ographic study because it is a significant ‘cog’ in the Earth’s climate machine, representing roughly half of the total tropical oceans that in turn represent roughly half of the total global ocean area. Prior drilling in both the Deep Sea Drilling Project (DSDP and the Ocean Drilling Program (ODP outlined the changes that have occurred through the Cenozoic (e.g., van Andel et al., 1975; Pisias et al., 1995. Not only did the earlier work fail to cover sufficient timeintervals but also many of the sites were cored with ‘first-generation’ scientific drilling technology with incomplete and disturbed sediment recovery and thus cannot be used for detailed studies.

  6. A perspective of Middle-Atmosphere Dynamics (MAD) studies at the New International Equatorial Observatory (NIEO)

    Science.gov (United States)

    Yamanaka, M. D.; Fukao, S.

    1989-01-01

    The equatorial region has attracted many MAD studies mainly based on data of limited locations and resolutions. Established at NIEO are: (1) Climatology of the equatorial middle atmosphere (all of the mean zonal flow, the meridional and/or east-west circulations and the planetary/gravity waves are described based on massive, reliable data statistics); (2) Troposphere-stratosphere coupling at the equator (the candidate location of NIEO is just at the stratospheric fountain area where the tracers and waves are pumped up into the middle atmosphere); and (3) Mesosphere-thermosphere coupling at the equator; thermospheric superrotation, which may be caused either by ion drag or by tidal breaking, is examined in detail by observations covering a wide altitude range from the mesosphere through the thermosphere.

  7. Tectonic setting of the Seychelles, Mascarene and Amirante Plateaus in the Western Equatorial Indian Ocean

    International Nuclear Information System (INIS)

    Mart, Y.

    1988-01-01

    A system of marine plateaus occurs in the western equatorial Indian Ocean, forming an arcuate series of wide and shallow banks with small islands in places. The oceanic basins that surround the Seychelles - Amirante region are of various ages and reflect a complex seafloor spreading pattern. The structural analysis of the Seychelle - Amirante - Mascarene region reflects the tectonic evolution of the western equatorial Indian Ocean. It is suggested that due to the seafloor spreading during a tectonic stage, the Seychelles continental block drifted southwestwards to collide with the oceanic crust of the Mascarene Basin, forming an elongated folded structure at first, and then a subduction zone. The morphological similarity, the lithological variability and the different origin of the Seychelles Bank, the Mascarene Plateau and the Amirante Arc emphasizes the significant convergent effects of various plate tectonic processes on the development of marine plateaus

  8. Observation of low energy particle precipitation at low altitude in the equatorial zone

    International Nuclear Information System (INIS)

    Miah, M.A.

    1989-01-01

    Precipitation of protons (∼ 1 MeV) in the equatorial zone was investigated by the Phoenix-1 experiment on board the S81-1 mission from May-November, 1982. The protons show a precipitation peak along the line of minimum magnetic field strength with a full width at half maximum (FWHM) of 13 0 . The index of equatorial pitch angle distribution is q ∼ 19. The peak proton flux shows a fifth-power altitude dependence, and the proton flux shows approximately a factor of 3 times increase in 1982 compared to that in 1969 due, possibly, to the stronger (∼ 1.2 times) solar maximum conditions of 10.7 cm radiation in 1982. (author)

  9. Recycled iron fuels new production in the eastern equatorial Pacific Ocean.

    Science.gov (United States)

    Rafter, Patrick A; Sigman, Daniel M; Mackey, Katherine R M

    2017-10-24

    Nitrate persists in eastern equatorial Pacific surface waters because phytoplankton growth fueled by nitrate (new production) is limited by iron. Nitrate isotope measurements provide a new constraint on the controls of surface nitrate concentration in this region and allow us to quantify the degree and temporal variability of nitrate consumption. Here we show that nitrate consumption in these waters cannot be fueled solely by the external supply of iron to these waters, which occurs by upwelling and dust deposition. Rather, a substantial fraction of nitrate consumption must be supported by the recycling of iron within surface waters. Given plausible iron recycling rates, seasonal variability in nitrate concentration on and off the equator can be explained by upwelling rate, with slower upwelling allowing for more cycles of iron regeneration and uptake. The efficiency of iron recycling in the equatorial Pacific implies the evolution of ecosystem-level mechanisms for retaining iron in surface ocean settings where it limits productivity.

  10. Sensitivity of population smoke exposure to fire locations in Equatorial Asia

    Science.gov (United States)

    Kim, Patrick S.; Jacob, Daniel J.; Mickley, Loretta J.; Koplitz, Shannon N.; Marlier, Miriam E.; DeFries, Ruth S.; Myers, Samuel S.; Chew, Boon Ning; Mao, Yuhao H.

    2015-02-01

    High smoke concentrations in Equatorial Asia, primarily from land conversion to oil palm plantations, affect a densely populated region and represent a serious but poorly quantified air quality concern. Continued expansion of the oil palm industry is expected but the resulting population exposure to smoke is highly dependent on where this expansion takes place. We use the adjoint of the GEOS-Chem chemical transport model to map the sensitivity of smoke concentrations in major Equatorial Asian cities, and for the population-weighted region, to the locations of the fires. We find that fires in southern Sumatra are particularly detrimental, and that a land management policy protecting peatswamp forests in Southeast Sumatra would be of great air quality benefit. Our adjoint sensitivities can be used to immediately infer population exposure to smoke for any future fire emission scenario.

  11. Excitation of electromagnetic proton cyclotron instability by parallel electric field in the equatorial magnetosphere

    International Nuclear Information System (INIS)

    Dixit, S.K.; Azif, Z.A.; Gwal, A.K.

    1994-01-01

    The characteristics of the growth rate of electromagnetic ion cyclotron (EMIC) instability is investigated in a mixture of cold species of ions and warm proton in the presence of weak parallel static electric field. An attempt has been made to explain the excitation of EMIC waves through linear wave-particle (W-P) interaction in the equatorial magnetospheric region. The proton cyclotron instability is modified in presence of weak parallel electric field and the growth rate is computed for equatorial magnetospheric plasma parameters. The results of theoretical investigations of the growth rate are used to explain the excitation mechanism of extremely low frequency/very low frequency (ELF/VLF) waves as observed by satellites. (author). 29 refs., 4 figs

  12. Spatial correlation of the ionsphere total electron content at the equatorial anomaly crest

    International Nuclear Information System (INIS)

    Huang, Y.

    1984-01-01

    The spatial correlation of the ionospheric total electron content (TEC) at the equatorial anomaly crest was studied by recording Faraday rotation angle of the ETS-II geostationary satellite at Lunping and Kaohsiung whose subionospheric points are located at 23.0 0 N, 121.0 0 N, and 20.9 0 N, 121.1 0 E, respectively, and are about 280 km apart. The results show that the spatial correlation of TEC at the equatorial crest region is smaller than that at other places. The day-to-day variabilities of TEC differences between two subionospheric points are quite large. The day-to-day variabilities of the fountain effect seem to play an important role

  13. Equatorial spread F studies using SAMI3 with two-dimensional and three-dimensional electrostatics

    Directory of Open Access Journals (Sweden)

    H. C. Aveiro

    2013-12-01

    Full Text Available This letter presents a study of equatorial F region irregularities using the NRL SAMI3/ESF model, comparing results using a two-dimensional (2-D and a three-dimensional (3-D electrostatic potential solution. For the 3-D potential solution, two cases are considered for parallel plasma transport: (1 transport based on the parallel ambipolar field, and (2 transport based on the parallel electric field. The results show that the growth rate of the generalized Rayleigh–Taylor instability is not affected by the choice of the potential solution. However, differences are observed in the structures of the irregularities between the 2-D and 3-D solutions. Additionally, the plasma velocity along the geomagnetic field computed using the full 3-D solution shows complex structures that are not captured by the simplified model. This points out that only the full 3-D model is able to fully capture the complex physics of the equatorial F region.

  14. Numerical simulations of type II gradient drift irregularities in the equatorial electrojet

    International Nuclear Information System (INIS)

    Ferch, R.L.; Sudan, R.N.

    1977-01-01

    Two-dimensional numerical studies of the development of type II irregularities in the equatorial electrojet have been carried out using a method similar to that of McDonald et al., (1974) except that ion inertia has been neglected. This simplification is shown to be a valid approximation whenever the electron drift velocity is small in comparison with the ion acoustic velocity and the values of the other parameters are those appropriate for the equatorial E layer. This code enables us to follow the development of quasi-steady state turbulence from appropriate initial pertubations. The two-dimensional turbulent spectrum of electron density perturbations excited is studied both for the case of devlopment from initial perturbations and for the case of a continuously pumped single driving wave

  15. Geomagnetically Induced Currents Around the World During the 17 March 2015 Storm

    Science.gov (United States)

    Carter, B. A.; Yizengaw, E.; Pradipta, R.; Weygand, J. M.; Piersanti, M.; Pulkkinen, Antti Aleksi; Moldwin, M. B.; Norman, R.; Zhang, K.

    2016-01-01

    Geomagnetically induced currents (GICs) represent a significant space weather issue for power grid and pipeline infrastructure, particularly during severe geomagnetic storms. In this study, magnetometer data collected from around the world are analyzed to investigate the GICs caused by the 2015 St. Patricks Day storm. While significant GIC activity in the high-latitude regions due to storm time substorm activity is shown for this event, enhanced GIC activity was also measured at two equatorial stations in the American and Southeast Asian sectors. This equatorial GIC activity is closely examined, and it is shown that it is present both during the arrival of the interplanetary shock at the storm sudden commencement (SSC) in Southeast Asia and during the main phase of the storm approximately 10 h later in South America. The SSC caused magnetic field variations at the equator in Southeast Asia that were twice the magnitude of those observed only a few degrees to the north, strongly indicating that the equatorial electrojet (EEJ) played a significant role. The large equatorial magnetic field variations measured in South America are also examined, and the coincident solar wind data are used to investigate the causes of the sudden changes in the EEJ approximately 10 h into the storm. From this analysis it is concluded that sudden magnetopause current increases due to increases in the solarwind dynamic pressure, and the sudden changes in the resultant magnetospheric and ionospheric current systems, are the primary drivers of equatorial GICs.

  16. {sup 10}Be/{sup 230}Th ratios as proxy for particle flux in the equatorial Pacific ocean

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, R.F.; Fleisher, M.Q. [LDEO of Columbia Univ. (United States); Kubik, P.W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Suter, M. [Eidgenoessische Technische Hochschule, Zurich (Switzerland)

    1997-09-01

    Particulate {sup 10}Be/{sup 230}Th ratios collected by sediment traps in the central equatorial Pacific Ocean exhibit a positive correlation with particle flux, but little or no correlation with particle composition. (author) 1 fig., 4 refs.

  17. Spatial and temporal variability in nutrients and carbon uptake during 2004 and 2005 in the eastern equatorial Pacific Ocean

    DEFF Research Database (Denmark)

    Palacz, A. P.; Chai, F.

    2012-01-01

    The eastern equatorial Pacific plays a great role in the global carbon budget due to its enhanced biological productivity linked to the equatorial upwelling. However, as confirmed by the Equatorial Biocomplexity cruises in 2004 and 2005, nutrient upwelling supply varies strongly, partly due...... and intraseasonal time scales. Here, high resolution Pacific ROMS-CoSiNE (Regional Ocean Modeling System-Carbon, Silicon, Nitrogen Ecosystem) model results were evaluated with in situ and remote sensing data. The results of model-data comparison revealed a good agreement in domain-average hydrographic....... In order to fully resolve the complexity of biological and physical interactions in the eastern equatorial Pacific, we recommended improving CoSiNE and other models by introducing more phytoplankton groups, variable Redfield and carbon to chlorophyll ratios, as well as resolving the Fe-Si co...

  18. Response of the equatorial Pacific to chlorophyll pigment in a mixed layer isopycnal ocean general circulation model

    Digital Repository Service at National Institute of Oceanography (India)

    Nakamoto, S.; PrasannaKumar, S.; Oberhuber, J.M.; Ishizaka, J.; Muneyama, K.; Frouin, R.

    The influence of phytoplankton on the upper ocean dynamics and thermodynamics in the equatorial Pacific is investigated using an isopycnal ocean general circulation model (OPYC) coupled with a mixed layer model and remotely sensed chlorophyll...

  19. Polar and equatorial coronal hole winds at solar minima: From the heliosphere to the inner corona

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, L.; Landi, E., E-mail: lzh@umich.edu [Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48105 (United States)

    2014-02-01

    Fast solar wind can be accelerated from at least two different sources: polar coronal holes and equatorial coronal holes. Little is known about the relationship between the wind coming from these two different latitudes and whether these two subcategories of fast wind evolve in the same way during the solar cycle. Nineteen years of Ulysses observations, from 1990 to 2009, combined with ACE observations from 1998 to the present provide us with in situ measurements of solar wind properties that span two entire solar cycles. These missions provide an ideal data set to study the properties and evolution of the fast solar wind originating from equatorial and polar holes. In this work, we focus on these two types of fast solar wind during the minima between solar cycles 22 and 23 and 23 and 24. We use data from SWICS, SWOOPS, and VHM/FGM on board Ulysses and SWICS, SWEPAM, and MAG on board ACE to analyze the proton kinetic, thermal, and dynamic characteristics, heavy ion composition, and magnetic field properties of these two fast winds. The comparison shows that: (1) their kinetic, thermal, compositional, and magnetic properties are significantly different at any time during the two minima and (2) they respond differently to the changes in solar activity from cycle 23 to 24. These results indicate that equatorial and polar fast solar wind are two separate subcategories of fast wind. We discuss the implications of these results and relate them to remote-sensing measurements of the properties of polar and equatorial coronal holes carried out in the inner corona during these two solar minima.

  20. Investigation of Jupiter's Equatorial Hotspots and Plumes Using Cassini ISS Observations

    Science.gov (United States)

    Choi, David S.; Showman, A. P.; Vasavada, A. R.; Simon-Miller, A. A.

    2012-01-01

    We present updated analysis of Jupiter's equatorial meteorology from Cassini observations. For two months preceding the spacecraft's closest approach, the ISS onboard regularly imaged the atmosphere. We created time-lapse movies from this period in order to analyze the dynamics of equatorial 5-micron hot spots and their interactions with adjacent latitudes. Hot spots are quasi-stable, rectangular dark areas on visible-wavelength images, with defined eastern edges that sharply contrast with surrounding clouds, but a diffuse western edge serving as a nebulous boundary with adjacent equatorial plumes. Hot spots exhibit significant variations in size and shape over timescales of days and weeks. Some of these changes correspond with passing vortex systems from adjacent latitudes interacting with hot spots. Strong anticyclonic gyres present to the south and southeast of the dark areas appear to circulate into hot spots. Impressive, bright white plumes occupy spaces in between hot spots. Compact cirrus-iike 'scooter' clouds flow rapidly through the plumes before disappearing within the dark areas. This raises the possibility that the plumes and fast-moving clouds are at higher altitudes, because their speed does not match previously published zonal wind profiles. Most profiles represent the drift speed of the hot spots at their latitude from pattern matching of the entire longitudinal image strip. If a downward branch of an equatorially-trapped Rossby waves controls the overall appearance of hot spots, however, the westward phase velocity of the wave leads to underestimates of the true jet stream speed. Instead, our expanded data set demonstrating the rapid flow of these scooter clouds may be more illustrative of the actual jet stream speed at these latitudes. This research was supported by a NASA JDAP grant and the NASA Postdoctoral Program.

  1. Deglacial Western Equatorial Pacific pCO2 Reconstruction Using Boron Isotopes of Planktonic Foraminiferas

    Science.gov (United States)

    Kubota, K.; Yokoyama, Y.; Ishikawa, T.; Sagawa, T.; Ikehara, M.; Yamazaki, T.

    2017-12-01

    During the last deglaciation (ca. 19 - 11 ka), partial pressure of CO2 (pCO2) of the atmosphere increased by 80 μatm. Many paleoceanographers point out that the ocean had played an important role in atmospheric CO2 rise, since the ocean have 60 times larger capacity to store carbon compared to the atmosphere. However, evidence on where carbon was transferred from the ocean to the atmosphere is still lacking, hampering our understanding of global carbon cycles in glacial-interglacial timescales. Boron isotope of skeletons of marine calcifying organisms such as corals and foraminiferas can pin down where CO2 source/sink existed, because boron isotopes of marine calcium carbonates is dependent on seawater pH, from which pCO2 of the past seawater can be reconstructed. In previous studies using the boron isotope teqnique, Martinez-Boti et al. (2015, Nature) and Kubota et al. (2014, Scientific Reports) revealed that central and eastern parts of the equatorial Pacific acted as a CO2 source (i.e., CO2 emission) during the last deglaciation, suggesting the equatorial Pacific's contribution to atmospheric CO2 rise. However, some conflicting results have been confirmed in a marine sediment record from the western part of the equatorial Pacific (Palmer & Pearson, 2003, Science), making the conclusion elusive. In this presentation, we will show new results of Mg/Ca, oxygen isotope, and boron isotope measurements during the last 35 ka on two species of surface dwelling foraminiferas (Globigerinoides ruber and G. sacculifer) which was hand-picked separatedly from a well-dated marine sediment core recovered from the West Caroline Basin (KR05-15 PC01) (Yamazaki et al., 2008, GRL). From the new records, we will discuss how the equatorial Pacific behaved during the last deglaciation and how it related to the global carbon cycles.

  2. A study of evolution/suppression parameters of equatorial postsunset plasma instability

    Directory of Open Access Journals (Sweden)

    O. S. Oyekola

    2009-01-01

    Full Text Available Evening equatorial pre-reversal vertical ion E×B drift (VZP and the peak of the ionospheric F2 maximum altitude (hmF2P of the postsunset equatorial F-layer, which are the essential parameters requisite for the generation or inhibition of postsunset bottomside equatorial irregularities were deduced from ionosonde observations made in the Africa region (Ouagadougou: ~3° N dip latitude between January 1987 and December 1990 for solar activity minimum, medium, and maxima (F10.7=85, 141, 214, and 190, respectively for quiet geomagnetic conditions. We investigate variations of evening equatorial pre-reversal drift and the corresponding altitude at four levels of solar activity. Our observations show strong variations with solar variability. Correlation analysis between these parameters indicates that the correlation coefficient value between hmF2P versus VZP decreases considerably with increasing solar flux value. There seems to be no significant link between these parameters under high solar activity, especially for solar intensity F10.7>200 units. We conclude that meridional neutral wind in the F-region contributes substantially to the variations of the pre-reversal vertical plasma drifts enhancement and the peak hmF2, particularly the electrodynamics during twilight high solar flux conditions.

  3. Deep-sea environment and biodiversity of the West African Equatorial margin

    OpenAIRE

    Sibuet, Myriam; Vangriesheim, Annick

    2009-01-01

    The long-term BIOZAIRE multidisciplinary deep-sea environmental program on the West Equatorial African margin organized in partnership between Ifremer and TOTAL aimed at characterizing the benthic community structure in relation with physical and chemical processes in a region of oil and gas interest. The morphology of the deep Congo submarine channel and the sedimentological structures of the deep-sea fan were established during the geological ZAIANGO project and helped to select study sites...

  4. Genotype distribution of cervical human papillomavirus DNA in women with cervical lesions in Bioko, Equatorial Guinea

    OpenAIRE

    Garc?a-Espinosa, Benjam?n; Nieto-Bona, Ma Paz; Rueda, Sonsoles; Silva-S?nchez, Lu?s Fernando; Piernas-Morales, Ma Concepci?n; Carro-Campos, Patricia; Cort?s-Lambea, Lu?s; Moro-Rodr?guez, Ernesto

    2009-01-01

    Abstract Background The HVP vaccine is a useful tool for preventing cervical cancer. The purpose of this study is to determine the most frequent HPV genotypes in Equatorial Guinea in order to develop future vaccination strategies to apply in this country. Methods A campaign against cervical cancer was carried out in the area on a total of 1,680 women. 26 of the women, following cytological screening, were treated surgically with a loop electrosurgical excision procedure (LEEP). Cases were stu...

  5. Long range forecasting of summer monsoon rainfall from SST in the central equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Sadhuram, Y; Murthy, T.V.R.

    of summer monsoon rainfall from SST in the central equatorial Indian ocean Y. Sadhuram and T. V. Ramana Murthy National Institute of Oceanography, Regional Centre, 176, Lawson's Bay Colony, . Visakhapatnam-530017 ABSTRACT Severalprediction tedmiques have... and droughts associated with strong and weak monsoons greatly influence the economy of the country. Most of the droughts and floods are associated with EI-Nino and La- Nina respectively (Webster andYang3 and krishna Kumar et al\\. The relationship between ENSO...

  6. Glossina palpalis palpalis populations from Equatorial Guinea belong to distinct allopatric clades.

    Science.gov (United States)

    Cordon-Obras, Carlos; Cano, Jorge; Knapp, Jenny; Nebreda, Paloma; Ndong-Mabale, Nicolas; Ncogo-Ada, Policarpo Ricardo; Ndongo-Asumu, Pedro; Navarro, Miguel; Pinto, Joao; Benito, Agustin; Bart, Jean-Mathieu

    2014-01-17

    Luba is one of the four historical foci of Human African Trypanosomiasis (HAT) on Bioko Island, in Equatorial Guinea. Although no human cases have been detected since 1995, T. b. gambiense was recently observed in the vector Glossina palpalis palpalis. The existence of cryptic species within this vector taxon has been previously suggested, although no data are available regarding the evolutionary history of tsetse flies populations in Bioko. A phylogenetic analysis of 60 G. p. palpalis from Luba was performed sequencing three mitochondrial (COI, ND2 and 16S) and one nuclear (rDNA-ITS1) DNA markers. Phylogeny reconstruction was performed by Distance Based, Maximum Likelihood and Bayesian Inference methods. The COI and ND2 mitochondrial genes were concatenated and revealed 10 closely related haplotypes with a dominant one found in 61.1% of the flies. The sequence homology of the other 9 haplotypes compared to the former ranged from 99.6 to 99.9%. Phylogenetic analysis clearly clustered all island samples with flies coming from the Western African Clade (WAC), and separated from the flies belonging to the Central Africa Clade (CAC), including samples from Mbini and Kogo, two foci of mainland Equatorial Guinea. Consistent with mitochondrial data, analysis of the microsatellite motif present in the ITS1 sequence exhibited two closely related genotypes, clearly divergent from the genotypes previously identified in Mbini and Kogo. We report herein that tsetse flies populations circulating in Equatorial Guinea are composed of two allopatric subspecies, one insular and the other continental. The presence of these two G. p. palpalis cryptic taxa in Equatorial Guinea should be taken into account to accurately manage vector control strategy, in a country where trypanosomiasis transmission is controlled but not definitively eliminated yet.

  7. On some peculiarities of production of ionospheric equatorial bubbles in zones with increased recombination

    International Nuclear Information System (INIS)

    Vepreva, M.N.; Sazonov, S.V.

    1991-01-01

    Numerical study of dynamics of electromagnetic disturbances of equatorial ionosphere F region which are longitudinal ones relative to B geomagnetic field and occur due to Rayleigh-Taylor and gradient-drift instability activity in zones with increased recombination, is conducted. Arbitrary initial disturbance is determined to be delivered mainly into the first space mode of resonator formed by B force line plunge in high-conducting E layer. Oscillation condition is studied

  8. Analytical approach to the investigation of Rayleigh-Taylor structures of the equatorial F region

    International Nuclear Information System (INIS)

    Komarov, V.N.; Sazonov, S.V.

    1991-01-01

    On the basis of approximation of a strong vertical extension the nonlinear dynamics of Rayleigh-Taylor structures in the equatorial F region is analytically studied. The successive approximation method, proposed herein, is true for structures having longitudinal symmetry. Using this method it is managed to describe the mushroom-shaped bubble with a shock wave profile in its head part. The nonlinearity leads to bubble formation under conditions with aggravation, limiting the growth of positive disturbances at the same time

  9. Propagation of equatorial noise to low altitudes: Decoupling from the magnetosonic mode

    Czech Academy of Sciences Publication Activity Database

    Santolík, Ondřej; Parrot, M.; Němec, F.

    2016-01-01

    Roč. 43, č. 13 (2016), s. 6694-6704 ISSN 0094-8276 R&D Projects: GA ČR(CZ) GA14-31899S; GA MŠk(CZ) LH15304 Institutional support: RVO:68378289 Keywords : equatorial noise * magnetosonic waves * polarization and propagation analysis * ray tracing Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 4.253, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/2016GL069582/full

  10. Large-scale shifts in phytoplankton groups in the Equatorial Pacific during ENSO cycles

    Directory of Open Access Journals (Sweden)

    I. Masotti

    2011-03-01

    Full Text Available The El Niño Southern Oscillation (ENSO drives important changes in the marine productivity of the Equatorial Pacific, in particular during major El Niño/La Niña transitions. Changes in environmental conditions associated with these climatic events also likely impact phytoplankton composition. In this work, the distribution of four major phytoplankton groups (nanoeucaryotes, Prochlorococcus, Synechococcus, and diatoms was examined between 1996 and 2007 by applying the PHYSAT algorithm to the ocean color data archive from the Ocean Color and Temperature Sensor (OCTS and Sea-viewing Wide Field-of-view Sensor (SeaWiFS. Coincident with the decrease in chlorophyll concentrations, a large-scale shift in the phytoplankton composition of the Equatorial Pacific, that was characterized by a decrease in Synechococcus and an increase in nanoeucaryote dominance, was observed during the early stages of both the strong El Niño of 1997 and the moderate El Niño of 2006. A significant increase in diatoms dominance was observed in the Equatorial Pacific during the 1998 La Niña and was associated with elevated marine productivity. An analysis of the environmental variables using a coupled physical-biogeochemical model (NEMO-PISCES suggests that the Synechococcus dominance decrease during the two El Niño events was associated with an abrupt decline in nutrient availability (−0.9 to −2.5 μM NO3 month−1. Alternatively, increased nutrient availability (3 μM NO3 month−1 during the 1998 La Niña resulted in Equatorial Pacific dominance diatom increase. Despite these phytoplankton community shifts, the mean composition is restored after a few months, which suggests resilience in community structure.

  11. Range expansion drives dispersal evolution in an equatorial three-species symbiosis.

    Directory of Open Access Journals (Sweden)

    Guillaume Léotard

    Full Text Available Recurrent climatic oscillations have produced dramatic changes in species distributions. This process has been proposed to be a major evolutionary force, shaping many life history traits of species, and to govern global patterns of biodiversity at different scales. During range expansions selection may favor the evolution of higher dispersal, and symbiotic interactions may be affected. It has been argued that a weakness of climate fluctuation-driven range dynamics at equatorial latitudes has facilitated the persistence there of more specialized species and interactions. However, how much the biology and ecology of species is changed by range dynamics has seldom been investigated, particularly in equatorial regions.We studied a three-species symbiosis endemic to coastal equatorial rainforests in Cameroon, where the impact of range dynamics is supposed to be limited, comprised of two species-specific obligate mutualists--an ant-plant and its protective ant--and a species-specific ant parasite of this mutualism. We combined analyses of within-species genetic diversity and of phenotypic variation in a transect at the southern range limit of this ant-plant system. All three species present congruent genetic signatures of recent gradual southward expansion, a result compatible with available regional paleoclimatic data. As predicted, this expansion has been accompanied by the evolution of more dispersive traits in the two ant species. In contrast, we detected no evidence of change in lifetime reproductive strategy in the tree, nor in its investment in food resources provided to its symbiotic ants.Despite the decreasing investment in protective workers and the increasing investment in dispersing females by both the mutualistic and the parasitic ant species, there was no evidence of destabilization of the symbiosis at the colonization front. To our knowledge, we provide here the first evidence at equatorial latitudes that biological traits associated

  12. Range expansion drives dispersal evolution in an equatorial three-species symbiosis.

    Science.gov (United States)

    Léotard, Guillaume; Debout, Gabriel; Dalecky, Ambroise; Guillot, Sylvain; Gaume, Laurence; McKey, Doyle; Kjellberg, Finn

    2009-01-01

    Recurrent climatic oscillations have produced dramatic changes in species distributions. This process has been proposed to be a major evolutionary force, shaping many life history traits of species, and to govern global patterns of biodiversity at different scales. During range expansions selection may favor the evolution of higher dispersal, and symbiotic interactions may be affected. It has been argued that a weakness of climate fluctuation-driven range dynamics at equatorial latitudes has facilitated the persistence there of more specialized species and interactions. However, how much the biology and ecology of species is changed by range dynamics has seldom been investigated, particularly in equatorial regions. We studied a three-species symbiosis endemic to coastal equatorial rainforests in Cameroon, where the impact of range dynamics is supposed to be limited, comprised of two species-specific obligate mutualists--an ant-plant and its protective ant--and a species-specific ant parasite of this mutualism. We combined analyses of within-species genetic diversity and of phenotypic variation in a transect at the southern range limit of this ant-plant system. All three species present congruent genetic signatures of recent gradual southward expansion, a result compatible with available regional paleoclimatic data. As predicted, this expansion has been accompanied by the evolution of more dispersive traits in the two ant species. In contrast, we detected no evidence of change in lifetime reproductive strategy in the tree, nor in its investment in food resources provided to its symbiotic ants. Despite the decreasing investment in protective workers and the increasing investment in dispersing females by both the mutualistic and the parasitic ant species, there was no evidence of destabilization of the symbiosis at the colonization front. To our knowledge, we provide here the first evidence at equatorial latitudes that biological traits associated with dispersal are

  13. ENSO-driven nutrient variability recorded by central equatorial Pacific corals

    Science.gov (United States)

    LaVigne, M.; Nurhati, I. S.; Cobb, K. M.; McGregor, H. V.; Sinclair, D. J.; Sherrell, R. M.

    2012-12-01

    Recent evidence for shifts in global ocean primary productivity suggests that surface ocean nutrient availability is a key link between global climate and ocean carbon cycling. Time-series records from satellite, in situ buoy sensors, and bottle sampling have documented the impact of the El Niño Southern Oscillation (ENSO) on equatorial Pacific hydrography and broad changes in biogeochemistry since the late 1990's, however, data are sparse prior to this. Here we use a new paleoceanographic nutrient proxy, coral P/Ca, to explore the impact of ENSO on nutrient availability in the central equatorial Pacific at higher-resolution than available from in situ nutrient data. Corals from Christmas (157°W 2°N) and Fanning (159°W 4°N) Islands recorded a well-documented decrease in equatorial upwelling as a ~40% decrease in P/Ca during the 1997-98 ENSO cycle, validating the application of this proxy to Pacific Porites corals. We compare the biogeochemical shifts observed through the 1997-98 event with two pre-TOGA-TAO ENSO cycles (1982-83 and 1986-87) reconstructed from a longer Christmas Island core. All three corals revealed ~30-40% P/Ca depletions during ENSO warming as a result of decreased regional wind stress, thermocline depth, and equatorial upwelling velocity. However, at the termination of each El Niño event, surface nutrients did not return to pre-ENSO levels for ~4-12 months after, SST as a result of increased biological draw down of surface nutrients. These records demonstrate the utility of high-resolution coral nutrient archives for understanding the impact of tropical Pacific climate on the nutrient and carbon cycling of this key region.

  14. Azimuthal directions of equatorial noise propagation determined using 10 years of data from the Cluster spacecraft

    Czech Academy of Sciences Publication Activity Database

    Němec, F.; Santolík, Ondřej; Pickett, J. S.; Hrbáčková, Zuzana; Cornilleau-Wehrlin, N.

    2013-01-01

    Roč. 118, č. 11 (2013), 7160–7169 ISSN 2169-9380 R&D Projects: GA ČR GAP205/10/2279 Institutional support: RVO:68378289 Keywords : equatorial noise * fast magnetosonic waves * fast magnetosonic waves Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.440, year: 2013 http://onlinelibrary.wiley.com/doi/10.1002/2013JA019373/abstract

  15. Repeated Storage of Respired Carbon in the Equatorial Pacific Ocean Over the Last Three Glacial Cycles

    Science.gov (United States)

    Jacobel, A. W.; McManus, J. F.; Anderson, R. F.; Winckler, G.

    2017-12-01

    As the largest reservoir of carbon actively exchanging with the atmosphere on glacial-interglacial timescales, the deep ocean has been implicated as the likely location of carbon dioxide sequestration during Pleistocene glaciations. Despite strong theoretical underpinnings for this expectation, it has been challenging to identify unequivocal evidence for respired carbon storage in the paleoceanographic record. Data on the rate of ocean ventilation derived from paired planktonic-benthic foraminifera radiocarbon ages conflict across the equatorial Pacific, and different proxy reconstructions contradict one another about the depth and origin of the watermass containing the respired carbon. Because any change in the storage of respiratory carbon must be accompanied by corresponding changes in dissolved oxygen concentrations, proxy data reflecting bottom water oxygenation are of value in addressing these apparent inconsistencies. We present new records of the redox sensitive metal uranium from the central equatorial Pacific to qualitatively identify intervals associated with respiratory carbon storage over the past 350 kyr. Our data reveal periods of deep ocean authigenic uranium deposition in association with each of the last three glacial maxima. Equatorial Pacific export productivity data show intervals with abundant authigenic uranium are not associated with local productivity increases, indicating episodic precipitation of authigenic uranium does not directly reflect increases in situ microbial respiration, but rather occurs in response to basin-wide decreases in deep water oxygen concentrations. We combine our new data with previously published results to propose a picture of glacial carbon storage and equatorial Pacific watermass structure that is internally consistent. We conclude that respired carbon storage in the Pacific was a persistent feature of Pleistocene glaciations.

  16. Polar and equatorial coronal hole winds at solar minima: From the heliosphere to the inner corona

    International Nuclear Information System (INIS)

    Zhao, L.; Landi, E.

    2014-01-01

    Fast solar wind can be accelerated from at least two different sources: polar coronal holes and equatorial coronal holes. Little is known about the relationship between the wind coming from these two different latitudes and whether these two subcategories of fast wind evolve in the same way during the solar cycle. Nineteen years of Ulysses observations, from 1990 to 2009, combined with ACE observations from 1998 to the present provide us with in situ measurements of solar wind properties that span two entire solar cycles. These missions provide an ideal data set to study the properties and evolution of the fast solar wind originating from equatorial and polar holes. In this work, we focus on these two types of fast solar wind during the minima between solar cycles 22 and 23 and 23 and 24. We use data from SWICS, SWOOPS, and VHM/FGM on board Ulysses and SWICS, SWEPAM, and MAG on board ACE to analyze the proton kinetic, thermal, and dynamic characteristics, heavy ion composition, and magnetic field properties of these two fast winds. The comparison shows that: (1) their kinetic, thermal, compositional, and magnetic properties are significantly different at any time during the two minima and (2) they respond differently to the changes in solar activity from cycle 23 to 24. These results indicate that equatorial and polar fast solar wind are two separate subcategories of fast wind. We discuss the implications of these results and relate them to remote-sensing measurements of the properties of polar and equatorial coronal holes carried out in the inner corona during these two solar minima.

  17. Equatorial Scintillation Study at Ilorin and Nsukka, Nigeria during Year 2011-2012

    Science.gov (United States)

    Akala, A.

    2017-12-01

    This study presents GNSS scintillations over Ilorin (8.48 oN, 4.54 oE, and mag lat: 1.83oS) and Nsukka (6.84 oN, 7.37 oE, and mag lat: 2.94oS), Nigeria during year 2011-2012. The two stations are located within the inner flank of the equatorial ionization anomaly. Firstly, we investigated the climatology of equatorial scintillations at the two stations. We suppressed multipath effects on the data by imposing a 300 elevation masking on the data. In addition, we investigated scintillation occurrences at the two locations on a satellite-by-satellite basis at varying elevation angles. The source of scintillation records at low-elevation angle is attributed to multipath, while that at high-elevation angle is attributed to ionospheric irregularities. Seasonally, scintillations recorded highest occurrences during March equinox, and the least during June solstice. The trend of scintillations, at both low- and high-elevation angles at the two stations were almost the same. EGNOS satellites signals scintillated at the two locations during the time intervals when GPS satellites signals experienced scintillations. These results could support the development of scintillation models for equatorial Africa, and could also be of benefit to GPS and EGNOS service providers and designers, with a view to providing robust services for GNSS user community in Africa.

  18. On the how latitude scanning photometer signatures of equatorial ionosphere plasma bubbles

    International Nuclear Information System (INIS)

    Abdu, M.A.; Sobral, J.H.A.; Nakamura, Y.

    1985-01-01

    Meridional and east-west scan 6300 (angstrom) night airglow photometer are being extensively used at the low latitude station Cachoeira Paulista (23 0 S 45 0 W, dip latitude 14 0 ), Brazil, for investigation of trans-equatorial ionospheric plasma bubble dynamics. The zonal velocities of the flux aligned plasma bubbles can be determined, in a straingforward way, from the east-west displacement of the airglow intensity valleys observed by the east-west scan photometer. On the other hand, the determination of the other velocity component of the plasma bubble motion (namely, vertical motion in the equatorial plane) has to be based on the meridional propagation of the airglow valleys observed by the meriodinal scan photometer. Such determinatios of the bubbles vertical rise velocity should, however, involved considerations on different bubble parameters such as, for exemple, the phase of the bubble event (whether growth, mature or decay phase), the limited east-west extension, and the often observed westward tilt of the bubble. In this brief report there were condidered in some detail, possible influences of these different factors on the interpretation of low latitude scanning photometer data to infer trans-equatorial plasma bubble dynamics. (author) [pt

  19. Population exposure to hazardous air quality due to the 2015 fires in Equatorial Asia.

    Science.gov (United States)

    Crippa, P; Castruccio, S; Archer-Nicholls, S; Lebron, G B; Kuwata, M; Thota, A; Sumin, S; Butt, E; Wiedinmyer, C; Spracklen, D V

    2016-11-16

    Vegetation and peatland fires cause poor air quality and thousands of premature deaths across densely populated regions in Equatorial Asia. Strong El-Niño and positive Indian Ocean Dipole conditions are associated with an increase in the frequency and intensity of wildfires in Indonesia and Borneo, enhancing population exposure to hazardous concentrations of smoke and air pollutants. Here we investigate the impact on air quality and population exposure of wildfires in Equatorial Asia during Fall 2015, which were the largest over the past two decades. We performed high-resolution simulations using the Weather Research and Forecasting model with Chemistry based on a new fire emission product. The model captures the spatio-temporal variability of extreme pollution episodes relative to space- and ground-based observations and allows for identification of pollution sources and transport over Equatorial Asia. We calculate that high particulate matter concentrations from fires during Fall 2015 were responsible for persistent exposure of 69 million people to unhealthy air quality conditions. Short-term exposure to this pollution may have caused 11,880 (6,153-17,270) excess mortalities. Results from this research provide decision-relevant information to policy makers regarding the impact of land use changes and human driven deforestation on fire frequency and population exposure to degraded air quality.

  20. Mid-Pliocene equatorial Pacific sea surface temperature reconstruction: a multi-proxy perspective

    Science.gov (United States)

    Dowsett, Harry J.; Robinson, Marci M.

    2009-01-01

    The Mid-Pliocene is the most recent interval of sustained global warmth, which can be used to examine conditions predicted for the near future. An accurate spatial representation of the low-latitude Mid-Pliocene Pacific surface ocean is necessary to understand past climate change in the light of forecasts of future change. Mid-Pliocene sea surface temperature (SST) anomalies show a strong contrast between the western equatorial Pacific (WEP) and eastern equatorial Pacific (EEP) regardless of proxy (faunal, alkenone and Mg/Ca). All WEP sites show small differences from modern mean annual temperature, but all EEP sites show significant positive deviation from present-day temperatures by as much as 4.4°C. Our reconstruction reflects SSTs similar to modern in the WEP, warmer than modern in the EEP and eastward extension of the WEP warm pool. The east-west equatorial Pacific SST gradient is decreased, but the pole to equator gradient does not change appreciably. We find it improbable that increased greenhouse gases (GHG) alone would cause such a heterogeneous warming and more likely that the cause of Mid-Pliocene warmth is a combination of several forcings including both increased meridional heat transport and increased GHG.

  1. Assessing and Optimizing Argo profile mapping : An example in the Equatorial Pacific

    Science.gov (United States)

    Gasparin, Florent; Roemmich, Dean; Gilson, John; Sprintall, Janet

    2014-05-01

    Estimation of subsurface temperature, salinity and velocity has been revolutionized over the last decade as a result of development and deployment of the Argo Program. Argo products have become one of the major observational tools in Oceanography, used in a wide range of basic research, operational models, and education applications. To assess the skill of Argo in estimating oceanic conditions at different scales of variability in the Equatorial Pacific, we optimize Argo profile mapping by focusing on the covariance function. Decorrelation scales are discussed as well as impacts of several different interpolation schemes. The optimization is based on three points 1) Functional representation of the Argo sampled covariance, 2) Realism/Accuracy of the mapping errors and 3) Comparison with independent data such as TAO moorings and sea surface height. The last points show that Argo can represent more than 90% of the total TAO variance and around 80% of the intraseasonal TAO variability (between 10 and 100 days) at the Equator. As an illustration of the improvement, we show how Argo profiles can reveal the vertical structure and vertical phase propagation corresponding to the steric height annual cycle. We also discuss how this unique equatorial wave phenomena is modified during El Nino/La Nina events. This work anticipates a field experiment beginning in early 2014 and can be used for assessing and adapting the equatorial observational network.

  2. Observations in equatorial anomaly region of total electron content enhancements and depletions

    Directory of Open Access Journals (Sweden)

    N. Dashora

    2005-10-01

    Full Text Available A GSV 4004A GPS receiver has been operational near the crest of the equatorial anomaly at Udaipur, India for some time now. The receiver provides the line-of-sight total electron content (TEC, the phase and amplitude scintillation index, σφ and S4, respectively. This paper presents the first results on the nighttime TEC depletions associated with the equatorial spread F in the Indian zone. The TEC depletions are found to be very well correlated with the increased S4 index. A new feature of low-latitude TEC is also reported, concerning the observation of isolated and localized TEC enhancements in the nighttime low-latitude ionosphere. The TEC enhancements are not correlated with the S4 index. The TEC enhancements have also been observed along with the TEC depletions. The TEC enhancements have been interpreted as the manifestation of the plasma density enhancements reported by Le et al. (2003.

    Keywords. Ionosphere (Equatorial ionosphere; Ionospheric irregularities

  3. The magnetic field of the equatorial magnetotail from 10 to 40 earth radii

    Science.gov (United States)

    Fairfield, D. H.

    1986-01-01

    A statistical study of IMP 6, 7, and 8 magnetotail magnetic field measurements near the equatorial plane reveals new information about various aspects of magnetospheric structure. More magnetic flux crosses the equatorial plane on the dawn and dusk flanks of the tail than near midnight, but no evidence is found for a dependence on the interplanetary magnetic field sector polarity. Field magnitudes within 3 earth radii of the equatorial plane near dawn are more than twice as large as those near dusk for Xsm = -20 to -10 earth radii. The frequency of occurrence of southward fields is greatest near midnight, and such fields are seen almost twice as often for Xsm = -20 to -10 earth radii as for Xsm beyond -20 earth radii. This latter result supports the idea that the midnight region of the tail between 10 and 20 is a special location where neutral lines are particularly apt to form. Such a neutral line will approach nearest the earth in the midnight and premidnight region, where substorms are thought to have their onset.

  4. Study of equatorial Kelvin waves using the MST radar and radiosonde observations

    Directory of Open Access Journals (Sweden)

    P. Kishore

    2005-06-01

    Full Text Available In this paper an attempt has been made to study equatorial Kelvin waves using a high power coherent VHF radar located at Gadanki (13.5° N, 79.2° E, a tropical station in the Indian sub-continent. Simultaneous radiosonde observations taken from a nearby meteorological station located in Chennai (13.04° N, 80.17° E were also used to see the coherence in the observed structures. These data sets were analyzed to study the mean winds and equatorial waves in the troposphere and lower stratosphere. Equatorial waves with different periodicities were identified. In the present study, particular attention has been given to the fast Kelvin wave (6.5-day and slow Kelvin wave (16-day. Mean zonal wind structures were similar at both locations. The fast Kelvin wave amplitudes were somewhat similar in both observations and the maximum amplitude is about 8m/s. The phase profiles indicated a slow downward progression. The slow Kelvin wave (16-day amplitudes shown by the radiosonde measurements are a little larger than the radar derived amplitudes. The phase profiles showed downward phase progression and it translates into a vertical wavelength of ~10-12km. The radar and radiosonde derived amplitudes of fast and slow Kelvin waves are larger at altitudes near the tropopause (15-17km, where the mean wind attains westward maximum.

  5. Survival probability of precipitations and rain attenuation in tropical and equatorial regions

    Science.gov (United States)

    Mohebbi Nia, Masoud; Din, Jafri; Panagopoulos, Athanasios D.; Lam, Hong Yin

    2015-08-01

    This contribution presents a stochastic model useful for the generation of a long-term tropospheric rain attenuation time series for Earth space or a terrestrial radio link in tropical and equatorial heavy rain regions based on the well-known Cox-Ingersoll-Ross model previously employed in research in the fields of finance and economics. This model assumes typical gamma distribution for rain attenuation in heavy rain climatic regions and utilises the temporal dynamic of precipitation collected in equatorial Johor, Malaysia. Different formations of survival probability are also discussed. Furthermore, the correlation between these probabilities and the Markov process is determined, and information on the variance and autocorrelation function of rain events with respect to the particular characteristics of precipitation in this area is presented. The proposed technique proved to preserve the peculiarities of precipitation for an equatorial region and reproduce fairly good statistics of the rain attenuation correlation function that could help to improve the prediction of dynamic characteristics of rain fade events.

  6. Study of the behaviour of the equatorial ionization anomaly (EIA) during solar flares

    Science.gov (United States)

    Aggarwal, Malini; Astafyeva, Elvira

    2014-05-01

    A solar flare occurring in the sun's chromosphere is observed in various wavebands (radio to x-rays). The response of the solar flare which causes sudden changes in the earth's ionosphere is not yet well understood though investigations suggested that its impact depends on the size and location of occurrence of solar flare on sun. Considering this, we have carried an investigation to study the response of two strong and gradual solar flares: 2 Apr 2001 (X20, limb) and 7 Feb 2010 (M6.4, disk) on the earth's equatorial-low latitude regions using multi-technique observations of satellite and ground-based instruments. We found a weakening of strength of equatorial ionization anomaly (EIA) in total electron content during both the flares as observed by TOPEX, JASON-1 and JASON-2 altimeter measurements. The H component of the geomagnetic field also shows a sudden change at equatorial and low latitude stations in the sunlit hemisphere during the flare. The observations of ionosonde at low-latitudes indicate a strong absorption of higher-frequency radio signals. The detail response of these flare on EIA of the earth's ionosphere will be presented and discussed.

  7. Population exposure to hazardous air quality due to the 2015 fires in Equatorial Asia

    Science.gov (United States)

    Crippa, P.; Castruccio, S.; Archer-Nicholls, S.; Lebron, G. B.; Kuwata, M.; Thota, A.; Sumin, S.; Butt, E.; Wiedinmyer, C.; Spracklen, D. V.

    2016-11-01

    Vegetation and peatland fires cause poor air quality and thousands of premature deaths across densely populated regions in Equatorial Asia. Strong El-Niño and positive Indian Ocean Dipole conditions are associated with an increase in the frequency and intensity of wildfires in Indonesia and Borneo, enhancing population exposure to hazardous concentrations of smoke and air pollutants. Here we investigate the impact on air quality and population exposure of wildfires in Equatorial Asia during Fall 2015, which were the largest over the past two decades. We performed high-resolution simulations using the Weather Research and Forecasting model with Chemistry based on a new fire emission product. The model captures the spatio-temporal variability of extreme pollution episodes relative to space- and ground-based observations and allows for identification of pollution sources and transport over Equatorial Asia. We calculate that high particulate matter concentrations from fires during Fall 2015 were responsible for persistent exposure of 69 million people to unhealthy air quality conditions. Short-term exposure to this pollution may have caused 11,880 (6,153-17,270) excess mortalities. Results from this research provide decision-relevant information to policy makers regarding the impact of land use changes and human driven deforestation on fire frequency and population exposure to degraded air quality.

  8. Study of Large-Scale Wave Structure and Development of Equatorial Plasma Bubbles Using the C/NOFS Satellite

    Science.gov (United States)

    2012-10-31

    scientific journals. The papers are listed below in chronological order. Kelley, M.C., F.S. Rodrigues, J.J. Makela, R. Tsunoda, P.A. Roddy, D.E. Hunton...source region be located on the dip equator. To illustrate, Figure 6 presents a sequence of satellite OLR maps, which were taken over Peru on 19-20...to large-scale wave structure and equatorial spread F, presented at the International Symposium for Equatorial Aeronomy, Paracas, Peru , March 2012

  9. Terrestrial ring current - from in situ measurements to global images using energetic neutral atoms

    International Nuclear Information System (INIS)

    Roelof, E.C.; Williams, D.J.

    1988-01-01

    Electrical currents flowing in the equatorial magnetosphere, first inferred from ground-based magnetic disturbances, are carried by trapped energetic ions. Spacecraft measurements have determined the spectrum and composition of those currents, and the newly developed technique of energetic-neutral-atom imaging allows the global dynamics of that entire ion population to be viewed from a single spacecraft. 71 references

  10. Shutdown dose rates at ITER equatorial ports considering radiation cross-talk from torus cryopump lower port

    Energy Technology Data Exchange (ETDEWEB)

    Juárez, Rafael, E-mail: rjuarez@ind.uned.es [Departamento de Ingeniería Energética, ETSII-UNED, Calle Juan del Rosal 12, Madrid 28040 (Spain); Pampin, Raul [F4E, Torres Diagonal Litoral B3, Josep Pla 2, Barcelona 08019 (Spain); Levesy, Bruno [ITER Organization, 13115 Route de Vinon sur Verdon, St Paul Lez Durance (France); Moro, Fabio [ENEA, Via Enrico Fermi 45, Frascati, Rome (Italy); Suarez, Alejandro [ITER Organization, 13115 Route de Vinon sur Verdon, St Paul Lez Durance (France); Sanz, Javier [Departamento de Ingeniería Energética, ETSII-UNED, Calle Juan del Rosal 12, Madrid 28040 (Spain)

    2015-11-15

    Shutdown dose rates for planned maintenance purposes is an active research field in ITER. In this work the radiation (neutron and gamma) cross-talk between ports in the most conservative case foreseen in ITER is investigated: the presence of a torus cryopump lower port, mostly empty for pumping efficiency reasons. There will be six of those ports: #4, #6, #10, #12, #16 and #18. The equatorial ports placed above them will receive a significant amount of additional radiation affecting the shutdown dose rates during in situ maintenance activities inside the cryostat, and particularly in the port interspace area. In this study a general situation to all the equatorial ports placed above torus cryopump lower ports is considered: a generic diagnostics equatorial port placed above the torus cryopump lower port (LP#4). In terms of shutdown dose rates at equatorial port interspace after 10{sup 6} s of cooling time, 405 μSv/h has been obtained, of which 160 μSv/h (40%) are exclusively due to radiation cross-talk from a torus cryopump lower port. Equatorial port activation due to only “local neutrons” contributes 166 μSv/h at port interspace, showing that radiation cross-talk from such a lower port is a phenomenon comparable in magnitude to the neutron leakage though the equatorial port plug.

  11. Redox Conditions and Related Color Change in Eastern Equatorial Pacific Sediments: IODP Site U1334

    Science.gov (United States)

    Kordesch, W. E.; Gussone, N. C.; Hathorne, E. C.; Kimoto, K.; Delaney, M. L.

    2011-12-01

    This study was prompted by a 65 m thick brown-green color change in deep-sea sediments of IODP Site U1334 (0-38 Ma, 4799 m water depth) that corresponds to its equatorial crossing (caused by the Northward movement of the pacific plate). Green sediment is a visual indicator of reducing conditions in sediment due to enhanced organic matter deposition and burial. Here we use geochemical redox indicators to characterize the effect of equatorial upwelling on bottom water. The modern redox signal is captured in porewater profiles (nitrate, manganese, iron, sulfate) while trace metal Enrichment Factors (EF) in bulk sediment (manganese, uranium, molybdenum, rhenium) normalized to the detrital component (titanium) record redox state at burial. To measure export productivity we also measure biogenic barium. Porewater profiles reveal suboxic diagenesis; profiles follow the expected sequence of nitrate, manganese oxide, and iron oxide reduction with increasing depth. Constant sulfate (~28 μM) implies anoxia has not occurred. Bulk sediment Mn EF are enriched (EF > 1) throughout the record (Mn EF = 15-200) while U and Mo enrichment corresponds to green color and equatorial proximity (U EF = 4-19; Mo EF = 0-7). Constant Mn enrichment implies continuous oxygenation. Uranium and Mo enrichment near the equator represents suboxic conditions also seen in the porewater. Low Re concentrations (below detection) provide additional evidence against anoxia. A comparison of Mn EF from total digestions to samples treated with an additional reductive cleaning step distinguishes between Mn-oxides and Mn-carbonates, indicating oxygenated and reducing conditions respectively. Mn-carbonate occurrence agrees with U and Mo EF; conditions were more reducing near the equator. Bio-Ba shows significant variability over this interval (22-99 mmol g-1). Our geochemical results indicate that bottom waters became suboxic at the equator as a result of equatorial upwelling-influenced increases in organic

  12. Shutdown dose rate analysis of European test blanket modules shields in ITER Equatorial Port #16

    Energy Technology Data Exchange (ETDEWEB)

    Juárez, Rafael, E-mail: rjuarez@ind.uned.es [Departamento de Ingeniería Energética, ETSII-UNED, Calle Juan del Rosal 12, Madrid 28040 (Spain); Sauvan, Patrick; Perez, Lucia [Departamento de Ingeniería Energética, ETSII-UNED, Calle Juan del Rosal 12, Madrid 28040 (Spain); Panayotov, Dobromir; Vallory, Joelle; Zmitko, Milan; Poitevin, Yves [Fusion for Energy (F4E), Torres Diagonal Litoral B3, Josep Pla 2, Barcelona 08019 (Spain); Sanz, Javier [Departamento de Ingeniería Energética, ETSII-UNED, Calle Juan del Rosal 12, Madrid 28040 (Spain)

    2016-11-01

    Highlights: • Nuclear analysis for European TBMs and shields, in ITER Equatorial Port #16, has been conducted in support of the ‘Concept Design Review’ from ITER. • The objective of the work is the characterization of the Shutdown Dose Rates at Equatorial Port #16 interspace. • The role played by the TBM and TBM shields, the equatorial port gaps and the vacuum vessel permeation, in terms of neutron flux transmission is assessed. • The role played by the TBM, TBM shields, Port Plug Frame, Pipe Forest and the machine in terms of activation is also investigated. - Abstract: ‘Fusion for Energy’ (F4E) is designing, developing, and implementing the European Helium-Cooled Lead-Lithium (HCLL) and Helium-Cooled Pebble-Bed (HCPB) Test Blanket Systems (TBSs) for ITER (Nuclear Facility INB-174). An essential element of the Conceptual Design Review (CDR) of these TBSs is the demonstration of capability of Test Blanket Modules (TBM) and their shields to fulfil their function and comply with the design requirements. One of the TBM shields highly relevant design aspects is the project target for shutdown dose rates (SDDR) in the interspace. We investigated two functions of the TBMs and TBM shields—the neutron flux attenuation along the shields, and the reduction of the activation of the components contributing to SDDR. It is shown that TBMs and TBM shields reduce significantly the neutron flux in the port plug (PP). In terms of neutron flux attenuation, the TBM shield provides sufficient neutron flux reduction, being responsible for 5 × 10{sup 6} n/cm{sup 2} s at port interspace, while the EPP gaps and BSM gaps are responsible for 5 × 10{sup 7} n/cm{sup 2} s each. When considering closed upper, lower and lateral neighbour equatorial ports (thus, excluding the cross-talk between ports), a SDDR of 121 μSv/h averaged near the port closure flange was obtained, out of which, only 4 μSv/h are due to the activation of TBMs and TBM shields. Maximum SDDR in the range

  13. Assessing the Skill of Chlorophyll Forecasts: Latest Development and Challenges Ahead Using the Case of the Equatorial Pacific

    Science.gov (United States)

    Rousseaux, Cecile S.; Gregg, Watson W.

    2018-01-01

    Using a global ocean biogeochemical model combined with a forecast of physical oceanic and atmospheric variables from the NASA Global Modeling and Assimilation Office, we assess the skill of a chlorophyll concentrations forecast in the Equatorial Pacific for the period 2012-2015 with a focus on the forecast of the onset of the 2015 El Nino event. Using a series of retrospective 9-month hindcasts, we assess the uncertainties of the forecasted chlorophyll by comparing the monthly total chlorophyll concentration from the forecast with the corresponding monthly ocean chlorophyll data from the Suomi-National Polar-orbiting Partnership Visible Infrared Imaging Radiometer Suite (S-NPP VIIRS) satellite. The forecast was able to reproduce the phasing of the variability in chlorophyll concentration in the Equatorial Pacific, including the beginning of the 2015-2016 El Nino. The anomaly correlation coefficient (ACC) was significant (p less than 0.05) for forecast at 1-month (R=0.33), 8-month (R=0.42) and 9-month (R=0.41) lead times. The root mean square error (RMSE) increased from 0.0399 microgram chl L(exp -1) for the 1-month lead forecast to a maximum of 0.0472 microgram chl L(exp -1) for the 9-month lead forecast indicating that the forecast of the amplitude of chlorophyll concentration variability was getting worse. Forecasts with a 3-month lead time were on average the closest to the S-NPP VIIRS data (23% or 0.033 microgram chl L(exp -1)) while the forecast with a 9-month lead time were the furthest (31% or 0.042 microgram chl L(exp -1)). These results indicate the potential for forecasting chlorophyll concentration in this region but also highlights various deficiencies and suggestions for improvements to the current biogeochemical forecasting system. This system provides an initial basis for future applications including the effects of El Nino events on fisheries and other ocean resources given improvements identified in the analysis of these results.

  14. Free troposphere as a major source of CCN for the equatorial pacific boundary layer: long-range transport and teleconnections

    Directory of Open Access Journals (Sweden)

    A. D. Clarke

    2013-08-01

    Full Text Available Airborne aerosol measurements in the central equatorial Pacific during PASE (Pacific Atmospheric Sulfur Experiment revealed that cloud condensation nuclei (CCN activated in marine boundary layer (MBL clouds were strongly influenced by entrainment from the free troposphere (FT. About 65% entered at sizes effective as CCN in MBL clouds, while ~25% entered the MBL too small to activate but subsequently grew via gas to particle conversion. The remaining ~10% were inferred to be sea salt aerosol. FT aerosols at low carbon monoxide (CO mixing ratios ( The observed FT transport over thousands of kilometers indicates teleconnections between MBL CCN and cloud-scavenged sources of both natural and/or residual combustion origin. Nonetheless, in spite of its importance, this source of CCN number is not well represented in most current models and is generally not detectable by satellite because of the low aerosol scattering in such layers as a result of cloud scavenging. In addition, our measurements confirm nucleation in the MBL was not evident during PASE and argue against a localized linear relation in the MBL between dimethyl sulfide (DMS and CCN suggested by the CLAW hypothesis. However, when the FT is not impacted by long-range transport, sulfate aerosol derived from DMS pumped aloft in the ITCZ (Inter-Tropical Convergence Zone can provide a source of CCN to the boundary layer via FT teleconnections involving more complex non-linear processes.

  15. New species of Hebefustis Siebenaller & Hessler 1977 (Isopoda, Asellota, Nannoniscidae) from the Clarion Clipperton Fracture Zone (equatorial NE Pacific).

    Science.gov (United States)

    Kaiser, Stefanie

    2014-03-27

    Macrofaunal collections obtained during the French-German BIONOD expedition to the Clarion Clipperton Fracture Zone (CCFZ), equatorial NE Pacific, in spring 2012 yielded two new nannoniscid species, Hebefustis juansenii sp. n. and H. vecino sp. n., which are described in the current paper. The number and position of posterolateral spines of the pleotelson distinguishes the two new species from all other species in the genus. Both species are similar to each other differ, though, in the length of maxilliped epipodite, the presence of a robust spine on pereonite 2 (in H. juansenii sp. n.) as well as the shape of pereonite 4 anterior margin. They also resemble H. primitivus Menzies, 1962 but can be differentiated from the latter by the shape of lateral margins of pereonites 1-4 and the setation and shape of male pleopod 1. A distribution map and a taxonomic key to all known species in the genus are provided, as well as a checklist of known nannoniscid species from the Pacific is presented.

  16. Selected Abstracts of the 2nd Congress of joint European Neonatal Societies (jENS 2017; Venice (Italy; October 31-November 4, 2017; Session "Neonatal Gastrointestinal Physiology and NEC"

    Directory of Open Access Journals (Sweden)

    --- Various Authors

    2017-10-01

    Full Text Available Selected Abstracts of the 2nd Congress of joint European Neonatal Societies (jENS 2017; Venice (Italy; October 31-November 4, 201758th ESPR Annual Meeting, 7th International Congress of UENPS, 3rd International Congress of EFCNIORGANIZING INSTITUTIONSEuropean Society for Paediatric Research (ESPR, European Society for Neonatology (ESN, Union of European Neonatal & Perinatal Societies (UENPS, European Foundation for the Care of Newborn Infants (EFCNIORGANIZING COMMITTEELuc Zimmermann (President of ESPR, Morten Breindahl (President of ESN, Manuel Sánchez Luna (President of UENPS, Silke Mader (Chairwoman of the Executive Board and Co-Founder of EFCNISCIENTIFIC COMMITTEEVirgilio P. Carnielli (Congress President Chair, Pierre Gressens (Past Scientific President, Umberto Simeoni, Manon Benders, Neil Marlow, Ola D. Saugstad, Petra Hüppi, Agnes van den HoogenSession "Neonatal Gastrointestinal Physiology and NEC"ABS 1. DETRIMENTAL MUCOSAL EFFECT OF IBUPROFEN IN THE IMMATURE HUMAN INTESTINE • E. Tremblay, E. Ferretti, M.-P. Thibault, D. Grynspan, K.M. Burghardt, M. Bettolli, C. Babakissa, E. Levy, J.-F. Beaulieu; Research Consortium on Child Intestinal InflammationABS 2. CORRELATION BETWEEN CALPROTECTIN LEVELS IN MECONIUM AND VITAMIN D STATUS IN CORD BLOOD: ASSOCIATION WITH INTESTINAL DISTRESS DURING NEONATAL PERIOD • S.H. Park, W.H. Kim, Y.M. LeeABS 3. COMPARISON OF FECAL CALPROTECTIN LEVELS ACCORDING TO FEEDING KINDS IN VERY PRETERM INFANTS • J.H. Park, N.H. Lee, S.Y. Shin, C.S. Kim, S.L. Lee, W.M. LeeABS 4. NEONATAL MORBIDITY OF EXTREME PRETERM INFANTS BEFORE AND AFTER THE INTRODUCTION OF A DONOR HUMAN MILK BANK AT THE PERINATAL CENTER GROßHADERN • V. Lieftüchter, M. Kujawa, A. Schuze, A.W. Flemmer, S. Herber-JonatABS 5. IS NEAR INFRARED SPECTROSCOPY A RELIABLE TECHNIQUE TO MEASURE GUT PERFUSION IN PRETERM INFANTS? • J. Banerjee, T.S. Leung, N. AladangadyABS 6. EARLY BIOCHEMICAL MARKERS ASSOCIATED WITH DEVELOPMENT OF NECROTIZING

  17. Development of intermediate-scale structure at different altitudes within an equatorial plasma bubble: Implications for L-band scintillations

    Science.gov (United States)

    Bhattacharyya, A.; Kakad, B.; Gurram, P.; Sripathi, S.; Sunda, S.

    2017-01-01

    An important aspect of the development of intermediate-scale length (approximately hundred meters to few kilometers) irregularities in an equatorial plasma bubble (EPB) that has not been considered in the schemes to predict the occurrence pattern of L-band scintillations in low-latitude regions is how these structures develop at different heights within an EPB as it rises in the postsunset equatorial ionosphere due to the growth of the Rayleigh-Taylor instability. Irregularities at different heights over the dip equator map to different latitudes, and their spectrum as well as the background electron density determine the strength of L-band scintillations at different latitudes. In this paper, VHF and L-band scintillations recorded at different latitudes together with theoretical modeling of the scintillations are used to study the implications of this structuring of EPBs on the occurrence and strength of L-band scintillations at different latitudes. Theoretical modeling shows that while S4 index for scintillations on a VHF signal recorded at an equatorial station may be >1, S4 index for scintillations on a VHF signal recorded near the crest of the equatorial ionization anomaly (EIA) generally does not exceed the value of 1 because the intermediate-scale irregularity spectrum at F layer peak near the EIA crest is shallower than that found in the equatorial F layer peak. This also explains the latitudinal distribution of L-band scintillations. Thus, it is concluded that there is greater structuring of an EPB on the topside of the equatorial F region than near the equatorial F layer peak.

  18. Relationship between vertical ExB drift and F2-layer characteristics in the equatorial ionosphere at solar minimum conditions

    Science.gov (United States)

    Oyekola, Oyedemi S.

    2012-07-01

    Equatorial and low-latitude electrodynamics plays a dominant role in determining the structure and dynamics of the equatorial and low-latitude ionospheric F-region. Thus, they constitute essential input parameters for quantitative global and regional modeling studies. In this work, hourly median value of ionosonde measurements namely, peak height F2-layer (hmF2), F2-layer critical frequency (foF2) and propagation factor M(3000)F2 made at near equatorial dip latitude, Ouagadougou, Burkina Faso (12oN, 1.5oW; dip: 1.5oN) and relevant F2-layer parameters such as thickness parameter (Bo), electron temperature (Te), ion temperature (Ti), total electron content (TEC) and electron density (Ne, at the fixed altitude of 300 km) provided by the International Reference Ionosphere (IRI) model for the longitude of Ouagadougou are contrasted with the IRI vertical drift model to explore in detail the monthly climatological behavior of equatorial ionosphere and the effects of equatorial vertical plasma drift velocities on the diurnal structure of F2-layer parameters. The analysis period covers four months representative of solstitial and equinoctial seasonal periods during solar minimum year of 1987 for geomagnetically quiet-day. We show that month-by-month morphological patterns between vertical E×B drifts and F2-layer parameters range from worst to reasonably good and are largely seasonally dependent. A cross-correlation analysis conducted between equatorial drift and F2-layer characteristics yield statistically significant correlations for equatorial vertical drift and IRI-Bo, IRI-Te and IRI-TEC, whereas little or no acceptable correlation is obtained with observational evidence. Assessment of the association between measured foF2, hmF2 and M(3000)F2 illustrates consistent much more smaller correlation coefficients with no systematic linkage. In general, our research indicates strong departure from simple electrodynamically controlled behavior.

  19. The Açu Reef morphology, distribution, and inter reef sedimentation on the outer shelf of the NE Brazil equatorial margin

    Science.gov (United States)

    do Nascimento Silva, Luzia Liniane; Gomes, Moab Praxedes; Vital, Helenice

    2018-05-01

    Submerged reefs, referred to as the Açu Reefs, have been newly observed on both sides of the Açu Incised Valley on the northeastern equatorial Brazilian outer shelf. This study aims to understand the roles of shelf physiography, its antecedent morphologies, and its inter reef sedimentation on the different development stages of the biogenic reef during last deglacial sea-level rise. The data sets consist of side-scan sonar imagery, one sparker seismic profile, 76 sediment samples, and underwater photography. Seven backscatter patterns (P1 to P7) were identified and associated with eleven sedimentary carbonate and siliciclastic facies. The inherited relief, the mouth of the paleo incised valley, and the interreef sediment distribution play major controls on the deglacial reef evolution. The reefs occur in a depth-limited 25-55 m water depth range and in a 6 km wide narrow zone of the outer shelf. The reefs crop out in a surface area over 100 km2 and occur as a series of NW-SE preferentially orientated ridges composed of three parallel ridge sets at 45, 35, and 25 m of water depth. The reefs form a series of individual, roughly linear ridges, tens of km in length, acting as barriers in addition to scattered reef mounds or knolls, averaging 4 m in height and grouped in small patches and aggregates. The reefs, currently limited at the transition between the photic and mesophotic zones, are thinly covered by red algae and scattered coral heads and sponges. Taking into account the established sea-level curves from the equatorial Brazilian northeastern shelf / Rochas Atoll and Barbados, the shelf physiography, and the shallow bedrock, the optimal conditions for reef development had to occur during a time interval (11-9 kyr BP) characterized by a slowdown of the outer shelf flooding, immediately following Meltwater Pulse-1B. This 2 kyr short interval provided unique conditions for remarkable reef backstepping into distinct parallel ridge sets. Furthermore, the Açu Reefs

  20. Evidence of late Palaeocene-early Eocene equatorial rain forest refugia in southern Western Ghats, India.

    Science.gov (United States)

    Prasad, V; Farooqui, A; Tripathi, S K M; Garg, R; Thakur, B

    2009-11-01

    Equatorial rain forests that maintain a balance between speciation and extinction are hot-spots for studies of biodiversity. Western Ghats in southern India have gained attention due to high tropical biodiversity and endemism in their southern most area. We attempted to track the affinities of the pollen fl ora of the endemic plants of Western Ghat area within the fossil palynoflora of late Palaeocene-early Eocene (approximately 55-50 Ma) sedimentary deposits of western and northeastern Indian region. The study shows striking similarity of extant pollen with twenty eight most common fossil pollen taxa of the early Palaeogene. Widespread occurrences of coal and lignite deposits during early Palaeogene provide evidence of existence of well diversified rain forest community and swampy vegetation in the coastal low lying areas all along the western and northeastern margins of the Indian subcontinent. Prevalence of excessive humid climate during this period has been seen as a result of equatorial positioning of Indian subcontinent, superimposed by a long term global warming phase (PETM and EECO) during the early Palaeogene. The study presents clear evidence that highly diversifi ed equatorial rain forest vegetation once widespread in the Indian subcontinent during early Palaeogene times, are now restricted in a small area as a refugia in the southernmost part of the Western Ghat area. High precipitation and shorter periods of dry months seem to have provided suitable environment to sustain lineages of ancient tropical vegetation in this area of Western Ghats in spite of dramatic climatic changes subsequent to the post India-Asia collision and during the Quaternary and Recent times.

  1. Japan contribution to studies of low-latitude and equatorial ionosphere over Southeast Asia

    Science.gov (United States)

    Yamamoto, M.; Ishii, M.; Otsuka, Y.; Shiokawa, K.; Saito, A.; Tsuda, T.; Fukao, S.

    2008-12-01

    A dense observation network to study ionosphere is deployed over Southeast Asian countries of Indonesia, Thailand, and Vietnam. The Equatorial Atmosphere Radar (EAR) at Kototabang, Indonesia is the center facility, and supporting instruments, i.e., an ionosonde, a VHF ionosphere radar, an optical imager, a GPS scintillation receiver, a magnetometer, a meteor radar, etc. are collocated. NICT operates the ionosonde network SEALION (South East Asian Low-latitude IOnosonde Network) that meridionally extends from the EAR site to Chumphong and Chiang Mai in Thailand, and two more sites (Baq Liu and Phy Thuy) in Vietnam. Additional facilities are an MF radar at Pameungpeuk, Indonesia, and an optical imager at Darwin, Australia. We have been observing plasma bubbles since 2001, that, for example, contributed clarification of time- spatial structures of the phenomena, their relationship to the pre-reversal enhancement, control of bubble occurrence by the meridional winds, etc. We are starting studies of their seeding by means of atmospheric waves that propages from the lower atmosphere, too. In 2008, Nagoya University will soon install three Fabry-Perot interferometers at the EAR site, Chiang Mai, and Darwin. We also have a plan to install digital beacon receivers in some of these sites. Next research program that follows CPEA (Coupling Processes in the Equatorial Atmosphere, 2001-2007) is under planning now. Our main facilities cover ± 10° of geomagnetic latitude, where the magnetic declination is relatively small, and the geomagnetic equator is in the geographic northern hemisphere. We will review our achievements, and show on-going efforts and future plans. Collaboration with the C/NOFS satellite, and comparisons to results from the American sector should be beneficial for global-scale understanding of the equatorial ionosphere/atmosphere.

  2. Asymmetric Response of the Equatorial Pacific SST to Climate Warming and Cooling

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fukai [Physical Oceanography Laboratory/Qingdao Collaborative Innovation Center of Marine Science and Technology, Ocean University of China, and Qingdao National Laboratory for Marine Science and Technology, Qingdao, China; Luo, Yiyong [Physical Oceanography Laboratory/Qingdao Collaborative Innovation Center of Marine Science and Technology, Ocean University of China, and Qingdao National Laboratory for Marine Science and Technology, Qingdao, China; Lu, Jian [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, Washington; Garuba, Oluwayemi [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, Washington; Wan, Xiuquan [Physical Oceanography Laboratory/Qingdao Collaborative Innovation Center of Marine Science and Technology, Ocean University of China, and Qingdao National Laboratory for Marine Science and Technology, Qingdao, China

    2017-09-01

    The response of the equatorial Pacific Ocean to heat fluxes of equal amplitude but opposite sign is investigated using the Community Earth System Model (CESM). Results show a strong asymmetry in SST changes. In the eastern equatorial Pacific (EEP), the warming responding to the positive forcing exceeds the cooling to the negative forcing; while in the western equatorial Pacific (WEP), it is the other way around and the cooling surpasses the warming. This leads to a zonal dipole asymmetric structure, with positive values in the east and negative values in the west. A surface heat budget analysis suggests that the SST asymmetry is mainly resulted from the oceanic horizontal advection and vertical entrainment, with both of their linear and nonlinear components playing a role. For the linear component, its change appears to be more significant over the EEP (WEP) in the positive (negative) forcing scenario, favoring the seesaw pattern of the SST asymmetry. For the nonlinear component, its change acts to warm (cool) the EEP (WEP) in both scenarios, also favorable for the development of the SST asymmetry. Additional experiments with a slab ocean confirm the dominant role of ocean dynamical processes for this SST asymmetry. The net surface heat flux, in contrast, works to reduce the SST asymmetry through its shortwave radiation and latent heat flux components, with the former being related to the nonlinear relationship between SST and convection, and the latter being attributable to Newtonian damping and air-sea stability effects. The suppressing effect of shortwave radiation on SST asymmetry is further verified by partially coupled overriding experiments.

  3. Nitrogen uptake and regeneration pathways in the equatorial Pacific: a basin scale modeling study

    Directory of Open Access Journals (Sweden)

    R. Le Borgne

    2009-11-01

    Full Text Available It is well known that most primary production is fueled by regenerated nitrogen in the open ocean. Therefore, studying the nitrogen cycle by focusing on uptake and regeneration pathways would advance our understanding of nitrogen dynamics in the marine ecosystem. Here, we carry out a basin-scale modeling study, by assessing model simulations of nitrate and ammonium, and rates of nitrate uptake, ammonium uptake and regeneration in the equatorial Pacific. Model-data comparisons show that the model is able to reproduce many observed features of nitrate, ammonium, such as the deep ammonium maximum (DAM. The model also reproduces the observed de-coupling of ammonium uptake and regeneration, i.e., regeneration rate greater than uptake rate in the lower euphotic zone. The de-coupling largely explains the observed DAM in the equatorial Pacific Ocean. Our study indicates that zooplankton excretion and remineralization of organic nitrogen play a different role in nitrogen regeneration. Rates of zooplankton excretion vary from <0.01 mmol m−3 d−1 to 0.1 mmol m−3 d−1 in the upper euphotic zone while rates of remineralization fall within a narrow range (0.015–0.025 mmol m−3 d−1 . Zooplankton excretion contributes up to 70% of total ammonium regeneration in the euphotic zone, and is largely responsible for the spatial variability of nitrogen regeneration. However, remineralization provides a steady supply of ammonium in the upper ocean, and is a major source of inorganic nitrogen for the oligotrophic regions. Overall, ammonium generation and removal are approximately balanced over the top 150 m in the equatorial Pacific.

  4. Equatorial Oscillation and Planetary Wave Activity in Saturn's Stratosphere Through the Cassini Epoch

    Science.gov (United States)

    Guerlet, S.; Fouchet, T.; Spiga, A.; Flasar, F. M.; Fletcher, L. N.; Hesman, B. E.; Gorius, N.

    2018-01-01

    Thermal infrared spectra acquired by Cassini/Composite InfraRed Spectrometer (CIRS) in limb-viewing geometry in 2015 are used to derive 2-D latitude-pressure temperature and thermal wind maps. These maps are used to study the vertical structure and evolution of Saturn's equatorial oscillation (SEO), a dynamical phenomenon presenting similarities with the Earth's quasi-biennal oscillation (QBO) and semi-annual oscillation (SAO). We report that a new local wind maximum has appeared in 2015 in the upper stratosphere and derive the descent rates of other wind extrema through time. The phase of the oscillation observed in 2015, as compared to 2005 and 2010, remains consistent with a ˜15 year period. The SEO does not propagate downward at a regular rate but exhibits faster descent rate in the upper stratosphere, combined with a greater vertical wind shear, compared to the lower stratosphere. Within the framework of a QBO-type oscillation, we estimate the absorbed wave momentum flux in the stratosphere to be on the order of ˜7 × 10-6 N m-2. On Earth, interactions between vertically propagating waves (both planetary and mesoscale) and the mean zonal flow drive the QBO and SAO. To broaden our knowledge on waves potentially driving Saturn's equatorial oscillation, we searched for thermal signatures of planetary waves in the tropical stratosphere using CIRS nadir spectra. Temperature anomalies of amplitude 1-4 K and zonal wave numbers 1 to 9 are frequently observed, and an equatorial Rossby (n = 1) wave of zonal wave number 3 is tentatively identified in November 2009.

  5. Observations of unusual pre-dawn response of the equatorial F-region during geomagnetic disturbances

    Science.gov (United States)

    Lima, W.; Becker-Guedes, F.; Fagundes, P.; Sahai, Y.; Abalde, J.; Pillat, V.

    It is known that the disturbed solar wind-magnetosphere interactions have important effects on equatorial and low-latitude ionospheric electrodynamics. The response of equatorial ionosphere during storm-time is an important aspect of space weather studies. It has been observed that during geomagnetic disturbances both suppression as well as generation of equatorial spread-F (ESF) or plasma irregularities takes place. However, the mechanism(s) associated with the generation of ESF still needs further investigations. This work reports some unusual events of pre-dawn occurrence of ionospheric F-region satellite traces followed by spread-F and cusp-like spread-F from ionospheric sounding observations carried out by a Canadian Advanced Digital Ionosonde (CADI) localized at Palmas (10.2°, 48.2°W, dip latitude 5.7°S), Brazil during 2002, every 5 minutes. For the present work we have scaled and analyzed the ionospheric sounding data for three events (April 20, September 04 and 08, 2002), which are associated with geomagnetic disturbances. In the events studied, the ionograms show the occurrence of satellite trace followed by cusp-like spread. The cusp like features move up in frequency and height and finally attain the F-layer peak value (foF2) and then disappear. They had duration of about 30 min and always occurred in the early morning hours. Our studies involved seven geomagnetic disturbances as well as quiet days during the year 2002, but only on these three occasions we observed these features. We present and discuss these observations in this paper and suggest possible mechanisms for the occurrence of these unusual features.

  6. OH Airglow and Equatorial Variations Observed by ISUAL Instrument on Board the FORMOSAT 2 Satellite

    Directory of Open Access Journals (Sweden)

    Jan-Bai Nee

    2010-01-01

    Full Text Available OH airglow observed by the ISUAL (Imager of Sprites and Upper Atmospheric Lightning instrument on board the FORMOSAT 2 satellite is reported in this paper. The satellite is sun-synchronous and it returns to the same orbit at the same local time daily. By using this property, we can study the upper atmosphere in detail. With a CCD camera, ISUAL has measured the emission layers of OH Meinel band at 630 nm for several two-week periods in 2004 and 2007 in equatorial regions. ISUAL images are snapshots of the atmosphere 250 km (height ¡_ 1200 km (horizontal distance. These images of OH airglow are analyzed to derive its peak height and latitudinal variations. ISUAL observation is unique in its capability of continuous observation of the upper atmosphere as the satellite travels from south to north along a specific orbit. However, 630 nm filter also measured O(1D at 200 km, and there are interferences between O(1D and OH airglows as as observed from a distance in space. We have studied the overlap of two airglows by simulations, and our final analyses show that OH airglow can be correctly derived with its average peak height of 89 ¡_ 2.1 km usually lying within ¡_10¢X latitude about the equator. ISUAL data reveal detailed structures of equatorial OH airglow such as the existences of a few secondary maxima within the equatorial regions, and the oscillations of the peak latitudes. These results are discussed and compared with previous reports.

  7. A near-infrared, optical, and ultraviolet polarimetric and timing investigation of complex equatorial dusty structures

    Science.gov (United States)

    Marin, F.; Rojas Lobos, P. A.; Hameury, J. M.; Goosmann, R. W.

    2018-05-01

    Context. From stars to active galactic nuclei, many astrophysical systems are surrounded by an equatorial distribution of dusty material that is, in a number of cases, spatially unresolved even with cutting edge facilities. Aims: In this paper, we investigate if and how one can determine the unresolved and heterogeneous morphology of dust distribution around a central bright source using time-resolved polarimetric observations. Methods: We used polarized radiative transfer simulations to study a sample of circumnuclear dusty morphologies. We explored a grid of geometrically variable models that are uniform, fragmented, and density stratified in the near-infrared, optical, and ultraviolet bands, and we present their distinctive time-dependent polarimetric signatures. Results: As expected, varying the structure of the obscuring equatorial disk has a deep impact on the inclination-dependent flux, polarization degree and angle, and time lags we observe. We find that stratified media are distinguishable by time-resolved polarimetric observations, and that the expected polarization is much higher in the infrared band than in the ultraviolet. However, because of the physical scales imposed by dust sublimation, the average time lags of months to years between the total and polarized fluxes are important; these time lags lengthens the observational campaigns necessary to break more sophisticated, and therefore also more degenerated, models. In the ultraviolet band, time lags are slightly shorter than in the infrared or optical bands, and, coupled to lower diluting starlight fluxes, time-resolved polarimetry in the UV appears more promising for future campaigns. Conclusions: Equatorial dusty disks differ in terms of inclination-dependent photometric, polarimetric, and timing observables, but only the coupling of these different markers can lead to inclination-independent constraints on the unresolved structures. Even though it is complex and time consuming, polarized

  8. Morphology and physiology of the marine straminipilan fungi, the aplanochytrids isolated from the equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Damare, V.; Raghukumar, S.

    cysteine and the aromatic amino acids did not induce any growth. Enzymatic studies−Ten isolates showed degrada-tion of milk protein indicating production of protease enzyme but none of the isolates produced lipase, amylase or chitinase enzymes (Table 4... represents 5 µm. Table 4Protease activity of 14 isolates of aplanochytrids isolated from equatorial Indian Ocean, as observed by the zone of clearance of milk protein. Isolate no. Zone of clearance of milk protein (mm) S1961 16.5 S1962 nil S1963 18...

  9. Magnetic activity effect on equatorial spread-F under high and low solar activity conditions

    Energy Technology Data Exchange (ETDEWEB)

    Subbarao, K S.V.; Somayajulu, V V; Krishna Murthy, B V

    1986-08-01

    The effect of magnetic activity on spread-F at two equatorial stations, Trivandrum and Huancayo, separated in longitude by about 150 deg, under high and low solar activity conditions has been investigated. Magnetic activity produces strong inhibition effect on spread-F at Huancayo compared to that at Trivandrum especially during high solar activity period. This results in a decrease of spread-F with solar activity at Huancayo in contrast to Trivandrum. These findings are explained in terms of F-region electrodynamics and Rayleigh-Taylor instability mechanism for spread-F.

  10. Features of highly structured equatorial plasma irregularities deduced from CHAMP observations

    DEFF Research Database (Denmark)

    Xiong, C.; Luhr, H.; Ma, S. Y.

    2012-01-01

    In this study five years of CHAMP (Challenging Mini-satellite Payload) fluxgate magnetometer (FGM) data is used to investigate the characteristics of Equatorial Plasma Bubbles (EPBs). We filtered the FGM data by using bandpasses with four different cut-off periods to get the EPBs with different......). Since the height of the F-layer is highly correlated with the vertical plasma drift and solar flux, we sorted the ROCSAT-1 data into different groups by F10.7. From the integrated vertical drift we have estimated the post-sunset uplift of the ionosphere. By comparing the properties of EPB occurrence...

  11. Wideband satellite phase coherent beacon observations at auroral and equatorial latitudes - A review

    International Nuclear Information System (INIS)

    Rino, C.L.; Livingston, R.C.; Cousins, M.D.; Fair, B.C.

    1978-01-01

    This paper presents a brief review of some of the principal results from the first two years of operation of the Wideband satellite which transmits phase-coherent signals from S-band to VHF. The auroral zone data show narrow regions of enhanced scintillation well equatorward of the discrete aurora. Such enhancements can be explained as a purely geometrical effect if the irregularities within the major precipitation regions have a sheet-like structure. Evidence of a localized irregularity source at the poleward boundary of the plasma trough is also found. Model computations are discussed and applied to the interpretation of equatorial data

  12. {sup 10}Be in rhodochrosite nodules from Neogene sediments along the Galapagos Ridge, equatorial Pacific

    Energy Technology Data Exchange (ETDEWEB)

    Aldahan, A., E-mail: ala.aldahan@geo.uu.s [Department of Earth Sciences, Uppsala University, Uppsala (Sweden); Department of Geology, United Arab Emirates University, Al Ain (United Arab Emirates); Morad, S. [Department of Earth Sciences, Uppsala University, Uppsala (Sweden); Department of Petroleum Geosciences, Petroleum Institute, Abu Dhabi (United Arab Emirates); Possnert, G. [Tandem Laboratory, Uppsala University, Uppsala (Sweden); Sturesson, U. [Department of Earth Sciences, Uppsala University, Uppsala (Sweden); ElSaiy, A. [Department of Geology, United Arab Emirates University, Al Ain (United Arab Emirates)

    2010-04-15

    Microcrystalline, calcian rhodochrosite occurs as nodules around burrows in late Neogene pelagic sediments from the Galapagos Ridge in the Guatemala Basin, eastern equatorial Pacific (DSDP Leg 68; Site 503). {sup 10}Be isotope revealed that the rhodochrosite nodules have formed under growth conditions much faster than those reported for Fe-Mn nodules. The overall REE patterns of the nodules and host pelagic sediments indicate element derivation mainly from marine pore water. However, variations in the shale normalised Eu values suggest influx of hydrothermal fluids into mounds area at Galapagos, which is also evidenced by the similar minor and major element contents in the nodules and host sediments.

  13. Dependence on zenith angle of the strength of 3-meter equatorial electrojet irregularities

    International Nuclear Information System (INIS)

    Ierkic, H.M.; Fejer, B.G.; Farley, D.T.

    1980-01-01

    Radar measurements in Peru were used to deduce the zenith angle dependence of the scattering cross section of plasma irregularities generated by instabilities in the equatorial electrojet. The irregularities probed by the 50 MHz Jicamarca radar had a wavelength of 3m. The cross section for the type 2 irregularities was isotopic in the plane perpendicular to the magnetic field, while the cross section for the stronger type 1 irregularities varied with zenith angle at a rate of approximately 0.3 dB/degree; the horizontally traveling waves were more than 100 times stronger than those traveling vertically

  14. Characteristics of equatorial gravity waves derived from mesospheric airglow imaging observations

    Directory of Open Access Journals (Sweden)

    S. Suzuki

    2009-04-01

    Full Text Available We present the characteristics of small-scale (<100 km gravity waves in the equatorial mesopause region derived from OH airglow imaging observations at Kototabang (100.3° E, 0.2° S, Indonesia, from 2002 to 2005. We adopted a method that could automatically detect gravity waves in the airglow images using two-dimensional cross power spectra of gravity waves. The propagation directions of the waves were likely controlled by zonal filtering due to stratospheric mean winds that show a quasi-biennial oscillation (QBO and the presence of many wave sources in the troposphere.

  15. Bottomside sinusoidal irregularities in the equatorial F region. II - Cross-correlation and spectral analysis

    Science.gov (United States)

    Cragin, B. L.; Hanson, W. B.; Mcclure, J. P.; Valladares, C. E.

    1985-01-01

    Equatorial bottomside sinusoidal (BSS) irregularities have been studied by applying techniques of cross-correlation and spectral analysis to the Atmosphere Explorer data set. The phase of the cross-correlations of the plasma number density is discussed and the two drift velocity components observed using the retarding potential analyzer and ion drift meter on the satellite are discussed. Morphology is addressed, presenting the geographical distributions of the occurrence of BSS events for the equinoxes and solstices. Physical processes including the ion Larmor flux, interhemispheric plasma flows, and variations in the lower F region Pedersen conductivity are invoked to explain the findings.

  16. Scintillations associated with bottomside sinusoidal irregularities in the equatorial F region

    Science.gov (United States)

    Basu, S.; Basu, S.; Valladares, C. E.; Dasgupta, A.; Whitney, H. E.

    1986-01-01

    Multisatellite scintillation observations and spaced receiver drift measurements are presented for a category of equatorial F region plasma irregularities characterized by nearly sinusoidal waveforms in the ion number density. The observations were made at Huancayo, Peru, and the measurements at Ancon, Peru, associated with irregularities observed by the Atmospheric-Explorer-E satellite on a few nights in December 1979. Utilizing ray paths to various geostationary satellites, it was found that the irregularities grow and decay almost simultaneously in long-lived patches extending at least 1000 km in the east-west direction.

  17. Nonlinear oscillation regime of electromagnetic disturbances in the equatorial F region

    International Nuclear Information System (INIS)

    Sazonov, S.V.

    1990-01-01

    Nonlinear oscillation regime of electromagnetic dicturbances within equatorial ionosphere F-region resulted from Rayleigh-Taylor instability, gradient-drift instability and recombination processes is investigated on the basis of two-liquid quasihydrodynamics equations. It is shown, that at positive linear increment the oscillations are developing in regime with aggregation and are terminated by increment the effect of threshold destabilization, when under certain initial conditions underlgoes oscillation nonlinear swinging, resulting, as well, in bubble formation in contrast to small damping oscillations, is detected

  18. Tuna fisheries and populational dinamic in aggregated schools in the western equatorial Atlantic

    OpenAIRE

    Guelson Batista da Silva

    2013-01-01

    O presente trabalho tem por objetivo a caracterizaÃÃo dos aspectos tecnolÃgicos e da composiÃÃo das capturas, complementados com estudos sobre o crescimento e a alimentaÃÃo das principais espÃcies na pesca de atuns e afins em cardumes associados no AtlÃntico Oeste Equatorial. Para tanto, foram acompanhados 109 desembarques em Areia Branca, RN, no perÃodo entre jun/2010 e mai/2013, assim como o embarque em nove cruzeiros de pesca no perÃodo entre fev/2011 e dez/2012. O estudo de idade e cresci...

  19. Hiss or equatorial noise? Ambiguities in analyzing suprathermal ion plasma wave resonance

    Czech Academy of Sciences Publication Activity Database

    Sarno-Smith, L. K.; Liemohn, M. W.; Skoug, R. M.; Santolík, Ondřej; Morley, S. K.; Breneman, A.; Larsen, B. A.; Reeves, G.; Wygant, J. R.; Hospodarsky, G.; Kletzing, C.; Moldwin, M. B.; Katus, R. M.; Zou, S.

    2016-01-01

    Roč. 121, č. 10 (2016), s. 9619-9631 ISSN 2169-9380 R&D Projects: GA MŠk(CZ) LH15304 Grant - others:AV ČR(CZ) AP1401 Program:Akademická prémie - Praemium Academiae Institutional support: RVO:68378289 Keywords : equatorial noise * low-energy ions * plasma waves * plasmasphere * plasmaspheric hiss Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.733, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/2016JA022975/abstract

  20. Geochronological correlation of the late Precambrian sequences on and around the stable zones of Equatorial Africa

    International Nuclear Information System (INIS)

    Cahen, L.

    1982-01-01

    Very few radiometric age determinations have a bearing on the late Precambrian sequences of the stable zones of Equatorial Africa. A geochronological correlation of these sequences must therefore rest upon a compilation of ages from these stable zones and the corresponding mobile zones. About 15 ages of varying precision more or less well tied up with the stratigraphical sequences, together with results of the study of stromatolite assemblages allow a provisional correlation to be made. One conclusion of this correlation is that most mixtites surrounding the Congo basin are in a 950 +- 50 Ma age bracket and are presumably to be correlated. (Auth.)

  1. 10Be in rhodochrosite nodules from Neogene sediments along the Galapagos Ridge, equatorial Pacific

    International Nuclear Information System (INIS)

    Aldahan, A.; Morad, S.; Possnert, G.; Sturesson, U.; ElSaiy, A.

    2010-01-01

    Microcrystalline, calcian rhodochrosite occurs as nodules around burrows in late Neogene pelagic sediments from the Galapagos Ridge in the Guatemala Basin, eastern equatorial Pacific (DSDP Leg 68; Site 503). 10 Be isotope revealed that the rhodochrosite nodules have formed under growth conditions much faster than those reported for Fe-Mn nodules. The overall REE patterns of the nodules and host pelagic sediments indicate element derivation mainly from marine pore water. However, variations in the shale normalised Eu values suggest influx of hydrothermal fluids into mounds area at Galapagos, which is also evidenced by the similar minor and major element contents in the nodules and host sediments.

  2. The prospection of uranium and thorium ores in desert country and in equatorial forest regions of the Union Francaise

    International Nuclear Information System (INIS)

    Lecoq, J.J.; Bigotte, G.; Hinault, J.; Leconte, J.R.

    1958-01-01

    Since it was founded, the D.R.E.M. has carried out important prospection work in the overseas territories which now make up the Communaute Francaise. This work, now involving almost a million km 2 , represents an experiment scarcely equalled throughout the world. Research in these territories presents both general and technical difficulties, which are especially severe in countries with extreme climates: deserts or dense equatorial forests. The adaptation of various methods of radioactive ore prospection to these regions is described, and also the results obtained. Three particular examples are given in detail: - general exploration in the Hoggar, and reconnoitring of particular indications; - general exploration in the equatorial forest of French Guyana; - detailed study of a sign of uraniferous occurrences and its surroundings in the equatorial zone (Mounana deposit near Franceville (Gabon)). (author) [fr

  3. Radar Observations of 8.3-m scale equatorial spread F irregularities over Trivandrum

    Directory of Open Access Journals (Sweden)

    D. Tiwari

    2004-03-01

    Full Text Available In this paper, we present observations of equatorial spread F (ESF irregularities made using a newly installed 18MHz radar located at Trivandrum. We characterize the morphology and the spectral parameters of the 8.3-m ESF irregularities which are found to be remarkably different from that observed so extensively at the 3-m scale size. We also present statistical results of the irregularities in the form of percentage occurrence of the echoes and spectral parameters (SNR, Doppler velocity, Spectral width. The Doppler spectra are narrower, less structured and less variable in time as compared to those observed for 3-m scale size. We have never observed the ESF irregularity velocities to be supersonic here unlike those at Jicamarca, and the velocities are found to be within ±200ms–1. The spectral widths are found to be less than 150ms–1. Hence, the velocities and spectral width both are smaller than those reported for 3-m scale size. The velocities and spectral widths are further found to be much smaller than those of the American sector. These observations are compared with those reported elsewhere and discussed in the light of present understanding on the ESF irregularities at different wavelengths.

    Key words. Ionoshphere (equatorial ionosphere, plasma waves and instabilities; ionospheric irregularities

  4. Radar Observations of 8.3-m scale equatorial spread F irregularities over Trivandrum

    Directory of Open Access Journals (Sweden)

    D. Tiwari

    2004-03-01

    Full Text Available In this paper, we present observations of equatorial spread F (ESF irregularities made using a newly installed 18MHz radar located at Trivandrum. We characterize the morphology and the spectral parameters of the 8.3-m ESF irregularities which are found to be remarkably different from that observed so extensively at the 3-m scale size. We also present statistical results of the irregularities in the form of percentage occurrence of the echoes and spectral parameters (SNR, Doppler velocity, Spectral width. The Doppler spectra are narrower, less structured and less variable in time as compared to those observed for 3-m scale size. We have never observed the ESF irregularity velocities to be supersonic here unlike those at Jicamarca, and the velocities are found to be within ±200ms–1. The spectral widths are found to be less than 150ms–1. Hence, the velocities and spectral width both are smaller than those reported for 3-m scale size. The velocities and spectral widths are further found to be much smaller than those of the American sector. These observations are compared with those reported elsewhere and discussed in the light of present understanding on the ESF irregularities at different wavelengths. Key words. Ionoshphere (equatorial ionosphere, plasma waves and instabilities; ionospheric irregularities

  5. Sub-kilometer Simulation of Equatorial Plasma Bubble and Comparison with Satellite Observations

    Science.gov (United States)

    Yokoyama, T.; Pfaff, R. F., Jr.; Stolle, C.; Su, S. Y.

    2016-12-01

    Equatorial plasma bubble (EPB) is a well-known phenomenon in the equatorial ionospheric F region. As it causes severe scintillation in the amplitude and phase of radio signals, it is important to understand and forecast the occurrence of EPB from a space weather point of view. The development of EPB is presently believed as an evolution of the generalized Rayleigh-Taylor instability. We have already developed a 3D high-resolution bubble (HIRB) model with a grid spacing of as small as 1 km and presented nonlinear growth of EPB which shows very turbulent internal structures such as bifurcation and pinching. Recent upgrade of the HIRB model has made it possible to conduct the simulation with sub-kilometer grid spacing. The simulation results can be compared with various in situ satellite observations such as plasma drift velocity, plasma density, magnetic field, and their structures and power spectra, e.g. from the C/NOFS, ROCSAT, CHAMP, or Swarm missions. Our initial results show encouraging agreement between model results and observational data.

  6. Diagnosing the Growth of Equatorial Typhoon Vamei (2001 from an Energy Standpoint

    Directory of Open Access Journals (Sweden)

    Gin-Rong Liu

    2010-01-01

    Full Text Available Surprisingly, on 27 December 2001, a storm named Typhoon Vamei formed near in Singaporean waters. An examination on the SSM/I-derived rainfall rates and air-sea parameters showed that significant higher latent heat release and air-sea energy flux during convective rainfall activities played a key role in the typhoon¡¦s growth. A quantitative analysis revealed that the energy flux from the ocean to the atmosphere and the latent heat release during the rainfall activities both increased significantly during the initial growth stage. However, the values rapidly decreased just before the storm reached typhoon strength. Separately, in contrast to a case that occurred in 1999, the total thermal energy calculated from Typhoon Vamei¡¦s formation was two times higher. Thus, despite a very weak Coriolis force in the equatorial belt, the special terrain of Borneo Island and narrow channel in the equatorial South China Sea caused a Borneo vortex via northeasterly cold surges, together with the accumulated energy was sufficiently strong enough to induce the formation of Typhoon Vamei.

  7. Western equatorial African forest-savanna mosaics: a legacy of late Holocene climatic change?

    Directory of Open Access Journals (Sweden)

    A. Ngomanda

    2009-10-01

    Full Text Available Past vegetation and climate changes reconstructed using two pollen records from Lakes Maridor and Nguène, located in the coastal savannas and inland rainforest of Gabon, respectively, provide new insights into the environmental history of western equatorial African rainforests during the last 4500 cal yr BP. These pollen records indicate that the coastal savannas of western equatorial Africa did not exist during the mid-Holocene and instead the region was covered by evergreen rainforests. From ca. 4000 cal yr BP a progressive decline of inland evergreen rainforest, accompanied by the expansion of semi-deciduous rainforest, occurred synchronously with grassland colonisation in the coastal region of Gabon. The contraction of moist evergreen rainforest and the establishment of coastal savannas in Gabon suggest decreasing humidity from ca. 4000 cal yr BP. The marked reduction in evergreen rainforest and subsequent savanna expansion was followed from 2700 cal yr BP by the colonization of secondary forests dominated by the palm, Elaeis guineensis, and the shrub, Alchornea cordifolia (Euphorbiaceae. A return to wetter climatic conditions from about 1400 cal yr BP led to the renewed spread of evergreen rainforest inland, whereas a forest-savanna mosaic still persists in the coastal region. There is no evidence to suggest that the major environmental changes observed were driven by human impact.

  8. Vertical and longitudinal electron density structures of equatorial E- and F-regions

    Directory of Open Access Journals (Sweden)

    P. S. Brahmanandam

    2011-01-01

    Full Text Available From global soundings of ionospheric electron density made with FORMOSAT 3/COSMIC satellites for September 2006–August 2009, day-night variations in vertical and longitudinal structures of the electron densities in equatorial E- and F-regions for different seasons are investigated for the first time. The results reveal that the wavenumber-3 and wavenumber-4 patterns dominated the nighttime (22:00–04:00 LT F-region longitudinal structures in solstice and in equinox seasons, respectively. In daytime (08:00–18:00 LT F-region, the wavenumber-4 patterns governed the longitudinal structures in the September equinox and December solstice, and wavenumber-3 in March equinox and June solstice respectively. A comparison of the daytime and nighttime longitudinal electron density structures indicates that they are approximately 180° out of phase with each other. It is believed that this out of phase relation is very likely the result of the opposite phase relation between daytime and nighttime nonmigrating diurnal tidal winds that modulate background E-region dynamo electric field at different places, leading to the day-night change in the locations of the equatorial plasma fountains that are responsible for the formation of the F-region longitudinal structures. Further, a good consistency between the locations of the density structures in the same seasons of the different years for both daytime and nighttime epochs has been noticed indicating that the source mechanism for these structures could be the same.

  9. Equatorial plasma bubbles in the ionosphere over Eritrea: occurrence and drift speed

    Directory of Open Access Journals (Sweden)

    R. H. Wiens

    2006-07-01

    Full Text Available An all-sky imager was installed in Asmara, Eritrea (15.4° N, 38.9° E, 7° N dip and used to monitor the OI 630-nm nightglow. Nine months of data were studied between September 2001 and May 2002, a time including the recent maximum in the solar activity cycle. Equatorial plasma bubbles (EPBs were recorded on 63% of nights with adequate viewing conditions. The station location within view of the equatorial ionization anomaly and with a magnetic declination near zero makes it an excellent test case for comparison with satellite studies of the seasonal variation of EPBs with longitude. The imager was accompanied by two Cornell GPS scintillation monitors, and the amplitude scintillation data are compared to the all-sky data. GPS scintillations indicate the beginning of EPBs, but die out sooner in the post-midnight period than the larger scale EPBs. Both phenomena exhibit clear occurrence maxima around the equinoxes. Ionospheric zonal drift speeds have been deduced from EPB and GPS scintillation pattern movement. Average near-midnight EPB drift speeds are between 100 and 120 m/s most months, with the GPS scintillation speeds being about the same. A winter drift speed maximum is evident in both EPB and GPS scintillation monthly means.

  10. Lighting programs for male and female meat quails (Coturnix coturnix) raised in equatorial region.

    Science.gov (United States)

    Aguiar, G C; Freitas, E R; Watanabe, P H; Figueiredo, C W S; Silva, L P; Nascimento, G A J; Lima, R C; Nepomuceno, R C; Sá, N L

    2017-09-01

    The aim of the present study was to evaluate the effect of lighting programs for male and female meat quails raised in an equatorial region on performance and carcass traits. A total of 1,500 sexed quails (Coturnix coturnix) was distributed in a completely randomized design in a 2 × 3 factorial arrangement, with 2 sexes (male and female) and 3 lighting programs (natural, intermittent, and continuous) with 5 replicates of 50 birds. The lighting programs were applied in the period from 7 to 49 d of age, being natural (12 h and 30 min of natural light and 11 h and 30 min of dark), intermittent (12 h and 30 min of natural light and 5 h and 30 min of artificial light, alternating lighting periods with one h and 06 min and periods of darkness with one h and 12 min), and continuous (23 h of natural + artificial light and one h of dark). Regardless of lighting program, female quails were heavier than males, and birds subjected to natural light weighed less than those exposed to continuous and intermittent lighting programs. Quails exposed to intermittent and continuous light presented higher weight gain and feed intake, and worse feed conversion ratio compared to birds under a natural light regimen. It is concluded that in an equatorial region, it is possible to use a lighting program with only natural light for raising male and female meat quails from 7 to 49 d of age. © 2017 Poultry Science Association Inc.

  11. Growth rates, grazing, sinking, and iron limitation of equatorial Pacific phytoplankton

    International Nuclear Information System (INIS)

    Chavez, F.P.; Buck, K.R.; Coale, K.H.; Martin, J.H.; DiTullio, G.R.; Welschmeyer, N.A.; Barber, R.T.; Jacobson, A.C.

    1991-01-01

    Concentrations of phytoplankton and NO 3 are consistently low and high in surface waters of the oceanic eastern and central equatorial Pacific, and phytoplankton populations are dominated by small solitary phytoplankton. Growth rates of natural phytoplankton populations, needed to assess the relative importance of many of the processes considered in the equatorial Pacific, were estimated by several methods. The growth rates of natural phytoplankton populations were found to be ∼0.7 d -1 or 1 biomass doubling d -1 and were similar for all methods. To keep this system in its observed balance requires that loss rates approximate observed growth rates. Grazing rates, measured with a dilution grazing experiment, were high, accounting for a large fraction of the daily production. Additions of various forms of Fe to 5-7-d incubations utilizing ultraclean techniques resulted in significant shifts in autotrophic and heterotrophic assemblages between initial samples, controls, and Fe enrichments, which were presumably due to Fe, grazing by both protistan and metazoan components, and incubation artifacts. Estimated growth rates of small pennate diatoms showed increases in Fe enrichments with respect to controls. The growth rates of the pennate diatoms were similar to those estimated for the larger size fraction of the natural populations

  12. An Analysis of Cassini Observations Regarding the Structure of Jupiter's Equatorial Atmosphere

    Science.gov (United States)

    Choi, David S.; Simon-Miller, Amy A.

    2012-01-01

    A variety of intriguing atmospheric phenomena reside on both sides of Jupiter's equator. 5-micron bright hot spots and opaque plumes prominently exhibit dynamic behavior to the north, whereas compact, dark chevron-shaped features and isolated anticyclonic disturbances periodically occupy the southern equatorial latitudes. All of these phenomena are associated with the vertical and meridional perturbations of Rossby waves disturbing the mean atmospheric state. As previous observational analysis and numerical simulations have investigated the dynamics of the region, an examination of the atmosphere's vertical structure though radiative transfer analysis is necessary for improved understanding of this unique environment. Here we present preliminary analysis of a multispectral Cassini imaging data set acquired during the spacecraft's flyby of Jupiter in 2000. We evaluated multiple methane and continuum spectral channels at available viewing angles to improve constraints on the vertical structure of the haze and cloud layers comprising these interesting features. Our preliminary results indicate distinct differences in the structure for both hemispheres. Upper troposphere hazes and cloud layers are prevalent in the northern equatorial latitudes, but are not present in corresponding southern latitudes. Continued analysis will further constrain the precise structure present in these phenomena and the differences between them.

  13. Global peak flux profile of proton precipitation in the equatorial zone

    International Nuclear Information System (INIS)

    Miah, M.A.

    1991-01-01

    Particle precipitation near the equator within ± 30deg geomagnetic latitude was investigated by the Phoenix-1 instrumentation on board the S81-1 mission. The monitor telescope on board the mission was sensitive to protons in the energy range 0.6-9.1 MeV, to alpha particles in the energy range 0.4-80 MeV/nucleon and Z→3 particles ( 12 C) of energy greater than 0.7 MeV/nucleon. The peak efficiency of the telescope was for particles of ∼88deg pitch angles at the line of minimum magnetic field. Careful separation of the magnetically quiet time equatorial particle data from global data coverage and subsequent analysis shows that the ML detector on board the mission detected mostly protons. The proton peak flux profile follows the line of minimum magnetic field. The full width at half maximum (FWHM) of the equatorial zone is ∼ 13deg, which is well within the EUV emission zone. (author). 14 refs., 9 figs

  14. Genotype distribution of cervical human papillomavirus DNA in women with cervical lesions in Bioko, Equatorial Guinea

    Directory of Open Access Journals (Sweden)

    Carro-Campos Patricia

    2009-09-01

    Full Text Available Abstract Background The HVP vaccine is a useful tool for preventing cervical cancer. The purpose of this study is to determine the most frequent HPV genotypes in Equatorial Guinea in order to develop future vaccination strategies to apply in this country. Methods A campaign against cervical cancer was carried out in the area on a total of 1,680 women. 26 of the women, following cytological screening, were treated surgically with a loop electrosurgical excision procedure (LEEP. Cases were studied histologically and were genotyped from paraffin blocks by applying a commercial kit that recognized 35 HPV types. Results Cytological diagnoses included 17 HSIL, 1 LSIL, 5 ASC-H and 3 AGUS. Histological diagnosis resulted in 3 cases of microinvasive squamous cell carcinoma stage IA of FIGO, 9 CIN-3, 8 CIN-2, 2 CIN-1, 3 flat condylomas and mild dysplasia of the endocervical epithelium. Fifteen of twenty-five cases genotyped were positive for HPV (60%. HPV 16 and 33 were identified in four cases each, HPV 58 in two other cases, and HPV 18, 31, 52, and 82 in one case, with one HPV 16 and 58 coinfection. Conclusion The frequency of HPV types in the African area varies in comparison to other regions, particularly in Europe and USA. Vaccination against the five most common HPV types (16, 33, 58, 18, and 31 should be considered in the geographic region of West Africa and specifically in Equatorial Guinea.

  15. Contribution of storm time substorms to the prompt electric field disturbances in the equatorial ionosphere

    International Nuclear Information System (INIS)

    Hui, Debrup; Chakrabarty, D.; Sekar, R.; Reeves, G. D.

    2017-01-01

    This study tries to bring out the fact that storm time substorms can compete and at times significantly contribute to the geomagnetically disturbed time prompt penetration electric field effects on low and equatorial latitudes. Observations of unusual equatorial plasma drift data from Jicamarca Unattended Long-term Investigations of the Ionosphere and Atmosphere during two space weather events show that substorms can induce both eastward and westward penetration electric fields under steady southward interplanetary magnetic field (IMF B z ) conditions. During the first event on 2 January 2005, the enhancement of the daytime eastward electric field over Jicamarca due to substorm is found to be comparable with the Sq and interplanetary electric field (IEFy) generated electric fields combined. During the second event on 19 August 2006, the substorm is seen to weaken the daytime eastward field thereby inducing a westward field in spite of the absence of northward turning of IMF B z (overshielding). The westward electric field perturbation in the absence of any overshielding events is observationally sparse and contrary to the earlier results. Further, the substorm-induced field is found to be strong enough to compete or almost nullify the effects of storm time IEFy fields. This study also shows quantitatively that at times substorm contribution to the disturbed time prompt electric fields can be significant and thus should be taken into consideration in evaluating penetration events over low latitudes.

  16. The evolution of the equatorial thermocline and the early Pliocene El Padre mean state

    Science.gov (United States)

    Ford, Heather L.; Ravelo, A. Christina; Dekens, Petra S.; LaRiviere, Jonathan P.; Wara, Michael W.

    2015-06-01

    The tropical Pacific thermocline strength, depth, and tilt are critical to tropical mean state and variability. During the early Pliocene (~3.5 to 4.5 Ma), the Eastern Equatorial Pacific (EEP) thermocline was deeper and the cold tongue was warmer than today, which resulted in a mean state with a reduced zonal sea surface temperature gradient or El Padre. However, it is unclear whether the deep thermocline was a local feature of the EEP or a basin-wide condition with global implications. Our measurements of Mg/Ca of Globorotalia tumida in a western equatorial Pacific site indicate Pliocene subsurface temperatures warmer than today; thus, El Padre included a basin-wide thermocline that was relatively warm, deep, and weakly tilted. At ~4 Ma, thermocline steepening was coupled to cooling of the cold tongue. Since ~4 Ma, the basin-wide thermocline cooled/shoaled gradually, with implications for thermocline feedbacks in tropical dynamics and the interpretation of TEX86-derived temperatures.

  17. Observation of proton chorus waves close to the equatorial plane by Cluster

    Science.gov (United States)

    Grison, B.; Pickett, J. S.; Santolik, O.; Robert, P.; Cornilleau-Wehrlin, N.; Engebretson, M. J.; Constantinescu, D. O.

    2009-12-01

    Whistler mode chorus waves are a widely studied phenomena. They are present in numerous regions of the magnetosphere and are presumed to originate in the magnetic equatorial region. In a spectrogram they are characterized by narrowband features with rise (or fall) in frequency over short periods of time. Being whistler mode waves around a few tenths of the electron cyclotron frequency they interact mainly with electrons. In the present study we report observations by the Cluster spacecraft of what we call proton chorus waves. They have spectral features with rising frequency, similar to the electron chorus waves, but they are detected in a frequency range that starts roughly at 0.50fH+ up to fH+ (the local proton gyro-frequency). The lower part of their spectrum seems to originate from monochromatic Pc 1 waves (1.5 Hz). Proton chorus waves are detected close to the magnetic equatorial plane in both hemispheres during the same event. Our interpretation of these waves as proton chorus is supported by polarization analysis with the Roproc procedures and the Prassadco software using both the magnetic (STAFF-SC) and electric (EFW) parts of the fluctuations spectrum.

  18. Thermo-hydraulic analysis of the generic equatorial port plug design

    International Nuclear Information System (INIS)

    Rodríguez, E.; Guirao, J.; Ordieres, J.; Cortizo, J.L.; Iglesias, S.

    2012-01-01

    Highlights: ► Thermo-hydraulic transient performance evaluation and optimization of the GEPP structure cooling/heating system under neutronic heating and baking conditions. ► The optimization of the GEPP box structure's cooling system includes positioning and minimization of number and size of gun drilled channels, complying with the flow and functional requirements during operating and baking conditions. - Abstract: The port-based ITER diagnostic systems are housed primarily in two locations, the equatorial and upper port plugs. The port plug structure provides confinement function, maintains ultra-high vacuum quality and the first confinement barrier for radioactive materials at the ports. The port plug structure design, from the ITER International Organisation (IO), is cooled and heated by pressurized water which flows through a series of gun-drilled water channels and water pipes. The cooling function is required to remove nuclear heating due to radiation during operation of ITER, while the heating function is intended to heat up uniformly the machine during baking condition. The work presented provides coupled thermo-hydraulic analysis and optimization of a Generic Equatorial Port Plug (GEPP) structure cooling and heating system. The optimization performed includes positioning, minimization of number and size of gun drilled channels, complying with the flow and functional requirements during operating and baking conditions.

  19. Magnetic-field-aligned characteristics of plasma bubbles in the nighttime equatorial ionosphere

    International Nuclear Information System (INIS)

    Tsunoda, R.T.

    1980-01-01

    Measurements of both incoherent-scatter (IS) and backscatter from field-aligned irregularities (FAI) were made in 1978 with ALTAIR, a fully-steerable high-power radar, to investigate the magnetic-field-aligned characteristics of equatorial plasma bubbles. By operating the radar in a latitude-scan IS mode it was possible to map the location and percentage depletion of plasma bubbles as a function of altitude. By showing that backscatter from FAI is spatially collocated with the upper wall of plasma bubbles it was possible to use the spatial displacement of a field aligned backscatter region to estimate the upward bubble velocity. Besides showing that plasma bubbles are indeed aligned along magnetic field lines, this data set is used to show that a plasma bubble with a percentage depletion of as much as 90% does not have as large an upward velocity as predicted by two-dimensional models. Instead, the inferred bubble velocity is shown to be in better agreement with the bubble velocity predicted by theoretical models using flux-integrated values of electron density and Pedersen conductivity. The need to use flux-tube-integrated values when comparing theory and observation is further stressed by the presence of a non-uniform latitudinal distribution of electron density (i.e. the equatorial anomaly) that was found in the latitude-scan data. (author)

  20. Equatorial Precession Drove Mid-Latitude Changes in ENSO-Scale Variation in the Earliest Miocene

    Science.gov (United States)

    Fox, B.; D'Andrea, W. J.; Lee, D. E.; Wilson, G. S.

    2014-12-01

    Foulden Maar is an annually laminated lacustrine diatomite deposit from the South Island of New Zealand. The deposit was laid down over ~100 kyr of the latest Oligocene and earliest Miocene, during the peak and deglaciation phase of the Mi-1 Antarctic glaciation event. At this time, New Zealand was located at approximately the same latitude as today (~45°S). Evidence from organic geochemical proxies (δD, δ13C) and physical properties (density, colour) indicates the presence of an 11-kyr cycle at the site. Although it is known that 11-kyr insolation (half-precession) cycles occur between the Tropics, this cycle is rarely seen in sedimentary archives deposited outside the immediate vicinity of the Equator. Records from Foulden Maar correlate well with the amplitude and phase of the modelled equatorial half-precession cycle for the earliest Miocene. High-resolution (50 µm) colour intensity measurements and lamina thickness measurements both indicate the presence of significant ENSO-like (2-8 year) variation in the Foulden Maar sediments. Early results from targeted lamina thickness measurements suggest that ENSO-band variation is modulated by the 11-kyr cycle, with power in the ENSO band increasing during periods of increased insolation at the Equator. This implies that equatorial half-precession had a significant effect on ENSO-like variation in the early Miocene, and that this effect was felt as far afield as the mid-latitudes of the Southern Hemisphere.

  1. Deep-sea environment and biodiversity of the West African Equatorial margin

    Science.gov (United States)

    Sibuet, Myriam; Vangriesheim, Annick

    2009-12-01

    The long-term BIOZAIRE multidisciplinary deep-sea environmental program on the West Equatorial African margin organized in partnership between Ifremer and TOTAL aimed at characterizing the benthic community structure in relation with physical and chemical processes in a region of oil and gas interest. The morphology of the deep Congo submarine channel and the sedimentological structures of the deep-sea fan were established during the geological ZAIANGO project and helped to select study sites ranging from 350 to 4800 m water depth inside or near the channel and away from its influence. Ifremer conducted eight deep-sea cruises on board research vessels between 2000 and 2005. Standardized methods of sampling together with new technologies such as the ROV Victor 6000 and its associated instrumentation were used to investigate this poorly known continental margin. In addition to the study of sedimentary environments more or less influenced by turbidity events, the discovery of one of the largest cold seeps near the Congo channel and deep coral reefs extends our knowledge of the different habitats of this margin. This paper presents the background, objectives and major results of the BIOZAIRE Program. It highlights the work achieved in the 16 papers in this special issue. This synthesis paper describes the knowledge acquired at a regional and local scale of the Equatorial East Atlantic margin, and tackles new interdisciplinary questions to be answered in the various domains of physics, chemistry, taxonomy and ecology to better understand the deep-sea environment in the Gulf of Guinea.

  2. Numerical experiments on the atmospheric response to cold Equatorial Pacific conditions ('La Nina') during northern summer

    International Nuclear Information System (INIS)

    Storch, H. von; Schriever, D.; Arpe, K.; Branstator, G.W.; Legnani, R.; Ulbrich, U.

    1993-01-01

    The effect of cold conditions in the central and eastern Equatorial Pacific during Northern Summer is examined in a series of numerical experiments with the low resolution (T21) atmospheric general circulation model ECHAM2. Anomalous sea surface temperatures (SST) as observed in June 1988 were prescribed and the effect on the global circulation is examined. In the model atmosphere, the anomalous cold water in the Equatorial Pacific excites a strong and stable response over the tropical Central and East Pacific. From here stationary Rossby waves radiate into both hemispheres. The Northern Hemisphere wave train is weak and affects only the Northeast Pacific area; the Southern Hemisphere wave train arches from the Central Pacific over the southern tip of South America to the South Atlantic. This response is not only present in the basic anomaly experiment with the T21 GCM but also in experiments with SST anomalies confined to the tropics and with an envelope-formulation of the SST anomalies, in experiments with a linear model, and in high resolution (T42) model experiments. The model output is also compared to the actually observed atmospheric state in June 1988. (orig./KW)

  3. Genotype distribution of cervical human papillomavirus DNA in women with cervical lesions in Bioko, Equatorial Guinea.

    Science.gov (United States)

    García-Espinosa, Benjamín; Nieto-Bona, Ma Paz; Rueda, Sonsoles; Silva-Sánchez, Luís Fernando; Piernas-Morales, Ma Concepción; Carro-Campos, Patricia; Cortés-Lambea, Luís; Moro-Rodríguez, Ernesto

    2009-09-09

    The HVP vaccine is a useful tool for preventing cervical cancer. The purpose of this study is to determine the most frequent HPV genotypes in Equatorial Guinea in order to develop future vaccination strategies to apply in this country. A campaign against cervical cancer was carried out in the area on a total of 1,680 women. 26 of the women, following cytological screening, were treated surgically with a loop electrosurgical excision procedure (LEEP). Cases were studied histologically and were genotyped from paraffin blocks by applying a commercial kit that recognized 35 HPV types. Cytological diagnoses included 17 HSIL, 1 LSIL, 5 ASC-H and 3 AGUS. Histological diagnosis resulted in 3 cases of microinvasive squamous cell carcinoma stage IA of FIGO, 9 CIN-3, 8 CIN-2, 2 CIN-1, 3 flat condylomas and mild dysplasia of the endocervical epithelium. Fifteen of twenty-five cases genotyped were positive for HPV (60%). HPV 16 and 33 were identified in four cases each, HPV 58 in two other cases, and HPV 18, 31, 52, and 82 in one case, with one HPV 16 and 58 coinfection. The frequency of HPV types in the African area varies in comparison to other regions, particularly in Europe and USA. Vaccination against the five most common HPV types (16, 33, 58, 18, and 31) should be considered in the geographic region of West Africa and specifically in Equatorial Guinea.

  4. A diagnostic model for equatorial spread F. 2. The effect of magnetic activity

    International Nuclear Information System (INIS)

    Kelley, M.C.; Maruyama, Takashi

    1992-01-01

    By using a numerical model the authors have studied electric field effects on the generation of equatorial spread F (ESF) in the postmidnight hours. Equatorial electric fields are zonally westward during late evening and postmidnight hours on normal days, while they sometimes reverse to eastward in magnetically disturbed days. The quiet time westward configuration and typical low altitude of the layer results in stable bottomside gradient or at most one with a very low generalized Rayleigh-Taylor growth rate. The model calculation shows that the growth rate becomes significant when the electric field reverses to eastward and may remain so even when the electric field disturbance weakens due to the upward altitude excursion of the layer. These results account for the correlation of ESF occurrence penetration of magnetospheric electric fields during such magnetic activity. The results also show the crucial role of layer height in the physics. They have calculated the growth rates for specific nights in which perturbation of electric fields and plumes were observed at Jicamarca. These case studies suggest that a quantitative requirement for the generation of plumes is that about 10 e-folding times of the linear instability growth occur. They also suggest that a statistical study using ionosonde data could be very valuable in a testing whether a local version of this quantitative measure of event intensity could be useful in predicting plume activity

  5. The intermediate layers and associated tidal motions observed by a digisonde in the equatorial anomaly region

    Directory of Open Access Journals (Sweden)

    C.-C. Lee

    2003-04-01

    Full Text Available This investigation presents an initial attempt to analyze a full year of daily ionosonde observations relevant to the determination of plasma densities, tidal structures, and ion transports in the equatorial anomaly region of the lower ionosphere. Particular focus is on the intermediate layers, their seasonal and diurnal variations, and cause-effect relationships. The ionogram database was recorded using a digisonde portable sounder (DPS at National Central University (NCU, 24 °58' N, 121°11' E during 1996. Statistical results indicate that the intermediate layers appear primarily during the daytime of the spring/winter months. The monthly median height characteristics reveal that the layers descend from high to low altitudes and different tidal motions control the layers in different months. Generally, the semi-diurnal and quarter-diurnal tides, which cause ionization convergence, are mainly in the spring/winter and summer/autumn months, respectively. Variations in the electron densities of the layers also indicate that the density increases could result from a great number of molecular and metallic ions. Furthermore, a novel approach to ionogram presentation is introduced to investigate the intermediate layers. This approach allows the DPS to characterize the detailed daily information of the intermediate layers.Key words. Ionosphere (equatorial ionosphere; ionosphere-atmosphere interactions; ionospheric irregularities

  6. Final design of the generic equatorial port plug structure for ITER diagnostic systems

    International Nuclear Information System (INIS)

    Udintsev, V.S.; Maquet, P.; Alexandrov, E.; Casal, N.; Cuenca, D.; Drevon, J.-M.; Feder, R.; Friconneau, J.P.; Giacomin, T.; Guirao, J.; Iglesias, S.; Josseaume, F.; Levesy, B.; Loesser, D.; Ordieres, J.; Quinn, E.; Pak, S.; Penot, C.; Pitcher, C.S.; Portalès, M.

    2015-01-01

    The Diagnostic Generic Equatorial Port Plug (GEPP) is designed to be common to all equatorial port-based diagnostic systems. It is designed to survive throughout the lifetime of ITER for 20 years, 30,000 discharges, and 3000 disruptions. The EPP structure dimensions (without Diagnostic First Walls and Diagnostic Shield Modules) are L2.9 × W1.9 × H2.4 m"3. The length of the fully integrated EPP is 3174 mm. The weight of the EPP structure is about 15 t, whereas the total weight of the integrated EPP may be up to 45 t. The EPP structure provides a flexible platform for a variety of diagnostics. The Diagnostic Shield Module assemblies, or drawers, allow a modular approach with respect to diagnostic integration and maintenance. In the nuclear phase of ITER operations, they will be remotely inserted into the EPP structure in the Hot Cell Facility. The port plug structure must also contribute to the nuclear shielding, or plugging, of the port and further contain circulated water to allow cooling during operation and heating during bake-out. The Final Design of the GEPP has been successfully passed in late 2013 and is now heading toward manufacturing. The final design of the GEPP includes interfaces, manufacturing, R&D, operation and maintenance, load cases and analysis of failure modes.

  7. Quantum jointly assisted cloning of an unknown three-dimensional equatorial state

    Science.gov (United States)

    Ma, Peng-Cheng; Chen, Gui-Bin; Li, Xiao-Wei; Zhan, You-Bang

    2018-02-01

    We present two schemes for perfectly cloning an unknown single-qutrit equatorial state with assistance from two and N state preparers, respectively. In the first scheme, the sender wishes to teleport an unknown single-qutrit equatorial state from two state preparers to a remote receiver, and then to create a perfect copy of the unknown state at her location. The scheme consists of two stages. The first stage of the scheme requires the usual teleportation. In the second stage, to help the sender realize the quantum cloning, two state preparers perform single-qutrit projective measurements on their own qutrits from the sender, then the sender can acquire a perfect copy of the unknown state. It is shown that, only if the two state preparers collaborate with each other, the sender can create a copy of the unknown state by means of some appropriate unitary operations. In the second scheme, we generalized the jointly assisted cloning in the first scheme to the case of N state prepares. In the present schemes, the total probability of success for assisted cloning of a perfect copy of the unknown state can reach 1.

  8. Zonal asymmetry of daytime 150-km echoes observed by Equatorial Atmosphere Radar in Indonesia

    Directory of Open Access Journals (Sweden)

    T. Yokoyama

    2009-03-01

    Full Text Available Multi-beam observations of the daytime ionospheric E-region irregularities and the so-called 150-km echoes with the 47-MHz Equatorial Atmosphere Radar (EAR in West Sumatra, Indonesia (0.20° S, 100.32° E, 10.36° S dip latitude are presented. 150-km echoes have been frequently observed by the EAR, and their characteristics are basically the same as the equatorial ones, except for an intriguing zonal asymmetry; stronger echoes in lower altitudes in the east directions, and weaker echoes in higher altitudes in the west. The highest occurrence is seen at 5.7° east with respect to the magnetic meridian, and the altitude gradually increases as viewing from the east to west. Arc structures which return backscatter echoes are proposed to explain the asymmetry. While the strength of radar echoes below 105 km is uniform within the wide coverage of azimuthal directions, the upper E-region (105–120 km echoes also show a different type of zonal asymmetry, which should be generated by an essentially different mechanism from the lower E-region and 150-km echoes.

  9. Equatorial 150 km echoes and daytime F region vertical plasma drifts in the Brazilian longitude sector

    Directory of Open Access Journals (Sweden)

    F. S. Rodrigues

    2013-10-01

    Full Text Available Previous studies showed that conventional coherent backscatter radar measurements of the Doppler velocity of the so-called 150 km echoes can provide an alternative way of estimating ionospheric vertical plasma drifts during daytime hours (Kudeki and Fawcett, 1993; Chau and Woodman, 2004. Using observations made by a small, low-power 30 MHz coherent backscatter radar located in the equatorial site of São Luís (2.59° S, 44.21° W; −2.35° dip lat, we were able to detect and monitor the occurrence of 150 km echoes in the Brazilian sector. Using these measurements we estimated the local time variation of daytime vertical ionospheric drifts in the eastern American sector. Here, we present a few interesting cases of 150 km-echoes observations made by the São Luís radar and estimates of the diurnal variation of vertical drifts. These cases exemplify the variability of the vertical drifts in the Brazilian sector. Using same-day 150 km-echoes measurements made at the Jicamarca Radio Observatory in Peru, we also demonstrate the variability of the equatorial vertical drifts across the American sector. In addition to first estimates of the absolute vertical plasma drifts in the eastern American (Brazilian sector, we also present observations of abnormal drifts detected by the São Luís radar associated with the 2009 major sudden stratospheric warming event.

  10. Mechanism of seasonal eddy kinetic energy variability in the eastern equatorial Pacific Ocean

    Science.gov (United States)

    Wang, Minyang; Du, Yan; Qiu, Bo; Cheng, Xuhua; Luo, Yiyong; Chen, Xiao; Feng, Ming

    2017-04-01

    Enhanced mesoscale eddy activities or tropical instability waves (TIWs) exist along the northern front of the cold tongue in the eastern equatorial Pacific Ocean. In this study, we investigate seasonal variability of eddy kinetic energy (EKE) over this region and its associated dynamic mechanism using a global, eddy-resolving ocean general circulation model (OGCM) simulation, the equatorial mooring data, and satellite altimeter observations. The seasonal-varying enhanced EKE signals are found to expand westward from 100°W in June to 180°W in December between 0°N and 6°N. This westward expansion in EKE is closely connected to the barotropically-baroclinically unstable zonal flows that are in thermal-wind balance with the seasonal-varying thermocline trough along 4°N. By adopting an 1½-layer reduced-gravity model, we confirm that the seasonal perturbation of the thermocline trough is dominated by the anticyclonic wind stress curl forcing, which develops due to southerly winds along 4°N from June to December.

  11. Corporate philanthropy and conflicts of interest in public health: ExxonMobil, Equatorial Guinea, and malaria.

    Science.gov (United States)

    Shah, Naman K

    2013-01-01

    Equatorial Guinea, the most prosperous country in Africa, still bears a large malaria burden. With massive wealth from oil reserves, and nearly half its population living in island ecotypes favourable for malaria control, only poor governance can explain continued parasite burden. By financially backing the country's dictator and other officials through illicit payments, the oil company ExxonMobil contributed to the state's failure. Now ExxonMobil, having helped perpetuate malaria in Equatorial Guinea, gives money to non-governmental organizations, charitable foundations, and universities to advocate for and undertake malaria work. How, and on what terms, can public health engage with such an actor? We discuss challenges in the identification and management of conflicts of interest in public health activities. We reviewed the business and foundation activities of ExxonMobil and surveyed organizations that received ExxonMobil money about their conflict of interest policies. Reforms in ExxonMobil's business practices, as well as its charitable structure, and reforms in the way public health groups screen and manage conflicts of interest are needed to ensure that any relationship ultimately improves the health of citizens.

  12. Singapore Haze in June 2013: Consequences of Land-Use Change, Fires, and Anomalous Meteorology for Air Quality in Equatorial Asia

    Science.gov (United States)

    Koplitz, S.; Mickley, L. J.; Jacob, D. J.; Kim, P. S.; DeFries, R. S.; Marlier, M. E.; Schwartz, J.; Buonocore, J.; Myers, S. S.

    2014-12-01

    Much of Equatorial Asia is currently undergoing extensive burning from agricultural fires and rapid land-use conversion to oil palm plantations, with substantial consequences for air quality and health. In June 2013, Singapore experienced severe smoke levels, with surface particulate matter concentrations greater than ten times average. Unlike past haze events in Singapore (e.g. September 1997 and October 2006), the June 2013 pollution event occurred during El Nino-neutral conditions. Using a combination of observations and chemical transport modeling, we examine relationships between sea surface temperatures, wind fields, fire patterns, and aerosol optical depth during the June 2013 haze event. We find reasonable agreement between satellite measurements of aerosol optical depth (AOD) from the MODIS and MISR instruments and in-situ measurements from the AERONET stations across Equatorial Asia for 2005-2010 (MODIS R2 = 0.39, bias = -1.6%; MISR R2 = 0.27, bias = -42%). However, AOD observations fail to capture the Singapore pollution event of June 2013. Simulations with the GEOS-Chem model suggest that anomalously high dust concentrations during June 2013 may have impaired the ability of MODIS to monitor the haze over Singapore. In contrast, we show that the OMI Aerosol Index can effectively capture these smoke events and may be used to monitor future haze episodes in Equatorial Asia. We find that the June 2013 haze in Singapore may be attributed to anomalously strong westerlies carrying smoke from Riau Province in Indonesia. These westerlies, 5 m s-1 faster than the 2005-2010 mean June winds, are consistent with the phase of the Madden-Julian Oscillation (MJO) crossing the Maritime Continent at that time. These westerlies may have been further enhanced by a negative phase of the Indian Ocean Dipole (IOD), an east-west gradient in sea surface temperature anomalies across the Indian Ocean, with cold sea surface temperature anomalies (-3 C°) off the Arabian coast and

  13. Secure Service Oriented Architectures (SOA) Supporting NEC (Architecture orientee service (soa) gerant la NEC)

    Science.gov (United States)

    2009-01-01

    develop this demonstrator within a so short period of time without the availability of products from the commercial market and the open source...Binary Web Services [FastInfoset]. There seems to be no .NET implementation available. BiM . BiM [ BiM ] is based on the MPEG-7 standard and has been...designed and implemented by Siemens and Expway. This is a commercial product (although an evaluation version is available). BiM generally ANNEX A

  14. Bow Shock Generator Current Systems: MMS Observations of Possible Current Closure

    Science.gov (United States)

    Hamrin, M.; Gunell, H.; Lindkvist, J.; Lindqvist, P.-A.; Ergun, R. E.; Giles, B. L.

    2018-01-01

    We use data from the first two dayside seasons of the Magnetospheric Multiscale (MMS) mission to study current systems associated with quasi-perpendicular bow shocks of generator type. We have analyzed 154 MMS bow shock crossings near the equatorial plane. We compute the current density during the crossings and conclude that the component perpendicular to the shock normal (J⊥) is consistent with a pileup of the interplanetary magnetic field (IMF) inside the magnetosheath. For predominantly southward IMF, we observe a component Jn parallel (antiparallel) to the normal for GSM Y > 0 (MMS probing region. For IMF clock angles near 90∘, we find indications of the current system being tilted toward the north-south direction, obtaining a significant Jz component, and we suggest that the current closes off the equatorial plane at higher latitudes where the spacecraft are not probing. The observations are complicated for several reasons. For example, variations in the solar wind and the magnetospheric currents and loads affect the closure, and Jn is distributed over large regions, making it difficult to resolve inside the magnetosheath proper.

  15. The HIA instrument on board the Tan Ce 1 Double Star near-equatorial spacecraft and its first results

    Directory of Open Access Journals (Sweden)

    H. Rème

    2005-11-01

    Full Text Available On 29 December 2003, the Chinese spacecraft Tan Ce 1 (TC-1, the first component of the Double Star mission, was successfully launched within a low-latitude eccentric orbit. In the framework of the scientific cooperation between the Academy of Sciences of China and ESA, several European instruments, identical to those developed for the Cluster spacecraft, were installed on board this spacecraft. The HIA (Hot Ion Analyzer instrument on board the TC-1 spacecraft is an ion spectrometer nearly identical to the HIA sensor of the CIS instrument on board the 4 Cluster spacecraft. This instrument has been specially adapted for TC-1. It measures the 3-D distribution functions of the ions between 5 eV/q and 32 keV/q without mass discrimination. TC-1 is like a fifth Cluster spacecraft to study the interaction of the solar wind with the magnetosphere and to study geomagnetic storms and magnetospheric substorms in the near equatorial plane. HIA was commissioned in February 2004. Due to the 2 RE higher apogee than expected, some in-flight improvements were needed in order to use HIA in the solar wind in the initial phase of the mission. Since this period HIA has obtained very good measurements in the solar wind, the magnetosheath, the dayside and nightside plasma sheet, the ring current and the radiation belts. We present here the first results in the different regions of the magnetosphere and in the solar wind. Some of them are very new and include, for example, ion dispersion structures in the bow shock and ion beams close to the magnetopause. The huge interest in the orbit of TC-1 is strongly demonstrated.

  16. The HIA instrument on board the Tan Ce 1 Double Star near-equatorial spacecraft and its first results

    Directory of Open Access Journals (Sweden)

    H. Rème

    2005-11-01

    Full Text Available On 29 December 2003, the Chinese spacecraft Tan Ce 1 (TC-1, the first component of the Double Star mission, was successfully launched within a low-latitude eccentric orbit. In the framework of the scientific cooperation between the Academy of Sciences of China and ESA, several European instruments, identical to those developed for the Cluster spacecraft, were installed on board this spacecraft.

    The HIA (Hot Ion Analyzer instrument on board the TC-1 spacecraft is an ion spectrometer nearly identical to the HIA sensor of the CIS instrument on board the 4 Cluster spacecraft. This instrument has been specially adapted for TC-1. It measures the 3-D distribution functions of the ions between 5 eV/q and 32 keV/q without mass discrimination.

    TC-1 is like a fifth Cluster spacecraft to study the interaction of the solar wind with the magnetosphere and to study geomagnetic storms and magnetospheric substorms in the near equatorial plane.

    HIA was commissioned in February 2004. Due to the 2 RE higher apogee than expected, some in-flight improvements were needed in order to use HIA in the solar wind in the initial phase of the mission. Since this period HIA has obtained very good measurements in the solar wind, the magnetosheath, the dayside and nightside plasma sheet, the ring current and the radiation belts. We present here the first results in the different regions of the magnetosphere and in the solar wind. Some of them are very new and include, for example, ion dispersion structures in the bow shock and ion beams close to the magnetopause. The huge interest in the orbit of TC-1 is strongly demonstrated.

  17. Whale Shark (Rhincodon typus) Seasonal Occurrence, Abundance and Demographic Structure in the Mid-Equatorial Atlantic Ocean.

    Science.gov (United States)

    Macena, Bruno C L; Hazin, Fábio H V

    2016-01-01

    Whale sharks are generally associated with environmental factors that drive their movements to specific locations where food availability is high. Consequently, foraging is believed to be the main reason for the formation of whale shark aggregations. Feeding aggregations occur mainly in nearshore areas and are composed primarily of immature individuals. Conversely, aggregations of mature adults are rarely observed, and their occurrence is correlated with oceanic environments. Despite an increase in the number of whale shark studies, information on mating and parturition grounds is still lacking. In the present work, we assessed the ecological and behavioural aspects of the whale sharks that visit the archipelago of São Pedro and São Paulo (ASPSP), located ~1,000 km off the coast of Brazil in the equatorial Atlantic Ocean. Forty-nine whale sharks were recorded from February 2005 to May 2014. The estimated mean ± SD size was 8.27 ± 2.52 m (range: 2.5-14.0 m) with no significant differences in size across the year. The maturational stages were classified by size as immature (9.0 m; 46.51%); with almost half of the observed animals being mature specimens. The majority of sightings occurred between February and June. During this period, the ocean current weakens and the waters are enriched by eggs and larvae of fishes and invertebrates that attract marine life to forage. At the same time, evidence of reproductive activity in adult females (i.e. swollen abdomen and bite marks on the pectoral fins), and the potential mating behaviour exhibited by one male, suggest that the ASPSP area might also have a role in whale shark reproduction. Irrespective of its use for feeding or reproduction, this insular habitat serves as a meeting point for both juvenile and adult whale sharks, and may play an important ecological role for the species.

  18. [Initial evaluation of a programme to prevent mother-to-child transmission of human immunodeficiency virus infection in Equatorial Guinea].

    Science.gov (United States)

    Badillo-Navarro, Katie; Prieto-Tato, Luis; Obiang-Esomoyo, Jacinta; Avedillo-Jiménez, Pedro; Vargas-Brizuela, Antonio; Rojo-Conejo, Pablo

    2014-01-01

    The prevalence of human immunodeficiency virus (HIV)-infected pregnant women in Equatorial Guinea (EG) has been reported as 7.3%. In 2008 an updated version of the PMTCT protocol was accepted according to the current WHO guidelines. The aim of this study was to describe the characteristics and outcome of children exposed to HIV after the introduction of the protocol. A retrospective review was conducted on the clinical characteristics of the infants born to HIV-infected mothers in the Hospital Regional de Bata and Primary Health Care Centre Maria Rafols in Bata (EG) between June 2008 and November 2011. The diagnosis of HIV infection in children was based on rapid serology tests. A total of 103 children were included, of which 47 were males. Fifty three patients (51%) completed the follow-up (51%). Fourteen children (26%) were diagnosed with HIV infection (11 presumptive diagnosis, 3 due to persistence of antibodies at 18 months). Six children (12%) died before a definitive diagnosis. Just over than half (52%) of mothers received antiretroviral therapy (ART) during pregnancy. The transmission rate in children whose mothers received ART was 16% (3/19), compared with 43% (10/23) in children whose mothers did not receive it. Only one child was infected (8%) when the mother received ART, and child received postnatal prophylaxis. The PMTCT protocol compliance was still very low. Antiretroviral therapy in pregnant women decreased the rate of vertical transmission, but the rate still remains very high. Many children were lost to follow-up. Strategies to prevent loss to follow-up and methods for earlier virological diagnostic are needed. Copyright © 2012 Elsevier España, S.L. All rights reserved.

  19. Provenance and supply of Fe-enriched terrigenous sediments in the western equatorial Pacific and their relation to precipitation variations during the late Quaternary

    NARCIS (Netherlands)

    Wu, J.W.; Liu, Z.; Zhou, nn.

    2013-01-01

    Iron (Fe) deposition in the equatorial Pacific has important implications for the global carbon cycle, while the provenance of Fe supply and its change remain highly debated. Here, we geochemically characterize the provenance of terrigenous sediments deposited on the pathways of the Equatorial

  20. Optimal conditions for high current proton irradiations at the university of Wisconsin's ion beam laboratory

    International Nuclear Information System (INIS)

    Wetteland, C. J.; Field, K. G.; Gerczak, T. J.; Eiden, T. J.; Maier, B. R.; Albakri, O.; Sridharan, K.; Allen, T. R.

    2013-01-01

    The National Electrostatics Corporation's (NEC) Toroidal Volume Ion Source (TORVIS) source is known for exceptionally high proton currents with minimal service downtime as compared to traditional sputter sources. It has been possible to obtain over 150μA of proton current from the source, with over 70μA on the target stage. However, beam fluxes above ∼1×10 17 /m2-s may have many undesirable effects, especially for insulators. This may include high temperature gradients at the surface, sputtering, surface discharge, cracking or even disintegration of the sample. A series of experiments were conducted to examine the role of high current fluxes in a suite of ceramics and insulating materials. Results will show the optimal proton irradiation conditions and target mounting strategies needed to minimize unwanted macro-scale damage, while developing a procedure for conducting preliminary radiation experiments.

  1. Jet formation and equatorial superrotation in Jupiter's atmosphere: Numerical modelling using a new efficient parallel code

    Science.gov (United States)

    Rivier, Leonard Gilles

    Using an efficient parallel code solving the primitive equations of atmospheric dynamics, the jet structure of a Jupiter like atmosphere is modeled. In the first part of this thesis, a parallel spectral code solving both the shallow water equations and the multi-level primitive equations of atmospheric dynamics is built. The implementation of this code called BOB is done so that it runs effectively on an inexpensive cluster of workstations. A one dimensional decomposition and transposition method insuring load balancing among processes is used. The Legendre transform is cache-blocked. A "compute on the fly" of the Legendre polynomials used in the spectral method produces a lower memory footprint and enables high resolution runs on relatively small memory machines. Performance studies are done using a cluster of workstations located at the National Center for Atmospheric Research (NCAR). BOB performances are compared to the parallel benchmark code PSTSWM and the dynamical core of NCAR's CCM3.6.6. In both cases, the comparison favors BOB. In the second part of this thesis, the primitive equation version of the code described in part I is used to study the formation of organized zonal jets and equatorial superrotation in a planetary atmosphere where the parameters are chosen to best model the upper atmosphere of Jupiter. Two levels are used in the vertical and only large scale forcing is present. The model is forced towards a baroclinically unstable flow, so that eddies are generated by baroclinic instability. We consider several types of forcing, acting on either the temperature or the momentum field. We show that only under very specific parametric conditions, zonally elongated structures form and persist resembling the jet structure observed near the cloud level top (1 bar) on Jupiter. We also study the effect of an equatorial heat source, meant to be a crude representation of the effect of the deep convective planetary interior onto the outer atmospheric layer. We

  2. Structure and variances of equatorial zonal circulation in a multimodel ensemble

    Energy Technology Data Exchange (ETDEWEB)

    Yu, B. [Environment Canada, Climate Data and Analysis Section, Climate Research Division, Toronto, ON (Canada); Zwiers, F.W. [University of Victoria, Pacific Climate Impacts Consortium, Victoria, BC (Canada); Boer, G.J. [Environment Canada, Canadian Centre for Climate Modeling and Analysis, Climate Research Division, Victoria, BC (Canada); Ting, M.F. [Columbia University, Lamont-Doherty Earth Observatory, Palisades, NY (United States)

    2012-11-15

    The structure and variance of the equatorial zonal circulation, as characterized by the atmospheric mass flux in the equatorial zonal plane, is examined and inter-compared in simulations from 9 CMIP3 coupled climate models with multiple ensemble members and the NCEP-NCAR and ERA-40 reanalyses. The climate model simulations analyzed here include twentieth century (20C3M) and twenty-first century (SRES A1B) simulations. We evaluate the 20C3M modeled zonal circulations by comparing them with those in the reanalyses. We then examine the variability of the circulation, its changes with global warming, and the associated thermodynamic maintenance. The tropical zonal circulation involves three major components situated over the Pacific, Indian, and Atlantic oceans. The three cells are supported by the corresponding diabatic heating extending deeply throughout the troposphere, with heating centers apparent in the mid-troposphere. Seasonal features appear in the zonal circulation, including variations in its intensity and longitudinal migration. Most models, and hence the multi-model mean, represent the annual and seasonal features of the circulation and the associated heating reasonably well. The multi-model mean reproduces the observed climatology better than any individual model, as indicated by the spatial pattern correlation and mean square difference of the mass flux and the diabatic heating compared to the reanalysis based values. Projected changes in the zonal circulation under A1B forcing are dominated by mass flux changes over the Pacific and Indian oceans. An eastward shift of the Pacific Walker circulation is clearly evident with global warming, with anomalous rising motion apparent over the equatorial central Pacific and anomalous sinking motions in the west and east, which favors an overall strengthening of the Walker circulation. The zonal circulation weakens and shifts westwards over the Indian Ocean under external forcing, whereas it strengthens and shifts

  3. Antifouling effect of hydrogen peroxide release from enzymatic marine coatings: Exposure testing under equatorial and Mediterranean conditions

    DEFF Research Database (Denmark)

    Olsen, S.M.; Kristensen, J.B.; Laursen, B.S.

    2010-01-01

    Mediterranean and equatorial climatic conditions, is investigated. During seawater exposure of the coatings, starch is first converted to glucose by glucoamylase (rate-controlling step) and subsequently glucose is rapidly oxidised by hexose oxidase in a reaction producing hydrogen peroxide. The coatings...

  4. A New 50 MHz Phased-Array Radar on Pohnpei: A Fresh Perspective on Equatorial Plasma Bubbles

    Science.gov (United States)

    Tsunoda, R. T.

    2014-12-01

    A new, phased-array antenna-steering capability has recently been added to an existing 50-MHz radar on Pohnpei, Federated States of Micronesia, in the central Pacific region. This radar, which we refer to as PAR-50, is capable of scanning in the vertical east-west plane, ±60° about the zenith. The alignment in the magnetic east-west direction allows detection of radar backscatter from small-scale irregularities that develop in the equatorial ionosphere, including those associated with equatorial plasma bubbles (EPBs). The coverage, about ±800 km in zonal distance, at an altitude of 500 km, is essentially identical to that provided by ALTAIR, a fully-steerable incoherent-scatter radar, which has been used in a number of studies of EPBs. Unlike ALTAIR, which has only been operated for several hours on a handful of selected nights, the PAR-50 has already been operated continuously, while performing repeated scans, since April 2014. In this presentation, we describe the PAR-50, then, compare it to ALTAIR and the Equatorial Atmospheric Radar (EAR); the latter is the only other phased-array system in use for equatorial studies. We then assess what we have learned about EPBs from backscatter radar measurements, and discuss how the PAR-50 can provide a fresh perspective to our understanding. Clearly, the ability to sort out the space-time ambiguities in EPB development from sequences of spatial maps of EPBs is crucial to our understanding of how EPBs develop.

  5. Millennial-scale iron fertilization of the eastern equatorial Pacific over the past 100,000 years

    Science.gov (United States)

    Loveley, Matthew R.; Marcantonio, Franco; Wisler, Marilyn M.; Hertzberg, Jennifer E.; Schmidt, Matthew W.; Lyle, Mitchell

    2017-10-01

    The eastern equatorial Pacific Ocean plays a crucial role in global climate, as it is a substantial source of CO2 to the atmosphere and accounts for a significant portion of global new export productivity. Here we present a 100,000-year sediment core from the eastern equatorial Pacific, and reconstruct dust flux, export productivity and bottom-water oxygenation using excess-230Th-derived fluxes of 232Th and barium, and authigenic uranium concentrations, respectively. We find that during the last glacial period (71,000 to 41,000 years ago), increased delivery of dust to the eastern equatorial Pacific was coeval with North Atlantic Heinrich stadial events. Millennial-scale pulses of increased dust flux coincided with episodes of heightened biological productivity, suggesting that dissolution of dust released iron that promoted ocean fertilization. We also find that periods of low atmospheric CO2 concentrations were associated with suboxic conditions and increased storage of respired carbon in the deep eastern equatorial Pacific. Increases in CO2 concentrations during the deglaciation are coincident with increases in deep Pacific and Southern Ocean water oxygenation levels. We suggest that deep-ocean ventilation was a primary control on CO2 outgassing in this region, with superimposed pulses of high productivity providing a negative feedback.

  6. Equatorial E Region Electric Fields and Sporadic E Layer Responses to the Recovery Phase of the November 2004 Geomagnetic Storm

    Science.gov (United States)

    Moro, J.; Resende, L. C. A.; Denardini, C. M.; Xu, J.; Batista, I. S.; Andrioli, V. F.; Carrasco, A. J.; Batista, P. P.; Schuch, N. J.

    2017-12-01

    Equatorial E region electric fields (EEFs) inferred from coherent radar data, sporadic-E (Es) layers observed from a digital ionosonde data, and modeling results are used to study the responses of the equatorial E region over São Luís (SLZ, 2.3°S, 44.2°W, -7° dip angle), Brazil, during the super storm of November 2004. The EEF is presented in terms of the zonal (Ey) and vertical (Ez) components in order to analyze the corresponding characteristics of different types of Es seen in ionograms and simulated with the E region ionospheric model. We bring out the variabilities of Ey and Ez components with storm time changes in the equatorial E region. In addition, some aspects of the electric fields and Es behavior in three cases of weak, very weak, and strong Type II occurrences during the recovery phase of the geomagnetic storm are discussed. The connection between the enhanced occurrence and suppressions of the Type II irregularities and the q-type Es (Esq) controlled by electric fields, with the development or disruption of the blanketing sporadic E (Esb) layers produced by wind shear mechanism, is also presented. The mutual presence of Esq along with the Esb occurrences is a clear indicator of the secular drift of the magnetic equator and hence that of the equatorial electrojet (EEJ) over SLZ. The results show evidence about the EEJ and Es layer electrodynamics and coupling during geomagnetic disturbance time electric fields.

  7. Platinum group elements and gold in ferromanganese crusts from Afanasiy-Nikitin seamount, equatorial Indian Ocean: Sources and fractionation

    Digital Repository Service at National Institute of Oceanography (India)

    Banakar, V.K.; Hein, J.R.; Rajani, R.P.; Chodankar, A.R.

    The major element relationships in ferromanganese (Fe–Mn) crusts from Afanasiy–Nikitin seamount (ANS), eastern equatorial Indian Ocean, appear to be atypical. High positive correlations (r = 0.99) between Mn/Co and Fe/Co ratios, and lack...

  8. Effect of magnetic activity on plasma bubbles over equatorial and low-latitude regions in East Asia

    Directory of Open Access Journals (Sweden)

    G. Li

    2009-01-01

    Full Text Available The dependence of plasma bubble occurrence in the eveningside ionosphere, with magnetic activity during the period years 2001–2004, is studied here based on the TEC observations gathered by ground-based GPS receivers which are located in the equatorial and low-latitude regions in East Asia. The observed plasma bubbles consist of the plasma-bubble events in the equatorial (stations GUAM, PIMO and KAYT, and low-latitude regions (stations WUHN, DAEJ and SHAO. It is shown that most equatorial plasma-bubble events commence at 20:00 LT, and may last for >60 min. The magnetic activity appears to suppress the generation of equatorial plasma bubbles with a time delay of more than 3 h (4–9 h. While in the low-latitude regions, most plasma-bubble events commence at about 23:00 LT and last for <45 min. The best correlation between Kp and low-latitude plasma-bubble occurrence is found with an 8–9 h delay, a weak correlation exists for time delays of 6–7 h. This probably indicates that over 3 h delayed disturbance dynamo electric fields obviously inhibit the development of plasma bubbles in the pre-midnight sector.

  9. THE ATMOSPHERIC CYCLING AND AIR-SEA EXCHANGE OF MERCURY SPECIES IN THE SOUTH AND EQUATORIAL ATLANTIC OCEAN. (R829796)

    Science.gov (United States)

    Measurements of gas-, particle- and precipitation-phases of atmospheric mercury(Hg) were made in the South and equatorial Atlantic Ocean as part of the 1996IOC Trace Metal Baseline Study (Montevideo, Uruguay to Barbados). Total gaseousmercury (TGM) ranged from ...

  10. Protein involvement in the fusion between the equatorial segment of acrosome-reacted human spermatozoa and liposomes

    NARCIS (Netherlands)

    Arts, EGJM; Wijchman, JG; Jager, S; Hoekstra, D

    1997-01-01

    Artificial membranes (liposomes) can interact with the equatorial segment (ES) of human spermatozoa, provided that the acrosome reaction (AR) has occurred [Arts, Kuiken, Jager and Hoekstra (1993) fur. J. Biochem. 217, 1001-1009]. Using fluorescently labelled liposomes, this interaction can be seen

  11. Ecological dispersal barrier across the equatorial Atlantic in a migratory planktonic copepod

    Science.gov (United States)

    Goetze, Erica; Hüdepohl, Patricia T.; Chang, Chantel; Van Woudenberg, Lauren; Iacchei, Matthew; Peijnenburg, Katja T. C. A.

    2017-11-01

    Resolving the large-scale genetic structure of plankton populations is important to understanding their responses to climate change. However, few studies have reported on the presence and geographic extent of genetically distinct populations of marine zooplankton at ocean-basin scales. Using mitochondrial sequence data (mtCOI, 718 animals) from 18 sites across a basin-scale Atlantic transect (39°N-40°S), we show that populations of the dominant migratory copepod, Pleuromamma xiphias, are genetically subdivided across subtropical and tropical waters (global FST = 0.15, global ΦST = 0.21, both P marine plankton, and we suggest that this may be a dominant mechanism driving the large-scale genetic structure of zooplankton species. Our results also demonstrate the potential importance of the Atlantic equatorial province as a region of evolutionary novelty for the holoplankton.

  12. An asymptotically consistent approximant for the equatorial bending angle of light due to Kerr black holes

    Science.gov (United States)

    Barlow, Nathaniel S.; Weinstein, Steven J.; Faber, Joshua A.

    2017-07-01

    An accurate closed-form expression is provided to predict the bending angle of light as a function of impact parameter for equatorial orbits around Kerr black holes of arbitrary spin. This expression is constructed by assuring that the weak- and strong-deflection limits are explicitly satisfied while maintaining accuracy at intermediate values of impact parameter via the method of asymptotic approximants (Barlow et al 2017 Q. J. Mech. Appl. Math. 70 21-48). To this end, the strong deflection limit for a prograde orbit around an extremal black hole is examined, and the full non-vanishing asymptotic behavior is determined. The derived approximant may be an attractive alternative to computationally expensive elliptical integrals used in black hole simulations.

  13. An asymptotically consistent approximant for the equatorial bending angle of light due to Kerr black holes

    International Nuclear Information System (INIS)

    Barlow, Nathaniel S; Faber, Joshua A; Weinstein, Steven J

    2017-01-01

    An accurate closed-form expression is provided to predict the bending angle of light as a function of impact parameter for equatorial orbits around Kerr black holes of arbitrary spin. This expression is constructed by assuring that the weak- and strong-deflection limits are explicitly satisfied while maintaining accuracy at intermediate values of impact parameter via the method of asymptotic approximants (Barlow et al 2017 Q. J. Mech. Appl. Math . 70 21–48). To this end, the strong deflection limit for a prograde orbit around an extremal black hole is examined, and the full non-vanishing asymptotic behavior is determined. The derived approximant may be an attractive alternative to computationally expensive elliptical integrals used in black hole simulations. (paper)

  14. Publisher Correction: Recycled iron fuels new production in the eastern equatorial Pacific Ocean.

    Science.gov (United States)

    Rafter, Patrick A; Sigman, Daniel M; Mackey, Katherine R M

    2017-12-05

    The original version of this Article contained errors in Fig. 2b and Table 2. In Fig. 2b, the white circle labels were incorrectly positioned as they referred to scenarios that were used in an earlier version of the Article. In Table 2, the following three sentences were removed from the legend 'The last two calculations are discussed in the "Methods". The first assumes that all dissolved plus the ≈0.3 nmol kg -1 of particulate iron (measured in the eastern equatorial Pacific 30 ) is bioavailable. The last calculation assumes EUC dissolved iron concentrations from 140° W'. These errors have now been corrected in both the PDF and HTML versions of the Article.

  15. Atla Regio, Venus: Geology and origin of a major equatorial volcanic rise

    Science.gov (United States)

    Senske, D. A.; Head, James W., III

    1992-01-01

    Regional volcanic rises form a major part of the highlands in the equatorial region of Venus. These broad domical uplands, 1000 to 3000 km across, contain centers of volcanism forming large edifices and are associated with extension and rifting. Two classes of rises are observed: (1) those that are dominated by tectonism, acting as major centers for converging rifts such as Beta Regio and Alta Regio, and are termed tectonic junctions; and (2) those forming uplands characterized primarily by large-scale volcanism forming edifices. Western Eistla Regio and Bell Regio, where zones of extension and rifting are less developed. Within this second class of features the edifices are typically found at the end of a single rift, or are associated with a linear belt of deformation. We examine the geologic characteristics of the tectonic junction at Alta Regio, concentrating on documenting the styles of volcanism and assessing mechanisms for the formation of regional topography.

  16. The optical properties of equatorial cirrus in the pilot radiation observation experiment

    Energy Technology Data Exchange (ETDEWEB)

    Platt, C.M.R.; Young, S.A.; Manson, P.; Patterson, G.R. [CSIRO, Victoria (Australia)] [and others

    1996-04-01

    The development of a sensitive filter radiometer for the Atmospheric Radiation Measurement (ARM) Program has been reported. The aim was to develop a reliable and fast instrument that could be used alongside a lidar to obtain near realtime optical properties of clouds, particularly high ice clouds, as they drifted over an ARM Cloud and Radiation Testbed (CART) site allowing calculation of the radiation divergence in the atmosphere over the site. Obtaining cloud optical properties by the lidar/radiometer, or LIRAD, method was described by Platt et al.; the latter paper also describes a year`s data on mid-latitude cirrus. The optical properties of equatorial cirrus (i.e., cirrus within a few degrees of the equator) have hardly been studied at all. The same is true of tropical cirrus, although a few observations have been reported by Davis and Platt et al.This paper describes obersvations performed on cirrus clouds, analysis methods used, and results.

  17. Equatorial electrodynamics and neutral background in the Asian sector during the 2009 stratospheric sudden warming

    DEFF Research Database (Denmark)

    Liu, Huixin; Yamamoto, Mamoru; Ram, S. Tulasi

    2011-01-01

    Using ground observations of total electron content (TEC) and equatorial electrojet (EEJ) in the Asian sector, along with plasma and neutral densities obtained from the CHAMP satellite, we investigate the ionospheric electrodynamics and neutral background in this longitude sector during the major...... perturbation possesses a significant hemispheric asymmetry in terms of onset date and magnitude. It starts on the same day as the SSW peak in the Northern Hemisphere but 2 days later in the Southern Hemisphere. Its magnitude is twice as strong in the north than in the south. Third, strong counter electrojet...... occurs in the afternoon, following the strengthening of the eastward EEJ in the morning. Fourth, semidiurnal perturbation in both TEC and EEJ possesses a phase shift, at a rate of about 0.7 h/day. Comparisons with results reported in the Peruvian sector reveal clear longitude dependence in the amplitude...

  18. Rayleigh-Taylor and wind-driven instabilities of the nighttime equatorial ionosphere

    International Nuclear Information System (INIS)

    Chiu, Y.T.; Straus, J.M.

    1979-01-01

    We have made a thorough re-examination of the Rayleigh-Taylor instability in the nighttime equatorial ionosphere from approx.100 km to the bottomside F region. We have taken into account explicitly the following effects which have been ignored by other workers in various combinations: (1) The eastward drift of the ionosphere caused by the nighttime polarization electric field, (2) the eastward nighttime neutral wind, and (3) recombination in the F and E regions. We found that, well below the bottomside F region, the Rayleigh-Taylor mode can be unstable and is driven by an eastward neutral wind rather than by gravitational drift. Formation of ionospheric bubbles below the bottomside F region is consistent with the observation of lower ionospheric ions in F region ionospheric holes; furthermore, seasonal and shorter term variations in spread-F occurrence may be associated with variations in the neutral wind and polarization electric field

  19. Initial investigations of microscale cellular convection in an equatorial marine atmospheric boundary layer revealed by lidar

    Science.gov (United States)

    Cooper, D. I.; Eichinger, W. E.; Ecke, R. E.; Kao, J. C. Y.; Reisner, J. M.; Tellier, L. L.

    During the Combined Sensor Program (CSP) in March of 1996, the Los Alamos National Laboratory (LANL) fielded an advanced scanning Raman lidar. The lidar was part of a larger suite of micrometeorological sensors to quantify processes associated with the ocean-atmosphere interface, including intermittency and coherent atmospheric features in the “warm pool” of the Tropical Western Pacific (TWP) near Manus Island (2° S. lat, 147° E. long). Initial inspection of the data has revealed excellent information on the microscale vertical and horizontal spatial and temporal structure of the equatorial Marine Atmospheric Boundary Layer (MABL). The data from this experiment have added to the increasing body of measurements on surface layer convection and intermittency including, for the first time, the observation of microscale cellular convective structures such as hexagonal patterns associated with Rayleigh-Bénard cells.

  20. VHF and UHF radar observations of equatorial F region ionospheric irregularities and background densities

    Science.gov (United States)

    Towle, D. M.

    1980-02-01

    A series of measurements of the properties of equatorial ionospheric irregularities were made at Kwajalein, Marshall Islands (M.I.) in August 1977 and July-August 1978. These measurements, sponsored by the Defense Nuclear Agency (DNA), involved coordinated ground-based and in situ sensors. The ARPA Long-Range Tracking and Instrumentation Radar (ALTAIR), operated by Lincoln Laboratory, obtained backscatter and transmission data during five nights in August 1977 and eight nights in July-August 1978. This report describes the ALTAIR data from the night of August 11, 1978, which yield direct quantitative measurements of 1-m and 3/8-m irregularities and of plasma depleted regions. These plasma depleted regions, previously predicted on the basis of theoretical analysis and in situ data, were observed during the decay phase and not the generative phase of the field-aligned irregularities.

  1. First record of Naushonia sp. (Decapoda: Laomediidae) larva from the Equatorial Atlantic.

    Science.gov (United States)

    De Albuquerque Lira, Simone Maria; De Santana, Claudeilton Severino; Schwamborn, Ralf

    2018-02-26

    The first zoeal-stage larva of a possibly new species of mud shrimp Naushonia (Decapoda: Gebiidea: Laomediidae) was described from plankton samples taken off the Fernando de Noronha Archipelago, being the first occurrence at the oceanic islands of the Equatorial Atlantic. Five zoea I larvae were obtained and dissected for observation of mouthparts. This zoea I of Naushonia sp. is well distinguished from the first larvae of N. portoricensis (Rathbun 1901) from the Caribbean and N. cangronoides (Kingsley 1897) from the Northwest Atlantic in terms of development and setation of appendages, and possibly belongs to a new, undescribed species. The present study widens the knowledge on tropical oceanic decapod larvae and provides detailed drawings and new photographic illustrations with extended depth of field of these organisms.

  2. Magnetization modeling in the north and equatorial Atlantic Ocean using MAGSAT data

    Science.gov (United States)

    Hayling, K. L.; Harrison, C. G. A.

    1986-01-01

    Magsat 2 x 2-deg scalar anomalous-magnetic-field data (Langel et al., 1982) for the northern and equatorial Atlantic are inverted and combined with physiographic data and laboratory results on the magnetization of oceanic rocks and the oceanic crust to construct models explaining the shorter-wavelength component of the anomalies. An annihilator is applied to the inversion results to eliminate reverse-magnetized sources and facilitate comparisons of areas inverted separately, and a latitude effect on source spacing is tentatively attributed to greater noise contamination at lower latitudes. It is found that remanent magnetization combined with considerable crustal thickening can best explain the high intensity levels observed, although viscous magnetization or contamination of the data by noncrustal sources must also be considered.

  3. Monitoring Mars LOD Variations from a High Altitude Circular Equatorial Orbit: Theory and Simulation

    Science.gov (United States)

    Barriot, J.; Dehant, V.; Duron, J.

    2003-12-01

    We compute the perturbations of a high altitude circular equatorial orbit of a martian probe under the influence of an annual variation of the martian lenght of day. For this purpose, we use the first order perturbations of the newtonian equations of motion, where the small parameter is given from the hourglass model of Chao and Rubincam, which allow a simple computation of CO2 exchanges during the martian year. We are able to demonstrate that the perturbations contains two components: the first one is a sine/cosine modulation at the orbit frequency, the second one is composed of terms of the form exp(t)*sin(t), so the orbit may not stable in the long term (several martian years), with perturbations growing exponentially. We give the full theory and numbers.

  4. Balligratus, new genus of wingless ground beetles from equatorial Andean montane forest (Coleoptera: Carabidae: Lachnophorini).

    Science.gov (United States)

    Moret, Pierre; Ortuño, Vicente M

    2017-04-27

    A new carabid beetle genus, Balligratus gen. nov., belonging to the tribe Lachnophorini, is described. It is geographically restricted to the equatorial Andes, and ecologically linked to the montane pluvial forest ecosystem, at elevations ranging from 1,200 to 3,600 m. As other carabid lineages that have radiated in such environments, Balligratus gen. nov. is a wingless clade, characterized by the loss of flight wings associated with metathoracic reduction, constriction of the elytral base, and reduced eye size. This evolution is unique among Lachnophorini. Four new species are described, all of them from Ecuador: Balligratus brevis sp. nov., Balligratus globosus sp. nov., Balligratus gracilis sp. nov. and Balligratus humerangulus sp. nov.

  5. Testing models for the formation of the equatorial ridge on Iapetus via crater counting

    Science.gov (United States)

    Damptz, Amanda L.; Dombard, Andrew J.; Kirchoff, Michelle R.

    2018-03-01

    Iapetus's equatorial ridge, visible in global views of the moon, is unique in the Solar System. The formation of this feature is likely attributed to a key event in the evolution of Iapetus, and various models have been proposed as the source of the ridge. By surveying imagery from the Cassini and Voyager missions, this study aims to compile a database of the impact crater population on and around Iapetus's equatorial ridge, assess the relative age of the ridge from differences in cratering between on ridge and off ridge, and test the various models of ridge formation. This work presents a database that contains 7748 craters ranging from 0.83 km to 591 km in diameter. The database includes the study area in which the crater is located, the latitude and longitude of the crater, the major and minor axis lengths, and the azimuthal angle of orientation of the major axis. Analysis of crater orientation over the entire study area reveals that there is no preference for long-axis orientation, particularly in the area with the highest resolution. Comparison of the crater size-frequency distributions show that the crater distribution on the ridge appears to be depleted in craters larger than 16 km with an abruptly enhanced crater population less than 16 km in diameter up to saturation. One possible interpretation is that the ridge is a relatively younger surface with an enhanced small impactor population. Finally, the compiled results are used to examine each ridge formation hypothesis. Based on these results, a model of ridge formation via a tidally disrupted sub-satellite appears most consistent with our interpretation of a younger ridge with an enhanced small impactor population.

  6. Features of highly structured equatorial plasma irregularities deduced from CHAMP observations

    Directory of Open Access Journals (Sweden)

    C. Xiong

    2012-08-01

    Full Text Available In this study five years of CHAMP (Challenging Mini-satellite Payload fluxgate magnetometer (FGM data is used to investigate the characteristics of Equatorial Plasma Bubbles (EPBs. We filtered the FGM data by using band-passes with four different cut-off periods to get the EPBs with different maximum spatial scale sizes in the meridional plane ranging from 76–608 km. Associated with the EPB observations at about 400 km, the typical altitude of CHAMP during the year 2000–2005, we also investigate the post-sunset equatorial vertical plasma drift data from ROCSAT-1 (Republic of China Satellite 1. Since the height of the F-layer is highly correlated with the vertical plasma drift and solar flux, we sorted the ROCSAT-1 data into different groups by F10.7. From the integrated vertical drift we have estimated the post-sunset uplift of the ionosphere. By comparing the properties of EPB occurrence for different scale sizes with the global distribution of plasma vertical uplift, we have found that EPBs reaching higher altitudes are more structured than those which are sampled by CHAMP near the top side of the depleted fluxtube. Such a result is in accord with 3-D model simulations (Aveiro and Hysell, 2010. Small-scale EPB structures are observed by CHAMP when the irregularities reach apex heights of 800 km and more. Such events are encountered primarily in the Brazilian sector during the months around November, when the post-sunset vertical plasma drift is high.

  7. Features of highly structured equatorial plasma irregularities deduced from CHAMP observations

    Science.gov (United States)

    Xiong, C.; Lühr, H.; Ma, S. Y.; Stolle, C.; Fejer, B. G.

    2012-08-01

    In this study five years of CHAMP (Challenging Mini-satellite Payload) fluxgate magnetometer (FGM) data is used to investigate the characteristics of Equatorial Plasma Bubbles (EPBs). We filtered the FGM data by using band-passes with four different cut-off periods to get the EPBs with different maximum spatial scale sizes in the meridional plane ranging from 76-608 km. Associated with the EPB observations at about 400 km, the typical altitude of CHAMP during the year 2000-2005, we also investigate the post-sunset equatorial vertical plasma drift data from ROCSAT-1 (Republic of China Satellite 1). Since the height of the F-layer is highly correlated with the vertical plasma drift and solar flux, we sorted the ROCSAT-1 data into different groups by F10.7. From the integrated vertical drift we have estimated the post-sunset uplift of the ionosphere. By comparing the properties of EPB occurrence for different scale sizes with the global distribution of plasma vertical uplift, we have found that EPBs reaching higher altitudes are more structured than those which are sampled by CHAMP near the top side of the depleted fluxtube. Such a result is in accord with 3-D model simulations (Aveiro and Hysell, 2010). Small-scale EPB structures are observed by CHAMP when the irregularities reach apex heights of 800 km and more. Such events are encountered primarily in the Brazilian sector during the months around November, when the post-sunset vertical plasma drift is high.

  8. Tropospheric ozone over Equatorial Africa: regional aspects from the MOZAIC data

    Directory of Open Access Journals (Sweden)

    B. Sauvage

    2005-01-01

    Full Text Available We analyze ozone observations recorded over Equatorial Africa between April 1997 and March 2003 by the MOZAIC programme, providing the first ozone climatology deriving from continental in-situ data over this region. Three-dimensional streamlines strongly suggests connections between the characteristics of the ozone monthly mean vertical profiles, the most persistent circulation patterns in the troposphere over Equatorial Africa (on a monthly basis such as the Harmattan, the African Easterly Jet, the Trades and the regions of ozone precursors emissions by biomass burning. During the biomass burning season in each hemisphere, the lower troposphere exhibits layers of enhanced ozone (i.e. 70 ppbv over the coast of Gulf of Guinea in December-February and 85 ppbv over Congo in June-August. The characteristics of the ozone monthly mean vertical profiles are clearly connected to the regional flow regime determined by seasonal dynamic forcing. The mean ozone profile over the coast of Gulf of Guinea in the burning season is characterized by systematically high ozone below 650hPa ; these are due to the transport by the Harmattan and the AEJ of the pollutants originating from upwind fires. The confinement of high ozone to the lower troposphere is due to the high stability of the Harmattan and the blocking Saharan anticyclone which prevents efficient vertical mixing. In contrast, ozone enhancements observed over Central Africa during the local dry season (June-August are not only found in the lower troposphere but throughout the troposphere. Moreover, this study highlights a connection between the regions of the coast of Gulf of Guinea and regions of Congo to the south that appears on a semi annual basis. Vertical profiles in wet-season regions exhibit ozone enhancements in the lower troposphere due to biomass burning products transport from fires situated in the opposite dry-season hemisphere.

  9. Equatorial origin for Lower Jurassic radiolarian chert in the Franciscan Complex, San Rafael Mountains, southern California

    Science.gov (United States)

    Hagstrum, J.T.; Murchey, B.L.; Bogar, R.S.

    1996-01-01

    Lower Jurassic radiolarian chert sampled at two localities in the San Rafael Mountains of southern California (???20 km north of Santa Barbara) contains four components of remanent magnetization. Components A, B???, and B are inferred to represent uplift, Miocene volcanism, and subduction/accretion overprint magnetizations, respectively. The fourth component (C), isolated between 580?? and 680??C, shows a magnetic polarity stratigraphy and is interpreted as a primary magnetization acquired by the chert during, or soon after, deposition. Both sequences are late Pliensbachian to middle Toarcian in age, and an average paleolatitude calculated from all tilt-corrected C components is 1?? ?? 3?? north or south. This result is consistent with deposition of the cherts beneath the equatorial zone of high biologic productivity and is similar to initial paleolatitudes determined for chert blocks in northern California and Mexico. This result supports our model in which deep-water Franciscan-type cherts were deposited on the Farallon plate as it moved eastward beneath the equatorial productivity high, were accreted to the continental margin at low paleolatitudes, and were subsequently distributed northward by strike-slip faulting associated with movements of the Kula, Farallon, and Pacific plates. Upper Cretaceous turbidites of the Cachuma Formation were sampled at Agua Caliente Canyon to determine a constraining paleolatitude for accretion of the Jurassic chert sequences. These apparently unaltered rocks, however, were found to be completely overprinted by the A component of magnetization. Similar in situ directions and demagnetization behaviors observed in samples of other Upper Cretaceous turbidite sequences in southern and Baja California imply that these rocks might also give unreliable results.

  10. Properties of the Equatorial Magnetotail Flanks ˜50-200 RE Downtail

    Science.gov (United States)

    Artemyev, A. V.; Angelopoulos, V.; Runov, A.; Wang, C.-P.; Zelenyi, L. M.

    2017-12-01

    In space, thin boundaries separating plasmas with different properties serve as a free energy source for various plasma instabilities and determine the global dynamics of large-scale systems. In planetary magnetopauses and shock waves, classical examples of such boundaries, the magnetic field makes a significant contribution to the pressure balance and plasma dynamics. The configuration and properties of such boundaries have been well investigated and modeled. However, much less is known about boundaries that form between demagnetized plasmas where the magnetic field is not important for pressure balance. The most accessible example of such a plasma boundary is the equatorial boundary layer of the Earth's distant magnetotail. Rather, limited measurements since its first encounter in the late 1970s by the International Sun-Earth Explorer-3 spacecraft revealed the basic properties of this boundary, but its statistical properties and structure have not been studied to date. In this study, we use Geotail and Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) missions to investigate the equatorial boundary layer from lunar orbit (˜55 Earth radii, RE, downtail) to as far downtail as ˜200 RE. Although the magnetic field has almost no effect on the structure of the boundary layer, the layer separates well the hot, rarefied plasma sheet from dense cold magnetosheath plasmas. We suggest that the most important role in plasma separation is played by polarization electric fields, which modify the efficiency of magnetosheath ion penetration into the plasma sheet. We also show that the total energies (bulk flow plus thermal) of plasma sheet ions and magnetosheath ions are very similar; that is, magnetosheath ion thermalization (e.g., via ion scattering by magnetic field fluctuations) is sufficient to produce hot plasma sheet ions without any additional acceleration.

  11. Drift velocities of 150-km Field-Aligned Irregularities observed by the Equatorial Atmosphere Radar

    Directory of Open Access Journals (Sweden)

    Yuichi Otsuka

    2013-11-01

    Full Text Available Between 130 and 170 km altitude in the daytime ionosphere, the so-called 150-km field-aligned irregularities (FAIs have been observed since the 1960s at equatorial regions with several very high frequency (VHF radars. We report statistical results of 150-km FAI drift velocities on a plane perpendicular to the geomagnetic field, acquired by analyzing the Doppler velocities of 150-km FAIs observed with the Equatorial Atmosphere Radar (EAR at Kototabang, Indonesia during the period from Aug. 2007 to Oct. 2009. We found that the southward/upward perpendicular drift velocity of the 150-km FAIs tends to decrease in the afternoon and that this feature is consistent with that of F-region plasma drift velocities over the magnetic equator. The zonal component of the 150-km FAI drift velocity is westward and decreases with time, whereas the F-region plasma drift velocity observed with the incoherent scatter radar at Jicamarca, Peru, which is westward, reaches a maximum at about noon. The southward/upward and zonal drift velocities of the 150-km FAIs are smaller than that of the F-region plasma drift velocity by approximately 3 m/s and 25 m/s, respectively, on average. The large difference between the 150-km FAI and F-region plasma drift velocities may not arise from a difference in the magnetic latitudes at which their electric fields are generated. Electric fields generated at the altitude at which the 150-km FAIs occur may not be negligible.

  12. Numerical simulation of draining and drying procedure for the ITER Generic Equatorial Port Plug cooling system

    International Nuclear Information System (INIS)

    Tanchuk, Victor; Grigoriev, Sergey; Lyublin, Boris; Maquet, Philippe; Senik, Konstantin; Pak, Sunil; Udintsev, Victor

    2016-01-01

    Highlights: • The cooling system of the ITER Generic Equatorial Port Plug (GEPP) is of a complicated combination of horizontal and vertical channels. • The calculation model for the entire GEPP cooling circuit comprising 12 sub-circuits and built up of 2421 finite-volume elements has been developed. • Transient analysis of this model simulating the draining procedure by the KORSAR/B1 code has been performed. • Water in amount of 263 g of initial 531 kg in the GEPP remains in the dead-ends of the DSM and DFW channels in 150 s of draining procedure. • Almost 3 h are required to boil off 263 g of water trapped in the dead-ends. - Abstract: For effective vacuum leak testing all cooling circuits serving the ITER vessel and in-vessel components shall be drained and dried so that after this procedure taking less than 100 h the purge gas passing through a component has water content less than 100 ppm. This process is four-stage, with the first stage using a short blast of compressed nitrogen to blow most of water in the coolant channels out of the circuit. This process is hindered by volumes which trap water due to gravity. To remove the trapped water, it is necessary, first, to heat up the structure by hot and compressed nitrogen, and then water is evaporated by depressurized nitrogen. The cooling system of the ITER Diagnostic Equatorial Port Plugs is of a complicated hydraulic configuration. The system branching might make difficult removal of water from the piping in the scheduled draining mode. The authors have proposed the KORSAR computation code to simulate draining of the GEPP cooling circuit. The numerical simulation performed has made it possible to describe the process dynamics during draining of the entire GEPP cooling circuit and to define the process time, amount and location of residual water and evolution of two-phase flow regime.

  13. A long history of equatorial deep-water upwelling in the Pacific Ocean

    Science.gov (United States)

    Zhang, Yi Ge; Pagani, Mark; Henderiks, Jorijntje; Ren, Haojia

    2017-06-01

    Cold, nutrient- and CO2-rich waters upwelling in the eastern equatorial Pacific (EEP) give rise to the Pacific cold tongue. Quasi-periodic subsidence of the thermocline and attenuation in wind strength expressed by El Niño conditions decrease upwelling rates, increase surface-water temperatures in the EEP, and lead to changes in regional climates both near and far from the equatorial Pacific. EEP surface waters have elevated CO2 concentrations during neutral (upwelling) or La Niña (strong upwelling) conditions. In contrast, approximate air-sea CO2 equilibrium characterizes El Niño events. One hypothesis proposes that changes in physical oceanography led to the establishment of a deep tropical thermocline and expanded mixed-layer prior to 3 million years ago. These effects are argued to have substantially reduced deep-water upwelling rates in the EEP and promoted a "permanent El Niño-like" climate state. For this study, we test this supposition by reconstructing EEP "excess CO2" and upwelling history for the past 6.5 million years using the alkenone-pCO2 methodology. Contrary to previous assertions, our results indicate that average temporal conditions in the EEP over the past ∼6.5 million years were characterized by substantial CO2 disequilibrium and high nutrient delivery to surface waters - characteristics that imply strong upwelling of deep waters. Upwelling appears most vigorous between ∼6.5 to 4.5 million years ago coinciding with high accumulation rates of biogenic material during the late Miocene - early Pliocene "biogenic bloom".

  14. Equatorial thermospheric wind changes during the solar cycle: Measurements at Arequipa, Peru, from 1983 to 1990

    International Nuclear Information System (INIS)

    Biondi, M.A.; Meriwether, J.W. Jr.; Fejer, B.G.; Gonzalez, S.A.; Hallenbeck, D.C.

    1991-01-01

    Fabry-Perot interferometer measurements of Doppler shifts in the nightglow 630-nm emission line have been used to determine near-equatorial thermospheric wind velocities at Arequipa, Peru, over ∼ 2/3 of a solar cycle. Monthly-average nocturnal variations in the meridional and zonal wind components were calculated from the nightly data to remove short term (day-to-day) variability, facilitating display of seasonal changes in the wind patterns, as well as any additional changes introduced by the progression of the solar cycle. The measured seasonal variations in the wind patterns are more pronounced than the solar cycle variations and are more readily understandable in terms of the expected, underlying forcing and damping processes. For most of the years, at the winter solstice, there is a weak (≤ 100 m/s) transequatorial flow from the summer to the winter hemisphere in the early and the late night, with essentially zero velocities in between. At the equinoxes, an early-night poleward (southward) flow at solar minimum (1986) is replaced by an equatorward (northward) flow at solar maximum (1989-1990). The zonal flows are predominantly eastward throughout the night, except for the solar minimum equinoxes, where brief westward flows appear in the early and the late night. The peak eastward velocities increase toward solar maximum; at the winter solstice, they are ∼ 100-130 m/s in 1983, 1984 and 1986, reaching ∼ 200 m/s in 1988, 1989 and 1990. The present equatorial thermospheric wind determinations agree in some respects with the satellite-data-based horizontal wind model IIWM-87 and the vector spherical harmonic form of the thermospheric general circulation model

  15. Neutral carbohydrate geochemistry of particulate material in the central equatorial Pacific

    Science.gov (United States)

    Hernes, Peter J.; Hedges, John I.; Peterson, Michael L.; Wakeham, Stuart G.; Lee, Cindy

    Neutral carbohydrate compositions were determined for particulate samples from plankton net tows, shallow floating sediment traps, mid-depth and deep moored sediment traps, and sediment cores collected along a north-south transect in the central equatorial Pacific Ocean during the U.S. JGOFS EqPac program. Total neutral carbohydrate depth profiles and patterns along the transect follow essentially the same trends as bulk and organic carbon (OC) fluxes—attenuating with depth, high near the equator and decreasing poleward. OC-normalized total aldose (TCH 2,O) yields along the transect and with depth do not show any consitent patterns. Relative to a planktonic source, neutral carbohydrate compositions in sediment trap and sediment core samples reflect preferential loss of ribose and storage carbohydrates rich in glucose, and preferential preservation of structural carbohydrates rich in rhamnose, xylose, fucose, and mannose. There is also evidence for an intermediately labile component rich in galactose. It appears that compositional signatures of neutral carbohydrates in sediments are more dependent upon their planktonic source than on any particular diagenetic pathway. Relative to other types of organic matter, neutral carbohydrates are better preserved in calcareous oozes from 12°S to 5°N than in red clays at 9°N based on OC-normalized TCH 2O yields, due to either differing sources or sorption characteristics. Weight per cent glucose generally decreases with increased degradation of organic material in the central equatorial Pacific region. Based on weight per cent glucose, comparisons of samples between Survey I (El Niõn) and Survey II (non-El Niño) indicate that during Survey I, organic material in the epipelagic zone in the northern hemisphere may have undergone more degradation than organic material in the southern hemisphere.

  16. Were equatorial regions less affected by the 2009 influenza pandemic? The Brazilian experience.

    Directory of Open Access Journals (Sweden)

    Cynthia Schuck-Paim

    Full Text Available Although it is in the Tropics where nearly half of the world population lives and infectious disease burden is highest, little is known about the impact of influenza pandemics in this area. We investigated the mortality impact of the 2009 influenza pandemic relative to mortality rates from various outcomes in pre-pandemic years throughout a wide range of latitudes encompassing the entire tropical, and part of the subtropical, zone of the Southern Hemisphere (+5(°N to -35(°S by focusing on a country with relatively uniform health care, disease surveillance, immunization and mitigation policies: Brazil. To this end, we analyzed laboratory-confirmed deaths and vital statistics mortality beyond pre-pandemic levels for each Brazilian state. Pneumonia, influenza and respiratory mortality were significantly higher during the pandemic, affecting predominantly adults aged 25 to 65 years. Overall, there were 2,273 and 2,787 additional P&I- and respiratory deaths during the pandemic, corresponding to a 5.2% and 2.7% increase, respectively, over average pre-pandemic annual mortality. However, there was a marked spatial structure in mortality that was independent of socio-demographic indicators and inversely related with income: mortality was progressively lower towards equatorial regions, where low or no difference from pre-pandemic mortality levels was identified. Additionally, the onset of pandemic-associated mortality was progressively delayed in equatorial states. Unexpectedly, there was no additional mortality from circulatory causes. Comparing disease burden reliably across regions is critical in those areas marked by competing health priorities and limited resources. Our results suggest, however, that tropical regions of the Southern Hemisphere may have been disproportionally less affected by the pandemic, and that climate may have played a key role in this regard. These findings have a direct bearing on global estimates of pandemic burden and the

  17. Numerical simulation of draining and drying procedure for the ITER Generic Equatorial Port Plug cooling system

    Energy Technology Data Exchange (ETDEWEB)

    Tanchuk, Victor, E-mail: Victor.Tanchuk@sintez.niiefa.spb.su [JSC “D.V. Efremov Institute of Electrophysical Apparatus”, 196641 St. Petersburg (Russian Federation); Grigoriev, Sergey; Lyublin, Boris [JSC “D.V. Efremov Institute of Electrophysical Apparatus”, 196641 St. Petersburg (Russian Federation); Maquet, Philippe [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul-lez-Durance (France); Senik, Konstantin [JSC “D.V. Efremov Institute of Electrophysical Apparatus”, 196641 St. Petersburg (Russian Federation); Pak, Sunil [National Fusion Research Institute, Daejeon (Korea, Republic of); Udintsev, Victor [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul-lez-Durance (France)

    2016-11-01

    Highlights: • The cooling system of the ITER Generic Equatorial Port Plug (GEPP) is of a complicated combination of horizontal and vertical channels. • The calculation model for the entire GEPP cooling circuit comprising 12 sub-circuits and built up of 2421 finite-volume elements has been developed. • Transient analysis of this model simulating the draining procedure by the KORSAR/B1 code has been performed. • Water in amount of 263 g of initial 531 kg in the GEPP remains in the dead-ends of the DSM and DFW channels in 150 s of draining procedure. • Almost 3 h are required to boil off 263 g of water trapped in the dead-ends. - Abstract: For effective vacuum leak testing all cooling circuits serving the ITER vessel and in-vessel components shall be drained and dried so that after this procedure taking less than 100 h the purge gas passing through a component has water content less than 100 ppm. This process is four-stage, with the first stage using a short blast of compressed nitrogen to blow most of water in the coolant channels out of the circuit. This process is hindered by volumes which trap water due to gravity. To remove the trapped water, it is necessary, first, to heat up the structure by hot and compressed nitrogen, and then water is evaporated by depressurized nitrogen. The cooling system of the ITER Diagnostic Equatorial Port Plugs is of a complicated hydraulic configuration. The system branching might make difficult removal of water from the piping in the scheduled draining mode. The authors have proposed the KORSAR computation code to simulate draining of the GEPP cooling circuit. The numerical simulation performed has made it possible to describe the process dynamics during draining of the entire GEPP cooling circuit and to define the process time, amount and location of residual water and evolution of two-phase flow regime.

  18. The effect of the equatorially symmetric zonal winds of Saturn on its gravitational field

    Science.gov (United States)

    Kong, Dali; Zhang, Keke; Schubert, Gerald; Anderson, John D.

    2018-04-01

    The penetration depth of Saturn’s cloud-level winds into its interior is unknown. A possible way of estimating the depth is through measurement of the effect of the winds on the planet’s gravitational field. We use a self-consistent perturbation approach to study how the equatorially symmetric zonal winds of Saturn contribute to its gravitational field. An important advantage of this approach is that the variation of its gravitational field solely caused by the winds can be isolated and identified because the leading-order problem accounts exactly for rotational distortion, thereby determining the irregular shape and internal structure of the hydrostatic Saturn. We assume that (i) the zonal winds are maintained by thermal convection in the form of non-axisymmetric columnar rolls and (ii) the internal structure of the winds, because of the Taylor-Proundman theorem, can be uniquely determined by the observed cloud-level winds. We calculate both the variation ΔJn , n = 2, 4, 6 … of the axisymmetric gravitational coefficients Jn caused by the zonal winds and the non-axisymmetric gravitational coefficients ΔJnm produced by the columnar rolls, where m is the azimuthal wavenumber of the rolls. We consider three different cases characterized by the penetration depth 0.36, R S, 0.2, R S and 0.1, R S, where R S is the equatorial radius of Saturn at the 1-bar pressure level. We find that the high-degree gravitational coefficient (J 12 + ΔJ 12) is dominated, in all the three cases, by the effect of the zonal flow with |ΔJ 12/J 12| > 100% and that the size of the non-axisymmetric coefficients ΔJ mn directly reflects the depth and scale of the flow taking place in the Saturnian interior.

  19. Serological markers suggest heterogeneity of effectiveness of malaria control interventions on Bioko Island, equatorial Guinea.

    Directory of Open Access Journals (Sweden)

    Jackie Cook

    Full Text Available In order to control and eliminate malaria, areas of on-going transmission need to be identified and targeted for malaria control interventions. Immediately following intense interventions, malaria transmission can become more heterogeneous if interventions are more successful in some areas than others. Bioko Island, Equatorial Guinea, has been subject to comprehensive malaria control interventions since 2004. This has resulted in substantial reductions in the parasite burden, although this drop has not been uniform across the island.In 2008, filter paper blood samples were collected from 7387 people in a cross-sectional study incorporating 18 sentinel sites across Bioko, Equatorial Guinea. Antibodies were measured to P. falciparum Apical Membrane Antigen-1 (AMA-1 by Enzyme Linked Immunosorbent Assay (ELISA. Age-specific seropositivity rates were used to estimate seroconversion rates (SCR. Analysis indicated there had been at least a 60% decline in SCR in four out of five regions on the island. Changes in SCR showed a high degree of congruence with changes in parasite rate (PR and with regional reductions in all cause child mortality. The mean age adjusted concentration of anti-AMA-1 antibodies was mapped to identify areas where individual antibody responses were higher than expected. This approach confirmed the North West of the island as a major focus of continuing infection and an area where control interventions need to be concentrated or re-evaluated.Both SCR and PR revealed heterogeneity in malaria transmission and demonstrated the variable effectiveness of malaria control measures. This work confirms the utility of serological analysis as an adjunct measure for monitoring transmission. Age-specific seroprevalence based evidence of changes in transmission over time will be of particular value when no baseline data are available. Importantly, SCR data provide additional evidence to link malaria control activities to contemporaneous

  20. The Genesis of Tropical Cyclone Bilis (2000) Associated with Cross-equatorial Surges

    Institute of Scientific and Technical Information of China (English)

    XU Yamei

    2011-01-01

    The purpose of this paper is to explore how a tropical cyclone forms from a pre-existing large-scale depression which has been observed and associated with cross-equatorial surges in the western North Pacific. Tropical cyclone Bilis (2000) was selected as the case to study. The research data used are from the results of the non-hydrostatic mesoscale model (MM5), which has successfully simulated the transformation of a pre-existing weak large-scale tropical depression into a strong tropical storm. The scale separation technique is used to separate the synoptic-scale and sub-synoptic-scale fields from the model output fields. The scale-separated fields show that the pre-existing synoptic-scale tropical depression and the subsynoptic scale tropical cyclone formed later were different scale systems from beginning to end. It is also shown that the pre-existing synoptic-scale tropical depression did not contract to become the tropical cyclone. A series of weak, sub-synoptic-scale low and high pressure systems appeared and disappeared in the synopticscale depression, with one of the low systems near the center of the synoptic-scale depression having deepened to become the tropical cyclone. The roles of the synoptic-scale flow and the sub-synoptic scale disturbances in the formation of the tropical cyclone are investigated by diagnoses of the scale-separated vertical vorticity equation. The results show that the early development of the sub-synoptic scale vortex was fundamentally dependent on the strengthening synoptic-scale environmental depression. The depression was strengthened by cross-equatorial surges, which increased the convergence of the synoptic-scale depression at low levels and triggered the formation of the tropical cyclone.