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Sample records for brazilian equatorial e-region

  1. Hybrid simulations of coupled Farley-Buneman/gradient drift instabilities in the equatorial E region ionosphere

    Science.gov (United States)

    Young, Matthew A.; Oppenheim, Meers M.; Dimant, Yakov S.

    2017-05-01

    Plasma irregularities in the equatorial E region ionosphere are classified as Type I or Type II, based on coherent radar spectra. Type I irregularities are attributed to the Farley-Buneman instability and Type II to the gradient drift instability that cascades to meter-scale irregularities detected by radars. This work presents the first kinetic simulations of coupled Farley-Buneman and gradient drift turbulence in the equatorial E region ionosphere for a range of zeroth-order vertical electric fields, using a new approach to solving the electrostatic potential equation. The simulation models a collisional quasi-neutral plasma with a warm, inertialess electron fluid and a distribution of NO+ ions. A 512 m wave with a maximum/minimum of ±0.25 of the background density perturbs the plasma. The density wave creates an electrostatic field that adds to the zeroth-order vertical and ambipolar fields, and drives Farley-Buneman turbulence even when these fields are below the instability threshold. Wave power spectra show that Type II irregularities develop in all simulation runs and that Type I irregularities with wavelengths of a few meters develop in the trough of the background wave in addition to Type II irregularities as the zeroth-order electric field magnitude increases. Linear fluid theory predicts the growth of Type II irregularities reasonably well, but it does not fully capture the simultaneous growth of Type I irregularities in the region of peak total electric field. The growth of localized Type I irregularities represents a parametric instability in which the electric field of the large-scale background wave drives pure Farley-Buneman turbulence. These results help explain observations of meter-scale irregularities advected by kilometer-scale waves.

  2. 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.

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

    Science.gov (United States)

    Farley, D. T.

    2009-04-01

    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.

  4. Automatically identification of Equatorial Spread-F on ionograms recorded in the Brazilian Equatorial region

    Science.gov (United States)

    Pillat, V. G.; Fagundes, P. R.; Guimarães, L. N. F.

    2016-12-01

    The most interesting equatorial ionospheric phenomena are the F-region large-scale irregularities and the equatorial ionization anomaly (EIA). F-region large-scale irregularity is a night-time phenomenon and its signature is multiples echoes recorded on ionograms, usually called Spread-F. These irregularities are generated in the bottom side of the equatorial F-region. Whereas the irregularity gets high altitude they end up extending to lower latitudes and usually drift eastward. With advancement of digital ionosonde, it is now possible to carry out an ionospheric sounding with a 5 minutes cadence or even with 1-minute cadence. To understand season and solar cycle Spread-F variation in several stations it is necessary deal with a large number of ionograms. Therefore, more sophisticated analysis tools are needed. Thus, development of algorithms to identify and analyse different aspects of ionograms have become very important to ionospheric physics researchers. The main objective of this paper is to present the performance of a computational tool, called UDIDA-scaling. This tool is based on fuzzy relation, in the identification of Spread-F on ionograms recorded in the Brazilian Equatorial sector (Manaus (2.9° S, 60.0° W, dip latitude 6.4° S) and Palmas (10.2° S, 48.2° W, dip latitude 5.5° S)), during a geomagnetic disturbed and a quiet period.

  5. Equatorial E region electric fields at the dip equator: 2. Seasonal variabilities and effects over Brazil due to the secular variation of the magnetic equator

    Science.gov (United States)

    Moro, J.; Denardini, C. M.; Resende, L. C. A.; Chen, S. S.; Schuch, N. J.

    2016-10-01

    In this work, the seasonal dependency of the E region electric field (EEF) at the dip equator is examined. The eastward zonal (Ey) and the daytime vertical (Ez) electric fields are responsible for the overall phenomenology of the equatorial and low-latitude ionosphere, including the equatorial electrojet (EEJ) and its plasma instability. The electric field components are studied based on long-term backscatter radars soundings (348 days for both systems) collected during geomagnetic quiet days (Kp ≤ 3+), from 2001 to 2010, at the São Luís Space Observatory (SLZ), Brazil (2.33°S, 44.20°W), and at the Jicamarca Radio Observatory (JRO), Peru (11.95°S, 76.87°W). Among the results, we observe, for the first time, a seasonal difference between the EEF in these two sectors in South America based on coherent radar measurements. The EEF is more intense in summer at SLZ, in equinox at JRO, and has been highly variable with season in the Brazilian sector compared to the Peruvian sector. In addition, the secular variation on the geomagnetic field and its effect on the EEJ over Brazil resulted that as much farther away is the magnetic equator from SLZ, later more the EEJ is observed (10 h LT) and sooner it ends (16 h LT). Moreover, the time interval of type II occurrence decreased significantly after the year 2004, which is a clear indication that SLZ is no longer an equatorial station due to the secular variation of the geomagnetic field.

  6. Were Equatorial Regions Less Affected by the 2009 Influenza Pandemic? The Brazilian Experience

    Science.gov (United States)

    Schuck-Paim, Cynthia; Viboud, Cécile; Simonsen, Lone; Miller, Mark A.; Moura, Fernanda E. A.; Fernandes, Roberto M.; Carvalho, Marcia L.; Alonso, Wladimir J.

    2012-01-01

    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 assessment of the

  7. 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

  8. Comparative study on the ionospheric response to minor and major sudden stratospheric events in the Brazilian equatorial and low latitudes

    Science.gov (United States)

    Fagundes, Paulo Roberto; Kavutarapu, Venkatesh; Gil Pillat, Valdir; Vieira, Francisco

    2016-07-01

    The Total electron Content (TEC), derivate from GPS, becomes one of the most powerful techniques to study the space-time ionospheric (F-region) electrodynamics, during the quiet and disturbed periods. The number of GPS stations in Brazil increased significantly during the last few years; currently more than 100 GPS stations are in operation over the Brazilian region. The GPS-TEC values are derived using the differential delay technique from the dual frequency measurements at L1 and L2 frequencies over the considered locations at equatorial and low latitudes. The present study investigates the ionospheric total electron content (GPS-TEC) response in the Southern Hemisphere equatorial and low latitudes, due to major and minor sudden stratospheric warming (SSW) events, which took place during 2009 and 2012. During both the SSW events, the TEC values are depleted to the order of 20-30% all over the Brazil from equator to beyond Equatorial Ionization Anomaly (EIA) regions. In addition, the EIA were suppressed during the SSW events for several days. However, the TEC depletion and EIA suppression lasted for a longer period during SSW-2012 when compared with the SSW-2009; despite the SSW-2012 is considerd as a minor event.

  9. Equatorial and Low-Latitude Ionospheric Response to the Extreme Space Weather Event of March 2015, in the Brazilian Sector.

    Science.gov (United States)

    Fagundes, P. R.; Cardoso, F. A.; Fejer, B. G.; Kavutarapu, V.; Ribeiro, B. A.; Pillat, V. G.

    2015-12-01

    Fagundes PR, Cardoso FA and Venkatesh KPhysics and Astronomy Laboratory, Universidade do Vale do Paraiba (UNIVAP), Sao Jose dos Campos, Sao Paulo, Brazil In the present investigation we discuss the results on the response of the ionosphere (F-region) in the Brazilian sector, during extreme space weather event of March 2015. This geomagnetic storm has been considered as one of strongest storms in the solar cycle 24 where, the Dst index reached a minimum of -227 nT at 23:00 UT (17/03/2015) with KP reaching to 8-, and the monthly mean F10.7 solar flux was 125 sfu. This space weather event was studied using a large network of 110 GPS stations. It has been noticed that the Total Electron Content (TEC) was severely disturbed during the geomagnetic storm main and recovery phases. A wavelike oscillation with three peaks is observed from equator to low latitudes during the storm main phase on 17th and 18th March, 2015. Using a latitudinal chain of 8 GPS stations from equatorial region to low latitudes the storm time behavior of the Equatorial Ionization Anomaly (EIA) is investigated. It was noticed that the wavelike oscillation peak latitudinal extent decreases from the beginning of main phase to the recovery phase. The first maximum extends beyond from 2oS to 20oS, the second one from 8oS to 18oS and the third one from 13oS to 17oS. In addition, a strong negative phase in TEC variations is observed during the recovery phase on March 18, 2015. This negative phase is found to be stronger at low-latitude compared to the equatorial region. An anomalous behavior of EIA caused by the wavelike oscillations is observed during the main phase on March 17, 2015. Also, due to the strong negative phase in TEC resulted in strong EIA suppression on March 18, 2015.

  10. Spectral fluctuation analysis of ionospheric inhomogeneities over Brazilian territory. Part I: Equatorial F-region plasma bubbles

    Science.gov (United States)

    Fornari, G.; Rosa, R. R.; de Meneses, F. C.; Muralikrishna, P.

    2016-11-01

    In this Part I of a more general paper on the analysis of ionospheric irregularities over Brazilian territory, we apply the Detrended Fluctuation Analysis (DFA) method to evaluate in situ equatorial F-region plasma bubbles events carried out with a sounding rocket over equatorial region in Brazil. The range of scaling exponents derived from the DFA technique are compared to previous results obtained using Power Spectral Density (PSD) technique (which is widely used in this area despite its recognized inaccuracy to analyze short series). The results obtained in this first part of our investigation, using DFA, also show a wide range of spectral index variation with standard deviation of the same order found from the previous application using PSD (σm ≫ 10 %). Therefore, since the dependence of the technique are disregarded, our findings also supports that the observed lack of a universality class characterized by the nonexistence of a single spectral index (with σm ≈ 2 %) may be due to non-homogeneity energy cascades that can appear in the incoherent ionospheric turbulent process.

  11. Equatorial ionospheric irregularities produced by the Brazilian ionospheric modification experiment (BIME)

    Energy Technology Data Exchange (ETDEWEB)

    Klobuchar, J.A.; Abdu, M.A.

    1989-03-01

    On two separate evenings in September 1982, rockets were launched into the bottomside equatorial F2 region off the coast of Natal, Brazil, to inject chemicals, consisting of mainly H2O and CO2, to create a hole in ionization. The chemicals were injected near the height where the density gradient was steepest, and at a time when the F2 region was rising rapidly, to see whether plasma bubble irregularities could be generated from instabilities triggered by the ionization hole. The eastward drifts of these artificial depletions were observed by the time difference in the TEC features observed at various TEC monitoring stations, and from the changing range of oblique ionosonde echoes observed by an ionosonde located 300 km magnetically east of the chemical release point. Their subsequent evolution into plasma bubble irregularities was demonstrated from the observations of spread F echoes, strong-amplitude scintillation, and TEC depletion at distances of from 300 to 500 km eastward of the release points. The fact that similar behavior of the ionosphere was observed during the evenings of both rocket chemical releases, and on no other nights of the campaign, is strong evidence of successful artificial generation of bubble irregularities by chemical injection into the bottomside F2 region.

  12. Equatorial ionospheric irregularities produced by the Brazilian ionospheric modification experiment (BIME)

    Energy Technology Data Exchange (ETDEWEB)

    Klobuchar, J.A. (Air Force Geophysics Lab., Hanscom Air Force Base, MA (USA)); Abdu, M.A. (Instituto de Pesquisas Espaciais, Sao Jose dos Campos (Brazil))

    1989-03-01

    On two separate evenings in September 1982, rockets were launched into the bottomside equatorial F{sub 2} region off the coast of Natal, Brazil, to inject chemicals, consisting of mainly H{sub 2}O and CO{sub 2}, to create a hole in ionization. The chemicals were injected near the height where the density gradient was steepest, and at a time when the F{sub 2} region was rising rapidly to see whether plasma bubble irregularities could be generated from instabilities triggered by the ionization hole. On both occasions, hole-induced depletions in total electron content (TEC) of more than 10{sup 16} el/m{sup 2} were observed over horizontal distances of at least 60 km from the chemical injection point. The eastward drifts of these artificial depletions were observed by the time difference in the TEC features observed at various TEC monitoring stations, and from the changing range of oblique ionosonde echoes observed by an ionosonde located 300 km magnetically east of the chemical release point. Their subsequent evolution into plasma bubble irregularities was demonstrated from the observations of spread F echoes, strong amplitude scintillation, and TEC depletion at distances of from 300 to 500 km eastward of the release points. The fact that similar behavior of the ionosphere was observed during the evenings of both rocket chemical releases, and on no other nights of the campaign, is strong evidence of successful artificial generation of bubble irregularities by chemical injection into the bottomside F{sub 2} region.

  13. Marine environmental changes at the Brazilian equatorial margin related to Amazon River evolution during the Neogene

    Science.gov (United States)

    Lammertsma, Emmy; Troelstra, Simon; Sangiorgi, Francesca; Chemale, Farid, Jr.; do Carmo, Dermeval A.; D'Avila, Roberto; Soares, Emilson; Hoorn, Carina

    2014-05-01

    Today, the nutrient-rich Amazon River outflow causes massive algal blooms in the western equatorial Atlantic Ocean, forming a considerable carbon sink as well as a primary food source in the otherwise oligotrophic surface water. However, the history of this high-productivity system is largely unknown, although a strong relation to the evolution of the Amazon River can be expected. The Amazon submarine fan provides direct evidence for the development of a transcontinental river system, of which the base of the primarily Andean-sourced siliciclastic deposits is dated as late Miocene. Ditch cuttings from Amazon Fan exploration 'Well 2' were made available by Petrobras for microfossil and lithological research. 'Well 2' is located on the uppermost fan at a water depth of 750 meters. Organic-walled dinoflagellate cyst and foraminifer assemblages were studied to reconstruct Neogene marine environmental changes in relation to the Amazon River development. Planktonic foraminifera are present throughout the studied section and largely confirm the already available biostratigraphic age determination based on nannofossils. Benthic foraminifer assemblages indicate that the paleo-water depth has not substantially deviated from current conditions. The ecological affinities of most observed dinocyst taxa are well known, which allows us to reconstruct changes in paleo-productivity based on the assemblages. Mineral composition suggests that local river systems already drained into the Amazon basin before the onset of the transcontinental system, but environmental conditions remained oligotrophic at this time. Decreased abundances of both dinocysts and planktonic foraminifera during the Pleistocene are related to highest sedimentation rates (dilution effect). Overall, a complex interplay of orogenesis, climatic and sea level variations during the Neogene are responsible for the fluvially-induced changes in the marine environment at the Atlantic margin.

  14. Ionospheric response to the 2006 sudden stratospheric warming event over the equatorial and low latitudes in the Brazilian sector using GPS observations

    Science.gov (United States)

    de Jesus, R.; Batista, I. S.; Fagundes, P. R.; Venkatesh, K.; de Abreu, A. J.

    2017-02-01

    The main purpose of this paper is to study the response of the ionospheric F-region using GPS-TEC measurements at equatorial and low latitude regions over the Brazilian sector during an sudden stratospheric warming (SSW) event in the year 2006. In this work, we present vertical total electron content (VTEC) and phase fluctuations derived from GPS network in Brazil. The continuous wavelet transform (CWT) was employed to check the periodicities of the ∆VTEC during the SSW event. The results show a strong decrease in VTEC and ∆VTEC values in the afternoon over low latitudes from DOY 05-39 (during the SSW event) mainly after the second SSW temperature peak. The ionospheric ∆VTEC pattern over Brazilian sector shows diurnal and semidiurnal oscillations during the 2006 SSW event. In addition, for the first time, variations in ∆VTEC (low latitude stations) with periods of about 02-08 day have been reported during an SSW event. Using GPS stations located in the Brazilian sector, it is reported for the first time that equatorial ionospheric irregularities were not suppressed by the SSW event.

  15. Molecular findings from influenza A(H1N1pdm09 detected in patients from a Brazilian equatorial region during the pandemic period

    Directory of Open Access Journals (Sweden)

    Maria José Couto Oliveira

    2014-11-01

    Full Text Available After the World Health Organization officially declared the end of the first pandemic of the XXI century in August 2010, the influenza A(H1N1pdm09 virus has been disseminated in the human population. In spite of its sustained circulation, very little on phylogenetic data or oseltamivir (OST resistance is available for the virus in equatorial regions of South America. In order to shed more light on this topic, we analysed the haemagglutinin (HA and neuraminidase (NA genes of influenza A(H1N1pdm09 positive samples collected during the pandemic period in the Pernambuco (PE, a northeastern Brazilian state. Complete HA sequences were compared and amino acid changes were related to clinical outcome. In addition, the H275Y substitution in NA, associated with OST resistance, was investigated by pyrosequencing. Samples from PE were grouped in phylogenetic clades 6 and 7, being clustered together with sequences from South and Southeast Brazil. The D222N/G HA gene mutation, associated with severity, was found in one deceased patient that was pregnant. Additionally, the HA mutation K308E, which appeared in Brazil in 2010 and was only detected worldwide the following year, was identified in samples from hospitalised cases. The resistance marker H275Y was not identified in samples tested. However, broader studies are needed to establish the real frequency of resistance in this Brazilian region.

  16. Female gender but not season of birth is associated with mood seasonality in a near-equatorial Brazilian city

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    Taciano L. Milfont

    2012-01-01

    Full Text Available OBJECTIVE: Studies conducted mainly in countries located in the Northern Hemisphere have shown that season of birth influences mood seasonality. Greater mood seasonality has been observed for individuals born during spring/summer months than those born during autumn/winter months. Expanding past research to the Southern Hemisphere, in this study we examine the influence of season of birth on mood seasonality in a sample of 1,247 healthy young Brazilians. METHOD: The Seasonal Pattern Assessment Questionnaire was used to compute a global seasonality score as a measure of mood seasonality in a cross-sectional study. RESULTS: Analysis of covariance was conducted to examine the effects of month of birth and gender on mood seasonality, with age entered as a covariate. A main effect of gender was observed, F (1, 1197 = 17.86, p .05. CONCLUSION: The unexpected finding is tentatively explained by differences in geographic location and weather fluctuations between the sampling location in Brazil and other countries where season of birth has been found to influence mood seasonality. Additional studies with larger samples from the Southern Hemisphere are necessary to shed additional light on the possible significant influence of season of birth on mood.

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

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    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.

  18. Equatorial electrojet in the south Atlantic anomaly region

    Indian Academy of Sciences (India)

    Peru; Carnegie Institution of Washington, Report No. 620. Hirono M 1952 A theory of diurnal magnetic variations in equatorial regions and conductivity of the ionospheric E region; J. Geomagn. Geoelectr. 4 7–21. Onwumechili C A, Kawasaki K and Akasofu S I 1973. Relationship between the equatorial electrojet and polar.

  19. 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...

  20. Meridional equatorial electrojet current in the American sector

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    R. G. Rastogi

    1999-02-01

    Full Text Available Huancayo is the only equatorial electrojet station where the daytime increase of horizontal geomagnetic field (H is associated with a simultaneous increase of eastward geomagnetic field (Y. It is shown that during the counter electrojet period when ∆H is negative, ∆Y also becomes negative. Thus, the diurnal variation of ∆Y at equatorial latitudes is suggested to be a constituent part of the equatorial electrojet current system. Solar flares are known to increase the H field at an equatorial station during normal electrojet conditions (nej. At Huancayo, situated north of the magnetic equator, the solar flare effect, during nej, consists of positive impulses in H and Y and negative impulse in Z field. During counter electrojet periods (cej, a solar flare produces a negative impulse in H and Y and a positive impulse in Z at Huancayo. It is concluded that both the zonal and meridional components of the equatorial electrojet in American longitudes, as in Indian longitudes, flows in the same, E region of the ionosphere.Key words. Geomagnetism and paleomagnetism (dynamo theories · Ionosphere (equatorial ionosphere; ionosphere disturbances

  1. Meridional equatorial electrojet current in the American sector

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    R. G. Rastogi

    Full Text Available Huancayo is the only equatorial electrojet station where the daytime increase of horizontal geomagnetic field (H is associated with a simultaneous increase of eastward geomagnetic field (Y. It is shown that during the counter electrojet period when ∆H is negative, ∆Y also becomes negative. Thus, the diurnal variation of ∆Y at equatorial latitudes is suggested to be a constituent part of the equatorial electrojet current system. Solar flares are known to increase the H field at an equatorial station during normal electrojet conditions (nej. At Huancayo, situated north of the magnetic equator, the solar flare effect, during nej, consists of positive impulses in H and Y and negative impulse in Z field. During counter electrojet periods (cej, a solar flare produces a negative impulse in H and Y and a positive impulse in Z at Huancayo. It is concluded that both the zonal and meridional components of the equatorial electrojet in American longitudes, as in Indian longitudes, flows in the same, E region of the ionosphere.

    Key words. Geomagnetism and paleomagnetism (dynamo theories · Ionosphere (equatorial ionosphere; ionosphere disturbances

  2. Equatorial MST radars: Further consideration

    Science.gov (United States)

    Lagos, P.

    1983-01-01

    The results presented give additional support to the need of equatorial MST radars in order to obtain more information on the nature of equatorial waves in the MST region. Radar deduced winds such as obtained at Jicamarca for periods of months indicate that with these data the full range of equatorial waves, with time scales of seconds to years, can be studied.

  3. Planetary wave oscillations in the equatorial MLT region and in the E- and F- region of the equatorial ionosphere.

    Science.gov (United States)

    Ramkumar, T.; Gurubaran, S.; Sastri, J.; Rajaram, R.

    The ordered current flows existing in the E and F region of the equatorial ionosphere is believed to be mainly due to the dynamo action of the tidal waves in the neutral winds of the atmosphere. During day times, the emfs induced in the E-region of the ionosphere, because of the high electrical conductivity existing there, are easily mapped on to the F region of the ionosphere through the highly conducting equipotential geomagnetic field lines. So, any changes in the E region electric fie ld due to the perturbations in the tidal winds will produce similar changes in the F region electric field also. Correspondingly the vertical plasma drifts and hence the plasma frequencies in the latter region will show the modulation effects. It is believed that sometimes the lower atmospheric (troposphere and stratosphere) free resonant or any other unstable planetary (period of oscillation varies over a few days to a few tens of days) waves may propagate well above 100 km. These waves then produce current systems through dynamo mechanism or modulate the upward propagating tidal or gravity waves and hence the dynamo currents corresponding to the periods of planetary wave oscillations. In the present paper we present the results on the possible influences of the equatorial mesospheric planetary waves on the equatorial electrojet strength (EEJS), and the equatorial F-region parameters like hpF2 (M3000), h'F, and foF2. For this study, we used the mesospheric wind data obtained with the MF (1.98 MHz) partial reflection radar, located at the Indian dip equatorial site Tirunelveli. The equatorial electrojet strength (EEJS) is obtained by taking the difference of the geomagnetic field variations measured both at the EEJ station Trivandrum and the off EEJ station Alibag. To study the other E and F-region parameters, we used the data obtained- with the ionosonde, located at the EEJ site Kodaikanal. Along with the fast Fourier transform (FFT) technique, we also utilized the wavelet

  4. Brazilian Space Weather Program

    Science.gov (United States)

    Padilha, Antonio; Takahashi, Hisao; de Paula, Eurico; Sawant, Hanumant; de Campos Velho, Haroldo; Vitorello, Icaro; Costa, Joaquim; Souza, Jonas; Cecatto, José; Mendes, Odim; Gonzalez Alarcon, Walter Demétrio

    A space weather program is being initiated at the Brazilian National Institute for Space Research (INPE) to study events from their initiation on the sun to their impacts on the earth, including their effects on space-based and ground-based technological systems. The program is built on existing capabilities at INPE, which include scientists with a long tradition and excellence in the observation, analysis and modeling of solar and solar-terrestrial phenomena and an array of geophysical instruments that spans all over the Brazilian territory from the north to south of the magnetic dip equator. Available sensors include solar radio frequency receivers and telescopes, optical instruments and solar imagers, GNSS receivers, ionosondes, radars, allsky imagers, magnetometers and cosmic ray detectors. In the equatorial region, ionosphere and thermosphere constitute a coupled system with electrodynamical and plasma physical processes being responsible for a variety of peculiar phenomena. The most important of them are the equatorial electrojet current system and its instabilities, the equatorial ionization anomaly, and the plasma instabilities/irregularities of the night-time ionosphere (associated with the plasma bubble events). In addition, space weather events modify the equatorial ionosphere in a complex and up to now unpredictable manner. Consequently, a main focus of the program will be on monitoring the low, middle and upper atmosphere phenomena and developing a predictive model of the equatorial ionosphere through data assimilation, that could help to mitigate against the deleterious effects on radio communications and navigation systems. The technological, economic and social importance of such activities was recognized by the Brazilian government and a proposal for funding was approved for the period 2008-2011. New ground instruments will be installed during this period allowing us to extend our current capability to provide space weather observations, accurate

  5. 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.

  6. The Equatorial Ekman Layer

    CERN Document Server

    Marcotte, Florence; Soward, Andrew

    2016-01-01

    The steady incompressible viscous flow in the wide gap between spheres rotating about a common axis at slightly different rates (small Ekman number E) has a long and celebrated history. The problem is relevant to the dynamics of geophysical and planetary core flows, for which, in the case of electrically conducting fluids, the possible operation of a dynamo is of considerable interest. A comprehensive asymptotic study, in the limit E<<1, was undertaken by Stewartson (J. Fluid Mech. 1966, vol. 26, pp. 131-144). The mainstream flow, exterior to the E^{1/2} Ekman layers on the inner/outer boundaries and the shear layer on the inner sphere tangent cylinder C, is geostrophic. Stewartson identified a complicated nested layer structure on C, which comprises relatively thick quasi-geostrophic E^{2/7} (inside C) and E^{1/4} (outside C) layers. They embed a thinner E^{1/3} ageostrophic shear layer (on C), which merges with the inner sphere Ekman layer to form the E^{2/5} Equatorial Ekman layer of axial length E^{...

  7. Type-1 echoes from the mid-latitude E-Region ionosphere

    Directory of Open Access Journals (Sweden)

    C. Haldoupis

    1997-07-01

    Full Text Available This paper presents more data on the properties of type-1 irregularities in the nighttime mid-latitude E-region ionosphere. The measurements were made with a 50-MHz Doppler radar system operating in Crete, Greece. The type-1 echoes last from several seconds to a few minutes and are characterized by narrow Doppler spectra with peaks corresponding to wave phase velocities of 250–350 m/s. The average velocity of 285 m/s is about 20% lower than nominal E-region ion-acoustic speeds, probably because of the presence of heavy metallic ions in the sporadic-E-layers that appear to be associated with the mid-latitude plasma instabilities. Sometimes the type-1 echoes are combined with a broad spectrum of type-2 echoes; at other times they dominate the spectrum or may appear in the absence of any type-2 spectral component. We believe these echoes are due to the modified two-stream plasma instability driven by a polarization electric field that must be larger than 10 mV/m. This field is similar in nature to the equatorial electrojet polarization field and can arise when patchy nighttime sporadic-E-layers have the right geometry.

  8. Irregularities and Forecast Studies of Equatorial Spread

    Science.gov (United States)

    2016-07-13

    document in the published literature . The result implies that the aeronomy of the postsunset equatorial ionosphere is sufficiently well understood for...of equatorial spread F in the Peruvian sector, J. Geophys. Res. Space Physics, 119, 38153827, doi:10.1002/2014JA019889. ◦ Hysell, D. L., M. A. Milla...L. Condori, and J. W. Meriwether (2014), Data-driven numer- ical simulations of equatorial spread F in the Peruvian sector: 2. Autumnal equinox, J

  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. Observation of isotropic electron temperature in the turbulent E region

    Directory of Open Access Journals (Sweden)

    S. Saito

    Full Text Available Using EISCAT radar data, we find that electrons are strongly heated in the magnetic field-line direction during high electric field events. The remote site data show that the electron temperature increases in almost the same way in the field-perpendicular direction; electron heating by E region plasma turbulence is isotropic. We discuss the implications of our observation for the "plasmon"-electron as well as the wave Joule heating models of the anomalous electron heating in the E region.

    Key words. Ionosphere (auroral ionosphere; plasma temperature and density; plasma waves and instabilities

  11. 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.

  12. 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.

  13. Characteristics of low latitude ionospheric E-region irregularities ...

    Indian Academy of Sciences (India)

    The autocorrelation functions, power spectral densities, signal de-correlation times are computed to study the temporal features of ionospheric E-region irregularities linked with daytime scintillations. Derived spectral index ranges between −2 and −9. Assuming velocity of irregularities, the characteristic lengths of the ...

  14. First observational evidence for opposite zonal electric fields in equatorial E and F region altitudes during a geomagnetic storm period

    Science.gov (United States)

    Tulasi Ram, S.; Balan, N.; Veenadhari, B.; Gurubaran, S.; Ravindran, S.; Tsugawa, T.; Liu, H.; Niranjan, K.; Nagatsuma, T.

    2012-09-01

    The strong westward electrojet and simultaneous upward drift of the equatorial ionospheric peak observed over South-East Asia and Indian equatorial regions during the prolonged Dst minimum phase of an intense geomagnetic storm during 14-15 December 2006 are investigated for the altitudinal variation of zonal electric field polarity using ground based and space-borne observations. The results show first observational evidence for simultaneous existence of daytime westward and eastward zonal electric fields at equatorial E and F region altitudes, respectively, in a wide longitude sector. While the westward electric fields at E region altitudes cause westward electrojet, at the same time, the eastward zonal electric fields at F region altitudes cause the upward drift of the equatorial ionospheric peak and reinforcement of the equatorial ionization anomaly (EIA) even in the topside ionosphere (˜660 km). The reversal of the electric fields is found to occur at ˜280 km height. A clear bifurcation of F region plasma at ˜280 km is evident in the iso-electron density contours due to these oppositely polarized zonal electric fields, which manifests as an unusually deep cusp between F1 and F2 layers on equatorial ionograms.

  15. Auroral E-region electron density gradients measured

    Directory of Open Access Journals (Sweden)

    C. Haldoupis

    2000-09-01

    Full Text Available In the theory of E-region plasma instabilities, the ambient electric field and electron density gradient are both included in the same dispersion relation as the key parameters that provide the energy for the generation and growth of electrostatic plasma waves. While there exist numerous measurements of ionospheric electric fields, there are very few measurements and limited knowledge about the ambient electron density gradients, ∇Ne, in the E-region plasma. In this work, we took advantage of the EISCAT CP1 data base and studied statistically the vertical electron density gradient length, Lz=Ne/(dNe/dz, at auroral E-region heights during both eastward and westward electrojet conditions and different ambient electric field levels. Overall, the prevailing electron density gradients, with Lz ranging from 4 to 7 km, are found to be located below 100 km, but to move steadily up in altitude as the electric field level increases. The steepest density gradients, with Lz possibly less than 3 km, occur near 110 km mostly in the eastward electrojet during times of strong electric fields. The results and their implications are examined and discussed in the frame of the linear gradient drift instability theory. Finally, it would be interesting to test the implications of the present results with a vertical radar interferometer.Key words: Ionosphere (auroral ionosphere; ionospheric irregularities; plasma waves and instabilities  

  16. Auroral E-region electron density gradients measured

    Directory of Open Access Journals (Sweden)

    G. Hussey

    Full Text Available In the theory of E-region plasma instabilities, the ambient electric field and electron density gradient are both included in the same dispersion relation as the key parameters that provide the energy for the generation and growth of electrostatic plasma waves. While there exist numerous measurements of ionospheric electric fields, there are very few measurements and limited knowledge about the ambient electron density gradients, ∇Ne, in the E-region plasma. In this work, we took advantage of the EISCAT CP1 data base and studied statistically the vertical electron density gradient length, Lz=Ne/(dNe/dz, at auroral E-region heights during both eastward and westward electrojet conditions and different ambient electric field levels. Overall, the prevailing electron density gradients, with Lz ranging from 4 to 7 km, are found to be located below 100 km, but to move steadily up in altitude as the electric field level increases. The steepest density gradients, with Lz possibly less than 3 km, occur near 110 km mostly in the eastward electrojet during times of strong electric fields. The results and their implications are examined and discussed in the frame of the linear gradient drift instability theory. Finally, it would be interesting to test the implications of the present results with a vertical radar interferometer.Key words: Ionosphere (auroral ionosphere; ionospheric irregularities; plasma waves and instabilities  

  17. Complex Dynamics of Equatorial Scintillation

    Science.gov (United States)

    Piersanti, Mirko; Materassi, Massimo; Forte, Biagio; Cicone, Antonio

    2017-04-01

    Radio power scintillation, namely highly irregular fluctuations of the power of trans-ionospheric GNSS signals, is the effect of ionospheric plasma turbulence. The scintillation patterns on radio signals crossing the medium inherit the ionospheric turbulence characteristics of inter-scale coupling, local randomness and large time variability. On this basis, the remote sensing of local features of the turbulent plasma is feasible by studying radio scintillation induced by the ionosphere. The distinctive character of intermittent turbulent media depends on the fluctuations on the space- and time-scale statistical properties of the medium. Hence, assessing how the signal fluctuation properties vary under different Helio-Geophysical conditions will help to understand the corresponding dynamics of the turbulent medium crossed by the signal. Data analysis tools, provided by complex system science, appear to be best fitting to study the response of a turbulent medium, as the Earth's equatorial ionosphere, to the non-linear forcing exerted by the Solar Wind (SW). In particular we used the Adaptive Local Iterative Filtering, the Wavelet analysis and the Information theory data analysis tool. We have analysed the radio scintillation and ionospheric fluctuation data at low latitude focusing on the time and space multi-scale variability and on the causal relationship between forcing factors from the SW environment and the ionospheric response.

  18. Equatorial wave expansion of instantaneous flows for diagnosis of equatorial waves from data: Formulation and illustration

    Science.gov (United States)

    Barton, Cory; Cai, Ming

    2017-10-01

    This paper presents a method for expanding horizontal flow variables in data using the free solutions to the shallow-water system as a basis set. This method for equatorial wave expansion of instantaneous flows (EWEIF) uses dynamic constraints in conjunction with projections of data onto parabolic cylinder functions to determine the amplitude of all equatorial waves. EWEIF allows us to decompose an instantaneous wave flow into individual equatorial waves with a presumed equivalent depth without using temporal or spatial filtering a priori. Three sets of EWEIF analyses are presented. The first set is to confirm that EWEIF is capable of recovering the individual waves constructed from theoretical equatorial wave solutions under various scenarios. The other two sets demonstrate the ability of the EWEIF method to derive time series of individual equatorial waves from instantaneous wave fields without knowing a priori exactly which waves exist in the data as well as their spatial and temporal scales using outputs of an equatorial β-channel shallow-water model and ERA-Interim data. The third set of demonstrations shows, for the first time, the continuous evolutions of individual equatorial waves in the stratosphere whose amplitude is synchronized with the background zonal wind as predicted by quasi-biennial oscillation theory.

  19. 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.

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

    Science.gov (United States)

    Simon-Miller, A. A.; Rogers, J. H.; Gierasch, P. J.; Choi, D.; Allison, M. D.; Adamoli, G.; Mettig, H.-J.

    2012-03-01

    Jupiter's south equatorial winds and clouds are consistent with a high frequency, gravity-inertia, wave. A second, westward-moving, Rossby wave was also identified. Asymmetry with the north equatorial clouds are likely due to the Great Red Spot.

  1. E-region echo characteristics governed by auroral arc electrodynamics

    Directory of Open Access Journals (Sweden)

    S. E. Milan

    Full Text Available Observations of a pair of auroral arc features by two imagers, one ground- and one space-based, allows the associated field-aligned current (FAC and electric field structure to be inferred. Simultaneous observations of HF radar echoes provide an insight into the irregularity-generating mechanisms. This is especially interesting for the E-region echoes observed, which form the focus of our analysis, and from which several conclusions can be drawn, summarized as follows. Latitudinal variations in echo characteristics are governed by the FAC and electric field background. Particularly sharp boundaries are found at the edges of auroral arcs. Within regions of auroral luminosity, echoes have Doppler shifts below the ion-acoustic speed and are proportional to the electric field, suggesting scatter from gradient drift waves. Regions of downward FAC are associated with mixed high and low Doppler shift echoes. The high Doppler shift component is greatly in excess of the ion-acoustic speed, but seems to be commensurate with the driving electric field. The low Doppler shift component appears to be much depressed below expectations.

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

  2. Equatorial electrojet in east Brazil longitudes

    Indian Academy of Sciences (India)

    which data were used in the paper. Table 1. Coordinates of stations used: IGRF year September–October 1994. Station name. Belem. Alcantara. Sao Luiz ..... Onwumechili C, Kawasaki A and Akasofu S I 1973 Relation- ship between the equatorial electrojet and polar magnetic variations; Planet. Space. Sci. 21 1–16.

  3. Coccolithophores in the equatorial Atlantic Ocean

    DEFF Research Database (Denmark)

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

    2000-01-01

    The present study was initiated to ascertain the significance of coccolithophores as a proxy for paleoceanographic and paleoproductivity studies in the equatorial Atlantic. Data from a range of different samples, from the plankton, surface sediments as well as sediment cores are shown and compare...

  4. Equatorial Spread F Development/Disruption under Disturbance Electric Fields during Some Recent Intense Magnetic Storms.

    Science.gov (United States)

    Abdu, M. A.; Paula, E. R.; Batista, I. S.; Reinisch, B. W.; Denardini, C. M.; Sobral, J. H.

    2006-05-01

    Equatorial spread F (ESF) and associated plasma bubble irregularity development can be initiated or inhibited under disturbance electric fields associated with magnetic storms. Case studies of ESF intensification/inhibition under intense storm conditions are rare, however. We have addressed this question using the data collected from the Brazilian network of Digisondes, a VHF radar and GPS scintillation receivers, complemented by Digisonde data from Jicamarca and satellite born measurements. Dawn-dusk electric fields penetrating to equatorial latitude in the early phase of a storm event cause disruption of ESF development under a nightside westward electric field, that causes a rapid descent of the F layer. Large intensity prompt penetration electric fields occurring on the evening/post sunset ionosphere cause rapid uplifts of the F layer, and existing ESF patch structures seen by the radar to move to higher altitudes often exceeding the limits of the instruments (>1300 km) so that possible generation of irregularities by disturbance electric fields can only be detected by scintillation receivers. Disturbance dynamo electric fields are found to strongly influence the ESF development, which is inhibited during post sunset hours while subject to intensification during post midnight hours. The possible role of a disturbance trans-equatorial wind in suppressing the ESF generation is also examined

  5. Brazilian Firms

    Directory of Open Access Journals (Sweden)

    Vicente Lima Crisóstomo

    2016-01-01

    Full Text Available This work makes an analysis of the determinants of Corporate Social Responsibility (CSR of Brazilian firms, as proxied by firm membership of the ISE Index of BM&FBOVESPA. Besides other proposed determinants of CSR present in the literature (firm size, profitability, growth opportunities, the work examines ownership concentration and the persistence on CSR status. Logit regression estimates have been run for a sample of 1649 firm-year observations in the period 2006-2011. The findings show that CSR of Brazilian firms is inversely correlated to its ownership concentration indicating that controlling voting shareholders may not see social concerns as a priority. Besides, firms tend to maintain their present CSR status. The results also indicate that leading CSR firms are larger, face more growth opportunities, and are persistent in their superior CSR situation.

  6. Brazilian energy

    Energy Technology Data Exchange (ETDEWEB)

    O`Shaughnessy, H.

    1997-04-01

    Brazilian Energy provides all the information necessary for energy companies to invest and operate in Brazil, including: a review of Brazil`s natural resources; an assessment of privatisation strategies at the federal, state and regional level; an analysis of the electricity industry and the future for Electrobras; an analysis of the oil industry and, in particular, Petrobras; a discussion of the fuel alcohol industry; the discovery of local natural gas, its prospects and the involvement of the auto industry; an assessment of the problems facing the coal industry and its future; a discussion of the regulatory framework for the newly privatised companies; the importance of intra-regional energy links and the booming membership of Mercosur; the difficulties experienced by foreign investors doing business in Brazil; brief profiles of the key energy companies; profiles of key people influencing the privatisation process in Brazil. Brazilian energy is essential reading for those wishing to advise and assist Brazil in this period of change and development, as well as those who wish to invest or become key players in the Brazilian energy sector. (author)

  7. Lithospheric Flexural Modeling of Iapetus' Equatorial Ridge

    Science.gov (United States)

    Zheng, W.; Ip, W.-H.; Teng, L. S.

    2012-04-01

    Iapetus, which is one of Saturn's ball-shaped satellites, has some unique features in the Solar System. This satellite has a mean radius of 735 km, and there is an approximately 20-kilometer-high mountain lying precisely on its equator. The mountain is known as an "equatorial ridge" since it makes Iapetus appear walnut shaped. The origin of the equatorial ridge is attributed to several hypotheses, including different endogenesis and exogenesis processes. In this work, we attempted to construct a flexural model of the equatorial ridge using elastic lithosphere theory. The equatorial ridge is treated as a linear load which exerts uniform force on Iapetus' hard shell (i.e. elastic lithosphere of Iapetus). To calculate the deflection of surface, we use the Digital Terrain Model (DTM) data of Iapetus' leading side published by Giese et al. (2008). Giese et al. also pointed out that the elastic lithospheric thickness of Iapetus must exceed 100 km to support the ridge without deflecting. However, we found possible evidence in the DTM data that implied deflection. There are two sites of surface depression on the northern side of the equatorial ridge. The few-kilometer deflection implies a thinner lithosphere than previous suggested. Assume that the thickness of elastic lithosphere is only 5% below of the radius of Iapetus, so the flat-Earth and one-plate condition could adapt to the flexure model of Iapetus. Based on analysis of the distance between a bulge and the ridge, the calculated lithospheric thickness is 6-10 km. The new result seems controversial, but the modeled surface profile is highly consistent with numerical ridge DTM profile extracted from Giese et al. (2008). Thinner lithosphere also supports the contraction model proposed by Sandwell and Schubert (2010) since the bucking harmonic degree increases. In the other hand, the transformation layer between hard shell and plastic inner core may need constraint on thermal history or crystal form of ice. In

  8. Latitudinal extent of the equatorial anomaly

    Energy Technology Data Exchange (ETDEWEB)

    Klobuchar, J.A.; Anderson, D.N.; Doherty, P.H.

    1990-05-03

    The latitudinal extent of the equatorial anomaly has been studied using a theoretical model of the ionosphere which incorporates measured values of vertical E x B drift at the earth's magnetic equator. Realistic values of neutral winds are also included. The equatorial anomaly region, typically between plus and minus 20 degrees magnetic latitude, is that part of the world where the highest values of electron density and Total Electron Content, (TEC), normally occur, and hence is very important to high frequency propagation and to trans-ionospheric propagation effects. During the daytime, upward E x B drift at the magnetic equator drives the ionization across field lines to higher latitudes, causing crests in ionization to occur at approximately plus and minus 15 deg dip latitude. The latitude range over which the anomaly makes a significant difference in values of foF2 and TEC is calculated as a percent departure from the case with no equatorial electric field. Results from the model studies with different values of realistic electric fields show that the effects of the anomaly can be highly variable and widespread in latitude and local time.

  9. Seasonal Cycle of Cross Equatorial Flow in the Central Equatorial Indian Ocean

    Science.gov (United States)

    McPhaden, Michael; Wang, Yi

    2017-04-01

    This study investigates the seasonal cycle of meridional currents in the upper layers of central equatorial Indian Ocean using acoustic Doppler current profiler (ADCP) data and other data sets along 80.5°E for the period 2004-13. The ADCP data set is the most comprehensive collection of direct velocity measurements in the central Indian Ocean to date, providing new insights into cross equatorial flow in this region. Mean meridional currents are characterized by subsurface divergence between 50-100 m depths with relatively weak convergence above, driven by the annual mean westward pressure gradient force and the surface westerly wind stress respectively. However, in response to a mean northward component of the surface wind stress, the maximum mean surface layer convergence is shifted off the equator to 0.75°N. Evidence is also presented for the existence of a shallow equatorial roll, consisting of a northward wind-driven surface drift overlaying a southward subsurface flow. Cross equatorial transports during boreal summer and winter indicate that a quasi-steady Sverdrup transport balance dominates the seasonal cycle of upper-layer meridional currents. In addition, semi-annually varying westerly monsoon transition winds force Ekman convergence in the surface layer and set up transient zonal pressure gradients that drive seasonally enhanced meridional 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.

  10. Role of the Interannual equatorial Kelvin wave propagations in the equatorial Atlantic on the Angola Benguela current system.

    Science.gov (United States)

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

    2017-04-01

    The link between equatorial Atlantic Ocean variability and the coastal region of Angola and Namibia is investigated at interannual time scales from 1998 to 2012. An index of the equatorial Kelvin wave activity is defined based on equatorial PIRATA in situ data. Results show a significant correlation between monthly dynamic height anomalies derived from the Prediction and Research Moored Array in the Tropical Atlantic (PIRATA), monthly Sea Surface Height anomalies (SSHA) derived from altimetry and SSHA calculated with an Ocean Linear Model. This allows interpreting PIRATA record into equatorial Kelvin wave signal. 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 SSH anomalies shows that they precede by one month extreme interannual SST anomalies along the African coast, suggesting that major warm and cold events in the Angola-Benguela current system are remotely forced by ocean atmosphere interactions in the equatorial Atlantic. Wave dynamics along the equatorial wave guide, as inferred from the Ocean Linear Model, 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 polewards along the African coast triggering extreme warm and cold events respectively. A proxy index based on linear ocean dynamics appears to be significantly more skilful in forecasting coastal variability than an index based on wind variability.

  11. Observed effects in the equatorial and low-latitude ionosphere in the South American and African sectors during the 2012 minor sudden stratospheric warming

    Science.gov (United States)

    de Jesus, R.; Batista, I. S.; de Abreu, A. J.; Fagundes, P. R.; Venkatesh, K.; Denardini, C. M.

    2017-05-01

    In this paper, the effects of a minor sudden stratospheric warming (SSW) event of 2012 in the ionosphere over South American and African sectors have been studied using C/NOFS satellite data and GPS observations. Also, the magnetometer measurements obtained at two stations in the equatorial and low-latitude regions in the South American sector are presented. There were significant Vertical Total Electron Content (VTEC) depletions in the afternoon in both South American and African sectors during the 2012 minor SSW event. A novel feature of the present study is the reduction of the quasi 16-day oscillation (periods ranging from 11 to 20 days) in the daily averaged VTEC in the Brazilian and African sector during an SSW event. Also, the results for the Brazilian sector show an amplification of the 2-6 day period in the daily averaged VTEC at equatorial and low-latitude regions, after the SSW temperature peak. This investigation shows that a minor SSW can affect the irregularities at ionospheric heights in the Brazilian and African sectors. Ground-based magnetometer measurements in the American sector shows strongly enhanced equatorial electrojet (EEJ) after the SSW temperature peak.

  12. Identifying equatorial ionospheric irregularities using in situ ion drifts

    National Research Council Canada - National Science Library

    R. A. Stoneback; R. A. Heelis

    2014-01-01

    Previous climatological investigations of ionospheric irregularity occurrence in the equatorial ionosphere have utilized in situ measurements of plasma density to identify the presence of an irregularity...

  13. Equatorial Oscillations in Jupiter's and Saturn's Atmospheres

    Science.gov (United States)

    Flasar, F. Michael; Guerlet, S.; Fouchet, T.; Schinder, P. J.

    2011-01-01

    Equatorial oscillations in the zonal-mean temperatures and zonal winds have been well documented in Earth's middle atmosphere. A growing body of evidence from ground-based and Cassini spacecraft observations indicates that such phenomena also occur in the stratospheres of Jupiter and Saturn. Earth-based midinfrared measurements spanning several decades have established that the equatorial stratospheric temperatures on Jupiter vary with a cycle of 4-5 years and on Saturn with a cycle of approximately 15 years. Spectra obtained by the Composite Infrared Spectrometer (CIRS) during the Cassini swingby at the end of 2000, with much better vertical resolution than the ground-based data, indicated a series of vertically stacked warm and cold anomalics at Jupiter's equator; a similar structurc was seen at Saturn's equator in CIRS limb measurements made in 2005, in the early phase of Cassini's orbital tour. The thermal wind equation implied similar patterns of mean zonal winds increasing and decreasing with altitude. On Saturn the peak-to-pcak amplitude of this variation was nearly 200 meters per second. The alternating vertical pattern of wanner and colder cquatorial tcmperatures and easterly and westerly tendencies of the zonal winds is seen in Earth's equatorial oscillations, where the pattern descends with time, The Cassini Jupiter and early Saturn observations were snapshots within a limited time interval, and they did not show the temporal evolution of the spatial patterns. However, more recent Saturn observations by CIRS (2010) and Cassini radio-occultation soundings (2009-2010) have provided an opportunity to follow the change of the temperature-zonal wind pattern, and they suggest there is descent, at a rate of roughly one scale height over four years. On Earth, the observed descent in the zonal-mean structure is associated with the absorption of a combination of vertically propagating waves with easlerly and westerly phase velocities. The peak-to-peak zonal wind

  14. 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.

  15. Signatures of 3–6 day planetary waves in the equatorial mesosphere and ionosphere

    Directory of Open Access Journals (Sweden)

    B. R. Clemesha

    2006-12-01

    Full Text Available Common periodic oscillations have been observed in meteor radar measurements of the MLT winds at Cariri (7.4° S, 36.5° W and Ascension Island (7.9° S, 14.4° W and in the minimum ionospheric virtual height, h'F, measured at Fortaleza (3.9° S, 38.4° W in 2004, all located in the near equatorial region. Wavelet analysis of these time series reveals that there are 3–4-day, 6–8-day and 12–16-day oscillations in the zonal winds and h'F. The 3–4 day oscillation appeared as a form of a wave packet from 7–17 August 2004. From the wave characteristics analyzed this might be a 3.5-day Ultra Fast Kelvin wave. The 6-day oscillation in the mesosphere was prominent during the period of August to November. In the ionosphere, however, it was apparent only in November. Spectral analysis suggests that this might be a 6.5-day wave previously identified. The 3.5-day and 6.5-day waves in the ionosphere could have important roles in the initiation of equatorial spread F (plasma bubble. These waves might modulate the post-sunset E×B uplifting of the base of the F-layer via the induced lower thermosphere zonal wind and/or the E-region conductivity.

  16. High altitude large-scale plasma waves in the equatorial electrojet at twilight

    Directory of Open Access Journals (Sweden)

    J. L. Chau

    2004-12-01

    Full Text Available Jicamarca radar observations of a new class of large-scale plasma waves in the equatorial electrojet (EEJ are presented and characterized. The study is based on long-term (204 days, single-baseline interferometry observations made in 2003 using a low-power radar mode, also known as JULIA mode, along with a few hours of observations made in an aperture synthesis imaging mode. The large-scale waves are found to occur at high altitudes in the E-region, mainly between 120 and 140km, around twilight (between 18:30 and 20:00 LT, with durations of a few minutes to an hour. In our long-term observations, these large-scale waves occur very often (between 1 and 5 out 10 nights, drift westward (~70 ms–1, exhibit very narrow spectral widths, and have both positive and negative Doppler shifts. The imaging results show that the large-scale waves occur along tilted bands that sweep westward and downward (~30–60ms–1, with a horizontal separation between bands of about 10–15km. The cause of the waves remains unknown.

    Key words. Ionosphere (ionospheric irregularities; equatorial ionosphere; instruments and techniques

  17. Observational features of equatorial coronal hole jets

    Directory of Open Access Journals (Sweden)

    G. Nisticò

    2010-03-01

    Full Text Available Collimated ejections of plasma called "coronal hole jets" are commonly observed in polar coronal holes. However, such coronal jets are not only a specific features of polar coronal holes but they can also be found in coronal holes appearing at lower heliographic latitudes. In this paper we present some observations of "equatorial coronal hole jets" made up with data provided by the STEREO/SECCHI instruments during a period comprising March 2007 and December 2007. The jet events are selected by requiring at least some visibility in both COR1 and EUVI instruments. We report 15 jet events, and we discuss their main features. For one event, the uplift velocity has been determined as about 200 km s−1, while the deceleration rate appears to be about 0.11 km s−2, less than solar gravity. The average jet visibility time is about 30 min, consistent with jet observed in polar regions. On the basis of the present dataset, we provisionally conclude that there are not substantial physical differences between polar and equatorial coronal hole jets.

  18. Observational features of equatorial coronal hole jets

    Directory of Open Access Journals (Sweden)

    G. Zimbardo

    2010-03-01

    Full Text Available Collimated ejections of plasma called "coronal hole jets" are commonly observed in polar coronal holes. However, such coronal jets are not only a specific features of polar coronal holes but they can also be found in coronal holes appearing at lower heliographic latitudes. In this paper we present some observations of "equatorial coronal hole jets" made up with data provided by the STEREO/SECCHI instruments during a period comprising March 2007 and December 2007. The jet events are selected by requiring at least some visibility in both COR1 and EUVI instruments. We report 15 jet events, and we discuss their main features. For one event, the uplift velocity has been determined as about 200 km s−1, while the deceleration rate appears to be about 0.11 km s−2, less than solar gravity. The average jet visibility time is about 30 min, consistent with jet observed in polar regions. On the basis of the present dataset, we provisionally conclude that there are not substantial physical differences between polar and equatorial coronal hole jets.

  19. 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.

  20. Fading of Jupiter's South Equatorial Belt

    Science.gov (United States)

    Sola, Michael A.; Orton, Glenn; Baines, Kevin; Yanamandra-Fisher, Padma

    2011-01-01

    One of Jupiter's most dominant features, the South Equatorial Belt, has historically gone through a "fading" cycle. The usual dark, brownish clouds turn white, and after a period of time, the region returns to its normal color. Understanding this phenomenon, the latest occurring in 2010, will increase our knowledge of planetary atmospheres. Using the near infrared camera, NSFCAM2, at NASA's Infrared Telescope Facility in Hawaii, images were taken of Jupiter accompanied by data describing the circumstances of each observation. These images are then processed and reduced through an IDL program. By scanning the central meridian of the planet, graphs were produced plotting the average values across the central meridian, which are used to find variations in the region of interest. Calculations using Albert4, a FORTRAN program that calculates the upwelling reflected sunlight from a designated cloud model, can be used to determine the effects of a model atmosphere due to various absorption, scattering, and emission processes. Spectra that were produced show ammonia bands in the South Equatorial Belt. So far, we can deduce from this information that an upwelling of ammonia particles caused a cloud layer to cover up the region. Further investigations using Albert4 and other models will help us to constrain better the chemical make up of the cloud and its location in the atmosphere.

  1. An alternative possibility to equatorial plasma bubble forecasting through mathematical modeling and Digisonde data

    Science.gov (United States)

    Sousasantos, J.; Kherani, E. A.; Sobral, J. H. A.

    2017-02-01

    Equatorial plasma bubbles (EPBs), or large-scale plasma depleted regions, are one of the subjects of great interest in space weather research since such phenomena have been extensively reported to cause strong degrading effects on transionospheric radio propagation at low latitudes, especially over the Brazilian region, where satellite communication interruptions by the EPBs have been, frequently, registered. One of the most difficult tasks for this field of scientific research is the forecasting of such plasma-depleted structures. This forecasting capability would be of significant help for users of positioning/navigation systems operating in the low-latitude/equatorial region all over the world. Recently, some efforts have been made trying to assess and improve the capability of predicting the EPB events. The purpose of this paper is to present an alternative approach to EPB prediction by means of the use of mathematical numerical simulation associated with ionospheric vertical drift, obtained through Digisonde data, focusing on telling beforehand whether ionospheric plasma instability processes will evolve or not into EPB structures. Modulations in the ionospheric vertical motion induced by gravity waves prior to the prereversal enhancement occurrence were used as input in the numerical model. A comparison between the numerical results and the observed EPB phenomena through CCD all-sky image data reveals a considerable coherence and supports the hypothesis of a capability of short-term forecasting.

  2. Sporadic-E associated with the Leonid meteor shower event of November 1998 over low and equatorial latitudes

    Directory of Open Access Journals (Sweden)

    H. Chandra

    2001-01-01

    Full Text Available Rapid radio soundings were made over Ahmedabad, a low latitude station during the period 16–20 November 1998 to study the sporadic-E layer associated with the Leonid shower activity using the KEL Aerospace digital ionosonde. Hourly ionograms for the period 11 November to 24 November were also examined during the years from 1994 to 1998. A distinct increase in sporadic-E layer occurrence is noticed on 17, 18 and 19 November from 1996 to 1998. The diurnal variations  of  f0Es and fbEs also show significantly enhanced values for the morning hours of 18 and 19 November 1998. The ionograms clearly show strong sporadic-E reflections at times of peak shower activity with multiple traces in the altitude range of 100–140 km in few ionograms. Sporadic-E layers with multiple structures in altitude are also seen in some of the ionograms (quarter hourly at Thumba, situated near the magnetic equator. Few of ionograms recorded at Kodaikanal, another equatorial station, also show sporadic- E reflections in spite of the transmitter power being significantly lower. These new results highlighting the effect of intense meteor showers in the equatorial and low latitude E-region are presented.Key words. Ionosphere (equatorial ionosphere – Radio science (ionospheric physics

  3. Sporadic-E associated with the Leonid meteor shower event of November 1998 over low and equatorial latitudes

    Directory of Open Access Journals (Sweden)

    H. Chandra

    Full Text Available Rapid radio soundings were made over Ahmedabad, a low latitude station during the period 16–20 November 1998 to study the sporadic-E layer associated with the Leonid shower activity using the KEL Aerospace digital ionosonde. Hourly ionograms for the period 11 November to 24 November were also examined during the years from 1994 to 1998. A distinct increase in sporadic-E layer occurrence is noticed on 17, 18 and 19 November from 1996 to 1998. The diurnal variations 
    of  f0Es and fbEs also show significantly enhanced values for the morning hours of 18 and 19 November 1998. The ionograms clearly show strong sporadic-E reflections at times of peak shower activity with multiple traces in the altitude range of 100–140 km in few ionograms. Sporadic-E layers with multiple structures in altitude are also seen in some of the ionograms (quarter hourly at Thumba, situated near the magnetic equator. Few of ionograms recorded at Kodaikanal, another equatorial station, also show sporadic- E reflections in spite of the transmitter power being significantly lower. These new results highlighting the effect of intense meteor showers in the equatorial and low latitude E-region are presented.

    Key words. Ionosphere (equatorial ionosphere – Radio science (ionospheric physics

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

    Indian Academy of Sciences (India)

    1998-11-14

    Nov 14, 1998 ... 1979). In addition to the prompt penetration elec- tric fields, there are disturbance dynamo electric fields caused by the disturbed time winds that. Keywords. Equatorial electrojet; equatorial ionosphere; geomagnetic storms. J. Earth Syst. Sci. 125, No. 3, April 2016, pp. 669–675 c Indian Academy of Sciences.

  5. Short Communication: Equatorial electrojet strength in the African ...

    African Journals Online (AJOL)

    H, which is an indicator of the strength of the equatorial eastward electric field at this station, occurs later in the local summer months than during local winter months. ... The results emphasize the importance of solar activity and local seasonal variations on the strength of the equatorial electrojet current and are shown to be ...

  6. Evidence of Late Palaeocene-Early Eocene equatorial rain forest ...

    Indian Academy of Sciences (India)

    2009-11-02

    Nov 2, 2009 ... 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 diversified equatorial rain ...

  7. Variable influence on the equatorial troposphere associated with ...

    Indian Academy of Sciences (India)

    A cooling of the upper troposphere induces enhanced convective activity near the equatorial region of the Southern Hemisphere and suppressed convective activity in the off-equatorial ... Institute for Meteorology, Freie Universit¨at, Berlin, Germany. ... Swedish Meteorological and Hydrological Institute, Norrkoping, Sweden.

  8. Jupiter's Equatorially Antisymmetric Gravitational Field and its Interior Dynamics

    Science.gov (United States)

    Zhang, Keke; Kong, Dali; Schubert, Gerald; Anderson, John D.

    2017-10-01

    The equatorially anti-symmetric gravitational field of Jupiter is nearly unaffected by its rotational distortion and,hence, it provides a direct window into the equatorially anti-symmetric fluid motion taking place in Jupiter's interior.We present a new accurate approach, based on the thermal-gravitational wind equation in spherical geometry(a two-dimensional kernel integral equation with the Green's function in its integrand), for estimating the location/structure/amplitude of the Jovian equatorially antisymmetric zonal flow of Jupiter via its equatorially anti-symmetric gravitational field and understanding the dynamics of Jupiter's deep interior. The mathematical and numerical difficulties in computing the equatorially anti-symmetric gravitational field are discussed.

  9. Dynamics of upwelling annual cycle in the equatorial Atlantic Ocean

    Science.gov (United States)

    Wang, Li-Chiao; Jin, Fei-Fei; Wu, Chau-Ron; Hsu, Huang-Hsiung

    2017-04-01

    The annual upwelling is an important component of the equatorial Atlantic annual cycle. A simple theory is proposed using the framework of Zebiak-Cane (ZC) ocean model for insights into the dynamics of the upwelling annual cycle. It is demonstrated that in the Atlantic equatorial region this upwelling is dominated by Ekman processing in the west, whereas in the east it is primarily owing to shoaling and deepening of the thermocline resulting from equatorial mass meridional recharge/discharge and zonal redistribution processes associated with wind-driven equatorial ocean waves. This wind-driven wave upwelling plays an important role in the development of the annual cycle in the sea surface temperature of the cold tongue in the eastern equatorial Atlantic.

  10. New results on equatorial thermospheric winds and temperatures from Ethiopia, Africa

    Science.gov (United States)

    Tesema, Fasil; Mesquita, Rafael; Meriwether, John; Damtie, Baylie; Nigussie, Melessew; Makela, Jonathan; Fisher, Daniel; Harding, Brian; Yizengaw, Endawoke; Sanders, Samuel

    2017-03-01

    Measurements of equatorial thermospheric winds, temperatures, and 630 nm relative intensities were obtained using an imaging Fabry-Perot interferometer (FPI), which was recently deployed at Bahir Dar University in Ethiopia (11.6° N, 37.4° E, 3.7° N magnetic). The results obtained in this study cover 6 months (53 nights of useable data) between November 2015 and April 2016. The monthly-averaged values, which include local winter and equinox seasons, show the magnitude of the maximum monthly-averaged zonal wind is typically within the range of 70 to 90 ms-1 and is eastward between 19:00 and 21:00 LT. Compared to prior studies of the equatorial thermospheric wind for this local time period, the magnitude is considerably weaker as compared to the maximum zonal wind speed observed in the Peruvian sector but comparable to Brazilian FPI results. During the early evening, the meridional wind speeds are 30 to 50 ms-1 poleward during the winter months and 10 to 25 ms-1 equatorward in the equinox months. The direction of the poleward wind during the winter months is believed to be mainly caused by the existence of the interhemispheric wind flow from the summer to winter hemispheres. An equatorial wind surge is observed later in the evening and is shifted to later local times during the winter months and to earlier local times during the equinox months. Significant night-to-night variations are also observed in the maximum speed of both zonal and meridional winds. The temperature observations show the midnight temperature maximum (MTM) to be generally present between 00:30 and 02:00 LT. The amplitude of the MTM was ˜ 110 K in January 2016 with values smaller than this in the other months. The local time difference between the appearance of the MTM and a pre-midnight equatorial wind was generally 60 to 180 min. A meridional wind reversal was also observed after the appearance of the MTM (after 02:00 LT). Climatological models, HWM14 and MSIS-00, were compared to the

  11. Strong Equatorial Seasonality during Early Eocene greenhouse

    Science.gov (United States)

    Samanta, Arpita; Sarkar, Anindya

    2017-04-01

    A warm greenhouse climate, punctuated by a series of rapid warming events (known as hyperthermals), is characteristic of the Late Paleocene to Early Eocene period. Rapid addition of 13C depleted carbon to the exogenic carbon cycle, in an otherwise overall higher atmospheric CO2 level, is thought to set off the hyperthermal events. For understanding the fate of ongoing global warming and response of the climate system and biota, researchers for past few decades are paying more attention to comprehend this climatic enigma. Existing proxies from the most distinct hyperthermal event i.e., PETM indicate that the mean annual sea surface temperature (MASST) was comparatively higher (by ˜8 ˚ C) at high latitude and to a lesser extent towards the equator. Apart from the prominent hyperthermal events the rest of the Early Eocene was significantly warmer and thought to be more equable compare to present. Terrestrial proxy records from the mid-latitude regions indicated that the Mean Annual Temperature (MAT) and Minimum Winter Temperature (MWT) was high, thus reducing the seasonality or difference between MWT and Maximum Summer Temperature (MST). In absence of proxy data from the low latitude region, a ≥40 ˚ C summer temperature was predicted assuming a mild Eocene temperature gradient of ˜0.4 ˚ C/ ˚ latitude and mid-latitude temperature data. Even question was raised about the existence of the tropical rain forest in such climatic extreme. Recent pollen census data, on contrary, suggest proliferation of the tropical rain forest during this climatic extreme. Important in this context is that there is a very few direct evidence of Late Paleocene-Early Eocene MAT and seasonality data from the low latitude/equatorial regions. To resolve this issue, oxygen and carbon isotope ratios of larger benthic foraminifera (Nummulites burdigalensis) were measured in laser based carbonate device attached with the Delta V advantage continuous flow stable isotope ratio mass spectrometer

  12. Forecasting Ocean Chlorophyll in the Equatorial Pacific

    Directory of Open Access Journals (Sweden)

    Cecile S. Rousseaux

    2017-07-01

    Full Text Available 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 Niño 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 Niño. The anomaly correlation coefficient (ACC was significant (p < 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 μg chl L−1 for the 1-month lead forecast to a maximum of 0.0472 μg chl L−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 μg chl L−1 while the forecast with a 9-month lead time were the furthest (31% or 0.042 μg chl L−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 Niño events on fisheries and other ocean resources given improvements identified in the analysis of these results.

  13. 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.

    Intraseasonal variability in meridional current in the eastern equatorial Indian Ocean is investigated by use of results from a high-resolution ocean general circulation model. Both the simulated and observed meridional current variability...

  14. 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)

  15. Climate Prediction Center Equatorial Southern Oscillation Index (1949-present)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This is one of the CPC?s Monthly Atmospheric and SST Indices. It contains Equatorial Southern Oscillation Index (standardized sea level pressure differences between...

  16. An Investigation of the Ionospheric Disturbances Due to the 2014 Sudden Stratospheric Warming Events Over Brazilian Sector

    Science.gov (United States)

    de Jesus, R.; Batista, I. S.; Jonah, O. F.; de Abreu, A. J.; Fagundes, P. R.; Venkatesh, K.; Denardini, C. M.

    2017-11-01

    The present study investigates the ionospheric F region response in the Brazilian sector due to sudden stratospheric warming (SSW) events of 2014. The data used for this work are obtained from GPS receivers and magnetometer measurements during day of year (DOY) 01 to 120, 2014 at different stations in the equatorial and low-latitude regions in the Brazilian sector. In addition, the data obtained from Communication/Navigation Outage Forecasting System satellites during DOY 01 to 75 of 2014 are used. The main novelty of this research is that, during the 2014 SSW events, daytime vertical total electron content (VTEC) shows a strong increase on the order of about 23% and 11% over the equatorial and low-latitude regions, respectively. We also observed that the nighttime VTEC (SSW days) is increased by 8% and 33% over equatorial and low-latitude regions, respectively. The magnetometer measurements show a strong counterelectrojet during the SSW days. The results show an amplification of the 0.5 day and 2-16 day periods in the VTEC and equatorial electrojet during the SSWs. The occurrences of ionospheric irregularities during the SSW events are around 84% and 53% in the equatorial and low-latitude regions, respectively, which is less frequent when compared with those during the pre-SSW periods.

  17. Forecasting scintillation activity and equatorial spread F

    Science.gov (United States)

    Anderson, David N.; Redmon, Robert J.

    2017-03-01

    When transionospheric radio waves propagate through an irregular ionosphere with plasma depletions or "bubbles," they are subject to sporadic enhancement and fading, which is referred to as scintillation. Communication and navigation systems may be subject to these detrimental effects if the scintillation is strong enough. It is critical to have knowledge of the current ionospheric conditions so that system operators can distinguish between the natural radio environment and system-induced failures. In this paper we briefly describe the Forecasting Ionospheric Real-time Scintillation Tool UHF scintillation forecasting technique, which utilizes the observed characteristic parameter h'F from a ground-based, ionospheric sounder near the magnetic equator. The prereversal enhancement in vertical E × B drift velocity after sunset is the prime driver for creating plasma depletions and bubbles. In addition, there exists a "threshold" in the h'F value at 1930 LT, h'Fthr, such that, on any given evening, if h'F is significantly above h'Fthr, then scintillation activity is likely to occur, and if it is below h'Fthr, scintillation activity is unlikely to occur. We use this technique to explain the lack of scintillation activity prior to the Halloween storm in October 2003 in the Peruvian longitude sector. In addition, we have carried out a study which forecasts the occurrence or nonoccurrence of equatorial spread F (ESF), on a night-to-night basis, in five longitude sectors. The overall forecasting success is greater than 80% for each of the five longitude sectors.

  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

    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. On Irrotational Flows Beneath Periodic Traveling Equatorial Waves

    Science.gov (United States)

    Quirchmayr, Ronald

    2017-06-01

    We discuss some aspects of the velocity field and particle trajectories beneath periodic traveling equatorial surface waves over a flat bed in a flow with uniform underlying currents. The system under study consists of the governing equations for equatorial ocean waves within a non-inertial frame of reference, where Euler's equation of motion has to be suitably adjusted, in order to account for the influence of the earth's rotation.

  20. 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.

  1. A classification of spectral populations observed in HF radar backscatter from the E region auroral electrojets

    Directory of Open Access Journals (Sweden)

    S. E. Milan

    Full Text Available Observations of HF radar backscatter from the auroral electrojet E region indicate the presence of five major spectral populations, as opposed to the two predominant spectral populations, types I and II, observed in the VHF regime. The Doppler shift, spectral width, backscatter power, and flow angle dependencies of these five populations are investigated and described. Two of these populations are identified with type I and type II spectral classes, and hence, are thought to be generated by the two-stream and gradient drift instabilities, respectively. The remaining three populations occur over a range of velocities which can greatly exceed the ion acoustic speed, the usual limiting velocity in VHF radar observations of the E region. The generation of these spectral populations is discussed in terms of electron density gradients in the electrojet region and recent non-linear theories of E region irregularity generation.

    Key words. Ionosphere (ionospheric irregularities

  2. A classification of spectral populations observed in HF radar backscatter from the E region auroral electrojets

    Directory of Open Access Journals (Sweden)

    S. E. Milan

    2001-02-01

    Full Text Available Observations of HF radar backscatter from the auroral electrojet E region indicate the presence of five major spectral populations, as opposed to the two predominant spectral populations, types I and II, observed in the VHF regime. The Doppler shift, spectral width, backscatter power, and flow angle dependencies of these five populations are investigated and described. Two of these populations are identified with type I and type II spectral classes, and hence, are thought to be generated by the two-stream and gradient drift instabilities, respectively. The remaining three populations occur over a range of velocities which can greatly exceed the ion acoustic speed, the usual limiting velocity in VHF radar observations of the E region. The generation of these spectral populations is discussed in terms of electron density gradients in the electrojet region and recent non-linear theories of E region irregularity generation.Key words. Ionosphere (ionospheric irregularities

  3. Brazilian antidoping public policy.

    Science.gov (United States)

    Almeida, Claudio Bispo de; Rodrigues, Deyvis Nascimento

    2014-07-01

    Doping, used to improve sports performance, is legally prohibited. This paper describes Brazilian regulations, resolutions, and Federal laws addressing the issue of doping and antidoping which were collected in 2012 from official websites. We conclude that Brazilian laws have constrained doping, and have been updated over the years to conform to worldwide legal guidelines. Study limitations are noted.

  4. Tiger sharks can connect equatorial habitats and fisheries across the Atlantic Ocean basin.

    Science.gov (United States)

    Afonso, André S; Garla, Ricardo; Hazin, Fábio H V

    2017-01-01

    Increasing our knowledge about the spatial ecology of apex predators and their interactions with diverse habitats and fisheries is necessary for understanding the trophic mechanisms that underlie several aspects of marine ecosystem dynamics and for guiding informed management policies. A preliminary assessment of tiger shark (Galeocerdo cuvier) population structure off the oceanic insular system of Fernando de Noronha (FEN) and the large-scale movements performed by this species in the equatorial Atlantic Ocean was conducted using longline and handline fishing gear and satellite telemetry. A total of 25 sharks measuring 175-372 cm in total length (TL) were sampled. Most sharks were likely immature females ranging between 200 and 260 cm TL, with few individuals shark size-distribution previously reported for coastal waters off the Brazilian mainland, where most individuals measured shark-1; SD = 65.6). These sharks exhibited a considerable variability in their horizontal movements, with three sharks showing a mostly resident behavior around FEN during the extent of the respective tracks, two sharks traveling west to the South American continent, and two sharks moving mostly along the middle of the oceanic basin, one of which ending up in the northern hemisphere. Moreover, one shark traveled east to the African continent, where it was eventually caught by fishers from Ivory Coast in less than 474 days at liberty. The present results suggest that young tiger sharks measuring sharks are able to connect marine trophic webs from the neritic provinces of the eastern and western margins of the Atlantic Ocean across the equatorial basin and that they may experience mortality induced by remote fisheries. All this information is extremely relevant for understanding the energetic balance of marine ecosystems as much as the exposure of this species to fishing pressure in this yet poorly-known region.

  5. Ionospheric storm effects in the nighttime E region caused by neutralized ring current particles

    Directory of Open Access Journals (Sweden)

    R. Bauske

    1997-03-01

    Full Text Available During magnetic storms an anomalous increase in the ionization density of the nighttime E region is observed at low and middle latitudes. It has been suggested that this effect is caused by the precipitation of neutralized ring current particles. Here a coupled ring current decay-ionosphere model is used to confirm the validity of this explanation.

  6. Late Paleozoic Deglaciation in Western Equatorial Pangaea

    Science.gov (United States)

    Soreghan, G. S.; Soreghan, M. J.; Eble, C. F.; Sweet, D.; Davogustto, O.; Young, R. A.; Elmore, R. D.

    2005-12-01

    The late Paleozoic icehouse is Earth's best-documented pre-Quaternary icehouse, long thought analogous to our modern world wherein glaciation is confined largely to high-latitude regions. However, emerging data from the Ancestral Rocky Mountains, an intraplate orogenic system in western equatorial Pangaea, indicate that glaciation extended to low latitudes as well. Key data exist in the Uncompahgre-uplift - Paradox basin system (western U.S.) in the form of a preserved Permo-Pennsylvanian glacial valley (ancestral Unaweep Canyon) and associated glacial and proglacial strata (proximal Cutler Formation). Within western Colorado, Unaweep Canyon is a deep, enigmatic, Precambrian-cored gorge that orthogonally bisects the western Uncompahgre Plateau, and is occupied by two underfit creeks flowing from a divide in its midst. A Cenozoic origin for the canyon is difficult to reconcile with geologic data; limited outcrop and well data confirm the canyon harbors a thick fill that includes a basal unit of probable late Paleozoic age as inferred by palynomorph, provenance, and preliminary paleomagnetic data. Geomorphologic attributes of the gorge walls together with preliminary results of cross-canyon gravity profiles indicate the canyon shape is best explained by a glacial genesis. Furthermore, the Permo-Pennsylvanian Cutler Formation onlaps Precambrian basement at the western mouth of the gorge, and contains facies of inferred proglacial (glaciolacustrine and glaciofluvial) origin, including (1) subaqueous sediment gravity flows, dropstones, and large slump blocks of an ice-contact Gilbert-type lacustrine delta, and (2) large-scale, laterally extensive cross-bedded conglomerates that record high-magnitude, outburst-type floods typical of deglaciation. The Cutler facies represent the proximal part of a system that ultimately extended to sea level in the distal Paradox basin. Maximum reasonable depositional gradients on this system yield maximum elevations of 500-1000 m for the

  7. Mesopelagic fishes across the tropical and equatorial Atlantic: Biogeographical and vertical patterns

    Science.gov (United States)

    Olivar, M. Pilar; Hulley, P. Alexander; Castellón, Arturo; Emelianov, Mikhail; López, Cristina; Tuset, Víctor M.; Contreras, Tabit; Molí, Balbina

    2017-02-01

    In this investigation we analysed the changes in fish species occurrences and relative abundances across the tropical and equatorial Atlantic, and their vertical distribution patterns in relation to the different environmental scenarios. The study covers a wide region encompassing different water masses, and marked differences in productivity, from an oligotrophic zone close to the Brazilian coast, to a very productive upwelling region close to the Northwest African upwelling. Fishes were collected with a medium-sized midwater trawl (Mesopelagos), complemented by hauls made with a macrozooplankton net (MOCNESS). Species richness in the region was higher than in subtropical, temperate and cold regions. The total number of species and their overall abundance was lower in the stations closer to the Brazilian coast. Abundant species across the entire region were the gonostomatids Cyclothone alba, Cyclothone acclinidens, Cyclothone pallida and Cyclothone pseudopallida, the myctophid Lampanyctus alatus, the sternoptychid Sternoptyx diaphana, and the phosichthyid Vinciguerria nimbaria. The occurrences and abundances of C. parapallida, Lampanyctus nobilis and Lepidophanes guentheri were related to zones where AAIW waters occupied the mesopelagic layers, while other species such as Cyclothone livida and Polyipnus polli increased their abundance when AAIW disappears from their living depths. The presence of Eastern North Atlantic Central Water (ENACW) was associated with the occurrence of several myctophids (Benthosema glaciale, Ceratoscopelus maderensis, Diaphus holti, Diaphus rafinesquii, Hygophum hygomii, Lampanyctus crocodilus, Myctophum punctatum, Symbolophorus veranyi), and the gonostomatid Cyclothone braueri. In spite of the important differences in hydrographic features across the tropical and equatorial Atlantic, all stations showed either the general night migration into the epipelagic layers carried out by myctophids, phosicthyids, and some stomiids, or the

  8. 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.

  9. 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.

  10. 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.

  11. Gravity Wave-Induced Ionospheric Irregularities in the Postsunset Equatorial Valley Region

    Science.gov (United States)

    Hysell, D. L.; Fritts, D. C.; Laughman, B.; Chau, J. L.

    2017-11-01

    Plasma irregularities in the postsunset equatorial valley region ionosphere are investigated experimentally and through numerical simulation. Coherent radar backscatter observed at the Jicamarca Radio Observatory shows two classes of irregularities in different altitude bands—one mainly below about 125 km and the other mainly above. Irregularities in both bands are organized into wavefronts with wavelengths of a few kilometers. However, only the irregularities in the high-altitude band exhibit consistent propagation speeds and directions. Some previous observations of irregularities in the nighttime electrojet suggest that gravity waves may sometimes influence their morphology. The possibility that the valley region irregularities are also related to gravity waves (GWs) is therefore investigated numerically. A model of a GW packet propagating through a tidal wind field is used to drive another model which predicts the resulting ionospheric electrodynamics. The combined simulation shows that GWs can induce field-aligned currents and excite resistive drift waves which could be responsible for the valley region irregularities in the high-altitude band. The GWs also induce irregularities in the upper E region directly through simple dynamo action which subsequently deform under the influence of shear flow. This may explain the irregularities in the low-altitude band.

  12. Propagation and dispersion of electrostatic waves in the ionospheric E region

    Directory of Open Access Journals (Sweden)

    K. Iranpour

    1997-07-01

    Full Text Available Low-frequency electrostatic fluctuations in the ionospheric E region were detected by instruments on the ROSE rockets. The phase velocity and dispersion of plasma waves in the ionospheric E region are determined by band-pass filtering and cross-correlating data of the electric-field fluctuations detected by the probes on the ROSE F4 rocket. The results were confirmed by a different method of analysis of the same data. The results show that the waves propagate in the Hall-current direction with a velocity somewhat below the ion sound speed obtained for ionospheric conditions during the flight. It is also found that the waves are dispersive, with the longest wavelengths propagating with the lowest velocity.

  13. Wind observations by the E-Region Wind Interferometer, ERWIN-2 at Eureka

    Science.gov (United States)

    Kristoffersen, S.; Brown, S.; Ward, W. E.

    2009-05-01

    The E-region wind interferometer, ERWIN, was refurbished and moved from Resolute Bay to the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka (80N) in the winter of 2008. ERWIN is a field widened Michelson interferometer which measures winds in the E-region using Doppler shifts in hydroxyl, oxygen green line and O2 airglow emssions. The referbished instrument is constructed around the old interferometer and includes imaging capabilities using a CCD detector and an optical system which allows simultaneous viewing in four directions and zenith. The instrument operates by seqentially viewing the three emissions. The observation cadence for the three emissions is ~2 minutes making this the fastest wind measuring instrument in the world for the mesopause region. An overview of the instrument operation and results from the first year of observations (including winds during stratospheric warmings) are presented.

  14. Propagation and dispersion of electrostatic waves in the ionospheric E region

    Directory of Open Access Journals (Sweden)

    K. Iranpour

    Full Text Available Low-frequency electrostatic fluctuations in the ionospheric E region were detected by instruments on the ROSE rockets. The phase velocity and dispersion of plasma waves in the ionospheric E region are determined by band-pass filtering and cross-correlating data of the electric-field fluctuations detected by the probes on the ROSE F4 rocket. The results were confirmed by a different method of analysis of the same data. The results show that the waves propagate in the Hall-current direction with a velocity somewhat below the ion sound speed obtained for ionospheric conditions during the flight. It is also found that the waves are dispersive, with the longest wavelengths propagating with the lowest velocity.

  15. High Frequency Backscatter from the Polar and Auroral E-Region Ionosphere

    Science.gov (United States)

    Forsythe, Victoriya V.

    The Earth's ionosphere contains collisional and partially-ionized plasma. The electric field, produced by the interaction between the Earth's magnetosphere and the solar wind, drives the plasma bulk motion, also known as convection, in the F-region of the ionosphere. It can also destabilize the plasma in the E-region, producing irregularities or waves. Intermediate-scale waves with wavelengths of hundreds of meters can cause scintillation and fading of the Global Navigation Satellite System (GNSS) signals, whereas the small-scale waves (lambda tilted E-layer, the height and aspect angle conditions are more important. Finally, the fundamental dependence of the E-region irregularity phase velocity on the component of the plasma convection is investigated using two new SuperDARN radars at high southern latitudes where plasma convection estimates are accurately deduced from all SuperDARN radars in the southern hemisphere. Statistical analysis is presented showing that the predominance of the E-region echoes of a particular polarity is strongly dictated by the orientation of the convection plasma flow which itself has a significant asymmetry towards westward zonal flow.

  16. Investigation of the relationship between optical auroral forms and HF radar E region backscatter

    Directory of Open Access Journals (Sweden)

    S. E. Milan

    2000-06-01

    Full Text Available The SuperDARN HF radars have been employed in the past to investigate the spectral characteristics of coherent backscatter from L-shell aligned features in the auroral E region. The present study employs all-sky camera observations of the aurora from Husafell, Iceland, and the two SuperDARN radars located on Iceland, Þykkvibær and Stokkseyri, to determine the optical signature of such backscatter features. It is shown that, especially during quiet geomagnetic conditions, the backscatter region is closely associated with east-west aligned diffuse auroral features, and that the two move in tandem with each other. This association between optical and radar aurora has repercussions for the instability mechanisms responsible for generating the E region irregularities from which radars scatter. This is discussed and compared with previous studies investigating the relationship between optical and VHF radar aurora. In addition, although it is known that E region backscatter is commonly observed by SuperDARN radars, the present study demonstrates for the first time that multiple radars can observe the same feature to extend over at least 3 h of magnetic local time, allowing precipitation features to be mapped over large portions of the auroral zone.Key words: Ionosphere (particle precipitation; plasma waves and instabilities

  17. Brazilian Consensus on Photoprotection

    Science.gov (United States)

    Schalka, Sérgio; Steiner, Denise; Ravelli, Flávia Naranjo; Steiner, Tatiana; Terena, Aripuanã Cobério; Marçon, Carolina Reato; Ayres, Eloisa Leis; Addor, Flávia Alvim Sant'anna; Miot, Helio Amante; Ponzio, Humberto; Duarte, Ida; Neffá, Jane; da Cunha, José Antônio Jabur; Boza, Juliana Catucci; Samorano, Luciana de Paula; Corrêa, Marcelo de Paula; Maia, Marcus; Nasser, Nilton; Leite, Olga Maria Rodrigues Ribeiro; Lopes, Otávio Sergio; Oliveira, Pedro Dantas; Meyer, Renata Leal Bregunci; Cestari, Tânia; dos Reis, Vitor Manoel Silva; Rego, Vitória Regina Pedreira de Almeida

    2014-01-01

    Brazil is a country of continental dimensions with a large heterogeneity of climates and massive mixing of the population. Almost the entire national territory is located between the Equator and the Tropic of Capricorn, and the Earth axial tilt to the south certainly makes Brazil one of the countries of the world with greater extent of land in proximity to the sun. The Brazilian coastline, where most of its population lives, is more than 8,500 km long. Due to geographic characteristics and cultural trends, Brazilians are among the peoples with the highest annual exposure to the sun. Epidemiological data show a continuing increase in the incidence of non-melanoma and melanoma skin cancers. Photoprotection can be understood as a set of measures aimed at reducing sun exposure and at preventing the development of acute and chronic actinic damage. Due to the peculiarities of Brazilian territory and culture, it would not be advisable to replicate the concepts of photoprotection from other developed countries, places with completely different climates and populations. Thus the Brazilian Society of Dermatology has developed the Brazilian Consensus on Photoprotection, the first official document on photoprotection developed in Brazil for Brazilians, with recommendations on matters involving photoprotection. PMID:25761256

  18. 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.

    brings nutrient-rich subsurface waters to the euphotic zone, thus the ocean currents supports perinnial phytoplankton bloom. The phytoplankton inhibits downward solar radiation penetration in the equatorial Pacific, resulting in cross equatorial density...

  19. Mesoscale model simulation of low level equatorial winds over ...

    Indian Academy of Sciences (India)

    The large-scale vegetation fires instigated by the local farmers during the dry period of the major El Ni˜no event in 1997 can be considered as one of the worst environmental disasters that have occurred in southeast Asia in recent history. This study investigated the local meteorology characteristics of an equatorial ...

  20. Trans-Equatorial High Frequency Link Between Mauritius And Europe

    African Journals Online (AJOL)

    Although these effects occur more severely in the trans-equatorial path, little data exists that provides information on the size and rate at which they occur over these paths. An opportunity has arisen to set up a transequatorial HF link between Europe and Mauritius. In this paper, the initial purpose of setting up this link, the ...

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

    NARCIS (Netherlands)

    Werf, van der G.R.; Dempewolf, J.; Trigg, S.N.; Randerson, J.T.; Peters, W.

    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

  2. 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.; de Fries, 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

  3. 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...

  4. equatorial electrojet strength in the african sector during high and ...

    African Journals Online (AJOL)

    Preferred Customer

    Department of Geology and Geophysics, Faculty of Science, Addis Ababa University. PO Box 1176, Addis Ababa, Ethiopia, E-mail: hbeimnet@hotmail.com. ABSTRACT: The daily ..... Printing Press, Addis Ababa, Ethiopia. 2. Chandra, H., Sinha, H.S.S. and Rastogi, R.G. (2000). Equatorial electrojet studies from rocket and.

  5. Page 1 SOME REMARKS ON THE EQUATORIAL SPORADIC E ...

    Indian Academy of Sciences (India)

    MATSUSHITA (1951) had found that both the latitudinal variations of maximum frequency (FE.) reflected from the Es layer and the solar daily range of geomagnetic H field show a sharp maximum over the magnetic equator, and thus a close association between equatorial Es and the electro- jet currents was suggested.

  6. Variable influence on the equatorial troposphere associated with ...

    Indian Academy of Sciences (India)

    1Institute for Meteorology, Freie Universität, Berlin, Germany. 2Swedish Meteorological and Hydrological Institute, Norrkoping, Sweden. 3German Weather Service, Offenbach am ... rial region of the Southern Hemisphere and suppressed convective activity in the off-equatorial Northern. Hemisphere. After selecting vortex ...

  7. equatorial electrojet strength in the african sector during high and ...

    African Journals Online (AJOL)

    Preferred Customer

    current system magnifying the solar quiet daily variations (Sq), the lunar quiet day variations and solar flare effects. This high concentration of electric current flowing from west to east in a narrow belt flanking the dip equator on the sunward hemisphere has been termed the equatorial electrojet. The overhead current system.

  8. 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.

    propagating biweekly waves with zonal wavelength in the range 2100 to 6100 km. An ocean model forced by high-resolution scatterometer wind stress is used to show that the observed biweekly variability is due to equatorially trapped mixed Rossby-gravity waves...

  9. Variability Of Plasma Bubble In The Equatorial Ionosphere At Midnight

    African Journals Online (AJOL)

    There are various types of ionospheric irregularities. Among these is the plasma bubble occurrence. They are most prominent at night time in the equatorial ionosphere. Many of the bubbles drift with approximately the velocity of the background plasma, but it is possible to infer that most bubbles have moved upward at some ...

  10. Different Strokes: Spanish Policy toward Cuba and Equatorial ...

    African Journals Online (AJOL)

    Spanish policy toward Cuba and Equatorial Guinea up to the end of the 19th century differed markedly. The policy itself is difficult to define but the general principle emphasized the exploitation of the resources of the colonies for the benefit of Spain. It also provided for the spread of Spanish culture and the Christian faith.

  11. Zonal structure and seasonal variability of the Atlantic Equatorial Undercurrent

    NARCIS (Netherlands)

    Johns, William E.; Brandt, Peter; Bourlès, Bernard; Tantet, Alexis; Papapostolou, A.; Houk, A.

    2014-01-01

    Simultaneous mooring arrays were maintained along the path of the Equatorial Undercurrent (EUC) at three longitudes (23?W, 10?W, and 0?E), from October 2007 to June 2011, as part of the CLIVAR Tropical Atlantic Climate Experiment. The measurements allow for the first time a description of the

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

    Indian Academy of Sciences (India)

    by equatorial Kelvin waves observed over the Galapagos;. Geophys. Res. Lett. 28 3143–3146. Holton J R and Lindzen R S 1972 An updated theory for the quasi-biennial oscillation; J. Atmos. Sci. 29 1076–. 1080. Holton J R, Alexander M J and Boehm M T 2001 Evi- dence for short vertical wavelength Kelvin waves in.

  13. Lidar Observation of Ozone Profiles in the Equatorial Tropopause Region

    Science.gov (United States)

    Abo, M.; Shibata, Y.; Nagasawa, C.

    2014-12-01

    Tropospheric ozone in the tropics zone is significant in terms of the oxidizing efficiency and greenhouse effect. However, in the upper troposphere, the ozone budget in the tropics has not been fully understood yet because of the sparsity of the range-resolved observations of vertical ozone concentration profiles. We have constructed the lidar facility for survey of atmospheric structure over troposphere, stratosphere, mesosphere and low thermosphere over Kototabang (100.3E, 0.2S), Indonesia in the equatorial region. The lidar system consists of the Mie and Raman lidars for tropospheric aerosol, water vapor and cirrus cloud measurements, the Rayleigh lidar for stratospheric and mesospheric temperature measurements and the Resonance lidar for metallic species such as Na, Fe, Ca ion measurements and temperature measurements in the mesopause region. The lidar observations started from 2004, and routine observations of clouds and aerosol in the troposphere and stratosphere are continued now. We have installed DIAL (differential absorption lidar) system for high-resolution measurements of vertical ozone profiles in the equatorial tropopause region over Kototabang. There were many ozone DIAL systems in the world, but their systems are almost optimized for stratospheric ozone layer measurement or tropospheric ozone measurement. Because of deep ozone absorption in the UV region, the wavelength selection is important. Over the equatorial region, the tropopause height is almost 17km. So we use 305nm for on-line and 355nm for off-line using second harmonics of dye laser and third harmonics of Nd:YAG laser. We have observed large ozone enhancement in the upper troposphere, altitude of 13-17km in June 2014, concurring with a zonal wind oscillation associated with the equatorial Kelvin wave around the tropopause[1] at equatorial region. References Fujiwara, M. et al., JGR, 103, D15, 19,173-19,182, 1998.

  14. New results on equatorial thermospheric winds and temperatures from Ethiopia, Africa

    Directory of Open Access Journals (Sweden)

    F. Tesema

    2017-03-01

    Full Text Available Measurements of equatorial thermospheric winds, temperatures, and 630 nm relative intensities were obtained using an imaging Fabry–Perot interferometer (FPI, which was recently deployed at Bahir Dar University in Ethiopia (11.6° N, 37.4° E, 3.7° N magnetic. The results obtained in this study cover 6 months (53 nights of useable data between November 2015 and April 2016. The monthly-averaged values, which include local winter and equinox seasons, show the magnitude of the maximum monthly-averaged zonal wind is typically within the range of 70 to 90 ms−1 and is eastward between 19:00 and 21:00 LT. Compared to prior studies of the equatorial thermospheric wind for this local time period, the magnitude is considerably weaker as compared to the maximum zonal wind speed observed in the Peruvian sector but comparable to Brazilian FPI results. During the early evening, the meridional wind speeds are 30 to 50 ms−1 poleward during the winter months and 10 to 25 ms−1 equatorward in the equinox months. The direction of the poleward wind during the winter months is believed to be mainly caused by the existence of the interhemispheric wind flow from the summer to winter hemispheres. An equatorial wind surge is observed later in the evening and is shifted to later local times during the winter months and to earlier local times during the equinox months. Significant night-to-night variations are also observed in the maximum speed of both zonal and meridional winds. The temperature observations show the midnight temperature maximum (MTM to be generally present between 00:30 and 02:00 LT. The amplitude of the MTM was  ∼  110 K in January 2016 with values smaller than this in the other months. The local time difference between the appearance of the MTM and a pre-midnight equatorial wind was generally 60 to 180 min. A meridional wind reversal was also observed after the appearance of the MTM (after 02:00 LT. Climatological

  15. 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

    Science.gov (United States)

    Sridharan, R.; Devasia, C. V.; Jyoti, N.; Tiwari, Diwakar; Viswanathan, K. S.; Subbarao, K. S. V.

    2002-12-01

    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.

  16. Indigenous Brazilian Management Practices

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    Zandra Balbinot

    2012-12-01

    Full Text Available The present research seeks to understand to what extent companies in emerging countries, specifically, Brazilian, adopt dominant management practices, the so-called Euro-American practices, possess their one, or show a syncretism between the two. Methods: Mixed research. One phase was to collect data using a survey about cultural dimensions adopted from GLOBE (House 1998 management practices and also from Brazilian academy. Another was to collect data through interviews, which were analyzed in parallel. Results: Of the seven dominant cultural dimensions, indigenous practices influenced two. Another three were influenced by dominant management practices. Two of the local dimensions, even with internationalization, merged practices with Brazilian cultural traits. Even so, the practices derived from Jeitinho diminished relative to the international relations and experience of managers. Conclusions: The paper shows the existence of powerful Brazilian Indigenous Managerial Practices such as personalism and formalism. These practices have great influence on international business negotiations. On the other hand, it also shows that there are still dominant managerial practices specially in the case of more internationalized Brazilian managers

  17. Nonlinear wave structures in collisional plasma of auroral E-region ionosphere

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    A. V. Volosevich

    1997-07-01

    Full Text Available Studies of the auroral plasma with small-scale inhomogenieties producing the VHF-radar reflections (radar aurora when observed in conditions of the saturated Farley-Buneman instability within the auroral E region, show strong nonlinear interactions and density fluctuations of 5–15%. Such nonlinearity and high fluctation amplitudes are inconsistent with the limitations of the weak turbulence theory, and thus a theory for arbitrary amplitudes is needed. To this end, a nonlinear theory is described for electrostatic MHD moving plasma structures of arbitrary amplitude for conditions throughout the altitude range of the collisional auroral E region. The equations are derived, from electron and ion motion self-consistent with the electric field, for the general case of the one-dimensional problem. They take into account nonlinearity, electron and ion inertia, diffusion, deviation from quasi-neutrality, and dynamical ion viscosity. The importance of the ion viscosity for dispersion is stressed, while deviation from the quasi-neutrality can be important only at rather low plasma densities, not typical for the auroral E region. In a small amplitude limit these equations have classical nonlinear solutions of the type of "electrostatic shock wave" or of knoidal waves. In a particular case these knoidal waves degrade to a dissipative soliton. A two-dimensional case of a quasi-neutral plasma is considered in the plane perpendicular to the magnetic field by way of the Poisson brackets, but neglecting the nonlinearity and ion inertia. It is shown that in these conditions an effective saturation can be achieved at the stationary turbulence level of order of 10%.

  18. Nonlinear wave structures in collisional plasma of auroral E-region ionosphere

    Directory of Open Access Journals (Sweden)

    A. V. Volosevich

    Full Text Available Studies of the auroral plasma with small-scale inhomogenieties producing the VHF-radar reflections (radar aurora when observed in conditions of the saturated Farley-Buneman instability within the auroral E region, show strong nonlinear interactions and density fluctuations of 5–15%. Such nonlinearity and high fluctation amplitudes are inconsistent with the limitations of the weak turbulence theory, and thus a theory for arbitrary amplitudes is needed. To this end, a nonlinear theory is described for electrostatic MHD moving plasma structures of arbitrary amplitude for conditions throughout the altitude range of the collisional auroral E region. The equations are derived, from electron and ion motion self-consistent with the electric field, for the general case of the one-dimensional problem. They take into account nonlinearity, electron and ion inertia, diffusion, deviation from quasi-neutrality, and dynamical ion viscosity. The importance of the ion viscosity for dispersion is stressed, while deviation from the quasi-neutrality can be important only at rather low plasma densities, not typical for the auroral E region. In a small amplitude limit these equations have classical nonlinear solutions of the type of "electrostatic shock wave" or of knoidal waves. In a particular case these knoidal waves degrade to a dissipative soliton. A two-dimensional case of a quasi-neutral plasma is considered in the plane perpendicular to the magnetic field by way of the Poisson brackets, but neglecting the nonlinearity and ion inertia. It is shown that in these conditions an effective saturation can be achieved at the stationary turbulence level of order of 10%.

  19. Rocket-borne wave, field, and plasma observations in unstable polar cap E-region

    Science.gov (United States)

    Olesen, J. K.; Primdahl, F.; Spangslev, F.; Ungstrup, E.; Bahnsen, A.; Fahleson, U.; Falthammar, C.-G.; Pedersen, A.

    1976-01-01

    This paper presents initial results from the first comprehensively instrumented rocket flown through a Farley-unstable polar cap E-region. Ground-based ionosondes and magnetometers at two locations and HF radar backscatter at the launch site were used to determine the presence of a geographically widespread ionospheric plasma instability. The observed wave direction, electric field, and current density fit the predictions of the linear theory of the Farley instability, whereas the gradient-drift instability seems to be excluded by the geometry of the observations.

  20. Radar backscatter from plasma irregularities of the lower E region induced by neutral turbulence

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    K. Schlegel

    Full Text Available Recently, one of the authors (A. V. G. developed a theory of low-frequency plasma irregularities which are created as a consequence of neutral turbulence in the D and lower E regions. In the following this theory will be applied to coherent backscatter experiments with radars in a frequency range between 5 and 150 MHz. We discuss the dependence of the backscatter cross-section on ionospheric as well as on turbulence parameters. The backscatter increases strongly with decreasing radar frequency. Above 15 MHz the effects discussed here can probably only be detected by very powerful radars with large antenna arrays.

  1. Jupiter's South Equatorial Jet: Speed variations with and without the South Equatorial Disturbance

    Science.gov (United States)

    Adamoli, G.; Mettig, H.-J.; Jacquesson, M.; Vedovato, M.; Rogers, J. H.

    2011-10-01

    Amateur observers are now producing frequent highquality images of Jupiter to give a near-continuous record of its weather systems, with sufficient resolution to record zonal wind profiles in many regions. As an example of the level of detail now obtainable from amateur imaging and analysis, we show recent results on the diverse speeds within the jet at 7ºS (SEBn), and their modulation by the South Equatorial Disturbance (SED). The SED is a largescale wave in the jet [ref.1]. From analysis of amateur images, we have previously shown that there are substantial longitudinal variations in the peak speed, as traced by the motions of the small chevronshaped features on the SEBn edge [ref.2]. When the SED is present and conspicuous, the speed of the jet is markedly reduced east of the SED and sometimes, to a variable extent, at all longitudes. When the SED is absent or inconspicuous, the maximum jet speed is observed all around the planet, but some individual features move more slowly over shorter intervals. Here we present new data which confirms these phenomena at higher resolution and provides some insight into the underlying dynamics. In 2008, the SED was prominent, and the speed gradient to its east was clearly demonstrated by numerous chevrons; many of them were seen to accelerate. In 2010, the SED disappeared as the SEB whitened, and the alternative regime was observed: there were longlived bands of disturbance moving with the peak jet speed, and many individual spots moving with the same speed, but many others were moving more slowly. Characteristics of the slower spots suggested that they were partially detached from the regular array of chevrons in the jet peak.

  2. Multi-frequency observations of E-region HF radar aurora

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    S. E. Milan

    Full Text Available Multi-frequency observations of E-region coherent backscatter from decametre waves reveal that auroral echoes tend to comprise two spectral components superimposed, one at low Doppler shifts, below 250 ms-1, and the other Doppler shifted to near the ion-acoustic speed or above, up to 800 ms-1. The low Doppler shift component occurs at all look directions; Doppler shifts near the ion acoustic speed occur when looking at low flow angles along the direction of the electron drift in the electrojet, and Doppler shifts in excess of the ion acoustic speed occur at intermediate flow angles. The latter population appears most commonly at radar frequencies near 10–12 MHz, with its occurrence decreasing dramatically at higher frequencies. The velocity of the high Doppler shift echoes increases with increasing radar frequency, or irregularity wave number k. The velocity of the low Doppler shift population appears to be suppressed significantly below the line-of-sight component of the electron drift. Initial estimates of the altitude from which scatter occurs suggest that the high Doppler shift echoes originate from higher in the E-region than the low Doppler shift echoes, certainly in the eastward electrojet. We discuss these observations with reference to the theories of de/stabilization of two-stream waves by electron density gradients and electrostatic ion cyclotron waves excited by field-parallel electron drifts.

    Key words. Ionosphere (ionospheric irregularities

  3. Multi-frequency observations of E-region HF radar aurora

    Directory of Open Access Journals (Sweden)

    S. E. Milan

    2003-03-01

    Full Text Available Multi-frequency observations of E-region coherent backscatter from decametre waves reveal that auroral echoes tend to comprise two spectral components superimposed, one at low Doppler shifts, below 250 ms-1, and the other Doppler shifted to near the ion-acoustic speed or above, up to 800 ms-1. The low Doppler shift component occurs at all look directions; Doppler shifts near the ion acoustic speed occur when looking at low flow angles along the direction of the electron drift in the electrojet, and Doppler shifts in excess of the ion acoustic speed occur at intermediate flow angles. The latter population appears most commonly at radar frequencies near 10–12 MHz, with its occurrence decreasing dramatically at higher frequencies. The velocity of the high Doppler shift echoes increases with increasing radar frequency, or irregularity wave number k. The velocity of the low Doppler shift population appears to be suppressed significantly below the line-of-sight component of the electron drift. Initial estimates of the altitude from which scatter occurs suggest that the high Doppler shift echoes originate from higher in the E-region than the low Doppler shift echoes, certainly in the eastward electrojet. We discuss these observations with reference to the theories of de/stabilization of two-stream waves by electron density gradients and electrostatic ion cyclotron waves excited by field-parallel electron drifts.Key words. Ionosphere (ionospheric irregularities

  4. Non-magnetic aspect sensitive auroral echoes from the lower E region observed at 50 MHz

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    R. Rüster

    1999-10-01

    Full Text Available Backscatter from E-region irregularities was observed at aspect angles close to 90° (almost parallel to the direction of the magnetic field using the ALOMAR SOUSY radar at Andoya/Norway. Strong electric fields and increased E-region electron temperatures simultaneously measured with the incoherent scatter facility EISCAT proved that the Farley-Buneman plasma instability was excited. In addition, strong particle precipitation was present as inferred from EISCAT electron densities indicating that the gradient drift instability may have been active, too. Backscatter at such large aspect angles was not expected and has not been observed before. The characteristics of the observed echoes, however, are in many aspects completely different from usual auroral radar results: the Doppler velocities are only of the order of 10 m/s, the half-width of the spectra is around 5 m/s, the echoes originate at altitudes well below 100 km, and they seem to be not aspect-sensitive with respect to the magnetic field direction. We, therefore, conclude that the corresponding irregularities are not caused by the mentioned instabilities and that other mechanism have to be invoked.Key words. Ionosphere (plasma waves and instabilities; ionosphere irregularities; particle precipitaion · Meteorology and atmospheric dynamics (middle atmosphere dynamics

  5. 30 MHz radar observations of artificial E region field-aligned plasma irregularities

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    D. L. Hysell

    2008-02-01

    Full Text Available Artificial E region field aligned irregularities (FAIs have been observed during heating experiments at the HAARP facility using a new 30 MHz coherent scatter radar imager deployed near Homer, Alaska. Irregularities were observed during brief experiments on three quiet days in July and August, 2007, when the daytime E region critical frequency was close to 3 MHz. Irregularities were consistently generated and detected during experiments with O-mode HF pumping on zenith with a 1-min on, 1-min off CW modulation. The scattering cross sections, rise, and fall times of the echoes were observed as well as their spectral properties. Results were found to be mainly in agreement with observations from other mid- and high-latitude sites with some discrepancies. Radar images of the irregularity-filled volume on one case exhibited clear variations in backscatter power and Doppler shift across the volume. The images furthermore show the emergence of a small irregularity-filled region to the south southwest of the main region in the approximate direction of magnetic zenith.

  6. Radar observations of artificial E-region field-aligned irregularities

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    E. Nossa

    2009-07-01

    Full Text Available Artificial E region field aligned plasma density irregularities (FAIs were generated using HAARP in four different experimental modes and observed with a coherent scatter radar imager located 450 km to the southwest where it could detect field-aligned backscatter. The experiments were conducted in July of 2008, during the Polar Aeronomy and Radio Science Summer School (PARS, during quiet conditions in the daytime when the E layer was dense and absorption was modest. The echoes observed during zenith and magnetic zenith heating experiments were deflected from their nominally anticipated horizontal positions toward the midpoint position. The occurrence of hysteresis when heating with amplitude modulated pulses implied the development of the resonance instability, although the threshold for the onset of instability appeared to be higher than what has been predicted theoretically. Heating experiments involving pump frequencies slightly above and below the second electron gyroharmonic frequency produced no significant differences in the observed echoes. Finally, heating with a pump frequency slightly above the E region critical frequency appears to have produced FAIs at two distinct altitudes where the upper-hybrid resonance condition could be satisfied.

  7. Mid-latitude E-region bulk motions inferred from digital ionosonde and HF radar measurements

    Directory of Open Access Journals (Sweden)

    J. Delloue

    2004-11-01

    Full Text Available In the mid-latitude E-region there is now evidence suggesting that neutral winds play a significant role in driving the local plasma instabilities and electrodynamics inside sporadicE layers. Neutral winds can be inferred from coherent radar backscatter measurements of the range-/azimuth-time-intensity (RTI/ATI striations of quasi-periodic (QP echoes, or from radar interferometer/imaging observations. In addition, neutral winds in the E-region can be estimated from angle-of-arrival ionosonde measurements of sporadic-E layers. In the present paper we analyse concurrent ionosonde and HF coherent backscatter observations obtained when a Canadian Advanced Digital Ionosonde (CADI was operated under a portion of the field-of-view of the Valensole high frequency (HF radar. The Valensole radar, a mid-latitude radar located in the south of France with a large azimuthal scanning capability of 82° (24° E to 58° W, was used to deduce zonal bulk motions of QP echoing regions using ATI analysis. The CADI was used to measure angle-of-arrival information in two orthogonal horizontal directions and thus derive the motion of sporadic-E patches drifting with the neutral wind. This paper compares the neutral wind drifts of the unstable sporadic-E patches as determined by the two instruments. The CADI measurements show a predominantly westward aligned motion, but the measured zonal drifts are underestimated relative to those observed with the Valensole radar.

  8. Possible interaction between thermal electrons and vibrationally excited N2 in the lower E-region

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    K.-I. Oyama

    2011-03-01

    Full Text Available As one of the tasks to find the energy source(s of thermal electrons, which elevate(s electron temperature higher than neutral temperature in the lower ionosphere E-region, energy distribution function of thermal electron was measured with a sounding rocket at the heights of 93–131 km by the applying second harmonic method. The energy distribution function showed a clear hump at the energy of ~0.4 eV. In order to find the reason of the hump, we conducted laboratory experiment. We studied difference of the energy distribution functions of electrons in thermal energy range, which were measured with and without EUV radiation to plasma of N2/Ar and N2/O2 gas mixture respectively. For N2/Ar gas mixture plasma, the hump is not clearly identified in the energy distribution of thermal electrons. On the other hand for N2/O2 gas mixture, which contains vibrationally excited N2, a clear hump is found when irradiated by EUV. The laboratory experiment seems to suggest that the hump is produced as a result of interaction between vibrationally excited N2 and thermal electrons, and this interaction is the most probable heating source for the electrons of thermal energy range in the lower E-region. It is also suggested that energy distribution of the electrons in high energy part may not be Maxwellian, and DC probe measures the electrons which are non Maxwellian, and therefore "electron temperature" is calculated higher.

  9. Genetic Structure and Natal Origins of Immature Hawksbill Turtles (Eretmochelys imbricata) in Brazilian Waters

    Science.gov (United States)

    Proietti, Maira C.; Reisser, Julia; Marins, Luis Fernando; Rodriguez-Zarate, Clara; Marcovaldi, Maria A.; Monteiro, Danielle S.; Pattiaratchi, Charitha; Secchi, Eduardo R.

    2014-01-01

    Understanding the connections between sea turtle populations is fundamental for their effective conservation. Brazil hosts important hawksbill feeding areas, but few studies have focused on how they connect with nesting populations in the Atlantic. Here, we (1) characterized mitochondrial DNA control region haplotypes of immature hawksbills feeding along the coast of Brazil (five areas ranging from equatorial to temperate latitudes, 157 skin samples), (2) analyzed genetic structure among Atlantic hawksbill feeding populations, and (3) inferred natal origins of hawksbills in Brazilian waters using genetic, oceanographic, and population size information. We report ten haplotypes for the sampled Brazilian sites, most of which were previously observed at other Atlantic feeding grounds and rookeries. Genetic profiles of Brazilian feeding areas were significantly different from those in other regions (Caribbean and Africa), and a significant structure was observed between Brazilian feeding grounds grouped into areas influenced by the South Equatorial/North Brazil Current and those influenced by the Brazil Current. Our genetic analysis estimates that the studied Brazilian feeding aggregations are mostly composed of animals originating from the domestic rookeries Bahia and Pipa, but some contributions from African and Caribbean rookeries were also observed. Oceanographic data corroborated the local origins, but showed higher connection with West Africa and none with the Caribbean. High correlation was observed between origins estimated through genetics/rookery size and oceanographic/rookery size data, demonstrating that ocean currents and population sizes influence haplotype distribution of Brazil's hawksbill populations. The information presented here highlights the importance of national conservation strategies and international cooperation for the recovery of endangered hawksbill turtle populations. PMID:24558419

  10. Industrial concessions, fires and air pollution in Equatorial Asia

    Science.gov (United States)

    Spracklen, D. V.; Reddington, C. L.; Gaveau, D. L. A.

    2015-09-01

    Forest and peatland fires in Indonesia emit large quantities of smoke leading to poor air quality across Equatorial Asia. Marlier et al (2015 Environ. Res. Lett. 10 085005) explore the contribution of fires occurring on oil palm, timber (wood pulp and paper) and natural forest logging concessions to smoke emissions and exposure of human populations to the resulting air pollution. They find that one third of the population exposure to smoke across Equatorial Asia is caused by fires in oil palm and timber concessions in Sumatra and Kalimantan. Logging concessions have substantially lower fire emissions, and contribute less to air quality degradation. This represents a compelling justification to prevent reclassification of logging concessions into oil palm or timber concessions after logging. This can be achieved by including logged forests in the Indonesian moratorium on new plantations in forested areas.

  11. Equatorial enhancement of the nighttime OH mesospheric infrared airglow

    Energy Technology Data Exchange (ETDEWEB)

    Baker, D J [Utah State University, EL-302, Logan, UT 84322-4140 (United States); Thurgood, B K [Utah State University, EL-302, Logan, UT 84322-4140 (United States); Harrison, W K [Utah State University, EL-302, Logan, UT 84322-4140 (United States); Mlynczak, M G [NASA Langley Research Center, Mail Stop 401-B, Hampton, VA 23665-5225 (United States); Russell, J M [Center for Atmospheric Sciences, Hampton University, 23 Tyler Street Hampton, VA 23668 (United States)

    2007-05-15

    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 ({delta}v=2) airglow layer consistent with the high average diurnal solar flux. The brightening of the OH airglow typically means more H+O{sub 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. 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.

  13. The Morphology of Equatorial Plasma Bubbles – a review

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    Hyosub Kil

    2015-03-01

    Full Text Available Plasma bubbles that occur in the equatorial F-region make up one of the most distinguishing phenomena in the ionosphere. Bubbles represent plasma depletions with respect to the background ionosphere, and are the major source of electron density irregularities in the equatorial F-region. Such bubbles are seen as plasma depletion holes (in situ satellite observations, vertical plumes (radar observations, and emission-depletion bands elongated in the north-south direction (optical observations. However, no technique can observe the whole three-dimensional structure of a bubble. Various aspects of bubbles identified using different techniques indicate that a bubble has a “shell” structure. This paper reviews the development of the concepts of “bubble” and “shell” in this context.

  14. Tiger sharks can connect equatorial habitats and fisheries across the Atlantic Ocean basin.

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    André S Afonso

    Full Text Available Increasing our knowledge about the spatial ecology of apex predators and their interactions with diverse habitats and fisheries is necessary for understanding the trophic mechanisms that underlie several aspects of marine ecosystem dynamics and for guiding informed management policies. A preliminary assessment of tiger shark (Galeocerdo cuvier population structure off the oceanic insular system of Fernando de Noronha (FEN and the large-scale movements performed by this species in the equatorial Atlantic Ocean was conducted using longline and handline fishing gear and satellite telemetry. A total of 25 sharks measuring 175-372 cm in total length (TL were sampled. Most sharks were likely immature females ranging between 200 and 260 cm TL, with few individuals < 200 cm TL being caught. This contrasts greatly with the tiger shark size-distribution previously reported for coastal waters off the Brazilian mainland, where most individuals measured < 200 cm TL. Also, the movements of 8 individuals measuring 202-310 cm TL were assessed with satellite transmitters for a combined total of 757 days (mean = 94.6 days∙shark-1; SD = 65.6. These sharks exhibited a considerable variability in their horizontal movements, with three sharks showing a mostly resident behavior around FEN during the extent of the respective tracks, two sharks traveling west to the South American continent, and two sharks moving mostly along the middle of the oceanic basin, one of which ending up in the northern hemisphere. Moreover, one shark traveled east to the African continent, where it was eventually caught by fishers from Ivory Coast in less than 474 days at liberty. The present results suggest that young tiger sharks measuring < 200 cm TL make little use of insular oceanic habitats from the western South Atlantic Ocean, which agrees with a previously-hypothesized ontogenetic habitat shift from coastal to oceanic habitats experienced by juveniles of this species in this region

  15. Total mercury in the night shark, Carcharhinus signatus in the western equatorial Atlantic Ocean

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    Alexandre Gomes Ferreira

    2004-08-01

    Full Text Available Mercury is the only element capable to biomagnificate along the food chain, and carnivorous fish tend to accumulate high concentrations of this element. Total mercury in muscle tissue of Carcharhinus signatus sampled along the western equatorial Atlantic Ocean was measured by atomic emission spectrophotometry with ICP/AES. The average total mercury concentrations were consistently greater than the maximum limit for human consumption established by the Brazilian Health Ministry for carnivorous fishes (1000 µg. kg-1 w.w.. Therefore, an average consumption of 0.1 kg/day of C. signatus would result in an average daily ingestion of 174.2 µg of Hg, more than five times the 30 µg/day intake established by the World Health Organization. In the range of lengths studied, body length could not be used as an indicator of the Hg contamination degree for C. signatus. Also, sex cannot be considered a determining factor in the total mercury accumulation in C. signatus.O mercúrio (Hg é o único metal que comprovadamente biomagnifica através da cadeia alimentar, e sendo assim, espécies de peixes predadores tendem a apresentar altas concentrações deste metal. Porções de tecido muscular de C. signatus coletados na região oeste equatorial do oceano Atlântico foram submetidas a extração ácida e tiveram a concentração de mercúrio determinada com acessório gerador de vapor a frio acoplado a um ICP-AES. A concentração média de Hg apresentou valores acima do limite máximo permissível para consumo humano estabelecido pela legislação brasileira (1000 µg.kg-1 de peso úmido. Conseqüentemente, um consumo médio de 0,1 kg.dia-1 de C. signatus resultaria numa ingestão media de 174,2 µg de Hg, mais de cinco vezes o consumo máximo de 30 µg.dia-1 estabelecido pela Organizacao Munidal da Saúde. Dentro das classes de tamanho analisadas, o comprimento total não pode ser utilizado como indicador do grau de contaminação por mercúrio em C. signatus

  16. 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.

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

    OpenAIRE

    Werf, van der, J.J. (Jos); Dempewolf, J.; Trigg, S. N; Randerson, J. T.; Peters, W.

    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 emissions from Indonesia, Malaysia, and Papua New Guinea during 2000¿2006. We found that average fire emissions from this region [128 ± 51 (1¿) Tg carbon (C) year¿1, T = 1012] were comparable to fo...

  18. Air-Sea Coupling Over The Equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Gopika, N.

    subcontinent and adjoining areas of Southeast Asia. Recurrence of these summer monsoon rains is critical to agricultural production that provides life-sustaining support for a billion people in the region. The reversing monsoon winds also generate a unique... with latitude makes the equatorial areas a special region. This makes the equator as a wave-guide within which the signal of atmospheric forcing could be transferred over long distances without much energy loss. For 13 example, the zonal momentum...

  19. The 2010-2011 revival of Jupiter's South Equatorial Belt

    Science.gov (United States)

    Giles, R. S.; Fletcher, L. N.; Irwin, P. G. J.; Orton, G. S.; Rogers, J. H.

    2013-09-01

    In 2009-2010, Jupiter's South Equatorial Belt (SEB) faded to a very pale colour before the 2010-2011 revival restored the belt to its ordinary dark appearance. Mid-infrared images of the revival were taken using VISIR (VLT) across a range of wavelengths from 7 to 25 μm. These were used to retrieve changes in temperature and aerosol optical depth as the revival proceeded between November 2010 and September 2011.

  20. Equatorial electrojet in the south Atlantic anomaly region

    Indian Academy of Sciences (India)

    Features of the equatorial electrojet are studied at Sao Luiz (2.6°S, 44.2°W, inclination −0.25°) in eastern Brazil and Sikasso (11.3°N, 5.7°W, inclination 0.1°) in the western African sector. The stations are situated on either side of the lowest magnetic field intensity in the region of rapid changes in the declination. The daily ...

  1. 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.

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

    Digital Repository Service at National Institute of Oceanography (India)

    Palike, H.; Lyle, M.W.; Nishi, H.; Raffi, I.; Ridgwell, A.; Gamage, K.; Klaus, A.; Acton, G.; Anderson, L.; Backman, J.; Baldauf, J.; Beltran, C.; Bohaty, S.M.; Bown, P.; Busch, W.; Channell, J.E.T.; Chun, C.O.J.; Delaney, M.; Dewangan, P.; et al.

    an important role in climate regulation1. Integrated Ocean Drilling Program (IODP) Expeditions 320/321, the "Pacific Equatorial Age Transect" (PEAT), exploited the northward Pacific plate trajectory during the Cenozoic to recover a continuous sediment... the locus of carbonate deposition between shelf and deep ocean. Therefore, increasing solute supply should be coupled to increased weathering, a warmer climate, and higher CO2, unless changes in orbital configuration significantly enhance or reduce...

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

    Indian Academy of Sciences (India)

    ECMWF Re-Analysis (ERA-interim) data of winds for the year 2007 between the pressure levels 1 and 1000 hPa (0–49 km) have been analyzed for equatorial wave activity over a tropical station Gadanki (13.5°N, 79.2°E). Available wind observations made by MST radar located at the same site have also been used to ...

  4. Large-Scale Phytoplankton Blooms in the Equatorial Pacific

    Science.gov (United States)

    Ryan, J. P.; Polito, P. S.; Strutton, P. G.; Chavez, F. P.

    2001-05-01

    Between March and December of 1998, large blooms of phytoplankton occurred across 10,000 km of the equatorial Pacific during and following the transition to La Niña. The physical forcing and dynamics of these blooms were studied using satellite sea surface height, temperature and chlorophyll, and in situ mooring observations. Physical conditions and processes that influence euphotic zone nutrient supply and hence bloom formation include thermocline (nutricline) depth, upwelling (wind-driven and along-isopycnal) and turbulent vertical mixing. Anomalously shallow thermocline depth was central to the development of all blooms. Sea surface height (η ), a proxy for thermocline depth, was decomposed via two-dimensional finite impulse response filtering into components ranging across interannual to intraseasonal time scales. Eastward propagation of bloom genesis followed eastward propagation of basin-scale thermocline shoaling that accounted for 78% of the η variance and represented the oceanic transition to La Niña. Genesis of the greatest bloom across >2500 km coincided with the largest scale thermocline shoaling that resulted from processes in the semiannual band acting on top of the interannual, basin-scale transition. Propagation of this bloom ~4500 km further east at ~66 km day-1 was related to advective transport in the Equatorial Undercurrent. Spatial distribution of the bloom was closely related to η variation in the intraseasonal tropical instability wave (TIW) band, and the effect of meridional advection by TIW currents was pronounced. Genesis of the last bloom coincided with maximum local thermocline shoaling detected by moored observations but not η . Mooring observations indicated regional differences in the processes that enhanced nutrient supply to the euphotic zone in association with anomalously shallow thermocline depth during the blooms. In the western equatorial Pacific, wind-driven upwelling and turbulent vertical mixing were indicated. In the

  5. Airglow observations over the equatorial ionization anomaly zone in Taiwan

    Directory of Open Access Journals (Sweden)

    T. C. Chow

    2011-05-01

    Full Text Available Airglow imaging at mid-latitude stations often show intensity modulations associated with medium scale travelling ionospheric disturbances (MSTID, while those carried out near the equatorial regions reveal depletions caused by equatorial plasma bubbles (EPB. Two all sky cameras are used to observe plasma depletions in the 630.0 nm emission over the equatorial ionization anomaly (EIA region, Taiwan (23° N, 121° E; 13.5° N Magnetic during 1998–2002 and 2006–2007. The results show EPB and MSTID depletions in different solar activity conditions. Several new features of the EPB depletions such as bifurcation, secondary structure on the walls, westward tilt, etc., are discussed in this paper. Evidence of tilted depletions with secondary structures developing on the eastern wall that later evolve to appear as bifurcations, are presented for the first time. Moreover, detail investigations are carried out using International Reference Ionosphere (IRI model as well as the electron density from Ionosonde and Global Positioning System (GPS Occultation Experiment (GOX onboard FORMOSAT-3/COSMIC satellite, to understand the conditions that favor the propagation of MSTID to the latitude of Taiwan.

  6. On the interpretation of the equatorially antisymmetric Jovian gravitational field

    Science.gov (United States)

    Kong, Dali; Zhang, Keke; Schubert, Gerald

    2017-07-01

    Since the odd zonal gravitational coefficients of Jupiter are nearly unaffected by the planet's rotational distortion, an effective way of estimating the internal structure of the equatorially antisymmetric Jovian winds is to measure the odd coefficients induced by their equatorially antisymmetric component and then apply a mathematical theory to 'invert' them. The thermal-gravitational wind equation (TGWE) provides this theoretical basis for interpretation. Here, we show that the kernel term of the TGWE requires that its solutions satisfy a solvability condition. The thermal wind equation is a diagnostic relation that generates a 'solution' for any zonal wind profile, but that 'solution' does not necessarily satisfy the solvability condition required for the TGWE. We develop a new approach to solving the TGWE that respects the solvability condition. We then calculate the odd zonal gravitational coefficients of Jupiter using a profile of zonal winds that satisfies the solvability condition and is equatorially antisymmetric and consistent with the observed cloud-level winds of Jupiter. We also explain the subtle but profound difference between the TWE and the TGWE via an analogous inhomogeneous ordinary differential equation. The developed method can be readily extended for inversion of the data soon to be acquired by the Juno spacecraft.

  7. E-region decameter-scale plasma waves observed by the dual TIGER HF radars

    Directory of Open Access Journals (Sweden)

    B. A. Carter

    2009-01-01

    Full Text Available The dual Tasman International Geospace Environment Radar (TIGER HF radars regularly observe E-region echoes at sub-auroral magnetic latitudes 58°–60° S including during geomagnetic storms. We present a statistical analysis of E-region backscatter observed in a period of ~2 years (late 2004–2006 by the TIGER Bruny Island and Unwin HF radars, with particular emphasis on storm-time backscatter. It is found that the HF echoes normally form a 300-km-wide band at ranges 225–540 km. In the evening sector during geomagnetic storms, however, the HF echoes form a curved band joining to the F-region band at ~700 km. The curved band lies close to the locations where the geometric aspect angle is zero, implying little to no refraction during geomagnetic storms, which is an opposite result to what has been reported in the past. The echo occurrence, Doppler velocity, and spectral width of the HF echoes are examined in order to determine whether new HF echo types are observed at sub-auroral latitudes, particularly during geomagnetic storms. The datasets of both TIGER radars are found to be dominated by low-velocity echoes. A separate population of storm-time echoes is also identified within the datasets of both radars with most of these echoes showing similar characteristics to the low-velocity echo population. The storm-time backscatter observed by the Bruny Island radar, on the other hand, includes near-range echoes (r<405 km that exhibit some characteristics of what has been previously termed the High Aspect angle Irregularity Region (HAIR echoes. We show that these echoes appear to be a storm-time phenomenon and further investigate this population by comparing their Doppler velocity with the simultaneously measured F- and E-region irregularity velocities. It is suggested that the HAIR-like echoes are observed only by HF radars with relatively poor geometric aspect angles when electron density is low and when the electric field is particularly

  8. Modulation of precipitation over West Africa by equatorial waves

    Science.gov (United States)

    Schlüter, Andreas; van der Linden, Roderick; Vogel, Peter; Fink, Andreas H.; Knippertz, Peter

    2017-04-01

    Equatorial waves can couple with deep convection and thus modulate rainfall on the synoptic timescale throughout the tropics. Until now, however, no comparative study of the influence of all the different wave types on precipitation has been performed specifically for West Africa. To fill this gap, the following wave types were analyzed for the pre-/post- and full monsoon season (April to October): (1) the Madden-Julian Oscillation (MJO), (2) Kelvin waves, (3) equatorial Rossby waves, (4) eastward-propagating inertia gravity waves, (5) mixed Rossby-gravity waves and (6) tropical disturbances/African Easterly Waves. The different wave types were filtered in the wavenumber-frequency spectrum of outgoing longwave radiation. Eight different wave phases were defined from a phase diagram that can be calculated from the time-derivative of the filtered wave signal. Subsequently, composites of dynamical and thermodynamical fields for each wave phase of the different wave types were plotted using the ERA Interim reanalysis from the European Centre for Medium-Range Weather Forecasts. This way the propagation of the wave can be depicted. All aforementioned wave types, except the fast eastward-propagating inertia gravity wave, show consistent and significant influence on West African rainfall. The influence of the waves can be seen far into the subtropics for some wave types. The expected theoretical structure is confirmed by the analysis of upper- and lower-level divergence, wind and geopotential height. An interaction between the tropical and extratropical regime appears to occur for the MJO and equatorial Rossby waves. The mechanism involved in this interaction, however, is not fully understood. Composites of low-level wind shear, convective available potential energy and mid-level moisture are used to analyze whether waves create favorable conditions for the organization of convection. Additionally, the source regions of moisture were identified using moisture fields and

  9. CUTLASS HF radar observations of high-velocity E-region echoes

    Directory of Open Access Journals (Sweden)

    M. V. Uspensky

    2001-04-01

    Full Text Available A short event of high-velocity E-region echo observations by the Pykkvibaer HF radar is analysed to study echo parameters and the echo relation to the Farley-Buneman plasma instability. The echoes were detected in several beams aligned closely to the magnetic L-shell direction. Two echo groups were identified: one group corresponded to the classical type 1 echoes with velocities close to the nominal ion-acoustic speed of 400 ms–1 , while the other group had significantly larger velocities, of the order of 700 ms–1 . The mutual relationship between the echo power, Doppler velocity, spectral width and elevation angles for these two groups was studied. Plotting of echo parameters versus slant range showed that all ~700 ms–1 echoes originated from larger heights and distances of 500–700 km, while all ~400 ms–1 echoes came from lower heights and from farther distances; 700–1000 km. We argue that both observed groups of echoes occurred due to the Farley-Buneman plasma instability excited by strong ( ~70 mVm–1 and uniformly distributed electric fields. We show that the echo velocities for the two groups were different because the echoes were received from different heights. Such a separation of echo heights occurred due to the differing amounts of ionospheric refraction at short and large ranges. Thus, the ionospheric refraction and related altitude modulation of ionospheric parameters are the most important factors to consider, when various characteristics of E-region decametre irregularities are derived from HF radar measurements.Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; polar ionosphere

  10. Seasonal Characteristics of the Longitudinal Wavenumber-4 Structure in the Equatorial Ionospheric Anomaly

    Directory of Open Access Journals (Sweden)

    E. Kim

    2008-12-01

    Full Text Available Using the global total electron contents (TEC measured by the TOPEX satellite from Aug. 1992 to Oct. 2005, we investigate the variations of the longitudinal wavenumber-4 (LW-4 structure in the equatorial anomaly (EA crests with season, local time, and solar activity. Our study shows that the LW-4 structure in the EA crests (5~20 degrees MLAT in both hemispheres has clear four peaks at fixed longitude sectors during the daytime for both equinoxes and June solstice. In spite of being called a wavelike structure, however, the magnitudes and spatial intervals of the four peaks are far from being the same or regular. After sunset, the four-peak structure begins to move eastward with gradual weakening in its amplitude during equinoxes and this weakening proceeds much faster during June solstice. Interestingly, the longitudinal variations during December solstice do not show clear four-peak structure. All these features of the LW-4 structure are almost the same for both low and high solar activity conditions although the ion densities are greatly enhanced from low to high solar activities. With the irrelevancy of the magnetic activity in the LW-4, this implies that the large changes of the upper atmospheric ion densities, one of the important factors for ion-neutral interactions, have little effect on the formation of the LW-4 structure. On the other hand, we found that the monthly variation of the LW-4 is remarkably similar to that of the zonal component of wavenumber-3 diurnal tides at low latitudes, which implies that the lower atmospheric tidal forcing, transferred to the upper atmosphere, seems to have a dominant role in producing the LW-4 structure in the EA crests via the E-region dynamo.

  11. Equatorial scintillations in relation to the development of ionization anomaly

    Science.gov (United States)

    Ray, S.; Paul, A.; Dasgupta, A.

    2006-07-01

    The irregularities in the electron density distribution of the ionosphere over the equatorial region frequently disrupt space-based communication and navigation links by causing severe amplitude and phase scintillations of signals. Development of a specification and forecast system for scintillations is needed in view of the increased reliance on space-based communication and navigation systems, which are vulnerable to ionospheric scintillations. It has been suggested in recent years that a developed equatorial anomaly in the afternoon hours, with a steep gradient of the F-region ionization or Total Electron Content (TEC) in the region between the crest and the trough, may be taken as a precursor to scintillations on transionospheric links. Latitudinal gradient of TEC measured using Faraday Rotation technique from LEO NOAA 12/14 transmissions during the afternoon hours at Calcutta shows a highly significant association with L-band scintillations recorded on the INMARSAT link, also from Calcutta, during the equinoxes, August through October 2000, and February through April 2001. style="line-height: 20px;"> The daytime equatorial electrojet is believed to control the development of the equatorial anomaly and plays a crucial role in the subsequent development of F-region irregularities in the post-sunset hours. The diurnal maximum and integrated value (integrated from the time of onset of plasma influx to off-equatorial latitudes till local sunset) of the strength of the electrojet in the Indian longitude sector shows a significant association with post-sunset L-band scintillations recorded at Calcutta during the two equinoxes mentioned earlier. style="line-height: 20px;"> Generation of equatorial irregularities over the magnetic equator in the post-sunset hours is intimately related to the variation of the height of the F-layer around sunset. Ionosonde data from Kodaikanal, a station situated close to the magnetic equator, has been utilized to calculate the vertical

  12. Equatorial scintillations in relation to the development of ionization anomaly

    Directory of Open Access Journals (Sweden)

    S. Ray

    2006-07-01

    Full Text Available The irregularities in the electron density distribution of the ionosphere over the equatorial region frequently disrupt space-based communication and navigation links by causing severe amplitude and phase scintillations of signals. Development of a specification and forecast system for scintillations is needed in view of the increased reliance on space-based communication and navigation systems, which are vulnerable to ionospheric scintillations. It has been suggested in recent years that a developed equatorial anomaly in the afternoon hours, with a steep gradient of the F-region ionization or Total Electron Content (TEC in the region between the crest and the trough, may be taken as a precursor to scintillations on transionospheric links. Latitudinal gradient of TEC measured using Faraday Rotation technique from LEO NOAA 12/14 transmissions during the afternoon hours at Calcutta shows a highly significant association with L-band scintillations recorded on the INMARSAT link, also from Calcutta, during the equinoxes, August through October 2000, and February through April 2001. The daytime equatorial electrojet is believed to control the development of the equatorial anomaly and plays a crucial role in the subsequent development of F-region irregularities in the post-sunset hours. The diurnal maximum and integrated value (integrated from the time of onset of plasma influx to off-equatorial latitudes till local sunset of the strength of the electrojet in the Indian longitude sector shows a significant association with post-sunset L-band scintillations recorded at Calcutta during the two equinoxes mentioned earlier. Generation of equatorial irregularities over the magnetic equator in the post-sunset hours is intimately related to the variation of the height of the F-layer around sunset. Ionosonde data from Kodaikanal, a station situated close to the magnetic equator, has been utilized to calculate the vertical drift of the F-layer over the

  13. Carbonate sediment production in the equatorial continental shelf of South America: Quantifying Halimeda incrassata (Chlorophyta) contributions

    Science.gov (United States)

    Carneiro, Pedro Bastos de Macêdo; Morais, Jader Onofre de

    2016-12-01

    The middle and outer continental shelves of eastern equatorial South America (ESA) are characterized by intense production of carbonate sediments. Qualitative analyses of sediment deposits suggest that the calcareous green alga Halimeda incrassata is among the top CaCO3 producers. Nevertheless, no study so far has quantified its real contributions. To better understand the sediment dynamic in this area, we measured biomass, growth rates and calcium carbonate production by this alga. The species exhibited high growth rates (3.38 segments.individual-1.day-1), coverage (174 individuals.m-2) and biomass (214.02 g.m-2). Substitution of segments may allow a sedimentation rate of 1.53 mm.yr-1 and a complete turnover of the population every 60.2 days. The rapid growth indicates that this alga can produce as much CaCO3 (1.19 kg CaCO3.m-2.year-1) as other tropical organisms, such as corals and rhodoliths. In a conservative estimate, 773.500 tonnes of CaCO3 are produced per year in a 5000 km2 area off the northern coast of Brazil. Sedimentation rate seems to be higher than that promoted by continental inputs in middle and outer continental shelf. On the other hand, population turnover is twice as slow as in other H. incrassata assemblages, suggesting that South American populations are sensible to physical disturbances. New studies are necessary to accurately estimate H. incrassata coverage along the Brazilian coast and to integrate data on other CaCO3 producers, such as foraminifera and coralline algae. This would allow a better understanding of the role of South American continental shelf on the global carbon budget. Furthermore, analysis on the health of these organisms is urgent, since a decline in their populations could negatively affect ecosystems functioning and services.

  14. Vulnerability to longline fisheries of three hammerhead shark Sphyrna species in the south-western and equatorial Atlantic Ocean.

    Science.gov (United States)

    Bezerra, N P A; Travassos, P; Hazin, F H V

    2016-08-01

    Catch and effort data from 29 418 longline sets from Brazilian tuna longline vessels operating in the south-western and equatorial Atlantic Ocean between 2004 and 2011 were analysed to investigate the distribution, catch rate and size of three species of hammerhead sharks (Sphyrna lewini, Sphyrna mokarran and Sphyrna zygaena). During that period, 6172 hammerhead sharks were caught. Among the elasmobranchs, the highest percentage of hammerhead sharks were caught in 2007, when they accounted for 3·90% of the group, while the lowest value of 0·40% was recorded in 2010. In general, the spatial distribution of the mean catch per unit effort (CPUE) by years and quarters showed a trend of higher catches near the equatorial region and in southern Brazil. The nominal mean CPUE was 0·12 Sphyrna spp. 1000(-1) hooks, with the highest value being recorded in 2007 (0·30 Sphyrna spp. 1000(-1) hooks). The standardized yearly CPUE estimated by a generalized linear model assuming a zero inflated negative binomial (ZINB) distribution were not much different from nominal values. Of the 205 sexed specimens, 117 were females and 88 were males, resulting in a sex ratio with a predominance of females (1·30:1·00), although not statistically significant. The total length of females ranged from 1200 to 2800 mm and of males from 1100 to 3100 mm. Juvenile hammerhead sharks represented 82 and 54% of the sexed female and male specimens, respectively. © 2016 The Fisheries Society of the British Isles.

  15. The Brazilian School Principals

    Directory of Open Access Journals (Sweden)

    Ângelo Ricardo de Souza

    2007-09-01

    Full Text Available This article discusses the policy nature of school principal, considering the thoughts of many authors about school administration and the debate about politics, power and burocracy. The study still presents a profile of Brazilian school principals with the data of Basic Education Evaluation System – SAEB, of 2003, specially comparing elements about gender, experience and formation of school principals, and aspects linked with methodology to provide/indicate the school principal and its possible democratic vocation.

  16. Brazilian Trichoptera Checklist II

    Directory of Open Access Journals (Sweden)

    Henrique Paprocki

    2014-10-01

    Full Text Available A second assessment of Brazilian Trichoptera species records is presented here. A total of 625 species were recorded for Brazil. This represents an increase of 65.34% new species recorded during the last decade. The Hydropsychidae (124 spp., followed by the Hydroptilidae (102 spp. and Polycentropodidae (97 spp., are the families with the greatest richness recorded for Brazil. The knowledge on Trichoptera biodiversity in Brazil is geographically unequal. The majority of the species is recorded for the southeastern region.

  17. CUTLASS HF radar observations of high-velocity E-region echoes

    Directory of Open Access Journals (Sweden)

    M. V. Uspensky

    Full Text Available A short event of high-velocity E-region echo observations by the Pykkvibaer HF radar is analysed to study echo parameters and the echo relation to the Farley-Buneman plasma instability. The echoes were detected in several beams aligned closely to the magnetic L-shell direction. Two echo groups were identified: one group corresponded to the classical type 1 echoes with velocities close to the nominal ion-acoustic speed of 400 ms1 , while the other group had significantly larger velocities, of the order of 700 ms1 . The mutual relationship between the echo power, Doppler velocity, spectral width and elevation angles for these two groups was studied. Plotting of echo parameters versus slant range showed that all ~700 ms1 echoes originated from larger heights and distances of 500–700 km, while all ~400 ms1 echoes came from lower heights and from farther distances; 700–1000 km. We argue that both observed groups of echoes occurred due to the Farley-Buneman plasma instability excited by strong ( ~70 mVm1 and uniformly distributed electric fields. We show that the echo velocities for the two groups were different because the echoes were received from different heights. Such a separation of echo heights occurred due to the differing amounts of ionospheric refraction at short and large ranges. Thus, the ionospheric refraction and related altitude modulation of ionospheric parameters are the most important factors to consider, when various characteristics of E-region decametre irregularities are derived from HF radar measurements.

    Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; polar ionosphere

  18. BRAZILIAN NEWS PORTALS CHARACTERISTICS

    Directory of Open Access Journals (Sweden)

    Heloiza G. Herckovitz

    2011-02-01

    Full Text Available A content analysis of four Brazilian news media portals found that economic news dominated the top headlines with little attention paid to education, the environment and welfare. Other trends included a focus on local events and national news sources, reliance on few sources, mostly official ones, and a low percentage of news that fitted the concept of newsworthiness (a combination of both social significance and deviance concepts. Other findings of a study of 432 top news stories published by UOL, Estadão, iG and Terra during a 15-day period between February and March 2008 indicate that the top portions of the portals’ front pages carry news that lacks story depth, editorial branding, and multimedia applications. The results suggest that online news portals are in their infancy although Brazil has the largest online population of Latin America. This study hopes to shed light on the gatekeeping process in Brazilian news portals. Brazilian media portals have yet to become a significant editorial force able to provide knowledge about social issues and public affairs in a socially responsible fashione.

  19. 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.

    2012-10-01

    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 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 7-day period. This oscillating motion has a wavelength of 20 deg and a speed of 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.

  20. 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.

  1. 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.

  2. 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 high latitudes can overwhelm the damping effects of weak gradients in Pedersen conductance near dusk.

  3. Jupiter's South Equatorial Belt Revival in 2010/11

    Science.gov (United States)

    Rogers, J.; Jacquesson, M.; Adamoli, G.; Vedovato, M.; Mettig, H.-J.

    2011-10-01

    A Revival of the South Equatorial Belt (SEB) is the most impressive organised disturbance that occurs on Jupiter. It starts with a single vigorous outbreak from which vigorous storms and disturbances spread around the planet in the different zonal currents. The Revival that began in 2010 has been better observed than any before it. Here we present analysis of the amateur images of the event, in visible light and a methane absorption band. These results substantiate previous descriptions of SEB Revivals with much greater precision, showing a high degree of organisation, but also raise new puzzles as the usual zonal wind patterns were altered.

  4. Equatorial ionospheric electrodynamic perturbations during Southern Hemisphere stratospheric warming events

    DEFF Research Database (Denmark)

    Olson, M. E.; Fejer, B. G.; Stolle, Claudia

    2013-01-01

    We use ground-based and satellite measurements to examine, for the first time, the characteristics of equatorial electrodynamic perturbations measured during the 2002 major and 2010 minor Southern Hemisphere sudden stratospheric warming (SSW) events. Our data suggest the occurrence of enhanced...... quasi 2 day fluctuations during the 2002 early autumnal equinoctial warming. They also show a moderately large multi-day perturbation pattern, resembling those during arctic SSW events, during 2002 late equinox, as the major SSW was weakening. We also compare these data with extensive recent results...

  5. Positive and negative GPS-TEC ionospheric storm effects during the extreme space weather event of March 2015 over the Brazilian Sector

    Science.gov (United States)

    Fagundes, Paulo Roberto; Fejer, B. G.; Kavutarapu, Venkatesh; Gil Pillat, Valdir; Cardoso, Felipe Antonio; Ribeiro, Brunno Augusto

    2016-07-01

    We studied the response of the ionosphere (F-region) in the Brazilian sector during extreme space weather event of 17 March 2015 using a large network of 102 GPS-TEC stations. It is observed that the Vertical Total Electron Content (VTEC) was severely disturbed during the storm main and recovery phases. A wavelike oscillation with three peaks was observed in the TEC diurnal variation from equator to low latitudes during the storm main phase on 17th and 18th March, 2015. The latitudinal extent of the wavelike oscillation peaks decreased from the beginning of main phase towards the recovery phase. The first peak extended from beyond 0S to 30S, the second occurred from 6S to 25S, whereas the third diurnal peaks was confined from 13S to 25S. In addition, a strong negative phase in VTEC variations was observed during the recovery phase on March 18-19, 2015. This ionospheric negative phase was stronger at low-latitudes than in the equatorial region. Also, two latitudinal chains of GPS-TEC stations from equatorial region to low latitudes in the East and West Brazilian sectors are used to investigate the storm time behavior of the Equatorial Ionization Anomaly (EIA) in the East and West Brazilian sectors. We observed an anomalous behavior in EIA caused by the wavelike oscillations during the storm main phase on 17 March, and suppression of the EIA, resulting from the negative phase in VTEC, in the storm recovery phase.

  6. Anomalous heating of the polar E region by unstable plasma waves. II - Theory

    Science.gov (United States)

    St.-Maurice, J. P.; Schlegel, K.; Banks, P. M.

    1981-01-01

    It is found that anomalous electron temperatures in the disturbed high-latitude E region can be quantitatively explained in terms of heating by unstable plasma waves. The electron temperatures at 110 km have been measured to be as high as 1500 K instead of the expected value of about 300 K. It is shown that by using quasi-linear theory there is an ample source of heat in the unstable waves and that the measured electron temperature profiles have a shape very similar to what is expected from plasma wave heating by the modified two-stream instability. It is found that there is even more heating going to the ion gas, but that the resulting effect on the ion temperature may be difficult to measure. The best estimate of the wave heating rates leads to the conclusion that wave heating can be as much as 50% of the Joule heating for dc electric field strengths of the order of 45 mV/m or greater.

  7. Long-term variations and trends in the polar E-region

    Science.gov (United States)

    Bjoland, L. M.; Ogawa, Y.; Hall, C.; Rietveld, M.; Løvhaug, U. P.; La Hoz, C.; Miyaoka, H.

    2017-10-01

    As the EISCAT UHF radar system in Northern Scandinavia started its operations in the early 1980s, the collected data cover about three solar cycles. These long time-series provide us the opportunity to study long-term variations and trends of ionospheric parameters in the high latitude region. In the present study we have used the EISCAT Tromsø UHF data to investigate variations of the Hall conductivity and ion temperatures in the E-region around noon. Both the ion temperature and the peak altitude of the Hall conductivity are confirmed to depend strongly on solar zenith angle. However, the dependence on solar activity seems to be weak. In order to search for trends in these parameters, the ion temperature and peak altitude of the Hall conductivity data were adjusted for their seasonal and solar cycle dependence. A very weak descent (∼0.2 km/ decade) was seen in the peak altitude of the Hall conductivity. The ion temperature at 110 km shows a cooling trend (∼10 K/ decade). However, other parameters than solar zenith angle and solar activity seem to affect the ion temperature at this altitude, and a better understanding of these parameters is necessary to derive a conclusive trend. In this paper, we discuss what may cause the characteristics of the variations in the electric conductivities and ion temperatures in the high latitude region.

  8. Southern high-latitude Digisonde observations of ionosphere E-region Bragg scatter during intense lacuna conditions

    Directory of Open Access Journals (Sweden)

    D. P. Monselesan

    2004-09-01

    Full Text Available During summer months at solar cycle minimum, F-region lacuna and slant-Es conditions (SEC are common features of daytime ionograms recorded around local magnetic noon at Casey, Antarctica. Digisonde measurements of drift velocity height profiles show that the occurrence of lacuna prevents the determination of F-region drift velocities and also affects E-region drift velocity measurements. Unique E-region spectral features revealed as intervals of Bragg scatter superimposed on typical background E-region reflection were observed in Digisonde Doppler spectra during intense lacuna conditions. Daytime E-region Doppler spectra recorded at carrier frequencies from 1.5 to 2.7MHz, below the E-region critical frequency foE, have two side-peaks corresponding to Bragg scatter at approximately ±1-2Hz symmetrically located on each side of a central-peak corresponding to near-zenith total reflections. Angle-of-arrival information and ray-tracing simulations show that echo returns are coming from oblique directions most likely resulting from direct backscatter from just below the total reflection height for each sounding frequency. The Bragg backscatter events are shown to manifest during polar lacuna conditions, and to affect the determination of E-region background drift velocities, and as such must be considered when using standard Doppler-sorted interferometry (DSI techniques to estimate ionospheric drift velocities. Given the Doppler and spatial separation of the echoes determined from high-resolution Doppler measurements, we are able to estimate the Bragg scatter phase velocity independently from the bulk E-region motion. The phase velocity coincides with the ExB direction derived from in situ fluxgate magnetometer records. When ionospheric refraction is considered, the phase velocity amplitudes deduced from DSI are comparable to the ion-acoustic speed expected in the E-region. We briefly consider the plausibility that these previously unreported polar

  9. Study of zonal large scale wave structure (LSWS) and equatorial scintillation with low-latitude GRBR network over Southeast Asia and African sectors

    Science.gov (United States)

    Ram Sudarsanam, Tulasi; Yamamoto, Mamoru; Gurubaran, Subramanian; Tsunoda, Roland

    2012-07-01

    The day-to-day variability of Equatorial Spread-F, when and where the equatorial plasma bubbles (EPBs) may initiate, were the challenging problems that puzzling the space weather researchers for several decades. The zonal large scale wave structure (LSWS) at the base of F-layer is the earliest manifestation of seed perturbation for the evolution of EPBs by R-T instability processes, hence, found to play deterministic role on the development of ESF. Yet, only a little is known about LSWS with lack of sufficient observations, primarily because of inability to detect the LSWS with the currently existing instruments except with steerable incoherent scatter radar such as ALTAIR radar. This situation, however, was recently changed with launch of C/NOFS in a unique low-inclination (13 ^{o}) orbit. With the availability of CERTO beacon transmissions from C/NOFS in a near equatorial orbit, it is now possible to detect and resolve the roles by LSWS on a regular basis. A ground based low-latitude GNU Radio Beacon Receiver (GRBR) Network has been recently established that provide coverage of Southeast Asia, Pacific and African low-latitude regions. Recent observations suggest that these wave structures with zonal wave lengths varying between 200 and 800 km can be earliest detected even before E-region sunset and found to grow significantly after sunset, probably, aided by the polarization electric fields. Further, these zonal structures consistently found to be aligned with field lines for several hundreds of kilometers and EPBs were found to grow from the westward walls of upwellings. The characteristic differences on the strength of LSWS between the Asian and African longitudes were identified during the recent increasing solar activity and discussed in this paper.

  10. A Numerical Investigation on Tidal and Gravity Wave Contributions to the Summer Time Na Variations in the Midlatitude E Region

    Science.gov (United States)

    Cai, Xuguang; Yuan, Tao; Eccles, J. Vincent

    2017-10-01

    The Na density variations in the E region have been studied over the past few decades. Although considerable progress in understanding and in modeling the metal layer observations has been made, Na density features above 100 km have yet to be explained. Various studies have linked them to the Na+ variations, a major reservoir for Na in E region. But the lack of comprehensive modeling investigations and of wind and temperature observations prevents further understanding on this important ion-neutral coupling topic. In this study, we conduct a numerical simulation on the summer time Na density behavior in the midlatitude E region, where both the ion density and the neutral atmosphere are modulated by tidal and gravity waves. Simulation results show good agreement with Na lidar measurements and reveal that atmospheric waves can transport Na upward to generate Na layers and variations in E region considerably. The vertical wind component of the large amplitude tidal wave can extend the Na layer above 120 km into the thermosphere. The simulation also demonstrates that the modulation of large amplitude gravity (GW) wave can generate small-scale sporadic Na layers (Nas) in the E region. Finally, eddy diffusion enhancement in the GW saturation process can significantly alter the Nas spatial and temporal structures.

  11. Jupiter's North Equatorial Belt: An historic change in cyclic behaviour with acceleration of the North Equatorial jet

    Science.gov (United States)

    Rogers, J.; Adamoli, G.; Hahn, G.; Jacquesson, M.; Vedovato, M.; Mettig, H.-J.

    2013-09-01

    Systematic amateur records of Jupiter's atmosphere go back to the 19th century, documenting some large-scale patterns which only recur after many decades. Modern amateur images reveal fine details of the atmospheric dynamics which were hitherto undetectable except from spacecraft. A recent transformation of the North Equatorial Belt (NEB) illustrates the power of these records to identify alarge - scale phenomenon that had not occurred for nearly a century - the NEB narrowing and revival - and to reveal a marked apparent acceleration of the associated jet at 7ºN, which deepens our understanding of the atmospheric dynamics.

  12. Investigating the effect of geomagnetic storm and equatorial electrojet on equatorial ionospheric irregularity over East African sector

    Science.gov (United States)

    Seba, Ephrem Beshir; Nigussie, Melessew

    2016-11-01

    The variability of the equatorial ionosphere is still a big challenge for ionospheric dependent radio wave technology users. To mitigate the effect of equatorial ionospheric irregularity on trans-ionospheric radio waves considerable efforts are being done to understand and model the equatorial electrodynamics and its connection to the creation of ionospheric irregularity. However, the effect of the East-African ionospheric electrodynamics on ionospheric irregularity is not yet well studied due to lack of multiple ground based instruments. But, as a result of International Heliophysical Year (IHY) initiative, which was launched in 2007, some facilities are being deployed in Africa since then. Therefore, recently deployed instruments, in the Ethiopian sector, such as SCINDA-GPS receiver (2.64°N dip angle) for TEC and amplitude scintillation index (S4) data and two magnetometers, which are deployed on and off the magnetic equator, data collected in the March equinoctial months of the years 2011, 2012, and 2015 have been used for this study in conjunction with geomagnetic storm data obtained from high resolution OMNI WEB data center. We have investigated the triggering and inhibition mechanisms for ionospheric irregularities using, scintillation index (S4), equatorial electrojet (EEJ), interplanetary electric field (IEFy), symH index, AE index and interplanetary magnetic field (IMF) Bz on five selected storm and two storm free days. We have found that when the eastward EEJ fluctuates in magnitude due to storm time induced electric fields at around noontime, the post-sunset scintillation is inhibited. All observed post-sunset scintillations in equinox season are resulted when the daytime EEJ is non fluctuating. The strength of noontime EEJ magnitude has shown direct relation with the strength of the post-sunset scintillations. This indicates that non-fluctuating EEJ stronger than 20 nT, can be precursor for the occurrence of the evening time ionospheric irregularities

  13. The policy of the Portuguese language in equatorial guinea

    Directory of Open Access Journals (Sweden)

    Charlott Eloize Leviski

    2015-12-01

    Full Text Available http://dx.doi.org/10.5007/1984-8420.2015v16n2p62 The officialization of the Portuguese language in Equatorial Guinea, a Central African country, and its subsequent binding to the Community of Portuguese Language Countries is addressed in this paper. The discussion is heading from an interdisciplinary perspective between History and Linguistics, which seeks to emphasize the political di­mension of linguistic description of the Fá d´ambô, language spoken in Annobón prov­ince, one of Equatorial Guinea’s territory, since it has been used as evidence of connec­tion with Portuguese culture and language. By way of a critical approach, the article tries to reflect on the extent to which the historic rescue of language would be an attempt to establish a continuity with a missing link, interpreting the language policy of descriptive linguistics through the concept of invention of tradition. (HOBSBAWM, 2015.

  14. Neutronic analysis of the Diagnostic Equatorial Ports in ITER

    Energy Technology Data Exchange (ETDEWEB)

    Suarez, Alejandro [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France); Bertalot, Luciano, E-mail: luciano.bertalot@iter.org [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France); Maquet, Philippe; Pitcher, Charles Spencer; Portales, Mickael [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France); Serikov, Arkady [Karlsruhe Institute of Technology KIT, 76344 Eggenstein-Leopoldshafen (Germany); Udintsev, Victor; Walsh, Michael [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France)

    2015-10-15

    Highlights: • Reduction of the streaming around Equatorial Ports. • Solutions for the mitigation of narrow gap streaming. • Importance of the environment and the radiation cross talk. - Abstract: The Diagnostic Port Plugs provide an infrastructure for integrating the diagnostics necessary to operate the machine, while withstanding the nuclear and mechanical loads. They have to provide neutron shielding in order to ensure accessibility to the Port Interspace (PI) region for maintenance operations. This report is about the study to mitigate the ITER Shutdown Dose Rate in Port Interspace. This is a strong design driver for the Equatorial Port Plugs (EPPs) requiring a neutron attenuation of 7 orders of magnitude while maintaining the weight limit. To achieve this challenging task, the design has evolved to an improved double labyrinth configuration with welded shims at the back of the EPP to reduce the gap with the Vacuum Vessel Port Extension. This proved to be very successful for this task. Neutron stoppers have been placed after the gaps necessary for the insertion of the Diagnostic Shielding Modules (DSMs) housed inside the EPP. Effort was also placed in the further development of the DSMs. The latest design relies on a stainless steel structure and lightweight efficient neutron absorbing materials inside. Studies of cross talk with lower ports and the influence of the streaming through the blanket area are presented to give the status of the radiation environment in the Port Interspace region and their contribution to the Shutdown Dose Rate (SDR).

  15. 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.

  16. Check-list of the Piperaceae of Equatorial Guinea

    Directory of Open Access Journals (Sweden)

    Fero, Maximiliano

    2002-06-01

    Full Text Available A check-list of the Piperaceae from Equatorial Guinea is presented, with 13 species. Three species are known from Annobón, 13 species from Bioko and 5 species from Río Muni. The best represented genus is Peperomia, with 10 species. The other two genera. Piper and Pothomorphe, are represented by two and one species, respectively. Additionally, bibliographic references on Piperaceae of Equatorial Guinea (223 records have been gathered and revised. Peperomia mollera and Piper capense are recorded as new to Río Muni.Se presenta el catálogo florístico de la familia Piperaceae para Guinea Ecuatorial, en el que se recogen un total de 13 especies englobadas en tres géneros. En Annobón están presentes tres especies, 13 en Bioko y cinco en Río Muni. Peperomia es el género mejor representado, con 10 especies. Los otros dos géneros, Pothomorphe y Piper, están representados por una y dos especies, respectivamente. Se han recopilado y revisado las referencias bibliográficas previas para la zona hasta un total de 223 citas. Peperomia mollera y Piper capense se citan por primera vez para Río Muni.

  17. Check list of the Melastomataceae of Equatorial Guinea

    Directory of Open Access Journals (Sweden)

    Geerinck, Daniel

    2003-12-01

    Full Text Available A chec klist of the Melastomataceae of Equatorial Guinea is presented with 57 taxa. Three species were accepted based only on literature records, their distribution área strongly suggests their presence in Equatorial Guinea. Six species are known from Annobón, 23 from Bioko and 49 from Río Muni. Best-represented genera are Memecylon (10, Calvoa (10 and Tristemma (7. Twenty-six taxa are newly recorded for the country. Heterotis obamae Lejoly & Lisowski is set in synonymy with the previously described Heterotis arenaria Jacq.-Fél.Se presenta el catálogo florístico de la familia Melastomataceae en Guinea Ecuatorial. Se recogen un total de 57 táxones. Tres especies fueron aceptadas teniendo en cuenta solamente la literatura. Su distribución sugiere que su presencia en Guinea Ecuatorial es muy probable. En Annobón están presentes 6 especies, 23 en Bioko y 49 en Río Muni. Los géneros mejor representados son Memecylon (10 especies, Calvoa (10 y Tristemma (7.Veintiséis táxones son citados por primera vez en Guinea Ecuatorial. Se propone Heterotis obamae Lejoly & Lisowski como sinónimo de Heterotis arenaria Jacq.-Fél.

  18. Equatorial convergence of India and early Cenozoic climate trends.

    Science.gov (United States)

    Kent, Dennis V; Muttoni, Giovanni

    2008-10-21

    India's northward flight and collision with Asia was a major driver of global tectonics in the Cenozoic and, we argue, of atmospheric CO(2) concentration (pCO(2)) and thus global climate. Subduction of Tethyan oceanic crust with a carpet of carbonate-rich pelagic sediments deposited during transit beneath the high-productivity equatorial belt resulted in a component flux of CO(2) delivery to the atmosphere capable to maintain high pCO(2) levels and warm climate conditions until the decarbonation factory shut down with the collision of Greater India with Asia at the Early Eocene climatic optimum at approximately 50 Ma. At about this time, the India continent and the highly weatherable Deccan Traps drifted into the equatorial humid belt where uptake of CO(2) by efficient silicate weathering further perturbed the delicate equilibrium between CO(2) input to and removal from the atmosphere toward progressively lower pCO(2) levels, thus marking the onset of a cooling trend over the Middle and Late Eocene that some suggest triggered the rapid expansion of Antarctic ice sheets at around the Eocene-Oligocene boundary.

  19. Climatology characterization of equatorial plasma bubbles using GPS data

    Directory of Open Access Journals (Sweden)

    Magdaleno Sergio

    2017-01-01

    Full Text Available The climatology of equatorial plasma bubbles (EPBs for the period 1998–2008 was studied using slant total electron content (sTEC derived from global positioning system (GPS data. The sTEC values were calculated from data measured at 67 International GNSS Service (IGS stations distributed worldwide around the geomagnetic equator and embracing the region of the ionospheric equatorial anomaly (IEA. EPBs and their characteristics were obtained using the Ionospheric Bubble Seeker (IBS application, which detects and distinguishes sTEC depletions associated with EPBs. This technique bases its analysis on the time variation of the sTEC and on the population variance of this time variation. IBS finds an EPB by default when an sTEC depletion is greater than 5 TEC units (TECu. The analysis of the spatial behavior shows that the largest rate of EPB takes place at the equator and in the South America-Africa sector, while their occurrence decreases as the distance from the magnetic equator increases. The depth and duration of the sTEC depletions also maximize at the equator and in the South America-Africa sector and weaken departing from the equator. The results of the temporal analysis for the data of the IGS stations located in AREQ, NKLG, IISC, and GUAM indicate that the greatest rate of EPB occurrence is observed for high solar activity.

  20. Fourier Series Approximations to J2-Bounded Equatorial Orbits

    Directory of Open Access Journals (Sweden)

    Wei Wang

    2014-01-01

    Full Text Available The current paper offers a comprehensive dynamical analysis and Fourier series approximations of J2-bounded equatorial orbits. The initial conditions of heterogeneous families of J2-perturbed equatorial orbits are determined first. Then the characteristics of two types of J2-bounded orbits, namely, pseudo-elliptic orbit and critical circular orbit, are studied. Due to the ambiguity of the closed-form solutions which comprise the elliptic integrals and Jacobian elliptic functions, showing little physical insight into the problem, a new scheme, termed Fourier series expansion, is adopted for approximation herein. Based on least-squares fitting to the coefficients, the solutions are expressed with arbitrary high-order Fourier series, since the radius and the flight time vary periodically as a function of the polar angle. As a consequence, the solutions can be written in terms of elementary functions such as cosines, rather than complex mathematical functions. Simulations enhance the proposed approximation method, showing bounded and negligible deviations. The approximation results show a promising prospect in preliminary orbits design, determination, and transfers for low-altitude spacecrafts.

  1. Further notes on Brazilian Conidae

    NARCIS (Netherlands)

    Mol, van J.-J.; Tursch, B.; Kempf, M.

    1971-01-01

    Since the publication of a survey of brazilian Conidae (Van Moll et al., 1967) new extensive dredgings effected by one of us (M.K.) along considerable portions of the Brazilian coast have brought a rich material allowing us to add to the previous work and to correct certain opinions therein

  2. Simultaneous observations of equatorial F-region plasma depletions over Brazil during the Spread-F Experiment (SpreadFEx

    Directory of Open Access Journals (Sweden)

    P.-D. Pautet

    2009-06-01

    Full Text Available From September to November 2005, the NASA Living with a Star program supported the Spread-F Experiment campaign (SpreadFEx in Brazil to study the effects of convectively generated gravity waves on the ionosphere and their role in seeding Rayleigh-Taylor instabilities, and associated equatorial plasma bubbles. Several US and Brazilian institutes deployed a broad range of instruments (all-sky imagers, digisondes, photometers, meteor/VHF radars, GPS receivers covering a large area of Brazil. The campaign was divided in two observational phases centered on the September and October new moon periods. During these periods, an Utah State University (USU all-sky CCD imager operated at São João d'Aliança (14.8° S, 47.6° W, near Brasilia, and a Brazilian all-sky CCD imager located at Cariri (7.4° S, 36° W, observed simultaneously the evolution of the ionospheric bubbles in the OI (630 nm emission and the mesospheric gravity wave field. The two sites had approximately the same magnetic latitude (9–10° S but were separated in longitude by ~1500 km.

    Plasma bubbles were observed on every clear night (17 from Brasilia and 19 from Cariri, with 8 coincident nights. These joint datasets provided important information for characterizing the ionospheric depletions during the campaign and to perform a novel longitudinal investigation of their variability. Measurements of the drift velocities at both sites are in good agreement with previous studies, however, the overlapping fields of view revealed significant differences in the occurrence and structure of the plasma bubbles, providing new evidence for localized generation. This paper summarizes the observed bubble characteristics important for related investigations of their seeding mechanisms associated with gravity wave activity.

  3. Simultaneous observations of equatorial F-region plasma depletions over Brazil during the Spread-F Experiment (SpreadFEx

    Directory of Open Access Journals (Sweden)

    P.-D. Pautet

    2009-06-01

    Full Text Available From September to November 2005, the NASA Living with a Star program supported the Spread-F Experiment campaign (SpreadFEx in Brazil to study the effects of convectively generated gravity waves on the ionosphere and their role in seeding Rayleigh-Taylor instabilities, and associated equatorial plasma bubbles. Several US and Brazilian institutes deployed a broad range of instruments (all-sky imagers, digisondes, photometers, meteor/VHF radars, GPS receivers covering a large area of Brazil. The campaign was divided in two observational phases centered on the September and October new moon periods. During these periods, an Utah State University (USU all-sky CCD imager operated at São João d'Aliança (14.8° S, 47.6° W, near Brasilia, and a Brazilian all-sky CCD imager located at Cariri (7.4° S, 36° W, observed simultaneously the evolution of the ionospheric bubbles in the OI (630 nm emission and the mesospheric gravity wave field. The two sites had approximately the same magnetic latitude (9–10° S but were separated in longitude by ~1500 km. Plasma bubbles were observed on every clear night (17 from Brasilia and 19 from Cariri, with 8 coincident nights. These joint datasets provided important information for characterizing the ionospheric depletions during the campaign and to perform a novel longitudinal investigation of their variability. Measurements of the drift velocities at both sites are in good agreement with previous studies, however, the overlapping fields of view revealed significant differences in the occurrence and structure of the plasma bubbles, providing new evidence for localized generation. This paper summarizes the observed bubble characteristics important for related investigations of their seeding mechanisms associated with gravity wave activity.

  4. Counter electrojet features in the Brazilian sector: simultaneous observation by radar, digital sounder and magnetometers

    Directory of Open Access Journals (Sweden)

    C. M. Denardini

    2009-04-01

    Full Text Available In the present work we show new results regarding equatorial counter electrojet (CEJ events in the Brazilian sector, based on the RESCO radar, two set of fluxgate magnetometer systems and a digital sounder. RESCO radar is a 50 MHz backscatter coherent radar installed in 1998 at São Luís (SLZ, 2.33° S, 44.60° W, an equatorial site. The Digital sounder routinely monitors the electron density profile at the radar site. The magnetometer systems are fluxgate-type installed at SLZ and Eusébio (EUS, 03.89° S, 38.44° W. From the difference between the horizontal component of magnetic field at SLZ station and the same component at EUS (EEJ ground strength several cases of westward morning electrojet and its normal inversion to the eastward equatorial electrojet (EEJ have been observed. Also, the EEJ ground strength has shown some cases of CEJ events, which been detected with the RESCO radar too. Detection of these events were investigated with respect to their time and height of occurrence, correlation with sporadic E (Es layers at the same time, and their spectral characteristics as well as the radar echo power intensity.

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

    NARCIS (Netherlands)

    Qin, Xuerong; Sen Gupta, Alex; Van Sebille, Erik|info:eu-repo/dai/nl/304831921

    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

  6. A note on new indices for the equatorial Indian Ocean oscillation

    Indian Academy of Sciences (India)

    It is now well known that there is a strong association of the extremes of the Indian summer monsoon rainfall (ISMR) with the El Niño and southern oscillation (ENSO) and the Equatorial Indian Ocean Oscillation (EQUINOO), later being an east–west oscillation in convection anomaly over the equatorial Indian Ocean. So far ...

  7. A first look at past sea surface temperatures in the equatorial Indian Ocean from Mg/Ca in foraminifera

    Digital Repository Service at National Institute of Oceanography (India)

    Saraswat, R.; Nigam, R.; Weldeab, S.; Mackensen, A.; Naidu, P.D.

    Sea surface temperature (SST) for the central equatorial Indian Ocean, has been reconstructed over the last approx. 137 kyr, from Mg/Ca of the planktonic foraminiferal species Globigerinoides ruber. According to our record the equatorial Indian...

  8. Variability of the diurnal tide in the equatorial MLT

    Science.gov (United States)

    Riggin, Dennis M.; Lieberman, Ruth S.

    2013-09-01

    For many years the amplitude of the diurnal tide in the mesosphere, lower thermosphere (MLT) has been known to be deeply modulated over a wide range of time scales. These time scales range from a few days, to seasonal dependencies, and up to interannual time scales. The causes of the variability have remained elusive, but can fall into two main categories. The first is source variability, the variability arising from variations in water vapor heating, latent heating, and ozone heating. The second potential cause is interaction of the diurnal tide with the background, including the effects of the zonal mean structure, planetary waves, gravity waves and turbulence. In this paper we focus on the second category of tidal variability. Measurements at the equator allow us to focus on particular mechanisms of tidal variability. We are close to the main sources driving the tide, equatorial convection and water vapor heating. The equatorial mean zonal winds are relatively weak so we also avoid the filtering of the tide due to the midlatitude jets. Although we cannot observe wave-mean and wave-wave interactions directly, a decadal climatology allows to diagnose how much tidal-background interaction might contribute to tidal variability. We make use of data from the SABER instrument, providing continuous temperature measurements and augment these with some equatorial radar wind observations. Two-month averages of SABER temperatures are required to unambiguously define migrating tidal temperature fields which confine our study mainly for variability on a seasonal time scale or longer. The temperature tide has a repeatable seasonal variation that is shown to stem directly from the sources and which can be observed as low as tropopause heights. Refraction and reflection are found to play an important role in the vertical structure of the tide and found to influence temporal variability in both amplitude and phase when the tide propagates into the mesosphere. An anti

  9. 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

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

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    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

  11. Brazilian Nanotechnology Initiative

    Science.gov (United States)

    Fazzio, Adalberto

    2015-03-01

    In Brazil there is intense research activity in nanotechnology, most of these developed in universities and research institutes. The Brazilian Nanotechnology Initiative (BNI) aims to integrate government actions to promote the competitiveness of the Brazilian industry. This initiative is founded on support for research and development in the laboratories of the National Laboratories for Nanotechnology (SisNANO), starting from an improvement in infrastructure and opening of laboratories for users of academia and business, promoting interaction and transfer knowledge between academia and business. Country currently has 26 thematic networks of nanotechnology, 16 -Virtual-National Institutes of Technology, seven National- Laboratories and 18 Associate Laboratories, which comprise the SisNANO. Seeking to expand and share governance with other government actors, the Interministries Committee for Nanotechnology was set up, composed of 10 ministries, and has the task of coordinating the entire program of the Federal Government Nanotechnology.Cooperation activities are an important part of BNI. Currently Brazil has cooperation programs with U.S., China, Canada and European Union among others. Recently, Brazil decided to join the European NanoReg program where 60 research groups are joining efforts to provide protocols and standards that can help regulatory agencies and governments.

  12. 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.

  13. Sensitivity studies of the E region neutral response to the postmidnight diffuse aurora

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    H. F. Parish

    2006-07-01

    Full Text Available Measurements of the neutral thermosphere within the postmidnight substorm recovery phase diffuse aurora show very large horizontal winds, and strong vertical structure. Rocket, satellite, and ground based observations during the ARIA (Atmospheric Response in Aurora campaigns, and earlier dawn side rocket observations, indicate neutral winds of up to 200 m/s, and a characteristic jet-like wind maximum around 110 to 120-km altitude, with strong shears above and below. The observed wind magnitudes are found to have a dependence on geomagnetic activity level, but recent modeling studies suggest that tides which propagate up from the troposphere and stratosphere may play an important role in generating the strong vertical variations in the neutral winds. The relative importance of auroral and tidal forcing in producing the measured wind structure is not known, however. Simulations have been performed using a three dimensional (3-D high resolution limited area thermosphere model to understand the processes which generate the observed neutral structure within the postmidnight diffuse aurora. Parameters measured during the ARIA I observational campaign have been used to provide auroral forcing inputs for the model. Global background winds and tides have been provided by the CTIP (Coupled Thermosphere Ionosphere Plasmasphere model. The sensitivity of the response of the neutral atmosphere to changes in different parameters has been examined. Variations in the amplitudes and phases of the propagating tides in the background winds are found to have significant effects on the neutral structure in the E region, and the wind structure below around 110km is found to be mainly produced by tidal forcing. Changes in the electric field and ion density affect the winds above around 120 km, and the importance of auroral forcing is found to depend on background winds. Variations in the orientation of the aurora relative to the background field, which may be caused

  14. The ionospheric response in the Brazilian sector during the super geomagnetic storm on 20 November 2003

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    F. Becker-Guedes

    2007-05-01

    Full Text Available A very intense geomagnetic storm (superstorm began with storm sudden commencement (SSC at 08:03 UT on 20 November 2003, as a result of the coronal mass ejection (CME by sunspot 484 hurled into space on 18 November 2003. The geomagnetic storm attained |Dst|max=472 nT at 20:00 UT (20 November. In this paper we present the simultaneous ionospheric sounding observations, using the Canadian Advanced Digital Ionosondes (CADIs, carried out from Palmas (PAL; 10.2° S, 48.2° W; dip latitude 5.5° S; a near equatorial station and São José dos Campos (SJC; 23.2° S, 45.9° W; dip latitude 17.6° S; station located under the crest of equatorial ionospheric anomaly, Brazil. In addition, total electron content (TEC measurements from several GPS receiving stations in the Brazilian sector during this storm are presented. The simultaneous ionospheric sounding observations carried out at SJC and PAL, and TEC observations on 3 consecutive days viz., 19 November (quiet, 20 November (disturbed and 21 November (recovery phase are presented. Salient features from the ionospheric observations in the Brazilian sector during the superstorm are discussed. The difference in the observed ionospheric response at the two stations (PAL and SJC is considerable. This is not surprising given that PAL is close to the magnetic equator and SJC is near the crest of the equatorial ionospheric anomaly (EIA. It should be pointed out that soon after the SSC (about 4 h later, the F-region critical frequency (foF2, the F-region peak height (hpF2, and variations of virtual heights at different frequencies (iso-frequency plots all show wavelike oscillations of the F-region during daytime at both the ionospheric sounding stations. Unusual rapid uplifting of F-region at PAL was observed during both the main and recovery phases of the storm.

  15. Solar cycle signatures in the NCEP equatorial annual oscillation

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    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.

  16. Origin of HIV type 1 in colonial French Equatorial Africa?

    Science.gov (United States)

    Chitnis, A; Rawls, D; Moore, J

    2000-01-01

    Sociocultural factors during the postcolonial period have been implicated as paramount in generating conditions that promoted both the origin and subsequent epidemic spread of HIV-1 in Africa. We suggest, however, that the origin of the disease may lie in the interaction between colonial practices (e.g., labor camps, nonsterile vaccination campaigns) and traditional bushmeat hunting in French Equatorial Africa. Both the epidemiology of HIV-2 and the colonial history of West Africa appear more complex, but similar conditions existed there and may have contributed to the origin of HIV-2. Focusing the search for the origins of HIV-1 and HIV-2 on this earlier time period may contribute to understanding the evolution of the HIV viruses and the dynamics of emerging diseases.

  17. Climatically driven changes in oceanic processes throughout the equatorial Pacific

    Science.gov (United States)

    Paytan, Adina; Lyle, Mitch; Mix, Alan; Chase, Zanna

    2004-12-01

    The mass accumulation rates of sedimentary components (carbonate, organic carbon, opal, barite, reactive phosphate, iron, terrigenous minerals, etc.) are used in many paleoceanographic reconstructions to learn about temporal and spatial changes in surficial Earth processes including wind stress and direction, oceanic circulation, weathering rates, marine productivity and ecosystem structure, climate change, and more. In most studies it is assumed/desired that the sediment accumulation represents the production and deposition of particles from the overlying water column since substantial horizontal transport imply homogenization of paleoceanographic proxies and little confidence in any paleoceanographic time series. In this note we highlight some discrepancies between the different approaches used to reconstruct sediment mass accumulation rates and specifically discuss the consequences of these discrepancies to the reconstruction of paleoproductivity in the equatorial Pacific. We pose research questions and suggest possible approaches/research strategies for the community to solve them.

  18. The influence of thermocline slope on equatorial thermocline displacement

    Science.gov (United States)

    Hughes, Roger L.

    1981-02-01

    The influence of a zonal slope in the thermocline on both wave- and wind-induced equatorial upwelling is studied. It is shown that the vertical displacement of the thermocline induced by a long Kelvin or planetary wave varies as the thermocline depth to the power -3/8, as the wave propagates into a region of changed thermocline depth The zonal and meridional velocities induced by a wave vary as the thermocline depth to the power -7/8. The wind-induced upwelling associated with a zonal slope of the thermocline is shown to be strongly confined to the equator. The importance of thermocline slope on the Ekman divergence is found to increase with time from the initial application of the wind stress perturbation. In the Pacific Ocean the meridional velocity may be altered by up to 60% by the thermocline slope before the influence of the boundaries becomes important.

  19. SpIES: The Spitzer IRAC Equatorial Survey

    Science.gov (United States)

    Timlin, John D.; Ross, Nicholas P.; Richards, Gordon T.; Lacy, Mark; Ryan, Erin L.; Stone, Robert B.; Bauer, Franz E.; Brandt, W. N.; Fan, Xiaohui; Glikman, Eilat; Haggard, Daryl; Jiang, Linhua; LaMassa, Stephanie M.; Lin, Yen-Ting; Makler, Martin; McGehee, Peregrine; Myers, Adam D.; Schneider, Donald P.; Urry, C. Megan; Wollack, Edward J.; Zakamska, Nadia L.

    2016-07-01

    We describe the first data release from the Spitzer-IRAC Equatorial Survey (SpIES); a large-area survey of ˜115 deg2 in the Equatorial SDSS Stripe 82 field using Spitzer during its “warm” mission phase. SpIES was designed to probe sufficient volume to perform measurements of quasar clustering and the luminosity function at z ≥slant 3 to test various models for “feedback” from active galactic nuclei (AGNs). Additionally, the wide range of available multi-wavelength, multi-epoch ancillary data enables SpIES to identify both high-redshift (z ≥slant 5) quasars as well as obscured quasars missed by optical surveys. SpIES achieves 5σ depths of 6.13 μJy (21.93 AB magnitude) and 5.75 μJy (22.0 AB magnitude) at 3.6 and 4.5 μm, respectively—depths significantly fainter than the Wide-field Infrared Survey Explorer (WISE). We show that the SpIES survey recovers a much larger fraction of spectroscopically confirmed quasars (˜98%) in Stripe 82 than are recovered by WISE (˜55%). This depth is especially powerful at high-redshift (z ≥slant 3.5), where SpIES recovers 94% of confirmed quasars, whereas WISE only recovers 25%. Here we define the SpIES survey parameters and describe the image processing, source extraction, and catalog production methods used to analyze the SpIES data. In addition to this survey paper, we release 234 images created by the SpIES team and three detection catalogs: a 3.6 μm only detection catalog containing ˜6.1 million sources, a 4.5 μm only detection catalog containing ˜6.5 million sources, and a dual-band detection catalog containing ˜5.4 million sources.

  20. BeppoSAX equatorial uncontrolled re-entry

    Science.gov (United States)

    Portelli, C.

    The X-ray astronomy satellite BeppoSAX (Satellite per Astronomia X, "Beppo" in honor of Giuseppe Occhialini), is a project of the Italian Space Agency (ASI) with participation of the Netherlands Agency for Aerospace Programs (NIVR). BeppoSAX was launched by an Atlas G Centaur directly into a circular 600 km- orbit at 3.9 degrees inclination on April 30th, 1996. The satellite is a three axis stabilized spacecraft with a total mass of about 1400 kg. The current (May 1, 2002) flight altitude is about 470 km and its uncontrolled re-entry is predicted late in 2002, or in 2003, with a 26 kg of hydrazine on board that could not be vented or used for controlled re-entry due to gyro's package total failure. Due to the relatively high mass of BeppoSAX, it has to be expected that parts of the satellite will survive the re-entry into the earth atmosphere. The Italian Space Agency has committed a study to HTG for the analysis of the destructive phase of the uncontrolled atmospheric re-entry by means of a dedicated European software tool (SCARAB). The expected outputs will be used in order to determine how much of the spacecraft and how many fragments parts of it will reach the ground on the equatorial earth zone. This paper will address the peculiarities of the spacecraft initial status, its risks at end of life and the SCARAB modelling as well as its 6D flight dynamics re-entry analysis results also in terms of the destruction history tree. Consideration will be made on the ground dispersion and casualt y area due to the very restricted equatorial zone impacted. References B. Fritsche, H. Klinkrad, A. Kashkovsky, E.Grinberg; Spacecraft Disintegration during uncontrolled atmospheric entry ; IAA-99-IAA.6.7.02; 50t h IAC 4-8 Oct. 1999

  1. Outgassing of the Eastern Equatorial Pacific during the Pliocene period.

    Science.gov (United States)

    Guillermic, M.; Tripati, A.

    2016-12-01

    The transition from the warm, ice-free conditions of the early Cenozoic to present-day glacial state with ice sheets in both hemispheres has been ascribed to long- and short-term changes in atmospheric CO2. The processes causing long-term changes in atmospheric CO2 levels are of debate. One possible explanation for changes in atmospheric CO2 relates to changes in air-sea exchange due to fluctuations in ocean carbon sources and sinks, as modulated by the stratification of surface waters. While nutrient consumption in low-latitude environments and associated export of CO2 to the deep sea works to sequester CO2 in the ocean interior, the return of deep water to the surface in the high latitudes and upwelling at the equator and in the eastern portion of ocean basins releases CO2. Quantitative estimates for surface water pH and pCO2 in different regions of the ocean and identification of CO2-sources and sinks are needed to better understand the role of the ocean in driving and/or amplifying variations in the atmospheric CO2 reservoir and climate change. Here we present preliminary results of surface water pH for the early Pliocene to Holocene based on boron isotope measurements of planktic foraminifera for the Eastern Equatorial Pacific. We develop records of B/Ca, Mg/Ca ratios, boron isotopes, and oxygen isotopes measurements in foraminifera tests (Globigeneroides sacculifer, Globigeneroides ruber, Neogloboquadrina dutertrei). We reconstruct changes in ocean CO2 outgassing in the Eastern Equatorial Pacific using records from ODP Site 847 (0°N, 95°W, 3373 m water depth). These data are used to examine if there is evidence for changes in stratification and CO2 outgassing during the early Pliocene warm period and during Pliocene intensification of Northern Hemisphere glaciation.

  2. 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

  3. Pharmacogenetics in the Brazilian population

    Directory of Open Access Journals (Sweden)

    Guilherme eSuarez-Kurtz

    2010-10-01

    Full Text Available Brazil is the 5th largest country in the world and its present population, in excess of 190 million, is highly heterogeneous, as a result of centuries of admixture between Amerindians, Europeans and Sub-Saharan Africans. The estimated individual proportions of biogeographical ancestry vary widely and continuously among Brazilians, most individuals - irrespective of self-identification as White, Brown or Black, the major categories of the Brazilian Census race/color system - having significant degrees of European and African ancestry, while a sizeable number display also Amerindian ancestry. These features have important pharmacogenetic (PGx implications: first, extrapolation of PGx data from relatively well-defined ethnic groups is clearly not applicable to the majority of Brazilians; second, the frequency distribution of polymorphisms in pharmacogenes (e.g. CYP3A5, CYP2C9, GSTM1, ABCB1, GSTM3, VKORC, etc varies continuously among Brazilians and is not captured by race/color self-identification; third, the intrinsic heterogeneity of the Brazilian population must be acknowledged in the design and interpretation of PGx studies in order to avoid spurious conclusions based on improper matching of study cohorts. The peculiarities of PGx in Brazilians are illustrated with data for different therapeutic groups, such as anticoagulants, HIV-protease inhibitors and nonsteroidal antinflammatory drugs, and the challenges and advantages created by population admixture for the study and implementation of PGx are discussed. PGx data for Amerindian groups and Brazilian-born, first generation Japanese are presented to illustrate the rich diversity of the Brazilian population. Finally, I introduce the reader to the Brazilian Pharmacogenetic Network or Refargen (www.refargen.org.br, a nationwide consortium of research groups, with the mission to provide leadership in PGx research and education in Brazil, with a population health impact.

  4. Vertical rise velocity of equatorial plasma bubbles estimated from Equatorial Atmosphere Radar (EAR) observations and HIRB model simulations

    Science.gov (United States)

    Tulasi Ram, S.; Ajith, K. K.; Yokoyama, T.; Yamamoto, M.; Niranjan, K.

    2017-06-01

    The vertical rise velocity (Vr) and maximum altitude (Hm) of equatorial plasma bubbles (EPBs) were estimated using the two-dimensional fan sector maps of 47 MHz Equatorial Atmosphere Radar (EAR), Kototabang, during May 2010 to April 2013. A total of 86 EPBs were observed out of which 68 were postsunset EPBs and remaining 18 EPBs were observed around midnight hours. The vertical rise velocities of the EPBs observed around the midnight hours are significantly smaller ( 26-128 m/s) compared to those observed in postsunset hours ( 45-265 m/s). 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 three-dimensional numerical high-resolution bubble (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. The smaller vertical rise velocities (Vr) and lower maximum altitudes (Hm) of EPBs during midnight hours are discussed in terms of weak polarization electric fields within the bubble due to weaker background electric fields and reduced background ion density levels.type="synopsis">type="main">Plain Language SummaryEquatorial plasma bubbles are plasma density irregularities in the ionosphere. The radio waves passing through these irregular density structures undergo severe degradation/scintillation that could cause severe disruption of satellite-based communication and augmentation systems such as GPS navigation. These bubbles develop at geomagnetic equator, grow vertically, and elongate along the field lines to latitudes away from the equator. The knowledge on bubble rise velocities and their maximum attainable

  5. Ionospheric Turbulence: Case Studies in Equatorial Spread F and Development of a Rocket-Borne Interferometer

    Science.gov (United States)

    Labelle, James William, III

    In March, 1983, two rockets were launched into the disturbed nighttime equatorial F-region from Punta Lobos, Peru. The plasma density measurements from these flights confirm that the topside spread F "plumes" identifiable in the backscatter power maps produced at the nearby Jicamarca Radar Observatory are correlated with large scale ((TURN)20 km) density depletions. The downward gradients of these depletions are highly structured, consistent with the linear theory of the gravitational instability. The wavenumber spectrum associated with these density irregularities occasionally exhibits a k('-1.5) form for wavelengths longer than about one kilometer, as reported previously by Rina et al. 1981 . These observations are shown to be consistent with the nonlinear theory of Sudan and Keskinen 1984 , although they also may be explained by at least two linear mechanisms: the generation of turbulence on the steepened walls of spread F bubbles, and the nonlocal role of the E-region in the development of spread F. At shorter wavelengths, the spectrum exhibits a subrange for which (delta)n/n is proportional to (delta)(phi), as previously reported by Kelley et al. 1982b , and interpreted by them as evidence for the role of low-frequency drift waves in spread F. an empirical calculation shows that the diffusion coefficient deduced from a consideration of global energy balance in spread F equals the enhanced diffusion coefficient that is expected to arise due to the drift waves; furthermore, this diffusion coefficient is in agreement with a convective transport model for drift wave induced anomalous diffusion. In an attempt to resolve the ambiguities involved in measuring wavenumber spectra with sounding rockets, a number of rocket experiments involving spatially separated plasma density probes have been performed at both high and low latitudes. This spaced-probe technique has proven effective in certain experiments--for example, measurement of the phase velocities of waves

  6. The rise of Brazilian agriculture

    DEFF Research Database (Denmark)

    Jensen, Hans Grinsted; Vink, Nick; Sandrey, Ron

    2014-01-01

    The purpose of this article is to explore some of the possible lessons for South African agriculture from the Brazilian experience. To this end, the article discusses the performance of Brazilian agriculture in terms of land and labour use, production, and exports. This is followed by aspects...... of Brazilian agricultural policies, namely farmer support, the research and technology transfer system and land issues. The implications for South African agriculture can be summarized as the recognition that history, geography, the development path and agricultural policies all matter. The article...... then identifies five important lessons for agricultural development in South Africa....

  7. brazilian subsidiaries of multinationals

    Directory of Open Access Journals (Sweden)

    Felipe Mendes Borini

    2012-01-01

    Full Text Available The theme of corporate social responsibility (CSR has not been widely examined in the context of multinationals. This dearth is even greater with respect to subsidiaries, particularly the subject of reverse transfer of practices, that is, the transfer of practices developed in subsidiaries back to the parent company. Because of this theoretical gap, the present article investigates the factors involved on reverse transfer of CSR practices. The research hypotheses test the importance of developing nonlocation-bound capabilities, of integration between subsidiaries and parent and of institutional distance. The data were obtained by a survey of the main foreign subsidiaries in Brazil. All told, we analyzed 150 Brazilian subsidiaries of multinationals, by applying multiple linear regression. The results indicate that the reverse transfer of CSR depends on the development of nonlocation-bound capabilities of the subsidiaries and integration between the parent company and its foreign subsidiaries.

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

    Science.gov (United States)

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

    2016-05-31

    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 Pacific, upwelling of water from the Equatorial Undercurrent supplies far more dissolved iron than is delivered by dust, by as much as two orders of magnitude. Nevertheless, recent studies have inferred that the greater supply of dust during ice ages stimulated greater utilization of nutrients within the region of upwelling on the equator, thereby contributing to the sequestration of carbon in the ocean interior. Here we present proxy records for dust and for biological productivity over the past 500 ky at three sites spanning the breadth of the equatorial Pacific Ocean to test the dust fertilization hypothesis. Dust supply peaked under glacial conditions, consistent with previous studies, whereas proxies of export production exhibit maxima during ice age terminations. Temporal decoupling between dust supply and biological productivity indicates that other factors, likely involving ocean dynamics, played a greater role than dust in regulating equatorial Pacific productivity.

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

    Science.gov (United States)

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

    2016-05-01

    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 Pacific, upwelling of water from the Equatorial Undercurrent supplies far more dissolved iron than is delivered by dust, by as much as two orders of magnitude. Nevertheless, recent studies have inferred that the greater supply of dust during ice ages stimulated greater utilization of nutrients within the region of upwelling on the equator, thereby contributing to the sequestration of carbon in the ocean interior. Here we present proxy records for dust and for biological productivity over the past 500 ky at three sites spanning the breadth of the equatorial Pacific Ocean to test the dust fertilization hypothesis. Dust supply peaked under glacial conditions, consistent with previous studies, whereas proxies of export production exhibit maxima during ice age terminations. Temporal decoupling between dust supply and biological productivity indicates that other factors, likely involving ocean dynamics, played a greater role than dust in regulating equatorial Pacific productivity.

  10. Brazilian Eratosthenes Project

    Science.gov (United States)

    Langhi, R.; Vilaça, J.

    2014-10-01

    The objective of Brazilian Eratosthenes Project is the development and application of teaching training actions according the ``docent autonomy" concept to basic Astronomy Education. Argentina coordinates the project in South America, but Brazil works in this project since 2010 with the theme ``Projeto Eratóstenes Brasil" in the homepage: http://sites.google.com/site/projetoerato. Two schools measure a sticks shadow and communicate their results. After, they calculate an average radius of Earth. The stick (gnomon) should stay in vertical position in the leveled ground. Since 2010, the project received hundreds of Brazilian schools with different experiments that were constructed with autonomy, because our site doesn't show some itinerary pre-ready to elaborate the experiments. To collect data for our research, we will use interviews via Skype with the teachers. These data are useful to researches about Science Education area and the Teaching Formation. Teaching professional practice could change and we see modifications in the teachers work, what depends of their realities and context. This project intents to respect the docent autonomy. This autonomy to responsible modifications during continued formation is called ``activist formative model" according Langhi & Nardi (Educação em Astronomia: repensando a formação de professores. São Paulo: Escrituras Editora, 2012). This project discusses about researches in Astronomy Education - still extreme rare in Brazil, when we compare with other areas in Science Education. We believe that actions like this could motivate the students to learn more Astronomy. Furthermore, this national action can be a rich source of data to investigations about teaching formation and scientific divulgation.

  11. INNOVATION IN BRAZILIAN SMALL COMPANIES

    Directory of Open Access Journals (Sweden)

    Tonny Kerley de Alencar Rodrigues

    2015-03-01

    Full Text Available This study aims to identify the interfaces and boundaries of innovation orientation of Brazilian MSEs because despite the importance of innovation for Brazilian MSEs, a thorough analysis of such initiatives in Brazil still has not actually happened. The search was developed from a quantitative approach, of applied nature and descriptive. For that a structured questionnaire was used where were interviewed 700 MSEs using a probabilistic sampling. The study offers two important conclusions. The challenges for innovation can be perceived along three dimensions: design innovation, the implementation of innovation and functional area of innovation. And the data confirms that small Brazilian companies generally have difficulties to sell their innovations. The study offers two important conclusions. The challenges for innovation can be perceived along three dimensions: design innovation, the implementation of innovation and functional area of innovation. And the data confirms that small Brazilian companies generally have difficulties to sell their innovations.

  12. Morphology of equatorial plasma bubbles during low and high solar activity years over Indian sector

    Science.gov (United States)

    Kumar, Sanjay

    2017-05-01

    In the present study, slant total electron content (STEC) data computed from ground based GPS measurements over Hyderabad (Geog. Lat. 17.41° N, geog. long. 78.55° E, mag. lat. 08.81° N) and two close stations at Bangalore (Geog. Lat. 13.02°/13.03° N, geog. long. 77.57°/77.51° E, mag. lat. 04.53°/04.55° N) in Indian region during 2007-2012, have been used to study the occurrences and characteristics of equatorial plasma bubbles (EPBs). The analysis found maximum EPB occurrences during the equinoctial months and minimum during the December solstice throughout 2007-2012 except during the solar minimum years in 2007-2009. During 2007-2009, the maximum EPB occurrences were observed in June solstice which could not be predicted by the model proposed by Tsunoda (J. Geophys. Res., 90:447-456, 1985). The equinox maximum in EPB occurrences for high solar activity years could be caused by the vertical F-layer drift due to pre-reversal electric field (PRE), and expected to be maximum when day-night terminator aligns with the magnetic meridian i.e. during the equinox months whereas maximum occurrences during the solstice months of solar minimum could be caused by the seed perturbation in plasma density induced by gravity waves from tropospheric origins. Generally EPB occurrences are found to be more prominent during nighttime hours (2000-2400 hours) than the daytime hours. Peak in EPB occurrences is in early night for high solar activity years whereas same is late night for low solar activity. The day and nighttime EPB occurrences have been analyzed and found to vary in accordance with solar activity with an annual correlation coefficient (R) of ˜0.99 with F_{10.7} cm solar Flux. Additionally, solar activity influence on EPB occurrences is seasonal dependent with a maximum influence during the equinox season (R=0.88) and a minimum during winter season (R =0.73). The solar activity influences on EPB occurrences are found in agreement with the previous works reported in

  13. Seasonal influence of drifting seaweeds on the structure of fish assemblages on the eastern equatorial Brazilian coast

    Directory of Open Access Journals (Sweden)

    Natália Carla Fernandes de Medeiros Dantas

    Full Text Available Abstract The present study compared fish assemblages in two adjacent areas, one with drifting algae (A and another without it (WA, in order to assess seasonal changes in diversity and composition. Both areas were located in São Cristóvão beach, Rio Grande do Norte state, on the semi-arid North-Northeastern coast of Brazil. A total of 4988 individuals were caught, the most species-rich families being Scianidae, Ariidae, Engraulidae and Carangidae. Species richness and abundance were slightly higher in site A, but diversity and evenness were higher in site WA. However, with the exception of evenness, such differences were not significant at any time during the study. Species composition was also similar between the two sites over the year. Nevertheless, in spite of the similarities, seasonal changes of environmental conditions, particularly rainfall, seemed to influence fish assemblages differently in the two areas. This may have led to changes in assemblage structure, causing the differentiation of the communities in the dry season. The present study presents evidence that fish assemblages in habitats with and without drifting seaweeds are not static and may become more similar or different, depending on the environmental conditions, suggesting that there is a complex relationship between primary productivity, trophic level and the structure of fish assemblages.

  14. Innovation in brazilian small companies

    OpenAIRE

    Tonny Kerley de Alencar Rodrigues; Átila de Melo Lira; Irenilza Alencar Naas

    2015-01-01

    This study aims to identify the interfaces and boundaries of innovation orientation of Brazilian MSEs because despite the importance of innovation for Brazilian MSEs, a thorough analysis of such initiatives in Brazil still has not actually happened. The search was developed from a quantitative approach, of applied nature and descriptive. For that a structured questionnaire was used where were interviewed 700 MSEs using a probabilistic sampling. The study offers two important conclusions. The ...

  15. Alfvén wave characteristics of equatorial plasma irregularities in the ionosphere derived from CHAMP observations

    Directory of Open Access Journals (Sweden)

    Hermann eLühr

    2014-08-01

    Full Text Available We report magnetic field observations of the components transverse to the main field in the frequency range 1-25 Hz from times of equatorial plasma irregularity crossings. These field variations are interpreted as Alfvénic signatures accompanying intermediate-scale (150 m – 4 km plasma density depletions. Data utilized are the high-resolution CHAMP magnetic field measurements sampled at 50 Hz along the north-south satellite track. The recorded signals do not reflect the temporal variation but the spatial distribution of Alfvénic signatures. This is the first comprehensive study of Alfvénic signatures related to equatorial plasma bubbles that covers the whole solar cycle from 2000 to 2010. A detailed picture of the wave characteristics can be drawn due to the large number (almost 9000 of events considered. Some important findings are: Alfvénic features are a common feature of intermediate-scale plasma structures. The zonal and meridional magnetic components are generally well correlated suggesting skewed current sheets. The sheets have an orientation that is on average deflect by about 32° away from magnetic east towards upward or downward depending on the hemisphere. We have estimated the Poynting flux flowing into the E region. Typical values are distributed over the range 10-8 - 10-6 W/m2. Large Poynting fluxes are related to steep spectra of the Alfvénic signal, which imply passages through regularly varying electron density structures. No dependence of the Poynting flux level on solar activity has been found. But below a certain solar flux value (F10.7 < 100 sfu practically no events are detected. There is a clear tendency that large Poynting flux events occur preferably at early hours after sunset (e.g. 20:00 local time. Towards later times the occurrence peak shifts successively towards lower energy levels. Finally we compare our observations with the recently published results of the high-resolution 3-D model simulations by Dao et

  16. GPS Observations of Plasma Bubbles and Scintillations over Equatorial Africa

    Science.gov (United States)

    Carrano, C. S.; Valladares, C. E.; Semala, G. K.; Bridgwood, C. T.; Adeniyi, J.; Amaeshi, L. L.; Damtie, B.; D'Ujanga Mutonyi, F.; Ndeda, J. D.; Baki, P.; Obrou, O. K.; Okere, B.; Tsidu, G. M.

    2010-12-01

    Sponsored in part by the International Heliophysical Year (IHY) program, Boston College, Air Force Research Laboratory (AFRL), and several universities in Africa have collaborated to deploy a network of GPS receivers throughout equatorial Africa, a region which has been largely devoid of ground-based ionospheric monitoring instruments. High date-rate GPS receivers capable of measuring Total Electron Content (TEC) and GPS scintillations were installed at Abidjan, Ivory Coast (5.3°N, 4.0°W, dip 3.5°S); Addis Ababa (9.0°N, 38.8°E, dip 0.1°N ); Bahir Dar, Ethiopia (26.1°N, 50.6°E, dip 20.1°N); Cape Verde (16.6°S, 22.9°W, dip 4.9°N); Ilorin, Nigeria (8.4°S, 4.7°E, dip 1.9°S); Kampala, Uganda (0.3°S, 32.6°E, dip 9.2°S); Lagos, Nigeria (6.5°N, 3.4°E, dip 3.1°S); Nairobi, Kenya (1.3°S, 36.8°W, dip 10.7°S); Nsukka, Nigeria (6.8°S, 7.4°W, dip 3.0°S); and Zanzibar, Tanzania (6.2°S, 39.2°E, dip 15.9°S). In this paper we report on the longitudinal, local time and seasonal occurrence of plasma bubbles and L band scintillations over equatorial Africa in 2009 and 2010, as a first step toward establishing the climatology of ionospheric irregularities over Africa. The scintillation intensity is obtained by measuring the standard deviation of normalized GPS signal power. The plasma bubbles are detected using an automated technique, whereby the GPS TEC is detrended to remove the diurnal variation and excursions exceeding a particular threshold are extracted for further analysis. A harmonic analysis (FFT) of these extracted events is performed to exclude wavelike features indicative of gravity waves or traveling ionospheric disturbances, and the remaining events are identified as plasma bubbles. Our findings suggest that the occurrence of plasma bubbles and L band scintillations over Africa are well correlated, but that some discrepancies in their morphologies are evident. While plasma bubbles and scintillations are generally observed during equinoctial

  17. Gradient-drift instability and turbulence in the equatorial electrojet

    Science.gov (United States)

    Hu, Shuanghui

    The gradient-drift instability is of the Rayleigh-Taylor type, and is excited when equilibrium density gradients point in the direction of equilibrium electric fields. The linear and nonlinear evolution of the gradient-drift waves responsible for type II irregularities is studied theoretically using observed profiles in the equatorial electrojet. An outstanding challenge for theory is to account for the dominance of kilometer-scale structures in daytime as well as nighttime despite the fact that the density profiles during such conditions are quite different. A two-dimensional numerical system is designed to simulate gradient-drift turbulence in the equatorial electrojet, and to demonstrate the nonlinear energy cascade process. In the daytime, linearly unstable kilometer-scale waves grow at maximum growth rates as a result of the competition between the density-gradient drive and the damping due to diffusion, velocity shear, and recombination. The nonlinear mode coupling cascades energy from the linearly unstable long waves to the stable short waves, and results in turbulently saturated states with kilometer-scale structures, consistent with radar and in situ measurements. The vertical electron velocity spectra, constructed from the simulation output, show 1-2 km vertical structures which are qualitatively in agreement with high-resolution radar observations at the Jicamarca Radio Observatory in Peru. The nighttime density profiles, obtained by rocket flights at Alcantara (Brazil) during the Guara campaign in 1994, are much more jagged than the daytime ones and provide a strong density-gradient drive, with alternating stable and unstable regions in the vertical direction. In contrast with the daytime, the strong density-gradient drive produces peak linear growth rates at wavelengths of 10-20 meters. However, the kilometer-scale waves are also linearly unstable with sufficiently high growth rates that they play a crucial role in the nonlinear evolution of these

  18. Equatorial F-layer heights, evening prereversal electric field, and night E-layer density in the American sector: IRI validation with observations

    Science.gov (United States)

    Abdu, M. A.; Batista, I. S.; Reinisch, B. W.; Carrasco, A. J.

    2004-01-01

    The equatorial F-layer height variations resulting from the variabilities in the zonal electric fields and winds and associated variability in ionospheric dynamo strength are important factors in determining the distribution and structuring of the electron density of the equatorial ionization anomaly (EIA) region. Especially, the evening enhancement in the F-layer heights and the associated prereversal enhancement in the zonal electric field due to the F-layer dynamo are believed to provide the most basic precondition for the equatorial spread F/ plasma bubble irregularity (ESF) generation. A realistic description by the International Reference Ionosphere (IRI) of the quiet time equatorial F-layer heights is therefore of fundamental importance for applications related to the studies of the ESF and EIA variabilities. The existing IRI description scheme (that uses the CCIR coefficients) appears to represent the equatorial F-layer peak density ( N mF 2/ƒ oF2) better than the peak height ( h mF2) and the heights of specific densities, the largest disagreement with observations being verified during the evening hours. Digisonde data from the three permanent stations in Brazil: São Luis (2.33°S, 44.2°W, dip angle: -.5°); Fortaleza (3.9°S, 38.45°W, dip angle: -9°); and Cachoeira Paulista (22.6°S, 315°E; dip angle: -28°) and from Jicamarca (12°S, 76.9°W; dip latitude: 1°N) in Peru have been analysed, to determine the quiet time mean behavior of the key F-layer parameters as a function of local time, season, and solar activity. These are complemented by data from the three conjugate point stations: Boa Vista (02.8°N; 60.66°W, dip angle: 22.5°) in the north and Campo Grande (20.45°S; 54.65°W, dip angle: -22.5°) in the south, and an equatorial station, Cachimbo (9.47°S; 54.83°W, dip angle: -3.9°) that were operated during the 2002 COPEX (Conjugate Point Experiment) campaign conducted in Brazil. The data for São Luis and Jicamarca are used to evaluate

  19. Relevance of bacterioplankton abundance and production in the oligotrophic equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, V.; Rodrigues, V.; Ramaiah, N.; Paul, J.T.

    Bacterioplankton abundance and production, chlorophyll a (Chl a) concentrations and primary production (PP) were measured from the equatorial Indian Ocean (EIO) during northeast (NEM), southwest (SWM) and spring intermonsoon (SpIM) seasons from 1...

  20. 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...

  1. 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....

  2. Upper ocean variability of the equatorial Indian Ocean and its relation to chlorophyll pigment concentration.

    Digital Repository Service at National Institute of Oceanography (India)

    Narvekar, J.; PrasannaKumar, S.

    Hydrographic data from the upper ocean together with atmospheric data and satellite data are used to understand the variability of upper ocean and its relation to surface chlorophyll in the Equatorial Indian Ocean. The sea surface temperature showed...

  3. 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...

  4. 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.

    in the eastern basin. The computed surface currents agreed well with the Acoustic Doppler Current Profiler (ADCP) measured currents and OGCM for Earth Simulator (OFES) simulated currents. The interannual variability of the equatorial jets revealed that the fall...

  5. The field of the equatorial electrojet from CHAMP data

    Directory of Open Access Journals (Sweden)

    J.-L. Le Mouël

    2006-03-01

    Full Text Available We apply a simple linear transform, the along-track second derivative, to four years of scalar and vectorial data from the CHAMP satellite. This transform, reminiscent of techniques used in the interpretation of aeromagnetic surveys, is applied either to the geocentric spherical components of the field or to its intensity. After averaging in time and space, we first produce a map of the crustal field, then maps of the equatorial electrojet field at all local times and all universal times. The seasonal variation of the electrojet, its evolution with the solar cycle, and the effect of geomagnetic activity are discussed. The variation of the electrojet with longitude, an intriguing feature revealed by satellite data, is described in some detail, and it is shown that this longitude dependance is stable in time. The existence of a counterelectrojet in the morning, everywhere except over the Pacific Ocean, is established. The signatures of closure electric currents and of interhemispheric currents are also evidenced.

  6. 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.

  7. Equatorial ionospheric disturbance observed through a transequatorial HF propagation experiment

    Directory of Open Access Journals (Sweden)

    T. Maruyama

    2006-07-01

    Full Text Available A transequatorial radio-wave propagation experiment at shortwave frequencies (HF-TEP was done between Shepparton, Australia, and Oarai, Japan, using the radio broadcasting signals of Radio Australia. The receiving facility at Oarai was capable of direction finding based on the MUSIC (Multiple Signal Classification algorithm. The results were plotted in azimuth-time diagrams (AT plots. During the daytime, the propagation path was close to the great circle connecting Shepparton and Oarai, thus forming a single line in the AT plots. After sunset, off-great-circle paths, or satellite traces in the AT plot, often appeared abruptly to the west and gradually returned to the great circle direction. However, there were very few signals across the great circle to the east. The off-great-circle propagation was very similar to that previously reported and was attributed to reflection by an ionospheric structure near the equator. From the rate of change in the direction, we estimated the drift velocity of the structure to range mostly from 100 to 300 m/s eastward. Multiple instances of off-great-circle propagation with a quasi-periodicity were often observed and their spatial distance in the east-west direction was within the range of large-scale traveling ionospheric disturbances (LS-TIDs. Off-great-circle propagation events were frequently observed in the equinox seasons. Because there were many morphological similarities, the events were attributed to the onset of equatorial plasma bubbles.

  8. Measuring the equatorial plasma bubble drift velocities over Morroco

    Science.gov (United States)

    Lagheryeb, Amine; Benkhaldoun, Zouhair; Makela, Jonathan J.; Harding, Brian; Kaab, Mohamed; Lazrek, Mohamed; Fisher, Daniel J.; Duly, Timothy M.; Bounhir, Aziza; Daassou, Ahmed

    2015-08-01

    In this work, we present a method to measure the drift velocities of equatorial plasma bubbles (EPBs) in the low latitude ionosphere. To calculate the EPB drift velocity, we use 630.0-nm airglow images collected by the Portable Ionospheric Camera and Small Scale Observatory (PICASSO) system deployed at the Oukkaimden observatory in Morocco. To extract the drift velocity, the individual images were processed by first spatially registering the images using the star field. After this, the stars were removed from the images using a point suppression methodology, the images were projected into geographic coordinates assuming an airglow emission altitude of 250 km. Once the images were projected into geographic coordinates, the intensities of the airglow along a line of constant geomagnetic latitude (31°) are used to detect the presence of an EPB, which shows up as a depletion in airglow intensity. To calculate the EPB drift velocity, we divide the spatial lag between depletions found in two images (found by the application of correlation analysis) by the time difference between these two images. With multiple images, we will have several velocity values and consequently we can draw the EPB drift velocity curve. Future analysis will compare the estimates of the plasma drift velocity with the thermospheric neutral wind velocity estimated by a collocated Fabry-Perot interferometer (FPI) at the observatory.

  9. Modelling ionospheric scintillation under the crest of the equatorial anomaly

    Science.gov (United States)

    Alfonsi, L.; Wernik, A. W.; Materassi, M.; Spogli, L.

    2017-10-01

    WAM is realized making use of the plasma density data collected via the retarding potential analyser on board the Dynamics Explorer 2 spacecraft, capable to model the scintillation climatology over the northern hemisphere high latitude ionosphere. More recently, WAM has been tuned to model the ionospheric scintillations also over the equatorial latitudes. The effort has been done to support the CIGALA (Concept for Ionospheric Scintillation Mitigation for Professional GNSS in Latin America) project in the assessment of the scintillations climatology over Latin America. The concept of the new release of WAM is the same already adopted for the high latitudes: the in situ measurements, supplemented with an ionospheric model and with the irregularity anisotropy model, are treated to describe the morphology of scintillation, provided a suitable propagation model is used. Significant differences have been included in the low latitudes release to account for the anisotropy of the irregularities and for strong scattering regime. The paper describes the new WAM formulation and presents comparisons of the model predictions with the actual measurements collected in Brazil.

  10. Inferring Past Climate in Equatorial East Africa using Glacier Models

    Science.gov (United States)

    Doughty, A. M.; Kelly, M. A.; Anderson, B.; Russell, J. M.; Jackson, M. S.

    2016-12-01

    Mountain glaciers in the northern and southern middle latitudes advanced nearly synchronously during the Last Glacial Maximum (LGM), but the timing and magnitude of cooling is less certain for the tropics. Knowing the degree of cooling in high altitude, low latitude regions advances our understanding of the cryosphere in understudied areas and contributes to our understanding of what causes ice ages. Here we use a 2-D ice flow and mass balance model to simulate glacier extents in the Rwenzori Mountains of Uganda and the Democratic Republic of the Congo during the Last Glacial Maximum. In particular, we model steady-state ice extent that matches the dated moraines in the Rwenzori Mountains to infer past climate. Steady-state simulations of LGM glacier extents, which match moraines dated to 20,000 years ago, can be obtained with a 20% reduction in precipitation and a 7°C cooling to match the associated moraines. A 0-50% reduction in precipitation combined with a 5-8°C cooling, respectively, agrees well with paleoclimate estimates from independent proxy records. As expected in a high precipitation environment, these glaciers are very sensitive to decreases in temperature, converting large volumes of precipitation from rain to snow as well as decreasing melting. Glaciers in equatorial Africa appear to have been waxing and waning synchronously and by the same magnitude as glaciers in the middle latitudes, suggesting a common, global forcing mechanism.

  11. Bottom-type scattering layers and equatorial spread F

    Directory of Open Access Journals (Sweden)

    J. L. Chau

    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

  12. Stormtime dynamics of the global thermosphere and equatorial ionosphere

    Directory of Open Access Journals (Sweden)

    W. J. Burke

    2009-05-01

    Full Text Available During magnetic storms the development of equatorial plasma bubbles (EPBs and distributions of thermospheric densities are strongly influenced by the histories of imposed magnetospheric electric (εM fields. Periods of intense EPB activity driven by penetration εM fields in the main phase are followed by their worldwide absence during recovery. A new method is applied to estimate global thermospheric energy (Eth budgets from orbit-averaged densities measured by accelerometers on polar-orbiting satellites. During the main phase of storms Eth increases as long as the stormtime εM operates, then exponentially decays toward quiet-time values during early recovery. Some fraction of the energy deposited at high magnetic latitudes during the main phase propagates into the subauroral ionosphere-thermosphere where it affects chemical and azimuthal-wind dynamics well into recovery. We suggest a scenario wherein fossils of main phase activity inhibit full restoration of quiet-time dayside dynamos and pre-reversal enhancements of upward plasma drifts near dusk denying bottomside irregularities sufficient time to grow into EPBs.

  13. Stormtime dynamics of the global thermosphere and equatorial ionosphere

    Directory of Open Access Journals (Sweden)

    W. J. Burke

    2009-05-01

    Full Text Available During magnetic storms the development of equatorial plasma bubbles (EPBs and distributions of thermospheric densities are strongly influenced by the histories of imposed magnetospheric electric (εM fields. Periods of intense EPB activity driven by penetration εM fields in the main phase are followed by their worldwide absence during recovery. A new method is applied to estimate global thermospheric energy (Eth budgets from orbit-averaged densities measured by accelerometers on polar-orbiting satellites. During the main phase of storms Eth increases as long as the stormtime εM operates, then exponentially decays toward quiet-time values during early recovery. Some fraction of the energy deposited at high magnetic latitudes during the main phase propagates into the subauroral ionosphere-thermosphere where it affects chemical and azimuthal-wind dynamics well into recovery. We suggest a scenario wherein fossils of main phase activity inhibit full restoration of quiet-time dayside dynamos and pre-reversal enhancements of upward plasma drifts near dusk denying bottomside irregularities sufficient time to grow into EPBs.

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

    Science.gov (United States)

    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

    2008-12-23

    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 emissions from Indonesia, Malaysia, and Papua New Guinea during 2000-2006. We found that average fire emissions from this region [128 +/- 51 (1sigma) Tg carbon (C) year(-1), T = 10(12)] were comparable to fossil fuel emissions. In Borneo, carbon emissions from fires were highly variable, fluxes during the moderate 2006 El Niño more than 30 times greater than those during the 2000 La Niña (and with a 2000-2006 mean of 74 +/- 33 Tg C yr(-1)). Higher rates of forest loss and larger areas of peatland becoming vulnerable to fire in drought years caused a strong nonlinear relation between drought and fire emissions in southern Borneo. Fire emissions from Sumatra showed a positive linear trend, increasing at a rate of 8 Tg C year(-2) (approximately doubling during 2000-2006). These results highlight the importance of including deforestation in future climate agreements. They also imply that land manager responses to expected shifts in tropical precipitation may critically determine the strength of climate-carbon cycle feedbacks during the 21st century.

  15. Seasonal Variation of the North/South Equatorial Current Bifurcation

    Science.gov (United States)

    Chen, Z.

    2016-02-01

    The seasonal variation of the North/South Equatorial Current (NEC/SEC) bifurcation off the Philippine/Madagascar/Australian coast is investigated. It is shown that the seasonal cycles of the NEC/SEC bifurcation are generally analogous to each other, all of which shift synchronously back and forth seasonally and arrive at their southernmost positions in boreal late spring and early summer. It is demonstrated that the linear, reduced gravity, long Rossby model, which works well for the NEC bifurcation, is insufficient to reproduce the seasonal cycles of the SEC bifurcation off the Madagascar/Australian coast particularly in their south-north migrations. This can be attributed to the existence of the isolated island in the Madagascar case and the seasonally-varying wind forcing around the Australian coast, while they are almost absent in the NEC bifurcation case. Without considering the existence of an island and the alongshore winds, we propose a simple bifurcation model under the framework of linear Rossby wave dynamics. It is found that the seasonal bifurcation latitude is predominantly determined by the spatial pattern of the wind and baroclinic Rossby wave propagation. This model explains the roles of local/remote wind forcing and baroclinic adjustment in the south-north migration and peak seasons of the bifurcation latitude.

  16. Can Logging in Equatorial Africa Affect Adjacent Parks?

    Directory of Open Access Journals (Sweden)

    Somnath Baidya Roy

    2005-06-01

    Full Text Available Tropical deforestation can cause fundamental regional-scale shifts in vegetation structure and diversity. This is particularly true in Africa. Although national parks are being established to protect areas from deforestation and to conserve biodiversity, these parks are not immune to disturbances outside their boundaries. We used regional-scale atmospheric simulation experiments to investigate how deforestation in timber concessions might affect precipitation inside adjacent, undisturbed national parks in the equatorial African countries of Gabon and the Republic of Congo. The experiments revealed a complex response. Some parks showed rainfall reduced as much as 15%, while others showed slight increases. Rainfall inside parks was particularly sensitive to upwind deforestation along the path of airborne moisture traveling inland from the ocean. A variety of shortcomings in the current modeling procedures limit the ability to extrapolate from experiments such as ours to provide spatially explicit, long-term forecasts of climate. We describe what advances in modeling are needed to produce regional-scale predictions that are robust enough to be useful to managers and policy makers.

  17. Analysis of Korean astronomical records with Chinese equatorial coordinates

    Science.gov (United States)

    Lee, K. W.

    2012-08-01

    The historical documents of ancient Korea contain abundant records on various astronomical phenomena. The historical documents of the Joseon dynasty contain observational values based on Chinese equatorial coordinate system (i.e., angular distances from the reference star of a lunar mansion and the North Pole). However, quantitative analysis of the observational values has not been carried out. In this study, we investigate the observational accuracy during the Joseon dynasty by comparing the astronomical records of Joseonwangjo Sillok (Annals of the Joseon Dynasty) and Seungjeongwon Ilgi (Daily Records of the Royal Secretariat) with modern astronomical calculations. Consequently, we find that the observational accuracy during the early Joseon dynasty was approximately 1.2° 0.3° in the right ascension and declination, respectively. On the other hand, we find that the observational accuracy during the later Joseon dynasty was considerably poor. Observations of Halley's comet in 1759 were off by approximately 7° in declination. We believe that further investigation is required to verify the reason for this poor accuracy. Thus, we list the complete records used for this study in the appendix. We believe that these records also can contribute to modern studies on phenomena such as supernovae or Halley's comet. In conclusion, we believe that this study is useful for understanding ancient Korean astronomical records, even though we have considered a small number of astronomical events.

  18. Radio-tomographic images of postmidnight equatorial plasma depletions

    Science.gov (United States)

    Hei, Matthew A.; Bernhardt, Paul A.; Siefring, Carl L.; Wilkens, Matthew R.; Huba, Joseph D.; Krall, Jonathan F.; Valladares, Cesar E.; Heelis, Roderick A.; Hairston, Marc R.; Coley, W. Robin; Chau, Jorge L.; De La Jara, Cesar

    2014-01-01

    the first time, equatorial plasma depletions (EPDs) have been imaged in the longitude-altitude plane using radiotomography. High-resolution (~10 km) reconstructions of electron density were derived from total electron content (TEC) measurements provided by a receiver array in Peru. TEC data were obtained from VHF/UHF signals transmitted by the Coherent Electromagnetic Radio Tomography (CERTO) beacon on the C/NOFS satellite. EPDs generated premidnight were observed near dawn. On one night, the bubble densities were highly reduced, 100-1000 km wide, and embedded within a layerlike ionosphere. Three nights later, the EPDs exhibited similar features but were embedded in a locally uplifted ionosphere. The C/NOFS in situ instruments detected a dawn depletion where the reconstruction showed lifted EPDs, implying that the postmidnight electric fields raised sections of ionosphere to altitudes where embedded/reactivated fossil EPDs were detected as dawn depletions. Satellites flying under domelike distortions of the ionosphere may observe these distortions as broad plasma decreases (BPDs).

  19. 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.

  20. Study of Equatorial Ionospheric Irregularities for the Assessment of Impacts on Communication/Navigation System (7)

    Science.gov (United States)

    2013-05-27

    Final Report of AFRL-AOARD Project 11-4040 (2011-2013) “Study of Equatorial Ionospheric Irregularities for the Assessment of Impacts on...DEC 2013 2. REPORT TYPE Final 3. DATES COVERED 01-08-2011 to 01-08-2013 4. TITLE AND SUBTITLE Study of Equatorial Ionospheric Irregularities ...in both temporal and amplitude variations. Second, since the ionospheric density irregularities are the source of ionospheric radiowave scintillation

  1. Productivity patterns in the equatorial Pacific over the last 30,000 years

    Science.gov (United States)

    Costa, Kassandra M.; Jacobel, Allison W.; McManus, Jerry F.; Anderson, Robert F.; Winckler, Gisela; Thiagarajan, Nivedita

    2017-05-01

    The equatorial Pacific traverses a number of productivity regimes, from the highly productive coastal upwelling along Peru to the near gyre-like productivity lows along the international dateline, making it an ideal target for investigating how biogeochemical systems respond to changing oceanographic conditions over time. However, conflicting reconstructions of productivity during periods of rapid climate change, like the last deglaciation, render the spatiotemporal response of equatorial Pacific productivity ambiguous. In this study, surface productivity since the last glacial period (30,000 years ago) is reconstructed from seven cores near the Line Islands, central equatorial Pacific, and integrated with productivity records from across the equatorial Pacific. Three coherent deglacial patterns in productivity are identified: (1) a monotonic glacial-Holocene increase in productivity, primarily along the Equator, associated with increasing nutrient concentrations over time; (2) a deglacial peak in productivity 15,000 years ago due to transient entrainment of nutrient rich southern-sourced deep waters; and (3) possible precessional cycles in productivity in the eastern equatorial Pacific that may be related to Intertropical Convergence Zone migration and potential interactions with El Niño-Southern Oscillation dynamics. These findings suggest that productivity was generally lower during the glacial period, a trend observed zonally across the equatorial Pacific, while deglacial peaks in productivity may be prominent only in the east.

  2. Equatorial segment protein (ESP) is a human alloantigen involved in sperm-egg binding and fusion.

    Science.gov (United States)

    Wolkowicz, M J; Digilio, L; Klotz, K; Shetty, J; Flickinger, C J; Herr, J C

    2008-01-01

    The equatorial segment of the sperm head is known to play a role in fertilization; however, the specific sperm molecules contributing to the integrity of the equatorial segment and in binding and fusion at the oolemma remain incomplete. Moreover, identification of molecular mediators of fertilization that are also immunogenic in humans is predicted to advance both the diagnosis and treatment of immune infertility. We previously reported the cloning of Equatorial Segment Protein (ESP), a protein localized to the equatorial segment of ejaculated human sperm. ESP is a biomarker for a subcompartment of the acrosomal matrix that can be traced through all stages of acrosome biogenesis (Wolkowicz et al, 2003). In the present study, ESP immunoreacted on Western blots with 4 (27%) of 15 antisperm antibody (ASA)-positive serum samples from infertile male patients and 2 (40%) of 5 ASA-positive female sera. Immunofluorescent studies revealed ESP in the equatorial segment of 89% of acrosome-reacted sperm. ESP persisted as a defined equatorial segment band on 100% of sperm tightly bound to the oolemma of hamster eggs. Antisera to recombinant human ESP inhibited both oolemmal binding and fusion of human sperm in the hamster egg penetration assay. The results indicate that ESP is a human alloantigen involved in sperm-egg binding and fusion. Defined recombinant sperm immunogens, such as ESP, may offer opportunities for differential diagnosis of immune infertility.

  3. 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

  4. Amazon, priority for Brazilian National Defense Policy

    National Research Council Canada - National Science Library

    Pereira, Sergio

    2000-01-01

    .... The Brazilian national defense policy, issued in 1996, the first in the history of the country, established directives to orient the Brazilian military strategic planning as well as diplomatic...

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

    Directory of Open Access Journals (Sweden)

    Andrew G Bauman

    Full Text Available 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 <1%. Other, unidentifiable families represented 10% of the 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

  6. 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.

  7. An idealized study of near equatorial river plumes

    Science.gov (United States)

    Palma, Elbio D.; Matano, Ricardo P.

    2017-05-01

    The dynamics of near equatorial river plumes (NERPs) are investigated using a highly idealized model. The spreading of a NERP from an eastern boundary is characterized by a continuous shedding of westward propagating eddies. This process transfers the bulk of the freshwater discharge to the deep ocean, thus distinguishing NERPs from their midlatitude counterparts. In the long-term limit, a NERP can be rationalized as a β-plume emanating from a coastal source. The evolution of NERPs in an unstratified basin is quite different from that in a stratified one. The spin-up in an unstratified basin is characterized by the formation of an anticyclonic bulge, which spreads westward thus creating a density stratification that favors the subsequent development of smaller and faster moving secondary eddies. The collision of the secondary eddies with the leading bulge arrests the effects of mixing thus allowing the further spreading of the buoyancy anomaly. In a stratified basin, the generation of anticyclonic eddies is accompanied by a concurrent generation of cyclones, which pump saltier waters to the surface hence leading to smaller sea surface salinity (SSS) anomalies. NERPs are sensitive to variations of the freshwater flux (Qfw) and the geomorphological setting. Larger Qfw generates bigger eddies, which spread at a rate proportional to the square root of the normalized flux. Wide shelves allow the interaction of the eddies with the bottom, thus promoting a cyclonic shift of the axis of the eddy train. The inclination of the coast affects the dynamical balance controlling the near-field behavior of NERPs.

  8. Genetic population structure of Anopheles gambiae in Equatorial Guinea

    Directory of Open Access Journals (Sweden)

    Caccone Adalgisa

    2007-10-01

    Full Text Available Abstract Background Patterns of genetic structure among mosquito vector populations in islands have received particular attention as these are considered potentially suitable sites for experimental trials on transgenic-based malaria control strategies. In this study, levels of genetic differentiation have been estimated between populations of Anopheles gambiae s.s. from the islands of Bioko and Annobón, and from continental Equatorial Guinea (EG and Gabon. Methods Genotyping of 11 microsatellite loci located in chromosome 3 was performed in three island samples (two in Bioko and one in Annobón and three mainland samples (two in EG and one in Gabon. Four samples belonged to the M molecular form and two to the S-form. Microsatellite data was used to estimate genetic diversity parameters, perform demographic equilibrium tests and analyse population differentiation. Results High levels of genetic differentiation were found between the more geographically remote island of Annobón and the continent, contrasting with the shallow differentiation between Bioko island, closest to mainland, and continental localities. In Bioko, differentiation between M and S forms was higher than that observed between island and mainland samples of the same molecular form. Conclusion The observed patterns of population structure seem to be governed by the presence of both physical (the ocean and biological (the M-S form discontinuity barriers to gene flow. The significant degree of genetic isolation between M and S forms detected by microsatellite loci located outside the "genomic islands" of speciation identified in A. gambiae s.s. further supports the hypothesis of on-going incipient speciation within this species. The implications of these findings regarding vector control strategies are discussed.

  9. Brazilian medical publications: citation patterns for Brazilian-edited and non-Brazilian literature

    Directory of Open Access Journals (Sweden)

    J.R. Cunha-Melo

    2006-08-01

    Full Text Available Today, the quality of a scientific article depends on the periodical in which it is published and on the number of times the article is cited in the literature. In Brazil, the criteria for the evaluation of this scientific production are improving. However, there is still some resistance, with authors arguing that Brazilian publications must be preferentially addressed to the national readers and, therefore, they should ideally be written in Portuguese. In order to determine the kind of scientific journals cited in the reference lists of articles published in medical periodicals edited in Brazil, in the present study we determine the rate of Portuguese/English citations. Three issues of 43 periodicals (19 indexed in SciELO, 10 in PubMed, 10 in LILACS, and 4 in the ISI-Thompson base of different medical specialties were analyzed, and the number of both Portuguese and English citations in the reference list of each article was recorded. The results showed that in Brazilian-edited journals the mean number of citations/article was 20.9 ± 6.9 and the percentage of citations of international non-Brazilian periodicals was 86.0 ± 11.2%. Of the latter, 94.4 ± 7.0 are indexed by ISI-Thompson. Therefore, we conclude that Brazilian medical scientists cite the international non-Brazilian periodicals more than the national journals, and most of the cited papers are indexed by ISI-Thompson.

  10. A GUERRA DO PARAGUAI NA HISTORIOGRAFIA NACIONAL E REGIONAL: UM PARADIGMA DE PESQUISA HISTÓRICA NO PIAUÍ

    OpenAIRE

    Araújo, Johny Santana; Universidade Federal do Piauí

    2013-01-01

    O presente estudo tem como objetivo analisar a historiografia sobre a Guerra do Paraguai a partir da interlocução da historiografia nacional e regional (entende-se a historiografia piauiense). Pretendemos dessa maneira, de forma concisa, expor as deferentes perspectivas abordadas sobre o conflito, mostrar como a mesma foi interpretada pelo conhecimento histórico em diferentes períodos. Num primeiro momento, a leitura sobre guerra a partir de uma perspectiva positivista, em seguida o viés revi...

  11. Phase locking of equatorial Atlantic variability through the seasonal migration of the ITCZ

    Science.gov (United States)

    Richter, Ingo; Xie, Shang-Ping; Morioka, Yushi; Doi, Takeshi; Taguchi, Bunmei; Behera, Swadhin

    2017-06-01

    The equatorial Atlantic is marked by significant interannual variability in sea-surface temperature (SST) that is phase-locked to late boreal spring and early summer. The role of the atmosphere in this phase locking is examined using observations, reanalysis data, and model output. The results show that equatorial zonal surface wind anomalies, which are a main driver of warm and cold events, typically start decreasing in June, despite SST and sea-level pressure gradient anomalies being at their peak during this month. This behavior is explained by the seasonal northward migration of the intertropical convergence zone (ITCZ) in early summer. The north-equatorial position of the Atlantic ITCZ contributes to the decay of wind anomalies in three ways: (1) horizontal advection associated with the cross-equatorial winds transports air masses of comparatively low zonal momentum anomalies from the southeast toward the equator. (2) The absence of deep convection leads to changes in vertical momentum transport that reduce the equatorial wind anomalies at the surface, while anomalies aloft remain relatively strong. (3) The cross-equatorial flow is associated with increased total wind speed, which increases surface drag and deposit of momentum into the ocean. Previous studies have shown that convection enhances the surface wind response to SST anomalies. The present study indicates that convection also amplifies the surface zonal wind response to sea-level pressure gradients in the western equatorial Atlantic, where SST anomalies are small. This introduces a new element into coupled air-sea interaction of the tropical Atlantic.

  12. Using ionospheric scintillation observations for studying the morphology of equatorial ionospheric bubbles

    Science.gov (United States)

    Dandekar, B. S.; Groves, K. M.

    2004-06-01

    For a study of the equatorial ionosphere, ionospheric scintillation data at VHF and L-band frequencies have been routinely collected by ground-based receivers at Ancon, Peru, Antofagasta, Chile, and Ascension Island, UK, since May 1994. The receivers routinely monitor VHF transmissions from two geosynchronous satellites located at 100°W longitude and 23°W longitude, and L-band signals from satellites located at 75°W longitude and 15°W longitude. This combination provides a network of seven usable, reasonably separated links for monitoring ionospheric equatorial bubble activity in the South American longitude sector. A data set of seven years covering the period from 1995 to 2001 was studied to determine the temporal, diurnal, and seasonal behavior of equatorial bubbles. The results of our statistical study are presented here. In general the equatorial ionospheric bubble activity shows a strong systematic and primary dependence in temporal, diurnal, and seasonal variation, and a secondary weak dependence on geomagnetic and solar flux activity. At present, the dependence on solar and magnetic activity is not usable for near-time and short-term prediction of the equatorial bubble activity. Equatorial bubbles usually start 1 hour after sunset, the activity peaks before local midnight, and vanishes by early morning. The activity peaks in the months of November and January-February and is practically absent (weak) from May to August. On a daily basis on the average one sees 1 to 3 bubbles. The duration of bubbles is about 70 min, and the time spacing between the bubbles is 1 to 2 hours. The bubble activity in general follows the phase of solar cycle activity. The observed systematic behavior of the equatorial bubbles allows for a now cast and short-term forecast of the bubble activity in the South American sector.

  13. Multifractal analysis of vertical total electron content (VTEC at equatorial region and low latitude, during low solar activity

    Directory of Open Access Journals (Sweden)

    M. J. A. Bolzan

    2013-01-01

    Full Text Available This paper analyses the multifractal aspects of the GPS data (measured during a period of low solar activity obtained from two Brazilian stations: Belém (01.3° S, 48.3° W and São José dos Campos (SJC (23.2° S, 45.9° W. The results show that the respective geographic sites show important scaling differences as well as similarities when their multifractal signatures for vertical total electron content (VTEC are compared. The f(α spectra have a narrow shape for great scales, which indicates the predominance of deterministic phenomena, such as solar rotation (27 days over intermittent phenomena. Furthermore, the f(α spectra for both sites have a strong multifractality degree at small scales. This strong multifractality degree observed at small scales (1 to 12 h at both sites is because the ionosphere over Brazil is a non-equilibrium system. The differences found were that Belém presented a stronger multifractality at small scales (1 h to 12 h compared with SJC, particularly in 2006. The reason for this behaviour may be associated with the location of Belém, near the geomagnetic equator, where at this location the actions of X-rays, ultraviolet, and another wavelength from the Sun are more direct, strong, and constant throughout the whole year. Although the SJC site is near ionospheric equatorial anomaly (IEA peaks, this interpretation could explain the higher values found for the intermittent parameter μ for Belém compared with SJC. Belém also showed the presence of one or two flattening regions for f(α spectra at the same scales mentioned before. These differences and similarities also were interpreted in terms of the IEA content, where this phenomenon is an important source of intermittence due the presence of the VTEC peaks at ±20° geomagnetic latitudes.

  14. Multifractal analysis of vertical total electron content (VTEC at equatorial region and low latitude, during low solar activity

    Directory of Open Access Journals (Sweden)

    M. J. A. Bolzan

    2013-01-01

    Full Text Available This paper analyses the multifractal aspects of the GPS data (measured during a period of low solar activity obtained from two Brazilian stations: Belém (01.3° S, 48.3° W and São José dos Campos (SJC (23.2° S, 45.9° W. The results show that the respective geographic sites show important scaling differences as well as similarities when their multifractal signatures for vertical total electron content (VTEC are compared. The f(α spectra have a narrow shape for great scales, which indicates the predominance of deterministic phenomena, such as solar rotation (27 days over intermittent phenomena. Furthermore, the f(α spectra for both sites have a strong multifractality degree at small scales. This strong multifractality degree observed at small scales (1 to 12 h at both sites is because the ionosphere over Brazil is a non-equilibrium system. The differences found were that Belém presented a stronger multifractality at small scales (1 h to 12 h compared with SJC, particularly in 2006. The reason for this behaviour may be associated with the location of Belém, near the geomagnetic equator, where at this location the actions of X-rays, ultraviolet, and another wavelength from the Sun are more direct, strong, and constant throughout the whole year. Although the SJC site is near ionospheric equatorial anomaly (IEA peaks, this interpretation could explain the higher values found for the intermittent parameter μ for Belém compared with SJC. Belém also showed the presence of one or two flattening regions for f(α spectra at the same scales mentioned before. These differences and similarities also were interpreted in terms of the IEA content, where this phenomenon is an important source of intermittence due the presence of the VTEC peaks at ±20° geomagnetic latitudes.

  15. The role of total wind in the vertical dynamics of ions in the E-region at high latitudes

    Directory of Open Access Journals (Sweden)

    M. Voiculescu

    2005-06-01

    Full Text Available A seasonally dependent total neutral wind model obtained from experimental data is used to evaluate the diurnal variation of the vertical ion velocity in the E-region at a high-latitude location (Tromsø, for each season, in the presence of an electric field with a typical diurnal variation for quiet auroral days. The diurnal variation and spatial locations of the vertical convergence of ions are analyzed and the effect of the total wind on the occurrence of sporadic E-layers is inferred. The results show that the structure of the wind is an important factor in controlling the vertical velocities of ions, favoring or hindering the sporadic E-layer formation. The ion convergence conditions are improved when the permanent wind is removed, which suggests that sporadic E-layers occur when the mean wind has small values, thus allowing the electric field and/or the semidiurnal tide to control the ion dynamics. We conclude that for quiet days the formation of the sporadic layers is initiated by the electric field, while their evolution and dynamics is controlled by the wind. We also find that the seasonal variation of the Es layers cannot be related to the seasonally dependent wind shear. Although we focus on sporadic E-layers, our results can be used in the analysis of other processes involving the vertical dynamics of ions in the E-region at high latitudes.

  16. Artificial E-region field-aligned plasma irregularities generated at pump frequencies near the second electron gyroharmonic

    Directory of Open Access Journals (Sweden)

    D. L. Hysell

    2009-07-01

    Full Text Available E region ionospheric modification experiments have been performed at HAARP using pump frequencies about 50 kHz above and below the second electron gyroharmonic frequency. Artificial E region field-aligned plasma density irregularities (FAIs were created and observed using the imaging coherent scatter radar near Homer, Alaska. Echoes from FAIs generated with pump frequencies above and below 2Ωe did not appear to differ significantly in experiments conducted on summer afternoons in 2008, and the resonance instability seemed to be at work in either case. We argue that upper hybrid wave trapping and resonance instability at pump frequencies below the second electron gyroharmonic frequency are permitted theoretically when the effects of finite parallel wavenumbers are considered. Echoes from a sporadic E layer were observed to be somewhat weaker when the pump frequency was 50 kHz below the second electron gyroharmonic frequency. This may indicate that finite parallel wavenumbers are inconsistent with wave trapping in thin sporadic E ionization layers.

  17. Possible evidence for partial demagnetization of electrons in the auroral E-region plasma during electron gas heating

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    C. Haldoupis

    Full Text Available A previous study, based on incoherent and coherent radar measurements, suggested that during auroral E-region electron heating conditions, the electron flow in the auroral electrojet undergoes a systematic counterclockwise rotation of several degrees relative to the E×B direction. The observational evidence is re-examined here in the light of theoretical predictions concerning E-region electron demagnetization caused by enhanced anomalous cross-field diffusion during strongly-driven Farley-Buneman instability. It is shown that the observations are in good agreement with this theory. This apparently endorses the concept of wave-induced diffusion and anomalous electron collision frequency, and consequently electron demagnetization, under circumstances of strong heating of the electron gas in the auroral electrojet plasma. We recognize, however, that the evidence for electron demagnetization presented in this report cannot be regarded as definitive because it is based on a limited set of data. More experimental research in this direction is thus needed.

  18. The role of vibrationally excited oxygen and nitrogen in the D and E regions of the ionosphere

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    A. V. Pavlov

    1994-08-01

    Full Text Available In this paper we present the results of a study of the effect of vibrationally excited oxygen, O*2, and nitrogen, N*2, on the electron density, Ne, and the electron temperature, Te, in the D and E regions. The sources of O*2 are O-atom recombination, the photodissociation of O3, and the reaction of O3 with O at D region altitudes. The first calculations of O*2( j number densities, Nj, are obtained by solving continuity equations for the models of harmonic and anharmonic oscillator energy levels, j=1-22. It is found that day time values of Nj are less than nighttime values. We also show that the photoionization of O*2 ( j ≥ 11 by Lα-radiation has no influence on the D region Ne. In the nighttime D region the photoionization O*2 ( j ≥ 11 by scattered Lα-radiation can be a new source of O+2. We show that the N*2 and O*2 de-excitation effect on the electron temperature is small in the E region of the ionosphere and cannot explain experimentally observed higher electron temperatures.

  19. Comparison of frailty among Japanese, Brazilian Japanese descendants and Brazilian community-dwelling older women.

    Science.gov (United States)

    Sampaio, Priscila Yukari Sewo; Sampaio, Ricardo Aurélio Carvalho; Yamada, Minoru; Ogita, Mihoko; Arai, Hidenori

    2015-06-01

    To investigate frailty in Japanese, Brazilian Japanese descendants and Brazilian older women. The collected data included sociodemographic and health-related characteristics, and the frailty index Kihon Checklist. We analyzed the differences between the mean scores of Kihon Checklist domains (using ancova) and the percentage of frail women (using χ(2)-test). We carried out a binary logistic regression with Kihon Checklist domains. A total of 211 participants (Japanese n = 84, Brazilian Japanese descendants n = 55, Brazilian n = 72) participated in this research. The Brazilian participants had the highest total Kihon Checklist scores (more frail), whereas the Brazilian Japanese descendants had the lowest scores (P Brazilian group had more participants with oral dysfunction (P Brazilian women were likely to be more frail than the participants in other groups. More than the environment itself, the lifestyle and sociodemographic conditions could affect the frailty of older Brazilian women. © 2014 Japan Geriatrics Society.

  20. 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

  1. INNOVATION IN BRAZILIAN SMALL COMPANIES

    National Research Council Canada - National Science Library

    Rodrigues, Tonny Kerley de Alencar; Lira, Átila De Melo; Naas, Irenilza De Alencar

    2015-01-01

    .... And the data confirms that small Brazilian companies generally have difficulties to sell their innovations. Keywords: innovation, small enterprises, patents. 1. INTRODUCTION Companies worldwide are looking to technological innovation as feasible for your market expansion (BURNS; STALKER, 1961; NELSON, 1993) alternative. In Brazil, the change an...

  2. BRAZILIAN EXPORTS OF MANUFACTURED WOOD

    Directory of Open Access Journals (Sweden)

    Rafael de Azevedo Calderon

    2010-08-01

    Full Text Available The present work deals with the Brazilian exports of sawnwood of non-coniferous, veneer sheets and plywood, from 1961 to 2002. The data regarding the three studied products, sawnwood of non-coniferous, veneer sheets and plywood, were joined through the method of Fisher so that an econometric evaluation of the market of the three products could be carried out. Supply and demand models of the Brazilian exports were specified. The results were satisfactory and they match with the literature. The supply of exports presented a positive answer in relation to the exporter's remuneration, to the production, to the use of the installed capacity (cycles of domestic economical activity and to the tendency, and negative in relation to the internal demand. The demand for the Brazilian exports was influenced positively by the world income, participation index and tendency, and negatively for the relative price. The low elasticity-price of the found demand can have implications in the conservation of the Brazilian forest resources because the exporters can increase the prices, reduce the amounts and still increase the incomes.

  3. Deforestation in the Brazilian Amazon

    NARCIS (Netherlands)

    Boekhout van Solinge, T.|info:eu-repo/dai/nl/156696207

    2015-01-01

    This essay takes a (green) criminological and multidisciplinary perspective on deforestation in the Brazilian Amazon, by focusing on the crimes and damages that are associated with Amazonian deforestation. The analysis and results are partly based on longer ethnographic stays in North Brazil (Amazon

  4. 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

  5. Excitation of equatorial Kelvin and Yanai waves by tropical cyclones in an ocean general circulation model

    Directory of Open Access Journals (Sweden)

    R. L. Sriver

    2013-01-01

    Full Text Available Tropical cyclones (TCs actively contribute to the dynamics of Earth's coupled climate system. They influence oceanic mixing rates, upper-ocean heat content, and air–sea fluxes, with implications for atmosphere and ocean dynamics on multiple spatial and temporal scales. Using an ocean general circulation model with modified surface wind forcing, we explore how TC winds can excite equatorial ocean waves in the tropical Pacific. We highlight a situation where three successive TCs in the western North Pacific region, corresponding to events in 2003, excite a combination of Kelvin and Yanai waves in the equatorial Pacific. The resultant thermocline adjustment significantly modifies the thermal structure of the upper equatorial Pacific and leads to eastward zonal heat transport. Observations of upper-ocean temperature by the Tropical Atmosphere Ocean (TAO buoy array and sea-level height anomalies using altimetry reveal wave passage during the same time period with similar properties to the modeled wave, although our idealized model methodology disallows precise identification of the TC forcing with the observed waves. Results indicate that direct oceanographic forcing by TCs may be important for understanding the spectrum of equatorial ocean waves, thus remotely influencing tropical mixing and surface energy budgets. Because equatorial Kelvin waves are closely linked to interannual variability in the tropical Pacific, these findings also suggest TC wind forcing may influence the timing and amplitude of El Niño events.

  6. Resonant Scattering of Radiation Belt Electrons by Off-Equatorial Magnetosonic Waves

    Science.gov (United States)

    Ni, Binbin; Zou, Zhengyang; Fu, Song; Cao, Xing; Gu, Xudong; Xiang, Zheng

    2018-02-01

    Fast magnetosonic (MS) waves are commonly regarded as electromagnetic waves that are characteristically confined within ±3° of the geomagnetic equator. We report two typical off-equatorial MS events observed by Van Allen Probes, that is, the 8 May 2014 event that occurred at the geomagnetic latitudes of 7.5°-9.2° both inside and outside the plasmasphere with the wave amplitude up to 590 pT and the 9 January 2014 event that occurred at the latitudes of—(15.7°-17.5°) outside the plasmasphere with a smaller amplitude about 81 pT. Detailed test particle simulations quantify the electron resonant scattering rates by the off-equatorial MS waves to find that they can cause the pitch angle scattering and momentum diffusion of radiation belt electrons with equatorial pitch angles belt electron butterfly distributions for a broad energy range from 100 keV to >1 MeV within an hour. Our study clearly demonstrates that the presence of off-equatorial MS waves, in addition to equatorial MS waves, can contribute importantly to the dynamical variations of radiation belt electron fluxes and their pitch angle distribution.

  7. Equatorial Atlantic interannual variability and its relation to dynamic and thermodynamic processes

    Directory of Open Access Journals (Sweden)

    J. Jouanno

    2017-11-01

    Full Text Available The contributions of the dynamic and thermodynamic forcing to the interannual variability of the equatorial Atlantic sea surface temperature (SST are investigated using a set of interannual regional simulations of the tropical Atlantic Ocean. The ocean model is forced with an interactive atmospheric boundary layer, avoiding damping toward prescribed air temperature as is usually the case in forced ocean models. The model successfully reproduces a large fraction (R2  =  0.55 of the observed interannual variability in the equatorial Atlantic. In agreement with leading theories, our results confirm that the interannual variations of the dynamical forcing largely contributes to this variability. We show that mean and seasonal upper ocean temperature biases, commonly found in fully coupled models, strongly favor an unrealistic thermodynamic control of the equatorial Atlantic interannual variability.

  8. Covariant glacial-interglacial dust fluxes in the equatorial Pacific and Antarctica.

    Science.gov (United States)

    Winckler, Gisela; Anderson, Robert F; Fleisher, Martin Q; McGee, David; Mahowald, Natalie

    2008-04-04

    Dust plays a critical role in Earth's climate system and serves as a natural source of iron and other micronutrients to remote regions of the ocean. We have generated records of dust deposition over the past 500,000 years at three sites spanning the breadth of the equatorial Pacific Ocean. Equatorial Pacific dust fluxes are highly correlated with global ice volume and with dust fluxes to Antarctica, which suggests that dust generation in interhemispheric source regions exhibited a common response to climate change over late-Pleistocene glacial cycles. Our results provide quantitative constraints on the variability of aeolian iron supply to the equatorial Pacific Ocean and, more generally, on the potential contribution of dust to past climate change and to related changes in biogeochemical cycles.

  9. 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

    2014-06-11

    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 (14)C 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.

  10. 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.

  11. Ionospheric electron content within the equatorial F2 layer anomaly belt

    Science.gov (United States)

    Rastogi, R. G.; Klobuchar, J. A.

    1990-01-01

    Results are presented on continuous TEC measurements, taken along a chain of stations spaced between 0 deg N and 25 deg N and aligned roughly along the same longitude sector in India, that describe the day-to-day behavior of the location of equatorial anomaly in the TEC during the period of the 1975-1976 sunspot minimum, when the ATS spacecraft was visible from India. It was found that the presence or absence of the latitudinal anomaly in TEC on a particular day depended only on the strength of the electrojet current, as determined by the difference of the horizontal magnetic field at stations on the magnetic equator and stations outside the equatorial electrojet, rather than on the horizontal magnetic field measured only at equatorial stations.

  12. Ionospheric electron content depletions associated with amplitude scintillations in the equatorial region

    Science.gov (United States)

    Dasgupta, A.; Aarons, J.; Klobuchar, J. A.; Basu, S.; Bushby, A.

    1982-02-01

    Klobuchar et al. (1978) and Yeh et al. (1979) have shown that the Faraday rotation technique can be used to observe ionospheric electron content depletions associated with amplitude scintillations of transionospherically propagated signals. However, no long term study on the behavior of the ionization depletions associated with scintillations in the equatorial region has yet been reported. The present investigation is concerned with the results of such measurements at an equatorial station in Peru during a period of about one year. The results combined with observations on amplitude scintillations of satellite signals in the VHF to microwave range have been used to obtain information on the nature and evolution of equatorial ionospheric irregularities. The ionization depletions may be taken as the manifestation of tens of km scale irregularities occupying a considerable vertical range around the F-region, whereas km scale irregularities are responsible for VHF scintillations.

  13. The role of Ekman flow and planetary waves in the oceanic cross-equatorial heat transport

    Science.gov (United States)

    Schopf, P. S.

    1980-01-01

    A numerical model is used to mechanistically simulate the oceans' seasonal cross-equatorial heat transport. The basic process of Ekman pumping and drift is able to account for a large amount of the cross-equatorial flux. Increased easterly wind stress in the winter hemisphere causes Ekman surface drift poleward, while decreased easterly stress allows a reduction in the poleward drift in the summer hemisphere. The addition of planetary and gravity waves to this model does not alter the net cross-equatorial flow, although the planetary waves are clearly seen. On comparison with Oort and Vonder Haar (1976), this adiabatic advective redistribution of heat is seen to be plausible up to 10-20 deg N, beyond which other dynamics and thermodynamics are indicated.

  14. Sources of Fe to the equatorial Pacific Ocean from the Holocene to Miocene

    Science.gov (United States)

    Ziegler, Christa L.; Murray, Richard W.; Plank, Terry; Hemming, Sidney R.

    2008-06-01

    Biological productivity in the modern equatorial Pacific Ocean, a region with high nutrients and low chlorophyll, is currently limited by the micronutrient Fe. In order to test whether Fe was limiting in the past and to identify potential pathways of Fe delivery that could drive Fe fertilization (i.e., dust delivery from eolian inputs vs. Fe supplied by the Equatorial Undercurrent), we chemically isolated the terrigenous material from sediment along a cross-equatorial transect in the central equatorial Pacific at 140°W and at Ocean Drilling Program Site 850 in the eastern equatorial Pacific. We quantified the contribution from each potential Fe-bearing terrigenous source using a suite of chemical- and isotopic discrimination strategies as well as multivariate statistical techniques. We find that the distribution of the terrigenous sources (i.e., Asian loess, South American ash, Papua New Guinea, and ocean island basalt) varies through time, latitude, and climate. Regardless of which method is used to determine accumulation rate, there also is no relationship between flux of any particular Fe source and climate. Moreover, there is no connection between a particular Fe source or pathway (eolian vs. Undercurrent) to total productivity during the Last Glacial Maximum, Pleistocene glacial episodes, and the Miocene "Biogenic Bloom". This would suggest an alternative process, such as an interoceanic reorganization of nutrient inventories, may be responsible for past changes in total export in the open ocean, rather than simply Fe supply from dust and/or Equatorial Undercurrent processes. Additionally, perhaps a change in Fe source or flux is related to a change in a particular component of the total productivity (e.g., the production of organic matter, calcium carbonate, or biogenic opal).

  15. The role of vibrationally excited oxygen and nitrogen in the D and E regions of the ionosphere

    Directory of Open Access Journals (Sweden)

    A. V. Pavlov

    Full Text Available In this paper we present the results of a study of the effect of vibrationally excited oxygen, O*2, and nitrogen, N*2, on the electron density, Ne, and the electron temperature, Te, in the D and E regions. The sources of O*2 are O-atom recombination, the photodissociation of O3, and the reaction of O3 with O at D region altitudes. The first calculations of O*2( j number densities, Nj, are obtained by solving continuity equations for the models of harmonic and anharmonic oscillator energy levels, j=1-22. It is found that day time values of Nj are less than nighttime values. We also show that the photoionization of O*2 ( j ≥ 11 by Lα-radiation has no influence on the D region Ne. In the nighttime D region the photoionization O*2 ( j ≥ 11 by scattered Lα-radiation can be a new source of O+2. We show that the N*2 and O*2 de-excitation effect on the electron temperature is small in the E region of the ionosphere and cannot explain experimentally observed higher electron temperatures.

  16. More evidence for a planetary wave link with midlatitude E region coherent backscatter and sporadic E layers

    Directory of Open Access Journals (Sweden)

    K. Schlegel

    Full Text Available Measurements of midlatitude E region coherent backscatter obtained during four summers with SESCAT, a 50 MHz Doppler system operating in Crete, Greece, and concurrent ionosonde recordings from the same ionospheric volume obtained with a CADI for one of these summers, are used to analyse the long-term variability in echo and Es occurrence. Echo and Es layer occurrences, computed in percent of time over a 12-h nighttime interval, take the form of time sequences. Linear power spectrum analysis shows that there are dominant spectral peaks in the range of 2–9 days, the most commonly observed periods appearing in two preferential bands, of 2–3 days and 4–7 days. No connection with geomagnetic activity was found. The characteristics of these periodicities compare well with similar properties of planetary waves, which suggests the possibility that planetary waves are responsible for the observed long-term periodicities. These findings indicate also a likely close relation between planetary wave (PW activity and the well known but not well understood seasonal Es dependence. To test the PW postulation, we used simultaneous neutral wind data from the mesopause region around 95 km, measured from Collm, Germany. Direct comparison of the long-term periodicities in echo and Es layer occurrence with those in the neutral wind show some reasonable agreement. This new evidence, although not fully conclusive, is the first direct indication in favour of a planetary wave role on the unstable midlatitude E region ionosphere. Our results suggest that planetary waves observation is a viable option and a new element into the physics of midlatitude Es layers that needs to be considered and investigated.Key words: Ionosphere (ionosphere irregularities; mid-latitude ionosphere – Meteorology and atmospheric dynamics (waves and tides

  17. Investigations of conjugate MSTIDS over the Brazilian sector during daytime

    Science.gov (United States)

    Jonah, O. F.; Kherani, E. A.; De Paula, E. R.

    2017-09-01

    This study focuses on the daytime medium-scale traveling ionospheric disturbances (MSTIDs) observed at conjugate hemispheres. It is the first time that the geomagnetical conjugate daytime MSTIDs are observed over the South America sector. To observe the MSTID characteristics, we used detrended total electron content (TEC) derived from Global Navigation Satellite Systems receivers located at Brazilian sector covering the Northern and Southern Hemispheres along the same magnetic meridian. The geographic grid of 1°N to 14°S in latitude and 60°S to 50°S in longitude was selected for this study. The cross-correlation method between two latitudes and longitudes in time was used to observe the propagation of the MSTID waves. The following features are noted: (a) MSTIDs are well developed at both hemispheres; (b) the peak MSTIDs amplitudes vary from one hemisphere to another; hence, we suppose that MSTIDs generated in Southern Hemisphere or Northern Hemisphere mirrored in the conjugate hemisphere; (c) the gravity wave-induced electric fields from one hemisphere map along the field lines and generate the mirrored MSTIDs in the conjugate region. To investigate the hemispheric mapping mechanism, a rough approximation for the integrated field line conductivity ratio of E and F regions is calculated using digisonde E and F region parameters. We noted that during the period of mapping the decrease in E region conductivity results in an increase in total conductivity. This shows that the E region was partially short circuited; hence, electric field generated at F region could map to the conjugate hemisphere during daytime: daytime MSTIDs at conjugate regions; mechanisms responsible for daytime electrified MSTIDs; gravity wave-induced electric field role in daytime MSTIDs.

  18. The Brazilian INPE-UFSM NANOSATC-BR CubeSat Development Capacity Building Program

    Science.gov (United States)

    Schuch, Nelson Jorge; Cupertino Durao, Otavio S.

    Equatorial Electrojet (EEJ). The Program has support from The Brazilian Space Agency (AEB).

  19. Saturn's Equatorial Oscillation: Evidence of Descending Thermal Structure from Cassini Radio Occultations

    Science.gov (United States)

    Schinder, P. J.; Flasar, F. M.; Marouf, E. A.; French, R. G.; McGhee, C. A.; Kliore, A. J.; Rappaport, N. J.; Barbinis, E.; Fleischman, D.; Anabtawi, A.

    2011-01-01

    A series of near-equatorial radio occultations of Cassini by Saturn occurred in 2005 and again in 2009-2010. Comparison of the temperature-pressure profiles obtained from the two sets of occultations shows evidence of a descending pattern in the stratosphere that is similar to those associated with equatorial oscillations in Earth's middle atmosphere. This is the first time that this descent has been observed in another planetary atmosphere. If absorption of upwardly propagating waves drives the descent, the implied absorbed flux is 0.05 square meters per square second at least as large if not greater than on Earth.

  20. Interaction of the electron density fluctuations with electron cyclotron waves from the equatorial launcher in ITER

    Science.gov (United States)

    Snicker, A.; Poli, E.; Maj, O.; Guidi, L.; Köhn, A.; Weber, H.; Conway, G. D.; Henderson, M.; Saibene, G.

    2018-01-01

    We present a numerical investigation of electron cyclotron beams interacting with electron density fluctuations in the ITER 15 MA H-mode scenario. In particular, here we study how the beam from the equatorial launcher, which shall be utilized to influence the sawtooth instability, is affected by the fluctuations. Moreover, we present the theory and first estimates of the power that is scattered from the injected O-mode to a secondary X-mode in the presence of the fluctuations. It is shown that for ITER parameters the scattered power stays within acceptable limits and broadening of the equatorial beams is less than those from the upper launcher.

  1. Jupiter's clouds - Equatorial plumes and other cloud forms in the Pioneer 10 images

    Science.gov (United States)

    Fountain, J. W.; Coffeen, D. L.; Doose, L. R.; Gehrels, T.; Swindell, W.; Tomasko, M. G.

    1974-01-01

    The imaging photopolarimeter experiment aboard the Pioneer 10 spacecraft produced two-dimensional maps of intensity and polarization in red and blue light at high resolution during flyby of Jupiter in December 1973. The present article describes cloud forms seen in the equatorial zone and compares them with rotational periods as a function of latitude derived from earth-based observations of features on Jupiter. A striking new feature consists of a bright, well-defined nucleus in the equatorial zone, with a plume apparently drawn out from the core of the nucleus.

  2. Disruption of Saturn's Equatorial Stratospheric Oscillation by the Great Storm of 2011

    Science.gov (United States)

    Fletcher, Leigh; Guerlet, Sandrine; Orton, Glenn; Cosentino, Richard; Fouchet, Thierry; Irwin, Patrick; Li, Liming

    2017-04-01

    Saturn's equatorial stratosphere exhibits at pattern of periodic oscillations in temperatures and zonal winds with a 15-year period (Fouchet et al., 2008, doi:10.1038/nature06912; Orton et al., 2008, doi:10.1038/nature06897). This pattern is analogous to Earth's Quasi-Biennial Oscillation (QBO) and Jupiter's Quasi-Quadrennial Oscillation (QQO), and may be driven by interaction of the mean zonal flow with waves spawned by tropospheric meteorology. Inversions of Cassini Composite Infrared Spectrometer (CIRS) limb and nadir spectra allowed the construction of a time series of Saturn's equatorial temperatures from 2004 to 2016, revealing the slow downward propagation of the temperature/wind pattern in the 0.1-100 mbar range. However, this pattern was spectacularly disrupted in 2011 at the same time as a large tropospheric storm system and associated stratospheric vortex (the 'beacon') were both active in the Saturn's northern springtime hemisphere (Fletcher et al., 2012, doi: 10.1016/j.icarus.2012.08.024). Temperatures were perturbed throughout Saturn's tropical stratosphere (30N-30S), with substantial cooling (10-K at 1 mbar) at 10N and 10S by 2012. This coincided with the removal of bright near-equatorial bands of methane emission observed from ground-based observatories at 7.8 µm. 1-mbar temperatures at 10N/10S did not recover to their pre-storm levels until 2014-15, when the familiar temperature/wind pattern of Saturn's equatorial oscillation was re-established and had resumed its downward propagation. The 2011 Saturnian storm therefore had a dramatic impact on the equatorial oscillation, shifting it into a new phase whose temporal period is yet to be determined. Horizontally and vertically propagating waves, emanating from both the storm and the beacon near 40N, could have transported momentum into the equatorial wind system to drive temperature changes across the equatorial region. Similar disruption associated with the 1990 equatorial storm could explain why

  3. A review on the numerical simulation of equatorial plasma bubbles toward scintillation evaluation and forecasting

    Science.gov (United States)

    Yokoyama, Tatsuhiro

    2017-12-01

    Equatorial plasma bubbles (EPBs) have been a longstanding and increasingly important subject because they cause severe scintillations in radio waves from Global Navigation Satellite System satellites. The phenomenon was found in the 1930s as irregular ionosonde observations and was termed equatorial spread F (ESF). ESF is interpreted as plasma density irregularities associated with EPBs that have nonlinearly evolved into the topside ionosphere. Numerical simulations have been powerful tools to study the fully nonlinear evolution of EPBs, which cannot be wholly understood from theoretical predictions. In this paper, historical achievements in the numerical simulation of EPBs are reviewed, and future directions toward scintillation evaluation and forecast are discussed. [Figure not available: see fulltext.

  4. 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

  5. Comparison of equatorial electron content in the Indian and American longitudes

    Energy Technology Data Exchange (ETDEWEB)

    Klobuchar, J.A.; Rastogi, R.G.

    1988-06-01

    Total electron content (TEC) measurements taken at the magnetically equatorial stations located at Ootacamund, India and Huancayo, Peru by the group delay technique from radio beacon signals transmitted from the ATS 6 geostationary satellite show excellent agreement, though these stations are at widely different longitudes and are at nearly opposite geographic latitudes. Data from both stations were taken during the solar minimum period 1975-1976. The equivalent slab thickness, the ratio TEC/N(max) also indicated similar F region profile shape in the two longitude sectors. The standard deviation of equatorial daytime TEC is significantly smaller than at other latitudes. 20 references.

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

    Directory of Open Access Journals (Sweden)

    N. Chakrabarti

    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

  7. Passages on Brazilian scientific cinema.

    Science.gov (United States)

    de Almeida, Jane; da Silva, Cicero Inacio; Suppia, Alfredo; Stalbaum, Brett

    2017-07-01

    The article examines the conditions of production and recognition of scientific cinema in Brazil by comparing three distinct moments and contexts: the first moment takes place in the nineteenth century, and it is related to the contribution of a Brazilian astronomer otherwise little known to Brazilian film scholars, the second addresses Benedito Junqueira Duarte's voluminous mid-twentieth-century filmography, and the third moment documents recent scientific film experiences within ultra high resolution movies transmitted over photonic networks. Future trajectories for aesthetic concerns and practical issues such as the archiving of ultra high definition cinema are usefully informed by these histories of scientific cinema, even as a current generation of multidisciplinary teams including scientists, filmmakers, computer scientists, and network engineers reinvent, rediscover, and necessarily expand the scientific cinema toward concerns of real time collaboration and teaching.

  8. Brands Repositioning: Brazilian case studies

    OpenAIRE

    Serralvo, Francisco Antonio; Furrier, Márcio Tadeu

    2008-01-01

    Based on the assumption of the increasing relevance of both brand positioning and equity in the context of marketing management in competitive environments, the objective of this work was to deepen the existing knowledge on the brand repositioning process. Four theoretical models of reference obtained after literature review supported the empiric verification represented by content analysis of six reports (cases) of Brazilian brands repositioning experiences awarded with the “Top of Marketing...

  9. The ionospheric response in the Brazilian sector during the super geomagnetic storm on 20 November 2003

    Directory of Open Access Journals (Sweden)

    F. Becker-Guedes

    2007-05-01

    Full Text Available A very intense geomagnetic storm (superstorm began with storm sudden commencement (SSC at 08:03 UT on 20 November 2003, as a result of the coronal mass ejection (CME by sunspot 484 hurled into space on 18 November 2003. The geomagnetic storm attained |Dst|max=472 nT at 20:00 UT (20 November. In this paper we present the simultaneous ionospheric sounding observations, using the Canadian Advanced Digital Ionosondes (CADIs, carried out from Palmas (PAL; 10.2° S, 48.2° W; dip latitude 5.5° S; a near equatorial station and São José dos Campos (SJC; 23.2° S, 45.9° W; dip latitude 17.6° S; station located under the crest of equatorial ionospheric anomaly, Brazil. In addition, total electron content (TEC measurements from several GPS receiving stations in the Brazilian sector during this storm are presented. The simultaneous ionospheric sounding observations carried out at SJC and PAL, and TEC observations on 3 consecutive days viz., 19 November (quiet, 20 November (disturbed and 21 November (recovery phase are presented. Salient features from the ionospheric observations in the Brazilian sector during the superstorm are discussed. The difference in the observed ionospheric response at the two stations (PAL and SJC is considerable. This is not surprising given that PAL is close to the magnetic equator and SJC is near the crest of the equatorial ionospheric anomaly (EIA. It should be pointed out that soon after the SSC (about 4 h later, the F-region critical frequency (foF2, the F-region peak height (hpF2, and variations of virtual heights at different frequencies (iso-frequency plots all show wavelike oscillations of the F-region during daytime at both the ionospheric sounding stations. Unusual rapid uplifting of F-region at PAL was observed during both the main and recovery phases of the storm.

  10. Brazilian Participation in World War II

    Science.gov (United States)

    2006-12-15

    internal rebellions and secessionist movements such as the Canudos rebellion in 1897 and 1898 in Bahia province. As a 2 result, the Brazilian Army...Brazilian Army would play an important role in ending this dictatorship. Brazil had accepted large numbers of Italian and German immigrants for more than...including the Brazilian Armed Forces. They had a significant influence on decision makers. In the 1930s, German immigrants numbered more than 900,000 and

  11. Brazilian Studies Then and Now

    Directory of Open Access Journals (Sweden)

    Anthony Pereira

    2012-09-01

    Full Text Available In 1912 the Brazilian diplomat and scholar Manuel de Oliveira Lima gave six lectures at Stanford University that encapsulated his views of what we now call Brazilian Studies. This article summarizes Oliveira Lima’s lectures. It then points out three aspects of Oliveira Lima’s worldview that are problematic from the perspective of the twenty-first century: his Eurocentrism; the unproblematic nature of the nation-state in his thinking; and his largely negative view of Brazil’s racial heritage. The third part of the essay analyzes three aspects of Oliveira Lima’s lectures that are still contemporary. These are the need to establish an adequate comparative context for the study of Brazil; the difficulty of justifying an academic discipline that revolves around the study of a single country; and the challenge of uniting disparate and specialized disciplines in order to appreciate Brazil’s complexity and trajectory in the modern world. In the conclusion, some guidelines for maintaining Brazilian Studies as a vibrant field are suggested.

  12. Asymmetry of the TEC Anomaly from the Meridional Neutral Wind and Equatorial Electrojet Perspectives

    Science.gov (United States)

    Khadka, S.; Valladares, C. E.; Pradipta, R.; Sheehan, R.

    2015-12-01

    The equatorial ionization anomaly (EIA) is significant ionospheric phenomena caused by the so-called fountain effect, which is driven by a zonal eastward electric field. This process involves the altitudinal coupling, electrodynamics and inhomogeneity of ionospheric plasma densities in the equatorial and low latitude regions. Not only eastward electric field, but neutral winds also play a role in controlling the actual configuration of the EIA. In the present study, an attempt is made to reveal the effect of the longitudinal variability of the equatorial electrojet (EEJ) strengths associated with eastward electric field and meridional neutral winds for the generation and control of the asymmetries on EIA crests of TEC (Total Electron Content) about the magnetic equator in the American sector. Our results show that as EEJ is stronger (weaker), EIA crests are formed farther (closer) from equator on the western (eastern) side of South America. A physics-based numerical model is used to study the effects of daytime meridional neutral winds and EEJ on consequent evolution of asymmetry in equatorial TEC anomalies during afternoon and onwards. This result implies that the electric field associated with the EEJ together with meridional neutral winds may play a key role in the development of observed asymmetries of EIA crests and dictate the shape, size, amplitude and separation of the EIA crests as seen through ionospheric TEC distribution measured using GPS (Global Positioning System) in the low latitudes ionosphere.

  13. Non-trough foF2 enhancements at near-equatorial dip latitudes

    Directory of Open Access Journals (Sweden)

    A. T. Kobea

    Full Text Available Fine resolution series from three equatorial ionosondes of the IEEY network in West Africa have revealed small-scale daytime peak F2 structures, superposed on the slowly varying minimum or "trough" distribution in the ±5° magnetic latitude zone. We report this new morphology, concentrating on foF2 enhancements of two types: near-equatorial crests (which travel either northwards or southwards and magnetic field-aligned domes, whose onsets last only tens of minutes. Both types are observed to start at mid-morning or early afternoon hours. We relate their occurrence with the available variations of Vz=E × B upward drift which feeds the equatorial plasma fountain. We suggest the foF2 enhancements to be triggered by brief slow-downs of the Vz velocity near F2 peak altitude in our West African sector. Their short latitude extent differentiates them from the larger-scale tropical crest system. Further analysis of these features should lead to weather-like models of the low latitude ionosphere variations, where unstable local coupling between processes seems to be the trigger.Key words. Ionosphere (Equatorial ionosphere · Ionosphere-atmosphere interaction · Plasma temperature and density

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

    African Journals Online (AJOL)

    Seasonal variation with equinoctial maxima and solstial minima was also observed from the analysis. The presence of equinoctial maxima is likely to be due to enhanced equatorial electron density and the electric field at equinox. The day to day variability may be attributed to electric field, a dawn to dusk phenomenon.

  15. EVIDENCE FOR THE EXISTENCE OF LIPID-DIFFUSION BARRIERS IN THE EQUATORIAL SEGMENT OF HUMAN SPERMATOZOA

    NARCIS (Netherlands)

    ARTS, EGJM; JAGER, S; HOEKSTRA, D

    1994-01-01

    Liposomes consisting of negatively charged phospholipids interact almost exclusively with the equatorial segment (ES) of human spermatozoa provided the cells have undergone the acrosome reaction (AR) [Arts, Kuiken, Jager and Hoekstra (1993) Eur. J. Biochem. 217, 1001-1009]. Using fluorescently

  16. 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.

    Three satellite-tracked drifting buoys released in the south equatorial current in the Indian Ocean followed the path of the current moving westward approximately zonally in the vicinity of 10 degrees S latitude. On nearing the east coast of Africa...

  17. Solar flux variation of the electron temperature morning overshoot in the equatorial F region

    DEFF Research Database (Denmark)

    Stolle, Claudia; Liu, H.; Truhlik, V.

    2011-01-01

    Using 8 years of CHAMP satellite observations of the equatorial electron temperature, T-e, we investigate its behavior during the morning overshoot and at ionospheric altitudes below 450 km including its variation with solar activity. The morning T-e has a maximum at the dip equator and decreases...

  18. A note on new indices for the equatorial Indian Ocean oscillation

    Indian Academy of Sciences (India)

    and Carpenter 1983) is well known. Recent studies have shown that, in addition to ENSO, equatorial. Indian Ocean oscillation (EQUINOO) also plays an important role in the interannual variation of. ISMR (Gadgil et al. 2003, 2004, 2007; Ihara et al. 2007; Francis and Gadgil 2010; Boschat et al. 2012;. Rajeevan et al. 2012).

  19. Anomalous circulation in the eastern equatorial Indian Ocean during southwest 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.

    Geostrophic circulation derived from hydrographic data collected during July-August, 1994 along 80, 84 and 88E between 5N and 3S latitudinal belt in the eastern equatorial Indian Ocean is presented. A broad westward flow north of the equator...

  20. Some results of analysis of inverted echo-sounder records from the Atlantic Equatorial region

    Directory of Open Access Journals (Sweden)

    Alberto dos Santos Franco

    1985-01-01

    Full Text Available The tidal analysis of data from the Equatorial region, given by inverted echo-sounders, show considerable residuals in the frequency band of approximately 2 cycles per day. In the even harmonics of 4 and 6 cycles per day, tidal components statistically not negligible are also identified. Spectral analysis of temperature series from the same area show, on the other hand, variabilities in the same frequency bands, which suggests the occurrence of internal waves with energy distributed in these frequency bands, in the Atlantic Equatorial area.Análises de dados de maré, da zona equatorial, obtidos com ecobatímetros invertidos, mostram consideráveis resíduos na faixa de freqüências com aproximadamente dois ciclos por dia. Nos harmônicos pares com 4 e 6 ciclos por dia são também identificadas componentes de maré estatisticamente não desprezíveis. Análises espectrais de séries de temperatura obtidas na mesma área mostram, 218 por outro lado, variabilidades na mesma faixa de freqüências, o que sugere a ocorrência, na área equatorial Atlântica, de ondas internas com energia distribuída nessas faixas espectrais.

  1. 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.

  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. The Effect of Equatorial Spread F on Relative Orbit Determination of GRACE Using Differenced GPS Observations

    Directory of Open Access Journals (Sweden)

    Kyoung-Min Roh

    2009-12-01

    Full Text Available In this paper, relative orbit of Low Earth Orbit satellites is determined using only GPS measurements and the effects of Equatorial Spread-F (ESF, that is one of biggest ionospheric irregularities, are investigated. First, relative orbit determiation process is constructed based on doubly differenced GPS observations. In order to see orbit determination performance, relative orbit of two GRACE satellites is estimated for one month in 2004 when no ESF is observed. The root mean square of the achieved baselines compared with that from K-Band Ranger sensor is about 2 ~ 3 mm and average of 95% of ambiguities are resolved. Based on this performance, the relative orbit is estimated for two weeks of two difference years, 2003 when there are lots of ESF occurred, and 2004 when only few ESF occurred. For 2003, the averaged baseline error over two weeks is about 15 mm. That is about 4 times larger than the case of 2004 (3.6 mm. Ionospheric status achieved from K-Band Ranging sensor also shows that more Equatorial Spread-F occurred at 2003 than 2004. Investigation on raw observations and screening process revealed that the ionospheric irregualarities caused by Equatorial Spread-F gave significant effects on GPS signal like signal loss or enhancement ionospheric error, From this study, relative orbit determination using GPS observations should consider the effect of Equatorial Spread-F and adjust orbit determination strategy, especially at the time of solar maximum.

  4. Ionospheric electron content within the equatorial F sub 2 layer anomaly belt

    Energy Technology Data Exchange (ETDEWEB)

    Rastogi, R.G. (Indian Inst. of Geomagnetism, Bombay (India)); Klobuchar, J.A. (Air Force Geophysics Lab., Hanscom Air Force Base, MA (United States))

    1990-11-01

    This paper describes some new results on the day-to-day behavior of the location of the equatorial anomaly in the columnar electron content. The measurements were made from a unique network of stations covering dip latitudes from 0{degree}N to 25{degree}N during the period in 1975-1976 near sunspot minimum when the ATS 67 satellite was visible from India. The latitudinal distribution of the total electron content on a particular day was found to depend only on the strength of the electrojet current, as determined by the difference of the horizontal magnetic field at stations on the magnetic equator and another outside the equatorial electrojet, rather than on the horizontal magnetic field measured only at the equatorial station. During magnetically disturbed periods the presence or absence of the anomaly was also found to depend only upon the strength of the electrojet current. The varying electrojet current, that is, the equatorial electric field, is very effective in moving the ionization to the anomaly latitudes of 15{degree}-20{degree}, but the columnar electron content over the magnetic equator remains relatively constant.

  5. Ionospheric electron content within the equatorial F2 layer anomaly belt

    Energy Technology Data Exchange (ETDEWEB)

    Rastogi, R.G.; Klobuchar, J.A.

    1990-11-01

    This Reprint describes some new results on the day-to-day behavior of the equatorial anomaly in the columnar electron content. The measurements were made from a unique network of stations covering dip latitudes from 0 to 25 N during the period in 1975-1976 near sunspot minimum when the ATS 6 satellite was visible from India. The latitudinal distribution of the total electron content on a particular day was found to depend only on the strength of the electrojet current, as determined by the difference of the horizontal magnetic field at stations on the magnetic equator and another outside the equatorial electrojet, rather than on the horizontal magnetic field measured only at the equatorial station. During magnetically disturbed periods the presence or absence of the anomaly was also found to depend only upon the strength of the electrojet current. The varying electrojet current, that is, the equatorial electric field, is very effective in moving the ionization to the anomaly latitudes of 15-20, but the columnar electron content over the magnetic equator remains relatively constant.

  6. 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 ...

  7. 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 ...

  8. Zonal winds in the equatorial upper thermosphere : Decomposing the solar flux, geomagnetic activity, and seasonal dependencies

    NARCIS (Netherlands)

    Liu, H.; Lühr, H.; Watanabe, S.; Köhler, W.; Henize, V.; Visser, P.N.A.M.

    2006-01-01

    Using 3 years (2002–2004), over 16,400 orbits of measurements from the accelerometer on board the CHAMP satellite, we have studied the climatology of the equatorial zonal wind in the upper thermosphere. Several main features are noticed. The most prominent one is that the solar flux significantly

  9. Nutrient characteristics of the water masses and their seasonal variability in the eastern equatorial Indian Ocean.

    Science.gov (United States)

    Sardessai, S; Shetye, Suhas; Maya, M V; Mangala, K R; Prasanna Kumar, S

    2010-01-01

    Nutrient characteristics of four water masses in the light of their thermohaline properties are examined in the eastern Equatorial Indian Ocean during winter, spring and summer monsoon. The presence of low salinity water mass with "Surface enrichments" of inorganic nutrients was observed relative to 20 m in the mixed layer. Lowest oxygen levels of 19 microM at 3 degrees N in the euphotic zone indicate mixing of low oxygen high salinity Arabian Sea waters with the equatorial Indian Ocean. The seasonal variability of nutrients was regulated by seasonally varying physical processes like thermocline elevation, meridional and zonal transport, the equatorial undercurrent and biological processes of uptake and remineralization. Circulation of Arabian Sea high salinity waters with nitrate deficit could also be seen from low N/P ratio with a minimum of 8.9 in spring and a maximum of 13.6 in winter. This large deviation from Redfield N/P ratio indicates the presence of denitrified high salinity waters with a seasonal nitrate deficit ranging from -4.85 to 1.52 in the Eastern Equatorial Indian Ocean. 2010 Elsevier Ltd. All rights reserved.

  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. Equatorial anomaly variability as a function of the local time and the longitude

    CERN Document Server

    Pulinets, S A; Hernández-Pajáres, M

    2002-01-01

    The equatorial anomaly dynamics is very difficult to study due to necessity of its monitoring in space (latitude-longitude) and local time simultaneously. This task is impossible for the single-point measurements, and only the satellite technology may help. The present paper is devoted to the preliminary analysis of the equatorial anomaly dynamics combining two techniques - the topside sounding and GPS TEC measurements. The topside sounding gives the unique opportunity to build the global structure of the equatorial anomaly for the fixed local time (LT-maps) and to reveal the longitudinal variations, while the chains of GPS receivers along the meridian permit to study the latitudinal variations of TEC in local time. Two meridional chains of GPS receivers were selected: at 115 deg. E and 70 deg. W longitudes. Combining of two technologies makes it possible to obtain three-dimensional global dynamics of the equatorial anomaly. The paper demonstrates the power of the technique itself while the more detailed and ...

  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. Demographic history of wood stork (Mycteria americana Brazilian Pantanal colonies revealed by mitochondrial DNA analysis

    Directory of Open Access Journals (Sweden)

    Iara Freitas Lopes

    2006-01-01

    Full Text Available We used mitochondrial DNA (mtDNA sequences to investigate the demographic history of the wood stork (Mycteria americana populations in the Brazilian Pantanal. Sequences of 390/460 bp fragment of the mtDNA control region were analyzed in 62 wood stork specimens from 8 colonies using neutrality tests, phylogeographic, and coalescent analyses. Population expansion was supported by the significantly negative values of Tajima’s (D = -2.071 and Fu’s (Fs = -14.544 statistics and the unimodal pattern of mismatch distribution. Nested clade analyses indicated a historic range expansion event and recurrent gene flow that was restricted by isolation by distance as explanations for the haplotype distribution among the sampled colonies. High genetic diversity and the strictly unidirectional gene flow pattern emphasized the conservation importance of preserving the southern Pantanal colonies. Coalescence analyses suggested that northern and southern colonies diverged approximately 6,250 years before the present (YBP, and that their most recent common ancestor was approximately 18,900 YBP. Our results suggest that the contemporary wood stork Pantanal population originated from a more geographically limited founder population. Potential source populations may have occurred in the southern Pantanal or ancestry may reside in populations inhabiting the Brazilian central plateau or areas closer to the equatorial region.

  14. 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.

  15. Timing and magnitude of equatorial Atlantic surface warming during the last glacial bipolar oscillation

    Directory of Open Access Journals (Sweden)

    S. Weldeab

    2012-10-01

    Full Text Available The timing and magnitude of millennial-scale thermal oscillation in the equatorial Atlantic during the last glacial and marine isotope stage 3 have been perceived as merely a response to meltwater-induced perturbations of the northern high latitude climate. The relatively asymmetric distribution of available temperature records has so far impeded testing whether this view is valid across the equatorial Atlantic. This study presents a centennially resolved record of Mg/Ca-derived sea surface temperature (SST estimates from the eastern equatorial Atlantic (EEA and a core top-based proxy validation. Multivariate analysis of the EEA core top data indicates that the Mg/Ca ratio varies by 8 ± 2% per unit SST (°C and 1 ± 0.9% per unit salinity (psu change, indicating that temperature is the most dominant factor controlling planktonic foraminiferal Mg/Ca variation. The EEA SST time series exhibits a close correlation between episodes of rapid equatorial surface water warming, the onset of massive meltwater inputs into the North Atlantic (Heinrich events H3–H6, and Antarctic climate changes, indicating that the EEA was very sensitive to millennial-scale bipolar oscillations. Rapid EEA SST rise between 0.8 °C and 2 °C, synchronous with the onset of Heinrich events, is consistent with the concept of tropical Atlantic warming in response to meltwater-induced perturbation of Atlantic meridional ocean circulation (AMOC. At variance with model results that suggest a basin-wide SST rise during and rapid surface cooling concomitant with the termination of Heinrich events, this study indicates persistently elevated EEA SST during and up to 2300 yr after the abrupt termination of Heinrich events. This study emphasizes that changes in wind-induced low-latitude zonal surface currents were crucial in shaping the spatial heterogeneity and duration of equatorial Atlantic surface water warmth.

  16. Radiative and Dynamical Feedbacks Over the Equatorial Cold-Tongue: Results from Seven Atmospheric GCMs

    Energy Technology Data Exchange (ETDEWEB)

    Sun, D; Zhang, T; Covey, C; Klein, S; Collins, W; Kiehl, J; Meehl, J; Held, I; Suarez, M

    2005-01-04

    The equatorial Pacific is a region with strong negative feedbacks. Yet coupled GCMs have exhibited a propensity to develop a significant SST bias in that region, suggesting an unrealistic sensitivity in the coupled models to small energy flux errors that inevitably occur in the individual model components. Could this 'hypersensitivity' exhibited in a coupled model be due to an underestimate of the strength of the negative feedbacks in this region? With this suspicion, the feedbacks in the equatorial Pacific in seven atmospheric GCMs (AGCMs) have been quantified using the interannual variations in that region and compared with the corresponding calculations from the observations. The seven AGCMs are: the NCAR CAM1, the NCAR CAM2,the NCAR CAM3, the NASA/NSIPP Atmospheric Model, the Hadley Center Model, the GFDL AM2p10, and the GFDL AM2p12. All the corresponding coupled runs of these seven AGCMs have an excessive cold-tongue in the equatorial Pacific. The net atmospheric feedback over the equatorial Pacific in the two GFDL models is found to be comparable to the observed value. All other models are found to have a weaker negative net feedback from the atmosphere--a weaker regulating effect on the underlying SST than the real atmosphere. A weaker negative feedback from the cloud albedo and a weaker negative feedback from the atmospheric transport are the two leading contributors to the weaker regulating effect from the model atmosphere. All models overestimate somewhat the positive feedback from water vapor. These results confirm the suspicion that an underestimate of negative feedbacks from the atmosphere over the equatorial Pacific region is a prevalent problem. The results also suggest, however, that a weaker regulatory effect from the atmosphere is unlikely solely responsible for the 'hypersensitivity' in all models. The need to validate the feedbacks from the ocean transport is therefore highlighted.

  17. D- and E-region effects in the auroral zone during a moderately active 24-h period in July 2005

    Directory of Open Access Journals (Sweden)

    J. K. Hargreaves

    2007-08-01

    Full Text Available The effects of energetic electron precipitation into the auroral region at a time of enhanced solar wind have been investigated during a continuous period of 24 h, using the European Incoherent Scatter (EISCAT radar, an imaging riometer, and particle measurements on an orbiting satellite. The relative effects in the E region (120 km and D region (90 km are found to vary during the day, consistent with a gradual hardening of the incoming electron spectrum from pre-midnight to morning. Whereas the night spectra are single peaked, the daytime spectra are found to be double peaked, suggesting the presence of two distinct populations.

    A comparison between the radiowave absorption observed with the riometer and values estimated from the radar data shows generally good agreement, but with some discrepancies suggesting the occurrence of some small-scale features. The height and thickness of the absorbing region are estimated. Two periods of enhanced precipitation and the related radio absorption, one near magnetic midnight and one in the early morning, are studied in detail, including their horizontal structure and movement of the absorption patches.

    A sharp reduction of electron flux recorded on a POES satellite is related to the edge of an absorption region delineated by the imaging riometer. The observed particle flux is compared with a value deduced from the radar data during the overpass, and found to be in general agreement.

  18. D- and E-region effects in the auroral zone during a moderately active 24-h period in July 2005

    Directory of Open Access Journals (Sweden)

    J. K. Hargreaves

    2007-08-01

    Full Text Available The effects of energetic electron precipitation into the auroral region at a time of enhanced solar wind have been investigated during a continuous period of 24 h, using the European Incoherent Scatter (EISCAT radar, an imaging riometer, and particle measurements on an orbiting satellite. The relative effects in the E region (120 km and D region (90 km are found to vary during the day, consistent with a gradual hardening of the incoming electron spectrum from pre-midnight to morning. Whereas the night spectra are single peaked, the daytime spectra are found to be double peaked, suggesting the presence of two distinct populations. A comparison between the radiowave absorption observed with the riometer and values estimated from the radar data shows generally good agreement, but with some discrepancies suggesting the occurrence of some small-scale features. The height and thickness of the absorbing region are estimated. Two periods of enhanced precipitation and the related radio absorption, one near magnetic midnight and one in the early morning, are studied in detail, including their horizontal structure and movement of the absorption patches. A sharp reduction of electron flux recorded on a POES satellite is related to the edge of an absorption region delineated by the imaging riometer. The observed particle flux is compared with a value deduced from the radar data during the overpass, and found to be in general agreement.

  19. E-region mid-latitude decametre irregularities observed at four radar frequencies. Experiment and first results

    Directory of Open Access Journals (Sweden)

    A. Bourdillon

    Full Text Available In this paper an experiment designed for multifrequency azimuthal Doppler-spectrum investigations of decametre-scale plasma irregularities in the mid-latitude E region is introduced and some preliminary results are presented. The observations were made with the high-frequency Valensole radar in the south of France. The radar operated in a multifrequency mode that allowed simultaneous measurements of Doppler spectra at the four frequencies of 9.23, 11.03, 12.71 and 16.09 MHz, which correspond to scatter from field-aligned irregularities with wavelengths of 16.2, 13.6, 11.8 and 9.3 m, respectively. In addition, a digital ionosonde was operating beneath a small part of the radar viewing region. The data show that lower-frequency echoes are stronger, more frequent and more spatially extended than higher-frequency ones, in general agreement with theory and rocket measurements. On the other hand, the preliminary analysis shows no pronounced differences of the Doppler spectrum with radar frequency. Some trends in the spectral moments do exist, however, which can be understood as the result of temporal and/or spatial mixing of backscatter from directly generated (primary plasma waves by the gradient drift instability and secondary low-velocity waves. Finally, a close relation of mid-latitude coherent backscatter with patchy sporadic E-layers is present in the data, but the details of this relation remain unresolved.

  20. 36th Brazilian Workshop on Nuclear Physics

    CERN Document Server

    Brandão de Oliveira, José Roberto; Barbosa Shorto, Julian Marco; Higa, Renato

    2014-01-01

    The Brazilian Workshop on Nuclear Physics (RTFNB, acronym in Portuguese) is organized annually by the Brazilian Physics Society since 1978, in order to: promote Nuclear Physics research in the country; stimulate and reinforce collaborations among nuclear physicists from around the country; disseminate advances in nuclear physics research and its applications; disseminate, disclose and evaluate the scientific production in this field.

  1. The new Brazilian national forest inventory

    Science.gov (United States)

    Joberto V. de Freitas; Yeda M. M. de Oliveira; Doadi A. Brena; Guilherme L.A. Gomide; Jose Arimatea Silva; < i> et al< /i>

    2009-01-01

    The new Brazilian national forest inventory (NFI) is being planned to be carried out through five components: (1) general coordination, led by the Brazilian Forest Service; (2) vegetation mapping, which will serve as the basis for sample plot location; (3) field data collection; (4) landscape data collection of 10 x 10-km sample plots, based on high-resolution...

  2. Brazilian Studies and Brazilianists: Conceptual remarks

    Directory of Open Access Journals (Sweden)

    Vinicius Mariano de Carvalho

    2017-01-01

    Full Text Available This article discusses the concept of Brazilian Studies. It does not intend to outline a defence for a new discipline, or to propose paradigms for that elusive field called ‘area studies’. It will, bring some reflections on epistemological and methodological issues realted to what it is been called Brazilian Studies.

  3. Types and myths in Brazilian thought

    Directory of Open Access Journals (Sweden)

    Octavio Ianni

    2005-01-01

    Full Text Available "Ideal types" elaborated by different authors and that have become emblematic, notorious or even definitive, sometimes representing myths are quite frequent in Brazilian thought. That is the case of the bandeirantes (colonial crusaders, the gaúcho, Jeca Tatu, Macunaíma, cordial man and others. It is worth contemplating this aspect of Brazilian culture and thought.

  4. Sociocultural Influences on Brazilian Children's Drawings.

    Science.gov (United States)

    Stokrocki, Mary

    2000-01-01

    Reports on insights about sociocultural influences on Brazilian children's drawings, using visual anthropology to examine children's drawings that depicted what they like to do. Discusses visual anthropology, provides information on Brazilian educational influences, and presents the context and findings of the study. (CMK)

  5. The Brazilian Synchrotron Light Source

    CERN Document Server

    Tavares, P F

    2005-01-01

    The Brazilian Synchrotron Radiation Laboratory has been operating the only light source in the southern hemisphere since July 1997. Over this 7 year period, approximately 22000 hours of beam time were delivered to users from all over Brazil as well as from 10 other countries. In this article, we report on the present configuration of the 1.37 GeV electron storage ring and associated instrumentation, describe recent improvements to the light source and analyze future prespectives including the installation of insertion devices and additional beamlines.

  6. Elementary education in brazilian legislation

    OpenAIRE

    Veronese, Josiane Rose Petry; Vieira, Cleverton Elias

    2003-01-01

    The education was a present subject, directly or indirectly, in every Brazilian Constitutions. In the Federal Constitution of 1988, two aspects about education can be detached: the participation of the civil society in the elaboration of devices that regulate the national education and the treatment given to basic education, raised to the category of subjective public right. Child and Adolescent Statute practically repeats the devices of the&n...

  7. Observations of day-to-day variability in precursor signatures to equatorial F-region plasma depletions

    Directory of Open Access Journals (Sweden)

    P. R. Fagundes

    Full Text Available In December 1995, a campaign was carried out to study the day-to-day variability in precursor signatures to large-scale ionospheric F-region plasma irregularities, using optical diagnostic techniques, near the magnetic equator in the Brazilian sector. Three instruments were operated simultaneously: (a an all-sky (180° field of view imaging system for observing the OI 630 nm nightglow emission at Alcântara (2.5°S, 44.4°W; (b a digisonde (256-Lowell at São Luis (2.6°S, 44.2°W; and (c a multi-channel tilting filter-type zenith photometer for observing the OI 630 nm and mesospheric nightglow emissions at Fortaleza (3.9°S, 38.4°W. During the period December 14-18, 1995 (summer in the southern hemisphere, a good sequence of the OI 630 nm imaging observations on five consecutive nights were obtained, which are presented and discussed in this study. The observing period was geomagnetically quiet to moderate 
    (Kp = 0+ to 5+; Dst = 18 nT to -37 nT. On four nights, out of the five observation nights, the OI 630 nm imaging pictures showed formations of transequatorial north-south aligned intensity depletions, which are the optical signatures of large-scale ionospheric F-region plasma bubbles. However, considerable day-to-day variability in the onset and development of the plasma depleted bands was observed. On one of the nights it appears that the rapid uplifting of the F-layer in the post-sunset period, in conjunction with gravity wave activity at mesospheric heights, resulted in generation of very strong plasma bubble irregularities. One of the nights showed an unusual formation of north-south depleted band in the western sector of the imaging system field of view, but the structure did not show any eastward movement, which is a normal characteristic of plasma bubbles. This type of irregularity structure, which probably can be observed only by wide-angle imaging system, needs more investigations for a better understanding of

  8. The effect of ionizing photons (VUV + soft X-rays) in the equatorial and polar surfaces of the Europa moon

    Science.gov (United States)

    Pilling, Sergio; Alexandre Souza Bergantini, M.

    Europa is the sixth-closest moon of the planet Jupiter, and the smallest of the four Galilean satellites, but still the sixth-largest moon in the Solar System being only slightly smaller than Earth's Moon. Its cold surface is covered mainly by water ice and a small fraction of other molecular frozen species such as CO _{2}, NH _{3}, and SO _{2}. Since Europa has only a very thin O _{2} rich atmosphere, the surface is constantly exposed to space ionizing agents such as UV and soft X-rays photons, electrons and ions. In this work we investigate the effects produced by vacuum ultraviolet (VUV) and soft X-rays (and possibly secondary electrons) on the surface of Europa Moon, simulating this way the space weathering and the prebiotic photochemistry induced by solar photons on this moon. The experiments have been performed using a high vacuum portable chamber from the Laboratorio de Astroquimica e Astrobiologia (LASA/UNIVAP) coupled to the spherical grating monochromator (SGM) beamline in the Brazilian Synchrotron Light Source (LNLS) at Campinas, Brazil. The beamline was operated in off-focus and white beam mode, which produces a wide band spectral range of photons, mainly from 6 eV up to 1200 eV, with the total average flux at the sample of about 1x10 (14) photons cm (-2) s (-1) . The experiments simulate roughly 10.7 years of solar irradiation (energy delivered) on the Europa surface. In-situ sample analyses were performed by a Fourier transform infrared spectrometer. The samples were produced by the adsorption of a gaseous mixture containing H _{2}O:CO _{2}:NH _{3}:SO _{2} (10:1:1:1) at very low temperature (12 K) and than were slowly heated (2 K/min) to the temperatures in which the irradiation occur, i.e. at 90K and 50K, simulating this way the equatorial and polar regions of the moon. This scenario simulates the cold molecular delivery from comets in the early phases of this Jupiter’s moon. The infrared spectra of irradiated samples have presented the formation

  9. Observations of day-to-day variability in precursor signatures to equatorial F-region plasma depletions

    Directory of Open Access Journals (Sweden)

    P. R. Fagundes

    1999-08-01

    Full Text Available In December 1995, a campaign was carried out to study the day-to-day variability in precursor signatures to large-scale ionospheric F-region plasma irregularities, using optical diagnostic techniques, near the magnetic equator in the Brazilian sector. Three instruments were operated simultaneously: (a an all-sky (180° field of view imaging system for observing the OI 630 nm nightglow emission at Alcântara (2.5°S, 44.4°W; (b a digisonde (256-Lowell at São Luis (2.6°S, 44.2°W; and (c a multi-channel tilting filter-type zenith photometer for observing the OI 630 nm and mesospheric nightglow emissions at Fortaleza (3.9°S, 38.4°W. During the period December 14-18, 1995 (summer in the southern hemisphere, a good sequence of the OI 630 nm imaging observations on five consecutive nights were obtained, which are presented and discussed in this study. The observing period was geomagnetically quiet to moderate  (Kp = 0+ to 5+; Dst = 18 nT to -37 nT. On four nights, out of the five observation nights, the OI 630 nm imaging pictures showed formations of transequatorial north-south aligned intensity depletions, which are the optical signatures of large-scale ionospheric F-region plasma bubbles. However, considerable day-to-day variability in the onset and development of the plasma depleted bands was observed. On one of the nights it appears that the rapid uplifting of the F-layer in the post-sunset period, in conjunction with gravity wave activity at mesospheric heights, resulted in generation of very strong plasma bubble irregularities. One of the nights showed an unusual formation of north-south depleted band in the western sector of the imaging system field of view, but the structure did not show any eastward movement, which is a normal characteristic of plasma bubbles. This type of irregularity structure, which probably can be observed only by wide-angle imaging system, needs more investigations for a better understanding of its behaviour

  10. Variation in the diel vertical distributions of larvae and transforming stages of oceanic fishes across the tropical and equatorial Atlantic

    Science.gov (United States)

    Olivar, M. Pilar; Contreras, Tabit; Hulley, P. Alexander; Emelianov, Mikhail; López-Pérez, Cristina; Tuset, Víctor; Castellón, Arturo

    2018-01-01

    The vertical distributions of early developmental stages of oceanic fishes were investigated across the tropical and equatorial Atlantic, from oligotrophic waters close to the Brazilian coast to more productive waters close to the Mauritanian Upwelling Region. Stratification of the water column was observed throughout the study region. Fishes were caught with a MOCNESS-1 net with mouth area of 1 m2 at 11 stations. Each station was sampled both during the day and at night within a single 24-h period. The investigation covered both larvae and transforming stages from the surface to 800 m depth. Distribution patterns were analysed, and weighted mean depths for the larvae and transforming stages of each species were calculated for day and night conditions. Forty-seven different species were found. The highest number of species occurred in the three stations south of Cape Verde Islands, characterized by a mixture of South Atlantic Central Water (SACW) and Eastern North Atlantic Central Water (ENACW). There was a marked drop in species richness in the three stations closer to the African upwelling, dominated by ENACW. The highest abundances occurred in the families Myctophidae, Sternoptychidae, Gonostomatidae and Phosichthyidae. Day and night vertical distributions of larvae and transforming stages showed contrasting patterns, both in the depths of the main concentration layers in the water column, and in the diel migration patterns (where these were observed). Larvae generally showed a preference for the upper mixed layer (ca. 0-50 m) and upper thermocline (ca. 50-100 m), except for sternoptychids, which were also abundant in the lower thermocline layer (100-200 m) and even extended into the mesopelagic zone (down to 500 m). Transforming stages showed a more widespread distribution, with main concentrations in the mesopelagic zone (200-800 m). Larvae showed peak concentrations in the more illuminated and zooplankton-rich upper mixed layers during the day and a wider

  11. Ion and neutral temperature distributions in the E-region observed by the EISCAT Tromsø and Svalbard radars

    Directory of Open Access Journals (Sweden)

    S. Maeda

    Full Text Available Simultaneous Common Program Two experiments by the EISCAT UHF radar at Tromsø and the EISCAT Svalbard radar at Longyearbyen from 00:00 to 15:00 UT on 22 September 1998 and 9 March 1999 have been utilized to investigate distributions of the ion and neutral temperatures in the E-region between 105 and 115 km. During the experiments, soft particle precipitations in the dayside cusp were observed over the Svalbard radar site by the Defense Meteorological Satellite Program (DMSP F11 satellite. It is found that the dayside electric field in the regions of the low-latitude boundary of the polar cap and the cusp was greater and more variable than that in the auroral region. The ion temperature, parallel to the geomagnetic field at Longyearbyen, was higher than that at Tromsø during the daytime from 06:00 to 12:00 UT. The steady-state ion energy equation has been applied to derive neutral temperature under the assumption of no significant heat transport and viscous heating. The estimated neutral temperature at Longyearbyen was also higher than that at Tromsø. The ion and neutral energy budget was discussed in terms of the ion frictional heating and the Joule heating. The results indicate two possibilities: either the neutral temperature was high in the low latitude boundary of the polar cap and the cusp, or the heat transport by the polar cap neutral winds toward the dayside sector was significant.

    Key words. Ionosphere (auroral ionosphere; ionosphere–atmosphere interactions; polar ionosphere

  12. Comparison of postmenopausal endogenous sex hormones among Japanese, Japanese Brazilians, and non-Japanese Brazilians

    Directory of Open Access Journals (Sweden)

    Maciel Maria

    2011-02-01

    Full Text Available Abstract Background Differences in sex hormone levels among populations might contribute to the variation in breast cancer incidence across countries. Previous studies have shown higher breast cancer incidence and mortality among Japanese Brazilians than among Japanese. To clarify the difference in hormone levels among populations, we compared postmenopausal endogenous sex hormone levels among Japanese living in Japan, Japanese Brazilians living in the state of São Paulo, and non-Japanese Brazilians living in the state of São Paulo. Methods A cross-sectional study was conducted using a control group of case-control studies in Nagano, Japan, and São Paulo, Brazil. Participants were postmenopausal women older than 55 years of age who provided blood samples. We measured estradiol, estrone, androstenedione, dehydroepiandrosterone sulfate (DHEAS, testosterone and free testosterone by radioimmunoassay; bioavailable estradiol by the ammonium sulfate precipitation method; and sex hormone-binding globulin (SHBG by immunoradiometric assay. A total of 363 women were included for the present analyses, comprising 185 Japanese, 44 Japanese Brazilians and 134 non-Japanese Brazilians. Results Japanese Brazilians had significantly higher levels of estradiol, bioavailable estradiol, estrone, testosterone and free testosterone levels, and lower SHBG levels, than Japanese. Japanese Brazilians also had significantly higher levels of bioavailable estradiol, estrone and DHEAS and lower levels of SHBG and androstenedione than non-Japanese Brazilians. Levels of estradiol, testosterone and free testosterone, however, did not differ between Japanese Brazilians and non-Japanese Brazilians. These differences were observed even after adjustment for known breast cancer risk factors. We also found an increase in estrogen and androgen levels with increasing body mass index, but no association for most of the other known risk factors. Conclusions We found higher levels of

  13. The phylogeography of African Brazilians.

    Science.gov (United States)

    Gonçalves, Vanessa F; Carvalho, Cláudia M B; Bortolini, Maria Cátira; Bydlowski, Sérgio P; Pena, Sérgio D J

    2008-01-01

    Approximately four million Africans were taken as slaves to Brazil, where they interbred extensively with Amerindians and Europeans. We have previously shown that while most White Brazilians carry Y chromosomes of European origin, they display high proportions of African and Amerindian mtDNA lineages, because of sex-biased genetic admixture. We studied the Y chromosome and mtDNA haplogroup structure of 120 Black males from Sao Paulo, Brazil. Only 48% of the Y chromosomes, but 85% of the mtDNA haplogroups were characteristic of sub-Saharan Africa, confirming our previous observation of sexually biased mating. We mined literature data for mtDNA and Y chromosome haplogroup frequencies for African native populations from regions involved in Atlantic Slave Trade. Principal Components Analysis and Bayesian analysis of population structure revealed no genetic differentiation of Y chromosome marker frequencies between the African regions. However, mtDNA examination unraveled considerable genetic structure, with three clusters at Central-West Africa, West Africa and Southeast Africa. A hypothesis is proposed to explain this structure. Using these mtDNA data we could obtain for the first time an estimate of the relative ancestral contribution of Central-West (0.445), West (0.431) and Southeast Africa (0.123) to African Brazilians from Sao Paulo. These estimates are consistent with historical information. Copyright 2008 S. Karger AG, Basel.

  14. 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.

  15. Detecting cross-equatorial wind change as a fingerprint of climate response to anthropogenic aerosol forcing

    Science.gov (United States)

    Wang, Hai; Xie, Shang-Ping; Tokinaga, Hiroki; Liu, Qinyu; Kosaka, Yu

    2016-04-01

    Anthropogenic aerosols are a major driver of the twetieth century climate change. In climate models, the aerosol forcing, larger in the Northern than Southern Hemispheres, induces an interhemispheric Hadley circulation. In support of the model result, we detected a robust change in the zonal mean cross-equatorial wind over the past 60 years from ship observations and reanalyses, accompanied by physically consistent changes in atmospheric pressure and marine cloud cover. Single-forcing experiments indicate that the observed change in cross-equatorial wind is a fingerprint of aerosol forcing. This zonal mean mode follows the evolution of global aerosol forcing that is distinct from regional changes in the Atlantic sector. Atmospheric simulations successfully reproduce this interhemispheric mode, indicating the importance of sea surface temperature mediation in response to anthropogenic aerosol forcing. As societies awaken to reduce aerosol emissions, a phase reversal of this interhemispheric mode is expected in the 21st century.

  16. C/NOFS Observations of AC Electric Field Fields Associated with Equatorial Spread-F

    Science.gov (United States)

    Pfaff, R.; Liebrecht, C.

    2009-01-01

    The Vector Electric Field Investigation (VEFI) on the C/NOFS equatorial satellite provides a unique data set in which to acquire detailed knowledge of irregularities associated with the equatorial ionosphere and in particular with spread-F depletions. We present vector AC electric field observations, primarily gathered within the ELF band (1 Hz to 250 Hz) on C/NOFS that address a variety of key questions regarding how plasma irregularities, from meter to kilometer scales, are created and evolve. The data will be used to explore the anisotropy/isotropy of the waves, their wavelength and phase velocity, as well as their spectral distributions. When analyzed in conjunction with the driving DC electric fields and detailed plasma number density measurements, the combined data reveal important information concerning the instability mechanisms themselves. We also present high resolution, vector measurements of intense lower hybrid waves that have been detected on numerous occasions by the VEFI burst memory VLF electric field channels.

  17. 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...... maximum spatial scale sizes in the meridional plane ranging from 76-608 km. Associated with the EPB observations at about 400km, the typical altitude of CHAMP during the year 2000-2005, we also investigate the postsunset equatorial vertical plasma drift data from ROCSAT1 (Republic of China Satellite 1...... 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...

  18. 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.

  19. 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.

  20. Equatorial F-region ionization differences between March and September, 1979

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, D.N.; Klobuchar, J.A.; Dasgupta, A.

    1982-01-01

    Ionospheric total electron content and the F-region maximum electron density at a number of stations in the equatorial region, during the recent solar activity maximum period 1979 to 1980, show significant differences between the two equinoctial periods. Ionization during the month of March is higher than in September, irrespective of the station location both in Northern and Southern Hemispheres, and in different longitude sectors. The observed pattern is compared with those predicted by different models, in particular with one of the authors which includes processes such as ionization production, loss, electrodynamic drifts, winds and global composition changes involved in the equatorial ionosphere. It is found that a change in the neutral composition is primarily responsible for the observed F-region density differences between March and September.

  1. 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.

  2. Brazilian scientific production on herbal medicines used in dentistry

    OpenAIRE

    R.D. Castro; J.A. Oliveira; Vasconcelos,L.C.; Maciel,P.P.; Brasil,V.L.M.

    2014-01-01

    The objective of this study was to critically analyze the scientific production published in specialized Brazilian journals concerning the use of medicinal plants in dentistry. A literature review was carried out using an indirect documentation technique by means of a bibliographical study. Four examiners performed independent searches in Brazilian journals of medicinal plants indexed in the database SciELO (Brazilian Journal of Pharmacognosy; Brazilian Journal of Medicinal Plants; Brazilian ...

  3. 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.

    Solar insolation changes are amongst various factors that affect sea-surface temperature (SST) which in turn modulate global climate. Out of all the oceanic regions, equatorial region receives the maximum solar insolation and thus is the locale...

  4. 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.

    to the eastern equatorial Pacific. This chlorophyll-induced response of the undercurrent enhances upwelling around 110W, resulting in a lower sea surface temperature (SST) than without chlorophyll. Thus, thermal gradients due to absorption of solar radiation...

  5. {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.

  6. Climatic instability in west equatorial Africa during the Mid- and Late Holocene

    OpenAIRE

    F. Marret; Maley, Jean; Scourse, J

    2006-01-01

    Millennial-scale climatic variations have punctuated the Holocene characterised by abrupt changes from warm to cool or wetter to drier conditions. Amongst these climatic events, there is increased evidence for an abrupt multicentennial shift of climatic conditions around 3.8/3.7 kyr BP (4.1 cal. kyr BP) in mid- to low-latitude regions which had a profound impact on landscape and population migration. In the Mediterranean region, subtropical, tropical and equatorial Africa, a number of contine...

  7. 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.

  8. Surprising detection of an equatorial dust lane on the AGB star IRC+10216

    Science.gov (United States)

    Jeffers, S. V.; Min, M.; Waters, L. B. F. M.; Canovas, H.; Pols, O. R.; Rodenhuis, M.; de Juan Ovelar, M.; Keller, C. U.; Decin, L.

    2014-12-01

    Aims: Understanding the formation of planetary nebulae remains elusive because in the preceding asymptotic giant branch (AGB) phase these stars are heavily enshrouded in an optically thick dusty envelope. Methods: To further understand the morphology of the circumstellar environments of AGB stars we observe the closest carbon-rich AGB star IRC+10216 in scattered light. Results: When imaged in scattered light at optical wavelengths, IRC+10216 surprisingly shows a narrow equatorial density enhancement, in contrast to the large-scale spherical rings that have been imaged much further out. We use radiative transfer models to interpret this structure in terms of two models: firstly, an equatorial density enhancement, commonly observed in the more evolved post-AGB stars, and secondly, in terms of a dust rings model, where a local enhancement of mass-loss creates a spiral ring as the star rotates. Conclusions: We conclude that both models can be used to reproduce the dark lane in the scattered light images, which is caused by an equatorially density enhancement formed by dense dust rather than a bipolar outflow as previously thought. We are unable to place constraints on the formation of the equatorial density enhancement by a binary system. Final reduced images (FITS) are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/572/A3Based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  9. A Comparison of Trans-Equatorial Ionosphere Propagation Predictions from AMBCOM With Measured Data

    Science.gov (United States)

    1993-03-01

    Islands to Rarotonga in the Cook Islands was of special interest because the two islands arc...receiver on Rarotonga in the Cook Islands . 3 C. THE TRANS-EQUATORIAL IONOSPHERE 1. Geomagnetic and Solar Parameters a. The Geomagnetic Coordinate System The...propagation. One path studied was from Kauai in the Hawaiian Islands to Rarotonga in the Cook Islands . The two terminals of this 4800 km path are

  10. 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.

  11. Pharmacokinetics of Naja sumatrana (Equatorial Spitting Cobra) Venom and Its Major Toxins in Experimentally Envenomed Rabbits

    OpenAIRE

    Michelle Khai Khun Yap; Nget Hong Tan; Si Mui Sim; Shin Yee Fung; Choo Hock Tan

    2014-01-01

    Background The optimization of snakebite management and the use of antivenom depend greatly on the knowledge of the venom's composition as well as its pharmacokinetics. To date, however, pharmacokinetic reports on cobra venoms and their toxins are still relatively limited. In the present study, we investigated the pharmacokinetics of Naja sumatrana (Equatorial spitting cobra) venom and its major toxins (phospholipase A2, neurotoxin and cardiotoxin), following intravenous and intramuscular adm...

  12. Public health professionals? perceptions of mental health services in Equatorial Guinea, Central-West Africa

    OpenAIRE

    Reuter, Peter Robert; McGinnis, Shannon Marcail; Reuter, Kim Eleanor

    2016-01-01

    Introduction Mental health disorders constitute 13% of global disease burden, the impacts of which are disproportionality felt in sub-Saharan Africa. Equatorial Guinea, located in Central-West Africa, has the highest per-capita investment in healthcare on the African continent, but only two studies have discussed mental health issues in the country and none of have examined the perspective of professionals working in the field. The purpose of this study was to gain a preliminary understanding...

  13. Evolution of nutricline dynamics in the equatorial Pacific during the late Pliocene

    Science.gov (United States)

    Bolton, C. T.; Gibbs, S.; Wilson, P.

    2009-12-01

    The tropics have played a central role in modulating Earth’s climate throughout the Plio-Pleistocene, with tropical productivity fluctuations a key mechanism in the operation of the global carbon cycle and linkage of high and low latitude climates. Published records of tropical sea surface temperatures (SSTs) during the Plio-Pleistocene appear to vary primarily in tune with high latitude climate both on orbital and secular timescales. Yet contemporaneous changes in equatorial primary productivity are less well constrained, particularly at sites where climate is not dominated by upwelling or monsoon systems. Furthermore, the role of thermocline dynamics (tilt and mean depth changes) in forcing SST and productivity on orbital timescales remains uncertain. Here we report new, high-resolution calcareous nannofossil records from two Ocean Drilling Program (ODP) sites in the western and eastern equatorial Pacific (WEP, EEP) during marine isotope stages (MIS) 95 to 101; about 2400 to 2600 thousand years ago (ka). Our records of paleoproductivity and nutricline depth reveal synchronous, large-amplitude glacial-interglacial (G-IG) productivity variations at both ends of the equatorial Pacific indicating (i) remote (high latitude) forcing of primary productivity and (ii) no primary role for east-west tilting of the equatorial Pacific thermocline, with important implications regarding the operation of El Niño-like dynamics in the Pliocene Pacific. Instead, the paleoproductivity variations and phase relationships that we document suggest the interaction of two mechanisms operating on obliquity timescales: a ‘bottom-up’ forcing transmitted via the upwelling of high latitude source waters in conjunction with the ‘top-down’ forcing of atmospheric greenhouse gases.

  14. 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.

  15. Iron-rich Basal sediments from the eastern equatorial pacific: leg 16, deep sea drilling project.

    Science.gov (United States)

    Cronan, D S; Van Andel, T H; Heath, G R; Dinkelman, M G; Bennett, R H; Bukry, D; Charleston, S; Kaneps, A; Rodolfo, K S; Yeats, R S

    1972-01-07

    Iron-rich sediments chemically similar to those forming at present on the crest of the East Pacific Rise have been found just above basement at widely separated drill sites in the eastern equatorial Pacific, including three sites of Leg 16 of the Deep Sea Drilling Project. These sediments were probably formed when the basement was at the crest of this rise and have moved to their present location as a result of sea-floor spreading.

  16. Magnetic-Field-Aligned Characteristics of Plasma Bubbles in the Nighttime Equatorial Ionosphere.

    Science.gov (United States)

    1979-07-01

    be the Rayleigh-Taylor instability [Dungey, 1956; Balsley et al., 1972; Haerendel, 1974; Hudson and Kennel , 1975]. This theory [Scannapieco and Ossakow...9, p. 519, 1974. Hudson, M. K. and C. F. Kennel , "Linear Theory of Equatorial Spread F," J. Geophys. Res., Vol. 80, p. 4581, 1975. Torbert, "Evidence...DEPARTMENT OF THE AIR FORCE (Continued) DEPARTMENT OF DEFENSE CONTRACTORS (Continued) Ballistic Missile Office Charles Stark Draper Lab., Inc. Air Force

  17. 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.

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

    Science.gov (United States)

    Gnanaseelan, C.; Deshpande, Aditi

    2017-05-01

    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

  19. Equatorial Oceanic Waves and the Evolution of 2007 Positive Indian Ocean Dipole

    Directory of Open Access Journals (Sweden)

    Iskhaq Iskandar

    2014-01-01

    Full Text Available The role of equatorial oceanic waves on the evolution of the 2007 positive Indian Ocean Dipole (pIOD event was evaluated using available observations and output from a quasi-analytical linear wave model. It was found that the 2007 pIOD event was a weak and short-lived event: developed in the mid-summer (July, matured in the early-fall (September, and terminated in the mid-fall (October. The evolution of the 2007 pIOD event was linked to the equatorial wave dynamics. The event development was associated with the generation of upwelling equatorial Kelvin waves (westward current anomalies generated by easterly wind anomalies. The event termination was associated with the occurrence of eastward zonal current anomalies resulting from a complex interplay between the wind-forced down welling Kelvin waves and the eastern-boundary-reflected Rossby waves. Results from a quasi-analytical linear wave model show that during the event development and maturation, the wind-forced Kelvin waves played a dominant role in generating zonal current anomalies along the equatorial Indian Ocean, while the eastern-boundary-reflected Rossby waves tended to weaken the wind-forced Kelvin wave signals. During the event termination our model shows that the initiation of anomalous eastward current resulted from the reflected Rossby waves at the eastern boundary. The wind-forced Kelvin waves associated with the seasonal reversal of the monsoon further strengthened the eastward zonal currents generated by the boundary-generated Rossby waves in late-October/early-November. This highlights the importance of the eastern-boundary-reflected Rossby waves on the IOD event termination.

  20. Gyroscope precession along unbound equatorial plane orbits around a Kerr black hole

    CERN Document Server

    Bini, Donato; Jantzen, Robert T

    2016-01-01

    The precession of a test gyroscope along unbound equatorial plane geodesic orbits around a Kerr black hole is analyzed with respect to a static reference frame whose axes point towards the "fixed stars." The accumulated precession angle after a complete scattering process is evaluated and compared with the corresponding change in the orbital angle. Limiting results for the non-rotating Schwarzschild black hole case are also discussed.

  1. Gyroscope precession along bound equatorial plane orbits around a Kerr black hole

    CERN Document Server

    Bini, Donato; Jantzen, Robert T

    2016-01-01

    The precession of a test gyroscope along stable bound equatorial plane orbits around a Kerr black hole is analyzed and the precession angular velocity of the gyro's parallel transported spin vector and the increment in precession angle after one orbital period is evaluated. The parallel transported Marck frame which enters this discussion is shown to have an elegant geometrical explanation in terms of the electric and magnetic parts of the Killing-Yano 2-form and a Wigner rotation effect.

  2. Numerical analysis of global ionospheric current system including the effect of equatorial enhancement

    Directory of Open Access Journals (Sweden)

    S. Tsunomura

    1999-05-01

    Full Text Available A modeling method is proposed to derive a two-dimensional ionospheric layer conductivity, which is appropriate to obtain a realistic solution of the polar-originating ionospheric current system including equatorial enhancement. The model can be obtained by modifying the conventional, thin shell conductivity model. It is shown that the modification for one of the non-diagonal terms (Σθφ in the conductivity tensor near the equatorial region is very important; the term influences the profile of the ionospheric electric field around the equator drastically. The proposed model can reproduce well the results representing the observed electric and magnetic field signatures of geomagnetic sudden commencement. The new model is applied to two factors concerning polar-originating ionospheric current systems. First, the latitudinal profile of the DP2 amplitude in the daytime is examined, changing the canceling rate for the dawn-to-dusk electric field by the region 2 field-aligned current. It is shown that the equatorial enhancement would not appear when the ratio of the total amount of the region 2 field-aligned current to that of region 1 exceeds 0.5. Second, the north-south asymmetry of the magnetic fields in the summer solstice condition of the ionospheric conductivity is examined by calculating the global ionospheric current system covering both hemispheres simultaneously. It is shown that the positive relationship between the magnitudes of high latitude magnetic fields and the conductivity is clearly seen if a voltage generator is given as the source, while the relationship is vague or even reversed for a current generator. The new model, based on the International Reference Ionosphere (IRI model, can be applied to further investigations in the quantitative analysis of the magnetosphere-ionosphere coupling problems.Key words. Ionosphere (electric fields and currents; equatorial ionosphere; ionosphere-magnetosphere interactions

  3. Numerical analysis of global ionospheric current system including the effect of equatorial enhancement

    Directory of Open Access Journals (Sweden)

    S. Tsunomura

    Full Text Available A modeling method is proposed to derive a two-dimensional ionospheric layer conductivity, which is appropriate to obtain a realistic solution of the polar-originating ionospheric current system including equatorial enhancement. The model can be obtained by modifying the conventional, thin shell conductivity model. It is shown that the modification for one of the non-diagonal terms (Σθφ in the conductivity tensor near the equatorial region is very important; the term influences the profile of the ionospheric electric field around the equator drastically. The proposed model can reproduce well the results representing the observed electric and magnetic field signatures of geomagnetic sudden commencement. The new model is applied to two factors concerning polar-originating ionospheric current systems. First, the latitudinal profile of the DP2 amplitude in the daytime is examined, changing the canceling rate for the dawn-to-dusk electric field by the region 2 field-aligned current. It is shown that the equatorial enhancement would not appear when the ratio of the total amount of the region 2 field-aligned current to that of region 1 exceeds 0.5. Second, the north-south asymmetry of the magnetic fields in the summer solstice condition of the ionospheric conductivity is examined by calculating the global ionospheric current system covering both hemispheres simultaneously. It is shown that the positive relationship between the magnitudes of high latitude magnetic fields and the conductivity is clearly seen if a voltage generator is given as the source, while the relationship is vague or even reversed for a current generator. The new model, based on the International Reference Ionosphere (IRI model, can be applied to further investigations in the quantitative analysis of the magnetosphere-ionosphere coupling problems.

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

  4. Effects of strong IMF Bz southward events on the equatorial and mid-latitude ionosphere

    Directory of Open Access Journals (Sweden)

    E. Astafyeva

    2009-03-01

    Full Text Available Dayside ionospheric response to five intense geomagnetic storms (Dst<−120 nT that occurred in 2001–2005 was investigated by use of simultaneous TEC measurements by the CHAMP, SAC-C, TOPEX/Jason-1 satellites. Since the satellites passed over different longitudinal sectors and measured TEC in different range of altitudes, it was possible to obtain information about altitudinal and longitudinal ionosphere redistribution during these storms. Severe enhancements (up to ~350% of the equatorial and mid-latitude TEC above ~430 km with concurrent traveling of the equatorial anomaly crests for a distance of 10–15° of latitude were observed during two of the five events analyzed here (6 November 2001 and 8 November 2004. This phenomenon, known as the dayside ionosphere uplift, or the "daytime super-fountain effect", occurred after sudden drop in IMF Bz and consequent penetration of the electric fields to the low-latitude ionosphere. However, the same order Bz negative events caused comparatively weak changes in the dayside TEC (up to ~80 TECU during the other three events of 18 June 2003, 11 February 2004 and 24 August 2005. At the main phase of these storms there were mostly observed formation of the "typical" dual peak structure of the equatorial anomaly rather than the reinforcement of the fountain effect and the anomaly itself. Possible reasons and factors responsible for the development of the extreme ionosphere effects are discussed in the paper.

  5. Indonesia coverage simulation of SAR satellite at near-equatorial orbit

    Science.gov (United States)

    Septanto, Harry; Utama, Satriya; Heru Triharjanto, Robertus; Suhermanto

    2017-01-01

    Properties of SAR (Synthetic Aperture Radar) that able to penetrate the cloud and does not depend on the sunlight are a number of advantages when utilized for monitoring tropical region like the IMC (Indonesian Maritime Continent). Moreover, since having areas along equatorial belt, the IMC is at a shortcoming from perspective of highly inclined LEO (Low Earth Orbit) satellite. It would result shorter and infrequent pass times when compared with a near-equatorial LEO satellite whose low inclination. This paper reports on the investigation of a near-equatorial LEO SAR satellite coverage property through simulations. The simulations is run in nine scenarios of orbit parameter that consist of combinations of attitude {500 km, 600 km, 700 km} and inclination {80, 90, 100}. The target area is defined as 50 km x 50 km around Jakarta. Meanwhile, the SAR sensor simulation is run with swath width of 40 km, incidence angle around 250-290 and Stripmap mode. Minimum, Maximum and Mean Access Revisit of the target for each scenarios are resulted.

  6. 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.

  7. Public health professionals' perceptions of mental health services in Equatorial Guinea, Central-West Africa.

    Science.gov (United States)

    Reuter, Peter Robert; McGinnis, Shannon Marcail; Reuter, Kim Eleanor

    2016-01-01

    Mental health disorders constitute 13% of global disease burden, the impacts of which are disproportionality felt in sub-Saharan Africa. Equatorial Guinea, located in Central-West Africa, has the highest per-capita investment in healthcare on the African continent, but only two studies have discussed mental health issues in the country and none of have examined the perspective of professionals working in the field. The purpose of this study was to gain a preliminary understanding of Equatoguinean health care professionals' perspectives on the mental health care system. Nine adult participants (directors or program managers) were interviewed in July 2013 in Malabo, Equatorial Guinea from government agencies, aid organizations, hospitals, and pharmacies. Interviews were designed to collect broad information about the mental healthcare system in Equatorial Guinea including the professionals' perspectives and access to resources. This research was reviewed and approved by an ethical oversight committee. All individuals interviewed indicated that the mental health system does not currently meet the needs of the community. Professionals cited infrastructural capacity, stigmatization, and a lack of other resources (training programs, knowledgeable staff, medications, data) as key factors that limit the effectiveness of mental healthcare. This study provides a preliminary understanding of the existing mental health care needs in the country, highlighting opportunities for enhanced healthcare services.

  8. 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

  9. 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

  10. Patterns and causes of longitude-dependent variation in total electron content at the equatorial anomaly

    Science.gov (United States)

    Scheinberg, A. L.; Coster, A. J.; Erickson, P. J.; Zhang, S.

    2011-12-01

    The terrestrial ionosphere has significant spatial variations in its electron density. One of these is the equatorial anomaly, which is thought to be generated by electromagnetic drift forces which cause electrons to move upward and then descend along field lines to higher latitudes. Given this mechanism, we test the conjecture that longitudinal variations in the equatorial magnetic field have a direct effect on the anomaly's magnitude and location. To assess the magnitude and location of the anomaly, we use total electron content (TEC) measurements from the world wide GPS geodetic receiver network, which observes differential delays between dual-frequency coherent transmissions. The global nature of the GPS measurement network allows spatial and temporal TEC distributions to be monitored. In general, the impact of local variations in the geomagnetic field on TEC is poorly understood globally. We analyze equatorial TEC data across recent years of geomagnetically quiet observations to determine any linear correlations with the magnetic field intensity. Our results suggest that magnetic field intensity is not a dominant influence on longitudinal TEC variation along the anomaly. We then compare our results with independent lines of evidence in search of an explanation to account for the observed longitudinal variation.

  11. Equatorial distributions of energetic ion moments in Saturn's magnetosphere using Cassini/MIMI measurements

    Science.gov (United States)

    Dialynas, K.; Roussos, E.; Regoli, L.; Paranicas, C.; Krimigis, S. M.; Kane, M.; Mitchell, D. G.; Hamilton, D. C.

    2016-12-01

    We use kappa distribution fits to combined Charge Energy Mass Spectrometer (CHEMS, 3 to 236 keV/e), Low Energy Magnetosphere Measurements System (LEMMS, 0.024 220 keV for H+) proton and singly ionized energetic ion spectra to calculate the >20 keV energetic ion moments inside Saturn's magnetosphere. Using a realistic magnetic field model (Khurana et al. 2007) and data from the entire Cassini mission to date (2004-2016), we map the ion measurements to the equatorial plane and via the modeled kappa distribution spectra we produce the equatorial distributions of all ion integral moments, focusing on partial density, integral intensity, partial pressure, integral energy intensity; as well as the characteristic energy (EC=IE/In), Temperature and κ-index of these ions as a function of Local Time (00:00 to 24:00 hrs) and L-Shell (5-20). A modified version of the semi-empirical Roelof and Skinner [2000] model is then utilized to retrieve the equatorial H+ and O+ pressure, density and temperature in Saturn's magnetosphere in both local time and L-shell. We find that a) although the H+ and O+ partial pressures and densities are nearly comparable, the >20 keV protons have higher number and energy intensities at all radial distances (L>5) and local times; b) the 12

  12. Wintertime Phytoplankton Blooms in the Western Equatorial Indian Ocean Associated With the Madden-Julian Oscillation

    Science.gov (United States)

    Liao, Xiaomei; Du, Yan; Zhan, Haigang; Wang, Tianyu; Feng, Ming

    2017-12-01

    This study investigated boreal wintertime phytoplankton blooms in the western equatorial Indian Ocean (WEIO) and the underlying physical mechanisms. The Sea viewing Wide field of View sensor (SeaWiFS) chlorophyll-a (Chla) concentrations show that phytoplankton blooms occur in the WEIO during December-March. The development of these blooms is not only a seasonal process but also consists of 2-3 intraseasonal events induced by the Madden-Julian Oscillation (MJO). During a typical intraseasonal event, enhanced cross-equatorial wind induces strong upwelling and ocean mixing, thus increasing the supply of nutrients to the surface in equatorial regions. Argo profiles clearly show various responses to the intraseasonal wind bursts, including shoaling of the thermocline and deepening of the mixed layer. Further analysis reveals that the former is the dominant mechanism for the blooms along the equator, while the latter controls the high Chla concentrations off the coast of Somalia. Surface ocean circulations not only account for the blooms south of the equator but also modulate the thermocline depth in the WEIO. The shallower thermocline during the early period of the northeast monsoon season provides favorable conditions for a stronger Chla response to intraseasonal forcing.

  13. 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.

  14. 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.

  15. Observed Intraseasonal Oceanic Variations in the Eastern Equatorial Indian Ocean and in the Outflow Straits of the Indonesian Throughflow

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    Iskhaq Iskandar

    2010-09-01

    Full Text Available The observed currents in the eastern equatorial Indian Ocean and in the outflow straits of the Indonesian Throughflow (ITF are shown to have significant intraseasonal variations and coherency during January 2004 – November 2006. The wavelet analysis between the eastern equatorial Indian Ocean and the ITF straits demonstrates significant intraseasonal coherency for the observed current at 50m depth. At 150m depth, the intraseasonal coherency only occurs between the observed currents in the eastern equatorial Indian Ocean and in the Lombok and Ombai Straits. On the other hand, at 350m depth the intraseasonal coherency is only found between the eastern equatorial Indian Ocean and the Ombai Strait. This intraseasonal coherency is associated with the wind-forced equatorial Kelvin waves which propagate eastward along the equatorial and coastal wave guides. Near-surface intraseasonal variations are associated with the first baroclinic mode with typical phase speed of 2.91 ± 0.46 m s-1, while the deeper layer intraseasonal variations are associated with the second baroclinic mode with typical phase speed of 1.59 ± 0.18 m s-1. Moreover, the lag correlations between the zonal winds and the observed currents at the ITF straits further demonstrate the source of intraseasonal variations in the ITF.

  16. Epipelagic copepod distributions in the eastern equatorial Pacific during the weak La Niña event of 2001

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    Pritha Tutasi

    2011-07-01

    Full Text Available We determined the distribution and abundance of pelagic copepods in the eastern equatorial Pacific between the coast of Ecuador and the Galapagos Islands under oceanographic conditions associated with the weak La Niña event of 2001. In September-October 2001, negative anomalies of sea surface temperature from this event still remained in the eastern equatorial Pacific, mainly between Ecuador and the Galapagos Islands. The event allowed the incursion of the Humboldt Current farther north and of the Equatorial Undercurrent into the study area, favouring a strong Equatorial Front and upwelling processes. There was evidence of mesoscale eddies in the study area and of the presence of the South Equatorial Current going westward at about 1°N. We identified 107 copepod species and analyzed the distribution of the 10 most abundant ones: Oncaea venusta, Subeucalanus pileatus, S. crassus, S. subtenuis, Paraeucalanus attenuatus, Pleuromamma borealis, Scolecithrix danae, Clausocalanus farrani, Temora discaudata and Calanus chilensis. Copepod distribution and abundance exhibited marked latitudinal differences related to the oceanographic conditions; abundance was highest to the southeast of the Galapagos Islands. Oncaea venusta, Pleuromamma borealis, Calanus chilensis, and Subeucalanus subtenuis were the species that best defined the Equatorial Front and the upwelling process.

  17. Neymar, defender of brazilian tradition

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    Francisca Islandia Cardoso da Silva

    2016-09-01

    Full Text Available The purpose of this article is to analyze how university students of Teresina-PI appropriate of the message of a report of the television show Esporte Espetacular. There was use of the technique of focus groups and analytical-descriptive method for collecting and analyzing data. The sample consisted of 24 university students, aged between 18 and 24 years. The report features Neymar as responsible to follow the "tradition" of Brazilians and to be crowned as the best player in the world. The subjects of research said that the speech conveyed by the report can reproduce and create a reality sometimes dreamlike, because objective to confer to Neymar great importance with regard to national identity.

  18. Best Practices in Brazilian Companies

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    Catia dos Reis Machado

    2013-04-01

    Full Text Available Competitive intelligence (CI is a systematic and ethical collection, analysis, dissemination and management of information about the external environment that may affect the plans, decisions and operations of the organization. Knowledge management (KM can be seen as a tool to promote organizational knowledge through the use of activities designed to identify, create, store, share and use knowledge. Companies face a challenge in the era of knowledge, it is the extraction and management of knowledge produced by people in the organization. CI and KM combined generates organizational intelligence. The exploratory study, based on literature and multicase study, we sought to identify best practices in processes of CI and KM in Brazilian companies. We identified practices related to the CI design process, the stages of the CI, the use of networks, and knowledge management. We also identified, points of attention on the internal/external organizational environment.

  19. 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

  20. Short-Term Variations in the Equatorial Rotation Rate of Sunspot Groups

    Science.gov (United States)

    Javaraiah, J.; Bertello, L.

    2016-12-01

    We have detected several periodicities in the solar equatorial rotation rate of sunspot groups in the catalog Greenwich Photoheliographic Results (GPR) during the period 1931 - 1976, the Solar Optical Observing Network (SOON) during the period 1977 - 2014, and the Debrecen Photoheliographic Data (DPD) during the period 1974 - 2014. We have compared the results from the fast Fourier transform (FFT), the maximum entropy method (MEM), and the Morlet wavelet power-spectra of the equatorial rotation rates determined from SOON and DPD sunspot-group data during the period 1986 - 2007 with those of the Mount Wilson Doppler-velocity data during the same period determined by Javaraiah et al. ( Solar Phys. 257, 61, 2009). We have also compared the power-spectra computed from the DPD and the combined GPR and SOON sunspot-group data during the period 1974 - 2014 to those from the GPR sunspot-group data during the period 1931 - 1973. Our results suggest a ˜ 250-day period in the equatorial rotation rate determined from both the Mt. Wilson Doppler-velocity data and the sunspot-group data during 1986 - 2007. However, a wavelet analysis reveals that this periodicity appears mostly around 1991 in the velocity data, while it is present in most of the solar cycles covered by the sunspot-group data, mainly near the minimum epochs of the solar cycles. We also found the signature of a period of ˜ 1.4 years in the velocity data during 1990 - 1995, and in the equatorial rotation rate of sunspot groups mostly around the year 1956. The equatorial rotation rate of sunspot groups reveals a strong ˜ 1.6-year periodicity around 1933 and 1955, a weaker one around 1976, and a strong ˜ 1.8-year periodicity around 1943. Our analysis also suggests periodicities of ˜ 5 years, ˜ 7 years, and ˜ 17 years, as well as some other short-term periodicities. However, short-term periodicities are mostly present at the time of solar minima. Hence, short-term periodicities cannot be confirmed because of

  1. Space weather impact on the equatorial and low latitude F-region ionosphere over India

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    R. S. Dabas

    2006-03-01

    Full Text Available For a detailed study of the space weather impact on the equatorial and low latitude F-region, the ionospheric response features are analysed during the periods of three recent and most severe magnetic storm events of the present solar cycle which occurred in October and November 2003, and November 2004. The F-layer base height (h'F, peak height (hmF2 and critical frequency (foF2 data, from Trivandrum, an equatorial station and Delhi, a low latitude location, are examined during the three magnetic storm periods. The results of the analysis clearly shows that the height of the F-region (both h'F and hmF2, at the equator and low latitude, simultaneously increases by 200 to 300 km, in association with maximum negative excursion of Dst values around the midnight hours with a large depletion of ionization over the equator, which is followed by an ionization enhancement at low latitude during the recovery phase of the storm. At Delhi, fast variations up to 200 m/s are also observed in the F-layer vertical upward/downward velocity, calculated using Doppler shifts, associated with the maximum negative excursion of Dst. This shows that during magnetic disturbances, the equatorial ionization anomaly (EIA expands to a much wider latitude than the normal fountain driven by the E/F-layer dynamo electric fields. It is also observed that during the main phase of the storm, at low latitude there is generally an enhancement of F-region ionization with an increase in h'F/hmF2 but in the equatorial region, the ionization collapses with a decrease in h'F/hmF2, especially after sunset hours. In addition, at the equator the normal pre-sunset hours' enhancement in h'F is considerably suppressed during storm periods. This might be due to changes in magnitude and direction of the zonal electric field affecting the upward

  2. Space weather impact on the equatorial and low latitude F-region ionosphere over India

    Directory of Open Access Journals (Sweden)

    R. S. Dabas

    2006-03-01

    Full Text Available For a detailed study of the space weather impact on the equatorial and low latitude F-region, the ionospheric response features are analysed during the periods of three recent and most severe magnetic storm events of the present solar cycle which occurred in October and November 2003, and November 2004. The F-layer base height (h'F, peak height (hmF2 and critical frequency (foF2 data, from Trivandrum, an equatorial station and Delhi, a low latitude location, are examined during the three magnetic storm periods. The results of the analysis clearly shows that the height of the F-region (both h'F and hmF2, at the equator and low latitude, simultaneously increases by 200 to 300 km, in association with maximum negative excursion of Dst values around the midnight hours with a large depletion of ionization over the equator, which is followed by an ionization enhancement at low latitude during the recovery phase of the storm. At Delhi, fast variations up to 200 m/s are also observed in the F-layer vertical upward/downward velocity, calculated using Doppler shifts, associated with the maximum negative excursion of Dst. This shows that during magnetic disturbances, the equatorial ionization anomaly (EIA expands to a much wider latitude than the normal fountain driven by the E/F-layer dynamo electric fields. It is also observed that during the main phase of the storm, at low latitude there is generally an enhancement of F-region ionization with an increase in h'F/hmF2 but in the equatorial region, the ionization collapses with a decrease in h'F/hmF2, especially after sunset hours. In addition, at the equator the normal pre-sunset hours' enhancement in h'F is considerably suppressed during storm periods. This might be due to changes in magnitude and direction of the zonal electric field affecting the upward E×B drift and hence the plasma distribution in the form of a decrease in electron density in the equatorial region and an increase in the low latitude

  3. Cerebrotendinous xanthomatosis: report of two Brazilian brothers.

    NARCIS (Netherlands)

    Lange, M.C.; Zetola, V.F.; Teive, H.; Scola, R.H.; Trentin, A.P.; Zavala, J.A.; Pereira, E.R.; Raskin, S.; Werneck, L.C.; Sistermans, E.A.

    2004-01-01

    Cerebrotendinous xanthomatosis is a treatable rare autossomal recessive disease characterized by lipid storage secondary to a sterol 27-hydroxylase deficiency in the formation of cholic and chenodeoxycholic acids. We describe two Brazilian brothers with cognitive impairement and chronic diarrhea.

  4. Possible relationship between the equatorial electrojet (EEJ) and daytime vertical E × B drift velocities in F region from ROCSAT observations

    Science.gov (United States)

    Kumar, Sandeep; Veenadhari, B.; Tulasi Ram, S.; Su, S.-Y.; Kikuchi, T.

    2016-10-01

    The vertical E × B drift is very important parameter as its day to day variability has great influence on the variability in the low latitude F-region ion and electron density distributions. The measurements of vertical ion velocity from the first Republic of China Satellite (ROCSAT-1) provide a unique data base for the development of possible relationship between vertical E × B drifts and ground based magnetometer observation. An attempt has been made to derive quantitative relationship between F-region vertical E × B drifts measured by ROCSAT-1 (600 km) and ground measured equatorial electrojet for the solar maximum period 2001-2003 for Indian and Japanese sectors. The results consistently indicate existence of linear relationship between the measured vertical E × B drifts at topside F-region and EEJ for both the sectors, with a moderate to high correlation coefficients. The linear relationship between ROCSAT-1 measured E × B drifts and EEJ for Indian and Japanese sectors has been compared with a similar relationship with Jicamarca Unattended Long-term Ionosphere Atmosphere Radar (JULIA) measured E × B drifts (150 km echos) and EEJ strength from Peruvian sector during 2003. It has been found that ROCSAT-1 measured E × B drifts shows linear relationship with EEJ, however, exhibits a larger scatter unlike JULIA radar observed E × B drifts. This may be attributed to the large height difference as ROCSAT-1 measures E × B drifts at 600 km altitude and the EEJ is E-region (110 km) phenomenon.

  5. The Response of Equatorial Ionization Anomaly in 120°E to the Geomagnetic Storm of 18 August 2003 at Different Altitudes From Multiple Satellite Observations

    Science.gov (United States)

    Luo, Weihua; Zhu, Zhengping; Xiong, Chao; Chang, Shanshan

    2017-12-01

    In this paper, the variations of equatorial ionization anomaly (EIA) in 120°E region during the 17-20 August 2003 storm are investigated from measurements of satellites at different altitudes from Challenging Minisatellite Payload (CHAMP), Gravity Recovery and Climate Experiment (GRACE), scientific satellite of the Republic of China (ROCSAT-1), and Defense Meteorological Satellite Program missions. The results showed that (1) at CHAMP and GRACE altitudes, the EIA was inhibited before the storm sudden commencement (SSC) and also during the storm recovery phase, but it was enhanced significantly during the storm main phase of the storm. (2) The variations of EIA strength and interhemispheric density asymmetry of the two crests were similar at CHAMP and GRACE altitudes, while the location asymmetry of the two crests was different at CHAMP and GRACE altitudes. (3) The irregularities and long-duration scintillation were recorded before the SSC of the storm, when the EIA was inhibited. The irregularities at different altitudes and short-duration scintillation were observed during the main phase of the storm, when the EIA was enhanced significantly. (4) The EIA enhancement can be attributed to the enhanced electric field due to prompt penetration interplanetary electric fields and the storm time neutral wind, while the suppression of EIA on 17 August can be attributed to the absence of the equatorward neutral wind, which varied with the altitudes. The EIA inhibition during the recovery phase may be caused mainly by the neutral wind. Our results suggest that the neutral wind is the crucial factor causing the variations in EIA and the occurrence of scintillation.

  6. Meteor radar measurements of MLT winds near the equatorial electro jet region over Thumba (8.5° N, 77° E: comparison with TIDI observations

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    S. R. John

    2011-07-01

    Full Text Available The All-Sky interferometric meteor (SKYiMET radar (MR derived winds in the vicinity of the equatorial electrojet (EEJ are discussed. As Thumba (8.5° N, 77° E; dip lat. 0.5° N is under the EEJ belt, there has been some debate on the reliability of the meteor radar derived winds near the EEJ height region. In this regard, the composite diurnal variations of zonal wind profiles in the mesosphere-lower thermosphere (MLT region derived from TIMED Doppler Interferometer (TIDI and ground based meteor radar at Thumba are compared. In this study, emphasis is given to verify the meteor radar observations at 98 km height region, especially during the EEJ peaking time (11:00 to 14:00 LT. The composite diurnal cycles of zonal winds over Thumba are constructed during four seasons of the year 2006 using TIDI and meteor radar observations, which showed good agreement especially during the peak EEJ hours, thus assuring the reliability of meteor radar measurements of neutral winds close to the EEJ height region. It is evident from the present study that on seasonal scales, the radar measurements are not biased by the EEJ. The day-time variations of HF radar measured E-region drifts at the EEJ region are also compared with MR measurements to show there are large differences between ionospheric drifts and MR measurements. The significance of the present study lies in validating the meteor radar technique over Thumba located at magnetic equator by comparing with other than the radio technique for the first time.

  7. Futebol mulato: racial constructs in Brazilian football

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    Tiago Fernandes Maranhao

    2011-05-01

    Full Text Available The aim of this paper is to review Gilberto Freyre’s ideas about futebol mulato and the way these ideas have spread the notion of the Brazilian mulatto as a symbol of a ‘racial democracy’, unique in Brazil, around the world. The notion first appeared in 1938 in an article by Freyre for the Diários Associados, an important Brazilian newspaper. Football (soccer was employed by Freyre as the special arena where the multiracial Brazilian nation could shine and show the world a different way of being, opposed to the white and ‘rational’ way of European football. In Freyre’s work, the so-called ‘football-art’ was compared to poetry, while the European style was equated with prose. This essay argues that Freyre’s ideas were useful in constructing the Brazilian identity, a nation of harmony in all its aspects, including the area of race, and how the idea of the mulatto has been used to minimise social disparities within Brazilian society. Freyre’s ideas remain contemporary; many Brazilian intellectuals still refer to these concepts. As well, the press in this huge country, and especially in World Cup years, uses the concepts of mulatto and football-art to characterize Brazil and differentiate it from other countries.

  8. Phylodynamics of the Brazilian feline immunodeficiency virus.

    Science.gov (United States)

    Cano-Ortiz, Lucía; Junqueira, Dennis Maletich; Comerlato, Juliana; Costa, Cristina Santos; Zani, André; Duda, Naila Blatt; Tochetto, Caroline; Dos Santos, Raissa Nunes; da Costa, Fernanda Vieira Amorim; Roehe, Paulo Michel; Franco, Ana Cláudia

    2017-11-01

    Feline immunodeficiency virus (FIV), like other retroviruses, displays large genomic divergence when different isolates are compared. In this study, 31 FIV positive samples of domestic cats from Porto Alegre, RS, Brazil were used aiming at a detailed genomic characterization and a better understanding of the molecular epidemiology of the virus in Brazil. The proviral env genes were partially amplified, sequenced and compared with another 237 sequences from different continents. We identified several Brazilian highly supported clades (A, B1, B2, C and D) that suggest independent events of introduction of FIV in Brazil. Forty six reference-sequences from the GenBank were used with our 31 sequences to infer the virus subtypes. Our sequences belong to the subtype B and three of them result from a recombination with the previously described subtype F. The other 28 Brazilian samples belonging to subtype B and another 46 Brazilian sequences from the GenBank were used to estimate the time to the most recent common ancestor of each Brazilian clade, using a Bayesian approach and a relaxed molecular clock model. The analyses of Brazilian sequences suggest several different entries of the virus in the Brazilian cat population between 1981 and 1991. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. 3rd BRAZILIAN CONSENSUS ON Helicobacter pylori

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    Luiz Gonzaga Coelho

    2013-04-01

    Full Text Available Significant progress has been obtained since the Second Brazilian Consensus Conference on Helicobacter pylori Infection held in 2004, in São Paulo, SP, Brazil, and justify a third meeting to establish updated guidelines on the current management of H. pylori infection. The Third Brazilian Consensus Conference on H pylori Infection was organized by the Brazilian Nucleus for the Study of Helicobacter, a Department of the Brazilian Federation of Gastroenterology and took place on April 12-15, 2011, in Bento Gonçalves, RS, Brazil. Thirty-one delegates coming from the five Brazilian regions and one international guest, including gastroenterologists, pathologists, epidemiologists, and pediatricians undertook the meeting. The participants were allocated in one of the five main topics of the meeting: H pylori, functional dyspepsia and diagnosis; H pylori and gastric cancer; H pylori and other associated disorders; H pylori treatment and retreatment; and, epidemiology of H pylori infection in Brazil. The results of each subgroup were submitted to a final consensus voting to all participants. Relevant data were presented, and the quality of evidence, strength of recommendation, and level of consensus were graded. Seventy per cent and more votes were considered as acceptance for the final statement. This article presents the main recommendations and conclusions to guide Brazilian doctors involved in the management of H pylori infection.

  10. THE COURSE OF TRANSLATION AND INTERPRETATION PUBLICATIONS OF BRAZILIAN SIGN LANGUAGE IN SOME BRAZILIAN TRANSLATION JOURNALS

    Directory of Open Access Journals (Sweden)

    Silvana Aguiar dos Santos

    2016-07-01

    Full Text Available This essay describes and analyses the course of publications about Translation and Interpretation of Brazilian sign language in some Brazilian Translation journals. Results show a sum of 36 works published, distributed over Translation journals of different regions of Brazil. The established subjects and the ones that emerged from 1990 to 2014 were also examined in these publications.

  11. The Direct Response in the Equatorial Pacific to the 11 year Solar Cycle Forcing and its mechanisms

    Science.gov (United States)

    Huo, Wenjuan; Xiao, Ziniu

    2017-04-01

    The equatorial Pacific response to 11-year solar cycle is assessed in observation and ensemble historical-Nat simulations from the Coupled Model Intercomparison Project, Phase 5 (CMIP5). We find the central equatorial Pacific is sensitive to the solar forcing. A significant positive correlation is found between observed sea surface temperature (SST) anomaly and sunspot number (SSN) index with a lag of 2 years in the central Pacific. The 11-year solar signal particularly exits in the SST and zonal wind anomalies from spectrum analysis. Based on composite analysis, a warming response appears in the central Pacific with lagging the solar cycle by 1-2 years in observation, and 2-3 years in simulation results. Associated with the ocean temperature anomaly, an anomalous twin Walker circulation cells arise in the equatorial Pacific with their updraft branch centered over the central equatorial Pacific, which is significantly both in observation and simulation. Mixed layer heat budget analysis shows that the atmosphere radiation fluxes modulated by the amounts of cloud cover are responsible for the warming response pattern in the central Pacific. There is a significant positive correlation between the meridional gradient of cloud cover (Δα, Subtropics-Tropic) and zonal SST gradient (ΔT, east-west) in the equatorial Pacific. The warming response in the central equatorial Pacific is amplified by the coupled atmosphere and ocean processes. On the one hand, owing to the zonal SST gradient decreasing in the western and central Pacific but increasing in the eastern and central Pacific, anomalous zonal wind convergence appears in the central Pacific in the three years following the solar peak. The ocean heat transport effect is negative in the central equatorial Pacific, more warm water accumulates locally. On the other hand, anomalous ascending motion over the central Pacific increases the high cloud amount and lets more shortwave radiation come into surface, which combined

  12. Extra-tropical origin of equatorial Pacific cold bias in climate models with links to cloud albedo

    Science.gov (United States)

    Burls, Natalie J.; Muir, Leslie; Vincent, Emmanuel M.; Fedorov, Alexey

    2017-09-01

    General circulation models frequently suffer from a substantial cold bias in equatorial Pacific sea surface temperatures (SSTs). For instance, the majority of the climate models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) have this particular problem (17 out of the 26 models evaluated in the present study). Here, we investigate the extent to which these equatorial cold biases are related to mean climate biases generated in the extra-tropics and then communicated to the equator via the oceanic subtropical cells (STCs). With an evident relationship across the CMIP5 models between equatorial SSTs and upper ocean temperatures in the extra-tropical subduction regions, our analysis suggests that cold SST biases within the extra-tropical Pacific indeed translate into a cold equatorial bias via the STCs. An assessment of the relationship between these extra-tropical SST biases and local surface heat flux components indicates a link to biases in the simulated shortwave fluxes. Further sensitivity studies with a climate model (CESM) in which extra-tropical cloud albedo is systematically varied illustrate the influence of cloud albedo perturbations, not only directly above the oceanic subduction regions but across the extra-tropics, on the equatorial bias. The CESM experiments reveal a quadratic relationship between extra-tropical Pacific albedo and the root-mean-square-error in equatorial SSTs—a relationship with which the CMIP5 models generally agree. Thus, our study suggests that one way to improve the equatorial cold bias in the models is to improve the representation of subtropical and mid-latitude cloud albedo.

  13. Auroral E-region electron density height profile modificationby electric field driven vertical plasma transport:some evidence in EISCAT CP-1 data statistics

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    T. Bösinger

    2004-03-01

    Full Text Available A model developed several years ago by Huuskonen et al. (1984 predicted that vertical transport of ions in the nocturnal auroral E-region ionosphere can shift the electron density profiles in altitude during times of sufficiently large electric fields. If the vertical plasma transport effect was to operate over a sufficiently long enough time, then the real height of the E-region electron maximum should be shifted some km upwards (downwards in the eastward (westward auroral electrojet, respectively, when the electric field is strong, exceeding, say, 50 mV/m. Motivated by these predictions and the lack of any experimental verification so far, we made use of the large database of the European Incoherent Scatter (EISCAT radar to investigate if the anticipated vertical plasma transport is at work in the auroral E-region ionosphere and thus to test the Huuskonen et al. (1984 model. For this purpose a new type of EISCAT data display was developed which enabled us to order a large number of electron density height profiles, collected over 16 years of EISCAT operation, according to the electric field magnitude and direction as measured at the same time at the radar's magnetic field line in the F-region. Our analysis shows some signatures in tune with a vertical plasma transport in the auroral E-region of the type predicted by the Huuskonen et al. model. The evidence brought forward is, however, not unambiguous and requires more rigorous analysis.

    Key words. Ionosphere (auroral ionosphere; plasma convection; electric fields and currents

  14. ISKANDARnet IOMOS: Near real-time equatorial space weather monitoring and alert system in Peninsular Malaysia

    Science.gov (United States)

    Musa, Tajul Ariffin; Leong, Shien Kwun; Abdullah, Khairul Anuar; Othman, Rusli

    2012-11-01

    This work proposes ISKANDARnet Ionospheric Outburst MOnitoring and alert System (IOMOS), along with Ionospheric Outburst Index (IOX) to develop an operational near real-time space weather service for Malaysia. The IOMOS is based on Global Positioning System (GPS) Network-based Real-Time Kinematic (NRTK) concept which is by nature for atmospheric (ionosphere and troposphere) modeling within the network coverage. The elegance of this solution lies in the fact that IOMOS utilize differential ionospheric residual from network of GPS baselines which incur no additional cost for operation. Users will be informed about the ionospheric perturbation through Short Message Service (SMS), email or Twitter®. This approach will ultimately beneficial for the navigation and satellite positioning communities, particularly during the coming Solar Cycle 24. In addition, a combination of local and global GPS network has been employed to study the equatorial ionosphere geomorphology and climatology in the Malaysian sector. Equatorial Total Electron Content (TEC) over Malaysia shows semi-annual, annual, and seasonal variations with maximum values appearing during equinoctial months and minimum during solstices months. The TEC value during vernal equinox is about 21% higher than autumnal equinox, and December solstice exceeds that at the June solstice by around 14%. It is also found that semi-annual variation is present at all levels of solar activity, whereas June solstice predominates December solstice during high solar activity for annual and seasonal variations. In near future, a near real-time TEC derivation system will be developed to support equatorial ionosphere modeling to enhance space weather service for Malaysia.

  15. 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.

  16. 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.

  17. Water-mass evolution in the Cretaceous Western Interior Seaway of North America and equatorial Atlantic

    Directory of Open Access Journals (Sweden)

    J. S. Eldrett

    2017-07-01

    Full Text Available The Late Cretaceous Epoch was characterized by major global perturbations in the carbon cycle, the most prominent occurring near the Cenomanian–Turonian (CT transition marked by Oceanic Anoxic Event 2 (OAE-2 at 94.9–93.7 Ma. The Cretaceous Western Interior Seaway (KWIS was one of several epicontinental seas in which a complex water-mass evolution was recorded in widespread sedimentary successions. This contribution integrates new data on the main components of organic matter, geochemistry, and stable isotopes along a north–south transect from the KWIS to the equatorial western Atlantic and Southern Ocean. In particular, cored sedimentary rocks from the Eagle Ford Group of west Texas (∼ 90–98 Ma demonstrate subtle temporal and spatial variations in palaeoenvironmental conditions and provide an important geographic constraint for interpreting water-mass evolution. High-latitude (boreal–austral, equatorial Atlantic Tethyan and locally sourced Western Interior Seaway water masses are distinguished by distinct palynological assemblages and geochemical signatures. The northward migration of an equatorial Atlantic Tethyan water mass into the KWIS occurred during the early–middle Cenomanian (98–95 Ma followed by a major re-organization during the latest Cenomanian–Turonian (95–94 Ma as a full connection with a northerly boreal water mass was established during peak transgression. This oceanographic change promoted de-stratification of the water column and improved oxygenation throughout the KWIS and as far south as the Demerara Rise off Suriname. In addition, the recorded decline in redox-sensitive trace metals during the onset of OAE-2 likely reflects a genuine oxygenation event related to open water-mass exchange and may have been complicated by variable contribution of organic matter from different sources (e.g. refractory/terrigenous material, requiring further investigation.

  18. Water-mass evolution in the Cretaceous Western Interior Seaway of North America and equatorial Atlantic

    Science.gov (United States)

    Eldrett, James S.; Dodsworth, Paul; Bergman, Steven C.; Wright, Milly; Minisini, Daniel

    2017-07-01

    The Late Cretaceous Epoch was characterized by major global perturbations in the carbon cycle, the most prominent occurring near the Cenomanian-Turonian (CT) transition marked by Oceanic Anoxic Event 2 (OAE-2) at 94.9-93.7 Ma. The Cretaceous Western Interior Seaway (KWIS) was one of several epicontinental seas in which a complex water-mass evolution was recorded in widespread sedimentary successions. This contribution integrates new data on the main components of organic matter, geochemistry, and stable isotopes along a north-south transect from the KWIS to the equatorial western Atlantic and Southern Ocean. In particular, cored sedimentary rocks from the Eagle Ford Group of west Texas (˜ 90-98 Ma) demonstrate subtle temporal and spatial variations in palaeoenvironmental conditions and provide an important geographic constraint for interpreting water-mass evolution. High-latitude (boreal-austral), equatorial Atlantic Tethyan and locally sourced Western Interior Seaway water masses are distinguished by distinct palynological assemblages and geochemical signatures. The northward migration of an equatorial Atlantic Tethyan water mass into the KWIS occurred during the early-middle Cenomanian (98-95 Ma) followed by a major re-organization during the latest Cenomanian-Turonian (95-94 Ma) as a full connection with a northerly boreal water mass was established during peak transgression. This oceanographic change promoted de-stratification of the water column and improved oxygenation throughout the KWIS and as far south as the Demerara Rise off Suriname. In addition, the recorded decline in redox-sensitive trace metals during the onset of OAE-2 likely reflects a genuine oxygenation event related to open water-mass exchange and may have been complicated by variable contribution of organic matter from different sources (e.g. refractory/terrigenous material), requiring further investigation.

  19. 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 genetic break observed in the equatorial Atlantic (between gyre FCT and ΦCT = 0.23, P genetic transition coincides with an area of low abundance for the species. Transitional regions between the subtropical gyres and the equatorial province also harbor a distinct mitochondrial clade (clade 2), have higher haplotype and nucleotide diversities relative to the northern and/or southern subtropical gyres (e.g., mean h = 0.831 EQ, 0.742 North, 0.594 South, F2,11 = 20.53, P genetically differentiated from the majority of sites in the central gyre and temperate zones of the same hemisphere (significant pairwise ΦST 0.038-0.267, 79% significant). Our observations support the hypothesis that regions of low abundance within species mark areas of suboptimal habitat that serve as dispersal barriers for 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.

  20. 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

  1. Impacts of the IOD-associated temperature and salinity anomalies on the intermittent equatorial undercurrent anomalies

    Science.gov (United States)

    Li, Junde; Liang, Chujin; Tang, Youmin; Liu, Xiaohui; Lian, Tao; Shen, Zheqi; Li, Xiaojing

    2017-11-01

    The study of Equatorial Undercurrent (EUC) has attracted a broad attention in recent years due to its strong response and feedback to the Indian Ocean Dipole. In this paper, we first produce a high-quality simulation of three-dimensional temperature, salinity and zonal current simulation from 1982 to 2014, using a high-resolution ocean general circulation model. On this basis, with two sensitivity experiments, we investigate the role of temperature and salinity anomalies in driving and enhancing the EUC during the positive IOD events by examining the variation of the EUC seasonal cycle and diagnosing the zonal momentum budget along the equatorial Indian Ocean. Our results show that during January-March, the EUC can appear along the entire equatorial Indian Ocean in all years, but during August-November, the EUC can appear and reach the eastern Indian Ocean only during the positive IOD events. The zonal momentum budget analysis indicates that the pressure gradient force contributes most to the variation of the eastward acceleration of zonal currents in the subsurface. During the positive IOD events, strong negative subsurface temperature anomalies exist in the eastern Indian Ocean, with negative surface salinity anomalies in the central and eastern Indian Ocean, resulting in a large pressure gradient force to drive EUC during the August-November. Further, the results of two sensitivity experiments indicate that the temperature anomalies significantly impact the pressure gradient force, playing a leading role in driving the EUC, while the surface salinity anomalies can secondarily help to intensify the eastward EUC through increasing the zonal density gradient in the eastern Indian Ocean and impacting the vertical momentum advection in the subsurface.

  2. 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.

  3. Observations of the generation of eastward equatorial electric fields near dawn

    Directory of Open Access Journals (Sweden)

    M. C. Kelley

    2014-09-01

    Full Text Available We report and discuss interesting observations of the variability of electric fields and ionospheric densities near sunrise in the equatorial ionosphere made by instruments onboard the Communications/Navigation Outage Forecasting System (C/NOFS satellite over six consecutive orbits. Electric field measurements were made by the Vector Electric Field Instrument (VEFI, and ionospheric plasma densities were measured by Planar Langmuir Probe (PLP. The data were obtained on 17 June 2008, a period of solar minimum conditions. Deep depletions in the equatorial plasma density were observed just before sunrise on three orbits, for which one of these depletions was accompanied by a very large eastward electric field associated with the density depletion, as previously described by de La Beaujardière et al. (2009, Su et al. (2009 and Burke et al. (2009. The origin of this large eastward field (positive upward/meridional drift, which occurred when that component of the field is usually small and westward, is thought to be due to a large-scale Rayleigh–Taylor process. On three subsequent orbits, however, a distinctly different, second type of relationship between the electric field and plasma density near dawn was observed. Enhancements of the eastward electric field were also detected, one of them peaking around 3 mV m−1, but they were found to the east (later local time of pre-dawn density perturbations. These observations represent sunrise enhancements of vertical drifts accompanied by eastward drifts such as those observed by the San Marco satellite (Aggson et al., 1995. Like the San Marco measurements, the enhancements occurred during winter solstice and low solar flux conditions in the Pacific longitude sector. While the evening equatorial ionosphere is believed to present the most dramatic examples of variability, our observations exemplify that the dawn sector can be highly variable as well.

  4. Electrojet control of ambient ionization near the crest of the equatorial anomaly in the Indian zone

    Directory of Open Access Journals (Sweden)

    S. K. Chakraborty

    2009-01-01

    Full Text Available A long-term (1978–1990 database of total electron content (TEC from a location (Calcutta: 22.58° N, 88.38° E geographic, dip: 32° N near the northern crest of the equatorial ionization anomaly has extensively been studied to characterize the contribution of fountain effect in the maintenance of ambient ionization. The equatorial electrojet (EEJ data obtained from ground magnetometer recording are used to assess the contribution of equatorial fountain. Analysis made with instantaneous values, day's maximum values and time-integrated values of EEJ strength exhibit more or less similar features. When instantaneous values of EEJ are considered TEC variations exhibit two maxima in correlation, one around 10:00–12:00 IST and the other around 18:00–20:00 IST. The later maximum in correlation coefficient is conspicuously absent when integrated values of EEJ are considered. An impulse-like feature is reflected in the diurnal TEC variation during the time intervals (09:00–10:00 IST and (18:00–19:00 IST. The statistical analysis reveals greater correspondence with high level of significance between diurnal TEC and EEJ in the descending epoch of solar cycle than in the ascending one. On the seasonal basis, TEC in the summer solstitial months are observed to be more sensitive to the changes in EEJ strength than in the equinoctial and winter solstitial months. Combining the effects of solar flux, season, local time and EEJ an empirical formula for monthly mean diurnal TEC has been developed and validated using observed TEC data. An estimation of the relative contributions of the several terms appearing in the formula reveals much more solar flux contribution (~50–70% in the maintenance of ambient ionization around the present location than the EEJ effects (maximum~20%.

  5. Electrojet control of ambient ionization near the crest of the equatorial anomaly in the Indian zone

    Directory of Open Access Journals (Sweden)

    S. K. Chakraborty

    2009-01-01

    Full Text Available A long-term (1978–1990 database of total electron content (TEC from a location (Calcutta: 22.58° N, 88.38° E geographic, dip: 32° N near the northern crest of the equatorial ionization anomaly has extensively been studied to characterize the contribution of fountain effect in the maintenance of ambient ionization. The equatorial electrojet (EEJ data obtained from ground magnetometer recording are used to assess the contribution of equatorial fountain. Analysis made with instantaneous values, day's maximum values and time-integrated values of EEJ strength exhibit more or less similar features. When instantaneous values of EEJ are considered TEC variations exhibit two maxima in correlation, one around 10:00–12:00 IST and the other around 18:00–20:00 IST. The later maximum in correlation coefficient is conspicuously absent when integrated values of EEJ are considered. An impulse-like feature is reflected in the diurnal TEC variation during the time intervals (09:00–10:00 IST and (18:00–19:00 IST. The statistical analysis reveals greater correspondence with high level of significance between diurnal TEC and EEJ in the descending epoch of solar cycle than in the ascending one. On the seasonal basis, TEC in the summer solstitial months are observed to be more sensitive to the changes in EEJ strength than in the equinoctial and winter solstitial months. Combining the effects of solar flux, season, local time and EEJ an empirical formula for monthly mean diurnal TEC has been developed and validated using observed TEC data. An estimation of the relative contributions of the several terms appearing in the formula reveals much more solar flux contribution (~50–70% in the maintenance of ambient ionization around the present location than the EEJ effects (maximum~20%.

  6. 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

  7. Permeability measuremens of brazilian Eucalyptus

    Directory of Open Access Journals (Sweden)

    Marcio Rogério da Silva

    2010-09-01

    Full Text Available The permeability of Brazilian Eucalyptus grandis and Eucalyptus citriodora wood was measured in a custom build gas analysis chamber in order to determine which species could be successfully treated with preservatives. Liquid permeability was tested using an emulsion of Neen oil and a control of distillated water. Air was used to test the gas phase permeability. For both Eucalyptus grandis and Eucalyptus citriodora, the longitudinal permeability of gas was shown to be about twice as great as the liquid phase permeability. No radial permeability was observed for either wood. The permeability of air and water through the sapwood of Eucalyptus grandis was greater than that through the sapwood of Eucalyptus citriodora. The permeability of neen oil preservative through the sapwood of Eucalyptus grandis was also greater than through the sapwood of E. Citradora, but the difference was not statistically significant. Scanning Electron Microscopy images showed that the distribution and obstruction in the vessels could be correlated with observed permeability properties. Irrespective of the causes of differences in permeability between the species, the fluid phase flux through the sapwood of both species was significant, indicating that both Eucalyptus grandis and Eucalyptus citriodora could be successfully treated with wood preservative.

  8. Group dialogue empowers Brazilian women.

    Science.gov (United States)

    Badiani, R; Becker, J

    1995-11-01

    In response to an alarming rise in human immunodeficiency virus (HIV) infection among Brazilian women during the early 1990s, the Sociedade Civil Bem-Estar Familiar no Brazil (BEMFAM) developed a project that integrates HIV prevention with clinical services, community-based prevention activities, and sexually transmitted disease diagnosis and treatment. Preliminary interviews with clinic clients revealed that women's fears they would be considered unfaithful were impeding their ability to suggest condom use to their sexual partners. Condom use within a relationship was considered appropriate only for pregnancy prevention. To facilitate dialogue about sexual health, BEMFAM developed a women's group intervention project. All women who attend a BEMFAM clinic are invited to participate in a one-hour group discussion before receiving medical services. Novela-style booklets with stories and characters women can relate to their own lives are used to stimulate discussion. Participants learn to use condoms correctly by putting them on a penis model and anticipate situations in which they would be able to negotiate condom use. The group setting enables women to gain confidence and practice assertiveness in a non-threatening, supportive environment. Their identification with other women's stories empowers women to take control of their health and sexual lives. Between October 1994 and July 1995, 3464 women participated in group discussions organized by BEMFAM and 40,688 condoms were distributed; 18% of these women returned to the clinic for additional condoms.

  9. Brazilian Cerrado Soil Actinobacteria Ecology

    Directory of Open Access Journals (Sweden)

    Monique Suela Silva

    2013-01-01

    Full Text Available A total of 2152 Actinobacteria strains were isolated from native Cerrado (Brazilian Savannah soils located in Passos, Luminárias, and Arcos municipalities (Minas Gerais State, Brazil. The soils were characterised for chemical and microbiological analysis. The microbial analysis led to the identification of nine genera (Streptomyces, Arthrobacter, Rhodococcus, Amycolatopsis, Microbacterium, Frankia, Leifsonia, Nakamurella, and Kitasatospora and 92 distinct species in both seasons studied (rainy and dry. The rainy season produced a high microbial population of all the aforementioned genera. The pH values of the soil samples from the Passos, Luminárias, and Arcos regions varied from 4.1 to 5.5. There were no significant differences in the concentrations of phosphorus, magnesium, and organic matter in the soils among the studied areas. Samples from the Arcos area contained large amounts of aluminium in the rainy season and both hydrogen and aluminium in the rainy and dry seasons. The Actinobacteria population seemed to be unaffected by the high levels of aluminium in the soil. Studies are being conducted to produce bioactive compounds from Actinobacteria fermentations on different substrates. The present data suggest that the number and diversity of Actinobacteria spp. in tropical soils represent a vast unexplored resource for the biotechnology of bioactives production.

  10. Aflatoxins in Brazilian Peanut Confection.

    Science.gov (United States)

    2016-04-07

    The study's objectives were to evaluate a method for the determination of aflatoxins (AFs) in the Brazilian peanut confection "Paçoca" and to apply the method in investigating AF concentrations in Paçoca marketed in São Paulo State throughout 2013. Results of another survey conducted between 1994 and 2002 with another method were also reported. The current method consists of immunoaffinity column cleanup, LC with postcolumn derivatization for AF fluorescence enhancement, and fluorescence determination for the toxins. The mean recovery and mean RSD r values were 88.6 and 7.9%, respectively. The LODs for aflatoxin B 1 , aflatoxin B 2 , aflatoxin G 1 , and aflatoxin G 2 were 0.04, 0.01, 0.02, and 0.01 ng/g; and the LOQs were 0.15, 0.04, 0.07, and 0.04 ng/g, respectively. Results of the two survey studies indicate that the contamination of AFs in Paçoca remains a public health problem. In the 2013 survey, 71 of 100 samples (71%) had AFs contamination ranging from 0.3 to 41.8 ng/g, with 12 samples (12%) containing >20 ng/g of the toxins, whereas in the 1994-2002 survey, 73 of 150 samples (51%) had AFs contamination ranging from 9 to 1439 ng/g with 65 samples (45%) containing levels >20 ng/g.

  11. Case Study: Brazilian Virtual Herbarium

    Directory of Open Access Journals (Sweden)

    Cameron Neylon

    2017-10-01

    Full Text Available The Brazilian Virtual Herbarium (BVH is a project of the Brazillian Centro de Referência em Informação Ambiental (CRIA that has been running since 2009. The Virtual Herbarium provides an infrastructure that gathers digital records of plant specimens from primary source, mainly in Brazil, and makes them available through a central web portal. The source herbaria have complete control over what data is made through the portal and the data collected by BVH is made fully available. BVH in common with many data infrastructures, faces challenges in retaining funding. Most funding sources are project based and as has been noted elsewhere this creates problems for the sustaining of infrastructures. BVH therefore has an interest in demonstrating the use of the data resources it hosts. Through the OCSDNet project it has strengthened its capacity in this area to develop tools showing its wide usage. Overall the BVH hosts over eight million records (as of October 2017 and received 70 billion data requests in October 2017. Its users are mainly in Brazil but there is also substantial global usage. The primary uses are for research and education. There are a broad range of educational users, including universities but also schools. Through providing a central aggregation and access point BHV provides a data infrastructure that is greater – and more useful – than the sum of its parts.

  12. Educating Brazilian workers about AIDS.

    Science.gov (United States)

    1991-12-01

    This article contains a the script for a slide-tape presentation entitled Working Against AIDS, a presentation developed by the Brazil Family Planning Association (BEMFAM) which is designed to debunk common misconceptions about the disease. This audio-visual, which targets Brazilian workers, can be used during talks, seminars, and meetings. A discussion of the issues involved usually follows the presentation of Working Against AIDS. The presentation contains 30 illustrated slides (these are included in the article). The presentation begins by explaining that much of the information concerning AIDS is prejudicial and misleading. The next few slides point out some of the common misconceptions about AIDS, such as claims denying the existence of the disease, or suggestions that only homosexuals and prostitutes are at risk. The presentation then goes on to explain the ways in which the virus can and cannot be transmitted. Then it discusses how the virus destroys the body's natural defenses and explains the ensuing symptoms. Slides 14 and 15 point out that no cure yet exists for AIDS, making prevention essential. Slides 16-23 explain what actions are considered to be high risk and which ones do not entail risk. Noting that AIDS can be prevented, slide 24 says that the disease should not present an obstacle to spontaneous manifestations of human relations. The next slide explains that condoms should always be used when having sex with someone who could be infected with AIDS. Finally slides 26-30 demonstrate the proper way to use and dispose of a condom.

  13. Brazilian Cerrado soil Actinobacteria ecology.

    Science.gov (United States)

    Suela Silva, Monique; Naves Sales, Alenir; Teixeira Magalhães-Guedes, Karina; Ribeiro Dias, Disney; Schwan, Rosane Freitas

    2013-01-01

    A total of 2152 Actinobacteria strains were isolated from native Cerrado (Brazilian Savannah) soils located in Passos, Luminárias, and Arcos municipalities (Minas Gerais State, Brazil). The soils were characterised for chemical and microbiological analysis. The microbial analysis led to the identification of nine genera (Streptomyces, Arthrobacter, Rhodococcus, Amycolatopsis, Microbacterium, Frankia, Leifsonia, Nakamurella, and Kitasatospora) and 92 distinct species in both seasons studied (rainy and dry). The rainy season produced a high microbial population of all the aforementioned genera. The pH values of the soil samples from the Passos, Luminárias, and Arcos regions varied from 4.1 to 5.5. There were no significant differences in the concentrations of phosphorus, magnesium, and organic matter in the soils among the studied areas. Samples from the Arcos area contained large amounts of aluminium in the rainy season and both hydrogen and aluminium in the rainy and dry seasons. The Actinobacteria population seemed to be unaffected by the high levels of aluminium in the soil. Studies are being conducted to produce bioactive compounds from Actinobacteria fermentations on different substrates. The present data suggest that the number and diversity of Actinobacteria spp. in tropical soils represent a vast unexplored resource for the biotechnology of bioactives production.

  14. On the plausible linkage of thermospheric meridional winds with the equatorial spread F

    Science.gov (United States)

    Devasia, C. V.; Jyoti, N.; Subbarao, K. S. V.; Viswanathan, K. S.; Tiwari, Diwakar; Sridharan, R.

    2002-01-01

    Some of the characteristic features of thermospheric meridional winds during equinoctial period, associated with equatorial spread F (ESF) and their possible role in the triggering of ESF are presented through case studies of observational events under different geophysical conditions that essentially control the post-sunset F-layer height (/h'F) rise. The present study reveals that the polarity and magnitude of the meridional winds become significant with the equatorward wind being present when the /h'F is below a critical height for the instability to get triggered. The distinctly different characteristic features of the meridional winds during ESF and non-ESF events are presented and discussed.

  15. Ionospheric storm of early November 1993 in the Indian equatorial region

    Science.gov (United States)

    Sastri, J. Hanumath; Jyoti, N.; Somayajulu, V. V.; Chandra, H.; Devasia, C. V.

    2000-08-01

    An investigation is made of the response of equatorial ionosphere in the Indian (75°E) sector to the major magnetic storm of November 3, 1993, using data from the ionosonde and magnetometer networks spanning the region 0.3-34.5°N dip. Some outstanding and new aspects of the storm time ionospheric behaviour are revealed. An anomalous and striking positive gradient in ƒ0F2 from the magnetic equator to 34.5° dip developed under counter electrojet (CEJ) condition in the morning on November 4, corresponding to the early stage of the storm main phase. This storm effect is attributed to plasma transport by a poleward surge in transequatorial winds due to large scale atmospheric gravity waves (AGWs) launched by auroral heating. Remarkable wave-like variations in hpF2 and ƒ0F2 immediately followed at locations away from dip equator till local sunset, with concomitant disruptions in the development of the equatorial ionization anomaly (EIA). Rapid variations in meridional neutral winds due to large-scale AGWs are assessed as the cause of the oscillations in hpF2 and the associated cyclic sequence of development and inhibition of EIA as the outcome of the combined effects of plasma transport due to meridional winds and the plasma "fountain" driven by E×B drift. Just after the onset of the storm recovery phase at 1800 LT, a sudden and anomalous drop (54-57%) in ƒ0F2 prevailed throughout the anomaly region over the interval 1915-2330 LT, with an apparent time delay in occurrence toward the magnetic equator. This premidnight collapse of equatorial F region is interpreted in terms of horizontal transport of plasma across the equator toward the opposite hemisphere by an equatorward surge in meridional winds. The case study showed that besides disturbances in the zonal electric field due to prompt penetration and ionospheric disturbance dynamo effects, perturbations in neutral meridional winds played a prominent role in the ionospheric storm of November 4, 1993, in the

  16. 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.

    , 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... measurements in the equatorial Indian Ocean. Under the OOS program, 3 locations at 93°E, 83°E and 76°E (Fig. 1) were selected along the equator for deploying the current meter moorings (Murty et al., 2002). The National Institute of Oceanography (NIO), Goa...

  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...... stratospheric sudden warming (SSW) in January 2009. Our analysis reveals the following prominent features. First, the TEC response in tropical regions is strongly latitude dependent, with monotonic depletion at the dip equator but a semidiurnal perturbation at low latitudes. Second, the TEC semidiurnal...

  18. Late Quaternary surface circulation in the east equatorial South Atlantic: Evidence from Alkenone sea surface temperatures

    Science.gov (United States)

    Schneider, Ralph R.; Müller, Peter J.; Ruhland, GöTz

    1995-04-01

    Angola Basin and Walvis Ridge records of past sea surface temperatures (SST) derived from the alkenone Uk37 index are used to reconstruct the surface circulation in the east equatorial South Atlantic for the last 200,000 years. Comparison of SST estimates from surface sediments between 5° and 20°S with modern SST data suggests that the alkenone temperatures represent annual mean values of the surface mixed layer. Alkenone-derived temperatures for the warm climatic maxima of the Holocene and the penultimate interglacial are 1 to 4°C higher than latest Holocene values. All records show glacial to interglacial differences of about 3.5°C in annual mean SST, which is about 1.5°C greater than the difference estimated by CLIMAP (1981) for the eastern Angola Basin. At the Walvis Ridge, significant SST variance is observed at all of the Earth's orbital periodicities. SST records from the Angola Basin vary predominantly at 23- and 100-kyr periodicities. For the precessional cycle, SST changes at the Walvis Ridge correspond to variations of boreal summer insolation over Africa and lead ice volume changes, suggesting that the east equatorial South Atlantic is sensitive to African monsoon intensity via trade-wind zonality. Angola Basin SST records lag those from the Walvis Ridge and the equatorial Atlantic by about 3 kyr. The comparison of Angola Basin and Walvis Ridge SST records implies that the Angola-Benguela Front (ABF) (currently at about 14-16°S) has remained fairly stationary between 12° and 20°S (the limits of our cores) during the last two glacial-interglacial cycles. The temperature contrast associated with the ABF exhibits a periodic 23-kyr variability which is coherent with changes in boreal summer insolation over Africa. These observations suggest that surface waters north of the present ABF have not directly responded to monsoon-modulated changes in the trade-wind vector, that the central field of zonally directed trades in the southern hemisphere was not

  19. Living coccolithophores during the northeast monsoon from the Equatorial Indian Ocean: Implications on hydrography

    Digital Repository Service at National Institute of Oceanography (India)

    Guptha, M.V.S.; Mergulhao, L.P.; Murty, V.S.N.; Shenoy, D.M.

    electron microscopeandcoatedwithGold-Palladiumalloy at 100A1 in a Sputter Coatter. This gold-coated stub was scanned using Joel SEM 5800 LV for coccolithophorididentificationandquantification, 1 m/s -3 -6 -9 -12 12 9 6 3 0 -3 -6 -9 -12 40Ê 45Ê 50Ê 55Ê 60Ê 65Ê... theinvestigatedfilerarea(mm 2 ). 4. Results The present study on extant coccolithophores fromthe central equatorial Indian Ocean during thenortheastmonsoonyieldedatotalof35species that were represented by both coccospheres and coccoliths(Plates1and2).Amongthem,30taxa...

  20. Massive sulfide ores of the northern equatorial Mid-Atlantic Ridge

    Science.gov (United States)

    Cherkashev, G. A.; Ivanov, V. N.; Bel'tenev, V. I.; Lazareva, L. I.; Rozhdestvenskaya, I. I.; Samovarov, M. L.; Poroshina, I. M.; Sergeev, M. B.; Stepanova, T. V.; Dobretsova, I. G.; Kuznetsov, V. Yu.

    2013-09-01

    The optimal set of prospecting methods, including geophysical (geoelectrical), geological (mineralogical-geochemical), and hydrological observations, was developed during the long-term investigations of the sulfide mineralization in the northern equatorial zone of the Mid-Atlantic Ridge. The application of these methods made it possible to discover six massive sulfide deposits and considerably extend the boundaries of another two ore objects. The ores associated with ultramafic rocks are characterized by elevated Cu, Au, and Co concentrations. It is established that the ore formation was a multistage process that resulted in the accumulation of large deposits (over 10 million tons).

  1. {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.

  2. 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.

  3. Dominance of foreign citations in Brazilian orthopedics journals.

    Science.gov (United States)

    Teixeira, Renan Kleber Costa; Yamaki, Vitor Nagai; Rosa, Rita de Cássia Rodrigues; de Barros, Rui Sergio Monteiro; Botelho, Nara Macedo

    2014-01-01

    To evaluate whether there is any preference for citing journals from other countries to the detriment of Brazilian journals, in three Brazilian orthopedics journals. All the references of articles published in 2011 by the journals Acta Ortopédica Brasileira, Coluna/Columna and Revista Brasileira de Ortopedia were evaluated to as certain how many of these came from Brazilian journals and how many from foreign journals. 3813 references distributed among 187 articles were analyzed. Out of this total, 306 (8.02%) were from Brazilian journals. There was no difference between the three journals analyzed. There were 76 articles (40.64%) without any citations of articles in Brazilian journals and only two articles (1%) cited more Brazilian articles than articles published elsewhere. There is a need for Brazilian researchers to cite articles from Brazilian journals more often.

  4. Brazilian Review of Finance 2013 Editorial Report

    Directory of Open Access Journals (Sweden)

    Ricardo Pereira Câmara Leal

    2014-06-01

    Full Text Available RBFin is the main Brazilian publication outlet of academic papers about finance. The contents of the Review are open and online with a printed version distributed to members of the Brazilian Finance Society. Using the Open Journals System to manage the editorial process, publication of RBFin adheres to a strict publication schedule. The Review is indexed by EconLit, RedALyC, Google Scholar, Gale, Proquest and Ebsco and is listed in the JEL, DOAJ, Latindex, OpenJGate, and Cabell's directories. RBFin is rated B1 in the business area of the Brazilian classification system and B2 in Economics. The editorial board undergoes partial turnover every year and comprises 19 individuals from four countries, the Brazilian members being affiliated with universities in five different Brazilian states. The acceptance rate was 27% for papers submitted in 2012, the most recent year in which all submissions have already received a final decision. The average number of days between receipt and acceptance for articles submitted in 2013 was 203. The worst case was 361 days. The average number of days between receipt and publication was 294. The worst case was 575 days. Fifty-three individuals served as reviewers in 2013.

  5. Global power and Brazilian nuclear decisions

    Energy Technology Data Exchange (ETDEWEB)

    Metri, Paulo, E-mail: pmetri@terra.com.br [Clube de Engenharia, Rio de Janeiro, RJ (Brazil)

    2017-07-01

    Brazilian society declares no intention to development a nuclear artifact. This is on its Constitution. The submarine of nuclear propulsion may be used as a weapon of defense and, therefore, has a peaceful objective. Nationalism must be applied only to benefit the society. Nationalist attention has always been devoted, at various occasions, to the Brazilian nuclear sector. However, since Brazilian society has many needs and the Brazilian government always had numerous energy options, this sector has not been developed as it could be. Other successful applications of nuclear technology, besides electric generation, are not considered here. At present, the country is experiencing a moment of harassment of liberal forces. It is difficult to know if the population understands what is going on, due to the traditional media control. This media belongs to the capital. The rise and the fall of the nationalist strand in a country follow a global tendency and also depend of actions of the international capital. In nationalist periods, more decisions with positive social impact are taken. Therefore, sovereignty is necessary to increase the benefits to society. Unfortunately, the Brazilians deceived by the companies of mass communication and corrupt political leaderships allow the country to be dominated. Even the armed forces had their projects paralyzed. The nuclear sector, as all other, suffers with the low budget and the future is difficult to predict. (author)

  6. Citizenship and decoloniality in Brazilian education

    Directory of Open Access Journals (Sweden)

    Viviane Conceição Antunes

    2014-08-01

    Full Text Available Reflecting on the importance of multiculturalism in teaching process and observing the otherness are primarily a challenge. This enables us to rethink what we have within ourselves, also to reconstitute memories involving discriminatory and unethical attitudes, which takes place in social fellowship. Based on the studies of Walsh (2007, 2009, Gomes (2007 and Tavares (2011, this work relies on decoloniality studies, mainly on the relevance of the history of Africa and Africanness in Brazilian education. Our corpus of analysis is found in the "Diretrizes Curriculares Nacionais para a Educação Básica" (DCN, 2013, the Brazilian Legislative Syllabus for Basic Education. Our focus is on the chapters concerning the Native-Brazilian and Quilomboa Education and ethnic-racial relations. Our most important aims are: to show the intercultural theoretical framework in which they are based on; to understand the immediate link established between the Native-Brazilian education and intercultural perspective; to clarify how the African diaspora was carried out in this particular case. Based on some Excel resources we were able to: 1 stablish the predominance of functional framework of interculturalism throughout these chapters, along with some critical features of interculturalism, as the issue of curricular decoloniality; 2 observe the established relationship between bilingualism and multiculturalism in the guidelines of Native-Brazilian education; and 3 identify a search for an effective inclusion of Africanness in curricula supported by the historical recognition and visibility of their sociocultural contribution.

  7. The Brazilian national system of forest permanent plots

    Science.gov (United States)

    Yeda Maria Malheiros de Oliveira; Maria Augusta Doetzer Rosot; Patricia Povoa de Mottos; Joberto Veloso de Freitas; Guilherme Luis Augusto Gomide; < i> et al< /i>

    2009-01-01

    The Brazilian National System of Forest Permanent Plots (SisPP) is a governmental initiative designed and being implemented in partnership by the Ministry of Environment (MMA), represented by the National Forest Programme (PNF) and the Brazilian Forest Service (SFB) and the Embrapa Forestry (a research center of the Brazilian Agricultural Research Corporation - Embrapa...

  8. Quiet time observations of equatorially trapped megaelectronvolt radiation belt ions with nuclear charge Z greater than or equal to 4

    Science.gov (United States)

    Spjeldvik, W. N.; Fritz, T. A.

    1978-01-01

    Data from the equatorial satellite Explorer 45 were used to study ion fluxes during the geomagnetically quiescent period June 1-15, 1972. A heavy-ion solid-state ion detector system obtained count rates close to the equatorial plane in the energy passband 1.82-4.8 MeV per ion during a single satellite pass through the radiation belts. Fluxes of these ions are interpreted as oxygen ions and are found to maximize in the L shell range 3-3.5 with peak equatorially mirroring flux of 0.38 ions/(sq cm s sr keV). This peak is not as sharply confined in L shell as is the helium ion peak.

  9. Relation between the variations of the solar wind and the noon-time equatorial ionospheric electric fields

    Science.gov (United States)

    Manoj, C.; Maus, S.; Alken, P.; Gentile, L.; Burke, W.

    2007-12-01

    We compare the solar wind measurements from ACE satellite with the vertical plasma drift (observed by JULIA radar) and the EEJ magnetic signals (observed at HUA observatory) from the South American equatorial sector. The aim is to understand the effect of solar wind on the variations of the electric field in the noon time equatorial ionosphere. We restrict our study to local noon time conditions, geomagnetically active days and while interplanetary Bz is negative. The estimates of electric field intensities (E_VS) at equatorial plain of the magnetosphere were made from ACE data using a combination of Volland-Stern and Siscoe-Hill models (Burke et al, 2007). The JULIA and magnetometer data were high-pass filtered to remove the regular daily variations. The relation between the data set will be presented as a coherence spectrum. In addition, the use of the ACE measurements to improve the climatological models of EEJ during geomagnetically active days will be explored.

  10. [Brazilian Consensus on Chagas Disease, 2015].

    Science.gov (United States)

    Dias, João Carlos Pinto; Ramos, Alberto Novaes; Gontijo, Eliane Dias; Luquetti, Alejandro; Shikanai-Yasuda, Maria Aparecida; Coura, José Rodrigues; Torres, Rosália Morais; Melo, José Renan da Cunha; Almeida, Eros Antonio de; Oliveira, Wilson de; Silveira, Antônio Carlos; Rezende, Joffre Marcondes de; Pinto, Fabiane Scalabrini; Ferreira, Antonio Walter; Rassi, Anis; Fragata, Abílio Augusto; Sousa, Andréa Silvestre de; Correia, Dalmo; Jansen, Ana Maria; Andrade, Glaucia Manzan Queiroz; Britto, Constança Felícia De Paoli de Carvalho; Pinto, Ana Yecê das Neves; Rassi, Anis; Campos, Dayse Elisabeth; Abad-Franch, Fernando; Santos, Silvana Eloi; Chiari, Egler; Hasslocher-Moreno, Alejandro Marcel; Moreira, Eliane Furtado; Marques, Divina Seila de Oliveira; Silva, Eliane Lages; Marin-Neto, José Antonio; Galvão, Lúcia Maria da Cunha; Xavier, Sergio Salles; Valente, Sebastião Aldo da Silva; Carvalho, Noêmia Barbosa; Cardoso, Alessandra Viana; Silva, Rafaella Albuquerque E; Costa, Veruska Maia da; Vivaldini, Simone Monzani; Oliveira, Suelene Mamede; Valente, Vera da Costa; Lima, Mayara Maia; Alves, Renato Vieira

    2016-06-01

    Chagas disease is a neglected chronic condition that presents high morbidity and mortality burden, with considerable psychological, social, and economic impact. The disease represents a significant public health issue in Brazil, with different regional patterns. This document presents the evidence that resulted in the Brazilian Consensus on Chagas Disease. The objective was to review and standardize strategies for diagnosis, treatment, prevention, and control of Chagas disease in the country, based on the available scientific evidence. The consensus is based on collaboration and contribution of renowned Brazilian experts with vast knowledge and experience on various aspects of the disease. It is the result of close collaboration between the Brazilian Society of Tropical Medicine and the Ministry of Health. This document shall strengthen the development of integrated control measures against Chagas disease in the country, focusing on epidemiology, management, comprehensive care (including families and communities), communication, information, education, and research.

  11. Influence of solar activity on middle atmosphere associated with phases of equatorial quasi-biennial oscillation

    Science.gov (United States)

    Mohanakumar, K.

    1989-01-01

    Earlier studies on the influence of solar activity variations within a 11-year solar cycle on temperature changes in the middle atmosphere revealed that while the temperature in the mesosphere showed strong responses to changes in solar activity, the stratosphere remained almost unaffected. Recent studies showed that when the temperature data were grouped into east or west phase of the equatorial quasi-biennial oscillation (QBO) in stratospheric zonal wind, significant relationships of temperature in the lower stratosphere and troposphere could be obtained with 10.7 cm solar radio flux. Positive correlations in high latitude regions and negative correlations in mid-latitude and tropical regions were obtained during winter when the QBO was in its west phase. During the east phase, converse relationships were indicated. These results inspired this study on the response of solar activity in 11-year cycle on the temperature structure of the middle atmosphere in the two phases of equatorial QBO of zonal wind at 50 mb, in tropics, mid-latitude and antarctic regions.

  12. 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.

  13. 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.

  14. Western equatorial African forest-savanna mosaics: a legacy of late Holocene climatic change?

    Science.gov (United States)

    Ngomanda, A.; Chepstow-Lusty, A.; Makaya, M.; Favier, C.; Schevin, P.; Maley, J.; Fontugne, M.; Oslisly, R.; Jolly, D.

    2009-10-01

    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.

  15. 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.

  16. 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.

  17. 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.

  18. The intermediate layers and associated tidal motions observed by a digisonde in the equatorial anomaly region

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    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

  19. Paleogene equatorial penguins challenge the proposed relationship between biogeography, diversity, and Cenozoic climate change

    Science.gov (United States)

    Clarke, Julia A.; Ksepka, Daniel T.; Stucchi, Marcelo; Urbina, Mario; Giannini, Norberto; Bertelli, Sara; Narváez, Yanina; Boyd, Clint A.

    2007-01-01

    New penguin fossils from the Eocene of Peru force a reevaluation of previous hypotheses regarding the causal role of climate change in penguin evolution. Repeatedly it has been proposed that penguins originated in high southern latitudes and arrived at equatorial regions relatively recently (e.g., 4–8 million years ago), well after the onset of latest Eocene/Oligocene global cooling and increases in polar ice volume. By contrast, new discoveries from the middle and late Eocene of Peru reveal that penguins invaded low latitudes >30 million years earlier than prior data suggested, during one of the warmest intervals of the Cenozoic. A diverse fauna includes two new species, here reported from two of the best exemplars of Paleogene penguins yet recovered. The most comprehensive phylogenetic analysis of Sphenisciformes to date, combining morphological and molecular data, places the new species outside the extant penguin radiation (crown clade: Spheniscidae) and supports two separate dispersals to equatorial (paleolatitude ≈14°S) regions during greenhouse earth conditions. One new species, Perudyptes devriesi, is among the deepest divergences within Sphenisciformes. The second, Icadyptes salasi, is the most complete giant (>1.5 m standing height) penguin yet described. Both species provide critical information on early penguin cranial osteology, trends in penguin body size, and the evolution of the penguin flipper. PMID:17601778

  20. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Guirao, J., E-mail: julio@natec-ingenieros.com [Numerical Technologies, S. L., Marques de San Esteban No. 52, 33206 Gijon (Spain); Rodriguez, E. [Department of Mechanical Engineering, University of Oviedo, Campus de Viesques, 33203 Gijon (Spain); Ordieres, J. [Numerical Technologies, S. L., Marques de San Esteban No. 52, 33206 Gijon (Spain); Cabanas, M.F.; Garcia, C.H. Rojas [Electrical Engineering Department, University of Oviedo, Campus de Viesques, 33203 Gijon (Spain)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Electromagnetic transient performance evaluation of the GEPP structure. Black-Right-Pointing-Pointer Three different plasma current disruption cases: MD UP LIN36, VDE UP LIN36 and VDE DW LIN36 were analyzed. Black-Right-Pointing-Pointer 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.

  2. Equatorial mountain lakes show extended periods of thermal stratification with recent climate change

    Directory of Open Access Journals (Sweden)

    Neal Michelutti

    2016-03-01

    Full Text Available Climate change in the Andes has already affected phenology, glaciology, and other ecosystem attributes, and now threatens to alter long-standing fundamental limnological properties. In the equatorial Andes, most lakes have traditionally been described as having waters that circulate continuously (polymictic, with only rare episodes of stratification. This characterization, albeit based on relatively few studies, is widely accepted, despite accelerated regional warming over the past 30 years.Here, we show that protracted periods of thermal stratification are presently the norm, not the exception, in equatorial mountain lakes. Annual circulation and stratification patterns recorded in four lakes from Ecuador’s southern Sierra show extended periods of stratification, which are stable and do not break down with nocturnal cooling. These data contrast with earlier research from this region, which reported full water column mixing and only infrequent stratification, but are not surprising in light of recent trends toward rising temperatures and declining wind velocities. Paleolimnological studies show that changes to the thermal regimes of these lakes likely began several decades ago and have resulted in ecosystem-scale changes including regime shifts in phytoplankton and declines in aquatic production.

  3. 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.

  4. Paleogene equatorial penguins challenge the proposed relationship between biogeography, diversity, and Cenozoic climate change.

    Science.gov (United States)

    Clarke, Julia A; Ksepka, Daniel T; Stucchi, Marcelo; Urbina, Mario; Giannini, Norberto; Bertelli, Sara; Narváez, Yanina; Boyd, Clint A

    2007-07-10

    New penguin fossils from the Eocene of Peru force a reevaluation of previous hypotheses regarding the causal role of climate change in penguin evolution. Repeatedly it has been proposed that penguins originated in high southern latitudes and arrived at equatorial regions relatively recently (e.g., 4-8 million years ago), well after the onset of latest Eocene/Oligocene global cooling and increases in polar ice volume. By contrast, new discoveries from the middle and late Eocene of Peru reveal that penguins invaded low latitudes >30 million years earlier than prior data suggested, during one of the warmest intervals of the Cenozoic. A diverse fauna includes two new species, here reported from two of the best exemplars of Paleogene penguins yet recovered. The most comprehensive phylogenetic analysis of Sphenisciformes to date, combining morphological and molecular data, places the new species outside the extant penguin radiation (crown clade: Spheniscidae) and supports two separate dispersals to equatorial (paleolatitude approximately 14 degrees S) regions during greenhouse earth conditions. One new species, Perudyptes devriesi, is among the deepest divergences within Sphenisciformes. The second, Icadyptes salasi, is the most complete giant (>1.5 m standing height) penguin yet described. Both species provide critical information on early penguin cranial osteology, trends in penguin body size, and the evolution of the penguin flipper.

  5. HF radar observations of equatorial spread-F over West Africa

    Directory of Open Access Journals (Sweden)

    J.-F. Cécile

    Full Text Available New experimental data depicting equatorial spread-F were taken during an HF radar sounding campaign in Korhogo (Ivory Coast, 9°24N, 5°37W, dip 4°S. Range-time-intensity maps of the radar echoes have been analyzed to identify the signatures of density depletions and bottomside spread-F. Density depletions are well known features of equatorial spread-F, and are believed to emerge after the development of a Rayleigh-Taylor instability on the bottomside F-layer. A simple model is developed and used to simulate the flow of density depletions over the radar field of view. The simulation permits an interpretation of the data that yields the zonal flow velocity as a function of local time. Comparisons with previous measurements are undertaken to assess the consistency of the computational results, and qualitative arguments are presented to identify bottomside spread-F. Using the computational results as reference, a morphological study of ionograms showing spread-F is undertaken which reveals the specific signature of bottomside spread-F on ionograms recorded just after sunset.

  6. HF radar observations of equatorial spread-F over West Africa

    Directory of Open Access Journals (Sweden)

    J.-F. Cécile

    1996-04-01

    Full Text Available New experimental data depicting equatorial spread-F were taken during an HF radar sounding campaign in Korhogo (Ivory Coast, 9°24N, 5°37W, dip 4°S. Range-time-intensity maps of the radar echoes have been analyzed to identify the signatures of density depletions and bottomside spread-F. Density depletions are well known features of equatorial spread-F, and are believed to emerge after the development of a Rayleigh-Taylor instability on the bottomside F-layer. A simple model is developed and used to simulate the flow of density depletions over the radar field of view. The simulation permits an interpretation of the data that yields the zonal flow velocity as a function of local time. Comparisons with previous measurements are undertaken to assess the consistency of the computational results, and qualitative arguments are presented to identify bottomside spread-F. Using the computational results as reference, a morphological study of ionograms showing spread-F is undertaken which reveals the specific signature of bottomside spread-F on ionograms recorded just after sunset.

  7. The longitudinal variability of equatorial electrojet and vertical drift velocity in the African and American sectors

    Directory of Open Access Journals (Sweden)

    E. Yizengaw

    2014-03-01

    Full Text Available While the formation of equatorial electrojet (EEJ and its temporal variation is believed to be fairly well understood, the longitudinal variability at all local times is still unknown. This paper presents a case and statistical study of the longitudinal variability of dayside EEJ for all local times using ground-based observations. We found EEJ is stronger in the west American sector and decreases from west to east longitudinal sectors. We also confirm the presence of significant longitudinal difference in the dusk sector pre-reversal drift, using the ion velocity meter (IVM instrument onboard the C/NOFS satellite, with stronger pre-reversal drift in the west American sector compared to the African sector. Previous satellite observations have shown that the African sector is home to stronger and year-round ionospheric bubbles/irregularities compared to the American and Asian sectors. This study's results raises the question if the vertical drift, which is believed to be the main cause for the enhancement of Rayleigh–Taylor (RT instability growth rate, is stronger in the American sector and weaker in the African sector – why are the occurrence and amplitude of equatorial irregularities stronger in the African sector?

  8. 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.

  9. Analysis of the seasonal variations of equatorial plasma bubble occurrence observed from Haleakala, Hawaii

    Directory of Open Access Journals (Sweden)

    J. J. Makela

    2004-09-01

    Full Text Available Over 300 nights of airglow and GPS scintillation data collected between January 2002 and August 2003 (a period near solar maximum from the Haleakala Volcano, Hawaii are analyzed to obtain the seasonal trends for the occurrence of equatorial plasma bubbles in the Pacific sector (203° E. A maximum probability for bubble development is seen in the data in April (45% and September (83%. A broad maximum of occurrence is seen in the data from June to October (62%. Many of the bubbles observed from June through August occur later in the evening, and, as seen in the optical data, tend to be "fossilized". This suggests that the active growth region during these months is to the west of the observing location. These seasonal trends are consistent with previous data sets obtained both from other ground-based and satellite studies of the occurrence of equatorial bubbles in the Pacific sector. However, our data suggests a much greater probability of bubble occurrence than is seen in other data sets, with bubbles observed on over 40% of the nights studied.

  10. 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.

  11. Spatio-temporal evolutions of non-orthogonal equatorial wave modes derived from observations

    Science.gov (United States)

    Barton, Cory

    Equatorial waves have been studied extensively due to their importance to the tropical climate and weather systems. Historically, their activity is diagnosed mainly in the wavenumber-frequency domain. Recently, many studies have projected observational data onto parabolic cylinder functions (PCFs), which represent the meridional structure of individual wave modes, to attain time-dependent spatial wave structures. The non-orthogonality of wave modes has yet posed a problem when attempting to separate data into wave fields where the waves project onto the same structure functions. We propose the development and application of a new methodology for equatorial wave expansion of instantaneous flows using the full equatorial wave spectrum. By creating a mapping from the meridional structure function amplitudes to the equatorial wave class amplitudes, we are able to diagnose instantaneous wave fields and determine their evolution. Because all meridional modes are shared by some subset of the wave classes, we require constraints on the wave class amplitudes to yield a closed system with a unique solution for all waves' spatial structures, including IG waves. A synthetic field is analyzed using this method to determine its accuracy for data of a single vertical mode. The wave class spectra diagnosed using this method successfully match the correct dispersion curves even if the incorrect depth is chosen for the spatial decomposition. In the case of more than one depth scale, waves with varying equivalent depth may be similarly identified using the dispersion curves. The primary vertical mode is the 200 m equivalent depth mode, which is that of the peak projection response. A distinct spectral power peak along the Kelvin wave dispersion curve for this value validates our choice of equivalent depth, although the possibility of depth varying with time and height is explored. The wave class spectra diagnosed assuming this depth scale mostly match their expected dispersion curves

  12. Climate change in the Brazilian northeast

    Science.gov (United States)

    Rodrigues, Regina R.; Haarsma, Reindert J.; Hoelzemann, Judith J.

    2012-10-01

    Climate Change, Impacts and Vulnerabilities in Brazil: Preparing the Brazilian Northeast for the Future; Natal, Brazil, 27 May to 01 June 2012 The variability of the semiarid climate of the Brazilian northeast has enormous environmental and social implications. Because most of the population in this area depends on subsistence agriculture, periods of severe drought in the past have caused extreme poverty and subsequent migration to urban centers. From the ecological point of view, frequent and prolonged droughts can lead to the desertification of large areas. Understanding the causes of rainfall variability, in particular periods of severe drought, is crucial for accurate forecasting, mitigation, and adaptation in this important region of Brazil.

  13. Huntington disease: DNA analysis in brazilian population

    OpenAIRE

    RASKIN, SALMO; ALLAN, NASSER; TEIVE, HÉLIO A.G.; CARDOSO, FRANCISCO; HADDAD, MÔNICA SANTORO; LEVI, GILBERTO; BOY, RAQUEL; LERENA JR, JUAN; SOTOMAIOR, VANESSA SANTOS; JANZEN-DÜCK, MÔNICA; JARDIM, LAURA BANNACH; FELLANDER, FLÁVIO R.; ANDRADE, LUIZ AUGUSTO FRANCO

    2000-01-01

    Huntington disease (HD) is associated with expansions of a CAG trinucleotide repeat in the HD gene. Accurate measurement of a specific CAG repeat sequence in the HD gene in 92 Brazilian controls without HD, 44 Brazilian subjects with clinical findings suggestive of HD and 40 individuals from 6 putative HD families, showed a range from 7 to 33 repeats in normal subjects and 39 to 88 repeats in affected subjects. A trend between early age at onset of first symptoms and increasing number of repe...

  14. Numerical modeling of the equatorial electrojet UT-variation on the basis of the model GSM TIP

    Directory of Open Access Journals (Sweden)

    M. V. Klimenko

    2007-06-01

    Full Text Available In the presented work the results of numerical modeling of the UT-variation of the equatorial electrojet, executed on the basis of the model GSM TIP are presented, taking into account the dynamo electric fields generated by thermospheric winds in a current-carrying layer of the ionosphere at heights 80–175 km above a surface of the Earth. To the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP, developed in WD IZMIRAN, a new block for the calculation of electric fields in the ionosphere has been added. In this block the solution of the three-dimensional equation describing the conservation law of the full current in the Earth's ionosphere is reduced to the solution of the two-dimensional equation by integration along geomagnetic field lines. Calculations of parameters of the near-Earth space plasmas have been executed for quiet equinoctial conditions on 22 March 1987 during the minimum of solar activity.

    It has been shown, that there is a distinct semidiurnal harmonic in the diurnal behavior of the linear density of the equatorial electrojet with maxima at 23:00 UT and 15:00 UT, as well as with minima at 06:00 UT and 20:00 UT. The greatest and smallest values of the peak intensity of the equatorial electrojet with respect to the diurnal behavior can differ by a factor of two. The longitudinal extent of the area of the equatorial electrojet does hardly show any UT-variation, but the greatest longitudinal extent is at 06 UT. With the growth of the peak intensity of the equatorial electrojet its latitudinal extent also increases (on ~5–10° a little. At the same time the equatorial electrojet in the maxima of intensity has approximately an identical width, whereas in the minima the electrojet is narrow in the morning and wide in the afternoon.

    As for the surface density of the equatorial electrojet, its UT-variation is much weaker and equals ~1–3 A/km2 and the peak

  15. 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

  16. Equatorial Scintillation Predictions from C/NOFS Planar Langmuir Probe Electron Density Fluctuation Data

    Science.gov (United States)

    2014-09-05

    satellite over a selected receiving station , followed by the application of a scintillation model to detected near- overhead irregularities to estimate the...Network Decision Aid (SCINDA) receiver for validation of a purely space -based scintillation detection, mapping and prediction model. Status of...International Congress of the Brazilian Geophysical Society & EXPOGEf (13 th CISBGf, Rio de Janeiro, RJ, Brazil, August 2013): co- chair of Session

  17. Security of the Brazilian Amazon Area

    Science.gov (United States)

    1992-04-01

    Thk document may not be Mased fog openi puiks&adM tr it ha beat domed by the appropriate militarvice or TIC M AY5, 1921 SECURITY OF THE BRAZILIAN AMAZON...34Seguridad y Ecologia. Reforinulacion de tin concepto". Nueva Sociedad . (may/June 1990 - no 107): 21- 26. McIntyre, Loren. "Last Days of Eden

  18. Anthropometry of Brazilian Air Force pilots.

    Science.gov (United States)

    da Silva, Gilvan V; Halpern, Manny; Gordon, Claire C

    2017-10-01

    Anthropometric data are essential for the design of military equipment including sizing of aircraft cockpits and personal gear. Currently, there are no anthropometric databases specific to Brazilian military personnel. The aim of this study was to create a Brazilian anthropometric database of Air Force pilots. The methods, protocols, descriptions, definitions, landmarks, tools and measurements procedures followed the instructions outlined in Measurer's Handbook: US Army and Marine Corps Anthropometric Surveys, 2010-2011 - NATICK/TR-11/017. The participants were measured countrywide, in all five Brazilian Geographical Regions. Thirty-nine anthropometric measurements related to cockpit design were selected. The results of 2133 males and 206 females aged 16-52 years constitute a set of basic data for cockpit design, space arrangement issues and adjustments, protective gear and equipment design, as well as for digital human modelling. Another important implication is that this study can be considered a starting point for reducing gender bias in women's career as pilots. Practitioner Summary: This paper describes the first large-scale anthropometric survey of the Brazilian Air Force pilots and the development of the related database. This study provides critical data for improving aircraft cockpit design for ergonomics and comprehensive pilot accommodation, protective gear and uniform design, as well as digital human modelling.

  19. Spirometry reference values in the Brazilian population.

    Science.gov (United States)

    Rufino, R; Costa, C H; Lopes, A J; Maiworm, A I; Maynard, K; Silva, L M R A; Dias, R M

    2017-03-02

    The aim of the present study was to provide new spirometry reference equations in a sample of the Brazilian population for the following parameters: forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), FEV1/FVC ratio, peak of expiratory flow (PEF), forced expiratory flow at 50% (FEF50%), 75% average vital capacity (FEF25-75%), and average forced expiratory flow time (FEFT). This was a prospective study using results from chest radiographs, electrocardiograms, and questionnaires to investigate the participants' respiratory symptoms, sedentarism, and comorbidities (Charlson comorbidity index). From December 2010 to July 2014, individuals were randomly selected from various locations in the state of Rio de Janeiro. All individuals were examined by a single technician in the morning at the laboratory, and performed the spirometry with the same spirometer. Spirometry values were tabulated for the creation of three equation models: linear regression, logarithmic regression, and logarithms through a method that incorporates the lambda, median, and coefficient of variation (LMS method). Initially, 7003 individuals from both genders were contacted, and 454 were recruited. The data from the new equations were compared with one Brazilian and eight international equations, resulting in a high correlation (r>0.9). The values derived from the LMS method and linear regression were very similar (P>0.5), and both could be used to acquire the reference values for Brazilian spirometry. Data derived from the equations of this study were different from the current Brazilian equation, which could be justified by the different method used.

  20. A Grammar of Spoken Brazilian Portuguese.

    Science.gov (United States)

    Thomas, Earl W.

    This is a first-year text of Portuguese grammar based on the Portuguese of moderately educated Brazilians from the area around Rio de Janeiro. Spoken idiomatic usage is emphasized. An important innovation is found in the presentation of verb tenses; they are presented in the order in which the native speaker learns them. The text is intended to…

  1. Transcultural Diabetes Nutrition Algorithm: Brazilian Application

    Directory of Open Access Journals (Sweden)

    Fabio Moura

    2015-09-01

    Full Text Available The prevalence of obesity, pre-diabetes, and type 2 diabetes (T2D is increasing worldwide, especially in the developing nations of South America. Brazil has experienced an exponential increase in the prevalence of these chronic non-communicable diseases. The rising prevalence is probably due to changing eating patterns, sedentary living, and a progressive aging of the population. These trends and their underlying causes carry untoward consequences for all Brazilians and the future of Brazilian public health and the healthcare system. Lifestyle changes that include healthy eating (nutrition therapy and regular physical activity (structured exercise represent efficient inexpensive measures to prevent and/or treat the aforementioned disorders and are recommended for all afflicted patients. Regrettably, the implementation of lifestyle changes is fraught with clinical and personal challenges in real life. The transcultural Diabetes Nutrition Algorithm (tDNA is a therapeutic tool intended to foster implementation of lifestyle recommendations and to improve disease-related outcomes in common clinical settings. It is evidence-based and amenable to cultural adaptation. The Brazilian Diabetes Association, Society of Cardiology and Ministry of Health guidelines for nutrition therapy and physical exercise were considered for the Brazilian adaptation. The resultant tDNA-Brazil and its underlying recommendations are presented and explained.

  2. Brazilian Review of Finance 2012 Editorial Report

    Directory of Open Access Journals (Sweden)

    Ricardo Pereira Câmara Leal

    2013-03-01

    Full Text Available RBFin is the main Brazilian publication outlet of academic papers about finance. The contents of the Review are open and online; a printed version is maintained, in part, thanks to a grant from CNPq/CAPES. Using the Open Journals System to manage the editorial process, publication of RBFin adheres to a strict publication schedule. The journal is indexed by EconLit, Google Scholar, DOAJ, Gale and Ebsco and is listed in the JEL, Latindex, OpenJGate, and Cabell's directories. RBFin is rated B1 in the business area of the Brazilian classification system. The editorial board undergoes partial turnover every year and comprises 18 individuals from four countries, the Brazilian members being affiliated with universities in five different Brazilian states. The acceptance rate was 30% for papers submitted in 2010, the most recent year in which all submissions have already received a final decision. The average number of days between receipt and acceptance for all articles published in 2011 was 266. The worst case was 462 days. The average number of days between receipt and publication was 432. The worst case was 599 days. The average number of hits per article as of January 2012 was 1,249. Sixty-four individuals served as reviewers in 2011.

  3. Hemoglobin Variant Profiles among Brazilian Quilombola Communities.

    Science.gov (United States)

    Santiago, Rayra P; Oliveira, Rodrigo M; Soares, Leonardo F; Figueiredo, Camylla V B; Silva, Denise Oliveira; Hurtado-Guerrero, Ana F; Fiuza, Luciana M; Guarda, Caroline C; Adorno, Elisângela V; Barbosa, Cynara G; Gonçalves, Marilda S

    2017-03-01

    Brazilian Quilombolas are communities composed of African-derived populations that have their territories guaranteed by the Brazilian Constitution. The present study investigated the hemoglobin (Hb) variants among these population groups. This study was conducted in a total of 2843 individuals of Brazilian Quilombola communities of the Bahia, Pará, and Piauí states. All the participants had their Hb profiles evaluated. The Hb S (HBB: c.20A>T) variant was described in all the studied localities. However, the individuals in Bahia State had the highest frequency of the Hb C (HBB: c.19G>A) variant; individuals from Piauí State had a higher frequency of the Hb D-Punjab (HBB: c.364G>C) variant compared to the other states, and individuals from Pará State only carried the Hb S variant. The present study revealed a specific distribution of Hb variants that could represent different waves of African influence in these Brazilian populations.

  4. Selective logging in the Brazilian Amazon.

    Science.gov (United States)

    G. P. Asner; D. E. Knapp; E. N. Broadbent; P. J. C. Oliveira; M Keller; J. N. Silva

    2005-01-01

    Amazon deforestation has been measured by remote sensing for three decades. In comparison, selective logging has been mostly invisible to satellites. We developed a large-scale, high-resolution, automated remote-sensing analysis of selective logging in the top five timber-producing states of the Brazilian Amazon. Logged areas ranged from 12,075 to 19,823 square...

  5. The Brazilian investment in science and technology

    Directory of Open Access Journals (Sweden)

    Pinheiro-Machado R.

    2001-01-01

    Full Text Available An analysis of Brazilian federal expenditures in science and technology is presented is this study. The 1990-1999 data were compiled from records provided by two federal agencies (MCT and CNPq responsible for managing most of the national budget related to these activities. The results indicate that the federal investments in Brazilian science and technology stagnated during the last decade (US$ 2.32 billion in 1990, US$ 2.39 billion in 1996, and US$ 2.36 billion in 1999. In contrast, a great increase in private investments in research was acknowledged both by industry and by the government during the same period, from US$ 2.12 to US$ 4.64 billion. However, this investment did not result in an increase in invention patents granted to residents (492 in 1990 and only 232 in 1997 or in a reduction of patent costs. Despite this unfavorable scenario, the number of graduate programs in the country has increased two-fold in the last decade and the contribution of Brazilians to the database of the Institute for Scientific Information has increased 4.7-fold from 1990 (2,725 scientific publications to 2000 (12,686 scientific publications. Unstable federal resources for science, together with the poor returns of private resources in terms of developing new technologies, may jeopardize the future of Brazilian technological development.

  6. Lizards of Brazilian Amazonia (Reptilia: Squamata)

    NARCIS (Netherlands)

    Avila-Pires, T.C.S.

    1995-01-01

    Eighty-nine species of lizards, six of which polytypic (forming a total of 97 taxa), are presently known from Brazilian Amazonia. This number includes six species and one subspecies described as new to science in this paper: Stenocercus fimbriatus, Lepidoblepharis hoogmoedi, Leposoma osvaldoi, L.

  7. Bullying in Brazilian Schools and Restorative Practices

    Science.gov (United States)

    Grossi, Patricia Krieger; dos Santos, Andreia Mendes

    2012-01-01

    Bullying is a widespread phenomenon that affects many children and adolescents in Brazilian schools. A pilot research study was carried out in four schools (one private and three public) located in Porto Alegre, RS, Brazil. A combination of self-administered questionnaires and focus groups with students as well as interviews with teachers were…

  8. Translating Ovide Decroly's Ideas to Brazilian Teachers

    Science.gov (United States)

    Hai, Alessandra Arce; Simon, Frank; Depaepe, Marc

    2015-01-01

    This article seeks to analyse, comprehend and apprehend the appropriation processes of Ovide Decroly's ideas in Brazil through the translation of his books and that of Amélie Hamaïde into Portuguese. The article discusses the following questions. Why did Brazilian intellectuals and teachers need to import Decroly's ideas to be applied in Brazilian…

  9. Earning management in Brazilian financial institutions

    Directory of Open Access Journals (Sweden)

    Adriana Bruscato Bortoluzzo

    2016-06-01

    Full Text Available ABSTRACT The present study aims to study earnings management in a significant sample of 123 banks in the Brazilian market between 2001 and 2012. Given the important role that banks play in a country's economy, it is important to understand that there are discretionary factors involved in the reporting of a financial institution's profitability. Credit provisioning guidelines for Brazilian financial institutions are described in Resolution 2682/99 of the National Monetary Council (Conselho Monetário Nacional. Because of the discretion allowed in this resolution, loan loss provision is used as instrument of earnings management, which is not an illegal practice, but this behavior does affect the risk perception of agents and analysts, and they should be aware of it and understand it. We found that credit provisioning is used as an earnings management mechanism to smooth the net income of Brazilian financial institutions. Brazilian banks tend to avoid not only negative net income pre-loan loss provisions and taxes, but also negative net income pre-loan loss provisions and taxes in relation to the previous period. Contrary to the previous studies, it is not clear if banks avoid lower net income pre-loan loss provisions and taxes than a given peer group.

  10. Recent trends in Brazilian Historical Linguistics

    OpenAIRE

    SILVA, Rosa Virgínia Mattos e

    1999-01-01

    The paper concentrates on the new directions taken by Historical Linguistics in Brazil, which gives special attention to Brazilian Portuguese, studying dialectal and sociolinguistic aspects. A special reference is made to projects that bring together researchers from several universities in the country.

  11. 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.

  12. 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.

  13. 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.

    The Vessel-Mounted Acoustic Doppler Current Profiler (VM-ADCP) measured currents in the upper 200 m along the cruise track covering the southeastern Arabian Sea and the Eastern Equatorial Indian Ocean during northern winter monsoon (10-31 December...

  14. Comparison of drift velocities of nighttime equatorial plasma depletions with ambient plasma drifts and thermospheric neutral winds

    NARCIS (Netherlands)

    Liu, G.; England, S.L.; Frey, H.U.; Immel, T.J.; Lin, C.S.; Pacheco, E.E.; Häusler, K.; Doornbos, E.N.

    2013-01-01

    This is the first study to compare plasma depletion drifts with the ambient plasma drifts and neutral winds in the post sunset equatorial ionosphere using global-scale satellite observations. The local time and latitude variations of the drift velocities of O+ plasma depletions at 350–400?km

  15. High-resolution 14C dating of a 25,000-year lake-sediment record from equatorial East Africa

    NARCIS (Netherlands)

    Blaauw, M.; van Geel, B.; Kristen, I.; Plessen, B.; Lyaruu, A.; Engstrom, D.R.; van der Plicht, J.; Verschuren, D.

    2011-01-01

    We dated a continuous, ∼22-m long sediment sequence from Lake Challa (Mt. Kilimanjaro area, Kenya/Tanzania) to produce a solid chronological framework for multi-proxy reconstructions of climate and environmental change in equatorial East Africa over the past 25,000 years. The age model is based on a

  16. High-resolution C-14 dating of a 25,000-year lake-sediment record from equatorial East Africa

    NARCIS (Netherlands)

    van Geel, Bas; Kristen, Iris; Plessen, Birgit; Lyaruu, Anna; Engstrom, Daniel R.; van der Plicht, Johannes; Verschuren, Dirk; Blaauw, Maarten

    2011-01-01

    We dated a continuous, similar to 22-m long sediment sequence from Lake Challa (Mt. Kilimanjaro area, Kenya/Tanzania) to produce a solid chronological framework for multi-proxy reconstructions of climate and environmental change in equatorial East Africa over the past 25,000 years. The age model is

  17. 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.

  18. 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.

  19. Jupiter's North Equatorial Belt expansion and thermal wave activity ahead of Juno's arrival

    Science.gov (United States)

    Fletcher, L. N.; Orton, G. S.; Sinclair, J. A.; Donnelly, P.; Melin, H.; Rogers, J. H.; Greathouse, T. K.; Kasaba, Y.; Fujiyoshi, T.; Sato, T. M.; Fernandes, J.; Irwin, P. G. J.; Giles, R. S.; Simon, A. A.; Wong, M. H.; Vedovato, M.

    2017-07-01

    The dark colors of Jupiter's North Equatorial Belt (NEB, 7-17°N) appeared to expand northward into the neighboring zone in 2015, consistent with a 3-5 year cycle. Inversions of thermal-IR imaging from the Very Large Telescope revealed a moderate warming and reduction of aerosol opacity at the cloud tops at 17-20°N, suggesting subsidence and drying in the expanded sector. Two new thermal waves were identified during this period: (i) an upper tropospheric thermal wave (wave number 16-17, amplitude 2.5 K at 170 mbar) in the mid-NEB that was anticorrelated with haze reflectivity; and (ii) a stratospheric wave (wave number 13-14, amplitude 7.3 K at 5 mbar) at 20-30°N. Both were quasi-stationary, confined to regions of eastward zonal flow, and are morphologically similar to waves observed during previous expansion events.

  20. Capabilities of the ITER Electron Cyclotron Equatorial Launcher for Heating and Current Drive

    Directory of Open Access Journals (Sweden)

    Ramponi G.

    2012-09-01

    Full Text Available The ITER Electron Cyclotron Equatorial Launcher is designed to be one of the heating systems to assist and sustain the development of various ITER plasma scenarios starting with the very first plasma operation. Here the capabilities for Heating and Current Drive of this system are reviewed. In particular, the optimum launching conditions are investigated for two scenarios at burn, comparing toroidal and poloidal steering options. Then, the EC capabilities are investigated for different plasma parameters corresponding to various phases of the ITER plasma discharge, from current ramp-up up to burn, and for a wide range of magnetic field, focusing in particular on the EC potential for heating and for L to H-mode assist. It is found that the EC system can contribute to a wide range of heating scenarios during the ramp-up of the magnetic field, significantly increasing the applicable range as a function of magnetic field.

  1. Exotic outcross between late Miocene polycystine radiolaria from the central equatorial Pacific Ocean

    Science.gov (United States)

    Goll, Robert M.

    1985-09-01

    Sphaerospyris? sp. is a unique megalocephalic nassellarian that has been studied in two piston cores from the central equatorial Pacific Ocean. This large morph first appeared about 9.5 Ma (near the top of the Diartus petterssoni Biozone) and had its last occurrence about 6.5 Ma (near the base of the Dimymocyrtis penultimus Biozone). There is no descendant lineage. The species was not found in time-equivalent recovery from Deep Sea Drilling Project Sites 65, 77, 83, and 289. The rare and somewhat sporadic occurrence of Sphaerospyris? sp. is attributed to hybridization between Acanthosphaera? sp. (Spumellarida) and Nephrospyris leibnitziana (Nassellarida). Skeletal characters of the parent species appear to have been exchanged through the process of introgression, which was the most important evolutionary agent in these lineages. The introduction of new morphological variants by introgression may have general significance in pelagic plankton communities.

  2. 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.

  3. The Palermo Merz Equatorial Telescope. An Instrument, a Manuscript, Some Drawings.

    Science.gov (United States)

    Chinnici, Ileana; Brenni, Paolo

    2015-01-01

    A manuscript by Georg and Sigmund Merz dated 1862 and containing instructions for assembling the equatorial telescope acquired by the Palermo Observatory is conserved in the archives of the Museo Astronomico e Copernicano in Rome. It is a rare document that reveals "tricks of the trade" and technical knowledge not usually included in textbooks or treatises. It was sent to the Palermo Observatory as an aid to the installation of the telescope, which made a signal contribution to the development of solar physics in Italy in the 19th century. Based on the study of unpublished sources (consisting of texts and drawings), the history of the instrument has been retraced. This paper presents a detailed description of the Merz manuscript (including a complete transcript) and some technical drawings recently discovered in the archives of the Palermo Observatory.

  4. Model studies of the latitudinal extent of the equatorial anomaly during equinoctial conditions

    Energy Technology Data Exchange (ETDEWEB)

    Klobuchar, J.A.; Anderson, D.N.; Doherty, P.H. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States) Boston College, Newton, MA (United States))

    1991-08-01

    The latitudinal extent of the equatorial anomaly region (typically between +/- 20-deg magnetic latitude) at equinoctial conditions was investigated using a theoretical model of the ionosphere which incorporates realistic values of neutral winds and data on vertical E x B drift at the earth's magnetic equator. It was found that the differences between the average location of the latitudinal crest in the peak electron density from solar minimum to solar maximum conditions are only 2 to 3 deg in average altitude and that the effects of large E x B drifts are seen at greater distances from the equator during solar maximum conditions. Results from the model studies with different values of realistic electric fields show that the effects of the anomaly can be more highly variable and widespread in latitude and local time than is generally assumed. 22 refs.

  5. The spectral extent of chorus in the off-equatorial magnetosphere

    Science.gov (United States)

    Bunch, N. L.; Spasojevic, M.; Shprits, Y. Y.; Gu, X.; Foust, F.

    2013-04-01

    Magnetospheric chorus waves are a major driver of acceleration and loss in the Earth's outer electron radiation belt. The spectral extent of chorus is a key parameter in quantifying the global effect of chorus on energetic particle populations by determining the range of resonant electron energies. However, statistics of spectral properties are sparse, particularly in the off-equatorial magnetosphere. We use a database of chorus observations from the Polar spacecraft to generate statistics on the normalized chorus frequency (with the respect to the minimum field line gyrofrequency, Ωmin) as a function of magnetic local time (MLT) (0 normalized chorus peak frequency is found to decrease with increasing R0, and decreases with increasing latitude below ˜ 25°. When fit to a Gaussian spectral model, lower band chorus is found to have a bandwidth forms may improve the accuracy of wave models within radiation belt simulations.

  6. Characteristics of VLF emissions observed by DE-1 in the equatorial magnetosphere

    Science.gov (United States)

    Ondoh, T.; Nakamura, Y.

    Whistler-triggered hiss, banded hiss, ELF hiss, impulsive VLF waves and magnetospheric chorus are analysed by using analog data of wideband electric fields (650 Hz - 40 kHz) from DE-1 satellite received at Kashima, Japan in the NASA DE guest investigator program. The whistler-triggered hiss was observed after a whistler trace at frequencies below about 15 kHz in low-latitude plasmasphere, and its generation models are discussed. Wave modes of banded hiss, impulsive VLF waves and ELF hiss successively observed for about one minute are discussed in terms of the spin modulated effect of whistler-mode ELF hiss. Magnetospheric chorus with a frequency gap around 5.8 kHz was observed in the geomagnetic storm recovery phase. This indicates a field decrease by about one fifth of the quiet-time geomagnetic field produced by a storm-time equatorial ring current.

  7. Nonlinear features of equatorial baroclinic Rossby waves detected in Topex altimeter observations

    Directory of Open Access Journals (Sweden)

    R. E. Glazman

    1996-01-01

    Full Text Available Using a recently proposed technique for statistical analysis of non-gridded satellite altimeter data, regime of long equatorially-trapped baroclinic Rossby waves is studied. One-dimensional spatial and spatiotemporal autocorrelation functions of sea surface height (SSH variations yield a broad spectrum of baroclinic Rossby waves and permit determination of their propagation speed. The 1-d wavenumber spectrum of zonal variations is given by a power-law k-2 on scales from about 103 km to 104 km. We demonstrate that the observed wave regime exhibits features of soliton turbulence developing in the long baroclinic Rossby waves. However, being limited to second statistical moments, the present analysis does not allow us to rule out a possibility of weak wave turbulence.

  8. 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.

  9. Karstic terrain in the equatorial layered deposits within a crater in northern Sinus Meridiani, Mars.

    Science.gov (United States)

    Baioni, Davide

    2017-04-01

    This work investigates the equatorial layered deposits (ELDs) located within a crater located in northern Sinus Meridiani, Mars (4.430 N, 3.320 W), which display traits that are consistent with formation by karst-driven processes. Here, shallow depressions showing a variety of plan forms ranging from rounded, circular, elongated, polygonal and drop-like to elliptical can be observed. The morphologic and morphometric analyses performed, highlight that these depressions display strong morphometric (sizes) and morphologic (shapes, bottoms, walls) similarities with the karst depressions that are common on limestone and evaporite terrains on the Earth and other regions on Mars. On the basis of the characteristics of the investigated landforms and the similarities of features on Earth and Mars, and after discarding other possible origins such as, aeolian, periglacial, volcanic or impact related processes, it has been inferred that the depressions are karstic dolines formed polygenetically by corrosion and solution-related intra-crater processes.

  10. Topside equatorial zonal ion velocities measured by C/NOFS during rising solar activity

    Directory of Open Access Journals (Sweden)

    W. R. Coley

    2014-02-01

    Full Text Available The Ion Velocity Meter (IVM, a part of the Coupled Ion Neutral Dynamic Investigation (CINDI instrument package on the Communication/Navigation Outage Forecast System (C/NOFS spacecraft, has made over 5 yr of in situ measurements of plasma temperatures, composition, densities, and velocities in the 400–850 km altitude range of the equatorial ionosphere. These measured ion velocities are then transformed into a coordinate system with components parallel and perpendicular to the geomagnetic field allowing us to examine the zonal (horizontal and perpendicular to the geomagnetic field component of plasma motion over the 2009–2012 interval. The general pattern of local time variation of the equatorial zonal ion velocity is well established as westward during the day and eastward during the night, with the larger nighttime velocities leading to a net ionospheric superrotation. Since the C/NOFS launch in April 2008, F10.7 cm radio fluxes have gradually increased from around 70 sfu to levels in the 130–150 sfu range. The comprehensive coverage of C/NOFS over the low-latitude ionosphere allows us to examine variations of the topside zonal ion velocity over a wide level of solar activity as well as the dependence of the zonal velocity on apex altitude (magnetic latitude, longitude, and solar local time. It was found that the zonal ion drifts show longitude dependence with the largest net eastward values in the American sector. The pre-midnight zonal drifts show definite solar activity (F10.7 dependence. The daytime drifts have a lower dependence on F10.7. The apex altitude (magnetic latitude variations indicate a more westerly flow at higher altitudes. There is often a net topside subrotation at low F10.7 levels, perhaps indicative of a suppressed F region dynamo due to low field line-integrated conductivity and a low F region altitude at solar minimum.

  11. Relationships between electron density, height and sub-peak ionospheric thickness in the night equatorial ionosphere

    Directory of Open Access Journals (Sweden)

    K. J. W. Lynn

    2006-07-01

    Full Text Available The development and decay of the southern equatorial anomaly night-time peak in electron density as seen at a number of ionosonde reflection points extending from New Guinea and Indonesia into northern Australia was examined in terms of the characteristic rise and fall in height associated with the sunset ionisation-drift vortex at the magnetic equator. The observations relate to measurements made in November 1997. Following sunset, the ionospheric profile was observed to narrow as the maximum electron density increased during a fall in height that took the peak of the layer at Vanimo and Sumedang down to some 240 km. The fall was followed by a strong rise in which the electron density sub-peak profile expanded from a slab width (as given by POLAN of 20 km to over 100km with no corresponding change in peak electron density. The post-sunset equatorial fall in height and associated changes in profile density and thickness continued to be seen with diminishing amplitude and increasing local time delay in moving from the anomaly peak at Vanimo to the southernmost site of observation at Townsville. Secondary events on a lesser scale sometimes occurred later in the night and may provide evidence of the multiple vortices suggested by Kudeki and Bhattacharyya (1999. Doppler measurements of vertical velocity as seen at Sumedang in Java are compared with the observed changes in electron density profile in the post-sunset period. The normal post-sunset variation in ionospheric parameters was disrupted on the night of 7 November, the night before a negative ionospheric storm was observed.

  12. Palaeoceanographic productivity changes in the Eastern Equatorial Atlantic since the penultimate glaciation

    Science.gov (United States)

    Lem, Rachael; Marshall, Jim; Leng, Melanie; Marret, Fabienne

    2017-04-01

    A 150,000 year multiproxy record from the eastern equatorial Atlantic, offshore Gabon, has been investigated in order to examine the effects of changing glacial - interglacial climate on marine productivity. Higher δ13C values of the benthic foraminifera Planulina wuellerstorfi are documented during the penultimate glaciation (150 -130 kyr BP) in comparison to the Last Glacial Maximum [LGM] (24.5 - 19 kyr BP). In conjunction with higher CaCO3 and larger variability in the isotopic difference between surface and bottom waters during the penultimate glaciation, this suggests that the eastern equatorial Atlantic was much more productive at this time than the LGM, most likely driven by increased nutrient input through strong bottom water upwelling. The benthic δ18O and planktonic δ18O record of Globigerinoides ruber (white) infer that both the surface and bottom waters were warmer during the penultimate glaciation than the LGM. The sea surface temperature [SST] record assimilated through Mg/Ca analysis of the G. ruber evidences much lower SSTs during the last deglaciation in comparison with other regional records, and with the present day SST, which together with high Fe input, we attribute this to a greatly enhanced discharge of the Ogooué River. Bulk coccolith carbonate δ13C demonstrates a shift towards lower δ13C values from the penultimate glaciation towards present day which does not dovetail the other proxies. The δ18O coccolith record mirrors that of G. ruber during the two glacial periods, but presents much higher isotopic values during the interglacials. We interpret this as a shift in seasonality in the calcification of the coccoliths between glacial and interglacial periods, which in combination with the long term decline in δ13C values reflects a change in the habitat preferences of this phytoplankton over the last glacial - interglacial cycle.

  13. Calculation of the cross-sectional shape of a fibril from equatorial scattering.

    Science.gov (United States)

    Roig-Solvas, Biel; Makowski, Lee

    2017-12-01

    An alternate formulation of helical diffraction theory is used to generate cross-sectional shapes of fibrous structures from equatorial scattering. We demonstrate this approach with computationally generated scattering intensities and then apply it to scattering data from Tobacco Mosaic Virus (TMV) and in vitro assembled fibrils of Aβ40 peptides. Refining the cross-sectional shape of TMV from SAXS data collected on a 26mg/ml solution resulted in a circular shape with outer diameter of ∼180Å and inner diameter of ∼40Å consistent with the known structure of TMV. We also utilized this method to analyze the equatorial scattering from TMV collected by Don Caspar from a concentrated (24% ∼295mg/ml) gel of TMV as reported in his Ph.D. thesis in 1955. This data differs from the SAXS data in having a sharp interference peak at ∼250Å spacing, indicative of strong interparticle interactions in the gel. Analysis of this data required consideration of interatomic vectors as long as 2000Å and resulted in generation of images that were interpreted as representative of local organization of TMV particles in the sample. Peaks in the images were separated, on average by about 250Å with a density consistent with Caspar's original measurements. Analysis of SAXS data from Aβ fibrils resulted in a cross-sectional shape that could be interpreted in terms of structural models that have been constructed from ssNMR and cryoEM. These results demonstrate an unexpected use of the small-angle region of fiber diffraction patterns to derive fundamental structural properties of scattering objects. Copyright © 2017. Published by Elsevier Inc.

  14. From the African Coast, the invention of two territories: Equatorial Guinea and Ivory Coast

    Directory of Open Access Journals (Sweden)

    Adjoa Nathalie Chiyé Kessé

    2014-08-01

    Full Text Available From the African coast starts Latin American history and part of Europe’s. This article includes a comprehensive analysis on the cultural influence of Africa especially Equatorial Guinea and Côte d’Ivoire in Latin America. From the first European incursions into African coast (xvi century and throughout the colonial era, the paper highlights interethnic relations that occurred following the meeting and coexistence between cultures of both continents, an analysis that is essential to study the survival of traditions, beliefs and African customs that survive today in many regions of Latin America. Considering the importance now given to the recovery of identity traits of the past for studies of multi-ethnicity and re-construction of identities, this article can be used by researchers at Afro-descendance, notable in Latin America, whose research is related to African identity traits in their respective nations. Equatorial Guinea was a Spanish colony along with the Protectorate of Morocco and Western Sahara. The duration of this colony ran from 1885 to 1968. In 1926, it became the Spanish Guinea, and in 1968 it acquired its independance from Spain while retaining the Spanish cultural architecture. Furthermore, the French presence in this first stage of the conquest in Côte d’Ivoire, is provided by the army. The colonial authorities in Paris were not yet sufficiently organized to move their representatives to what was then known as the Poor or Bad People Coast or Coast of teeth. It was the military from Senegal, as base of the French colonial army who assumed the conquest and organization of the Ivorian territory for immediate exploitation of economic resources. It is this improvised framework without legal planning, which led to the idea of the invention of Africa supported by Valentin Mudimbe (1988 and Achille Mbembe (2000.

  15. Responses of equatorial anomaly to the October-November 2003 superstorms

    Directory of Open Access Journals (Sweden)

    B. Zhao

    2005-03-01

    Full Text Available The responses of Equatorial Ionization Anomaly (EIA to the superstorms of October-November 2003 were investigated using the total electron content (TEC measured with global positioning system (GPS receivers in China, Southeast Asia, Australian (CSAA, and the American regions. Enhanced EIA was seen to be correlated with the southward turning of the interplanetary magnetic field Bz. In both the CSAA and American regions, EIA was intensified, corresponding to a large increase in the F-layer peak height (hmF2 measured by ionosonde and digisonde at middle and equatorial latitudes. However, the enhanced EIA was shown to be more significant during the daytime in the American region, which was associated with a series of large substorms when Bz was stable southward. The prompt penetration electric field and the wind disturbances dynamo electric field are suggested to be responsible for this observation according to current theory, although some features cannot be totally decipherable. Both the ionogram and magnetometer data show the existence of a weak shielding effect whose effect still needs further study. A clear asymmetric ionospheric response was shown in our TEC observations, even though it was only one month after autumnal equinox. The southern EIA crest was totally obliterated on 29 and 30 October in the CSAA region and on 31 October in the American region. Ion temperatures from the Defense Meteorological Satellite Program (DMSP spacecraft revealed that the unequal energy injection at the polar region might be the reason for this effect. It is concluded that different physical processes have varying degrees of importance on the evolution of EIA in the CSAA and American regions.

  16. 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.

  17. Responses of equatorial anomaly to the October-November 2003 superstorms

    Directory of Open Access Journals (Sweden)

    B. Zhao

    2005-03-01

    Full Text Available The responses of Equatorial Ionization Anomaly (EIA to the superstorms of October-November 2003 were investigated using the total electron content (TEC measured with global positioning system (GPS receivers in China, Southeast Asia, Australian (CSAA, and the American regions. Enhanced EIA was seen to be correlated with the southward turning of the interplanetary magnetic field Bz. In both the CSAA and American regions, EIA was intensified, corresponding to a large increase in the F-layer peak height (hmF2 measured by ionosonde and digisonde at middle and equatorial latitudes. However, the enhanced EIA was shown to be more significant during the daytime in the American region, which was associated with a series of large substorms when Bz was stable southward. The prompt penetration electric field and the wind disturbances dynamo electric field are suggested to be responsible for this observation according to current theory, although some features cannot be totally decipherable. Both the ionogram and magnetometer data show the existence of a weak shielding effect whose effect still needs further study. A clear asymmetric ionospheric response was shown in our TEC observations, even though it was only one month after autumnal equinox. The southern EIA crest was totally obliterated on 29 and 30 October in the CSAA region and on 31 October in the American region. Ion temperatures from the Defense Meteorological Satellite Program (DMSP spacecraft revealed that the unequal energy injection at the polar region might be the reason for this effect. It is concluded that different physical processes have varying degrees of importance on the evolution of EIA in the CSAA and American regions.

  18. Characteristics of rainfall queues for rain attenuation studies over radio links at subtropical and equatorial Africa

    Science.gov (United States)

    Alonge, Akintunde A.; Afullo, Thomas J.

    2014-08-01

    Attenuation due to precipitation remains an important design factor in the future deployment of terrestrial and earth-space communication radio links. Largely, there are concerted efforts to understand the dynamics of precipitation in attenuation occurrence at subtropical, tropical, and equatorial region of Africa. In this deliberate approach, rainfall spikes pertaining to rain cells are conceptualized as distinct rain spike traffic over radio links, by applying queueing theory concepts. The queue distributions at Durban (29°52'S, 30°58'E) and Butare (2°36'S, 29°44'E)—respectively, of subtropical and equatorial climates—are investigated from distrometer measurements. The data sets at both sites are observed over four rain regimes: drizzle, widespread, shower, and thunderstorm. The queue parameters of service time and inter-arrival of rain spikes traffic at both regions are found to be Erlang-k distributed (Ek) and exponentially distributed (M), respectively. It is established that the appearance of rain rates over radio links invariably follows a First Come, First Served (FCFS), multi-server (s), infinite queue, and semi-Markovian process, designated as M/Ek/s/∞/FCFS discipline. Modeled queue parameters at both regions are found to vary significantly over different regimes. However, these queue parameters over the entire data set suggest similar queue patterns at both sites. More importantly, power law relationships describing other queue-related parameters are formulated. The paper concludes by demonstrating an application of queueing theory for rainfall synthesis. The proposed technique will provide an alternative method of estimating rain cell sizes and rain attenuation over satellite and terrestrial links.

  19. Response of equatorial ionosphere to episodes of asymmetric ring current activity

    Directory of Open Access Journals (Sweden)

    J. H. Sastri

    1997-10-01

    Full Text Available We present the characteristics of the response of equatorial ionospheric zonal electric field and F-region plasma density to the asymmetric ring current intensifications that occurred in succession on 16 December 1991, corresponding to the STEP/EITS-2 campaign period. The study is based on high-time- resolution (1-min data of asymmetic ring current indices, ASY(H/D and F-region vertical plasma drift, Vz measurements at Kodaikanal (10.25°N; 77.5°E; dip 4°, India and quarter-hourly ionosonde data of Fortaleza (4°S; 322°E; dip –9°, Brazil. It is shown that short-lived disturbances in F-layer vertical plasma drift, Vz and height (h'F/hpF2 indicative of westward and eastward electric fields prevail simultaneously in the dusk (18–21 LT and predawn (02–05 LT sectors, respectively, in association with the decay phase of asymmetic ring current events. Electric fields of opposite polarity do also seem to manifest at these local times, particularly in the early-morning sector in conjunction with the intensification of the asymmetric ring current. At a given location, electric field disturbances associated with individual asymmetric ring current events are thus bipolar in nature, with fields of opposite polarity during the growth and decay phases. The nature and polarity structure of the observed electric field disturbances are in agreement with the theoretical/model predictions of prompt penetration of high-latitude electric fields to the equatorial region.

  20. 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.