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Sample records for na margem equatorial

  1. Probing the equatorial groove of the hookworm protein and vaccine candidate antigen, Na-ASP-2.

    PubMed

    Mason, Lyndel; Tribolet, Leon; Simon, Anne; von Gnielinski, Natascha; Nienaber, Lisa; Taylor, Paul; Willis, Charlene; Jones, Malcolm K; Sternberg, Paul W; Gasser, Robin B; Loukas, Alex; Hofmann, Andreas

    2014-05-01

    Hookworm activation-associated secreted proteins can be structurally classified into at least three different groups. The hallmark feature of Group 1 activation-associated secreted proteins is a prominent equatorial groove, which is inferred to form a ligand binding site. Furthermore, a conserved tandem histidine motif is located in the centre of the groove and believed to provide or support a yet to be determined catalytic activity. Here, we report three-dimensional crystal structures of Na-ASP-2, an L3-secreted activation-associated secreted protein from the human hookworm Necator americanus, which demonstrate transition metal binding ability of the conserved tandem histidine motif. We further identified moderate phosphohydrolase activity of recombinant Na-ASP-2, which relates to the tandem histidine motif. By panning a random 12-mer peptide phage library, we identified a peptide with high similarity to the human calcium-activated potassium channel SK3, and confirm binding of the synthetic peptide to recombinant Na-ASP-2 by differential scanning fluorimetry. Potential binding modes of the peptide to Na-ASP-2 were studied by molecular dynamics simulations which clearly identify a preferred topology of the Na-ASP-2:SK3 peptide complex.

  2. Equatorial Guinea.

    PubMed

    1989-03-01

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

  3. Equatorial Guinea.

    PubMed

    1984-06-01

    Attention in this discussion of Equatorial Guinea is directed to the following: the people, history, geography, government, political conditions, the economy, foreign relations, and relations between the US and Equatorial Guinea. The population was estimated at 304,000 in 1983 and the annual growth rate was estimated in the range of 1.7-2.5. The infant mortality rate is 142.9/1000 with a life expectancy of 44.4 years for males and 47.6 years for females. The majority of the Equatoguinean people are of Bantu origin. The largest tribe, the Fang, is indigenous to the mainland, although many now also live on Bioko Island. Portuguese explorers found the island of Bioko in 1471, and the Portuguese retained control until 1778, when the island, adjacent islets, and the commercial rights to the mainland between the Niger and Ogooue Rivers were ceded to Spain. Spain lacked the wealth and the interest to develop an extensive economic infrastructure in Equatorial Guinea during the 1st half of this century, but the Spanish did help Equatorial Guinea achieve 1 of the highest literacy rates in Africa. They also founded a good network of health care facilities. In March 1968, under pressure from Guinean nationalists, Spain announced that it would grant independence to Equatorial Guinea as rapidly as possible. A referendum was held on August 11, 1968, and 63% of the electorate voted in favor of the constitution, which provided for a government with a general assembly and presidentially appointed judges in the Supreme Court. After the coup in August 1979, power was placed in the hands of a Supreme Military Council. A new constitution came into effect after a popular vote in August 1982, abolishing the Supreme Military Council. Under the terms of the constitution, the president was given extensive powers. By the end of 1983, a 60-member Chamber of Representatives of the people had been formed. The government, which is credited with restoring greater personal freedom, is regarded

  4. Multiwavelength observations of NaSt1 (WR 122): equatorial mass loss and X-rays from an interacting Wolf-Rayet binary

    NASA Astrophysics Data System (ADS)

    Mauerhan, Jon; Smith, Nathan; Van Dyk, Schuyler D.; Morzinski, Katie M.; Close, Laird M.; Hinz, Philip M.; Males, Jared R.; Rodigas, Timothy J.

    2015-07-01

    NaSt1 (aka Wolf-Rayet 122) is a peculiar emission-line star embedded in an extended nebula of [N II] emission with a compact dusty core. The object was previously characterized as a Wolf-Rayet (WR) star cloaked in an opaque nebula of CNO-processed material, perhaps analogous to η Car and its Homunculus nebula, albeit with a hotter central source. To discern the morphology of the [N II] nebula we performed narrow-band imaging using the Hubble Space Telescope and Wide-field Camera 3. The images reveal that the nebula has a disc-like geometry tilted ≈12° from edge-on, composed of a bright central ellipsoid surrounded by a larger clumpy ring. Ground-based spectroscopy reveals radial velocity structure (±10 km s-1) near the outer portions of the nebula's major axis, which is likely to be the imprint of outflowing gas. Near-infrared adaptive-optics imaging with Magellan AO has resolved a compact ellipsoid of Ks-band emission aligned with the larger [N II] nebula, which we suspect is the result of scattered He I line emission (λ2.06 μm). Observations with the Chandra X-ray Observatory have revealed an X-ray point source at the core of the nebula that is heavily absorbed at energies <1 keV and has properties consistent with WR stars and colliding-wind binaries. We suggest that NaSt1 is a WR binary embedded in an equatorial outflow that formed as the result of non-conservative mass transfer. NaSt1 thus appears to be a rare and important example of a stripped-envelope WR forming through binary interaction, caught in the brief Roche lobe overflow phase.

  5. Equatorial potassium currents in lenses.

    PubMed

    Wind, B E; Walsh, S; Patterson, J W

    1988-02-01

    Earlier work with the vibrating probe demonstrated the existence of outward potassium currents at the equator and inward sodium currents at the optical poles of the lens. By adding microelectrodes to the system, it is possible to relate steady currents (J) to the potential difference (PD) measured with a microelectrode. By injecting an outward current (I), it is possible to determine resistances and also the PD at which the steady outward potassium current becomes zero (PDJ = 0). At this PD the concentration gradient for potassium efflux and the electrical gradient for potassium influx are balanced so that there is no net flow of potassium across the membranes associated with the production of J. The PDJ = 0 for 18 rat lenses was 86 mV and that for 12 frogs lenses was -95 mV. This agrees with the potassium equilibrium potential and provides strong evidence to support the view that the outward equatorial current, J, is a potassium current. With the injection of outward current, I, the PD becomes more negative, the outward equatorial current, J, decreases, and the inward current at the optical poles increases. This suggests that there are separate electrical loops for K+ and Na+ that are partially linked by the Na, K-pump. Using Ohm's law, it is possible to calculate the input resistance (R = delta PD/I), the resistance related to the production of J (RJ = delta PD/delta J), and the effect of the combined resistances (delta J/I). The driving force for J can be estimated (PDJ = 0-PD). The relationships among currents, voltages and resistance can be used to determine the characteristics of the membranes that are associated with the outward potassium current observed at the equator. The effects of graded deformation of the lens were determined. The effects were reversible. The sites of inward and outward currents were not altered. Following deformation, the equatorial current, J, increased, and the PD became less negative. The PDJ = 0 remains the same so the ratio of K

  6. Study of equatorial scintillations

    NASA Technical Reports Server (NTRS)

    Pomalaza, J.; Woodman, R.; Tisnado, G.; Nakasone, E.

    1972-01-01

    Observations of the amplitude scintillations produced by the F-region in equatorial areas are presented. The equipment used for conducting the observations is described. The use of transmissions from the ATS-1, ATS-3, and ATS-5 for obtaining data is described. The two principal subjects discussed are: (1) correlation between satellite and incoherent radar observations of scintillations and (2) simultaneous observations of scintillations at 136 MHz and 1550 MHz.

  7. An Equatorial Scintillation Model

    DTIC Science & Technology

    1985-09-30

    been incor- porated into Program WBMOD along with subroutines for computing both link geometry and scintillation indices, the latter by means of...phase4screen diffraction theory. , Earlier versions of WBMOD , which are operational at USAF Global Weather Central and at several other user locations...which has been incorporated in WBMOD Version 8DI, is based on similarly extensive analysis of Wideband data from two equatorial stations. It describes

  8. An equatorial scintillation model

    NASA Astrophysics Data System (ADS)

    Fremouw, E. J.; Robins, R. E.

    1985-09-01

    Radiowave scintillation in the presence of natural and/or high altitude nuclear disturbances has the potential to disrupt numerous transionospheric radio and radar systems. This report develops a model characterizing the plasma density irregularities that produce scintillation in the naturally disturbed equatorial F layer. The model has been incorporated into Program WBMOD along with subroutines for computing both link geometry and scintillation indices, the latter by means of phase screen diffraction theory. The model is based on similarly extensive analysis of Wideband data from two equatorial stations. It describes irregularities at an effective height of 350 km that are isotropic across the geomagnetic field and elongated by a factor of 50 along the field and whose one dimensional spatial power spectrum obeys a single regime power law with a (negative) spectral index of 1.5. The height-integrated spectral strength of the irregularities is modeled as a function of solar epoch (sunspot number), the angle between the sunset terminator and the geomagnetic field line through the equatorial F layer point in question (a measure of seasonal and longitudinal variation), time after E-layer sunset on that field line, and the F-layer magnetic apex latitude of the point. The report also highlights a factor missing from complete characterization of the joint seasonal/longitudinal variation of scintillation, thought to depend upon thermospheric neutral winds.

  9. Jupiter Equatorial Region

    NASA Image and Video Library

    1998-03-06

    This photographic mosaic of images from NASA's Galileo spacecraft covers an area of 34,000 kilometers by 22,000 kilometers (about 21,100 by 13,600 miles) in Jupiter's equatorial region. The dark region near the center of the mosaic is an equatorial "hotspot" similar to the site where the Galileo Probe parachuted into Jupiter's atmosphere in December 1995. These features are holes in the bright, reflective, equatorial cloud layer where heat from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright oval in the upper right of the mosaic as well as the other smaller bright features are examples of upwelling of moist air and condensation. These images were taken on December 17, 1996, at a range of 1.5 million kilometers (about 930,000 miles) by the Solid State Imaging camera system aboard Galileo. North is at the top. The mosaic covers latitudes 1 to 19 degrees and is centered at longitude 336 degrees west. The smallest resolved features are tens of kilometers in size. http://photojournal.jpl.nasa.gov/catalog/PIA00604

  10. Metallic ions in the equatorial ionosphere

    NASA Technical Reports Server (NTRS)

    Aikin, A. C.; Goldberg, R. A.

    1972-01-01

    Four positive ion composition measurements of the equatorial E region made at Thumba, India, are presented. During the day, the major ions between 90 and 125 km are NO(+) and O2(+). A metallic ion layer centered at 92 km is observed, and found to contain Mg(+), Fe(+), Ca(+), K(+), Al(+), and Na(+) ions. The layer is explained in terms of a similarly shaped latitude distribution of neutral atoms which are photoionized and charge-exchanged with NO(+) and O2(+). Three body reactions form molecular metallic ions which are rapidly lost by dissociative ion-electron recombination. Nighttime observations show downward drifting of the metallic ion layer caused by equatorial dynamo effects. These ions react and form neutral metals which exchange charges with NO(+) and O2(+) to produce an observed depletion of those ions within the metallic ion region.

  11. Equatorial Wave Line, Pacific Ocean

    NASA Technical Reports Server (NTRS)

    1993-01-01

    This Equatorial Wave Line (2.0 N, 102.5W) seen in the Pacific Ocean is of great interest to oceanographers because of the twice annual upwelling of the oceans nutrients. As a result of nearly constant easterly winds, cool nutrient rich water wells up at the equator. The long narrow line is an equatorial front or boundry between warm surface equatorial water and cool recently upwelled water as the intermix of nutrients takes place.

  12. Iapetus' Equatorial Region

    NASA Image and Video Library

    2007-10-09

    Cassini made a close flyby of Saturn's moon Iapetus on Sept. 10, 2007, and the visual and infrared mapping spectrometer obtained these images during that event. These two images show a higher resolution version of the equatorial region shown in PIA10010. The equatorial region includes the equatorial bulge which shows no differences in these compositions compared to surrounding regions. The color image on the right shows the results of mapping for three components of Iapetus' surface: carbon dioxide that is trapped or adsorbed in the surface (red), water in the form of ice (green), and a newly-discovered effect due to trace amount of dark particles in the ice creating what scientists call Rayleigh scattering (blue). The Rayleigh scattering effect is the main reason why the Earth's sky appears blue. There is a complex transition zone from the dark region, on the right, which is high in carbon dioxide, to the more ice-rich region on the left. Some crater floors are filled with carbon dioxide-rich dark material. As the ice becomes cleaner to the left, the small dark particles become more scattered and increase the Rayleigh scattering effect, again indicative of less than 2 percent dark sub-0.5-micron particles. The visual and infrared mapping spectrometer is like a digital camera, but instead of using three colors, it makes images in 352 colors, or wavelengths, from the ultraviolet to the near-infrared. The many wavelengths produce a continuous spectrum in each pixel, and these spectra measure how light is absorbed by different materials. By analyzing the absorptions expressed in each pixel, a map of the composition at each location on the moon can be constructed. http://photojournal.jpl.nasa.gov/catalog/PIA10011

  13. Equatorial oceanography. [review of research

    NASA Technical Reports Server (NTRS)

    Cane, M. A.; Sarachik, E. S.

    1983-01-01

    United States progress in equatorial oceanography is reviewed, focusing on the low frequency response of upper equatorial oceans to forcing by the wind. Variations of thermocline depth, midocean currents, and boundary currents are discussed. The factors which determine sea surface temperature (SST) variability in equatorial oceans are reviewed, and the status of understanding of the most spectacular manifestation of SST variability, the El Nino-Southern Oscillation phenomenon, is discussed. The problem of observing surface winds, regarded as a fundamental factor limiting understanding of the equatorial oceans, is addressed. Finally, an attempt is made to identify those current trends which are expected to bear fruit in the near and distant future.

  14. Modeling the equatorial electrojet

    NASA Astrophysics Data System (ADS)

    Stening, R. J.

    1985-02-01

    The equatorial electrojet is studied using a conductivity model with electron collision frequencies consistent with laboratory results. Electric fields and currents are calculated by an equivalent circuit method, and the results are compared with observations. Results are obtained for the electrojet height profile, the height and latitude of the cross-section profile, the height-integrated current density, the internal currents contribution, the scaling problem, the horizontal and vertical magnetic variation with latitude, and the effects of local winds in the F region.

  15. Anomalous opening of the Equatorial Atlantic due to an equatorial mantle thermal minimum

    NASA Astrophysics Data System (ADS)

    Bonatti, Enrico

    1996-09-01

    margins are particularly well developed in the Equatorial Atlantic. After further continental separation the cold equatorial mantle caused a low degree of melting (with Na-rich MORB and alkali basalt rather than normal MORB and with undepleted mantle peridotities), thin crust, depressed ridge segments and a prevalence of amagmatic extension. Similar conditions still exist today. Long transforms offsetting short ridge segments kept sea floor spreading unstable and dominated by transform tectonics, with transform migration, transpression, and transtension causing strong vertical motion, emersion and subsidence of lithospheric blocks, development of deep pull-apart basins, and preservation of relict slivers of old lithosphere (occasionally even of continental lithosphere) within younger crust. The equatorial transforms are caused ultimately by a long lived thermal minimum in the upper mantle and not vice versa; however, they then create second-order 'rebound' thermal effects that help maintain the thermal minimum in the upper mantle. It can be speculated that mantle thermal minima at the Earth's equator might be related to true polar wander triggered by subduction of dense masses into the mantle.

  16. Equatorial MU Radar project

    NASA Astrophysics Data System (ADS)

    Yamamoto, Mamoru; Hashiguchi, H.; Tsuda, Toshitaka; Yamamoto, Masayuki

    Research Institute for Sustainable Humanosphere, Kyoto University (RISH) has been studying the atmosphere by using radars. The first big facility was the MU (Middle and Upper atmosphere) radar installed in Shiga, Japan in 1984. This is one of the most powerful and multi-functional radar, and is successful of revealing importance of atmospheric waves for the dynamical vertical coupling processes. The next big radar was the Equatorial Atmosphere Radar (EAR) installed at Kototabang, West Sumatra, Indonesia in 2001. The EAR was operated under close collaboration with LAPAN (Indonesia National Institute for Aeronautics and Space), and conducted the long-term continuous observations of the equatorial atmosphere/ionosphere for more than 10 years. The MU radar and the EAR are both utilized for inter-university and international collaborative research program for long time. National Institute for Polar Research (NIPR) joined EISCAT Scientific Association together with Nagoya University, and developed the PANSY radar at Syowa base in Antarctica as a joint project with University of Tokyo. These are the efforts of radar study of the atmosphere/ionosphere in the polar region. Now we can find that Japan holds a global network of big atmospheric/ionospheric radars. The EAR has the limitation of lower sensitivity compared with the other big radars shown above. RISH now proposes a plan of Equatorial MU Radar (EMU) that is to establish the MU-radar class radar next to the EAR. The EMU will have an active phased array antenna with the 163m diameter and 1055 cross-element Yagis. Total output power of the EMU will be more than 500kW. The EMU can detect turbulent echoes from the mesosphere (60-80km). In the ionosphere incoherent-scatter observations of plasma density, drift, and temperature would be possible. Multi-channel receivers will realize radar-imaging observations. The EMU is one of the key facilities in the project "Study of coupling processes in the solar-terrestrial system

  17. Equatorial Spread F Fossil Plumes

    DTIC Science & Technology

    2010-11-01

    2007, 2007. Steenburgh, R. A., Smithtro, C. G., and Groves, K. M.: Ionospheric scintillation effects on single frequency GPS , Space Weather, 6, S04D02...issues, J. Geophys. Res., 107, 1468, doi:10.1029/2002JA009430, 2002. Retterer, J. M.: Forecasting low-latitude radio scintillation with 3- D ionospheric ... Ionosphere (Equatorial ionosphere ; Ionosphere - atmosphere interactions; Ionospheric irregularities) 1 Introduction Equatorial spread F (ESF), the result of

  18. Modeling studies of equatorial plasma fountain and equatorial anomaly

    NASA Astrophysics Data System (ADS)

    Balan, N.; Bailey, G. J.

    The importance of diffusion, electrodynamic drift, amd neutral wind on the generation and modulation of the equatorial plasma fountain of the Earth's ionosphere is studied using the Sheffield University Plasmasphere-Ionosphere Model (SUPIM) for the ionosphere above Jicamarca (77 degW) under magnetically quiet (Ap = 4) equinoctial conditions (day 264) at medium solar activity (F10.7 = 145). The study also investigates the effects of the fountain, which include the equatorial anomaly. The F-region vertical E x B drift velocity measured at the equatorial station Jicamarca is used to represent the electrodynamic drift. The neutral wind is obtained from the HWM90 thermospheric wind model. As expected, the F-region electrodynamic drift generates the plasma fountain and the anomaly, which are symmetric with respect to the equator. The neutral wind makes the fountain and the anomaly asymmetric, with larger plasma flow (towards the hemisphere of stronger poleward wind) and stronger anomaly crest occurring in opposite hemispheres. The paper also addresses many important (some new) features which are related to the fountain. The features are: (1) the possibility of existence of an additional layer (called the G-layer) in the equatorial ionosphere, (2) the reverse plasma fountain, (3) the equatorial anomaly in vertical ionospheric electron content (IEC), (4) the presence (in Nmax) and absence (in IEC) of noon bite-out, (5) the occurrence of nighttime increase in ionization, and (6) plasma bubbles and spread-F.

  19. Equatorial Wave Line, Pacific Ocean

    NASA Image and Video Library

    1993-01-19

    STS054-95-042 (13-19 Jan 1993) --- The Equatorial Pacific Ocean is represented in this 70mm view. The international oceanographic research community is presently conducting a program called Joint Global Ocean Flux Study (JGOFS) to study the global ocean carbon budget. A considerable amount of effort within this program is presently being focused on the Equatorial Pacific Ocean because of the high annual average biological productivity. The high productivity is the result of nearly constant easterly winds causing cool, nutrient-rich water to well up at the equator. In this view of the sun glint pattern was photographed at about 2 degrees north latitude, 103 degrees west longitude, as the Space Shuttle passed over the Equatorial Pacific. The long narrow line is the equatorial front, which defines the boundary between warm surface equatorial water and cool, recently upwelled water. Such features are of interest to the JGOFS researchers and it is anticipated that photographs such as this will benefit the JGOFS program.

  20. The variability of equatorial currents

    NASA Technical Reports Server (NTRS)

    Cane, M. A.

    1981-01-01

    The temporal variations of upper ocean currents along the equator, specially the equatorial undercurrent are discussed. Many mechanisms were proposed as explanations of the steady state undercurrent including vertical mixing, horizontal mixing, thermohaline effects, and nonlinear effects. All of these theories succeed to some extent in simulating some of the observed features of the undercurrent. To distinguish among these ideas, the time variability of equatorial currents was considered. Observations of surface currents, currents in the thermocline, and surface winds at the equator are shown.

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

    NASA Astrophysics Data System (ADS)

    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.

  2. Interplay Between the Equatorial Geophysical Processes

    NASA Astrophysics Data System (ADS)

    Sridharan, R.

    2006-11-01

    r_sridharanspl@yahoo.com With the sun as the main driving force, the Equatorial Ionosphere- thermosphere system supports a variety of Geophysical phenomena, essentially controlled by the neutral dynamical and electro dynamical processes that are peculiar to this region. All the neutral atmospheric parameters and the ionospheric parameters show a large variability like the diurnal, seasonal semi annual, annual, solar activity and those that are geomagnetic activity dependent. In addition, there is interplay between the ionized and the neutral atmospheric constituents. They manifest themselves as the Equatorial Electrojet (EEJ), Equatorial Ionization Anomaly (EIA), Equatorial Spread F (ESF), Equatorial Temperature and Wind Anomaly (ETWA). Recent studies have revealed that these phenomena, though apparently might show up as independent ones, are in reality interlinked. The interplay between these equatorial processes forms the theme for the present talk.

  3. Equatorial refuge amid tropical warming

    NASA Astrophysics Data System (ADS)

    Karnauskas, Kristopher B.; Cohen, Anne L.

    2012-07-01

    Upwelling across the tropical Pacific Ocean is projected to weaken in accordance with a reduction of the atmospheric overturning circulation, enhancing the increase in sea surface temperature relative to other regions in response to greenhouse-gas forcing. In the central Pacific, home to one of the largest marine protected areas and fishery regions in the global tropics, sea surface temperatures are projected to increase by 2.8°C by the end of this century. Of critical concern is that marine protected areas may not provide refuge from the anticipated rate of large-scale warming, which could exceed the evolutionary capacity of coral and their symbionts to adapt. Combining high-resolution satellite measurements, an ensemble of global climate models and an eddy-resolving regional ocean circulation model, we show that warming and productivity decline around select Pacific islands will be mitigated by enhanced upwelling associated with a strengthening of the equatorial undercurrent. Enhanced topographic upwelling will act as a negative feedback, locally mitigating the surface warming. At the Gilbert Islands, the rate of warming will be reduced by 0.7+/-0.3°C or 25+/-9% per century, or an overall cooling effect comparable to the local anomaly for a typical El Niño, by the end of this century. As the equatorial undercurrent is dynamically constrained to the Equator, only a handful of coral reefs stand to benefit from this equatorial island effect. Nevertheless, those that do face a lower rate of warming, conferring a significant advantage over neighbouring reef systems. If realized, these predictions help to identify potential refuges for coral reef communities from anticipated climate changes of the twenty-first century.

  4. Aerosol Transport Over Equatorial Africa

    NASA Technical Reports Server (NTRS)

    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

  5. Aerosol Transport Over Equatorial Africa

    NASA Technical Reports Server (NTRS)

    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

  6. Radio wave scintillations at equatorial regions

    NASA Technical Reports Server (NTRS)

    Poularikas, A. D.

    1972-01-01

    Radio waves, passing through the atmosphere, experience amplitude and phase fluctuations know as scintillations. A characterization of equatorial scintillation, which has resulted from studies of data recorded primarily in South America and equatorial Africa, is presented. Equatorial scintillation phenomena are complex because they appear to vary with time of day (pre-and postmidnight), season (equinoxes), and magnetic activity. A wider and more systematic geographical coverage is needed for both scientific and engineering purposes; therefore, it is recommended that more observations should be made at earth stations (at low-geomagnetic latitudes) to record equatorial scintillation phenomena.

  7. Central Equatorial Pacific Experiment (CEPEX)

    SciTech Connect

    Not Available

    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.

  8. Instability of some equatorially trapped waves

    PubMed Central

    Constantin, Adrian; Germain, Pierre

    2013-01-01

    [1] A high-frequency asymptotics approach within the Lagrangian framework shows that some exact equatorially trapped three-dimensional waves are linearly unstable when their steepness exceeds a specific threshold. Citation: Constantin, A., and P. Germain (2013), Instability of some equatorially trapped waves, J. Geophys. Res. Oceans, 118, 2802–2810, doi:10.1002/jgrc.20219. PMID:26213669

  9. EQUATORIAL SUPERROTATION ON TIDALLY LOCKED EXOPLANETS

    SciTech Connect

    Showman, Adam P.; Polvani, Lorenzo M.

    2011-09-01

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

  10. On the modelling of equatorial waves

    NASA Astrophysics Data System (ADS)

    Constantin, A.

    2012-03-01

    The present theory of geophysical waves that either raise or lower the equatorial thermocline, based on the reduced-gravity shallow-water equations on the β-plane, ignores vertical variations of the flow. In particular, the vertical structure of the Equatorial Undercurrent is absent. As a remedy we propose a simple approach by modeling this geophysical process as a wave-current interaction in the f-plane approximation, the underlying current being of positive constant vorticity. The explicit dispersion relation allows us to conclude that, despite its simplicity, the proposed model captures to a reasonable extent essential features of equatorial waves.

  11. Equatorial thermosphere anomaly: Observations and simulations

    NASA Astrophysics Data System (ADS)

    Lei, J.; Thayer, J. P.; Wang, W.; Richmond, A. D.

    2011-12-01

    Several mechanisms including heat transport due to zonal winds, chemical heating and field-aligned ion drag have been proposed to explain the formation of the Equatorial Thermosphere Anomaly (ETA), but the real cause of the ETA formation in thermosphere temperature is still a mystery. Various observations of the ionosphere and thermosphere have been used to investigate the variations of equatorial anomalies in both the ETA and EIA, and their interactions. The similarities and differences between the ETA and the EIA can provide important insight to the physical connections of this ion-neutral coupling problem. Meanwhile, the combination of observations and theoretical models allows us to understand the fundamental physical and chemical ion-neutral processes in the equatorial F region. This talk will highlight the recent progress of the formation of the ETA associated with the ion-neutral coupling in the equatorial region.

  12. Longitudinal variations of the equatorial electojet

    NASA Astrophysics Data System (ADS)

    Shume, Esayas

    We have utilized a three dimensional electrostatic potential model to explain the longitudinal variations of the equatorial electrojet. The model runs were constrained by net H component magnetic field measurements from three equatorial stations, namely, Huancayo (Peru) 12.05 S, 284.67 E; Addis Ababa (Ethiopia) 9.8 N, 38.8 E; Tirunelveli (India) 8.42 N, 77.48 E. The model runs were done in an iterative fashion until the computed and measured H component magnetic field values come into a close agreement. The physical mechanisms for the longitudinal variations of the equatorial electrojet were inferred by comparing and contrasting the resulting computed vertical polarization electric field (which drives the equatorial electrojet), and zonal current density profiles for the three stations mentioned above.

  13. Anaglyph Image of Vesta Equatorial Region II

    NASA Image and Video Library

    2011-10-05

    This anaglyph image shows the topography of part of Vesta equatorial region; this uneven topography is mostly due to large, ancient, rather degraded ruin eroded craters. You need 3D glasses to view this image.

  14. Complex Dynamics of Equatorial Scintillation

    NASA Astrophysics Data System (ADS)

    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.

  15. EQUATORIAL ZONAL JETS AND JUPITER's GRAVITY

    SciTech Connect

    Kong, D.; Liao, X.; Zhang, K.; Schubert, G.

    2014-08-20

    The depth of penetration of Jupiter's zonal winds into the planet's interior is unknown. A possible way to determine the depth is to measure the effects of the winds on the planet's high-order zonal gravitational coefficients, a task to be undertaken by the Juno spacecraft. It is shown here that the equatorial winds alone largely determine these coefficients which are nearly independent of the depth of the non-equatorial winds.

  16. The storm-time equatorial electrojet

    NASA Technical Reports Server (NTRS)

    Burrows, K.; Sastry, T. S. G.; Sampath, S.; Stolarik, J. D.; Usher, M. J.

    1977-01-01

    A Petrel rocket carrying a double cell rubidium magnetometer was launched from the Thumba Equatorial Rocket Launching Station during the early main phase of a magnetic storm. No ionospheric currents associated with the storm were observed, and the large field depression at the flight time must therefore be attributed to currents at higher altitudes. The equatorial enhancement of ionospheric magnetic storm currents, predicted on the basis of theory and earlier ground data, was not observed.

  17. The storm-time equatorial electrojet

    NASA Technical Reports Server (NTRS)

    Burrows, K.; Sastry, T. S. G.; Sampath, S.; Stolarik, J. D.; Usher, M. J.

    1976-01-01

    A Petrel rocket carrying a double cell rubidium magnetometer was launched from the Thumba Equatorial Rocket Launching Station during the early main phase of a magnetic storm. No ionospheric currents associated with the storm were observed and the large field depression, at the flight time, must therefore be attributed to currents at higher altitudes. The equatorial enhancement of ionospheric magnetic storm currents, predicted on the basis of theory and earlier ground data, was not observed.

  18. Jupiter Great Red Spot and South Equatorial Belt

    NASA Image and Video Library

    1996-09-26

    NASA Voyager 2 shows the Great Red Spot and the south equatorial belt extending into the equatorial region. At right is an interchange of material between the south equatorial belt and the equatorial zone. The clouds in the equatorial zone are more diffuse and do not display the structures seen in other locations. Considerable structure is evident within the Great Red Spot. http://photojournal.jpl.nasa.gov/catalog/PIA00456

  19. Latitudinal comparisons of equatorial Pacific zooplankton

    NASA Astrophysics Data System (ADS)

    Roman, M. R.; Dam, H. G.; Le Borgne, R.; Zhang, X.

    Zooplankton biomass and rates of ingestion, egestion and production in the equatorial Pacific Ocean along 140°W and 180° exhibit maximum values in the High-Nutrient Low-Chlorophyll (HNLC) zone associated with equatorial upwelling (5°S-5°N) as compared to the more oligotrophic regions to the north and south. Zooplankton biomass and rates are not usually highest on the equator, but increase "downstream" of the upwelling center as the zooplankton populations exhibit a delayed response to enhanced phytoplankton production. The vertical distribution of zooplankton biomass in the equatorial HNLC area tends to be concentrated in surface waters and is more uniform with depth in oligotrophic regions to the north and south of the equatorial upwelling zone. In general, the amount of mesozooplankton (>200 μm) carbon biomass is approximately 25% of estimated phytoplankton biomass and 30% of bacterial biomass in the HNLC area of the equatorial Pacific Ocean. Zooplankton grazing on phytoplankton is low in the equatorial Pacific Ocean, generally <5% of the total chlorophyll-a standing stock grazed per day. Based on estimates of metabolic demand, it is apparent that zooplankton in the equatorial Pacific Ocean are omnivores, consuming primarily microzooplankton and detritus. Estimated zooplankton growth rates in the warm waters of the HNLC equatorial Pacific Ocean are high, ranging from 0.58 d -1 for 64-200 μm zooplankton to 0.08 d -1 for 1000-2000 μm zooplankton. Thus, the numerical and functional response of equatorial zooplankton to increases in phytoplankton production are more rapid than normally occurs in sub-tropical and temperate waters. Potential zooplankton fecal pellet production, estimated from metabolic demand, is approximately 1.6 times the estimated gravitational carbon flux at 150 m in the zone of equatorial upwelling (5°S-5°N) and 1.1 times the export flux in the more oligotrophic regions to the north and south. The active flux of carbon by diel migrant

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Equatorial waves in the stratosphere of Uranus

    NASA Technical Reports Server (NTRS)

    Hinson, David P.; Magalhaes, Julio A.

    1991-01-01

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

  2. Irregularities and Forecast Studies of Equatorial Spread

    DTIC Science & Technology

    2016-07-13

    AFRL-AFOSR-VA-TR-2016-0262 Irregularties and Forecast Studies of Equatorial Spread David Hysell CORNELL UNIVERSITY 373 PINE TREE RD ITHACA, NY 14850...NAME(S) AND ADDRESS(ES) CORNELL UNIVERSITY 373 PINE TREE RD ITHACA, NY 14850-2820 US 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING

  3. Equatorial Scintillation Initiated From Low Altitude Forcing

    NASA Astrophysics Data System (ADS)

    Bishop, R. L.

    2007-12-01

    Equatorial scintillation is often associated with equatorial plasma bubbles (ESF). Thus, understanding the forcing mechanisms behind bubble formation is necessary in order to predict the occurrence of most equatorial scintillation. Gravity waves are a strong driver for initiating spread-F. However identifying the source of the gravity waves remains a difficult task. Since the 1950's tropospheric/ionospheric coupling by gravity waves has been presented as a viable coupling mechanism in the literature. Recent GPS, ionosonde, and ISR studies have linked mid- and low latitude scintillation to the passage of large convective tropospheric storms. In this talk, an overview of recent observational and modeling work is presented showing the coupling between the two regions. Next, using GPS occultation data, evidence of equatorial scintillation due to nearby tropical storms is shown. The source of gravity waves within the tropical storms is then described and the type of gravity waves capable of reaching the bottom-side F-region is characterized. Finally, specific storm examples occurring at low magnetic latitudes are shown and their affects on the local ionosphere are discussed.

  4. The Dynamics of Equatorial F Layer Irregularities.

    DTIC Science & Technology

    2014-09-26

    RD-8158 650 THE DYNAMICS OF EQUATORIAL F LAYER IRREGULARITIE5(U) BOSTON UNIV MR DEPT OF ASTRONOMY J AARONS ET AL. 38 JUN 85 RCBU-6276-5 N88814-82-K...Jules Aarons and Michael Mendillo, Co-Principal Investigators Department of Astronomy Boston University Boston, MA 02215 BOSTON UNIVERSITY Thi doumnt

  5. Anaglyph Image of Vesta Equatorial Region I

    NASA Image and Video Library

    2011-10-04

    This anaglyph image shows the topography of part of Vesta equatorial region. These craters are classed as ruin eroded craters and are most clear in the center of the image, above the troughs. You need 3D glasses to view this image.

  6. Internal gravity waves in the equatorial Pacific

    SciTech Connect

    Skyllingstad, E.D.; Denbo, D.W. )

    1992-09-01

    Mixing in the ocean surface layer is an important process in the transport of heat, momentum, and CO[sub 2] into the deep ocean, For example, the flux of heat into the cold, upwelling water in equatorial regions provides one of the major heat sources driving the ocean circulation. Direct measurements of the ocean mixed layer have provided good estimates of the bulk layer properties. However, estimates of the small-scale effects of intenial waves and related turbulence have remained ambiguous because of the difficulty in observing these processes. Until more detailed measurements become available, numerical models can provide a convenient and cost-effective way to analyze the details of the surface mixed layer. Modeling the surface layer of the equatorial Pacific Ocean is challenging because of the strong vertical current shear and density stratification common to the region. The primary zonal current is the eastward flowing Equatorial Undercurrent (EUC) centered at roughly 120 m depth, with a speed of about 1.5 ms[sup [minus]1] as shown in Figure 1. The EUC is forced by a zonal pressure gradient resulting from the westward directed surface wind stress. Above the EUC, the wind stress directly forces thee South Equatorial Current (SEC), which flows westward with a speed of about 0.5 ms[sup [minus]1]. The shear zone generated by these currents is marginally stable and exhibits a diurnal cycle of turbulence dependent on convection forced by surface cooling. In addition, surface convection forces internal gravity waves, which can transport momentum away from the surface current to deeper waters. In this report, we discuss recent modeling results for the equatorial Pacific showing the generation of convection, turbulence, and internal waves.

  7. Internal gravity waves in the equatorial Pacific

    SciTech Connect

    Skyllingstad, E.D.; Denbo, D.W.

    1992-09-01

    Mixing in the ocean surface layer is an important process in the transport of heat, momentum, and CO{sub 2} into the deep ocean, For example, the flux of heat into the cold, upwelling water in equatorial regions provides one of the major heat sources driving the ocean circulation. Direct measurements of the ocean mixed layer have provided good estimates of the bulk layer properties. However, estimates of the small-scale effects of intenial waves and related turbulence have remained ambiguous because of the difficulty in observing these processes. Until more detailed measurements become available, numerical models can provide a convenient and cost-effective way to analyze the details of the surface mixed layer. Modeling the surface layer of the equatorial Pacific Ocean is challenging because of the strong vertical current shear and density stratification common to the region. The primary zonal current is the eastward flowing Equatorial Undercurrent (EUC) centered at roughly 120 m depth, with a speed of about 1.5 ms{sup {minus}1} as shown in Figure 1. The EUC is forced by a zonal pressure gradient resulting from the westward directed surface wind stress. Above the EUC, the wind stress directly forces thee South Equatorial Current (SEC), which flows westward with a speed of about 0.5 ms{sup {minus}1}. The shear zone generated by these currents is marginally stable and exhibits a diurnal cycle of turbulence dependent on convection forced by surface cooling. In addition, surface convection forces internal gravity waves, which can transport momentum away from the surface current to deeper waters. In this report, we discuss recent modeling results for the equatorial Pacific showing the generation of convection, turbulence, and internal waves.

  8. The family of anisotropically scaled equatorial waves

    NASA Astrophysics Data System (ADS)

    RamíRez GutiéRrez, Enver; da Silva Dias, Pedro Leite; Raupp, Carlos; Bonatti, Jose Paulo

    2011-04-01

    In the present work we introduce the family of anisotropic equatorial waves. This family corresponds to equatorial waves at intermediate states between the shallow water and the long wave approximation model. The new family is obtained by using anisotropic time/space scalings on the linearized, unforced and inviscid shallow water model. It is shown that the anisotropic equatorial waves tend to the solutions of the long wave model in one extreme and to the shallow water model solutions in the other extreme of the parameter dependency. Thus, the problem associated with the completeness of the long wave model solutions can be asymptotically addressed. The anisotropic dispersion relation is computed and, in addition to the typical dependency on the equivalent depth, meridional quantum number and zonal wavenumber, it also depends on the anisotropy between both zonal to meridional space and velocity scales as well as the fast to slow time scales ratio. For magnitudes of the scales compatible with those of the tropical region, both mixed Rossby-gravity and inertio-gravity waves are shifted to a moderately higher frequency and, consequently, not filtered out. This draws attention to the fact that, for completeness of the long wave like solutions, it is necessary to include both the anisotropic mixed Rossby-gravity and inertio-gravity waves. Furthermore, the connection of slow and fast manifolds (distinguishing feature of equatorial dynamics) is preserved, though modified for the equatorial anisotropy parameters used δ ∈ < 1]. New possibilities of horizontal and vertical scale nonlinear interactions are allowed. Thus, the anisotropic shallow water model is of fundamental importance for understanding multiscale atmosphere and ocean dynamics in the tropics.

  9. Wave Forcing of Saturn's Equatorial Oscillation

    NASA Technical Reports Server (NTRS)

    Flasar, F. M.; Schlinder, P. J.; Guerlet, S.; Fouchet, T.

    2011-01-01

    Ground-based measurements and Cassini data from CIRS thermal-infrared spectra and radio-occultation soundings have characterized the spatial structure and temporal behavior of a 15-year equatorial oscillation in Saturn's stratosphere. The equatorial region displays a vertical pattern of alternating warm and cold anomalies and, concomitantly, easterly and westerly winds relative to the cloud-top winds, with a peak-to-peak amplitude of 200 m/s. Comparison of the Cassini data over a four-year period has established that the pattern of mean zonal winds and temperatures descends at a rate of roughly I scale height over 4 years. This behavior is reminiscent of the equatorial oscillations in Earth's middle atmosphere. Here the zonal-mean spatial structure and descending pattern are driven by the absorption of vertically propagating waves. The maximum excursions in the pattern of easterly and westerly winds is determined by the limits of the zonal phase velocities of the waves. Here we report on the characterization of the waves seen in the temperature profiles retrieved from the Cassini radio-occultation soundings. The equatorial profiles exhibit a complex pattern of wavelike structure with dimensions one pressure scale height and smaller. We combine a spectral decomposition with a WKBJ analysis, where the vertical wavelength is assumed to vary slowly with the ambient static stability and doppler-shifted phase velocity of the wave. Use of the temperature and zonal wind maps from CIRS makes this approach viable. On Earth, the wave forcing associated with the equatorial oscillations generates secondary meridional circulations that affect the mean flow and planetary wave ducting well away from the equator. This may relate to the triggering of the recently reported mid-latitude storms on Saturn.

  10. How predictable are equatorial Atlantic surface winds?

    NASA Astrophysics Data System (ADS)

    Richter, Ingo; Doi, Takeshi; Behera, Swadhin

    2017-04-01

    Sensitivity tests with the SINTEX-F general circulation model (GCM) as well as experiments from the Coupled Model Intercomparison Project phase 5 (CMIP5) are used to examine the extent to which sea-surface temperature (SST) anomalies contribute to the variability and predictability of monthly mean surface winds in the equatorial Atlantic. In the SINTEX-F experiments, a control experiment with prescribed observed SST for the period 1982-2014 is modified by inserting climatological values in certain regions, thereby eliminating SST anomalies. When SSTs are set to climatology in the tropical Atlantic only (30S to 30N), surface wind variability over the equatorial Atlantic (5S-5N) decreases by about 40% in April-May-June (AMJ). This suggests that about 60% of surface wind variability is due to either internal atmospheric variability or SSTs anomalies outside the tropical Atlantic. A further experiment with climatological SSTs in the equatorial Pacific indicates that another 10% of variability in AMJ may be due to remote influences from that basin. Experiments from the CMIP5 archive, in which climatological SSTs are prescribed globally, tend to confirm the results from SINTEX-F but show a wide spread. In some models, the equatorial Atlantic surface wind variability decreases by more than 90%, while in others it even increases. Overall, the results suggest that about 50-60% of surface wind variance in AMJ is predictable, while the rest is due to internal atmospheric variability. Other months show significantly lower predictability. The relatively strong internal variability as well as the influence of remote SSTs suggest a limited role for coupled ocean-atmosphere feedbacks in equatorial Atlantic variability.

  11. Equatorial Electrojet Observations in the African Continent

    NASA Astrophysics Data System (ADS)

    Yizengaw, E.; Moldwin, M. B.; Mebrahtu, A.; Damtie, B.; Pfaff, R.; Zesta, E.

    2008-12-01

    Although Satellite observations in the African sector show unique equatorial ionospheric structures that can severely impact navigation and communication systems, the study of ionospheric disturbances in this region is difficult due to the lack of ground-based instruments. This has created a gap in global understanding of the physics behind the evolution and formation of plasma irregularities in the equatorial region, which imposes limitations on ionospheric density modeling efforts. Therefore, in order to have a more complete global understanding of equatorial ionosphere motion, the international space science community has begun to develop an observational infrastructure in the African sector. This includes the deployment of a number of arrays of small instruments, including the AMBER magnetometer array, through the International Heliophysical Year (IHY) cooperative program with the United Nations Basic Space Science (UNBSS) program. Two AMBER magnetometers have been deployed successfully at Adigrat (~6°N magnetic) in Ethiopia and at Medea in Algeria (28°N magnetic), and became fully operational on 03 August 2008. The remaining two AMBER magnetometers will be deployed soon in Cameroon and Namibia. One of the prime scientific objectives of AMBER is to understand the processes governing electrodynamics of the equatorial ionosphere as a function of latitude, local time, magnetic activity, and season in the African region. The most credible driving mechanism of ionospheric plasma (E × B drift) can be estimated using two magnetometers, one right at the equator and the other about 6 off the equator. Therefore, using the AMBER magnetometer at Adigrat and the INTERMAGNET magnetometer located at Addis Ababa (0.9°N magnetic) in Ethiopia, the equatorial electrojet (E × B drift) activities in that longitudinal sector of the African continent is estimated. The paper also presents the comparison between the estimated vertical drift and the drift values obtained from the

  12. Empirical modelling of equatorial ionospheric scintillation

    NASA Astrophysics Data System (ADS)

    Pasricha, P. K.; Reddy, B. M.

    1986-06-01

    A computer-based model of ionospheric scintillations has been developed by Fremouw (socalled the WBMOD model) to give a mean scintillation index for a given set of observing conditions. The WBMOD model incorporates some of the scintillation observations made with the DNA wideband satellite. A comparison is made between the scintillation morphology observed at an equatorial station Ooty with the one evolved with the WBMOD model. Morphological features at other stations in the equatorial region are briefly described. The WBMOD model predicts the pre-midnight maximum seen at the Indian longitudes. The seasonal pattern reproduced by the model incorporates longitudinal variability. The solar activity dependence in the model seems to be rather high. Empirical expressions giving the dependence of scintillation index on morphological parameters are obtained

  13. Long waves in the equatorial Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Philander, George; Halpern, David; Hansen, Donald; Legeckis, Richard; Miller, Laury; Watts, Randolph; Wimbush, Mark; Paul, Carl; Watts, Randolph; Weisberg, Robert

    Westward traveling waves, with a period of 3 weeks and a wavelength of ˜1000 km, are observed intermittently in the central and eastern equatorial Pacific Ocean (see cover). The waves were first detected in 1975 in satellite measurements of the sea surface temperature [Legeckis, 1977]. Since then, additional measurements (under the auspices of the NOAA program Equatorial Pacific Ocean Climate Studies (EPOCS)) with a variety of instruments—drifting buoys, current meters and temperature sensors on moorings, and inverted echo sounders—have provided considerable information about these waves and have confirmed the hypothesis that they are caused by instabilities associated primarily with the latitudinal shear of the surface currents near the equator [Philander, 1978a; Cox, 1980].

  14. Some Pivotal Questions Facing Equatorial Aeronomy

    NASA Astrophysics Data System (ADS)

    Mendillo, Michael

    The equatorial and low latitude F-layer experiences coupling from higher latitudes and from atmospheric regions below the thermosphere. These are in addition to the in-situ energy and dynamical processes that might be considered to be localized, i.e., within the latitudes spanned by the equatorial ionization anomaly (EIA) region. In this review, two types of recent studies will be described that strive to advance our understanding of the region. Assessments of the low latitude domain within global models (e.g., TIME-GCM) have just started to occur, with data-model comparisons on temporal scales of diurnal, day-to-day, and seasonal. Small scale irregularities, thought to be organized by large-scale processes ordered by the geomagnetic field, are now the topics of study using observations made along common magnetic field lines, linking one hemisphere to the other.

  15. Effect of ouabain on lens equatorial currents.

    PubMed

    Wind, B E; Walsh, S; Patterson, J W

    1988-11-01

    The equatorial potassium current measured with the vibrating probe is a segment of the potassium electrical loop. The equatorial current, J, was measured simultaneously with the PD and with the response to an injected current, I. The injection of sufficient inward current, I, made the PD more negative and increased the electrical gradient so that the current J became zero. The PD at which this occurs (PDJ-0) is the reversal potential. Following treatment with ouabain, the PD and PDJ-0 both become less negative. Since the driving force for the current, J, is equal to the difference between PD and PDJ-0, J may increase, stay the same or decrease depending on the relative changes in PD and PDJ-0. In the presence of ouabain, the PDJ-0 changes in parallel with or more rapidly than the PD.

  16. Equatorial ionospheric electrodynamics during solar flares

    NASA Astrophysics Data System (ADS)

    Zhang, Ruilong; Liu, Libo; Le, Huijun; Chen, Yiding

    2017-05-01

    Previous investigations on ionospheric responses to solar flares focused mainly on the photoionization caused by the increased X-rays and extreme ultraviolet irradiance. However, little attention was paid to the related electrodynamics. In this letter, we explored the equatorial electric field (EEF) and electrojet (EEJ) in the ionosphere at Jicamarca during flares from 1998 to 2008. It is verified that solar flares increase dayside eastward EEJ but decrease dayside eastward EEF, revealing a negative correlation between EEJ and EEF. The decreased EEF weakens the equatorial fountain effect and depresses the low-latitude electron density. During flares, the enhancement in the Cowling conductivity may modulate ionospheric dynamo and decrease the EEF. Besides, the decreased EEF is closely related to the enhanced ASY-H index that qualitatively reflects Region 2 field-aligned current (R2 FAC). We speculated that solar flares may also decrease EEF through enhancing R2 FAC that leads to an overshielding-like effect.

  17. Equatorial Anomaly TEC Observation in China

    NASA Astrophysics Data System (ADS)

    Ma, G.; Zhang, D. H.; Chen, Y.; Wu, Y.; Luo, R.; Xiao, F.; Shen, H.; Huang, W.; Tan, J.

    2005-12-01

    Since May 2005, a GPS receiver chain had been established at equatorial anomaly region in China. The chain is composed of 4 GPS receivers located at Fuzhou Xiamen Guangzhou and Nanning. Shown in the following are geographic and geomagnetic coordinates of the 4 stations. 1,Fuzhou: (26.1N, 119.3E--14.4N, 188.4E); 2,Xiamen: (24.5N, 118.1E--13.2N, 187.4E); 3,Guangzhou: (23.1N, 113.2E--11.8N, 182.8E); 4,Nanning : (22.8N, 108.3E-- 11.4N, 178.2E). The aim of the observation is to study the TEC and ionospheric scintillation at equatorial anomaly in China area. This paper presents a preliminary result of TEC observed with the chain, including geomagnetic quiet times and TEC response to geomagnetic storms.

  18. TEC Observation at Equatorial Anomaly in China

    NASA Astrophysics Data System (ADS)

    Shen, H.; Ma, G.; Chen, Y.; Huang, W.; Zhang, D.; Wu, Y.; Luo, R.; Xiao, F.; Qin, J.

    2006-05-01

    Since May 2005, a GPS receiver chain had been established at equatorial anomaly region in south China. The chain is composed of 4 GPS receivers located at Fuzhou, Xiamen, Guangzhou and Nanning whose geomagnetic latitudes are 14.4°N, 13.2°N, 11.8°N, 11.4°N, respectively. The GPS observation is set at 1 Hz sampling rate, which enabled GPS-TEC data with a high time resolution. The four sites are just in northern equatorial anomaly, so they have favorable condition for the observation to study the TEC variations and ionospheric scintillation. With the data we have obtained, TEC enhancement with different scales and TEC depletions have been recognized. This paper presents the preliminary results of TEC observation with the chain, with emphasis on spatial scale of the TEC related phenomena.

  19. Models of the Equatorial Ocean Circulation.

    DTIC Science & Technology

    1980-01-01

    doctoral committee for their encouragement and advice in the development of this work. I am especially indebted to Dr. Julian P. McCreary of Nova University...large scale wind fluctuations thousands of kilometers to the west in the Central Pacific ( McCreary , 1977). A better understanding of such events could...all equatorial oceans can be found in Knauss (1963); Philander (1973b); Leetmaa, McCreary and Moore (1980); Tsuchiya (1975); Cochrane et al. (1979) and

  20. Evidence for Ancient Equatorial Ice Sheets on Mars?

    NASA Astrophysics Data System (ADS)

    Kite, E. S.

    2004-12-01

    During August 2004, a survey of available high-resolution MOLA gridded topography and THEMIS VIS imagery in the Equatorial Transition Zone of Mars was carried out. Other data sets, paticurlarly THEMIS IR and MOC NA, were exploited to study areas of interest. Although ~100 metres-per-pixel THEMIS daytime IR coverage is almost complete at the equator, ~18 metres-per-pixel THEMIS VIS coverage was patchy at the time of the survey, and repeat observations are lacking. Therefore, the THEMIS VIS survey could only capture a subset of the geomorphology of the Equatorial Transition Zone. Nevertheless, a suite of features were catalogued: some may be of relevance to the problem of the genesis and postdepositional history of the Medusae Fossae Formation. At the THEMIS scale, the features include eskers, subparallel hummocky ridge packages, ridge-bounded hummocky terrain, metre-scale layering, small-scale chaos terrain / outflow channel landsystems, dissected terrain, rim and central mound crater-interior deposits, polygonally fractured and channelized mesa tops, "wirebrush," "eggbox/bullseye," outcrops of a pasty lithology, and apparent cwms and aretes. At MOLA scale (as noted by other workers) they include rampart craters and trough-and-lobe landscapes. One possible framework for an initial synthesis of these early results will be adumbrated, exploiting recent progress in numerical modelling of the Martian water cycle at high obliquity, and the chaotic diffusion of Mars' obliquity over geological time. Finally, the relationship of these initial results to those of other workers will be described, and some future research directions will be sketched out.

  1. Sunrise enhancement of equatorial vertical plasma drift

    NASA Astrophysics Data System (ADS)

    Liu, Libo; Zhang, Ruilong; Le, Huijun

    2016-04-01

    Sunrise enhancement in vertical plasma drift over equatorial regions is not discernible in the statistical picture compared with the significant enhancement during dusk hours. In this report, it is the first time to investigate the occurrence of the dawn enhancement in the equatorial ionospheric vertical plasma drift from ROCSAT-1 observations during geomagnetic quiet times. The dawn enhancements occur most frequently in June solstice and least frequently in December solstice. The statistical survey shows that the occurrence depends on the magnetic declination. The enhancement has the strongest amplitude in regions near 320° longitude and peaks during June solstice. The dawn enhancement reaches its peak after the sunrise in conjugated E regions. Furthermore, it is found that the dawn enhancement is closely related to the difference between the sunrise times in the conjugated E regions (sunrise time lag). The dawn enhancement occurs easily in regions with a large sunrise time lag. Moreover, we will report the effects of the sunrise enhancement of vertical plasma drift on the equatorial ionosphere as indicated from the observations and model simulations. We thanks National Central University of Taiwan providing the ROCSAT-1 data. The Ap and F107 indices are obtained from the National Geophysical Data Center (http://spidr.ngdc.noaa.gov/spidr/). This research is supported by National Natural Science Foundation of China (41231065), the Chinese Academy of Sciences project (KZZD-EW-01-3), National Key Basic Research Program of China (2012CB825604) and National Natural Science Foundation of China (41321003).

  2. Equatorial scintillations: advances since ISEA-6

    SciTech Connect

    Not Available

    1985-01-01

    Our understanding of the morphology of equatorial scintillations has advanced due to more intensive observations at the equatorial anomaly locations in the different longitude zones. The unmistakable effect of the sunspot cycle in controlling irregularity belt width and electron concentration responsible for strong scintillation in the controlling the magnitude of scintillations has been recognized by interpreting scintillation observations inthe light of realistic models of total electron content at various longitudes. A hypothesis based on the alignment of the solar terminator with the geomagnetic flux tubes as an indicator of enhanced scintillation occurrence and another based on the influence of a transequatorial thermospheric neutral wind have been postulated to describe the observed longitudinal variation. A distinct class of equatorial irregularities known as the bottomside sinusoidal (BSS) type was identified. These irregularities occur in very large patches, sometimes in excess of several thousand kilometers in the E-W direction and are associated with frequency spread on ionograms. Scintillations caused by such irregularities exist only in the VHF band, exhibit Fresnel oscillations in intensity spectra and are found to give rise to extremely long durations (approx. several hours) of uninterrrupted scintillations.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. Lunar influence on equatorial atmospheric angular momentum

    NASA Astrophysics Data System (ADS)

    Bizouard, Christian; Zotov, Leonid; Sidorenkov, Nikolay

    2014-11-01

    This study investigates the relationship between the equatorial atmospheric angular momentum oscillation in the nonrotating frame and the quasi-diurnal lunar tidal potential. Between 2 and 30 days, the corresponding equatorial component, called Celestial Atmospheric Angular Momentum (CEAM), is mostly constituted of prograde circular motions, especially of a harmonic at 13.66 days, a sidelobe at 13.63 days, and of a weekly broadband variation. A simple equilibrium tide model explains the 13.66 day pressure term as a result of the O1 lunar tide. The powerful episodic fluctuations between 5 and 8 days possibly reflect an atmospheric normal mode excited by the tidal waves Q1 (6.86 days) and σ1 (7.095 days). The lunar tidal influence on the spectral band from 2 to 30 days is confirmed by two specific features, not occurring for seasonal band dominated by the solar thermal effect. First, Northern and Southern Hemispheres contribute equally and synchronously to the CEAM wind term. Second, the pressure and wind terms are proportional, which follows from angular momentum budget considerations where the topographic and friction torques on the solid Earth are much smaller than the one resulting from the equatorial bulge. Such a configuration is expected for the case of tidally induced circulation, where the surface pressure variation is tesseral and cannot contribute to the topographic torque, and tidal winds blow only at high altitudes. The likely effects of the lunar-driven atmospheric circulation on Earth's nutation are estimated and discussed in light of the present-day capabilities of space geodetic techniques.

  6. An equatorial coronal hole at solar minimum

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  7. Miocene actinommid Radiolaria from the equatorial Pacific

    USGS Publications Warehouse

    Blueford, J.R.

    1982-01-01

    Actinommids (spumellarian Radiolaria) are a group of microfossils in which taxonomy and phylogeny hitherto have been based on features of morphology that change with the growth of individuals. To make Miocene actinommids from the equatorial Pacific useful in biostratigraphy, paleocenography, and paleoecology, ontogenetically invariant morphological features can be analyzed by methods of numerical taxonomy to group the specimens into genera, which are further subdivided into species by visual comparison. According to these criteria, 31 species, 18 of which are new, are recognized in the Late Miocene section of DSDP Sites 77 and 289, and an informal revision of actinommid higher taxa is tentatively proposed.

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

    NASA Technical Reports Server (NTRS)

    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

  9. The equatorial electrojet satellite and surface comparison

    NASA Technical Reports Server (NTRS)

    Cain, J. C. (Editor); Sweeney, R. E. (Editor)

    1972-01-01

    The OGO 4 and 6 (POGO) magnetic field results for the equatorial electrojet indicate that while the present models are approximately correct, the possibility of a westward component must be incorporated. The scatter diagrams of POGO amplitudes and surface data show a correlation. The ratios between the amplitudes estimated from surface data and those at 400 km altitude are as follows: India 5 to 8, East Africa (Addis Ababa) 4, Central Africa 3, West Africa (Nigeria) 3, South America (Huancayo) 5, and Philippines 5. The variation in the ratio is due to the conductivity structure of the earth in various zones.

  10. Equatorial trench at the "saturated" magnetopause

    NASA Astrophysics Data System (ADS)

    Dmitriev, A. V.; Suvorova, A.

    2011-12-01

    Magnetic data from GOES geosynchronous satellites were applied to study the shape of low-latitude magnetopause during strong geomagnetic disturbances mainly related to coronal ejecta. From minimum variance analysis, we determined the magnetopause orientation and compared it with model predictions. A specific pattern of the magnetopause shape at low latitudes was found for strong southward interplanetary magnetic field, under which the IMF influence to the magnetopause is saturated. The shape of saturated magnetopause is substantially distorted by a duskward shifting and equatorial trench in the nose region. The origin of observed magnetopause distortions is discussed.

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

    NASA Astrophysics Data System (ADS)

    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.

  12. Fading of Jupiter's South Equatorial Belt

    NASA Technical Reports Server (NTRS)

    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.

  13. Preliminary report: STOIC CGCM intercomparison - equatorial sections

    SciTech Connect

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

    1999-03-01

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

  14. Fading of Jupiter's South Equatorial Belt

    NASA Technical Reports Server (NTRS)

    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.

  15. Shape of the dayside equatorial magnetopause

    NASA Astrophysics Data System (ADS)

    Simunek, Jiri; Safrankova, Jana; Nemecek, Zdenek; Prech, Lubomir

    2017-04-01

    A magnetopause location is generally believed to be determined by the solar wind dynamic pressure and by a sign and value of the interplanetary magnetic field (IMF) vertical (Bz) component. The contribution of other parameters is usually considered to be minor or negligible near the equatorial plane. A great majority of present magnetopause models describes the magnetopause shape with an ellipsoid or paraboloid of revolution. The axis of such surface usually reflects the Earth orbital motion around the Sun. Ten years of magnetopause observations near the equatorial plane by the THEMIS spacecraft allow to tests of this description and facilitates search for a better approximation of the magnetopause shape. We present a statistical study based on more than several thousand magnetopause crossings identified in the THEMIS data. The study accounts for a dependence of the magnetopause location on the upstream solar wind dynamic pressure and expects that all other effects can be averaged. The study suggests a very simple expression for the shape of the dayside magnetopause and examines the influence of IMF and solar wind parameters on this shape. The effects of magnetospheric current systems are also discussed.

  16. Midday reversal of equatorial ionospheric electric field

    NASA Astrophysics Data System (ADS)

    Rastogi, R. G.

    1997-10-01

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

  17. LF radio wave propagation at equatorial regions

    NASA Astrophysics Data System (ADS)

    Boudjada, Mohammed Y.; Sawas, Sami; Galopeau, Patrick H. M.; Eichelberger, Hans; Schwingenschuh, Konrad

    2016-04-01

    We analyse night-side electric field observations recorded by the ICE experiment onboard the DEMETER micro-satellite. We show the presence of multiple spaced frequency bands between 30 kHz and 500 kHz, and sometimes in the range 3 MHz - 3.5 MHz, the upper frequency of the instrument. The frequency bandwidth is found to be less than 5 kHz and the time duration about several minutes. The frequency bands are recorded close to the equatorial plane, when the satellite latitudes extend between -05° and +05°. Particular enhancements occur at two geographical longitudes: 130°E and 160°W. Those LF radio waves may be associated to density irregularities in the equatorial region. These irregularities are occurring along the ray path between the emission source region and the satellite. We discuss in this study the locations where such frequency bands are generated, and we show that the observed spectral features may be comparable to the kilometric continuum radiation which is considered as a non-thermal radio emission.

  18. Gravity Wave Seeding of Equatorial Plasma Bubbles

    NASA Technical Reports Server (NTRS)

    Singh, Sardul; Johnson, F. S.; Power, R. A.

    1997-01-01

    Some examples from the Atmosphere Explorer E data showing plasma bubble development from wavy ion density structures in the bottomside F layer are described. The wavy structures mostly had east-west wavelengths of 150-800 km, in one example it was about 3000 km. The ionization troughs in the wavy structures later broke up into either a multiple-bubble patch or a single bubble, depending upon whether, in the precursor wavy structure, shorter wavelengths were superimposed on the larger scale wavelengths. In the multiple bubble patches, intrabubble spacings vaned from 55 km to 140 km. In a fully developed equatorial spread F case, east-west wavelengths from 690 km down to about 0.5 km were present simultaneously. The spacings between bubble patches or between bubbles in a patch appear to be determined by the wavelengths present in the precursor wave structure. In some cases, deeper bubbles developed on the western edge of a bubble patch, suggesting an east-west asymmetry. Simultaneous horizontal neutral wind measurements showed wavelike perturbations that were closely associated with perturbations in the plasma horizontal drift velocity. We argue that the wave structures observed here that served as the initial seed ion density perturbations were caused by gravity waves, strengthening the view that gravity waves seed equatorial spread F irregularities.

  19. Topside sounder observations of equatorial bubbles

    NASA Technical Reports Server (NTRS)

    Dyson, P. L.; Benson, R. F.

    1978-01-01

    Large scale regions of depleted equatorial ionospheric plasma, called equatorial bubbles, are investigated using topside sounder data. The sounder's unique remote measuring capability enables the magnetic field-aligned nature of the bubbles to be investigated. A search of all available Alouette 2 and ISIS 1 ionograms during nighttime perigee passes near the magnetic equator has revealed a variety of echo signatures associated with bubbles. In addition to a sudden drop in electron density, these signatures usually include in situ spread F and ducted traces. The ducted traces have been used to determine the electron density distribution and to infer changes in ion composition along the magnetic field line within the duct associated with the bubble. In some cases it can be determined that the bubble is asymmetric with respect to the magnetic equator. Even though such features require 3 dimensional models for their explanation, the great field-aligned extent of the bubbles (relative to their cross section) suggests that current theories, which ignore variations along the magnetic field, are still applicable.

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

    SciTech Connect

    Not Available

    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.

  1. Nighttime ionospheric D region: Equatorial and nonequatorial

    NASA Astrophysics Data System (ADS)

    Thomson, Neil R.; McRae, Wayne M.

    2009-08-01

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

  2. Ion composition and drift observations in the nighttime equatorial ionosphere

    NASA Technical Reports Server (NTRS)

    Goldberg, R. A.; Aikin, A. C.; Murthy, B. V. K.

    1974-01-01

    The first in situ measurements of ion composition in the nighttime equatorial E and F region ionospheres (90-300 km) are presented and discussed. These profiles were obtained by two rocket-borne ion mass spectrometers launched from Thumba, India on March 9-10, 1970 at solar zenith angles of 112 deg and 165 deg. Ionosonde data established that the composition was measured at times bounding a period of F region downward drift. During this period the ions O(+) and N(+) were enhanced by one to three orders of magnitude between 220 and 300 km. Below the drift region (200 km), O(+) ceased to be the major ionic constituent, but the concentrations of O(+) and N(+) remained larger than predicted from known radiation sources and loss processes. Here also, both the O2(+) and NO(+) profiles retained nearly the same shape and magnitude throughout the night in agreement with theories assuming scattered UV radiation to be the maintaining source. Light metallic ions including Mg(+), Na(+) and possibly Si(+) were observed to altitude approaching 300 km, while the heavier ions Ca(+) and K(+) were seen in reduced quantity to 200 km. All metal ion profiles exhibited changes which can be ascribed to vertical drifting.

  3. A Three-Way Comparison of Sea Level from the Central Equatorial Pacific, 1985-89

    DTIC Science & Technology

    1993-01-01

    of Sea Level from the Central Equatorial Pacific,1985-89 (Xiaoli Zhu, Mark lVimbush, Kathleen A. Donohue,tor, Dr. Julian P. McCreary , but, in the... McCreary and observed sea-level data sets (tide gauges, suit in error ranges at least equal to those of Anderson. 1991; Neelin etal.. 1992). Analy...GEOS -"Fand isNa!da ea level of3 to ( McCreary , 19811. Gentetal.(1983)discuss of a few centimeters. 4cm (Cheney etal.. 1991b). TOGA Notes .Innuarv 1993

  4. Phytochelatin concentrations in the equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Ahner, Beth A.; Lee, Jennifer G.; Price, Neil M.; Morel, François M. M.

    1998-11-01

    Phytochelatin, an intracellular metal-binding polypeptide synthesized in eucaryotic algae in response to metals such as Cd and Cu, was measured in particulate samples collected from the equatorial Pacific. The concentrations in these samples (normalized to total particulate chl a) were unexpectedly high compared to laboratory culture data and were on average slightly more than in coastal areas where the metal concentrations are typically much greater. In part, the high field concentrations can be explained by the low cellular concentrations of chlorophyll a resulting from very low ambient Fe, but laboratory experiments provide a possible explanation for the rest of the difference. At low concentrations of inorganic Cd (Cd'=3 pM), increasing amounts of phytochelatin were induced by decreasing Zn concentrations in the culture medium of two diatoms: Thalassiosira weissflogii, a coastal species, and T. parthenaia, an isolate from the equatorial Pacific. In all previous studies, phytochelatin production has been directly correlated with increasing metal concentrations. Decreasing Co also resulted in higher phytochelatin concentrations in T. weissflogii and Emiliania huxleyi. Replicating the field concentrations of Zn, Co, and Cd in the laboratory results in cellular concentrations (amol -1 cell) that are very similar to those estimated for the field. Contrary to the expectation that high metal concentrations in the equatorial upwelling would cause elevated phytochelatin concentrations, there was no increase in phytochelatin concentrations from 20° S to 10° N—near surface samples were roughly the same at all stations. Also, most of the depth profiles had a distinct subsurface maximum. Neither of these features is readily explained by the available Zn and Cd data. Incubations with additions of Cd and Cu performed on water sampled at four separate stations induced significantly higher concentrations of phytochelatins than those in controls in a majority of the samples

  5. Electromagnetic and Stress Analyses of the ITER Equatorial Thermal Shield

    NASA Astrophysics Data System (ADS)

    Lei, Mingzhun; Song, Yuntao; Wang, Songke; Wang, Xianwei

    2013-08-01

    The ITER equatorial thermal shield is located inside the cryostat and outside the vacuum vessel, and its purpose is to provide a thermal shield from hot components to the superconducting magnets. Electromagnetic analysis of the equatorial thermal shield was performed using the ANSYS code, because electromagnetic load was one of the main loads. The 40° sector finite element model was established including the vacuum vessel, equatorial thermal shield, and superconducting magnets. The main purpose of this analysis was to investigate the eddy current and electromagnetic force in the equatorial thermal shield during plasma disruption. Stress analysis was implemented under the electromagnetic load. The results show that the equatorial thermal shield can accommodate the calculated electromagnetic loads.

  6. Equatorial radius of the earth: A dynamical determination

    NASA Technical Reports Server (NTRS)

    Khan, M. A.

    1972-01-01

    An interesting variation on the familiar method of determining the earth's equatorial radius a sub e, from a knowledge of the earth's equatorial gravity is suggested. The value of equatorial radius thus found is 6378,142 + or - 5 meters. The associated parameters are GM = 3,986008 + or - 4 X 1014 cu cm/sec/sec which includes the relative mass of atmosphere approximately 0.000001 x GM, the equatorial gravity gamma sub e = 978,030.9 milligals (constrained in this solution by the Potsdam Correction of 13.67 milligals as the Potsdam Correction is more directly, or less indirectly, measurable than the equatorial gravity) and an ellipsoidal flattening of f = 1/298.255.

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

    NASA Astrophysics Data System (ADS)

    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.

  8. Formation of Jets and Equatorial Superrotation on Jupiter

    NASA Astrophysics Data System (ADS)

    Liu, Junjun; Schneider, T.

    2008-09-01

    The zonal flow in Jupiter's upper troposphere is organized into alternating retrograde and prograde jets, with a prograde (superrotating) jet at the equator. Existing models posit as the driver of the flow either differential radiative heating of the atmosphere or intrinsic heat fluxes emanating from the deep interior; however, they do not reproduce all large-scale features of Jupiter's jets and thermal structure. Here it is shown that the difficulties in accounting for Jupiter's jets and thermal structure resolve if the effects of differential radiative heating and intrinsic heat fluxes are considered together and if upper-tropospheric dynamics are linked to a magnetohydrodynamic drag deep in the atmosphere. Baroclinic eddies generated by differential radiative heating can account for the off-equatorial jets; meridionally propagating equatorial Rossby waves generated by intrinsic convective heat fluxes can account for the equatorial superrotation. The zonal flow extends deeply into the atmosphere, with its speed changing with depth, up to depths at which the magnetohydrodynamic drag acts. The theory is supported by simulations with an energetically consistent general circulation model of Jupiter's outer atmosphere. A simulation that incorporates differential radiative heating and intrinsic heat fluxes reproduces Jupiter's observed jets and thermal structure. A control simulation that incorporates only differential radiative heating but no intrinsic heat fluxes produces off-equatorial jets but no equatorial superrotation; another control simulation that incorporates only intrinsic heat fluxes but no differential radiative heating produces equatorial superrotation but no off-equatorial jets. The proposed mechanisms act in the atmospheres of all giant planets. Saturn's prograde equatorial jet is wider and stronger than Jupiter's due to its larger tropospheric gravity wave speed and consequently greater equatorial Rossby radius. Uranus and Neptune do not exhibit

  9. The Eastern Equatorial Pacific Chlorophyll Dynamics: Update of the `Equatorial Box' Project

    NASA Astrophysics Data System (ADS)

    Westberry, T.; Wang, X.; Murtugudde, R.; Behrenfeld, M.; Roesler, C.

    2006-12-01

    The `Equatorial Box' Project utilizes the mooring observations along the 125 and 140 TAO lines to provide carbon component data, including chlorophyll, primary production, POC and DOC. These parameters together with other oceanographic properties can be used to validate ocean circulation-ecosystem models. In turn, a validated model can offer considerable promise for not only filling the gaps in the spatial and temporal coverage from the available observations, but also enhancing our understanding of the mechanisms underlying the variability. Here, we present both measured and simulated vertical-meridional chlorophyll distributions and primary production along 125W and 140W. While there is a permanent layer of deep chlorophyll maximum at 30-60 m, there is no deep maximum in phytoplankton carbon biomass or primary production. Our analyses focus on impact of nutrient stress and light conditions on chlorophyll dynamics in the eastern equatorial Pacific. We also compare modeled primary productivity with ocean color derived rates.

  10. Electric field observations of equatorial bubbles

    NASA Technical Reports Server (NTRS)

    Aggson, T. L.; Maynard, N. C.; Hanson, W. B.; Saba, Jack L.

    1992-01-01

    Results from the double floating probe experiment performed on the San Marco D satellite are presented, with emphasis on the observation of large incremental changes in the convective electric field vector at the boundary of equatorial plasma bubbles. Attention is given to isolated bubble structures in the upper ionospheric F regions; these observed bubble encounters are divided into two types - type I (live bubbles) and type II (dead bubbles). Type I bubbles show varying degrees of plasma depletion and large upward velocities range up to 1000 km/s. The geometry of these bubbles is such that the spacecraft orbit may cut them where they are tilting either eastward or (more often) westward. Type II bubbles exhibit plasma density depletion but no appreciable upward convection. Both types of events are usually surrounded by a halo of plasma turbulence, which can extend considerably beyond the region of plasma depletion.

  11. Electric field observations of equatorial bubbles

    NASA Astrophysics Data System (ADS)

    Aggson, T. L.; Maynard, N. C.; Hanson, W. B.; Saba, Jack L.

    1992-03-01

    Results from the double floating probe experiment performed on the San Marco D satellite are presented, with emphasis on the observation of large incremental changes in the convective electric field vector at the boundary of equatorial plasma bubbles. Attention is given to isolated bubble structures in the upper ionospheric F regions; these observed bubble encounters are divided into two types - type I (live bubbles) and type II (dead bubbles). Type I bubbles show varying degrees of plasma depletion and large upward velocities range up to 1000 km/s. The geometry of these bubbles is such that the spacecraft orbit may cut them where they are tilting either eastward or (more often) westward. Type II bubbles exhibit plasma density depletion but no appreciable upward convection. Both types of events are usually surrounded by a halo of plasma turbulence, which can extend considerably beyond the region of plasma depletion.

  12. Equatorial trench at the magnetopause under saturation

    NASA Astrophysics Data System (ADS)

    Dmitriev, A.; Suvorova, A.

    2012-08-01

    Magnetic data from GOES geosynchronous satellites were applied for statistical study of the low-latitude dayside magnetopause under a strong interplanetary magnetic field of southward orientation when the reconnection at the magnetopause was saturated. From minimum variance analysis, we determined the magnetopause orientation and compared it with predictions of a reference model. The magnetopause shape was found to be substantially distorted by a duskward shifting such that the nose region appeared in the postnoon sector. At equatorial latitudes, the shape of magnetopause was characterized by a prominent bluntness and by a trench formed in the postnoon sector. The origin of distortions was regarded in the context of the storm-time magnetospheric currents and the large-scale quasi-state reconnection at the dayside magnetopause.

  13. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view to the west, from between the cloud layers and over the patchy white clouds to the east of the hotspot. This is probably an area where moist convection is occurring over large horizontal distances, similar to the atmosphere over the equatorial ocean on Earth. The clouds are high and thick, and are observed to change rapidly over short time scales.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756

  14. Solar cycle and equatorial stratopause temperature

    NASA Astrophysics Data System (ADS)

    Mohanakumar, K.; Devanarayanan, S.

    1983-03-01

    The relationship between the stratopause temperature and solar activity, as represented by the Zuerich sunspot number, is studied. Stratopause temperatures were obtained from monthly mean temperature data of four equatorial rocket launching stations: Ascension Island, Kwajalein, and Fort Sherman during 1969-76, and Thumba during December 1970-76. The data were divided into winter, summer, and equinoctial periods, and the correlation coefficient, regression coefficient, and value of N were calculated. Positive, significant values of both coefficients are found for all the stations, showing that the stratopause temperature is influenced by the sunspot cycle, especially during the equinoctial periods. A wavy pattern is observed in the stratopause temperature over both Thumba and Kwajalein.

  15. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view to the west, from between the cloud layers and over the patchy white clouds to the east of the hotspot. This is probably an area where moist convection is occurring over large horizontal distances, similar to the atmosphere over the equatorial ocean on Earth. The clouds are high and thick, and are observed to change rapidly over short time scales.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756

  16. Particle entry into the equatorial magnetosphere.

    NASA Technical Reports Server (NTRS)

    Fritz, T. A.; Barfield, J. N.; Smith, P. H.; Hoffman, R. A.; Konradi, A.

    1973-01-01

    Explorer-45 data are reviewed which concern the behavior and dynamics of protons associated with the storm-time and quiet-time extraterrestrial ring current at the equatorial plane. The quiet-time proton energy spectrum exhibits a peak in the interval between 100 and 200 keV. During storm conditions, the intensities of the higher energy protons decrease while the intensities of protons from 10 to 100 keV are greatly enhanced, making them the dominant contributor to the storm-time particle energy density. It is shown that during magnetic storms, the ratio of the particle energy density to the magnetic field energy density reaches values greater than unity, and that the plasmasphere has a strong influence on the characteristics of particle injection.

  17. Geomagnetic equatorial anomaly in zonal plasma flow

    NASA Technical Reports Server (NTRS)

    Aggson, T. L.; Herrero, F. A.; Mayr, H. G.; Brace, L. H.; Maynard, N. C.

    1987-01-01

    The observation of a geomagnetic signature in the zonal eastward plasma flow, which is a striking feature of the equatorial ionosphere in the evening quadrant is reported. These observations were derived fronm (E x B)/B-squared measurements made with the cylindrical double-floating-probe experiment carried on the Dynamics Explorer 2 satellite. The signature consists of a crest-trough-crest effect in the latitude dependence of the eastward plasma flow with the crests at + or - 8 dip latitude and the trough nearly centered at the dip equator at all geographic longitudes. This phenomenon can be readily interpreted in terms of the altitude dependence of the F region dynamo electric field, and it is related to dip equator signatures in the plasma density and the magnetic declination which have been reported earlier.

  18. Ozone variability in the equatorial middle atmosphere

    SciTech Connect

    Sun, Chirong; Leovy, C. )

    1990-08-20

    Ozone variability in the equatorial middle atmosphere is investigated and related to temperature and zonal wind variations using data from the Nimbus 7 and Solar Mesosphere Explorer (SME) satellite. The dominant component of the seasonal variability at most levels from the middle stratosphere to the lower thermosphere is the semiannual oscillation (SAO) which has maxima near 10, 3, 0.07, 0.01 mbar, and near or above 0.0024 mbar. There is evidence that the 10-mbar peak is due to vertical advection of odd nitrogen (NO{sub y}) by the semiannually varying residual mean circulation, while temperature dependence of chemical reactions coupled with the thermal SAO near the stratopause and in the upper mesosphere is responsible for the peaks near 3 and 0.07 mbar. The seasonal dependence suggests a contribution from gravity wave modulated vertical mixing of water vapor near the 0.01 mbar level, and the authors speculate that semiannually modulated mixing of atomic oxygen by the (1,1) mode of the thermal tide contributes to the SAO ozone peak above 0.0024 mbar. The negative correlation between temperature and ozone is so strong in the 7- to 0.5-mbar layer that ozone is a useful proxy for temperature variability on time scales from a few days to many months. A preliminary look at annual and interannual variations shows that differing patterns of winter high latitude Rossby wave variability in the two hemispheres are reflected in the signatures of equatorial ozone and temperature in the same layer.

  19. Dynamical variability in Saturn Equatorial Atmosphere

    NASA Astrophysics Data System (ADS)

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

    2003-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Shibata, Yasukuni; Nagasawa, Chikao; Abo, Makoto

    2016-06-01

    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. A DIAL (differential absorption lidar) system for vertical ozone profiles have been installed in the equatorial tropopause region over Kototabang, Indonesia (100.3E, 0.2S). We have observed large ozone enhancement in the upper troposphere, altitude of 13 - 17 km, concurring with a zonal wind oscillation associated with the equatorial Kelvin wave around the tropopause at equatorial region.

  1. ENSO related sea surface salinity variability in the equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Qu, T.

    2016-12-01

    Recently available satellite and Argo data have shown coherent, large-scale sea surface salinity (SSS) variability in the equatorial Pacific. Based on this variability, several SSS indices of El Nino have been introduced by previous studies. Combining results from an ocean general circulation model with available satellite and in-situ observations, this study investigates the SSS variability and its associated SSS indices in the equatorial Pacific. The ocean's role and in particular the vertical entrainment of subtropical waters in this variability are discussed, which suggests that the SSS variability in the equatorial Pacific may play some active role in ENSO evolution.

  2. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view to the southeast, from between the cloud layers and over the north center of the region. The tall white clouds in the lower cloud deck are probably much like large terrestrial thunderclouds. They may be regions where atmospheric water powers vertical convection over large horizontal distances.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756 nm. This model is overly simplistic, but is based on

  3. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view to the northeast, from between the cloud layers and above the streaks in the lower cloud leading towards the hotspot. The upper haze layer has some features that match the lower cloud, such as the bright streak in the foreground of the frame. These are probably thick clouds that span several tens of vertical kilometers.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756 nm. This model is overly

  4. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view from the southwest looking northeast, from an altitude just above the high haze layer. The streaks in the lower cloud leading towards the hotspot are visible. The upper haze layer is mostly flat, with notable small peaks that can be matched with features in the lower cloud. In reality, these areas may represent a continuous vertical cloud column.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756

  5. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view to the northeast, from between the cloud layers and above the streaks in the lower cloud leading towards the hotspot. The hotspot is clearly visible as a deep blue feature. The cloud streaks end near the hotspot, consistent with the idea that clouds traveling along these streak lines descend and evaporate as they approach the hotspot. The upper haze layer is slightly bowed upwards above the hotspot.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional

  6. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view from above and to the south of the visualized area, showing the entire model. The entire region is overlain by a thin, transparent haze. In places the haze is high and thick, especially to the east (to the right of) the hotspot.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756 nm. This model is overly simplistic, but is based on more sophisticated studies of Jupiter's cloud structure. The upper

  7. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view to the northeast, from between the cloud layers and above the streaks in the lower cloud leading towards the hotspot. The hotspot is clearly visible as a deep blue feature. The cloud streaks end near the hotspot, consistent with the idea that clouds traveling along these streak lines descend and evaporate as they approach the hotspot. The upper haze layer is slightly bowed upwards above the hotspot.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional

  8. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view to the northeast, from between the cloud layers and above the streaks in the lower cloud leading towards the hotspot. The upper haze layer has some features that match the lower cloud, such as the bright streak in the foreground of the frame. These are probably thick clouds that span several tens of vertical kilometers.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756 nm. This model is overly

  9. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view to the southeast, from between the cloud layers and over the north center of the region. The tall white clouds in the lower cloud deck are probably much like large terrestrial thunderclouds. They may be regions where atmospheric water powers vertical convection over large horizontal distances.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756 nm. This model is overly simplistic, but is based on

  10. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view from above and to the south of the visualized area, showing the entire model. The entire region is overlain by a thin, transparent haze. In places the haze is high and thick, especially to the east (to the right of) the hotspot.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756 nm. This model is overly simplistic, but is based on more sophisticated studies of Jupiter's cloud structure. The upper

  11. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view from the southwest looking northeast, from an altitude just above the high haze layer. The streaks in the lower cloud leading towards the hotspot are visible. The upper haze layer is mostly flat, with notable small peaks that can be matched with features in the lower cloud. In reality, these areas may represent a continuous vertical cloud column.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756

  12. Strong Equatorial Seasonality during Early Eocene greenhouse

    NASA Astrophysics Data System (ADS)

    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

  13. Equatorial cloud level convection on Venus

    NASA Astrophysics Data System (ADS)

    Lee, Yeon Joo; Imamura, Takeshi; Sugiyama, Koichiro; Sato, Takao M.; Maejima, Yasumitsu

    2016-10-01

    In the equatorial region on Venus, a clear cloud top morphology difference depending on solar local time has been observed through UV images. Laminar flow shaped clouds are shown on the morning side, and convective-like cells on the afternoon side (Titov et al. 2012). Baker et al. (1998) suggested that deep convective motions in the low-to-middle cloud layers at the 40-60 km range can explain cellular shapes. Imamura et al. (2014), however argued that this cannot be a reason, as convection in the low-to-middle cloud layers can be suppressed near sub solar regions due to a stabilizing effect by strong solar heating. We suggest that the observed feature may be related to strong solar heating at local noon time (Lee et al. 2015). Horizontal uneven distribution of an unknown UV absorber and/or cloud top structure may trigger horizontal convection (Toigo et al. 1994). In order to examine these possibilities, we processed 1-D radiative transfer model calculations from surface to 100 km altitude (SHDOM, Evans 1998), which includes clouds at 48-71 km altitudes (Crisp et al. 1986). The results on the equatorial thermal cooling and solar heating profiles were employed in a 2D fluid dynamic model calculation (CReSS, Tsuboki and Sakakibara 2007). The calculation covered an altitude range of 40-80 km and a 100-km horizontal distance. We compared three conditions; an 'effective' global circulation condition that cancels out unbalanced net radiative energy at equator, a condition without such global circulation effect, and the last condition assumed horizontally inhomogeneous unknown UV absorber distribution. Our results show that the local time dependence of lower level cloud convection is consistent with Imamura et al.'s result, and suggest a possible cloud top level convection caused by locally unbalanced net energy and/or horizontally uneven solar heating. This may be related to the observed cloud morphology in UV images. The effective global circulation condition, however

  14. Periodic equatorial water flows from a Hamiltonian perspective

    NASA Astrophysics Data System (ADS)

    Ionescu-Kruse, Delia; Martin, Calin Iulian

    2017-04-01

    The main result of this paper is a Hamiltonian formulation of the nonlinear governing equations for geophysical periodic stratified water flows in the equatorial f-plane approximation allowing for piecewise constant vorticity.

  15. The Matsuno-Gill model and equatorial superrotation

    NASA Astrophysics Data System (ADS)

    Showman, Adam P.; Polvani, Lorenzo M.

    2010-09-01

    Equatorial superrotation can be generated in global general circulation models (GCMs) when forced with longitudinally varying heating, similar to that postulated in the Matsuno-Gill model. However, the implications of the classical Matsuno-Gill theory for equatorial superrotation have not, to date, been addressed. Here, we show that the classic, shallow-water Matsuno-Gill solutions do not exhibit equatorial superrotation: although the flow converges westerly momentum from high latitudes to the equator—promoting superrotation—they also contain an artificial source of easterly momentum at the equator that cancels the latitudinal momentum convergence and prevents superrotation from emerging. This artificial momentum source results from a physically inconsistent representation of vertical momentum transport in the model. We show that if the Matsuno-Gill model is modified to properly account for momentum exchange with an underlying quiescent layer, the solutions naturally exhibit equatorial superrotation, at any forcing amplitude.

  16. POGO observations of the equatorial electrojet

    NASA Technical Reports Server (NTRS)

    Cain, J. C.; Sweeney, R. E.

    1972-01-01

    During intervals in 1967 to 1970, the OGO-4 and 6 spacecraft made over 2000 traversals over the equatorial electrojet in the altitude range 400-800 km when local times were between 9 and 15 hours. These spacecraft carried total field magnetometers making measurements to an accuracy of 2 gamma with a sample rate greater than once a second. Delta F values, the deviations from these observations, were formed from an internal reference model. The results were plotted for a 30 deg band about the equator, and the characteristics of the electrojet effect in the data were investigated. This effect was characterized by a sharp negative V-signature of some 16-19 deg in width and a variable amplitude. The position of this minimum was found to lie within 0.5 deg of the dip equator. A slight northward shift was noted at the longitude of Huancayo. The jet amplitudes were normalized to 400 km amplitudes and observed to be highly variable in time. Amplitudes over the longitude range 50 to 90 deg W averaged 60% higher than elsewhere, as expected, due to the weaker main field. However, though the scatter of amplitudes is high, the expected minima in east Asia was not evident. It was speculated that this could be due to a less conducting upper mantle in this area.

  17. An improved model of equatorial scintillation

    NASA Astrophysics Data System (ADS)

    Secan, J. A.; Bussey, R. M.; Fremouw, E. J.; Basu, Sa.

    1995-05-01

    One of the main limitations of the modeling work that went into the equatorial section of the Wideband ionospheric scintillation model (WBMOD) was that the data set used in the modeling was limited to two stations near the dip equator (Ancon, Peru, and Kwajalein Island, in the North Pacific Ocean) at two fixed local times (nominally 1000 and 2200). Over the past year this section of the WBMOD model has been replaced by a model developed using data from three additional stations (Ascension Island, in the South Atlantic Ocean, Huancayo, Peru, and Manila, Phillipines; data collected under the auspices of the USAF Phillips Laboratory Geophysics Directorate) which provide a greater diversity in both latitude and longitude, as well as cover the entire day. The new model includes variations with latitude, local time, longitude, season, solar epoch, and geomagnetic activity levels. The way in which the irregularity strength parameter CkL is modeled has also been changed. The new model provides the variation of the full probability distribution function (PDF) of log (CkL) rather than simply the average of log (CkL). This permits the user to specify a threshold on scintillation level, and the model will calculate the percent of the time that scintillation will exceed that level in the user-specified scenario. It will also permit calculation of scintillation levels at a user-specified percentile. A final improvement to the WBMOD model is the implementation of a new theory for calculating S4 on a two-way channel.

  18. Climatology of the equatorial lower stratosphere

    NASA Technical Reports Server (NTRS)

    Dunkerton, T. J.; Delisi, D. P.

    1985-01-01

    Twenty years of radiosonde data have been analyzed in an attempt to develop a latitudinal structure climatology of winds, temperature and geopotential at 30 and 50 mb in the equatorial stratosphere. The fine latitudinal resolution provided by the WMO station network reveals several interesting features in the latitudinal structure of the annual and quasi-biennial cycles which dominate this region. For example, the westerly and easterly acceleration phases of the quasi-biennial oscillation are markedly different. Westerly accelerations appear first at the equator, spreading outward with time to higher latitudes, and are more intense, on average, than the easterly accelerations. The easterly accelerations are more uniform in latitude, but less uniform in time, sometimes occurring in two stages. The quasi-biennial wind and temperature oscillations are symmetric about the equator, while the annual harmonic in zonal wind is antisymmetric about the equator, but is not proportional to the Coriolis parameters. Monthly mean zonal wind and temperature appear to be in thermal wind balance at the equator. Some brief remarks are also made concerning variability of the quasi-biennial oscillation and the effects of El Chichon.

  19. Condor equatorial electrojet campaign: Radar results

    SciTech Connect

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

    1987-12-01

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

  20. Equatorial Electrojet Instabilities - New Fluid Model Approach

    NASA Astrophysics Data System (ADS)

    Hassan, Ehab; Horton, Wendell; Smolyakov, Andrei; Hatch, David

    2014-10-01

    A fluid model combines both Farley-Buneman (Type-I) and Gradient-Drift (Type-II) plasma instabilities in the equatorial electrojet. The ion viscosity and electron inertia are considered in the ion and electron equations of motion, respectively. These two terms play an important role in stabilizing the growing modes in the linear regime and in driving Farley-Buneman instability into the saturation state. The simulation is stable in the saturated state and the results show good agreements with a number of rocket measurements and radar observations, where we find (1) a saturation of the plasma density around 7% relative to the ionosphere background, (2) the horizontal secondary electric field stabilizes at 8.7 (mV/m), (3) the phase velocity of the perturbed density wave has a value close to the ion-acoustic speed inside the electrojet, (5) an up-down asymmetry in the vertical particle fluxes of plasma density, (5) an east-west asymmetry in the plasma drifts in the zonal direction, and (6) a generation of the small-scale; of the order of 3 meter scale length and less, irregularities embedded in the large-scale structures in the vertical direction. The break-up of the large-scale structures into small-scale structures explains the disappearance of Type-II echoes in the presence of Ty.

  1. Forecasting scintillation activity and equatorial spread F

    NASA Astrophysics Data System (ADS)

    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.

  2. Onset conditions for equatorial spread F

    SciTech Connect

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

    1992-09-01

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

  3. Catastrophic ape decline in western equatorial Africa.

    PubMed

    Walsh, Peter D; Abernethy, Kate A; Bermejo, Magdalena; Beyers, Rene; De Wachter, Pauwel; Akou, Marc Ella; Huijbregts, Bas; Mambounga, Daniel Idiata; Toham, Andre Kamdem; Kilbourn, Annelisa M; Lahm, Sally A; Latour, Stefanie; Maisels, Fiona; Mbina, Christian; Mihindou, Yves; Obiang, Sosthène Ndong; Effa, Ernestine Ntsame; Starkey, Malcolm P; Telfer, Paul; Thibault, Marc; Tutin, Caroline E G; White, Lee J T; Wilkie, David S

    2003-04-10

    Because rapidly expanding human populations have devastated gorilla (Gorilla gorilla) and common chimpanzee (Pan troglodytes) habitats in East and West Africa, the relatively intact forests of western equatorial Africa have been viewed as the last stronghold of African apes. Gabon and the Republic of Congo alone are thought to hold roughly 80% of the world's gorillas and most of the common chimpanzees. Here we present survey results conservatively indicating that ape populations in Gabon declined by more than half between 1983 and 2000. The primary cause of the decline in ape numbers during this period was commercial hunting, facilitated by the rapid expansion of mechanized logging. Furthermore, Ebola haemorrhagic fever is currently spreading through ape populations in Gabon and Congo and now rivals hunting as a threat to apes. Gorillas and common chimpanzees should be elevated immediately to 'critically endangered' status. Without aggressive investments in law enforcement, protected area management and Ebola prevention, the next decade will see our closest relatives pushed to the brink of extinction.

  4. Equatorial Staphyloma Associated with Neurofibromatosis Type 1

    PubMed Central

    Shimada, Yoshiaki; Horiguchi, Masayuki

    2016-01-01

    We report a case of a 38-year-old man who presented with a recently self-detected lump under his left eyebrow. Previous ophthalmological history was unremarkable except for unilateral high myopia (left eye) since childhood. The appearance of the left eye was seemingly normal; however, with the top lid pulled up on downward gaze, a dark brown bulge emerged. The bulge was 10 × 7 mm and approximately 4 mm in height, and was covered by the extended superior rectus muscle. The diagnosis of equatorial staphyloma was made after coronal T1-weighted magnetic resonance imaging of the orbit revealed the dilatation of the vitreous cavity. Ocular movements were fully maintained and visual acuity was largely spared: 20/15 in the right eye without correction and 20/25 in the left eye with −10.00 spheres and −4.00 × 80 degrees cylinders. His past and family histories were unremarkable; however, small neurofibromas and café au lait spots all over his body led to the diagnosis of neurofibromatosis type 1 (NF1). From this case, similar to previous reports, we suggest that manifestations of NF1 are extremely variable and unpredictable. PMID:27721788

  5. The formation of an equatorial coronal hole

    NASA Astrophysics Data System (ADS)

    Yang, Liheng; Jiang, Yunchun; Zhang, Jun

    2010-02-01

    The formation of an equatorial coronal hole (CH) from 2006 January 9 to 12 was simultaneously observed by GOES-12/SXI, SOHO/EIT and SOHO/MDI instruments. The varieties of soft X-ray and EUV brightness, coronal temperature, and total magnetic flux in the CH were examined and compared with that of a quiet-sun (QS) region nearby. The following results are obtained. (1) A preexisting dark lane appeared on the location of the followed CH and was reinforced by three enhanced networks. (2) The CH gradually formed in about 81 hours and was predominated by positive magnetic flux. (3) During the formation, the soft X-ray and EUV brightness, coronal temperature, and total magnetic flux obviously decreased in the CH, but were almost no change in the QS region. The decrease of the total magnetic flux may be the result of magnetic reconnection between the open and closed magnetic lines, probably indicating the physical mechanism for the birth of the CH.

  6. Vertical motions in the equatorial middle atmosphere

    NASA Technical Reports Server (NTRS)

    Weisman, M. L.

    1979-01-01

    A single station vertical velocity equation which considers ageostrophic and diabatic effects derived from the first law of thermodynamics and a generalized thermal wind relation is presented. An analysis and verification procedure which accounts for measurement and calculation errors as well as time and space continuity arguments and theoretical predictions are described. Vertical velocities are calculated at every kilometer between 25 and 60 km and for approximately every three hours for the above diurnal period at Kourou (French Guiana), Fort Sherman (Panama Canal Zone), Ascension Island, Antigua (British West Indies) and Natal (Brazil). The results, plotted as time series cross sections, suggest vertical motions ranging in magnitude from 1 or 2 cm/sec at 30 km to as much as 15 cm/sec at 60 km. Many of the general features of the results agree well with atmospheric tidal predictions but many particular features suggest that both smaller time scale gravity waves (periods less than 6 hours) and synoptic type waves (periods greater than 1 day) may be interacting significantly with the tidal fields. The results suggest that vertical motions can be calculated for the equatorial middle atmosphere and must be considered a significant part of the motion for time scales from 8 to 24 hours.

  7. An equatorial temperature and wind anomaly (ETWA)

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  8. On Irrotational Flows Beneath Periodic Traveling Equatorial Waves

    NASA Astrophysics Data System (ADS)

    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.

  9. On Irrotational Flows Beneath Periodic Traveling Equatorial Waves

    NASA Astrophysics Data System (ADS)

    Quirchmayr, Ronald

    2016-08-01

    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.

  10. Overview of the Equatorial Electrojet and Related Ionospheric Current Systems

    DTIC Science & Technology

    2007-11-02

    NUWC-NPT Technical Report 11,676 25 April 2005 Overview of the Equatorial Electrojet and Related Ionospheric Current Systems John P. Casey...Overview of the Equatorial Electrojet and Related Ionospheric Current Systems PR A590045 6. AUTHOR(S) John P. Casey 7. PERFORMING ORGANIZATION NAME(S) AND...that flows in the ionosphere in a narrow zone above the magnetic dip equator during the daytime. The electrojet current produces a large enhancement of

  11. Photoelectron escape fluxes over the equatorial and midlatitude regions

    NASA Technical Reports Server (NTRS)

    Narasingarao, B. C.; Singh, R. N.; Maier, E. J.

    1972-01-01

    Satellite measurements of photoelectron escape flux around noontime made by Explorer 31 in 600-800 km altitude range are reported for the equatorial and midlatitude regions. The pitch angle distributions and the spectral distributions are derived from the data. Analyzed data show that the flux for equatorial regions is lower by a factor 2 to 3 in comparison to that of midlatitude regions. Theoretical calculations are also made to compare with observed escape fluxes.

  12. Influence of Assimilation of Subsurface Temperature Measurements on Simulations of Equatorial Undercurrent and South Equatorial Current Along the Pacific Equator

    NASA Technical Reports Server (NTRS)

    Halpern, David; Leetmaan, Ants; Reynolds, Richard W.; Ji, Ming

    1997-01-01

    Equatorial Pacific current and temperature fields were simulated with and without assimilation of subsurface temperature measurements for April 1992 - March 1995, and compared with moored bouy and research vessel current measurements.

  13. Influence of Assimilation of Subsurface Temperature Measurements on Simulations of Equatorial Undercurrent and South Equatorial Current Along the Pacific Equator

    NASA Technical Reports Server (NTRS)

    Halpern, David; Leetmaan, Ants; Reynolds, Richard W.; Ji, Ming

    1997-01-01

    Equatorial Pacific current and temperature fields were simulated with and without assimilation of subsurface temperature measurements for April 1992 - March 1995, and compared with moored bouy and research vessel current measurements.

  14. Eastward traverse of equatorial plasma plumes observed with the Equatorial Atmosphere Radar in Indonesia

    NASA Astrophysics Data System (ADS)

    Fukao, S.; Yokoyama, T.; Tayama, T.; Yamamoto, M.; Maruyama, T.; Saito, S.

    2006-07-01

    The zonal structure of radar backscatter plumes associated with Equatorial Spread F (ESF), probably modulated by atmospheric gravity waves, has been investigated with the Equatorial Atmosphere Radar (EAR) in West Sumatra, Indonesia (0.20° S, 100.32° E; dip latitude 10.1° S) and the FM-CW ionospheric sounders on the same magnetic meridian as the EAR. The occurrence locations and zonal distances of the ESF plumes were determined with multi-beam observations with the EAR. The ESF plumes drifted eastward while keeping distances of several hundred to a thousand kilometers. Comparing the occurrence of the plumes and the F-layer uplift measured by the FM-CW sounders, plumes were initiated within the scanned area around sunset only, when the F-layer altitude rapidly increased. Therefore, the PreReversal Enhancement (PRE) is considered as having a zonal variation with the scales mentioned above, and this variation causes day-to-day variability, which has been studied for a long time. Modulation of the underlying E-region conductivity by gravity waves, which causes inhomogeneous sporadic-E layers, for example, is a likely mechanism to determine the scale of the PRE.

  15. Equatorial Kelvin Waves: A UARS MLS View.

    NASA Astrophysics Data System (ADS)

    Canziani, Pablo O.; Holton, James R.; Fishbein, Evan; Froidevaux, Lucien; Waters, Joe W.

    1994-10-01

    Data from the Microwave Limb Sounder instrument on the Upper Atmosphere Research Satellite are used to compare two periods of Kelvin wave activity during different stages of the equatorial quasi-biennial oscillation. The analysis is carried out using an asynoptic mapping technique. A wide bandpass filter is used to isolate the frequency bands where Kelvin waves have been identified in previous studies. Time-height and time-latitude plots of the bandpassed data are used to identify Kelvin wave activity in the temperature and ozone fields. Frequency spectra of temperature and ozone amplitudes are constructed to further analyze the latitudinal and meridional distribution of Kelvin wave activity in zonal wavenumbers 1 and 2. The characteristics identified in these plots agree well with theoretical predictions and previous observations of middle atmosphere Kelvin waves.The time-height and time-latitude plots support the existence of Kelvin waves in discrete frequency bands; the slow, fast, and ultrafast Kelvin modes are all identified in the data. The characteristics of these modes do not vary much despite different mean flow conditions in the two periods examined.For the Kelvin wave-induced perturbations in ozone, the change from a transport-dominated regime below 10 hPa to a photochemically controlled regime above 10 hPa is clearly apparent in the height dependence of the phase difference between temperature and ozone. The ratios of the ozone perturbation amplitude to the temperature perturbation amplitude for the various observed Kelvin wave modes are in agreement with model estimates and LIMS (Limb Infrared Monitor of the Stratosphere) observations in the lower half of the region sampled but appear to be too large in the upper stratosphere and lower mesosphere.

  16. Isostatic compensation of equatorial highlands on Venus

    NASA Technical Reports Server (NTRS)

    Kucinskas, Algis B.; Turcotte, Donald L.

    1994-01-01

    Spherical harmonic models for Venus' global topography and gravity incorporating Magellan data are used to test isostatic compensation models in five 30 deg x 30 deg regions representative of the main classes of equatorial highlands. The power spectral density for the harmonic models obeys a power-law scaling with spectral slope Beta approximately 2 (Brown noise) for the topography and Beta approximately 3 (Kaula's law) for the geoid, similar to what is observed for Earth. The Venus topography spectrum has lower amplitudes than Earth's which reflects the dominant lowland topography on Venus. Observed degree geoid to topography ratios (GTRs) on Venus are significantly smaller than degree GTRs for uncompensated topography, indicative of substantial compensation. Assuming a global Airy compensation, most of the topography is compensated at depths greater than 100 km, suggesting a thick lithosphere on Venus. For each region considered we obtain a regional degree of compensation C from a linear regression of Bouguer anomaly versus Bouguer gravity data. Geoid anomaly (N) versus topography variation (h) data for each sample were compared, in the least-squares sense, to theoretical correlations for Pratt, Airy, and thermal thinning isostasy models yielding regional GTR, zero-elevation crustal thickness (H), and zero elevation thermal lithosphere thickness (y(sub L(sub 0)), respectively. We find the regional compensation to be substantial (C approximately 52-80%), and the h, N data correlations in the chosen areas can be explained by isostasy models applicable on the Earth and involving variations in crustal thickness (Airy) and/or lithospheric (thermal thinning) thickness. However, a thick crust and lithosphere (y(sub L(sub 0)) approximately 300 km) must be assumed for Venus.

  17. Equatorial Kelvin waves: A UARS MLS view

    NASA Technical Reports Server (NTRS)

    Canziani, Pablo O.; Holton, James R.; Fishbein, Evan; Froidevaux, Lucien; Waters, Joe W.

    1994-01-01

    Data from the Microwave Limb Sounder (MLS) instrument on the Upper Atmosphere Research Satellite (UARS) are used to compare two periods of Kelvin wave activity during different stages of the equatorial quasi-biennial oscillation. The analysis is carried out using an asynoptic mapping technique. A wide bandpass filter is used to isolate the frequency bands where Kelvin waves have been identified in previous studies. Time-height and time-latitude plots of the bandpassed data are used to identify Kelvin wave activity in the temperature and ozone fields. Frequency spectra of temperature and ozone amplitudes are constructed to further analyze the latitudinal and meridional distribution of Kelvin wave activity in zonal wavenumbers 1 and 2. The characteristics identified in these plots agree well with theoretical predictions and previous observations of middle atmosphere Kelvin waves. The time-height and time-latitude plots support the existence of Kelvin waves in discrete frequency bands; the slow, fast, and ultrafast Kelvin modes are all identified in the data. The characteristics of these modes do not vary much despite different mean flow conditions in the two periods examined. For the Kelvin wave-induced perturbations in ozone, the change from a transport-dominated regime below 10 hPa to a photochemically controlled regime above 10 hPa is clearly apparent in the height dependence of the phase difference between temperature and ozone. The ratios of the ozone perturbation amplitude to the temperature perturbation amplitude for the various observed Kelvin wave modes are in agreement with model estimates and LIMS (Limb Infrared Monitor of the Stratosphere) observations in the lower half of the region sampled but appear to be too large in the upper stratosphere and lower mesosphere.

  18. Climatology of equatorial stratosphere over Lagos, Nigeria

    NASA Astrophysics Data System (ADS)

    Oyekola, Oyedemi Samuel

    We have used 12 complete calendar years (January 1993-December 2004) of monthly averages of measurements made by the Dobson spectrophotometer instrument over an urban site, Lagos (6.6oN, 3.3oE), southwest Nigeria, to study equatorial stratospheric column ozone variations and trends. Our results indicate that the time-averaged total column ozone has a seasonal cy-cle, which maximizes in June and July with a value of 259 Dobson units (DU) and minimizes in February with a magnitude of 250 DU. Statistical analysis of the climatological mean monthly total Dobson O3 record for 1993-2004 show that the local trend is approximately +0.041±0.0011 DU/year (+0.49±0.013% per decade). Spectral analysis was applied to the monthly averages series. The significant periodicity at 95% confidence level demonstrate prominent spectra peaks near 1.9 and 3.6 years, representative of quasi-biennial oscillation (QBO) and quasi-triennial oscillation (QTO), respectively. Signal due to semiannual variation is also identified at Lagos sounding site. Comparison with the ozone observations from Total Ozone Mapping Spectrom-eter (TOMS) on board the Earth-Probe (EP) satellite for the period from 1997 to 2002 reveal that EP/TOMS instrument consistently larger than the ground-based measurement from Dob-son station. Percentage mean relative disparity ranges from -11% to 15%. The root mean square error (RMSE) between satellite and ground-based observations over Lagos ranges be-tween ˜35-83 DU with largest and lowest variability occurring during the ascending phase of solar activity (1999, 10.7 cm radio flux, F10.7 equals 154 flux units) and during the peak phase of solar activity (2001, F10.7 equals 181), respectively.

  19. More on accreting black hole spacetime in equatorial plane

    NASA Astrophysics Data System (ADS)

    Salahshoor, K.; Nozari, K.; Khesali, A. R.

    2017-02-01

    Spacetime around an accreting black hole is an interesting issue to study. The metric of an isolated black hole (rotating or non-rotating) spacetime has been well-known for decades. Although metrics of some spacetimes containing accreting black holes are known in some situations, the issue has some faces that are not well-known yet and need further investigation. In this paper, we construct a new form of metric which the effect of accretion disk on black hole spacetime is taken into account in the equatorial plane. We study motion and trajectories of massive particles and also photons falling from infinity towards black hole in equatorial plane around the black hole. We use an exponential form for the density profile of the accretion disk in equatorial plane as ρ =ρ0e^{-α r}. We show that with this density profile, the disk is radially stable if α ≤ 3 × 10^{-3} (in units of length inverse). In order to study some important quantities related to the accretion disks such as locations of marginally stable circular orbits (r_{ms} or r_{ISCO}), marginally bounded circular orbits (r_{mb}), and also photon orbits in equatorial plane, we use the effective potential approach. We show that in this spacetime metric the innermost stable circular orbit in equatorial plane is given by r_{ISCO}=4.03 μ (where μ =MG/c 2) which is different, but comparable, with the Schwarzschild spacetime result, r^{(Sch)}_{ISCO}=6 μ . We show that the maximum radiation efficiency of the accretion disk, η , in equatorial plane is 8.6 percent which is greater than the corresponding value for Schwarzschild spacetime. Finally, we show that in this setup photons can have stable circular orbits in equatorial plane unlike the Schwarzschild spacetime.

  20. Polar and equatorial ionosphere interaction during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Biktash, L.

    The solar wind-magnetosphere-ionosphere coupling as applied to the polar and equatorial ionosphere dynamics is examined. To do this simultaneous observations of the IMF, ground-based measurements of the ionospheric parameters and geomagnetic field variations from the high latitudes to the equator are used during magnetic storms. It is shown that the auroral electric fields during magnetically disturbed conditions by the magnetospheric current systems can play a dominant role in the equatorial ionosphere processes. During magnetic storms the equatorial ionosphere parameters h'F, foF2 and etc. widely deviated from quiet day conditions and different kinds of ionospheric irregularities are formed. The equatorial ionospheric irregularities manifest as spread F in ionograms, reversals of drift velocities, scintillation of radio transmissions through the ionosphere, etc. These phenomena can interpret as the result of direct penetration of electric fields from the high latitude field-aligned currents (FAC) to the equatorial ionosphere. Model of direct penetration of FAC electric field of Polar Regions 1 and Region 2, which are controlled by the solar wind, to the equatorial ionosphere is presented. From this model the solar wind electric field through the FAC is likely to the factor wich generate or inhibit the equatorward penetration of the high latitude electric field. We demonstrate that the model is suitable to explain h'F, foF2 variations and scintillation activity during geomagnetic storms. Taking into account of the equatorial and auroral electric fields coupling, relationship, between these regions can be useful to study difficult auroral conditions during magnetic storms.

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

    NASA Astrophysics Data System (ADS)

    Münnich, M.; Neelin, J. D.

    2005-11-01

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

  2. Late Paleozoic Deglaciation in Western Equatorial Pangaea

    NASA Astrophysics Data System (ADS)

    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

  3. Equatorial Winds on Saturn and the Stratospheric Oscillation

    NASA Technical Reports Server (NTRS)

    Li, Liming; Jian, Xun; Ingersoll, Andrew P.; DelGenio, Anthony D.; Porco, Carolyn C.; West, Robert A.; Vasavada, Ashwin R.; Ewald, Shawn P.; Conrath, Barney J.; Gierasch, Peter J.; Simon-Miller, Amy A.; Nixon, Conor A.; Achterberg, Richard K.; Orton, Glenn S.; Fletcher, Leigh N.; Baines, Kevin H.

    2011-01-01

    The zonal jets on the giant planets are generally thought to be stable with time. Recently, there are still some debates about the general thought. Here, we report a significant temporal variation of the equatorial jet at high-altitude on Saturn. Long-term (2004-2009) observations by Cassini reveal that wind speed at the 60-mbar level increased from 270 m/s in 2004 to 290 m/s in 2008, while the wind speed has been mostly constant over time at the 500-mbar level in the southern equatorial region. The Cassini observations further reveal that the equatorial jet intensified approximately 60 m/s in the stratosphere (1-5 mbar) from 2005 to 2008. The fact that the wind acceleration is weaker at the 60-mbar level (approximately 20 m/s) than at the 1-mbar level (approximately 60 m/s) demonstrates that the equatorial oscillation is damped when it propagates downwards to the tropopause around 60 mbar. The direct measurement of the varying equatorial jet around the tropopause also serves as a key boundary condition when deriving the thermal wind fields in the stratosphere.

  4. Meridional equatorial electrojet current in the American sector

    NASA Astrophysics Data System (ADS)

    Rastogi, R. G.

    1999-02-01

    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.

  5. Equatorial winds on Saturn and the stratospheric oscillation

    NASA Astrophysics Data System (ADS)

    Li, Liming; Jiang, Xun; Ingersoll, Andrew P.; Del Genio, Anthony D.; Porco, Carolyn C.; West, Robert A.; Vasavada, Ashwin R.; Ewald, Shawn P.; Conrath, Barney J.; Gierasch, Peter J.; Simon-Miller, Amy A.; Nixon, Conor A.; Achterberg, Richard K.; Orton, Glenn S.; Fletcher, Leigh N.; Baines, Kevin H.

    2011-11-01

    The zonal jets on the giant planets have been thought to be stable in time. A decline in the velocity of Saturn's equatorial jet has been identified, on the basis of a comparison of cloud-tracking data across two decades, but the differences in cloud speeds have since been suggested to stem from changes in cloud altitude in combination with vertical wind shear, rather than from temporal changes in wind strength at a given height. Here, we combine observations of cloud tracks and of atmospheric temperatures taken by two instruments on the Cassini spacecraft to reveal a significant temporal variation in the strength of the high-altitude equatorial jet on Saturn. Specifically, we find that wind speeds at atmospheric pressure levels of 60mbar, corresponding to Saturn's tropopause, increased by about 20ms-1 between 2004 and 2008, whereas the wind speed has been essentially constant over time in the southern equatorial troposphere. The observations further reveal that the equatorial jet intensified by about 60ms-1 between 2005 and 2008 in the stratosphere, that is, at pressure levels of 1-5mbar. Because the wind acceleration is weaker near the tropopause than higher up, in the stratosphere, we conclude that the semi-annual equatorial oscillation of Saturn's middle atmosphere is also damped as it propagates downwards.

  6. Equatorial Mountain Torques and Cold Surges in a GCM

    NASA Astrophysics Data System (ADS)

    Lott, Francois; Mailler, Sylvain

    2014-05-01

    The dynamical relations between the equatorial atmospheric angular momentum, the equatorial mountain torque and the cold surges are analysed in a General Circultaion Model (GCM). First we show that the global equatorial atmospheric momentum budget is very well closed in the model which is a clear benefit when we compare with results from the NCEP reanalysis. We then confirm that the equatorial torques due to the Tibetan plateau, the Rockies and the Andes are well related to the cold surges developping over South Eastern China, North America, and the Southern South America respectively. For all these mountains, a peack in the Equatorial mountain torque component that points locally toward the pole preceeds by few days the development of the cold surges, yielding a predictive interest to our results. We also analyse the contributions to the torques of the parameterized mountain stresses and find that they contribute substantially. In experiments without the parameterized stresses, we also find that the explicit terms partly compensate the parameterized contributions to the torque, and the cold surges are not much affected. This shows that the cold surges can be well captured by models, providing that the synoptic conditions prior to their onset are well represented. The compensation between torques is nevertheless not complete and some weekening of the cold surges is found when the mountain forcings are reduced. This illustrates how the exact torques are needed at a given time to produce the correct synoptic scale dynamics at a later stage.

  7. Equatorial superrotation in a thermally driven zonally symmetric circulation

    NASA Technical Reports Server (NTRS)

    Mayr, H. G.; Harris, I.

    1981-01-01

    Near the equator where the Coriolis force vanishes, the momentum balance for the axially symmetric circulation is established between horizontal and vertical diffusion, which, a priori, does not impose constraints on the direction or magnitude of the zonal winds. Solar radiation absorbed at low latitudes is a major force in driving large scale motions with air rising near the equator and falling at higher latitudes. In the upper leg of the meridional cell, angular momentum is redistributed so that the atmosphere tends to subrotate (or corotate) at low latitudes and superrotate at high latitudes. In the lower leg, however, the process is reversed and produces a tendency for the equatorial region to superrotate. The outcome depends on the energy budget which is closely coupled to the momentum budget through the thermal wind equation; a pressure (temperature) maximum is required to sustain equatorial superrotation. Such a condition arises in regions which are convectively unstable and the temperature lapse rate is superadiabatic. It should arise in the tropospheres of Jupiter and Saturn; planetary energy from the interior is carried to higher altitudes where radiation to space becomes important. Upward equatorial motions in the direct and indirect circulations (Ferrel-Thomson type) imposed by insolation can then trap dynamic energy for equatorial heating which can sustain the superrotation of the equatorial region.

  8. Sources of variability in equatorial topside ionospheric and plasmaspheric temperatures

    NASA Astrophysics Data System (ADS)

    Varney, Roger H.; Hysell, David L.; Huba, J. D.

    2013-10-01

    Jicamarca measurements of electron temperatures at high altitudes (500-1500km) from the last solar minimum routinely show variations of hundreds of Kelvin from day-to-day. Possible sources of these variations are explored using the SAMI2-PE is another model of the ionosphere including photoelectron transport (SAMI2-PE) model, which includes a multistream photoelectron transport model. Changes to the electric fields, meridional winds, and thermospheric densities can all change the electron densities and temperatures at high altitudes. The high altitude electron temperatures are primarily determined by a balance between heating from photoelectrons which travel up the field lines and thermal diffusion which carries heat back down the field lines. The winds and electric fields will change the altitude and densities of the off-equatorial F-region peaks, especially on the field lines connected to the equatorial arcs. The densities and temperatures in the plasmasphere will self consistently adjust themselves to achieve diffusive equilibrium with the off-equatorial F-regions. Furthermore, decreases in the density and/or altitude of the F-region makes it easier for photoelectrons to escape to high altitudes. These connections between the equatorial plasmasphere, the off-equatorial F-regions, and the neutral thermosphere suggest that high altitude measurements at Jicamarca could be used to study thermospheric variability.

  9. Effects of Ca++ depletion on lens equatorial currents in frog lenses.

    PubMed

    Patterson, J W; Walsh, S; Wind, B E

    1989-01-01

    The combination of the vibrating probe measuring the outward equatorial current (J) with microelectrodes measuring PD and the response to injected current provides one of the best means of relating macro findings of lens currents to the micro data that have been reported using the patch clamp technique. In standard frog Ringers solution the equatorial current appears to be a relatively pure K+ current with a reversal potential of -95 mV. This agrees with the reversal potential of the 45 pS K+ channel. When Ca++ is removed from the medium bathing the lens the input resistance (R) decreases, the PD becomes less negative and the current J increases. This process can be reversed by adding Ca++ or Mn++ to the Ca++ deficient medium. When all Ca++ is removed from the medium by adding EGTA in the absence of Ca++, the increase in J is less than expected. However, if Na+ is replaced by TMA in the Ca++ depleted EGTA medium the current is seven times as great. These changes are consistent with those found in non-selective cation channels in the absence of Ca++.

  10. Iron sources and pathways into the Pacific Equatorial Undercurrent

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    Using a novel observationally constrained Lagrangian iron model forced by outputs from an eddy-resolving biogeochemical ocean model, we examine the sensitivity of the Equatorial Undercurrent (EUC) iron distribution to EUC source region iron concentrations. We find that elevated iron concentrations derived from New Guinea Coastal Undercurrent (NGCU) alone is insufficient to explain the high concentrations observed in the EUC. In addition, due to the spread in transit times, interannual NGCU iron pulses are scavenged, diluted, or eroded, before reaching the eastern equatorial Pacific. With an additional iron source from the nearby New Ireland Coastal Undercurrent, EUC iron concentrations become consistent with observations. Furthermore, as both the New Guinea and New Ireland Coastal Undercurrents strengthen during El Niño, increased iron input into the EUC can enhance the iron supply into the eastern equatorial Pacific. Notably, during the 1997/1998 El Niño, this causes a simulated 30% iron increase at a 13 month lag.

  11. The effect of islands on low frequency equatorial motions

    NASA Technical Reports Server (NTRS)

    Cane, M. A.; Du Penhoat, Y.

    1982-01-01

    A complete analytic solution is presented for the influence of equatorial islands on steady low-frequency waves. If the island is small (the meridional extent is much less than the equatorial radius of deformation, R), the waves pass it almost undisturbed, with the mass flux incident on the upstream side flowing around it nearly equally to the north and to the south and continuing on downstream in the lee of the island. For large islands (comparable in extent with R or larger), the principal response is organized as it would be if the island barrier were meridionally infinite. An incident Kelvin wave is largely reflected as long Rossby waves; symmetric long Rossby waves are reflected as equatorial Kelvin waves, while antisymmetric ones stop at the island barrier. In all cases, a boundary current composed of short Rossby waves forms at the eastern side of the island and accomplishes the required meridional redistribution of the zonal mass flux.

  12. Propagation of VLF waves through the equatorial anomaly

    NASA Astrophysics Data System (ADS)

    Tanaka, Y.; Cairo, L.

    1980-12-01

    The propagation characteristics of artificial VLF waves (NBA, 24.0 kHz) through the equatorial ionosphere have been studied by means of data obtained onboard the FR-1 satellite at 750 km altitude over Latin America. Large latitudinal variations of the vertical component of the wave normal generally appear in the evening at geomagnetic latitudes of 10 to 15 deg, and they also appear on most of the passes examined at night at latitudes of 5 to 10 deg. Ray and wave normal directions of the VLF waves are computed in various models of field-aligned equatorial anomaly. The latitudinal variations in the evening are due to large negative latitudinal gradients of electron density associated with the equatorial anomaly, and the latitudinal variations at night are due to relatively small density gradients.

  13. The Equatorial Ridges of Pan and Atlas: Terminal Accretionary Ornaments?

    NASA Astrophysics Data System (ADS)

    Charnoz, Sébastien; Brahic, André; Thomas, Peter C.; Porco, Carolyn C.

    2007-12-01

    In the outer regions of Saturn’s main rings, strong tidal forces balance gravitational accretion processes. Thus, unusual phenomena may be expected there. The Cassini spacecraft has recently revealed the strange “flying saucer” shape of two small satellites, Pan and Atlas, located in this region, showing prominent equatorial ridges. The accretion of ring particles onto the equatorial surfaces of already-formed bodies embedded in the rings may explain the formation of the ridges. This ridge formation process is in good agreement with detailed Cassini images showing differences between rough polar and smooth equatorial terrains. We propose that Pan and Atlas ridges are kilometers-thick “ring-particle piles” formed after the satellites themselves and after the flattening of the rings but before the complete depletion of ring material from their surroundings.

  14. Bistability between equatorial and axial dipoles during magnetic field reversals.

    PubMed

    Gissinger, Christophe; Petitdemange, Ludovic; Schrinner, Martin; Dormy, Emmanuel

    2012-06-08

    Numerical simulations of the geodynamo in the presence of heterogeneous heating are presented. We study the dynamics and the structure of the magnetic field when the equatorial symmetry of the flow is broken. If the symmetry breaking is sufficiently strong, the m=0 axial dipolar field is replaced by a hemispherical magnetic field, dominated by an oscillating m=1 magnetic field. Moreover, for moderate symmetry breaking, a bistability between the axial and the equatorial dipole is observed. In this bistable regime, the axial magnetic field exhibits chaotic switches of its polarity, involving the equatorial dipole during the transition period. This new scenario for magnetic field reversals is discussed within the framework of Earth's dynamo.

  15. IMF polarity effects on the equatorial ionospheric F-region

    SciTech Connect

    Sastri, J.H.

    1985-01-01

    An exploratory study is made of the influence, during the equinoxes, of the interplanetary magnetic field (IMF) sector structure on the ionospheric F-region using ionosonde data from several equatorial stations for a 3-yr period around the 19th sunspot cycle maximum. It is found that, compared with days having positive IMF polarity, the post-sunset increase of h'F near the dip equator and the depth of the equatorial ionization anomaly (EIA) are reduced during the vernal equinox and enhanced during the autumnal equinox on days with negative IMF polarity. Similar trends are also noted in the data for the 20th sunspot cycle maximum, but with reduced amplitude. The systematic changes in the F-region characteristics suggest a modification of the equatorial zonal electric fields in association with the IMF polarity-related changes in the semi-annual variation of geomagnetic activity. 24 references.

  16. The equatorial ridges of Pan and Atlas: terminal accretionary ornaments?

    PubMed

    Charnoz, Sébastien; Brahic, André; Thomas, Peter C; Porco, Carolyn C

    2007-12-07

    In the outer regions of Saturn's main rings, strong tidal forces balance gravitational accretion processes. Thus, unusual phenomena may be expected there. The Cassini spacecraft has recently revealed the strange "flying saucer" shape of two small satellites, Pan and Atlas, located in this region, showing prominent equatorial ridges. The accretion of ring particles onto the equatorial surfaces of already-formed bodies embedded in the rings may explain the formation of the ridges. This ridge formation process is in good agreement with detailed Cassini images showing differences between rough polar and smooth equatorial terrains. We propose that Pan and Atlas ridges are kilometers-thick "ring-particle piles" formed after the satellites themselves and after the flattening of the rings but before the complete depletion of ring material from their surroundings.

  17. The seismicity of the equatorial Mid-Atlantic Ridge and its long-offset transforms

    NASA Astrophysics Data System (ADS)

    Smith, D. K.; Dziak, R. P.; Palmiotto, C.; Parnell-Turner, R. E.; Zheleznov, A.

    2012-12-01

    An array of eight hydrophones is monitoring seismicity of the equatorial Atlantic between 20N and 10S. The array is obtaining a two-year, continuous record of seismicity, which will provide an important new view of the spatial and temporal patterns of seismicity at the slow-spreading equatorial Mid-Atlantic Ridge (MAR) and its long-offset transforms. The hydroacoustically-recorded seismicity, which will be in hand in 2014, can be used to address several key questions concerning the modes of spreading along the strongly offset equatorial MAR, the short-term earthquake predictability on some of the longest transform faults in the oceans, and the dynamics of the NA-SA-AF triple junction whose exact location is not known. In addition, seismic patterns of the entire South Atlantic will be obtained (at reduced location accuracy), and will aid in understanding the dynamics of the southern MAR, Walvis Ridge, Rio Grande Rise, and other prominent seafloor features. The hydroacoustic data will also allow characterization of cetacean populations in the region as well as an assessment of the ambient noise levels due to shipping and oil exploration. To provide additional information on the short-term earthquake predictability (retrospective) on oceanic transform faults, we are identifying all magnitude mb >5 earthquakes in our existing hydroacoustic databases and searching for systematic foreshock activity associated with these events. We have multi-year earthquake databases accumulated from past hydrophone experiments along the Central, Southwest and Southeast Indian Ridges, the Juan de Fuca Ridge system, and the northern MAR. Preliminary results are very promising, and there appear to be several examples of clear foreshocks preceding mainshocks by several hours. Also as part of this project, we are compiling a bathymetric map of the equatorial MAR and its transforms between 20N and 10S. There have been several international mapping efforts in this region and the integration of

  18. A Linear Stratified Ocean Model of the Equatorial Undercurrent

    NASA Astrophysics Data System (ADS)

    McCreary, J. P.

    1981-01-01

    A linear stratified ocean model is used to study the wind-driven response of the equatorial ocean. The model is an extension of the Lighthill (1969) model that allows the diffusion of heat and momentum into the deeper ocean, and so can develop non-trivial steady solutions. To retain the ability to expand solutions into sums of vertical normal modes, mixing coefficients must be inversely proportional to the square of the background Vaisala frequency. The model is also similar to the earlier homogeneous ocean model of Stommel (1960). He extended Ekman dynamics to the equator by allowing his model to generate a barotropic pressure field. The present model differs in that the presence of stratification allows the generation of a baroclinic pressure field as well. The most important result of this paper is that linear theory can produce a realistic equatorial current structure. The model Undercurrent has a reasonable width and depth scale. There is westward flow both above and below the Undercurrent. The meridional circulation conforms to the 'classical' picture suggested by Cromwell (1953). Unlike the Stommel solution, the response here is less sensitive to variations of parameters. Ocean boundaries are not necessary for the existence of the Undercurrent but are necessary for the existence of the deeper Equatorial Intermediate Current. The radiation of equatorially trapped Rossby and Kelvin waves is essential to the development of a realistic Undercurrent. Because the system supports the existence of these waves, low-order vertical modes can very nearly adjust to Sverdrup balance (defined below), which in a bounded ocean and for winds without curl is a state of rest. As a result, higher-order vertical modes are much more visible in the total solution. This property accounts for the surface trapping and narrow width scale of the equatorial currents. The high-order modes tend to be in Yoshida balance (defined below) and generate the characteristic meridional circulation

  19. A recent, equatorial, periglacial environment on Mars

    NASA Astrophysics Data System (ADS)

    Balme, M. R.; Gallagher, C.; Murray, J. B.; Muller, J.-P.

    2009-04-01

    During the Viking era, Mars' recent climatic history was held to be cold and dry with little evidence for long-lived liquid water near the surface; signs of a past wetter, warmer climate were confined to ancient Noachian or Hesperian-aged terrains. Recent missions have revealed contemporary near-surface water-ice to be abundant at high latitudes, and a population of mid-latitude fluvial-like gullies that appear to have formed by transient melting of ice or snow. Thus today's view of Mars' recent surface evolution is one of global permafrost existing within a framework of climate change, the timescales of which are governed by obliquity cycles with periods of tens to hundreds of thousands of years. However, in recent mapping work of the equatorial Elysium Planitia region using the latest very high resolution images of Mars (HiRISE; 25cm/pixel) we have found evidence for longer-lived, geologically recent liquid water at the martian surface. This suggests that there was a recent period when the climate was warmer than current obliquity cycle-based models predict. The Elysium Planitia region of Mars is both geologically young (late Amazonian period; <100 Ma) and hosts a variety of landforms that are morphologically similar to those of periglacial and permafrost environments on Earth. The region was exposed to massive flooding from deep underground sources during the late Amazonian, as demonstrated by the distinctive fluvial morphologies seen in the outflow channel Athabasca Vallis. These floods would have provided both the source of ice and particulate material required for a periglacial or permafrost landscape and there was probably a long-lived, but slowly freezing, lake or sea in the downstream Elysium basin. However, the provenance of the materials and landforms of this region is disputed: many authors still regard the Athabasca Vallis and Elysium basin as being flood lava provinces, with effusive volcanic materials reoccupying earlier flood landscapes (a classic

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

    NASA Technical Reports Server (NTRS)

    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.

  1. Optimal joint remote state preparation of equatorial states

    NASA Astrophysics Data System (ADS)

    Li, Xihan; Ghose, Shohini

    2015-12-01

    We present a scheme for optimal joint remote state preparation of two-qubit equatorial states. Our protocol improves on a previous scheme (Choudhury and Dhara in Quantum Inf Process 14:373-379, 2015) that had a success probability of 25 %, which increased to 50 % when extra classical information is sent to the receiver. We show that using our modified scheme, the desired state can be prepared deterministically with the same quantum channel. Moreover, we generalize the scheme to prepare N-qubit equatorial states in which the receiver can reconstruct the original state with 100 % success probability.

  2. Equatorial waves in a stratospheric GCM - Effects of vertical resolution

    NASA Technical Reports Server (NTRS)

    Boville, Byron A.; Randel, William J.

    1992-01-01

    It is noted that equatorially trapped wave modes, e.g., Kelvin and Rossby-gravity waves, are thought to play a critical role in forcing the quasi-biennial oscillation of the lower tropical stratosphere. The ability of a GCM to simulate these waves is examined and the changes in the wave properties as a function of the vertical resolution of the model are investigated. The dependence of the equatorial wave simulation of vertical resolution is examined utilizing three experiments with vertical grid spacings of about 2.8, 1.4, and 0.7 km. At high vertical resolution, the simulated waves are shown to agree with the available observations.

  3. Equatorial Atmospheric and Ionospheric Modeling for Space Surveillance

    DTIC Science & Technology

    2010-11-04

    170 Longitude (deg E) 30 15 -15 0 La tit ud e (d eg N ) Equatorial Anomaly SMH 11/24/99 Equatorial Spread-F A l t i t u d e ( k m ) Local Time...Operation T E C ( 1 0 1 6 e l e c t r o n s m - 2 ) Model Integration and Test SMH 11/24/99 Two Frequency Radar vs IECM TEC -6.5 6.50 E l e v a t i o n

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

    PubMed

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

    2009-12-01

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

  5. Water depth-composition trends in ferromanganese crusts adjacent to the California margin compared to those in equatorial Pacific crusts

    NASA Astrophysics Data System (ADS)

    Conrad, T. A.; Hein, J. R.

    2013-12-01

    Ferromanganese (Fe-Mn) crusts have been used as proxies for paleo-seawater chemistry; however, element concentrations and growth rates in crusts can vary depending on the region, latitude, and water depth. Here we will look at 130 Fe-Mn crusts from seven seamounts adjacent to the California (CA) margin to explore trends in composition with water depth and latitude. Crusts were collected by ROV, resulting in a dataset with exact water depth and location coordinates. Water depth ranges from 570 to 3,934 m along a 700-km transect running roughly parallel to the CA margin. Crust samples used for comparison were collected by dredging along transects following the Gilbert Ridge and Tokelau Seamounts in the western equatorial Pacific, with water depths ranging from about 1,500 to 4,800 m. In addition to variations with latitude and water depth, element concentrations in CA margin crusts are influenced by high primary productivity in surface waters, terrestrial input, and upwelling along the continental margin. Elements associated with terrestrial input, including Na, Si, Al, K, Pb, and particularly Th, are enriched in CA margin crusts relative to crusts from the equatorial Pacific transects. Si is also associated with the biogenic phase, as are P, Ba, and Cu but these elements are lower in CA margin crusts. Ba is a proxy for primary productivity. CA margin crusts show Ba increasing with increasing water depth, while equatorial Pacific crusts show the inverse trend. In equatorial Pacific crusts, Ba correlates with decreasing latitude, which reflects increasing proximity to the high productivity zone of equatorial upwelling; additionally, local obstructional upwelling associated with primary productivity around seamounts and islands enhances the productivity signal. Cu, which is associated with the manganese oxide phase, in addition to the biogenic phase, also increases with water depth along the CA margin; this is consistent with the seawater profile for dissolved Cu. In

  6. History of the Italian San Marco equatorial mobile range

    NASA Technical Reports Server (NTRS)

    Nesbitt, H. N.

    1971-01-01

    Events leading to the development of the San Marco Equatorial Range are presented. Included are background information leading to the cooperative space program between the United States and Italy, conceptual planning, training activities, equipment design and fabrication, and range utilization. The technical support provided the San Marco Program by Scout Project Office, and other NASA installations is described.

  7. Equatorial decline of reef corals during the last Pleistocene interglacial

    NASA Astrophysics Data System (ADS)

    Kiessling, Wolfgang; Simpson, Carl; Beck, Brian; Mewis, Heike; Pandolfi, John M.

    2012-12-01

    The Last Interglacial (LIG; ca. 125,000 y ago) resulted from rapid global warming and reached global mean temperatures exceeding those of today. The LIG thus offers the opportunity to study how life may respond to future global warming. Using global occurrence databases and applying sampling-standardization, we compared reef coral diversity and distributions between the LIG and modern. Latitudinal diversity patterns are characterized by a tropical plateau today but were characterized by a pronounced equatorial trough during the LIG. This trough is governed by substantial range shifts away from the equator. Range shifts affected both leading and trailing edges of species range limits and were much more pronounced in the Northern Hemisphere than south of the equator. We argue that interglacial warming was responsible for the loss of equatorial diversity. Hemispheric differences in insolation during the LIG may explain the asymmetrical response. The equatorial retractions are surprisingly strong given that only small temperature changes have been reported in the LIG tropics. Our results suggest that the poleward range expansions of reef corals occurring with intensified global warming today may soon be followed by equatorial range retractions.

  8. Evolution of Ion Clouds in the Equatorial Ionosphere

    NASA Astrophysics Data System (ADS)

    Petrochuk, Yevgeny; Blaunstein, Nathan; Mishin, Evgeny; Pedersen, Todd; Caton, Ron; Viggiano, Al; Schuman, Nick

    2015-11-01

    We report on the results of 2- and 3-dimentional numerical investigations of the evolution of samarium ion clouds injected in the equatorial ionosphere, alike the recent MOSC experiments. The ambient conditions are described by a standard model of the quiet-time equatorial ionosphere from 90 to 350 km. The altitudinal distribution of the transport processes and ambient electric and magnetic fields is taken into account. The fast process of stratification of ion clouds and breaking into small plasmoids occur only during the late stage of the cloud evolution. The role of the background plasma and its depletion zones formed due to the short-circuiting currents is not as evident as in mid latitudes. It is also revealed that the altitudinal dependence of the diffusion and drift plays a minor role in the cloud evolution at the equator. Likewise, the cloud remains stable with respect to the Raleigh-Taylor and gradient-drift instabilities. These two features are defined by the equatorial near-horizontal magnetic field which leads to a strongly-elongated ellipsoid-like plasma cloud. The critical dip angle separating the stable (equatorial) and unstable (mid-latitude) cloud regimes will be defined in future simulation studies, as well as the dependence on the ambient electric field and neutral wind. 2Space Vehicles Directorate, Air Force Research Laboratory

  9. Upwelling: a unit of disturbance in equatorial spread F

    NASA Astrophysics Data System (ADS)

    Tsunoda, Roland T.

    2015-12-01

    Plasma structure in the nighttime equatorial F layer, often referred to as equatorial spread F (ESF), is not uniformly distributed, either in time or in space. Observations indicate that ESF in the bottomside F layer takes the form of patches; plasma structure within the F layer takes the form of localized plasma depletions, called equatorial plasma bubbles (EPBs), which tend to occur in clusters. Another observed feature is an upwelling, which has been described as a localized, upward modulation of isodensity contours in the bottomside F layer. Interestingly, zonal widths of ESF patches, EPB clusters, and upwellings are similar. Moreover, all display an east-west asymmetry. The objective of this paper is to show, for the first time, that an ESF patch is the bottomside counterpart of an EPB cluster, and that both are products of the electrodynamical process that takes place within an upwelling. The process can be described as having three phases: (1) amplification of upwelling amplitude during the post-sunset rise of the F layer, (2) launching of the first EPB of the evening, from crest of the upwelling, and (3) structuring of plasma within the upwelling. Hence, an upwelling, whose presence is responsible for the formation of ESF patches and EPB clusters, can be envisioned as a unit of disturbance that occurs in the nighttime equatorial ionosphere.

  10. Do Sverdrup transports account for the Pacific North Equatorial Countercurrent

    SciTech Connect

    Meyers, G.

    1980-02-20

    Poleward and equatorward geostrophic transports calculated from density are nearly equal to Sverdrup transports calculated from the curl of the wind stress in the North and South Pacific subtropical gyres. But the Sverdrup transports do not account for the Pacific North Equatorial Countercurrent.

  11. Exact Nonlinear Internal Equatorial Waves in the f-plane

    NASA Astrophysics Data System (ADS)

    Hsu, Hung-Chu

    2016-07-01

    We present an explicit exact solution of the nonlinear governing equations for internal geophysical water waves propagating westward above the thermocline in the f-plane approximation near the equator. Moreover, the mass transport velocity induced by this internal equatorial wave is eastward and a westward current occurs in the transition zone between the great depth where the water is still and the thermocline.

  12. The equatorial electrojet current modelling from SWARM satellite data

    NASA Astrophysics Data System (ADS)

    Benaissa, Mahfoud

    2016-07-01

    Equatorial ElectroJet (EEJ) is an intense eastward electric current circulating in the ionospheric magnetic equator band between 100 and 130 km of altitude in E region. These currents vary by day, by season, by solar activity, and also with the main magnetic field of internal origin. The irregularity of the ionosphere has a major impact on the performance of communication systems and navigation (GPS), industry.... Then it becomes necessary study the characteristics of EEJ. In this paper, we present a study of the equatorial electrojet (EEJ) phenomenon along one year (2014) period. In addition, the satellite data used in this study are obtained with SWARM satellite scalar magnetometer data respecting magnetically quiet days with KP < 2. In this paper, we process to separate and extract the electrojet intensity signal from other recorded signal-sources interfering with the main signal and reduce considerably the signal to noise ratio during the SWARM measurements. This pre-processing step allows removing all external contributions in regard to EEJ intensity value. Key words: Ionosphere (Equatorial ionosphere; Electric fields and currents; Equatorial electrojet (EEJ)); SWARM.

  13. Local Stability for an Exact Steady Purely Azimuthal Equatorial Flow

    NASA Astrophysics Data System (ADS)

    Ionescu-Kruse, Delia; Martin, Calin Iulian

    2016-12-01

    The aim of this paper is to present a short-wavelength stability analysis of an exact steady equatorial flow which does not vary in the azimuthal direction, but has an arbitrary variation with depth. We show that for some velocity profiles of the basic flow, this flow is locally stable to short-wavelength perturbations.

  14. On the variability of surface insolation in the equatorial Pacific

    NASA Technical Reports Server (NTRS)

    Rodriguez, C.; Laszlo, I.; Pinker, R. T.

    1990-01-01

    The potential of a new parameter, surface solar irradiance, for climate studies in the equatorial Pacific is presented. Methods to estimate this parameter use the model of Pinker and Laszlo (1989, 1990) to derive the surface solar irradiance from the visible radiance as observed from satellites. Evidence is provided that the surface insolation can be advantageous in climate studies.

  15. Commercial Logging and HIV Epidemic, Rural Equatorial Africa

    PubMed Central

    Bourgeois, Anke; Mpoudi, Mireille; Butel, Christelle; Peeters, Martine; Mpoudi-Ngolé, Eitel; Delaporte, Eric

    2004-01-01

    We found a high seroprevalence of HIV among young women in a commercial logging area in Cameroon. The vulnerability of these young women could be related to commercial logging and the social and economic networks it induces. The environmental changes related to this industry in Equatorial Africa may facilitate HIV dissemination. PMID:15550206

  16. Observations of ULF wave related equatorial electrojet and density fluctuations

    NASA Astrophysics Data System (ADS)

    Yizengaw, E.; Zesta, E.; Moldwin, M.; Damtie, B.; Mebrahtu, A.; Anad, F.; Pfaff, R. F.

    2011-12-01

    Global magnetospheric Ultra Low Frequency (ULF) pulsations with frequencies in the Pc 4-5 range (f = 1.0 - 8 mHz) have been observed for decades in space and on Earth. ULF pulsations contribute to magnetospheric particle transport and diffusion and play an important role in magnetospheric dynamics. However, only a few studies have been performed on ionospheric observations of ULF wave-related perturbations in the vicinity of the equatorial region. In this paper we report on Pc5 wave related electric field and thus vertical drift velocity oscillations at the equator as observed by ground magnetometers and radar. We show that the magnetometer estimated equatorial ExB drift oscillate with the same frequency as ULF Pc5 waves, creating significant ionospheric density fluctuations. For independent confirmation of the vertical drift velocity fluctuation, we used JULIA 150 km radar drift velocities and found similar fluctuation with the period of 8-10 minutes. We also show ionospheric density fluctuations during the period when we observed ULF wave activities. All these demonstrate that the Pc5 wave can penetrate to the equatorial ionosphere and modulate the equatorial electrodynamics. Finally, in order to detect the ULF activities both on the ground and in space, we use groundbased magnetometer data from African Meridian B-field Education and Research (AMBER) and the South American Meridional B-field Array (SAMBA). From space, we use magnetic field observations from the GOES 12 and the Communication/Navigation Outage and Forecast System (C/NOFS) satellites. Using the WIND spacecraft as the upstream solar wind monitor, we present direct evidence that solar wind number density and ram pressure fluctuations observed far upstream from the terrestrial magnetosphere are the main drivers of ULF wave activity inside the magnetosphere. Finally, we show that the ULF waves in the same frequency range are observed in the magnetosphere by the geosynchronous GOES spacecraft, in the

  17. Statistical forecasting of tropical rainfall using equatorial waves

    NASA Astrophysics Data System (ADS)

    Schlüter, Andreas; Klar, Manuel; Vogel, Peter; Gneiting, Tilmann; Fink, Andreas H.; Knippertz, Peter

    2017-04-01

    Despite their high socio-economic importance, forecasts of tropical rainfall on a synoptic timescale are still quite poor. Due to the complex nature of convection, numerical weather prediction (NWP) models largely fail to deliver reliable and accurate precipitation forecasts for the tropics. In this study, we propose a new statistical method for the prediction of tropical rainfall using the information about the phasing of equatorial waves. For certain temporal and spatial scales, statistical forecast methods for tropical precipitation have skill comparable to complex and expensive numerical predictions. For example, recent work has shown that climatology or persistence forecasts, thus a very simple statistical model, performs as well as postprocessed ensemble forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF) over tropical Africa. Thus, we believe that additional exploitation of information about the larger-scale atmospheric setting could lead to statistical forecast models of tropical precipitation that are comparable or even more accurate than current NWP forecasts. Predictability of tropical precipitation on the synoptic timescale is mainly governed by convectively coupled equatorial waves which modulate the distribution and intensity of rainfall. Therefore, information about the phasing and intensity of equatorial wave activity should be included in statistical models for tropical rainfall. Here, we present a simple statistical forecast that incorporates information about these waves. To obtain knowledge about future wave phasing, the current wave signal can be extrapolated or filtered from signals in NWP output. Exemplarily, we tested the improvement of forecast quality over two locations in West Africa using the a priori knowledge about the phasing of these equatorial waves. For both locations, equatorial waves successfully predict rainfall occurrence and rainfall amount. The new model clearly outperforms the ECMWF forecast. This

  18. Post-midnight occurrence of equatorial plasma bubbles

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  19. Lagrangian mixed layer modeling of the western equatorial Pacific

    NASA Technical Reports Server (NTRS)

    Shinoda, Toshiaki; Lukas, Roger

    1995-01-01

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

  20. Longitudinal Differences of Ionospheric Vertical Density Distribution and Equatorial Electrodynamics

    NASA Technical Reports Server (NTRS)

    Yizengaw, E.; Zesta, E.; Moldwin, M. B.; Damtie, B.; Mebrahtu, A.; Valledares, C.E.; Pfaff, R. F.

    2012-01-01

    Accurate estimation of global vertical distribution of ionospheric and plasmaspheric density as a function of local time, season, and magnetic activity is required to improve the operation of space-based navigation and communication systems. The vertical density distribution, especially at low and equatorial latitudes, is governed by the equatorial electrodynamics that produces a vertical driving force. The vertical structure of the equatorial density distribution can be observed by using tomographic reconstruction techniques on ground-based global positioning system (GPS) total electron content (TEC). Similarly, the vertical drift, which is one of the driving mechanisms that govern equatorial electrodynamics and strongly affect the structure and dynamics of the ionosphere in the low/midlatitude region, can be estimated using ground magnetometer observations. We present tomographically reconstructed density distribution and the corresponding vertical drifts at two different longitudes: the East African and west South American sectors. Chains of GPS stations in the east African and west South American longitudinal sectors, covering the equatorial anomaly region of meridian approx. 37 deg and 290 deg E, respectively, are used to reconstruct the vertical density distribution. Similarly, magnetometer sites of African Meridian B-field Education and Research (AMBER) and INTERMAGNET for the east African sector and South American Meridional B-field Array (SAMBA) and Low Latitude Ionospheric Sensor Network (LISN) are used to estimate the vertical drift velocity at two distinct longitudes. The comparison between the reconstructed and Jicamarca Incoherent Scatter Radar (ISR) measured density profiles shows excellent agreement, demonstrating the usefulness of tomographic reconstruction technique in providing the vertical density distribution at different longitudes. Similarly, the comparison between magnetometer estimated vertical drift and other independent drift observation

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

    NASA Technical Reports Server (NTRS)

    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.

  2. New absolute spectroscopic measurement of the solar equatorial rotation rate

    NASA Technical Reports Server (NTRS)

    Snider, J. L.

    1983-01-01

    An atomic-beam resonance-scattering technique applied to the 7699 A solar potassium absorption line is used to make an absolute spectroscopic determination of the solar equatorial rotation rate. This is believed to be a new method which has not previously been used for studying solar rotation. The measurements were made during 1979-82, initially with a permanent apparatus at Oberlin College and more recently with a portable apparatus installed at the Snow Telescope on Mt. Wilson. After carefully allowing for possible systematic errors, it is concluded that the solar sidereal equatorial rotation rate is 13.8 + or - 0.3 deg/day and that it has not varied significantly over the period of these observations.

  3. Westward propagating twin gyres in the equatorial Indian Ocean

    NASA Astrophysics Data System (ADS)

    Reddy, P. Rahul Chand; Salvekar, P. S.; Deo, A. A.; Ganer, D. W.

    2004-01-01

    A reduced-gravity (1$\\frac{1}{2-layer) model forced by daily climatological winds simulates twin, anticyclonic gyres, which propagate westward on either side of the equator. The gyres form at the beginning of both the Southwest Monsoon and the Northeast monsoon in the equatorial eastern Indian Ocean, and subsequently propagate across the basin. Their existence is supported by velocity observations taken during WOCE in 1995 and by TOPEX/Poseidon sea-level observations during 1993. They are also present in the ECCO model/data product. They form at the front of a Rossby-wave packet generated by the reflection of the equatorial jet (EJ) from the eastern boundary of the basin. They are likely either Rossby solitons or result from the nonlinear interaction between the EJ and the Rossby-wave front.

  4. The effect of subtropical aerosol loading on equatorial precipitation

    NASA Astrophysics Data System (ADS)

    Dagan, G.; Chemke, R.

    2016-10-01

    Cloud-aerosol interactions are considered as one of the largest sources of uncertainties in the study of climate change. Here another possible cloud-aerosol effect on climate is proposed. A series of large eddy simulations (LES) with bin microphysics reveal a sensitivity of the total atmospheric water vapor amount to aerosol concentration. Under polluted conditions the rain is suppressed and the total amount of water vapor in the atmosphere increases with time compared to clean precipitating conditions. Theoretical examination of this aerosol effect on water vapor transport from the subtropics to the tropics, and hence on the equatorial rain and Hadley circulation, is conducted using an idealized general circulation model (GCM). It is shown that a reduction in the subtropical rain amount results in increased water vapor advection to the tropics and enhanced equatorial rain and Hadley circulation. This joins previously proposed mechanisms on the radiative aerosol effect on the general circulation.

  5. The dawn enhancement of the equatorial ionospheric vertical plasma drift

    NASA Astrophysics Data System (ADS)

    Zhang, Ruilong; Liu, Libo; Chen, Yiding; Le, Huijun

    2015-12-01

    Previous studies have reported that a dawn enhancement does not present in the statistical picture of the equatorial ionospheric vertical plasma drift, while it clearly shows in case measurements. In this statistical study, it is the first time to investigate the occurrence of the dawn enhancement in the equatorial ionospheric vertical plasma drift from ROCSAT-1 observations during geomagnetic quiet times. The dawn enhancements occur most frequently in June solstice and least frequently in December solstice. The statistical survey shows that the occurrence depends on the magnetic declination. The enhancement has the strongest amplitude in regions near 320° longitude and peaks during June solstice. The dawn enhancement reaches its peak after the sunrise in conjugated E regions. Furthermore, it is found that the dawn enhancement is closely related to the difference between the sunrise times in the conjugated E regions (sunrise time lag). The dawn enhancement occurs easily in regions with a large sunrise time lag.

  6. Altitude and latitude dependence of the equatorial electrojet

    NASA Astrophysics Data System (ADS)

    Singh, A.; Cole, K. D.

    1988-07-01

    A self-consistent and high-resolution dynamo model is used to investigate the effects of day-to-day or seasonal variation of altitude and latitude profiles of the E-plasma density in the equatorial ionosphere on equatorial electrojet (EEJ) structure. Variations in the E-layer peak altitude and amplitude are shown to significantly affect EEJ structure. The results indicate that, for any shape, the EEJ peak appears at or below the E-layer peak altitude. Distinct double peaks occur in the EEJ structure if the E-layer peak is above 105 km or if the gradient is large. The effect of the latitudinal variation of the integrated conductivities of ionospheric field lines upon the amplitude and altitude of the EEJ peak is discussed.

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

    NASA Astrophysics Data System (ADS)

    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.

  8. Lunar-solar interactions in the equatorial electrojet

    NASA Astrophysics Data System (ADS)

    Gasperini, F.; Forbes, J. M.

    2014-05-01

    To first order the ground magnetic signature of the equatorial electrojet (EEJ) reflects the height integral of J = σE, where σis a conductivity and E represents some combination of the global dynamo-generated electric field and the electric field due to local winds. Day-to-day variations in the conductivity are strongly controlled by the solar flux, while E depends on solar and lunar tides, planetary waves, and the disturbance dynamo. In this study we demonstrate how complexity is introduced into the EEJ due to the interaction between lunar tide variability in the equatorial electric field and solar-driven variability in the E region conductivity. Toward this end, we analyze magnetometer data from the Huancayo observatory both in the time and frequency domain. We present results for the year 1990, and we show that 86% of the variance in the EEJ is due to the lunar-solar interaction.

  9. Bottomside sinusoidal irregularities in the equatorial F region

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  10. Modeling study of equatorial ionospheric height and spread F occurrence

    NASA Astrophysics Data System (ADS)

    Maruyama, Takashi

    1996-03-01

    In the ionospheric F region at equatorial latitudes, the strength of the zonal electric field in the evening hours is closely connected with the generation of equatorial spread F and plasma bubbles. Many researchers discuss the electric fields and dynamics of the ionosphere in terms of the time derivative of F layer virtual heights (dh'F/dt) scaled on the ionograms, and this paper examines the accuracy of zonal electric fields derived by such a method. Although the effect of transequatorial thermospheric wind had been thought to be negligible, model calculations of ion concentration show that this wind significantly changes ionospheric height in the evening hours. Further, the electric field strength is estimated based on observed dh'F/dt, considering the apparent vertical drift of the ionosphere due to the thermospheric wind effect. Rayleigh-Taylor growth rates calculated for those electric fields agree quantitatively with the spread F occurrence.

  11. Equatorial plasma bubbles/range spread firregularities and the QBO

    NASA Astrophysics Data System (ADS)

    Chen, Pei-Ren

    1993-11-01

    Investigation of the relationship between the percentage occurrence of equatorial plasma bubbles/range spread F irregularities (EPBRSI) and the Quasi-Biennial Oscillation (QBO) of the lower stratospheric mean zonal wind in the equatorial zone reveals a QBO-modulation effect on the percentage occurrence of the EPBRSI. A longitudinal dependence of this QBO-modulation effect has also been found: the percentage occurrence of EPBRSI increases (decreases) in the easterly phase of the QBO in the Indian-East African sector (in the American sector) and decreases (increases) in the westerly phase of the QBO in the Indian-East African sector (in the American sector). It is suggested that this represents new evidence that the low-latitude ionosphere is modulated by atmospheric planetary waves from below.

  12. Equatorial Enhancement of the Nighttime OH Mesospheric Infrared Airglow

    NASA Technical Reports Server (NTRS)

    Baker, D. J.; Mlynczak, M. G.; Russell, J. M.

    2007-01-01

    Global measurements of the hydroxyl mesospheric airglow over an extended period of time have been made possible by the NASA SABER infrared sensor aboard the TIMED satellite which has been functioning since December of 2001. The orbital mission has continued over a significant portion of a solar cycle. Experimental data from SABER for several years have exhibited equatorial enhancements of the nighttime mesospheric OH (delta v = 2) airglow layer consistent with the high average diurnal solar flux. The brightening of the OH airglow typically means more H + O3 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.

  13. Relationship between Fe /+/ ions and equatorial spread F.

    NASA Technical Reports Server (NTRS)

    Hanson, W. B.; Sanatani, S.

    1971-01-01

    Evaluation of observations from the retarding potential analyzer on Ogo 6 near the magnetic equator, demonstrating an intimate relationship between the presence of Fe(+) ions and irregularities in the total ion concentration. The ionospheric irregularities (or structure) are probably another manifestation of equatorial spread F, although this has not yet been verified. Nearly half the nighttime equatorial crossings below 700 km exhibit both Fe(+) and structure, but only 10% of the passes without Fe(+) have structure. Approximately one-third of the passes with Fe(+) are not structured, which indicates that Fe(+) may be a necessary but not sufficient condition for structure formation. The Atlantic region shows an extremely high and detailed correlation between Fe(+) ions and the irregularities.

  14. Bispectral analysis of equatorial spread F density irregularities

    NASA Technical Reports Server (NTRS)

    Labelle, J.; Lund, E. J.

    1992-01-01

    Bispectral analysis has been applied to density irregularities at frequencies 5-30 Hz observed with a sounding rocket launched from Peru in March 1983. Unlike the power spectrum, the bispectrum contains statistical information about the phase relations between the Fourier components which make up the waveform. In the case of spread F data from 475 km the 5-30 Hz portion of the spectrum displays overall enhanced bicoherence relative to that of the background instrumental noise and to that expected due to statistical considerations, implying that the observed f exp -2.5 power law spectrum has a significant non-Gaussian component. This is consistent with previous qualitative analyses. The bicoherence has also been calculated for simulated equatorial spread F density irregularities in approximately the same wavelength regime, and the resulting bispectrum has some features in common with that of the rocket data. The implications of this analysis for equatorial spread F are discussed, and some future investigations are suggested.

  15. Influence of the E region dynamo on equatorial spread F

    SciTech Connect

    Hanson, W.B.; Sanatani, S.; Patterson, T.N.L.

    1983-04-01

    The integrated E region Pedersen conductivity can be an important parameter in determining whether the bottomside of the equatorial F layer will be stable against the Rayleigh-Taylor gravitational instability. The F layer is observed to become unstable when it rises to great heights after sunset. One effect of this height rise is to decrease the stabilizing influence of ion-neutral collisions at F region heights. It is shown here that the same eastward electric field that raises the F layer also decreases the Pedersen conductivity of the E region, which further destabilizes convective overturning. Because the conductivity of magnetic tubes that penetrate the main F layer is large compared to the E layer contribution, these effects are important only for the bottomside of the equatorial F layer.

  16. Relationship between Fe /+/ ions and equatorial spread F.

    NASA Technical Reports Server (NTRS)

    Hanson, W. B.; Sanatani, S.

    1971-01-01

    Evaluation of observations from the retarding potential analyzer on Ogo 6 near the magnetic equator, demonstrating an intimate relationship between the presence of Fe(+) ions and irregularities in the total ion concentration. The ionospheric irregularities (or structure) are probably another manifestation of equatorial spread F, although this has not yet been verified. Nearly half the nighttime equatorial crossings below 700 km exhibit both Fe(+) and structure, but only 10% of the passes without Fe(+) have structure. Approximately one-third of the passes with Fe(+) are not structured, which indicates that Fe(+) may be a necessary but not sufficient condition for structure formation. The Atlantic region shows an extremely high and detailed correlation between Fe(+) ions and the irregularities.

  17. Small-Scale Magnetic Reconnection at Equatorial Coronal Hole Boundaries

    NASA Astrophysics Data System (ADS)

    Lamb, Derek; DeForest, C. E.

    2011-05-01

    Coronal holes have long been known to be the source of the fast solar wind at both high and low latitudes. The equatorial extensions of polar coronal holes have long been assumed to have substantial magnetic reconnection at their boundaries, because they rotate more rigidly than the underlying photosphere. However, evidence for this reconnection has been sparse until very recently. We present some evidence that reconnection due to the evolution of small-scale magnetic fields may be sufficient to drive coronal hole boundary evolution. We hypothesize that a bias in the direction of that reconnection is sufficient to give equatorial coronal holes their rigid rotation. We discuss the prospects for investigating this using FLUX, a reconnection-controlled coronal MHD simulation framework. This work was funded by the NASA SHP-GI program.

  18. A Possible Approach to the Equatorial Plasma Bubbles Forecasting Problem

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    Equatorial Plasma Bubbles (EPBs) are large regions of plasma depletion which arise in the nighttime equatorial ionosphere under certain conditions. In the last decades, several advances have been achieved in the knowledge of such extraordinary events, however, the predictability of these depleted structures still continues to be a problem for the space weather research. The forecasting capability is highly desirable, since these plasma depleted structures affects drastically the radio signals causing interferences in telecommunications and also interruptions in the satellite communications. The work presented here offers an alternative possibility to the EPB prediction using numerical simulation associated with Digisonde data. This hybrid approach presents some promising results and possibly may offer an alternative method to the forecast of the EPB events.

  19. Influence of the E region dynamo on equatorial spread F

    NASA Technical Reports Server (NTRS)

    Hanson, W. B.; Sanatani, S.; Patterson, T. N. L.

    1983-01-01

    The integrated E region Pedersen conductivity can be an important parameter in determining whether the bottomside of the equatorial F layer will be stable against the Rayleigh-Taylor gravitational instability. The F layer is observed to become unstable when it rises to great heights after sunset. One effect of this height rise is to decrease the stabilizing influence of ion-neutral collisions at F region heights. It is shown here that the same eastward electric field that raises the F layer also decreases the Pedersen conductivity of the E region, which further destabilizes convective overturning. Because the conductivity of magnetic tubes that penetrate the main F layer is large compared to the E layer contribution, these effects are important only for the bottomside of the equatorial F layer.

  20. Day-To Variability of the Quiet-Time Equatorial Electrojet and Post-Sunset Occurrence of Equatorial Ionospheric Scintillations

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Archana; Okpala, Kingsley

    Strength of the equatorial electrojet (EEJ) derived from measurements of the horizontal component H of the geomagnetic field at an equatorial station, Tirunelveli, and a low-latitude station Alibag, outside the influence of the EEJ, on International quiet (IQ) days of the years 2001-2005, have been subjected to Principal Component Analysis to determine the principal components (PCs) that describe the variability of the quiet-time EEJ. It is found that the first three PCs together account for 94% of the variability of the EEJ observed during the IQ days of this period. PC1 itself represents about 64% of the EEJ variations, while PC2 and PC3 respectively account for 23% and 7% of the quiet-time variability of the EEJ during these years when the daily adjusted 10.7 cm solar flux, Sa, decreased from values exceeding 200 to around 100. The temporal structure of PC1 is such that it contributes only to the variability of the normal electrojet and cannot explain events such as the counter-electrojet (CEJ). A model is constructed for quiet-day PC1 scores as a function of day number and solar activity to describe a major part of the variability of the normal quiet-time EEJ. However, the CEJ and other 'abnormal' variations such as an afternoon enhancement of the EEJ, are only associated with PC2 and PC3. The quiet-day PC2 and PC3 scores obtained in this study, therefore, indicate the influence of forcing of the equatorial ionosphere from below. The day-to-day variability of the quiet-time pre-reversal enhancement of the post-sunset equatorial F region zonal electric field, which plays a crucial role in the occurrence of scintillation-producing equatorial ionospheric irregularities, is also influenced by forcing from below. In this context, occurrence of scintillations on a 251 MHz signal, transmitted from a geostationary satellite, and recorded at Tirunelveli, is studied in relation to the PC scores, which describe the variability of the EEJ, in order to identify a possible

  1. Equatorial Superrotation on Earth Induced by Optically Thick Dust Clouds

    NASA Astrophysics Data System (ADS)

    Zhu, X.; Oman, L. D.; Waugh, D. W.; Lloyd, S. A.

    2008-12-01

    How does the Earth's atmosphere respond to exceptional aerosol events, and what is the mechanism leading to consequent past and possible future climate shifts? One possible mechanism leading to aerosol-induced climate shifts is the striking atmospheric dynamics phenomenon of equatorial superrotation, such as that found on Venus and Saturn's moon Titan, with its enhanced meridional transport. Recently, a significant breakthrough has been made in our theoretical understanding of atmospheric superrotation on Venus and Titan. Extending this result regarding superrotation in planetary atmospheres to the concept of superrotation in Earth's atmosphere serves not only to shed insight into long-standing and seemingly disparate questions of Earth's climate (such as the mechanism of mass extinction and geo-engineering mitigation of global warming) but also to develop a common theoretical framework to address the impacts of profound changes of atmospheric aerosols and their consequences. The three-dimensional Goddard Institute for Space Studies (GISS) modelE GCM and Johns Hopkins University Applied Physics Laboratory (JHU/APL) two-dimensional radiative-dynamical model are used to investigate the induction of equatorial superrotation in Earth's stratosphere, as well as its effect on meridional transport of dust and aerosols in association with the supervolcano eruptions. Preliminary results show that an equatorial superrotational wind in the upper troposphere was initiated and lasted for more than two years following the Mt Toba eruption near the equator about 71,000 years ago. The circulation structure at mid-latitude was also altered, indicating a global impact of an equatorial injection of an aerosol layer.

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

    NASA Technical Reports Server (NTRS)

    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.

  3. Vertical fine structure observations in the eastern equatorial Pacific

    SciTech Connect

    Hayes, S.P.

    1981-11-20

    Measurements of vertical displacement and horizontal velocity finestructure near the equator at 110/sup 0/W in the eastern Pacific Ocean are reported. Profiles were scaled to a constant Bruent-Vaeisaelae frequency ocean (N/sub 0/ = 1 cph) in accordance with a WKBJ approximation. A total of 57 CTD casts between 3/sup 0/N and 3/sup 0/S taken during five cruises in 1979 were analyzed. Results show an equatorial enhancement of vertical displacement is similar variance for vertical wavelengths longer than 50 sdbar (stretched decibars). This enhancement is similar to that which has been reported at 125/sup 0/W and 179/sup 0/E. Difference between locations can be accounted for by the observed temporal variability at 110/sup 0/W. Coherence between vertical displacement profiles separated in time by dealys of 2 hours to 120 hour indicate that the high wave number structures were largely associated with time scales of 4 days and less. Meridionally, vertical structures longer than 300 sdbar were coherent within 50 km of the equator. We interpret this vertical displacement fine structure enhancement as high wave number equatorially trapped inertial-gravity waves. The velocity fine structure measurements in July 1979 also indicate equatorially enhanced horizontal kinetic energy for vertical wave lengths longer than 100 sdbar. The velocity structures persisted over the 56 hour of measurement and appeared to have longer time scales than the vertical displacements. Meridional energy measurement and appeared to have longer time scales than the vertical displacements. Meridional energy exceeded zonal energy; however, the two components were coherent. We interpret these velocity structures as inertial-gravity waves which were produced off the equator and are propagating through the equatorial region.

  4. Equatorial irregularity belt and its movement during a magnetic storm

    NASA Technical Reports Server (NTRS)

    Vats, H. O.; Chandra, H.; Deshpande, M. R.; Rastogi, R. G.; Murthy, B. S.; Janve, A. V.; Rai, R. K.; Singh, M.; Gurm, H. S.; Jain, A. R.

    1978-01-01

    Evidence for an equatorial irregularity belt and its movement during a magnetic storm has been obtained from Faraday rotation measurements at a chain of 140-MHz radio beacons receiving from the ATS-6 satellite. The stations covered a latitude region from the magnetic equator to the 45 deg N dip on the Indian subcontinent. An irregularity belt extending from the magnetic equator to about 27 deg N latitude was observed during the main phase of the magnetic storm of 10 January, 1976.

  5. Time Sequence of Jupiter's Equatorial Region (Time Sets 2 & 4)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Time sequence of Jupiter's equatorial region at 756 nanometers (nm). The mosaics cover an area of 34,000 kilometers by 22,000 kilometers and were taken ten hours (approximately one Jovian rotation) apart. The dark region near the center of the mosaic is an equatorial 'hotspot' similar to the Galileo Probe entry site. The near-infrared continuum filter shows the features of Jupiter's main visible cloud deck.

    Jupiter's atmospheric circulation is dominated by alternating jets of east/west (zonal) winds. The bands have different widths and wind speeds but have remained constant as long as telescopes and spacecraft have measured them. The top half of these mosaics lies within Jupiter's North Equatorial Belt, a westward (left) current. The bottom half shows part of the Equatorial Zone, a fast moving eastward current. The clouds near the hotspot are the fastest moving features in these mosaics, moving at about 100 meters per second, or 224 miles per hour.

    North is at the top. The mosaics cover latitudes 1 to 19 degrees and are centered at longitude 336 degrees West. The grid lines, fixed in longitude, mark 350 degrees west (on the left edge) with decreasing longitude lines marking every 5 degrees moving east (to the right). The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  6. The Growth and Decay of Equatorial Backscatter Plumes.

    DTIC Science & Technology

    1980-02-01

    instabilities. However, other characteristics have been found that suggest key roles played by the eastward neutral wind and by altitude-modulation of the...and (c) an Eastward Neutral wind . . . 33 2 I INTRODUCTION Current theoretical understanding of the development of equatorial irregularities is that...Bibl et al., 1977). The ionograms showed a quiet F layer whose bottomside rose from 250 km altitude at 0700 UT to greater than 300 km by 0800 UT

  7. Geomagnetic Activity and the Equatorial Scintillation of Satellite Signals.

    DTIC Science & Technology

    1980-05-19

    BEORE COMPLETING FORM i. �T NUMBER 2 GOVT ACCESSION No. 3 . RECIPIENT’S CATALOG NUMBER NOSC Technical Report 554 (TR 554) /. 4. TITLE (and SW 441111...Occurrence and intensity of equatorial scintillation have been correlated with daily summed geomagnetic 3 -hour Kp indices, through scintillation data from...satellites at two elevation angles for uhf and 1--hand. They also have been correlated with the individual 3 -hour Kp indices and the correlations

  8. Time Sequence of Jupiter's Equatorial Region (Time Sets 2 & 4)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Time sequence of Jupiter's equatorial region at 756 nanometers (nm). The mosaics cover an area of 34,000 kilometers by 22,000 kilometers and were taken ten hours (approximately one Jovian rotation) apart. The dark region near the center of the mosaic is an equatorial 'hotspot' similar to the Galileo Probe entry site. The near-infrared continuum filter shows the features of Jupiter's main visible cloud deck.

    Jupiter's atmospheric circulation is dominated by alternating jets of east/west (zonal) winds. The bands have different widths and wind speeds but have remained constant as long as telescopes and spacecraft have measured them. The top half of these mosaics lies within Jupiter's North Equatorial Belt, a westward (left) current. The bottom half shows part of the Equatorial Zone, a fast moving eastward current. The clouds near the hotspot are the fastest moving features in these mosaics, moving at about 100 meters per second, or 224 miles per hour.

    North is at the top. The mosaics cover latitudes 1 to 19 degrees and are centered at longitude 336 degrees West. The grid lines, fixed in longitude, mark 350 degrees west (on the left edge) with decreasing longitude lines marking every 5 degrees moving east (to the right). The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  9. Modeling study of equatorial ionospheric height and spread F occurrence

    SciTech Connect

    Maruyama, Takashi

    1996-03-01

    The author looks at the question of the height of the ionosphere in the equatorial region, and its relationship to spread F. Model calculations indicate that transequatorial thermospheric winds are a factor in influencing the ionospheric height, particularly in evening hours. Taking into account thermospheric winds, in inferring electric field strengths in order to account for observed vertical drifts, the author also looks at the question of the Rayleigh-Taylor stability of the ionosphere in the face of such electric fields.

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

    NASA Astrophysics Data System (ADS)

    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.

  11. Behaviour of magnetotelluric source fields within the equatorial zone

    NASA Astrophysics Data System (ADS)

    Padilha, Antonio L.

    1999-10-01

    It is well known that equatorial electrojet (EEJ) currents can significantly affect the geomagnetic variations. However, in a recent study (Padilha et al., 1997) it was observed that magnetotelluric (MT) soundings carried out across the dip equator in the Brazilian equatorial zone were not affected significantly due to EEJ currents. By using new results from geomagnetic variation signals, measured simultaneously to the MT experiment at a chain of equatorial and mid-latitude stations, an attempt is made here to explain the MT results in terms of the behaviour of the primary inducing field during the survey. Most of the analysis is performed by considering a single frequency (0.885 mHz), representative of the MT frequency interval. It is observed that the amplitude of the geomagnetic variations appears horizontally homogeneous within the study area (from -3° to +3° of geomagnetic latitude), indicating that the primary field in the analysed frequency range may be considered sufficiently uniform in the horizontal direction thus satisfying the Tikhonov-Cagniard plane-wave criterion. The same geomagnetic data also show that, if any EEJ source effect exists, it would be restricted to the transition zone (between 3° and 5°, at both sides of the dip equator). Dmitriev-Berdichevsky's constraints calculated at two different frequencies and a modelling exercise using EEJ parameters derived from a magnetometer array were able to explain the MT observations and have shown that source effects would just appear in frequencies lower than 1 mHz (resistive regions) and 0.1 mHz (conductive regions). Considering the characteristics of propagation and amplification of geomagnetic variations at the equatorial zone it is concluded that EEJ currents could be used as a source for lithospheric MT studies in these regions.

  12. Variability of the productive habitat in the eastern equatorial Pacific

    NASA Technical Reports Server (NTRS)

    Feldman, Gene Carl

    1986-01-01

    It is shown that satellite ocean color data can be used to define the spatial extent of the region of enhanced biological production (the productive habitat) in the eastern equatorial Pacific. The degree of interannual variability in the areal extent of the productive habitat and in the estimated primary production of the region is determined. Frequency distributions of satellite-derived pigment concentrations are used to determine whether major changes in phytoplankton biomass have taken place from one period to the next.

  13. Automatically identification of Equatorial Spread-F occurrence on ionograms

    NASA Astrophysics Data System (ADS)

    Pillat, Valdir Gil; Fagundes, Paulo Roberto; Guimarães, Lamartine Nogueira Frutuoso

    2015-12-01

    F-region large-scale irregularities, also called plasma bubbles, are one of the most interesting equatorial ionospheric phenomena. These irregularities are generated in the equatorial region and afterwards extend to lower latitudes. They are one of the important topics of investigation in equatorial ionosphere electrodynamics and, therefore, are subject to intense theoretical and experimental research. The ionosonde is the most used scientific equipment to study the ionosphere and the F-region. With advancement of digital ionosonde, it is now possible to carry out an ionospheric sounding with a cadence of 5 min or even with 1-minute cadence. To analyse a large amount of ionograms, more sophisticated tools are needed. Thus, development of algorithms to identify and analyse different aspects of ionograms has become very important to space science researchers. Multiple echoes recorded on ionograms are the signature of these irregularities in the ionograms, usually called Spread-F. Spread-F is classified into three types: range, frequency, and mixed. Thus, automatic identification of Spread-F is important in ionospheric studies, because studies usually involve the analysis and interpretation of large numbers of ionograms. The main objective of this paper is to present a new computational tool, based on fuzzy relation, designed to automatically identify the occurrence of Spread-F in ionograms. The test was conducted in ionograms recorded in the Brazilian sector (São José dos Campos (23.2°S, 45.9°W, dip latitude 17.6°S-low latitude) and Palmas (10.2°S, 48.2°W, dip latitude 5.5°S-near the magnetic equatorial)). The automatic identification of Spread-F occurrence was compared with those obtained manually and good agreement was found.

  14. Automatically identification of Equatorial Spread-F occurrence on ionograms

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    F-region large-scale irregularities, also called plasma bubbles, are one of the most interesting equatorial ionospheric phenomena. These irregularities are generated in the equatorial region and afterwards extend to lower latitudes. They are one of the important topics of investigation in equatorial ionosphere electrodynamics and, therefore, are subject to intense theoretical and experimental research. The ionosonde is the most used scientific equipment to study the ionosphere and the F-region. With advancement of digital ionosonde, it is now possible to carry out an ionospheric sounding with a cadence of 5 minutes or even with 1-minute cadence. To analyse a large amount of ionograms, more sophisticated tools are needed. Thus, development of algorithms to identify and analyse different aspects of ionograms has become very important to space science researchers. Multiple echoes recorded on ionograms are the signature of these irregularities in the ionograms, usually called Spread-F. Spread-F is classified into three types: range, frequency, and mixed. Thus, automatic identification of Spread-F is important in ionospheric studies, because studies usually involve the analysis and interpretation of large numbers of ionograms. The main objective of this paper is to present a new computational tool, based on fuzzy relation, designed to automatically identify the occurrence of Spread-F in ionograms. The test was conducted in ionograms recorded in the Brazilian sector (São José dos Campos (23.2° S, 45.9° W, dip latitude 17.6° S - low latitude) and Palmas (10.2° S, 48.2° W, dip latitude 5.5° S - near the magnetic equatorial)). The automatic identification of Spread-F occurrence was compared with those obtained manually and good agreement was found.

  15. Cross-equatorial and boundary layer exchange: A FGGE review

    NASA Technical Reports Server (NTRS)

    Young, J. A.

    1985-01-01

    The Global Weather Experiment (FGGE) provided unique data on the interesting phenomenon of cross-equatorial flow. Such motion is a key element of the seasonal cycle of the tropics, especially in monsoonal regions. The IIb obserations, IIIb assimilations, and implied dynamics of the flows are reviewed. Additional emphasis is given to the low level branches concentrated in the planetary boundary layer, including air sea interaction and vertical turbulence processes. The results of a recent MONEX Boundary Layer Workshop are summarized.

  16. Stratospheric constituent response to vertically propagating equatorial waves

    NASA Astrophysics Data System (ADS)

    Salby, Murry L.

    1988-02-01

    Planetary-scale equatorial waves play an important role in the dynamics of the tropical atmosphere. They are believed to be excited in unsteady convective heating in the tropical troposphere. From convective centers in the intertropical convergence zone (ITCZ), equatorial waves propagate vertically into the upper atmosphere where they are eventually absorbed, e.g., through radiative dissipation. A spectrum of vertically propagating Kelvin waves was revealed to be trapped about the equator, radiating vertically out of the tropical troposphere. Two other Kelvin waves were found with phase velocities 2 and 4 times as fast. The ultrafast Kelvin waves move at nearly 120 m/s and are seen to propagate to the highest altitude observed by Nimbus-7 LIMS. Each class has the form of a Kelvin wave, a Gaussian centered on the equator and propagating vertically, and all satisfy the dispersion relationship for equatorial Kelvin waves. These vertically propagating Kelvin waves account for a substantial fraction of the temperature variability in the tropical stratosphere. In combination, they lead to temperature fluctuations in excess of 5K in the upper stratosphere and mesosphere. Because several chemical constituents are photochemically controlled in this region, vertically propagating Kelvin waves are expected to lead to variations in the abundances of such species.

  17. On the return current of the equatorial electrojet

    NASA Astrophysics Data System (ADS)

    Onwumechili, C. A.

    In practically all cases, investigators have found it compelling to include westward currents on the flanks of the dip equator in order to fit well the observed dip equatorial magnetic variation profiles. There are three sources of the return currents: the geometry of field lines in the dynamo region, the polarization at the boundaries of enhanced conductivity at the dip equator, and the local neutral winds varying with height. These combine constructively, taking advantage of the peaks of conductivities around 5-deg-dip latitude, to provide for the return currents of practically all the eastward electrojet current. The return currents flow on the flanks of the dip equator for about 3.5 deg to about 20-deg-dip latitude, in any case not extending beyond the Sq focus. The negative correlation between the width and the intensity of the equatorial electrojet has been confirmed with data derived from physical model, indicating its origin in the return currents. The ionospheric current system so far detected by rockets is essentially in two layers. The intense lower layer including the return currents peaking around 5-deg-dip latitude may be associated with the equatorial electrojet; and the weak upper layer that maintains fairly steady altitude characteristics everywhere may be associated with the worldwide part of the Sq currents.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Vertical structure models of the 1990 equatorial disturbance on Saturn

    NASA Astrophysics Data System (ADS)

    Kuehn, D. M.; Barnet, Christopher Dwight; Beebe, R. F.

    1993-03-01

    In September 1990, an atmospheric disturbance in the form of an abnormally high albedo area developed in the equatorial region of Saturn. Events of this nature are exceedingly rare for this planet as they have been detected in the equatorial region on only two other occasions in over a century. In ongoing monitoring of the atmospheres of the outer planets, CCD imaging observations of Saturn by New Mexico State University's Tortugas Mountain Station were made before, during, and after the disturbance's formation through both broad-band filters and narrow-band visible/near-IR filters centered in methane absorption bands. Also, multispectral Hubble Space Telescope observations were made within weeks of the event and later in 1991. These observations were calibrated and scans of reflectivity at constant latitude are being modeled with a vertically inhomogeneous, multiple scattering model previously used to model Jupiter's South Equatorial Belt brightening event in 1989. In addition, the reflectivity of the disturbance as a function of the scattering angles is being obtained so as to model this feature's vertical structure in particular. A preliminary report of the modeling results will be presented.

  20. Vertical structure models of the 1990 equatorial disturbance on Saturn

    NASA Technical Reports Server (NTRS)

    Kuehn, D. M.; Barnet, Christopher Dwight; Beebe, R. F.

    1993-01-01

    In September 1990, an atmospheric disturbance in the form of an abnormally high albedo area developed in the equatorial region of Saturn. Events of this nature are exceedingly rare for this planet as they have been detected in the equatorial region on only two other occasions in over a century. In ongoing monitoring of the atmospheres of the outer planets, CCD imaging observations of Saturn by New Mexico State University's Tortugas Mountain Station were made before, during, and after the disturbance's formation through both broad-band filters and narrow-band visible/near-IR filters centered in methane absorption bands. Also, multispectral Hubble Space Telescope observations were made within weeks of the event and later in 1991. These observations were calibrated and scans of reflectivity at constant latitude are being modeled with a vertically inhomogeneous, multiple scattering model previously used to model Jupiter's South Equatorial Belt brightening event in 1989. In addition, the reflectivity of the disturbance as a function of the scattering angles is being obtained so as to model this feature's vertical structure in particular. A preliminary report of the modeling results will be presented.

  1. Solar activity effects on the equatorial thermosphere temperature profile

    NASA Astrophysics Data System (ADS)

    Arduini, C.; Laneve, G.; Nobile, L.

    In this paper we present the effects of solar activity on the temperature profiles of the equatorial thermosphere as derived from the neutral density data collected by the San Marco 5 (SM5) satellite. This satellite flew during the increasing part of the solar cycle 22 (1988). It had a quasi-equatorial orbit, with inclination lower than 3 deg. The range of measurements, from April to December, allows the inference of seasonal and diurnal effects on the temperature profiles. The density data are collected every second along arcs of orbit lasting up to 50 minutes. The analysis of these densities has been already partially presented and provided evidence for several interesting features, in particular the vertical structure of the diurnal harmonic content and its seasonal variations. The temperatures derived from the same data set provide a useful complement to this picture. The SM5 satellite carried on board 5 instruments for studying the equatorial ionosphere and thermosphere, among them, the Drag Balance Instrument (DBI) for measuring the neutral density and the Ion Drift Meter and Potential Retarding Analyzer (IVI) that allow the evaluation of ions concentration, velocity and temperature. It is possible, therefore, to compare the neutral temperature derived from the neutral density data with the ion temperature given by the IVI.

  2. Jupiter Equatorial Region in a Methane Band Time Set 1

    NASA Image and Video Library

    1998-03-06

    Mosaic of an equatorial "hotspot" on Jupiter at 889 nanometers (nm). The mosaic covers an area of 34,000 kilometers by 11,000 kilometers. Light at 889 nm is strongly absorbed by atmospheric methane. This image shows the features of a hazy cloud layer tens of kilometers above Jupiter's main visible cloud deck. This haze varies in height but appears to be present over the entire region. Small patches of very bright clouds may be similar to terrestrial thunderstorms. The dark region near the center of the mosaic is an equatorial "hotspot" similar to the Galileo Probe entry site. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. North is at the top. The mosaic covers latitudes 1 to 10 degrees and is centered at longitude 336 degrees West. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft. http://photojournal.jpl.nasa.gov/catalog/PIA01200

  3. Strong postmidnight equatorial ionospheric anomaly observations during magnetically quiet periods

    NASA Astrophysics Data System (ADS)

    Yizengaw, Endawoke; Moldwin, Mark B.; Sahai, Yogeshwar; de Jesus, Rodolfo

    2009-12-01

    We have examined the quiet time equatorial electrodynamics of the ionosphere in the postmidnight sector using satellite, GPS total electron content (TEC) and ionosonde data. ROCSAT-1 vertical drift data are used to estimate the equatorial ionosphere electrodynamics, TOPEX altimeter and GPS TEC are used to obtain the density structure of the ionosphere. Ionosonde data measure the postmidnight F layer height as function of local time. We analyzed 4 years (2001-2004) of quiet time (Kp ≤ 3) observations in the postmidnight sector. We found that very strong equatorial ionospheric anomalies (EIAs) in the postmidnight (0100-0500 LT) sector during magnetically quiet periods are common and are capable of disrupting satellite communication and navigation systems. The coordinated multi-instrument observations clearly demonstrate that these strong EIAs are not simply the EIAs observed in earlier local time sectors that have corotated into the postmidnight sector as has been suggested by previous studies. We demonstrate that they are triggered by a reversed vertically upward drift, which is suggested to be generated by thermospheric neutral wind through F region dynamo. This clearly demonstrates that the Earth's postmidnight ionosphere is dynamic even in magnetically quiet periods contrary to simple theoretical model predictions.

  4. Winds analysis for polar and equatorial stratospheric balloons flights

    NASA Astrophysics Data System (ADS)

    Ivano, Musso; Cardillo, Andrea; Ibba, Roberto; Spoto, Domenico; Amaro, Francesco; Memmo, Adelaide

    Astrophysicists, meteorologists and biologists are only some of the scientists that are requiring stratospheric flights and in particular Long Duration Balloon Flights for their researches and experiments. The Italian Space Agency (ASI) is therefore coordinating an effort for the developing of stratospheric balloons' campaigns from North Pole, where ASI collaborates with Andoya Rocket Range preparing the Nobile/Amundsen Stratospheric Balloon Centre at Svalbard and from the ASI satellite receiving station in Malindi Kenya. Flights have been ongoing by other agencies in Antarctica. From the Northern Polar Region and Equatorial Africa similar flights will be possible without the logistical difficulties of that area. Answering to a specific scientific requirement, polar nocturnal and equatorial flights are now being investigated. Missions during polar winter are interesting because they provide regions of the sky where measurements are normally impossible. Trajectories are evaluated with a statistical wind analysis. Summer flights provide circular paths from Svalbard around the Pole and a safe recovery in Greenland after two weeks or more. The nocturnal flights do not have the same stability: isobaric lines are not centred above the Pole and trajectories around Svalbard involving Russia, Norway and Greenland are usual between December and February. For the equatorial missions we have analysed the statistical properties of trajectories considering the biennal oscillation and the seasonal effects of the stratospheric winds.

  5. Stacked jets in the deep equatorial Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Eden, Carsten; Dengler, Marcus

    2008-04-01

    Middepth current measurements in the equatorial Atlantic are characterized by elevated levels of energy contained in zonal flows of high baroclinic mode number. These alternating zonal flows, often called equatorial stacked jets, have amplitudes up to 20 cm s-1 and vertical wavelengths of 600 m. The jets are most pronounced in the depth range between 500 and 2500 m. Repeated direct velocity observations at 35°W indicate that the jets are coherent within ±1° of the equator. Individual jets can persist for 1-2 years, but they appear and decay rather irregularly. The equatorial stacked jets are also found in realistic general circulation model simulations. The features grow in amplitude with increasing horizontal and vertical model resolution. However, even at very high model resolutions, their amplitudes are still underestimated. In all model simulations, high levels of energy related to the stacked jets are found in the vicinity of the western boundary currents (WBCs). Depth range and strength of the WBCs in different experiments are related to depth range and strength of the jets. In the interior, stacked jets are characterized by eastward wave propagation suggesting that high baroclinic mode Kelvin waves radiate energy generated in the WBC into the interior and form the stacked jets.

  6. Geomagnetic activity effects on the equatorial neutral thermosphere

    SciTech Connect

    Burrage, M.D.; Abreu, V.J.; Orsini, N. ); Fesen, C.G. ); Roble, R.G. )

    1992-04-01

    The effects of geomagnetic activity on the equatorial neutral thermosphere are investigated with mass spectrometer measurements from the Atmosphere Explorer E (AE-E) satellite and simulations generated by the National Center for Atmospheric Research thermosphere/ionosphere general circulation model (TIGCM). A study of the local time dependence of the equatorial geomagnetic storm response concentrates on a disturbed period from March 20 (day 79) to March 31 (day 90), 1979. This interval was the subject of an intense data-gathering and analysis campaign for the Coordinated Data Analysis Workshop 6, and global TIGCM predictions are available for the specific conditions of the storm as a function of universal time. The AE-E measurements demonstrate that significant geomagnetic storm-induced perturbations of upper thermospheric N{sub 2} and O densities extend into the equatorial zone but are mainly restricted to the midnight/early morning sector. The qualitative features of the observations are reproduced by the TIGCM, although in general, the model simulations overestimate the storm temperature and density enhancements, primarily in the nighttime thermosphere. This suggests that either the nighttime cooling rates in the TIGCM are too small or that the specified auroral forcing of the model are too persistent.

  7. A truncated oceanic spectral model for equatorial thermodynamic studies

    NASA Astrophysics Data System (ADS)

    Smith, Neville R.

    1988-12-01

    A β-plane model for equatorial circulation is transformed in terms of Hermite functions into a form where the meridional dependence is expressed in terms of spectral components. Linear analysis reveals a wave-dispersion relation similar in character to the regular model but with anti-Kelvin and anti-Yanai modes present. Depending upon the length scale used for the expansion, the evanescent frequency zone between the planetary and inertia-gravity modes, and between the two Yanai modes, may be changed. The truncated model offers an alternative view of the place of the primary wave modes in the overall scheme of equatorial planetary and gravity waves. The anti-Kelvin and anti-Yanai modes play an important role in returning the balance of the equatorial energy flux to the west at the eastern boundary. Transformation of the primitive equations into spectral form with low-order meridional wave number truncation yields a tractable, economical set of equations which have applications in the study of thermodynamic processes, parameterizations and for economical testing of numerical techniques. Second-order models are derived and they clearly expose the many couplings due to non-linear effects, diffusion, viscosity, pressure terms and the β effect.

  8. Tropical Cyclone - Equatorial Ionosphere Coupling: A Statistical Study

    NASA Astrophysics Data System (ADS)

    Bhagavathiammal, G. J.

    2016-07-01

    This paper describes the equatorial ionosphere response to tropical cyclone events which was observed over the Indian Ocean. This statistical study tries to reveal the possible Tropical Cyclone (TC) - Ionosphere coupling. Tropical cyclone track and data can be obtained from the India Meteorological Department, New Delhi. Digisonde/Ionosonde data for the equatorial latitudes can be obtained from Global Ionospheric Radio Observatory. It is believed that TC induced convection as the driving agent for the increased gravity wave activity in the lower atmosphere and these propagating gravity waves deposit their energy and momentum into the upper atmosphere as Travelling Ionospheric Disturbances (TIDs). The convective regions are identified with the help of Outgoing Long wave radiation (OLR) data from NOAA Climate Data Center/ Precipitation data from TRMM Statellite. The variability of ionospheric parameter like Total Electron Content (TEC), foF2, h'F2 and Drift velocity are examined during TC periods. This study will report the possibility of TC-Ionosphere Coupling in equatorial atmosphere.

  9. Global geologic mapping of Mars: The western equatorial region

    USGS Publications Warehouse

    Scott, D.H.

    1985-01-01

    Global geologic mapping of Mars was originally accomplished following acquisition of orbital spacecraft images from the Mariner 9 mission. The mapping program represented a joint enterprise by the U.S. Geological Survey and other planetary scientists from universities in the United States and Europe. Many of the Mariner photographs had low resolution or poor albedo contrast caused by atmospheric haze and high-sun angles. Some of the early geologic maps reflect these deficiencies in their poor discrimination and subdivision of rock units. New geologic maps made from higher resolution and better quality Viking images also represent a cooperative effort, by geologists from the U.S. Geological Survey, Arizona State University, and the University of London. This second series of global maps consists of three parts: 1) western equatorial region, 2) eastern equatorial region, and 3) north and south polar regions. These maps, at 1:15 million scale, show more than 60 individual rock-stratigraphic units assigned to three Martian time-stratigraphic systems. The first completed map of the series covers the western equatorial region of Mars. Accompanying the map is a description of the sequence and distribution of major tectonic, volcanic, and fluvial episodes as recorded in the stratigraphic record. ?? 1985.

  10. Modulation of precipitation over West Africa by equatorial waves

    NASA Astrophysics Data System (ADS)

    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

  11. Convectively Coupled Equatorial Waves in Reanalysis and CMIP5 Simulations

    NASA Astrophysics Data System (ADS)

    Castanheira, J. M.; Marques, C. A. F.

    2014-12-01

    Convectively coupled equatorial waves (CCEWs) are a result of the interplay between the physics and dynamics in the tropical atmosphere. As a result of such interplay, tropical convection appears often organized into synoptic to planetary-scale disturbances with time scales matching those of equatorial shallow water waves. CCEWs have broad impacts within the tropics, and their simulation in general circulation models is still problematic. Several studies showed that dispersion of those waves characteristics fit the dispersion curves derived from the Matsuno's (1966) solutions of the shallow water equations on the equatorial beta plane, namely, Kelvin, equatorial Rossby, mixed Rossby-gravity, and inertio-gravity waves. However, the more common methodology used to identify those waves is yet controversial. In this communication a new methodology for the diagnosis of CCEWs will be presented. It is based on a pre-filtering of the geopotential and horizontal wind, using 3--D normal modes functions of the adiabatic linearized equations of a resting atmosphere, followed by a space--time spectral analysis to identify the spectral regions of coherence. The methodology permits a direct detection of various types of equatorial waves, compares the dispersion characteristics of the coupled waves with the theoretical dispersion curves and allows an identification of which vertical modes are more involved in the convection. Moreover, the proposed methodology is able to show the existence of free dry waves and moist coupled waves with a common vertical structure, which is in conformity with the effect of convective heating/cooling on the effective static stability, as traduced in the gross moist stability concept. The methodology is also sensible to Doppler shifting effects. The methodology has been applied to the ERA-Interim horizontal wind and geopotential height fields and to the interpolated Outgoing Longwave Radiation (OLR) data produced by the National Oceanic and

  12. Patterns of equatorial drifts according to diverse observational probes

    NASA Astrophysics Data System (ADS)

    Oyekola, Oyedemi S.

    We examine morphological patterns of observational results of the equatorial vertical E×B drifts obtained from different probing methods (VHF radar at Jicamarca, Ion Drift Meter on the AE-E satellite, drifts derived from ionosonde h’F data at Ibadan (Nigeria) over 1-year, and HF Doppler at Trivandrum (India)) during the evening and nighttime periods for geomagnetic quiet-day and high solar activity conditions (F10.7 ranges from ~160-208 sfu) for three different seasonal periods. A direct comparison between these measurements and the International Reference Ionosphere 2007 (IRI-2007) model-predictions of equatorial vertical plasma drifts are also made. Our results show that while VHF, AE-E and ionosonde-inferred drifts generally exhibit the typical characteristic features of quiet-time equatorial electrodynamics but reveal substantial disparities in the observational techniques of F-region vertical drifts. The trends in the experimental data agree reasonably with the Scherliess-Fejer climatological curves for the three seasons. In contrast, an IRI representation grossly overestimates and show large departure from the Ibadan and Trivandrum Doppler drift patterns between 1500-0100 LT. The model peak velocity occurs at about two hours earlier than the ionosonde and HF-Doppler velocity peaks. The magnitudes of the velocity peak differ by approximately 28 percent. The dusk reversal times fluctuate significantly and occur between about 1800-2200 LT for all the drift techniques. On the other hand, reversal times near sunrise show less variation. The essential feature of equatorial electrodynamics is the evening prereversal enhancement (PRE) peak velocity; a key parameter required to trigger postsunset ionospheric irregularities. We demonstrate that the simulated PRE ranges between about 20-50 m/s with average value (standard deviation) of roughly 37+/-11 m/s; whereas Ibadan ionosonde PRE velocities vary from about 20 to 45 m/s, with typical average value (standard

  13. Candidate ice-rich material within equatorial craters on Mars

    NASA Astrophysics Data System (ADS)

    Shean, D. E.

    2010-12-01

    The floors and walls of many mid-latitude (~30-60°) craters on Mars appear to be mantled by relatively young material(s) with distinct morphology and erosional properties [1,2]. Collectively, this material (“fill”) is often interpreted as ice-rich, with emplacement and modification related to climatically controlled/induced processes [1,3]. Here, I document material and associated landforms within 38 craters between ~4-12°S and ~335-355°W in the Sinus Sabaeus region (south of Schiaparelli Crater) that appear morphologically similar to material and landforms within mid-latitude craters. The morphological similarities between the equatorial and mid-latitude fill material suggest that they potentially share a similar composition, are subjected to similar erosional processes, and share a similar emplacement mechanism. Nearly all craters containing fill material in Sinus Sabaeus are ~2.0-9.0 km in diameter (median 5.3 km) and they tend to be relatively young with steep interior wall slopes of ~15-30°. At least 30 additional craters in the region display evidence suggestive of past fill presence. A survey of available Mars Reconnaissance Orbiter Context Camera (CTX) data at equatorial latitudes did not identify this material or evidence for its former presence within any other equatorial craters. Near-surface ice is unstable at equatorial latitudes under present conditions, suggesting that emplacement could have occurred under different climate conditions in the past. High-obliquity (35-45°) general circulation model simulations [4] show surface ice accumulation in Sinus Sabaeus and Tharsis, where similar material and landforms have been documented within steep-walled depressions and troughs [5]. The documentation of this material in Sinus Sabaeus is consistent with the hypothesis that past obliquity-driven climate change resulted in equatorward volatile migration on Mars. This fill material is >80-100 m thick in some craters. It is unclear from available data

  14. Off-equatorial jets in Jupiter's and Saturn's atmospheres

    NASA Astrophysics Data System (ADS)

    Liu, Junjun; Schneider, T.

    2013-10-01

    Jupiter and Saturn have similar radii, rotation rates, and atmospheres. Yet their off-equatorial jets differ markedly: Jupiter has 1 20 off-equatorial jets, with speeds at the level of the visible clouds around 20 m/s; Saturn has only 10 wider off-equatorial jets, with speeds around 100 m/s. Here it is shown that the differences between the off-equatorial jets can be accounted for by differences in the magnetohydrodynamic (MHD) drag the jets experience in the planetary interiors. The relation between jet characteristics and drag strength is examined systematically through simulations with a general circulation model (GCM). The GCM domain is a thin spherical shell in the upper atmosphere of a giant planet, with flow parameters relevant for Jupiter. Rayleigh drag at an artificial lower boundary (with mean pressure of bar) is used as a simple representation of the MHD drag the flow on giant planets experiences at depth. The drag coefficient is varied to investigate how it affects characteristics of off-equatorial jets. As the drag coefficient decreases, the eddy length scale and eddy kinetic energy increase. Jets become wider and stronger, with increased interjet spacing. Generally, the jet widths scale with the Rhines scale, which is of similar magnitude as the Rossby radius in the simulations. The jet strengths increases primarily through strengthening of the barotropic component, which increases as the drag coefficient decreases because the overall kinetic energy dissipation remains roughly constant: an increasing mean flow strength in the drag layer roughly balances a decreasing drag coefficient to lead to the same kinetic energy dissipation. The overall kinetic energy dissipation remains roughly constant presumably because it is controlled by baroclinic conversion of potential to kinetic energy in the upper troposphere, where differential solar heating has an influence; this baroclinic conversion is only weakly dependent on bottom drag and barotropic flow

  15. Off-equatorial Jets in Giant Planet Atmospheres

    NASA Astrophysics Data System (ADS)

    Schneider, T.; Liu, J.

    2013-12-01

    Jupiter and Saturn have similar radii, rotation rates, and atmospheres. Yet their off-equatorial jets differ markedly: Jupiter has 15--20 off-equatorial jets, with speeds at the level of the visible clouds around 20 m/s; Saturn has only 5--10 wider off-equatorial jets, with speeds around 100 m/s. Here it is shown that the differences between the off-equatorial jets can be accounted for by differences in the magnetohydrodynamic (MHD) drag the jets experience in the planetary interiors. The relation between jet characteristics and drag strength is examined systematically through simulations with a general circulation model (GCM). The GCM domain is a thin spherical shell in the upper atmosphere of a giant planet, with flow parameters relevant for Jupiter. Rayleigh drag at an artificial lower boundary (with mean pressure of 3~bar) is used as a simple representation of the MHD drag the flow on giant planets experiences at depth. The drag coefficient is varied to investigate how it affects characteristics of off-equatorial jets. As the drag coefficient decreases, the eddy length scale and eddy kinetic energy increase. Jets become wider and stronger, with increased interjet spacing. Coherent vortices also become more prevalent. Generally, the jet widths scale with the Rhines scale, which is of similar magnitude as the Rossby radius in the simulations. The jet strengths increases primarily through strengthening of the barotropic component, which increases as the drag coefficient decreases because the overall kinetic energy dissipation remains roughly constant: an increasing mean flow strength in the drag layer roughly balances a decreasing drag coefficient to lead to the same kinetic energy dissipation, which is dominated by the drag on the mean flow. The overall kinetic energy dissipation remains roughly constant presumably because it is controlled by baroclinic conversion of potential to kinetic energy in the upper troposphere, where differential solar heating has an

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

    NASA Astrophysics Data System (ADS)

    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.

    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

  17. Characterizing Cratering at the Iapetus Equatorial Ridge using Stereo Topography

    NASA Astrophysics Data System (ADS)

    Persaud, D. M.

    2015-12-01

    Since the arrival of the Cassini probe to the Saturnian system in 2004, the flattened shape and extreme equatorial ridge of the moon Iapetus have posed a number of questions regarding its geophysical evolution. Current models suggest either tidal despinning or a collapsed ring system formed the ridge, with 26Al decay serving as an additional heating mechanism and warm ice or liquid water beneath a thick lithosphere potentially allowing for large-scale topography and deformation to occur (Sandwell and Schubert 2010). Structure at the ridge itself provides further questions in understanding the deformation of Iapetus at its equator. Persaud and Phillips (2014) use stereo topography to present a trend of crater relaxation and crater diameter that suggests a secondary heating event has relaxed younger, smaller craters focused at this region. The extreme slopes along the ridge, however, complicate understanding the order of events that have occurred on Iapetus, including ridge formation, crater relaxation, secondary thermal events, and mass wasting. We use topographic profiles of Iapetus impact craters extracted from digital elevation models (DEMs) constructed with stereo images from the Cassini ISS Instrument to characterize crater complexity and transition diameters versus crater floor geometry, proximity to the equatorial ridge, and relaxation percentage. We then use these results to begin to develop a geometric model of events at the ridge on Iapetus to understand its deformation history. We will present results and discussion of using stereo topography for these analyses. References: Sandwell, D., and G. Schubert. A contraction model for the flattening and equatorial ridge of Iapetus, Icarus 210, 817-822, 2010. Persaud, D.M., and C.B. Phillips. Methods of Estimating Initial Crater Depths on Icy Satellites using Stereo Topography, AGU Fall Meeting 2014, abstract 17043. This work was supported by the 2015 NASA Ames Academy for Space Exploration.

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    A detailed study of the chevron-shaped dark spots on the strong southern equatorial wind jet near 7.5 S planetographic latitude shows variations in velocity with longitude and time. The presence of the large anticyclonic South Equatorial Disturbance (SED) has a profound effect on the chevron velocity, causing slower velocities to its east and accelerations over distance from the disturbance. 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 N latitude. Their repetitive nature is consistent with a gravity-inertia wave (n = 75 to 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, for the first time, high spatial resolution movies from Cassini images show that the chevrons oscillate in latitude with a 6.7 +/- 0.7-day period. This oscillating motion has a wavelength of approx 20 and a speed of 101 +/- 3 m/s, following a pattern similar to that seen in the Rossby wave plumes of the North Equatorial Zone, and possibly reinforced by it. All dates show chevron latitude variability, but it is unclear if this larger wave is present during other epochs, as there are no other suitable 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 is likely due to the presence of the Great Red Spot, either through changes in stratification and stability or by acting as a wave boundary.

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

    NASA Technical Reports Server (NTRS)

    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.

  20. Ocean atmosphere thermal decoupling in the eastern equatorial Indian ocean

    NASA Astrophysics Data System (ADS)

    Joseph, Sudheer; Ravichandran, M.; Kumar, B. Praveen; Jampana, Raju V.; Han, Weiqing

    2016-09-01

    Eastern equatorial Indian ocean (EEIO) is one of the most climatically sensitive regions in the global ocean, which plays a vital role in modulating Indian ocean dipole (IOD) and El Niño southern oscillation (ENSO). Here we present evidences for a paradoxical and perpetual lower co-variability between sea-surface temperature (SST) and air-temperature (Tair) indicating instantaneous thermal decoupling in the same region, where signals of the strongly coupled variability of SST anomalies and zonal winds associated with IOD originate at inter-annual time scale. The correlation minimum between anomalies of Tair and SST occurs in the eastern equatorial Indian ocean warm pool region (≈70°E-100°E, 5°S-5°N), associated with lower wind speeds and lower sensible heat fluxes. At sub-monthly and Madden-Julian oscillation time scales, correlation of both variables becomes very low. In above frequencies, precipitation positively contributes to the low correlation by dropping Tair considerably while leaving SST without any substantial instant impact. Precipitation is led by positive build up of SST and post-facto drop in it. The strong semi-annual response of SST to mixed layer variability and equatorial waves, with the absence of the same in the Tair, contributes further to the weak correlation at the sub-annual scale. The limited correlation found in the EEIO is mainly related to the annual warming of the region and ENSO which is hard to segregate from the impacts of IOD.

  1. Preface: C/NOFS Results and Equatorial Ionospheric Dynamics

    NASA Technical Reports Server (NTRS)

    Klenzing, J.; de La Beaujardiere, O.; Gentile, L. C.; Retterer, J.; Rodrigues, F. S.; Stoneback, R. A.

    2014-01-01

    The Communication/Navigation Outage Forecasting System (C/NOFS) satellite was launched into orbit in April 2008 as part of an ongoing effort to understand and identify plasma irregularities that adversely impact the propagation of radio waves in the upper atmosphere. Combined with recent improvements in radar, airglow, and ground-based studies, as well as state-of-the-art modeling techniques, the C/NOFS mission has led to new insights into equatorial ionospheric electrodynamics. In order to document these advances, the C/NOFS Results and Equatorial Dynamics Technical Interchange Meeting was held in Albuquerque, New Mexico from 12 to 14 March 2013. The meeting was a great success with 55 talks and 22 posters, and covered topics including the numerical simulations of plasma irregularities, the effects of atmospheric tides, stratospheric phenomena, and magnetic storms on the upper atmosphere, causes and predictions of scintillation-causing ionospheric irregularities, current and future instrumentation efforts in the equatorial region. The talks were broken into the following three topical sessions: A. Ambient Ionosphere and Thermosphere B. Transient Phenomena in the Low-Latitude Ionosphere C. New Missions, New Sensors, New Science and Engineering Issues. The following special issue was planned as a follow-up to the meeting. We would like to thank Mike Pinnock, the editors and staff of Copernicus, and our reviewers for their work in bringing this special issue to the scientific community. Our thanks also go to Patricia Doherty and the meeting organizing committee for arranging the C/NOFS Technical Interchange Meeting.

  2. Interannual atmospheric variability forced by the deep equatorial Atlantic Ocean.

    PubMed

    Brandt, Peter; Funk, Andreas; Hormann, Verena; Dengler, Marcus; Greatbatch, Richard J; Toole, John M

    2011-05-26

    Climate variability in the tropical Atlantic Ocean is determined by large-scale ocean-atmosphere interactions, which particularly affect deep atmospheric convection over the ocean and surrounding continents. Apart from influences from the Pacific El Niño/Southern Oscillation and the North Atlantic Oscillation, the tropical Atlantic variability is thought to be dominated by two distinct ocean-atmosphere coupled modes of variability that are characterized by meridional and zonal sea-surface-temperature gradients and are mainly active on decadal and interannual timescales, respectively. Here we report evidence that the intrinsic ocean dynamics of the deep equatorial Atlantic can also affect sea surface temperature, wind and rainfall in the tropical Atlantic region and constitutes a 4.5-yr climate cycle. Specifically, vertically alternating deep zonal jets of short vertical wavelength with a period of about 4.5 yr and amplitudes of more than 10 cm s(-1) are observed, in the deep Atlantic, to propagate their energy upwards, towards the surface. They are linked, at the sea surface, to equatorial zonal current anomalies and eastern Atlantic temperature anomalies that have amplitudes of about 6 cm s(-1) and 0.4 °C, respectively, and are associated with distinct wind and rainfall patterns. Although deep jets are also observed in the Pacific and Indian oceans, only the Atlantic deep jets seem to oscillate on interannual timescales. Our knowledge of the persistence and regularity of these jets is limited by the availability of high-quality data. Despite this caveat, the oscillatory behaviour can still be used to improve predictions of sea surface temperature in the tropical Atlantic. Deep-jet generation and upward energy transmission through the Equatorial Undercurrent warrant further theoretical study.

  3. Formerly emerging crustal blocks in the equatorial Atlantic

    NASA Astrophysics Data System (ADS)

    Bonatti, Enrico; Chermak, Andy

    1981-02-01

    Anomalous crustal topographic highs, exceeding the level predicted by the thermal contraction model by up to 2-3 km, are observed along the Romanche Transform Zone in the equatorial Atlantic. Previous studies of shallow-water reef limestones recovered from one of the shallowest sites on these crustal highs indicated that this site was at or above sea level 5 million years ago and subsided since at an average rate one order of magnitude faster than the subsidence estimated by thermal contraction of the crust. Seismic reflection profiles obtained across the Romanche Transform Zone suggest that the anomalous highs are capped by reef limestones not only where limestones were actually sampled, but also at other locations. These findings support the idea that long segments of crust reached close to sea level in the past along the Romanche Transform Zone. The vertical crustal motions are probably caused by tectonism typical of long-offset transforms. Inasmuch as the Romanche has been a ridge—ridge transform since the earliest stages of the opening of the equatorial Atlantic, it is likely that intense vertical tectonic motions occurred along it throughout the evolution of the Atlantic. Support for this hypothesis is provided by the recovery during DSDP Leg 4 of shallow water reef limestone of the Eocene Age from the summit of the North Brazilian Ridge along the western extension of the Romanche Fracture Zone. The presence of shallow or emergent crust across the equatorial zone during the early stages of opening had probably important consequences upon the water circulation between the North and the South Atlantic, and may even have provided "land bridges" for faunal migrations between Africa and South America in early Cenozoic times after the two continents had already separated.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. Equatorial spread-F (ESF) and vertical winds

    NASA Astrophysics Data System (ADS)

    Raghavarao, R.; Suhasini, R.; Mayr, H. G.; Hoegy, W. R.; Wharton, L. E.

    1999-05-01

    The Equatorial Spread-F (ESF) phenomenon is recorded in ionograms as a hierarchy of plasma instabilities in the F-layer of the equatorial ionosphere. The ESF is characterized by irregularities in the plasma (electron and ion) density and electric field distributions perpendicular to the Earth's magnetic field. Large scale irregularities are generated by a primary plasma instability that develops in electric fields and plasma densities. Other secondary instabilities then develop and generate irregularities at several scale sizes that often produce a plasma `hole' or `bubble' that rises up with high E×B velocities. The ESF/plasma bubble phenomenon has been studied extensively with experimental techniques and modeling, which revealed important features. In the bottom side F-layer, near sunset, when the vertical density gradient steepens as the layer is supported by the horizontal (North-South) Earth's magnetic field lines against the omnipresent Earth's gravitational acceleration (g), the plasma conditions can give rise to Rayleigh-Taylor (RT) type instability. But the observed day to day variability of the ESF occurrence suggested that other agencies may also be involved in generating the instability. Sekar and Raghavarao (1987) with linear theory, and Raghavarao, Sekar and Suhasini (1992), with non-linear numerical modeling, suggested that vertical downward (upward) winds in the ambient gas have the potential to cause (inhibit) the ESF/bubble phenomenon. The presence of downward winds near the equator was reported earlier. In this paper, we show evidence for the presence of downward winds collocated with irregularities in electric fields and plasma densities as revealed by an unique combination of highly accurate measurements with instruments onboard the DE-2 satellite. The observations reported here are also consistent with the notion that the build-up of the equatorial ionization anomaly (EIA) prior to local sunset is important for the ESF instability.

  6. Spatial Variations of Scintillation and TEC During Equatorial Spread F

    NASA Astrophysics Data System (ADS)

    Groves, K.; Basu, S.; Pedersen, T. R.; Beach, T. L.; Quinn, J. M.; Taliaferro, B.; de Paula, E. R.; Batista, I. S.; Abdu, M. A.; Livingston, R. C.; Ning, P.; Carrano, C.

    2004-05-01

    Numerous studies of geophysical observables associated with large-scale instabilities in the post-sunset equatorial ionosphere have been conducted for several decades; these observables include electric fields, electron density profiles, total electron content (TEC), plasma and neutral drift, scintillations and coherent radar backscatter. Despite a general understanding of the local correlations between these parameters during the on-set and evolution of equatorial bubbles, detailed knowledge of the variations of these parameters as a function of latitude on a given magnetic meridian is lacking. During the Oct-Nov 2002 Conjugate Points Equatorial Experiment (COPEX) campaign was conducted at three sites in western Brazil; one site was situated at the magnetic equator while the other two were selected at magnetic conjugate locations approximately ± 10° MLat. The campaign was organized and coordinated by the Aeronomy Group at the Brazilian National Institute for Space Research (Instituto Nacional de Pesquisas Espaciais- INPE). A number of diagnostic instruments, including digisondes, GPS scintillation and TEC diagnostics, VHF scintillations and plasma drifts, and all-sky imagers were operated routinely throughout the campaign period. The work presented here focuses on the meridional variations of GPS and VHF scintillations from the northern to the southern anomaly regions (~± 15° MLat) and their correlation with total electron content over the same spatial extent. The key issue for consideration is whether the scintillation intensity is directly proportional to electron density (i.e., TEC) across a flux tube implying constant Δ N/N within the instability region, or whether some other relative scaling between the density and scintillation exists. The results provide insight into the distribution of irregularities and, indirectly, the energetics of instabilities within a flux tube. The outcome of this investigation directly impacts techniques to extrapolate local

  7. 234Th and particle cycling in the central equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Dunne, John P.; Murray, James W.; Young, Jennifer; Balistrieri, Laurie S.; Bishop, James

    US JGOFS-EgPac 234Th data sets for 1992 boreal spring (Survey I, TT007) and fall (Survey 11, TT011) cruises from 12°N to 12°S along 140°W were used to determine rates of 234Th and particle cycling using a thorium sorption model and three coupled particle-thorium models. Sampling methodology had a large impact on model results — estimates of particulate organic carbon varied by a factor of 3 between bottle and in-situ filtration techniques. Adsorption rate constants and residence times from the thorium sorption model showed strong depth, latitudinal and seasonal variability which we were able to attribute to changes in particle concentration. A reevaluation of the `particle concentration effect' on the adsorption rate constant, k', showed that our values of k' increased with particle concentration and were consistent with other study sites with similar particle concentrations. Recycling of particulate organic carbon in the euphotic zone of the central equatorial Pacific was 2-10 times faster than sites previously studied. Calculations of adsorption rate constants from the thorium sorption, coupled particle- 234Th and phytoplankton models were extremely dependent on the model treatment of remineralization. Results from the coupled particle- 234Th model, where particles have a constant ]ability, suggested that 234Th recycled three to four times between the dissolved and paticulate phases before being removed from the euphotic zone. Aggregation rate constants and sinking rates in the central equatorial system were compared with other sites using the size-fractionated model developed by Clegg and Whitfield (1991, Deep-Sea Research, 38, 91-120). Removal of particles by sinking from the equatorial euphotic zone depended on a mechanism of differential recycling of organic matter in the euphotic zone in which only a fraction of the particles are remineralized and the more refractory particles sink.

  8. Jovian Equatorial H Lyman-alpha and the Ionosphere

    NASA Astrophysics Data System (ADS)

    Ballester, Gilda E.

    An excess of H Ly alpha emission has been a persistent feature in Jupiter's equatorial upper atmosphere since its discovery in 1978. This Ly alpha 'bulge' was found by high-resolution IUE observations to be due to broadening of the Jovian line increasing the resonant scattering of the solar Ly alpha, rather than from a local enhancement in the H density. The line broadening implies that the H column at the bulge is disturbed by a localized, non-thermal process, and two mechanisms have been proposed to explain this: one by the generation of turbulence from strong thermospheric winds or jets meeting at the bulge region and originating in the active Jovian auroral zones, the other involving a superthermal population of H atoms produced by a process analogous to the equatorial anomaly and tropical arcs on the Earth. Some line broadening was also observed in the off-bulge region while modelling of the usual bulge profile does not predict this behavior, but these observations may have been performed at a time of an unusually large extension of the bulge. We propose to make a series of high-dispersion observations (of improved S/N) for a detailed longitudinal study of the line profile which would be of benefit independently of the particular bulge conditions (to be determined with low-dispersion exposures). In addition, new insight will be gained with simultaneous ground-based observations of the newly discovered global ionospheric H3+ emissions. These emissions are diagnostic of the ionospheric temperature and ion density, and have already shown very particular characteristics in the H Ly alpha bulge region. Coordinated observations of the whole longitudinal range should therefore set new constraints on the mechanisms operating in the Jovian equatorial upper atmosphere.

  9. Equatorial Pacific Thermostad response to El Niño

    NASA Astrophysics Data System (ADS)

    Johnson, Gregory C.; Birnbaum, Abigail N.

    2016-11-01

    El Niños are characterized by a shift of warm surface water from the western to eastern equatorial Pacific due to weakening of easterly trade winds. This shift is associated with the pycnocline (or thermocline), the large vertical density gradient beneath the surface mixed layer, shoaling in the west and deepening in the east, inducing a redistribution of ocean heat with global impacts. Here the response of the Equatorial Pacific Thermostad, a layer of low vertical stratification below the pycnocline to, El Niño is investigated using a monthly Argo float climatology and Argo float deep velocity data. A mean, seasonal cycle, trend, and time-lagged linear response to the Niño3.4 index are fit by least squares to temperature and salinity at each grid point as well as to deep float velocities (omitting the trend). The results of these fits are used to characterize the response of physical properties in the Thermostad, including layer thickness and velocity, to El Niño by comparing the mean properties following neutral conditions (Niño3.4 = 0°C) versus those following a moderate El Niño (Niño3.4 = 1°C). Following an El Niño, a strengthening of the westward-flowing Equatorial Intermediate Current of about 2.7 × 106 m3 s-1 shifts about 97 × 1012 m3 of Thermostad water from the east to the west, allowing conservation of volume within the Thermostad as the pycnocline above deepens in the east and shoals in the west. This transport and volume change imply a 14 month time scale, consistent with El Niño.

  10. Longitudinal variation of the equatorial ionosphere: Modeling and experimental results

    NASA Astrophysics Data System (ADS)

    Souza, J. R.; Asevedo, W. D.; dos Santos, P. C. P.; Petry, A.; Bailey, G. J.; Batista, I. S.; Abdu, M. A.

    2013-02-01

    We describe a new version of the Parameterized Regional Ionospheric Model (PARIM) which has been modified to include the longitudinal dependences. This model has been reconstructed using multidimensional Fourier series. To validate PARIM results, the South America maps of critical frequencies for the E (foE) and F (foF2) regions were compared with the values calculated by Sheffield Plasmasphere-Ionosphere Model (SUPIM) and IRI representations. PARIM presents very good results, the general characteristics of both regions, mainly the presence of the equatorial ionization anomaly, were well reproduced for equinoctial conditions of solar minimum and maximum. The values of foF2 and hmF2 recorded over Jicamarca (12°S; 77°W; dip lat. 1°N; mag. declination 0.3°) and sites of the conjugate point equatorial experiment (COPEX) campaign Boa Vista (2.8°N; 60.7°W; dip lat. 11.4°; mag. declination -13.1°), Cachimbo (9.5°S; 54.8°W; dip lat. -1.8°; mag. declination -15.5°), and Campo Grande (20.4°S; 54.6°W; dip lat. -11.1°; mag. declination -14.0°) have been used in this work. foF2 calculated by PARIM show good agreement with the observations, except during morning over Boa Vista and midnight-morning over Campo Grande. Some discrepancies were also found for the F-region peak height (hmF2) near the geomagnetic equator during times of F3 layer occurrences. IRI has underestimated both foF2 and hmF2 over equatorial and low latitude sectors during evening-nighttimes, except for Jicamarca where foF2 values were overestimated.

  11. Jupiter's Equatorial Region in a Methane band (Time set 1)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Mosaic of Jupiter's equatorial region at 727 nanometers (nm). The mosaic covers an area of 34,000 kilometers by 22,000 kilometers. Light at 727 nm is moderately absorbed by atmospheric methane. This image shows the features of Jupiter's main visible cloud deck and upper tropospheric haze, with higher features enhanced in brightness over lower features. The dark region near the center of the mosaic is an equatorial 'hotspot' similar to the Galileo Probe entry site. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright oval in the upper right of the mosaic as well as the other smaller bright features are examples of upwelling of moist air and condensation.

    North is at the top. The mosaic covers latitudes 1 to 19 degrees and is centered at longitude 336 degrees West. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  12. Jupiter's Equatorial Region in Violet Light (Time set 1)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Mosaic of an equatorial 'hotspot' on Jupiter at 410 nanometers (nm). The mosaic covers an area of 34,000 kilometers by 11,000 kilometers. Light at 410 nm is affected by the sizes and compositions of cloud particles, as well as the trace chemicals that give Jupiter's clouds their colors. This image shows the features of Jupiter's main visible cloud deck and the hazy cloud layer above it. The dark region near the center of the mosaic is an equatorial 'hotspot' similar to the Galileo Probe entry site. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance.

    North is at the top. The mosaic covers latitudes 1 to 10 degrees and is centered at longitude 336 degrees West. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  13. Jupiter's Equatorial Region in a Methane band (Time set 3)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Mosaic of an equatorial 'hotspot' on Jupiter at 889 nanometers (nm). The mosaic covers an area of 34,000 kilometers by 11,000 kilometers. Light at 889 nm is strongly absorbed by atmospheric methane. This image shows the features of a hazy cloud layer tens of kilometers above Jupiter's main visible cloud deck. This haze varies in height but appears to be present over the entire region. Small patches of very bright clouds may be similar to terrestrial thunderstorms. The dark region near the center of the mosaic is an equatorial 'hotspot' similar to the Galileo Probe entry site. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance.

    North is at the top. The mosaic covers latitudes 1 to 10 degrees and is centered at longitude 336 degrees West. The planetary limb runs along the right edge of the image. Cloud patterns appear foreshortened as they approach the limb. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  14. Jupiter's Equatorial Region in Violet Light (Time set 2)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Mosaic of an equatorial 'hotspot' on Jupiter at 410 nanometers (nm). The mosaic covers an area of 34,000 kilometers by 11,000 kilometers. Light at 410 nm is affected by the sizes and compositions of cloud particles, as well as the trace chemicals that give Jupiter's clouds their colors. This image shows the features of Jupiter's main visible cloud deck and the hazy cloud layer above it. The dark region near the center of the mosaic is an equatorial 'hotspot' similar to the Galileo Probe entry site. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance.

    North is at the top. The mosaic covers latitudes 1 to 10 degrees and is centered at longitude 336 degrees West. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  15. Jupiter's Equatorial Region at 889 nanometers (Time set 2)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Mosaic of an equatorial 'hotspot' on Jupiter at 889 nanometers (nm). The mosaic covers an area of 34,000 kilometers by 11,000 kilometers. Light at 889 nm is strongly absorbed by atmospheric methane. This image shows the features of a hazy cloud layer tens of kilometers above Jupiter's main visible cloud deck. This haze varies in height but appears to be present over the entire region. Small patches of very bright clouds may be similar to terrestrial thunderstorms. The dark region near the center of the mosaic is an equatorial 'hotspot' similar to the Galileo Probe entry site. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance.

    North is at the top. The mosaic covers latitudes 1 to 10 degrees and is centered at longitude 336 degrees West. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  16. Jupiter's Equatorial Region in a Methane band (Time set 4)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Mosaic of Jupiter's equatorial region at 727 nanometers (nm). The mosaic covers an area of 34,000 kilometers by 22,000 kilometers. Light at 727 nm is moderately absorbed by atmospheric methane. This image shows the features of Jupiter's main visible cloud deck and upper-tropospheric haze, with higher features enhanced in brightness over lower features. The dark region near the center of the mosaic is an equatorial 'hotspot' similar to the Galileo Probe entry site. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright oval in the upper right of the mosaic as well as the other smaller bright features are examples of upwelling of moist air and condensation.

    North is at the top. The mosaic covers latitudes 1 to 19 degrees and is centered at longitude 336 degrees West. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  17. Jupiter's Equatorial Region in a Methane band (Time set 1)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Mosaic of an equatorial 'hotspot' on Jupiter at 889 nanometers (nm). The mosaic covers an area of 34,000 kilometers by 11,000 kilometers. Light at 889 nm is strongly absorbed by atmospheric methane. This image shows the features of a hazy cloud layer tens of kilometers above Jupiter's main visible cloud deck. This haze varies in height but appears to be present over the entire region. Small patches of very bright clouds may be similar to terrestrial thunderstorms. The dark region near the center of the mosaic is an equatorial 'hotspot' similar to the Galileo Probe entry site. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance.

    North is at the top. The mosaic covers latitudes 1 to 10 degrees and is centered at longitude 336 degrees West. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  18. Jupiter's Equatorial Region in Violet Light (Time set 3)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Mosaic of an equatorial 'hotspot' on Jupiter at 410 nanometers (nm). The mosaic covers an area of 34,000 kilometers by 11,000 kilometers. Light at 410 nm is affected by the sizes and compositions of cloud particles, as well as the trace chemicals that give Jupiter's clouds their colors. This image shows the features of Jupiter's main visible cloud deck and the hazy cloud layer above it. The dark region near the center of the mosaic is an equatorial 'hotspot' similar to the Galileo Probe entry site. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance.

    North is at the top. The mosaic covers latitudes 1 to 10 degrees and is centered at longitude 336 degrees West. The planetary limb runs along the right edge of the image. Cloud patterns appear foreshortened as they approach the limb. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  19. Jupiter's Equatorial Region in a Methane band (Time set 3)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Mosaic of Jupiter's equatorial region at 727 nanometers (nm). The mosaic covers an area of 34,000 kilometers by 22,000 kilometers. Light at 727 nm is moderately absorbed by atmospheric methane. This image shows the features of Jupiter's main visible cloud deck and upper-tropospheric haze, with higher features enhanced in brightness over lower features. The dark region near the center of the mosaic is an equatorial 'hotspot' similar to the Galileo Probe entry site. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright oval in the upper right of the mosaic as well as the other smaller bright features are examples of upwelling of moist air and condensation.

    North is at the top. The mosaic covers latitudes 1 to 19 degrees and is centered at longitude 336 degrees West. The planetary limb runs along the right edge of the image. Cloud patterns appear foreshortened as they approach the limb. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  20. Jupiter's Equatorial Region at 727 nanometers (Time set 2)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Mosaic of Jupiter's equatorial region at 727 nanometers (nm). The mosaic covers an area of 34,000 kilometers by 22,000 kilometers. Light at 727 nm is moderately absorbed by atmospheric methane. This image shows the features of Jupiter's main visible cloud deck and upper tropospheric haze, with higher features enhanced in brightness over lower features. The dark region near the center of the mosaic is an equatorial 'hotspot' similar to the Galileo Probe entry site. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright oval in the upper right of the mosaic as well as the other smaller bright features are examples of upwelling of moist air and condensation.

    North is at the top. The mosaic covers latitudes 1 to 19 degrees and is centered at longitude 336 degrees West. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

  1. Ocean atmosphere thermal decoupling in the eastern equatorial Indian ocean

    NASA Astrophysics Data System (ADS)

    Joseph, Sudheer; Ravichandran, M.; Kumar, B. Praveen; Jampana, Raju V.; Han, Weiqing

    2017-07-01

    Eastern equatorial Indian ocean (EEIO) is one of the most climatically sensitive regions in the global ocean, which plays a vital role in modulating Indian ocean dipole (IOD) and El Niño southern oscillation (ENSO). Here we present evidences for a paradoxical and perpetual lower co-variability between sea-surface temperature (SST) and air-temperature (Tair) indicating instantaneous thermal decoupling in the same region, where signals of the strongly coupled variability of SST anomalies and zonal winds associated with IOD originate at inter-annual time scale. The correlation minimum between anomalies of Tair and SST occurs in the eastern equatorial Indian ocean warm pool region (≈70°E-100°E, 5°S-5°N), associated with lower wind speeds and lower sensible heat fluxes. At sub-monthly and Madden-Julian oscillation time scales, correlation of both variables becomes very low. In above frequencies, precipitation positively contributes to the low correlation by dropping Tair considerably while leaving SST without any substantial instant impact. Precipitation is led by positive build up of SST and post-facto drop in it. The strong semi-annual response of SST to mixed layer variability and equatorial waves, with the absence of the same in the Tair, contributes further to the weak correlation at the sub-annual scale. The limited correlation found in the EEIO is mainly related to the annual warming of the region and ENSO which is hard to segregate from the impacts of IOD.

  2. Regulation of primary productivity rate in the equatorial Pacific

    SciTech Connect

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

    1991-12-01

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

  3. A Tropical Ocean Recharge Mechanism for Climate Variability. Part I: Equatorial Heat Content Changes Induced by the Off-Equatorial Wind.

    NASA Astrophysics Data System (ADS)

    Wang, Xiaochun; Jin, Fei-Fei; Wang, Yuqing

    2003-11-01

    A reduced-gravity shallow-water model, an oceanic general circulation model for the Pacific region, and the analytical model of the equatorial β plane bounded in the zonal direction are used to investigate the equatorial thermocline response to tropical and subtropical wind stress forcing. The results show that the wind stress forcing in the tropical and subtropical region can generate a nearly zonal uniform thermocline depth change in the equatorial region. The response timescale is longer when the wind stress is placed farther away from the equator. There exist latitude bands around 10° 15°N and 10° 15°S where the forcing can cause a relatively large equatorial response. When the forcing is located in the eastern basin, the response timescale is longer and its magnitude is larger than the case when the forcing is located in the western basin. Thus the eastern tropical to subtropical region is a relatively effective area for off-equatorial wind stress to generate an equatorial thermocline response. When the wind stress forcing has a longer period, the response of the equatorial thermocline has a larger magnitude. The results from this study's numerical experiments and the analytical solution are consistent. The present study has implications for the broad-scale ocean atmosphere interaction in the tropical region.

  4. The influence of the equatorial QBO on sudden stratospheric warmings

    NASA Technical Reports Server (NTRS)

    Holton, James R.; Austin, John

    1991-01-01

    A global primitive-equation model of the stratosphere and mesosphere is integrated for specified planetary-wave forcing at the 100-mb level with mean zonal flow conditions corresponding to the westerly and easterly phases of the equatorial QBO, respectively. The responses in the two QBO phases were compared for integrations with wavenumber-1 forcing-amplitude maxima at 100 mb and 60 deg N varying from 100 to 400 m. The phase of the QBO had little effect on the results in the weak-wave (100-m) cases, which did not produce warmings, and strong-wave (400-m) cases, which produced major sudden warmings.

  5. Equatorial waves simulated by the NCAR community climate model

    NASA Technical Reports Server (NTRS)

    Cheng, Xinhua; Chen, Tsing-Chang

    1988-01-01

    The equatorial planetary waves simulated by the NCAR CCM1 general circulation model were investigated in terms of space-time spectral analysis (Kao, 1968; Hayashi, 1971, 1973) and energetic analysis (Hayashi, 1980). These analyses are particularly applied to grid-point data on latitude circles. In order to test some physical factors which may affect the generation of tropical transient planetary waves, three different model simulations with the CCM1 (the control, the no-mountain, and the no-cloud experiments) were analyzed.

  6. Peri-equatorial paleolatitudes for Jurassic radiolarian cherts of Greece

    USGS Publications Warehouse

    Aiello, I.W.; Hagstrum, J.T.; Principi, G.

    2008-01-01

    Radiolarian-rich sediments dominated pelagic deposition over large portions of the Tethys Ocean during middle to late Jurassic time as shown by extensive bedded chert sequences found in both continental margin and ophiolite units of the Mediterranean region. Which paleoceanographic mechanisms and paleotectonic setting favored radiolarian deposition during the Jurassic, and the nature of a Tethys-wide change from biosiliceous to biocalcareous (mainly nannofossil) deposition at the beginning of Cretaceous time, have remained open questions. Previous paleomagnetic analyses of Jurassic red radiolarian cherts in the Italian Apennines indicate that radiolarian deposition occurred at low peri-equatorial latitudes, similar to modern day deposition of radiolarian-rich sediments within equatorial zones of high biologic productivity. To test this result for other sectors of the Mediterranean region, we undertook paleomagnetic study of Mesozoic (mostly middle to upper Jurassic) red radiolarian cherts within the Aegean region on the Peloponnesus and in continental Greece. Sampled units are from the Sub-Pelagonian Zone on the Argolis Peninsula, the Pindos-Olonos Zone on the Koroni Peninsula, near Karpenissi in central Greece, and the Ionian Zone in the Varathi area of northwestern Greece. Thermal demagnetization of samples from all sections removed low-temperature viscous and moderate-temperature overprint magnetizations that fail the available fold tests. At Argolis and Koroni, however, the cherts carry a third high-temperature magnetization that generally exhibits a polarity stratigraphy and passes the available fold tests. We interpret the high-temperature component to be the primary magnetization acquired during chert deposition and early diagenesis. At Kandhia and Koliaky (Argolis), the primary declinations and previous results indicate clockwise vertical-axis rotations of ??? 40?? relative to "stable" Europe. Due to ambiguities in hemispheric origin (N or S) and thus

  7. Wind Patterns in Jupiter's Equatorial Region (Time set 1)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Wind patterns of Jupiter's equatorial region. This mosaic covers an area of 34,000 kilometers by 22,000 kilometers and was taken using the 756 nanometer (nm) near-infrared continuum filter. The dark region near the center of the mosaic is an equatorial 'hotspot' similar to the Galileo Probe entry site. The near-infrared continuum filter shows the features of Jupiter's main visible cloud deck.

    Jupiter's atmospheric circulation is dominated by alternating jets of east/west (zonal) winds. The bands have different widths and wind speeds but have remained constant as long as telescopes and spacecraft have measured them. The top half of these mosaics lies within Jupiter's North Equatorial Belt, a westward (left) current. The bottom half shows part of the Equatorial Zone, a fast moving eastward current. The clouds near the hotspot are the fastest moving features in these mosaics, moving at about 100 meters per second, or 224 miles per hour.

    Superimposed on the zonal wind currents is the Jovian 'weather'. The arrows show the winds measured by an observer moving eastward (right) at the speed of the hotspot. (The observer's perspective is that the hotspot is 'still' while the rest of the planet moves around it.) Clouds south of the hotspot appear to be moving towards it, as seen in the flow aligned with cloud streaks to the southwest and in the clockwise flow to the southeast. Interestingly, there is little cloud motion away from the hotspot in any direction. This is consistent with the idea that dry air is converging over this region and sinking, maintaining the cloud-free nature of the hotspot.

    North is at the top. The mosaic covers latitudes 1 to 19 degrees and is centered at longitude 336 degrees West. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA

  8. Wave Properties of Equatorial Magnetosonic Waves as Observed by Cluster

    NASA Astrophysics Data System (ADS)

    Balikhin, M. A.; Walker, S. N.; Shprits, Y.

    2014-12-01

    A survey of the Cluster STAFF data set shows a number of periods in which Equatorial Magnetosonic Waves display a discrete spectrum. In some of these instances, the frequency of emissions varies in the same fashion as the background magnetic field, indicating that the wars are observed within their source region. This paper analyses the propagation characteristics of these emissions and investigates the appropriateness of the quasi-linear assumption of a gaussian spectrum used in the numerical modelling of their role in the electron dynamics within the radiation belts based in the Chirikov resonance overlap criterion.

  9. Wind Patterns in Jupiter's Equatorial Region (Time set 1)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Wind patterns of Jupiter's equatorial region. This mosaic covers an area of 34,000 kilometers by 22,000 kilometers and was taken using the 756 nanometer (nm) near-infrared continuum filter. The dark region near the center of the mosaic is an equatorial 'hotspot' similar to the Galileo Probe entry site. The near-infrared continuum filter shows the features of Jupiter's main visible cloud deck.

    Jupiter's atmospheric circulation is dominated by alternating jets of east/west (zonal) winds. The bands have different widths and wind speeds but have remained constant as long as telescopes and spacecraft have measured them. The top half of these mosaics lies within Jupiter's North Equatorial Belt, a westward (left) current. The bottom half shows part of the Equatorial Zone, a fast moving eastward current. The clouds near the hotspot are the fastest moving features in these mosaics, moving at about 100 meters per second, or 224 miles per hour.

    Superimposed on the zonal wind currents is the Jovian 'weather'. The arrows show the winds measured by an observer moving eastward (right) at the speed of the hotspot. (The observer's perspective is that the hotspot is 'still' while the rest of the planet moves around it.) Clouds south of the hotspot appear to be moving towards it, as seen in the flow aligned with cloud streaks to the southwest and in the clockwise flow to the southeast. Interestingly, there is little cloud motion away from the hotspot in any direction. This is consistent with the idea that dry air is converging over this region and sinking, maintaining the cloud-free nature of the hotspot.

    North is at the top. The mosaic covers latitudes 1 to 19 degrees and is centered at longitude 336 degrees West. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA

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

    NASA Astrophysics Data System (ADS)

    Olson, M. E.; Fejer, B. G.; Stolle, C.; Lühr, H.; Chau, J. L.

    2013-03-01

    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 that showed the fundamentally important role of lunar semidiurnal tidal effects on low latitude electrodynamic perturbations during arctic SSW events.

  11. Provisional hourly values of equatorial Dst for 1971

    NASA Technical Reports Server (NTRS)

    Sugiura, M.; Poros, D. J.

    1972-01-01

    Tables and plots of provisional hourly values of the equatorial Dst index for 1971 are given, a table of daily mean Dst values for 1971 is also provided. The base line values for the four observatories, Hermanus, Kakioka, Honolulu, and San Juan, were obtained from extrapolations using the coefficients for the secular variations determined for the previous years. Examining the Dst values for quiet days, the base lines so determined appear to be slightly low, so that the Dst index for quiet periods tends to be high.

  12. Importance of the Equatorial Undercurrent on the sea surface salinity in the eastern equatorial Atlantic in boreal spring

    NASA Astrophysics Data System (ADS)

    Da-Allada, C. Y.; Jouanno, J.; Gaillard, F.; Kolodziejczyk, N.; Maes, C.; Reul, N.; Bourlès, B.

    2017-01-01

    The physical processes implied in the sea surface salinity (SSS) increase in the equatorial Atlantic Cold Tongue (ACT) region during boreal spring and the lag observed between boreal spring SSS maximum and sea surface temperature (SST) summer minimum are examined using mixed-layer salinity budgets computed from observations and model during the period 2010-2012. The boreal spring SSS maximum is mainly explained by an upward flux of high salinity originating from the core of the Equatorial Undercurrent (EUC) through vertical mixing and advection. The vertical mixing contribution to the mixed-layer salt budget peaks in April-May. It is controlled primarily by (i) an increased zonal shear between the surface South Equatorial Current and the subsurface EUC and (ii) the presence of a strong salinity stratification at the mixed-layer base from December to May. This haline stratification that is due to both high precipitations below the Inter Tropical Convergence Zone and zonal advection of low-salinity water from the Gulf of Guinea explains largely the seasonal cycle of the vertical advection contribution to the mixed-layer salt budget. In the ACT region, the SST reaches its maximum in March/April and minimum in July/August. This SST minimum appears 1 month after the maximum of SSS. The 1 month lag observed between the maximum of SSS in June and the minimum of SST in July is explained by the shallowing of the EUC salinity core in June, then the weakening/erosion of the EUC in June-July which dramatically reduces the lateral subsurface supply of high-saline waters.

  13. The Continuous Mutual Evolution of Equatorial Waves and the Quasi-Biennial Oscillation of Zonal Flow in the Equatorial Stratosphere

    NASA Astrophysics Data System (ADS)

    Barton, C.; Cai, M.; Shin, C. S.; Chagnon, J.

    2014-12-01

    The continuous mutual evolution of equatorial waves and the background QBO is demonstrated using daily NCEP-DOE reanalysis for the period from January 1, 1979 to December 31, 2010. Using a novel diagnostic technique, the phase speed, vertical tilting, and form stress of equatorial waves in the stratosphere are obtained continuously on daily basis. The results indicate that on top of a weak-amplitude annual cycle signal, all of these wave properties have a pronounced QBO signal with a downward propagation that evolves continuously together with the background QBO. Our analysis also highlights the potential role of wave-induced form stress in driving the QBO regime change. We find that the dominant waves in the equatorial stratosphere propagate very slowly relative to the ground at all times, implying that their observed intrinsic phase speed evolution follows the background QBO nearly exactly but with opposite sign, as the established theory predicts. By revealing the continuous evolution of the form stress associated with the vertically tilted waves, the new diagnostic method also demonstrates the dominance of eastward-tilted eastward-propagating waves contributing to a deceleration of easterly flow at high altitudes, which causes a downward propagation of the easterly flow signal. Similarly, the dominance of westward-tilted westward-propagating waves acts to reverse westerly flow to easterly flow and causes a downward propagation of westerly flow signal. Our results suggest that in addition to the wave-breaking processes, such continuously alternating downward transfer of westerly and easterly angular momentum by westward-tilted westward-propagating waves and eastward-tilted eastward-propagating waves contributes to the wave-mean flow interaction mechanism for the QBO.

  14. On the relationship between the postmidnight thermospheric equatorial mass anomaly and equatorial ionization anomaly under geomagnetic quiet conditions

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Liu, Libo; Zhao, Biqiang; Lei, Jiuhou; Wan, Weixing

    2011-12-01

    The equatorial mass anomaly (EMA) in the thermosphere and equatorial ionization anomaly (EIA) in the ionosphere are two interesting phenomena in low-equatorial latitude regions. Previous studies have shown that the EMA appears between 1000 and 2000 local time (LT) and its location of trough is aligned with dip equator, indicating the plausible role of the EIA structure in the development of EMA. In this report, we conducted a statistical study of the occurrence of postmidnight EMA and EIA on the basis of the CHAMP in situ measurements during 2002-2008. Our results revealed that clear EMA and EIA structures are sometimes visible in the postmidnight sector (0100-0600 LT) during geomagnetic quiet periods (Kp < 3). The postmidnight EMA is not necessarily accompanied by the EIA signature in both case study and statistics sense being distinct from the daytime situation. In addition, the occurrence rates of postmidnight EMA and EIA display contrasting behavior with respect to their local time, longitudinal and solar activity dependences. The highest occurrence rate for EMA is 8% at around 0300 LT, while the occurrence rate of the EIA decreases gradually from about 30% at around 2300 LT to ˜5% at 0600 LT. Longitudinal occurrence of postmidnight EIA presents a wave-like pattern; however, no salient feature appears for the longitudinal occurrence of EMA. Postmidnight EMA is more likely to occur at lower solar activity, whereas an opposite trend presents in the EIA. On the basis of above results, our findings imply that a simple EIA-EMA cause-effect relationship does not hold in the postmidnight sector.

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

    NASA Astrophysics Data System (ADS)

    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

  16. Artesunate/Amodiaquine Malaria Treatment for Equatorial Guinea (Central Africa)

    PubMed Central

    Charle, Pilar; Berzosa, Pedro; de Lucio, Aida; Raso, José; Nseng Nchama, Gloria; Benito, Agustín

    2013-01-01

    The objectives of this study were: 1) to evaluate the safety and efficacy of combination artesunate (AS)/amodiaquine (AQ) therapy, and 2) to determine the difference between recrudescence and resistance. An in vivo efficacy study was conducted in Equatorial Guinea. A total of 122 children 6–59 months of age from two regional hospitals were randomized and subjected to a 28-day clinical and parasitological follow-up. A blood sample on Whatman paper was taken on Days 0, 7, 14, 21, and 28 or on any day in cases of treatment failure, with the parasite DNA then being extracted for molecular analysis purposes. A total of 4 children were excluded, and 9 cases were lost to follow-up. There were 17 cases of late parasitological failure, 3 cases of late clinical failure, and 89 cases of adequate clinical and parasitological response. The parasitological failure rate was 18.3% (20 of 109) and the success rate 81.70% (95% confidence interval [72.5–87.9%]). After molecular correction, real treatment efficacy stood at 97.3%. Our study showed the good efficacy of combination AS/AQ therapy. This finding enabled this treatment to be recommended to Equatorial Guinea's National Malaria Control Program to change the official treatment policy as of March 2008. PMID:23530078

  17. Iron deficiency and phytoplankton growth in the equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Fitzwater, Steve E.; Coale, Kenneth H.; Gordon, R. Michael; Johnson, Kenneth S.; Ondrusek, Michael E.

    Several experiments were conducted in the equatorial Pacific at 140°W during the Joint Global Ocean Flux Study, equatorial Pacific, 1992 Time-series I (TS-I, 23 March-9 April), Time-series II (TS-II, 2-20 October) and FeLINE II cruises (10 March-14 April), to investigate the effects of added Fe on phytoplankton communities. Seven series of deckboard iron-enrichment experiments were performed, with levels of added Fe ranging from 0.13 to 1000 nM. Time-course measurements included nutrients, chlorophyll a and HPLC pigments. Results of these experiments showed that subnanomolar (sub-nM) additions of Fe increased net community specific growth rates, with resultant chlorophyll a increases and nutrient decreases. Community growth rates followed Michaelis-Menten type kinetics resulting in maximum rates of 0.99 doublings per day and a half-saturation constant of 0.12 nM iron. The dominant group responding to iron enrichment was diatoms.

  18. Variability of equatorial counter electrojet signatures in the Indian region

    NASA Astrophysics Data System (ADS)

    Chandrasekhar, N. Phani; Archana, R. K.; Nagarajan, Nandini; Arora, Kusumita

    2017-02-01

    The limited longitudinal extent of equatorial counter electrojet (CEJ) has been inferred by several workers based on the analysis of ground data. However, the scale length of CEJ characteristics at 2 h or less has not been estimated so far. The present study seeks to characterize the longitudinal variability of CEJ phenomena at a longitudinal separation of 15° by using hourly averaged variations at two equatorial electrojet (EEJ) pairs of stations: Hyderabad and Vencode at 77°E and Port Blair and Campbell Bay at 93°E. The nature of CEJ events is classified by time of occurrence and studied by using 12 months of concurrent data at the two longitudes. From examination of 323 CEJ events at VEN (Vencode) and 239 at CBY (Campbell Bay) over a period of 346 days, the observations are as follows: (i) the occurrence of CEJ is not simultaneous at VEN and CBY for about 40% of events; (ii) the amplitude and occurrence frequency of CEJ events is greater at VEN than at CBY during both Kp < 2 and Kp ≥ 2; and (iii) the influence of westward currents on the EEJ peak was evidenced by early or late peak occurrences comprising about 175 days at VEN and 89 days at CBY. It is established here that considerable variability of CEJ signatures is observed between the two longitudes at 15° separation, revealing the impact of local electrodynamics. These local processes therefore significantly influence the characteristics of EEJ.

  19. Recurring slope lineae in equatorial regions of Mars

    USGS Publications Warehouse

    McEwen, Alfred S.; Dundas, Colin M.; Mattson, Sarah S.; Toigo, Anthony D.; Ojha, Lujendra; Wray, James J.; Chojnacki, Matthew; Byrne, Shane; Murchie, Scott L.; Thomas, Nicolas

    2014-01-01

    The presence of liquid water is a requirement of habitability on a planet. Possible indicators of liquid surface water on Mars include intermittent flow-like features observed on sloping terrains. These recurring slope lineae are narrow, dark markings on steep slopes that appear and incrementally lengthen during warm seasons on low-albedo surfaces. The lineae fade in cooler seasons and recur over multiple Mars years. Recurring slope lineae were initially reported to appear and lengthen at mid-latitudes in the late southern spring and summer and are more common on equator-facing slopes where and when the peak surface temperatures are higher. Here we report extensive activity of recurring slope lineae in equatorial regions of Mars, particularly in the deep canyons of Valles Marineris, from analysis of data acquired by the Mars Reconnaissance Orbiter. We observe the lineae to be most active in seasons when the slopes often face the sun. Expected peak temperatures suggest that activity may not depend solely on temperature. Although the origin of the recurring slope lineae remains an open question, our observations are consistent with intermittent flow of briny water. Such an origin suggests surprisingly abundant liquid water in some near-surface equatorial regions of Mars.

  20. Nonmigrating tidal modulation of the equatorial thermosphere and ionosphere anomaly

    NASA Astrophysics Data System (ADS)

    Lei, Jiuhou; Thayer, Jeffrey P.; Wang, Wenbin; Yue, Jia; Dou, Xiankang

    2014-04-01

    The modulation of nonmigrating tides on both the ionospheric equatorial ionization anomaly (EIA) and the equatorial thermosphere anomaly (ETA) is investigated on the basis of simulations from the Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME-GCM). Our simulations demonstrate the distinct features of the EIA and ETA seen in observations after the inclusion of field-aligned ion drag in the model. Both the EIA and the ETA in the constant local time frame display an obvious zonal wave-4 structure associated with the modulation of nonmigrating tides. However, the modeled EIA and ETA show a primary zonal wave-1 structure when only the migrating tides are specified at the model lower boundary. Our simulations reveal that the zonal wave-4 structure of the ETA under both low and high solar activity conditions is mainly caused by the direct response of the upper thermosphere to the diurnal eastward wave number 3 and semidiurnal eastward wave number 2 nonmigrating tides from the lower atmosphere. There is a minor contribution from the ion-neutral coupling. The zonal wave-4 structure of the EIA is also caused by these nonmigrating tides but through the modulation of the neutral wind dynamo.

  1. Equatorial broad plasma depletions associated with the enhanced fountain effect

    NASA Astrophysics Data System (ADS)

    Lee, Woo Kyoung; Kil, Hyosub; Kwak, Young-Sil; Paxton, Larry J.; Zhang, Yongliang; Galkin, Ivan; Batista, Inez S.

    2014-01-01

    plasma depletions (BPDs), plasma depletions whose longitudinal width is over several hundred kilometers, have been detected in the equatorial F region by low-earth-orbit satellites during both magnetically quiet and magnetically disturbed periods. A few hypotheses were suggested to explain the creation of BPDs, but the underlying mechanism of this phenomenon is still under debate. We investigate the origin of BPDs by analyzing the simultaneous in situ and optical observations of the ionosphere on 30 May 2003 (Kp = 8+), 24 April 2012 (Kp = 7-), and 31 October 2012 (Kp = 0+). BPDs on 30 May 2003 were detected by the Republic of China Satellite-1 at an altitude of 600 km, and BPDs on the other days were detected by the Communication/Navigation Outage Forecasting System satellite near an altitude of 400 km. Our results show that the detection of BPDs is closely associated with background ionospheric morphology; BPDs are detected on the days when the equatorial ionization anomaly (EIA) is intense and the crests of the EIA have moved poleward. Measurements of upward plasma motion support the existence of ionospheric uplift at BPD locations. These observations and the detection of BPDs near the magnetic equator lead to the interpretation that the satellite detection of BPDs during those 3 days is likely related to the uplift of the F peak height above the satellite orbits.

  2. Equatorial ionosphere 'fountain- effect' above imminent earthquake epicenter

    NASA Astrophysics Data System (ADS)

    Ruzhin, Yu.; Depueva, A. H.; Devi, M.

    2003-04-01

    Existence of lithosphere-ionosphere interaction is known for a long time, but it does not mean that the ionospheric morphology above areas of earthquakes preparation is investigated sufficiently well. It was shown that seismo-precursor variations of the atmosphere electricity cause appropriate electric field at the ionospheric heights, which being added to existing natural field may both increase or decrease its action on the ionospheric plasma characteristics: drifts, aeronomy, plasma chemistry, ion composition etc. Anomalous variations appear inside whole ionosphere volume from the lowest boundary of Earth's plasma shell (100 km) up to 1000km and higher. Under fortunate coincidence seismo-precursor electric field can generate natural ionosphere phenomena, 'fountain- effect', leading to Appleton anomaly in the equatorial ionosphere over future earthquake position. Our basic idea is to take into account dependence of the observable effects on a geographical position of the earthquake epicenter. As for low latitudes it is proved by specificity of formation and dynamics of equatorial ionosphere (seismogenic ""fountain" effect , first of all), and also by features of earth crust structure close to the equator (mainly meridionally alongated tectonic faults). Ionospheric effects of low-latitude earthquakes were not investigated separately so far though rather semo-active zones are located namely at low latitudes: India, Peru, Oceania. We used the data of topside sounding of ALOUETTE-1 and ISS-b satellites, and also data of ground-based vertical sounding stationary stations Kodaikanal, Huancayo, Djibouti etc. and records of the total electron content (TEC).

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Equatorial Noise Emissions and Their Quasi-Periodic Modulation

    NASA Astrophysics Data System (ADS)

    Nemec, F.; Santolik, O.; Hrbackova, Z.; Pickett, J. S.; Cornilleau-Wehrlin, N.; Parrot, M.; Hayosh, M.

    2015-12-01

    Equatorial noise (EN) emissions are electromagnetic waves at frequencies between the proton cyclotron frequency and the lower hybrid frequency routinely observed in the equatorial region of the inner magnetosphere. They propagate in the extraordinary mode nearly perpendicular to the ambient magnetic field, and they exhibit a harmonic structure related to the ion cyclotron frequency in the source region. We analyze more than 2000 EN events observed by the wave instruments on board the Cluster spacecraft, and we find that about 5% of EN events are not continuous in time, but exhibit a quasi-periodic (QP) modulation of the wave intensity. Typical modulation periods are on the order of minutes. The events predominantly occur in the noon-to-dawn local time sector, and their occurrence is related to the periods of increased geomagnetic activity and higher solar wind speeds. We suggest that the QP modulation of EN events may be due to compressional ULF pulsations, which periodically modulate the wave growth in the source region. These compressional ULF pulsations were identified in about half of the events. Finally, we demonstrate that EN emissions with QP modulation of the wave intensity can propagate down to altitudes as low as 700 km.

  5. Ternary fission of 260No in equatorial configuration

    NASA Astrophysics Data System (ADS)

    Ismail, M.; Seif, W. M.; Hashem, A. S.

    2016-10-01

    Spontaneous ternary fission is one of the observed decay modes of heavy nuclei. We systematically investigate the equatorial ternary fission of the 260No isotope. In the framework of the three-cluster model, the three-body interaction potential is calculated in terms of the folded M3Y-Reid nucleon-nucleon force and the Coulomb one. The relative orientations of the deformed heavy nuclei participating in the fragmentation process are taken into account. All possible emitted light particles with even mass numbers A = 4-52 are considered. The favored fragmentation channels are estimated as the ones characterized with peaks in the Q-value and local minima in the fragmentation potential. In the absence of nuclear deformations, the closed shell effects are found to play the key role in determining the channels of minimum fragmentation potential and the involved two heavier fragments tend to be of comparable sizes. Inclusion of nuclear deformations manifest the participation of highly deformed prolate nuclei, with large mass asymmetry, as heavy fragment partners in the estimated favored fragmentation channels. The results indicate that the equatorial ternary fission of 260No is most favored with the light emitted nuclei 4,6,8 2He and 10 4Be through the fragmentation channels 155 60Nd + 4 2He + 101 0Zr, 153 60Nd + 6 2He + 101 40Zr, 152 60Nd + 8 2He + 100 40Zr, and 152 0Nd + 10 4Be + 98 38Sr, respectively.

  6. Candidate ice-rich material within equatorial craters on Mars

    NASA Astrophysics Data System (ADS)

    Shean, David E.

    2010-12-01

    The floors and walls of many mid-latitude (˜30-60°) craters on Mars appear to be mantled by relatively young material(s) with distinct morphology and erosional properties. Collectively, this material (“fill”) is often interpreted as ice-rich, with emplacement and modification related to climatological processes. Here, I document material and associated landforms within 38 craters between 4-13°S in the Sinus Sabaeus region that appear morphologically similar to material and landforms within mid-latitude craters. These equatorial/mid-latitude materials may also share a common composition and emplacement mechanism. Near-surface ice is unstable at equatorial latitudes under present conditions, suggesting that emplacement could have occurred under different climate conditions in the past. High-obliquity (35-45°) general circulation model (GCM) simulations show surface ice accumulation in Sinus Sabaeus and Tharsis, where similar material and landforms have been documented. These observations are consistent with the hypothesis that past obliquity-driven climate change resulted in equatorward volatile migration on Mars.

  7. Absolute electron density measurements in the equatorial ionosphere

    NASA Technical Reports Server (NTRS)

    Baker, K. D.; Howlett, L. C.; Rao, N. B.; Ulwick, J. C.; Labelle, J.

    1985-01-01

    Accurate measurement of the electron density profile and its variations is crucial to further progress in understanding the physics of the disturbed equatorial ionosphere. To accomplish this, a plasma frequency probe was included in the payload complement of two rockets flown during the Condor rocket campaign conducted from Peru in March 1983. This paper presents density profiles of the disturbed equatorial ionosphere from a night-time flight in which spread-F conditions were present and from a day-time flight during strong electrojet conditions. Results from both flights are in excellent agreement with simultaneous radar data in that the regions of highly disturbed plasma coincide with the radar signatures. The spread-F rocket penetrated a topside depletion during both the upleg and downleg. The electrojet measurements showed a profile peaking at 1.3 x 10 to the 5th per cu cm at 106 km, with large scale fluctuations having amplitudes of roughly 10 percent seen only in the upward gradient in electron density. This is in agreement with plasma instability theory. It is further shown that simultaneous measurements by fixed-bias Langmuir probes, when normalized at a single point to the altitude profile of electron density, are inadequate to correctly parameterize the observed enhancements and depletions.

  8. LF equatorial emissions recorded by DEMETER/ICE experiment

    NASA Astrophysics Data System (ADS)

    Boudjada, Mohammed; Parrot, Michel; Schwingenschuh, Konrad; Eichelberger, Hans; Lammer, Helmut; Sawas, Sami; Denisenko, Valery; Besser, Bruno

    2016-07-01

    We report on electric field observations recorded on the Earth's night-side by DEMETER/ICE experiment. DEMETER is a low-altitude satellite with polar and circular orbits. Observations were recorded at invariant latitudes less than 65° and an altitude of about 650 km. The sun-synchronous night-side orbits correspond to up-going half-orbits with a local time equal to 22:30. We consider in our analysis the low frequency emissions observed at frequencies less than 500 kHz. We show the occurrence of multiple spaced frequency bands between 30 kHz and 500 kHz, and occasionally harmonic components appear in the upper frequency of the instrument (i.e. between 3 MHz - 3.5 MHz,). Those bands are recorded close to the equatorial plane, when the satellite latitudes are between -05° and +05°, and particular enhancements occur at two geographical longitudes, i.e. 130°E and 160°W. We assume that those low frequency radio waves may be associated to density irregularities in the equatorial region. Probably these irregularities are localized along ray paths between the emission source regions and the satellite. We discuss the source locations of such frequency bands, and we show that the observed spectral features may be linked to the plasmasphere dynamic.

  9. Absolute electron density measurements in the equatorial ionosphere

    NASA Technical Reports Server (NTRS)

    Baker, K. D.; Howlett, L. C.; Rao, N. B.; Ulwick, J. C.; Labelle, J.

    1985-01-01

    Accurate measurement of the electron density profile and its variations is crucial to further progress in understanding the physics of the disturbed equatorial ionosphere. To accomplish this, a plasma frequency probe was included in the payload complement of two rockets flown during the Condor rocket campaign conducted from Peru in March 1983. This paper presents density profiles of the disturbed equatorial ionosphere from a night-time flight in which spread-F conditions were present and from a day-time flight during strong electrojet conditions. Results from both flights are in excellent agreement with simultaneous radar data in that the regions of highly disturbed plasma coincide with the radar signatures. The spread-F rocket penetrated a topside depletion during both the upleg and downleg. The electrojet measurements showed a profile peaking at 1.3 x 10 to the 5th per cu cm at 106 km, with large scale fluctuations having amplitudes of roughly 10 percent seen only in the upward gradient in electron density. This is in agreement with plasma instability theory. It is further shown that simultaneous measurements by fixed-bias Langmuir probes, when normalized at a single point to the altitude profile of electron density, are inadequate to correctly parameterize the observed enhancements and depletions.

  10. Genesis and effects of long waves in the equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Hansen, Donald V.; Paul, Carl A.

    1984-11-01

    Data from 20 satellite-tracked drifting buoys deployed in the eastern equatorial Pacific Ocean during the summer of 1979 were used to investigate the nature, effects, and energetics of currents associated with cusp-shaped long waves observed in satellite IR imagery of the sea surface during all except El Nino years. It is shown that the long waves are associated with a vigorous pattern of mesoscale eddies lying primarily between the equator and 7°N. The spatial structure of the eddy kinetic energy closely resembles the eigenfunctions obtained from Philander's (1978) investigation of barotropic instability of that part of the South Equatorial Current lying north of the equator. Computation of the energy exchange between the eddies and the mean field suggests an e folding time of about two weeks for the eddies and a braking effect on the mean flow comparable to a change of surface wind stress of a few tenths of a dyne per square centimeter. The eddies also effect an equatorward transport of heat that amounts to about two thirds of the poleward heat transport of the divergent Ekman transport in the near-surface waters.

  11. SpIES: The Spitzer IRAC Equatorial Survey

    NASA Astrophysics Data System (ADS)

    Timlin, John; Ross, Nicholas; Richards, Gordon T.; Lacy, Mark; Bauer, Franz E.; Brandt, W. Niel; Fan, Xiaohui; Haggard, Daryl; Makler, Martin; Myers, Adam D.; Schneider, Donald P.; Strauss, Michael A.; Urry, C. Megan; Zakamska, Nadia L.; SpIES Team

    2016-01-01

    We describe the first data release from the Spitzer-IRAC Equatorial Survey (SpIES); a large-area survey of the Equatorial SDSS Stripe 82 field using Warm Spitzer. SpIES was designed to probe enough volume to perform measurements of the z>3 quasar clustering and luminosity function in order to test various "AGN feedback'' models. Additionally, the wide range of multi-wavelength, multi-epoch ancillary data makes SpIES a prime location to identify both high-redshift (z>6) quasars as well as obscured quasars missed by optical surveys. SpIES maps ~115deg2 of Stripe 82 to depths of 6.3 uJy (21.9 AB Magnitudes) and 5.75 uJy (22.0 AB Magnitudes) at [3.6] and [4.5] microns respectively; depths significantly greater than WISE. Here we define the SpIES survey parameters and describe the image processing, source extraction, and catalog production methods used to analyze the SpIES data. Amongst our preliminary science results, we show high significance detections of spectroscopically confirmed, z~5 quasars in the SpIES data. This work is based [in part] on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech.

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

    PubMed

    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.

  13. Equatorial convergence of India and early Cenozoic climate trends

    PubMed Central

    Kent, Dennis V.; Muttoni, Giovanni

    2008-01-01

    India's northward flight and collision with Asia was a major driver of global tectonics in the Cenozoic and, we argue, of atmospheric CO2 concentration (pCO2) 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 CO2 delivery to the atmosphere capable to maintain high pCO2 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 ≈50 Ma. At about this time, the India continent and the highly weatherable Deccan Traps drifted into the equatorial humid belt where uptake of CO2 by efficient silicate weathering further perturbed the delicate equilibrium between CO2 input to and removal from the atmosphere toward progressively lower pCO2 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. PMID:18809910

  14. Phanerozoic geological evolution of the Equatorial Atlantic domain

    NASA Astrophysics Data System (ADS)

    Basile, Christophe; Mascle, Jean; Guiraud, René

    2005-10-01

    The Phanerozoic geological evolution of the Equatorial Atlantic domain has been controlled since the end of Early Cretaceous by the Romanche and Saint Paul transform faults. These faults did not follow the PanAfrican shear zones, but were surimposed on Palæozoic basins. From Neocomian to Barremian, the Central Atlantic rift propagated southward in Cassiporé and Marajó basins, and the South Atlantic rift propagated northward in Potiguar and Benue basins. During Aptian times, the Equatorial Atlantic transform domain appeared as a transfer zone between the northward propagating tip of South Atlantic and the Central Atlantic. Between the transform faults, oceanic accretion started during Late Aptian in small divergent segments, from south to north: Benin-Mundaú, deep Ivorian basin-Barreirinhas, Liberia-Cassiporé. From Late Aptian to Late Albian, the Togo-Ghana-Ceará basins appeared along the Romanche transform fault, and Côte d'Ivoire-Parà-Maranhão basins along Saint Paul transform fault. They were rapidly subsiding in intra-continental settings. During Late Cretaceous, these basins became active transform continental margins, and passive margins since Santonian times. In the same time, the continental edge uplifted leading either to important erosion on the shelf or to marginal ridges parallel to the transform faults in deeper settings.

  15. Iron limitation of phytoplankton photosynthesis in the equatorial Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Kolber, Zbigniew S.; Barber, Richard T.; Coale, Kenneth H.; Fitzwateri, Steve E.; Greene, Richard M.; Johnson, Kenneth S.; Lindley, Steven; Falkowski, Paul G.

    1994-09-01

    THE surface waters of the equatorial Pacific have unusually high nitrate and phosphate concentrations, but relatively low phyto-plankton biomass1-3. This 'high nitrate, low chlorophyll' (HNLC)4 phenomenon has been ascribed to 'top-down' grazing pressure by herbivores, which prevent the phytoplankton from fully utilizing the available nutrients5. In the late 1980s, however, Martin and co-workers proposed that iron, which is delivered to the remote open ocean in aeolean dust6, is the key factor limiting the standing crop of phytoplankton in HNLC areas7,8. Using a sensitive fluor-escence method9, we have followed changes in photochemical energy conversion efficiency9-10 of the natural phytoplankton com-munity both before and after artificial enrichment with iron of a small area (7.5 x 7.5 km) of the equatorial Pacific Ocean11. Our results show that iron limits phytoplankton photosynthesis in all size classes in this region by impairing intrinsic photochemical energy conversion, thereby supporting the hypothesis of physiologi-cal ('bottom up') limitation by this element.

  16. New observations of ionospheric instabilities in the equatorial electrojet

    NASA Astrophysics Data System (ADS)

    Alken, P.; Maus, S.

    2009-12-01

    The equatorial electrojet (EEJ) is an intense current system flowing along the magnetic equator in the ionospheric E-region on the day-side. Early attempts to model the EEJ found that ionospheric instabilities led to significant changes in the current which had to be accounted for. Early modelers used ad-hoc empirical correction factors in the relevant ionospheric parameters to attempt to account for instability effects. Modern EEJ models continue to use these correction factors, which are still not well understood theoretically. In the last decade, a wealth of new data has been recorded by both satellites and ground radars which allows us to revisit the issue of modeling these ionospheric instabilities. In this work, we use radar and magnetic field measurements at Jicamarca in addition to magnetometer measurements from the CHAMP satellite to study the effects of ionospheric instabilities on the EEJ. We find that the effects of ionospheric instabilities lead to non-linear behavior between the eastward electric field strength and the resulting electrojet current. As predicted, the ratio of current to electric field is highest for westward and weak eastward electric fields, and the ratio decreases with stronger eastward electric fields. Quantifying this non-linearity should help improve the accuracy of equatorial electrodynamic models.

  17. Loss of thermal refugia near equatorial range limits.

    PubMed

    Lima, Fernando P; Gomes, Filipa; Seabra, Rui; Wethey, David S; Seabra, Maria I; Cruz, Teresa; Santos, António M; Hilbish, Thomas J

    2016-01-01

    This study examines the importance of thermal refugia along the majority of the geographical range of a key intertidal species (Patella vulgata Linnaeus, 1758) on the Atlantic coast of Europe. We asked whether differences between sun-exposed and shaded microhabitats were responsible for differences in physiological stress and ecological performance and examined the availability of refugia near equatorial range limits. Thermal differences between sun-exposed and shaded microhabitats are consistently associated with differences in physiological performance, and the frequency of occurrence of high temperatures is most probably limiting the maximum population densities supported at any given place. Topographical complexity provides thermal refugia throughout most of the distribution range, although towards the equatorial edges the magnitude of the amelioration provided by shaded microhabitats is largely reduced. Importantly, the limiting effects of temperature, rather than being related to latitude, seem to be tightly associated with microsite variability, which therefore is likely to have profound effects on the way local populations (and consequently species) respond to climatic changes. © 2015 John Wiley & Sons Ltd.

  18. Climatology characterization of equatorial plasma bubbles using GPS data

    NASA Astrophysics Data System (ADS)

    Magdaleno, Sergio; Herraiz, Miguel; Altadill, David; de la Morena, Benito A.

    2017-01-01

    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.

  19. Convectively Coupled Equatorial Waves: A New Methodology for Identifying Wave Structures in Observational Data.

    NASA Astrophysics Data System (ADS)

    Yang, Gui-Ying; Hoskins, Brian; Slingo, Julia

    2003-07-01

    Convectively coupled equatorial waves are fundamental components of the interaction between the physics and dynamics of the tropical atmosphere. A new methodology, which isolates individual equatorial wave modes, has been developed and applied to observational data. The methodology assumes that the horizontal structures given by equatorial wave theory can be used to project upper- and lower-tropospheric data onto equatorial wave modes. The dynamical fields are first separated into eastward- and westward-moving components with a specified domain of frequency-zonal wavenumber. Each of the components for each field is then projected onto the different equatorial modes using the y structures of these modes given by the theory. The latitudinal scale yo of the modes is predetermined by data to fit the equatorial trapping in a suitable latitude belt y = ±Y. The extent to which the different dynamical fields are consistent with one another in their depiction of each equatorial wave structure determines the confidence in the reality of that structure. Comparison of the analyzed modes with the eastward- and westward-moving components in the convection field enables the identification of the dynamical structure and nature of convectively coupled equatorial waves.In a case study, the methodology is applied to two independent data sources, ECMWF Reanalysis and satellite-observed window brightness temperature (Tb) data for the summer of 1992. Various convectively coupled equatorial Kelvin, mixed Rossby-gravity, and Rossby waves have been detected. The results indicate a robust consistency between the two independent data sources. Different vertical structures for different wave modes and a significant Doppler shifting effect of the background zonal winds on wave structures are found and discussed.It is found that in addition to low-level convergence, anomalous fluxes induced by strong equatorial zonal winds associated with equatorial waves are important for inducing equatorial

  20. Annual cycle of equatorial East-West circulation over the Indian and Pacific oceans

    SciTech Connect

    Murakami, T.; Wang, B. )

    1993-05-01

    Along the equator, the easterlies are strongest above the convective center over the maritime continent, while westerlies reach their maximum just above the dry zone over the equatorial Pacific. This is different from what is anticipated. The present study provides evidence that the midlatitude-equatorial coupling is primarily responsible for the maintenance of the annual mean total 200-mb zonal winds along the equator, whereas convection contributes a great deal to the annual mean upper-level equatorial divergent winds. Annual cycles occurring over the extratropics act as a transient eddy forcing of the equatorial annual mean 200-mb zonal wind through three-dimensional convergence of localized Eliassen-Palm (E-P) fluxes and accelerate the 200-mb annual mean westerlies (easterlies) over the equatorial Indian Ocean where E-P fluxes are horizontally divergent (convergent). The baroclinic contribution appears to be minimal. The annual cycles differ remarkably between the equatorial Indian and eastern Pacific oceans. The annual cycle in the equatorial Indian Ocean is characterized by (1) the eastward phase propagation of monthly mean anomaly zonal winds with an inverse relationship between the surface and 200 mb and (2) the highest SST occurring about three (four) months prior to the strongest surface westerlies. The annual cycle in the equatorial eastern Pacific exhibits coherent westward propagation of monthly mean anomaly SST and surface zonal winds, indicating the importance of planetary boundary-layer processes. The equatorial convection apparently contributes little to the annual cycle of the upper-level east-west equatorial circulation. The annual cycle in the upper-level zonal winds over the equatorial eastern Pacific is largely controlled by a pronounced annual cycle of the 200-mb zonal wind occurring in the extratropics of each hemisphere. 45 refs., 9 figs.

  1. Longitudinal Variability of Equatorial Plasma Bubbles Observed by DMSP and ROCSAT-1

    DTIC Science & Technology

    2007-11-02

    interest in geophysical causes of equatorial displays and ionograms , EPBs are also referred to as plasma spread F (ESF) and equatorial plasma bubbles...propagation, they are not identical. The term that plumes/bubbles have elongated, wedge-like cross sec- ESF describes irregular signatures on ionograms

  2. Simulational studies of the Farley-Buneman in the equatorial electrojet

    SciTech Connect

    Otani, N.; Seyler, C.; Kelley, M.

    1995-07-01

    The Farley-Buneman instability in the equatorial electrojet current system in the E-region of the ionosphere has been identified as the cause of the observed Type I electron density irregularities. The goal of this work was to study the instability in the equatorial region.

  3. Midlatitude Rossby wave forcing of equatorial Kelvin waves

    NASA Astrophysics Data System (ADS)

    Biello, J. A.; Kiladis, G. N.; Back, A.

    2015-12-01

    Observations strongly suggest that convectively coupled Kelvin waves can be generated by extratropical wave activity. This mechanism is particularly efficient over Australia, where wave activity appears immediately after the extratropical Rossby waves propagate into the region during the Austral winter. This interaction occurs where the zonal wind is strongly sheared both in the meridional and vertical directions. In order to understand this phenomenon the authors study the linear primitive equations in the presence of barotropic and baroclinic shear and the dispersion characteristics of the sheared Matsuno modes are calculated. Depending on the shear strength, the waves are stable or unstable and can be categorized into three groups. First there are the classical Matsuno modes modified by shear. Second there are extratropical "free" Rossby waves. Third, there are Rossby waves meridionally confined to the shear layer - these latter modes can be unstable, or stable and part of the continuous spectrum. In examples where the zonal winds are barotropically and baroclinically stable, we show that a continuous spectrum of Rossby waves exists. If the zonal winds are strong enough, the Rossby waves in the continuous spectrum have an equatorial signature exactly like the Matsuno Kelvin wave - despite the fact that, in these examples, the Matsuno Kelvin wave also exists on its own and that all modes are stable. For stronger shears, these continuous spectrum modes become unstable. Although the appear similar to Sakai's Rossby/Kelvin instability, their existence arises from a completely different phenomenon. The Sakai instability requires the frequency of a stable equatorial Rossby mode to coincide with the stable Kelvin wave frequency in order for the two modes to create a stable/unstable pair. Our results show that unstable Rossby waves need only have their frequencies Doppler shifted to that of the Kelvin wave frequency by the underlying shear in order that they acquire a

  4. Spread F - an old equatorial aeronomy problem finally resolved?

    NASA Astrophysics Data System (ADS)

    Woodman, R. F.

    2009-05-01

    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 form irregularities from

  5. Plasma turbulence in the equatorial ionospheric F region

    NASA Astrophysics Data System (ADS)

    McDaniel, Rickey Dale

    Equatorial spread F is a spectacular phenomenon in which the equatorial region ionosphere is reshaped after sunset. The plasma instabilities responsible for equatorial spread F are fascinating since they occur on time scales ranging from seconds to hours and length scales from centimeters to tens of kilometers. The plasma irregularities that occur in the F region also influence the performance and reliability of space borne and ground based electronic systems and may cause the disruption of satellite operations, communications, navigation, and electrical power distribution grids, leading to potentially broad economic losses. The ionospheric model equations that describe these plasma instabilities display different dynamical behavior based on the value of the ion-neutral collision frequency. The transition occurs at the so-called inertial regime of the ionosphere, where the model equations are similar to the Navier Stokes equations except applied to inhomogeneous fluids. A general analytic solution does not exist for these nonlinear equations; however, a numerical model is developed by maintaining charge neutrality in the vicinity of a circular bubble rising from the collisional to the inertial regime. Using this model, we are able to determine the location of the inertial regime as a function of local time, longitude, season, and solar cycle. The model results determine that the regime occurs generally from about 2000 and 2100 local time and 500-900 km apex height. Also, the model predicts that solar minimum periods are generally more conducive for inertial effects than solar maximum periods. Time series analysis performed on Dynamics Explorer II ion density data show that a turbulent cascade form in the inertial regime predicted by the model. Intermediate scale density power spectra all obey k-5/3 spectra scaling when measured in altitude and local time windows predicted by our model as failing within the inertial regime. Meanwhile, density power spectra for data

  6. Interannual Variability of Boreal Summer Rainfall in the Equatorial Atlantic

    NASA Technical Reports Server (NTRS)

    Gu, Guojun; Adler, Robert F.

    2007-01-01

    Tropical Atlantic rainfall patterns and variation during boreal summer [June-July-August (JJA)] are quantified by means of a 28-year (1979-2006) monthly precipitation dataset from the Global Precipitation Climatology Project (GPCP). Rainfall variability during boreal spring [March-April-May (MAM)] is also examined for comparison in that the most intense interannual variability is usually observed during this season. Comparable variabilities in the Intertropical Convergence Zone (ITCZ) strength and the basin-mean rainfall are found during both seasons. Interannual variations in the ITCZ's latitudinal location during JJA however are generally negligible, in contrasting to intense year-to-year fluctuations during MAM. Sea surface temperature (SST) oscillations along the equatorial region (usually called the Atlantic Nino events) and in the tropical north Atlantic (TNA) are shown to be the two major local factors modulating the tropical Atlantic climate during both seasons. During MAM, both SST modes tend to contribute to the formation of an evident interhemispheric SST gradient, thus inducing anomalous shifting of the ITCZ and then forcing a dipolar structure of rainfall anomalies across the equator primarily in the western basin. During JJA the impacts however are primarily on the ITCZ strength likely due to negligible changes in the ITCZ latitudinal location. The Atlantic Nino reaches its peak in JJA, while much weaker SST anomalies appear north of the equator in JJA than in MAM, showing decaying of the interhemispheric SST mode. SST anomalies in the tropical central-eastern Pacific (the El Nino events) have a strong impact on tropical Atlantic including both the tropical north Atlantic and the equatorial-southern Atlantic. However, anomalous warming in the tropical north Atlantic following positive SST anomalies in the tropical Pacific disappears during JJA because of seasonal changes in the large-scale circulation cutting off the ENSO influence passing through the

  7. Dissolution kinetics of calcium carbonate in equatorial Pacific sediments

    NASA Astrophysics Data System (ADS)

    Berelson, William M.; Hammond, Douglas E.; McManus, James; Kilgore, Tammy E.

    1994-06-01

    Benthic chambers were deployed in the equatorial eastern Pacific Ocean on a transect along the equator between 103°W and 140°W and on a transect across the equator at 140°W in order to establish the rate of calcium carbonate dissolution on the seafloor. Dissolution was determined from the rate of alkalinity increase within an incubation chamber, measured over an 80-120 hour incubation period. Dissolution rates were lowest at eastern Pacific sites (0.2-0.4 mmol CaCO3/m2/d) and highest at the equatorial, 140°W sites (0.5-0.7 mmol/m2/d). Both oxygen consumption rates and the degree of bottom water saturation govern dissolution rates. Measured dissolution and oxygen consumption rates are used with a numerical model to constrain the value of the dissolution rate constant k, formulated according to the equation developed by Keir [1980]: dissolution rate = kγ(1-Ω)n. The observed dissolution fluxes are predicted by the model when k = 5 to 100%/d and n = 4.5. This range of k values has important implications regarding the type of carbonate dissolving and its location within the sediment column. At low values of k, organic carbon rain rates to the seafloor become the dominant driving force of carbonate dissolution. At higher values of k, the degree of bottom water undersaturation becomes more important. Dissolution of carbonate within equatorial Pacific sediments can be adequately described with k = 20 ± 10%/d, a rate constant much lower than some previously used values. Dissolution rates do not vary significantly over chamber boundary layer thicknesses between 200 and 800 μm, indicating that dissolution is not controlled by hydrodynamic conditions. Chambers acidified with HCl yield very large dissolution rates, but for a given degree of acidification the dissolution rate was constant for sites ranging from water depths of 3300-4400 m. This implies that there are not more and less easily dissolved forms of CaCO3 arriving on the seafloor between these depths. A budget

  8. Response of the Equatorial Ionosphere to the Geomagnetic DP 2 Current System

    NASA Technical Reports Server (NTRS)

    Yizengaw, E.; Moldwin, M. B.; Zesta, E.; Magoun, M.; Pradipta, R.; Biouele, C. M.; Rabiu, A. B.; Obrou, O. K.; Bamba, Z.; Paula, E. R. De

    2016-01-01

    The response of equatorial ionosphere to the magnetospheric origin DP 2 current system fluctuations is examined using ground-based multiinstrument observations. The interaction between the solar wind and fluctuations of the interplanetary magnetic field (IMF) Bz, penetrates nearly instantaneously to the dayside equatorial region at all longitudes and modulates the electrodynamics that governs the equatorial density distributions. In this paper, using magnetometers at high and equatorial latitudes, we demonstrate that the quasiperiodic DP 2 current system penetrates to the equator and causes the dayside equatorial electrojet (EEJ) and the independently measured ionospheric drift velocity to fluctuate coherently with the high-latitude DP 2 current as well as with the IMF Bz component. At the same time, radar observations show that the ionospheric density layers move up and down, causing the density to fluctuate up and down coherently with the EEJ and IMF Bz.

  9. Response of the Equatorial Ionosphere to the Geomagnetic DP 2 Current System

    NASA Technical Reports Server (NTRS)

    Yizengaw, E.; Moldwin, M. B.; Zesta, E.; Magoun, M.; Pradipta, R.; Biouele, C. M.; Rabiu, A. B.; Obrou, O. K.; Bamba, Z.; Paula, E. R. De

    2016-01-01

    The response of equatorial ionosphere to the magnetospheric origin DP 2 current system fluctuations is examined using ground-based multiinstrument observations. The interaction between the solar wind and fluctuations of the interplanetary magnetic field (IMF) Bz, penetrates nearly instantaneously to the dayside equatorial region at all longitudes and modulates the electrodynamics that governs the equatorial density distributions. In this paper, using magnetometers at high and equatorial latitudes, we demonstrate that the quasiperiodic DP 2 current system penetrates to the equator and causes the dayside equatorial electrojet (EEJ) and the independently measured ionospheric drift velocity to fluctuate coherently with the high-latitude DP 2 current as well as with the IMF Bz component. At the same time, radar observations show that the ionospheric density layers move up and down, causing the density to fluctuate up and down coherently with the EEJ and IMF Bz.

  10. Image measurements of short-period gravity waves at equatorial latitudes

    NASA Astrophysics Data System (ADS)

    Taylor, M. J.; Pendleton, W. R.; Clark, S.; Takahashi, H.; Gobbi, D.; Goldberg, R. A.

    1997-11-01

    A high-performance, all-sky imaging system has been used to obtain novel data on the morphology and dynamics of short-period (<1 hour) gravity waves at equatorial latitudes. Gravity waves imaged in the upper mesosphere and lower thermosphere were recorded in three nightglow emissions, the near-infrared OH emission, and the visible wavelength OI (557.7 nm) and Na (589.2 nm) emissions spanning the altitude range ˜80-100 km. The measurements were made from Alcantara, Brazil (2.3°S, 44.5°W), during the period August-October 1994 as part of the NASA/Instituto Nacional de Pesquisas Espaciais "Guara campaign". Over 50 wave events were imaged from which a statistical study of the characteristics of equatorial gravity waves has been performed. The data were found to divide naturally into two groups. The first group corresponded to extensive, freely propagating (or ducted) gravity waves with observed periods ranging from 3.7 to 36.6 min, while the second group consisted of waves of a much smaller scale and transient nature. The later group exhibited a bimodal distribution for the observed periods at 5.18±0.26 min and 4.32±0.15 min, close to the local Brunt-Vaisala period and the acoustic cutoff period, respectively. In comparison, the larger-scale waves exhibited a clear tendency for their horizontal wavelengths to increase almost linearly with observed period. This trend was particularly well defined around the equinox and can be represented by a power-law relationship of the form λh=(3.1±0.5)τob1.06±0.10, where λh is measured in kilometers and τob in minutes. This result is in very good agreement with previous radar and passive optical measurements but differs significantly from the relationship λh ∝ τ1.5ob inferred from recent lidar studies. The larger-scale waves were also found to exhibit strong anisotropy in their propagation headings with the dominant direction of motion toward the-NE-ENE suggesting a preponderance for wave generation over the South

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

    NASA Astrophysics Data System (ADS)

    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.

  12. Coincident observations of ionospheric troughs and the equatorial plasmapause

    NASA Technical Reports Server (NTRS)

    Grebowsky, J. M.; Maynard, N. C.; Tulunay, Y. K.; Lanzerotti, L. J.

    1976-01-01

    Electron-density observations made in the topside ionosphere by the Ariel 4 and Isis 2 satellites are examined in conjunction with results obtained by Explorer 45 when it traversed the near-equatorial plasmapause with one hour (both UT and MLT) of the Ariel and Isis traversals of the same L coordinate. Both dusk and night observations are analyzed, and an attempt is made to show that depressions in ionospheric electron density occur in the vicinity of the plasmapause field line. It is concluded that the electron distributions observed in the electron-density troughs at 550 km near dusk by Ariel and at 1400 km near midnight by Isis do not always parallel variations in the light-ion distribution inferred from the Explorer plasmapause traversals and that there appears to be no specific feature of the main ionospheric trough which can be used to identify the plasmapause field line except in a statistical sense.

  13. How did the equatorial ridge on Saturn's moon Iapetus form?

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2012-04-01

    Saturn's moon Iapetus is one of the most unusual moons in our solar system. Perhaps the most bizarre feature of Iapetus is its equatorial ridge, a 20-kilometer-high, 200-kilometer-wide mountain range that runs exactly along the equator, circling more than 75% of the moon. No other body in the solar system exhibits such a feature; as Dombard et al. show, previous models have been unable to adequately explain how the ridge formed. The authors propose that the ridge formed from an ancient giant impact that produced a subsatellite around Iapetus. Tidal interactions with Iapetus ultimately led to orbital decay, eventually bringing the subsatellite close enough that the same forces tore it apart, forming a debris ring around Iapetus. Material from this debris ring then rained down on Iapetus, the researchers say, creating the mountain ring along the equator. (Journal of Geophysical Research-Planets, doi:10.1029/2011JE004010, 2012)

  14. Response of the lower equatorial ionosphere to strong tropospheric disturbances

    NASA Astrophysics Data System (ADS)

    Vanina-Dart, L. B.; Pokrovskaya, I. V.; Sharkov, E. A.

    2008-04-01

    A morphological analysis of the results of sounding the lower equatorial ionosphere (the D region) in the region of action of strong tropospheric vortex disturbances (tropical cyclones, TC) is presented in this work. Based on the rocket sounding of the lower ionosphere at Thumba rocket site (8° N, 77° E) in May-June 1985 and on the satellite monitoring of TC in the northern Indian Ocean, it is demonstrated that a sharp depletion (by a factor of 2-4) of the electron concentration at altitudes of 60-80 km could be a response of the ionosphere during the TC active phase. In this case the lower boundary of the D region rose by several kilometers (not more than 5 km), and the temperature in the region of the stratopause slightly (by 2°-3°) increases. It is assumed that internal gravity waves (IGWs) generated by TC cause the effect on the lower ion-osphere.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  16. Implications of the small aspect angles of equatorial spread F

    SciTech Connect

    Hysell, D.L.; Farley, D.T.

    1996-03-01

    Small-scale equatorial spread F irregularities are almost perfectly aligned with the geomagnetic field. The authors develop here an analytic plasma kinetic theory of small-scale, quasi-field-aligned irregularities that include ion viscosity and finite Larmor radius effects. They conclude, for one thing, that the measured aspect angles are too small to be consistent with a dissipative drift wave source of 3-m irregularities. Nonlinearly driven flute modes appear to be the only available mechanism. The authors compare the relative influence of parallel and perpendicular dissipation and conclude that the aspect width depends only weakly on any single geophysical parameters, such as collision frequency, gradient length, temperature, etc. This finding is consistent with their observation that the measured aspect angles vary little with altitude and only weakly with instability level. 29 refs., 5 figs.

  17. Pelagic microplastics around an archipelago of the Equatorial Atlantic.

    PubMed

    Ivar do Sul, Juliana A; Costa, Monica F; Barletta, Mário; Cysneiros, Francisco José A

    2013-10-15

    Plastic marine debris is presently widely recognised as an important environmental pollutant. Such debris is reported in every habitat of the oceans, from urban tourist beaches to remote islands and from the ocean surface to submarine canyons, and is found buried and deposited on sandy and cobble beaches. Plastic marine debris varies from micrometres to several metres in length and is potentially ingested by animals of every level of the marine food web. Here, we show that synthetic polymers are present in subsurface plankton samples around Saint Peter and Saint Paul Archipelago in the Equatorial Atlantic Ocean. To explain the distribution of microplastics around the Archipelago, we proposed a generalised linear model (GLM) that suggests the existence of an outward gradient of mean plastic-particle densities. Plastic items can be autochthonous or transported over large oceanic distances. One probable source is the small but persistent fishing fleet using the area.

  18. Equatorial pacific seismic reflectors as indicators of global oceanographic events.

    PubMed

    Mayer, L A; Shipley, T H; Winterer, E L

    1986-08-15

    The origin of a series of regionally correlatable seismic horizons in the Neogene sediments of the central equatorial Pacific is examined through seismic modeling and the detailed analyses of stratigraphic and physical property relationships in Deep Sea Drilling Project cores. These regionally traceable reflectors are synchronous; the younger reflectors are the direct result of carbonate dissolution events, the older ones of stratigraphically selective diagenetic processes. The changes in ocean chemistry associated with these events appear to be linked to global reorganizations of surface and bottom-water circulation patterns, the most dramatic of which are associated with reorganizations of North Atlantic bottom waters. These deepwater seismic horizons appear to correlate with the major events on the "relative sea-level" curve of Vail et al. for the Neogene.

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

    NASA Astrophysics Data System (ADS)

    Gallagher, D.

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

  20. Scale analysis of equatorial plasma irregularities derived from Swarm constellation

    NASA Astrophysics Data System (ADS)

    Xiong, Chao; Stolle, Claudia; Lühr, Hermann; Park, Jaeheung; Fejer, Bela G.; Kervalishvili, Guram N.

    2016-07-01

    In this study, we investigated the scale sizes of equatorial plasma irregularities (EPIs) using measurements from the Swarm satellites during its early mission and final constellation phases. We found that with longitudinal separation between Swarm satellites larger than 0.4°, no significant correlation was found any more. This result suggests that EPI structures include plasma density scale sizes less than 44 km in the zonal direction. During the Swarm earlier mission phase, clearly better EPI correlations are obtained in the northern hemisphere, implying more fragmented irregularities in the southern hemisphere where the ambient magnetic field is low. The previously reported inverted-C shell structure of EPIs is generally confirmed by the Swarm observations in the northern hemisphere, but with various tilt angles. From the Swarm spacecrafts with zonal separations of about 150 km, we conclude that larger zonal scale sizes of irregularities exist during the early evening hours (around 1900 LT).

  1. Terrestrial structured radio emissions occurring close to the equatorial regions

    NASA Astrophysics Data System (ADS)

    Boudjada, Mohammed Y.; Galopeau, Patrick H. M.; Sawas, Sami; Berthelier, Jean-Jacques

    2015-04-01

    We study the occurrence of terrestrial radio emissions observed by the electric field experiment (ICE) onboard DEMETER micro-satellite. We principally consider the ICE observations recorded in the HF frequency range between 10 kHz and 3.175 MHz. A dynamic spectrum is recorded each half-orbit with a time and frequency resolutions, respectively, in the order of 3.25 kHz and 2.048 sec. The terrestrial structured radio emission is found to occur when the satellite is approaching the equatorial region of the Earth. It appears as a structured narrow band 'continuum' with a positive or negative low frequency drift rate, less than 1 kHz/s. The bandwidth is, on average, of about 30 kHz. We derive from our investigation the beam and the probable location of the emission source. We discuss the origin of this terrestrial radio emission and its dependence, or not, on the solar and geomagnetic activities.

  2. El Nino/la Nina Transition In The Equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Lewis, M.; Turk, D.; McPhadden, Mike; Lagerloef, G.; Asanuma, I.

    A massive bloom of phytoplankton in the normally oligotrophic Western Pacific was the first manifestation of the termination of the 1997-1998 El Nino, by most measures, the strongest on record. This bloom represented a 4-fold increase in the background chlorophyll distribution, as viewed by the Sea-Viewing, Wide Field of View Sensor (SeaWiFS). A combination of physical and bio-optical observations from satellites, moored buoys, and ships lead to the conclusion that this bloom was a direct result of the interaction of surface currents with a series of island atolls (Kiribati) that induced strong vertical mixing and subsequent downstream advection of waters rich in nutrients. The increase in phytoplankton concentration represents a lower limit to a dramatically increased level of exported carbon from the normally biologically poor western Pacific region, and is a novel observation of topographic influences which are not normally resolved by most models of equatorial ocean dynamics.

  3. Intense low-energy ion populations at low equatorial altitudes

    NASA Technical Reports Server (NTRS)

    Williams, D. J.; Frank, L. A.

    1984-01-01

    The ISEE 1 satellite trajectory often passed through the magnetospheric region during the time from November 1977 to April 1978. On every occasion, the medium energy particles instrument (MEPI) of the satellite recorded an intense ion population in a region corresponding to low equatorial altitudes. An intensity peak was observed in the lowest MEPI energy channel. A comparison of high bit rate MEPI data with simultaneous data from the LEPEDEA plasma instrument on Nov. 29, 1977 1930-2000 UT shows additional peaks in the ion population existing in the L of 2 to at least 4. In the present report, data characterizing these ion populations are presented, and implications are discussed in terms of source and loss mechanisms.

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

    SciTech Connect

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

    1990-10-01

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

  5. Observations of discrete harmonics emerging from equatorial noise.

    PubMed

    Balikhin, Michael A; Shprits, Yuri Y; Walker, Simon N; Chen, Lunjin; Cornilleau-Wehrlin, Nicole; Dandouras, Iannis; Santolik, Ondrej; Carr, Christopher; Yearby, Keith H; Weiss, Benjamin

    2015-07-14

    A number of modes of oscillations of particles and fields can exist in space plasmas. Since the early 1970s, space missions have observed noise-like plasma waves near the geomagnetic equator known as 'equatorial noise'. Several theories were suggested, but clear observational evidence supported by realistic modelling has not been provided. Here we report on observations by the Cluster mission that clearly show the highly structured and periodic pattern of these waves. Very narrow-banded emissions at frequencies corresponding to exact multiples of the proton gyrofrequency (frequency of gyration around the field line) from the 17th up to the 30th harmonic are observed, indicating that these waves are generated by the proton distributions. Simultaneously with these coherent periodic structures in waves, the Cluster spacecraft observes 'ring' distributions of protons in velocity space that provide the free energy for the waves. Calculated wave growth based on ion distributions shows a very similar pattern to the observations.

  6. Observations of discrete harmonics emerging from equatorial noise

    NASA Astrophysics Data System (ADS)

    Balikhin, Michael A.; Shprits, Yuri Y.; Walker, Simon N.; Chen, Lunjin; Cornilleau-Wehrlin, Nicole; Dandouras, Iannis; Santolik, Ondrej; Carr, Christopher; Yearby, Keith H.; Weiss, Benjamin

    2015-07-01

    A number of modes of oscillations of particles and fields can exist in space plasmas. Since the early 1970s, space missions have observed noise-like plasma waves near the geomagnetic equator known as `equatorial noise'. Several theories were suggested, but clear observational evidence supported by realistic modelling has not been provided. Here we report on observations by the Cluster mission that clearly show the highly structured and periodic pattern of these waves. Very narrow-banded emissions at frequencies corresponding to exact multiples of the proton gyrofrequency (frequency of gyration around the field line) from the 17th up to the 30th harmonic are observed, indicating that these waves are generated by the proton distributions. Simultaneously with these coherent periodic structures in waves, the Cluster spacecraft observes `ring' distributions of protons in velocity space that provide the free energy for the waves. Calculated wave growth based on ion distributions shows a very similar pattern to the observations.

  7. Unstable density distribution associated with equatorial plasma bubble

    SciTech Connect

    Kherani, E. A. Meneses, F. Carlos de; Bharuthram, R.; Singh, S.; Lakhina, G. S.

    2016-04-15

    In this work, we present a simulation study of equatorial plasma bubble (EPB) in the evening time ionosphere. The fluid simulation is performed with a high grid resolution, enabling us to probe the steepened updrafting density structures inside EPB. Inside the density depletion that eventually evolves as EPB, both density and updraft are functions of space from which the density as implicit function of updraft velocity or the density distribution function is constructed. In the present study, this distribution function and the corresponding probability distribution function are found to evolve from Maxwellian to non-Maxwellian as the initial small depletion grows to EPB. This non-Maxwellian distribution is of a gentle-bump type, in confirmation with the recently reported distribution within EPB from space-borne measurements that offer favorable condition for small scale kinetic instabilities.

  8. Studies on equatorial shock formation during plasmaspheric refilling

    NASA Technical Reports Server (NTRS)

    Singh, N.

    1994-01-01

    Investigations based on small-scale simulations of microprocesses occurring when a magnetic flux tube refills with a cold plasma are summarized. Results of these investigations are reported in the following attached papers: (1) 'Numerical Simulation of Filling a Magnetic Flux Tube with a Cold Plasma: The Role of Ion Beam-Driven Instabilities'; and (2) 'Numerical Simulation of Filling a Magnetic Flux Tube with a Cold Plasma: Effects of Magnetically Trapped Hot Plasma'. Other papers included are: 'Interaction of Field-Aligned Cold Plasma Flows with an Equatorially-Trapped Hot Plasma: Electrostatic Shock Formation'; and 'Comparison of Hydrodynamic and Semikinetic Treatments for a Plasma Flow along Closed Field Lines'. A proposal for further research is included.

  9. Simulations of the equatorial thermosphere anomaly: Geomagnetic activity modulation

    NASA Astrophysics Data System (ADS)

    Lei, Jiuhou; Wang, Wenbin; Thayer, Jeffrey P.; Luan, Xiaoli; Dou, Xiankang; Burns, Alan G.; Solomon, Stanley C.

    2014-08-01

    The modulation of geomagnetic activity on the equatorial thermosphere anomaly (ETA) in thermospheric temperature under the high solar activity condition is investigated using the Thermosphere Ionosphere Electrodynamics General Circulation Model simulations. The model simulations during the geomagnetically disturbed interval, when the north-south component of the interplanetary magnetic field (Bz) oscillates between southward and northward directions, are analyzed and also compared with those under the quiet time condition. Our results show that ionospheric electron densities increase greatly in the equatorial ionization anomaly (EIA) crest region and decrease around the magnetic equator during the storm time, resulting from the enhanced eastward electric fields. The impact of both the direct heat deposition at high latitudes and the modulation of the storm time enhanced EIA crests on the ETA are subsequently studied. The increased plasma densities over the EIA crest region enhance the field-aligned ion drag that accelerates the poleward meridional winds and consequently their associated adiabatic cooling effect. This process alone produces a deeper temperature trough over the magnetic equator as a result of the enhanced divergence of meridional winds. Moreover, the enhanced plasma-neutral collisional heating at higher latitudes associated with the ionospheric positive storm effect causes a weak increase of the ETA crests. On the other hand, strong changes of the neutral temperature are mainly confined to higher latitudes. Nevertheless, the changes of the ETA purely due to the increased plasma density are overwhelmed by those associated with the storm time heat deposition, which is the major cause of an overall elevated temperature in both the ETA crests and trough during the geomagnetically active period. Associated with the enhanced neutral temperature at high latitudes due to the heat deposition, the ETA crest-trough differences become larger under the minor

  10. Longitudinal and geomagnetic activity modulation of the equatorial thermosphere anomaly

    NASA Astrophysics Data System (ADS)

    Lei, Jiuhou; Thayer, Jeffrey P.; Forbes, Jeffrey M.

    2010-08-01

    In this paper we examine the detailed similarities and differences between the equatorial thermosphere anomaly (ETA) and the equatorial ionization anomaly (EIA) from 20 March to 6 April 2002, when both the ETA and the EIA are distinct in the Challenging Minisatellite Payload (CHAMP) observations. The characteristics of the ETA and the EIA are obtained from the CHAMP accelerometer, in situ electron density measurements, and total electron content (TEC) above the CHAMP satellite. Our results show that the trough locations of the ETA and the EIA in latitude show a good agreement, and both correspond well with the dip magnetic equator, while the ETA crests are usually located poleward of the EIA. Meanwhile, the latitudinal locations of the ETA crests exhibit strong hemispheric asymmetry and large variability during our study interval. The longitudinal variations between the EIA and the ETA show significant differences. The EIA crests from the CHAMP observations show strong wave 4 structures, but the primary component in the ETA is wave 1. Moreover, the ETA densities show strong variations in response to geomagnetic activity, whereas CHAMP in situ electron densities and TEC at the EIA do not reflect such large day-to-day variability. Therefore, a simple EIA-ETA relationship cannot explain the dependence of the longitudinal and geomagnetic activity modulation of the ETA and the EIA. The meridional ion drag, which is significantly modulated by enhanced equatorward winds during elevated geomagnetic activity, is probably responsible for some of the observed features in the ETA, although no unambiguous explanation for ETA formation yet exists.

  11. Poynting vector and wave vector directions of equatorial chorus

    NASA Astrophysics Data System (ADS)

    Taubenschuss, Ulrich; Santolík, Ondřej; Breuillard, Hugo; Li, Wen; Le Contel, Olivier

    2016-12-01

    We present new results on wave vectors and Poynting vectors of chorus rising and falling tones on the basis of 6 years of THEMIS (Time History of Events and Macroscale Interactions during Substorms) observations. The majority of wave vectors is closely aligned with the direction of the ambient magnetic field (B0). Oblique wave vectors are confined to the magnetic meridional plane, pointing away from Earth. Poynting vectors are found to be almost parallel to B0. We show, for the first time, that slightly oblique Poynting vectors are directed away from Earth for rising tones and toward Earth for falling tones. For the majority of lower band chorus elements, the mutual orientation between Poynting vectors and wave vectors can be explained by whistler mode dispersion in a homogeneous collisionless cold plasma. Upper band chorus seems to require inclusion of collisional processes or taking into account azimuthal anisotropies in the propagation medium. The latitudinal extension of the equatorial source region can be limited to ±6∘ around the B0 minimum or approximately ±5000 km along magnetic field lines. We find increasing Poynting flux and focusing of Poynting vectors on the B0 direction with increasing latitude. Also, wave vectors become most often more field aligned. A smaller group of chorus generated with very oblique wave normals tends to stay close to the whistler mode resonance cone. This suggests that close to the equatorial source region (within ˜20∘ latitude), a wave guidance mechanism is relevant, for example, in ducts of depleted or enhanced plasma density.

  12. Tectonic evolution of Brazilian equatorial continental margin basins

    SciTech Connect

    Azevedo, R.P. )

    1993-02-01

    The structural style and stratigraphic relationships of sedimentary basins along the Brazilian Equatorial Atlantic Continental Margin were used to construct an empirical tectonic model for the development of ancient transform margins. The model is constrained by detailed structural and subsidence analyses of several basins along the margin. The structural framework of the basins was defined at shallow and deep levels by the integration of many geophysical and geological data sets. The Barreirinhas and Para-Maranhao Basins were divided in three tectonic domains: the Tutoia, Caete, and Tromai subbasins. The Caete area is characterized by northwest-southeast striking and northeast-dipping normal faults. A pure shear mechanism of basin formation is suggested for its development. The structure of the Tutoia and Tromai subbasins are more complex and indicative of a major strike-slip component with dextral sense of displacement, during early stages of basin evolution. These two later subbasins were developed on a lithosphere characterized by an abrupt transition (<50 km wide) from an unstretched continent to an oceanic lithosphere. The subsidence history of these basins do not comply with the classical models developed for passive margins or continental rifting. The thermo-mechanical model proposed for the Brazilian equatorial margin includes heterogeneous stretching combined with shearing at the plate margin. The tectonic history comprises: (1) Triassic-Jurassic limited extension associated with the Central Atlantic evolution; (2) Neocomian intraplate deformation consisting of strike-slip reactivation of preexisting shear zones; (3) Aptian-Cenomanian two-phase period of dextral shearing; and (4) Late Cretaceous-Cenozoic sea-floor spreading.

  13. Equatorial F2 characteristic variability: A review of recent observations

    NASA Astrophysics Data System (ADS)

    Somoye, E. O.; Akala, A. O.; Adeniji-Adele, R. A.; Iheonu, E. E.; Onori, E. O.; Ogwala, A.

    2013-10-01

    This paper reviews the variability of equatorial/low latitude F2 characteristics with emphasis on the most general results reported by authors. On a general note, diurnal variation of ionospheric F2 layer characteristics coefficient of variability (CV) is characterised by post- and pre-midnight peaks at all seasons, epochs and longitude. The post-midnight peak is greater than pre-midnight peak for all the characteristics considered except h'F2 CV during high solar activity (HSA) possibly due to occurrence of post-sunset pre-reversal enhancement (PRE) in height of reflection prominent during HSA. NmF2 CV is greater than CV of MUF and h'F2. MUF CV and foF2 CV are of the same order of magnitude. While seasonal trend is little or nil in daytime CV of F2 layer characteristics, nighttime CV is greater in general at the equinoxes and June Solstice. Nighttime F2 layer characteristics CV are found to decrease with increasing sunspot. This is not the case with daytime CV. Except for h'F2 CV, daytime CV of F2 layer characteristics are independent of latitude while nighttime CV decreases with latitude. Equatorial stations east (Vanimo, 2.7°S, 141.3°E, dip 22.5°S) and west (Huancayo, 12°S, 75.3°W, dip 1.9°N) of the Greenwich Meridian (GM) have greater nighttime CV than those in the neighbourhood of the GM (Ouagadougou, 12.4°N, 1.5°W, dip 7.6°N) with those stations west of GM having the greatest CV, implying longitudinal effect on CV. During magnetic storms CV are reported to be greater than during quiet periods.

  14. Digital ionosonde observations during equatorial spread F-italic

    SciTech Connect

    Argo, P.E.; Kelley, M.C.

    1986-05-01

    In this paper we present and discuss equatorial spread F-italic data taken with a digital ionosonde/HF radar located at Huancayo, Peru. A modified phenomenology is developed which uses the system's ability to do echo location. The onset of irregularities is seen to occur in the east and to move westward, while inside this large-scale structure the plasma is found to drift eastward. A very curious difference has been identified between spread F-italic observations with the ionosonde and with the VHF radar at Jicamarca. At VHF, spread F-italic onset often occurs when the ionosphere is rising, whereas in all five examples presented here, the digital ionosonde detected onset when the apparent ionosphere motion was downward. The result even held on the one night of common data taking. The effect could be instrumental but may be related to the considerable orographic differences in the two sites. Isolated scattering patches are observed and are tentatively identified as detached or ''fossil'' plumes. At frequencies above the nominal f-italic/sub 0/F-italic/sub 2/ the system (and other ionosondes) may in fact function as a coherent radar. During one night, data were obtained simultaneously with the HF radar, a rocket, and the Jicamarca VHF radar. Comparisons of these data are discussed in detail. Finally, additional evidence is presented that acoustic gravity waves play a role in the development of equatorial spread F-italic and in the formation of detached plumes. To be self-consistent, the gravity waves must come from nearby sources such as the tropical rain forest to the east of Jicamarca.

  15. SpIES: The Spitzer IRAC Equatorial Survey

    NASA Technical Reports Server (NTRS)

    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; Lamassa, Stephanie M.; Urry, C. Megan; Wollack, Edward J.

    2016-01-01

    We describe the first data release from the Spitzer-IRAC Equatorial Survey (SpIES); a large-area survey of approx.115 sq deg 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 > or = 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 > or = 5) quasars as well as obscured quasars missed by optical surveys. SpIES achieves 5 sigma depths of 6.13 µJy (21.93 AB magnitude) and 5.75 µJy (22.0 AB magnitude) at 3.6 and 4.5 microns, 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 (approx.98%) in Stripe 82 than are recovered by WISE (55%). This depth is especially powerful at high-redshift (z > or = 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 microns only detection catalog containing approx. 6.1 million sources, a 4.5 microns only detection catalog containing approx. 6.5 million sources, and a dual-band detection catalog containing approx. 5.4 million sources.

  16. Numerical simulation of equatorial plasma bubbles over Cachimbo: COPEX campaign

    NASA Astrophysics Data System (ADS)

    Carrasco, A. J.; Batista, I. S.; Abdu, M. A.

    2014-08-01

    The problem of day-to-day variability in onset of equatorial spread F (ESF) is addressed using data from the 2002 COPEX observational campaign in Brazil and numerical modeling. The observational results show that for values of virtual height of the F layer base less than 355 km at around 18:35 LT, and for the prereversal peak enhancement of the vertical plasma drift (Vp) less than 30 m/s, the spread-F (ESF) was absent on four nights over Cachimbo (9.5°S, 54.8°W, dip latitude = -2.1°). In this work we analyze the geophysical conditions for the generation of the irregularities by comparing the nights with and without the ESF. In the comparison a numerical code is used to simulate plasma irregularity development in an extended altitude range from the bottom of the equatorial F layer. The code uses the flux corrected transport method with Boris-Book’s flux limiter for the spatial integration and a predictor-corrector method for the direct time integration of the continuity equation for O+ and the SOR (Successive-Over-Relaxation) method for electric potential equation. The code is tested with different evening eastward electric fields (or vertical drifts Vp < 30 m/s and Vp > 30 m/s) in order to study the influence of the prereversal enhancement in the zonal electric field on plasma bubble formation and development. The code also takes into account the zonal wind, the vertical electric field and the collision frequency of ions with neutrals and the amplitude of initial perturbation. The simulation shows a good agreement with the observational results of the ESF. The results of the code suggest that the instability can grow at the F layer bottomside by the Rayleigh-Taylor mechanism only when the Vp > 30 m/s. In the analyzed cases we have considered the competition of other geophysical parameters in the generation of plasma structures.

  17. On the Timing of Glacial Terminations in the Equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Khider, D.; Ahn, S.; Lisiecki, L. E.; Lawrence, C.; Kienast, M.

    2015-12-01

    Understanding the mechanisms through which the climate system responds to orbital insolation changes requires establishing the timing of events imprinted on the geological record. In this study, we investigate the relative timing of the glacial terminations across the equatorial Pacific in order to identify a possible mechanism through which the tropics may have influenced a global climate response. The relative termination timing between the eastern and western equatorial Pacific was assessed from 15 published SST records based on Globigerinoides ruber Mg/Ca or alkenone thermometry. The novelty of our study lies in the accounting of the various sources of uncertainty inherent to paleoclimate reconstruction and timing analysis. Specifically, we use a Monte-Carlo process allowing sampling of possible realizations of the time series that are functions of the uncertainty of the benthic δ18O alignment to a global benthic curve, of the SST uncertainty, and of the uncertainty in the change point, which we use as a definition for the termination timing. We find that the uncertainty on the relative timing estimates is on the order of several thousand years, and stems from age model uncertainty (60%) and the uncertainty in the change point detection (40%). Random sources of uncertainty are the main contributor, and, therefore, averaging over a large datasets and/or higher resolution records should yield more precise and accurate estimates of the relative lead-lag. However, at this time, the number of records is not sufficient to identify any significant differences in the timing of the last three glacial terminations in SST records from the Eastern and Western Tropical Pacific.

  18. Equatorial ground ice on Mars: Steady-state stability

    NASA Technical Reports Server (NTRS)

    Mellon, Michael T.; Jakosky, Bruce M.; Postawko, Susan E.

    1993-01-01

    Current Martian equatorial surface temperatures are too warm for water ice to exist at the surface for any appreciable length of time before subliming into the atmosphere. Subsurface temperatures are generally warmer still and, despite the presence of a diffusive barrier of porous regolith material, it has been shown by Smoluchowski, Clifford and Hillel, and Fanale et al. that buried ground ice will also sublime and be lost to the atmosphere in a relatively short time. We investigate the behavior of this subliming subsurface ice and show that it is possible for ice to maintain at a steady-state depth, where sublimation and diffusive loss to the atmosphere is balanced by resupply from beneath by diffusion and recondensation of either a deeper buried ice deposits or ground water. We examine the behavior of equatorial ground ice with a numercial time-marching molecular diffusion model. In our model we allow for diffusion of water vapor through a porous regolith, variations in diffusivity and porosity with ice content, and recondensation of sublimed water vapor. A regolith containing considerable amounts of ice can still be very porous, allowing water vapor to diffuse up from deeper within the ice layer where temperatures are warmer due to the geothermal gradient. This vapor can then recondense nearer to the surface where ice had previously sublimed and been lost to the atmosphere. As a result we find that ice deposits migrate to find a steady-state depth, which represents a balance between diffusive loss to the atmosphere through the overlying porous regolith and diffusive resupply through a porous icy regolith below. This depth depends primarily on the long-term mean surface temperature and the nature of the geothermal gradient, and is independent of the ice-free porosity and the regolith diffusivity. Only the rate of loss of ground ice depends on diffusive properties.

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

    NASA Astrophysics Data System (ADS)

    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.

  20. SpIES: The Spitzer IRAC Equatorial Survey

    NASA Technical Reports Server (NTRS)

    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; hide

    2016-01-01

    We describe the first data release from the Spitzer-IRAC Equatorial Survey (SpIES); a large-area survey of approx.115 sq deg 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 > or = 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 > or = 5) quasars as well as obscured quasars missed by optical surveys. SpIES achieves 5 sigma depths of 6.13 µJy (21.93 AB magnitude) and 5.75 µJy (22.0 AB magnitude) at 3.6 and 4.5 microns, 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 (approx.98%) in Stripe 82 than are recovered by WISE (55%). This depth is especially powerful at high-redshift (z > or = 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 microns only detection catalog containing approx. 6.1 million sources, a 4.5 microns only detection catalog containing approx. 6.5 million sources, and a dual-band detection catalog containing approx. 5.4 million sources.

  1. New Results on the Midnight Temperature Maximum Near Equatorial Latitudes

    NASA Astrophysics Data System (ADS)

    Meriwether, J.; Faivre, M.; Veliz, O.

    2007-05-01

    New observations of the equatorial thermospheric dynamics observed from Arequipa, Peru (16.2 S, 72.4 W) obtained with an imaging Fabry-Perot interferometer during the southern hemisphere winter of 2005 (June- August) show an interesting correlation of the formation of the midnight temperature maximum (MTM) with the strength of the semi-diurnal tidal meridional wind. The observations are obtained in eight azimuthal directions at 60 degree zenith angle. Each direction represents an exposure of 120 s and the Doppler shifts and Doppler broadening are analyzed with uncertainties of 8-10 m/s and 30-35 K, respectively. These results are used to prepare horizontal wind maps. When the amplitude of the meridional flow is weak, there is generally not observed any temperature enhancement near midnight. When the meridional flow equatorward is strong, 50-100 m/s, then there is observed about two hours later a significant increase in temperature of typically 100 K. This time delay between the northward component of the thermospheric wind vector and the peak of the MTM structure is observed to be about 30 minutes for two nights obtained during the spring equinox. These results suggest that the semi-diurnal tidal mode forms the MTM by convergence upon the geographical equator to the north of Arequipa. After the compressional heating has taken place, then there is a return "wave" formed that transports the heated air to the region of Arequipa. The decrease of the time delay between winter and the spring equinox is a result of the convergence region forming closer to Arequipa than during the winter. Observations of the horizontal wind maps over successive nights in early July show that the thermospheric wind structure varies considerably from night to night with a variation in the appearance of the meridional wind structure by several hours from night to night. It is tempting to suggest a relationship between this variability and the production of the equatorial spread-F phenomenon.

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

    PubMed

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

    NASA Astrophysics Data System (ADS)

    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.Plain Language Summary<span class="hlt">Equatorial</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27185933','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27185933"><span>Ocean dynamics, not dust, have controlled <span class="hlt">equatorial</span> Pacific productivity over the past 500,000 years.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Winckler, Gisela; Anderson, Robert F; Jaccard, Samuel L; Marcantonio, Franco</p> <p>2016-05-31</p> <p>Biological productivity in the <span class="hlt">equatorial</span> 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 <span class="hlt">Equatorial</span> Undercurrent to the surface. The <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> Pacific, upwelling of water from the <span class="hlt">Equatorial</span> 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 <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> Pacific productivity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22011810','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22011810"><span>CONVECTIVE BURSTS AND THE COUPLING OF SATURN'S <span class="hlt">EQUATORIAL</span> STORMS AND INTERIOR ROTATION</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Heimpel, Moritz; Aurnou, Jonathan M. E-mail: aurnou@ucla.edu</p> <p>2012-02-10</p> <p>Temporal variations of Saturn's <span class="hlt">equatorial</span> jet and magnetic field hint at rich dynamics coupling the atmosphere and the deep interior. However, it has been assumed that rotation of the interior dynamo must be steady over tens of years of modern observations. Here we use a numerical convection model and scaling estimates to show how <span class="hlt">equatorial</span> convective bursts can transfer angular momentum to the deeper interior. The numerical model allows angular momentum transfer between a fluid outer spherical shell and a rigid inner sphere. Convection drives a prograde <span class="hlt">equatorial</span> jet exhibiting quasiperiodic bursts that fill the <span class="hlt">equatorial</span> volume outside the tangent cylinder. For each burst strong changes in the <span class="hlt">equatorial</span> surface velocity are associated with retrograde torque on the inner sphere. Our results suggest that Saturn's Great White Spot, a giant storm that was observed to fill the <span class="hlt">equatorial</span> region in 1990, could mobilize a volume of fluid carrying roughly 15% of Saturn's moment of inertia. Conservation of angular momentum then implies that a 20% change in the <span class="hlt">equatorial</span> jet angular velocity could change the average interior rotation rate by about 0.1%-roughly an order of magnitude less than the apparent rotation rate changes associated with Saturn's kilometric radio (SKR) signal. However, if the SKR signal originates outside the liquid metal core in a 'planetary tachocline' that separates the layer of fast zonal flow from the magnetically controlled and slowly convecting deep interior, then convective bursts can provide a possible mechanism for the observed {approx}1% SKR changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960003094','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960003094"><span>The streaming-trapped ion interface in the <span class="hlt">equatorial</span> inner magnetosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lin, J.; Horwitz, J. L.; Gallagher, D.; Pollock, C. J.</p> <p>1994-01-01</p> <p>Spacecraft measurements of core ions on L=4-7 field-lines typically show trapped ion distributions near the magnetic equator, and frequently indicate field-aligned ion streams at higher latitudes. The nature of the transition between them may indicate both the microphysics of hot-cold plasma interactions and overall consequences for core plasma evolution. We have undertaken a statistical analysis and characterization of this interface and its relation to the <span class="hlt">equatorial</span> region of the inner magnetosphere. In this analysis, we have characterized such features as the <span class="hlt">equatorial</span> ion flux anisotropy, the penetration of field-aligned ionospheric streams into the <span class="hlt">equatorial</span> region, the scale of the transition into trapped ion populations, and the transition latitude. We found that most transition latitudes occur within 13 deg of the equator. The typical values of <span class="hlt">equatorial</span> ion anisotropies are consistent with bi-Maxwellian temperature ratios of T(sub perpendicular)/T(sub parallel) in the range of 3-5. The latitudinal scales for the edges of the trapped ion populations display a rather strong peak in the 2-3 deg range. We also found that there is a trend for the penetration ratio, the anisotropy half width, and the transition scale length to decrease with a higher <span class="hlt">equatorial</span> ion anisotropy. We may interpret these features in terms of Liouville mapping of <span class="hlt">equatorially</span> trapped ions and the reflection of the incoming ionospheric ion streams from the <span class="hlt">equatorial</span> potential peaks associated with such trapped ions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PNAS..113.6119W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PNAS..113.6119W"><span>Ocean dynamics, not dust, have controlled <span class="hlt">equatorial</span> Pacific productivity over the past 500,000 years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Winckler, Gisela; Anderson, Robert F.; Jaccard, Samuel L.; Marcantonio, Franco</p> <p>2016-05-01</p> <p>Biological productivity in the <span class="hlt">equatorial</span> 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 <span class="hlt">Equatorial</span> Undercurrent to the surface. The <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> Pacific, upwelling of water from the <span class="hlt">Equatorial</span> 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 <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> Pacific productivity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4896667','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4896667"><span>Ocean dynamics, not dust, have controlled <span class="hlt">equatorial</span> Pacific productivity over the past 500,000 years</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Winckler, Gisela; Anderson, Robert F.; Jaccard, Samuel L.; Marcantonio, Franco</p> <p>2016-01-01</p> <p>Biological productivity in the <span class="hlt">equatorial</span> 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 <span class="hlt">Equatorial</span> Undercurrent to the surface. The <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> Pacific, upwelling of water from the <span class="hlt">Equatorial</span> 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 <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> Pacific productivity. PMID:27185933</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017OcDyn..67..857S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017OcDyn..67..857S"><span>Interannual variability of zonal currents in the <span class="hlt">equatorial</span> Indian Ocean: respective control of IOD and ENSO</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sachidanandan, Chinnu; Lengaigne, Matthieu; Muraleedharan, Pillathu Moolayil; Mathew, Basil</p> <p>2017-07-01</p> <p>The observational record is too short to confidently differentiate the relative contributions of Indian Ocean Dipole (IOD) and El Niño-Southern Oscillation (ENSO) on the interannual variability of the <span class="hlt">equatorial</span> current system in the Indian Ocean because of the strong tendency of these two modes to co-occur. In this study, we analyse a five-decade simulation from an ocean general circulation model forced to describe the main interannual variations of surface and subsurface <span class="hlt">equatorial</span> zonal currents in the Indian Ocean. This simulation is first shown to accurately capture the surface and subsurface zonal current variations in the <span class="hlt">equatorial</span> region derived from the available observations. Through an EOF analysis on the model outputs, our results further reveals two main modes of <span class="hlt">equatorial</span> current interannual variability: a dominant mode with largest amplitude in fall largely describing the variability of the fall Wyrtki jet intensity followed a few months later by a secondary mode maximum in winter largely describing the interannual variability of the subsurface currents in that season. Our analysis further confirms that the IOD is largely responsible for the interannual modulation of fall Wyrtki jet intensity by modulating the <span class="hlt">equatorial</span> wind intensity during that season. The IOD is also responsible for strong subsurface current variations until December, induced by the delayed effect of the IOD wind signal onto the <span class="hlt">equatorial</span> thermocline tilt. The <span class="hlt">equatorial</span> current system response to ENSO is weaker and delayed compared to that of the IOD. The remote and delayed impact of ENSO in the IO indeed induces <span class="hlt">equatorial</span> wind variations in winter that modulate the winter surface current intensity and the spring <span class="hlt">equatorial</span> undercurrent intensity through its delayed impact on the thermocline tilt.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993graz.iafcS....C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993graz.iafcS....C"><span>A space system integrating earth observation and mobile communications for <span class="hlt">equatorial</span> remote areas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ceballos, Decio C.</p> <p>1993-10-01</p> <p>The integration of two constellations of light and low-cost satellites, the <span class="hlt">Equatorial</span> Communications (ECO) system and a polar orbit system for World Observation and Monitoring (WOM), is proposed. The WOM involves eight satellites and portable data reception and processing equipment. Onboard data compression enables UHF transmission of earth observation data. A system for global coverage with a temporal result of two passes per day is proposed. The ECO involves eight satellites in an <span class="hlt">equatorial</span> constellation at 2000 mm. This system can supply low-orbit communications for <span class="hlt">equatorial</span> countries and assist in the daily monitoring of ecologically protected areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JESS..126...19B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JESS..126...19B"><span>Variable influence on the <span class="hlt">equatorial</span> troposphere associated with SSW using ERA-Interim</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bal, Sourabh; Schimanke, Semjon; Spangehl, Thomas; Cubasch, Ulrich</p> <p>2017-03-01</p> <p>Sudden stratospheric warming (SSW) events are identified to investigate their influence on the <span class="hlt">equatorial</span> tropospheric climate. Composite analysis of warming events from Era-Interim (1979-2013) record a cooling of the tropical lower stratosphere with corresponding changes in the mean meridional stratospheric circulation. A cooling of the upper troposphere induces enhanced convective activity near the <span class="hlt">equatorial</span> region of the Southern Hemisphere and suppressed convective activity in the off-<span class="hlt">equatorial</span> Northern Hemisphere. After selecting vortex splits, the see-saw pattern of convective activity in the troposphere grows prominent and robust.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/86354','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/86354"><span>Longitudinal variation of sudden commencement of geomagnetic storm at <span class="hlt">equatorial</span> stations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rastogi, R.G.</p> <p>1993-09-01</p> <p>The author reports the observation of a correlation between the strength of storm sudden commencements in the <span class="hlt">equatorial</span> electrojet region with the <span class="hlt">equatorial</span> electrojet current itself, as a function of daytime, latitude, and longitude. The author argues that electric fields generated at the magnetopause by interaction with solar wind plasma transmits to the polar region along field lines, and there converts to magnetic waves which rapidly propogate to <span class="hlt">equatorial</span> regions in the conducting plasma between the ionosphere and the earth. The strength of the arrival fields is dependent upon the ionospheric conductivity at the particular location in question.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930054671&hterms=effect+consideration&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Deffect%2Bconsideration%2527','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930054671&hterms=effect+consideration&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Deffect%2Bconsideration%2527"><span>Considerations of variations in ionospheric field effects in mapping <span class="hlt">equatorial</span> lithospheric Magsat magnetic anomalies</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ravat, D.; Hinze, W. J.</p> <p>1993-01-01</p> <p>The longitudinal, seasonal, and altitude-dependent variability of the magnetic field in <span class="hlt">equatorial</span> latitudes is investigated to determine the effect of these variabilities on the isolation of lithospheric Magsat magnetic anomalies. It was found that the amplitudes of the dawn dip-latitude averages were small compared to the dusk averages, and that they were of the opposite sign. The longitudinal variation in the <span class="hlt">equatorial</span> amplitudes of the dawn dip-latitude averages was not entirely consistent with the present knowledge of the electrojet field. Based on the results, a procedure is implemented for reducing the <span class="hlt">equatorial</span> ionospheric effects from the Magsat data on the lithospheric component.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007DSRII..54..496F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007DSRII..54..496F"><span>Modeling carbon and silicon cycling in the <span class="hlt">equatorial</span> Pacific</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fujii, Masahiko; Chai, Fei</p> <p>2007-03-01</p> <p>The <span class="hlt">equatorial</span> Pacific is a region of significant particulate inorganic carbon (PIC) and biogenic silica sedimentation, the majority of which is carried out by coccolithophorids and diatoms. We developed an ecosystem model that explicitly includes three phytoplankton functional groups (picoplankton, coccolithophorids, and diatoms), two zooplankton functional groups (microzooplankton and mesozooplankton), nutrients (nitrate NO 3, ammonium NH 4, and silicate Si(OH) 4), detritus (particulate organic matter, biogenic silica, and PIC), total alkalinity, total CO 2, and partial pressure of CO 2 at the surface water (pCO 2sea). The model is capable of reproducing many biogeochemical features for the region, such as high-nutrient low-chlorophyll condition, significant exposure of phytoplankton under grazing controls by zooplankton, and large CO 2 release to the atmosphere. The export ratio of PIC to particulate organic carbon (rain ratio) to the deep water was 0.16, higher than the global-mean values, implying predominant PIC sedimentation in the <span class="hlt">equatorial</span> Pacific upwelling region. Comparison between calcification and no-calcification model results indicates that when coccolithophorids are present, the community interactions actually induce more diatom biomass, export fluxes of detritus, and CO 2 release to the atmosphere. The model results show remarkable calcification in the subsurface layers, which suggests more field data on calcification processes are needed. Increase of source (120 m depth) Si(OH) 4 concentration associated with the tropical instability waves lead to a linear increase in biogenic silica export. Higher Si(OH) 4 concentration stimulates diatom growth, which causes a decrease in picoplankton because feeding pressure by mesozooplankton switched from picoplankton's grazer, microzooplankton, to the abundant diatoms. Surface coccolithophorid biomass has its maximum at intermediate source Si(OH) 4 concentrations as a result of higher grazing pressure on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMSA14A..02B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMSA14A..02B"><span>DEMETER Observations of <span class="hlt">Equatorial</span> Plasma Depletions and Related Ionospheric Phenomena</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Berthelier, J.; Malingre, M.; Pfaff, R.; Jasperse, J.; Parrot, M.</p> <p>2008-12-01</p> <p>DEMETER, the first micro-satellite of the CNES MYRIAD program, was launched from Baikonour on June 29, 2004 on a nearly circular, quasi helio-synchronous polar orbit at ~ 715 km altitude. The DEMETER mission focuses primarily on the search for a possible coupling between seismic activity and ionospheric disturbances as well as on the effects of natural phenomena such as tropospheric thunderstorms and man-made activities on the ionosphere. The scientific payload provides fairly complete measurements of the ionospheric plasma, energetic particles above ~ 70 keV, and plasma waves, up to 20 kHz for the magnetic and 3.3 MHz for the electric components. Several studies related to space weather and ionospheric physics have been conducted over the past years. Following a brief description of the payload and the satellite modes of operation, this presentation will focus on a set of results that provide a new insight into the physics of instabilities in the night-time <span class="hlt">equatorial</span> ionosphere. The observations were performed during the major magnetic storm of November 2004. Deep plasma depletions were observed on several night-time passes at low latitudes characterized by the decrease of the plasma density by nearly 3 orders of magnitude relative to the undisturbed plasma, and a significant abundance of molecular ions. These features can be best interpreted as resulting from the rise of the F-layer above the satellite altitude over an extended region of the ionosphere. In one of the passes, DEMETER was operated in the Burst mode and the corresponding high resolution data allowed for the discovery of two unexpected phenomena. The first one is the existence of high intensity monochromatic wave packets at the LH frequency that develop during the decay phase of intense bursts of broadband LH turbulence. The broadband LH turbulence is triggered by whistlers emitted by lightning from atmospheric thunderstorms beneath the satellite. The second unexpected feature is the detection of a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A12D..04Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A12D..04Z"><span>Characteristics of Extreme Summer Convection over <span class="hlt">equatorial</span> America and Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zuluaga, M. D.; Houze, R.</p> <p>2013-12-01</p> <p>Fourteen years of Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) version 7 data for June-August show the temporal and spatial characteristics of extreme convection over <span class="hlt">equatorial</span> regions of the American and African continents. We identify three types of extreme systems: storms with deep convective cores (contiguous convective 40 dBZ echoes extending ≥10 km in height), storms with wide convective cores (contiguous convective 40 dBZ echoes with areas >1,000 km2) and storms with broad stratiform regions (stratiform echo >50,000 km2). European Centre for Medium-Range Weather Forecast (ECMWF) reanalysis is used to describe the environmental conditions around these forms of extreme convection. Storms with deep convective cores occur mainly over land: in the <span class="hlt">equatorial</span> Americas, maximum occurrence is in western Mexico, Northern Colombia and Venezuela; in Africa, the region of maximum occurrence is a broad zone enclosing the central and west Sudanian Savanna, south of the Sahel region. Storms with wide convective radar echoes occur in these same general locations. In the American sector, storms with broad stratiform precipitation regions (typifying robust mesoscale convective systems) occur mainly over the eastern tropical Pacific Ocean and the Colombia-Panama bight. In the African sector, storms with broad stratiform precipitation areas occur primarily over the eastern tropical Atlantic Ocean near the coast of West Africa. ECMWF reanalyses show how the regions of extreme deep convection associated with both continents are located mainly in regions affected by diurnal heating and influenced by atmospheric jets in regions with strong humidity gradients. Composite analysis of the synoptic conditions leading to the three forms of extreme convection provides insights into the forcing mechanisms in which these systems occur. These analyses show how the monsoonal flow directed towards the Andes slopes is mainly what concentrates the occurrence of extreme</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080044786&hterms=Radioactivity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DRadioactivity','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080044786&hterms=Radioactivity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DRadioactivity"><span>Iapetus' Geophysics: Rotation Rate, Shape, and <span class="hlt">Equatorial</span> Ridge</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Castillo-Rogez, J. C.; Matson, D. L.; Sotin, C.; Johnson, T. V.; Lunine, J. I.; Thomas, P. C.</p> <p>2007-01-01</p> <p>Iapetus has preserved evidence that constrains the modeling of its geophysical history from the time of its accretion until now. The evidence is (a) its present 79.33-day rotation or spin rate, (b) its shape that corresponds to the equilibrium figure for a hydrostatic body rotating with a period of approximately 16 h, and (c) its high, <span class="hlt">equatorial</span> ridge, which is unique in the Solar System. This paper reports the results of an investigation into the coupling between Iapetus' thermal and orbital evolution for a wide range of conditions including the spatial distributions with time of composition, porosity, short-lived radioactive isotopes (SLRI), and temperature. The thermal model uses conductive heat transfer with temperature-dependent conductivity. Only models with a thick lithosphere and an interior viscosity in the range of about the water ice melting point can explain the observed shape. Short-lived radioactive isotopes provide the heat needed to decrease porosity in Iapetus? early history. This increases thermal conductivity and allows the development of the strong lithosphere that is required to preserve the 16-h rotational shape and the high vertical relief of the topography. Long-lived radioactive isotopes and SLRI raise internal temperatures high enough that significant tidal dissipation can start, and despin Iapetus to synchronous rotation. This occurred several hundred million years after Iapetus formed. The models also constrain the time when Iapetus formed because the successful models are critically dependent upon having just the right amount of heat added by SLRI decay in this early period. The amount of heat available from short-lived radioactivity is not a free parameter but is fixed by the time when Iapetus accreted, by the canonical concentration of Al-26, and, to a lesser extent, by the concentration of Fe-60. The needed amount of heat is available only if Iapetus accreted between 2.5 and 5.0Myr after the formation of the calcium aluminum</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3785506','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3785506"><span>Priority Areas for Large Mammal Conservation in <span class="hlt">Equatorial</span> Guinea</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Murai, Mizuki; Ruffler, Heidi; Berlemont, Antoine; Campbell, Genevieve; Esono, Fidel; Agbor, Anthony; Mbomio, Domingo; Ebana, Agustín; Nze, Antonio; Kühl, Hjalmar S.</p> <p>2013-01-01</p> <p>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, <span class="hlt">Equatorial</span> 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 <span class="hlt">Equatorial</span> Africa, and we recommend a focus on cross-boundary conservation, in particular in the Monte Alén-Monts de Cristal and R</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18509441','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18509441"><span>Snowball Earth termination by destabilization of <span class="hlt">equatorial</span> permafrost methane clathrate.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kennedy, Martin; Mrofka, David; von der Borch, Chris</p> <p>2008-05-29</p> <p>The start of the Ediacaran period is defined by one of the most severe climate change events recorded in Earth history--the recovery from the Marinoan 'snowball' ice age, approximately 635 Myr ago (ref. 1). Marinoan glacial-marine deposits occur at <span class="hlt">equatorial</span> palaeolatitudes, and are sharply overlain by a thin interval of carbonate that preserves marine carbon and sulphur isotopic excursions of about -5 and +15 parts per thousand, respectively; these deposits are thought to record widespread oceanic carbonate precipitation during postglacial sea level rise. This abrupt transition records a climate system in profound disequilibrium and contrasts sharply with the cyclical stratigraphic signal imparted by the balanced feedbacks modulating Phanerozoic deglaciation. Hypotheses accounting for the abruptness of deglaciation include ice albedo feedback, deep-ocean out-gassing during post-glacial oceanic overturn or methane hydrate destabilization. Here we report the broadest range of oxygen isotope values yet measured in marine sediments (-25 per thousand to +12 per thousand) in methane seeps in Marinoan deglacial sediments underlying the cap carbonate. This range of values is likely to be the result of mixing between ice-sheet-derived meteoric waters and clathrate-derived fluids during the flushing and destabilization of a clathrate field by glacial meltwater. The <span class="hlt">equatorial</span> palaeolatitude implies a highly volatile shelf permafrost pool that is an order of magnitude larger than that of the present day. A pool of this size could have provided a massive biogeochemical feedback capable of triggering deglaciation and accounting for the global postglacial marine carbon and sulphur isotopic excursions, abrupt unidirectional warming, cap carbonate deposition, and a marine oxygen crisis. Our findings suggest that methane released from low-latitude permafrost clathrates therefore acted as a trigger and/or strong positive feedback for deglaciation and warming. Methane hydrate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000SPD....31.0502L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000SPD....31.0502L"><span><span class="hlt">Equatorial</span> Rossby Waves and Periodicities of Flare Activities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lou, Y.-Q.</p> <p>2000-05-01</p> <p>The Gamma-Ray Spectrometer (GRS) aboard the Solar Maximum Mission (SMM) first revealed a 154-day periodicity in solar flare rates. Subsequently, periodicities in various solar flare activities and sunspot areas or groups during a few years around solar maxima have been extensively monitored using different diagnostics and at many electromagnetic wavelengths. Notable periods are ~ 154, 128, 102, 78 and 51 days during maxima of different solar cycles from various data sets. The origin of such long-time periodicities particularly prominent during solar maxima remains a mystery for nearly two decades. For slow and large-scale photospheric dynamics, the shallow magnetofluid approximation can be invoked when the Rossby number R0≡ U/(2Ω sun L) is small, where U (< ~ 103 cm s-1) and L (≳ Rsun) are typical horizontal velocity and spatial scales. Physical properties of <span class="hlt">equatorially</span> trapped Kelvin waves, Poincaré waves, Rossby waves and mixed Rossby-Poincaré waves are examined. For typical solar parameters, period estimates of Rossby and mixed Rossby-Poincaré waves are ~ 151-155, 126-127, 101-102, 76-78 and 51-54 days in good agreement with inferred periodicities. The effect of large-scale subsurface magnetic fields is estimated. Two methods (i.e., surface velocity correlations and precise diameter measurements) of directly detecting <span class="hlt">equatorially</span> trapped solar Rossby-type waves are emphasized. Plausible connections among the large-scale photospheric wave dynamics, Rossby radius of deformation, sunspot zones, subsurface magnetic fields, magnetic flux emergence, active regions and solar flare activities are discussed. The scenario of a dynamic feedback cycle is advanced for excitations of these low-frequency Rossby-type waves during solar maxima. It would be of considerable interest to examine whether large-scale coronal mass ejections also carry the similar periodicities in the current solar maximum using SOHO observations. This work was supported in part by grants of</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080044786&hterms=Radioactivity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DRadioactivity','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080044786&hterms=Radioactivity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DRadioactivity"><span>Iapetus' Geophysics: Rotation Rate, Shape, and <span class="hlt">Equatorial</span> Ridge</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Castillo-Rogez, J. C.; Matson, D. L.; Sotin, C.; Johnson, T. V.; Lunine, J. I.; Thomas, P. C.</p> <p>2007-01-01</p> <p>Iapetus has preserved evidence that constrains the modeling of its geophysical history from the time of its accretion until now. The evidence is (a) its present 79.33-day rotation or spin rate, (b) its shape that corresponds to the equilibrium figure for a hydrostatic body rotating with a period of approximately 16 h, and (c) its high, <span class="hlt">equatorial</span> ridge, which is unique in the Solar System. This paper reports the results of an investigation into the coupling between Iapetus' thermal and orbital evolution for a wide range of conditions including the spatial distributions with time of composition, porosity, short-lived radioactive isotopes (SLRI), and temperature. The thermal model uses conductive heat transfer with temperature-dependent conductivity. Only models with a thick lithosphere and an interior viscosity in the range of about the water ice melting point can explain the observed shape. Short-lived radioactive isotopes provide the heat needed to decrease porosity in Iapetus? early history. This increases thermal conductivity and allows the development of the strong lithosphere that is required to preserve the 16-h rotational shape and the high vertical relief of the topography. Long-lived radioactive isotopes and SLRI raise internal temperatures high enough that significant tidal dissipation can start, and despin Iapetus to synchronous rotation. This occurred several hundred million years after Iapetus formed. The models also constrain the time when Iapetus formed because the successful models are critically dependent upon having just the right amount of heat added by SLRI decay in this early period. The amount of heat available from short-lived radioactivity is not a free parameter but is fixed by the time when Iapetus accreted, by the canonical concentration of Al-26, and, to a lesser extent, by the concentration of Fe-60. The needed amount of heat is available only if Iapetus accreted between 2.5 and 5.0Myr after the formation of the calcium aluminum</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMSA43C..06C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMSA43C..06C"><span>GPS Observations of Plasma Bubbles and Scintillations over <span class="hlt">Equatorial</span> Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>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.</p> <p>2010-12-01</p> <p>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 <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016cosp...41E1482O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016cosp...41E1482O"><span>Investigation of plasma motion in the <span class="hlt">equatorial</span> ionosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oyekola, Oyedemi S.</p> <p>2016-07-01</p> <p>The structure of evening and nighttime F-region vertical drift component of is vital for understanding the physics of the development of the occurrence of <span class="hlt">equatorial</span> irregularities. In addition, postsunset ionospheric height has also been attributed as one of the most important factors for the occurrence of <span class="hlt">equatorial</span> irregularities. We report vertical plasma drift velocities derived from the base (h'F) and the peak height (hmF2) of F-layer using 1-year of data obtained at Ibadan (Geog Long 3.9oE) during International Geophysical Year (1957-58) period for geomagnetic quiet-time and high solar activity conditions. We compared our results with International Reference Ionosphere 2012 model (IRI-2012). The results of this investigation include: (a) overall local- time characteristics of vertical drift between 1800 LT and 0600 LT are in good agreement for equinoxes, December, and June; (b) annual vertical drift derived from time variation of h'F and hmF2 and the corresponding annual variation of h'F and hmF2 variation indicate low correlation (R = 0.30), while IRI-2012 model vertical drift and IRI-2012 model of hmF2 show fairly good correlation ( R = 0.67); (c) regression analysis between time variation of h'F and Scherliess / Fejer model demonstrate correlation coefficient of approximately 0.74 (equinox), 0.85 (December), 0.57 (June) and 0.74 (all-year), while that of time variation of hmF2 and IRI-2012 vertical velocities show 0.95 (equinox), 0.74 (December), 0.43 (June), and 0.74 (all-year); (d) plasma motion derived from the time rate of change of h'F and those of hmF2 are correlated at 0.94, 0.88, 0.63, and 0.90 for equinoxes, December, June, and all-year, respectively; (e) the evening prereversal vertical drifts enhancement rage between ~20 - 45 m/s, ~18 - 46 m/s, ~20 - 50 m/s for time variation of h'F, hmF2, and Scherliess / Fejer model, respectively; (f) the corresponding peak altitudes vary between 430 - 540 km (h'F), 560 - 740 km ( hmF2), and 570 - 620 km (IRI</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994ThApC..49...27D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994ThApC..49...27D"><span>Persistence in rainfall occurrence over Tropical south-east Asia and <span class="hlt">equatorial</span> Pacific</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dahale, S. D.; Panchawagh, N.; Singh, S. V.; Ranatunge, E. R.; Brikshavana, M.</p> <p>1994-03-01</p> <p>Daily rainfall observations during the principal rainy seasons over a large part of Tropical Asia and the <span class="hlt">equatorial</span> Pacific are analysed for persistence by fitting Markov chains of various order. Daily rainfall data of 98 stations from India, Sri Lanka and Thailand falling in the monsoonal regime and 9 stations in the non-monsoonal regime of the <span class="hlt">equatorial</span> Pacific are examined. The appropriate order of Markov chain is determined by analyzing wet and dry spell length characteristics and by applying the Schwarz Baysian Criterion to the arbitrary sequences of 5-day length. Markov chains of order greater than 1 are found to characterize the persistence in rainfall over India and to some extent over wet zones of Sri Lanka and central <span class="hlt">equatorial</span> Pacific. Simple Markov chains are suggested for Thailand, the dry zone of Sri Lanka and the stations of central <span class="hlt">equatorial</span> Pacific lying some what away from the equator.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720024769','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720024769"><span>Provisional hourly values of <span class="hlt">equatorial</span> Dst for January to June 1972</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sugiura, M.; Poros, D. J.</p> <p>1972-01-01</p> <p>Provisional hourly values of <span class="hlt">equatorial</span> atmospheric radiation conditions for the period January to June 1972 were obtained. The data are presented in numerical tables with graphical presentation of the digital data included.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/9367955','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/9367955"><span>Insolation cycles as a major control of <span class="hlt">equatorial</span> indian ocean primary production</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Beaufort; Lancelot; Camberlin; Cayre; Vincent; Bassinot; Labeyrie</p> <p>1997-11-21</p> <p>Analysis of a continuous sedimentary record taken in the Maldives indicates that strong primary production fluctuations (70 to 390 grams of carbon per square meter per year) have occurred in the <span class="hlt">equatorial</span> Indian Ocean during the past 910,000 years. The record of primary production is coherent and in phase with the February <span class="hlt">equatorial</span> insolation, whereas it shows diverse phase behavior with delta18O, depending on the orbital frequency (eccentricity, obliquity, or precession) examined. These observations imply a direct control of productivity in the <span class="hlt">equatorial</span> oceanic system by insolation. In the <span class="hlt">equatorial</span> Indian Ocean, productivity is driven by the wind intensity of westerlies, which is related to the Southern Oscillation; therefore, it is suggested that a precession forcing on the Southern Oscillation is responsible for the observed paleoproductivity dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060037487&hterms=fishbein&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dfishbein','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060037487&hterms=fishbein&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dfishbein"><span>Temperature and Wind Variations in the <span class="hlt">Equatorial</span> Stratosphere: Instability and the Semiannual Oscillation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Elson, L. S.; Fishbein, E. F.; Waters, J. W.</p> <p>1995-01-01</p> <p>UARS Microwave Limb Sounder data and data from the UK meteorological Office indicate that the <span class="hlt">equatorial</span> zonal mean temperature exhibits a cold anomaly symmetric about the equator, typically lasting 10-20 days and with changes of about 12 K.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920038623&hterms=productivity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dproductivity','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920038623&hterms=productivity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dproductivity"><span>Measurements of nitrogen productivity in the <span class="hlt">equatorial</span> Pacific</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilkerson, Frances P.; Dugdale, Richard C.</p> <p>1992-01-01</p> <p>During the R/V Wecoma WEC88 cruise that sampled a meridional transect along 150 deg W from 15 deg N to 15 deg S, uptake of nitrate and ammonium by phytoplankton was measured using the stable isotope N-15 with simulated in-situ bottle incubations and shipboard mass spectrometry. A set of 25 daily productivity stations showed the influence of <span class="hlt">equatorial</span> upwelling on nitrate distribution and N-15 uptake in a band from 6 deg N to 7.5 deg S compared with the oligotrophic waters to the north and south, with the highest values of nitrate uptake occurring at the equator. During a 5-day time series at the equator, there was an increase in nitrate accompanied by increased nitrate uptake. Interestingly, nitrate uptake rates (equivalent to new production rates) at the equator were lower than those predicted by previous investigators. Holdover experiments and uptake versus irradiance curves showed that the phytoplankton was in an early stage of metabolic adaptation and that can be a contributing factor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012MNRAS.422L..11P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012MNRAS.422L..11P"><span>Ubiquitous <span class="hlt">equatorial</span> accretion disc winds in black hole soft states</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ponti, G.; Fender, R. P.; Begelman, M. C.; Dunn, R. J. H.; Neilsen, J.; Coriat, M.</p> <p>2012-05-01</p> <p>High-resolution spectra of Galactic black holes (GBHs) reveal the presence of highly ionized absorbers. In one GBH, accreting close to the Eddington limit for more than a decade, a powerful accretion disc wind is observed to be present in softer X-ray states and it has been suggested that it can carry away enough mass and energy to quench the radio jet. Here we report that these winds, which may have mass outflow rates of the order of the inner accretion rate or higher, are a ubiquitous component of the jet-free soft states of all GBHs. We furthermore demonstrate that these winds have an <span class="hlt">equatorial</span> geometry with opening angles of few tens of degrees, and so are only observed in sources in which the disc is inclined at a large angle to the line of sight. The decrease in Fe XXV/Fe XXVI line ratio with Compton temperature, observed in the soft state, suggests a link between higher wind ionization and harder spectral shapes. Although the physical interaction between the wind, accretion flow and jet is still not fully understood, the mass flux and power of these winds and their presence ubiquitously during the soft X-ray states suggest they are fundamental components of the accretion phenomenon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2251778L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2251778L"><span>Measuring the <span class="hlt">equatorial</span> plasma bubble drift velocities over Morroco</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lagheryeb, Amine; Benkhaldoun, Zouhair; Makela, Jonathan J.; Harding, Brian; Kaab, Mohamed; Lazrek, Mohamed; Fisher, Daniel J.; Duly, Timothy M.; Bounhir, Aziza; Daassou, Ahmed</p> <p>2015-08-01</p> <p>In this work, we present a method to measure the drift velocities of <span class="hlt">equatorial</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930013949','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930013949"><span>Annual and longitudinal variations of the Pacific North <span class="hlt">Equatorial</span> Countercurrent</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lolk, Nina K.</p> <p>1992-01-01</p> <p>The climatological annual cycle of the Pacific North <span class="hlt">Equatorial</span> Countercurrent (NECC) simulated by an ocean general circulation model (OGCM) was studied. The longitudinal variation of transports, degree of geostrophy, and the relationship between Ekman pumping and vertical displacement of the thermocline were emphasized. The longitudinal variation was explored using six sections along 150 deg E, 180 deg, 160 deg W, 140 deg W, 125 deg W, and 110 deg W. A primitive equation OGCM of the Pacific Ocean was run for three years and the fields used were from the third year. The fields consisted of zonal, meridional, and vertical current components and temperature and salinity averaged every three days. The model was forced with the Hellerman and Rosenstein climatological wind stress. The mean annual eastward transport (19.9 Sv) was largest at 160 deg W. The maximum-current boundaries along 160 deg W were 9.2 deg N (1.0 deg), 5.1 deg N (1.1 deg), and 187 m (90.6 m). The annual-cycle amplitude of the NECC was greatest between 160 deg W and 140 deg W. Although the NECC is geostrophic to the first order, deviations from geostrophy were found in the boreal spring and summer near the southern boundary and near the surface. Meridional local acceleration played a role between 3 deg N-5 deg N.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4510698','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4510698"><span>Observations of discrete harmonics emerging from <span class="hlt">equatorial</span> noise</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Balikhin, Michael A.; Shprits, Yuri Y.; Walker, Simon N.; Chen, Lunjin; Cornilleau-Wehrlin, Nicole; Dandouras, Iannis; Santolik, Ondrej; Carr, Christopher; Yearby, Keith H.; Weiss, Benjamin</p> <p>2015-01-01</p> <p>A number of modes of oscillations of particles and fields can exist in space plasmas. Since the early 1970s, space missions have observed noise-like plasma waves near the geomagnetic equator known as ‘<span class="hlt">equatorial</span> noise'. Several theories were suggested, but clear observational evidence supported by realistic modelling has not been provided. Here we report on observations by the Cluster mission that clearly show the highly structured and periodic pattern of these waves. Very narrow-banded emissions at frequencies corresponding to exact multiples of the proton gyrofrequency (frequency of gyration around the field line) from the 17th up to the 30th harmonic are observed, indicating that these waves are generated by the proton distributions. Simultaneously with these coherent periodic structures in waves, the Cluster spacecraft observes ‘ring' distributions of protons in velocity space that provide the free energy for the waves. Calculated wave growth based on ion distributions shows a very similar pattern to the observations. PMID:26169360</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP14A..02D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP14A..02D"><span>Inferring Past Climate in <span class="hlt">Equatorial</span> East Africa using Glacier Models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Doughty, A. M.; Kelly, M. A.; Anderson, B.; Russell, J. M.; Jackson, M. S.</p> <p>2016-12-01</p> <p>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 <span class="hlt">equatorial</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999JGR...104.3297V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999JGR...104.3297V"><span>Diel variability of photosynthetic picoplankton in the <span class="hlt">equatorial</span> Pacific</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vaulot, Daniel; Marie, Dominique</p> <p>1999-02-01</p> <p>The diel variability in cell abundance, light scatter, and pigment fluorescence of three autotrophic picoplankton groups (Prochlorococcus, Synechococcus, picoeukaryotes) measured by flow cytometry was investigated in surface waters of the <span class="hlt">equatorial</span> Pacific Ocean (5°S, 150°W) during 5 days with about 1 hour temporal resolution. The diel variability of vertical profiles was examined at the same station on days 2 and 4. Prochlorococcus division rate was also estimated from cell cycle measurements. A more limited data set was obtained at a station located in very oligotrophic waters (16°S, 150°W). All three picoplankton populations exhibited very marked diel variability. Cell division was highly synchronized but not phased identically for all three populations: Synechococcus divided first, followed 2 hours later by Prochlorococcus and 7 hours later by picoeukaryotes. Cells grew in size only once the sun had risen, but growth did continue in the dark for a short period. Growth processes occurred in parallel at the top and the bottom of the mixed layer, inducing uniform profiles for cell abundance and scatter. For chlorophyll fluorescence, in contrast, prokaryotes displayed opposite patterns during the light period between surface (decrease due to very strong quenching) and depth (increase). This created steep vertical gradients during the day that vanished at night because of convective mixing. In the top 25 m, strong light intensities (including UV radiation) had very pronounced detrimental effects on prokaryotes, especially on Prochlorococcus, inducing fluorescence quenching, slowed down growth, and retardation of DNA synthesis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PrOce.134..256F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PrOce.134..256F"><span>Anthropogenic CO2 changes in the <span class="hlt">Equatorial</span> Atlantic Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fajar, N. M.; Guallart, E. F.; Steinfeldt, R.; Ríos, A. F.; Pelegrí, J. L.; Pelejero, C.; Calvo, E.; Pérez, F. F.</p> <p>2015-05-01</p> <p>Methods based on CO2 and chlorofluorocarbon (CFC) data are used to describe and evaluate the anthropogenic CO2 (Cant) concentrations, Cant specific inventories, and Cant storage rates in the <span class="hlt">Equatorial</span> Atlantic Ocean. The Cant variability in the water masses is evaluated from the comparison of two hydrographic sections along 7.5°N carried out in 1993 and 2010. During both cruises, high Cant concentrations are detected in the upper layers, with values decreasing progressively towards the deep layers. Overall, the Cant concentrations increase from 1993 to 2010, with a large increment in the upper North Atlantic Deep Water layer of about 0.18 ± 0.03 μmol kg-1 y-1. In 2010, the Cant inventory along the whole section amounts to 58.9 ± 2.2 and 45.1 ± 2.0 mol m-2 using CO2 and CFC based methods, respectively, with most Cant accumulating in the western basin. Considering the time elapsed between the two cruises, Cant storage rates of 1.01 ± 0.18 and 0.75 ± 0.17 mol m-2 y-1 (CO2 and CFC based methods, respectively) are obtained. Below ∼1000 m, these rates follow the pace expected from a progressive increase of Cant at steady state; above ∼1000 m, Cant increases faster, mainly due to the retreat of the Antarctic Intermediate Waters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992JGR....97..669W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992JGR....97..669W"><span>Measurements of nitrogen productivity in the <span class="hlt">equatorial</span> Pacific</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wilkerson, Frances P.; Dugdale, Richard C.</p> <p>1992-01-01</p> <p>During the R/V Wecoma WEC88 cruise that sampled a meridional transect along 150°W from 15°N to 15°S, uptake of nitrate and ammonium by phytoplankton was measured using the stable isotope 15N with simulated in situ bottle incubations and shipboard mass spectrometry. A set of 25 daily productivity stations showed the influence of <span class="hlt">equatorial</span> upwelling on nitrate distribution and 15N uptake in a band from 6°N to 7.5°S compared with the oligotrophic waters to the north and south, with the highest values of nitrate uptake occurring at the equator (0.14 mg-at. m-2 h-1). During a 5-day time series at the equator, there was an increase in nitrate accompanied by increased nitrate uptake. Interestingly, nitrate uptake rates (equivalent to new production rates) at the equator were lower than those predicted by previous investigators. Holdover experiments and uptake versus irradiance curves showed that the phytoplankton there were in an early stage of metabolic adaptation and that may have been a contributing factor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.V13A0638M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.V13A0638M"><span>Hydrothermal pits in sediments of the <span class="hlt">equatorial</span> Pacific</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moore, T. C.; Lyle, M.; Mitchel, N. C.; Pälike, H.; Backman, J.</p> <p>2006-12-01</p> <p>Swath mapping and seismic surveying of the <span class="hlt">equatorial</span> Pacific sediment mound have revealed the common occurrence of pits in the sediment surface. The pits are sub-circular to elongate with horizontal dimensions of 1 to 4 km and are on the order of 50 100m deep. They often are seen in clusters or in linear trends; and in denser fields of such pits, they may appear to overlap. They were mapped in sediment overlying crust from 15 Ma to 55 Ma in age. Their density in the region is about 1 per 220 km2 and their occurrence shows no relationship to water depth, age of crust, latitude or longitude. They most frequently occur over sedimented basement highs where sediment is 300-350 m thick and do not seem to occur where sediment thickness in adjacent valleys is greater than ~500m or less than ~150m. They are believed to be related to hydrothermally driven discharge through vertical conduits of higher permeability in the sediment. These conduits are associated with faulting and fracturing over basement highs and along basement faults that extend well into the sediment column. The pervasive presence of such features on the seafloor indicates the profound effect that such "old-crust" hydrothermal circulation must have on ocean chemistry, crustal weathering, and ecology of the sub seafloor microbial community.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780050664&hterms=huancayo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dhuancayo','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780050664&hterms=huancayo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dhuancayo"><span>The localized origin of <span class="hlt">equatorial</span> F region irregularity patches</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Aarons, J.; Buchau, J.; Mcclure, J. P.; Basu, S.</p> <p>1978-01-01</p> <p>An intensive study of nighttime irregularities of electron density in the <span class="hlt">equatorial</span> ionosphere was performed in October 1976 by making 50-MHz radar backscatter measurements at Jicamarca, Peru, and scintillation measurements of 249-MHz transmissions from Les 9 at two ground stations (Ancon and Huancayo, both in Peru) as well as by aircraft flying in the vicinity of the stations. The 137-MHz scintillations from the orbiting Wideband satellite were also recorded at Huancayo. The results of such measurements made on October 16-17, 1976, are discussed in this report. We find that on this particular night a large-scale irregularity patch evolved first in the west, as was detected by the radar at Jicamarca, and drifted eastward to cause successive onsets of scintillation activity on propagation paths from Ancon and Huancayo. The observations indicate the east-west dimension of the large-scale structure to be 400 km drifting eastward at a speed of approximately 100 m/s, having a lifetime of several hours, and containing a hierarchy of irregularity scale sizes in the range of kilometers to meters causing both scintillations at 249 MHz and radar backscatter at 50 MHz.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920001543','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920001543"><span>SO2-rich <span class="hlt">equatorial</span> basins and epeirogeny of Io</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mcewen, Alfred S.</p> <p>1991-01-01</p> <p>Comparison of Io's large scale topography with an SO2 abundance map shows that SO2 is concentrated in <span class="hlt">equatorial</span> topographic basins. In these basins, about 30 pct. of the surface is covered by SO2 at all elevations above the mean triaxial figure, and SO2 coverage increases with decreasing elevation to as much as 56 pct. at elevations below -1.5 km. The correlation is not good from long 240 to 360 degs where bright areas are covered by red, Pele type plume fallout, and in the polar regions where the topography is poorly known. The histogram of SO2 abundance binned by elevation appears bimodal, with a secondary concentration of SO2 at high elevations, but it is not certain that this is significant. Additional observations suggest that the basins have relatively little higher frequency topographic relief. The distribution of active plumes and hotspots show no obvious correlation with the topography. However, the Pele type plume all erupted from regions higher than the mean figure, and five of the eight Prometheus type plumes are more energetic and are associated with high temperature hotspots, whereas Prometheus type plumes are long lived and require large volatile reservoirs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A13A0273Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A13A0273Z"><span>Impact of ENSO on Western Pacific Cross-<span class="hlt">equatorial</span> Flows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Y.; Kim, H.</p> <p>2015-12-01</p> <p>The Western Pacific cross-<span class="hlt">equatorial</span> flows (CEFs) show evident interannual variability in boreal summer. Results from Principle Component Analysis indicate that El Niño/Southern Oscillation modulates the interannual variability of Western Pacific CEFs. Both Matsuno-Gill mechanism and Lindzen-Nigam mechanism are introduced and applied in order to better explain the development of CEFs. Using the Mixed Layer Model by Stevens (2002) and methods stated by Back and Bretherton (2009), the low-level CEFs are decomposed into two pressure gradient contributions: free-atmosphere and boundary layer; and further found mainly contributed by the latter one. The intensity of boundary layer pressure gradient is highly coincide with the distribution of sea surface temperature (SST) gradient on Western Pacific, which is intensified by El Niño in boreal summer. These results show that the Lindzen-Nigam mechanism plays a major role on CEFs' interannual change. An atmosphere general circulation model is included to support the influence of SST forcing on low-level CEFs. North American Multi-Model Ensemble is further adopted to understand the seasonal predictability of CEFs.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AdSpR..46..626S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AdSpR..46..626S"><span>Mathematical modeling of plasma drifts over <span class="hlt">equatorial</span> low latitude regions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sundaresan, S.; Nageswara Rao, B.</p> <p>2010-09-01</p> <p>This paper presents a mathematical model to simulate ionospheric plasma drifts at <span class="hlt">equatorial</span> low latitude regions by coupling of E- and F-regions. The governing non-linear differential equations (of elliptic and parabolic nature) are solved numerically through finite-difference schemes and obtained neutral winds and electric fields. The temperature and electron density profiles are generated utilizing MSIS-86 atmospheric model. The continuity equation is employed to obtain night-time E-region density profile using measured ionograms at Trivandrum (India). The computed vertical and zonal plasma drifts are comparable with measured Jacamarca plasma drifts with little variations during noon and evening times. The plasma drifts at Trivandrum (8.5° N, 76.5° E, dip 0.5° N) are compared with those of Jicamarca (12° S, 76.9° W, dip 2° N). Neutral wind simulations of present model agree well with those of horizontal wind model (HWM-93). The post-sunset enhancement and its reversal are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AAS...22533618T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AAS...22533618T"><span>SpIES:The Spitzer IRAC <span class="hlt">Equatorial</span> Survey</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Timlin, John; Ross, Nicholas; Richards, Gordon T.; Lacy, Mark; Bauer, Franz E.; Brandt, W. Niel; Fan, Xiaohui; Haggard, Daryl; Makler, Martin; Myers, Adam D.; Strauss, Michael A.; Urry, C. Megan; SpIES Team</p> <p>2015-01-01</p> <p>The Spitzer-IRAC <span class="hlt">Equatorial</span> Survey, SpIES, is an Exploration Science program using Warm Spitzer to map over 100deg^2 of the SDSS Stripe 82 field, and is the largest extragalactic area surveyed by Spitzer. The primary science drivers are: the measurement of z>3 quasar clustering and the luminosity function in order to test different "AGN feedback'' models; to identify obscured AGN (and take advantage of the wide range of multi-wavelength, multi-epoch ancillary data on the Stripe 82 field); to identify z>6 quasars, and to support other wide-field ancillary science. With our observations very recently completed, we present the first preliminary science results from SpIES. This work is based [in part] on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19075224','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19075224"><span>Climate regulation of fire emissions and deforestation in <span class="hlt">equatorial</span> Asia.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>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</p> <p>2008-12-23</p> <p>Drainage of peatlands and deforestation have led to large-scale fires in <span class="hlt">equatorial</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2629304','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2629304"><span>Climate regulation of fire emissions and deforestation in <span class="hlt">equatorial</span> Asia</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>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.</p> <p>2008-01-01</p> <p>Drainage of peatlands and deforestation have led to large-scale fires in <span class="hlt">equatorial</span> 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 (1σ) Tg carbon (C) year−1, T = 1012] 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. PMID:19075224</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMSA51B2186B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMSA51B2186B"><span>Solar Flare Response in the Topside, <span class="hlt">Equatorial</span> Ionosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burrell, A. G.; Zhu, J.; Ridley, A. J.; Stoneback, R.</p> <p>2012-12-01</p> <p>During solar flares, the sudden increase in the X-ray and extreme ultraviolet (EUV) irradiance leads to sudden changes in the global ionospheric state. Near the geomagnetic equator, these changes are thought to be heavily influenced by alterations to the E-region density, which in turn changes the E×B drift. Although departures from climatological values are small for ionospheric characteristics, the topside ionosphere is expected to take much longer to recover from the influence of solar flares than the bottomside does. Using data from the Coupled Ion Neutral Dynamics Investigation (CINDI) mission onboard the Communication/Navigation Outage Forecasting System (C/NOFS) satellite and simulations from the Global Ionosphere-Thermosphere Model (GITM), the response of the topside <span class="hlt">equatorial</span> ionosphere to several solar flares will be examined. Comparing the modeled and measured responses of ion characteristics will help elucidate the influence of the E×B drift, the neutral wind, and the pressure gradient in shaping the ionospheric response to increased levels of solar X-ray and EUV irradiance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1110072H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1110072H"><span>Source extension of chorus waves in the <span class="hlt">equatorial</span> plane</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hayosh, M.; Santolik, O.; Parrot, M.</p> <p>2009-04-01</p> <p>We use measurements of the Cluster spacecraft and a ray tracing simulation to estimate the location and size of the global source of whistler-mode chorus emissions. In this study we use the data provided simultaneously by the STAFF-SA instruments on the four Cluster spacecraft on 19 August, 2003. To determine the direction of propagation of chorus we calculate Poynting vector whereas a ray-tracing method is used to estimate the chorus source extension. For the first time this analysis has been made along whole particular Cluster orbit in both hemispheres. Our study shows that minimum size of the global chorus source region in the <span class="hlt">equatorial</span> plane is between 1-3 Earth's radii. The resulting location of the chorus source region is at radial distances between 3 and 8 Earth radii. This result is in agreement with previous analysis of Cluster data by Parrot et al., 2003, 2004 and with the study of Santolik et al., 2005 who analyzed data from the Double Star TC-1 spacecraft.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920038623&hterms=Productivity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DProductivity','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920038623&hterms=Productivity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DProductivity"><span>Measurements of nitrogen productivity in the <span class="hlt">equatorial</span> Pacific</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilkerson, Frances P.; Dugdale, Richard C.</p> <p>1992-01-01</p> <p>During the R/V Wecoma WEC88 cruise that sampled a meridional transect along 150 deg W from 15 deg N to 15 deg S, uptake of nitrate and ammonium by phytoplankton was measured using the stable isotope N-15 with simulated in-situ bottle incubations and shipboard mass spectrometry. A set of 25 daily productivity stations showed the influence of <span class="hlt">equatorial</span> upwelling on nitrate distribution and N-15 uptake in a band from 6 deg N to 7.5 deg S compared with the oligotrophic waters to the north and south, with the highest values of nitrate uptake occurring at the equator. During a 5-day time series at the equator, there was an increase in nitrate accompanied by increased nitrate uptake. Interestingly, nitrate uptake rates (equivalent to new production rates) at the equator were lower than those predicted by previous investigators. Holdover experiments and uptake versus irradiance curves showed that the phytoplankton was in an early stage of metabolic adaptation and that can be a contributing factor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800037021&hterms=peak+factor&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dpeak%2Bfactor','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800037021&hterms=peak+factor&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dpeak%2Bfactor"><span>The <span class="hlt">equatorial</span> total electron content and shape factor</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Donnelly, R. F.; Davies, K.; Anderson, D. N.</p> <p>1979-01-01</p> <p>The diurnal variations of electron content and shape factor observed at an <span class="hlt">equatorial</span> station during sunspot minimum are shown to be consistent with the electron density profiles observed at Jicamarca during sunspot minimum. The rapid increase in electron content and the shape factor at sunrise results from the EUV production of ionization in the E and F regions. Day-to-day variations in daytime electron content are observed to be quite small at the equator. The evening decrease in the shape factor results from an upward drift of the F region at sunset and the evening decay of the E and bottomside F regions. The nighttime peak or plateau in the shape factor is produced by the slow downward drift of the electron density profile. The deep predawn dip in the shape factor is caused by the main peak of the F layer reaching low altitudes where high loss rates cause a large reduction in ionization below 300 km and very flat electron density profile.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AdSpR..60.1698A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AdSpR..60.1698A"><span>Modelling ionospheric scintillation under the crest of the <span class="hlt">equatorial</span> anomaly</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alfonsi, L.; Wernik, A. W.; Materassi, M.; Spogli, L.</p> <p>2017-10-01</p> <p>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 <span class="hlt">equatorial</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5453300','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5453300"><span>Geology, hydrocarbon potential of Rio Muni area, <span class="hlt">Equatorial</span> Guinea</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ross, D.; Hempstead, N. )</p> <p>1993-08-30</p> <p>The Republic of <span class="hlt">Equatorial</span> Guinea, located in the oil producing province of West Africa, consists of three islands and an enclave in continental Africa with a total surface area of about 28,000 sq km. The islands are in the Gulf of Guinea. The largest, Bioko, lies off Nigeria and Cameroon. The continental enclave, Rio Muni, is bounded to the north by Cameroon and to the east and south by Gabon. The coastal basin of Rio Muni, which is the subject of this article, contributes the major portion of areas offered in the current exploration licensing round. Some 5,275 km of seismic data have been recorded the past 10 years covering most of the offshore and onshore areas of Rio Muni. The quality of seismic data is generally good. Data from all size wells drilled in the area and an aeromagnetic survey of the whole onshore and offshore are also available. The paper describes the West African setting, exploration history, basin development, presalt play, postsalt Aptian play, Albian play, clastic play, Senonian/Paleogene play, and the current licensing round.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010GeoRL..3714807B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010GeoRL..3714807B"><span>Fertilizing the Amazon and <span class="hlt">equatorial</span> Atlantic with West African dust</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bristow, Charlie S.; Hudson-Edwards, Karen A.; Chappell, Adrian</p> <p>2010-07-01</p> <p>Atmospheric mineral dust plays a vital role in Earth's climate and biogeochemical cycles. The Bodélé Depression in Chad has been identified as the single biggest source of atmospheric mineral dust on Earth. Dust eroded from the Bodélé is blown across the Atlantic Ocean towards South America. The mineral dust contains micronutrients such as Fe and P that have the potential to act as a fertilizer, increasing primary productivity in the Amazon rain forest as well as the <span class="hlt">equatorial</span> Atlantic Ocean, and thus leading to N2 fixation and CO2 drawdown. We present the results of chemical analysis of 28 dust samples collected from the source area, which indicate that up to 6.5 Tg of Fe and 0.12 Tg of P are exported from the Bodélé Depression every year. This suggests that the Bodélé may be a more significant micronutrient supplier than previously proposed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSA23A2331N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSA23A2331N"><span><span class="hlt">Equatorial</span> and Low-Latitudes Ionospheric Reaction to Solar Flares</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nicoli Candido, C. M.; Becker-Guedes, F.; Paula, E. R.; Takahashi, H.</p> <p>2015-12-01</p> <p>Solar X-ray and extreme ultraviolet (EUV) photons are responsible for ionizing the terrestrial atmosphere and create the ionosphere. During solar flares, a fast increase in the electron density at different altitude regions takes place due to the abrupt enhance of the X-ray and EUV fluxes reaching Earth. With these changes in the ionosphere, radio communication and navigation can be drastically affected. The magnitudes of these Space Weather events can be related to the X-ray peak brightness and duration, which drive the intensity of the ionosphere response when the associated electromagnetic wave hit the sunlit side of the Earth's atmosphere. Other aspects defining these changes in a particular region are the local time, the solar zenith angle, and the position of the flare in the solar disc for each event. In order to improve the understand of radio signal degradation and loss in the Brazilian sector due to solar abrupt electromagnetic emissions, total electron content (TEC) data obtained by a GPS network formed by tents of dual-frequency receivers spread all over Brazilian territory were analyzed. It was observed different ionospheric local changes during several X-ray events identified by GOES satellite regarding the 0.1-0.8 nm range, and some case studies were ponder for a more detailed analysis of these effects. Considering the results, we have made an estimation of the ionospheric disturbances range for a particular event with great chance to affect space based communications in the <span class="hlt">equatorial</span> and low-latitude regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSA23A2335F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSA23A2335F"><span>Impact of Midnight Thermosphere Dynamics on the <span class="hlt">Equatorial</span> Ionosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fuller-Rowell, T. J.; Fang, T. W.; Akmaev, R. A.; Stoneback, R.; Wang, H.; Wu, F.</p> <p>2015-12-01</p> <p>During the recent solar minimum, a large amount of C/NOFS satellite measurements have revealed an upward drift that occurs during the post-midnight period (~2-3 LT). The upward drift is also frequently shown in radar measurements. The phenomenon has not yet been explained and the physics are still unknown. Our simulations have successfully reproduced the unusual upward drift using the coupled Whole Atmosphere Model and Global Ionosphere Plasmasphere Model (WAM/GIP). Model produces significant day-to-day variability in the nighttime <span class="hlt">equatorial</span> ionosphere. Simulations also reveal strong seasonal and longitudinal dependence of the upward drift. Our analysis indicates that the upward drifts are driven by thermosphere dynamics associated with the midnight temperature maximum (MTM). The MTM locally reverses the typical large-scale zonal and meridional wind pattern, in turn affecting the nighttime F-layer electrodynamics. The longitudinal variation of the drifts depends on the magnitude and position of the MTM peak relative to the magnetic equator. In this talk, we will present the morphology and characteristics of the post-midnight upward drift shown in the simulations and explain its causal mechanism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22932385','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22932385"><span>A Cenozoic record of the <span class="hlt">equatorial</span> Pacific carbonate compensation depth.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pälike, Heiko; Lyle, Mitchell W; Nishi, Hiroshi; Raffi, Isabella; Ridgwell, Andy; Gamage, Kusali; Klaus, Adam; Acton, Gary; Anderson, Louise; Backman, Jan; Baldauf, Jack; Beltran, Catherine; Bohaty, Steven M; Bown, Paul; Busch, William; Channell, Jim E T; Chun, Cecily O J; Delaney, Margaret; Dewangan, Pawan; Dunkley Jones, Tom; Edgar, Kirsty M; Evans, Helen; Fitch, Peter; Foster, Gavin L; Gussone, Nikolaus; Hasegawa, Hitoshi; Hathorne, Ed C; Hayashi, Hiroki; Herrle, Jens O; Holbourn, Ann; Hovan, Steve; Hyeong, Kiseong; Iijima, Koichi; Ito, Takashi; Kamikuri, Shin-ichi; Kimoto, Katsunori; Kuroda, Junichiro; Leon-Rodriguez, Lizette; Malinverno, Alberto; Moore, Ted C; Murphy, Brandon H; Murphy, Daniel P; Nakamura, Hideto; Ogane, Kaoru; Ohneiser, Christian; Richter, Carl; Robinson, Rebecca; Rohling, Eelco J; Romero, Oscar; Sawada, Ken; Scher, Howie; Schneider, Leah; Sluijs, Appy; Takata, Hiroyuki; Tian, Jun; Tsujimoto, Akira; Wade, Bridget S; Westerhold, Thomas; Wilkens, Roy; Williams, Trevor; Wilson, Paul A; Yamamoto, Yuhji; Yamamoto, Shinya; Yamazaki, Toshitsugu; Zeebe, Richard E</p> <p>2012-08-30</p> <p>Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the <span class="hlt">equatorial</span> Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0-3.5 kilometres during the early Cenozoic (approximately 55 million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950048925&hterms=fishbein&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dfishbein','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950048925&hterms=fishbein&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dfishbein"><span><span class="hlt">Equatorial</span> Kelvin wave variability during 1992 and 1993</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Canziani, Pablo O.; Holton, James R.; Fishbein, Evan; Froidevaux, Lucien</p> <p>1995-01-01</p> <p>Temperature and ozone data from the Microwave Limb Sounder (MLS) instrument on Upper Atmosphere Research Satellite (UARS) are used to analyze the variability of Kelvin wave activity during the first two years of the UARS mission. The analysis is carried out using the asynoptic mapping technique. Time frequency plots for zonal wavenumbers 1 and 2, at two heights representing the middle stratosphere and the stratopause, respectively, are used to analyze the temporal variability of the waves, and its possible relationship to the <span class="hlt">equatorial</span> quasi-biennial oscillation (QBO) and semiannual oscillation (SAO). Kelvin wave activity reaches a maximum during the solstice seasons and almost disappears during the equinoxes, in agreement with previous studies. Eastward propagating variance is estimated for wave periods from 4 to 20 days, at all UARS pressure surfaces currently available for MLS. The semiannual modulation of variance is observed to extend down to the lower limits of the height ranges of the temperature and ozone retrievals. Furthermore, a superposed QBO modulation is detected up to the stratopause. Comparison between the variance in eastward propagating waves and the mean zonal wind shows a possible participation of kelvin waves in the forcing of the QBO. At the stratopause the role of Kelvin waves in forcing the SAO appears to be limited, in agreement with previous results. Between the 21-hPa and 4.6-hPa surfaces there appears to be a transition zone where there is no clear relationship between Kelvin wave activity and mean zonal flow acceleration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990JAtS...47.1666G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990JAtS...47.1666G"><span>Seasonal variation in <span class="hlt">equatorial</span> mesospheric temperatures observed by SME</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Garcia, Rolando R.; Clancy, R. Todd</p> <p>1990-07-01</p> <p>Observations made by the Solar Mesosphere Explorer (SME) satellite from 1982 through 1986 are used to examine the seasonal variation of temperature in the <span class="hlt">equatorial</span> mesosphere between 58.5 and 90 km. Near the equator, seasonal variability is dominated by a strong semiannual oscillation (SAO) whose amplitude increases from about 3 K in the lower mesosphere to 7.3 K near 80 km. Above 80 k, the SAO amplitude decreases to a minimum at 83 km, but increases again sharply above that level, reaching 16.6 K at 90 km. The structure of the temperature SAO is consistent with previous observations of the SAOs in temperature and zonal wind, although the very large amplitude at 90 km may be due in part to contamination by the diurnal tide. Just below 80 km, temperatures are warm (cold) near the solstices (equinoxes), implying westerly (easterly) accelerations above; the behavior at 58.5 km lags that at 80 km by about 2 months.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6005762','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6005762"><span>Seasat A Satellite Scatterometer measurements of <span class="hlt">equatorial</span> surface winds</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Halpern, D. )</p> <p>1989-04-15</p> <p>Seasat A Satellite Scatterometer measurements of surface wind components were made under normal weather conditions with unsurpassed space and time resolutions during August and September 1978. Longitudinal distributions of the monthly mean zonal component were markedly different in each ocean: in the Pacific the zonal profile resembled a semicircle; a linear change occurred in the Atlantic, and quasi-uniform values prevailed in the Indian Ocean. Only in the Atlantic and Pacific was the prevailing direction of the zonal component westward. In the Pacific the monthly mean standard deviations increased towards the west. This indicated that the larger day-to-day wind variability observed at the western islands compared to moored buoy measurements in the eastern region was a natural phenomenon and not caused by islands. The average monthly mean slope of the wave number spectra throughout the 550- to 2,200-km wavelength band was {minus}1.7, which was approximately equal to the {minus}5/3 power law associated with turbulent motions. That the spectra levels of the zonal wind, but not the meridional component, were substantially different in each <span class="hlt">equatorial</span> ocean represents an enigma. Largest spectral values occurred in the Atlantic where variances were nearly 10 times greater than in the Pacific, which contained the smallest values.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JGRA..113.9318P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JGRA..113.9318P"><span><span class="hlt">Equatorial</span> plasma bubbles with enhanced ion and electron temperatures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Park, Jaeheung; Min, Kyoung Wook; Kim, Vitaly P.; Kil, Hyosub; Su, Shin-Yi; Chao, Chi Kuang; Lee, Jae-Jin</p> <p>2008-09-01</p> <p>While the ion and electron temperatures inside <span class="hlt">equatorial</span> plasma bubbles (EPBs) are normally lower than those in an ambient plasma, bubbles with enhanced temperatures (BETs) are found occasionally in the topside ionosphere. Here we report the characteristics of BETs identified from observations of the first Republic of China Satellite (ROCSAT-1), the first Korea Multi-purpose Satellite (KOMPSAT-1), and the Defense Meteorological Satellite Program (DMSP) F15 during the solar maximum period between 2000 and 2001. The oxygen ion fraction inside the BETs, which was no lower than that of the ambient ionosphere, was similar to the case of ordinary low-temperature EPBs. These observations indicate that the BETs and low-temperature EPBs detected on the topside were produced by the upward drift of low-density plasma from lower altitudes. The feature that distinguishes BETs from normal EPBs is the occurrence of an unusually fast poleward field-aligned plasma flow relative to the ambient plasma. The BETs occurred preferentially around geomagnetic latitudes of 10° in the summer hemisphere, where the ambient ion and electron temperatures are lower than those in the conjugate winter hemisphere. The occurrence of BETs did not show any notable dependence on geomagnetic activities. The characteristics of the BETs suggest that the BETs were produced by adiabatic plasma heating associated with a fast poleward oxygen ion transport along magnetic flux tubes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AN....333..648L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AN....333..648L"><span>Analysis of Korean astronomical records with Chinese <span class="hlt">equatorial</span> coordinates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, K. W.</p> <p>2012-08-01</p> <p>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 <span class="hlt">equatorial</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSA51B2404Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSA51B2404Y"><span>Understanding the Longitudinal Variability of <span class="hlt">Equatorial</span> Electrodynamics using integrated Ground- and Space-based Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yizengaw, E.; Moldwin, M.; Zesta, E.</p> <p>2015-12-01</p> <p>The currently funded African Meridian B-Field Education and Research (AMBER) magnetometer array comprises more than thirteen magnetometers stationed globally in the vicinity of geomagnetic equator. One of the main objectives of AMBER network is to understand the longitudinal variability of <span class="hlt">equatorial</span> electrodynamics as function of local time, magnetic activity, and season. While providing complete meridian observation in the region and filling the largest land-based gap in global magnetometer coverage, the AMBER array addresses two fundamental areas of space physics: first, the processes governing electrodynamics of the <span class="hlt">equatorial</span> ionosphere as a function of latitude (or L-shell), local time, longitude, magnetic activity, and season, and second, ULF pulsation strength at low/mid-latitude regions and its connection with <span class="hlt">equatorial</span> electrojet and density fluctuation. The global AMBER network can also be used to augment observations from space-based instruments, such us the triplet SWARM mission and the upcoming ICON missions. Thus, in coordination with space-based and other ground-based observations, the AMBER magnetometer network provides a great opportunity to understand the electrodynamics that governs <span class="hlt">equatorial</span> ionosphere motions. In this paper we present the longitudinal variability of the <span class="hlt">equatorial</span> electrodynamics using the combination of instruments onboard SWARM and C/NOFS satellites and ground-based AMBER network. Both ground- and pace-based observations show stronger dayside and evening sector <span class="hlt">equatorial</span> electrodynamics in the American and Asian sectors compared to the African sector. On the other hand, the African sector is home to stronger and year-round ionospheric bubbles/irregularities compared to the American and Asian sectors. This raises the question if the evening sector <span class="hlt">equatorial</span> electrodynamics (vertical drift), which is believed to be the main cause for the enhancement of Rayleigh-Taylor (RT) instability growth rate, is stronger in the</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790009216','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790009216"><span>Rocket observations of electron-density irregularities in the <span class="hlt">equatorial</span> ionosphere below 200 km</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Klaus, D. E.; Smith, L. G.</p> <p>1978-01-01</p> <p>Nike Apache rockets carring instrumentation to measure electron density and its fine structure in the <span class="hlt">equatorial</span> ionosphere were launched from Chilca, Peru in May and June 1975. The fine structure experiment and the data reduction system are described. Results obtained from this system are presented and compared with those obtained by VHF radar and from other rocket studies. A description of the <span class="hlt">equatorial</span> ionosphere and its features is also presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5222875','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5222875"><span>Nighttime <span class="hlt">equatorial</span> thermospheric meridional winds from ionospheric h prime F data</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Krishna Murthy, B.V.; Hari, S.S.; Somayajulu, V.V. )</p> <p>1990-04-01</p> <p>The thermosphere has been a subject of intense experimental and theoretical study in the recent years. A number of experimental techniques have been used to obtain the thermospheric parameters. Nighttime <span class="hlt">equatorial</span> thermospheric meridional winds have been derived using h{prime}F data from two <span class="hlt">equatorial</span> stations nearly on the same magnetic meridian. It is shown that the winds derived are quite consistent with earlier observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA595005','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA595005"><span>Study of <span class="hlt">Equatorial</span> Ionospheric Irregularities for the Assessment of Impacts on Communication/Navigation System (7)</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2013-05-27</p> <p>wave can propagate upward to the lower ionosphere to become a seed for the Rayleigh - Taylor instability process that generates the ionospheric ...Final Report of AFRL-AOARD Project 11-4040 (2011-2013) “Study of <span class="hlt">Equatorial</span> 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 <span class="hlt">Equatorial</span> Ionospheric Irregularities</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996JAtS...53.1937K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996JAtS...53.1937K"><span>The Descent Rates of the Shear Zones of the <span class="hlt">Equatorial</span> QBO.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kinnersley, Jonathan S.; Pawson, Steven</p> <p>1996-07-01</p> <p>The influence of vertical advection on the descent rate of the zero-wind line in both phases of the <span class="hlt">equatorial</span> quasi-biennial oscillation (QBO) is investigated with the help of the `THIN AIR' stratosphere two-and-a-half-dimensional model. The model QBO is forced by two symmetric easterly and westerly waves, and yet the model reproduces qualitatively the observed asymmetry in the descent rates of the two shear zones due to the enhanced heating during easterly descent combined with the <span class="hlt">equatorial</span> heating induced by the extratropical planetary waves. Observations show that the maximum easterly accelerations occur predominantly from May until July, which is when the modeled <span class="hlt">equatorial</span> planetary-wave-induced heating rates are weakest. Hence, model results are consistent with the theory that vertical advection induced by extratropical planetary waves slows significantly the descent of the easterly shear zone. The model also shows the observed increase in vertical wind shear during stalling of the easterly descent (which increases the impact of vertical advection). In the model, the effect of cross-<span class="hlt">equatorial</span> advection of momentum by the mean flow is negligible compared to the vertical advection. Changes in the propagation of planetary waves depending on the sign of the <span class="hlt">equatorial</span> zonal wind have a small effect on the modeled <span class="hlt">equatorial</span> heating rates and therefore do not play a large part in producing the modeled asymmetry in descent rates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17978344','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17978344"><span><span class="hlt">Equatorial</span> segment protein (ESP) is a human alloantigen involved in sperm-egg binding and fusion.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wolkowicz, M J; Digilio, L; Klotz, K; Shetty, J; Flickinger, C J; Herr, J C</p> <p>2008-01-01</p> <p>The <span class="hlt">equatorial</span> segment of the sperm head is known to play a role in fertilization; however, the specific sperm molecules contributing to the integrity of the <span class="hlt">equatorial</span> 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 <span class="hlt">Equatorial</span> Segment Protein (ESP), a protein localized to the <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> segment of 89% of acrosome-reacted sperm. ESP persisted as a defined <span class="hlt">equatorial</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GBioC..31..850C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GBioC..31..850C"><span>Productivity patterns in the <span class="hlt">equatorial</span> Pacific over the last 30,000 years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Costa, Kassandra M.; Jacobel, Allison W.; McManus, Jerry F.; Anderson, Robert F.; Winckler, Gisela; Thiagarajan, Nivedita</p> <p>2017-05-01</p> <p>The <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> Pacific, and integrated with productivity records from across the <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> Pacific, while deglacial peaks in productivity may be prominent only in the east.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986PrOce..16...91M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986PrOce..16...91M"><span>A synthesis of the first GARP Globa Experiment (FGGE) in the <span class="hlt">equatorial</span> Atlantic Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Molinari, R. L.; Garzoli, S. L.; Katz, E. J.; Harrison, D. E.; Richardson, P. L.; Reverdin, G.</p> <p></p> <p>A synthesis of near-surface oceanographic and surface meteorological data collected during the First GARP Global Experiment, FGGE, is presented to portray the oceanic response to the seasonal wind forcing for the period December 1978 to November 1979, inclusive. Major wind events during FGGE are in phase with events given in climatology. In particular, the February-March-April relaxation and May enhancement of <span class="hlt">equatorial</span> winds occurs within one month of the mean event. Accordingly, the oceanic responses, such as the May, June, July appearance of an <span class="hlt">equatorial</span> cold water tongue, the acceleration of the South <span class="hlt">Equatorial</span> Current (SEC) and the vertical displacement of the <span class="hlt">equatorial</span> thermocline occur at the average time. Furthermore, the curl distribution in the vicinity of the North <span class="hlt">Equatorial</span> Countercurrent (NECC) during 1979 is similar to the climatological distribution in terms of phase and amplitude, except for a westward displacement in the position of the maximum curl. As predicted from linear theory, the 1979 thermocline response across the NECC is in phase with the climatological response with a westward displacement of the maximum thermocline movement. Deeper than average <span class="hlt">equatorial</span> thermoclines and a weaker SEC may, in part, be responsible for the anomalously warm sea-surface temperatures observed on the equator between 10°W and 30°W from June to November.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.6437R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.6437R"><span>Mixing in the <span class="hlt">equatorial</span> thermocline: the importance of small vertical scale velocity features</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Richards, K. J.; Natarov, A.</p> <p>2009-04-01</p> <p>The overturning cells in the ocean are closed by isopycnic mixing. For the shallow sub-tropical cells the majority of this mixing occurs in the <span class="hlt">equatorial</span> thermocline. In addition the level of mixing in the <span class="hlt">equatorial</span> thermocline influences the characteristics of ENSO. Mixing in the <span class="hlt">equatorial</span> thermocline is therefore important. But it is poorly understood. Here we present recent high vertical resolution observations that show a predominance of small vertical scale features in the velocity field in the <span class="hlt">equatorial</span> thermocline. These features have a vertical scale of order 10m and a meridional coherency that can extend in excess of a hundred kilometres. Estimates suggest these features contribute significantly to both vertical and lateral mixing. We speculate that the observed small vertical scale features are produced by a combination of instabilities of the <span class="hlt">equatorial</span> current system and wind-induced near-inertial oscillations, which in turn provide a significant control on the level of mixing in the <span class="hlt">equatorial</span> thermocline. The picture is very different to that assumed in present-day climate models and calls for a rethinking of the way mixing processes are prescribed in such models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMOS33A1812H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMOS33A1812H"><span>Ocean Color and the <span class="hlt">Equatorial</span> Annual Cycle in the Pacific</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hammann, A. C.; Gnanadesikan, A.</p> <p>2012-12-01</p> <p>The presence of chlorophyll, colored dissolved organic matter (CDOM) and other scatterers in ocean surface waters affect the flux divergence of solar radiation and thus the vertical distribution of radiant heating of the ocean. While this may directly alter the local mixed-layer depth and temperature (Martin 1985; Strutton & Chavez 2004), non-local changes are propagated through advection (Manizza et al. 2005; Murtugudde et al. 2002; Nakamoto et al. 2001; Sweeny et al. 2005). In and coupled feedbacks (Lengaigne et al. 2007; Marzeion & Timmermann 2005). Anderson et al. (2007), Anderson et al. (2009) and Gnanadesikan & Anderson (2009) have performed a series of experiments with a fully coupled climate model which parameterizes the e-folding depth of solar irradiance in terms of surface chlorophyll-a concentration. The results have so far been discussed with respect to the climatic mean state and ENSO variability in the tropical Pacific. We extend the discussion here to the Pacific <span class="hlt">equatorial</span> annual cycle. The focus of the coupled experiments has been the sensitivity of the coupled system to regional differences in chlorophyll concentration. While runs have been completed with realistic SeaWiFS-derived monthly composite chlorophyll ('green') and with a globally chlorophyll-free ocean ('blue'), the concentrations in two additional runs have been selectively set to zero in specific regions: the oligotrophic subtropical gyres ('gyre') in one case and the mesotrophic gyre margins ('margin') in the other. The annual cycle of ocean temperatures exhibits distinctly reduced amplitudes in the 'blue' and 'margin' experiments, and a slight reduction in 'gyre' (while ENSO variability almost vanishes in 'blue' and 'gyre', but amplifies in 'margin' - thus the frequently quoted inverse correlation between ENSO and annual amplitudes holds only for the 'green' / 'margin' comparison). It is well-known that on annual time scales, the anomalous divergence of surface currents and vertical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020022492&hterms=tide&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dtide','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020022492&hterms=tide&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dtide"><span>Modeling Tides, Planetary Waves, and <span class="hlt">Equatorial</span> Oscillations in the MLT</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mengel, J. G.; Mayr, H. G.; Drob, D. P.; Porter, H. S.; Bhartia, P. K. (Technical Monitor)</p> <p>2001-01-01</p> <p>Applying Hines Doppler Spread Parameterization for gravity waves (GW), our 3D model reproduces some essential features that characterize the observed seasonal variations of tides and planetary waves in the upper mesosphere. In 2D, our model also reproduces the large Semi-Annual Oscillation (SAO) and Quasi Biennial Oscillation (QBO) observed in this region at low latitudes. It is more challenging to describe these features combined in a more comprehensive self consistent model, and we give a progress report that outlines the difficulties and reports some success. In 3D, the GW's are partially absorbed by tides and planetary waves to amplify them. Thus the waves are less efficient in generating the QBO and SAO at <span class="hlt">equatorial</span> latitudes. Some of this deficiency is compensated by the fact that the GW activity is observed to be enhanced at low latitudes. Increasing the GW source has the desired effect to boost the QBO, but the effect is confined primarily to the stratosphere. With increasing altitude, the meridional circulation becomes more important in redistributing the momentum deposited in the background flow by the GW's. Another factor involved is the altitude at which the GW's originate, which we had originally chosen to be the surface. Numerical experiments show that moving this source altitude to the top of the troposphere significantly increases the efficiency for generating the QBO without affecting much the tides and planetary waves in the model. Attention to the details in which the GW source comes into play thus appears to be of critical importance in modeling the phenomenology of the MLT. Among the suite of numerical experiments reported, we present a simulation that produced significant variations of tides and planetary waves in the upper mesosphere. The effect is related to the QBO generated in the model, and GW filtering is the likely cause.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JSAES..63....1S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JSAES..63....1S"><span>Diagenetic processes in cretaceous sandstones from occidental Brazilian <span class="hlt">Equatorial</span> Margin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schrank, A. B. S.; De Ros, L. F.</p> <p>2015-11-01</p> <p>Despite a great interest in Brazilian <span class="hlt">Equatorial</span> Margin exploration, very little was published on the diagenesis of sandstones from that area. A wide recognition petrographic study was performed to identify the major diagenetic processes that impacted the porosity of Lower Cretaceous sandstones of the Pará-Maranhão, São Luís, Bragança-Viseu and Barreirinhas basins. Arkoses from the Pará-Maranhão Basin show neoformed or infiltrated clay coatings, mica replacement and expansion by kaolinite and vermiculite, and precipitation of grain-replacive and pore-filling quartz, kaolinite, albite, chlorite, calcite, dolomite, siderite, pyrite and titanium oxides. Compaction, quartz and calcite cementation were the main porosity-reducing processes. Barreirinhas Basin lithic arkoses and subarkoses display clay coatings, compaction of metamorphic fragments into pseudomatrix, and precipitation of grain-replacive and pore-filling kaolinite, quartz, albite, chlorite, calcite, dolomite, TiO2 and pyrite. The main porosity-reducing processes were calcite cementation in the subarkoses, and compaction and quartz cementation in lithic arkoses. Quartzarenites from this basin were early- and pervasively cemented by dolomite. Arkoses and lithic arkoses of the São Luís and Bragança-Viseu basins show clay coatings, pseudomatrix from mud intraclasts compaction, and precipitation of pore-filling and grain-replacive kaolinite, vermiculite, smectite, quartz, albite, chlorite, illite, calcite, dolomite, hematite, TiO2 and pyrite. Compaction of mud intraclasts and dissolution of feldspars and heavy minerals were the main porosity-modification processes. These preliminary results may contribute to the understanding of the spatial and temporal distribution of the diagenetic processes and their impacts on the porosity of the sandstones from these basins.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016cosp...41E1483O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016cosp...41E1483O"><span>Evening and nighttime features of <span class="hlt">equatorial</span> ionospheric F2 layer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oyekola, Oyedemi S.</p> <p>2016-07-01</p> <p>We have used ionosonde observations recorded at Ibadan (7.4 degree North, 3.9 degree East) during the International Geophysical year (1957-58) to investigate evening and nighttime characteristic features of <span class="hlt">equatorial</span> ionosphere during high solar flux and quiet magnetic conditions. We have also used International Reference Ionosphere model (IRI-2012) data. Our results show that the base of the ionosphere descends at a rate of -27.5 km/hr between 2000 LT and 0400 LT, whereas the observed bottomside peak of the ionosphere move down at a rate of -29.3 km/hr between 1900 and 0500 LT, while IRI2012 bottomside peak show -29.8 km/hr between 2000 LT and 0500 LT. The downward flow rate of plasma concentration between 1900 LT and 0500 LT and between 1800 LT and 0400 LT is approximately 0.040 electron per cubic metre per hour and 0.081 electron per cubic metre per hour, respectively for observed and for modeled NmF2. Month-by-month averaged altitudes (h'F, hmF2, and modeled hmF2) indicate significant local time variation. In addition, the month-by month variation indicates nighttime double crest of averaged peak height (hmF2) in the ionosonde measurements and in the IRI-2012 empirical model with a trough in June-August for data and In July for model. The monthly mean downward vertical drift velocities derived from local time variation of h'F and hmF2 together with global drift model essential demonstrate much fluctuations. We found a "domed shape" in modeled drift velocity, indicating equatorward plasma between April and September.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSA42A..06H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSA42A..06H"><span>Multiscale <span class="hlt">equatorial</span> electrojet turbulence for GNSS disruption physics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Horton, W., Jr.; Hassan, E.; Litt, S. K.; Smolyakov, A. I.; Rainwater, D.</p> <p>2015-12-01</p> <p>The spatial and spectral characteristics of the turbulent plasma density and electric fields are modeled in ionospheric E region using a new set of nonlinear plasma fluid equations. The fluid model combines both Farley-Buneman (Type-I) and Gradient-Drift (Type-II) plasma instabilities in the <span class="hlt">equatorial</span> electrojet region. The unified model of the plasma instabilities includes the ion viscosity in the ion momentum equation and electron inertia in the electron momentum equation. Electron heating from the electrojet currents is included. Nonlinear simulations in 2D and 3D in massively parallel codes for the coupled equations are run on TACC and NERSC computers. Rising plumes and falling spikes of high-density plasma are ubiquitous as in earlier 2D simulations. 3D movies of structures like TIDs are shown. The simulation results show some agreement with a number of features of rocket and radar observations as reported in Hassan et al. JGR 2015. At sunset, the strong electric fields driven both by neutral thermosphere winds and the dynamo electric field the turbulence are severe. The source field aligned currents [FACs] is the solar wind dynamo electric field. During periods of magnetospheric storms and substorms these plasma currents surge to large values producing ionospheric storms. The turbulent fluctuations in the ionosphere are intrinsic part of the dynamics of ionosphere-magnetosphere coupling. The plasma fluctuations are a source of multipath GNSS rays and loss-of-lock. Monitoring of ionosphere irregularities is used as a diagnostic tool for the state of the ionosphere for GNSS disruption and space weather issues. The theoretical/simulation model of ionospheric irregularities is based on advanced nonlinear plasma physics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5205640','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5205640"><span>Chemical fluctuations associated with vertically propagating <span class="hlt">equatorial</span> Kelvin waves</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Salby, M.L.; Callaghan, P. ); Soloman, S. NOAA, Boulder, CO ); Garcia, R.R. )</p> <p>1990-11-20</p> <p>Satellite retrievals of ozone and nitrogen dioxide from the Nimbus-7 Limb Infrared Monitor of the Stratosphere (LIMS) reveal distinct spectral features which are collocated in frequency with Kelvin wave temperature fluctuations. These features represent a significant component of the unsteady variance in retrievals of O{sub 3} and nighttime NO{sub 2} in the tropics and are very similar to Kelvin wave temperature disturbances. Chemical fluctuations occur symmetrically about the equator, in phase across the tropics, and propagate downward, all consistent with the behavior of <span class="hlt">equatorial</span> Kelvin waves. The phase structure of ozone perturbations mirrors that of temperature fluctuations in the upper stratosphere and mesosphere, only shifted 180{degree}. The regular phase tilt with altitude disappears in the middle to lower stratosphere, where it is replaced by more or less barotropic behavior. That change in phase structure marks a transition fromn photochemical control in the upper stratosphere and mesosphere to dynamical control in the lower stratosphere. Fluctuations in ozone are consistent with dynamical and chemical mechanisms operating on that species. The response of ozone in a detailed photochemical calculation driven by observed temperature variability locks into agreement with the observed ozone variability above about 4 mbar, where O{sub 3} is under photochemical control. At lower altitudes, vertical transport is able to explain both the magnitude and phase of the observed fluctuations in ozone. The same considerations have only mixed success in explaining the observed variability of nitrogen dioxide. The amplitude of nighttime NO{sub 2} fluctuations is underestimated in the photochemical calculation by about a factor of 2. Although large enough to explain the discrepancy, contributions from vertical transport have the wrong phase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AnGeo..33.1485S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AnGeo..33.1485S"><span>Magnetospheric conditions near the <span class="hlt">equatorial</span> footpoints of proton isotropy boundaries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sergeev, V. A.; Chernyaev, I. A.; Angelopoulos, V.; Ganushkina, N. Y.</p> <p>2015-12-01</p> <p>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 <span class="hlt">equatorial</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4439049','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4439049"><span>Coral Settlement on a Highly Disturbed <span class="hlt">Equatorial</span> Reef System</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bauman, Andrew G.; Guest, James R.; Dunshea, Glenn; Low, Jeffery; Todd, Peter A.; Steinberg, Peter D.</p> <p>2015-01-01</p> <p>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 <span class="hlt">equatorial</span> 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 of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMOS53B1972D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMOS53B1972D"><span>Changes in the <span class="hlt">Equatorial</span> Undercurrent from 1861 to present</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Drenkard, E.; Karnauskas, K. B.</p> <p>2012-12-01</p> <p>The Pacific <span class="hlt">Equatorial</span> Undercurrent (EUC) is a vital component of the tropical Pacific circulation. It transports massive amounts of cold, nutrient- and carbon-rich water eastward, where upwelling feeds the cold tongue, reinforces the zonal SST gradient, and plays an important role in global biogeochemical cycling at seasonal and longer time scales. To first-order, the momentum budget of the EUC is a balance between an eastward oceanic zonal pressure gradient force that is established by the trade winds and downward mixing of westward momentum from the surface current. The EUC is located between 100 and 300m depth and is constrained to within ~2 degrees latitude of the equator by the Coriolis force. A recent study has proposed that Pacific islands and atolls near the equator that experience topographic upwelling of cooler EUC waters, may be spared the brunt of global warming because global climate models project future strengthening of the EUC. This strengthening is in response to increasing atmospheric CO2-forcing by way of a weakening of the trade winds and surface current. Given the ongoing increase in atmospheric CO2 and global temperatures, a natural question is whether or not these changes have already been occurring. Our analyses of an ocean reanalysis product (SODA) indicate that EUC intensification is already underway. Various metrics including core velocity and volume transport calculated from the extended SODA reanalysis (1871-2008) indicate that the EUC has strengthened significantly over the past 130 years. Trends in zonal wind stress and the surface current appear to be consistent with the mechanism governing the annual cycle and future projections when considering the spatiotemporal evolution of these changes. The role of data assimilation and boundary forcing of reanalyses products, and implications of this observed change in characterizing the response of the overall tropical Pacific coupled climate system to global warming will be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6536278','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6536278"><span>Phase space variations of near <span class="hlt">equatorially</span> mirroring ring current ions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Williams, D.J.</p> <p>1981-01-01</p> <p>We present Isee 1 observations of near <span class="hlt">equatorially</span> mirroring ring current ions before and after the magnetic storm of November 25-26, 1977. The data are presented as phase space densities, f(s/sup 2//cm/sup 6/), versus the first adiabatic invariant, m(MeV/G), for the L range approx.2.7-8 R/sub E/. The m range covered varies from approx.50-1000 MeV/G at L = 8 to approx.1-100 MeV/G at L = 2.7. The prestorm phase space densities show an intensity peak at a m value which varies with L as m/sub peak/approx.38 MeV/G for 5< or approx. =L< or approx. =8 and m/sub peak/approx.10e/sup( 0.7L/-3) for 2.7< or approx. =L< or approx. =5. Phase space densities remain nearly constant throughout the storm for m values greater that m/sub peak/ and are enhanced for m values less than m/sub peak/. Thus high-energy ions respond adiabatically to the magnetic field changes caused by the low-energy ion enhancements. This result agrees with earlier Explorer 45 results (Lyons and Williams, 1976). The Isee 1 data are compared directly with the Explorer 45 data and are found to agree very well. The time difference of approx.6 years and local time separation of approx.12 hours between the two data sets lead to the conclusion that the ring current ion behavior presented here is a characteristic feature of geomagnetic storms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020022492&hterms=3d+modeling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3D3d%2Bmodeling','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020022492&hterms=3d+modeling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3D3d%2Bmodeling"><span>Modeling Tides, Planetary Waves, and <span class="hlt">Equatorial</span> Oscillations in the MLT</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mengel, J. G.; Mayr, H. G.; Drob, D. P.; Porter, H. S.; Bhartia, P. K. (Technical Monitor)</p> <p>2001-01-01</p> <p>Applying Hines Doppler Spread Parameterization for gravity waves (GW), our 3D model reproduces some essential features that characterize the observed seasonal variations of tides and planetary waves in the upper mesosphere. In 2D, our model also reproduces the large Semi-Annual Oscillation (SAO) and Quasi Biennial Oscillation (QBO) observed in this region at low latitudes. It is more challenging to describe these features combined in a more comprehensive self consistent model, and we give a progress report that outlines the difficulties and reports some success. In 3D, the GW's are partially absorbed by tides and planetary waves to amplify them. Thus the waves are less efficient in generating the QBO and SAO at <span class="hlt">equatorial</span> latitudes. Some of this deficiency is compensated by the fact that the GW activity is observed to be enhanced at low latitudes. Increasing the GW source has the desired effect to boost the QBO, but the effect is confined primarily to the stratosphere. With increasing altitude, the meridional circulation becomes more important in redistributing the momentum deposited in the background flow by the GW's. Another factor involved is the altitude at which the GW's originate, which we had originally chosen to be the surface. Numerical experiments show that moving this source altitude to the top of the troposphere significantly increases the efficiency for generating the QBO without affecting much the tides and planetary waves in the model. Attention to the details in which the GW source comes into play thus appears to be of critical importance in modeling the phenomenology of the MLT. Among the suite of numerical experiments reported, we present a simulation that produced significant variations of tides and planetary waves in the upper mesosphere. The effect is related to the QBO generated in the model, and GW filtering is the likely cause.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP13D..07N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP13D..07N"><span>Pleistocene dynamics of the Pacific South <span class="hlt">Equatorial</span> Countercurrent</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nuernberg, D.; Raddatz, J.; Rippert, N.; Tiedemann, R.</p> <p>2014-12-01</p> <p>The Western Pacific Warm Pool (WPWP) with extremely high sea-surface-temperatures (SST) is a key area for global climate. It also acts as a crossroad for mode and intermediate water masses such as the South <span class="hlt">Equatorial</span> Countercurrent (SECC) transporting water masses originating from higher latitudes. The SECC flows above the main thermocline and strongly interacts with the Intertropical Convergence Zone (ITCZ) and South Pacific Convergence Zone (SPCZ). To constrain changes in sea-surface and subsurface water mass dynamics affecting thermocline depth, we reconstruct SST, subSST and salinity conditions using combined δ18O and Mg/Ca signals of surface (Globigerinoides ruber, Globigerinoides sacculifer) and subsurface dwelling (Globorotalia tumida) planktonic foraminifera. Our study is based on RV SONNE SO-225 piston cores retrieved from Manihiki plateau, which is located at the southeastern margin of the WPWP (between ~ 5°S-15°S and 170-160°W). The proxy records cover the last ~ 3 Myr SSTMg/Ca remained nearly constant throughout the entire Pleistocene varying between ~30 to 32 (°C), while the subSSTMg/Ca reconstructions reveal pronounced variations from ~10 to 16 (°C). Our results imply that the WPWP thermocline depth has undergone significant vertical movements throughout the Pleistocene. Notably, thermocline depth is continuously decreasing from the early to the late Pleistocene, and coincides with the change from the 41 kyr to a dominant 100 kyr climate periodicity between 1 and 1.7 Ma. We hypothesize that the repeated change in thermocline depth is due to either 1) changes in mode or intermediate water masses advection from Southern Ocean sources via "ocean tunneling", 2) changes in the tropical Pacific wind regime, and/or 3) changes in the Western Pacific Monsoon sytem.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6701225','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6701225"><span>Planetary wave and solar emission signatures in the <span class="hlt">equatorial</span> electrojet</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Parish, H.F.; Forbes, J.M.; Kamalabadi, F. )</p> <p>1994-01-01</p> <p>Recent analyses of observational data reveal the presence of perturbations in the E and F regions of the <span class="hlt">equatorial</span> ionosphere with periods ranging from 2 to 45 days. The characteristic periods of many of these perturbations suggest an association with free Rossby (resonant mode) oscillations, perhaps excited either in the lower atmosphere or in situ. In the present work, the authors analyze hourly magnetic observations from Huancayo Observatory, Peru (12.00[degrees]S, 75.30[degrees]W geographic; 0.72[degrees]S, 4.78[degrees]W geomagnetic), for the presence and persistence of these oscillations during the whole year of 1979. The measured variations can be interpreted in terms of oscillations of the wind field in the E region (approximately 100-160 km), which in turn cause perturbations in the electric fields generated by the wind-driven atmospheric dynamo and in the magnetic field intensity measured at the ground. The observations suggest that the effects of planetary wave oscillations with periods close to 2.5, 3, 6, 7, 9, 10.5, and 16 days may regularly propagate into the thermosphere and ionosphere, causing oscillations which are significant in magnitude. On the basis of an averaged periodogram analysis, they estimate that planetary wave effects may account for up to 75% of the total energy in [delta]H values in the 2 to 35 day period range, suggesting that planetary waves may provide an important contribution to the dynamics and electrodynamics of the lower ionosphere and thermosphere. EUV fluxes during 1979 are noted to have a predominant 13.5-day periodicity during the first half of the year and the more typical 27-day oscillation during the latter half of 1979. These features can in principle affect the [delta]H variations through their influence on the E region conductivity. The authors examine such influence here, especially those that affect the interpretation of the quasi 16-day oscillation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRA..120.1460H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRA..120.1460H"><span>Multiscale <span class="hlt">equatorial</span> electrojet turbulence:Baseline 2-D model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hassan, Ehab; Horton, W.; Smolyakov, A. I.; Hatch, D. R.; Litt, S. K.</p> <p>2015-02-01</p> <p>The spatial and spectral characteristics of the turbulent plasma density, electric fields, and ion drift in ionospheric E region are studied using a new set of nonlinear plasma fluid equations. The fluid model combines both Farley-Buneman (Type-I) and Gradient-Drift (Type-II) plasma instabilities in the <span class="hlt">equatorial</span> electrojet. In our unified model of the plasma instabilities, we include the ion viscosity in the ion momentum equation and electron inertia in the electron momentum equation. These two terms play an important role in stabilizing the growing modes in the linear regime and in driving the Farley-Buneman instability into the saturation state. The simulation results show good agreements with a number of features of rocket and radar observations, such as (1) saturation of plasma density perturbations depends on the solar condition and reaches 7-15% relative to the background, (2) fluctuation of the horizontal secondary electric field reaches 8-15 mV/m, (3) stabilization of the phase velocity of the perturbed density wave around the value of the ion-acoustic speed inside the electrojet, (4) "up-down" asymmetry in the vertical fluxes of the plasma density, (5) "east-west" asymmetry of the plasma zonal drifts, and (6) generation of small scale of the order of meter scale lengths irregularities embedded in large-scale structures. Spectral analysis of the density fluctuations reveals the energy cascade due to the nonlinear coupling between structures of different scales. The break-up of the large-scale structures into small-scale structures explains the disappearance of Type-II echoes in the presence of Type-I instabilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFMPP52B..06P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFMPP52B..06P"><span><span class="hlt">Equatorial</span> Pacific ``stable isotope reference curve'' for the Oligocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pälike, H.; Norris, R.; Herle, J. O.; Wilson, P. A.; Lear, C. H.; Coxall, H. K.; Tripati, A. K.</p> <p>2005-12-01</p> <p>We present an uninterrupted chronology of climate and ocean carbon chemistry from ODP Site 1218 recovered in the <span class="hlt">equatorial</span> Pacific, from the Eocene / Oligocene to the Oligocene / Miocene boundary, ~34 to 23 Ma. Using astronomically age calibrated data we find a strong imprint of the 405, 127 and 96-thousand-year (kyr) Earth's eccentricity as well as a dominant influence of the 1.2 million year (Myr) obliquity amplitude modulation cycles on periodically re-occurring Oligocene glacial and carbon cycle events. In combination, these astronomical modulations act as the ``heartbeat'' of the Oligocene climate system. The response of the climate system to intricate orbital variations is striking and suggests a fundamental role of the carbon cycle in the interaction between solar forcing and climate. Our record provides a new high-resolution view of the Oligocene climate system, prompts a re-evaluation of the previously hypothesised late Oligocene deglaciation, and sheds new light on Oligocene inter-ocean isotope gradients. Salient observations include foraminiferal benthic stable oxygen and carbon isotopes that co-vary, a phase lag of δ13C w.r.t. δ18O for the 405 kyr cycle, preferential filtering of longer orbital periods in δ13C, presumably due to σCO2 reservoir buffering. We then use simple orbitally forced carbon cycle box models and manage to re-create the patterns observed in our data, including the overall strong amplitude of 405 kyr cycles in δ13C. Depending on ice-sheet presence and pCO2 concentrations, our model predicts re-occurring conditions favouring glaciations every 2.4 Myr, including the Eocene/Oligocene transition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ClDy...43.2943P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ClDy...43.2943P"><span>Mean meridional currents in the central and eastern <span class="hlt">equatorial</span> Atlantic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Perez, Renellys C.; Hormann, Verena; Lumpkin, Rick; Brandt, Peter; Johns, William E.; Hernandez, Fabrice; Schmid, Claudia; Bourlès, Bernard</p> <p>2014-12-01</p> <p>Ship-based acoustic Doppler current profiler (ADCP) velocity measurements collected by several major field programs in the tropical Atlantic are averaged and combined with estimates of the mean near-surface velocity derived from drifters and Argo float surface drifts (ADCP+D) to describe the mean cross-<span class="hlt">equatorial</span> and vertical structure of the meridional currents along 23°W and 10°W. Data from moored ADCPs and fixed-depth current meters, a satellite-derived velocity product, and a global ocean reanalysis were additionally used to evaluate the mean ADCP+D meridional velocity. The dominant circulation features in the long-term mean ADCP+D meridional velocity in the upper 100 m are the tropical cells (TCs) located approximately between 5°S and 5°N, with near-surface poleward flow and subsurface equatorward flow that is stronger and shallower in the northern cell compared to the southern cell. The thickness of the surface limb of the TCs decreases and the northern cell is found to shift further south of the equator from the central to eastern tropical Atlantic. Analysis of two-season means estimated from the ship-based ADCP, near-surface drift, and moored velocity data, as well as the simulated fields, indicates that the maximum poleward velocity in the surface limb of the TCs intensifies during December-May along 23°W largely due to seasonal compensation between the geostrophic and ageostrophic (or wind-driven) components of the meridional velocity, whereas the maximum equatorward flow in the subsurface limb of the northern cell intensifies during June-November along both 23°W and 10°W due to the seasonality of the geostrophic meridional velocity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21848.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21848.html"><span>Analysis Sharpens Mars Hydrogen Map, Hinting <span class="hlt">Equatorial</span> Water Ice</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-09-28</p> <p>Re-analysis of 2002-2009 data from a hydrogen-finding instrument on NASA's Mars Odyssey orbiter increased the resolution of maps of hydrogen abundance. The reprocessed data (lower map) shows more "water-equivalent hydrogen" (darker blue) in some parts of this <span class="hlt">equatorial</span> region of Mars. Puzzingly, this suggests the possible presence of water ice just beneath the surface near the equator, though it would not be thermodynamically stable there. The upper map uses raw data from Odyssey's neutron spectrometer instrument, which senses the energy state of neutrons coming from Mars, providing an indication of how much hydrogen is present in the top 3 feet (1 meter) of the surface. Hydrogen detected by Odyssey at high latitudes of Mars in 2002 was confirmed to be in the form of water ice by the follow-up NASA Phoenix Mars Lander mission in 2008. A 2017 reprocessing of the older data applied image-reconstruction techniques often used to reduce blurring from medical imaging data. The results are shown here for an area straddling the equator for about one-fourth the circumference of the planet, centered at 175 degrees west longitude. The white contours outline lobes of a formation called Medusae Fossae, coinciding with some areas of higher hydrogen abundance in the enhanced-resolution analysis. The black line indicates the limit of a relatively young lava plain, coinciding with areas of lower hydrogen abundance in the enhanced-resolution analysis. The color-coding key for hydrogen abundance in both maps is indicated by the horizontal bar, in units expressed as how much water would be present in the ground if the hydrogen is all in the form of water. Units of the equivalent water weight, as a percentage of the material in the ground, are correlated with counts recorded by the spectrometer, ranging from less than 1 weight-percent water equivalent (red) to more than 30 percent (dark blue). https://photojournal.jpl.nasa.gov/catalog/PIA21848</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5019308','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5019308"><span>Bottomside sinusoidal waves, a new class of <span class="hlt">equatorial</span> plasma irregularities</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Valladares, C.E.</p> <p>1983-01-01</p> <p>A new category of <span class="hlt">equatorial</span> F region plasma irregularities having properties easily distinguished from those of plasma bubbles, depletions or broadened turbulence is described. This new class of irregularities has been identified in the data from the Retarding Potential Analizer (RPA) and the Ion Drift Meter (IDM) on the Atmosphere Explorer satellites AE-C and -E. They are observed in the bottomside at night in a narrow belt extending approximately +/-12/sup 0/ from the dip equator, and up to 7500 km or more in the east-west direction. High resolution data from the RPA reveal nearly sinusoidal waves in the ion number density N/sub i/ with peak-to-peak (..delta..N/sub i)/(N/sub i/) amplitudes that span more than 3 orders of magnitude, from values less than 0.1% to more than 100%. These distinctive ''Bottom Side Sinusoidal'' (BSS) irregularities typically have a central wavelength lying in the range from 300 m to 3 km, and relatively narrow spectra. The power spectral index is often large (5 or 6) at the shorter wavelengths but the spectrum usually decays much less rapidly on the longer wavelength side. The vertical drift velocity also has a wavelike structure that appears to be anticorrelated with the N/sub i/ variations, such that regions of lower density plasma move upward and higher density regions move downward with respect to the mean ionospheric drift. Anticorrelated wavelikle drift and density fluctuations are consistent with plasma that is Rayleigh-Taylor (R-T) unstable. Considerations of altitude and latitude localization and cross-field ambipolar diffusion effects introduce a peak in the R-T growth rate near 1 km and also restrict the range of wavelengths that becomes unstable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25992562','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25992562"><span>Coral settlement on a highly disturbed <span class="hlt">equatorial</span> reef system.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bauman, Andrew G; Guest, James R; Dunshea, Glenn; Low, Jeffery; Todd, Peter A; Steinberg, Peter D</p> <p>2015-01-01</p> <p>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 <span class="hlt">equatorial</span> 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 of Singapore</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRC..122.3599P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRC..122.3599P"><span>An idealized study of near <span class="hlt">equatorial</span> river plumes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palma, Elbio D.; Matano, Ricardo P.</p> <p>2017-05-01</p> <p>The dynamics of near <span class="hlt">equatorial</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003RaSc...38.1075D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003RaSc...38.1075D"><span>Evolution and dynamics of <span class="hlt">equatorial</span> plasma bubbles: Relationships to ExB drift, postsunset total electron content enhancements, and <span class="hlt">equatorial</span> electrojet strength</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dabas, R. S.; Singh, Lakha; Lakshmi, D. R.; Subramanyam, P.; Chopra, P.; Garg, S. C.</p> <p>2003-08-01</p> <p>The growth in altitude/latitude of <span class="hlt">equatorial</span> plasma bubbles was monitored, using simultaneous recordings of VHF scintillations at five locations situated between 3° and 23°N magnetic latitudes along a common meridian (84°E) during February 1980. The onsets of postsunset scintillation were mostly abrupt in character, and their occurrence at higher latitudes was conditional on their prior appearance at lower latitudes, indicating a causal link to irregularities associated with rising <span class="hlt">equatorial</span> plasma bubbles. The day-to-day occurrence and the latitudinal, and effectively altitudinal, growths are examined in relation to the prereversal enhancement in h'F during sunset hours and its rate of rise, the onset of a postsunset secondary maximum (PSSM) in ionospheric electron content (IEC), and <span class="hlt">equatorial</span> electrojet strength (EEJ) variations. It is observed that the bubble and associated irregularities, after its onset over the magnetic equator, reached the highest altitudes/latitudes only on those days when a prior PSSM in IEC is observed there in addition to high values of h'F, dh'F/dt and bubble rise velocity; otherwise it will be confined to near <span class="hlt">equatorial</span> latitudes only. Also, the <span class="hlt">equatorial</span> h'F, dh'F/dt, magnitude of PSSM and intensity of 4 GHz scintillations at low latitude are all showing positive correlation with daytime EEJ strength variations. It is concluded that, after the initial development of a bubble, the ExB drift and the PSSM play an important role in the subsequent growth and evolution, and EEJ is a useful parameter for the prediction of the development.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFMOS11A1449E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFMOS11A1449E"><span>Pacific decadal variability in the view of linear <span class="hlt">equatorial</span> wave theory</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Emile-Geay, J. B.; Cane, M. A.</p> <p>2006-12-01</p> <p>It has recently been proposed, within the framework of the linear shallow water equations, that tropical Pacific decadal variability can be accounted for by basin modes with eigenperiods of 10 to 20 years, amplifying a mid- latitude wind forcing with an essentially white spectrum (Cessi and Louazel 2001; Liu 2003). We question this idea here, using a different formalism of linear <span class="hlt">equatorial</span> wave theory. We compute the Green's function for the wind forced response of a linear <span class="hlt">equatorial</span> shallow water ocean, and use the results of Cane and Moore (1981) to obtain a compact, closed form expression for the motion of the <span class="hlt">equatorial</span> thermocline, which applies to all frequencies lower than seasonal. At very low frequencies (decadal timescales), we recover the planetary geostrophic solution used by Cessi and Louazel (2001), as well as the <span class="hlt">equatorial</span> wave solution of Liu (2003), and give a formal explanation for this convergence. Using this more general solution to explore more realistic wind forcings, we come to a different interpretation of the results. We find that the <span class="hlt">equatorial</span> thermocline is inherently more sensitive to local than to remote wind forcing, and that planetary Rossby modes only weakly alter the spectral characteristics of the response. Tropical winds are able to generate a strong <span class="hlt">equatorial</span> response with periods of 10 to 20 years, while midlatitude winds can only do so for periods longer than about 50 years. Since the decadal pattern of observed winds shows similar amplitude for tropical and midlatitude winds, we conclude that the latter are unlikely to be responsible for the observed decadal tropical Pacific SST variability. References : Cane, M. A., and Moore, D. W., 1981: A note on low-frequency <span class="hlt">equatorial</span> basin modes. J. Phys. Oceanogr., 11(11), 1578 1584. Cessi, P., and Louazel, S., 2001: Decadal oceanic response to stochastic wind forcing. J. Phys. Oceanogr., 31, 3020 3029. Liu, Z., 2003: Tropical ocean decadal variability and resonance of planetary</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A11N0261B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A11N0261B"><span>Extra-tropical origin of <span class="hlt">equatorial</span> Pacific cold bias in climate models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burls, N.; Muir, L.; Vincent, E. M.; Fedorov, A. V.</p> <p>2015-12-01</p> <p>General circulation models frequently suffer from a substantial cold bias in <span class="hlt">equatorial</span> 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 this project). Our study investigates the extent to which these <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> SSTs and upper ocean temperatures in the extra-tropical subduction regions, our analysis confirms that cold SST biases within the extra-tropical Pacific translate into a cold <span class="hlt">equatorial</span> SST bias via the STCs. An assessment of the relationship between these extra-tropical SST biases and 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 extended extra-tropical Pacific, on the <span class="hlt">equatorial</span> bias. The CESM experiments reveal a quadratic relationship between extra-tropical albedo and the root-mean-square-error in <span class="hlt">equatorial</span> SSTs - a relationship with which the CMIP5 models generally agree. Thus, our study suggests that one way to improve the <span class="hlt">equatorial</span> cold bias is to improve the representation of cloud albedo in mid-latitudes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSPC24B2149B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSPC24B2149B"><span>Extra-tropical origin of <span class="hlt">equatorial</span> Pacific cold bias in climate models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burls, N.; Muir, L.; Vincent, E. M.; Fedorov, A. V.</p> <p>2016-02-01</p> <p>General circulation models frequently suffer from a substantial cold bias in <span class="hlt">equatorial</span> 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 this project). Our study investigates the extent to which these <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> SSTs and upper ocean temperatures in the extra-tropical subduction regions, our analysis confirms that cold SST biases within the extra-tropical Pacific translate into a cold <span class="hlt">equatorial</span> SST bias via the STCs. An assessment of the relationship between these extra-tropical SST biases and 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 extended extra-tropical Pacific, on the <span class="hlt">equatorial</span> bias. The CESM experiments reveal a quadratic relationship between extra-tropical albedo and the root-mean-square-error in <span class="hlt">equatorial</span> SSTs - a relationship with which the CMIP5 models generally agree. Thus, our study suggests that one way to improve the <span class="hlt">equatorial</span> cold bias is to improve the representation of cloud albedo in mid-latitudes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...48.3615R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...48.3615R"><span>Phase locking of <span class="hlt">equatorial</span> Atlantic variability through the seasonal migration of the ITCZ</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Richter, Ingo; Xie, Shang-Ping; Morioka, Yushi; Doi, Takeshi; Taguchi, Bunmei; Behera, Swadhin</p> <p>2017-06-01</p> <p>The <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> 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-<span class="hlt">equatorial</span> position of the Atlantic ITCZ contributes to the decay of wind anomalies in three ways: (1) horizontal advection associated with the cross-<span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> wind anomalies at the surface, while anomalies aloft remain relatively strong. (3) The cross-<span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> Atlantic, where SST anomalies are small. This introduces a new element into coupled air-sea interaction of the tropical Atlantic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999JGR...10420551R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999JGR...10420551R"><span>The role of the Indonesian Throughflow in <span class="hlt">equatorial</span> Pacific thermocline ventilation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rodgers, Keith B.; Cane, Mark A.; Naik, Naomi H.; Schrag, Daniel P.</p> <p>1999-09-01</p> <p>The role of the Indonesian Throughflow (ITF) in the thermocline circulation of the low-latitude Pacific Ocean is explored using a high-resolution primitive equation ocean circulation model. Seasonally forced runs for a domain with an open Indonesian passage are compared with seasonally forced runs for a closed Pacific domain. Three cases are considered: one with no throughflow, one with 10 Sv of imposed ITF transport, and one with 20 Sv of ITF transport. Two idealized tracers, one that tags northern component subtropical water and another that tags southern component subtropical water, are used to diagnose the mixing ratio of northern and southern component waters in the <span class="hlt">equatorial</span> thermocline. It is found that the mixing ratio of north/south component waters in the <span class="hlt">equatorial</span> thermocline is highly sensitive to whether the model accounts for an ITF. Without an ITF, the source of <span class="hlt">equatorial</span> undercurrent water is primarily of North Pacific origin, with the ratio of northern to southern component water being approximately 2.75 to 1. The ratio of northern to southern component water in the <span class="hlt">Equatorial</span> Undercurrent with 10 Sv of ITF is approximately 1.4 to 1, and the ratio with 20 Sv of imposed ITF is 1 to 1.25. Estimates from data suggest a mean mixing ratio of northern to southern component water of less than 1 to 1. Assuming that the mixing ratio changes approximately linearly as the ITF transport varies between 10 and 20 Sv, an approximate balance between northern and southern component water is reached when the ITF transport is approximately 16 Sv. It is also shown that for the isopycnal surfaces within the core of the <span class="hlt">equatorial</span> undercurrent, a 2°C temperature front exists across the equator in the western <span class="hlt">equatorial</span> Pacific, beneath the warm pool. The implications of the model results and the temperature data for the heat budget of the <span class="hlt">equatorial</span> Pacific are considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.3171B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.3171B"><span>Multiple embryos, multiple nepionts and multiple <span class="hlt">equatorial</span> layers in Cycloclypeus carpenteri.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Briguglio, Antonino; Kinoshita, Shunichi; Wolfgring, Erik; Hohenegger, Johann</p> <p>2016-04-01</p> <p>In this study, 17 specimens of Cycloclypeus carpenteri have been analyzed by means of microCT scanning. We used CT scanning technique as it enables the visualization and the quantifications of internal structures of hollow specimens without their destruction. It has been observed that many specimens possessing the natural morphology of this taxon, actually contain multiple embryos (up to 16 in one single specimen) and, in some few cases, multiple nepionts each with its own heterosteginid chambers (up to three separated nepionts). The diameter of each proloculus has been measured, and as a result, they are very variable even within the same specimen, therefore questioning the long known theory that schizonts have smaller proloculi than gamonts and also questioning the fact that proloculi in the same species should all have comparable size. Furthermore, we have observed the presence of additional <span class="hlt">equatorial</span> planes on several specimens. Such additional planes are always connected to what seems to be the main <span class="hlt">equatorial</span> plane. Such connections are T-shaped and are located at the junction between two <span class="hlt">equatorial</span> layers; these junctions are made by a chamberlet, which possesses an unusually higher number of apertures. The connections between <span class="hlt">equatorial</span> planes are always perfectly synchronized with the relative growth step and the same chamber can be therefore followed along the multiple <span class="hlt">equatorial</span> planes. Apparently there is a perfect geometric relationship between the creation of additional <span class="hlt">equatorial</span> planes and the position of the nepionts. Whenever the nepionts are positioned on different planes, additional planes are created and the angle of the nepionts is related to the banding angle of the <span class="hlt">equatorial</span> planes. The presence of additional planes do not hamper the life of the cell, on the contrary, it seems that the cell is still able to build nicely shaped chamberlets and, after volumetric calculations, it seems all specimens managed to keep their logistic growth</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5305777','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5305777"><span>Theory for modeling the <span class="hlt">equatorial</span> evening ionosphere and the origin of the shear in the horizontal plasma flow</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Haerendel, G.; Eccles, J.V.; Cakir, S. )</p> <p>1992-02-01</p> <p>Companion papers in this series present (1) the role of <span class="hlt">equatorial</span> E region postsunset ionosphere, (2) the origin of horizontal plasma shear flow in the postsunset <span class="hlt">equatorial</span> ionosphere (this paper), (3) the Colored Bubbles experiments results, and (4) computer simulations of artificial initiation of plasma density depletions (bubbles) in the <span class="hlt">equatorial</span> ionosphere. Within this paper, equations describing the time evolution of the <span class="hlt">equatorial</span> ionosphere are developed using flux tube integrated and flux tube weighted quantities which model the chemistry, dynamics, and electrodynamics of the <span class="hlt">equatorial</span> ionosphere. The resulting two-dimensional set of equations can be used to investigate <span class="hlt">equatorial</span> ionosphere. The resulting two-dimensional set of equations can be used to investigate <span class="hlt">equatorial</span> electric fields neglecting small-scale phenomena ({lambda} < 1 km). An immediate result derived from the integrated current equations is an equation describing the physics of the shear in the horizontal flow of the <span class="hlt">equatorial</span> plasma during the evening hours. The profile of the horizontal flow has three important contributing terms relating to the neutral wind dynamo, Hall conduction, and the <span class="hlt">equatorial</span> electrojet current divergence. Using a one-dimensional model of the velocity shear equation and the integrated ionosphere transport equations, a time history of the development of the shear feature during postsunset hours is presented. The one-dimensional model results are compared to the velocity shear measurements from the Colored Bubbles experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Natur.529..519C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Natur.529..519C"><span>No iron fertilization in the <span class="hlt">equatorial</span> Pacific Ocean during the last ice age</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Costa, K. M.; McManus, J. F.; Anderson, R. F.; Ren, H.; Sigman, D. M.; Winckler, G.; Fleisher, M. Q.; Marcantonio, F.; Ravelo, A. C.</p> <p>2016-01-01</p> <p>The <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> Pacific remains uncertain. Here we present meridional transects of dust (derived from the 232Th proxy), phytoplankton productivity (using opal, 231Pa/230Th and excess Ba), and the degree of nitrate consumption (using foraminifera-bound δ15N) from six cores in the central <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> Pacific during the LGP. As these nutrients are today dominantly sourced from the Subantarctic Zone of the Southern Ocean, we propose that the central <span class="hlt">equatorial</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26819045','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26819045"><span>No iron fertilization in the <span class="hlt">equatorial</span> Pacific Ocean during the last ice age.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Costa, K M; McManus, J F; Anderson, R F; Ren, H; Sigman, D M; Winckler, G; Fleisher, M Q; Marcantonio, F; Ravelo, A C</p> <p>2016-01-28</p> <p>The <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> Pacific during the LGP. As these nutrients are today dominantly sourced from the Subantarctic Zone of the Southern Ocean, we propose that the central <span class="hlt">equatorial</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1981JGR....86.3173Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1981JGR....86.3173Z"><span>Nitric oxide from nitrite photolysis in the central <span class="hlt">equatorial</span> Pacific</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zafiriou, O. C.; McFarland, M.</p> <p>1981-04-01</p> <p>Sunlight photolyzes nitrite in seawater: NO2- + HOH + hv = NO + OH + OH-. We studied nitrite loss and nitric oxide production attributed to this reaction in surface waters of the <span class="hlt">equatorial</span> Pacific near 170°W. Net photochemical loss rates of 2-15% per day were derived from two different types of laboratory incubation experiments. The net nitrite loss rate in the surface water of this region is calculated to average 4 × 10-13 mol l-l s-l during the day, or ˜6 × 10-2 mol m-2 y-1. Nitric oxide was detected in situ with a floating gas-seawater equilibrator. NO was always detectable in nitrite-containing seawater during the day but was undetectable at night or in nitrite-free water. Near sunrises and sunsets the estimated NO vapor pressure, pNO(sea) covaried with the ambient UV insolation in air according to log pNO(sea) = a log UVair + b. Best-fit values to the in situ data indicate a ≈ 1 with r2 ≥ 0.9; simple kinetic models rationalize a values of O, ½, or 1. During the day, pNO(sea) averaged ˜3.1 × 10-8 atm, corresponding to ˜4.6 × 10-11 M [NO]aq. The ambient atmospheric pNO was ˜104 -fold lower, implying a substantial seawater supersaturation and a sea → air flux. From the stagnant-boundary layer model and our measurements, we estimate ˜2 × 10-16 mol 1-1 s-1 (˜1.3 × 108 molecule cm-2 s-1) of NO efflux in daylight, an insignificant NO loss from the sea. The photochemical NO source and the estimated dark reaction sink are, within the accuracy of the data, in balance. These results provide evidence for the presence of NO, a free radical, in surface seawater. They substantiate that photochemical reactions produce measurable concentrations of reactive intermediates in surface seawater and that these enter into rapid secondary reactions. These processes may reach sufficient intensity to provide significant effects, such as sea → air fluxes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUSMSA31A..16H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUSMSA31A..16H"><span>A Campaign to Study <span class="hlt">Equatorial</span> Ionospheric Phenomena over Guam</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Habash Krause, L.; Balthazor, R.; Dearborn, M.; Enloe, L.; Lawrence, T.; McHarg, M.; Petrash, D.; Reinisch, B. W.; Stuart, T.</p> <p>2007-05-01</p> <p>With the development of a series of ground-based and space-based experiments, the United States Air Force Academy (USAFA) is in the process of planning a campaign to investigate the relationship between <span class="hlt">equatorial</span> ionospheric plasma dynamics and a variety of space weather effects, including: 1) ionospheric plasma turbulence in the F region, and 2) scintillation of radio signals at low latitudes. A Digisonde Portable Sounder DPS-4 will operate from the island of Guam (with a magnetic latitude of 5.6° N) and will provide measurements of ionospheric total electron content (TEC), vertical drifts of the bulk ionospheric plasma, and electron density profiles. Additionally, a dual-frequency GPS TEC/scintillation monitor will be located along the Guam magnetic meridian at a magnetic latitude of approximately 15° N. In campaign mode, we will combine these ground-based observations with those collected from space during USAFA's FalconSAT-3 and FalconSAT-5 low-earth orbit satellite missions, the first of which is scheduled to be active over a period of several months beginning in the 2007 calendar year. The satellite experiments are designed to characterize in situ irregularities in plasma density, and include measurements of bulk ion density and temperature, minority-to- majority ion mixing ratios, small scale (10 cm to 1 m) plasma turbulence, and ion distribution spectra in energy with sufficient resolution for observations of non-thermalized distributions that may be associated with velocity- space instabilities. Specific targets of investigation include: a) a comparison of plasma turbulence observed on- orbit with spread F on ionograms as measured with the Digisonde, b) a correlation between the vertical lifting of the ionospheric layer over Guam and the onset of radio scintillation activity along the Guam meridian at 15° N magnetic latitude, and c) a correlation between on-orbit turbulence and ionospheric scintillation at 15° N magnetic latitude. These relationships</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950036312&hterms=Bergman&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DBergman','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950036312&hterms=Bergman&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DBergman"><span><span class="hlt">Equatorial</span> wave activity derived from fluctuations in observed convection</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bergman, John W.; Salby, Murry L.</p> <p>1994-01-01</p> <p>The spectrum of <span class="hlt">equatorial</span> wave activity propagating vertically into the stratosphere is calculated from high-resolution imagery of the global convective pattern. Synoptic Global Cloud Imagery (GCI), constructed from six satellites simultaneously observing the earth, is used to diabatically force the linearized primitive equations. Having resolution of 0.5 deg and 3 h, that imagery captures the dominant scales of organized convection, including several harmonics of the diurnal cycle. Its global coverage with high space-time resolution allows the GCI to represent heating variability and dynamical behavior excited by it over a wide range of scales. The dynamical response above the heating is evaluated globally in terms of a space-time spectrum of Hough modes, one which includes planetary-scale Kelvin waves, Rossby waves, and gravity waves down to the resolution of the GCI. The geopotential response, which is indicative of temperature fluctuations observed by satellite, is very red in frequency. Therefore, planetary-scale waves with periods longer than two days dominate the spectrum of geopotential, while high-frequency gravity waves make a comparatively small contribution. Some 80% of the geopotential variance is accounted for by the Kelvin and gravest-symmetric Rossby modes, while the Rossby-gravity mode is comparatively weak. In horizontal eddy motion, the excited wave spectrum is still dominated by planetary-scale components. However, meridional wind fluctuations associated with the Rossby-gravity mode have variance comparable to that of zonal wind fluctuations associated with the Kelvin mode, even though the Rossby-gravity mode is nearly invisible in the geopotential response. Estimates of tropospheric heating lead to amplitudes and propagation characteristics that are broadly consistent with satellite and radiosonde observations of wave activity in the lower stratosphere. The space-time spectrum of EP flux is significantly whiter than the response in either</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMOS51B0969S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMOS51B0969S"><span>Compound-specific nitrogen isotopes of <span class="hlt">equatorial</span> Pacific sedimentary record</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sauthoff, W.; Ravelo, A. C.; Mccarthy, M. D.</p> <p>2014-12-01</p> <p>Compound specific nitrogen isotopic analysis of amino acids (δ15N-AA) is a technique that is widely used in regional ecology and food web studies, with newly expanding applications in organic geochemistry. However, its applicability to marine sediment has been minimally examined. This study is one of the first δ15N-AA applications into the paleorecord of marine sediment. We explore how δ15N-AA measurements provide insights into past changes in water column N cycling and N utilization, and into post-depositional processes that impact sedimentary N. This is possible because δ15N-AA investigates the molecular-level basis of the bulk sedimentary δ15N signal, revealing possible diagenetic alteration of sedimentary organic matter. Our goal was is to investigate the extent of alteration (vs. preservation) of individual sedimentary amino acid δ15N values from surface nitrate δ15N across a wide range of depositional environments. The δ15N of bulk sediment differs from that of the surface nitrate δ15N signal because of water column processes or more often because of alteration of the signal during initial sedimentation. To investigate this alteration we compare δ15N-AA to bulk δ15N measurements in a suite of <span class="hlt">equatorial</span> Pacific core tops (378-4360 m below sea level) across contrasting oceanographic and sedimentary depositional conditions (e.g. high vs. low productivity, hypoxic vs. oxic bottom waters). To examine down core diagenetic alteration of the sediment record, we present δ15N-AA and bulk δ15N of selected deeper depths to observe 1) if diagenetic shift is coherently resolved by both types of measurements and 2) if select individual δ15N-AA values remain representative of the surface organic δ15N signal. We hypothesize that compound specific analysis (δ15N-AA) will provide a molecular level assessment of mechanism for diagenetic changes in bulk organic δ15N values while also preserving detailed information about planktonic ecosystem structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AdSpR..59.1526T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AdSpR..59.1526T"><span>Characteristics of <span class="hlt">equatorial</span> electrojet derived from Swarm satellites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thomas, Neethal; Vichare, Geeta; Sinha, A. K.</p> <p>2017-03-01</p> <p>The vector magnetic field measurements from three satellite constellation, Swarm mission (Alpha 'Swarm-A', Bravo 'Swarm-B', and Charlie 'Swarm-C') during the quiet days (daily ∑Kp ⩽ 10) of the years 2014-2015 are used to study the characteristic features of <span class="hlt">equatorial</span> electrojet (EEJ). A program is developed to identify the EEJ signature in the X (northward) component of the magnetic field recorded by the satellite. An empirical model is fitted into the observed EEJ signatures separately for both the hemispheres, to obtain the parameters of electrojet current such as peak current density, total eastward current, the width of EEJ, position of the electrojet axis, etc. The magnetic field signatures of EEJ at different altitudes are then estimated. Swarm B and C are orbiting at different heights (separation ∼50 km) and during the month of April 2014, both the satellites were moving almost simultaneously over nearby longitudes. Therefore, we used those satellite passes to validate the methodology used in the present study. The magnetic field estimates at the location of Swarm-C obtained using the observations of Swarm B are compared with the actual observations of Swarm-C. A good correlation between the actual and the computed values (correlation coefficient = 0.98) authenticates the method of analysis. The altitudinal variation of the amplitude and the width of the EEJ signatures are also depicted. The ratio of the total eastward flowing forward to westward return currents is found to vary between 0.1 and 1.0. The forward and return current values in the northern hemisphere are found to be ∼0.5 to 2 times of those in the southern hemisphere, thereby indicating the hemispheric asymmetry. The latitudinal extents of the forward and return currents are found to have longitudinal dependence similar to that of the amplitude and the width of EEJ showing four peak structures. Local time dependence of EEJ parameters has also been investigated. In general, the results</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011DSRII..58..325T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011DSRII..58..325T"><span>Metal quotas of plankton in the <span class="hlt">equatorial</span> Pacific Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Twining, Benjamin S.; Baines, Stephen B.; Bozard, James B.; Vogt, Stefan; Walker, Elyse A.; Nelson, David M.</p> <p>2011-03-01</p> <p>The micronutrient metals Mn, Fe, Co, Ni and Zn are required for phytoplankton growth, and their availability influences ocean productivity and biogeochemistry. Here we report the first direct measurements of these metals in phytoplankton and protozoa from the <span class="hlt">equatorial</span> Pacific Ocean. Cells representing 4 functional groups (diatoms, autotrophic flagellates, heterotrophic flagellates and autotrophic picoplankton) were collected from the surface mixed layer using trace-metal clean techniques during transects across the equator at 110°W and along the equator between 110°W and 140°W. Metal quotas were determined for individual cells with synchrotron x-ray fluorescence microscopy, and cellular stoichiometries were calculated relative to measured P and S, as well as to C calculated from biovolume. Bulk particulate (>3 μm) metal concentrations were also determined at 3 stations using inductively coupled plasma mass spectrometry for comparison to single-cell stoichiometries. Phosphorus-normalized Mn, Fe, Ni and Zn ratios were significantly higher in diatoms than other cell types, while Co stoichiometries were highest in autotrophic flagellates. The magnitude of these effects ranged from approximately 2-fold for Mn in diatoms and autotrophic flagellates to nearly an order of magnitude for Fe in diatoms and picoplankton. Variations in S-normalized metal stoichiometries were also significant but of lower magnitude (1.4 to 6-fold). Cobalt and Mn quotas were 1.6 and 3-fold higher in autotrophic than heterotrophic flagellates. Autotrophic picoplankton were relatively enriched in Ni but depleted in Zn, matching expectations based on known uses of these metals in prokaryotes and eukaryotes. Significant spatial variability in metal stoichiometries was also observed. At two stations deviations in Fe stoichiometries reflected features in the dissolved Fe distribution. At these same stations, high Ni stoichiometries in autotrophic flagellates were correlated with elevated ammonium</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950006440','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950006440"><span>Guest investigator program study: Physics of <span class="hlt">equatorial</span> plasma bubbles</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tsunoda, Roland T.</p> <p>1994-01-01</p> <p>Plasma bubbles are large-scale (10 to 100 km) depletions in plasma density found in the night-time <span class="hlt">equatorial</span> ionosphere. Their formation has been found to entail the upward transport of plasma over hundreds of kilometers in altitude, suggesting that bubbles play significant roles in the physics of many of the diverse and unique features found in the low-latitude ionosphere. In the simplest scenario, plasma bubbles appear first as perturbations in the bottomside F layer, which is linearly unstable to the gravitationally driven Rayleigh-Taylor instability. Once initiated, bubbles develop upward through the peak of the F layer into its topside (sometimes to altitudes in excess of 1000 km), a behavior predicted by the nonlinear form of the same instability. While good general agreement has been found between theory and observations, little is known about the detailed physics associated with plasma bubbles. Our research activity centered around two topics: the shape of plasma bubbles and associated electric fields, and the day-to-day variability in the occurrence of plasma bubbles. The first topic was pursued because of a divergence in view regarding the nonlinear physics associated with plasma bubble development. While the development of perturbations in isodensity contours in the bottomside F layer into plasma bubbles is well accepted, some believed bubbles to be cylinder-like closed regions of depleted plasma density that floated upward leaving a turbulent wake behind them (e.g., Woodman and LaHoz, 1976; Ott, 1978; Kelley and Ott, 1978). Our results, summarized in a paper submitted to the Journal of Geophysical Research, consisted of incoherent scatter radar measurements that showed unambiguously that the depleted region is wedgelike and not cylinderlike, and a case study and modeling of SM-D electric field instrument (EFI) measurements that showed that the absence of electric-field perturbations outside the plasma-depleted region is a distinct signature of wedge</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000EP%26S...52..237O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000EP%26S...52..237O"><span>Daily variations of geomagnetic H D and Z-field at <span class="hlt">equatorial</span> latitudes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Okeke, F. N.; Hamano, Y.</p> <p>2000-04-01</p> <p>With the establishment of the new geomagnetic field observations in the Ocean Hemisphere Network Project (OHP) in Japan, minutes values of geomagnetic components, H D and Zhave been recorded. The hourly mean values were used to study the variations in these three components at these new <span class="hlt">equatorial</span> electrojet regions. The results of the analysis carried out revealed that the amplitude of dHhas diurnal variation which peaks during the day at about local noon in all the three <span class="hlt">equatorial</span> electrojet regions. This diurnal variation in Hwith Sq(H) enhancement in all the three regions are attributed to the enhanced dynamo action at these regions. Diurnal variation as observed in Dindicates that the <span class="hlt">equatorial</span> electrojet current system has both east-west and north-south components. The pronounced magnitude of Zvariation as observed in Kiritimati is attributed mainly to sea induction. Also some abnormal features were observed on 23rd of January at Huancayo, in the components. Seasonal variations with more pronounced equinoctial maximum were observed in Hthan in Z. Dcomponent showed no consistent seasonal variation in all the regions. The equinoctial maximum is due to enhanced <span class="hlt">equatorial</span> electron density at equinox. More research work, if carried out in these new regions will be useful in making more new contributions to the field of the dynamics of the <span class="hlt">equatorial</span> electrojet region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRA..119.8524R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRA..119.8524R"><span>Seismo-ionospheric coupling appearing as <span class="hlt">equatorial</span> electron density enhancements observed via DEMETER electron density measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ryu, K.; Lee, E.; Chae, J. S.; Parrot, M.; Pulinets, S.</p> <p>2014-10-01</p> <p>We report the processes and results of statistical analysis on the ionospheric electron density data measured by the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite over a period of 6 years (2005-2010), in order to investigate the correlation between seismic activity and <span class="hlt">equatorial</span> plasma density variations. To simplify the analysis, three <span class="hlt">equatorial</span> regions with frequent earthquakes were selected and then one-dimensional time series analysis between the daily seismic activity indices and the <span class="hlt">equatorial</span> ionization anomaly (EIA) intensity indices, which represent relative <span class="hlt">equatorial</span> electron density increase, were performed for each region. The statistically significant values of the lagged cross-correlation function, particularly in the region with minimal effects of longitudinal asymmetry, indicate that some of the very large earthquakes with M > 5.0 in the low-latitude region can accompany observable precursory and concurrent EIA enhancements, even though the seismic activity is not the most significant driver of the <span class="hlt">equatorial</span> ionospheric evolution. The physical mechanisms of the seismo-ionospheric coupling is consistent with our observation, and the possibility of earthquake prediction using the EIA intensity variation is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006ihy..workE.102V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006ihy..workE.102V"><span>Solar Cycle Effects on <span class="hlt">Equatorial</span> Electrojet Strength and Low Latitude Ionospheric Variability (P10)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Veenadhari, B.; Alex, S.</p> <p>2006-11-01</p> <p>veena_iig@yahoo.co.in The most obvious indicators of the activity of a solar cycle are sunspots, flares, plages, and soon. These are intimately linked to the solar magnetic fields, heliospheric processes which exhibit complex but systematic variations. The changes in geomagnetic activity, as observed in the ground magnetic records follow systematic correspondence with the solar activity conditions. Thus the transient variations in the magnetic field get modified by differing solar conditions. Also the solar cycle influences the Earth causing changes in geomagnetic activity, the magnetosphere and the ionosphere. Daily variations in the ground magnetic field are produced by different current systems in the earth’s space environment flowing in the ionosphere and magnetosphere which has a strong dependence on latitude and longitude of the location. The north-south (Horizontal) configuration of the earth’s magnetic field over the equator is responsible for the narrow band of current system over the <span class="hlt">equatorial</span> latitudes and is called the <span class="hlt">Equatorial</span> electrojet (EEJ) and is a primary driver for <span class="hlt">Equatorial</span> Ionization anomaly (EIA). <span class="hlt">Equatorial</span> electric fields and plasma drifts play the fundamental roles on the morphology of the low latitude ionosphere and strongly vary during geomagnetically quiet and disturbed periods. Quantitative study is done to illustrate the development process of EEJ and its influence on ionospheric parameters. An attempt is also made to examine and discuss the response of the <span class="hlt">equatorial</span> electrojet parameters to the fast varying conditions of solar wind and interplanetary parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ThApC.127..551C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ThApC.127..551C"><span>Impact of East Asian winter monsoon on MJO over the <span class="hlt">equatorial</span> western Pacific</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Xiong; Li, Chongyin; Ling, Jian; Tan, Yanke</p> <p>2017-02-01</p> <p>This paper investigates the processes and mechanisms by which the East Asian winter monsoon (EAWM) affects the Madden-Julian oscillation (MJO) over the <span class="hlt">equatorial</span> western Pacific in boreal winter (November-April). The results show that both the EAWM and MJO over the <span class="hlt">equatorial</span> western Pacific have prominent interannual and interdecadal variabilities, and they are closely related, especially on the interannual timescales. The EAWM influences MJO via the feedback effect of convective heating, because the strong northerlies of EAWM can enhance the ascending motion and lead the convection to be strengthened over the <span class="hlt">equatorial</span> western Pacific by reinforcing the convergence in the lower troposphere. Daily composite analysis in the phase 4 of MJO (i.e., strong MJO convection over the Maritime Continent and <span class="hlt">equatorial</span> western Pacific) shows that the kinetic energy, outgoing longwave radiation (OLR), moisture flux, vertical velocity, zonal wind, moist static energy, and atmospheric stability differ greatly between strong and weak EAWM processes over the western Pacific. The strong EAWM causes the intensity of MJO to increase, and the eastward propagation of MJO to become more persistent. MJO activities over the <span class="hlt">equatorial</span> western Pacific have different modes. Furthermore, these modes have differing relationships with the EAWM, and other factors can also affect the activities of MJO; consequently, the relationship between the MJO and EAWM shows both interannual and interdecadal variabilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP52A..07C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP52A..07C"><span><span class="hlt">Equatorial</span> Pacific Coral Geochemical Records Show Recent Weakening of the Walker Circulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carilli, J.; Mcgregor, H. V.; Gaudry, J. J.; Donner, S. D.; Gagan, M. K.; Stevenson, S. L.; Wong, H.; Fink, D.</p> <p>2014-12-01</p> <p><span class="hlt">Equatorial</span> Pacific ocean-atmosphere interactions affect climate globally, and a key component of the coupled system is the Walker Circulation, which is driven by sea surface temperature (SST) gradients across the <span class="hlt">equatorial</span> Pacific. There is conflicting evidence as to whether the SST gradient and Walker Circulation have strengthened or weakened over the late 20th century. We present new records of SST and sea surface salinity (SSS) spanning 1959-2010 based on paired measurements of Sr/Ca and d18O in a massive Porites coral from Butaritari atoll in the Gilbert Islands, Republic of Kiribati, in the central-western <span class="hlt">equatorial</span> Pacific. The records show 2-7 year variability correlated with the El Niño-Southern Oscillation (ENSO) and corresponding shifts in the extent of the Indo-Pacific Warm Pool, and decadal-scale signals related to the Pacific Decadal Oscillation. In addition, the Butaritari coral records reveal a small but significant increase in SST (0.39˚C) from 1959 to 2010 with no accompanying change in SSS, a trend that persists even when ENSO variability is removed. In contrast, larger increases in SST and SSS are evident in coral records from the <span class="hlt">equatorial</span> Pacific Line Islands, located east of Butaritari. Taken together, the <span class="hlt">equatorial</span> Pacific coral records suggest an overall reduction in the east-west SST and SSS gradient over the last several decades, and a recent weakening of the Walker Circulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.V12A..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.V12A..07S"><span>Seismicity of the <span class="hlt">Equatorial</span> Mid-Atlantic Ridge and its Large Offset Transforms recorded during a multi-year hydrophone array deployment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smith, D. K.; Dziak, R. P.; Haxel, J.; Meyer, R. P.</p> <p>2015-12-01</p> <p>To increase our understanding of the slow-spreading, <span class="hlt">equatorial</span> Mid-Atlantic Ridge (MAR), we deployed an array of eight autonomous hydrophones centered on the ridge axis between ~20°N and ~10°S. The hydrophones were deployed for 2+ years (500 Hz sample rate) and obtained a continuous record of the regional seismicity. This region is especially interesting for many reasons. A strongly segmented MAR is offset by some of the longest transform faults in the global oceans. In addition, the North America-South America-Africa (<span class="hlt">NA</span>-SA-AF) triple junction is thought to be between 10°N and 20°N at the MAR, but its exact location is not well-defined. And finally, the <span class="hlt">NA</span>-SA plate boundary is not clearly delineated by teleseismicity or prominent seafloor structures despite known relative motion between the plates. Seven of the eight hydrophones were recovered in January 2015 and earthquake location analysis is underway. These seismic data will be used to understand the modes of spreading, short-term earthquake predictability, and triple junction dynamics. In particular, we will use patterns in the earthquake data to address the following: 1) Whether long-lived detachment faults play a central role in accretion at the <span class="hlt">equatorial</span> MAR similar to what is observed to the north (Escartin et al., 2008). 2) Whether foreshock sequences can be used to predict (retrospectively) earthquakes with magnitudes ≥ 5.4 mb on <span class="hlt">equatorial</span> Atlantic transform faults as they can be on Pacific transforms (McGuire et al., 2005). A total of eighteen teleseismic earthquakes ≥ 5.4 mb occurred in this region during the hydrophone deployment providing a robust data base to test this foreshock precursor hypothesis. 3) Lastly, whether or not the geometry and crustal stress patterns induced by the <span class="hlt">NA</span>-SA-AF triple junction are apparent in the earthquake data. If so, the earthquake patterns will help improve our understanding of triple junction dynamics and overall lithospheric strength.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JASTP.147...71V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JASTP.147...71V"><span>First observational evidence for the connection between the meteoric activity and occurrence of <span class="hlt">equatorial</span> counter electrojet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vineeth, C.; Mridula, N.; Muralikrishna, P.; Kumar, K. K.; Pant, T. K.</p> <p>2016-09-01</p> <p>This paper presents the first direct observational evidence for the possible role of meteoric activity in the generation of the <span class="hlt">equatorial</span> Counter Electrojets (CEJ), an enigmatic daytime electrodynamical process over the geomagnetic <span class="hlt">equatorial</span> upper atmosphere. The investigation carried out using the data from Proton Precession Magnetometer and Meteor Wind Radar over a geomagnetic dip <span class="hlt">equatorial</span> station, Trivandrum (8.5°N, 77°E, 0.5°N dip lat.) in India, revealed that the occurrence of the afternoon CEJ events during a month is directly proportional to the average monthly meteor counts over this location. The observation is found to be very consistent during the considered period of study, i.e the years 2006 and 2007. The study vindicates that the meteor showers play a major role in setting up the background condition conducive for the generation of CEJ by reducing the strength of the upward polarization field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4052749','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4052749"><span>Larger CO2 source at the <span class="hlt">equatorial</span> Pacific during the last deglaciation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kubota, Kaoru; Yokoyama, Yusuke; Ishikawa, Tsuyoshi; Obrochta, Stephen; Suzuki, Atsushi</p> <p>2014-01-01</p> <p>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 <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> Pacific offshore Tahiti based on a newly calibrated boron isotope paleo-pH proxy. Our new data, together with recalibrated existing data, indicate that a significant pCO2 increase (pH decrease), accompanied by anomalously large marine 14C reservoir ages, occurred following not only the Younger Dryas, but also Heinrich Stadial 1. These findings indicate an expanded zone of <span class="hlt">equatorial</span> upwelling and resultant CO2 emission, which may be derived from higher subsurface dissolved inorganic carbon concentration. PMID:24918354</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4398445','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4398445"><span>Natural Light Exposure, Sleep and Depression among Day Workers and Shiftworkers at Arctic and <span class="hlt">Equatorial</span> Latitudes</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Marqueze, Elaine Cristina; Vasconcelos, Suleima; Garefelt, Johanna; Skene, Debra J.; Moreno, Claudia Roberta; Lowden, Arne</p> <p>2015-01-01</p> <p>Objectives This study aimed to investigate the relationship between individual natural light exposure, sleep need, and depression at two latitudes, one extreme with a few hours of light per day during winter, and the other with equal hours of light and darkness throughout the year. Methods This cross-sectional study included a sample of Brazilian workers (<span class="hlt">Equatorial</span>, n = 488 workers) and a Swedish sample (Arctic, n = 1,273). Results The reported mean total natural light exposure per 4-week cycle differed significantly between the <span class="hlt">Equatorial</span> and Arctic regions. However, shiftworkers from both sites reported similar hours of natural light exposure. Short light exposure was a predictor for insufficient sleep. Conclusion Reduced exposure to natural light appears to increase the perception of obtaining insufficient sleep. Arctic workers were more prone to develop depression than <span class="hlt">Equatorial</span> workers. PMID:25874859</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15249015','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15249015"><span>Amino acid contents along the visual and <span class="hlt">equatorial</span> axes of a pig lens by Raman spectroscopy.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Medina-Gutiérrez, C; Frausto-Reyes, C; Quintanar-Stephano, J L; Sato-Berrú, R</p> <p>2004-08-01</p> <p>Using near infrared Raman microspectroscopy with laser light of 830 nm, the distribution of amino acids along the visual and <span class="hlt">equatorial</span> axes of a normal pig lens was studied. The classification of pig lens Raman spectra in these axes was performed using principal component analysis and linear discriminant analysis. The analysis of the scattered light selectively collected from point to point, along the visual axis, indicated that the tyrosine and tryptophan increases and then, at approximately 4 mm position, decreases. Moreover, in the <span class="hlt">equatorial</span> plane, the nuclear part has the highest concentration of these amino acids. However, the phenylalanine content increases from anterior to posterior cortex of the lens as long as in the <span class="hlt">equatorial</span> axis it slightly increases and then at approximately 2-2.3 mm position, decreases. The changes in amino acid conformation along the visual axis, similarly to the changes in protein conformation, may explain the refractive gradient of the lens.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940010198','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940010198"><span>Effects of the <span class="hlt">equatorial</span> ionosphere on L-band Earth-space transmissions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Smith, Ernest K.; Flock, Warren L.</p> <p>1993-01-01</p> <p>Ionosphere scintillation can effect satellite telecommunication up to Ku-band. Nighttime scintillation can be attributed to large-scale inhomogeneity in the F-region of the ionosphere predominantly between heights of 200 and 600 km. Daytime scintillation has been attributed to sporadic E. It can be thought of as occurring in three belts: <span class="hlt">equatorial</span>, high-latitude, and mid-latitude, in order of severity. <span class="hlt">Equatorial</span> scintillation occurs between magnetic latitudes +/- 25 degrees, peaking near +/- 10 degrees. It commonly starts abruptly near 2000 local time and dies out shortly after midnight. There is a strong solar cycle dependence and a seasonal preference for the equinoxes, particularly the vernal one. <span class="hlt">Equatorial</span> scintillation occurs more frequently on magnetically quiet than on magnetically disturbed days in most longitudes. At the peak of the sunspot cycle scintillation depths as great as 20 dB were observed at L-band.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016RaSc...51..742K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016RaSc...51..742K"><span>On the mutual relationship of the <span class="hlt">equatorial</span> electrojet, TEC and scintillation in the Peruvian sector</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khadka, Sovit M.; Valladares, Cesar; Pradipta, Rezy; Pacheco, Edgardo; Condor, Percy</p> <p>2016-06-01</p> <p>This paper presents the interrelationship between the <span class="hlt">equatorial</span> electrojet (EEJ) strength, Global Positioning System (GPS)-derived total electron content (TEC), and postsunset scintillation from ground observations with the aim of finding reliable precursors of the occurrence of ionospheric irregularities. Mutual relationship studies provide a possible route to predict the occurrence of TEC fluctuation and scintillation in the ionosphere during the late afternoon and night respectively based on daytime measurement of the <span class="hlt">equatorial</span> ionosphere. Data from ground based observations in the low latitudes of the west American longitude sector were examined during the 2008 solar minimum. We find a strong relationship exists between the noontime <span class="hlt">equatorial</span> electrojet and GPS-derived TEC distributions during the afternoon mediated by vertical E × B drift via the fountain effect, but there is little or no relationship with postsunset ionospheric scintillation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMPP34A..02L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMPP34A..02L"><span>The Neogene <span class="hlt">equatorial</span> Pacific: A view from 2009 IODP drilling on Expedition 320/321. (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lyle, M. W.; Shackford, J.; Holbourn, A. E.; Tian, J.; Raffi, I.; Pälike, H.; Nishi, H.</p> <p>2013-12-01</p> <p>The <span class="hlt">equatorial</span> Pacific responds strongly to global climate and is a source of ENSO, the largest global decadal climate oscillation. <span class="hlt">Equatorial</span> Pacific circulation and upwelling result from global atmospheric circulation patterns so it is unsurprising that oceanographic changes in the <span class="hlt">equatorial</span> Pacific reverberate globally. IODP expedition 320/321 (Pacific <span class="hlt">Equatorial</span> Age Transect) drilled 8 sites to reconstruct a 50-million-year record of ocean change for the <span class="hlt">equatorial</span> Pacific. The resulting record, when spliced together, will resolve orbital variations through most of the Cenozoic. All sedimentary sequences have now been scanned by XRF, so that biogeochemical changes through the Cenozoic can be studied. Here we report data from IODP Sites U1335, U1336, U1337, and U1338, the Neogene part of the PEAT megasplice. Sediments of the Neogene <span class="hlt">equatorial</span> Pacific are primarily biogenic carbonates, with about 15% biogenic silica tests and 5% assorted other components, including clays. Typically, highest sediment deposition occurs when plate tectonic movement carries a drill site underneath the <span class="hlt">equatorial</span> zone, indicating that <span class="hlt">equatorial</span> upwelling and high productivity have been consistent features of the Neogene <span class="hlt">equatorial</span> Pacific. Sedimentation rates become significantly slower and dissolution of both biogenic carbonates and silica are more pronounced when sites are beyond 3° in latitude away from the equator, as biogenic sediment production drops but dissolution does not. The differences between <span class="hlt">equatorial</span> and off-equator sites allow assessment of productivity vs dissolution as drivers of the sediment record. Carbonate dissolution can also be assessed by a ratio of XRF-estimated carbonate to dissolution resistant biogenic residue, like barite. There is a common stratigraphy of carbonate variation in the Neogene <span class="hlt">equatorial</span> Pacific, as proposed by earlier work from DSDP Leg 85 and ODP Leg 138. The new Exp 320/321 drilling extends the high-resolution record from ~0-5 Ma</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5098756','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5098756"><span>Plasma sheets, plasma currents and electric field double layers in the <span class="hlt">equatorial</span> ionosphere</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gupta, S.P.</p> <p>1981-01-01</p> <p>Plasma measurements carried out in the <span class="hlt">equatorial</span> ionosphere at altitudes of 80-200 km are discussed. It is found that within this region the ion collision frequency exceeds the gyro-frequency. For electrons, however, the collision frequency is much lower than their gyro-frequency. It is pointed out that the earth's magnetic field is horizontal in the <span class="hlt">equatorial</span> ionosphere, particularly at altitudes of approximately 100 km, where the curvature of the magnetic field can be neglected. The results obtained from rocket-borne probes in the <span class="hlt">equatorial</span> ionosphere over Thumba (India) are presented. Localized regions illustrating the polarity of the vertical electric field are shown, as are current density profiles obtained at different times of the day. It is found that as expected, the vertical electric field becomes very small during a weak magnetic storm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/458874','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/458874"><span>Glacial to interglacial fluctuations in productivity in the <span class="hlt">equatorial</span> Pacific as indicated by marine barite</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Paytan, A.; Kastner, M.; Chavez, F.P.</p> <p>1996-11-22</p> <p>An empirical correlation between marine barite (BaSO{sub 4}) accumulation rate in core-top sediment samples from two <span class="hlt">equatorial</span> Pacific transects (at 140{degrees}W and 110{degrees}W) and the estimated primary productivity of the overlying water column were used to evaluate glacial to interglacial changes in productivity. Fluctuations in barite accumulation rates down-core indicate that during glacial periods of the past 450,000 years, the productivity in the central and eastern <span class="hlt">equatorial</span> Pacific was about two times that during intervening interglacial periods. This result is consistent with other evidence that productivity was high in the eastern and central <span class="hlt">equatorial</span> Pacific during the last glacial. 48 refs., 3 figs.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeoRL..41.3172Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeoRL..41.3172Z"><span>Long-term trend of Pacific South <span class="hlt">Equatorial</span> Current bifurcation over 1950-2010</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhai, Fangguo; Hu, Dunxin; Wang, Qingye; Wang, Fujun</p> <p>2014-05-01</p> <p>This study investigates the long-term change of the Pacific South <span class="hlt">Equatorial</span> Current (SEC) bifurcation latitude (SBL) over 1950-2010 with Simple Ocean Data Assimilation version 2.2.4. Results indicate that the SBL averaged within upper 200 m has migrated southward at 0.020°S yr-1, comparable in magnitude with -0.024°N yr-1 for the North <span class="hlt">Equatorial</span> Current bifurcation latitude (NBL). The SEC transport into the Coral Sea has increased. Due to the southward SBL migration, most of the increased SEC water was transported equatorward, contributing to the <span class="hlt">Equatorial</span> Undercurrent intensification. Experiments with a nonlinear 1.5 layer reduced gravity model indicate that the southward migration of SBL is mainly caused by positive Ekman flux divergence trend in the eastern tropical South Pacific, while that of NBL is caused by negative Ekman flux divergence trend in the western tropical North Pacific.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AnGeo..35..123B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AnGeo..35..123B"><span>Observations of <span class="hlt">equatorial</span> ionization anomaly over Africa and Middle East during a year of deep minimum</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bolaji, Olawale; Owolabi, Oluwafisayo; Falayi, Elijah; Jimoh, Emmanuel; Kotoye, Afolabi; Odeyemi, Olumide; Rabiu, Babatunde; Doherty, Patricia; Yizengaw, Endawoke; Yamazaki, Yosuke; Adeniyi, Jacob; Kaka, Rafiat; Onanuga, Kehinde</p> <p>2017-01-01</p> <p>In this work, we investigated the veracity of an ion continuity equation in controlling <span class="hlt">equatorial</span> ionization anomaly (EIA) morphology using total electron content (TEC) of 22 GPS receivers and three ground-based magnetometers (Magnetic Data Acquisition System, MAGDAS) over Africa and the Middle East (Africa-Middle East) during the quietest periods. Apart from further confirmation of the roles of <span class="hlt">equatorial</span> electrojet (EEJ) and integrated <span class="hlt">equatorial</span> electrojet (IEEJ) in determining hemispheric extent of EIA crest over higher latitudes, we found some additional roles played by thermospheric meridional neutral wind. Interestingly, the simultaneous observations of EIA crests in both hemispheres of Africa-Middle East showed different morphology compared to that reported over Asia. We also observed interesting latitudinal twin EIA crests domiciled at the low latitudes of the Northern Hemisphere. Our results further showed that weak EEJ strength associated with counter electrojet (CEJ) during sunrise hours could also trigger twin EIA crests over higher latitudes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800048218&hterms=EKMAN&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DEKMAN','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800048218&hterms=EKMAN&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DEKMAN"><span>The role of Ekman flow and planetary waves in the oceanic cross-<span class="hlt">equatorial</span> heat transport</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schopf, P. S.</p> <p>1980-01-01</p> <p>A numerical model is used to mechanistically simulate the oceans' seasonal cross-<span class="hlt">equatorial</span> heat transport. The basic process of Ekman pumping and drift is able to account for a large amount of the cross-<span class="hlt">equatorial</span> 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-<span class="hlt">equatorial</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006cosp...36..887C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006cosp...36..887C"><span>Observations of total electron content enhancements in <span class="hlt">equatorial</span> anomaly region in China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Y.; Ma, G.; Shen, H.; Huang, W.</p> <p></p> <p>A GPS receiver chain has been established at <span class="hlt">equatorial</span> anomaly region in China The chain is composed of 4 GPS receivers located at Fuzhou 26 1 o N 119 3 o E Xiamen 24 5 o N 118 1 o E LGuangzhou 23 1 o N 113 2 o E and Nanning 22 8 o N 108 3 o E The aim is to study the TEC and ionospheric scintillation at <span class="hlt">equatorial</span> anomaly in China area This paper presents the observation of an isolated and localized TEC enhancement using the GPS TEC data The TEC enhancements always appear in nighttime even after midnight and during geomagnetic quiet time and low solar activity The occurrence is more often in autumn than in winter The cases studied here occur near the <span class="hlt">equatorial</span> anomaly region sim 15 o to 20 o from magnetic equator In some cases the density observations from DMSP satellites at about 800km reveal the similar ion density enhancements</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002GBioC..16.1046K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002GBioC..16.1046K"><span>Wet deposition of trace elements and radon daughter systematics in the South and <span class="hlt">equatorial</span> Atlantic atmosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Guebuem; Church, Thomas M.</p> <p>2002-09-01</p> <p>Atmospheric samples were collected aboard ship in the South and <span class="hlt">equatorial</span> Atlantic (35°S-10°N) between 19 May and 20 June 1996. We measured 222Rn in air, 210Pb in aerosol, and trace elements (Fe, Mn, Zn, Pb, Cu, Cd, Ni, and Cr), 210Pb, and 210Po in precipitation samples. The large variation of 222Rn in air suggests a significant change in the incursion of continental air with time and latitude in the remote Atlantic. In the <span class="hlt">equatorial</span> and subtropical Atlantic (20°S-10°N), 222Rn activity was lower but 210Pb/222Rn ratios were higher than those at higher latitudes. The higher 210Pb/222Rn ratios in the <span class="hlt">equatorial</span> Atlantic appear to be due to prevailing trade easterly winds which transport a supported source of 210Pb in Saharan dust from the African Sahel. The enrichment of noncrustal trace elements in precipitation samples from the remote <span class="hlt">equatorial</span> Atlantic was small on account of the remoteness from the continental emission regions and as a result of dilution with Saharan dust. The wet depositional fluxes of major crustal elements (Fe and Mn) were two- to three-fold higher, while those of Cd and Zn were two- to ten-fold lower, in the South and <span class="hlt">equatorial</span> Atlantic relative to the western North Atlantic (Bermuda) or North Atlantic coast (Lewes, Delaware). Thus, dominant wet precipitation of Saharan dust in the Intertropical Convergence Zone (ITCZ) areas of the <span class="hlt">equatorial</span> Atlantic appears to be a large potential source of micronutrients (i.e., Fe) to surface seawater.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.P41B2059S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.P41B2059S"><span>An Enduring Rapidly Moving Storm as a Guide to Saturn's <span class="hlt">Equatorial</span> Jet Complex Structure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sanchez-Lavega, A.; Wong, M. H.; Simon, A. A.; Hueso, R.; Perez-Hoyos, S.; Antuñano, A.; Rojas, J. F.; del Rio-Gaztelurrutia, T.; Barrado-Izagirre, N.; Garate-Lopez, I.; Garcia-Melendo, E.; Sanz-Requena, J. F.; Gomez-Forrelad, J. M.; De Pater, I.; Li, L.</p> <p>2015-12-01</p> <p>Saturn has an intense and broad eastward <span class="hlt">equatorial</span> jet at cloud level whose variability and meridional and vertical structure are complex and actively debated. Due to its 27º rotation axis tilt and orbital eccentricity, Saturn is under a strong seasonal insolation cycle, enhanced at equator by the ring shadowing periods. These factors make it a good natural laboratory to test models of <span class="hlt">equatorial</span> jet generation in giant planets. We report on a bright <span class="hlt">equatorial</span> storm observed in 2015 that moved rapidly but steadily at a high speed of 450 ms-1, not reported since Voyagers times (Sanchez-Lavega et al., Icarus 147, 405-420, 2000). Imaging with the Hubble Space Telescope (HST) WFC3 showed detailed storm morphology at red wavelengths (689, 750 and 937 nm) confirming its high speed. Other <span class="hlt">equatorial</span> clouds moved with velocities matching the Cassini ISS profile (García-Melendo et al., Icarus, 215, 62-74, 2011), while the storm matches the Voyager 1 and 2 profile. We interpret this result as the simultaneous detection of the wind profile at two separated altitude levels within the cloud layer. In addition, the HST methane band and ultraviolet images, allowed retrieving winds at a third altitude level of motion, in the haze layer above the cloud deck. Combining the current wind data with previous dates allowed us to construct a vertical - meridional section of the structure of Saturn's <span class="hlt">equatorial</span> jet at cloud level. We discuss the implications of these results on the long-term stability of Saturn's <span class="hlt">equatorial</span> jet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUSMSA44A..01B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUSMSA44A..01B"><span>Space-Time Variabilty of Ionospheric Scintillaion in the <span class="hlt">Equatorial</span> Region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Basu, S.; Makela, J.; Christensen, A.; Groves, K.; Dasgupta, A.</p> <p>2004-05-01</p> <p>The marked day-to-day variability of <span class="hlt">equatorial</span> ionospheric irregularities (scale lengths of tens of m to hundreds of m) has been investigated by performing multi-frequency scintillation observations at specific locations by many investigators worldwide. In addition to such temporal variability, multi-satellite observations from one station reveal extreme spatial variability when a region with intense irregularities may remain separated from a benign region by only 500 km over an entire night. In this paper, we show that the GUVI sensor on the TIMED satellite can image the <span class="hlt">equatorial</span> anomaly on a global scale and such images can be used to specify in space and time the scintillating and non-scintillating regions. We present a case study of GUVI images on two successive nights during an equinoctial period. On one night the <span class="hlt">equatorial</span> anomaly was well-developed at all longitudes when the crests of the <span class="hlt">equatorial</span> anomaly were widely separated in latitude. This indicated the presence of a strong zonal electric field at the magnetic equator, which is also a pre-requisite for the formation of ionospheric irregularities. It is shown that on this night scintillations were indeed observed at widely separated locations around the globe. The adjacent day showed the collapse of the <span class="hlt">equatorial</span> anomaly over a wide longitude swath implying that irregularities are not likely to be formed in these regions. The scintillation observations at Calcutta, India and at Singapore located in this region indicate the absence of scintillation. The study reveals that the GUVI images of the <span class="hlt">equatorial</span> anomaly can be used to specify scintillating and non-scintillating regions on a global scale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFMOS31C..07Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFMOS31C..07Z"><span>Sources of Fe to the <span class="hlt">Equatorial</span> Pacific Ocean from the Holocene to Miocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ziegler, C. L.; Murray, R. W.; Plank, T.; Hemming, S. R.</p> <p>2007-12-01</p> <p>Biological productivity in the modern <span class="hlt">equatorial</span> Pacific Ocean, a region with high nutrients and low chlorophyll, is currently limited by the micronutrient Fe. Whether this region was Fe limited in the past remains unclear. 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 versus Fe supplied by the <span class="hlt">Equatorial</span> Undercurrent), we chemically isolated the terrigenous material from marine sediment along a cross-<span class="hlt">equatorial</span> meridional transect in the central <span class="hlt">equatorial</span> Pacific at 140W and at Ocean Drilling Program Site 850 in the eastern <span class="hlt">equatorial</span> Pacific. We quantified the contribution from each potential Fe-bearing terrigenous source using a complete 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 clear connection between a particular Fe source or pathway (eolian versus 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, is responsible for past changes in carbon export in the open ocean, rather than simply Fe supply from dust and/or <span class="hlt">Equatorial</span> Undercurrent processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008E%26PSL.270..258Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008E%26PSL.270..258Z"><span>Sources of Fe to the <span class="hlt">equatorial</span> Pacific Ocean from the Holocene to Miocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ziegler, Christa L.; Murray, Richard W.; Plank, Terry; Hemming, Sidney R.</p> <p>2008-06-01</p> <p>Biological productivity in the modern <span class="hlt">equatorial</span> 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 <span class="hlt">Equatorial</span> Undercurrent), we chemically isolated the terrigenous material from sediment along a cross-<span class="hlt">equatorial</span> transect in the central <span class="hlt">equatorial</span> Pacific at 140°W and at Ocean Drilling Program Site 850 in the eastern <span class="hlt">equatorial</span> 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 <span class="hlt">Equatorial</span> 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).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AdSpR..54.1913S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AdSpR..54.1913S"><span>Satellite-observed biological variability in the <span class="hlt">equatorial</span> Pacific during the 2009-2011 ENSO cycle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shi, Wei; Wang, Menghua</p> <p>2014-11-01</p> <p>The event of 2009-2011 El Niño Southern Oscillation (ENSO) provides an opportunity to gain insight into the biological variability of the <span class="hlt">equatorial</span> Pacific Ocean for an entire ENSO cycle with satellite and in situ observations. Even though El Niño and La Niña in general led to respectively weakened and enhanced chlorophyll-a concentration and net primary production (NPP) along the <span class="hlt">equatorial</span> Pacific Ocean during the 2009-2011 ENSO cycle, biological responses were highly disparate along the equator and attributed to different driving mechanisms. In the eastern <span class="hlt">equatorial</span> Pacific east of 150°E, the El Niño-La Niña biological change was in general small except for the transition period even though sea surface temperature (SST) showed over ∼5 °C drop from El Niño to La Niña. In the central-eastern (170°W-140°W) <span class="hlt">equatorial</span> Pacific, moderate change of biological activity is attributed to the changes of thermocline driven by the eastward propagating <span class="hlt">equatorial</span> Kelvin waves and changes of zonal currents and undercurrents. Highest biological response in this ENSO cycle was located in the central (170°E-170°W) and central-western (150°E-170°E) <span class="hlt">equatorial</span> Pacific with quadruple chlorophyll-a concentration and over ∼400 mg C m-2 d-1 increase of NPP from El Niño in 2009 to La Niña in 2010. However, spatial pattern of ENSO biological variability as represented with NPP is not exactly the same as chlorophyll-a variability. Wind-driving mixing of nutrients and eastward advection of the oligotrophic warm pool waters are attributed to this significant biological variability in this region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015DPS....4740003S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015DPS....4740003S"><span>An endurign rapidly moving storm as a guide to Saturn's <span class="hlt">equatorial</span> jet complex structure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sanchez-Lavega, Agustin; Wong, Mike H.; Simon, Amy; Hueso, Ricardo; Perez-Hoyos, Santiago; Antuñano, Arrate; Rojas, Jose Felix; del Rio-Gaztelurrutia, Teresa; Barrado-Izagirre, Naiara; Garate-Lopez, Itziar; Garcia-Melendo, Enrique; Francisco Sanz-Requena, Jose; Gomez-Forrellad, Josep Maria; de Pater, Imke</p> <p>2015-11-01</p> <p>Saturn has an intense and broad eastward <span class="hlt">equatorial</span> jet at cloud level whose variability and meridional and vertical structure are complex and actively debated. Due to its 27º rotation axis tilt and orbital eccentricity, Saturn is under a strong seasonal insolation cycle, enhanced at equator by the ring shadowing periods. These factors make it a good natural laboratory to test models of <span class="hlt">equatorial</span> jet generation in giant planets. We report on a bright <span class="hlt">equatorial</span> storm at 6 degrees North latitude observed in 2015 that moved rapidly but steadily at a high speed of 450 ms-1, not reported since Voyagers times (Sanchez-Lavega et al., Icarus 147, 405-420, 2000). Imaging with the Hubble Space Telescope (HST) WFC3 showed detailed storm morphology at red wavelengths (689, 750 and 937 nm) confirming its high speed. Other <span class="hlt">equatorial</span> clouds moved with lower velocities matching the Cassini ISS profile (García-Melendo et al., Icarus, 215, 62-74, 2011), while the storm matches the Voyager 1 and 2 profile. We interpret this result as the simultaneous detection of the wind profile at two separated altitude levels within the cloud layer. In addition, the HST methane band and ultraviolet images, allowed retrieving winds at a third altitude level of motion, in the haze layer above the cloud deck. Combining the current wind data with previous dates allowed us to construct a vertical - meridional section of the structure of Saturn’s <span class="hlt">equatorial</span> jet at cloud level. We discuss the implications of these results on the long-term stability of Saturn’s <span class="hlt">equatorial</span> jet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008cosp...37..625S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008cosp...37..625S"><span>Modeling of <span class="hlt">equatorial</span> and low latitude ionosphere over Indian zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Singh Dabas, Raj</p> <p></p> <p>Ionospheric Modeling is important for both scientific and practical purposes. Since the largest variability occurs in the ionospheric F-region and for practical HF communication and other applications it would be suffice to model the changes in the F-region parameters of the ionosphere. Ionospheric Electron Content (IEC) is another parameter useful for the determination of phase path, group delay, dispersion, refraction and Faraday polarization rotation of transionospheric signals. In the present study, two HF prediction models for short and long term and one IEC model are developed for <span class="hlt">equatorial</span> and low latitude ionosphere. Short term HF prediction model is based on Multiple Regression Analysis (MRA) for the dependence of F- region parameters namely foF2 and M(3000)F2, on solar 2800 MHz flux (F10), and geomagnetic index Ap whereas for long term prediction, Second Degree (SD) coefficients are generated by fitting monthly median foF2 and M(3000)F2 with corresponding 12 monthly mean sunspot numbers (R12) using data over three solar cycles. For MRA, daily foF2, M(3000)F2 values for each hour, obtained from Delhi (28.6N, 77.1E) digital ionosonde for about half a solar cycle are used. MRA coefficients, separately for quiet (Ap¡25) and disturbed (Ap˜25) periods, for foF2 and M(3000)F2, are obtained for every month over 24 UT times using daily F10 and Ap values. Whereas SD coefficients are obtained each month at all local times for all the 14 stations covering a geographic latitude range from about 0 to 45N. Similar to SD model, IEC model is also developed using monthly median foF2 and hmF2 values for each hours for all the 14 stations which are feed into IRI 2000 model to calculate respective IEC values for two altitudes namely 1000km and 2000km. Then second degree coefficients, separately for above two altitudes, are obtained for each month at all local times for all the 14 stations. In this way once appropriate coefficients for each hour for all the twelve months</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990062583&hterms=tropospheric+scintillation&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dtropospheric%2Bscintillation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990062583&hterms=tropospheric+scintillation&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dtropospheric%2Bscintillation"><span>Occurrence of <span class="hlt">Equatorial</span> F Region Irregularities: Evidence for Tropospheric Seeding</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>McClure, J. P.; Singh, S.; Bamgboye, D. K.; Johnson, F. S.; Kil, Hyosub</p> <p>1998-01-01</p> <p>We present a new gap-free version of the seasonal and longitudinal 0 (s/l) variations of P(sub EFI), the <span class="hlt">equatorial</span> F region irregularity (EFI) occurrence probability, based on data from the AE-E spacecraft. The agreement of this and three earlier partial P(sub EFI) patterns verifies all four. We reinterpret another earlier gap-ridden pattern, that of D(bar)(sub RSF), a topside ionogram index of average darkening by range spread F. We compare it with P(sub EFI) and, using ionosonde radio science considerations, we conclude that D(bar)(sub RSF) = P(sub EFI) times a factor depending on the average number of topside plasma bubbles visible to the ionosonde. The s/l variations of D(baar)(sub RSF) thus imply s/l variations in the average spacing of bubbles, whose seeds have an occurrence probability pattern P(sub seed). For discussion we assume P(sub EFI) = P(sub inst)P(sub seed) is the pattern of F region instability. The P(sub EFI) pattern, which is by definition independent of seed and/or bubble spacing, is far too complex to be explained by the dominant paradigm, that of changes in P(sub inst) by simple changes in the F region altitude and/or north-south asymmetry. We examine evidence behind this dominance, and find it unconvincing. Both the asymmetry and sunset-node/altitude hypotheses of 1984 and 1985, respectively, seem to be partly based on misunderstood data, and their features appear displaced in time and space from those of our repeatable P(sub EFI) pattern. In contrast, if P(sub seed) variations influence the P(sub EFI) pattern and depend on thermospheric gravity waves from tropospheric convection near the dip equator, then the seasonal maxima (minima) Of P(sub EFI) could be explained, since they all occur above relatively warm (cold) surface features, where convection is maximal (minimal). Also, the hypothesis of the dominance of the P(sub seed) term could explain an unusual December/January P(sub EFI) maximum in the deep, wide, normal Pacific minimum in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990062583&hterms=nino+regions&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dnino%2Bregions','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990062583&hterms=nino+regions&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dnino%2Bregions"><span>Occurrence of <span class="hlt">Equatorial</span> F Region Irregularities: Evidence for Tropospheric Seeding</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>McClure, J. P.; Singh, S.; Bamgboye, D. K.; Johnson, F. S.; Kil, Hyosub</p> <p>1998-01-01</p> <p>We present a new gap-free version of the seasonal and longitudinal 0 (s/l) variations of P(sub EFI), the <span class="hlt">equatorial</span> F region irregularity (EFI) occurrence probability, based on data from the AE-E spacecraft. The agreement of this and three earlier partial P(sub EFI) patterns verifies all four. We reinterpret another earlier gap-ridden pattern, that of D(bar)(sub RSF), a topside ionogram index of average darkening by range spread F. We compare it with P(sub EFI) and, using ionosonde radio science considerations, we conclude that D(bar)(sub RSF) = P(sub EFI) times a factor depending on the average number of topside plasma bubbles visible to the ionosonde. The s/l variations of D(baar)(sub RSF) thus imply s/l variations in the average spacing of bubbles, whose seeds have an occurrence probability pattern P(sub seed). For discussion we assume P(sub EFI) = P(sub inst)P(sub seed) is the pattern of F region instability. The P(sub EFI) pattern, which is by definition independent of seed and/or bubble spacing, is far too complex to be explained by the dominant paradigm, that of changes in P(sub inst) by simple changes in the F region altitude and/or north-south asymmetry. We examine evidence behind this dominance, and find it unconvincing. Both the asymmetry and sunset-node/altitude hypotheses of 1984 and 1985, respectively, seem to be partly based on misunderstood data, and their features appear displaced in time and space from those of our repeatable P(sub EFI) pattern. In contrast, if P(sub seed) variations influence the P(sub EFI) pattern and depend on thermospheric gravity waves from tropospheric convection near the dip equator, then the seasonal maxima (minima) Of P(sub EFI) could be explained, since they all occur above relatively warm (cold) surface features, where convection is maximal (minimal). Also, the hypothesis of the dominance of the P(sub seed) term could explain an unusual December/January P(sub EFI) maximum in the deep, wide, normal Pacific minimum in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996JGR...101.4805O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996JGR...101.4805O"><span>Coronal holes near the <span class="hlt">equatorial</span> plane and the solar wind abundance of iron</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ogilvie, K. W.; Coplan, M. A.; Yellin, K. A.</p> <p>1996-03-01</p> <p>Composition analysis of the solar wind from two <span class="hlt">equatorial</span> coronal holes has been carried out with the Ion Composition Instrument on the ISEE-3 spacecraft. The abundances of oxygen, neon and iron were determined as coronal hole-related material flowed past the spacecraft. The results show that the edges of the hole-related flow are sharply defined with abundances closer to the abundances in the photosphere than in the slower solar wind. These results are similar to those found in flows from the southern polar coronal hole and suggest an underlying unity between the polar and <span class="hlt">equatorial</span> regions of the sun.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010cosp...38.3858Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010cosp...38.3858Y"><span><span class="hlt">Equatorial</span> ionospheric electrodynamics observations in the African sector using recently deployed magnetometer and GPS networks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yizengaw, Endawoke</p> <p></p> <p>Recent ground-and space-based observations have shown that geomagnetic storms can have dramatic longitudinal differences in <span class="hlt">equatorial</span> ionospheric electrodynamics, such as enhanced generation of F-region plasma irregularities and super fountain effect at low latitudes. For example, satellite observations have shown very unique <span class="hlt">equatorial</span> ionospheric density struc-tures in the African region. The African region is the longitude sector where the peak in large scale bubble activity (zonal width, depletion level, and spacing) is maximum. No other region in the globe shows similar characteristics. Most recent in situ density observations from C/NOFS also reveal similar maximal bubble activities in Africa. However, the dearth of ground-based in-strumentation in the region makes it impossible to confirm these unique <span class="hlt">equatorial</span> ionospheric structures from the ground and that leads the investigation of the physics into speculative dead ends. This initiated several open questions, which include: What are the possible governing mechanisms that create unique <span class="hlt">equatorial</span> structures in Africa? In order to answer such open questions, recently limited progress has been made and very few ground-based instruments, including AMBER magnetometers and ACORN GPS network, have been either deployed in the region or in process. Some of many objectives of AMBER magnetometers network, in coordination with ground-and space-based GPS receiver observations, is to understand the fundamental electrodynamics that govern <span class="hlt">equatorial</span> ionospheric motion and the penetration of ULF Pc5 wave into <span class="hlt">equatorial</span> latitudes and its impact on the <span class="hlt">equatorial</span> electrodynamics. This paper presents initial results from AMBER magnetometer network. The initial electro-dynamics result in Africa is also compared with similar observations in the American sector. The electron density structure in response to the electrodynamics is also investigated using the available ground-based GPS receivers in the region as well as data</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017IJTP...56..781C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017IJTP...56..781C"><span>Optimal Joint Remote State Preparation of Arbitrary <span class="hlt">Equatorial</span> Multi-qudit States</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cai, Tao; Jiang, Min</p> <p>2017-03-01</p> <p>As an important communication technology, quantum information transmission plays an important role in the future network communication. It involves two kinds of transmission ways: quantum teleportation and remote state preparation. In this paper, we put forward a new scheme for optimal joint remote state preparation (JRSP) of an arbitrary <span class="hlt">equatorial</span> two-qudit state with hybrid dimensions. Moreover, the receiver can reconstruct the target state with 100 % success probability in a deterministic manner via two spatially separated senders. Based on it, we can extend it to joint remote preparation of arbitrary <span class="hlt">equatorial</span> multi-qudit states with hybrid dimensions using the same strategy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900025060&hterms=precipitation+index&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dprecipitation%2Bindex','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900025060&hterms=precipitation+index&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dprecipitation%2Bindex"><span>Observation of low energy particle precipitation at low altitude in the <span class="hlt">equatorial</span> zone</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Miah, M. A.</p> <p>1989-01-01</p> <p>Precipitation of protons in the <span class="hlt">equatorial</span> zone was investigated by the Phoenix-1 experiment on the S81-1 mission from May to November, 1982. The protons show a precipitation peak along the line of minimum magnetic field strength with a FWHM of 13 deg. The index of <span class="hlt">equatorial</span> pitch angle distribution is about 19. The peak proton flux shows a fifth-power altitude dependence, and the proton flux shows approximately a factor of 3 times increase in 1982 compared to that in 1969 due, possibly, to the stronger solar maximum conditions of 10.7-cm radiation in 1982.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6765423','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6765423"><span>Comparison of <span class="hlt">equatorial</span> electron content in the Indian and American longitudes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Klobuchar, J.A.; Rastogi, R.G.</p> <p>1988-06-01</p> <p>Total electron content (TEC) measurements taken at the magnetically <span class="hlt">equatorial</span> 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 <span class="hlt">equatorial</span> daytime TEC is significantly smaller than at other latitudes. 20 references.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/8662572','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/8662572"><span>Comparison of Galileo Probe and Earth-Based Translation Rates of Jupiter's <span class="hlt">Equatorial</span> Clouds</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Beebe; Simon; Huber</p> <p>1996-05-10</p> <p>The Doppler wind speeds derived from Galileo probe data are comparable with the maximum translation speeds observed in the <span class="hlt">equatorial</span> zone by Voyager 1 and the Hubble Space Telescope. Slower published values of east-west winds are based on measurements of larger features and should be interpreted as translation rates of large weather systems interacting with the wind. The nature of the hot-spot region that the Galileo probe entered is compatible with a high-speed jet at 6 degrees north. The hot spot is associated with an <span class="hlt">equatorial</span> weather system that spans 5 degrees of latitude and translates at 103 meters per second.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830041486&hterms=satellites+fall&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsatellites%2Bfall','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830041486&hterms=satellites+fall&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsatellites%2Bfall"><span><span class="hlt">Equatorial</span> long waves in geostationary satellite observations and in a multichannel sea surface temperature analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Legeckis, R.; Pichel, W.; Nesterczuk, G.</p> <p>1983-01-01</p> <p>Geostationary satellite observations of a zonally oriented sea surface temperature front in the eastern <span class="hlt">equatorial</span> Pacific were made between 1975 and 1981. Long waves appeared along the front mainly during the summer and fall, except during 1976, the year of an El Nino. The waves have averaged periods of 25 days and wavelengths of 1000 km. At the end of 1981, the long waves also were detected in a new sea surface temperature analysis based on multichannel infrared measurements from a polar-orbiting satellite. This quantitative analysis may improve the ability to resolve low-frequency <span class="hlt">equatorial</span> wave motions from satellite observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991JATP...53..965S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991JATP...53..965S"><span>Response of night-time <span class="hlt">equatorial</span> F-region to magnetic disturbances</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Somayajulu, V. V.; Murthy, B. V. K.; Subbarao, K. S. V.</p> <p>1991-10-01</p> <p>The responsne of the <span class="hlt">equatorial</span> night-time F-region to magnetic stormtime disturbances has been examined using mainly ionograms recorded at Trivandrum and magnetograms recorded at high, middle and low latitudes during the magnetic storm of 23-26 November 1986. The analysis revealed a close coupling between the <span class="hlt">equatorial</span> F-region and high-latitude magnetic field disturbances originating in solar wind-magnetosphere interactions. The presence of spread-F on ionograms during this period is found to be consistent with the Rayleigh-Taylor instability mechanism for the gro