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Sample records for main ionospheric trough

  1. Main ionospheric trough in the daytime sector studied on the basis of vertical sounding data

    Energy Technology Data Exchange (ETDEWEB)

    Benkova, N.P.; Kozlov, E.F.; Mozhaev, A.M.; Osipov, N.K.; Samorokin, N.I.

    1980-09-01

    Data for 1969-1973 are used to study the displacement of the main ionospheric trough during daytime magnetic storms. The depth of the trough and electron density gradients on the sides of the trough are determined. The trough is found to move in a southeasterly direction during daytime storms. The results agree with theoretical conclusions that explain the formation of the trough by the collective transport of ionospheric plasma in a sunward direction.

  2. Modelling the Main Ionospheric Trough Across the Northern Hemisphere

    National Research Council Canada - National Science Library

    Mitchell, Cathryn

    2004-01-01

    This report results from a contract tasking University of Bath as follows: The contractor will investigate disturbances in the Northern Hemisphere ionosphere using a Multi-instrument data analysis (MIDAS) imaging algorithm...

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

    Science.gov (United States)

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

    2007-05-01

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

  4. Altitude variation of the plasmapause signature in the main ionospheric trough

    Czech Academy of Sciences Publication Activity Database

    Grebowsky, J. M.; Benson, R. F.; Webb, P. A.; Truhlík, Vladimír; Bilitza, D.

    2009-01-01

    Roč. 71, č. 16 (2009), s. 1669-1676 ISSN 1364-6826 R&D Projects: GA AV ČR IAA300420603 Institutional research plan: CEZ:AV0Z30420517 Keywords : Plasmapause * Ionosphere * Midlatitude Trough Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.643, year: 2009

  5. Wave and plasma measurements and GPS diagnostics of the main ionospheric trough as a hybrid method used for Space Weather purposes

    Directory of Open Access Journals (Sweden)

    H. Rothkaehl

    2008-02-01

    Full Text Available The region of the main ionospheric trough is a unique region of the ionosphere, where different types of waves and instabilities can be generated. This region of the ionosphere acts like a lens, focusing a variety of indicators from the equator of plasmapause and local ionospheric plasma. This paper reports the results of monitoring the mid-latitude trough structure, dynamics and wave activity. For these purposes, the data gathered by the currently-operating DEMETER satellite and past diagnostics located on IK-19, Apex, and MAGION-3 spacecraft, as well as TEC measurements were used. A global-time varying picture of the ionospheric trough was reconstructed using the sequence of wave spectra registered and plasma measurements in the top-side ionosphere. The authors present the wave activity from ULF frequency band to the HF frequency detected inside the trough region and discuss its properties during geomagnetic disturbances. It is thought that broadband emissions are correlated with low frequency radiation, which is excited by the wave-particle interaction in the equatorial plasmapause and moves to the ionosphere along the geomagnetic field line. In the ionosphere, the suprathermal electrons can interact with these electrostatic waves and excite electron acoustic waves or HF longitudinal plasma waves.

    Furthermore, the electron density trough can provide useful data on the magnetosphere ionosphere dynamics and morphology and, in consequence, can be used for Space Weather purposes.

  6. Wave and plasma measurements and GPS diagnostics of the main ionospheric trough as a hybrid method used for Space Weather purposes

    Directory of Open Access Journals (Sweden)

    H. Rothkaehl

    2008-02-01

    Full Text Available The region of the main ionospheric trough is a unique region of the ionosphere, where different types of waves and instabilities can be generated. This region of the ionosphere acts like a lens, focusing a variety of indicators from the equator of plasmapause and local ionospheric plasma. This paper reports the results of monitoring the mid-latitude trough structure, dynamics and wave activity. For these purposes, the data gathered by the currently-operating DEMETER satellite and past diagnostics located on IK-19, Apex, and MAGION-3 spacecraft, as well as TEC measurements were used. A global-time varying picture of the ionospheric trough was reconstructed using the sequence of wave spectra registered and plasma measurements in the top-side ionosphere. The authors present the wave activity from ULF frequency band to the HF frequency detected inside the trough region and discuss its properties during geomagnetic disturbances. It is thought that broadband emissions are correlated with low frequency radiation, which is excited by the wave-particle interaction in the equatorial plasmapause and moves to the ionosphere along the geomagnetic field line. In the ionosphere, the suprathermal electrons can interact with these electrostatic waves and excite electron acoustic waves or HF longitudinal plasma waves. Furthermore, the electron density trough can provide useful data on the magnetosphere ionosphere dynamics and morphology and, in consequence, can be used for Space Weather purposes.

  7. Studies of sporadic E (Es) associated with the main ionospheric trough

    International Nuclear Information System (INIS)

    Rodger, A.S.; Morrell, C.; Dudeney, J.R.

    1983-01-01

    Sporadic E, or E(s) events under the main F region trough have been confirmed on the basis of ionograms from a vertical incidence ionosonde at Halley Bay, Antarctica. Analyses indicate that E(s) is frequently observable under both the equatorward and the poleward edges of the trough, as well as poleward of it. Before magnetic midnight, E(s) layers whose semithickness resembles those of the normal E layer are common, in contrast to layers seen after magnetic midnight which show the characteristics of thin E(s) layers. A possible explanation of the observed change in the E(s) layer characteristics at magnetic midnight is related to differences in the type and spectra of the precipitating particles. It is shown that the redistribution of ionization by the convection electric field may be important. 40 references

  8. Satellite and ground measurements of latitude distribution of upper ionosphere parameters in the region of the main trough of ionization

    International Nuclear Information System (INIS)

    Filippov, V.M.; Alekseev, V.N.; Afonin, V.V.

    1988-01-01

    Results of simultaneous complex measurements of subauroral ionosphere structure at observations of charged-particle precipitation at Interkosmos-19 satellite, electron concentration and temperature at Kosmos-900 satellite, ionosphere parameters and plasma convection at Zhigansk (L∼4) and Jakutsk (L∼3) stations and 630.0 mm line luminescence by scanning photometer at Zhigansk station, carried out on the 26 - 27.03.1979, are presented. It is found, that the through polar edge is formed by low-energy electron precipitations in diffuse auroral zone. It is confirmed by spatial coincidence of diffuse precipitations equatorial boundary, determined by satellite and ground optical measurements, with the ionization main through polar edge, determined by ground ionospherical observation and satellite measurements Ne at Kosmos-900 satellite. Results of these complex experiments show as well, that one of the main mechanisms of main ionospherical through formation may be plasma convection peculiarities within F region at subauroral zone widthes

  9. Ionospheric trough Model used for Telecommunication Purposes

    International Nuclear Information System (INIS)

    Rothkaehl, H.; Stanislawska, I.

    1999-01-01

    The mid-latitude trough is dynamical phenomena influenced the COST 251 area. Modelled parameters in COST 251 project are critically dependent on its location and magnitude. The particular importance to HF propagation assessments involving off-great-circle modes of incorporating a representation of the position of the trough is noted. ITU-R prediction maps (ITU-R, 1997) which are currently used in most international propagation assessments do not include this fact. (author)

  10. Movements of the mid-latitude ionospheric trough

    International Nuclear Information System (INIS)

    Rodger, A.S.; Pinnock, M.

    1982-01-01

    A new method for monitoring the position and movement of large ionospheric structures is described. The technique uses data from an ionosonde nominally operating at vertical incidence, but relies on there being present a significant gradient in electron concentration. The position and dynamics of the poleward edge of the mid-latitude trough over Halley Bay, Antarctica (L = 4.2) is investigated using this method. Analyses show that the trough moves rapidly equatorward over Halley Bay in the early evening hours, during geomagnetically active periods. For magnetically quiet periods, the trough is not observed till after midnight, when its equatorward motion is comparatively slow. These results showed marked differences from those predicted from published empirical relationships describing variations in trough position with time, particularly before midnight. Changes in the position of the plasma pause with time, determined from two theoretical models and from observations are compared with these results for the trough. Also, one case study is presented in which there is determination of the positions of both the trough and the plasmapause over a 7 h period. Similarities and differences in their relative positions and movements of the two features are identified and their possible causes are briefly discussed. (author)

  11. Seasonal variation and solar activity dependence of the quiet-time ionospheric trough

    Science.gov (United States)

    Ishida, T.; Ogawa, Y.; Kadokura, A.; Hiraki, Y.; Häggström, I.

    2014-08-01

    We have conducted a statistical analysis of the ionospheric F region trough, focusing on its seasonal variation and solar activity dependence under geomagnetically quiet and moderate conditions, using plasma parameter data obtained via Common Program 3 observations performed by the European Incoherent Scatter (EISCAT) radar between 1982 and 2011. We have confirmed that there is a major difference in frictional heating between the high- and low-latitude sides of the EISCAT field of view (FOV) at ~73°0'N-60°5'N (geomagnetic latitude) at an altitude of 325 km, which is associated with trough formation. Our statistical results show that the high-latitude and midlatitude troughs occur on the high- and low-latitude sides of the FOV, respectively. Seasonal variations indicate that dissociative recombination accompanied by frictional heating is a main cause of trough formation in sunlit regions. During summer, therefore, the occurrence rate is maintained at 80-90% in the postmidnight high-latitude region owing to frictional heating by eastward return flow. Solar activity dependence on trough formation indicates that field-aligned currents modulate the occurrence rate of the trough during the winter and equinox seasons. In addition, the trough becomes deeper via dissociative recombination caused by an increased ion temperature with F10.7, at least in the equinox and summer seasons but not in winter.

  12. O+ trough zones in the polar cap ionosphere-magnetosphere coupling region

    Science.gov (United States)

    Horwitz, James; Zeng, Wen; Jaafari, Fajer

    Regions of low-density troughs in O+ have been observed at 1 RE altitude in the polar cap ionosphere-magnetosphere region by the Thermal Ion Dynamics Experiment(TIDE) on the POLAR spacecraft. In this presentation, the UT Arlington Dynamic Fluid-Kinetic (DyFK) code is employed to investigate the formation of such O+ density troughs. We utilize convection paths of flux tubes in the high-latitude region as prescribed by an empirical convection model with solar wind inputs to track the evolution of ionospheric plasma transport and in particular O+ densities along these tubes with time/space. The flux tubes are subjected to auroral processes of precipitation and wave-driven ion heating when they pass through the auroral oval, which tends to elevate the plasma densities in these tubes. When the F-regions of such tubes traverse locations where the F-region is in darkness, recombination there causes the higher-altitude regions to drain and the densities to decline throughout. Owing to the varying effects of these processes, significant and low trough-like densities at higher altitudes developed along these flux tubes. The modeled densities near 6000 km altitudes will be compared with multiple POLAR passes featuring POLAR/TIDE-measured O+ densities for inside and outside of such trough regions.

  13. A modelling study of the post-sunset formation of plasma temperature troughs in the equatorial topside ionosphere

    International Nuclear Information System (INIS)

    Bailey, G.J.; Moffett, R.J.; Simmons, P.A.; Footitt, R.J.

    1986-01-01

    Results of model calculations are used to study the post-sunset development of plasma temperature troughs along tubes of plasma at equatorial latitudes. The calculations show that for about 90 minutes after sunset the ion field-aligned velocities are directed poleward in both hemispheres even though the meridional neutral air wind blows from the summer hemisphere to the winter hemisphere. After about 90 minutes the ion field-aligned velocities become directed from the summer hemisphere to the winter hemisphere in both hemispheres. As time advances plasma temperature troughs are formed along the tubes of plasma. Initially the plasma temperature troughs increase in depth, but because in the calculations the tubes of plasma are taken to be moving towards the Earth, the plasma temperature troughs then decrease in depth. At sunspot maximum the plasma temperature troughs are deep and narrow in dip latitude; at sunspot minimum they are shallow and wide. It is shown that the ion field-aligned velocities and the depth of the plasma temperature troughs are extremely sensitive to the neutral atomic hydrogen concentration, especially when the topside ionosphere is dominated by O + . Indications are that the MSIS-83 sunspot maximum concentrations of neutral atomic hydrogen in the topside ionosphere at equatorial latitudes are too low by a factor of about 2. The neutral atomic hydrogen concentration determines whether the transequatorial O + flow is a subsonic ''breeze'' or a supersonic ''wind''

  14. Variations of ionospheric plasma concentration in the region of the main ionospheric through during the magnetic storm on 18-19.12, 1978 in relation to interplanetary magnetic field variations

    International Nuclear Information System (INIS)

    Gdalevich, G.L.; Eliseev, A.Yu.; Kolomijtsev, O.P.; Afonin, V.V.; Ozerov, V.D.; Soboleva, T.N.

    1986-01-01

    The variations of ion concentration in the region of the main ionospheric trough at the height approximately 500 km during the storm on 18-19, 12, 1978 are considered by data from ''Kosmos-900'' satellite. Three These changes in ion density are compared with variations of interplanetary medium parameters, in particular with Ey=-VBz, with the component of the interplanetary electric field. The comparison results are discussed. Exact correlation of ionospheric disturbance development with variations of interplanetary medium parameters is observed. This effect is expressed in the evening section both in the high and mean latitudes and it is obv ously caused by magnetosphere rearrangement in the region of the minimum pole trough, and on the equatorial wall - by convection field penetration to the mean latitude. The movement of the equatorial boundary of diffusion precipitations, which is much responsible for formation of the polar trough wall, corresponds to the boundary movement of corotating and convective plasma or to the last closed equipotentiality. But some delay of the precipitation boundary due to the responsiveness of precipitation processes is observed on the recovery phase

  15. Ionosphere

    Energy Technology Data Exchange (ETDEWEB)

    Taieb, C [Centre National d' Etudes des Telecommunications (CNET), 92 - Issy-les-Moulineaux (France)

    1977-11-01

    This paper comprises four parts. The first one deals with the neutral atmosphere, its structure, its composition, its variations. The second one describes the ionospheric plasma, (the ionized part) and explains its formation. The influence of the geomagnetic field is discussed in the third chapter, the fourth one being concerned with the means of studying the ionosphere: ionograms obtained by ionosondes or incoherent scattering sounding or from satellite measurements.

  16. On a predominant ionization source in the main maximum of the Venus nightside ionosphere

    International Nuclear Information System (INIS)

    Gringauz, K.I.; Verigin, M.I.; Breus, T.K.; Shvachunova, L.A.

    1983-01-01

    New considerations in favour of the previously made hypothesis, made on the basis of data using ''Venera-9 and 10'' satellites, that electron fluxes are the main ionization sources, creating the upper maximum of electron concentration in the night Venus atmosphere, are presented. Analysis of arguments, made by certain american authors, suggesting that O + ion transfer from the day Venus ionosphere to the night one should be considered as the main source of night ionization is made, and inconsistency of the argument shown

  17. Relationship between ionospheric F2-layer critical frequency, F10.7, and F10.7P around African EIA trough

    Science.gov (United States)

    Ikubanni, S. O.; Adeniyi, J. O.

    2017-02-01

    Improved ionospheric modeling requires a better understanding of the relationship between ionospheric parameters and their influencing solar and geomagnetic sources. Published reports of the validation of the International Reference Ionosphere (IRI) for quiet-time revealed either underestimation or overestimation at a greater magnitude during high solar fluxes, especially at low latitude. With daily foF2 data from Ouagadougou (geor. 12.4°N, 1.5°W) covering a solar cycle, we have presented preliminary results from the analysis of solar dependence of six different classifications of the data: (i) daily values, (ii) monthly mean, (iii) daily quiet values (with Ap ⩽ 20), (iv) monthly-quiet-mean values, (v) monthly median, and (vi) monthly-quiet-median values. All six classifications show good nonlinear relationship with both F10.7 and F10.7P, however, the differences between the dependence of classes (i) and (iii) of foF2 on the two solar indices is more substantial than those of classes (ii), (iv), (v), and (vi). Of all the six classes, the monthly averages are best related to both solar activity indices. Further analysis shows that magnetic disturbances are non-influential in the variations of the monthly mean of both solar activity indices; this makes both good indices for quiet-time modeling. Likewise, F10.7 and F10.7P are indistinguishable for long-term modeling around the African EIA trough region. While monthly median values may be best for mid-latitude region, either the mean/median values could be used for low-latitude region. However, it could be worthwhile to examine the distribution of the data from the station under consideration.

  18. Analysis of fine ELF wave structures observed poleward from the ionospheric trough by the low-altitude satellite DEMETER

    Czech Academy of Sciences Publication Activity Database

    Parrot, M.; Nĕmec, F.; Santolík, Ondřej

    2014-01-01

    Roč. 119, č. 3 (2014), s. 2052-2060 ISSN 2169-9380 R&D Projects: GA ČR GAP205/10/2279; GA MŠk LH12231 Institutional support: RVO:68378289 Keywords : trough * EMIC * substorm Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.426, year: 2014 http://onlinelibrary.wiley.com/doi/10.1002/2013JA019557/abstract

  19. How does the predicted geomagnetic main field variation alter the thermosphere-ionosphere storm-time response?

    Science.gov (United States)

    Maute, A. I.; Lu, G.; Richmond, A. D.

    2017-12-01

    Earth's magnetic main field plays an important role in the thermosphere-ionosphere (TI) system, as well as its coupling to Earth's magnetosphere. The ionosphere consists of a weakly ionized plasma strongly influenced by the main field and embedded in the thermosphere. Therefore, ion-neutral coupling and ionospheric electrodynamics can influence the plasma distribution and neutral dynamics. There are strong longitude variations of the TI storm response. At high latitude magnetosphere-ionosphere coupling is organized by the geomagnetic main field, leading in general to stronger northern middle latitude storm time response in the American sector due to the geomagnetic dipole location. In addition, the weak geomagnetic main field in the American sector leads to larger local ExB drift and can alter the plasma densities. During geomagnetic storms the intense energy input into the high latitude region is redistributed globally, leading to thermospheric heating, wind circulation changes and alterations of the ionospheric electrodynamics. The storm time changes are measurable in the plasma density, ion drift, temperature, neutral composition, and other parameters. All these changes depend, to some degree, on the geomagnetic main field which changes on decadal time scales. In this study, we employ a forecast model of the geomagnetic main field based on data assimilation and geodynamo modeling [Aubert et al., 2015]. The main field model predicts that in 50 years the South Atlantic Anomaly is further weakened by 2 mT and drifts westward by approximately 10o. The dipole axis moves northward and westward by 2o and 6o, respectively. Simulating the March 2015 geomagnetic storm with the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIE-GCM) driven by the Assimilative Mapping of Ionospheric Electrodynamics (AMIE), we evaluate the thermosphere-ionosphere response using the geomagnetic main field of 2015, 2065, and 2115. We compare the TI response for 2015 with

  20. Saturn's polar ionospheric flows and their relation to the main auroral oval

    Directory of Open Access Journals (Sweden)

    S. W. H. Cowley

    2004-04-01

    current bounding the region of open and closed field lines. Estimates indicate that auroras of brightness from a few kR to a few tens of kR can be produced by precipitating accelerated magnetospheric electrons of a few keV to a few tens of keV energy, if the current flows in a region which is sufficiently narrow, of the order of or less than ~1000 km (~1° latitude wide. Arguments are also given which indicate that the auroras should typically be significantly brighter on the dawn side of the oval than at dusk, by roughly an order of magnitude, and should be displaced somewhat towards dawn by the down-tail outflow at dusk associated with the Vasyliunas cycle. Model estimates are found to be in good agreement with data derived from high quality images newly obtained using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope, both in regard to physical parameters, as well as local time effects. The implication of this picture is that the form, position, and brightness of Saturn's main auroral oval provide remote diagnostics of the magnetospheric interaction with the solar wind, including dynamics associated with magnetopause and tail plasma interaction processes. Key words. Magnetospheric physics (auroral phenomena, magnetosphere-ionosphere interactions, solar windmagnetosphere interactions

  1. Saturn's polar ionospheric flows and their relation to the main auroral oval

    Directory of Open Access Journals (Sweden)

    S. W. H. Cowley

    2004-04-01

    upward current bounding the region of open and closed field lines. Estimates indicate that auroras of brightness from a few kR to a few tens of kR can be produced by precipitating accelerated magnetospheric electrons of a few keV to a few tens of keV energy, if the current flows in a region which is sufficiently narrow, of the order of or less than ~1000 km (~1° latitude wide. Arguments are also given which indicate that the auroras should typically be significantly brighter on the dawn side of the oval than at dusk, by roughly an order of magnitude, and should be displaced somewhat towards dawn by the down-tail outflow at dusk associated with the Vasyliunas cycle. Model estimates are found to be in good agreement with data derived from high quality images newly obtained using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope, both in regard to physical parameters, as well as local time effects. The implication of this picture is that the form, position, and brightness of Saturn's main auroral oval provide remote diagnostics of the magnetospheric interaction with the solar wind, including dynamics associated with magnetopause and tail plasma interaction processes.

    Key words. Magnetospheric physics (auroral phenomena, magnetosphere-ionosphere interactions, solar windmagnetosphere interactions

  2. Ionospheric Digital Database

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The ionosphere is that part of the Earth's atmosphere that results mainly from the photo ionization of the upper atmosphere. Traditionally, the following ionospheric...

  3. INSPIRE Project (IoNospheric Sounding for Pre-seismic anomalies Identification REsearch): Main Results and Future Prospects

    Science.gov (United States)

    Pulinets, S. A.; Andrzej, K.; Hernandez-Pajares, M.; Cherniak, I.; Zakharenkova, I.; Rothkaehl, H.; Davidenko, D.

    2017-12-01

    The INSPIRE project is dedicated to the study of physical processes and their effects in ionosphere which could be determined as earthquake precursors together with detailed description of the methodology of ionospheric pre-seismic anomalies definition. It was initiated by ESA and carried out by international consortium. The physical mechanisms of the ionospheric pre-seismic anomalies generation from ground to the ionosphere altitudes were formulated within framework of the Lithosphere-Atmosphere-Ionosphere-Magnetosphere Coupling (LAIMC) model (Pulinets et al., 2015). The general algorithm for the identification of the ionospheric precursors was formalized which also takes into account the external Space Weather factors able to generate the false alarms. Importance of the special stable pattern called the "precursor mask" was highlighted which is based on self-similarity of pre-seismic ionospheric variations. The role of expert decision in pre-seismic anomalies interpretation for generation of seismic warning is important as well. The algorithm performance of the LAIMC seismo-ionospheric effect detection module has been demonstrated using the L'Aquila 2009 earthquake as a case study. The results of INSPIRE project have demonstrated that the ionospheric anomalies registered before the strong earthquakes could be used as reliable precursors. The detailed classification of the pre-seismic anomalies was presented in different regions of the ionosphere and signatures of the pre-seismic anomalies as detected by ground and satellite based instruments were described what clarified methodology of the precursor's identification from ionospheric multi-instrumental measurements. Configuration for the dedicated multi-observation experiment and satellite payload was proposed for the future implementation of the INSPIRE project results. In this regard the multi-instrument set can be divided by two groups: space equipment and ground-based support, which could be used for real

  4. Trough for piglets

    DEFF Research Database (Denmark)

    2006-01-01

    A trough is disclosed for supplying piglets with mineral supplements in the suckling period. The trough is designed to awaken the piglets' curiosity and thus make them root in the bottom of the trough, where the mineral supplements are dispensed in form of a dry powder mixture, and thus reduce...

  5. Ionospheric topside sounding.

    Science.gov (United States)

    Calvert, W

    1966-10-14

    Over the past few years, the satellite topside sounders have significantly contributed to the understanding of the upper ionosphere. A great quantity of radio echo data has been accumulated, from which the ionospheric electrondensity distribution can be determined. The topside measurements of electron density essentially agree with similar measurements from the ground, except for an occasional 10-percent discrepancy near the peak of the ionosphere. While horizontal non-uniformity is a likely cause, this discrepancy has not yet been adequately explained. The electron-density scale heights measured at a constant altitude indicate both a higher temperature and a heavier mean ion mass at high latitudes. At low latitudes the topside measurements have shown the detailed latitudinal structure of the equatorial anomaly, demonstrating control by the geomagnetic field. A variety of electron-density irregularities have been studied. Most are greatly elongated along the magnetic field, and produce echoes either by lateral scattering, if they are thin, or by longitudinal ducting, if they are thick. Some of the thick irregularities are continuous between the hemispheres and support conjugate echo propagation. The topside sounders have revealed the complex structure of the ionosphere near the auroral zone and at higher latitudes. At night an east-west trough of greatly reduced electron density occurs equatorward of the auroral zone. At the auroral zone itself the electron density is high and quite variable, both in space and time. The electron density at the polar cap within the auroral zone is often uniform and smooth. Ionospheric irregularities are common in the area of the trough and the auroral zone. Among other satellites, the topside sounders have been used in various plasma studies involving the excitation and propagation of waves. These studies suggest that the ionosphere is an appropriate region for future plasma physics investigations, especially with rocket and

  6. Ionospheric research at INPE

    International Nuclear Information System (INIS)

    Abdu, M.A.

    1984-01-01

    Ionosphere investigations at INPE are mainly concerned with the problems of equatorial and tropical ionospheres and their electrodynamic coupling with the high latitude ionosphere. Present research objectives include investigations in the following specific areas: equatorial ionospheric plasma dynamics; plasma irregularity generation and morphology, and effects on space borne radar operations; ionospheric response to disturbance dynamo and magnetospheric electric fields; aeronomic effcts of charged particle precipitation in the magnetic anomaly, etc. These problems are being investigated using experimental datacollected from ionospheric diagnostic instruments being operated at different locations in Brazil. These instruments are: ionosondes, VHF electronic polarimeters, L-band scintillation receivers, airglow photometers, riometers and VLF receivers. A brief summary of the research activities and some recnet results will be presented. (Author) [pt

  7. The F-region trough: seasonal morphology and relation to interplanetary magnetic field

    Directory of Open Access Journals (Sweden)

    M. Voiculescu

    2006-03-01

    Full Text Available We present here the results of a statistical study of the ionospheric trough observed in 2003 by means of satellite tomography. We focus on the seasonal morphology of the trough occurrence and investigate the trough latitude, width and the horizontal gradients at the edges, at different magnetic local times, as well as their relations to geomagnetic activity and the interplanetary magnetic field. A seasonal effect is noticed in the diurnal variation of the trough latitude, indicating that summer clearly differs from the other seasons. In winter the troughs seem to follow the solar terminator. The width of the trough has a diurnal variation and it depends on the season, as well. The broadest troughs are observed in winter and the narrowest ones in summer. A discontinuity in the diurnal variation of the trough latitude is observed before noon. It is suggested that this is an indication of a difference between the generation mechanisms of morningside and eveningside troughs. The density gradients at the edges have a complex dependence on the latitude of the trough and on geomagnetic activity. The photoionization and the auroral precipitation are competing in the formation of the trough walls at different magnetic local times. An important finding is that the interplanetary magnetic field plays a role in the occurrence of the trough at different levels of geomagnetic activity. This is probably associated with the topology of the polar cap convection pattern, which depends on the directions of the IMF components By and Bz.

  8. Signature of rapid subauroral ion drifts in the high-latitude ionosphere structure

    International Nuclear Information System (INIS)

    Galperin, Y.I.; Khalipov, V.L.; Filippov, V.M.

    1986-01-01

    Characteristics of fast subauroral ion drifts were studied for several cases where synchronous satellite measurements and ground-based ionospheric data from vertical and oblique-incidence sounding were available. Also some relevant data were analyzed concerning apparent irregularities drift velocity measurements by the multipoint spaced receiver at HF range (DI method). Changes of high-latitude ionosphere structure were investigated to identify the signature on the ionograms, and to provide a semiquantitative description of this phenomenon. It is shown that, above a particular station, the time development of the rapid subauroral ion drift band, or the ''polarization jet'' according to Galperin et al., 1973, 1974 in about 5-30 minutes leads to the formation of a trough which is narrow in latitude (approximately 100-200 km) but extended in longitude (several hours of MLT) and rather deep (N sub(emin)approximately 2.10 4 cm -3 in the electron density distribution in the F-region. Such narrow troughs can be observed in the evening sector superimposed on the undisturbed ionization density level, while in the near-midnight sector they contribute to the deepening of the preexisting, and much wider, main ionospheric through A qualitative scenario for the formation of the ''trough in the trough'' on the nightside, as a result of the increase of the loss processes related to rapid drift speed, is supported by ''synthetic'' ionograms deduced from numerical ray-tracing calculations for a model electron density distribution that is in reasonable accord with the observed vertical and oblique sounding ionograms and from satellite data

  9. Observations of subauroral ionospheric dynamics during SED plume passage at Millstone Hill

    Science.gov (United States)

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

    2017-12-01

    Storm enhanced density (SED) is a characteristic ionospheric storm time structure, with a significant plasma density enhancement in a narrow zone. SED structures often (but not always) span the continental US with a base in the US northeast at the afternoon and dusk sector, extending westward or northwest into the high latitude dayside cusp region. It is a typical and repeatable space weather phenomenon occurring during the main phase of magnetic storms with intensity ranging from active to disturbed levels. Observations of stormtime ionospheric density enhancement at subauroral latitudes have a long history, and were termed the 'dusk effect' until relatively recently, when dense networks of GNSS receivers have allowed us to view this structure with much finer spatial and temporal resolution. The formation of a SED plume is a topic under intensive community investigation, but in general it is believed that stormtime ionospheric dynamics and processes within the coupling magnetosphere-ionosphere-thermosphere system are responsible. For instance, poleward and sunward plasma drifts at the edge of the expanded dusk sector high-latitude convection can be important. Subauroral polarization stream (SAPS) are often observed at the poleward edge of the SED plume where ionospheric conductivity is low. SAPS is a huge westward ion flow that can convect ionospheric plasma from the afternoon or evening sector where solar photoionization production is waning, creating low density or density troughs. Stormtime penetration electric fields also exist, creating enhanced low and mid latitude upward ion drifts that move ionospheric plasma upward from the low altitude region where they are produced. This provides another important ionization source to contribute to maintaining the SED plume. This paper will provide analysis of the relative strength of these factors by using joint datasets of current geospace storm events obtained with the Millstone Hill incoherent scatter radar, GNSS

  10. Observations by the CUTLASS radar, HF Doppler, oblique ionospheric sounding, and TEC from GPS during a magnetic storm

    Directory of Open Access Journals (Sweden)

    D. V. Blagoveshchensky

    2005-07-01

    Full Text Available Multi-diagnostic observations, covering a significant area of northwest Europe, were made during the magnetic storm interval (28–29 April 2001 that occurred during the High Rate SolarMax IGS/GPS-campaign. HF radio observations were made with vertical sounders (St. Petersburg and Sodankyla, oblique incidence sounders (OIS, on paths from Murmansk to St. Petersburg, 1050 km, and Inskip to Leicester, 170 km, Doppler sounders, on paths from Cyprus to St. Petersburg, 2800 km, and Murmansk to St. Petersburg, and a coherent scatter radar (CUTLASS, Hankasalmi, Finland. These, together with total electron content (TEC measurements made at GPS stations from the Euref network in northwest Europe, are presented in this paper. A broad comparison of radio propagation data with ionospheric data at high and mid latitudes, under quiet and disturbed conditions, was undertaken. This analysis, together with a geophysical interpretation, allow us to better understand the nature of the ionospheric processes which occur during geomagnetic storms. The peculiarity of the storm was that it comprised of three individual substorms, the first of which appears to have been triggered by a compression of the magnetosphere. Besides the storm effects, we have also studied substorm effects in the observations separately, providing an improved understanding of the storm/substorm relationship. The main results of the investigations are the following. A narrow trough is formed some 10h after the storm onset in the TEC which is most likely a result of enhanced ionospheric convection. An enhancement in TEC some 2–3 h after the storm onset is most likely a result of heating and upwelling of the auroral ionosphere caused by enhanced currents. The so-called main effect on ionospheric propagation was observed at mid-latitudes during the first two substorms, but only during the first substorm at high latitudes. Ionospheric irregularities observed by CUTLASS were clearly related to the

  11. The ionosphere

    International Nuclear Information System (INIS)

    Taieb, C.

    1977-01-01

    This paper comprises four parts. The first one is dealing with the neutral atmosphere, its structure, its composition, its variations. The second one describes the ionospheric plasma, (the ionized part) and explains its formation. The influence of the geomagnetic field is discussed in the third chapter, the fourth one being concerned with the means of studying the ionosphere: ionograms obtained by ionosondes or incoherent scattering sounding or from satellite measurements [fr

  12. Ionosphere and Radio Communication

    Indian Academy of Sciences (India)

    The upperionosphere is used for radio communication and navigationas it reflects long, medium, as well as short radio waves. Sincesolar radiation is the main cause of the existence of ionosphere,any variation in the radiations can affect the entireradio communication system. This article attempts to brieflyintroduce the ...

  13. The F-region trough: seasonal morphology and relation to interplanetary magnetic field

    Directory of Open Access Journals (Sweden)

    M. Voiculescu

    2006-03-01

    Full Text Available We present here the results of a statistical study of the ionospheric trough observed in 2003 by means of satellite tomography. We focus on the seasonal morphology of the trough occurrence and investigate the trough latitude, width and the horizontal gradients at the edges, at different magnetic local times, as well as their relations to geomagnetic activity and the interplanetary magnetic field. A seasonal effect is noticed in the diurnal variation of the trough latitude, indicating that summer clearly differs from the other seasons. In winter the troughs seem to follow the solar terminator. The width of the trough has a diurnal variation and it depends on the season, as well. The broadest troughs are observed in winter and the narrowest ones in summer. A discontinuity in the diurnal variation of the trough latitude is observed before noon. It is suggested that this is an indication of a difference between the generation mechanisms of morningside and eveningside troughs. The density gradients at the edges have a complex dependence on the latitude of the trough and on geomagnetic activity. The photoionization and the auroral precipitation are competing in the formation of the trough walls at different magnetic local times. An important finding is that the interplanetary magnetic field plays a role in the occurrence of the trough at different levels of geomagnetic activity. This is probably associated with the topology of the polar cap convection pattern, which depends on the directions of the IMF components By and Bz.

  14. Ionospheric behaviour during storm recovery phase

    Science.gov (United States)

    Buresova, D.; Lastovicka, J.; Boska, J.; Sindelarova, T.; Chum, J.

    2012-04-01

    Intensive ionospheric research, numerous multi-instrumental observations and large-scale numerical simulations of ionospheric F region response to magnetic storm-induced disturbances during the last several decades were primarily focused on the storm main phase, in most cases covering only a few hours of the recovery phase following after storm culmination. Ionospheric behaviour during entire recovery phase still belongs to not sufficiently explored and hardly predictable features. In general, the recovery phase is characterized by an abatement of perturbations and a gradual return to the "ground state" of ionosphere. However, observations of stormy ionosphere show significant departures from the climatology also within this phase. This paper deals with the quantitative and qualitative analysis of the ionospheric behaviour during the entire recovery phase of strong-to-severe magnetic storms at middle latitudes for nowadays and future modelling and forecasting purposes.

  15. The sedimentation rates in the Okinawa Trough during the Late Quaternary

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    On the basis of accelerator mass spectrometer radiocarbon (AMS 14C) dating, sedimentation rates of 11 cores collected from the northern to southern Okinawa Trough are discussed. The sedimentation rates in the Okinawa Trough roughly range from 11 to 39 cm/ka, and the average is 23.0 cm/ka. China's continental matter is the main sediment source of the middle Okinawa Trough and has important contribution to the northern and southern Okinawa Trough. The sedimentation rates during the marine oxygen isotope (MIS)2 are uniformly higher than those during MIS 1 in the northern and middle Okinawa Trough while they are on the contrary in the southern Okinawa Trough. Sedimentation rates in the Okinawa Trough can be one of the proxies of sediment source and an indicator of cooling events.

  16. Linear magnetic anomalies and tectonic development of the middle Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    -By analyzing the magnetic anomalies, the linear magnetic anomalies in the middle Okinawa Trough are identified. It means that the crust along the spreading axis is broken, and new oceanic crust is formed. Geophysical data have revealed that a model of three extensive episodes occurs in the Okinawa Trough, which can be named as "doming episode" from the Middle to Late Miocene (Phase I), the episode from the Pliocence to Early Pleistocene (Phase Ⅱ ), and the recent "spreading episode" (Phase Ⅲ ). The magnetic anomalies in the middle Okinawa Trough are very similar to those found in the middle Red Sea, indicating that the Okinawa Trough is developing towards the "Red Sea stage". Similar to the Red Sea, there are a "main trough" and a "axial trough" in the Okinawa Trough.

  17. Ionospheric Modeling for Precise GNSS Applications

    NARCIS (Netherlands)

    Memarzadeh, Y.

    2009-01-01

    The main objective of this thesis is to develop a procedure for modeling and predicting ionospheric Total Electron Content (TEC) for high precision differential GNSS applications. As the ionosphere is a highly dynamic medium, we believe that to have a reliable procedure it is necessary to transfer

  18. Martian Ionospheric Observation and Modeling

    Science.gov (United States)

    González-Galindo, Francisco

    2018-02-01

    The Martian ionosphere is a plasma embedded within the neutral upper atmosphere of the planet. Its main source is the ionization of the CO2-dominated Martian mesosphere and thermosphere by the energetic EUV solar radiation. The ionosphere of Mars is subject to an important variability induced by changes in its forcing mechanisms (e.g., the UV solar flux) and by variations in the neutral atmosphere (e.g., the presence of global dust storms, atmospheric waves and tides, changes in atmospheric composition, etc.). Its vertical structure is dominated by a maximum in the electron concentration placed at about 120–140 km of altitude, coincident with the peak of the ionization rate. Below, a secondary peak produced by solar X-rays and photoelectron-impact ionization is observed. A sporadic third layer, possibly of meteoric origin, has been also detected below. The most abundant ion in the Martian ionosphere is O2+, although O+ can become more abundant in the upper ionospheric layers. While below about 180–200 km the Martian ionosphere is dominated by photochemical processes, above those altitudes the dynamics of the plasma become more important. The ionosphere is also an important source of escaping particles via processes such as dissociative recombination of ions or ion pickup. So, characterization of the ionosphere provides or can provide information about such disparate systems and processes as the solar radiation getting to the planet, the neutral atmosphere, the meteoric influx, the atmospheric escape to space, or the interaction of the planet with the solar wind. It is thus not surprising that the interest about this region dates from the beginning of the space era. From the first measurements provided by the Mariner 4 mission in the 1960s to the contemporaneous observations, still ongoing, by the Mars Express and MAVEN orbiters, our current knowledge of this atmospheric region is the consequence of the accumulation of more than 50 years of discontinuous

  19. Ionospheric disturbance dynamo

    International Nuclear Information System (INIS)

    Blanc, M.; Richmond, A.D.

    1980-01-01

    A numerical simulation study of the thermospheric winds produced by auroral heating during magnetic storms, and of their global dynamo effects, establishes the main features of the ionospheric disturbanc dynamo. Driven by auroral heating, a Hadley cell is created with equatorward winds blowing above about 120 km at mid-latitudes. The transport of angular momentum by these winds produces a subrotation of the midlatitude thermosphere, or westward motion with respect to the earth. The westward winds in turn drive equatorward Pedersen currents which accumulate charge toward the equator, resulting in the generation of a poleward electric field, a westward E x B drift, and an eastward current. When realistic local time conductivity variations are simulated, the eastward mid-latitude current is found to close partly via lower latitudes, resulting in an 'anti-Sq' type of current vortex. Both electric field and current at low latitudes thus vary in opposition to their normal quiet-day behavior. This total pattern of distrubance winds, electric fields, and currents is superimposed upon the background quiet-day pattern. When the neutral winds are artificially confined on the nightside, the basic pattern of predominantly westward E x B plasma drifts still prevails on the nightside but no longer extends into the dayside. Considerable observational evidence exists, suggesting that the ionospheric disturbance dynamo has an appreciable influence on storm-time ionospheric electric fields at middle and low latitudes

  20. Global ionospheric effects of geomagnetic storm on May 2-3, 2010 and their influence on HF radio wave propagation

    Science.gov (United States)

    Kotova, Daria; Klimenko, Maxim; Klimenko, Vladimir; Zakharov, Veniamin

    2013-04-01

    geomagnetic storm. A comparison of the ordinary and extraordinary modes of HF radio ray paths in quiet and disturbed conditions has been done. We considered in more detail the features of the radio ray paths in the presence of F3 layer in the equatorial ionosphere, the main ionospheric trough and tongue of ionization at high latitudes. It is shown that the results obtained with use of radio propagation and GSM TIP models adequately describe HF radio ray paths in the Earth's ionosphere and can be used in applications. These investigations were carried out at financial support of Russian Foundation for Basic Research (RFBR) - Grant # 12-05-31217 and RAS Program 22.

  1. Ionospheric control of the magnetosphere: conductance

    Directory of Open Access Journals (Sweden)

    A. J. Ridley

    2004-01-01

    Full Text Available It is well known that the ionosphere plays a role in determining the global state of the magnetosphere. The ionosphere allows magnetospheric currents to close, thereby allowing magnetospheric convection to occur. The amount of current which can be carried through the ionosphere is mainly determined by the ionospheric conductivity. This paper starts to quantify the nonlinear relationship between the ionospheric conductivity and the global state of the magnetosphere. It is found that the steady-state magnetosphere acts neither as a current nor as a voltage generator; a uniform Hall conductance can influence the potential pattern at low latitudes, but not at high latitude; the EUV generated conductance forces the currents to close in the sunlight, while the potential is large on the nightside; the solar generated Hall conductances cause a large asymmetry between the dawn and dusk potential, which effects the pressure distribution in the magnetosphere; a uniform polar cap potential removes some of this asymmetry; the potential difference between solar minimum and maximum is ∼11%; and the auroral precipitation can be related to the local field-aligned current through an exponential function. Key words. Ionosphere (ionosphere-magnetosphere interactions; modelling and forecasting; polar ionosphere

  2. Ionospheric control of the magnetosphere: conductance

    Directory of Open Access Journals (Sweden)

    A. J. Ridley

    2004-01-01

    Full Text Available It is well known that the ionosphere plays a role in determining the global state of the magnetosphere. The ionosphere allows magnetospheric currents to close, thereby allowing magnetospheric convection to occur. The amount of current which can be carried through the ionosphere is mainly determined by the ionospheric conductivity. This paper starts to quantify the nonlinear relationship between the ionospheric conductivity and the global state of the magnetosphere. It is found that the steady-state magnetosphere acts neither as a current nor as a voltage generator; a uniform Hall conductance can influence the potential pattern at low latitudes, but not at high latitude; the EUV generated conductance forces the currents to close in the sunlight, while the potential is large on the nightside; the solar generated Hall conductances cause a large asymmetry between the dawn and dusk potential, which effects the pressure distribution in the magnetosphere; a uniform polar cap potential removes some of this asymmetry; the potential difference between solar minimum and maximum is ∼11%; and the auroral precipitation can be related to the local field-aligned current through an exponential function.

    Key words. Ionosphere (ionosphere-magnetosphere interactions; modelling and forecasting; polar ionosphere

  3. Ionospheric TEC Weather Map Over South America

    Science.gov (United States)

    Takahashi, H.; Wrasse, C. M.; Denardini, C. M.; Pádua, M. B.; de Paula, E. R.; Costa, S. M. A.; Otsuka, Y.; Shiokawa, K.; Monico, J. F. Galera; Ivo, A.; Sant'Anna, N.

    2016-11-01

    Ionospheric weather maps using the total electron content (TEC) monitored by ground-based Global Navigation Satellite Systems (GNSS) receivers over South American continent, TECMAP, have been operationally produced by Instituto Nacional de Pesquisas Espaciais's Space Weather Study and Monitoring Program (Estudo e Monitoramento Brasileiro de Clima Especial) since 2013. In order to cover the whole continent, four GNSS receiver networks, (Rede Brasileiro de Monitoramento Contínuo) RBMC/Brazilian Institute for Geography and Statistics, Low-latitude Ionospheric Sensor Network, International GNSS Service, and Red Argentina de Monitoreo Satelital Continuo, in total 140 sites, have been used. TECMAPs with a time resolution of 10 min are produced in 12 h time delay. Spatial resolution of the map is rather low, varying between 50 and 500 km depending on the density of the observation points. Large day-to-day variabilities of the equatorial ionization anomaly have been observed. Spatial gradient of TEC from the anomaly trough (total electron content unit, 1 TECU = 1016 el m-2 (TECU) 80) causes a large ionospheric range delay in the GNSS positioning system. Ionospheric plasma bubbles, their seeding and development, could be monitored. This plasma density (spatial and temporal) variability causes not only the GNSS-based positioning error but also radio wave scintillations. Monitoring of these phenomena by TEC mapping becomes an important issue for space weather concern for high-technology positioning system and telecommunication.

  4. Improvement Design of Parabolic Trough

    Science.gov (United States)

    Ihsan, S. I.; Safian, M. A. I. M.; Taufek, M. A. M.; Mohiuddin, A. K. M.

    2017-03-01

    The performance of parabolic trough solar collector (PTSC) has been evaluated using different heat transfer working fluids; namely water and SAE20 W50 engine oil. New and slightly improved PTSC was developed to run the experimental study. Under the meteorological conditions of Malaysia, authors found that PTSC can operate at a higher temperature than water collector but the performance efficiency of collector using engine oil is much lower than the water collector.

  5. Upper ionosphere and magnetospheric-ionospheric coupling

    International Nuclear Information System (INIS)

    Manzano, J.R.

    1989-02-01

    After a presentation of the ionospheric physics and of the earth magnetosphere morphology, generation and dynamics, the magnetosphere-ionosphere coupling in quiet and perturbed conditions is discussed. Some summary information about other planetary magnetospheres, particularly Venus and Jupiter magnetospheres, are finally given. 41 refs, 24 figs

  6. ON TECTONIC PROBLEMS OF THE OKINAWA TROUGH

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The Okinawa Trough is a very active tectonic zone at the margin of the Northwest Pacific and is typical of back-arc rifting at the young stage of tectonic evolution. Many scientists from Japan, China, Germany, France, the U.S.A. and Russia have done a lot of geologic and geophysical investigations there. It is well known that the Okinawa Trough is an active back-arc rift with extremely high heat flow, very strong hydrothermal circulation, strong volcanic and magmatic activity, frequent earthquakes, rapid subsidence and rifting, well-developed fault and central graben. But up to now, there are still some important tectonic problems about the Okinawa Trough that require clarification on some aspects such as the type of its crust, its forming time, its tectonic evolution, the distribution of its central grabens, the relationship between its high heat flow and tectonic activity. Based on the data obtained from seismic survey, geomagnetic and gravity measurements, submarine sampling and heat flow measurements in the last 15 years, the author discusses the following tectonic problems about the Okinawa Trough: (1) If the Okinawa Trough develops oceanic crust or not. (2) Is the South Okinawa Trough tectonically more active than the North Okinawa Trough with shallower water and few investigation data on it. (3) The formation time of the Okinawa Trough and its tectonic evolution. The Okinawa Trough has a very thin continental crust. Up to now, there is no evidence of oceanic crust in the Okinawa Trough. The North, Middle and South Okinawa Trough are all very strongly active areas. From 6 Ma B.P., the Okinawa Trough began to form. Since 2 Ma, the Okinawa Trough has been very active.

  7. ON TECTONIC PROBLEMS OF THE OKINAWA TROUGH

    Institute of Scientific and Technical Information of China (English)

    李乃胜

    2001-01-01

    The Okinawa Trough is a very active tectonic zone at the margin of the Northwest Pacific and is typical of back-arc rifting at the young stage of tectonic evolution. Many scientists from Japan,China, Germany, France, the U. S.A. and Russia have done a lot of geologic and geophysical investigations there. It is well known that the Okinawa Trough is an active back-arc rift with extremely high heat flow, very strong hydrothermal circulation, strong volcanic and magmatic activity, frequent earthquakes,rapid subsidence and rifting, well-developed fault and central graben. But up to now, there are still some important tectonic problems about the Okinawa Trough that require clarification on some aspects such as the type of its crust, its forming time, its tectonic evolution, the distribution of its central grabens, the relationship between its high heat flow and tectonic activity. Based on the data obtained from seismic sur-vey, geomagnetic and gravity measurements, submarine sampling and heat flow measurements in the last 15 years, the author discusses the following tectonic problems about the Okinawa Trough: (1) If the Okinawa Trough develops oceanic crust or not. (2) Is the South Okinawa Trough tectonically more active than the North Okinawa Trough with shallower water and few investigation data on it. (3) The formation time of the Okinawa Trough and its tectonic evolution. The Okinawa Trough has a very thin continental crust. Up to now, there is no evidence of oceanic crust in the Okinawa Trough. The North, Middle and South Okinawa Trough are all very strongly active areas. From 6 Ma B.P. , the Okinawa Trough began to form. Since 2 Ma, the Okinawa Trough has been very active.

  8. Features of High-Latitude Ionospheric Irregularities Development as Revealed by Ground-Based GPS Observations, Satellite-Borne GPS Observations and Satellite In Situ Measurements over the Territory of Russia during the Geomagnetic Storm on March 17-18, 2015

    Science.gov (United States)

    Zakharenkova, I. E.; Cherniak, Iu. V.; Shagimuratov, I. I.; Klimenko, M. V.

    2018-01-01

    The dynamic picture of the response of the high- and mid-latitude ionosphere to the strong geomagnetic disturbances on March 17-18, 2015, has been studied with ground-based and satellite observations, mainly, by transionospheric measurements of delays of GPS (Global Positioning System) signals. The advantages of the joint use of ground-based GPS measurements and GPS measurements on board of the Swarm Low-Earth-Orbit satellite mission for monitoring of the appearance of ionospheric irregularities over the territory of Russia are shown for the first time. The results of analysis of ground-based and space-borne GPS observations, as well as satellite, in situ measurements, revealed large-scale ionospheric plasma irregularities observed over the territory of Russia in the latitude range of 50°-85° N during the main phase of the geomagnetic storm. The most intense ionospheric irregularities were detected in the auroral zone and in the region of the main ionospheric trough (MIT). It has been found that sharp changes in the phase of the carrier frequency of the navigation signal from all tracked satellites were recorded at all GPS stations located to the North from 55° MLAT. The development of a deep MIT was related to dynamic processes in the subauroral ionosphere, in particular, with electric fields of the intense subauroral polarization stream. Analysis of the electron and ion density values obtained by instruments on board of the Swarm and DMSP satellites showed that the zone of highly structured auroral ionosphere extended at least to heights of 850-900 km.

  9. Advanced photovoltaic-trough development

    Energy Technology Data Exchange (ETDEWEB)

    Spencer, R.; Yasuda, K.; Merson, B.

    1982-04-01

    The scope of the work on photvoltaic troughs includes analytical studies, hardware development, and component testing. Various aspects of the system have been optimized and improvements have been realized, particularly in the receiver and reflecting surface designs. An empirical system performance model has been developed that closely agrees with measured system performance. This in-depth study of single-axis reflecting linear focus photovoltaic concentrators will be very beneficial in the development of improved models for similar systems as well as other phtovoltaic concentrator designs.

  10. Climatology of GNPs ionospheric scintillation at high and mid latitudes under different solar activity conditions

    International Nuclear Information System (INIS)

    Spogli, L.; Alfonsi, L.; De Franceschi, G.; Romano, V.; Aquino, M.H.O.; Dodson, A.

    2010-01-01

    We analyze data of ionospheric scintillation over North European regions for the same period (October to November) of two different years (2003 and 2008), characterized by different geomagnetic conditions. The work aims to develop a scintillation climatology of the high- and mid-latitude ionosphere, analyzing the behaviour of the scintillation occurrence as a function of the magnetic local time (MLT) and of the altitude adjusted corrected magnetic latitude (M lat), to characterize scintillation scenarios under different solar activity conditions. The results shown herein are obtained merging observations from a network of GISTMs (GPS Ionospheric Scintillation and TEC Monitor) located over a wide range of latitudes in the northern hemisphere. Our findings confirm the associations of the occurrence of the ionospheric irregularities with the expected position of the auroral oval and of the ionospheric trough walls and show the contribution of the polar cap patches even under solar minimum conditions.

  11. Fabrication of trough-shaped solar collectors

    Science.gov (United States)

    Schertz, William W.

    1978-01-01

    There is provided a radiant energy concentration and collection device formed of a one-piece thin-walled plastic substrate including a plurality of nonimaging troughs with certain metallized surfaces of the substrate serving as reflective side walls for each trough. The one-piece plastic substrate is provided with a seating surface at the bottom of each trough which conforms to the shape of an energy receiver to be seated therein.

  12. Solar photovoltaic reflective trough collection structure

    Science.gov (United States)

    Anderson, Benjamin J.; Sweatt, William C.; Okandan, Murat; Nielson, Gregory N.

    2015-11-19

    A photovoltaic (PV) solar concentration structure having at least two troughs encapsulated in a rectangular parallelepiped optical plastic structure, with the troughs filled with an optical plastic material, the troughs each having a reflective internal surface and approximately parabolic geometry, and the troughs each including photovoltaic cells situated so that light impinging on the optical plastic material will be concentrated onto the photovoltaic cells. Multiple structures can be connected to provide a solar photovoltaic collection system that provides portable, efficient, low-cost electrical power.

  13. Thermospheric storms and related ionospheric effects

    International Nuclear Information System (INIS)

    Chandra, S.; Spencer, N.W.

    1976-01-01

    A comparative study of thermospheric storms for the equinox and winter conditions is presented based on the neutral composition measurements from the Aeros-A Nate (Neutral Atmosphere Temperature Experiment) experiment. The main features of the two storms as inferred from the changes in N 2 , Ar, He, and O are described, and their implications to current theories of thermospheric storms are discussed. On the basis of the study of the F region critical frequency measured from a chain of ground-based ionospheric stations during the two storm periods, the general characteristics of the ionospheric storms and the traveling ionospheric disturbances are described. It is suggested that the positive and negative phases of ionospheric storms are the various manifestations of thermospheric storms

  14. High latitude ionospheric structure

    International Nuclear Information System (INIS)

    1984-06-01

    The Earth's ionosphere is an important element in solar-terrestrial energy transfer processes. As a major terrestrial sink for many solar and magnetospheric events, the ionosphere has characteristic features that are traced to such seemingly remote phenomena as solar flares, radiation belt wave-particle interactions and magnetospheric substorms. In considering the multiple of solar-terrestrial plasma interactions, it is important to recognize that the high-latitude ionosphere is not altogether a simple receptor of various energy deposition processes. The high-altitude ionosphere plays an active feedback role by controlling the conductivity at the base of far-reaching magnetic field lines and by providing a plasma source for the magnetosphere. Indeed, the role of the ionosphere during magnetospheric substorms is emerging as a topic for meaningful study in the overall picture of magnetospheric-ionospheric coupling

  15. Monitoring of surface chemical and underground nuclear explosions with help of ionospheric radio-sounding above test site

    International Nuclear Information System (INIS)

    Krasnov, V.M.; Drobzheva, Ya.V.

    2000-01-01

    We describe the basic principles, advantages and disadvantages of ionospheric method to monitor surface chemical and underground nuclear explosions. The ionosphere is 'an apparatus' for the infra-sound measurements immediately above the test site. Using remote radio sounding of the ionosphere you can obtain that information. So you carry out the inspection at the test site. The main disadvantage of the ionospheric method is the necessity to sound the ionosphere with radio waves. (author)

  16. 241-AZ-101 pump removal trough analysis

    International Nuclear Information System (INIS)

    Coverdell, B.L.

    1995-01-01

    As part of the current Hanford mission of environmental cleanup, various long length equipment must be removed from highly radioactive waste tanks. The removal of equipment will utilize portions of the Equipment Removal System for Project W320 (ERS-W320), specifically the 50 ton hydraulic trailer system. Because the ERS-W320 system was designed to accommodate much heavier equipment it is adequate to support the dead weight of the trough, carriage and related equipment for 241AZ101 pump removal project. However, the ERS-W320 components when combined with the trough and its' related components must also be analyzed for overturning due to wind loads. Two troughs were designed, one for the 20 in. diameter carriage and one for the 36 in. diameter carriage. A proposed 52 in. trough was not designed and, therefore is not included in this document. In order to fit in the ERS-W320 strongback the troughs were design with the same widths. Structurally, the only difference between the two troughs is that more material was removed from the stiffener plates on the 36 in trough. The reduction in stiffener plate material reduces the allowable load. Therefore, only the 36 in. trough was analyzed

  17. Impulsive Alfven coupling between the magnetosphere and ionosphere

    International Nuclear Information System (INIS)

    Reddy, R.V.; Watanabe, K.; Sato, T.; Watanabe, T.H.

    1994-04-01

    Basic properties of the impulsive Alfven interaction between the magnetosphere and ionosphere have been studied by means of a three-dimensional self-consistent simulation of the coupled magnetosphere and ionosphere system. It is found that the duration time of an impulsive perturbation at the magnetospheric equator, the latitudinal distribution of the Alfven propagation time along the field lines, and the ratio between the magnetospheric impedance and the ionospheric resistance is the main key factors that determine the propagation dynamics and the ionospheric responses for an impulsive MHD perturbation in the magnetosphere. (author)

  18. Feasibility study of short-term earthquake prediction using ionospheric anomalies immediately before large earthquakes

    Science.gov (United States)

    Heki, K.; He, L.

    2017-12-01

    We showed that positive and negative electron density anomalies emerge above the fault immediately before they rupture, 40/20/10 minutes before Mw9/8/7 earthquakes (Heki, 2011 GRL; Heki and Enomoto, 2013 JGR; He and Heki 2017 JGR). These signals are stronger for earthquake with larger Mw and under higher background vertical TEC (total electron conetent) (Heki and Enomoto, 2015 JGR). The epicenter, the positive and the negative anomalies align along the local geomagnetic field (He and Heki, 2016 GRL), suggesting electric fields within ionosphere are responsible for making the anomalies (Kuo et al., 2014 JGR; Kelley et al., 2017 JGR). Here we suppose the next Nankai Trough earthquake that may occur within a few tens of years in Southwest Japan, and will discuss if we can recognize its preseismic signatures in TEC by real-time observations with GNSS.During high geomagnetic activities, large-scale traveling ionospheric disturbances (LSTID) often propagate from auroral ovals toward mid-latitude regions, and leave similar signatures to preseismic anomalies. This is a main obstacle to use preseismic TEC changes for practical short-term earthquake prediction. In this presentation, we show that the same anomalies appeared 40 minutes before the mainshock above northern Australia, the geomagnetically conjugate point of the 2011 Tohoku-oki earthquake epicenter. This not only demonstrates that electric fields play a role in making the preseismic TEC anomalies, but also offers a possibility to discriminate preseismic anomalies from those caused by LSTID. By monitoring TEC in the conjugate areas in the two hemisphere, we can recognize anomalies with simultaneous onset as those caused by within-ionosphere electric fields (e.g. preseismic anomalies, night-time MSTID) and anomalies without simultaneous onset as gravity-wave origin disturbances (e.g. LSTID, daytime MSTID).

  19. A comparative study on chaoticity of equatorial/low latitude ionosphere over Indian subcontinent during geomagnetically quiet and disturbed periods

    Directory of Open Access Journals (Sweden)

    K. Unnikrishnan

    2010-12-01

    Full Text Available In the present study, the latitudinal aspect of chaotic behaviour of ionosphere during quiet and storm periods are analyzed and compared by using GPS TEC time series measured at equatorial trough, crest and outside crest stations over Indian subcontinent, by employing the chaotic quantifiers like Lyapunov exponent (LE, correlation dimension (CD, entropy and nonlinear prediction error (NPE. It is observed that the values of LE are low for storm periods compared to those of quiet periods for all the stations considered here. The lowest value of LE is observed at the trough station, Agatti (2.38° N, Geomagnetically, and highest at crest station, Mumbai (10.09° N, Geomagnetically for both quiet and storm periods. The values of correlation dimension computed for TEC time series are in the range 2.23–2.74 for quiet period, which indicate that equatorial ionosphere may be described with three variables during quiet period. But the crest station Mumbai shows a higher value of CD (3.373 during storm time, which asserts that four variables are necessary to describe the system during storm period. The values of non linear prediction error (NPE are lower for Agatti (2.38° N, Geomagnetically and Jodhpur (18.3° N, Geomagnetically, during storm period, compared to those of quiet period, mainly because of the predominance of non linear aspects during storm periods The surrogate data test is carried out and on the basis of the significance of difference of the original data and surrogates for various aspects, the surrogate data test rejects the null hypothesis that the time series of TEC during storm and quiet times represent a linear stochastic process. It is also observed that using state space model, detrended TEC can be predicted, which reasonably reproduces the observed data. Based on the values of the above quantifiers, the features of chaotic behaviour of equatorial trough crest and outside the crest regions of ionosphere during geomagnetically

  20. Tear trough – Anatomy and treatment by autologous fat grafting

    Directory of Open Access Journals (Sweden)

    Chang Yung Chia

    2016-07-01

    Full Text Available Tear trough is the main irregularity at midface, of which treatment is difficult. There is no agreement in literature about its anatomy and best treatment. The author presented an anatomical study and personal autologous fat grafting technique for tear trough treatment. Anatomical dissections were done on two fresh cadavers to examine the skin, subcutaneous, muscle and bone layers, spaces, and attachments. Safety and efficacy were evaluated via retrospective analysis of the last 200 consecutive procedures performed by the author. Tear trough is caused by the abrupt transition of the palpebral orbicular oculi muscle (OOM (i.e., thin skin without subcutaneous fat compartment to the orbital OOM (i.e., thicker skin with malar fat compartment. The tear trough region is located at the OOM bony origin at the medial canthus where no specific ligament was found. The grafted fat volume stabilized at two or three months after the procedure, instead of six months as stated in literature, with excellent results and no severe complications. Tear trough is a personal characteristic, a natural anatomical depression caused by subcutaneous irregularity and can worsen with age. The lack of volume is not effectively corrected by surgeries and thus it must be filled. Fat grafting has several advantages over alloplastic fillers, although it may be more difficult. Fat graft is autologous and abundant, and tissue transplantation could enhance skin quality. Fat grafting is a simple, safe, and effective solution for adding extra volume to correct the deflation phenomenon of the midface aging process. There is no specific anatomical plane for volume injection; the fat graft must be evenly distributed in the deep and superficial plane for uniformity.

  1. The structure of mid- and high-latitude ionosphere during September 1999 storm event obtained from GPS observations

    Directory of Open Access Journals (Sweden)

    I. I. Shagimuratov

    Full Text Available TEC data, obtained from over 60 GPS stations, were used to study the ionospheric effects of the 12–16 September 1999 magnetic storm over Europe. The spatial and temporal changes of the ionosphere were analysed as a time series of TEC maps, which present 15 min averages of TEC. The data set consisting of GPS observations, collected by a dense network of European stations, with sampling rate of 30 s, enable the creation of TEC maps with high spatial and temporal resolution. The storm included the positive as well as the negative phase. The positive phase took place during the first storm day of 12 September 1999. The short-lived daytime TEC enhancement was observed at all latitudes. The maximal enhancement reached a factor of 1.3–1.5. On the second and third days, the negative phase of the storm developed. The TEC decrease was registered regardless of time of the day. The TEC depression exceeded 70% relative to quiet days. On the following days (15 and 16 September, a significant daytime enhancement of TEC was observed once again. The complex occurrence of the ionospheric storm was probably related to the features of development of the magnetic storm. We found out that during the storm the large and medium-scale irregularities developed in the high-latitude ionosphere. The multi-stations technique, employed to create TEC maps, was particularly successful while studying the mid-latitude ionospheric trough. We found out that the essential changes of TEC during the storm, which were registered at the auroral and sub-auroral ionosphere, were connected with the effect of the trough and its dynamics, which depends on geomagnetic activity.

    Key words. Ionosphere (ionospheric disturbances; auroral ionosphere; mid-latitude ionosphere

  2. Sudden Ionospheric Disturbances (SID)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Sudden ionospheric disturbances (SID) are caused by solar flare enhanced X-rays in the 1 to 10 angstrom range. Solar flares can produce large increases of ionization...

  3. Tsunami Ionospheric warning and Ionospheric seismology

    Science.gov (United States)

    Lognonne, Philippe; Rolland, Lucie; Rakoto, Virgile; Coisson, Pierdavide; Occhipinti, Giovanni; Larmat, Carene; Walwer, Damien; Astafyeva, Elvira; Hebert, Helene; Okal, Emile; Makela, Jonathan

    2014-05-01

    The last decade demonstrated that seismic waves and tsunamis are coupled to the ionosphere. Observations of Total Electron Content (TEC) and airglow perturbations of unique quality and amplitude were made during the Tohoku, 2011 giant Japan quake, and observations of much lower tsunamis down to a few cm in sea uplift are now routinely done, including for the Kuril 2006, Samoa 2009, Chili 2010, Haida Gwai 2012 tsunamis. This new branch of seismology is now mature enough to tackle the new challenge associated to the inversion of these data, with either the goal to provide from these data maps or profile of the earth surface vertical displacement (and therefore crucial information for tsunami warning system) or inversion, with ground and ionospheric data set, of the various parameters (atmospheric sound speed, viscosity, collision frequencies) controlling the coupling between the surface, lower atmosphere and the ionosphere. We first present the state of the art in the modeling of the tsunami-atmospheric coupling, including in terms of slight perturbation in the tsunami phase and group velocity and dependance of the coupling strength with local time, ocean depth and season. We then show the confrontation of modelled signals with observations. For tsunami, this is made with the different type of measurement having proven ionospheric tsunami detection over the last 5 years (ground and space GPS, Airglow), while we focus on GPS and GOCE observation for seismic waves. These observation systems allowed to track the propagation of the signal from the ground (with GPS and seismometers) to the neutral atmosphere (with infrasound sensors and GOCE drag measurement) to the ionosphere (with GPS TEC and airglow among other ionospheric sounding techniques). Modelling with different techniques (normal modes, spectral element methods, finite differences) are used and shown. While the fits of the waveform are generally very good, we analyse the differences and draw direction of future

  4. Particle precipitation influence in the conductivity of the auroral ionosphere during magnetic storms

    International Nuclear Information System (INIS)

    Monreal M, R.; Llop, C.

    2002-01-01

    The study of the energy transfer between the different regions of the solar wind - magnetosphere - ionosphere system is probably the main goal in Solar-Terrestrial Physics. In the magnetosphere - ionosphere coupling, the ionosphere power dissipation is highly sensitive to the conductivity in such a way that a detailed knowledge of this property in the auroral and polar ionosphere is of great interest because it is important not only to determine Joule heat, but also for electric fields and currents models including the field aligned currents coupling the magnetosphere and ionosphere. The main sources of ionization and subsequent conductivity in the ionosphere are due to the emission of electromagnetic radiation and charged energetic particles from the sun. In this work it is analysed the influence of the precipitating electrons on the auroral ionosphere conductivity during magnetic storms. It is shown that the conductance values appear sub estimated for high levels of activity due to the saturation produced during very intense magnetic storms. (Author)

  5. Morphological evolution of Jinshan Trough in Hangzhou Bay (China) from 1960 to 2011

    Science.gov (United States)

    Liu, Yifei; Xia, Xiaoming; Chen, Shenliang; Jia, Jianjun; Cai, Tinglu

    2017-11-01

    An extensive system of tidal channels, starting with Jinshan Trough in the east, is located along the north shore of Hangzhou Bay, China. This contribution investigates the morphological evolution of Jinshan Trough by using 17 bathymetric charts from a series covering a period of 51 years from 1960 to 2011. Three stages of evolution during this period are distinguishable based on the morphology and annual mean volume data. The first stage (1960-1987) is characterized by extension of the trough; the second stage (1987-1996) is a relatively stable period with some adjustments in the trough morphology; the third stage (1996-2011) is marked by the processes of erosion and deposition in the beginning of the period and a subsequent slow erosion process. Spatio-temporal variability of the trough was evaluated by using empirical orthogonal function (EOF) analysis. The first eigenfunction indicates that erosion is the main evolution process and there exists three stages similar to those distinguished from volume variations. The second eigenfunction mainly reflects erosion and deposition in the northwest part of the trough located in the flood tidal current shadow area of the artificial headland in Jinshan. The third eigenfunction mainly reflects annual fluctuations of erosion and deposition in the side slope at the artificial headland in Jinshan. A particularly intense erosion process occurred between 1996 and 1998. The major effects on morphological evolution in Jinshan Trough from 1960 to 2011 were investigated and tentative conclusions were presented. Continuous coastal reclamations in Jinshan had the most pronounced effect on the morphological evolution during the first and the second stages. The storm surge had a pronounced effect on the evolution at the beginning of the third stage.

  6. Ionosphere and Radio Communication

    Indian Academy of Sciences (India)

    One basic problem associated with these is that as soon as a space .... as a depression in plasma density or trough at the geomagnetic equator and two .... and their numerous students at PRL, over a period of nearly thirty years have been ...

  7. OUT Success Stories: Solar Trough Power Plants

    Science.gov (United States)

    Jones, J.

    2000-08-01

    The Solar Electric Generating System (SEGS) plants use parabolic-trough solar collectors to capture the sun's energy and convert it to heat. The SEGS plants range in capacity from 13.8 to 80 MW, and they were constructed to meet Southern California Edison Company's periods of peak power demand.

  8. Ionosphere Waves Service - A demonstration

    Science.gov (United States)

    Crespon, François

    2013-04-01

    In the frame of the FP7 POPDAT project the Ionosphere Waves Service was developed by ionosphere experts to answer several questions: How make the old ionosphere missions more valuable? How provide scientific community with a new insight on wave processes that take place in the ionosphere? The answer is a unique data mining service accessing a collection of topical catalogues that characterize a huge number of Atmospheric Gravity Waves, Travelling Ionosphere Disturbances and Whistlers events. The Ionosphere Waves Service regroups databases of specific events extracted by experts from a ten of ionosphere missions which end users can access by applying specific searches and by using statistical analysis modules for their domain of interest. The scientific applications covered by the IWS are relative to earthquake precursors, ionosphere climatology, geomagnetic storms, troposphere-ionosphere energy transfer, and trans-ionosphere link perturbations. In this presentation we propose to detail the service design, the hardware and software architecture, and the service functions. The service interface and capabilities will be the focus of a demonstration in order to help potential end-users for their first access to the Ionosphere Waves Service portal. This work is made with the support of FP7 grant # 263240.

  9. Interpreting Observations of Large-Scale Traveling Ionospheric Disturbances by Ionospheric Sounders

    Science.gov (United States)

    Pederick, L. H.; Cervera, M. A.; Harris, T. J.

    2017-12-01

    From July to October 2015, the Australian Defence Science and Technology Group conducted an experiment during which a vertical incidence sounder (VIS) was set up at Alice Springs Airport. During September 2015 this VIS observed the passage of many large-scale traveling ionospheric disturbances (TIDs). By plotting the measured virtual heights across multiple frequencies as a function of time, the passage of the TID can be clearly displayed. Using this plotting method, we show that all the TIDs observed during the campaign by the VIS at Alice Springs show an apparent downward phase progression of the crests and troughs. The passage of the TID can be more clearly interpreted by plotting the true height of iso-ionic contours across multiple plasma frequencies; the true heights can be obtained by inverting each ionogram to obtain an electron density profile. These plots can be used to measure the vertical phase speed of a TID and also reveal a time lag between events seen in true height compared to virtual height. To the best of our knowledge, this style of analysis has not previously been applied to other swept-frequency sounder observations. We develop a simple model to investigate the effect of the passage of a large-scale TID on a VIS. The model confirms that for a TID with a downward vertical phase progression, the crests and troughs will appear earlier in virtual height than in true height and will have a smaller apparent speed in true height than in virtual height.

  10. Ionospheric earthquake precursors

    International Nuclear Information System (INIS)

    Bulachenko, A.L.; Oraevskij, V.N.; Pokhotelov, O.A.; Sorokin, V.N.; Strakhov, V.N.; Chmyrev, V.M.

    1996-01-01

    Results of experimental study on ionospheric earthquake precursors, program development on processes in the earthquake focus and physical mechanisms of formation of various type precursors are considered. Composition of experimental cosmic system for earthquake precursors monitoring is determined. 36 refs., 5 figs

  11. Midday reversal of equatorial ionospheric electric field

    Directory of Open Access Journals (Sweden)

    R. G. Rastogi

    1997-10-01

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

  12. Midday reversal of equatorial ionospheric electric field

    Directory of Open Access Journals (Sweden)

    R. G. Rastogi

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

  13. On purpose simulation model for molten salt CSP parabolic trough

    Science.gov (United States)

    Caranese, Carlo; Matino, Francesca; Maccari, Augusto

    2017-06-01

    The utilization of computer codes and simulation software is one of the fundamental aspects for the development of any kind of technology and, in particular, in CSP sector for researchers, energy institutions, EPC and others stakeholders. In that extent, several models for the simulation of CSP plant have been developed with different main objectives (dynamic simulation, productivity analysis, techno economic optimization, etc.), each of which has shown its own validity and suitability. Some of those models have been designed to study several plant configurations taking into account different CSP plant technologies (Parabolic trough, Linear Fresnel, Solar Tower or Dish) and different settings for the heat transfer fluid, the thermal storage systems and for the overall plant operating logic. Due to a lack of direct experience of Molten Salt Parabolic Trough (MSPT) commercial plant operation, most of the simulation tools do not foresee a suitable management of the thermal energy storage logic and of the solar field freeze protection system, but follow standard schemes. ASSALT, Ase Software for SALT csp plants, has been developed to improve MSPT plant's simulations, by exploiting the most correct operational strategies in order to provide more accurate technical and economical results. In particular, ASSALT applies MSPT specific control logics for the electric energy production and delivery strategy as well as the operation modes of the Solar Field in off-normal sunshine condition. With this approach, the estimated plant efficiency is increased and the electricity consumptions required for the plant operation and management is drastically reduced. Here we present a first comparative study on a real case 55 MWe Molten Salt Parabolic Trough CSP plant placed in the Tibetan highlands, using ASSALT and SAM (System Advisor Model), which is a commercially available simulation tool.

  14. Magnetic and solar effects on ionospheric absorption at high latitude

    Directory of Open Access Journals (Sweden)

    M. Pietrella

    2002-06-01

    Full Text Available Some periods of intense solar events and of strong magnetic storms have been selected and their effects on the ionospheric D region have been investigated on the basis of ionospheric absorption data derived from riometer measurements made at the Italian Antarctic Base of Terra Nova Bay (geographic coordinates: 74.69 S, 164.12 E; geomagnetic coordinates: 77.34 S, 279.41 E. It was found that sharp increases in ionospheric absorption are mainly due to solar protons emission with an energy greater than 10 MeV. Moreover, the day to night ratios of the ionospheric absorption are greater than 2 in the case of strong events of energetic protons emitted by the Sun, while during magnetic storms, these ratios range between 1 and 2.

  15. High-resolution records of thermocline in the Okinawa Trough since about 10000 aBP

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The present paper uses planktonic foraminifera and their stableisotopes to study the changes in the depth of thermocline (DOT) in the Okinawa Trough since the last 10000 a based on the analysis of Core B-3GC in the northern Okinawa Trough, together with that of the core in the southern Okinawa Trough. As results show, the thermocline was shallow before 6400 aBP, and deepened afterward, then became shallow again from 4000 to 2000 aBP. The DOT fluctuations display a positive correlation with those of sea surface temperature (SST). In addition, the changes in the northern Okinawa Trough are similar to those in the southern trough, implying a possible connection with the variation of the Kuroshio Current. The changes of SST and DOT suggest that the Kuroshio Current changed its intensity or main axis from 4000 to 2000 aBP and around about 6400 aBP respectively. Moreover, the changes of DOT from 8200 to 6400 aBP may indicate a gradual intensification of the Kuroshio Current.

  16. Balanced Cross Section for Restoration of Tectonic Evolution in the Southwest Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    Wu Shiguo; Ni Xianglong; Guo Junhua

    2007-01-01

    On the basis of the multi-channel seismic data and the other data, using 2DMove software,the tectonic evolution in three seismic profiles was restored since Pliocene. The tectonic restoration results show that: (1) the initial active center lay in the west slope and then was transferred to east and south via trough center during the evolution process; (2) several main normal faults controlled the evolution of the southern Okinawa Trough; (3) since Late Pliocene, the southern Okinawa Trough has experienced two spreading stages. The early is depression in Early-Middle Pleistocene and the late is back-arc spreading in Late Pleistocene and Holocene, which is in primary oceanic crust spreading stage.

  17. A trough for improved SFG spectroscopy of lipid monolayers

    Science.gov (United States)

    Franz, Johannes; van Zadel, Marc-Jan; Weidner, Tobias

    2017-05-01

    Lipid monolayers are indispensable model systems for biological membranes. The main advantage over bilayer model systems is that the surface pressure within the layer can be directly and reliably controlled. The sensitive interplay between surface pressure and temperature determines the molecular order within a model membrane and consequently determines the membrane phase behavior. The lipid phase is of crucial importance for a range of membrane functions such as protein interactions and membrane permeability. A very reliable method to probe the structure of lipid monolayers is sum frequency generation (SFG) vibrational spectroscopy. Not only is SFG extremely surface sensitive but it can also directly access critical parameters such as lipid order and orientation, and it can provide valuable information about protein interactions along with interfacial hydration. However, recent studies have shown that temperature gradients caused by high power laser beams perturb the lipid layers and potentially obscure the spectroscopic results. Here we demonstrate how the local heating problem can be effectively reduced by spatially distributing the laser pulses on the sample surface using a translating Langmuir trough for SFG experiments at lipid monolayers. The efficiency of the trough is illustrated by the detection of enhanced molecular order due to reduced heat load.

  18. Studying Peculiarities of Ionospheric Response to the 2015 March 17-19 Geomagnetic Storm in East Asia: Observations and Simulation

    Science.gov (United States)

    Romanova, Elena; Zherebtsov, Gelii; Polekh, Nelya; Wang, Xiao; Wang, Guojun; Zolotukhina, Nina; Shi, Jiankui

    2016-07-01

    We report results of the research into effects of the strong geomagnetic storm in the ionosphere of high, middle, and low latitudes on March 17-19, 2015. The research relies on measurements made at the network of ionospheric stations located near the 120°E meridian. The analysis of experimental data has revealed that at the beginning of the main storm phase the equatorial wall of the main ionospheric trough (MIT) shifted towards geographic latitudes 58-60°N, which caused negative disturbances in subauroral latitudes and positive disturbances in middle latitudes. Further displacement of the MIT equatorial wall towards a geographic latitude of 52° N led to a decrease in the F2-layer critical frequency (foF2) up to 2 MHz in middle latitudes during evening and night hours, and to the appearance of sporadic layers in these latitudes due to energetic particle precipitation. Such phenomena are largely specific to the subauroral ionosphere. During the recovery storm phase on March 18, 2015 during daylight hours, negative disturbances were recorded at all the stations. Since prolonged negative disturbances are usually associated with a reduction in the ratio of concentrations of atomic oxygen and molecular nitrogen [O]/[N2] which is transported by disturbed thermospheric wind from auroral latitudes to middle and low ones, we analyzed measurements of [O]/[N2], made by GUVI (Global Ultraviolet Imager, http://guvi.jhuapl.edu/site/gallery/guvi-galleryl3on2.shtml), during this storm. The storm appeared to be characterized by very low values of [O]/[N2] which were recorded in the longitude sector 60 - 150°E up to 15°N on March 18. The discovered peculiarities of the ionospheric response to the storm were interpreted using a theoretical model of ionosphere-plasmosphere coupling developed at ISTP SB RAS. The simulation showed that the displacement of MIT equatorial wall resulted in foF2 variations similar to those observed during the main storm phase in subauroral and middle

  19. Ionosphere monitoring and forecast activities within the IAG working group "Ionosphere Prediction"

    Science.gov (United States)

    Hoque, Mainul; Garcia-Rigo, Alberto; Erdogan, Eren; Cueto Santamaría, Marta; Jakowski, Norbert; Berdermann, Jens; Hernandez-Pajares, Manuel; Schmidt, Michael; Wilken, Volker

    2017-04-01

    . Performance tests are being conducted at the moment in order to improve UPC predicted products for 1-, 2-days ahead. In addition, UPC is working to enable short-term predictions based on UPC real-time GIMs (labelled URTG) and implementing an improved prediction approach. TUM developed a forecast method based on a time series analysis of TEC products which are either B-spline coefficients estimated by a Kalman filter or TEC grid maps derived from the B-spline coefficients. The forecast method uses a Fourier series expansion to extract the trend functions from the estimated TEC product. Then the trend functions are carried out to provide predicted TEC products. The forecast algorithm developed by GMV is based on the ionospheric delay estimation from previous epochs using GNSS data and the main dependence of ionospheric delays on solar and magnetic conditions. Since the ionospheric behavior is highly dependent on the region of the Earth, different region-based algorithmic modifications have been implemented in GMV's magicSBAS ionospheric algorithms to be able to estimate and forecast ionospheric delays worldwide. Different TEC prediction approaches outlined here will certainly help to learn about forecasting ionospheric ionization.

  20. Electric and electrothermal conductivity of planetary ionospheres

    International Nuclear Information System (INIS)

    Pavlov, A.V.

    1984-01-01

    In the first, second and third approximations of expansion of the Chapman-Enskog method in Sonin polynomials, an explicit form is found of coefficients of electrical and electrothermal electron condituctjvity in a magnetic field in a multicomponent ionosphere with allowance for the electron temperature difference from the heavy component temperature. The generic expressions for the electron transport coefficients are reduced to the form suitable for practical applications. In the first approximation of expansion in Sonin polynomials, the equations are derived for determining the ion diffusion velocities in a magnetic field in a multicomponent gas mixtures. +he approximating expressions for frequencies of electron collisions with main neutral components of planet upper atmospheres are refined. In the first, second and third approximations the equations are derived for determining velocities of ambipolar ion diffusion in a multicomponent ionosphere without a magnetic field (or parallel to it). The explicit form of the electron thermodiffusion factor, being a part of these equations, has been found

  1. Ionospheric scintillation observations over Kenyan region - Preliminary results

    Science.gov (United States)

    Olwendo, O. J.; Xiao, Yu; Ming, Ou

    2016-11-01

    Ionospheric scintillation refers to the rapid fluctuations in the amplitude and phase of a satellite signal as it passes through small-scale plasma density irregularities in the ionosphere. By analyzing ionospheric scintillation observation datasets from satellite signals such as GPS signals we can study the morphology of ionospheric bubbles. At low latitudes, the diurnal behavior of scintillation is driven by the formation of large-scale equatorial density depletions which form one to two hours after sunset via the Rayleigh-Taylor instability mechanism near the magnetic equator. In this work we present ionospheric scintillation activity over Kenya using data derived from a newly installed scintillation monitor developed by CRIRP at Pwani University (39.78°E, 3.24°S) during the period August to December, 2014. The results reveal the scintillation activity mainly occurs from post-sunset to post-midnight hours, and ceases around 04:00 LT. We also found that the ionospheric scintillation tends to appear at the southwest and northwest of the station. These locations coincide with the southern part of the Equatorial Ionization Anomaly crest over Kenya region. The occurrence of post-midnight L-band scintillation events which are not linked to pre-midnight scintillation observations raises fundamental question on the mechanism and source of electric fields driving the plasma depletion under conditions of very low background electron density.

  2. Reconstruction of the ionospheric electron density by geostatistical inversion

    Science.gov (United States)

    Minkwitz, David; van den Boogaart, Karl Gerald; Hoque, Mainul; Gerzen, Tatjana

    2015-04-01

    The ionosphere is the upper part of the atmosphere where sufficient free electrons exist to affect the propagation of radio waves. Typically, the ionosphere extends from about 50 - 1000 km and its morphology is mainly driven by solar radiation, particle precipitation and charge exchange. Due to the strong ionospheric impact on many applications dealing with trans-ionospheric signals such as Global Navigation Satellite Systems (GNSS) positioning, navigation and remote sensing, the demand for a highly accurate reconstruction of the electron density is ever increasing. Within the Helmholtz Alliance project "Remote Sensing and Earth System Dynamics" (EDA) the utilization of the upcoming radar mission TanDEM-L and its related products are prepared. The TanDEM-L mission will operate in L-band with a wavelength of approximately 24 cm and aims at an improved understanding of environmental processes and ecosystem change, e.g. earthquakes, volcanos, glaciers, soil moisture and carbon cycle. Since its lower frequency compared to the X-band (3 cm) and C-band (5 cm) radar missions, the influence of the ionosphere will increase and might lead to a significant degradation of the radar image quality if no correction is applied. Consequently, our interest is the reconstruction of the ionospheric electron density in order to mitigate the ionospheric delay. Following the ionosphere's behaviour we establish a non-stationary and anisotropic spatial covariance model of the electron density separated into a vertical and horizontal component. In order to estimate the model's parameters we chose a maximum likelihood approach. This approach incorporates GNSS total electron content measurements, representing integral measurements of the electron density between satellite to receiver ray paths, and the NeQuick model as a non-stationary trend. Based on a multivariate normal distribution the spatial covariance model parameters are optimized and afterwards the 3D electron density can be

  3. Solar wind and seasonal influence on ionospheric currents from Swarm and CHAMP measurements

    DEFF Research Database (Denmark)

    Laundal, K. M.; Finlay, C. C.; Olsen, N.

    2018-01-01

    the ionosphere with the magnetosphere. The model provides ionospheric current values at any location as continuous functions of solar wind speed, interplanetary magnetic field (IMF), dipole tilt angle, and the F10.7 index of solar flux. Geometric distortions due to variations in the Earth's main magnetic field...

  4. Optical properties of V-trough concentrators

    Energy Technology Data Exchange (ETDEWEB)

    Fraidenraich, N. [Universidade Federal de Pernambuco, Recife, PE Brasil (Brazil); Almeida, G. J.

    1991-07-01

    A new approach to study the optical behavior of V-trough concentrators is developed, based on the use of three characteristic angles defining the appearance, disappearance and return to the outside space of the cavity of a reflection mode. The probability of occurrence of a given number of reflections for beam radiation is determined as a function of these angles and the optical efficiency calculated. It is shown that the optical efficiency can be approximated by a function of two parameters, the angular acceptance function, T, and the mean number of reflections, n, as T * p{sup n/T}. Deviations between exact and approximate optical efficiency increase as n increases or as p decreases. For troughs with C ≤ 2.5 the maximal error for beam radiation is 3.4% for p ≥ 0.8 (8.3% for p ≥ 0.7). For diffuse radiation the maximal error is less than 2% for configurations whose optical efficiency is above 0.6. A further simplification was introduced to obtain the optical efficiency for diffuse radiation, approximating T by an analytical expression and n by an empirical linear function of the inverse of the vertex angle. Results accurate up to 5% for p = 0.8, were obtained. Increasing the concentration ratio, C, from 1.5 to 2.5 for a vertex angle being one third of the acceptance angle, decreased the optical efficiency from 0.74 to 0.59, for p = 0.8. For a given C, the dependence of the optical efficiency on the vertex angle is rather weak, suggesting that large trough angles might be favoured by cost-benefit analysis. (author)

  5. Mineralogy and geological significance of hydrothermal deposits from the Okinawa Trough

    Science.gov (United States)

    Zhang, Xia; Zhai, Shikui; Yu, Zenghui; Wang, Shujie; Cai, Zongwei

    2018-04-01

    The study of hydrothermal deposits in the Okinawa Trough can help us to uncover the hydrothermal mineralization characteristics in the back-arc basin during the early expanding stage. Mineralogy and geological significance of hydrothermal deposits from both the middle and southern trough are studied in this paper. First of all, using optical microscope to confirm the mineral compositions, characteristics of crystal shape, paragenetic relationship and minerals crystallization order. Then the minerals chemical composition were analyzed in virtue of electron microprobe. On these basis, the paragenetic sequence and the mineralization characteristics of the hydrothermal deposits were discussed. The results show that the hydrothermal deposit from the mid-Okinawa Trough belongs to Zn-Cu-rich type, consisting dominantly of sulfide minerals such as sphalerite, chalcopyrite, pyrite, etc. The minerals crystallization order is first generation pyrite(PyI)-sphalerite-chalcopyrite-galena-second generation pyrite(PyII)-amorphous silica. While the deposit from the southern Okinawa Trough is Ba-Zn-Pb-rich type mainly composing of barite, sphalerite, galena, etc. The minerals crystallization order is barite-pyrite-sphalerite-tetrahedrite-galena-chalcopyrite-amorphous silica. Hydrothermal fluid temperature in the mid-Okinawa Trough undergoes a process from high to low, which is high up to 350 °C in the early stage, but decreasing gradually with the evolution of hydrothermal fluid. On the contrary, the hydrothermal activity in the southern Okinawa Trough is low temperature dominated, but the mineralization environment is unstable and the fluid temperature changes drastically during the period of hydrothermal activity.

  6. Alignment method for parabolic trough solar concentrators

    Science.gov (United States)

    Diver, Richard B [Albuquerque, NM

    2010-02-23

    A Theoretical Overlay Photographic (TOP) alignment method uses the overlay of a theoretical projected image of a perfectly aligned concentrator on a photographic image of the concentrator to align the mirror facets of a parabolic trough solar concentrator. The alignment method is practical and straightforward, and inherently aligns the mirror facets to the receiver. When integrated with clinometer measurements for which gravity and mechanical drag effects have been accounted for and which are made in a manner and location consistent with the alignment method, all of the mirrors on a common drive can be aligned and optimized for any concentrator orientation.

  7. The study of the focal trough in panoramic radiograph

    International Nuclear Information System (INIS)

    Park, C. S.; Kim, H. P.

    1982-01-01

    In the study of the focal trough of panoramic radiograph, using the Moritta company Panex EC a series of 48 exposures were taken with the 6-18 brass pins placed in the holes of the plastic model plate, then evaluated by 4 observers. The author analyzed the focal trough defined by the sharpness criteria and calculated the vertical and horizontal magnification range in the corrected focal trough. The results were as follows; 1. Continuous focal trough was not defined in the anterior region using a very high degree of sharpness. 2. As degree of sharpness used in the analysis became less, focal trough was continuous in the anterior and posterior regions, symmetrized bilaterally, and the widths of the focal trough increased more in the posterior region. 3. As sharpness criteria were reduced, the percentage range of image magnification increased in both vertical and horizontal magnification, and especially the percentage range of horizontal magnification was greater than that of vertical magnification.

  8. Earth-ionosphere cavity

    International Nuclear Information System (INIS)

    Tran, A.; Polk, C.

    1976-01-01

    To analyze ELF wave propagation in the earth-ionosphere cavity, a flat earth approximation may be derived from the exact equations, which are applicable to the spherical cavity, by introducing a second-order or Debye approximation for the spherical Hankel functions. In the frequency range 3 to 30 Hz, however, the assumed conditions for the Debye approximation are not satisfied. For this reason an exact evaluation of the spherical Hankel functions is used to study the effects of the flat earth approximation on various propagation and resonance parameters. By comparing the resonance equation for a spherical cavity with its flat earth counterpart and by assuming that the surface impedance Z/sub i/ at the upper cavity boundary is known, the relation between the eigenvalue ν and S/sub v/, the sine of the complex angle of incidence at the lower ionosphere boundary, is established as ν(ν + 1) = (kaS/sub v/) 2 . It is also shown that the approximation ν(ν + 1) approximately equals (ν + 1/2) 2 which was used by some authors is not adequate below 30 Hz. Numerical results for both spherical and planar stratification show that (1) planar stratification is adequate for the computation of the lowest three ELF resonance frequencies to within 0.1 Hz; (2) planar stratification will lead to errors in cavity Q and wave attenuation which increase with frequency; (3) computation of resonance frequencies to within 0.1 Hz requires the extension of the lower boundary of the ionosphere to a height where the ratio of conduction current to displacement current, (sigma/ωepsilon 0 ), is less than 0.3; (4) atmospheric conductivity should be considered down to ground level in computing cavity Q and wave attenuation

  9. A snapshot of the polar ionosphere

    International Nuclear Information System (INIS)

    Whitteker, J.H.

    1976-01-01

    This paper presents a picture of the north polar F layer and topside ionosphere obtained primarily from three satellites (Alouette 2, ISIS 1, ISIS 2), that passed over the region within a time interval of ca. 50 min on 25 April 1971, a magnetically quiet day. The horizontal distribution of electron densities at the peak of the F layer is found to be similar to synoptic results from the IGY. Energetic particle and ionospheric plasma data are also presented, and the F layer data are discussed in terms of these measurements, and also in terms of electric field and neutral N 2 density measurements made by other satellites on other occasions. The major features observed are as follows: A tongue of F region ionization extends from the dayside across the polar cap, which is accounted for by antisunward drift due to magnetospheric convection. In the F layer and topside ionosphere, the main effect of auroral precipitation appears to be heating and expansion of the topside. A region of low F layer density appears on the morning side of the polar cap, which may be due to convection and possibly also to enhanced N 2 densities. (author)

  10. Equinoctial transitions in the ionosphere and thermosphere

    Directory of Open Access Journals (Sweden)

    A. V. Mikhailov

    2001-07-01

    Full Text Available Equinoctial summer/winter transitions in the parameters of the F2-region are analyzed using ground-based ionosonde and incoherent scatter observations. Average transition from one type of diurnal NmF2 variation to another takes 20–25 days, but cases of very fast (6–10 days transitions are observed as well. Strong day-time NmF2 deviations of both signs from the monthly median, not related to geomagnetic activity, are revealed for the transition periods. Both longitudinal and latitudinal variations take place for the amplitude of such quiet time NmF2 deviations. The summer-type diurnal NmF2 variation during the transition period is characterized by decreased atomic oxygen concentration [O] and a small equatorward thermospheric wind compared to winter-type days with strong poleward wind and increased [O]. Molecular N2 and O2 concentrations remain practically unchanged in such day-to-day transitions. The main cause of the F2-layer variations during the transition periods is the change of atomic oxygen abundance in the thermosphere related to changes of global thermospheric circulation. A possible relationship with an equinoctial transition of atomic oxygen at the E-region heights is discussed.Key words. Atmospheric composition and structure (thermosphere – composition and chemistry – Ionosphere (ionosphere- atmosphere interactions; ionospheric disturbances

  11. A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990

    Directory of Open Access Journals (Sweden)

    A. V. Pavlov

    2006-05-01

    Full Text Available We have presented a comparison between the modeled NmF2 and hmF2, and NmF2 and hmF2, which were observed in the low-latitude ionosphere simultaneously by the Kokubunji, Yamagawa, Okinawa, Manila, Vanimo, and Darwin ionospheric sounders, by the middle and upper atmosphere (MU radar during 17-22 March 1990, and by the Arecibo radar for the time period of 20-22 March 1990. A comparison between the electron and ion temperatures measured by the MU and Arecibo radars and those produced by the model of the ionosphere and plasmasphere is presented. The empirical zonal electric field, the meridional neutral wind taken from the HWM90 wind model, and the NRLMSISE-00 neutral temperature and densities are corrected so that the model results agree reasonably with the ionospheric sounder observations, and the MU and Arecibo radar data. It is proved that the nighttime weakening of the equatorial zonal electric field (in comparison with that produced by the empirical model of Fejer and Scherliess (1997 or Scherliess and Fejer (1999, in combination with the corrected wind-induced plasma drift along magnetic field lines, provides the development of the nighttime enhancements in NmF2 observed over Manila during 17-22 March 1990. As a result, the new physical mechanism of the nighttime NmF2 enhancement formation close to the geomagnetic equator includes the nighttime weakening of the equatorial zonal electric field and equatorward nighttime plasma drift along magnetic field lines caused by neutral wind in the both geomagnetic hemispheres. It is found that the latitudinal positions of the crests depend on the E×B drift velocity and on the neutral wind velocity. The relative role of the main mechanisms of the equatorial anomaly suppression observed during geomagnetic storms is studied for the first time in terms of storm-time variations of the model crest-to-trough ratios of the equatorial anomaly. During most of the studied time period, a total contribution from

  12. Study of ionospheric disturbances over the China mid- and low-latitude region with GPS observations

    Science.gov (United States)

    Ning, Yafei; Tang, Jun

    2018-01-01

    Ionospheric disturbances constitute the main restriction factor for precise positioning techniques based on global positioning system (GPS) measurements. Simultaneously, GPS observations are widely used to determine ionospheric disturbances with total electron content (TEC). In this paper, we present an analysis of ionospheric disturbances over China mid- and low-latitude area before and during the magnetic storm on 17 March 2015. The work analyses the variation of magnetic indices, the amplitude of ionospheric irregularities observed with four arrays of GPS stations and the influence of geomagnetic storm on GPS positioning. The results show that significant ionospheric TEC disturbances occurred between 10:30 and 12:00 UT during the main phase of the large storm, and the static position reliability for this period are little affected by these disturbances. It is observed that the positive and negative disturbances propagate southward along the meridian from mid-latitude to low-latitude regions. The propagation velocity is from about 200 to 700 m s-1 and the amplitude of ionospheric disturbances is from about 0.2 to 0.9 TECU min-1. Moreover, the position dilution of precession (PDOP) with static precise point positioning (PPP) on storm and quiet days is 1.8 and 0.9 cm, respectively. This study is based on the analysis of ionospheric variability with differential rate of vertical TEC (DROVT) and impact of ionospheric storm on positioning with technique of GPS PPP.

  13. Alleviate Cellular Congestion Through Opportunistic Trough Filling

    Directory of Open Access Journals (Sweden)

    Yichuan Wang

    2014-04-01

    Full Text Available The demand for cellular data service has been skyrocketing since the debut of data-intensive smart phones and touchpads. However, not all data are created equal. Many popular applications on mobile devices, such as email synchronization and social network updates, are delay tolerant. In addition, cellular load varies significantly in both large and small time scales. To alleviate network congestion and improve network performance, we present a set of opportunistic trough filling schemes that leverage the time-variation of network congestion and delay-tolerance of certain traffic in this paper. We consider average delay, deadline, and clearance time as the performance metrics. Simulation results show promising performance improvement over the standard schemes. The work shed lights on addressing the pressing issue of cellular overload.

  14. Petroleum resources assessment of the Okinawa Trough

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Jae Ho; Kwak, Young Hoon; Bong, Pil Yoon; Son, Jin Dam; Cheong, Tae Jin; Lee, Ho Young; Ryu, Byung Jae; Son, Byeong Kook; Hwang, In Gul; Kwon, Young Ihn; Lee, Yong Joo; Kim, Hag Ju; Yi, Sung Soog; Park, Kwan Soon; Park, Keun Pil; Shin, Chang Soo; Sunwoo, Don [Korea Inst. of Geology Mining and Materials, Taejon (Korea, Republic of)

    1995-12-01

    The hydrocarbon potential has been evaluated for the Tertiary strata in the northwestern margin of the Okinawa Trough on the basis of the pale-ontological, petrological, geochemical data from two wells (Nikkan 8-9 and JDZ 7-3), and geophysical data. Abundant marine micro-fossils such as foraminifera, calcareous nannofossils and dinocysts were yielded in the sedimentary section of the above wells. Abundant palynomorphs originated from nearby onshore are also encountered. Based on nannofossils, the bio-stratigraphic zones from NN12 (Amaurolithus tricorniculatus Zone) to NN19 (Pseudoemiliania lacunosa Zone) are established. The sedimentary sequences are divided by local unconformity into Lower and Upper Groups, the ages of which are Late Miocene and Pliocene to Pleistocene, respectively. According to the geochemical analysis results, it is hard to expect a source rock that can generate enough hydrocarbons necessary for migration in the drilled intervals. Even though the thermal maturity reached the oil generation zone in the penetrated intervals, the calculation by the program GENEX of BEICIP shows that the amount of the generated hydrocarbons is not enough for the migration. A good source rock may be expected in the depth deeper than 4300 m horizon. Analysis of over 3300 Line-km of multichannel seismic data integrated with 2 well data serves to detail the structural and stratigraphic evolution of the western margin of the Okinawa Trough, offshore southern part of Korea peninsula. The overall tectonic style is characterized by a series of half-Graben and tilted fault blocks bounded by listric faults. Tectonics of the rift phase have been established on the basis of structural and stratigraphic analyses of depositional sequences and their seismic expressions. The potential hydrocarbon traps associated with titled fault block, fault and roll-over structure exist. (author). 44 refs.

  15. The Response of the Thermosphere and Ionosphere to Magnetospheric Forcing

    Science.gov (United States)

    Rees, D.; Fuller-Rowell, T. J.

    1989-06-01

    thermosphere. A first experimental view of the strong coupling between the thermosphere and ionosphere has also emerged from these combined new data-sets. In parallel with the development of observing techniques, numerical models of the thermosphere and ionosphere have matured. We are at a state where the combined thermosphere and ionosphere can be modelled self-consistently. We can now realistically simulate the response of the combined system to the magnetospheric forcing, and also investigate the many and varied feedback processes between the two components. The models can be used to understand and interpret the diversity of experimental observations, and provide the framework for evaluating phenomena which are as yet not well understood. The dominant thermosphere--ionosphere interactions which appear from the modelling studies and which have counterparts in the experimental database can be summarized. In the winter polar region, ionization enhancements are observed which are due to auroral particle precipitation in both the E-region and in the F-region. The former are relatively easy to understand, since decay rates are generally rapid, and large-scale transport is unimportant. The sole caveat will be related to sporadic-E layers of long-lived metallic ions. In the polar F-region, neutral winds, neutral composition changes, convection changes and solar photoionization all cause important modifications of plasma distributions. In the winter, plasma convection and winds cause important effects in the horizontal and vertical transport of plasma, respectively. As such, plumes of high density (or low-density) plasma are transported large distances from their origin, and local plasma densities are rarely explicable by local sources and sinks. The exact distributions will depend very much on detailed plasma convection patterns. However, the winter subauroral trough and localized polar troughs will be created when the combination of convection and corotation cause plasma

  16. Sounding rockets explore the ionosphere

    International Nuclear Information System (INIS)

    Mendillo, M.

    1990-01-01

    It is suggested that small, expendable, solid-fuel rockets used to explore ionospheric plasma can offer insight into all the processes and complexities common to space plasma. NASA's sounding rocket program for ionospheric research focuses on the flight of instruments to measure parameters governing the natural state of the ionosphere. Parameters include input functions, such as photons, particles, and composition of the neutral atmosphere; resultant structures, such as electron and ion densities, temperatures and drifts; and emerging signals such as photons and electric and magnetic fields. Systematic study of the aurora is also conducted by these rockets, allowing sampling at relatively high spatial and temporal rates as well as investigation of parameters, such as energetic particle fluxes, not accessible to ground based systems. Recent active experiments in the ionosphere are discussed, and future sounding rocket missions are cited

  17. Atmosphere-Ionosphere Electrodynamic Coupling

    Science.gov (United States)

    Sorokin, V. M.; Chmyrev, V. M.

    Numerous phenomena that occur in the mesosphere, ionosphere, and the magnetosphere of the Earth are caused by the sources located in the lower atmosphere and on the ground. We describe the effects produced by lightning activity and by ground-based transmitters operated in high frequency (HF) and very low frequency (VLF) ranges. Among these phenomena are the ionosphere heating and the formation of plasma density inhomogeneities, the excitation of gamma ray bursts and atmospheric emissions in different spectral bands, the generation of ULF/ELF/VLF electromagnetic waves and plasma turbulence in the ionosphere, the stimulation of radiation belt electron precipitations and the acceleration of ions in the upper ionosphere. The most interesting results of experimental and theoretical studies of these phenomena are discussed below. The ionosphere is subject to the action of the conductive electric current flowing in the atmosphere-ionosphere circuit. We present a physical model of DC electric field and current formation in this circuit. The key element of this model is an external current, which is formed with the occurrence of convective upward transport of charged aerosols and their gravitational sedimentation in the atmosphere. An increase in the level of atmospheric radioactivity results in the appearance of additional ionization and change of electrical conductivity. Variation of conductivity and external current in the lower atmosphere leads to perturbation of the electric current flowing in the global atmosphere-ionosphere circuit and to the associated DC electric field perturbation both on the Earth's surface and in the ionosphere. Description of these processes and some results of the electric field and current calculations are presented below. The seismic-induced electric field perturbations produce noticeable effects in the ionosphere by generating the electromagnetic field and plasma disturbances. We describe the generation mechanisms of such experimentally

  18. Space weather and the Earth ionosphere from auroral zone to equator

    Science.gov (United States)

    Biktash, L.

    2007-08-01

    Space weather conditions, geomagnetic variations, virtual ionospheric height and the critical frequency foF2 data during the geomagnetic storms are studied to demonstrate relationships between these phenomena. We examine the solar wind conditions and the auroral equatorial ionosphere response to illustrate what kind of solar wind parameters during the geomagnetic storms leads to short-term variations of the critical frequency foF2 and virtual height at the Earth ionosphere from the auroral zone to the equator. Model simulations as disturbed ionospheric wind dynamo do not allow explaining a significant part of the experimental data. Additional investigations of the ionospheric characteristics are required to clear up the origin of the short-term equatorial ionospheric variations. The critical frequency foF2 and virtual heights observed by the ionosondes are good indicators of the true layer heights and electron concentration and may provide information about the equatorial ionosphere dynamics. Intensive magnetospheric and ionospheric currents during geomagnetic storms disturb the quiet ionosphere and cause the observed short-term variations of the ionospheric characteristics. The ionosheric wind dynamo is considered as an important and the main mechanism in generation of ionospheric electric currents and fields. The disturbed ionospheric wind dynamo can be the generator of the equatorial ionospheric electric currents during geomagnetic storms in the aftermath of strong auroral heating. The magnetospheric electric field directly penetrating into the low-latitude ionosphere can be another source of electric field. During disturbed space weather conditions magnetospheric electric fields disturb the auroral ionosphere forming auroral electrojets and by the high-latitude electric field and termospheric disturbances can penetrate to the equatorial ionosphere. That is the reason the equatorial ionospheric electric field variations like geomagnetic variations are complex

  19. The worldwide ionospheric data base

    Science.gov (United States)

    Bilitza, Dieter

    1989-01-01

    The worldwide ionospheric data base is scattered over the entire globe. Different data sets are held at different institutions in the U.S., U.S.S.R., Australia, Europe, and Asia. The World Data Centers on the different continents archive and distribute part of the huge data base; the scope and cross section of the individual data holdings depend on the regional and special interest of the center. An attempt is made to pull together all the strings that point toward different ionospheric data holdings. Requesters are provided with the information about what is available and where to get it. An attempt is also made to evaluate the reliability and compatibility of the different data sets based on the consensus in the ionospheric research community. The status and accuracy of the standard ionospheric models are also discussed because they may facilitate first order assessment of ionospheric effects. This is a first step toward an ionospheric data directory within the framework of NSSDC's master directory.

  20. The worldwide ionospheric data base

    International Nuclear Information System (INIS)

    Bilitza, D.

    1989-04-01

    The worldwide ionospheric data base is scattered over the entire globe. Different data sets are held at different institutions in the U.S., U.S.S.R., Australia, Europe, and Asia. The World Data Centers on the different continents archive and distribute part of the huge data base; the scope and cross section of the individual data holdings depend on the regional and special interest of the center. An attempt is made to pull together all the strings that point toward different ionospheric data holdings. Requesters are provided with the information about what is available and where to get it. An attempt is also made to evaluate the reliability and compatibility of the different data sets based on the consensus in the ionospheric research community. The status and accuracy of the standard ionospheric models are also discussed because they may facilitate first order assessment of ionospheric effects. This is a first step toward an ionospheric data directory within the framework of NSSDC's master directory

  1. Influence of Ionospheric Weather on GNSS Radio Occultation Signals

    Science.gov (United States)

    Yue, X.; Schreiner, W. S.; Pedatella, N. M.; Kuo, Y. H.

    2016-12-01

    Transient loss of lock (LOL) is one of the key space weather effects on the Global Navigation Satellite System (GNSS). Based on the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Global Positioning System (GPS) radio occultation (RO) observations during 2007-2011, we have analyzed the signal cycle slip (CS) occurrence comprehensively and its correlation to the ionospheric weather phenomena such as sporadic E (Es), equatorial F region irregularity (EFI), and the ionospheric equatorial ionization anomaly (EIA). The high vertical resolution of RO observations enables us to distinguish the CS resulting from different ionospheric layers clearly on a global scale. In the E layer, the CS is dominated by the Es occurrence, while in the F layer, the CS is mainly related to the EIA and EFI at low and equatorial latitudes. In the polar region, the CS is primarily related to polar cap electron density gradients. The overall average CS (> 6 cycles) occurrence is 23% per occultation, with the E (50-150 km) and F (150-600 km) layers contributing 8.3% and 14.7%, respectively. Awareness of the effect of the ionospheric weather on the CS of the low-Earth-orbit (LEO)-based GNSS signal could be beneficial to a variety of applications, including the LEO-based GNSS data processing and the corresponding hardware/firmware design.

  2. Irregular ionization and scintillation of the ionosphere in equator region

    International Nuclear Information System (INIS)

    Shinno, Kenji

    1974-01-01

    The latest studies on the scintillation in satellite communication and its related irregularities of ionosphere are reviewed. They were made clear by means of spread-F, the direct measurement with scientific satellites, VHF radar observation, and radio wave propagation in equator region. The fundamental occurrence mechanism may be instability of plasma caused by the interaction of movement of neutral atmosphere and magnetic field. Comparison of the main characteristics of scintillation, namely the dependence on region, solar activity, season, local time, geomagnetic activity, movement in ionosphere, scattering source, frequency and transmission mode, was made and the correlation among spread-F, TEP and scintillation was summarized. The latest principal studies were the observations made by Intelsat and by ATS. Scintillation of Syncom-3 and Intelsat-II-F2 and spread-F by ionosphere observation were compared by Huang. It is reasonable to consider that the occurrence of scintillation is caused by the irregularities in ionosphere which are particular in equator region, because of the similar characteristics of spread-F and VHF propagation in the equator region. These three phenomena may occur in relation to the irregularities of ionosphere. Interpretation of spread-F and the abnormal propagation wave across the equator are given. The study using VHF radar and the movement of irregular ionization by the direct observation with artificial satellites are reviewd. (Iwakiri, K.)

  3. Radiometric evidence of Middle Devonian inversion of the Hill End Trough, northeast Lachlan Fold Belt

    International Nuclear Information System (INIS)

    Pakham, G.H.

    1999-01-01

    The publication of a new geological time-scale by the Australian Geological Survey Organisation and radiometric dates from the Hill End goldfield have prompted the re-examination of the timing of deformation of the Hill End Trough to determine whether it occurred in Middle Devonian or Early Carboniferous time. Palaeontological evidence from the western trough margin and the Capertee High dates the end of deposition in the trough as late Emsian or early Eifelian (385-382 Ma). After a mid-Devonian hiatus of at least 15 million years, paralic sedimentation commenced on the Molong and Capertee Highs in late Frasnian or early Famennian time (367-363 Ma). No Upper Devonian sedimentary formations occur in the Hill End Trough. Structural relationships indicate that the oldest mineral veins at Hill End preceded cleavage formation in the deformed trough sedimentary rocks. Early vein muscovites have Middle Devonian 40 Ar/ 39 Ar dates of 380-370 Ma. Regional metamorphic biotites from Hill End have well constrained 40 Ar/ 39 Ar closing ages of 360-358 Ma (mid-Famennian). The metamorphic (thermal) maximum which outlasted penetrative deformation. is estimated here by modelling to have been about 370 Ma (latest Givetian). This clearly places the earlier main deformation in the Middle Devonian. Deformation probably began by terminating trough deposition in latest Emsian to early Eifelian time and ended in early Givetian time at about 375 Ma ago. Published pressure and temperature data from the Hill End goldfield suggest that deformation thickened the 6 km sediment column to around 11 km. The thermal model suggests there was post-deformation erosion of about 4km and little if any further erosion occurred during Late Devonian to Early Carboniferous time. The shortening accompanying the inversion of the northern Hill End Trough may have been taken up in the region to the south, both east and west of the Copperhannia Thrust, and east of the southern termination of the Capertee High

  4. Paleoceanographic records in the sedimentary cores from the middle Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Two gravity piston cores (Cores 155 and 180) involved in this study were collected from the middle Okinawa Trough. Stratigraphy of the two cores was divided and classified based on the features of planktonic foraminifera oxygen isotope changes together with depositional sequence, millennium-scale climatic event comparison, carbonate cycles and AMS14C dating. Some paleoclimatic information contained in sediments of these cores was extracted to discuss the paleoclimatic change rules and the short-time scale events presented in interglacial period. Analysis on the variation of oxygen isotope values in stage two shows that the middle part of the Okinawa Trough may have been affected by fresh water from the Yellow River and the Yangtze River during the Last Glacial Maximum (LGM). The oxygen isotope value oscillating ranges of the cores have verified that the marginal sea has an amplifying effect on climate changes. The Δ13c of benthic foraminifera Uvigerina was lighter in the glacial period than that in the interglacial period, which indicates that the Paleo-Kuroshio's main stream moved eastward and its influence area decreased. According to the temperature difference during the "YD" period existing in Core 180 and other data, we can reach the conclusion that the climatic changes in the middle Okinawa Trough area were controlled by global climatic changes, but some regional factors had also considerable influence on the climate changes. Some results in this paper support Fairbanks's point that the "YD" event was a brief stagnation of sea level rising during the global warming up procession. Moreover, the falling of sea level in the glacial period weakened the exchange between the bottom water of the Okinawa Trough and the deep water of the northwestern Pacific Ocean and resulted in low oxygen state of bottom water in this area. These procedures are the reasons for carbonate cycle in the Okinawa Trough area being consistent with the "Atlantic type " carbonate cycle.

  5. Paleoceanographic records in the sedimentary cores from the middle Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    LIUYanguang; FUYunxia; DUDewen; MENGXianwei; LIANGRuicai; LITiegang; WUShiying

    2003-01-01

    Two gravity piston cores (Cores 155 and 180) involved in this study were collected from the middle Okinawa Trough. Stratigraphy of the two cores was divided and classified based on the features of planktonic foraminifera oxygen isotope changes together with depositional sequence,millennium-scale climatic event comparison, carbonate cycles and AMS14C dating. Some paleoclimatic information contained in sediments of these cores was extracted to discuss the paleoclimatic change rules and the short-time scale events presented in interglacial period. Analysis on the variation of oxygen isotope values in stage two shows that the middle part of the Okinawa Trough may have been affected by fresh water from the Yellow River and the Yangtze River during the Last Glacial Maximum (LGM). The oxygen isotope value oscillating ranges of the cores have verified that the marginal sea has an amplifying effect on climate changes.The δ13C of benthic foraminifera Uvigerina was lighter in the glacial period than that in the interglacial period, which indicates that the Paleo-Kuroshio's main stream moved eastward and its influence area decreased. According to the temperature difference during the “YD” period existing in Core 180 and other data, we can reach the conclusion that the climatic changes in the middle Okinawa Trough area were controlled by global climatic changes, but some regional factors had also considerable influence on the climatechanges. Some results in this paper support Fairbanks's point that the “YD” event was a brief stagnation of sea level rising during the global warming up procession. Moreover,the falling of sea level in the glacial period weakened the exchange between the bottom water of the Okinawa Trough and the deep water of the northwestern Pacific Ocean and resulted in low oxygen state of bottom water in this area.These procedures are the reasons for carbonate cycle in the Okinawa Trough area being consistent with the “Atlantic type”carbonate cycle.

  6. The effect of vibrationally excited nitrogen on the low-latitude ionosphere

    Directory of Open Access Journals (Sweden)

    B. Jenkins

    1997-11-01

    Full Text Available The first five vibrationally excited states of molecular nitrogen have been included in the Sheffield University plasmasphere ionosphere model. Vibrationally excited molecular nitrogen reacts much more strongly with atomic oxygen ions than ground-state nitrogen; this means that more O+ ions are converted to NO+ ions, which in turn combine with the electrons to give reduced electron densities. Model calculations have been carried out to investigate the effect of including vibrationally excited molecular nitrogen on the low-latitude ionosphere. In contrast to mid-latitudes, a reduction in electron density is seen in all seasons during solar maximum, the greatest effect being at the location of the equatorial trough.

  7. Analysis of pre-earthquake ionospheric anomalies before the global M = 7.0+ earthquakes in 2010

    Directory of Open Access Journals (Sweden)

    W. F. Peng

    2012-03-01

    Full Text Available The pre-earthquake ionospheric anomalies that occurred before the global M = 7.0+ earthquakes in 2010 are investigated using the total electron content (TEC from the global ionosphere map (GIM. We analyze the possible causes of the ionospheric anomalies based on the space environment and magnetic field status. Results show that some anomalies are related to the earthquakes. By analyzing the time of occurrence, duration, and spatial distribution of these ionospheric anomalies, a number of new conclusions are drawn, as follows: earthquake-related ionospheric anomalies are not bound to appear; both positive and negative anomalies are likely to occur; and the earthquake-related ionospheric anomalies discussed in the current study occurred 0–2 days before the associated earthquakes and in the afternoon to sunset (i.e. between 12:00 and 20:00 local time. Pre-earthquake ionospheric anomalies occur mainly in areas near the epicenter. However, the maximum affected area in the ionosphere does not coincide with the vertical projection of the epicenter of the subsequent earthquake. The directions deviating from the epicenters do not follow a fixed rule. The corresponding ionospheric effects can also be observed in the magnetically conjugated region. However, the probability of the anomalies appearance and extent of the anomalies in the magnetically conjugated region are smaller than the anomalies near the epicenter. Deep-focus earthquakes may also exhibit very significant pre-earthquake ionospheric anomalies.

  8. Ionospheric Gradient Threat Mitigation in Future Dual Frequency GBAS

    Directory of Open Access Journals (Sweden)

    Michael Felux

    2017-01-01

    Full Text Available The Ground Based Augmentation System (GBAS is a landing system for aircraft based on differential corrections for the signals of Global Navigation Satellite Systems (GNSS, such as GPS or Galileo. The main impact on the availability of current single frequency systems results from the necessary protection against ionospheric gradients. With the introduction of Galileo and the latest generation of GPS satellites, a second frequency is available for aeronautical navigation. Dual frequency methods allow forming of ionospheric free combinations of the signals, eliminating a large part of the ionospheric threats to GBAS. However, the combination of several signals increases the noise in the position solution and in the calculation of error bounds. We, therefore, developed a method to base positioning algorithms on single frequency measurements and use the second frequency only for monitoring purposes. In this paper, we describe a detailed derivation of the monitoring scheme and discuss its implications for the use in an aviation context.

  9. Wind effect on the motion of medium-scale travelling ionospheric disturbances in the E region of the ionosphere

    International Nuclear Information System (INIS)

    Kikvilashvili, G.B.; Sharadze, Z.S.; Mosashvili, N.V.

    1988-01-01

    Madium-scale travelling ionospheric disturbances (MSTID) in the ionosphere E region in Tbilisi area are investigated by means of spectral analysis of f 0 E s and f b E s variations, synchronously recorded in the three scattered points. The winds at the E s layers formation heights were measured simultaneously by D1 method in one of these points. It is established, that the MSTID motion direction in summer-time E region is controlled by the background thermospheric winds: disturbances mostly more across and against the wind. Tidal winds make the main contribution into the MSTID rate day variations

  10. Acoustically damped metal oil trough for internal combustion engines. Schallgedaempfte Blech-Oelwanne fuer Brennkraftmaschinen

    Energy Technology Data Exchange (ETDEWEB)

    Kubis, H.

    1991-03-28

    The invention refers to an acoustically damped oil trough. As there are strict requirements for reducing the noise emission from internal combustion engines, according to the invention it is proposed that the oil trough should be surrounded by an outer trough, where the outer trough is made of plastic or sheet steel in one or more layers. To avoid noise bridges, the oil trough and outer trough are separated by elastomer elements. The outer trough achieves a reasonably priced increase in sound insulation. It is also possible to backfit an outer trough on engines.

  11. AATR an ionospheric activity indicator specifically based on GNSS measurements

    Science.gov (United States)

    Juan, José Miguel; Sanz, Jaume; Rovira-Garcia, Adrià; González-Casado, Guillermo; Ibáñez, D.; Perez, R. Orus

    2018-03-01

    This work reviews an ionospheric activity indicator useful for identifying disturbed periods affecting the performance of Global Navigation Satellite System (GNSS). This index is based in the Along Arc TEC Rate (AATR) and can be easily computed from dual-frequency GNSS measurements. The AATR indicator has been assessed over more than one Solar Cycle (2002-2017) involving about 140 receivers distributed world-wide. Results show that it is well correlated with the ionospheric activity and, unlike other global indicators linked to the geomagnetic activity (i.e. DST or Ap), it is sensitive to the regional behaviour of the ionosphere and identifies specific effects on GNSS users. Moreover, from a devoted analysis of different Satellite Based Augmentation System (SBAS) performances in different ionospheric conditions, it follows that the AATR indicator is a very suitable mean to reveal whether SBAS service availability anomalies are linked to the ionosphere. On this account, the AATR indicator has been selected as the metric to characterise the ionosphere operational conditions in the frame of the European Space Agency activities on the European Geostationary Navigation Overlay System (EGNOS). The AATR index has been adopted as a standard tool by the International Civil Aviation Organization (ICAO) for joint ionospheric studies in SBAS. In this work we explain how the AATR is computed, paying special attention to the cycle-slip detection, which is one of the key issues in the AATR computation, not fully addressed in other indicators such as the Rate Of change of the TEC Index (ROTI). After this explanation we present some of the main conclusions about the ionospheric activity that can extracted from the AATR values during the above mentioned long-term study. These conclusions are: (a) the different spatial correlation related with the MOdified DIP (MODIP) which allows to clearly separate high, mid and low latitude regions, (b) the large spatial correlation in mid

  12. Analysis of ionospheric structure influences on residual ionospheric errors in GNSS radio occultation bending angles based on ray tracing simulations

    Science.gov (United States)

    Liu, Congliang; Kirchengast, Gottfried; Sun, Yueqiang; Zhang, Kefei; Norman, Robert; Schwaerz, Marc; Bai, Weihua; Du, Qifei; Li, Ying

    2018-04-01

    The Global Navigation Satellite System (GNSS) radio occultation (RO) technique is widely used to observe the atmosphere for applications such as numerical weather prediction and global climate monitoring. The ionosphere is a major error source to RO at upper stratospheric altitudes, and a linear dual-frequency bending angle correction is commonly used to remove the first-order ionospheric effect. However, the higher-order residual ionospheric error (RIE) can still be significant, so it needs to be further mitigated for high-accuracy applications, especially from 35 km altitude upward, where the RIE is most relevant compared to the decreasing magnitude of the atmospheric bending angle. In a previous study we quantified RIEs using an ensemble of about 700 quasi-realistic end-to-end simulated RO events, finding typical RIEs at the 0.1 to 0.5 µrad noise level, but were left with 26 exceptional events with anomalous RIEs at the 1 to 10 µrad level that remained unexplained. In this study, we focused on investigating the causes of the high RIE of these exceptional events, employing detailed along-ray-path analyses of atmospheric and ionospheric refractivities, impact parameter changes, and bending angles and RIEs under asymmetric and symmetric ionospheric structures. We found that the main causes of the high RIEs are a combination of physics-based effects - where asymmetric ionospheric conditions play the primary role, more than the ionization level driven by solar activity - and technical ray tracer effects due to occasions of imperfect smoothness in ionospheric refractivity model derivatives. We also found that along-ray impact parameter variations of more than 10 to 20 m are possible due to ionospheric asymmetries and, depending on prevailing horizontal refractivity gradients, are positive or negative relative to the initial impact parameter at the GNSS transmitter. Furthermore, mesospheric RIEs are found generally higher than upper-stratospheric ones, likely due to

  13. A point focusing double parabolic trough concentrator

    Energy Technology Data Exchange (ETDEWEB)

    Murphree, Quincy C. [Kentucky Mountain Bible College, Vancleve, KY (United States)

    2001-07-01

    This article shows that a point focusing solar concentrator can be made from two reflective parabolic troughs, a primary and a secondary, by orienting their longitudinal axes in perpendicular directions and separating them by the difference of their focal lengths along the optical axis. This offers a new alternative to the conventional 3-D paraboloidal concentrator permitting more flexibility in designs for applications requiring high concentrations. Both advantages and disadvantages are discussed. The intensity concentration ratio distribution is calculated in the focal plane and has elliptically shaped contours due to the inherent compensation of errant rays by the concave secondary. The ratio of the major to minor axes was 2.61 for the case considered, resulting in a concentration {approx}2.61 times that of a comparable concentrator without the compensation afforded by a concave secondary. Still, geometrical constraints limit the concentration to about 2000 suns for mirror quality errors of 5 mr. Optimisation of the compensation effect holds potential for improved performance for other concentrator designs. Finally, the functional dependence of the peak concentration and shading factor upon design parameters are presented. (Author)

  14. Parabolic Trough Solar Collector Initial Trials

    Directory of Open Access Journals (Sweden)

    Ghalya Pikra

    2012-03-01

    Full Text Available This paper discusses initial trials of parabolic trough solar collector (PTSC in Bandung. PTSC model consists of concentrator, absorber and tracking system. Concentrator designs are made with 2m aperture width, 6m length and 0.75m focal distance. The design is equipped with an automatic tracking system which is driven using 12V and 24Watt DC motor with 0.0125rpm rotational speed. Absorber/receiver is designed with evacuated tube type, with 1 inch core diameter and tube made of AISI304 and coated with black oxide, the outer tube is borosilicate glass with a 70 mm diameter and 1.5 m length. Working fluid stored in single type of thermal storage tank, a single phase with 37.7 liter volume. PTSC model testing carried out for 2 hours and 10 minutes produces heat output and input of 11.5 kW and 0.64 kW respectively. 

  15. Near real-time PPP-based monitoring of the ionosphere using dual-frequency GPS/BDS/Galileo data

    Science.gov (United States)

    Liu, Zhinmin; Li, Yangyang; Li, Fei; Guo, Jinyun

    2018-03-01

    Ionosphere delay is very important to GNSS observations, since it is one of the main error sources which have to be mitigated even eliminated in order to determine reliable and precise positions. The ionosphere is a dispersive medium to radio signal, so the value of the group delay or phase advance of GNSS radio signal depends on the signal frequency. Ground-based GNSS stations have been used for ionosphere monitoring and modeling for a long time. In this paper we will introduce a novel approach suitable for single-receiver operation based on the precise point positioning (PPP) technique. One of the main characteristic is that only carrier-phase observations are used to avoid particular effects of pseudorange observations. The technique consists of introducing ionosphere ambiguity parameters obtained from PPP filter into the geometry-free combination of observations to estimate ionospheric delays. Observational data from stations that are capable of tracking the GPS/BDS/GALILEO from the International GNSS Service (IGS) Multi-GNSS Experiments (MGEX) network are processed. For the purpose of performance validation, ionospheric delays series derived from the novel approach are compared with the global ionospheric map (GIM) from Ionospheric Associate Analysis Centers (IAACs). The results are encouraging and offer potential solutions to the near real-time ionosphere monitoring.

  16. Lightning impact on micro-second long ionospheric variability

    Science.gov (United States)

    Koh, Kuang Liang; Liu, Zhongjian; Fullekrug, Martin

    2017-04-01

    Lightning discharges cause electron heating and enhanced ionisation in the D region ionosphere which disturb the transmission of VLF communications [Inan et al., 2010]. A disturbance of such nature was measured in a VLF transmission with a sampling rate of 1 MHz, enabling much faster ionospheric variability to be observed when compared to previous studies which typically report results with a time resolution >5-20ms. The disturbance resembles "Long Recovery Early VLF" (LORE) events [Haldoupis et al. 2013, Cotts & Inan 2007]. LOREs exhibit observable ionospheric effects that last longer (>200s) than other lightning related disturbances. It was proposed that the mechanism behind the long-lasting effects of LOREs is different to shorter events [Gordillo-Vázquez et al. 2016]. The ionospheric variability inferred from the transmitted signal is seen to change dramatically after the lightning onset, suggesting that there are fast processes in the ionosphere affected or produced which have not been considered in previous research. The ionospheric variability inferred from the main two frequencies of the transmission is different. A possible explanation is a difference in the propagation paths of the two main frequencies of the transmission [Füllekrug et al., 2015]. References Inan, U.S., Cummer, S.A., Marshall, R.A., 2010. A survey of ELF and VLF research on lightning-ionosphere interactions and causative discharges. J. Geophys. Res. 115, A00E36. doi:10.1029/2009JA014775 Cotts, B.R.T., Inan, U.S., 2007. VLF observation of long ionospheric recovery events. Geophys. Res. Lett. 34, L14809. doi:10.1029/2007GL030094 Haldoupis, C., Cohen, M., Arnone, E., Cotts, B., Dietrich, S., 2013. The VLF fingerprint of elves: Step-like and long-recovery early VLF perturbations caused by powerful ±CG lightning EM pulses. J. Geophys. Res. Space Physics 118, 5392-5402. doi:10.1002/jgra.50489 Gordillo-Vázquez, F.J., Luque, A., Haldoupis, C., 2016. Upper D region chemical kinetic modeling of

  17. Technical Manual for the SAM Physical Trough Model

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, M. J.; Gilman, P.

    2011-06-01

    NREL, in conjunction with Sandia National Lab and the U.S Department of Energy, developed the System Advisor Model (SAM) analysis tool for renewable energy system performance and economic analysis. This paper documents the technical background and engineering formulation for one of SAM's two parabolic trough system models in SAM. The Physical Trough model calculates performance relationships based on physical first principles where possible, allowing the modeler to predict electricity production for a wider range of component geometries than is possible in the Empirical Trough model. This document describes the major parabolic trough plant subsystems in detail including the solar field, power block, thermal storage, piping, auxiliary heating, and control systems. This model makes use of both existing subsystem performance modeling approaches, and new approaches developed specifically for SAM.

  18. Isolated ionospheric disturbances as deduced from global GPS network

    Directory of Open Access Journals (Sweden)

    E. L. Afraimovich

    2004-01-01

    Full Text Available We investigate an unusual class of medium-scale traveling ionospheric disturbances of the nonwave type, isolated ionospheric disturbances (IIDs that manifest themselves in total electron content (TEC variations in the form of single aperiodic negative TEC disturbances of a duration of about 10min (the total electron content spikes, TECS. The data were obtained using the technology of global detection of ionospheric disturbances using measurements of TEC variations from a global network of receivers of the GPS. For the first time, we present the TECS morphology for 170 days in 1998–2001. The total number of TEC series, with a duration of each series of about 2.3h (2h18m, exceeded 850000. It was found that TECS are observed in no more than 1–2% of the total number of TEC series mainly in the nighttime in the spring and autumn periods. The TECS amplitude exceeds the mean value of the "background" TEC variation amplitude by a factor of 5–10 as a minimum. TECS represent a local phenomenon with a typical radius of spatial correlation not larger than 500km. The IID-induced TEC variations are similar in their amplitude, form and duration to the TEC response to shock-acoustic waves (SAW generated during rocket launchings and earthquakes. However, the IID propagation velocity is less than the SAW velocity (800–1000m/s and are most likely to correspond to the velocity of background medium-scale acoustic-gravity waves, on the order of 100–200m/s. Key words. Ionosphere (ionospheric irregularities, instruments and techniques - Radio science (ionospheric propagation

  19. Study of the mid-latitude ionospheric response to geomagnetic storms in the European region

    Science.gov (United States)

    Berényi, Kitti Alexandra; Barta, Veronika; Kis, Arpad

    2016-07-01

    Geomagnetic storms affect the ionospheric regions of the terrestrial upper atmosphere through different physical and atmospheric processes. The phenomena that can be regarded as a result of these processes, generally is named as "ionospheric storm". The processes depend on altitude, segment of the day, the geomagnetic latitude and longitude, strength of solar activity and the type of the geomagnetic storm. We examine the data of ground-based radio wave ionosphere sounding measurements of European ionospheric stations (mainly the data of Nagycenk Geophysical Observatory) in order to determine how and to what extent a geomagnetic disturbance of a certain strength affects the mid-latitude ionospheric regions in winter and in summer. For our analysis we used disturbed time periods between November 2012 and June 2015. Our results show significant changing of the ionospheric F2 layer parameters on strongly disturbed days compared to quiet ones. We show that the critical frequencies (foF2) increase compared to their quiet day value when the ionospheric storm was positive. On the other hand, the critical frequencies become lower, when the storm was negative. In our analysis we determined the magnitude of these changes on the chosen days. For a more complete analysis we compare also the evolution of the F2 layer parameters of the European ionosonde stations on a North-South geographic longitude during a full storm duration. The results present the evolution of an ionospheric storm over a geographic meridian. Furthermore, we compared the two type of geomagnetic storms, namely the CME caused geomagnetic storm - the so-called Sudden impulse (Si) storms- and the HSS (High Speed Solar Wind Streams) caused geomagnetic storms -the so-called Gradual storms (Gs)- impact on the ionospheric F2-layer (foF2 parameter). The results show a significant difference between the effect of Si and of the Gs storms on the ionospheric F2-layer.

  20. Floor cooler for floor trough of a nuclear reactor

    International Nuclear Information System (INIS)

    Friedrich, H.J.

    1985-01-01

    Cooling pipes are situated below the floor trough of a BWR, which are connected to the annular distribution or collection pipes. The distribution and collection pipes are connected by parallel hairpin pipes with involute shape to the centre of the floor trough. These hairpin pipes are situated in a lower plane than the annular distribution pipe to the centre and in a higher plane from the centre to the outer annular collector pipe. (orig./HP) [de

  1. Climatology of the autumn Red Sea trough

    Science.gov (United States)

    Awad, Adel M.; Mashat, Abdul-Wahab S.

    2018-03-01

    In this study, the Sudan low and the associated Red Sea trough (RST) are objectively identified using the mean sea level pressure (SLP) data from the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis dataset covering the period 1955-2015. The Sudan low was detected in approximately 60.6% of the autumn periods, and approximately 83% of the detected low-pressure systems extended into RSTs, with most generated at night and during cold months. The distribution of the RSTs demonstrated that Sudan, South Sudan and Red Sea are the primary development areas of the RSTs, generating 97% of the RSTs in the study period. In addition, the outermost areas affected by RSTs, which include the southern, central and northern Red Sea areas, received approximately 91% of the RSTs originating from the primary generation areas. The synoptic features indicated that a Sudan low developed into an RST when the Sudan low deepened in the atmosphere, while the low pressures over the southern Arabian Peninsula are shallow and the anticyclonic systems are weakened over the northern Red Sea. Moreover, stabile areas over Africa and Arabian Peninsula form a high stability gradient around the Red Sea and the upper maximum winds weaken. The results of the case studies indicate that RSTs extend northward when the upper cyclonic and anticyclonic systems form a high geopotential gradient over Arabian Peninsula. Furthermore, the RST is oriented from the west to the east when the Azores high extends eastward and the Siberian high shrinks eastward or shifts northward.

  2. The De Long Trough: a newly discovered glacial trough on the East Siberian continental margin

    Directory of Open Access Journals (Sweden)

    M. O'Regan

    2017-09-01

    Full Text Available Ice sheets extending over parts of the East Siberian continental shelf have been proposed for the last glacial period and during the larger Pleistocene glaciations. The sparse data available over this sector of the Arctic Ocean have left the timing, extent and even existence of these ice sheets largely unresolved. Here we present new geophysical mapping and sediment coring data from the East Siberian shelf and slope collected during the 2014 SWERUS-C3 expedition (SWERUS-C3: Swedish – Russian – US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions. The multibeam bathymetry and chirp sub-bottom profiles reveal a set of glacial landforms that include grounding zone formations along the outer continental shelf, seaward of which lies a  >  65 m thick sequence of glacio-genic debris flows. The glacial landforms are interpreted to lie at the seaward end of a glacial trough – the first to be reported on the East Siberian margin, here referred to as the De Long Trough because of its location due north of the De Long Islands. Stratigraphy and dating of sediment cores show that a drape of acoustically laminated sediments covering the glacial deposits is older than ∼ 50 cal kyr BP. This provides direct evidence for extensive glacial activity on the Siberian shelf that predates the Last Glacial Maximum and most likely occurred during the Saalian (Marine Isotope Stage (MIS 6.

  3. The study of the midlatitude ionospheric response to geomagnetic activity at Nagycenk Geophysical Observatory

    Science.gov (United States)

    Berényi, Kitti; Kis, Árpád; Barta, Veronika; Novák, Attila

    2016-04-01

    Geomagnetic storms affect the ionospheric regions of the terrestrial upper atmosphere, causing several physical and chemical atmospheric processes. The changes and phenomena, which can be seen as a result of these processes, generally called ionospheric storm. These processes depend on altitude, term of the day, and the strength of solar activity, the geomagnetic latitude and longitude. The differences between ionospheric regions mostly come from the variations of altitude dependent neutral and ionized atmospheric components, and from the physical parameters of solar radiation. We examined the data of the ground-based radio wave ionosphere sounding instruments of the European ionospheric stations (mainly the data of Nagycenk Geophysical Observatory), called ionosonde, to determine how and what extent a given strength of a geomagnetic disturbance affect the middle latitude ionospheric regions in winter. We chose the storm for the research from November 2012 and March 2015. As the main result of our research, we can show significant differences between the each ionospheric (F1 and F2) layer parameters on quiet and strong stormy days. When we saw, that the critical frequencies (foF2) increase from their quiet day value, then the effect of the ionospheric storm was positive, otherwise, if they drop, they were negative. With our analysis, the magnitude of these changes could be determined. Furthermore we demonstrated, how a full strong geomagnetic storm affects the ionospheric foF2 parameter during different storm phases. It has been showed, how a positive or negative ionospheric storm develop during a geomagnetic storm. For a more completed analysis, we compared also the evolution of the F2 layer parameters of the European ionosonde stations on a North-South geographic longitude during a full storm duration. Therefore we determined, that the data of the ionosonde at Nagycenk Geophysical Observatory are appropriate, it detects the same state of ionosphere like the

  4. Weak Lensing by Galaxy Troughs in DES Science Verification Data

    Energy Technology Data Exchange (ETDEWEB)

    Gruen, D. [Ludwig Maximilian Univ., Munich (Germany); Max Planck Inst. for Extraterrestrial Physics, Garching (Germany). et al.

    2015-09-29

    We measure the weak lensing shear around galaxy troughs, i.e. the radial alignment of background galaxies relative to underdensities in projections of the foreground galaxy field over a wide range of redshift in Science Verification data from the Dark Energy Survey. Our detection of the shear signal is highly significant (10σ–15σ for the smallest angular scales) for troughs with the redshift range z ϵ [0.2, 0.5] of the projected galaxy field and angular diameters of 10 arcmin…1°. These measurements probe the connection between the galaxy, matter density, and convergence fields. By assuming galaxies are biased tracers of the matter density with Poissonian noise, we find agreement of our measurements with predictions in a fiducial Λ cold dark matter model. Furthermore, the prediction for the lensing signal on large trough scales is virtually independent of the details of the underlying model for the connection of galaxies and matter. Our comparison of the shear around troughs with that around cylinders with large galaxy counts is consistent with a symmetry between galaxy and matter over- and underdensities. In addition, we measure the two-point angular correlation of troughs with galaxies which, in contrast to the lensing signal, is sensitive to galaxy bias on all scales. Finally, the lensing signal of troughs and their clustering with galaxies is therefore a promising probe of the statistical properties of matter underdensities and their connection to the galaxy field.

  5. Metrology and ionospheric observation standards

    Science.gov (United States)

    Panshin, Evgeniy; Minligareev, Vladimir; Pronin, Anton

    Accuracy and ionospheric observation validity are urgent trends nowadays. WMO, URSI and national metrological and standardisation services bring forward requirements and descriptions of the ionospheric observation means. Researches in the sphere of metrological and standardisation observation moved to the next level in the Russian Federation. Fedorov Institute of Applied Geophysics (IAG) is in charge of ionospheric observation in the Russian Federation and the National Technical Committee, TC-101 , which was set up on the base of IAG- of the standardisation in the sphere. TC-101 can be the platform for initiation of the core international committee in the network of ISO The new type of the ionosounde “Parus-A” is engineered, which is up to the national requirements. “Parus-A” calibration and test were conducted by National metrological Institute (NMI) -D.I. Mendeleyev Institute for Metrology (VNIIM), signed CIMP MRA in 1991. VNIIM is a basic NMI in the sphere of Space weather (including ionospheric observations), the founder of which was celebrated chemist and metrologist Dmitriy I. Mendeleyev. Tests and calibration were carried out for the 1st time throughout 50-year-history of ionosonde exploitation in Russia. The following metrological characteristics were tested: -measurement range of radiofrequency time delay 0.5-10 ms; -time measurement inaccuracy of radio- frequency pulse ±12mcs; -frequency range of radio impulse 1-20 MHz ; -measurement inaccuracy of radio impulse carrier frequency± 5KHz. For example, the sound impulse simulator that was built-in in the ionosounde was used for measurement range of radiofrequency time delay testing. The number of standards on different levels is developed. - “Ionospheric observation guidance”; - “The Earth ionosphere. Terms and definitions”.

  6. Dynamics of the polar ionosphere structure disturbance in the Svalgaard-Mansurov effect

    International Nuclear Information System (INIS)

    Osipov, N.K.; Mozhaev, A.M.; Larina, T.N.; Ponomarev, Yu.N.

    1988-01-01

    Nonstationary disturbance model of the ionsphere of polar caps caused by change of B y component sign of interplanetary magnetic field is considered. It is shown that nonstationary convection transfer of ionospheric plasma represents the main and the most fast mechanism regulating reconstruction of ionosphere structure in polar caps during magnetosphere substorms, caused by the change of B y sign. Calculations show that characteristic time of sufficient change of ionosphere structure at ∼1500 km distances is on the order of 10-25 min

  7. Risk factors associated with high linezolid trough plasma concentrations.

    Science.gov (United States)

    Morata, L; De la Calle, C; Gómez-Cerquera, J M; Manzanedo, L; Casals, G; Brunet, M; Cobos-Trigueros, N; Martínez, J A; Mensa, J; Soriano, A

    2016-06-01

    The major concern of linezolid is the adverse events. High linezolid trough serum concentration (Cmin) has been associated with toxicity. The aim of this study was to analyze factors associated with high Cmin. Main clinical characteristics of 104 patients treated with 600 mg/12 hours of linezolid were retrospectively reviewed. Samples were obtained just before the next dose after at least three doses and within the first 8 days of treatment. High Cmin was considered when it was >8 mg/L. Univariate and multivariate analysis were performed. 34.6% patients had a Cmin >8 mg/L, and they were older and had more frequently an estimated glomerular filtration by MDRD 8 was the renal function. Patients with an eGF 80 mL/min (OR: 4.273) and there was a trend towards a high Cmin in patients with eGF between 40-80 mL/min (OR: 2.109). High Cmin were frequent, especially in patients with MDRD <40 mL/min. Therapeutic drug monitoring could be useful to avoid toxicity in patients with renal dysfunction.

  8. Control concepts for direct steam generation in parabolic troughs

    Energy Technology Data Exchange (ETDEWEB)

    Valenzuela, Loreto; Zarza, Eduardo [CIEMAT, Plataforma Solar de Almeria, Tabernas (Almeria) (Spain); Berenguel, Manuel [Universidad de Almeria, Dept. de Lenguajes y Computacion, Almeria (Spain); Camacho, Eduardo F. [Universidad de Sevilla, Dept. de Ingenieria de Sistemas y Automatica, Sevilla (Spain)

    2005-02-01

    A new prototype parabolic-trough collector system was erected at the Plataforma Solar de Almeria (PSA) (1996-1998) to investigate direct steam generation (DSG) in a solar thermal power plant under real solar conditions. The system has been under evaluation for efficiency, cost, control and other parameters since 1999. The main objective of the control system is to obtain steam at constant temperature and pressure at the solar field outlet, so that changes in inlet water conditions and/or in solar radiation affect the amount of steam, but not its quality or the nominal plant efficiency. This paper presents control schemes designed and tested for two operating modes, 'Recirculation', for which a proportional-integral-derivative (PI/PID) control functions scheme has been implemented, and 'Once-through', requiring more complex control strategies, for which the scheme is based on proportional-integral (PI), feedforward and cascade control. Experimental results of both operation modes are discussed. (Author)

  9. New Model for Ionospheric Irregularities at Mars

    Science.gov (United States)

    Keskinen, M. J.

    2018-03-01

    A new model for ionospheric irregularities at Mars is presented. It is shown that wind-driven currents in the dynamo region of the Martian ionosphere can be unstable to the electromagnetic gradient drift instability. This plasma instability can generate ionospheric density and magnetic field irregularities with scale sizes of approximately 15-20 km down to a few kilometers. We show that the instability-driven magnetic field fluctuation amplitudes relative to background are correlated with the ionospheric density fluctuation amplitudes relative to background. Our results can explain recent observations made by the Mars Atmosphere and Volatile EvolutioN spacecraft in the Martian ionosphere dynamo region.

  10. A Review of Ionospheric Scintillation Models.

    Science.gov (United States)

    Priyadarshi, S

    This is a general review of the existing climatological models of ionospheric radio scintillation for high and equatorial latitudes. Trans-ionospheric communication of radio waves from transmitter to user is affected by the ionosphere which is highly variable and dynamic in both time and space. Scintillation is the term given to irregular amplitude and phase fluctuations of the received signals and related to the electron density irregularities in the ionosphere. Key sources of ionospheric irregularities are plasma instabilities; every irregularities model is based on the theory of radio wave propagation in random media. It is important to understand scintillation phenomena and the approach of different theories. Therefore, we have briefly discussed the theories that are used to interpret ionospheric scintillation data. The global morphology of ionospheric scintillation is also discussed briefly. The most important (in our opinion) analytical and physical models of scintillation are reviewed here.

  11. Nighttime ionospheric D region: Equatorial and nonequatorial

    Science.gov (United States)

    Thomson, Neil R.; McRae, Wayne M.

    2009-08-01

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

  12. Nonlinear dynamic processes in modified ionospheric plasma

    Science.gov (United States)

    Kochetov, A.; Terina, G.

    Presented work is a contribution to the experimental and theoretical study of nonlinear effects arising on ionospheric plasma under the action of powerful radio emission (G.I. Terina, J. Atm. Terr. Phys., 1995, v.57, p.273; A.V. Kochetov et. al., Advances in Space Research, 2002, in press). The experimental results were obtained by the method of sounding of artificially disturbed ionosphere by short radio pulses. The amplitude and phase characteristics of scattered signal as of "caviton" type (CS) (analogy of narrow-band component of stimulation electromagnetic emission (SEE)) as the main signal (MS) of probing transmitter are considered. The theoretical model is based on numerical solution of driven nonlinear Shrödinger equation (NSE) in inhomogeneous plasma. The simulation allows us to study a self-consistent spatial-temporal dynamics of field and plasma. The observed evolution of phase characteristics of MS and CS qualitatively correspond to the results of numerical simulation and demonstrate the penetration processes of powerful electromagnetic wave in supercritical (in linear approach) plasma regions. The modeling results explain also the periodic generation of CS, the travel CS maximum down to density gradient, the aftereffect of CS. The obtained results show the excitation of strong turbulence and allow us to interpret CS, NC and so far inexplicable phenomena as "spikes" too. The work was supported in part by Russian Foundation for Basic Research (grants Nos. 99-02-16642, 99-02- 16399).

  13. The Comprehensive Inner Magnetosphere-Ionosphere Model

    Science.gov (United States)

    Fok, M.-C.; Buzulukova, N. Y.; Chen, S.-H.; Glocer, A.; Nagai, T.; Valek, P.; Perez, J. D.

    2014-01-01

    Simulation studies of the Earth's radiation belts and ring current are very useful in understanding the acceleration, transport, and loss of energetic particles. Recently, the Comprehensive Ring Current Model (CRCM) and the Radiation Belt Environment (RBE) model were merged to form a Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model. CIMI solves for many essential quantities in the inner magnetosphere, including ion and electron distributions in the ring current and radiation belts, plasmaspheric density, Region 2 currents, convection potential, and precipitation in the ionosphere. It incorporates whistler mode chorus and hiss wave diffusion of energetic electrons in energy, pitch angle, and cross terms. CIMI thus represents a comprehensive model that considers the effects of the ring current and plasmasphere on the radiation belts. We have performed a CIMI simulation for the storm on 5-9 April 2010 and then compared our results with data from the Two Wide-angle Imaging Neutral-atom Spectrometers and Akebono satellites. We identify the dominant energization and loss processes for the ring current and radiation belts. We find that the interactions with the whistler mode chorus waves are the main cause of the flux increase of MeV electrons during the recovery phase of this particular storm. When a self-consistent electric field from the CRCM is used, the enhancement of MeV electrons is higher than when an empirical convection model is applied. We also demonstrate how CIMI can be a powerful tool for analyzing and interpreting data from the new Van Allen Probes mission.

  14. Multiscale Modeling of Ionospheric Irregularities

    Science.gov (United States)

    2014-10-22

    numerical simulations of ionospheric plasma density structures associated with nonlinear evolution of the Rayleigh-Taylor (RT) instabilities in...model was developed to resolve the transport pat- terns of plasma density coupled with neutral atmospheric dynamics. Inclusion of neutral dynamics in...trapping electromagnetic (EM) waves in parabolic cavities, which are created by the refractive index gradients along the propagation paths. Keywords

  15. Interplanetary phenomenon, geomagnetic and ionospheric ...

    African Journals Online (AJOL)

    The analysis of the D(foF2) plots appear to show that the storm event is characterized by (i) the occurrence of positive ionospheric storm at the high latitudes and mid latitude stations of Khabarovsk, Yamagawa and Okinawa stations before the beginning of the storm event (ii) Presence of strong negative phase at Manila, ...

  16. The ionospheric eclipse factor method (IEFM) and its application to determining the ionospheric delay for GPS

    DEFF Research Database (Denmark)

    Yuan, Y.; Tscherning, C.C.; Knudsen, Per

    2006-01-01

    A new method for modeling the ionospheric delay using global positioning system (GPS) data is proposed, called the ionospheric eclipse factor method (IEFM). It is based on establishing a concept referred to as the ionospheric eclipse factor (IEF) lambda of the ionospheric pierce point (IPP....... The IEFM-based ionospheric delay estimates are validated by combining an absolute positioning mode with several ionospheric delay correction models or algorithms, using GPS data at an international Global Navigation Satellite System (GNSS) service (IGS) station (WTZR). Our results indicate that the IEFM...

  17. Prediction of total electron content using the international reference ionosphere

    International Nuclear Information System (INIS)

    Mcnamara, L.F.

    1984-01-01

    It is pointed out that the International Reference Ionosphere (IRI) is an empirical model of the ionosphere based on experimental observations. Rawer et al. (1978) have discussed the goals and status of the IRI. The aim of the IRI is related to the establishment of a compendium of height profiles through the ionosphere for the four main parameters, taking into account plasma density, temperature of ions and electrons, and ion composition. The present model is inadequate in some areas, and the IRI working group has encouraged tests of the model's validity. The present investigation is concerned with a test of the model's ability to reproduce observations of total electron content (TEC) over a wide range of conditions. The TEC observations were obtained with the aid of the Faraday rotation technique, which provides the TEC out to about 2000 km. Tests using the Bent ionospheric model indicate that the altitude range 1000 to 2000 km contributes up to five percent of the TEC. 12 references

  18. Weak ionization of the global ionosphere in solar cycle 24

    Directory of Open Access Journals (Sweden)

    Y. Q. Hao

    2014-07-01

    Full Text Available Following prolonged and extremely quiet solar activity from 2008 to 2009, the 24th solar cycle started slowly. It has been almost 5 years since then. The measurement of ionospheric critical frequency (foF2 shows the fact that solar activity has been significantly lower in the first half of cycle 24, compared to the average levels of cycles 19 to 23; the data of global average total electron content (TEC confirm that the global ionosphere around the cycle 24 peak is much more weakly ionized, in contrast to cycle 23. The weak ionization has been more notable since the year 2012, when both the ionosphere and solar activity were expected to be approaching their maximum level. The undersupply of solar extreme ultraviolet (EUV irradiance somewhat continues after the 2008–2009 minimum, and is considered to be the main cause of the weak ionization. It further implies that the thermosphere and ionosphere in the first solar cycle of this millennium would probably differ from what we have learned from the previous cycles of the space age.

  19. A very bright SAR arc: implications for extreme magnetosphere-ionosphere coupling

    Directory of Open Access Journals (Sweden)

    J. Baumgardner

    2007-01-01

    Full Text Available In contrast to the polar aurora visible during geomagnetic storms, stable auroral red (SAR arcs offer a sub-visual manifestation of direct magnetosphere-ionosphere (M-I coupling at midlatitudes. The SAR arc emission at 6300 Å is driven by field-aligned magnetospheric energy transport from ring current/plasmapause locations into the ionosphere-thermosphere system. The first SAR arc was observed at the dawn of the space age (1956, and the typical brightness levels and occurrence patterns obtained from subsequent decades of observations appear to be consistent with the downward heat conduction theory, i.e., heated ambient F-layer electrons excite oxygen atoms to produce a spectrally pure emission. On very rare occasions, a SAR arc has been reported to be at brightness levels visible to the naked eye. Here we report on the first case of a very bright SAR arc (~13 kilo-Rayleighs observed by four diagnostic systems that sampled various aspects of the sub-auroral domain near Millstone Hill, MA, on the night of 29 October 1991: an imaging spectrograph, an all-sky camera, an incoherent scatter radar (ISR, and a DMSP satellite. Simulations of emission using the ISR and DMSP data with the MSIS neutral atmosphere succeed in reproducing the brightness levels observed. This provides a robust confirmation of M-I coupling theory in its most extreme aeronomic form within the innermost magnetosphere (L~2 during a rare superstorm event. The unusually high brightness value appears to be due to the rare occurrence of the heating of dense ionospheric plasma just equatorward of the trough/plasmapause location, in contrast to the more typical heating of the less dense F-layer within the trough.

  20. A very bright SAR arc: implications for extreme magnetosphere-ionosphere coupling

    Directory of Open Access Journals (Sweden)

    J. Baumgardner

    2008-01-01

    Full Text Available In contrast to the polar aurora visible during geomagnetic storms, stable auroral red (SAR arcs offer a sub-visual manifestation of direct magnetosphere-ionosphere (M-I coupling at midlatitudes. The SAR arc emission at 6300 Å is driven by field-aligned magnetospheric energy transport from ring current/plasmapause locations into the ionosphere-thermosphere system. The first SAR arc was observed at the dawn of the space age (1956, and the typical brightness levels and occurrence patterns obtained from subsequent decades of observations appear to be consistent with the downward heat conduction theory, i.e., heated ambient F-layer electrons excite oxygen atoms to produce a spectrally pure emission. On very rare occasions, a SAR arc has been reported to be at brightness levels visible to the naked eye. Here we report on the first case of a very bright SAR arc (~13 kilo-Rayleighs observed by four diagnostic systems that sampled various aspects of the sub-auroral domain near Millstone Hill, MA, on the night of 29 October 1991: an imaging spectrograph, an all-sky camera, an incoherent scatter radar (ISR, and a DMSP satellite. Simulations of emission using the ISR and DMSP data with the MSIS neutral atmosphere succeed in reproducing the brightness levels observed. This provides a robust confirmation of M-I coupling theory in its most extreme aeronomic form within the innermost magnetosphere (L~2 during a rare superstorm event. The unusually high brightness value appears to be due to the rare occurrence of the heating of dense ionospheric plasma just equatorward of the trough/plasmapause location, in contrast to the more typical heating of the less dense F-layer within the trough.

  1. Preface: International Reference Ionosphere - Progress in Ionospheric Modelling

    Science.gov (United States)

    Bilitza Dieter; Reinisch, Bodo

    2010-01-01

    The international reference ionosphere (lRI) is the internationally recommended empirical model for the specification of ionospheric parameters supported by the Committee on Space Research (COSPAR) and the International Union of Radio Science (URSI) and recognized by the International Standardization Organization (ISO). IRI is being continually improved by a team of international experts as new data become available and better models are being developed. This issue chronicles the latest phase of model updates as reported during two IRI-related meetings. The first was a special session during the Scientific Assembly of the Committee of Space Research (COSPAR) in Montreal, Canada in July 2008 and the second was an IRI Task Force Activity at the US Air Force Academy in Colorado Springs in May 2009. This work led to several improvements and additions of the model which will be included in the next version, IRI-201O. The issue is divided into three sections focusing on the improvements made in the topside ionosphere, the F-peak, and the lower ionosphere, respectively. This issue would not have been possible without the reviewing efforts of many individuals. Each paper was reviewed by two referees. We thankfully acknowledge the contribution to this issue made by the following reviewers: Jacob Adeniyi, David Altadill, Eduardo Araujo, Feza Arikan, Dieter Bilitza, Jilijana Cander, Bela Fejer, Tamara Gulyaeva, Manuel Hermindez-Pajares, Ivan Kutiev, John MacDougal, Leo McNamara, Bruno Nava, Olivier Obrou, Elijah Oyeyemi, Vadym Paznukhov, Bodo Reinisch, John Retterer, Phil Richards, Gary Sales, J.H. Sastri, Ludger Scherliess, Iwona Stanislavska, Stamir Stankov, Shin-Yi Su, Manlian Zhang, Y ongliang Zhang, and Irina Zakharenkova. We are grateful to Peggy Ann Shea for her final review and guidance as the editor-in-chief for special issues of Advances in Space Research. We thank the authors for their timely submission and their quick response to the reviewer comments and humbly

  2. Characterising the Ionosphere (La caracterisation de l’ionosphere)

    Science.gov (United States)

    2009-01-01

    2003; Valdivia , 2003; Tong et al ., 2004). Tidal motions and planetary waves in the thermosphere have significant influence on ionospheric...such as storms, earthquakes and volcanic explosions may produce F2-layer signatures (Rishbeth, 2006 ). Kazimirovsky et al . (2003) have reviewed such...possible effects. Pulinets et al . ( 2006 ) have published a case study of anomalous variations of the total electron content (TEC) registered over the

  3. Lagopedo: two F-region ionospheric depletion experiments

    International Nuclear Information System (INIS)

    Pongratz, M.B.; Smith, G.M.; Sutherland, C.D.; Zinn, J.

    1977-01-01

    A significant depletion of ionospheric plasma was produced by a chemical release experiment in the F-layer ionosphere over Hawaii. The results of measurements of the hole produced in the ionospheric plasma are reported

  4. Federal technology alert. Parabolic-trough solar water heating

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-04-01

    Parabolic-trough solar water heating is a well-proven renewable energy technology with considerable potential for application at Federal facilities. For the US, parabolic-trough water-heating systems are most cost effective in the Southwest where direct solar radiation is high. Jails, hospitals, barracks, and other facilities that consistently use large volumes of hot water are particularly good candidates, as are facilities with central plants for district heating. As with any renewable energy or energy efficiency technology requiring significant initial capital investment, the primary condition that will make a parabolic-trough system economically viable is if it is replacing expensive conventional water heating. In combination with absorption cooling systems, parabolic-trough collectors can also be used for air-conditioning. Industrial Solar Technology (IST) of Golden, Colorado, is the sole current manufacturer of parabolic-trough solar water heating systems. IST has an Indefinite Delivery/Indefinite Quantity (IDIQ) contract with the Federal Energy Management Program (FEMP) of the US Department of Energy (DOE) to finance and install parabolic-trough solar water heating on an Energy Savings Performance Contract (ESPC) basis for any Federal facility that requests it and for which it proves viable. For an ESPC project, the facility does not pay for design, capital equipment, or installation. Instead, it pays only for guaranteed energy savings. Preparing and implementing delivery or task orders against the IDIQ is much simpler than the standard procurement process. This Federal Technology Alert (FTA) of the New Technology Demonstration Program is one of a series of guides to renewable energy and new energy-efficient technologies.

  5. Modeling ionospheric pre-reversal enhancement and plasma bubble growth rate using data assimilation

    Science.gov (United States)

    Rajesh, P. K.; Lin, C. C. H.; Chen, C. H.; Matsuo, T.

    2017-12-01

    We report that assimilating total electron content (TEC) into a coupled thermosphere-ionosphere model by using the ensemble Kalman filter results in improved specification and forecast of eastward pre-reversal enhancement (PRE) electric field (E-field). Through data assimilation, the ionospheric plasma density, thermospheric winds, temperature and compositions are adjusted simultaneously. The improvement of dusk-side PRE E-field over the prior state is achieved primarily by intensification of eastward neutral wind. The improved E-field promotes a stronger plasma fountain and deepens the equatorial trough. As a result, the horizontal gradients of Pedersen conductivity and eastward wind are increased due to greater zonal electron density gradient and smaller ion drag at dusk, respectively. Such modifications provide preferable conditions and obtain a strengthened PRE magnitude closer to the observation. The adjustment of PRE E-field is enabled through self-consistent thermosphere and ionosphere coupling processes captured in the model. The assimilative outputs are further utilized to calculate the flux tube integrated Rayleigh-Taylor instability growth rate during March 2015 for investigation of global plasma bubble occurrence. Significant improvements in the calculated growth rates could be achieved because of the improved update of zonal electric field in the data assimilation forecast. The results suggest that realistic estimate or prediction of plasma bubble occurrence could be feasible by taking advantage of the data assimilation approach adopted in this work.

  6. Influence of Magnetic Topology on Mars' Ionospheric Structure

    Science.gov (United States)

    Adams, D.; Xu, S.; Mitchell, D. L.; Fillingim, M. O.; Lillis, R. J.; Andersson, L.; Fowler, C. M.; Benna, M.; Connerney, J. E. P.; Elrod, M. K.; Girazian, Z.; Vogt, M.

    2017-12-01

    The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has been in Mars' orbit since September 2014 (>1 Mars year), and has collected particle and field data within the ionosphere over wide ranges of altitudes, latitudes, and local times. This study uses MAVEN data to (1) analyze the influence of magnetic topology on the day-side ionosphere and (2) identify the sources of the night-side ionosphere. On the day side, magnetic strength and elevation angle are commonly used as proxies for magnetic topology. In this study, we use pitch-angle-resolved suprathermal electron measurements by the Solar Wind Electron Analyzer (SWEA) to directly deduce the magnetic topology instead of using a proxy. On the night side, the main sources of ionospheric plasma are bulk transport and plasma pressure gradient flow from the day side, as well as in situ production by electron impact ionization (EII). Plasma transport at Mars is complicated by the presence of intense crustal magnetic fields. Closed crustal magnetic fields form isolated plasma environments ("miniature magnetospheres") that inhibit external sources of cold ionospheric plasma as well as suprathermal (ionizing) electrons. Inside these closed magnetic loops, we study how the plasma evolves with bulk flow transport as the only source. By comparing closed and non-closed magnetic configurations, the effects of pressure gradient flow and EII can be distinguished. Finally, the densities of O2+, O+, and NO+, as measured by the Neutral Gas and Ion Mass Spectrometer (NGIMS), are examined. Inside miniature magnetospheres on the night side, the abundances of these species are found to be primarily controlled by the different recombination rates, as there is little plasma created within these regions by EII or transported from the neighboring regions by plasma pressure gradient flow.

  7. Ionospheric effects of thunderstorms and lightning

    Energy Technology Data Exchange (ETDEWEB)

    Lay, Erin H. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-02-03

    Tropospheric thunderstorms have been reported to disturb the lower ionosphere (~65-90 km) by convective atmospheric gravity waves and by electromagnetic field changes produced by lightning discharges. However, due to the low electron density in the lower ionosphere, active probing of its electron distribution is difficult, and the various perturbative effects are poorly understood. Recently, we have demonstrated that by using remotely-detected ?me waveforms of lightning radio signals it is possible to probe the lower ionosphere and its fluctuations in a spatially and temporally-resolved manner. Here we report evidence of gravity wave effects on the lower ionosphere originating from the thunderstorm. We also report variations in the nighttime ionosphere atop a small thunderstorm and associate the variations with the storm’s electrical activity. Finally, we present a data analysis technique to map ionospheric acoustic waves near thunderstorms.

  8. Developing an ionospheric map for South Africa

    Directory of Open Access Journals (Sweden)

    D. I. Okoh

    2010-07-01

    Full Text Available The development of a map of the ionosphere over South Africa is presented in this paper. The International Reference Ionosphere (IRI model, South African Bottomside Ionospheric Model (SABIM, and measurements from ionosondes in the South African Ionosonde Network, were combined within their own limitations to develop an accurate representation of the South African ionosphere. The map is essentially in the form of a computer program that shows spatial and temporal representations of the South African ionosphere for a given set of geophysical parameters. A validation of the map is attempted using a comparison of Total Electron Content (TEC values derived from the map, from the IRI model, and from Global Positioning System (GPS measurements. It is foreseen that the final South African ionospheric map will be implemented as a Space Weather product of the African Space Weather Regional Warning Centre.

  9. Optimising position control of a solar parabolic trough

    Directory of Open Access Journals (Sweden)

    Puramanathan Naidoo

    2011-03-01

    Full Text Available In today’s climate of growing energy needs and increasing environmental concerns, alternatives to the use of non-renewable and polluting fossil fuels have to be investigated. One such alternative is solar energy. This study is based on the implementation of a mathematical computation – the PSA (Plataforma Solar de Almeria computation developed at PSA (the European Test Centre for solar energy applications – embedded in a control algorithm to locate the position of the sun. Tests were conducted on a solar parabolic trough (SPT constructed at the Solar Thermal Applications Research Laboratory of the Mangosuthu University of Technology (Durban, South Africa for optimal position control using the PSA value. The designed control algorithm embedded in an industrial Siemens S7-314 C-2PtP programmable logic controller compared the PSA computation to a measured position of the SPT to optimally rotate the SPT to a desired position with the constant movement of the sun. The two main angles of the sun relative to the position of the SPT on earth, the zenith angle and the azimuth angle, both calculated in the PSA from the vertical and horizontal planes, respectively, were applied to the control algorithm to generate an appropriate final tracking angle within a 0.007 radian (0° 24′ 3.6″ tolerance, in accordance to the construction specifications and solar collector testing standards of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE, 1991. These values, together with the longitude and latitude applicable to the geographical location of the SPT, were processed in the control software to rotate the SPT to an optimal position with respect to the position of the sun in its daily path, for solar-to-thermal conversion.

  10. Tracking local control of a parabolic trough collector

    International Nuclear Information System (INIS)

    Ajona, J.I.; Alberdi, J.; Gamero, E.; Blanco, J.

    1992-01-01

    In the local control, the sun position related to the trough collector is measured by two photo-resistors. The provided electronic signal is then compared with reference levels in order to get a set of B logical signals which form a byte. This byte and the commands issued by a programmable controller are connected to the inputs of o P.R.O.M. memory which is programmed with the logical equations of the control system. The memory output lines give the control command of the parabolic trough collector motor. (Author)

  11. ULF Waves in the Ionospheric Alfven Resonator: Modeling of MICA Observations

    Science.gov (United States)

    Streltsov, A. V.; Tulegenov, B.

    2017-12-01

    We present results from a numerical study of physical processes responsible for the generation of small-scale, intense electromagnetic structures in the ultra-low-frequency range frequently observed in the close vicinity of bright discrete auroral arcs. In particular, our research is focused on the role of the ionosphere in generating these structures. A significant body of observations demonstrate that small-scale electromagnetic waves with frequencies below 1 Hz are detected at high latitudes where the large-scale, downward magnetic field-aligned current (FAC) interact with the ionosphere. Some theoretical studies suggest that these waves can be generated by the ionospheric feedback instability (IFI) inside the ionospheric Alfven resonator (IAR). The IAR is the region in the low-altitude magnetosphere bounded by the strong gradient in the Alfven speed at high altitude and the conducting bottom of the ionosphere (ionospheric E-region) at low altitude. To study ULF waves in this region we use a numerical model developed from reduced two fluid MHD equations describing shear Alfven waves in the ionosphere and magnetosphere of the earth. The active ionospheric feedback on structure and amplitude of magnetic FACs that interact with the ionosphere is implemented through the ionospheric boundary conditions that link the parallel current density with the plasma density and the perpendicular electric field in the ionosphere. Our numerical results are compared with the in situ measurements performed by the Magnetosphere-Ionosphere Coupling in the Alfven Resonator (MICA) sounding rocket, launched on February 19, 2012 from Poker Flat Research Range in Alaska to measure fields and particles during a passage through a discreet auroral arc. Parameters of the simulations are chosen to match actual MICA parameters, allowing the comparison in the most precise and rigorous way. Waves generated in the numerical model have frequencies between 0.30 and 0.45 Hz, while MICA measured

  12. Inverse problem of radiofrequency sounding of ionosphere

    Science.gov (United States)

    Velichko, E. N.; Yu. Grishentsev, A.; Korobeynikov, A. G.

    2016-01-01

    An algorithm for the solution of the inverse problem of vertical ionosphere sounding and a mathematical model of noise filtering are presented. An automated system for processing and analysis of spectrograms of vertical ionosphere sounding based on our algorithm is described. It is shown that the algorithm we suggest has a rather high efficiency. This is supported by the data obtained at the ionospheric stations of the so-called “AIS-M” type.

  13. Ionospheric Change and Solar EUV Irradiance

    Science.gov (United States)

    Sojka, J. J.; David, M.; Jensen, J. B.; Schunk, R. W.

    2011-12-01

    The ionosphere has been quantitatively monitored for the past six solar cycles. The past few years of observations are showing trends that differ from the prior cycles! Our good statistical relationships between the solar radio flux index at 10.7 cm, the solar EUV Irradiance, and the ionospheric F-layer peak density are showing indications of divergence! Present day discussion of the Sun-Earth entering a Dalton Minimum would suggest change is occurring in the Sun, as the driver, followed by the Earth, as the receptor. The dayside ionosphere is driven by the solar EUV Irradiance. But different components of this spectrum affect the ionospheric layers differently. For a first time the continuous high cadence EUV spectra from the SDO EVE instrument enable ionospheric scientists the opportunity to evaluate solar EUV variability as a driver of ionospheric variability. A definitive understanding of which spectral components are responsible for the E- and F-layers of the ionosphere will enable assessments of how over 50 years of ionospheric observations, the solar EUV Irradiance has changed. If indeed the evidence suggesting the Sun-Earth system is entering a Dalton Minimum periods is correct, then the comprehensive EVE solar EUV Irradiance data base combined with the ongoing ionospheric data bases will provide a most fortuitous fiduciary reference baseline for Sun-Earth dependencies. Using the EVE EUV Irradiances, a physics based ionospheric model (TDIM), and 50 plus years of ionospheric observation from Wallops Island (Virginia) the above Sun-Earth ionospheric relationship will be reported on.

  14. Investigation of the seismo-ionospheric effects on the base of GPS/GLONASS measurements

    Science.gov (United States)

    Zakharenkova, I.; Cherniak, Iu.; Shagimuratov, I.; Suslova, O.

    2012-04-01

    During last years the monitoring of the ionospheric effects of different origin is carried out mainly with use of Global Navigating Satellite Systems (GPS / GLONASS). By means of measurements of the signals temporal delays it is possible to do the mapping of total electron content (TEC) in a column of unit cross section through the Earth's ionosphere and investigate its temporal evolution depended on the variations of electron concentration (NmF2) in the F2 ionospheric region. In the given report we present results of analysis of spatial-temporal variability of the ionosphere during the earthquake preparation phase for several major earthquakes which took place in Japan. It was revealed that for considered events mainly positive TEC anomalies appeared 1-5 days prior to the earthquake. The enhancement of electron concentration reached the value of 30-70% relative to the quiet geomagnetic conditions. In order to analyze the revealed effects in more details it was additionally involved data of GPS TEC values over GPS stations located at different distances from earthquake epicenters and data of vertical sounding of the ionosphere (NICT database). The hourly values of critical frequency of ionospheric F2 and Es layers were obtained from manually scaled ionograms recorded at Japanese ionospheric sounding stations Wakkanai, Kokubunji and Yamagawa. Acknowledgments. We acknowledge the IGS community for providing GPS permanent data and WDC for Ionosphere, Tokyo, National Institute of Information and Communications Technology (NICT) for providing ionosonde data. This work was supported by Russian Federation President grant MK-2058.2011.5.

  15. HAARP-Induced Ionospheric Ducts

    International Nuclear Information System (INIS)

    Milikh, Gennady; Vartanyan, Aram

    2011-01-01

    It is well known that strong electron heating by a powerful HF-facility can lead to the formation of electron and ion density perturbations that stretch along the magnetic field line. Those density perturbations can serve as ducts for ELF waves, both of natural and artificial origin. This paper presents observations of the plasma density perturbations caused by the HF-heating of the ionosphere by the HAARP facility. The low orbit satellite DEMETER was used as a diagnostic tool to measure the electron and ion temperature and density along the satellite orbit overflying close to the magnetic zenith of the HF-heater. Those observations will be then checked against the theoretical model of duct formation due to HF-heating of the ionosphere. The model is based on the modified SAMI2 code, and is validated by comparison with well documented experiments.

  16. Parabolic-trough technology roadmap: A pathway for sustained commercial development and deployment of parabolic-trough technology

    International Nuclear Information System (INIS)

    David Kearney; Hank Price

    1999-01-01

    Technology roadmapping is a needs-driven technology planning process to help identify, select, and develop technology alternatives to satisfy a set of market needs. The DOE's Office of Power Technologies' Concentrating Solar Power (CSP) Program recently sponsored a technology roadmapping workshop for parabolic trough technology. The workshop was attended by an impressive cross section of industry and research experts. The goals of the workshop were to evaluate the market potential for trough power projects, develop a better understanding of the current state of the technology, and to develop a conceptual plan for advancing the state of parabolic trough technology. This report documents and extends the roadmap that was conceptually developed during the workshop

  17. Complex network description of the ionosphere

    Science.gov (United States)

    Lu, Shikun; Zhang, Hao; Li, Xihai; Li, Yihong; Niu, Chao; Yang, Xiaoyun; Liu, Daizhi

    2018-03-01

    Complex networks have emerged as an essential approach of geoscience to generate novel insights into the nature of geophysical systems. To investigate the dynamic processes in the ionosphere, a directed complex network is constructed, based on a probabilistic graph of the vertical total electron content (VTEC) from 2012. The results of the power-law hypothesis test show that both the out-degree and in-degree distribution of the ionospheric network are not scale-free. Thus, the distribution of the interactions in the ionosphere is homogenous. None of the geospatial positions play an eminently important role in the propagation of the dynamic ionospheric processes. The spatial analysis of the ionospheric network shows that the interconnections principally exist between adjacent geographical locations, indicating that the propagation of the dynamic processes primarily depends on the geospatial distance in the ionosphere. Moreover, the joint distribution of the edge distances with respect to longitude and latitude directions shows that the dynamic processes travel further along the longitude than along the latitude in the ionosphere. The analysis of small-world-ness indicates that the ionospheric network possesses the small-world property, which can make the ionosphere stable and efficient in the propagation of dynamic processes.

  18. Ionospheric research for space weather service support

    Science.gov (United States)

    Stanislawska, Iwona; Gulyaeva, Tamara; Dziak-Jankowska, Beata

    2016-07-01

    Knowledge of the behavior of the ionosphere is very important for space weather services. A wide variety of ground based and satellite existing and future systems (communications, radar, surveillance, intelligence gathering, satellite operation, etc) is affected by the ionosphere. There are the needs for reliable and efficient support for such systems against natural hazard and minimalization of the risk failure. The joint research Project on the 'Ionospheric Weather' of IZMIRAN and SRC PAS is aimed to provide on-line the ionospheric parameters characterizing the space weather in the ionosphere. It is devoted to science, techniques and to more application oriented areas of ionospheric investigation in order to support space weather services. The studies based on data mining philosophy increasing the knowledge of ionospheric physical properties, modelling capabilities and gain applications of various procedures in ionospheric monitoring and forecasting were concerned. In the framework of the joint Project the novel techniques for data analysis, the original system of the ionospheric disturbance indices and their implementation for the ionosphere and the ionospheric radio wave propagation are developed since 1997. Data of ionosonde measurements and results of their forecasting for the ionospheric observatories network, the regional maps and global ionospheric maps of total electron content from the navigational satellite system (GNSS) observations, the global maps of the F2 layer peak parameters (foF2, hmF2) and W-index of the ionospheric variability are provided at the web pages of SRC PAS and IZMIRAN. The data processing systems include analysis and forecast of geomagnetic indices ap and kp and new eta index applied for the ionosphere forecasting. For the first time in the world the new products of the W-index maps analysis are provided in Catalogues of the ionospheric storms and sub-storms and their association with the global geomagnetic Dst storms is

  19. A STUDY ON THE KOREAN IONOSPHERIC VARIABILITY

    Directory of Open Access Journals (Sweden)

    Seok-Hee Bae

    1992-06-01

    Full Text Available The ionosphere in accordance with solar activity can affect the transmission of radio waves. The effect of the ionosphere on the radio wave propagation are scattering of radio waves, attenuation, angle error, ranging error, and time delay. The present study is based on the Korean ionospheirc data obtained at the AnYang Radio Research Laboratory from January 1985 through October 1989. The data are analyzed to show the daily and the annual variations of the ionosphere. The data are also used to simulate the density distribution of the Korean ionosphere following the Chapman law.

  20. Ionospheric phenomena before strong earthquakes

    Directory of Open Access Journals (Sweden)

    A. S. Silina

    2001-01-01

    Full Text Available A statistical analysis of several ionospheric parameters before earthquakes with magnitude M > 5.5 located less than 500 km from an ionospheric vertical sounding station is performed. Ionospheric effects preceding "deep" (depth h > 33 km and "crust" (h 33 km earthquakes were analysed separately. Data of nighttime measurements of the critical frequencies foF2 and foEs, the frequency fbEs and Es-spread at the middle latitude station Dushanbe were used. The frequencies foF2 and fbEs are proportional to the square root of the ionization density at heights of 300 km and 100 km, respectively. It is shown that two days before the earthquakes the values of foF2 averaged over the morning hours (00:00 LT–06:00 LT and of fbEs averaged over the nighttime hours (18:00 LT–06:00 LT decrease; the effect is stronger for the "deep" earthquakes. Analysing the coefficient of semitransparency which characterizes the degree of small-scale turbulence, it was shown that this value increases 1–4 days before "crust" earthquakes, and it does not change before "deep" earthquakes. Studying Es-spread which manifests itself as diffuse Es track on ionograms and characterizes the degree of large-scale turbulence, it was found that the number of Es-spread observations increases 1–3 days before the earthquakes; for "deep" earthquakes the effect is more intensive. Thus it may be concluded that different mechanisms of energy transfer from the region of earthquake preparation to the ionosphere occur for "deep" and "crust" events.

  1. Triton's Ionosphere: Chemistry and Composition

    Science.gov (United States)

    Delitsky, Mona

    2006-09-01

    The ionosphere of Triton was observed by the Voyager spacecraft in 1989 to have a remarkably high electron density of 40,000/cc at its peak altitude. Delitsky et al. (1990) modeled this ionosphere using only N2 and CH4, the constituents of the atmosphere known at that time, and found that, at the extremely cold temperatures in the Triton atmosphere, cluster ions would form. These clusters are created when N+ or N2+ resulting from photolysis or radiolysis accrete neutral N2 molecules and form ions such as (N2+(N2)n). In these clusters, n can be very high, around 50-100, depending on temperature. Cluster ions easily sweep up electrons at the low altitudes where they form (keeping the e- content low) which leads to dissociative recombination. This neutralizes the cluster ions and releases the N2 molecules back into the atmosphere. In 1991, CO and CO2 were observed on Triton (Cruikshank et al. 1991). At Tritonian temperatures, CO will have a very high vapor pressure and could constitute up to 6% of the Triton atmosphere. Any N+ or N2+ will charge exchange with CO (and NO from chemistry) to yield CO+, NO+ and C+. These then become the core ions to the clusters (CO+(N2)n), (NO+(N2)n), or (C+(N2)n). (Delitsky et al. 1992, Delitsky, 1995). Clusters cannot form at higher altitudes and lower pressures and so at the peak altitude, the ionosphere is comprised almost totally of C+ ions. From modeling, CO + hv -> C+ (+ O) does not appear to be an important source of the C+ . Rather, the charge exchange reaction, CO+ + C -> C+ + CO produces the C+ which charge balances the electrons in the ionosphere. Ref: Cruikshank et al., BAAS, 23,1208 (1991);.. Delitsky et al. GRL, 17, 1725 (1990); ..Delitsky et al. Neptune conf, 1992; ..Delitsky, BAAS, 27, 1100 (1995)

  2. Soliton collapse during ionospheric heating

    International Nuclear Information System (INIS)

    Sheerin, J.P.; Nicholson, D.R.; Payne, G.L.; Duncan, L.M.

    1984-01-01

    We present analytical and numerical work which indicates that during ionospheric heating with high-powered hf radio waves, the oscillating two-stream instability may dominate the parametric decay instability. The oscillating two-stream instability saturates nonlinearly through the formation of solitons which undergo a collisionally damped collapse. Using the heater and radar facilities at Arecibo Observatory, we have investigated this phenomenon experimentally. Recent results from our theoretical and experimental investigations are presented

  3. Electrodynamics of the Martian Ionosphere

    Science.gov (United States)

    Ledvina, S. A.; Brecht, S. H.

    2017-12-01

    The presence of the Martian crustal magnetic fields makes a significant modification to the interaction between the solar wind/IMF and the ionosphere of the planet. This paper presents the results of 3-D hybrid simulations of Martian solar wind interaction containing the Martian crustal fields., self-consistent ionospheric chemistry and planetary rotation. It has already been reported that the addition of the crustal fields and planetary rotation makes a significant modification of the ionospheric loss from Mars, Brecht et al., 2016. This paper focuses on two other aspects of the interaction, the electric fields and the current systems created by the solar wind interaction. The results of several simulations will be analyzed and compared. The electric fields around Mars due to its interaction with the solar wind will be examined. Special attention will be paid to the electric field constituents (∇ X B, ∇Pe, ηJ). Regions where the electric field is parallel to the magnetic field will be found and the implications of these regions will be discussed. Current systems for each ion species will be shown. Finally the effects on the electric fields and the current systems due to the rotation of Mars will be examined.

  4. TRIO (Triplet Ionospheric Observatory) Mission

    Science.gov (United States)

    Lee, D.; Seon, J.; Jin, H.; Kim, K.; Lee, J.; Jang, M.; Pak, S.; Kim, K.; Lin, R. P.; Parks, G. K.; Halekas, J. S.; Larson, D. E.; Eastwood, J. P.; Roelof, E. C.; Horbury, T. S.

    2009-12-01

    Triplets of identical cubesats will be built to carry out the following scientific objectives: i) multi-observations of ionospheric ENA (Energetic Neutral Atom) imaging, ii) ionospheric signature of suprathermal electrons and ions associated with auroral acceleration as well as electron microbursts, and iii) complementary measurements of magnetic fields for particle data. Each satellite, a cubesat for ion, neutral, electron, and magnetic fields (CINEMA), is equipped with a suprathermal electron, ion, neutral (STEIN) instrument and a 3-axis magnetometer of magnetoresistive sensors. TRIO is developed by three institutes: i) two CINEMA by Kyung Hee University (KHU) under the WCU program, ii) one CINEMA by UC Berkeley under the NSF support, and iii) three magnetometers by Imperial College, respectively. Multi-spacecraft observations in the STEIN instruments will provide i) stereo ENA imaging with a wide angle in local times, which are sensitive to the evolution of ring current phase space distributions, ii) suprathermal electron measurements with narrow spacings, which reveal the differential signature of accelerated electrons driven by Alfven waves and/or double layer formation in the ionosphere between the acceleration region and the aurora, and iii) suprathermal ion precipitation when the storm-time ring current appears. In addition, multi-spacecraft magnetic field measurements in low earth orbits will allow the tracking of the phase fronts of ULF waves, FTEs, and quasi-periodic reconnection events between ground-based magnetometer data and upstream satellite data.

  5. Artificial periodic irregularities in the auroral ionosphere

    Directory of Open Access Journals (Sweden)

    M. T. Rietveld

    1996-12-01

    Full Text Available Artificial periodic irregularities (API are produced in the ionospheric plasma by a powerful standing electromagnetic wave reflected off the F region. The resulting electron-density irregularities can scatter other high-frequency waves if the Bragg scattering condition is met. Such measurements have been performed at mid-latitudes for two decades and have been developed into a useful ionospheric diagnostic technique. We report here the first measurements from a high-latitude station, using the EISCAT heating facility near Tromsø, Norway. Both F-region and lower-altitude ionospheric echoes have been obtained, but the bulk of the data has been in the E and D regions with echoes extending down to 52-km altitude. Examples of API are shown, mainly from the D region, together with simultaneous VHF incoherent-scatter-radar (ISR data. Vertical velocities derived from the rate of phase change during the irregularity decay are shown and compared with velocities derived from the ISR. Some of the API-derived velocities in the 75–115-km height range appear consistent with vertical neutral winds as shown by their magnitudes and by evidence of gravity waves, while other data in the 50–70-km range show an unrealistically large bias. For a comparison with ISR data it has proved difficult to get good quality data sets overlapping in height and time. The initial comparisons show some agreement, but discrepancies of several metres per second do not yet allow us to conclude that the two techniques are measuring the same quantity. The irregularity decay time-constants between about 53 and 70 km are compared with the results of an advanced ion-chemistry model, and height profiles of recorded signal power are compared with model estimates in the same altitude range. The calculated amplitude shows good agreement with the data in that the maximum occurs at about the same height as that of the measured amplitude. The calculated time-constant agrees very well with the

  6. Modeling, Simulation and Performance Evaluation of Parabolic Trough

    African Journals Online (AJOL)

    Mekuannint

    Mekuannint Mesfin and Abebayehu Assefa. Department of Mechanical Engineering. Addis Ababa University ... off design weather conditions as well. Keywords: Parabolic Trough Collector (PTC);. Heat Transfer ... of a conventional Rankine cycle power plant with solar fields that are used to increase the temperature of heat ...

  7. Modeling, Simulation and Performance Evaluation of Parabolic Trough

    African Journals Online (AJOL)

    Mekuannint

    Heat Transfer Fluid (HTF); TRNSYS power plant model; STEC library; Solar Advisor Model (SAM);. TRNSYS solar field model; Solar Electric. Generation System (SEGS). INTRODUCTION. Parabolic troughs are currently most used means of power generation option of solar sources. Solar electric generation systems (SEGs) ...

  8. Strawberry Production in Soilless Substrate Troughs – Plant Growth

    Science.gov (United States)

    Soilless substrates made of peat moss, coconut coir, perlite, rockwool or bark are pathogen free and they have been used in strawberry production in Europe in troughs or containers. Open field strawberry production in soilless substrate is new to California growers. The objective of this study was t...

  9. Optimized molten salt receivers for ultimate trough solar fields

    Science.gov (United States)

    Riffelmann, Klaus-J.; Richert, Timo; Kuckelkorn, Thomas

    2016-05-01

    Today parabolic trough collectors are the most successful concentrating solar power (CSP) technology. For the next development step new systems with increased operation temperature and new heat transfer fluids (HTF) are currently developed. Although the first power tower projects have successfully been realized, up to now there is no evidence of an all-dominant economic or technical advantage of power tower or parabolic trough. The development of parabolic trough technology towards higher performance and significant cost reduction have led to significant improvements in competitiveness. The use of molten salt instead of synthetic oil as heat transfer fluid will bring down the levelized costs of electricity (LCOE) even further while providing dispatchable energy with high capacity factors. FLABEG has developed the Ultimate TroughTM (UT) collector, jointly with sbp Sonne GmbH and supported by public funds. Due to its validated high optical accuracy, the collector is very suitable to operate efficiently at elevated temperatures up to 550 °C. SCHOTT will drive the key-innovations by introducing the 4th generation solar receiver that addresses the most significant performance and cost improvement measures. The new receivers have been completely redesigned to provide a product platform that is ready for high temperature operation up to 550 °C. Moreover distinct product features have been introduced to reduce costs and risks in solar field assembly and installation. The increased material and design challenges incurred with the high temperature operation have been reflected in sophisticated qualification and validation procedures.

  10. Parabolic Trough Solar Power for Competitive U.S. Markets

    International Nuclear Information System (INIS)

    Price, Henry W.

    1998-01-01

    Nine parabolic trough power plants located in the California Mojave Desert represent the only commercial development of large-scale solar power plants to date. Although all nine plants continue to operate today, no new solar power plants have been completed since 1990. Over the last several years, the parabolic trough industry has focused much of its efforts on international market opportunities. Although the power market in developing countries appears to offer a number of opportunities for parabolic trough technologies due to high growth and the availability of special financial incentives for renewables, these markets are also plagued with many difficulties for developers. In recent years, there has been some renewed interest in the U.S. domestic power market as a result of an emerging green market and green pricing incentives. Unfortunately, many of these market opportunities and incentives focus on smaller, more modular technologies (such as photovoltaics or wind power), and as a result they tend to exclude or are of minimum long-term benefit to large-scale concentrating solar power technologies. This paper looks at what is necessary for large-scale parabolic trough solar power plants to compete with state-of-the-art fossil power technology in a competitive U.S. power market

  11. Gravity Anomalies Over The Gongola Arm, Upper Benue Trough ...

    African Journals Online (AJOL)

    A regional gravity survey of the Gongola Arm of the Benue trough was carried out with the aim of determining structures of interest. The results of the gravity interpretation showed that the area of study is characterized by negative Bouguer anomalies that trend in the NE-SW direction and range in value from -75 to -15 mGal ...

  12. The crustal structure along the Mbere trough in South Adamawa ...

    African Journals Online (AJOL)

    The Mbere Cretaceous trough is located in the southern part of the Adamawa province. A gravity interpretation based on data obtained from three NW-SE profiles on the residual anomaly map has been carried out using a 2.5D modelling program. Spectral analysis has been used to estimate the depth of geological ...

  13. Inversion tectonics of the benue trough | Mamah | Global Journal of ...

    African Journals Online (AJOL)

    Spreading was, however, arrested by the rotation of the hot spot plumes onto the shoulders of the trough such as unto the Cameroom volcanic line by a sequence of events including crustal thinning and doming, rifting and faulting, grabens and horst formation, volcanism and subsidence, imbricate sedimentation and ...

  14. Gas Turbine/Solar Parabolic Trough Hybrid Designs: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Turchi, C. S.; Ma, Z.; Erbes, M.

    2011-03-01

    A strength of parabolic trough concentrating solar power (CSP) plants is the ability to provide reliable power by incorporating either thermal energy storage or backup heat from fossil fuels. Yet these benefits have not been fully realized because thermal energy storage remains expensive at trough operating temperatures and gas usage in CSP plants is less efficient than in dedicated combined cycle plants. For example, while a modern combined cycle plant can achieve an overall efficiency in excess of 55%; auxiliary heaters in a parabolic trough plant convert gas to electricity at below 40%. Thus, one can argue the more effective use of natural gas is in a combined cycle plant, not as backup to a CSP plant. Integrated solar combined cycle (ISCC) systems avoid this pitfall by injecting solar steam into the fossil power cycle; however, these designs are limited to about 10% total solar enhancement. Without reliable, cost-effective energy storage or backup power, renewable sources will struggle to achieve a high penetration in the electric grid. This paper describes a novel gas turbine / parabolic trough hybrid design that combines solar contribution of 57% and higher with gas heat rates that rival that for combined cycle natural gas plants. The design integrates proven solar and fossil technologies, thereby offering high reliability and low financial risk while promoting deployment of solar thermal power.

  15. Magnetotail processes and their ionospheric signatures

    Science.gov (United States)

    Ferdousi, B.; Raeder, J.; Zesta, E.; Murphy, K. R.; Cramer, W. D.

    2017-12-01

    In-situ observations in the magnetotail are sparse and limited to single point measurements. In the ionosphere, on the other hand, there is a broad range of observations, including magnetometers, auroral imagers, and various radars. Since the ionosphere is to some extent a mirror of plasmasheet processes it can be used as a monitor of magnetotail dynamics. Thus, it is of great importance to understand the coupling between the ionosphere and the magnetosphere in order to properly interpret the ionosphere and ground observations in terms of magnetotail dynamics. For this purpose, the global magnetohydrodynamic model OpenGGCM is used to investigate magnetosphere-ionosphere coupling. One of the key processes in magnetotail dynamics are bursty bulk flows (BBFs) which are the major means by which momentum and energy get transferred through the magnetotail and down to the ionosphere. BBFs often manifested in the ionosphere as auroral streamers. This study focuses on mapping such flow bursts from the magnetotail to the ionosphere along the magnetic field lines for three states of the magnetotail: pre-substorm onset through substorm expansion and during steady magnetospheric convection (SMC) following the substorm. We find that the orientation of streamers in the ionosphere differes for different local times, and that, for both tail and ionospheric signatures, activity increases during the SCM configutation compared to the pre-onset and quiet times. We also find that the background convection in the tail impacts the direction and deflection of the BBFs and the subsequent orientation of the auroral streamers in the ionosphere.

  16. Shear Alfven Wave Injection in the Magnetosphere by Ionospheric Modifications in the Absence of Electrojet Currents

    Science.gov (United States)

    Papadopoulos, K.; Eliasson, B.; Shao, X.; Labenski, J.; Chang, C.

    2011-12-01

    A new concept of generating ionospheric currents in the ULF/ELF range with modulated HF heating using ground-based transmitters even in the absence of electrojet currents is presented. The new concept relies on using HF heating of the F-region to modulate the electron temperature and has been given the name Ionospheric Current Drive (ICD). In ICD, the pressure gradient associated with anomalous or collisional F-region electron heating drives a local diamagnetic current that acts as an antenna to inject mainly Magneto-Sonic (MS) waves in the ionospheric plasma. The electric field associated with the MS wave drives Hall currents when it reaches the E region of the ionosphere. The Hall currents act as a secondary antenna that inject waves in the Earth-Ionosphere Waveguide (EIW) below and shear Alfven waves or EMIC waves upwards towards the conjugate regions. The paper presents: (i) Theoretical results using a cold Hall MHD model to study ICD and the generation of ULF/ELF waves by the modulation of the electron pressure at the F2-region with an intense HF electromagnetic wave. The model solves equations governing the dynamics of the shear Alfven and magnetosonic modes, of the damped modes in the diffusive Pedersen layer, and of the weakly damped helicon wave mode in the Hall-dominated E-region. The model incorporates realistic profile of the ionospheric conductivities and magnetic field configuration. We use the model to simulate propagation and dynamics of the low-frequency waves and their injection into the magnetosphere from the HAARP and Arecibo ionospheric heaters. (ii) Proof of principle experiments using the HAARP ionospheric heater in conjunction with measurements by the DEMETER satellite This work is supported by ONR MURI grant and DARPA BRIOCHE Program

  17. Formation of dipole vortex in the ionosphere

    International Nuclear Information System (INIS)

    Shukla, P.K.; Yu, M.Y.

    1985-01-01

    It is shown that isolated dipole vortices can exist in the F-region of the ionosphere. These are associated with the Rayleigh-Taylor and E x B 0 gradient drift instabilities. The vortices may be responsible for the rapid structuring of barium clouds as well as other phenomena observed in the upper ionosphere

  18. Artificial neural network applications in ionospheric studies

    Directory of Open Access Journals (Sweden)

    L. R. Cander

    1998-06-01

    Full Text Available The ionosphere of Earth exhibits considerable spatial changes and has large temporal variability of various timescales related to the mechanisms of creation, decay and transport of space ionospheric plasma. Many techniques for modelling electron density profiles through entire ionosphere have been developed in order to solve the "age-old problem" of ionospheric physics which has not yet been fully solved. A new way to address this problem is by applying artificial intelligence methodologies to current large amounts of solar-terrestrial and ionospheric data. It is the aim of this paper to show by the most recent examples that modern development of numerical models for ionospheric monthly median long-term prediction and daily hourly short-term forecasting may proceed successfully applying the artificial neural networks. The performance of these techniques is illustrated with different artificial neural networks developed to model and predict the temporal and spatial variations of ionospheric critical frequency, f0F2 and Total Electron Content (TEC. Comparisons between results obtained by the proposed approaches and measured f0F2 and TEC data provide prospects for future applications of the artificial neural networks in ionospheric studies.

  19. Ionospheric Anomaly before Kyushu|Japan Earthquake

    Directory of Open Access Journals (Sweden)

    YANG Li

    2017-05-01

    Full Text Available GIM data released by IGS is used in the article and a new method of combining the Sliding Time Window Method and the Ionospheric TEC correlation analysis method of adjacent grid points is proposed to study the relationship between pre-earthquake ionospheric anomalies and earthquake. By analyzing the abnormal change of TEC in the 5 grid points around the seismic region, the abnormal change of ionospheric TEC is found before the earthquake and the correlation between the TEC sequences of lattice points is significantly affected by earthquake. Based on the analysis of the spatial distribution of TEC anomaly, anomalies of 6 h, 12 h and 6 h were found near the epicenter three days before the earthquake. Finally, ionospheric tomographic technology is used to do tomographic inversion on electron density. And the distribution of the electron density in the ionospheric anomaly is further analyzed.

  20. ACCOUNTING INFORMATION INTEGRATION TROUGH AN ENTERPRISE PORTAL

    Directory of Open Access Journals (Sweden)

    Gianina RIZESCU

    2014-06-01

    Full Text Available If companies are lacking integrated enterprise software applications, or they simply do not use them on a large scale, accounting departments have to face lots of difficulties, concerning both the inflexibility in achieving good results and the limited possibility of communicating these results. Thus, most times, accounting departments are limited to generating predefined reports provided by a software application and the most they can do is export these reports into Microsoft Excel. Another cause which leads to late obtaining and publishing of accounting information is the lack of data from other departments and their corresponding software applications. That is why, in many enterprises, accounting data becomes irrelevant for the users. The main goal of this article is to show how accounting can benefit from an integrated software solution, namely an enterprise portal.

  1. Whistlers and related ionospheric phenomena

    CERN Document Server

    Helliwell, Robert A

    2006-01-01

    The investigation of whistlers and related phenomena is a key element in studies of very-low-frequency propagation, satellite communication, the outer ionosphere, and solar-terrestrial relationships. This comprehensive text presents a history of the study of the phenomena and includes all the elements necessary for the calculation of the characteristics of whistlers and whistler-mode signals.An introduction and brief history are followed by a summary of the theory of whistlers and a detailed explanation of the calculation of their characteristics. Succeeding chapters offer a complete atlas of

  2. The role of meltwater in high-latitude trough-mouth fan development : the Disko Trough-Mouth Fan, West Greenland.

    OpenAIRE

    Cofaigh, Colm Ó.; Hogan, Kelly A.; Jennings, Anne E.; Callard, S. Louise; Dowdeswell, Julian A.; Noormets, Riko; Evans, Jeff

    2018-01-01

    The Disko Trough-Mouth Fan (TMF) is a major submarine sediment fan located along the central west Greenland continental margin offshore of Disko Trough. The location of the TMF at the mouth of a prominent cross-shelf trough indicates that it is a product of repeated glacigenic sediment delivery from former fast-flowing outlets of the Greenland Ice Sheet, including an ancestral Jakobshavn Isbrae, which expanded to the shelf edge during successive glacial cycles. This study focuses on the upper...

  3. Towards to Resilience Science -Research on the Nankai trough seismogenic zone-

    Science.gov (United States)

    Kaneda, Yoshiyuki; Shiraki, Wataru; Fujisawa, Kazuhito; Tokozakura, Eiji

    2017-04-01

    For the last few decades, many destructive earthquakes and tsunamis occurred in the world. Based on lessons learnt from 2004 Sumatra Earthquake/Tsunamis, 2010 Chilean Earthquake/Tsunami and 2011 East Japan Earthquake/Tsunami, we recognized the importance of real time monitoring on Earthquakes and Tsunamis for disaster mitigation. Recently, Kumamoto Earthquake occurred in 2006. This destructive Earthquake indicated that multi strong motions including pre shock and main shock generated severe earthquake damages buildings. Furthermore, we recognize recovers/ revivals are very important and difficult. In Tohoku area damaged by large tsunamis, recovers/revivals have been under progressing after over 5 years passed after the 2011 Tohoku Earthquake. Therefore, we have to prepare the pre plan before next destructive disasters such as the Nankai trough mega thrust earthquake. As one of disaster countermeasures, we would like to propose that Disaster Mitigation Science. This disaster mitigation science is including engineering, science, medicine and social science such as sociology, informatics, law, literature, art, psychology etc. For Urgent evacuations, there are some kinds of real time monitoring system such as Dart buoy and ocean floor network. Especially, the real time monitoring system using multi kinds of sensors such as the accelerometer, broadband seismometer, pressure gauge, difference pressure gauge, hydrophone and thermometer is indispensable for Earthquakes/ Tsunamis monitoring. Furthermore, using multi kind of sensors, we can analyze and estimate broadband crustal activities around mega thrust earthquake seismogenic zones. Therefore, we deployed DONET1 and DONET2 which are dense ocean floor networks around the Nankai trough Southwestern Japan. We will explain about Resilience Science and real time monitoring systems around the Nankai trough seismogenic zone.

  4. The ionospheric eclipse factor method (IEFM) and its application to determining the ionospheric delay for GPS

    Science.gov (United States)

    Yuan, Y.; Tscherning, C. C.; Knudsen, P.; Xu, G.; Ou, J.

    2008-01-01

    A new method for modeling the ionospheric delay using global positioning system (GPS) data is proposed, called the ionospheric eclipse factor method (IEFM). It is based on establishing a concept referred to as the ionospheric eclipse factor (IEF) λ of the ionospheric pierce point (IPP) and the IEF’s influence factor (IFF) bar{λ}. The IEF can be used to make a relatively precise distinction between ionospheric daytime and nighttime, whereas the IFF is advantageous for describing the IEF’s variations with day, month, season and year, associated with seasonal variations of total electron content (TEC) of the ionosphere. By combining λ and bar{λ} with the local time t of IPP, the IEFM has the ability to precisely distinguish between ionospheric daytime and nighttime, as well as efficiently combine them during different seasons or months over a year at the IPP. The IEFM-based ionospheric delay estimates are validated by combining an absolute positioning mode with several ionospheric delay correction models or algorithms, using GPS data at an international Global Navigation Satellite System (GNSS) service (IGS) station (WTZR). Our results indicate that the IEFM may further improve ionospheric delay modeling using GPS data.

  5. Shaping of an ion cloud's velocity field by differential braking due to Alfven wave dissipation in the ionosphere, 1. Coupling with an infinite ionosphere

    International Nuclear Information System (INIS)

    Nalesso, G.F.; Jacobson, A.R.

    1988-01-01

    We study the interaction of a plasma cloud, jetting across the geomagnetic field with the surrounding ionosphere. The cloud is assumed of finite extension in the direction normal to both the direction of motion and the magnetic field, while the ionosphere is considered a collisional anisotropic magnetized plasma. It is shown that two main mechanisms contribute to the cloud's braking: momentum exchange with the ionosphere via Alfven waves and momentum dissipation due to resistive currents. Due to the finite size of the cloud a differential braking of the different transverse harmonics of the Alfven wave appears when the momentum exchange mechanism is dominant. The result is a sharpening of the cloud's velocity field. copyright American Geophysical Union 1988

  6. Main Memory

    NARCIS (Netherlands)

    P.A. Boncz (Peter); L. Liu (Lei); M. Tamer Özsu

    2008-01-01

    htmlabstractPrimary storage, presently known as main memory, is the largest memory directly accessible to the CPU in the prevalent Von Neumann model and stores both data and instructions (program code). The CPU continuously reads instructions stored there and executes them. It is also called Random

  7. Absorber Alignment Measurement Tool for Solar Parabolic Trough Collectors: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Stynes, J. K.; Ihas, B.

    2012-04-01

    As we pursue efforts to lower the capital and installation costs of parabolic trough solar collectors, it is essential to maintain high optical performance. While there are many optical tools available to measure the reflector slope errors of parabolic trough solar collectors, there are few tools to measure the absorber alignment. A new method is presented here to measure the absorber alignment in two dimensions to within 0.5 cm. The absorber alignment is measured using a digital camera and four photogrammetric targets. Physical contact with the receiver absorber or glass is not necessary. The alignment of the absorber is measured along its full length so that sagging of the absorber can be quantified with this technique. The resulting absorber alignment measurement provides critical information required to accurately determine the intercept factor of a collector.

  8. Wave--particle interactions in the magnetosphere and ionosphere

    International Nuclear Information System (INIS)

    Thorne, R.M.

    1975-01-01

    Two distinct aspects of the interaction between waves and particles in the earth's magnetosphere and ionosphere were discussed at the Yosemite Conference on Magnetosphere-Ionosphere Coupling; these will be briefly reviewed. Intense field-aligned currents flow between the ionosphere and magnetosphere at auroral latitudes. Under certain conditions these currents can become unstable, permitting potential drops to be established along the field lines. The present status of experimental evidence favoring such parallel electric fields is somewhat controversial. Theoretical models for their origin invoke regions of anomalous resistivity or electrostatic double layers. To date it is impossible to distinguish between these alternatives on the basis of experimental data. The nonadiabatic behavior of magnetospheric ring current particles during geomagnetic storms is largely controlled by wave-particle processes. During the storm main phase, intense fluctuating convection electric fields are responsible for injecting trapped particles into the outer radiation zone. The outer radiation zone also moves in closer to the earth following the storm time compression of the plasmapause. Simultaneous pitch angle scattering by higher-frequency plasma turbulence causes precipitation loss near the strong diffusion limit throughout the outer magnetosphere. During the storm recov []ry phase the plasmapause slowly moves out toward its prestorm location; energetic particle loss at such times appears to be dominated by cyclotron resonant scattering from electromagnetic turbulence. (auth)

  9. Aerosols: The key to understanding Titan's lower ionosphere

    Science.gov (United States)

    Molina-Cuberos, G. J.; Cardnell, S.; García-Collado, A. J.; Witasse, O.; López-Moreno, J. J.

    2018-04-01

    The Permittivity Wave and Altimetry system on board the Huygens probe observed an ionospheric hidden layer at a much lower altitude than the main ionosphere during its descent through the atmosphere of Titan, the largest satellite of Saturn. Previous studies predicted a similar ionospheric layer. However, neither previous nor post-Huygens theoretical models have been able to reproduce the measurements of the electrical conductivity and charge densities reported by the Mutual Impedance (MI) and Relaxation Probe (RP) sensors. The measurements were made from an altitude of 140 km down to the ground and show a maximum of charge densities of ≈ 2 ×109 m-3 positive ions and ≈ 450 ×106 m-3 electrons at approximately 65 km. Such a large difference between positive and negative charge densities has not yet been understood. Here, by making use of electron and ion capture processes in to aerosols, we are able to model both electron and positive ion number densities and to reconcile experimental data and model results.

  10. Ionospheric modification and parametric instabilities

    International Nuclear Information System (INIS)

    Fejer, J.A.

    1979-01-01

    Thresholds and linear growth rates for stimulated Brillouin and Raman scattering and for the parametric decay instability are derived by using arguments of energy transfer. For this purpose an expression for the ponderomotive force is derived. Conditions under which the partial pressure force due to differential dissipation exceeds the ponderomotive force are also discussed. Stimulated Brillouin and Raman scattering are weakly excited by existing incoherent backscatter radars. The parametric decay instability is strongly excited in ionospheric heating experiments. Saturation theories of the parametric decay instability are therefore described. After a brief discussion of the purely growing instability the effect of using several pumps is discussed as well as the effects of inhomogenicity. Turning to detailed theories of ionospheric heating, artificial spread F is discussed in terms of a purely growing instability where the nonlinearity is due to dissipation. Field-aligned short-scale striations are explained in terms of dissipation of the parametrically excited Langmuir waves (plasma oscillations): they might be further amplified by an explosive instability (except the magnetic equator). Broadband absorption is probably responsible for the 'overshoot' effect: the initially observed level of parametrically excited Langmuir waves is much higher than the steady state level

  11. Theoretical Study of the Compound Parabolic Trough Solar Collector

    OpenAIRE

    Dr. Subhi S. Mahammed; Dr. Hameed J. Khalaf; Tadahmun A. Yassen

    2012-01-01

    Theoretical design of compound parabolic trough solar collector (CPC) without tracking is presented in this work. The thermal efficiency is obtained by using FORTRAN 90 program. The thermal efficiency is between (60-67)% at mass flow rate between (0.02-0.03) kg/s at concentration ratio of (3.8) without need to tracking system.The total and diffused radiation is calculated for Tikrit city by using theoretical equations. Good agreement between present work and the previous work.

  12. Modular Trough Power Plant Cycle and Systems Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Price, H.; Hassani, V.

    2002-01-01

    This report summarizes an analysis to reduce the cost of power production from modular concentrating solar power plants through a relatively new and exciting concept that merges two mature technologies to produce distributed modular electric power in the range of 500 to 1,500 kWe. These are the organic Rankine cycle (ORC) power plant and the concentrating solar parabolic (CSP) trough technologies that have been developed independent of each other over many years.

  13. The sharp peak-flat trough pattern and critical speculation

    OpenAIRE

    Roehner, B. M.; Sornette, D.

    1998-01-01

    We find empirically a characteristic sharp peak-flat trough pattern in a large set of commodity prices. We argue that the sharp peak structure reflects an endogenous inter-market organization, and that peaks may be seen as local ``singularities'' resulting from imitation and herding. These findings impose a novel stringent constraint on the construction of models. Intermittent amplification is not sufficient and nonlinear effects seem necessary to account for the observations.

  14. Analysis of Earthquake Source Spectra in Salton Trough

    Science.gov (United States)

    Chen, X.; Shearer, P. M.

    2009-12-01

    Previous studies of the source spectra of small earthquakes in southern California show that average Brune-type stress drops vary among different regions, with particularly low stress drops observed in the Salton Trough (Shearer et al., 2006). The Salton Trough marks the southern end of the San Andreas Fault and is prone to earthquake swarms, some of which are driven by aseismic creep events (Lohman and McGuire, 2007). In order to learn the stress state and understand the physical mechanisms of swarms and slow slip events, we analyze the source spectra of earthquakes in this region. We obtain Southern California Seismic Network (SCSN) waveforms for earthquakes from 1977 to 2009 archived at the Southern California Earthquake Center (SCEC) data center, which includes over 17,000 events. After resampling the data to a uniform 100 Hz sample rate, we compute spectra for both signal and noise windows for each seismogram, and select traces with a P-wave signal-to-noise ratio greater than 5 between 5 Hz and 15 Hz. Using selected displacement spectra, we isolate the source spectra from station terms and path effects using an empirical Green’s function approach. From the corrected source spectra, we compute corner frequencies and estimate moments and stress drops. Finally we analyze spatial and temporal variations in stress drop in the Salton Trough and compare them with studies of swarms and creep events to assess the evolution of faulting and stress in the region. References: Lohman, R. B., and J. J. McGuire (2007), Earthquake swarms driven by aseismic creep in the Salton Trough, California, J. Geophys. Res., 112, B04405, doi:10.1029/2006JB004596 Shearer, P. M., G. A. Prieto, and E. Hauksson (2006), Comprehensive analysis of earthquake source spectra in southern California, J. Geophys. Res., 111, B06303, doi:10.1029/2005JB003979.

  15. Morphotectonics of the central Muertos thrust belt and Muertos Trough (northeastern Caribbean)

    Science.gov (United States)

    Granja, Bruna J.L.; ten Brink, Uri S.; Carbó-Gorosabel, Andrés; Muñoz-Martín, A.; Gomez, Ballesteros M.

    2009-01-01

    Multibeam bathymetry data acquired during the 2005 Spanish R/V Hesp??rides cruise and reprocessed multichannel seismic profiles provide the basis for the analysis of the morphology and deformation in the central Muertos Trough and Muertos thrust belt. The Muertos Trough is an elongated basin developed where the Venezuelan Basin crust is thrusted under the Muertos fold-and-thrust belt. Structural variations along the Muertos Trough are suggested to be a consequence of the overburden of the asymmetrical thrust belt and by the variable nature of the Venezuelan Basin crust along the margin. The insular slope can be divided into three east-west trending slope provinces with high lateral variability which correspond to different accretion stages: 1) The lower slope is composed of an active sequence of imbricate thrust slices and closed fold axes, which form short and narrow accretionary ridges and elongated slope basins; 2) The middle slope shows a less active imbricate structure resulting in lower superficial deformation and bigger slope basins; 3) The upper slope comprises the talus region and extended terraces burying an island arc basement and an inactive imbricate structure. The talus region is characterized by a dense drainage network that transports turbidite flows from the islands and their surrounding carbonate platform areas to the slope basins and sometimes to the trough. In the survey area the accommodation of the ongoing east-west differential motion between the Hispaniola and the Puerto Rico-Virgin Islands blocks takes place by means of diffuse deformation. The asymmetrical development of the thrust belt is not related to the geological conditions in the foreland, but rather may be caused by variations in the geometry and movement of the backstop. The map-view curves of the thrust belt and the symmetry of the recesses suggest a main north-south convergence along the Muertos margin. The western end of the Investigator Fault Zone comprises a broad band of

  16. Ion escape fluxes from the terrestrial high-latitude ionosphere

    International Nuclear Information System (INIS)

    Barakat, A.R.; Schunk, R.W.; Moore, T.E.; Waite, J.H. Jr.

    1987-01-01

    The coupled continuity and momentum equations for H + , O + , and electrons were solved for the terrestrial ionosphere in order to determine the limiting ion escape fluxes at high latitudes. The effects of solar cycle, season, geomagnetic activity, and the altitude of the acceleration region on the ion escape fluxes were studied for average conditions. In addition, a systematic parameter study was conducted to determine the extent to which variations in ionospheric conditions (for example, electron temperature, ion temperature, induced vertical ion drifts, etc.) can affect the results. The main conclusions of the study are as follows: (1) as solar activity increases, the general trend is for an increase in the limiting O + escape flux and a decrease in the limiting H + escape flux; (2) in winter the limiting escape fluxes of both O + and H + are larger than those in summer, particularly for low geomagnetic activity; (3) the O + content of the ion outflow increases with increasing ''demand'' imposed on the ionosphere by a high-altitude acceleration process, with increasing solar activity, with increasing geomagnetic activity, with increasing solar elevation from winter to summer, and with a lowering of the altitude of the acceleration region; (4) when H + is in a near-diffusive equilibrium state and a selective mechanism accelerates O + , the limiting O + escape flux is significantly reduced compared to that obtained when an H + outflow also occurs; and (5) at a given time or location the general trends described above can be significantly modified or even reversed owing to natural variations of the ionospheric ion and electron temperatures, induced vertical ion drifts, etc. The general trends obtained for average conditions appear to mimic the qualitative behavior determined from statistically averaged data for comparable absolute escape flux magnitudes

  17. Holocene tephra deposits in the northern Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The mineralogical and geochemical characteristics of sediments of Core CSH1, which was collected from the northern Okinawa Trough, indicate that large amounts of volcanic materials have deposited in the northern Okinawa Trough during the Holocene. On the basis of down-core variations in mineral and element contents of sediments, two layers in the uppermost section of Core CSH1 characterized by high quartz, Na2O, MnO, K2O, uranium contents and low contents of clay minerals, volatiles, Fe2O3, MgO, CaO and strontium, have been identified as the tephra deposits. Systematic grain-size measurements also suggest that sediments from the northern Okinawa Trough are made up of terrigenous materials and volcanic ashes with different proportion during the Holocene. The sediments of tephra layers in Core CSH1 show bi-modal patterns in grain-size distribution with modal grain-sizes of 74.3 and 7.81 μm,respectively. According to the radiocarbon dating on shells of zooplankton foraminifera, two tephra layers in Core CSH1, formed at 7 250 and 10 870 a BP (cal), approximately correspond to the K-Ah tephra [7 300 a BP (cal)] and the eruption of Kuju Volcano (12~10 ka BP), respectively.

  18. Chronostratigraphy and deposition rates in the Okinawa Trough region

    Institute of Scientific and Technical Information of China (English)

    李培英; 王永吉; 刘振夏

    1999-01-01

    Six representative cores from Okinawa Trough have been dated using AMS 14C, Standard 14C and ESR methods, and comparatively analysed. Systematic measurements of the oriented samples taken from the cores were conducted for obtaining their remnant magnetic polarity. With the aid of the dates obtained, particularly the AMS 14C ages of planktonic foraminiferal tests, two polarity events and two polar wanderings of the earth magnetic field have been defined. Calculations of the deposition rates for all the six core sites indicate rather high values in the trough plain, at least equivalent to those rates reported for the region of the East China Sea. They commonly range from 10 to 30 cm/ka, and even greater than 40 cm/ka in some localities. The deposition rate varied widely with topography and periods of time. In general, it is greater during the postglacial period than during the last glaciation. The chronostratigraphy in the Okinawa Trough region established through this study argues against the pr

  19. Full parabolic trough qualification from prototype to demonstration loop

    Science.gov (United States)

    Janotte, Nicole; Lüpfert, Eckhard; Pottler, Klaus; Schmitz, Mark

    2017-06-01

    On the example of the HelioTrough® collector development the full accompanying and supporting qualification program for large-scale parabolic trough collectors for solar thermal power plants is described from prototype to demonstration loop scale. In the evaluation process the actual state and the optimization potential are assessed. This includes the optical and geometrical performance determined by concentrator shape, deformation, assembly quality and local intercept factor values. Furthermore, its mechanical performance in terms of tracking accuracy and torsional stiffness and its thermal system performance on the basis of the overall thermal output and heat loss are evaluated. Demonstration loop tests deliver results of collector modules statistical slope deviation of 1.9 to 2.6 mrad, intercept factor above 98%, peak optical performance of 81.6% and heat loss coefficients from field tests. The benefit of such a closely monitored development lies in prompt feedback on strengths, weaknesses and potential improvements on the new product at any development stage from first module tests until demonstration loop evaluation. The product developer takes advantage of the achieved technical maturity, already before the implementation in a commercial power plant. The well-understood performance characteristics allow the reduction of safety margins making the new HelioTrough collector competitive from the start.

  20. Humidification dehumidification desalination system using parabolic trough solar air collector

    International Nuclear Information System (INIS)

    Al-Sulaiman, Fahad A.; Zubair, M. Ifras; Atif, Maimoon; Gandhidasan, Palanichamy; Al-Dini, Salem A.; Antar, Mohamed A.

    2015-01-01

    This paper deals with a detailed thermodynamic analysis to assess the performance of an HDH system with an integrated parabolic trough solar collector (PTSC). The HDH system considered is an open air, open water, air heated system that uses a PTSC as an air heater. Two different configurations were considered of the HDH system. In the first configuration, the solar air heater was placed before the humidifier whereas in the second configuration the solar air heater was placed between the humidifier and the dehumidifier. The current study revealed that PTSCs are well suited for air heated HDH systems for high radiation location, such as Dhahran, Saudi Arabia. The comparison between the two HDH configurations demonstrates that the gained output ratio (GOR) of the first configuration is, on average, about 1.5 whereas for the second configuration the GOR increases up to an average value of 4.7. The study demonstrates that the HDH configuration with the air heater placed between the humidifier and the dehumidifier has a better performance and a higher productivity. - Highlights: • Thermodynamic analysis of an HDH system driven by a parabolic trough solar collector was conducted. • The first configuration reveals a GOR of 1.5 while the second configuration reveals a GOR of 4.7. • Effective heating of the HDH system was obtained through parabolic trough solar collector

  1. Noble gas and carbon isotopes in Mariana Trough basalt glasses

    International Nuclear Information System (INIS)

    Bernard, M.; Jambon, A.; Gamo, T.; Nishio, Y.; Sano, Y.

    1998-01-01

    Noble gas elemental and isotopic compositions have been measured as well as the abundance of C and its isotopic ratios in 11 glasses from submarine pillow basalts collected from the Mariana Trough. The 3 He/ 4 He ratios of 8.22 and 8.51 R atm of samples dredged from the central Mariana Trough (similar18N) agree well with that of the Mid-Ocean Ridge Basalt (MORB) glasses (8.4±0.3 R atm ), whereas a mean ratio of 8.06±0.35 R atm in samples from the northern Mariana Trough (similar20N) is slightly lower than those of MORB. One sample shows apparent excess of 20 Ne and 21 Ne relative to atmospheric Ne, suggesting incorporation of solar-type Ne in the magma source. There is a positive correlation between 3 He/ 4 He and 40 Ar/ 36 Ar ratios, which may be explained by mixing between MORB-type and atmospheric noble gases. Excess 129 Xe is observed in the sample which also shows 20 Ne and 21 Ne excesses. Observed δ 13 C values of similar20N samples vary from -3.76 per thousand to -2.80 per thousand, and appear higher than those of MORB, and the corresponding CO 2 / 3 He ratios are higher than those of MARA samples at similar18N, suggesting C contribution from the subducted slab. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  2. Main Memory

    OpenAIRE

    Boncz, Peter; Liu, Lei; Özsu, M.

    2008-01-01

    htmlabstractPrimary storage, presently known as main memory, is the largest memory directly accessible to the CPU in the prevalent Von Neumann model and stores both data and instructions (program code). The CPU continuously reads instructions stored there and executes them. It is also called Random Access Memory (RAM), to indicate that load/store instructions can access data at any location at the same cost, is usually implemented using DRAM chips, which are connected to the CPU and other per...

  3. Isotopic feature and uranium dating of the volcanic rocks in the Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Volcanic rocks from the northern and middle Okinawa Trough were dated by uranium-series dating method. Differential fractions using magnetic procedure were designed to separate samples. New report on the ages and isotopic data of rocks in the northern trough (especially black pumice) was discussed. Based on the uranium dates and Sr-Nd isotopic ratio, magmatic evolution process of the Okinawa Trough was noted. Firstly, there have been wide silicic volcanic activities in the Okinawa Trough from late Pleistocene to present, and the volcanic rocks can be divided into three subgroups. Secondly, magma generally came from PREMA source area under the Okinawa Trough. Magmatic evolution in the northern trough was similar to the middle, but different to the south. Finally, volcanic activities indicated that opening of the southern Okinawa Trough did not happen due to the collision between Luson Arc and Eurasian Plate until the early Pleistocene.

  4. Seismo-ionospheric anomalies and implications from recent GNSS observations in India and South-East Asia

    Directory of Open Access Journals (Sweden)

    C.D. Reddy

    2016-01-01

    Full Text Available The lithosphere and the atmosphere/ionosphere, continuously exchange energy through various coupling mechanisms. Earthquake creates waves of energy, e.g. direct shock acoustic waves (SAWs and Rayleigh wave induced acoustic waves (RAWs. In the event of an earthquake occurring beneath the sea, atmospheric gravity waves (AGWs are also generated. If the earthquake is large enough (Mw > 6, SAWs, RAWs and AGWs induce detectable ionospheric plasma perturbations. Inferring the seismological information from these seismo-ionospheric manifestations is the subject that pertains to ionospheric seismology. Both ground and satellite based advanced radio techniques are being used in monitoring ionospheric plasma perturbations. In this study, seismo-ionospheric anomalies and implications from recent GNSS observations in India and South-East Asia are discussed, mainly pertaining to the following. (1 From the ionospheric plasma response to 2015 Nepal earthquake, the estimated group velocity for Andaman and Indian shield regions are 2100 ms−1 and 3900 ms−1 respectively and validated from ground measurements. (2 Atmospheric acoustic resonance at 4.0 mHz and a train of wave packet of TEC variation resulting from the beat phenomenon observed at the site ‘umlh’ and (3 GNSS-based tsunami warning which is going to be promising tool in augmenting the existing tsunami warning systems.

  5. The Evidence from Inclusions in Pumices for the Direct Degassing of Volatiles from the Magma to the Hydrothermal Fluids in the Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    YU Zenghui; ZHAI Shikui; ZHAO Guangtao

    2002-01-01

    This article presents the evidence in support of the direct magma degassing as the principal mechanism of volatilesreleasing into the hydrothermal fluids in the Okinawa Trough, as contrasted to the argument for the hydrothermal strippingof volatiles from the volcanic rocks.Laser Raman microprobe and stepped-heating techniques are employed to determine the compositions and contents of thevolatiles in pumices in the middle Okinawa Trough. The results show that the volatiles are similar to the gases in the hy-drothermal fluids and hydrothermal minerals in composition, the mean percent content of each component and variationtrend. This indicates the direct influence of magma degassing on the hydrothermal fluids. In addition, the contents ofvolatiles in pumices are rather low and do not support the hydrothermal stripping as the main mechanism to enrich the fluidswith gases. The results are consistent with the idea that the direct magma degassing is more important than hydrothermalstripping in supplying gases to the hydrothermal fluids in the Okinawa Trough.

  6. Lower and Middle Ordovician conodonts of Laurentian affinity from blocks of limestone in the Rosroe Formation, South Mayo Trough, western Ireland and their palaeogeographic implication

    DEFF Research Database (Denmark)

    Stouge, Svend; Harper, David A. T.; Sevastopulo, George D.

    2016-01-01

    The Middle Ordovician Rosroe Formation consists of some 1350m of coarse, mainly siliciclastic to volcaniclastic sedimentary rocks, deposited in a submarine fan environment, and is restricted to the southern limb of the South Mayo Trough, western Ireland. Discrete allochthonous blocks, reaching 5m...

  7. Characterizing structures on borehole images and logging data of the Nankai trough accretionary prism: new insights

    Science.gov (United States)

    Jurado, Maria Jose

    2016-04-01

    IODP has extensively used the D/V Chikyu to drill the Kumano portion of the Nankai Trough, including two well sites within the Kumano Basin. IODP Expeditions 338 and 348 drilled deep into the inner accretionary prism south of the Kii Peninsula collecting a suite of LWD data, including natural gamma ray, electrical resistivity logs and borehole images, suitable to characterize structures (fractures and faults) inside the accretionary prism. Structural interpretation and analysis of logging-while-drilling data in the deep inner prism revealed intense deformation of a generally homogenous lithology characterized by bedding that dips steeply (60-90°) to the NW, intersected by faults and fractures. Multiple phases of deformation are characterized. IODP Expedition borehole images and LWD data acquired in the last decade in previous and results of NantroSEIZE IODP Expeditions (314, 319) were also analyzed to investigate the internal geometries and structures of the Nankai Trough accretionary prism. This study focused mainly on the characterization of the different types of structures and their specific position within the accretionary prism structures. New structural constraints and methodologies as well as a new approach to the characterization of study of active structures inside the prism will be presented.

  8. Impact of pressure losses in small-sized parabolic-trough collectors for direct steam generation

    International Nuclear Information System (INIS)

    Lobón, David H.; Valenzuela, Loreto

    2013-01-01

    Using PTC (parabolic-trough solar collectors) for industrial thermal processes in the temperature range up to 300 °C is not new, but in recent years there is a boosted interest in this type of concentrating solar technology. One of the problems that arise when designing PTC solar fields is how to deal with the pressure losses which are critical when producing saturated steam directly in the collectors. Depending on the characteristics of the collector, mainly on the receiver diameter, and on the nominal process conditions defined, a solar field configuration can be feasible or not. This paper presents a sensitivity analysis done using a software tool developed to study the thermo-hydraulic behaviour of PTC systems using water-steam as heat transfer fluid. In the case study presented, a small-sized PTC designed for industrial process heat applications is considered, which has a focal length of 0.2 m, an aperture area of 2 m 2 , and its receiver pipe has an inner diameter of 15 mm. Varied process conditions are inlet water pressure, temperature, and mass flow rate, solar irradiance and incidence angle of solar radiation. Results show that working pressure definition is particularly critical to make feasible or not the direct steam generation in solar collectors. - Highlights: • DSG (Direct steam generation) in small-sized parabolic-trough collectors. • Thermo-hydraulic sensitivity analysis. • Influence of working pressure and receiver geometry in DSG process

  9. Deep drivers of mesoscale circulation in the central Rockall Trough

    Science.gov (United States)

    Sherwin, T. J.; Alyenik, D.; Dumont, E.; Inall, M.

    2014-11-01

    Mesoscale variability in the central Rockall Trough between about 56 and 58° N has been investigated using a combination of ship-borne, underwater glider and gridded satellite altimeter measurements. Altimeter observations show that mesoscale features such as eddies and large scale circulation cells are ubiquitous phenomena. They have horizontal length scales of order 100 km with vertical scales of over 1000 m and are associated with mean current speeds (over the upper 1000 m) of 15 ± 7 cm s-1. Monthly area averaged surface Eddy Kinetic Energy (EKE) has substantial inter-annual variability, which at times can dominate a mean seasonal signal that varies from a maximum in May (74 cm2 s-2) to a minimum in October (52 cm2 s-2) and has increased gradually since 1992 at about 1.1 cm2 s-2 per year. A five month glider mission in the Trough showed that much of this energy comes from features that are located over 1000 m below the surface in the deep cold waters of the Trough (possibly from eddies associated the North Atlantic Current). The surface currents from altimeters had similar magnitude to the drift currents averaged over 1000 m from the glider in the stratified autumn, but were half the deep water speed during late winter. Although the mesoscale features move in an apparent random manner they may also be quasi-trapped by submarine topography such as seamounts. Occasionally anti-cyclonic and cyclonic cells combine to cause a coherent westward deflection of the European slope current that warms the Rockall side of the Trough. Such deflections contribute to the inter-annual variability in the observed temperature and salinity that are monitored in the upper 800 m of the Trough. By combining glider and altimeter measurements it is shown that altimeter measurements fail to observe a 15 cm s-1 northward flowing slope current on the eastern side and a small persistent southward current on the western side. There is much to be gained from the synergy between satellite

  10. Positive and negative ionospheric storms occurring during the 15 May 2005 geomagnetic superstorm

    Science.gov (United States)

    Horvath, Ildiko; Lovell, Brian C.

    2015-09-01

    This study focuses on the 15 May 2005 geomagnetic superstorm and aims to investigate the global variation of positive and negative storm phases and their development. Observations are provided by a series of global total electron content maps and multi-instrument line plots. Coupled Thermosphere-Ionosphere-Plasmasphere electrodynamics (CTIPe) simulations are also employed. Results reveal some sunward streaming plumes of storm-enhanced density (SED) over Asia and a well-developed midlatitude trough over North America forming isolated positive and negative storms, respectively. The simultaneous development of positive and negative storms over North America is also shown. Then, some enhanced auroral ionizations maintained by strong equatorward neutral winds appeared in the depleted nighttime ionosphere. Meanwhile, the northern nighttime polar region became significantly depleted as the SED plume plasma could not progress further than the dayside cusp. Oppositely, a polar tongue of ionization (TOI) developed in the daytime southern polar region. According to CTIP simulations, solar heating locally maximized (minimized) over the southern (northern) magnetic pole. Furthermore, strong upward surges of molecular-rich air created O/N2 decreases both in the auroral zone and in the trough region, while some SED-related downward surges produced O/N2 increases. From these results we conclude for the time period studied that (1) composition changes contributed to the formation of positive and negative storms, (2) strengthening polar convection and increasing solar heating of the polar cap supported polar TOI development, and (3) a weaker polar convection and minimized solar heating of the polar cap aided the depletion of polar plasma.

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

    Directory of Open Access Journals (Sweden)

    F. Becker-Guedes

    2007-05-01

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

  12. The zonal-mean and regional tropospheric pressure responses to changes in ionospheric potential

    Science.gov (United States)

    Zhou, Limin; Tinsley, Brian; Wang, Lin; Burns, Gary

    2018-06-01

    Global reanalysis data reveal daily surface pressure responses to changes in the global ionospheric potential in both polar and sub-polar regions. We use 21 years of data to show that the pressure response to externally-induced ionospheric potential changes, that are due to the interplanetary magnetic field east-west (IMF By) component, are present in two separate decadal intervals, and follow the opposite ionospheric potential changes in the Arctic and Antarctic for a given By. We use the 4 years of available data to show that the pressure responses to changes in internally generated ionospheric potential, that are caused by low-latitude thunderstorms and highly electrified clouds, agree in sign and sensitivity with those externally generated. We have determined that the daily varying pressure responses are stronger in local winter and spring. The pressure responses at polar latitudes are predominantly over the Antarctic and Greenland ice caps, and those at sub-polar latitudes are of opposite sign, mainly over oceans. A lead-lag analysis confirms that the responses maximize within two days of the ionospheric potential input. Regions of surface pressure fluctuating by about 4 hPa in winter are found with ionospheric potential changes of about 40 kV. The consistent pressure response to the independent external and internal inputs strongly supports the reality of a cloud microphysical mechanism affected by the global electric circuit. A speculative mechanism involves the ionosphere-earth current density Jz, which produces space charge at cloud boundaries and electrically charged droplets and aerosol particles. Ultrafine aerosol particles, under the action of electro-anti-scavenging, are enabled to grow to condensation nuclei size, affecting cloud microphysics and cloud opacity and surface pressure on time scales of hours.

  13. Lower Ionosphere Sensitivity to Solar X-ray Flares Over a Complete Solar Cycle Evaluated From VLF Signal Measurements

    Science.gov (United States)

    Macotela, Edith L.; Raulin, Jean-Pierre; Manninen, Jyrki; Correia, Emília; Turunen, Tauno; Magalhães, Antonio

    2017-12-01

    The daytime lower ionosphere behaves as a solar X-ray flare detector, which can be monitored using very low frequency (VLF) radio waves that propagate inside the Earth-ionosphere waveguide. In this paper, we infer the lower ionosphere sensitivity variation over a complete solar cycle by using the minimum X-ray fluence (FXmin) necessary to produce a disturbance of the quiescent ionospheric conductivity. FXmin is the photon energy flux integrated over the time interval from the start of a solar X-ray flare to the beginning of the ionospheric disturbance recorded as amplitude deviation of the VLF signal. FXmin is computed for ionospheric disturbances that occurred in the time interval of December-January from 2007 to 2016 (solar cycle 24). The computation of FXmin uses the X-ray flux in the wavelength band below 0.2 nm and the amplitude of VLF signals transmitted from France (HWU), Turkey (TBB), and U.S. (NAA), which were recorded in Brazil, Finland, and Peru. The main result of this study is that the long-term variation of FXmin is correlated with the level of solar activity, having FXmin values in the range (1 - 12) × 10-7 J/m2. Our result suggests that FXmin is anticorrelated with the lower ionosphere sensitivity, confirming that the long-term variation of the ionospheric sensitivity is anticorrelated with the level of solar activity. This result is important to identify the minimum X-ray fluence that an external source of ionization must overcome in order to produce a measurable ionospheric disturbance during daytime.

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

    Directory of Open Access Journals (Sweden)

    L. Z. Biktash

    2004-09-01

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

  15. Ionosphere dynamics over the Southern Hemisphere during the 31 March 2001 severe magnetic storm using multi-instrument measurement data

    Directory of Open Access Journals (Sweden)

    E. Yizengaw

    2005-03-01

    Full Text Available The effects of the 31 March 2001 severe magnetic storm on the Southern Hemisphere ionosphere have been studied using ground-based and satellite measurements. The prime goal of this comprehensive study is to track the ionospheric response from high-to-low latitude to obtain a clear understanding of storm-time ionospheric change. The study uses a combination of ionospheric Total Electron Content (TEC obtained from GPS signal group delay and phase advance measurements, ionosonde data, and data from satellite in-situ measurements, such as the Defense Metrological Satellite Program (DMSP, TOPographic EXplorer (TOPEX, and solar wind data from the Advanced Composition Explorer (ACE. A chain of Global Positioning System (GPS stations near the 150° E meridian has been used to give comprehensive latitude coverage extending from the cusp to the equatorial region. A tomographic inversion algorithm has been applied to the GPS TEC measurements to obtain maps of the latitudinal structure of the ionospheric during this severe magnetic storm period, enabling both the spatial and temporal response of the ionosphere to be studied. Analysis of data from several of the instruments indicates that a strong density enhancement occurred at mid-latitudes at 11:00 UT on 31 March 2001 and was followed by equatorward propagating large-scale Travelling Ionospheric Disturbances (TIDs. The tomographic reconstruction revealed important features in ionospheric structure, such as quasi-wave formations extending finger-like to higher altitudes. The most pronounced ionospheric effects of the storm occurred at high- and mid-latitudes, where strong positive disturbances occurred during the storm main phase, followed by a long lasting negative storm effect during the recovery phase. Relatively minor storm effects occurred in the equatorial region.

  16. The Earth's ionosphere plasma physics and electrodynamics

    CERN Document Server

    Kelley, Michael C

    2007-01-01

    Although interesting in its own right, due to the ever-increasing use of satellites for communication and navigation, weather in the ionosphere is of great concern. Every such system uses trans-ionospheric propagation of radio waves, waves which must traverse the commonly turbulent ionosphere. Understanding this turbulence and predicting it are one of the major goals of the National Space Weather program. Acquiring such a prediction capability will rest on understanding the very topics of this book, the plasma physics and electrodynamics of the system. Fully updated to reflect advances in the field in the 20 years since the first edition published Explores the buffeting of the ionosphere from above by the sun and from below by the lower atmosphere Unique text appropriate both as a reference and for coursework.

  17. Associating an ionospheric parameter with major earthquake ...

    Indian Academy of Sciences (India)

    ionospheric disturbance (SID) and 'td' is the dura- tion of the ... dayside of the earth, ionizing atmospheric parti- ... the increased emanation of excited radon molecules from the ground ..... tration following strong earthquake; Int. J. Remote Sens.

  18. Ionospheric Oblique Incidence Soundings by Satellites

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The oblique incidence sweep-frequency ionospheric sounding technique uses the same principle of operation as the vertical incidence sounder. The primary difference...

  19. Digital processing of ionospheric electron content data

    Science.gov (United States)

    Bernhardt, P. A.

    1979-01-01

    Ionospheric electron content data contain periodicities that are produced by a diversity of sources including hydromagnetic waves, gravity waves, and lunar tides. Often these periodicities are masked by the strong daily variation in the data. Digital filtering can be used to isolate the weaker components. The filtered data can then be further processed to provide estimates of the source properties. In addition, homomorphic filtering may be used to identify nonlinear interactions in the ionosphere.

  20. Ionospheric disturbances under low solar activity conditions

    Czech Academy of Sciences Publication Activity Database

    Burešová, Dalia; Laštovička, Jan; Hejda, Pavel; Bochníček, Josef

    2014-01-01

    Roč. 54, č. 2 (2014), s. 185-196 ISSN 0273-1177 R&D Projects: GA ČR(CZ) GAP209/11/1908 Institutional support: RVO:68378289 ; RVO:67985530 Keywords : ionosphere * solar minimum * magnetic storm s * ionospheric variability Subject RIV: DG - Athmosphere Sciences, Meteorology; DG - Athmosphere Sciences, Meteorology (GFU-E) Impact factor: 1.358, year: 2014 http://www.sciencedirect.com/science/article/pii/S027311771400221X

  1. Geodetic Space Weather Monitoring by means of Ionosphere Modelling

    Science.gov (United States)

    Schmidt, Michael

    2017-04-01

    The term space weather indicates physical processes and phenomena in space caused by radiation of energy mainly from the Sun. Manifestations of space weather are (1) variations of the Earth's magnetic field, (2) the polar lights in the northern and southern hemisphere, (3) variations within the ionosphere as part of the upper atmosphere characterized by the existence of free electrons and ions, (4) the solar wind, i.e. the permanent emission of electrons and photons, (5) the interplanetary magnetic field, and (6) electric currents, e.g. the van Allen radiation belt. It can be stated that ionosphere disturbances are often caused by so-called solar storms. A solar storm comprises solar events such as solar flares and coronal mass ejections (CMEs) which have different effects on the Earth. Solar flares may cause disturbances in positioning, navigation and communication. CMEs can effect severe disturbances and in extreme cases damages or even destructions of modern infrastructure. Examples are interruptions to satellite services including the global navigation satellite systems (GNSS), communication systems, Earth observation and imaging systems or a potential failure of power networks. Currently the measurements of solar satellite missions such as STEREO and SOHO are used to forecast solar events. Besides these measurements the Earth's ionosphere plays another key role in monitoring the space weather, because it responses to solar storms with an increase of the electron density. Space-geodetic observation techniques, such as terrestrial GNSS, satellite altimetry, space-borne GPS (radio occultation), DORIS and VLBI provide valuable global information about the state of the ionosphere. Additionally geodesy has a long history and large experience in developing and using sophisticated analysis and combination techniques as well as empirical and physical modelling approaches. Consequently, geodesy is predestinated for strongly supporting space weather monitoring via

  2. LIFDAR: A Diagnostic Tool for the Ionosphere

    Science.gov (United States)

    Kia, O. E.; Rodgers, C. T.; Batholomew, J. L.

    2011-12-01

    ITT Corporation proposes a novel system to measure and monitor the ion species within the Earth's ionosphere called Laser Induced Fluorescence Detection and Ranging (LIFDAR). Unlike current ionosphere measurements that detect electrons and magnetic field, LIFDAR remotely measures the major contributing ion species to the electron plasma. The LIFDAR dataset has the added capability to demonstrate stratification and classification of the layers of the ionosphere to ultimately give a true tomographic view. We propose a proof of concept study using existing atmospheric LIDAR sensors combined with a mountaintop observatory for a single ion species that is prevalent in all layers of the atmosphere. We envision the LIFDAR concept will enable verification, validation, and exploration of the physics of the magneto-hydrodynamic models used in ionosphere forecasting community. The LIFDAR dataset will provide the necessary ion and electron density data for the system wide data gap. To begin a proof of concept, we present the science justification of the LIFDAR system based on the model photon budget. This analysis is based on the fluorescence of ionized oxygen within the ionosphere versus altitude. We use existing model abundance data of the ionosphere during normal and perturbed states. We propagate the photon uncertainties from the laser source through the atmosphere to the plasma and back to the collecting optics and detector. We calculate the expected photon budget to determine signal to noise estimates based on the targeted altitude and detection efficiency. Finally, we use these results to derive a LIFDAR observation strategy compatible with operational parameters.

  3. First Ionospheric Results From the MAVEN Radio Occultation Science Experiment (ROSE)

    Science.gov (United States)

    Withers, Paul; Felici, M.; Mendillo, M.; Moore, L.; Narvaez, C.; Vogt, M. F.; Jakosky, B. M.

    2018-05-01

    Radio occultation observations of the ionosphere of Mars can span the full vertical extent of the ionosphere, in contrast to in situ measurements that rarely sample the main region of the ionosphere. However, most existing radio occultation electron density profiles from Mars were acquired without clear context for the solar forcing or magnetospheric conditions, which presents challenges for the interpretation of these profiles. Here we present 48 ionospheric electron density profiles acquired by the Mars Atmosphere and Volatile EvolutioN mission (MAVEN) Radio Occultation Science Experiment (ROSE) from 5 July 2016 to 27 June 2017 at solar zenith angles of 54° to 101°. Latitude coverage is excellent, and comprehensive context for the interpretation of these profiles is provided by other MAVEN instruments. The profiles show a 9-km increase in ionospheric peak altitude in January 2017 that is associated with a lower atmospheric dust storm, variations in electron densities in the M1 layer that cannot be explained by variations in the solar soft X-ray flux, and topside electron densities that are larger in strongly magnetized regions than in weakly magnetized regions. MAVEN Radio Occultation Science Experiment electron density profiles are publicly available on the NASA Planetary Data System.

  4. GNSS, Satellite Altimetry and Formosat-3/COSMIC for Determination of Ionosphere Parameters

    Science.gov (United States)

    Mahdi Alizadeh Elizei, M.; Schuh, Harald; Schmidt, Michael; Todorova, Sonya

    The dispersion of ionosphere with respect to the microwave signals allows gaining information about the parameters of this medium in terms of the electron density (Ne), or the Total Elec-tron Content (TEC). In the last decade space geodetic techniques, such as Global Navigation Satellite System (GNSS), satellite altimetry missions, and Low Earth Orbiting (LEO) satel-lites have turned into a promising tool for remote sensing the ionosphere. The dual-frequency GNSS observations provide the main input data for development of Global Ionosphere Maps (GIM). However, the GNSS stations are heterogeneously distributed, with large gaps particu-larly over the sea surface, which lowers the precision of the GIM over these areas. Conversely, dual-frequency satellite altimetry missions provide information about the ionosphere precisely above the sea surface. In addition, LEO satellites such as Formosat-3/COSMIC (F-3/C) pro-vide well-distributed information of ionosphere around the world. In this study we developed GIMs of VTEC from combination of GNSS, satellite altimetry and F-3/C data with temporal resolution of 2 hours and spatial resolution of 5 degree in longitude and 2.5 degree in latitude. The combined GIMs provide a more homogeneous global coverage and higher precision and reliability than results of each individual technique.

  5. Tracker: A three-dimensional raytracing program for ionospheric radio propagation

    Energy Technology Data Exchange (ETDEWEB)

    Argo, P.E.; DeLapp, D.; Sutherland, C.D.; Farrer, R.G.

    1994-12-01

    TRACKER is an extension of a three-dimensional Hamiltonian raytrace code developed some thirty years ago by R. Michael Jones. Subsequent modifications to this code, which is commonly called the {open_quotes}Jones Code,{close_quotes} were documented by Jones and Stephensen (1975). TRACKER incorporates an interactive user`s interface, modern differential equation integrators, graphical outputs, homing algorithms, and the Ionospheric Conductivity and Electron Density (ICED) ionosphere. TRACKER predicts the three-dimensional paths of radio waves through model ionospheres by numerically integrating Hamilton`s equations, which are a differential expression of Fermat`s principle of least time. By using continuous models, the Hamiltonian method avoids false caustics and discontinuous raypath properties often encountered in other raytracing methods. In addition to computing the raypath, TRACKER also calculates the group path (or pulse travel time), the phase path, the geometrical (or {open_quotes}real{close_quotes}) pathlength, and the Doppler shift (if the time variation of the ionosphere is explicitly included). Computational speed can be traded for accuracy by specifying the maximum allowable integration error per step in the integration. Only geometrical optics are included in the main raytrace code; no partial reflections or diffraction effects are taken into account. In addition, TRACKER does not lend itself to statistical descriptions of propagation -- it requires a deterministic model of the ionosphere.

  6. Plasmaspheric-ionospheric contents deduced from ATS-6 measurements over Lannion

    International Nuclear Information System (INIS)

    Fleury, R.

    1978-01-01

    The present paper deals with ATS-6 radio beacon measurements at the Lannion Station, of the total columnar electron content between transmitter and receiver and the ionospheric columnar content along the ray path between the receiver and the satellite. The main equations of the method of analysis proposed by Davies et al. (1975) are summarized

  7. Geomagnetic and ionospheric data analysis over Antarctica: a contribution to the long term trends investigation

    Directory of Open Access Journals (Sweden)

    L. Alfonsi

    2008-05-01

    Full Text Available The analysis of the foF2 ionosonde data acquired at mid and high latitudes reveals a general decreasing of the F2 plasma frequency over more than two solar cycles, showing steeper trends over the high latitude stations and, in particular, over Antarctica. A careful analysis of the foF2 hourly data, opportunely catalogued in different levels of magneto-ionospheric conditions, highlights the role of the geomagnetic activity in the secular change of the ionosphere and confirms the latitudinal dependence of the trends. These results suggest interesting relations with some recent findings on the rapid decrease of some important physical and statistical quantities related to the geomagnetic field over the whole globe and mainly in Antarctica. In this paper we discuss the possibility of a connection between the ionospheric trends and a possible imminent geomagnetic reversal or excursion.

  8. Geomagnetic and ionospheric data analysis over Antarctica: a contribution to the long term trends investigation

    Directory of Open Access Journals (Sweden)

    L. Alfonsi

    2008-05-01

    Full Text Available The analysis of the foF2 ionosonde data acquired at mid and high latitudes reveals a general decreasing of the F2 plasma frequency over more than two solar cycles, showing steeper trends over the high latitude stations and, in particular, over Antarctica. A careful analysis of the foF2 hourly data, opportunely catalogued in different levels of magneto-ionospheric conditions, highlights the role of the geomagnetic activity in the secular change of the ionosphere and confirms the latitudinal dependence of the trends. These results suggest interesting relations with some recent findings on the rapid decrease of some important physical and statistical quantities related to the geomagnetic field over the whole globe and mainly in Antarctica. In this paper we discuss the possibility of a connection between the ionospheric trends and a possible imminent geomagnetic reversal or excursion.

  9. Consistency of seven different GNSS global ionospheric mapping techniques during one solar cycle

    Science.gov (United States)

    Roma-Dollase, David; Hernández-Pajares, Manuel; Krankowski, Andrzej; Kotulak, Kacper; Ghoddousi-Fard, Reza; Yuan, Yunbin; Li, Zishen; Zhang, Hongping; Shi, Chuang; Wang, Cheng; Feltens, Joachim; Vergados, Panagiotis; Komjathy, Attila; Schaer, Stefan; García-Rigo, Alberto; Gómez-Cama, José M.

    2018-06-01

    In the context of the International GNSS Service (IGS), several IGS Ionosphere Associated Analysis Centers have developed different techniques to provide global ionospheric maps (GIMs) of vertical total electron content (VTEC) since 1998. In this paper we present a comparison of the performances of all the GIMs created in the frame of IGS. Indeed we compare the classical ones (for the ionospheric analysis centers CODE, ESA/ESOC, JPL and UPC) with the new ones (NRCAN, CAS, WHU). To assess the quality of them in fair and completely independent ways, two assessment methods are used: a direct comparison to altimeter data (VTEC-altimeter) and to the difference of slant total electron content (STEC) observed in independent ground reference stations (dSTEC-GPS). The main conclusion of this study, performed during one solar cycle, is the consistency of the results between so many different GIM techniques and implementations.

  10. Lithosphere-Surfacesphere–Atmosphere-Ionosphere coupling model for Vrancea seismic zone in Romania

    Energy Technology Data Exchange (ETDEWEB)

    Zoran, Maria; Savastru, Roxana; Savastru, Dan [National Institute of R& D for Optoelectronics, MG5 Bucharest -Magurele, 077125 Romania, maria@dnt.ro (Romania)

    2016-03-25

    This paper presents a complex multidisciplinary approach concept to explain the nature of short-term earthquake precursors observed in land surface, atmosphere, ionosphere and magnetosphere for strong intermediate depth earthquakes recorded in Vrancea region in Romania. A developed Lithosphere-Surfacesphere-Atmosphere-Ionosphere (LSAI) coupling model can explain most of these presignals as a synergy between different anomalies of geophysical/geochemical parameters. These anomalies prior to medium to strong earthquakes are attributed to the thermodynamic, degassing and ionization processes in the Earth-Atmosphere system and micro-fracturing in the rocks especially along area’s active faults. The main outcome of this paper is an unified concept for systematic validation of different types of earthquake precursors of which Land Surface Temperature (LST), outgoing Long wave Radiation (OLR), Surface Latent Heat Flux (SLHF), Air Temperature (AT), radon gas concentration, ionospheric Total Electron Content (TEC) are the most reliable parameters within the chain of the processes described by LSAI model.

  11. Main findings

    International Nuclear Information System (INIS)

    2014-01-01

    Licensing regimes vary from country to country. When the license regime involves several regulators and several licenses, this may lead to complex situations. Identifying a leading organisation in charge of overall coordination including preparation of the licensing decision is a useful practice. Also, if a stepwise licensing process is implemented, it is important to fix in legislation decisions and/or time points and to identify the relevant actors. There is considerable experience in civil and mining engineering that can be applied when constructing a deep geological disposal facility. Specific challenges are, however, the minimization of disturbances to the host rock and the understanding of its long-term behavior. Construction activities may affect the geo-hydraulic and geochemical properties of the various system components which are important safety features of the repository system. Clearly defined technical specifications and an effective quality management plan are important in ensuring successful repository implementation which is consistent with safety requirements. Monitoring plan should also be defined in advance. The regulatory organization should prepare itself to the licensing review before construction by allocating sufficient resources. It should increase its competence, e.g., by interacting early with the implementer and through its own R and D. This will allow the regulator to define appropriate technical conditions associated to the construction license and to elaborate a relevant inspection plan of the construction work. After construction, obtaining the operational license is the most important and crucial step. Main challenges include (a) establishing sufficient confidence so that the methods for closing the individual disposal units comply with the safety objectives and (b) addressing the issue of ageing of materials during a 50-100 years operational period. This latter challenge is amplified when reversibility/retrievability is required

  12. Measurements of ionospheric TEC in the direction of GPS satellites and comparison with three ionospheric models

    Directory of Open Access Journals (Sweden)

    E. Zuccheretti

    1997-06-01

    Full Text Available The IEN Galileo Ferraris uses GPS for time and frequency synchronization. To obtain high performance it is important to reduce the error due to the ionospheric time-delay in GPS measurements. Evaluations of TEC in the direction of GPS satellites, obtained from three different ionospheric models, have been compared with corresponding measurements by GPS signal.

  13. Southern European ionospheric TEC maps based on Kriging technique to monitor ionosphere behavior

    Science.gov (United States)

    Rodríguez-Bouza, Marta; Paparini, Claudia; Otero, Xurxo; Herraiz, Miguel; Radicella, Sandro M.; Abe, Oladipo E.; Rodríguez-Caderot, Gracia

    2017-10-01

    Global or regional Maps of the ionospheric Total Electron Content (TEC) are an efficient tool to monitor the delay introduced by the ionosphere in the satellite signals. Ionospheric disturbance periods are of particular interest because these conditions can strongly affect satellite navigation range measurements. This work presents post-processing regional vertical TEC maps over Southern Europe ([35°N-50°N] latitude) obtained by applying Kriging interpolation to GPS derived TEC over more than 100 Global Navigation Satellite System (GNSS) stations. These maps are used to study the behavior of the ionosphere during space weather events and their effects. To validate these maps, hereafter called Southern European Ionospheric Maps (SEIMs), their TEC values have been compared with those obtained from EGNOS Message Server (EMS) and with direct experimental TEC data from GNSS stations. Ionospheric space weather events related to geomagnetic storms of March 17th, 2013, February 19th, 2014 and March 17th, 2015 have been selected. To test the methodology, one period of quiet days has been also analyzed. TEC values obtained by SEIMs in the Ionospheric Grid Points (IGPs) defined by EGNOS are very close to those given by EMS and in the period of major geomagnetic storms the difference does not exceed 6 TEC units. These results confirm the good performance of the technique used for obtaining the SEIMs that can be a useful tool to study the ionosphere behavior during geomagnetic storms and their effects in the region of interest.

  14. From COST 271 to 296 EU actions on ionospheric monitoring and modelling for terrestrial and Earth space radio systems

    Science.gov (United States)

    Zolesi, B.; Cander, Lj. R.; Altadill, D.

    The ionospheric community has long been aware that co-operative research on an international basis is essential to deal with temporal and spatial changes in the ionosphere that influence the performance of terrestrial and Earth-space radio systems. The EU COST (Co-operation in the field of Scientific and Technical Research) 271 Action on "Effects of the Upper Atmosphere on Terrestrial and Earth-space Communications" has had during the period of October 2000-August 2004 the following main objectives: (1) to evaluate the influence of upper atmospheric conditions on terrestrial and Earth-space communications, (2) to develop methods and techniques to improve ionospheric models over Europe for telecommunication and navigation applications and (3) to transfer the results to the appropriate radiocommunication study groups of the International Telecommunication Union (ITU-R) and other national and international organizations dealing with the modern communication systems. At the beginning of 2005 the new 296 Action in the COST Telecommunications, Information Science and Technology domain on "Mitigation of Ionospheric Effects on Radio Systems (MIERS)" was approved for the period 2005-2009. The main objectives of the MIERS are: (a) to support and enhanced the existing European facilities for historical and real-time digital ionospheric data collection and exchange; (b) to develop an integrated approach to ionospheric modelling, create the mechanism needed to ingest processed data into models, extend and develop suitable mitigation models and define the protocols needed to link models together; and (c) to strengthen the areas of expertise that already exist by stimulating closer cooperation between scientists and users, focusing the scope of all the previous COST ionospheric related studies to the mitigation of ionospheric effects on radio systems. This paper summarises briefly how the major objectives of the COST271 Action have been achieved and what are the most important

  15. Theoretical Study of the Compound Parabolic Trough Solar Collector

    Directory of Open Access Journals (Sweden)

    Dr. Subhi S. Mahammed

    2012-06-01

    Full Text Available Theoretical design of compound parabolic trough solar collector (CPC without tracking is presented in this work. The thermal efficiency is obtained by using FORTRAN 90 program. The thermal efficiency is between (60-67% at mass flow rate between (0.02-0.03 kg/s at concentration ratio of (3.8 without need to tracking system.The total and diffused radiation is calculated for Tikrit city by using theoretical equations. Good agreement between present work and the previous work.

  16. Ionospheric Response to the Magnetic Storm of 22 June 2015

    Science.gov (United States)

    Mansilla, Gustavo A.

    2018-03-01

    A global study is made of the response of the total electron content of the ionosphere (TEC) to the geomagnetic storm occurred on 22 June 2015 (one of the strongest geomagnetic storms of the current Solar Cycle 24). Using data from 44 sites, a hemispheric comparison is made by considering high latitudes (> 50°), middle latitudes (30°-50°) and low latitudes (30°N-30°S). The main features observed were: increases in TEC at high latitudes prior to the storm main phase, a considerable asymmetry of TEC response at middle and low latitudes of the Northern Hemisphere and the Southern Hemisphere and decreases at equatorial latitudes. The long duration enhancements in TEC were well correlated with increases in the O/N2 ratio but decreases in TEC had not associated decreases in the O/N2 ratio as occur with the decreases in the electron density. Besides, prompt penetration electric fields can play an important role in the equatorial and low-latitude ionosphere during main phase of the storm.

  17. Investigation of a strong positive ionospheric storm during geomagnetic disturbances occurred in the Brazilian sector

    Science.gov (United States)

    de Abreu, A. J.; Sahai, Y.; Fagundes, P. R.; de Jesus, R.; Bittencourt, J. A.; Pillat, V. G.

    2012-12-01

    In this paper, we have investigated the responses of the ionospheric F region at equatorial and low latitude regions in the Brazilian sector during the super geomagnetic storm on 15-16 May 2005. The geomagnetic storm reached a minimum Dst of -263 nT at 0900 UT on 15 May. In this paper, we present vertical total electron content (vTEC) and phase fluctuations (in TECU/min) from Global Positioning System (GPS) observations obtained at Belém (BELE), Brasília (BRAZ), Presidente Prudente (UEPP), and Porto Alegre (POAL), Brazil, during the period 14-17 May 2005. Also, we present ionospheric parameters h'F, hpF2, and foF2, using the Canadian Advanced Digital Ionosonde (CADI) obtained at Palmas (PAL) and São José dos Campos (SJC), Brazil, for the same period. The super geomagnetic storm has fast decrease in the Dst index soon after SSC at 0239 UT on 15 May. It is a good possibility of prompt penetration of electric field of magnetospheric origin resulting in uplifting of the F region. The vTEC observations show a trough at BELE and a crest above UEPP, soon after SSC, indicating strengthening of nighttime equatorial anomaly. During the daytime on 15 and 16 May, in the recovery phase, the variations in foF2 at SJC and the vTEC observations, particularly at BRAZ, UEPP, and POAL, show large positive ionospheric storm. There is ESF on the all nights at PAL, in the post-midnight (UT) sector, and phase fluctuations only on the night of 14-15 May at BRAZ, after the SSC. No phase fluctuations are observed at the equatorial station BELE and low latitude stations (BRAZ, UEPP, and POAL) at all other times. This indicates that the plasma bubbles are generated and confined on this magnetically disturbed night only up to the low magnetic latitude and drifted possibly to west.

  18. GNSS Derived Ionospheric TEC Observed Through Different TEC Calibration Techniques in the Brazilian Sector

    Science.gov (United States)

    Becker-Guedes, F.; Carmo, C. S.; Camargo, P. O.; Monico, J. F. G.; Nicoli Candido, C. M.

    2017-12-01

    Global Navigation Satellite System (GNSS) is becoming a reliable tool for use in air navigation systems. Its use as the main technology for determination of airplanes positioning has various economic and logistic benefits but it depends strongly on the ionospheric layer influences. The Brazilian sector ionosphere, mainly over the equatorial ionization anomaly (EIA), presents remarkable errors in the GNSS signal as compared to North America and Europe. In order to study the total electron content latitudinal variation of the Brazilian ionosphere we used a pair of GNSS receivers on the ground, one located in the equatorial region (Sao Luis) and other in the southern crest of the EIA (Cachoeira Paulista), to collect the GNSS observables and calculate the vertical TEC using different methods that has proven to work well to describe the ionospheric behavior in the North America and in Europe. We compared this results with a modified Nagoya TEC calculation method used by the EMBRACE (Estudo e Monitoramento BRAsileiro do Clima Espacial - Brazilian Study and Monitoring of Space Weather) program. This work intends to follow the performance of different TEC tuning methods to evaluate the spurious effects of the ionospheric EIA gradients in the TEC determination under typical conditions of the low-latitudes ionosphere in the Brazilian sector. The calculated TEC under different solar cycle conditions, geomagnetic activity, and seasonal variations show deviations in the performance of each method and stress the importance of well adjust the GNSS observations to local conditions in order to optimize the TEC evaluation. This study contributes to a better understanding of local GNSS signal errors in the global intent of offering conditions to improve the accuracy, integrity, availability, and continuity requirements for the use of GNSS for air navigation in South America.

  19. Kilometer-Spaced GNSS Array for Ionospheric Irregularity Monitoring

    Science.gov (United States)

    Su, Yang

    This dissertation presents automated, systematic data collection, processing, and analysis methods for studying the spatial-temporal properties of Global Navigation Satellite Systems (GNSS) scintillations produced by ionospheric irregularities at high latitudes using a closely spaced multi-receiver array deployed in the northern auroral zone. The main contributions include 1) automated scintillation monitoring, 2) estimation of drift and anisotropy of the irregularities, 3) error analysis of the drift estimates, and 4) multi-instrument study of the ionosphere. A radio wave propagating through the ionosphere, consisting of ionized plasma, may suffer from rapid signal amplitude and/or phase fluctuations known as scintillation. Caused by non-uniform structures in the ionosphere, intense scintillation can lead to GNSS navigation and high-frequency (HF) communication failures. With specialized GNSS receivers, scintillation can be studied to better understand the structure and dynamics of the ionospheric irregularities, which can be parameterized by altitude, drift motion, anisotropy of the shape, horizontal spatial extent and their time evolution. To study the structuring and motion of ionospheric irregularities at the sub-kilometer scale sizes that produce L-band scintillations, a closely-spaced GNSS array has been established in the auroral zone at Poker Flat Research Range, Alaska to investigate high latitude scintillation and irregularities. Routinely collecting low-rate scintillation statistics, the array database also provides 100 Hz power and phase data for each channel at L1/L2C frequency. In this work, a survey of seasonal and hourly dependence of L1 scintillation events over the course of a year is discussed. To efficiently and systematically study scintillation events, an automated low-rate scintillation detection routine is established and performed for each day by screening the phase scintillation index. The spaced-receiver technique is applied to cross

  20. Comparative ionospheres: Terrestrial and giant planets

    Science.gov (United States)

    Mendillo, Michael; Trovato, Jeffrey; Moore, Luke; Müller-Wodarg, Ingo

    2018-03-01

    The study of planetary ionospheres within our solar system offers a variety of settings to probe mechanisms of photo-ionization, chemical loss, and plasma transport. Ionospheres are a minor component of upper atmospheres, and thus their mix of ions observed depends on the neutral gas composition of their parent atmospheres. The same solar irradiance (x-rays and extreme-ultra-violet vs. wavelength) impinges upon each of these atmospheres, with solar flux magnitudes changed only by the inverse square of distance from the Sun. If all planets had the same neutral atmosphere-with ionospheres governed by photochemical equilibrium (production = loss)-their peak electron densities would decrease as the inverse of distance from the Sun, and any changes in solar output would exhibit coherent effects throughout the solar system. Here we examine the outer planet with the most observations of its ionosphere (Saturn) and compare its patterns of electron density with those at Earth under the same-day solar conditions. We show that, while the average magnitudes of the major layers of molecular ions at Earth and Saturn are approximately in accord with distance effects, only minor correlations exist between solar effects and day-to-day electron densities. This is in marked contrast to the strong correlations found between the ionospheres of Earth and Mars. Moreover, the variability observed for Saturn's ionosphere (maximum electron density and total electron content) is much larger than found at Earth and Mars. With solar irradiance changes far too small to cause such effects, we use model results to explore the roles of other agents. We find that water sources from Enceladus at low latitudes, and 'ring rain' at middle latitudes, contribute substantially to variability via water ion chemistry. Thermospheric winds and electrodynamics generated at auroral latitudes are suggested causes of high latitude ionospheric variability, but remain inconclusive due to the lack of relevant

  1. Probabilistic tsunami hazard assessment considering time-lag of seismic event on Nankai trough

    International Nuclear Information System (INIS)

    Sugino, Hideharu; Sakagami, Masaharu; Ebisawa, Katsumi; Korenaga, Mariko

    2011-01-01

    In the area in front of Nankai trough, tsunami wave height may increase if tsunamis attacking from some wave sources overlap because of time-lag of seismic event on Nankai trough. To evaluation tsunami risk of the important facilities located in front of Nankai trough, we proposed the probabilistic tsunami hazard assessment considering uncertainty on time-lag of seismic event on Nankai trough and we evaluated the influence that the time-lag gave to tsunami hazard at the some representative points. (author)

  2. Multi-parameter optimization design of parabolic trough solar receiver

    International Nuclear Information System (INIS)

    Guo, Jiangfeng; Huai, Xiulan

    2016-01-01

    Highlights: • The optimal condition can be obtained by multi-parameter optimization. • Exergy and thermal efficiencies are employed as objective function. • Exergy efficiency increases at the expense of heat losses. • The heat obtained by working fluid increases as thermal efficiency grows. - Abstract: The design parameters of parabolic trough solar receiver are interrelated and interact with one another, so the optimal performance of solar receiver cannot be obtained by the convectional single-parameter optimization. To overcome the shortcoming of single-parameter optimization, a multi-parameter optimization of parabolic trough solar receiver is employed based on genetic algorithm in the present work. When the thermal efficiency is taken as the objective function, the heat obtained by working fluid increases while the average temperature of working fluid and wall temperatures of solar receiver decrease. The average temperature of working fluid and the wall temperatures of solar receiver increase while the heat obtained by working fluid decreases generally by taking the exergy efficiency as an objective function. Assuming that the solar radiation intensity remains constant, the exergy obtained by working fluid increases by taking exergy efficiency as the objective function, which comes at the expense of heat losses of solar receiver.

  3. Methodology and consistency of slant and vertical assessments for ionospheric electron content models

    Science.gov (United States)

    Hernández-Pajares, Manuel; Roma-Dollase, David; Krankowski, Andrzej; García-Rigo, Alberto; Orús-Pérez, Raül

    2017-12-01

    A summary of the main concepts on global ionospheric map(s) [hereinafter GIM(s)] of vertical total electron content (VTEC), with special emphasis on their assessment, is presented in this paper. It is based on the experience accumulated during almost two decades of collaborative work in the context of the international global navigation satellite systems (GNSS) service (IGS) ionosphere working group. A representative comparison of the two main assessments of ionospheric electron content models (VTEC-altimeter and difference of Slant TEC, based on independent global positioning system data GPS, dSTEC-GPS) is performed. It is based on 26 GPS receivers worldwide distributed and mostly placed on islands, from the last quarter of 2010 to the end of 2016. The consistency between dSTEC-GPS and VTEC-altimeter assessments for one of the most accurate IGS GIMs (the tomographic-kriging GIM `UQRG' computed by UPC) is shown. Typical error RMS values of 2 TECU for VTEC-altimeter and 0.5 TECU for dSTEC-GPS assessments are found. And, as expected by following a simple random model, there is a significant correlation between both RMS and specially relative errors, mainly evident when large enough number of observations per pass is considered. The authors expect that this manuscript will be useful for new analysis contributor centres and in general for the scientific and technical community interested in simple and truly external ways of validating electron content models of the ionosphere.

  4. New aspects of the ionospheric response to the October 2003 superstorms from multiple-satellite observations

    Science.gov (United States)

    Lei, Jiuhou; Wang, Wenbin; Burns, Alan G.; Yue, Xinan; Dou, Xiankang; Luan, Xiaoli; Solomon, Stanley C.; Liu, Yong C.-M.

    2014-03-01

    The total electron content (TEC) data measured by the Jason, CHAMP, GRACE, and SAC-C satellites, the in situ electron densities from CHAMP and GRACE, and the vertical E × B drifts from the ROCSAT, have been utilized to examine the ionospheric response to the October 2003 superstorms. The combination of observations from multiple satellites provides a unique global view of ionospheric storm effects, especially over the Pacific Ocean and American regions, which were under sunlit conditions during the main phases of the October 2003 superstorms. The main results of this study are as follows: (1) There were substantial increases in TEC in the daytime at low and middle latitudes during both superstorms. (2) The enhancements were greater during the 30 October superstorm and occurred over a wider range of local times. (3) They also tended to peak at earlier local times during this second event. (4) These TEC enhancement events occurred at the local times when there were enhancements in the upward vertical drift. (5) The strong upward vertical drifts are attributed to penetration electric fields, suggesting that these penetration electric fields played a significant role in the electron density enhancements during these superstorms. Overall, the main contribution of this study is the simultaneous view of the storm time ionospheric response from multiple satellites, and the association of local time differences in ionospheric plasma response with measured vertical drift variations.

  5. Magnetosphere-ionosphere coupling currents in Jupiter's middle magnetosphere: effect of magnetosphere-ionosphere decoupling by field-aligned auroral voltages

    Directory of Open Access Journals (Sweden)

    J. D. Nichols

    2005-03-01

    Full Text Available We consider the effect of field-aligned voltages on the magnetosphere-ionosphere coupling current system associated with the breakdown of rigid corotation of equatorial plasma in Jupiter's middle magnetosphere. Previous analyses have assumed perfect mapping of the electric field and flow along equipotential field lines between the equatorial plane and the ionosphere, whereas it has been shown that substantial field-aligned voltages must exist to drive the field-aligned currents associated with the main auroral oval. The effect of these field-aligned voltages is to decouple the flow of the equatorial and ionospheric plasma, such that their angular velocities are in general different from each other. In this paper we self-consistently include the field-aligned voltages in computing the plasma flows and currents in the system. A third order differential equation is derived for the ionospheric plasma angular velocity, and a power series solution obtained which reduces to previous solutions in the limit that the field-aligned voltage is small. Results are obtained to second order in the power series, and are compared to the original zeroth order results with no parallel voltage. We find that for system parameters appropriate to Jupiter the effect of the field-aligned voltages on the solutions is small, thus validating the results of previously-published analyses.

  6. Electric fields in the ionosphere

    International Nuclear Information System (INIS)

    Kirchhoff, V.W.J.H.

    1975-01-01

    F-region drift velocities, measured by incoherent-scatter radar, were analyzed in terms of diurnal, seasonal, magnetic-activity, and solar-cycle effects. A comprehensive electric field model was developed that includes the effects of the E and F-region dynamos, magnetospheric sources, and ionospheric conductivities, for both the local and conjugate regions. The E-region dynamo dominates during the day, but at night the F-region and convection are more important. This model provides much better agreement with observations of the F-region drifts than previous models. Results indicate that larger magnitudes occur at night, and that daily variation is dominated by the diurnal mode. Seasonal variations in conductivities and thermospheric winds indicate a reversal in direction in the early morning during winter from south to northward. On magnetic perturbed days the drifts deviate rather strongly from the quiet days average, especially around 13 L.T. for the northward and 18 L.T. for the westward component

  7. Theory of ionospheric heating experiments

    International Nuclear Information System (INIS)

    Cragin, B.L.

    1975-01-01

    A brief description of the F region ionospheric heating experiments is given including some historical notes and a brief summary of the observations. A theory for the phenomenon of ''artificial spread F'' is presented. The explanation is in terms of scattering by approximately field-aligned, large scale ionization density irregularities, which are produced by a thermal version of the stimulated Brillouin scattering instability in which the heating wave decays into another electromagnetic wave and an electrostatic wave of very low frequency. This thermal instability differs from conventional stimulated Brillouin scattering in that the low frequency wave is driven by differential heating in the interference pattern of the two electromagnetic waves, rather than by the usual ponderomotive force. Some aspects of the theory of the phenomenon of ''wide-band attenuation'' or ''anomalous absorption'' of a probing electromagnetic wave. Some general results from the theory of wave propagation in a random medium are used to derive equations describing the absorption of a probing electromagnetic wave due to scattering (by large scale irregularities) into new electromagnetic waves or (by small scale irregularities) into electron plasma oscillations

  8. Ionospheric Scintillation Effects on GPS

    Science.gov (United States)

    Steenburgh, R. A.; Smithtro, C.; Groves, K.

    2007-12-01

    . Ionospheric scintillation of Global Positioning System (GPS) signals threatens navigation and military operations by degrading performance or making GPS unavailable. Scintillation is particularly active, although not limited to, a belt encircling the earth within 20 degrees of the geomagnetic equator. As GPS applications and users increases, so does the potential for detrimental impacts from scintillation. We examined amplitude scintillation data spanning seven years from Ascension Island, U.K.; Ancon, Peru; and Antofagasta, Chile in the Atlantic/Americas longitudinal sector at as well as data from Parepare, Indonesia; Marak Parak, Malaysia; Pontianak, Indonesia; Guam; and Diego Garcia, U.K.; in the Pacific longitudinal sector. From these data, we calculate percent probability of occurrence of scintillation at various intensities described by the S4 index. Additionally, we determine Dilution of Precision at one minute resolution. We examine diurnal, seasonal and solar cycle characteristics and make spatial comparisons. In general, activity was greatest during the equinoxes and solar maximum, although scintillation at Antofagasta, Chile was higher during 1998 rather than at solar maximum.

  9. Ionospheric scintillation monitoring and modelling

    Directory of Open Access Journals (Sweden)

    Mariusz Pozoga

    2009-06-01

    Full Text Available

    This paper presents a review of the ionospheric scintillation monitoring and modelling by the European groups

    involved in COST 296. Several of these groups have organized scintillation measurement campaigns at low and

    high latitudes. Some characteristic results obtained from the measured data are presented. The paper also addresses the modeling activities: four models, based on phase screen techniques, with different options and application domains are detailed. Finally some new trends for research topics are given. This includes the wavelet analysis, the high latitudes analysis, the construction of scintillation maps and the mitigation techniques.


  10. Fourier and Wavelet Based Characterisation of the Ionospheric Response to the Solar Eclipse of August, the 11th, 1999, Measured Through 1-minute Vertical Ionospheric Sounding

    Science.gov (United States)

    Sauli, P.; Abry, P.; Boska, J.

    2004-05-01

    The aim of the present work is to study the ionospheric response induced by the solar eclipse of August, the 11th, 1999. We provide Fourier and wavelet based characterisations of the propagation of the acoustic-gravity waves induced by the solar eclipse. The analysed data consist of profiles of electron concentration. They are derived from 1-minute vertical incidence ionospheric sounding measurements, performed at the Pruhonice observatory (Czech republic, 49.9N, 14.5E). The chosen 1-minute high sampling rate aims at enabling us to specifically see modes below acoustic cut-off period. The August period was characterized by Solar Flux F10.7 = 128, steady solar wind, quiet magnetospheric conditions, a low geomagnetic activity (Dst index varies from -10 nT to -20 nT, Σ Kp index reached value of 12+). The eclipse was notably exceptional in uniform solar disk. These conditions and fact that the culmination of the solar eclipse over central Europe occurred at local noon are such that the observed ionospheric response is mainly that of the solar eclipse. We provide a full characterization of the propagation of the waves in terms of times of occurrence, group and phase velocities, propagation direction, characteristic period and lifetime of the particular wave structure. However, ionospheric vertical sounding technique enables us to deal with vertical components of each characteristic. Parameters are estimated combining Fourier and wavelet analysis. Our conclusions confirm earlier theoretical and experimental findings, reported in [Altadill et al., 2001; Farges et al., 2001; Muller-Wodarg et al.,1998] regarding the generation and propagation of gravity waves and provide complementary characterisation using wavelet approaches. We also report a new evidence for the generation and propagation of acoustic waves induced by the solar eclipse through the ionospheric F region. Up to our knowledge, this is the first time that acoustic waves can be demonstrated based on ionospheric

  11. Ionospheric Caustics in Solar Radio Observations

    Science.gov (United States)

    Koval, A.; Chen, Y.; Stanislavsky, A.

    2016-12-01

    The Earth ionosphere possesses by natural focusing and defocusing effects on radio waves due to presence of variable ionospheric irregularities which could act like convergent and divergent lenses on incident radiation. In particular, the focusing of emission from the Sun was firstly detected on the Nançay Decameter Array dynamic spectra in the 1980s. On time-frequency spectrograms the intensity variations form specific structures different from well-known solar radio bursts and clearly distinguishing on a background of solar radiation. Such structures have been identified as ionospheric caustics (ICs) and considered to be the result of radio waves refraction on medium scale travelling ionospheric disturbances (MSTIDs). Although nowadays the ICs are registered by different radio observatories due to augmentation of low-frequency radio telescopes, the most recent papers devoted to ICs in solar radio records date back to the 1980s. In this study, we revisit the ICs issue with some new results by conducting a statistical analysis of occurrence rate of ICs in solar dynamic spectra in meter-decameter wavelength range for long continuous period (15 years). The seasonal variations in ICs appearance have been found for the first time. Besides, we report the possible solar cycle dependence of ICs emergence. The radio waves propagation in the ionosphere comprising MSTIDs will be considered. The present research renews the subject of ICs in the low-frequency solar radio astronomy after about 35-year letup.

  12. Three-dimensional distribution of random velocity inhomogeneities at the Nankai trough seismogenic zone

    Science.gov (United States)

    Takahashi, T.; Obana, K.; Yamamoto, Y.; Nakanishi, A.; Kaiho, Y.; Kodaira, S.; Kaneda, Y.

    2012-12-01

    The Nankai trough in southwestern Japan is a convergent margin where the Philippine sea plate is subducted beneath the Eurasian plate. There are major faults segments of huge earthquakes that are called Tokai, Tonankai and Nankai earthquakes. According to the earthquake occurrence history over the past hundreds years, we must expect various rupture patters such as simultaneous or nearly continuous ruptures of plural fault segments. Japan Agency for Marine-Earth Science and Technology (JAMSTEC) conducted seismic surveys at Nankai trough in order to clarify mutual relations between seismic structures and fault segments, as a part of "Research concerning Interaction Between the Tokai, Tonankai and Nankai Earthquakes" funded by Ministry of Education, Culture, Sports, Science and Technology, Japan. This study evaluated the spatial distribution of random velocity inhomogeneities from Hyuga-nada to Kii-channel by using velocity seismograms of small and moderate sized earthquakes. Random velocity inhomogeneities are estimated by the peak delay time analysis of S-wave envelopes (e.g., Takahashi et al. 2009). Peak delay time is defined as the time lag from the S-wave onset to its maximal amplitude arrival. This quantity mainly reflects the accumulated multiple forward scattering effect due to random inhomogeneities, and is quite insensitive to the inelastic attenuation. Peak delay times are measured from the rms envelopes of horizontal components at 4-8Hz, 8-16Hz and 16-32Hz. This study used the velocity seismograms that are recorded by 495 ocean bottom seismographs and 378 onshore seismic stations. Onshore stations are composed of the F-net and Hi-net stations that are maintained by National Research Institute for Earth Science and Disaster Prevention (NIED) of Japan. It is assumed that the random inhomogeneities are represented by the von Karman type PSDF. Preliminary result of inversion analysis shows that spectral gradient of PSDF (i.e., scale dependence of

  13. An ionospheric index suitable for estimating the degree of ionospheric perturbations

    Science.gov (United States)

    Wilken, Volker; Kriegel, Martin; Jakowski, Norbert; Berdermann, Jens

    2018-03-01

    Space weather can strongly affect trans-ionospheric radio signals depending on the used frequency. In order to assess the strength of a space weather event from its origin at the sun towards its impact on the ionosphere a number of physical quantities need to be derived from scientific measurements. These are for example the Wolf number sunspot index, the solar flux density F10.7, measurements of the interplanetary magnetic field, the proton density, the solar wind speed, the dynamical pressure, the geomagnetic indices Auroral Electrojet, Kp, Ap and Dst as well as the Total Electron Content (TEC), the Rate of TEC, the scintillation indices S4 and σ(ϕ) and the Along-Arc TEC Rate index index. All these quantities provide in combination with an additional classification an orientation in a physical complex environment. Hence, they are used for brief communication of a simplified but appropriate space situation awareness. However, space weather driven ionospheric phenomena can affect many customers in the communication and navigation domain, which are still served inadequately by the existing indices. We present a new robust index, that is able to properly characterize temporal and spatial ionospheric variations of small to medium scales. The proposed ionospheric disturbance index can overcome several drawbacks of other ionospheric measures and might be suitable as potential driver for an ionospheric space weather scale.

  14. Electromagnetic fields of ionospheric point dipoles in the earthionosphere waveguide

    International Nuclear Information System (INIS)

    Rybachek, S.T.

    1985-01-01

    This paper addresses the problem of excitation of the spherical earth-anisotropic ionosphere waveguide by ionospheric dipole sources. The solution obtained is based on a generalized reciprocity theorem which provides a relationship to the problem of finding electromagnetic fields in the ionosphere created by sources located in the waveguide. Some results of the calculations are presented

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

    Indian Academy of Sciences (India)

    154°E, dip angle = 37.3°, sub-ionospheric dip = 34°) have been analyzed to study the behaviour of ionospheric E-region irregularities during the active solar and magnetic periods. The autocorrelation functions, power spectral densities, signal de-correlation times are computed to study the temporal features of ionospheric ...

  16. Bottom water oxygenation changes in the northern Okinawa Trough since the last 88ka: Controlled by local hydrology and climate

    Science.gov (United States)

    Zou, Jianjun; Shi, Xuefa; Zhu, Aimei; Bai, Yazhi; Selvaraj, Kandasamy

    2014-05-01

    Dissolved oxygen content in oceanic bottom water is closely related to the surface organic carbon export and subsurface water stratification, regulating the biogeochemical cycles of some key nutrients and trace elements in intermediate and deep water columns. Further, the rate of organic carbon flux to sediments and bottom water oxygen concentration together determine the intensity of reducing conditions in sediments. In this study, we obtain high-resolution geochemical elements (TOC, TN, TS, CaCO3, Cd, U, Mn and Mo) in a radiocarbon (14C) and δ18O dated, sediment core CSH1 collected from the northern Okinawa Trough to reconstruct the history of bottom water redox conditions over 88 ka. Our data revealed the presence of hypoxic bottom water in the northern Okinawa Trough during late MIS5a-early MIS4, Last Glacial Maximum, and the early Last Deglacial intervals. During the Holocene and the early MIS5a, the dissolved oxygen content in bottom water has increased with decreasing water stratification, which was probably caused by the increased upwelling from the bottom in tandem with the climbing of Kuroshio Current and subdued freshwater effect in the northern Okinawa Trough. The reasons that caused the change of dissolved oxygen content in bottom water in the northern Okinawa Trough varied during different periods. The main factors are related to sea level, strengths of East Asian monsoon and the Kuroshio Current, and the shift of Westerly Jet Axis. The semi-closed topography in the northern Okinawa Trough provides a space framework for the presence of anoxia, while the sea level together with the Kuroshio Current, the East Asian monsoon and the Westerly Jet Axis seems to affect the strength of water stratification and the nutrient supply; thereby, regulating the dissolved oxygen exchange between surface and bottom waters. This work was supported by the National Natural Science Foundation of China(Grant No.:40906035,40710069004) and by basic scientific fund for

  17. Sounding rocket/ground-based observation campaign to study Medium-Scale Traveling Ionospheric Disturbances (MSTID)

    Science.gov (United States)

    Yamamoto, M.; Yokoyama, T.; Saito, A.; Otsuka, Y.; Yamamoto, M.; Abe, T.; Watanabe, S.; Ishisaka, K.; Saito, S.; Larsen, M.; Pfaff, R. F.; Bernhardt, P. A.

    2012-12-01

    An observation campaign is under preparation. It is to launch sounding rockets S-520-27 and S-310-42 from Uchinoura Space Center of JAXA while ground-based instruments measure waves in the ionosphere. It is scheduled in July/August 2013. The main purpose of the experiment is to reveal generation mechanism of Medium-Scale Traveling Ionospheric Disturbance (MSTID). The MSTID is the ionospheric wave with 1-2 hour periodicity, 100-200 km horizontal wavelength, and southwestward propagation. It is enhanced in the summer nighttime of the mid-latitude ionosphere. The MSTID is not only a simple atmospheric-wave modulation of the ionosphere, but shows similarity to characteristics of the Perkins instability. A problem is that growth rate of the Perkins instability is too small to explain the phenomena. We now hypothesize a generation mechanism that electromagnetic coupling of the F- and E-regions help rapid growth of the MSTID especially at its initial stage. In the observation campaign, we will use the sounding rocket S-520-27 for in-situ measurement of ionospheric parameters, i.e., electron density and electric fields. Wind velocity measurements in both F- and E-regions are very important as well. For the F-region winds, we will conduct Lithium-release experiment under the full-moon condition. This is a big technical challenge. Another rocket S-310-42 will be used for the E-region wind measurement with the TMA release. On the ground, we will use GEONET (Japanese vast GPS receiver network) to monitor horizontal distribution of GPS-TEC on the realtime bases. In the presentation we will show MSTID characteristics and the proposed generation mechanism, and discuss plan and current status of the project.

  18. Electric field effects on ionospheric and thermospheric parameters above the EISCAT station for summer conditions

    Directory of Open Access Journals (Sweden)

    V. V. Klimenko

    Full Text Available Numerical calculations of the thermospheric and ionospheric parameters above EISCAT are presented for quiet geomagnetic conditions in summer. The Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP was used. The numerical results were obtained both with a self-consistent calculation of the electric fields of magnetospheric and dynamo-action origin and with the magnetospheric electric fields only. It was found that the dynamo-electric field has some effect on the ionospheric convection pattern during quiet geomagnetic conditions. It has a marked effect mainly on the zonal neutral wind component above EISCAT (±20 m/s at 140 km altitude. We have studied the effects of various field-aligned current (FAC distributions on thermosphere/ionosphere parameters and we show that a qualitative agreement can be obtained with region-I and -II FAC zones at 75° and 65° geomagnetic latitude, respectively. The maximum FAC intensities have been assumed at 03–21 MLT for both regions with peak values of 2.5×10–7 A m–2 (region I and 1.25×10–7 A m–2 (region II. These results are in agreement with statistical potential distribution and FAC models constructed by use of EISCAT data. The lack of decreased electron density in the night-time sector as observed by the EISCAT radar was found to be due to the spatial distribution of ionospheric convection resulting from electric fields of magnetospheric origin.

    Key words. Electric fields and currents · Ionosphere- atmosphere interactions · Modelling and forecasting

  19. Electric field effects on ionospheric and thermospheric parameters above the EISCAT station for summer conditions

    Directory of Open Access Journals (Sweden)

    V. V. Klimenko

    1998-10-01

    Full Text Available Numerical calculations of the thermospheric and ionospheric parameters above EISCAT are presented for quiet geomagnetic conditions in summer. The Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP was used. The numerical results were obtained both with a self-consistent calculation of the electric fields of magnetospheric and dynamo-action origin and with the magnetospheric electric fields only. It was found that the dynamo-electric field has some effect on the ionospheric convection pattern during quiet geomagnetic conditions. It has a marked effect mainly on the zonal neutral wind component above EISCAT (±20 m/s at 140 km altitude. We have studied the effects of various field-aligned current (FAC distributions on thermosphere/ionosphere parameters and we show that a qualitative agreement can be obtained with region-I and -II FAC zones at 75° and 65° geomagnetic latitude, respectively. The maximum FAC intensities have been assumed at 03–21 MLT for both regions with peak values of 2.5×10–7 A m–2 (region I and 1.25×10–7 A m–2 (region II. These results are in agreement with statistical potential distribution and FAC models constructed by use of EISCAT data. The lack of decreased electron density in the night-time sector as observed by the EISCAT radar was found to be due to the spatial distribution of ionospheric convection resulting from electric fields of magnetospheric origin.Key words. Electric fields and currents · Ionosphere- atmosphere interactions · Modelling and forecasting

  20. Multi-Instrument Investigation of Ionospheric Flow Channels and Their Impact on the Ionosphere and Thermosphere during Geomagnetic Storms

    Science.gov (United States)

    2017-12-29

    AFRL-AFOSR-JP-TR-2018-0009 Multi-instrument investigation of ionospheric flow channels and their impact on the ionosphere and thermosphere during...SUBTITLE Multi-instrument investigation of ionospheric flow channels and their impact on the ionosphere and thermosphere during geomagnetic storms 5a...Experiment) and GOCE (Gravity field and steady- state Ocean Circulation Explorer) satellite data. We also created a series of computer algorithms to

  1. Trough Concentrations of Vancomycin in Patients Undergoing Extracorporeal Membrane Oxygenation.

    Directory of Open Access Journals (Sweden)

    So Jin Park

    Full Text Available To investigate the appropriateness of the current vancomycin dosing strategy in adult patients with extracorporeal membrane oxygenation (ECMO, between March 2013 and November 2013, patients who were treated with vancomycin while on ECMO were enrolled. Control group consisted of 60 patients on vancomycin without ECMO, stayed in medical intensive care unit during the same study period and with the same exclusion criteria. Early trough levels were obtained within the fourth dosing, and maintenance levels were measured at steady state. A total of 20 patients were included in the analysis in ECMO group. Sixteen patients received an initial intravenous dose of 1.0 g vancomycin followed by 1.0 g every 12 hours. The non-steady state trough level of vancomycin after starting administration was subtherapeutic in 19 patients (95.00% in ECMO group as compared with 40 patients (66.67% in the control group (p = 0.013. Vancomycin clearance was 1.27±0.51 mL/min/kg, vancomycin clearance/creatinine clearance ratio was 0.90 ± 0.37, and elimination rate constant was 0.12 ± 0.04 h-1. Vancomycin dosingfrequency and total daily dose were significantly increased after clinical pharmacokinetic services of the pharmacist based on calculated pharmacokinetic parameters (from 2.10 ± 0.72 to 2.90 ± 0.97 times/day, p = 0.002 and from 32.54 ± 8.43 to 42.24 ± 14.62mg/kg, p = 0.014 in ECMO group in contrast with those (from 2.11 ± 0.69 to 2.37 ± 0.86 times/day, p = 0.071 and from 33.91 ± 11.85 to 31.61 ± 17.50 mg/kg, p = 0.350 in the control group.Although the elimination rate for vancomycin was similar with population parameter of non ECMO patients, the current dosing strategy of our institution for vancomycinin our ICU was not sufficient to achieve the target trough in the initial period in most patients receiving ECMO.

  2. Ionospheric irregularities in periods of meteorological disturbances

    Science.gov (United States)

    Borchevkina, O. P.; Karpov, I. V.

    2017-09-01

    The results of observations of the total electron content (TEC) in periods of storm disturbances of meteorological situation are presented in the paper. The observational results have shown that a passage of a meteorological storm is accompanied by a substantial decrease in values of TEC and critical frequencies of the ionospheric F2 region. The decreases in values of these ionospheric parameters reach 50% and up to 30% in TEC and critical frequency of the F2 layer, respectively, as compared to meteorologically quiet days. Based on qualitative analysis, it is found that the processes related to formation of local regions of thermospheric heating due to a dissipation of AGW coming into the upper atmosphere from the region of the meteorological disturbance in the lower atmosphere are a possible cause of these ionospheric disturbances.

  3. Performance Analysis and Optimization of a Parabolic Trough Solar Power Plant in the Middle East Region

    Directory of Open Access Journals (Sweden)

    Praveen R. P.

    2018-03-01

    Full Text Available The Middle East is one among the areas of the world that receive high amounts of direct solar radiation. As such, the region holds a promising potential to leverage clean energy. Owing to rapid urbanization, energy demands in the region are on the rise. Along with the global push to curb undesirable outcomes such as air pollution, emissions of greenhouse gases, and climate change, an urgent need has arisen to explore and exploit the abundant renewable energy sources. This paper presents the design, performance analysis and optimization of a 100 MWe parabolic trough collector Solar Power Plant with thermal energy storage intended for use in the Middle Eastern regions. Two representative sites in the Middle East which offer an annual average direct normal irradiance (DNI of more than 5.5 kWh/m2/day has been chosen for the analysis. The thermodynamic aspect and annual performance of the proposed plant design is also analyzed using the System Advisor Model (SAM version 2017.9.5. Based on the analysis carried out on the initial design, annual power generated from the proposed concentrating solar power (CSP plant design in Abu Dhabi amounts to 333.15 GWh whereas that in Aswan recorded a value of 369.26 GWh, with capacity factors of 38.1% and 42.19% respectively. The mean efficiency of the plants in Abu Dhabi and Aswan are found to be 14.35% and 14.98% respectively. The optimization of the initial plant design is also carried out by varying two main design parameters, namely the solar multiple and full load hours of thermal energy storage (TES. Based on the findings of the study, the proposed 100 MW parabolic trough collector solar power plant with thermal energy storage can contribute to the sustainable energy future of the Middle East with reduced dependency on fossil fuels.

  4. Ionospheric Impacts on UHF Space Surveillance

    Science.gov (United States)

    Jones, J. C.

    2017-12-01

    Earth's atmosphere contains regions of ionized plasma caused by the interaction of highly energetic solar radiation. This region of ionization is called the ionosphere and varies significantly with altitude, latitude, local solar time, season, and solar cycle. Significant ionization begins at about 100 km (E layer) with a peak in the ionization at about 300 km (F2 layer). Above the F2 layer, the atmosphere is mostly ionized but the ion and electron densities are low due to the unavailability of neutral molecules for ionization so the density decreases exponentially with height to well over 1000 km. The gradients of these variations in the ionosphere play a significant role in radio wave propagation. These gradients induce variations in the index of refraction and cause some radio waves to refract. The amount of refraction depends on the magnitude and direction of the electron density gradient and the frequency of the radio wave. The refraction is significant at HF frequencies (3-30 MHz) with decreasing effects toward the UHF (300-3000 MHz) range. UHF is commonly used for tracking of space objects in low Earth orbit (LEO). While ionospheric refraction is small for UHF frequencies, it can cause errors in range, azimuth angle, and elevation angle estimation by ground-based radars tracking space objects. These errors can cause significant errors in precise orbit determinations. For radio waves transiting the ionosphere, it is important to understand and account for these effects. Using a sophisticated radio wave propagation tool suite and an empirical ionospheric model, we calculate the errors induced by the ionosphere in a simulation of a notional space surveillance radar tracking objects in LEO. These errors are analyzed to determine daily, monthly, annual, and solar cycle trends. Corrections to surveillance radar measurements can be adapted from our simulation capability.

  5. VHF Scintillation in an Artificially Heated Ionosphere

    Science.gov (United States)

    Suszcynsky, D. M.; Layne, J.; Light, M. E.; Pigue, M. J.; Rivera, L.

    2017-12-01

    As part of an ongoing project to characterize very-high-frequency (VHF) radio wave propagation through structured ionospheres, Los Alamos National Laboratory has been conducting a set of experiments to measure the scintillation effects of VHF transmissions under a variety of ionospheric conditions. Previous work (see 2015 Fall AGU poster by D. Suszcynsky et al.) measured the S4 index and ionospheric coherence bandwidth in the 32 - 44 MHz frequency range under naturally scintillated conditions in the equatorial region at Kwajalein Atoll during three separate campaigns centered on the 2014 and 2015 equinoxes. In this paper, we will present preliminary results from the February and September, 2017 High Altitude Auroral Research Project (HAARP) Experimental Campaigns where we are attempting to make these measurements under more controlled conditions using the HAARP ionospheric heater in a twisted-beam mode. Two types of measurements are made by transmitting VHF signals through the heated ionospheric volume to the Radio Frequency Propagation (RFProp) satellite experiment. The S4 scintillation index is determined by measuring the power fluctuations of a 135-MHz continuous wave signal and the ionospheric coherence bandwidth is simultaneously determined by measuring the delay spread of a frequency-modulated continuous wave (FMCW) signal in the 130 - 140 MHz frequency range. Additionally, a spatial Fourier transform of the CW time series is used to calculate the irregularity spectral density function. Finally, the temporal evolution of the time series is used to characterize spread-Doppler clutter effects arising from preferential ray paths to the satellite due to refraction off of isolated density irregularities. All results are compared to theory and scaled for comparison to the 32 - 44 MHz Kwajalein measurements.

  6. Air-borne shape measurement of parabolic trough collector fields

    Science.gov (United States)

    Prahl, Christoph; Röger, Marc; Hilgert, Christoph

    2017-06-01

    The optical and thermal efficiency of parabolic trough collector solar fields is dependent on the performance and assembly accuracy of its components such as the concentrator and absorber. For the purpose of optical inspection/approval, yield analysis, localization of low performing areas, and optimization of the solar field, it is essential to create a complete view of the optical properties of the field. Existing optical measurement tools are based on ground based cameras, facing restriction concerning speed, volume and automation. QFly is an airborne qualification system which provides holistic and accurate information on geometrical, optical, and thermal properties of the entire solar field. It consists of an unmanned aerial vehicle, cameras and related software for flight path planning, data acquisition and evaluation. This article presents recent advances of the QFly measurement system and proposes a methodology on holistic qualification of the complete solar field with minimum impact on plant operation.

  7. Test results, Industrial Solar Technology parabolic trough solar collector

    Energy Technology Data Exchange (ETDEWEB)

    Dudley, V.E. [EG and G MSI, Albuquerque, NM (United States); Evans, L.R.; Matthews, C.W. [Sandia National Labs., Albuquerque, NM (United States)

    1995-11-01

    Sandia National Laboratories and Industrial Solar Technology are cost-sharing development of advanced parabolic trough technology. As part of this effort, several configurations of an IST solar collector were tested to determine the collector efficiency and thermal losses with black chrome and black nickel receiver selective coatings, combined with aluminized film and silver film reflectors, using standard Pyrex{reg_sign} and anti-reflective coated Pyrex{reg_sign} glass receiver envelopes. The development effort has been successful, producing an advanced collector with 77% optical efficiency, using silver-film reflectors, a black nickel receiver coating, and a solgel anti-reflective glass receiver envelope. For each receiver configuration, performance equations were empirically derived relating collector efficiency and thermal losses to the operating temperature. Finally, equations were derived showing collector performance as a function of input insolation value, incident angle, and operating temperature.

  8. Diurnal variations of Titan's ionosphere

    Science.gov (United States)

    Cui, J.; Galand, M.; Yelle, R. V.; Vuitton, V.; Wahlund, J.-E.; Lavvas, P. P.; Müller-Wodarg, I. C. F.; Cravens, T. E.; Kasprzak, W. T.; Waite, J. H.

    2009-06-01

    We present our analysis of the diurnal variations of Titan's ionosphere (between 1000 and 1300 km) based on a sample of Ion Neutral Mass Spectrometer (INMS) measurements in the Open Source Ion (OSI) mode obtained from eight close encounters of the Cassini spacecraft with Titan. Although there is an overall ion depletion well beyond the terminator, the ion content on Titan's nightside is still appreciable, with a density plateau of ˜700 cm-3 below ˜1300 km. Such a plateau is a combined result of significant depletion of light ions and modest depletion of heavy ones on Titan's nightside. We propose that the distinctions between the diurnal variations of light and heavy ions are associated with their different chemical loss pathways, with the former primarily through “fast” ion-neutral chemistry and the latter through “slow” electron dissociative recombination. The strong correlation between the observed night-to-day ion density ratios and the associated ion lifetimes suggests a scenario in which the ions created on Titan's dayside may survive well to the nightside. The observed asymmetry between the dawn and dusk ion density profiles also supports such an interpretation. We construct a time-dependent ion chemistry model to investigate the effect of ion survival associated with solid body rotation alone as well as superrotating horizontal winds. For long-lived ions, the predicted diurnal variations have similar general characteristics to those observed. However, for short-lived ions, the model densities on the nightside are significantly lower than the observed values. This implies that electron precipitation from Saturn's magnetosphere may be an additional and important contributor to the densities of the short-lived ions observed on Titan's nightside.

  9. Theory of imperfect magnetosphere-ionosphere coupling

    International Nuclear Information System (INIS)

    Kan, J.R.; Lee, L.C.

    1980-01-01

    Atheory of magnetosphere-ionosphere coupling in the presence of field-aligned potential drops is formulated within the framework of magnetohydrodynamic equations. Our formulation allows the magnetosphere as well as the ionosphere to respond self-consistently to the parallel potential drop along auroral field lines. Equipotential contours are distorted into a V-shaped structure near the convection reversal boundary and S-shaped on the equatorward side, each gives rise to an inverted V precipitation band. The loading effect of the imperfect coupling results in a valley in the electric field profile which occurs equatorward of the convection reversal boundary

  10. Time properties of ionospheric wave disturbances

    International Nuclear Information System (INIS)

    Kaliev, M.Z.; Krasnikov, I.M.; Litvinov, Yu.G.; Chakenov, B.D.; Yakovets, A.F.

    1989-01-01

    Records of Doppler frequency shifts of an ionospheric signal, taken in separate observation posts in the vicinity of Alma-Ata in 1986-1987, are analyzed. It is shown that the coherent parts of Doppler shift oscillations are wave disturbance trains in the ionospheric F region. The relation between the train duration and its central frequency is established. With the frequency decrease the mean train length increases, while the maximum train length, determined in the experiment, is about 6h. The probabilities of train detection in the low and high-frequency ranges are nearly the same, and moreover, they are equal in day time and at night

  11. Using DORIS measurements for ionosphere modeling

    Science.gov (United States)

    Dettmering, Denise; Schmidt, Michael; Limberger, Marco

    2013-04-01

    Nowadays, most of the ionosphere models used in geodesy are based on terrestrial GNSS measurements and describe the Vertical Total Electron Content (VTEC) depending on longitude, latitude, and time. Since modeling the height distribution of the electrons is difficult due to the measurement geometry, the VTEC maps are based on the the assumption of a single-layer ionosphere. Moreover, the accuracy of the VTEC maps is different for different regions of the Earth, because the GNSS stations are unevenly distributed over the globe and some regions (especially the ocean areas) are not very well covered by observations. To overcome the unsatisfying measurement geometry of the terrestrial GNSS measurements and to take advantage of the different sensitivities of other space-geodetic observation techniques, we work on the development of multi-dimensional models of the ionosphere from the combination of modern space-geodetic satellite techniques. Our approach consists of a given background model and an unknown correction part expanded in terms of B-spline functions. Different space-geodetic measurements are used to estimate the unknown model coefficients. In order to take into account the different accuracy levels of the observations, a Variance Component Estimation (VCE) is applied. We already have proven the usefulness of radio occultation data from space-borne GPS receivers and of two-frequency altimetry data. Currently, we test the capability of DORIS observations to derive ionospheric parameters such as VTEC. Although DORIS was primarily designed for precise orbit computation of satellites, it can be used as a tool to study the Earth's ionosphere. The DORIS ground beacons are almost globally distributed and the system is on board of various Low Earth Orbiters (LEO) with different orbit heights, such as Jason-2, Cryosat-2, and HY-2. The last generation of DORIS receivers directly provides phase measurements on two frequencies. In this contribution, we test the DORIS

  12. The remote atmospheric and ionospheric detection system

    International Nuclear Information System (INIS)

    McCoy, R.P.; Wolfram, K.D.; Meier, R.R.

    1986-01-01

    The Remote Atmospheric and Ionospheric Detection System (RAIDS) experiment, to fly on a TIROS spacecraft in the late 1980's, consists of a comprehensive set of one limb imaging and seven limb scanning optical sensors. These eight instruments span the spectral range from the extreme ultraviolet to the near infrared, allowing simultaneous observations of the neutral and ion composition on the day and night side as well as in the auroral region. The primary objective of RAIDS is to demonstrate a system for remote sensing of the ionosphere to produce global maps of the electron density, peak altitude and critical frequency

  13. Early to middle Jurassic salt in Baltimore Canyon trough

    Science.gov (United States)

    McKinney, B. Ann; Lee, Myung W.; Agena, Warren F.; Poag, C. Wylie

    2005-01-01

    A pervasive, moderately deep (5-6 s two-way traveltime), high-amplitude reflection is traced on multichannel seismic sections over an approximately 7500 km² area of Baltimore Canyon Trough. The layer associated with the reflection is about 25 km wide, about 60 m thick in the center, and thins monotonically laterally, though asymmetrically, at the edges. Geophysical characteristics are compatible with an interpretation of this negative-polarity reflector as a salt lens deposited on the top of a synrift evaporite sequence. However, alternative interpretations of the layer as gas-saturated sediments, an overpressured shale, or a weathered igneous intrusion are also worthy of consideration.Geophysical analyses were made on three wavelet- and true-amplitude processed multichannel seismic dip lines. The lens-shaped layer demarked by the reflection has a velocity of 4.4 km/s; the lens lies within strata having velocities of 5.3 to 5.7 km/s. A trough marking the onset of the lens has an amplitude that is 10 to 20 db greater than reflections from the encasing layers and an apparent reflection coefficient of -0.24. Using amplitude versus offset analysis methods, we determined that observed reflection coefficients, though variable, decrease consistently with respect to increasing offset. Linear inversion yields a low density, about 2.2 g/cc. Integration of one of the true-amplitude-processed lines and one-dimensional modeling of the layer provide data on the impedance contrast and interference patterns that further reinforce the salt lens interpretation.The thin, horizontal salt lens was probably deposited or precipitated during the Jurassic in a shallow, narrow (peripheral) rift basin, as rifting progressed down the North Atlantic margin. Unlike thicker deposits in other areas that deformed and flowed, often into diapir structures, this thin lens has remained relatively undisturbed since deposition.

  14. The trochlear cleft: the ''black line'' of the trochlear trough

    International Nuclear Information System (INIS)

    Wissman, Robert D.; Nepute, Joshua; Fischer, Nathaniel von; Radhakrishnan, Rupa; Hendry, Daniel; Ingalls, Jerrell; Kenter, Keith

    2012-01-01

    The ''cartilage black line sign'' is a recently described T2 dark cartilage lesion that we have identified appearing as a cleft in the trochlear trough. The purpose of our study was to define the MR imaging characteristics of a trochlear cleft, determine its incidence, and correlate the MR findings with arthroscopy. A total of 1,300 consecutive MR examinations of the knee were retrospectively reviewed by consensus of two fellowship-trained musculoskeletal radiologists. The MR imaging characteristics and location of a trochlear cleft were determined. Imaging results were compared to arthroscopy when available. Patient age and gender were compared to 25 randomly selected control patients without trochlear clefts. A total of 25 (1.9%) individuals (11 females and 14 males; age range 19-45 years; mean age 28 years) were diagnosed with a trochlear cleft. The control group consisted of 11 females and 14 males; age range 19-83 years; mean age 46 years. Mean cleft length was 7 mm (range 6-12 mm); cleft location was consistently in the lower trochlear trough. No full-thickness cartilage defects were identified in the eight individuals in whom arthroscopic correlation was available. A grade 2 cartilage lesion was identified in a single individual; another progressed from grade 0 to a full-thickness trochlear lesion over an 8-month interval. Eight individuals were athletes. No significant difference in gender was noted between the two groups, however, the study group was significantly younger p < 0.0001. A trochlear cleft is a rare finding in young active individuals. It most likely indicates an incomplete cartilage fissure which may rarely progress to a full-thickness defect. (orig.)

  15. An experimental study of thermal characterization of parabolic trough receivers

    International Nuclear Information System (INIS)

    Lei, Dongqiang; Li, Qiang; Wang, Zhifeng; Li, Jian; Li, Jianbin

    2013-01-01

    Highlights: ► A new test stand of heat loss has been developed at IEECAS. ► A correlation between heat loss and absorber temperature is presented, 270 W/m 400 °C. ► The ratio of end loss in total heat loss increases with decreasing the temperature. ► The emittance test stand using a high vacuum system and vacuum gauge is built. ► Emittance first decreases, then rapidly increases with increasing the temperature. - Abstract: The receiver is a key component of the parabolic trough solar station. The receiver requires the most challenging technology and has a decisive influence on the thermal and economic performance of a power plant. The Institute of Electrical Engineering Chinese Academy Sciences (IEECAS) and Himin Solar Co., Ltd. (HSC) cooperated to develop solar receivers for the first 50 MW parabolic trough project in Inner Mongolia, China. This paper examines overall heat loss, end loss and thermal emittance of the coating of a newly designed receiver in order to evaluate its thermal characterization. A series of heat loss tests are conducted in a newly developed test stand following the steady state equilibrium method. The tests provide a correlation between heat loss and the absorber temperature. This paper presents a new testing method to accurately test the coating emittance. The method uses a receiver with a high vacuum system and a vacuum gauge to maintain continuous exhaust and high vacuum throughout the heat loss testing. A heat loss comparison between the receiver and other existing receivers provides a reference that enabled further optimization. Theoretical and experimental analysis examines the effects of end loss both with and without a heat insulator and a coil heater. The emittance curves of different coatings are acquired and the reasons for initial emittance decrease and then remarkable increase versus temperature are analyzed

  16. Ionospheric quasi-static electric field anomalies during seismic activity in August–September 1981

    Directory of Open Access Journals (Sweden)

    M. Gousheva

    2009-01-01

    Full Text Available The paper proposes new results, analyses and information for the plate tectonic situation in the processing of INTERCOSMOS-BULGARIA-1300 satellite data about anomalies of the quasi-static electric field in the upper ionosphere over activated earthquake source regions at different latitudes. The earthquake catalogue is made on the basis of information from the United State Geological Survey (USGS website. The disturbances in ionospheric quasi-static electric fields are recorded by IESP-1 instrument aboard the INTERCOSMOS-BULGARIA-1300 satellite and they are compared with significant seismic events from the period 14 August–20 September 1981 in magnetically very quiet, quiet and medium quiet days. The main tectonic characteristics of the seismically activated territories are also taken in account. The main goal of the above research work is to enlarge the research of possible connections between anomalous vertical electric field penetrations into the ionosphere and the earthquake manifestations, also to propose tectonic arguments for the observed phenomena. The studies are represented in four main blocks: (i previous studies of similar problems, (ii selection of satellite, seismic and plate tectonic data, (iii data processing with new specialized software and observations of the quasi-static electric field and (iiii summary, comparison of new with previous results in our studies and conclusion. We establish the high informativity of the vertical component Ez of the quasi-static electric field in the upper ionosphere according observations by INTERCOSMOS-BULGARIA-1300 that are placed above considerably activated earthquake sources. This component shows an increase of about 2–10 mV/m above sources, situated on mobile structures of the plates. The paper discusses the observed effects. It is represented also a statistical study of ionospheric effects 5–15 days before and 5–15 days after the earthquakes with magnitude M 4.8–7.9.

  17. New sidescan sonar and gravity evidence that the Nova-Canton Trough is a fracture zone

    Science.gov (United States)

    Joseph, Devorah; Taylor, Brian; Shor, Alexander N.

    1992-05-01

    A 1990 sidescan sonar survey in the eastern region of the Nova-Canton Trough mapped 138°-striking abyssal-hill fabric trending into 70°-striking trough structures. The location and angle of intersection of the abyssal hills with the eastern Nova-Canton Trough effectively disprove a spreading-center origin of this feature. Free-air gravity anomalies derived from satellite altimetry data show continuity, across the Line Islands, of the Nova-Canton Trough with the Clipperton Fracture Zone. The Canton-Clipperton trend is copolar, about a pole at 30°S, 152°W, with other coeval Pacific-Farallon fracture-zone segments, from the Pau to Marquesas fracture zones. This copolarity leads us to postulate a Pacific-Farallon spreading pattern for the magnetic quiet zone region north and east of the Manihiki Plateau, with the Nova-Canton Trough originating as a transform fault in this system.

  18. Analysis of the positive ionospheric response to a moderate geomagnetic storm using a global numerical model

    Directory of Open Access Journals (Sweden)

    A. A. Namgaladze

    2000-04-01

    Full Text Available Current theories of F-layer storms are discussed using numerical simulations with the Upper Atmosphere Model, a global self-consistent, time dependent numerical model of the thermosphere-ionosphere-plasmasphere-magnetosphere system including electrodynamical coupling effects. A case study of a moderate geomagnetic storm at low solar activity during the northern winter solstice exemplifies the complex storm phenomena. The study focuses on positive ionospheric storm effects in relation to thermospheric disturbances in general and thermospheric composition changes in particular. It investigates the dynamical effects of both neutral meridional winds and electric fields caused by the disturbance dynamo effect. The penetration of short-time electric fields of magnetospheric origin during storm intensification phases is shown for the first time in this model study. Comparisons of the calculated thermospheric composition changes with satellite observations of AE-C and ESRO-4 during storm time show a good agreement. The empirical MSISE90 model, however, is less consistent with the simulations. It does not show the equatorward propagation of the disturbances and predicts that they have a gentler latitudinal gradient. Both theoretical and experimental data reveal that although the ratio of [O]/[N2] at high latitudes decreases significantly during the magnetic storm compared with the quiet time level, at mid to low latitudes it does not increase (at fixed altitudes above the quiet reference level. Meanwhile, the ionospheric storm is positive there. We conclude that the positive phase of the ionospheric storm is mainly due to uplifting of ionospheric F2-region plasma at mid latitudes and its equatorward movement at low latitudes along geomagnetic field lines caused by large-scale neutral wind circulation and the passage of travelling atmospheric disturbances (TADs. The calculated zonal electric field disturbances also help to create the positive ionospheric

  19. Analysis of the positive ionospheric response to a moderate geomagnetic storm using a global numerical model

    Directory of Open Access Journals (Sweden)

    A. A. Namgaladze

    Full Text Available Current theories of F-layer storms are discussed using numerical simulations with the Upper Atmosphere Model, a global self-consistent, time dependent numerical model of the thermosphere-ionosphere-plasmasphere-magnetosphere system including electrodynamical coupling effects. A case study of a moderate geomagnetic storm at low solar activity during the northern winter solstice exemplifies the complex storm phenomena. The study focuses on positive ionospheric storm effects in relation to thermospheric disturbances in general and thermospheric composition changes in particular. It investigates the dynamical effects of both neutral meridional winds and electric fields caused by the disturbance dynamo effect. The penetration of short-time electric fields of magnetospheric origin during storm intensification phases is shown for the first time in this model study. Comparisons of the calculated thermospheric composition changes with satellite observations of AE-C and ESRO-4 during storm time show a good agreement. The empirical MSISE90 model, however, is less consistent with the simulations. It does not show the equatorward propagation of the disturbances and predicts that they have a gentler latitudinal gradient. Both theoretical and experimental data reveal that although the ratio of [O]/[N2] at high latitudes decreases significantly during the magnetic storm compared with the quiet time level, at mid to low latitudes it does not increase (at fixed altitudes above the quiet reference level. Meanwhile, the ionospheric storm is positive there. We conclude that the positive phase of the ionospheric storm is mainly due to uplifting of ionospheric F2-region plasma at mid latitudes and its equatorward movement at low latitudes along geomagnetic field lines caused by large-scale neutral wind circulation and the passage of travelling atmospheric disturbances (TADs. The calculated zonal electric field disturbances also help

  20. Ground-based acoustic parametric generator impact on the atmosphere and ionosphere in an active experiment

    Directory of Open Access Journals (Sweden)

    Y. G. Rapoport

    2017-01-01

    Full Text Available We develop theoretical basics of active experiments with two beams of acoustic waves, radiated by a ground-based sound generator. These beams are transformed into atmospheric acoustic gravity waves (AGWs, which have parameters that enable them to penetrate to the altitudes of the ionospheric E and F regions where they influence the electron concentration of the ionosphere. Acoustic waves are generated by the ground-based parametric sound generator (PSG at the two close frequencies. The main idea of the experiment is to design the output parameters of the PSG to build a cascade scheme of nonlinear wave frequency downshift transformations to provide the necessary conditions for their vertical propagation and to enable penetration to ionospheric altitudes. The PSG generates sound waves (SWs with frequencies f1 = 600 and f2 = 625 Hz and large amplitudes (100–420 m s−1. Each of these waves is modulated with the frequency of 0.016 Hz. The novelty of the proposed analytical–numerical model is due to simultaneous accounting for nonlinearity, diffraction, losses, and dispersion and inclusion of the two-stage transformation (1 of the initial acoustic waves to the acoustic wave with the difference frequency Δf = f2 − f1 in the altitude ranges 0–0.1 km, in the strongly nonlinear regime, and (2 of the acoustic wave with the difference frequency to atmospheric acoustic gravity waves with the modulational frequency in the altitude ranges 0.1–20 km, which then reach the altitudes of the ionospheric E and F regions, in a practically linear regime. AGWs, nonlinearly transformed from the sound waves, launched by the two-frequency ground-based sound generator can increase the transparency of the ionosphere for the electromagnetic waves in HF (MHz and VLF (kHz ranges. The developed theoretical model can be used for interpreting an active experiment that includes the PSG impact on the atmosphere–ionosphere system

  1. Ionospheric detection of tsunami earthquakes: observation, modeling and ideas for future early warning

    Science.gov (United States)

    Occhipinti, G.; Manta, F.; Rolland, L.; Watada, S.; Makela, J. J.; Hill, E.; Astafieva, E.; Lognonne, P. H.

    2017-12-01

    Detection of ionospheric anomalies following the Sumatra and Tohoku earthquakes (e.g., Occhipinti 2015) demonstrated that ionosphere is sensitive to earthquake and tsunami propagation: ground and oceanic vertical displacement induces acoustic-gravity waves propagating within the neutral atmosphere and detectable in the ionosphere. Observations supported by modelling proved that ionospheric anomalies related to tsunamis are deterministic and reproducible by numerical modeling via the ocean/neutral-atmosphere/ionosphere coupling mechanism (Occhipinti et al., 2008). To prove that the tsunami signature in the ionosphere is routinely detected we show here perturbations of total electron content (TEC) measured by GPS and following tsunamigenic earthquakes from 2004 to 2011 (Rolland et al. 2010, Occhipinti et al., 2013), nominally, Sumatra (26 December, 2004 and 12 September, 2007), Chile (14 November, 2007), Samoa (29 September, 2009) and the recent Tohoku-Oki (11 Mars, 2011). Based on the observations close to the epicenter, mainly performed by GPS networks located in Sumatra, Chile and Japan, we highlight the TEC perturbation observed within the first 8 min after the seismic rupture. This perturbation contains information about the ground displacement, as well as the consequent sea surface displacement resulting in the tsunami. In addition to GNSS-TEC observations close to the epicenter, new exciting measurements in the far-field were performed by airglow measurement in Hawaii show the propagation of the internal gravity waves induced by the Tohoku tsunami (Occhipinti et al., 2011). This revolutionary imaging technique is today supported by two new observations of moderate tsunamis: Queen Charlotte (M: 7.7, 27 October, 2013) and Chile (M: 8.2, 16 September 2015). We finally detail here our recent work (Manta et al., 2017) on the case of tsunami alert failure following the Mw7.8 Mentawai event (25 October, 2010), and its twin tsunami alert response following the Mw7

  2. Application of Wuhan Ionospheric Oblique Backscattering Sounding System (WIOBSS) for the investigation of midlatitude ionospheric irregularities

    Science.gov (United States)

    Wang, Jin; Zhou, Xiaoming; Qiao, Lei; Gong, Wanlin

    2018-03-01

    An upgrade of Wuhan Ionospheric Backscattering Sounding System (WIOBSS) was developed in 2015. Based on the Universal Serial Bus (USB), and a high performance FPGA, the newly designed WIOBSS has a completely digital structure, which makes it portable and flexible. Two identical WIOBSSs, which were situated at Mile (24.31°N, 103.39°E) and Puer (22.74°N, 101.05°E) respectively, were used to investigate the ionospheric irregularities. The comparisons of group distance, Doppler shift and width between Mile-Puer and Puer-Mile VHF ionospheric propagation paths indicate that the reciprocity of the irregularities is satisfied at midlatitude region. The WIOBSS is robust in the detection of ionospheric irregularities.

  3. Concurrent immunomodulator therapy is associated with higher adalimumab trough levels during scheduled maintenance therapy.

    Science.gov (United States)

    Bond, Ashley; Dodd, Susanna; Fisher, Gareth; Skouras, Thomas; Subramanian, Sreedhar

    2017-02-01

    Combination therapy with infliximab and immunomodulators is superior to monotherapy, resulting in better outcomes and higher trough levels of infliximab. The role of concurrent immunomodulatory therapy on adalimumab trough levels has not been adequately investigated. We evaluated the impact of concomitant immunomodulation on adalimumab trough levels in patients on scheduled maintenance therapy. We conducted a prospective observational, cross-sectional study of all inflammatory bowel disease patients on maintenance therapy who had adalimumab trough levels measured between January 2013 and January 2016. Drug level and anti-drug antibody measurements were performed on sera using a solid phase assay. Pairwise comparison of means was used to compare trough levels in patients with and without concomitant immune modulator therapy. In total, 79 patients were included. Twenty-three patients (29.1%) were on weekly dosing whereas 56 (70.9%) were on alternate weeks. Median adalimumab trough levels were comparable in patients with and without clinical remission (6.8 μg/ml (IQR 5.6-8.1) versus 6.7 μg/ml (IQR 3.9-8.1), respectively. Patients with an elevated faecal calprotectin >250 μg/g had lower adalimumab trough levels (median 6.7, IQR 3.9-8) compared to patients with faecal calprotectin <250 μg/g (median 7.7, IQR 6.1-8.1) though this did not achieve statistical significance (p = .062). Median adalimumab trough levels among patients on concurrent immunomodulators was 7.2 μg/ml (IQR 5.7-8.1) compared to those not on concurrent immunomodulator, 6.1 μg/ml (IQR 2.7-7.7, p = .0297). Adalimumab trough levels were significantly higher in patients on concurrent immunomodulators during maintenance therapy. There was a trend towards a lower adalimumab trough level in patients with elevated calprotectin.

  4. Aeolian sand transport over complex intertidal bar-trough beach topography

    Science.gov (United States)

    Anthony, Edward J.; Ruz, Marie-Hélène; Vanhée, Stéphane

    2009-04-01

    Aeolian sand transport on macrotidal beaches with complex intertidal bar-trough topography (ridge-and-runnel beaches) was assessed from experiments in northern France that involved measurements of wind speed, saltation, surface moisture contents, and rates of sand trapping across surveyed portions of the upper beach profile. Beaches exhibiting intertidal bars and troughs are much more complex, topographically, than simple reflective or dissipative beaches. Furthermore, the intertidal bar-trough morphology commonly exhibits strong cross-shore variations in the moisture contents of the beach surface and in patterns of bedform development. The results of four 30-minute experiments, conducted along topographically surveyed portions of the upper beach-dune toe profile, show that troughs act as extremely efficient sand interceptors, because of their permanently saturated state, which also inhibits sand mobilisation. Troughs, thus, limit or segment the dry fetch during conditions of intermittent saltation. Flow lines, inferred from the wind profiles, suggest that complex interactions at the boundary layer are generated by the bar-trough topography. Troughs systematically appear to be characterised by air expansion, while bar faces generate ramp wind acceleration for onshore winds, and sometimes immediate downwind deceleration for offshore winds. These effects may also contribute to cross-shore variations in the rates of sand trapping. Finally, a simple conceptual model of effective fetch development, integrating the effects of the spring-neap tidal range and of gross bar-trough morphological variability over time, is proposed for bar-trough beaches. The model highlights the key theme of fetch segmentation induced by cross-shore differentiation in the moisture contents of the beach surface hinged on the complex topography of multiple bars and troughs.

  5. A review of ionospheric effects on Earth-space propagation

    Science.gov (United States)

    Klobuchar, J. A.

    1984-01-01

    A short description is given of each ionospheric total electron content (TEC) effect upon radio waves, along with a representative value of the magnitude of each of these effects under normal ionospheric conditions. A discussion is given of the important characteristics of average ionospheric TEC behavior and the temporal and spatial variability of TEC. Radio waves undergo several effects when they pass through the Earth's ionosphere. One of the most important of these effects is a retardation, or group delay, on the modulation or information carried on the radio wave that is due to its encounter with the free, thermal electrons in the Earth's ionosphere. Other effects the ionosphere has on radio waves include: radio frequency (RF) carrier phase advance; Doppler shift of the RF carrier of the radio wave; Faraday rotation of the plane of polarization of linearly polarized waves; angular refraction or bending of the radio wave path as it travels through the ionosphere; and amplitude and phase scintillations.

  6. Control scheme for direct steam generation in parabolic troughs under recirculation operation mode

    Energy Technology Data Exchange (ETDEWEB)

    Valenzuela, L.; Zarza, E. [CIEMAT, Plataforma Solar de Almeria, Ctra. Senes s/n, P.O. Box 22, E-04200 Tabernas, Almeria (Spain); Berenguel, M. [Universidad de Almeria, Dpto. Lenguajes y Computacion, Ctra. Sacramento s/n, E-04120 Almeria (Spain); Camacho, E.F. [Universidad de Sevilla, Dpto. de Ingenieria de Sistemas y Automatica, Camino de los Descubrimientos s/n, E-41092 Sevilla (Spain)

    2006-01-15

    Electricity production using solar thermal energy is one of the main research areas at present in the field of renewable energies, these systems being characterised by the need of reliable control systems aimed at maintaining desired operating conditions in the face of changes in solar radiation, which is the main source of energy. A new prototype of solar system with parabolic trough collectors was implemented at the Plataforma Solar de Almeria (PSA, South-East Spain) to investigate the direct steam generation process under real solar conditions in the parabolic solar collector field of a thermal power plant prototype. This paper presents details and some results of the application of a control scheme designed and tested for the recirculation operation mode, for which the main objective is to obtain steam at constant temperature and pressure at the outlet of the solar field, so that changes produced in the inlet water conditions and/or solar radiation will only affect the amount of steam produced by the solar field. The steam quality and consequently the nominal efficiency of the plant are thus maintained. (author)

  7. Coupled storm-time magnetosphere-ionosphere-thermosphere simulations including microscopic ionospheric turbulence

    Science.gov (United States)

    Merkin, V. G.; Wiltberger, M. J.; Zhang, B.; Liu, J.; Wang, W.; Dimant, Y. S.; Oppenheim, M. M.; Lyon, J.

    2017-12-01

    During geomagnetic storms the magnetosphere-ionosphere-thermosphere system becomes activated in ways that are unique to disturbed conditions. This leads to emergence of physical feedback loops that provide tighter coupling between the system elements, often operating across disparate spatial and temporal scales. One such process that has recently received renewed interest is the generation of microscopic ionospheric turbulence in the electrojet regions (electrojet turbulence, ET) that results from strong convective electric fields imposed by the solar wind-magnetosphere interaction. ET leads to anomalous electron heating and generation of non-linear Pedersen current - both of which result in significant increases in effective ionospheric conductances. This, in turn, provides strong non-linear feedback on the magnetosphere. Recently, our group has published two studies aiming at a comprehensive analysis of the global effects of this microscopic process on the magnetosphere-ionosphere-thermosphere system. In one study, ET physics was incorporated in the TIEGCM model of the ionosphere-thermosphere. In the other study, ad hoc corrections to the ionospheric conductances based on ET theory were incorporated in the conductance module of the Lyon-Fedder-Mobarry (LFM) global magnetosphere model. In this presentation, we make the final step toward the full coupling of the microscopic ET physics within our global coupled model including LFM, the Rice Convection Model (RCM) and TIEGCM. To this end, ET effects are incorporated in the TIEGCM model and propagate throughout the system via thus modified TIEGCM conductances. The March 17, 2013 geomagnetic storm is used as a testbed for these fully coupled simulations, and the results of the model are compared with various ionospheric and magnetospheric observatories, including DMSP, AMPERE, and Van Allen Probes. Via these comparisons, we investigate, in particular, the ET effects on the global magnetosphere indicators such as the

  8. Ionospheric effects during severe space weather events seen in ionospheric service data products

    Science.gov (United States)

    Jakowski, Norbert; Danielides, Michael; Mayer, Christoph; Borries, Claudia

    Space weather effects are closely related to complex perturbation processes in the magnetosphere-ionosphere-thermosphere systems, initiated by enhanced solar energy input. To understand and model complex space weather processes, different views on the same subject are helpful. One of the ionosphere key parameters is the Total Electron Content (TEC) which provides a first or-der approximation of the ionospheric range error in Global Navigation Satellite System (GNSS) applications. Additionally, horizontal gradients and time rate of change of TEC are important for estimating the perturbation degree of the ionosphere. TEC maps can effectively be gener-ated using ground based GNSS measurements from global receiver networks. Whereas ground based GNSS measurements provide good horizontal resolution, space based radio occultation measurements can complete the view by providing information on the vertical plasma density distribution. The combination of ground based TEC and vertical sounding measurements pro-vide essential information on the shape of the vertical electron density profile by computing the equivalent slab thickness at the ionosonde station site. Since radio beacon measurements at 150/400 MHz are well suited to trace the horizontal structure of Travelling Ionospheric Dis-turbances (TIDs), these data products essentially complete GNSS based TEC mapping results. Radio scintillation data products, characterising small scale irregularities in the ionosphere, are useful to estimate the continuity and availability of transionospheric radio signals. The different data products are addressed while discussing severe space weather events in the ionosphere e.g. events in October/November 2003. The complementary view of different near real time service data products is helpful to better understand the complex dynamics of ionospheric perturbation processes and to forecast the development of parameters customers are interested in.

  9. The topside ionosphere above Arecibo at equinox during sunspot maximum

    International Nuclear Information System (INIS)

    Bailey, G.J.

    1980-01-01

    The coupled time-dependent 0 + and H + continuity and momentum equations and 0 + , H + and electron heat balance equations are solved simultaneously within the L = 1.4 (Arecibo) magnetic flux tube between an altitude of 120 km and the equatorial plane. The results of the calculations are used in a study of the topside ionosphere above Arecibo at equinox during sunspot maximum. Magnetically quiet conditions are assumed. The results of the calculations show that the L = 1.4 magnetic flux tube becomes saturated from an arbitrary state within 2-3 days. During the day the ion content of the magnetic flux tube consists mainly of 0 + whereas 0 + and H + are both important during the night. There is an altitude region in the topside ionosphere during the day where ion-counterstreaming occurs with H + flowing downward and 0 + flowing upward. The conditions causing this ion-counterstreaming are discussed. There is a net chemical gain of H + at the higher altitudes. This H + diffuses both upwards and downwards whilst 0 + diffuses upwards from its solar e.u.v. production source which is most important at the lower altitudes. During the night the calculated 0 + and H + temperatures are very nearly equal whereas during the day there are occasions when the H + temperature exceeds the 0 - temperature by about 300 K. (author)

  10. Ionosphere and thermosphere responses during August 1972 storms - a review

    International Nuclear Information System (INIS)

    Matsushita, S.

    1976-01-01

    Various reports of ionospheric responses during the August 1972 storm events are reviewed with respect to the phenomena in three major world sectors, N-S America, Afro-Europe, and Austro-Asia, in order to have a global picture. Emphasized highlights are (1) extensive investigation of the sudden increase of the total electron content estimated from Faraday-rotation measurements of satellite signals; (2) a dramatic upward surge above 300 km latitude, soon after a flare, measured by the Millstone Hill incoherent scatter radar; (3) electron density profiles, electric fields and conductivities, and neutral winds, at the time of the geomagnetic storm sudden commencement and during the succeeding storms, measured by the Chatanika incoherent scatter radar; and, (4) approximately 2.5-h oscillatory F2 density variations in Eastern Asia during the F2 storm main phase. To show temporal variations of the latitudinal distributions of storm-time F2 electron densities, in three longitudinal sectors separated about 60 0 longitude each, newly investigated results of the F2 hourly data at 35 stations in the Asia-Australia-Pacific sector are then exhibited. Finally, current theories or at least theoretical ideas of ionospheric storm mechanisms are briefly introduced, and a few remarks on the August events in the light of those theories are presented. (Auth.)

  11. Ionospheric precursors for crustal earthquakes in Italy

    Directory of Open Access Journals (Sweden)

    L. Perrone

    2010-04-01

    Full Text Available Crustal earthquakes with magnitude 6.0>M≥5.5 observed in Italy for the period 1979–2009 including the last one at L'Aquila on 6 April 2009 were considered to check if the earlier obtained relationships for ionospheric precursors for strong Japanese earthquakes are valid for the Italian moderate earthquakes. The ionospheric precursors are based on the observed variations of the sporadic E-layer parameters (h'Es, fbEs and foF2 at the ionospheric station Rome. Empirical dependencies for the seismo-ionospheric disturbances relating the earthquake magnitude and the epicenter distance are obtained and they have been shown to be similar to those obtained earlier for Japanese earthquakes. The dependences indicate the process of spreading the disturbance from the epicenter towards periphery during the earthquake preparation process. Large lead times for the precursor occurrence (up to 34 days for M=5.8–5.9 tells about a prolong preparation period. A possibility of using the obtained relationships for the earthquakes prediction is discussed.

  12. Ionospheric error analysis in gps measurements

    Directory of Open Access Journals (Sweden)

    G. Pugliano

    2008-06-01

    Full Text Available The results of an experiment aimed at evaluating the effects of the ionosphere on GPS positioning applications are presented in this paper. Specifically, the study, based upon a differential approach, was conducted utilizing GPS measurements acquired by various receivers located at increasing inter-distances. The experimental research was developed upon the basis of two groups of baselines: the first group is comprised of "short" baselines (less than 10 km; the second group is characterized by greater distances (up to 90 km. The obtained results were compared either upon the basis of the geometric characteristics, for six different baseline lengths, using 24 hours of data, or upon temporal variations, by examining two periods of varying intensity in ionospheric activity respectively coinciding with the maximum of the 23 solar cycle and in conditions of low ionospheric activity. The analysis revealed variations in terms of inter-distance as well as different performances primarily owing to temporal modifications in the state of the ionosphere.

  13. Data ingestion and assimilation in ionospheric models

    Czech Academy of Sciences Publication Activity Database

    Burešová, Dalia; Nava, B.; Galkin, I.; Angling, M.; Stankov, S. M.; Coisson, P.

    2009-01-01

    Roč. 52, 3/4 (2009), s. 235-253 ISSN 1593-5213 R&D Projects: GA ČR GA205/08/1356; GA MŠk OC 091 Institutional research plan: CEZ:AV0Z30420517 Keywords : ionosphere * models * data assimilation * data ingestion Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 0.548, year: 2009

  14. Broadband Ionospheric Scintillation Measurements from Space

    Science.gov (United States)

    Suszcynsky, D. M.; Light, M. E.; Pigue, M. J.

    2014-12-01

    The U.S. Department of Energy's Radio Frequency Propagation (RFProp) experiment consists of a satellite-based radio receiver suite to study various aspects of trans-ionospheric signal propagation and detection in four frequency bands, 2 - 55 MHz, 125 - 175 MHz, 365 - 415 MHz and 825 - 1100 MHz. In this paper, we present an overview of the RFProp on-orbit research and analysis effort with particular focus on an equatorial scintillation experiment called ESCINT. The 3-year ESCINT project is designed to characterize equatorial ionospheric scintillation in the upper HF and lower VHF portions of the radio spectrum (20 - 150 MHz). Both a 40 MHz continuous wave (CW) signal and 30 - 42 MHz swept frequency signal are transmitted to the satellite receiver suite from the Reagan Test Site at Kwajalein Atoll in the Marshall Islands (8.7° N, 167.7° E) in four separate campaigns centered on the 2014 and 2015 equinoxes. Results from the first campaign conducted from April 22 - May 15, 2014 will be presented including (a) coherence bandwidth measurements over a full range of transmission frequencies and scintillation activity levels, (b) spread-Doppler clutter effects arising from preferential ray paths to the satellite due to refraction off of isolated density irregularities, and (c) supporting ray-trace simulations. The broadband nature of the measurements is found to offer unique insight into both the structure of ionospheric irregularities and their impact on HF/VHF trans-ionospheric radio wave propagation.

  15. ionFR: Ionospheric Faraday rotation [Dataset

    NARCIS (Netherlands)

    Sotomayor-Beltran, C.; et al., [Unknown; Hessels, J.W.T.; van Leeuwen, J.; Markoff, S.; Wijers, R.A.M.J.

    2013-01-01

    IonFR calculates the amount of ionospheric Faraday rotation for a specific epoch, geographic location, and line-of-sight. The code uses a number of publicly available, GPS-derived total electron content maps and the most recent release of the International Geomagnetic Reference Field. ionFR can be

  16. Positive ionospheric storm effects at Latin America longitude during the superstorm of 20–22 November 2003: revisit

    Directory of Open Access Journals (Sweden)

    B. Zhao

    2012-05-01

    Full Text Available Positive ionospheric storm effects that occurred during the superstorm on 20 November 2003 are investigated using a combination of ground-based Global Positioning System (GPS total electron content (TEC, and the meridian chain of ionosondes distributed along the Latin America longitude of ~280° E. Both the ground-based GPS TEC and ionosonde electron density profile data reveal significant enhancements at mid-low latitudes over the 280° E region during the main phase of the November 2003 superstorm. The maximum enhancement of the topside ionospheric electron content is 3.2–7.7 times of the bottomside ionosphere at the locations of the ionosondes distributed around the mid- and low latitudes. Moreover, the height of maximum electron density exceeds 400 km and increases by 100 km compared with the quiet day over the South American area from middle to low latitudes, which might have resulted from a continuous eastward penetration electric field and storm-generated equatorward winds. Our results do not support the conclusions of Yizengaw et al. (2006, who suggested that the observed positive storm over the South American sector was mainly the consequence of the changes of the bottomside ionosphere. The so-called "unusual" responses of the topside ionosphere for the November 2003 storm in Yizengaw et al. (2006 are likely associated with the erroneous usage of magnetometer and incomplete data.

  17. SUPRATHERMAL ELECTRONS IN TITAN’S SUNLIT IONOSPHERE: MODEL–OBSERVATION COMPARISONS

    Energy Technology Data Exchange (ETDEWEB)

    Vigren, E.; Edberg, N. J. T.; Wahlund, J.-E. [Swedish Institute of Space Physics, Uppsala (Sweden); Galand, M.; Sagnières, L. [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom); Wellbrock, A.; Coates, A. J. [Mullard Space Science Laboratory, University College London, Dorking, Surrey RH5 6NT (United Kingdom); Cui, J. [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Lavvas, P. [Université Reims Champagne-Ardenne, Reims (France); Snowden, D. [Department of Physics, Central Washington University, Ellensburg, WA 98926 (United States); Vuitton, V., E-mail: erik.vigren@irfu.se [Univ. Grenoble Alpes, CNRS, IPAG, Grenoble (France)

    2016-08-01

    The dayside ionosphere of the Saturnian satellite Titan is generated mainly from photoionization of N{sub 2} and CH{sub 4}. We compare model-derived suprathermal electron intensities with spectra measured by the Cassini Plasma Spectrometer/Electron Spectrometer (CAPS/ELS) in Titan's sunlit ionosphere (altitudes of 970–1250 km) focusing on the T40, T41, T42, and T48 Titan flybys by the Cassini spacecraft. The model accounts only for photoelectrons and associated secondary electrons, with a main input being the impinging solar EUV spectra as measured by the Thermosphere Ionosphere Mesosphere Energy and Dynamics/Solar EUV Experiment and extrapolated to Saturn. Associated electron-impact electron production rates have been derived from ambient number densities of N{sub 2} and CH{sub 4} (measured by the Ion Neutral Mass Spectrometer/Closed Source Neutral mode) and related energy-dependent electron-impact ionization cross sections. When integrating up to electron energies of 60 eV, covering the bulk of the photoelectrons, the model-based values exceed the observationally based values typically by factors of ∼3 ± 1. This finding is possibly related to current difficulties in accurately reproducing the observed electron number densities in Titan's dayside ionosphere. We compare the utilized dayside CAPS/ELS spectra with ones measured in Titan's nightside ionosphere during the T55–T59 flybys. The investigated nightside locations were associated with higher fluxes of high-energy (>100 eV) electrons than the dayside locations. As expected, for similar neutral number densities, electrons with energies <60 eV give a higher relative contribution to the total electron-impact ionization rates on the dayside (due to the contribution from photoelectrons) than on the nightside.

  18. The excitation of plasma convection in the high-latitude ionosphere

    International Nuclear Information System (INIS)

    Lockwood, M.; Cowley, S.W.H.; Freeman, M.P.

    1990-01-01

    Recent observations of ionospheric flows by ground-based radars, in particular by the European Incoherent Scatter (EISCAT) facility using the Polar experiment, together with previous analyses of the response of geomagnetic disturbance to variations of the interplanetary magnetic field (IMF), suggest that convection in the high-latitude ionosphere should be considered to be the sum of two intrinsically time-dependent patterns, one driven by solar wind-magnetosphere coupling at the dayside magnetopause, the other by the release of energy in the geomagnetic tail (mainly by dayside and nightside reconnection, respectively). The flows driven by dayside coupling are largest on the dayside, where they usually dominate, are associated with an expanding polar cap area, and are excited and decay on ∼ 10-min time scales following southward and northward turnings of the IMF, respectively. The latter finding indicates that the production of new open flux at the dayside magnetopause excites magnetospheric and ionospheric flow only for a short interval, ∼ 10 min, such that the flow driven by this source subsequently decays on this time scale unless maintained by the production of more open flux tubes. Correspondingly, the flows excited by the release of energy in the tail, mainly during substorms, are largest on the nightside, are associated with a contracting polar cap boundary, and are excited on ∼ 1-hour time scales following a southward turn of the IMF. In general, the total ionospheric flow will be the sum of the flows produced by these two sources, such that due to their different response times to changes in the IMF, considerable variations in the flow pattern can occur for a given direction and strength ofthe IMF. Consequently, the ionospheric electric field cannot generally be regarded as arising from a simple mapping of the solar wind electric field along open flux tubes

  19. A new ionospheric storm scale based on TEC and foF2 statistics

    Science.gov (United States)

    Nishioka, Michi; Tsugawa, Takuya; Jin, Hidekatsu; Ishii, Mamoru

    2017-01-01

    In this paper, we propose the I-scale, a new ionospheric storm scale for general users in various regions in the world. With the I-scale, ionospheric storms can be classified at any season, local time, and location. Since the ionospheric condition largely depends on many factors such as solar irradiance, energy input from the magnetosphere, and lower atmospheric activity, it had been difficult to scale ionospheric storms, which are mainly caused by solar and geomagnetic activities. In this study, statistical analysis was carried out for total electron content (TEC) and F2 layer critical frequency (foF2) in Japan for 18 years from 1997 to 2014. Seasonal, local time, and latitudinal dependences of TEC and foF2 variabilities are excluded by normalizing each percentage variation using their statistical standard deviations. The I-scale is defined by setting thresholds to the normalized numbers to seven categories: I0, IP1, IP2, IP3, IN1, IN2, and IN3. I0 represents a quiet state, and IP1 (IN1), IP2 (IN2), and IP3 (IN3) represent moderate, strong, and severe positive (negative) storms, respectively. The proposed I-scale can be used for other locations, such as polar and equatorial regions. It is considered that the proposed I-scale can be a standardized scale to help the users to assess the impact of space weather on their systems.

  20. Features of HF Radio Wave Attenuation in the Midlatitude Ionosphere Near the Skip Zone Boundary

    Science.gov (United States)

    Denisenko, P. F.; Skazik, A. I.

    2017-06-01

    We briefly describe the history of studying the decameter radio wave attenuation by different methods in the midlatitude ionosphere. A new method of estimating the attenuation of HF radio waves in the ionospheric F region near the skip zone boundary is presented. This method is based on an analysis of the time structure of the interference field generated by highly stable monochromatic X-mode radio waves at the observation point. The main parameter is the effective electron collision frequency νeff, which allows for all energy losses in the form of equivalent heat loss. The frequency νeff is estimated by matching the assumed (model) and the experimentally observed structures. Model calculations are performed using the geometrical-optics approximation. The spatial attenuation caused by the influence of the medium-scale traveling ionospheric disturbances is taken into account. Spherical shape of the ionosphere and the Earth's magnetic field are roughly allowed for. The results of recording of the level of signals from the RWM (Moscow) station at a frequency of 9.996 MHz at point Rostov are used.

  1. Auroral Current and Electrodynamics Structure (ACES) Observations of Ionospheric Feedback in the Alfven Resonator

    Science.gov (United States)

    Cohen, Ian J.; Lessard, Marc; Lund, Eric J.; Bounds, Scott R.; Kletzing, Craig; Kaeppler, Stephen R.; Sigsbee, Kristine M.; Streltsov, Anatoly V.; Labelle, James W.; Dombrowski, Micah P.; hide

    2011-01-01

    In 2009, the Auroral Current and Electrodynamics Structure (ACES) High and Low sounding rockets were launched from the Poker Flat Rocket Range (PFRR) in Alaska, with the science objective of gathering in-situ data to quantify current closure in a discrete auroral arc. As ACES High crossed through the return current of an arc (that was monitored using an all sky camera from the ground at Fort Yukon), its instruments recorded clear Alfv nic signatures both poleward and equatorward of the return current region, but not within the main region of the return current itself. These data provide an excellent opportunity to study ionospheric feedback and how it interacts with the Alfv n resonator. We compare the observations with predictions and new results from a model of ionospheric feedback in the ionospheric Alfv n resonator (IAR) and report the significance and impact of these new data for the Magnetosphere-Ionosphere Coupling in the Alfv n Resonator (MICA) rocket mission to launch from PFRR this winter. MICA s primary science objectives specifically focus on better understanding the small-scale structure that the model predicts should exist within the return current region.

  2. Ionospheric response to particle precipitation within aurora

    International Nuclear Information System (INIS)

    Wahlund, J.E.

    1992-03-01

    The aurora is just the visible signature of a large number of processes occurring in a planetary ionosphere as a response to energetic charged particles falling in from the near-empty space far above the planetary atmosphere. This thesis, based on measurements using the EISCAT incoherent scatter radar system in northern Scandinavia, discusses ionospheric response processes and especially a mechanism leading to atmospheric gas escape from a planet. One of the most spectacular events in the high latitude atmosphere on earth are the 'auroral arcs' - dynamic rayed sheets of light. An investigation of the conditions of the ionosphere surrounding auroral arcs shows that strong field-aligned bulk ion outflows appear in the topside ionosphere which account for a large fraction of the escape of atmospheric oxygen from earth. Four different additional ionospheric responses are closely related to this ion outflow; 1. enhanced electron temperatures of several thousand Kelvin above an altitude of about 250 km, 2. enhanced ionization around an altitude of 200 km corresponding to electron precipitation with energies of a few hundred eV, 3. the occurrence of naturally enhanced ion acoustic fluctuations seen in the radar spectrum, most likely produced by an ion-ion two-stream instability, and 4. upward directed field-aligned currents partly carried by the outflowing ions. From these observations, it is suggested that the energy dissipation into the background plasma through Joule heating, the production of a few hundred eV energetic run-away electrons, and strong ion outflows are partly produced by the simultaneous presence of ion acoustic turbulence and field-aligned currents above auroral arcs. (20 refs.) (au)

  3. Experimental observations of the spatial structure of wave-like disturbances generated in midlatitude ionosphere by high power radio waves

    Science.gov (United States)

    Kunitsyn, V.; Andreeva, E.; Padokhin, A. M.; Nazarenko, M.; Frolov, V.; Komrakov, G.; Bolotin, I.

    2012-12-01

    with a square wave modulation of the ERP at a frequency lower than or of the order of the Brunt-Vaisala frequency of the neutral atmosphere. The observed wavelike structures, which are possibly AGWs, diverge from the heated area of the ionosphere (observed like a narrow trough with dimensions corresponding to the diagram pattern of the Sura heater), the spatial period of these disturbances is 200-250 km and they are easily traced up to a distance of 700-800 km from the heated region. These observations are in good agreement with complimentary GPS/GLONASS data. We also present the examples of amplitude scintillations of the signals of low-orbital radio beacons corresponding to small-scale field-aligned irregularities in the heated area of ionosphere. The possibility of generation of electromagnetic waves by moving wave-like structures in ionosphere (like AGWs induced by HF-heating observed in our experiments) is also addressed in this work. The authors are grateful to the staff of the Sura facility for their help in conducting the experiments and acknowledge the support of the Russian Foundation for Basic Research (grants 10-05-01126, 11-02-00374, 11-05-01157, 12-02-31839, 12-05-33065, 12-05-10068), grant of the President of Russian Federation MK-2544.2012.5 and Lomonosov Moscow State University Program of Development.

  4. Paleocene Pacific Plate reorganization mirrored in formation of the Suvarov Trough, Manihiki Plateau

    Science.gov (United States)

    Pietsch, Ricarda; Uenzelmann-Neben, Gabriele

    2016-10-01

    The Suvarov Trough is a graben structure that deviates from the Danger Islands Troughs within the Manihiki Plateau, a Large Igneous Province (LIP) located in the Central Pacific. New high-resolution seismic reflection data provide evidence that the graben formed in two phases during the Paleocene (65-45 Ma). In a first phase extension occurred in southwestward direction, pulling apart the northern part of the Suvarov Trough and a parallel trending unnamed trough. In a second phase a change of extensional force direction occurred from southwest to west-northwest, forming the southern part of the Suvarov Trough that extends onto the High Plateau. The formation of the Suvarov Trough is accompanied by a series of normal fault systems that apparently formed simultaneously. Comparing the seismic results to existing Pacific paleo strain reconstructions, the timing of increased strain and local deformation direction fits well to our findings. We thus suggest that the multiple strike directions of the Suvarov Trough represent an extensional structure that was caused by the major, stepwise Pacific Plate reorganization during the Paleocene.

  5. Vancomycin AUC/MIC and Corresponding Troughs in a Pediatric Population.

    Science.gov (United States)

    Kishk, Omayma A; Lardieri, Allison B; Heil, Emily L; Morgan, Jill A

    2017-01-01

    Adult guidelines suggest an area under the curve/minimum inhibitory concentration (AUC/MIC) > 400 corresponds to a vancomycin trough serum concentration of 15 to 20 mg/L for methicillin-resistant Staphylococcus aureus infections, but obtaining these troughs in children are difficult. The primary objective of this study was to assess the likelihood that 15 mg/kg of vancomycin every 6 hours in a child achieves an AUC/MIC > 400. This retrospective chart review included pediatric patients >2 months to AUCs were calculated four times using three pharmacokinetic methods. A total of 36 patients with 99 vancomycin trough serum concentrations were assessed. Baseline characteristics were similar between groups. For troughs in group 1 (n = 55), the probability of achieving an AUC/MIC > 400 ranged from 16.4% to 90.9% with a median trough concentration of 11.4 mg/L, while in group 2 (n = 44) the probability of achieving AUC/MIC > 400 ranged from 15.9% to 54.5% with mean trough concentration of 9.2 mg/L. The AUC/MICs were not similar between the different pharmacokinetic methods used; however, a trapezoidal equation (Method A) yielded the highest correlation coefficient (r 2 = 0.59). When dosing every 6 hours, an AUC/MIC of 400 correlated to a trough serum concentration of 11 mg/L. The probability of achieving an AUC/MIC > 400 using only a trough serum concentration and an MIC with patients receiving 15 mg/kg every 6 hours is variable based on the method used to calculate the AUC. An AUC/MIC of 400 in children correlated to a trough concentration of 11 mg/L using a trapezoidal Method to calculate AUC.

  6. Parabolic Trough Collector Cost Update for the System Advisor Model (SAM)

    Energy Technology Data Exchange (ETDEWEB)

    Kurup, Parthiv [National Renewable Energy Lab. (NREL), Golden, CO (United States); Turchi, Craig S. [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2015-11-01

    This report updates the baseline cost for parabolic trough solar fields in the United States within NREL's System Advisor Model (SAM). SAM, available at no cost at https://sam.nrel.gov/, is a performance and financial model designed to facilitate decision making for people involved in the renewable energy industry. SAM is the primary tool used by NREL and the U.S. Department of Energy (DOE) for estimating the performance and cost of concentrating solar power (CSP) technologies and projects. The study performed a bottom-up build and cost estimate for two state-of-the-art parabolic trough designs -- the SkyTrough and the Ultimate Trough. The SkyTrough analysis estimated the potential installed cost for a solar field of 1500 SCAs as $170/m2 +/- $6/m2. The investigation found that SkyTrough installed costs were sensitive to factors such as raw aluminum alloy cost and production volume. For example, in the case of the SkyTrough, the installed cost would rise to nearly $210/m2 if the aluminum alloy cost was $1.70/lb instead of $1.03/lb. Accordingly, one must be aware of fluctuations in the relevant commodities markets to track system cost over time. The estimated installed cost for the Ultimate Trough was only slightly higher at $178/m2, which includes an assembly facility of $11.6 million amortized over the required production volume. Considering the size and overall cost of a 700 SCA Ultimate Trough solar field, two parallel production lines in a fully covered assembly facility, each with the specific torque box, module and mirror jigs, would be justified for a full CSP plant.

  7. On the importance of high-altitude low-frequency electric fluctuations for the escape of ionospheric ions

    International Nuclear Information System (INIS)

    Lundin, R.; Gustafsson, G.; Eriksson, A.I.; Marklund, G.

    1990-01-01

    Simultaneous measurements of electric fields and upward moving ionospheric ions from the Viking satellite show that upward escape of ionospheric ions in the tens of eV to tens of keV energy range occurs together with low-frequency electric fluctuations, LEFs (frequencies less than ∼1 Hz). Upward flowing ions are observed when the electric field fluctuations are sufficiently strong in the altitude range ∼2,000-13,500 km covered by Viking. Furthermore, the temperature of the upflowing ions is found to be well correlated with the power spectral density (PSD) of the LEFs. This suggests a conversion of electric field energy into ion thermal energy. A good correlation between the ion temperature and the wave power in the electrostatic ion cyclotron (EIC) frequency range is also found. However, the heating/acceleration and the corresponding escape of ionospheric ions is believed to be primarily caused by LEFs, first because of the much higher power in the LEFs than the power in the EIC frequency range and second because the PSD clearly peaks below ∼1 Hz while the frequency range of the EIC mostly appears as a monotonic tail or background of an overall PSD increase at low frequencies. Electric fluctuations, and the associated escape of ionospheric ions, are mainly observed inside or above the acceleration region. Below the acceleration region, predominantly downward accelerated electrons are observed. This can be understood as a short-circuiting of electric fluctuations by the plasma in the topside ionosphere where the plasma is gaining kinetic energy by the electric field. Thus the electric energy from the source/dynamo in the outer magnetosphere is dissipated in the topside layer of the ionosphere, causing an acceleration and escape of ionospheric plasma

  8. Weak lensing by galaxy troughs with modified gravity

    Energy Technology Data Exchange (ETDEWEB)

    Barreira, Alexandre [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching (Germany); Bose, Sownak; Li, Baojiu; Llinares, Claudio, E-mail: barreira@mpa-garching.mpg.de, E-mail: sownak.bose@durham.ac.uk, E-mail: baojiu.li@durham.ac.uk, E-mail: claudio.llinares@durham.ac.uk [Institute for Computational Cosmology, Durham University, South Road DH1 3LE, Durham (United Kingdom)

    2017-02-01

    We study the imprints that theories of gravity beyond GR can leave on the lensing signal around line of sight directions that are predominantly halo-underdense (called troughs) and halo-overdense. To carry out our investigations, we consider the normal branch of DGP gravity, as well as a phenomenological variant thereof that directly modifies the lensing potential. The predictions of these models are obtained with N-body simulation and ray-tracing methods using the ECOSMOG and Ray-Ramses codes. We analyse the stacked lensing convergence profiles around the underdense and overdense lines of sight, which exhibit, respectively, a suppression and a boost w.r.t. the mean in the field of view. The modifications to gravity in these models strengthen the signal w.r.t. ΛCDM in a scale-independent way. We find that the size of this effect is the same for both underdense and overdense lines of sight, which implies that the density field along the overdense directions on the sky is not sufficiently evolved to trigger the suppression effects of the screening mechanism. These results are robust to variations in the minimum halo mass and redshift ranges used to identify the lines of sight, as well as to different line of sight aperture sizes and criteria for their underdensity and overdensity thresholds.

  9. PROMOTING GENDER EQUALITY TROUGH EQUAL LIFE STANDARD IN EU COUNTRIES

    Directory of Open Access Journals (Sweden)

    Aleksandar Dashtevski

    2018-06-01

    Full Text Available After the World War II, especially in the early fifties there is an expansion of gender rights. Women are massively employed all over the world in all sectors of social life, contributing to an increase in both their own standard of living and the standard in their own countries. As the importance and role of women grows, this is achieved with increasing respect for its rights. Gender means elimination of inequality and promote equality between women and men in all areas of social life. If we want to achieve gender equality as a whole, it is inevitable to achieve an economic consolidation of the two sexes. Economic strengthening is possible trough equal pay. Experience shows that payments are not equal when it comes to wages for men and women. Therefore, the EU is constantly working to regulate this area, with special regulations, which are mandatory for the member states, but should also be respected by countries that would like to join the union. This led to the promotion of gender equality through an equal life.

  10. Ionospheric Bow Wave Induced by the Moon Shadow Ship Over the Continent of United States on 21 August 2017

    Science.gov (United States)

    Sun, Yang-Yi; Liu, Jann-Yenq; Lin, Charles Chien-Hung; Lin, Chi-Yen; Shen, Ming-Hsueh; Chen, Chieh-Hung; Chen, Chia-Hung; Chou, Min-Yang

    2018-01-01

    A moon shadow of the total solar eclipse swept through the continent of United States (CONUS) from west to east on 21 August 2017. Massive total electron content (integration of electron density from 0 km to 20,200 km altitude) observations from 2,255 ground-based Global Navigation Satellite System receivers show that the moon shadow ship generates a great ionospheric bow wave front which extends 1,500 km away from the totality path covering the entire CONUS. The bow wave front consists of the acoustic shock wave due to the supersonic/near-supersonic moon shadow ship and the significant plasma recombination due to the reduction in solar irradiation within the shadow area. The deep bow wave trough (-0.02 total electron content unit (1 TECU = 1016 el m-2) area) nearly coincides with the 100% obscuration moving along the totality path over the CONUS through the entire eclipse period. The supersonic moon shadow ship induces a bow wave crest in front of the ship ( 80% obscuration). It is the first time to find the acoustic shock wave-formed bow wave trough and crest near the totality.

  11. Two new methods used to simulate the circumferential solar flux density concentrated on the absorber of a parabolic trough solar collector

    Science.gov (United States)

    Guo, Minghuan; Wang, Zhifeng; Sun, Feihu

    2016-05-01

    The optical efficiencies of a solar trough concentrator are important to the whole thermal performance of the solar collector, and the outer surface of the tube absorber is a key interface of energy flux. So it is necessary to simulate and analyze the concentrated solar flux density distributions on the tube absorber of a parabolic trough solar collector for various sun beam incident angles, with main optical errors considered. Since the solar trough concentrators are linear focusing, it is much of interest to investigate the solar flux density distribution on the cross-section profile of the tube absorber, rather than the flux density distribution along the focal line direction. Although a few integral approaches based on the "solar cone" concept were developed to compute the concentrated flux density for some simple trough concentrator geometries, all those integral approaches needed special integration routines, meanwhile, the optical parameters and geometrical properties of collectors also couldn't be changed conveniently. Flexible Monte Carlo ray trace (MCRT) methods are widely used to simulate the more accurate concentrated flux density distribution for compound parabolic solar trough concentrators, while generally they are quite time consuming. In this paper, we first mainly introduce a new backward ray tracing (BRT) method combined with the lumped effective solar cone, to simulate the cross-section flux density on the region of interest of the tube absorber. For BRT, bundles of rays are launched at absorber-surface points of interest, directly go through the glass cover of the absorber, strike on the uniformly sampled mirror segment centers in the close-related surface region of the parabolic reflector, and then direct to the effective solar cone around the incident sun beam direction after the virtual backward reflection. All the optical errors are convoluted into the effective solar cone. The brightness distribution of the effective solar cone is supposed

  12. Seismic Correlation and Coupling from Underground, Surface, to the Ionosphere

    Science.gov (United States)

    Wang, J. S.; Waysand, G.

    2009-12-01

    Electromagnetic activity correlated to seismicity is displayed in a variety of ways. Earthquake precursors and aftershocks associated with local fault slips have been detected regionally by visual observations and radar reflections, and globally by satellite measurements of electromagnetic profiles. Magnetic excitations have recently been measured underground that associated with major earthquakes (e.g., the 2008 Sichuan and the 2006 Pingtung earthquakes). In all cases, the frequencies are extremely low; hence, the corresponding wavelengths are extremely large. In other term, wherever an earthquake occurs on Earth, any electromagnetic measurement of it is always near-field from the signal source. Thus, signal-to-noise ratio is the only limiting factor. The increasing abundance of observations, and the variety of instruments enabling these observations, requires investigators to look beyond borders of their individual discipline and adopt a global approach to the problem. To elucidate the dynamic generation and propagation of seismic-induced electromagnetic signals, it is important to assess from small to large scales the variability of (1) the seismic-electromagnetic coupling at localized zones and block boundaries, (2) the potential signal paths through the earth geomagnetic fields, and (3) the ionosphere and atmospheric measurements and observations. The pre-earthquake signals as potential precursors have generated great interests for decades, especially with the deployments of satellites for geophysical measurements. The emerging understanding is that stress buildups and releases induce electromagnetic emissions which are likely associated with charged particle movements, propagations mainly along waveguides through the earth magnetic field to the atmosphere and ionosphere. The globally distributed perturbations and profiles above ground are systematically mapped. The signals could also be transmitted nearly vertically from epicenters to the ground and beyond

  13. A 3D Multi-fluid MHD Study of the Interaction of the Solar Wind with the Ionosphere/Atmosphere System of Venus.

    Science.gov (United States)

    Najib, D.; Nagy, A.; Toth, G.; Ma, Y.-J.

    2011-10-01

    We use the latest version of our four species multifluid model to study the interaction of the solar wind with Venus. The model solves simultaneously the continuity, momentum and energy equations of the different ions. The lower boundary of our model is at 100 km, below the main ionospheric peak, and the radial resolution is about 10 km in the ionosphere, thus the model does a very good job in reproducing the ionosphere and the associated processes. We carry out calculations for high and low solar activity conditions and establish the importance of mass loading by the extended exosphere of Venus. We demonstrate the importance of using the multi-fluid rather than a single fluid model. We also calculate the atmospheric escape of the ionospheric species and compare our model results with the observed parameters from Pioneer Venus and Venus Express.

  14. Ionospheric midlatitude electric current density inferred from multiple magnetic satellites

    DEFF Research Database (Denmark)

    Shore, R. M.; Whaler, K. A.; Macmillan, S.

    2013-01-01

    A method for inferring zonal electric current density in the mid-to-low latitude F region ionosphere is presented. We describe a method of using near-simultaneous overflights of the Ørsted and CHAMP satellites to define a closed circuit for an application of Ampère's integral law to magnetic data...... for estimates of main and crustal magnetic fields. Current density in the range ±0.1 μA/m2 is resolved, with the distribution of electric current largely matching known features such as the Appleton anomaly. The currents appear unmodulated at times of either high-negative Dst or high F10.7, which has...... implications for any future efforts to model their effects. We resolve persistent current intensifications between geomagnetic latitudes of 30 and 50° in the postmidnight, predawn sector, a region typically thought to be relatively free of electric currents. The cause of these unexpected intensifications...

  15. The lower ionosphere response to its disturbances by powerful radio waves

    Science.gov (United States)

    Bakhmetieva, N. V.; Frolov, V. L.; Vyakhirev, V. D.; Kalinina, E. E.; Akchurin, A. D.; Zykov, E. Yu.

    2018-04-01

    The paper presents data from some campaigns at Sura heating facility in 2011-1016. The experiments on probing of the artificial disturbed region of the lower ionosphere were carried out at two observation sites. One of them was located near Vasil'sursk 1 km from Sura facility (56.1°N; 46.1°E) and the other site was located at the Observatory (55.85°N; 48.8°E) of Kazan State University, 170 km to the East. Investigation of the features of the disturbed region of the lower ionosphere based on its diagnostics by the methods of the vertical sounding and oblique backscattering is the main goal of this paper. Ionosphere disturbance was fulfilled by the effect of the powerful radio wave of the ordinary or extraordinary polarization emitted by transmitters of the Sura facility with effective radiated power ERP = 50-120 MW at the frequency of 4.3, 4.7 and 5.6 MHz. Pumping waves were emitted with period from 30 s to 15 min. The disturbed region of the ionosphere in Vasil'sursk was probed by the vertical sounding technique using the partial reflexion radar at the frequency of 2.95 and 4.7 MHz. For the oblique sounding of the disturbed region the modified ionosonde Cyclon-M, operating at ten frequencies from 2.01 to 6.51 MHz was used at the Observatory site. On many heating sessions simultaneous variations of the probing partial reflection signals in Vasil'sursk and backscattered signals in Observatory were observed at the height at 40-100 km below the reflection height of the pumping wave. These observations were correlated with the pumping periods of the Sura facility. Possible mechanisms of the appearance of the disturbance in the lower ionosphere and its effect on the probing radio waves are discussed.

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

    Directory of Open Access Journals (Sweden)

    F. Becker-Guedes

    2007-05-01

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

  17. Patient-reported non-adherence and immunosuppressant trough levels are associated with rejection after renal transplantation.

    Science.gov (United States)

    Scheel, Jennifer; Reber, Sandra; Stoessel, Lisa; Waldmann, Elisabeth; Jank, Sabine; Eckardt, Kai-Uwe; Grundmann, Franziska; Vitinius, Frank; de Zwaan, Martina; Bertram, Anna; Erim, Yesim

    2017-03-29

    Different measures of non-adherence to immunosuppressant (IS) medication have been found to be associated with rejection episodes after successful transplantation. The aim of the current study was to investigate whether graft rejection after renal transplantation is associated with patient-reported IS medication non-adherence and IS trough level variables (IS trough level variability and percentage of sub-therapeutic IS trough levels). Patient-reported non-adherence, IS trough level variability, percentage of sub-therapeutic IS trough levels, and acute biopsy-proven late allograft rejections were assessed in 267 adult renal transplant recipients who were ≥12 months post-transplantation. The rate of rejection was 13.5%. IS trough level variability, percentage of sub-therapeutic IS trough levels as well as patient-reported non-adherence were all significantly and positively associated with rejection, but not with each other. Logistic regression analyses revealed that only the percentage of sub-therapeutic IS trough levels and age at transplantation remained significantly associated with rejection. Particularly, the percentage of sub-therapeutic IS trough levels is associated with acute rejections after kidney transplantation whereas IS trough level variability and patient-reported non-adherence seem to be of subordinate importance. Patient-reported non-adherence and IS trough level variables were not correlated; thus, non-adherence should always be measured in a multi-methodological approach. Further research concerning the best combination of non-adherence measures is needed.

  18. Low-Frequency Waves in HF Heating of the Ionosphere

    Science.gov (United States)

    Sharma, A. S.; Eliasson, B.; Milikh, G. M.; Najmi, A.; Papadopoulos, K.; Shao, X.; Vartanyan, A.

    2016-02-01

    Ionospheric heating experiments have enabled an exploration of the ionosphere as a large-scale natural laboratory for the study of many plasma processes. These experiments inject high-frequency (HF) radio waves using high-power transmitters and an array of ground- and space-based diagnostics. This chapter discusses the excitation and propagation of low-frequency waves in HF heating of the ionosphere. The theoretical aspects and the associated models and simulations, and the results from experiments, mostly from the HAARP facility, are presented together to provide a comprehensive interpretation of the relevant plasma processes. The chapter presents the plasma model of the ionosphere for describing the physical processes during HF heating, the numerical code, and the simulations of the excitation of low-frequency waves by HF heating. It then gives the simulations of the high-latitude ionosphere and mid-latitude ionosphere. The chapter also briefly discusses the role of kinetic processes associated with wave generation.

  19. A clear link connecting the troposphere and ionosphere: ionospheric reponses to the 2015 Typhoon Dujuan

    Science.gov (United States)

    Kong, Jian; Yao, Yibin; Xu, Yahui; Kuo, Chungyen; Zhang, Liang; Liu, Lei; Zhai, Changzhi

    2017-09-01

    The global navigation satellite system (GNSS) total electron content (TEC) sequences were used to capture the arrival time and location of the ionosphere disturbances in response to the 2015 Typhoon Dujuan. After removing the de-trended TEC variation, the clear ionosphere disturbances on the typhoon landing day could be distinguished, and these disturbances disappeared from the TEC sequences before and after the typhoon landing day. The foF2 data observed by Xiamen ionosonde station also show ionosphere disturbances. Based on the advantages of GNSS multi-point observations, the disturbances horizontal velocity in the ionosphere were estimated according to the linear theory for a dispersion relation of acoustic gravity waves (AGWs) in an isothermal atmosphere. The average horizontal velocity (˜ 240 m/s) and the radial velocity (˜ 287 m/s) were used in the two-dimensional grid search for the origin point on the Earth's surface. The origin area was determined to be on the eastern side of Taiwan. Lastly, a possible physical mechanism is discussed in this study. When typhoons land on Taiwan, the severe convective storms and the drag effect from the Central Mountains create an ideal location for development of AGWs. Topographic conditions, like the high lapse rate, contribute to the formation of AGWs, which then propagates into the ionosphere altitude.

  20. Severe ionosphere disturbances caused by the sudden response of evening subequatorial ionospheres to geomagnetic storms

    International Nuclear Information System (INIS)

    Tanaka, T.

    1981-01-01

    By monitoring C band beacon signals from geostationary satellites in Japan, we have observed anomalously strong ionospheric scintillations several times during three years from 1978 to 1980. These severe scinitillations occur associated with geomagnetic storms and accompany sudden and intense ionospheric perturbations in the low-latiude region. Through the analysis of these phenomena we have identified a new type of ionospheric disturbances characterized by intensifications of equatorial anomalies and successive severe ionospheric scintillations that extend to the C band range. The events occur only during a limited local time interval after the sunset, when storm time decreases of midlatitude geomagnetic fields in the same meridan take place during the same time interval. From the viewpoint of ionospheric storms, these disturbances precede the occurrence of midlatitude negative phases and storm time depressions of equatorial anomalies to indicate that the cause of the events is different from distrubed thermospheric circulations. The timing and magnitude of substorms at high-latitudes not always correlate with the events. We have concluded that the phenomena are closely related with penetrations toward low-latitudes of electric fields owing to the partial closure of asymmetrical ring currents

  1. On some peculiarities of production of ionospheric equatorial bubbles in zones with increased recombination

    International Nuclear Information System (INIS)

    Vepreva, M.N.; Sazonov, S.V.

    1991-01-01

    Numerical study of dynamics of electromagnetic disturbances of equatorial ionosphere F region which are longitudinal ones relative to B geomagnetic field and occur due to Rayleigh-Taylor and gradient-drift instability activity in zones with increased recombination, is conducted. Arbitrary initial disturbance is determined to be delivered mainly into the first space mode of resonator formed by B force line plunge in high-conducting E layer. Oscillation condition is studied

  2. Reconstructing sea surface temperature, sea surface salinity and partial pressure of carbon dioxide in atmosphere in the Okinawa Trough during the Holocene and their paleoclimatic implications

    Institute of Scientific and Technical Information of China (English)

    MENGXianwei; LIUYanguang; LlUZhenxia; DUDewen; HUANGQiyu; Y.Saito

    2003-01-01

    The sediment core DGKS9603 collected from the Okinawa Trough was used as research target. By use of unsaturated index U37k of long-chain alkenone, δ13C of POC and of planktonic foraminifera (G sacculifer), the evolutions of sea surface temperature and partial pressure of carbon dioxide in the atmosphere during the Holocene were reconstructed in the Okinawa Trough. And in combination of δ18O of planktonic foraminifera, the relative difference of sea surface salinity during the Holocene was also reconstructed.Consequently, three cooling events (E1-E3) were identified,each of which occurred at 1.7-1.6, 5.1-4.8 and 8.1-7.4kaBP (cal), respectively. Of the three events, E2 and E3 are globally comparable, their occurrence mechanism would be that the main stream of the Kuroshio Current shifted eastward due to the enhanced circulation of the northeastern Pacific Ocean, which was driven in turn by amplified intensity of sunshine and subsequent enhancement of subtropical high pressure; E1 corresponds to the Small Ice-Age Event occurring between 1550 and 1850AD in China. In the Okinawa Trough, E1 might be also related to the eastward shift of main stream of the Kuroshio current driven by powerful Asia winter monsoon.

  3. Reconstructing sea surface temperature, sea surface salinity and partial pressure of carbon dioxide in atmos- phere in the Okinawa Trough during the Holocene and their paleoclimatic implications

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The sediment core DGKS9603 collected from the Okinawa Trough was used as research target. By use of unsaturated index of long-chain alkenone, δ13C of POC and of planktonic foraminifera (G. Sacculifer), the evolutions of sea surface temperature and partial pressure of carbon dioxide in the atmosphere during the Holocene were reconstructed in the Okinawa Trough. And in combination of δ18O of planktonic foraminifera, the relative difference of sea surface salinity during the Holocene was also reconstructed. Consequently, three cooling events (E1-E3) were identified, each of which occurred at 1.7-1.6, 5.1-4.8 and 8.1-7.4 kaBP (cal), respectively. Of the three events, E2 and E3 are globally comparable, their occurrence mechanism would be that the main stream of the Kuroshio Current shifted eastward due to the enhanced circulation of the northeastern Pacific Ocean, which was driven in turn by amplified intensity of sunshine and subsequent enhancement of subtropical high pressure; E1 corresponds to the Small Ice-Age Event occurring between 1550 and 1850AD in China. In the Okinawa Trough, E1 might be also related to the eastward shift of main stream of the Kuroshio current driven by powerful Asia winter monsoon.

  4. Hydrocarbon test in lower-layer atmosphere to predict deep-sea petroleum or hydrate in the Okinawa Trough: an example

    Institute of Scientific and Technical Information of China (English)

    Gong Jianming; Chen Jianwen; Li Gang; Zhang Xunhua; Li Jipeng; Huang Fulin

    2003-01-01

    Light hydrocarbon (methane, ethane, propane, butane and CO2) test and C isotopic analysis of CO2 are conducted for over 100 lower-layer atmospheric samples from the East China Sea slope and the Okinawa Trough. The results show that the lower-layer atmosphere mainly consists of CO2 and then of CH4, and the CO2 concentrations are calculated to have a high average value of 0.87 ω/10-2 ,about three times that of the regional background (0.3 ω/10-2). The result also shows that the average value of C isotope - 20.8 × 10 -3 is given to the CO2, inferring that it is inorganic gas.Thus, for the future ' s work in the Okinawa Trough, special attention should be paid to CO2 hydrate,which is very possibly an important hydrate type.

  5. Report on Radiocarbon Analysis of Surface Sediments from the Fore-Arc Basin of Nankai Trough

    National Research Council Canada - National Science Library

    Pohlman, John

    2004-01-01

    .... Radiocarbon analysis of the total organic carbon (TOC) and total inorganic carbon (TIC) on 30 sediment samples from two multicores and six piston cores was performed to investigate the fate of methane carbon in sediment of the Nankal Trough...

  6. Wind Tunnel Tests of Parabolic Trough Solar Collectors: March 2001--August 2003

    Energy Technology Data Exchange (ETDEWEB)

    Hosoya, N.; Peterka, J. A.; Gee, R. C.; Kearney, D.

    2008-05-01

    Conducted extensive wind-tunnel tests on parabolic trough solar collectors to determine practical wind loads applicable to structural design for stress and deformation, and local component design for concentrator reflectors.

  7. Gas Turbine/Solar Parabolic Trough Hybrid Design Using Molten Salt Heat Transfer Fluid: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Turchi, C. S.; Ma, Z.

    2011-08-01

    Parabolic trough power plants can provide reliable power by incorporating either thermal energy storage (TES) or backup heat from fossil fuels. This paper describes a gas turbine / parabolic trough hybrid design that combines a solar contribution greater than 50% with gas heat rates that rival those of natural gas combined-cycle plants. Previous work illustrated benefits of integrating gas turbines with conventional oil heat-transfer-fluid (HTF) troughs running at 390?C. This work extends that analysis to examine the integration of gas turbines with salt-HTF troughs running at 450 degrees C and including TES. Using gas turbine waste heat to supplement the TES system provides greater operating flexibility while enhancing the efficiency of gas utilization. The analysis indicates that the hybrid plant design produces solar-derived electricity and gas-derived electricity at lower cost than either system operating alone.

  8. Longitudinal effect in the night-time mid-latitude ionosphere according to the Interkosmos-19 data

    International Nuclear Information System (INIS)

    Deminov, M.G.; Karpachev, A.T.

    1988-01-01

    Longitudinal effects in the night-time mid-latitude external ionosphere for summer and winter conditions of the high solar activity period are analysed. The high amplitude of longitudinal changes of the external ionosphere, including changes of the height (upto 150 km) and the concentration (7-8 times) of the F2-layer maximum, is shown to be provided under winter mid-night-time conditions with high values of the zone component of the wind velocity and strong latitude gradients and with longitudinal changes of the meridional projection of the wind velocity. N changes with the longitude before the Sun setting, when the zone component of the wind velocity is maximum, made the main contribution in summer to longitudinal changes of the electron concentration of the N night ionosphere. The wind velocity phase shift during the season lleads to the fact that the maximum amplitude of N longitudinal changes is observed till midnight in summer and after midnight in winter

  9. Simple model for post seismic ionospheric disturbances above an earthquake epicentre and along connecting magnetic field lines

    Directory of Open Access Journals (Sweden)

    R. Marchand

    2008-12-01

    Full Text Available The detection of ionospheric disturbances associated with seismic activity is one of the main objectives of the DEMETER micro-satellite. Its scientific payload provides a comprehensive set of electron and ion measurements. The present work describes a simple model of post-seismic disturbances in the ionosphere above the epicentre. Following a major seism, the neutral atmosphere is assumed to be subject to an acoustic pulse propagating upward, to high altitudes. By coupling this perturbation to the two-dimensional ionospheric model SAMI2 it is then possible to calculate the variations in a number of plasma parameters in the plume region and along connecting magnetic field lines, for an event of representative magnitude. The feasibility of identifying the signature of seismic events from satellite observations is then assessed in view of representative DEMETER measurements and of their natural variability.

  10. Solar cycle variations in the ionosphere of Mars

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Cano, B.; Lester, M.; Witasse, Ol; Blelly, P.L.; Cartacci, M.; Radicella, S.M.; Herraiz, M.

    2016-07-01

    Solar cycle variations in solar radiation create notable changes in the Martian ionosphere, which have been analysed with Mars Express plasma datasets in this paper. In general, lower densities and temperatures of the ionosphere are found during the low solar activity phase, while higher densities and temperatures are found during the high solar activity phase. In this paper, we assess the degree of influence of the long term solar flux variations in the ionosphere of Mars. (Author)

  11. 4 GHz ionospheric scintillations observed at Taipei

    International Nuclear Information System (INIS)

    Huang, Y.N.; Jeng, B.S.

    1978-01-01

    In a study of ionospheric scintillations 3950 MHz beacon signals from geostationary communication satellites Intelsat-IV-F8 and Intelsat-IV-F1 were recorded on a strip chart and magnetic tape at the Taipei Earth Station. While the strip charts were used to monitor the occurrence of the scintillation, the magnetic tape output was digitized and processed by a computerized system to yield a detailed analysis of scintillation events. It was found that diurnal variations were similar to the diurnal patterns of sporadic E at greater than 5 MHz and VHF band ionospheric scintillations during daytime as reported by Huang (1978). Eight typical scintillation events were selected for the calculation of the scintillation index, S4, and other parameters. The mean S4 index for the 8 events was found to be 0.15. Numerical and graphic results are presented for the cumulative amplitude distributions, message reliability, autocorrelation functions and power spectra

  12. Radio techniques for probing the terrestrial ionosphere.

    Science.gov (United States)

    Hunsucker, R. D.

    The subject of the book is a description of the basic principles of operation, plus the capabilities and limitations of all generic radio techniques employed to investigate the terrestrial ionosphere. The purpose of this book is to present to the reader a balanced treatment of each technique so they can understand how to interpret ionospheric data and decide which techniques are most effective for studying specific phenomena. The first two chapters outline the basic theory underlying the techniques, and each following chapter discusses a separate technique. This monograph is entirely devoted to techniques in aeronomy and space physics. The approach is unique in its presentation of the principles, capabilities and limitations of the most important presently used radio techniques. Typical examples of data are shown for the various techniques, and a brief historical account of the technique development is presented. An extended annotated bibliography of the salient papers in the field is included.

  13. ULF Generation by Modulated Ionospheric Heating

    Science.gov (United States)

    Chang, C.; Labenski, J.; Wallace, T.; Papadopoulos, K.

    2013-12-01

    Modulated ionospheric heating experiments designed to generate ULF waves using the HAARP heater have been conducted since 2007. Artificial ULF waves in the Pc1 frequency range were observed from space and by ground induction magnetometers located in the vicinity of the heater as well as at long distances. Two distinct generation mechanisms of artificial ULF waves were identified. The first was electroject modulation under geomagnetically disturbed conditions. The second was pressure modulation in the E and F regions of the ionosphere under quiet conditions. Ground detections of ULF waves near the heater included both Shear Alfven waves and Magnetosonic waves generated by electrojet and/or pressure modulations. Distant ULF detections involved Magnetosonic wave propagation in the Alfvenic duct with pressure modulation as the most likely source. Summary of our observations and theoretical interpretations will be presented at the meeting. We would like to acknowledge the support provided by the staff at the HAARP facility during our ULF experiments.

  14. Ground-based measurements of ionospheric dynamics

    Science.gov (United States)

    Kouba, Daniel; Chum, Jaroslav

    2018-05-01

    Different methods are used to research and monitor the ionospheric dynamics using ground measurements: Digisonde Drift Measurements (DDM) and Continuous Doppler Sounding (CDS). For the first time, we present comparison between both methods on specific examples. Both methods provide information about the vertical drift velocity component. The DDM provides more information about the drift velocity vector and detected reflection points. However, the method is limited by the relatively low time resolution. In contrast, the strength of CDS is its high time resolution. The discussed methods can be used for real-time monitoring of medium scale travelling ionospheric disturbances. We conclude that it is advantageous to use both methods simultaneously if possible. The CDS is then applied for the disturbance detection and analysis, and the DDM is applied for the reflection height control.

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

    Digital Repository Service at National Institute of Oceanography (India)

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

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

  16. Performance comparison of solar parabolic trough system with glass and film reflector

    International Nuclear Information System (INIS)

    Xu, Qian; Li, Longlong; Li, Huairui; Huang, Weidong; Li, Yongping

    2014-01-01

    Highlights: • Solar trough model should consider refractive surface error with glass reflector. • Solar trough system with glass mirror has less efficiency than that with film mirror. • Solar trough system has very low efficiency in a winter day at high latitude. - Abstract: This paper considers the refractive surface error transfer process to present an optical performance model of solar trough system as well as the reflective surface error. We validate the optical model through comparing the calculation results with the experimental data. The optimized design parameters are presented based on the maximization of the annual average net heat efficiency. The results show that maximum relative error of 20% for the optical efficiency may produce if the refractive surface error transfer process is ignored. It indicates that the refractive surface error should be considered in predicting the performance of the solar trough system especially for the glass reflector as well as the reflective surface error. We apply the model to compare the performance of solar parabolic trough system with vacuum tube receiver under two kinds of reflectors, which are glass mirror and film mirror. The results indicate that both parabolic trough systems with a vacuum tube receiver and a north–south axis tracking system are relatively inefficient in winter days, and the net energy output in the winter solstice is less than one sixth of the summer. The net heat efficiency of solar trough system with film mirror is 50% less than that of the system with the glass mirror at noon of the winter solstice and latitude 40 if the design and parameter of the two systems are the same. The results indicate that film reflector is more preferable than glass reflector especially in high latitude if they have the same optical property

  17. Processes influencing differences in Arctic and Antarctic Trough Mouth Fan sedimentology

    OpenAIRE

    Gales, J; Hillenbrand, C-D; Larter, R; Laberg, J-S; Melles, M; Benetti, S; Passchier, S

    2018-01-01

    Trough Mouth Fans (TMFs) are sediment depocentres that form along high-latitude continental margins at the mouths of some cross-shelf troughs. They reflect the dynamics of past ice sheets over multiple glacial cycles and processes operating on (formerly) glaciated continental shelves and slopes, such as erosion, reworking, transport and deposition. The similarities and differences in TMF morphology and formation processes of the Arctic and Antarctic regions remain poorly constrained. Here, we...

  18. Variations of the electron concentration in the polar ionosphere

    International Nuclear Information System (INIS)

    Chasovitin, Yu.K.; Shushkova, V.B.

    1980-01-01

    The possibility of constructing an empirical model of electron concentration in the polar ionosphere is considered. The results of rocket measurements carried out at Fort Churchill and on the Hays island at 70-210 km heights are used to analyse the distribution of electron concentration in the non-illuminated sector of the auroral oval, in the subauroral ionosphere and in the polar cap. Taking account of magnetospheric-ionospheric relationships and the geomagnetic environment, certain regularities in the distribution of electron concentration in the polar field, which may serve as a basis for constructing an empirical model of the polar ionosphere have been identified

  19. Numerical Simulation of Ionospheric Electron Concentration Depletion by Rocket Exhaust

    International Nuclear Information System (INIS)

    Huang Yong; Shi Jiaming; Yuan Zhongcai

    2011-01-01

    In terms of the diffusive process of the gases injected from rocket exhaust into the ionosphere and the relevant chemical reactions between the gases and the composition of ionosphere, the modifications in ionosphere caused by the injected hydrogen and carbon dioxide gas from the rocket exhaust are investigated. The results show that the diffusive process of the injected gases at the ionospheric height is very fast, and the injected gases can lead to a local depletion of electron concentration in the F-region. Furthermore, the plasma 'hole' caused by carbon dioxide is larger, deeper and more durable than that by the hydrogen. (astrophysics and space plasma)

  20. Ionospheric wave and irregularity measurements using passive radio astronomy techniques

    International Nuclear Information System (INIS)

    Erickson, W.C.; Mahoney, M.J.; Jacobson, A.R.; Knowles, S.H.

    1988-01-01

    The observation of midlatitude structures using passive radio astronomy techniques is discussed, with particular attention being given to the low-frequency radio telescope at the Clark Lake Radio Observatory. The present telescope operates in the 10-125-MHz frequency range. Observations of the ionosphere at separations of a few kilometers to a few hundreds of kilometers by the lines of sight to sources are possible, allowing the determination of the amplitude, wavelength, direction of propagation, and propagation speed of ionospheric waves. Data are considered on large-scale ionospheric gradients and the two-dimensional shapes and sizes of ionospheric irregularities. 10 references

  1. Ionospheric Irregularities at Mars Probed by MARSIS Topside Sounding

    Science.gov (United States)

    Harada, Y.; Gurnett, D. A.; Kopf, A. J.; Halekas, J. S.; Ruhunusiri, S.

    2018-01-01

    The upper ionosphere of Mars contains a variety of perturbations driven by solar wind forcing from above and upward propagating atmospheric waves from below. Here we explore the global distribution and variability of ionospheric irregularities around the exobase at Mars by analyzing topside sounding data from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument on board Mars Express. As irregular structure gives rise to off-vertical echoes with excess propagation time, the diffuseness of ionospheric echo traces can be used as a diagnostic tool for perturbed reflection surfaces. The observed properties of diffuse echoes above unmagnetized regions suggest that ionospheric irregularities with horizontal wavelengths of tens to hundreds of kilometers are particularly enhanced in the winter hemisphere and at high solar zenith angles. Given the known inverse dependence of neutral gravity wave amplitudes on the background atmospheric temperature, the ionospheric irregularities probed by MARSIS are most likely associated with plasma perturbations driven by atmospheric gravity waves. Though extreme events with unusually diffuse echoes are more frequently observed for high solar wind dynamic pressures during some time intervals, the vast majority of the diffuse echo events are unaffected by varying solar wind conditions, implying limited influence of solar wind forcing on the generation of ionospheric irregularities. Combination of remote and in situ measurements of ionospheric irregularities would offer the opportunity for a better understanding of the ionospheric dynamics at Mars.

  2. Geomagnetic oriented electromagnetic radiation in the ionosphere

    International Nuclear Information System (INIS)

    Benton, C.U.; Fowles, H.M.; Goen, P.K.

    1976-08-01

    Strong bursts of electromagnetic radiation were observed in the ionosphere during the Waso rocket Electromagnetic Pulse (EMP) experiment. The pulses have a frequency content from below 20 MHz to above 70 MHz. They vary in duration between 5 μs and 2 ms and in peak-amplitudes of 2 mV/m to greater than 200 mV/m. These pulses show a high degree of geomagnetic correlation and are of unknown origin

  3. PRECURSORS OF EARTHQUAKES: VLF SIGNALSIONOSPHERE IONOSPHERE RELATION

    Directory of Open Access Journals (Sweden)

    Mustafa ULAS

    2013-01-01

    Full Text Available lot of people have died because of earthquakes every year. Therefore It is crucial to predict the time of the earthquakes reasonable time before it had happed. This paper presents recent information published in the literature about precursors of earthquakes. The relationships between earthquakes and ionosphere are targeted to guide new researches in order to study further to find novel prediction methods.

  4. An investigation of ionospheric F region response in the Brazilian sector to the super geomagnetic storm of May 2005

    Science.gov (United States)

    de Abreu, A. J.; Sahai, Y.; Fagundes, P. R.; de Jesus, R.; Bittencourt, J. A.; Pillat, V. G.

    2011-10-01

    In this paper, we have investigated the responses of the ionospheric F region at equatorial and low latitude regions in the Brazilian sector during the super geomagnetic storm on 15-16 May 2005. The geomagnetic storm reached a minimum Dst of -263 nT at 0900 UT on 15 May. In this paper, we present vertical total electron content (vTEC) and phase fluctuations (in TECU/min) from Global Positioning System (GPS) observations obtained at Belém, Brasília, Presidente Prudente, and Porto Alegre, Brazil, during the period 14-17 May 2005. Also, we present ionospheric parameters h'F, hpF2, and foF2, using the Canadian Advanced Digital Ionosonde (CADI) obtained at Palmas and São José dos Campos, Brazil, for the same period. The super geomagnetic storm has fast decrease in the Dst index soon after SSC at 0239 UT on 15 May. It is a good possibility of prompt penetration of electric field of magnetospheric origin resulting in uplifting of the F region. The vTEC observations show a trough at BELE and a crest above UEPP, soon after SSC, indicating strengthening of nighttime equatorial anomaly. During the daytime on 15 and 16 May, in the recovery phase, the variations in foF2 at SJC and the vTEC observations, particularly at BRAZ, UEPP, and POAL, show large positive ionospheric storm. There is ESF on the all nights at PAL, in the post-midnight (UT) sector, and phase fluctuations only on the night of 14-15 May at BRAZ, after the SSC. No phase fluctuations are observed at the equatorial station BELE and low latitude stations (BRAZ, UEPP, and POAL) at all other times. This indicates that the plasma bubbles are generated and confined on this magnetically disturbed night only up to the low magnetic latitude and drifted possibly to west.

  5. Heat transfer analysis of parabolic trough solar receiver

    International Nuclear Information System (INIS)

    Padilla, Ricardo Vasquez; Demirkaya, Gokmen; Goswami, D. Yogi; Stefanakos, Elias; Rahman, Muhammad M.

    2011-01-01

    Highlights: → In this paper a detailed one dimensional numerical heat transfer analysis of a PTC is performed. → The receiver and envelope were divided into several segments and mass and energy balance were applied in each segment. → Improvements either in the heat transfer correlations or radiative heat transfer analysis are presented. → The proposed heat transfer model was validated with experimental data obtained from Sandia National Laboratory. → Our results showed a better agreement with experimental data compared to other models. -- Abstract: Solar Parabolic Trough Collectors (PTCs) are currently used for the production of electricity and applications with relatively higher temperatures. A heat transfer fluid circulates through a metal tube (receiver) with an external selective surface that absorbs solar radiation reflected from the mirror surfaces of the PTC. In order to reduce the heat losses, the receiver is covered by an envelope and the enclosure is usually kept under vacuum pressure. The heat transfer and optical analysis of the PTC is essential to optimize and understand its performance under different operating conditions. In this paper a detailed one dimensional numerical heat transfer analysis of a PTC is performed. The receiver and envelope were divided into several segments and mass and energy balance were applied in each segment. Improvements either in the heat transfer correlations or radiative heat transfer analysis are presented as well. The partial differential equations were discretized and the nonlinear algebraic equations were solved simultaneously. Finally, to validate the numerical results, the model was compared with experimental data obtained from Sandia National Laboratory (SNL) and other one dimensional heat transfer models. Our results showed a better agreement with experimental data compared to other models.

  6. Performance and durability testing of parabolic trough receivers

    Science.gov (United States)

    Lei, Dongqiang; Fu, Xuqiang; Zhao, Dongming; Yuan, Guofeng; Wang, Zhifeng; Guo, Minghuan

    2017-06-01

    The paper describes the key performance and durability testing facilities of the parabolic trough receiver developed by Institute of Electrical Engineering, Chinese Academy of Sciences. The indoor heat loss test can be applied at 4-7 different temperature levels within 200-550 on receivers. The optical efficiency test bench consists of 12 metal halide lamps as the solar simulator and a 5 m length half-elliptical cylinder reflector with flat end reflectors. 3 ultra-precision temperature sensors are used in receiver each end to get the temperature difference. The residual gas analysis test bench is applied to analyze and predict the vacuum lifetime of the receiver. It can test the variations of composition and partial pressure of residual gases with temperature and time in the receiver annulus space by a high sensitivity quadrupole mass spectrometer gas analyzer. A coating accelerated ageing test bench, which is also used to test the thermal cycle, has been developed. This test bench uses the absorber tube of the recevier as the resistance heater to heat up the whole receiver. The coating lifetime can be predicted by the Arrhenius parameters. For the cycling test, the compressed air is used to directly cool the inner surface of the absorber tube. The thermal cycling test is performed with temperature cycles from 150 °C to 450 °C for 160 cycles. The maximum thermal cycling frequency is 8 cycles per day. The mechanical fatigue test bench is used to test the bellows and the glass-to-metal seals durability at the same time. Both bellows are expanded and compressed to 6.5 mm in turn with 10,000 cycles. A new rotating test bench was also developed to test the thermal efficiency of the receiver.

  7. Seismic Reflectivity of the Crust in the Northern Salton Trough

    Science.gov (United States)

    Bauer, K.; Fuis, G. S.; Goldman, M.; Persaud, P.; Ryberg, T.; Langenheim, V. E.; Scheirer, D. S.; Rymer, M. J.; Hole, J. A.; Stock, J. M.; Catchings, R.

    2015-12-01

    The Salton Trough in southern California is a tectonically active pull-apart basin that was formed by migrating step-overs between strike-slip faults, of which the San Andreas Fault (SAF) and the Imperial Fault are the current, northernmost examples. The Salton Seismic Imaging Project (SSIP) was undertaken to improve our knowledge of fault geometry and seismic velocities within the sedimentary basins and underlying crystalline crust around the SAF. Such data are useful as input for modeling scenarios of strong ground shaking in the surrounding high-population areas. We used pre-stack depth migration of line segments from shot gathers in several seismic profiles that were acquired in the northern part of the SSIP study area (Lines 4 - 7). Our migration approach can be considered as an infinite-frequency approximation of the Fresnel volume pre-stack depth migration method. We use line segments instead of the original waveform data. We demonstrate the method using synthetic data and analyze real data from Lines 4 - 7 to illustrate the relationship between distinct phases in the time domain and their resulting image at depth. We show both normal-moveout reflections from sub-horizontal interfaces and reverse-moveout reflections from steep interfaces, such as faults. Migrated images of dipping faults, such as the SAF and the Pinto Mountain Fault, are presented in this way. The SAF is imaged along Line 4, through the Mecca Hills, as a number of steeply dipping fault segments that collectively form a flower structure, above 5 km depth, that sole into a moderately NE-dipping fault below that depth. The individual migrated reflection packages correlate with mapped surface fault traces in the Mecca Hills. A similar geometry is seen on Line 6, from Palm Springs through Yucca Valley, where fault splays sole or project into a moderately dipping SAF below 10-km depth. We also show and discuss the reflectivity pattern of the middle and lower crust for Lines 4 - 7.

  8. Dual-frequency radio soundings of planetary ionospheres avoid misinterpretations of ionospheric features

    Science.gov (United States)

    Paetzold, M.; Andert, T.; Bird, M. K.; Häusler, B.; Hinson, D. P.; Peter, K.; Tellmann, S.

    2017-12-01

    Planetary ionospheres are usually sounded at single frequency, e.g. S-band or X-band, or at dual-frequencies, e.g. simultaneous S-band and X-band frequencies. The differential Doppler is computed from the received dual-frequency sounding and it has the advantage that any residual motion by the spaceraft body is compensated. The electron density profile is derived from the propagation of the two radio signals through the ionospheric plasma. Vibrational motion of small amplitude by the spacecraft body may still be contained in the single frequency residuals and may be translated into electron densities. Examples from Mars Express and Venus Express shall be presented. Cases from other missions shall be presented where wave-like structures in the upper ionosphere may be a misinterpretation.

  9. Space weather: Modeling and forecasting ionospheric

    International Nuclear Information System (INIS)

    Calzadilla Mendez, A.

    2008-01-01

    Full text: Space weather is the set of phenomena and interactions that take place in the interplanetary medium. It is regulated primarily by the activity originating in the Sun and affects both the artificial satellites that are outside of the protective cover of the Earth's atmosphere as the rest of the planets in the solar system. Among the phenomena that are of great relevance and impact on Earth are the auroras and geomagnetic storms , these are a direct result of irregularities in the flow of the solar wind and the interplanetary magnetic field . Given the high complexity of the physical phenomena involved (magnetic reconnection , particle inlet and ionizing radiation to the atmosphere) one of the great scientific challenges today is to forecast the state of plasmatic means either the interplanetary medium , the magnetosphere and ionosphere , for their importance to the development of various human activities such as radio , global positioning , navigation, etc. . It briefly address some of the international ionospheric modeling methods and contributions and participation that currently has the space group of the Institute of Geophysics Geophysics and Astronomy (IGA) in these activities of modeling and forecasting ionospheric. (author)

  10. The performance analysis of the Trough Concentrating Solar Photovoltaic/Thermal system

    Energy Technology Data Exchange (ETDEWEB)

    Li, M., E-mail: liming@ynnu.edu.c [Solar Energy Research Institute, Yunnan Normal University, 650092 Kunming (China); Li, G.L. [School of Physics and Electronic Information, Yunnan Normal University, Kunming 650092 (China); Ji, X.; Yin, F.; Xu, L. [Solar Energy Research Institute, Yunnan Normal University, 650092 Kunming (China)

    2011-06-15

    Research highlights: {yields} A 2 m{sup 2} Trough Concentrating Photovoltaic/Thermal (TCPV/T) system is built, a single crystalline silicon solar cell array, a polycrystalline silicon cell array, a Super cell array and a GaAs cell array are respectively used in the experiments. {yields} Another 10 m{sup 2} TCPV/T system using the GaAs cell array and a concentrating silicon cell array are also constructed and characterized. {yields} The economic performance analysis show the electricity generating cost of the TCPV/T system with the concentrating silicon cell array can catch up with flat-plate PV system. -- Abstract: The electrical and thermal performance of a 2 m{sup 2} Trough Concentrating Photovoltaic/Thermal (TCPV/T) system with an energy flux ratio 10.27 are characterized by experiments. A single crystalline silicon solar cell array, a polycrystalline silicon cell array, a Super cell array and a GaAs cell array are respectively used in the experiments. The experimental results show that the electrical performance of the system with the GaAs cell array is better than that of crystal silicon solar cell arrays. The superior output performance of the GaAs cell array mainly benefits from its lower series resistance. But the thermal performances of the system using the single crystal silicon solar cell array and the polycrystalline silicon solar cell array are better. It results from the widths of the two types of cells in the system close to that of the focal line. Another 10 m{sup 2} TCPV/T system with an energy flux ratio of 20 using the GaAs cell array and a concentrating silicon cell array are also constructed and characterized. The experimental results indicate that the photoelectric efficiency of the GaAs cell array is 23.83%, and the instantaneous electrical efficiency and thermal efficiency of the system are 9.88% and 49.84% respectively. While the instantaneous electrical efficiency and thermal efficiency of the system using the low-cost concentrating

  11. The performance analysis of the Trough Concentrating Solar Photovoltaic/Thermal system

    International Nuclear Information System (INIS)

    Li, M.; Li, G.L.; Ji, X.; Yin, F.; Xu, L.

    2011-01-01

    Research highlights: → A 2 m 2 Trough Concentrating Photovoltaic/Thermal (TCPV/T) system is built, a single crystalline silicon solar cell array, a polycrystalline silicon cell array, a Super cell array and a GaAs cell array are respectively used in the experiments. → Another 10 m 2 TCPV/T system using the GaAs cell array and a concentrating silicon cell array are also constructed and characterized. → The economic performance analysis show the electricity generating cost of the TCPV/T system with the concentrating silicon cell array can catch up with flat-plate PV system. -- Abstract: The electrical and thermal performance of a 2 m 2 Trough Concentrating Photovoltaic/Thermal (TCPV/T) system with an energy flux ratio 10.27 are characterized by experiments. A single crystalline silicon solar cell array, a polycrystalline silicon cell array, a Super cell array and a GaAs cell array are respectively used in the experiments. The experimental results show that the electrical performance of the system with the GaAs cell array is better than that of crystal silicon solar cell arrays. The superior output performance of the GaAs cell array mainly benefits from its lower series resistance. But the thermal performances of the system using the single crystal silicon solar cell array and the polycrystalline silicon solar cell array are better. It results from the widths of the two types of cells in the system close to that of the focal line. Another 10 m 2 TCPV/T system with an energy flux ratio of 20 using the GaAs cell array and a concentrating silicon cell array are also constructed and characterized. The experimental results indicate that the photoelectric efficiency of the GaAs cell array is 23.83%, and the instantaneous electrical efficiency and thermal efficiency of the system are 9.88% and 49.84% respectively. While the instantaneous electrical efficiency and thermal efficiency of the system using the low-cost concentrating silicon cell array are 7.51% and 42

  12. [Survival of VTEC O157 and non-O157 in water troughs and bovine feces].

    Science.gov (United States)

    Polifroni, Rosana; Etcheverría, Analía I; Arroyo, Guillermo H; Padola, Nora L

    2014-01-01

    Verotoxin-producing Escherichia coli (VTEC) is the etiologic agent of hemolytic-uremic syndrome (HUS), which typically affects children ranging in age from six months to five years old. Transmission is produced by consumption of contaminated food, by direct contact with animals or the environment and from person to person. In previous studies we determined that the environment of a dairy farm is a non-animal reservoir; thus, we proposed to study the survival of 4 VTEC isolates (O20:H19; O91:H21; O157:H7 and O178:H19) in sterile water troughs and bovine feces by viable bacteria count and detection of virulence genes by PCR. It was demonstrated that the survival of different VTEC isolates (O157 and non-O157) varied in terms of their own characteristics as well as of the environmental conditions where they were found. The main differences between isolates were their survival time and the maximal counts reached. The competitive and adaptive characteristics of some isolates increase the infection risk for people that are visiting or working on a farm, as well as the risk for reinfection of the animals and food contamination. Copyright © 2014 Asociación Colombiana de Psiquiatría. Publicado por Elsevier España. All rights reserved.

  13. Biomarkers, carbon isotopic composition and source rock potentials of Awgu coals, middle Benue trough, Nigeria

    Science.gov (United States)

    Adedosu, Taofik A.; Sonibare, Oluwadayo O.; Tuo, Jincai; Ekundayo, Olusegun

    2012-05-01

    Coal and carbonaceous shale samples were collected from two boreholes (BH 94 and BH 120) in Awgu formation of Middle Benue Trough, Nigeria. Source rock potentials of the samples were studied using biomarkers and carbon isotopic composition. Biomarkers in the aliphatic fractions in the samples were studied using Gas Chromatography-Mass Spectrometry (GC-MS). The Carbon isotope analysis of individual n-alkanes in the aliphatic fraction was performed using Gas Chromatography-Combustion-Isotope Ratio Mass Spectrometer (GC-IRMS). The abundance of hopanes, homohopanes (C31-C35), and C29 steranes in the samples indicate terrestrial plant, phytoplankton and cyanobacteria contributions to the organic matter that formed the coal. High (Pr/Ph) ratio (3.04-11.07) and isotopic distribution of individual alkanes showed that the samples consisted of mixed terrestrial/marine organic matter deposited under oxic condition in lacustrine-fluvial/deltaic depositional environment. The maturity parameters derived from biomarker distributions showed that the samples are in the main phase of oil window.

  14. Ionosphere Waves Service (IWS – a problem-oriented tool in ionosphere and Space Weather research produced by POPDAT project

    Directory of Open Access Journals (Sweden)

    Ferencz Csaba

    2014-05-01

    Full Text Available In the frame of the FP7 POPDAT project the Ionosphere Waves Service (IWS has been developed and opened for public access by ionosphere experts. IWS is forming a database, derived from archived ionospheric wave records to assist the ionosphere and Space Weather research, and to answer the following questions: How can the data of earlier ionospheric missions be reprocessed with current algorithms to gain more profitable results? How could the scientific community be provided with a new insight on wave processes that take place in the ionosphere? The answer is a specific and unique data mining service accessing a collection of topical catalogs that characterize a huge number of recorded occurrences of Whistler-like Electromagnetic Wave Phenomena, Atmosphere Gravity Waves, and Traveling Ionosphere Disturbances. IWS online service (http://popdat.cbk.waw.pl offers end users to query optional set of predefined wave phenomena, their detailed characteristics. These were collected by target specific event detection algorithms in selected satellite records during database buildup phase. Result of performed wave processing thus represents useful information on statistical or comparative investigations of wave types, listed in a detailed catalog of ionospheric wave phenomena. The IWS provides wave event characteristics, extracted by specific software systems from data records of the selected satellite missions. The end-user can access targets by making specific searches and use statistical modules within the service in their field of interest. Therefore the IWS opens a new way in ionosphere and Space Weather research. The scientific applications covered by IWS concern beyond Space Weather also other fields like earthquake precursors, ionosphere climatology, geomagnetic storms, troposphere-ionosphere energy transfer, and trans-ionosphere link perturbations.

  15. Ionosphere Waves Service (IWS) - a problem-oriented tool in ionosphere and Space Weather research produced by POPDAT project

    Science.gov (United States)

    Ferencz, Csaba; Lizunov, Georgii; Crespon, François; Price, Ivan; Bankov, Ludmil; Przepiórka, Dorota; Brieß, Klaus; Dudkin, Denis; Girenko, Andrey; Korepanov, Valery; Kuzmych, Andrii; Skorokhod, Tetiana; Marinov, Pencho; Piankova, Olena; Rothkaehl, Hanna; Shtus, Tetyana; Steinbach, Péter; Lichtenberger, János; Sterenharz, Arnold; Vassileva, Any

    2014-05-01

    In the frame of the FP7 POPDAT project the Ionosphere Waves Service (IWS) has been developed and opened for public access by ionosphere experts. IWS is forming a database, derived from archived ionospheric wave records to assist the ionosphere and Space Weather research, and to answer the following questions: How can the data of earlier ionospheric missions be reprocessed with current algorithms to gain more profitable results? How could the scientific community be provided with a new insight on wave processes that take place in the ionosphere? The answer is a specific and unique data mining service accessing a collection of topical catalogs that characterize a huge number of recorded occurrences of Whistler-like Electromagnetic Wave Phenomena, Atmosphere Gravity Waves, and Traveling Ionosphere Disturbances. IWS online service (http://popdat.cbk.waw.pl) offers end users to query optional set of predefined wave phenomena, their detailed characteristics. These were collected by target specific event detection algorithms in selected satellite records during database buildup phase. Result of performed wave processing thus represents useful information on statistical or comparative investigations of wave types, listed in a detailed catalog of ionospheric wave phenomena. The IWS provides wave event characteristics, extracted by specific software systems from data records of the selected satellite missions. The end-user can access targets by making specific searches and use statistical modules within the service in their field of interest. Therefore the IWS opens a new way in ionosphere and Space Weather research. The scientific applications covered by IWS concern beyond Space Weather also other fields like earthquake precursors, ionosphere climatology, geomagnetic storms, troposphere-ionosphere energy transfer, and trans-ionosphere link perturbations.

  16. Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) Model - An Unified Concept for Earthquake Precursors Validation

    Science.gov (United States)

    Pulinets, S.; Ouzounov, D.

    2010-01-01

    The paper presents a conception of complex multidisciplinary approach to the problem of clarification the nature of short-term earthquake precursors observed in atmosphere, atmospheric electricity and in ionosphere and magnetosphere. Our approach is based on the most fundamental principles of tectonics giving understanding that earthquake is an ultimate result of relative movement of tectonic plates and blocks of different sizes. Different kind of gases: methane, helium, hydrogen, and carbon dioxide leaking from the crust can serve as carrier gases for radon including underwater seismically active faults. Radon action on atmospheric gases is similar to the cosmic rays effects in upper layers of atmosphere: it is the air ionization and formation by ions the nucleus of water condensation. Condensation of water vapor is accompanied by the latent heat exhalation is the main cause for observing atmospheric thermal anomalies. Formation of large ion clusters changes the conductivity of boundary layer of atmosphere and parameters of the global electric circuit over the active tectonic faults. Variations of atmospheric electricity are the main source of ionospheric anomalies over seismically active areas. Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) model can explain most of these events as a synergy between different ground surface, atmosphere and ionosphere processes and anomalous variations which are usually named as short-term earthquake precursors. A newly developed approach of Interdisciplinary Space-Terrestrial Framework (ISTF) can provide also a verification of these precursory processes in seismically active regions. The main outcome of this paper is the unified concept for systematic validation of different types of earthquake precursors united by physical basis in one common theory.

  17. Solar eclipses at high latitudes: ionospheric effects in the lower ionosphere

    Science.gov (United States)

    Cherniakov, S.

    2017-12-01

    The partial reflection facility of the Polar Geophysical Institute (the Tumanny observatory, 69.0N, 35.7E) has observed behavior of the high-latitude lower ionosphere during the 20 March 2015 total solar eclipse. There were several effects during the eclipse. At the heights of 60-80 km the ionosphere has shown the effect of a "short night", but at the higher altitudes local enhanced electron concentration had a wave-like form. Data received by the riometer of the Tumanny observatory have also shown wave-like behavior. The behavior can be explained by influence of acoustic-gravity waves which originated after cooling of the atmosphere during the lunar shadow supersonic movement, and transport processes during the eclipse. During the 21 August 2017 solar eclipse there was a substorm at the high latitudes. But after the end of the substorm in the region of the Tumanny observatory the observed amplitudes of the reflected waves had wave effects which could be connected with the coming waves from the region of the eclipse. The wave features were also shown in the behavior of the total electron content (TEC) of the lower ionosphere. During several solar eclipses it was implemented observations of lower ionosphere behavior by the partial reflection facility of the Tumanny observatory. The consideration of the lower ionosphere TEC had revealed common features in the TEC behavior during the eclipses. The photochemical theory of processes in the lower ionosphere is very complicated and up to now it is not completely developed. Therefore introduction of the effective coefficients determining the total speed of several important reactions has been widely adopted when modeling the D-region of the ionosphere. However, experimental opportunities for obtaining effective recombination coefficients are rather limited. One of the methods to estimate effective recombination coefficients uses the phenomenon of a solar eclipse. During solar eclipses at the partial reflection facility of

  18. Ionospheric Storm Effects and Equatorial Plasma Irregularities During the 17-18 March 2015 Event

    Science.gov (United States)

    Zhou, Yun-Liang; Luhr, Hermann; Xiong, Chao; Pfaff, Robert F.

    2016-01-01

    The intense magnetic storm on 17-18 March 2015 caused large disturbances of the ionosphere. Based on the plasma density (Ni) observations performed by the Swarm fleet of satellites, the Gravity Recovery and Climate Experiment mission, and the Communications/Navigation Outage Forecasting System satellite, we characterize the storm-related perturbations at low latitudes. All these satellites sampled the ionosphere in morning and evening time sectors where large modifications occurred. Modifications of plasma density are closely related to changes of the solar wind merging electric field (E (sub m)). We consider two mechanisms, prompt penetration electric field (PPEF) and disturbance dynamo electric field (DDEF), as the main cause for the Ni redistribution, but effects of meridional wind are also taken into account. At the start of the storm main phase, the PPEF is enhancing plasma density on the dayside and reducing it on the nightside. Later, DDEF takes over and causes the opposite reaction. Unexpectedly, there appears during the recovery phase a strong density enhancement in the morning/pre-noon sector and a severe Ni reduction in the afternoon/evening sector, and we suggest a combined effect of vertical plasma drift, and meridional wind is responsible for these ionospheric storm effects. Different from earlier studies about this storm, we also investigate the influence of storm dynamics on the initiation of equatorial plasma irregularities (EPIs). Shortly after the start of the storm main phase, EPIs appear in the post-sunset sector. As a response to a short-lived decline of E (sub m), EPI activity appears in the early morning sector. Following the second start of the main phase, EPIs are generated for a few hours in the late evening sector. However, for the rest of the storm main phase, no more EPIs are initiated for more than 12 hours. Only after the onset of recovery phase does EPI activity start again in the post-midnight sector, lasting more than 7 hours

  19. Some necessary parameters for a critical velocity interaction between the ionospheric plasma and a xenon cloud

    International Nuclear Information System (INIS)

    Axnaes, I.

    1979-12-01

    The conditions for an experiment to study the critical ionization velocity effect in the interaction between a Xenon cloud, released from a satellite, and the ionospheric plasma are investigated. The model used is based on the assumption that there exists an effective process that transfers the energy, that is available in the relative motion, to the electrons. Some necessary conditions to obtain significant heating or deceleration of the plasma penetrating the cloud are calculated. The conditions are mainly given by the energy available in the relative motion and the rates of the different binary collision processes involved. As the released gas cloud expands the possibilities for a critical velocity interaction will exist only within a certain range of cloud radii. It is shown that the charge transfer collision cross section between the ionospheric ions and the cloud atoms is an important parameter and that Xenon is a very suitable gas in that respect. (author)

  20. Coupling of the Magnetosphere-Ionosphere/Thermosphere and Oxygen Outflow-- MIT Mission

    Science.gov (United States)

    Fu, S.

    2017-12-01

    The goal of the MIT mission is to understand the coupling of the magnetosphere and ionosphere from the prospective of particles. It will focus on the outflow of the ionosphere particles (mainly oxygen ions) from the Earth, including the acceleration mechanisms of oxygen ions and their relative importance in different regions, the importance of these ions while transferred into the magnetosphere and the roles they played in magnetosphere activities. A constellation of four satellites orbiting at three elliptical orbits will provide the unique opportunities to observed there ions at three different altitude with temporal changes of the flux of these particles and the magnetic field environments. The conceptual design of the spacecraft and a summary of the payload will be presented. The MIT mission was selected as one of the five candidates for the upcoming mission plan in China.

  1. MONITOR Ionospheric Network: two case studies on scintillation and electron content variability

    Directory of Open Access Journals (Sweden)

    Y. Béniguel

    2017-03-01

    Full Text Available The ESA MONITOR network is composed of high-frequency-sampling global navigation satellite systems (GNSS receivers deployed mainly at low and high latitudes to study ionosphere variability and jointly with global GNSS data and ionospheric processing software in support of the GNSS and its satellite-based augmentation systems (SBAS like the European EGNOS. In a recent phase of the project, the network was merged with the CNES/ASECNA network and new receivers were added to complement the latter in the western African sector. This paper summarizes MONITOR, presenting two case studies on scintillations (using almost 2 years of data measurements. The first case occurred during the major St. Patrick's Day geomagnetic storm in 2015. The second case study was performed in the last phase of the project, which was supported by ESA EGNOS Project Office, when we paid special attention to extreme events that might degrade the system performance of the European EGNOS.

  2. Critical frequencies of the ionospheric F1 and F2 layers during the last four solar cycles: Sunspot group type dependencies

    Science.gov (United States)

    Yiǧit, Erdal; Kilcik, Ali; Elias, Ana Georgina; Dönmez, Burçin; Ozguc, Atila; Yurchshyn, Vasyl; Rozelot, Jean-Pierre

    2018-06-01

    The long term solar activity dependencies of ionospheric F1 and F2 regions' critical frequencies (f0F1 and f0F2) are analyzed for the last four solar cycles (1976-2015). We show that the ionospheric F1 and F2 regions have different solar activity dependencies in terms of the sunspot group (SG) numbers: F1 region critical frequency (f0F1) peaks at the same time with the small SG numbers, while the f0F2 reaches its maximum at the same time with the large SG numbers, especially during the solar cycle 23. The observed differences in the sensitivity of ionospheric critical frequencies to sunspot group (SG) numbers provide a new insight into the solar activity effects on the ionosphere and space weather. While the F1 layer is influenced by the slow solar wind, which is largely associated with small SGs, the ionospheric F2 layer is more sensitive to Coronal Mass Ejections (CMEs) and fast solar winds, which are mainly produced by large SGs and coronal holes. The SG numbers maximize during of peak of the solar cycle and the number of coronal holes peaks during the sunspot declining phase. During solar minimum there are relatively less large SGs, hence reduced CME and flare activity. These results provide a new perspective for assessing how the different regions of the ionosphere respond to space weather effects.

  3. Gas Hydrate Petroleum System Modeling in western Nankai Trough Area

    Science.gov (United States)

    Tanaka, M.; Aung, T. T.; Fujii, T.; Wada, N.; Komatsu, Y.

    2017-12-01

    Since 2003, we have been conducting Gas Hydrate (GH) petroleum system models covering the eastern Nankai Trough, Japan, and results of resource potential from regional model shows good match with the value depicted from seismic and log data. In this year, we have applied this method to explore GH potential in study area. In our study area, GH prospects have been identified with aid of bottom simulating reflector (BSR) and presence of high velocity anomalies above the BSR interpreted based on 3D migration seismic and high density velocity cubes. In order to understand the pathway of biogenic methane from source to GH prospects 1D-2D-3D GH petroleum system models are built and investigated. This study comprises lower Miocene to Pleistocene, deep to shallow marine sedimentary successions of Pliocene and Pleistocene layers overlain the basement. The BSR were interpreted in Pliocene and Pleistocene layers. Based on 6 interpreted sequence boundaries from 3D migration seismic and velocity data, construction of a depth 3D framework model is made and distributed by a conceptual submarine fan depositional facies model derived from seismic facies analysis and referring existing geological report. 1D models are created to analyze lithology sensitivity to temperature and vitrinite data from an exploratory well drilled in the vicinity of study area. The PSM parameters are applied in 2D and 3D modeling and simulation. Existing report of the explanatory well reveals that thermogenic origin are considered to exist. For this reason, simulation scenarios including source formations for both biogenic and thermogenic reaction models are also investigated. Simulation results reveal lower boundary of GH saturation zone at pseudo wells has been simulated with sensitivity of a few tens of meters in comparing with interpreted BSR. From sensitivity analysis, simulated temperature was controlled by different peak generation temperature models and geochemical parameters. Progressive folding

  4. Frictional Behavior of Altered Basement Approaching the Nankai Trough

    Science.gov (United States)

    Saffer, D. M.; Ikari, M.; Rooney, T. O.; Marone, C.

    2017-12-01

    The frictional behavior of basement rocks plays an important role in subduction zone faulting and seismicity. This includes earthquakes seaward of the trench, large megathrust earthquakes where seamounts are subducting, or where the plate interface steps down to basement. In exhumed subduction zone rocks such as the Shimanto complex in Japan, slivers of basalt are entrained in mélange which is evidence of basement involvement in the fault system. Scientific drilling during the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) recovered basement rock from two reference sites (C0011 and C0012) located seaward of the trench offshore the Kii Peninsula during Integrated Ocean Discovery Program (IODP) Expeditions 322 and 333. The basement rocks are pillow basalts that appear to be heterogeneously altered, resulting in contrasting dense blue material and more vesicular gray material. Major element geochemistry shows differences in silica, calcium oxides and loss-on-ignition between the two types of samples. Minor element geochemistry reveals significant differences in vanadium, chromium, and barium. X-ray diffraction on a bulk sample powder representing an average composition shows a phyllosilicate content of 20%, most of which is expandable clays. We performed laboratory friction experiments in a biaxial testing apparatus as either intact sample blocks, or as gouge powders. We combine these experiments with measurements of Pennsylvania slate for comparison, including a mixed-lithology intact block experiment. Intact Nankai basement blocks exhibit a coefficient of sliding friction of 0.73; for Nankai basement powder, slate powder, slate blocks and slate-on-basement blocks the coefficient of sliding friction ranges from 0.44 to 0.57. At slip rates ranging from 3x10-8 to 3x10-4 m/s we observe predominantly velocity-strengthening frictional behavior, indicating a tendency for stable slip. At rates of < 1x10-6 m/s some velocity-weakening was observed, specifically in

  5. New advantages of the combined GPS and GLONASS observations for high-latitude ionospheric irregularities monitoring: case study of June 2015 geomagnetic storm

    Science.gov (United States)

    Cherniak, Iurii; Zakharenkova, Irina

    2017-05-01

    Monitoring, tracking and nowcasting of the ionospheric plasma density disturbances using dual-frequency measurements of the Global Positioning System (GPS) signals are effectively carried out during several decades. Recent rapid growth and modernization of the ground-based segment gives an opportunity to establish a great database consisting of more than 6000 stations worldwide which provide GPS signals measurements with an open access. Apart of the GPS signals, at least two-third of these stations receive simultaneously signals transmitted by another Global Navigation Satellite System (GNSS)—the Russian system GLONASS. Today, GLONASS signal measurements are mainly used in navigation and geodesy only and very rarely for ionosphere research. We present the first results demonstrating advantages of using several independent but compatible GNSS systems like GPS and GLONASS for improvement of the permanent monitoring of the high-latitude ionospheric irregularities. For the first time, the high-resolution two-dimensional maps of ROTI perturbation were made using not only GPS but also GLONASS measurements. We extend the use of the ROTI maps for analyzing ionospheric irregularities distribution. We demonstrate that the meridional slices of the ROTI maps can be effectively used to study the occurrence and temporal evolution of the ionospheric irregularities. The meridional slices of the geographical sectors with a high density of the GPS and GLONASS measurements can represent spatio-temporal dynamics of the intense ionospheric plasma density irregularities with very high resolution, and they can be effectively used for detailed study of the space weather drivers on the processes of the ionospheric irregularities generation, development and their lifetimes. Using a representative database of 5800 ground-based GNSS stations located worldwide, we have investigated the occurrence of the high-latitude ionospheric plasma density irregularities during the geomagnetic storm of

  6. Study of ionospheric anomalies due to impact of typhoon using ...

    Indian Academy of Sciences (India)

    Page 1 ... landing of typhoon Matsa, with TEC increasing from its monthly median over the typhoon area by. Keywords. Principal Component Analysis; total electron content; global ionospheric map; .... dent on temperature and wind structure in the atmosphere. Coupling between typhoon processes and the ionosphere has ...

  7. Monitoring the three-dimensional ionospheric electron density ...

    Indian Academy of Sciences (India)

    In this paper, an IRI model assisted GPS-based Computerized Ionospheric Tomography (CIT) technique is developed to inverse the ionospheric ... are usually installed along a fixed longitude chain. Kunitsyn et al (1997) first confirmed the .... The IED value at the center of each pixel is gen- erated from the IRI2001 model and ...

  8. Impact of Galileo on Global Ionosphere Map Estimation

    NARCIS (Netherlands)

    Undetermined, U.

    2006-01-01

    The upcoming GNSS Galileo, with its new satellite geometry and frequency plan, will not only bring many benefits for navigation and positioning but also help to improve ionosphere delay estimation. This paper investigates ionosphere estimation with Galileo and compares it with the results from

  9. Probing ionospheric structures using the LOFAR radio telescope

    NARCIS (Netherlands)

    Mevius, M.; van der Tol, S.; Pandey, V.N.; Vedantham, H. K.; Brentjens, M. A.; Bruyn, A. G.; Abdalla, F. B.; Asad, K. M. B.; Bregman, J. D.; Brouw, W. N.; Bus, S.; Chapman, E.; Ciardi, B.; Fernandez, E. R.; Ghosh, A.; Harker, G.; Iliev, I. T.; Jelic, Vibor; Kazemi, S.; Koopmans, L. V. E.; Noordam, J. E.; Offringa, A. R.; Patil, A. H.; Weeren, R. J.; Wijnholds, S.; Yatawatta, S.; Zaroubi, S.

    2016-01-01

    LOFAR is the LOw-Frequency Radio interferometer ARray located at midlatitude (52°53'N). Here we present results on ionospheric structures derived from 29 LOFAR nighttime observations during the winters of 2012/2013 and 2013/2014. We show that LOFAR is able to determine differential ionospheric total

  10. Bayesian estimation for ionospheric calibration in radio astronomy

    NARCIS (Netherlands)

    Van der Tol, S.

    2009-01-01

    Radio astronomical observations at low frequencies (< 250 MHz), can be severely distorted by fluctuations in electron density in the ionosphere. The free electrons cause a phase change of electromagnetic waves traveling through the ionosphere. This effect increases for lower frequencies. For this

  11. The F-Region Equatorial Ionospheric Electrodynamics Drifts ...

    African Journals Online (AJOL)

    The ionospheric plasma drift is one of the most essential parameters for understanding the dynamics of ionospheric F-region. F-region electromagnetic drifts are calculated for three seasonal conditions from ionosonde observations acquired during quiet period of a typical year of high and low solar activity at Ibadan (7.4oN, ...

  12. Ionospheric Electron Densities at Mars: Comparison of Mars Express Ionospheric Sounding and MAVEN Local Measurement

    Czech Academy of Sciences Publication Activity Database

    Němec, F.; Morgan, D. D.; Fowler, C.M.; Kopf, A.J.; Andersson, L.; Gurnett, D. A.; Andrews, D.J.; Truhlík, Vladimír

    2017-01-01

    Roč. 122, č. 12 (2017), s. 12393-12405 E-ISSN 2169-9402 Institutional support: RVO:68378289 Keywords : Mars * ionosphere * MARSIS * Mars Express * MAVEN * radar sounding Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) http://onlinelibrary.wiley.com/doi/10.1002/2017JA024629/full

  13. A study of the ionospheric signature of ion supply from the ionosphere to the magnetosphere

    International Nuclear Information System (INIS)

    Loranc, M.A.P.

    1988-01-01

    Recent studies have demonstrated the importance of the ionosphere as a source of magnetospheric plasma; in particular, the observations of upwelling ions (UWI) by the DE-1 Retarding Ion Mass Spectrometer have illustrated the significance of low-energy ion supply to the magnetosphere. The composition of the UWI implies an ionospheric source, and the Dynamics Explorer dual satellite mission provides an opportunity to search for the ionospheric signature of UWI. Magnetometer data from both satellites are used to determine magnetic conjunctions of the satellites; these conjunctions are searched for correlated observations of UWI and upward flowing thermal ion (UFI) events. Four cases of correlated observations are presented as proof of that the UFI are indeed the ionospheric signature of UWI; it is found from these examples that the event are associated with intense field-aligned currents at both satellites and with anti-sunward convection, enhanced fluxes of low-energy precipitating electrons from the boundary plasma sheet, and upward thermal ion fluxes in excess of 10 9 cm -2 s -1 at DE-2. While USI are primarily a dayside phenomena, UFI are found in all local time sectors sampled by DE-2

  14. Exergy analysis of parabolic trough solar collectors integrated with combined steam and organic Rankine cycles

    International Nuclear Information System (INIS)

    Al-Sulaiman, Fahad A.

    2014-01-01

    Highlights: • As the solar irradiation increases, the exergetic efficiency increases. • The R134a combined cycle has best exergetic performance, 26%. • The R600a combined cycle has the lowest exergetic efficiency, 20%. • The main source of exergy destruction is the solar collector. • There is an exergetic improvement potential of 75% in the systems considered. - Abstract: In this paper, detailed exergy analysis of selected thermal power systems driven by parabolic trough solar collectors (PTSCs) is presented. The power is produced using either a steam Rankine cycle (SRC) or a combined cycle, in which the SRC is the topping cycle and an organic Rankine cycle (ORC) is the bottoming cycle. Seven refrigerants for the ORC were examined: R134a, R152a, R290, R407c, R600, R600a, and ammonia. Key exergetic parameters were examined: exergetic efficiency, exergy destruction rate, fuel depletion ratio, irreversibility ratio, and improvement potential. For all the cases considered it was revealed that as the solar irradiation increases, the exergetic efficiency increases. Among the combined cycles examined, the R134a combined cycle demonstrates the best exergetic performance with a maximum exergetic efficiency of 26% followed by the R152a combined cycle with an exergetic efficiency of 25%. Alternatively, the R600a combined cycle has the lowest exergetic efficiency, 20–21%. This study reveals that the main source of exergy destruction is the solar collector where more than 50% of inlet exergy is destructed, or in other words more than 70% of the total destructed exergy. In addition, more than 13% of the inlet exergy is destructed in the evaporator which is equivalent to around 19% of the destructed exergy. Finally, this study reveals that there is an exergetic improvement potential of 75% in the systems considered

  15. Modeling study of the ionospheric responses to the quasi-biennial oscillations of the sun and stratosphere

    Science.gov (United States)

    Wang, Jack C.; Tsai-Lin, Rong; Chang, Loren C.; Wu, Qian; Lin, Charles C. H.; Yue, Jia

    2018-06-01

    The Quasi-biennial Oscillation (QBO) is a persistent oscillation in the zonal mean zonal winds of the low latitude middle atmosphere that is driven by breaking planetary and gravity waves with a period near two years. The atmospheric tides that dominate the dynamics of the mesosphere and lower thermosphere region (MLT, between heights of 70-120 km) are excited in the troposphere and stratosphere, and propagate through QBO-modulated zonal mean zonal wind fields. This allows the MLT tidal response to also be modulated by the QBO, with implications for ionospheric/thermospheric variability. Interannual oscillations in solar radiation can also directly drive the variations in the ionosphere with similar periodicities through the photoionization. Many studies have observed the connection between the solar activity and QBO signal in ionospheric features such as total electron content (TEC). In this research, we develop an empirical model to isolate stratospheric QBO-related tidal variability in the MLT diurnal and semidiurnal tides using values from assimilated TIMED satellite data. Migrating tidal fields corresponding to stratospheric QBO eastward and westward phases, as well as with the quasi-biennial variations in solar activity isolated by the Multi-dimensional Ensemble Empirical Mode Decomposition (MEEMD) analysis from Hilbert-Huang Transform (HHT), are then used to drive the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). The numerical experiment results indicate that the ionospheric QBO is mainly driven by the solar quasi-biennial variations during the solar maximum, since the solar quasi-biennial variation amplitude is directly proportionate to the solar cycle. The ionospheric QBO in the model is sensitive to both the stratospheric QBO and solar quasi-biennial variations during the solar minimum, with solar effects still playing a stronger role.

  16. Updated climatological model predictions of ionospheric and HF propagation parameters

    International Nuclear Information System (INIS)

    Reilly, M.H.; Rhoads, F.J.; Goodman, J.M.; Singh, M.

    1991-01-01

    The prediction performances of several climatological models, including the ionospheric conductivity and electron density model, RADAR C, and Ionospheric Communications Analysis and Predictions Program, are evaluated for different regions and sunspot number inputs. Particular attention is given to the near-real-time (NRT) predictions associated with single-station updates. It is shown that a dramatic improvement can be obtained by using single-station ionospheric data to update the driving parameters for an ionospheric model for NRT predictions of f(0)F2 and other ionospheric and HF circuit parameters. For middle latitudes, the improvement extends out thousands of kilometers from the update point to points of comparable corrected geomagnetic latitude. 10 refs

  17. A Study on the Radio Propagation in the Korean Ionosphere

    Directory of Open Access Journals (Sweden)

    Seok-Hee Bae

    1992-06-01

    Full Text Available The effects of the ionosphere on the radio wave propagation are scattering of radio waves, attenuation, angle error, ranging error, and time delay. If ionospheric conditions are suitable, the charged particles can remove energy from radio waves and thus attenuate the signal. Also, a radio wave traveling a path along which the electron density is not constant undergoes changes in direction, position and time of propagation. The present study is based on Korean ionospheric data obtained at the AnYong Radio Research Institute from Jan. 1985 through Oct. 1989. The data are used to simulate the Korean ionosphere following the Chapman law. The effects of the model ionosphere on the radio wave propagation, such as the angle, position error, time delay, and the attenuation, are studies for the various cases of the wave frequency and the altitude.

  18. Evaluation of Inversion Methods Applied to Ionospheric ro Observations

    Science.gov (United States)

    Rios Caceres, Arq. Estela Alejandra; Rios, Victor Hugo; Guyot, Elia

    The new technique of radio-occultation can be used to study the Earth's ionosphere. The retrieval processes of ionospheric profiling from radio occultation observations usually assume spherical symmetry of electron density distribution at the locality of occultation and use the Abel integral transform to invert the measured total electron content (TEC) values. This pa-per presents a set of ionospheric profiles obtained from SAC-C satellite with the Abel inversion technique. The effects of the ionosphere on the GPS signal during occultation, such as bending and scintillation, are examined. Electron density profiles are obtained using the Abel inversion technique. Ionospheric radio occultations are validated using vertical profiles of electron con-centration from inverted ionograms , obtained from ionosonde sounding in the vicinity of the occultation. Results indicate that the Abel transform works well in the mid-latitudes during the daytime, but is less accurate during the night-time.

  19. Crustal and upper mantle velocity structure of the Salton Trough, southeast California

    Science.gov (United States)

    Parsons, T.; McCarthy, J.

    1996-01-01

    This paper presents data and modelling results from a crustal and upper mantle wide-angle seismic transect across the Salton Trough region in southeast California. The Salton Trough is a unique part of the Basin and Range province where mid-ocean ridge/transform spreading in the Gulf of California has evolved northward into the continent. In 1992, the U.S. Geological Survey (USGS) conducted the final leg of the Pacific to Arizona Crustal Experiment (PACE). Two perpendicular models of the crust and upper mantle were fit to wide-angle reflection and refraction travel times, seismic amplitudes, and Bouguer gravity anomalies. The first profile crossed the Salton Trough from the southwest to the northeast, and the second was a strike line that paralleled the Salton Sea along its western edge. We found thin crust (???21-22 km thick) beneath the axis of the Salton Trough (Imperial Valley) and locally thicker crust (???27 km) beneath the Chocolate Mountains to the northeast. We modelled a slight thinning of the crust further to the northeast beneath the Colorado River (???24 km) and subsequent thickening beneath the metamorphic core complex belt northeast of the Colorado River. There is a deep, apparently young basin (???5-6 km unmetamorphosed sediments) beneath the Imperial Valley and a shallower (???2-3 km) basin beneath the Colorado River. A regional 6.9-km/s layer (between ???15-km depth and the Moho) underlies the Salton Trough as well as the Chocolate Mountains where it pinches out at the Moho. This lower crustal layer is spatially associated with a low-velocity (7.6-7.7 km/s) upper mantle. We found that our crustal model is locally compatible with the previously suggested notion that the crust of the Salton Trough has formed almost entirely from magmatism in the lower crust and sedimentation in the upper crust. However, we observe an apparently magmatically emplaced lower crust to the northeast, outside of the Salton Trough, and propose that this layer in part

  20. Modeling ionospheric foF2 by using empirical orthogonal function analysis

    Directory of Open Access Journals (Sweden)

    E. A

    2011-08-01

    Full Text Available A similar-parameters interpolation method and an empirical orthogonal function analysis are used to construct empirical models for the ionospheric foF2 by using the observational data from three ground-based ionosonde stations in Japan which are Wakkanai (Geographic 45.4° N, 141.7° E, Kokubunji (Geographic 35.7° N, 140.1° E and Yamagawa (Geographic 31.2° N, 130.6° E during the years of 1971–1987. The impact of different drivers towards ionospheric foF2 can be well indicated by choosing appropriate proxies. It is shown that the missing data of original foF2 can be optimal refilled using similar-parameters method. The characteristics of base functions and associated coefficients of EOF model are analyzed. The diurnal variation of base functions can reflect the essential nature of ionospheric foF2 while the coefficients represent the long-term alteration tendency. The 1st order EOF coefficient A1 can reflect the feature of the components with solar cycle variation. A1 also contains an evident semi-annual variation component as well as a relatively weak annual fluctuation component. Both of which are not so obvious as the solar cycle variation. The 2nd order coefficient A2 contains mainly annual variation components. The 3rd order coefficient A3 and 4th order coefficient A4 contain both annual and semi-annual variation components. The seasonal variation, solar rotation oscillation and the small-scale irregularities are also included in the 4th order coefficient A4. The amplitude range and developing tendency of all these coefficients depend on the level of solar activity and geomagnetic activity. The reliability and validity of EOF model are verified by comparison with observational data and with International Reference Ionosphere (IRI. The agreement between observations and EOF model is quite well, indicating that the EOF model can reflect the major changes and the temporal distribution characteristics of the mid-latitude ionosphere of the

  1. The atmosphere and ionosphere of Io

    International Nuclear Information System (INIS)

    McElroy, M.B.; Yung, Y.L.

    1975-01-01

    A variety of models for Io's atmosphere, ionosphere, surface, and environment are developed and discussed in the context of recent observational data. The sodium emission detected by Brown appears to require a collisional excitation process in Io's atmosphere, and the extended sodium emission measured by Trafton et al. may require scattering of the planetary radiation by an extended sodium cloud. The sodium is presumably present initially in bound form on Io's surface and may be released by the sputtering mechanism suggested by Matson et al. The ionosphere detected by the radio occultation experiment on Pioneer 10 could be attributed to photoionization of atmospheric sodium if Io's atmosphere could sustain significant vertical motions, of order 1 s/sup -1/ directed up during the day, down at night. Vertical motions of this magnitude could be driven by condensation of atmospheric NH 3 . The total density of gas at Io's surface appears to lie in the range 10 10 -10 12 molecules cm/sup -3/. Corpuscular ionization could play an additional role for the ionosphere. In this case the sateSe should exhibit an exceedingly bright, approx.10 kR, airglow at Lα. The incomplete hydrogen torus observed by Judge and Carlson in the vicinity of Io requires a large supply of hydrogen from the satellite's atmosphere. The escape flux should be of order 10 11 cm/sup -2/ s/sup -1/ and could be maintained by photolysis of atmospheric NH 3 . The observed geometry of the hydrogen torus appears to require a surprisingly short lifetime, approx.10 5 s, for neutral hydrogen near Io's orbit, and may indicate the presence of a large flux, approx.10 9 cm/sup -2/ s/sup -1/, of low-energy protons in Jupiter's magnetosphere. Implications of the hydrogen torus for the energy and mass balance of Jupiter's magnetosphere are discussed briefly, and observational programs are identified which might illuminate present uncertainties in our understanding of Io

  2. Comparative analyses of the bacterial community of hydrothermal deposits and seafloor sediments across Okinawa Trough

    Science.gov (United States)

    Wang, Long; Yu, Min; Liu, Yan; Liu, Jiwen; Wu, Yonghua; Li, Li; Liu, Jihua; Wang, Min; Zhang, Xiao-Hua

    2018-04-01

    As an ideal place to study back-arc basins and hydrothermal eco-system, Okinawa Trough has attracted the interests of scientists for decades. However, there are still no in-depth studies targeting the bacterial community of the seafloor sediments and hydrothermal deposits in Okinawa Trough. In the present study, we reported the bacterial community of the surface deposits of a newly found hydrothermal field in the southern Okinawa Trough, and the horizontal and vertical variation of bacterial communities in the sediments of the northern Okinawa Trough. The hydrothermal deposits had a relatively high 16S rRNA gene abundance but low bacterial richness and diversity. Epsilonproteobacteria and Bacteroidetes were predominant in hydrothermal deposits whereas Deltaproteobacteria, Gammaproteobacteria and Chloroflexi were abundant across all samples. The bacterial distribution in the seafloor of Okinawa Trough was significantly correlated to the content of total nitrogen, and had consistent relationship with total carbon. Gradual changes of sulfur-oxidizing bacteria were found with the distance away from hydrothermal fields, while the hydrothermal activity did not influence the distribution of the major clades of sulfate-reducing bacteria. Higher abundance of the sulfur cycle related genes (aprA and dsrB), and lower abundance of the bacterial ammonia-oxidizing related gene (amoA) were quantified in hydrothermal deposits. In addition, the present study also compared the inter-field variation of Epsilonproteobacteria among multi-types of hydrothermal vents, revealing that the proportion and diversity of this clade were quite various.

  3. Equatorial Ionospheric Irregularities Study from ROCSAT Data

    Science.gov (United States)

    2017-10-20

    UNLIMITED: PB Public Release 13. SUPPLEMENTARY NOTES 14. ABSTRACT Ionospheric irregularity/scintillation occurrences can be caused by external driving ...Academia Sinica, Taipei, Taiwan e-mail: chliu2@gate.sinica.edu.tw phone :886-3-4227151x34757 CoPI: Shin-Yi Su Institution: National Central...University, Chung-Li, Taiwan e-mail: sysu@csrsr.ncu.edu.tw phone :886-3-4227151x57643 CoPI: Lung-Chi Tsai Institution: National Central University, Chung-Li

  4. Troposphere - ionosphere interaction during tropospheric MCC events

    International Nuclear Information System (INIS)

    Manzano, J.R.; Zossi Artigas, M.M. de; Filippi Manzano, A.N. de; Cosio Ragone, A.H. de

    1995-09-01

    The present paper describes the investigation of possible effects of the type of large meteorological events known as Mesoscale Convective Complexes (MCC) on the F-region of the ionosphere over Argentina. These warm-season weather systems of huge size are present in the United States (Maddox, 1980) and in South Americal (Velasco and Fritsch, 1987). Their extension can be as large as 1,300,000 Km 2 and they tend to move in different directions over the earth surface. It is expected that these meteorological events should leave its signature in the upper region of the atmosphere. 13 refs, 12 figs, 1 tab

  5. The International Reference Ionosphere: Model Update 2016

    Science.gov (United States)

    Bilitza, Dieter; Altadill, David; Reinisch, Bodo; Galkin, Ivan; Shubin, Valentin; Truhlik, Vladimir

    2016-04-01

    The International Reference Ionosphere (IRI) is recognized as the official standard for the ionosphere (COSPAR, URSI, ISO) and is widely used for a multitude of different applications as evidenced by the many papers in science and engineering journals that acknowledge the use of IRI (e.g., about 11% of all Radio Science papers each year). One of the shortcomings of the model has been the dependence of the F2 peak height modeling on the propagation factor M(3000)F2. With the 2016 version of IRI, two new models will be introduced for hmF2 that were developed directly based on hmF2 measurements by ionosondes [Altadill et al., 2013] and by COSMIC radio occultation [Shubin, 2015], respectively. In addition IRI-2016 will include an improved representation of the ionosphere during the very low solar activities that were reached during the last solar minimum in 2008/2009. This presentation will review these and other improvements that are being implemented with the 2016 version of the IRI model. We will also discuss recent IRI workshops and their findings and results. One of the most exciting new projects is the development of the Real-Time IRI [Galkin et al., 2012]. We will discuss the current status and plans for the future. Altadill, D., S. Magdaleno, J.M. Torta, E. Blanch (2013), Global empirical models of the density peak height and of the equivalent scale height for quiet conditions, Advances in Space Research 52, 1756-1769, doi:10.1016/j.asr.2012.11.018. Galkin, I.A., B.W. Reinisch, X. Huang, and D. Bilitza (2012), Assimilation of GIRO Data into a Real-Time IRI, Radio Science, 47, RS0L07, doi:10.1029/2011RS004952. Shubin V.N. (2015), Global median model of the F2-layer peak height based on ionospheric radio-occultation and ground-based Digisonde observations, Advances in Space Research 56, 916-928, doi:10.1016/j.asr.2015.05.029.

  6. Study of Ionospheric Indexes T and MF2 related to R12 for Solar Cycles 19-21

    Science.gov (United States)

    Villanueva, Lucia

    2013-04-01

    Modern worldwide communications are mainly based on satellite systems, remote communication networks, and advanced technologies. The most important space weather "meteorological" events produce negative effects on signal transmissions. Magnetic storm conditions that follow coronal mass ejections are particularly of great importance for radio communication at HF frequencies (3-30 MHz range), because the Ionization increase (or decrease), significantly over (or below), the Average Values. Nowadays new technologies make possible to establish Geophysical Observatories and monitor the sun almost in real time giving information about geomagnetic indices. Space Weather programs have interesting software predictions of foF2 producing maps and plots, every some minutes. The Average Values of the ionospheric parameters mainly depend on the position, hour, season and the phase of the 11-year cycle of the solar activity. Around 1990´s several ionospheric indexes were suggested to better predict the state of the foF2 monthly media, as: IF2, G, T and MF2, based on foF2 data from different latitude ionospheric observatories. They really show better seasonal changes than monthly solar indexes of solar flux F10.7 or the international sunspot numbers Ri. The main purpose of this paper is to present an analogic model for the ionospheric index MF2, to establish the average long term predictions of this index. Changes of phase from one cycle to the other of one component of the model is found to fit the data. The usefulness of this model could be the prediction of the ionospheric normal conditions for one entire solar cycle having just the prediction of the maximum of the next smooth sunspot number R12. In this presentation, comparisons of the Australian T index and and the Mikhailov MF2 index show an hysteresis variation with the solar monthly index Ri, such dependence is quite well represented by a polynomial fit of degree 6 for rising and decaying fases for solar cycles 19, 20 and

  7. St. Patrick's Day 2015 geomagnetic storm analysis based on Real Time Ionosphere Monitoring

    Science.gov (United States)

    García-Rigo, Alberto

    2017-04-01

    Ionosphere Monitoring (RTIM) is a new Working Group within the International Association of Geodesy (IAG) Sub-Commission 4.3 "Atmosphere Remote Sensing". The complementary expertise of the participating research groups allows to analyse the ionospheric behaviour from a broad perspective, taking benefit of comparing multiple independent real time and near real time ionospheric approaches. In this context, a detailed analysis will be presented for the days in March, 2015 surrounding St. Patrick's Day 2015 geomagnetic storm, based on the existing ionospheric models (global or regional) within the group, which are mainly based on Global Navigation Satellite Systems (GNSS) and ionosonde data. For this purpose, a variety of ionospheric parameters will be considered, including Total Electron Content (TEC), F2 layer critical frequency (foF2), F2 layer peak (hmF2), bottomside half-thickness (B0) and ionospheric disturbance W-index. Also, ionospheric high-frequency perturbations such as Travelling Ionospheric Disturbances (TIDs), scintillations and the impact of solar flares facing the Earth will be presented to derive a clear picture of the ionospheric dynamics. Among other sources of information to take part in the comparisons, there will be (1) scintillation results -from MONITOR ESA/ESTEC-funded project- derived by means of S4 index and Sigma Phi (IEEA), specially significant in the African sector and European high latitudes, (2) dynamics of the global maps of W-index with 1h resolution derived from JPL Global Ionospheric Maps (GIMs; IZMIRAN), (3) deviations from expected quiet-time behavior analysed in terms of foF2, hmF2, B0 and B1 based on IRTAM and GIRO network of digisondes (Lowell), showing F2 layer peculiar changes due to the storm, (4) statistics based on the median of the VTEC for the 15 previous days considering VTEC european regional maps (ROB), (5) time series of VTEC data that are derived by running the NRT ionosphere model of DGFI-TUM in offline mode, which show

  8. Structural control of the Gagua "Wedge" Zone east of Taiwan Island on the southern Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    ZHENG; Yanpeng; LIU; Baohua; WU; Jinlong; LIANG; Ruicai; L

    2005-01-01

    Based on compositive analysis and interpretation of the observed and historical data, the geophysical field characters and structural properties of the Gagua "Wedge" Zone of the sea area east of Taiwan Island and the primary tectonic stress direction and its variabilities of backarc spreading in the southern Okinawa Trough are studied. It is concluded from the study results that the Gagua "Wedge" Zone is structurally consistent with the Gagua ridge and two fault basins on both sides of the Gagua ridge, and adjusts the moving direction and distance of the western Philippine Sea plate to make the northwestward motion of the plate on its east side change to the northward subduction of the plate on its west side so that the primary tectonic stress direction of the Okinawa Trough changed from NW-SE to nearly N-S, which provided the stress source for the Okinawa Trough to enter the second spreading stage.

  9. Evidence and mechanism of Hurricane Fran-Induced ocean cooling in the Charleston Trough

    Science.gov (United States)

    Xie, Lian; Pietrafesa, L. J.; Bohm, E.; Zhang, C.; Li, X.

    Evidence of enhanced sea surface cooling during and following the passage of Hurricane Fran in September 1996 over an oceanic depression located on the ocean margin offshore of Charleston, South Carolina (referred to as the Charleston Trough), [Pietrafesa, 1983] is documented. Approximately 4C° of sea surface temperature (SST) reduction within the Charleston Trough following the passage of Hurricane Fran was estimated based on SST imagery from Advanced Very High Resolution Radiometer (AVHRR) on the NOAA-14 polar orbiting satellite. Simulations using a three-dimensional coastal ocean model indicate that the largest SST reduction occurred within the Charleston Trough. This SST reduction can be explained by oceanic mixing due to storm-induced internal inertia-gravity waves.

  10. Balancing vancomycin efficacy and nephrotoxicity: should we be aiming for trough or AUC/MIC?

    Science.gov (United States)

    Patel, Karisma; Crumby, Ashley S; Maples, Holly D

    2015-04-01

    Sixty years later, the question that still remains is how to appropriately utilize vancomycin in the pediatric population. The Infectious Diseases Society of America published guidelines in 2011 that provide guidance for dosing and monitoring of vancomycin in adults and pediatrics. However, goal vancomycin trough concentrations of 15-20 μg/mL for invasive infections caused by methicillin-resistant Staphylococcus aureus were based primarily on adult pharmacokinetic and pharmacodynamic data that achieved an area under the curve to minimum inhibitory concentration ratio (AUC/MIC) of ≥400. Recent pediatric literature shows that vancomycin trough concentrations needed to achieve the target AUC/MIC are different than the adult goal troughs cited in the guidelines. This paper addresses several thoughts, including the role of vancomycin AUC/MIC in dosing strategies and safety monitoring, consistency in laboratory reporting, and future directions for calculating AUC/MIC in pediatrics.

  11. Alfven waves in the auroral ionosphere: A numerical model compared with measurements

    International Nuclear Information System (INIS)

    Knudsen, D.J.; Kelley, M.C.; Vickrey, J.F.

    1992-01-01

    The authors solve a linear numerical model of Alfven waves reflecting from the high-latitude ionosphere, both to better understanding the role of the ionosphere in the magnetosphere/ionosphere coupling process and to compare model results with in situ measurements. They use the model to compute the frequency-dependent amplitude and phase relations between the meridional electric and the zonal magnetic fields due to Alfven waves. These relations are compared with measurements taken by an auroral sounding rocket flow in the morningside oval and by the HILAT satellite traversing the oval at local noon. The sounding rocket's trajectory was mostly parallel to the auroral oval, and is measured enhanced fluctuating field energy in regions of electron precipitation. The rocket-measured phase data are in excellent agreement with the Alfven wave model, and the relation between the modeled and the measured by HILAT are related by the height-integrated Pedersen conductivity Σ p , indicating that the measured field fluctuations were due mainly to structured field-aligned current systems. A reason for the relative lack of Alfven wave energy in the HILAT measurements could be the fact that the satellite traveled mostly perpendicular to the oval and therefore quickly traversed narrow regions of electron precipitation and associated wave activity

  12. Cosmic noise absorption and ionospheric currents at the South Pole and Frobisher Bay: Initial results

    International Nuclear Information System (INIS)

    Rosenberg, T.J.; Wolfe, A.; Lanzerotti, L.J.

    1987-01-01

    Studies of the conjugacy of auroral and ionospheric phenomena at very high latitudes are an important aspect of magnetospheric physics research. The extent to which auroral phenomena in opposite hemispheres are similar in occurrence and in the details of their temporal, spatial, and spectral characteristics can be used to infer the commonality of the source(s) of the disturbances. At one extreme in this consideration is the questions of whether sources lie on open or closed magnetic field lines. The University of Maryland and AT ampersand T Bell Laboratories have operated riometers and fluxgate magnetometers, respectively, at South Pole since 1982. Corresponding measurements at Frobisher Bay were begun in mid-1985. Riometers record the absorption of cosmic radio noise in the ionosphere produced by the enhances precipitation of energetic charged particles. The studies of the riometer data relate mainly to the effects of the influx of magnetospheric electrons, which give rise to auroral absorption of the cosmic signals. Intense currents (electrojets) that often flow in the ionosphere in association with auroral absorption events produce magnetic field changes that can be recorded on the ground by appropriately sited magnetometers. This report presents some initial results of the comparison of the two data sets

  13. Ionospheric effects of rocket exhaust products (HEAO-C, Skylab and SPS-HLLV)

    International Nuclear Information System (INIS)

    Zinn, J.; Sutherland, D.; Stone, S.N.; Duncan, L.M.; Behnke, R.

    1980-10-01

    This paper reviews the current state of our understanding of the problem of ionospheric F-layer depletions produced by chemical effects of the exhaust gases from large rockets, with particular emphasis on the Heavy Lift Launch Vehicles (HLLV) proposed for use in the construction of solar power satellites. The currently planned HLLV flight profile calls for main second-stage propulsion confined to altitudes below 124 km, and a brief orbit-circularization maneuver at apogee. The second-stage engines deposit 9 x 10 31 H 2 O and H 2 molecules between 56 and 124 km. Model computations show that they diffuse gradually into the ionospheric F region, where they lead to weak but widespread and persistent depletions of ionization and continuous production of H atoms. The orbit-circularization burn deposits 9 x 10 29 exhaust molecules at about 480-km altitude. These react rapidly with the F2 region 0 + ions, leading to a substantial (factor-of-three) reduction in plasma density, which extends over a 1000- by 2000-km region and persists for four to five hours. Also described are experimental airglow and incoherent-scatter radar measurements performed in conjunction with the 1979 launch of satellite HEAO-C, together with prelaunch and post-launch computations of the ionospheric effects. Several improvements in the model have been driven by the experimental observations. The computer model is described in some detail

  14. Magnetosphere-ionosphere coupling during periods of extended high auroral activity: a case study

    Directory of Open Access Journals (Sweden)

    S. Liléo

    2008-03-01

    Full Text Available Results are presented from a case study of a plasma boundary crossing by the Cluster spacecraft during an extended period of high auroral activity. The boundary between the magnetotail lobe region of the Southern Hemisphere and the plasma sheet boundary layer, was characterized by intense electric and magnetic field variations, structured upward accelerated ion beams, narrow-scale large field-aligned Poynting fluxes directed upward away from the ionosphere, and a relatively sharp plasma density gradient.

    The observations are shown to be consistent with the concept of a multi-layered boundary with temporal and/or spatial variations in the different layers. H+ and O+ ion beams are seen to be accelerated upwards both by means of a field-aligned electric field and by magnetic pumping caused by large-amplitude and low-frequency electric field fluctuations. The peak energy of the ion beams may here be used as a diagnostic tool for the temporal evolution of the spatial structures, since the temporal changes occur on a time-scale shorter than the times-of-flight of the detected ion species.

    The case study also shows the boundary region to be mainly characterized by a coupling of the detected potential structures to the low ionosphere during the extended period of high auroral activity, as indicated by the intense field-aligned Poynting fluxes directed upward away from the ionosphere.

  15. Magnetosphere-ionosphere coupling during periods of extended high auroral activity: a case study

    Directory of Open Access Journals (Sweden)

    S. Liléo

    2008-03-01

    Full Text Available Results are presented from a case study of a plasma boundary crossing by the Cluster spacecraft during an extended period of high auroral activity. The boundary between the magnetotail lobe region of the Southern Hemisphere and the plasma sheet boundary layer, was characterized by intense electric and magnetic field variations, structured upward accelerated ion beams, narrow-scale large field-aligned Poynting fluxes directed upward away from the ionosphere, and a relatively sharp plasma density gradient. The observations are shown to be consistent with the concept of a multi-layered boundary with temporal and/or spatial variations in the different layers. H+ and O+ ion beams are seen to be accelerated upwards both by means of a field-aligned electric field and by magnetic pumping caused by large-amplitude and low-frequency electric field fluctuations. The peak energy of the ion beams may here be used as a diagnostic tool for the temporal evolution of the spatial structures, since the temporal changes occur on a time-scale shorter than the times-of-flight of the detected ion species. The case study also shows the boundary region to be mainly characterized by a coupling of the detected potential structures to the low ionosphere during the extended period of high auroral activity, as indicated by the intense field-aligned Poynting fluxes directed upward away from the ionosphere.

  16. Ionization balance in Titan's nightside ionosphere

    Science.gov (United States)

    Vigren, E.; Galand, M.; Yelle, R. V.; Wellbrock, A.; Coates, A. J.; Snowden, D.; Cui, J.; Lavvas, P.; Edberg, N. J. T.; Shebanits, O.; Wahlund, J.-E.; Vuitton, V.; Mandt, K.

    2015-03-01

    Based on a multi-instrumental Cassini dataset we make model versus observation comparisons of plasma number densities, nP = (nenI)1/2 (ne and nI being the electron number density and total positive ion number density, respectively) and short-lived ion number densities (N+, CH2+, CH3+, CH4+) in the southern hemisphere of Titan's nightside ionosphere over altitudes ranging from 1100 and 1200 km and from 1100 to 1350 km, respectively. The nP model assumes photochemical equilibrium, ion-electron pair production driven by magnetospheric electron precipitation and dissociative recombination as the principal plasma neutralization process. The model to derive short-lived-ion number densities assumes photochemical equilibrium for the short-lived ions, primary ion production by electron-impact ionization of N2 and CH4 and removal of the short-lived ions through reactions with CH4. It is shown that the models reasonably reproduce the observations, both with regards to nP and the number densities of the short-lived ions. This is contrasted by the difficulties in accurately reproducing ion and electron number densities in Titan's sunlit ionosphere.

  17. Ionospheric hot spot at high latitudes

    International Nuclear Information System (INIS)

    Schunk, R.W.; Sojka, J.J.

    1982-01-01

    A hot spot (or spots) can occur in the high-latitude ionosphere depending on the plasma convection pattern. The hot spot corresponds to a small magnetic local time-magnetic latitude region of elevated ion temperatures located near the dusk and/or dawn meridians. For asymmetric convection electric field patterns, with enhanced flow in either the dusk or dawn sector of the polar cap, a single hot spot should occur in association with the strong convection cell. However, on geomagnetically disturbed days, two strong convection cells can occur, and hence, two hot spots should exist. The hot spot should be detectable when the electric field in the strong convection cell exceeds about 40 mV m -1 . For electric fields of the order of 100 mV m -1 in the convection cell, the ion temperature in the hot spot is greatest at low altitudes, reaching 4000 0 K at 160 km, and decreases with altitude in the F-region. An ionospheric hot spot (or spots) can be expected at all seasons and for a wide range of solar cycle conditions

  18. The Effect of Ionospheric Variability on the Accuracy of High Frequency Position Location

    Science.gov (United States)

    1981-08-01

    these problems are not the major ones in radio source location 1H. Rishbeth and 0. K. Garriot, 1969, Introduction to Ionospheric Physics, Academic Press ...ionospheric distur- banca ; and (4) employ an integrated network of ionosondes. The firt option recognizes the basic constraints of the available ionospheric...Rishbeth, H., and 0. K. Garriot, 1969, Introduction to Ionospheric Physics, Academic Press , NY. 2. Georges, T. M., 1967, Ionospheric Effects of

  19. Long-term trends in the ionospheric E and F1 regions

    Directory of Open Access Journals (Sweden)

    J. Bremer

    2008-05-01

    Full Text Available Ground based ionosonde measurements are the most essential source of information about long-term variations in the ionospheric E and F1 regions. Data of such observations have been derived at many different ionospheric stations all over the world some for more than 50 years. The standard parameters foE, h'E, and foF1 are used for trend analyses in this paper. Two main problems have to be considered in these analyses. Firstly, the data series have to be homogeneous, i.e. the observations should not be disturbed by artificial steps due to technical reasons or changes in the evaluation algorithm. Secondly, the strong solar and geomagnetic influences upon the ionospheric data have carefully to be removed by an appropriate regression analysis. Otherwise the small trends in the different ionospheric parameters cannot be detected.

    The trends derived at individual stations differ markedly, however their dependence on geographic or geomagnetic latitude is only small. Nevertheless, the mean global trends estimated from the trends at the different stations show some general behaviour (positive trends in foE and foF1, negative trend in h'E which can at least qualitatively be explained by an increasing atmospheric greenhouse effect (increase of CO2 content and other greenhouse gases and decreasing ozone values. The positive foE trend is also in qualitative agreement with rocket mass spectrometer observations of ion densities in the E region. First indications could be found that the changing ozone trend at mid-latitudes (before about 1979, between 1979 until 1995, and after about 1995 modifies the estimated mean foE trend.

  20. Chemistry of the galactic cosmic ray induced ionosphere of Titan

    Science.gov (United States)

    Molina-Cuberos, G. J.; López-Moreno, J. J.; Rodrigo, R.; Lara, L. M.

    1999-09-01

    Titan's lower ionosphere (from 1 to 400 km) has been studied with a one-dimensional ion-neutral model. In this region of the atmosphere, galactic cosmic rays (GCRs) are the main ionization source. They penetrate to the deeper atmosphere and ionize the neutral constituents of Titan's atmosphere (mainly N2, CH4, Ar, H2, and CO) to produce N2+, N+, Ar+, CH4+, CH3+, CH2+, H2+, H+, and CO+. Fast reactions with the neutrals convert these ions into ions such as CH5+, C2H5+, and N2H+. Different pathways are proposed to obtain the ion and electron densities. The most abundant ions are cluster ions, like CH5+.CH4, HCO+.H2, and HCNH+.C2H4, and long chain hydrocarbon ions. In atmospheres very rich in N2, such as Titan's, ions like H4C7N+ and CH3CNH+ also represent an important contribution to the total positive ion density. Three-body reactions may play an important role in the dense atmosphere of Titan, and special attention is devoted to them. The calculated electron density in the lower atmosphere reaches a peak of ~2150 cm-3 at an altitude of 90 km.

  1. Development of the Plate Boundary Observatory GPS Low Latency Salton Trough Radio Network

    Science.gov (United States)

    Walls, C.; Miller, S.; Wilson, B.; Lawrence, S.; Arnitz, E.

    2008-05-01

    UNAVCO is developing a 20 GPS station low latency radio network that spans the San Andreas and San Jacinto faults in the region of highest strain in southern California and the narrowest part of the North America-Pacific plate boundary. The Salton Trough Radio Network (STRN) is instrumented with Ethernet bridge Intuicom EB6+ (900 MHz) radios to transmit a high rate low latency data stream from each permanent GPS site for the purpose of the following: 1) telemeter 15 second data (1 MB/day/station) to the Plate Boundary Observatory archive, 2) accommodate the timely download of 1 and 5 sample per second data following large earthquakes (4 MB/hour/station), and 3) test the UStream of 1Hz BINEX and RTCM data. Three of four phases have been completed. Office radio testing yielded transfer rates of 30-50 KB/s with subsecond latency while streaming 1 Hz data. Latency climbed to ~1.8 seconds while simultaneously streaming 1 Hz and downloading hourly 1 and 5 sample per second data files. Field testing demonstrated rates on the order of 30 KB/s. At present the radios are installed and have transfer rates of 10-40 KB/s between sites that span 10-32 km. The final phase will be the installation of the main telemetry relay where master radios will be connected to a high speed ISP near the town of Brawley. The high-rate low latency UStream data will be available to researchers who are developing prototype earthquake early warning systems in Southern California. A goal of the STRN is to make the data available rapidly enough for GPS-derived coseismic and dynamic displacements to be integrated into early warning system earthquake models. The improved earthquake models will better assist emergency response. UStream data will also aid surveyors who wish to use PBO GPS stations as permanent, high-quality base stations in real-time kinematic surveys.

  2. Micrinite maceral evidence of hydrocarbon generation in cretaceous coal measures of the middle Benue trough, Nigeria

    International Nuclear Information System (INIS)

    Obaje, N. G.; Ukpabio, E. J.; Funtua, I. I.

    1999-01-01

    Maceral analysis on samples from the coal and coal-bearing strata of the Awgu Formation in the Middle Benue Trough of Nigeria allows the subdivision of the coal beds and inter seam sediments into three different petrographic/coal facies, namely: a vitrinite-fusinite coal facies which is rich in vitrinite, poor in liptinite, with variable amounts of inertinite and low mineral matter content; a trimaceritic coal facies which is rich in vitrinite, liptinite and inertinite with low mineral matter content; and a shaley coal facies which, expectedly, is dominated by mineral matter and has variable amounts of vitrinite, liptinite and inertinite. Micrinite macerals constitute 8.2% and 4.5 on mineral matter-counted basis in samples from the trimaceritic and shaley coal facies respectively. These amounts, in both cases, are considered to be very high. They occur as finely particulate, rounded grains approximately I um in diameter. Most of the micrinite are closely associated with highly reflecting, almost unrecognizable liptinite. The nature and origin of micrinite and its significance to oil and gas generation have been studied extensively. As secondary macerals, they are generally believed to be relics of oil generation from oil-prone macerals, mainly liptinitic and vitrinitic macerals with which they are closely associated. Reflectance measurements on the associated vitrinite macerals indicate a thermal maturity range of 0.74 - 1.25 % Rm. This range corresponds to the zone of oil generation in most minerogenic oil source rocks. In the study area, however, only the trimaceritic coal facies and some parts of the shaley coal facies that are rich in liptinite alongside the associated micrinite macerals are considered to have generated oil. The vitrinite-fusinite coal facies with its high content of humic organic matter (vitrinite + Inertinite) can only generate gas (wet + dry) within the given thermal maturity range

  3. Sensor for Measuring Hydrogen Partial Pressure in Parabolic Trough Power Plant Expansion Tanks

    Energy Technology Data Exchange (ETDEWEB)

    Glatzmaier, Greg C.; Cooney, Daniel A.

    2017-06-27

    The National Renewable Energy Laboratory and Acciona Energy North America are working together to design and implement a process system that provides a permanent solution to the issue of hydrogen buildup at parabolic trough power plants. We are pursuing a method that selectively removes hydrogen from the expansion tanks that serve as reservoirs for the heat transfer fluid (HTF) that circulates in the collector field and power block components. Our modeling shows that removing hydrogen from the expansion tanks at a design rate reduces and maintains dissolved hydrogen in the circulating HTF to a selected target level. Our collaborative work consists of several tasks that are needed to advance this process concept to a development stage, where it is ready for implementation at a commercial power plant. Our main effort is to design and evaluate likely process-unit operations that remove hydrogen from the expansion tanks at a specified rate. Additionally, we designed and demonstrated a method and instrumentation to measure hydrogen partial pressure and concentration in the expansion-tank headspace gas. We measured hydrogen partial pressure in the headspace gas mixture using a palladium-alloy membrane, which is permeable exclusively to hydrogen. The membrane establishes a pure hydrogen gas phase that is in equilibrium with the hydrogen in the gas mixture. We designed and fabricated instrumentation, and demonstrated its effectiveness in measuring hydrogen partial pressures over a range of three orders of magnitude. Our goal is to install this instrument at the Nevada Solar One power plant and to demonstrate its effectiveness in measuring hydrogen levels in the expansion tanks under normal plant operating conditions.

  4. Influence of Ionospheric Irregularities on GNSS Remote Sensing

    Directory of Open Access Journals (Sweden)

    M. V. Tinin

    2015-01-01

    Full Text Available We have used numerical simulation to study the effects of ionospheric irregularities on accuracy of global navigation satellite system (GNSS measurements, using ionosphere-free (in atmospheric research and geometry-free (in ionospheric research dual-frequency phase combinations. It is known that elimination of these effects from multifrequency GNSS measurements is handi-capped by diffraction effects during signal propagation through turbulent ionospheric plasma with the inner scale being smaller than the Fresnel radius. We demonstrated the possibility of reducing the residual ionospheric error in dual-frequency GNSS remote sensing in ionosphere-free combination by Fresnel inversion. The inversion parameter, the distance to the virtual screen, may be selected from the minimum of amplitude fluctuations. This suggests the possibility of improving the accuracy of GNSS remote sensing in meteorology. In the study of ionospheric disturbances with the aid of geometry-free combination, the Fresnel inversion eliminates only the third-order error. To eliminate the random TEC component which, like the measured average TEC, is the first-order correction, we should use temporal filtering (averaging.

  5. Performance Analysis of Different NeQuick Ionospheric Model Parameters

    Directory of Open Access Journals (Sweden)

    WANG Ningbo

    2017-04-01

    Full Text Available Galileo adopts NeQuick model for single-frequency ionospheric delay corrections. For the standard operation of Galileo, NeQuick model is driven by the effective ionization level parameter Az instead of the solar activity level index, and the three broadcast ionospheric coefficients are determined by a second-polynomial through fitting the Az values estimated from globally distributed Galileo Sensor Stations (GSS. In this study, the processing strategies for the estimation of NeQuick ionospheric coefficients are discussed and the characteristics of the NeQuick coefficients are also analyzed. The accuracy of Global Position System (GPS broadcast Klobuchar, original NeQuick2 and fitted NeQuickC as well as Galileo broadcast NeQuickG models is evaluated over the continental and oceanic regions, respectively, in comparison with the ionospheric total electron content (TEC provided by global ionospheric maps (GIM, GPS test stations and JASON-2 altimeter. The results show that NeQuickG can mitigate ionospheric delay by 54.2%~65.8% on a global scale, and NeQuickC can correct for 71.1%~74.2% of the ionospheric delay. NeQuick2 performs at the same level with NeQuickG, which is a bit better than that of GPS broadcast Klobuchar model.

  6. Tracking local control of a parabolic trough collector; Control local de seguimiento cilindro parabolico ACE20

    Energy Technology Data Exchange (ETDEWEB)

    Ajona, J I; Alberdi, J; Gamero, E; Blanco, J

    1992-07-01

    In the local control, the sun position related to the trough collector is measured by two photo-resistors. The provided electronic signal is then compared with reference levels in order to get a set of B logical signals which form a byte. This byte and the commands issued by a programmable controller are connected to the inputs of o P.R.O.M. memory which is programmed with the logical equations of the control system. The memory output lines give the control command of the parabolic trough collector motor. (Author)

  7. Tracking local control of a parabolic trough collector. Control local de Seguimiento cilindro parabolico ACE 20

    Energy Technology Data Exchange (ETDEWEB)

    Ajona Maeztu, J.I.; Alberdi Primicia, J.; Gamero Aranda, E.; Blanco, J.

    1991-01-01

    In the local control, the sun position related to the trough collector is measured by two photo-resistors. the provided electronic signal is then compared with reference levels in order to get a set of 8 logical signals which form a byte. This byte and the commands issued by a programmable controller are connected to the inputs of a P.R.O.M. memory which is programmed with the logical ecuations of the control system. the memory output lines give the control commands of the parabolic trough collector motor. (author)

  8. Tracking local control of a parabolic trough collector; Control local de Seguimiento cilindro parabolico ACE 20

    Energy Technology Data Exchange (ETDEWEB)

    Ajona Maeztu, J.I.; Alberdi Primicia, J.; Gamero Aranda, E.; Blanco, J.

    1991-12-31

    In the local control, the sun position related to the trough collector is measured by two photo-resistors. the provided electronic signal is then compared with reference levels in order to get a set of 8 logical signals which form a byte. This byte and the commands issued by a programmable controller are connected to the inputs of a P.R.O.M. memory which is programmed with the logical ecuations of the control system. the memory output lines give the control commands of the parabolic trough collector motor. (author)

  9. Optical and mechanical tolerances in hybrid concentrated thermal-PV solar trough.

    Science.gov (United States)

    Diaz, Liliana Ruiz; Cocilovo, Byron; Miles, Alexander; Pan, Wei; Blanche, Pierre-Alexandre; Norwood, Robert A

    2018-05-14

    Hybrid thermal-PV solar trough collectors combine concentrated photovoltaics and concentrated solar power technology to harvest and store solar energy. In this work, the optical and mechanical requirements for optimal efficiency are analyzed using non-sequential ray tracing techniques. The results are used to generate opto-mechanical tolerances that can be compared to those of traditional solar collectors. We also explore ideas on how to relieve tracking tolerances for single-axis solar collectors. The objective is to establish a basis for tolerances required for the fabrication and manufacturing of hybrid solar trough collectors.

  10. Many play concepts seen over wide area in Erris, Slyne troughs off Ireland

    International Nuclear Information System (INIS)

    Murphy, N.J.; Croker, P.F.

    1992-01-01

    This paper reports that the Erris and Slyne troughs are underexplored Mesozoic sedimentary basins off Ireland's northwest coast. The Irish Minister for Energy announced on Apr. 19, 1991, a frontier acreage licensing round of 128 blocks covering 29,000 sq km in these basins and the adjacent Rockall trough. Closing date for the round is June 30, 1993, set to allow two seasons for the acquisition of new geophysical and geological data over the area. Ireland has recently announced a new petroleum taxation regime. Revised licensing terms, which will acknowledge the specific circumstances of frontier acreage, will be announced

  11. GNSS monitoring of the ionosphere for Space Weather services

    Science.gov (United States)

    Krankowski, A.; Sieradzki, R.; Zakharenkova, I. E.; Cherniak, I. V.

    2012-04-01

    The International GNSS Service (IGS) Ionosphere Working Group routinely provides the users global ionosphere maps (GIMs) of vertical total electron content (vTEC). The IGS GIMs are provided with spatial resolution of 5.0 degrees x 2.5 degrees in longitude and latitude, respectively. The current temporal resolution is 2 hours, however, 1-hour maps are delivered as a pilot project. There are three types IGS GIMs: the final, rapid and predicted. The latencies of the IGS ionospheric final and rapid products are 10 days and 1 day, respectively. The predicted GIMs are generated for 1 and 2 days in advance. There are four IGS Associate Analysis Centres (IAACs) that provide ionosphere maps computed with independent methodologies using GNSS data. These maps are uploaded to the IGS Ionosphere Combination and Validation Center at the GRL/UWM (Geodynamics Research Laboratory of the University of Warmia and Mazury in Olsztyn, Poland) that produces the IGS official ionospheric products, which are published online via ftp and www. On the other hand, the increasing number of permanently tracking GNSS stations near the North Geomagnetic Pole allow for using satellite observations to detect the ionospheric disturbances at high latitudes with even higher spatial resolution. In the space weather service developed at GRL/UWM, the data from the Arctic stations belonging to IGS/EPN/POLENET networks were used to study TEC fluctuations and scintillations. Since the beginning of 2011, a near real-time service presenting the conditions in the ionosphere have been operational at GRL/UWM www site. The rate of TEC index (ROTI) expressed in TECU/min is used as a measure of TEC fluctuations. The service provides 2-hour maps of the TEC variability. In addition, for each day the daily map of the ionospheric fluctuations as a function geomagnetic local time is also created. This presentation shows the architecture, algorithms, performance and future developments of the IGS GIMs and this new space

  12. A modern trans-ionospheric propagation sensing system

    Science.gov (United States)

    Bishop, G. J.; Klobuchar, J. A.; Ronn, A. E.; Bedard, M. G.

    1989-09-01

    One of the most important potential problems with modern military systems which utilize spacecraft is the effect of the ionosphere on the radio signals which pass to and from the spacecraft. Such systems include active communications and navigation satellites as well as both ground-based and potential space-based ranging systems. The major effects the ionosphere can have on such systems are the additional time delay the electrons in the earth's ionosphere add to the free space path delay, the short term rate of change of this additional delay, amplitude scintillation or fading effects the signal encounters due to irregularities in the ionosphere, and Faraday rotation of linearly polarized radio waves transmitted through the ionosphere. While some of these effects were studied adequate models of these effects on military systems still do not exist. A modern trans-ionospheric sensing system, called TISS, is being procured which will consist of a number of stations located throughout the world, making real time measurements of the time delay of the ionosphere, and its rate of change, as well as amplitude scintillation, along several different viewing directions from each station. These trans-ionospheric measurements will be used to allow models, which currently provide only monthly propagation parameters. The real-time specifications of these parameters can then be used as decision aids in both the tactical and the strategic military environments. The TISS will include first order artificial intelligence design to aid in gathering the most appropriate sets of available real-time trans-ionospheric propagation data, and will communicate these data sets to the Air Weather Service Forecasting Center where they will be tailored to specific military customers.

  13. Predicting ionospheric scintillation: Recent advancements and future challenges

    Science.gov (United States)

    Carter, B. A.; Currie, J. L.; Terkildsen, M.; Bouya, Z.; Parkinson, M. L.

    2017-12-01

    Society greatly benefits from space-based infrastructure and technology. For example, signals from Global Navigation Satellite Systems (GNSS) are used across a wide range of industrial sectors; including aviation, mining, agriculture and finance. Current trends indicate that the use of these space-based technologies is likely to increase over the coming decades as the global economy becomes more technology-dependent. Space weather represents a key vulnerability to space-based technology, both in terms of the space environment effects on satellite infrastructure and the influence of the ionosphere on the radio signals used for satellite communications. In recent decades, the impact of the ionosphere on GNSS signals has re-ignited research interest into the equatorial ionosphere, particularly towards understanding Equatorial Plasma Bubbles (EPBs). EPBs are a dominant source of nighttime plasma irregularities in the low-latitude ionosphere, which can cause severe scintillation on GNSS signals and subsequent degradation on GNSS product quality. Currently, ionospheric scintillation event forecasts are not being routinely released by any space weather prediction agency around the world, but this is likely to change in the near future. In this contribution, an overview of recent efforts to develop a global ionospheric scintillation prediction capability within Australia will be given. The challenges in understanding user requirements for ionospheric scintillation predictions will be discussed. Next, the use of ground- and space-based datasets for the purpose of near-real time ionospheric scintillation monitoring will be explored. Finally, some modeling that has shown significant promise in transitioning towards an operational ionospheric scintillation forecasting system will be discussed.

  14. Magnetic storm effect on the occurrence of ionospheric irregularities at an equatorial station in the African sector

    Directory of Open Access Journals (Sweden)

    Olushola Abel Oladipo

    2014-01-01

    Full Text Available Large-scale ionospheric irregularities usually measured by GPS TEC fluctuation indices are regular occurrence at the equatorial region shortly after sunset around solar maximum. Magnetic storm can trigger or inhibit the generation of these irregularities depending on the local time the main phase of a particular storm occurs. We studied the effect of nine (9 distinct storms on the occurrence of ionospheric irregularities at Fraceville in Gabon (Lat = −1.63˚, Long = 13.55˚, dip lat. = −15.94˚, an equatorial station in the African sector. These storms occurred between November 2001 and September 2002. We used TEC fluctuation indices (i.e. ROTI and ROTIAVE estimated from 30 s interval Rinex data and also we used the storm indices (i.e. Dst, dDst/dt, and IMF BZ to predict the likely effect of each storm on the irregularities occurrence at this station. The results obtained showed that most of the storms studied inhibited ionospheric irregularities. Only one out of all the storms studied (i.e. September 4, 2002 storms with the main phase on the night of September 7-8 triggered post-midnight ionospheric irregularities. There are two of the storms during which ionospheric irregularities were observed. However, these may not be solely attributed to the storms event because the level of irregularities observed during these two storms is comparable to that observed during previous days before the storms. For this station and for the storms investigated, it seems like a little modification to the use of Aarons categories in terms of the local time the maximum negative Dst occurs could lead to a better prediction. However, it would require investigating many storms during different level of solar activities and at different latitudes to generalize this modification.

  15. Considering the potential of IAR emissions for ionospheric sounding

    Science.gov (United States)

    Potapov, A. S.; Polyushkina, T. N.; Tsegmed, B.; Oinats, A. V.; Pashinin, A. Yu.; Edemskiy, I. K.; Mylnikova, A. A.; Ratovsky, K. G.

    2017-11-01

    Knowledge of the ionospheric state allows us to adjust the forecasts of radio wave propagation, specify the environment models, and follow the changes of space weather. At present, probing of the ionosphere is produced by radio sounding with ground ionosondes, as well as by raying signals from satellites. We want to draw attention to the possibility of the diagnosis of the ionospheric parameters by detecting ultra-low frequency (ULF) electromagnetic emission generated in the so-called ionospheric Alfvén resonator (IAR). To do this, we present observations of the IAR emission made simultaneously for the first time at three stations using identical induction magnetometers. The stations are within one-hour difference of local time, two of them are mid-latitudinal; the third one is situated in the auroral zone. We compare frequency and frequency difference between adjacent harmonics of the observed multi-band emission with ionospheric parameters measured at the stations using ionosondes and GPS-observations. Diurnal variations of the ionospheric and ULF emission characteristics are also compared. The results show that there is quite a stable correlation between the resonant frequencies of the resonator bands and the critical frequency of the F2 layer of the ionosphere, namely, the frequency of the IAR emission varies inversely as the critical frequency of the ionosphere. This is due to the fact that the frequency of oscillation captured in the resonator is primarily determined by the Alfvén velocity (which depends on the plasma density) in the ionospheric F2 layer. The correlation is high; it varies at different stations, but is observed distinctly along the whole meridian. However, coefficients of a regression equation that connects the ionosphere critical frequency with DSB frequency vary significantly from day to day at all stations. The reason for such a big spread of the regression parameters is not clear and needs further investigation before we are able to

  16. The Rocket Investigation of Current Closure in the Ionosphere (RICCI) mission: A novel application of CubeSats from a sounding rocket platform

    Science.gov (United States)

    Cohen, I. J.; Anderson, B. J.; Lessard, M.; Bonnell, J. W.; Bounds, S. R.; Lysak, R. L.; Erlandson, R. E.

    2017-12-01

    The transfer of energy and momentum between the terrestrial magnetosphere and ionosphere is substantially mediated by large-scale field-aligned currents (FACs), driven by magnetopause dynamics and magnetospheric pressures and closing through the ionosphere where the dissipation and drag are governed. While significant insight into ionospheric electrodynamics and the nature of magnetosphere-ionosphere (M-I) coupling have been gained by rocket and satellite measurements, in situ measurement of these ionospheric closure currents remains challenging. To date the best estimates of ionospheric current densities are inferred from ground-based radar observations combining electric fields calculated from drifts with conductivities derived from densities. RICCI aims to observe the structure of the ionospheric currents in situ to determine how the altitude structure of these currents is related to precipitation and density cavities, electromagnetic dynamics, and governs energy dissipation in the ionosphere. In situ measurement of the current density using multi-point measurements of the magnetic field requires precise attitude knowledge for which the only demonstrated technique is the use of star camera systems. The low vehicle rotation rates required for miniature commercial off-the-shelf (COTS) star cameras prohibit the use of available rocket sub-payload technologies at Wallops Flight Facility (WFF) which use high rates of spin to stabilize attitude. However, CubeSat attitude systems are already designed to achieve low vehicle rotation rates, so RICCI will use a set of three CubeSat sub-payloads deployed from a main low altitude payload with apogee of 160 km to provide precise current density measurement through the ionospheric closure altitude regime, together with a second rocket with apogee near 320 km to measure the incident input energy flux and convection electric field. The two rocket payloads and CubeSate sub-payloads are all instrumented with star cameras and

  17. Impact of high-latitude energy input on the mid- and low-latitude ionosphere and thermosphere

    Science.gov (United States)

    Lu, G.; Sheng, C.

    2017-12-01

    High-latitude energy input has a profound impact on the ionosphere and thermosphere especially during geomagnetic storms. Intense auroral particle precipitation ionizes neutral gases and modifies ionospheric conductivity; collisions between neutrals and fast-moving ions accelerate the neutral winds and produce Joule frictional heating; and the excess Joule and particle heating causes atmospheric upwelling and changes neutral composition due to the rising of the heavier, molecular-rich air. In addition, impulsive Joule heating launches large-scale gravity waves that propagate equatorward toward middle and low latitudes and even into the opposite hemisphere, altering the mean global circulation of the thermosphere. Furthermore, high-latitude electric field can also directly penetrate to lower latitudes under rapidly changing external conditions, causing prompt ionospheric variations in the mid- and low-latitude regions. To study the effects of high-latitude energy input, we apply the different convection and auroral precipitation patterns based on both empirical models and the AMIE outputs. We investigate how the mid- and low-latitude regions respond to the different specifications of high-latitude energy input. The main purpose of the study is to delineate the various dynamical, electrodynamical, and chemical processes and to determine their relative importance in the resulting ionospheric and thermospheric properties at mid and low latitudes.

  18. Interhemispheric differences and solar cycle effects of the high-latitude ionospheric convection patterns deduced from Cluster EDI observations

    Science.gov (United States)

    Förster, Matthias; Haaland, Stein

    2015-04-01

    Here, we present a study of ionospheric convection at high latitudes that is based on satellite measurements of the Electron Drift Instrument (EDI) on-board the Cluster satellites, which were obtained over a full solar cycle (2001-2013). The mapped drift measurements are covering both hemispheres and a variety of different solar wind and interplanetary magnetic field (IMF) conditions. The large amount of data allows us to perform more detailed statistical studies. We show that flow patterns and polar cap potentials can differ between the two hemispheres on statistical average for a given IMF orientation. In particular, during southward directed IMF conditions, and thus enhanced energy input from the solar wind, we find that the southern polar cap has a higher cross polar cap potential. We also find persistent north-south asymmetries which cannot be explained by external drivers alone. Much of these asymmetries can probably be explained by significant differences in the strength and configuration of the geomagnetic field between the Northern and Southern Hemisphere. Since the ionosphere is magnetically connected to the magnetosphere, this difference will also be reflected in the magnetosphere in the form of different feedback from the two hemispheres. Consequently, local ionospheric conditions and the geomagnetic field configuration are important for north-south asymmetries in large regions of geospace. The average convection is higher during periods with high solar activity. Although local ionospheric conditions may play a role, we mainly attribute this to higher geomagnetic activity due to enhanced solar wind - magnetosphere interactions.

  19. The Nova-Canton Trough and the Late Cretaceous evolution of the central Pacific

    Science.gov (United States)

    Joseph, Devorah; Taylor, Brain; Shor, Alexander N.; Yamazaki, Toshitsugu

    Free-air gravity anomalies derived from satellite altimetry data show that the major Pacific fracture zones, from the Pau to Marquesas, are co-polar about an Euler pole located at 150.5°W, 34.6°S for the period preceding chron 33 and including a large portion of the Cretaceous Normal Superchron. They also show continuity of the Clipperton Fracture Zone through the Line Islands to the Nova-Canton ridge and trough; this Canton-Clipperton trend is co-polar to the same pole. Sidescan-sonar and bathymetry data in the Nova-Canton Trough region reveal N140°E-striking abyssal hill topography south of the N70°E-striking structures of the Nova-Canton Trough and crustal fabric striking normal to the trough (N160°E) to the north. We conclude that the Nova-Canton Trough is the Middle Cretaceous extension of the Clipperton Fracture Zone. We propose that the anomalous depths (7000-8400 m) of the trough between 167°30'-168°30'W are the result of a complex plate reorganization. Conjugate magnetic anomaly lineations M1-M3 in the Phoenix lineations between the Central Pacific Fracture Zone and the Phoenix Fracture Zone and the absence of lineations younger than anomaly M3 west of the Phoenix Fracture Zone suggest that spreading may have gradually ceased along the Pacific-Phoenix system from west to east. We infer that the remaining active segment of the Pacific-Phoenix spreading system after anomaly M1 time was the easternmost section of the Phoenix lineations. At ˜M0 time, the Pacific-Phoenix spreading axis stretched from lineated bathymetric depressions lying between 180°W and the Phoenix Islands to ˜168°W and included the western deep of the Nova-Canton Trough. We hypothesize that accretion terminated on the Pacific-Phoenix spreading axis shortly after M0 time and that the absence of an M0 isochron in the region between the eastern Phoenix lineations and the Nova-Canton Trough, or along the Nova-Canton Trough itself, may be due to a decrease in spreading rate prior to

  20. Element enrichment and U-series isotopic characteristics of the hydrothermal sulfides at Jade site in the Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The geochemical and U-series isotopic characteristics of hydrothermal sulfide samples from the Jade site (127°04.5′E, 27°15′N, water depth 1300-1450 m) at Jade site in the Okinawa Trough were analyzed. In the hydrothermal sulfide samples bearing sulfate (samples HOK1 and HOK2), the LREEs are relatively enriched. All the hydrothermal sulfide samples except HOK1 belong to Zn-rich hydrothermal sulfide. In comparison with Zn-rich hydrothermal sulfides from other fields, the contents of Zn, Pb, Ag, Cd, Au and Hg are higher, the contents of Fe, Al, Cr, Co, Ni, Sr, Te, Cs, Ti and U lower, and the 210Pb radioactivity ratios and 210Pb/Pb ratios very low. In the hydrothermal sulfide mainly composed of sphalerite, the correlations between rare elements Hf and U, and Hf and Mn as well as that between dispersive elements Ga and Zn, are strongly positive; also the contents of Au and Ag are related to Fe-sulfide, because the low temperature promotes enrichment of Au and Ag. Meanwhile, the positive correlations between Fe and Bi and between Zn and Cd are not affected by the change of mineral assemblage. Based on the 210Pb/Pb ratios of hydrothermal sulfide samples (3.99×10-5-5.42×10?5), their U isotopic composition (238U content 1.15-2.53 ppm, 238U activity 1.07-1.87 dpm/g, 234U activity 1.15-2.09 dpm/g and 234U/238U ratio 1.07-1.14) and their 232Th and 230Th contents are at base level, and the chronological age of hydrothermal sulfide at Jade site in the Okinawa Trough is between 200 and 2000 yr.

  1. Amplitude versus offset analysis to marine seismic data acquired in Nankai Trough, offshore Japan where methane hydrate exists

    Science.gov (United States)

    Hato, M.; Inamori, T.; Matsuoka, T.; Shimizu, S.

    2003-04-01

    Occurrence of methane hydrates in the Nankai Trough, located off the south-eastern coast of Japan, was confirmed by the exploratory test well drilling conducted by Japan’s Ministry of International Trade and Industry in 1999. Confirmation of methane hydrate has given so big impact to the Japan's future energy strategy and scientific and technological interest was derived from the information of the coring and logging results at the well. Following the above results, Japan National Oil Corporation (JNOC) launched the national project, named as MH21, for establishing the technology of methane hydrate exploration and related technologies such as production and development. As one of the research project for evaluating the total amount of the methane hydrate, Amplitude versus Offset (AVO) was applied to the seismic data acquired in the Nankai Trough area. The main purpose of the AVO application is to evaluate the validity of delineation of methane hydrate-bearing zones. Since methane hydrate is thought to accompany with free-gas in general just below the methane hydrate-bearing zones, the AVO has a possibility of describing the presence of free-gas. The free-gas is thought to be located just below the base of methane hydrate stability zone which is characterized by the Bottom Simulating Reflectors (BSRs) on the seismic section. In this sense, AVO technology, which was developed as gas delineation tools, can be utilized for methane hydrate exploration. The result of AVO analysis clearly shows gas-related anomaly below the BSRs. Appearance of the AVO anomaly has so wide variety. Some of the anomalies might not correspond to the free-gas existence, however, some of them may show free-gas. We are now going to develop methodology to clearly discriminate free-gas from non-gas zone by integrating various types of seismic methods such as seismic inversion and seismic attribute analysis.

  2. 9 CFR 82.21 - Vehicles, cages, coops, containers, troughs, and other equipment used for infected poultry.

    Science.gov (United States)

    2010-01-01

    ..., troughs, and other equipment used for infected poultry. 82.21 Section 82.21 Animals and Animal Products... ANIMALS (INCLUDING POULTRY) AND ANIMAL PRODUCTS EXOTIC NEWCASTLE DIS- EASE (END) AND CHLAMYDIOSIS Chlamydiosis in Poultry § 82.21 Vehicles, cages, coops, containers, troughs, and other equipment used for...

  3. A comparison of the relative locations of the mid-latitude electron density trough and the scintillation boundary

    International Nuclear Information System (INIS)

    Tulunay, Y.K.; Demir, O.; Tauriainen, A.

    1976-01-01

    The mid-latitude electron density trough position and the scintillation boundary have been compared for magnetically quiet periods by using the data returned by Ariel 3 and Explorer 22 satellites. The scintillation boundary is found southward of the trough during daytime, but at night the positions are reversed. (author)

  4. Geochemistry of trace elements and Sr- Nd isotopes of foraminifera shell from the Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Trace elemental associations and Sr - Nd isotopic compositions are of important to recognition of biogenic material from mixed marine sediments. The foraminifera shell from the Okinawa Trough strongly enrichesSr, P, Mn andBa, enriches Li, U, Th, Sc, Co, Cu, Pb, Zn, Cr, Rb, Y, Sb and light rare earth elements, slightly enriches V, Ga, Zr, Nb, Cd and middle rare earth elements,is short of Mo, In, Sn, Cs, Hf, Ta, W, Ti, Bi and heavy rare earth elements. The mechanism of elemental enrichment in forminifera is the concentrations of trace elements in sea water and selective absorption of trace elements during foraminifera living, as well as the geochemical affinity between major elements and trace elements. The REE (rare earth elements) partition pattern of foraminifera shell of the Okinawa Trough shows enrichment of middle rare earth elements with slightly negative Ce anomaly,which are different from those of foraminifera of the Pacific Ocean. The Sr, Nd isotopic ratios of the Okinawa Trough foraminifera are 0.709 769 and 0.512 162, respectively, which are different not only from those of oceanic water, but also from those of river water of China's Mainland, the former is slightly higher than those of oceanic water, but much lower than those of river water; the latter is slightly lower than those of oceanic water, but higher than those of river water, demonstrating that the Okinawa Trough sea water has been influenced by river water of China's Mainland.

  5. Upstream sediment input effects on experimental dune trough scour in sediment mixtures

    NARCIS (Netherlands)

    Kleinhans, M.G.

    2005-01-01

    Understanding causes of dune irregularity, especially dune trough scour, is important for the modeling of vertical sorting of sediment mixtures in morphological models of rivers with sediment mixtures. Sediment in dunes is generally sorted in a fining-upward manner, which affects the sediment

  6. Overland conveyors. Cable or trough belt for 100 km transport haulage

    Energy Technology Data Exchange (ETDEWEB)

    Maton, A.E. [Maton Engineering Pty. Ltd., Orange Grove, WA (Australia)

    2009-07-01

    With the advances in belt conveyor technology today systems of 100 kilometres length are increasingly being considered. This article provides a comparison of two concepts for a 100 kilometre system of five 20 kilometre flights based on trough belt and cable belt technology. (orig.)

  7. Influence of pen area and trough space on feedlot performance of ...

    African Journals Online (AJOL)

    performance. There was no advantage in allowing more than 170 mm trough space or more than 5,5 m2 floor area per animal with the conditions and climate under which these trials were conducted ... pen area on feed intake and feedlot performance. A total of 196 dehorned ... Standard deviation (kg). 0,19. 0,18. 0,19. 0,15.

  8. Numerical simulation of tropical-temperate troughs over Southern Africa using the CSU RAMS model

    CSIR Research Space (South Africa)

    Van den Heever, SC

    1997-08-01

    Full Text Available ) and the wet (1981) late summer case studies has been examined. Model simulations reveal that the tropical-temperate troughs form when an upper westerly wave coincides with an easterly, wave or depression in lower levels. These systems occur preferentially over...

  9. Investigation on the dynamic behaviour of a parabolic trough power plant during strongly cloudy days

    International Nuclear Information System (INIS)

    Al-Maliki, Wisam Abed Kattea; Alobaid, Falah; Starkloff, Ralf; Kez, Vitali; Epple, Bernd

    2016-01-01

    Highlights: • A detailed dynamic model of a parabolic trough solar thermal power plant is done. • Simulated results are compared to the experimental data from the real power plant. • Discrepancy between model result and real data is caused by operation strategy. • The model strategy increased the operating hours of power plant by around 2.5–3 h. - Abstract: The objective of this study is the development of a full scale dynamic model of a parabolic trough power plant with a thermal storage system, operated by the Actividades de Construcción y Servicios Group in Spain. The model includes solar field, thermal storage system and the power block and describes the heat transfer fluid and steam/water paths in detail. The parabolic trough power plant is modelled using Advanced Process Simulation Software (APROS). To validate the model, the numerical results are compared to the measured data, obtained from “Andasol II” during strongly cloudy periods in the summer days. The comparisons show a qualitative agreement between the dynamic simulation model and the measurements. The results confirm that the thermal storage enables the parabolic trough power plant to provide a constant power rate when the storage energy discharge is available, despite significant oscillations in the solar radiation.

  10. A numerical analysis of the energy behavior of a parabolic trough ...

    African Journals Online (AJOL)

    The solar power is a clean and a durable energy; there are several techniques for using them. When necessary to elevated temperatures of heat transfer fluid, this energy must concentration. This paper presents the efficiencies study of a linear solar concentrator of a parabolic trough type. This study was conducted on the ...

  11. A twin study of the trough plasma steady-state concentration of metformin

    DEFF Research Database (Denmark)

    Stage, Tore B; Damkier, Per; Pedersen, Rasmus S

    2015-01-01

    OBJECTIVE: The aim of this study was to determine the intrapair similarity in trough steady-state plasma concentrations of metformin in monozygotic and dizygotic twin pairs. METHODS: We included 16 twin pairs (eight monozygotic and eight dizygotic twin pairs) for this study after contacting 524 t...

  12. Basinal Structure Of Yola Arm Of The Upper Benue Trough Nigeria ...

    African Journals Online (AJOL)

    Aeromagnetic data interpretation of the Yola arm of the Upper Benue Trough has previously been carried out. However, no detail modeling of the Crustal Structures has been undertaken. Two composite reduced Aeromagnetic maps on a scale of 1:250,000 were digitized and processed using computer techniques.

  13. The MITRA as a solar and ionospheric instrument

    Science.gov (United States)

    Beeharry, G. K.

    2015-12-01

    The MITRA is an international/pan-African radioastronomy project which aims to do extremely wide field imaging with heterogeneous non coplanar arrays. It can be used for solar and ionospheric studies.

  14. CAT scanning of the ionosphere: Pros and cons

    Indian Academy of Sciences (India)

    First page Back Continue Last page Graphics. Excellent Spatial coverage. Excellent Spatial coverage. Snapshots of the large scale features (km-scale) of the ionosphere. bottomside and topside. Information on remote and inaccessible regions. Inexpensive.

  15. Global GPS Ionospheric Modelling Using Spherical Harmonic Expansion Approach

    Directory of Open Access Journals (Sweden)

    Byung-Kyu Choi

    2010-12-01

    Full Text Available In this study, we developed a global ionosphere model based on measurements from a worldwide network of global positioning system (GPS. The total number of the international GPS reference stations for development of ionospheric model is about 100 and the spherical harmonic expansion approach as a mathematical method was used. In order to produce the ionospheric total electron content (TEC based on grid form, we defined spatial resolution of 2.0 degree and 5.0 degree in latitude and longitude, respectively. Two-dimensional TEC maps were constructed within the interval of one hour, and have a high temporal resolution compared to global ionosphere maps which are produced by several analysis centers. As a result, we could detect the sudden increase of TEC by processing GPS observables on 29 October, 2003 when the massive solar flare took place.

  16. Ionospheric/protonospheric electron content studies using ATS-6

    International Nuclear Information System (INIS)

    Hajeb-Hosseinieh, H.; Kersley, L.; Edwards, K.J.

    1978-01-01

    Measurements of ionospheric and protonospheric contents obtained at Aberystwyth from observations of the ATS-6 satellite radio beacon are reported. The monthly median diurnal behavior shows protonospheric contributions of approximately 15 to 20% to the total content along the ray path by day, rising to a predawn maximum of 35% in summer and more than 40% in winter. The protonospheric results are shown to be typical of those expected from other European stations and differences from earlier American measurements are explained in terms of ionospheric interactions in the conjugate hemisphere. The temporal gradients of protonospheric content provide information on the net integrated ionospheric/protonospheric plasma fluxes and the results obtained indicate the importance of plasma exchange with both local and conjugate ionospheres

  17. Low ionospheric reactions on tropical depressions prior hurricanes

    Science.gov (United States)

    Nina, Aleksandra; Radovanović, Milan; Milovanović, Boško; Kovačević, Andjelka; Bajčetić, Jovan; Popović, Luka Č.

    2017-10-01

    We study the reactions of the low ionosphere during tropical depressions (TDs) which have been detected before the hurricane appearances in the Atlantic Ocean. We explore 41 TD events using very low frequency (VLF) radio signals emitted by NAA transmitter located in the USA and recorded by VLF receiver located in Belgrade (Serbia). We found VLF signal deviations (caused ionospheric turbulence) in the case of 36 out of 41 TD events (88%). Additionally, we explore 27 TDs which have not been developed in hurricanes and found similar low ionospheric reactions. However, in the sample of 41 TDs which are followed by hurricanes the typical low ionosphere perturbations seem to be more frequent than other TDs.

  18. Global scale ionospheric irregularities associated with thunderstorm activity

    International Nuclear Information System (INIS)

    Pulinets, Sergey A.; Depuev, Victor H.

    2003-01-01

    The potential difference near 280 kV exists between ground and ionosphere. This potential difference is generated by thunderstorm discharges all over the world, and return current closes the circuit in the areas of fair weather (so-called fair weather current). The model calculations and experimental measurements clearly demonstrate non-uniform latitude-longitude distribution of electric field within the atmosphere. The recent calculations show that the strong large scale vertical atmospheric electric field can penetrate into the ionosphere and create large scale irregularities of the electron concentration. To check this the global distributions of thunderstorm activity obtained with the satellite monitoring for different seasons were compared with the global distributions of ionosphere critical frequency (which is equivalent to peak electron concentration) obtained with the help of satellite topside sounding. The similarity of the obtained global distributions clearly demonstrates the effects of thunderstorm electric fields onto the Earth's ionosphere. (author)

  19. Horizontal dimensions of ionosphere agitation provoked by underground nuclear explosions

    International Nuclear Information System (INIS)

    Drobzheva, Ya.V.; Krasnov, V.M.; Sokolova, O.I.

    2001-01-01

    The horizontal dimensions of ionosphere agitation provoked by underground nuclear explosions have been experimentally determined for 13 explosions conducted at the Balapan test site of the Semipalatinsk test site. (author)

  20. The Shock Wave in the ionosphere during an Earthquake

    Directory of Open Access Journals (Sweden)

    Kuznetsov Vladimir

    2016-01-01

    Full Text Available Fundamentally new model of the shock wave (SW generation in atmosphere and ionosphere during earthquake is proposed. The model proceeds from the idea of cooperative shock water crystallization in a cloud.

  1. Measurements of the Absorptive Properties of the Ionosphere

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Absorption of radio waves occurs when electrons responding to the wave fields collide with and transfer energy to the neutral particles. A study of ionospheric...

  2. The Multifractal Structure of Small-Scale Artificial Ionospheric Turbulence

    Directory of Open Access Journals (Sweden)

    Vybornov F. I.

    2013-03-01

    Full Text Available We present the results of investigation of a multifractal structure of the artificial ionospheric turbulence when the midlatitude ionosphere is affected by high-power radio waves. The experimental studies were performed on the basis of the SURA heating facility with the help of radio sounding of the disturbed region of ionospheric plasma by signals from the Earth’s orbital satellities. In the case of vertical radio sounding of the disturbed ionosphere region, the measured multipower and generalized multifractal spectra of turbulence coincide well with similar multifractal characteristics of the ionosperic turbulence under the natural conditions. In the case of oblique sounding of the disturbance region at small angles between the line of sight to the satellite and the direction of the Earth’s magnetic field, a nonuniform structure of the small-scale turbulence with a relatively narrow multipower spectrum and small variations in the generalized multifractal spectrum of the electron density was detected.

  3. Modeling the Electrodynamics of the Low-Latitude Ionosphere

    National Research Council Canada - National Science Library

    Wohlwend, Christian S

    2008-01-01

    .... This two-part study focused on the gravity wave seeding mechanism of equatorial plasma depletions in the ionosphere and the associated-equatorial spread F, as well as the differences between a two...

  4. Dust Acoustic Mode Manifestations in Earth's Dusty Ionosphere

    International Nuclear Information System (INIS)

    Kopnin, S.I.; Popel, S.I.

    2005-01-01

    Dust acoustic mode manifestations in the dusty ionosphere are studied. The reason for an appearance of the low-frequency radio noises associated with such meteor fluxes as Perseids, Orionids, Leonids, and Gemenids is determined

  5. Signatures of mesospheric particles in ionospheric data

    Directory of Open Access Journals (Sweden)

    M. Friedrich

    2009-02-01

    Full Text Available The state of the ionosphere during the 2007 ECOMA/MASS campaign is described by in-situ observations by three sounding rockets launched from the Andøya Rocket Range and by ground based observations. The ground based measurements included the incoherent scatter radar EISCAT near Tromsø (both on UHF and VHF, as well as an MF radar, a meteor radar and an imaging riometer all located in the close vicinity of the rocket range. The pronounced electron density bite-outs seen by two of the rockets could not be detected from the ground, but the associated PMSE (Polar Mesospheric Summer Echoes provide indirect evidence of pronounced perturbations of mesospheric electron densities.

  6. Magnetosphere - Ionosphere - Thermosphere (MIT) Coupling at Jupiter

    Science.gov (United States)

    Yates, J. N.; Ray, L. C.; Achilleos, N.

    2017-12-01

    Jupiter's upper atmospheric temperature is considerably higher than that predicted by Solar Extreme Ultraviolet (EUV) heating alone. Simulations incorporating magnetosphere-ionosphere coupling effects into general circulation models have, to date, struggled to reproduce the observed atmospheric temperatures under simplifying assumptions such as azimuthal symmetry and a spin-aligned dipole magnetic field. Here we present the development of a full three-dimensional thermosphere model coupled in both hemispheres to an axisymmetric magnetosphere model. This new coupled model is based on the two-dimensional MIT model presented in Yates et al., 2014. This coupled model is a critical step towards to the development of a fully coupled 3D MIT model. We discuss and compare the resulting thermospheric flows, energy balance and MI coupling currents to those presented in previous 2D MIT models.

  7. The D-region of the ionosphere

    International Nuclear Information System (INIS)

    Mitra, A.P.

    1978-01-01

    The D-region of the ionosphere, traditionally defined as the region of ionization below 100 km, is a link between the non-ionized stratosphere below and the dense plasma above. In it, minor neutral constituents play a dominant role and chemical reactions, both neutral and ionic, are dominant. It plays a very important role in the propagation of radiowaves at all frequencies below 30 MHz, and is particularly important in effecting communication over areas of the earth, such as polar regions, that are inaccessible to synchronous satellite links. Work which has been carried out on the neutral environment, D-region ionization, positive and negative ions found in the D-region, disturbances in the D-region (of solar origin and due to local dynamics or thermal changes), and the chemistry of the region, is considered. Possible future D-region studies are outlined. (UK)

  8. Does Io's ionosphere influence Jupiter's radio bursts.

    Science.gov (United States)

    Webster, D. L.; Alksne, A. Y.; Whitten, R. C.

    1972-01-01

    Goldreich and Lynden-Bell's theory of Jupiter's Io-correlated decametric radiation sets a lower limit to Io's conductivity, high enough to carry the current associated with the radiated power. Dermott's analysis of conductivities of rocks and ice shows no such conductivity at Io's temperature. However, we show that if Io has even a small atmosphere, say of methane as suggested by Binder and Cruikshank, or of argon or nitrogen, it will have an ionosphere with adequate conductivity to meet the above criterion. A requirement for higher conductivity was found by Goldreich and Lynden-Bell on the basis of motion of magnetic lines past Io. This requirement appears to us unnecessary in view of experiments which prove that motion of the lines is not the source of the electromotance.

  9. VLF Observation of Long Ionospheric Recovery Events

    Science.gov (United States)

    Cotts, B. R.; Inan, U. S.

    2006-12-01

    On the evening of 20 November 1992, three early/fast events were observed on the great circle path (GCP) from the NAU transmitter in Puerto Rico to Gander (GA), Newfoundland. These events were found to have significantly longer recovery times (up to 20 minutes) than any previously documented events. Typical early/fast events and Lightning-induced Electron Precipitation (LEP) events affect the D-region ionosphere near the night-time VLF-reflection height of ~85 km and exhibit recovery to pre-event levels of gigantic jets. In this context, preliminary results indicate that the lightning-associated VLF long recovery events appear to be more common in oceanic thunderstorms. In this paper, we present occurrence statistics and other measured properties of VLF long recovery events, observed on all-sea based and land based VLF great circle paths.

  10. Ionospheric drift measurements: Skymap points selection

    Czech Academy of Sciences Publication Activity Database

    Kouba, Daniel; Boška, Josef; Galkin, I. A.; Santolík, Ondřej; Šauli, Petra

    2008-01-01

    Roč. 43, č. 1 (2008), RS1S90/1-RS1S90/11 ISSN 0048-6604 R&D Projects: GA ČR GA205/06/1619; GA ČR GA205/06/1267; GA AV ČR IAA300420504 Grant - others:GA MŠk(CZ) OC 296; MIERS(XE) COST 296 Institutional research plan: CEZ:AV0Z30420517 Keywords : digisonde drift measurement * plasma drift * radio sounding * ionosphere * Doppler shift * skymap processing Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.092, year: 2008 http://www.agu.org/pubs/crossref/2008/2007RS003633.shtml

  11. Ionogram inversion for a tilted ionosphere

    International Nuclear Information System (INIS)

    Wright, J.W.

    1990-01-01

    Digital ionosondes such as the Dynasonde disclose that the ionosphere is seldom horizontal even when it is plane stratified to a good approximation. The local magnetic dip does not then determine correctly the radiowave propagation angle for inversion of the ionogram to a plasma density profile. The measured echo direction of arrival can be used together with the known dip for an improved propagation angle. The effects are small for simple one-parameter laminae but become important when differential (ordinary, extraordinary) retardations are used to aid correction for valley and starting ambiguities. The resulting profile describes the plasma distribution along the direction of observation, rather than the vertical; it thus conveys information about horizontal gradients. Observations suggest that advantages in inversion methods may be practicable for application to modern ionosonde recordings, by which local lateral structure can be described in greater detail. 20 refs

  12. Seismicity of the 24 May 2014 Mw 7.0 Aegean Sea earthquake sequence along the North Aegean Trough

    Science.gov (United States)

    Görgün, Ethem; Görgün, Burçak

    2015-11-01

    The northern Aegean Sea was hit by a large size (Mw = 7.0) earthquake on 2014 May 24. Centroid moment tensor solutions for 40 events with moment magnitudes (Mw) between 3.3 and 7.0 are computed by applying a waveform inversion method on data from the Turkish and Greek broadband seismic networks. The time span of data covers the period between 2014 May 24 and 2014 June 26. The mainshock is a shallow focus strike-slip event at a depth of 15 km. Focal depths of aftershocks range from 6 to 30 km. The seismic moment (Mo) of the mainshock is estimated as 4.60 × 1019 Nm. The calculated rupture duration of the North Aegean Sea mainshock is 40 s. The focal mechanisms of the aftershocks are mainly strike-slip faulting with a minor normal component. The geometry of focal mechanisms reveals a strike-slip faulting regime with NE-SW trending direction of T-axis in the entire activated region. A stress tensor inversion of focal mechanism data is performed to acquire a more accurate picture of the northern Aegean Sea stress field along the North Aegean Trough. The stress tensor inversion results indicate a predominant strike-slip stress regime with a NW-SE oriented maximum principal compressive stress (σ1). In the development of the North Aegean Trough in Aegean Sea is in good agreement with the resolved stress tensors. With respect the newly determined focal mechanisms, the effect of the propagating of the North Anatolian Fault into Aegean Sea is very clearly pronounced. According to high-resolution hypocenter relocation of the North Aegean Sea seismic sequence, three main clusters are revealed. The aftershock activity in the observation period between 2014 May 24 and 2014 July 31 extends from the mainshock cluster from NE to the SW direction. Seismic cross-sections indicate that a complex pattern of the hypocenter distribution with the activation of seventeen segments. The eastern cluster is associated with a fault plane trending mainly ENE-WSW and dipping vertical, while the

  13. Understanding the Compositional Variability of the Major Components of Hydrothermal Plumes in the Okinawa Trough

    Directory of Open Access Journals (Sweden)

    Zhigang Zeng

    2018-01-01

    Full Text Available Studies of the major components of hydrothermal plumes in seafloor hydrothermal fields are critical for an improved understanding of biogeochemical cycles and the large-scale distribution of elements in the submarine environment. The composition of major components in hydrothermal plume water column samples from 25 stations has been investigated in the middle and southern Okinawa Trough. The physical and chemical properties of hydrothermal plume water in the Okinawa Trough have been affected by input of the Kuroshio current, and its influence on hydrothermal plume water from the southern Okinawa Trough to the middle Okinawa Trough is reduced. The anomalous layers of seawater in the hydrothermal plume water columns have higher K+, Ca2+, Mn2+, B3+, Ca2+/SO42-, and Mn2+/Mg2+ ratios and higher optical anomalies than other layers. The Mg2+, SO42-, Mg2+/Ca2+, and SO42-/Mn2+ ratios of the anomalous layers are lower than other layers in the hydrothermal plume water columns and are consistent with concentrations in hydrothermal vent fluids in the Okinawa Trough. This suggests that the chemical variations of hydrothermal plumes in the Tangyin hydrothermal field, like other hydrothermal fields, result in the discharge of high K+, Ca2+, and B3+ and low Mg2+ and SO42- fluid. Furthermore, element ratios (e.g., Sr2+/Ca2+, Ca2+/Cl− in hydrothermal plume water columns were found to be similar to those in average seawater, indicating that Sr2+/Ca2+ and Ca2+/Cl− ratios of hydrothermal plumes might be useful proxies for chemical properties of seawater. The hydrothermal K+, Ca2+, Mn2+, and B3+ flux to seawater in the Okinawa Trough is about 2.62–873, 1.04–326, 1.30–76.4, and 0.293–34.7 × 106 kg per year, respectively. The heat flux is about 0.159–1,973 × 105 W, which means that roughly 0.0006% of ocean heat is supplied by seafloor hydrothermal plumes in the Okinawa Trough.

  14. Kriging with Unknown Variance Components for Regional Ionospheric Reconstruction

    Directory of Open Access Journals (Sweden)

    Ling Huang

    2017-02-01

    Full Text Available Ionospheric delay effect is a critical issue that limits the accuracy of precise Global Navigation Satellite System (GNSS positioning and navigation for single-frequency users, especially in mid- and low-latitude regions where variations in the ionosphere are larger. Kriging spatial interpolation techniques have been recently introduced to model the spatial correlation and variability of ionosphere, which intrinsically assume that the ionosphere field is stochastically stationary but does not take the random observational errors into account. In this paper, by treating the spatial statistical information on ionosphere as prior knowledge and based on Total Electron Content (TEC semivariogram analysis, we use Kriging techniques to spatially interpolate TEC values. By assuming that the stochastic models of both the ionospheric signals and measurement errors are only known up to some unknown factors, we propose a new Kriging spatial interpolation method with unknown variance components for both the signals of ionosphere and TEC measurements. Variance component estimation has been integrated with Kriging to reconstruct regional ionospheric delays. The method has been applied to data from the Crustal Movement Observation Network of China (CMONOC and compared with the ordinary Kriging and polynomial interpolations with spherical cap harmonic functions, polynomial functions and low-degree spherical harmonic functions. The statistics of results indicate that the daily ionospheric variations during the experimental period characterized by the proposed approach have good agreement with the other methods, ranging from 10 to 80 TEC Unit (TECU, 1 TECU = 1 × 1016 electrons/m2 with an overall mean of 28.2 TECU. The proposed method can produce more appropriate estimations whose general TEC level is as smooth as the ordinary Kriging but with a smaller standard deviation around 3 TECU than others. The residual results show that the interpolation precision of the

  15. High Resolution Reconstruction of the Ionosphere for SAR Applications

    Science.gov (United States)

    Minkwitz, David; Gerzen, Tatjana; Hoque, Mainul

    2014-05-01

    Caused by ionosphere's strong impact on radio signal propagation, high resolution and highly accurate reconstructions of the ionosphere's electron density distribution are demanded for a large number of applications, e.g. to contribute to the mitigation of ionospheric effects on Synthetic Aperture Radar (SAR) measurements. As a new generation of remote sensing satellites the TanDEM-L radar mission is planned to improve the understanding and modelling ability of global environmental processes and ecosystem change. TanDEM-L will operate in L-band with a wavelength of approximately 24 cm enabling a stronger penetration capability compared to X-band (3 cm) or C-band (5 cm). But accompanied by the lower frequency of the TanDEM-L signals the influence of the ionosphere will increase. In particular small scale irregularities of the ionosphere might lead to electron density variations within the synthetic aperture length of the TanDEM-L satellite and in turn might result into blurring and azimuth pixel shifts. Hence the quality of the radar image worsens if the ionospheric effects are not mitigated. The Helmholtz Alliance project "Remote Sensing and Earth System Dynamics" (EDA) aims in the preparation of the HGF centres and the science community for the utilisation and integration of the TanDEM-L products into the study of the Earth's system. One significant point thereby is to cope with the mentioned ionospheric effects. Therefore different strategies towards achieving this objective are pursued: the mitigation of the ionospheric effects based on the radar data itself, the mitigation based on external information like global Total Electron Content (TEC) maps or reconstructions of the ionosphere and the combination of external information and radar data. In this presentation we describe the geostatistical approach chosen to analyse the behaviour of the ionosphere and to provide a high resolution 3D electron density reconstruction. As first step the horizontal structure of

  16. Ionosphere research with a HF/MF cubesat radio instrument

    Science.gov (United States)

    Kallio, Esa; Aikio, Anita; Alho, Markku; Fontell, Mathias; Harri, Ari-Matti; Kauristie, Kirsti; Kestilä, Antti; Koskimaa, Petri; Mäkelä, Jakke; Mäkelä, Miika; Turunen, Esa; Vanhamäki, Heikki; Verronen, Pekka

    2017-04-01

    New technology provides new possibilities to study geospace and 3D ionosphere by using spacecraft and computer simulations. A type of nanosatellites, CubeSats, provide a cost effective possibility to provide in-situ measurements in the ionosphere. Moreover, combined CubeSat observations with ground-based observations gives a new view on auroras and associated electromagnetic phenomena. Especially joint and active CubeSat - ground based observation campaigns enable the possibility of studying the 3D structure of the ionosphere. Furthermore using several CubeSats to form satellite constellations enables much higher temporal resolution. At the same time, increasing computation capacity has made it possible to perform simulations where properties of the ionosphere, such as propagation of the electromagnetic waves in the medium frequency, MF (0.3-3 MHz) and high frequency, HF (3-30 MHz), ranges is based on a 3D ionospheric model and on first-principles modelling. Electromagnetic waves at those frequencies are strongly affected by ionospheric electrons and, consequently, those frequencies can be used for studying the plasma. On the other hand, even if the ionosphere originally enables long-range telecommunication at MF and HF frequencies, the frequent occurrence of spatiotemporal variations in the ionosphere disturbs communication channels, especially at high latitudes. Therefore, study of the MF and HF waves in the ionosphere has both a strong science and technology interests. We introduce recently developed simulation models as well as measuring principles and techniques to investigate the arctic ionosphere by a polar orbiting CubeSat whose novel AM radio instrument measures HF and MF waves. The cubesat, which contains also a white light aurora camera, is planned to be launched in late 2017 (http://www.suomi100satelliitti.fi/eng). The new models are (1) a 3D ray tracing model and (2) a 3D full kinetic electromagnetic simulation. We also introduce how combining of the

  17. Electon density profiles of the topside ionosphere

    Directory of Open Access Journals (Sweden)

    D. Bilitza

    2002-06-01

    Full Text Available The existing uncertainties about the electron density profiles in the topside ionosphere, i.e., in the height region from h m F 2 to ~ 2000 km, require the search for new data sources. The ISIS and Alouette topside sounder satellites from the sixties to the eighties recorded millions of ionograms but most were not analyzed in terms of electron density profiles. In recent years an effort started to digitize the analog recordings to prepare the ionograms for computerized analysis. As of November 2001 about 350 000 ionograms have been digitized from the original 7-track analog tapes. These data are available in binary and CDF format from the anonymous ftp site of the National Space Science Data Center. A search site and browse capabilities on CDAWeb assist the scientific usage of these data. All information and access links can be found at http://nssdc.gsfc.nasa.gov/space/isis/isis-status. html. This paper describes the ISIS data restoration effort and shows how the digital ionograms are automatically processed into electron density profiles from satellite orbit altitude (1400 km for ISIS-2 down to the F peak. Because of the large volume of data an automated processing algorithm is imperative. The TOPside Ionogram Scaler with True height algorithm TOPIST software developed for this task is successfully scaling ~ 70% of the ionograms. An «editing process» is available to manually scale the more difficult ionograms. The automated processing of the digitized ISIS ionograms is now underway, producing a much-needed database of topside electron density profiles for ionospheric modeling covering more than one solar cycle.

  18. Ionospheric data available on CD-ROM and on NDADS

    International Nuclear Information System (INIS)

    Bilitza, D.

    1996-01-01

    Information is provided on two CD-ROMs (for PCs) with ionospheric data: the ionosonde CD issued by NGDC/WDC-A-STP/NOAA/Boulder and the Atmosphere Explorer CD produced by NSSDC/WDC-A-R and S/NASA/Greenbelt. We also briefly describe the ionospheric/thermospheric data available through NSSDC's automated mail retrieval system (NDADS) and explain the procedure for obtaining NDADS data. (author). 3 figs

  19. Ionospheric threats to the integrity of airborne GPS users

    Science.gov (United States)

    Datta-Barua, Seebany

    The Global Positioning System (GPS) has both revolutionized and entwined the worlds of aviation and atmospheric science. As the largest and most unpredictable source of GPS positioning error, the ionospheric layer of the atmosphere, if left unchecked, can endanger the safety, or "integrity," of the single frequency airborne user. An augmentation system is a differential-GPS-based navigation system that provides integrity through independent ionospheric monitoring by reference stations. However, the monitor stations are not in general colocated with the user's GPS receiver. The augmentation system must protect users from possible ionosphere density variations occurring between its measurements and the user's. This study analyzes observations from ionospherically active periods to identify what types of ionospheric disturbances may cause threats to user safety if left unmitigated. This work identifies when such disturbances may occur using a geomagnetic measure of activity and then considers two disturbances as case studies. The first case study indicates the need for a non-trivial threat model for the Federal Aviation Administration's Local Area Augmentation System (LAAS) that was not known prior to the work. The second case study uses ground- and space-based data to model an ionospheric disturbance of interest to the Federal Aviation Administration's Wide Area Augmentation System (WAAS). This work is a step in the justification for, and possible future refinement of, one of the WAAS integrity algorithms. For both WAAS and LAAS, integrity threats are basically caused by events that may be occurring but are unobservable. Prior to the data available in this solar cycle, events of such magnitude were not known to be possible. This work serves as evidence that the ionospheric threat models developed for WARS and LAAS are warranted and that they are sufficiently conservative to maintain user integrity even under extreme ionospheric behavior.

  20. SAR Imaging through the Earth’s Ionosphere

    Science.gov (United States)

    2013-11-06

    Xiaoqing Pi, Anthony Freeman, Bruce Chapman, Paul Rosen, and Zhenhong Li . Imaging ionospheric inhomogeneities using spaceborne synthetic aperture radar. J...resolution SAR phase correction. IEEE Trans. Aerosp. Electron. Syst., 30(3):827–835, 1994. [30] Lianlin Li and Fang Li . Ionosphere tomography based on...Manduchi and G. A. Mian . Accuracy analysis for correlation-based image registartion algorithms. In Proceedings of the 1993 IEEE International

  1. Far-field coseismic ionospheric disturbances of Tohoku earthquake

    Czech Academy of Sciences Publication Activity Database

    Krasnov, V. M.; Drobzheva, Ya. V.; Chum, Jaroslav

    2015-01-01

    Roč. 135, December (2015), s. 12-21 ISSN 1364-6826 R&D Projects: GA ČR(CZ) GC15-07281J Institutional support: RVO:68378289 Keywords : earthquake * infrasonic waves * ionospheric disturbances * infrasound triggered by the earthquake * co-seismic ionospheric perturbations * modeling * remote sensing Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.463, year: 2015 http://www.sciencedirect.com/science/article/pii/S1364682615300584

  2. Ionospheric parameters as the precursors of disturbed geomagnetic conditions

    Science.gov (United States)

    Blagoveshchensky, D. V.; Sergeeva, M. A.; Kozlovsky, A.

    2017-12-01

    Geomagnetic storms and substorms are the principal elements of the disturbed Space Weather conditions. The aim of the study was to reveal the ionospheric precursors that can be used to forecast geomagnetic disturbance beginning. To study the ionospheric processes before, during and after magnetic storms and substorms data from Sodankylä Geophysical Observatory was used (geomagnetic coordinates: 64.1oN, 119.2oE). In earlier works the Main Effect (ME) was revealed for substorms. It consists of the following steps: (a) the increase of critical frequency foF2 from its quiet median before and during the substorm growth phase, four-five hours before To moment that is the moment of the expansion phase onset, (b) the foF2 decrease to the level lower than its median just after To and until Te that is the moment of the end of the expansion phase, (c) the issue ;a; repeated during the recovery phase (d) two bell-shape spikes in the cutoff frequency values foEs: first spike occurs three hours before To, second spike - during the expansion phase within the interval between To and Te. In the present work it is shown that ME manifestations can be used as precursors of magnetic substorms at high-latitudes (geomagnetic latitudes 50oN-65oN). In particular, the foF2 growth some hours before To can be used as a precursor of substorm development. The first foEs bell-shaped spike also can be used for short-term forecasting, two-three hours in advance of a substorm. Furthermore, the storms between 2008 and 2012 were studied. It was revealed that the similar ME also takes place in the case of magnetic storms but within the different time scale. More specifically, the first ME maximum in foF2 values occurs one-two days before the storm beginning and can be used as its precursor. In addition, the foEs spike takes place approximately ten hours before a storm and also can be used for the prediction of the storm beginning.

  3. Model and control scheme for recirculation mode direct steam generation parabolic trough solar power plants

    International Nuclear Information System (INIS)

    Guo, Su; Liu, Deyou; Chen, Xingying; Chu, Yinghao; Xu, Chang; Liu, Qunming; Zhou, Ling

    2017-01-01

    Highlights: •A nonlinear dynamic model of recirculation DSG parabolic trough is developed. •Collector row, water separator and spray attemperator are modeled, respectively. •The dynamic behaviors of the collector field are simulated and analyzed. •Transfer functions of water level and outlet fluid temperature are derived. •Multi-model switching generalized predictive control strategy is developed. -- Abstract: This work describes and evaluates a new nonlinear dynamic model, and a new generalized predictive control scheme for a collector field of direct steam generation parabolic troughs in recirculation mode. Modeling the dynamic behaviors of collector fields is essential to design, testing and validation of automatic control systems for direct steam generation parabolic troughs. However, the behaviors of two-phase heat transfer fluids impose challenges to simulating and developing process control schemes. In this work, a new nonlinear dynamic model is proposed, based on the nonlinear distributed parameter and the nonlinear lumped parameter methods. The proposed model is used to simulate and analyze the dynamic behaviors of the entire collector field for recirculation mode direct steam generation parabolic troughs under different weather conditions, without excessive computational costs. Based on the proposed model, transfer functions for both the water level of the separator and outlet steam temperatures are derived, and a new multi-model switching generalized predictive control scheme is developed for simulated control of the plant behaviors for a wide region of operational conditions. The proposed control scheme achieves excellent control performance and robustness for systems with long delay, large inertia and time-varying parameters, and efficiently solves the model mismatching problem in direct steam generation parabolic troughs. The performances of the model and control scheme are validated with design data from the project of Integration of Direct

  4. Optical analysis of a photovoltaic V-trough system installed in western India.

    Science.gov (United States)

    Maiti, Subarna; Sarmah, Nabin; Bapat, Pratap; Mallick, Tapas K

    2012-12-20

    The low concentrating photovoltaic (PV) system such as a 2× V-trough system can be a promising choice for enhancing the power output from conventional PV panels with the inclusion of thermal management. This system is more attractive when the reflectors are retrofitted to the stationary PV panels installed in a high aspect ratio in the north-south direction and are tracked 12 times a year manually according to preset angles, thus eliminating the need of diurnal expensive tracking. In the present analysis, a V-trough system facing exactly the south direction is considered, where the tilt angle of the PV panels' row is kept constant at 18.34°. The system is installed on the terrace of CSIR-Central Salt and Marine Chemicals Research Institute in Bhavnagar, Gujarat, India (21.47 N, 71.15 E). The dimension of the entire PV system is 9.64 m×0.55 m. The V-troughs made of anodized aluminum reflectors (70% specular reflectivity) had the same dimensions. An in-house developed; experimentally validated Monte Carlo ray-trace model was used to study the effect of the angular variation of the reflectors throughout a year for the present assembly. Results of the ray trace for the optimized angles showed the maximum simulated optical efficiency to be 85.9%. The spatial distribution of solar intensity over the 0.55 m dimension of the PV panel due to the V-trough reflectors was also studied for the optimized days in periods that included solstices and equinoxes. The measured solar intensity profiles with and without the V-trough system were used to calculate the actual optical efficiencies for several sunny days in the year, and results were validated with the simulated efficiencies within an average error limit of 10%.

  5. Pseudobreakup and substorm growth phase in the ionosphere and magnetosphere

    International Nuclear Information System (INIS)

    Koskinin, H.E.J.; Pellinen, R.J.; Pulkkinen, T.I.; Lopez, R.E.; Baker, D.N.; Boesinger, T.

    1993-01-01

    The authors present space and ground based observations made during the growth phase and the onset of a substorm on August 31, 1986. Roughly 20 minutes after the var-epsilon parameter at the magnetopause had exceeded 10 11 W, the AMPTE Charge Composition Explorer spacecraft observed an increase in energetic particle fluxes consistent with magnetic field depolarization. The craft was close to magnetic midnight at a geocentric distance of 8.7R E . The event had the initial signature of a substorm onset, but it did not lead to a full-scale substorm expansion based on several ground based observations. There were no large particle injection events at geostationary orbit. After another 20 minutes the event did enter a normal substorm expansion phase. The authors interpret the initial activation as a open-quotes pseudobreakupclose quotes. They correlate observations made by spacecraft in the near-Earth plasma sheet, with ground based observations of the ionospheric development from magnetometer and electric field measurements from the STARE radar. The strength and the consequences are concluded to be the main differences of pseudobreakups and ordinary breakups

  6. Ionospheric flow during extended intervals of northward but By -dominated IMF

    Directory of Open Access Journals (Sweden)

    J. B. Sigwarth

    Full Text Available We present SuperDARN radar observations of the nightside high-latitude ionospheric flow during two 6-hour intervals of quasi-steady northward interplanetary magnetic field (IMF. During both intervals (01:30–07:30 UT on 2 December and 21:00–03:00 UT on 14/15 December 1999, the solar wind and IMF remained relatively steady with Bz positive and By negative, such that the IMF clock angle was ~ - 50° to - 60°. Throughout both intervals the radar data clearly indicate the presence of a highly distorted By-dominated twin cell flow pattern, indicative of an open magnetosphere, which is confirmed by DMSP and auroral data. Estimates of the changes in open flux present during each interval indicate approximately balanced dayside and nightside reconnection at rates of ~ 30–35 kV over the full 6 h. However, strong bursts of flow with speeds of over ~ 1000 ms-1 are observed near magnetic midnight on time scales of ~ 1 h, which are associated with increases in the transpolar voltage. These are indicative of the net closure of open flux by recon-nection in the tail. During one large flow burst, the night-side reconnection rate is estimated to have been ~ 1.5 times the dayside rate, i.e. ~ 45–60 kV compared with ~ 30–40 kV. Magnetic bays, which would indicate the formation of a sub-storm current wedge, are not observed in association with these bursts. In addition, no low-latitude Pi2s or geostationary particle injections were observed, although some local, small amplitude Pi2-band (5–50 mHz activity does accompany the bursts. Coincident measurements of the flow and of the low amplitude magnetic perturbations reveal nightside ionospheric conductances of no more than a few mho, indicative of little associated precipitation. Therefore, we suggest that the flow bursts are the ionospheric manifestation of bursty reconnection events occurring in the more distant geomagnetic tail. The main implication of these findings is that, under the circumstances

  7. Evaluation of the performance of DIAS ionospheric forecasting models

    Directory of Open Access Journals (Sweden)

    Tsagouri Ioanna

    2011-08-01

    Full Text Available Nowcasting and forecasting ionospheric products and services for the European region are regularly provided since August 2006 through the European Digital upper Atmosphere Server (DIAS, http://dias.space.noa.gr. Currently, DIAS ionospheric forecasts are based on the online implementation of two models: (i the solar wind driven autoregression model for ionospheric short-term forecast (SWIF, which combines historical and real-time ionospheric observations with solar-wind parameters obtained in real time at the L1 point from NASA ACE spacecraft, and (ii the geomagnetically correlated autoregression model (GCAM, which is a time series forecasting method driven by a synthetic geomagnetic index. In this paper we investigate the operational ability and the accuracy of both DIAS models carrying out a metrics-based evaluation of their performance under all possible conditions. The analysis was established on the systematic comparison between models’ predictions with actual observations obtained over almost one solar cycle (1998–2007 at four European ionospheric locations (Athens, Chilton, Juliusruh and Rome and on the comparison of the models’ performance against two simple prediction strategies, the median- and the persistence-based predictions during storm conditions. The results verify operational validity for both models and quantify their prediction accuracy under all possible conditions in support of operational applications but also of comparative studies in assessing or expanding the current ionospheric forecasting capabilities.

  8. Modeling the Ionosphere with GPS and Rotation Measure Observations

    Science.gov (United States)

    Malins, J. B.; Taylor, G. B.; White, S. M.; Dowell, J.

    2017-12-01

    Advances in digital processing have created new tools for looking at and examining the ionosphere. We have combined data from dual frequency GPSs, digital ionosondes and observations from The Long Wavelength Array (LWA), a 256 dipole low frequency radio telescope situated in central New Mexico in order to examine ionospheric profiles. By studying polarized pulsars, the LWA is able to very accurately determine the Faraday rotation caused by the ionosphere. By combining this data with the international geomagnetic reference field, the LWA can evaluate ionospheric profiles and how well they predict the actual Faraday rotation. Dual frequency GPS measurements of total electron content, as well as measurements from digisonde data were used to model the ionosphere, and to predict the Faraday rotation to with in 0.1 rad/m2. Additionally, it was discovered that the predicted topside profile of the digisonde data did not accurate predict faraday rotation measurements, suggesting a need to reexamine the methods for creating the topside predicted profile. I will discuss the methods used to measure rotation measure and ionosphere profiles as well as discuss possible corrections to the topside model.

  9. New Method for Solving Inductive Electric Fields in the Ionosphere

    Science.gov (United States)

    Vanhamäki, H.

    2005-12-01

    We present a new method for calculating inductive electric fields in the ionosphere. It is well established that on large scales the ionospheric electric field is a potential field. This is understandable, since the temporal variations of large scale current systems are generally quite slow, in the timescales of several minutes, so inductive effects should be small. However, studies of Alfven wave reflection have indicated that in some situations inductive phenomena could well play a significant role in the reflection process, and thus modify the nature of ionosphere-magnetosphere coupling. The input to our calculation method are the time series of the potential part of the ionospheric electric field together with the Hall and Pedersen conductances. The output is the time series of the induced rotational part of the ionospheric electric field. The calculation method works in the time-domain and can be used with non-uniform, time-dependent conductances. In addition no particular symmetry requirements are imposed on the input potential electric field. The presented method makes use of special non-local vector basis functions called Cartesian Elementary Current Systems (CECS). This vector basis offers a convenient way of representing curl-free and divergence-free parts of 2-dimensional vector fields and makes it possible to solve the induction problem using simple linear algebra. The new calculation method is validated by comparing it with previously published results for Alfven wave reflection from uniformly conducting ionosphere.

  10. Uplift of Ionospheric Oxygen Ions During Extreme Magnetic Storms

    Science.gov (United States)

    Tsurutani, Bruce T.; Mannucci, Anthony J.; Verkhoglyadova, Olga P.; Huba, Joseph; Lakhina, Gurbax S.

    2013-01-01

    Research reported earlier in literature was conducted relating to estimation of the ionospheric electrical field, which may have occurred during the September 1859 Carrington geomagnetic storm event, with regard to modern-day consequences. In this research, the NRL SAMI2 ionospheric code has been modified and applied the estimated electric field to the dayside ionosphere. The modeling was done at 15-minute time increments to track the general ionospheric changes. Although it has been known that magnetospheric electric fields get down into the ionosphere, it has been only in the last ten years that scientists have discovered that intense magnetic storm electric fields do also. On the dayside, these dawn-to-dusk directed electric fields lift the plasma (electrons and ions) up to higher altitudes and latitudes. As plasma is removed from lower altitudes, solar UV creates new plasma, so the total plasma in the ionosphere is increased several-fold. Thus, this complex process creates super-dense plasmas at high altitudes (from 700 to 1,000 km and higher).

  11. Drag Reduction trough Special paints Coated on the hull

    OpenAIRE

    Izaguirre Alza, Patricia; Pérez Rojas, Luis; Núñez Basáñez, José Fernando

    2010-01-01

    The economic recession, the environmental impact as well as the continuous fossil fuel consumption encourage actions that focus on saving energy. In the vessels sector, one of the main objectives has always been to reach a hydro-dynamically optimum hull which gave the desired speed with minimum power. Hydrodynamic drag is basically divided into two parts: a) the friction between the water and the hull, and b) the wave generation due to the free-surface air-water. Presented in this paper...

  12. Worldwide Hourly Values of Ionospheric Characteristics: foF2, M(3000)F2, hF2,FoF1, M(3000)F1, hF, FoE, hE, foE2, hE2, foEs, fbEs, fmI, and FxI

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The ionosphere is that part of the Earth's atmosphere that results mainly from the ionizing effect of Solar electromagnetic radiation. For poleware latitudes, the...

  13. Tectonics of the southern Bleckenstedt trough in the mining area of the oolitic iron ore deposit (midle coral oolithe) of Konrad mine near Salzgitter, Lower Saxony

    International Nuclear Information System (INIS)

    Schloenbach, R.

    1985-01-01

    The regional tectonic development of the Bleckenstedt trough and the large-scale faults in Konrad mine (N-S, trough fault, NW-SE, Sauingen trough, E-W, Bleckenstedt fault), which date from a different period, were evaluated, and a tectogenetic analysis of the small-scale tectonic structure was related to halokinetic movements. (DG) [de

  14. Initial results form the operation of two argon ion generators in the auroral ionosphere

    International Nuclear Information System (INIS)

    Erlandson, R.E.; Cahill, L.J. Jr.; Pollock, C.J.; Arnoldy, R.L.; Scales, W.A.; Kintner, P.M.

    1987-01-01

    Two argon ion generators were operated during a sounding rocket flight from Sondre Stromfjord, Greenland, on February 10, 1985. The ion generators were flown to investigate ion beam dynamics and beam effects on the ionosphere. The other major purpose of the flight was investigation of auroral electrodynamics as the rocket passed over auroral arcs. One generator emitted an ion beam perpendicular to the magnetic field and the other a beam parallel to the field. Ion detectors, an electric field meter and wave receivers were carried on the main payload to provide diagnostic measurements during the ion beam operations. Seventeen operations of the generators were observed over a 480-s interval before the rocket reentered the atmosphere. There was evidence of heating of the ionosphere around the subpayload during each ion beam emission. Ions of energy 100 to 200 eV, the ion beam energy range, were observed at the main payload during the first seven operations of each generator, with payload separation distances up to 800 m, reaching the main payload from directions appropriate for beam ions. Waves were observed during most of the first seven operations of each beam. Hydrogen, helium and oxygen cyclotron harmonics were observed in some of the perpendicular-beam operations. Waves were weak or absent during the first and third parallel-beam operations at separation distances near 80 and 320 m. In general the waves generated by the parallel beam were weaker than those generated by the perpendicular beam

  15. A Methodology to Assess Ionospheric Models for GNSS

    Science.gov (United States)

    Rovira-Garcia, Adria; Juan, José Miguel; Sanz, Jaume; González-Casado, Guillermo; Ibánez, Deimos

    2015-04-01

    Testing the accuracy of the ionospheric models used in the Global Navigation Satellite System (GNSS) is a long-standing issue. It is still a challenging problem due to the lack of accurate enough slant ionospheric determinations to be used as a reference. The present study proposes a methodology to assess any ionospheric model used in satellite-based applications and, in particular, GNSS ionospheric models. The methodology complements other analysis comparing the navigation based on different models to correct the code and carrier-phase observations. Specifically, the following ionospheric models are assessed: the operational models broadcast in the Global Positioning System (GPS), Galileo and the European Geostationary Navigation Overlay System (EGNOS), the post-process Global Ionospheric Maps (GIMs) from different analysis centers belonging to the International GNSS Service (IGS) and, finally, a new GIM computed by the gAGE/UPC research group. The methodology is based in the comparison between the predictions of the ionospheric model with actual unambiguous carrier-phase measurements from a global distribution of permanent receivers. The differences shall be separated into the hardware delays (a receiver constant plus a satellite constant) per data interval, e.g., a day. The condition that these Differential Code Biases (DCBs) are commonly shared throughout the world-wide network of receivers and satellites provides a global character to the assessment. This approach generalizes simple tests based on double differenced Slant Total Electron Contents (STECs) between pairs of satellites and receivers on a much local scale. The present study has been conducted during the entire 2014, i.e., the last Solar Maximum. The seasonal and latitudinal structures of the results clearly reflect the different strategies used by the different models. On one hand, ionospheric model corrections based on a grid (IGS-GIMs or EGNOS) are shown to be several times better than the models

  16. The private-public cooperation in innovation trough technology centres

    International Nuclear Information System (INIS)

    Callejon, M.; Barge-Gil, A.; Lopez, A.

    2007-01-01

    The Technology Centres (TCS) are important suppliers of technology for Spanish firms. The objective of this paper is to improve the knowledge about Spanish TCS. Firstly, we present the main characteristics and the evolution of the Spanish TCS. The second question examined refers to the great heterogeneity of this kind of agents. In this sense, we present a cluster analysis using two basic characteristics of the TCS: services to firms and technological strength. Thirdly, we analyze the adjustment of the TCS to the National Innovation System and their foreseeable evolution as basic agents of this system. Finally, we summarize the programs of public support for TCS started up by the Ministry of Industry, Tourism and Trade. (Author) 11 refs

  17. Main Memory DBMS

    NARCIS (Netherlands)

    P.A. Boncz (Peter); L. Liu (Lei); M. Tamer Özsu

    2008-01-01

    htmlabstractA main memory database system is a DBMS that primarily relies on main memory for computer data storage. In contrast, normal database management systems employ hard disk based persisntent storage.

  18. A New Approach for Identifying Ionospheric Gradients in the Context of the Gagan System

    Science.gov (United States)

    Kudala, Ravi Chandra

    The Indian Space Research Organization and the Airports Authority of India are jointly implementing the Global Positioning System (GPS) aided GEO Augmented Navigation (GAGAN) system in order to meet the following required navigation performance (RNP) parameters: integrity, continuity, accuracy, and availability (for aircraft operations). Such a system provides the user with orbit, clock, and ionospheric corrections in addition to ranging signals via the geostationary earth orbit satellite (GEOSAT). The equatorial ionization anomaly (EIA), due to rapid non-uniform electron-ion recombination that persists on the Indian subcontinent, causes ionospheric gradients. Ionospheric gradients represent the most severe threat to high-integrity differential GNSS systems such as GAGAN. In order to ensure integrity under conditions of an ionospheric storm, the following three objectives must be met: careful monitoring, error bounding, and sophisticated storm-front modeling. The first objective is met by continuously tracking data due to storms, and, on quiet days, determining precise estimates of the threat parameters from reference monitoring stations. The second objective is met by quantifying the above estimates of threat parameters due to storms through maximum and minimum typical thresholds. In the context GAGAN, this work proposes a new method for identifying ionospheric gradients, in addition to determining an appropriate upper bound, in order to sufficiently understand error during storm days. Initially, carrier phase data of the GAGAN network from Indian TEC stations for both storm and quiet days was used for estimating ionospheric spatial and temporal gradients (the vertical ionospheric gradient (σVIG) and the rate of the TEC index (ROTI), respectively) in multiple viewing directions. Along similar lines, using the carrier to noise ratio (C/N0) for the same data, the carrier to noise ratio index (σCNRI) was derived. Subsequently, the one-toone relationship between

  19. Effect of Ionosphere on Geostationary Communication Satellite Signals

    Science.gov (United States)

    Erdem, Esra; Arikan, Feza; Gulgonul, Senol

    2016-07-01

    Geostationary orbit (GEO) communications satellites allow radio, television, and telephone transmissions to be sent live anywhere in the world. They are extremely important in daily life and also for military applications. Since, satellite communication is an expensive technology addressing crowd of people, it is critical to improve the performance of this technology. GEO satellites are at 35,786 kilometres from Earth's surface situated directly over the equator. A satellite in a geostationary orbit (GEO) appears to stand still in the sky, in a fixed position with respect to an observer on the earth, because the satellite's orbital period is the same as the rotation rate of the Earth. The advantage of this orbit is that ground antennas can be fixed to point towards to satellite without their having to track the satellite's motion. Radio frequency ranges used in satellite communications are C, X, Ku, Ka and even EHG and V-band. Satellite signals are disturbed by atmospheric effects on the path between the satellite and the receiver antenna. These effects are mostly rain, cloud and gaseous attenuation. It is expected that ionosphere has a minor effect on the satellite signals when the ionosphere is quiet. But there are anomalies and perturbations on the structure of ionosphere with respect to geomagnetic field and solar activity and these conditions may cause further affects on the satellite signals. In this study IONOLAB-RAY algorithm is adopted to examine the effect of ionosphere on satellite signals. IONOLAB-RAY is developed to calculate propagation path and characteristics of high frequency signals. The algorithm does not have any frequency limitation and models the plasmasphere up to 20,200 km altitude, so that propagation between a GEO satellite and antenna on Earth can be simulated. The algorithm models inhomogeneous, anisotropic and time dependent structure of the ionosphere with a 3-D spherical grid geometry and calculates physical parameters of the

  20. Cubesat-Based Dtv Receiver Constellation for Ionospheric Tomography

    Science.gov (United States)

    Bahcivan, H.; Leveque, K.; Doe, R. A.

    2013-12-01

    The Radio Aurora Explorer mission, funded by NSF's Space Weather and Atmospheric Research program, has demonstrated the utility of CubeSat-based radio receiver payloads for ionospheric research. RAX has primarily been an investigation of microphysics of meter-scale ionospheric structures; however, the data products are also suitable for research on ionospheric effects on radio propagation. To date, the spacecraft has acquired (1) ground-based UHF radar signals that are backscattered from meter-scale ionospheric irregularities, which have been used to measure the dispersion properties of meter-scale plasma waves and (2) ground-based signals, directly on the transmitter-spacecraft path, which have been used to measure radio propagation disturbances (scintillations). Herein we describe the application of a CubeSat constellation of UHF receivers to expand the latter research topic for global-scale ionospheric tomography. The enabling factor for this expansion is the worldwide availability of ground-based digital television (DTV) broadcast signals whose characteristics are optimal for scintillation analysis. A significant part of the populated world have transitioned, or soon to be transitioned, to DTV. The DTV signal has a standard format that contains a highly phase-stable pilot carrier that can be readily adapted for propagation diagnostics. A multi-frequency software-defined radar receiver, similar to the RAX payload, can measure these signals at a large number of pilot carrier frequencies to make radio ray and diffraction tomographic measurements of the ionosphere and the irregularities contained in it. A constellation of CubeSats, launched simultaneously, or in sequence over years, similar to DMSPs, can listen to the DTV stations, providing a vast and dense probing of the ionosphere. Each spacecraft can establish links to a preprogrammed list of DTV stations and cycle through them using time-division frequency multiplexing (TDFM) method. An on board program can

  1. Oceanic Sub-Moho Reflectors in and Around the Segmentation Boundary Between the Tonankai-Nankai Earthquake Area, the Central Nankai Trough

    Science.gov (United States)

    Nakanishi, A.; Kodaira, S.; Miura, S.; Ito, A.; Sato, T.; Park, J.; Obana, K.; Kaneda, Y.

    2006-12-01

    The Nankai Trough is a unique subduction zone because the recurrence intervals of M8 class earthquakes and the segmentation of rupture zones are well documented on the basis of geophysical, geological and historic data. In 2004, large intraslab earthquake (Mw7.5) occurred southeast off the Kii Peninsula, the central Nankai Trough. Recent ocean bottom seismograph observation off the Kii Peninsula shows seismicity concentrated in the oceanic crust and the uppermost mantle. To understand the genesis of such intraslab earthquakes and its relation to large interplate earthquakes as well as to obtain an entire structural image of Nankai Trough subduction seismogenic zone, a wide-angle reflection/refraction survey across the coseismic rupture zone of the Tonankai earthquake was conducted in 2004. This research is part of "Structure research on plate dynamics of the presumed rupture zone of the Tonankai-Nankai Earthquakes" funded by Ministry of Education, Culture, Sports, Science and Technology. The result of structural image shows a bit thicker oceanic crust (>8km) subducting landward, and the existence of oceanic sub-Moho reflectors in the uppermost mantle. The aftershocks of the 2004 off Kii Peninsula earthquake are distributed within the oceanic crust and the uppermantle, which is not consistent with the estimated fault plane of main shock. Comparing the structural image with this aftershock distribution and usual seismicity in the uppermost mantle, the depth of the oceanic sub-Moho reflectors and the intraslab events within the uppermantle are both distributed around 20km. We consider that such sub-Moho reflectors may become a seismic fault of intraslab earthquakes.

  2. A finite-volume model of a parabolic trough photovoltaic/thermal collector: Energetic and exergetic analyses

    International Nuclear Information System (INIS)

    Calise, Francesco; Palombo, Adolfo; Vanoli, Laura

    2012-01-01

    This paper presents a detailed finite-volume model of a concentrating photovoltaic/thermal (PVT) solar collector. The PVT solar collector consists in a parabolic trough concentrator and a linear triangular receiver. The bottom surfaces of the triangular receiver are equipped with triple-junction cells whereas the top surface is covered by an absorbing surface. The cooling fluid (water) flows inside a channel along the longitudinal direction of the PVT collector. The system was discretized along its axis and, for each slice of the discretized computational domain, mass and energy balances were considered. The model allows one to evaluate both thermodynamic and electrical parameters along the axis of the PVT collector. Then, for each slice of the computational domain, exergy balances were also considered in order to evaluate the corresponding exergy destruction rate and exergetic efficiency. Therefore, the model also calculates the magnitude of the irreversibilities inside the collector and it allows one to detect where these irreversibilities occur. A sensitivity analysis is also performed with the scope to evaluate the effect of the variation of the main design/environmental parameters on the energetic and exergetic performance of the PVT collector. -- Highlights: ► The paper investigates an innovative concentrating photovoltaic thermal solar collector. ► The collector is equipped with triple-junction photovoltaic layers. ► A local exergetic analysis is performed in order to detect sources of irreversibilities. ► Irreversibilities are mainly due to the heat transfer between sun and PVT collector.

  3. Thermodynamic performance assessment of an integrated geothermal powered supercritical regenerative organic Rankine cycle and parabolic trough solar collectors

    International Nuclear Information System (INIS)

    Cakici, Duygu Melek; Erdogan, Anil; Colpan, Can Ozgur

    2017-01-01

    In this study, the thermodynamic performance of an integrated geothermal powered supercritical regenerative organic Rankine cycle (ORC) and parabolic trough solar collectors (PTSC) is assessed. A thermal model based on the principles of thermodynamics (mass, energy, and exergy balances) and heat transfer is first developed for the components of this integrated system. This model gives the performance assessment parameters of the system such as the electrical and exergetic efficiencies, total exergy destruction and loss, productivity lack, fuel depletion ratio, and improvement potential rate. To validate this model, the data of an existing geothermal power plant based on a supercritical ORC and literature data for the PTSC are used. After validation, parametric studies are conducted to assess the effect of some of the important design and operating parameters on the performance of the system. As a result of these studies, it is found that the integration of ORC and PTSC systems increases the net power output but decreases the electrical and exergetic efficiencies of the integrated system. It is also shown that R134a is the most suitable working fluid type for this system; and the PTSCs and air cooled condenser are the main sources of the exergy destructions. - Highlights: • A geothermal power plant integrated with PTSC is investigated. • Different approaches for defining the exergetic efficiency are used. • The PTSCs and ACC are the main sources of the exergy destructions. • R134a gives the highest performance for any number of collectors studied.

  4. Biogeochemical processes controlling authigenic carbonate formation within the sediment column from the Okinawa Trough

    Science.gov (United States)

    Li, Jiwei; Peng, Xiaotong; Bai, Shijie; Chen, Zhiyan; Van Nostrand, Joy D.

    2018-02-01

    Authigenic carbonates are one type of conspicuous manifestation in seep environments that can provide long-term archives of past seepage activity and methane cycling in the oceans. Comprehensive investigations of the microbial community functional structure and their roles in the process of carbonate formation are, however, lacking. In this study, the mineralogical, geochemical, and microbial functional composition were examined in seep carbonate deposits collected from the west slope of the northern section of the Okinawa Trough (OT). The aim of this work was to explore the correspondence between the mineralogical phases and microbial metabolism during carbonate deposit formation. The mineralogical analyses indicated that authigenic carbonate minerals (aragonite, magnesium-rich calcite, dolomite, ankerite and siderite) and iron-bearing minerals (limonite, chlorite, and biotite) were present in these carbonate samples. The carbon and oxygen isotopic values of the carbonate samples varied between -51.1‰ to -4.7‰ and -4.8‰ to 3.7‰, respectively. A negative linear correlation between carbon and oxygen isotopic compositions was found, indicating a mixture of methane-derived diagenetic (low δ13C/high 18O) carbonates and detrital origin (high δ13C/low 18O) carbonates at the OT. GeoChip analyses suggested that various metabolic activities of microorganisms, including methanogenesis, methane oxidation, sulfite oxidation, sulfate reduction, and metal biotransformations, all occurred during the formation process. On the basis of these findings, the following model for the methane cycle and seep carbonate deposit formation in the sediment column at the OT is proposed: (1) in the upper oxidizing zone, aerobic methane oxidation was the main way of methane consumption; (2) in the sulfate methane transition zone, sulfate-dependent AOM (anaerobic oxidation of methane) consumes methane, and authigenic minerals such as aragonite, magnesium-calcite, and sulfide minerals

  5. The Role of Ionospheric Outflow Preconditioning in Determining Storm Geoeffectiveness

    Science.gov (United States)

    Welling, D. T.; Liemohn, M. W.; Ridley, A. J.

    2012-12-01

    It is now well accepted that ionospheric outflow plays an important role in the development of the plasma sheet and ring current during geomagnetic storms. Furthermore, even during quiet times, ionospheric plasma populates the magnetospheric lobes, producing a reservoir of hydrogen and oxygen ions. When the Interplanetary Magnetic Field (IMF) turns southward, this reservoir is connected to the plasma sheet and ring current through magnetospheric convection. Hence, the conditions of the ionosphere and magnetospheric lobes leading up to magnetospheric storm onset have important implications for storm development. Despite this, there has been little research on this preconditioning; most global simulations begin just before storm onset, neglecting preconditioning altogether. This work explores the role of preconditioning in determining the geoeffectiveness of storms using a coupled global model system. A model of ionospheric outflow (the Polar Wind Outflow Model, PWOM) is two-way coupled to a global magnetohydrodynamic model (the Block-Adaptive Tree Solar wind Roe-type Upwind Scheme, BATS-R-US), which in turn drives a ring current model (the Ring current Atmosphere interactions Model, RAM). This unique setup is used to simulate an idealized storm. The model is started at many different times, from 1 hour before storm onset to 12 hours before. The effects of storm preconditioning are examined by investigating the total ionospheric plasma content in the lobes just before onset, the total ionospheric contribution in the ring current just after onset, and the effects on Dst, magnetic elevation angle at geosynchronous, and total ring current energy density. This experiment is repeated for different solar activity levels as set by F10.7 flux. Finally, a synthetic double-dip storm is constructed to see how two closely spaced storms affect each other by changing the preconditioning environment. It is found that preconditioning of the magnetospheric lobes via ionospheric

  6. An alternative ionospheric correction model for global navigation satellite systems

    Science.gov (United States)

    Hoque, M. M.; Jakowski, N.

    2015-04-01

    The ionosphere is recognized as a major error source for single-frequency operations of global navigation satellite systems (GNSS). To enhance single-frequency operations the global positioning system (GPS) uses an ionospheric correction algorithm (ICA) driven by 8 coefficients broadcasted in the navigation message every 24 h. Similarly, the global navigation satellite system Galileo uses the electron density NeQuick model for ionospheric correction. The Galileo satellite vehicles (SVs) transmit 3 ionospheric correction coefficients as driver parameters of the NeQuick model. In the present work, we propose an alternative ionospheric correction algorithm called Neustrelitz TEC broadcast model NTCM-BC that is also applicable for global satellite navigation systems. Like the GPS ICA or Galileo NeQuick, the NTCM-BC can be optimized on a daily basis by utilizing GNSS data obtained at the previous day at monitor stations. To drive the NTCM-BC, 9 ionospheric correction coefficients need to be uploaded to the SVs for broadcasting in the navigation message. Our investigation using GPS data of about 200 worldwide ground stations shows that the 24-h-ahead prediction performance of the NTCM-BC is better than the GPS ICA and comparable to the Galileo NeQuick model. We have found that the 95 percentiles of the prediction error are about 16.1, 16.1 and 13.4 TECU for the GPS ICA, Galileo NeQuick and NTCM-BC, respectively, during a selected quiet ionospheric period, whereas the corresponding numbers are found about 40.5, 28.2 and 26.5 TECU during a selected geomagnetic perturbed period. However, in terms of complexity the NTCM-BC is easier to handle than the Galileo NeQuick and in this respect comparable to the GPS ICA.

  7. On the effect of ionospheric delay on geodetic relative GPS positioning

    NARCIS (Netherlands)

    Georgiadou, P.Y.; Kleusberg, A.

    1988-01-01

    Uncorrected ionospheric delay is one of the factors limiting the accuracy in geodetic relative positioning with single frequency Global Positioning System (GPS) carrier phase observations. Dual frequency measurements can be combined to eliminate the ionospheric delay in the observations. A

  8. Assessment of the Impact of Various Ionospheric Models on High-Frequency Signal Raytracing

    National Research Council Canada - National Science Library

    Werner, Joshua T

    2007-01-01

    .... Ionospheric refraction can strongly affect the propagation of HF signals. Consequently, Department of Defense missions such as over-the-horizon RADAR, HF communications, and geo-location all depend on an accurate specification of the ionosphere...

  9. Ionospheric Values (Daily Work Sheets), F-Plots, Tabulations, Booklets, Catalogs, and Log Books

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These ionospheric data consist of scaling notes, equipment usage logs, and ionospheric values in the form of daily work sheets, F-Plots, tabulations, and booklets....

  10. DEVELOPMENT AND PRELIMINARY TESTING OF A PARABOLIC TROUGH SOLAR WATER HEATER

    Directory of Open Access Journals (Sweden)

    O. A. Lasode

    2011-06-01

    Full Text Available Solar energy is a high-temperature, high-energy radiant energy source, with tremendous advantages over other alternative energy sources. It is a reliable, robust renewable resource which is largely undeveloped. The design and fabrication of parabolic trough solar water heater for water heating was executed. The procedure employed includes the design, construction and testing stages. The equipment which is made up of the reflector surface (curved mirror, reflector support, absorber pipe and a stand was fabricated using locally sourced materials. The results obtained. compared favourably with other research works in the literature. It depicts that employing a suitable design, selection of time of heating and proper focusing of the reflected rays to the focal spot region, solar radiation can efficiently be utilized for water heating in a tropical environment. This work presents a parabolic trough solar water heater as a suitable renewable energy technology for reducing water-heating costs.

  11. Interseismic Coupling-Based Earthquake and Tsunami Scenarios for the Nankai Trough

    Science.gov (United States)

    Baranes, H.; Woodruff, J. D.; Loveless, J. P.; Hyodo, M.

    2018-04-01

    Theoretical modeling and investigations of recent subduction zone earthquakes show that geodetic estimates of interseismic coupling and the spatial distribution of coseismic rupture are correlated. However, the utility of contemporary coupling in guiding construction of rupture scenarios has not been evaluated on the world's most hazardous faults. Here we demonstrate methods for scaling coupling to slip to create rupture models for southwestern Japan's Nankai Trough. Results show that coupling-based models produce distributions of ground surface deformation and tsunami inundation that are similar to historical and geologic records of the largest known Nankai earthquake in CE 1707 and to an independent, quasi-dynamic rupture model. Notably, these models and records all support focused subsidence around western Shikoku that makes the region particularly vulnerable to flooding. Results imply that contemporary coupling mirrors the slip distribution of a full-margin, 1707-type rupture, and Global Positioning System measurements of surface motion are connected with the trough's physical characteristics.

  12. Heat Loss Testing of Schott's 2008 PTR70 Parabolic Trough Receiver

    Energy Technology Data Exchange (ETDEWEB)

    Burkholder, Frank [National Renewable Energy Lab. (NREL), Golden, CO (United States); Kutscher, Chuck [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2009-05-01

    Two Schott 2008 model year PTR70 HCEs were tested on NREL's heat loss test stand from 100 - 500 deg C in 50 deg C increments. Absorber emittance was determined from the laboratory testing so that the performance of the HCEs could be modeled in a parabolic trough collector. Collector/HCE simulation results for many different field operation conditions were used to create heat loss correlationcoefficients for Excelergy and SAM. SAM estimates that the decreased emittance of the 2008 PTR70 will decrease the LCOE for parabolic trough power plants by 0.5 cents/kWh and increase the electricity generated by 5% relative to previous PTR70s. These conclusions assume that the 2008 PTR70 is supplied at the same cost and with the same optical performance as earlier PTR70 models.

  13. Seismic stratigraphic architecture of the Disko Bay trough-mouth fan system, West Greenland

    Science.gov (United States)

    Hofmann, Julia C.; Knutz, Paul C.

    2015-04-01

    Spatial and temporal changes of the Greenland Ice Sheet on the continental shelf bordering Baffin Bay remain poorly constrained. Then as now, fast-flowing ice streams and outlet glaciers have played a key role for the mass balance and stability of polar ice sheets. Despite their significance for Greenland Ice Sheet dynamics and evolution, our understanding of their long-term behaviour is limited. The central West Greenland margin is characterized by a broad continental shelf where a series of troughs extend from fjords to the shelf margin, acting as focal points for trough-mouth fan (TMF) accummulations. The sea-ward bulging morphology and abrupt shelf-break of these major depositional systems is generated by prograding depocentres that formed during glacial maxima when ice streams reached the shelf edge, delivering large amounts of subglacial sediment onto the continental slope (Ó Cofaigh et al., 2013). The aim of this study is to unravel the seismic stratigraphic architecture and depositional processes of the Disko Bay TMF, aerially the largest single sedimentary system in West Greenland, using 2D and 3D seismic reflection data, seabed bathymetry and stratigraphic information from exploration well Hellefisk-1. The south-west Disko Bay is intersected by a deep, narrow trough, Egedesminde Dyb, which extends towards the southwest and links to the shallower and broader cross-shelf Disko Trough (maximum water depths of > 1000 m and a trough length of c. 370 km). Another trough-like depression (trough length of c. 120 km) in the northern part of the TMF, indicating a previous position of the ice stream, can be distinguished on the seabed topographic map and the seismic images. The Disko Bay TMF itself extends from the shelf edge down to the abyssal plain (abyssal floor depths of 2000 m) of the southern Baffin Bay. Based on seismic stratigraphic configurations relating to reflection terminations, erosive patterns and seismic facies (Mitchum et al., 1977), the TMF

  14. Sensitivity analysis on the effect of key parameters on the performance of parabolic trough solar collectors

    Science.gov (United States)

    Muhlen, Luis S. W.; Najafi, Behzad; Rinaldi, Fabio; Marchesi, Renzo

    2014-04-01

    Solar troughs are amongst the most commonly used technologies for collecting solar thermal energy and any attempt to increase the performance of these systems is welcomed. In the present study a parabolic solar trough is simulated using a one dimensional finite element model in which the energy balances for the fluid, the absorber and the envelope in each element are performed. The developed model is then validated using the available experimental data . A sensitivity analysis is performed in the next step in order to study the effect of changing the type of the working fluid and the corresponding Reynolds number on the overall performance of the system. The potential improvement due to the addition of a shield on the upper half of the annulus and enhancing the convection coefficient of the heat transfer fluid is also studied.

  15. Sensitivity analysis on the effect of key parameters on the performance of parabolic trough solar collectors

    International Nuclear Information System (INIS)

    Muhlen, Luis S W; Najafi, Behzad; Rinaldi, Fabio; Marchesi, Renzo

    2014-01-01

    Solar troughs are amongst the most commonly used technologies for collecting solar thermal energy and any attempt to increase the performance of these systems is welcomed. In the present study a parabolic solar trough is simulated using a one dimensional finite element model in which the energy balances for the fluid, the absorber and the envelope in each element are performed. The developed model is then validated using the available experimental data . A sensitivity analysis is performed in the next step in order to study the effect of changing the type of the working fluid and the corresponding Reynolds number on the overall performance of the system. The potential improvement due to the addition of a shield on the upper half of the annulus and enhancing the convection coefficient of the heat transfer fluid is also studied.

  16. Study on a Mid-Temperature Trough Solar Collector with Multisurface Concentration

    Directory of Open Access Journals (Sweden)

    Zhengliang Li

    2015-01-01

    Full Text Available A new trough solar concentrator which is composed of multiple reflection surfaces is developed in this paper. The concentrator was analyzed firstly by using optical software. The variation curves of the collecting efficiency affected by tracking error and the deviation angle were given out. It is found that the deviation tolerance for the collector tracking system is about 8 degrees when the receiver is a 90 mm flat. The trough solar concentrators were tested under real weather conditions. The experiment results indicate that, the new solar concentrator was validated to have relative good collecting efficiency, which can be more than 45 percent when it operated in more 145°C. It also has the characteristics of rdust, wind, and snow resistance and low tracking precision requirements.

  17. DESIGN AND ENGINEERING BACKGROUND FOR STATION NETWORKS OF VERTICAL IONOSPHERE SOUNDING

    Directory of Open Access Journals (Sweden)

    A. Y. Grishentsev

    2013-05-01

    Full Text Available The paper deals with analysis of the network stations structure for ionosphere vertical sounding. Design features and creation principle of the program complexes for automated processing, analysis and storage of ionosphere sounding are considered. Conceptual model of complex database control system is created. The results of work are used in research practice of leading national organizations to study the ionosphere. Obtained application results of suggested algorithms and programs for automated processing and analysis of ionosphere vertical sounding are shown.

  18. Parallel electric fields from ionospheric winds

    International Nuclear Information System (INIS)

    Nakada, M.P.

    1987-01-01

    The possible production of electric fields parallel to the magnetic field by dynamo winds in the E region is examined, using a jet stream wind model. Current return paths through the F region above the stream are examined as well as return paths through the conjugate ionosphere. The Wulf geometry with horizontal winds moving in opposite directions one above the other is also examined. Parallel electric fields are found to depend strongly on the width of current sheets at the edges of the jet stream. If these are narrow enough, appreciable parallel electric fields are produced. These appear to be sufficient to heat the electrons which reduces the conductivity and produces further increases in parallel electric fields and temperatures. Calculations indicate that high enough temperatures for optical emission can be produced in less than 0.3 s. Some properties of auroras that might be produced by dynamo winds are examined; one property is a time delay in brightening at higher and lower altitudes

  19. Ionospheric shock waves triggered by rockets

    Directory of Open Access Journals (Sweden)

    C. H. Lin

    2014-09-01

    Full Text Available This paper presents a two-dimensional structure of the shock wave signatures in ionospheric electron density resulting from a rocket transit using the rate of change of the total electron content (TEC derived from ground-based GPS receivers around Japan and Taiwan for the first time. From the TEC maps constructed for the 2009 North Korea (NK Taepodong-2 and 2013 South Korea (SK Korea Space Launch Vehicle-II (KSLV-II rocket launches, features of the V-shaped shock wave fronts in TEC perturbations are prominently seen. These fronts, with periods of 100–600 s, produced by the propulsive blasts of the rockets appear immediately and then propagate perpendicularly outward from the rocket trajectory with supersonic velocities between 800–1200 m s−1 for both events. Additionally, clear rocket exhaust depletions of TECs are seen along the trajectory and are deflected by the background thermospheric neutral wind. Twenty minutes after the rocket transits, delayed electron density perturbation waves propagating along the bow wave direction appear with phase velocities of 800–1200 m s−1. According to their propagation character, these delayed waves may be generated by rocket exhaust plumes at earlier rocket locations at lower altitudes.

  20. Sedimentary response to volcanic activity in the Okinawa Trough since the last deglaciation

    Institute of Scientific and Technical Information of China (English)

    蒋富清; 李安春; 李铁刚

    2010-01-01

    To investigate the relationsh