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Sample records for medium-scale traveling ionospheric

  1. Observation of medium-scale traveling ionospheric disturbances over Peninsular Malaysia based on IPP trajectories

    Science.gov (United States)

    Husin, Asnawi; Abdullah, M.; Momani, M. A.

    2011-04-01

    Using vertical total electron content (VTEC) data that were derived from the Malaysia Real Time Kinematic GPS network (MyRTKnet), we analyzed the time variation of the VTEC with the occurrence of medium-scale traveling ionospheric disturbances (MSTIDs) based on ionospheric pierce point (IPP) trajectories. MSTIDs are known as ionospheric disturbance phenomena that generally induce perturbations in important ionospheric parameters such as the ionospheric total electron content (TEC). A method was developed to detect the existence of MSTIDs by identifying rapid fluctuations in the TEC by subjecting the TEC data time series to high-pass filtering. Data were evaluated using the GPS MyRTKnet network over Peninsular Malaysia in the month of September 2007 (a time period with relatively low geomagnetic activity). Two-dimensional maps over Peninsular Malaysia were constructed based on the IPP trajectories. Analysis of the cross correlation of detrended VTEC data from six MyRTKnet stations (PASP, KRAI, GMUS, CAME, TLKI and SBKB) yielded MSTID velocities of around 100 ± 50 m s-1 in the daytime and 60 ± 30 m s-1 in the nighttime, with occurrences of 17.6% and 13.7%, respectively. The results show that although the MSTID wave structure propagates southwestward, some waves also move northward. These waves were connected to the effect of the meridional neutral wind in the upper regions of the ionosphere (400 km).

  2. Studies of medium scale travelling ionospheric disturbances using TIGER SuperDARN radar sea echo observations

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    L.-S. He

    2004-12-01

    Full Text Available

    Seasonal and diurnal variations in the direction of propagation of medium-scale travelling ionospheric disturbances (MSTIDs have been investigated by analyzing sea echo returns detected by the TIGER SuperDARN radar located in Tasmania (43.4° S, 147.2° E geographic; –54.6°Λ. A strong dependency on local time was found, as well as significant seasonal variations. Generally, the propagation direction has a northward (i.e. equatorward component. In the early morning hours the direction of propagation is quite variable throughout the year. It then becomes predominantly northwest and changes to northeast around 09:00 LT. In late fall and winter it changes back to north/northwest around 15:00 LT. During the other seasons, northward propagation is very obvious near dawn and dusk, but no significant northward propagation is observed at noon.

    It is suggested that the variable propagation direction in the morning is related to irregular magnetic disturbances that occur at this local time. The changes in the MSTID propagation directions near dawn and dusk are generally consistent with changes in ionospheric electric fields occurring at these times and is consistent with dayside MSTIDs being generated by the Lorentz force.

    Key words. Ionosphere (ionospheric disturbances; wave propagation; ionospheric irregularities; signal processing

  3. Medium-scale traveling ionospheric disturbances triggered by Super Typhoon Nepartak (2016)

    Science.gov (United States)

    Chou, Min-Yang; Lin, Charles C. H.; Yue, Jia; Chang, Loren C.; Tsai, Ho-Fang; Chen, Chia-Hung

    2017-08-01

    Two remarkable typhoon-induced traveling ionospheric disturbances (TIDs) with concentric and northwest-southeast (NW-SE) alignments, respectively, associated with concentric gravity waves (CGWs) and ionosphere instabilities possibly seeded by CGWs, were observed in total electron content (TEC) derived from ground-based Global Navigation Satellite System networks in Taiwan and Japan when the Category 5 Super Typhoon Nepartak approached Taiwan on 7 July 2016. The concentric TIDs (CTIDs) first appear with horizontal phase velocities of 161-200 m/s, horizontal wavelengths of 160-270 km, and periods of 15-22 min during 08:00-11:20 UT. Following the CTIDs, the NW-SE aligned nighttime medium-scale TIDs (MSTIDs) are formed on the west edge of the CTIDs over the Taiwan Strait during 11:30-14:00 UT. It is suggested that the MSTIDs are produced by the electrodynamical coupling of Perkins instability and CGW-induced polarization electric fields. This study proposes connections of typhoon-induced CTIDs and subsequently occurring MSTIDs in the low-latitude ionosphere.

  4. Medium-Scale Traveling Ionospheric Disturbances (MSTIDs) resulting from Chelyabinsk Meteor Blast

    Science.gov (United States)

    Sheeks, B. J.; Warren, N.; Coster, A. J.

    2013-12-01

    A global network of GPS receivers continuously make line-of-sight (LOS) measurements of the total electron content (TEC) of the ionosphere. This TEC measurement data can be analyzed to 'persistently monitor' natural and man-made activity in the atmosphere (such as volcanic eruptions, earthquakes, rocket launches, etc) which propagate into the ionosphere to produce TIDs (Traveling Ionospheric Disturbances). As an example we have analyzed in detail the TIDs resulting from the 15 Feb 2013 Chelyabinsk meteor blast as observed by the Artu GPS receiver site in Arti, Russia close to the event. Seven of the GPS satellite measurements with LOS pierce points within 1000 km of the blast show disturbances. Four of these clearly show VTEC oscillations with ~12 minute periods. The other three show much weaker responses, but their LOS pierce points are far from the blast and their aspects between the geomagnetic field & blast propagation vector are unfavorable (near broadside). By fitting all seven measurements we estimate a propagation speed of ~380 m/s for these medium-scale TIDs. As future 'persistent surveillance' efforts we intend to investigate the observability of man-made activities such as static rocket engine firings in TEC measurements. Analysis of MSTIDs resulting from the Chelyabinsk meteor blast

  5. GPS observations of medium-scale traveling ionospheric disturbances over Europe

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    Y. Otsuka

    2013-02-01

    Full Text Available Two-dimensional structures of medium-scale traveling ionospheric disturbances (MSTIDs over Europe have been revealed, for the first time, by using maps of the total electron content (TEC obtained from more than 800 GPS receivers of the European GPS receiver networks. From statistical analysis of the TEC maps obtained 2008, we have found that the observed MSTIDs can be categorized into two groups: daytime MSTID and nighttime MSTID. The daytime MSTID frequently occurs in winter. Its maximum occurrence rate in monthly and hourly bin exceeds 70% at lower latitudes over Europe, whereas it is approximately 45% at higher latitudes. Since most of the daytime MSTIDs propagate southward, we speculate that they could be caused by atmospheric gravity waves in the thermosphere. The nighttime MSTIDs also frequently occur in winter but most of them propagate southwestward, in a direction consistent with the theory that polarization electric fields play an important role in generating the nighttime MSTIDs. The nighttime MSTID occurrence rate shows distinct latitudinal difference: The maximum of the occurrence rate in monthly and hourly bin is approximately 50% at lower latitudes in Europe, whereas the nighttime MSTID was rarely observed at higher latitudes. We have performed model calculations of the plasma density perturbations caused by a gravity wave and an oscillating electric field to reproduce the daytime and nighttime MSTIDs, respectively. We find that TEC perturbations caused by gravity waves do not show dip angle dependencies, while those caused by the oscillating electric field have a larger amplitude at lower latitudes. These dip angle dependencies of the TEC perturbation amplitude could contribute to the latitudinal variation of the MSTID occurrence rate. Comparing with previous studies, we discuss the longitudinal difference of the nighttime MSTID occurrence rate, along with the E- and F-region coupling processes. The seasonal variation, of the

  6. Medium-Scale Traveling Ionospheric Disturbances and Plasma Bubbles Observed by an All-Sky Airglow Imager at Yonaguni, Japan

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    Tadahiko Ogawa

    2009-01-01

    Full Text Available We report on night time air glow imaging observations of the low latitude ionosphere by means of a 630-m all-sky imager in stalled in March 2006 at Yonaguni, Japan (24.5°N, 123.0°E; 14.6°N geomagnetic, about 100 km east of Taiwan. The imager detected medium-scale traveling ionospheric disturbances (MSTIDs for about 7 hours on the night of 26 May 2006. A dense GPS net work in Japan also ob served the same MSTID event on this night. The imager and GEONET data indicate that most of the MSTIDs prop a gated south west ward from the north of Japan to the south of Yonaguni and Taiwan over 4000 km, with a southern limit of 19°N (geomagnetic latitude 9°N or lower. On the night of 10 November 2006, the imager observed two weak emission bands that were embedded on the F-region anomaly crest to the south of Yonaguni. The simultaneous electron density profiles from the FORMOSAT-3/COS MIC mission demonstrate that the weak emission bands are due to density depletions in equatorial plasma bubbles. These case studies suggest that the Yonaguni imager in collaboration with other instruments is very suit able for the study of ionospheric disturbances in and around the northern F-region anomaly crest.

  7. Medium-Scale Traveling Ionospheric Disturbances and Plasma Bubbles Observed by an All-Sky Airglow Imager at Yonaguni, Japan

    Directory of Open Access Journals (Sweden)

    Tadahiko Ogawa

    2009-01-01

    Full Text Available We report on night time air glow imaging observations of the low latitude ionosphere by means of a 630-m all-sky imager in stalled in March 2006 at Yonaguni, Japan _ _ _ geomagnetic, about 100 km east of Taiwan. The imager detected medium-scale traveling ionospheric disturbances (MSTIDs for about 7 hours on the night of 26 May 2006. A dense GPS net work in Japan also ob served the same MSTID event on this night. The imager and GEONET data indicate that most of the MSTIDs prop a gated south west ward from the north of Japan to the south of Yonaguni and Taiwan over 4000 km, with a southern limit of _ (geomagnetic latitude _ or lower. On the night of 10 November 2006, the imager observed two weak emission bands that were embedded on the F-region anomaly crest to the south of Yonaguni. The simultaneous electron density profiles from the FORMOSAT-3/COS MIC mission demonstrate that the weak emission bands are due to density depletions in equatorial plasma bubbles. These case studies suggest that the Yonaguni imager in collaboration with other instruments is very suit able for the study of ionospheric disturbances in and around the northern F-region anomaly crest.

  8. Mesoscale field-aligned irregularity structures (FAIs) of airglow associated with medium-scale traveling ionospheric disturbances (MSTIDs)

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    Sun, Longchang; Xu, Jiyao; Wang, Wenbin; Yue, Xinan; Yuan, Wei; Ning, Baiqi; Zhang, Donghe; Meneses, F. C.

    2015-11-01

    In this paper, we report the evolution (generation, amplification, and dissipation) of optically observed mesoscale field-aligned irregularity structures (FAIs) (~150 km) associated with a medium-scale traveling ionospheric disturbance (MSTID) event. There have not been observations of mesoscale FAIs of airglow before. The mesoscale FAIs were generated in an airglow-depleted front of southwestward propagating MSTIDs that were simultaneously observed by an all-sky imager, a GPS monitor, and a digisonde around Xinglong (40.4°N, 30.5° magnetic latitude), China, on 17/18 February 2012. A normalized cross-correlation method has been used to obtain the velocities of mesoscale FAIs and MSTIDs. The mesoscale FAIs had an obvious northwestward relative velocity to main-body MSTIDs (about 87.0 m/s on average). The direction of this relative velocity was roughly parallel to the depleted fronts. Furthermore, the evolution of the mesoscale FAIs was mostly controlled by the intensity of the depleted fronts. Occurred in a highly elevated ionosphere that had a total electron content depletion associated with large negative airglow perturbations (-25%), the mesoscale FAIs grew rapidly when they experienced southeastward wind, which had a speed of about 100 m/s and were measured by a Fabry-Perot interferometer. A northeastward polarization electric field within a depleted airglow front can play a controlling role in the development of the mesoscale FAIs. The electric field can significantly elevate the ionosphere and move the mesoscale FAIs northwestward by the E × B drift. The processes for the generation and development of the polarization electric field and the mesoscale FAIs, however, need further study.

  9. Spread F, GPS phase fluctuations, and medium-scale traveling ionospheric disturbances over Wuhan during solar maximum

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    Chen, Wei-Sheng; Lee, Chien-Chih; Chu, Fang-Dar; Su, Shin-Yi

    2011-03-01

    This study employs a digisonde and a GPS receiver at Wuhan (30.5°N, 114.4°E), China to observe spread F, GPS phase fluctuations, and medium-scale traveling ionospheric disturbances (MSTIDs) at nighttime in 2000. The MSTIDs are derived from the perturbations of total electron content (TEC). In this study, we explored the seasonal and nighttime occurrence rates as well as the one-to-one correspondences for these phenomena. The results show that, for the seasonal variations, three phenomena all are highly active in summer, which confirms that irregularities over Wuhan mainly relate to MSTIDs. Moreover, all spread F types have a minor occurrence peak in winter but none for the MSTIDs and the GPS phase fluctuations. Besides, none of large GPS phase fluctuations event had occurred during observation periods, which indicates that the strength of irregularities related to MSTIDs are weaker than that of equatorial plasma bubbles. For the nighttime variations, the frequency spread F occurs earlier than other spread F types which implies that disturbances start at the altitude near the F-region peak. For the one-to-one correspondences, the occurrence rates of each spread F type and GPS phase fluctuations are low during MSTIDs occurred. This implies that smaller scale irregularities which are observed as spread F or GPS phase fluctuations may only appear in some phase of MSTIDs.

  10. Sources and Characteristics of Medium Scale Traveling Ionospheric Disturbances Observed by SuperDARN Radars in the North American Sector

    Science.gov (United States)

    Frissell, N. A.; Baker, J. B.; Ruohoniemi, J. M.; Greenwald, R. A.; Gerrard, A. J.; Miller, E. S.; West, M. L.

    2015-12-01

    Medium Scale Traveling Ionospheric Disturbances (MSTIDs) are wave-like perturbations of the F-region ionosphere with horizontal wavelengths on the order of several hundred kilometers, and periods between 15 - 60 min. In SuperDARN radar data, MSTID signatures are manifested as quasi-periodic enhancements of ground backscatter (i.e. skip focusing) which propagate through the radar field-of-view. At high latitudes, SuperDARN observations of MSTIDs have generally been attributed to atmospheric gravity waves (AGWs) launched by auroral sources (e.g. Joule heating). However, recent studies with newer mid-latitude radars have shown MSTIDs are routinely observed in the subauroral ionosphere as well. To develop a more complete picture of MSTID activity, we have surveyed observations from four high latitude and six mid latitude SuperDARN radars located in the North American sector collected between 2011 and 2015 during the months of November to May. Consistent with previous SuperDARN MSTID studies, all radars observed MSTIDs with horizontal wavelengths between ~250 - 500 km and horizontal velocities between ~100 - 250 m/s. The majority of the MSTIDs were observed to propagate in a predominantly southward direction, with bearings ranging from ~135 ̊ - 250 ̊ geographic azimuth. This is highly suggestive of high latitude auroral sources; however, no apparent correlation with geomagnetic or space weather activity could be identified. Rather, comparison of the SuperDARN MSTID time-series data with northern hemisphere geopotential data from the European Center for Medium Range Weather Forecasting (ECMWF) operational model reveals a strong correlation of MSTID activity with dynamics in the polar vortex structure on two primary time scales. First, a seasonal effect manifests as enhanced MSTID activity from November through January, followed by a depressed period from February to May. This appears to correspond with the seasonal development and later decay of the polar vortex. A

  11. Large-scale and Medium-scale Traveling Ionospheric Disturbances Registered during Magnetic Storms over North-Eastern Region of Russian Federation

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    Ivanova, Vera; Kurkin, Vladimir

    2016-07-01

    Earth's ionosphere is dynamical steadily changed medium. On a level with daily and seasonal variations of ionospheric parameters there are irregular components connected with wave motions in neutral atmosphere. F2 ionosphere region disturbances are developed in global scale during geomagnetic storms and characterized considerable variations in F2-region critical frequencies and heights. High frequency oblique-incidence sounding method allows us to diagnose ionospheric parameters variations in regions poorly equipped with vertical sounding stations. In this work we provide the analysis of large-scale and medium-scale traveling ionospheric disturbances (LS and MS TID's accordingly) registered during experiments from 2006 till 2011 which carried out by means of the monthly duration sets with 5-min intervals over oblique-incidence sounding paths located in the north-eastern region of Russian Federation. For the analysis we have been chosen experimental data obtained during minor and moderate geomagnetic storms. After ionograms processing maximum observed frequencies (MOF) deviations from median values were calculated. Using MOF deviations from medians the analysis of LS TID's appearance cases was carried out. Studied MOF deviations from medians can be caused by cusps on ionograms also. These cusps move with the course of time through the sequences of ionograms along upper rays from region with higher delays to region with lower delays. Such cusps on ionograms are caused by MS TID's. In this work the analysis of MS TID events registration by these cusps on ionograms was carried out. Then the comparison between LS and MS TID's appearance probability was performed. It is shown that registered MOF variations are caused by superposition of wave-like processes of different scales taken place in ionosphere during magnetic storms. This work was supported by the RFBR grants No 14-05-00259-a and No 14-05-00578-a.

  12. Model of traveling ionospheric disturbances

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    Fedorenko Yury P.

    2013-10-01

    Full Text Available A multiscale semi-empirical model of traveling ionospheric disturbances (TIDs is developed. The model is based on the following assumptions: (1 TIDs are generated by acoustic-gravity waves (AGWs and propagate as pressure waves; (2 time intervals between adjacent extrema of atmospheric pressure oscillations in a disturbance source are constant; (3 the pressure extrema propagate from the source up to ~14 000 km at a constant horizontal velocity; (4 the velocity of each extremum is determined only by its number in a TID train. The model was validated using literature data on disturbances generated by about 20 surface and high-altitude nuclear explosions, two volcano explosions, one earthquake and by energetic proton precipitation events in the magnetospheric cusp of the northern hemisphere. Model tests using literature data show that the spatial and temporal TID periods may be predicted with an accuracy of 12%. Adequacy of the model was also confirmed by our observations collected using transionospheric sounding. The following TID parameters: amplitudes, horizontal spatial periods, and a TID front inclination angle in a vertical plane are increasing as the distance between an AGW and the excitation source is increasing. Diurnal and seasonal variability of the TID occurrence, defined as ratio of TID events to the total number of observations for the corresponding period, is not observed. However, the TID occurrence was growing from ~50% in 1987 to ~98% in 2010. The results of other studies asserting that the TID occurrence does not depend on the number of sunspots and magnetic activity are confirmed. The TID occurrence has doubled over the period from 1987 to 2010 indicating increasing solar activity which is not associated with sunspot numbers. The dynamics of spatial horizontal periods was studied in a range of 150–35 000 km.

  13. GPS radio interferometry of travelling ionospheric disturbances

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    Afraimovich, E. L.; Palamartchouk, K. S.; Perevalova, N. P.

    1998-01-01

    This paper presents some results investigating the new possibilities of radio interferometry of Travelling Ionospheric Disturbances (TIDs) that are based on exploiting standard measurements of transionospheric radio signal characteristics and coordinate-time measurements using dual-frequency multichannel receivers of the Global Positioning System (GPS). A Statistical Angle-of-arrival and Doppler Method for GPS radio interferometry (SADM-GPS) is proposed for determining the characteristics of the TIDs dynamics by measuring variations of GPS phase derivatives with respect to time and spatial coordinates. These data are used to calculate corresponding values of the velocity vector, in view of a correction for satellite motions based on the current information available regarding the angular coordinates of the satellites. Subsequently, velocity and direction distributions are constructed and analyzed to verify the hypothesis of whether there is a predominant displacement. If it exists, then the pattern can be considered to be travelling, and the mean travel velocity can be determined from the velocity distribution. Through a computer simulation it was shown that multi-satellite GPS radio interferometry in conjunction with the SADM-GPS algorithm allows the detection and measurement of the velocity vector of TIDs in virtually the entire azimuthal range of possible TID propagation directions. The use of the proposed method is exemplified by an investigation of TIDs during the solar eclipse of 9 March 1997, using the GPS-radio interferometer GPSINT at Irkutsk.

  14. Investigation of Traveling Ionospheric Disturbances during a Midlatitude Spread F Event

    CERN Document Server

    Smith, Galen

    2010-01-01

    During a midlatitude spread F (MSF) event, data was collected to investigate the circumstances that may lead to MSF. Using the Total Electron Content (TEC) derived from the NCAT-SCINDA GPS station and the Continuous Operating Reference Stations (CORS) Traveling Ionospheric Disturbances (TID) were analyzed during a period of MSF over Wallops Island, Virginia. In addition to the TEC analysis, scintillation calculations have been made using the NCAT-SCINDA GPS receiver, USRP receiver and a Narrow Band (NB) receiver. Scintillation levels on the GPS, USRP and NB signals were very low throughout the period of MSF. Analysis of TEC data from multiple CORS sites has shown the presence of medium scale atmospheric gravity waves (AGW) within the MSF event region propagating towards low latitudes with a small eastward component. This is consistent with theories showing AGW may lead to MSF if an oppositely directed neutral wind is present. This study was performed in conjunction with a sounding rocket experiment investigat...

  15. Ionospheric travelling convection vortices observed by the Greenland magnetometer chain

    DEFF Research Database (Denmark)

    Kotsiaros, Stavros; Stolle, Claudia; Friis-Christensen, Eigil

    2013-01-01

    The Greenland magnetometer array continuously provides geomagnetic variometer data since the early eighties. With the polar cusp passing over it almost every day, the array is suitable to detect ionospheric traveling convection vortices (TCVs), which were rst detected by Friis-Christensen et al...

  16. Ionospheric travelling convection vortices observed by the Greenland magnetometer chain

    DEFF Research Database (Denmark)

    Kotsiaros, Stavros; Stolle, Claudia; Friis-Christensen, Eigil

    2013-01-01

    The Greenland magnetometer array continuously provides geomagnetic variometer data since the early eighties. With the polar cusp passing over it almost every day, the array is suitable to detect ionospheric traveling convection vortices (TCVs), which were rst detected by Friis-Christensen et al...

  17. Tropospheric jet stream as a source of traveling ionospheric disturbances observed by GPS

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    Wautelet, Gilles; Warnant, René

    2014-05-01

    The integrity and the reliability of real-time precise positioning applications with Global Positioning System (GPS) are affected by the ionospheric variability with time and space. As a consequence, scientific community aims at describing, explaining and forecasting the occurrence and the amplitude of ionospheric irregularities observed by GPS. The use of the geometric-free combination of GPS dual frequency signals allows to retrieve the Total Electron Content (TEC) along the satellite-to-receiver path, which is the basic trans-ionospheric observable. Based on L1/L2 GPS phase measurements collected at a given station, the TEC high-frequency variability is isolated. A climatological study performed over 10 years in Western Europe shows that TEC irregularities are mostly observed daytime during quiet geomagnetic background in autumn and winter and correspond to classical Medium-Scale Traveling Ionospheric Disturbances (MSTIDs). The latter are generally understood as the ionospheric signature of Atmospheric Gravity Waves (AGWs), either generated in situ (solar terminator) or in the lower atmosphere and propagating upward. Because of its associated strong wind shears, the tropospheric jetstream, occurring mainly during autumn and winter months, constitutes an ideal candidate for AGW generation. This paper analyzes the spatial correlation between the presence of both MSTIDs and strong jetstream over Western Europe. This correlation is positive when the ionospheric pierce point of the satellite is located above regions of interest where wind shears are very large. In practice, we have selected regions for which wind speed is larger than 50 m/s. In addition, the propagation of AGWs up to the ionospheric layer is taken into account by assuming horizontal and vertical velocities of 200 and 50 m/s respectively. It comes that the region of interest of the correlation study is computed using an isotropic slant propagation of the AGW, which is supposed to be generated at a

  18. Concentric traveling ionosphere disturbances triggered by Super Typhoon Meranti (2016)

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    Chou, Min Yang; Lin, Charles C. H.; Yue, Jia; Tsai, Ho Fang; Sun, Yang Yi; Liu, Jann Yenq; Chen, Chia Hung

    2017-02-01

    Concentric traveling ionosphere disturbances (CTIDs) in total electron content triggered by Super Typhoon Meranti on 13 September 2016 are detected by using the ground-based Global Navigation Satellite Systems network in Taiwan. The CTIDs emanated outward before the typhoon landfall and lasted for more than 10 h. The characteristics of CTIDs agree with the gravity wave theory and exhibit spatial and temporal scales in wave periods of 8-30 min, horizontal wavelengths of 160-200 km, and horizontal phase velocities of 106-220 m/s. We also observe the CTIDs showing the stationary wave character. Broad spectra of CTIDs are excited after the rainbands of typhoon impinged on Central Mountain Range of Taiwan. The ray-tracing technique confirms that the CTIDs were excited by convective clouds, spiral rainbands, and the eyewall of Typhoon Meranti. This study provides new evidence of typhoon-induced concentric gravity waves in the ionosphere.

  19. GPS observation of the Travelling Ionospheric disturbances from Moscow megacity.

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    Zakharov, V. I.; Gorchakov, G. I.

    2016-07-01

    In our work we study the effect of the Moscow metropolis on the travelling disturbances, that appear and shown at ionospheric heights above the megacity in the abnormal conditions of the summer 2010. GPS- interferometry method is carried out for regional monitoring ionospheric disturbances by using GNSS-signals, received at Moscow region Navigational and geodetic support network and the International Geophysical Survay (IGS) network. We processed over 21000 hours of individual GPS observations in the period from June to August 2010. Detected traveling ionospheric disturbances (TIDs), which are distributed by the Moscow megacity and are grouped in the ring around it. Prolonged observations (˜100 days) provide us the opportunity to "accumulate signal" and reveal the influence of urban heat island from the megacity (such as Moscow) in the surface layer of the atmosphere. We suppose,that the changes in the urban heat island can lead to the appearance of the waves and the spread of disturbances in the atmosphere upto the ionosphere. We present the empirical distribution functions of the speed, observed duration and direction of the TIDs propagation. So, it was shown that the observed TIDs are acousto-gravity waves and, in particular, may be caused by effects of the megacity. Briefly summarizing the results, it can be argued that these studies illustrate the influence of the lower atmosphere on the processes in the upper. The methods of GPS- observations using special algorithms classification allocated wave structures allow to identify the ground source for this influence. This work, alongside with the general physical, has undoubtedly important ecological value, and the results may be useful for prognostic purposes. Work was partially supported by RFBR grant 15-45-03266.

  20. GPS observation of traveling ionospheric disturbances related to Moscow megacity

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    Zakharov, V. I.; Gorchakov, G. I.

    2017-01-01

    We present the results of GPS-signal radio interferometry observations obtained in the period of summer 2010 (97 days) at the stations in the Moscow region. The stations belong to MNGS (Moscow Navigational and Geodetic Support) and IGS (International Geophysical Services) networks. We observed traveling ionospheric disturbances (TIDs) in a ring form around Moscow. Empirical functions of the parameters (motion speed and observation period) are obtained and discussed. It is shown that the observed distributions are manifestations of the acoustic-gravity waves and may be associated with a special heat regime, including the urban heat island established in the Moscow region during summer 2010 in the conditions of a blocking anticyclone.

  1. Large-scale traveling ionospheric disturbances using ionospheric imaging at storm time: A case study on 17 march 2013

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    Tang, Jun; Yao, Yibin; Kong, Jian; Zhang, Liang

    2016-07-01

    A moderate geomagnetic storm occurred on March 17, 2013, during which large-scale traveling ionospheric disturbances (LSTIDs) are observed over China by ionosondes and GPS from Crustal Movement Observation Network of China (CMONOC) and the International GNSS Service (IGS). Ionosonde data and computerized ionospheric tomography (CIT) technique are employed to analyze the disturbances in our study. The maximum entropy cross spectral analysis (MECSA) method is used to obtain the propagation parameters of the LSTIDs. Spatio-temporal variations of ionospheric electron density (IED) and total electron content (TEC) during this geomagnetic storm over China are investigated. Disturbance images of IED and TEC are also presented in the paper. The results show two LSTID events at about 12:00 UT and 15:00 UT during the main phase of the storm. Besides, the LSTIDs with a duration of 40 min are detected over China. It is confirmed that the LSTIDs travel from north to south with a horizontal velocity of 400-500 m/s, and moved southwestwards with a horizontal velocity of 250-300 m/s, respectively.

  2. Traveling ionospheric disturbances triggered by the 2009 North Korean underground nuclear explosion

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, X.; Tang, L. [Wuhan Univ. (China). School of Geodesy and Geomatics

    2015-04-01

    Underground nuclear explosions (UNEs) can induce acoustic-gravity waves, which disturb the ionosphere and initiate traveling ionospheric disturbances (TIDs). In this paper, we employ a multi-step and multi-order numerical difference method with dual-frequency GPS data to detect ionospheric disturbances triggered by the North Korean UNE on 25 May 2009. Several International GNSS Service (IGS) stations with different distances (400 to 1200 km) from the epicenter were chosen for the experiment. The results show that there are two types of disturbances in the ionospheric disturbance series: high-frequency TIDs with periods of approximately 1 to 2 min and low-frequency waves with period spectrums of 2 to 5 min. The observed TIDs are situated around the epicenter of the UNE, and show similar features, indicating the origin of the observed disturbances is the UNE event. According to the amplitudes, periods and average propagation velocities, the high-frequency and low-frequency TIDs can be attributed to the acoustic waves in the lower ionosphere and higher ionosphere, respectively. (orig.)

  3. Radio interferometric detection of a traveling ionospheric disturbance excited by the explosion of Mount St. Helens

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    Roberts, D. H.; Rogers, A. E. E.; Allen, B. R.; Bennett, C. L.; Burke, B. F.; Greenfield, P. E.; Lawrence, C. R.; Clark, T. A.

    1982-01-01

    A large-amplitude traveling ionospheric disturbance (TID) was detected over Owens Valley, California, on May 18, 1980, by a highly sensitive very long baseline interferometry (VLBI) radio astronomy experiment. This TID is interpreted as the response of the ionosphere to a gravity wave excited in the neutral atmosphere by the explosion of Mount St. Helens that took place at 1532 UT on that day. A model, invoking the point-excitation of internal gravity waves in an isothermal atmosphere, which fits observations of the TID at several other stations, leads to identification of the features observed in the VLBI data. Small-amplitude higher-frequency changes in the ionosphere were detected for several hours after the passage of the large-amplitude Mount St. Helens TID, but it is not clear whether these were excited by the passage of the gravity wave or were background fluctuations.

  4. Radio interferometric detection of a traveling ionospheric disturbance excited by the explosion of Mount St. Helens

    Science.gov (United States)

    Roberts, D. H.; Rogers, A. E. E.; Allen, B. R.; Bennett, C. L.; Burke, B. F.; Greenfield, P. E.; Lawrence, C. R.; Clark, T. A.

    1982-01-01

    A large-amplitude traveling ionospheric disturbance (TID) was detected over Owens Valley, California, on May 18, 1980, by a highly sensitive very long baseline interferometry (VLBI) radio astronomy experiment. This TID is interpreted as the response of the ionosphere to a gravity wave excited in the neutral atmosphere by the explosion of Mount St. Helens that took place at 1532 UT on that day. A model, invoking the point-excitation of internal gravity waves in an isothermal atmosphere, which fits observations of the TID at several other stations, leads to identification of the features observed in the VLBI data. Small-amplitude higher-frequency changes in the ionosphere were detected for several hours after the passage of the large-amplitude Mount St. Helens TID, but it is not clear whether these were excited by the passage of the gravity wave or were background fluctuations.

  5. Traveling ionospheric disturbances propagating ahead of the Tohoku-Oki tsunami: a case study

    Science.gov (United States)

    Kherani, E. A.; Rolland, L.; Lognonné, P.; Sladen, A.; Klausner, V.; de Paula, E. R.

    2016-02-01

    We document two kinds of traveling ionospheric disturbances, namely, CTIDs (Co-tsunami-Traveling-Ionospheric-disturbances) and ATIDs (Ahead-of-Tsunami-Traveling-Ionospheric-disturbances) related to the Tohoku-Oki tsunami of 2011 March 11. They are referred to the disturbances that remain behind and ahead of the principal tsunami wave front, respectively. We first note their presence in a numerical experiment performed using a simulation code coupling the tsunami, atmosphere and ionosphere. This code uses the tsunami wavefield as an input and simulates acoustic-gravity waves (AGWs) in the atmosphere and TIDs, in the form of total electron content (TEC) disturbance, in the ionosphere. The simulated TEC reveals the excitation of CTIDs (at about 2 TECU) and ATIDs (at about 1 TECU), representing up to 5 per cent disturbance over the ambient electron density, and they arise from the dissipation of AGWs in the thermosphere. A novel outcome is that during the tsunami passage between ˜6° and 12° of epicentral distance, strong ATIDs arrive ˜20-60 min ahead of the tsunami wave front covering ˜3°-10° of distance from the tsunami location. Simulation results are compared with the far-field observations using GNSS satellites and confirm that ATIDs are the first detected TEC maximum, occurring 20-60 min ahead of the tsunami arrival. Our simulation also confirms the presence of largest TEC maximum representing CTIDs, 10-20 min after the first tsunami wave. ATIDs reported in this study have characteristics that can be potentially used for the early warning of the tsunami.

  6. Ground observation and AMIE-TIEGCM modeling of a large-scale traveling ionospheric disturbance

    Science.gov (United States)

    Shiokawa, K.; Lu, G.; Nishitani, N.; Sato, N.

    We show comparison of ground observation and modeling of a prominent large-scale traveling ionospheric disturbance (LSTID) observed in Japan during the major magnetic storm of March 31, 2001 (Shiokawa et al., JGR, 2003). The LSTID was detected as an enhancement of the 630-nm airglow intensity, an enhancement of GPS-TEC, a decrease of F-layer virtual height, and an increase of foF2. They moved equatorward with a velocity of 400-500 m/s. These results suggest that an enhancement of poleward neutral wind (propagating equatorward as a traveling atmospheric wave) caused the observed ionospheric features of the LSTID. The ion drift measurement by the MU radar and Doppler wind measurement by a Fabry-Perot interferometer (630-nm and 558-nm airglow) at Shigaraki actually showed poleward wind enhancement during the LSTID event. To model this LSTID event, we used the assimilative mapping of ionospheric electrodynamics (AMIE) technique as inputs to the thermosphere-ionosphere-electrodynamics general circulation model (TIEGCM). The model shows fine structures of the poleward wind enhancement both propagated from the auroral zone and generated directly at midlatitudes.

  7. On the dynamics of large-scale traveling ionospheric disturbances over Europe on 20 November 2003

    Science.gov (United States)

    Borries, Claudia; Jakowski, Norbert; Kauristie, Kirsti; Amm, Olaf; Mielich, Jens; Kouba, Daniel

    2017-01-01

    Ionospheric disturbances, often associated with geomagnetic storms, may cause threats to radio systems used for communication and navigation. One example is the super storm on 20 November 2003, when plenty of strong and unusual perturbations were reported. This paper reveals additional information on the dynamics in the high-latitude ionosphere over Europe during this storm. Here analyses of wavelike traveling ionospheric disturbances (TIDs) over Europe are presented, based on estimates of the total electron content (TEC) derived from ground-based Global Navigation Satellite System (GNSS) measurements. These TIDs are ionospheric signatures of thermospheric surges initiated by space weather events. The source region of these TIDs is characterized by enhanced spatial gradients, TEC depression, strong uplift of the F2 layer, the vicinity of the eastward auroral electrojet, and strong aurora E layers. Joule heating is identified as the most probable driver for the TIDs observed over Europe during 20 November 2003. The sudden heating of the thermosphere leads to strong changes in the pressure and thermospheric wind circulation system, which in turn generates thermospheric wind surges observed as TID signatures in the TEC. Either the dissipation of the eastward auroral electrojet or particle precipitation are considered as the source mechanism for the Joule heating. In the course of the storm, the TEC observations show a southward shift of the source region of the TIDs. These meridional dislocation effects are obviously related to a strong compression of the plasmasphere. The presented results demonstrate the complex interaction processes in the thermosphere-ionosphere-magnetosphere system during this extreme storm.

  8. Modeling of the travelling ionospheric disturbances. Case study of ASG-EUPOS network

    Science.gov (United States)

    Zanimonskiy, Yevgen M.; Nykiel, Grzegorz; Figurski, Mariusz; Yampolski, Yuri M.

    2016-04-01

    Traveling ionospheric disturbances (TIDs) - this is quite established term for a relatively stable spatial structures, which are characterized by a certain distribution of the electron concentration and are moved as a whole, especially in the horizontal direction. In most cases TIDs are associated with atmospheric gravity waves (AGW) and are expected to be a quasi-plane wave. Effective modern method of studying TIDs is the sounding of ionosphere by GNSS signals received by the dense regional network. Method of the orthogonal projection of the ionosphere electronic content variations for the total electron content (TEC) mapping allows visualizing the ionospheric irregularities (Zanimonskiy et. al. 2016). Such maps can be used to detect TIDs, their modeling and determination of model parameters, such as: direction and speed of movement, spatial period and the height of the ionosphere layer, in which TIDs are localized. In this paper traveling ionospheric disturbances detected over Poland are presented for the day of St. Patrick (March 2015). Into the calculation process observational data from dense regional network deployed in Poland (ASG-EUPOS) were used. Estimated TIDs were characterized by relative frequent occurrence, up to several times a day, and were observed from a few tens of minutes to hour. The direction of detected TIDs movement in most cases was opposite to the horizontal wind calculated by Horizontal Wind Model 07 at the height of TID. Furthermore, the amplitudes of estimated TEC variations during the TID passage were proportional to the background TEC values and consequently to the higher level of the geomagnetic activity. The extremely high TEC variations and speed of TIDs were registered during the severe geomagnetic storm are discussed in this paper. Further works are carried out to the investigation of quantitative relation between the parameters of TIDs and horizontal winds, as well as to accumulation of statistics and characteristics of TIDs

  9. Concentric traveling ionospheric disturbances triggered by the launch of a SpaceX Falcon 9 rocket

    Science.gov (United States)

    Lin, Charles C. H.; Shen, Ming-Hsueh; Chou, Min-Yang; Chen, Chia-Hung; Yue, Jia; Chen, Po-Cheng; Matsumura, Mitsuru

    2017-08-01

    We report the first observation of concentric traveling ionospheric disturbances (CTIDs) triggered by the launch of a SpaceX Falcon 9 rocket on 17 January 2016. The rocket-triggered ionospheric disturbances show shock acoustic wave signature in the time rate change (time derivative) of total electron content (TEC), followed by CTIDs in the 8-15 min band-pass filtering of TEC. The CTIDs propagated northward with phase velocity of 241-617 m/s and reached distances more than 1000 km away from the source on the rocket trajectory. The wave characteristics of CTIDs with periods of 10.5-12.7 min and wavelength 200-400 km agree well with the gravity wave dispersion relation. The optimal wave source searching and gravity wave ray tracing technique suggested that the CTIDs have multiple sources which are originated from 38-120 km altitude before and after the ignition of the second-stage rocket, 200 s after the rocket was launched.

  10. GPS network observation of traveling ionospheric disturbances following the Chelyabinsk meteorite blast

    Science.gov (United States)

    Ding, Feng; Mao, Tian; Hu, Lianhuan; Ning, Baiqi; Wan, Weixing; Wang, Yungang

    2016-11-01

    We use the Global Positioning System (GPS) network in northwest China and central Asia to monitor traveling ionospheric disturbances (TIDs), which were possibly excited by the large meteorite blast over Chelyabinsk, Russia, on 15 February 2013. Two TIDs were observed. The first TID was observed 13 min after the blast within a range of 270-600 km from the blast site. It propagated radially from the blast site with a mean velocity and period of 369 m s-1 and 12 min, respectively. The second TID was found in northwest China, 1.5 h after the time of the blast, at ˜ 2500-3100 km from the blast site. This latter TID propagated southeastward with a velocity and period of 410 m s-1 and 23 min, respectively. Severe dissipation of the perturbation total electronic content (TEC) amplitude was observed. Any TIDs propagating in a global range was not found after the meteorite blast. Features of TIDs were compared with those excited by early nuclear explosion tests. It is inferred from our analysis that the energy release of the Chelyabinsk meteorite blast may not be large enough to excite such ionospheric disturbances in a global range as some nuclear explosions did.

  11. Seismo-traveling ionospheric disturbances of earthquake and tsunami waves observed by space- and ground-based GPS receivers

    Science.gov (United States)

    Liu, J. Y. G.; Chen, C. Y.; Lin, C. H.

    2015-12-01

    FORMOSAT-3/COSMIC (F3/C) is a constellation of six microsatellites launched on April 15, 2006 and has been orbiting with 72° inclination at 700 to 800 km above the earth since December 2007. The main payload of the F3/C is the GPS Occultation eXperiment (GOX) which carries out probing the radio occultation (RO) total electron content between GPS satellite and F3/C. Therefore, F3/C provides us an excellent opportunity to vertically scan ionospheric electron density from 100 up to 800 km altitude. On the other hand, worldwide ground-based GPS receivers can be employed to observe traveling ionospheric disturbances of the TEC. Here, we present the ionosphere response to seismic and tsunami waves by means of F3/C RO TEC and worldwide ground-based GPS TEC as well as existing data of infrasondes, magnetometers, and Doppler sounding systems during the 11 March 2011 M9.0 Tohoku earthquake.

  12. Density duct formation in the wake of a travelling ionospheric disturbance: Murchison Widefield Array observations

    CERN Document Server

    Loi, Shyeh Tjing; Murphy, Tara; Erickson, Philip J; Bell, Martin E; Rowlinson, Antonia; Arora, Balwinder Singh; Morgan, John; Ekers, Ronald D; Hurley-Walker, Natasha; Kaplan, David L

    2016-01-01

    Geomagnetically-aligned density structures with a range of sizes exist in the near-Earth plasma environment, including 10-100 km-wide VLF/HF wave-ducting structures. Their small diameters and modest density enhancements make them difficult to observe, and there is limited evidence for any of the several formation mechanisms proposed to date. We present a case study of an event on 26 August 2014 where a travelling ionospheric disturbance (TID) shortly precedes the formation of a complex collection of field-aligned ducts, using data obtained by the Murchison Widefield Array (MWA) radio telescope. Their spatiotemporal proximity leads us to suggest a causal interpretation. Geomagnetic conditions were quiet at the time, and no obvious triggers were noted. Growth of the structures proceeds rapidly, within 0.5 hr of the passage of the TID, attaining their peak prominence 1-2 hr later and persisting for several more hours until observations ended at local dawn. Analyses of the next two days show field-aligned structu...

  13. Analysis of traveling ionospheric disturbances (TIDs) in GPS TEC launched by the 2011 Tohoku earthquake

    Science.gov (United States)

    Crowley, Geoff; Azeem, Irfan; Reynolds, Adam; Duly, Timothy M.; McBride, Patrick; Winkler, Clive; Hunton, Don

    2016-05-01

    Traveling ionospheric disturbances (TIDs) have been detected using various measurement techniques, including HF sounders, incoherent scatter radars, in situ measurements, and optical techniques. However, observations of TIDs have tended to be sparse and there is a need for additional observations to provide new scientific insight into the geophysical source phenomenology and wave propagation physics. The dense network of GPS receivers around the globe offers a relatively new data source to observe and monitor TIDs. In this paper, we use total electron content (TEC) measurements from ~4000 GPS receivers throughout the continental United States to observe TIDs associated with the 11 March 2011 Tohoku tsunami. The tsunami propagated across the Pacific to the U.S. west coast over several hours, and we show that corresponding TIDs were observed in the US. Using this network of GPS receivers we present a 2D imaging of TEC perturbations and calculate various TID parameters, including horizontal wavelength, speed, and period. Well-formed, planar TIDs were detected over the west coast of the U.S. ~10 h after the earthquake. Fast Fourier transform analysis of the observed waveforms revealed that the period of the wave was 15.1 min with a horizontal wavelength of 194.8 km, phase velocity of 233.0 m/s, and an azimuth of 105.2° (propagating nearly due east in the direction of the tsunami wave). These results are consistent with the TID observations in airglow measurements from Hawaii earlier in the day and with other GPS TEC observations.

  14. Seismo-Traveling Ionospheric Disturbances Triggered by the 12 May 2008 M 8.0 Wenchuan Earthquake

    Directory of Open Access Journals (Sweden)

    Jann-Yenq Liu

    2012-01-01

    Full Text Available A network of 6 ground-based GPS receivers in East Asia was employed to study seismo-traveling ionospheric disturbances (STIDs triggered by an M 8.0 earthquake which occurred at Wenchuan on 12 May 2008. The network detected 5 STIDs on the south side of the epicenter area. A study on the distances of the detected STIDs to the epicenter versus their associated traveling times shows that the horizontal speed is about 600 m s-1. Applying the circle method, we find that the 5 circles intercept at a point right above the epicenter when the horizontal speed of 600 m s-1 is given. Global searches of the ray-tracing and the beam-forming techniques confirm that the STIDs are induced by vertical motions in the Earth¡¦s surface during the Wenchuan Earthquake.

  15. Seismo-Traveling Ionospheric Disturbances Triggered by the 12 May 2008 M 8.0 Wenchuan Earthquake

    Directory of Open Access Journals (Sweden)

    Jann-Yenq Liu

    2012-01-01

    Full Text Available A network of 6 ground-based GPS receivers in East Asia was employed to study seismo-traveling ionospheric disturbances (STIDs triggered by an M 8.0 earthquake which occurred at Wenchuan on 12 May 2008. The network detected 5 STIDs on the south side of the epicenter area. A study on the distances of the detected STIDs to the epicenter versus their associated traveling times shows that the horizontal speed is about 600 m s-1. Applying the circle method, we find that the 5 circles intercept at a point right above the epicenter when the horizontal speed of 600 m s-1 is given. Global searches of the ray-tracing and the beam-forming techniques confirm that the STIDs are induced by vertical motions in the _ surface during the Wenchuan Earthquake.

  16. A study of Traveling Ionospheric Disturbances and Atmospheric Gravity Waves using EISCAT Svalbard Radar IPY-data

    Directory of Open Access Journals (Sweden)

    A. Vlasov

    2011-11-01

    Full Text Available We present a statistical study of Traveling Ionospheric Disturbances (TIDs as observed by the EISCAT Svalbard Radar (ESR during the continuous IPY-run (March 2007–February 2008 with field-aligned measurements. We have developed a semi-automatic routine for searching and extracting Atmospheric Gravity Wave (AGW activity. The collected data shows that AGW-TID signatures are common in the high-latitude ionosphere especially in the field-aligned ion velocity data (244 cases of AGW-TID signatures in daily records, but they can be observed also in electron density (26 cases, electron temperature (12 cases and ion temperature (26 cases. During the IPY campaign (in solar minimum conditions AGW-TID events appear more frequently during summer months than during the winter months. It remains still as a topic for future studies whether the observed seasonal variation is natural or caused by seasonal variation in the performance of the observational method that we use (AGW-TID signature may be more pronounced in a dense ionosphere. In our AGW-TID dataset the distribution of the oscillation periods has two peaks, one around 0.5–0.7 h and the other around 1.1–1.3 h. The diurnal occurrence rate has a deep minimum in the region of magnetic midnight, which might be partly explained by irregular auroral activity obscuring the TID signatures from our detection routines. As both the period and horizontal phase speed estimates (as derived from the classical AGW dispersion relation show values typical both for large scale TIDs and mesoscale TIDs it is difficult to distinguish whether the generator for high-latitude AGW-TIDs resides typically in the troposphere or in the near-Earth space. The results of our statistical analysis give anyway some valuable reference information for the future efforts to learn more about the dominating TID source mechanisms in polar cap conditions, and to improve AGW simulations.

  17. GPS and GLONASS observations of large-scale traveling ionospheric disturbances during the 2015 St. Patrick's Day storm

    Science.gov (United States)

    Zakharenkova, Irina; Astafyeva, Elvira; Cherniak, Iurii

    2016-12-01

    Using a comprehensive database of 5300 ground-based Global Navigation Satellite Systems (GNSS) stations we have investigated large-scale traveling ionospheric disturbances (LSTIDs) during 17-18 March 2015 (St. Patrick's Day storm). For the first time, the high-resolution, two-dimensional maps of the total electron content perturbation were made using not only GPS but also GLONASS measurements. Several LSTIDs originated from the auroral regions in the Northern and Southern Hemispheres were observed simultaneously over Europe, North America, and South America. This storm is considered as a two-step main phase storm. During the first main phase LSTIDs propagated over the whole daytime European region and over high latitudes of North America. During the second main phase we report (1) intense LSTIDs propagated equatorward in North America and Europe, (2) convergence of several LSTIDs originated from the opposite hemispheres in the interference zone over geomagnetic equator in South America, and (3) "super" LSTIDs with the wavefront length of more than 10,000 km observed simultaneously in North America and Europe. LSTIDs observed in three sectors had wavelength of 1200-2500 km and wave periods of 50-80 min. During the recovery phase on the background of the negative ionospheric storm developed over North America we detect signatures of the stream-like structures elongated within the latitudinal range of 29°N-42°N across the U.S. These structures persisted through the nighttime to the early morning from 04 UT to 13 UT on 18 March 2015, and they were associated with the subauroral polarization stream-induced nighttime ionospheric flows.

  18. Observing Traveling Ionospheric Disturbances Caused by Tsunamis Using GPS TEC Measurements

    Science.gov (United States)

    Galvan, David A.; Komjathy, Attila; Hickey, Michael; Foster, James; Mannucci, Anthony J.

    2010-01-01

    Ground-based Global Positioning System (GPS) measurements of ionospheric Total Electron Content (TEC) show variations consistent with atmospheric internal gravity waves caused by ocean tsunamis following two recent seismic events: the American Samoa earthquake of September 29, 2009, and the Chile earthquake of February 27, 2010. Fluctuations in TEC correlated in time, space, and wave properties with these tsunamis were observed in TEC estimates processed using JPL's Global Ionospheric Mapping Software. These TEC estimates were band-pass filtered to remove ionospheric TEC variations with wavelengths and periods outside the typical range of internal gravity waves caused by tsunamis. Observable variations in TEC appear correlated with the tsunamis in certain locations, but not in others. Where variations are observed, the typical amplitude tends to be on the order of 1% of the background TEC value. Variations with amplitudes 0.1 - 0.2 TECU are observable with periods and timing affiliated with the tsunami. These observations are compared to estimates of expected tsunami-driven TEC variations produced by Embry Riddle Aeronautical University's Spectral Full Wave Model, an atmosphere-ionosphere coupling model, and found to be in good agreement in some locations, though there are cases when the model predicts an observable tsunami-driven signature and none is observed. These TEC variations are not always seen when a tsunami is present, but in these two events the regions where a strong ocean tsunami was observed did coincide with clear TEC observations, while a lack of clear TEC observations coincided with smaller tsunami amplitudes. There exists the potential to apply these detection techniques to real-time GPS TEC data, providing estimates of tsunami speed and amplitude that may be useful for early warning systems.

  19. Observing Traveling Ionospheric Disturbances Caused by Tsunamis Using GPS TEC Measurements

    Science.gov (United States)

    Galvan, David A.; Komjathy, Attila; Hickey, Michael; Foster, James; Mannucci, Anthony J.

    2010-01-01

    Ground-based Global Positioning System (GPS) measurements of ionospheric Total Electron Content (TEC) show variations consistent with atmospheric internal gravity waves caused by ocean tsunamis following two recent seismic events: the American Samoa earthquake of September 29, 2009, and the Chile earthquake of February 27, 2010. Fluctuations in TEC correlated in time, space, and wave properties with these tsunamis were observed in TEC estimates processed using JPL's Global Ionospheric Mapping Software. These TEC estimates were band-pass filtered to remove ionospheric TEC variations with wavelengths and periods outside the typical range of internal gravity waves caused by tsunamis. Observable variations in TEC appear correlated with the tsunamis in certain locations, but not in others. Where variations are observed, the typical amplitude tends to be on the order of 1% of the background TEC value. Variations with amplitudes 0.1 - 0.2 TECU are observable with periods and timing affiliated with the tsunami. These observations are compared to estimates of expected tsunami-driven TEC variations produced by Embry Riddle Aeronautical University's Spectral Full Wave Model, an atmosphere-ionosphere coupling model, and found to be in good agreement in some locations, though there are cases when the model predicts an observable tsunami-driven signature and none is observed. These TEC variations are not always seen when a tsunami is present, but in these two events the regions where a strong ocean tsunami was observed did coincide with clear TEC observations, while a lack of clear TEC observations coincided with smaller tsunami amplitudes. There exists the potential to apply these detection techniques to real-time GPS TEC data, providing estimates of tsunami speed and amplitude that may be useful for early warning systems.

  20. Observations of Traveling Ionospheric Disturbances (TIDs) Over the United States Associated With the Tsunami Generated by the 2011 Tohoku Earthquake

    Science.gov (United States)

    Duly, T. M.; Azeem, I.; Crowley, G.; Vadas, S.; Makela, J. J.; Reynolds, A.

    2015-12-01

    The March 11, 2011 Tohoku earthquake generated a massive tsunami off the Pacific coast of Japan which in turn forced intense atmospheric gravity waves (AGW) that were seen in GPS Total Electron Content (TEC) data and airglow measurements as traveling ionospheric disturbance (TID) signatures as far away as Hawaii. What is unknown is how far these TIDs traveled after being launched by the tsunami and the role of the underlying neutral atmosphere on their propagation characteristics. For the first time, we show that TIDs associated with the Tohoku tsunami were observed in GPS TEC data for several hours over the west coast of the US and as far inland as Colorado. The results presented here show a range of TIDs generated by gravity wave packets propagating into the ionosphere from below. We present results indicating the presence of TIDs with periods ranging from 15 to 30 minutes, and horizontal wavelengths from 150 km to 400 km. The azimuth of the observed TID wave train was 121.8 ± 1.8° (angle measured in degrees east of north), which matches the azimuth of the tsunami near the Pacific coast of the US. The observed period of the TIDs was one of the spectral components of the tsunami wave packet as it approached the Pacific coast of the US. These results suggest that the tsunami was the source of the TIDs over the US. Additionally, the TID periods and horizontal wavelengths clearly vary in longitude. These variations agree with theoretical gravity wave results concerning propagation and dissipation in the thermosphere.

  1. First observations of poleward large-scale traveling ionospheric disturbances over the African sector during geomagnetic storm conditions

    Science.gov (United States)

    Habarulema, John Bosco; Katamzi, Zama Thobeka; Yizengaw, Endawoke

    2015-08-01

    This paper presents first observations of poleward traveling ionospheric disturbances (TIDs) during strong geomagnetic conditions over the African sector. By analyzing different data sets we have observed both positive and negative ionospheric responses during the storm period of 08-10 March 2012. Considering the African region as a whole, three longitudinal sectors were strategically selected to establish the entire regional response. On both sides of the geomagnetic equator, results show poleward shift in peak total electron content (TEC) enhancements/depletions at different times which are associated to large-scale TIDs. The observed phenomena are linked to the global ionospheric response and electrodynamics. The understanding has been established using data from International GNSS Service receiver network, radio occultation electron density profiles, derived E×B drift measurements from magnetometer observations and regional ground-based and satellite data. Contrary to other related studies, generated regional TEC perturbation maps were not enough to show obvious directions of the large-scale TIDs due to insufficient data over the northern hemispheric part of the African sector. There appears to be a switch between positive and negative storm phases during the same storm period especially in the Southern Hemisphere part of the African region where "enough" data were available. However, a detailed analysis revealed that the positive storm phase corresponded to the expansion of the equatorial ionization anomaly (EIA) toward some parts of midlatitude regions (and possibly with the contribution from low-latitude electrodynamics associated to equatorial electrojet), while the other part recorded a negative storm phase due to storm-induced changes from the auroral origin. We have observed a simultaneous occurrence of both poleward and equatorward propagating TIDs over the African sector during the same geomagnetic storm period. Our results show that short-lived large

  2. Comparative climatological study of large-scale traveling ionospheric disturbances over North America and China in 2011-2012

    Science.gov (United States)

    Ding, Feng; Wan, Weixing; Li, Qiang; Zhang, Rui; Song, Qian; Ning, Baiqi; Liu, Libo; Zhao, Biqiang; Xiong, Bo

    2014-01-01

    This paper describes a comparative study of the climatology of large-scale traveling ionospheric disturbances (LSTIDs) over North America and China based on observations obtained in 2011-2012 using two GPS networks characterized by dense regional coverage. We identified a total of 390 LSTIDs in China and 363 events in North America. These can be categorized into three types, namely south, north, and westward propagating LSTIDs. The southward LSTIDs over North America show similar diurnal and seasonal variations to those of geomagnetic disturbances, but the southward LSTIDs over China do not show such variations. The occurrence of southward LSTIDs over China increases at ~1-2 h after the time of geomagnetic activity maximum; this increase lasts several hours until the geomagnetic minimum, which happens during the local evening. The southward LSTIDs over North America show a semiannual variation with two peaks in March and October, while the southward LSTIDs over China show a major peak in January. Northward LSTIDs occur much less frequently than their southward counterparts, and they are mainly observed in China. They mostly occur during geomagnetic activity maximum, indicating a possible relation with the degree of geomagnetic activity. Westward LSTIDs are seen in both regions during local sunrise and may be excited by the moving solar terminator. No relationship was found between these latter LSTIDs and the geomagnetic disturbances. The propagation direction of westward events changed from northwestward during winter solstice to southwestward at summer solstice. This is consistent with the seasonal orientation of the solar terminator.

  3. Large-scale traveling ionospheric disturbances observed using GPS receivers over high-latitude and equatorial regions

    Science.gov (United States)

    Idrus, Intan Izafina; Abdullah, Mardina; Hasbi, Alina Marie; Husin, Asnawi; Yatim, Baharuddin

    2013-09-01

    This paper presents the first results of large-scale traveling ionospheric disturbances (LSTIDs) observation during two moderate magnetic storm events on 28 May 2011 (SYM-H∼ -94 nT and Dst∼-80 nT) and 6 August 2011 (SYM-H∼-126 nT and Dst∼-113 nT) over the high-latitude region in Russia, Sweden, Norway, Iceland and Greenland and equatorial region in the Peninsular Malaysia using vertical total electron content (VTEC) from the Global Positioning System (GPS) observations measurement. The propagation of the LSTID signatures in the GPS TEC measurements over Peninsular Malaysia was also investigated using VTEC map. The LSTIDs were found to propagate both equatorward and poleward directions during these two events. The results showed that the LSTIDs propagated faster at high-latitude region with an average phase velocity of 1074.91 m/s than Peninsular Malaysia with an average phase velocity of 604.84 m/s. The LSTIDs at the high-latitude region have average periods of 150 min whereas the ones observed over Peninsular Malaysia have average periods of 115 min. The occurrences of these LSTIDs were also found to be the subsequent effects of substorm activities in the auroral region. To our knowledge, this is the first result of observation of LSTIDs over Peninsular Malaysia during the 24th solar cycle.

  4. Observational investigation of the possible correlation between medium-scale TIDs and mid-latitude spread F

    Science.gov (United States)

    Yu, Shimei; Xiao, Zuo; Aa, Ercha; Hao, Yongqiang; Zhang, Donghe

    2016-08-01

    Global navigation satellite system (GNSS) receivers at two stations, CHAN (43.83°N, 125.27°E) and URUM (43.70°N, 87.60°E) in China, are used to retrieve the total electron content (TEC) from 2001 to 2012, and detect medium-scale traveling ionospheric disturbances (MSTIDs) above the two stations. At either station, MSTIDs occurrence is found to depend on season and solar cycle, that is, lower during equinoctial seasons and low solar activity, in accordance with the general morphological features of mid-latitude spread F (MSF). More interestingly, a significant longitudinal difference exists between the two stations that, both MSTIDs and MSF are more prevalent at CHAN than at URUM over the 12 years. These results imply a strong connection between MSTIDs and MSF, and provide new observational evidences that gravity waves (GWs), manifested in MSTIDs here, might play an important role in triggering MSF in the overhead ionosphere. Since GWs at mid-latitude mostly originate in the lower atmosphere, we infer that the atmospheric background at CHAN is more favorable for generating GWs. This is probably true considering very different surface meteorological conditions for the two stations over such a large longitudinal span (∼38°). CHAN station is near the coast of western Pacific Ocean and URUM station is in the very center of the Europe-Asia continent, and they are in different climate zones. We therefore suggest that the surface meteorological condition is one of the significant factors to be considered in explaining and modeling MSF formation and variations.

  5. The Quiet Rise of Medium-Scale Farms in Malawi

    Directory of Open Access Journals (Sweden)

    Ward Anseeuw

    2016-06-01

    Full Text Available Medium-scale farms have become a major force in Malawi’s agricultural sector. Malawi’s most recent official agricultural survey indicates that these account for over a quarter of all land under cultivation in Malawi. This study explores the causes and multifaceted consequences of the rising importance of medium-scale farms in Malawi. We identify the characteristics and pathways of entry into farming based on surveys of 300 medium-scale farmers undertaken in 2014 in the districts of Mchinji, Kasungu and Lilongwe. The area of land acquired by medium-scale farmers in these three districts is found to have almost doubled between 2000 and 2015. Just over half of the medium-scale farmers represent cases of successful expansion out of small-scale farming status; the other significant proportion of medium-scale farmers are found to be urban-based professionals, entrepreneurs and/or civil servants who acquired land, some very recently, and started farming in mid-life. We also find that a significant portion of the land acquired by medium-scale farmers was utilized by others prior to acquisition, that most of the acquired land was under customary tenure, and that the current owners were often successful in transferring the ownership structure of the acquired land to a long-term leaseholding with a title deed. The study finds that, instead of just strong endogenous growth of small-scale famers as a route for the emergence of medium-scale farms, significant farm consolidation is occurring through land acquisitions, often by urban-based people. The effects of farmland acquisitions by domestic investors on the country’s primary development goals, such as food security, poverty reduction and employment, are not yet clear, though some trends appear to be emerging. We consider future research questions that may more fully shed light on the implications of policies that would continue to promote land acquisitions by medium-scale farms.

  6. Radio and optical observations of large-scale traveling ionospheric disturbances during a strong geomagnetic storm of 6-8 April 2000

    CERN Document Server

    Afraimovich, E L; Leonovich, L A; Lesyuta, O S; Mikhalev, A V; Ashkaliev, Y F; Aushev, V M; Vodyannikov, V V; Yakovets, A F; Ashkaliev, Ya. F.

    2001-01-01

    Basic properties of the mid-latitude large-scale traveling ionospheric disturbances (LS TIDs) during the maximum phase of a strong magnetic storm of 6-8 April 2000 are shown. Total electron content (TEC) variations were studied by using data from GPS receivers located in Russia and Central Asia. The nightglow response to this storm at mesopause and termospheric altitudes was also measured by optical instruments FENIX located at the observatory of the Institute of Solar-Terrestrial Physics, (51.9 deg. N, 103.0 deg. E) and MORTI located at the observatory of the Institute of Ionosphere (43.2 deg. N, 77.0 deg. E). Observations of the O (557.7 nm, 630.0 nm, 360-410 nm, and 720-830 nm) emissions originating from atmospheric layers centered at altitudes of 90 km, 97 km, and 250 km were carried out at Irkutsk and of the O_2 (866.5 nm) emission originating from an atmospheric layer centered at altitude of 95 km was carried out at Almaty. Variations of the f_0F2 and virtual altitude of the F2 layer were measured at Al...

  7. Determining dynamic parameters of different-scale ionospheric irregularities over northern Siberia

    Science.gov (United States)

    Afraimovich, E. L.; Lipko, Y. V. Y. V.; Vugmeister, B. O.

    2000-01-01

    In 1995-1996, observations were carried out at Norilsk (geomagnetic latitude and longitude 64.2 degN and 160.4 degE) to determine dynamic parameters of irregularities in the high-latitude ionosphere. The short-baseline spaced-receiver method that has been implemented at the ionospheric facility of the Norilsk Integrated Magnetic-Ionospheric Station, provides a means of simultaneously measuring parameters of small-scale irregularities (spatial scale of 3-5 km) by the Similar-Fading Method (SFM), as well as of medium-scale irregularities (time scale of 10-30 min, spatial scale of hundreds of kilometres) by the Statistical Angle-of-arrival and Doppler Method (SADM). About 20 h of the observational data for the F2-layer under quiet geomagnetic conditions (Kp = 3) and about 15 h for the sporadic E-layer (Kp ~ 3) were processed. It has been found that the propagation directions and velocities of different-scale irregularities do not coincide. Small-scale irregularities of the F2-layer travel predominantly eastward or westward. The velocity of the F2-layer irregularities is about 100 m/s, and under disturbed conditions it is up to 200-250 m/s. Small-scale irregularities of the sporadic E-layer travel mostly in the northward direction. It is confirmed that the Es-layer is characterised by high velocities of the irregularities (as high as 1000 m/s). Medium-scale irregularities with periods in the range of 10-30 min travel mostly in a southward direction with velocities of 20-40 m/s.

  8. A simplified traveling ionospheric disturbance (TID) specification model based on TID Detector Built In Texas (TIDDBIT) and GPS total electron content (TEC) measurements.

    Science.gov (United States)

    Duly, T. M.; Crowley, G.; Azeem, I.

    2015-12-01

    There is currently a great deal of interest in Traveling Ionospheric Disturbances (TIDs) from both an observational and modeling perspective, especially as they apply to operational systems that rely on nowcasting the ionospheric state. ASTRA has developed a new observational system to measure TID characteristics called TIDDBIT (TID Detector Built in Texas). TIDDBIT is a fully digital HF Doppler sounder that uses CW signals across a spaced array. TIDDBIT systems have been deployed in Texas, Virginia, Florida, Hawaii, and Peru. TIDDBIT measures the entire wave packet, including the horizontal and vertical phase propagation speeds as a function of TID period from the acoustic (1-min) to the gravity wave (10-90 min) part of the spectrum. It is desirable to be able to use these data to specify the TID structure not only at the measurement height, but to extend it in 3D to greater and lower heights, and beyond the immediate vicinity of the TIDDBIT system. We present a simplified model to specify TIDs based on the ion continuity equation for plasma density (Hooke 1970). Linearity of the neutral wind perturbations is assumed, and the different spectral components of the measured TID perturbations are added linearly. We use TID observations from the TIDDBIT sounder in Virginia and Peru as input into the model, and develop a 4D regional specification (spanning ~500 x 500 km in the horizontal direction and 90-1000 km altitude range) of both the perturbed electron density and the perturbed neutral wind from the corresponding atmospheric gravity wave (AGW). The model is also applied to TID measurements derived by GPS TEC measurements from the continental United States during the 11 March 2011 Tohoku Earthquake to study the theoretical launch angle of AGWs from the west coast of the United States.

  9. Joint observations of a traveling ionospheric disturbance with the Paratunka OMTI camera and the Hokkaido HF radar

    Directory of Open Access Journals (Sweden)

    A. Koustov

    2009-06-01

    Full Text Available On 10 September 2007 between 10:00 and 14:00 UT, the OMTI all-sky imager at Paratunka (Kamchatka, Russia, GLAT~52° observed the onset and south-western progression of a localized depletion region in the airglow intensity. The perturbation, while being stretched in the NW-SE direction, crossed the entire field of view of the camera. During the event, the Hokkaido SuperDARN HF radar was monitoring echoes in the Paratunka longitudinal sector. It was detecting a localized band of ground scatter echoes progressing equatorward synchronously with the motion of the optical perturbation. It is suggested that both features resulted from the onset and south-western progression of a localized region with enhanced electric field that influenced the distribution of the plasma density in the ionosphere. Modeling of the HF ground scatter dynamics based on numerical ray tracing demonstrated qualitative consistency with the observations.

  10. Profitability and sustainability of small - medium scale palm biodiesel plant

    Science.gov (United States)

    Solikhah, Maharani Dewi; Kismanto, Agus; Raksodewanto, Agus; Peryoga, Yoga

    2017-06-01

    The mandatory of biodiesel application at 20% blending (B20) has been started since January 2016. It creates huge market for biodiesel industry. To build large-scale biodiesel plant (> 100,000 tons/year) is most favorable for biodiesel producers since it can give lower production cost. This cost becomes a challenge for small - medium scale biodiesel plants. However, current biodiesel plants in Indonesia are located mainly in Java and Sumatra, which then distribute biodiesel around Indonesia so that there is an additional cost for transportation from area to area. This factor becomes an opportunity for the small - medium scale biodiesel plants to compete with the large one. This paper discusses the profitability of small - medium scale biodiesel plants conducted on a capacity of 50 tons/day using CPO and its derivatives. The study was conducted by performing economic analysis between scenarios of biodiesel plant that using raw material of stearin, PFAD, and multi feedstock. Comparison on the feasibility of scenarios was also conducted on the effect of transportation cost and selling price. The economic assessment shows that profitability is highly affected by raw material price so that it is important to secure the source of raw materials and consider a multi-feedstock type for small - medium scale biodiesel plants to become a sustainable plant. It was concluded that the small - medium scale biodiesel plants will be profitable and sustainable if they are connected to palm oil mill, have a captive market, and are located minimally 200 km from other biodiesel plants. The use of multi feedstock could increase IRR from 18.68 % to 56.52 %.

  11. Traveling planetary wave ionospheric disturbances and their role in the generation of equatorial spread-F and GPS phase fluctuations during the last extreme low solar activity and comparison with high solar activity

    Science.gov (United States)

    de Abreu, A. J.; Fagundes, P. R.; Bolzan, M. J. A.; Gende, M.; Brunini, C.; de Jesus, R.; Pillat, V. G.; Abalde, J. R.; Lima, W. L. C.

    2014-09-01

    This investigation studies traveling planetary wave ionospheric disturbance (TPWID) type oscillations on the modulation of the F region virtual height rise during the E×B electric field pre-reversal enhancement (PRE), near sunset hours. We also studied their role in the generation of equatorial spread F (ESF) and GPS phase fluctuations during periods of the last extreme low solar activity (LSA) of January 2009 to April 2010 (F10.7bar=73). A comparison is made with periods of high solar activity (HSA) in 2003 and 2004 near equatorial region. The ionospheric irregularities investigated are medium (bottom-side) and large (plasma bubble) scales. Ionospheric F region oscillations with period of days are due to the TPWIDs, which play an important role in producing favorable or unfavorable conditions for equatorial ionospheric irregularities, changing the electron vertical profile and F region height. In this paper, we present simultaneous ionospheric sounding (ionosonde) and GPS vertical total electron content (vTEC) observations carried out near equatorial region (Palmas 10.2°S, 48.2°W) and low latitude region (São José dos Campos 23.2°S, 45.9°W; located under the southern crest of the equatorial ionospheric anomaly), Brazil. Observations show that the occurrence of fresh ESF during LSA and HSA and fresh GPS phase fluctuations at equatorial region follow the trend of day-to-day variations in the F region virtual height, which are due to electric field PRE modulated by TPWID wave like oscillations. During LSA, the altitude of 250 km acts as a threshold height for the generation of fresh ionospheric irregularities, whereas during HSA, the threshold height is 300 km. The observations also found a strong increase in the generation of fresh ionospheric irregularities from October 2009 to March 2010 during LSA and from September 2003 to March 2004 during the HSA. Furthermore, in LSA, the period of fresh ionospheric irregularities was less than during HSA, though both

  12. Ionospheric Weather and Climate—— A Review on Chinese Works From 2004 to 2006

    Institute of Scientific and Technical Information of China (English)

    WAN Weixing; XIAO Zuo

    2006-01-01

    This paper reviews the recent studies on the ionospheric weather and climate. As a national report prepared for COSPAR, the works concerned here are limited to those made by Chinese scientists during 2004-2006. The main contents include the sudden ionospheric disturbances, the ionospheric storms, the traveling ionospheric disturbances, ionospheric variability, the annual and semiannual ionospheric variations, the solar cycle ionospheric variations, and the long term ionospheric changes.

  13. Probing disturbances over canadian ionosphere using advance data analysis of wave decomposition

    Science.gov (United States)

    Kherani, Esfhan

    2016-07-01

    Using CHAIN network of GPS receivers, we present disturbances in total electron content (TEC) of the ionosphere on magnetically quiet day of 8 December 2009 and construct travel-time diagram to understand the propagation characteristics of these disturbances. We employ the wave decomposition method to identify the TEC disturbances. We found N-shaped amplified TEC disturbances at higher latitude around 80 N that appear during intensification of ionospheric current at ˜11 UT, suggesting them to be associated with energy input from magnetosphere. These TEC disturbances have spectral peak in between 55-65 minutes, originate in the vicnity of (80N,270W), propagate both southeastward and southwestward with similar velocity ˜80 m/s and arrives at latitude ˜55N around 20 UT. These propagation characteristcs classify them as medium-scale Traveling ionospheric disturbances (MSTIDs) and possibly of gravity wave origin. Noteworthy results of our study are following: (1) presence of dayside MSTIDs whose nightside counterpart is recently reported by Shiokawa et al (2012), (2) long-distance ˜2500 km propagation of dayside MSTIDs that is not reported for the nightside counterpart, (3) dayside MSIDs acquire largest amplitudes in 65-75 during 15-17 UT, similar to the nightside MSTIDs, (4) amplification of amplitudes of MSTIDs in the auroral oval latitudes and (5) identification of driving sources in two latitudes that enable them to propagate long distance.

  14. Minimum description length methods of medium-scale simultaneous inference

    CERN Document Server

    Bickel, David R

    2010-01-01

    Nonparametric statistical methods developed for analyzing data for high numbers of genes, SNPs, or other biological features tend to overfit data with smaller numbers of features such as proteins, metabolites, or, when expression is measured with conventional instruments, genes. For this medium-scale inference problem, the minimum description length (MDL) framework quantifies the amount of information in the data supporting a null or alternative hypothesis for each feature in terms of parametric model selection. Two new MDL techniques are proposed. First, using test statistics that are highly informative about the parameter of interest, the data are reduced to a single statistic per feature. This simplifying step is already implicit in conventional hypothesis testing and has been found effective in empirical Bayes applications to genomics data. Second, the codelength difference between the alternative and null hypotheses of any given feature can take advantage of information in the measurements from all other...

  15. The in-medium scale evolution in jet modification

    CERN Document Server

    Majumder, A

    2009-01-01

    The in-medium modification of the scale dependence of the fragmentation function in dense matter, brought about by higher twist corrections to the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equations, is derived. A phenomenologically motivated resummation is outlined which incorporates the next-to-leading twist single gluon emission kernel along with the vacuum emission kernel and provides an in-medium virtuality evolution of the final fragmentation function of a hard jet propagating through dense matter. The concept of a fragmentation function is generalized to include a dependence on distance travelled in the medium. Following this, numerical implementations are carried out and compared to experimental results on the single inclusive suppression observed in Deep-Inelastic scattering (DIS) off a large nucleus.

  16. Solar wind Alfvén waves: a source of pulsed ionospheric convection and atmospheric gravity waves

    Directory of Open Access Journals (Sweden)

    P. Prikryl

    2005-02-01

    Full Text Available A case study of medium-scale travelling ionospheric disturbances (TIDs that are correlated with solar wind Alfvén waves is presented. The HF radar ground-scatter signatures of TIDs caused by atmospheric gravity waves with periods of 20-40min are traced to a source at high latitudes, namely pulsed ionospheric flows (PIFs due to bursts in the convection electric field and/or the associated ionospheric current fluctuations inferred from ground magnetic field perturbations. The significance of PIFs and TIDs in the context of solar-terrestrial interaction is that Alfvénic fluctuations of the interplanetary magnetic field (IMF observed in the solar wind plasma streaming from a coronal hole correlate with PIFs and TIDs. The link between the solar wind Alfvén waves and TIDs is corroborated by the ground magnetic field signatures of ionospheric current fluctuations that are associated with the IMF-By oscillations and TIDs. The observed PIFs and the associated negative-to-positive deflections of the ground magnetic field X component are interpreted as ionospheric signatures of magnetic reconnection pulsed by solar wind Alfvén waves at the dayside magnetopause. Although the clarity of the radar line-of-sight velocity data may have been affected by anomalous HF propagation due to intervening TIDs, the application of a pure state filtering technique to analyze the radar data time series reveals a one-to-one correspondence between PIFs, TIDs and solar wind Alfvén waves. The spectra of solar wind and ground magnetic field perturbations are similar to those of PIFs and TIDs. The ground-scatter signatures indicate TID wavelengths, phase velocities and travel times that are consistent with ray tracing, which shows a subset of possible gravity wave group paths that reach the F region from a source in the E region after the wave energy first travel downward to the upper mesosphere where the waves are reflected upward. The observed one

  17. Ionospheric data assimilation and forecasting during storms

    Science.gov (United States)

    Chartier, Alex T.; Matsuo, Tomoko; Anderson, Jeffrey L.; Collins, Nancy; Hoar, Timothy J.; Lu, Gang; Mitchell, Cathryn N.; Coster, Anthea J.; Paxton, Larry J.; Bust, Gary S.

    2016-01-01

    Ionospheric storms can have important effects on radio communications and navigation systems. Storm time ionospheric predictions have the potential to form part of effective mitigation strategies to these problems. Ionospheric storms are caused by strong forcing from the solar wind. Electron density enhancements are driven by penetration electric fields, as well as by thermosphere-ionosphere behavior including Traveling Atmospheric Disturbances and Traveling Ionospheric Disturbances and changes to the neutral composition. This study assesses the effect on 1 h predictions of specifying initial ionospheric and thermospheric conditions using total electron content (TEC) observations under a fixed set of solar and high-latitude drivers. Prediction performance is assessed against TEC observations, incoherent scatter radar, and in situ electron density observations. Corotated TEC data provide a benchmark of forecast accuracy. The primary case study is the storm of 10 September 2005, while the anomalous storm of 21 January 2005 provides a secondary comparison. The study uses an ensemble Kalman filter constructed with the Data Assimilation Research Testbed and the Thermosphere Ionosphere Electrodynamics General Circulation Model. Maps of preprocessed, verticalized GPS TEC are assimilated, while high-latitude specifications from the Assimilative Mapping of Ionospheric Electrodynamics and solar flux observations from the Solar Extreme Ultraviolet Experiment are used to drive the model. The filter adjusts ionospheric and thermospheric parameters, making use of time-evolving covariance estimates. The approach is effective in correcting model biases but does not capture all the behavior of the storms. In particular, a ridge-like enhancement over the continental USA is not predicted, indicating the importance of predicting storm time electric field behavior to the problem of ionospheric forecasting.

  18. Small and Medium Scale Agribusiness Assessment. Peace Corps Information Collection & Exchange Reprint No. TR43.

    Science.gov (United States)

    Peace Corps, Washington, DC. Information Collection and Exchange Div.

    This manual is intended for Peace Corps volunteer use as they assist small- and medium-scale farmers in feasibility assessment and business plan development for agribusiness. Part I discusses the role of the Peace Corps in agribusiness development. It defines agribusiness, outlines the significance of agribusiness in economic development,…

  19. 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 re

  20. A design study for a medium-scale field demonstration of the viscous barrier technology

    Energy Technology Data Exchange (ETDEWEB)

    Moridis, G. [Lawrence Berkeley National Lab., CA (United States); Yen, P. [Bechtel Corp., San Francisco, CA (United States); Persoff, P.; Finsterle, S.; Williams, P.; Myer, L.; Pruess, K. [Lawrence Berkeley National Lab., CA (United States)

    1996-09-01

    This report is the design study for a medium-scale field demonstration of Lawrence Berkeley National Laboratory`s new subsurface containment technology for waste isolation using a new generation of barrier liquids. The test site is located in central California in a quarry owned by the Los Banos Gravel Company in Los Banos, California, in heterogeneous unsaturated deposits of sand, silt, and -ravel typical of many of the and DOE cleanup sites and particularly analogous to the Hanford site. The coals of the field demonstration are (a) to demonstrate the ability to create a continuous subsurface barrier isolating a medium-scale volume (30 ft long by 30 ft wide by 20 ft deep, i.e. 1/10th to 1/8th the size of a buried tank at the Hanford Reservation) in the subsurface, and (b) to demonstrate the continuity, performance, and integrity of the barrier.

  1. AschFlow - A dynamic landslide run-out model for medium scale hazard analysis.

    Science.gov (United States)

    Luna, Byron Quan; Blahut, Jan; van Asch, Theo; van Westen, Cees; Kappes, Melanie

    2015-04-01

    Landslides and debris flow hazard assessments require a scale-dependent analysis in order to mitigate damage and other negative consequences at the respective scales of occurrence. Medium or large scale landslide run-out modelling for many possible landslide initiation areas has been a cumbersome task in the past. This arises from the difficulty to precisely define the location and volume of the released mass and from the inability of the run-out models to compute the displacement with a large amount of individual initiation areas (computational exhaustive). Most of the existing physically based run-out models have complications in handling such situations and therefore empirical methods have been used as a practical mean to predict landslides mobility at a medium scale (1:10,000 to 1:50,000). In this context, a simple medium scale numerical model for rapid mass movements in urban and mountainous areas was developed. The deterministic nature of the approach makes it possible to calculate the velocity, height and increase in mass by erosion, resulting in the estimation of various forms of impacts exerted by debris flows at the medium scale The established and implemented model ("AschFlow") is a 2-D one-phase continuum model that simulates, the entrainment, spreading and deposition process of a landslide or debris flow at a medium scale. The flow is thus treated as a single phase material, whose behavior is controlled by rheology (e.g. Voellmy or Bingham). The developed regional model "AschFlow" was applied and evaluated in well documented areas with known past debris flow events.

  2. Measurement of ionospheric large-scale irregularity

    Institute of Scientific and Technical Information of China (English)

    韩文焌; 郑怡嘉; 张喜镇

    1996-01-01

    Based on the observations of a meter-wave aperture synthesis radio telescope,as the scale length of ionospheric irregularity is greatly larger than the baseline length of interferometer,the phase error induced by the output signal of interferometer due to ionosphere is proportional to the baseline length and accordingly the expressions for extracting the information about ionosphere are derived.By using the ray theory and considering that the antenna is always tracking to the radio source in astronomical observation,the wave motion expression of traveling ionospheric disturbance observed in the total electron content is also derived,which is consistent with that obtained from the conception of thin-phase screen;then the Doppler velocity due to antenna tracking is introduced.Finally the inversion analysis for the horizontal phase velocity of TID from observed data is given.

  3. Inductive ionospheric solver for magnetospheric MHD simulations

    Directory of Open Access Journals (Sweden)

    H. Vanhamäki

    2011-01-01

    Full Text Available We present a new scheme for solving the ionospheric boundary conditions required in magnetospheric MHD simulations. In contrast to the electrostatic ionospheric solvers currently in use, the new solver takes ionospheric induction into account by solving Faraday's law simultaneously with Ohm's law and current continuity. From the viewpoint of an MHD simulation, the new inductive solver is similar to the electrostatic solvers, as the same input data is used (field-aligned current [FAC] and ionospheric conductances and similar output is produced (ionospheric electric field. The inductive solver is tested using realistic, databased models of an omega-band and westward traveling surge. Although the tests were performed with local models and MHD simulations require a global ionospheric solution, we may nevertheless conclude that the new solution scheme is feasible also in practice. In the test cases the difference between static and electrodynamic solutions is up to ~10 V km−1 in certain locations, or up to 20-40% of the total electric field. This is in agreement with previous estimates. It should also be noted that if FAC is replaced by the ground magnetic field (or ionospheric equivalent current in the input data set, exactly the same formalism can be used to construct an inductive version of the KRM method originally developed by Kamide et al. (1981.

  4. Inductive ionospheric solver for magnetospheric MHD simulations

    Science.gov (United States)

    Vanhamäki, H.

    2011-01-01

    We present a new scheme for solving the ionospheric boundary conditions required in magnetospheric MHD simulations. In contrast to the electrostatic ionospheric solvers currently in use, the new solver takes ionospheric induction into account by solving Faraday's law simultaneously with Ohm's law and current continuity. From the viewpoint of an MHD simulation, the new inductive solver is similar to the electrostatic solvers, as the same input data is used (field-aligned current [FAC] and ionospheric conductances) and similar output is produced (ionospheric electric field). The inductive solver is tested using realistic, databased models of an omega-band and westward traveling surge. Although the tests were performed with local models and MHD simulations require a global ionospheric solution, we may nevertheless conclude that the new solution scheme is feasible also in practice. In the test cases the difference between static and electrodynamic solutions is up to ~10 V km-1 in certain locations, or up to 20-40% of the total electric field. This is in agreement with previous estimates. It should also be noted that if FAC is replaced by the ground magnetic field (or ionospheric equivalent current) in the input data set, exactly the same formalism can be used to construct an inductive version of the KRM method originally developed by Kamide et al. (1981).

  5. High-resolution ionospheric observations and modeling over Belgium during the solar eclipse of 20 March 2015 including first results of ionospheric tilt and plasma drift measurements

    Science.gov (United States)

    Verhulst, Tobias G. W.; Sapundjiev, Danislav; Stankov, Stanimir M.

    2016-06-01

    The ionospheric behavior over Belgium during the partial solar eclipse of 20 March 2015 is analyzed based on high-resolution solar radio flux, vertical incidence sounding, and GPS TEC measurements. First results of ionosonde-based ionospheric plasma drift and tilt observations are presented and analyzed, including some traveling ionospheric disturbances caused by the eclipse. Also, collocated ionosonde and GPS measurements are used to reconstruct the time evolution of the vertical electron density distribution using the Royal Meteorological Institute (RMI) ionospheric specification system, called Local Ionospheric Electron Density profile Reconstruction (LIEDR).

  6. Medium scale spatial structures of polycyclic aromatic hydrocarbons in the topsoil of Tianjin area

    Energy Technology Data Exchange (ETDEWEB)

    Wang, X.J.; Zheng, Y.; Liu, R.M.; Li, B.G.; Cao, J.; Tao, S. [Peking University, Beijing (China). Dept. of Urban & Environmental Science, MOE Lab. for Earth Surface Process

    2003-07-01

    The spatial distribution patterns of polycyclic aromatic hydrocarbons (PAHs) in soil are important to regional environmental assessment. In this paper, the spatial structural features of sixteen prior PAH compounds in the topsoil of Tianjin area, as well as soil properties, were studied. Results showed that medium scale spatial autocorrelations were well revealed. Spherical models with sills could be used to fit all experimental variograms. The spatial structures of PAHs contents demonstrated significant anisotropy. Air precipitation caused by the combustion of coal was the key factor in the formation of the spatial structural patterns of PAHs in the topsoil of Tianjin area.

  7. Market Assessment of Biomass Gasification and Combustion Technology for Small- and Medium-Scale Applications

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, D.; Haase, S.

    2009-07-01

    This report provides a market assessment of gasification and direct combustion technologies that use wood and agricultural resources to generate heat, power, or combined heat and power (CHP) for small- to medium-scale applications. It contains a brief overview of wood and agricultural resources in the U.S.; a description and discussion of gasification and combustion conversion technologies that utilize solid biomass to generate heat, power, and CHP; an assessment of the commercial status of gasification and combustion technologies; a summary of gasification and combustion system economics; a discussion of the market potential for small- to medium-scale gasification and combustion systems; and an inventory of direct combustion system suppliers and gasification technology companies. The report indicates that while direct combustion and close-coupled gasification boiler systems used to generate heat, power, or CHP are commercially available from a number of manufacturers, two-stage gasification systems are largely in development, with a number of technologies currently in demonstration. The report also cites the need for a searchable, comprehensive database of operating combustion and gasification systems that generate heat, power, or CHP built in the U.S., as well as a national assessment of the market potential for the systems.

  8. Analysis of Medium-Scale Solar Thermal Systems and Their Potential in Lithuania

    Directory of Open Access Journals (Sweden)

    Rokas Valančius

    2015-06-01

    Full Text Available Medium-scale solar hot water systems with a total solar panel area varying from 60 to 166 m2 have been installed in Lithuania since 2002. However, the performance of these systems varies depending on the type of energy users, equipment and design of the systems, as well as their maintenance. The aim of this paper was to analyse operational SHW systems from the perspective of energy production and economic benefit as well as to outline the differences of their actual performance compared to the numerical simulation results. Three different medium-scale solar thermal systems in Lithuania were selected for the analysis varying in both equipment used (flat type solar collectors, evacuated tube collectors and type of energy user (swimming pool building, domestic hot water heating, district heating. The results of the analysis showed that in the analysed cases the gap between measured and modelled data of heat energy produced by SHW systems was approx. 11%. From the economical perspective, the system with flat type solar collectors used for domestic hot water production was proved to be most efficient. However, calculation of Internal Rate of Return showed that a grant of 35% is required for this project to be fully profitable.

  9. Connected Traveler

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Alex

    2015-11-01

    The Connected Traveler project is a multi-disciplinary undertaking that seeks to validate potential for transformative transportation system energy savings by incentivizing efficient traveler behavior. This poster outlines various aspects of the Connected Traveler project, including market opportunity, understanding traveler behavior and decision-making, automation and connectivity, and a projected timeline for Connected Traveler's key milestones.

  10. 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...

  11. Evaluation of Critical Success Factors For Successful Six Sigma Implementation in Indian Medium Scale Automotive Enterprises

    Directory of Open Access Journals (Sweden)

    Rajeshkumar U. Sambhe,

    2011-03-01

    Full Text Available Large scale organisations are expecting high quality products from their suppliers those are owners of SMEs’. In today scenario, many Indian SMEs’ operate their processes at the two to three sigma quality levels. So there is Six Sigma implementation needs and have been attracting much attention. Consequently, a good design ethodology for implementation of Six Sigma in manufacturing products as well as that of services is needed. The purpose of this paper is to propose and evaluation of critical success factors for successful Six Sigma implementation in medium scale automotive industries in India. The proposed method centers on critical success factors which enables the industries in the initial stage to focus on those factors which needs more concentration and it supports for successful mplementation without investing on expensive consultation

  12. Insights into the nature of northwest-to-southeast aligned ionospheric wavefronts from contemporaneous Very Large Array and ionosondes observations

    CERN Document Server

    Helmboldt, J F

    2012-01-01

    The results of contemporaneous summer nighttime observations of midlatitude medium scale traveling ionospheric disturbances (MSTIDs) with the Very Large Array (VLA) in New Mexico and nearby ionosondes in Texas and Colorado are presented. Using 132, 20-minute observations, several instances of MSTIDs were detected, all having wavefronts aligned northwest to southeast and mostly propagating toward the southwest, consistent with previous studies of MSTIDs. However, some were also found to move toward the northeast. It was found that both classes of MSTIDs were only found when sporadic-E (Es) layers of moderate peak density (1.53 MHz that was not present when 1.5

  13. 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.

  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. Travelers' Health: Pregnant Travelers

    Science.gov (United States)

    ... Zika is present and take precautions to avoid sexual transmission of the virus. If travel cannot be avoided, pregnant women should strictly follow steps to prevent mosquito bites. Additional information, including the most current list of countries and territories where Zika virus is a risk, ...

  16. Quasiperiodic behavior of electrons in the ionosphere

    Energy Technology Data Exchange (ETDEWEB)

    Lysak, R.L.; Knuth, K.H.; Thompson, B.J. [Univ. of Minnesota, Minneapolis, MN (United States). School of Physics and Astronomy

    1995-12-31

    Electrons traveling in the ionosphere-inner magnetosphere region can become trapped by the quasi-static electric field at auroral altitudes and magnetic mirroring at ionospheric heights. A model is developed to simulate electron trajectories influenced by electric field fluctuations, and a dynamical analysis is performed on the resulting orbits. For fluctuations in the frequency range of 1 Hz, a bounce resonance may develop between electrons with typical travel times of few seconds. These electrons can remain trapped indefinitely, resulting in distinct quasiperiodic behavior. A stroboscopic map (a Poincare map with time as a state variable of the system) is applied, and the results form a 2-Torus in velocity phase space. The poster includes discussions on the acceleration process, the dynamical analysis, behavior in phase space, physical implications of the system, and a statistical summary of electron orbits.

  17. An Initial Investigation of Ionospheric Gradients for Detection of Ionospheric Disturbances over Turkey

    Science.gov (United States)

    Koroglu, Meltem; Arikan, Feza; Koroglu, Ozan

    2015-04-01

    Ionosphere is an ionized layer of earth's atmosphere which affect the propagation of radio signals due to highly varying electron density structure. Total Electron Content (TEC) and Slant Total Electron Content (STEC) are convenient measures of total electron density along a ray path. STEC model is given by the line integral of the electron density between the receiver and GPS satellite. TEC and STEC can be estimated by observing the difference between the two GPS signal time delays that have different frequencies L1 (1575 MHz) and L2 (1227 MHz). During extreme ionospheric storms ionospheric gradients becomes larger than those of quiet days since time delays of the radio signals becomes anomalous. Ionosphere gradients can be modeled as a linear semi-infinite wave front with constant propagation speed. One way of computing the ionospheric gradients is to compare the STEC values estimated between two neighbouring GPS stations. In this so-called station-pair method, ionospheric gradients are defined by dividing the difference of the time delays of two receivers, that see the same satellite at the same time period. In this study, ionospheric gradients over Turkey are computed using the Turkish National Permanent GPS Network (TNPGN-Active) between May 2009 and September 2012. The GPS receivers are paired in east-west and north-south directions with distances less than 150 km. GPS-STEC for each station are calculated using IONOLAB-TEC and IONOLAB-BIAS softwares (www.ionolab.org). Ionospheric delays are calculated for each paired station for both L1 and L2 frequencies and for each satellite in view with 30 s time resolution. During the investigation period, different types of geomagnetic storms, Travelling Ionospheric Disturbances (TID), Sudden Ionospheric Disturbances (SID) and various earthquakes with magnitudes between 3 to 7.4 have occured. Significant variations in the structure of station-pair gradients have been observed depending on location of station-pairs, the

  18. [Travelers' vaccines].

    Science.gov (United States)

    Ouchi, Kazunobu

    2011-09-01

    The number of Japanese oversea travelers has gradually increased year by year, however they usually pay less attention to the poor physical condition at the voyage place. Many oversea travelers caught vaccine preventable diseases in developing countries. The Vaccine Guideline for Oversea Travelers 2010 published by Japanese Society of Travel Health will be helpful for spreading the knowledge of travelers' vaccine and vaccine preventable diseases in developing countries. Many travelers' vaccines have not licensed in Japan. I hope these travelers' vaccines, such as typhoid vaccine, meningococcal vaccine, cholera vaccine and so on will be licensed in the near future.

  19. Highly Uniform Carbon Nanotube Field-Effect Transistors and Medium Scale Integrated Circuits.

    Science.gov (United States)

    Chen, Bingyan; Zhang, Panpan; Ding, Li; Han, Jie; Qiu, Song; Li, Qingwen; Zhang, Zhiyong; Peng, Lian-Mao

    2016-08-10

    Top-gated p-type field-effect transistors (FETs) have been fabricated in batch based on carbon nanotube (CNT) network thin films prepared from CNT solution and present high yield and highly uniform performance with small threshold voltage distribution with standard deviation of 34 mV. According to the property of FETs, various logical and arithmetical gates, shifters, and d-latch circuits were designed and demonstrated with rail-to-rail output. In particular, a 4-bit adder consisting of 140 p-type CNT FETs was demonstrated with higher packing density and lower supply voltage than other published integrated circuits based on CNT films, which indicates that CNT based integrated circuits can reach to medium scale. In addition, a 2-bit multiplier has been realized for the first time. Benefitted from the high uniformity and suitable threshold voltage of CNT FETs, all of the fabricated circuits based on CNT FETs can be driven by a single voltage as small as 2 V.

  20. Virtual Commissioning of Small to Medium Scale Industry Using the Concepts of Digital Manufacturing

    Directory of Open Access Journals (Sweden)

    Akash.M.R

    2015-04-01

    Full Text Available Small scale industries produce certain products depending on the type of industry they have established. If these small scale industries decide to become medium scale certain changes have to be incorporated in plant layout to meet certain requirements. Certain changes include change in layout design, introducing new machines and equipments in the industry in order to produce new component .To implement these changes in the company we have to get information regarding the new component the company would produce based on this information we have design new plant layout. The purpose of this project is to plan a suitable plant layout which could meet company requirement. To design a new plant layout we are using Delmia as the simulation software. DELMIA Production System Simulation allows the process planner to validate the manufacturing system dynamically. Product flow and operation time, as well as scheduled maintenance and random equipment failure events, are simulated to help the planner understand how they will impact the system’s capacity. Process planners can determine if changes to the system are needed to achieve the desired production demands.

  1. Design of an Energy Monitoring System for a Medium-Scale Plant

    Directory of Open Access Journals (Sweden)

    Erdal Irmak

    2012-02-01

    Full Text Available In this study, energy monitoring system of a medium scale industrial plant is achieved through a computer interface both in real time and retrospective using recent data. In order to measure the energy, a measurement card is designed to convert the voltage and current signals in suitable levels for a programmable logic controller (PLC. Current and voltage signals received from the measurement card are sensed by the analogue channels of the PLC. A zero-crossing detector is also designed to measure the power factor of the system. Time difference between the signals which are obtained from the zero-crossing detector is measured by using FM 350-01 counter module. All data received are transferred into a database located at the host computer by the PLC using RS485/RS232 communication protocol. Data obtained from the system can be monitored momentarily through an interface that is designed in C# programming language. Furthermore, retrospective energy analysis of the system is made possible by saving the data obtained continuously. Thus, active, reactive and apparent power values can be observed for a specific time interval. By using the retrospective energy analysis system, time periods in which the energy is more consumed can be determined. Thanks to this feature, work load of the plant can be programmed to specific times when the energy is cheaper in order to reduce the energy costs.

  2. Connected Traveler

    Energy Technology Data Exchange (ETDEWEB)

    2016-06-01

    The Connected Traveler framework seeks to boost the energy efficiency of personal travel and the overall transportation system by maximizing the accuracy of predicted traveler behavior in response to real-time feedback and incentives. It is anticipated that this approach will establish a feedback loop that 'learns' traveler preferences and customizes incentives to meet or exceed energy efficiency targets by empowering individual travelers with information needed to make energy-efficient choices and reducing the complexity required to validate transportation system energy savings. This handout provides an overview of NREL's Connected Traveler project, including graphics, milestones, and contact information.

  3. Altitude-Limiting Airbrake System for Small to Medium Scale Rockets

    Science.gov (United States)

    Aaron, Robert F., III

    2013-01-01

    The goal of the overall internship opportunity this semester was to learn and practice the elements of engineering design through direct exposure to real engineering problems. The primary exposure was to design and manufacture an airbrake device for use with small-medium scale rocket applications. The idea was to take the presented concept of a solution and transform said concept into a reliable fully-functioning and reusable mechanism. The mechanism was to be designed as an insurance feature so that the overall altitude of a rocket with relatively undetermined engine capabilities does not unexpectedly exceed the imposed 10,000 foot ceiling, per range requirements. The airbrake concept was introduced to the Prototype Development Lab as a rotation-driven four tiered offset track pin mechanism, i.e. the airbrake was deployed by rotating a central shaft attached directly to the bottom plate. The individual airbrake fins were subsequently deployed using multiple plates with tracks of offset curvature. The fins were created with guide pins to follow the tracks in each of the offset plates, thus allowing the simultaneous rotational deployment of all fins by only rotating one plate. The concept of this solution was great; though it did not function in application. The rotating plates alone brought up problems like the entire back half of the rocket rotating according to the motion of the aforementioned base plate. Subsequently, the solution currently under development became a static linear actuator-driven spring-loaded fin release system. This solution is almost instantaneously triggered electronically when the avionics detect that the rocket has reached the calculated altitude of deceleration. This altitude will allow enough time remaining to the overall ceiling to adequately decelerate the rocket prior to reaching the ceiling.

  4. Occupational exposure in small and medium scale industry with specific reference to heat and noise.

    Science.gov (United States)

    Singh, Lakhwinder Pal; Bhardwaj, Arvind; Deepak, Kishore Kumar

    2010-01-01

    This study was undertaken to assess heat and noise exposure and occupational safety practices in small and medium scale casting and forging units (SMEs) of Northern India. We conducted personal interviews of 350 male workers of these units through a comprehensive questionnaire and collected information on heat and noise exposure, use of protective equipment, sweat loss and water intake, working hour. The ambient wet bulb globe temperature (WBGT index) was measured using quest temp 34/36o area heat stress monitor. A-weighted Leq ambient noise was measured using a quest sound level meter "ANSI SI. 43-1997 (R 2002) type-1 model SOUNDPRO SE/DL". We also incorporated OSHA norms for hearing conservation which include - an exchange rate of 5dB(A), criterion level at 90dB(A), criterion time of eight hours, threshold level is equal to 80dB(A), upper limit is equal to 140dB(A) and with F/S response rate. Results of the study revealed that occupational heat exposure in melting, casting, forging and punching sections is high compared to ACGIH/NIOSH norms. Ambience noise in various sections like casting / molding, drop forging, cutting presses, punching, grinding and barreling process was found to be more than 90dB(A). About 95% of the workers suffered speech interference where as high noise annoyance was reported by only 20%. Overall, 68% workers were not using any personal protective equipment (PPE). The study concluded that the proportion of SME workers exposed to high level heat stress and noise (60 - 72 hrs/week) is high. The workers engaged in forging and grinding sections are more prone to noise induced hearing loss (NIHL) at higher frequencies as compared to workers of other sections. It is recommended that there is a strong need to implement the standard of working hours as well as heat stress and noise control measures.

  5. Natural gas origins of large and medium-scale gas fields in China sedimentary basins

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    China sedimentary basins present abundant natural gas resource thanks to its unique geological settings.Marine highly-matured hydrocarbon source rocks,widespread coal-measure strata and low temperature Quaternary saline strata,etc.,indicate the wide foreground of China natural gas resources. Up to now,most of the petroliferous basins have been discovered to have wholesale natural gas accumulation from Precambrian,Paleozoic,Mesozoic to Cenozoic in the east,the central,the west and the coast of China.These large and medium-scale gas reservoirs are mainly composed of hydrocarbon gas with big dry coefficient,tiny non-hydrocarbon,wide carbon isotope distribution and varying origin types,the hydrocarbon gas includes coal-formed gas,oil-formed gas,biogenic gas and inorganic gas, etc.Coal-formed gas is the main type of China natural gas resources,in particular several explored large-scale gas fields(>100 billion cubic meter)of Kela 2,Sulige and Daniudi,etc.,they all belong to coal-formed gas fields or the gas fields consisting mostly of coal-formed gas.Oil-formed gas is also abundant in China marine basins,for example marine natural gas of Sichuan Basin generated from crude oil cracking gas.Primary and secondary biogenic gas fields were discovered respectively in the Qaidam Basin and Western Slope of Songliao Basin.In addition,inorganic gases are mainly distributed in the eastern China,in particular the Songliao Basin with abundant carbon dioxide accumulation,indicating that the eastern China present large exploration potential of inorganic gas.

  6. Occupational exposure in small and medium scale industry with specific reference to heat and noise

    Directory of Open Access Journals (Sweden)

    Lakhwinder Pal Singh

    2010-01-01

    Full Text Available This study was undertaken to assess heat and noise exposure and occupational safety practices in small and medium scale casting and forging units (SMEs of Northern India. We conducted personal interviews of 350 male workers of these units through a comprehensive questionnaire and collected information on heat and noise exposure, use of protective equipment, sweat loss and water intake, working hour. The ambient wet bulb globe temperature (WBGT index was measured using quest temp 34/36o area heat stress monitor. A-weighted Leq ambient noise was measured using a quest sound level meter "ANSI SI. 43-1997 (R 2002 type-1 model SOUNDPRO SE/DL". We also incorporated OSHA norms for hearing conservation which include - an exchange rate of 5dB(A, criterion level at 90dB(A, criterion time of eight hours, threshold level is equal to 80dB(A, upper limit is equal to 140dB(A and with F/S response rate. Results of the study revealed that occupational heat exposure in melting, casting, forging and punching sections is high compared to ACGIH/NIOSH norms. Ambience noise in various sections like casting / molding, drop forging, cutting presses, punching, grinding and barreling process was found to be more than 90dB(A. About 95% of the workers suffered speech interference where as high noise annoyance was reported by only 20%. Overall, 68% workers were not using any personal protective equipment (PPE. The study concluded that the proportion of SME workers exposed to high level heat stress and noise (60 - 72 hrs/week is high. The workers engaged in forging and grinding sections are more prone to noise induced hearing loss (NIHL at higher frequencies as compared to workers of other sections. It is recommended that there is a strong need to implement the standard of working hours as well as heat stress and noise control measures.

  7. Debris flow hazard modelling on medium scale: Valtellina di Tirano, Italy

    Directory of Open Access Journals (Sweden)

    J. Blahut

    2010-11-01

    Full Text Available Debris flow hazard modelling at medium (regional scale has been subject of various studies in recent years. In this study, hazard zonation was carried out, incorporating information about debris flow initiation probability (spatial and temporal, and the delimitation of the potential runout areas. Debris flow hazard zonation was carried out in the area of the Consortium of Mountain Municipalities of Valtellina di Tirano (Central Alps, Italy. The complexity of the phenomenon, the scale of the study, the variability of local conditioning factors, and the lacking data limited the use of process-based models for the runout zone delimitation. Firstly, a map of hazard initiation probabilities was prepared for the study area, based on the available susceptibility zoning information, and the analysis of two sets of aerial photographs for the temporal probability estimation. Afterwards, the hazard initiation map was used as one of the inputs for an empirical GIS-based model (Flow-R, developed at the University of Lausanne (Switzerland. An estimation of the debris flow magnitude was neglected as the main aim of the analysis was to prepare a debris flow hazard map at medium scale. A digital elevation model, with a 10 m resolution, was used together with landuse, geology and debris flow hazard initiation maps as inputs of the Flow-R model to restrict potential areas within each hazard initiation probability class to locations where debris flows are most likely to initiate. Afterwards, runout areas were calculated using multiple flow direction and energy based algorithms. Maximum probable runout zones were calibrated using documented past events and aerial photographs. Finally, two debris flow hazard maps were prepared. The first simply delimits five hazard zones, while the second incorporates the information about debris flow spreading direction probabilities, showing areas more likely to be affected by future debris flows. Limitations of the modelling arise

  8. BUDGET UAV SYSTEMS FOR THE PROSPECTION OF SMALL- AND MEDIUM-SCALE ARCHAEOLOGICAL SITES

    Directory of Open Access Journals (Sweden)

    W. Ostrowski

    2016-06-01

    Full Text Available One of the popular uses of UAVs in photogrammetry is providing an archaeological documentation. A wide offer of low-cost (consumer grade UAVs, as well as the popularity of user-friendly photogrammetric software allowing obtaining satisfying results, contribute to facilitating the process of preparing documentation for small archaeological sites. However, using solutions of this kind is much more problematic for larger areas. The limited possibilities of autonomous flight makes it significantly harder to obtain data for areas too large to be covered during a single mission. Moreover, sometimes the platforms used are not equipped with telemetry systems, which makes navigating and guaranteeing a similar quality of data during separate flights difficult. The simplest solution is using a better UAV, however the cost of devices of such type often exceeds the financial capabilities of archaeological expeditions. The aim of this article is to present methodology allowing obtaining data for medium scale areas using only a basic UAV. The proposed methodology assumes using a simple multirotor, not equipped with any flight planning system or telemetry. Navigating of the platform is based solely on live-view images sent from the camera attached to the UAV. The presented survey was carried out using a simple GoPro camera which, from the perspective of photogrammetric use, was not the optimal configuration due to the fish eye geometry of the camera. Another limitation is the actual operational range of UAVs which in the case of cheaper systems, rarely exceeds 1 kilometre and is in fact often much smaller. Therefore the surveyed area must be divided into sub-blocks which correspond to the range of the drone. It is inconvenient since the blocks must overlap, so that they will later be merged during their processing. This increases the length of required flights as well as the computing power necessary to process a greater number of images. These issues make

  9. Budget Uav Systems for the Prospection of - and Medium-Scale Archaeological Sites

    Science.gov (United States)

    Ostrowski, W.; Hanus, K.

    2016-06-01

    One of the popular uses of UAVs in photogrammetry is providing an archaeological documentation. A wide offer of low-cost (consumer) grade UAVs, as well as the popularity of user-friendly photogrammetric software allowing obtaining satisfying results, contribute to facilitating the process of preparing documentation for small archaeological sites. However, using solutions of this kind is much more problematic for larger areas. The limited possibilities of autonomous flight makes it significantly harder to obtain data for areas too large to be covered during a single mission. Moreover, sometimes the platforms used are not equipped with telemetry systems, which makes navigating and guaranteeing a similar quality of data during separate flights difficult. The simplest solution is using a better UAV, however the cost of devices of such type often exceeds the financial capabilities of archaeological expeditions. The aim of this article is to present methodology allowing obtaining data for medium scale areas using only a basic UAV. The proposed methodology assumes using a simple multirotor, not equipped with any flight planning system or telemetry. Navigating of the platform is based solely on live-view images sent from the camera attached to the UAV. The presented survey was carried out using a simple GoPro camera which, from the perspective of photogrammetric use, was not the optimal configuration due to the fish eye geometry of the camera. Another limitation is the actual operational range of UAVs which in the case of cheaper systems, rarely exceeds 1 kilometre and is in fact often much smaller. Therefore the surveyed area must be divided into sub-blocks which correspond to the range of the drone. It is inconvenient since the blocks must overlap, so that they will later be merged during their processing. This increases the length of required flights as well as the computing power necessary to process a greater number of images. These issues make prospection highly

  10. Solar wind effects on ionospheric convection: a review

    DEFF Research Database (Denmark)

    Lu, G.; Cowley, S.W.H.; Milan, S.E.

    2002-01-01

    ), and travelling convection vortices (TCVs). Furthermore, the large-scale ionospheric convection configuration has also demonstrated a strong correspondence to variations in the interplanetary medium and substorm activity. This report briefly discusses the progress made over the past decade in studies...

  11. Long-Term Observation of Small and Medium-Scale Gravity Waves over the Brazilian Equatorial Region

    Science.gov (United States)

    Essien, Patrick; Buriti, Ricardo; Wrasse, Cristiano M.; Medeiros, Amauri; Paulino, Igo; Takahashi, Hisao; Campos, Jose Andre

    2016-07-01

    This paper reports the long term observations of small and medium-scale gravity waves over Brazilian equatorial region. Coordinated optical and radio measurements were made from OLAP at Sao Joao do Cariri (7.400S, 36.500W) to investigate the occurrences and properties and to characterize the regional mesospheric gravity wave field. All-sky imager measurements were made from the site. for almost 11 consecutive years (September 2000 to November 2010). Most of the waves propagated were characterized as small-scale gravity. The characteristics of the two waves events agreed well with previous gravity wave studies from Brazil and other sites. However, significant differences in the wave propagation headings indicate dissimilar source regions. The observed medium-scale gravity wave events constitute an important new dataset to study their mesospheric properties at equatorial latitudes. These data exhibited similar propagation headings to the short period events, suggesting they originated from the same source regions. It was also observed that some of the medium-scale were capable of propagating into the lower thermosphere where they may have acted directly as seeds for the Rayleigh-Taylor instability development. The wave events were primarily generated by meteorological processes since there was no correlation between the evolution of the wave events and solar cycle F10.7.

  12. Economic Appraisal of Small and Medium Scale Poultry Egg Production in Ife and Ilesha Metropolis, Osun State, Nigeria.

    Directory of Open Access Journals (Sweden)

    Busari Ahmed Olugbenga

    2015-07-01

    Full Text Available The study appraised the economic performance of small and medium scale poultry egg production in Ife and Ilesha metropolis, Osun State Nigeria. A purposive sampling was used to select one hundred and twenty poultry egg farmers, cluster sampling was used to select areas where small and medium scale were concentrated in the study area then sixty (60 small scale and sixty (60 medium scale were randomly selected to form the population of the study. Data were collected through structured interview schedule. Descriptive statistics such as means and percentages were employed for budgetary analysis and economic performance. The ordinary least square was used to determine the significant variables influencing the gross margin of poultry egg farmers at different levels of scale of production. The study shows that the gross margin of small farms was ₦575.65 while the gross margin of medium farms was ₦43672.62. The total production cost of small and medium farms were ₦1480.25 and ₦29654.43 respectively. The results further reveal that costs of feed constituted the largest share of the total costs for the two categories of farm size. The amount spent on drug and feed were the only significant determining factors of revenue accruable to both categories of poultry egg farmers. Although, poultry egg production was profitable in the study area, the level of profit depended on the scale of operation.

  13. ADOPTION OF GOOD MANAGEMENT PRACTICE (GMP IN SMALL AND MEDIUM SCALE VANNAMEI SHRIMP FARMS ON THE NORTHERN SHORE EAST JAVA

    Directory of Open Access Journals (Sweden)

    Paula Florina

    2012-09-01

    Full Text Available The objectives of this research were to describe the value chain of Vannamei shrimp industry on the northern shore of East Java, to identify the current management practice that is being implemented by small to medium scale shrimp farmers, to analyze the level of adoption of Good Management Practice by small to medium scale shrimp farmers and to identify the challenges that prevent small to medium scale farmers from adopting Good Management Practice. This research utilized descriptive qualitative method using multiple-case study. Data collection was conducted through interviews with experts and various actors in shrimp industry and interviews and observations in shrimp farms. From this research it can be concluded that the farming activity gives the largest contribution in final product value, that the current management practice in observed intensive Vannamei shrimp farms is in line with recommendations of various institutions with the exception of waste management, that the observed intensive Vannamei shrimp farms have high adoption level of Good Management Practice (GMP for various stages of shrimp farming activity with the exception of waste management, and that there is a tendency that farmers follow the good practices that have direct impact to the success of the production, and that the main challenges of GMP adoption are the lack of a comprehensive GMP manual, the lack of structured technology dissemination, and the lack of incentive for the farmers to adopt waste management practices.Keywords: Litopenaeus Vannamei, Shrimp Farm, Good Management Practice, Value Chain, Multiple-Case Study

  14. Probabilistic Risk Assessment in Medium Scale for Rainfall-Induced Earthflows: Catakli Catchment Area (Cayeli, Rize, Turkey

    Directory of Open Access Journals (Sweden)

    H. A. Nefeslioglu

    2011-01-01

    Full Text Available The aim of the present study is to introduce a probabilistic approach to determine the components of the risk evaluation for rainfall-induced earthflows in medium scale. The Catakli catchment area (Cayeli, Rize, Turkey was selected as the application site of this study. The investigations were performed in four different stages: (i evaluation of the conditioning factors, (ii calculation of the probability of spatial occurrence, (iii calculation of the probability of the temporal occurrence, and (iv evaluation of the consequent risk. For the purpose, some basic concepts such as “Risk Cube”, “Risk Plane”, and “Risk Vector” were defined. Additionally, in order to assign the vulnerability to the terrain units being studied in medium scale, a new more robust and more objective equation was proposed. As a result, considering the concrete type of roads in the catchment area, the economic risks were estimated as 3.6×106€—in case the failures occur on the terrain units including element at risk, and 12.3×106€—in case the risks arise from surrounding terrain units. The risk assessments performed in medium scale considering the technique proposed in the present study will supply substantial economic contributions to the mitigation planning studies in the region.

  15. A Review of Low Frequency Electromagnetic Wave Phenomena Related to Tropospheric-Ionospheric Coupling Mechanisms

    Science.gov (United States)

    Simoes, Fernando; Pfaff, Robert; Berthelier, Jean-Jacques; Klenzing, Jeffrey

    2012-01-01

    Investigation of coupling mechanisms between the troposphere and the ionosphere requires a multidisciplinary approach involving several branches of atmospheric sciences, from meteorology, atmospheric chemistry, and fulminology to aeronomy, plasma physics, and space weather. In this work, we review low frequency electromagnetic wave propagation in the Earth-ionosphere cavity from a troposphere-ionosphere coupling perspective. We discuss electromagnetic wave generation, propagation, and resonance phenomena, considering atmospheric, ionospheric and magnetospheric sources, from lightning and transient luminous events at low altitude to Alfven waves and particle precipitation related to solar and magnetospheric processes. We review in situ ionospheric processes as well as surface and space weather phenomena that drive troposphere-ionosphere dynamics. Effects of aerosols, water vapor distribution, thermodynamic parameters, and cloud charge separation and electrification processes on atmospheric electricity and electromagnetic waves are reviewed. We also briefly revisit ionospheric irregularities such as spread-F and explosive spread-F, sporadic-E, traveling ionospheric disturbances, Trimpi effect, and hiss and plasma turbulence. Regarding the role of the lower boundary of the cavity, we review transient surface phenomena, including seismic activity, earthquakes, volcanic processes and dust electrification. The role of surface and atmospheric gravity waves in ionospheric dynamics is also briefly addressed. We summarize analytical and numerical tools and techniques to model low frequency electromagnetic wave propagation and solving inverse problems and summarize in a final section a few challenging subjects that are important for a better understanding of tropospheric-ionospheric coupling mechanisms.

  16. Ionosphere and Radio Communication

    Indian Academy of Sciences (India)

    Saradi Bora

    2017-02-01

    The Earth's ionosphere consists of plasma produced by thephotoionization of thin upper atmospheric gases by UV raysand photons of short wavelength from the sun. 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 readers to the study of ionosphere in the contextof its use as a radio reflector, with particular reference toIndia.

  17. 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...

  18. Ionospheric scintillation detection based on GPS observations, a case study over Iran

    Science.gov (United States)

    Sobhkhiz Miandehi, Sahar; Alizadeh Elizei, M. Mahdi; Schuh, Harald

    2017-04-01

    Global Positioning System (GPS) which is used extensively for various purposes such as navigation, surveying, remote sensing and telecommunication, is strongly affected by the earth's upper atmosphere, the ionosphere. Ionosphere is a highly variable region with complex physical characteristics in which the density of free electrons are large enough to have considerable effects on signals' propagation travelling through this dispersive medium. As GPS signals travel through the ionosphere, they may experience rapid amplitude fluctuations or unexpected phase changes. This is referred to as ionospheric scintillation. Ionospheric scintillation which is caused by small scale irregularities in the electron density, is one of the dominant propagation disturbances at radio frequency signals. These irregularities severely affect the accuracy and reliability of GPS measurements. Therefore it is necessary to investigate ionospheric scintillation and its effects on GPS observations. The focus of this paper is to detect ionospheric scintillations over Iran's region, during different periods of solar activity and to investigate these effects on GPS observations in more detail. Furthermore the effects of these irregularities on regional modeling of ionosphere over Iran is also investigated. The results show that effectiveness of this phenomenon depends on geographic location, local time and global geomagnetic storm index (kp index). The required data for this investigation are ground based measurements of permanent GPS stations over Iran, established by the National Cartographic Center of Iran (NCC).

  19. Travelling diabetics.

    Science.gov (United States)

    Chełmińska, Katarzyna; Jaremin, Bogdan

    2002-01-01

    During the past several decades, the number of both business and tourist travels has greatly increased. Among them are persons suffering from chronic diseases, including diabetics for whom travels pose the additional health-hazard. Irrespective of better education, self-control and constantly improving quality of specialistic equipment available, diabetics still are the group of patients requiring particular attention. In the case of travelling diabetics, problems may occur concerning the transport and storage of insulin, as well as control of glycaemia, all caused by irregularity of meals, variable diet, physical activity, stress, kinetosis (sea voyages), and the change of time zones. The travel may as well evoke ailments caused by the change of climate and concomitant diseases such as traveller's diarrhoea, malaria, etc. Apart from avoiding glycaemia fluctuations, important for retaining health of diabetics is the prevention of other diseases and carrying the necessary drugs.

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

    Science.gov (United States)

    Bhagavathiammal, G. J.

    2016-07-01

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

  1. Observational study of daytime ionospheric irregularities associated with typhoon

    Institute of Scientific and Technical Information of China (English)

    XIAO SaiGuan; SHI JianKui; ZHANG DongHe; HAO YongQiang; HUANG WeiQuan

    2012-01-01

    Spread-F is a manifestation of ionospheric irregularities and generally takes place at nighttime.However,it can also be observed seldom at daytime.It is recognized that acoustic gravity waves (AGWs) play an important role in triggering plasma instability which results in spread-F in the ionosphere.The typhoon is a main source of the AGWs.In this paper,two cases of ionospheric daytime spread-F in the period of typhoon were analyzed.One case was on July 29,1988 and the other was on August 01,1989.The results showed the following:1) There were some wave-like disturbances appearing in the HF Doppler records firstly,consequently the Doppler echo traces became scattered,which indicated that the ionospheric spread-F was triggered; 2) the blurred echo traces in the both two cases appeared in the morning (08:30-11:30 Beijing time) and lasted for more than two hours; 3) with the blurred echoes gradually weakening,the traveling ionospheric disturbances (TIDs) still existed and became clearer; 4) the frequency shifts in the two cases were both positive,implying the effective reflecting surface of the radio wave in the ionosphere moved downwards.These results provide good observational evidence for daytime spread-F during the typhoon period in Asian region.

  2. Travelers' Health: Travel and Breastfeeding

    Science.gov (United States)

    ... I J K L M N O P Q R S T U V W X Y Z # ... search/groups ). Mothers who plan to use a breast pump while traveling may need an electrical current ... during travel because exclusive breastfeeding means feeding only breast milk, no other foods or drinks, which protects ...

  3. [Travel medicine].

    Science.gov (United States)

    Schubert, S; Grimm, M

    2009-07-01

    Travel medicine deals with travellers' diseases. The target group is therefore distinct from tropical medicine. It has gained in significance due to the increase in tourism and professional work abroad in the last 50 years. Dangerous and widespread diseases in tropical countries, in particular tropical malaria, have come into focus in industrialized countries because of their appearance in travellers. Travel medicine deals not only with infectious or transmittable diseases, but also with the ability of patients with chronic diseases to travel, the medical aspects of flying, as well as the health hazards of professional work or high-risk sports abroad. The risk of disease as a result of travelling can be minimized by advice and prophylactic measures, such as vaccinations and drug prophylaxis against malaria, if indicated. On return, medical symptoms should be investigated promptly to ensure early detection of life-threatening disease courses, particularly tropical malaria, as well as to prevent the occurrence of small-scale epidemics. A small number of diseases can also emerge after several years, such as benign types of malaria, amoebic liver abscess and visceral leishmaniasis (kala-azar). Aids also belongs to these diseases. Therefore, in this era of HIV pandemic travellers concerned should be made aware of the risks.

  4. 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

  5. TRAVEL INFORMATION

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Mauritius Travel From August 31 to September 6, a high- level government delegation from Mauritius visited China. The delegation was headed by the President of Mauritius, Sir Anerood Jugnauth, and included the Minister of Tourism,

  6. Travelling Concepts

    DEFF Research Database (Denmark)

    Simonsen, Karen-Margrethe

    2013-01-01

    Review of "Travelling Concepts, Metaphors, and Narratives: Literary and Cultural Studies in an Age of Interdisciplinary Research" ed. by Sibylle Baumgarten, Beatrice Michaelis and Ansagar Nünning, Trier; Wissenschaftlicher Verlag Trier, 2012......Review of "Travelling Concepts, Metaphors, and Narratives: Literary and Cultural Studies in an Age of Interdisciplinary Research" ed. by Sibylle Baumgarten, Beatrice Michaelis and Ansagar Nünning, Trier; Wissenschaftlicher Verlag Trier, 2012...

  7. Reply to comment by Kil et al. on "The night when the auroral and equatorial ionospheres converged"

    Science.gov (United States)

    Martinis, Carlos; Baumgardner, Jeffrey; Mendillo, Michael; Wroten, Joei; Coster, Anthea J.; Paxton, Larry J.

    2016-10-01

    One of the goals of the Martinis et al. (2015) (M15) paper was to stimulate interest in the topic of "severe events during moderate geomagnetic storms"—and we succeeded. We welcome the Comment by Kil et al. (2016) (K16) who identified weak signatures related to medium-scale traveling ionospheric disturbances (MSTIDs) and tried to argue that airglow depletion signatures of equatorial spread F (ESF) were not present. We agree with K16 in that MSTIDs were present to the north of the all-sky imager, but only during the early observations. They are easily distinguished from the ESF-related dark structures observed at the same time to the south of the imager. We stress some observational facts that K16 overlooked or erroneously used to support their case. M15 offered evidence and discussion evidence and discussion of a dynamical pattern—both in space and time domains—and the counter arguments by K16 should have dealt with the same places and same times. We also point out that the GPS data shown by K16 do not provide any information below 30° geographic latitude in the longitude sector covered by the all-sky imager. This is the region where the ESF structures appeared first and grew to reach higher latitudes. We believe that the issues addressed by K16 do not provide conclusive evidence to rule out the interpretation given by M15 on the nature of the airglow depletions observed at McDonald Observatory.

  8. [Traveller's diarrhoea].

    Science.gov (United States)

    Vila, Jordi; Oliveira, Ines; Zboromyrska, Yuliya; Gascon, Joaquim

    2016-11-01

    Traveller's diarrhoea (TD) is acquired primarily through ingestion of food and drinks contaminated with pathogens that cause diarrhoea. They can be bacteria, protozoa, helminths, and viruses. Globally, the most common causes of TD are two pathotypes of Escherichia coli (enterotoxigenic and enteroaggregative) and Campylobacter, although there are significant variations by geographic area visited. Most TD occurs in individuals traveling to low-middle income countries. The type of travel, length of stay, traveller's age, and the presence of certain underlying conditions are important risk factors to consider for the acquisition of TD. While TD is usually a mild and self-limiting disease, half of travellers with TD experience some limitation of activities during their trip, while up to 10% will experience persistent diarrhoea or other complications. The purpose of this article is to provide an updated microbiological, epidemiological, and clinical profile of traveller's diarrhoea, including known risk factors, as well as to make recommendations on the prevention and treatment of TD. Copyright © 2016 Elsevier España, S.L.U. and Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.

  9. 3 dimensional ionospheric electron density reconstruction based on GPS measurements

    Science.gov (United States)

    Stolle, C.; Schlüter, S.; Jacobi, C.; Jakowski, N.

    When radio waves as sended by the naviagtion system GPS are passing through the ionosphere they are subject to delays in phase, travel time and polarisation which is an effect of the free electrons. The measured integrated value of Total Electron Content can be utilised for three-dimensional reconstruction of electron density patterns in the ionosphere. Here a tomographic approach is represented. Scince the distribution of data is very sparse and patchy we decided for an algebraic iterative algorithm. The ground based GPS data collected by IGS receivers can be combined by space based GPS of radio limb sounding, incoherent scatter radar and ionosondes data. Hereby, radio occultation data improve beside the amount of available data especially the vertical resolution of electron density distribution. Ionosonde peack electron densities are taken as stop criteria determination for iteration. Reconstructed ionospheric scenarios and validations of the system by independent measurements are presented.

  10. Travelers' Health: Cruise Ship Travel

    Science.gov (United States)

    ... vectorborne diseases such as malaria, dengue, yellow fever, Japanese encephalitis, and Zika are endemic. New diseases might ... environmental conditions, as well as unaccustomed changes in diet and physical activity. Foreign travel may increase the ...

  11. Travelers' Health: Cruise Ship Travel

    Science.gov (United States)

    ... Water Disinfection Infographics for Travelers MERS Health Advisory poster Food and Water: What's Safer Health Advisory: MERS ... cruise ships can vary widely depending on ship size, itinerary, length of cruise, and passenger demographics. Generally, ...

  12. Characterizing Extreme Ionospheric Storms

    Science.gov (United States)

    Sparks, L.; Komjathy, A.; Altshuler, E.

    2011-12-01

    Ionospheric storms consist of disturbances of the upper atmosphere that generate regions of enhanced electron density typically lasting several hours. Depending upon the storm magnitude, gradients in electron density can sometimes become large and highly localized. The existence of such localized, dense irregularities is a major source of positioning error for users of the Global Positioning System (GPS). Consequently, satellite-based augmentation systems have been implemented to improve the accuracy and to ensure the integrity of user position estimates derived from GPS measurements. Large-scale irregularities generally do not pose a serious threat to estimate integrity as they can be readily detected by such systems. Of greater concern, however, are highly localized irregularities that interfere with the propagation of a signal detected by a user measurement but are poorly sampled by the receivers in the system network. The most challenging conditions have been found to arise following disturbances of large magnitude that occur only rarely over the course of a solar cycle. These extremely disturbed conditions exhibit behavior distinct from moderately disturbed conditions and, hence, have been designated "extreme storms". In this paper we examine and compare the behavior of the extreme ionospheric storms of solar cycle 23 (or, more precisely, extreme storms occurring between January 1, 2000, and December 31, 2008), as represented in maps of vertical total electron content. To identify these storms, we present a robust means of quantifying the regional magnitude of an ionospheric storm. Ionospheric storms are observed frequently to occur in conjunction with magnetic storms, i.e., periods of geophysical activity as measured by magnetometers. While various geomagnetic indices, such as the disturbance storm time (Dst) and the planetary Kp index, have long been used to rank the magnitudes of distinct magnetic storms, no comparable, generally recognized index exists for

  13. A Statistical Quality Control System in a Medium-Scale Weaving Mill: I. Control of Fabric Defects

    Directory of Open Access Journals (Sweden)

    Özlem DÜLGEROĞLU KISAOĞLU

    2010-03-01

    Full Text Available Establishing a control system in a medium-scale weaving mill by using statistical process control techniques was worked on and considered that the control system also would be a model for weaving mills. To determine production parameters and control them according to a definite sampling plan, the loom stoppages were investigated with their reasons and the defects on the fabric were detected during running of looms in process inspection. Therefore three different kinds of cord and a poplin fabric were observed. Analysis of loom-stoppages gives information about problems which are present in yarns, weaving preparation, weaving processes, and particularly indicates yarn quality, weaving machine adjustments and weaving preparation processes. In conclusion of woven fabric quality evaluations it was determined that the rate of defects originated from yarn is rather higher than that of defects originated from weaving preparation/weaving process.

  14. A Statistical Quality Control System in a Medium-Scale Weaving Mill: II. Control of Loom Stoppages

    Directory of Open Access Journals (Sweden)

    Özlem DÜLGEROĞLU KISAOĞLU

    2010-03-01

    Full Text Available Establishing a control system in a medium-scale weaving mill by using statistical process control techniques was worked on and considered that the control system also would be a model for weaving mills. To determine production parameters and control them according to a definite sampling plan, the loom stoppages were investigated with their reasons and the defects on the fabric were detected during running of looms in process inspection. Therefore three different kinds of cord and a poplin fabric were observed. Analysis of loom-stoppages gives information about problems which are present in yarns, weaving preparation, weaving processes, and particularly indicates yarn quality, weaving machine adjustments and weaving preparation processes. In conclusion of woven fabric quality evaluations it was determined that the rate of defects originated from yarn is rather higher than that of defects originated from weaving preparation/weaving process.

  15. Influence of Intuition and Capability on Accelerated Product Development in Big-Medium Scaled Food Companies in Indonesia

    Directory of Open Access Journals (Sweden)

    Pepey Riawati Kurnia

    2013-06-01

    Full Text Available To face the pressure of competition, more and more companies perform accelerated product development by shortening the product development time so that the product will arrive at the market at the shortest time. Food industry has also performed accelerated product development. Using evolution theory, contingency theory, market-based view, and resource-based view a research model has been built. Results of the research’s initial identification show that food industry in Indonesia is in growth level towards maturity level. Meanwhile, competition in the food industry is in moderate level towards hypercompetition level. Tactics of accelerated product development often carried out is by simplifying the product development steps to eliminating the product development steps. The innovation type used is incremental innovation since it is fast and easy. Results of the research give information that intuition and capabilities are the main motivating factors for big-medium scaled food companies in Indonesia to accelerate product development.

  16. Analytical Investigation and Control System Set-up of Medium Scale PV Plants for Power Flow Management

    Directory of Open Access Journals (Sweden)

    Rosario Miceli

    2012-11-01

    Full Text Available In the field of photovoltaic (PV plants and energy conversion from renewable sources, a large part of the technical literature is more devoted to practical aspects (new solar cells, electrically driven PV panels, safety, reduction of parasitic currents, etc. than to theoretical investigations. Despite this tendency, this paper presents a mathematical analysis of a medium scale photovoltaic power generation system connected to the distribution network and of its control system. In such a system, the conversion stage is unique due to the absence of a boost chopper. The conducted analysis leads to the interesting conclusion that the inverter used in the plant presents two degrees of freedom, easy to exploit in a control system in which the inverter simultaneously realizes the interconnection to the grid and the MPPT control. The structure of the control system is then presented, discussed and validated by means of numerical simulations.

  17. Travel Fever

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    China to become the world’s No.1 tourist destination by 2015 May 19 is a special day in China’s history. On that day 400 years ago,Xu Xiake (1587-1641),wellknown geographer,traveler and explorer of the Ming Dynasty (1368-1644),started a lifelong journey,leading to the publication of the monumental Xu Xiake’s Travel Notes,known for its detailed and accurate geographical information. The book also provided valuable insight into local customs and habits.

  18. Saturn's ionosphere and plasmasphere

    Science.gov (United States)

    Moore, Luke Edward

    2008-01-01

    A number of puzzling phenomena were revealed when the Voyager spacecraft flew past Saturn in 1981 to measure the ionized portions (ionosphere) of its upper atmosphere (thermosphere). Most of these issues have remained unexplained in the intervening 25 years due to a lack of conclusive observational data. With the arrival of Cassini at Saturn in July 2004, however, a new era of observations began, providing the promise of fresh evidence and demanding the development of a contemporary theoretical framework in order to re-examine old mysteries and understand new discoveries. This dissertation presents studies of Saturn's ionosphere and inner plasmasphere based on new time-dependent photochemical and diffusive transport models that solve the ion equations of continuity in one dimension. Calculations are conducted within the overall framework of a self-consistent, three-dimensional general circulation model (GCM) of Saturn's thermosphere, and the results of these studies are combined with GCM results to provide the building blocks of a new comprehensive model, the Saturn-Thermosphere- Ionosphere-Model (STIM). The one-dimensional model calculations are used to constrain and investigate a number of unresolved issues and to make testable predictions based on those investigations. Five primary topics are addressed: (1) the additional loss processes required to bring predicted electron densities into agreement with observations, (2) the discrepancy between theory and observations regarding the diurnal variation of peak electron density, (3) the effects of shadowing by Saturn's rings on its ionosphere, (4) the yet unknown electron and ion temperatures at Saturn, and (5) the ionospheric contribution to Saturn's plasmasphere. The models show that a steady influx of water into Saturn's atmosphere--from its rings or icy satellites--is required to explain observed electron densities. Additionally, the time-variability of the water source may be the cause of frequently observed

  19. Time travel?

    CERN Document Server

    Deser, Stanley D; Deser, Stanley; Jackiw, Roman

    1992-01-01

    To travel into the past, to observe it, perhaps to influence it and correct mistakes of one's youth, has been an abiding fantasy of mankind for as long as we have been aware of a past. Here are described some recent scientific investigations on this topic.

  20. Traveler's Diarrhea

    Science.gov (United States)

    ... probably safe to eat or drink the following:Soft drinks that are carbonated (such as cola).Hot drinks, ... for Staying HealthyInternational travel has its share of health and safety challenges. Talk to your doctor about the area ...

  1. Analysis of ionospheric disturbances associated with powerful cyclones in East Asia and North America

    Science.gov (United States)

    Li, Wang; Yue, Jianping; Yang, Yang; Li, Zhen; Guo, Jinyun; Pan, Yi; Zhang, Kefei

    2017-08-01

    East Asia and North America are the regions most heavily affected by powerful cyclones. In this paper we investigate the morphological characteristics of ionospheric disturbances induced by cyclones in different continents. The global ionosphere map supplied by the Center for Orbit Determination in Europe (CODE), International Reference Ionosphere Model (IRI) 2012, and Wallops Island ionosonde station data are used to analyse the ionospheric variations during powerful typhoons/hurricanes in East Asia and North America, respectively. After eliminating the ionospheric anomalies due to the solar-terrestrial environment, the total electron content (TEC) time series over the point with maximum wind speed is detected by the sliding interquartile range method. The results indicate that significant ionospheric disturbances are observed during powerful tropical cyclones in East Asia and North America, respectively, and that all the ionospheric anomalies are positive. In addition, the extent and magnitude of travelling ionospheric disturbances are associated with the category of tropical cyclone, and the extent of TEC anomalies in longitude is more pronounced than that in latitude. Furthermore, the maximum ionospheric anomaly does not coincide with the eye of the storm, but appears in the region adjacent to the centre. This implies that ionospheric disturbances at the edges of cyclones are larger than those in the eye of the winds. The phenomenon may be associated with the gravity waves which are generated by strong convective cells that occur in the spiral arms of tropical cyclones. This comprehensive analysis suggests that the presence of powerful typhoons/hurricanes may be a possible source mechanism for ionospheric anomalies.

  2. Extreme Ionospheric Gradients Observed in South Korea during the Last Solar Cycle

    Science.gov (United States)

    Jung, S.; Choi, Y.; Kim, M.; Lee, J.

    2012-12-01

    CONUS threat model. The other 12 dates are newly selected based on two space weather indices, planetary K (Kp) and disturbance, storm time (Dst). An ionospheric gradient of 90.97 mm/km was discovered at 0414UT on November 6, 2001 between stations NAWW and SONC, when PRN 21 was at 20.1° elevation. Most of severe gradients were observed from satellites at low elevation and traveling in a southerly direction of the Korean Peninsula. To locate enhanced-delay regions, we investigate both global ionospheric delay maps generated using the IONosphere MAP Exchange format (IONEX) data provided by International GNSS Service (IGS) and regional delay maps produced using the Korean GPS network stations. To validate observed ionospheric anomaly events, we examine whether similarly large ionospheric gradients are discovered at other nearby station pairs and other satellites whose Ionospheric Pierce Point (IPP) tracks take similar paths. The results from a series of checks support that the equatorial ionospheric anomaly caused severe ionospheric gradients observed from southern stations in South Korea. This study provides a better understanding of ionospheric behavior within the Korean Peninsula under ionospheric storm conditions, and helps investigate the operation and performance of GBAS. Ionospheric threat model developed in each region could be combined into a future global threat model for GBAS.

  3. Variation properties of ionospheric eclipse factor and ionospheric influence factor

    Institute of Scientific and Technical Information of China (English)

    ZHAO Chunmei; YUAN Yunbin; OU Jikun; CHEN Jinping

    2005-01-01

    The concepts and calculation methods of ionospheric eclipse factor (IEF) and ionospheric influence factor (IFF) are further illustrated. The temporal and spacial variation properties of IEF and IFF are studied, which shows that the properties are influenced by the geographic position and season. The possibility of improving the precision of using GPS data to determine ionospheric delay based on the above variation properties is also analysed.

  4. Ionospheric Feedback Instability in the Coupling of Magnetosphere-Ionosphere

    Institute of Scientific and Technical Information of China (English)

    王旭宇; 曹晋滨

    2003-01-01

    The ionospheric feedback instability is discussed by using the conductivity argument. We give an exact quantitative description to show that the free energy for this instability comes from the reduction of the Joule dissipation produced by the pre-existing convection electric field through self-consistent changes in ionization and conducactive ionosphere is pumped into the magnetosphere, wlich is contrary to the usual case whereby energy carried electron E × B drift. The electron conductivity is controlled by the ion Perdersen conductivity rather than by the electrons Pedersen conductivity. We also provide a qualitative theoretical explanation to the intense aurora favoured by a lower ambient ionospheric conductivity in the ionospheric feedback instability.

  5. Plains Traveler

    Science.gov (United States)

    2006-01-01

    10 April 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dust devil traveling across a plain west-southwest of Schiaparelli Crater, in far eastern Sinus Meridiani. The dust devil is casting a shadow toward the northeast, just south (below) of an egg-shaped crater. Location near: 6.4oS, 349.3oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Southern Summer

  6. Travel during Pregnancy

    Science.gov (United States)

    ... Events Advocacy For Patients About ACOG Travel During Pregnancy Home For Patients Search FAQs Travel During Pregnancy ... Pregnancy FAQ055, February 2016 PDF Format Travel During Pregnancy Pregnancy When is the best time to travel ...

  7. Local Ionospheric Scintillation Analysis

    Science.gov (United States)

    2017-03-14

    WORK UNIT NUMBER 7.  PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) ASIAN INSTITUTE OF TECHNOLOGY MOO 9 PHAHOLYOTHIN RD KM.42 KLONG NUNG PATHUM 12120...carried out as part of the densification and maintenance of the SCINDA network in South East Asia. 15.  SUBJECT TERMS Ionosphere, AOARD 16...Theoretical Physics (ICTP), International Civil Aviation Organization (ICAO), Boston College, University of California Los Angeles and AMBER projects

  8. Observation of ionospheric gravity waves induced by the 2011 Tohoku earthquake and tsunami using GPS networks in Japan

    Science.gov (United States)

    Tang, Long; Guo, Bofeng; Zhang, Xiaohong

    2017-04-01

    Recent observation results show the atmospheric gravity waves produced by both tsunami and earthquake can propagate upward to the atmosphere and interact with the plasma at the ionospheric height, leading to the generation of ionospheric disturbances. Carefully analyzing the propagation characteristics of ionospheric disturbances is necessary in order to distinguish the sources. Here, we use the GPS total electron content (TEC) observations in Japan to detect the ionospheric disturbances after the 2011 Tohoku earthquake, respectively. The Tohoku (Japan) earthquake (Mw=9) occurred at 05:46 UT on 11 March 2011 and then triggered powerful tsunami. The fundamental work is to properly isolate the ionospheric disturbances from raw TEC observations. Here, a second-order number difference method is employed to extract disturbance series and analyze the propagation characteristics of the ionospheric disturbances. The results show there are two types of gravity waves in the ionosphere over Japan, which is produced by the tsunami waves and the seismic rupture process, respectively. The earthquake-driven ionospheric gravity waves are distributed around the epicenter (including the areas over and far from the ocean) whereas the tsunami-driven ionospheric gravity waves are observed above the ocean. The earthquake-driven ionospheric gravity waves have different horizontal velocities, including about 210 m/s and 170 m/s, and frequency of about 1.5 mHz. The tsunami-driven ionospheric gravity waves have velocity of about 280 m/s, which are faster than that of the earthquake-driven ionospheric gravity waves, and frequency of about 1.0 mHz. In addition, the tsunami-driven ionospheric gravity waves have similar propagation characteristics in terms of horizontal velocity, direction, travel time, waveform and frequency compared to the tsunami waves causing them. In short, this study distinguishes the tsunami signals in ionosphere from ionospheric disturbances triggered by the earthquake

  9. An outbreak of urticarial form of swine erysipelas in a medium-scale piggery in Kiambu District, Kenya : case reoprt

    Directory of Open Access Journals (Sweden)

    J.K. Wabacha

    1998-07-01

    Full Text Available This report concerns an outbreak that occurred during July/August 1997. Ten pigs from a herd of 181 pigs in a medium-scale, semi-closed piggery in Kiambu District, Kenya, contracted the clinical disease. The main clinical findings in affected pigs included: fever (40.5-41.8 oC, prostration, inappetence, dog-sitting posture, abortion, erythema and raised, firm to the touch and easily palpated light pink to dark purple diamond-shaped to square/rectangular spots on the skin around the belly and the back. Based on the pathognomonic skin lesions, a clinical diagnosis of swine erysipelas was made. The diagnosis was confirmed by the isolation of Erysipelothrix rhusiopathiae organisms from the blood and skin biopsies taken from the affected pigs. Response to treatment with a combination of procaine penicillin and dihydrostreptomycin at the dosage rate of 20 000 IU/kg body weight (based on procaine penicillin for 3 days was good and all the affected pigs recovered fully. The farm was placed under quarantine to prevent spread of the disease.

  10. High-Performance Complementary Transistors and Medium-Scale Integrated Circuits Based on Carbon Nanotube Thin Films.

    Science.gov (United States)

    Yang, Yingjun; Ding, Li; Han, Jie; Zhang, Zhiyong; Peng, Lian-Mao

    2017-03-29

    Solution-derived carbon nanotube (CNT) network films with high semiconducting purity are suitable materials for the wafer-scale fabrication of field-effect transistors (FETs) and integrated circuits (ICs). However, it is challenging to realize high-performance complementary metal-oxide semiconductor (CMOS) FETs with high yield and stability on such CNT network films, and this difficulty hinders the development of CNT-film-based ICs. In this work, we developed a doping-free process for the fabrication of CMOS FETs based on solution-processed CNT network films, in which the polarity of the FETs was controlled using Sc or Pd as the source/drain contacts to selectively inject carriers into the channels. The fabricated top-gated CMOS FETs showed high symmetry between the characteristics of n- and p-type devices and exhibited high-performance uniformity and excellent scalability down to a gate length of 1 μm. Many common types of CMOS ICs, including typical logic gates, sequential circuits, and arithmetic units, were constructed based on CNT films, and the fabricated ICs exhibited rail-to-rail outputs because of the high noise margin of CMOS circuits. In particular, 4-bit full adders consisting of 132 CMOS FETs were realized with 100% yield, thereby demonstrating that this CMOS technology shows the potential to advance the development of medium-scale CNT-network-film-based ICs.

  11. Critical Factors Inhibiting Performance of Small- and Medium-Scale Contractors in Sub-Saharan Region: A Case for Malawi

    Directory of Open Access Journals (Sweden)

    Paul John Kulemeka

    2015-01-01

    Full Text Available The construction industry is dominated by small- and medium-scale contractors (SMCs who face an emerging trend of unique challenges in the implementation of projects. The study was aimed at examining inhibiting factors that influence performance of SMCs in terms of “quality of work,” “tender estimation,” “tender preparation,” and “timely completion of construction projects” in Malawi. A survey questionnaire was administered to 370 players in the construction industry which included public sector clients, contractors, consultants, and construction resource trainers in order to elicit data from 118 variables that were identified through a careful literature review. The inhibiting factors were generally dominated by economic issues, which was an emerging trend to what has been previously reported in the sub-Saharan region. The first highest ranked inhibiting factors were high lending interest regimes offered by financial institutions; stringent conditions to access capital; fluctuation of currency; stringent requirements for obtaining bonds; and high taxes. The research lays the foundation for further understanding of inhibitors on performance of SMCs in an evolving world which is being impacted by global factors and punctuated by sudden changes.

  12. Environmental Assessment for Small- and Medium-Scale Road Projects Implemented in Local Authority Areas: A Case Study from Thailand

    Directory of Open Access Journals (Sweden)

    Suparb Trethanya

    2009-11-01

    Full Text Available In developing countries like Thailand, an Environmental Assessment (EA is conducted only for projects prescribed by environmental legislation. Numerous projects, especially those that are small- and medium-scale in size and scope, are implemented in areas by a local authority without any type of EA. Based on a comparative analysis of the environmental status of large-, medium- and small-scale road development projects implemented by a local authority in Thailand, this paper attempts to justify the enforcement of EAs for medium- and small-scale projects. The justification is mainly based on theperceptions of people affected by these projects. Environmental impact scores, computed on the basis of people’s perceptions, reveal that, irrespective of the size of a project, the impacts caused by different sized projects are perceived as similar. Since every development project is implemented for the purpose of human development, this paper proposes to integrate environmental screening and initial EAs into the existing development control measures enforced by urban planning regulations and laws.

  13. Travelling with HIV

    DEFF Research Database (Denmark)

    Nielsen, Ulla S; Jensen-Fangel, Søren; Pedersen, Gitte

    2013-01-01

    We aimed to describe travel patterns, extent of professional pre-travel advice and health problems encountered during travel among HIV-infected individuals.......We aimed to describe travel patterns, extent of professional pre-travel advice and health problems encountered during travel among HIV-infected individuals....

  14. Climatological study of ionospheric irregularities over the European mid-latitude sector with GPS

    Science.gov (United States)

    Wautelet, Gilles; Warnant, René

    2014-03-01

    High-frequency variability of the ionosphere, or irregularities, constitutes the main threat for real-time precise positioning techniques based on Global Navigation Satellite Systems (GNSS) measurements. Indeed, during periods of enhanced ionospheric variability, GNSS users in the field—who cannot verify the integrity of their measurements—will experience positioning errors that can reach several decimeters, while the nominal accuracy of the technique is cm-level. In the frame of this paper, a climatological analysis of irregularities over the European mid-latitude region is presented. Based on a 10 years GPS dataset over Belgium, the work analyzes the occurrence rate (as a function of the solar cycle, season and local time) as well as the amplitude of ionospheric irregularities observed at a single GPS station. The study covers irregularities either due to space weather events (solar origin) or of terrestrial origin. If space weather irregularities are responsible for the largest effects in terms of ionospheric error, their occurrence rate highly depends on solar activity. Indeed, the occurrence rate of ionospheric irregularities is about 9 % during solar maximum, whereas it drops to about 0 % during medium or low solar activity periods. Medium-scale ionospheric disturbances (MSTIDs) occurring during daytime in autumn/winter are the most recurrent pattern of the time series, with yearly proportions slightly varying with the solar cycle and an amplitude of about 10 % of the TEC background. Another recurrent irregularity type, though less frequent than MSTIDs, is the noise-like variability in TEC observed during summer nighttime, under quiet geomagnetic conditions. These summer nighttime irregularities exhibit amplitudes ranging between 8 and 15 % of the TEC background.

  15. Ionospheric response to magnetar flare: signature of SGR J1550-5418 on coherent ionospheric Doppler radar

    Science.gov (United States)

    Mahrous, Ayman

    2017-03-01

    This paper presents observational evidence of frequent ionospheric perturbations caused by the magnetar flare of the source SGR J1550-5418, which took place on 22 January 2009. These ionospheric perturbations are observed in the relative change of the total electron content (ΔTEC/Δt) measurements from the coherent ionospheric Doppler radar (CIDR). The CIDR system makes high-precision measurements of the total electron content (TEC) change along ray-paths from ground receivers to low Earth-orbiting (LEO) beacon spacecraft. These measurements can be integrated along the orbital track of the beacon satellite to construct the relative spatial, not temporal, TEC profiles that are useful for determining the large-scale plasma distribution. The observed spatial TEC changes reveal many interesting features of the magnetar signatures in the ionosphere. The onset phase of the magnetar flare was during the CIDR's nighttime satellite passage. The nighttime small-scale perturbations detected by CIDR, with ΔTEC/Δt ≥ 0.05 TECU s-1, over the eastern Mediterranean on 22 January 2009 were synchronized with the onset phase of the magnetar flare and consistent with the emission of hundreds of bursts detected from the source. The maximum daytime large-scale perturbation measured by CIDR over northern Africa and the eastern Mediterranean was detected after ˜ 6 h from the main phase of the magnetar flare, with ΔTEC/Δt ≤ 0.10 TECU s-1. These ionospheric perturbations resembled an unusual poleward traveling ionospheric disturbance (TID) caused by the extraterrestrial source. The TID's estimated virtual velocity is 385.8 m s-1, with ΔTEC/Δt ≤ 0.10 TECU s-1.

  16. A Correlational Study between IT Governance and the Effect on Strategic Management Functioning among Senior & Middle Management in Medium Scale Software Organizations

    Science.gov (United States)

    Kurien, Sam

    2013-01-01

    The purpose of the study was to explore whether there are relationships between elements of information technology (IT) governance, strategic planning, and strategic functions among senior and mid-level management at medium-scaled software development firms. Several topics and models of IT governance literature were discussed and the gap in…

  17. A Correlational Study between IT Governance and the Effect on Strategic Management Functioning among Senior & Middle Management in Medium Scale Software Organizations

    Science.gov (United States)

    Kurien, Sam

    2013-01-01

    The purpose of the study was to explore whether there are relationships between elements of information technology (IT) governance, strategic planning, and strategic functions among senior and mid-level management at medium-scaled software development firms. Several topics and models of IT governance literature were discussed and the gap in…

  18. Capturing medium scale heterogeneity in surface water-groundwater interactions: challenges and advantages of high resolution temperature data

    Science.gov (United States)

    Shanafield, M.; Cook, P. G.; McCallum, J.; Noorduijn, S.

    2013-12-01

    capturing and quantifying streambed heterogeneity at a medium scale.

  19. Ionospheric Signatures of North Korean Nuclear Test on 12 February 2013

    Science.gov (United States)

    Yoon, M.; Kim, D.; Yang, Y. M.; Lee, J.; Komjathy, A.

    2014-12-01

    Previous studies on interactions between the atmospheric waves and ionospheric perturbations concluded that the acoustic-gravity waves triggered by solid earth events such as earthquakes, tsunamis and underground nuclear tests may be used in detecting the ionospheric perturbations. Ionospheric perturbations have been observed using sounding radars and GPS remote sensing techniques since 1970s. As primary examples, ionospheric disturbances associated with 2006 and 2009 North Korean underground nuclear tests were observed using GPS measurements. In this work, we processed GNSS stations in South Korea and Japan and analyzed traveling ionospheric disturbances that were coincident with the 2013 North Korean underground test. North Korea conducted the third underground nuclear test at 2:57 UTC on February 12, 2013. The magnitude of earthquake generated by this event was registered to be an Mw 5.1 event. After analyzing GPS measurements from nearby stations, strong ionospheric perturbations were observed 15-30 minutes after the reported event, and the disturbances were shown to have primarily two different wave trains. The maximum VTEC perturbations turned out to be between 0.4 to 0.7 TECU. Five stations located in the northwest-to-southeast direction were also scrutinized for the propagation direction and amplitude variation related to ionospheric wave structures. The results clearly showed that the maximum amplitude of the waves may be higher as the stations are closer to the epicenter indicating that the waveforms may propagate away from the epicenter. In this research, we will analyze the characteristics of the detected ionospheric perturbations associated with the underground nuclear test. These findings are expected to verify our modeling results. We hope to get a better understanding of the influence of man-made hazards on the temporal and spatial variability of the global ionosphere.

  20. 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

    European ionosondes. Also we studied the prominent phenomena (e.g. TIDs- Travelling Ionospheric Disturbances), and plasma irregularities (e.g. spread-F) of the ionosphere in the function of geomagnetic activity. As we compared the occurrences of TIDs and spread-F phenomena on the quiet days with their occurrences on moderate and strong stormy days, we can see significant correlation between the magnitude of the Ae-index and the daily number of the occurrence of TIDs, but at the same time there is no definite connection between the daily number of the occurrence of spread-F phenomenas and the intensity of geomagnetic activity.

  1. Travelers' Health: Water Disinfection for Travelers

    Science.gov (United States)

    ... Chapter 2 - Food Poisoning from Marine Toxins Water Disinfection for Travelers Howard D. Backer RISK FOR TRAVELERS ... of iodine and chlorine (see Halogens below). Chemical Disinfection HALOGENS The most common chemical water disinfectants are ...

  2. Travel/Travelers and Parasitic Diseases

    Science.gov (United States)

    ... care providers. Health departments, the travel industry, multinational corporations, missionary and volunteer organizations, and travelers can also ... PPT, MPEG) on this site? Adobe PDF file Microsoft PowerPoint file Microsoft Word file Microsoft Excel file ...

  3. Travelers' Health: HIV Infection

    Science.gov (United States)

    ... Last-Minute Travel Long-Term Travel Mass Gatherings Medical Tourism Mental Health Motion Sickness Natural Disasters Pregnant Travelers ... for purposes of medical treatment (see Chapter 2, Medical Tourism ), the blood and blood products used in the ...

  4. Travelers' Health: Mumps

    Science.gov (United States)

    ... submit Start of Search Controls Search Form Controls Travelers' Health Note: Javascript is disabled or is not ... FAQ Stamaril clinics Disease Directory Resources Resources for Travelers Adventure Travel Animal Safety Blood Clots Bug Bites ...

  5. Travelers' Health: Motion Sickness

    Science.gov (United States)

    ... Disease Directory Resources Resources for Travelers Adventure Travel Animal Safety Blood Clots Bug Bites Business Travel Cold ... motion sickness. Adding distractions—controlling breathing, listening to music, or using aromatherapy scents such as mint or ...

  6. Experimentally investigate ionospheric depletion chemicals in artificially created ionosphere

    Energy Technology Data Exchange (ETDEWEB)

    Liu Yu; Cao Jinxiang; Wang Jian; Zheng Zhe; Xu Liang; Du Yinchang [CAS Key Laboratory of Basic Plasma Physics, Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2012-09-15

    A new approach for investigating ionosphere chemical depletion in the laboratory is introduced. Air glow discharge plasma closely resembling the ionosphere in both composition and chemical reactions is used as the artificially created ionosphere. The ionospheric depletion experiment is accomplished by releasing chemicals such as SF{sub 6}, CCl{sub 2}F{sub 2}, and CO{sub 2} into the model discharge. The evolution of the electron density is investigated by varying the plasma pressure and input power. It is found that the negative ion (SF{sub 6}{sup -}, CCl{sub 2}F{sub 2}{sup -}) intermediary species provide larger reduction of the electron density than the positive ion (CO{sub 2}{sup +}) intermediary species. The negative ion intermediary species are also more efficient in producing ionospheric holes because of their fast reaction rates. Airglow enhancement attributed to SF{sub 6} and CO{sub 2} releases agrees well with the published data. Compared to the traditional methods, the new scheme is simpler to use, both in the release of chemicals and in the electron density measurements. It is therefore more efficient for investigating the release of chemicals in the ionosphere.

  7. Sustaining “Lilliputs” in the Global Knowledge-Based Economy: Prospects for Micro, Small, and Medium-Scale Enterprises in the Developing World

    Directory of Open Access Journals (Sweden)

    Maria Divina Gracia Z. Roldan

    2015-06-01

    Full Text Available Micro, small, and medium-scale enterprises (MSMEs comprise bulk of business entities in the developing world. Their contribution is seen in terms of employment generation and capital formation. Seen as the engine of growth in present knowledge-based economies, MSMEs play a crucial role in the economic sustainability of Asian developing countries. This paper discusses the role of MSMEs in Asia, with the Philippines as a case in point. It examines issues and challenges these enterprises face, as well as, their role and impact in developing the Philippine economy and human capital. It explores mechanisms of European linkaging and assistance to the Philippine MSME sector. The paper posits that a supportive policy environment is necessary for these enterprises to achieve their potential for sustainable growth in a global knowledge-based economy. Keywords: Sustainability, micro, small & medium-scale enterprises, knowledge-based economy, European linkaging mechanisms

  8. The Connected Traveler

    Energy Technology Data Exchange (ETDEWEB)

    Young, Stanley

    2017-04-24

    The Connected Traveler project is a multi-disciplinary undertaking that seeks to validate potential for transformative transportation system energy savings by incentivizing energy efficient travel behavior.

  9. Ionospheric precursors to scintillation activity

    Directory of Open Access Journals (Sweden)

    Paul S.J. Spencer

    2014-03-01

    Full Text Available Ionospheric scintillation is the rapid fluctuation of both phase and amplitude of trans-ionospheric radio waves due to small scale electron density irregularities in the ionosphere. Prediction of the occurrence of scintillation at L band frequencies is needed to mitigate the disruption of space-based communication and navigation systems. The purpose of this paper is to present a method of using tomographic inversions of the ionospheric electron density obtained from ground-based GPS data to infer the location and strength of the post-sunset plasma drift vortex. This vortex is related to the pre-reversal enhancement in the eastwards electric field which has been correlated to the subsequent occurrence of scintillation.

  10. Modeling of critical factors for integrating sustainability with innovation for Indian small- and medium-scale manufacturing enterprises: An ISM and MICMAC approach

    OpenAIRE

    Bisma Mannan; Sonal Khurana; Abid Haleem

    2016-01-01

    The growth of any country depends upon the existence of small- and medium-scale enterprises (SMEs). The greater the number of SMEs present in any country, the economy of the country increases in the same proportion. This paper uses the qualitative research technique to study the critical factors which affect the integration of sustainability with innovation taking into account Indian manufacturing SMEs. An ISM approach is applied to establish the interrelationship between the various critical...

  11. Models of Titan's Ionosphere

    Science.gov (United States)

    Robertson, I. P.; Cravens, T. E.; Waite, J. H.; Wahlund, J.; Yelle, R. V.; Vuitton, V.; Coates, A.; Magee, B.; Gell, D. A.

    2007-12-01

    During the TA and T18 encounters with Titan, in situ measurements were made of Titan's atmosphere and ionosphere by several instruments on board the Cassini Orbiter, including the Ion and Neutral Mass Spectrometer (INMS), the Langmuir probe on the Cassini Radio and Plasma Wave Experiment (RPWS), and the Cassini Plasma Spectrometer Subsystem (CAPS). Both of these encounters were on the day as well as the night side of Titan. The model uses neutral densities measured by the INMS instrument and the electron temperature was measured by the RPWS instrument. The model also includes energetic electron fluxes measured by the CAPS instrument, which act as an important source of ionization on the night side. The modeled ion densities are compared with densities measured by INMS in its Open Source mode.

  12. High Resolution Ionospheric Mapping Using Spaceborne Synthetic Aperture Radars

    Science.gov (United States)

    Meyer, F. J.; Chotoo, K.; Roth, A. P.

    2012-12-01

    properties, and (if applicable) geographic location. Three case studies will be presented to highlight the type and quality of ionospheric information that can be retrieved: (1) The high spatial resolution of SAR-derived TEC maps is emphasized in a case study that focuses on high resolution mapping of aurora arcs in central Alaska. Here, TEC enhancements associated with aurora activity are mapped and compared to reference observations from sky cameras and GPS; (2) observations of mid-latitudal traveling ionospheric disturbances are shown to showcase the accuracy of SAR-derived TEC maps. Several SAR-based TEC mapping methods are compared to highlight their respective advantages and disadvantages regarding processing complexity and estimation accuracy; (3) a third example focuses on analyzing post-sunset scintillation phenomena in equatorial regions. SAR is used to assess the frequency of occurrence of scintillation and analyze their associated power spectra. To conclude the paper, the temporal and spatial sampling of the ionosphere provided by the fleet of current and future spaceborne SAR sensors is analyzed to provide an assessment of the global ionospheric mapping capabilities of SAR.

  13. Travel time and travel cost in European air travel

    OpenAIRE

    Dusek, Tamas

    2012-01-01

    The aim of the study is to examine two issues of consumer air travel accessibility in Europe, namely flight time and ticket costs. The first part of the paper discusses the various methodological problems of creating time matrix and cost matrix of air travel. Because of problems of conceptualizing of the air travel network and the modifiable areal unit problem the analysis is conducted on several spatial levels. The smallest network consists of 15 busiest airports and the largest network has ...

  14. Positive and negative ionospheric responses to the March 2015 geomagnetic storm from BDS observations

    Science.gov (United States)

    Jin, Shuanggen; Jin, Rui; Kutoglu, H.

    2017-06-01

    The most intense geomagnetic storm in solar cycle 24 occurred on March 17, 2015, and the detailed ionospheric storm morphologies are difficultly obtained from traditional observations. In this paper, the Geostationary Earth Orbit (GEO) observations of BeiDou Navigation Satellite System (BDS) are for the first time used to investigate the ionospheric responses to the geomagnetic storm. Using BDS GEO and GIMs TEC series, negative and positive responses to the March 2015 storm are found at local and global scales. During the main phase, positive ionospheric storm is the main response to the geomagnetic storm, while in the recovery phase, negative phases are pronounced at all latitudes. Maximum amplitudes of negative and positive phases appear in the afternoon and post-dusk sectors during both main and recovery phases. Furthermore, dual-peak positive phases in main phase and repeated negative phase during the recovery are found from BDS GEO observations. The geomagnetic latitudes corresponding to the maximum disturbances during the main and recovery phases show large differences, but they are quasi-symmetrical between southern and northern hemispheres. No clear zonal propagation of traveling ionospheric disturbances is detected in the GNSS TEC disturbances at high and low latitudes. The thermospheric composition variations could be the dominant source of the observed ionospheric storm effect from GUVI [O]/[N2] ratio data as well as storm-time electric fields. Our study demonstrates that the BDS (especially the GEO) observations are an important data source to observe ionospheric responses to the geomagnetic storm.

  15. Positive and negative ionospheric responses to the March 2015 geomagnetic storm from BDS observations

    Science.gov (United States)

    Jin, Shuanggen; Jin, Rui; Kutoglu, H.

    2017-01-01

    The most intense geomagnetic storm in solar cycle 24 occurred on March 17, 2015, and the detailed ionospheric storm morphologies are difficultly obtained from traditional observations. In this paper, the Geostationary Earth Orbit (GEO) observations of BeiDou Navigation Satellite System (BDS) are for the first time used to investigate the ionospheric responses to the geomagnetic storm. Using BDS GEO and GIMs TEC series, negative and positive responses to the March 2015 storm are found at local and global scales. During the main phase, positive ionospheric storm is the main response to the geomagnetic storm, while in the recovery phase, negative phases are pronounced at all latitudes. Maximum amplitudes of negative and positive phases appear in the afternoon and post-dusk sectors during both main and recovery phases. Furthermore, dual-peak positive phases in main phase and repeated negative phase during the recovery are found from BDS GEO observations. The geomagnetic latitudes corresponding to the maximum disturbances during the main and recovery phases show large differences, but they are quasi-symmetrical between southern and northern hemispheres. No clear zonal propagation of traveling ionospheric disturbances is detected in the GNSS TEC disturbances at high and low latitudes. The thermospheric composition variations could be the dominant source of the observed ionospheric storm effect from GUVI [O]/[N2] ratio data as well as storm-time electric fields. Our study demonstrates that the BDS (especially the GEO) observations are an important data source to observe ionospheric responses to the geomagnetic storm.

  16. Remote Sensing of Atmospheric and Ionospheric Disturbances using Radio Science Techniques

    Science.gov (United States)

    Yang, Y. M.; Paik, M.; Oudrhiri, K.; Buccino, D.; Kahan, D. S.

    2016-12-01

    Atmospheres and ionospheres can have significant impacts on radio frequency signal propagation such as Deep Space Network and Global Navigation Satellite System (GNSS, including Global Position System (GPS)) measurements. Previous studies indicate that Earth's atmospheric, surface, and interior processes, such as seismic activities, tsunamis, meteor impacts, and volcanic eruptions, are able to trigger atmospheric acoustic and gravity waves (AGWs), which potentially induce traveling ionospheric disturbances (TIDs) in the upper atmosphere. These perturbations are relatively small to the background of atmospheric and ionospheric profiles but detectable to radio frequency signals. In this research, we will demonstrate the ability of using ground- and space-based radio science techniques to detect and characterize atmospheric and ionospheric wave propagation from solid earth events including seismic activities and tsunamis. The detected wave trains with wave characteristics such as propagation speeds and wavelengths are classified through analysis of the line of sight (LOS) and radio occultation measurements made by different frequency radio waves. Dominant and different physical characteristics of AGW and TID propagations are found to be associated with specific surface wave propagations. In this research, we compare observations made by different frequency radio signals, corresponding model simulations, and other geophysical measurements of surface wave propagation such as seismometers, infrasound arrays and DART buoys. Results are shown to improve our understanding of the interactions between surface, atmosphere, and ionosphere. The better understanding of the coupling between planetary interior, surface, atmosphere, and ionosphere will benefit from innovative radio science techniques.

  17. Childhood and Travel Literature.

    Science.gov (United States)

    Espey, David

    If children are not present in most travel literature--precisely because the genre has most typically been the domain of solitary male travelers who are escaping domestic obligation, routine, the familiar, and the family--they nevertheless are an integral part of the genre. The traveler is in many ways a child, an innocent abroad. Traveler writers…

  18. Travel-related illness.

    Science.gov (United States)

    Ziegler, Carol C

    2013-06-01

    Travel abroad for business and pleasure should be safe and meaningful for the traveler. To assure that safe experience, certain processes should be considered before travel. A thorough pretravel health assessment will offer patients and health care providers valuable information for anticipatory guidance before travel. The destination-based risk assessment will help determine the risks involved in travel to specific locations and guide in the development of contingency plans for all travelers, especially those with chronic conditions. Diseases are more prevalent overseas, and immunizations and vaccinations are all important considerations for persons traveling abroad.

  19. IAR signatures in the ionosphere: Modeling and observations at the Chibis-M microsatellite

    Science.gov (United States)

    Pilipenko, V.; Dudkin, D.; Fedorov, E.; Korepanov, V.; Klimov, S.

    2017-02-01

    A peculiar feature of geomagnetic variations at middle/low latitudes in the ULF band, just below the fundamental tone of the Schumann resonance, is the occurrence of a multi-band spectral resonant structure, observed by high-sensitivity induction magnetometers during nighttime. The occurrence of such spectral structure was commonly attributed to the Ionospheric Alfvén Resonator (IAR) in the upper ionosphere. Rather surprisingly, while ground observations of the IAR are ubiquitous, there are practically no reports on the IAR signatures from space missions. According to the new paradigm, the multi-band spectral structure excited by a lightning discharge is in fact produced by a regular sequence of an original pulse from a stroke and echo-pulses reflected from the IAR upper boundary. Upon the interaction of initial lightning-generated pulse with the anisotropic lower ionosphere, it partially penetrates into the ionosphere, travels up the ionosphere as an Alfvén pulse, and reflects back from the upper IAR boundary. The superposition of the initial pulse and echo-pulses produces spectra with multiple spectral peaks. Our modeling of Alfvénic pulse propagation in a system with the altitude profile of Alfven velocity modeling the realistic ionosphere has shown that IAR spectral signatures are to be evident only on the ground and above the IAR. Inside the IAR, the superposition of upward and downward propagating pulses produces a more complicated spectral pattern and the IAR spectral signatures deteriorate. We have used electric field data from the low-orbit Chibis-M microsatellite to search for IAR signatures in the ionosphere. We found evidence that the multi-band structure revealed by spectral analysis in the frequency range of interest is indeed the result of a sequence of lightning-produced pulses. According to the proposed conception it seems possible to comprehend why the IAR signatures are less evident in the ionosphere than on the ground.

  20. Ionospheric Signatures of the Earthquake in South Korea on 31 March 2014

    Science.gov (United States)

    Choi, P. H.; Yoon, M.; Yang, Y. M.; Lee, J.; Komjathy, A.

    2015-12-01

    Previous studies on interactions between the atmospheric waves and ionospheric perturbations concluded that the acoustic-gravity waves triggered by solid earth events such as earthquakes, tsunamis and underground nuclear tests may be used in detecting the ionospheric perturbations. Ionospheric perturbations have been observed using sounding radars and GPS remote sensing techniques since 1970s. As primary examples, ionospheric disturbances associated with the Tohoku earthquake and tsunami on March 11, 2011 were observed and analyzed using GPS measurements. In this work, we processed GPS stations in South Korea and analyzed traveling ionospheric disturbances that were coincident with the 2014 South Korean earthquake. The 31 March 2014 earthquake occurred at 19:48 UTC and the magnitude of this event was registered to be 5.0 Mw. This earthquake is the fourth strongest in South Korea since records began. After analyzing GPS measurements from nearby stations, strong ionospheric perturbations were observed about 20 minutes after the reported event, and the disturbances were shown to have primarily a wave train with periods of 60-120 minutes. The maximum VTEC perturbations turned out to be between 0.6 to 1.3 TECU. In this research, we will analyze the characteristics of the detected ionospheric perturbations associated with the earthquake and compare these results with those from man-made earthquakes such as underground nuclear tests. These findings are expected to verify our modeling results. We also hope to get a better understanding of the influence of both natural hazards and man-made hazards on the temporal and spatial variability of the global ionosphere

  1. 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...

  2. Satellite Observations of Ionospheric Earthquake Precursors

    Science.gov (United States)

    Grimal'Skij, V. V.; Ivchenko, V. N.; Lizunov, G. V.

    The authors review satellite observations of seismogenic phenomena in the ionosphere. Based on literature data, hypothetical patterns of seismogenic phenomena were reconstructed. The authors discuss the reasons which allow the ionospheric "anomalies" to be correlated with eartquake precursors.

  3. Coseismic ionospheric disturbances triggered by the Chi-Chi earthquake

    Science.gov (United States)

    Liu, J. Y.; Tsai, H. F.; Lin, C. H.; Kamogawa, M.; Chen, Y. I.; Lin, C. H.; Huang, B. S.; Yu, S. B.; Yeh, Y. H.

    2010-08-01

    At 17:47 UT on 20 September 1999, a large earthquake of magnitude Mw 7.6 struck the central Taiwan near a small town of Chi-Chi. The ground-based receivers of the global positioning system (GPS) in the Taiwan area detected coseismic ionospheric disturbances (CIDs) in the total electron content (TEC) triggered by the Chi-Chi earthquake. When the CIDs travel away from the origin on the Earth surface and then propagate into the ionosphere, their amplitudes and periods generally become smaller and longer, respectively. Moreover, two global grid searches, adapting the ray-tracing and the beam-forming techniques, have been used to analyze the observed GPS TEC. We have not only estimated the average speed of the CIDs propagating in the atmosphere and ionosphere but also determined the location of CID origin on the Earth surface by using the two techniques. The results show that the observed CIDs result from shock-acoustic waves triggered by sudden and large vertical motions of the Chi-Chi earthquake.

  4. Use of Southern California Integrated GPS Network (SCIGN) to image post-seismic perturbations of the ionosphere.

    Science.gov (United States)

    Artru, J.; Ducic, V.; Lognonné, P.

    2002-12-01

    Post-seismic perturbations in the atmosphere and ionosphere are induced by solid earth-atmosphere coupling, and can be monitored systematically after large earthquakes, e.g. using Doppler sounding. We will focus here on the capacity of short-scale imagery of the ionosphere offered by dense GPS networks. SCIGN is composed of 250 receivers in Southern California that provide continuous measurements of Total Electron Content along each receiver-satellite. A reconstruction of 2-D vertical electron content maps is performed, with a special attention paid on the accuracy and resolution achieved. We applied our technique to the detection of post-seismic ionospheric perturbations by the Hector Mine Earthquake in Southern California on October 16th, 1999. Two regimes of seismic perturbations are found, the first one related to seismic waves traveling in the ionosphere at about 3 km/s whereas the second regime would be induced by the onset of a gravity wave.

  5. Low-latitude ionospheric effects on SBAS

    Science.gov (United States)

    Arenas, J.; Sardón, E.; Sainz, A.; Ochoa, B.; Magdaleno, S.

    2016-06-01

    Satellite-based augmentation systems (SBAS) provide augmentation to Global Navigation Satellite Systems (GNSS) users in three areas: (1) broadcasting accurate corrections to GNSS satellite ephemeris, (2) providing a real-time empirical ionospheric model in the service area, and (3) providing integrity information in the form of estimates of the confidence of the ephemeris corrections and ionospheric delays. Ionospheric effects on SBAS are twofold: (a) the input data used by the SBAS will be affected by ionospheric effects, and (b) the more perturbed the ionosphere is, the more difficult it will be to provide accurate and reliable ionospheric information to the users. The ionosphere at low latitudes presents larger variability and more intense phenomena than at midlatitudes. Therefore, SBAS providing service to low-latitude regions will be more affected than those at other latitudes. From the different low-latitude ionospheric effects, this paper will focus on those having the largest impact on SBAS, which are total electron content temporal and spatial gradients, ionospheric scintillations, and depletions. This paper will present the impact of these effects on EGNOS (European Global Navigation Overlay System), the European SBAS. Although EGNOS can be considered as a midlatitude SBAS, it has to provide coverage down to rather low latitudes, so sometimes low-latitude ionospheric effects are observed in the EGNOS data. It will be shown how EGNOS performs under nominal conditions and how its performance is degraded when low-latitude ionospheric phenomena occur. Real EGNOS data affected by low-latitude ionospheric phenomena will be used.

  6. Ionospheric signatures of gravity waves produced by the 2004 Sumatra and 2011 Tohoku tsunamis: A modeling study

    Science.gov (United States)

    Yu, Yonghui; Wang, Wenqing; Hickey, Michael P.

    2017-01-01

    Ionospheric fluctuations inferred from observations of total electron content have previously been attributed to tsunamis and have confirmed the strong coupling between Earth's ocean and ionosphere via atmospheric gravity waves (AGWs). To further advance our understanding of this wave coupling process we employ a linear full-wave model and a nonlinear time-dependent model to examine the ionospheric response to the AGW perturbations induced by the 2004 Sumatra and the 2011 Tohoku tsunamis. In the 2004 case, our modeling analyses reveal that one component of the propagating AGWs becomes dynamically unstable in the E-region ionosphere at a range exceeding 2000 km in a direction 340° clockwise from north. Another component becomes convectively unstable in the E-region ionosphere at a range exceeding 700 km in a direction 250° clockwise from north. In the 2011 case, a significant enhancement in the ionospheric disturbance occurs in a direction northwest from the epicenter about 1 h following the tsunami onset, in general agreement with observations. Our simulations also indicate that the AGW propagating toward the southeast is responsible for a traveling ionospheric disturbance that remains of an observable amplitude for over 4 h during which time it propagates horizontally almost 4000 km.

  7. Rabies in travelers.

    Science.gov (United States)

    Gautret, Philippe; Parola, Philippe

    2014-03-01

    Most cases of rabies in travelers are associated with dog bites and occur in adults who are commonly migrants. The incidence of injuries to travelers caused by potentially rabid animals is approximately 0.4 % per month of stay. Dogs account for 51 % of cases, but nonhuman primates are the leading animals responsible for injuries in travelers returning from Southeast Asia. Travel to Southeast Asia, India and North Africa, young age, and traveling for tourism are risk factors for potential exposure. More than 70 % of travelers are not immunized prior to departing and do not receive adequate care when injured. The intradermal vaccination route has been proven economical, safe and immunogenic in travelers. The immunity provided by the three-dose series is long-lasting and should be considered an investment for future travel. Abbreviated schedules may be used for last-minute travelers.

  8. Spherical harmonic series solution of fields excited by vertical electric dipole in earth-ionosphere cavity

    Institute of Scientific and Technical Information of China (English)

    Yuanxin WANG; Wensheng FAN; Weiyan PAN; Hongqi ZHANG

    2008-01-01

    The spherical harmonic series expression of electromagnetic fields excited by ELF/SLF vertical electric dipole in the spherical earth-ionosphere cavity is derived when the earth and ionosphere are regarded as non-ideal conductors. A method of speeding numerical convergence has been presented. The electromagnetic fields in the cavity are calculated by this algorithm, and the results show that the electromagnetic fields between the earth and the ionosphere are the sum of two traveling waves in the SLF band. Moreover, the results are in complete agreement with that of the well-known spherical second-order approximation in the SLF band. The electromagnetic fields in the cavity are a type of standing wave in the ELF band and the variation of the amplitude versus frequency coincides with Schumann's resonance.

  9. Using the Co-Production of Knowledge for Developing Realistic Natural Disaster Scenarios for Small-to-Medium Scale Emergency Management Exercises

    Science.gov (United States)

    Robinson, T.; Wilson, T. M.; Davies, T. R.; Orchiston, C.; Thompson, J.

    2014-12-01

    Disaster scenarios for Emergency Management (EM) exercises are a widely-used and effective tool for communicating hazard information to policy makers, EM personnel, lifelines operators and communities in general. It is crucial that the scenarios are as realistic as possible. Major disasters however, contain a series of cascading consequences, both environmental and social, which are difficult to model. Consequently, only recently have large-scale exercises included such processes; incorporating these in small- and medium-scale scenarios has yet to be attempted. This study details work undertaken in a recent medium-scale earthquake exercise in New Zealand to introduce such cascading processes into the disaster scenario. Given limited time, data, and funding, we show that the co-production of knowledge between natural disaster scientists, EM personnel, and governance and lifelines organisations can yield detailed, realistic scenarios. Using the co-production process, scenario development was able to identify where the pre-exercise state of knowledge was insufficient. This enabled a focussed research response driven by end-user needs. This found that in general, seismic hazard (ground shaking) and its likely impacts were well known and understood by all parties. However, subsequent landsliding and associated effects were poorly known and understood and their potential impacts unconsidered. Scenario development therefore focussed primarily on understanding these processes and their potential effects. This resulted in cascading hazards being included in a medium-scale NZ exercise for the first time. Further, all participants were able to focus on the potential impacts on their specific sectors, increasing the level of knowledge of cascading processes across all parties. Using group based discussions throughout the design process allowed a detailed scenario to be created, fostered stronger inter-disciplinary relationships, and identified areas for further research

  10. Ionospheric disturbances in Asian region of Russia during sudden stratospheric warmings

    Science.gov (United States)

    Kurkin, Vladimir; Chernigovskaya, Marina; Medvedeva, Irina; Orlov, Igor

    This paper presents an investigation of the subauroral and mid-latitude ionosphere variations in the Asian region of Russia during stratospheric warmings in 2008, 2009 and 2010. We used the data from network of vertical and oblique-incidence sounding ionosounders of ISTP SB RAS. Irkutsk chirp-sounder (vertical incidence sounding) run every 1 minute on 24-hour basis for 30 days in winter of 2008, 2009 and 2010 to study small-scale and medium-scale distur-bances. The experiments on the radio paths Magadan-Irkutsk, Khabarovsk-Irkutsk and Norilsk -Irkutsk were conducted in order to study large-scale ionospheric disturbances. The frequency range was from 4 to 30 MHz, the sweep rate used 500 kHz/sec. To identify the stratospheric warming events the Berlin Meteorological University data (http://strat-www.met.fu-berlin.de) on stratospheric warming at standard isobaric levels and the atmospheric temperature height profiles measured by the Microwave Limb Sounder (MLS) aboard the EOS Aura spacecraft were used. The increase of wave activity in upper ionosphere over Asian region of Russia has recorded during stratospheric warmings. Spectrums of multi-scale variations were derived from the data obtained during the prolonged experiments. The analysis of experimental data has revealed the amplitudes of planetary waves in ionosphere during stratospheric warmings in 2008 and 2010 larger than ones in winter 2009 as opposed to amplitude variations of temperature in stratosphere. This work was supported by Russian Foundation for Basic Research (grant 08-05-00658).

  11. Mapping travelling convection vortex events with respect to energetic particle boundaries

    DEFF Research Database (Denmark)

    Moretto, T.; Yahnin, A.

    1998-01-01

    Thirteen events of high-latitude ionospheric travelling convection vortices during very quiet conditions were identified in the Greenland magnetometer data during 1990 and 1991. The latitudes of the vortex centres for these events are compared to the energetic electron trapping boundaries...

  12. Impulse Travel Time from the Magnetotail to the Aurora Region during substorm: OpenGGCM Simulation

    Science.gov (United States)

    Ferdousi, Banafsheh; Raeder, Jimmy

    2016-07-01

    The onset of substorms is an unsolved problem in Space Physics although there are many models explaining the substorm process. Studying the processes that occur during first 2 minutes of substorm depends critically on the correct timing between different signals in the plasma sheet and the ionosphere. This has been difficult to accomplish with data alone, since signals are sometimes ambiguous, or they have not been observed in the right locations. To investigate signal propagation paths and signal travel times, we use Magnetohydrodynamic global simulations of the Earth magnetosphere: OpenGGCM. The waves are created at different locations in the magnetotail by perturbing plasma pressure in the plasma sheet. Thus, we can study wave path in the magnetotail and determine its travel time to the ionosphere. Contrary to previous studies, we find that wave travel reach the ionosphere from the midtail around 60 seconds. We also find that waves travel faster through the lobes, and the Tamao path is not generally the preferred path for waves originating in the plasma sheet. Furthermore, we find that the impulses that are generated closer to earth lead to dispersed ionosphere signatures, whereas the impulses originated in midtail region lead to more localized signatures.

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

    Science.gov (United States)

    2009-01-01

    Astronomical Journal, 76, 2, pp. 123-140, 1971. Garcia-Fernandez, M., M. Hernandez-Pajares, J.M. Juan , J. Sanz, Improvement of ionospheric electron density...Katlenburg- Lindau , ProduServ GmbH Verlagsservice, Berlin, pp. 371-390, 1996. Jakowski, N., A. Wehrenpfennig, S. Heise, C. Reigber, H. Luehr, L

  14. Travel Inside the Ear

    Science.gov (United States)

    ... Home » Health Info » Hearing, Ear Infections, and Deafness Travel Inside the Ear Video When sound waves reach ... are smaller than an orange seed. It then travels into the inner ear, which is filled with ...

  15. Traveling Safely with Medicines

    Science.gov (United States)

    ... Medications Safely My Medicine List How to Administer Traveling Safely with Medicines Planes, trains, cars – even boats ... your trip, ask your pharmacist about how to travel safely with your medicines. Make sure that you ...

  16. Travelers' Health: Yellow Fever

    Science.gov (United States)

    ... Drugs Cruise Ship Travel Families with Children Fish Poisoning in Travelers Food and Water Getting Health Care ... removal of their thymus or have had indirect radiation therapy in the distant past, these people can ...

  17. End to End Travel

    Data.gov (United States)

    US Agency for International Development — E2 Solutions is a web based end-to-end travel management tool that includes paperless travel authorization and voucher document submissions, document approval...

  18. Ionosphere correction algorithm for spaceborne SAR imaging

    Institute of Scientific and Technical Information of China (English)

    Lin Yang; Mengdao Xing; Guangcai Sun

    2016-01-01

    For spaceborne synthetic aperture radar (SAR) ima-ging, the dispersive ionosphere has significant effects on the pro-pagation of the low frequency (especial y P-band) radar signal. The ionospheric effects can be a significant source of the phase error in the radar signal, which causes a degeneration of the image quality in spaceborne SAR imaging system. The background ionospheric effects on spaceborne SAR through modeling and simulation are analyzed, and the qualitative and quantitative analysis based on the spatio-temporal variability of the ionosphere is given. A novel ionosphere correction algorithm (ICA) is proposed to deal with the ionospheric effects on the low frequency spaceborne SAR radar signal. With the proposed algorithm, the degradation of the image quality caused by the ionosphere is corrected. The simulation re-sults show the effectiveness of the proposed algorithm.

  19. Daytime Ionosphere Retrieval Algorithm for the Ionospheric Connection Explorer (ICON)

    Science.gov (United States)

    Stephan, Andrew W.; Korpela, Eric J.; Sirk, Martin M.; England, Scott L.; Immel, Thomas J.

    2017-07-01

    The NASA Ionospheric Connection Explorer Extreme Ultraviolet spectrograph, ICON EUV, will measure altitude profiles of the daytime extreme-ultraviolet (EUV) OII emission near 83.4 and 61.7 nm that are used to determine density profiles and state parameters of the ionosphere. This paper describes the algorithm concept and approach to inverting these measured OII emission profiles to derive the associated O+ density profile from 150-450 km as a proxy for the electron content in the F-region of the ionosphere. The algorithm incorporates a bias evaluation and feedback step, developed at the U.S. Naval Research Laboratory using data from the Special Sensor Ultraviolet Limb Imager (SSULI) and the Remote Atmospheric and Ionospheric Detection System (RAIDS) missions, that is able to effectively mitigate the effects of systematic instrument calibration errors and inaccuracies in the original photon source within the forward model. Results are presented from end-to-end simulations that convolved simulated airglow profiles with the expected instrument measurement response to produce profiles that were inverted with the algorithm to return data products for comparison to truth. Simulations of measurements over a representative ICON orbit show the algorithm is able to reproduce hmF2 values to better than 5 km accuracy, and NmF2 to better than 12% accuracy over a 12-second integration, and demonstrate that the ICON EUV instrument and daytime ionosphere algorithm can meet the ICON science objectives which require 20 km vertical resolution in hmF2 and 18% precision in NmF2.

  20. Modelling urban travel times

    NARCIS (Netherlands)

    Zheng, F.

    2011-01-01

    Urban travel times are intrinsically uncertain due to a lot of stochastic characteristics of traffic, especially at signalized intersections. A single travel time does not have much meaning and is not informative to drivers or traffic managers. The range of travel times is large such that certain tr

  1. Modelling urban travel times

    NARCIS (Netherlands)

    Zheng, F.

    2011-01-01

    Urban travel times are intrinsically uncertain due to a lot of stochastic characteristics of traffic, especially at signalized intersections. A single travel time does not have much meaning and is not informative to drivers or traffic managers. The range of travel times is large such that certain

  2. Traveling and Asthma

    Science.gov (United States)

    ... Emergency Room? What Happens in the Operating Room? Traveling and Asthma KidsHealth > For Kids > Traveling and Asthma A A A What's in this ... t have to get in the way of travel fun. Let's find out how to be prepared ...

  3. Travel epidemiology. WHO perspective.

    Science.gov (United States)

    Gezairy, Hussein A

    2002-12-01

    International travel is undertaken by large, and ever increasing numbers of people for professional, social, recreational and humanitarian purposes, and this upward trend looks set to continue. Travelers are exposed to a variety of health risks of the unfamiliar environment of the visited area. The risk of exposure is determined by destination, duration of the visit, purpose of the visit, behavior of the traveler and underlying physical and biological status of the traveler. However, most risks can be minimized by suitable precautions taken before, during and after travel. Travelers can themselves, also, easily introduce any infectious agents they may harbor to the visited area. Many infectious diseases have been introduced in many parts of the world through travel and trade. Travel has been identified as a prime factor in the global spread of infectious diseases. In a world of rapid air travel, no country is safe from infectious diseases. An outbreak in one country can easily and rapidly be transmitted across long distances to affect other countries through travel and trade. The World Health Organization devotes great attention to prevention and control of global spread of infectious diseases and minimizing the negative effect of international travel on health. The main strategies of the World Health Organization for minimizing the negative effects of expanding travel on global health security include developing the necessary strategies, rules and regulations; strengthening global communicable diseases surveillance and response; dissemination of related information throughout the world and strengthening national capacity for communicable diseases surveillance and response.

  4. Modelling urban travel times

    NARCIS (Netherlands)

    Zheng, F.

    2011-01-01

    Urban travel times are intrinsically uncertain due to a lot of stochastic characteristics of traffic, especially at signalized intersections. A single travel time does not have much meaning and is not informative to drivers or traffic managers. The range of travel times is large such that certain tr

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

    Directory of Open Access Journals (Sweden)

    E. Astafyeva

    2009-03-01

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

  6. TRACKER: A three-dimensional raytracing program for ionospheric radio propagation

    Science.gov (United States)

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

    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 'Jones Code' 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 'real') 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.

  7. 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.

  8. Ionospheric redistribution during geomagnetic storms.

    Science.gov (United States)

    Immel, T J; Mannucci, A J

    2013-12-01

    [1]The abundance of plasma in the daytime ionosphere is often seen to grow greatly during geomagnetic storms. Recent reports suggest that the magnitude of the plasma density enhancement depends on the UT of storm onset. This possibility is investigated over a 7year period using global maps of ionospheric total electron content (TEC) produced at the Jet Propulsion Laboratory. The analysis confirms that the American sector exhibits, on average, larger storm time enhancement in ionospheric plasma content, up to 50% in the afternoon middle-latitude region and 30% in the vicinity of the high-latitude auroral cusp, with largest effect in the Southern Hemisphere. We investigate whether this effect is related to the magnitude of the causative magnetic storms. Using the same advanced Dst index employed to sort the TEC maps into quiet and active (Dststorm strength that corresponds closely to the TEC variation but follows it by 3-6h. For this and other reasons detailed in this report, we conclude that the UT-dependent peak in storm time TEC is likely not related to the magnitude of external storm time forcing but more likely attributable to phenomena such as the low magnetic field in the South American region. The large Dst variation suggests a possible system-level effect of the observed variation in ionospheric storm response on the measured strength of the terrestrial ring current, possibly connected through UT-dependent modulation of ion outflow.

  9. Calibrating for Ionospheric Phase Delays

    Science.gov (United States)

    Macdoran, P. F.

    1985-01-01

    Technique determines ionospheric phase delay on real-time universally applicable basis in terms of electrons per meter squared by coherently modulating two L-band carrier frequencies received from two Global Positioning System satelites. Two pseudorandom number sequences cross-correlated to derive delay time.

  10. Travelers' Health: Water Disinfection for Travelers

    Science.gov (United States)

    ... Water Disinfection Infographics for Travelers MERS Health Advisory poster Food and Water: What's Safer Health Advisory: MERS ... prevent recontamination during storage Table 2-10. Microorganism size and susceptibility to filtration ORGANISM AVERAGE SIZE (µm) ...

  11. Comprehensive care of travelers.

    Science.gov (United States)

    Pust, R E; Peate, W F; Cordes, D H

    1986-12-01

    Travel, especially if it is international, often means major changes for the family. Family physicians should assess the epidemiologic risk and psychosocial significance of travel or relocation in light of the family's life-cycle stage and antecedent health. Using core references, which are kept current in partnership with public health agencies, family physicians are able to provide comprehensive immunization, medications, and patient education for all travel risks. Families are given medical record summaries and recommended sources of care at their destination. Eight weeks after their return patients are reassessed for newly acquired illness and helped to integrate the perspectives gained during the travel into the family's future dynamics. Taking advantage of growing travel medicine opportunities, family medicine educators should base the care of travelers and teaching of residents on defined competence priorities. Travelers' health provides a mutually rewarding model of shared care with public health consultants in the community medicine curriculum.

  12. Ionospheric Anomalies of the 2011 Tohoku Earthquake with Multiple Observations during Magnetic Storm Phase

    Science.gov (United States)

    Liu, Yang

    2017-04-01

    days. Associated with geomagnetic storm at similar time, radio occultation data provided by COSMIC were deeply investigated within the whole month. It's quite different that the storm or earthquake didn't trigger scintillation burst. This is probably due to the storm occurrence local time was in noon sector, which has little impact on ionospheric irregularities increase, but help to enhance the effect of westward electricity, which on the other hand diminishes scintillation bubbles (Li et al 2008). A small geomagnetic disturbance was also found almost a week prior to the earthquake, the relationship of this event to the major earthquake is worth further discussion. Similar analysis of GNSS TECs have been done, the results indicated that it can be also referred as precursor to the major earthquake. Li G, Ning B, Zhao B, et al. Effects of geomagnetic storm on GPS ionospheric scintillations at Sanya[J]. Journal of Atmospheric and Solar-Terrestrial Physics, 2008, 70(7):1034-1045. Liu J Y, Chen Y I, Chuo Y J, et al. A statistical investigation of pre-earthquake ionospheric anomaly[J]. Journal of Geophysical Research Atmospheres, 2006, 111(A5). Liu J Y, Sun Y Y. Seismo-traveling ionospheric disturbances of ionograms observed during the 2011 Mw 9.0 Tohoku Earthquake[J]. Earth, Planets and Space, 2011, 63(7):897-902. Zhao B, Wang M, Yu T, et al. Is an unusual large enhancement of ionospheric electron density linked with the 2008 great Wenchuan earthquake?[J]. Journal of Geophysical Research Atmospheres, 2008, 113(A11):A11304. Pulinets S A. Seismic activity as a source of the ionospheric variability [J]. Advances in Space Research, 1998, 22(6):903-906.

  13. Ionospheric Modelling using GPS to Calibrate the MWA. II: Regional ionospheric modelling using GPS and GLONASS to estimate ionospheric gradients

    CERN Document Server

    Arora, B S; Ord, S M; Tingay, S J; Bell, M; Callingham, J R; Dwarakanath, K S; For, B -Q; Hancock, P; Hindson, L; Hurley-Walker, N; Johnston-Hollitt, M; Kapinska, A D; Lenc, E; McKinley, B; Offringa, A R; Procopio, P; Staveley-Smith, L; Wayth, R B; Wu, C; Zheng, Q

    2016-01-01

    We estimate spatial gradients in the ionosphere using the Global Positioning System (GPS) and GLONASS (Russian global navigation system) observations, utilising data from multiple GPS stations in the vicinity of Murchison Radio-astronomy Observatory (MRO). In previous work the ionosphere was characterised using a single-station to model the ionosphere as a single layer of fixed height and this was compared with ionospheric data derived from radio astronomy observations obtained from the Murchison Widefield Array (MWA). Having made improvements to our data quality (via cycle slip detection and repair) and incorporating data from the GLONASS system, we now present a multi-station approach. These two developments significantly improve our modelling of the ionosphere. We also explore the effects of a variable-height model. We conclude that modelling the small-scale features in the ionosphere that have been observed with the MWA will require a much denser network of Global Navigation Satellite System (GNSS) statio...

  14. Business Strategy Analysis of Small and Medium Scaled Electrical Design Enterprises%中小电力设计企业经营战略

    Institute of Scientific and Technical Information of China (English)

    余静

    2013-01-01

      Nowadays, with the development of the national electric power system reform, the separation of major business and supporting business has been ice-breaking started. The large scaled electrical design enterprises already have clear road map. But the small and medium scaled electrical design enterprises do not seem to have any clear target. Under the situation of without clear program of reform, the small and medium scaled electrical design enterprises have to find a way to suvive, to explore a series of business strategy to promote development and growth. At the same time, it has been an important task faced by the small and medium scaled electrical design enterprises on how to promote the rational distribution of electrical design market, how to ensure that enterprises and workers stable, and how to protect power engineering construction avoid from interference. This paper affords solutions of all the questions described above.%  随着国家电力体制改革向纵深发展,电网主辅分离改革工作已经破冰启动、大型电力设计企业已经有了明确的去向,而中小电力设计企业何去何从还没有明确的改革方案的情况下,中小电力设计企业需要找到市场竞争形势变革的突破口,需要找到自己的生存和发展之路,选择切实可行的经营战略使自己生存下来,并促进电力设计市场合理布局的形成、保证企业和职工稳定、保障电力工程的建设不受影响,已成为中小电力设计企业面临的重要课题。

  15. 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

  16. Peptides and Anti-peptide Antibodies for Small and Medium Scale Peptide and Anti-peptide Affinity Microarrays: Antigenic Peptide Selection, Immobilization, and Processing.

    Science.gov (United States)

    Zhang, Fan; Briones, Andrea; Soloviev, Mikhail

    2016-01-01

    This chapter describes the principles of selection of antigenic peptides for the development of anti-peptide antibodies for use in microarray-based multiplex affinity assays and also with mass-spectrometry detection. The methods described here are mostly applicable to small to medium scale arrays. Although the same principles of peptide selection would be suitable for larger scale arrays (with 100+ features) the actual informatics software and printing methods may well be different. Because of the sheer number of proteins/peptides to be processed and analyzed dedicated software capable of processing all the proteins and an enterprise level array robotics may be necessary for larger scale efforts. This report aims to provide practical advice to those who develop or use arrays with up to ~100 different peptide or protein features.

  17. 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.

  18. 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.

  19. The Image of travelling

    DEFF Research Database (Denmark)

    Grand, Karina Lykke

    2017-01-01

    and experienced and how he interpreted this knowledge, visually and in words. Rørbye is my primary research focus, but his artistic struggles are very similar to other artists travelling in Italy at the time. I therefore use Martinus Rørbye’s Italian sojourn as a prism of interpretation.......The Danish painter Martinus Rørbye was among of the Danish artists to reinvent the traditions of the genre of travel painting in the 1830s. His changes and developments of a new complex pictorial strategy were in many ways an answer to the changes in society, especially the advent of tourism....... The new travel image had its focus on concurrency, everyday life and the secular world, resulting in images that anticipated the photographic travel image, the snapshot and the travel postcard. The advent of this new strategy proved to have a very long after-life, as tourists and travellers of today still...

  20. Histoplasmosis in Israeli travelers.

    Science.gov (United States)

    Segel, Michael J; Rozenman, Judith; Lindsley, Mark D; Lachish, Tamar; Berkman, Neville; Neuberger, Ami; Schwartz, Eli

    2015-06-01

    Histoplasmosis is a common endemic human mycoses acquired mostly in the Americas. We reviewed 23 cases of histoplasmosis in Israeli travelers; 22 had traveled to Central or South America and one to North America. Fourteen cases had been exposed to bat habitats and were symptomatic, presenting ≤ 3 months after their return. Asymptomatic patients (N = 9) were diagnosed during the evaluation of incidental radiological findings or because a travel partner had been suspected of Histoplasma infection, 16-120 months after their return. Serological testing was positive in 75% of symptomatic cases but only 22% of asymptomatic cases. Histoplasmosis should be considered in travelers returning from the Americas with respiratory or febrile illness within weeks of return, particularly if exposed to bat habitats. Travel history is essential in patients presenting with pulmonary nodules, even years after travel to endemic countries.

  1. TRAVEL AND HOME LEAVE

    CERN Multimedia

    Human Resources Division

    2002-01-01

    Administrative procedures for : Travel to the home station and home leave (hl) Additional travel to the home station (at) Travel to the home station and home leave for family reasons (hlf) As part of the process of simplifying administrative procedures, HR and AS Divisions have devised a new, virtually automatic procedure for payment of travel expenses to the home station. The changes are aimed at rationalising administrative procedures and not at reducing benefits. The conditions of eligibility are unchanged. The new procedure, which will be operational with effect from 1st June 2002, will greatly simplify the administrative processing of claims for travel expenses and the recording of home leaves. Currently, requests for payment are introduced manually into the Advances and Claims system (AVCL) by divisional secretariats. All travel to the home station starting prior to 1st June 2002 will be processed according to the existing system whereas that starting on 1st June and after will be processed accordi...

  2. 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

  3. 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.

  4. FORMS OF YOUTH TRAVEL

    OpenAIRE

    Moisã Claudia Olimpia

    2011-01-01

    Taking into account the suite of motivation that youth has when practicing tourism, it can be said that the youth travel takes highly diverse forms. These forms are educational tourism, volunteer programs and “work and travel”, cultural exchanges or sports tourism and adventure travel. In this article, we identified and analyzed in detail the main forms of youth travel both internationally and in Romania. We also illustrated for each form of tourism the specific tourism products targeting you...

  5. Update on travelers' health.

    Science.gov (United States)

    Weber, Carol J

    2005-10-01

    As an international traveler, contact your health care provider at least 4 to 6 weeks before departure to obtain needed vaccinations and prophylactic medications. Be aware of the occurrence of any disease outbreaks in the countries you are visiting. While traveling, don't forget that one of the most important practices in preventing illness from infections is handwashing. Wash your hands carefully and frequently with soap and water, and if soap and water are not available use an alcohol-based hand rub. Be a responsible traveler by becoming informed about health risks and what to do to avoid them before you travel.

  6. Detection of ionospheric Alfvén resonator signatures in the equatorial ionosphere

    Science.gov (United States)

    Simões, Fernando; Klenzing, Jeffrey; Ivanov, Stoyan; Pfaff, Robert; Freudenreich, Henry; Bilitza, Dieter; Rowland, Douglas; Bromund, Kenneth; Liebrecht, Maria Carmen; Martin, Steven; Schuck, Peter; Uribe, Paulo; Yokoyama, Tatsuhiro

    2012-11-01

    The ionosphere response resulting from minimum solar activity during cycle 23/24 was unusual and offered unique opportunities for investigating space weather in the near-Earth environment. We report ultra low frequency electric field signatures related to the ionospheric Alfvén resonator detected by the Communications/Navigation Outage Forecasting System (C/NOFS) satellite in the equatorial region. These signatures are used to constrain ionospheric empirical models and offer a new approach for monitoring ionosphere dynamics and space weather phenomena, namely aeronomy processes, Alfvén wave propagation, and troposphere-ionosphere-magnetosphere coupling mechanisms.

  7. Signal Propagation from the Tail to the Ionosphere

    Science.gov (United States)

    Ferdousi, B.; Raeder, J.

    2014-12-01

    The night side of magnetosphere is a very dynamic region, where substorms can release substantial amounts of energy in an explosive fashion. Even though many physical models explaining the substorm process have been proposed, the onset mechanism (initiation) of substorms is still an unsolved problem in Space Physics. It is presently not resolved whether the onset mechanism is triggered by current disruption (CD) process, by some other ideal MHD instability such as the ballooning mode, or by magnetic reconnection process (Rx). The former two processes would initiate a substorm close to Earth somewhere between 6 and 8 RE downtail, whereas a reconnection trigger is thought to occur around 20 RE. Recent observations by the THEMIS mission suggests that substorms are triggered by magnetic reconnection mechanism in mid-tail region (Angelopoulos et al., 2009 ), but those results are disputed (Lui et al., 2009). Distinguishing these processes depends critically on the correct timing of different signals in the plasma sheet and the ionosphere in order to establish a time sequence of events. This has been difficult to accomplish with data alone, since signals are sometimes ambiguous, or they have not been observed in the right locations. To investigate signal propagation paths and signal travel times, we use OpenGGCM global simulation. By launching wave pulses from various locations in the magnetosphere, we investigate the path taken by the waves and time it takes for different wave to reach the ionosphere. We find that the Tamao path is not generally preferred path for waves originating in the plasma sheet. We also find that a point source in the tail can lead to spread out signal in the ionosphere.

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

    Directory of Open Access Journals (Sweden)

    T. Maruyama

    2006-07-01

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

  9. Information for travellers' physicians.

    Science.gov (United States)

    Allison, D J; Blinco, K

    1990-07-01

    Physicians can obtain advice about international travel for their patients from many different sources of information. The authors review some of the most common sources based on their experience at the International Travellers' Clinic operated by the New Brunswick Department of Health and Community Services in Fredericton. They identify readily available handbooks and periodicals and compare two computer software programs.

  10. Information for Travellers' Physicians

    OpenAIRE

    Allison, David J; Blinco, Kimberley

    1990-01-01

    Physicians can obtain advice about international travel for their patients from many different sources of information. The authors review some of the most common sources based on their experience at the International Travellers' Clinic operated by the New Brunswick Department of Health and Community Services in Fredericton. They identify readily available handbooks and periodicals and compare two computer software programs.

  11. CARLSON WAGONLIT TRAVEL

    CERN Multimedia

    2006-01-01

    CARLSON WAGONLIT TRAVEL informs you that our agency will be closed from 22 December 2006 at 16:30 until 8 January 2007 at 8:30. For all URGENT MATTERS you can contact our CARLSON WAGONLIT TRAVEL branch at W.H.O. (Mr Pierre Plumettaz), phone: 022 791 55 95. We wish you already a Merry Christmas and a Happy New Year!

  12. Traveling and Asthma

    Science.gov (United States)

    ... What Happens in the Operating Room? Traveling and Asthma KidsHealth > For Kids > Traveling and Asthma A A A What's in this article? Pack ... Or how about sleepover camp? If you have asthma , you'll be packing more than your clothes ...

  13. The traveling transect

    DEFF Research Database (Denmark)

    Braae, Ellen Marie; Diedrich, Lisa; Lee, Gini

    2013-01-01

    conditions, correspond to the fields of natural sciences and to spatial aesthetics. The Travelling Transect method, inspired by Alexander von Humboldt’s method of transareal travelling and transversal collecting of ephemeral information from site, informs our exploratory fieldwork in the water landscapes...

  14. Traveler response to information

    NARCIS (Netherlands)

    Chorus, C.G.

    2007-01-01

    The past few years have witnessed an impressive progress in the capabilities of travel information services. It is expected that in a few years, travelers will be constantly informed, pre-trip as well as en-route, about their optimal departure time, route and transport mode. The information is based

  15. Travel and transport

    DEFF Research Database (Denmark)

    Bill, Jan; Roesdahl, Else

    2007-01-01

    On the interrelationship between travel, transport and society; on land transport, sea and river transport, and on winter transport;  on the related technologies and their developments......On the interrelationship between travel, transport and society; on land transport, sea and river transport, and on winter transport;  on the related technologies and their developments...

  16. Traveling with children

    Science.gov (United States)

    ... let them inspect it. Small jars of baby food travel well. They make little waste and you can dispose of them easily. Air ... not eat raw fruits or vegetables. Eat only food that is hot and has been cooked ... and hotels for guidance and assistance. For foreign travel, check ...

  17. An unusual geometry of the ionospheric signature of the cusp: implications for magnetopause merging sites

    Directory of Open Access Journals (Sweden)

    G. Chisham

    Full Text Available The HF radar Doppler spectral width boundary (SWB in the cusp represents a very good proxy for the equatorward edge of cusp ion precipitation in the dayside ionosphere. For intervals where the Interplanetary Magnetic Field (IMF has a southward component (Bz < 0, the SWB is typically displaced poleward of the actual location of the open-closed field line boundary (or polar cap boundary, PCB. This is due to the poleward motion of newly-reconnected magnetic field lines during the cusp ion travel time from the reconnection X-line to the ionosphere. This paper presents observations of the dayside ionosphere from SuperDARN HF radars in Antarctica during an extended interval ( ~ 12 h of quasi-steady IMF conditions (By ~ Bz < 0. The observations show a quasi-stationary feature in the SWB in the morning sector close to magnetic local noon which takes the form of a 2° poleward distortion of the boundary. We suggest that two separate reconnection sites exist on the magnetopause at this time, as predicted by the anti-parallel merging hypothesis for these IMF conditions. The observed cusp geometry is a consequence of different ion travel times from the reconnection X-lines to the southern ionosphere on either side of magnetic local noon. These observations provide strong evidence to support the anti-parallel merging hypothesis. This work also shows that mesoscale and small-scale structure in the SWB cannot always be interpreted as reflecting structure in the dayside PCB. Localised variations in the convection flow across the merging gap, or in the ion travel time from the reconnection X-line to the ionosphere, can lead to localised variations in the offset of the SWB from the PCB. These caveats should also be considered when working with other proxies for the dayside PCB which are associated with cusp particle precipitation, such as the 630 nm cusp auroral emission.

    Key words. Ionosphere (plasma convection – Magnetospheric physics (magnetopause

  18. Epidemiology of traveler's diarrhea.

    Science.gov (United States)

    Castelli, F; Carosi, G

    1995-01-01

    Annually, over 75 million international passengers travel to tropical areas, more than 20 million of whom come from industrialized countries. They experience a high rate of traveler's diarrhea (TD), varying from 20 to 56%, which may result in serious limitations to their activities. The cause of TD is considered to be infectious in the overwhelming majority of cases and, apart from differences in relative importance, the list of responsible microbial agents is fairly constant regardless of geographic origin. The ingestion of contaminated food or water is considered to be the principal mode of transmission of the enteric pathogens of TD. Several factors have been proposed as playing a role in the etiogenesis of diarrhea in travelers, including personal (age, socioeconomic status, body weight, preexisting gastrointestinal illnesses), behavioral (mode of travel, standard of accommodation, eating in public places, dietary errors) and travel-related (destination, duration of stay, country of origin, season) factors, which are reviewed in detail.

  19. Ionospheric electron density perturbations during the 7-10 March 2012 geomagnetic storm period

    Science.gov (United States)

    Belehaki, Anna; Kutiev, Ivan; Marinov, Pencho; Tsagouri, Ioanna; Koutroumbas, Kostas; Elias, Panagiotis

    2017-02-01

    From 7 to 10 March 2012 a series of magnetospheric disturbances caused perturbations in the ionospheric electron density. Analyzing the interplanetary causes in each phase of this disturbed period, in comparison with the total electron content (TEC) disturbances, we have concluded that the interplanetary solar wind controls largely the ionospheric response. An interplanetary shock detected at 0328UT on 7 March caused the formation of prompt penetrating electric fields in the dayside that transported plasma from the near-equatorial region to higher in attitudes and latitudes forming a giant plasma fountain which is part of the so-called dayside ionospheric super-fountain. The super-fountain produces an increase in TEC which is the dominant effect at middle latitude, masking the effect of the negative storm. Simultaneously, inspecting the TEC maps, we found evidence for a turbulence in TEC propagating southward probably caused by large scale travelling ionospheric disturbances (LSTIDs) linked to auroral electrojet intensification. On 8 March, a magnetospheric sudden impulse at 1130UT accompanied with strong pulsations in all interplanetary magnetic field (IMF) components and with northward Bz component during the growth phase of the storm. These conditions triggered a pronounced directly driven substorm phase during which we observe LSTID. However, the analysis of DMSP satellite observations, provided with strong evidence for Sub-Auroral Polarization Streams (SAPS) formation that erode travelling ionospheric disturbances (TID) signatures. The overall result of these mechanisms can be detected in maps of de-trended TEC, but it is difficult to identify separately each of the sources of the observed perturbations, i.e. auroral electrojet activity and LSTIDs, super-fountain and SAPS. In order to assess the capability of the ionospheric profiler called Topside Sounder Model - assisted Digisonde (TaD model) to detect such perturbations in the electron density, electron

  20. Multi-instrument observations of the solar eclipse on 20 March 2015 and its effects on the ionosphere over Belgium and Europe

    Science.gov (United States)

    Stankov, Stanimir M.; Bergeot, Nicolas; Berghmans, David; Bolsée, David; Bruyninx, Carine; Chevalier, Jean-Marie; Clette, Frédéric; De Backer, Hugo; De Keyser, Johan; D'Huys, Elke; Dominique, Marie; Lemaire, Joseph F.; Magdalenić, Jasmina; Marqué, Christophe; Pereira, Nuno; Pierrard, Viviane; Sapundjiev, Danislav; Seaton, Daniel B.; Stegen, Koen; Van der Linden, Ronald; Verhulst, Tobias G. W.; West, Matthew J.

    2017-08-01

    A total solar eclipse occurred on 20 March 2015, with a totality path passing mostly above the North Atlantic Ocean, which resulted in a partial solar eclipse over Belgium and large parts of Europe. In anticipation of this event, a dedicated observational campaign was set up at the Belgian Solar-Terrestrial Centre of Excellence (STCE). The objective was to perform high-quality observations of the eclipse and the associated effects on the geospace environment by utilising the advanced space- and ground-based instrumentation available to the STCE in order to further our understanding of these effects, particularly on the ionosphere. The study highlights the crucial importance of taking into account the eclipse geometry when analysing the ionospheric behaviour during eclipses and interpreting the eclipse effects. A detailed review of the eclipse geometry proves that considering the actual obscuration level and solar zenith angle at ionospheric heights is much more important for the analysis than at the commonly referenced Earth's surface or at the plasmaspheric heights. The eclipse occurred during the recovery phase of a strong geomagnetic storm which certainly had an impact on (some of) the ionospheric characteristics and perhaps caused the omission of some "low-profile" effects. However, the analysis of the ionosonde measurements, carried out at unprecedented high rates during the eclipse, suggests the occurrence of travelling ionospheric disturbances (TIDs). Also, the high temporal and spatial resolution measurements proved very important in revealing and estimating some finer details of the delay in the ionospheric reaction and the ionospheric disturbances.

  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. The fine structure of the ionosphere

    DEFF Research Database (Denmark)

    D'Angelo, N.; Michelsen, Poul

    1967-01-01

    We consider in this note the excitation of ion-acoustic waves by vertical gradients of density in the ionosphere. The conclusion is reached that the fine structure of the ionosphere is probably affected by the resulting instability, as comparison with observations seems to indicate. Recently, Liu...

  3. 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 t

  4. 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.

  5. Probing ionospheric structure using LOFAR data

    NARCIS (Netherlands)

    Mevius, M.; Van Der Tol, S.; Pandey, V. N.

    2015-01-01

    To obtain high quality images with the Lofar low frequency radio telescope, accurate ionospheric characterization and calibration is essential. The large field of view of LOFAR (several 10s of square degrees) requires good knowledge of the spatial variation of the ionosphere. In this work to probe t

  6. Ionospheric Calibration of Low Frequency Radio Interferometric Observations using the Peeling Scheme: I. Method Description and First Results

    CERN Document Server

    Intema, H T; Cotton, W D; Cohen, A S; Van Bemmel, I M; Röttgering, H J A

    2009-01-01

    Calibration of radio interferometric observations becomes increasingly difficult towards lower frequencies. Below ~300 MHz, spatially variant refractions and propagation delays of radio waves traveling through the ionosphere cause phase rotations that can vary significantly with time, viewing direction and antenna location. In this article we present a description and first results of SPAM (Source Peeling and Atmospheric Modeling), a new calibration method that attempts to iteratively solve and correct for ionospheric phase errors. To model the ionosphere, we construct a time-variant, 2-dimensional phase screen at fixed height above the Earth's surface. Spatial variations are described by a truncated set of discrete Karhunen-Loeve base functions, optimized for an assumed power-law spectral density of free electrons density fluctuations, and a given configuration of calibrator sources and antenna locations. The model is constrained using antenna-based gain phases from individual self-calibrations on the availa...

  7. 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.

  8. Plasma interactions in the Martian Nightside Ionosphere

    Science.gov (United States)

    Andersson, L.; Fowler, C. M.; Ergun, R.; Weber, T. D.; Andrews, D. J.; Morooka, M. W.; Delory, G. T.; Eriksson, A. I.; Mitchell, D. L.; McFadden, J. P.; Connerney, J. E. P.

    2015-12-01

    Based on measurements from a number of missions at Mars the nightside ionosphere is patchy. The new mission MAVEN dedicated to observe the upper atmosphere and the plasma interactions provides the first comprehensive observations of the low altitude nightside ionosphere. Observations show that at density gradients the plasma is unstable and significant wave power, heated/accelerated electrons, and heated ions are co-located. Below 300 km, thermal electrons (>3 eV) are observed at the gradients to low density regions. The nightside ionosphere below 180 km is thought to be maintained by electron impact ionization and therefore these regions with thermal electrons may be the primary energy source for the low altitude ionosphere. Outside of the low density regions the plasma is cold. These observations suggest that the wave heating might be the primary process in the Matrian nightside ionosphere. The characteristics of these regions associated with density gradients will be presented and discussed in this presentation.

  9. First Observations of GNSS Ionospheric Scintillations From DemoGRAPE Project

    Science.gov (United States)

    Alfonsi, L.; Cilliers, P. J.; Romano, V.; Hunstad, I.; Correia, E.; Linty, N.; Dovis, F.; Terzo, O.; Ruiu, P.; Ward, J.; Riley, P.

    2016-10-01

    The Istituto Nazionale di Geofisica e Vulcanologia leads an international project funded by the Italian National Program for Antarctic Research, called Demonstrator of Global Navigation Satellite System (GNSS) Research and Application for Polar Environment (DemoGRAPE), in partnership with Politecnico di Torino, Istituto Superiore Mario Boella, and with South African National Space Agency and the Brazilian National Institute of Space Physics, as key collaborators. DemoGRAPE is a new prototype of support for the satellite navigation in Antarctica. Besides the scientific interest, the accuracy of satellite navigation in Antarctica is of paramount importance since there is always the danger that people and vehicles can fall into a crevasse during a snowstorm, when visibility is limited and travel is restricted to following specified routes using satellite navigation systems. The variability of ionospheric delay and ionospheric scintillation are two of the primary factors which affect the accuracy of satellite navigation. The project will provide a demonstrator of cutting edge technology for the empirical assessment of the ionospheric delay and ionospheric scintillations in the polar regions. The scope of the project includes new equipment for the recording and dissemination of GNSS data and products installed at the South African and Brazilian bases in Antarctica. The new equipment will facilitate the exchange of software and derived products via the Cloud computing technology infrastructure. The project portal is accessible at www.demogrape.net. We report the first Global Navigation Satellite System (GNSS) signal scintillations observed in Antarctica.

  10. Power spectrum analysis of ionospheric fluctuations with the Murchison Widefield Array

    CERN Document Server

    Loi, Shyeh Tjing; Murphy, Tara; Cairns, Iver H; Bell, Martin; Hurley-Walker, Natasha; Morgan, John; Lenc, Emil; Offringa, A R; Feng, L; Hancock, P J; Kaplan, D L; Kudryavtseva, N; Bernardi, G; Bowman, J D; Briggs, F; Cappallo, R J; Corey, B E; Deshpande, A A; Emrich, D; Gaensler, B M; Goeke, R; Greenhill, L J; Hazelton, B J; Johnston-Hollitt, M; Kasper, J C; Kratzenberg, E; Lonsdale, C J; Lynch, M J; McWhirter, S R; Mitchell, D A; Morales, M F; Morgan, E; Oberoi, D; Ord, S M; Prabu, T; Rogers, A E E; Roshi, A; Shankar, N Udaya; Srivani, K S; Subrahmanyan, R; Tingay, S J; Waterson, M; Wayth, R B; Webster, R L; Whitney, A R; Williams, A; Williams, C L

    2015-01-01

    Low-frequency, wide field-of-view (FoV) radio telescopes such as the Murchison Widefield Array (MWA) enable the ionosphere to be sampled at high spatial completeness. We present the results of the first power spectrum analysis of ionospheric fluctuations in MWA data, where we examined the position offsets of radio sources appearing in two datasets. The refractive shifts in the positions of celestial sources are proportional to spatial gradients in the electron column density transverse to the line of sight. These can be used to probe plasma structures and waves in the ionosphere. The regional (10-100 km) scales probed by the MWA, determined by the size of its FoV and the spatial density of radio sources (typically thousands in a single FoV), complement the global (100-1000 km) scales of GPS studies and local (0.01-1 km) scales of radar scattering measurements. Our data exhibit a range of complex structures and waves. Some fluctuations have the characteristics of travelling ionospheric disturbances (TIDs), whi...

  11. Charged particles in Titan's ionosphere

    Science.gov (United States)

    Tripathi, Sachchida

    2010-05-01

    Charged particles in Titan's ionosphere Marykutty Michael1, Sachchida Nand Tripathi1,2,3, Pratima Arya1 1Indian Institute of Technology Kanpur 2Oak Ridge Associated Universities 3NASA Goddard Space Flight Center Observations by two instruments onboard the Cassini spacecraft, Ion Neutral Mass Spectrometer (INMS) and CAssini Plasma Spectrometer (CAPS), revealed the existence of heavy hydrocarbon and nitrile species with masses of several thousand atomic mass units at altitudes of 950 - 1400 km in the atmosphere of Titan (Waite et al., 2007; Crary et al., 2009). Though these particles were believed to be molecules, they are most likely aerosols formed by the clumping of smaller molecules (Waite et al., 2009). These particles were estimated to have a density of 10-3 kg m-3 and a size of up to 256 nm. The existence of very heavy ions has also been observed by the CAPS components with a mass by charge ratio of up to 10000 (Coates et al., 2007, 2009; Sittler et al., 2009). The goal of this paper is to find out whether the so called heavy ions (or charged particles) are generated by the charge transfer of ions and electrons to the particles. The charging of these particles has been studied by using the charge balance equations that include positive ions, negative ions, electrons, neutral and charged particles. Information on the most abundant ion clusters are obtained from Vuitton et al., (2009) and Wilson and Atreya, (2004). Mass by charge ratio thus calculated will be compared with those observed by Coates et al. (2007). References: Coates AJ, et al., Discovery of heavy negative ions in Titan's ionosphere, Geophys. Res. Lett., 34:L22103, 2007. Coates AJ, et al., Heavy negative ions in titan's ionosphere: altitude and latitude dependence. Planet. Space Sci., doi:10.1016/j.pss.2009.05.009, 2009. Crary F.J., et al., Heavy ions, temperatures and winds in titan's ionosphere: Combined cassini caps and inms observations. Planet. Space Sci., doi:10.1016/j.pss.2009.09.006, 2009

  12. 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

  13. Understanding taxi travel patterns

    Science.gov (United States)

    Cai, Hua; Zhan, Xiaowei; Zhu, Ji; Jia, Xiaoping; Chiu, Anthony S. F.; Xu, Ming

    2016-09-01

    Taxis play important roles in modern urban transportation systems, especially in mega cities. While providing necessary amenities, taxis also significantly contribute to traffic congestion, urban energy consumption, and air pollution. Understanding the travel patterns of taxis is thus important for addressing many urban sustainability challenges. Previous research has primarily focused on examining the statistical properties of passenger trips, which include only taxi trips occupied with passengers. However, unoccupied trips are also important for urban sustainability issues because they represent potential opportunities to improve the efficiency of the transportation system. Therefore, we need to understand the travel patterns of taxis as an integrated system, instead of focusing only on the occupied trips. In this study we examine GPS trajectory data of 11,880 taxis in Beijing, China for a period of three weeks. Our results show that taxi travel patterns share similar traits with travel patterns of individuals but also exhibit differences. Trip displacement distribution of taxi travels is statistically greater than the exponential distribution and smaller than the truncated power-law distribution. The distribution of short trips (less than 30 miles) can be best fitted with power-law while long trips follow exponential decay. We use radius of gyration to characterize individual taxi's travel distance and find that it does not follow a truncated power-law as observed in previous studies. Spatial and temporal regularities exist in taxi travels. However, with increasing spatial coverage, taxi trips can exhibit dual high probability density centers.

  14. [Thromboembolism in travelers].

    Science.gov (United States)

    Bihari, I; Sándor, T

    2001-11-11

    The association between long haul travel and the risk of venous thromboembolism are suspected for long time. Mostly air travel related thrombosis series have been reported in the literature. Risk factors can be classified as: 1. travel related factors (coach position, immobilization, prolonged air travel, narrow seat and room, diuretic effect of alcohol, insufficient fluid intake, dehydration, direct pressure on leg veins, rare inspiration). 2. air plane related risk factors (low humidity, relative hypoxia, stress). 3. patient related factors (hereditary and acquired thrombophylia, previous deep venous thrombosis, age over 40, recent surgery or trauma, gravidity, puerperium, oestrogen containing pills, varicosity, chronic heart disease, obesity, fever, diarrhoea, vomiting, smoking). No patient related factors were found in some cases. To reduce the hazards air travellers are rightly concerned to know the level of the risk and the airlines should be responsible for this information. People should discuss with their physician what prophlylactic measures should be taken, such as compression stockings or low molecular weight heparin. Not only flight but car, bus and train travellers are also at risk of developing venous thromboembolism. Long haul travel alone is a separate risk factor for venous thromboembolism.

  15. Modeling of critical factors for integrating sustainability with innovation for Indian small- and medium-scale manufacturing enterprises: An ISM and MICMAC approach

    Directory of Open Access Journals (Sweden)

    Bisma Mannan

    2016-12-01

    Full Text Available The growth of any country depends upon the existence of small- and medium-scale enterprises (SMEs. The greater the number of SMEs present in any country, the economy of the country increases in the same proportion. This paper uses the qualitative research technique to study the critical factors which affect the integration of sustainability with innovation taking into account Indian manufacturing SMEs. An ISM approach is applied to establish the interrelationship between the various critical factors. And with the help of Fuzzy Micmac technique, driver dependence power diagraph is created. From our analysis, it has been found that “government regulation” has the highest dominating power which helps in successful execution of integrating sustainability with innovation. Variables “employee nature” and “working culture” have the highest dependence power. The success of these variables depends on the success of the variables below them. Finally, the limitations of using the above techniques are discussed and then the suggestions are made for the further research.

  16. 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

  17. [Traveling with immunosuppression].

    Science.gov (United States)

    Birkenfeld, G

    2014-03-01

    The rapidly increasing number of patients with immunosuppression is followed by their expectation to lead-as much as possible-a "normal" life, including long-distance travel. The advice and preventive measures for diseases associated with travelling depend overall on the mode of the patient's immunosuppression. This report explains the individual preventive possibilities, limits and risks for travellers with asplenia, common variable immunodeficiency, chronic inflammatory bowel and rheumatic diseases, HIV, as well as for patients having undergone solid organ or bone marrow transplantation or chemotherapy.

  18. Ionospheric Challenges for GNSS Based Augmentation Systems

    Science.gov (United States)

    Doherty, P.; Valladares, C. E.

    2007-12-01

    The ionosphere is a highly dynamic physical phenomenon that presents a variable source of error for Global Navigation Satellite System (GNSS) signals and GNSS based operational systems. The Federal Aviation Administration's (FAA) Wide-Area Augmentation System (WAAS) was designed to enhance the GNSS standard positioning service by providing additional accuracy, availability and integrity that is sufficient for use in commercial aviation. It is the first of a number of planned regional Satellite Based Augmentation Systems (SBAS). Other systems in development include the European EGNOS system, the MSAS system in Japan and the GAGAN system in India. In addition, the South American countries are investigating the feasibility of operating an SBAS system in this region. Much of the WAAS ionospheric research and development focused on defining and mitigating ionospheric challenges characteristic of the mid-latitude regions, where the ionosphere is well studied and relatively quiescent. The EGNOS and MSAS systems will primarily operate under a similarly quiescent mid-latitude ionosphere. SBAS system development in South America, India and other low-latitude regions, however, will have to contend with much more extreme conditions. These conditions include strong spatial and temporal gradients, plasma depletions and scintillation. All of these conditions have a potential to limit SBAS performance in the low latitude regions. This presentation will review the effects that the ionosphere has on the mid-latitude WAAS system. It will present the techniques that are used to mitigate ionospheric disturbances induced on the system during severe geomagnetic activity and it will quantify the effect that this activity has on system performance. The presentation will then present data from the South American Low-latitude Ionospheric Sensor Network (LISN) that can be used to infer the ionospheric effects on SBAS performance in the most challenging low-latitude ionospheric environment

  19. Connecting Stratospheric and Ionospheric Anomalies

    Science.gov (United States)

    Spraggs, M. E.; Goncharenko, L. P.; Zhang, S.; Coster, A. J.; Benkevitch, L. V.

    2014-12-01

    This study investigates any relationship between lunar phases and ionospheric anomalies that appear at low latitudes concurrently with sudden stratospheric warmings (SSWs). The study utilizes World-wide GPS Receiver Network Total Electron Content (TEC) data spanning 13 years (2001-2014) and focuses on the changes in the equatorial ionization anomaly the Western hemisphere. TEC is highly variable due to the influences of solar flux, geomagnetic activity, and seasonal variation and these influences are removed by the use of model. This empirical TEC model is a combination of linear dependencies of solar flux (F10.7) and geomagnetic activity (Ap3) with a third degree polynomial dependency for day-of-year (DOY). With such dependencies removed, the remaining TEC variation could be resolved and attributed to an appropriate mechanism. Lunar phase and apside was investigated in particular, especially the new and full moon phases during perigees when tidal forcing would be most powerful. Lunar tidal forcing on planetary waves is also examined as being physically responsible for setting up conditions that may give rise to SSWs and ionospheric anomalies. Preliminary results suggest that such anomalies may be enhanced in intensity during the full or new moon and even more so during perigee by different amounts depending on whether the SSW is a major (40-60%) or minor (20-45%) event.

  20. Malaria and Travelers

    Science.gov (United States)

    ... a CDC Malaria Branch clinician. malaria@cdc.gov Malaria and Travelers Recommend on Facebook Tweet Share Compartir ... may be at risk for infection. Determine if malaria transmission occurs at the destinations Obtain a detailed ...

  1. Carlson Wagonlit Travel

    CERN Multimedia

    Carlson Wagonlit Travel

    2005-01-01

    Dear customers, On 3 January we informed you that the airlines had decided to cease paying commission to travel agencies in Switzerland. This measure has since been progressively introduced, with rare exceptions. Consequently, in agreement with CERN, we are obliged to apply new transaction fees for private travel, with immediate effect. Carlson Wagonlit Travel (CWT) offers: A personalized, professional and competent consultancy service To seek the most economical and best solution adapted to your needs Neutrality in comparing prices and benefits Additional information concerning e.g. visa regulations, insurance, vaccinations, etc. Support in the event of problems We draw your attention to the fact that, in spite of the increase, these prices remain very competitive on today's market. Thank you for your trust and understanding. Yours truly, Carlson Wagonlit Travel CERN agency

  2. Travelers' Health: Cryptosporidiosis

    Science.gov (United States)

    ... cryptosporidiosis was associated with travel to Asia, particularly India, and Latin America. Another study found a 6. ... 22. Lalonde LF, Gajadhar AA. Effect of storage media, temperature, and time on preservation of Cryptosporidium parvum ...

  3. Travelers' Health: Rabies

    Science.gov (United States)

    ... from rabies in a UK traveller returning from India. Euro Surveill. 2005 Jul;10(30):E050728 5. ... Follow CDC Email Recommend Tweet Post RSS CDC Media Listen Watch YouTube About CDC Employment Newsroom Training/ ...

  4. Travel Inside the Ear

    Medline Plus

    Full Text Available ... Info » Hearing, Ear Infections, and Deafness Travel Inside the Ear Video When sound waves reach your ear, ... heard a soft sound or a loud sound. The sound passes through the outer ear and is ...

  5. Travel Inside the Ear

    Medline Plus

    Full Text Available ... stirrup. These are the smallest bones in your body. Together they are smaller than an orange seed. It then travels into the inner ear, which ... organizations Related Topics ...

  6. Traveling-wave photodetector

    Science.gov (United States)

    Hietala, Vincent M.; Vawter, Gregory A.

    1993-01-01

    The traveling-wave photodetector of the present invention combines an absorptive optical waveguide and an electrical transmission line, in which optical absorption in the waveguide results in a photocurrent at the electrodes of the electrical transmission line. The optical waveguide and electrical transmission line of the electrically distributed traveling-wave photodetector are designed to achieve matched velocities between the light in the optical waveguide and electrical signal generated on the transmission line. This velocity synchronization provides the traveling-wave photodetector with a large electrical bandwidth and a high quantum efficiency, because of the effective extended volume for optical absorption. The traveling-wave photodetector also provides large power dissipation, because of its large physical size.

  7. Travelers' Health: Diphtheria

    Science.gov (United States)

    ... Traveler Registration During Trip After Your Trip CDC-TV Videos Resources For Clinicians In-Clinic Quick Links ... toxoid vaccine before departure. After a childhood primary series and a booster dose during adolescence, routine booster ...

  8. Travelling or not?

    DEFF Research Database (Denmark)

    Helles, Rasmus; Lai, Signe Sophus

    2017-01-01

    The article presents a quantitative content analysis (Krippendorff, 2013) of the first episode of the 32 Danish drama series produced between 2005 and 2014. A number of these have experienced unprecedented, international success, with series such as Borgen (2010-13) and The Killing (2007......-12) travelling to multiple countries on several continents. The article shows that there are systematic differences in terms of formal characteristics, themes, and characters’ communicative style between the series that travel and the series that do not. Especially, the analysis finds that the presence of strong...... female lead characters is systematically linked to the positive travel patterns of the series, and that this cuts across different genres of series. The analysis also finds that series, which have explicitly low production values and simple narrative structure, systematically travels poorer....

  9. Travelers' Health: Leishmaniasis, Cutaneous

    Science.gov (United States)

    ... Water Disinfection Infographics for Travelers MERS Health Advisory poster Food and Water: What's Safer Health Advisory: MERS ... noise, they are small (approximately one-third the size of mosquitoes), and their bites might not be ...

  10. Travelers' Health: Rabies

    Science.gov (United States)

    ... Water Disinfection Infographics for Travelers MERS Health Advisory poster Food and Water: What's Safer Health Advisory: MERS ... weight may be small in relation to the size and number of wounds. RIG is difficult to ...

  11. Air Travel Health Tips

    Science.gov (United States)

    ... healthy snacks, like fresh or dried fruit, veggies, trail mix, or granola bars.Other helpful carry-on ... phone number with you in case of an emergency. If you have a severe food allergy, travel ...

  12. Travelers' Health: Leishmaniasis, Cutaneous

    Science.gov (United States)

    ... Climates Humanitarian Aid Workers Humanitarian Aid Workers in Ecuador Insurance International Adoption Jet Lag Last-Minute Travel ... military personnel, construction workers, and people who do research outdoors at night or twilight. However, even short- ...

  13. EUV measurement of ionospheric oxygen ions

    Science.gov (United States)

    Nakasaka, Y.; Yamazaki, A.; Yoshikawa, I.; Tashiro, S.; Miyake, W.; Nakamura, M.

    2001-12-01

    We have measured the OII emission from the F-layer ionosphere by the sounding rocket SS-520-2, which was launched from the Svalbard Rocket Experiment Site, Ny Aalesund in Norway, last December. This was the first in situ EUV observation of the ionospheric Oxygen ions. Oxygen ion is the main component of the ionospheric F layer. We have studied the oxygen ions distribution in the ionosphere by means of optical observation. Oxygen ions resonantly scatter the solar OII(83.4nm) line. We have built an extreme ultraviolet (XUV) scanner, which is sensitive to the OII 83.4-nm emission and contamination free from the Lyman-alpha line, especially for the sounding rocket SS-520-2. The rocket flew along the magnetospheric cusp region, and 600 sec after the launch it reached its apex at 1108 km in altitude, and its total operation time was 1100sec. In the downleg of the flight, below 350 km in altitude (900-1100sec after the launch), XUV observed very high intensity (200~300 Rayleigh) of OII emissions from the ionospheric F layer. We have estimated the column density of the oxygen ion along the XUV_fs line-of-sight from the measured OII intensity. In this presentation, we will discuss the density profile of the oxygen ions in the ionospheric F region, i.e., the dependence on the altitude, longitude and latitude. We will compare the obtained distribution with the model of the ionosphere.

  14. Real-Time Detection of Tsunami Ionospheric Disturbances with a Stand-Alone GNSS Receiver: A Preliminary Feasibility Demonstration

    Science.gov (United States)

    Savastano, Giorgio; Komjathy, Attila; Verkhoglyadova, Olga; Mazzoni, Augusto; Crespi, Mattia; Wei, Yong; Mannucci, Anthony J.

    2017-04-01

    It is well known that tsunamis can produce gravity waves that propagate up to the ionosphere generating disturbed electron densities in the E and F regions. These ionospheric disturbances can be studied in detail using ionospheric total electron content (TEC) measurements collected by continuously operating ground-based receivers from the Global Navigation Satellite Systems (GNSS). Here, we present results using a new approach, named VARION (Variometric Approach for Real-Time Ionosphere Observation), and estimate slant TEC (sTEC) variations in a real-time scenario. Using the VARION algorithm we compute TEC variations at 56 GPS receivers in Hawaii as induced by the 2012 Haida Gwaii tsunami event. We observe TEC perturbations with amplitudes of up to 0.25 TEC units and traveling ionospheric perturbations (TIDs) moving away from the earthquake epicenter at an approximate speed of 316 m/s. We perform a wavelet analysis to analyze localized variations of power in the TEC time series and we find perturbation periods consistent with a tsunami typical deep ocean period. Finally, we present comparisons with the real-time tsunami MOST (Method of Splitting Tsunami) model produced by the NOAA Center for Tsunami Research and we observe variations in TEC that correlate in time and space with the tsunami waves.

  15. Real-Time Detection of Tsunami Ionospheric Disturbances with a Stand-Alone GNSS Receiver: A Preliminary Feasibility Demonstration

    Science.gov (United States)

    Savastano, Giorgio; Komjathy, Attila; Verkhoglyadova, Olga; Mazzoni, Augusto; Crespi, Mattia; Wei, Yong; Mannucci, Anthony J.

    2017-01-01

    It is well known that tsunamis can produce gravity waves that propagate up to the ionosphere generating disturbed electron densities in the E and F regions. These ionospheric disturbances can be studied in detail using ionospheric total electron content (TEC) measurements collected by continuously operating ground-based receivers from the Global Navigation Satellite Systems (GNSS). Here, we present results using a new approach, named VARION (Variometric Approach for Real-Time Ionosphere Observation), and estimate slant TEC (sTEC) variations in a real-time scenario. Using the VARION algorithm we compute TEC variations at 56 GPS receivers in Hawaii as induced by the 2012 Haida Gwaii tsunami event. We observe TEC perturbations with amplitudes of up to 0.25 TEC units and traveling ionospheric perturbations (TIDs) moving away from the earthquake epicenter at an approximate speed of 316 m/s. We perform a wavelet analysis to analyze localized variations of power in the TEC time series and we find perturbation periods consistent with a tsunami typical deep ocean period. Finally, we present comparisons with the real-time tsunami MOST (Method of Splitting Tsunami) model produced by the NOAA Center for Tsunami Research and we observe variations in TEC that correlate in time and space with the tsunami waves. PMID:28429754

  16. Travel patterns in China.

    Directory of Open Access Journals (Sweden)

    Tini Garske

    Full Text Available The spread of infectious disease epidemics is mediated by human travel. Yet human mobility patterns vary substantially between countries and regions. Quantifying the frequency of travel and length of journeys in well-defined population is therefore critical for predicting the likely speed and pattern of spread of emerging infectious diseases, such as a new influenza pandemic. Here we present the results of a large population survey undertaken in 2007 in two areas of China: Shenzhen city in Guangdong province, and Huangshan city in Anhui province. In each area, 10,000 randomly selected individuals were interviewed, and data on regular and occasional journeys collected. Travel behaviour was examined as a function of age, sex, economic status and home location. Women and children were generally found to travel shorter distances than men. Travel patterns in the economically developed Shenzhen region are shown to resemble those in developed and economically advanced middle income countries with a significant fraction of the population commuting over distances in excess of 50 km. Conversely, in the less developed rural region of Anhui, travel was much more local, with very few journeys over 30 km. Travel patterns in both populations were well-fitted by a gravity model with a lognormal kernel function. The results provide the first quantitative information on human travel patterns in modern China, and suggest that a pandemic emerging in a less developed area of rural China might spread geographically sufficiently slowly for containment to be feasible, while spatial spread in the more economically developed areas might be expected to be much more rapid, making containment more difficult.

  17. Why They Travel Alone?

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    "WHY Chinese Women Travel Alone" was the theme of a special edition of "Truth Talk" a popular talk show on China Central Television (CCTV), which focused on a few middle-aged women from different cultural backgrounds, social classes, and various educational backgrounds who had all branched out on their own for one reason or another. Each woman spoke of her experiences and feelings while travelling alone. They were all

  18. Testing Ionospheric Faraday Rotation Corrections in CASA

    Science.gov (United States)

    Kooi, Jason E.; Moellenbrock, George

    2015-04-01

    The Earth’s ionosphere introduces direction- and time-dependent effects over a range of physical and temporal scales and so is a major source for unmodeled phase offsets for low frequency radioastronomical observations. Ionospheric effects are often the limiting factor to making sensitive radioastronomical measurements to probe the solar corona or coronal mass ejections at low frequencies (CASA) package. CASA, which was developed to meet the data post-processing needs of next generation telescopes such as the Karl G. Jansky Very Large Array (VLA), did not previously have the capability to mitigate ionospheric effects. This algorithm uses GPS-based global ionosphere maps to mitigate the first and second order ionospheric effects (dispersion delay and Faraday rotation, respectively). We investigated several data centers as potential sources for global ionospheric models and chose the International Global Navigation Satellite System Service data product because data from other sources are generally too sparse to use without additional interpolation schemes. This implementation of ionospheric corrections in CASA has been tested on several sets of VLA observations and all of them showed a significant reduction of the dispersion delay. In order to rigorously test CASA’s ability to mitigate ionospheric Faraday rotation, we made VLA full-polarization observations of the standard VLA phase calibrators J0359+5057 and J0423+4150 in August 2014, using L band (1 - 2 GHz), S band (2 - 4 GHz), and C band (4 - 6 GHz) frequencies in the D array configuration. The observations were 4 hours in duration, beginning near local sunrise. In this paper, we give a general description of how these corrections are implemented as well as discussion of the code’s ability to mitigate the ionospheric effects present in these test observations over a range of times and elevation angles. This work was supported at the University of Iowa by grant ATM09-56901.

  19. Freedom of Movement (Common Travel Area) (Travel Documentation) Bill 2014

    DEFF Research Database (Denmark)

    Butler, Graham; Hunt, Brian; Flanagan, Terence

    2014-01-01

    Private Members' Bill (legislation) introduced in Dáil Éireann (House of Deputies), Houses of the Oireachtas (Irish Parliament). An Act to reinforce the Common Travel Area by providing for passport-free travel for persons who are entitled to travel within the Common Travel Area without a passport...

  20. Freedom of Movement (Common Travel Area) (Travel Documentation) Bill 2014

    DEFF Research Database (Denmark)

    Butler, Graham; Hunt, Brian; Flanagan, Terence

    2014-01-01

    Private Members' Bill (legislation) introduced in Dáil Éireann (House of Deputies), Houses of the Oireachtas (Irish Parliament). An Act to reinforce the Common Travel Area by providing for passport-free travel for persons who are entitled to travel within the Common Travel Area without a passport...

  1. [Vaccination for international travelers].

    Science.gov (United States)

    Arrazola, M Pilar; Serrano, Almudena; López-Vélez, Rogelio

    2016-05-01

    Traveler's vaccination is one of the key strategies for the prevention of infectious diseases during international travel. The risk of acquiring an infectious disease is determined in each case by the characteristics of the traveler and the travel, so the pre-departure medical advice of the traveler must be individualized. The World Health Organization classifies travelerś vaccines into three groups. - Vaccines for routine use in national immunization programs: Haemophilus influenzae type b, hepatitis B, polio, measles-mumps-rubella, tetanus-diphtheria-whooping a cough, and chickenpox. - Vaccinations required by law in certain countries before to enter them: yellow fever, meningococcal disease and poliomyelitis. - Vaccines recommended depending on the circumstances: cholera, japanese encephalitis, tick-borne encephalitis, meningococcal disease, typhoid fever, influenza, hepatitis A, hepatitis B, rabies and BCG. This review is intended to introduce the reader to the field of international vaccination. Copyright © 2016 Elsevier España, S.L.U. y Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.

  2. Travels in Architectural History

    Directory of Open Access Journals (Sweden)

    Davide Deriu

    2016-11-01

    Full Text Available Travel is a powerful force in shaping the perception of the modern world and plays an ever-growing role within architectural and urban cultures. Inextricably linked to political and ideological issues, travel redefines places and landscapes through new transport infrastructures and buildings. Architecture, in turn, is reconstructed through visual and textual narratives produced by scores of modern travellers — including writers and artists along with architects themselves. In the age of the camera, travel is bound up with new kinds of imaginaries; private records and recollections often mingle with official, stereotyped views, as the value of architectural heritage increasingly rests on the mechanical reproduction of its images. Whilst students often learn about architectural history through image collections, the place of the journey in the formation of the architect itself shifts. No longer a lone and passionate antiquarian or an itinerant designer, the modern architect eagerly hops on buses, trains, and planes in pursuit of personal as well as professional interests. Increasingly built on a presumption of mobility, architectural culture integrates travel into cultural debates and design experiments. By addressing such issues from a variety of perspectives, this collection, a special 'Architectural Histories' issue on travel, prompts us to rethink the mobile conditions in which architecture has historically been produced and received.

  3. Parameters of seismic source as deduced from 1Hz ionospheric GPS data: Ionospheric Seismology or Ionosphere as a natural indicator of numerous geophysical events

    Science.gov (United States)

    Astafyeva, Elvira

    2013-04-01

    The Earth's ionosphere is known to be highly responsive to a large variety of geophysical phenomena coming from above (solar-driven variations, solar flares, magnetospheric events, etc) and from below (earthquakes, tsunamis, volcano eruptions, explosions). Therefore, study of ionospheric response to these events sheds light on the interplanetary/ionosphere and lithosphere/atmosphere/ionosphere couplings. Apart from the pure scientific interests in ionospheric studies, knowledge on the storm-time and quiet-time ionospheric behavior is vitally important for all GNSS users, since the ionosphere changes the amplitude and phase of transionospheric radio signals. The purpose of the ERC Starting Grant project "SIREAL" is to perform a wide spectrum of ionosphere-related research, from ionospheric seismology to ionospheric storms and GNSS/GPS performance during extreme ionospheric and space weather events. The main focus of the project is made on such rare and interdisciplinary subject as ionospheric seismology. Ionospheric seismology is a sufficiently new branch of geophysics, aiming to study ionospheric response to large earthquakes and to investigate the main properties of various ionospheric disturbances generated by quake-like events, including shallow earthquakes, tsunamis and volcano eruptions. Recent work by Astafyeva et al. (2011, Geophys. Res. Lett., L22104, DOI:10.1029/2011GL049623),showed that in some cases, use of high-precision GPS data can provide ionospheric images of seismic fault (its location and dimensions) about ~7-8 min after an earthquake, which opens new opportunities for short-time tsunami warnings. On the example of the Tohoku-oki earthquake on 11 March 2011, here we will show first results of the ERC project, on how the use of 1 Hz ionospheric GPS measurements can provide information on seismic parameters.

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

    OpenAIRE

    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

    2014-01-01

    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...

  5. Preprocessing of ionospheric echo Doppler spectra

    Institute of Scientific and Technical Information of China (English)

    FANG Liang; ZHAO Zhengyu; WANG Feng; SU Fanfan

    2007-01-01

    The real-time information of the distant ionosphere can be acquired by using the Wuhan ionospheric oblique backscattering sounding system(WIOBSS),which adopts a discontinuous wave mechanism.After the characteristics of the ionospheric echo Doppler spectra were analyzed,the signal preprocessing was developed in this paper,which aimed at improving the Doppler spectra.The results indicate that the preprocessing not only makes the system acquire a higher ability of target detection but also suppresses the radio frequency interference by 6-7 dB.

  6. Advances in regional ionospheric mapping over europe

    Directory of Open Access Journals (Sweden)

    L. R. Cander

    1998-06-01

    Full Text Available Over the past several years significant advances have been made in all areas of ionospheric modelling and mapping studies. Ionospheric models and maps of varying complexity have been formulated from analytic and simple numerical models that are user friendly" calculations to complete general circulation models that require hours on today’s supercomputers. All have their place and are used in different applications. This review describes progress in regional ionospheric mapping over Europe in the frame of the COST 238 and 251 projects.

  7. Effects of long work hours and poor sleep characteristics on workplace injury among full-time male employees of small- and medium-scale businesses.

    Science.gov (United States)

    Nakata, Akinori

    2011-12-01

    The aim of this study was to investigate the effects of long work hours and poor sleep characteristics on workplace injury. A total of 1891 male employees, aged 18-79 years (mean 45 years), in 296 small- and medium-scale businesses in a suburb of Tokyo were surveyed by means of a self-administered questionnaire during August-December 2002. Work hours and sleep characteristics, including daily sleep hours, subjective sleep sufficiency, sleep quality and easiness to wake up in the morning, were evaluated. Information on workplace injury in the past 1-year period was self-reported. The risk of workplace injury associated with work hours and poor sleep was estimated using multivariate logistic regression with odds ratio (ORs) and 95% confidence intervals as measures of associations. Compared with those working 6-8 h day(-1) with good sleep characteristics, positive interactive effects for workplace injury were found between long work hours (>8-10 h day(-1) or >10 h day(-1) ) and short sleep duration (sleep (aOR, 1.94-1.99), sleep poorly at night (aOR, 2.23-2.49) and difficulty waking up in the morning (aOR, 1.56-1.59). Long work hours (aOR, 1.31-1.48), subjective insufficient sleep (aOR, 1.49) and sleeping poorly at night (aOR, 1.72) were also independently associated with workplace injury. This study suggests that long work hours coupled with poor sleep characteristics are synergistically associated with increased risk of workplace injury. Greater attention should be paid to manage/treat poor sleep and reduce excessive work hours to improve safety at the workplace.

  8. Application of lightning discharge generated radio atmospherics/tweeks in lower ionospheric plasma diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Maurya, A K; Singh, R; Veenadhari, B [Indian Institute of Geomagnetism, New Panvel, Navi Mumbai - 410 218 (India); Pant, P [Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital - 263129, Uttrakhand (India); Singh, A K, E-mail: ajeet.iig@gmail.co, E-mail: akmaurya@iigs.iigm.res.i [Physics Department, Banaras Hindu University, Varanasi - 221005 (India)

    2010-02-01

    Lightning discharges during thunderstorm are the significant natural source of electromagnetic waves. They generate electromagnetic pulses, which vary from few Hz to tens of MHz, but the maximum radiated energy is confined in extremely low (ELF: 3-3000Hz) and very low (VLF: 3-30 KHz) frequency band. These pulsed signals with frequency dispersion are known as radio atmospherics or tweeks. These waves propagate through the process of multiple reflections in the earth-ionosphere waveguide over long distances with very low attenuation (2-3 dB/1000km). Since these waves are reflected by lower boundary of ionosphere, these are used extensively for probing the D-region ionosphere. D-region is important to the space weather, as well as the submarine communication and navigational aid. In this perspective the measurement of electron density profiles of the D-region is undoubtedly of great interest to both the development of reliable models and radio wave propagation. Earlier work on the tweeks is mainly focused to the theoretical considerations related to polarization, waveform analysis, and occurrence time and propagation mechanism. In this study we investigate tweeks to determine the equivalent night time electron densities at reflection height of the D-region. Distance traveled by the VLF waves from the causative lightning discharges to the receiving station has also been calculated. Tweeks recorded at a low latitude ground station of Allahabad (Geomag. lat. 16.05{sup 0} N) during the night of 23 March 2007 have been used in the present analysis. Based on the analysis of the fundamental cut-off frequency of tweeks, the estimated equivalent electron density of the D-region has been found to be in the range of {approx}20 to 25 el/cm{sup 3} at ionospheric reflection height of {approx}80 to 95 km respectively. Propagation distance in Earth-Ionosphere wave guide (EIWG) from causative lightning source to experimental site varies from {approx}1500 to 8000 km.

  9. Ionospheric variations during sudden stratospheric warming in the high- and mid-latitude regions

    Science.gov (United States)

    Yasyukevich, Anna; Voeykov, Sergey; Mylnikova, Anna

    2017-04-01

    The ionospheric dynamic in the high- and middle-latitude regions during the periods of sudden stratospheric warmings (SSW) was studied by using the international network of phase dual-frequency GPS/GLONASS receivers and the vertical sounding data. Twelve SSW events that occurred in the Northern Hemisphere 2006 through 2013 were considered. In order to identify the possible response of the ionosphere to SSW events, we carried out the analysis of the total electron (TEC) and the F2-layer maximum electron density (NmF2) deviations from the background level. We have also studied changes of the level of total electron content (TEC) wave-like variations characterized by a special index WTEC. The index reflects the intensity of medium- and large-scale traveling ionospheric disturbances. The dynamics of the high- and middle-latitude ionosphere at the points near the SSW areas was found to differ from the regular. For a large number of events, it is shown that, despite quiet geomagnetic conditions, a noticeable decrease in the NmF2 and TEC values (by 5-10% relative to the background level) is observed during the SSW evolution and maximum stages. On the contrary, for 10-20 days after the SSW maxima, NmF2 and TEC significantly exceed the monthly averaged values. Moreover, these electron density changes are observed for both strong and weak stratospheric warmings, and are recorded mainly during daytime. The observed SSW effects in the polar and mid-latitude ionosphere are assumed to be probably associated with the changes in the neutral composition at the thermospheric heights that affect the F2-layer electron density. The study is supported by the Russian Foundation for Basic Research under Grant No. 16-35-60018, as well as by the RF President Grant of Public Support for RF Leading Scientific Schools (NSh-6894.2016.5).

  10. MarsCAT: Mars Array of ionospheric Research Satellites using the CubeSat Ambipolar Thruster

    Science.gov (United States)

    Bering, E. A., III; Pinsky, L.; Li, L.; Jackson, D. R.; Chen, J.; Reed, H.; Moldwin, M.; Kasper, J. C.; Sheehan, J. P.; Forbes, J.; Heine, T.; Case, A. W.; Stevens, M. L.; Sibeck, D. G.

    2015-12-01

    The MarsCAT (Mars Array of ionospheric Research Satellites using the CubeSat Ambipolar Thruster) Mission is a two 6U CubeSat mission to study the ionosphere of Mars proposed for the NASA SIMPLeX opportunity. The mission will investigate the plasma and magnetic structure of the Martian ionosphere, including transient plasma structures, magnetic field structure and dynamics, and energetic particle activity. The transit plan calls for a piggy back ride with Mars 2020 using a CAT burn for MOI, the first demonstration of CubeSat propulsion for interplanetary travel. MarsCAT will make correlated multipoint studies of the ionosphere and magnetic field of Mars. Specifically, the two spacecraft will make in situ observations of the plasma density, temperature, and convection in the ionosphere of Mars. They will also make total electron content measurements along the line of sight between the two spacecraft and simultaneous 3-axis local magnetic field measurements in two locations. Additionally, MarsCAT will demonstrate the performance of new CubeSat telemetry antennas designed at the University of Houston that are designed to be low profile, rugged, and with a higher gain than conventional monopole (whip) antennas. The two MarsCAT CubeSats will have five science instruments: a 3-axis DC magnetometer, adouble-Langmuir probe, a Faraday cup, a solid state energetic particle detector (Science Enhancement Option), and interspacecraft total electron content radio occulation experiment. The MarsCAT spacecraft will be solar powered and equipped with a CAT thruster that can provide up to 4.8 km/s of delta-V, which is sufficient to achieve Mars orbit using the Mars 2020 piggyback. They have an active attitude control system, using a sun sensor and flight-proven star tracker for determination, and momentum wheels for 3-axis attitude control.

  11. Risk assessment in travel medicine.

    Science.gov (United States)

    Leggat, Peter A

    2006-01-01

    Risk assessment is an integral part of pre-travel and post- assessment. Risk assessment largely determines what health and safety advice and interventions are given within the relevant prevailing travel health guidelines. Risk assessment needs time and depends on information, including that given by the traveller. Risk assessment also needs to be documented. Risk assessment of the traveller preferably starts before they enter the consulting room, where travellers may complete a pre-travel health questionnaire. Armed with this information, risk assessment may be assisted by access to computerised travel health databases and the published literature. Experience of travel to the destination may also assist in risk assessment and the tour operator, overseas employer or agency, the traveller or even the travel health advisers themselves may provide this information.

  12. 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...

  13. Space weather. Ionospheric control of magnetotail reconnection.

    Science.gov (United States)

    Lotko, William; Smith, Ryan H; Zhang, Binzheng; Ouellette, Jeremy E; Brambles, Oliver J; Lyon, John G

    2014-07-11

    Observed distributions of high-speed plasma flows at distances of 10 to 30 Earth radii (R(E)) in Earth's magnetotail neutral sheet are highly skewed toward the premidnight sector. The flows are a product of the magnetic reconnection process that converts magnetic energy stored in the magnetotail into plasma kinetic and thermal energy. We show, using global numerical simulations, that the electrodynamic interaction between Earth's magnetosphere and ionosphere produces an asymmetry consistent with observed distributions in nightside reconnection and plasmasheet flows and in accompanying ionospheric convection. The primary causal agent is the meridional gradient in the ionospheric Hall conductance which, through the Cowling effect, regulates the distribution of electrical currents flowing within and between the ionosphere and magnetotail.

  14. The magnetohydrodynamic description of Earth's ionosphere

    CERN Document Server

    Pandey, B P

    2016-01-01

    The wave propagation in the partially ionized ionosphere plays an important role in the magnetosphere ionosphere coupling. For example, the ionosphere may supports very low-frequency Alfven wave which can be caused by a balance between the bulk fluid inertia (mostly due to neutrals in the lower and middle E region) and the deformation of the magnetic field. The plasma neutral collisional momentum exchange facilitates the transfer of the magnetic stress (felt directly by the ions) to the neutrals. Therefore, in the low-frequency (with respect to the neutral ion collision frequency) limit, waves through the ionosphere can propagate with very little damping. In the vanishing plasma inertia limit, waves can be excited due to the loading of neutral inertia on the field lines and thus may have very long wavelength and can easily couple to the magnetosphere. The frequency of these waves are below few Hz.

  15. On the Ionospheric Holes of Venus

    Science.gov (United States)

    Collinson, G.; Fedorov, A.; Futaana, Y.; Masunaga, K.; Hartle, R. E.; Stenberg, G.; Budnik, E.; Grebowsky, J. M.; Holmstrom, M.; andre, N.; Barabash, S. V.; Zhang, T.

    2013-12-01

    One of the most intriguing unsolved mysteries that endures from the Pioneer Venus Orbiter is that of ~1000km wide ``Holes" in the nightside Ionosphere. The phenomena remains unexplained, despite their frequent observation during the first three years of the mission, and more than thirty years having elapsed since their first description in the literature. We present new observations by the ESA Venus Express of Ionospheric Holes at very high altitudes, providing us with the opportunity to study this fascinating phenomena with modern instrumentation. We discuss the insight that these new data give us into the effect of Ionospheric Holes on atmospheric escape, and the evidence that suggests that Ionospheric Holes are due to an internal planetary magnetic field.

  16. SHOCK WAVE IN IONOSPHERE DURING EARTHQUAKE

    Directory of Open Access Journals (Sweden)

    V.V. Kuznetsov

    2016-11-01

    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

  17. 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.

  18. Remote Sensing of Ionosphere by IONOLAB Group

    Science.gov (United States)

    Arikan, Feza

    2016-07-01

    Ionosphere is a temporally and spatially varying, dispersive, anisotropic and inhomogeneous medium that is characterized primarily by its electron density distribution. Electron density is a complex function of spatial and temporal variations of solar, geomagnetic, and seismic activities. Ionosphere is the main source of error for navigation and positioning systems and satellite communication. Therefore, characterization and constant monitoring of variability of the ionosphere is of utmost importance for the performance improvement of these systems. Since ionospheric electron density is not a directly measurable quantity, an important derivable parameter is the Total Electron Content (TEC), which is used widely to characterize the ionosphere. TEC is proportional to the total number of electrons on a line crossing the atmosphere. IONOLAB is a research group is formed by Hacettepe University, Bilkent University and Kastamonu University, Turkey gathered to handle the challenges of the ionosphere using state-of-the-art remote sensing and signal processing techniques. IONOLAB group provides unique space weather services of IONOLAB-TEC, International Reference Ionosphere extended to Plasmasphere (IRI-Plas) model based IRI-Plas-MAP, IRI-Plas-STEC and Online IRI-Plas-2015 model at www.ionolab.org. IONOLAB group has been working for imaging and monitoring of ionospheric structure for the last 15 years. TEC is estimated from dual frequency GPS receivers as IONOLAB-TEC using IONOLAB-BIAS. For high spatio-temporal resolution 2-D imaging or mapping, IONOLAB-MAP algorithm is developed that uses automated Universal Kriging or Ordinary Kriging in which the experimental semivariogram is fitted to Matern Function with Particle Swarm Optimization (PSO). For 3-D imaging of ionosphere and 1-D vertical profiles of electron density, state-of-the-art IRI-Plas model based IONOLAB-CIT algorithm is developed for regional reconstruction that employs Kalman Filters for state

  19. [Counsel for traveling children].

    Science.gov (United States)

    Sorge, F; Gendrel, D

    2013-01-01

    Consultation of child traveler has two main objectives: to assess of health risk related to the child's health status and history and also the risk related to travel environment; to counsel and prescribe preventive measure to reduce these travel health risks. The evaluation is based on physical examination and a detailed interview including personal history and information regarding the regions of proposed travel. Up to date knowledge of the epidemiology of visited sites, preventive measures and presumptive treatment is required. Essential health recommendations include, in case of exposure, prevention of malaria, arthropod borned diseases and vaccine preventable diseases. For all destinations advice regarding prevention of diarrhea, accident risks and aggravation of preexisting chronic diseases is needed. Universal primary prevention counselling is valuable for all travellers regardless of their age. In the case of children, special attention must be given to food and water hygiene, sun and heat exposure, swimming risks and transports security measures. Evaluation of risk and health education take time and often several visits are needed to complete the immunization schedule before departure.

  20. Colored Traveling Salesman Problem.

    Science.gov (United States)

    Li, Jun; Zhou, MengChu; Sun, Qirui; Dai, Xianzhong; Yu, Xiaolong

    2015-11-01

    The multiple traveling salesman problem (MTSP) is an important combinatorial optimization problem. It has been widely and successfully applied to the practical cases in which multiple traveling individuals (salesmen) share the common workspace (city set). However, it cannot represent some application problems where multiple traveling individuals not only have their own exclusive tasks but also share a group of tasks with each other. This work proposes a new MTSP called colored traveling salesman problem (CTSP) for handling such cases. Two types of city groups are defined, i.e., each group of exclusive cities of a single color for a salesman to visit and a group of shared cities of multiple colors allowing all salesmen to visit. Evidences show that CTSP is NP-hard and a multidepot MTSP and multiple single traveling salesman problems are its special cases. We present a genetic algorithm (GA) with dual-chromosome coding for CTSP and analyze the corresponding solution space. Then, GA is improved by incorporating greedy, hill-climbing (HC), and simulated annealing (SA) operations to achieve better performance. By experiments, the limitation of the exact solution method is revealed and the performance of the presented GAs is compared. The results suggest that SAGA can achieve the best quality of solutions and HCGA should be the choice making good tradeoff between the solution quality and computing time.

  1. Artificial Aurora and Ionospheric Heating by HAARP

    Science.gov (United States)

    Hadavandkhani, S.; Nikouravan, Bijan; Ghazimaghrebi, F.

    2016-08-01

    A recent experiment was achieved at HAARP to study the scaling of the ionospherically generated ELF signal with power transmitted from the high frequency (HF) array. The results were in excellent agreement with computer simulations. The outcomes approving that the ELF power increases with the square of the incident HF power. This paper present a review on the situation of the ionized particles in Ionospheric layer when stimulated by artificial an ELF and VLF external high energy radio waves.

  2. Modeling Weather in the Ionosphere using the Navy's Highly Integrated Thermosphere and Ionosphere Demonstration System (HITIDES)

    Science.gov (United States)

    McDonald, S. E.; Sassi, F.; Zawdie, K.; McCormack, J. P.; Coker, C.; Huba, J.; Krall, J.

    2016-12-01

    The Naval Research Laboratory (NRL) has recently developed a ground-to-space atmosphere-ionosphere prediction capability, the Highly Integrated Thermosphere and Ionosphere Demonstration System (HITIDES). HITIDES is the U.S. Navy's first coupled, physics-based, atmosphere-ionosphere model, one in which the atmosphere extends from the ground to the exobase ( 500 km altitude) and the ionosphere reaches several 10,000 km in altitude. HITIDES has been developed by coupling the extended version of the Whole Atmosphere Community Climate Model (WACCM-X) with NRL's ionospheric model, Sami3 is Another Model of the Ionosphere (SAMI3). Integrated into this model are the effects of drivers from atmospheric weather (day-to-day meteorology), the Sun, and the changing high altitude composition. To simulate specific events, HITIDES can be constrained by data analysis products or observations. We have performed simulations of the ionosphere during January-February 2010 in which lower atmospheric weather patterns have been introduced using the Navy Operational Global Atmospheric Prediction System-Advanced Level Physics High Altitude (NOGAPS-ALPHA) data assimilation products. The same time period has also been simulated using the new atmospheric forecast model, the NAVy Global Environmental Model (NAVGEM), which has replaced NOGAPS-ALPHA. The two simulations are compared with each other and with observations of the low latitude ionosphere. We will discuss the importance of including lower atmospheric meteorology in ionospheric simulations to capture day-to-day variability as well as large-scale longitudinal structure in the low-latitude ionosphere. In addition, we examine the effect of the variability on HF radio wave propagation by comparing simulated ionograms calculated from the HITIDES ionospheric specifications to ionosonde measurements.

  3. Ionospheric Response Due to Seismic Activity

    Science.gov (United States)

    Sharma, Dinesh Kumar

    2016-07-01

    Signatures of the seismic activity in the ionospheric F2 region have been studied by analyzing the measurement of electron and ion temperatures during the occurrence of earthquake. The ionospheric electron and ion temperatures data recorded by the RPA payload aboard the Indian SROSS-C2 satellite during the period from January 1995 to December 2000 were used for the altitude range 430-630 km over Indian region. The normal day's electron and ion temperatures have been compared to the temperatures recorded during the seismic activity. The details of seismic events were obtained from USGS earthquake data information website. It has been found that the average electron temperature is enhanced during the occurrence of earthquakes by 1.2 to 1.5 times and this enhancement was for ion temperature ranging from 1.1to 1.3 times over the normal day's average temperatures. The above careful quantitative analysis of ionospheric electron and ion temperatures data shows the consistent enhancement in the ionospheric electron and ion temperatures. It is expected that the seismogenic vertical electrical field propagates up to the ionospheric heights and induces Joule heating that may cause the enhancement in ionospheric temperatures.

  4. Computerized ionospheric tomography with the IRI model

    Science.gov (United States)

    Arikan, Orhan; Arikan, Feza; Erol, Cemil B.

    Computerized ionospheric tomography (CIT) is a method to estimate ionospheric electron density distribution by using the global positioning system (GPS) signals recorded by the GPS receivers. Ionospheric electron density is a function of latitude, longitude, height and time. A general approach in CIT is to represent the ionosphere as a linear combination of basis functions. In this study, the model of the ionosphere is obtained from the IRI in latitude and height only. The goal is to determine the best representing basis function from the set of Squeezed Legendre polynomials, truncated Legendre polynomials, Haar Wavelets and singular value decomposition (SVD). The reconstruction algorithms used in this study can be listed as total least squares (TLS), regularized least squares, algebraic reconstruction technique (ART) and a hybrid algorithm where the reconstruction from the TLS algorithm is used as the initial estimate for the ART. The error performance of the reconstruction algorithms are compared with respect to the electron density generated by the IRI-2001 model. In the investigated scenario, the measurements are obtained from the IRI-2001 as the line integral of the electron density profiles, imitating the total electron content estimated from GPS measurements. It has been observed that the minimum error between the reconstructed and model ionospheres depends on both the reconstruction algorithm and the basis functions where the best results have been obtained for the basis functions from the model itself through SVD.

  5. Computerized ionospheric tomography based on geosynchronous SAR

    Science.gov (United States)

    Hu, Cheng; Tian, Ye; Dong, Xichao; Wang, Rui; Long, Teng

    2017-02-01

    Computerized ionospheric tomography (CIT) based on spaceborne synthetic aperture radar (SAR) is an emerging technique to construct the three-dimensional (3-D) image of ionosphere. The current studies are all based on the Low Earth Orbit synthetic aperture radar (LEO SAR) which is limited by long repeat period and small coverage. In this paper, a novel ionospheric 3-D CIT technique based on geosynchronous SAR (GEO SAR) is put forward. First, several influences of complex atmospheric environment on GEO SAR focusing are detailedly analyzed, including background ionosphere and multiple scattering effects (induced by turbulent ionosphere), tropospheric effects, and random noises. Then the corresponding GEO SAR signal model is constructed with consideration of the temporal-variant background ionosphere within the GEO SAR long integration time (typically 100 s to 1000 s level). Concurrently, an accurate total electron content (TEC) retrieval method based on GEO SAR data is put forward through subband division in range and subaperture division in azimuth, obtaining variant TEC value with respect to the azimuth time. The processing steps of GEO SAR CIT are given and discussed. Owing to the short repeat period and large coverage area, GEO SAR CIT has potentials of covering the specific space continuously and completely and resultantly has excellent real-time performance. Finally, the TEC retrieval and GEO SAR CIT construction are performed by employing a numerical study based on the meteorological data. The feasibility and correctness of the proposed methods are verified.

  6. A generalized trigonometric series function model for determining ionospheric delay

    Institute of Scientific and Technical Information of China (English)

    YUAN Yunbin; OU Jikun

    2004-01-01

    A generalized trigonometric series function (GTSF) model, with an adjustable number of parameters, is proposed and analyzed to study ionosphere by using GPS, especially to provide ionospheric delay correction for single frequency GPS users. The preliminary results show that, in comparison with the trigonometric series function (TSF) model and the polynomial (POLY) model, the GTSF model can more precisely describe the ionospheric variation and more efficiently provide the ionospheric correction when GPS data are used to investigate or extract the earth's ionospheric total electron content. It is also shown that the GTSF model can further improve the precision and accuracy of modeling local ionospheric delays.

  7. [Pregnancy and traveling].

    Science.gov (United States)

    Walentiny, C

    2009-03-01

    The second trimester is the safest time for travelling, because the pregnant woman feels generally most at ease and the risk of spontaneous abortion and pre-term labour is very low. Possible risks must be discussed with the obstetrician before travelling. If the pregnancy is uncomplicated most airlines allow flying up to the 36th (domestic flights) and 35th (international flights) week of gestation. Unless the fetal oxygen supply is already impaired at ground level due to an underlying disease, flying does not pose a risk of fetal hypoxia. Radiation exposure during a long distant flight is low compared to the average annual exposure dosage, but the risk of thrombosis is increased. Altitudes up to 2,500 m pose no problem. Sufficient time to acclimatize must be taken when travelling to high altitudes and exercise kept to a minimum. Scuba diving is contraindicated. Since only a few drugs are completely safe during pregnancy a thorough risk/benefit evaluation is mandatory. Treatment of infections can be considerably complicated, but any necessary treatment should not be withheld because of the fear of potential fetal injury. Good knowledge of local medical resources is essential before travelling. Several personal protective measures minimize the risk of infection: food and water precautions, protection from insect bites and avoidance of crowds, unsafe sex and, if need be, freshwater. Many vaccinations are recommended for travellers. However, live vaccines are contraindicated in pregnant women because of theoretical considerations. Exceptionally a yellow fever vaccination may be given after the first trimester. Killed, inactivated or polysaccharide vaccines can be given after the first trimester after a thorough risk/benefit evaluation. Because of the potentially devastating effect of malaria to the mother and the child, travelling to endemic malaria regions should be avoided. If the risk of infection is high chemoprophylaxis with mefloquine is indicated. In low

  8. Culture shock and travelers.

    Science.gov (United States)

    Stewart, L; Leggat, P A

    1998-06-01

    As travel has become easier and more affordable, the number of people traveling has risen sharply. People travel for many and varied reasons, from the business person on an overseas assignment to backpackers seeking new and exotic destinations. Others may take up residence in different regions, states or countries for family, business or political reasons. Other people are fleeing religious or political persecution. Wherever they go and for whatever reason they go, people take their culture with them. Culture, like language, is acquired innately in early childhood and is then reinforced through formal and complex informal social education into adulthood. Culture provides a framework for interpersonal and social interactions. Therefore, the contact with a new culture is often not the exciting or pleasurable experience anticipated. When immersed in a different culture, people no longer know how to act when faced with disparate value systems. Contact with the unfamiliar culture can lead to anxiety, stress, mental illness and, in extreme cases, physical illness and suicide. "Culture shock" is a term coined by the anthropologist Oberg. It is the shock of the new. It implies that the experience of the new culture is an unpleasant surprise or shock, partly because it is unexpected and partly because it can lead to a negative evaluation of one's own culture. It is also known as cross-cultural adjustment, being that period of anxiety and confusion experienced when entering a new culture. It affects people intellectually, emotionally, behaviorally and physically and is characterized by symptoms of psychological distress. Culture shock affects both adults and children. In travelers or workers who have prolonged sojourns in foreign countries, culture shock may occur not only as they enter the new culture, but also may occur on their return to their original culture. Children may also experience readjustment problems after returning from leading sheltered lives in expatriate

  9. Time a traveler's guide

    CERN Document Server

    Pickover, Clifford A

    1998-01-01

    ""Bucky Fuller thought big,"" Wired magazine recently noted, ""Arthur C. Clarke thinks big, but Cliff Pickover outdoes them both."" In his newest book, Cliff Pickover outdoes even himself, probing a mystery that has baffled mystics, philosophers, and scientists throughout history--What is the nature of time? In Time: A Traveler's Guide, Pickover takes readers to the forefront of science as he illuminates the most mysterious phenomenon in the universe--time itself. Is time travel possible? Is time real? Does it flow in one direction only? Does it have a beginning and an end? What is eternity? P

  10. Malaria prevention in travelers.

    Science.gov (United States)

    Genton, Blaise; D'Acremont, Valérie

    2012-09-01

    A common approach to malaria prevention is to follow the "A, B, C, D" rule: Awareness of risk, Bite avoidance, Compliance with chemoprophylaxis, and prompt Diagnosis in case of fever. The risk of acquiring malaria depends on the length and intensity of exposure; the risk of developing severe disease is primarily determined by the health status of the traveler. These parameters need to be assessed before recommending chemoprophylaxis and/or stand-by emergency treatment. This review discusses the different strategies and drug options available for the prevention of malaria during and post travel.

  11. Intergalactic Travel Bureau

    Science.gov (United States)

    Koski, Olivia; Rosin, Mark; Guerilla Science Team

    2014-03-01

    The Intergalactic Travel Bureau is an interactive theater outreach experience that engages the public in the incredible possibilities of space tourism. The Bureau is staffed by professional actors, who play the role of space travel agents, and professional astrophysicists, who play the role of resident scientists. Members of the public of all ages were invited to visit with bureau staff to plan the vacation of their dreams-to space. We describe the project's successful nine day run in New York in August 2013. Funded by the American Physical Society Public Outreach and Informing the Public Grants.

  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. Travel health. Part 1: preparing the tropical traveller.

    Science.gov (United States)

    Carroll, Bernadette; Daniel, Amanda; Behrens, Ron H

    The health threats of modern day travel change as population, wealth and tourism increase across the world. A series of three articles have been written to describe the spectrum of health issues associated with travel. Pre-travel health advice has become more focused on risk assessment and educating the traveller about infectious disease and the more frequent non-infectious hazards associated with travel, while ensuring they are not unnecessarily exposed to injury from vaccines and drugs. In part one, the role of the health advisor and the needs of the traveller are examined. The importance of risk assessment during a consultation is described and factors that influence recommendations and prescribing are explored. As most travel-associated morbidity and mortality is non-vaccine preventable, the focus of the pre-travel consultation should be on educating the traveller and influencing behaviour change. The second article in this series deals with the highest risk group of travellers--residents who visit friends and relatives. It highlights their specific problems and special needs and how to influence their risk of disease by addressing their health beliefs and their cultural dimension of risk. The third article explores the common, and not so common, clinical problems found in returned travellers. Nurses have to deal with a large range of clinical problems and diagnostic dilemmas when attending to the returned traveller. The review provides a perspective on the frequency and severity of problems and how nurses should manage travel associated disease.

  14. Travel Inside the Ear

    Medline Plus

    Full Text Available ... Search form Search A–Z Index Español Menu Home Health Info Hearing, Ear Infections, and Deafness Balance ... Committees Contact Us Get Involved You are here Home » Health Info » Hearing, Ear Infections, and Deafness Travel ...

  15. Flu and Holiday Travel

    Centers for Disease Control (CDC) Podcasts

    2010-12-13

    This podcast explains the ways people can stay healthy and avoid the flu when traveling this winter.  Created: 12/13/2010 by National Center for Emerging and Zoonotic Infectious Diseases (NCEZID).   Date Released: 12/13/2010.

  16. Gulliver's Travels. [Lesson Plan].

    Science.gov (United States)

    Rooks, Kirsten; McLean, Mary

    Based on Jonathan Swift's novel "Gulliver's Travels," this lesson plan presents activities designed to help students understand that Swift comments on undesirable outcomes of advances in science; and other authors have also warned against abuse of science. The main activity of the lesson involves students developing a poster illustrating views of…

  17. Traveling in France.

    Science.gov (United States)

    Philyaw, Henry; And Others

    This minicourse guide for teachers of French is intended to help motivate and prepare students for travel in France. Activities are outlined in eleven related areas, including (1) planning for the trip, (2) currency, (3) going through customs, (4) tipping, (5) shopping, (6) guided tours, (7) touring on your own, (8) social life and entertainment,…

  18. Beijing Time Travel

    Institute of Scientific and Technical Information of China (English)

    ROBERT T.TUOHEY

    2010-01-01

    @@ Dally travel within Beijing need not be anymore troublesome than going about any major metropolis.Simply,certain basic facts need to be kept in mind,and ordinary precautions taken.Essentially,it's the same situation as midtown Manhattan or downtown Tokyo,except everyone's speaking Chinese.

  19. Beijing Time Travel

    Institute of Scientific and Technical Information of China (English)

    ROBERT; T.TUOHEY

    2010-01-01

    Daily travel within Beijing need not be anymore troublesome than going about any major metropolis.Simply,certain basic facts need to be kept in mind,and ordinary precautions taken.Essentially,it’s the same situation as midtown Manhattan or downtown Tokyo,except everyone’s speaking Chinese.

  20. Travelers' Health: Hepatitis A

    Science.gov (United States)

    ... total anti-HAV result and a negative IgM anti-HAV result indicate past infection or vaccination and immunity. The presence of serum IgM anti- ... the risk for adverse effects, screening for total anti-HAV before travel can be ... Postvaccination testing for serologic response is not indicated. ...

  1. Zero Energry Travel

    CERN Document Server

    Ahmad, Othman; Chekima, Ali

    2011-01-01

    It is fundamentally possible to travel with zero energy based on Newton Laws of Motion. According to the first law of motion, a body will continue to travel for infinite distance unless it is acted upon by another force. For a body in motion, the force which stops perpetual motion is friction. However, there are many circumstances that friction is zero, for example in space, where there is vacuum. On earth, gravity makes objects to be in constant contact with each other generating friction but technology exists to separate them in the air using powerful magnetic forces. At low speeds, the friction caused by air is minimal but we can create vacuum even on land for high speed travel. Another condition for travelling is for it to stop at its destination. On land, we can recover the kinetic energy back into electrical energy using brushless permanent magnet generators. These generators can also convert electric energy into kinetic energy in order to provide motion. This article reviews technologies that will allo...

  2. Ionospheric Impacts on UHF Space Surveillance

    Science.gov (United States)

    Jones, J.; Ceron-Gomez, D.; Richards, G.

    2016-09-01

    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 350 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 electron 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 uncertainty 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 correlations with ionospheric variability. Corrections to surveillance radar measurements can be adapted from our simulation capability.

  3. Midlatitude ionospheric changes to four great geomagnetic storms of solar cycle 23 in Southern and Northern Hemispheres

    Science.gov (United States)

    Merline Matamba, Tshimangadzo; Habarulema, John Bosco; Burešová, Dalia

    2016-12-01

    This paper presents an investigation of ionospheric response to great (Dst ≤-350 nT) geomagnetic storms that occurred during solar cycle 23. The storm periods analyzed are 29 March to 2 April 2001, 27-31 October 2003, 18-23 November 2003, and 6-11 November 2004. Global Navigation Satellite System, total electron content (TEC), and ionosonde critical frequency of F2 layer (foF2) data over Southern Hemisphere (African sector) and Northern Hemisphere (European sector) midlatitudes were used to study the ionospheric responses within 15°E-40°E longitude and ±31° to ±46° geomagnetic latitude. Midlatitude regions within the same longitude sector in both hemispheres were selected in order to assess the contribution of the low-latitude changes especially the expansion of equatorial ionization anomaly (EIA) also called the dayside ionospheric superfountain effect during these storms. In all storm periods, both negative and positive ionospheric responses were observed in both hemispheres. Negative ionospheric responses were mainly due to changes in neutral composition, while the expansion of the EIA led to pronounced positive storm effects at midlatitudes for some storm periods. In other cases (e.g., 29 October 2003), penetration electric fields, EIA expansion, and large-scale traveling ionospheric disturbances were found to be present during the positive storm effect at midlatitudes in both hemispheres. An increase in TEC on the 28 October 2003 was because of the large solar flare with previously determined intensity of X45 ±5.

  4. Valuation of Travel Time and TravelIer Information

    NARCIS (Netherlands)

    Rietveld, Piet

    2003-01-01

    The value of travel time plays an important role in cost benefit analysis of infrastructureprojects. However, the issue of uncertainty on travel times and the implications this has forestimations of travel time values has received much less attention in the literature. In thispaper we compare

  5. Valuation of Travel Time and TravelIer Information

    NARCIS (Netherlands)

    Rietveld, Piet

    2003-01-01

    The value of travel time plays an important role in cost benefit analysis of infrastructureprojects. However, the issue of uncertainty on travel times and the implications this has forestimations of travel time values has received much less attention in the literature. In thispaper we compare variou

  6. Experimental evidence of electromagnetic pollution of ionosphere

    Science.gov (United States)

    Pronenko, Vira; Korepanov, Valery; Dudkin, Denis

    The Earth’s ionosphere responds to external perturbations originated mainly in the Sun, which is the primary driver of the space weather (SW). But solar activity influences on the ionosphere and the Earth's atmosphere (i.e., the energy transfer in the direction of the Sun-magnetosphere-ionosphere-atmosphere-surface of the Earth), though important, is not a unique factor affecting its state - there is also a significant impact of the powerful natural and anthropogenic processes, which occur on the Earth’s surface and propagating in opposite direction along the Earth’s surface-atmosphere-ionosphere-magnetosphere chain. Numerous experimental data confirm that the powerful sources and consumers of electrical energy (radio transmitters, power plants, power lines and industrial objects) cause different ionospheric phenomena, for example, changes of the electromagnetic (EM) field and plasma in the ionosphere, and affect on the state of the Earth atmosphere. Anthropogenic EM effects in the ionosphere are already observed by the scientific satellites and the consequences of their impact on the ionosphere are not currently known. Therefore, it is very important and urgent task to conduct the statistically significant research of the ionospheric parameters variations due to the influence of the powerful man-made factors, primarily owing to substantial increase of the EM energy production. Naturally, the satellite monitoring of the ionosphere and magnetosphere in the frequency range from tens of hertz to tens of MHz with wide ground support offers the best opportunity to observe the EM energy release, both in the global and local scales. Parasitic EM radiation from the power supply lines, when entering the ionosphere-magnetosphere system, might have an impact on the electron population in the radiation belt. Its interaction with trapped particles will change their energy and pitch angles; as a result particle precipitations might occur. Observations of EM emission by

  7. Ionosphere-magnetosphere energy interplay in the regions of diffuse aurora

    Science.gov (United States)

    Khazanov, G. V.; Glocer, A.; Sibeck, D. G.; Tripathi, A. K.; Detweiler, L. G.; Avanov, L. A.; Singhal, R. P.

    2016-07-01

    Both electron cyclotron harmonic (ECH) waves and whistler mode chorus waves resonate with electrons of the Earth's plasma sheet in the energy range from tens of eV to several keV and produce the electron diffuse aurora at ionospheric altitudes. Interaction of these superthermal electrons with the neutral atmosphere leads to the production of secondary electrons (E whistler mode chorus waves, however, can also interact with the secondary electrons that are coming from both of the magnetically conjugated ionospheres after they have been produced by initially precipitated high-energy electrons that came from the plasma sheet. After their degradation and subsequent reflection in magnetically conjugate atmospheric regions, both the secondary electrons and the precipitating electrons with high (E > 600 eV) initial energies will travel back through the loss cone, become trapped in the magnetosphere, and redistribute the energy content of the magnetosphere-ionosphere system. Thus, scattering of the secondary electrons by ECH and whistler mode chorus waves leads to an increase of the fraction of superthermal electron energy deposited into the core magnetospheric plasma.

  8. The ionospheric behavior in conjugate hemispheres during the 3 October 2005 solar eclipse

    Directory of Open Access Journals (Sweden)

    H. Le

    2009-01-01

    Full Text Available We investigate the ionospheric behavior in conjugate hemispheres during the 3 October 2005 solar eclipse, on the basis of observations of electron temperature (Te from the Defense Meteorological Satellites Program (DMSP spacecraft, F2 layer critical frequency (foF2 and F2 layer peak height (hmF2 at the Grahamstown ionosonde station, and total electron content (TEC from the Global Positioning System (GPS station SUTH. The observations show that when the eclipse occurred in the Northern Hemisphere, there was a decrease in Te, an increase in foF2 and TEC, and an uprising in hmF2 in its conjugate region compared with their reference values. We also simulated the ionosphere behavior during this eclipse using a mid- and low-latitude ionospheric model. The simulations agree well with the observations. Because of the eclipse effect, there are far fewer photoelectrons travelling along the magnetic field lines from the eclipse region to the conjugate region, resulting in reduced photoelectron heating in the conjugate hemisphere which causes a drop in electron temperature and subsequent disturbances in the region.

  9. Observation of Sudden Ionospheric Disturbances over Istanbul in Response to X-Ray Flare Events

    Science.gov (United States)

    Ceren Kalafatoglu Eyiguler, Emine; Kaymaz, Zerefsan; Ceren Moral, Aysegul

    2016-07-01

    Sudden ionospheric disturbances (SID) are the enhanced electron density structures in the D region ionosphere which occur in response to the increase in X-ray flares and EUV flux. SIDs can be monitored using Very Low Frequency (VLF) radio signals (3-30 kHz) which travel between the D-region and the surface of the Earth. In this study, we use SID monitors obtained from the Stanford University Solar Center and two antennas which were built at the Istanbul Technical University to track the ionospheric disturbances in the VLF range. Our antennas are capable of capturing signals from several VLF transmitting stations. In this work, we focus on the variations in the signal strength of the closest VLF transmitting station 'TBB' which is operating at 26.7 kHz frequency at BAFA, Turkey (37.43N, 27.15E). We present ITU SID observations from both antennas; show the daily variation, general structure and the typical patterns we observe as well as case studies of significant events. Our initial analysis shows close relationship between observed X-ray flares from geosynchronous GOES 13 and GOES 15 satellites and VLF station signal strength received by the monitors.

  10. Mesoscale ionospheric tomography at the Auroral region

    Science.gov (United States)

    Luntama, J.; Kokkatil, G. V.

    2008-12-01

    FMI (Finnish Meteorological Institute) has used observations from the dense GNSS network in Finland for high resolution regional ionospheric tomography. The observation system used in this work is the VRS (Virtual Reference Station) network in Finland operated by Geotrim Ltd. This network contains 86 GNSS ground stations providing two frequency GPS and GLONASS observations with the sampling rate of 1 Hz. The network covers the whole Finland and the sampling of the ionosphere is very good for observing mesoscale ionospheric structures at the Auroral region. The ionospheric tomography software used by FMI is the MIDAS (Multi-Instrument Data Analysis System) algorithm developed and implemented by the University of Bath (Mitchell and Spencer, 2003). MIDAS is a 3-D extension of the 2-D tomography algorithm originally presented by Fremouw et al. (1992). The research at FMI is based on ground based GNSS data collected in December 2006. The impacts of the two geomagnetic storms during the month are clearly visible in the retrieved electron density and TEC maps and they can be correlated with the magnetic field disturbances measured by the IMAGE magnetometer network. This is the first time that mesoscale structures in the ionospheric plasma can be detected from ground based GNSS observations at the Auroral region. The continuous high rate observation data from the Geotrim network allows monitoring of the temporal evolution of these structures throughout the storms. Validation of the high resolution electron density and TEC maps is a challenge as independent reference observations with a similar resolution are not available. FMI has compared the 3-D electron density maps against the 2-D electron density plots retrieved from the observations from the Ionospheric Tomography Chain operated by the Sodankylä Geophysical Observatory (SGO). Additional validation has been performed with intercomparisons with observations from the ground based magnetometer and auroral camera network

  11. 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.

  12. Traveler's Health: Avoid Bug Bites

    Science.gov (United States)

    ... Blood Clots Bug Bites Business Travel Cold Climates Counterfeit Drugs Cruise Ship Travel Families with Children Fish ... insect repellents that contain at least 20% DEET (products include Cutter Backwoods and Off! Deep Woods) for ...

  13. Epidemic spreading by objective traveling

    Science.gov (United States)

    Tang, Ming; Liu, Zonghua; Li, Baowen

    2009-07-01

    A fundamental feature of agent traveling in social networks is that traveling is usually not a random walk but with a specific destination and goes through the shortest path from starting to destination. A serious consequence of the objective traveling is that it may result in a fast epidemic spreading, such as SARS etc. In this letter we present a reaction-traveling model to study how the objective traveling influences the epidemic spreading. We consider a random scale-free meta-population network with sub-population at each node. Through a SIS model we theoretically prove that near the threshold of epidemic outbreak, the objective traveling can significantly enhance the final infected population and the infected fraction at a node is proportional to its betweenness for the traveling agents and approximately proportional to its degree for the non-traveling agents. Numerical simulations have confirmed the theoretical predictions.

  14. 75 FR 43395 - Campaign Travel

    Science.gov (United States)

    2010-07-26

    ... Campaign Travel AGENCY: Federal Election Commission. ACTION: Announcement of effective date. SUMMARY: On... of the Honest Leadership and Open Government Act governing campaign travel on noncommercial aircraft.... SUPPLEMENTARY INFORMATION: On December 7, 2009, the Commission published final rules governing campaign...

  15. Knowledge Representation in Travelling Texts

    DEFF Research Database (Denmark)

    Mousten, Birthe; Locmele, Gunta

    2014-01-01

    Today, information travels fast. Texts travel, too. In a corporate context, the question is how to manage which knowledge elements should travel to a new language area or market and in which form? The decision to let knowledge elements travel or not travel highly depends on the limitation...... and the purpose of the text in a new context as well as on predefined parameters for text travel. For texts used in marketing and in technology, the question is whether culture-bound knowledge representation should be domesticated or kept as foreign elements, or should be mirrored or moulded—or should not travel...... at all! When should semantic and pragmatic elements in a text be replaced and by which other elements? The empirical basis of our work is marketing and technical texts in English, which travel into the Latvian and Danish markets, respectively....

  16. Charge Balance in the Martian Ionosphere

    Science.gov (United States)

    Esman, Teresa; Yelle, Roger V.; Stone, Shane W.; Andersson, Laila; Fowler, Christopher Michael; Benna, Mehdi; Eparvier, Francis; Mahaffy, Paul; Ergun, Bob; Elrod, Meredith K.; MAVEN

    2016-10-01

    We present empirical models of the Martian ionosphere in conjunction with data from the Langmuir Probe and Waves (LPW), Neutral Gas and Ion Mass Spectrometer (NGIMS), and Extreme Ultraviolet Monitor (EUVM) instruments aboard the Mars Atmosphere and Volatile Evolution mission (MAVEN) spacecraft. Among the data provided by MAVEN are electron densities and temperatures, ion and neutral densities, and solar extreme ultraviolet (EUV) flux. We explore a number of contributors to the CO2 photoionization rate, with a specific focus on the role of electron temperatures, which, prior to MAVEN, were not well-known. We compare our results with expectations of the ionospheric structure and behavior to confirm our understanding of the basic structure of the Martian ionosphere in the photochemical region. We show that the ionosphere of Mars is well matched by photochemical equilibrium to within the accuracy of the measurements. These results will aid in the development of more complex ionospheric and escape models and lead to a comprehensive and global scale picture of thermal ion escape on Mars.

  17. CARLSON WAGONLIT TRAVEL

    CERN Multimedia

    CARLSON WAGONLIT TRAVEL

    2004-01-01

    CARLSON WAGONLIT TRAVEL would like to remind you of the entry formalities applicable to those travelling to the United States. Nationals of Switzerland and of the following countries : Andorra, Australia, Austria, Belgium, Brunei, Denmark, Finland, France, Germany, Iceland, Ireland, Italy, Japan, Liechtenstein, Luxemburg, Monaco, Netherlands, New Zealand, Norway, Portugal, San Marino, Singapore, Slovenia, Spain, Sweden and the United Kingdom, entering the United States under the Visa Waiver Program (no visa requirement), must be in possession of an machine-readable passport that is valid for at least six months after the date of the return trip. Children, including infants, must have their own passport. An entry in the parents' passport is not sufficient. For entry into the United States, an e-ticket (fax or e-mail confirmation or passenger receipt) or a return ticket to the departure point or a ticket to a subsequent onward destination (valid for 90 days) must be presented together with the green ...

  18. Representation of the Auroral and Polar Ionosphere in the International Reference Ionosphere (IRI)

    Science.gov (United States)

    Bilitza, Dieter; Reinisch, Bodo

    2013-01-01

    This issue of Advances in Space Research presents a selection of papers that document the progress in developing and improving the International Reference Ionosphere (IRI), a widely used standard for the parameters that describe the Earths ionosphere. The core set of papers was presented during the 2010 General Assembly of the Committee on Space Research in Bremen, Germany in a session that focused on the representation of the auroral and polar ionosphere in the IRI model. In addition, papers were solicited and submitted from the scientific community in a general call for appropriate papers.

  19. Diversity does not travel!

    DEFF Research Database (Denmark)

    Lund, Rebecca; Tienari, Janne

    2013-01-01

    In this chapter we offer insights into the social construction of diversity in Finnish organizations and society. In Finnish organizations, gender is highlighted while other markers of diversity are blotted out. 'Non-Finns' become subject to cultural assimilation. The US-based concept of Diversity...... Management becomes adopted and adapted in particular ways. Standardized concepts of diversity and its management do not travel, rather they become translated locally. In organizational practice, globalization is slow and laborious....

  20. Malaria and Tropical Travel

    Centers for Disease Control (CDC) Podcasts

    2008-05-15

    Malaria is a serious mosquito-borne disease that can lead to death. This podcast discusses malaria risk when traveling to tropical areas, as well as how to protect yourself and your family from malaria infection.  Created: 5/15/2008 by National Center for Zoonotic, Vector-Borne, and Enteric Diseases (NCZVED).   Date Released: 5/29/2008.

  1. Aging and space travel

    Science.gov (United States)

    Mohler, S. R.

    1982-01-01

    The matter of aging and its relation to space vehicle crewmembers undertaking prolonged space missions is addressed. The capabilities of the older space traveler to recover from bone demineralization and muscle atrophy are discussed. Certain advantages of the older person are noted, for example, a greater tolerance of monotony and repetitious activities. Additional parameters are delineated including the cardiovascular system, the reproductive system, ionizing radiation, performance, and group dynamics.

  2. Atmospheric effects assessment program: Ionospheric sounding

    Science.gov (United States)

    Sprague, R. A.

    1994-02-01

    This document reports efforts on two main goals: to study the short-term ionospheric variability and to study the effects of this variability on high frequency (HF) skywave field strength. To achieve the first goal, ionospheric soundings are being done at 5-minute intervals at San Diego, CA, and at Logan, UT. This time interval was chosen to adequately resolve variations produced by locally generated gravity waves. To study the effects of short-term ionospheric variability on high frequency communications, a circuit is being established to measure the variability of the received HF signal strength. The chosen circuit will have the transmitter located in Forsyth, MT, and the receiver in Imperial Beach, CA (approximately 20 miles south of NRaD).

  3. [Traveling with small children].

    Science.gov (United States)

    Olivier, C

    1997-01-01

    Traveling with children especially in the tropics requires special planning. Contraindications are rare but care providers should obtain information about medical and transfusional facilities at the destination. Children should receive all vaccinations required for international travel and for specific countries, taking into account age, location, duration of stay, and purpose of trip. A first aid kit should be packed containing a thermometer, bandages, antiseptic agents, a total sunscreen preparation, a mosquito net, sterile compresses, tablets for water disinfection, and indispensable medications (antimalarial agents, antipyretics, oral rehydration solutions, antiemetics, and eye wash). The main indication for chemoprophylaxis is malaria. Chloroquine is recommended for most locations but proguanil may be necessary in areas of resistance. Special attention must be paid to skin care in infants: maintaining cleanliness, avoiding cuts insofar as possible, and treating any wounds. Clothing must be carefully laundered and adequate to prevent overexposure to sunlight and insect bites. Insect bites must also be prevented by applying repellents, using mosquito nets, and wearing insecticide-treated garments. Handwashing by people who prepare meals and by the children before eating is important to prevent food poisoning. Breast feeding is advisable for infants. Thorough cooking of meats, rinsing of fresh produce, drinking of bottled beverages, and sterilization of water are also important food safety measures. These precautions are usually adequate to allow safe travel with children.

  4. Time - A Traveler's Guide

    Science.gov (United States)

    Pickover, Clifford A.

    1999-09-01

    "Bucky Fuller thought big," Wired magazine recently noted, "Arthur C. Clarke thinks big, but Cliff Pickover outdoes them both." In his newest book, Cliff Pickover outdoes even himself, probing a mystery that has baffled mystics, philosophers, and scientists throughout history--What is the nature of time?In Time: A Traveler's Guide , Pickover takes readers to the forefront of science as he illuminates the most mysterious phenomenon in the universe--time itself. Is time travel possible? Is time real? Does it flow in one direction only? Does it have a beginning and an end? What is eternity? Pickover's book offers a stimulating blend of Chopin, philosophy, Einstein, and modern physics, spiced with diverting side-trips to such topics as the history of clocks, the nature of free will, and the reason gold glitters. Numerous diagrams ensure readers will have no trouble following along.By the time we finish this book, we understand a wide variety of scientific concepts pertaining to time. And most important, we will understand that time travel is, indeed, possible.

  5. Carlson Wagonlit Travel

    CERN Multimedia

    2006-01-01

    Carlson Wagonlit Travel wishes to remind you of the following conditions concerning travel to the USA. Passport conditions Since 26 October 2004, nationals of the countries covered by the US Visa Waiver Programme have been required to present a valid machine-readable passport when entering the United States. Failing this, they require a valid US non-immigrant visa in addition to their passport. Passports issued after 25 October 2005 must also bear a digital photograph. Passports issued after 25 October 2006 must contain biometric data to allow visa-free entry to the US. Advanced Passenger Information System (APIS) form Since 4 October 2005, all non-US citizens travelling to the USA have been required to complete the APIS form before departure and present it when they check in. This new procedure will certainly increase the time it takes to check in. We therefore advise passengers to present themselves at the respective check-in desk in good time. The APIS form can be downloaded from our homepage: w...

  6. When CERN travels abroad

    CERN Multimedia

    CERN Bulletin

    2010-01-01

    For the first time the new CERN travelling exhibition has gone abroad. The venue is Torino, in Italy, where it is being shown at the Museum of Natural Science in the framework of the activities of the EuroScience Open Forum (ESOF 2010). Soon after the event, the exhibition will fly to Copenhagen. The CERN traveling exhibition was inaugurated in 2009. The new ‘Accelerating Science’ exhibition was inaugurated in 2009 as part of the celebrations to mark the 450th anniversary of the University of Geneva. “CERN’s travelling exhibition is an important tool for outreach in our Member states as it carries the main messages that constitute the backbone of the Laboratory’s education and communication policy”, explains Rolf Landua, head of the Education Group, which manages the exhibition. “The 2010 European Science Open Forum in Torino will gather a lot of experts and visitors from the general public who will be able to experience in an ...

  7. Reflected solar wind ions and downward accelerated ionospheric ions during the January 1997 magnetic cloud event

    Science.gov (United States)

    Dempsey, D. L.; Burch, J. L.; Huddleston, M. M.; Pollock, C. J.; Waite, J. H., Jr.; Wüest, M.; Moore, T. E.; Shelley, E. G.

    On January 11, 1997, at 03:40:00 UT, while Polar was traveling up the dusk flank toward apogee, two ion instruments, TIDE and TIMAS, detected upflowing H+ with an energy/pitch-angle dispersion resembling an ionospheric reflection of freshly injected solar wind ions. In the same region of space, TIDE and TIMAS observed cold beams of O+ and H+ traveling down the field line with equal bulk velocities. We interpret these ion signatures as concurrent observations of mirrored solar wind ions and downward accelerated ionospheric ions. By 03:42:00, an energy/pitch-angle dispersion of downward moving ions at very low energies was clearly evident in the TIDE data. This additional signature is interpreted as an indication of reconnection on the same field line in the southern hemisphere. We explain this unique combination of plasma distributions in terms of high-latitude reconnection and magnetic field line convection during northward-IMF conditions associated with the January 1997 magnetic cloud event.

  8. GNSS data filtering optimization for ionospheric observation

    Science.gov (United States)

    D'Angelo, G.; Spogli, L.; Cesaroni, C.; Sgrigna, V.; Alfonsi, L.; Aquino, M. H. O.

    2015-12-01

    In the last years, the use of GNSS (Global Navigation Satellite Systems) data has been gradually increasing, for both scientific studies and technological applications. High-rate GNSS data, able to generate and output 50-Hz phase and amplitude samples, are commonly used to study electron density irregularities within the ionosphere. Ionospheric irregularities may cause scintillations, which are rapid and random fluctuations of the phase and the amplitude of the received GNSS signals. For scintillation analysis, usually, GNSS signals observed at an elevation angle lower than an arbitrary threshold (usually 15°, 20° or 30°) are filtered out, to remove the possible error sources due to the local environment where the receiver is deployed. Indeed, the signal scattered by the environment surrounding the receiver could mimic ionospheric scintillation, because buildings, trees, etc. might create diffusion, diffraction and reflection. Although widely adopted, the elevation angle threshold has some downsides, as it may under or overestimate the actual impact of multipath due to local environment. Certainly, an incorrect selection of the field of view spanned by the GNSS antenna may lead to the misidentification of scintillation events at low elevation angles. With the aim to tackle the non-ionospheric effects induced by multipath at ground, in this paper we introduce a filtering technique, termed SOLIDIFY (Standalone OutLiers IDentIfication Filtering analYsis technique), aiming at excluding the multipath sources of non-ionospheric origin to improve the quality of the information obtained by the GNSS signal in a given site. SOLIDIFY is a statistical filtering technique based on the signal quality parameters measured by scintillation receivers. The technique is applied and optimized on the data acquired by a scintillation receiver located at the Istituto Nazionale di Geofisica e Vulcanologia, in Rome. The results of the exercise show that, in the considered case of a noisy

  9. Multi-GNSS for Ionospheric Scintillation Studies

    Science.gov (United States)

    Morton, Y.

    2015-12-01

    GNSS have been widely used for ionospheric monitoring. We anticipate over 160 GNSS satellites broadcasting 400 signals by 2023, nearly double the number today. With their well-defined signal structures, high spatial density and spectral diversity, GNSS offers low cost and distributed passive sensing of ionosphere effects. There are, however, many challenges to utilize GNSS resources to characterize and forecast ionospheric scintillation. Originally intended for navigation purposes, GNSS receivers are designed to filter out nuisance effects due to ionosphere effects. GNSS measurements are plagued with errors from multipath, oscillator jitters, processing artifacts, and neutral atmosphere effects. Strong scintillation events are often characterized by turbulent structures in ionosphere, causing simultaneous deep amplitude fading and abrupt carrier phase changes. The combined weak signal and high carrier dynamics imposes conflicting requirements for GNSS receiver design. Therefore, GNSS receivers often experience cycle slips and loss of lock of signals during strong scintillation events. High quality, raw GNSS signals bearing space weather signatures and robust receiver algorithms designed to capture these signatures are needed in order for GNSS to be a reliable and useful agent for scintillation monitoring and forecasting. Our event-driven, reconfigurable data collection system is designed to achieve this purpose. To date, our global network has collected ~150TB of raw GNSS data during space weather events. A suite of novel receiver processing algorithms has been developed by exploitating GNSS spatial, frequency, temporal, and constellation diversity to process signals experiencing challenging scintillation impact. The algorithms and data have advanced our understanding of scintillation impact on GNSS, lead to more robust receiver technologies, and enabled high spatial and temporal resolution depiction of ionosphere responses to solar and geomagnetic conditions. This

  10. Superluminal travel requires negative energies

    OpenAIRE

    Olum, Ken D.

    1998-01-01

    I investigate the relationship between faster-than-light travel and weak-energy-condition violation, i.e., negative energy densities. In a general spacetime it is difficult to define faster-than-light travel, and I give an example of a metric which appears to allow superluminal travel, but in fact is just flat space. To avoid such difficulties, I propose a definition of superluminal travel which requires that the path to be traveled reach a destination surface at an earlier time than any neig...

  11. Towards the Implementation of GPS-based Tsunami Early Warning System Using Ionospheric Measurements

    Science.gov (United States)

    Yang, Y. M.; Komjathy, A.; Meng, X.; Verkhoglyadova, O. P.; Mannucci, A. J.

    2014-12-01

    Natural hazards and solid Earth events, such as earthquakes, tsunamis and volcanic eruptions are actual sources that may trigger acoustic and gravity waves resulting in traveling ionospheric disturbances (TIDs) in the upper atmosphere. Trans-ionospheric radio wave measurements sense the total electron content (TEC) along the signal propagation path. In this research, we introduce a novel GPS-based detection and estimation technique for remote sensing of atmospheric wave-induced TIDs including space weather phenomena induced by major natural hazard events, using TEC time series collected from worldwide ground-based dual-frequency GNSS receiver networks. We will demonstrate the ability of using ground-based dual-frequency GPS measures to detect and monitor tsunami wave propagations from previous great earthquake and tsunami events including: 2011 Tohoku and 2010 Chile earthquakes and tsunamis. Two major TIDs with different propagation speeds and wavelengths were identified through analysis of the GPS remote sensing observations. Dominant physical characteristics of atmospheric wave-induced TIDs are found to be associated with specific tsunami propagations and oceanic Rayleigh waves. We compared GPS-based observations, corresponding model simulations and other geophysical measurements. Our results lead to a better understanding of the tsunami-induced ionosphere responses. In addition, we investigate ionospheric signatures caused by the 1964 Great Alaska Earthquake and tsunami using the GPS-based method. Based on current distribution of Plate Boundary Observatory (PBO) GPS stations, the simulated results indicate that tsunami-induced TIDs may be detected about 60 minutes prior to tsunamis arriving at the US west coast. It is expected that this GPS-based technology becomes an integral part of future early-warning systems.

  12. Magnetic zenith effect in ionospheric modifications

    Energy Technology Data Exchange (ETDEWEB)

    Gurevich, A.V.; Zybin, K.P.; Carlson, H.C.; Pedersen, T

    2002-12-09

    The theory of ionospheric modification for the beam of powerful radio emission directed along magnetic field lines is developed. Nonlinear process of beam self-focusing on striations is shown to determine strong amplification of heating and acceleration of plasma electrons. It results in a dramatic enhancement of optic emission from the magnetic zenith region in ionospheric F-layer. An excellent agreement between the theory and recent fundamental observations at HAARP facility (Alaska) [T. Pedersen et al., Geophys. Res. Lett. (2002), in press] is demonstrated.

  13. Rockfall travel distance analysis by using empirical models (Solà d'Andorra la Vella, Central Pyrenees

    Directory of Open Access Journals (Sweden)

    R. Copons

    2009-12-01

    Full Text Available The prediction of rockfall travel distance below a rock cliff is an indispensable activity in rockfall susceptibility, hazard and risk assessment. Although the size of the detached rock mass may differ considerably at each specific rock cliff, small rockfall (<100 m3 is the most frequent process. Empirical models may provide us with suitable information for predicting the travel distance of small rockfalls over an extensive area at a medium scale (1:100 000–1:25 000. "Solà d'Andorra la Vella" is a rocky slope located close to the town of Andorra la Vella, where the government has been documenting rockfalls since 1999. This documentation consists in mapping the release point and the individual fallen blocks immediately after the event. The documentation of historical rockfalls by morphological analysis, eye-witness accounts and historical images serve to increase available information. In total, data from twenty small rockfalls have been gathered which reveal an amount of a hundred individual fallen rock blocks. The data acquired has been used to check the reliability of the main empirical models widely adopted (reach and shadow angle models and to analyse the influence of parameters which affecting the travel distance (rockfall size, height of fall along the rock cliff and volume of the individual fallen rock block. For predicting travel distances in maps with medium scales, a method has been proposed based on the "reach probability" concept. The accuracy of results has been tested from the line entailing the farthest fallen boulders which represents the maximum travel distance of past rockfalls. The paper concludes with a discussion of the application of both empirical models to other study areas.

  14. Home range and travels

    Science.gov (United States)

    Stickel, L.F.; King, John A.

    1968-01-01

    The concept of home range was expressed by Seton (1909) in the term 'home region,' which Burr (1940, 1943) clarified with a definition of home range and exemplified in a definitive study of Peromyscus in the field. Burt pointed out the ever-changing characteristics of home-range area and the consequent absence of boundaries in the usual sense--a finding verified by investigators thereafter. In the studies summarized in this paper, sizes of home ranges of Peromyscus varied within two magnitudes, approximately from 0.1 acre to ten acres, in 34 studies conducted in a variety of habitats from the seaside dunes of Florida to the Alaskan forests. Variation in sizes of home ranges was correlated with both environmental and physiological factors; with habitat it was conspicuous, both in the same and different regions. Food supply also was related to size of home range, both seasonally and in relation to habitat. Home ranges generally were smallest in winter and largest in spring, at the onset of the breeding season. Activity and size also were affected by changes in weather. Activity was least when temperatures were low and nights were bright. Effects of rainfall were variable. Sizes varied according to sex and age; young mice remained in the parents' range until they approached maturity, when they began to travel more widely. Adult males commonly had larger home ranges than females, although there were a number of exceptions. An inverse relationship between population density and size of home range was shown in several studies and probably is the usual relationship. A basic need for activity and exploration also appeared to influence size of home range. Behavior within the home range was discussed in terms of travel patterns, travels in relation to home sites and refuges, territory, and stability of size of home range. Travels within the home range consisted of repeated use of well-worn trails to sites of food, shelter, and refuge, plus more random exploratory travels

  15. Rabies vaccination for international travelers.

    Science.gov (United States)

    Gautret, Philippe; Parola, Philippe

    2012-01-05

    Rabies prevention in travelers is a controversial issue. According to experts, the decision to vaccinate results from an individual risk assessment based on the duration of stay, the likelihood of engagement in at-risk activities, the age of the traveler, the rabies endemicity and access to appropriate medical care in the country of destination. However, no detailed information is available regarding the last two determinants in many regions. Twenty-two cases of rabies were reported in tourists, expatriates and migrant travelers over the last decade, including three cases following short-term travel of no more than two weeks. Studies on rabies post-exposure prophylaxis (PEP) in travelers show that overall, 0.4% (range 0.01-2.3%) of travelers have experienced an at-risk bite per month of stay in a rabies-endemic country, while 31% of expatriates and 12% of tourists were vaccinated against rabies before traveling. The main reason cited by travelers for not being vaccinated is the cost of the vaccine. The majority of patients who sustained a high risk injury was not vaccinated against rabies before traveling and were not properly treated abroad. From available studies, the following risk factors for injuries sustained from potentially rabid animals may be identified: traveling to South-East Asia, India or North Africa, young age, and traveling for tourism. The duration of travel does not appear to be a risk factor. It should be noted that "at-risk activities" have not been addressed in these studies. Detailed rabies distribution maps and information on the availability of rabies biologics are urgently needed in order to identify those travelers who need pre-travel vaccination. Meanwhile, cost-minimization of rabies pre-exposure vaccination may be achieved in several ways, notably by using the intra-dermal method of vaccination.

  16. Solar illumination control of ionospheric outflow above polar cap arcs

    CERN Document Server

    Maes, L; De Keyser, J; Dandouras, I; Fear, R C; Fontaine, D; Haaland, S

    2016-01-01

    We measure the flux density, composition, and energy of outflowing ions above the polar cap, accelerated by quasi-static electric fields parallel to the magnetic field and associated with polar cap arcs, using Cluster. Mapping the spacecraft position to its ionospheric foot point, we analyze the dependence of these parameters on the solar zenith angle (SZA). We find a clear transition at SZA between We find a clear transition at SZA between $\\sim$94$^{\\circ}$ and $\\sim$107$^{\\circ}$, with the O$^{+}$ flux higher above the sunlit ionosphere. This dependence on the illumination of the local ionosphere indicates that significant O$^{+}$ upflow occurs locally above the polar ionosphere. The same is found for H$^{+}$, but to a lesser extent. This effect can result in a seasonal variation of the total ion upflow from the polar ionosphere. Furthermore, we show that low-magnitude field-aligned potential drops are preferentially observed above the sunlit ionosphere, suggesting a feedback effect of ionospheric conducti...

  17. Behavior of Parameters of Nighttime Electron Density Enhancements of the Ionospheric F2 Layer

    Science.gov (United States)

    Yakovets, Artur; Gordienko, Galina

    2017-04-01

    There is known a wide class of disturbances of the F2-layer of the ionosphere, which are superimposed on the regular diurnal variations of the electron density. Different types of disturbances are characterized by different mechanisms of their generation. Traveling ionospheric disturbances appear to be the most characteristic features of the inhomogeneous structure of the ionosphere. Another type of ionospheric disturbances presents the nighttime electron density enhancements in the ionospheric F2- layer maximum (NmF2). This type of irregularities is described in numerous papers. There is a concept that, in spite of the various mechanisms of ionospheric disturbances generation a response of F2-layer parameters exhibits similar features associated with the upward lift and the simultaneous expansion of the layer and then its subsequent downward movement, including layer compression, which results in the formation of the electron density peak in the layer maximum at the moment of greatest compression. The aim of this study is a verification of this concept on the example of disturbances related with the nighttime electron density enhancements, and the definition of precise quantitative relationships between the variations of different F2-layer parameters for such disturbances. By using the data of the ionospheric vertical sounding in Almaty, (76° 55'E, 43°15'N) during 2001-2012, analysis of the behavior the F2-layer parameters during the night electron density enhancements was carried out within framework of a single concept of effects of various types of ionospheric plasma perturbations in variations of height and half-thickness of the F2-layer, accompanied by increasing and decreasing NmF2 at moments of maximum compression and expansion of the layer. For a quantitative analysis of the parameters of nighttime enhancements we have selected 20 nights characterized by low magnetic activity (Dst> - 50 nT) and evident manifestations of the nighttime electron density

  18. Simulated Response of the Magnetosphere-Ionosphere System to Different Forms of Empirically Regulated Ionospheric Outflows

    Science.gov (United States)

    Lotko, W.; Lyon, J.; Melanson, P.; Murr, D.; Wiltberger, M.

    2006-12-01

    Empirically derived power-law relations between the locally measured Poynting flux (S) flowing toward the ionosphere and the number flux of ions (F) flowing away from the ionosphere exhibit significant differences that depend on the choice of satellite data samples (Strangeway et al., 2005; Zheng et al., 2005). Such relations attempt to capture in lumped form the causality of electromagnetic power flows into collisionless ion acceleration in the topside ionosphere and low-altitude magnetosphere and the resulting ion outflows -- effects that are otherwise difficult to treat in first-principles fluid models for the field-aligned mass transport. We have implemented a power-law relation of the form F = A*S**b, where A and b are adjustable parameters ultimately constrained by observation, as a low-altitude boundary condition on the LFM global simulation model. This boundary condition allows ions of ionospheric origin to enter the magnetospheric simulation domain and to mix with plasma of solar wind origin in populating the magnetosphere. According to the empirical relation, more ionospheric ions are causally injected into the simulation domain as the Poynting flux through the low-altitude boundary increases. In this paper, we report results from simulations using different values of the parameters A and b to determine the sensitivity of the magnetospheric response to the form of the empirical relation. Simulation diagnostics for the transpolar potential, field-aligned current, ionospheric conductivity, precipitating electron energy flux, and Joule dissipation rate will be presented.

  19. Fellow travellers: Working memory and mental time travel in rodents.

    Science.gov (United States)

    Dere, Ekrem; Dere, Dorothea; de Souza Silva, Maria Angelica; Huston, Joseph P; Zlomuzica, Armin

    2017-03-19

    The impairment of mental time travel is a severe cognitive symptom in patients with brain lesions and a number of neuropsychiatric disorders. Whether animals are also able to mentally travel in time both forward and backward is still a matter of debate. In this regard, we have proposed a continuum of mental time travel abilities across different animal species, with humans being the species with the ability to perform most sophisticated forms of mental time travel. In this review and perspective article, we delineate a novel approach to understand the evolution, characteristics and function of human and animal mental time travel. Furthermore, we propose a novel approach to measure mental time travel in rodents in a comprehensive manner using a test battery composed of well-validated and easy applicable tests. Copyright © 2017. Published by Elsevier B.V.

  20. Multi-instrument observations of the solar eclipse on 20 March 2015 and its effects on the ionosphere over Belgium and Europe

    Directory of Open Access Journals (Sweden)

    Stankov Stanimir M.

    2017-01-01

    Full Text Available A total solar eclipse occurred on 20 March 2015, with a totality path passing mostly above the North Atlantic Ocean, which resulted in a partial solar eclipse over Belgium and large parts of Europe. In anticipation of this event, a dedicated observational campaign was set up at the Belgian Solar-Terrestrial Centre of Excellence (STCE. The objective was to perform high-quality observations of the eclipse and the associated effects on the geospace environment by utilising the advanced space- and ground-based instrumentation available to the STCE in order to further our understanding of these effects, particularly on the ionosphere. The study highlights the crucial importance of taking into account the eclipse geometry when analysing the ionospheric behaviour during eclipses and interpreting the eclipse effects. A detailed review of the eclipse geometry proves that considering the actual obscuration level and solar zenith angle at ionospheric heights is much more important for the analysis than at the commonly referenced Earth’s surface or at the plasmaspheric heights. The eclipse occurred during the recovery phase of a strong geomagnetic storm which certainly had an impact on (some of the ionospheric characteristics and perhaps caused the omission of some “low-profile” effects. However, the analysis of the ionosonde measurements, carried out at unprecedented high rates during the eclipse, suggests the occurrence of travelling ionospheric disturbances (TIDs. Also, the high temporal and spatial resolution measurements proved very important in revealing and estimating some finer details of the delay in the ionospheric reaction and the ionospheric disturbances.

  1. Travel Demand Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Southworth, Frank [ORNL; Garrow, Dr. Laurie [Georgia Institute of Technology

    2011-01-01

    This chapter describes the principal types of both passenger and freight demand models in use today, providing a brief history of model development supported by references to a number of popular texts on the subject, and directing the reader to papers covering some of the more recent technical developments in the area. Over the past half century a variety of methods have been used to estimate and forecast travel demands, drawing concepts from economic/utility maximization theory, transportation system optimization and spatial interaction theory, using and often combining solution techniques as varied as Box-Jenkins methods, non-linear multivariate regression, non-linear mathematical programming, and agent-based microsimulation.

  2. Time, travel and infection.

    Science.gov (United States)

    Cliff, Andrew; Haggett, Peter

    2004-01-01

    The collapse of geographical space over the last 200 years has had profound effects on the circulation of human populations and on the transfer of infectious diseases. Three examples are used to illustrate the process: (a) the impact of the switch from sail to steamships in importing measles into Fiji over a 40-year period; (b) changes in measles epidemic behaviour in Iceland over a 150-year period; and (c) changes in the spread of cholera within the United States over a 35-year period. In each case, the link between time, travel and disease has been an intimate one.

  3. The SUN S TRAVELS

    Institute of Scientific and Technical Information of China (English)

    Robert; Louis; Stevenson

    2005-01-01

    The sun is not a-bed, when I At night upon my pillow lie; Stilt round the earth his Way he takes, And morning after morning makes. White here at home, in shining day, We round the sunny garden play, Each tittle Indian sleepy - head Is being kissed and put to bed. And When at eve I rise from tea, Day dawns beyond the Atlantic Sea; And all the children in the West Are getting up and being dressed.The SUN'S TRAVELS@Robert Louis Stevenson

  4. Health hazards of international travel.

    Science.gov (United States)

    Cossar, J H; Reid, D

    1989-01-01

    The growth of travel and the increasing numbers of those affected by travel-related illnesses, some of a serious nature, will cause this subject to demand the attention of the medical profession, the travel trade, travellers themselves and the health authorities of countries receiving tourists. Provision of appropriate advice for the traveller is a shared responsibility, best channelled mainly through travel agencies; it can moreover be shown to be cost-beneficial. Continued monitoring of illness in travellers and provision of information systems geared to this problem and its prevention are fully justified. They should be based on traditional channels of communication and currently-available modern technology, and be readily accessible to medical and related workers. Increased collaboration between medical workers, health educators and those involved in the travel trade would be a positive and useful contribution towards the reduction of illness and discomfort among travellers and the associated expense incurred by the various national health services concerned. There are clearly economic benefits from the development of international tourism, but these have to be balanced in countries accepting tourists by attention to the prevention of illnesses associated with travel.

  5. 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.

  6. Global Assimilation of Ionospheric Measurements (GAIM)

    Science.gov (United States)

    Schunk, R. W.; Scherliess, L.; Sojka, J. J.; Thompson, D. C.; Anderson, D. N.; Codrescu, M.; Minter, C.; Fuller-Rowell, T. J.; Heelis, R. A.; Hairston, M.; Howe, B. M.

    2001-12-01

    The ionosphere is a highly dynamic medium that can vary significantly from day to day and from hour to hour at a given location, and these variations can have detrimental effects on military and civilian systems. In an effort to minimize or circumvent the detrimental effects, a physics-based data assimilation model of the ionosphere and neutral atmosphere is under development with funding from the DoD MURI program. Two university consortia are involved, with USU and USC as the lead institutions. When completed, the GAIM (Global Assimilation of Ionospheric Measurements) model will provide specifications and forecasts on a spatial grid that can be global, regional, or local (50 km x 50 km). GAIM will use a physics-based ionosphere-plasmasphere model and a Kalman filter as a basis for assimilating a diverse set of real-time (or near real-time) measurements. Some of the data to be assimilated include in situ density measurements from satellites, ionosonde electron density profiles, occultation data, ground-based GPS TECs, TECs between ground stations and LEO satellites with radio beacons, and line-of-sight UV emissions from selected satellites. The resulting specifications and forecasts will be in the form of 3-dimensional electron density distributions from 90 km to geosynchronous altitude (35,000 km). An initial form of GAIM already exists and recent results from the USU consortium will be presented.

  7. 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

  8. 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.

  9. 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.

  10. Method for Canceling Ionospheric Doppler Effect

    Science.gov (United States)

    Vessot, R. F. C.

    1982-01-01

    Unified transponder system with hydrogen-maser oscillators at both stations can compensate for both motional and ionospheric components of Doppler shift. Appropriate choices of frequency shift in output of mixer m3. System exploits proportionality between dispersive component of frequency shift and reciprocal of frequency to achieve cancellation of dispersive component at output.

  11. 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.

  12. Ionospheric response to particle precipitation within aurora

    Energy Technology Data Exchange (ETDEWEB)

    Wahlund, J.E. (Swedish Inst. of Space Physics, Uppsala (Sweden))

    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).

  13. Ionospheric response to particle precipitation within aurora

    Energy Technology Data Exchange (ETDEWEB)

    Wahlund, J.E. [Swedish Inst. of Space Physics, Uppsala (Sweden)

    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).

  14. GPS, GNSS, and Ionospheric Density Gradients

    Science.gov (United States)

    Kintner, P. M.; O'Hanlon, B.; Humphreys, T. E.

    2009-12-01

    Ionospheric density and density gradients affect GNSS signals in two ways. They can introduce ranging errors or irregularities that form on the density gradients producing scintillation. Here we focus on the issue of ranging errors. There are two approaches to mitigating ranging errors produced by ionospheric density gradients which can be 20-30 m during major magnetic storms. The first approach is to use a reference receiver(s) to determine the ionospheric contribution to ranging errors. The ranging error is then transmitted to the user for correction within the mobile receiver. This approach is frequently referred to as differential GPS and, when multiple reference receivers are used, the system is referred to as an augmentation system. This approach is vulnerable to ionospheric gradients depending on the reference receiver spacing(s) and latency in applying the correction within the mobile receiver. The second approach is to transmit navigation signals at two frequencies and then use the relative delay between the two signals to both estimate the ranging error and calculate the correct range. Currently the dual frequency technique is used by US military receivers with an encryption key and some civilian receivers which must be stationary and average over times long compared to those required for navigation. However, the technology of space based radio navigation is changing. GPS will soon be a system with three frequencies and multiple codes. Furthermore Europe, Russia, and China are developing independent systems to complement and compete with GPS while India and Japan are developing local systems to enhance GPS performance in their regions. In this talk we address two questions. How do density gradients affect augmentation systems including the social consequences and will the new GPS/GNSS systems with multiple civilian frequencies be able to remove ionospheric errors. The answers are not at all clear.

  15. Electrodynamics of ionospheric weather over low latitudes

    Science.gov (United States)

    Abdu, Mangalathayil Ali

    2016-12-01

    The dynamic state of the ionosphere at low latitudes is largely controlled by electric fields originating from dynamo actions by atmospheric waves propagating from below and the solar wind-magnetosphere interaction from above. These electric fields cause structuring of the ionosphere in wide ranging spatial and temporal scales that impact on space-based communication and navigation systems constituting an important segment of our technology-based day-to-day lives. The largest of the ionosphere structures, the equatorial ionization anomaly, with global maximum of plasma densities can cause propagation delays on the GNSS signals. The sunset electrodynamics is responsible for the generation of plasma bubble wide spectrum irregularities that can cause scintillation or even disruptions of satellite communication/navigation signals. Driven basically by upward propagating tides, these electric fields can suffer significant modulations from perturbation winds due to gravity waves, planetary/Kelvin waves, and non-migrating tides, as recent observational and modeling results have demonstrated. The changing state of the plasma distribution arising from these highly variable electric fields constitutes an important component of the ionospheric weather disturbances. Another, often dominating, component arises from solar disturbances when coronal mass ejection (CME) interaction with the earth's magnetosphere results in energy transport to low latitudes in the form of storm time prompt penetration electric fields and thermospheric disturbance winds. As a result, drastic modifications can occur in the form of layer restructuring (Es-, F3 layers etc.), large total electron content (TEC) enhancements, equatorial ionization anomaly (EIA) latitudinal expansion/contraction, anomalous polarization electric fields/vertical drifts, enhanced growth/suppression of plasma structuring, etc. A brief review of our current understanding of the ionospheric weather variations and the

  16. Remote Oxygen Sensing by Ionospheric Excitation (ROSIE

    Directory of Open Access Journals (Sweden)

    K. S. Kalogerakis

    2009-05-01

    Full Text Available The principal optical observable emission resulting from ionospheric modification (IM experiments is the atomic oxygen red line at 630 nm, originating from the O(1D–3P transition. Because the O(1D atom has a long radiative lifetime, it is sensitive to collisional relaxation and an observed decay faster than the radiative rate can be attributed to collisions with atmospheric species. In contrast to the common practice of ignoring O-atoms in interpreting such observations in the past, recent experimental studies on the relaxation of O(1D by O(3P have revealed the dominant role of oxygen atoms in controlling the lifetime of O(1D at altitudes relevant to IM experiments. Using the most up-to-date rate coefficients for collisional relaxation of O(1D by O, N2, and O2, it is now possible to analyze the red line decays observed in IM experiments and thus probe the local ionospheric composition. In this manner, we can demonstrate an approach to remotely detect O-atoms at the altitudes relevant to IM experiments, which we call remote oxygen sensing by ionospheric excitation (ROSIE. The results can be compared with atmospheric models and used to study the temporal, seasonal, altitude and spatial variation of ionospheric O-atom density in the vicinity of heating facilities. We discuss the relevance to atmospheric observations and ionospheric heating experiments and report an analysis of representative IM data.

  17. Traveling-Wave Tubes

    Science.gov (United States)

    Kory, Carol L.

    1998-01-01

    The traveling-wave tube (TWT) is a vacuum device invented in the early 1940's used for amplification at microwave frequencies. Amplification is attained by surrendering kinetic energy from an electron beam to a radio frequency (RF) electromagnetic wave. The demand for vacuum devices has been decreased largely by the advent of solid-state devices. However, although solid state devices have replaced vacuum devices in many areas, there are still many applications such as radar, electronic countermeasures and satellite communications, that require operating characteristics such as high power (Watts to Megawatts), high frequency (below 1 GHz to over 100 GHz) and large bandwidth that only vacuum devices can provide. Vacuum devices are also deemed irreplaceable in the music industry where musicians treasure their tube-based amplifiers claiming that the solid-state and digital counterparts could never provide the same "warmth" (3). The term traveling-wave tube includes both fast-wave and slow-wave devices. This article will concentrate on slow-wave devices as the vast majority of TWTs in operation fall into this category.

  18. Time travel a history

    CERN Document Server

    Gleick, James

    2016-01-01

    From the acclaimed author of The Information and Chaos, here is a mind-bending exploration of time travel: its subversive origins, its evolution in literature and science, and its influence on our understanding of time itself. The story begins at the turn of the previous century, with the young H. G. Wells writing and rewriting the fantastic tale that became his first book and an international sensation: The Time Machine. It was an era when a host of forces was converging to transmute the human understanding of time, some philosophical and some technological: the electric telegraph, the steam railroad, the discovery of buried civilizations, and the perfection of clocks. James Gleick tracks the evolution of time travel as an idea that becomes part of contemporary culture—from Marcel Proust to Doctor Who, from Jorge Luis Borges to Woody Allen. He investigates the inevitable looping paradoxes and examines the porous boundary between pulp fiction and modern physics. Finally, he delves into a temporal shift that...

  19. The Travelling Telescope

    Science.gov (United States)

    Murabona Oduori, Susan

    2015-08-01

    The telescope has been around for more than 400 years, and through good use of it scientists have made many astonishing discoveries and begun to understand our place in the universe. Most people, however, have never looked through one. Yet it is a great tool for cool science and observation especially in a continent and country with beautifully dark skies. The Travelling Telescope project aims to invite people outside under the stars to learn about those curious lights in the sky.The Travelling Telescope aims to promote science learning to a wide range of Kenyan schools in various locations exchanging knowledge about the sky through direct observations of celestial bodies using state of the art telescopes. In addition to direct observing we also teach science using various hands-on activities and astronomy software, ideal for explaining concepts which are hard to understand, and for a better grasp of the sights visible through the telescope. We are dedicated to promoting science using astronomy especially in schools, targeting children from as young as 3 years to the youth, teachers, their parents and members of the public. Our presentation focuses on the OAD funded project in rural coastal Kenya.

  20. Ion Acoustic Travelling Waves

    CERN Document Server

    Webb, G M; Ao, X; Zank, G P

    2013-01-01

    Models for travelling waves in multi-fluid plasmas give essential insight into fully nonlinear wave structures in plasmas, not readily available from either numerical simulations or from weakly nonlinear wave theories. We illustrate these ideas using one of the simplest models of an electron-proton multi-fluid plasma for the case where there is no magnetic field or a constant normal magnetic field present. We show that the travelling waves can be reduced to a single first order differential equation governing the dynamics. We also show that the equations admit a multi-symplectic Hamiltonian formulation in which both the space and time variables can act as the evolution variable. An integral equation useful for calculating adiabatic, electrostatic solitary wave signatures for multi-fluid plasmas with arbitrary mass ratios is presented. The integral equation arises naturally from a fluid dynamics approach for a two fluid plasma, with a given mass ratio of the two species (e.g. the plasma could be an electron pr...

  1. SAPS onset timing during substorms and the westward traveling surge

    Science.gov (United States)

    Mishin, Evgeny, V.

    2016-07-01

    We present multispacecraft observations in the magnetosphere and conjugate ionosphere of the onset time of subauroral polarization streams (SAPS) and tens of keV ring current injections on the duskside in three individual substorms. This is probably the first unequivocal determination of the substorm SAPS onset timing. The time lag between the SAPS and substorm onsets is much shorter than the gradient-curvature drift time of ˜10 keV ions in the plasmasphere. It seemingly depends on the propagation time of substorm-injected plasma from the dipolarization onset region to the plasmasphere, as well as on the SAPS position. These observations suggest that fast onset SAPS and ring current injections are causally related to the two-loop system of the westward traveling surge.

  2. CONCEPTUAL CLARIFICATIONS REGARDING YOUTH TRAVEL

    OpenAIRE

    Lect. Ph.D Student Moisa Claudia Olimpia

    2010-01-01

    Currently, there is no clear definition for the youth travel concept. This concept emerged much latter than the first forms of manifestation of tourism for young people, namely the beginning of the ’90s when the first studies regarding youth travel were also conducted. No doubt, the concept of youth travel ensues from three notions, namely: youth, tourism and vacation – in the sense of free time. All the definitions used by tourism organizations, by various national tourism administrations an...

  3. IONOSPHERIC CORRECTION METHOD FOR PRECISE POSITIONING WITH GPS ACTIVE NETWORK

    Institute of Scientific and Technical Information of China (English)

    GAOShan; CHENWu; HUCong-wei; CHENYong-qi; DINGXiao-li

    2005-01-01

    The ionospheric delay error is a major error source which degrades the positioning accuracy in network real time kinematic (RTK) positioning over a long distance. Different approaches are proposed to estimate GPS errors based on GPS reference network, such as virtual reference stations (VRSs) and network corrections. A new method is used to model the ionospheric total electronic content (TEC) distribution in space. Unlike most ionospheric models, only the ionospheric delays along the satellite tracks are modelled. Therefore, the models are of high precise resolution of the ionospheric TEC distribution in both spatial and temporal scales. A new algorithm is used to solve the equation singularity problem. Experiments demonstrate that the new ionospheric correction method can be used to describe the ionospheric variation at a low latitude area where ionospheric activities are strong. Also, the accuracy of the ionospheric model is enough to support centimeter-level positioning within the network. As ionospheric models are satellite-based models (each satellite has one model), the model parameters can be easily incorporated with the existing differential GPS Radio Technical Commission for Maritime Service (DGPS RTCM) 104 format.

  4. Modeling of Ionospheric Delay for SBAS Using Spherical Harmonics Functions

    Directory of Open Access Journals (Sweden)

    Deokhwa Han

    2013-06-01

    Full Text Available In SBAS (satellite-based augmentation system, it is important to estimate ionospheric delay accurately to guarantee user's accuracy and integrity. Grid based ionospheric models are generally used to estimate ionospheric delay for SBAS. In grid based model, SBAS broadcasts vertical ionospheric delays at the grid point, and users get their ionospheric delay by interpolating those values. Ionospheric model based on spherical harmonics function is another method to estimate ionospheric delay. This is a function based approach and spherical harmonics function is a 2-D fourier series, containing the product of latitude dependent associated Legendre functions and the sum of the longitude dependent sine and cosine terms. Using ionospheric delay measurements, coefficients for each spherical harmonics functions are estimated. If these coefficients are known, user can reconstruct ionospheric delay. In this paper, we consider the spherical harmonics based model and propose a ionospheric delay estimation strategy for SBAS that can be used to mitigate ionospheric delay estimation error, especially in storm condition. First, coefficients are estimated under initial order and degree. Then residual errors for each measurement are modeled by higher order and degree terms, then coefficients for these terms are estimated. Because SBAS message capacity is limited, in normal condition, initial order terms are only used to estimate ionospheric delay. If ionospheric storm is detected and there is need to mitigate the error, higher order terms are also used and error can be decreased. To compare the accuracy of spherical harmonics based model with grid based model, some post-processing test results are presented. Raw observation data is obtained from RINEX format and the root mean square(RMS and max value of residual errors are presented.

  5. Travel opinion leaders and seekers

    DEFF Research Database (Denmark)

    Yoo, Kyung-Hyan; Gretzel, Ulrike; Zach, Florian

    2011-01-01

    While opinion leadership has been recognized as important in tourism, there has been very little empirical research investigating the phenomenon. Given new developments in social media technologies, it is especially important to understand whether travel opinion leadership and seeking are drivers...... media use. The findings suggest that travel opinion leadership and seeking are distinct but connected. Both opinion leaders and seekers are technology savvy, young, educated, involved in travel planning and engaged in social media use for travel. What distinguishes opinion leaders is their greater...

  6. Communication from Carlson Wagonlit Travel

    CERN Multimedia

    2008-01-01

    Entry requirements for the USA: "ESTA" (Electronic System for Travel Authorization) online registration The requirement to register before entering the USA announced by the Department of Homeland Security (DHS) is to be introduced on 12 January 2009. Visitors to the USA will then be required to register their personal data and travel data online not less than 72 hours prior to travel. https://esta.cbp.dhs.gov/ General information on entry requirements for the USA are also available on the Carlson Wagonlit Travel website under the heading „CWT informs": http://www.carlsonwagonlit.ch

  7. Communication from Carlson Wagonlit Travel

    CERN Multimedia

    2009-01-01

    Entry requirements for the USA: "ESTA" (Electronic System for Travel Authorization) online registration The requirement to register before entering the USA announced by the Department of Homeland Security (DHS) is to be introduced on 12 January 2009. Visitors to the USA will then be required to register their personal data and travel data online not less than 72 hours prior to travel. https://esta.cbp.dhs.gov/ General information on entry requirements for the USA is also available on the Carlson Wagonlit Travel website under the heading „CWT informs": http://www.carlsonwagonlit.ch

  8. Description of ionospheric disturbances observed by Vertical Ionospheric Sounding at 3 MHz

    Directory of Open Access Journals (Sweden)

    James Arokiasami Baskaradas

    2014-03-01

    Full Text Available High Frequency radio waves reflected by the ionosphere can provide a relevant amount of information within the composite received signal. The ionosphere is indeed a frequency dispersive, bi-refractive, absorbing medium, in which multipath propagation occurs due to disturbance on a varied time-spatial scale. On the time-spatial level of Small Scale Disturbances (SSD the ionosphere dynamics, detectable by Vertical Ionospheric Sounding (VIS, is mainly dependent on wrinkled layers acting as multi-reflectors. The present paper discusses different aspects of the effects of multipath fading suffered by the wave along the propagation path and potentially associated with SSD. To achieve these objectives, a VIS campaign at a fixed frequency of 3.0 MHz was conducted at the ionospheric observatory in Rome (Latitude 41.8 N; Longitude 12.5 E, by collecting a series of measurements of the power variations in received echo signals recorded between two consecutive ionograms whose sounding repetition rate was set to 15 min. The obtained results show that: 1 the fading suffered by the wave follows either a Rayleigh trend or a Nakagami-Rice trend, or a mix of them, the mixed case being the most frequent (about 65 % of the analysed cases; 2 the predominant periodicities characterizing the power variation are less than 25 s; such values are compatible with the small scale ionospheric disturbances; 3 for all the 24 hours of the day the ionospheric reflector is pretty stable and for time intervals of 10-30 s the periods of stability occur with a percentage of occurrence ranging between 55% and 95 %; for time intervals of 190- 210 s the periods of stability occur instead with a percentage of occurrence ranging between 5% and 54 %.

  9. Solar wind travel time

    Science.gov (United States)

    Russell, C. T.

    A useful rule of thumb in solar terrestrial studies is that the solar wind travels 4 Earth radii (RE) per minute. Long-term studies of solar wind velocity [e.g., Luhmann et al., 1993; 1994] show that the median velocity is about 420 km/s, corresponding to 3.96 RE min-1. The quartiles are about 370 km/s and 495 km/s, corresponding to 3.48 Re min-1 and 4.66 Re min-1 respectively. This number helps estimate the delays expected when observing a discontinuity at a solar wind monitor; one example is ISEE-3 when it was at the forward libration point (about 60 min). It is also helpful for estimating how much time passes before the dayside magnetosphere is compressed as denser solar wind flows by (about 2.5 min).

  10. SUNSCEEN FOR TRAVELLERS

    Directory of Open Access Journals (Sweden)

    Novita Lavi N

    2013-05-01

    Full Text Available The sun exposure brings negative effects on the skin such like early aging, spots and skin cancer as the most terrible effect. To reduce the adverse effects of the sun, it is not enough just to behavioral therapy, but also had no protection from the outside. Especially for travellers that exposed by the sun excessively. There is sunscreen, product specially formulated to absorb or deflect ultraviolet rays. A sunscreen preparation contains chemical compounds that can absorb, scatter or reflect sunlight on the skin. This writing contains about effect of ultraviolet, skin protection from ultraviolet from behavioral aspect, variaty and contents of sunscreen and sunscreen application for travellers. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

  11. International Travelers' Sociodemographic, Health, and Travel Characteristics: An Italian Study.

    Science.gov (United States)

    Troiano, Gianmarco; Mercone, Astrid; Bagnoli, Alessandra; Nante, Nicola

    Approximately the 8% of travelers requires medical care, with the diagnosis of a vaccine-preventable disease. The aim of our study was to analyze the socio-demographic, health and travel characteristics of the Italian international travelers. We conducted a cross sectional study from January 2015 to June 2016, at the Travel Medicine Clinic of Siena, asking the doctor to interview patients who attended the Clinic, recording socio-demographic and travel information, malaria prophylaxis, vaccinations. The data were organized in a database and processed by software Stata®. We collected 419 questionnaires. Patients chose 71 countries for their travels; the favorite destinations were: India (6.31%), Thailand (6.31%), and Brazil (5.10%). The mean length of stay was 36.17 days. Italians, students, and freelancers tended to stay abroad for a longer time (mean: 36.4 days, 59.87 days and 64.16 days respectively). 33.17% of our sample used drugs for malaria chemoprophylaxis: 71.9% of them used Atovaquone/Proguanil (Malarone®), 26.6% used Mefloquine (Lariam®), 1.5% other drugs. The vaccinations that travelers mostly got in our study were to prevent hepatitis A (n = 264), the typhoid fever (n = 187), the Tetanus + Diphtheria + Pertussis (n = 165), the Yellow fever (n = 118) and the cholera (n = 78). Twenty-eight (6.68%) refused some recommended vaccinations. The vaccines mostly refused were for Typhoid fever (n = 20), hepatitis a (n = 9), and cholera (n = 9). Our results demonstrated that Italian international travelers are at-risk because of their poor vaccinations adherence. This implies that pre-travel counseling is fundamental to increase the knowledge of the risks and the compliance of future travelers. Copyright © 2016 Icahn School of Medicine at Mount Sinai. Published by Elsevier Inc. All rights reserved.

  12. Mesoscale ionospheric electrodynamics of omega bands determined from ground-based electromagnetic and satellite optical observations

    Directory of Open Access Journals (Sweden)

    O. Amm

    2005-02-01

    Full Text Available We present ground-based electromagnetic data from the MIRACLE and BEAR networks and satellite optical observations from the UVI and PIXIE instruments on the Polar satellite of an omega band event over Northern Scandinavia on 26 June 1998, which occured close to the morning side edge of a substorm auroral bulge. Our analysis of the data concentrates on one omega band period from 03:18-03:27 UT, for which we use the method of characteristics combined with an analysis of the UVI and PIXIE data to derive a time series of instantaneous, solely data-based distributions of the mesoscale ionospheric electrodynamic parameters with a 1-min time resolution. In addition, the AMIE method is used to derive global Hall conductance patterns. Our results show that zonally alternating regions of enhanced ionospheric conductances ("tongues" up to ~60S and low conductance regions are associated with the omega bands. The tongues have a poleward extension of ~400km from their base and a zonal extension of ~380km. While they are moving coherently eastward with a velocity of ~770ms-1, the structures are not strictly stationary. The current system of the omega band can be described as a superposition of two parts: one consists of anticlockwise rotating Hall currents around the tongues, along with Pedersen currents, with a negative divergence in their centers. The sign of this system is reversing in the low conductance areas. It causes the characteristic ground magnetic signature. The second part consists of zonally aligned current wedges of westward flowing Hall currents and is mostly magnetically invisible below the ionosphere. This system dominates the field-aligned current (FAC pattern and causes alternating upward and downward FAC at the flanks of the tongues with maximum upward FAC of ~25µA m-2. The total FAC of ~2MA are comparable to the ones diverted inside a westward traveling surge. Throughout the event, the overwhelming part of the FAC

  13. Saturn's Ionospheric Clock(s): A Concept for Generating and Maintaining Saturn's Observed Magnetospheric Periodicities

    Science.gov (United States)

    Mitchell, D. G.; Brandt, P. C.; Ukhorskiy, A. Y.

    2010-12-01

    Saturn’s 10.X hour periodicity, observed throughout the magnetosphere, remains a mystery. It has been observed in many regions, modulating many phenomena. During the Cassini mission most observations have shown a period at about 10.8 hours, expressed in Saturn kilometric radiation from the high latitude auroral zone, in magnetic field components (both equatorial and high latitude) from 3 to 12 Rs, in current sheet encounters in the outer magnetosphere and magnetotail, in energetic neutral atom emission from the equatorial magnetosphere, and in plasma and energetic particles throughout the magnetosphere. More recently, various authors have shown at least two dominant periods expressed (in SKR and in magnetic field components), with slightly different values in the southern and northern hemispheres. The cause of this behavior is still not accounted for. Although loosely associated with Saturn’s rotation, the variability in the period precludes a direct connection with Saturn’s interior (e.g., a magnetic anomaly). Other candidates that have been discussed by others are an ionospheric source (conductivity anomaly), a perturbation in the cold plasma circulation pattern, a magnetospheric cam, asymmetric ring current particle pressure, and/or a natural frequency of the magnetosphere (cavity mode or traveling wave front of some sort). In this paper we present a concept that derives its energy from the subcorotating cold, dense plasma (which exhibits a rotation period on the order of 13 to 14 hours throughout L-shells between ~3 and 20), but is triggered by a process linked with the ionosphere. Key components of the model include significant slippage between the ionosphere and the magnetosphere (with the ionosphere rotating at the expressed period in each hemisphere, only slightly more slowly than the planet interior), subcorotating cold dense plasma with a source in the inner magnetosphere, predominantly radial transport of the cold dense plasma in the rotational

  14. Ionospheric effects on repeat-pass SAR interferometry

    Science.gov (United States)

    Feng, Jian; Zhen, Weimin; Wu, Zhensen

    2017-10-01

    InSAR measurements can be significantly affected by the atmosphere when the radar signal propagates through the atmosphere since it varies with space and time. Great efforts have been made in recent years to better understand the properties of the tropospheric effects and to develop methods for mitigating these effects. By using the basic principles of InSAR, the quantitative analysis of ionospheric delay effects on topography and surface deformation have been introduced for the first time. The measurement errors can be related to the vertical ionospheric total electron content (vTEC). By using the ionospheric observations, the effects of temporal ionospheric variations on InSAR have been analyzed. The results indicate that the ionospheric variations with time, season, solar cycle and geomagnetic activities can compromise the effectiveness of InSAR for both the measurement of topography and surface determination. The repeat-pass SAR interferometry errors induced by ionosphere should be corrected by actual measurements.

  15. 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.

  16. 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.

  17. Carlson Wagonlit Travel is moving

    CERN Multimedia

    2013-01-01

    The renovation of the Main Building continues!   Because of this, Carlson Wagonlit Travel will move from building 62 to building 510 on 4 October and the agency will be closed in the afternoon. An emergency service will be organised for official travels only. Phone: 022 799 75 73 & 022 799 75 78 / e-mail: cern@carlsonwagonlit.ch

  18. 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)

  19. Trans-Ionospheric High Frequency Signal Ray Tracing

    Science.gov (United States)

    Wright, S.; Gillespie, R. J.

    2012-09-01

    All electromagnetic radiation undergoes refraction as it propagates through the atmosphere. Tropospheric refraction is largely governed by interaction of the radiation with bounded electrons; ionospheric refraction is primarily governed by free electron interactions. The latter phenomenon is important for propagation and refraction of High Frequency (HF) through Extremely High Frequency (EHF) signals. The degree to which HF to EHF signals are bent is dependent upon the integrated refractive effect of the ionosphere: a result of the signal's angle of incidence with the boundaries between adjacent ionospheric regions, the magnitude of change in electron density between two regions, as well as the frequency of the signal. In the case of HF signals, the ionosphere may bend the signal so much that it is directed back down towards the Earth, making over-the-horizon HF radio communication possible. Ionospheric refraction is a major challenge for space-based geolocation applications, where the ionosphere is typically the biggest contributor to geolocation error. Accurate geolocation requires an algorithm that accurately reflects the physical process of a signal transiting the ionosphere, and an accurate specification of the ionosphere at the time of the signal transit. Currently implemented solutions are limited by both the algorithm chosen to perform the ray trace and by the accuracy of the ionospheric data used in the calculations. This paper describes a technique for adapting a ray tracing algorithm to run on a General-Purpose Graphics Processing Unit (GPGPU or GPU), and using a physics-based model specifying the ionosphere at the time of signal transit. This technique allows simultaneous geolocation of significantly more signals than an equivalently priced Central Processing Unit (CPU) based system. Additionally, because this technique makes use of the most widely accepted numeric algorithm for ionospheric ray tracing and a timely physics-based model of the ionosphere

  20. Monitoring Travel Time Reliability on Freeways

    NARCIS (Netherlands)

    Tu, Huizhao

    2008-01-01

    Travel time and travel time reliability are important attributes of a trip. The current measures of reliability have in common that in general they all relate to the variability of travel times. However, travel time reliability does not only rely on variability but also on the stability of travel

  1. Monitoring Travel Time Reliability on Freeways

    NARCIS (Netherlands)

    Tu, Huizhao

    2008-01-01

    Travel time and travel time reliability are important attributes of a trip. The current measures of reliability have in common that in general they all relate to the variability of travel times. However, travel time reliability does not only rely on variability but also on the stability of travel ti

  2. Preliminary Results on TID (Travelling Ionospheric Disturbances) over Ebro from TEC Data.

    Science.gov (United States)

    1982-10-30

    auroral zone during magnetio substOrms (Chimonas and Etnes,1970, Testud , 1970, Titheridge,1971) while several causes have been poin-ted out for the...88 62 Testud , J.. 1970 Jro.At.Terr.,A202,32087 Mutnri, .. 1971 Jus.GoPhys.esL1,6915 TOkuao,I., .Om andLle195JAmerPhs,715 0. tsui .ad .g 19J73

  3. 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.

  4. Array-based GNSS Ionospheric Sensing: Estimability and Precision Analyses

    Science.gov (United States)

    Teunissen, Peter

    2016-04-01

    Array-based GNSS Ionospheric Sensing: Estimability and Precision Analyses PJG Teunissen1,2, A Khodabandeh1 and B Zhang1 1GNSS Research Centre, Curtin University, Perth, Australia 2Geoscience and Remote Sensing, Delft University of Technology, The Netherlands Introduction: The Global Navigation Satellite Systems (GNSS) have proved to be an effective means of measuring the Earth's ionosphere. The well-known geometry-free linear combinations of the GNSS data serve as the input of an external ionospheric model to capture both the spatial and temporal characteristics of the ionosphere. Next to the slant ionospheric delays experienced by the GNSS antennas, the geometry-free combinations also contain additional unknown delays that are caused by the presence of the carrier-phase ambiguous cycles and/or the code instrumental delays. That the geometry-free combinations, without an external ionospheric model, cannot unbiasedly determine the slant ionospheric delays reveals the lack of information content in the GNSS data. Motivation and objectives: With the advent of modernized multi-frequency signals, one is confronted with many different combinations of the GNSS data that are capable of sensing the ionosphere. Owing to such diversity and the lack of information content in the GNSS data, various estimable ionospheric delays of different interpretations (and of different precision) can therefore be formed. How such estimable ionospheric delays should be interpreted and the extent to which they contribute to the precision of the unbiased slant ionosphere are the topics of this contribution. Approach and results: In this contribution, we apply S-system theory to study the estimability and precision of the estimable slant ionospheric delays that are measured by the multi-frequency GNSS data. Two different S-systems are presented, leading to two different estimable parameters of different precision: 1) the phase-driven ionospheric delays and 2) the code-driven ionospheric delays

  5. Joule heating of Io's ionosphere by unipolar induction currents

    Science.gov (United States)

    Herbert, F.; Lichtenstein, B. R.

    1980-01-01

    Electrical induction in Io's ionosphere, due to the corotating plasma bound to the Jovian magnetosphere, is one possible source for the attainment of the high temperatures suggested by the large scale height of Io's ionosphere. Unipolar induction models are constructed to calculate ionospheric joule heating numerically, whose heating rates lie between 10 to the -9th and 10 to the -8th W/cu m. The binding and coupling of the ionosphere is due to the dense, and possibly ionized, neutral SO2 atmosphere, and there appears to be no need to postulate the existence of an intrinsic Ionian magnetic field in order to retain the observed ionnosphere.

  6. Ionospheric Signatures in Radio Occultation Data

    Science.gov (United States)

    Mannucci, Anthony J.; Ao, Chi; Iijima, Byron A.; Kursinkski, E. Robert

    2012-01-01

    We can extend robustly the radio occultation data record by 6 years (+60%) by developing a singlefrequency processing method for GPS/MET data. We will produce a calibrated data set with profile-byprofile data characterization to determine robust upper bounds on ionospheric bias. Part of an effort to produce a calibrated RO data set addressing other key error sources such as upper boundary initialization. Planned: AIRS-GPS water vapor cross validation (water vapor climatology and trends).

  7. THE EVOLUTION OF AN IONOSPHERIC HOLE.

    Science.gov (United States)

    The release of 10 to the 26th power molecules of sulfur hexafluoride at 220-km altitude generated an ionospheric hole which lasted about 30 minutes...Rate equations are set up and solved to explore the time and space variation of electron densities within the region. It is shown that due to the ...geomagnetic-field-constrained diffusion of electrons, the estimated lifetime of the hole is much longer than if unhindered radial diffusion could take

  8. An Evaluation of HF Ionospheric Backscatter Echoes

    Science.gov (United States)

    1975-11-01

    the Feldstein- Starkov Auroral Belt Model for Various Levels of Magnetic Activity at 1200 Hours I/Jcal Time, Daytime Ionospheric Model A 2-7...Contours of Zero-Degree Aspect Angle for 20 MHz K-Uiyer Kchoes as Viewed from a Midlatitude Location, with the Feldstein- Starkov Auroral Belt Model for...Kchoes as Viewed from a Midlatitude Location, with the Feldstein- Starkov Auroral Belt Model for Various Levels of Magnetic Activity at 1200 Hours

  9. Ionospheric and Thermospheric Imaging from Geosynchronous Orbit

    Science.gov (United States)

    McCoy, R. P.; Wood, K.; Dymond, K. F.; Thonnard, S. E.; Cannon, K.; Makela, J.

    2001-12-01

    The Office of Naval Research is sponsoring the development of an ultraviolet imaging system to test the concept of real-time synoptic observations of the ionosphere and thermosphere from geosynchronous orbit. The observational hardware consists of two ultraviolet telescopes mounted to a two-axis gimbal to measure airglow radiances on the disk and limb of the Earth. A far-ultraviolet telescope will use a filter wheel with filters to image atomic oxygen emission at 130.4 nm, 135.6 nm, and molecular nitrogen emission at 143.0 nm. An extreme-ultraviolet telescope will image the oxygen ion airglow at 83.4 nm. The oxygen emission measurements will be used to infer nightside ionospheric total electron content (TEC) on the disk and electron density profiles on the limb. On the dayside the oxygen ion measurements will be used to determine electron density profiles, and the oxygen and nitrogen measurements will be used to infer thermospheric neutral density profiles on the limb and O/N2 ratios on the disk. The telescope fields of view cover a 1000 km x 1000 km region with 10 km x 10 km resolution. A goal for nightside TEC measurements is to obtain images with 100 second integrations and to be able to track ionospheric irregularities in real time as "weather systems". Ratios of oxygen nightglow measurements will be used to explore the possibility of providing three dimensional measurements of the ionosphere. These telescopes will be mounted aboard an Air Force Space Test Program satellite which will be launched into geosynchronous orbit over the continental U. S. for about year and then moved over the Indian Ocean for an additional seven years.

  10. 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.

  11. 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

    Ionospheric disturbances can affect technologies in space and on Earth disrupting satellite and airline operations, communications networks, navigation systems. As the world becomes ever more dependent on these technologies, ionospheric disturbances as part of space weather pose an increasing risk to the economic vitality and national security. Therefore, having the knowledge of ionospheric state in advance during space weather events is becoming more and more important. To promote scientific cooperation we recently formed a Working Group (WG) called "Ionosphere Predictions" within the International Association of Geodesy (IAG) under Sub-Commission 4.3 "Atmosphere Remote Sensing" of the Commission 4 "Positioning and Applications". The general objective of the WG is to promote the development of ionosphere prediction algorithm/models based on the dependence of ionospheric characteristics on solar and magnetic conditions combining data from different sensors to improve the spatial and temporal resolution and sensitivity taking advantage of different sounding geometries and latency. Our presented work enables the possibility to compare total electron content (TEC) prediction approaches/results from different centers contributing to this WG such as German Aerospace Center (DLR), Universitat Politècnica de Catalunya (UPC), Technische Universität München (TUM) and GMV. DLR developed a model-assisted TEC forecast algorithm taking benefit from actual trends of the TEC behavior at each grid point. Since during perturbations, characterized by large TEC fluctuations or ionization fronts, this approach may fail, the trend information is merged with the current background model which provides a stable climatological TEC behavior. The presented solution is a first step to regularly provide forecasted TEC services via SWACI/IMPC by DLR. UPC forecast model is based on applying linear regression to a temporal window of TEC maps in the Discrete Cosine Transform (DCT) domain

  12. Equinoctial transitions in the ionosphere and thermosphere

    Directory of Open Access Journals (Sweden)

    A. V. Mikhailov

    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

  13. Assimilative modeling of low latitude ionosphere

    Science.gov (United States)

    Pi, Xiaoqing; Wang, Chunining; Hajj, George A.; Rosen, I. Gary; Wilson, Brian D.; Mannucci, Anthony J.

    2004-01-01

    In this paper we present an observation system simulation experiment for modeling low-latitude ionosphere using a 3-dimensional (3-D) global assimilative ionospheric model (GAIM). The experiment is conducted to test the effectiveness of GAIM with a 4-D variational approach (4DVAR) in estimation of the ExB drift and thermospheric wind in the magnetic meridional planes simultaneously for all longitude or local time sectors. The operational Global Positioning System (GPS) satellites and the ground-based global GPS receiver network of the International GPS Service are used in the experiment as the data assimilation source. 'The optimization of the ionospheric state (electron density) modeling is performed through a nonlinear least-squares minimization process that adjusts the dynamical forces to reduce the difference between the modeled and observed slant total electron content in the entire modeled region. The present experiment for multiple force estimations reinforces our previous assessment made through single driver estimations conducted for the ExB drift only.

  14. Statistical properties of ionospheric stimulated electromagnetic emissions

    Directory of Open Access Journals (Sweden)

    R. L. Karlsson

    2006-08-01

    Full Text Available We have analysed the statistical properties of the stimulated electromagnetic emissions (SEE spectral features in the steady state, reached after a long period of continuous HF pumping of the ionosphere in experiments performed at the Sura ionospheric radio research facility in Russia. Using a digital filter bank method, we have been able to analyse complex valued signals within narrow frequency bands. Each of the SEE spectral features are thereby separated into a number of narrow spectral components. Statistical tests were performed for all these spectral components and the distributions of the spectral amplitudes and phases were evaluated. Also, a test for sinusoidal components was performed. These tests showed that all observed SEE features were indistinguishable from coloured Gaussian noise. The test results exclude that the SEE features can be the result of a single isolated coherent process, but does not rule out that there could be many statistically independent parametric wave-wave processes taking place simultaneously at various parts of the HF-pumped ionosphere, as long as the superposition from all these is incoherent. Furthermore, from the test results, we cannot exclude the possibility that the waveforms of some, or all, of the SEE features may be chaotic.

  15. Travel Writing on the Edge: An Intermedial Approach to Travel Books and Travel Blogs

    Directory of Open Access Journals (Sweden)

    Calzati Stefano

    2015-08-01

    Full Text Available After discussing the limits and potentialities of the definitions of travel writing proposed by Paul Fussell (1980. Patrick Holland and Graham Huggan (1998 and Jan Borm (2004, the article presents a characterization of travel writing both as a genre with a precise rhetorical status, as well as a praxis of knoivledge, which derives from the interplay between travelling and writing. Building on this, a comparison between two Italian travel books and two Italian travel blogs about China is proposed. Specifically, by considering these texts as “intermedial transpositions” (Wolf 2008 that realize the same generic and epistemological matrix (i.e. travel writing, a Multimodal Critical Discourse Analysis (MCDA is conducted in order to assess: 1 how the book and the blog, as different medial formats, interpret the rhetorical features of the travel writing genre: and 2 to what extent the gnoseological and cross-cultural potentials of travel writing, as a praxis of knowledge, is affected by the process of transposition.

  16. Carlson Wagonlit Travel

    CERN Multimedia

    Carlson Wagonlit Travel

    2005-01-01

    Chères clientes, chers clients, Le 3 janvier dernier, nous vous avons informé de la décision des compagnies aériennes de supprimer les commissions versées aux agences de voyages suisses. Cette mesure a été introduite progressivement pour être appliquées maintenant par toutes les compagnies, à quelques rares exceptions près. En conséquence, en accord avec le CERN, nous serons dans l'obligation d'appliquer une nouvelle liste de prix de nos transactions pour les voyages privés. Elle sera applicable dès le lundi 25 juillet 2005. Carlson Wagonlit Travel (CWT) vous propose : Son service de conseil personnalisé, professionnel et compétent Sa recherche de la solution la plus économique et la mieux adaptée à vos besoins Sa neutralité dans les comparaisons de prix et prestations Des informations com...

  17. Testing Plasma Physics in the Ionosphere

    Science.gov (United States)

    Papadopoulos, Konstantinos

    TESTING PLASMA PHYSICS IN THE IONOSPHERE K. Papadopoulos University of Maryland College Park, MD 20742 Ionospheric heaters supplemented by ground and space based diagnostic instruments, such as radars, optical cameras and photometers, HF/VLF/ELF/ULF receivers and magnetometers, radio beacons, riometers and ionosondes have for a long time being used to conduct plasma physics, geophysical and radio science investigations. The latest entry to ionospheric heating, the HF transmitter associated with the High Frequency Active Ionospheric Research Program (HAARP), was completed in February 2007. The transmitter consists of 180 antenna elements spanning 30.6 acres and can radiate 3.6 MW of HF power in the 2.8-10.0 MHz frequency range. With increasing frequency the beam-width varies from 15-5 degrees, corresponding to 20-30 dB gain and resulting in Effective Radiating Power (ERP) between .36 - 4.0 GW. The antenna can point to any direction in a cone of 30 degrees from the vertical, with a reposition time of 15 degrees in 15 microseconds resulting in super-luminous scanning speeds. The transmitter can synthesize essentially any desired waveform within the regulatory allowed bandwidth in linear and circular polarization. These capabilities far exceed those of previous ionospheric heaters and allow for new frontier research in plasma physics, geophysics and radio science. Following a brief discussion of the relationship of the new capabilities of the facility with thresholds of physical processes that could not be achieved previously, the presentation will discuss recent results in the areas of ULF/ELF/VLF generation and propagation and wave-particle interactions in the magnetosphere acquired with the completed facility. The presentation will conclude with a detailed discussion of possible frontier science experiments in the areas of Langmuir turbulence, parametric instabilities, electron acceleration, optical emissions and field aligned striations and duct generation, made

  18. Ionospheric effects during first 2 hours after the "Chelyabinsk" meteorite impact

    Science.gov (United States)

    Berngardt, Oleg; Kurkin, Vladimir; Zherebtsov, Gelii; Grigorieva, Svetlana; Kusonski, Oleg

    In this paper, we analyzed the ionospheric effects within the 100-1500 km ranges from the Chelyabinsk meteorite explosion site from the ISTP SB RAS EKB radar data, and from the IG UB RAS PARUS ionosonde data. Both instruments are located at the Arti Observatory, approximately 200 km north of the supposed explosion location. The ionospheric disturbance caused by the meteorite flyby, explosion, and impact had high dynamics and amplitude. Essential effects, however, were observed at more than 100-200 km from the explosion site, and farther, up to 1500 km. Almost simultaneously with the explosion and for 3 minutes (03:20-03:23 UT), there was a motion away from the radar 400 km southwest of the latter (and approximately 200 km west of the explosion site) at the E-layer height with the characteristic velocities 200 m/s and high spectral width. A short delay of the detected effect at a significant distance from the explosion site also testifies to the hypothesis of a large short-living irregularity formations at the heights of the lower E-layer, with the transversal size of several hundreds of kilometers. The first disturbance in the F-layer was observed 15 minutes after the explosion, and it propagated away from the radar almost radially. The radial disturbances were observed up to about 80-100 minutes. The main disturbances in the F-layer were nearly radial waves with the center close to the explosion site. Analyzing the experimental data allowed us to determine the equivalent ionospheric velocities for individual travel mode. The work was done under financial support of RFBR grant #14-05-00514-a.

  19. Temporal variations of the Venus ionosphere during solar flares

    Science.gov (United States)

    Uesugi, A.; Fujiwara, H.; Fukunishi, H.

    2006-12-01

    The effects of long-term solar activity changes such as 11-year cycle and 27-day cycle on the Venus ionosphere have been investigated by a number of researchers using data obtained from some spacecrafts. However, the effects of short-term solar activity changes, particularly the effect of solar flares, are still unknown because there are no simultaneous observations of the Venus ionosphere and solar flares. The past observations of the Earth's ionosphere suggest significant and instantaneous changes of the Venus ionosphere during solar flares. Recently, Mars Global Surveyor (MGS) revealed the temporal variations of the Mars ionosphere during solar flares. The electron density of the Mars ionosphere was enhanced by ~10% at the main peak and 200% at the secondary peak at that time. The recent satellite observations of the solar X- rays enable us to model the Earth's and planetary ionospheres more exactly. In order to investigate the temporal variations of the Venus ionosphere during solar flares, we have developed a 1-D photochemical model for estimating vertical profiles of ions and electrons. We have also modeled temporal variations of solar flare using the EUV/X-rays data obtained by TIMED/SEE (0.1-194 nm) and GOES (0.1-0.8 nm) on October 28, 2003. Using the photochemical and solar flare models, we have calculated temporal variations of ion composition in the dayside Venus ionosphere. In addition, time constants for production and loss of ionospheric compositions through the photochemical reactions can be examined. We discuss differences of the response to solar flare among three planets, Venus, Earth and Mars. Then, the characteristics of the Venus ionosphere will be clarified.

  20. Knowledge Representation in Travelling Texts

    DEFF Research Database (Denmark)

    Mousten, Birthe; Locmele, Gunta

    2014-01-01

    and the purpose of the text in a new context as well as on predefined parameters for text travel. For texts used in marketing and in technology, the question is whether culture-bound knowledge representation should be domesticated or kept as foreign elements, or should be mirrored or moulded—or should not travel...... at all! When should semantic and pragmatic elements in a text be replaced and by which other elements? The empirical basis of our work is marketing and technical texts in English, which travel into the Latvian and Danish markets, respectively....

  1. Last-Minute Travel Application

    OpenAIRE

    Hubner, Andre; Lenz, Mario; Borch, Roman; Posthoff, Michael

    2000-01-01

    In this article, we present a last-minute travel application as part of a complete virtual travel agency. Each year, a significant amount of tour packages are sold as last minute tours in Germany. It is impossible for a travel agent to keep track of all the offered tour packages. Electronic-commerce applications might present the best possible tour package for a specific customer request. Traditional database-driven applications, as used by most of the tour operators, are not sufficient enoug...

  2. Danish long distance travel A study of Danish travel behaviour and the role of infrequent travel activities

    DEFF Research Database (Denmark)

    Knudsen, Mette Aagaard

    2014-01-01

    .g. socio-economic variables. The analysis of Danish travel activities described in the three different travel surveys has outlined detailed information on Danish travel behaviour at an aggregated level during the past two decades. It has above all revealed the significant role of leisure travel. Private...... in a study of leisure travel, with an analysis of the income elasticity of this travel segment. Due to the different survey methodologies, the samples of leisure activities describe the whole span from daily leisure travel activities embedded into people’s daily routines to the infrequent holiday activities....... The applied model describes the travel distance of leisure travel including the probability of having leisure activities or not. The study finds increasing income elasticities of travelling or not and increasing income elasticities of travel distances as the leisure purposes become less frequently completed...

  3. Catchment mixing processes and travel time distributions

    National Research Council Canada - National Science Library

    Botter, Gianluca

    2012-01-01

    ...) of travel, residence and evapotranspiration times, which are comprehensive descriptors of the fate of rainfall water particles traveling through catchments, and provide key information on hydrologic...

  4. Ionospheric plasma disturbances generated by naturally occurring large-scale anomalous heat sources

    Science.gov (United States)

    Pradipta, Rezy; Lee, Min-Chang; Coster, Anthea J.; Tepley, Craig A.; Sulzer, Michael P.; Gonzalez, Sixto A.

    2017-04-01

    We report the findings from our investigation on the possibility of large-scale anomalous thermal gradients to generate acoustic-gravity waves (AGWs) and traveling ionospheric disturbances (TIDs). In particular, here we consider the case of summer 2006 North American heat wave event as a concrete example of such large-scale natural thermal gradients. This special scenario of AGW/TID generation was formulated based on the results of our experiments at the Arecibo Observatory in July 2006, followed by a systematic monitoring/surveillance of total electron content (TEC) fluctuations over North America in 2005-2007 using the MIT Haystack Observatory's Madrigal database. The data from our Arecibo experiments indicate a continual occurrence of intense AGW/TID over the Caribbean on 21-24 July 2006, and the Madrigal TEC data analysis shows that the overall level of TID activity over North America had increased by ∼0.2 TECU during the summer 2006 heat wave event. Our proposed scenario is in agreement with these empirical observations, and is generally consistent with a number of past ionospheric HF heating experiments related to AGW/TID generation.

  5. Multiple ionospheric perturbations during the Saint Patrick's Day storm 2015 in the European-African sector

    Science.gov (United States)

    Borries, Claudia; Mahrous, Ayman M.; Ellahouny, Nada M.; Badeke, Ronny

    2016-11-01

    Strong ionospheric perturbations were generated by the intense geomagnetic storm on 17 March 2015. In this article, we are studying perturbations in the European-African sector observed in the total electron content (TEC). Focal points are wavelike phenomena considered as large-scale traveling ionospheric disturbances (LSTIDs). In the European-African sector, the storm produced three different types of LSTIDs: (1) a concurrent TEC perturbation at all latitudes simultaneously; (2) one LSTID propagating toward the equator, having very large wave parameters (wavelength: ≈3600 km, period: ≈120 min, and speed: ≈500 m/s); and (3) several LSTIDs propagating toward the equator with typical wave parameters (wavelength: ≈2100 km, period: ≈60 min, and speed ≈600 m/s). The third type of LSTIDs is considered to be exited as most LSTIDs either due to variations in the Joule heating or variations in the Lorentz force, whereas the first two perturbation types are rather unusual in their appearance. They occurred during the partial recovery phase when the geomagnetic perturbations were minor and the interplanetary magnetic field turned northward. A westward prompt penetration electric field is considered to excite the first perturbation signature, which indicates a sudden TEC depletion. For the second LSTID type, variations in the Lorentz force because of perturbed electric fields and a minor particle precipitation effect are extracted as possible excitation mechanisms.

  6. 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

  7. Analysis of Ionospheric Delay Estimates from GNSS Carrier Phase Measurements

    Science.gov (United States)

    Gao, Yang

    2016-07-01

    There is an increased demand for more precise ionospheric information such as ionospheric augmentation for fast ambiguity convergence and resolution in real-time kinematic (RTK) and precise point positioning (PPP). More precise ionospheric information is also highly desired to improve the understanding of the space weather dynamics and its impacts on various applications such as aviation and communication systems. Carrier phase measurements from GNSS offer the best precision for precise applications. Current ionospheric models, however, are mostly derived from code or carrier-smoothed code measurements. Ionopsheric models based on carrier phase measurements are expected to provide improved accuracy and should be investigated. In this contribution, various data analyses will be conducted on ionospheric estimates from carrier phase measurements. Since carrier phase measurements are ambiguous and they are also affected by fractional biases, proper observation model is necessary and will be developed. With proper observation model, the analysis results are used to investigate the differences and characteristics of the ionospheric estimates between the code and carrier phase derived estimates and subsequently to help develop methods for precise estimation of the biases in carrier phase measurements and the recovery of the ionospheric effects. Data acquired at different geographic locations and under different ionospheric conditions will be processed for numerical analysis.

  8. The state of the ionosphere above Alma Ata

    Science.gov (United States)

    Rudina, M. P.; Solonitsyna, N. F.

    1972-01-01

    The basic patterns are described in the behavior of critical frequencies and minimum effective heights of the ionosphere's reflecting E, F1, and F2 layers, according to ionospheric recorder measurements from 1943 to 1967. The variations of critical frequencies and virtual heights are compared with the relative sunspot numbers and the flux of the sun's radio emission at 10.7 cm.

  9. Ninth Workshop 'Solar Influences on the Magnetosphere, Ionosphere and Atmosphere'

    Science.gov (United States)

    Georgieva, Kayta; Kirov, Boian; Danov, Dimitar

    2017-08-01

    The 9th Workshop "Solar Influences on the Magnetosphere, Ionosphere and Atmosphere" is an international forum for scientists working in the fields of: Sun and solar activity, Solar wind-magnetosphere-ionosphere interactions, Solar influences on the lower atmosphere and climate, Solar effects in the biosphere, Instrumentation for space weather monitoring and Data processing and modelling.

  10. Impact of Galileo on Global Ionosphere Map Estimation

    NARCIS (Netherlands)

    Anh Quan Le

    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 GPS-o

  11. Impact of Galileo on Global Ionosphere Map Estimation

    NARCIS (Netherlands)

    Anh Quan Le

    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

  12. Preseismic Lithosphere-Atmosphere-Ionosphere Coupling

    Science.gov (United States)

    Kamogawa, Masashi

    Preseismic atmospheric and ionospheric disturbances besides preseismic geo-electric potential anomalies and ultra-low-frequency (ULF) geomagnetic variations observed on the ground have been reported. Both the phenomena have been found since the 1980s and a number of papers have been published. Since most of the reported phenomena transiently appear with accompanying quiescence before the mainshock, this prevents us to intuitively recognize a correlation between the anomaly appearance and the earthquake occurrence. Some of them, however, showed that anomalies monotonically grew into the mainshock, of which a variation supports the concept of seismic nucleation process under the pre-earthquake state. For example, Heki [GRL, 2011] reported that ionospheric electron density monotonically enhanced tens of minutes prior to the subduction mega-earthquake. However, this preseismic enhancement is apparent variation attributed to tsunamigenic ionospheric hole [Kakinami and Kamogawa et al, GRL, 2012], namely wide and long-duration depression of ionospheric electron after tsunami-excited acoustic waves reach the ionosphere. Since the tsunamigenic ionospheric hole could be simulated [Shinagawa et al., GRL, 2013], the reported variations are high-possibly pseudo phenomena [Kamogawa and Kakinami, JGR, 2013]. Thus, there are barely a few reports which show the preseismic monotonic variation supported by the concept of the seismic nucleation process. As far as we discuss the preseismic geoelectromagnetical and atmospheric-ionospheric anomalies, preseismic transient events from a few weeks to a few hours prior to the mainshock are paid attention to for the precursor study. In order to identify precursors from a number of anomalies, one has to show a statistical significance of correlation between the earthquake and the anomalies, to elucidate the physical mechanism, or to conduct both statistical and physical approach. Since many speculation of the physical mechanism have been

  13. The future of air travel

    National Research Council Canada - National Science Library

    Ben Iannotta

    2015-01-01

      Here, Iannotta discusses the future of air travel. Among other things, safety technologies that seemed exotic will become the norm, like the auto industry's hands-free Bluetooth systems and side-curtain airbags...

  14. Mosquito Bite Prevention For Travelers

    Science.gov (United States)

    ... and parasites that can cause diseases like chikungunya, dengue, Zika, and malaria. If you are traveling to an area where malaria is found, talk to your healthcare provider about malaria prevention medication that may be available. Protect yourself and ...

  15. DCHA Travel & Mission Support System

    Data.gov (United States)

    US Agency for International Development — DTRAMS is a travel data collection system for DCHA that collects information on both the basic details of an employee's trips (destination, length, purpose, etc.)...

  16. PPL Travel & Mission Support System

    Data.gov (United States)

    US Agency for International Development — PTRAMS is a travel data collection system for PPL that collects information on both the basic details of an employee's trips (destination, length, purpose, etc.) and...

  17. GH Travel & Mission Support System

    Data.gov (United States)

    US Agency for International Development — HTRAMS is a travel data collection system for GH that collects information on both the basic details of an employee's trips (destination, length, purpose, etc.) and...

  18. Travelers' Health: Viral Hemorrhagic Fevers

    Science.gov (United States)

    ... Climates Humanitarian Aid Workers Humanitarian Aid Workers in Ecuador Insurance International Adoption Jet Lag Last-Minute Travel ... Landry ML, Warnock DW, editors. Manual of Clinical Microbiology. 10th ed. Washington, DC: ASM Press; 2011. p. ...

  19. Transmedia storytelling on travel stories

    Directory of Open Access Journals (Sweden)

    Adolfo Baltar Moreno

    2016-01-01

    Full Text Available Travel stories form part of a great tradition inside Western Culture which has served historically to describe, to understand and to imagine other cul - tures and communities, far or near, being constituted into a real narra - tive genre. This type of story has been and is a reflection of the perception of the world based on the imaginary worlds created by the travelling narrators. How do modern authors of travel stories take advantage of the opportunities offered by transmedia storytelling? The present article explores the potential of these types of stories as a privileged object of study for transmedia storytelling studies, from the analysis of a sample of 80 narrative productions based on experiences of travel and presented in diverse editions of the Festival Le Grand Bivouac (France. It also shows the existence of a new contemporary trend inside this narrative form that transcends its literary nature.

  20. Analyze and Study Ionospheric Scintillation and Total Electron Content Variability (Ionospheric Studies and TEC Variations).

    Science.gov (United States)

    1981-03-01

    iicitit 1i1 priidui r I ltc I urf~ lewi mixing used in the scintillation computations together with thc derived value oft wtiietIsI ParLcls (It "sni...latituden 71. 785-801 irregularities ini the top side ionosphere hasedmii Isis I thermal Feldstein. Y I., and 6 V Starkov (1967), D~ynamics of aurtiral ion

  1. Long distance travel ‘today’

    DEFF Research Database (Denmark)

    Christensen, Linda

    2014-01-01

    This paper presents an overview of the Dane’s long distance travel. It is a part of the Drivers and Limits project about long distance travel. Long distance travel is in the project defined as infrequent travel with overnight stay. Danes 15-85 years-old travel in average 5.5 long distance travel...... per year og which a third is for international destinations, a third is for domestic second homes and a third are other domestic trips. However, 87% of the kilometres are for international destinations and only 4% are for domestic second homes. Travel activity is very uneven distributed with only half...... of the population having had a journey during the last three month. At the other hand 60% have travelled internationally during the last year and only 2% have never travelled abroad. The paper presents among other things how the travel activity is distributed on travel purpose and mode and how the mode choice...

  2. Sequentially pulsed traveling wave accelerator

    Science.gov (United States)

    Caporaso, George J.; Nelson, Scott D.; Poole, Brian R.

    2009-08-18

    A sequentially pulsed traveling wave compact accelerator having two or more pulse forming lines each with a switch for producing a short acceleration pulse along a short length of a beam tube, and a trigger mechanism for sequentially triggering the switches so that a traveling axial electric field is produced along the beam tube in synchronism with an axially traversing pulsed beam of charged particles to serially impart energy to the particle beam.

  3. A model of multidestination travel

    DEFF Research Database (Denmark)

    Morisugi, H.; Tussyadiah, Iis; Kono, T.

    2006-01-01

    , specifically address the choice of a single destination. This article is intended to explain multiple destination choice using Lancaster's characteristics model and a discussion of model implications of some marketing strategies for destinations as well as for tour operators. The model developed herein...... explains that packages of multiple destinations can create preferable combinations of characteristics for certain travelers. Furthermore, the model provides useful strategies for tour operators in combining destinations into a travel menu or package. © 2006 Sage Publications....

  4. The spatial structure of the dayside ionospheric trough

    Directory of Open Access Journals (Sweden)

    S. E. Pryse

    Full Text Available Tomographic imaging provides a powerful technique for obtaining images of the spatial distribution of ionospheric electron density at polar latitudes. The method, which involves monitoring radio transmissions from the Navy Navigation Satellite System at a meridional chain of ground receivers, has particular potential for complementing temporal measurements by other observing techniques such as the EISCAT incoherent-scatter radar facility. Tomographic reconstructions are presented here from a two-week campaign in November 1995 that show large-scale structuring of the polar ionosphere. Measurements by the EISCAT radar confirm the authenticity of the technique and provide additional information of the plasma electron and ion temperatures. The dayside trough, persistently observed at high latitudes during a geomagnetically quiet period but migrating to lower latitudes with increasing activity, is discussed in relationship to the pattern of the polar-cap convection.

    Key words. Ionosphere-magnetosphere interactions · Polar ionosphere · Radio science · Ionospheric propagation

  5. Mitigation and exploitation of the ionosphere: A military perspective

    Science.gov (United States)

    Cannon, Paul S.

    2009-02-01

    The ionosphere is a critical element in the design and operation of many military RF systems. While judicious engineering choices, such as transmission frequency, can mitigate many ionospheric effects, the research scientist and engineer are being asked to meet ever more demanding operational requirements. These, in turn, require ever more sophisticated situational awareness, mitigation, and exploitation techniques, which are being variously realized against a backdrop of evolving ground- and space-based instrumentation. The latter, in combination with improved modeling and assimilative techniques, promises a new generation of more capable real-time ionospheric models. Through examples this paper describes the benefits and problems associated with the ionospheric medium. HF communications and space radar systems are discussed as exemplars, and an emphasis is placed on the need to understand the engineering details of those systems if ionospheric research and development is to provide its full benefit.

  6. Storm-Time Ionospheric Disturbances Monitored by GPS Beacon Measurements

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The Total Electron Content (TEC) during three great storms, from April to August 2000, was collected by means of a GPS receiver located in Jingzhou (30. 4° N, 112. 2° E). The time-latitude-dependent features of ionospheric storms are identified using TEC difference images based on the deviations of TEC during storm relative to quiet time. The responses of ionospheric TEC to magnetic storms were analyzed. The results show that: 1) In middle and low latitude, ionospheric storms effects are more apparent in local day time than at night; 2) Ionospheric storm effects are more dominant near the hump of the equatorial anomaly region than in other regions of TEC measurements; 3) The positive effects during the main phase of iono spheric storm may be caused by electric fields in low latitude; 4) During the recovery period of ionospheric storm, the negative phase of storm may be due to the perturbation of the neutral gas composition.

  7. Design of a flexible and low-power ionospheric sounder

    Science.gov (United States)

    Morris, Alex

    Characterizing the structure of the ionosphere has practical applications for telecommunications and scientific applications for studies of the near-Earth space environment. Among several methods for measuring parameters of the ionosphere is ionospheric sounding, a radar technique that determines the electron content of the ionosphere as a function of height. Various research, military, and commercial institutions operate hundreds of ground-based ionosondes throughout the globe, and new ionosondes continue to be deployed in increasingly remote and distant locations. This thesis presents the design of an ionospheric sounder that reduces the power, size, and cost compared to existing systems. Key improvements include the use of an open-source software-defined radio platform and channel-aware dynamic sounding scheduling.

  8. Infectious Risks of Traveling Abroad.

    Science.gov (United States)

    Chen, Lin H; Blair, Barbra M

    2015-08-01

    A popular leisure activity, international travel can be associated with some infections. The most common travel-related illnesses appear to be gastrointestinal, dermatologic, respiratory, and systemic febrile syndromes. The pretravel medical consultation includes immunizations, malaria chemoprophylaxis, self-treatment for traveler's diarrhea, and advice on the prevention of a myriad of other infectious causes including dengue, chikungunya, rickettsiosis, leptospirosis, schistosomiasis, and strongyloidiasis. Travel to locations experiencing outbreaks such as Ebola virus disease, Middle East respiratory syndrome, avian influenza, and chikungunya call for specific alerts on preventive strategies. After travel, evaluation of an ill traveler must explore details of exposure, including destinations visited; activities; ingestion of contaminated food or drinks; contact with vectors, animals, fresh water, or blood and body fluids; and other potential exposures. Knowledge of the geographic distribution of infectious diseases is important in generating the differential diagnoses and testing accordingly. Empiric treatment is sometimes necessary when suspicion of a certain diagnosis is strong and confirmatory tests are delayed or lacking, particularly for infections that are rapidly progressive (for example, malaria) or for which timing of testing is prolonged (such as leptospirosis).

  9. Application of the nudged elastic band method to the point-to-point radio wave ray tracing in IRI modeled ionosphere

    Science.gov (United States)

    Nosikov, I. A.; Klimenko, M. V.; Bessarab, P. F.; Zhbankov, G. A.

    2017-07-01

    Point-to-point ray tracing is an important problem in many fields of science. While direct variational methods where some trajectory is transformed to an optimal one are routinely used in calculations of pathways of seismic waves, chemical reactions, diffusion processes, etc., this approach is not widely known in ionospheric point-to-point ray tracing. We apply the Nudged Elastic Band (NEB) method to a radio wave propagation problem. In the NEB method, a chain of points which gives a discrete representation of the radio wave ray is adjusted iteratively to an optimal configuration satisfying the Fermat's principle, while the endpoints of the trajectory are kept fixed according to the boundary conditions. Transverse displacements define the radio ray trajectory, while springs between the points control their distribution along the ray. The method is applied to a study of point-to-point ionospheric ray tracing, where the propagation medium is obtained with the International Reference Ionosphere model taking into account traveling ionospheric disturbances. A 2-dimensional representation of the optical path functional is developed and used to gain insight into the fundamental difference between high and low rays. We conclude that high and low rays are minima and saddle points of the optical path functional, respectively.

  10. Assessment of the Ionospheric and Tropospheric Effects in Location Errors of Data Collection Platforms in Equatorial Region during High and Low Solar Activity Periods

    Directory of Open Access Journals (Sweden)

    Áurea Aparecida da Silva

    2012-01-01

    Full Text Available The geographical locations of data collection platforms (DCP in the Brazilian Environmental Data Collection System are obtained by processing Doppler shift measurements between satellites and DCP. When the signals travel from a DCP to a satellite crossing the terrestrial atmosphere, they are affected by the atmosphere layers, which generate a delay in the signal propagation, and cause errors in its final location coordinates computation. The signal propagation delay due to the atmospheric effects consists, essentially, of the ionospheric and tropospheric effects. This work provides an assessment of ionospheric effects using IRI and IONEX models and tropospheric delay compensation using climatic data provided by National Climatic Data Center. Two selected DCPs were used in this study in conjunction with SCD-2 satellite during high and low solar activity periods. Results show that the ionospheric effects on transmission delays are significant (about hundreds of meters in equatorial region and should be considered to reduce DCP location errors, mainly in high solar activity periods, while in those due to tropospheric effects the zenith errors are about threemeters. Therefore it is shown that the platform location errors can be reduced when the ionospheric and tropospheric effects are properly considered.

  11. Rockfall travel distance analysis by using empirical models (Solà d'Andorra la Vella, Central Pyrenees)

    Science.gov (United States)

    Copons, R.; Vilaplana, J. M.; Linares, R.

    2009-12-01

    The prediction of rockfall travel distance below a rock cliff is an indispensable activity in rockfall susceptibility, hazard and risk assessment. Although the size of the detached rock mass may differ considerably at each specific rock cliff, small rockfall (government has been documenting rockfalls since 1999. This documentation consists in mapping the release point and the individual fallen blocks immediately after the event. The documentation of historical rockfalls by morphological analysis, eye-witness accounts and historical images serve to increase available information. In total, data from twenty small rockfalls have been gathered which reveal an amount of a hundred individual fallen rock blocks. The data acquired has been used to check the reliability of the main empirical models widely adopted (reach and shadow angle models) and to analyse the influence of parameters which affecting the travel distance (rockfall size, height of fall along the rock cliff and volume of the individual fallen rock block). For predicting travel distances in maps with medium scales, a method has been proposed based on the "reach probability" concept. The accuracy of results has been tested from the line entailing the farthest fallen boulders which represents the maximum travel distance of past rockfalls. The paper concludes with a discussion of the application of both empirical models to other study areas.

  12. Asymmetry of the Venus nightside ionosphere: Magnus force effects

    Science.gov (United States)

    Pérez-de-Tejada, H.

    2008-11-01

    A study of the dawn-dusk asymmetry of the Venus nightside ionosphere is conducted by examining the configuration of the ionospheric trans-terminator flow around Venus and also the dawn-ward displacement of the region where most of the ionospheric holes and the electron density plateau profiles are observed (dawn meaning the west in the retrograde rotation of Venus and that corresponds to the trailing side in its orbital motion). The study describes the position of the holes and the density plateau profiles which occur at neighboring locations in a region that is scanned as the trajectory of the Pioneer Venus Orbiter (PVO) sweeps through the nightside hemisphere with increasing orbit number. The holes are interpreted as crossings through plasma channels that extend downstream from the magnetic polar regions of the Venus ionosphere and the plateau profiles represent cases in which the electron density maintains nearly constant values in the upper ionosphere along the PVO trajectory. From a collection of PVO passes in which these profiles were observed it is found that they appear at neighboring positions of the ionospheric holes in a local solar time (LST) map including cases where only a density plateau profile or an ionospheric hole was detected. It is argued that the ionospheric holes and the density plateau profiles have a common origin at the magnetic polar regions where plasma channels are formed and that the density plateau profiles represent crossings through a friction layer that is adjacent to the plasma channels. It is further suggested that the dawn-dusk asymmetry in the position of both features in the nightside ionosphere results from a fluid dynamic force (Magnus force) that is produced by the combined effects of the trans-terminator flow and the rotational motion of the ionosphere that have been inferred from the PVO measurements.

  13. 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.

  14. Cyclotron resonance absorption in ionospheric plasma

    Science.gov (United States)

    Villalon, Elena

    1991-04-01

    The mode conversion of ordinary polarized electromagnetic waves into electrostatic cyclotron waves in the inhomogeneous ionospheric plasma is investigated. Near resonance the warm plasma dispersion relation is a function of the angle theta between the geomagnetic field and the density gradient and of the wave frequency omega, which lies between the electron cyclotron frequency and its doubling. The differential equations describing the electric field amplitudes near the plasma resonance are studied, including damping at the second gyroharmonic. The energy transmission coefficients and power absorbed by the cyclotron waves are calculated. The vertical penetration of the plasma wave amplitudes is estimated using a WKB analysis of the wave equation.

  15. Localized lower hybrid acceleration of ionospheric plasma

    Science.gov (United States)

    Kintner, P. M.; Vago, J.; Chesney, S.; Arnoldy, R. L.; Lynch, K. A.; Pollock, C. J.; Moore, T. E.

    1992-01-01

    Observations of the transverse acceleration of ions in localized regions of intense lower hybrid waves at altitudes near 1000 km in the auroral ionosphere are reported. The acceleration regions are thin filaments with dimensions across geomagnetic field lines of about 50-100 m corresponding to 5-10 thermal ion gyroradii or one hot ion gyroradius. Within the acceleration region lower hybrid waves reach peak-to-peak amplitudes of 100-300 mV/m and ions are accelerated transversely with characteristic energies of the order of 10 eV. These observations are consistent with theories of lower hybrid wave collapse.

  16. Signatures of the ionospheric Alfvén resonator from AUREOL-3 ULF/ELF fluctuation measurements

    Science.gov (United States)

    Zhao, Z. Y.; Ni, B. B.

    2006-01-01

    From the AUREOL-3 satellite, simultaneous measurements of plasma density and ULF/ELF electric and magnetic fields on March 16, 1982 were obtained. Based on spectra analysis and impedance function calculation of data from 04:48:37 to 04:52:10 UT time (hh:mm:ss), the origin of the field fluctuations below 5.0 Hz is examined. A high coherence exists between the correlated variations of the mutually orthogonal electric and magnetic fields. Below 2.0 Hz an oscillatory phase difference of about ±π implies the excitation of traveling waves. The phase difference of ±π/2 appears at 4.0 Hz, indicative of a standing wave. Taking into account the local magnetic field and plasma density, for the frequencies between 0.3 and 4.0 Hz, the impedance comes very near to the local Alfvén impedance. In this way, the peaks at 0.5 and 4.0 Hz are identified, respectively, as a traveling and a standing shear Alfvén wave, which presumably resulted from the operation of the ionospheric Alfvén resonator (IAR). At the lowest frequency below 0.1 Hz, the approach of the wave impedance to the reciprocal of local height-integrated Pedensen conductivity implies the AUREOL-3 satellite's crossing of spatially structured field-aligned currents closed through the ionosphere, as suggested by Forget et al. (1991. Ionospheric closure of small scale Birkeland currents. Journal of Geophysical Research 96, 1843 1847).

  17. Danish long distance travel A study of Danish travel behaviour and the role of infrequent travel activities

    OpenAIRE

    Knudsen, Mette Aagaard; Rich, Jeppe; Nielsen, Otto Anker

    2014-01-01

    Historically there has been a lack of knowledge with respect to long distance travel. Due to the considerable contribution of long distance travel to total travelled kilometres and the related energy consumption from the transport sector and derived impacts on greenhouse emissions, this is problematic. The average travel distance has steadily increased during the latest decades together with the increasing motorisation of daily travel and international aviation. Previously most focus has been...

  18. Measurement of the Characteristics of TIDs Using Small and Regional Networks of GPS Receivers during the Campaign of 17-30 July of 2008

    Science.gov (United States)

    2012-01-01

    M. Sato, Y. Otsuka , T. Takami, and T. Tsuda, “Middle and upper atmosphere radar observations of the dispersion relation for ionospheric gravity waves...vol. 108, no. 21, pp. 1–12, 2003. [17] S. Suzuki, K. Shiokawa, Y. Otsuka , T. Ogawa, and P.Wilkinson, “Statistical characteristics of gravity waves...Ihara, Y. Otsuka , and T. Ogawa, “Statisti- cal study of nighttime medium-scale traveling ionospheric disturbances using midlatitude airglow images

  19. A relational approach to analysing leisure travel

    NARCIS (Netherlands)

    Ettema, D.F.; Schwanen, T.

    2012-01-01

    Leisure travel makes up a very significant part of daily travel and therefore needs to be considered in any travel demand management or general land use and transportation policy. Yet, research into leisure mobility has tended to ignore important aspects of leisure travel, such as its joint characte

  20. Practical advice for perioperative travel nurses.

    Science.gov (United States)

    Brumley, Cindy L

    2002-10-01

    Travel nursing presents unique opportunities that permanent employees may never experience. Today's nursing shortage allows travel nurses to fill temporary staff positions while experiencing the sights, culture, and cuisine of a location of their choosing. This creates a beneficial situation for travel nurses, hospitals, travel companies, and, ultimately, patients. Knowledgeable, flexible nurses and traveler-friendly hospitals can extend contracts if mutually agreeable, thus prolonging the benefits. Before beginning the adventure, however, travelers must have realistic expectations. Many disappointed travelers may have been more successful had they done better research.

  1. The value of travel time variance

    DEFF Research Database (Denmark)

    Fosgerau, Mogens; Engelson, Leonid

    2011-01-01

    This paper considers the value of travel time variability under scheduling preferences that are defined in terms of linearly time varying utility rates associated with being at the origin and at the destination. The main result is a simple expression for the value of travel time variability...... that does not depend on the shape of the travel time distribution. The related measure of travel time variability is the variance of travel time. These conclusions apply equally to travellers who can freely choose departure time and to travellers who use a scheduled service with fixed headway. Depending...... on parameters, travellers may be risk averse or risk seeking and the value of travel time may increase or decrease in the mean travel time....

  2. Observational Study of Travelers' Diarrhea.

    Science.gov (United States)

    Meuris

    1995-03-01

    Background: European air travelers returning from Algeria, Egypt, Mexico, Morocco, and Tunisia were interviewed about their experience of travelers' diseases upon arrival in Brussels. Diarrhea was mentioned by 37% of the adults and 27% of the children. These subjects were questioned about the types of measures taken, type and duration of drug treatment (if any), and about duration of diarrhea and side effects experienced. Methods: Final analysis was performed based on 2160 interviews. The largest proportion of diarrhea was reported in the age group 15-24 years (46%). Results: The majority of the 2160 subjects had opted for drug treatment (81%): 927 subjects for loperamide alone, 235 for loperamide in combination with nifuroxazide, and 178 for nifuroxazide alone. Other drugs had been used less frequently. The median time to recovery was 2.4 days with loperamide compared to 3.2 days with nifuroxazide and to 3.4 days for the no-treatment group. Conclusions: A stratification of the results by severity of the diarrhea suggests a rank of antidiarrheal potency as follows: loperamide > nifuroxazide > no-drug treatment. The side effect with the highest incidence was constipation (2.4% with loperamide). (J Travel Med 2:11-15, 1995) Travelers' diarrhea is usually defined as the passage of at least three unformed stools per day or any number of such stools when accompanied by fever, abdominal cramping, or vomiting. The definition may be broadened to include more trivial bowel disturbance.1,2 The duration of this self-limited disease generally is 3 to 5 days. Medical intervention aims at shortening the duration of disease, thus allowing the sufferer to resume his or her usual activities at an early stage. A shortened period of recovery to physical well-being has obvious favorable economic implications if the traveler is on business and may help the maintenance of a desired level of quality of life while a traveler is on holiday. An observational study of various medical

  3. Choosing between travel agencies and the Internet

    OpenAIRE

    2015-01-01

    M.A. (Tourism and Hospitality Management) Travel agents have been traditionally seen as the key intermediary between suppliers of travel services and the traveller. Developments in the field of information technology offer consumers an alternative to booking via a travel agent - the option to plan and arrange holidays online. Due to the ever developing nature of technology, travellers have the luxury of a multitude of choices in their everyday life - particularly so in making decisions reg...

  4. Ionospheric heating with oblique HF waves

    Science.gov (United States)

    Field, Edward C., Jr.; Bloom, Ron M.

    1990-10-01

    Calculations of ionospheric electron density perturbations and ground-level signal changes produce by intense oblique high frequency (HF) transmitters are presented. This analysis considers radio field focusing at caustics, the consequent joule-heating of the surrounding plasma, heat conduction, diffusion, and recombination processes: these being the effects of a powerful oblique 'modifying' wave. It neglects whatever plasma instabilities might occur. Then effects on a secondary 'test' wave that is propagated along the same path as the first are investigated. Calculations predict ground-level field-strength reductions of several dB in the test wave for modifying waves having ERP in the 85 to 90 dBW range. These field-strength changes are similar in sign, magnitude, and location to ones measured in Soviet experiments. The results are sensitive to the model ionosphere assumed, so future experiments should employ the widest possible range of frequencies and propagation conditions. An effective power of 90 dBW seems to be a sort of threshold that, if exceeded, results in substantial rather than small signal changes. The conclusions are based solely on joule-heating and subsequent defocusing of waves passing through caustic regions.

  5. Ionospheric irregularities at Antarctic using GPS measurements

    Indian Academy of Sciences (India)

    Sunita Tiwari; Amit Jain; Shivalika Sarkar; Sudhir Jain; A K Gwal

    2012-04-01

    The purpose of this work is to study the behaviour of the ionospheric scintillation at high latitude during geomagnetically quiet and disturbed conditions which is one of the most relevant themes in the space weather studies. Scintillation is a major problem in navigation application using GPS and in satellite communication at high latitudes. Severe amplitude fading and strong scintillation affect the reliability of GPS navigational system and satellite communication. To study the effects of the ionospheric scintillations, GPS receiver installed at Antarctic station Maitri (Geog. 70.76°S; 11.74°E) was used. The data is collected by using GISTM 4004A, NOVATEL’S GPS receiver during March 2008. Studies show that percentage occurrence of phase scintillation is well correlated with geomagnetic activity during the observation period. The result also shows that very intense scintillations can degrade GPS based location determination due to loss of lock of satellites. These findings indicate that the dependence of scintillations and irregularity occurrence on geomagnetic activity is associated with the magnetic local time (MLT). Large number of patches are reported and their activity depends on the magnetic activity index.

  6. Ionospheric electron content: the European perspective

    Directory of Open Access Journals (Sweden)

    R. Leitinger

    1998-06-01

    Full Text Available The electron content of the ionosphere is an important quantity which indicates overall ionization. It is measured by means of propagation effects on radio signals which penetrate the ionosphere. In Europe relevant investigations started after the launch of the first artificial satellites. Soon the necessity arose to organize international cooperation: the regional as well as the global geographical distribution of ionization parameters is important knowledge for any meaningful geophysical interpretation of ionization parameters. Despite the fact that international scientific Unions and Committees existed and had proven their usefulness and potential, private initiatives were taken to organize cooperation in the field of research based on transionospheric propagation effects. Only in 1971 three international groups joined together to form the "Beacon Satellite Group"as a "Working Party" of COSPAR. The "Beacon Satellite Group" still exists but is now a Working Group of URSI, the International Union for Radio Science. This contribution tries to summarize the European perspective with special emphasis on the long standing cooperation between the Istituto di Ricerca sulle Onde Elettromagnetiche (IROE at Firenze and the Institut für Meteorologie und Geophysik of the University of Graz. Examples are given of important results.

  7. The physical basis of ionospheric electrodynamics

    Directory of Open Access Journals (Sweden)

    V. M. Vasyliūnas

    2012-02-01

    Full Text Available The conventional equations of ionospheric electrodynamics, highly succesful in modeling observed phenomena on sufficiently long time scales, can be derived rigorously from the complete plasma and Maxwell's equations, provided that appropriate limits and approximations are assumed. Under the assumption that a quasi-steady-state equilibrium (neglecting local dynamical terms and considering only slow time variations of external or aeronomic-process origin exists, the conventional equations specify how the various quantities must be related numerically. Questions about how the quantities are related causally or how the stress equilibrium is established and on what time scales are not anwered by the conventional equations but require the complete plasma and Maxwell's equations, and these lead to a picture of the underlying physical processes that can be rather different from the commonly presented intuitive or ad hoc explanations. Particular instances include the nature of the ionospheric electric current, the relation between electric field and plasma bulk flow, and the interrelationships among various quantities of neutral-wind dynamo.

  8. Poliomyelitis--prevention in travellers.

    Science.gov (United States)

    Mayer, Cora A; Neilson, Amy A

    2010-03-01

    This article is the second in a series providing a summary of prevention strategies and vaccination for infections that may be acquired by travellers. The series aims to provide practical strategies to assist general practitioners in giving travel advice, as a synthesis of multiple information sources which must otherwise be consulted. Poliomyelitis is a potentially fatal viral illness, which may cause acute flaccid paralysis and permanent central nervous system damage. Ongoing global efforts to eradicate poliomyelitis have been under way since 1988. Travellers are at risk of infection in countries with endemic wild poliomyelitis virus or imported cases, and can spread the infection to areas where poliomyelitis has been eradicated. While all adults should be immune to poliomyelitis, it is important that at-risk travellers are vaccinated appropriately. Vaccine options and regions currently reporting poliomyelitis are presented from a number of sources, which may facilitate the process of giving travel advice in a general practice setting, although it is also important to seek up-to-date epidemiological information.

  9. The Linkage Between the Ionospheric Trough and Ring Current

    Science.gov (United States)

    Brandt, P. C.; Zheng, Y.; Talaat, E.; Sotirelis, T.; Foster, J. C.; Erickson, P. J.

    2007-05-01

    We present data-model investigations of how the ring current couples to the sub-auroral ionosphere. The ring current pressure distribution during storm and substorms is highly asymetrical and sets up the region 2 current system that closes through the sub-auroral ionosphere. Of particular interest is what happens in the so-called ionospheric trough region, which is a region in the evening ionosphere with extremely low conductance (few tenths of a mho). Observations show strong westward flows in the ionospheric trough (Sub-Auroral Polarization Stream - SAPS) and sometimes highly structured and variable. The Comprehensive Ring Current Model models the ring current by using the bounce averaged Boltzmann equation and allowing the ring current to close through the ionosphere. Our model ionosphere includes dayside and auroral conductance as well as semi-empirical representation of the trough conductance. By using realistic representations of the conductances we seek to explore how the ring current pressure distribution (and therefore the region 2 current system) is linked to the presence of the trough. We use data from the IMAGE satellite, the Millstone Hill and SuperDARN radar facilities.

  10. Advanced Ionospheric Probe scientific mission onboard FORMOSAT-5 satellite

    Directory of Open Access Journals (Sweden)

    Zai-Wun Lin

    2017-01-01

    Full Text Available Advanced Ionospheric Probe (AIP is a piggyback science payload developed by National Central University for FORMOSAT-5 satellite to explore space weather/climate and seismic precursors associated with strong earthquakes. The AIP is an all-in-one plasma sensor that measures ionospheric plasma concentrations, velocities, and temperatures in a time-sharing way and is capable of measuring ionospheric plasma irregularities at a sample rate up to 8192 Hz over a wide range of spatial scales. Electroformed gold grids used in the AIP in theory construct planar electric potential surfaces better than woven grids. Moreover, a plasma injection test performed in the Space Plasma Simulation Chamber has verified that no significant hysteresis is found in current-voltage curves measured by the AIP. It indicates that the AIP can make an accurate measurement of the ionospheric plasma parameters in space. Finally, Ionospheric Plasma and Electrodynamics Instrument (IPEI observations onboard the ROCSAT-1 satellite are applied to show that the scientific objectives of ionospheric space weather/climate and seismo-ionospheric precursors (SIPs of the FORMOSAT-5/AIP can be fulfilled. The observations reveal that ion parameter global distributions are helpful in studying the formation and variation in temperature crests and troughs in the 2200 - 2300 local time sector, as well as SIPs in the density and the velocity over the epicenter area, which are anticipated for the FORMOSAT-5 satellite orbit.

  11. 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.

  12. Future Trends in Business Travel Decision Making

    Science.gov (United States)

    Mason, Keith J.

    2002-01-01

    This research surveys twenty large companies and their travellers to identify and evaluate the effects of pressures on the business travel market in the future. The influence of the following areas on the decision making process are addressed: (1) Corporate travel policies and increasing professionalism in corporate purchasing; (2) The development of global strategic airline alliances; (3) The emergence of low cost airlines on short haul markets; and (4) The development of internet based booking tools and travel agency IT. The survey shows differences in views between travel managers, and travellers with regard to corporate travel policies. While travel managers see policy rules, travellers interpret these as guidelines, indicating travel managers will need to take further actions to exercise true control of travel budgets. The data shows that companies are more likely to prescribe a class of airline ticket, than the choice of airline itself. Corporate hierarchical bias in travel policies is still common both for short and particularly long haul flying. Other findings show that while travel managers believe that their companies are likely to sign global deals with strategic airline groups within a five year period in a bid to consolidating spending, they also believe that nearly a third of short haul flying will be taken with low cost carriers, indicating further penetration in this business travel market by these carriers. The paper also provides other predictions about the business travel market, based on the survey findings.

  13. Long-term ionospheric anomaly monitoring for ground based augmentation systems

    Science.gov (United States)

    Jung, Sungwook; Lee, Jiyun

    2012-08-01

    Extreme ionospheric anomalies can pose a potential integrity threat to ground-based augmentation of the Global Positioning System (GPS), and thus the development of ionospheric anomaly threat models for each region of operation is essential for system design and operation. This paper presents a methodology for automated long-term ionospheric anomaly monitoring, which will be used to build an ionospheric anomaly threat model, evaluate its validity over the life cycle of the system, continuously monitor ionospheric anomalies, and update the threat model if necessary. This procedure automatically processes GPS data collected from external networks and estimates ionospheric gradients at regular intervals. If ionospheric gradients large enough to be potentially hazardous to users are identified, manual data examination is triggered. This paper also develops a simplified truth processing method to create precise ionospheric delay estimates in near real-time, which is the key to automating the ionospheric monitoring procedure. The performance of the method is examined using data from the 20 November 2003 and 9 November 2004 ionospheric storms. These results demonstrate the effectiveness of simplified truth processing within long-term ionosphere monitoring. From the case studies, the automated procedure successfully identified extreme ionospheric anomalies, including the two worst ionospheric gradients observed and validated previously based on manual analysis. The automation of data processing enables us to analyze ionospheric data continuously going forward and to more accurately categorize ionospheric behavior under both nominal and anomalous conditions.

  14. 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

  15. Toxoplasmosis as a travel risk.

    Science.gov (United States)

    Sepúlveda-Arias, Juan C; Gómez-Marin, Jorge E; Bobić, Branko; Naranjo-Galvis, Carlos A; Djurković-Djaković, Olgica

    2014-01-01

    Toxoplasma gondii is a protozoan parasite with worldwide distribution that infects more than one third of the global population. Primary infection in immunocompetent individuals is usually asymptomatic; however, different organs can be affected in immunocompromised individuals leading to the development of encephalitis, myocarditis or pneumonitis. The prevalence of infection with Toxoplasma as well as its genetic structure varies geographically and for that reason travel may be considered as a risk factor to acquire the infection. As toxoplasmosis is a foodborne disease, health care providers should give health education on prevention measures to all prospective travelers in order to decrease the risk of infection in endemic areas. This review presents an overview of the infection with T. gondii with some considerations for travelers to and from endemic zones.

  16. Fundamental Travel Demand Model Example

    Science.gov (United States)

    Hanssen, Joel

    2010-01-01

    Instances of transportation models are abundant and detailed "how to" instruction is available in the form of transportation software help documentation. The purpose of this paper is to look at the fundamental inputs required to build a transportation model by developing an example passenger travel demand model. The example model reduces the scale to a manageable size for the purpose of illustrating the data collection and analysis required before the first step of the model begins. This aspect of the model development would not reasonably be discussed in software help documentation (it is assumed the model developer comes prepared). Recommendations are derived from the example passenger travel demand model to suggest future work regarding the data collection and analysis required for a freight travel demand model.

  17. Elasticity of Long Distance Travelling

    DEFF Research Database (Denmark)

    Knudsen, Mette Aagaard

    2011-01-01

    With data from the Danish expenditure survey for 12 years 1996 through 2007, this study analyses household expenditures for long distance travelling. Household expenditures are examined at two levels of aggregation having the general expenditures on transportation and leisure relative to five other...... aggregated commodities at the highest level, and the specific expenditures on plane tickets and travel packages at the lowest level. The Almost Ideal Demand System is applied to determine the relationship between expenditures on transportation and leisure and all other purchased non-durables within...... packages has higher income elasticity of demand than plane tickets but also higher than transportation and leisure in general. The findings within price sensitiveness are not as sufficient estimated, but the model results indicate that travel packages is far more price elastic than plane tickets which...

  18. Travel epidemiology: the Saudi perspective.

    Science.gov (United States)

    Memish, Ziad A; Venkatesh, S; Ahmed, Qanta A

    2003-02-01

    The Kingdom of Saudi Arabia occupies four-fifths of the Arabian Peninsula, with a land area of 2 million square kilometres. Saudi Arabia holds a unique position in the Islamic world, as the custodian of the two holiest places of Islam, in Mecca and Medina. Annually, some 2 million Muslims from over 140 countries embark on Hajj. This extraordinary en masse migration is a unique forum for the study of travel epidemiology since the Hajj carries various health risks, both communicable and non-communicable, often on a colossal scale. Non-communicable hazards of the Hajj include stampede and motor vehicle trauma, fire-related burn injuries and accidental hand injury during animal slaughter. Communicable hazards in the form of outbreaks of multiple infectious diseases have been reported repeatedly, during and following the Hajj. Meningococcal meningitis, gastroenteritis, hepatitis A, B and C, and various zoonotic diseases comprise some of the possible infectious hazards at the Hajj. Many of these infectious and non-infectious hazards can be avoided or averted by adopting appropriate prophylactic measures. Physicians and health personnel must be aware of these risks to appropriately educate, immunize and prepare these travellers facing the unique epidemiological challenges of Hajj in an effort to minimize untoward effects. Travel epidemiology related to the Hajj is a new and exciting area, which offers valuable insights to the travel specialist. The sheer scale of numbers affords a rare view of migration medicine in action. As data is continually gathered and both national and international policy making is tailored to vital insights gained through travel epidemiology, the Hajj will be continually safeguarded. Practitioners will gain from findings of travel related epidemiological changes in evolution at the Hajj: the impact of vaccinating policies, infection control policies and public health are afforded a real-world laboratory setting at each annual Hajj, allowing us to

  19. Temperature enhancement induced by ionosphere heating in low altitude region

    Institute of Scientific and Technical Information of China (English)

    Bin Xu; Jian Wu; Zhensen Wu; Jun Wu; Haiqin Che; Yubo Yan; Kun Xue

    2008-01-01

    The assumption that the electron temperature is approximately equal to the ion temperature is not rational during the high frequency (HF) heating in low ionosphere region. Thus, using the theoretical formula of incoherent scatter spectra with collisional plasma, the incoherent scatter data are analyzed during ionosphere heating at 91.7 km height on August 15th 2006. The enhancements of electron temperature are obtained, and the incremental percent is up to 37% and 46% at the universal time of 10:22 and 10:30, respectively. By using the same initialization value, the ionosphere heating process is simulated by Ohmic theory and the experimental results are basically consistent with the simulation.

  20. Active experiments in the ionosphere and geomagnetic field variations

    Science.gov (United States)

    Sivokon, V. P.; Cherneva, N. V.; Khomutov, S. Y.; Serovetnikov, A. S.

    2014-11-01

    Variations of ionospheric-magnetospheric relation energy, as one of the possible outer climatology factors, may be traced on the basis of analysis of natural geophysical phenomena such as ionosphere artificial radio radiation and magnetic storms. Experiments on active impact on the ionosphere have been carried out for quite a long time in Russia as well. The most modern heating stand is located in Alaska; it has been used within the HAARP Program. The possibility of this stand to affect geophysical fields, in particular, the geomagnetic field is of interest.

  1. Ionospheric Effects of Geomagnetic Storms in Different Longitude Sectors

    Institute of Scientific and Technical Information of China (English)

    G. A. Zherebtsov; O.M. Pirog; N.M. Polekh

    2005-01-01

    This paper analyzes the state of the ionosphere during two geomagnetic storms of a different intensity evolving in different sectors of local time in different seasons. There were used the data from a network of ionospheric stations located in the opposite longitudinal sectors of 80°-150° E and 250°-310° E.This analysis has permitted us to conclude that the detected differences in the variations of the disturbances are likely to be determined by the local time difference of the geomagnetic storm development, its intensity and by the different illumination conditions of the ionosphere.

  2. Martian ionosphere response to solar wind variability during solar minimum

    Science.gov (United States)

    Sanchez-Cano, Beatriz; Lester, Mark; Witasse, Olivier; Mays, M. Leila; Hall, Benjamin E. S.; Milan, Stephen E.; Cartacci, Marco; Blelly, Pierre-Louis; Andrews, David; Opgenoorth, Hermann; Odstrcil, Dusan

    2016-04-01

    Solar cycle variations in solar radiation create notable density changes in the Martian ionosphere. In addition to this long-term variability, there are numerous short-term and non-recurrent solar events that hit Mars which need to be considered, such as Interplanetary Coronal Mass Ejections (ICMEs), Co-Rotation Interaction Regions (CIRs), solar flares, or solar wind high speed streams. The response of the Martian plasma system to each of these events is often unusual, especially during the long period of extreme low solar activity in 2008 and 2009. This work shows the long-term solar cycle impact on the ionosphere of Mars using data from The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS), and The Analyzer of Space Plasma and Energetic Atoms (ASPERA-3), and with empirical and numerical models on Mars Express. Particular attention is given to the different ionospheric responses observed during the last, extended solar minimum. Mars' ionospheric response followed a similar pattern to the response observed in the Earth's ionosphere, despite the large differences related to the inner-origin of the magnetic field of both planets. The ionospheric temperature was cooler, the topside scale height was smaller and almost constant with altitude, the secondary ionospheric layer practically disappeared and the whole atmospheric total electron content (TEC) suffered an extreme reduction of about 30-40%, not predicted before by models. Moreover, there is a larger probability for the induced magnetic field to be present in the ionosphere, than in other phases of the solar cycle. The short-term variability is also addressed with the study of an ICME followed by a fast stream that hit Mars in March 2008, where solar wind data are provided by ACE and STEREO-B and supported by simulations using the WSA-ENLIL Model. The solar wind conditions lead to the formation of a CIR centred on the interface of the fast and the slow solar wind streams. Mars' system reacted to

  3. Ionospheric modelling using GPS to calibrate the MWA. 1: Comparison of first order ionospheric effects between GPS models and MWA observations

    CERN Document Server

    Arora, B S; Ord, S M; Tingay, S J; Hurley-Walker, N; Bell, M; Bernardi, G; Bhat, R; Briggs, F; Callingham, J R; Deshpande, A A; Dwarakanath, K S; Ewall-Wice, A; Feng, L; For, B -Q; Hancock, P; Hazelton, B J; Hindson, L; Jacobs, D; Johnston-Hollitt, M; Kapińska, A D; Kudryavtseva, N; Lenc, E; McKinley, B; Mitchell, D; Oberoi, D; Offringa, A R; Pindor, B; Procopio, P; Riding, J; Staveley-Smith, L; Wayth, R B; Wu, C; Zheng, Q; Bowman, J D; Cappallo, R J; Corey, B E; Emrich, D; Goeke, R; Greenhill, L J; Kaplan, D L; Kasper, J C; Kratzenberg, E; Lonsdale, C J; Lynch, M J; McWhirter, S R; Morales, M F; Morgan, E; Prabu, T; Rogers, A E E; Roshi, A; Shankar, N Udaya; Srivani, K S; Subrahmanyan, R; Waterson, M; Webster, R L; Whitney, A R; Williams, A; Williams, C L

    2015-01-01

    We compare first order (refractive) ionospheric effects seen by the Murchison Widefield Array (MWA) with the ionosphere as inferred from Global Positioning System (GPS) data. The first order ionosphere manifests itself as a bulk position shift of the observed sources across an MWA field of view. These effects can be computed from global ionosphere maps provided by GPS analysis centres, namely the Center for Orbit Determination in Europe (CODE), using data from globally distributed GPS receivers. However, for the more accurate local ionosphere estimates required for precision radio astronomy applications, data from local GPS networks needs to be incorporated into ionospheric modelling. For GPS observations, the ionospheric parameters are biased by GPS receiver instrument delays, among other effects, also known as receiver Differential Code Biases (DCBs). The receiver DCBs need to be estimated for any non-CODE GPS station used for ionosphere modelling, a requirement for establishing dense GPS networks in arbitr...

  4. Value of travel time savings

    DEFF Research Database (Denmark)

    Le Masurier, P.; Polak, J.; Pawlak, Janet

    2015-01-01

    A team of specialist market researchers and Value of Time experts comprising members from SYSTRA, Imperial College London and the Technical University of Denmark has conducted a formal audit and peer review of research undertaken by Arup/ITS Leeds/Accent to derive Value of Travel Time Savings...... Preference (RP) models that were used to derive final Values of Travel Time (VTT). This report contains the findings of our audit and peer review of the procedures adopted by the research team during data collection of the three surveys (SP, RP and Employers Surveys); a peer review of the reported approach...

  5. Black Holes: A Traveler's Guide

    Science.gov (United States)

    Pickover, Clifford A.

    1998-03-01

    BLACK HOLES A TRAVELER'S GUIDE Clifford Pickover's inventive and entertaining excursion beyond the curves of space and time. "I've enjoyed Clifford Pickover's earlier books . . . now he has ventured into the exploration of black holes. All would-be tourists are strongly advised to read his traveler's guide." -Arthur C. Clarke. "Many books have been written about black holes, but none surpass this one in arousing emotions of awe and wonder towards the mysterious structure of the universe." -Martin Gardner. "Bucky Fuller thought big. Arthur C. Clarke thinks big, but Cliff Pickover outdoes them both." -Wired. "The book is fun, zany, in-your-face, and refreshingly addictive." -Times Higher Education Supplement.

  6. Traveling-Wave Membrane Photomixers

    Science.gov (United States)

    Wyss, R. A.; Martin, S. C.; Nakamura, B. J.; Neto, A.; Pasqualini, D.; Siegel, P. H.; Kadow, C.; Gossard, A. C.

    2001-01-01

    Traveling-wave photomixers have superior performance when compared with lumped area photomixers in the 1 to 3 THz frequency range. Their large active area and distributed gain mechanism assure high thermal damage threshold and elimination of the capacitive frequency roll-off. However, the losses experienced by the radio frequency wave traveling along the coplanar strips waveguide (due to underlying semi-infinite GaAs substrate) were a serious drawback. In this paper we present device designs and an experimental setup that make possible the realization of photomixers on membranes which eliminate the losses.

  7. Rabies and Risk to Travelers

    Centers for Disease Control (CDC) Podcasts

    2007-10-01

    Each year over 55,000 people die because of rabies, mostly from being bitten by rabid dogs. Over half of all rabies infections occur in children under the age of 15 who live in developing countries, but travelers are not immune. This podcast discusses some of the activities that put travelers at risk for rabies and describes ways to prevent infection.  Created: 10/1/2007 by National Center for the Prevention, Detection and Control of Infectious Diseases (NCPDCID).   Date Released: 10/5/2007.

  8. Hematospermia in a returned traveler.

    Science.gov (United States)

    Lang, Raynell; Minion, Jessica; Wong, Alexander

    2017-01-01

    Hematospermia is a common complaint among patients seen in outpatient urology clinics. The differential diagnosis is broad and includes inflammatory, infectious, neoplastic, structural, systemic, and traumatic causes. The most common infectious causes are uropathogens and sexually transmitted infections. However, with increasing global travel, physicians must maintain a high clinical suspicion for pathogens not endemic to their region, including Echinococcus, Mycobacterium tuberculosis, and Schistosoma.1 We present a case of hematospermia in a traveler returning from Eastern Africa with exposure to Lake Malawi. The patient's microscopic analysis of semen was positive for Schistosoma haematobium, revealing a rare presentation of S. haematobium infection.

  9. Safe travels? HIV transmission among Britons travelling abroad.

    Science.gov (United States)

    Rice, B; Gilbart, V L; Lawrence, J; Smith, R; Kall, M; Delpech, V

    2012-05-01

    The aim of the study was to identify and describe the characteristics of persons born in the UK who acquire HIV infection abroad. Analyses using case reports and follow-up data from the national HIV database held at the Health Protection Agency were performed. Fifteen per cent (2066 of 13 891) of UK-born adults diagnosed in England, Wales and Northern Ireland between 2002 and 2010 acquired HIV infection abroad. Thailand (534), the USA (117) and South Africa (108) were the countries most commonly reported. As compared with UK-born adults acquiring HIV infection in the UK, those acquiring HIV infection abroad were significantly (P sex with a commercial sex worker (5.6% vs. 1%, respectively). Among men infected in Thailand, 11% reported sex with a commercial sex worker. A substantial number of UK-born adults are acquiring HIV infection in countries with generalized HIV epidemics, and in common holiday destinations. Of particular concern is the high proportion of men infected reporting sex with a commercial sex worker. We recommend HIV prevention and testing efforts be extended to include travellers abroad, and that sexual health advice be provided routinely in travel health consultations and in occupational health travel advice packs, particularly to those travelling to high HIV prevalence areas and destinations for sex tourism. Safer sex messages should include an awareness of the potential detrimental health and social impacts of the sex industry. © 2012 British HIV Association.

  10. Travelers' Health: Traveling Safely with Infants and Children

    Science.gov (United States)

    ... be used with caution in the presence of children to avoid burns and inadvertent ingestion. For more information about repellent ... above. These seats often must be carried from home, since availability of ... abroad. In general, children are safest traveling in the rear seat; no ...

  11. Multi-Technique Study of Ionospheric Structures Causing Degradation in Trans-Ionospheric Communications Systems.

    Science.gov (United States)

    1987-04-20

    Szuszczewicz, E.P., P. Rodriguez, M. Singh and S. Mango , "Ionospheric irregularities and their potential impact on synthetic aperture radars’, Radio Sci., 18, No...largest in which we have assumed a vertical gradient scale length of scalcs. gravity wave seeding , and velocity shear instabilities. 20 km and a...undulations were due to gravity wave seeding as sive as a plume cannot grow from thermal noise in a few described by Klostermeyer [1978] Once seeded

  12. Environmental Impact of Long Distance Travel

    DEFF Research Database (Denmark)

    Christensen, Linda

    2016-01-01

    This paper presents an analysis of the CO2 emission resulting from long distance travel by Danes. The emissions are analysed as the Danes’ footprint the whole way from Denmark to the final destination. International travel represents 31% of the Danes’ CO2 emission from passenger travel and the cl......This paper presents an analysis of the CO2 emission resulting from long distance travel by Danes. The emissions are analysed as the Danes’ footprint the whole way from Denmark to the final destination. International travel represents 31% of the Danes’ CO2 emission from passenger travel...... and the climate burden from long overseas distances is especially high even though only few travel overseas. The travel activity is furthermore increasing much more for long distances than for European destinations. Domestic travel activity with overnight stay is nearly stagnating. The study furthermore shows...

  13. Ionospheric Correction Based on Ingestion of Global Ionospheric Maps into the NeQuick 2 Model

    Directory of Open Access Journals (Sweden)

    Xiao Yu

    2015-01-01

    Full Text Available The global ionospheric maps (GIMs, generated by Jet Propulsion Laboratory (JPL and Center for Orbit Determination in Europe (CODE during a period over 13 years, have been adopted as the primary source of data to provide global ionospheric correction for possible single frequency positioning applications. The investigation aims to assess the performance of new NeQuick model, NeQuick 2, in predicting global total electron content (TEC through ingesting the GIMs data from the previous day(s. The results show good performance of the GIMs-driven-NeQuick model with average 86% of vertical TEC error less than 10 TECU, when the global daily effective ionization indices (Az versus modified dip latitude (MODIP are constructed as a second order polynomial. The performance of GIMs-driven-NeQuick model presents variability with solar activity and behaves better during low solar activity years. The accuracy of TEC prediction can be improved further through performing a four-coefficient function expression of Az versus MODIP. As more measurements from earlier days are involved in the Az optimization procedure, the accuracy may decrease. The results also reveal that more efforts are needed to improve the NeQuick 2 model capabilities to represent the ionosphere in the equatorial and high-latitude regions.

  14. Artificial periodic irregularities in the auroral ionosphere

    Directory of Open Access Journals (Sweden)

    M.T. Rietveld

    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

  15. LEISA: CubeSat for Ionospheric Characterization

    Science.gov (United States)

    Suddarth, S. C.; Vera, A.; Pollard, H.; Burgett, T.; King, B.; Hulem, D.; MacGillivray, J.; Montoya, M.; Stanton, W.; Trujillo, B.; Wilson, S.; Heileman, G.

    2012-12-01

    The University of New Mexico / Configurable Space Microsystems Innovation and Applications Center (COSMIAC) is designing a highly affordable research satellite called LEISA (Low Earth Ionospheric Spectrum Analyzer) to characterize Ionospheric properties that affect electromagnetic wave propagation. By measuring spectral distortion of both natural and man-made impulses LEISA will measure Total Electron Content (TEC), magnetic field strength, refractive effects, plasma properties, and higher-order electron density profile effects. Additionally, LEISA may shed light on the relationships between lightning effects and thunderstorm weather in the troposphere and the potential relationship between the acoustic/seismic events around thunderstorms and Ionospheric weather. The LEISA design effort has led to a number of innovations that may be relevant to other small science spacecraft. The design is particularly challenging because of the need to implement broadband RF reception from 20-200 MHz as well as to capture and process the resulting signals within a 1u spacecraft (10cm x 10cm x 10cm) with less than 2 watts of average available power. One particular challenge is the deployable electrically small biconic wideband UHF antenna that deploys to approximately 1.5m in length and .5 m in width. The resulting antenna system deploys from a diminutive 500 cubic centimeter volume. The remaining electronics must fit within the remaining 500 cubic centimeters, leading the team to develop a system-on-a-chip (SoC) design using a Xilinx Spartan 6 FPGA. The resulting circuit handles the spectrogram capture as well as all command and data handling functions within an average power footprint of approximately 200mW, reserving energy for analog-to-digital conversion (ADC) during capture events. LEISA builds upon prior work by Los Alamos National Laboratory with FORTE and Cibola Flight Experiment. In addition to being much more affordable, LEISA offers the potential of geo-locating events

  16. Ionospheric response to geomagnetic disturbances in the north-eastern region of Asia during the minimum of 23rd cycle of solar activity

    Science.gov (United States)

    Kurkin, V. I.; Pirog, O. M.; Polekh, N. M.; Mikhalev, A. V.; Poddelsky, I. N.; Stepanov, A. E.

    2008-12-01

    We present the results of studies of the subauroral and mid-latitude ionosphere variations in the north-eastern region of Asia. We used the data from network of vertical and oblique-incidence sounding ionosondes and optical measurements. Long-term experiments on the radio paths Magadan-Irkutsk and Norilsk-Irkutsk were carried out within the period 2005-2007. Vertical sounding stations operated in standard regime. Observation of airglow near Irkutsk was provided by the zenith photometer that measured intensities of 557.7 and 630.0 nm atomic oxygen emissions. The results may be summarized as follows. (1) Large daytime negative disturbances are observed during the main and recovery phases mainly at high latitudes, whereas the positive disturbances observed during the main phase at mid latitudes. The disturbances changed their sign between Yakutsk and Irkutsk. (2) During the main and recovery storm phases the fall of foF2 associated with the equatorward wall of the main ionospheric trough is observed in the afternoon and evening. (3) Fluctuations of the electron density more intensive at mid latitudes during the storm main phase are observed during all considered periods. They are classed as traveling ionospheric disturbances (TID). Such sharp gradients of electron density are responsible for the strong changes in the characteristics of the radio wave propagation, particularity MOF. (4) A large-scale ionospheric disturbance is noted at the meridional chain of ionosonds in December 2006 as the sharp increase of foF2. It appears in the evening in the minimum of Dst at high latitude and propagate to equator. (5) A maximum of 630 nm emission above Irkutsk corresponds to the foF2 increase. (6) The obtained experimental data on the net of vertical and oblique-incidence sounding with high time resolution show that such net is the effective facility to study the conditions of the radio wave propagation and can be used for the diagnostic of the ionosphere.

  17. Scientific Studies of the High-Latitude Ionosphere with the Ionosphere Dynamics and ElectroDynamics - Data Assimilation (IDED-DA) Model

    Science.gov (United States)

    2014-09-23

    titlelScientific Studies of the High-Latitude Ionosphere with the Ionosphere Dynamics and Electrodynamics-Data Assimilation (IDED-DA) Model...awardnumberl]N00014-13-l-0267 [awardnumber2] [awardnumbermore] [keywords]Ionosphere, Assimilation , Simulations [specialcat] [pillRobert W...totalminoritypostdocs] [bestaccomplishment] With only ground magnetometer measurements, our high-latitude data assimilation model can track the

  18. The value of travel time variance

    OpenAIRE

    Fosgerau, Mogens; Engelson, Leonid

    2010-01-01

    This paper considers the value of travel time variability under scheduling preferences that are de�fined in terms of linearly time-varying utility rates associated with being at the origin and at the destination. The main result is a simple expression for the value of travel time variability that does not depend on the shape of the travel time distribution. The related measure of travel time variability is the variance of travel time. These conclusions apply equally to travellers who can free...

  19. Communication from Carlson Wagonlit Travel

    CERN Multimedia

    2009-01-01

    We are pleased to inform our customers that the range of tourist guides and roadmaps on sale in our offices has now been extended. We aim to help you prepare your upcoming holiday or business trip in any way we can. Please do not hesitate to contact us should you need any further information. The team at CARLSON WAGONLIT TRAVEL

  20. Writing Travel in the Anthropocene

    DEFF Research Database (Denmark)

    Graulund, Rune

    2016-01-01

    by a rapid increase in the mobility of people, goods and information, but primarily examine the impact of the Anthropocene on the notion of travel. For in a world in which the peak of Mount Everest is littered with toilet paper and the Great Pacific Garbage Patch is potentially twice the size of the US...

  1. A Travel To Hong Kong

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    This summer holiday,I had travelled to Hong Kong with many other students.We went to Hong Kong by plane.Hong Kong is very small,but there are many people living there. In Hong Kong,all of the buildings are very tall.There are lots of shops there and

  2. Twitter for travel medicine providers.

    Science.gov (United States)

    Mills, Deborah J; Kohl, Sarah E

    2016-03-01

    Travel medicine practitioners, perhaps more so than medical practitioners working in other areas of medicine, require a constant flow of information to stay up-to-date, and provide best practice information and care to their patients. Many travel medicine providers are unaware of the popularity and potential of the Twitter platform. Twitter use among our travellers, as well as by physicians and health providers, is growing exponentially. There is a rapidly expanding body of published literature on this information tool. This review provides a brief overview of the ways Twitter is being used by health practitioners, the advantages that are peculiar to Twitter as a platform of social media, and how the interested practitioner can get started. Some key points about the dark side of Twitter are highlighted, as well as the potential benefits of using Twitter as a way to disseminate accurate medical information to the public. This article will help readers develop an increased understanding of Twitter as a tool for extracting useful facts and insights from the ever increasing volume of health information. © International Society of Travel Medicine, 2016. All rights reserved. Published by Oxford University Press. For permissions, please e-mail: journals.permissions@oup.com.

  3. CITM: Asian's Largest Travel Show

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Jointly hosted by China National Tourism Administration, Yunnan Provincial People's Government and General Administration of Civil Aviation of China, China International Travel Mart (CITM) is a major step to develop inbound tourism, to increase tourism receipts in foreign exchanges, and to enhance the international status of China's tourism industry.

  4. Bacterial infec tions in travellers

    African Journals Online (AJOL)

    This review will concentrate on common infections, namely bacterial ... as pyrexia of unknown origin. ... cause of fever without lung involvement (Pontiac fever). Gram- negative ... Frequent use of DEET-based insect repel- lants .... No firm evidence for chemoprophylaxis, but some studies show benefit in short-term travellers.

  5. Your Travel Dollar. Money Management.

    Science.gov (United States)

    Baran, Nancy H., Ed.

    This illustrated guide was designed to familiarize consumers with planning a vacation trip, whether domestic or abroad. The guide covers setting up a budget; package tours; cruises and charter flights; travel agencies and clubs; and arranging stays in hotels/motels, rental condominiums, bed-and-breakfasts, hostels, campsites, and private…

  6. Time Travel in the Library

    Science.gov (United States)

    Brown, Donna W.

    2005-01-01

    A Time Travel project in the library gives enthusiasm to students to connect with the past and reinforces their research skills while instilling respect for the past years. The librarian should choose one specific decade to highlight in the library and create an extravaganza that would allow memorabilia from that time period to be located without…

  7. Travel to the Rio Olympics

    Centers for Disease Control (CDC) Podcasts

    2016-07-21

    Learn how to stay healthy and safe when travelling to the 2016 Olympic Games in Rio de Janeiro.  Created: 7/21/2016 by National Center for Emerging and Zoonotic Infectious Diseases (NCEZID).   Date Released: 7/21/2016.

  8. Research on ionospheric tomography based on variable pixel height

    Science.gov (United States)

    Zheng, Dunyong; Li, Peiqing; He, Jie; Hu, Wusheng; Li, Chaokui

    2016-05-01

    A novel ionospheric tomography technique based on variable pixel height was developed for the tomographic reconstruction of the ionospheric electron density distribution. The method considers the height of each pixel as an unknown variable, which is retrieved during the inversion process together with the electron density values. In contrast to conventional computerized ionospheric tomography (CIT), which parameterizes the model with a fixed pixel height, the variable-pixel-height computerized ionospheric tomography (VHCIT) model applies a disturbance to the height of each pixel. In comparison with conventional CIT models, the VHCIT technique achieved superior results in a numerical simulation. A careful validation of the reliability and superiority of VHCIT was performed. According to the results of the statistical analysis of the average root mean square errors, the proposed model offers an improvement by 15% compared with conventional CIT models.

  9. 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.

  10. 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...

  11. ADAPTIVE MODEL REFINEMENT FOR THE IONOSPHERE AND THERMOSPHERE

    Data.gov (United States)

    National Aeronautics and Space Administration — ADAPTIVE MODEL REFINEMENT FOR THE IONOSPHERE AND THERMOSPHERE ANTHONY M. D’AMATO∗, AARON J. RIDLEY∗∗, AND DENNIS S. BERNSTEIN∗∗∗ Abstract. Mathematical models of...

  12. Identification of rocket-induced acoustic waves in the ionosphere

    Science.gov (United States)

    Mabie, Justin; Bullett, Terence; Moore, Prentiss; Vieira, Gerald

    2016-10-01

    Acoustic waves can create plasma disturbances in the ionosphere, but the number of observations is limited. Large-amplitude acoustic waves generated by energetic sources like large earthquakes and tsunamis are more readily observed than acoustic waves generated by weaker sources. New observations of plasma displacements caused by rocket-generated acoustic waves were made using the Vertically Incident Pulsed Ionospheric Radar (VIPIR), an advanced high-frequency radar. Rocket-induced acoustic waves which are characterized by low amplitudes relative to those induced by more energetic sources can be detected in the ionosphere using the phase data from fixed frequency radar observations of a plasma layer. This work is important for increasing the number and quality of observations of acoustic waves in the ionosphere and could help improve the understanding of energy transport from the lower atmosphere to the thermosphere.

  13. Fine structure in the ionospheric D-region

    Science.gov (United States)

    Thrane, E. V.; Grandal, B.; Fla, T.; Brekke, A.

    1981-07-01

    The 'partial reflection' method developed by Gardner and Pawsey (1953) turned out to be a useful tool for studies of the ionospheric D-region. A comparison is conducted of the observations of weak radio echoes from the ionospheric D-region, with model computations of radio wave scattering. The model computations are based on volume scattering from irregular ionospheric structures measured in situ in a sounding rocket. The experimental data were obtained from a rocket-borne electrostatic ion-current probe combined with simultaneous recordings of partial reflections. It is found that the intensity and height variation of partial reflections measured during the rocket flight are consistent with volume scattering from the ionospheric irregularities measured by the electrostatic probe in the rocket. The power spectra of ion density fluctuations derived from the rocket data indicate that these fluctuations are caused by turbulence in the neutral air. It is, therefore, concluded that such turbulence is an important source of partial reflections.

  14. 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.

  15. Numerical modelling of the thermosphere-ionosphere coupling during substorm

    Science.gov (United States)

    Korenkov, Yu. N.; Bessarab, F. S.; Klimenko, V. V.; Surotkin, V. A.; Smertin, V. M.

    The numerical calculation results of the thermospheric parameters ([O]/[N_2] ratio and Tn) and critical frequencies of F2-region of ionosphere, foF2, in the global scale for the recovery phase of the substorm are presented. The calculations were executed with the use of the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) was constructed in the Kaliningrad Observatory of the IZMIRAN and modified in the Polar Geophysical Institute. The influences of the global distribution of Joule dissipation on the neutral atmosphere and ionosphere parameters are discussed. It is emphasised that the Joule dissipation in the neutral atmosphere is a main cause of the negative disturbance in the F2 region of the ionosphere.

  16. Theoretical studies on ionospheric irregularities and ion diode performance

    Science.gov (United States)

    Sudan, R. N.

    1993-08-01

    Work accomplished is divided into three parts: ionospheric physics; ion diodes, magnetic insulation, and plasma opening switches; and subgrid modeling in numerical computations and other research. Abstracts of published and conference papers are presented.

  17. Ionogram inversion for a tilted ionosphere

    Energy Technology Data Exchange (ETDEWEB)

    Wright, J.W. (British Antartic Survey, Cambridge (England))

    1990-12-01

    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.

  18. Cyclotron resonance absorption in ionospheric plasma

    Energy Technology Data Exchange (ETDEWEB)

    Villalon, E. (Northeastern Univ., Boston, MA (USA) Geophysics Lab., Hanscom AFB, MA (USA))

    1991-04-01

    The mode conversion of ordinary polarized electromagnetic waves into electrostatic cyclotron waves in the inhomogeneous ionospheric plasma is investigated. Near resonance the warm plasma dispersion relation is a function of the angle {theta} between the geomagnetic field and the density gradient and of the wave frequency {omega}, where {Omega} {le} {omega} {le} 2{Omega} and {Omega} is the electron cyclotron frequency. The differential equations describing the electric field amplitudes near the plasma resonance are studied, including damping at the second gyroharmonic. For certain values of {omega} and {theta} (e.g., {theta} < 45{degree}, {omega} {approximately} 2{Omega}) the wave equations reduce to the parabolic cylinder equation. The energy transmission coefficients and power absorbed by the cyclotron waves are calculated. The vertical penetration of the plasma wave amplitudes is iestimated using a WKB analysis of the wave equation.

  19. Understanding ionospheric instabilities eludes current approaches

    Science.gov (United States)

    Bhattacharya, Atreyee

    2012-07-01

    Ionized gases are heavily concentrated in the ionosphere's F zone, the region between 200 and 500 kilometers in altitude, which is critical for transmitting long-distance radio signals on Earth. However, instabilities in the F region plasma, which can last from seconds to hours and can be spread over centimeters to tens of kilometers, disrupt transmission of radio signals. The plasma instabilities, restricted to the equatorial region following sunset, are called equatorial spread F (ESF). Earth-based instruments perceive ESF events as “twinkling” radio signals. ESF events, first detected in the 1930s, affect the performance and reliability of space-borne and ground-based electronic systems; they can disrupt satellite operations and related communications and navigation systems.

  20. 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.