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Sample records for mid-latitude f-region drifts

  1. Imaging observations of nighttime mid-latitude F-region field-aligned irregularities by an MU radar ultra-multi-channel system

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    S. Saito

    2008-08-01

    Full Text Available Mid-latitude F-region field-aligned irregularities (FAIs were studied by using the middle-and-upper atmosphere (MU radar ultra-multi-channel system with the radar imaging technique. On 12 June 2006, F-region FAI echoes with a period of about one hour were observed intermittently. These echoes were found to be embedded in medium-scale traveling ionospheric disturbances (MSTIDs observed as variations of total electron content (TEC. The echoes drifting away from (toward the radar were observed in the depletion (enhancement phase of the MSTID. The Doppler velocity of the echoes is consistent with the range rates in the the range-time-intensity (RTI maps. Fine scale structures with a spatial scale of 10 km or less were found by the radar imaging analysis. Those structures with positive Doppler velocities (moving away from the radar appeared to drift north- (up- westward, and those with negative Doppler velocities south- (down- eastward approximately along the wavefronts of the MSTID. FAIs with positive Doppler velocities filling TEC depletion regions were observed.

  2. Enhanced antisunward convection and F region scintillations at mid-latitudes during storm onset

    International Nuclear Information System (INIS)

    Foster, J.C.; Aarons, J.

    1988-01-01

    Millstone Hill radar observations over a wide span of latitudes detail the onset of 300 m/s antisunward (westward) convection at mid and low latitudes in the morning sector as a region of storm-enhanced sunward convection retreats poleward. Ring current observations reported by Lui et al. (1987) suggest that the magnetospheric shielding layer was coincident with the observed reversal between sunward and antisunward convection. A strong southward component of the F region neutral wind is observed at latitudes equatorward of the convection reversal. These observations are in agreement with the model of Spiro et al. (1988), who find that storm-enhanced neutrral winds at latitudes equatorward of the shielding layer can generate a long-lived perturbation electric field in the inner magnetosphere. The observations show the growth of the subauroral electric field as the shielding boundary moves poleward. They observe 136-MHz scintillations in both the auroral sunwarrd convection region and the region of subauroral antisunward convection when the convection electric fields exceed 5 mV/m

  3. Response of equatorial, low- and mid-latitude F-region in the American sector during the intense geomagnetic storm on 24-25 October 2011

    Science.gov (United States)

    de Jesus, R.; Sahai, Y.; Fagundes, P. R.; de Abreu, A. J.; Brunini, C.; Gende, M.; Bittencourt, J. A.; Abalde, J. R.; Pillat, V. G.

    2013-07-01

    In this paper, we present and discuss the response of the ionospheric F-region in the American sector during the intense geomagnetic storm which occurred on 24-25 October 2011. In this investigation ionospheric sounding data obtained of 23, 24, 25, and 26 October 2011 at Puerto Rico (United States), Jicamarca (Peru), Palmas, São José dos Campos (Brazil), and Port Stanley, are presented. Also, the GPS observations obtained at 12 stations in the equatorial, low-, mid- and high-mid-latitude regions in the American sector are presented. During the fast decrease of Dst (about ˜54 nT/h between 23:00 and 01:00 UT) on the night of 24-25 October (main phase), there is a prompt penetration of electric field of magnetospheric origin resulting an unusual uplifting of the F region at equatorial stations. On the night of 24-25 October 2011 (recovery phase) equatorial, low- and mid-latitude stations show h'F variations much larger than the average variations possibly associated with traveling ionospheric disturbances (TIDs) caused by Joule heating at high latitudes. The foF2 variations at mid-latitude stations and the GPS-VTEC observations at mid- and low-latitude stations show a positive ionospheric storm on the night of 24-25 October, possibly due to changes in the large-scale wind circulation. The foF2 observations at mid-latitude station and the GPS-VTEC observations at mid- and high-mid-latitude stations show a negative ionospheric storm on the night of 24-25 October, probably associated with an increase in the density of molecular nitrogen. During the daytime on 25 October, the variations in foF2 at mid-latitude stations show large negative ionospheric storm, possibly due to changes in the O/N2 ratio. On the night of 24-25, ionospheric plasma bubbles (equatorial irregularities that extended to the low- and mid-latitude regions) are observed at equatorial, low- and mid-latitude stations. Also, on the night of 25-26, ionospheric plasma bubbles are observed at equatorial

  4. Simulated East-west differences in F-region peak electron density at Far East mid-latitude region

    Science.gov (United States)

    Ren, Z.; Wan, W.

    2017-12-01

    In the present work, using Three-Dimensional Theoretical Ionospheric Model of the Earth in Institute of Geology and Geophysics, Chinese Academy of Sciences (TIME3D-IGGCAS), we simulated the east-west differences in Fregion peak electron density (NmF2) at Far East mid-latitude region.We found that, after removing the longitudinal variations of neutral parameters, TIME3D-IGGCAS can better represent the observed relative east-west difference (Rew) features. Rew is mainly negative (West NmF2 > East NmF2) at noon and positive (East NmF2 >West NmF2) at evening-night. The magnitude of daytime negative Rew is weak at local winter and strong at local summer, and the daytime Rew show two negative peaks around two equinoxes. With the increasing of solar flux level, the magnitude of Rew mainly become larger, and two daytime negative peaks slight shifts to June Solstice. With the decreasing of geographical latitude, Rew mainly become positive, and two daytime negative peaks slight shifts to June Solstice. Our simulation also suggested that the thermospheric zonal wind combined with the geomagnetic field configuration play a pivotal role in the formation of the ionospheric east-west differences at Far East midlatitude region.

  5. East-west ion drifts at mid-latitudes observed by Dynamics Explorer 2

    International Nuclear Information System (INIS)

    Heelis, R.A.; Coley, W.R.

    1992-01-01

    Zonal ion drifts measured from the polar orbiting DE 2 spacecraft are examined to determine the effects of dynamo electric fields and penetration of high latitude electric fields at middle latitudes. Construction of a local time distribution from satellite data results in a mixture of local time and season as well as a range of magnetic activity encompassing Kp ≤ 2 and Kp ≥ 3. Thus some combination of magnetospheric effects, expected to dominate during disturbed times, are seen during both quiet and disturbed times and solar tidal influences are most easily observed during quiet times. During quiet times, at invariant latitudes near 25 degrees, the solar diurnal tide dominates the local time distribution of the ion drift. At latitudes above 50 degrees a diurnal component of comparable magnitude is also present, but its magnetospheric origin produces a shift in phase of almost 180 degrees from the lower latitude diurnal tide. In the intervening region, between 20 degrees and 50 degrees invariant latitude, semidurnal and terdiurnal components in the local time distribution of the drift velocity are also seen. These components are generally larger than those seen by ground based radars during quiet times and may be attributable in part to a difference in solar activity and in part to a combination of the solar tides and magnetospheric penetration fields

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

    African Journals Online (AJOL)

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

  7. The Occurrence of Small-scale Irregularities in the Mid-latitude Ionosphere from SuperDARN HF Radar Observations

    Science.gov (United States)

    Ruohoniemi, J. M.; Baker, J. B.; Maimaiti, M.; Oksavik, K.; Erickson, P. J.; Scales, W.; Eltrass, A.

    2017-12-01

    The mid-latitude radars of the SuperDARN network routinely observe backscatter from nighttime decameter-scale F region irregularities at latitudes well equatorward of the auroral boundary. This Sub-Auroral Ionospheric Scatter (SAIS) is strongly distinguished from auroral and SAPS backscatter by low Doppler velocities ( tens m/s) and stable, long-lived ( hours) occurrence in discrete events that are extended in both latitude and longitude. Statistical and event studies of SAIS with the SuperDARN radars indicate that the subauroral F region ionosphere is replete with irregularities during events, at least poleward of the 50° Λ horizon of the North American mid-latitude radars, and that radar observation of SAIS backscatter is then primarily limited by the magnetic aspect condition. Joint experiments with incoherent scatter radar have furnished sets of plasma measurements suitable for testing theories of plasma instability. Modeling work stimulated by the observations has explored the temperature-gradient instability (TGI) and the gradient drift instability (GDI) as possible sources of the irregularities. In this talk we review the findings on the occurrence of the SAIS category of mid-latitude F region irregularities, summarize the results of the modeling work, and discuss future research directions.

  8. Nightside Quiet-Time Mid-Latitude Ionospheric Convection and Its Connection to Penetration Electric Fields

    Science.gov (United States)

    Ruohoniemi, J. M.; Maimaiti, M.; Baker, J. B.; Ribeiro, A. J.

    2017-12-01

    Previous studies have shown that during quiet geomagnetic conditions F-region subauroral ionospheric plasma exhibits drifts of a few tens of m/s, predominantly in the westward direction. However, the exact driving mechanisms for this plasma motion are still not well understood. Recent expansion of SuperDARN radars into the mid-latitude region has provided new opportunities to study subauroral ionospheric convection over large areas and with greater spatial resolution and statistical significance than previously possible. Mid-latitude SuperDARN radars tend to observe subauroral ionospheric backscatter with low Doppler velocities on most geomagnetically quiet nights. In this study, we have used two years of data obtained from the six mid-latitude SuperDARN radars in the North American sector to derive a statistical model of quiet-time nightside mid-latitude plasma convection between 52°- 58° magnetic latitude. The model is organized in MLAT-MLT coordinates and has a spatial resolution of 1°x 7 min with each grid cell typically counting thousands of velocity measurements. Our results show that the flow is predominantly westward (20 - 60 m/s) and weakly northward (0 -20 m/s) near midnight but with a strong seasonal dependence such that the flows tend to be strongest and most spatially variable in winter. These statistical results are in good agreement with previously reported observations from ISR measurements but also show some interesting new features, one being a significant latitudinal variation of zonal flow velocity near midnight in winter. In this presentation, we describe the derivation of the nightside quite-time subauroral convection model, analyze its most prominent features, and discuss the results in terms of the Ionosphere-Thermosphere coupling and penetration electric fields.

  9. A preliminary comparison of F region plasma drifts and E region irregularity drifts in the auroral zone

    International Nuclear Information System (INIS)

    Ecklund, W.L.; Balsley, B.B.; Carter, D.A.

    1977-01-01

    During several days in April--May 1976 the Chatanika, Alaska, incoherent scatter radar and a temporary Doppler auroral radar located at Aniak, Alaska, were directed toward ionospheric volumes along a common magnetic field line in order to compare E region and F region drifts and associated electric fields. The Chatanika radar measured F region plasma drifts via the incoherent scatter technique, while the Aniak radar measured the drifts of E region irregularities (i.e., the radar aurora). The radar geometry was arranged so that both radars measured approximately the same velocity component of a magnetically westward or eastward motion. Preliminary data show good agreement between the drift velocity components measured by the two techniques during most of the experimental period. This result indicates that relatively modest auroral radar systems may be used, with some qualifications, to determine auroral electric fields

  10. The effect of vertical drift on the equatorial F-region stability

    Science.gov (United States)

    Hanson, W. B.; Cragin, B. L.; Dennis, A.

    1986-01-01

    Time-dependent ionospheric model calculations for day-time and night-time solutions are presented. The behavior of the growth rate and ion-electron recombination rate for the Rayleigh-Taylor instability on the F-region bottomside is examined as a function of the vertical eastward electric field-magnetic field strength drift velocity. It is observed that on the bottomside F-layer the growth rate exceeds the ion-electron recombination rate even without vertical drift; however, an eastward electric field-magnetic field strength drift can produce an increase in the growth rate by an order of magnitude. The calculated data are compared with previous research and good correlation is detected. The formation of bubbles from a seeding mechanism is investigated.

  11. Equatorial F-region plasma depletion drifts: latitudinal and seasonal variations

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    A. A. Pimenta

    2003-12-01

    Full Text Available The equatorial ionospheric irregularities have been observed in the past few years by different techniques (e.g. ground-based radar, digisonde, GPS, optical instruments, in situ satellite and rocket instrumentation, and its time evolution and propagation characteristics can be used to study important aspects of ionospheric dynamics and thermosphere-ionosphere coupling. At present, one of the most powerful optical techniques to study the large-scale ionospheric irregularities is the all-sky imaging photometer system, which normally measures the strong F-region nightglow 630 nm emission from atomic oxygen. The monochromatic OI 630 nm emission images usually show quasi-north-south magnetic field-aligned intensity depletion bands, which are the bottomside optical signatures of large-scale F-region plasma irregularities (also called plasma bubbles. The zonal drift velocities of the plasma bubbles can be inferred from the space-time displacement of the dark structures (low intensity regions seen on the images. In this study, images obtained with an all-sky imaging photometer, using the OI 630 nm nightglow emission, from Cachoeira Paulista (22.7° S, 45° W, 15.8° S dip latitude, Brazil, have been used to determine the nocturnal monthly and latitudinal variation characteristics of the zonal plasma bubble drift velocities in the low latitude (16.7° S to 28.7° S region. The east and west walls of the plasma bubble show a different evolution with time. The method used here is based on the western wall of the bubble, which presents a more stable behavior. Also, the observed zonal plasma bubble drift velocities are compared with the thermospheric zonal neutral wind velocities obtained from the HWM-90 model (Hedin et al., 1991 to investigate the thermosphere-ionosphere coupling. Salient features from this study are presented and discussed.Key words. Ionosphere (ionosphere-atmosphere interactions; ionospheric irregularities; instruments and techniques

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

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    J. Park

    2013-06-01

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

  13. Equatorial F-region plasma depletion drifts: latitudinal and seasonal variations

    Directory of Open Access Journals (Sweden)

    A. A. Pimenta

    Full Text Available The equatorial ionospheric irregularities have been observed in the past few years by different techniques (e.g. ground-based radar, digisonde, GPS, optical instruments, in situ satellite and rocket instrumentation, and its time evolution and propagation characteristics can be used to study important aspects of ionospheric dynamics and thermosphere-ionosphere coupling. At present, one of the most powerful optical techniques to study the large-scale ionospheric irregularities is the all-sky imaging photometer system, which normally measures the strong F-region nightglow 630 nm emission from atomic oxygen. The monochromatic OI 630 nm emission images usually show quasi-north-south magnetic field-aligned intensity depletion bands, which are the bottomside optical signatures of large-scale F-region plasma irregularities (also called plasma bubbles. The zonal drift velocities of the plasma bubbles can be inferred from the space-time displacement of the dark structures (low intensity regions seen on the images. In this study, images obtained with an all-sky imaging photometer, using the OI 630 nm nightglow emission, from Cachoeira Paulista (22.7° S, 45° W, 15.8° S dip latitude, Brazil, have been used to determine the nocturnal monthly and latitudinal variation characteristics of the zonal plasma bubble drift velocities in the low latitude (16.7° S to 28.7° S region. The east and west walls of the plasma bubble show a different evolution with time. The method used here is based on the western wall of the bubble, which presents a more stable behavior. Also, the observed zonal plasma bubble drift velocities are compared with the thermospheric zonal neutral wind velocities obtained from the HWM-90 model (Hedin et al., 1991 to investigate the thermosphere-ionosphere coupling. Salient features from this study are presented

  14. Characteristics and sources of the electron density irregularities in the mid latitude E and Fregions

    Science.gov (United States)

    2017-05-10

    and has since been monitoring the occurrence of field-aligned irregularities ( FAIs ) in the northern middle latitudes. We investigated the...characteristics and occurrence climatology of the FAIs in the middle latitude E- and F-region ionosphere using the Daejeon VHF radar data. Depending on the...sunset and post-sunrise periods. The F-region FAIs in the mid-latitude are bounded to occur during the nighttime between local sunset and sunrise [J

  15. Morphology of F-region vertical E×B drifts in the African sector using ionosonde measurements

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    C. C. Oluwafemi

    2007-06-01

    Full Text Available F-region vertical velocities are derived from the ground-based ionosonde data for Ibadan (7.4°N, 3.9°E; dip 6°S: an equatorial station in the African zone, to study the general characteristics of electrodynamics of equatorial ionosphere, such as their variation with season, solar cycle, and magnetic activity at different local time sectors. The results show profound seasonal and geomagnetic effects. Except for equinoctial period, there is an excellent consistency in the magnitudes (nearly 20 m/s and patterns of upward daytime F-region drifts at low and high solar activity periods. Evening F-region exhibits strong motion with absolute mean value for quiet-time (15 m/s greater than on disturbed-time (10 m/s. The average downward quiet midnight-early morning hours sector value is well below than 10 m/s. The evening reversal time is earliest and latest during solstitial periods. Prereversal peak is season dependent and varies strongly with magnetic activity. We show that prereversal peak, daytime, and nighttime maximum drifts saturate at particular values of F10.7 cm solar radio flux index, effects not noticed with corresponding sunspot number. Our observations confirm several previous results from other equatorial sites utilizing different experimental techniques.

  16. Equatorial 150 km echoes and daytime F region vertical plasma drifts in the Brazilian longitude sector

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    F. S. Rodrigues

    2013-10-01

    Full Text Available Previous studies showed that conventional coherent backscatter radar measurements of the Doppler velocity of the so-called 150 km echoes can provide an alternative way of estimating ionospheric vertical plasma drifts during daytime hours (Kudeki and Fawcett, 1993; Chau and Woodman, 2004. Using observations made by a small, low-power 30 MHz coherent backscatter radar located in the equatorial site of São Luís (2.59° S, 44.21° W; −2.35° dip lat, we were able to detect and monitor the occurrence of 150 km echoes in the Brazilian sector. Using these measurements we estimated the local time variation of daytime vertical ionospheric drifts in the eastern American sector. Here, we present a few interesting cases of 150 km-echoes observations made by the São Luís radar and estimates of the diurnal variation of vertical drifts. These cases exemplify the variability of the vertical drifts in the Brazilian sector. Using same-day 150 km-echoes measurements made at the Jicamarca Radio Observatory in Peru, we also demonstrate the variability of the equatorial vertical drifts across the American sector. In addition to first estimates of the absolute vertical plasma drifts in the eastern American (Brazilian sector, we also present observations of abnormal drifts detected by the São Luís radar associated with the 2009 major sudden stratospheric warming event.

  17. Drift motions of small-scale irregularities in the high-latitude F region: An experimental comparison with plasma drift motions

    International Nuclear Information System (INIS)

    Ruohoniemi, J.M.; Greenwald, R.A.; Baker, K.B.; Villain, J.P.; McCready, M.A.

    1987-01-01

    On the evening of January 6, 1986, coordinated observations were carried out with the Johns Hopkins University Applied Physics Laboratory HF coherent scatter radar at Goose Bay, Labrador, and the SRI International incoherent scatter radar at Sondre Stromfjord, Greenland. The common field of view comprised a section of high-latitude F region ionosphere centered on the great circle plane between the radar sites. Over a 40-min period, the HF radar observed strong backscatter from small-scale (13.9 m) field-aligned irregularities. The bulk line-of-sight drift velocity of the irregularities is deduced from the backscatter data. The returns collected simultaneously with the incoherent scatter radar are processed for estimates of the mean line-of-sight ion velocity. Approximately 100 distinct comparisons are possible between the two sets of velocity estimates. Reversals exceeding 1,000 m/s are present in both. In this paper, the authors demonstrate a correspondence between the measured irregularity and ion drifts that is consistent with the supposition that the motion of the irregularities is dominated by convective drift of the ambient plasma. This indicates that the small-scale irregularities detected by HF radars in the high-latitude F region can serve as tracers of ionospheric convective drift

  18. A numerical study of ionospheric profiles for mid-latitudes

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    S.-R. Zhang

    1995-05-01

    Full Text Available This paper presents a numerical model and results for the mid-latitude ionospheric profile below the peak of the F2-layer. The basis of the model is the solving of equations for four ionic species O+, NO+, O+2 and N+2, as well as the meta-stable O+(2D and O+(2P. Diffusion and wind-induced drifts and 21 photo-chemical reactions are also taken into account. Neutral atmospheric density and temperature are derived from the MSIS86 model and solar extreme ultraviolate irradiance from the EUV91 model. In an effort to obtain a more realistic ionospheric profile, the key point at foF2 and hmF2 is fitted from the simulation to observations. The model also utilizes the vertical drifts derived from ionosonde data with the help of the Servo model. It is shown that the ionospheric height of peak can be reproduced more accurately under the derived vertical drifts from the Servo theory than with the HWM90 model. Results from the simulation are given for Wuchang (30.5°N, 114.4°E and Wakkanai (45.6°N, 141.7°E, showing the profile changes with season and solar activity, and the E-F valley structure (the depth and the width. This simulation also reveals the importance of meta-stable ions and dynamical transport processes on the formation of the F1-ledge and F1-F2 valley.

  19. Physical Modeling of the Processes Responsible for the Mid-Latitude Storm Enhanced Plasma Density

    Science.gov (United States)

    Fuller-Rowell, T. J.; Maruyama, N.; Fedrizzi, M.; Codrescu, M.; Heelis, R. A.

    2016-12-01

    Certain magnetic local time sectors at mid latitudes see substantial increases in plasma density in the early phases of a geomagnetic storm. The St. Patrick's Day storms of 2013 and 2015 were no exception, both producing large increases of total electron content at mid latitudes. There are theories for the build up of the storm enhanced density (SED), but can current theoretical ionosphere-thermosphere coupled models actually reproduce the response for an actual event? Not only is it necessary for the physical model to contain the appropriate physics, they also have to be forced by the correct drivers. The SED requires mid-latitude zonal transport to provide plasma stagnation in sunlight to provide the production. The theory also requires a poleward drift perpendicular to the magnetic field to elevate the plasma out of the body of the thermosphere to regions of substantially less loss rate. It is also suggested that equatorward winds are necessary to further elevate the plasma to regions of reduced loss. However, those same winds are also likely to transport molecular nitrogen rich neutral gas equatorward, potentially canceling out the benefits of the neutral circulation. Observations of mid-latitude zonal plasma flow are first analyzed to see if this first necessary ingredient is substantiated. The drift observations are then used to tune the driver to determine if, with the appropriate electric field driver, the latest physical models can reproduce the substantial plasma build up. If it can, the simulation can also be used to assess the contribution of the equatorward meridional wind; are they an asset to the plasma build up, or does the enhanced molecular species they carry counteract their benefit.

  20. Analysis of Mid-Latitude Plasma Density Irregularities in the Presence of Finite Larmor Radius Effects

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    Sotnikov, V. I.; Kim, T. C.; Mishin, E. V.; Kil, H.; Kwak, Y. S.; Paraschiv, I.

    2017-12-01

    Ionospheric irregularities cause scintillations of electromagnetic signals that can severely affect navigation and transionospheric communication, in particular during space storms. At mid-latitudes the source of F-region Field Aligned Irregularities (FAI) is yet to be determined. They can be created in enhanced subauroral flow channels (SAI/SUBS), where strong gradients of electric field, density and plasma temperature are present. Another important source of FAI is connected with Medium-scale travelling ionospheric disturbances (MSTIDs). Related shear flows and plasma density troughs point to interchange and Kelvin-Helmholtz type instabilities as a possible source of plasma irregularities. A model of nonlinear development of these instabilities based on the two-fluid hydrodynamic description with inclusion of finite Larmor radius effects will be presented. This approach allows to resolve density irregularities on the meter scale. A numerical code in C language to solve the derived nonlinear equations for analysis of interchange and flow velocity shear instabilities in the ionosphere was developed. This code will be used to analyze competition between interchange and Kelvin-Helmholtz instabilities in the mid-latitude region. The high-resolution simulations with continuous density and velocity profiles will be driven by the ambient conditions corresponding to the in situ data obtained during the 2016 Daejeon (Korea) and MU (Japan) radar campaign and data collected simultaneously by the Swarm satellites passed over Korea and Japan. PA approved #: 88ABW-2017-3641

  1. Mid-latitude afforestation shifts general circulation and tropical precipitation.

    Science.gov (United States)

    Swann, Abigail L S; Fung, Inez Y; Chiang, John C H

    2012-01-17

    We show in climate model experiments that large-scale afforestation in northern mid-latitudes warms the Northern Hemisphere and alters global circulation patterns. An expansion of dark forests increases the absorption of solar energy and increases surface temperature, particularly in regions where the land surface is unable to compensate with latent heat flux due to water limitation. Atmospheric circulation redistributes the anomalous energy absorbed in the northern hemisphere, in particular toward the south, through altering the Hadley circulation, resulting in the northward displacement of the tropical rain bands. Precipitation decreases over parts of the Amazon basin affecting productivity and increases over the Sahel and Sahara regions in Africa. We find that the response of climate to afforestation in mid-latitudes is determined by the amount of soil moisture available to plants with the greatest warming found in water-limited regions. Mid-latitude afforestation is found to have a small impact on modeled global temperatures and on global CO(2), but regional heating from the increase in forest cover is capable of driving unintended changes in circulation and precipitation. The ability of vegetation to affect remote circulation has implications for strategies for climate mitigation.

  2. Tropical influence on boreal summer mid-latitude stationary waves

    Energy Technology Data Exchange (ETDEWEB)

    Douville, Herve [Meteo-France/CNRM-GAME, Toulouse (France); CNRM/GMGEC/VDR, Toulouse (France); Bielli, S.; Deque, M.; Tyteca, S.; Voldoire, A. [Meteo-France/CNRM-GAME, Toulouse (France); Cassou, C. [CNRS-Cerfacs, Toulouse (France); Hall, N.M.J. [CNES/LEGOS, Toulouse (France)

    2011-11-15

    While organized tropical convection is a well-known source of extratropical planetary waves, state-of-the-art climate models still show serious deficiencies in simulating accurately the atmospheric response to tropical sea surface temperature (SST) anomalies and the associated teleconnections. In the present study, the remote influence of the tropical atmospheric circulation is evaluated in ensembles of global boreal summer simulations in which the Arpege-Climat atmospheric General Circulation Model (GCM) is nudged towards 6-h reanalyses. The nudging is applied either in the whole tropical band or in a regional summer monsoon domain. Sensitivity tests to the experimental design are first conducted using prescribed climatological SST. They show that the tropical relaxation does not improve the zonal mean extratropical climatology but does lead to a significantly improved representation of the mid-latitude stationary waves in both hemispheres. Low-pass filtering of the relaxation fields has no major effect on the model response, suggesting that high-frequency tropical variability is not responsible for extratropical biases. Dividing the nudging strength by a factor 10 only decreases the magnitude of the response. Model errors in each monsoon domain contribute to deficiencies in the model's mid-latitude climatology, although an exaggerated large-scale subsidence in the central equatorial Pacific appears as the main source of errors for the representation of stationary waves in the Arpege-Climat model. Case studies are then conducted using either climatological or observed SST. The focus is first on summer 2003 characterized by a strong and persistent anticyclonic anomaly over western Europe. This pattern is more realistic in nudging experiments than in simulations only driven by observed SST, especially when the nudging domain is centred over Central America. Other case studies also show a significant tropical forcing of the summer mid-latitude stationary waves

  3. Trapped waves on the mid-latitude β-plane

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    Paldor, Nathan; Sigalov, Andrey

    2008-08-01

    A new type of approximate solutions of the Linearized Shallow Water Equations (LSWE) on the mid-latitude β-plane, zonally propagating trapped waves with Airy-like latitude-dependent amplitude, is constructed in this work, for sufficiently small radius of deformation. In contrast to harmonic Poincare and Rossby waves, these newly found trapped waves vanish fast in the positive half-axis, and their zonal phase speed is larger than that of the corresponding harmonic waves for sufficiently large meridional domains. Our analysis implies that due to the smaller radius of deformation in the ocean compared with that in the atmosphere, the trapped waves are relevant to observations in the ocean whereas harmonic waves typify atmospheric observations. The increase in the zonal phase speed of trapped Rossby waves compared with that of harmonic ones is consistent with recent observations that showed that Sea Surface Height features propagated westwards faster than the phase speed of harmonic Rossby waves.

  4. New Particle Formation in the Mid-Latitude Upper Troposphere

    Science.gov (United States)

    Axisa, Duncan

    Primary aerosol production due to new particle formation (NPF) in the upper troposphere and the impact that this might have on cloud condensation nuclei (CCN) concentration can be of sufficient magnitude to contribute to the uncertainty in radiative forcing. This uncertainty affects our ability to estimate how sensitive the climate is to greenhouse gas emissions. Therefore, new particle formation must be accurately defined, parametrized and accounted for in models. This research involved the deployment of instruments, data analysis and interpretation of particle formation events during the Mid-latitude Airborne Cirrus Properties Experiment (MACPEX) campaign. The approach combined field measurements and observations with extensive data analysis and modeling to study the process of new particle formation and growth to CCN active sizes. Simultaneous measurements of O3, CO, ultrafine aerosol particles and surface area from a high-altitude research aircraft were used to study tropospheric-stratospheric mixing as well as the frequency and location of NPF. It was found that the upper troposphere was an active region in the production of new particles by gas-to-particle conversion, that nucleation was triggered by convective clouds and mixing processes, and that NPF occurred in regions with high relative humidity and low surface area. In certain cases, mesoscale and synoptic features enhanced mixing and facilitated the formation of new particles in the northern mid-latitudes. A modeling study of particle growth and CCN formation was done based on measured aerosol size distributions and modeled growth. The results indicate that when SO2 is of sufficient concentration NPF is a significant source of potential CCN in the upper troposphere. In conditions where convective cloud outflow eject high concentrations of SO2, a large number of new particles can form especially in the instance when the preexisting surface area is low. The fast growth of nucleated clusters produces a

  5. Theory and observations of the low- and mid-latitude ionosphere

    International Nuclear Information System (INIS)

    Chandler, M.O.

    1982-01-01

    Measured and calculated values of electron concentration, electron temperature and ion temperature in the low- and mid-latitude ionosphere are presented and discussed. The existence of horizontal, spatial gradients in electron temperature on 13 September 1980 above Arecibo, Puerto Rico is shown. The gradients were northward with maximum values of about 1.5 km -1 . The ionosphere model presented by Young et al. (1979) was tested by comparison with another theoretical model and with observations. The tests show that the model values of electron concentration are in agreement with the observations, but that the model electron temperatures are too low. An increase in the model electron heating rate by a factor of 1.5 to 4 is shown to result in better agreement. The suggestion is made that the photoelectron transport equations are incorrect in calculating the photoelectron flux at low energies. The possibility of an error in the electron cooling rate due to interactions with positive ions could not be ruled out. The model is used to explain the observed electron temperature gradients. By assuming the existence of a poleward meridional neutral wind with a poleward velocity gradient, it is shown that the resulting change in the height of the F-region causes differences in electron temperature such as those observed at Arecibo on 13 September 1980. Comparisons of simultaneous measurements from the Arecibo and Millstone Hill observatories are presented. These observations show that significant differences existed in the electron temperature as a function of latitude on 27 June 1981

  6. Habitable periglacial landscapes in martian mid-latitudes

    Science.gov (United States)

    Ulrich, M.; Wagner, D.; Hauber, E.; de Vera, J.-P.; Schirrmeister, L.

    2012-05-01

    Subsurface permafrost environments on Mars are considered to be zones where extant life could have survived. For the identification of possible habitats it is important to understand periglacial landscape evolution and related subsurface and environmental conditions. Many landforms that are interpreted to be related to ground ice are located in the martian mid-latitudinal belts. This paper summarizes the insights gained from studies of terrestrial analogs to permafrost landforms on Mars. The potential habitability of martian mid-latitude periglacial landscapes is exemplarily deduced for one such landscape, that of Utopia Planitia, by a review and discussion of environmental conditions influencing periglacial landscape evolution. Based on recent calculations of the astronomical forcing of climate changes, specific climate periods are identified within the last 10 Ma when thaw processes and liquid water were probably important for the development of permafrost geomorphology. No periods could be identified within the last 4 Ma which met the suggested threshold criteria for liquid water and habitable conditions. Implications of past and present environmental conditions such as temperature variations, ground-ice conditions, and liquid water activity are discussed with respect to the potential survival of highly-specialized microorganisms known from terrestrial permafrost. We conclude that possible habitable subsurface niches might have been developed in close relation to specific permafrost landform morphology on Mars. These would have probably been dominated by lithoautotrophic microorganisms (i.e. methanogenic archaea).

  7. Movements of the mid-latitude ionospheric trough

    International Nuclear Information System (INIS)

    Rodger, A.S.; Pinnock, M.

    1982-01-01

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

  8. Cluster observations of mid-latitude hiss near the plasmapause

    Directory of Open Access Journals (Sweden)

    A. Masson

    2004-07-01

    Full Text Available In the vicinity of the plasmapause, around the geomagnetic equator, the four Cluster satellites often observe banded hiss-like electromagnetic emissions (BHE; below the electron gyrofrequency but above the lower hybrid resonance, from 2kHz to 10kHz. We show that below 4kHz, these waves propagate in the whistler mode. Using the first year of scientific operations of WHISPER, STAFF and WBD wave experiments on Cluster, we have identified the following properties of the BHE waves: (i their location is strongly correlated with the position of the plasmapause, (ii no MLT dependence has been found, (iii their spectral width is generally 1 to 2kHz, and (iv the central frequency of their emission band varies from 2kHz to 10kHz. All these features suggest that BHE are in fact mid-latitude hiss emissions (MLH. Moreover, the central frequency was found to be correlated with the Kp index. This suggests either that these banded emissions are generated in a given f/fce range, or that there is a Kp dependent Doppler shift between the satellites and a possible moving source of the MLH.

  9. Cosmic rays linked to rapid mid-latitude cloud changes

    Directory of Open Access Journals (Sweden)

    B. A. Laken

    2010-11-01

    Full Text Available The effect of the Galactic Cosmic Ray (GCR flux on Earth's climate is highly uncertain. Using a novel sampling approach based around observing periods of significant cloud changes, a statistically robust relationship is identified between short-term GCR flux changes and the most rapid mid-latitude (60°–30° N/S cloud decreases operating over daily timescales; this signal is verified in surface level air temperature (SLAT reanalysis data. A General Circulation Model (GCM experiment is used to test the causal relationship of the observed cloud changes to the detected SLAT anomalies. Results indicate that the anomalous cloud changes were responsible for producing the observed SLAT changes, implying that if there is a causal relationship between significant decreases in the rate of GCR flux (~0.79 GU, where GU denotes a change of 1% of the 11-year solar cycle amplitude in four days and decreases in cloud cover (~1.9 CU, where CU denotes a change of 1% cloud cover in four days, an increase in SLAT (~0.05 KU, where KU denotes a temperature change of 1 K in four days can be expected. The influence of GCRs is clearly distinguishable from changes in solar irradiance and the interplanetary magnetic field. However, the results of the GCM experiment are found to be somewhat limited by the ability of the model to successfully reproduce observed cloud cover. These results provide perhaps the most compelling evidence presented thus far of a GCR-climate relationship. From this analysis we conclude that a GCR-climate relationship is governed by both short-term GCR changes and internal atmospheric precursor conditions.

  10. Deep depletions of total electron content associated with severe mid-latitude gigahertz scintillations during geomagnetic storms

    International Nuclear Information System (INIS)

    Ogawa, T.; Kumagai, H.

    1985-01-01

    Using 136-MHz Faraday rotation data obtained at three closely spaced stations, we present evidence that severe nightime gigahertz scintillations, which appear rarely at mid-latitudes around Japan only during geomagnetic storm conditions, are closely associated with deep depletions of total electron content (TEC). The TEC depletions amount to 2--8 x 10 16 el/m 2 (10--30% of the background TEC), and their durations range from 10 min to 1 hour. These depletions move northeastward or eastward with velocities between 60 and 260 m/s. The depletions are probably not counterparts of the equatorial bubbles but seem to be formed in localized regions around Japan under complicated and peculiar ionospheric conditions. There is an indication that the oscillation of the F region caused by large-scale TID's propagating from north to south (approx.600 m/s) may initiate the generation of the depletion

  11. New results on the mid-latitude midnight temperature maximum

    Science.gov (United States)

    Mesquita, Rafael L. A.; Meriwether, John W.; Makela, Jonathan J.; Fisher, Daniel J.; Harding, Brian J.; Sanders, Samuel C.; Tesema, Fasil; Ridley, Aaron J.

    2018-04-01

    (18 %). Also seen is a northwestward propagation of the MTM signature with a latitude-dependent amplitude. This behavior suggests either a latitudinal dependence of thermosphere tidal dissipation or a night-to-night variation of the composition of the higher-order tidal modes that contribute to the production of the MTM peak at mid-latitudes. Also presented in this paper is the perturbation on the divergence of the wind fields, which is associated with the passage of each MTM peak analyzed with the 2-D interpolation.

  12. A Mid-Latitude Skywave Propagation Experiment: Overview and Results

    Science.gov (United States)

    Munton, D. C.; Calfas, R. S.; Gaussiran, T., II; Rainwater, D.; Flesichmann, A. M.; Schofield, J. R.

    2016-12-01

    We will describe a mid-latitude HF skywave propagation experiment conducted during 19-27 January, 2014. There were two primary goals to the experiment. First, we wanted to build an understanding of the impact that medium scale traveling ionospheric disturbances have on the angles of arrival of the HF signals. The second goal was to provide a diverse data set that could serve as a baseline for propagation model development and evaluation. We structured individual tests during the experiment to increase the knowledge of temporal and spatial length scales of various ionospheric features. The experiment was conducted during both day and night periods and spanned a wide range of ionospheric states. We conducted the experiment at White Sands Missile Range, New Mexico and in the surrounding area. As part of the experiment, we deployed a number of active HF transmitters, and an array of dipole antennas to provide angle of arrival measurements. We also deployed a smaller array of more novel compact electro-magnetic vector sensors (EMVSs). Other instrumentation specific to the remote sensing of the ionosphere included digisondes, GNSS receivers, beacon satellite receivers, and optical instruments. We will provide a complete description of the experiment configuration and the data products.Finally, we will provide a discussion of experimental results, focusing on ionospheric conditions during the angle-of-arrival determinations, and the impact ionospheric disturbances can have on these measurements. We use the angle-of-arrival determinations to estimate TID properties, including velocity and direction.This research is based upon work supported in part by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA), via US Navy Contract N00024-07-D-6200. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements

  13. A Comprehensive Assessment of Radio Occultation Ionospheric Measurements at Mid-Latitudes

    Science.gov (United States)

    Keele, C.; Brum, C. G. M.; Rodrigues, F. S.; Aponte, N.; Sulzer, M. P.

    2015-12-01

    The GPS radio occultation (RO) has become a widely used technique for global measurements of the ionospheric electron density (Ne). To advance our understanding of the accuracy of the RO profiles at mid latitudes, we performed a comprehensive comparison of RO measurements made by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites and observations of Ne profiles made by the Arecibo Observatory incoherent scatter radar (ISR). COSMIC is formed by six satellites in circular, 800 km altitude low-Earth orbit (LEO) at 72° inclination. The satellites orbit in their own plane, approximately 24° apart in ascending node. The satellites are equipped with dual-frequency GPS receivers capable of making measurements of the total electron content (TEC) along the signal path and, therefore, RO observations. The Arecibo ISR, located at(18.35°N, 66.75°W; ˜28.25°N dip latitude), operates at a frequency of 430 MHz with a maximum bandwidth of about 1 MHz. The large collecting area provided by the 300 m dish antenna combined with high peak power transmitters (2.0-2.5 MW) allows the radar to make accurate Ne measurements throughout the entire ionospheric F-region and topside heights. We analyzed 74 and 89 days of line feed and Gregorian data, respectively, collected between 2006 and 2014. There were 638 RO profiles measured within 10° of latitude and 20° of longitude from Arecibo Observatory and within ±10 minutes of the radar measurements. Preliminary analyses of the observations show patterns in the relationship between densities measured by the Arecibo ISR and densities estimated from the COSMIC ROs. We will present and discuss the behavior of the patterns. We will also present results of a numerical model representing the patterns and discuss the possibility of using this model to improve RO estimates of density profiles.

  14. Storm time electric field penetration observed at mid-latitude

    International Nuclear Information System (INIS)

    Yeh, H.C.; Foster, J.C.; Rich, F.J.; Swider, W.

    1991-01-01

    During the height of the February 8-9, 1986, magnetic storm the Millstone Hill radar was in the evening local time sector (1600-2200 MLT). Radar observations indicate that high speed (>1,000 m s -1 ) westward ion flow penetrated deeply below 50 degree invariant latitude (Λ) and persisted for 6 hours between 2100 UT on February 8 and 0300 UT on February 9. The double-peaked ion convection feature was pronounced throughout the period, and the separation in the dual maxima ranged from 4 degree to 10 degree. The latitude positions of the high-latitude ion drift peak and the convection reversal varied in unison. The low-latitude ion drift peak (∼49 degree Λ or L =2.3) did not show significant universal time/magnetic local time (UT/MLT) variation in its latitude location but showed a decrease in magnitude during the initial recovery phase of the storm. Using simultaneous particle (30 eV-30 keV) precipitation data from the DMSP F6 and F7 satellites, the authors find the high-latitude ion drift peak to coincide with the boundary plasma sheet/central plasma sheet transition in the high ionospheric conductivity (>15 mho) region. The low-latitude ion drift peak lay between the equatorward edges of the electron and soft ( + dominated ring current energy density in magnetic latitude. The low-latitude ion drift peak is the low-altitude signature of the electric field shielding effect associated with ring current penetration into the outer layer of the storm time plasmasphere

  15. The sub-auroral electric field as observed by DMSP and the new SuperDARN mid-latitude radars

    Science.gov (United States)

    Talaat, E. R.; Sotirelis, T.; Hairston, M. R.; Ruohoniemi, J. M.; Greenwald, R. A.; Lester, M.

    2008-12-01

    In this paper we present analyses of the sub-auroral electric field environment as observed from both space and ground. We discuss the dependency of the configuration and strength of the sub-auroral electric field on IMF and geomagnetic activity, longitudinal, seasonal, and solar cycle variability. Primarily, e use ~20 years of electric field measurement dataset derived from the suite of DMSP ion drift meters. A major component of our analysis is correctly specifying the aurora boundary, as the behavior and magnitude of these fields will be drastically different away from the high-conductance auroral oval. As such, we use the coincident particle flux measurements from the DMSP SSJ4 monitors. We also present the solar minimum observations of the sub-auroral flow newly available from the mid-latitude SuperDARN radars at Wallops and Blackstone in Virginia. Preliminary comparisons between these flows and the DMSP climatology are discussed.

  16. An introduction to mid-latitude ecotone: sustainability and environmental challenges

    Directory of Open Access Journals (Sweden)

    J. Moon

    2017-12-01

    Full Text Available The mid-latitude zone can be broadly defined as part of the hemisphere between 30°–60° latitude. This zone is home to over 50 % of the world population and encompasses about 36 countries throughout the principal region, which host most of the world’s development and poverty related problems. In reviewing some of the past and current major environmental challenges that parts of mid-latitudes are facing, this study sets the context by limiting the scope of mid-latitude region to that of Northern hemisphere, specifically between 30°–45° latitudes which is related to the warm temperate zone comprising the Mid-Latitude ecotone – a transition belt between the forest zone and southern dry land territories. The ongoing climate change reveals a substantial increase of temperature and simultaneous decrease in the amount of precipitation across vast continental regions in the mid-latitudes. According to climatic predictions, these tendencies will continue during the 21st century, which will likely increase the frequency and severity of droughts and water stress of vegetation. Along with climate change, ongoing land degradation and deforestation are observed in many regions of the mid-latitude region. For example, the Korean peninsula, which is divided into South and North Korea, is characterized by drastically different forest conditions. Deforestation in North Korea has been exacerbating at a noticeable pace due to excessive logging and human intervention. Such problems are not confined to Korean peninsula but are witnessed across vast regions of the mid-latitude region. Within this context – acquiring better understanding in the role of terrestrial ecosystems located at different latitudes is critical – for building resilience against the negative impact of climate change and for maintaining the stability of the environment and landscapes.

  17. Arctic-Mid-Latitude Linkages in a Nonlinear Quasi-Geostrophic Atmospheric Model

    Directory of Open Access Journals (Sweden)

    Dörthe Handorf

    2017-01-01

    Full Text Available A quasi-geostrophic three-level T63 model of the wintertime atmospheric circulation of the Northern Hemisphere has been applied to investigate the impact of Arctic amplification (increase in surface air temperatures and loss of Arctic sea ice during the last 15 years on the mid-latitude large-scale atmospheric circulation. The model demonstrates a mid-latitude response to an Arctic diabatic heating anomaly. A clear shift towards a negative phase of the Arctic Oscillation (AO− during low sea-ice-cover conditions occurs, connected with weakening of mid-latitude westerlies over the Atlantic and colder winters over Northern Eurasia. Compared to reanalysis data, there is no clear model response with respect to the Pacific Ocean and North America.

  18. Intensity fluctuations of mid-latitude background VLF-noises and the interplanetary magnetic field

    International Nuclear Information System (INIS)

    Gorshkov, Yu.N.; Klejmenova, N.G.

    1986-01-01

    Influence of interplanetary magnetic field (IMF) sector structure polarity and also variations of solar wind velocity and density on the intensity of mid-latitude VLF background noises are studied. For analysis continuous observations of VLF radiations in Magadan Observatory (phi=53.7 deg, L=2.7) from November, 1972 to June, 1973 were used. It is shown that IMF sector sign has no sufficient effect on the level of mid-latitude VLF background noises at the frequences f < 4-5 kHz. In magnetoperturbed periods when IMF Bsub(z)-component was directed to the South and the Earth was in the region of high-speed plasma flux, in mid-latitudes abatement of intensity of VLF background noises was seen

  19. PCA and vTEC climatology at midnight over mid-latitude regions

    Science.gov (United States)

    Natali, M. P.; Meza, A.

    2017-12-01

    The effect of the thermospheric vertical neutral wind on vertical total electron content (vTEC) variations including longitudinal anomaly, remaining winter anomaly, mid-latitude summer night anomaly, and semiannual anomaly is studied at mid-latitude regions around zero magnetic declination at midnight during high solar activity. By using the principal component analysis (PCA) numerical technique, this work studies the spatial and temporal variations of the ionosphere at midnight over mid-latitude regions during 2000-2002. PCA is applied to a time series of global vTEC maps produced by the International Global Navigation Satellite System (GNSS) Service. Four regions were studied in particular, each located at mid-latitude and approximately centered at zero magnetic declination, with two in the northern hemisphere and two in southern hemisphere, and all are located near and far from geomagnetic poles in each case. This technique provides an effective method to analyze the main ionospheric variabilities at mid-latitudes. PCA is also applied to the vTEC computed using the International Reference Ionosphere (IRI) 2012 model, to analyze the capability of this model to represent ionospheric variabilities at mid-latitude. Also, the Horizontal Wind Model 2007 (HWM07) is used to improve our climatology interpretation, by analyzing the relationship between vTEC and thermospheric wind, both quantitatively and qualitatively. At midnight, the behavior of mean vTEC values strongly responds to vertical wind variation, experiencing a decrease of about 10-15% with the action of the positive vertical component of the field-aligned neutral wind lasting for 2 h in all regions except for Oceania. Notable results include: a significant increase toward higher latitudes during summer in the South America and Asia regions, associated with the mid-latitude summer night anomaly, and an increase toward higher latitudes in winter in the North America and Oceania regions, highlighting the

  20. Hydrological indications of aeolian salts in mid-latitude deserts of ...

    Indian Academy of Sciences (India)

    Hydrological indications of aeolian salts in mid-latitude deserts of northwestern China. B Q Zhu. Supplementary data. Figure S1. Photograph views of Quaternary and modern sediments of aeolian and lacustrine/fluvial facies that consisted of clay and sand/silt sand alternations in the Taklamakan and Badanjilin Deserts.

  1. Low-latitude plasma drifts from a simulation of the global atmospheric dynamo

    International Nuclear Information System (INIS)

    Crain, D.J.; Heelis, R.A.; Bailey, G.J.; Richmond, A.D.

    1993-01-01

    The authors work with a dynamo model to address questions about plasma drifts in the E region, primarily at low latitudes. Tidal winds have been known to have a big influence on electric fields in the E region, and magnetic fields and ion drifts in the equatorial F region. Recent work has centered on self consistency in simulations, using realistic wind distributions, 3-D current distributions, and more accurate measures of the currents and conductivities. The wind dynamo in the ionosphere is well accepted as the main source of electric fields in the low and mid latitudes. The authors present a self consistent model of the plasma distribution and the dynamo driven electric potential distribution. Their results are compared with other simulations. A major concern in their model was reproducing ion drift observations in the equatorial region. Their conclusion is that the F region plays a significant role in the low latitude dyanamo effects, much larger than was previously assumed. When they build into their model realistic ionospheric conditions, allow for appropriate wind distributions, and allow a self consistent redistribution of plasma in the night, they find the model simulates measured ion drifts more closely. Their model is normalized against observations at Jicamarca. By allowing E x B drifts in the ionosphere, and F region zonal winds they can reproduce many of the night changes in the ion drifts at Jicamarca

  2. Mid-latitude mesospheric clouds and their environment from SOFIE observations

    Science.gov (United States)

    Hervig, Mark E.; Gerding, Michael; Stevens, Michael H.; Stockwell, Robert; Bailey, Scott M.; Russell, James M.; Stober, Gunter

    2016-11-01

    Observations from the Solar Occultation For Ice Experiment (SOFIE) on the Aeronomy of Ice in the Mesosphere (AIM) satellite are used to examine noctilucent clouds (NLC) and their environment at middle latitudes ( 56°N and 52°S). Because SOFIE is uniquely capable of measuring NLC, water vapor, and temperature simultaneously, the local cloud environment can be specified to examine what controls their formation at mid-latitudes. Compared to higher latitudes, mid-latitude NLCs are less frequent and have lower ice mass density, by roughly a factor of five. Compared to higher latitudes at NLC heights, mid-latitude water vapor is only 12% lower while temperatures are more than 10 K higher. As a result the reduced NLC mass and frequency at mid-latitudes can be attributed primarily to temperature. Middle and high latitude NLCs contain a similar amount of meteoric smoke, which was not anticipated because smoke abundance increases towards the equator in summer. SOFIE indicates that mid-latitude NLCs may or may not be associated with supersaturation with respect to ice. It is speculated that this situation is due in part to SOFIE uncertainties related to the limb measurement geometry combined with the non-uniform nature of NLCs. SOFIE is compared with concurrent NLC, temperature, and wind observations from Kühlungsborn, Germany (54°N) during the 2015 summer. The results indicate good agreement in temperature and NLC occurrence frequency, backscatter, and height. SOFIE indicates that NLCs were less frequent over Europe during 2015 compared to other longitudes, in contrast to previous years at higher latitudes that showed no clear longitude dependence. Comparisons of SOFIE and the Solar Backscatter Ultraviolet (SBUV) indicate good agreement in average ice water column (IWC), although differences in occurrence frequency were often large.

  3. Scotland's forgotten carbon: a national assessment of mid-latitude fjord sedimentary carbon stocks

    Directory of Open Access Journals (Sweden)

    C. Smeaton

    2017-12-01

    Full Text Available Fjords are recognised as hotspots for the burial and long-term storage of carbon (C and potentially provide a significant climate regulation service over multiple timescales. Understanding the magnitude of marine sedimentary C stores and the processes which govern their development is fundamental to understanding the role of the coastal ocean in the global C cycle. In this study, we use the mid-latitude fjords of Scotland as a natural laboratory to further develop methods to quantify these marine sedimentary C stores on both the individual fjord and national scale. Targeted geophysical and geochemical analysis has allowed the quantification of sedimentary C stocks for a number of mid-latitude fjords and, coupled with upscaling techniques based on fjord classification, has generated the first full national sedimentary C inventory for a fjordic system. The sediments within these mid-latitude fjords hold 640.7 ± 46 Mt of C split between 295.6 ± 52 and 345.1 ± 39 Mt of organic and inorganic C, respectively. When compared, these marine mid-latitude sedimentary C stores are of similar magnitude to their terrestrial equivalents, with the exception of the Scottish peatlands, which hold significantly more C. However, when area-normalised comparisons are made, these mid-latitude fjords are significantly more effective as C stores than their terrestrial counterparts, including Scottish peatlands. The C held within Scotland's coastal marine sediments has been largely overlooked as a significant component of the nation's natural capital; such coastal C stores are likely to be key to understanding and constraining improved global C budgets.

  4. Scotland's forgotten carbon: a national assessment of mid-latitude fjord sedimentary carbon stocks

    Science.gov (United States)

    Smeaton, Craig; Austin, William E. N.; Davies, Althea L.; Baltzer, Agnes; Howe, John A.; Baxter, John M.

    2017-12-01

    Fjords are recognised as hotspots for the burial and long-term storage of carbon (C) and potentially provide a significant climate regulation service over multiple timescales. Understanding the magnitude of marine sedimentary C stores and the processes which govern their development is fundamental to understanding the role of the coastal ocean in the global C cycle. In this study, we use the mid-latitude fjords of Scotland as a natural laboratory to further develop methods to quantify these marine sedimentary C stores on both the individual fjord and national scale. Targeted geophysical and geochemical analysis has allowed the quantification of sedimentary C stocks for a number of mid-latitude fjords and, coupled with upscaling techniques based on fjord classification, has generated the first full national sedimentary C inventory for a fjordic system. The sediments within these mid-latitude fjords hold 640.7 ± 46 Mt of C split between 295.6 ± 52 and 345.1 ± 39 Mt of organic and inorganic C, respectively. When compared, these marine mid-latitude sedimentary C stores are of similar magnitude to their terrestrial equivalents, with the exception of the Scottish peatlands, which hold significantly more C. However, when area-normalised comparisons are made, these mid-latitude fjords are significantly more effective as C stores than their terrestrial counterparts, including Scottish peatlands. The C held within Scotland's coastal marine sediments has been largely overlooked as a significant component of the nation's natural capital; such coastal C stores are likely to be key to understanding and constraining improved global C budgets.

  5. The importance of resolution on the response of mid-latitude transients to enhanced CO2

    International Nuclear Information System (INIS)

    Senior, C.A.

    1994-01-01

    The impact of global warming on the activity of the mid-latitude transients is not well understood. Work with simple models suggests that there will be two competing effects on transient activity. Firstly, there will be a reduction in the baroclinicity due to a smaller pole-equator temperature gradient and secondly there will be increased moisture availability in a warmer atmosphere. A comparison of the mid-latitude transients from two versions of the Hadley Centre for Climate Prediction and Research GCM run at different resolutions is presented and the importance of resolution on the simulation of the high and low frequency variability is discussed. At higher resolution, one of the largest responses of the model to a doubling of atmospheric CO 2 is an enhancement of the westerly flow in the North Atlantic, but this is much reduced at lower resolution. Consistency is sort between changes in the time mean flow and the transient behavior

  6. Synoptic-scale circulation patterns during summer derived from tree rings in mid-latitude Asia

    Science.gov (United States)

    Seim, Andrea; Schultz, Johannes A.; Leland, Caroline; Davi, Nicole; Byambasuren, Oyunsanaa; Liang, Eryuan; Wang, Xiaochun; Beck, Christoph; Linderholm, Hans W.; Pederson, Neil

    2017-09-01

    Understanding past and recent climate and atmospheric circulation variability is vital for regions that are affected by climate extremes. In mid-latitude Asia, however, the synoptic climatology is complex and not yet fully understood. The aim of this study was to investigate dominant synoptic-scale circulation patterns during the summer season using a multi-species tree-ring width (TRW) network comprising 78 sites from mid-latitude Asia. For each TRW chronology, we calculated an atmospheric circulation tree-ring index (ACTI), based on 1000 hPa geopotential height data, to directly link tree growth to 13 summertime weather types and their associated local climate conditions for the period 1871-1993. Using the ACTI, three groups of similarly responding tree-ring sites can be associated with distinct large-scale atmospheric circulation patterns: 1. growth of drought sensitive trees is positively affected by a cyclone over northern Russia; 2. temperature sensitive trees show positive associations to a cyclone over northwestern Russia and an anticyclone over Mongolia; 3. trees at two high elevation sites show positive relations to a zonal cyclone extending from mid-latitude Eurasia to the West Pacific. The identified synoptic-scale circulation patterns showed spatiotemporal variability in their intensity and position, causing temporally varying climate conditions in mid-latitude Asia. Our results highlight that for regions with less pronounced atmospheric action centers during summer such as the occurrence of large-scale cyclones and anticyclones, synoptic-scale circulation patterns can be extracted and linked to the Northern Hemisphere circulation system. Thus, we provide a new and solid envelope for climate studies covering the past to the future.

  7. Using GPS TEC measurements to probe ionospheric spatial spectra at mid-latitudes

    Science.gov (United States)

    Lay, E. H.; Parker, P. A.; Light, M. E.; Carrano, C. S.; Debchoudhury, S.; Haaser, R. A.

    2017-12-01

    The physics of how random ionospheric structure causes signal degradation is well understood as weak forward scattering through an effective diffraction grating created by plasma irregularities in the ionosphere. However, the spatial scale spectrum of those irregularities required for input into scintillation models and models of traveling ionospheric disturbances is poorly characterized, particularly at the kilometer to tens of kilometer scale lengths important for very-high-frequency (VHF) scintillation prediction. Furthermore, the majority of characterization studies have been performed in low-latitude or high-latitude regions where geomagnetic activity dominates the physical processes. At mid-latitudes, tropospheric and geomagnetic phenomena compete in disturbing the ionosphere, and it is not well understood how these multiple sources affect the drivers that influence the spatial spectrum. In this study, we are interested in mid-latitude electron density irregularities on the order of 10s of kilometers that would affect VHF signals. Data from the GPS networks Japan GEONET and the Plate Boundary Observatory (PBO, UNAVCO) in the western United States were analyzed for this study. Japan GEONET is a dense network of GPS receivers (station spacing of tens of km), with fairly evenly spaced positions over all of Japan. The PBO, on the other hand, has several pockets of extremely dense coverage (station spacing within a few km), but is less dense on average. We analyze a day with a large solar storm (2015/03/17, St. Patrick's Day Storm) to allow high scintillation potential at mid-latitudes, a day with low geomagnetic activity and low thunderstorm activity (2016/01/31), and a day with low geomagnetic activity and high thunderstorm activity (2015/08/02). We then perform two-dimensional spatial analyses on the TEC data from these two networks on scale lengths of 20 to 200 km to infer the spatial scale spectra.

  8. Recent Basal Melting of a Mid-Latitude Glacier on Mars

    Science.gov (United States)

    Butcher, Frances E. G.; Balme, M. R.; Gallagher, C.; Arnold, N. S.; Conway, S. J.; Hagermann, A.; Lewis, S. R.

    2017-12-01

    Evidence for past basal melting of young (late Amazonian-aged), debris-covered glaciers in Mars' mid-latitudes is extremely rare. Thus, it is widely thought that these viscous flow features (VFFs) have been perennially frozen to their beds. We identify an instance of recent, localized wet-based mid-latitude glaciation, evidenced by a candidate esker emerging from a VFF in a tectonic rift in Tempe Terra. Eskers are sedimentary ridges deposited in ice-walled meltwater conduits and are indicative of glacial melting. We compare the candidate esker to terrestrial analogues, present a geomorphic map of landforms in the rift, and develop a landsystem model to explain their formation. We propose that the candidate esker formed during a transient phase of wet-based glaciation. We then consider the similarity between the geologic setting of the new candidate esker and that of the only other candidate esker to be identified in association with an existing mid-latitude VFF; both are within tectonic graben/rifts proximal to volcanic provinces. Finally, we calculate potential basal temperatures for a range of VFF thicknesses, driving stresses, mean annual surface temperatures, and geothermal heat fluxes, which unlike previous studies, include the possible role of internal strain heating. Strain heating can form an important additional heat source, especially in flow convergence zones, or where ice is warmer due to elevated surface temperatures or geothermal heat flux. Elevated geothermal heat flux within rifts, perhaps combined with locally-elevated strain heating, may have permitted wet-based glaciation during the late Amazonian, when cold climates precluded more extensive wet-based glaciation on Mars.

  9. A Regional GPS Receiver Network For Monitoring Mid-latitude Total Electron Content During Storms

    Science.gov (United States)

    Vernon, A.; Cander, Lj. R.

    A regional GPS receiver network has been used for monitoring mid-latitude total elec- tron content (TEC) during ionospheric storms at the current solar maximum. Differ- ent individual storms were examined to study how the temporal patterns of changes develop and how they are related to solar and geomagnetic activity for parameter de- scriptive of plasmaspheric-ionospheric ionisation. Use is then made of computer con- touring techniques to produce snapshot maps of TEC for different study cases. Com- parisons with the local ionosonde data at different phases of the storms enable the storm developments to be studied in detail.

  10. Delayed storm-time increases in the whistler rate at mid-latitudes

    International Nuclear Information System (INIS)

    Andrews, M.K.

    1975-01-01

    The occurrence of whistlers during 105 magnetic storms in the period 1963 to 1968 is studied. Evidence that more whistlers occur during the storm recovery period is presented. Assuming that the increased whistler rate implies the presence of more ducts, similarities are noted between the storm-time duct population and the incidence of mid-latitude spread-F in both time and space. It is suggested that a fresh examination of the physical processes involved in spread-F may aid understanding of the formation of whistler ducts. (author)

  11. Mid-latitude summer response of the middle atmosphere to short-term solar UV changes

    Directory of Open Access Journals (Sweden)

    P. Keckhut

    1995-06-01

    Full Text Available Temperature and wind data obtained with Rayleigh lidar since 1979 and Russian rockets since 1964 are analyzed to deduce the summer response of the middle atmosphere to short-term solar UV changes. The equivalent width of the 1083 nm He I line is used as a proxy to monitor the short-term UV flux changes. Spectral analyses are performed on 108-day windows to extract the 27-day component from temperature, wind and solar data sets. Linear regressions between these spectral harmonics show some significant correlations around 45 km at mid-latitudes. For large 27-day solar cycles, amplitudes of 2 K and 6 m s-1 are calculated for temperature data series over the south of France (44°N, and on wind data series over Volgograd (49°N, respectively. Cross-spectrum analyses have indicated correlations between these atmospheric parameters and the solar proxy with a phase lag of less than 2 days. These statistically correlative results, which provide good qualitative agreement with numerical simulations, are both obtained at mid-latitude. However, the observed amplitudes are larger than expected, with numerical models suggesting that dynamical processes such as equatorial or gravity waves may be responsible.

  12. Mid-latitude summer response of the middle atmosphere to short-term solar UV changes

    Directory of Open Access Journals (Sweden)

    P. Keckhut

    Full Text Available Temperature and wind data obtained with Rayleigh lidar since 1979 and Russian rockets since 1964 are analyzed to deduce the summer response of the middle atmosphere to short-term solar UV changes. The equivalent width of the 1083 nm He I line is used as a proxy to monitor the short-term UV flux changes. Spectral analyses are performed on 108-day windows to extract the 27-day component from temperature, wind and solar data sets. Linear regressions between these spectral harmonics show some significant correlations around 45 km at mid-latitudes. For large 27-day solar cycles, amplitudes of 2 K and 6 m s-1 are calculated for temperature data series over the south of France (44°N, and on wind data series over Volgograd (49°N, respectively. Cross-spectrum analyses have indicated correlations between these atmospheric parameters and the solar proxy with a phase lag of less than 2 days. These statistically correlative results, which provide good qualitative agreement with numerical simulations, are both obtained at mid-latitude. However, the observed amplitudes are larger than expected, with numerical models suggesting that dynamical processes such as equatorial or gravity waves may be responsible.

  13. Mid-latitude Narrowband Stimulated Electromagnetic Emissions (NSEE): New Observations and Modeling

    Science.gov (United States)

    Nossa, E.; Mahmoudian, A.; Isham, B.; Bernhardt, P. A.; Briczinski, S. J., Jr.

    2017-12-01

    High power electromagnetic waves (EM) transmitted from the ground interact with the local plasma in the ionosphere and can produce Stimulated Electromagnetic Emissions (SEE) through the parametric decay instability (PDI). The classical SEE features known as wideband SEE (WSEE) with frequency offset of 1 kHz up to 100 kHz have been observed and studied in detail in the 1980s and 1990s. A new era of ionospheric remote sensing techniques was begun after the recent update of the HF transmitter at the HAARP. Sideband emissions of unprecedented strength have been reported during recent campaigns at HAARP, reaching up to 10 dB relative to the reflected pump wave which are by far the strongest spectral features of secondary radiation that have been reported. These emissions known as narrowband SEE (NSEE) are shifted by only up to a few tens of Hertz from radio-waves transmitted at several megahertz. One of these new NSEE features are emission lines within 100 Hz of the pump frequency and are produced through magnetized stimulated Brillouin scatter (MSBS) process. Stimulated Brillouin Scatter (SBS) is a strong SEE mode involving a direct parametric decay of the pump wave into an electrostatic wave (ES) and a secondary EM wave that sometimes could be stronger than the HF pump. SBS has been studied in laboratory plasma experiments by the interaction of high power lasers with plasmas. The SBS instability in magnetized ionospheric plasma was observed for the first time at HAARP in 2010. Our recent work at HAARP has shown that MSBS emission lines can be used to asses electron temperature in the heated region, ion mass spectrometry, determine minor ion species and their densities in the ionosphere, study the physics associated with electron acceleration and artificial airglow. Here, we present new observations of narrowband SEE (NSEE) features at the new mid-latitude heating facility at Arecibo. This includes the direct mode conversion of pump wave through MSBS process. Collected

  14. Classification of Arctic, Mid-Latitude and Tropical Clouds in the Mixed-Phase Temperature Regime

    Science.gov (United States)

    Costa, Anja; Afchine, Armin; Luebke, Anna; Meyer, Jessica; Dorsey, James R.; Gallagher, Martin W.; Ehrlich, André; Wendisch, Manfred; Krämer, Martina

    2016-04-01

    The degree of glaciation and the sizes and habits of ice particles formed in mixed-phase clouds remain not fully understood. However, these properties define the mixed clouds' radiative impact on the Earth's climate and thus a correct representation of this cloud type in global climate models is of importance for an improved certainty of climate predictions. This study focuses on the occurrence and characteristics of two types of clouds in the mixed-phase temperature regime (238-275K): coexistence clouds (Coex), in which both liquid drops and ice crystals exist, and fully glaciated clouds that develop in the Wegener-Bergeron-Findeisen regime (WBF clouds). We present an extensive dataset obtained by the Cloud and Aerosol Particle Spectrometer NIXE-CAPS, covering Arctic, mid-latitude and tropical regions. In total, we spent 45.2 hours within clouds in the mixed-phase temperature regime during five field campaigns (Arctic: VERDI, 2012 and RACEPAC, 2014 - Northern Canada; mid-latitude: COALESC, 2011 - UK and ML-Cirrus, 2014 - central Europe; tropics: ACRIDICON, 2014 - Brazil). We show that WBF and Coex clouds can be identified via cloud particle size distributions. The classified datasets are used to analyse temperature dependences of both cloud types as well as range and frequencies of cloud particle concentrations and sizes. One result is that Coex clouds containing supercooled liquid drops are found down to temperatures of -40 deg C only in tropical mixed clouds, while in the Arctic and mid-latitudes no liquid drops are observed below about -20 deg C. In addition, we show that the cloud particles' aspherical fractions - derived from polarization signatures of particles with diameters between 20 and 50 micrometers - differ significantly between WBF and Coex clouds. In Coex clouds, the aspherical fraction of cloud particles is generally very low, but increases with decreasing temperature. In WBF clouds, where all cloud particles are ice, about 20-40% of the cloud

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

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  16. Characterization of Nightside Mid-latitude Irregularities Observed with the Blackstone SuperDARN Radar

    Science.gov (United States)

    Ruohoniemi, J. M.; Ribeiro, A. J.; Baker, J. B.; Greenwald, R. A.; Newell, P. T.

    2009-12-01

    The new mid-latitude SuperDARN radars at Wallops Island and Blackstone observe strong coherent backscattering on an almost nightly basis from latitudes that appear to be subauroral. One study has demonstrated an excellent correlation with the occurrence of density and temperature gradients within the ionospheric projection of the plasmapause (Greenwald et al., Geophys. Res. Lett. [2006]). We have processed all the data collected with the Blackstone radar since its inception in February 2008 for a characterization of the occurrence and properties of ‘plasmapause’ scatter. We have determined the local time and Kp dependencies of the activity and the relation of the spatial distribution of the irregularities to magnetospheric boundaries and ionospheric density gradients. We establish that the irregularities are a feature of the quiet-time subauroral ionosphere and provide a valuable diagnostic of the electric fields in the inner magnetosphere.

  17. Wind structure during mid-latitude storms and its application in Wind Energy

    DEFF Research Database (Denmark)

    Larsén, Xiaoli Guo; Du, Jianting; Bolanos, Rodolfo

    2015-01-01

    in Denmark. The extreme wind and wave conditions in the coastal area for wind energy application are important but have rarely been studied in the literature. Our experiments are done to the Danish coasts where the mid-latitude depression systems are causes of the extreme wind and wave conditions....... The numerical modeling is done through an atmosphere-wave coupled system, where the atmospheric model is the Weather Research and Forecasting (WRF) model and the wave model is the Simulating WAves Nearshore (SWAN) model. Measurements from offshore stations, Horns Rev and the FINO platform, as well as satellite...... and the modeling will be presented. Here the “key” is referring both to the application of wind energy and the wind-wave coupling system. The various parameterization of the interface parameter for the atmospheric and wave modeling, the roughness length, has been examined. Data analysis reveals the importance...

  18. Modelling of the electron density height profiles in the mid-latitude ionospheric D-region

    Directory of Open Access Journals (Sweden)

    P. Y. Mukhtarov

    1996-06-01

    Full Text Available A new mid-latitude D-region (50-105 km model of the electron density is presented obtained on the basis of a full wave theory and by a trial-and-error inversion method. Daytime (at different solar zenith angles absorption measurements by A3-technique made in Bulgaria yielded data with the aid of which the seasonal and diurnal courses of the Ne(h-profiles were derived. Special attention is drawn to the event diurnal asymmetry, or uneven formation of the ionosphere as a function of insulation. The latter is probably connected with the influence of the diurnal fluctuations in the local temperature on the chemistry involved in the electron loss rate, as well as the diurnal variations of the main ionizing agent (NO in the D-region. That is why the Ne(h-profiles in the midlatitude D-region are modelled separately for morning and afternoon hours.

  19. Diurnal and Seasonal Variations in Mid-Latitude Geomagnetic Field During International Quiet Days: BOH Magnetometer

    Directory of Open Access Journals (Sweden)

    Junga Hwang

    2012-12-01

    Full Text Available Korea Astronomy and Space Science Institute researchers have installed and operated magnetometers at Bohyunsan Observatory to measure the Earth's magnetic field variations in South Korea. In 2007, we installed a fluxgate magnetometer (RFP-523C to measure H, D, and Z components of the geomagnetic field. In addition, in 2009, we installed a Overhauser proton sensor to measure the absolute total magnetic field F and a three-axis magneto-impedance sensor for spectrum analysis. Currently three types of magnetometer data have been accumulated. In this paper, we use the H, D, Z components of fluxgate magnetometer data to investigate the characteristics of mid-latitude geomagnetic field variation. To remove the temporary changes in Earth’s geomagnetic filed by space weather, we use the international quiet days’ data only. In other words, we performed a superposed epoch analysis using five days per each month during 2008-2011. We find that daily variations of H, D, and Z shows similar tendency compared to previous results using all days. That is, H, D, Z all three components’ quiet intervals terminate near the sunrise and shows maximum 2-3 hours after the culmination and the quiet interval start from near the sunset. Seasonal variations show similar dependences to the Sun. As it becomes hot season, the geomagnetic field variation’s amplitude becomes large and the quiet interval becomes shortened. It is well-known that these variations are effects of Sq current system in the Earth’s atmosphere. We confirm that the typical mid-latitude geomagnetic field variations due to the Sq current system by excluding all possible association with the space weather.

  20. Trans-pacific glacial response to the Antarctic Cold Reversal in the southern mid-latitudes

    Science.gov (United States)

    Sagredo, Esteban A.; Kaplan, Michael R.; Araya, Paola S.; Lowell, Thomas V.; Aravena, Juan C.; Moreno, Patricio I.; Kelly, Meredith A.; Schaefer, Joerg M.

    2018-05-01

    Elucidating the timing and regional extent of abrupt climate events during the last glacial-interglacial transition (∼18-11.5 ka) is critical for identifying spatial patterns and mechanisms responsible for large-magnitude climate events. The record of climate change in the Southern Hemisphere during this time period, however, remains scarce and unevenly distributed. We present new geomorphic, chronological, and equilibrium line altitude (ELA) data from a climatically sensitive mountain glacier at Monte San Lorenzo (47°S), Central Patagonia. Twenty-four new cosmogenic 10Be exposure ages from moraines provide a comprehensive glacial record in the mid-latitudes of South America, which constrain the timing, spatial extent and magnitude of glacial fluctuations during the Antarctic Cold Reversal (ACR, ∼14.5-12.9 ka). Río Tranquilo glacier advanced and reached a maximum extent at 13.9 ± 0.7 ka. Three additional inboard moraines afford statistically similar ages, indicating repeated glacier expansions or marginal fluctuations over the ACR. Our record represents the northernmost robust evidence of glacial fluctuations during the ACR in southern South America, documenting not only the timing of the ACR maximum, but also the sequence of glacier changes within this climate event. Based on ELA reconstructions, we estimate a cooling of >1.6-1.8 °C at the peak of the ACR. The Río Tranquilo record along with existing glacial reconstructions from New Zealand (43°S) and paleovegetation records from northwestern (41°S) and central-west (45°S) Patagonia, suggest an uniform trans-Pacific glacier-climate response to an ACR trigger across the southern mid-latitudes. We posit that the equatorial migration of the southern westerly winds provides an adequate mechanism to propagate a common ACR signal across the Southern Hemisphere.

  1. Mid-latitude continental temperatures through the early Eocene in western Europe

    Science.gov (United States)

    Inglis, Gordon N.; Collinson, Margaret E.; Riegel, Walter; Wilde, Volker; Farnsworth, Alexander; Lunt, Daniel J.; Valdes, Paul; Robson, Brittany E.; Scott, Andrew C.; Lenz, Olaf K.; Naafs, B. David A.; Pancost, Richard D.

    2017-02-01

    Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are increasingly used to reconstruct mean annual air temperature (MAAT) during the early Paleogene. However, the application of this proxy in coal deposits is limited and brGDGTs have only been detected in immature coals (i.e. lignites). Using samples recovered from Schöningen, Germany (∼48°N palaeolatitude), we provide the first detailed study into the occurrence and distribution of brGDGTs through a sequence of early Eocene lignites and associated interbeds. BrGDGTs are abundant and present in every sample. In comparison to modern studies, changes in vegetation type do not appear to significantly impact brGDGT distributions; however, there are subtle differences between lignites - representing peat-forming environments - and siliciclastic nearshore marine interbed depositional environments. Using the most recent brGDGT temperature calibration (MATmr) developed for soils, we generate the first continental temperature record from central-western continental Europe through the early Eocene. Lignite-derived MAAT estimates range from 23 to 26 °C while those derived from the nearshore marine interbeds exceed 20 °C. These estimates are consistent with other mid-latitude environments and model simulations, indicating enhanced mid-latitude, early Eocene warmth. In the basal part of the section studied, warming is recorded in both the lignites (∼2 °C) and nearshore marine interbeds (∼2-3 °C). This culminates in a long-term temperature maximum, likely including the Early Eocene Climatic Optimum (EECO). Although this long-term warming trend is relatively well established in the marine realm, it has rarely been shown in terrestrial settings. Using a suite of model simulations we show that the magnitude of warming at Schöningen is broadly consistent with a doubling of CO2, in agreement with late Paleocene and early Eocene pCO2 estimates.

  2. Seasonal ionospheric scintillation analysis during increasing solar activity at mid-latitude

    Science.gov (United States)

    Ahmed, Wasiu Akande; Wu, Falin; Agbaje, Ganiyu Ishola; Ednofri, Ednofri; Marlia, Dessi; Zhao, Yan

    2017-09-01

    Monitoring of ionospheric parameters (such as Total Electron Content and scintillation) is of great importance as it affects and contributes to the errors encountered by radio signals. It thus requires constant measurements to avoid disastrous situation for space agencies, parastatals and departments that employ GNSS applications in their daily operations. The research objective is to have a better understanding of the behaviour of ionospheric scintillation at midlatitude as it threatens the performances of satellite communication, navigation systems and military operations. This paper adopts seasonal ionospheric scintillation scenario. The mid-latitude investigation of ionospheric effect of scintillation was conducted during the increasing solar activity from 2011-2015. Ionospheric scintillation data were obtained from four ionospheric monitoring stations located at mid-latitude (i.e Shenzhen North Station, Beijing Changping North Station Branch, Beijing North Station and Beijing Miyun ground Station). The data was collected from January 2011 to December 2015. There were absence of data due to software problem or system failure at some locations. The scintillation phenomenon was computed using Global Ionospheric Scintillation and TEC Monitoring Model. There are four seasons which existed in China namely: Spring, Summer, Autumn and Winter. The relationship between TEC, amplitude and phase scintillation were observed for each of these seasons. The results indicated that the weak amplitude scintillation was observed as against phase scintillation which was high. Phase scintillation was gradually enhanced from 2011 to 2012 and later declined till 2014. TEC was also at peak around 00:00-10:00 UT (08:00-18:00 LT). The seasonal events temporal density characteristics comply with solar cycle prediction as such it ascended from 2011 to 2013 and then scintillation parameters declined significantly afterwards.

  3. Anthropogenic Changes in Mid-latitude Storm and Blocking Activities from Observations and Climate Models

    Science.gov (United States)

    Li, D.

    2017-12-01

    Fingerprints of anthropogenic climate change can be most readily detected in the high latitudes of Northern Hemisphere, where temperature has been rising faster than the rest of the globe and sea ice cover has shrunk dramatically over recent decades. Reducing the meridional temperature gradient, this amplified warming over the high latitudes influences weather in the middle latitudes by modulating the jet stream, storms, and atmospheric blocking activities. Whether observational records have revealed significant changes in mid-latitude storms and blocking activities, however, has remained a subject of much debate. Buried deep in strong year-to-year variations, the long-term dynamic responses of the atmosphere are more difficult to identify, compared with its thermodynamic responses. Variabilities of decadal and longer timescales further obscure any trends diagnosed from satellite observations, which are often shorter than 40 years. Here, new metrics reflecting storm and blocking activities are developed using surface air temperature and pressure records, and their variations and long-term trends are examined. This approach gives an inkling of the changes in storm and blocking activities since the Industrial Revolution in regions with abundant long-term observational records, e.g. Europe and North America. The relationship between Atlantic Multi-decadal Oscillation and variations in storm and blocking activities across the Atlantic is also scrutinized. The connection between observed centennial trends and anthropogenic forcings is investigated using a hierarchy of numerical tools, from highly idealized to fully coupled atmosphere-ocean models. Pre-industrial control simulations and a set of large ensemble simulations forced by increased CO2 are analyzed to evaluate the range of natural variabilities, which paves the way to singling out significant anthropogenic changes from observational records, as well as predicting future changes in mid-latitude storm and

  4. Comparative investigations of equatorial electrodynamics and low-to-mid latitude coupling of the thermosphere-ionosphere system

    Directory of Open Access Journals (Sweden)

    M. J. Colerico

    2006-03-01

    Full Text Available The thermospheric midnight temperature maximum (MTM is a highly variable, but persistent, large scale neutral temperature enhancement which occurs at low latitudes. Its occurrence can impact many fundamental upper atmospheric parameters such as pressure, density, neutral winds, neutral density, and F-region plasma. Although the MTM has been the focus of several investigations employing various instrumentation including photometers, satellites, and Fabry-Perot interferometers, limited knowledge exists regarding the latitude extent of its influence on the upper atmosphere. This is largely due to observational limitations which confined the collective geographic range to latitudes within ±23°. This paper investigates the MTM's latitudinal extent through all-sky imaging observations of its 6300Å airglow signature referred to by Colerico et al. (1996 as the midnight brightness wave (MBW. The combined field of view of three Southern Hemisphere imaging systems located at Arequipa, Peru, and Tucuman and El Leoncito, Argentina, for the first time extends the contiguous latitudinal range of imager observations to 8° S-39° S in the American sector. Our results highlight the propagation of MBW events through the combined fields of view past 39° S latitude, providing the first evidence that the MTM's effect on the upper atmosphere extends into mid-latitudes. The observations presented here are compared with modeled 6300Å emissions calculated using the NCAR thermosphere-ionosphere-electrodynamic general circulation model (TIEGCM in conjunction with an airglow code. We report that at this time TIEGCM is unable to simulate an MBW event due to the model's inability to reproduce an MTM of the same magnitude and occurrence time as those observed via FPI measurements made from Arequipa. This work also investigates the origins of an additional low latitude airglow feature referred to by Colerico et al. (1996 as the pre-midnight brightness wave (PMBW and

  5. Study of midlatitude ionospheric irregularities and E- and F-region coupling based on rocket and radar observations from Japan

    Science.gov (United States)

    Yamamoto, M.

    2015-12-01

    We have been studying ionspheric irregularities in mid-latitude region by using radars, sounding rockets, etc. The mid-latitude ionosphere was considered much stable than those in the equatorial or polar region in the past, but our studies for years have revealed that there are much active variabilities. We found variety of wave-like structures that are specific in the mid-latitudes. One of the phenomena is quasi-periodic echoes (QP echoes) first observed by the MU radar that reflects horizontal plasma-density structures associated to sporadic-E layers. Another phenomenon is medium-scale traveling ionospheric disturbance (MSTID) in the F-region. In the generation mechanism we think that Ionospheric E- and F-region coupling process is important. In this presentation, we will discuss nature of mid-latitude ionosphere based on our observations; the MU radar, sounding rocket campaigns of SEEK-1/2, and recent MSTID rocket experiment from JAXA Uchinoura Space Center in July 2013.

  6. A comparison of the relative locations of the mid-latitude electron density trough and the scintillation boundary

    International Nuclear Information System (INIS)

    Tulunay, Y.K.; Demir, O.; Tauriainen, A.

    1976-01-01

    The mid-latitude electron density trough position and the scintillation boundary have been compared for magnetically quiet periods by using the data returned by Ariel 3 and Explorer 22 satellites. The scintillation boundary is found southward of the trough during daytime, but at night the positions are reversed. (author)

  7. Does the bipolar seesaw extend to the terrestrial southern mid-latitudes?

    Science.gov (United States)

    Newnham, Rewi M.; Vandergoes, Marcus J.; Sikes, Elisabeth; Carter, Lionel; Wilmshurst, Janet M.; Lowe, David J.; McGlone, Matt S.; Sandiford, Anna

    2012-03-01

    High precision comparison of Greenland and Antarctic ice cores, suggesting a pervasive antiphased temperature relationship between the polar hemispheres during the last glaciation, lends strong support to the bipolar seesaw model (EPICA, 2006). The extent to which reorganisation of ocean-heat transport during abrupt climate change events affected the southern mid-latitudes remains unclear, however, owing to a paucity of well-dated records with robust climate proxies, variability between some records, and varying interpretations of their significance. Here we present temperature reconstructions for three key pollen records recognised by the NZ-INTIMATE (NZ-I) group which, along with the preliminary NZ-I climate event stratigraphy (Alloway et al., 2007) and published marine records, are compared with polar ice core records for the interval 30-10 cal. ka. We focus on key events within the context of Dansgard Oeschger cycles 4-1 and The Antarctic Cold Reversal/Younger Dryas intervals. The New Zealand records are broadly consistent with an extended bipolar seesaw whereby the oceanic southern mid-latitudes are warmed at times of MOC weakening or cessation in the North Atlantic, and vice versa. Variability between records indicate that other factors must be involved, however, and nor do these records refute alternative models that predict an antiphased inter-hemispheric pattern. Nevertheless an extended bipolar model may explain an early onset of LGM conditions in New Zealand and elsewhere in the Southern Hemisphere at a time when interstadials GI3 and GI4 kept Greenland warm. Similar inter-hemispheric dynamics have been invoked to explain an earlier termination of the LGM in Antarctica than in Greenland (Wolff et al., 2009) which is also evident in the New Zealand records. A prominent mid-LGM interstadial complex observed in several New Zealand records, connected by tephrochronology may represent another antiphased event although stronger chronological control is needed

  8. Interactions between tropical cyclones and mid-latitude systems in the Northeastern Pacific

    Science.gov (United States)

    Lugo, A.; Abarca, S. F.; Raga, G. B.; Vargas, D. C.

    2014-12-01

    Major challenges in tropical meteorology include the short-term forecast of tropical cyclone (TC) intensity, which is defined as the maximum tangential wind. Several efforts have been made in order to reach this goal over the last decade: Among these efforts, the study of lightning in the TC inner core (the region inside a disc of 100 km radius from the center) as a proxy to deep convection, has the potential to be used as a predictor to forecast intensity (DeMaria et al, 2012, Mon. Wea. Rev., 140, 1828-1842).While most studies focus their objectives in studying the lightning flash density in the inner core, we study the probability of flash occurrence for intensifying and weakening cyclones. We have analyzed the trajectories of the observed 62 tropical cyclones that developed in the basin from 2006 to 2009, and classified them into separate clusters according to their trajectories. These clusters can broadly be described as having trajectories mostly oriented: East-West, towards the central Pacific, NW far from the Mexican coast, parallel to the Mexican coast and recurving towards the Mexican coast.We estimate that probability of inner core lightning occurrence increases as cyclones intensify but the probability rapidly decrease as the systems weaken. This is valid for cyclones in most of the clusters. However, the cyclones that exhibit trajectories that recurve towards the Mexican coast, do not present the same relationship between intensity and inner-core lightning probability, these cyclones show little or no decrease in the lightning occurrence probability as they weaken.We hypothesize that one of the reasons for this anomalous behavior is likely the fact that these cyclones interact with mid-latitude systems. Mid-latitude systems are important in determining the recurving trajectory but they may also influence the TC by advecting mid-level moisture towards the TC inner core. This additional supply of moisture as the system is approaching land may enhance deep

  9. Sea Surface Warming and Increased Aridity at Mid-latitudes during Eocene Thermal Maximum 2

    Science.gov (United States)

    Harper, D. T.; Zeebe, R. E.; Hoenisch, B.; Schrader, C.; Lourens, L. J.; Zachos, J. C.

    2017-12-01

    Early Eocene hyperthermals, i.e. abrupt global warming events characterized by the release of isotopically light carbon to the atmosphere, can provide insight into the sensitivity of the Earth's climate system and hydrologic cycle to carbon emissions. Indeed, the largest Eocene hyperthermal, the Paleocene-Eocene Thermal Maximum (PETM), has provided one case study of extreme and abrupt global warming, with a mass of carbon release roughly equivalent to total modern fossil fuel reserves and a release rate 1/10 that of modern. Global sea surface temperatures (SST) increased by 5-8°C during the PETM and extensive evidence from marine and terrestrial records indicates significant shifts in the hydrologic cycle consistent with an increase in poleward moisture transport in response to surface warming. The second largest Eocene hyperthermal, Eocene Thermal Maximum 2 (ETM-2) provides an additional calibration point for determining the sensitivity of climate and the hydrologic cycle to massive carbon release. Marine carbon isotope excursions (CIE) and warming at the ETM-2 were roughly half as large as at the PETM, but reliable evidence for shifts in temperature and the hydrologic cycle are sparse for the ETM-2. Here, we utilize coupled planktic foraminiferal δ18O and Mg/Ca to determine ΔSST and ΔSSS (changes in sea surface temperature and salinity) for ETM-2 at ODP Sites 1209 (28°N paleolatitude in the Pacific) and 1265 (42°S paleolatitude in the S. Atlantic), accounting for potential pH influence on the two proxies by using LOSCAR climate-carbon cycle simulated ΔpH. Our results indicate a warming of 2-4°C at both mid-latitude sites and an increase in SSS of 1-3ppt, consistent with simulations of early Paleogene hydroclimate that suggest an increase in low- to mid-latitude aridity due to an intensification of moisture transport to high-latitudes. Furthermore, the magnitude of the CIE and warming for ETM-2 scales with the CIE and warming for the PETM, suggesting that

  10. Diagnosing sea ice from the north american multi model ensemble and implications on mid-latitude winter climate

    Science.gov (United States)

    Elders, Akiko; Pegion, Kathy

    2017-12-01

    Arctic sea ice plays an important role in the climate system, moderating the exchange of energy and moisture between the ocean and the atmosphere. An emerging area of research investigates how changes, particularly declines, in sea ice extent (SIE) impact climate in regions local to and remote from the Arctic. Therefore, both observations and model estimates of sea ice become important. This study investigates the skill of sea ice predictions from models participating in the North American Multi-Model Ensemble (NMME) project. Three of the models in this project provide sea-ice predictions. The ensemble average of these models is used to determine seasonal climate impacts on surface air temperature (SAT) and sea level pressure (SLP) in remote regions such as the mid-latitudes. It is found that declines in fall SIE are associated with cold temperatures in the mid-latitudes and pressure patterns across the Arctic and mid-latitudes similar to the negative phase of the Arctic Oscillation (AO). These findings are consistent with other studies that have investigated the relationship between declines in SIE and mid-latitude weather and climate. In an attempt to include additional NMME models for sea-ice predictions, a proxy for SIE is used to estimate ice extent in the remaining models, using sea surface temperature (SST). It is found that SST is a reasonable proxy for SIE estimation when compared to model SIE forecasts and observations. The proxy sea-ice estimates also show similar relationships to mid-latitude temperature and pressure as the actual sea-ice predictions.

  11. Impacts of Early Summer Eurasian Snow Cover Change on Atmospheric Circulation in Northern Mid-Latitudes

    Science.gov (United States)

    Nozawa, T.

    2016-12-01

    Recently, Japan Aerospace Exploration Agency (JAXA) has developed a new long-term snow cover extent (SCE) product using Advanced Very High Resolution Radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer (MODIS) data spanning from 1980's to date. This new product (JAXA/SCE) has higher spatial resolution and smaller commission error compared with traditional SCE dataset of National Oceanic and Atmospheric Administration (NOAA/SCE). Continuity of the algorithm is another strong point in JAXA/SCE. According to the new JAXA/SCE dataset, the Eurasian SCE has been significantly retreating since 1980's, especially in late spring and early summer. Here, we investigate impacts of early summer Eurasian snow cover change on atmospheric circulation in Northern mid-latitudes, especially over the East Asia, using the new JAXA/SCE dataset and a few reanalysis data. We will present analyzed results on relationships between early summer SCE anomaly over the Eurasia and changes in atmospheric circulations such as upper level zonal jets (changes in strength, positions, etc.) over the East Asia.

  12. The importance of moisture distribution for the growth and energetics of mid-latitude systems

    Directory of Open Access Journals (Sweden)

    V. Pavan

    1999-02-01

    Full Text Available A primitive equation model is used to study the sensitivity of baroclinic wave life cycles to the initial latitude-height distribution of humidity. Diabatic heating is parametrized only as a consequence of condensation in regions of large-scale ascent. Experiments are performed in which the initial relative humidity is a simple function of model level, and in some cases latitude bands are specified which are initially relatively dry. It is found that the presence of moisture can either increase or decrease the peak eddy kinetic energy of the developing wave, depending on the initial moisture distribution. A relative abundance of moisture at mid-latitudes tends to weaken the wave, while a relative abundance at low latitudes tends to strengthen it. This sensitivity exists because competing processes are at work. These processes are described in terms of energy box diagnostics. The most realistic case lies on the cusp of this sensitivity. Further physical parametrizations are then added, including surface fluxes and upright moist convection. These have the effect of increasing wave amplitude, but the sensitivity to initial conditions of relative humidity remains. Finally, 'control' and 'doubled CO2' life cycles are performed, with initial conditions taken from the time-mean zonal-mean output of equilibrium GCM experiments. The attenuation of the wave resulting from reduced baroclinicity is more pronounced than any effect due to changes in initial moisture.Key words. Meteorology and atmospheric dynamics (climatology; convective processes; synoptic-scale meteorology

  13. Equatorial Precession Drove Mid-Latitude Changes in ENSO-Scale Variation in the Earliest Miocene

    Science.gov (United States)

    Fox, B.; D'Andrea, W. J.; Lee, D. E.; Wilson, G. S.

    2014-12-01

    Foulden Maar is an annually laminated lacustrine diatomite deposit from the South Island of New Zealand. The deposit was laid down over ~100 kyr of the latest Oligocene and earliest Miocene, during the peak and deglaciation phase of the Mi-1 Antarctic glaciation event. At this time, New Zealand was located at approximately the same latitude as today (~45°S). Evidence from organic geochemical proxies (δD, δ13C) and physical properties (density, colour) indicates the presence of an 11-kyr cycle at the site. Although it is known that 11-kyr insolation (half-precession) cycles occur between the Tropics, this cycle is rarely seen in sedimentary archives deposited outside the immediate vicinity of the Equator. Records from Foulden Maar correlate well with the amplitude and phase of the modelled equatorial half-precession cycle for the earliest Miocene. High-resolution (50 µm) colour intensity measurements and lamina thickness measurements both indicate the presence of significant ENSO-like (2-8 year) variation in the Foulden Maar sediments. Early results from targeted lamina thickness measurements suggest that ENSO-band variation is modulated by the 11-kyr cycle, with power in the ENSO band increasing during periods of increased insolation at the Equator. This implies that equatorial half-precession had a significant effect on ENSO-like variation in the early Miocene, and that this effect was felt as far afield as the mid-latitudes of the Southern Hemisphere.

  14. Solar activity influence on climatic variations of stratosphere and mesosphere in mid-latitudes

    International Nuclear Information System (INIS)

    Taubenheim, J.; Entzian, G.; Voncossart, G.

    1989-01-01

    The direct modulation of temperature of the mid-latitude mesosphere by the solar-cycle EUV variation, which leads to greater heat input at higher solar activity, is well established. Middle atmosphere temperature modulation by the solar cycle is independently confirmed by the variation of reflection heights of low frequency radio waves in the lower ionosphere, which are regularly monitored over about 30 years. As explained elsewhere in detail, these reflection heights depend on the geometric altitude of a certain isobaric surface (near 80 k), and on the solar ionizing Lyman-alpha radiation flux. Knowing the solar cycle variation of Lyman-alpha how much the measured reflection heights would be lowered with the transition from solar minimum to maximum can be calculated, if the vertical baric structure of the neutral atmosphere would remain unchanged. Any discrepancy between expected and observed height change must be explained by an uplifting of the isobaric level from solar minimum to maximum, caused by the temperature rise in the mesosphere. By integrating the solar cycle temperature changes over the height region of the middle atmosphere, and assuming that the lower boundary (tropopause) has no solar cycle variation, the magnitude of this uplifting can be estimated. It is given for the Lidar-derived and for the rocket-measured temperature variations. Comparison suggests that the real amplitude of the solar cycle temperature variation in the mesosphere is underestimated when using the rocket data, but probably overestimated with the Lidar data

  15. Historical deforestation locally increased the intensity of hot days in northern mid-latitudes

    Science.gov (United States)

    Lejeune, Quentin; Davin, Edouard L.; Gudmundsson, Lukas; Winckler, Johannes; Seneviratne, Sonia I.

    2018-05-01

    The effects of past land-cover changes on climate are disputed1-3. Previous modelling studies have generally concluded that the biogeophysical effects of historical deforestation led to an annual mean cooling in the northern mid-latitudes3,4, in line with the albedo-induced negative radiative forcing from land-cover changes since pre-industrial time reported in the most recent Intergovernmental Panel on Climate Change report5. However, further observational and modelling studies have highlighted strong seasonal and diurnal contrasts in the temperature response to deforestation6-10. Here, we show that historical deforestation has led to a substantial local warming of hot days over the northern mid-latitudes—a finding that contrasts with most previous model results11,12. Based on observation-constrained state-of-the-art climate-model experiments, we estimate that moderate reductions in tree cover in these regions have contributed at least one-third of the local present-day warming of the hottest day of the year since pre-industrial time, and were responsible for most of this warming before 1980. These results emphasize that land-cover changes need to be considered when studying past and future changes in heat extremes, and highlight a potentially overlooked co-benefit of forest-based carbon mitigation through local biogeophysical mechanisms.

  16. Northern hemisphere mid-latitude geomagnetic anomaly revealed from Levantine Archaeomagnetic Compilation (LAC).

    Science.gov (United States)

    Shaar, R.; Tauxe, L.; Agnon, A.; Ben-Yosef, E.; Hassul, E.

    2015-12-01

    The rich archaeological heritage of Israel and nearby Levantine countries provides a unique opportunity for archaeomagnetic investigation in high resolution. Here we present a summary of our ongoing effort to reconstruct geomagnetic variations of the past several millennia in the Levant at decadal to millennial resolution. This effort at the Southern Levant, namely the "Levantine Archaeomagnetic Compilation" (LAC), presently consists of data from over 650 well-dated archaeological objects including pottery, slag, ovens, and furnaces. In this talk we review the methodological challenges in achieving a robust master secular variation curve with realistic error estimations from a large number of different datasets. We present the current status of the compilation, including the southern and western Levant LAC data (Israel, Cyprus, and Jordan) and other published north-eastern Levant data (Syria and southern Turkey), and outline the main findings emerging from these data. The main feature apparent from the new compilation is an extraordinary intensity high that developed over the Levant region during the first two millennia BCE. The climax of this event is a double peak intensity maximum starting at ca. 1000 BCE and ending at ca. 735 BCE, accompanied with at least two events of geomagnetic spikes. Paleomagnetic directions from this period demonstrate anomalies of up to 20 degrees far from the averaged GAD field. This leads us to postulate that the maximum in the intensity is a manifestation of an intense mid-latitude local positive geomagnetic anomaly that persisted for over two centuries.

  17. Characteristics of mid-latitude planetary waves in the lower atmosphere derived from radiosonde data

    Directory of Open Access Journals (Sweden)

    R. Wang

    2012-10-01

    Full Text Available The activities of mid-latitude planetary waves (PWs in the troposphere and lower stratosphere (TLS are presented by using the radiosonde data from 2000 to 2004 over four American stations (Miramar Nas, 32.9° N, 117.2° W; Santa Teresa, 31.9° N, 106.7° W; Fort Worth, 32.8° N, 97.3° W; and Birmingham, 33.1° N, 86.7° W and one Chinese station (Wuhan, 30.5° N, 114.4° E. Statistically, strong PWs mainly appear around subtropical jet stream in the troposphere and lower stratosphere. In the troposphere, the activities of the mid-latitude PWs are strong around the centre of the subtropical jet stream in winter and become small near the tropopause, which indicates that the subtropical jet stream may strengthen the propagation of PWs or even be one of the PW excitation sources. Among the three disturbance components of temperature, zonal and meridional winds, PWs at Wuhan are stronger in the temperature component, but weaker in the zonal wind component than at the other four American stations. While in the meridional wind component, the strengths of PW spectral amplitudes at the four American stations decrease from west to east, and their amplitudes are all larger than that of Wuhan. However, the PWs are much weaker in the stratosphere and only the lower frequency parts remain. The amplitudes of the PWs in the stratosphere increase with height and are strong in winter with the zonal wind component being the strongest. Using the refractive index, we found that whether the PWs could propagate upward to the stratosphere depends on the thickness of the tropopause reflection layer. In the case study of the 2000/2001 winter, it is observed that the quasi 16-day wave in the troposphere is a quasi standing wave in the vertical direction and propagates upward slowly with vertical wavelength greater than 24 km in the meridional component. It propagates eastward with the zonal numbers between 5 and 8, and the quasi 16-day wave at Wuhan is probably the same

  18. Characteristics and direct radiative effect of mid-latitude continental aerosols: the ARM case

    Directory of Open Access Journals (Sweden)

    M. G. Iziomon

    2003-01-01

    Full Text Available A multi-year field measurement analysis of the characteristics and direct radiative effect of aerosols at the Southern Great Plains (SGP central facility of the Atmospheric Radiation Measurement (ARM Program is presented. Inter-annual mean and standard deviation of submicrometer scattering fraction (at 550 nm and Ångström exponent å (450 nm, 700 nm at the mid-latitude continental site are indicative of the scattering dominance of fine mode aerosol particles, being 0.84±0.03 and 2.25±0.09, respectively. We attribute the diurnal variation of submicron aerosol concentration to coagulation, photochemistry and the evolution of the boundary layer. Precipitation does not seem to play a role in the observed afternoon maximum in aerosol concentration. Submicron aerosol mass at the site peaks in the summer (12.1±6.7mg m-3, with the summer value being twice that in the winter. Of the chemically analyzed ionic components (which exclude carbonaceous aerosols, SO4= and NH4+ constitute the dominant species at the SGP seasonally, contributing 23-30% and 9-12% of the submicron aerosol mass, respectively. Although a minor species, there is a notable rise in NO3- mass fraction in winter. We contrast the optical properties of dust and smoke haze. The single scattering albedo w0 shows the most remarkable distinction between the two aerosol constituents. We also present aircraft measurements of vertical profiles of aerosol optical properties at the site. Annually, the lowest 1.2 km contributes 70% to the column total light scattering coefficient. Column-averaged and surface annual mean values of hemispheric backscatter fraction (at 550 nm, w0 (at 550 nm and å (450 nm, 700 nm agree to within 5% in 2001. Aerosols produce a net cooling (most pronounced in the spring at the ARM site

  19. The importance of moisture distribution for the growth and energetics of mid-latitude systems

    Directory of Open Access Journals (Sweden)

    V. Pavan

    Full Text Available A primitive equation model is used to study the sensitivity of baroclinic wave life cycles to the initial latitude-height distribution of humidity. Diabatic heating is parametrized only as a consequence of condensation in regions of large-scale ascent. Experiments are performed in which the initial relative humidity is a simple function of model level, and in some cases latitude bands are specified which are initially relatively dry. It is found that the presence of moisture can either increase or decrease the peak eddy kinetic energy of the developing wave, depending on the initial moisture distribution. A relative abundance of moisture at mid-latitudes tends to weaken the wave, while a relative abundance at low latitudes tends to strengthen it. This sensitivity exists because competing processes are at work. These processes are described in terms of energy box diagnostics. The most realistic case lies on the cusp of this sensitivity. Further physical parametrizations are then added, including surface fluxes and upright moist convection. These have the effect of increasing wave amplitude, but the sensitivity to initial conditions of relative humidity remains. Finally, 'control' and 'doubled CO2' life cycles are performed, with initial conditions taken from the time-mean zonal-mean output of equilibrium GCM experiments. The attenuation of the wave resulting from reduced baroclinicity is more pronounced than any effect due to changes in initial moisture.

    Key words. Meteorology and atmospheric dynamics (climatology; convective processes; synoptic-scale meteorology

  20. Changes of benthic fauna in the Kattegat - An indication of climate change at mid-latitudes?

    Science.gov (United States)

    Göransson, Peter

    2017-07-01

    Several predictions point to changes in the marine benthic macrofauna associated with climate change, but so far only a few and minor changes have been reported. This study relates observed changes in the species composition to climate change by looking on the past decades in the Kattegat between Denmark and Sweden. A reduction of the total number species and a reduction of species with a northern range parallel to an increase of species with a southern range have been observed. The most likely explanation of the changes is the increase in temperature of the bottom water. Increased temperature could change the species distributions but also decrease primary production which impacts recruitment and growth. Hypoxia and bottom trawling could also act synergistic in this process. A sparse occurrence of previously encountered Arctic-Boreal species and critical foundation species, which gives the area its special character, suggests a change in biodiversity and might therefore be designated as early warning signals of a warmer climate. The northern fauna below the halocline with limited capacity of dispersal and low reproduction potential, can be considered as sensitive with low adaptive capacity to climate change. Therefore, not only tropical and high-latitude species, but also benthos on deep bottoms at mid-latitudes, could be vulnerable to warming. As many species live at the edge of their range in the Kattegat, and also are dependent of distant recruitment, large scale changes will probably be detected here at an early stage. It is important to protect relatively undisturbed reference areas in the Kattegat for future studies, but also for preserving a large number of ecosystem services, biotopes, habitats, and fish species.

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

    Science.gov (United States)

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

    2016-07-01

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

  2. Validation of Martilli's urban boundary layer scheme with measurements from two mid-latitude European cities

    Science.gov (United States)

    Hamdi, R.; Schayes, G.

    2007-08-01

    Martilli's urban parameterization scheme is improved and implemented in a mesoscale model in order to take into account the typical effects of a real city on the air temperature near the ground and on the surface exchange fluxes. The mesoscale model is run on a single column using atmospheric data and radiation recorded above roof level as forcing. Here, the authors validate Martilli's urban boundary layer scheme using measurements from two mid-latitude European cities: Basel, Switzerland and Marseilles, France. For Basel, the model performance is evaluated with observations of canyon temperature, surface radiation, and energy balance fluxes obtained during the Basel urban boundary layer experiment (BUBBLE). The results show that the urban parameterization scheme represents correctly most of the behavior of the fluxes typical of the city center of Basel, including the large heat uptake by the urban fabric and the positive sensible heat flux at night. For Marseilles, the model performance is evaluated with observations of surface temperature, canyon temperature, surface radiation, and energy balance fluxes collected during the field experiments to constrain models of atmospheric pollution and transport of emissions (ESCOMPTE) and its urban boundary layer (UBL) campaign. At both urban sites, vegetation cover is less than 20%, therefore, particular attention was directed to the ability of Martilli's urban boundary layer scheme to reproduce the observations for the Marseilles city center, where the urban parameters and the synoptic forcing are totally different from Basel. Evaluation of the model with wall, road, and roof surface temperatures gave good results. The model correctly simulates the net radiation, canyon temperature, and the partitioning between the turbulent and storage heat fluxes.

  3. The health status of adolescents living at mid-latitude or in the European North in relation to anthropogenic pollution

    Directory of Open Access Journals (Sweden)

    D. A. Kuznetsova

    2016-01-01

    Full Text Available The distribution of health groups among 14-year-old adolescents (n = 707 living since birth under the conditions of mid-latitudes (the towns of Kirov and Yaransk and in the European North (the town of Ukhta and the settlement of Sedyu was compared to determine the impact of anthropogenic pollution at different latitudes on this indicator. It was shown that the conditions of the European North in the absence of anthropogenic pollution failed to affect the number of 14-year-old boys and girls having health groups I, II, III, IV, and V. Anthropogenic pollution was found to decline the number of health group I adolescents living in the European North, without influencing this indicator in those dwelling at mid-latitudes, but, in spite of the latitude of their residence, to increase that of persons with health group II, without having an impact on the number of persons with health groups III, IV, and V.

  4. Titan’s mid-latitude surface regions with Cassini VIMS and RADAR

    Science.gov (United States)

    Solomonidou, Anezina; Lopes, Rosaly M. C.; Coustenis, Athena; Malaska, Michael; Rodriguez, Sebastien; Maltagliati, Luca; Drossart, Pierre; Janssen, Michael; Lawrence, Kenneth; Jaumann, Ralf; Sohl, Frank; Stephan, Katrin; Brown, Robert H.; Bratsolis, Emmanuel; Matsoukas, Christos

    2015-11-01

    The Cassini-Huygens mission instruments have revealed Titan to have a complex and dynamic atmosphere and surface. Data from the remote sensing instruments have shown the presence of diverse surface terrains in terms of morphology and composition, suggesting both exogenic and endogenic processes [1]. We define both the surface and atmospheric contributions in the VIMS spectro-imaging data by use of a radiative transfer code in the near-IR range [2]. To complement this dataset, the Cassini RADAR instrument provides additional information on the surface morphology, from which valuable geological interpretations can be obtained [3]. We examine the origin of key Titan terrains, covering the mid-latitude zones extending from 50ºN to 50ºS. The different geological terrains we investigate include: mountains, plains, labyrinths, craters, dune fields, and possible cryovolcanic and/or evaporite features. We have found that the labyrinth terrains and the undifferentiated plains seem to consist of a very similar if not the same material, while the different types of plains show compositional variations [3]. The processes most likely linked to their formation are aeolian, fluvial, sedimentary, lacustrine, in addition to the deposition of atmospheric products though the process of photolysis and sedimentation of organics. We show that temporal variations of surface albedo exist for two of the candidate cryovolcanic regions. The surface albedo variations together with the presence of volcanic-like morphological features suggest that the active regions are possibly related to the deep interior, possibly via cryovolcanism processes (with important implications for the satellite’s astrobiological potential) as also indicated by new interior structure models of Titan and corresponding calculations of the spatial pattern of maximum tidal stresses [4]. However, an explanation attributed to exogenic processes is also possible [5]. We will report on results from our most recent

  5. Ice exposures and landscape evolution in the Martian mid-latitudes

    Science.gov (United States)

    Dundas, C. M.; Bramson, A. M.; Ojha, L.; Wray, J. J.; Mellon, M. T.; Byrne, S.; McEwen, A. S.; Putzig, N. E.; Viola, D.; Sutton, S.

    2017-12-01

    The large-scale geographic distribution of Martian shallow ground ice is now relatively well-known, but the vertical structure of the ice is not as well understood. Here we report on erosional scarps in kilometer-scale pits near ±55-60 degrees latitude that expose cross-sections through ice-rich mantling deposits covering much of the mid-latitudes. HiRISE images of the scarps reveal ice-rich deposits (i.e., not regolith-pore-filling ice) that are >100 m thick and occur within 1 m of the top of the scarps. CRISM spectra confirm the presence of water ice through late summer, implying exposed ground ice rather than seasonal frost. SHARAD sounding radar data show some candidate reflectors similar to those inferred to be from the base of excess ice deposits elsewhere on Mars, but no internal structure is resolved. Ice-exposing impacts and thermokarst landforms convey information about excess ice abundance in the upper few meters, but not its deeper structure. The overall structure of the ice table is simple, with massive ice (sometimes layered) under a relatively thin lithic mantle, plus a boulder-rich interior lens in one scarp. The latter may be partly ice-cemented. The ice is commonly fractured. These observations demonstrate how deep ice sheets link with the shallow ice table, at least locally. The likely origin of the ice is accumulation of snow with some admixed dust during a different climate. This snow accumulation could be related to 370 ka changes observed at the poles [1] but some ice sheets may be tens of Myr old [2]. the origin of superposed boulder-sized rocks is puzzling; possible explanations include glacial flow, impact gardening, or some form of frost heave or cryoturbation. Repeat HiRISE observations demonstrate that the scarps are actively retreating, as boulders have fallen from one scarp and there are albedo changes elsewhere. This activity demonstrates that local sublimation is contributing to present-day Martian landscape evolution and is an

  6. Mid-latitude Ozone Depletion Events Caused by Halogens from the Great Salt Lake in Utah

    Science.gov (United States)

    Fibiger, D. L.; Goldberger, L.; Womack, C.; McDuffie, E. E.; Dube, W. P.; Franchin, A.; Middlebrook, A. M.; Thornton, J. A.; Brown, S. S.

    2017-12-01

    Halogens are highly reactive chemicals and play an important role in atmospheric chemistry. They can be involved in many cycles which influence the oxidizing capacity of the atmosphere, including through destruction of ozone (O3). While the influence of halogens on O3 is well documented in the arctic, there are very few observations of O3 depletion driven by halogens in the mid-latitudes. To date, the most comprehensive study observed co-occurring plumes of BrO and depleted O3 near the Dead Sea in 1997. During the Utah Wintertime Fine Particulate Study (UWFPS) in winter 2017, simultaneous measurements of a comprehensive suite of halogen measurements by I- chemical ionization mass spectrometry and O3 from cavity ring-down spectroscopy, both at 1-second time resolution, were taken on a NOAA Twin Otter Aircraft over the Great Salt Lake and in the surrounding valleys. Many O3 depletion events were observed over the lake with O3 values sometimes below the instrument detection limit of 0.5 ppbv. Corresponding increases in BrO and/or ClO were observed. Many of these events were caused by extremely high levels of halogens (up to 1 ppmv Cl2) emitted from the U.S. Magnesium plant on the edge of the lake. The O3 depletion caused by U.S. Magnesium was usually isolated to a distinct vertical layer, but in other cases O3 depletion was vertically mixed and the origin of halogen activation was not immediately clear. The most complete O3 depletion was observed over the lake, but there were smaller events of a few ppbv observed in the adjacent valleys, including the highly populated Salt Lake Valley, with corresponding plumes of BrO and ClO, due to transport from the lake. Additionally, meteorology played a role in the observed O3 depletion. The strongest O3 depletion was observed during inversion events, when there is a low boundary layer and little mixing out of the air above the lake. During non-inversion conditions, only small depletions were observed, covering a much smaller

  7. The photochemistry and kinetics of chlorine compounds important to stratospheric mid-latitude ozone destruction

    Science.gov (United States)

    Goldfarb, Leah

    1997-09-01

    The catalytic destruction of stratospheric ozone via chlorinated species was first proposed in the 1970's. Since that time a decline in column ozone abundance in the polar regions as well as at mid-latitudes has been observed. Much of this reduction has been attributed to the increases in anthropogenic chlorine compounds such as CFCs. This study summarizes experimental results obtained using pulsed-photolysis resonance fluorescence and pulsed- photolysis long-path absorption methods to study processes important to chlorine-catalyzed ozone destruction: the quantum yields of the products in the dissociation of ClONO2 and the reactions of free radicals with ClONO2 and ClO. The quantum yields for the production of O, Cl and ClO from ClONO2 were studied at specific laser wavelengths (193, 222, 248, and 308 nm). Cl and ClO yields were comparable at nearly all the wavelengths, expect for 193 nm, where the O atom yield was appreciable. The yields at 308 nm (a wavelength available in the stratosphere) were 0.64 ± 0.17 for Cl, 0.37 ± 0.18 for ClO and product yield for the former reaction, previously unreported, was determined to be ~1. The kinetics of the reaction of O atoms with ClO were measured using a new experimental system built specifically to investigate such radical-radical reactions. A slight negative temperature dependence (E/B = -90 ± 30) was observed over the temperature range (227-363 K). From the measured Arrhenius equation the rate constant at 240 K is 4.1 × 10-11 cm3molecule-1s-1 which is in excellent agreement (l.4% greater) with the currently recommended value. This observation is significant, since this reaction is the rate limiting the dominate chlorine catalytic cycle that destroys O3 near 40 km. To analyze the implications of the kinetic and photochemical information from this work, a box model was constructed. The vertical profile of ozone concentrations and loss rates calculated by this simple model compare well with atmospheric measurements and

  8. Effect of TADs on the F-region of Low midlatitude ionosphere during intense geomagnetic storm.

    Science.gov (United States)

    Upadhayaya, Arun Kumar; Joshi, Shivani; Singh Dabas, Raj; Das, Rupesh M.; Yadav, Sneha

    Effect of TAD's on the F region ionosphere of low-mid latitude ionosphere during three intense storms of20 th Nov,2003(-422nT),30 th Oct 2003(-383nT),07Nov,2004(-373nT)respectively are studued using ionosonde data of Delhi(28ø N 77øE).It has been seen that the electon density profile in the F1 region are greatly influenced by the TAD's presence. Further the pre-existing F1 cusp become better devloped during the passage of TAD's.

  9. Low and Mid-Latitude Ionospheric Irregularities Studies Using TEC and Radio Scintillation Data from the CITRIS Radio Beacon Receiver in Low-Earth-Orbit

    Science.gov (United States)

    Siefring, C. L.; Bernhardt, P. A.; Huba, J.; Krall, J.; Roddy, P. A.

    2009-12-01

    Unique data on ionospheric plasma irregularities from the Naval Research Laboratory (NRL) CITRIS (Scintillation and TEC Receiver in Space) instrument will be presented. CITRIS is a multi-band receiver that recorded TEC (Total Electron Content) and radio scintillations from Low-Earth Orbit (LEO) on STPSat1. The 555+/5 km altitude 35° inclination orbit covers low and mid-latitudes. The measurements require propagation from a transmitter to a receiver through the F-region plasma. CITRIS used both 1) satellite beacons in LEO, such as the NRL CERTO (Coherent Electromagnetic Radio TOmography) beacons and 2) the global network of ground-based DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) beacons. The TEC measurements allow for tracking of ionospheric disturbances and irregularities while the measurements of scintillations can simultaneously characterize their effects. CITRIS was operated in a complementary fashion with the C/NOFS (Communication/Navigations Outages Forecasting System) satellite during most of its first year of operations. C/NOFS carries a three-frequency 150/400/1067 MHz CERTO beacon and is dedicated to the study of Spread-F. In the case of Spread-F, ionospheric irregularities start with large scale size density gradients (100s of km) and cascade through complex processes to short scale sizes (10s of meters). It is typically the 100m-1km scale features that harm communication and navigation systems through scintillations. A multi-sensor approach is needed to completely understand this complex system, such as, the combination of CITRIS remote radio sensing and C/NOFS in-situ data. Several types of irregularities have been studied including Spread-F and the newly discovered dawn-side depletions. Comparisons with the physics based SAMI3 model are being performed to help our understanding of the morphology of the irregularities.

  10. Numerical simulation of mid-latitude ionospheric E-region based on SEEK and SEEK-2 observations

    Directory of Open Access Journals (Sweden)

    T. Yokoyama

    2005-10-01

    Full Text Available Observational campaigns of the mid-latitude ionospheric E-region with sounding rockets and ground-based instruments were conducted in 1996 (SEEK and 2002 (SEEK-2. Both of them were successfully conducted to bring important findings about the mid-latitude E-region and quasi-periodic (QP VHF radar echoes. The observational results in the SEEK and the SEEK-2 are compared with numerical simulations and discussed in this paper. While sporadic-E (Es-layers are actually formed by the observed neutral wind, it is difficult for the constant wind shear to produce the sharp Es-layer gradient. However, once they are formed in the lower E-region, they cannot easily be dissipated by the simple diffusive motion. The polarization electric field, calculated under the condition at the rocket launch time, shows similar amplitude and structure to the measurement around the Es-layer altitude. The structure of the plasma density and the electric field above the Es-layer observed in the SEEK-2 showed a wave-like pattern up to an altitude of 150 km. Considering a mapping of the polarization electric field generated within the Es-layers, gravity waves are the possible source of the wave-like structure of the measured electric fields and sub-peaks of the electron density above the main Es-layers. Fluctuation of the measured magnetic field is reproduced by Hall or field-aligned current driven by the polarization electric field. The current theoretical models for QP echoes and the polarization electric field are basically verified by the discussion in this paper. Keywords. Ionospheric irregularities – Mid-latitude ionosphere – Numerical simulation studies

  11. Changes on Mid-Latitude Cyclones due to Global Warming Simulated by a Global 20-km-mesh Atmospheric Model

    Science.gov (United States)

    Miyamoto, K.

    2005-12-01

    I investigate how the intensity and the activity of mid-latitude cyclones change as a result of global warming, based on a time-slice experiment with a super-high resolution Atmospheric General Circulation Model (20-km mesh TL959L60 MRI/JMA AGCM). The model was developed by the RR2002 project "Development of Super High Resolution Global and Regional Climate Models" funded by the Japanese Ministry of Education, Culture, Sports, Science and Technology. In this context, I use a 10-year control simulation with the climatological SST and a 10-year time-slice global warming simulation using the SST anomalies derived from the SRES A1B scenario run with the MRI-CGCM2.3 (T42L30 atmosphere, 0.5-2.0 x 2.5 L23 ocean) corresponding to the end of the 21st century. I have analyzed the sea-level pressure field and the kinetic energy field of the wind at the 500 hPa pressure level associated with mid-latitude transients from October through April. According to a comparison of 10-day average fields between present and future in the North Pacific, some statistically significant changes are found in a warmer climate for the both of sea-level pressure and the kinetic energy fields. In particular, from late winter through early spring, the sea-level pressure decreases on many parts of the whole Pacific. The kinetic energy of the wind becomes higher on center of the basin. Therefore, I suppose the Aleutian Low is likely to settle in longer by about one month than the present. Hereafter, I plan to investigate what kind of phenomena may accompany the changes on mid-latitude transients.

  12. Dissected Mantle Terrain on Mars: Formation Mechanisms and the Implications for Mid- latitude Near-surface Ground Ice

    Science.gov (United States)

    Searls, M. L.; Mellon, M. T.

    2008-12-01

    Determining the present and past distribution of surface and subsurface ice on Mars is critical for understanding the volatile inventory and climatic history of the planet. An analysis of a latitude-dependent layer of surface material known as the dissected mantle terrain can provide valuable insight into the distribution of ice in the recent past. The dissected mantle terrain is a surface unit that occurs globally in the mid-latitude of Mars. This unit is characterized by a smooth mantle of uniform thickness and albedo that is draped over the existing topography. This smooth mantle is disaggregated and dissected in places resulting in a hummocky pitted appearance. We propose that the mid-latitude dissected terrain results from collapse of a dusty mantle into the void left from desiccation of an underlying ice-rich (pure or dirty ice) layer. During period(s) of high obliquity, it is possible for ice to become stable at lower latitudes. Due to lack of direct solar insolation, surface ice deposits will preferentially accumulate on pole-ward facing slopes first. A mantle of dust and dirt is then deposited on top of these ice-rich deposits. As the climate changes, desiccation of the now buried ice leads to collapse of the overlying dusty layer resulting in a hummocky pitted appearance. This theory is supported by the pole-ward preference for the dissection pits as well an increase in dissection with increasing latitude. A study of the global distribution of the mid-latitude dissected terrain can provide invaluable clues towards unlocking the distribution of ice in the recent past. An analysis of HiRISE images and MOLA data indicate that the distribution of dissection pits varies from one region to the next. Knowing the distribution of ice in conjunction with ice stability modeling can provide a global view of the climate and orbital history of Mars at the time these features formed.

  13. Habitat-specific bioaccumulation of methylmercury in invertebrates of small mid-latitude lakes in North America

    Energy Technology Data Exchange (ETDEWEB)

    Chetelat, John, E-mail: john.chetelat@ec.gc.c [Groupe de recherche interuniversitaire en limnologie, Departement de sciences biologiques, Universite de Montreal, Montreal, Quebec H3C 3J7 (Canada); Amyot, Marc; Garcia, Edenise [Groupe de recherche interuniversitaire en limnologie, Departement de sciences biologiques, Universite de Montreal, Montreal, Quebec H3C 3J7 (Canada)

    2011-01-15

    We examined habitat-specific bioaccumulation of methylmercury (MeHg) in aquatic food webs by comparing concentrations in pelagic zooplankton to those in littoral macroinvertebrates from 52 mid-latitude lakes in North America. Invertebrate MeHg concentrations were primarily correlated with water pH, and after controlling for this influence, pelagic zooplankton had significantly higher MeHg concentrations than littoral primary consumers but lower MeHg than littoral secondary consumers. Littoral primary consumers and pelagic zooplankton are two dominant prey for fish, and greater MeHg in zooplankton is likely sufficient to increase bioaccumulation in pelagic feeders. Intensive sampling of 8 lakes indicated that habitat-specific bioaccumulation in invertebrates (of similar trophic level) may result from spatial variation in aqueous MeHg concentration or from more efficient uptake of aqueous MeHg into the pelagic food web. Our findings demonstrate that littoral-pelagic differences in MeHg bioaccumulation are widespread in small mid-latitude lakes. - Methylmercury levels in dominant invertebrate prey for fish differ between littoral and pelagic habitats within a lake.

  14. Habitat-specific bioaccumulation of methylmercury in invertebrates of small mid-latitude lakes in North America

    International Nuclear Information System (INIS)

    Chetelat, John; Amyot, Marc; Garcia, Edenise

    2011-01-01

    We examined habitat-specific bioaccumulation of methylmercury (MeHg) in aquatic food webs by comparing concentrations in pelagic zooplankton to those in littoral macroinvertebrates from 52 mid-latitude lakes in North America. Invertebrate MeHg concentrations were primarily correlated with water pH, and after controlling for this influence, pelagic zooplankton had significantly higher MeHg concentrations than littoral primary consumers but lower MeHg than littoral secondary consumers. Littoral primary consumers and pelagic zooplankton are two dominant prey for fish, and greater MeHg in zooplankton is likely sufficient to increase bioaccumulation in pelagic feeders. Intensive sampling of 8 lakes indicated that habitat-specific bioaccumulation in invertebrates (of similar trophic level) may result from spatial variation in aqueous MeHg concentration or from more efficient uptake of aqueous MeHg into the pelagic food web. Our findings demonstrate that littoral-pelagic differences in MeHg bioaccumulation are widespread in small mid-latitude lakes. - Methylmercury levels in dominant invertebrate prey for fish differ between littoral and pelagic habitats within a lake.

  15. Multi-layer structure of mid-latitude sporadic-E observed during the SEEK-2 campaign

    Directory of Open Access Journals (Sweden)

    T. Ono

    2005-10-01

    Full Text Available In the mid-latitude ionospheric region, sporadic-E layers (Es layers have often been observed, revealing multiple layers. The Es layers observed during the SEEK-2 rocket campaign showed double electron density peaks; namely, there are stable lower peaks and relatively unstable upper peaks. We examined the effects of wind shear and the electric fields on the generation of the multiple layer structure, in comparison with the electron density profile, the neutral wind, and the DC electric field observed by the S310 rocket experiments. The results showed that the neutral wind shear is mainly responsible for the generation of the lower layer, while the DC electric field makes a significant contribution to the formation of the upper layer. The difference between the lower and upper layers was also explained by the enhanced AC electric field observed at about 103–105 km altitude. The external DC electric field intensity is expected to be ~5 mV/m, which is enough to contribute to generate the Es layers in the ionosphere. Keywords. Ionosphere (Electric fields; Ionospheric irregularities, Mid-latitude ionosphere

  16. The topside ionospheric effective scale heights (HT) derived with ROCSAT-1 and ground-based Ionosonde observations at equatorial and mid-latitude stations

    Science.gov (United States)

    Ram Sudarsanam, Tulasi; Su, Shin-Yi; Liu, C. H.; Reinisch, Bodo

    In this study, we propose the assimilation of topside in situ electron density data from ROCSAT-1 satellite along with the ionosonde measurements for accurate determination of topside iono-spheric effective scale heights (HT) using -Chapman function. The reconstructed topside elec-tron density profiles using these scale heights exhibit an excellent similitude with Jicamarca Incoherent Scatter Radar (ISR) profiles, and are much better representations than the existing methods of Reinisch-Huang method and/or the empirical IRI-2007 model. The main advan-tage with this method is that it allows the precise determination of the effective scale height (HT) and the topside electron density profiles at a dense network of ionosonde/digisonde sta-tions where no ISR facilities are available. The demonstration of the method is applied by investigating the diurnal, seasonal and solar activity variations of HT over the dip-equatorial station Jicamarca and the mid-latitude station Grahamstown. The diurnal variation of scale heights over Jicamarca consistently exhibits a morning time descent followed by a minimum around 0700-0800 LT and a pronounced maximum at noon during all the seasons of both high and moderate solar activity periods. Further, the scale heights exhibit a secondary maximum during the post-sunset hours of equinoctial and summer months, whereas the post-sunset peak is absent during the winter months. These typical features are further investigated using the topside ion properties obtained by ROCSAT-1 as well as SAMI2 model simulations. The re-sults consistently indicate that the diurnal variation of the effective scale height (HT) does not closely follow the plasma temperature variation and at equatorial latitudes is largely controlled by the vertical ExB drift.

  17. Future C loss in mid-latitude mineral soils: climate change exceeds land use mitigation potential in France.

    Science.gov (United States)

    Meersmans, Jeroen; Arrouays, Dominique; Van Rompaey, Anton J J; Pagé, Christian; De Baets, Sarah; Quine, Timothy A

    2016-11-03

    Many studies have highlighted significant interactions between soil C reservoir dynamics and global climate and environmental change. However, in order to estimate the future soil organic carbon sequestration potential and related ecosystem services well, more spatially detailed predictions are needed. The present study made detailed predictions of future spatial evolution (at 250 m resolution) of topsoil SOC driven by climate change and land use change for France up to the year 2100 by taking interactions between climate, land use and soil type into account. We conclude that climate change will have a much bigger influence on future SOC losses in mid-latitude mineral soils than land use change dynamics. Hence, reducing CO 2 emissions will be crucial to prevent further loss of carbon from our soils.

  18. A simple climatology of westerly jet streams in global reanalysis datasets part 1: mid-latitude upper tropospheric jets

    Science.gov (United States)

    Rikus, Lawrie

    2018-04-01

    A simple closed contour object identification scheme has been applied to the zonal mean monthly mean zonal wind fields from nine global reanalysis data sets for 31 years of the satellite era (1979-2009) to identify objects corresponding to westerly jet streams. The results cluster naturally into six individual jet streams but only the mid-latitude upper-tropospheric jets are considered here. The time series of the jet properties from all reanalyses are decomposed into seasonal means and anomalies, and correlations between variables are evaluated, with the aim of identifying robust features which can form the basis of evaluation metrics for climate model simulations of the twentieth century. There is substantial agreement between all the reanalyses for all jet properties although there are some systematic differences with particular data sets. Some of the results from the object identification applied to the reanalyses are used in a simple example of a model evaluation score for the zonal mean jet seasonal cycle.

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

    International Nuclear Information System (INIS)

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

    1988-01-01

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

  20. Precursory enhancement of EIA in the morning sector: Contribution from mid-latitude large earthquakes in the north-east Asian region

    Science.gov (United States)

    Ryu, Kwangsun; Oyama, Koh-Ichiro; Bankov, Ludmil; Chen, Chia-Hung; Devi, Minakshi; Liu, Huixin; Liu, Jann-Yenq

    2016-01-01

    To investigate whether the link between seismic activity and EIA (equatorial ionization anomaly) enhancement is valid for mid-latitude seismic activity, DEMETER observations around seven large earthquakes in the north-east Asian region were fully analyzed (M ⩾ 6.8). In addition, statistical analysis was performed for 35 large earthquakes (M ⩾ 6.0) that occurred during the DEMETER observation period. The results suggest that mid-latitude earthquakes do contribute to EIA enhancement, represented as normalized equatorial Ne , and that ionospheric change precedes seismic events, as has been reported in previous studies. According to statistical studies, the normalized equatorial density enhancement is sensitive and proportional to both the magnitude and the hypocenter depth of an earthquake. The mechanisms that can explain the contribution of mid-latitude seismic activity to EIA variation are briefly discussed based on current explanations of the geochemical and ionospheric processes involved in lithosphere-ionosphere interaction.

  1. Classification of Global Land Development Phases by Forest and GDP Changes for Appropriate Land Management in the Mid-Latitude

    Directory of Open Access Journals (Sweden)

    Cholho Song

    2017-08-01

    Full Text Available To implement appropriate land management strategies, it is essential to identify past and current land cover and land use conditions. In addition, an assessment of land development phases (LDPs in a human-dominated landscape coupled with an analysis of the water-food-ecosystem (WFE nexus can deepen our understanding of sustainable land management. In this study, we proposed the concept of land development phases (LDPs by forest and GDP changes using previously-applied theoretical and empirical approaches. The positive relationship between GDP growth and forest stock changes was used to analyze the timing of forest stock changes as five-year averages, which were aggregated over 20 years to classify LDPs. In addition, forest area changes compared with GDP and GDP per capita changes were analyzed to identify LDPs. Based on two conceptual approaches, we suggested global land into three LDPs: degradation, restoration and sustainability. Using this approach, most of Europe, North America and northeast Asia were classified as sustainability phases, while Africa and Central Asia in the Mid-Latitude region appeared to have degradation or restoration phases. The LDPs described could be improved with further incorporation of solid data analysis and clear standards, but even at this stage, these LDP classifications suggest points for implementing appropriate land management. In addition, indices from comparative analysis of the LDPs with the WFE nexus can be connected with socio-economic global indices, such as the Global Hunger Index, the Food Production Index and the Climate Change Performance Index. The LDPs have the potential to facilitate appropriate land management strategies through integrating WFE nexus and ecosystem services; we propose future research that uses this integration for the Mid-Latitude region and worldwide.

  2. Butterflies, Black swans and Dragon kings: How to use the Dynamical Systems Theory to build a "zoology" of mid-latitude circulation atmospheric extremes?

    Science.gov (United States)

    Faranda, D.; Yiou, P.; Alvarez-Castro, M. C. M.

    2015-12-01

    A combination of dynamical systems and statistical techniques allows for a robust assessment of the dynamical properties of the mid-latitude atmospheric circulation. Extremes at different spatial and time scales are not only associated to exceptionally intense weather structures (e.g. extra-tropical cyclones) but also to rapid changes of circulation regimes (thunderstorms, supercells) or the extreme persistence of weather structure (heat waves, cold spells). We will show how the dynamical systems theory of recurrence combined to the extreme value theory can take into account the spatial and temporal dependence structure of the mid-latitude circulation structures and provide information on the statistics of extreme events.

  3. Mid-latitude electron precipitation into the atmosphere and related geophysical phenomena

    International Nuclear Information System (INIS)

    Chang, Y.C.

    1976-01-01

    Balloon observations of the x-ray flux of photons with energies greater than 25 keV, measured at an atmospheric depth of 8 g/cm at Roberval, Quebec (L=4.2) and satellite observations of the flux of electrons with energies greater than 35 keV in the dawn sector from L=4.2 to L=5.3 were analyzed. A differently structured cross-correlation curve was found during the first five minutes immediately after the onset of enhancement of the X-ray intensity. The technique of power spectral analysis was used to investigate periodicities in the flux. A dominant peak at the period of 0.83 second was found in the power spectral density of the counting rate of the greater than 200 keV channel during a relatively quiet-period of time from the point of view of electron precipitation. The precipitation of intermediate energy (250-500 keV) electrons responsible for the greater than 200 keV X rays was modulated at the bounce period of low energy (65-90 keV) electrons. The mechanism for the precipitation was pitch angle diffusion due to the electron-whistler mode wave interaction. Waves generated by low energy electrons in the equatorial region propagated outside of the region of growth. These waves could interact with higher energy electrons and modulate the flux of these electrons. A correlation study of the enhancement seen in the low energy channels of the S 3 satellite electron detector with the enhancement of X-ray fluxes during a substorm was made. The satellite data were used to locate where and when the injections occurred. Two sets of enhancements observed by the satellite were found to be injected at different local times at the same time which was within a few minutes of the onset of geomagnetic bays at several near-midnight ground stations. A model based on convection due to a static westward electric field and azimuthal drift due to the gradient and curvature of B was used to explain the energy dispersion and time delay of the substorm associated observations

  4. Volcanic terrain and the possible periglacial formation of "excess ice" at the mid-latitudes of Utopia Planitia, Mars

    Science.gov (United States)

    Soare, R. J.; Horgan, B.; Conway, S. J.; Souness, C.; El-Maarry, M. R.

    2015-08-01

    At the mid-latitudes of Utopia Planitia (UP), Mars, a suite of spatially-associated landforms exhibit geomorphological traits that, on Earth, would be consistent with periglacial processes and the possible freeze-thaw cycling of water. The suite comprises small-sized polygonally-patterned ground, polygon-junction and -margin pits, and scalloped, rimless depressions. Typically, the landforms incise a dark-toned terrain that is thought to be ice-rich. Here, we investigate the dark-toned terrain by using high resolution images from the HiRISE as well as near-infrared spectral-data from the OMEGA and CRISM. The terrain displays erosional characteristics consistent with a sedimentary nature and near-infrared spectra characterised by a blue slope similar to that of weathered basaltic-tephra. We also describe volcanic terrain that is dark-toned and periglacially-modified in the Kamchatka mountain-range of eastern Russia. The terrain is characterised by weathered tephra inter-bedded with snow, ice-wedge polygons and near-surface excess ice. The excess ice forms in the pore space of the tephra as the result of snow-melt infiltration and, subsequently, in-situ freezing. Based on this possible analogue, we construct a three-stage mechanism that explains the possible ice-enrichment of a broad expanse of dark-toned terrain at the mid-latitudes of UP: (1) the dark-toned terrain accumulates and forms via the regional deposition of sediments sourced from explosive volcanism; (2) the volcanic sediments are blanketed by atmospherically-precipitated (H2O) snow, ice or an admixture of the two, either concurrent with the volcanic-events or between discrete events; and, (3) under the influence of high obliquity or explosive volcanism, boundary conditions tolerant of thaw evolve and this, in turn, permits the migration, cycling and eventual formation of excess ice in the volcanic sediments. Over time, and through episodic iterations of this scenario, excess ice forms to decametres of

  5. Tropospheric mid-latitude geopotential wave characteristics associated with strong wind events in the North Atlantic/European region

    Science.gov (United States)

    Wild, Simon; Simmonds, Ian; Leckebusch, Gregor C.

    2015-04-01

    The variability of strong synoptic scale wind events in the mid-latitudes have long been linked to baroclinic wave activity in the mid troposphere. Previous studies have also shown that greater amplitudes of planetary waves in the mid troposphere are likely to increase the occurrence of regional extremes in temperature and precipitation. In this study we examine whether characteristics of planetary and synoptic mid-latitude waves show systematic anomalies in the North Atlantic/ European region which can be related to the occurrence of a strong surface wind event. We will mainly focus on two questions: 1) Do amplitudes for waves with different wave lengths show a systematic anomaly when a strong wind event occurs? 2) Can phases of the individual wave components be detected that favour strong wind events? In order to decompose the mid-tropospheric flow into longitudinal waves we employ the fast Fourier transform to the meridional mean of the geopotential height in 500hPa between 35° and 60°N for i) the entire latitude belt and ii) for a North Atlantic/European sector (36°W to 36°E). Our definition of strong wind events is based on the Storm Severity Index (SSI) alongside a wind tracking algorithm identifying areas of exceedances of the local 98th percentile of the 10m wind speed. First results using ERA-Interim Reanalysis from 1979 - 2014 for the extended winter season (ONDJFM) for the 50 most intense strong wind systems with respect to the SSI reveal a greater amplitude for all investigated wave numbers. Especially waves with wave lengths below 2000km show an increase of about 25% of the daily standard deviation on average. The distribution of wave phases for the different wave numbers with respect to the location of a strong wind event shows a less homogenous picture. There is however a high proportion of events that can be associated with phases around 3π/4 and 5π/4 of waves with lengths of around 6000km, equivalent to wave number 5 on a planetary scale

  6. Seasonal variations of the high-latitude F region for

    International Nuclear Information System (INIS)

    Sojka, J.J.; Schunk, R.W.; Raitt, W.J.

    1982-01-01

    We combined a plasma convection model with an inosphere-atmospheric composition model in order to study the seasonal variations of the high-latitude F region for strong convection. Our numerical study produced time-dependent, three-dimensional, ion density distributions for the ions NO + , O 2 + , N 2 + , O + , N + , and He + . We covered the high-latitude ionosphere above 42 0 N magnetic latitude and at altitudes between 160 and 800 km for a time period of one complete day. From our study we found the following: (1) For strong convection, the high-altitude ionosphere exhibits a significant UT variation both during winter and summer. (2) In general, the electron density is lower in winter than in summer. However, at certain universal times the electron density in the dayside polar cap is larger in winter than in summer owing to the effect of the mid-latitude 'winter anomaly' in combination with strong antisunward convection. (3) In both summer and winter, the major region of low electron density is associated with the main or mid-latitudde trough. The trough is deeper and its local time extend is much greater in winter than in summer. (4) Typically, the electron density exhibits a much larger variation with altitude in winter than in summer. (5) The ion composition and molecular/atomic ion transition altitude are highly UT dependent in both summer and winter. (6) The ion composition also displays a significant seasonal variation. However, at a given location the seasonal variation can be opposite at different universal times. (7) High-speed convection cells should display a marked seasonal variation, with a much larger concentration of molecular ions near the F region peak in summer than in winter

  7. Synoptic climate change as a driver of late Quaternary glaciations in the mid-latitudes of the Southern Hemisphere

    Science.gov (United States)

    Rother, H.; Shulmeister, J.

    2006-05-01

    The relative timing of late Quaternary glacial advances in mid-latitude (40-55° S) mountain belts of the Southern Hemisphere (SH) has become a critical focus in the debate on global climate teleconnections. On the basis of glacial data from New Zealand (NZ) and southern South America it has been argued that interhemispheric synchrony or asynchrony of Quaternary glacial events is due to Northern Hemisphere (NH) forcing of SH climate through either the ocean or atmosphere systems. Here we present a glacial snow-mass balance model that demonstrates that large scale glaciation in the temperate and hyperhumid Southern Alps of New Zealand can be generated with moderate cooling. This is because the rapid conversion of precipitation from rainfall to snowfall drives massive ice accumulation at small thermal changes (1-4°C). Our model is consistent with recent paleo-environmental reconstructions showing that glacial advances in New Zealand during the Last Glacial Maximum (LGM) and the Last Glacial Interglacial Transition (LGIT) occurred under very moderate cooling. We suggest that such moderate cooling could be generated by changes in synoptic climatology, specifically through enhanced regional flow of moist westerly air masses. Our results imply that NH climate forcing may not have been the exclusive driver of Quaternary glaciations in New Zealand and that synoptic style climate variations are a better explanation for at least some late Quaternary glacial events, in particular during the LGIT (e.g. Younger Dryas and/or Antarctic Cold Reversal).

  8. Synoptic climate change as a driver of late Quaternary glaciations in the mid-latitudes of the Southern Hemisphere

    Directory of Open Access Journals (Sweden)

    H. Rother

    2006-01-01

    Full Text Available The relative timing of late Quaternary glacial advances in mid-latitude (40-55° S mountain belts of the Southern Hemisphere (SH has become a critical focus in the debate on global climate teleconnections. On the basis of glacial data from New Zealand (NZ and southern South America it has been argued that interhemispheric synchrony or asynchrony of Quaternary glacial events is due to Northern Hemisphere (NH forcing of SH climate through either the ocean or atmosphere systems. Here we present a glacial snow-mass balance model that demonstrates that large scale glaciation in the temperate and hyperhumid Southern Alps of New Zealand can be generated with moderate cooling. This is because the rapid conversion of precipitation from rainfall to snowfall drives massive ice accumulation at small thermal changes (1-4°C. Our model is consistent with recent paleo-environmental reconstructions showing that glacial advances in New Zealand during the Last Glacial Maximum (LGM and the Last Glacial Interglacial Transition (LGIT occurred under very moderate cooling. We suggest that such moderate cooling could be generated by changes in synoptic climatology, specifically through enhanced regional flow of moist westerly air masses. Our results imply that NH climate forcing may not have been the exclusive driver of Quaternary glaciations in New Zealand and that synoptic style climate variations are a better explanation for at least some late Quaternary glacial events, in particular during the LGIT (e.g. Younger Dryas and/or Antarctic Cold Reversal.

  9. Beryllium-7 in near-surface atmospheric aerosols in mid-latitude (40 deg N) city Beijing, China

    International Nuclear Information System (INIS)

    Keyan Tan; Yongliang Yang; Xiaohua Zhu; Shu Chen; Xingchun Jiao; Nan Gai; Yi Huang

    2013-01-01

    A high-volume air sampler and a high-resolution gamma-ray spectrometer have been used to measure the activity of 7 Be in near-surface atmospheric aerosols at sampling frequency of 3 days week for 1 year from August 2009 to July 2010 at Beijing in the mid-latitude region of East Asia monsoon. The measurements indicate that the average concentration of 7 Be was 8.39 ± 0.49 mBq m -3 , which was significantly higher than values reported for other cities in the East Asia monsoon region and in the world during the same period. The maximum and minimum of the weekly means of 7 Be concentration were observed in September and May, respectively. The 7 Be concentrations varied in accordance with the monsoon phases. Low but frequent wet precipitation may have caused lower 7 Be observed in July when southeasterly was prevailing. Higher seasonal mean of 7 Be concentrations in autumn could be attributed to the abnormal atmospheric circulation in autumn 2009. (author)

  10. Investigation of the Effects of Solar and Geomagnetic Changes on the Total Electron Content: Mid-Latitude Region

    Science.gov (United States)

    Ulukavak, Mustafa; Yalcinkaya, Mualla

    2016-04-01

    The Global Positioning System (GPS) is used as an important tool for ionosphere monitoring and obtaining the Total Electron Content (TEC). GPS satellites, positioned in the Earth's orbit, are used as sensors to investigate the space weather conditions. In this study, solar and geomagnetic activity variations were investigated between the dates 1 March-30 June 2015 for the mid-latitude region. GPS-TEC variations were calculated for each selected International GNSS Service (IGS) station in Europe. GNSS data was obtained from Crustal Dynamics Data and Information System (CDDIS) archive. Solar and geomagnetic activity indices (Kp, F10.7 ve Dst) were obtained from the Oceanic and Atmospheric Administration (NOAA), the Canadian Space Weather Forecast Centre (CSWFC) and Data Analysis Center for geomagnetism and Space Magnetism Graduate School of Science, Kyoto University (WDC) archives. GPS-TEC variations were determined for the quiet periods of the solar and geomagnetic activities. GPS-TEC changes were then compared with respect to the quiet periods of the solar and geomagnetic activities. Global Ionosphere Maps (GIM) IONEX files, obtained from the IGS analysis center, was used to check the robustness of the GPS-TEC variations. The investigations revealed that it is possible to use the GPS-TEC data for monitoring the ionospheric disturbances.

  11. Amplified warming projections for high altitude regions of the northern hemisphere mid-latitudes from CMIP5 models

    International Nuclear Information System (INIS)

    Rangwala, Imtiaz; Sinsky, Eric; Miller, James R

    2013-01-01

    We use output from global climate models available from the Coupled Model Intercomparison Project Phase 5 (CMIP5) for three different greenhouse gas emission scenarios to investigate whether the projected warming in mountains by the end of the 21st century is significantly different from that in low elevation regions. To remove the effects of latitudinal variation in warming rates, we focus on seasonal changes in the mid-latitude band of the northern hemisphere between 27.5° N and 40° N, where the two major mountain systems are the Tibetan Plateau/Himalayas in Asia and the Rocky Mountains in the United States. Results from the multi-model ensemble indicate that warming rates in mountains will be enhanced relative to non-mountain regions at the same latitude, particularly during the cold season. The strongest correlations of enhanced warming with elevation are obtained for the daily minimum temperature during winter, with the largest increases found for the Tibetan Plateau/Himalayas. The model projections indicate that this occurs, in part, because of proportionally greater increases in downward longwave radiation at higher elevations in response to increases in water vapor. The mechanisms for enhanced increases in winter and spring maximum temperatures in the Rockies appear to be influenced more by increases in surface absorption of solar radiation owing to a reduced snow cover. Furthermore, the amplification of warming with elevation is greater for a higher greenhouse gas emission scenario. (letter)

  12. Multi-model assessment of the impact of soil moisture initialization on mid-latitude summer predictability

    Science.gov (United States)

    Ardilouze, Constantin; Batté, L.; Bunzel, F.; Decremer, D.; Déqué, M.; Doblas-Reyes, F. J.; Douville, H.; Fereday, D.; Guemas, V.; MacLachlan, C.; Müller, W.; Prodhomme, C.

    2017-12-01

    Land surface initial conditions have been recognized as a potential source of predictability in sub-seasonal to seasonal forecast systems, at least for near-surface air temperature prediction over the mid-latitude continents. Yet, few studies have systematically explored such an influence over a sufficient hindcast period and in a multi-model framework to produce a robust quantitative assessment. Here, a dedicated set of twin experiments has been carried out with boreal summer retrospective forecasts over the 1992-2010 period performed by five different global coupled ocean-atmosphere models. The impact of a realistic versus climatological soil moisture initialization is assessed in two regions with high potential previously identified as hotspots of land-atmosphere coupling, namely the North American Great Plains and South-Eastern Europe. Over the latter region, temperature predictions show a significant improvement, especially over the Balkans. Forecast systems better simulate the warmest summers if they follow pronounced dry initial anomalies. It is hypothesized that models manage to capture a positive feedback between high temperature and low soil moisture content prone to dominate over other processes during the warmest summers in this region. Over the Great Plains, however, improving the soil moisture initialization does not lead to any robust gain of forecast quality for near-surface temperature. It is suggested that models biases prevent the forecast systems from making the most of the improved initial conditions.

  13. 18-year variability of ultraviolet radiation penetration in the mid-latitude coastal waters of the western boundary Pacific

    Science.gov (United States)

    Kuwahara, Victor S.; Nozaki, Sena; Nakano, Junji; Toda, Tatsuki; Kikuchi, Tomohiko; Taguchi, Satoru

    2015-07-01

    The 18-year time-series shows in situ ultraviolet radiation (UVR) and photosynthetically active radiation (PAR) diffuse attenuation coefficient Kd(λ) have recurrent seasonal variability of high/low attenuation during summer/winter months, respectively, dependent on variability in water column stratification and concentrations of bio-optical properties. The mid-latitude coastal survey station displayed significant seasonality of the mixed layer depth (MLD) between 12 and 82 m which modified the distribution of chlorophyll a (4.6-24.9 mg m-2) and absorption of colored dissolved organic matter [aCDOM(320 nm) 0.043-1.34 m-1]. The median Kd(320 nm) displayed significant seasonality at 0.19-0.74 m-1 (C.V. = 44.1%) and seasonal variability within the euphotic layer [Z10%(320 nm) = 7-20%]. High attenuation of UVR with relatively moderate attenuation of PAR was consistently observed during the summer months when increased concentrations of terrestrially derived CDOM coupled with a shallow MLD were present. The winter season showed the opposite of low UVR and PAR attenuation due to a relatively deeper MLD coupled with low concentrations of bio-optical properties. Although the long term Kd(λ) did not vary significantly during the time-series, analysis of the interannual variability suggests there are positive and negative phases following the Pacific Decadal Oscillation (PDO) vis-a-vis variability in bio-optical properties (p < 0.001).

  14. Mid-Holocene paleoclimatic changes and solar activity in San'in District, mid-latitude North Pacific Region

    Science.gov (United States)

    Okazaki, Y.; Seto, K.; Sakai, T.; Ooki, A.; yamada, K.; Dettman, D. L.

    2011-12-01

    Evidence shows that solar activity influences climate on a global scale. In the mid-latitude region, climate change is expected to change precipitation patterns. Concurrently, variation in solar activity may influence phytoplankton productivity. It seems that these changes should be recorded in sediment and organic matter deposits in coastal lagoons. In this study, we discuss the relationship between climate change and solar activity in the mid-Holocene in the northern hemisphere mid-latitude region based on grain size analysis, total organic carbon (TOC) content and organic carbon accumulation rates (Corg A.R.) in coastal lagoon sediment core samples. The INB core was drilled to produce a high resolution record of Holocene paleoenvironmental change in the San'in District, western Japan. The core is 19.17m in total length and is divided into Unit I~VII by lithofacies. Holocene sediment, primarily organic silt, forms Unit III and above in this core. Unit III was deposited from 8.4 to 5.4 ka, when sea level rose during the Jomon transgression; its depositional environment is a coastal lagoon. Progradation of the river mouth during the sea level rise lead to an increase in the C/N ratio of organic matter. Unit IV contains the volcanic Shigaku pyroclastic flow (the sixth stage of volcanic activity of the Sanbe volcano), and Unit V reflects deposition in a freshwater lake or swamp. Above this aggredational sediments were deposited by small rivers. This study focused on the coastal lagoon sediments of Unit III (8.4 to 5.4 ka); we carried out CNS elemental analysis and grain size analysis with a resolution of approximately five years. TOC content is variable and increases from 0.5 to 5%. Variation in TOC content is relatively well correlated with atmospheric radiocarbon 14C (Delta 14C) and therefore with solar activity, although the relationship is unclear in the upper portion of Unit III. The trend in Corg A.R. is different than TOC contents, about 40g/m/yr at ~8ka and

  15. High- and mid-latitude quasi-2-day waves observed simultaneouslyby four meteor radars during summer 2000

    Directory of Open Access Journals (Sweden)

    E. Merzlyakov

    2004-03-01

    Full Text Available Results from the analysis of MLT wind measurements at Dixon (73.5°N, 80°E, Esrange (68°N, 21°E, Castle Eaton (UK (53°N, 2°W, and Obninsk (55°N, 37°E during summer 2000 are presented in this paper. Using S-transform or wavelet analysis, quasi-two-day waves (QTDWs are shown to appear simultaneously at high- and mid-latitudes and reveal themselves as several bursts of wave activity. At first this activity is preceded by a 51–53h wave with S=3 observed mainly at mid-latitudes. After a short recess (or quiet time interval for about 10 days near day 205, we observe a regular sequence of three bursts, the strongest of them corresponding to a QTDW with a period of 47–48h and S=4 at mid-altitudes. We hypothesize that these three bursts may be the result of constructive and destructive interference between several spectral components: a 47–48h component with S=4; a 60-h component with S=3; and a 80-h component with S=2. The magnitudes of the lower (higher zonal wave-number components increase (decrease with increasing latitude. The S-transform or wavelet analysis indicates when these spectral components create the wave activity bursts and gives a range of zonal wave numbers for observed bursts from about 4 to about 2 for mid- and high-latitudes. The main spectral component at Dixon and Esrange latitudes is the 60-h oscillation with S=3. The zonal wave numbers and frequencies of the observed spectral components hint at the possible occurrence of the nonlinear interaction between the primary QTDWs and other planetary waves. Using a simple 3-D nonlinear numerical model, we attempt to simulate some of the observed features and to explain them as a consequence of the nonlinear interaction between the primary 47–48h and the 9–10day waves, and the resulting linear superposition of primary and secondary waves. In addition to the QTDW bursts, we also infer forcing of the 4-day wave with S=2 and the 6–7day wave with S=1, possibly arising from

  16. Comparison of the decomposition VOC profile during winter and summer in a moist, mid-latitude (Cfb climate.

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    Shari L Forbes

    Full Text Available The investigation of volatile organic compounds (VOCs associated with decomposition is an emerging field in forensic taphonomy due to their importance in locating human remains using biological detectors such as insects and canines. A consistent decomposition VOC profile has not yet been elucidated due to the intrinsic impact of the environment on the decomposition process in different climatic zones. The study of decomposition VOCs has typically occurred during the warmer months to enable chemical profiling of all decomposition stages. The present study investigated the decomposition VOC profile in air during both warmer and cooler months in a moist, mid-latitude (Cfb climate as decomposition occurs year-round in this environment. Pig carcasses (Sus scrofa domesticus L. were placed on a soil surface to decompose naturally and their VOC profile was monitored during the winter and summer months. Corresponding control sites were also monitored to determine the natural VOC profile of the surrounding soil and vegetation. VOC samples were collected onto sorbent tubes and analyzed using comprehensive two-dimensional gas chromatography--time-of-flight mass spectrometry (GC × GC-TOFMS. The summer months were characterized by higher temperatures and solar radiation, greater rainfall accumulation, and comparable humidity when compared to the winter months. The rate of decomposition was faster and the number and abundance of VOCs was proportionally higher in summer. However, a similar trend was observed in winter and summer demonstrating a rapid increase in VOC abundance during active decay with a second increase in abundance occurring later in the decomposition process. Sulfur-containing compounds, alcohols and ketones represented the most abundant classes of compounds in both seasons, although almost all 10 compound classes identified contributed to discriminating the stages of decomposition throughout both seasons. The advantages of GC × GC-TOFMS were

  17. Temporal patterns of vegetation phenology and their responses to climate change in mid-latitude grasslands of the Northern Hemisphere

    Science.gov (United States)

    Ren, S.; Chen, X.; Qin, Q.; Zhang, Y.; Wu, Z.

    2017-12-01

    Grassland ecosystem is greatly sensitive to regional and global climate changes. In this study, the start (SOS) and end (EOS) date of growing season were extracted from NDVI data (1981 2014) across the mid-latitude (30°N 55°N) grasslands of Northern Hemisphere. We first validated their accuracy by ground observed phenological data and phenological metrics derived from gross primary production (GPP) data. And then, main climatic factors influencing the temporal patterns of SOS/EOS were explored by means of gridded meteorological data and partial correlation analysis. Based on the results of above statistical analysis, the similarities and differences of spring and autumn phenological responses to climate change among North American grasslands, Mid-West Asian grasslands, and Mongolian grasslands were analyzed. The main results and conclusions are as follows. First, a significant positive correlation was found between SOS/EOS and observed green-up/brown-off date (PSOS/EOS (PSOS/EOS can reflect temporal dynamics of terrestrial vegetation phenology. Second, SOS in Mid-West Asian grasslands showed a significant advancing trend (0.22 days/year, PSOS in North American grasslands and Mongolian grasslands was not significant. EOS in North American grasslands (0.31 dyas/year, PSOS/EOS inter-annual fluctuations and hydrothermal factors showed that a significant negative correlation was found between SOS and the pre-season temperature in 41.6% of pixels (PSOS and pre-season rainfall/snowfall in 14.6%/19.0% of pixels (PSOS and EOS are mainly affected by pre-season temperature and pre-season rainfall.

  18. Large scale spatially explicit modeling of blue and green water dynamics in a temperate mid-latitude basin

    Science.gov (United States)

    Du, Liuying; Rajib, Adnan; Merwade, Venkatesh

    2018-07-01

    Looking only at climate change impacts provides partial information about a changing hydrologic regime. Understanding the spatio-temporal nature of change in hydrologic processes, and the explicit contributions from both climate and land use drivers, holds more practical value for water resources management and policy intervention. This study presents a comprehensive assessment on the spatio-temporal trend of Blue Water (BW) and Green Water (GW) in a 490,000 km2 temperate mid-latitude basin (Ohio River Basin) over the past 80 years (1935-2014), and from thereon, quantifies the combined as well as relative contributions of climate and land use changes. The Soil and Water Assessment Tool (SWAT) is adopted to simulate hydrologic fluxes. Mann-Kendall and Theil-Sen statistical tests are performed on the modeled outputs to detect respectively the trend and magnitude of changes at three different spatial scales - the entire basin, regional level, and sub-basin level. Despite the overall volumetric increase of both BW and GW in the entire basin, changes in their annual average values during the period of simulation reveal a distinctive spatial pattern. GW has increased significantly in the upper and lower parts of the basin, which can be related to the prominent land use change in those areas. BW has increased significantly only in the lower part, likely being associated with the notable precipitation change there. Furthermore, the simulation under a time-varying climate but constant land use scenario identifies climate change in the Ohio River Basin to be influential on BW, while the impact is relatively nominal on GW; whereas, land use change increases GW remarkably, but is counterproductive on BW. The approach to quantify combined/relative effects of climate and land use change as shown in this study can be replicated to understand BW-GW dynamics in similar large basins around the globe.

  19. Validation of the Martilli's Urban Boundary Layer Scheme with measurements from two mid-latitude European cities

    Science.gov (United States)

    Hamdi, R.; Schayes, G.

    2005-07-01

    The Martilli's urban parameterization scheme is improved and implemented in a mesoscale model in order to take into account the typical effects of a real city on the air temperature near the ground and on the surface exchange fluxes. The mesoscale model is run on a single column using atmospheric data and radiation recorded above roof level as forcing. Here, the authors validate the Martilli's urban boundary layer scheme using measurements from two mid-latitude European cities: Basel, Switzerland and Marseilles, France. For Basel, the model performance is evaluated with observations of canyon temperature, surface radiation, and energy balance fluxes obtained during the Basel urban boundary layer experiment (BUBBLE). The results show that the urban parameterization scheme is able to reproduce the generation of the Urban Heat Island (UHI) effect over urban area and represents correctly most of the behavior of the fluxes typical of the city center of Basel, including the large heat uptake by the urban fabric and the positive sensible heat flux at night. For Marseilles, the model performance is evaluated with observations of surface temperature, canyon temperature, surface radiation, and energy balance fluxes collected during the field experiments to constrain models of atmospheric pollution and transport of emissions (ESCOMPTE) and its urban boundary layer (UBL) campaign. At both urban sites, vegetation cover is less than 20%, therefore, particular attention was directed to the ability of the Martilli's urban boundary layer scheme to reproduce the observations for the Marseilles city center, where the urban parameters and the synoptic forcing are totally different from Basel. Evaluation of the model with wall, road, and roof surface temperatures gave good results. The model correctly simulates the net radiation, canyon temperature, and the partitioning between the turbulent and storage heat fluxes.

  20. Validation of Martilli's urban boundary layer scheme with measurements from two mid-latitude European cities

    Directory of Open Access Journals (Sweden)

    R. Hamdi

    2007-08-01

    Full Text Available Martilli's urban parameterization scheme is improved and implemented in a mesoscale model in order to take into account the typical effects of a real city on the air temperature near the ground and on the surface exchange fluxes. The mesoscale model is run on a single column using atmospheric data and radiation recorded above roof level as forcing. Here, the authors validate Martilli's urban boundary layer scheme using measurements from two mid-latitude European cities: Basel, Switzerland and Marseilles, France. For Basel, the model performance is evaluated with observations of canyon temperature, surface radiation, and energy balance fluxes obtained during the Basel urban boundary layer experiment (BUBBLE. The results show that the urban parameterization scheme represents correctly most of the behavior of the fluxes typical of the city center of Basel, including the large heat uptake by the urban fabric and the positive sensible heat flux at night. For Marseilles, the model performance is evaluated with observations of surface temperature, canyon temperature, surface radiation, and energy balance fluxes collected during the field experiments to constrain models of atmospheric pollution and transport of emissions (ESCOMPTE and its urban boundary layer (UBL campaign. At both urban sites, vegetation cover is less than 20%, therefore, particular attention was directed to the ability of Martilli's urban boundary layer scheme to reproduce the observations for the Marseilles city center, where the urban parameters and the synoptic forcing are totally different from Basel. Evaluation of the model with wall, road, and roof surface temperatures gave good results. The model correctly simulates the net radiation, canyon temperature, and the partitioning between the turbulent and storage heat fluxes.

  1. Electron density and plasma waves in mid-latitude sporadic-E layer observed during the SEEK-2 campaign

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    M. Wakabayashi

    2005-10-01

    Full Text Available The SEEK-2 campaign was carried out over Kyushu Island in Japan on 3 August 2002, by using the two sounding rockets of S310-31 and S310-32. This campaign was planned to elucidate generation mechanisms of Quasi-Periodic Echoes (QPEs associated with mid-latitude sporadic-E (Es layers. Electron number densities were successfully measured in the Es layers by using the impedance probe on board two rockets. The plasma waves in the VLF and ELF ranges were also observed on board the S310-32 rocket. Results of electron density measurement showed that there were one or two major peaks in the Es layers along the rockets' trajectories near the altitude of about 10km. There were some smaller peaks associated with the main Es layers in the altitude range from 90 to 120 km. These density peaks were distributed in a very large extent during the SEEK-2 campaign. The Es layer structure is also measured by using the Fixed Bias Probe (FBP, which has a high spatial resolution of several meters (the impedance probe has an altitude resolution of about 400 m. The comparison with the total electron content (TEC measured by the Dual Band Beacon revealed that the Es layer was also modulated in the horizontal direction with the scale size of 30–40 km. It was shown that the QP echoes observed by the ground-based coherent radar come from the major density peak of the Es layer. The plasma wave instrument detected the enhancement of VLF and ELF plasma waves associated with the operation of the TMA release, and also with the passage of the Es layers. Keywords. Ionosphere (Ionospheric irregularities; Midlatitude ionosphere; Plasma temeperature and density

  2. Geomagnetic activity at Northern Hemisphere's mid-latitude ground stations: How much can be explained using TS05 model

    Science.gov (United States)

    Castillo, Yvelice; Pais, Maria Alexandra; Fernandes, João; Ribeiro, Paulo; Morozova, Anna L.; Pinheiro, Fernando J. G.

    2017-12-01

    For the 2007 to 2014 period, we use a statistical approach to evaluate the performance of Tsyganenko and Sitnov [2005] semi-empirical model (TS05) in estimating the magnetospheric transient signal observed at four Northern Hemisphere mid-latitude ground stations: Coimbra, Portugal; Panagyurishte, Bulgary; Novosibirsk, Russia and Boulder, USA. Using hourly mean data, we find that the TS05 performance is clearly better for the X (North-South) than for the Y (East-West) field components and for more geomagnetically active days as determined by local K-indices. In ∼ 50% (X) and ∼ 30% (Y) of the total number of geomagnetically active days, correlation values yield r ≥ 0.7. During more quiet conditions, only ∼ 30% (X) and ∼ 15% (Y) of the number of analyzed days yield r ≥ 0.7. We compute separate contributions from different magnetospheric currents to data time variability and to signal magnitude. During more active days, all tail, symmetric ring and partial ring currents contribute to the time variability of X while the partial ring and field aligned currents contribute most to the time variability of Y. The tail and symmetric ring currents are main contributors to the magnitude of X. In the best case estimations when r ≥ 0.7, remaining differences between observations and TS05 predictions could be explained by global induction in the Earth's upper layers and crustal magnetization. The closing of field aligned currents through the Earth's center in the TS05 model seems to be mainly affecting the Y magnetospheric field predictions.

  3. Lightning NOx influence on large-scale NOy and O3 plumes observed over the northern mid-latitudes

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    Alicia Gressent

    2014-11-01

    Full Text Available This paper describes the NOy plumes originating from lightning emissions based on 4 yr (2001–2005 of MOZAIC measurements in the upper troposphere of the northern mid-latitudes, together with ground- and space-based observations of lightning flashes and clouds. This analysis is primarily for the North Atlantic region where the MOZAIC flights are the most frequent and for which the measurements are well representative in space and time. The study investigates the influence of lightning NOx (LNOx emissions on large-scale (300–2000 km plumes (LSPs of NOy. One hundred and twenty seven LSPs (6% of the total MOZAIC NOy dataset have been attributed to LNOx emissions. Most of these LSPs were recorded over North America and the Atlantic mainly in spring and summer during the maximum lightning activity occurrence. The majority of the LSPs (74% is related to warm conveyor belts and extra-tropical cyclones originating from North America and entering the intercontinental transport pathway between North America and Europe, leading to a negative (positive west to east NOy (O3 zonal gradient with −0.4 (+18 ppbv difference during spring and −0.6 (+14 ppbv difference in summer. The NOy zonal gradient can correspond to the mixing of the plume with the background air. On the other hand, the O3 gradient is associated with both mixing of background air and with photochemical production during transport. Such transatlantic LSPs may have a potential impact on the European pollution. The remaining sampled LSPs are related to mesoscale convection over Western Europe and the Mediterranean Sea (18% and to tropical convection (8%.

  4. Assessing and evaluating urban VOC emissions in mid-latitude megacities from intensive observations in Paris and Los Angeles

    Science.gov (United States)

    Borbon, A.; Gilman, J. B.; Kuster, W. C.; McKeen, S. A.; Holloway, J. S.; Gros, V.; Gaimoz, C.; Beekmann, M.; De Gouw, J. A.

    2011-12-01

    Volatile Organic Compounds (VOC) affect urban air quality and regional climate change by contributing to ozone formation and the build-up of Secondary Organic Aerosols (SOA). Quantification of VOC emissions is a first critical step to predict VOC environmental impacts and to design effective abatement strategies. Indeed, the quality of ozone and SOA forecasts strongly depends on an accurate knowledge of the primary VOC emissions. However, commonly used bottom-up approaches are highly uncertain due to source multiplicity (combustion processes, storage and distribution of fossil fuels, solvent use, etc.) because of numerous controlling factors (driving conditions, fuel type, temperature, radiation, etc.), and their great variability in time and space. Field observations of VOC and other trace gases can provide valuable top-down constraints to evaluate VOC emission inventories at urban scales. In addition, the implementation of emission reduction measures raises the question of the increasing importance of VOC sources other than traffic. Here, we will evaluate VOC emissions of two mid-latitude megacities in the Northern Hemisphere: the Greater Paris area (Europe) and Los Angeles (USA). In 2009 and 2010, three intensive field campaigns took place in Paris and Los Angeles in the framework of the MEGAPOLI (EU FP7) and CalNex-2010 projects, respectively. Very detailed measurements of aerosol composition and properties, and their gaseous VOC precursors were carried out at ground-based sites (urban center and suburban) and on various mobile platforms. This contribution uses a comprehensive suite of VOC measurements collected by GC-MS/FID techniques at ground-based sites in both cities by a source-receptor methodology. First, emission ratios were estimated from the observations (uncertainty of ± 20%) and compared regarding regional characteristics and European vs. Californian control policies. Then, determined emission ratios were used to assess the accuracy of up

  5. Airborne measurements of aerosol optical properties related to early spring transport of mid-latitude sources into the Arctic

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    R. A. de Villiers

    2010-06-01

    Full Text Available Airborne lidar and in-situ measurements of the aerosol properties were conducted between Svalbard Island and Scandinavia in April 2008. Evidence of aerosol transport from Europe and Asia is given. The analysis of the aerosol optical properties based on a multiwavelength lidar (355, 532, 1064 nm including volume depolarization at 355 nm aims at distinguishing the role of the different aerosol sources (Siberian wild fires, Eastern Asia and European anthropogenic emissions. Combining, first aircraft measurements, second FLEXPART simulations with a calculation of the PBL air fraction originating from the three different mid-latitude source regions, and third level-2 CALIPSO data products (i.e. backscatter coefficient 532 nm,volume depolarization and color ratio between 1064 and 532 nm in aerosol layers along the transport pathways, appears a valuable approach to identify the role of the different aerosol sources even after a transport time larger than 4 days. Optical depth of the aerosol layers are always rather small (<4% while transported over the Arctic and ratio of the total attenuated backscatter (i.e. including molecular contribution provide more stable result than conventional aerosol backscatter ratio. Above Asia, CALIPSO data indicate more depolarization (up to 15% and largest color ratio (>0.5 for the northeastern Asia emissions (i.e. an expected mixture of Asian pollution and dust, while low depolarization together with smaller and quasi constant color ratio (≈0.3 are observed for the Siberian biomass burning emissions. A similar difference is visible between two layers observed by the aircraft above Scandinavia. The analysis of the time evolution of the aerosol optical properties revealed by CALIPSO between Asia and Scandinavia shows a gradual decrease of the aerosol backscatter, depolarization ratio and color ratio which suggests the removal of the largest particles in the accumulation mode. A similar study conducted for a European

  6. Surface ozone seasonality under global change: Influence from dry deposition and isoprene emissions at northern mid-latitudes

    Science.gov (United States)

    Clifton, O.; Paulot, F.; Fiore, A. M.; Horowitz, L. W.; Malyshev, S.; Shevliakova, E.; Correa, G. J. P.; Lin, M.

    2017-12-01

    Identifying the contributions of nonlinear chemistry and transport to observed surface ozone seasonal cycles over land using global models relies on an accurate representation of ozone uptake by vegetation (dry deposition). It is well established that in the absence of ozone precursor emission changes, a warming climate will increase surface ozone in polluted regions, and that a rise in temperature-dependent isoprene emissions would exacerbate this "climate penalty". However, the influence of changes in ozone dry deposition, expected to evolve with climate and land use, is often overlooked in air quality projections. With a new scheme that represents dry deposition within the NOAA GFDL dynamic vegetation land model (LM3) coupled to the NOAA GFDL atmospheric chemistry-climate model (AM3), we simulate the impact of 21st century climate and land use on ozone dry deposition and isoprene emissions. This dry deposition parameterization is a version of the Wesely scheme, but uses parameters explicitly calculated by LM3 that respond to climate and land use (e.g., stomatal conductance, canopy interception of water, leaf area index). The parameterization includes a nonstomatal deposition dependence on humidity. We evaluate climatological present-day seasonal cycles of ozone deposition velocities and abundances with those observed at northern mid-latitude sites. With a set of 2010s and 2090s decadal simulations under a high climate warming scenario (RCP8.5) and a sensitivity simulation with well-mixed greenhouse gases following RCP8.5 but air pollutants held at 2010 levels (RCP8.5_WMGG), we examine changes in surface ozone seasonal cycles. We build on our previous findings, which indicate that strong reductions in anthropogenic NOx emissions under RCP8.5 cause the surface ozone seasonal cycle over the NE USA to reverse, shifting from a summer peak at present to a winter peak by 2100. Under RCP8.5_WMGG, we parse the separate effects of climate and land use on ozone dry

  7. Mid-latitude trans-Pacific reconstructions and comparisons of coupled glacial/interglacial climate cycles based on soil stratigraphy of cover-beds

    Science.gov (United States)

    Alloway, B. V.; Almond, P. C.; Moreno, P. I.; Sagredo, E.; Kaplan, M. R.; Kubik, P. W.; Tonkin, P. J.

    2018-06-01

    South Westland, New Zealand, and southern Chile, are two narrow continental corridors effectively confined between the Pacific Ocean in the west and high mountain ranges in the east which impart significant influence over regional climate, vegetation and soils. In both these southern mid-latitude regions, evidence for extensive and repeated glaciations during cold phases of the Quaternary is manifested by arrays of successively older glacial drift deposits with corresponding outwash plain remnants. In South Westland, these variably aged glacial landforms are mantled by layered (multisequal) soils characterised by slow loess accretion and pedogenesis in an extreme leaching and weathering environment. These cover-bed successions have undergone repeated coupled phases of topdown and upbuilding soil formation that have been related to fluctuating cycles of interglacial/warm and glacial/cold climate during the Quaternary. In this study, we recognise multisequal soils overlying glacial landforms in southern continental Chile but, unlike the spodic (podzolic) soil sequences of South Westland, these are of dominantly volcanigenic (andic) provenance and are very similar to multisequal soils of andic provenance that predominate in, and adjacent to, areas of rhyolitic to andesitic volcanism in North Island, New Zealand. Here we develop a soil-stratigraphic model to explain the observed occurrence of multisequal soils mantling dominantly glacial landforms of southern continental Chile. Based on proxy data from southern Chile, we propose that persistent vegetation cover and high precipitation on the western side of the Andes, during colder-than-present episodes tended to suppress the widespread production of glacially-derived loessial materials despite the pervasive occurrence of glacial and glacio-fluvial deposits that have frequently inundated large tracts of this landscape during the Quaternary. Given the lack of loess cover-beds that have traditionally assisted in the

  8. Study of the tidal variations in mesospheric temperature at low and mid latitudes from WINDII and potassium lidar observations

    Directory of Open Access Journals (Sweden)

    M. Shepherd

    2004-04-01

    Full Text Available Zonal mean daytime temperatures from the Wind Imaging Interferometer (WINDII on the Upper Atmosphere Research Satellite (UARS and nightly temperatures from a potassium (K lidar are employed in the study of the tidal variations in mesospheric temperature at low and mid latitudes in the Northern Hemisphere. The analysis is applied to observations at 89km height for winter solstice, December to February (DJF, at 55° N, and for May and November at 28° N. The WINDII results are based on observations from 1991 to 1997. The K-lidar observations for DJF at Kühlungsborn (54° N were from 1996–1999, while those for May and November at Tenerife 28° N were from 1999. To avoid possible effects from year-to-year variability in the temperatures observed, as well as differences due to instrument calibration and observation periods, the mean temperature field is removed from the respective data sets, assuming that only tidal and planetary scale perturbations remain in the temperature residuals. The latter are then binned in 0.5h periods and the individual data sets are fitted in a least-mean square sense to 12-h and 8-h harmonics, to infer semidiurnal and terdiurnal tidal parameters. Both the K-lidar and WINDII independently observed a strong semidiurnal tide in November, with amplitudes of 13K and 7.4K, respectively. Good agreement was also found in the tidal parameters derived from the two data sets for DJF and May. It was recognized that insufficient local time coverage of the two separate data sets could lead to an overestimation of the semidiurnal tidal amplitude. A combined ground-based/satellite data set with full diurnal local time coverage was created which was fitted to 24h+12h+8h harmonics and a novel method applied to account for possible differences between the daytime and nighttime means. The results still yielded a strong semidiurnal tide in November at 28° N with an amplitude of 8.8K which is twice the SD amplitude in May and DJF. The

  9. Use of imploding spheres: An alternative to explosives as acoustic sources at mid-latitude SOFAR channel depths

    International Nuclear Information System (INIS)

    Harben, P.E.; Boro, C.; Dorman, L.; Pulli, J.

    2000-05-01

    depths (500 meters - 1200 meters in mid-latitudes). A much thinner walled sphere, a special order modification of a standard 22 liter laboratory boiling flask made by the Kontes Glass Company, was also tested and found to fail in the desired manner, i.e. catastrophically. A test off the coast of California successfully initiated implosion of a Kontes sphere at 685 meters depth. The recorded signal showed a peak pressure slightly larger than that from 1 lb of high explosive detonated at the same depth. The signal spectra showed relatively broad band higher frequency energy with little signal below about 50 Hz and a broad peak in the amplitude spectra between about 200 and 800 Hz, similar to that from an explosive source detonated at the same depth. Although additional testing and development is needed, an imploding sphere source for hydroacoustic calibrations appears viable. Since the source spectra frequencies are generally higher than the frequency band used for nuclear explosion monitoring, low frequency signals (1-50 Hz) will be absent from the implosion source spectra. Calibration will have to be accomplished with frequencies above 50 Hz unless larger spheres, multiple spheres, or shallower implosion depths are used. (author)

  10. The mid-latitude ionosphere under quiet geomagnetic conditions: propagation analysis of SuperDARN radar observations from large ionospheric perturbations

    OpenAIRE

    De Larquier, Sebastien

    2013-01-01

    The Earth's ionosphere is a dynamic environment strongly coupled to the neutral atmosphere, magnetosphere and solar activity. In the context of this research, we restrict our interest to the mid-latitude (a.k.a., sub-auroral) ionosphere during quiet geomagnetic conditions. The Super Dual Auroral Radar Network (SuperDARN) is composed of more than 30 low-power High Frequency (HF, from 8-18 MHz) Doppler radars covering the sub-auroral, auroral and polar ionosphere in both hemispheres. SuperDARN ...

  11. Evidence for long-lived polar vortex air in the mid-latitude summer stratosphere from in situ laser diode CH4 and H2O measurements

    Directory of Open Access Journals (Sweden)

    G. Durry

    2005-01-01

    Full Text Available A balloon borne diode laser spectrometer was launched in southern France in June 2000 to yield in situ stratospheric CH4 and H2O measurements. In the altitude region ranging from 20km to 25km, striking large spatial structures were observed in the vertical concentration profiles of both species. We suggest these patterns are due to the presence of long-lived remnants of the wintertime polar vortex in the mid-latitude summer stratosphere. To support this interpretation, a high resolution advection model for potential vorticity is used to investigate the evolution of the Arctic vortex after its breakdown phase in spring 2000.

  12. DC Electric Field measurement in the Mid-latitude Ionosphere during MSTID by S-520-27 Sounding Rocket Experiments

    Science.gov (United States)

    Ishisaka, K.; Yamamoto, M.; Yokoyama, T.; Tanaka, M.; Abe, T.; Kumamoto, A.

    2015-12-01

    In the middle latitude ionospheric F region, mainly in summer, wave structures of electron density that have wave length of 100-200 km and period of one hour are observed. This phenomena is called Medium Scale Traveling Ionosphiric Disturbance; MSTID. MSTID has been observed by GPS receiving network, and its characteristic were studied. In the past, MSTID was thought to be generated by the Perkins instability, but its growth ratio was too small to be effective so far smaller than the real. Recently coupling process between ionospheric E and F regions are studied by using two radars and by computer simulations. Through these studies, we now have hypothesis that MSTID is generated by the combination of E-F region coupling and Perkins instability. The S-520-27 sounding rocket experiment on E-layer and F-layer was planned in order to verify this hypothesis. S-520-27 sounding rocket was launched at 23:57 JST on 20th July, 2013 from JAXA Uchinoura Space Center. S-520-27 sounding rocket reached 316km height. The S-520-27 payload was equipped with Electric Field Detector (EFD) with a two set of orthogonal double probes to measure DC electric field in the spin plane of the payload. The electrodes of two double probe antennas were used to gather the potentials which were detected with high impedance pre-amplifier using the floating (unbiased) double probe technique. As a results of measurements of DC electric fields by the EFD, the natural electric field was about +/-5mV/m, and varied the direction from southeast to east. Then the electric field was mapped to the horizontal plane at 280km height along the geomagnetic field line. In this presentation, we show the detail result of DC electric field measurement by S-520-27 sounding rocket and then we discuss about the correlation between the natural electric field and TEC variation by using the GPS-TEC.

  13. Microinstabilities in the high latitude F region: a brief review

    International Nuclear Information System (INIS)

    Gary, S.P.

    1983-01-01

    This is a review of the theory of plasma microinstabilities that may arise in the high latitude F region ionosphere below 1000 km. Three free energy sources are considered: a density gradient perpendicular to the ambient magnetic field B, a current parallel to B and a steady electric field perpendicular to B. The BGK model for charged-neutral collisions is used, and the short wavelength properties of the universal density drift, current convective and E x B gradient drift instabilities are compared. At sufficiently high altitudes and sufficiently steep gradients, the universal instability is the short wavelength mode most likely to grow and, through wave-particle diffusion, to cause relatively steep wavenumber dependences in power spectra

  14. Mid-Latitude versus Polar-Latitude Transitional Impact Craters: Geometric Properties from Mars Orbiter Laser Altimeter (MOLA) Observations and Viking Images

    Science.gov (United States)

    Matias, A.; Garvin, J. B.; Sakimoto, S. E. H.

    1998-01-01

    One intriguing aspect of martian impact crater morphology is the change of crater cavity and ejecta characteristics from the mid-latitudes to the polar regions. This is thought to reflect differences in target properties such as an increasing presence of ice in the polar regions. Previous image-based efforts concerning martian crater morphology has documented some aspects of this, but has been hampered by the lack of adequate topography data. Recent Mars Orbiter Laser Altimeter (MOLA) topographic profiles provide a quantitative perspective for interpreting the detailed morphologies of martian crater cavities and ejecta morphology. This study is a preliminary effort to quantify the latitude-dependent differences in morphology with the goal of identifying target-dependent and crater modification effects from the combined of images and MOLA topography. We combine the available MOLA profiles and the corresponding Viking Mars Digital Image Mosaics (MDIMS), and high resolution Viking Orbiter images to focus on two transitional craters; one on the mid-latitudes, and one in the North Polar region. One MOLA pass (MGS Orbit 34) traverses the center of a 15.9 km diameter fresh complex crater located at 12.8degN 83.8degE on the Hesperian ridge plains unit (Hvr). Viking images, as well as MOLA data, show that this crater has well developed wall terraces and a central peak with 429 m of relative relief. Three MOLA passes have been acquired for a second impact crater, which is located at 69.5degN 41degE on the Vastitas Borealis Formation. This fresh rampart crater lacks terraces and central peak structures and it has a depth af 579 m. Correlation between images and MOLA topographic profiles allows us to construct basic facies maps of the craters. Eight main units were identified, four of which are common on both craters.

  15. Impacts of microphysics, radiation and environmental winds in mid-latitude and tropical squall-line systems, and their climatic implications

    International Nuclear Information System (INIS)

    Chin, Hung-Neng.

    1994-08-01

    Cloud-radiation feedback has been identified as the most important factor limiting general circulation models (GCMS) to further progress in climate change research (Cess et al., 1989). It is also regarded as a major uncertainty in estimating the impact of greenhouse gases on climate simulations. As a result, many GCMs showed high sensitivity to the treatment of clouds and cloud radiative properties. Therefore, a better understanding of cloud-radiation feedback on the large-scale environment is absolutely essential to improve the representation of cloud processes in GCMS. To this end, a cloud model with enhanced model physics is used to study the impact of cloud-radiation interactions on mesoscale convective systems (MCSs). Case studies representing a variety of convective systems are important to generalize the overall effects of anvil clouds on the large-scale environment. Our primary interesting is limited to the MCSs in an environment with substantial wind shear, such as squall-line systems, because they have longer lifetime and wider coverage to impact the earth radiation budget and climate. The objective of this study is to investigate the impacts of microphysics, radiation and environmental winds on mid-latitude continental and tropical oceanic squall-line systems. Comparisons between these two systems are presented. Recent studies indicated that the vertical shear of the environmental wind plays an important role in the formation of the anvil cloud through the tilting of MCSS. However, this process has not been represented in GCMS. A detailed investigation on the formation of anvil clouds and their relationship to cumulus portions of MCSs would help develop a better cloud parameterization for use in GCMS. Two important issues are addressed through these comparisons. First, what factors cause the differences between mid-latitude and tropical anvil clouds? Second, do these differences have climatic implications to improve our climate forecasting ability?

  16. Common volume coherent and incoherent scatter radar observations of mid-latitude sporadic E-layers and QP echoes

    Directory of Open Access Journals (Sweden)

    D. L. Hysell

    2004-09-01

    Full Text Available Common-volume observations of sporadic E-layers made on 14-15 June 2002 with the Arecibo incoherent scatter radar and a 30MHz coherent scatter radar imager located on St. Croix are described. Operating in dual-beam mode, the Arecibo radar detected a slowly descending sporadic E-layer accompanied by a series of dense E-region plasma clouds at a time when the coherent scatter radar was detecting quasi-periodic (QP echoes. Using coherent radar imaging, we collocate the sources of the coherent scatter with the plasma clouds observed by Arecibo. In addition to patchy, polarized scattering regions drifting through the radar illuminated volume, which have been observed in previous imaging experiments, the 30MHz radar also detected large-scale electrostatic waves in the E-region over Puerto Rico, with a wavelength of about 30km and a period of about 10min, propagating to the southwest. Both the intensity and the Doppler shifts of the coherent echoes were modulated by the wave.

  17. Atmospheric circulation changes and neoglacial conditions in the Southern Hemisphere mid-latitudes: insights from PMIP2 simulations at 6 kyr

    Science.gov (United States)

    Rojas, Maisa; Moreno, Patricio I.

    2011-07-01

    Glacial geologic studies in the Southern Hemisphere (SH) mid-latitudes (40-54°S) indicate renewed glacial activity in southern South America (Patagonia) and New Zealand's (NZ) South Island starting at ˜7 kyr, the so-called neoglaciation. Available data indicate that neoglacial advances in these regions occurred during a rising trend in atmospheric CO2 and CH4 concentrations, lower-than-present but increasing summer insolation and seasonality contrasts. In this paper we examine the climatological context in which neoglaciations occurred through analysis of the complete Paleoclimate Modelling Inter-comparison Project (PMIP2) database of simulations at 6 kyr for the SH. We observe that the amplitude of the annual insolation cycle in the SH did not change significantly at 6 kyr compared to the pre-industrial values, the largest difference occurring in autumn (MAM, negative anomalies) and spring (SON, positive anomalies). The simulated changes in temperatures over the SH respond to the insolation changes, with a 1-2 month delay over the oceans. This results in a reduced amplitude of the annual cycle of temperature and precipitation over most continental regions, except over Patagonia and NZ, that show a slight increase. In contrast, large-scale circulation features, such as the low and upper level winds and the subtropical anticyclones show an amplified annual cycle, as a direct response to the increased/decreased insolation during the transitional seasons SON/MAM. In the annual mean, there is a small but consistent equatorward shift of the latitude of maximum wind speed of 1-3° over the entire SH, which results in a small increase of wind speed over the South Pacific and Atlantic Oceans north of ˜50°S and a widespread decline south of 50°S. PMIP2 simulations for 6 kyr, indicate that in the annual mean, the SH mid-latitudes were colder, wetter and with stronger winds north of about 50°S. These conditions are consistent with the observed neoglacial advances in the

  18. Atmospheric circulation changes and neoglacial conditions in the Southern Hemisphere mid-latitudes: insights from PMIP2 simulations at 6 kyr

    Energy Technology Data Exchange (ETDEWEB)

    Rojas, Maisa [University of Chile, Department of Geophysics, Santiago (Chile); Moreno, Patricio I. [University of Chile, Department of Ecology, Santiago (Chile)

    2011-07-15

    Glacial geologic studies in the Southern Hemisphere (SH) mid-latitudes (40-54 S) indicate renewed glacial activity in southern South America (Patagonia) and New Zealand's (NZ) South Island starting at {proportional_to}7 kyr, the so-called neoglaciation. Available data indicate that neoglacial advances in these regions occurred during a rising trend in atmospheric CO{sub 2} and CH{sub 4} concentrations, lower-than-present but increasing summer insolation and seasonality contrasts. In this paper we examine the climatological context in which neoglaciations occurred through analysis of the complete Paleoclimate Modelling Inter-comparison Project (PMIP2) database of simulations at 6 kyr for the SH. We observe that the amplitude of the annual insolation cycle in the SH did not change significantly at 6 kyr compared to the pre-industrial values, the largest difference occurring in autumn (MAM, negative anomalies) and spring (SON, positive anomalies). The simulated changes in temperatures over the SH respond to the insolation changes, with a 1-2 month delay over the oceans. This results in a reduced amplitude of the annual cycle of temperature and precipitation over most continental regions, except over Patagonia and NZ, that show a slight increase. In contrast, large-scale circulation features, such as the low and upper level winds and the subtropical anticyclones show an amplified annual cycle, as a direct response to the increased/decreased insolation during the transitional seasons SON/MAM. In the annual mean, there is a small but consistent equatorward shift of the latitude of maximum wind speed of 1-3 over the entire SH, which results in a small increase of wind speed over the South Pacific and Atlantic Oceans north of {proportional_to}50 S and a widespread decline south of 50 S. PMIP2 simulations for 6 kyr, indicate that in the annual mean, the SH mid-latitudes were colder, wetter and with stronger winds north of about 50 S. These conditions are consistent

  19. Spread-F occurrences and relationships with foF2 and h'F at low- and mid-latitudes in China

    Science.gov (United States)

    Wang, Ning; Guo, Lixin; Zhao, Zhenwei; Ding, Zonghua; Lin, Leke

    2018-04-01

    Ionospheric irregularities are an important phenomenon in scientific studies and applications of radio-wave propagation. Spread-F echoes in ionograms are a type of high-frequency band irregularities that include frequency spread-F (FSF), range spread-F (RSF), and mixed spread-F (MSF) events. In this study, we obtained spread-F data from four ionosondes at low- and mid-latitudes near the 120°E chain in China during the 23rd solar cycle. We used these data to investigate spread-F occurrence percentages and variations with local time, season, latitude, and solar activity. The four ionosondes were located at Haikou (HK) (20°N, 110.34°E), Guangzhou (GZ) (23.14°N, 113.36°E), Beijing (BJ) (40.11°N, 116.28°E), and Changchun (CC) (43.84°N, 125.28°E). We also present possible correlations between spread-Fs and other ionospheric parameters, such as the critical frequency of the F2-layer (foF2) and the virtual height of the bottom-side F-layer (h'F). In particular, we investigated the possible threshold of the foF2 affecting the FSF and the relationship between the h'F and the RSF. The main conclusions are as follows: (a) the FSF occurrence percentages were anti-correlated with solar activity at all four sites; meanwhile, RSF occurrence rates increased with the increase in solar activity at HK, but not at the other three sites; (b) FSF occurrence rates were larger at the mid-latitudes than expected, while FSFs occurred more often after midnight; (c) the highest FSF occurrence rates mostly appeared during the summer months, while RSFs occurred mostly in the equinoctial months of 2000-2002 at HK and GZ; (d) a lower foF2 was suitable for FSF events; nevertheless, h'F and RSF occurrences satisfied the parabolic relationship; (e) the foF2 thresholds for FSFs were 15, 14, 7.6, and 7.8 MHz at HK, GZ, BJ, and CC, respectively. The h'Fs occurring between 240 and 290 km were more favorable for RSF occurrences. These results are important for understanding ionospheric

  20. Chemical characterization of organic aerosol above a mid-latitude forest reveals a complex mixture of highly-functionalized chemical species and diverse structural features with temporal variability

    Science.gov (United States)

    Gentner, D. R.; Ditto, J.; Barnes, E.; Khare, P.

    2017-12-01

    Highly-functionalized organic compounds are known to be a major component of the complex mixture of the particle-phase compounds that comprise organic aerosol, yet little is known about the identity of many of these compounds, and their formation pathways and roles in atmospheric processes are poorly understood. We present results from the comprehensive chemical speciation of PM10 organic aerosols collected in July 2016 at the remote mid-latitude forest field site during PROPHET. Samples were analyzed via liquid and gas chromatography coupled with a quadrupole time-of-flight tandem mass spectrometry (MS×MS) following electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI). 8 hr samples were collected during day- and night-time sampling periods rather than more typical 24-hour samples. This analysis of the organic aerosol yielded over 12,000 unique compounds for which we have high accuracy molecular masses, formulas, and additional information on structural features using MS×MS. O:C ratios were 0.3 on average, yet the top 10% of compounds ranged 0.7-2.3. 70% and 69% of day- and night-time samples were nitrogen-containing, whereas 26% and 24% contained sulfur, respectively. Within these broader molecular categories, we observed a wide variety of molecular features that reveal a diversity of functional groups and moieties. In this presentation, we present the results of our speciation, temporal variability, connections to air parcel back trajectories and other bulk properties, and potential formation pathways.

  1. The behaviour of stratospheric and upper tropospheric ozone in high and mid latitudes; the role of ozone as a climate gas

    Energy Technology Data Exchange (ETDEWEB)

    Kyroe, M.; Rummukainen, M.; Kivi, R.; Turunen, T.; Karhu, J. [Finnish Meteorological Inst., Sodankylae (Finland); Taalas, P. [Finnish Meteorological Inst., Helsinki (Finland)

    1996-12-31

    During the past few years, the dual role that ozone plays in climate change has been becoming increasingly obvious. First, continuous thinning of the ozone layer has been evident, even in the high and middle latitudes in the northern hemisphere. Secondly, ozone is also a greenhouse gas, affecting radiative transfer. Increases in tropospheric ozone have a positive forcing, whereas decreases in stratospheric ozone cause a negative forcing. During the last six years, measurements on total ozone and the vertical distribution of ozone have been performed at the Sodankylae Observatory. At Jokioinen Observatory, measurements on total ozone have been performed since 1990 and measurements on the vertical distribution of ozone since 1993. The overall project has focused on extending the national data series on total ozone and the vertical distribution of ozone. At the same time, the study has contributed to the study of interannual variability of the ozone layer. This SILMU project took part in the large-scale research activities, in addition to performing national studies. The results confirm that there has been fast chemical ozone destruction in the high latitudes in the northern hemisphere. This was particularly evident in the last two winters, 1994/95 and 1995/96. The new data also allows better trend analyses to be made on ozone in high and mid latitudes

  2. Tropospheric ozone column retrieval at northern mid-latitudes from the Ozone Monitoring Instrument by means of a neural network algorithm

    Directory of Open Access Journals (Sweden)

    P. Sellitto

    2011-11-01

    Full Text Available Monitoring tropospheric ozone from space is of critical importance in order to gain more thorough knowledge on phenomena affecting air quality and the greenhouse effect. Deriving information on tropospheric ozone from UV/VIS nadir satellite spectrometers is difficult owing to the weak sensitivity of the measured radiance spectra to variations of ozone in the troposphere. Here we propose an alternative method of analysis to retrieve tropospheric ozone columns from Ozone Monitoring Instrument radiances by means of a neural network algorithm. An extended set of ozone sonde measurements at northern mid-latitudes for the years 2004–2008 has been considered as the training and test data set. The design of the algorithm is extensively discussed. Our retrievals are compared to both tropospheric ozone residuals and optimal estimation retrievals over a similar independent test data set. Results show that our algorithm has comparable accuracy with respect to both correlative methods and its performance is slightly better over a subset containing only European ozone sonde stations. Possible sources of errors are analyzed. Finally, the capabilities of our algorithm to derive information on boundary layer ozone are studied and the results critically discussed.

  3. Tidal variations of O2 Atmospheric and OH(6-2 airglow and temperature at mid-latitudes from SATI observations

    Directory of Open Access Journals (Sweden)

    M. J. López-González

    2005-12-01

    Full Text Available Airglow observations with a Spectral Airglow Temperature Imager (SATI, installed at the Sierra Nevada Observatory (37.06° N, 3.38° W at 2900-m height, have been used to investigate the presence of tidal variations at mid-latitudes in the mesosphere/lower thermosphere region. Diurnal variations of the column emission rate and vertically averaged temperature of the O2 Atmospheric (0-1 band and of the OH Meinel (6-2 band from 5 years (1998-2003 of observations have been analysed. From these observations a clear tidal variation of both emission rates and rotational temperatures is inferred. It is found that the amplitude of the daily variation for both emission rates and temperatures is greater from late autumn to spring than during summer. The amplitude decreases by more than a factor of two during summer and early autumn with respect to the amplitude in the winter-spring months. Although the tidal modulations are preferentially semidiurnal in both rotational temperatures and emission rates during the whole year, during early spring the tidal modulations seem to be more consistent with a diurnal modulation in both rotational temperatures and emission rates. Moreover, the OH emission rate from late autumn to early winter has a pattern suggesting both diurnal and semidiurnal tidal modulations.

  4. The behaviour of stratospheric and upper tropospheric ozone in high and mid latitudes; the role of ozone as a climate gas

    Energy Technology Data Exchange (ETDEWEB)

    Kyroe, M; Rummukainen, M; Kivi, R; Turunen, T; Karhu, J [Finnish Meteorological Inst., Sodankylae (Finland); Taalas, P [Finnish Meteorological Inst., Helsinki (Finland)

    1997-12-31

    During the past few years, the dual role that ozone plays in climate change has been becoming increasingly obvious. First, continuous thinning of the ozone layer has been evident, even in the high and middle latitudes in the northern hemisphere. Secondly, ozone is also a greenhouse gas, affecting radiative transfer. Increases in tropospheric ozone have a positive forcing, whereas decreases in stratospheric ozone cause a negative forcing. During the last six years, measurements on total ozone and the vertical distribution of ozone have been performed at the Sodankylae Observatory. At Jokioinen Observatory, measurements on total ozone have been performed since 1990 and measurements on the vertical distribution of ozone since 1993. The overall project has focused on extending the national data series on total ozone and the vertical distribution of ozone. At the same time, the study has contributed to the study of interannual variability of the ozone layer. This SILMU project took part in the large-scale research activities, in addition to performing national studies. The results confirm that there has been fast chemical ozone destruction in the high latitudes in the northern hemisphere. This was particularly evident in the last two winters, 1994/95 and 1995/96. The new data also allows better trend analyses to be made on ozone in high and mid latitudes

  5. Using n-alkane records to constrain carbon cycle - hydrological cycle coupling: Case study from the Northern Hemisphere mid-latitudes during the PETM

    Science.gov (United States)

    Krishnan, S.; Pagani, M.; Tipple, B. J.

    2010-12-01

    The early Eocene was a warmer world compared to the present and is characterized by rising temperatures interspersed with rapid hyperthermal events. During the largest of these rapid warming events; the Paleocene-Eocene Thermal Maximum (PETM), proxy records suggest that sea surface temperatures (SST) rose by 3-5 deg. C in the tropics (Zachos et al., 2003, Tripati and Elderfield, 2004), >5 deg. C in the Arctic (Sluijs et al., 2006) and perhaps has high as 9 deg. C in some sub-Antarctic regions (Kennett and Stott, 1991; Thomas et al., 1999). This warming is believed to be the result of massive input of 13C-depleted carbon into the ocean-atmosphere system, evidenced by the large negative carbon isotope excursion (CIE) and carbonate dissolution associated with the event. However, there are several questions regarding the exact mechanism of warming and feedbacks between the carbon cycle and climate. Did climate shift prior to the main event that led to the release of isotopically light carbon? Do we observe consistent leads or lags between changes in carbon isotopes and hydrological conditions during warm intervals? This study aims to reconstruct hydrological changes in the in the Northern Hemisphere mid-latitudes during the PETM using terrestrial biomarkers. Terrestrial biomarkers, such leaf-wax lipids stored in sediments, have the unique advantage of recording carbon and hydrogen isotopic compositions of atmospheric CO2 (modified by plant fractionation) and precipitation (modified by plant fractionation and evapotranspiration), allowing evaluation of the relative timing of carbon and hydrogen isotopic (i.e., climate) shifts. In this study, we compile and present three mid-latitude PETM records from the Northern Hemisphere, i.e. Alamedilla (Spain), Cicogna and Forada (Italy). The Cicogna and Forada sections are located in the Belluno basin (~12 km apart). Preliminary results do not indicate any significant pre-excursion hydrogen isotope changes at Cicogna, while at

  6. The first coordinated observations of mid-latitude E-region quasi-periodic radar echoes and lower thermospheric 557.7-nm airglow

    Directory of Open Access Journals (Sweden)

    T. Ogawa

    2005-10-01

    Full Text Available We present the first coordinated observations of quasi-periodic (QP radar echoes from sporadic-E (Es field-aligned irregularities (FAIs, OI 557.7-nm airglow, and neutral winds in a common volume over Shigaraki, Japan (34.9° N, 136.1° E on the night of 5 August 2002 during the SEEK-2 campaign. QP echo altitudes of 90-110 km were lower than usual by 10 km, enabling us to make a detailed comparison among QP echoes, airglow intensity, and neutral wind at around 96 km altitude. Eastward movement of the QP echo regions is consistent with the motions of neutral winds, airglow structures, and FAIs, suggesting that the electrodynamics of Es-layers is fundamentally controlled by the neutral atmospheric dynamics. During the QP echo event, the echo altitudes clearly went up (down in harmony with an airglow enhancement (subsidence that also moved to the east. This fact suggests that the eastward-moving enhanced airglow region included an upward (downward component of neutral winds to raise (lower the altitude of the wind-shear node responsible for the Es formation. The airglow intensity, echo intensity, and Doppler velocity of FAIs at around 96 km altitude fluctuated with periods from 10 min to 1h, indicating that these parameters were modulated with short-period atmospheric disturbances. Some QP echo regions below 100km altitude contained small-scale QP structures in which very strong neutral winds exceeding 100 m/s existed. The results are compared with recent observations, theories, and simulations of QP echoes. Keywords. Ionosphere (Ionosphere-atmosphere interactions; Ionospheric irregularities; Mid-latitude ionosphere

  7. Diagnosis of the Tropical Moisture Exports to the Mid-Latitudes and the Role of Atmospheric Steering in the Extreme Precipitation

    Directory of Open Access Journals (Sweden)

    Mengqian Lu

    2017-12-01

    Full Text Available Three river basins, i.e., the Yangtze river, the Mississippi river and the Loire river, were presented as case studies to explore the association among atmospheric circulations, moisture exports and extreme precipitations in the mid-latitudes. The major moisture source regions in the tropics for the three river basins are first identified using the Tropical Moisture Exports (TMEs dataset. The space-time characteristics of their respective moisture sources are presented. Then, the trajectory curve clustering analysis is applied to the TMEs tracks originating from the identified source regions during each basin’s peak TMEs activity and flood seasons. Our results show that the moisture tracks for each basin can be categorized into 3 or 4 clusters with distinct spatial trajectory features. Our further analysis on these clustered trajectories reveals that the contributions of moisture release from different clusters are associated with their trajectory features and travel speeds. In order to understand the role of associated atmospheric steering, daily composites of the geopotential heights anomalies and the vertical integral of moisture flux anomalies from 7 days ahead to the extreme precipitation days (top 5% are examined. The evolutions of the atmospheric circulation patterns and the moisture fluxes are both consistent with the TMEs tracks that contribute more moisture releases to the study regions. The findings imply that atmospheric steering plays an important role in the moisture transport and release, especially for the extreme precipitations. We also find that the association between TMEs moisture release and precipitation is nonlinear. The extreme precipitation is associated with high TMEs moisture release for all of the three study regions.

  8. Measurements of the movement of the jet streams at mid-latitudes, in the Northern and Southern Hemispheres, 1979 to 2010

    Directory of Open Access Journals (Sweden)

    R. D. Hudson

    2012-08-01

    Full Text Available Previous studies have shown that the mean latitude of the sub-tropical jet streams in both hemispheres have shifted toward the poles over the last few decades. This paper presents a study of the movement of both the subtropical and Polar fronts, the location of the respective jet streams, between 1979 and 2010 at mid-latitudes, using total ozone measurements to identify the sharp horizontal boundary that occurs at the position of the fronts. Previous studies have shown that the two fronts are the boundaries of three distinct regimes in the stratosphere, corresponding to the Hadley, Ferrel, and polar meridionally overturning circulation cells in the troposphere. Over the period of study the horizontal area of the Hadley cell has increased at latitudes between 20 and 60 degrees while the area of the Polar cell has decreased. A linear regression analysis was performed to identify the major factors associated with the movement of the subtropical jet streams. These were: (1 changes in the Tropical land plus ocean temperature, (2 direct radiative forcing from greenhouse gases in the troposphere, (3 changes in the temperature of the lower tropical stratosphere, (4 the Quasi-Biennial Oscillation, and (5 volcanic eruptions. The dominant mechanism was the direct radiative forcing from greenhouse gases. Between 1979 and 2010 the poleward movement of the subtropical jet streams was 3.7 ± 0.3 degrees in the Northern Hemisphere and 6.5 ± 0.2 degrees in the Southern Hemisphere. Previous studies have shown that weather systems tend to follow the jet streams. The observed poleward movement in both hemispheres over the past thirty years represents a significant change in the position of the sub-tropical jet streams, which should lead to significant latitudinal shifts in the global weather patterns and the hydrologic cycle.

  9. Preearthquake anomalous ionospheric signatures observed at low-mid latitude Indian station, Delhi, during the year 2015 to early 2016: Preliminary results

    Science.gov (United States)

    Gupta, Sumedha; Upadhayaya, A. K.

    2017-08-01

    We have analyzed five major earthquake events measuring greater than 6 on Richter scale (M > 6) that occurred during the year 2015 to early 2016, affecting Indian region ionosphere, using F2 layer critical parameters (foF2, hmF2) obtained using Digisonde from a low-mid latitude Indian station, Delhi (28.6°N, 77.2°E, 19.2°N geomagnetic latitude, 42.4°N dip). Normal day-to-day variability occurring in ionosphere is segregated by calculating F2 layer critical frequency and peak height variations (ΔfoF2, ΔhmF2) from the normal quiet time behavior apart from computing interquartile range. We find that the ionospheric F2 region across Delhi by and large shows some significant perturbations 3-4 days prior to these earthquake events, resulting in a large peak electron density variation of 200%. These observed perturbations indicate towards a possibility of seismo-ionospheric coupling as the solar and geomagnetic indices were normally quiet and stable during the period of these events. It was also observed that the precursory effect of earthquake was predominantly seen even outside the earthquake preparation zone, as given by Dobrovolsky et al. (1979). The thermosphere neutral composition (O/N2) as observed by Global Ultraviolet Imager, across Delhi, during these earthquake events does not show any marked variation. Further, the effect of earthquake events on ionospheric peak electron density is compared to the lower atmosphere meteorological phenomenon of 2015 sudden stratospheric warming event.

  10. Bottomside sinusoidal irregularities in the equatorial F region. II - Cross-correlation and spectral analysis

    Science.gov (United States)

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

    1985-01-01

    Equatorial bottomside sinusoidal (BSS) irregularities have been studied by applying techniques of cross-correlation and spectral analysis to the Atmosphere Explorer data set. The phase of the cross-correlations of the plasma number density is discussed and the two drift velocity components observed using the retarding potential analyzer and ion drift meter on the satellite are discussed. Morphology is addressed, presenting the geographical distributions of the occurrence of BSS events for the equinoxes and solstices. Physical processes including the ion Larmor flux, interhemispheric plasma flows, and variations in the lower F region Pedersen conductivity are invoked to explain the findings.

  11. A spectral study of the mid-latitude sporadic E layer characteristic oscillations comparable to those of the tidal and the planetary waves

    Science.gov (United States)

    Pignalberi, A.; Pezzopane, M.; Zuccheretti, E.

    2015-01-01

    In this paper different spectral analyses are employed to investigate the tidal and planetary wave periodicities imprinted in the following two main characteristics of the sporadic E (Es) layer: the top frequency (ftEs) and the lowest virtual height (h‧Es). The study is based on ionograms recorded during the summertime of 2013, and precisely in June, July, August and September, by the Advanced Ionospheric Sounder by Istituto Nazionale di Geofisica e Vulcanologia (AIS-INGV) ionosondes installed at Rome (41.8°N, 12.5°E) and Gibilmanna (37.9°N, 14.0°E), Italy. It was confirmed that the diurnal and semidiurnal atmospheric tides play a fundamental role in the formation of the mid-latitude Es layers, acting through their vertical wind-shear forcing of the long-living metallic ions in the lower thermosphere, and at the same time it was found that the planetary atmospheric waves might affect the Es layers acting through their horizontal wind-shear forcing with periods close to the normal Rossby modes, that is 2, 5, 10 and 16 days. The wavelet analysis shows also that the ftEs and h‧Es tidal oscillations undergo a strong amplitude modulation with periods of several days and with important differences between the two parameters. This amplitude modulation, characterizing markedly the first thirty days of the ftEs spectrogram, suggests that Es layers are affected indirectly by planetary waves through their nonlinear interaction with the atmospheric tides at lower altitudes. This study wants to be a continuation of the Haldoupis et al. (2004) work in order to verify their results for the foEs characteristic and on the other hand to extend the study also to the h‧Es characteristic not yet shown so far. Anyhow, the study confirms that ionosonde data, especially those registered in summertime, represent a powerful tool for studying tidal and planetary waves properties and their climatology in the mesosphere-low-thermosphere region.

  12. Snow nitrate photolysis in polar regions and the mid-latitudes: Impact on boundary layer chemistry and implications for ice core records

    Science.gov (United States)

    Zatko, Maria C.

    The formation and recycling of nitrogen oxides (NOx=NO+NO 2) associated with snow nitrate photolysis has important implications for air quality and the preservation of nitrate in ice core records. This dissertation examines snow nitrate photolysis in polar and mid-latitude regions using field and laboratory based observations combined with snow chemistry column models and a global chemical transport model to explore the impacts of snow nitrate photolysis on boundary layer chemistry and the preservation of nitrate in polar ice cores. Chapter 1 describes how a global chemical transport model is used to calculate the photolysis-driven flux and redistribution of nitrogen across Antarctica, and Chapter 2 presents similar work for Greenland. Snow-sourced NOx is most dependent on the quantum yield for nitrate photolysis as well as the concentration of photolabile nitrate and light-absorbing impurities (e.g., black carbon, dust, organics) in snow. Model-calculated fluxes of snow-sourced NOx are similar in magnitude in Antarctica (0.5--7.8x108 molec cm-2 s -1) and Greenland (0.1--6.4x108 molec cm-2 s-1) because both nitrate and light-absorbing impurity concentrations in snow are higher (by factors of 2 and 10, respectively) in Greenland. Snow nitrate photolysis influences boundary layer chemistry and ice-core nitrate preservation less in Greenland compared to Antarctica largely due to Greenland's proximity to NOx-source regions. Chapter 3 describes how a snow chemistry column model combined with chemistry and optical measurements from the Uintah Basin Winter Ozone Study (UBWOS) 2014 is used to calculate snow-sourced NOx in eastern Utah. Daily-averaged fluxes of snow-sourced NOx (2.9x10 7--1.3x108 molec cm-2 s-1) are similar in magnitude to polar snow-sourced NO x fluxes, but are only minor components of the Uintah Basin boundary layer NOx budget and can be neglected when developing ozone reduction strategies for the region. Chapter 4 presents chemical and optical

  13. Ten-year trends of atmospheric mercury in the high Arctic compared to Canadian sub-Arctic and mid-latitude sites

    Directory of Open Access Journals (Sweden)

    A. S. Cole

    2013-02-01

    Full Text Available Global emissions of mercury continue to change at the same time as the Arctic is experiencing ongoing climatic changes. Continuous monitoring of atmospheric mercury provides important information about long-term trends in the balance between transport, chemistry, and deposition of this pollutant in the Arctic atmosphere. Ten-year records of total gaseous mercury (TGM from 2000 to 2009 were analyzed from two high Arctic sites at Alert (Nunavut, Canada and Zeppelin Station (Svalbard, Norway; one sub-Arctic site at Kuujjuarapik (Nunavik, Québec, Canada; and three temperate Canadian sites at St. Anicet (Québec, Kejimkujik (Nova Scotia and Egbert (Ontario. Five of the six sites examined showed a decreasing trend over this time period. Overall trend estimates at high latitude sites were: −0.9% yr−1 (95% confidence limits: −1.4, 0 at Alert and no trend (−0.5, +0.7 at Zeppelin Station. Faster decreases were observed at the remainder of the sites: −2.1% yr−1 (−3.1, −1.1 at Kuujjuarapik, −1.9% yr−1 (−2.1, −1.8 at St. Anicet, −1.6% yr−1 (−2.4, −1.0 at Kejimkujik and −2.2% yr−1 (−2.8, −1.7 at Egbert. Trends at the sub-Arctic and mid-latitude sites agree with reported decreases in background TGM concentration since 1996 at Mace Head, Ireland, and Cape Point, South Africa, but conflict with estimates showing an increase in global anthropogenic emissions over a similar period. Trends in TGM at the two high Arctic sites were not only less negative (or neutral overall but much more variable by season. Possible reasons for differences in seasonal and overall trends at the Arctic sites compared to those at lower latitudes are discussed, as well as implications for the Arctic mercury cycle. The first calculations of multi-year trends in reactive gaseous mercury (RGM and total particulate mercury (TPM at Alert were also performed, indicating increases from 2002 to 2009

  14. First airborne water vapor lidar measurements in the tropical upper troposphere and mid-latitudes lower stratosphere: accuracy evaluation and intercomparisons with other instruments

    Directory of Open Access Journals (Sweden)

    C. Schiller

    2008-09-01

    Full Text Available In the tropics, deep convection is the major source of uncertainty in water vapor transport to the upper troposphere and into the stratosphere. Although accurate measurements in this region would be of first order importance to better understand the processes that govern stratospheric water vapor concentrations and trends in the context of a changing climate, they are sparse because of instrumental shortcomings and observational challenges. Therefore, the Falcon research aircraft of the Deutsches Zentrum für Luft- und Raumfahrt (DLR flew a zenith-viewing water vapor differential absorption lidar (DIAL during the Tropical Convection, Cirrus and Nitrogen Oxides Experiment (TROCCINOX in 2004 and 2005 in Brazil. The measurements were performed alternatively on three water vapor absorption lines of different strength around 940 nm. These are the first aircraft DIAL measurements in the tropical upper troposphere and in the mid-latitudes lower stratosphere. Sensitivity analyses reveal an accuracy of 5% between altitudes of 8 and 16 km. This is confirmed by intercomparisons with the Fast In-situ Stratospheric Hygrometer (FISH and the Fluorescent Advanced Stratospheric Hygrometer (FLASH onboard the Russian M-55 Geophysica research aircraft during five coordinated flights. The average relative differences between FISH and DIAL amount to −3%±8% and between FLASH and DIAL to −8%±14%, negative meaning DIAL is more humid. The average distance between the probed air masses was 129 km. The DIAL is found to have no altitude- or latitude-dependent bias. A comparison with the balloon ascent of a laser absorption spectrometer gives an average difference of 0%±19% at a distance of 75 km. Six tropical DIAL under-flights of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS on board ENVISAT reveal a mean difference of −8%±49% at an average distance of 315 km. While the comparison with MIPAS is somewhat less significant due to poorer

  15. Relative drifts and stability of satellite and ground-based stratospheric ozone profiles at NDACC lidar stations

    Directory of Open Access Journals (Sweden)

    P. J. Nair

    2012-06-01

    Full Text Available The long-term evolution of stratospheric ozone at different stations in the low and mid-latitudes is investigated. The analysis is performed by comparing the collocated profiles of ozone lidars, at the northern mid-latitudes (Meteorological Observatory Hohenpeißenberg, Haute-Provence Observatory, Tsukuba and Table Mountain Facility, tropics (Mauna Loa Observatory and southern mid-latitudes (Lauder, with ozonesondes and space-borne sensors (SBUV(/2, SAGE II, HALOE, UARS MLS and Aura MLS, extracted around the stations. Relative differences are calculated to find biases and temporal drifts in the measurements. All measurement techniques show their best agreement with respect to the lidar at 20–40 km, where the differences and drifts are generally within ±5% and ±0.5% yr−1, respectively, at most stations. In addition, the stability of the long-term ozone observations (lidar, SBUV(/2, SAGE II and HALOE is evaluated by the cross-comparison of each data set. In general, all lidars and SBUV(/2 exhibit near-zero drifts and the comparison between SAGE II and HALOE shows larger, but insignificant drifts. The RMS of the drifts of lidar and SBUV(/2 is 0.22 and 0.27% yr−1, respectively at 20–40 km. The average drifts of the long-term data sets, derived from various comparisons, are less than ±0.3% yr−1 in the 20–40 km altitude at all stations. A combined time series of the relative differences between SAGE II, HALOE and Aura MLS with respect to lidar data at six sites is constructed, to obtain long-term data sets lasting up to 27 years. The relative drifts derived from these combined data are very small, within ±0.2% yr−1.

  16. Depositional environments and cyclo- and chronostratigraphy of uppermost Carboniferous-Lower Triassic -lacustrine deposits, southern Bogda Mountains, NW China - A terrestrfluvialial paleoclimatic record of mid-latitude NE Pangea

    Science.gov (United States)

    Yang, W.; Feng, Q.; Liu, Yajing; Tabor, N.; Miggins, D.; Crowley, J.L.; Lin, J.; Thomas, S.

    2010-01-01

    Two uppermost Carboniferous–Lower Triassic fluvial–lacustrine sections in the Tarlong–Taodonggou half-graben, southern Bogda Mountains, NW China, comprise a 1834 m-thick, relatively complete sedimentary and paleoclimatic record of the east coast of mid-latitude NE Pangea. Depositional environmental interpretations identified three orders (high, intermediate, and low) of sedimentary cycles. High-order cycles (HCs) have five basic types, including fluvial cycles recording repetitive changes of erosion and deposition and lacustrine cycles recording repetitive environmental changes associated with lake expansion and contraction. HCs are grouped into intermediate-order cycles (ICs) on the basis of systematic changes of thickness, type, and component lithofacies of HCs. Nine low-order cycles (LCs) are demarcated by graben-wide surfaces across which significant long-term environmental changes occurred. A preliminary cyclostratigraphic framework provides a foundation for future studies of terrestrial climate, tectonics, and paleontology in mid-latitude NE Pangea.Climate variabilities at the intra-HC, HC, IC, and LC scales were interpreted from sedimentary and paleosol evidence. Four prominent climatic shifts are present: 1) from the humid–subhumid to highly-variable subhumid–semiarid conditions at the beginning of Sakamarian; 2) from highly-variable subhumid–semiarid to humid–subhumid conditions across the Artinskian-Capitanian unconformity; 3) from humid–subhumid to highly-variable subhumid–semiarid conditions at early Induan; and 4) from the highly-variable subhumid–semiarid to humid–subhumid conditions across the Olenekian-Anisian unconformity. The stable humid–subhumid condition from Lopingian to early Induan implies that paleoclimate change may not have been the cause of the end-Permian terrestrial mass extinction. A close documentation of the pace and timing of the extinction and exploration of other causes are needed. In addition, the

  17. Geomagnetic storms in the Antarctic F-region

    International Nuclear Information System (INIS)

    Wrenn, G.L.; Rodger, A.S.; Rishbeth, H.

    1987-01-01

    New analysis procedures are used to show that the main phase mid-latitude storm effects conform to consistent patterns in local time when suitable selection rules are applied, with averaging over several years. Changes in the maximum plasma frequency, foF2, with respect to estimated quiet-time values, are analysed in terms of asub(p)(t), a new geomagnetic index derived to take account of integrated disturbance. Reduction of foF2 is greatest during the early morning hours, in summer, at higher geomagnetic latitudes, near solar minimum and through the more active periods. The various dependencies are quantitatively determined for the first time by creating an average 'steady state' disturbance, rather than following specific storm events. This approach permits tests of competing theories using available modelling programs. (author)

  18. Scintillations associated with bottomside sinusoidal irregularities in the equatorial F region

    Science.gov (United States)

    Basu, S.; Basu, S.; Valladares, C. E.; Dasgupta, A.; Whitney, H. E.

    1986-01-01

    Multisatellite scintillation observations and spaced receiver drift measurements are presented for a category of equatorial F region plasma irregularities characterized by nearly sinusoidal waveforms in the ion number density. The observations were made at Huancayo, Peru, and the measurements at Ancon, Peru, associated with irregularities observed by the Atmospheric-Explorer-E satellite on a few nights in December 1979. Utilizing ray paths to various geostationary satellites, it was found that the irregularities grow and decay almost simultaneously in long-lived patches extending at least 1000 km in the east-west direction.

  19. Nonlinear oscillation regime of electromagnetic disturbances in the equatorial F region

    International Nuclear Information System (INIS)

    Sazonov, S.V.

    1990-01-01

    Nonlinear oscillation regime of electromagnetic dicturbances within equatorial ionosphere F-region resulted from Rayleigh-Taylor instability, gradient-drift instability and recombination processes is investigated on the basis of two-liquid quasihydrodynamics equations. It is shown, that at positive linear increment the oscillations are developing in regime with aggregation and are terminated by increment the effect of threshold destabilization, when under certain initial conditions underlgoes oscillation nonlinear swinging, resulting, as well, in bubble formation in contrast to small damping oscillations, is detected

  20. F region electron density irregularity spectra near Auroral acceleration and shear regions

    International Nuclear Information System (INIS)

    Basu, S.; Basu, S.; MacKenzie, E.; Coley, W.R.; Hanson, W.B.; Lin, C.S.

    1984-01-01

    Spectral characteristics of auroral F region irregularities were studied by the use of high-resolution (approx.35 m) density measurements made by the retarding potential analyzer (RPA) on board the Atmosphere Explorer D (AE-D) satellite during two orbits when the satellite was traversing the high-latitude ionosphere in the evening sector. Coordinated DMSP passes provided synoptic coverage of auroral activity. The auroral energy input was estimated by intergrating the low-energy electron (LEE) data on AE-D. It was found that the one-dimensional in situ spectral index (p 1 ) of the irregularities at scale lengths of 1 values of approx.-3. This is interpreted as resulting from the effects of E region conductivity on the F region irregularity structure. The regions in between the precipitation structures, where presumably the E region conductivity was small, were generally associated with large shears in the horizontal E-W drifts and large velocities, as measured by the ion drift meter on board AE-D. The maximum drifts measured were approx.2 km s -1 , corresponding to an electric field of 100 mV m -1 . The large-velocity regions were also associated with substantial ion heating and electron density depletions. The largest shear magnitudes observed were approx.80 m s -1 km -1 , and the shear gradient scale lengths were approx.10 km, which was approximately the resolution of the ion drift meter data set used. The spectral characteristics of irregularities in the large, variable flow regions were very different, with p 1 being approx.-1

  1. Observing and modelling F-region ionospheric dynamics using the OII 7320A emission

    International Nuclear Information System (INIS)

    Carr, S.S.

    1992-01-01

    Limb-scan observations of Doppler line profiles from the (OII) lambda 7320A emission at F-Region altitudes, made with the Fabry-Perot interferometer (FPI) on the Dynamics Explorer-2 (DE-2) spacecraft, were analyzed to provide measurements of the meridional component of the ion convection velocity along the instrument line-of-sight. The DE-2 results presented demonstrate the first spaceborne use of the remote-sensing Doppler technique for measurements of ionospheric convection. The FPI meridional ion drift measurements were compared with nearly simultaneous in situ ion drift measurements from the Retarding Potential Analyzer (RPA) on DE-2. Once allowance is made for the temporal lag between the in situ and remote measurements, the results from the two techniques are found to be in good agreement, within specified experimental errors, giving confidence in the FPI measurements. The spaceborne interferometric technique has future utility for 2-dimensional imaging of polar ionospheric convection. Results from a simulated space-based observing platform, based on the DE-2 technique and an extension of a 7320A aeronomical model, are presented to demonstrate that a large fraction of the entire polar ionospheric convection pattern can be monitored from space during approximately 16-minute polar passes of a suitably-instrumented satellite. In the simulation, the polar-orbiting satellite's FPI system views the 7320A emission at various tangent point altitudes at +/- 45 deg and +/- 135 deg to the satellite velocity vector. By adjusting the horizon scan angle, several swaths of vectors at different horizontal spacing from the satellite can be recovered. Doppler line profiles from the (OII) 7320A emission at F-Region altitudes, made with the FPI at Sondre Stromfjord, Greenland, were analyzed to provide ion drift vectors and temperatures

  2. Electric field effects in the night-side subauroral F region

    International Nuclear Information System (INIS)

    Deminov, M.G.; Shubin, V.N.

    1988-01-01

    Theoretical analysis of peculiarities of subauroral ionosphere F-region electron concentration due to magnetospheric substorm electric fields is presented. For this purpose a simple model of electric field was used in which longitudinal current effect on subauroral ionosphere conducting layer is taken into account . This model represents the band of plasma fast western drift near the equatorial boundary of the auroral oval in the night-time sector with plasma leaking into this band both from medium latitudes and from the auroral oval region. In the morning sector the plasma drift rate is sufficiently lower and is oriented mainly to the east. It is shown that in the band of fast western plasma drift F-layer maximum altitude h m grows while N m layer concentration in the maximum drops which is mainly due to the increase of temperature and 0 + ion recombination coefficient. In the morning sector h m practically does not change and N m grows which leads to formation of a step-like structure of N m latitude distribution and to a shift of the main ionospheric gap minimum the equator at the rate of about 80 m/s during the first hours of substorm progress

  3. Stokes drift

    Science.gov (United States)

    van den Bremer, T. S.; Breivik, Ø.

    2017-12-01

    During its periodic motion, a particle floating at the free surface of a water wave experiences a net drift velocity in the direction of wave propagation, known as the Stokes drift (Stokes 1847 Trans. Camb. Philos. Soc. 8, 441-455). More generally, the Stokes drift velocity is the difference between the average Lagrangian flow velocity of a fluid parcel and the average Eulerian flow velocity of the fluid. This paper reviews progress in fundamental and applied research on the induced mean flow associated with surface gravity waves since the first description of the Stokes drift, now 170 years ago. After briefly reviewing the fundamental physical processes, most of which have been established for decades, the review addresses progress in laboratory and field observations of the Stokes drift. Despite more than a century of experimental studies, laboratory studies of the mean circulation set up by waves in a laboratory flume remain somewhat contentious. In the field, rapid advances are expected due to increasingly small and cheap sensors and transmitters, making widespread use of small surface-following drifters possible. We also discuss remote sensing of the Stokes drift from high-frequency radar. Finally, the paper discusses the three main areas of application of the Stokes drift: in the coastal zone, in Eulerian models of the upper ocean layer and in the modelling of tracer transport, such as oil and plastic pollution. Future climate models will probably involve full coupling of ocean and atmosphere systems, in which the wave model provides consistent forcing on the ocean surface boundary layer. Together with the advent of new space-borne instruments that can measure surface Stokes drift, such models hold the promise of quantifying the impact of wave effects on the global atmosphere-ocean system and hopefully contribute to improved climate projections. This article is part of the theme issue 'Nonlinear water waves'.

  4. On the ability of chemical transport models to simulate the vertical structure of the N2O, NO2 and HNO3 species in the mid-latitude stratosphere

    Directory of Open Access Journals (Sweden)

    G. Berthet

    2006-01-01

    Full Text Available In this paper we study the impact of the modelling of N2O on the simulation of NO2 and HNO3 by comparing in situ vertical profiles measured at mid-latitudes with the results of the Reprobus 3-D CTM (Three-dimensional Chemical Transport Model computed with the kinetic parameters from the JPL recommendation in 2002. The analysis of the measured in situ profile of N2O shows particular features indicating different air mass origins. The measured N2O, NO2 and HNO3 profiles are not satisfyingly reproduced by the CTM when computed using the current 6-hourly ECMWF operational analysis. Improving the simulation of N2O transport allows us to calculate quantities of NO2 and HNO3 in reasonable agreement with observations. This is achieved using 3-hourly winds obtained from ECMWF forecasts. The best agreement is obtained by constraining a one-dimensional version of the model with the observed N2O. This study shows that the modelling of the NOy partitioning with better accuracy relies at least on a correct simulation of N2O and thus of total NOy.

  5. The contribution of component variation and phytoplankton growth to the distribution variation of chromophoric dissolved organic matter content in a mid-latitude subtropical drinking water source reservoir for two different seasons.

    Science.gov (United States)

    Sun, Qiyuan; Jiang, Juan; Zheng, Yuyi; Wang, Feifeng; Wu, Chunshan; Xie, Rong-Rong

    2017-07-01

    The distribution variation in chromophoric dissolved organic matter (CDOM) content in mid-latitude subtropical drinking water source reservoirs (MDWSRs) has great significance in the security of aquatic environments and human health. CDOM distribution is heavily influenced by biogeochemical processes and anthropogenic activity. However, little is known regarding the impact of component variation and phytoplankton growth on CDOM distribution variation in MDWSR. Therefore, samples were collected from a representative MDWSR (the Shanzai Reservoir) for analysis. CDOM absorption and fluorescence coupling with parallel factor analysis were measured and calculated. The results indicated that only two CDOM components were found in the surface water of Shanzai Reservoir, fulvic acid, and high-excitation tryptophan, originating from terrestrial and autochthonous sources, respectively. The types of components did not change with the season. The average molecular weight of CDOM increased in proportion to its fulvic acid content. The distribution variation in CDOM content mainly resulted from the variation in two CDOM components in summer and from high-excitation tryptophan in winter. Phytoplankton growth strongly influenced the distribution variation of CDOM content in summer; the metabolic processes of Cyanobacteria and Bacillariophyta consumed fulvic acid, while that of Cryptophyta produced high-excitation tryptophan.

  6. Reducing Pesticide Drift

    Science.gov (United States)

    Provides information about pesticide spray drift, including problems associated with drift, managing risks from drift and the voluntary Drift Reduction Technology program that seeks to reduce spray drift through improved spray equipment design.

  7. Universal time dependence of nighttime F region densities at high latitudes

    International Nuclear Information System (INIS)

    Beaujardiere, O.D.L.; Wickwar, V.B.; Caudal, G.

    1985-01-01

    Coordinated EISCAT, Chatanika, and Millstone Hill incoherent scatter radar observations have revealed that in the auroral zone, the nighttime F region densities vary substantially with the longitude of the observing site: EISCAT's densities are the largest and Millstone Hill's are the lowest. The nighttime F region densities measured by the individual radars are not uniform: the regions where the densities are maximum are the so-called ''blobs'' or ''patches'' that have been reported previously. The observations are consistent with the hypothesis that the nighttime densities are produced in significant amounts not by particle precipitation, but by solar EUV radiation, and that they have been transported across the polar cap. The observed differences can be explained by the offset of the geographic and geomagnetic poles. A larger portion of the magnetospheric convection pattern is sunlit when EISCAT is in the midnight sector than when Chatanika is. In winter, when Millstone Hill is in the midnight sector, almost all the auroral oval is in darkness. This universal time effect, which was observed on all coordinated three-radar experiments (September 1981 to February 1982), is illustrated using two periods of coincident radar and satellite observations: November 18--19, and December 15--16, 1981. These two periods were selected because they corresponded to relatively steady conditions. Dynamics Explorer (DE) measurements are used to aid in interpreting the radar observations. De 1 auroral images show what portion of the oval was sunlit. DE 2 data are used to measure the ion drift across the polar cap. Because the altitude of the ionization peak was high, the decay time of the F region density was substantially longer than the transit time across the polar cap

  8. Significance of scatter radar studies of E and F region irregularities at high latitudes

    International Nuclear Information System (INIS)

    Greenwald, R.A.

    1983-01-01

    This chapter considers the mechanisms by which electron density irregularities may be generated in the high latitude ionosphere and the techniques through which they are observed with ground base radars. The capabilities of radars used for studying these irregularities are compared with the capabilities of radars used for incoherent scatter measurements. The use of irregularity scatter techniques for dynamic studies of larger scale structured phenomena is discussed. Topics considered include E-region irregularities, observations with auroral radars, plasma drifts associated with a westward travelling surge, and ionospheric plasma motions associated with resonant waves. It is shown why high latitude F-region irregularity studies must be made in the HF frequency band (3-30 MHz). The joint use of the European Incoherent Scatter Association (EISCAT), STARE and SAFARI facilities is examined, and it is concluded that the various techniques will enhance each other and provide a better understanding of the various processes being studied

  9. ARCAD3-SAFARI coordinated study of auroral and polar F-region ionospheric irregularities

    International Nuclear Information System (INIS)

    Villain, J.P.; Hanuise, C.; Beghin, C.

    1985-01-01

    Simultaneous observations of F-region ionospheric irregularities have been performed with the SAFARI ground based HF radars and the ISOPROBE experiment on board the AUREOL-3 satellite. Among seven orbits during which the satellite trajectory was directly in the radar beam or in the vicinity, four of them have been analysed in detail. The spectral power of the electron density variations ΔNe/Ne has been calculated for wavelengths between 20 m and 1 km from the ISOPROBE high time resolution thermal plasma measurements. One spectrum is obtained every 1.2 sec., which corresponds to about 10 km along the satellite trajectory. The SAFARI experiment is a set of two HF coherent radars located at Lycksele (Sweden) and Oulu (Finland). These radars are sensitive to F-region ionospheric irregularities of 10 m wavelength in the polar and auroral ionosphere. The phase velocity of the irregularities obtained from the Doppler spectrum is related to the ambient plasma drift. The presence of echoes observed with the SAFARI radars is compared with the spectral power of the electron density variations deduced from the ISOPROBE in-situ measurements. A good agreement is found between the two sets of observations and a numerical value of the spectral power corresponding to detection of echoes by the radar is given. A synoptical view of the event is given and interpreted according to the existing theories on plasma irregularities

  10. Drift chamber

    International Nuclear Information System (INIS)

    Inagaki, Yosuke

    1977-01-01

    Drift chamber is becoming an important detector in high energy physics as a precision and fast position detector because of its high spatial resolution and count-rate. The basic principle is that it utilizes the drift at constant speed of electrons ionized along the tracks of charged particles towards the anode wire in the nearly uniform electric field. The method of measuring drift time includes the analog and digital ones. This report describes about the construction of and the application of electric field to the drift chamber, mathematical analysis on the electric field and equipotential curve, derivation of spatial resolution and the factor for its determination, and selection of gas to be used. The performance test of the chamber was carried out using a small test chamber, the collimated β source of Sr-90, and 500 MeV/C electron beam from the 1.3 GeV electron synchrotron in the Institute of Nuclear Study, University of Tokyo. Most chambers to date adopted one dimensional read-out, but it is very advantageous if the two dimensional read-out is feasible with one chamber when the resolution in that direction is low. The typical methods of delay line and charge division for two dimensional read-out are described. The development of digital read-out system is underway, which can process the signal of a large scale drift chamber at high speed. (Wakatsuki, Y.)

  11. Effects of geomagnetic storms on the bottomside ionospheric F region

    Czech Academy of Sciences Publication Activity Database

    Burešová, Dalia

    2005-01-01

    Roč. 35, - (2005), s. 429-439 ISSN 0273-1177 R&D Projects: GA AV ČR(CZ) IAA3042102 Institutional research plan: CEZ:AV0Z30420517 Keywords : Ionosphere * Geomagnetic storm * Bottomside F region electron density Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 0.706, year: 2005

  12. Very high latitude F-region irregularities observed by HF-radar backscatter

    International Nuclear Information System (INIS)

    Baker, K.B.; Greenwald, R.A.; Tsunoda, R.T.

    1983-01-01

    In February and March, 1982, a coherent scatter HF radar was operated from Cleary, Alaska to observe 7- to 15-m wavelength F-region plasma irregularities near the poleward edge of the auroral zone and in the polar cap. The radar operated for five days from February 25 to March 1 and produced approximately 700,000 Doppler spectra during that time. Of those nearly 700,000 spectra, approximately 10% showed backscattered power 3 dB or more above the noise level. A ray tracing technique using electron densities determined by the Chatanika incoherent scatter radar was used to predict locations where the HF waves were approximately normal to the magnetic field. If those locations were also to contain small scale electron density structure, then one would expect them to backscatter the HF waves. Several comparisons were made between predicted and observed locations of radiowave backscatter and excellent agreement was obtained. In addition, comparisons of the Doppler velocities observed by the coherent scatter HF radar and those observed by the Chatanika radar showed good agreement, suggesting that the plasma irregularities observed by the HF radar drift with the ambient plasma. In addition, average vector velocities calculated for the entire 5-day period show a flow pattern consistent with polar cap convection models. This again indicates that the irregularities drift with the plasma, as is predicted by a number of theories of F-region plasma irregularities. In the summer of 1983, the research program begun with those measurements will be continued with a steerable phased-array HF radar located at Goose Bay, Labrador, that will view the same ionospheric region as does the Sondre Stromfjord incoherent scatter radar

  13. Plasma Irregularity Production in the Polar Cap F-Region Ionosphere

    Science.gov (United States)

    Lamarche, Leslie

    the asymmetry of the irregularity growth rate across the gradient reversal. Directional dependencies on the plasma density gradient, plasma drift, and wavevector are analyzed in the context of the recently developed general fluid theory of the gradient-drift instability. In the ionospheric F region, the strongest asymmetry is found when an elongated structure is oriented along the radar's boresight and moving perpendicular to its direction of elongation. These results have important implications for finding optimal configurations for oblique-scanning ionospheric radars such as SuperDARN to observe gradient reversals. To test the predictions of the developed model and the general theory of the gradient-drift instability, an experimental investigation is presented focusing on decameter-scale irregularities near a polar patch and the previously uninvestigated directional dependence of irregularity characteristics. Backscatter power and occurrence of irregularities are analyzed using measurements from the SuperDARN radar at Rankin Inlet, Canada, while background density gradients and convection electric fields are found from the north face of the Resolute Bay Incoherent Scatter Radar. It is shown that irregularity occurrence tends to follow the expected trends better than irregularity power, suggesting that while the gradient-drift instability may be a dominant process in generating small-scale irregularities, other mechanisms such as a shear-driven instability or nonlinear process may exert greater control over their intensity. It is concluded from this body of work that the production of small-scale plasma irregularities in the polar F-region ionosphere is controlled both by global factors such as solar illumination as well as local plasma density gradients and electric fields. In general, linear gradient-drift instability theory describes small-scale irregularity production well, particularly for low-amplitude perturbations. The production of irregularities is complex

  14. Direct evidence of plasma - density structuring in the auroral F-region ionosphere

    International Nuclear Information System (INIS)

    Tsunoda, R.T.; Haeggstroem, I.; Pellinen-Wannberg, A.; Steen, Aa.; Wannberg, G.

    1985-03-01

    We investigate the hypothesis that large-scale plasma-density enhancements found in the auroral F layer become structured via a magnetic-flux-tube interchange (MFTI) process. In such a process, plasma structure is produced when spatially irregular electric fields transport higher number-density plasma into a region containing lower number-density plasma, and vice versa. Direct experimental evidence of this process can be obtained by measuring concurrently the spatial distributions of F-region plasma density and electric field. Using the tristatic EISCAT radar facility, we measured these quantities in a two-dimensional plane transverse to the geomagnetic field, at 300-km altitude. We show, in a case study, that plasma-density structure found along the poleward wall of a blob was indeed accompanied by similar-scale variations in the ionospheric electric field, and that the sense of relative motion between high- and low-number-density plasma is consistent with ongoing structuring of the plasma via a MFTI process. From the estimated growth rate of 3 x 10 -3 s -1 , the observed plasma structure could have been produced in several minutes by the irregular electic field pattern. The source of the MFTI process, however, is not clear. The MFTI process did not appear to be driven by F-region polarization electric fields, a conclusion based on (1) the apparent lack of inverse correlation between plasma density and 'slip' velocity patterns, and (2) the positive growth rate found along the poleward wall of the blob in the presence of a westward Pedersen current. This conclusion excludes (at least for this data set) the gradient-drift and current-convective instabilities as primary sources of the ongoing structuring process. (Author)

  15. Response of the Ionospheric F-region in the Latin American Sector During the Intense Geomagnetic Storm of 21-22 January 2005

    Science.gov (United States)

    Sahai, Y.; Fagundes, P. R.; de Jesus, R.; de Abreu, A. J.; Crowley, G.; Pillat, V. G.; Guarnieri, F. L.; Abalde, J. R.; Bittencourt, J. A.

    2009-12-01

    Ionospheric storms are closely associated with geomagnetic storms and are an extreme example of space weather events. The response of the ionosphere to storms is rather complicated. In the present investigation, we have studied the response of the ionospheric F-region in the Latin American sector during the intense geomagnetic storm of 21-22 January 2005 (with storm sudden commencement (SSC) at 1712 UT on 21 January). This geomagnetic storm is anomalous (minimum Dst reached -105 nT at 0700 UT on 22 January) because the main phase occurred during the northward excursion of the Bz component of interplanetary magnetic fields (IMFs). The monthly mean F10.7 solar flux for the month of January 2005 was 99.0 sfu. The ionospheric F-region parameters observed at Ramey (18.5 N, 67.1 W; RAM), Puerto Rico, Jicamarca (12.0 S, 76.8 W; JIC), Peru, Manaus (2.9 S, 60.0 W; MAN), and São José dos Campos (23.2 S, 45.9 W; SJC), Brazil, during 21-22 January (geomagnetically disturbed) and 25 January (geomagnetically quiet) have been analyzed. Both JIC and MAN, the equatorial stations, show unusually rapid uplifting of the F-region peak heights(hpF2/hmF2) and a decrease in the NmF2 coincident with the time of SSC. At both RAM and SJC an uplifting of the F-region peak height is observed at about 2000 UT. The low-latitude station SJC shows a coincident decrease in NmF2 with the uplifting, whereas the mid-latitude station RAM shows a decrease in NmF2 earlier than the uplifting. Also, the observed variations in the F-region ionospheric parameters are compared with the TIMEGCM model run for 21-22 January and the model results show both similarities and differences from the observed results. Average GPS-TEC (21-22 and 25 January) and phase fluctuations (21, 22, 25, 26 January) observed at Belem (1.5 S, 48.5 W; BELE), Brasilia (15.9 S, 47.9 W; BRAZ), Presidente Prudente (22.3o S, 51.4 W; UEPP), and Porto Alegre (30.1 S, 51.1 W; POAL), Brazil, are also presented. These GPS stations belong to

  16. Effect of plasma instability on F region photoelectron distributions

    International Nuclear Information System (INIS)

    Bloomberg, H.W.

    1975-01-01

    Ionospheric suprathermal photoelectrons have relatively large cross sections for selected energies. In particular, electrons with energies of about 2.5 eV strongly excite nitrogen vibrational modes, while metastable states of oxygen are excited at about 5 eV. Thus an energy distribution based on chemical kinetic considerations give rise to a maximum at around 4 eV in the F region below 250 km. However, rocket experiments have shown that the expected peaks in the flux spectrum are relatively weak. This discrepancy is explained by the development of a linear instability leading to a wave-particle interaction. The linear mode is driven by the photoelectrons near the 4-eV maximum in the presence of a magnetic field. The effect is shown to be ineffective at sufficiently low altitudes, where collisionless theory fails. (auth)

  17. Effect of plasma instability on F region photoelectron distributions

    International Nuclear Information System (INIS)

    Bloomberg, H.W.

    1975-01-01

    Ionospheric suprathermal photoelectrons have relatively large cross sections for selected energies. In particular, electrons with energies of about 2.5 eV strongly excite nitrogen vibrational modes, while metastable states of oxygen are excited at about 5 eV. Thus an energy distribution based on chemical kinetic considerations gives rise to a maximum at around 4 eV in the F region below 250 km. However, rocket experiments have shown that the expected peaks in the flux spectrum are relatively weak. This discrepancy is explained by the development of a linear instability leading to a wave-particle interaction. the linear mode is driven by the photoelectrons near the 4-eV maximum in the presence of a magnetic field. The effect is shown to be ineffective at sufficiently low altitudes, where collisionless theory fails

  18. Bottomside sinusoidal irregularities in the equatorial F region

    Science.gov (United States)

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

    1983-01-01

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

  19. On the factors controlling occurrence of F-region coherent echoes

    Directory of Open Access Journals (Sweden)

    D. W. Danskin

    2002-09-01

    Full Text Available Several factors are known to control the HF echo occurrence rate, including electron density distribution in the ionosphere (affecting the propagation path of the radar wave, D-region radio wave absorption, and ionospheric irregularity intensity. In this study, we consider 4 days of CUTLASS Finland radar observations over an area where the EISCAT incoherent scatter radar has continuously monitored ionospheric parameters. We illustrate that for the event under consideration, the D-region absorption was not the major factor affecting the echo appearance. We show that the electron density distribution and the radar frequency selection were much more significant factors. The electron density magnitude affects the echo occurrence in two different ways. For small F-region densities, a minimum value of 1 × 1011 m-3 is required to have sufficient radio wave refraction so that the orthogonality (with the magnetic field lines condition is met. For too large densities, radio wave strong "over-refraction" leads to the ionospheric echo disappearance. We estimate that the over-refraction is important for densities greater than 4 × 1011 m-3. We also investigated the backscatter power and the electric field magnitude relationship and found no obvious relationship contrary to the expectation that the gradient-drift plasma instability would lead to stronger irregularity intensity/echo power for larger electric fields.Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; auroral ionosphere

  20. Radial plasma drifts deduced from VLF whistler mode signals - A modelling study

    Science.gov (United States)

    Poulter, E. M.; Andrews, M. K.; Bailey, G. J.; Moffett, R. J.

    1984-05-01

    VLF whistler mode signals have previously been used to infer radial plasma drifts in the equatorial plane of the plasmasphere and the field-aligned ionosphere-protonosphere coupling fluxes. Physical models of the plasmasphere consisting of O(+) adn H(+) ions along dipole magnetic field lines, and including radial E x B drifts, are applied to a mid-latitude flux tube appropriate to whistler mode signals received at Wellington, New Zealand, from the fixed frequency VLF transmitter NLK (18.6 kHz) in Seattle, U.S.A. These models are first shown to provide a good representation of the recorded Doppler shift and group delay data. They are then used to simulate the process of deducing the drifts and fluxes from the recorded data. Provided the initial whistler mode duct latitude and the ionospheric contributions are known, the drifts at the equatorial plane can be estimated to about + or - 20 m/s (approximately 10-15 percent), and the two hemisphere ionosphere-protonosphere coupling fluxes to about + or - 10 to the 12th/sq m-sec (approximately 40 percent).

  1. Evaluating anemometer drift: A statistical approach to correct biases in wind speed measurement

    Science.gov (United States)

    Azorin-Molina, Cesar; Asin, Jesus; McVicar, Tim R.; Minola, Lorenzo; Lopez-Moreno, Juan I.; Vicente-Serrano, Sergio M.; Chen, Deliang

    2018-05-01

    Recent studies on observed wind variability have revealed a decline (termed "stilling") of near-surface wind speed during the last 30-50 years over many mid-latitude terrestrial regions, particularly in the Northern Hemisphere. The well-known impact of cup anemometer drift (i.e., wear on the bearings) on the observed weakening of wind speed has been mentioned as a potential contributor to the declining trend. However, to date, no research has quantified its contribution to stilling based on measurements, which is most likely due to lack of quantification of the ageing effect. In this study, a 3-year field experiment (2014-2016) with 10-minute paired wind speed measurements from one new and one malfunctioned (i.e., old bearings) SEAC SV5 cup anemometer which has been used by the Spanish Meteorological Agency in automatic weather stations since mid-1980s, was developed for assessing for the first time the role of anemometer drift on wind speed measurement. The results showed a statistical significant impact of anemometer drift on wind speed measurements, with the old anemometer measuring lower wind speeds than the new one. Biases show a marked temporal pattern and clear dependency on wind speed, with both weak and strong winds causing significant biases. This pioneering quantification of biases has allowed us to define two regression models that correct up to 37% of the artificial bias in wind speed due to measurement with an old anemometer.

  2. The Storm Time Evolution of the Ionospheric Disturbance Plasma Drifts

    Science.gov (United States)

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

    2017-11-01

    In this paper, we use the C/NOFS and ROCSAT-1 satellites observations to analyze the storm time evolution of the disturbance plasma drifts in a 24 h local time scale during three magnetic storms driven by long-lasting southward IMF Bz. The disturbance plasma drifts during the three storms present some common features in the periods dominated by the disturbance dynamo. The newly formed disturbance plasma drifts are upward and westward at night, and downward and eastward during daytime. Further, the disturbance plasma drifts are gradually evolved to present significant local time shifts. The westward disturbance plasma drifts gradually migrate from nightside to dayside. Meanwhile, the dayside downward disturbance plasma drifts become enhanced and shift to later local time. The local time shifts in disturbance plasma drifts are suggested to be mainly attributed to the evolution of the disturbance winds. The strong disturbance winds arisen around midnight can constantly corotate to later local time. At dayside the westward and equatorward disturbance winds can drive the F region dynamo to produce the poleward and westward polarization electric fields (or the westward and downward disturbance drifts). The present results indicate that the disturbance winds corotated to later local time can affect the local time features of the disturbance dynamo electric field.

  3. Drift chamber detectors

    International Nuclear Information System (INIS)

    Duran, I.; Martinez Laso, L.

    1989-01-01

    A review of High Energy Physics detectors based on drift chambers is presented. The ionization, drift diffusion, multiplication and detection principles are described. Most common drift media are analysied, and a classification of the detectors according to its geometry is done. Finally the standard read-out methods are displayed and the limits of the spatial resolution are discussed. (Author)

  4. Drift Chambers detectors

    International Nuclear Information System (INIS)

    Duran, I.; Martinez laso, L.

    1989-01-01

    We present here a review of High Energy Physics detectors based on drift chambers. The ionization, drift diffusion, multiplication and detection principles are described. Most common drift media are analysed, and a classification of the detectors according to its geometry is done. Finally the standard read-out methods are displayed and the limits of the spatial resolution are discussed. (Author) 115 refs

  5. Drift velocities of 150-km Field-Aligned Irregularities observed by the Equatorial Atmosphere Radar

    Directory of Open Access Journals (Sweden)

    Yuichi Otsuka

    2013-11-01

    Full Text Available Between 130 and 170 km altitude in the daytime ionosphere, the so-called 150-km field-aligned irregularities (FAIs have been observed since the 1960s at equatorial regions with several very high frequency (VHF radars. We report statistical results of 150-km FAI drift velocities on a plane perpendicular to the geomagnetic field, acquired by analyzing the Doppler velocities of 150-km FAIs observed with the Equatorial Atmosphere Radar (EAR at Kototabang, Indonesia during the period from Aug. 2007 to Oct. 2009. We found that the southward/upward perpendicular drift velocity of the 150-km FAIs tends to decrease in the afternoon and that this feature is consistent with that of F-region plasma drift velocities over the magnetic equator. The zonal component of the 150-km FAI drift velocity is westward and decreases with time, whereas the F-region plasma drift velocity observed with the incoherent scatter radar at Jicamarca, Peru, which is westward, reaches a maximum at about noon. The southward/upward and zonal drift velocities of the 150-km FAIs are smaller than that of the F-region plasma drift velocity by approximately 3 m/s and 25 m/s, respectively, on average. The large difference between the 150-km FAI and F-region plasma drift velocities may not arise from a difference in the magnetic latitudes at which their electric fields are generated. Electric fields generated at the altitude at which the 150-km FAIs occur may not be negligible.

  6. Sudden post-midnight decrease in equatorial F-region electron densities associated with severe magnetic storms

    Directory of Open Access Journals (Sweden)

    D. R. Lakshmi

    1997-03-01

    Full Text Available A detailed analysis of the responses of the equatorial ionosphere to a large number of severe magnetic storms shows the rapid and remarkable collapse of F-region ionisation during post-midnight hours; this is at variance with the presently accepted general behaviour of the low-latitude ionosphere during magnetic storms. This paper discusses such responses as seen in the ionosonde data at Kodaikanal (Geomagn. Lat. 0.6 N. It is also observed that during magnetic storm periods the usual increase seen in the h'F at Kodaikanal during sunset hours is considerably suppressed and these periods are also characterised by increased foF2 values. It is suggested that the primary process responsible for these dramatic pre- and post-midnight changes in foF2 during magnetic storms could be due to changes in the magnitude as well as in the direction of usual equatorial electric fields. During the post-midnight periods the change in electric-field direction from westward to eastward for a short period causes an upward E × B plasma drift resulting in increased h'F and decreased electron densities in the equatorial region. In addition, it is also suggested that the enhanced storm-induced meridional winds in the thermosphere, from the poles towards the equator, may also cause the decreases in electron density seen during post-midnight hours by spatially transporting the F-region ionisation southwards away from Kodaikanal. The paper also includes a discussion on the effects of such decreases in ionisation on low-latitude HF communications.

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

    Science.gov (United States)

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

    2011-10-01

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

  8. Dike/Drift Interactions

    Energy Technology Data Exchange (ETDEWEB)

    E. Gaffiney

    2004-11-23

    This report presents and documents the model components and analyses that represent potential processes associated with propagation of a magma-filled crack (dike) migrating upward toward the surface, intersection of the dike with repository drifts, flow of magma in the drifts, and post-magma emplacement effects on repository performance. The processes that describe upward migration of a dike and magma flow down the drift are referred to as the dike intrusion submodel. The post-magma emplacement processes are referred to as the post-intrusion submodel. Collectively, these submodels are referred to as a conceptual model for dike/drift interaction. The model components and analyses of the dike/drift interaction conceptual model provide the technical basis for assessing the potential impacts of an igneous intrusion on repository performance, including those features, events, and processes (FEPs) related to dike/drift interaction (Section 6.1).

  9. Dike/Drift Interactions

    International Nuclear Information System (INIS)

    Gaffiney, E.

    2004-01-01

    This report presents and documents the model components and analyses that represent potential processes associated with propagation of a magma-filled crack (dike) migrating upward toward the surface, intersection of the dike with repository drifts, flow of magma in the drifts, and post-magma emplacement effects on repository performance. The processes that describe upward migration of a dike and magma flow down the drift are referred to as the dike intrusion submodel. The post-magma emplacement processes are referred to as the post-intrusion submodel. Collectively, these submodels are referred to as a conceptual model for dike/drift interaction. The model components and analyses of the dike/drift interaction conceptual model provide the technical basis for assessing the potential impacts of an igneous intrusion on repository performance, including those features, events, and processes (FEPs) related to dike/drift interaction (Section 6.1)

  10. The Drift Burst Hypothesis

    OpenAIRE

    Christensen, Kim; Oomen, Roel; Renò, Roberto

    2016-01-01

    The Drift Burst Hypothesis postulates the existence of short-lived locally explosive trends in the price paths of financial assets. The recent US equity and Treasury flash crashes can be viewed as two high profile manifestations of such dynamics, but we argue that drift bursts of varying magnitude are an expected and regular occurrence in financial markets that can arise through established mechanisms such as feedback trading. At a theoretical level, we show how to build drift bursts into the...

  11. Rectangular drift tube characteristics

    International Nuclear Information System (INIS)

    Denisov, D.S.; Musienko, Yu.V.

    1985-01-01

    Results on the study of the characteristics of a 50 x 100 mm aluminium drift tube are presented. The tube was filled with argon-methane and argon-isobutane mixtures. With 16 per cent methane concentration the largest deviation from a linear relation between the drift time and the drift path over 50 mm is less than 2 mm. The tube filled with argon-isobutane mixture is capable of operating in a limited streamer mode

  12. Dike/Drift Interactions

    Energy Technology Data Exchange (ETDEWEB)

    E.S. Gaffney

    2003-10-08

    This report documents the model of events associated with a potential intrusion of magma from a volcanic dike into a drift or drifts in the Yucca Mountain Nuclear Waste Repository. The following topics are included in this report: (1) A discussion of dike propagation, which provides the basis for describing the path that a representative dike, or swarm of dikes, would follow during an event. (2) A discussion of magma flow, which evaluates the interaction at the junction of the propagating dike with the drift and the movement of magmatic products into and down drifts and, potentially, through a drift to the surface by way of access drift or a secondary dike opened up along the drift. (3) A discussion of gas flow and conductive cooling of a magma-filled drift, describing how an adjacent drift that has not been intersected by a dike could be affected by post-intrusion phenomena. Note that a gas flow analysis is also addressed in ''Igneous Intrusion Impacts on Waste Form and Waste Packages'' (BSC 2003 [DIRS 161810]), and those results are consistent with the results presented in this report.

  13. Dike/Drift Interactions

    International Nuclear Information System (INIS)

    E.S. Gaffney

    2003-01-01

    This report documents the model of events associated with a potential intrusion of magma from a volcanic dike into a drift or drifts in the Yucca Mountain Nuclear Waste Repository. The following topics are included in this report: (1) A discussion of dike propagation, which provides the basis for describing the path that a representative dike, or swarm of dikes, would follow during an event. (2) A discussion of magma flow, which evaluates the interaction at the junction of the propagating dike with the drift and the movement of magmatic products into and down drifts and, potentially, through a drift to the surface by way of access drift or a secondary dike opened up along the drift. (3) A discussion of gas flow and conductive cooling of a magma-filled drift, describing how an adjacent drift that has not been intersected by a dike could be affected by post-intrusion phenomena. Note that a gas flow analysis is also addressed in ''Igneous Intrusion Impacts on Waste Form and Waste Packages'' (BSC 2003 [DIRS 161810]), and those results are consistent with the results presented in this report

  14. Drift Degradation Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Dwayne C. Kicker

    2001-09-28

    A statistical description of the probable block sizes formed by fractures around the emplacement drifts has been developed for each of the lithologic units of the repository host horizon. A range of drift orientations with the drift azimuth varied in 15{sup o} increments has been considered in the static analysis. For the quasi-static seismic analysis, and the time-dependent and thermal effects analysis, two drift orientations have been considered: a drift azimuth of 105{sup o} and the current emplacement drift azimuth of 75{sup o}. The change in drift profile resulting from progressive deterioration of the emplacement drifts has been assessed both with and without backfill. Drift profiles have been determined for four different time increments, including static (i.e., upon excavation), 200 years, 2,000 years, and 10,000 years. The effect of seismic events on rock fall has been analyzed. Block size distributions and drift profiles have been determined for three seismic levels, including a 1,000-year event, a 5,000-year event, and a 10,000-year event. Data developed in this modeling and analysis activity have been entered into the TDMS (DTN: MO0109RDDAAMRR.003). The following conclusions have resulted from this drift degradation analysis: (1) The available fracture data are suitable for supporting a detailed key block analysis of the repository host horizon rock mass. The available data from the north-south Main Drift and the east-west Cross Drift provide a sufficient representative fracture sample of the repository emplacement drift horizon. However, the Tptpln fracture data are only available from a relatively small section of the Cross Drift, resulting in a smaller fracture sample size compared to the other lithologic units. This results in a lower degree of confidence that the key block data based on the Tptpln data set is actually representative of the overall Tptpln key block population. (2) The seismic effect on the rock fall size distribution for all events

  15. An electrodeless drift chamber

    International Nuclear Information System (INIS)

    Allison, J.; Barlow, R.J.; Bowdery, C.K.; Duerdoth, I.; Rowe, P.G.

    1982-01-01

    We describe a chamber in which the drift field is controlled by the deposition of electrostatic charge on an insulating surface. The chamber operates with good efficiency and precision for observed drift distances of up to 45 cm, promises to be extremely robust and adaptable and offers a very cheap way of making particle detectors. (orig.)

  16. Modeling concept drift

    DEFF Research Database (Denmark)

    Borchani, Hanen; Martinez, Ana Maria; Masegosa, Andrés R.

    2015-01-01

    An often used approach for detecting and adapting to concept drift when doing classification is to treat the data as i.i.d. and use changes in classification accuracy as an indication of concept drift. In this paper, we take a different perspective and propose a framework, based on probabilistic ...... data set from a Spanish bank....

  17. Time dependent drift Hamiltonian

    International Nuclear Information System (INIS)

    Boozer, A.H.

    1982-04-01

    The motion of individual charged particles in a given magnetic and an electric fields is discussed. An idea of a guiding center distribution function f is introduced. The guiding center distribution function is connected to the asymptotic Hamiltonian through the drift kinetic equation. The general non-stochastic magnetic field can be written in a contravariant and a covariant forms. The drift Hamiltonian is proposed, and the canonical gyroradius is presented. The proposed drift Hamiltonian agrees with Alfven's drift velocity to lowest non-vanishing order in the gyroradius. The relation between the exact, time dependent equations of motion and the guiding center equation is clarified by a Lagrangian analysis. The deduced Lagrangian represents the drift motion. (Kato, T.)

  18. Abstraction of Drift Seepage

    International Nuclear Information System (INIS)

    J.T. Birkholzer

    2004-01-01

    This model report documents the abstraction of drift seepage, conducted to provide seepage-relevant parameters and their probability distributions for use in Total System Performance Assessment for License Application (TSPA-LA). Drift seepage refers to the flow of liquid water into waste emplacement drifts. Water that seeps into drifts may contact waste packages and potentially mobilize radionuclides, and may result in advective transport of radionuclides through breached waste packages [''Risk Information to Support Prioritization of Performance Assessment Models'' (BSC 2003 [DIRS 168796], Section 3.3.2)]. The unsaturated rock layers overlying and hosting the repository form a natural barrier that reduces the amount of water entering emplacement drifts by natural subsurface processes. For example, drift seepage is limited by the capillary barrier forming at the drift crown, which decreases or even eliminates water flow from the unsaturated fractured rock into the drift. During the first few hundred years after waste emplacement, when above-boiling rock temperatures will develop as a result of heat generated by the decay of the radioactive waste, vaporization of percolation water is an additional factor limiting seepage. Estimating the effectiveness of these natural barrier capabilities and predicting the amount of seepage into drifts is an important aspect of assessing the performance of the repository. The TSPA-LA therefore includes a seepage component that calculates the amount of seepage into drifts [''Total System Performance Assessment (TSPA) Model/Analysis for the License Application'' (BSC 2004 [DIRS 168504], Section 6.3.3.1)]. The TSPA-LA calculation is performed with a probabilistic approach that accounts for the spatial and temporal variability and inherent uncertainty of seepage-relevant properties and processes. Results are used for subsequent TSPA-LA components that may handle, for example, waste package corrosion or radionuclide transport

  19. The reconciliation of an F-region irregularity model with sunspot-cycle variations in spread-F occurrence

    International Nuclear Information System (INIS)

    Singleton, D.G.

    1974-11-01

    A recently proposed means of combining models of ionospheric F-layer peak electron density and irregularity incremental electron density (ΔN) so as to simulate the global occurrence probability of the frequency spreading component of spread-F is discussed. This procedure is then used to model experimental spread-F occurrence results. It is found possible to readily simulate the sunspot-maximum results, independently of season, with only small adjustments to the amplitudes of the empirical expressions used to ΔN in the several latitude regimes. However, at sunspot minimum and for each season, the ΔN model requires modification in the equatorial and mid-latitude regions of high irregularity incidence, before successful simulations of the spread-F data can be obtained. These modifications, which include a broadening of the equatorial region and a polewards shift to the mid-latitude region with decreasing sunspot number, are discussed in detail. It is concluded that the scintillation data base, from which the original ΔN model derives, is not sufficiently representative with regard to sunspot number and magnetic index. The use of the spread-F adaptation of the ΔN model, as well as its original scintillation version, to rectify these failings of the ΔN model are also discussed. (author)

  20. Drift Degradation Analysis

    International Nuclear Information System (INIS)

    G.H. Nieder-Westermann

    2005-01-01

    The outputs from the drift degradation analysis support scientific analyses, models, and design calculations, including the following: (1) Abstraction of Drift Seepage; (2) Seismic Consequence Abstraction; (3) Structural Stability of a Drip Shield Under Quasi-Static Pressure; and (4) Drip Shield Structural Response to Rock Fall. This report has been developed in accordance with ''Technical Work Plan for: Regulatory Integration Modeling of Drift Degradation, Waste Package and Drip Shield Vibratory Motion and Seismic Consequences'' (BSC 2004 [DIRS 171520]). The drift degradation analysis includes the development and validation of rockfall models that approximate phenomenon associated with various components of rock mass behavior anticipated within the repository horizon. Two drift degradation rockfall models have been developed: the rockfall model for nonlithophysal rock and the rockfall model for lithophysal rock. These models reflect the two distinct types of tuffaceous rock at Yucca Mountain. The output of this modeling and analysis activity documents the expected drift deterioration for drifts constructed in accordance with the repository layout configuration (BSC 2004 [DIRS 172801])

  1. Collisional drift fluids and drift waves

    International Nuclear Information System (INIS)

    Pfirsch, D.; Correa-Restrepo, D.

    1995-05-01

    The usual theoretical description of drift-wave turbulence (considered to be one possible cause of anomalous transport in a plasma), e.g. the Hasegawa-Wakatani theory, makes use of various approximations, the effect of which is extremely difficult to assess. This concerns in particular the conservation laws for energy and momentum. The latter is important as concerns charge separation and resulting electric fields which are possibly related to the L-H transition. Energy conservation is crucial for the stability behaviour; it will be discussed via an example. New collisional multispecies drift-fluid equations were derived by a new method which yields in a transparent way conservation of energy and total angular momentum, and the law for energy dissipation. Both electrostatic and electromagnetic field variations are considered. The method is based primarily on a Lagrangian for dissipationless fluids in drift approximation with isotropic pressures. The dissipative terms are introduced by adding corresponding terms to the ideal equations of motion and of the pressures. The equations of motion, of course, no longer result from a Lagrangian via Hamilton's principle. Their relation to the ideal equations imply, however, also a relation to the ideal Lagrangian of which one can take advantage. Instead of introducing heat conduction one can also assume isothermal behaviour, e.g. T ν (x)=const. Assumptions of this kind are often made in the literature. The new method of introducing dissipation is not restricted to the present kind of theories; it can equally well be applied to theories such as multi-fluid theories without using the drift approximation of the present paper. Linear instability is investigated via energy considerations and the implications of taking ohmic resistivity into account are discussed. (orig./WL)

  2. Drift Scale THM Model

    International Nuclear Information System (INIS)

    Rutqvist, J.

    2004-01-01

    This model report documents the drift scale coupled thermal-hydrological-mechanical (THM) processes model development and presents simulations of the THM behavior in fractured rock close to emplacement drifts. The modeling and analyses are used to evaluate the impact of THM processes on permeability and flow in the near-field of the emplacement drifts. The results from this report are used to assess the importance of THM processes on seepage and support in the model reports ''Seepage Model for PA Including Drift Collapse'' and ''Abstraction of Drift Seepage'', and to support arguments for exclusion of features, events, and processes (FEPs) in the analysis reports ''Features, Events, and Processes in Unsaturated Zone Flow and Transport and Features, Events, and Processes: Disruptive Events''. The total system performance assessment (TSPA) calculations do not use any output from this report. Specifically, the coupled THM process model is applied to simulate the impact of THM processes on hydrologic properties (permeability and capillary strength) and flow in the near-field rock around a heat-releasing emplacement drift. The heat generated by the decay of radioactive waste results in elevated rock temperatures for thousands of years after waste emplacement. Depending on the thermal load, these temperatures are high enough to cause boiling conditions in the rock, resulting in water redistribution and altered flow paths. These temperatures will also cause thermal expansion of the rock, with the potential of opening or closing fractures and thus changing fracture permeability in the near-field. Understanding the THM coupled processes is important for the performance of the repository because the thermally induced permeability changes potentially effect the magnitude and spatial distribution of percolation flux in the vicinity of the drift, and hence the seepage of water into the drift. This is important because a sufficient amount of water must be available within a

  3. Effects of a conducting E layer on classical F region cross-field plasma diffusion

    International Nuclear Information System (INIS)

    Vickrey, J.F.; Kelley, M.C.

    1982-01-01

    The rate of cross-field plasma diffusion in the F region ionosphere is significantly increased when the magnetic field lines thread a highly conducting E region below. This reduces the lifetime of small-scale F region electron density irregularities in the polar ionosphere where the presence of a highly conducting E region is comonplace. A simple mmodel is developed to describe the effects of a conducting E layer on classical F region plasma diffusion. In the absence of an E region, the difference in ion and electron diffusion rates leads to a charge separation and, hence, to an electrostatic field that retards ion diffusion. When the highly conducting magnetic field lines are tied to a conducting E region, however, electrons can flow along B to reduce the ambipolar diffusion electric field, and ions can proceed perpendicular to B at a rate approaching their own (higher) diffusion velocity. It is shown that the enhanced total diffusion rate that results depends strongly on the height of the F layer and on the ratio of the E to F region Pedersen conductivities

  4. Vertical and longitudinal electron density structures of equatorial E- and F-regions

    Directory of Open Access Journals (Sweden)

    P. S. Brahmanandam

    2011-01-01

    Full Text Available From global soundings of ionospheric electron density made with FORMOSAT 3/COSMIC satellites for September 2006–August 2009, day-night variations in vertical and longitudinal structures of the electron densities in equatorial E- and F-regions for different seasons are investigated for the first time. The results reveal that the wavenumber-3 and wavenumber-4 patterns dominated the nighttime (22:00–04:00 LT F-region longitudinal structures in solstice and in equinox seasons, respectively. In daytime (08:00–18:00 LT F-region, the wavenumber-4 patterns governed the longitudinal structures in the September equinox and December solstice, and wavenumber-3 in March equinox and June solstice respectively. A comparison of the daytime and nighttime longitudinal electron density structures indicates that they are approximately 180° out of phase with each other. It is believed that this out of phase relation is very likely the result of the opposite phase relation between daytime and nighttime nonmigrating diurnal tidal winds that modulate background E-region dynamo electric field at different places, leading to the day-night change in the locations of the equatorial plasma fountains that are responsible for the formation of the F-region longitudinal structures. Further, a good consistency between the locations of the density structures in the same seasons of the different years for both daytime and nighttime epochs has been noticed indicating that the source mechanism for these structures could be the same.

  5. The interhemispheric and F region dynamo currents revisited with the Swarm constellation

    DEFF Research Database (Denmark)

    Luehr, Hermann; Kervalishvili, Guram; Michaelis, Ingo

    2015-01-01

    Based on magnetic field data sampled by the Swarm satellite constellation it is possible for the first time to determine uniquely F region currents at low latitudes. Initial results are presented from the first 200days of formation flight (17 April to 5 November 2014). Detailed results have been...

  6. Seasonal snow accumulation in the mid-latitude forested catchment

    Czech Academy of Sciences Publication Activity Database

    Šípek, Václav; Tesař, Miroslav

    2014-01-01

    Roč. 69, č. 11 (2014), s. 1562-1569 ISSN 0006-3088 R&D Projects: GA TA ČR TA02021451 Institutional support: RVO:67985874 Keywords : snow depth * snow water equivalent * forested catchment Subject RIV: DA - Hydrology ; Limnology Impact factor: 0.827, year: 2014

  7. Energetics of lower tropospheric planetary waves over mid latitudes ...

    Indian Academy of Sciences (India)

    Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, Pune 411 008, India. ∗ e-mail: ... port by wave 0 over southern equatorial belt dur- ing March leads to a ..... 2005a Contrasting features of wave number one during northern ...

  8. Photographic and photometric observations of mid-latitude red arcs

    International Nuclear Information System (INIS)

    Alekseev, V.N.; Ievenko, I.B.; Oshchepkov, S.M.; Ignat'ev, V.M.; Zhondorov, V.A.

    1989-01-01

    Stable auroral red arcs (SAR-arcs) were observed in Majmaga (Φ S ∼56.5deg) at the Yakutsk meridian in November-December, 1987 and February, 1988. The SAR-arcs were observed to the equator of diffuse glow, located at lower latitudes with respect to discrete auroral forms, obviously, in the external plasmospheric projection area. It is noted that they appear both in disturbed periods and in those with medium magnetic activity (K p =3). The SAR-arc height is ∼450km

  9. Particulate emissions from a mid-latitude prescribed chaparral fire

    Science.gov (United States)

    Cofer, Wesley R., III; Levine, Joel S.; Sebacher, Daniel I.; Winstead, Edward L.; Riggin, Philip J.; Brass, James A.; Ambrosia, Vincent G.

    1988-01-01

    Particulate emission from a 400-acre prescribed chaparral fire in the San Dimas Experimental Forest was investigated by collecting smoke aerosol on Teflon and glass-fiber filters from a helicopter, and using SEM and EDAX to study the features of the particles. Aerosol particles ranged in size from about 0.1 to 100 microns, with carbon, oxygen, magnesium, aluminum, silicon, calcium, and iron as the primary elements. The results of ion chromatographic analysis of aerosol-particle extracts (in water-methanol) revealed the presence of significant levels of NO2(-), NO3(-), SO4(2-), Cl(-), PO4(3-), C2O4(2-), Na(+), NH4(+), and K(+). The soluble ionic portion of the aerosol was estimated to be about 2 percent by weight.

  10. Northern and Mid-Latitude Soil Database, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: The U.S. Department of Agriculture, Agriculture and Agri-Food Canada, the Russian Academy of Agricultural Sciences, the University of Copenhagen Institute...

  11. Magnetic storm effects on the mid-latitude plasmasphere

    International Nuclear Information System (INIS)

    Smith, A.J.; Clilverd, M.A.

    1991-01-01

    Whistler mode group delays observed at Faraday, Antarctica (65 o S,64 0 W) decrease after the onset of magnetic storms, and slowly recover to normal levels in 1 or 2 days. This is interpreted as a decrease (typically of ∼50%) and recovery of the plasmaspheric electron density at L = 2.5. Within 1 day of the main phase of storms with K p (max) between 6 and 8, the number of observed whistler ducts increases by a factor of 2 or 3, recovering in a few days. During the most intense storms (K p > 8) the duct number decreases. The frequency of occurrence of observed whistler mode signals increases during storms, due probably to enhanced ionospheric propagation of the signals; the storm time dependence implies that there is no link with the apparent increase in duct numbers. The amplitudes of received whistler mode signals are increased by up to a factor of 10 during storms: this is interpreted in terms of magnetospheric amplification through wave-particle interactions, though the evidence suggests that amplification is not necessarily the mechanism by which increased duct numbers are observed. There appears to be a real increase in the duct formation rate, consistent with Walker's (1978) theory in which ring current penetration of the plasmasphere creates a preferential region for duct formation 1.5 R E inside the plasmapause. (author)

  12. Drift Degradation Analysis

    International Nuclear Information System (INIS)

    D. Kicker

    2004-01-01

    Degradation of underground openings as a function of time is a natural and expected occurrence for any subsurface excavation. Over time, changes occur to both the stress condition and the strength of the rock mass due to several interacting factors. Once the factors contributing to degradation are characterized, the effects of drift degradation can typically be mitigated through appropriate design and maintenance of the ground support system. However, for the emplacement drifts of the geologic repository at Yucca Mountain, it is necessary to characterize drift degradation over a 10,000-year period, which is well beyond the functional period of the ground support system. This document provides an analysis of the amount of drift degradation anticipated in repository emplacement drifts for discrete events and time increments extending throughout the 10,000-year regulatory period for postclosure performance. This revision of the drift degradation analysis was developed to support the license application and fulfill specific agreement items between the U.S. Nuclear Regulatory Commission (NRC) and the U.S. Department of Energy (DOE). The earlier versions of ''Drift Degradation Analysis'' (BSC 2001 [DIRS 156304]) relied primarily on the DRKBA numerical code, which provides for a probabilistic key-block assessment based on realistic fracture patterns determined from field mapping in the Exploratory Studies Facility (ESF) at Yucca Mountain. A key block is defined as a critical block in the surrounding rock mass of an excavation, which is removable and oriented in an unsafe manner such that it is likely to move into an opening unless support is provided. However, the use of the DRKBA code to determine potential rockfall data at the repository horizon during the postclosure period has several limitations: (1) The DRKBA code cannot explicitly apply dynamic loads due to seismic ground motion. (2) The DRKBA code cannot explicitly apply loads due to thermal stress. (3) The DRKBA

  13. Drift Degradation Analysis

    Energy Technology Data Exchange (ETDEWEB)

    D. Kicker

    2004-09-16

    Degradation of underground openings as a function of time is a natural and expected occurrence for any subsurface excavation. Over time, changes occur to both the stress condition and the strength of the rock mass due to several interacting factors. Once the factors contributing to degradation are characterized, the effects of drift degradation can typically be mitigated through appropriate design and maintenance of the ground support system. However, for the emplacement drifts of the geologic repository at Yucca Mountain, it is necessary to characterize drift degradation over a 10,000-year period, which is well beyond the functional period of the ground support system. This document provides an analysis of the amount of drift degradation anticipated in repository emplacement drifts for discrete events and time increments extending throughout the 10,000-year regulatory period for postclosure performance. This revision of the drift degradation analysis was developed to support the license application and fulfill specific agreement items between the U.S. Nuclear Regulatory Commission (NRC) and the U.S. Department of Energy (DOE). The earlier versions of ''Drift Degradation Analysis'' (BSC 2001 [DIRS 156304]) relied primarily on the DRKBA numerical code, which provides for a probabilistic key-block assessment based on realistic fracture patterns determined from field mapping in the Exploratory Studies Facility (ESF) at Yucca Mountain. A key block is defined as a critical block in the surrounding rock mass of an excavation, which is removable and oriented in an unsafe manner such that it is likely to move into an opening unless support is provided. However, the use of the DRKBA code to determine potential rockfall data at the repository horizon during the postclosure period has several limitations: (1) The DRKBA code cannot explicitly apply dynamic loads due to seismic ground motion. (2) The DRKBA code cannot explicitly apply loads due to thermal

  14. Spiral silicon drift detectors

    International Nuclear Information System (INIS)

    Rehak, P.; Gatti, E.; Longoni, A.; Sampietro, M.; Holl, P.; Lutz, G.; Kemmer, J.; Prechtel, U.; Ziemann, T.

    1988-01-01

    An advanced large area silicon photodiode (and x-ray detector), called Spiral Drift Detector, was designed, produced and tested. The Spiral Detector belongs to the family of silicon drift detectors and is an improvement of the well known Cylindrical Drift Detector. In both detectors, signal electrons created in silicon by fast charged particles or photons are drifting toward a practically point-like collection anode. The capacitance of the anode is therefore kept at the minimum (0.1pF). The concentric rings of the cylindrical detector are replaced by a continuous spiral in the new detector. The spiral geometry detector design leads to a decrease of the detector leakage current. In the spiral detector all electrons generated at the silicon-silicon oxide interface are collected on a guard sink rather than contributing to the detector leakage current. The decrease of the leakage current reduces the parallel noise of the detector. This decrease of the leakage current and the very small capacities of the detector anode with a capacitively matched preamplifier may improve the energy resolution of Spiral Drift Detectors operating at room temperature down to about 50 electrons rms. This resolution is in the range attainable at present only by cooled semiconductor detectors. 5 refs., 10 figs

  15. An experimental study of the ion chemistry and thermal balance in the E- and F-regions above Wallops Island

    Science.gov (United States)

    Brace, L. H.; Mayr, H. G.; Pharo, M. W., III; Scott, L. R.; Taylor, H. A., Jr.

    1971-01-01

    E and F region positive ion composition, electron concentration and thermal balance vertical profile, discussing ionizing radiation spectrum, plasma cooling, primary chemical reaction rates and ionospheric formation

  16. Radial semiconductor drift chambers

    International Nuclear Information System (INIS)

    Rawlings, K.J.

    1987-01-01

    The conditions under which the energy resolution of a radial semiconductor drift chamber based detector system becomes dominated by the step noise from the detector dark current have been investigated. To minimise the drift chamber dark current attention should be paid to carrier generation at Si/SiO 2 interfaces. This consideration conflicts with the desire to reduce the signal risetime: a higher drift field for shorter signal pulses requires a larger area of SiO 2 . Calculations for the single shaping and pseudo Gaussian passive filters indicate that for the same degree of signal risetime sensitivity in a system dominated by the step noise from the detector dark current, the pseudo Gaussian filter gives only a 3% improvement in signal/noise and 12% improvement in rate capability compared with the single shaper performance. (orig.)

  17. Nonlinear drift tearing mode

    International Nuclear Information System (INIS)

    Zelenyj, L.M.; Kuznetsova, M.M.

    1989-01-01

    Nonlinear study of magnetic perturbation development under single-mode conditions in collision-free plasma in configurations with the magnetic field shear is investigated. Results are obtained with regard of transverse component of electrical field and its effect on ion dynamics within wide range of ion Larmor radius value and values of magnetic field shear. Increments of nonlinear drift tearing mode are obtained and it is shown that excitation drastic conditions of even linearly stable modes are possible. Mechanism of instability nonlinear stabilization is considered and the value of magnetic island at the saturation threshold is estimeted. Energy of nonlinear drift tearing mode is discussed

  18. The Drift Burst Hypothesis

    DEFF Research Database (Denmark)

    Christensen, Kim; Oomen, Roel; Renò, Roberto

    are an expected and regular occurrence in financial markets that can arise through established mechanisms such as feedback trading. At a theoretical level, we show how to build drift bursts into the continuous-time Itô semi-martingale model in such a way that the fundamental arbitrage-free property is preserved......, currencies and commodities. We find that the majority of identified drift bursts are accompanied by strong price reversals and these can therefore be regarded as “flash crashes” that span brief periods of severe market disruption without any material longer term price impacts....

  19. Spectral classification of medium-scale high-latitude F region plasma density irregularities

    International Nuclear Information System (INIS)

    Singh, M.; Rodriguez, P.; Szuszczewicz, E.P.; Sachs Freeman Associates, Bowie, MD)

    1985-01-01

    The high-latitude ionosphere represents a highly structured plasma. Rodriguez and Szuszczewicz (1984) reported a wide range of plasma density irregularities (150 km to 75 m) at high latitudes near 200 km. They have shown that the small-scale irregularities (7.5 km to 75 m) populated the dayside oval more often than the other phenomenological regions. It was suggested that in the lower F region the chemical recombination is fast enough to remove small-scale irregularities before convection can transport them large distances, leaving structured particle precipitation as the dominant source term for irregularities. The present paper provides the results of spectral analyses of pulsed plasma probe data collected in situ aboard the STP/S3-4 satellite during the period March-September 1978. A quantitative description of irregularity spectra in the high-latitude lower F region plasma density is given. 22 references

  20. Tapping with intentional drift

    NARCIS (Netherlands)

    Vardy, A.N.; Daffertshofer, A.; Beek, P.J.

    2009-01-01

    When tapping a desired frequency, subjects tend to drift away from this target frequency. This compromises the estimate of the correlation between inter-tap intervals (ITIs) as predicted by the two-level model of Wing and Kristofferson which consists of an internal timer ('clock') and motor delays.

  1. The KLOE drift chamber

    International Nuclear Information System (INIS)

    Ferrari, A.

    2002-01-01

    The design and construction of the large drift chamber of the KLOE experiment is presented. The track reconstruction is described, together with the calibration method and the monitoring systems. The stability of operation and the performance are studied with samples of e + e - , K S K L and K + K - events

  2. High resolution drift chambers

    International Nuclear Information System (INIS)

    Va'vra, J.

    1985-07-01

    High precision drift chambers capable of achieving less than or equal to 50 μm resolutions are discussed. In particular, we compare so called cool and hot gases, various charge collection geometries, several timing techniques and we also discuss some systematic problems. We also present what we would consider an ''ultimate'' design of the vertex chamber. 50 refs., 36 figs., 6 tabs

  3. Argus drift chamber

    Energy Technology Data Exchange (ETDEWEB)

    Danilov, M; Nagovizin, V; Hasemann, H; Michel, E; Schmidt-Parzefall, W; Wurth, R; Kim, P

    1983-11-15

    The ARGUS detector came into operation at the DORIS-II e/sup +/s/sup -/ storage ring at the end of 1982. Its two meter long drift chamber contains 5940 sense and 24588 field wires organized in uniform 18x18.8 mm/sup 2/ drift cells filling the whole volume. These cells form 36 layers, 18 of which provide stereo views. Each sense wire is equipped with a single hit TDC and ADC for coordinate and dE/dx measurements. The chamber is operated with propane to improve momentum and dE/dx resolution. The drift chamber design and initial performance are presented. With a very crude space-time relation approximation and without all the necessary corrections applied a spatial resolution of about 200 ..mu..m was obtained for half of the drift cell volume. Further corrections should improve this result. An intrinsic dE/dx resolution of 4.2% and an actual resolution of 5% were obtained for cosmic muons and also for Bhabha scattered electrons. An actual dE/dx resolution of 5.6% was obtained for pions from e/sup +/e/sup -/ annihilation data with almost no track selection. A relativistic rise of 30% was observed in good agreement with theory. The long-term stability is still to be investigated.

  4. Inland drift sand landscapes

    NARCIS (Netherlands)

    Fanta, J.; Siepel, H.

    2010-01-01

    Man has had a complex relationship with inland drift sands through the ages. For some centuries these landscapes were seen as a threat to society, especially agriculture and housing. At present we conserve these landscapes as important Natura 2000 priority habitats. In this book you may find these

  5. Guiding center drift equations

    International Nuclear Information System (INIS)

    Boozer, A.H.

    1979-03-01

    The quations for particle guiding center drift orbits are given in a new magnetic coordinate system. This form of the equations not only separates the fast motion along the lines from the slow motion across, but also requires less information about the magnetic field than many other formulations of the problem

  6. IN DRIFT CORROSION PRODUCTS

    Energy Technology Data Exchange (ETDEWEB)

    D.M. Jolley

    1999-12-02

    As directed by a written development plan (CRWMS M&O 1999a), a conceptual model for steel and corrosion products in the engineered barrier system (EBS) is to be developed. The purpose of this conceptual model is to assist Performance Assessment Operations (PAO) and its Engineered Barrier Performance Department in modeling the geochemical environment within a repository drift, thus allowing PAO to provide a more detailed and complete in-drift geochemical model abstraction and to answer the key technical issues (KTI) raised in the NRC Issue Resolution Status Report (IRSR) for the Evolution of the Near-Field Environment (NFE) Revision 2 (NRC 1999). This document provides the conceptual framework for the in-drift corrosion products sub-model to be used in subsequent PAO analyses including the EBS physical and chemical model abstraction effort. This model has been developed to serve as a basis for the in-drift geochemical analyses performed by PAO. However, the concepts discussed within this report may also apply to some near and far-field geochemical processes and may have conceptual application within the unsaturated zone (UZ) and saturated zone (SZ) transport modeling efforts.

  7. Analytical approach to the investigation of Rayleigh-Taylor structures of the equatorial F region

    International Nuclear Information System (INIS)

    Komarov, V.N.; Sazonov, S.V.

    1991-01-01

    On the basis of approximation of a strong vertical extension the nonlinear dynamics of Rayleigh-Taylor structures in the equatorial F region is analytically studied. The successive approximation method, proposed herein, is true for structures having longitudinal symmetry. Using this method it is managed to describe the mushroom-shaped bubble with a shock wave profile in its head part. The nonlinearity leads to bubble formation under conditions with aggravation, limiting the growth of positive disturbances at the same time

  8. Geomagnetic control of mesospheric nitric oxide concentration from simultaneous D and F region ionization measurements

    International Nuclear Information System (INIS)

    Pradhan, S.N.; Shirke, J.S.

    1978-01-01

    Investigations are made of D-region electron density profiles derived from 'partial reflection' measurements over a low latitude station (Ahmedabad) during a year of low solar activity. The index relating the electron density with the solar zenith angle is found to increase towards lower zenith angles suggesting both diurnal and seasonal variations in the Nitric oxide concentration. A close correlation is also found between the electron density at 80 km and the maximum ionization density in the F region above. This is interpreted as due to concomitant variation of a sizeable fraction of the Nitric oxide concentration in the mesosphere and lower thermosphere with the overhead F region ionization. A simplified global model is presented for the mesospheric Nitric oxide concentration based on the morphological features of F region and the relationship existing between the ionization levels in F and D regions. Many observed features of the D region ionization including the solar zenith angle dependence, latitudinal and geomagnetic anomaly and long term variability are explained on the basis of this model

  9. Dike Propagation Near Drifts

    International Nuclear Information System (INIS)

    2002-01-01

    The purpose of this Analysis and Model Report (AMR) supporting the Site Recommendation/License Application (SR/LA) for the Yucca Mountain Project is the development of elementary analyses of the interactions of a hypothetical dike with a repository drift (i.e., tunnel) and with the drift contents at the potential Yucca Mountain repository. This effort is intended to support the analysis of disruptive events for Total System Performance Assessment (TSPA). This AMR supports the Process Model Report (PMR) on disruptive events (CRWMS M and O 2000a). This purpose is documented in the development plan (DP) ''Coordinate Modeling of Dike Propagation Near Drifts Consequences for TSPA-SR/LA'' (CRWMS M and O 2000b). Evaluation of that Development Plan and the work to be conducted to prepare Interim Change Notice (ICN) 1 of this report, which now includes the design option of ''Open'' drifts, indicated that no revision to that DP was needed. These analyses are intended to provide reasonable bounds for a number of expected effects: (1) Temperature changes to the waste package from exposure to magma; (2) The gas flow available to degrade waste containers during the intrusion; (3) Movement of the waste package as it is displaced by the gas, pyroclasts and magma from the intruding dike (the number of packages damaged); (4) Movement of the backfill (Backfill is treated here as a design option); (5) The nature of the mechanics of the dike/drift interaction. These analyses serve two objectives: to provide preliminary analyses needed to support evaluation of the consequences of an intrusive event and to provide a basis for addressing some of the concerns of the Nuclear Regulatory Commission (NRC) expressed in the Igneous Activity Issue Resolution Status Report

  10. Style drift in private equity

    NARCIS (Netherlands)

    Cumming, D.; Fleming, G.; Schwienbacher, A.

    2009-01-01

    We introduce the concept of style drift to private equity investment. We present theory and evidence pertaining to style drifts in terms of a fund manager's stated focus on particular stages of entrepreneurial development. We develop a model that derives conditions under which style drifts are less

  11. Diogene pictorial drift chamber

    International Nuclear Information System (INIS)

    Gosset, J.

    1984-01-01

    A pictorial drift chamber, called DIOGENE, has been installed at Saturne in order to study central collisions of high energy heavy ions. It has been adapted from the JADE internal detector, with two major differences to be taken into account. First, the center-of-mass of these collisions is not identical to the laboratory reference frame. Second, the energy loss and the momentum ranges of the particles to be detected are different from the ones in JADE. It was also tried to keep the cost as small as possible, hence the choice of minimum size and minimum number of sensitive wires. Moreover the wire planes are shifted from the beam axis: this trick helps very much to quickly reject the bad tracks caused by the ambiguity of measuring drift distances (positive or negative) through times (always positive)

  12. Drift-Diffusion Equation

    Directory of Open Access Journals (Sweden)

    K. Banoo

    1998-01-01

    equation in the discrete momentum space. This is shown to be similar to the conventional drift-diffusion equation except that it is a more rigorous solution to the Boltzmann equation because the current and carrier densities are resolved into M×1 vectors, where M is the number of modes in the discrete momentum space. The mobility and diffusion coefficient become M×M matrices which connect the M momentum space modes. This approach is demonstrated by simulating electron transport in bulk silicon.

  13. Negative Drift in Populations

    DEFF Research Database (Denmark)

    Lehre, Per Kristian

    2011-01-01

    An important step in gaining a better understanding of the stochastic dynamics of evolving populations, is the development of appropriate analytical tools. We present a new drift theorem for populations that allows properties of their long-term behaviour, e.g. the runtime of evolutionary algorithms......, to be derived from simple conditions on the one-step behaviour of their variation operators and selection mechanisms....

  14. Consistent guiding center drift theories

    International Nuclear Information System (INIS)

    Wimmel, H.K.

    1982-04-01

    Various guiding-center drift theories are presented that are optimized in respect of consistency. They satisfy exact energy conservation theorems (in time-independent fields), Liouville's theorems, and appropriate power balance equations. A theoretical framework is given that allows direct and exact derivation of associated drift-kinetic equations from the respective guiding-center drift-orbit theories. These drift-kinetic equations are listed. Northrop's non-optimized theory is discussed for reference, and internal consistency relations of G.C. drift theories are presented. (orig.)

  15. Laboratory Course on Drift Chambers

    International Nuclear Information System (INIS)

    Garcia-Ferreira, Ix-B.; Garcia-Herrera, J.; Villasenor, L.

    2006-01-01

    Drift chambers play an important role in particle physics experiments as tracking detectors. We started this laboratory course with a brief review of the theoretical background and then moved on to the the experimental setup which consisted of a single-sided, single-cell drift chamber. We also used a plastic scintillator paddle, standard P-10 gas mixture (90% Ar, 10% CH4) and a collimated 90Sr source. During the laboratory session the students performend measurements of the following quantities: a) drift velocities and their variations as function of the drift field; b) gas gains and c) diffusion of electrons as they drifted in the gas

  16. Modeling polar cap F-region patches using time varying convection

    International Nuclear Information System (INIS)

    Sojka, J.J.; Bowline, M.D.; Schunk, R.W.; Decker, D.T.; Valladares, C.E.; Sheehan, R.; Anderson, D.N.; Heelis, R.A.

    1993-01-01

    Here the authors present the results of computerized simulations of the polar cap regions which were able to model the formation of polar cap patches. They used the Utah State University Time-Dependent Ionospheric Model (TDIM) and the Phillips Laboratory (PL) F-region models in this work. By allowing a time varying magnetospheric electric field in the models, they were able to generate the patches. This time varying field generates a convection in the ionosphere. This convection is similar to convective changes observed in the ionosphere at times of southward pointing interplanetary magnetic field, due to changes in the B y component of the IMF

  17. Studies of ionospheric F-region response in the Latin American sector during the geomagnetic storm of 21–22 January 2005

    Directory of Open Access Journals (Sweden)

    Y. Sahai

    2011-05-01

    American sector during the post-sunset pre-reversal time in the geomagnetic disturbance (21 January. The disturbance dynamo electric field possibly resulted in downward drift of the F-region plasma and inhibited the formation of spread-F.

  18. Studies of ionospheric F-region response in the Latin American sector during the geomagnetic storm of 21-22 January 2005

    Science.gov (United States)

    Sahai, Y.; Fagundes, P. R.; de Jesus, R.; de Abreu, A. J.; Crowley, G.; Kikuchi, T.; Huang, C.-S.; Pillat, V. G.; Guarnieri, F. L.; Abalde, J. R.; Bittencourt, J. A.

    2011-05-01

    sector during the post-sunset pre-reversal time in the geomagnetic disturbance (21 January). The disturbance dynamo electric field possibly resulted in downward drift of the F-region plasma and inhibited the formation of spread-F.

  19. ARCAD3-SAFARI coordinated study of auroral and polar F-region ionospheric irregularities

    International Nuclear Information System (INIS)

    Villain, J.P.; Hanuise, C.

    1986-01-01

    Simultaneous observations of F-region ionospheric irregularities have been performed with the SAFARI ground-based HF radars and the ISOPROBE experiment on board the AUREOL-3 satellite. Among seven orbits during which the satellite trajectory was directly in the radar beam or in the vicinity, four of them have been analyzed in detail. The spectral power of the electron density variations ΔNsub(e)/Nsub(e) has been calculated for wavelengths between 20 m and 1 km from the isoprobe high time resolution thermal plasma measurements. One spectrum is obtained every 1.2 s, a time which corresponds to about 10 km along the satellite trajectory. The presence of echoes observed in the F-region with the SAFARI radars is compared with the spectral power of the electron density variations deduced from the ISOPROBE ''in situ'' measurements. A good agreement is found between the two sets of observations and a numerical value of the spectral power corresponding to detection of echoes by the radar is given. A synoptical view of the event is given and interpreted according to the existing theories of plasma irregularities

  20. Global view of F-region electron density and temperature at solar maximum

    International Nuclear Information System (INIS)

    Brace, L.H.; Theis, R.F.; Hoegy, W.R.

    1982-01-01

    Dynamics Explorer-2 is permitting the first measurements of the global structure of the F-regions at very high levels of solar activity (S>200). Selected full orbits of Langmuir probe measurements of electron temperature, T/sub e/, and density, N/sub e/, are shown to illustrate this global structure and some of the ionospheric features that are the topic of other papers in this issue. The ionospheric thermal structure is of particular interest because T/sub e/ is a sensitive indicator of the coupling of magnetospheric energy into the upper atmosphere. A comparison of these heating effects with those observed at solar minimum shows that the magnetospheric sources are more important at solar maximum, as might have been expected. Heating at the cusp, the auroral oval and the plasma-pause is generally both greater and more variable. Electron cooling rate calculations employing low latitude measurements indicate that solar extreme ultraviolet heating of the F region at solar maximum is enhanced by a factor that is greater than the increase in solar flux. Some of this enhanced electron heating arises from the increase in electron heating efficiency at the higher N/sub e/ of solar maximum, but this appears insufficient to completely resolve the discrepancy

  1. Drifting black aurorae?

    International Nuclear Information System (INIS)

    Schoute-Vanneck, H.; Scourfield, M.W.J.; Nielsen, E.

    1990-01-01

    Characteristics of eastward drifting forms, previously described in the literature as black aurorae, have been identified in low-light level TV camera data. The TV field of view was within the field of view of STARE and that of an all-sky camera. On the basis of these observations the authors propose that these auroral forms are a manifestation of folds or waves on the borders of auroral bands propagating along the dark regions between neighboring auroral bands. Conditions under which the folds or waves occur are compatible with their formation by the Kelvin-Helmholtz electrostatic instability

  2. ABSTRACTION OF DRIFT SEEPAGE

    International Nuclear Information System (INIS)

    Wilson, Michael L.

    2001-01-01

    Drift seepage refers to flow of liquid water into repository emplacement drifts, where it can potentially contribute to degradation of the engineered systems and release and transport of radionuclides within the drifts. Because of these important effects, seepage into emplacement drifts is listed as a ''principal factor for the postclosure safety case'' in the screening criteria for grading of data in Attachment 1 of AP-3.15Q, Rev. 2, ''Managing Technical Product Inputs''. Abstraction refers to distillation of the essential components of a process model into a form suitable for use in total-system performance assessment (TSPA). Thus, the purpose of this analysis/model is to put the information generated by the seepage process modeling in a form appropriate for use in the TSPA for the Site Recommendation. This report also supports the Unsaturated-Zone Flow and Transport Process Model Report. The scope of the work is discussed below. This analysis/model is governed by the ''Technical Work Plan for Unsaturated Zone Flow and Transport Process Model Report'' (CRWMS MandO 2000a). Details of this activity are in Addendum A of the technical work plan. The original Work Direction and Planning Document is included as Attachment 7 of Addendum A. Note that the Work Direction and Planning Document contains tasks identified for both Performance Assessment Operations (PAO) and Natural Environment Program Operations (NEPO). Only the PAO tasks are documented here. The planning for the NEPO activities is now in Addendum D of the same technical work plan and the work is documented in a separate report (CRWMS MandO 2000b). The Project has been reorganized since the document was written. The responsible organizations in the new structure are the Performance Assessment Department and the Unsaturated Zone Department, respectively. The work plan for the seepage abstraction calls for determining an appropriate abstraction methodology, determining uncertainties in seepage, and providing

  3. Drift velocity monitoring of the CMS muon drift chambers

    CERN Document Server

    Sonnenschein, Lars

    2010-01-01

    The drift velocity in drift tubes of the CMS muon chambers is a key parameter for the muon track reconstruction and trigger. It needs to be monitored precisely in order to detect any deviation from its nominal value. A change in absolute pressure, a variation of the gas admixture or a contamination of the chamber gas by air affect the drift velocity. Furthermore the temperature and magnetic field influence its value. First data, taken with a dedicated Velocity Drift Chamber (VDC) built by RWTH Aachen IIIA are presented.

  4. The CLEO III drift chamber

    CERN Document Server

    Peterson, D; Briere, R A; Chen, G; Cronin-Hennessy, D; Csorna, S; Dickson, M; Dombrowski, S V; Ecklund, K M; Lyon, A; Marka, S; Meyer, T O; Patterson, J R; Sadoff, A; Thies, P; Thorndike, E H; Urner, D

    2002-01-01

    The CLEO group at the Cornell Electron Storage Ring has constructed and commissioned a new central drift chamber. With 9796 cells arranged in 47 layers ranging in radius from 13.2 to 79 cm, the new drift chamber has a smaller outer radius and fewer wires than the drift chamber it replaces, but allows the CLEO tracking system to have improved momentum resolution. Reduced scattering material in the chamber gas and in the inner skin separating the drift chamber from the silicon vertex detector provides a reduction of the multiple scattering component of the momentum resolution and an extension of the usable measurement length into the silicon. Momentum resolution is further improved through quality control in wire positioning and symmetry of the electric fields in the drift cells which have provided a reduction in the spatial resolution to 88 mu m (averaged over the full drift range).

  5. Electronics for proportional drift tubes

    International Nuclear Information System (INIS)

    Fremont, G.; Friend, B.; Mess, K.H.; Schmidt-Parzefall, W.; Tarle, J.C.; Verweij, H.; CERN-Hamburg-Amsterdam-Rome-Moscow Collaboration); Geske, K.; Riege, H.; Schuett, J.; CERN-Hamburg-Amsterdam-Rome-Moscow Collaboration); Semenov, Y.; CERN-Hamburg-Amsterdam-Rome-Moscow Collaboration)

    1980-01-01

    An electronic system for the read-out of a large number of proportional drift tubes (16,000) has been designed. This system measures deposited charge and drift-time of the charge of a particle traversing a proportional drift tube. A second event can be accepted during the read-out of the system. Up to 40 typical events can be collected and buffered before a data transfer to a computer is necessary. (orig.)

  6. Drift-Scale Radionuclide Transport

    International Nuclear Information System (INIS)

    Houseworth, J.

    2004-01-01

    The purpose of this model report is to document the drift scale radionuclide transport model, taking into account the effects of emplacement drifts on flow and transport in the vicinity of the drift, which are not captured in the mountain-scale unsaturated zone (UZ) flow and transport models ''UZ Flow Models and Submodels'' (BSC 2004 [DIRS 169861]), ''Radionuclide Transport Models Under Ambient Conditions'' (BSC 2004 [DIRS 164500]), and ''Particle Tracking Model and Abstraction of Transport Process'' (BSC 2004 [DIRS 170041]). The drift scale radionuclide transport model is intended to be used as an alternative model for comparison with the engineered barrier system (EBS) radionuclide transport model ''EBS Radionuclide Transport Abstraction'' (BSC 2004 [DIRS 169868]). For that purpose, two alternative models have been developed for drift-scale radionuclide transport. One of the alternative models is a dual continuum flow and transport model called the drift shadow model. The effects of variations in the flow field and fracture-matrix interaction in the vicinity of a waste emplacement drift are investigated through sensitivity studies using the drift shadow model (Houseworth et al. 2003 [DIRS 164394]). In this model, the flow is significantly perturbed (reduced) beneath the waste emplacement drifts. However, comparisons of transport in this perturbed flow field with transport in an unperturbed flow field show similar results if the transport is initiated in the rock matrix. This has led to a second alternative model, called the fracture-matrix partitioning model, that focuses on the partitioning of radionuclide transport between the fractures and matrix upon exiting the waste emplacement drift. The fracture-matrix partitioning model computes the partitioning, between fractures and matrix, of diffusive radionuclide transport from the invert (for drifts without seepage) into the rock water. The invert is the structure constructed in a drift to provide the floor of the

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

    Directory of Open Access Journals (Sweden)

    E. Blanc

    1998-06-01

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

  8. Coherent backscatter radar imaging in Brazil: large-scale waves in the bottomside F-region at the onset of equatorial spread F

    Directory of Open Access Journals (Sweden)

    F. S. Rodrigues

    2008-10-01

    Full Text Available The 30 MHz coherent backscatter radar located at the equatorial observatory in São Luís, Brazil (2.59° S, 44.21° W, −2.35° dip lat has been upgraded to perform coherent backscatter radar imaging. The wide field-of-view of this radar makes it well suited for radar imaging studies of ionospheric irregularities. Radar imaging observations were made in support to the spread F Experiment (SpreadFEx campaign. This paper describes the system and imaging technique and presents results from a bottom-type layer that preceded fully-developed radar plumes on 25 October 2005. The radar imaging technique was able to resolve decakilometric structures within the bottom-type layer. These structures indicate the presence of large-scale waves (~35 km in the bottomside F-region with phases that are alternately stable and unstable to wind-driven gradient drift instabilities. The observations suggest that these waves can also cause the initial perturbation necessary to initiate the Generalized Rayleigh-Taylor instability leading to spread F. The electrodynamic conditions and the scale length of the bottom-type layer structures suggest that the waves were generated by the collisional shear instability. These results indicate that monitoring bottom-type layers may provide helpful diagnostics for spread F forecasting.

  9. A Statistical study of the Doppler spectral width of high-latitude ionospheric F-region echoes recorded with SuperDARN coherent HF radars

    Directory of Open Access Journals (Sweden)

    J.-P. Villain

    2002-11-01

    Full Text Available The HF radars of the Super Dual Auroral Radar Network (SuperDARN provide measurements of the E × B drift of ionospheric plasma over extended regions of the high-latitude ionosphere. We have conducted a statistical study of the associated Doppler spectral width of ionospheric F-region echoes. The study has been conducted with all available radars from the Northern Hemisphere for 2 specific periods of time. Period 1 corresponds to the winter months of 1994, while period 2 covers October 1996 to March 1997. The distributions of data points and average spectral width are presented as a function of Magnetic Latitude and Magnetic Local Time. The databases are very consistent and exhibit the same features. The most stringent features are: a region of very high spectral width, collocated with the ionospheric LLBL/cusp/mantle region; an oval shaped region of high spectral width, whose equator-ward boundary matches the poleward limit of the Holzworth and Meng auroral oval. A simulation has been conducted to evaluate the geometrical and instrumental effects on the spectral width. It shows that these effects cannot account for the observed spectral features. It is then concluded that these specific spectral width characteristics are the signature of ionospheric/magnetospheric coupling phenomena.Key words. Ionosphere (auroral ionosphere; ionosphere-magnetosphere interactions; ionospheric irregularities

  10. A Statistical study of the Doppler spectral width of high-latitude ionospheric F-region echoes recorded with SuperDARN coherent HF radars

    Directory of Open Access Journals (Sweden)

    J.-P. Villain

    Full Text Available The HF radars of the Super Dual Auroral Radar Network (SuperDARN provide measurements of the E × B drift of ionospheric plasma over extended regions of the high-latitude ionosphere. We have conducted a statistical study of the associated Doppler spectral width of ionospheric F-region echoes. The study has been conducted with all available radars from the Northern Hemisphere for 2 specific periods of time. Period 1 corresponds to the winter months of 1994, while period 2 covers October 1996 to March 1997. The distributions of data points and average spectral width are presented as a function of Magnetic Latitude and Magnetic Local Time. The databases are very consistent and exhibit the same features. The most stringent features are: a region of very high spectral width, collocated with the ionospheric LLBL/cusp/mantle region; an oval shaped region of high spectral width, whose equator-ward boundary matches the poleward limit of the Holzworth and Meng auroral oval. A simulation has been conducted to evaluate the geometrical and instrumental effects on the spectral width. It shows that these effects cannot account for the observed spectral features. It is then concluded that these specific spectral width characteristics are the signature of ionospheric/magnetospheric coupling phenomena.

    Key words. Ionosphere (auroral ionosphere; ionosphere-magnetosphere interactions; ionospheric irregularities

  11. Progress in semiconductor drift detectors

    International Nuclear Information System (INIS)

    Rehak, P.; Walton, J.; Gatti, E.

    1985-01-01

    Progress in testing semiconductor drift detectors is reported. Generally better position and energy resolutions were obtained than resolutions published previously. The improvement is mostly due to new electronics better matched to different detectors. It is shown that semiconductor drift detectors are becoming versatile and reliable detectors for position and energy measurements

  12. CTF Void Drift Validation Study

    Energy Technology Data Exchange (ETDEWEB)

    Salko, Robert K. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Gosdin, Chris [Pennsylvania State Univ., University Park, PA (United States); Avramova, Maria N. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Gergar, Marcus [Pennsylvania State Univ., University Park, PA (United States)

    2015-10-26

    This milestone report is a summary of work performed in support of expansion of the validation and verification (V&V) matrix for the thermal-hydraulic subchannel code, CTF. The focus of this study is on validating the void drift modeling capabilities of CTF and verifying the supporting models that impact the void drift phenomenon. CTF uses a simple turbulent-diffusion approximation to model lateral cross-flow due to turbulent mixing and void drift. The void drift component of the model is based on the Lahey and Moody model. The models are a function of two-phase mass, momentum, and energy distribution in the system; therefore, it is necessary to correctly model the ow distribution in rod bundle geometry as a first step to correctly calculating the void distribution due to void drift.

  13. Drifting oscillations in axion monodromy

    Energy Technology Data Exchange (ETDEWEB)

    Flauger, Raphael [Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); McAllister, Liam [Department of Physics, Cornell University, Ithaca, NY 14853 (United States); Silverstein, Eva [Stanford Institute for Theoretical Physics, Stanford University, Stanford, CA 94305 (United States); Westphal, Alexander, E-mail: flauger@physics.ucsd.edu, E-mail: mcallister@cornell.edu, E-mail: evas@stanford.edu, E-mail: alexander.westphal@desy.de [Theory Group, Deutsches Elektronen-Synchrotron DESY, D-22603 Hamburg (Germany)

    2017-10-01

    We study the pattern of oscillations in the primordial power spectrum in axion monodromy inflation, accounting for drifts in the oscillation period that can be important for comparing to cosmological data. In these models the potential energy has a monomial form over a super-Planckian field range, with superimposed modulations whose size is model-dependent. The amplitude and frequency of the modulations are set by the expectation values of moduli fields. We show that during the course of inflation, the diminishing energy density can induce slow adjustments of the moduli, changing the modulations. We provide templates capturing the effects of drifting moduli, as well as drifts arising in effective field theory models based on softly broken discrete shift symmetries, and we estimate the precision required to detect a drifting period. A non-drifting template suffices over a wide range of parameters, but for the highest frequencies of interest, or for sufficiently strong drift, it is necessary to include parameters characterizing the change in frequency over the e-folds visible in the CMB. We use these templates to perform a preliminary search for drifting oscillations in a part of the parameter space in the Planck nominal mission data.

  14. Drifting oscillations in axion monodromy

    International Nuclear Information System (INIS)

    Flauger, Raphael; Westphal, Alexander

    2014-12-01

    We study the pattern of oscillations in the primordial power spectrum in axion monodromy inflation, accounting for drifts in the oscillation period that can be important for comparing to cosmological data. In these models the potential energy has a monomial form over a super-Planckian field range, with superimposed modulations whose size is model-dependent. The amplitude and frequency of the modulations are set by the expectation values of moduli fields. We show that during the course of inflation, the diminishing energy density can induce slow adjustments of the moduli, changing the modulations. We provide templates capturing the effects of drifting moduli, as well as drifts arising in effective field theory models based on softly broken discrete shift symmetries, and we estimate the precision required to detect a drifting period. A non-drifting template suffices over a wide range of parameters, but for the highest frequencies of interest, or for sufficiently strong drift, it is necessary to include parameters characterizing the change in frequency over the e-folds visible in the CMB. We use these templates to perform a preliminary search for drifting oscillations in a part of the parameter space in the Planck nominal mission data.

  15. Variations in the occurrence of SuperDARN F region echoes

    Directory of Open Access Journals (Sweden)

    M. Ghezelbash

    2014-02-01

    Full Text Available The occurrence of F region ionospheric echoes observed by a number of SuperDARN HF radars is analyzed statistically in order to infer solar cycle, seasonal, and diurnal trends. The major focus is on Saskatoon radar data for 1994–2012. The distribution of the echo occurrence rate is presented in terms of month of observation and magnetic local time. Clear repetitive patterns are identified during periods of solar maximum and solar minimum. For years near solar maximum, echoes are most frequent near midnight during winter. For years near solar minimum, echoes occur more frequently near noon during winter, near dusk and dawn during equinoxes and near midnight during summer. Similar features are identified for the Hankasalmi and Prince George radars in the northern hemisphere and the Bruny Island TIGER radar in the southern hemisphere. Echo occurrence for the entire SuperDARN network demonstrates patterns similar to patterns in the echo occurrence for the Saskatoon radar and for other radars considered individually. In terms of the solar cycle, the occurrence rate of nightside echoes is shown to increase by a factor of at least 3 toward solar maximum while occurrence of the near-noon echoes does not significantly change with the exception of a clear depression during the declining phase of the solar cycle.

  16. F-region Pedersen conductivity deduced using the TIMED/GUVI limb retrievals

    Directory of Open Access Journals (Sweden)

    Y. Zhang

    2006-07-01

    Full Text Available As a proxy of the Rayleigh-Taylor instability growth rate for equatorial plasma bubbles, we investigate the flux-tube integrated F-region Pedersen conductivity (ΣPF using the electron density profiles (EDPs provided by the Global Ultraviolet Imager (GUVI on board the Thermosphere Ionosphere and Mesosphere Energetics and Dynamics (TIMED satellite. The investigation is conducted using the EDPs obtained in the Atlantic sector at 19:00-22:00 LT during 4–17 August and 6-16 December 2002. The seasonal difference of the strength and location of the equatorial ionization anomalies (EIAs induces a significant difference in the deduced ΣPF. Much stronger EIAs are created at higher altitudes and latitudes in December rather than in August. At 19:00–20:00 LT, the peak value of the ΣPF has 23 mhos at 1100 km apex height during 14–16 December and 18mhos at 600 km during 15–17 August. The ΣPF decreases as local time progresses. Therefore, ΣPF provides a preferred condition for the growth of bubbles to higher altitudes at 19:00-20:00 LT than at later hours, in December rather than in August in the Atlantic sector.

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

    Science.gov (United States)

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

    2015-10-01

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

  18. Drift chamber data readout system

    International Nuclear Information System (INIS)

    Basiladze, S.G.; Lokhonyai, L.

    1980-01-01

    An electronic system for processing drift chamber signals is described. The system consists of 4-channel fast amplifier-discriminators of low threshold, 16-channel time-expanders transforming 0.5 μs time intervals to 10 μs and a 9-bit time-to-digital converter (TDC) recording up to 16 expanded time intervals. If the average track multiplicity is small, TDC is capable to process signals from 4 time-expanders (i.e., 64 drift gaps). In order to record multiple tracks per drift gap discriminator outputs can be connected to a number of time-expander channels. The fast clear input enables the system to be cleared within 0.5 μs. Efficient readout from TDC is facilated by reading only those channels which contain non-zero data (9 bits - drift time; 6 bits - wire number)

  19. Drift tubes of Linac 2

    CERN Multimedia

    Photographic Service

    1977-01-01

    Being redied for installation, those at the right are for tank 1, those on the left for tank 2. Contrary to Linac 1, which had drift-tubes supported on stems, here the tubes are suspended, for better mechanical stability.

  20. On nonlinear periodic drift waves

    International Nuclear Information System (INIS)

    Kauschke, U.; Schlueter, H.

    1990-09-01

    Nonlinear periodic drift waves are investigated on the basis of a simple perturbation scheme for both the amplitude and inverse frequency. The coefficients for the generation of the forced harmonics are derived, a nonlinear dispersion relation is suggested and a criterion for the onset of the modulational instability is obtained. The results are compared with the ones obtained with the help of a standard KBM-treatment. Moreover cnoidal drift waves are suggested and compared to an experimental observation. (orig.)

  1. The OPAL vertex drift chamber

    International Nuclear Information System (INIS)

    Carter, J.R.; Elcombe, P.A.; Hill, J.C.; Roach, C.M.; Armitage, J.C.; Carnegie, R.K.; Estabrooks, P.; Hemingway, R.; Karlen, D.; McPherson, A.; Pinfold, J.; Roney, J.M.; Routenburg, P.; Waterhouse, J.; Hargrove, C.K.; Klem, D.; Oakham, F.G.; Carter, A.A.; Jones, R.W.L.; Lasota, M.M.B.; Lloyd, S.L.; Pritchard, T.W.; Wyatt, T.R.

    1990-01-01

    A high precision vertex drift chamber has been installed in the OPAL experiment at LEP. The design of the chamber and the associated readout electronics is described. The performance of the system has been studied using cosmic ray muons and the results of these studies are presented. A space resolution of 50 μm in the drift direction is obtained using the OPAL central detector gas mixture at 4 bar. (orig.)

  2. Generalized drift-flux correlation

    International Nuclear Information System (INIS)

    Takeuchi, K.; Young, M.Y.; Hochreiter, L.E.

    1991-01-01

    A one-dimensional drift-flux model with five conservation equations is frequently employed in major computer codes, such as TRAC-PD2, and in simulator codes. In this method, the relative velocity between liquid and vapor phases, or slip ratio, is given by correlations, rather than by direct solution of the phasic momentum equations, as in the case of the two-fluid model used in TRAC-PF1. The correlations for churn-turbulent bubbly flow and slug flow regimes were given in terms of drift velocities by Zuber and Findlay. For the annular flow regime, the drift velocity correlations were developed by Ishii et al., using interphasic force balances. Another approach is to define the drift velocity so that flooding and liquid hold-up conditions are properly simulated, as reported here. The generalized correlation is used to reanalyze the MB-2 test data for two-phase flow in a large-diameter pipe. The results are applied to the generalized drift flux velocity, whose relationship to the other correlations is discussed. Finally, the generalized drift flux correlation is implemented in TRAC-PD2. Flow reversal from countercurrent to cocurrent flow is computed in small-diameter U-shaped tubes and is compared with the flooding curve

  3. Ancient paralogy in the cpDNA trnL-F region in Annonaceae: implications for plant molecular systematics

    NARCIS (Netherlands)

    Pirie, M.D.; Vargas, M.P.B.; Botermans, M.; Bakker, F.T.; Chatrou, L.W.

    2007-01-01

    The plastid trnL-F region has proved useful in molecular phylogenetic studies addressing diverse evolutionary questions from biogeographic history to character evolution in a broad range of plant groups. An important assumption for phylogenetic reconstruction is that data used in combined analyses

  4. UBV(RI)sub(c) photometry of some standard sequences in the Harvard F regions and in the Magellanic Clouds

    International Nuclear Information System (INIS)

    Menzies, J.W.; Laing, J.D.

    1988-01-01

    This paper presents the results of a photometric programme aimed at improving the UBV(RI)sub(c) standard sequences in the Harvard F regions and in the Small and Large Magellanic Clouds. Magnitudes and colours are given for 99 stars, and they are compared with the current values which were obtained or compiled by a previous author. (author)

  5. Observations of unusual pre-dawn response of the equatorial F-region during geomagnetic disturbances

    Science.gov (United States)

    Lima, W.; Becker-Guedes, F.; Fagundes, P.; Sahai, Y.; Abalde, J.; Pillat, V.

    It is known that the disturbed solar wind-magnetosphere interactions have important effects on equatorial and low-latitude ionospheric electrodynamics. The response of equatorial ionosphere during storm-time is an important aspect of space weather studies. It has been observed that during geomagnetic disturbances both suppression as well as generation of equatorial spread-F (ESF) or plasma irregularities takes place. However, the mechanism(s) associated with the generation of ESF still needs further investigations. This work reports some unusual events of pre-dawn occurrence of ionospheric F-region satellite traces followed by spread-F and cusp-like spread-F from ionospheric sounding observations carried out by a Canadian Advanced Digital Ionosonde (CADI) localized at Palmas (10.2°, 48.2°W, dip latitude 5.7°S), Brazil during 2002, every 5 minutes. For the present work we have scaled and analyzed the ionospheric sounding data for three events (April 20, September 04 and 08, 2002), which are associated with geomagnetic disturbances. In the events studied, the ionograms show the occurrence of satellite trace followed by cusp-like spread. The cusp like features move up in frequency and height and finally attain the F-layer peak value (foF2) and then disappear. They had duration of about 30 min and always occurred in the early morning hours. Our studies involved seven geomagnetic disturbances as well as quiet days during the year 2002, but only on these three occasions we observed these features. We present and discuss these observations in this paper and suggest possible mechanisms for the occurrence of these unusual features.

  6. The Drifting Star

    Science.gov (United States)

    2008-04-01

    By studying in great detail the 'ringing' of a planet-harbouring star, a team of astronomers using ESO's 3.6-m telescope have shown that it must have drifted away from the metal-rich Hyades cluster. This discovery has implications for theories of star and planet formation, and for the dynamics of our Milky Way. ESO PR Photo 09a/08 ESO PR Photo 09a/08 Iota Horologii The yellow-orange star Iota Horologii, located 56 light-years away towards the southern Horologium ("The Clock") constellation, belongs to the so-called "Hyades stream", a large number of stars that move in the same direction. Previously, astronomers using an ESO telescope had shown that the star harbours a planet, more than 2 times as large as Jupiter and orbiting in 320 days (ESO 12/99). But until now, all studies were unable to pinpoint the exact characteristics of the star, and hence to understand its origin. A team of astronomers, led by Sylvie Vauclair from the University of Toulouse, France, therefore decided to use the technique of 'asteroseismology' to unlock the star's secrets. "In the same way as geologists monitor how seismic waves generated by earthquakes propagate through the Earth and learn about the inner structure of our planet, it is possible to study sound waves running through a star, which forms a sort of large, spherical bell," says Vauclair. The 'ringing' from this giant musical instrument provides astronomers with plenty of information about the physical conditions in the star's interior. And to 'listen to the music', the astronomers used one of the best instruments available. The observations were conducted in November 2006 during 8 consecutive nights with the state-of-the-art HARPS spectrograph mounted on the ESO 3.6-m telescope at La Silla. Up to 25 'notes' could be identified in the unique dataset, most of them corresponding to waves having a period of about 6.5 minutes. These observations allowed the astronomers to obtain a very precise portrait of Iota Horologii: its

  7. Characteristic parameters of drift chambers calculation

    International Nuclear Information System (INIS)

    Duran, I.; Martinez-Laso, L.

    1989-01-01

    We present here the methods we used to analyse the characteristic parameters of drift chambers. The algorithms to calculate the electric potential in any point for any drift chamber geometry are presented. We include the description of the programs used to calculate the electric field, the drift paths, the drift velocity and the drift time. The results and the errors are discussed. (Author) 7 refs

  8. In-Drift Microbial Communities

    Energy Technology Data Exchange (ETDEWEB)

    D. Jolley

    2000-11-09

    As directed by written work direction (CRWMS M and O 1999f), Performance Assessment (PA) developed a model for microbial communities in the engineered barrier system (EBS) as documented here. The purpose of this model is to assist Performance Assessment and its Engineered Barrier Performance Section in modeling the geochemical environment within a potential repository drift for TSPA-SR/LA, thus allowing PA to provide a more detailed and complete near-field geochemical model and to answer the key technical issues (KTI) raised in the NRC Issue Resolution Status Report (IRSR) for the Evolution of the Near Field Environment (NFE) Revision 2 (NRC 1999). This model and its predecessor (the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document, CRWMS M and O 1998a) was developed to respond to the applicable KTIs. Additionally, because of the previous development of the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document (CRWMS M and O 1998a), the M and O was effectively able to resolve a previous KTI concern regarding the effects of microbial processes on seepage and flow (NRC 1998). This document supercedes the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document (CRWMS M and O 1998a). This document provides the conceptual framework of the revised in-drift microbial communities model to be used in subsequent performance assessment (PA) analyses.

  9. In-Drift Microbial Communities

    International Nuclear Information System (INIS)

    Jolley, D.

    2000-01-01

    As directed by written work direction (CRWMS M and O 1999f), Performance Assessment (PA) developed a model for microbial communities in the engineered barrier system (EBS) as documented here. The purpose of this model is to assist Performance Assessment and its Engineered Barrier Performance Section in modeling the geochemical environment within a potential repository drift for TSPA-SR/LA, thus allowing PA to provide a more detailed and complete near-field geochemical model and to answer the key technical issues (KTI) raised in the NRC Issue Resolution Status Report (IRSR) for the Evolution of the Near Field Environment (NFE) Revision 2 (NRC 1999). This model and its predecessor (the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document, CRWMS M and O 1998a) was developed to respond to the applicable KTIs. Additionally, because of the previous development of the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document (CRWMS M and O 1998a), the M and O was effectively able to resolve a previous KTI concern regarding the effects of microbial processes on seepage and flow (NRC 1998). This document supercedes the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document (CRWMS M and O 1998a). This document provides the conceptual framework of the revised in-drift microbial communities model to be used in subsequent performance assessment (PA) analyses

  10. Drift tubes of Linac 2

    CERN Multimedia

    CERN PhotoLab

    1977-01-01

    With the advent of the 800 MeV PS Booster in 1972, the original injector of the PS, a 50 MeV Alvarez-type proton linac, had reached its limits, in terms of intensity and stability. In 1973 one therefore decided to build a new linac (Linac 2), also with a drift-tube Alvarez structure and an energy of 50 MeV. It had a new Cockcroft-Walton preinjector with 750 keV, instead of the previous one with 500 keV. Linac 2 was put into service in 1980. The old Linac 1 was then used for the study of, and later operation with, various types of ions. This picture shows Linac 2 drift-tubes, suspended on stems coming from the top, in contrast to Linac 1, where the drift-tubes stood on stems coming from the bottom.

  11. Predicting public sector accountability : From agency drift to forum drift

    NARCIS (Netherlands)

    Schillemans, Thomas|info:eu-repo/dai/nl/229913881; Busuioc, Madalina

    2015-01-01

    Principal-agent theory has been the dominant theory at the heart of public sector accountability research. The notion of the potentially drifting agent-such as independent public agencies, opaque transnational institutions, or recalcitrant street-level bureaucrats-has been the guiding paradigm in

  12. F-region electron density and Te / Ti measurements using incoherent scatter power data collected at ALTAIR

    Directory of Open Access Journals (Sweden)

    M. Milla

    2006-07-01

    Full Text Available The ALTAIR UHF radar was used in an incoherent scatter experiment to observe the low-latitude ionosphere during the Equis 2 rocket campaign. The measurements provided the first high-resolution electron density maps of the low-latitude D- and E-region in the Pacific sector and also extended into the F-region and topside ionosphere. Although the sampling frequency was well below the Nyquist frequency of F-region returns, we were able to estimate Te / Ti ratio and infer unbiased electron density estimates using a regularized inversion technique described here. The technique exploits magnetic aspect angle dependence of ISR cross-section for Te>Ti.

  13. Collisional drift fluid equations and implications for drift waves

    International Nuclear Information System (INIS)

    Pfirsch, Dieter; Correa-Restrepo, Dario

    1996-01-01

    The usual theoretical description of drift-wave turbulence (considered to be one possible cause of anomalous transport in a plasma), e.g. the Hasegawa-Wakatani theory, makes use of various approximations, the effects of which are extremely difficult to assess. This concerns in particular the conservation laws for energy and momentum. The latter law is important in relation to charge separation and the resulting electric fields, which are possibly related to the L-H transition. Energy conservation is crucial to the stability behaviour, it will be discussed by means of an example. New collisional multi-species drift-fluid equations were derived by a new method which yields, in a transparent way, conservation of energy and total angular momentum and the law for energy dissipation. Both electrostatic and electromagnetic field variations are considered. The only restriction involved is the validity of the drift approximation; in particular, there are no assumptions restricting the geometry of the system. The method is based primarily on a Lagrangian for dissipationless fluids in the drift approximation with isotropic pressures. The dissipative terms are introduced by adding corresponding terms to the ideal equations of motion and of the pressures. The equations of motion, of course, no longer result from a Lagrangian via Hamilton's principle. However, their relation to the ideal equations also implies a relation to the ideal Lagrangian, which can be used to advantage. Instead of introducing heat conduction one can also assume isothermal behaviour, e.g. T v (x) = constant. Assumptions of this kind are often made in the literature. The new method of introducing dissipation is not restricted to the present kind of theory; it can equally well be applied to theories such as multi-fluid theories without using the drift approximation of the present paper. (author)

  14. Complexity in the scaling of velocity fluctuations in the high-latitude F-region ionosphere

    Directory of Open Access Journals (Sweden)

    M. L. Parkinson

    2008-09-01

    Full Text Available The temporal scaling properties of F-region velocity fluctuations, δvlos, were characterised over 17 octaves of temporal scale from τ=1 s to <1 day using a new data base of 1-s time resolution SuperDARN radar measurements. After quality control, 2.9 (1.9 million fluctuations were recorded during 31.5 (40.4 days of discretionary mode soundings using the Tasmanian (New Zealand radars. If the fluctuations were statistically self-similar, the probability density functions (PDFs of δvlos would collapse onto the same PDF using the scaling Psvs, τ=ταPvlos, τ and δvsvlosτ−α where α is the scaling exponent. The variations in scaling exponents α and multi-fractal behaviour were estimated using peak scaling and generalised structure function (GSF analyses, and a new method based upon minimising the differences between re-scaled probability density functions (PDFs. The efficiency of this method enabled calculation of "α spectra", the temporal spectra of scaling exponents from τ=1 s to ~2048 s. The large number of samples enabled calculation of α spectra for data separated into 2-h bins of MLT as well as two main physical regimes: Population A echoes with Doppler spectral width <75 m s−1 concentrated on closed field lines, and Population B echoes with spectral width >150 m s−1 concentrated on open field lines. For all data there was a scaling break at τ~10 s and the similarity of the fluctuations beneath this scale may be related to the large spatial averaging (~100 km×45 km employed by SuperDARN radars. For Tasmania Population B, the velocity fluctuations exhibited approximately mono fractal power law scaling between τ~8 s and 2048 s (34 min, and probably up to several hours. The scaling exponents were generally less than that expected for basic MHD

  15. Solar Drift-Pair Bursts

    Science.gov (United States)

    Stanislavsky, A.; Volvach, Ya.; Konovalenko, A.; Koval, A.

    2017-08-01

    In this paper a new sight on the study of solar bursts historically called drift pairs (DPs) is presented. Having a simple morphology on dynamic spectra of radio records (two short components separated in time, and often they are very similar) and discovered at the dawn of radio astronomy, their features remain unexplained totally up to now. Generally, the DPs are observed during the solar storms of type III bursts, but not every storm of type III bursts is linked with DPs. Detected by ground-based instruments at decameter and meter wavelengths, the DP bursts are limited in frequency bandwidth. They can drift from high frequencies to low ones and vice versa. Their frequency drift rate may be both lower and higher than typical rates of type III bursts at the same frequency range. The development of low-frequency radio telescopes and data processing provide additional possibilities in the research. In this context the fresh analysis of DPs, made from recent observations in the summer campaign of 2015, are just considered. Their study was implemented by updated tools of the UTR-2 radio telescope at 9-33 MHz. During 10-12 July of 2015, DPs forming the longest patterns on dynamic spectra are about 7% of the total number of recorded DPs. Their marvelous resemblance in frequency drift rates with the solar S-bursts is discussed.

  16. Job satisfaction and preference drift.

    NARCIS (Netherlands)

    Maassen van den Brink, H.; Groot, W.J.N.

    1999-01-01

    Most empirical studies do not find that higher wages lead to more job satisfaction. In this paper we argue that the insignificant effect of wages on job satisfaction is due to preference drift. We adapt the standard ordered response model to allow for preference shifts. The empirical results support

  17. VHF and HF radar measurements of E and R region plasma drifts at the magnetic equator

    International Nuclear Information System (INIS)

    Viswanathan, K.S.; Namboothiri, S.P.; Rao, P.B.

    1992-01-01

    Simultaneous observations of E region horizontal irregularity drifts by VHF backscatter radar and of F region vertical plasma drift by HF Doppler radar conducted during daytime on a few magnetically quiet days at Trivandrum (dip 0.2 degree N) are presented. A comparative study of the two measurements indicates broadly (1) a resemblance in the daytime changes of the E-W component between the electric field and (2) evidence of quasi-periodic electric field variations with periods ranging mostly from 1 to 2 hours. The electric fields derived from HF Doppler radar observations are somewhat lower than those deduced by HVHF radar observations. The correlation coefficient for the variations of the electric fields measured by the two experimental techniques is found to be in the range of about 0.5 to 0.9. The observed difference in the E and F region electric fields at the magnetic equator is discussed in terms of the measurement uncertainties and the limitations involved in deriving E-W electric fields. The observations are suggestive of a latitudinal variation in the E-W component of the electric field in the equatorial ionosphere

  18. Drift Chambers detectors; Detectores de deriva

    Energy Technology Data Exchange (ETDEWEB)

    Duran, I; Martinez laso, L

    1989-07-01

    We present here a review of High Energy Physics detectors based on drift chambers. The ionization, drift diffusion, multiplication and detection principles are described. Most common drift media are analysed, and a classification of the detectors according to its geometry is done. Finally the standard read-out methods are displayed and the limits of the spatial resolution are discussed. (Author) 115 refs.

  19. ATLAS Muon Drift Tube Electronics

    Energy Technology Data Exchange (ETDEWEB)

    Arai, Y [KEK, High Energy Accelerator Research Organisation, Tsukuba (Japan); Ball, B; Chapman, J W; Dai, T; Ferretti, C; Gregory, J [University of Michigan, Department of Physics, Ann Arbor, MI (United States); Beretta, M [INFN Laboratori Nazionali di Frascati, Frascati (Italy); Boterenbrood, H; Jansweijer, P P M [Nikhef National Institute for Subatomic Physics, Amsterdam (Netherlands); Brandenburg, G W; Fries, T; Costa, J Guimaraes da; Harder, S; Huth, J [Harvard University, Laboratory for Particle Physics and Cosmology, Cambridge, MA (United States); Ceradini, F [INFN Roma Tre and Universita Roma Tre, Dipartimento di Fisica, Roma (Italy); Hazen, E [Boston University, Physics Department, Boston, MA (United States); Kirsch, L E [Brandeis University, Department of Physics, Waltham, MA (United States); Koenig, A C [Radboud University Nijmegen/Nikhef, Dept. of Exp. High Energy Physics, Nijmegen (Netherlands); Lanza, A [INFN Pavia, Pavia (Italy); Mikenberg, G [Weizmann Institute of Science, Department of Particle Physics, Rehovot (Israel)], E-mail: brandenburg@physics.harvard.edu (and others)

    2008-09-15

    This paper describes the electronics used for the ATLAS monitored drift tube (MDT) chambers. These chambers are the main component of the precision tracking system in the ATLAS muon spectrometer. The MDT detector system consists of 1,150 chambers containing a total of 354,000 drift tubes. It is capable of measuring the sagitta of muon tracks to an accuracy of 60 {mu}m, which corresponds to a momentum accuracy of about 10% at p{sub T}= 1 TeV. The design and performance of the MDT readout electronics as well as the electronics for controlling, monitoring and powering the detector will be discussed. These electronics have been extensively tested under simulated running conditions and have undergone radiation testing certifying them for more than 10 years of LHC operation. They are now installed on the ATLAS detector and are operating during cosmic ray commissioning runs.

  20. ATLAS Muon Drift Tube Electronics

    CERN Document Server

    Arai, Y; Beretta, M; Boterenbrood, H; Brandenburg, G W; Ceradini, F; Chapman, J W; Dai, T; Ferretti, C; Fries, T; Gregory, J; Guimarães da Costa, J; Harder, S; Hazen, E; Huth, J; Jansweijer, P P M; Kirsch, L E; König, A C; Lanza, A; Mikenberg, G; Oliver, J; Posch, C; Richter, R; Riegler, W; Spiriti, E; Taylor, F E; Vermeulen, J; Wadsworth, B; Wijnen, T A M

    2008-01-01

    This paper describes the electronics used for the ATLAS monitored drift tube (MDT) chambers. These chambers are the main component of the precision tracking system in the ATLAS muon spectrometer. The MDT detector system consists of 1,150 chambers containing a total of 354,000 drift tubes. It is capable of measuring the sagitta of muon tracks to an accuracy of 60 microns, which corresponds to a momentum accuracy of about 10% at pT = 1 TeV. The design and performance of the MDT readout electronics as well as the electronics for controlling, monitoring and powering the detector will be discussed. These electronics have been extensively tested under simulated running conditions and have undergone radiation testing certifying them for more than 10 years of LHC operation. They are now installed on the ATLAS detector and are operating during cosmic ray commissioning runs.

  1. A Pascalian lateral drift sensor

    International Nuclear Information System (INIS)

    Jansen, H.

    2016-01-01

    A novel concept of a layer-wise produced semiconductor sensor for precise particle tracking is proposed herein. In contrast to common semiconductor sensors, local regions with increased doping concentration deep in the bulk termed charge guides increase the lateral drift of free charges on their way to the read-out electrode. This lateral drift enables charge sharing independent of the incident position of the traversing particle. With a regular grid of charge guides the lateral charge distribution resembles a normalised Pascal's triangle for particles that are stopped in depths lower than the depth of the first layer of the charge guides. For minimum ionising particles a sum of binomial distributions describes the lateral charge distribution. This concept decouples the achievable sensor resolution from the pitch size as the characteristic length is replaced by the lateral distance of the charge guides.

  2. A Pascalian lateral drift sensor

    Energy Technology Data Exchange (ETDEWEB)

    Jansen, H., E-mail: hendrik.jansen@desy.de

    2016-09-21

    A novel concept of a layer-wise produced semiconductor sensor for precise particle tracking is proposed herein. In contrast to common semiconductor sensors, local regions with increased doping concentration deep in the bulk termed charge guides increase the lateral drift of free charges on their way to the read-out electrode. This lateral drift enables charge sharing independent of the incident position of the traversing particle. With a regular grid of charge guides the lateral charge distribution resembles a normalised Pascal's triangle for particles that are stopped in depths lower than the depth of the first layer of the charge guides. For minimum ionising particles a sum of binomial distributions describes the lateral charge distribution. This concept decouples the achievable sensor resolution from the pitch size as the characteristic length is replaced by the lateral distance of the charge guides.

  3. MPS II drift chamber system

    International Nuclear Information System (INIS)

    Platner, E.D.

    1982-01-01

    The MPS II detectors are narrow drift space chambers designed for high position resolution in a magnetic field and in a very high particle flux environment. Central to this implementation was the development of 3 multi-channel custom IC's and one multi-channel hybrid. The system is deadtimeless and requires no corrections on an anode-to-anode basis. Operational experience and relevance to ISABELLE detectors is discussed

  4. Shear wall ultimate drift limits

    International Nuclear Information System (INIS)

    Duffey, T.A.; Goldman, A.; Farrar, C.R.

    1994-04-01

    Drift limits for reinforced-concrete shear walls are investigated by reviewing the open literature for appropriate experimental data. Drift values at ultimate are determined for walls with aspect ratios ranging up to a maximum of 3.53 and undergoing different types of lateral loading (cyclic static, monotonic static, and dynamic). Based on the geometry of actual nuclear power plant structures exclusive of containments and concerns regarding their response during seismic (i.e.,cyclic) loading, data are obtained from pertinent references for which the wall aspect ratio is less than or equal to approximately 1, and for which testing is cyclic in nature (typically displacement controlled). In particular, lateral deflections at ultimate load, and at points in the softening region beyond ultimate for which the load has dropped to 90, 80, 70, 60, and 50 percent of its ultimate value, are obtained and converted to drift information. The statistical nature of the data is also investigated. These data are shown to be lognormally distributed, and an analysis of variance is performed. The use of statistics to estimate Probability of Failure for a shear wall structure is illustrated

  5. E and F region study of the evening sector auroral oval: A Chatanika/Dynamics Explorer 2/NOAA 6 comparison

    International Nuclear Information System (INIS)

    Senior, C.; Sharber, J.R.; Winningham, J.D.; De La Beaujardiere, O.; Heelis, R.A.; Evans, D.S.; Sugiura, M.; Hoegy, W.R.

    1987-01-01

    Simultaneous data obtained with the Chatanika incoherent scatter radar and the Dynamics Explorer 2 (DE 2) and NOAA 6 satellites are used to relate the locations of the precipitating particles, field-aligned currents, and E and F region ionization structures in the evening-sector auroral oval. The auroral E layer observed by the radar extends about 2 degree equatorward of the electron precipitation region, and its equatorward edge coincides with the equatorward edges of the region 2 field-aligned current and intense convection region (E ≅ 50 mV/m). It is shown that precipitating protons are responsible for part of the E region ionization within the electron precipitation region as well as south of it. E region density profiles calculated from ion spectra measured by the DE 2 and NOAA 5 satellites are in fairly good agreement with the Chatanika data. in the F region, a channel of enhanced ionization density, elongated along the east-west direction and having a width of about 100 km, marks the poleward edge of the main trough. it is colocated with the equatorward boundary of the electron precipitation from the central plasma sheet. Although enhanced fluxes of soft electrons are observed at this boundary, the energy input to the ionospheric electron gas, calculated from the radar data, shows that this ionization channel is not locally produced by this soft precipitation, but that it is rather a convected feature. In fact, both the trough and the ionization channel are located in a region where the plasma flows sunward at high speed, but the flux tubes associated with theses two features have different convective time histories. Keeping in mind that several processes operate together in the F region, the data set is consistent with the included trough and ionization channel formation mechanisms

  6. Optimization of drift gases for accuracy in pressurized drift tubes

    CERN Document Server

    Kirchner, J J; Dinner, A R; Fidkowski, K J; Wyatt, J H

    2001-01-01

    Modern detectors such as ATLAS use pressurized drift tubes to minimize diffusion and achieve high coordinate accuracy. However, the coordinate accuracy depends on the exact knowledge of converting measured times into coordinates. Linear space-time relationships are best for reconstruction, but difficult to achieve in the $E \\propto \\frac{1}{r}$ field. Previous mixtures, which contained methane or other organic quenchers, are disfavored because of ageing problems. From our studies of nitrogen and carbon dioxide, two mixtures with only small deviations from linearity were determined and measured. Scaling laws for different pressures and magnetic fields are also given.

  7. Optimization of drift gases for accuracy in pressurized drift tubes

    International Nuclear Information System (INIS)

    Kirchner, J.J.; Becker, U.J.; Dinner, R.B.; Fidkowski, K.J.; Wyatt, J.H.

    2001-01-01

    Modern detectors such as ATLAS use pressurized drift tubes to minimize diffusion and achieve high coordinate accuracy. However, the coordinate accuracy depends on the exact knowledge of converting measured times into coordinates. Linear space-time relationships are best for reconstruction, but difficult to achieve in the E∝1/r field. Previous mixtures, which contained methane or other organic quenchers, are disfavored because of ageing problems. From our studies of nitrogen and carbon dioxide, two mixtures with only small deviations from linearity were determined and measured. Scaling laws for different pressures and magnetic fields are also given

  8. Measurement of the positron-drift time relation of a high-pressure drift chamber

    International Nuclear Information System (INIS)

    Pruefert, W.

    1989-04-01

    As a test of its performance, the measurement of the drift time versus drift distance relation of a high pressure drift chamber using cosmic rays is described. Two multiwire proportional chambers, mounted above and below the detector, are used to define the track of the cosmic particle in the drift chamber. The drift chamber is read out by FADCs (Flash Analog to Digital Converter), and the drift time is determined from the FADC signals by the DOS- (Difference Of Samples) method. The measured drift time versus drift distance relation showed good agreement with the relation, which is expected from the spatial dependence of the electric field and the dependence of the drift velocity on this field. (orig.) [de

  9. Pulse shape simulation for drift chambers with long drift paths

    International Nuclear Information System (INIS)

    Mayer, H.J.

    1987-01-01

    A detailed Monte Carlo program for the simulation of drift chamber pulse shapes is described. It has been applied to the case of a jet chamber with drift paths up to 24 cm. Results on pulse shapes and corresponding spatial and double hit resolution are discussed and compared to recent measurements of the OPAL central detector jet chamber full size prototype and to measurements of a small 20-wire prototype, which was designed to study the pulse shapes generated by tracks in a magnetic field. Simulated pulse shapes and spatial resolutions agree well with the experimental data. Clustering, saturation and wire crosstalk are shown to be necessary ingredients in the simulation. A deterioration in resolution due to the influence of crosstalk signals is correctly reproduced, as well as the cancellation of this effect by a hardwired first and second neighbour crosstalk compensation. The simulation correctly describes the asymmetry in spatial resolution observed for tracks with positive or negative inclination against the wire plane when a magnetic field is present. The effect of saturation on double hit resolution is found to be small. The magnetic field is predicted to improve the double hit resolution. (orig.)

  10. Pulse shape simulation for drift chambers with long drift paths

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, H J

    1987-09-15

    A detailed Monte Carlo program for the simulation of drift chamber pulse shapes is described. It has been applied to the case of a jet chamber with drift paths up to 24 cm. Results on pulse shapes and corresponding spatial and double hit resolution are discussed and compared to recent measurements of the OPAL central detector jet chamber full size prototype and to measurements of a small 20-wire prototype, which was designed to study the pulse shapes generated by tracks in a magnetic field. Simulated pulse shapes and spatial resolutions agree well with the experimental data. Clustering, saturation and wire crosstalk are shown to be necessary ingredients in the simulation. A deterioration in resolution due to the influence of crosstalk signals is correctly reproduced, as well as the cancellation of this effect by a hardwired first and second neighbour crosstalk compensation. The simulation correctly describes the asymmetry in spatial resolution observed for tracks with positive or negative inclination against the wire plane when a magnetic field is present. The effect of saturation on double hit resolution is found to be small. The magnetic field is predicted to improve the double hit resolution.

  11. Drift waves in a stellarator

    International Nuclear Information System (INIS)

    Bhattacharjee, A.; Sedlak, J.E.; Similon, P.L.; Rosenbluth, M.N.; Ross, D.W.

    1982-11-01

    We investigate the eigenmode structure of drift waves in a straight stellarator using the ballooning mode formalism. The electrons are assumed to be adiabatic and the ions constitute a cold, magnetized fluid. The effective potential has an overall parabolic envelope but is modulated strongly by helical ripples along B. We have found two classes of solutions: those that are strongly localized in local helical wells, and those that are weakly localized and have broad spatial extent. The weakly localized modes decay spatially due to the existence of Mathieu resonances between the periods of the eigenfunction and the effective potential

  12. Kinetic theory of drift waves

    International Nuclear Information System (INIS)

    Vlad, G.

    1988-01-01

    The linear stability of the electrostatic drift waves in slab geometry has been studied analytically and numerically. The effects of magnetic field with shear, of the finite Larmor radius, of an electron streaming, of a temperature gradient and of collisions have been retained. The analytical solution has been obtained using the matched asymptotic expansion technique, and an expression for the critical streaming parameter has been derived. Finally, assuming that the transport in the Reversed Field Pinches is dominated by this instability, a scaling law for the temperature in such machine is derived

  13. Experimental work on drift chambers

    International Nuclear Information System (INIS)

    Alcaraz, J.; Duran, I.; Gonzalez, E.; Martinez-Laso, L.; Olmos, P.

    1989-01-01

    An experimental work made on drift chambers is described in two chapters. In the firt chapter we present the description of the experimental installation used, as well as some details on the data adquisition systems and the characteristics on three ways used for calibration proposes (cosmic muons, β radiation and test beam using SPS at CERN facilities). The second chapter describes the defferent prototypes studied. The experimental set up and the analysis are given. Some results are discussed. The magnetic field effect is also studied. (Author)

  14. Drift vortices in continuous media

    International Nuclear Information System (INIS)

    Chernousenko, V.M.; Chernenko, I.V.; Chernyshenko, S.V.

    1989-01-01

    The work is devoted to investigation into the problems of large-scale cortex drift and generation in continuous media based on the solution of notably non-linear differential equations. Using the capability of the modern computer technique it is possible to consider a series of cases with regard to medium viscosity and its inhomogeneity and with regard to three-dimensional vortex nature. Based on the solutions obtained the large-scale steady-state vortex generation processes are considered. The results can be used when studying non-linear phenomena in plasma and processes of substance and energy transfer in non-equilibrium media. 16 refs.; 5 figs

  15. Disturbance zonal and vertical plasma drifts in the Peruvian sector during solar minimum phases

    Science.gov (United States)

    Santos, A. M.; Abdu, M. A.; Souza, J. R.; Sobral, J. H. A.; Batista, I. S.

    2016-03-01

    In the present work, we investigate the behavior of the equatorial F region zonal plasma drifts over the Peruvian region under magnetically disturbed conditions during two solar minimum epochs, one of them being the recent prolonged solar activity minimum. The study utilizes the vertical and zonal components of the plasma drifts measured by the Jicamarca (11.95°S; 76.87°W) incoherent scatter radar during two events that occurred on 10 April 1997 and 24 June 2008 and model calculation of the zonal drift in a realistic ionosphere simulated by the Sheffield University Plasmasphere-Ionosphere Model-INPE. Two main points are focused: (1) the connection between electric fields and plasma drifts under prompt penetration electric field during a disturbed periods and (2) anomalous behavior of daytime zonal drift in the absence of any magnetic storm. A perfect anticorrelation between vertical and zonal drifts was observed during the night and in the initial and growth phases of the magnetic storm. For the first time, based on a realistic low-latitude ionosphere, we will show, on a detailed quantitative basis, that this anticorrelation is driven mainly by a vertical Hall electric field induced by the primary zonal electric field in the presence of an enhanced nighttime E region ionization. It is shown that an increase in the field line-integrated Hall-to-Pedersen conductivity ratio (∑H/∑P), which can arise from precipitation of energetic particles in the region of the South American Magnetic Anomaly, is capable of explaining the observed anticorrelation between the vertical and zonal plasma drifts. Evidence for the particle ionization is provided from the occurrence of anomalous sporadic E layers over the low-latitude station, Cachoeira Paulista (22.67°S; 44.9°W)—Brazil. It will also be shown that the zonal plasma drift reversal to eastward in the afternoon two hours earlier than its reference quiet time pattern is possibly caused by weakening of the zonal wind

  16. Longitudinal differences observed in the ionospheric F-region during the major geomagnetic storm of 31 March 2001

    Directory of Open Access Journals (Sweden)

    Y. Sahai

    2004-09-01

    Full Text Available A new ionospheric sounding station using a Canadian Advanced Digital Ionosonde (CADI was established for routine measurements by the "Universidade do Vale do Paraiba (UNIVAP" at São José dos Campos (23.2° S, 45.9° W, Brazil, in August 2000. A major geomagnetic storm with gradual commencement at about 01:00 UT was observed on 31 March 2001. In this paper, we present and discuss salient features from the ionospheric sounding measurements carried out at S. J. Campos on the three consecutive UT days 30 March (quiet, 31 March (disturbed and 1 April (recovery 2001. During most of the storm period, the foF2 values showed negative phase, whereas during the two storm-time peaks, large F-region height variations were observed. In order to study the longitudinal differences observed in the F-region during the storm, the simultaneous ionospheric sounding measurements carried out at S. J. Campos, El Arenosillo (37.1° N, 6.7° W, Spain, Okinawa (26.3° N, 127.8° E, Japan and Wakkanai (45.5° N, 141.7° E, Japan, during the period 30 March-1 April 2001, have been analyzed. A comparison of the observed ionospheric parameters (h'F and foF2 in the two longitudinal zones (1. Japanese and 2. Brazilian-Spanish shows both similarities and differences associated with the geomagnetic disturbances. Some latitudinal differences are also observed in the two longitudinal zones. In addition, global ionospheric TEC maps from the worldwide network of GPS receivers are presented, showing widespread TEC changes during both the main and recovery phases of the storm. The ionospheric sounding measurements are compared with the ASPEN-TIMEGCM model runs appropriate for the storm conditions. The model results produce better agreement during the quiet period. During the disturbed period, some of the observed F-region height variations are well reproduced by the model results. The model foF2 and TEC results differ considerably during the recovery period and indicate much

  17. Longitudinal differences observed in the ionospheric F-region during the major geomagnetic storm of 31 March 2001

    Directory of Open Access Journals (Sweden)

    Y. Sahai

    2004-09-01

    Full Text Available A new ionospheric sounding station using a Canadian Advanced Digital Ionosonde (CADI was established for routine measurements by the "Universidade do Vale do Paraiba (UNIVAP" at São José dos Campos (23.2° S, 45.9° W, Brazil, in August 2000. A major geomagnetic storm with gradual commencement at about 01:00 UT was observed on 31 March 2001. In this paper, we present and discuss salient features from the ionospheric sounding measurements carried out at S. J. Campos on the three consecutive UT days 30 March (quiet, 31 March (disturbed and 1 April (recovery 2001. During most of the storm period, the foF2 values showed negative phase, whereas during the two storm-time peaks, large F-region height variations were observed. In order to study the longitudinal differences observed in the F-region during the storm, the simultaneous ionospheric sounding measurements carried out at S. J. Campos, El Arenosillo (37.1° N, 6.7° W, Spain, Okinawa (26.3° N, 127.8° E, Japan and Wakkanai (45.5° N, 141.7° E, Japan, during the period 30 March-1 April 2001, have been analyzed. A comparison of the observed ionospheric parameters (h'F and foF2 in the two longitudinal zones (1. Japanese and 2. Brazilian-Spanish shows both similarities and differences associated with the geomagnetic disturbances. Some latitudinal differences are also observed in the two longitudinal zones. In addition, global ionospheric TEC maps from the worldwide network of GPS receivers are presented, showing widespread TEC changes during both the main and recovery phases of the storm. The ionospheric sounding measurements are compared with the ASPEN-TIMEGCM model runs appropriate for the storm conditions. The model results produce better agreement during the quiet period. During the disturbed period, some of the observed F-region height variations are well reproduced by the model results. The model foF2 and TEC results differ considerably during the

  18. Drift-time measurement electronics

    International Nuclear Information System (INIS)

    Pernicka, M.

    1978-01-01

    The aim of the construction was to improve the time resolution without using the facility of time stretching, to have a fast read-out possibility, and to be still cheaper in price in comparison to other systems. A possibility was thus foreseen for using the firm Fairchild. These integrated circuits (IC) have, for example, a propagation delay of 0.75 ns for a gate. One can expect therefore less time jitter and less time difference between the different inputs. Furthermore this IC offers a greater flexibility and therefore the number of ICs decreases and distances become smaller. Working with clock frequencies up to 166.6 MHz is easily possible without running into timing problems. On the other hand, to make full use of the advantages of this IC, it was necessary to build the print as a multilayer. The only risk could be in the use of a completely new product. A further aim was to build for this system a second type of drift-time module with a short time range for measuring drift time and pulse length in rotated multiwire proportional chambers. A brief outline of the specifications of the different modules is given in table 1. (Auth.)

  19. Zonal drifts of ionospheric irregularities at temperate latitude in the Indian region

    Directory of Open Access Journals (Sweden)

    S. Kumar

    1995-07-01

    Full Text Available The systematic time differences observed in the onset of postsunset VHF scintillations recorded simultaneously at Ujjain (Geogr. lat. 23.2°N, Geogr. long. 75.6°E and Bhopal (Geogr. lat. 23.2°N, Geogr. long. 77.6°E, situated at the peak of the anomaly crest in the Indian region, have been analysed to determine the zonal drifts of scintillation-producing irregularities. The method is based on the assumption that the horizontal movement of irregularities does not change while crossing the F-region cross-over points of these stations. The calculated velocities of irregularities indicate an eastward drift decreasing from about 180 m s–1 to 55 m s–1 during the course of night. In the premidnight period, the drifts are reduced under the magnetically disturbed conditions. The average east-west extension of irregularites is found to be in the range of 200–500 km.

  20. The large cylindrical drift chamber of TASSO

    International Nuclear Information System (INIS)

    Boerner, H.; Fischer, H.M.; Hartmann, H.; Loehr, B.; Wollstadt, M.; Fohrmann, R.; Schmueser, P.; Cassel, D.G.; Koetz, U.; Kowalski, H.

    1980-03-01

    We have built and operated a large cylindrical drift chamber for the TASSO experiment at the DESY storage ring, PETRA. The chamber has a length of 3.5 m, a diameter of 2.5 m, and a total of 2340 drift cells. The cells are arranged in 15 concentric layers such that tracks can be reconstructed in three dimensions. A spatial resolution of 220 μm has been achieved for tracks of normal incidence on the drift cells. (orig.)

  1. Drift chamber tracking with neural networks

    International Nuclear Information System (INIS)

    Lindsey, C.S.; Denby, B.; Haggerty, H.

    1992-10-01

    We discuss drift chamber tracking with a commercial log VLSI neural network chip. Voltages proportional to the drift times in a 4-layer drift chamber were presented to the Intel ETANN chip. The network was trained to provide the intercept and slope of straight tracks traversing the chamber. The outputs were recorded and later compared off line to conventional track fits. Two types of network architectures were studied. Applications of neural network tracking to high energy physics detector triggers is discussed

  2. Electron injection in semiconductor drift detectors

    International Nuclear Information System (INIS)

    Rehak, P.; Gatti, E.; Longoni, A.; Sampietro, M.; Castoldi, A.; Vacchi, A.

    1990-01-01

    The paper reports the first successful results of a simple MOS structure to inject electrons at a given position in Silicon Drift Detectors. The structure allows on-line calibration of the drift velocity of electrons within the detector. The calibration is a practical method to trace the temperature dependence of the electron mobility. Several of these injection structures can be implemented in silicon drift detectors without additional steps in the fabrication process. 5 refs., 11 figs

  3. Cooling tower drift: comprehensive case study

    International Nuclear Information System (INIS)

    Laulainen, N.S.; Ulanski, S.L.

    1979-01-01

    A comprehensive experiment to study drift from mechanical drift cooling towers was conducted during June 1978 at the PG and E Pittsburg Power Plant. The data from this study will be used for validation of drift deposition models. Preliminary results show the effects of tower geometry and orientation with respect to the wind and to single- or two-tower operation. The effect of decreasing relative humidity during a test run can also be seen

  4. Construction update and drift velocity calibration for the CLAS drift chamber system

    International Nuclear Information System (INIS)

    Mestayer, M.D.; Barbosa, F.J.; Bonneau, P.; Burtin, E.; Christo, S.; Doolittle, G.; Dytman, S.A.; Gilfoyle, G.P.; Hyde-Wright, C.E.; Klein, A.; Kossov, M.V.; Kuhn, S.E.; Magahiz, R.; Miskimen, R.A.; Murphy, L.Y.; O'Meara, J.E.; Pyron, T.D.; Qin, L.; Raue, B.A.; Schumacher, R.A.; Tuzel, W.; Weinstein, L.B.; Yegneswaran, A.

    1995-01-01

    We briefly describe the drift chamber system for the CLAS detector at CEBAF, concentrating on the method which will be used to calibrate the drift velocity function. We identify key features of the function which should apply to any small-cell drift chamber geometry in which the cathode and anode surfaces are wires. Using these ideas, we describe a simple method to compensate for variations in the drift velocity function due to environmental changes. (orig.)

  5. Construction update and drift velocity calibration for the CLAS drift chamber system

    Energy Technology Data Exchange (ETDEWEB)

    Mestayer, M.D. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States); Barbosa, F.J. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States); Bonneau, P. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States); Burtin, E. [University of South Carolina, Columbia, SC (United States); Christo, S. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States); Doolittle, G. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States); Dytman, S.A. [University of Pittsburg, Pittsburg, PA (United States); Gilfoyle, G.P. [University of Richmond, Richmond, VA (United States); Hyde-Wright, C.E. [Old Dominion University, Norfolk, VA (United States); Klein, A. [Old Dominion University, Norfolk, VA (United States); Kossov, M.V. [Christopher Newport University, Newport News, VA (United States); Kuhn, S.E. [Old Dominion University, Norfolk, VA (United States); Magahiz, R. [Carnegie-Mellon Univ., Pittsburgh, PA (United States); Miskimen, R.A. [University of Massachussetts, Amherst, MA (United States); Murphy, L.Y. [CE Saclay, Gif sur Yvette (France); O`Meara, J.E. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States); Pyron, T.D. [Old Dominion University, Norfolk, VA (United States); Qin, L. [Old Dominion University, Norfolk, VA (United States); Raue, B.A. [Old Dominion University, Norfolk, VA (United States); Schumacher, R.A. [Carnegie-Mellon Univ., Pittsburgh, PA (United States); Tuzel, W. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States); Weinstein, L.B. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States); Yegneswaran, A. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States)

    1995-12-11

    We briefly describe the drift chamber system for the CLAS detector at CEBAF, concentrating on the method which will be used to calibrate the drift velocity function. We identify key features of the function which should apply to any small-cell drift chamber geometry in which the cathode and anode surfaces are wires. Using these ideas, we describe a simple method to compensate for variations in the drift velocity function due to environmental changes. (orig.).

  6. Electron drift time in silicon drift detectors: A technique for high precision measurement of electron drift mobility

    International Nuclear Information System (INIS)

    Castoldi, A.; Rehak, P.

    1995-01-01

    This paper presents a precise absolute measurement of the drift velocity and mobility of electrons in high resistivity silicon at room temperature. The electron velocity is obtained from the differential measurement of the drift time of an electron cloud in a silicon drift detector. The main features of the transport scheme of this class of detectors are: the high uniformity of the electron motion, the transport of the signal electrons entirely contained in the high-purity bulk, the low noise timing due to the very small anode capacitance (typical value 100 fF), and the possibility to measure different drift distances, up to the wafer diameter, in the same semiconductor sample. These features make the silicon drift detector an optimal device for high precision measurements of carrier drift properties. The electron drift velocity and mobility in a 10 kΩ cm NTD n-type silicon wafer have been measured as a function of the electric field in the range of possible operation of a typical drift detector (167--633 V/cm). The electron ohmic mobility is found to be 1394 cm 2 /V s. The measurement precision is better than 1%. copyright 1995 American Institute of Physics

  7. Seepage Model for PA Including Drift Collapse

    International Nuclear Information System (INIS)

    Li, G.; Tsang, C.

    2000-01-01

    The purpose of this Analysis/Model Report (AMR) is to document the predictions and analysis performed using the Seepage Model for Performance Assessment (PA) and the Disturbed Drift Seepage Submodel for both the Topopah Spring middle nonlithophysal and lower lithophysal lithostratigraphic units at Yucca Mountain. These results will be used by PA to develop the probability distribution of water seepage into waste-emplacement drifts at Yucca Mountain, Nevada, as part of the evaluation of the long term performance of the potential repository. This AMR is in accordance with the ''Technical Work Plan for Unsaturated Zone (UZ) Flow and Transport Process Model Report'' (CRWMS M andO 2000 [153447]). This purpose is accomplished by performing numerical simulations with stochastic representations of hydrological properties, using the Seepage Model for PA, and evaluating the effects of an alternative drift geometry representing a partially collapsed drift using the Disturbed Drift Seepage Submodel. Seepage of water into waste-emplacement drifts is considered one of the principal factors having the greatest impact of long-term safety of the repository system (CRWMS M andO 2000 [153225], Table 4-1). This AMR supports the analysis and simulation that are used by PA to develop the probability distribution of water seepage into drift, and is therefore a model of primary (Level 1) importance (AP-3.15Q, ''Managing Technical Product Inputs''). The intended purpose of the Seepage Model for PA is to support: (1) PA; (2) Abstraction of Drift-Scale Seepage; and (3) Unsaturated Zone (UZ) Flow and Transport Process Model Report (PMR). Seepage into drifts is evaluated by applying numerical models with stochastic representations of hydrological properties and performing flow simulations with multiple realizations of the permeability field around the drift. The Seepage Model for PA uses the distribution of permeabilities derived from air injection testing in niches and in the cross drift to

  8. Autoresonant control of drift waves

    DEFF Research Database (Denmark)

    Shagalov, A.G.; Rasmussen, Jens Juul; Naulin, Volker

    2017-01-01

    The control of nonlinear drift waves in a magnetized plasmas column has been investigated. The studies are based on the Hasegawa–Mima model, which is solved on a disk domain with radial inhomogeneity of the plasma density. The system is forced by a rotating potential with varying frequency defined...... on the boundary. To excite and control the waves we apply the autoresonant effect, taking place when the amplitude of the forcing exceeds a threshold value and the waves are phase-locked with the forcing. We demonstrate that the autoresonant approach is applicable for excitation of a range of steady nonlinear...... waves of the lowest azimuthal mode numbers and for controlling their amplitudes and phases. We also demonstrate the excitation of zonal flows (m = 0 modes), which are controlled via the forced modes....

  9. Single wire drift chamber design

    International Nuclear Information System (INIS)

    Krider, J.

    1987-01-01

    This report summarizes the design and prototype tests of single wire drift chambers to be used in Fermilab test beam lines. The goal is to build simple, reliable detectors which require a minimum of electronics. Spatial resolution should match the 300 μm rms resolution of the 1 mm proportional chambers that they will replace. The detectors will be used in beams with particle rates up to 20 KHz. Single track efficiency should be at least 99%. The first application will be in the MT beamline, which has been designed for calibration of CDF detectors. A set of four x-y modules will be used to track and measure the momentum of beam particles

  10. Drift effects in CANDU reactors

    International Nuclear Information System (INIS)

    Koclas, J.; Roy, R.; Marleau, G.

    1993-01-01

    The diffusion equation is an approximation to the transport equation which relies on the validity of Fick's law. Since this law is not explicitly integrated in the transport equation it can only be derived approximately using homogenization theories. However, such homogenization theories state that when the cell is not symmetric Fick's law breaks down due to the presence of an additional term to the neutron current, called the drift term. In fact, this term can be interpreted as a transport correction to Fick's law which tends to increase the neutron current in a direction opposite to that specified by the flux gradient. In this paper, we investigate how the presence of asymmetric liquid zone controllers will modify the flux distribution inside a CANDU core. 5 refs., 2 figs., 1 tab

  11. Energy drift in reversible time integration

    International Nuclear Information System (INIS)

    McLachlan, R I; Perlmutter, M

    2004-01-01

    Energy drift is commonly observed in reversible integrations of systems of molecular dynamics. We show that this drift can be modelled as a diffusion and that the typical energy error after time T is O(√T). (letter to the editor)

  12. TBV 361 RESOLUTION ANALYSIS: EMPLACEMENT DRIFT ORIENTATION

    International Nuclear Information System (INIS)

    Lin, M.; Kicker, D.C.; Sellers, M.D.

    1999-01-01

    The purpose of this To Be Verified/To Be Determined (TBX) resolution analysis is to release ''To Be Verified'' (TBV)-361 related to the emplacement drift orientation. The system design criterion in ''Subsurface Facility System Description Document'' (CRWMS M andO 1998a, p.9) specifies that the emplacement drift orientation relative to the dominant joint orientations should be at least 30 degrees. The specific objectives for this analysis include the following: (1) Collect and evaluate key block data developed for the repository host horizon rock mass. (2) Assess the dominant joint orientations based on available fracture data. (3) Document the maximum block size as a function of drift orientation. (4) Assess the applicability of the drift orientation/joint orientation offset criterion in the ''Subsurface Facility System Description Document'' (CRWMS M andO 1998a, p.9). (5) Consider the effects of seepage on drift orientation. (6) Verify that the viability assessment (VA) drift orientation complies with the drift orientation/joint orientation offset criterion, or provide justifications and make recommendations for modifying the VA emplacement drift layout. In addition to providing direct support to the System Description Document (SDD), the release of TBV-361 will provide support to the Repository Subsurface Design Department. The results from this activity may also provide data and information needs to support the MGR Requirements Department, the MGR Safety Assurance Department, and the Performance Assessment Organization

  13. Silicon drift detectors, present and future prospects

    Science.gov (United States)

    Takahashi, J.; Bellwied, R.; Beuttenmuller, R.; Caines, H.; Chen, W.; Dyke, H.; Hoffmann, G. W.; Humanic, T.; Kotov, I.; Kuczewski, P.; Leonhardt, W.; Li, Z.; Lynn, D.; Minor, R.; Munhoz, M.; Ott, G.; Pandey, S. U.; Schambach, J.; Soja, R.; Sugarbaker, E.; Willson, R. M.

    2001-04-01

    Silicon drift detectors provide unambiguous two-dimensional position information for charged particle detection with a single detector layer. A large area silicon drift detector was developed for the inner tracking detector of the STAR experiment at RHIC. In this paper, we discuss the lessons learned and the future prospects of this technology.

  14. FIELD INVESTIGATION OF THE DRIFT SHADOW

    International Nuclear Information System (INIS)

    G.W. Su; T.J. Kneafsey

    2006-01-01

    A drift shadow is an area immediately beneath an underground void that, in theory, will be relatively drier than the surrounding rock mass. Numerical and analytical models of water flow through unsaturated rock predict the existence of a drift shadow, but field tests confirming the existence of the drift shadow have yet to be performed. Proving the existence of drift shadows and understanding their hydrologic and transport characteristics could provide a better understanding of how contaminants move in the subsurface if released from waste emplacement drifts such as the proposed nuclear waste repository at Yucca Mountain, Nevada. We describe the field program that will be used to investigate the existence of a drift shadow--and the corresponding hydrological process at the Hazel-Atlas silica-sand mine located at the Black Diamond Mines Regional Preserve in Antioch, California. The location and configuration of this mine makes it an excellent site to observe and measure drift shadow characteristics. The mine is located in a porous sandstone unit of the Domengine formation, an approximately 230 meter thick series of interbedded Eocene-age shales, coals, and massive-bedded sandstones. The mining method used at the mine required the development of two parallel drifts, one above the other, driven along the strike of the mined sandstone stratum. This configuration provides the opportunity to introduce water into the rock mass in the upper drift and to observe and measure its flow around the underlying drift. The passive and active hydrologic tests to be performed are described. In the passive method, cores will be obtained in a radial pattern around a drift and will be sectioned and analyzed for in-situ water content using a gravimetric technique, as well as analyzed for chemistry. With the active hydrologic test, water will be introduced into the upper drift of the two parallel drifts and the flow of the water will be tracked as it passes near the bottom drift

  15. Role of drifts in diffusive shock acceleration

    International Nuclear Information System (INIS)

    Decker, R.B.

    1988-01-01

    The role played by shock-associated drifts during the diffusive acceleration of charged particles at collisionless MHD shocks is evaluated. In the rest frame of the shock, the total energy gained by a particle is shown to result from two coupled acceleration mechanisms, the usual first-order Fermi mechanism and the drift mechanism. When averaged over a distribution of particles, the ratio of the drift-associated energy gain to the total energy is found to be independent of the total energy at a given theta1 (the angle between the shock normal and the unperturbed upstream magnetic field) in agreement with theoretical predictions. No evidence is found for drift-associated deceleration, suggesting that drifts always augment acceleration. 35 references

  16. Drift reversal capability in helical systems

    International Nuclear Information System (INIS)

    Yokoyama, M.; Itoh, K.; Okamura, S.

    2002-10-01

    The maximum-J (J is the second adiabatic invariant) capability, i.e., the drift reversal capability, is examined in quasi-axisymmetric (QAS) stellarators and quasi-poloidally symmetric (QPS) stellarators as a possible mechanism for turbulent transport suppression. Due to the existence of non-axisymmetry of the magnetic field strength in QAS configurations, a local maximum of J is created to cause the drift reversal. The increase of magnetic shear in finite beta equilibria also has favorable effect in realizing the drift reversal. The radial variation of the uniform magnetic field component plays a crucial role for the drift reversal in a QPS configuration. Thus, the drift reversal capability and its external controllability are demonstrated for QAS and QPS stellarators, by which the impact of magnetic configuration on turbulent transport can be studied in experiments. (author)

  17. Drift reversal capability in helical systems

    International Nuclear Information System (INIS)

    Yokoyama, M.; Itoh, K.; Okamura, S.; Matsuoka, K.; Nakajima, N.; Itoh, S.-I.; Neilson, G.H.; Zarnstorff, M.C.; Rewoldt, G.

    2003-01-01

    The maximum-J (J is the second adiabatic invariant) capability, i.e., the drift reversal capability, is examined in quasi-axisymmetric (QAS) stellarators and quasi-poloidally symmetric (QPS) stellarators as a possible mechanism for turbulent transport suppression. Due to the existence of non-axisymmetry of the magnetic field strength in QAS configurations, a local maximum of J is created to cause the drift reversal. The increase of magnetic shear in finite beta equilibria also has favorable effect in realizing the drift reversal. The radial variation of the uniform magnetic field component plays a crucial role for the drift reversal in a QPS configuration. Thus, the drift reversal capability and its external controllability are demonstrated for QAS and QPS stellarators, by which the impact of magnetic configuration on turbulent transport can be studied in experiments. (author)

  18. Ground Control for Emplacement Drifts for LA

    International Nuclear Information System (INIS)

    Y. Sun

    2004-01-01

    The purpose of this calculation is to analyze the stability of repository emplacement drifts during the preclosure period, and to provide a final ground support method for emplacement drifts for the License Application (LA). The scope of the work includes determination of input parameter values and loads, selection of appropriate process and methods for the calculation, application of selected methods, such as empirical or analytical, to the calculation, development and execution of numerical models, and evaluation of results. Results from this calculation are limited to use for design of the emplacement drifts and the final ground support system installed in these drifts. The design of non-emplacement openings and their ground support systems is covered in the ''Ground Control for Non-Emplacement Drifts for LA'' (BSC 2004c)

  19. Dissipative drift instability in dusty plasma

    Directory of Open Access Journals (Sweden)

    Nilakshi Das

    2012-03-01

    Full Text Available An investigation has been done on the very low-frequency electrostatic drift waves in a collisional dusty plasma. The dust density gradient is taken perpendicular to the magnetic field B0⃗, which causes the drift wave. In this case, low-frequency drift instabilities can be driven by E1⃗×B0⃗ and diamagnetic drifts, where E1⃗ is the perturbed electric field. Dust charge fluctuation is also taken into consideration for our study. The dust- neutral and ion-neutral collision terms have been included in equations of motion. It is seen that the low-frequency drift instability gets damped in such a system. Both dust charging and collision of plasma particles with the neutrals may be responsible for the damping of the wave. Both analytical and numerical techniques have been used while developing the theory.

  20. Comparison between the ionospheric plasma drift and the motion of artificially induced irregularities as observed by HF backscatter radars

    International Nuclear Information System (INIS)

    Hanuise, C.; Hedberg, A.; Oksman, J.; Nielsen, E.; Stubbe, P.; Kopka, H.

    1986-01-01

    Theories of striation generation by powerful HF waves state that the irregularities should convect with the plasma, without propagating through the medium. This prediction has been checked by observing, with the two SAFARI radars, the backscatter from striations generated in the F-region by the HEATING facility at Tromso. The magnitude and direction of the Doppler velocity of the fluctuations is derived from the line-of-sight velocities measured by the two HF radar stations. The comparison between the electric field, derived from SAFARI, and the E-region current deduced from magnetometer data show that the magnitudes are well correlated. The directions of the velocity and this current are, however, not exactly antiparallel. Another comparison between the SAFARI F-region Doppler velocity and the E-region drift measured by STARE shows, on the average, a good agreement between the estimates. The experimental evidence therefore agrees with the theoretical suggestion that the irregularity motion should be the ExB drift

  1. Drift velocity and pressure monitoring of the CMS muon drift chambers

    CERN Document Server

    Sonnenschein, Lars

    2011-01-01

    The drift velocity in drift tubes of the CMS muon chambers is a key parameter for the muon track reconstruction and trigger. It needs to be monitored precisely in order to detect any deviation from its nominal value. A change in absolute pressure, a variation of the gas admixture or a contamination of the chamber gas by air affect the drift velocity. Furthermore, the temperature and magnetic field influence its value. First data, taken with a dedicated Velocity Drift Chamber (VDC) built by RWTH Aachen IIIA are presented. Another important parameter to be monitored is the pressure inside the muon drift tube chambers. The differential pressure must not exceed a certain value and the absolute pressure has to be kept slightly above ambient pressure to prevent air from entering into the muon drift tube chambers in case of a leak. Latest drift velocity monitoring results are discussed.

  2. Drift velocity and pressure monitoring of the CMS muon drift chambers

    CERN Document Server

    Sonnenschein, Lars

    2010-01-01

    The drift velocity in drift tubes of the CMS muon chambers is a key parameter for the muon track reconstruction and trigger. It needs to be monitored precisely in order to detect any deviation from its nominal value. A change in absolute pressure, a variation of the gas admixture or a contamination of the chamber gas by air affect the drift velocity. Furthermore, the temperature and magnetic field influence its value. First data, taken with a dedicated Velocity Drift Chamber (VDC) built by RWTH Aachen IIIA are presented. Another important parameter to be monitored is the pressure inside the muon drift tube chambers because the drift velocity depends on it. Furthermore the differential pressure must not exceed a certain value and the absolute pressure has to be kept slightly above ambient pressure to prevent air from entering into the muon drift tube chambers in case of a leak. Latest pressure monitoring results are discussed.

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

    International Nuclear Information System (INIS)

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

    1986-01-01

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

  4. Field investigation of the drift shadow

    International Nuclear Information System (INIS)

    Su, Grace W.; Kneafsey, Timothy J.; Ghezzehei, Teamrat A.; Marshall, Brian D.; Cook, Paul J.

    2005-01-01

    A drift shadow is an area immediately beneath an underground void that, in theory, will be relatively drier than the surrounding rockmass. Numerical and analytical models of water flow through unsaturated rock predict the existence of a drift shadow, but field tests confirming its existence have yet to be performed. Proving the existence of drift shadows and understanding their hydrologic and transport characteristics could provide a better understanding of how contaminants move in the subsurface if released from waste emplacement drifts such as the proposed nuclear waste repository at Yucca Mountain, Nevada. We describe the field program that will be used to investigate the existence of a drift shadow and the corresponding hydrological process at the Hazel-Atlas silica-sandmine located at the Black Diamond Mines Regional Preserve in Antioch, California. The location and configuration of this mine makes it an excellent site to observe and measure drift shadow characteristics. The mine is located in a porous sandstone unit of the Domengine Formation, an approximately 230 meter thick series of interbedded Eocene-age shales, coals, and massive-bedded sandstones. The mining method used at the mine required the development of two parallel drifts, one above the other, driven along the strike of the mined sandstone stratum. This configuration provides the opportunity to introduce water into the rockmass in the upper drift and to observe and measure its flow around the underlying drift. The passive and active hydrologic tests to be performed are described. In the passive method, cores will be obtained in a radial pattern around a drift and will be sectioned and analyzed for in-situ water content and chemical constituents. With the active hydrologic test, water will be introduced into the upper drift of the two parallel drifts and the flow of the water will be tracked as it passes near the bottom drift. Tensiometers, electrical resistance probes, neutron probes, and ground

  5. Night-time radial plasma drifts and coupling fluxes at L = 2.3 from whistler mode measurements

    International Nuclear Information System (INIS)

    Andrews, M.K.

    1980-01-01

    A method recently reported for measuring radial drifts in the equatorial plane, and ionosphere-magnetosphere coupling fluxes from the Doppler shifts and group delays on whistler mode signals is applied to VLF transmissions from station NLK on 18.6kHz. Data from 22 nights, primarily during the months November to February, are analysed. When averaged over a time of about 90 min, drifts found are accurate to +-20ms -1 , corresponding to an equatorial electric field accuracy of +-0.05mVm -1 , and fluxes, to +-1.5 x 10 12 el m -2 s -1 (two hemisphere total). Given currently accepted values of coupling fluxes, the flux accuracy is of marginal value on individual nights, but useful information on average behaviour may be obtained. It is found that fluxes generally contribute less than 20% to the measured Doppler shift, most of which is therefore produced by cross-L drifts. To an accuracy of about 20% then, Doppler data alone may give information on these drifts. Doppler shift data previously accumulated over a number of years and relating to signals in ducts near L = 2.3 are re-examined. Dominating the nightly behaviour is an inward drift which reaches a maximum of approximately 100m s -1 as the duct ends cross the dusk terminator, and an outward drift at dawn of the same magnitude which is intitiated when the duct end crosses the terminator in the E or lower F-region. In some months, separate effects can be seen corresponding to sunrise at each end of the duct. (author)

  6. Drift-modeling and monitoring comparisons

    International Nuclear Information System (INIS)

    Chen, N.C.J.; Hanna, S.R.

    1977-01-01

    Congress is looking into the conglomeration of nuclear reactors into energy centers of limited area. Drift from cooling towers can corrode and damage structures in the immediate vicinity of the towers, cause a public nuisance if located near parking lots or high-density traffic areas, and endanger local vegetation. The estimation of salt deposition has relied primarily on predictions from a variety of models, with very few direct measurements. One of the major efforts in our program is to evaluate the assumptions, limitations, and applicabilities of various analytical models for drift deposition prediction. Several drift deposition models are compared using a set of standard input conditions. The predicted maximum drift deposition differs by two orders of magnitude, and the downwind locations of the maximum differ by one order of magnitude. The discrepancies are attributed mainly to different assumptions in the models regarding the initial effective height of the droplets. Current programs in which drift characteristics at the tower mouth and drift deposition downwind of the tower are being measured are summarized. At the present time, drift deposition measurements, sufficiently comprehensive for model verifications, are unavailable. Hopefully, the Chalk Point Program will satisfy this need

  7. Seepage into drifts with mechanical degradation

    International Nuclear Information System (INIS)

    Li, Guomin; Tsang, Chin-Fu

    2002-01-01

    Seepage into drifts in unsaturated tuff is an important issue for the long-term performance of the potential nuclear waste repository at Yucca Mountain, Nevada. Drifts in which waste packages will potentially be emplaced are subject to degradation in the form of rockfall from the drift ceiling induced by stress relief, seismic, or thermal effects. The objective of this study is to calculate seepage rates for various drift-degradation scenarios and for different values of percolation flux for the Topopah Spring middle nonlithophysal (Tptpmn) and the Topopah Spring lower lithophysal (Tptpll) units. Seepage calculations are conducted by (1) defining a heterogeneous permeability model on the drift scale that is consistent with field data, (2) selecting calibrated parameters associated with the Tptpmn and Tptpll units, and (3) simulating seepage on detailed degraded-drift profiles, which were obtained from a separate rock mechanics engineering analysis. The simulation results indicate (1) that the seepage threshold (i.e., the percolation flux at which seepage first occurs) is not significantly changed by drift degradation, and (2) the degradation-induced increase in seepage above the threshold is influenced more by the shape of the cavity created by rockfall than the rockfall volume

  8. Observations of the F-region ionospheric irregularities in the South American sector during the October 2003 "Halloween Storms"

    Directory of Open Access Journals (Sweden)

    Y. Sahai

    2009-12-01

    Full Text Available The response of the ionospheric F-region in the South American sector during the super geomagnetic storms on 29 and 30 October 2003 is studied in the present investigation. In this paper, we present ionospheric sounding observations during the period 29–31 October 2003 obtained at Palmas (a near equatorial location and Sao Jose dos Campos (a location under the southern crest of the equatorial ionospheric anomaly, Brazil, along with observations during the period 27–31 October 2003 from a chain of GPS stations covering the South American sector from Imperatriz, Brazil, to Rio Grande, Argentina. Also, complementary observations that include sequences of all-sky images of the OI 777.4 and 630.0 nm emissions observed at El Leoncito, Argentina, on the nights of 28–29 (geomagnetically quiet night and 29–30 (geomagnetically disturbed night October 2003, and ion densities observed in the South American sector by the DMSP F13, F14 and F15 satellites orbiting at about 800 km on 29 and 30 October 2003 are presented. In addition, global TEC maps derived from GPS observations collected from the global GPS network of International GPS Service (IGS are presented, showing widespread and drastic TEC changes during the different phases of the geomagnetic disturbances. The observations indicate that the equatorial ionospheric irregularities or plasma bubbles extend to the Argentinean station Rawson (geom. Lat. 33.1° S and map at the magnetic equator at an altitude of about 2500 km.

  9. Aspect sensitive E- and F-region SPEAR-enhanced incoherent backscatter observed by the EISCAT Svalbard radar

    Directory of Open Access Journals (Sweden)

    R. S. Dhillon

    2009-01-01

    Full Text Available Previous studies of the aspect sensitivity of heater-enhanced incoherent radar backscatter in the high-latitude ionosphere have demonstrated the directional dependence of incoherent scatter signatures corresponding to artificially excited electrostatic waves, together with consistent field-aligned signatures that may be related to the presence of artificial field-aligned irregularities. These earlier high-latitude results have provided motivation for repeating the investigation in the different geophysical conditions that obtain in the polar cap ionosphere. The Space Plasma Exploration by Active Radar (SPEAR facility is located within the polar cap and has provided observations of RF-enhanced ion and plasma line spectra recorded by the EISCAT Svalbard UHF incoherent scatter radar system (ESR, which is collocated with SPEAR. In this paper, we present observations of aspect sensitive E- and F-region SPEAR-induced ion and plasma line enhancements that indicate excitation of both the purely growing mode and the parametric decay instability, together with sporadic E-layer results that may indicate the presence of cavitons. We note consistent enhancements from field-aligned, vertical and also from 5° south of field-aligned. We attribute the prevalence of vertical scatter to the importance of the Spitze region, and of that from field-aligned to possible wave/irregularity coupling.

  10. Nonlinear Gyrokinetic Theory With Polarization Drift

    International Nuclear Information System (INIS)

    Wang, L.; Hahm, T.S.

    2010-01-01

    A set of the electrostatic toroidal gyrokinetic Vlasov equation and the Poisson equation, which explicitly includes the polarization drift, is derived systematically by using Lie-transform method. The polarization drift is introduced in the gyrocenter equations of motion, and the corresponding polarization density is derived. Contrary to the wide-spread expectation, the inclusion of the polarization drift in the gyrocenter equations of motion does not affect the expression for the polarization density significantly. This is due to modification of the gyrocenter phase-space volume caused by the electrostatic potential [T. S. Hahm, Phys. Plasmas 3, 4658 (1996)].

  11. Pixelated CdZnTe drift detectors

    DEFF Research Database (Denmark)

    Kuvvetli, Irfan; Budtz-Jørgensen, Carl

    2005-01-01

    A technique, the so-called Drift Strip Method (DSM), for improving the CdZnTe detector energy response to hard X-rays and gamma-rays was applied as a pixel geometry. First tests have confirmed that this detector type provides excellent energy resolution and imaging performance. We specifically...... report on the performance of 3 mm thick prototype CZT drift pixel detectors fabricated using material from eV-products. We discuss issues associated with detector module performance. Characterization results obtained from several prototype drift pixel detectors are presented. Results of position...

  12. Computer controlled drifting of Si(Li) detectors

    International Nuclear Information System (INIS)

    Landis, D.A.; Wong, Y.K.; Walton, J.T.; Goulding, F.S.

    1989-01-01

    A relatively inexpensive computer-controlled system for performing the drift process used in fabricating Si(Li) detectors is described. The system employs a small computer to monitor the leakage current, applied voltage and temperature on eight individual drift stations. The associated computer program initializes the drift process, monitors the drift progress and then terminates the drift when an operator set drift time has elapsed. The improved control of the drift with this system has been well demonstrated over the past three years in the fabrication of a variety of Si(Li) detectors. A few representative system responses to detector behavior during the drift process are described

  13. Identification of runoff formation with two dyes in a mid-latitude mountain headwater

    Directory of Open Access Journals (Sweden)

    L. Vlček

    2017-06-01

    Full Text Available Subsurface flow in peat bog areas and its role in the hydrologic cycle has garnered increased attention as water scarcity and floods have increased due to a changing climate. In order to further probe the mechanisms in peat bog areas and contextualize them at the catchment scale, this experimental study identifies runoff formation at two opposite hillslopes in a peaty mountain headwater; a slope with organic peat soils and a shallow phreatic zone (0.5 m below surface, and a slope with mineral Podzol soils and no detectable groundwater (> 2 m below surface. Similarities and differences in infiltration, percolation and preferential flow paths between both hillslopes could be identified by sprinkling experiments with Brilliant Blue and Fluorescein sodium. To our knowledge, this is the first time these two dyes have been compared in their ability to stain preferential flow paths in soils. Dye-stained soil profiles within and downstream of the sprinkling areas were excavated parallel (lateral profiles and perpendicular (frontal profiles to the slopes' gradients. That way preferential flow patterns in the soil could be clearly identified. The results show that biomat flow, shallow subsurface flow in the organic topsoil layer, occurred at both hillslopes; however, at the peat bog hillslope it was significantly more prominent. The dye solutions infiltrated into the soil and continued either as lateral subsurface pipe flow in the case of the peat bog, or percolated vertically towards the bedrock in the case of the Podzol. This study provides evidence that subsurface pipe flow, lateral preferential flow along decomposed tree roots or logs in the unsaturated zone, is a major runoff formation process at the peat bog hillslope and in the adjacent riparian zone.

  14. Mid-latitude shrub steppe plant communities: climate change consequences for soil water resources.

    Science.gov (United States)

    Palmquist, Kyle A; Schlaepfer, Daniel R; Bradford, John B; Lauenroth, William K

    2016-09-01

    In the coming century, climate change is projected to impact precipitation and temperature regimes worldwide, with especially large effects in drylands. We use big sagebrush ecosystems as a model dryland ecosystem to explore the impacts of altered climate on ecohydrology and the implications of those changes for big sagebrush plant communities using output from 10 Global Circulation Models (GCMs) for two representative concentration pathways (RCPs). We ask: (1) What is the magnitude of variability in future temperature and precipitation regimes among GCMs and RCPs for big sagebrush ecosystems, and (2) How will altered climate and uncertainty in climate forecasts influence key aspects of big sagebrush water balance? We explored these questions across 1980-2010, 2030-2060, and 2070-2100 to determine how changes in water balance might develop through the 21st century. We assessed ecohydrological variables at 898 sagebrush sites across the western US using a process-based soil water model, SOILWAT, to model all components of daily water balance using site-specific vegetation parameters and site-specific soil properties for multiple soil layers. Our modeling approach allowed for changes in vegetation based on climate. Temperature increased across all GCMs and RCPs, whereas changes in precipitation were more variable across GCMs. Winter and spring precipitation was predicted to increase in the future (7% by 2030-2060, 12% by 2070-2100), resulting in slight increases in soil water potential (SWP) in winter. Despite wetter winter soil conditions, SWP decreased in late spring and summer due to increased evapotranspiration (6% by 2030-2060, 10% by 2070-2100) and groundwater recharge (26% and 30% increase by 2030-2060 and 2070-2100). Thus, despite increased precipitation in the cold season, soils may dry out earlier in the year, resulting in potentially longer, drier summer conditions. If winter precipitation cannot offset drier summer conditions in the future, we expect big sagebrush regeneration and survival will be negatively impacted, potentially resulting in shifts in the relative abundance of big sagebrush plant functional groups. Our results also highlight the importance of assessing multiple GCMs to understand the range of climate change outcomes on ecohydrology, which was contingent on the GCM chosen. © 2016 by the Ecological Society of America.

  15. An assessment of the Jenkinson and Collison synoptic classification to a continental mid-latitude location

    Science.gov (United States)

    Spellman, Greg

    2017-05-01

    A weather-type catalogue based on the Jenkinson and Collison method was developed for an area in south-west Russia for the period 1961-2010. Gridded sea level pressure data was obtained from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis. The resulting catalogue was analysed for frequency of individual types and groups of weather types to characterise long-term atmospheric circulation in this region. Overall, the most frequent type is anticyclonic (A) (23.3 %) followed by cyclonic (C) (11.9 %); however, there are some key seasonal patterns with westerly circulation being significantly more common in winter than summer. The utility of this synoptic classification is evaluated by modelling daily rainfall amounts. A low level of error is found using a simple model based on the prevailing weather type. Finally, characteristics of the circulation classification are compared to those for the original JC British Isles catalogue and a much more equal distribution of flow types is seen in the former classification.

  16. Mid-latitude Geomagnetic Field Analysis Using BOH Magnetometer: Preliminary Results

    Directory of Open Access Journals (Sweden)

    Junga Hwang

    2011-09-01

    Full Text Available Korea Astronomy and Space Science Institute researchers have installed and operated magnetometers at Mt. Bohyun Observatory to measure the Earth's magnetic field variations in South Korea. We, in 2007, installed a fluxgate magnetometer (RFP-523C to measure H, D, and Z components of the geomagnetic field. In addition, in 2009, we installed a Overhauser proton sensor to measure the absolute total magnetic field F and a three-axis magneto-impedance sensor for spectrum analysis. Currently three types of magnetometer data have been accumulated. In this paper, we provide the preliminary and the first statistical analysis using the BOH magnetometer installed at Mt. Bohyun Observatory. By superposed analysis, we find that daily variations of H, D, and Z shows similar tendency, that is, about 30 minutes before the meridian (11:28 a minimum appears and the time after about 3 hours and 30 minutes (15:28 a maximum appears. Also, a quiet interval start time (19:06 is near the sunset time, and a quiet interval end time (06:40 is near the sunrise time. From the sunset to the sunrise, the value of H has a nearly constant interval, that is, the sun affects the changes in H values. Seasonal variations show similar dependences to the sun. Local time variations show that noon region has the biggest variations and midnight region has the smallest variations. We compare the correlations between geomagnetic variations and activity indices as we expect the geomagnetic variation would contain the effects of geomagnetic activity variations. As a result, the correlation coefficient between H and Dst is the highest (r = 0.947, and other AL, AE, AU index and showed a high correlation. Therefore, the effects of geomagnetic storms and geomagnetic substorms might contribute to the geomagnetic changes significantly.

  17. Hydrological indications of aeolian salts in mid-latitude deserts of ...

    Indian Academy of Sciences (India)

    soils in low-latitude deserts, but is less common in the aeolian sediments from the ... indicating the chemistry of aeolian salts and the associated parent brines may ... erosion, deposition and other processes on sediment properties will bias the ...

  18. Seasonal variability and descent of mid-latitude sporadic E layers at Arecibo

    Directory of Open Access Journals (Sweden)

    N. Christakis

    2009-03-01

    Full Text Available Sporadic E layers (Es follow regular daily patterns in variability and altitude descent, which are determined primarily by the vertical tidal wind shears in the lower thermosphere. In the present study a large set of sporadic E layer incoherent scatter radar (ISR measurements are analyzed. These were made at Arecibo (Geog. Lat. ~18° N; Magnetic Dip ~50° over many years with ISR runs lasting from several hours to several days, covering evenly all seasons. A new methodology is applied, in which both weak and strong layers are clearly traced by using the vertical electron density gradient as a function of altitude and time. Taking a time base equal to the 24-h local day, statistics were obtained on the seasonal behavior of the diurnal and semidiurnal tidal variability and altitude descent patterns of sporadic E at Arecibo. The diurnal tide, most likely the S(1,1 tide with a vertical wavelength around 25 km, controls fully the formation and descent of the metallic Es layers at low altitudes below 110 km. At higher altitudes, there are two prevailing layers formed presumably by vertical wind shears associated mainly with semidiurnal tides. These include: 1 a daytime layer starting at ~130 km around midday and descending down to 105 km by local midnight, and 2 a less frequent and weaker nighttime layer which starts prior to midnight at ~130 km, descending downwards at somewhat faster rate to reach 110 km by sunrise. The diurnal and semidiurnal-like pattern prevails, with some differences, in all seasons. The differences in occurrence, strength and descending speeds between the daytime and nighttime upper layers are not well understood from the present data alone and require further study.

  19. Role of polar anticyclones and mid-latitude cyclones for Arctic summertime sea-ice melting

    Science.gov (United States)

    Wernli, Heini; Papritz, Lukas

    2018-02-01

    Annual minima in Arctic sea-ice extent and volume have been decreasing rapidly since the late 1970s, with substantial interannual variability. Summers with a particularly strong reduction of Arctic sea-ice extent are characterized by anticyclonic circulation anomalies from the surface to the upper troposphere. Here, we investigate the origin of these seasonal circulation anomalies by identifying individual Arctic anticyclones (with a lifetime of typically ten days) and analysing the air mass transport into these systems. We reveal that these episodic upper-level induced Arctic anticyclones are relevant for generating seasonal circulation anomalies. Sea-ice reduction is systematically enhanced during the transient episodes with Arctic anticyclones and the seasonal reduction of sea-ice volume correlates with the area-averaged frequency of Arctic anticyclones poleward of 70° N (correlation coefficient of 0.57). A trajectory analysis shows that these anticyclones result from extratropical cyclones injecting extratropical air masses with low potential vorticity into the Arctic upper troposphere. Our results emphasize the fundamental role of extratropical cyclones and associated diabatic processes in establishing Arctic anticyclones and, in turn, seasonal circulation anomalies, which are of key importance for understanding the variability of summertime Arctic sea-ice melting.

  20. High troposphere O3 filament at mid-latitude: a BORTAS campaign case study

    Science.gov (United States)

    Aruffo, Eleonora; Peterson, David; Di Carlo, Piero; Biancofiore, Fabio; Busilacchio, Marcella; Dari Salisburgo, Cesare; Giammaria, Franco; Bauguitte, Stephane; Lee, James; Moller, Sarah; Hopkins, James; Punjabi, Shalini; Lewis, Alistair C.; Palmer, Paul; Hyer, Edward

    2016-04-01

    During a flight (B625, 24 July 2011) of the BORTAS campaign (BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites, Nova Scotia, Canada, July-August 2011), an increase in the ozone (O3) concentrations has been observed at high altitude (about 7.5 Km a.s.l.) correlated with a significant growth of total peroxy nitrates (∑PNs), CO, NO2, NOy, black carbon (BC), isoprene and other species. We will illustrate the data analysis, the Hysplit back trajectories calculation and the analysis of the meteorological/physical conditions occurred during this case study in order to demonstrate that the O3 filament measured at high altitude over the Atlantic Ocean (between Nova Scotia and the Gulf of St. Lawrence) is a consequence of boreal biomass burning fires.

  1. On the influence of solar activity on the mid-latitude sporadic E layer

    Science.gov (United States)

    Pezzopane, Michael; Pignalberi, Alessio; Pietrella, Marco

    2015-09-01

    To investigate the influence of solar cycle variability on the sporadic E layer (Es), hourly measurements of the critical frequency of the Es ordinary mode of propagation, foEs, and of the blanketing frequency of the Es layer, fbEs, recorded from January 1976 to December 2009 at the Rome (Italy) ionospheric station (41.8° N, 12.5° E), were examined. The results are: (1) a high positive correlation between the F10.7 solar index and foEs as well as between F10.7 and fbEs, both for the whole data set and for each solar cycle separately, the correlation between F10.7 and fbEs being much higher than the one between F10.7 and foEs; (2) a decreasing long-term trend of the F10.7, foEs and fbEs time series, with foEs decreasing more rapidly than F10.7 and fbEs; (3) clear and statistically significant peaks at 11 years in the foEs and fbEs time series, inferred from Lomb-Scargle periodograms.

  2. Ames collaborative study of cosmic-ray neutrons. II. Low- and mid-latitude flights

    International Nuclear Information System (INIS)

    Stephens, L.D.; McCaslin, J.B.; Smith, A.R.; Thomas, R.H.; Hewitt, J.E.; Hughes, L.

    1978-01-01

    The continuing progress of the Ames Collaborative Study of Cosmic Ray Neutrons is described. Data obtained aboard flights from Hawaii at altitudes of 41,000 and 45,000 feet, and in the range of geomagnetic latitude 17 0 N less than or equal to lambda less than or equal to 21 0 N are reported. Preliminary estimates of neutron spectra were made

  3. A Lagrangian analysis of mid-latitude stratospheric ozone variability and long-term trends.

    Science.gov (United States)

    Koch, G.; Wernli, H.; Staehelin, J.; Peter, T.

    2002-05-01

    A systematic Lagrangian investigation is performed of wintertime high-resolution stratospheric ozone soundings at Payerne, Switzerland, from January 1970 to March 2001. For every ozone sounding, 10-day backward trajectories have been calculated on 16 isentropic levels using NCEP reanalysis data. Both the minimum/maximum latitude and potential vorticity (PV) averaged along the trajectories are used as indicators of the air parcels' ``origin''. The importance of transport for the understandin g of single ozone profiles is confirmed by a statistical analysis which shows that negative/positive ozone deviations gener ally coincide with transport from regions with climatologically low/high ozone values. The stable relationship between PV and ozone for the 32 year period indicates either no direct chemical impact or no temporal change of this impact. In the upper layer the PV-ozone relationship changes significantly after 1987 and a separate trend analysis for air masses transported from the polar, midlatitude and subtropical regions shows negative ozone trends in all three categories (with a maximum for the polar region). This is not direct evidence for, but would be in agreement with, an increased chemical ozone depletion in the Arctic since the late 1980s. The reasons for the negative trend in the mid-stratospheric air masses with subtropical origin that are in qualitative agreement with recent satellite observations are presently unknown.

  4. Transition region of TEC enhancement phenomena during geomagnetically disturbed periods at mid-latitudes

    Directory of Open Access Journals (Sweden)

    K. Unnikrishnan

    2005-12-01

    Full Text Available Large-scale TEC perturbations/enhancements observed during the day sectors of major storm periods, 12-13 February 2000, 23 September 1999, 29 October 2003, and 21 November 2003, were studied using a high resolution GPS network over Japan. TEC enhancements described in the present study have large magnitudes (≥25×1016 electrons/m2 compared to the quiet-time values and long periods (≥120 min. The sequential manner of development and the propagation of these perturbations show that they are initiated at the northern region and propagate towards the southern region of Japan, with velocities >350 m/s. On 12 February 2000, remarkably high values of TEC and background content are observed at the southern region, compared to the north, because of the poleward expansion of the equatorial anomaly crest, which is characterized by strong latitudinal gradients near 35° N (26° N geomagnetically. When the TEC enhancements, initiating at the north, propagate through the region 39-34° N (30-25° N geomagnetically, they undergo transitions characterized by a severe decrease in amplitude of TEC enhancements. This may be due to their interaction with the higher background content of the expanded anomaly crest. However, at the low-latitude region, below 34° N, an increase in TEC is manifested as an enhanced ionization pattern (EIP. This could be due to the prompt penetration of the eastward electric field, which is evident from high values of the southward Interplanetary Magnetic Field component (IMF Bz and AE index. The TEC perturbations observed on the other storm days also exhibit similar transitions, characterized by a decreasing magnitude of the perturbation component, at the region around 39-34° N. In addition to this, on the other storm days, at the low-latitude region, below 34° N, an increase in TEC (EIP feature also indicates the repeatability of the above scenario. It is found that, the latitude and time at which the decrease in magnitude of the perturbation component/amplitude of the TEC enhancement are matching with the latitude and time of the appearance of the high background content. In the present study, on 12 February 2000, the F-layer height increases at Wakkanai and Kokubunji, by exhibiting a typical dispersion feature of LSTID, or passage of an equatorward surge, which is matching with the time of occurrence of the propagating TEC perturbation component. Similarly, on 29 October 2003, the increase in F-layer heights by more than 150km at Wakkanai and 90 km at Kokubunji around 18:00 JST, indicates the role of the equatorward neutral wind. On that day, TEC perturbation observed at the northern region, after 18:30 JST, which propagates towards south, could be caused mainly by the equatorward neutral wind, leading to an F-layer height increase. These observations imply the role of the equatorward neutral wind, which increases the F-layer height, by lifting the ionization to the regions of lower loss during daytime, when production is still taking place, which, in turn, increases the TEC values.

    Large-scale traveling ionospheric disturbances (LSTIDs are considered as ionospheric manifestations of the passage of Atmospheric Gravity Waves (AGWs that are generated at the high latitude by energy input from the magnetosphere to the low-latitude ionosphere. This study shows that large-scale TEC perturbations observed here are produced at the northern region due to the combined effects of the equatorward neutral wind, the subsequent F-layer height increase, and LSTIDs. When these perturbation components propagate through the region, 39-34° N, they undergo transitions characterised by a decrease in magnitude. Also, at the low-latitude region, below 34° N, an increase in the TEC exhibits EIP feature, due to the prompt penetration of the eastward electric field.

  5. Climatologies of tides at mid-latitudes in the lower termosphere

    International Nuclear Information System (INIS)

    Cevolani, G.

    1991-01-01

    Time variations of the semi-diurnal and diurnal tides observed at Budrio (45N, 12E) in the wind structure of the lower termosphere ((80-110) km) throughout the period 1976-1990 are herewith represented as monthly contours of both amplitudes and phases vs. height. The semi-diurnal tide has more marked seasonal variations, showing amplitudes generally larger than the diurnal ones ((10-30) m/s vs. (5-15) m/s). The vertical wavelengths are longer in summer than in winter, at least below 100 km. Agreement with new numerical models for semi-diurnal tide at 50N appears to be satisfactory

  6. Average electron content gradients and nighttime electron fluxes in the mid-latitude ionosphere

    International Nuclear Information System (INIS)

    Ebel, A.; Schmidt, G.; Tauriainen, A.

    1976-01-01

    Observations of the total electron content (TEC) made at Lindau (52 0 N, 10 0 E) by means of low orbiting satellites during the period March 1970 to December 1972 enabled evaluation of the meridional component of the TEC gradient over the station. The behaviour of this component is investigated in connection with the temporal TEC changes using the medians of both quantities. The gradient reflects well known seasonal changes in the ionosphere such as the semiannual anomaly around noon which leads to relatively strong TEC increases towards the south (up to 9 x 10 15 m -2 degree -1 ). For the time shortly after midnight, a second semiannual variation of the gradient shows up with enhanced southward TEC increases. Regular northward ionization increases are found near sunrise in summer. Average TEC increases or markedly reduced decreases during the night were obtained for almost every month during the observation period. This special phenomenon of the nighttime ionosphere is discussed with respect to maximum input fluxes of different kinds, which would be necessary to produce the observed effects. Under normal nighttime conditions, the TEC gradients can lead to changes in the ionization of up to 3 x 10 12 m -2 s -1 due to horizontal plasma transport, when electric fields of reasonable strength (approximately 2 mV/m) are present. (author)

  7. Mid-Latitude Mobile Wideband HF- NVIS Channel Analysis: Part 1

    Science.gov (United States)

    2017-09-14

    commercial satellite communications (SATCOM) for beyond line-of-sight (LOS) links. However, standard HF systems operating over a 3-kHz bandwidth do not...citation of trade names and names of names of manufacturers is not to be construed as official government endorsement or approval of commercial ...Division EXECUTIVE SUMMARY High frequency (HF) links (2 to 30 MHz) are an alternative to the cost and tactical fragility of commercial satellite

  8. Experimental electron density profiles of the mid-latitude lower ionosphere and winter anomaly

    International Nuclear Information System (INIS)

    Rapoport, Z.Ts.; Sinel'nikov, V.M.

    1996-01-01

    Summarized measurements of high-latitude electron density profiles of N e lower ionosphere, obtained at M100B meteorological rockets by precision method of coherent frequencies during 1979-1990 at the Volgograd test site (φ = 48 deg 41' N; λ = 44 deg 21 E), are presented. The profiles obtained represent average values of electron density at various altitudes of lower ionosphere (h = 70-100 km) during night and day time hours in winter and non winter periods. Increased electron density values during daytime hours in winter are related to winter anomaly phenomenon. 36 refs.; 1 fig

  9. Relation of geomagnetic pulsations to parmeters of mid-latitude lower ionosphere

    International Nuclear Information System (INIS)

    Dorokhov, V.L.; Kostrov, L.S.; Martynenko, S.I.; Piven', L.A.; Pushin, V.F.; Shemet, A.S.

    1989-01-01

    Results of experimental investigation of the effect of geomagnetic pulsations on parameters of medium-latitude lower ionosphere with the use of methods of partial reflections and Doppler probing at short waves are presented. The relation between changes in geomagnetic field and intensity of partially reflected radiosignals is detected

  10. Effects of a mid-latitude solar eclipse on the thermosphere and ionosphere: a modelling study

    OpenAIRE

    Müller-Wodarg, I. C. F.; Aylward, A. D.; Lockwood, Mike

    1998-01-01

    A modelling study is presented which investigates in-situ generated changes of the thermosphere and ionosphere during a solar eclipse. Neutral temperatures are expected to drop by up to 40 degrees K at 240 km height in the totality footprint, with neutral winds of up to 26 m/s responding to the change of pressure. Both temperatures and winds are found to respond with a time lag of 30 min after the passing of the Moon's shadow. A gravity wave is generated in the neutral atmosphere and propagat...

  11. Differences in mid-latitude stratospheric winds between reanalysis data and versus radiosonde observations at Prague

    Czech Academy of Sciences Publication Activity Database

    Kozubek, Michal; Laštovička, Jan; Križan, Peter

    2014-01-01

    Roč. 32, č. 4 (2014), s. 353-366 ISSN 0992-7689 R&D Projects: GA ČR GAP209/10/1792; GA MŠk LD12070 Institutional support: RVO:68378289 Keywords : meteorology * atm ospheric dynamics * middle atm osphere dynamics Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.709, year: 2014 http://www.ann-geophys.net/32/353/2014/angeo-32-353-2014.html

  12. Structural Relationships Of Selected Tree Species at Several Mid-Latitude Deciduous Forest Sites in Virginia

    Science.gov (United States)

    1999-09-01

    are included in the deciduous analyses. They are mockernut hickory { Carya tomentosa), American elm {Ulmus americana), pecan { Carya illinoensis ), and...alba, white ash (Fraxinus americana), and pecan ( Carya illinoensis ). A number of these trees have plaques indicating the dates of planting (late 1700s

  13. Hydrological indications of aeolian salts in mid-latitude deserts of ...

    Indian Academy of Sciences (India)

    The compositional differences between aeolian salts and local natural waters is evident,indicating the chemistry of aeolian salts and the associated parent brines may be significantly differentthan that predicted for hydrologically closed systems. The formation of aeolian salts in the studieddeserts is strongly controlled by ...

  14. River response to variations of periglacial climate in mid-latitude Europe.

    NARCIS (Netherlands)

    Mol, J.; Vandenberghe, J.; Kasse, C.

    2000-01-01

    The Last Glaciation was characterised by considerable changes in climate. Many European river basins reacted to these changes by initial incision and subsequent pattern change. Earlier research explained this by the time lag of vegetation development after a climatic change, which considerably

  15. Airborne Observations of Water Vapor Deuterium Excess in the Mid-Latitude Lower Troposphere

    Science.gov (United States)

    Salmon, O. E.; Welp, L.; Shepson, P. B.; Stirm, B. H.

    2017-12-01

    Water vapor is responsible for over half of the natural atmospheric greenhouse effect. As global temperatures increase due to fossil fuel combustion, atmospheric water vapor concentrations are also expected to increase in positive feedback. Additionally, studies have shown that urban areas can influence humidity levels, and the frequency and intensity of precipitation events. It is thus important to understand anthropogenic modification of the hydrological cycle, particularly around urban areas, where over half of the world's population resides. Airborne measurements of water vapor isotopologues containing 2H and 18O were conducted to better understand processes influencing atmospheric moisture levels around urban areas. Airborne measurements were conducted around the Indianapolis and Washington, D.C.-Baltimore areas during afternoon hours in February and March 2016, using a Los Gatos Research Water Vapor Isotope Analyzer installed in Purdue University's experimental aircraft, the Airborne Laboratory for Atmospheric Research. The measurements of 2H and 18O allow for the calculation of deuterium excess (= δ2H - 8*δ18O), which provides information about non-equilibrium processes, such as kinetic effects, air parcel mixing, and transpiration. There are few studies that have reported observations of deuterium excess above the surface level ( 100 m). During the measurement campaign, vertical profiles were frequently conducted from 300 m above the ground to an altitude of approximately 1.5 km, effectively characterizing water vapor isotope profiles spanning the boundary layer and lower free troposphere. Measurements probed the transition from planetary boundary layer air to free troposphere air to provide high resolution deuterium excess information across this interface. Processes such as Rayleigh distillation, atmospheric mixing, and surface fluxes potentially impacting water vapor deuterium excess through the boundary layer and free troposphere with be discussed.

  16. Transition region of TEC enhancement phenomena during geomagnetically disturbed periods at mid-latitudes

    Directory of Open Access Journals (Sweden)

    K. Unnikrishnan

    2005-12-01

    Full Text Available Large-scale TEC perturbations/enhancements observed during the day sectors of major storm periods, 12-13 February 2000, 23 September 1999, 29 October 2003, and 21 November 2003, were studied using a high resolution GPS network over Japan. TEC enhancements described in the present study have large magnitudes (≥25×1016 electrons/m2 compared to the quiet-time values and long periods (≥120 min. The sequential manner of development and the propagation of these perturbations show that they are initiated at the northern region and propagate towards the southern region of Japan, with velocities >350 m/s. On 12 February 2000, remarkably high values of TEC and background content are observed at the southern region, compared to the north, because of the poleward expansion of the equatorial anomaly crest, which is characterized by strong latitudinal gradients near 35° N (26° N geomagnetically. When the TEC enhancements, initiating at the north, propagate through the region 39-34° N (30-25° N geomagnetically, they undergo transitions characterized by a severe decrease in amplitude of TEC enhancements. This may be due to their interaction with the higher background content of the expanded anomaly crest. However, at the low-latitude region, below 34° N, an increase in TEC is manifested as an enhanced ionization pattern (EIP. This could be due to the prompt penetration of the eastward electric field, which is evident from high values of the southward Interplanetary Magnetic Field component (IMF Bz and AE index. The TEC perturbations observed on the other storm days also exhibit similar transitions, characterized by a decreasing magnitude of the perturbation component, at the region around 39-34° N. In addition to this, on the other storm days, at the low-latitude region, below 34° N, an increase in TEC (EIP feature also indicates the repeatability of the above scenario. It is found that, the latitude and time at which the decrease in magnitude of the perturbation component/amplitude of the TEC enhancement are matching with the latitude and time of the appearance of the high background content. In the present study, on 12 February 2000, the F-layer height increases at Wakkanai and Kokubunji, by exhibiting a typical dispersion feature of LSTID, or passage of an equatorward surge, which is matching with the time of occurrence of the propagating TEC perturbation component. Similarly, on 29 October 2003, the increase in F-layer heights by more than 150km at Wakkanai and 90 km at Kokubunji around 18:00 JST, indicates the role of the equatorward neutral wind. On that day, TEC perturbation observed at the northern region, after 18:30 JST, which propagates towards south, could be caused mainly by the equatorward neutral wind, leading to an F-layer height increase. These observations imply the role of the equatorward neutral wind, which increases the F-layer height, by lifting the ionization to the regions of lower loss during daytime, when production is still taking place, which, in turn, increases the TEC values. Large-scale traveling ionospheric disturbances (LSTIDs are considered as ionospheric manifestations of the passage of Atmospheric Gravity Waves (AGWs that are generated at the high latitude by energy input from the magnetosphere to the low-latitude ionosphere. This study shows that large-scale TEC perturbations observed here are produced at the northern region due to the combined effects of the equatorward neutral wind, the subsequent F-layer height increase, and LSTIDs. When these perturbation components propagate through the region, 39-34° N, they undergo transitions characterised by a decrease in magnitude. Also, at the low-latitude region, below 34° N, an increase in the TEC exhibits EIP feature, due to the prompt penetration of the eastward electric field.

  17. Northern and Mid-Latitude Soil Database, Version 1, R1

    Data.gov (United States)

    National Aeronautics and Space Administration — The U.S. Department of Agriculture, Agriculture and Agri-Food Canada, the Russian Academy of Agricultural Sciences, the University of Copenhagen Institute of...

  18. Mid-latitude shrub steppe plant communities: Climate change consequences for soil water resources

    Science.gov (United States)

    Palmquist, Kyle A.; Schlaepfer, Daniel R.; Bradford, John B.; Lauenroth, Willliam K.

    2016-01-01

    In the coming century, climate change is projected to impact precipitation and temperature regimes worldwide, with especially large effects in drylands. We use big sagebrush ecosystems as a model dryland ecosystem to explore the impacts of altered climate on ecohydrology and the implications of those changes for big sagebrush plant communities using output from 10 Global Circulation Models (GCMs) for two representative concentration pathways (RCPs). We ask: 1) What is the magnitude of variability in future temperature and precipitation regimes among GCMs and RCPs for big sagebrush ecosystems and 2) How will altered climate and uncertainty in climate forecasts influence key aspects of big sagebrush water balance? We explored these questions across 1980-2010, 2030-2060, and 2070-2100 to determine how changes in water balance might develop through the 21st century. We assessed ecohydrological variables at 898 sagebrush sites across the western US using a process-based soil water model, SOILWAT to model all components of daily water balance using site-specific vegetation parameters and site-specific soil properties for multiple soil layers. Our modeling approach allowed for changes in vegetation based on climate. Temperature increased across all GCMs and RCPs, while changes in precipitation were more variable across GCMs. Winter and spring precipitation was predicted to increase in the future (7% by 2030-2060, 12% by 2070-2100), resulting in slight increases in soil water potential (SWP) in winter. Despite wetter winter soil conditions, SWP decreased in late spring and summer due to increased evapotranspiration (6% by 2030-2060, 10% by 2070-2100) and groundwater recharge (26% and 30% increase by 2030-2060 and 2070-2100). Thus, despite increased precipitation in the cold season, soils may dry out earlier in the year, resulting in potentially longer drier summer conditions. If winter precipitation cannot offset drier summer conditions in the future, we expect big sagebrush regeneration and survival will be negatively impacted, potentially resulting in shifts in the relative abundance of big sagebrush plant functional groups. Our results also highlight the importance of assessing multiple GCMs to understand the range of climate change outcomes on ecohydrology, which was contingent on the GCM chosen.

  19. Air-snow exchange of nitrogen oxides and ozone at a polluted mid-latitude site

    Science.gov (United States)

    Murphy, Jennifer G.; Hong, Angela C.; Quinn, Patricia K.; Bates, Tim

    2017-04-01

    Vertical gradients of O3, NO, NO2 and NOywere measured within and above the snowpack between January 17 to February 14, 2014 as part of the Uintah Basin Winter Ozone Study. During the first half of the campaign, the snowpack was relatively aged and contained high levels of inorganic ions and dissolved and particulate organics. A snowfall on Jan 31 added 5 cm of fresh snow with lower solute concentrations to the top of the snowpack. Vertical gradients (ΔC = C(25cm) - C(125cm)) in the measured gas phase species were used to investigate the role of the snowpack as a source or sink. Small positive gradients were seen for NO, peaking in the middle of the day, which much larger negative gradients were seen for O3 and NOy. Comparing the fresh to the aged snowpacks, there was a noticeable decrease in the gradient for O3, but not for NOy over the fresh snow, implying a chemical control of O3 deposition to the snow. The ratio of the gradient of NOx to the gradient of NOy was used to determine a snowpack NOy recycling ratio (emission/deposition) of approximately 4 %, consistent with independent estimates of low nitrate photolysis rates inferred from nitrogen isotopes by Zatko et al., (2016). Reference Zatko et al., The magnitude of the snow-sourced reactive nitrogen flux to the boundary layer in the Uintah Basin, Utah, USA, Atmos. Chem. Phys., 16, 13837-13851, 2016.

  20. Mid-latitude tropospheric ozone columns from the MOZAIC program: climatology and interannual variability

    Directory of Open Access Journals (Sweden)

    R. M. Zbinden

    2006-01-01

    Full Text Available Several thousands of ozone vertical profiles collected in the course of the MOZAIC programme (Measurements of Ozone, Water Vapour, Carbon Monoxide and Nitrogen Oxides by In-Service Airbus Aircraft from August 1994 to February 2002 are investigated to bring out climatological and interannual variability aspects. The study is centred on the most frequently visited MOZAIC airports, i.e. Frankfurt (Germany, Paris (France, New York (USA and the cluster of Tokyo, Nagoya and Osaka (Japan. The analysis focuses on the vertical integration of ozone from the ground to the dynamical tropopause and the vertical integration of stratospheric-origin ozone throughout the troposphere. The characteristics of the MOZAIC profiles: frequency of flights, accuracy, precision, and depth of the troposphere observed, are presented. The climatological analysis shows that the Tropospheric Ozone Column (TOC seasonal cycle ranges from a wintertime minimum at all four stations to a spring-summer maximum in Frankfurt, Paris, and New York. Over Japan, the maximum occurs in spring presumably because of the earlier springtime sun. The incursion of monsoon air masses into the boundary layer and into the mid troposphere then steeply diminishes the summertime value. Boundary layer contributions to the TOC are 10% higher in New York than in Frankfurt and Paris during spring and summer, and are 10% higher in Japan than in New York, Frankfurt and Paris during autumn and early spring. Local and remote anthropogenic emissions, and biomass burning over upstream regions of Asia may be responsible for the larger low- and mid-tropospheric contributions to the tropospheric ozone column over Japan throughout the year except during the summer-monsoon season. A simple Lagrangian analysis has shown that a minimum of 10% of the TOC is of stratospheric-origin throughout the year. Investigation of the short-term trends of the TOC over the period 1995–2001 shows a linear increase 0.7%/year in Frankfurt, 0.8%/year in Japan, 1.1%/year in New York and 1.6%/year in Paris for the reduced 1995–1999 period. Dominant ingredients of these positive short-term trends are the continuous increase of wintertime tropospheric ozone columns from 1996 to 1999 and the positive contributions of the mid troposphere whatever the season.

  1. How birds weather the weather: avian migration in the mid-latitudes

    NARCIS (Netherlands)

    Kemp, M.U.

    2012-01-01

    The life cycle of many bird species involves the twice-annual movement between a breeding ground and a wintering ground that we refer to as `migration'. To complete these journeys, birds must successfully navigate many obstacles including a dynamic atmosphere. To make optimal use of this

  2. Corona-producing ice clouds: A case study of a cold mid-latitude cirrus layer

    International Nuclear Information System (INIS)

    Sassen, K.; Mace, G.G.; Hallett, J.; Poellot, M.R.

    1998-01-01

    A high (14.0-km), cold (-71.0thinsp degree C) cirrus cloud was studied by ground-based polarization lidar and millimeter radar and aircraft probes on the night of 19 April 1994 from the Cloud and Radiation Testbed site in northern Oklahoma. A rare cirrus cloud lunar corona was generated by this 1 - 2-km-deep cloud, thus providing an opportunity to measure the composition in situ, which had previously been assumed only on the basis of lidar depolarization data and simple diffraction theory for spheres. In this case, corona ring analysis indicated an effective particle diameter of ∼22 μm. A variety of in situ data corroborates the approximate ice-particle size derived from the passive retrieval method, especially near the cloud top, where impacted cloud samples show simple solid crystals. The homogeneous freezing of sulfuric acid droplets of stratospheric origin is assumed to be the dominant ice-particle nucleation mode acting in corona-producing cirrus clouds. It is speculated that this process results in a previously unrecognized mode of acid-contaminated ice-particle growth and that such small-particle cold cirrus clouds are potentially a radiatively distinct type of cloud. copyright 1998 Optical Society of America

  3. Unintended Positional Drift and Its Potential Solutions

    DEFF Research Database (Denmark)

    Nilsson, Niels Christian; Serafin, Stefania; Nordahl, Rolf

    2013-01-01

    many users unintentionally move forward while walking in place. We refer to this phenomenon accidental movement as Unintended Positional Drift. The poster presents evidence of the phenomenon's existence and subsequently discusses different design solutions which potentially could circumvent the problem....

  4. CROSS DRIFT ALCOVE/NICHE UTILITIES ANALYSIS

    International Nuclear Information System (INIS)

    S. Goodin

    1999-01-01

    The purpose of this analysis is to provide the design basis and general arrangement requirements of the non-potable water, waste water, compressed air and ventilation (post excavation) utilities required in support of the Cross Drift alcoves and niches

  5. Travelling fronts in stochastic Stokes’ drifts

    KAUST Repository

    Blanchet, Adrien; Dolbeault, Jean; Kowalczyk, Michał

    2008-01-01

    By analytical methods we study the large time properties of the solution of a simple one-dimensional model of stochastic Stokes' drift. Semi-explicit formulae allow us to characterize the behaviour of the solutions and compute global quantities

  6. Self-shielding flex-circuit drift tube, drift tube assembly and method of making

    Science.gov (United States)

    Jones, David Alexander

    2016-04-26

    The present disclosure is directed to an ion mobility drift tube fabricated using flex-circuit technology in which every other drift electrode is on a different layer of the flex-circuit and each drift electrode partially overlaps the adjacent electrodes on the other layer. This results in a self-shielding effect where the drift electrodes themselves shield the interior of the drift tube from unwanted electro-magnetic noise. In addition, this drift tube can be manufactured with an integral flex-heater for temperature control. This design will significantly improve the noise immunity, size, weight, and power requirements of hand-held ion mobility systems such as those used for explosive detection.

  7. Strange Attractors in Drift Wave Turbulence

    International Nuclear Information System (INIS)

    Lewandowski, J.L.V.

    2003-01-01

    A multi-grid part-in-cell algorithm for a shearless slab drift wave model with kinetic electrons is presented. The algorithm, which is based on an exact separation of adiabatic and nonadiabatic electron responses, is used to investigate the presence of strange attractors in drift wave turbulence. Although the simulation model has a large number of degrees of freedom, it is found that the strange attractor is low-dimensional and that it is strongly affected by dissipative (collisional) effects

  8. SEEPAGE MODEL FOR PA INCLUDING DRIFT COLLAPSE

    International Nuclear Information System (INIS)

    C. Tsang

    2004-01-01

    The purpose of this report is to document the predictions and analyses performed using the seepage model for performance assessment (SMPA) for both the Topopah Spring middle nonlithophysal (Tptpmn) and lower lithophysal (Tptpll) lithostratigraphic units at Yucca Mountain, Nevada. Look-up tables of seepage flow rates into a drift (and their uncertainty) are generated by performing numerical simulations with the seepage model for many combinations of the three most important seepage-relevant parameters: the fracture permeability, the capillary-strength parameter 1/a, and the percolation flux. The percolation flux values chosen take into account flow focusing effects, which are evaluated based on a flow-focusing model. Moreover, multiple realizations of the underlying stochastic permeability field are conducted. Selected sensitivity studies are performed, including the effects of an alternative drift geometry representing a partially collapsed drift from an independent drift-degradation analysis (BSC 2004 [DIRS 166107]). The intended purpose of the seepage model is to provide results of drift-scale seepage rates under a series of parameters and scenarios in support of the Total System Performance Assessment for License Application (TSPA-LA). The SMPA is intended for the evaluation of drift-scale seepage rates under the full range of parameter values for three parameters found to be key (fracture permeability, the van Genuchten 1/a parameter, and percolation flux) and drift degradation shape scenarios in support of the TSPA-LA during the period of compliance for postclosure performance [Technical Work Plan for: Performance Assessment Unsaturated Zone (BSC 2002 [DIRS 160819], Section I-4-2-1)]. The flow-focusing model in the Topopah Spring welded (TSw) unit is intended to provide an estimate of flow focusing factors (FFFs) that (1) bridge the gap between the mountain-scale and drift-scale models, and (2) account for variability in local percolation flux due to

  9. Ponderomotive modification of drift tearing modes

    International Nuclear Information System (INIS)

    Urquijo, G.; Singh, R.; Sen, A.

    1997-01-01

    The linear characteristics of drift tearing modes are investigated in the presence of a significant background of radio-frequency (RF) waves in the ion cyclotron range of frequencies. The ponderomotive force, arising from the radial gradients in the RF field energy, is found to significantly modify the inner layer solutions of the drift tearing modes. It can have a stabilizing influence, even at moderate RF powers, provided the field energy has a decreasing radial profile at the mode rational surface. (author)

  10. Unstable universal drift eigenmodes in toroidal plasmas

    International Nuclear Information System (INIS)

    Cheng, C.Z.; Chen, L.

    1980-01-01

    The eigenmode equation describing ballooning collisionless drift instabilities is analyzed both analytically and numerically. A new branch of eigenmodes, which corresponds to quasi-bound states due to toroidal coupling effects such as ion delB drifts, is shown to be destabilized by electron Landau damping for typical tokamak parameters. This branch cannot be understood by the strong coupling approximation. However, the slab-like (Pearlstein--Berk-type) branch is found to remain stable and experience enhanced shear damping

  11. Effects of Fault Displacement on Emplacement Drifts

    International Nuclear Information System (INIS)

    Duan, F.

    2000-01-01

    The purpose of this analysis is to evaluate potential effects of fault displacement on emplacement drifts, including drip shields and waste packages emplaced in emplacement drifts. The output from this analysis not only provides data for the evaluation of long-term drift stability but also supports the Engineered Barrier System (EBS) process model report (PMR) and Disruptive Events Report currently under development. The primary scope of this analysis includes (1) examining fault displacement effects in terms of induced stresses and displacements in the rock mass surrounding an emplacement drift and (2 ) predicting fault displacement effects on the drip shield and waste package. The magnitude of the fault displacement analyzed in this analysis bounds the mean fault displacement corresponding to an annual frequency of exceedance of 10 -5 adopted for the preclosure period of the repository and also supports the postclosure performance assessment. This analysis is performed following the development plan prepared for analyzing effects of fault displacement on emplacement drifts (CRWMS M and O 2000). The analysis will begin with the identification and preparation of requirements, criteria, and inputs. A literature survey on accommodating fault displacements encountered in underground structures such as buried oil and gas pipelines will be conducted. For a given fault displacement, the least favorable scenario in term of the spatial relation of a fault to an emplacement drift is chosen, and the analysis is then performed analytically. Based on the analysis results, conclusions are made regarding the effects and consequences of fault displacement on emplacement drifts. Specifically, the analysis will discuss loads which can be induced by fault displacement on emplacement drifts, drip shield and/or waste packages during the time period of postclosure

  12. Drift waves in a weakly ionized plasma

    DEFF Research Database (Denmark)

    Popovic, M.; Melchior, H.

    1968-01-01

    A dispersion relation for low frequency drift waves in a weakly ionized plasma has been derived, and through numerical calculations the effect of collisions between the charged and the neutral particles is estimated.......A dispersion relation for low frequency drift waves in a weakly ionized plasma has been derived, and through numerical calculations the effect of collisions between the charged and the neutral particles is estimated....

  13. Calibration of the CMS Drift Tube Chambers and Measurement of the Drift Velocity with Cosmic Rays

    CERN Document Server

    Chatrchyan, S; Sirunyan, A M; Adam, W; Arnold, B; Bergauer, H; Bergauer, T; Dragicevic, M; Eichberger, M; Erö, J; Friedl, M; Frühwirth, R; Ghete, V M; Hammer, J; Hänsel, S; Hoch, M; Hörmann, N; Hrubec, J; Jeitler, M; Kasieczka, G; Kastner, K; Krammer, M; Liko, D; Magrans de Abril, I; Mikulec, I; Mittermayr, F; Neuherz, B; Oberegger, M; Padrta, M; Pernicka, M; Rohringer, H; Schmid, S; Schöfbeck, R; Schreiner, T; Stark, R; Steininger, H; Strauss, J; Taurok, A; Teischinger, F; Themel, T; Uhl, D; Wagner, P; Waltenberger, W; Walzel, G; Widl, E; Wulz, C E; Chekhovsky, V; Dvornikov, O; Emeliantchik, I; Litomin, A; Makarenko, V; Marfin, I; Mossolov, V; Shumeiko, N; Solin, A; Stefanovitch, R; Suarez Gonzalez, J; Tikhonov, A; Fedorov, A; Karneyeu, A; Korzhik, M; Panov, V; Zuyeuski, R; Kuchinsky, P; Beaumont, W; Benucci, L; Cardaci, M; De Wolf, E A; Delmeire, E; Druzhkin, D; Hashemi, M; Janssen, X; Maes, T; Mucibello, L; Ochesanu, S; Rougny, R; Selvaggi, M; Van Haevermaet, H; Van Mechelen, P; Van Remortel, N; Adler, V; Beauceron, S; Blyweert, S; D'Hondt, J; De Weirdt, S; Devroede, O; Heyninck, J; Kalogeropoulos, A; Maes, J; Maes, M; Mozer, M U; Tavernier, S; Van Doninck, W; Van Mulders, P; Villella, I; Bouhali, O; Chabert, E C; Charaf, O; Clerbaux, B; De Lentdecker, G; Dero, V; Elgammal, S; Gay, A P R; Hammad, G H; Marage, P E; Rugovac, S; Vander Velde, C; Vanlaer, P; Wickens, J; Grunewald, M; Klein, B; Marinov, A; Ryckbosch, D; Thyssen, F; Tytgat, M; Vanelderen, L; Verwilligen, P; Basegmez, S; Bruno, G; Caudron, J; Delaere, C; Demin, P; Favart, D; Giammanco, A; Grégoire, G; Lemaitre, V; Militaru, O; Ovyn, S; Piotrzkowski, K; Quertenmont, L; Schul, N; Beliy, N; Daubie, E; Alves, G A; Pol, M E; Souza, M H G; Carvalho, W; De Jesus Damiao, D; De Oliveira Martins, C; Fonseca De Souza, S; Mundim, L; Oguri, V; Santoro, A; Silva Do Amaral, S M; Sznajder, A; Fernandez Perez Tomei, T R; Ferreira Dias, M A; Gregores, E M; Novaes, S F; Abadjiev, K; Anguelov, T; Damgov, J; Darmenov, N; Dimitrov, L; Genchev, V; Iaydjiev, P; Piperov, S; Stoykova, S; Sultanov, G; Trayanov, R; Vankov, I; Dimitrov, A; Dyulendarova, M; Kozhuharov, V; Litov, L; Marinova, E; Mateev, M; Pavlov, B; Petkov, P; Toteva, Z; Chen, G M; Chen, H S; Guan, W; Jiang, C H; Liang, D; Liu, B; Meng, X; Tao, J; Wang, J; Wang, Z; Xue, Z; Zhang, Z; Ban, Y; Cai, J; Ge, Y; Guo, S; Hu, Z; Mao, Y; Qian, S J; Teng, H; Zhu, B; Avila, C; Baquero Ruiz, M; Carrillo Montoya, C A; Gomez, A; Gomez Moreno, B; Ocampo Rios, A A; Osorio Oliveros, A F; Reyes Romero, D; Sanabria, J C; Godinovic, N; Lelas, K; Plestina, R; Polic, D; Puljak, I; Antunovic, Z; Dzelalija, M; Brigljevic, V; Duric, S; Kadija, K; Morovic, S; Fereos, R; Galanti, M; Mousa, J; Papadakis, A; Ptochos, F; Razis, P A; Tsiakkouri, D; Zinonos, Z; Hektor, A; Kadastik, M; Kannike, K; Müntel, M; Raidal, M; Rebane, L; Anttila, E; Czellar, S; Härkönen, J; Heikkinen, A; Karimäki, V; Kinnunen, R; Klem, J; Kortelainen, M J; Lampén, T; Lassila-Perini, K; Lehti, S; Lindén, T; 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Avery, P; Barashko, V; Bourilkov, D; Chen, M; Di Giovanni, G P; Dobur, D; Drozdetskiy, A; Field, R D; Fu, Y; Furic, I K; Gartner, J; Holmes, D; Kim, B; Klimenko, S; Konigsberg, J; Korytov, A; Kotov, K; Kropivnitskaya, A; Kypreos, T; Madorsky, A; Matchev, K; Mitselmakher, G; Pakhotin, Y; Piedra Gomez, J; Prescott, C; Rapsevicius, V; Remington, R; Schmitt, M; Scurlock, B; Wang, D; Yelton, J; Ceron, C; Gaultney, V; Kramer, L; Lebolo, L M; Linn, S; Markowitz, P; Martinez, G; Rodriguez, J L; Adams, T; Askew, A; Baer, H; Bertoldi, M; Chen, J; Dharmaratna, W G D; Gleyzer, S V; Haas, J; Hagopian, S; Hagopian, V; Jenkins, M; Johnson, K F; Prettner, E; Prosper, H; Sekmen, S; Baarmand, M M; Guragain, S; Hohlmann, M; Kalakhety, H; Mermerkaya, H; Ralich, R; Vodopiyanov, I; Abelev, B; Adams, M R; Anghel, I M; Apanasevich, L; Bazterra, V E; Betts, R R; Callner, J; Castro, M A; Cavanaugh, R; Dragoiu, C; Garcia-Solis, E J; Gerber, C E; Hofman, D J; Khalatian, S; Mironov, C; Shabalina, E; Smoron, A; Varelas, N; Akgun, U; Albayrak, E A; Ayan, A S; Bilki, B; Briggs, R; Cankocak, K; Chung, K; Clarida, W; Debbins, P; Duru, F; Ingram, F D; Lae, C K; McCliment, E; Merlo, J P; Mestvirishvili, A; Miller, M J; Moeller, A; Nachtman, J; Newsom, C R; Norbeck, E; Olson, J; Onel, Y; Ozok, F; Parsons, J; Schmidt, I; Sen, S; Wetzel, J; Yetkin, T; Yi, K; Barnett, B A; Blumenfeld, B; Bonato, A; Chien, C Y; Fehling, D; Giurgiu, G; Gritsan, A V; Guo, Z J; Maksimovic, P; Rappoccio, S; Swartz, M; Tran, N V; Zhang, Y; Baringer, P; Bean, A; Grachov, O; Murray, M; Radicci, V; Sanders, S; Wood, J S; Zhukova, V; Bandurin, D; Bolton, T; Kaadze, K; Liu, A; Maravin, Y; Onoprienko, D; Svintradze, I; Wan, Z; Gronberg, J; Hollar, J; Lange, D; Wright, D; Baden, D; Bard, R; Boutemeur, M; Eno, S C; Ferencek, D; Hadley, N J; Kellogg, R G; Kirn, M; Kunori, S; Rossato, K; Rumerio, P; Santanastasio, F; Skuja, A; Temple, J; Tonjes, M B; Tonwar, S C; Toole, T; Twedt, E; Alver, B; Bauer, G; Bendavid, J; Busza, W; Butz, E; Cali, I A; Chan, M; D'Enterria, D; Everaerts, P; Gomez Ceballos, G; Hahn, K A; Harris, P; Jaditz, S; Kim, Y; Klute, M; Lee, Y J; Li, W; Loizides, C; Ma, T; Miller, M; Nahn, S; Paus, C; Roland, C; Roland, G; Rudolph, M; Stephans, G; Sumorok, K; Sung, K; Vaurynovich, S; Wenger, E A; Wyslouch, B; Xie, S; Yilmaz, Y; Yoon, A S; Bailleux, D; Cooper, S I; Cushman, P; Dahmes, B; De Benedetti, A; Dolgopolov, A; Dudero, P R; Egeland, R; Franzoni, G; Haupt, J; Inyakin, A; Klapoetke, K; Kubota, Y; Mans, J; Mirman, N; Petyt, D; Rekovic, V; Rusack, R; Schroeder, M; Singovsky, A; Zhang, J; Cremaldi, L M; Godang, R; Kroeger, R; Perera, L; Rahmat, R; Sanders, D A; Sonnek, P; Summers, D; Bloom, K; Bockelman, B; Bose, S; Butt, J; Claes, D R; Dominguez, A; Eads, M; Keller, J; Kelly, T; Kravchenko, I; Lazo-Flores, J; Lundstedt, C; Malbouisson, H; Malik, S; Snow, G R; Baur, U; Iashvili, I; Kharchilava, A; Kumar, A; Smith, K; Strang, M; Alverson, G; Barberis, E; Boeriu, O; Eulisse, G; Govi, G; McCauley, T; Musienko, Y; Muzaffar, S; 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Neumeister, N; Sedov, A; Shipsey, I; Yoo, H D; Zheng, Y; Jindal, P; Parashar, N; Cuplov, V; Ecklund, K M; Geurts, F J M; Liu, J H; Maronde, D; Matveev, M; Padley, B P; Redjimi, R; Roberts, J; Sabbatini, L; Tumanov, A; Betchart, B; Bodek, A; Budd, H; Chung, Y S; de Barbaro, P; Demina, R; Flacher, H; Gotra, Y; Harel, A; Korjenevski, S; Miner, D C; Orbaker, D; Petrillo, G; Vishnevskiy, D; Zielinski, M; Bhatti, A; Demortier, L; Goulianos, K; Hatakeyama, K; Lungu, G; Mesropian, C; Yan, M; Atramentov, O; Bartz, E; Gershtein, Y; Halkiadakis, E; Hits, D; Lath, A; Rose, K; Schnetzer, S; Somalwar, S; Stone, R; Thomas, S; Watts, T L; Cerizza, G; Hollingsworth, M; Spanier, S; Yang, Z C; York, A; Asaadi, J; Aurisano, A; Eusebi, R; Golyash, A; Gurrola, A; Kamon, T; Nguyen, C N; Pivarski, J; Safonov, A; Sengupta, S; Toback, D; Weinberger, M; Akchurin, N; Berntzon, L; Gumus, K; Jeong, C; Kim, H; Lee, S W; Popescu, S; Roh, Y; Sill, A; Volobouev, I; Washington, E; Wigmans, R; Yazgan, E; Engh, D; Florez, C; Johns, W; Pathak, S; Sheldon, P; Andelin, D; Arenton, M W; Balazs, M; Boutle, S; Buehler, M; Conetti, S; Cox, B; Hirosky, R; Ledovskoy, A; Neu, C; Phillips II, D; Ronquest, M; Yohay, R; Gollapinni, S; Gunthoti, K; Harr, R; Karchin, P E; Mattson, M; Sakharov, A; Anderson, M; Bachtis, M; Bellinger, J N; Carlsmith, D; Crotty, I; Dasu, S; Dutta, S; Efron, J; Feyzi, F; Flood, K; Gray, L; Grogg, K S; Grothe, M; Hall-Wilton, R; Jaworski, M; Klabbers, P; Klukas, J; Lanaro, A; Lazaridis, C; Leonard, J; Loveless, R; Magrans de Abril, M; Mohapatra, A; Ott, G; Polese, G; Reeder, D; Savin, A; Smith, W H; Sourkov, A; Swanson, J; Weinberg, M; Wenman, D; Wensveen, M; White, A

    2010-01-01

    This paper describes the calibration procedure for the drift tubes of the CMS barrel muon system and reports the main results obtained with data collected during a high statistics cosmic ray data-taking period. The main goal of the calibration is to determine, for each drift cell, the minimum time delay for signals relative to the trigger, accounting for the drift velocity within the cell. The accuracy of the calibration procedure is influenced by the random arrival time of cosmic muons. A more refined analysis of the drift velocity was performed during the offline reconstruction phase, which takes into account this feature of cosmic ray events.

  14. Strong drifts effects on neoclassical transport

    International Nuclear Information System (INIS)

    Tessarotto, M.; Gregoratto, D.; White, R.B.

    1996-01-01

    It is well known that strong drifts play an important role in plasma equilibrium, stability and confinement A significant example concerns, in particular for tokamak plasmas, the case of strong toroidal differential rotation produced by E x B drift which is currently regarded as potentially important for its influence in equilibrium, stability and transport. In fact, theoretically, it has been found that shear flow can substantially affect the stability of microinstabilities as well modify substantially transport. Recent experimental observations of enhanced confinement and transport regimes in Tokamaks, show, however, evidence of the existence of strong drifts in the plasma core. These are produced not only by the radial electric field [which gives rise to the E x B drift], but also by density [N s ], temperature [T s ] and mass flow [V = ωRe var-phi , with e var-phi the toroidal unit vector, R the distance for the symmetry axis of the torus and ω being the toroidal angular rotation velocity] profiles which are suitably steep. This implies that, in a significant part of the plasma core, the relevant scale lengths of the gradients [of N s , T s , ω], i.e., respectively L N , L T and L ω can be as large as the radial scale length characterizing the banana orbits, L b . Interestingly enough, the transport estimates obtained appear close or even lower than the predictions based on the simplest neoclassical model. However, as is well known, the latter applies, in a strict sense only in the case of weak drifts and also ignoring even the contribution of shear flow related to strong E x B drift. Thus a fundamental problem appears the extension of neoclassical transport theory to include the effect of strong drifts in Tokamak confinement systems. The goal of this investigation is to develop a general formulation of neoclassical transport embodying such important feature

  15. Relationship between vertical ExB drift and F2-layer characteristics in the equatorial ionosphere at solar minimum conditions

    Science.gov (United States)

    Oyekola, Oyedemi S.

    2012-07-01

    Equatorial and low-latitude electrodynamics plays a dominant role in determining the structure and dynamics of the equatorial and low-latitude ionospheric F-region. Thus, they constitute essential input parameters for quantitative global and regional modeling studies. In this work, hourly median value of ionosonde measurements namely, peak height F2-layer (hmF2), F2-layer critical frequency (foF2) and propagation factor M(3000)F2 made at near equatorial dip latitude, Ouagadougou, Burkina Faso (12oN, 1.5oW; dip: 1.5oN) and relevant F2-layer parameters such as thickness parameter (Bo), electron temperature (Te), ion temperature (Ti), total electron content (TEC) and electron density (Ne, at the fixed altitude of 300 km) provided by the International Reference Ionosphere (IRI) model for the longitude of Ouagadougou are contrasted with the IRI vertical drift model to explore in detail the monthly climatological behavior of equatorial ionosphere and the effects of equatorial vertical plasma drift velocities on the diurnal structure of F2-layer parameters. The analysis period covers four months representative of solstitial and equinoctial seasonal periods during solar minimum year of 1987 for geomagnetically quiet-day. We show that month-by-month morphological patterns between vertical E×B drifts and F2-layer parameters range from worst to reasonably good and are largely seasonally dependent. A cross-correlation analysis conducted between equatorial drift and F2-layer characteristics yield statistically significant correlations for equatorial vertical drift and IRI-Bo, IRI-Te and IRI-TEC, whereas little or no acceptable correlation is obtained with observational evidence. Assessment of the association between measured foF2, hmF2 and M(3000)F2 illustrates consistent much more smaller correlation coefficients with no systematic linkage. In general, our research indicates strong departure from simple electrodynamically controlled behavior.

  16. Single nozzle spray drift measurements of drift reducing nozzles at two forward speeds

    NARCIS (Netherlands)

    Stallinga, H.; Zande, van de J.C.; Michielsen, J.G.P.; Velde, van P.

    2016-01-01

    In 2011‒2012 single nozzle field experiments were carried out to determine the effect of different flat fan spray nozzles of the spray drift reduction classes 50, 75, 90 and 95% on spray drift at two different forward speeds (7.2 km h-1 and 14.4 km h-1). Experiments were performed with a single

  17. Optical drift effects in general relativity

    Science.gov (United States)

    Korzyński, Mikołaj; Kopiński, Jarosław

    2018-03-01

    We consider the question of determining the optical drift effects in general relativity, i.e. the rate of change of the apparent position, redshift, Jacobi matrix, angular distance and luminosity distance of a distant object as registered by an observer in an arbitrary spacetime. We present a fully relativistic and covariant approach, in which the problem is reduced to a hierarchy of ODE's solved along the line of sight. The 4-velocities and 4-accelerations of the observer and the emitter and the geometry of the spacetime along the line of sight constitute the input data. We build on the standard relativistic geometric optics formalism and extend it to include the time derivatives of the observables. In the process we obtain two general, non-perturbative relations: the first one between the gravitational lensing, represented by the Jacobi matrix, and the apparent position drift, also called the cosmic parallax, and the second one between the apparent position drift and the redshift drift. The applications of the results include the theoretical study of the drift effects of cosmological origin (so-called real-time cosmology) in numerical or exact Universe models.

  18. Drift chamber performance in the field of a superconducting magnet: measurement of the drift angle

    International Nuclear Information System (INIS)

    Sanders, G.H.; Sherman, S.; McDonald, K.T.; Smith, A.J.S.; Thaler, J.J.

    1977-01-01

    Results are presented of the first measurements in a study of drift chamber performance in magnetic fields up to 6 tesla. The angle of the electron drift was measured as a function of electric and magnetic field intensity. It appears that even at the high fields of superconducting magnets (3 to 6 tesla) the drift angle induced by the Lorentz force can be corrected for with tilted electric drift fields and/or the use of Xenon gas. At 3 tesla a drift field tilted at 45 0 with a magnitude of 3.5 kV/cm should restore normal operating conditions. At 4 tesla, a 45 0 tilt field would have a magnitude 5 kV/cm

  19. Spray particle drift mitigation using field corn (Zea mays L.) as a drift barrier.

    Science.gov (United States)

    Vieira, Bruno C; Butts, Thomas R; Rodrigues, Andre O; Golus, Jeffrey A; Schroeder, Kasey; Kruger, Greg R

    2018-04-24

    Herbicide particle drift reduces application efficacy and can cause severe impacts on nearby vegetation depending on the herbicide mode-of-action, exposure level, and tolerance to the herbicide. A particle drift mitigation effort placing windbreaks or barriers on the field boundaries to reduce off-target movement of spray particles has been utilized in the past. The objective of this research was to evaluate the effectiveness of field corn (Zea mays L.) at different heights as a particle drift barrier. Applications with a non-air inclusion flat fan nozzle (ER11004) resulted in greater particle drift when compared to an air inclusion nozzle (TTI11004). Eight rows of corn were used as barriers (0.91, 1.22, and 1.98 m height) which reduced the particle drift for both nozzles, especially at shorter downwind distances. Applications with the ER11004 nozzle without corn barriers had 1% of the applied rate (D 99 ) predicted to deposit at 14.8 m downwind, whereas this distance was reduced (up to 7-fold) when applications were performed with corn barriers. The combination of corn drift barriers and nozzle selection (TTI11004) provided satisfactory particle drift reduction when the D 99 estimates were compared to applications with the ER11004 nozzle without corn barriers (up to 10-fold difference). The corn drift barriers were effective in reducing particle drift from applications with the ER11004 and the TTI11004 nozzles (Fine and Ultra Coarse spray classifications, respectively). The corn drift barrier had appropriate porosity and width as the airborne spray was captured within its canopy instead of deflecting up and over it. This article is protected by copyright. All rights reserved.

  20. Approximate Stokes Drift Profiles in Deep Water

    Science.gov (United States)

    Breivik, Øyvind; Janssen, Peter A. E. M.; Bidlot, Jean-Raymond

    2014-09-01

    A deep-water approximation to the Stokes drift velocity profile is explored as an alternative to the monochromatic profile. The alternative profile investigated relies on the same two quantities required for the monochromatic profile, viz the Stokes transport and the surface Stokes drift velocity. Comparisons with parametric spectra and profiles under wave spectra from the ERA-Interim reanalysis and buoy observations reveal much better agreement than the monochromatic profile even for complex sea states. That the profile gives a closer match and a more correct shear has implications for ocean circulation models since the Coriolis-Stokes force depends on the magnitude and direction of the Stokes drift profile and Langmuir turbulence parameterizations depend sensitively on the shear of the profile. The alternative profile comes at no added numerical cost compared to the monochromatic profile.

  1. P-type silicon drift detectors

    International Nuclear Information System (INIS)

    Walton, J.T.; Krieger, B.; Krofcheck, D.; O'Donnell, R.; Odyniec, G.; Partlan, M.D.; Wang, N.W.

    1995-06-01

    Preliminary results on 16 CM 2 , position-sensitive silicon drift detectors, fabricated for the first time on p-type silicon substrates, are presented. The detectors were designed, fabricated, and tested recently at LBL and show interesting properties which make them attractive for use in future physics experiments. A pulse count rate of approximately 8 x l0 6 s -1 is demonstrated by the p-type silicon drift detectors. This count rate estimate is derived by measuring simultaneous tracks produced by a laser and photolithographic mask collimator that generates double tracks separated by 50 μm to 1200 μm. A new method of using ion-implanted polysilicon to produce precise valued bias resistors on the silicon drift detectors is also discussed

  2. Correcting sample drift using Fourier harmonics.

    Science.gov (United States)

    Bárcena-González, G; Guerrero-Lebrero, M P; Guerrero, E; Reyes, D F; Braza, V; Yañez, A; Nuñez-Moraleda, B; González, D; Galindo, P L

    2018-07-01

    During image acquisition of crystalline materials by high-resolution scanning transmission electron microscopy, the sample drift could lead to distortions and shears that hinder their quantitative analysis and characterization. In order to measure and correct this effect, several authors have proposed different methodologies making use of series of images. In this work, we introduce a methodology to determine the drift angle via Fourier analysis by using a single image based on the measurements between the angles of the second Fourier harmonics in different quadrants. Two different approaches, that are independent of the angle of acquisition of the image, are evaluated. In addition, our results demonstrate that the determination of the drift angle is more accurate by using the measurements of non-consecutive quadrants when the angle of acquisition is an odd multiple of 45°. Copyright © 2018 Elsevier Ltd. All rights reserved.

  3. Mean Lagrangian drift in continental shelf waves

    Science.gov (United States)

    Drivdal, M.; Weber, J. E. H.

    2012-04-01

    The time- and depth-averaged mean drift induced by barotropic continental shelf waves (CSW's) is studied theoretically for idealized shelf topography by calculating the mean volume fluxes to second order in wave amplitude. The waves suffer weak spatial damping due to bottom friction, which leads to radiation stress forcing of the mean fluxes. In terms of the total wave energy density E¯ over the shelf region, the radiation stress tensor component S¯11 for CSW's is found to be different from that of shallow water surface waves in a non-rotating ocean. For CSW's, the ratio ¯S11/¯E depends strongly on the wave number. The mean Lagrangian flow forced by the radiation stress can be subdivided into a Stokes drift and a mean Eulerian drift current. The magnitude of the latter depends on the ratio between the radiation stress and the bottom stress acting on the mean flow. When the effect of bottom friction acts equally strong on the waves and the mean current, calculations for short CSW's show that the Stokes drift and the friction-dependent wave-induced mean Eulerian current varies approximately in anti-phase over the shelf, and that the latter is numerically the largest. For long CSW's they are approximately in phase. In both cases the mean Lagrangian current, which is responsible for the net particle drift, has its largest numerical value at the coast on the shallow part of the shelf. Enhancing the effect of bottom friction on the Eulerian mean flow, results in a general current speed reduction, as well as a change in spatial structure for long waves. Applying realistic physical parameters for the continental shelf west of Norway, calculations yield along-shelf mean drift velocities for short CSW's that may be important for the transport of biological material, neutral tracers, and underwater plumes of dissolved oil from deep water drilling accidents.

  4. Accurate computer simulation of a drift chamber

    International Nuclear Information System (INIS)

    Killian, T.J.

    1980-01-01

    A general purpose program for drift chamber studies is described. First the capacitance matrix is calculated using a Green's function technique. The matrix is used in a linear-least-squares fit to choose optimal operating voltages. Next the electric field is computed, and given knowledge of gas parameters and magnetic field environment, a family of electron trajectories is determined. These are finally used to make drift distance vs time curves which may be used directly by a track reconstruction program. Results are compared with data obtained from the cylindrical chamber in the Axial Field Magnet experiment at the CERN ISR

  5. Drift estimation from a simple field theory

    International Nuclear Information System (INIS)

    Mendes, F. M.; Figueiredo, A.

    2008-01-01

    Given the outcome of a Wiener process, what can be said about the drift and diffusion coefficients? If the process is stationary, these coefficients are related to the mean and variance of the position displacements distribution. However, if either drift or diffusion are time-dependent, very little can be said unless some assumption about that dependency is made. In Bayesian statistics, this should be translated into some specific prior probability. We use Bayes rule to estimate these coefficients from a single trajectory. This defines a simple, and analytically tractable, field theory.

  6. Ultra-low mass drift chambers

    International Nuclear Information System (INIS)

    Assiro, R.; Cappelli, L.; Cascella, M.; De Lorenzis, L.; Grancagnolo, F.; Ignatov, F.; L'Erario, A.; Maffezzoli, A.; Miccoli, A.; Onorato, G.; Perillo, M.; Piacentino, G.; Rella, S.; Rossetti, F.; Spedicato, M.; Tassielli, G.

    2013-01-01

    We present a novel low mass drift chamber concept, developed in order to fulfill the stringent requirements imposed by the experiments for extremely rare processes, which require high resolutions (order of 100–200 keV/c) for particle momenta in a range (50–100 MeV/c) totally dominated by the multiple scattering contribution. We describe a geometry optimization procedure and a new wiring strategy with a feed-through-less wire anchoring system developed and tested on a drift chamber prototype under completion at INFN-Lecce

  7. Ultra-low mass drift chambers

    Science.gov (United States)

    Assiro, R.; Cappelli, L.; Cascella, M.; De Lorenzis, L.; Grancagnolo, F.; Ignatov, F.; L'Erario, A.; Maffezzoli, A.; Miccoli, A.; Onorato, G.; Perillo, M.; Piacentino, G.; Rella, S.; Rossetti, F.; Spedicato, M.; Tassielli, G.; Zavarise, G.

    2013-08-01

    We present a novel low mass drift chamber concept, developed in order to fulfill the stringent requirements imposed by the experiments for extremely rare processes, which require high resolutions (order of 100-200 keV/c) for particle momenta in a range (50-100 MeV/c) totally dominated by the multiple scattering contribution. We describe a geometry optimization procedure and a new wiring strategy with a feed-through-less wire anchoring system developed and tested on a drift chamber prototype under completion at INFN-Lecce .

  8. Properties of low-pressure drift chambers

    International Nuclear Information System (INIS)

    Breskin, A.; Trautner, N.

    1976-01-01

    Drift chambers operated with methylal vapour or ethylene at pressures in the range of 10-110 torr are described. A systematic study of position resolution, pulse height and rise time shows that especially for ethylene they are strongly influenced by electron diffusion. Intrinsic position resolution was found to be at least as good as found at atmospheric pressure. A relative pulse height resolution of 10% was obtained with 5.5 MeV alpha-particles. A simple mathematical model which can describe the processes in the drift chamber is presented. (Auth.)

  9. Silicon Drift Detectors development for position sensing

    International Nuclear Information System (INIS)

    Castoldi, A.; Guazzoni, C.; Hartmann, R.; Strueder, L.

    2007-01-01

    Novel Silicon Drift Detectors (SDDs) with multi-linear architecture specifically intended for 2D position sensing and imaging applications are presented and their achievable spatial, energy and time resolution are discussed. The capability of providing a fast timing of the interaction with nanosecond time resolution is a new available feature that allows operating the drift detector in continuous readout mode for coincidence imaging applications either with an external trigger or in self-timing. The application of SDDs with multi-linear architecture to Compton electrons' tracking within a single silicon layer and the achieved experimental results will be discussed

  10. Nonlinear dynamics of resistive electrostatic drift waves

    DEFF Research Database (Denmark)

    Korsholm, Søren Bang; Michelsen, Poul; Pécseli, H.L.

    1999-01-01

    The evolution of weakly nonlinear electrostatic drift waves in an externally imposed strong homogeneous magnetic field is investigated numerically in three spatial dimensions. The analysis is based on a set of coupled, nonlinear equations, which are solved for an initial condition which is pertur......The evolution of weakly nonlinear electrostatic drift waves in an externally imposed strong homogeneous magnetic field is investigated numerically in three spatial dimensions. The analysis is based on a set of coupled, nonlinear equations, which are solved for an initial condition which...... polarity, i.e. a pair of electrostatic convective cells....

  11. Accurate computer simulation of a drift chamber

    CERN Document Server

    Killian, T J

    1980-01-01

    The author describes a general purpose program for drift chamber studies. First the capacitance matrix is calculated using a Green's function technique. The matrix is used in a linear-least-squares fit to choose optimal operating voltages. Next the electric field is computed, and given knowledge of gas parameters and magnetic field environment, a family of electron trajectories is determined. These are finally used to make drift distance vs time curves which may be used directly by a track reconstruction program. The results are compared with data obtained from the cylindrical chamber in the Axial Field Magnet experiment at the CERN ISR. (1 refs).

  12. Small-scale lacustrine drifts in Lake Champlain, Vermont

    Science.gov (United States)

    Manley, Patricia L.; Manley, T.O.; Hayo, Kathryn; Cronin, Thomas

    2012-01-01

    High resolution CHIRP (Compressed High Intensity Radar Pulse) seismic profiles reveal the presence of two lacustrine sediment drifts located in Lake Champlain's Juniper Deep. Both drifts are positive features composed of highly laminated sediments. Drift B sits on a basement high while Drift A is built on a trough-filling acoustically-transparent sediment unit inferred to be a mass-transport event. These drifts are oriented approximately north–south and are parallel to a steep ridge along the eastern shore of the basin. Drift A, located at the bottom of a structural trough, is classified as a confined, elongate drift that transitions northward to become a system of upslope asymmetric mudwaves. Drift B is perched atop a structural high to the west of Drift A and is classified as a detached elongate drift. Bottom current depositional control was investigated using Acoustic Doppler Current Profilers (ADCPs) located across Drift A. Sediment cores were taken at the crest and at the edges of the Drift A and were dated. Drift source, deposition, and evolution show that these drifts are formed by a water column shear with the highest deposition occurring along its crest and western flank and began developing circa 8700–8800 year BP.

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

    Directory of Open Access Journals (Sweden)

    P.-D. Pautet

    2009-06-01

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

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

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

    Directory of Open Access Journals (Sweden)

    P.-D. Pautet

    2009-06-01

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

  15. A new variable transformation technique for the nonlinear drift vortex

    International Nuclear Information System (INIS)

    Orito, Kohtaro

    1996-02-01

    The dipole vortex solution of the Hasegawa-Mima equation describing the nonlinear drift wave is a stable solitary wave which is called the modon. The profile of the modon depends on the nonlinearity of the ExB drift. In order to investigate the nonlinear drift wave more accurately, the effect of the polarization drift needs to be considered. In case of containing the effect of the polarization drift the profile of the electrostatic potential is distorted in the direction perpendicular to the ExB drift. (author)

  16. Psychometric Consequences of Subpopulation Item Parameter Drift

    Science.gov (United States)

    Huggins-Manley, Anne Corinne

    2017-01-01

    This study defines subpopulation item parameter drift (SIPD) as a change in item parameters over time that is dependent on subpopulations of examinees, and hypothesizes that the presence of SIPD in anchor items is associated with bias and/or lack of invariance in three psychometric outcomes. Results show that SIPD in anchor items is associated…

  17. Resistive drift wave turbulence and transport

    International Nuclear Information System (INIS)

    Wakatani, M.

    1986-01-01

    Our efforts for studying the properties of resistive drift wave turbulence by using model mode-coupling equations are shown. It may be related to the edge turbulence and the associated anomalous transport in tokamaks or in stellarator/heliotron. (author)

  18. Effects of Drifting Macroalgae in Eelgrass Ecosystems

    DEFF Research Database (Denmark)

    Canal Vergés, Paula; Valdemarsen, Thomas Bruun; Kristensen, Erik

    2010-01-01

    and physical damage on eelgrass can occur when macroalgae are drifting as bedload. The ballistic effect of moving macroalgae on surface sediment was tested in the field as well as in a series of annular flume experiments, where simultaneous measurements of macroalgae transport and turbidity were measured...

  19. EU law revisions and legislative drift

    DEFF Research Database (Denmark)

    Borghetto, Enrico; Mäder, Lars Kai

    2014-01-01

    in force in their original form for several years while others are revised soon after their enactment. What factors account for this variation? We empirically analyze the proposition that in the presence of ‘legislative drift,’ i.e. the intertemporal variation of decision-makers’ preferences, major...

  20. Nonlinear radial propagation of drift wave turbulence

    International Nuclear Information System (INIS)

    Prakash, M.

    1985-01-01

    We study the linear and the nonlinear radial propagation of drift wave energy in an inhomogeneous plasma. The drift mode excited in such a plasma is dispersive in nature. The drift wave energy spreads out symmetrically along the direction of inhomogeneity with a finite group velocity. To study the effect of the nonlinear coupling on the propagation of energy in a collision free plasma, we solve the Hasegawa-Mima equation as a mixed initial boundary-value problem. The solutions of the linearized equation are used to check the reliability of our numerical calculations. Additional checks are also performed on the invariants of the system. Our results reveal that a pulse gets distorted as it propagates through the medium. The peak of the pulse propagates with a finite velocity that depends on the amplitude of the initial pulse. The polarity of propagation depends on the initial parameters of the pulse. We have also studied drift wave propagation in a resistive plasma. The Hasegawa-Wakatani equations are used to investigate this problem

  1. Study and analysis of drift chamber parameters

    International Nuclear Information System (INIS)

    Martinez Laso, L.

    1988-01-01

    The present work deals mainly with drift chambers. In the first chapter a summary of drift chamber properties is presented. The information has been collected from the extensive bibliography available in this field. A very simple calculation procedure of drift chamber parameters has been developed and is presented in detail in the second chapter. Some prototypes have been made following two geometries (multidrift chamber and Z-chambers). Several installations have been used for test and calibration of these prototypes. A complete description of these installations is given in the third chapter. Cosmic rays, beta particles from a Ru106 radiactive source and a test beam in the WA (West Area) of SPS at CERN have been used for experimental purposes. The analysis and the results are described for the different setups. The experimental measurements have been used to produce a complete cell parametrization (position as function of drift time) and to obtain spatial resolution values (in the range of 200-250 um). Experimental results are in good agreement with numerical calculations. (Author)

  2. Drift wave in pair-ion plasma

    Indian Academy of Sciences (India)

    ion plasma are discussed. It is shown that the temperature and/or mass difference of both species could produce drift wave in a pair-ion plasma. The results are discussed in the context of the fullerene pair-ion plasma experiment.

  3. Learning in the context of distribution drift

    Science.gov (United States)

    2017-05-09

    Figure 3 shows a heatmap of the pairwise drift in the joint distribution on the Landsat-8 French land usage satellite data. This data represents 10 meter...listed under the List of Publications. 1. White, C., Using Big Data for Smarter Decision Making. 2011, BI Research: Ashland, Or. 2. Cook , S., et al

  4. Comment on the drift mirror instability

    Czech Academy of Sciences Publication Activity Database

    Hellinger, Petr

    2008-01-01

    Roč. 15, č. 5 (2008), 054502/1-054502/2 ISSN 1070-664X R&D Projects: GA AV ČR IAA300420702 Institutional research plan: CEZ:AV0Z30420517 Keywords : drift mirror instability * linear theory Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.427, year: 2008

  5. Sealed drift tube cosmic ray veto counters

    International Nuclear Information System (INIS)

    Rios, R.; Tatar, E.; Bacon, J.D.; Bowles, T.J.; Hill, R.; Green, J.A.; Hogan, G.E.; Ito, T.M.; Makela, M.; Morris, C.L.; Mortenson, R.; Pasukanics, F.E.; Ramsey, J.; Saunders, A.; Seestrom, S.J.; Sondheim, W.E.; Teasdale, W.; Saltus, M.; Back, H.O.; Cottrell, C.R.

    2011-01-01

    We describe a simple drift tube counter that has been used as a cosmic ray veto for the UCNA experiment, a first-ever measurement of the neutron beta-asymmetry using ultra-cold neutrons. These detectors provide an inexpensive alternative to more conventional scintillation detectors for large area cosmic ray anticoincidence detectors.

  6. Learning drifting concepts with neural networks

    NARCIS (Netherlands)

    Biehl, Michael; Schwarze, Holm

    1993-01-01

    The learning of time-dependent concepts with a neural network is studied analytically and numerically. The linearly separable target rule is represented by an N-vector, whose time dependence is modelled by a random or deterministic drift process. A single-layer network is trained online using

  7. Fine structure in fast drift storm bursts

    International Nuclear Information System (INIS)

    McConnell, D.; Ellis, G.R.A.

    1981-01-01

    Recent observations with high time resolution of fast drift storm (FDS) solar bursts are described. A new variety of FDS bursts characterised by intensity maxima regularly placed in the frequency domain is reported. Possible interpretations of this are mentioned and the implications of the short duration of FDS bursts are discussed. (orig.)

  8. Abnormal evening vertical plasma drift and effects on ESF and EIA over Brazil-South Atlantic sector during the 30 October 2003 superstorm

    Science.gov (United States)

    Abdu, M. A.; de Paula, E. R.; Batista, I. S.; Reinisch, B. W.; Matsuoka, M. T.; Camargo, P. O.; Veliz, O.; Denardini, C. M.; Sobral, J. H. A.; Kherani, E. A.; de Siqueira, P. M.

    2008-07-01

    Equatorial F region vertical plasma drifts, spread F and anomaly responses, in the south American longitude sector during the superstorm of 30 October 2003, are analyzed using data from an array of instruments consisting of Digisondes, a VHF radar, GPS TEC and scintillation receivers in Brazil, and a Digisonde and a magnetometer in Jicamarca, Peru. Prompt penetrating eastward electric field of abnormally large intensity drove the F layer plasma up at a velocity ˜1200 ms-1 during post dusk hours in the eastern sector over Brazil. The equatorial anomaly was intensified and expanded poleward while the development of spread F/plasma bubble irregularities and GPS signal scintillations were weaker than their quiet time intensity. Significantly weaker F region response over Jicamarca presented a striking difference in the intensity of prompt penetration electric field between Peru and eastern longitudes of Brazil. The enhanced post dusk sector vertical drift over Brazil is attributed to electro-dynamics effects arising energetic particle precipitation in the South Atlantic Magnetic Anomaly (SAMA). These extraordinary results and their longitudinal differences are presented and discussed in this paper.

  9. Drift mechanism for energetic charged particles at shocks

    International Nuclear Information System (INIS)

    Webb, G.M.; Axford, W.I.; Terasawa, T.

    1983-01-01

    The energy changes of energetic charged particles at a plane shock due to the so-called drift mechanism are analyzed by using the ''adiabatic treatment.'' The analysis shows that for a fast MHD shock, particles lose energy owing to acceleration (curvature) drift in the magnetic field at the shock with the drift velocity being antiparallel to the electric field, and they gain energy owing to gradient drift parallel to the electric field. It is shown that particles with pitch angles aligned along the magnetic field which pass through the shock tend to lose energy owing to acceleration drift, whereas particles with pitch angles nonaligned to the magnetic field gain energy owing to gradient drift. Particles that are reflected by the shock always gain energy. Slow-mode shocks may be similarly analyzed, but in this case curvature drifts give rise to particle energy gains, and gradient drifts result in particle energy losses

  10. Barber's Point, Oahu, Hawaii Drift Card Study 2002-2004

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Drift cards were be released from Barber's Point, Oahu, approximately once a month during the two year span to get an idea of the distribution of card drift under...

  11. Electromagnetic drift modes in an inhomogeneous electron gas

    DEFF Research Database (Denmark)

    Shukla, P. K.; Pecseli, H. L.; Juul Rasmussen, Jens

    1986-01-01

    A pair of nonlinear equations is derived which describes the dynamics of the electromagnetic drift oscillations in a nonuniform magnetized electron gas. It is shown that the nonlinear electromagnetic drift modes can propagate in the form of dipole vortices...

  12. A drift chamber constructed of aluminized mylar tubes

    International Nuclear Information System (INIS)

    Baringer, P.; Jung, C.; Ogren, H.O.; Rust, D.R.

    1987-01-01

    A thin reliable drift chamber has been constructed to be used near the interaction point of the PEP storage ring in the HRS detector. It is composed of individual drift tubes with aluminized mylar walls. (orig.)

  13. A drift chamber constructed of aluminized mylar tubes

    Science.gov (United States)

    Baringer, P.; Jung, C.; Ogren, H. O.; Rust, D. R.

    1987-03-01

    A thin reliable drift chamber has been constructed to be used near the interaction point of the PEP storage ring in the HRS detector. It is composed of individual drift tubes with aluminized mylar walls.

  14. Drift-Scale THC Seepage Model

    Energy Technology Data Exchange (ETDEWEB)

    C.R. Bryan

    2005-02-17

    The purpose of this report (REV04) is to document the thermal-hydrologic-chemical (THC) seepage model, which simulates the composition of waters that could potentially seep into emplacement drifts, and the composition of the gas phase. The THC seepage model is processed and abstracted for use in the total system performance assessment (TSPA) for the license application (LA). This report has been developed in accordance with ''Technical Work Plan for: Near-Field Environment and Transport: Coupled Processes (Mountain-Scale TH/THC/THM, Drift-Scale THC Seepage, and Post-Processing Analysis for THC Seepage) Report Integration'' (BSC 2005 [DIRS 172761]). The technical work plan (TWP) describes planning information pertaining to the technical scope, content, and management of this report. The plan for validation of the models documented in this report is given in Section 2.2.2, ''Model Validation for the DS THC Seepage Model,'' of the TWP. The TWP (Section 3.2.2) identifies Acceptance Criteria 1 to 4 for ''Quantity and Chemistry of Water Contacting Engineered Barriers and Waste Forms'' (NRC 2003 [DIRS 163274]) as being applicable to this report; however, in variance to the TWP, Acceptance Criterion 5 has also been determined to be applicable, and is addressed, along with the other Acceptance Criteria, in Section 4.2 of this report. Also, three FEPS not listed in the TWP (2.2.10.01.0A, 2.2.10.06.0A, and 2.2.11.02.0A) are partially addressed in this report, and have been added to the list of excluded FEPS in Table 6.1-2. This report has been developed in accordance with LP-SIII.10Q-BSC, ''Models''. This report documents the THC seepage model and a derivative used for validation, the Drift Scale Test (DST) THC submodel. The THC seepage model is a drift-scale process model for predicting the composition of gas and water that could enter waste emplacement drifts and the effects of mineral

  15. Drift-Scale THC Seepage Model

    International Nuclear Information System (INIS)

    C.R. Bryan

    2005-01-01

    The purpose of this report (REV04) is to document the thermal-hydrologic-chemical (THC) seepage model, which simulates the composition of waters that could potentially seep into emplacement drifts, and the composition of the gas phase. The THC seepage model is processed and abstracted for use in the total system performance assessment (TSPA) for the license application (LA). This report has been developed in accordance with ''Technical Work Plan for: Near-Field Environment and Transport: Coupled Processes (Mountain-Scale TH/THC/THM, Drift-Scale THC Seepage, and Post-Processing Analysis for THC Seepage) Report Integration'' (BSC 2005 [DIRS 172761]). The technical work plan (TWP) describes planning information pertaining to the technical scope, content, and management of this report. The plan for validation of the models documented in this report is given in Section 2.2.2, ''Model Validation for the DS THC Seepage Model,'' of the TWP. The TWP (Section 3.2.2) identifies Acceptance Criteria 1 to 4 for ''Quantity and Chemistry of Water Contacting Engineered Barriers and Waste Forms'' (NRC 2003 [DIRS 163274]) as being applicable to this report; however, in variance to the TWP, Acceptance Criterion 5 has also been determined to be applicable, and is addressed, along with the other Acceptance Criteria, in Section 4.2 of this report. Also, three FEPS not listed in the TWP (2.2.10.01.0A, 2.2.10.06.0A, and 2.2.11.02.0A) are partially addressed in this report, and have been added to the list of excluded FEPS in Table 6.1-2. This report has been developed in accordance with LP-SIII.10Q-BSC, ''Models''. This report documents the THC seepage model and a derivative used for validation, the Drift Scale Test (DST) THC submodel. The THC seepage model is a drift-scale process model for predicting the composition of gas and water that could enter waste emplacement drifts and the effects of mineral alteration on flow in rocks surrounding drifts. The DST THC submodel uses a drift

  16. Ocean modelling aspects for drift applications

    Science.gov (United States)

    Stephane, L.; Pierre, D.

    2010-12-01

    Nowadays, many authorities in charge of rescue-at-sea operations lean on operational oceanography products to outline research perimeters. Moreover, current fields estimated with sophisticated ocean forecasting systems can be used as input data for oil spill/ adrift object fate models. This emphasises the necessity of an accurate sea state forecast, with a mastered level of reliability. This work focuses on several problems inherent to drift modeling, dealing in the first place with the efficiency of the oceanic current field representation. As we want to discriminate the relevance of a particular physical process or modeling option, the idea is to generate series of current fields of different characteristics and then qualify them in term of drift prediction efficiency. Benchmarked drift scenarios were set up from real surface drifters data, collected in the Mediterranean sea and off the coasts of Angola. The time and space scales that we are interested in are about 72 hr forecasts (typical timescale communicated in case of crisis), for distance errors that we hope about a few dozen of km around the forecast (acceptable for reconnaissance by aircrafts) For the ocean prediction, we used some regional oceanic configurations based on the NEMO 2.3 code, nested into Mercator 1/12° operational system. Drift forecasts were computed offline with Mothy (Météo France oil spill modeling system) and Ariane (B. Blanke, 1997), a Lagrangian diagnostic tool. We were particularly interested in the importance of the horizontal resolution, vertical mixing schemes, and any processes that may impact the surface layer. The aim of the study is to ultimately point at the most suitable set of parameters for drift forecast use inside operational oceanic systems. We are also motivated in assessing the relevancy of ensemble forecasts regarding determinist predictions. Several tests showed that mis-described observed trajectories can finally be modelled statistically by using uncertainties

  17. Longevity of Emplacement Drift Ground Support Materials

    International Nuclear Information System (INIS)

    D.H.Tang

    2001-01-01

    The purpose of this analysis is to evaluate the factors affecting the longevity of emplacement drift ground support materials and to develop a basis for the selection of materials for ground support that will function throughout the preclosure period of a potential repository at Yucca Mountain. REV 01 ICN 01 of this analysis is developed in accordance with AP-3.10Q, Analyses and Models, Revision 2, ICN 4, and prepared in accordance with the Technical Work Plan for Subsurface Design Section FY 01 Work Activities (CRWMS M and O 2001a). The objective of this analysis is to update the previous analysis (CRWMS M and O 2000a) to account for related changes in the Ground Control System Description Document (CRWMS M and O 2000b), the Monitored Geologic Repository Project Description Document, which is included in the Requirements and Criteria for Implementing a Repository Design that can be Operated Over a Range of Thermal Modes (BSC 2001), input information, and in environmental conditions, and to provide updated information on candidate ground support materials. Candidate materials for ground support are carbon steel and cement grout. Steel is mainly used for steel sets, lagging, channel, rock bolts, and wire mesh. Cement grout is only considered in the case of grouted rock bolts. Candidate materials for the emplacement drift invert are carbon steel and granular natural material. Materials are evaluated for the repository emplacement drift environment based on the updated thermal loading condition and waste package design. The analysis consists of the following tasks: (1) Identify factors affecting the longevity of ground support materials for use in emplacement drifts. (2) Review existing documents concerning the behavior of candidate ground support materials during the preclosure period. (3) Evaluate impacts of temperature and radiation effects on mechanical and thermal properties of steel. Assess corrosion potential of steel at emplacement drift environment. (4

  18. Parametric decay of lower hybrid wave into drift waves

    International Nuclear Information System (INIS)

    Sanuki, Heiji.

    1976-12-01

    A dispersion relation describing the parametric decay of a lower hybrid wave into an electrostatic drift wave and a drift Alfven wave is derived for an inhomogeneous magnetized plasma. Particularly the stimulated scattering of a drift Alfven wave in such a plasma was investigated in detail. The resonance backscattering instability is found to yield the minimum threshold. (auth.)

  19. Origin of short-period (30-300 s) Doppler frequency fluctuations of lower F region reflections in the equatorial electrojet region

    International Nuclear Information System (INIS)

    Sastri, J.H.; Ramesh, K.B.; Rao, J.V.S.V.; Somayajulu, V.V.

    1991-01-01

    Measurements of phase path P of lower F-region reflections at normal incidence at Kodaikanal revealed the ubiquitous presence of 30-300-s quasi-sinusoidal variations in the time rate of change of phase path, P (Doppler frequency shift) during day time. A study is made of the influence of the irregularities in the equatorial electrojet on the P fluctuations using simultaneous observations of F-region phase path at Kodaikanal and of equatorial electrojet with the VHF-backscatter radar at Thumba. It is shown that the spectral content of the Doppler fluctuations (quantified in terms of variance, sigma squared computed from P time series synthesized through FFT exp -1 (FFT) in the chosen period bands, 30-300 s/30-120 s of the FFT of original P times series) bears a significant positive linear relationship to the horizontal phase velocity of electrojet irregularities (3-m scale size) on a hourly basis. This result is in consonance with earlier findings (Sastri et al., 1990) of a significant linear relationship of sigma squared to the electrojet strength (estimated from H-field data) and a practical cessation of the P fluctuations at times of disappearance of Esq on ionograms (partial/complete counterelectrojet). The present work substantiates the interpretation that the short-period Doppler-frequency fluctuations are due to phase-path changes imposed on lower F region reflections by the refractive-index variations associated with the convective motions of plasma density irregularities (type I and II) in the daytime equatorial electrojet. 49 refs

  20. Passive appendages generate drift through symmetry breaking

    Science.gov (United States)

    Lācis, U.; Brosse, N.; Ingremeau, F.; Mazzino, A.; Lundell, F.; Kellay, H.; Bagheri, S.

    2014-10-01

    Plants and animals use plumes, barbs, tails, feathers, hairs and fins to aid locomotion. Many of these appendages are not actively controlled, instead they have to interact passively with the surrounding fluid to generate motion. Here, we use theory, experiments and numerical simulations to show that an object with a protrusion in a separated flow drifts sideways by exploiting a symmetry-breaking instability similar to the instability of an inverted pendulum. Our model explains why the straight position of an appendage in a fluid flow is unstable and how it stabilizes either to the left or right of the incoming flow direction. It is plausible that organisms with appendages in a separated flow use this newly discovered mechanism for locomotion; examples include the drift of plumed seeds without wind and the passive reorientation of motile animals.

  1. Hole drift mobility in poly(hexylphenylsilane)

    International Nuclear Information System (INIS)

    Kunimi, Y.; Seki, S.; Tagawa, S.

    2000-01-01

    Poly(n-alkylphenylsilane)s in which n-alkyl were changed from methyl to octyl were polymerized. Hole transport properties of poly(alkyllphenylsilane)s were systematically studied by the DC time-of-flight (TOF) technique. While the hole drift mobility of poly(methylphenylsilane) increased monotonously in entire field, those of poly(hexylphenylsilane) and poly(octylphenylsilane) decreased with increase in the field strength. Temperature dependence of hole drift mobility in those polymers was small. On the basis of Baessler's disorder formalism the mobility was analyzed quantitatively to disserve complex contributions of charge transport. The analyzed results indicated that with increase in the length of n-alkyl side-groups, the energetic disorder of hopping sites became smaller and the disorder of distance between hopping sites became larger. These results were supported by the results obtained by UV absorption measurement and positron annihilation life-time spectroscopy measurement. (author)

  2. Electromagnetic nonlinear gyrokinetics with polarization drift

    International Nuclear Information System (INIS)

    Duthoit, F.-X.; Hahm, T. S.; Wang, Lu

    2014-01-01

    A set of new nonlinear electromagnetic gyrokinetic Vlasov equation with polarization drift and gyrokinetic Maxwell equations is systematically derived by using the Lie-transform perturbation method in toroidal geometry. For the first time, we recover the drift-kinetic expression for parallel acceleration [R. M. Kulsrud, in Basic Plasma Physics, edited by A. A. Galeev and R. N. Sudan (North-Holland, Amsterdam, 1983)] from the nonlinear gyrokinetic equations, thereby bridging a gap between the two formulations. This formalism should be useful in addressing nonlinear ion Compton scattering of intermediate-mode-number toroidal Alfvén eigenmodes for which the polarization current nonlinearity [T. S. Hahm and L. Chen, Phys. Rev. Lett. 74, 266 (1995)] and the usual finite Larmor radius effects should compete

  3. Clean industrial room for drift tube assembling

    International Nuclear Information System (INIS)

    Glonti, G.L.; Gongadze, A.L.; Evtukhovich, P.G.

    2001-01-01

    Description of a clean industrial room for assembly of drift tubes for the muon spectrometer of the ATLAS experiment is presented. High quality specifications on the detectors to be produced demanded creation of a workplace with stable temperature and humidity, as well as minimum quantity of dust in the room. Checking of parameters of intra-room air during long period of continuous work has confirmed correctness of the designed characteristics of the climatic system installed in the clean room. The room large volume (∼ 190 m 3 ), the powerful and flexible climatic system, and simplicity of service allow assembling of detectors with length up to 5 m. Subsequent checking of functionality of the assembled detectors has shown high quality of assembling (the amount of rejected tubes does not exceed 2%). It demonstrates conformity to the assembling quality requirements for mass production of drift chambers for the muon spectrometer. (author)

  4. Clean Industrial Room for Drift Tube Assembling

    CERN Document Server

    Glonti, GL; Evtoukhovitch, P G; Kroa, G; Manz, A; Potrap, I N; Rihter, P; Stoletov, G D; Tskhadadze, E G; Chepurnov, V F; Chirkov, A V; Shelkov, G A

    2001-01-01

    Description of a clean industrial room for assembly of drift tubes for the muon spectrometer of the ATLAS experiment is presented. High quality specifications on the detectors to be produced demanded creation of a workplace with stable temperature and humidity, as well as minimum quantity of dust in the room. Checking of parameters of intra-room air during long period of continuous work has been confirmed correctness of the designed characteristics of the climatic system installed in the clean room. The room large volum (\\sim 190 m^3), the powerful and flexible climatic system, and simplicity of service allow assembling of detectors with length up to 5 m. Subsequent checking of functionality of the assembled detectors has shown high quality of assembling (the amount of rejected tubes does not exceed 2 %). It demonstrates conformity to the assembling quality requirements for mass production of drift chambers for the muon spectrometer.

  5. Toroidal effects on drift wave turbulence

    Energy Technology Data Exchange (ETDEWEB)

    LeBrun, M.J.; Tajima, T.; Gray, M.G.; Furnish, G.; Horton, W.

    1992-09-23

    The universal drift instability and other drift instabilities driven by density and temperature gradients in a toroidal system are investigated in both linear and nonlinear regimes via particle simulation. Runs in toroidal and cylindrical geometry show dramatic differences in plasma behavior, primarily due to the toroidicity-induced coupling of rational surfaces through the poloidal mode number m. In the toroidal system studied, the eigenmodes are seen to possess (i) an elongated, nearly global radial extent (ii) a higher growth rate than in the corresponding cylindrical system, (iii) an eigenfrequency nearly constant with radius, (iv) a global temperature relaxation and enhancement of thermal heat conduction. Most importantly, the measured Xi shows an increase with radius and an absolute value on the order of that observed in experiment. On the basis of our observations, we argue that the increase in Xi with radius observed in experiment is caused by the global nature of heat convection in the presence of toroidicity-induced mode coupling.

  6. Bottle appeal drifts across the Pacific

    Science.gov (United States)

    Ebbesmeyer, Curtis; Ingraham, W. James, Jr.; McKinnon, Richard; Okubo, Akira; Wang, Dong-Ping; Strickland, Richard; Willing, Peter

    Pacific drift currents were used by a group of oceanographers to estimate the path of a drift bottle that was found on a beach of Barkley Sound in Vancouver Island by Richard Strickland on June 10, 1990. The Chinese rice wine bottle, which remained unopened until December 18, 1991, contained six leaflets, one appealing for the release of China's well-known dissident, Wei Jingsheng. The bottle was one of thousands set adrift as part of a propaganda effort from the islands of Quemoy and Matsu off mainland China shortly after Wei was sentenced in 1979 to 15 years in prison (see Figure 1 for locations). Wei was in poor health and still in prison when the bottle made its way across the Pacific Ocean.

  7. The drift-flux correlation package MDS

    International Nuclear Information System (INIS)

    Hoeld, A.

    2001-01-01

    Based on the SONNENBURG drift-flux correlation, developed at GRS/Garching (Germany), a comprehensive drift-flux correlation package (MDS) has been established. Its aim is to support thermal-hydraulic mixture-fluid models, models being used for the simulation of the steady state and transient behaviour of characteristic thermal-hydraulic parameters of single- or two-phase fluids flowing along coolant channels of different types (being, e.g., parts of NPP-s, steam generators etc.). The characteristic properties of this package with respect to the behaviour at co- and counter-current flow, its inverse solutions needed for steady state simulations, its behaviour when approaching the lower or upper boundary of a two-phase region, its verification and behaviour with respect to other correlations will be discussed. An adequate driver code, MDSDRI, has been established too, allowing to test the package very thoroughly out of the complex thermal-hydraulic codes. (author)

  8. Ionospheric drift measurements: Skymap points selection

    Czech Academy of Sciences Publication Activity Database

    Kouba, Daniel; Boška, Josef; Galkin, I. A.; Santolík, Ondřej; Šauli, Petra

    2008-01-01

    Roč. 43, č. 1 (2008), RS1S90/1-RS1S90/11 ISSN 0048-6604 R&D Projects: GA ČR GA205/06/1619; GA ČR GA205/06/1267; GA AV ČR IAA300420504 Grant - others:GA MŠk(CZ) OC 296; MIERS(XE) COST 296 Institutional research plan: CEZ:AV0Z30420517 Keywords : digisonde drift measurement * plasma drift * radio sounding * ionosphere * Doppler shift * skymap processing Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.092, year: 2008 http://www.agu.org/pubs/crossref/2008/2007RS003633.shtml

  9. Pulsar magnetic alignment. The drifting subpulses

    International Nuclear Information System (INIS)

    Jones, P.B.

    1977-01-01

    According to Ruderman and Sutherland (Ap.J.;196:51 (1975)) the subpulse drift observed in certain pulsars is a consequence of the circulation around the magnetic axis of electron-positron discharges occurring within an acceleration region near the polar cap. The predicted period of circulation P 3 is of the correct order of magnitude, but the sense of circulation and therefore the direction of subpulse drift is not consistent with indirect evidence, from observed integrated pulse widths, on the variation with pulsar age of the angle between the spin and magnetic axes. It is shown that this problem is resolved by a model of the acceleration electric field based on space charge limited ion flow. (author)

  10. The drift-flux correlation package MDS

    Energy Technology Data Exchange (ETDEWEB)

    Hoeld, A. [Bernaysstr. 16A, Munich, F.R. (Germany)

    2001-07-01

    Based on the SONNENBURG drift-flux correlation, developed at GRS/Garching (Germany), a comprehensive drift-flux correlation package (MDS) has been established. Its aim is to support thermal-hydraulic mixture-fluid models, models being used for the simulation of the steady state and transient behaviour of characteristic thermal-hydraulic parameters of single- or two-phase fluids flowing along coolant channels of different types (being, e.g., parts of NPP-s, steam generators etc.). The characteristic properties of this package with respect to the behaviour at co- and counter-current flow, its inverse solutions needed for steady state simulations, its behaviour when approaching the lower or upper boundary of a two-phase region, its verification and behaviour with respect to other correlations will be discussed. An adequate driver code, MDSDRI, has been established too, allowing to test the package very thoroughly out of the complex thermal-hydraulic codes. (author)

  11. Toroidal effects on drift wave turbulence

    International Nuclear Information System (INIS)

    LeBrun, M.J.; Tajima, T.; Gray, M.G.; Furnish, G.; Horton, W.

    1992-01-01

    The universal drift instability and other drift instabilities driven by density and temperature gradients in a toroidal system are investigated in both linear and nonlinear regimes via particle simulation. Runs in toroidal and cylindrical geometry show dramatic differences in plasma behavior, primarily due to the toroidicity-induced coupling of rational surfaces through the poloidal mode number m. In the toroidal system studied, the eigenmodes are seen to possess (i) an elongated, nearly global radial extent (ii) a higher growth rate than in the corresponding cylindrical system, (iii) an eigenfrequency nearly constant with radius, (iv) a global temperature relaxation and enhancement of thermal heat conduction. Most importantly, the measured Xi shows an increase with radius and an absolute value on the order of that observed in experiment. On the basis of our observations, we argue that the increase in Xi with radius observed in experiment is caused by the global nature of heat convection in the presence of toroidicity-induced mode coupling

  12. Cylindrical geometry for proportional and drift chambers

    International Nuclear Information System (INIS)

    Sadoulet, B.

    1975-06-01

    For experiments performed around storage rings such as e + e - rings or the ISR pp rings, cylindrical wire chambers are very attractive. They surround the beam pipe completely without any dead region in the azimuth, and fit well with the geometry of events where particles are more or less spherically produced. Unfortunately, cylindrical proportional or drift chambers are difficult to make. Problems are discussed and two approaches to fabricating the cathodes are discussed. (WHK)

  13. Spin-drift transport in semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Miah, M Idrish [Nanoscale Science and Technology Centre and School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); Department of Physics, University of Chittagong, Chittagong, Chittagong-4331 (Bangladesh)

    2008-02-07

    We present a study on spin transport in semiconductors under applied electric fields. Our experiments detect photoinjected electron spins and their relaxation during drift transport in intrinsic and moderately n-doped GaAs, based on the extraordinary Hall (eH) effect. For relatively low electric field (E), the optically spin-induced eH effect in n-doped GaAs is found to be enhanced with increasing doping density and not to depend much on E, indicating that a substantial amount of optical spin polarization is preserved during the drift transport in these extrinsic semiconductors. However, when the spin-oriented electrons are injected with a high E, a very significant decrease is observed in the eH voltage (V{sub eH}) due to an increase in the spin precession frequency of the hot electrons. Spin relaxation by the D'yakonov-Perel' mechanism is calculated, and is suggested to be the reason for such a rapid spin relaxation for hot electrons under a high E. However, in an intrinsic GaAs (i-GaAs), a much weaker V{sub eH} is observed and, as the electron spins scattered by holes due to the Coulomb interaction in i-GaAs, the spin relaxation by the Bir-Aronov-Pikus mechanism is considered. Skew scattering and side jump as possible mechanisms of the optically spin-induced transverse Hall currents are discussed. Based on a spin drift-diffusion model, drift and diffusion contributions to the V{sub eH} are examined. The results are also discussed in comparison with theoretical investigations.

  14. Unstable universal drift eigenmodes in toroidal plasmas

    International Nuclear Information System (INIS)

    Cheng, C.Z.; Chen, L.

    1979-08-01

    The eigenmode equation describing ballooning collisionless drift instabilities is analyzed both analytically and numerically. A new branch of eigenmodes, which corresponds to quasi-bound states due to the finite toroidicity, is shown to be destabilized by electron Landau damping for typical Tokamak parameters. This branch cannot be understood by the strong coupling approximation. However, the slab-like (Pearlstein-Berk type) branch is found to remain stable and experience enhanced shear damping due to finite toroidicity

  15. Snow Drift Management: Summit Station Greenland

    Science.gov (United States)

    2016-05-01

    management Snow surveys Transport analysis Winds -- Speed 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF...that about 25% of the estimated snow that the wind transports to Summit each winter is deposited and forms drifts, mostly in close proxim- ity to...the structures. This analysis demonstrates that weather data ( wind speed and direction) and a transport analysis can aid in estimating the vol- ume of

  16. New developments on silicon drift detectors

    International Nuclear Information System (INIS)

    Rashevsky, A.

    1996-01-01

    In the frame of the project to develop large-area linear drift detectors few prototypes have been designed and produced. the function of these prototypes is to allow the evaluation of the solutions chosen for the geometry of the on-board electrodes and the production process. On these prototypes it is studied the static characteristics and measured time of-flight and charge collection injecting charges with an IR laser source. It is report the results from one of the prototypes

  17. The Absence of Stokes Drift in Waves

    OpenAIRE

    Chafin, Clifford

    2015-01-01

    Stokes drift has been as central to the history of wave theory as it has been distressingly absent from experiment. Neither wave tanks nor experiments in open bodies detect this without nearly canceling "eulerian flows." Acoustic waves have an analogous problem that is particularly problematic in the vorticity production at the edges of beams. Here we demonstrate that the explanation for this arises from subtle end-of-packet and wavetrain gradient effects such as microbreaking events and wave...

  18. Continued Drift, but without the Acrimony

    DEFF Research Database (Denmark)

    Nielsen, Kristian L.

    2013-01-01

    If the measure of Barack Obama's success in mending US–European relations is whether the tone has improved, his presidency has been a great success. If the measure of success, however, is halting the drifting apart of policy preferences, the picture looks a lot less rosy. This article argues....... The Obama administration realises that, and by this more limited measure, it has succeeded brilliantly....

  19. Cathode readout with stripped resistive drift tubes

    International Nuclear Information System (INIS)

    Bychkov, V.N.; Kekelidze, G.D.; Novikov, E.A.; Peshekhonov, V.D.; Shafranov, M.D.; Zhiltsov, V.E.

    1995-01-01

    A straw tube drift chamber prototype has been constructed and tested. The straw tube material is mylar film covered with a carbon layer with a resistivity of 0.5, 30 and 70 kΩ/□. Both the anode wire and the cathode strip signals were detected to study the behaviour of the chamber in the presence of X-ray ionization. The construction and the results of the study are presented. (orig.)

  20. Cathode readout with stripped resistive drift tubes

    Science.gov (United States)

    Bychkov, V. N.; Kekelidze, G. D.; Novikov, E. A.; Peshekhonov, V. D.; Shafranov, M. D.; Zhiltsov, V. E.

    1995-12-01

    A straw tube drift chamber prototype has been constructed and tested. The straw tube material is mylar film covered with a carbon layer with a resistivity of 0.5, 30 and 70 kΩ/□. Both the anode wire and the cathode strip signals were detected to study the behaviour of the chamber in the presence of X-ray ionization. The construction and the results of the study are presented.

  1. Drift bifurcation detection for dissipative solitons

    International Nuclear Information System (INIS)

    Liehr, A W; Boedeker, H U; Roettger, M C; Frank, T D; Friedrich, R; Purwins, H-G

    2003-01-01

    We report on the experimental detection of a drift bifurcation for dissipative solitons, which we observe in the form of current filaments in a planar semiconductor-gas-discharge system. By introducing a new stochastic data analysis technique we find that due to a change of system parameters the dissipative solitons undergo a transition from purely noise-driven objects with Brownian motion to particles with a dynamically stabilized finite velocity

  2. Transient chaotic transport in dissipative drift motion

    Energy Technology Data Exchange (ETDEWEB)

    Oyarzabal, R.S. [Pós-Graduação em Ciências/Física, Universidade Estadual de Ponta Grossa, 84030-900, Ponta Grossa, PR (Brazil); Szezech, J.D. [Departamento de Matemática e Estatística, Universidade Estadual de Ponta Grossa, 84030-900, Ponta Grossa, PR (Brazil); Batista, A.M., E-mail: antoniomarcosbatista@gmail.com [Departamento de Matemática e Estatística, Universidade Estadual de Ponta Grossa, 84030-900, Ponta Grossa, PR (Brazil); Souza, S.L.T. de [Departamento de Física e Matemática, Universidade Federal de São João del Rei, 36420-000, Ouro Branco, MG (Brazil); Caldas, I.L. [Instituto de Física, Universidade de São Paulo, 05315-970, São Paulo, SP (Brazil); Viana, R.L. [Departamento de Física, Universidade Federal do Paraná, 81531-990, Curitiba, PR (Brazil); Sanjuán, M.A.F. [Departamento de Física, Universidad Rey Juan Carlos, Tulipán s/n, 28933 Móstoles, Madrid (Spain)

    2016-04-22

    Highlights: • We consider a situation for which a chaotic transient is present in the dynamics of the two-wave model with damping. • The damping in plasma models can be a way for study a realistic behavior of confinement due the collisional effect. • The escape time as a function of the damping obey a power-law scaling. • We have made a qualitative transport analysis with a simple model that can be useful for more complete models. • We have shown that the pattern of the basin of attraction depends on the damping parameter. - Abstract: We investigate chaotic particle transport in magnetised plasmas with two electrostatic drift waves. Considering dissipation in the drift motion, we verify that the removed KAM surfaces originate periodic attractors with their corresponding basins of attraction. We show that the properties of the basins depend on the dissipation and the space-averaged escape time decays exponentially when the dissipation increases. We find positive finite time Lyapunov exponents in dissipative drift motion, consequently the trajectories exhibit transient chaotic transport. These features indicate how the transient plasma transport depends on the dissipation.

  3. Longevity of Emplacement Drift Ground Support Materials

    International Nuclear Information System (INIS)

    Tang, D.

    2000-01-01

    The purpose of this analysis is to evaluate the factors affecting the longevity of emplacement drift ground support materials and to develop a basis for selection of materials for ground support that will function throughout the preclosure period. The Development Plan (DP) for this analysis is given in CRWMS M and O (Civilian Radioactive Waste Management System Management and Operating Contractor) (1999a). The candidate materials for ground support are steel (carbon steel, ductile cast iron, galvanized steel, and stainless steel, etc.) and cement. Steel will mainly be used for steel sets, lagging, channels, rock bolts, and wire mesh. Cement usage is only considered in the case of grouted rock bolts. The candidate materials for the invert structure are steel and crushed rock ballast. The materials shall be evaluated for the repository emplacement drift environment under a specific thermal loading condition based on the proposed License Application Design Selection (LADS) design. The analysis consists of the following tasks: (1) Identify factors affecting the longevity of ground control materials for use in emplacement drifts. (2) Review existing documents concerning behavior of candidate ground control materials during the preclosure period. The major criteria to be considered for steel are mechanical and thermal properties, and durability, of which corrosion is the most important concern. (3) Evaluate the available results and develop recommendations for material(s) to be used

  4. Monitored Drift Chambers in the ATLAS Detector

    CERN Multimedia

    Herten, G

    Monitored Drift Chambers (MDT) are used in the ATLAS Detector to measure the momentum of high energy muons. They consist of drift tubes, which are filled with an Ar-CO2 gas mixture at 3 bar gas pressure. About 1200 drift chambers are required for ATLAS. They are up to 6 m long. Nevertheless the position of every wire needs to be known with a precision of 20 µm within a chamber. In addition, optical alignment sensors are required to measure the relative position of adjacent chambers with a precision of 30µm. This gigantic task seems impossible at first instance. Indeed it took many years of R&D to invent the right tools and methods before the first chamber could be built according to specifications. Today, at the time when 50% of the chambers have been produced, we are confident that the goal for ATLAS can be reached. The mechanical precision of the chambers could be verified with the x-ray tomograph at CERN. This ingenious device, developed for the MDT system, is able to measure the wire position insid...

  5. Internal Clock Drift Estimation in Computer Clusters

    Directory of Open Access Journals (Sweden)

    Hicham Marouani

    2008-01-01

    Full Text Available Most computers have several high-resolution timing sources, from the programmable interrupt timer to the cycle counter. Yet, even at a precision of one cycle in ten millions, clocks may drift significantly in a single second at a clock frequency of several GHz. When tracing the low-level system events in computer clusters, such as packet sending or reception, each computer system records its own events using an internal clock. In order to properly understand the global system behavior and performance, as reported by the events recorded on each computer, it is important to estimate precisely the clock differences and drift between the different computers in the system. This article studies the clock precision and stability of several computer systems, with different architectures. It also studies the typical network delay characteristics, since time synchronization algorithms rely on the exchange of network packets and are dependent on the symmetry of the delays. A very precise clock, based on the atomic time provided by the GPS satellite network, was used as a reference to measure clock drifts and network delays. The results obtained are of immediate use to all applications which depend on computer clocks or network time synchronization accuracy.

  6. Simplified Drift Analysis for Proving Lower Bounds in Evolutionary Computation

    DEFF Research Database (Denmark)

    Oliveto, Pietro S.; Witt, Carsten

    2011-01-01

    Drift analysis is a powerful tool used to bound the optimization time of evolutionary algorithms (EAs). Various previous works apply a drift theorem going back to Hajek in order to show exponential lower bounds on the optimization time of EAs. However, this drift theorem is tedious to read...... and to apply since it requires two bounds on the moment-generating (exponential) function of the drift. A recent work identifies a specialization of this drift theorem that is much easier to apply. Nevertheless, it is not as simple and not as general as possible. The present paper picks up Hajek’s line...

  7. Abstraction of Drift-Scale Coupled Processes

    International Nuclear Information System (INIS)

    Francis, N.D.; Sassani, D.

    2000-01-01

    This Analysis/Model Report (AMR) describes an abstraction, for the performance assessment total system model, of the near-field host rock water chemistry and gas-phase composition. It also provides an abstracted process model analysis of potentially important differences in the thermal hydrologic (TH) variables used to describe the performance of a geologic repository obtained from models that include fully coupled reactive transport with thermal hydrology and those that include thermal hydrology alone. Specifically, the motivation of the process-level model comparison between fully coupled thermal-hydrologic-chemical (THC) and thermal-hydrologic-only (TH-only) is to provide the necessary justification as to why the in-drift thermodynamic environment and the near-field host rock percolation flux, the essential TH variables used to describe the performance of a geologic repository, can be obtained using a TH-only model and applied directly into a TSPA abstraction without recourse to a fully coupled reactive transport model. Abstraction as used in the context of this AMR refers to an extraction of essential data or information from the process-level model. The abstraction analysis reproduces and bounds the results of the underlying detailed process-level model. The primary purpose of this AMR is to abstract the results of the fully-coupled, THC model (CRWMS M andO 2000a) for effects on water and gas-phase composition adjacent to the drift wall (in the near-field host rock). It is assumed that drift wall fracture water and gas compositions may enter the emplacement drift before, during, and after the heating period. The heating period includes both the preclosure, in which the repository drifts are ventilated, and the postclosure periods, with backfill and drip shield emplacement at the time of repository closure. Although the preclosure period (50 years) is included in the process models, the postclosure performance assessment starts at the end of this initial period

  8. Ground Control for Emplacement Drifts for SR

    International Nuclear Information System (INIS)

    Y. Sun

    2000-01-01

    This analysis demonstrates that a satisfactory ground control system can be designed for the Yucca Mountain site, and provides the technical basis for the design of ground support systems to be used in repository emplacement and non-emplacement drifts. The repository ground support design was based on analytical methods using acquired computer codes, and focused on the final support systems. A literature review of case histories, including the lessons learned from the design and construction of the ESF, the studies on the seismic damages of underground openings, and the use of rock mass classification systems in the ground support design, was conducted (Sections 6.3.4 and 6.4). This review provided some basis for determining the inputs and methodologies used in this analysis. Stability of the supported and unsupported emplacement and non-emplacement drifts was evaluated in this analysis. The excavation effects (i.e., state of the stress change due to excavation), thermal effects (i.e., due to heat output from waste packages), and seismic effects (i.e., from potential earthquake events) were evaluated, and stress controlled modes of failure were examined for two in situ stress conditions (k 0 =0.3 and 1.0) using rock properties representing rock mass categories of 1 and 5. Variation of rock mass units such as the non-lithophysal (Tptpmn) and lithophysal (Tptpll) was considered in the analysis. The focus was on the non-lithophysal unit because this unit appears to be relatively weaker and has much smaller joint spacing. Therefore, the drift stability and ground support needs were considered to be controlled by the design for this rock unit. The ground support systems for both emplacement and non-emplacement drifts were incorporated into the models to assess their performance under in situ, thermal, and seismic loading conditions. Both continuum and discontinuum modeling approaches were employed in the analyses of the rock mass behavior and in the evaluation of the

  9. In-Drift Precipitates/Salts Analysis

    International Nuclear Information System (INIS)

    Mariner, P.

    2001-01-01

    As directed by a written development plan (CRWMS M and O 1999a), an analysis of the effects of salts and precipitates on the repository chemical environment is to be developed and documented in an Analyses/Model Report (AMR). The purpose of this analysis is to assist Performance Assessment Operations (PAO) and the Engineered Barrier Performance Department in modeling the geochemical environment within a repository drift, thus allowing PAO to provide a more detailed and complete in-drift geochemical model abstraction and to answer the key technical issues (KTI) raised in the NRC Issue Resolution Status Report (IRSR) for the Evolution of the Near Field Environment (NFE) Revision 2 (NRC 1999). The purpose of this ICN is to qualify and document qualification of the AMR's technical products. The scope of this document is to develop a model of the processes that govern salt precipitation and dissolution and resulting water composition in the Engineered Barrier System (EBS). This model is developed to serve as a basis for the in-drift geochemical modeling work performed by PAO and is to be used in subsequent PAO analyses including the EBS physical and chemical model abstraction effort. However, the concepts may also apply to some near and far field geochemical processes and can have conceptual application within the unsaturated zone and saturated zone transport modeling efforts. The intended use of the model developed in this report is to estimate, within an appropriate level of confidence, the pH, chloride concentration, and ionic strength of water on the drip shield or other location within the drift during the post-closure period. These estimates are based on evaporative processes that are subject to a broad range of potential environmental conditions and are independent of the presence or absence of backfill. An additional intended use is to estimate the environmental conditions required for complete vaporization of water. The presence and composition of liquid water

  10. In-Drift Precipitates/Salts Analysis

    Energy Technology Data Exchange (ETDEWEB)

    P. Mariner

    2001-01-10

    As directed by a written development plan (CRWMS M&O 1999a), an analysis of the effects of salts and precipitates on the repository chemical environment is to be developed and documented in an Analyses/Model Report (AMR). The purpose of this analysis is to assist Performance Assessment Operations (PAO) and the Engineered Barrier Performance Department in modeling the geochemical environment within a repository drift, thus allowing PAO to provide a more detailed and complete in-drift geochemical model abstraction and to answer the key technical issues (KTI) raised in the NRC Issue Resolution Status Report (IRSR) for the Evolution of the Near Field Environment (NFE) Revision 2 (NRC 1999). The purpose of this ICN is to qualify and document qualification of the AMR's technical products. The scope of this document is to develop a model of the processes that govern salt precipitation and dissolution and resulting water composition in the Engineered Barrier System (EBS). This model is developed to serve as a basis for the in-drift geochemical modeling work performed by PAO and is to be used in subsequent PAO analyses including the EBS physical and chemical model abstraction effort. However, the concepts may also apply to some near and far field geochemical processes and can have conceptual application within the unsaturated zone and saturated zone transport modeling efforts. The intended use of the model developed in this report is to estimate, within an appropriate level of confidence, the pH, chloride concentration, and ionic strength of water on the drip shield or other location within the drift during the post-closure period. These estimates are based on evaporative processes that are subject to a broad range of potential environmental conditions and are independent of the presence or absence of backfill. An additional intended use is to estimate the environmental conditions required for complete vaporization of water. The presence and composition of liquid water

  11. A novel silicon drift detector with two dimensional drift time measurement

    International Nuclear Information System (INIS)

    Hijzen, E.A.; Schooneveld, E.M.; Van Eijk, C.W.E.; Hollander, R.W.; Sarro, P.M.; Van den Bogaard, A.

    1994-01-01

    Until now silicon drift detectors with two dimensional position resolution made use of drift time measurement in one dimension only. The resolution in the other dimension was obtained by dividing the collecting anode into small pixels. In this paper we present a new type of drift detector that uses drift time measurements for both dimensions. The design consists of concentric quadrilateral closed strips with a small collecting anode in the centre. At first electrons will travel perpendicular to the strips until they reach a diagonal. Then they will proceed along this diagonal until they are collected at the centre. Position resolution in two dimensions can be obtained when both the time the electrons need to reach the diagonal and the time they need to reach the centre are measured. The latter is obtained from the collecting anode, the former from a diagonal strip present at the back side of the detector. Compared to common 2D drift detectors this detector offers the advantage of a small amount of readout electronics. It also has the advantage of having just one small collecting anode with a very low capacitance, resulting in low noise and therefore in a good energy resolution. ((orig.))

  12. Intrafractional baseline drift during free breathing breast cancer radiation therapy.

    Science.gov (United States)

    Jensen, Christer Andre; Acosta Roa, Ana María; Lund, Jo-Åsmund; Frengen, Jomar

    2017-06-01

    Intrafraction motion in breast cancer radiation therapy (BCRT) has not yet been thoroughly described in the literature. It has been observed that baseline drift occurs as part of the intrafraction motion. This study aims to measure baseline drift and its incidence in free-breathing BCRT patients using an in-house developed laser system for tracking the position of the sternum. Baseline drift was monitored in 20 right-sided breast cancer patients receiving free breathing 3D-conformal RT by using an in-house developed laser system which measures one-dimensional distance in the AP direction. A total of 357 patient respiratory traces from treatment sessions were logged and analysed. Baseline drift was compared to patient positioning error measured from in-field portal imaging. The mean overall baseline drift at end of treatment sessions was -1.3 mm for the patient population. Relatively small baseline drift was observed during the first fraction; however it was clearly detected already at the second fraction. Over 90% of the baseline drift occurs during the first 3 min of each treatment session. The baseline drift rate for the population was -0.5 ± 0.2 mm/min in the posterior direction the first minute after localization. Only 4% of the treatment sessions had a 5 mm or larger baseline drift at 5 min, all towards the posterior direction. Mean baseline drift in the posterior direction in free breathing BCRT was observed in 18 of 20 patients over all treatment sessions. This study shows that there is a substantial baseline drift in free breathing BCRT patients. No clear baseline drift was observed during the first treatment session; however, baseline drift was markedly present at the rest of the sessions. Intrafraction motion due to baseline drift should be accounted for in margin calculations.

  13. Comparison of electrostatic and electromagnetic synchronization of drift waves and suppression of drift wave turbulence in a linear device

    Energy Technology Data Exchange (ETDEWEB)

    Brandt, C; Grulke, O; Klinger, T, E-mail: christian.brandt@lpmi.uhp-nancy.f [Max-Planck-Institute for Plasma Physics, EURATOM Association, Wendelsteinstrasse 1, D-17491 Greifswald (Germany)

    2010-05-15

    Experiments in a cylindrical magnetized plasma on the control of drift waves by means of two different spatiotemporal open-loop control systems-an electrostatic and an electromagnetic exciter-are reported. The drift wave dynamics is controlled by a mode-selective signal created with azimuthal arrangements of eight electrodes and eight saddle coils, respectively. Nonlinear interaction between the control signals and drift waves is observed, leading to synchronization of coherent drift waves and suppression of broadband drift wave turbulence. The cross-phase between density and potential fluctuations reduces from {approx}{pi}/2 in turbulence to {approx}0 in controlled turbulence. Hence, the cross-field transport is reduced to the level of coherent drift waves. For both control systems the coupling to the drift wave can be ascribed to the drive of parallel currents, on the one hand via direct electric contact and, on the other hand, via electromagnetic induction.

  14. Field experiment on spray drift: deposition and airborne drift during application to a winter wheat crop.

    Science.gov (United States)

    Wolters, André; Linnemann, Volker; van de Zande, Jan C; Vereecken, Harry

    2008-11-01

    A field experiment was performed to evaluate various techniques for measuring spray deposition and airborne drift during spray application to a winter wheat crop. The application of a spraying agent containing the fluorescent dye Brilliant Sulfo Flavine by a conventional boom sprayer was done according to good agricultural practice. Deposition was measured by horizontal collectors in various arrangements in and outside the treated area. Airborne spray drift was measured both with a passive and an active air collecting system. Spray deposits on top of the treated canopy ranged between 68 and 71% of the applied dose and showed only small differences for various arrangements of the collectors. Furthermore, only small variations were measured within the various groups of collectors used for these arrangements. Generally, the highest spray deposition outside the treated area was measured close to the sprayed plot and was accompanied by a high variability of values, while a rapid decline of deposits was detected in more remote areas. Estimations of spray deposits with the IMAG Drift Calculator were in accordance with experimental findings only for areas located at a distance of 0.5-4.5 m from the last nozzle, while there was an overestimation of a factor of 4 at a distance of 2.0-3.0 m, thus revealing a high level of uncertainty of the estimation of deposition for short distances. Airborne spray drift measured by passive and active air collecting systems was approximately at the same level, when taking into consideration the collector efficiency of the woven nylon wire used as sampling material for the passive collecting system. The maximum value of total airborne spray drift for both spray applications (0.79% of the applied dose) was determined by the active collecting system. However, the comparatively high variability of measurements at various heights above the soil by active and passive collecting systems revealed need for further studies to elucidate the spatial

  15. Development of an equipment diagnostic system that evaluates sensor drift

    International Nuclear Information System (INIS)

    Kanada, Masaki; Arita, Setsuo; Tada, Nobuo; Yokota, Katsuo

    2011-01-01

    The importance of condition monitoring technology for equipment has increased with the introduction of condition-based maintenance in nuclear power plants. We are developing a diagnostic system using process signals for plant equipment, such as pumps and motors. It is important to enable the diagnostic system to distinguish sensor drift and equipment failure. We have developed a sensor drift diagnostic method that combines some highly correlative sensor signals by using the MT (Mahalanobis-Taguchi) method. Furthermore, we have developed an equipment failure diagnostic method that measures the Mahalanobis distance from the normal state of equipment by the MT method. These methods can respectively detect sensor drift and equipment failure, but there are the following problems. In the sensor drift diagnosis, there is a possibility of misjudging the sensor drift when the equipment failure occurs and the process signal changes because the behavior of the process signal is the same as that of the sensor drift. Oppositely, in the equipment failure diagnosis, there is a possibility of misjudging the equipment failure when the sensor drift occurs because the sensor drift influences the change of process signal. To solve these problems, we propose a diagnostic method combining the sensor drift diagnosis and the equipment failure diagnosis by the MT method. Firstly, the sensor drift values are estimated by the sensor drift diagnosis, and the sensor drift is removed from the process signal. It is necessary to judge the validity of the estimated sensor drift values before removing the sensor drift from the process signal. We developed a method for judging the validity of the estimated sensor drift values by using the drift distribution based on the sensor calibration data. And then, the equipment failure is diagnosed by using the process signals after removal of the sensor drifts. To verify the developed diagnostic system, several sets of simulation data based on abnormal cases

  16. Suspended sediment drift and dispersion at Hibernia

    International Nuclear Information System (INIS)

    Tedford, T.; Drozdowski, A.; Hannah, C.G.

    2003-01-01

    Surface water waves and near-bottom currents around the Hibernia oil production platform on the Grand Banks of Newfoundland were examined to determine how the different seasons affect changes in wave magnitude and directions of water currents. Wave observations revealed a strong correlation with seasons, with the larger waves occurring in fall and early winter. There was no obvious seasonality in the size or direction of currents. The benthic boundary layer transport (BBLT) model was used to predict the drift and dispersion pathways of suspended drilling muds discharged from the Hibernia platform. The 2-year study from March 1998 to May 2000 involved 5-day BBLT model simulations covering the complete period of current meter deployment. The study focused on the sensitivity of the drift and dispersion to variability in the physical environment and uncertainty in the bottom stress calculation and particle settling velocity. The BBLT model incorporates a stress dependent particle settling velocity that includes the main features of the flocculations of drill mud fines under marine conditions. The study provides a better understanding of how drill mud concentration levels can change with variations in waves, currents, and bottom stress. It was determined that drift is generally oriented along the northwest/southeast axis, with a typical magnitude of 0.8 cm/sec for the fast settling velocity and 3.1 cm/sec for the slow settling velocity. It was concluded that near-surface or mid-depth discharges of drilling mud in the summer may not reach the sea floor. 17 refs., 13 tabs., 36 figs

  17. Indoor spray measurement of spray drift potential using a spray drift test bench : effect of drift-reducing nozzle types, spray boom height, nozzle spacing and forward speed

    NARCIS (Netherlands)

    Moreno Ruiz, J.R.

    2014-01-01

    In a series of indoor experiments spray drift potential was assessed when spraying over a spray drift testbench with two different driving speeds, 2m/s and 4m/s, two different spray boom heights, 30 cm and 50 cm, and two different nozzle spacing, 25 cm and 50 cm, for six different nozzle types. The

  18. Strange Attractors in Drift Wave Turbulence

    International Nuclear Information System (INIS)

    Lewandowski, Jerome L.V.

    2003-01-01

    There are growing experimental, numerical and theoretical evidences that the anomalous transport observed in tokamaks and stellarators is caused by slow, drift-type modes (such as trapped electron modes and ion-temperature gradient-driven modes). Although typical collision frequencies in hot, magnetized fusion plasmas can be quite low in absolute values, collisional effects are nevertheless important since they act as dissipative sinks. As it is well known, dissipative systems with many (strictly speaking more than two) degrees of freedom are often chaotic and may evolve towards a so-called attractor

  19. The Mark II Vertex Drift Chamber

    International Nuclear Information System (INIS)

    Alexander, J.P.; Baggs, R.; Fujino, D.

    1989-03-01

    We have completed constructing and begun operating the Mark II Drift Chamber Vertex Detector. The chamber, based on a modified jet cell design, achieves 30 μm spatial resolution and 2 gas mixtures. Special emphasis has been placed on controlling systematic errors including the use of novel construction techniques which permit accurate wire placement. Chamber performance has been studied with cosmic ray tracks collected with the chamber located both inside and outside the Mark II. Results on spatial resolution, average pulse shape, and some properties of CO 2 mixtures are presented. 10 refs., 12 figs., 1 tab

  20. Autocalibration of high precision drift tubes

    International Nuclear Information System (INIS)

    Bacci, C.; Bini, C.; Ciapetti, G.; De Zorzi, G.; Gauzzi, P.; Lacava, F.; Nisati, A.; Pontecorvo, L.; Rosati, S.; Veneziano, S.; Cambiaghi, M.; Casellotti, G.; Conta, C.; Fraternali, M.; Lanza, A.; Livan, M.; Polesello, G.; Rimoldi, A.; Vercesi, V.

    1997-01-01

    We present the results on MDT (monitored drift tubes) autocalibration studies obtained from the analysis of the data collected in Summer 1995 on the H8B Muon Test Beam. In particular we studied the possibility of autocalibration of the MDT using four or three layers of tubes, and we compared the calibration obtained using a precise external tracker with the output of the autocalibration procedure. Results show the feasibility of autocalibration with four and three tubes and the good accuracy of the autocalibration procedure. (orig.)

  1. Drift chambers in BM@N Experiment

    Directory of Open Access Journals (Sweden)

    Fedorišin Ján

    2017-01-01

    In first step, the radius vs drift time calibration curve is estimated and applied to calculate DCH hit closest approach coordinates. These coordinates are used to construct hits in each DCH under the assumption of track linearity. Hits in both the DCHs are subsequently aligned and fitted to produce global linear track candidates. Eventually the hit and track reconstruction is optimized by the autocalibration method. The coordinate resolutions are estimated from Gaussian fits of the DCH hit residual spectra for different DCH planes. Furthermore, the deuteron beam momentum value is reconstructed in order to check reliability of the employed track reconstruction algorithm.

  2. Unstable drift eigenmode in slab geometry

    International Nuclear Information System (INIS)

    Tsotsonis, S.; Hirose, A.

    1986-01-01

    The unstable Pearlstein-Berk mode of drift waves in plane, sheared slab geometry has later been shown to be stable when electron Landau resonance is rigorously treated. Based on the variational method previously developed the authors have found that in addition to the absolutely stable Pearlstein-Berk mode, there exists an absolutely unstable eigenfunction characterized by ω ≤ ω/sub chemical bonde/, and weak ''radial'' dependence. Also, the growth rate, only weakly depends on the magnetic shear and ion/electron temperature ratio

  3. Analysis of digisonde drift measurements quality

    Czech Academy of Sciences Publication Activity Database

    Kouba, Daniel; Koucká Knížová, Petra

    90-91, December (2012), s. 212-221 ISSN 1364-6826. [IAGA/ICMA/CAWSES-II TG4 Workshop on Vertical Coupling in the Atmosphere-Ionosphere System /4./. Prague, 14.02.2011-18.02.2011] R&D Projects: GA AV ČR KJB300420904; GA AV ČR IAA300420704 Institutional support: RVO:68378289 Keywords : Ionosphere * Plasma drifts * Skymap * Digisonde Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.417, year: 2012 http://www.sciencedirect.com/science/article/pii/S1364682612001290

  4. MAGSAT anomaly map and continental drift

    Science.gov (United States)

    Lemouel, J. L. (Principal Investigator); Galdeano, A.; Ducruix, J.

    1981-01-01

    Anomaly maps of high quality are needed to display unambiguously the so called long wave length anomalies. The anomalies were analyzed in terms of continental drift and the nature of their sources is discussed. The map presented confirms the thinness of the oceanic magnetized layer. Continental magnetic anomalies are characterized by elongated structures generally of east-west trend. Paleomagnetic reconstruction shows that the anomalies found in India, Australia, and Antarctic exhibit a fair consistency with the African anomalies. It is also shown that anomalies are locked under the continents and have a fixed geometry.

  5. Crowdsourcing and annotating NER for Twitter #drift

    DEFF Research Database (Denmark)

    Fromreide, Hege; Hovy, Dirk; Søgaard, Anders

    2014-01-01

    We present two new NER datasets for Twitter; a manually annotated set of 1,467 tweets (kappa=0.942) and a set of 2,975 expert-corrected, crowdsourced NER annotated tweets from the dataset described in Finin et al. (2010). In our experiments with these datasets, we observe two important points: (a......) language drift on Twitter is significant, and while off-the-shelf systems have been reported to perform well on in-sample data, they often perform poorly on new samples of tweets, (b) state-of-the-art performance across various datasets can beobtained from crowdsourced annotations, making it more feasible...

  6. Cathode Readout with Stripped Resistive Drift Tubes

    International Nuclear Information System (INIS)

    Bychkov, V.N.; Kekelidze, G.D.; Novikov, E.A.; Peshekhonov, V.D.; Shafranov, M.D.; Zhil'tsov, V.E.

    1994-01-01

    A straw tube drift chamber prototype has been constructed and tested. The straw tube material is mylar film covered with carbon layer of resistivity 0.5, 30 and 70 k Ohm/sq. The gas mixture used was Ar/CH 4 . Both the anode wire and cathode signals were detected in order to study the behaviour of the chamber in the presence of X-ray ionization. The construction and the results of the study are presented. 7 refs., 11 figs., 1 tab

  7. Hydrogen high pressure proportional drift detector

    International Nuclear Information System (INIS)

    Arefiev, A.; Balaev, A.

    1983-01-01

    The design and operation performances of a proportional drift detector PDD are described. High sensitivity of the applied PAD makes it possible to detect the neutron-proton elastic scattering in the energy range of recoil protons as low as 1 keV. The PDD is filled with hydrogen up to the pressure at 40 bars. High purity of the gas is maintained by a continuously operating purification system. The detector has been operating for several years in a neutron beam at the North Area of the CERN SPS

  8. Evaluation of prototype silicon drift detectors

    International Nuclear Information System (INIS)

    Ellison, J.; Hall, G.; Roe, S.; Lucas, A.

    1988-01-01

    Operating characteristics of several prototypes of silicon drift detectors are investigated. Detectors are made of unpolished silicon produced by the zone melting method and characterized by n-type conductivity and specific resistance of 3.6-4.6 kOhmxcm. The detectors comprise 40 parallel bands of 200 μm width and 1 cm length separated by 50 μm intervals. Data characterizing the potential distribution near anodes under the operating bias voltage, dependences of capacities and leakage as well as the detector space resolution

  9. Post-earnings announcement drift in Greece

    OpenAIRE

    Forbes, William; Giannopoulos, George

    2015-01-01

    This paper presents evidence regarding the post-earnings announcement drift (PEAD) anomaly for the Greek market in the years 2000–2006 (covering earnings announcements in the years 2001–2007). The impact of the introduction of International Financial Reporting Standards on the size and prevalence of the PEAD anomaly is examined. Unlike recent evidence for the US market we find PEAD to be\\ud alive and well, and of growing importance in our Greek sample. It may be the adoption of international ...

  10. Construction of the Cleo III drift chamber

    International Nuclear Information System (INIS)

    Csorna, S.; Marka, S.; Dickson, M.; Dombrowski, S. von; Peterson, D.; Thies, P.; Glenn, S.; Thorndike, E.H.; Kravchenko, I.

    1998-01-01

    The CLEO III group is constructing a new chamber to be installed as part of the staged luminosity upgrade program at the Cornell electron storage ring and compatible with the interaction region optics. Although having less radial extent than the current CLEO II tracking system, CLEO III will have equivalent momentum resolution because of material reduction in the drift chamber inner skin and gas. The thin inner skin requires special attention to the end-plate motion due to wire creep. During stringing, use of a robot will fully automate the wire handling on the upper end. (author)

  11. Drift Tube Linac Conditioning of Tank1

    CERN Document Server

    Shafqat, N; Toor, W A

    2014-01-01

    Tank1 of the Drift Tube Linac (DTL) of the Linac4 has been conditioned at the Linac4 tunnel. The tank was tuned for resonance at 352.2 MHz, and stable operation has been achieved with 725 µs long RF pulses at a repetition rate of 1 Hz. The maximum RF level that has been reached is 810 kW with a pulse width of 600 µs. Since this was the first RF structure exclusively conditioned in the Linac4 tunnel with the operation and control software of Linac4, some related issues and limitations had to be taken into account.

  12. Field experiment on spray drift: Deposition and airborne drift during application to a winter wheat crop

    NARCIS (Netherlands)

    Wolters, A.; Linnemann, V.; Zande, van de J.C.; Vereecken, H.

    2008-01-01

    A field experiment was performed to evaluate various techniques for measuring spray deposition and airborne drift during spray application to a winter wheat crop. The application of a spraying agent containing the fluorescent dye Brilliant Sulfo Flavine by a conventional boom sprayer was done

  13. Electromagnetic drift waves dispersion for arbitrarily collisional plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Wonjae, E-mail: wol023@ucsd.edu; Krasheninnikov, Sergei I., E-mail: skrash@mae.ucsd.edu [Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093 (United States); Angus, J. R. [Naval Research Laboratory, 4555 Overlook Avenue, Washington, DC 20375 (United States)

    2015-07-15

    The impacts of the electromagnetic effects on resistive and collisionless drift waves are studied. A local linear analysis on an electromagnetic drift-kinetic equation with Bhatnagar-Gross-Krook-like collision operator demonstrates that the model is valid for describing linear growth rates of drift wave instabilities in a wide range of plasma parameters showing convergence to reference models for limiting cases. The wave-particle interactions drive collisionless drift-Alfvén wave instability in low collisionality and high beta plasma regime. The Landau resonance effects not only excite collisionless drift wave modes but also suppress high frequency electron inertia modes observed from an electromagnetic fluid model in collisionless and low beta regime. Considering ion temperature effects, it is found that the impact of finite Larmor radius effects significantly reduces the growth rate of the drift-Alfvén wave instability with synergistic effects of high beta stabilization and Landau resonance.

  14. Precision alignment of permanent-magnet drift tubes

    International Nuclear Information System (INIS)

    Liska, D.J.; Dauelsberg, L.B.; Spalek, G.

    1986-01-01

    The Lawrence Berkeley National Laboratory (LBNL) technique of drift-tube alignment has been resurrected at Los Alamos for the precision alignment of 1-cm-bore drift tubes that carry high-gradient rare-earth-cobalt quadrupole. Because the quadrupole cannot be switched off, this technique is not applicable to a drift-tube assembly, but tests indicate that individual magnetic centers can be detected with a precision of +- 0.003 mm. Methods of transferring this information to machined alignment flats on the sides of the drift-tube body are discussed. With measurements of drift tubes designed for a 100-mA. 425-MHz drift-tube linac, we have detected offsets between the geometric and magnetic axes of up to +- 0.05 mm following final assembly and welding. This degree of offset is serious if not accommodated, because it represents the entire alignment tolerance for the 40-cell tank. The measurement equipment and technique are described

  15. Ground Control for Non-Emplacement Drifts for LA

    International Nuclear Information System (INIS)

    Tang, D.

    2004-01-01

    The purpose of this calculation is to analyze the stability of repository non-emplacement drifts during the preclosure period, and to provide a final ground support method for non-emplacement drifts for the License Application (LA). This calculation will provide input for the development of LA documents. The scope of this calculation is limited to the non-emplacement drifts including access mains, ramps, exhaust mains, turnouts, intersections between access mains and turnouts, and intersections between exhaust mains and emplacement drifts, portals, TBM launch chambers, observation drift and test alcove in the performance confirmation (PC) facilities, etc. The calculation is limited to the non-emplacement drifts subjected to a combined loading of in-situ stress, seismic stress, and/or thermal stress. Other effects such as hydrological and chemical effects are not considered in this analysis

  16. Laced permanent magnet quadrupole drift tube magnets

    International Nuclear Information System (INIS)

    Feinberg, B.; Behrsing, G.U.; Halbach, K.; Marks, J.S.; Morrison, M.E.; Nelson, D.H.

    1988-10-01

    A laced permanent magnet quadrupole drift tube magnet has been constructed for a proof-of-principle test. The magnet is a conventional tape-wound quadrupole electromagnet, using iron pole- pieces, with the addition of permanent magnet material (neodymium iron) between the poles to reduce the effects of saturation. The iron is preloaded with magnetic flux generated by the permanent magnet material, resulting in an asymmetrical saturation curve. Since the polarity of the quadrupole magnets in a drift tube linac is not reversed we can take advantage of this asymmetrical saturation to provide greater focusing strength. The magnet configuration has been optimized and the vanadium permendur poles needed in a conventional quadrupole have been replaced with iron poles. The use of permanent magnet material has allowed us to increase the focusing strength of the magnet by about 20% over that of a conventional tape-wound quadrupole. Comparisons will be made between this magnet and the conventional tape-wound quadrupole. 3 refs., 5 figs

  17. Metabolic drift in the aging brain.

    Science.gov (United States)

    Ivanisevic, Julijana; Stauch, Kelly L; Petrascheck, Michael; Benton, H Paul; Epstein, Adrian A; Fang, Mingliang; Gorantla, Santhi; Tran, Minerva; Hoang, Linh; Kurczy, Michael E; Boska, Michael D; Gendelman, Howard E; Fox, Howard S; Siuzdak, Gary

    2016-05-01

    Brain function is highly dependent upon controlled energy metabolism whose loss heralds cognitive impairments. This is particularly notable in the aged individuals and in age-related neurodegenerative diseases. However, how metabolic homeostasis is disrupted in the aging brain is still poorly understood. Here we performed global, metabolomic and proteomic analyses across different anatomical regions of mouse brain at different stages of its adult lifespan. Interestingly, while severe proteomic imbalance was absent, global-untargeted metabolomics revealed an energymetabolic drift or significant imbalance in core metabolite levels in aged mouse brains. Metabolic imbalance was characterized by compromised cellular energy status (NAD decline, increased AMP/ATP, purine/pyrimidine accumulation) and significantly altered oxidative phosphorylation and nucleotide biosynthesis and degradation. The central energy metabolic drift suggests a failure of the cellular machinery to restore metabostasis (metabolite homeostasis) in the aged brain and therefore an inability to respond properly to external stimuli, likely driving the alterations in signaling activity and thus in neuronal function and communication.

  18. EMPLACEMENT DRIFT ISOLATION DOOR CONTROL SYSTEM

    International Nuclear Information System (INIS)

    N.T. Raczka

    1998-01-01

    The purpose of this analysis is to review and refine key design concepts related to the control system presently under consideration for remotely operating the emplacement drift isolation doors at the potential subsurface nuclear waste repository at Yucca Mountain. This analysis will discuss the key design concepts of the control system that may be utilized for remotely monitoring, opening, and closing the emplacement drift isolation doors. The scope and primary objectives of this analysis are to: (1) Discuss the purpose and function of the isolation doors (Presented in Section 7.1). (2) Review the construction of the isolation door and other physical characteristics of the doors that the control system will interface with (Presented in Section 7.2). (3) Discuss monitoring and controlling the operation of the isolation doors with a digital control system (either a Programmable Logic Controller (PLC) system or a Distributed Control System (DCS)) (Presented in Section 7.3). (4) Discuss how all isolation doors can be monitored and controlled from a subsurface central control center (Presented in Section 7.4). This analysis will focus on the development of input/output (I/O) counts including the types of I/O, redundancy and fault tolerance considerations, and processor requirements for the isolation door control system. Attention will be placed on operability, maintainability, and reliability issues for the system operating in the subsurface environment with exposure to high temperatures and radiation

  19. PWCs and drift chambers at ISABELLE

    International Nuclear Information System (INIS)

    Okuno, H.; Teramoto, Y.; Wheeler, C.D.

    1978-01-01

    Rate effects in proportional chambers and drift chambers are addressed first. The widely used high-gas-gain chambers would have impaired performance at ISABELLE data rates. Improvement can be expected with lower gas gain, and this possibility is investigated with respect to position and time resolution. Results on chamber lifetime are summarized; space-charge effects, gain saturation, and radiation hardness of electronics are considered. The resolution of drift chambers is discussed in some detail; time resolution, double pulse resolution, and momentum resolution and multiple scattering are included. The expected high multiplicity of tracks from a single event, the high event rates, and the requirement for low gas gain necessitate revision of the methods for measuring the second coordinate. Known methods of two-dimensional point localization are summarized according to spatial accuracy, electronics requirements, and multihit capability. Delay lines, charge division, and cathode strips are considered. Particle identification by means of measurement of the relativistic rise of energy loss by conventional and unconventional means was investigated. 32 references, 3 figures, 4 tables

  20. Southern hemisphere observations of a long-term decrease in F region altitude and thermospheric wind providing possible evidence for global thermospheric cooling

    Science.gov (United States)

    Jarvis, M. J.; Jenkins, B.; Rodgers, G. A.

    1998-09-01

    F region peak heights, derived from ionospheric scaled parameters through 38-year data series from both Argentine Islands (65°S, 64°W) and Port Stanley (52°S, 58°W) have been analyzed for signatures of secular change. Long-term changes in altitude, which vary with month and time of day, were found at both sites. The results can be interpreted either as a constant decrease in altitude combined with a decreasing thermospheric wind effect or as a constant decrease in altitude which is altitude-dependent. Both interpretations leave inconsistencies when the results from the two sites are compared. The estimated long-term decrease in altitude is of a similar order of magnitude to that which has been predicted to result in the thermosphere from anthropogenic change related to greenhouse gases. Other possibilities should not, however, be ruled out.

  1. In-Drift Precipitates/Salts Model

    International Nuclear Information System (INIS)

    P. Mariner

    2004-01-01

    This report documents the development and validation of the in-drift precipitates/salts (IDPS) model. The IDPS model is a geochemical model designed to predict the postclosure effects of evaporation and deliquescence on the chemical composition of water within the Engineered Barrier System (EBS) in support of the Total System Performance Assessment for the License Application (TSPA-LA). Application of the model in support of TSPA-LA is documented in ''Engineered Barrier System: Physical and Chemical Environment Model'' (BSC 2004 [DIRS 169860]). Technical Work Plan for: Near-Field Environment and Transport In-Drift Geochemistry Model Report Integration (BSC 2004 [DIRS 171156]) is the technical work plan (TWP) for this report. It called for a revision of the previous version of the report (BSC 2004 [DIRS 167734]) to achieve greater transparency, readability, data traceability, and report integration. The intended use of the IDPS model is to estimate and tabulate, within an appropriate level of confidence, the effects of evaporation, deliquescence, and potential environmental conditions on the pH, ionic strength, and chemical compositions of water and minerals on the drip shield or other location within the drift during the postclosure period. Specifically, the intended use is as follows: (1) To estimate, within an appropriate level of confidence, the effects of evaporation and deliquescence on the presence and composition of water occurring within the repository during the postclosure period (i.e., effects on pH, ionic strength, deliquescence relative humidity, total concentrations of dissolved components in the system Na-K-H-Mg-Ca-Al-Cl-F-NO 3 -SO 4 -Br-CO 3 -SiO 2 -CO 2 -O 2 -H 2 O, and concentrations of the following aqueous species that potentially affect acid neutralizing capacity: HCO 3 - , CO 3 2- , OH - , H + , HSO 4 - , Ca 2+ , Mg 2+ , CaHCO 3 + , MgHCO 3 + , HSiO 3 - , and MgOH + ); (2) To estimate, within an appropriate level of confidence, mineral

  2. In-Drift Precipitates/Salts Model

    Energy Technology Data Exchange (ETDEWEB)

    P. Mariner

    2004-11-09

    This report documents the development and validation of the in-drift precipitates/salts (IDPS) model. The IDPS model is a geochemical model designed to predict the postclosure effects of evaporation and deliquescence on the chemical composition of water within the Engineered Barrier System (EBS) in support of the Total System Performance Assessment for the License Application (TSPA-LA). Application of the model in support of TSPA-LA is documented in ''Engineered Barrier System: Physical and Chemical Environment Model'' (BSC 2004 [DIRS 169860]). Technical Work Plan for: Near-Field Environment and Transport In-Drift Geochemistry Model Report Integration (BSC 2004 [DIRS 171156]) is the technical work plan (TWP) for this report. It called for a revision of the previous version of the report (BSC 2004 [DIRS 167734]) to achieve greater transparency, readability, data traceability, and report integration. The intended use of the IDPS model is to estimate and tabulate, within an appropriate level of confidence, the effects of evaporation, deliquescence, and potential environmental conditions on the pH, ionic strength, and chemical compositions of water and minerals on the drip shield or other location within the drift during the postclosure period. Specifically, the intended use is as follows: (1) To estimate, within an appropriate level of confidence, the effects of evaporation and deliquescence on the presence and composition of water occurring within the repository during the postclosure period (i.e., effects on pH, ionic strength, deliquescence relative humidity, total concentrations of dissolved components in the system Na-K-H-Mg-Ca-Al-Cl-F-NO{sub 3}-SO{sub 4}-Br-CO{sub 3}-SiO{sub 2}-CO{sub 2}-O{sub 2}-H{sub 2}O, and concentrations of the following aqueous species that potentially affect acid neutralizing capacity: HCO{sub 3}{sup -}, CO{sub 3}{sup 2-}, OH{sup -}, H{sup +}, HSO{sub 4}{sup -}, Ca{sup 2+}, Mg{sup 2+}, CaHCO{sub 3}{sup +}, MgHCO{sub 3

  3. A statistical study of diurnal, seasonal and solar cycle variations of F-region and topside auroral upflows observed by EISCAT between 1984 and 1996

    Directory of Open Access Journals (Sweden)

    C. Foster

    Full Text Available A statistical analysis of F-region and topside auroral ion upflow events is presented. The study is based on observations from EISCAT Common Programmes (CP 1 and 2 made between 1984 and 1996, and Common Programme 7 observations taken between 1990 and 1995. The occurrence frequency of ion upflow events (IUEs is examined over the altitude range 200 to 500 km, using field-aligned observations from CP-1 and CP-2. The study is extended in altitude with vertical measurements from CP-7. Ion upflow events were identified by consideration of both velocity and flux, with threshold values of 100 m s–1 and 1013 m–2 s–1, respectively. The frequency of occurrence of IUEs is seen to increase with increasing altitude. Further analysis of the field-aligned observations reveals that the number and nature of ion upflow events vary diurnally and with season and solar activity. In particular, the diurnal distribution of upflows is strongly dependent on solar cycle. Furthermore, events identified by the velocity selection criterion dominate at solar minimum, whilst events identified by the upward field-aligned flux criterion dominated at solar maximum. The study also provides a quantitative estimate of the proportion of upflows that are associated with enhanced plasma temperature. Between 50 and 60% of upflows are simultaneous with enhanced ion temperature, and approximately 80% of events are associated with either increased F-region ion or electron temperatures.

    Key words. Ionosphere (auroral ionosphere; particle acceleration

  4. Nonlinear drift waves in a dusty plasma with sheared flows

    Energy Technology Data Exchange (ETDEWEB)

    Vranjes, J. [K.U. Leuven (Belgium). Center for Plasma Astrophysics; Shukla, R.K. [Ruhr-Univ. Bochum (Germany). Inst. fuer Theoretische Physik IV

    2002-01-01

    Nonlinear properties of dust-modified drift waves and dust-drift waves in a dusty magnetoplasma with equilibrium sheared flows are examined. For this purpose, the relevant nonlinear equations for drift waves are analyzed for various profiles of the perpendicular and parallel plasma flows, and a variety of nonlinear solutions (viz. single and double vortex chains accompanied with zonal flows, tripolar and global vortices), which are driven by nommiform shear flows and nommiform dust density, is presented.

  5. Nonlinear drift waves in a dusty plasma with sheared flows

    International Nuclear Information System (INIS)

    Vranjes, J.; Shukla, R.K.

    2002-01-01

    Nonlinear properties of dust-modified drift waves and dust-drift waves in a dusty magnetoplasma with equilibrium sheared flows are examined. For this purpose, the relevant nonlinear equations for drift waves are analyzed for various profiles of the perpendicular and parallel plasma flows, and a variety of nonlinear solutions (viz. single and double vortex chains accompanied with zonal flows, tripolar and global vortices), which are driven by nommiform shear flows and nommiform dust density, is presented

  6. Test of a high resolution drift chamber prototype

    International Nuclear Information System (INIS)

    Comminchau, V.; Deutschmann, M.; Draheim, K.J.; Fritze, P.; Hangarter, K.; Hawelka, P.; Herten, U.; Tonutti, M.; Anderhub, H.; Fehlmann, J.; Hofer, H.; Klein, M.; Paradiso, J.A.; Schreiber, J.; Viertel, G.

    1984-06-01

    The performance of a drift chamber prototype for a colliding beam vertex detector in a test beam at DESY is described. At one (two) atmosphere gas pressure a spatial resolution of 40 μm (30 μm) per wire for one cm drift length was achieved with a 100 MHz Flash-ADC system. An excellent double track resolution of better than 300 μm over the full drift length of 5 cm can be estimated. (orig.)

  7. The Study of Westward Drift in the Main Geomagnetic Field

    Directory of Open Access Journals (Sweden)

    G. Bayanjargal

    2013-01-01

    Full Text Available We have obtained a solution for the velocity of westward drift from the induction equation in which an approach for main geomagnetic field was built. Distribution functions B(r, t entered into the induction equation have been built by the observatories' data in North America and the Europe from 1991 to 2006. The longitudinal −0.123 degree/year and latitudinal 0.068 degree/year drifts were defined in North America. And the longitudinal −0.257 degree/year drift was defined in Europe from 1991 to 2006. These drifts are similar to results of other studies.

  8. Tabulated In-Drift Geometric and Thermal Properties Used In Drift-Scale Models for TSPA-SR

    International Nuclear Information System (INIS)

    N.D. Francis

    2000-01-01

    The objective of this calculation is to provide in-drift physical properties required by the drift-scale models (both two- and three-dimensional) used in total system performance assessments (TSPA). The physical properties include waste package geometry, waste package thermal properties, emplacement drift geometry including backfill and invert geometry and properties (both thermal and hydrologic), drip shield geometry and thermal properties, all tabulated in a single source

  9. Measurements of electron drift and diffusion properties in a large cylindrical drift chamber (TPC) with parallel electric and magnetic fields

    International Nuclear Information System (INIS)

    Richstein, J.

    1986-01-01

    This work describes measurements on the drift of electrons in gases, using the TPC90, the prototype of the ALEPH Time Projection Chamber. Tracks which were created by UV-Laser ionization have been drifted over distances of up to 1.3 m in parallel electric and magnetic fields. Electron drift properties have been systematically measured as a function of these, in several gas mixtures. (orig./HSI)

  10. Multilevel Drift-Implicit Tau-Leap

    KAUST Repository

    Ben Hammouda, Chiheb

    2016-01-06

    The dynamics of biochemical reactive systems with small copy numbers of one or more reactant molecules is dominated by stochastic effects. For those systems, discrete state-space and stochastic simulation approaches were proved to be more relevant than continuous state-space and deterministic ones. In systems characterized by having simultaneously fast and slowtimescales, the existing discrete space-state stochastic path simulation methods such as the stochastic simulation algorithm (SSA) and the explicit tauleap method can be very slow. Implicit approximations were developed in the literature to improve numerical stability and provide efficient simulation algorithms for those systems. In this work, we propose an efficient Multilevel Monte Carlo method in the spirit of the work by Anderson and Higham (2012) that uses drift-implicit tau-leap approximations at levels where the explicit tauleap method is not applicable due to numerical stability issues. We present numerical examples that illustrate the performance of the proposed method.

  11. Wet drift chambers for precise luminosity

    International Nuclear Information System (INIS)

    Anderson, B.E.; Kennedy, B.W.; Ahmet, K.; Attree, D.J.; Barraclough, G.A.; Cresswell, M.J.; Hayes, D.A.; Miller, D.J.; Selby, C.; Sherwood, P.

    1994-01-01

    A set of high-precision compact drift chambers has been a vital component of the OPAL luminosity monitor since the start of data-taking at LEP. They were augmented in 1992 by the addition of Small Angle Reference Chambers with a very similar design to the original chamber. The performance of the chambers is reviewed, highlighting both the importance of using polyalkylene glycol (Breox) to maintain a uniform and parallel electric field and the construction techniques used to sustain the required field strength. We describe some of the operating problems, with their solutions, and show how the chambers have been used in achieving a systematic error of 0.41% on the luminosity measurement. ((orig.))

  12. Variable-energy drift-tube linacs

    International Nuclear Information System (INIS)

    Swenson, D.A.; Boyd, T.J. Jr.; Potter, J.M.; Stovall, J.E.

    1982-01-01

    Practical applications of ion linacs are more viable now than ever before because of the recent development of the radio-frequency quadrupole accelerating structure, as well as other technological advances developed under the Pion Generator for Medical Irradiations program. This report describes a practical technique for varying the energy of drift-tube linacs and thus further broadening the possibilities for linac applications. This technique involves using the post couplers (normally used to flatten and stabilize the electric fields) to create a step in the fields, thus terminating the acceleration process. In the examples given for a 70-MeV accelerator design, when using this technique the energy is continually variable down to 20 MeV, while maintaining a small energy spread

  13. Drift effects on electromagnetic geodesic acoustic modes

    Energy Technology Data Exchange (ETDEWEB)

    Sgalla, R. J. F., E-mail: reneesgalla@gmail.com [Institute of Physics, University of São Paulo, São Paulo 05508-900 (Brazil)

    2015-02-15

    A two fluid model with parallel viscosity is employed to derive the dispersion relation for electromagnetic geodesic acoustic modes (GAMs) in the presence of drift (diamagnetic) effects. Concerning the influence of the electron dynamics on the high frequency GAM, it is shown that the frequency of the electromagnetic GAM is independent of the equilibrium parallel current but, in contrast with purely electrostatic GAMs, significantly depends on the electron temperature gradient. The electromagnetic GAM may explain the discrepancy between the f ∼ 40 kHz oscillation observed in tokamak TCABR [Yu. K. Kuznetsov et al., Nucl. Fusion 52, 063044 (2012)] and the former prediction for the electrostatic GAM frequency. The radial wave length associated with this oscillation, estimated presently from this analytical model, is λ{sub r} ∼ 25 cm, i.e., an order of magnitude higher than the usual value for zonal flows (ZFs)

  14. Electro-mechanics of drift tube wires

    International Nuclear Information System (INIS)

    Milburn, R.H.

    1997-01-01

    The position and stability of the sense wires in very long drift tubes are affected by both gravitational and electrostatic forces, as well as by the wire tension. For a tube to be used as an element of a high-resolution detector all these forces and their effects must be understood in appropriately precise detail. In addition, the quality control procedures applied during manufacture and detector installation must be adequate to ensure that the internal wire positions remain within tolerances. It may be instructive to practitioners to review the simple theory of a taut wire in the presence of anisotropic gravitational and electrostatic fields to illustrate the conditions for stability, the equilibrium wire displacement from straightness, and the effect of the fields on the mechanical vibration frequencies. These last may be used to monitor the wire configuration externally. A number of practical formulae result and these are applied to illustrative examples. (orig.)

  15. A metal support for mining drifts

    Energy Technology Data Exchange (ETDEWEB)

    Lopukhov, N M; Dolotkin, Yu N; Parfenov, Yu A; Verner, Yu V

    1982-01-01

    The invention relates to underground coal production; namely, the area of reinforcing development workings in gently sloping coal seams, notably workings with pillarless working of the columns. The proposed metal support for mining drifts includes props made of special sections and a roof timber with curved and straight sections; yieldability units; and a shoe. To raise the support's reliability and work safety as it is erected and removed, the shoe is made of firmly interconnected special cross sections; one of them has holes in the side walls, while the prop has a lug firmly fastened to it, situated in the special section and fixed in it by a pin installed in the holes of the lug and special profile with a clearance. The end of the roof timber has a guide trough at an angle to the prop's axis.

  16. Physics issues of compact drift optimized stellarators

    International Nuclear Information System (INIS)

    Spong, D.A.; Hirshman, S.; Berry, L.A.

    2001-01-01

    Physics issues are discussed for compact stellarator configurations which achieve good confinement by the fact that the magnetic field modulus, vertical bar B vertical bar, in magnetic coordinates is dominated by poloidally symmetric components. Two distinct configuration types are considered: (1) those which achieve their drift optimization and rotational transform at low β and low bootstrap current by appropriate plasma shaping; and (2) those which have a greater reliance on plasma β and bootstrap currents for supplying the transform and obtaining quasi poloidal symmetry. Stability analysis of the latter group of devices against ballooning, kink and vertical displacement modes has indicated that stable 's on the order of 15% are possible. The first class of devices is being considered for a low β near-term experiment that could explore some of the confinement features of the high beta configurations. (author)

  17. Gamma sensitivity of pressurized drift tubes

    International Nuclear Information System (INIS)

    Baranov, S.A.; Bojko, I.R.; Shelkov, G.A.; Ignatenko, M.A.

    1995-01-01

    Using a set of commonly used radioactive sources, the efficiency of pressurized drift tubes for gammas with energy from 5.9 keV up to 1.3 MeV has been measured. The tube was made of aluminium and filled with Ar, 15%CO 2 and 2.5%iC 4 H 10 gas mixture at 3 atm. The measured efficiency is compared with the results of the calculations in the frame of our simple model as well as with that of the Monte Carlo simulation using GEANT code. The results of our calculations are in agreement with experimental data, while GEANT simulation tends to give lower efficiency in the energy range of 200 keV γ <1300 keV. The average efficiency of the tube in the field of ATLAS gamma background is about 0.45%. 8 refs., 7 figs., 1 tab

  18. Spectroscopic measurements with a silicon drift detector having a continuous implanted drift cathode-voltage divider

    CERN Document Server

    Bonvicini, V; D'Acunto, L; Franck, D; Gregorio, A; Pihet, P; Rashevsky, A; Vacchi, A; Vinogradov, L I; Zampa, N

    2000-01-01

    A silicon drift detector (SDD) prototype where the drift electrode also plays the role of a high-voltage divider has been realised and characterised for spectroscopic applications at near-room temperatures. Among the advantages of this design, is the absence of metal on the sensitive surface which makes this detector interesting for soft X-rays. The detector prototype has a large sensitive area (2x130 mm sup 2) and the charge is collected by two anodes (butterfly-like detector). The energy resolution of a such a detector has been investigated at near-room temperatures using a commercial, hybrid, low-noise charge-sensitive preamplifier. The results obtained for the X-ray lines from sup 5 sup 5 Fe and sup 2 sup 4 sup 1 Am are presented.

  19. Engineering Design of a Drift Tube for PEFP DTL II

    International Nuclear Information System (INIS)

    Kim, Yong Hwan; Kwon, Heok Jung; Kim, Kui Young; Kim, Han Sung; Seol, Keong Tae; Song, Young Gi; Jang, Ji Ho; Hong, In Seok; Choi, Hyun Mi; Han, Sang Hyo; Cho, Yong Sub

    2005-01-01

    As the second stage of the PEFP(Proton Engineering Frontier Project) whose final goal is to develop 100MeV, 20mA proton accelerator, Engineering design of the DTL(Drift Tube Linac) II is in proceeding. In this paper, the details of design of the DT(Drift Tube) and EQM(Electro-Quadrupole Magnet) will be reported

  20. Concentrated Hitting Times of Randomized Search Heuristics with Variable Drift

    DEFF Research Database (Denmark)

    Lehre, Per Kristian; Witt, Carsten

    2014-01-01

    Drift analysis is one of the state-of-the-art techniques for the runtime analysis of randomized search heuristics (RSHs) such as evolutionary algorithms (EAs), simulated annealing etc. The vast majority of existing drift theorems yield bounds on the expected value of the hitting time for a target...