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Sample records for regular thermospheric wind

  1. Southern Hemisphere Upper Thermospheric Wind Climatology

    Science.gov (United States)

    Dhadly, M. S.; Emmert, J. T.; Drob, D. P.

    2017-12-01

    This study is focused on the poorly understood large-scale upper thermospheric wind dynamics in the southern polar cap, auroral, and mid latitudes. The gaps in our understanding of the dynamic high-latitude thermosphere are largely due to the sparseness of thermospheric wind measurements. Using data from current observational facilities, it is unfeasible to construct a synoptic picture of the Southern Hemisphere upper thermospheric winds. However, enough data with wide spatial and temporal coverage have accumulated to construct a meaningful statistical analysis of winds as function of season, magnetic latitude, and magnetic local time. We use long-term data from nine ground-based stations located at different southern high latitudes and three space-based instruments. These diverse data sets possess different geometries and different spatial and solar coverage. The major challenge of the effort is to combine these disparate sources of data into a coherent picture while overcoming the sampling limitations and biases among the datasets. Our preliminary analyses show mutual biases present among some of them. We first address the biases among various data sets and then combine them in a coherent way to construct maps of neutral winds for various seasons. We then validate the fitted climatology against the observational data and compare with corresponding fits of 25 years of simulated winds from the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General Circulation Model. This study provides critical insight into magnetosphere-ionosphere-thermosphere coupling and sets a necessary benchmark for validating new observations and tuning first-principles models.

  2. Thermospheric winds in the auroral oval: observations of small scale structures and rapid fluctuations by a Doppler imaging system

    International Nuclear Information System (INIS)

    Batten, S.; Rees, D.

    1990-01-01

    At high geomagnetic latitudes, thermospheric wind flows are dramatically affected by the combined effects of magnetospheric ion convection and Joule and particle heating. Thermospheric winds have been observed by ground based and space-borne Fabry-Perot interferometers (FPIs). Short period, localized wind fluctuations have always been difficult to resolve with a conventional FPI, due to the limited time and spatial resolution. However, the highest quality wind data obtained by these instruments from the middle and upper thermosphere have implied that thermospheric winds may respond to the combination of strong local ion drag forcing and heating within the auroral oval and polar cap, with spatial scale sizes of 50-500 km, and with time scales as short as 10-30 min. Since the 1982/1983 winter, a prototype Doppler Imaging System (DIS) has been operated at Kiruna (67.84 0 N, 20.42 0 E). This instrument maps thermospheric wind flows over a region some 500 km in diameter centred on Kiruna and has observed many interesting features in the thermospheric wind fields. In particular, strong local wind gradients, rapid wind reversals and small scale structures are regularly observed, particularly during geomagnetically disturbed nights. (author)

  3. A search for thermospheric composition perturbations due to vertical winds

    Science.gov (United States)

    Krynicki, Matthew P.

    The thermosphere is generally in hydrostatic equilibrium, with winds blowing horizontally along stratified constant-pressure surfaces, driven by the dayside-to-nightside pressure gradient. A marked change in this paradigm resulted after Spencer et al. [1976] reported vertical wind measurements of 80 m·s-1 from analyses of AE-C satellite data. It is now established that the thermosphere routinely supports large-magnitude (˜30-150 m·s-1) vertical winds at auroral latitudes. These vertical winds represent significant departure from hydrostatic and diffusive equilibrium, altering locally---and potentially globally---the thermosphere's and ionosphere's composition, chemistry, thermodynamics and energy budget. Because of their localized nature, large-magnitude vertical wind effects are not entirely known. This thesis presents ground-based Fabry-Perot Spectrometer OI(630.0)-nm observations of upper-thermospheric vertical winds obtained at Inuvik, NT, Canada and Poker Flat, AK. The wind measurements are compared with vertical displacement estimates at ˜104 km2 horizontal spatial scales determined from a new modification to the electron transport code of Lummerzheim and Lilensten [1994] as applied to FUV-wavelength observations by POLAR spacecraft's Ultraviolet Imager [Torr et al. , 1995]. The modification, referred to as the column shift, simulates vertical wind effects such as neutral transport and disruption of diffusive equilibrium by vertically displacing the Hedin [1991] MSIS-90 [O2]/[N2] and [O]/([N2]+[O2]) mixing ratios and subsequently redistributing the O, O2, and N 2 densities used in the transport code. Column shift estimates are inferred from comparisons of UVI OI(135.6)-nm auroral observations to their corresponding modeled emission. The modeled OI(135.6)-nm brightness is determined from the modeled thermospheric response to electron precipitation and estimations of the energy flux and characteristic energy of the precipitation, which are inferred from UVI

  4. Optical measurements of winds in the lower thermosphere

    International Nuclear Information System (INIS)

    Wiens, R.H.; Shepherd, G.G.; Gault, W.A.; Kosteniuk, P.R.

    1988-01-01

    WAMDII, the wide-angle Michelson Doppler imaging interferometer, was used to measure the neutral wind in the lower thermosphere by the Doppler shift of the O I 557-nm line. Observations were made at Saskatoon (60.5 degree N invariant) around the spring equinox of 1985 with WAMDII coupled to an all-sky lens. With dopplergrams averaged over 3 to 30 min, no evidence was found for persistent highly localized winds on either of the two nights studied, one viewing only aurora and one viewing only airglow. The nocturnal variation was determined for both nights using average horizontal wind for the whole all-sky image. The pattern for the auroral case shows winds parallel to the aurora orientation in the evening but substantial crosswinds near midnight. High latitude general circulation models seem to represent this case better than local auroral generation models. The airglow case showed eastward winds in the morning sector

  5. Determination of the thermospheric neutral wind from incoherent scatter radar measurements

    International Nuclear Information System (INIS)

    Haeggstroem, I.; Murdin, J.; Rees, D.

    1984-11-01

    Measurements made by the EISCAT UHF incoherent scatter radar are used to derive thermospheric winds. The derived wind is compared to Fabry-Perot interferometer measurements of the neutral wind made simultaneously. The uncertainties in the radar derived wind are discussed. (author)

  6. Global empirical wind model for the upper mesosphere/lower thermosphere. I. Prevailing wind

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    Y. I. Portnyagin

    Full Text Available An updated empirical climatic zonally averaged prevailing wind model for the upper mesosphere/lower thermosphere (70-110 km, extending from 80°N to 80°S is presented. The model is constructed from the fitting of monthly mean winds from meteor radar and MF radar measurements at more than 40 stations, well distributed over the globe. The height-latitude contour plots of monthly mean zonal and meridional winds for all months of the year, and of annual mean wind, amplitudes and phases of annual and semiannual harmonics of wind variations are analyzed to reveal the main features of the seasonal variation of the global wind structures in the Northern and Southern Hemispheres. Some results of comparison between the ground-based wind models and the space-based models are presented. It is shown that, with the exception of annual mean systematic bias between the zonal winds provided by the ground-based and space-based models, a good agreement between the models is observed. The possible origin of this bias is discussed.

    Key words: Meteorology and Atmospheric dynamics (general circulation; middle atmosphere dynamics; thermospheric dynamics

  7. Simulations of large winds and wind shears induced by gravity wave breaking in the mesosphere and lower thermosphere (MLT) region

    OpenAIRE

    X. Liu; X. Liu; J. Xu; H.-L. Liu; J. Yue; W. Yuan

    2014-01-01

    Using a fully nonlinear two-dimensional (2-D) numerical model, we simulated gravity waves (GWs) breaking and their contributions to the formation of large winds and wind shears in the mesosphere and lower thermosphere (MLT). An eddy diffusion coefficient is used in the 2-D numerical model to parameterize realistic turbulent mixing. Our study shows that the momentum deposited by breaking GWs accelerates the mean wind. The resultant large background wind increases the GW's app...

  8. Seasonal Dependence of Geomagnetic Active-Time Northern High-Latitude Upper Thermospheric Winds

    Science.gov (United States)

    Dhadly, Manbharat S.; Emmert, John T.; Drob, Douglas P.; Conde, Mark G.; Doornbos, Eelco; Shepherd, Gordon G.; Makela, Jonathan J.; Wu, Qian; Nieciejewski, Richard J.; Ridley, Aaron J.

    2018-01-01

    This study is focused on improving the poorly understood seasonal dependence of northern high-latitude F region thermospheric winds under active geomagnetic conditions. The gaps in our understanding of the dynamic high-latitude thermosphere are largely due to the sparseness of thermospheric wind measurements. With current observational facilities, it is infeasible to construct a synoptic picture of thermospheric winds, but enough data with wide spatial and temporal coverage have accumulated to construct a meaningful statistical analysis. We use long-term data from eight ground-based and two space-based instruments to derive climatological wind patterns as a function of magnetic local time, magnetic latitude, and season. These diverse data sets possess different geometries and different spatial and solar activity coverage. The major challenge is to combine these disparate data sets into a coherent picture while overcoming the sampling limitations and biases among them. In our previous study (focused on quiet time winds), we found bias in the Gravity Field and Steady State Ocean Circulation Explorer (GOCE) cross-track winds. Here we empirically quantify the GOCE bias and use it as a correction profile for removing apparent bias before empirical wind formulation. The assimilated wind patterns exhibit all major characteristics of high-latitude neutral circulation. The latitudinal extent of duskside circulation expands almost 10∘ from winter to summer. The dawnside circulation subsides from winter to summer. Disturbance winds derived from geomagnetic active and quiet winds show strong seasonal and latitudinal variability. Comparisons between wind patterns derived here and Disturbance Wind Model (DWM07) (which have no seasonal dependence) suggest that DWM07 is skewed toward summertime conditions.

  9. Coupled Solar Wind-Magnetosphere-Ionosphere-Thermosphere System by QFT

    Science.gov (United States)

    Chen, Shao-Guang

    shoot to Sun from the center of Galaxy. The dynamic balance of forces on the solar surface plasma at once is broken and the plasma will upwards eject as the solar wind with redundant negative charge, at the same time, the solar surface remain a cavity as a sunspot whorl with the positive electric potential relative to around. The whorl caused by that the reaction of plasma eject front and upwards with the different velocity at different latitude of solar rotation, leads to the cavity around in the downwards and backwards helix movement. The solar rotation more slow, when the cavity is filled by around plasma in the reverse turn direction, the Jupiter at front had been produced a new cavity, so that we had observe the sunspot pair with different whorl directions and different magnetic polarity. Jupiter possess half mass of all planets in solar system, its action to stop net nuν _{0} flux is primary, so that Jupiter’s period of 11.8 sidereal years accord basically with the period of sunspot eruptions. The solar wind is essentially the plasma with additional electrons flux ejected from the solar surface: its additional electrons come from the ionosphere again eject into the ionosphere and leads to the direct connect between the solar wind and the ionosphere; its magnetism from its redundant negative charge and leads to the connect between the solar wind and the magnetosphere; it possess the high temperature of the solar surface and ejecting kinetic energy leads to the thermo-exchange connect between the solar wind and the thermosphere. Through the solar wind ejecting into and cross over the outside atmosphere carry out the electromagnetic, particles material and thermal exchanges, the Coupled Solar Wind-Magnetosphere-Ionosphere-Thermosphere System to be came into being. This conclusion is inferred only by QFT.

  10. Optical sensors for mapping temperature and winds in the thermosphere from a CubeSat platform

    Science.gov (United States)

    Sullivan, Stephanie Whalen

    The thermosphere is the region between approximately 80 km and 320 or more km above the earth's surface. While many people consider this elevation to be space rather than atmosphere, there is a small quantity of gasses in this region. The behavior of these gasses influences the orbits of satellites, including the International Space Station, causes space weather events, and influences the weather closer to the surface of the earth. Due to the location and characteristics of the thermosphere, even basic properties such as temperature are very difficult to measure. High spatial and temporal resolution data on temperatures and winds in the thermosphere are needed by both the space weather and earth climate modeling communities. To address this need, Space Dynamics Laboratory (SDL) started the Profiling Oxygen Emissions of the Thermosphere (POET) program. POET consists of a series of sensors designed to fly on sounding rockets, CubeSats, or larger platforms, such as IridiumNEXT SensorPODS. While each sensor design is different, they all use characteristics of oxygen optical emissions to measure space weather properties. The POET program builds upon the work of the RAIDS, Odin, and UARS programs. Our intention is to dramatically reduce the costs of building, launching, and operating spectrometers in space, thus allowing for more sensors to be in operation. Continuous long-term data from multiple sensors is necessary to understand the underlying physics required to accurately model and predict weather in the thermosphere. While previous spectrometers have been built to measure winds and temperatures in the thermosphere, they have all been large and expensive. The POET sensors use new focal plane technology and optical designs to overcome these obstacles. This thesis focuses on the testing and calibration of the two POET sensors: the Oxygen Profiling of the Atmospheric Limb (OPAL) temperature sensor and the Split-field Etalon Doppler Imager (SEDI) wind sensor.

  11. Substorm-related thermospheric density and wind disturbances derived from CHAMP observations

    Directory of Open Access Journals (Sweden)

    P. Ritter

    2010-06-01

    Full Text Available The input of energy and momentum from the magnetosphere is most efficiently coupled into the high latitude ionosphere-thermosphere. The phenomenon we are focusing on here is the magnetospheric substorm. This paper presents substorm related observations of the thermosphere derived from the CHAMP satellite. With its sensitive accelerometer the satellite can measure the air density and zonal winds. Based on a large number of substorm events the average high and low latitude thermospheric response to substorm onsets was deduced. During magnetic substorms the thermospheric density is enhanced first at high latitudes. Then the disturbance travels at an average speed of 650 m/s to lower latitudes, and 3–4 h later the bulge reaches the equator on the night side. Under the influence of the Coriolis force the travelling atmospheric disturbance (TAD is deflected westward. In accordance with present-day atmospheric models the disturbance zonal wind velocities during substorms are close to zero near the equator before midnight and attain moderate westward velocities after midnight. In general, the wind system is only weakly perturbed (Δvy<20 m/s by substorms.

  12. Tidal signatures of the thermospheric mass density and zonal wind at midlatitude: CHAMP and GRACE observations

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    C. Xiong

    2015-02-01

    Full Text Available By using the accelerometer measurements from CHAMP and GRACE satellites, the tidal signatures of the thermospheric mass density and zonal wind at midlatitudes have been analyzed in this study. The results show that the mass density and zonal wind at southern midlatitudes are dominated by a longitudinal wave-1 pattern. The most prominent tidal components in mass density and zonal wind are the diurnal tides D0 and DW2 and the semidiurnal tides SW1 and SW3. This is consistent with the tidal signatures in the F region electron density at midlatitudes as reported by Xiong and Lühr (2014. These same tidal components are observed both in the thermospheric and ionospheric quantities, supporting a mechanism that the non-migrating tides in the upper atmosphere are excited in situ by ion–neutral interactions at midlatitudes, consistent with the modeling results of Jones Jr. et al. (2013. We regard the thermospheric dynamics as the main driver for the electron density tidal structures. An example is the in-phase variation of D0 between electron density and mass density in both hemispheres. Further research including coupled atmospheric models is probably needed for explaining the similarities and differences between thermospheric and ionospheric tidal signals at midlatitudes.

  13. Comparison of high-latitude thermospheric meridional winds I: optical and radar experimental comparisons

    Energy Technology Data Exchange (ETDEWEB)

    Griffin, E.M.; Mueller-Wodarg, I.C.F.; Aruliah, A.; Aylward, A. [Atmospheric Physics Lab., Univ. Coll. London, London (United Kingdom)

    2004-07-01

    Thermospheric neutral winds at Kiruna, Sweden (67.4 N, 20.4 E) are compared using both direct optical fabry-perot interferometer (FPI) measurements and those derived from European incoherent scatter radar (EISCAT) measurements. This combination of experimental data sets, both covering well over a solar cycle of data, allows for a unique comparison of the thermospheric meridional component of the neutral wind as observed by different experimental techniques. Uniquely in this study the EISCAT measurements are used to provide winds for comparison using two separate techniques: the most popular method based on the work of Salah and Holt (1974) and the meridional wind model (MWM) (Miller et al., 1997) application of servo theory. The balance of forces at this location that produces the observed diurnal pattern are investigated using output from the coupled thermosphere and ionosphere (CTIM) numerical model. Along with detailed comparisons from short periods the climatological behaviour of the winds have been investigated for seasonal and solar cycle dependence using the experimental techniques. While there are features which are consistent between the 3 techniques, such as the evidence of the equinoctial asymmetry, there are also significant differences between the techniques both in terms of trends and absolute values. It is clear from this and previous studies that the high-latitude representation of the thermospheric neutral winds from the empirical horizontal wind model (HWM), though improved from earlier versions, lacks accuracy in many conditions. The relative merits of each technique are discussed and while none of the techniques provides the perfect data set to address model performance at high-latitude, one or more needs to be included in future HWM reformulations. (orig.)

  14. Empirical global model of upper thermosphere winds based on atmosphere and dynamics explorer satellite data

    Science.gov (United States)

    Hedin, A. E.; Spencer, N. W.; Killeen, T. L.

    1988-01-01

    Thermospheric wind data obtained from the Atmosphere Explorer E and Dynamics Explorer 2 satellites have been used to generate an empirical wind model for the upper thermosphere, analogous to the MSIS model for temperature and density, using a limited set of vector spherical harmonics. The model is limited to above approximately 220 km where the data coverage is best and wind variations with height are reduced by viscosity. The data base is not adequate to detect solar cycle (F10.7) effects at this time but does include magnetic activity effects. Mid- and low-latitude data are reproduced quite well by the model and compare favorably with published ground-based results. The polar vortices are present, but not to full detail.

  15. SAPS effects on thermospheric winds during the 17 March 2013 storm

    Science.gov (United States)

    Sheng, C.; Lu, G.; Wang, W.; Doornbos, E.; Talaat, E. R.

    2017-12-01

    Strong subauroral polarization streams (SAPS) were observed by DMSP satellites during the main phase of the 17 March 2013 geomagnetic storm. Both DMSP F18 and GOCE satellites sampled at 19 MLT during this period, providing near-simultaneous measurements of ion drifts and neutral winds near dusk. The fortuitous satellite conjunction allows us to directly examine the SAPS effects on thermospheric winds. In addition, two sets of model runs were carried out for this event: (1) the standard TIEGCM run with high-latitude forcing; (2) the SAPS-TIEGCM run by incoporating an empirical model of SAPS in the subauroral zone. The difference between these two runs represents the influence of SAPS forcing. In particular, we examine ion-neutral coupling at subauroral latitudes through detailed forcing term analysis to determine how the SAPS-related strong westward ion drifts alter thermospheric winds.

  16. MENTAT: A New Magnetic Meridional Neutral Wind Model for Earth's Thermosphere

    Science.gov (United States)

    Dandenault, P. B.

    2017-12-01

    We present a new model of thermosphere winds in the F region obtained from variations in the altitude of the peak density of the ionosphere (hmF2). The new Magnetic mEridional NeuTrAl Thermospheric (MENTAT) wind model produces magnetic-meridional neutral winds as a function of year, day of year, solar local time, solar flux, geographic latitude, and geographic longitude. The winds compare well with Fabry-Pérot Interferometer (FPI) wind observations and are shown to provide accurate specifications in regions outside of the observational database such as the midnight collapse of hmF2 at Arecibo, Puerto Rico. The model winds are shown to exhibit the expected seasonal, diurnal, and hourly behavior based on geophysical conditions. The magnetic meridional winds are similar to those from the well-known HWM14 model but there are important differences. For example, Townsville, Australia has a strong midnight collapse similar to that at Arecibo, but winds from HWM14 do not reproduce it. Also, the winds from hmF2 exhibit a moderate solar cycle dependence under certain conditions, whereas, HWM14 has no solar activity dependence. For more information, please visit http://www.mentatwinds.net/.

  17. A comparison of quiet time thermospheric winds between FPIs and models

    Science.gov (United States)

    Jiang, G.; Xu, J.; Wang, W.; Yuan, W.; Zhang, S.; Yu, T.; Zhang, X.; Huang, C.; Liu, W.; Li, Q.

    2017-12-01

    Abstract:The Fabry-Perot Interferometer (FPI) instruments installed at Xinglong, (geog.: 40.2oN, 117.4oE; geom.: 35oN), Kelan (geog.: 38.7oN, 111.6oE; geom.: 34oN) and Millstone Hill (geog.: 42.6oN, 71.5oW; geom.: 52oN) started to measure the thermosphere neutral winds near 250 km since April 2010, March 2010 and November 2011, respectively. In this work, the joined comparison of FPI observed winds and two models during geomagnetic quiet time are processed for the study of mid-latitudinal thermosphere. The years of FPI wind data we use are from 2010 to 2014. The two models we use are NCAR TIE-GCM (Thermosphere-Ionosphere-Electrodynamics General Circulation Model of National Center for Atmospheric Research) and HWM07 (Horizontal Wind Model, version 2007). The real solar and geomagnetic conditions were applied to the models.

  18. Comparison of high-latitude thermospheric meridional winds II: combined FPI, radar and model climatologies

    Energy Technology Data Exchange (ETDEWEB)

    Griffin, E.M.; Aruliah, A.; Mueller-Wodarg, I.C.F.; Aylward, A. [Atmospheric Physics Lab., Univ. Coll. London, London (United Kingdom)

    2004-07-01

    The climatological behaviour of the thermospheric meridional wind above Kiruna, Sweden (67.4 N, 20.4 E) has been investigated for seasonal and solar cycle dependence using six different techniques, comprising both model and experimental sources. Model output from both the empirical Horizontal Wind Model (HWM) (Hedin et al., 1988) and the numerical coupled thermosphere and ionosphere model (CTIM) are compared to the measured behaviour at kiruna, as a single site example. The empirical International Reference Ionosphere (IRI) model is used as input to an implementation of servo theory, to provide another climatology combining empirical input with a theoretical framework. The experimental techniques have been introduced in a companion paper in this issue and provide climatologies from direct measurements, using fabry-perot interferometers (FPI), together with 2 separate techniques applied to the European incoherent scatter radar (EISCAT) database to derive neutral winds. One of these techniques uses the same implementation of servo theory as has been used with the IRI model. Detailed comparisons for each season and solar activity category allow for conclusions to be drawn as to the major influences on the climatological behaviour of the wind at this latitude. Comparison of the incoherent scatter radar (ISR) derived neutral winds with FPI, empirical model and numerical model winds is important to our understanding and judgement of the validity of the techniques used to derive thermospheric wind databases. The comparisons also test model performance and indicate possible reasons for differences found between the models. In turn, the conclusions point to possible improvements in their formulation. In particular it is found that the empirical models are over-reliant on mid-latitude data in their formulation, and fail to provide accurate estimates of the winds at high-latitudes. (orig.)

  19. Analysis of Wind Vorticity and Divergence in the High-latitude Lower Thermosphere: Dependence on the Interplanetary Magnetic Field (IMF

    Directory of Open Access Journals (Sweden)

    Young-Sil Kwak

    2008-12-01

    Full Text Available To better understand the physical processes that control the high-latitude lower thermospheric dynamics, we analyze the divergence and vorticity of the high-latitude neutral wind field in the lower thermosphere during the southern summertime for different IMF conditions. For this study the National Center for Atmospheric Research Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR-TIEG CM is used. The analysis of the large-scale vorticity and divergence provides basic understanding flow configurations to help elucidate the momentum sources that ultimately determine the total wind field in the lower polar thermosphere and provides insight into the relative strengths of the different sources of momentum responsible for driving winds. The mean neutral wind pattern in the high-latitude lower thermosphere is dominated by rotational flow, imparted primarily through the ion drag force, rather than by divergent flow, imparted primarily through Joule and solar heating. The difference vorticity, obtained by subtracting values with zero IMF from those with non-zero IMF, in the high-latitude lower thermosphere is much larger than the difference divergence for all IMF conditions, indicating that a larger response of the thermospheric wind system to enhancement in the momentum input generating the rotational motion with elevated IMF than the corresponding energy input generating the divergent motion. the difference vorticity in the high-latitude lower thermosphere depends on the direction of the IMF. The difference vorticity for negative and positive B_y shows positive and negative, respectively, at higher magnetic latitudes than -70°. For negative B_z, the difference vorticities have positive in the dusk sector and negative in the dawn sector. The difference vorticities for positive B_z have opposite sign. Negative IMF B_z has a stronger effect on the vorticity than does positive B_z.

  20. Equatorial thermospheric wind changes during the solar cycle: Measurements at Arequipa, Peru, from 1983 to 1990

    International Nuclear Information System (INIS)

    Biondi, M.A.; Meriwether, J.W. Jr.; Fejer, B.G.; Gonzalez, S.A.; Hallenbeck, D.C.

    1991-01-01

    Fabry-Perot interferometer measurements of Doppler shifts in the nightglow 630-nm emission line have been used to determine near-equatorial thermospheric wind velocities at Arequipa, Peru, over ∼ 2/3 of a solar cycle. Monthly-average nocturnal variations in the meridional and zonal wind components were calculated from the nightly data to remove short term (day-to-day) variability, facilitating display of seasonal changes in the wind patterns, as well as any additional changes introduced by the progression of the solar cycle. The measured seasonal variations in the wind patterns are more pronounced than the solar cycle variations and are more readily understandable in terms of the expected, underlying forcing and damping processes. For most of the years, at the winter solstice, there is a weak (≤ 100 m/s) transequatorial flow from the summer to the winter hemisphere in the early and the late night, with essentially zero velocities in between. At the equinoxes, an early-night poleward (southward) flow at solar minimum (1986) is replaced by an equatorward (northward) flow at solar maximum (1989-1990). The zonal flows are predominantly eastward throughout the night, except for the solar minimum equinoxes, where brief westward flows appear in the early and the late night. The peak eastward velocities increase toward solar maximum; at the winter solstice, they are ∼ 100-130 m/s in 1983, 1984 and 1986, reaching ∼ 200 m/s in 1988, 1989 and 1990. The present equatorial thermospheric wind determinations agree in some respects with the satellite-data-based horizontal wind model IIWM-87 and the vector spherical harmonic form of the thermospheric general circulation model

  1. Thermospheric zonal mean winds and tides revealed by CHAMP

    NARCIS (Netherlands)

    Lieberman, R.S.; Akmaev, R.A.; Fuller-Rowell, T.J.; Doornbos, E.

    2013-01-01

    We present direct, global observations of longitudinally averaged CHAMP zonal winds gathered between 2003 and 2007. A diurnal variation dominates the global zonal wind. Westward flows are observed from the early morning through afternoon hours, while eastward flows peak in the evening. A semidiurnal

  2. Average thermospheric wind patterns over the polar regions, as observed by CHAMP

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    H. Lühr

    2007-06-01

    Full Text Available Measurements of the CHAMP accelerometer are utilized to investigate the average thermospheric wind distribution in the polar regions at altitudes around 400 km. This study puts special emphasis on the seasonal differences in the wind patterns. For this purpose 131 days centered on the June solstice of 2003 are considered. Within that period CHAMP's orbit is precessing once through all local times. The cross-track wind estimates of all 2030 passes are used to construct mean wind vectors for 918 equal-area cells. These bin averages are presented in corrected geomagnetic coordinates. Both hemispheres are considered simultaneously providing summer and winter responses for the same prevailing geophysical conditions. The period under study is characterized by high magnetic activity (Kp=4− but moderate solar flux level (F10.7=124. Our analysis reveals clear wind features in the summer (Northern Hemisphere. Over the polar cap there is a fast day-to-night flow with mean speeds surpassing 600 m/s in the dawn sector. At auroral latitudes we find strong westward zonal winds on the dawn side. On the dusk side, however, an anti-cyclonic vortex is forming. The dawn/dusk asymmetry is attributed to the combined action of Coriolis and centrifugal forces. Along the auroral oval the sunward streaming plasma causes a stagnation of the day-to-night wind. This effect is particularly clear on the dusk side. On the dawn side it is evident only from midnight to 06:00 MLT. The winter (Southern Hemisphere reveals similar wind features, but they are less well ordered. The mean day-to-night wind over the polar cap is weaker by about 35%. Otherwise, the seasonal differences are mainly confined to the dayside (06:00–18:00 MLT. In addition, the larger offset between geographic and geomagnetic pole in the south also causes hemispheric differences of the thermospheric wind distribution.

  3. Average thermospheric wind patterns over the polar regions, as observed by CHAMP

    Directory of Open Access Journals (Sweden)

    H. Lühr

    2007-06-01

    Full Text Available Measurements of the CHAMP accelerometer are utilized to investigate the average thermospheric wind distribution in the polar regions at altitudes around 400 km. This study puts special emphasis on the seasonal differences in the wind patterns. For this purpose 131 days centered on the June solstice of 2003 are considered. Within that period CHAMP's orbit is precessing once through all local times. The cross-track wind estimates of all 2030 passes are used to construct mean wind vectors for 918 equal-area cells. These bin averages are presented in corrected geomagnetic coordinates. Both hemispheres are considered simultaneously providing summer and winter responses for the same prevailing geophysical conditions. The period under study is characterized by high magnetic activity (Kp=4− but moderate solar flux level (F10.7=124. Our analysis reveals clear wind features in the summer (Northern Hemisphere. Over the polar cap there is a fast day-to-night flow with mean speeds surpassing 600 m/s in the dawn sector. At auroral latitudes we find strong westward zonal winds on the dawn side. On the dusk side, however, an anti-cyclonic vortex is forming. The dawn/dusk asymmetry is attributed to the combined action of Coriolis and centrifugal forces. Along the auroral oval the sunward streaming plasma causes a stagnation of the day-to-night wind. This effect is particularly clear on the dusk side. On the dawn side it is evident only from midnight to 06:00 MLT. The winter (Southern Hemisphere reveals similar wind features, but they are less well ordered. The mean day-to-night wind over the polar cap is weaker by about 35%. Otherwise, the seasonal differences are mainly confined to the dayside (06:00–18:00 MLT. In addition, the larger offset between geographic and geomagnetic pole in the south also causes hemispheric differences of the thermospheric wind distribution.

  4. Coordinated observations of postmidnight irregularities and thermospheric neutral winds and temperatures at low latitudes

    Science.gov (United States)

    Dao, Tam; Otsuka, Yuichi; Shiokawa, Kazuo; Nishioka, Michi; Yamamoto, Mamoru; Buhari, Suhaila M.; Abdullah, Mardina; Husin, Asnawi

    2017-07-01

    We investigated a postmidnight field-aligned irregularity (FAI) event observed with the Equatorial Atmosphere Radar at Kototabang (0.2°S, 100.3°E, dip latitude 10.4°S) in Indonesia on the night of 9 July 2010 using a comprehensive data set of both neutral and plasma parameters. We examined the rate of total electron content change index (ROTI) obtained from GPS receivers in Southeast Asia, airglow images detected by an all-sky imager, and thermospheric neutral winds and temperatures obtained by a Fabry-Perot interferometer at Kototabang. Altitudes of the F layer (h'F) observed by ionosondes at Kototabang, Chiang Mai, and Chumphon were also surveyed. We found that the postmidnight FAIs occurred within plasma bubbles and coincided with kilometer-scale plasma density irregularities. We also observed an enhancement of the magnetically equatorward thermospheric neutral wind at the same time as the increase of h'F at low-latitude stations, but h'F at a station near the magnetic equator remained invariant. Simultaneously, a magnetically equatorward gradient of thermospheric temperature was identified at Kototabang. The convergence of equatorward neutral winds from the Northern and Southern Hemispheres could be associated with a midnight temperature maximum occurring around the magnetic equator. Equatorward neutral winds can uplift the F layer at low latitudes and increase the growth rate of Rayleigh-Taylor instabilities, causing more rapid extension of plasma bubbles. The equatorward winds in both hemispheres also intensify the eastward Pedersen current, so a large polarization electric field generated in the plasma bubble might play an important role in the generation of postmidnight FAIs.

  5. Geomagnetically conjugate observation of plasma bubbles and thermospheric neutral winds at low latitudes

    Science.gov (United States)

    Fukushima, D.; Shiokawa, K.; Otsuka, Y.; Nishioka, M.; Kubota, M.; Tsugawa, T.; Nagatsuma, T.; Komonjinda, S.; Yatini, C. Y.

    2015-03-01

    This is the first paper that reports simultaneous observations of zonal drift of plasma bubbles and the thermospheric neutral winds at geomagnetically conjugate points in both hemispheres. The plasma bubbles were observed in the 630 nm nighttime airglow images taken by using highly sensitive all-sky airglow imagers at Kototabang, Indonesia (geomagnetic latitude (MLAT): 10.0°S), and Chiang Mai, Thailand (MLAT: 8.9°N), which are nearly geomagnetically conjugate stations, for 7 h from 13 to 20 UT (from 20 to 03 LT) on 5 April 2011. The bubbles continuously propagated eastward with velocities of 100-125 m/s. The 630 nm images at Chiang Mai and those mapped to the conjugate point of Kototabang fit very well, which indicates that the observed plasma bubbles were geomagnetically connected. The eastward thermospheric neutral winds measured by two Fabry-Perot interferometers were 70-130 m/s at Kototabang and 50-90 m/s at Chiang Mai. We compared the observed plasma bubble drift velocity with the velocity calculated from the observed neutral winds and the model conductivity, to investigate the F region dynamo contribution to the bubble drift velocity. The estimated drift velocities were 60-90% of the observed velocities of the plasma bubbles, suggesting that most of the plasma bubble velocity can be explained by the F region dynamo effect.

  6. Ionosonde and optical determinations of thermospheric neutral winds over the Antarctic Peninsula

    Science.gov (United States)

    Foppiano, A. J.; Won, Y.-I.; Torres, X. A.; Flores, P. A.; Veloso, A. Daniel; Arriagada, M. A.

    2016-11-01

    Ionosonde observations have been made at Great Wall station (62.22°S; 58.97°W), King George Island, and at further south Vernadsky station (65.25°S; 64.27°W), Argentine Islands, for many years. For several days at the two locations the magnetic meridional component of the thermospheric neutral wind has also been derived using three different algorithms with ionosonde data input. At King Sejong station (62.22°S; 58.78°W), close to Great Wall, almost simultaneous thermospheric winds were measured with a Fabry-Perot Interferometer (FPI) during a few days in 1997. All days correspond to intervals of low solar and geomagnetic activity levels and for different seasons. Here, the geographic meridional FPI winds measured at the geographic south pointing location are compared with the magnetic meridional component of the wind derived from ionosonde observations at Vernadsky. Also, the magnetic meridian FPI winds measured using all four cardinal pointing locations are compared with the magnetic meridional component of the wind derived from ionosonde observations at Great Wall. The patterns of the diurnal variations of the magnetic meridional component of ionosonde derived winds using the three different techniques are similar in most cases. However, the amplitudes of these variations and some individual values can differ by more than 150 m/s depending on season, particularly during daytime. Comparison of the autumn FPI with the ionosonde winds for Vernadsky and Great Wall shows that they coincide within observation uncertainties. Results for other seasons are not so good. Some of the discrepancies are discussed in relation to the hour-to-hour variability of ionosonde based winds and the latitudinal gradients of ionospheric characteristics. Other discrepancies need to be further explained. Recently reported FPI mean winds for tens of days in different seasons for Palmer (64.77°S; 64.05°W), Anvers Island, are found to be particularly close to ionosonde derived mean

  7. 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.

  8. FPI observations of nighttime mesospheric and thermospheric winds in China and their comparisons with HWM07

    Directory of Open Access Journals (Sweden)

    W. Yuan

    2013-08-01

    Full Text Available We analyzed the nighttime horizontal neutral winds in the middle atmosphere (~ 87 and ~ 98 km and thermosphere (~ 250 km derived from a Fabry–Perot interferometer (FPI, which was installed at Xinglong station (40.2° N, 117.4° E in central China. The wind data covered the period from April 2010 to July 2012. We studied the annual, semiannual and terannual variations of the midnight winds at ~ 87 km, ~ 98 km and ~ 250 km for the first time and compared them with Horizontal Wind Model 2007 (HWM07. Our results show the following: (1 at ~ 87 km, both the observed and model zonal winds have similar phases in the annual and semiannual variations. However, the HWM07 amplitudes are much larger. (2 At ~ 98 km, the model shows strong eastward wind in the summer solstice, resulting in a large annual variation, while the observed strongest component is semiannual. The observation and model midnight meridional winds agree well. Both are equatorward throughout the year and have small amplitudes in the annual and semiannual variations. (3 There are large discrepancies between the observed and HWM07 winds at ~ 250 km. This discrepancy is largely due to the strong semiannual zonal wind in the model and the phase difference in the annual variation of the meridional wind. The FPI annual variation coincides with the results from Arecibo, which has similar geomagnetic latitude as Xinglong station. In General, the consistency of FPI winds with model winds is better at ~ 87 and ~ 98 km than that at ~ 250 km. We also studied the seasonally and monthly averaged nighttime winds. The most salient features include the following: (1 the seasonally averaged zonal winds at ~ 87 and ~ 98 km typically have small variations throughout the night. (2 The model zonal and meridional nighttime wind variations are typically much larger than those of observations at ~ 87 km and ~ 98 km. (3 At ~ 250 km, model zonal wind compares well with the observation in the winter. For spring and

  9. Thermospheric neutral wind profile in moonlit midnight by Lithium release experiments in Japan

    Science.gov (United States)

    Yamamoto, M. Y.; Watanabe, S.; Abe, T.; Kakinami, Y.; Habu, H.; Yamamoto, M.

    2015-12-01

    Neutral wind profiles were observed in lower thermosphere at about between 90 km and 130 km altitude by using resonance scattering light of moonlit Lithium (Li) vapor released from sounding rockets in midnight (with almost full-moon condition) in 2013 in Japan. As a target of the Daytime Dynamo campaign, Li release experiment was operated at Wallops Flight Facility (WFF) of NASA, U.S.A. in July, 2013 (Pfaff et al., 2015, this meeting), while the same kind of rocket-ground observation campaign in midnight was carried out by using S-520-27/S-310-42 sounding rockets in Uchinoura Space Center (USC) of JAXA, Kagoshima, Japan, also in July 2013.Since imaging signal-to-noise (S/N) condition of the experiment was so severe, we conducted to apply airborne observation for imaging the faint moonlit Li tracers so as to reduce the illuminating intensity of the background skies as an order of magnitude. Two independent methods for calculating the wind profile were applied to the Lithium emission image sequences successfully obtained by the airborne imaging by special Li imagers aboard the airplanes in order to derive precise information of Li tracers motion under the condition of single observation site on a moving aircraft along its flight path at about 12 km altitude in lower stratosphere. Slight attitude-feedback motion of the aircraft's 3-axes attitude changes (rolling, yawing and pitching) was considered for obtaining precise coordinates on each snapshot. Another approach is giving a simple mathematic function for wind profile to resolve the shape displacement of the imaged Li tracers. As a result, a wind profile in moonlit thermosphere was calculated in a range up to about 150 m/s with some fluctuated parts possibly disturbed by wind shears. In the same experiment, another sounding rocket S-310-42 with a TMA canister was also launched from USC/JAXA at about 1 hour before the rocket with carrying the Lithium canisters, thus, we can derive the other 2 profiles determined by

  10. New results on equatorial thermospheric winds and the midnight temperature maximum

    Directory of Open Access Journals (Sweden)

    J. Meriwether

    2008-03-01

    Full Text Available Optical observations of thermospheric winds and temperatures determined with high resolution measurements of Doppler shifts and Doppler widths of the OI 630-nm equatorial nightglow emission have been made with improved accuracy at Arequipa, Peru (16.4° S, 71.4° W with an imaging Fabry-Perot interferometer. An observing procedure previously used at Arecibo Observatory was applied to achieve increased spatial and temporal sampling of the thermospheric wind and temperature with the selection of eight azimuthal directions, equally spaced from 0 to 360°, at a zenith angle of 60°. By assuming the equivalence of longitude and local time, the data obtained using this technique is analyzed to determine the mean neutral wind speeds and mean horizontal gradients of the wind field in the zonal and meridional directions. The new temperature measurements obtained with the improved instrumental accuracy clearly show the midnight temperature maximum (MTM peak with amplitudes of 25 to 200 K in all directions observed for most nights. The horizontal wind field maps calculated from the mean winds and gradients show the MTM peak is always preceded by an equatorward wind surge lasting 1–2 h. The results also show for winter events a meridional wind abatement seen after the MTM peak. On one occasion, near the September equinox, a reversal was observed during the poleward transit of the MTM over Arequipa. Analysis inferring vertical winds from the observed convergence yielded inconsistent results, calling into question the validity of this calculation for the MTM structure at equatorial latitudes during solar minimum. Comparison of the observations with the predictions of the NCAR general circulation model indicates that the model fails to reproduce the observed amplitude by a factor of 5 or more. This is attributed in part to the lack of adequate spatial resolution in the model as the MTM phenomenon takes place within a scale of 300–500 km and ~45 min in

  11. THz limb sounder (TLS) for lower thermospheric wind, oxygen density, and temperature

    Science.gov (United States)

    Wu, Dong L.; Yee, Jeng-Hwa; Schlecht, Erich; Mehdi, Imran; Siles, Jose; Drouin, Brian J.

    2016-07-01

    Neutral winds are one of the most critical measurements in the lower thermosphere and E region ionosphere (LTEI) for understanding complex electrodynamic processes and ion-neutral interactions. We are developing a high-sensitivity, low-power, noncryogenic 2.06 THz Schottky receiver to measure wind profiles at 100-140 km. The new technique, THz limb sounder (TLS), aims to measure LTEI winds by resolving the wind-induced Doppler shift of 2.06 THz atomic oxygen (OI) emissions. As a transition between fine structure levels in the ground electronic state, the OI emission is in local thermodynamic equilibrium (LTE) at altitudes up to 350 km. This LTE property, together with day-and-night capability and small line-of-sight gradient, makes the OI limb sounding a very attractive technique for neutral wind observations. In addition to the wind measurement, TLS can also retrieve [OI] density and neutral temperature in the LTEI region. TLS leverages rapid advances in THz receiver technologies including subharmonically pumped (SHP) mixers and Schottky-diode-based power multipliers. Current SHP Schottky receivers have produced good sensitivity for THz frequencies at ambient environment temperatures (120-150 K), which are achievable through passively cooling in spaceflight. As an emerging technique, TLS can fill the critical data gaps in the LTEI neutral wind observations to enable detailed studies on the coupling and dynamo processes between charged and neutral molecules.

  12. Numerical simulations of thermospheric dynamics: divergence as a proxy for vertical winds

    Directory of Open Access Journals (Sweden)

    S. L. Cooper

    2009-06-01

    Full Text Available A local scale, time dependent three-dimensional model of the neutral thermosphere was used to test the applicability of two previously published empirical relations between thermospheric vertical wind and velocity divergence, i.e., those due to Burnside et al. (1981 and Brekke (1997. The model self-consistently solves for vertical winds driven by heat and momentum deposited into the neutral atmosphere by high latitude ion convection. The Brekke condition accurately mimicked the overall "shape" of the three-dimensional model vertical wind field although, as written, it consistently overestimated the vertical wind magnitude by a factor of approximately 5/3, for the heating scenarios that we considered. This same general behavior was observed regardless of whether the forcing was static or rapidly changing with time. We discuss the likely reason for the Brekke condition overestimating the magnitude of our vertical winds, and suggest an alternative condition that should better describe vertical winds that are driven by local heating. The applicability of the Burnside condition was, by contrast, quite variable. During static heating, both the magnitude and the sign of the model vertical winds were predicted reliably at heights above those of maximum energy and momentum deposition per unit mass. However, below the thermal forcing, the Burnside condition predicted vertical winds of the wrong sign. It also introduced significant artefacts into the predicted vertical wind field when the forcing changed suddenly with time. If these results are of general applicability (which seems likely, given the way these relations are derived then the Burnside condition could usually be used safely at altitudes above hmF2. But it should be avoided below this height at all times, and even at high altitudes during periods of dynamic forcing. While the Brekke condition (or our modified version of it could likely be used in all circumstances

  13. Observing Equatorial Thermospheric Winds and Temperatures with a New Mapping Technique

    Science.gov (United States)

    Faivre, M. W.; Meriwether, J. W.; Sherwood, P.; Veliz, O.

    2005-12-01

    Application of the Fabry-Perot interferometer (FPI) at Arequipa, Peru (16.4S, 71.4 W) to measure the Doppler shifts and Doppler broadenings in the equatorial O(1D) 630-nm nightglow has resulted in numerous detections of a large-scale thermospheric phenomenon called the Midnight Temperature Maximum (MTM). A recent detector upgrade with a CCD camera has improved the accuracy of these measurements by a factor of 5. Temperature increases of 50 to 150K have been measured during nights in April and July, 2005, with error bars less than 10K after averaging in all directions. Moreover, the meridional wind measurements show evidence for a flow reversal from equatorward to poleward near local midnight for such events. A new observing strategy based upon the pioneering work of Burnside et al.[1981] maps the equatorial wind and temperature fields by observing in eight equally-spaced azimuth directions, each with a zenith angle of 60 degrees. Analysis of the data obtained with this technique gives the mean wind velocities in the meridional and zonal directions as well as the horizontal gradients of the wind field for these directions. Significant horizontal wind gradients are found for the meridional direction but not for the zonal direction. The zonal wind blows eastward throughout the night with a maximum speed of ~150 m/s near the middle of the night and then decreases towards zero just before dawn. In general, the fastest poleward meridional wind is observed near mid-evening. By the end of the night, the meridional flow tends to be more equatorward at speeds of about 50 m/s. Using the assumption that local time and longitude are equivalent over a period of 30 minutes, a map of the horizontal wind field vector field is constructed over a range of 12 degrees latitude centered at 16.5 S. Comparison between MTM nights and quiet nights (no MTM) revealed significant differences in the horizontal wind fields. Using the method of Fourier decomposition of the line-of-sight winds

  14. Equatorial thermospheric winds: New results using data from a network of three Fabry-Perot interferometers located in central Peru

    Science.gov (United States)

    Meriwether, J. W.; Dominquez, L. N.; Milla, M. A.; Chau, J. L.; Makela, J. J.; Fisher, D.

    2013-12-01

    A new observing strategy aimed at improving our understanding of the properties of the equatorial thermosphere wind field, such as the vorticity and divergence, has been developed to generate maps of the thermospheric wind field. Estimates of the neutral wind are obtained from measurements of the Doppler shift of the thermospheric 630.0-nm emission obtained from a sequence of eight evenly spaced azimuthal directions for each of the three Fabry-Perot interferometer (FPI) observatories located in central Peru (Jicamarca, Nazca, and Arequipa). Measurements towards the zenith and a frequency-stabilized laser reference are also included in each sequence, which takes ~25 minutes to complete. Six of the off-zenith observing directions from the Nazca FPI observatory are used to make common volume (CV) measurements, where two of the FPIs observe the same thermospheric volume with a centroid height of ~250 km at orthogonal angles. These CV positions are located ~225 km north and south of the Nazca FPI observatory. The data obtained during a coordinated observation of the two FPIs observing the same CV location are used to compute estimates of the zonal (u) and meridional (v) wind components. The set of Doppler shifts measured by the three FPIs during a single sequence is used to produce a map of the neutral wind field for that period of time. The construction of this map is based upon the use of a first-order polynomial expansion of the neutral wind field relative to the site coordinates of each FPI location. This expansion includes the first-order gradients of u and v with respect to the zonal (x) and meridional (y) directions. Computation of the best fit in a linear least squares sense of the model expansion parameters to the Doppler shift data for all three sites determines the values of these gradient parameters. Results obtained for mid-winter 2013 show the anti-cyclonic circulation expected near the terminator generated by the day-to-night pressure gradient. Sequences

  15. Horizontal and vertical winds and temperatures in the equatorial thermosphere: measurements from Natal, Brazil during August-September 1982

    International Nuclear Information System (INIS)

    Biondi, M.A.

    1985-01-01

    Fabry-Perot interferometer measurements of Doppler shifts and widths of the 630.0 nm nightglow line have been used to determine the neutral winds and temperatures in the equatorial thermosphere over Natal, Brazil during August-September 1982. During this period, in the early night (2130 U.T.) the average value of the horizontal wind vector was 95 m s -1 at 100 0 azimuth, and the temperature varied from a low of 950 K during geomagnetically quiet conditions to a high of approx. 1400 K during a storm (6 September). The meridional winds were small, -1 , and the eastward zonal winds reached a maximum value 1-3 h after sunset, in qualitative agreement with TGCM predictions. On 26 August, an observed persistent convergence in the horizontal meridional flow was accompanied by a downward vertical velocity and an increase in the thermospheric temperature measured overhead. Oscillations with periods of 40-45 min in both the zonal and vertical wind velocities were observed during the geomagnetic storm of 6 September, suggesting gravity wave modulation of the equatorial thermospheric flow. (author)

  16. Radar observations of high-latitude lower-thermospheric and upper-mesospheric winds and their response to geomagnetic activity

    International Nuclear Information System (INIS)

    Johnson, R.M.

    1987-01-01

    Observations made by the Chatanika, Alaska, incoherent scatter radar during the summer months of 1976 to 1081 are analyzed to obtain high resolution lower-thermospheric neutral winds. Average winds and their tidal components are presented and compared to previous observational and model results. Upper-mesospheric neutral-wind observations obtained by the Poke Flat, Alaska Mesosphere-Stratosphere-Troposphere (MST) radar during the summer months of 1980 to 1982 are investigated statistically for evidence of variations due to geomagnetic activity. Observation of upper-mesospheric neutral winds made during two energetic Solar Proton Events (SPEs) by the Poker Flat, MST radar are presented. These results allow the low-altitude limits of magnetospheric coupling to the neutral atmosphere to be determined. Lower-thermospheric neutral winds are coupled to the ion convection driven by typical magnetospheric forcing above about 100 km. Coupling to lower atmospheric levels does not occur except during intervals of extreme disturbance of the magnetosphere-ionosphere-thermosphere system which are also accompanied by dramatically increased ionization in the high-latitude mesosphere, such as SPEs

  17. A preliminary study of thermosphere and mesosphere wind observed by Fabry-Perot over Kelan, China

    Science.gov (United States)

    Yu, Tao; Huang, Cong; Zhao, Guangxin; Mao, Tian; Wang, Yungang; Zeng, Zhongcao; Wang, Jingsong; Xia, Chunliang

    2014-06-01

    A Fabry-Perot interferometer (FPI) system was deployed in Kelan (38.7°N, 111.6°E), center China in November 2011, which observes the airglows at wavelengths of 892.0 nm, 557.7 nm, and 630.0 nm from OH and OI emissions in the upper atmosphere, to derive the wind and temperature at heights around 87 km, 97 km, and 250 km, respectively. From late 2011 through 2013 a series of more than 4500 measurements at each height are validated according to manufacture data quality criteria. By using these data, the morphology of wind in the mesosphere and thermosphere is investigated in this study. Preliminary results are as follows: (1) As for the diurnal variation, meridional and zonal winds at heights of 87 km and 97 km, which are derived through 892.0 nm and 557.7 nm airglows, usually range from -50 m/s to 30 m/s and -50 m/s to 50 m/s, respectively, with typical random errors of about 6-10 m/s at 87 km and 2-3 m/s at 97 km. Meridional winds usually are northward at dusk, southward at middle night, and back to northward at dawn; and zonal winds usually are eastward at dusk, westward at middle night, and back to eastward at dawn. The monthly mean winds are in good agreement with those of HWM93 results. Meridional and zonal winds at a height of 250 km, which are derived through 630.0 nm nightglow, range from -110 m/s to 80 m/s with typical random errors of about 8-10 m/s. Meridional winds usually are northward at dusk, southward at middle night, and back to northward at dawn; and zonal winds usually are eastward at dusk, zero at middle night, and westward at dawn; and they are also well consistent with HWM93 results. (2) As for the seasonal variation, meridional winds at the heights of 87 km and 97 km have a visible annual variation at 12-17 LT and with a little semiannual variation at all other hours, but the zonal winds at the heights of 87 km and 97 km have a semiannual variation all night. The seasonal dependence of the winds, both meridional and zonal winds, at the height

  18. Temperature and Wind Measurements in Venus Lower Thermosphere between 2007 and 2015

    Science.gov (United States)

    Krause, Pia; Sornig, Manuela; Wischnewski, Carolin; Sonnabend, Guido; Stangier, Tobias; Herrmann, Maren; Kostiuk, Theodor; Livengood, Timothy A.; Pätzold, Martin

    2016-10-01

    The structure of Venus atmosphere and its thermal and dynamical behavior was intensely studied during the past decade by groundbased and the space mission Venus Express. A comprehensive understanding of the atmosphere, however, is still missing. Direct measurements of atmospheric parameters on various time scales and at different locations across the planet are essential for better understanding and to validate global circulation models. Line-resolved spectroscopy of infrared CO2 transitions provides a powerful tool to accomplish measurements of temperature and wind speed within the neutral atmosphere, using Doppler line-broadening and Doppler shift. Temperature is the motor to drive circulation, and wind speed is the result. Measuring both provides both the basis and an empirical test for circulation models. Non-LTE emission lines at 10 µm that originate from a pressure level of 1μbar, ~110 km altitude, probe the lower thermosphere and are measurable at high spectral resolution using the infrared heterodyne spectrometers THIS (University of Cologne), HIPWAC (NASA GSFC) and MILAHI (Tohoku University).Thermal and dynamical structures on the Venus day side are retrieved using a newly developed method that considers the influence of the spectrometer field-of-view (FoV) and the dispersion of spectral properties across the FoV. New conclusions from the ground-based observing campaigns between 2007 and 2015 will be presented based on this retrieval methodology. The spatial resolution on the planetary disk is different for each campaign, depending on the apparent diameter of the planet and the diffraction-limited FoV of the telescope. Previously, a comparison of the observing campaigns was limited due to the difference in spatial resolution. The new retrieval method enables comparing observations with different observing geometry. The observations yield a large quantity of temperature and wind measurements at different positions on the planetary disk, which supports

  19. Superstorms of November 2003 and 2004: the role of solar wind driving in the ionosphere-thermosphere dynamics

    Science.gov (United States)

    Verkhoglyadova, O. P.; Komjathy, A.; Mannucci, A. J.; Mlynczak, M. G.; Hunt, L. A.; Paxton, L. J.

    2017-12-01

    We revisit three complex superstorms of 19-20 November 2003, 7-8 November 2004 and 9-11 November 2004 to analyze ionosphere-thermosphere (IT) effects driven by different solar wind structures. We distinguish structures associated with ICMEs and their upstream sheaths. The efficiencies of the solar wind-magnetosphere connection throughout the storms are estimated by coupling functions. The daytime IT responses to the complex driving are characterized by combining measurements of characteristic IT parameters. We focus on low- and middle-latitude TEC, global thermospheric infrared nitric oxide emission, composition ratio and locations of the auroral boundary obtained from multiple satellite platforms and ground-based measurements (GPS, TIMED/SABER, TIMED/GUVI, DMSP/SSUSI). A variety of metrics are utilized to examine IT phenomena at 1 hour time scales. It is well-known that the November storm periods featured TEC responses that did not fit a typical pattern. The role of direct driving of IT dynamics by solar wind structures and the role of IT pre-conditioning in these storms are examined to explain the complex unusual ionospheric responses. We identify IT feedback effects that can be important for long-lasting strong storms.

  20. The Design and Implementation of the Wide-Angle Michelson Interferometer to Observe Thermospheric Winds.

    Science.gov (United States)

    Ward, William Edmund

    The design and implementation of a Wide-Angle Michelson interferometer (WAMI) as a high spectral resolution device for measuring Doppler shifts and temperatures in the thermosphere is discussed in detail. A general theoretical framework is developed to describe the behavior of interferometers and is applied to the WAMI. Notions concerning the optical coupling of various surfaces within an interferometer are developed and used to investigate the effects of misalignments in the WAMI optics. In addition, these notions in combination with ideas on the polarization behavior of interferometers are used to suggest how complex multisurfaced interferometers might be developed, what features affect their behavior most strongly, and how this behavior might be controlled. Those aspects of the Michelson interferometer important to its use as a high resolution spectral device are outlined and expressions relating the physical features of the interferometer and the spectral features of the radiation passing through the instrument, to the form of the observed interference pattern are derived. The sensitivity of the WAMI to misalignments in its optical components is explored, and quantitative estimations of the effects of these misalignments made. A working WAMI with cube corners instead of plane mirrors was constructed and is described. The theoretical notions outlined above are applied to this instrument and found to account for most of its features. A general digital procedure is developed for the analysis of the observed interference fringes which permits an estimation of the amplitude, visibility and phase of the fringes. This instrument was taken to Bird, northern Manitoba as part of the ground based support for the Auroral Rocket and Image Excitation Study (ARIES) rocket campaign. Doppler shifts and linewidth variations in O(^1 D) and O(^1S) emissions in the aurora were observed during several nights and constitute the first synoptic wind measurements taken with a WAMI. The

  1. The Relationship of High-Latitude Thermospheric Wind With Ionospheric Horizontal Current, as Observed by CHAMP Satellite

    Science.gov (United States)

    Huang, Tao; Lühr, Hermann; Wang, Hui; Xiong, Chao

    2017-12-01

    The relationship between high-latitude ionospheric currents (Hall current and field-aligned current) and thermospheric wind is investigated. The 2-D patterns of horizontal wind and equivalent current in the Northern Hemisphere derived from the CHAMP satellite are considered for the first time simultaneously. The equivalent currents show strong dependences on both interplanetary magnetic field (IMF) By and Bz components. However, IMF By orientation is more important in controlling the wind velocity patterns. The duskside wind vortex as well as the antisunward wind in the morning polar cap is more evident for positive By. To better understand their spatial relation in different sectors, a systematic superposed epoch analysis is applied. Our results show that in the dusk sector, the vectors of the zonal wind and equivalent current are anticorrelated, and both of them form a vortical flow pattern for different activity levels. The currents and zonal wind are intensified with the increase of merging electric field. However, on the dawnside, where the relation is less clear, antisunward zonal winds dominate. Plasma drift seems to play a less important role for the wind than neutral forces in this sector. In the noon sector, the best anticorrelation between equivalent current and wind is observed for a positive IMF By component and it is less obvious for negative By. A clear seasonal effect with current intensities increasing from winter to summer is observed in the noon sector. Different from the currents, the zonal wind intensity shows little dependence on seasons. Our results indicate that the plasma drift and the neutral forces are of comparable influence on the zonal wind at CHAMP altitude in the noon sector.

  2. Tidal winds from the mesosphere, lower thermosphere global radar network during the second LTCS campaign: December 1988

    International Nuclear Information System (INIS)

    Manson, A.H.; Meek, C.E.; Avery, S.K.; Fraser, G.J.; Vincent, R.A.; Phillips, A.; Clark, R.R.; Schminder, R.; Kurschner, D.; Kazimirovsky, E.S.

    1991-01-01

    Winds and tides were measured by nine MLT (mesophere, lower thermosphere) radars with locations between 70 degree N and 78 degree S, including an equatorial station at Christmas Island, 2 degree N (Avery et al., 1990). The mean winds were eastward (westward) in the northern (southern) hemisphere mesophere, consistent with midwinter circulations. For the 12-hour (semidiurnal) tide, observations and the model of Forbes and Vial (1989) were in generally good agreement: in both cases northward components were closer to being in phase in the two hemispheres, and winter wavelengths were shorter than those of the midlatitude summer. Major differences were large (small) amplitudes at 70 degree N for model(observations); and poor agreement of equatorial tidal profiles. For the 24-hour (diurnal tide), the radar observations and model of Forbes and Hagan (1988) were in useful agreement in the summer hemisphere. However, the short (long) wavelengths at mid (high) latitudes of the model's winter hemisphere were not observed during LTCS (lower Thermosphere Coupling Study) 2, nor in climatologies for December. Suggestions as to the reason for this disparity are presented

  3. Generation of the lower-thermospheric vertical wind estimated with the EISCAT KST radar at high latitudes during periods of moderate geomagnetic disturbance

    Directory of Open Access Journals (Sweden)

    S. Oyama

    2008-06-01

    Full Text Available Lower-thermospheric winds at high latitudes during moderately-disturbed geomagnetic conditions were studied using data obtained with the European Incoherent Scatter (EISCAT Kiruna-Sodankylä-Tromsø (KST ultrahigh frequency (UHF radar system on 9–10 September 2004. The antenna-beam configuration was newly designed to minimize the estimated measurement error of the vertical neutral-wind speed in the lower thermosphere. This method was also available to estimate the meridional and zonal components. The vertical neutral-wind speed at 109 km, 114 km, and 120 km heights showed large upward motions in excess of 30 m s−1 in association with an ionospheric heating event. Large downward speeds in excess of −30 m s−1 were also observed before and after the heating event. The meridional neutral-wind speed suddenly changed its direction from equatorward to poleward when the heating event began, and then returned equatorward coinciding with a decrease in the heating event. The magnetometer data from northern Scandinavia suggested that the center of the heated region was located about 80 km equatorward of Tromsø. The pressure gradient caused the lower-thermospheric wind to accelerate obliquely upward over Tromsø in the poleward direction. Acceleration of the neutral wind flowing on a vertically tilted isobar produced vertical wind speeds larger by more than two orders of magnitude than previously predicted, but still an order of magnitude smaller than observed speeds.

  4. Initial daytime and nighttime SOFDI observations of thermospheric winds from Fabry-Perot Doppler shift measurements of the 630-nm OI line-shape profile

    Directory of Open Access Journals (Sweden)

    A. J. Gerrard

    2011-09-01

    Full Text Available In this paper we present both night and day thermospheric wind observations made with the Second-generation, Optimized, Fabry-Perot Doppler Imager (SOFDI, a novel triple-etalon Fabry-Perot interferometer (FPI designed to make 24-h measurements of thermospheric winds from OI 630-nm emission. These results were obtained from the northeastern United States and from under the magnetic equator at Huancayo, Peru and demonstrate the current instrument capability for measurements of Doppler shifts for either night or day. We found the uncertainties in the measurements agree with expected values based upon forward modeling calculations; nighttime wind components having an uncertainty of ~20-m s−1 at 30-min resolution and daytime wind components having an uncertainty of ~70-m s−1 at 20-min resolution. The nighttime uncertainties are typically larger than those seen with traditional single-etalon FPIs, which occur at the cost of being able to achieve daytime measurements. The thermospheric wind measurements from Huancayo replicate recently reported CHAMP zonal winds and are in disagreement with current empirical wind climatologies. In addition, we discuss the incorporation of how multiple point heads in the SOFDI instrument will allow for unique studies of gravity wave activity in future measurements.

  5. Generation of the lower-thermospheric vertical wind estimated with the EISCAT KST radar at high latitudes during periods of moderate geomagnetic disturbance

    Directory of Open Access Journals (Sweden)

    S. Oyama

    2008-06-01

    Full Text Available Lower-thermospheric winds at high latitudes during moderately-disturbed geomagnetic conditions were studied using data obtained with the European Incoherent Scatter (EISCAT Kiruna-Sodankylä-Tromsø (KST ultrahigh frequency (UHF radar system on 9–10 September 2004. The antenna-beam configuration was newly designed to minimize the estimated measurement error of the vertical neutral-wind speed in the lower thermosphere. This method was also available to estimate the meridional and zonal components. The vertical neutral-wind speed at 109 km, 114 km, and 120 km heights showed large upward motions in excess of 30 m s−1 in association with an ionospheric heating event. Large downward speeds in excess of −30 m s−1 were also observed before and after the heating event. The meridional neutral-wind speed suddenly changed its direction from equatorward to poleward when the heating event began, and then returned equatorward coinciding with a decrease in the heating event. The magnetometer data from northern Scandinavia suggested that the center of the heated region was located about 80 km equatorward of Tromsø. The pressure gradient caused the lower-thermospheric wind to accelerate obliquely upward over Tromsø in the poleward direction. Acceleration of the neutral wind flowing on a vertically tilted isobar produced vertical wind speeds larger by more than two orders of magnitude than previously predicted, but still an order of magnitude smaller than observed speeds.

  6. Do Transient Electrodynamic Processes Support Enhanced Neutral Mass Densities in Earth's Cusp-Region Thermosphere via Divergent Upward Winds?

    Science.gov (United States)

    Conde, M.; Larsen, M. F.; Troyer, R.; Gillespie, D.; Kosch, M.

    2017-12-01

    Satellite accelerometer measurements show that Earth's thermosphere contains two substantial and permanent regions of enhanced mass density that are located at around 400 km altitude near the footprints of the north and south geomagnetic cusps. The additional mass in these regions must be supported against gravity, which requires that similarly localized perturbations must occur in one or more of the other fields (beyond mass density) that appear in the momentum conservation equation for the thermospheric neutral fluid. However more than a decade after the density enhancements were first discovered, there are still no observations of any other corresponding perturbations to terms appearing directly in this equation that would indicate what is supporting the extra mass. To date, most candidate mechanisms involve high-altitude transient electrodynamic heating (at 250 km and above) that drives upwelling and associated horizontal divergence. Indeed, there are very few viable mechanisms that don't ultimately cause substantial localized neutral wind perturbations to occur near the density anomalies. Thus, we report here on a study to search for signatures of these localized perturbations in winds, using several data sources. These are the WATS instrument that flew aboard the DE-2 spacecraft, the C-REX-1 rocket flight through the CUSP in 2014, and two ground-based Fabry-Perot instruments that are located in Antarctica at latitudes that pass under the geomagnetic cusps - i.e. at McMurdo and South Pole stations. Using these data, we will present both climatological averages and also individual case studies to illustrate what localized signatures occur (if any) in the neutral wind fields near the cusp-region density anomalies.

  7. Mid-latitude thermospheric wind changes during the St. Patrick's Day storm of 2015 observed by two Fabry-Perot interferometers in China

    Science.gov (United States)

    Huang, Cong; Xu, Ji-Yao; Zhang, Xiao-Xin; Liu, Dan-Dan; Yuan, Wei; Jiang, Guo-Ying

    2018-04-01

    In this work, we utilize thermospheric wind observations by the Fabry-Perot interferometers (FPI) from the Kelan (KL) station (38.7°N, 111.6°E, Magnetic Latitude: 28.9°N) and the Xinglong (XL) station (40.2°N, 117.4°E, Magnetic Latitude: 30.5°N) in central China during the St. Patrick's Day storm (from Mar. 17 to Mar. 19) of 2015 to analyze thermospheric wind disturbances and compare observations with the Horizontal Wind Model 2007 (HWM07). The results reveal that the wind measurements at KL show very similar trends to those at XL. Large enhancements are seen in both the westward and equatorward winds after the severe geomagnetic storm occurred. The westward wind speed increased to a peak value of 75 m/s and the equatorward wind enhanced to a peak value of over 100 m/s. There also exist obvious poleward disturbances in the meridional winds during Mar. 17 to Mar. 19. According to the comparison with HWM07, there exist evident wind speed and temporal differences between FPI-winds and the model outputs in this severe geomagnetic storm. The discrepancies between the observations and HWM07 imply that the empirical model should be used carefully in wind disturbance forecast during large geomagnetic storms and more investigations between measurements and numerical models are necessary in future studies.

  8. Climatologies of nighttime upper thermospheric winds measured by ground-based Fabry-Perot interferometers during geomagnetically quiet conditions: 2. High-latitude circulation and interplanetary magnetic field dependence

    DEFF Research Database (Denmark)

    Emmert, J.T.; Hernandez, G.; Jarvis, M.J.

    2006-01-01

    We analyze upper thermospheric (similar to 250 km) nighttime horizontal neutral wind patterns, during geomagnetically quiet (Kp S), Halley (76 degrees S, 27 degrees W), Millstone Hill (43 degrees N, 72 degrees W), Sondre...

  9. Multi-event study of high-latitude thermospheric wind variations at substorm onset with a Fabry-Perot interferometer at Tromsoe, Norway

    Science.gov (United States)

    Xu, H.; Shiokawa, K.; Oyama, S. I.; Otsuka, Y.

    2017-12-01

    We studied the high-latitude thermospheric wind variations near the onset time of isolated substorms. Substorm-related energy input from the magnetosphere to the polar ionosphere modifies the high-latitude ionosphere and thermosphere. For the first time, this study showed the characteristics of high-latitude thermospheric wind variations at the substorm onset. We also investigated the possibility of these wind variations as a potential trigger of substorm onset by modifying the ionospheric current system (Kan, 1993). A Fabry-Perot interferometer (FPI) at Tromsoe, Norway provided wind measurements estimated from Doppler shift of both red-line (630.0 nm for the F region) and green-line (557.7 nm for the E region) emissions of aurora and airglow. We used seven-year data sets obtained from 2009 to 2015 with a time resolution of 13 min. We first identified the onset times of local isolated substorms using ground-based magnetometer data obtained at the Tromsoe and Bear Island stations, which belongs to the IMAGE magnetometer chain. We obtained 4 red-line events and 5 green-line events taken place at different local times. For all these events, the peak locations of westward ionospheric currents identified by the ground-based magnetometer chain were located at the poleward side of Tromsoe. Then, we calculated two weighted averages of wind velocities for 30 min around the onset time and 30 min after the onset time of substorms. We evaluated differences between these two weighted averages to estimate the strength of wind changes. The observed wind changes at these substorm onsets were less than 49 m/s (26 m/s) for red-line (green-line) events, which are much smaller than the typical plasma convection speed. This indicates that the plasma motion caused by substorm-induced thermospheric winds through ion-neutral collisions is a minor effect as the driver of high-latitude plasma convection, as well as the triggering of substorm onset. We discuss possible causes of these

  10. Mean vertical wind in the mesosphere-lower thermosphere region (80–120 km deduced from the WINDII observations on board UARS

    Directory of Open Access Journals (Sweden)

    V. Fauliot

    Full Text Available The WINDII interferometer placed on board the Upper Atmosphere Research Satellite measures temperature and wind from the O(1S green-line emission in the Earth's mesosphere and lower thermosphere. It is a remote-sensing instrument providing the horizontal wind components. In this study, the vertical winds are derived using the continuity equation. Mean wind annually averaged at equinoxes and solstices is shown. Ascendance and subsidence to the order of 1–2 cm s–1 present a seasonal occurrence at the equator and tropics. Zonal Coriolis acceleration and adiabatic heating and cooling rate associated to the mean meridional and vertical circulations are evaluated. The line emission rate measured together with the horizontal wind shows structures in altitude and latitude correlated with the meridional and vertical wind patterns. The effect of wind advection is discussed.

  11. Mean vertical wind in the mesosphere-lower thermosphere region (80–120 km deduced from the WINDII observations on board UARS

    Directory of Open Access Journals (Sweden)

    V. Fauliot

    1997-09-01

    Full Text Available The WINDII interferometer placed on board the Upper Atmosphere Research Satellite measures temperature and wind from the O(1S green-line emission in the Earth's mesosphere and lower thermosphere. It is a remote-sensing instrument providing the horizontal wind components. In this study, the vertical winds are derived using the continuity equation. Mean wind annually averaged at equinoxes and solstices is shown. Ascendance and subsidence to the order of 1–2 cm s–1 present a seasonal occurrence at the equator and tropics. Zonal Coriolis acceleration and adiabatic heating and cooling rate associated to the mean meridional and vertical circulations are evaluated. The line emission rate measured together with the horizontal wind shows structures in altitude and latitude correlated with the meridional and vertical wind patterns. The effect of wind advection is discussed.

  12. Wind response in the lower thermosphere to the geomagnetic storm on March, 1989

    International Nuclear Information System (INIS)

    Kazimirovskij, Eh.S.; Vergasova, G.V.

    1991-01-01

    The horizontal wind response in the ionospheric D region above Irkutsk to the geomagnetic storm on March 13, 1989 is studied. The geomagnetic storm response is expressed through a stability loss of the wind system, a great speed increase of the meridional and zonal wind, in particular, and their dispersions, respectively, as well as changes in the semidaily tidal phase. The proof of the fact that the Earth magnetic field disturbances destabilize the system of horizontal winds in the lower ionosphere is given

  13. Winds in the high-latitude lower thermosphere: Dependence on the interplanetary magnetic field

    DEFF Research Database (Denmark)

    Richmond, A.D.; Lathuillere, C.; Vennerstrøm, Susanne

    2003-01-01

    -side cyclonic vortex that responds more strongly to B-z variations. The dependence of the wind on the IMF is nonlinear, especially with respect to IMF B-z. For positive B-z the difference winds are largely confined to the polar cap, while for negative B-z the difference winds extend to subauroral latitudes...... of similar to20 hours, a B-y-dependent magnetic-zonal-mean zonal wind generally exists, with maximum wind speeds at 80 magnetic latitude, typically 10 m/s at 105 km, increasing to about 60 m/s at 123 km and 80 m/s at 200 km. In the southern hemisphere the wind is cyclonic when the time-averaged B...

  14. Simultaneous measurements of the thermospheric wind profile at three separate positions in the dusk auroral oval

    International Nuclear Information System (INIS)

    Mikkelsen, I.S.; Friis-Christensen, E.; Larsen, M.F.; Kelley, M.C.; Vickrey, J.; Meriwether, J.; Shih, P.

    1987-01-01

    On March 20, 1985, two rockets were launched from Soendre Stroemfjord, Greenland, into the dusk auroral oval. Three trimethyl aluminium trails were released to measure the neutral wind profiles between 95 and 190 km of altitude at two points separated by 190 km normal to the invariant latitude circles and at a third point separated from the first two by 300 km along the invariant latitude circles. Two barium/strontium clouds were released at 250 km of altitude, extending two of the neutral wind profiles to this altitude. In the E region the tip of the wind vector traced an ellipse as a function of increasing altitude with maximum wind speeds of 100-150 m/s in the southeastward and northwestward directions. The F region winds were southward with speeds of 100-200 m/s. The zonal wind component between 115 and 140 km of altitude had a horizontal gradient in the southeastward direction, whereas the meridional wind component at the same heights was constant over the spatial extent covered by the measurements. The authors interpret the observed E region wind field as being part of a gravity wave with a period of 3 hours as estimated from the ellipticity of the wind hodograms. The wind vectors rotated 540 degree clockwise with increasing height, indicating that the wave energy is propagating upward. The Fabry-Perot interferometer at Soendre Stroemfjord was first able to detect the F region winds 45 min after the releases and measured winds of 100-400 m/s mainly in the southeastward or antisunward direction. The geomagnetic conditions were quiet, with Kp not exceeding 2 for the 24 hours preceding the experiment. The incoherent scatter radar at Soendre Stroemfjord observed a contracted plasma convection pattern associated with positive B y and B z components of the interplanetary magnetic field

  15. Neutral wind and density perturbations in the thermosphere created by gravity waves observed by the TIDDBIT sounder

    Science.gov (United States)

    Vadas, Sharon L.; Crowley, Geoff

    2017-06-01

    In this paper, we study the 10 traveling ionospheric disturbances (TIDs) observed at zobs˜283 km by the TIDDBIT ionospheric sounder on 30 October 2007 at 0400-0700 UT near Wallops Island, USA. These TIDs propagated northwest/northward and were previously found to be secondary gravity waves (GWs) from tropical storm Noel. An instrumented sounding rocket simultaneously measured a large neutral wind peak uH' with a similar azimuth at z ˜ 325 km. Using the measured TID amplitudes and wave vectors from the TIDDBIT system, together with ion-neutral theory, GW dissipative polarization relations and ray tracing, we determine the GW neutral horizontal wind and density perturbations as a function of altitude from 220 to 380 km. We find that there is a serious discrepancy between the GW dissipative theory and the observations unless the molecular viscosity, μ, decreases with altitude in the middle to upper thermosphere. Assuming that μ∝ρ¯q, where ρ¯ is the density, we find using GW dissipative theory that the GWs could have been observed at zobs and that one or more of the GWs could have caused the uH' wind peak at z≃325 km if q ˜ 0.67 for z≥220 km. This implies that the kinematic viscosity, ν=μ/ρ¯, increases less rapidly with altitude for z≥220 km: ν∝1/ρ¯0.33. This dependence makes sense because as ρ¯→0, the distance between molecules goes to infinity, which implies no molecular collisions and therefore no molecular viscosity μ.

  16. Climatological lower thermosphere winds as seen by ground-based and space-based instruments

    Directory of Open Access Journals (Sweden)

    J. M. Forbes

    2004-06-01

    Full Text Available Comparisons are made between climatological dynamic fields obtained from ground-based (GB and space-based (SB instruments with a view towards identifying SB/GB intercalibration issues for TIMED and other future aeronomy satellite missions. SB measurements are made from the High Resolution Doppler Imager (HRDI instrument on the Upper Atmosphere Research Satellite (UARS. The GB data originate from meteor radars at Obninsk, (55° N, 37° E, Shigaraki (35° N, 136° E and Jakarta (6° S, 107° E and MF spaced-antenna radars at Hawaii (22° N, 160° W, Christmas I. (2° N, 158° W and Adelaide (35° S, 138° E. We focus on monthly-mean prevailing, diurnal and semidiurnal wind components at 96km, averaged over the 1991-1999 period. We perform space-based (SB analyses for 90° longitude sectors including the GB sites, as well as for the zonal mean. Taking the monthly prevailing zonal winds from these stations as a whole, on average, SB zonal winds exceed GB determinations by ~63%, whereas meridional winds are in much better agreement. The origin of this discrepancy remains unknown, and should receive high priority in initial GB/SB comparisons during the TIMED mission. We perform detailed comparisons between monthly climatologies from Jakarta and the geographically conjugate sites of Shigaraki and Adelaide, including some analyses of interannual variations. SB prevailing, diurnal and semidiurnal tides exceed those measured over Jakarta by factors, on the average, of the order of 2.0, 1.6, 1.3, respectively, for the eastward wind, although much variability exists. For the meridional component, SB/GB ratios for the diurnal and semidiurnal tide are about 1.6 and 1.7. Prevailing and tidal amplitudes at Adelaide are significantly lower than SB values, whereas similar net differences do not occur at the conjugate Northern Hemisphere location of Shigaraki. Adelaide diurnal phases lag SB phases by several hours, but excellent agreement between the two data

  17. Modeling the Thermosphere as a Driven-Dissipative Thermodynamic System

    Science.gov (United States)

    2013-03-01

    8 Figure 2: Illustration of the geocentric solar magnetospheric coordinate system............15 Figure 3: Diagram of the...to test new methods of modeling the thermospheric environment. Thermosphere as a Driven-Dissipative Thermodynamic System One approach for modeling... approach uses empirical coupling and relaxation constants to model the 4 input of energy to the thermosphere from the solar wind during

  18. Application of Tikhonov regularization method to wind retrieval from scatterometer data II: cyclone wind retrieval with consideration of rain

    International Nuclear Information System (INIS)

    Zhong Jian; Huang Si-Xun; Fei Jian-Fang; Du Hua-Dong; Zhang Liang

    2011-01-01

    According to the conclusion of the simulation experiments in paper I, the Tikhonov regularization method is applied to cyclone wind retrieval with a rain-effect-considering geophysical model function (called GMF+Rain). The GMF+Rain model which is based on the NASA scatterometer-2 (NSCAT2) GMF is presented to compensate for the effects of rain on cyclone wind retrieval. With the multiple solution scheme (MSS), the noise of wind retrieval is effectively suppressed, but the influence of the background increases. It will cause a large wind direction error in ambiguity removal when the background error is large. However, this can be mitigated by the new ambiguity removal method of Tikhonov regularization as proved in the simulation experiments. A case study on an extratropical cyclone of hurricane observed with SeaWinds at 25-km resolution shows that the retrieved wind speed for areas with rain is in better agreement with that derived from the best track analysis for the GMF+Rain model, but the wind direction obtained with the two-dimensional variational (2DVAR) ambiguity removal is incorrect. The new method of Tikhonov regularization effectively improves the performance of wind direction ambiguity removal through choosing appropriate regularization parameters and the retrieved wind speed is almost the same as that obtained from the 2DVAR. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  19. The global thermospheric mapping study

    International Nuclear Information System (INIS)

    Oliver, W.L.; Salah, J.E.

    1988-01-01

    The Global Thermospheric Mapping Study (GTMS) is a multitechnique experimental pilot study of the Earth's thermosphere designed to map simultaneously its spatial and temporal morphology. This paper provides the background for the study and presents the analysis techniques employed at Millstone Hill and results to date on thermospheric structure and dynamics. The first latitudinal-temporal maps of exospheric temperature obtained from the incoherent scatter radar chain at 70W meridian are presented for the two solstice periods, revealing substantial seasonal differences between them. The observed structure shows a relatively depressed temperature at high latitude in summer in contrast to the mass spectrometer/incoherent scatter 1983 [MSIS-83] empirical model, which shows a maximum temperature at polar latitudes. The MSIS-83 model predictions are in good agreement with the observed latitudinal-temporal structure in winter. Comparison with the numerical predictions made for the June 26-28, 1984 period with the National Center for Atmospheric Research thermospheric general circulation model shows reasonable agreement in the latitudinal gradient but the observations indicate a cooler thermosphere by several hundred degrees. Neutral winds at mid-latitudes are presented showing the expected strong southward winds at night, which are found to be consistent with the temperature gradients observed in the latitudinal maps. There is good agreement in the June winds between the available numerical model calculations and the observations. Work performed elsewhere on the GTMS data base is summarized for completeness

  20. Thermospheric Density and Composition: an Integrated Research Approach

    Science.gov (United States)

    Richmond, A. D.; Akmaev, R.; Anderson, P. C.; Crowley, G.; Drob, D. P.; Lummerzheim, D.; Solomon, S. C.; Tobiska, W.

    2006-12-01

    The thermosphere, at altitudes of approximately 90-500 km, affects human technological systems through the drag it exerts on low-Earth-orbit spacecraft and debris, and through its influence on the embedded ionosphere, affecting radio-wave transmissions, and, consequently, communications and geolocation. We have formed a team under the NASA Living With a Star Targeted Research and Technology program to carry out an integrated research program on the focused science topic of thermospheric density and composition. Our goal is to improve scientific understanding of the thermosphere-ionosphere system, leading to improved first-principles models that accurately specify the variations of thermospheric density and composition with latitude, longitude, local time, solar flux, season, magnetic activity level, and orientation of the interplanetary magnetic field. We are developing improved quantitative models of solar and magnetospheric inputs to the thermosphere and improved physical parameterizations in the first-principles global models; we are analyzing thermospheric responses to solar and magnetospheric inputs on time scales from minutes to the length of the solar cycle; and we are developing an improved empirical model of thermospheric winds. These research products will be made available to the scientific community. This work is helping to clarify critical problem areas in thermospheric physics for planned NASA missions like the Ionosphere-Thermosphere Storm Probes, Geospace Electrodynamics Connections, and the Global-scale Observation of the Limb and Disk.

  1. Dependence of regular background noise of VLF radiation and thunder-storm activity on solar wind proton density

    International Nuclear Information System (INIS)

    Sobolev, A.V.; Kozlov, V.I.

    1997-01-01

    Correlation of the intensity of slowly changing regular background noise within 9.7 kHz frequency in Yakutsk (L = 3) and of the solar wind density protons was determined. This result explains the reverse dependence of the intensity of the regular background noise on the solar activity, 27-day frequency, increase before and following geomagnetic storms, absence of relation with K p index of geomagnetic activity. Conclusion is made that growth of density of the solar wind protons results in increase of the regular background noise and thunderstorm activity

  2. Application of the Tikhonov regularization method to wind retrieval from scatterometer data I. Sensitivity analysis and simulation experiments

    International Nuclear Information System (INIS)

    Zhong Jian; Huang Si-Xun; Du Hua-Dong; Zhang Liang

    2011-01-01

    Scatterometer is an instrument which provides all-day and large-scale wind field information, and its application especially to wind retrieval always attracts meteorologists. Certain reasons cause large direction error, so it is important to find where the error mainly comes. Does it mainly result from the background field, the normalized radar cross-section (NRCS) or the method of wind retrieval? It is valuable to research. First, depending on SDP2.0, the simulated ‘true’ NRCS is calculated from the simulated ‘true’ wind through the geophysical model function NSCAT2. The simulated background field is configured by adding a noise to the simulated ‘true’ wind with the non-divergence constraint. Also, the simulated ‘measured’ NRCS is formed by adding a noise to the simulated ‘true’ NRCS. Then, the sensitivity experiments are taken, and the new method of regularization is used to improve the ambiguity removal with simulation experiments. The results show that the accuracy of wind retrieval is more sensitive to the noise in the background than in the measured NRCS; compared with the two-dimensional variational (2DVAR) ambiguity removal method, the accuracy of wind retrieval can be improved with the new method of Tikhonov regularization through choosing an appropriate regularization parameter, especially for the case of large error in the background. The work will provide important information and a new method for the wind retrieval with real data. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  3. Equinoctial transitions in the ionosphere and thermosphere

    Directory of Open Access Journals (Sweden)

    A. V. Mikhailov

    2001-07-01

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

  4. Polar heating in Saturn's thermosphere

    Directory of Open Access Journals (Sweden)

    C. G. A. Smith

    2005-10-01

    Full Text Available A 3-D numerical global circulation model of the Kronian thermosphere has been used to investigate the influence of polar heating. The distributions of temperature and winds resulting from a general heat source in the polar regions are described. We show that both the total energy input and its vertical distribution are important to the resulting thermal structure. We find that the form of the topside heating profile is particularly important in determining exospheric temperatures. We compare our results to exospheric temperatures from Voyager occultation measurements (Smith et al., 1983; Festou and Atreya, 1982 and auroral H3+ temperatures from ground-based spectroscopic observations (e.g. Miller et al., 2000. We find that a polar heat source is consistent with both the Smith et al. determination of T∞~400 K at ~30° N and auroral temperatures. The required heat source is also consistent with recent estimates of the Joule heating rate at Saturn (Cowley et al., 2004. However, our results show that a polar heat source can probably not explain the Festou and Atreya determination of T∞~800 K at ~4° N and the auroral temperatures simultaneously. Keywords. Ionosphere (Planetary ionosphere – Magnetospherica physics (Planetary magnetospheres – Meterology and atmospheric dynamics (Thermospheric dynamics

  5. Resistive Heating in Saturn's Thermosphere

    Science.gov (United States)

    Vriesema, Jess W.; Koskinen, Tommi; Yelle, Roger V.

    2016-10-01

    The thermospheres of the jovian planets are several times hotter than solar heating alone can account for. On Saturn, resistive heating appears sufficient to explain these temperatures in auroral regions, but the particular mechanism(s) responsible for heating the lower latitudes remains unclear. Smith et al. (2005) suggested that electrodynamics of the equatorial region—particularly resistive heating caused by strong electrojet currents—might explain the observed temperatures at low latitudes. Müller-Wodarg et al. (2006) found that their circulation model could reproduce low-latitude temperatures only when they included resistive heating at the poles and applied a uniform, generic heating source globally. Smith et al. (2007) concluded that heating at the poles leads to meridional circulation that cools low latitudes and argued that in-situ heating is required to explain the temperatures at low latitudes.Resistive heating at low latitudes, arising from enhanced current generation driven by thermospheric winds, is a potentially important in-situ heating mechanism. Ion drag caused by low-latitude electrodynamics can modify global circulation and meridional transport of energy. We present an axisymmetric, steady-state formulation of wind-driven electrodynamics to investigate these possibilities throughout Saturn's thermosphere. At present, we assume a dipole magnetic field and neglect any contributions from the magnetosphere. We use ion mixing ratios from the model of Kim et al. (2014) and the observed temperature-pressure profile from Koskinen et al. (2015) to calculate the generalized conductivity tensor as described by Koskinen et al. (2014). Our model solves the coupled equations for charge continuity and Ohm's law with tensor conductivity while enforcing zero current across the boundaries. The resulting partial differential equation is solved for the current density throughout the domain and used to calculate the net resistive heating rate. We demonstrate

  6. Relationships of storm-time changes in thermospheric mass density with solar wind/IMF parameters and ring current index of Sym-H

    Science.gov (United States)

    Zhou, Yunliang; Ma, S. Y.; Xiong, Chao; Luehr, Hermann

    The total air mass densities at about 500 km altitude are derived using super-STAR accelerom-eter measurements onboard GRACE satellites for 25 great magnetic storms with minimum Dst less than 100 nT during 2002 to 2006 years. Taking NRLMSISE-00 model-predicted densities without active ap index input as a reference baseline of quiet-time mass density, the storm-time changes in upper thermospheric mass densities are obtained by subtraction for all the storm events and sorted into different grids of latitude by local time sector. The relationships of the storm-time density changes with various interplanetary parameters and magnetospheric ring current index of Sym-H are statistically investigated. The parameters include Akasofu energy coupling function, the merging electric field Em, the magnitude of IMF component in the GSM y-z plane etc. as calculated from OMNI data at 1 AU. It is found that the storm-time changes in the upper thermospheric mass density have the best linear correlation with the Sym-H index in general, showing nearly zero time delay at low-latitudes and a little time ahead at high-latitudes for most cases. Unexpectedly, the magnitude of IMF component in the y-z plane, Byz, shows correlation with storm-time mass density changes better and closer than Akasofu function and even Em. And, the mass density changes lag behind Byz about 1-4 hours for most cases at low-latitudes. The correlations considered above are local time dependent, showing the lowest at dusk sectors. For the largest superstorm of November 2003, the changes in mass density are correlated very closely with Byz, Em, and Sym-H index, showing correlation coefficients averaged over all latitudes in noon sector as high as 0.93, 0.91 and 0.90 separately. The physical factors controlling the lag times between the mass density changes at mid-low-latitudes and the interplanetary parameter variations are also analyzed. The results in this study may pro-vide useful suggestions for establishing

  7. A 3-D Chemistry Transport Model for Titan's Thermosphere

    Science.gov (United States)

    Doege, M. C.; Marsh, D. R.; Brasseur, G. P.; Mueller-Wodarg, I.; Tokano, T.; Newman, C. E.

    2008-12-01

    MOZART-2 (Horowitz et al., 2003) has been adapted to investigate seasonal and diurnal differences in neutral composition in Titan's atmosphere between the surface and 1,200 km altitude. The chemical scheme with 64 solution species and 383 reactions is based on a simplified version of the Lavvas et al. (2008) scheme, without haze production. Wind and temperature fields were taken from the Cologne GCM (Tokano, 2007) or TitanWRF (Richardson et al., 2007) for the troposphere and stratosphere, and from the London TGCM (Mueller-Wodarg, 2000) for the thermosphere. Pronounced hemispheric concentration gradients develop in the thermosphere, and a strong diurnal cycle in composition is found, similar to the findings of Mueller-Wodarg (2003) for methane. Sensitivity experiments with different strengths of thermospheric circulation to account for uncertainty about the wind fields in that region are presented.

  8. Coupled rotational dynamics of Jupiter's thermosphere and magnetosphere

    Directory of Open Access Journals (Sweden)

    C. G. A. Smith

    2009-01-01

    Full Text Available We describe an axisymmetric model of the coupled rotational dynamics of the thermosphere and magnetosphere of Jupiter that incorporates self-consistent physical descriptions of angular momentum transfer in both systems. The thermospheric component of the model is a numerical general circulation model. The middle magnetosphere is described by a simple physical model of angular momentum transfer that incorporates self-consistently the effects of variations in the ionospheric conductivity. The outer magnetosphere is described by a model that assumes the existence of a Dungey cycle type interaction with the solar wind, producing at the planet a largely stagnant plasma flow poleward of the main auroral oval. We neglect any decoupling between the plasma flows in the magnetosphere and ionosphere due to the formation of parallel electric fields in the magnetosphere. The model shows that the principle mechanism by which angular momentum is supplied to the polar thermosphere is meridional advection and that mean-field Joule heating and ion drag at high latitudes are not responsible for the high thermospheric temperatures at low latitudes on Jupiter. The rotational dynamics of the magnetosphere at radial distances beyond ~30 RJ in the equatorial plane are qualitatively unaffected by including the detailed dynamics of the thermosphere, but within this radial distance the rotation of the magnetosphere is very sensitive to the rotation velocity of the thermosphere and the value of the Pedersen conductivity. In particular, the thermosphere connected to the inner magnetosphere is found to super-corotate, such that true Pedersen conductivities smaller than previously predicted are required to enforce the observed rotation of the magnetosphere within ~30 RJ. We find that increasing the Joule heating at high latitudes by adding a component due to rapidly fluctuating electric fields is unable to explain the high equatorial temperatures. Adding a component of Joule

  9. Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI): Monolithic Interferometer Design and Test

    Science.gov (United States)

    Harlander, John M.; Englert, Christoph R.; Brown, Charles M.; Marr, Kenneth D.; Miller, Ian J.; Zastera, Vaz; Bach, Bernhard W.; Mende, Stephen B.

    2017-10-01

    The design and laboratory tests of the interferometers for the Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instrument which measures thermospheric wind and temperature for the NASA-sponsored Ionospheric Connection (ICON) Explorer mission are described. The monolithic interferometers use the Doppler Asymmetric Spatial Heterodyne (DASH) Spectroscopy technique for wind measurements and a multi-element photometer approach to measure thermospheric temperatures. The DASH technique and overall optical design of the MIGHTI instrument are described in an overview followed by details on the design, element fabrication, assembly, laboratory tests and thermal control of the interferometers that are the heart of MIGHTI.

  10. Some characteristics of midlatitude F layer storms generated by thermosphere-plasmasphere coupling processes

    International Nuclear Information System (INIS)

    Miller, N.J.

    1983-01-01

    In this dissertation, calculations are interpreted that have been made to describe stormtime variations in equinoctial dayside plasma parameters when the variations are primarily caused by processes dependent upon collisional coupling between the thermosphere and the plasmasphere. The calculations are made with a computer model formed by linking two theoretical models: a pre-existing thermospheric model that describes dayside variations in thermospheric parameters during stormtime heating of the thermosphere; a plasmaspheric model which was developed to describe dayside plasmaspheric variations caused by the thermospheric variations described by the thermospheric model and by variations in a magnetospheric electric field. Both portions of the computerized storm model solve partial differential equations describing conservation of species, momentum, and energy by replacing dependent variables with expansions in time series. The thermospheric portion of the storm model solves for variations in gas temperature, horizontal wind velocity, and densities of atomic oxygen and molecular nitrogen while the plasmaspheric portion of the storm model solves for variations in ion densities of oxygen and hydrogen, ion fluxes and electrons, and heat fluxes through ions and electrons. Other calculations that have been used to describe variations in thermospheric and plasmaspheric parameters are summarized and the advantages and limitations of the model calculations used to obtain results presented in this dissertation are noted

  11. Vorticity and divergence in the high-latitude upper thermosphere

    International Nuclear Information System (INIS)

    Thayer, J.P.; Killeen, T.L.

    1991-01-01

    Measurements made from the Dynamics Explorer-2 satellite in November 1981 through January 1982 and November 1982 through January 1983 have been analyzed to determine the divergence and vertical component of vorticity of the high-latitude neutral wind field in the upper thermosphere for quiet (kp≤6) geomagnetic conditions and for both northern (winter) and southern (summer) hemispheres in the polar thermosphere and provides insight into the relative strengths of the different sources of momentum and energy responsible for driving the winds. The principal findings from this work include the following: The mean neutral wind pattern is dominated by rotational flow rather than by divergent flow, with a typical vorticity: divergence ratio of ∼ 2:1 for active conditions and ∼ 4:1 for quiet conditions. Comparison of the divergence and vorticity patterns for quiet and active conditions indicates that the divergent component of the neutral flow intensifies more significantly with increasing geomagnetic activity than does the rotational component

  12. High Resolution Modeling of the Thermospheric Response to Energy Inputs During the RENU-2 Rocket Flight

    Science.gov (United States)

    Walterscheid, R. L.; Brinkman, D. G.; Clemmons, J. H.; Hecht, J. H.; Lessard, M.; Fritz, B.; Hysell, D. L.; Clausen, L. B. N.; Moen, J.; Oksavik, K.; Yeoman, T. K.

    2017-12-01

    The Earth's magnetospheric cusp provides direct access of energetic particles to the thermosphere. These particles produce ionization and kinetic (particle) heating of the atmosphere. The increased ionization coupled with enhanced electric fields in the cusp produces increased Joule heating and ion drag forcing. These energy inputs cause large wind and temperature changes in the cusp region. The Rocket Experiment for Neutral Upwelling -2 (RENU-2) launched from Andoya, Norway at 0745UT on 13 December 2015 into the ionosphere-thermosphere beneath the magnetic cusp. It made measurements of the energy inputs (e.g., precipitating particles, electric fields) and the thermospheric response to these energy inputs (e.g., neutral density and temperature, neutral winds). Complementary ground based measurements were made. In this study, we use a high resolution two-dimensional time-dependent non hydrostatic nonlinear dynamical model driven by rocket and ground based measurements of the energy inputs to simulate the thermospheric response during the RENU-2 flight. Model simulations will be compared to the corresponding measurements of the thermosphere to see what they reveal about thermospheric structure and the nature of magnetosphere-ionosphere-thermosphere coupling in the cusp. Acknowledgements: This material is based upon work supported by the National Aeronautics and Space Administration under Grants: NNX16AH46G and NNX13AJ93G. This research was also supported by The Aerospace Corporation's Technical Investment program

  13. Global excitation of wave phenomena in a dissipative multiconstituent medium. I - Transfer function of the earth's thermosphere. II - Impulsive perturbations in the earth's thermosphere

    Science.gov (United States)

    Mayr, H. G.; Harris, I.; Herrero, F. A.; Varosi, F.

    1984-01-01

    A transfer function approach is taken in constructing a spectral model of the acoustic-gravity wave response in a multiconstituent thermosphere. The model is then applied to describing the thermospheric response to various sources around the globe. Zonal spherical harmonics serve to model the horizontal variations in propagating waves which, when integrated with respect to height, generate a transfer function for a vertical source distribution in the thermosphere. Four wave components are characterized as resonance phenomena and are associated with magnetic activity and ionospheric disturbances. The waves are either trapped or propagate, the latter becoming significant when possessing frequencies above 3 cycles/day. The energy input is distributed by thermospheric winds. The disturbances decay slowly, mainly due to heat conduction and diffusion. Gravity waves appear abruptly and are connected to a sudden switching on or off of a source. Turn off of a source coincides with a reversal of the local atmospheric circulation.

  14. Full non-linear treatment of the global thermospheric wind system. I - Mathematical method and analysis of forces. II - Results and comparison with observations

    Science.gov (United States)

    Blum, P. W.; Harris, I.

    1975-01-01

    The equations of horizontal motion of the neutral atmosphere between 120 and 500 km are integrated with the inclusion of all nonlinear terms of the convective derivative and the viscous forces due to vertical and horizontal velocity gradients. Empirical models of the distribution of neutral and charged particles are assumed to be known. The model of velocities developed is a steady state model. In Part I the mathematical method used in the integration of the Navier-Stokes equations is described and the various forces are analyzed. Results of the method given in Part I are presented with comparison with previous calculations and observations of upper atmospheric winds. Conclusions are that nonlinear effects are only significant in the equatorial region, especially at solstice conditions and that nonlinear effects do not produce any superrotation.

  15. LATTICE: The Lower ATmosphere-Thermosphere-Ionosphere Coupling Experiment

    Science.gov (United States)

    Mlynczak, M. G.; Yee, J. H.

    2017-12-01

    We present the Lower Atmosphere-Thermosphere-Ionosphere Coupling Experiment (LATTICE), which is a candidate mission for proposal to a future NASA Announcement of Opportunity. LATTICE will make the first consistent measurements of global kinetic temperature from the tropopause up to at least 160 km, along with global vector winds from 100 to 160 km at all local times. LATTICE thus provides, for the first time, a consistent picture of the coupling of the terrestrial lower atmosphere to the thermosphere-ionosphere system, which is a major scientific goal outlined in the 2012 Heliophysics Decadal Survey. The core instruments on LATTICE are the Terahertz Limb Sounder (TLS) and the Sounding of the Atmosphere using Broadband Emission Radiometry-II (SABER-II) instrument. The TLS instrument measures the 147 µm (2.04 THz) fine structure line of atomic oxygen. From these measurements TLS will provide kinetic temperature, atomic oxygen density, and vector wind from 100 to at least 160 km altitude. SABER-II is an infrared radiometer and is optically identical to the legacy SABER instrument on the current TIMED satellite. SABER-II is half the mass, half the power, and one-third the volume of the legacy instrument, and expects the same radiometric performance. SABER-II will again measure kinetic temperature from 15 to 110 km and will make measurements of key parameters in the thermosphere-ionosphere system including NO+, the green line and red line emissions, as well as continuing legacy measurements of ozone, water vapor, atomic oxygen, and atomic hydrogen in the mesosphere and lower thermosphere. We will describe the LATTICE mission in detail including other potential instruments for diagnosing thermospheric composition and high latitude energy inputs, and for measuring solar ultraviolet irradiance.

  16. Lower thermosphere (80-100 km) dynamics response to solar and geomagnetic activity: Overview

    International Nuclear Information System (INIS)

    Kazimirovsky, E.S.

    1989-01-01

    The variations of solar and geomagnetic activity may affect the thermosphere circulation via plasma heating and electric fields, especially at high latitudes. The possibility exists that the energy involved in auroral and magnetic storms can produce significant changes of mesosphere and lower thermosphere wind systems. A study of global radar measurements of winds at 80 to 100 km region revealed the short term effects (correlation between wind field and geomagnetic storms) and long term variations over a solar cycle. It seems likely that the correlation results from a modification of planetary waves and tides propagated from below, thus altering the dynamical regime of the thermosphere. Sometimes the long term behavior points rather to a climatic variation with the internal atmospheric cause than to a direct solar control

  17. Low latitude ionosphere-thermosphere dynamics studies with inosonde chain in Southeast Asia

    Directory of Open Access Journals (Sweden)

    T. Maruyama

    2007-07-01

    Full Text Available An ionosonde network consisting of a meridional chain and an equatorial pair was established in the Southeast Asian area. Three of four ionosondes are along the magnetic meridian of 100° E; two are close to the magnetic conjugate points in Northern Thailand and West Sumatra, Indonesia, and the other is near the magnetic equator in the Malay Peninsula, Thailand. The fourth ionosonde is also near the magnetic equator in Vietnam but separated by about 6.3° towards east from the meridional chain. For a preliminary data analysis, nighttime ionospheric height variations at the three stations of the meridional chain were examined. The results demonstrate that the coordination of the network has a great potential for studying ionosphere/thermosphere dynamics. Through the assistance of model calculations, thermospheric neutral winds were inferred and compared with the HWM93 empirical thermospheric wind model. Higher-order wind variations that are not represented in the empirical model were found.

  18. Venus O2 visible and IR nightglow: Implications for lower thermosphere dynamics and chemistry

    Science.gov (United States)

    Bougher, S. W.; Borucki, W. J.

    1994-01-01

    The National Center for Atmospheric Research thermospheric general circulation model for the Venus thermosphere is modified to examine two observed night airglow features, both of which serve as sensitive tracers of the thermospheric circulation. New O2 nightglow data from the Pioneer Venus Orbiter (PVO) star tracker (O2 Herzberg II at 400-800 nm) and ground-based telescopes (O2 IR at 1.27 microns) yield additional model constraints for estimating Venus winds over 100-130 km. Atomic oxygen, produced by dayside CO2 photolysis peaking near 110 km, and transported to the nightside by the global wind system, is partially destroyed through three-body recombination, yielding the O2 Herzberg II visible nightglow. This emission is very sensitive to horizontal winds at altitudes between 100 and 130 km. Other trace species catalytic reactions also contribute to the production of the very strong nightside infrared (1.27 microns) emission. This paper examines the dynamical and chemical implications of these new data using the Venus thermospheric general circulation model (VTGCM) as an analysis tool. Three-dimensional calculations are presented for both solar maximum and solar medium conditions, corresponding to early PVO (1979-1981) and PVO entry (mid-1992) time periods. Very distinct periods are identified in which zonal winds are alternately weak and strong in the Venus lower thermosphere. VTGCM sensitivity studies are conducted to assess the impacts of potential changes in thermospheric zonal and day-to-night winds, and eddy diffusion on the corresponding nightglow intensities. It appears that cyclostrophic balance extends above 80 km periodically, owing to a reversal of the upper mesosphere latitudinal temperature gradient, and thereby producing strong zonal winds and correspondingly modified O2 nightglow distributions that are observed.

  19. Formation mechanisms of neutral Fe layers in the thermosphere at Antarctica studied with a thermosphere-ionosphere Fe/Fe+ (TIFe) model

    Science.gov (United States)

    Chu, Xinzhao; Yu, Zhibin

    2017-06-01

    With a thermosphere-ionosphere Fe/Fe+ (TIFe) model developed from first principles at the University of Colorado, we present the first quantitative investigation of formation mechanisms of thermospheric Fe layers observed by lidar in Antarctica. These recently discovered neutral metal layers in the thermosphere between 100 and 200 km provide unique tracers for studies of fundamental processes in the space-atmosphere interaction region. The TIFe model formulates and expands the TIFe theory originally proposed by Chu et al. that the thermospheric Fe layers are produced through the neutralization of converged Fe+ layers. Through testing mechanisms and reproducing the 28 May 2011 event at McMurdo, we conceive the lifecycle of meteoric metals via deposition, transport, chemistry, and wave dynamics for thermospheric Fe layers with gravity wave signatures. While the meteor injection of iron species is negligible above 120 km, the polar electric field transports metallic ions Fe+ upward from their main deposition region into the E-F regions, providing the major source of Fe+ (and accordingly Fe) in the thermosphere. Atmospheric wave-induced vertical shears of vertical and horizontal winds converge Fe+ to form dense Fe+ layers. Direct electron-Fe+ recombination is the major channel to neutralize Fe+ layers to form Fe above 120 km. Fe layer shapes are determined by multiple factors of neutral winds, electric field, and aurora activity. Gravity-wave-induced vertical wind plays a key role in forming gravity-wave-shaped Fe layers. Aurora particle precipitation enhances Fe+ neutralization by increasing electron density while accelerating Fe loss via charge transfer with enhanced NO+ and O2+ densities.Plain Language SummaryThe discoveries of neutral metal layers reaching near 200 km in the thermosphere have significant scientific merit because such discoveries challenge the current understandings of upper atmospheric composition, chemistry, dynamics, electrodynamics, and

  20. A theoretical study of thermospheric composition perturbations during an impulsive geomagnetic storm

    International Nuclear Information System (INIS)

    Burns, A.G.; Killeen, T.L.; Roble, R.G.

    1991-01-01

    The compositional response of the neutral thermosphere to an impulsive geomagnetic storm has been investigated using a numerical simulation made with the National Center for Atmospheric Research thermospheric general circulation model (NCAR-TGCM). Calculated time-dependent changes in neutral thermospheric composition have been studied, together with detailed neutral parcel trajectories and other diagnostic information from the model, to gain a greater understanding of the physical mechanisms responsible for composition variability during geomagnetic storms and, in particular, to investigate the causes of the positive and negative ionospheric storm effects. The following principal results were obtained from this study. (1) Calculated perturbations in thermospheric composition following the onset of an impulsive geomagnetic storm were found to be in good qualitative agreement with the previous experimental statistical study of storm time thermospheric morphology by Proelss. (2) During the initial (onset) phase of the simulated storm, upward vertical winds occurred in the auroral zone and downward winds occurred in the central magnetic polar cap. (3) The largest perturbations in mass mixing ratio of nitrogen at F region altitudes were found to be associated with parcels of neutral gas that travelled through the cusp region and with parcels that were trapped within the auroral zone for a long time. (4) Storm time enhancements in Ψ N 2 were found to occur in the midnight and early morning sectors both within and equatorward of the auroral zone, and these were determined to be associated with the advective effects of the large antisunward polar cap neutral winds

  1. The thermospheric effects of a rapid polar cap expansion

    Directory of Open Access Journals (Sweden)

    D. W. Idenden

    Full Text Available In a previous publication we used results from a coupled thermosphere-ionosphere-plasmasphere model to illustrate a new mechanism for the formation of a large-scale patch of ionisation arising from a rapid polar cap expansion. Here we describe the thermospheric response to that polar cap expansion, and to the ionospheric structure produced. The response is dominated by the energy and momentum input at the dayside throat during the expansion phase itself. These inputs give rise to a large-scale travelling atmospheric disturbance (TAD that propagates both antisunward across the polar cap and equatorward at speeds much greater than both the ion drifts and the neutral winds. We concentrate only on the initially poleward travelling disturbance. The disturbance is manifested in the neutral temperature and wind fields, the height of the pressure level surfaces and in the neutral density at fixed heights. The thermospheric effects caused by the ionospheric structure produced during the expansion are hard to discern due to the dominating effects of the TAD.

    Key words. Ionosphere (ionosphere · atmosphere interaction; modeling and forecasting; plasma convection.

  2. Zonally averaged chemical-dynamical model of the lower thermosphere

    International Nuclear Information System (INIS)

    Kasting, J.F.; Roble, R.G.

    1981-01-01

    A zonally averaged numerical model of the thermosphere is used to examine the coupling between neutral composition, including N 2 , O 2 and O, temperature, and winds at solstice for solar minimum conditions. The meridional circulation forced by solar heating results in a summer-to-winter flow, with a winter enhancement in atomic oxygen density that is a factor of about 1.8 greater than the summer hemisphere at 160 km. The O 2 and N 2 variations are associated with a latitudinal gradient in total number density, which is required to achieve pressure balance in the presence of large zonal jets. Latitudinal profiles OI (5577A) green line emission intensity are calculated by using both Chapman and Barth mechanisms. Composition of the lower thermosphere is shown to be strongly influenced by circulation patterns initiated in the stratosphere and lower mesosphere, below the lower boundary used in the model

  3. Thermosphere as a sink of magnetospheric energy - a review of recent observations of dynamics

    International Nuclear Information System (INIS)

    Killeen, T.L.

    1985-01-01

    It is pointed out that the past few years have seen an unprecedented influx of new experimental information on the dynamics of the neutral upper atmosphere of the earth. Vector wind measurements provide new information for studies of the thermospheric response to magnetospheric forcing. This response occurs through the medium of convecting ionospheric ions set into motion by electric fields of magnetospheric origin. The ultimate sink for much of the energy and momentum coming from the magnetosphere is the neutral thermosphere whose dynamics have, in the past, received far less attention than their ionospheric counterpart because of basic experimental limitations. In this paper, a review is provided of the progress made in the last few years on the basis of the Dynamics Explorer neutral wind observations, taking into account the coupling between the magnetosphere and the thermosphere via the ionosphere. 26 references

  4. Comparison of high-latitude thermospheric meridionalwinds I: optical and radar experimental comparisons

    Directory of Open Access Journals (Sweden)

    E. M. Griffin

    2004-03-01

    Full Text Available Thermospheric neutral winds at Kiruna, Sweden (67.4°N, 20.4°E are compared using both direct optical Fabry-Perot Interferometer (FPI measurements and those derived from European incoherent scatter radar (EISCAT measurements. This combination of experimental data sets, both covering well over a solar cycle of data, allows for a unique comparison of the thermospheric meridional component of the neutral wind as observed by different experimental techniques. Uniquely in this study the EISCAT measurements are used to provide winds for comparison using two separate techniques: the most popular method based on the work of Salah and Holt (1974 and the Meridional Wind Model (MWM (Miller et al., 1997 application of servo theory. The balance of forces at this location that produces the observed diurnal pattern are investigated using output from the Coupled Thermosphere and Ionosphere (CTIM numerical model. Along with detailed comparisons from short periods the climatological behaviour of the winds have been investigated for seasonal and solar cycle dependence using the experimental techniques. While there are features which are consistent between the 3 techniques, such as the evidence of the equinoctial asymmetry, there are also significant differences between the techniques both in terms of trends and absolute values. It is clear from this and previous studies that the high-latitude representation of the thermospheric neutral winds from the empirical Horizontal Wind Model (HWM, though improved from earlier versions, lacks accuracy in many conditions. The relative merits of each technique are discussed and while none of the techniques provides the perfect data set to address model performance at high-latitude, one or more needs to be included in future HWM reformulations.

    Key words. Meteorology and atmospheric dynamics (thermospheric dynamics, Ionosphere (ionosphere-atmosphere interactions, auroral ionosphere

  5. Comparison of high-latitude thermospheric meridionalwinds I: optical and radar experimental comparisons

    Directory of Open Access Journals (Sweden)

    E. M. Griffin

    2004-03-01

    Full Text Available Thermospheric neutral winds at Kiruna, Sweden (67.4°N, 20.4°E are compared using both direct optical Fabry-Perot Interferometer (FPI measurements and those derived from European incoherent scatter radar (EISCAT measurements. This combination of experimental data sets, both covering well over a solar cycle of data, allows for a unique comparison of the thermospheric meridional component of the neutral wind as observed by different experimental techniques. Uniquely in this study the EISCAT measurements are used to provide winds for comparison using two separate techniques: the most popular method based on the work of Salah and Holt (1974 and the Meridional Wind Model (MWM (Miller et al., 1997 application of servo theory. The balance of forces at this location that produces the observed diurnal pattern are investigated using output from the Coupled Thermosphere and Ionosphere (CTIM numerical model. Along with detailed comparisons from short periods the climatological behaviour of the winds have been investigated for seasonal and solar cycle dependence using the experimental techniques. While there are features which are consistent between the 3 techniques, such as the evidence of the equinoctial asymmetry, there are also significant differences between the techniques both in terms of trends and absolute values. It is clear from this and previous studies that the high-latitude representation of the thermospheric neutral winds from the empirical Horizontal Wind Model (HWM, though improved from earlier versions, lacks accuracy in many conditions. The relative merits of each technique are discussed and while none of the techniques provides the perfect data set to address model performance at high-latitude, one or more needs to be included in future HWM reformulations. Key words. Meteorology and atmospheric dynamics (thermospheric dynamics, Ionosphere (ionosphere-atmosphere interactions, auroral ionosphere

  6. A study of space shuttle plumes in the lower thermosphere

    Science.gov (United States)

    Meier, R. R.; Stevens, Michael H.; Plane, John M. C.; Emmert, J. T.; Crowley, G.; Azeem, I.; Paxton, L. J.; Christensen, A. B.

    2011-12-01

    During the space shuttle main engine burn, some 350 t of water vapor are deposited at between 100 and 115 km. Subsequent photodissociation of water produces large plumes of atomic hydrogen that can expand rapidly and extend for thousands of kilometers. From 2002 to 2007, the Global Ultraviolet Imager (GUVI) on NASA's Thermosphere Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite imaged many of these hydrogen plumes at Lyman α (121.567 nm) while viewing in the nadir. The images reveal rapid plume expansion and occasional very fast transport to both north and south polar regions. Some plumes persist for up to 6 d. Near-simultaneous direct detections of water vapor were made with the Sounding of the Atmosphere with Broadband Emission Radiometry (SABER) instrument, also on TIMED. We compare the spreading of the hydrogen plume with a two-dimensional model that includes photodissociation as well as both vertical and horizontal diffusion. Molecular diffusion appears to be sufficient to account for the horizontal expansion, although wind shears and turbulent mixing may also contribute. We compare the bulk motion of the observed plumes with wind climatologies derived from satellite observations. The plumes can move much faster than predictions of wind climatologies. But dynamical processes not contained in wind climatologies, such as the quasi-two-day wave, can account for at least some of the high speed observations. The plume phenomena raise a number of important questions about lower thermospheric and mesospheric processes, ranging from dynamics and chemistry to polar mesospheric cloud formation and climatology.

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

    Science.gov (United States)

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

    1989-06-01

    During the past six years, rapid advances in three observational techniques (ground-based radars, optical interferometers and satellite-borne instruments) have provided a means of observing a wide range of spectacular interactions between the coupled magnetosphere, ionosphere and thermosphere system. Perhaps the most fundamental gain has come from the combined data-sets from the NASA Dynamics Explorer (DE) Satellites. These have unambiguously described the global nature of thermospheric flows, and their response to magnetospheric forcing. The DE spacecraft have also described, at the same time, the magnetospheric particle precipitation and convective electric fields which force the polar thermosphere and ionosphere. The response of the thermosphere to magnetospheric forcing is far more complex than merely the rare excitation of 1 km s-1 wind speeds and strong heating; the heating causes large-scale convection and advection within the thermosphere. These large winds grossly change the compositional structure of the upper thermosphere at high and middle latitudes during major geomagnetic disturbances. Some of the major seasonal and geomagnetic storm-related anomalies of the ionosphere are directly attributable to the gross wind-induced changes of thermospheric composition; the mid-latitude ionospheric storm `negative phase', however, is yet to be fully understood. The combination of very strong polar wind velocities and rapid plasma convection forced by magnetospheric electric fields strongly and rapidly modify F-region plasma distributions generated by the combination of local solar and auroral ionization sources. Until recently, however, it has been difficult to interpret the observed complex spatial and time-dependent structures and motions of the thermosphere and ionosphere because of their strong and nonlinear coupling. It has recently been possible to complete a numerical and computational merging of the University College London (UCL) global thermospheric

  8. Simulations of the September 1987 lower thermospheric tides with the National Center for Atmospheric Research thermosphere-ionosphere general circulation model

    International Nuclear Information System (INIS)

    Fesen, C.G.; Roble, R.G.

    1991-01-01

    The National Center for Atmospheric Research thermosphere-ionosphere general circulation model (TIGCM) was used to simulate incoherent scatter radar observations of the lower thermosphere tides during the first Lower Thermosphere Coupling Study (LTCS) campaign, September 21-26, 1987. The TIGCM utilized time-varying histories of the model input fields obtained from the World Data Center for the LTCS period. These model inputs included solar flux, total hemispheric power, solar wind data from which the cross-polar-cap potential was derived, and geomagnetic K p index. Calculations were made for the semidiurnal ion temperatures and horizontal neutral winds at locations representative of Arecibo, Millstone Hill, and Sondrestrom. The diurnal tides at Sondrestrom were also simulated. Tidal inputs to the TIGCM lower boundary were obtained from the middle atmosphere model of Forbes and Vial (1989). The TIGCM tidal structures are in fair general agreement with the observations. The amplitudes tended to be better simulated than the phases, and the mid- and high-latitude locations are simulated better than the low-latitude thermosphere. This may indicate a need to incorporate coupling of the neutral atmosphere and ionosphere with the E region dynamo in the equatorial region to obtain a better representation of low-latitude thermospheric tides. The model simulations were used to investigate the daily variability of the tides due to the geomagnetic activity occurring during this period. In general, the ion temperatures were predicted to be affected more than the winds, and the diurnal components more than the semidiurnal. The effects are typically largest at high latitudes and higher altitudes, but discernible differences were produced at low latitudes

  9. Comparison of high-latitude thermospheric meridionalwinds II: combined FPI, radar and model Climatologies

    Directory of Open Access Journals (Sweden)

    E. M. Griffin

    2004-03-01

    Full Text Available The climatological behaviour of the thermospheric meridional wind above Kiruna, Sweden (67.4°N, 20.4°E has been investigated for seasonal and solar cycle dependence using six different techniques, comprising both model and experimental sources. Model output from both the empirical Horizontal Wind Model (HWM (Hedin et al., 1988 and the numerical Coupled Thermosphere and Ionosphere Model (CTIM are compared to the measured behaviour at Kiruna, as a single site example. The empirical International Reference Ionosphere (IRI model is used as input to an implementation of servo theory, to provide another climatology combining empirical input with a theoretical framework. The experimental techniques have been introduced in a companion paper in this issue and provide climatologies from direct measurements, using Fabry-Perot Interferometers (FPI, together with 2 separate techniques applied to the European Incoherent Scatter radar (EISCAT database to derive neutral winds. One of these techniques uses the same implementation of servo theory as has been used with the IRI model. Detailed comparisons for each season and solar activity category allow for conclusions to be drawn as to the major influences on the climatological behaviour of the wind at this latitude. Comparison of the incoherent scatter radar (ISR derived neutral winds with FPI, empirical model and numerical model winds is important to our understanding and judgement of the validity of the techniques used to derive thermospheric wind databases. The comparisons also test model performance and indicate possible reasons for differences found between the models. In turn, the conclusions point to possible improvements in their formulation. In particular it is found that the empirical models are over-reliant on mid-latitude data in their formulation, and fail to provide accurate estimates of the winds at high-latitudes.

    Key words. Meteorology and atmospheric dynamics (thermospheric dynamics

  10. Comparison of high-latitude thermospheric meridionalwinds II: combined FPI, radar and model Climatologies

    Directory of Open Access Journals (Sweden)

    E. M. Griffin

    2004-03-01

    Full Text Available The climatological behaviour of the thermospheric meridional wind above Kiruna, Sweden (67.4°N, 20.4°E has been investigated for seasonal and solar cycle dependence using six different techniques, comprising both model and experimental sources. Model output from both the empirical Horizontal Wind Model (HWM (Hedin et al., 1988 and the numerical Coupled Thermosphere and Ionosphere Model (CTIM are compared to the measured behaviour at Kiruna, as a single site example. The empirical International Reference Ionosphere (IRI model is used as input to an implementation of servo theory, to provide another climatology combining empirical input with a theoretical framework. The experimental techniques have been introduced in a companion paper in this issue and provide climatologies from direct measurements, using Fabry-Perot Interferometers (FPI, together with 2 separate techniques applied to the European Incoherent Scatter radar (EISCAT database to derive neutral winds. One of these techniques uses the same implementation of servo theory as has been used with the IRI model. Detailed comparisons for each season and solar activity category allow for conclusions to be drawn as to the major influences on the climatological behaviour of the wind at this latitude. Comparison of the incoherent scatter radar (ISR derived neutral winds with FPI, empirical model and numerical model winds is important to our understanding and judgement of the validity of the techniques used to derive thermospheric wind databases. The comparisons also test model performance and indicate possible reasons for differences found between the models. In turn, the conclusions point to possible improvements in their formulation. In particular it is found that the empirical models are over-reliant on mid-latitude data in their formulation, and fail to provide accurate estimates of the winds at high-latitudes. Key words. Meteorology and atmospheric dynamics (thermospheric dynamics

  11. Separation of dry and wet periods from regular weather station data for the analysis of wind erosion risk

    DEFF Research Database (Denmark)

    Naeini, Mohammadali Saremi; Fister, Wolfgang; Heckrath, Goswin Johann

    importance, soil moisture content is often ignored in the analysis of wind data for wind erosion studies. The main reason most probably being the lack of soil moisture sensors in conventional climate stations. Soil moisture at a given point in time is determined by rain (e.g. rainfall amount, duration......), climate (e.g. air temperature, solar radiation, evaporation) and soil (e.g. infiltration rate, adhesion). The purpose of this study is to overcome the lack of soil moisture data for wind erosion risk assessment by developing a method to estimate the soil wetness based on easy available weather data......, such as daily precipitation, hourly/sub hourly ambient air temperature and hourly/sub hourly relative humidity. This new method was used to identify periods of wet and dry soil moisture conditions of a time series from 20 weather stations in Denmark. The length of the time series varied between 8 to 37 years...

  12. Stratospheric warming influence on the mesosphere/lower thermosphere as seen by the extended CMAM

    Directory of Open Access Journals (Sweden)

    M. G. Shepherd

    2014-06-01

    Full Text Available The response of the upper mesosphere/lower thermosphere region to major sudden stratospheric warming (SSW is examined employing temperature, winds, NOX and CO constituents from the extended Canadian Middle Atmosphere Model (CMAM with continuous incremental nudging below 10 hPa (~ 30 km. The model results considered cover high latitudes (60–85° N from 10 to 150 km height for the December–March period of 2003/2004, 2005/2006 and 2008/2009, when some of the strongest SSWs in recent years were observed. NOX and CO are used as proxies for examining transport. Comparisons with ACE-FTS (Atmospheric Chemistry Experiment–Fourier Transform Spectrometer satellite observations show that the model represents well the dynamics of the upper mesosphere/lower thermosphere region, the coupling of the stratosphere–mesosphere, and the NOX and CO transport. New information is obtained on the upper mesosphere/lower thermosphere up to 150 km showing that the NOX volume mixing ratio in the 2003/2004 winter was very perturbed indicating transport from the lower atmosphere and intense mixing with large NOX influx from the thermosphere compared to 2006 and 2009. These results, together with those from other models and observations, clearly show the impact of stratospheric warmings on the thermosphere.

  13. High time resolution measurements of the thermosphere from Fabry-Perot Interferometer measurements of atomic oxygen

    Directory of Open Access Journals (Sweden)

    E. A. K. Ford

    2007-06-01

    Full Text Available Recent advances in the performance of CCD detectors have enabled a high time resolution study of the high latitude upper thermosphere with Fabry-Perot Interferometers (FPIs to be performed. 10-s integration times were used during a campaign in April 2004 on an FPI located in northern Sweden in the auroral oval. The FPI is used to study the thermosphere by measuring the oxygen red line emission at 630.0 nm, which emits at an altitude of approximately 240 km. Previous time resolutions have been 4 min at best, due to the cycle of look directions normally observed. By using 10 s rather than 40 s integration times, and by limiting the number of full cycles in a night, high resolution measurements down to 15 s were achievable. This has allowed the maximum variability of the thermospheric winds and temperatures, and 630.0 nm emission intensities, at approximately 240 km, to be determined as a few minutes. This is a significantly greater variability than the often assumed value of 1 h or more. A Lomb-Scargle analysis of this data has shown evidence of gravity wave activity with waves with short periods. Gravity waves are an important feature of mesosphere-lower thermosphere (MLT dynamics, observed using many techniques and providing an important mechanism for energy transfer between atmospheric regions. At high latitudes gravity waves may be generated in-situ by localised auroral activity. Short period waves were detected in all four clear nights when this experiment was performed, in 630.0 nm intensities and thermospheric winds and temperatures. Waves with many periodicities were observed, from periods of several hours, down to 14 min. These waves were seen in all parameters over several nights, implying that this variability is a typical property of the thermosphere.

  14. A theoretical and empirical study of the response of the high latitude thermosphere to the sense of the 'Y' component of the interplanetary magnetic field

    International Nuclear Information System (INIS)

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

    1986-01-01

    The strength and direction of the Interplanetary Magnetic Field (IMF) controls the transfer of solar wind momentum and energy to the high latitude thermosphere in a direct fashion. The sense of ''Y'' component of the IMF (BY) creates a significant asymmetry of the magnetospheric convection pattern as mapped onto the high latitude thermosphere and ionosphere. The resulting response of the polar thermospheric winds during periods when BY is either positive or negative is quite distinct, with pronounced changes in the relative strength of thermospheric winds in the dusk-dawn parts of the polar cap and in the dawn part of the auroral oval. In a study of four periods when there was a clear signature of BY, observed by the ISEE-3 satellite, with observations of polar winds and electric fields from the Dynamics Explorer-2 satellite and with wind observations by a ground-based Fabry-Perot interferometer located in Kiruna, Northern Sweden, it is possible to explain features of the high latitude thermospheric circulation using three dimensional global models including BY dependent, asymmetric, polar convection fields. Anomalously zonal wind velocities are often observed, for BY positive and when BY is negative. These are matched by the observation of strong anti-sunward polar-cap wind jets from the DE-2 satellite, on the dusk side with BY negative, and on the dawn side with BY positive. (author)

  15. The neutral thermosphere at Arecibo during geomagnetic storms

    International Nuclear Information System (INIS)

    Burnside, R.G.; Tepley, C.A.; Sulzer, M.P.; Fuller-Rowell, T.J.; Torr, D.G.; Roble, R.G.

    1991-01-01

    Over the past five years, simultaneous incoherent scatter and optical observations have been obtained at Arecibo, Puerto Rico, during two major geomagnetic storms. The first storm the authors examine occurred during the World Day campaign of 12-16 January 1988, where on 14 January 1988, Kp values greater than 7 were recorded. An ion-energy balance calculation shows that atomic oxygen densities at a fixed height on 14 January 1988 were about twice as large as they were on the quiet days in this period. Simultaneous radar and Fabry-Perot interferometer observations were used to infer nightime O densities on 14-15 January 1988 that were about twice as large as on adjacent quiet nights. On this night, unusually high westward ion velocities were observed at Arecibo. The Fabry-Perot measurements show that the normal eastward flow of the neutral wind was reversed on this night. The second storm they examine occured on the night of 13-14 July 1985, when Kp values reached only 4+, but the ionosphere and thermosphere responded in a similar manner as they did in January 1988. On the nights of both 13-14 July 1985 and 14-15 January 1988, the electron densities observed at Arecibo were significantly higher than they were on nearby geomagnetically quiet nights. These results indicate that major storm effects in thermospheric winds and composition propagate to low latitudes and have a pronounced effect on the ionospheric structure over Arecibo

  16. Lower thermosphere coupling study: Comparison of observations with predictions of the University College London-Sheffield thermosphere-ionosphere model

    International Nuclear Information System (INIS)

    Fuller-Rowell, T.J.; Rees, D.; Parish, H.F.; Virdi, T.S.; Williams, P.J.S.; Johnson, R.M.

    1991-01-01

    During the first Lower Thermosphere Coupling Study (LTCS), September 21-25 1987, data were recorded from the incoherent scatter radar sites at EISCAT, Millstone Hill, Sondrestrom, and Arecibo. These experimental facilities measured ionospheric parameters (Ne, Te, Ti, and plasma velocity) in the E and the F regions which have been used to determine the E region neutral wind and infer the neutral temperature in the height range 100-150 km. Propagating tides are clearly visible in some of the parameters, and the latitude structure and phase variations with height indicate the presence of at least the (2,2) and (2,4) global tidal Hough modes. The influence of geomagnetic forcing is also clearly present at high latitudes. The University College London-Sheffield University three-dimensional coupled thermosphere-ionosphere model has been used to simulate this period of observation, by imposing tidal forcing at the lower boundary and magnetospheric forcing at high latitudes, in an attempt to interpret and understand the experimental data. Model simulations are able to predict where the signature of a particular tidal mode is likely to be observed in the respective responses of the temperature and wind structure. The numerical simulations predict the range of observed tidal amplitudes at mid and high latitudes, provided the tidal forcing functions imposed near the lower boundary of the model are larger (400 m geopotential height variation) than those inferred from linear tidal models

  17. Thermospheric response observed over Fritz peak, Colorado, during two large geomagnetic storms near solar cycle maximum

    International Nuclear Information System (INIS)

    Hernandez, G.; Roble, R.G.; Ridley, E.C.; Allen, J.H.

    1982-01-01

    Nightime thermospheric winds and temperatures have been measured over Fritz Peak Observatory, Colorado (39.9 0 N, 105.5 0 W), with a high resolution Fabry-Perot spectrometer. The winds and temperatures are obtained from the Doppler shifts and line profiles of the (O 1) 15,867K (630 nm) line emission. Measurements made during two large geomagnetic storm periods near solar cycle maximum reveal a thermospheric response to the heat and momentum sources associated with these storms that is more complex than the ones measured near solar cycle minimum. In the earlier measurements made during solar cycle minimum, the winds to the north of Fritz Peak Observatory had an enhanced equatorward component and the winds to the south were also equatorward, usually with smaller velocities. The winds measured to the east and west of the observatory both had an enhanced westward wind component. For the two large storms near the present solar cycle maximum period converging winds are observed in each of the cardinal directions from Fritz Peak Observatory. These converging winds with speeds of hundreds of meters per second last for several hours. The measured neutral gas temperature in each of the directions also increases several hundred degrees Kelvin. Numerical experiments done with the NCAR thermospheric general circulation model (TGCM) suggest that the winds to the east and north of the station are driven by high-latitude heating and enhanced westward ion drag associated with magnetospheric convection. The cause of the enhanced poleward and eastward winds measured to the south and west of Fritz Peak Observatory, respectively, is not known. During geomagnetic quiet conditions the circulation is typically from the soutwest toward the northeast in the evening hours

  18. The Mars thermosphere. 2. General circulation with coupled dynamics and composition

    International Nuclear Information System (INIS)

    Bougher, S.W.; Roble, R.G.; Ridley, E.C.; Dickinson, R.E.

    1990-01-01

    The National Center for Atmospheric Research thermospheric general circulation model (TGCM) for the Earth's thermosphere has been modified to examine the three-dimensional structure and circulation of the upper mesosphere and thermosphere of Mars (MTGCM). The computational framework and major processes unique to a CO 2 thermosphere are similar to those utilized in a recent Venus TGCM. Solar EUV, UV, and IR heating alone combine to drive the Martian winds above ∼100 km. An equinox version of the code is used to examine the Mars global dynamics and structure for two specific observational periods spanning a range of solar activity: Viking 1 (July 1976) and Mariner 6-7 (August-September 1969). The MTGCM is then modified to predict the state of the Mars thermosphere for various combinations of solar and orbital conditions. Calculations show that no nightside cryosphere of the type observed on Venus is obtained on the Mars nightside. Instead, planetary rotation significantly modifies the winds and the day-to-night contrast in densities and temperatures, giving a diurnal behavior similar to the Earth under quiet solar conditions. Maximum exospheric temperatures are calculated near 1,500 LT (≤ 305 K), with minimum values at 0500 LT (≤ 175 K). The global temperature distribution is strongly modified by nightside adiabatic heating (subsidence) and dayside cooling (upwelling). The global winds also affect vertical density distributions; vertical eddy diffusion much weaker than used in previous one-dimensional models is required to maintain observed Viking profiles. A solar cycle variation in dayside exospheric temperatures of ∼195-305 K is simulated by the Viking and Mariner runs

  19. Dynamics of the low latitude thermosphere and ionosphere

    International Nuclear Information System (INIS)

    Burnside, R.G.

    1984-01-01

    Nighttime thermospheric neutral wind velocities were determined at Arecibo, Puerto Rico, by using a Fabry-Perot interferometer, which measures the Doppler shift of the O( 1 D) airglow emission. In summer, the winds are observed to flow toward the southeast between sunset and midnight. After midnight in summer, the meridional component of the wind usually slackens, while the zonal component may reverse. By contrast, in winter, the meridional wind is often small, and the predominant flow is eastward throughout the night. Vertical winds are inferred from the divergence of the horizontal flow. A maximum downward flow of about 5 m sπ 1 is observed near midnight in summer. Incoherent scatter radar measurements were used to calculate the O + diffusion velocity and infer the vertical profile of the meridional wind. Horizontal temperature gradients and ion-drag forces were evaluated from radar measurements. It is concluded that it may sometimes be necesary to include viscous forces to balance the meridional equation of motion for the neutral gas. Electrical conductivities of the E and F layers of the nighttime ionosphere were determined. The F layer Pedersen conductivity at the magnetically conjugate point was evaluated using ionosonde data. The F layer dynamo mechanism was found to be the source of most of the nighttime electric fields observed at Arecibo

  20. Resistive Heating and Ion Drag in Saturn's Thermosphere

    Science.gov (United States)

    Vriesema, Jess William; Koskinen, Tommi; Yelle, Roger V.

    2017-10-01

    One of the most puzzling observations of the jovian planets is that the thermospheres of Jupiter, Saturn, Uranus and Neptune are all several times hotter than solar heating can account for (Strobel and Smith 1973; Yelle and Miller 2004; Muller-Wodarg et al. 2006). On Saturn, resistive heating appears sufficient to explain these temperatures in auroral regions, but the particular mechanism(s) responsible for heating the lower latitudes remains unclear. The most commonly proposed heating mechanisms are breaking gravity waves and auroral heating at the poles followed by redistribution of energy to mid-and low latitudes. Both of these energy sources are potentially important but also come with significant problems. Wave heating would have to be continuous and global to produce consistently elevated temperatures and the strong Coriolis forces coupled with polar ion drag appear to hinder redistribution of auroral energy (see Strobel et al. 2016 for review). Here we explore an alternative: wind-driven electrodynamics that can alter circulation and produce substantial heating outside of the auroral region. Smith (2013) showed this in-situ mechanism to be potentially significant in Jupiter’s thermosphere. We present new results from an axisymmetric, steady-state model that calculates resistive (Joule) heating rates through rigorous solutions of the electrodynamic equations for the coupled neutral atmosphere and ionosphere of Saturn. At present, we assume a dipole magnetic field and neglect any contributions from the magnetosphere. We use ion mixing ratios from the model of Kim et al. (2014) and the observed temperature-pressure profile from Koskinen et al. (2015) to calculate the generalized conductivity tensor as described by Koskinen et al. (2014). We calculate the current density under the assumption that it has no divergence and use it to calculate the resistive heating rates and ion drag. Our results suggest that resistive heating and ion drag at low latitudes likely

  1. Magnetosphere-thermosphere coupling: An experiment in interactive modeling

    International Nuclear Information System (INIS)

    Forbes, J.M.; Harel, M.

    1989-01-01

    The Rice convection model (RCM) is utilized to investigate the electrodynamic coupling between the inner magnetosphere and the thermosphere including the effects of EUV- and convection-driven neutral winds under quasi-equilibrium conditions. A unique aspect of the study is that the convection-driven winds are included self-consistently and interactively; that is, a steady state wind parameterization is written analytically in terms of the electrostatic potential, which is in turn included in a closed-loop calculation for the electric potential itself. Simulations are performed from 1,400 UT to 1,600 UT during the CDAW-6 interval on March 22, 1979, when the cross-cap electric potential attains values of order 140-180 kV. During the early phases of the disturbance when the normal shielding from high latitudes breaks down, the neutral winds do not modify appreciably the disturbance electric fields at middle and low latitudes. As the system approaches a quasi-equilibrium state, the neutral winds play a much more significant role. The convection driven component of the neutral wind similarly acts to reduce the southward field in the noon sector, but gives rise to an enhancement in the dusk sector field extending to middle latitudes. The parameterized Pedersen effective winds are of order 300 ms -1 and reflect the familiar two-cell pattern with antisunward flow over the polar cap and return flows in the dawn and dusk sectors. These amplitudes and similarity with the ion drift motions reflect the relatively large contributions to the Pedersen effective winds originating in the upper E region and lower F region of the ionosphere. Possibilities for introducing further sophistication into the wind parameterization are discussed, as well as ramifications of the present study on the possible merging of the RCM with the NCAR TGCM to attain a higher degree of self-consistency and reality in modelling efforts

  2. Controlling of merging electric field and IMF magnitude on storm-time changes in thermospheric mass density

    NARCIS (Netherlands)

    Zhou, Y.L.; Ma, S.Y.; Liu, R.S.; Luehr, H.; Doornbos, E.

    2013-01-01

    The controls of merging electrical field, Em, and IMF (interplanetary magnetic field) magnitude, B, on the storm-time changes in upper thermospheric mass density are statistically investigated using GRACE accelerometer observations and the OMNI data of solar wind and IMF for 35 great storms during

  3. Thermospheric dynamics during the March 22, 1979, magnetic storm 1. Model simulations

    International Nuclear Information System (INIS)

    Roble, R.G.; Forbes, J.M.; Marcos, F.A.

    1987-01-01

    The physical processes involved in the transfer of energy from the solar wind to the magnetosphere and its release associated with substorms on March 22, 1979, have been studied in detail by the Coordinated Data Analysis Workshop 6 (CDAW 6). The information derived from the CDAW 6 study, as well as other information obtained from magnetospheric modeling, is used to prescribe the time-dependent variations of the parameterizations for the auroral and magnetospheric convection models that are incorporated within the National Center for Atmospheric Research thermospheric general circulation model (TGCM). The period preceding the magnetic storm (March 21) was geomagnetically quiet, and the TGCM was run until a diurnally reproducible pattern was obtained. The time variations of auroral particle precipitation and enhanced magnetospheric convection on March 22 caused a considerable disturbance in the high-latitude circulation, temperature, and composition during the storm period that began at about 1055 UT. Large- and medium-scale disturbances were launched during the event that propagated to equatorial latitudes. The thermospheric response in the northern hemisphere was larger than that generated in the southern hemisphere, because the auroral oval and magnetospheric convection pattenr in the northern hemisphere were in sunlight during the storm period whereas they were in darkness in the southern hemisphere. The storm response was also different in the upper and the lower thermosphere. In the upper thermosphere the winds generally followed the two-cell pattern of magnetospheric convecton with a lag of only 1/2 to 1 hour. In the lower thermosphere there was a pronounced asymmetry between the circulation cells on the dawnside and on the duskside of the polar cap

  4. The global distribution of thermospheric odd nitrogen for solstice conditions during solar cycle minimum

    Science.gov (United States)

    Gerard, J.-C.; Roble, R. G.; Rusch, D. W.; Stewart, A. I.

    1984-01-01

    A two-dimensional model of odd nitrogen in the thermosphere and upper mesosphere is described. The global distributions of nitric oxide and atomic nitrogen are calculated for the solstice period for quiet and moderate magnetic activity during the solar minimum period. The effect of thermospheric transport by winds is investigated along with the importance of particle-induced ionization in the auroral zones. The results are compared with rocket and satellite measurements, and the sensitivity of the model to eddy diffusion and neutral winds is investigated. Downward fluxes of NO into the mesosphere are given, and their importance for stratospheric ozone is discussed. The results show that the summer-to-winter pole meridional circulation transports both NO and N(S-4) across the solar terminator into the polar night region where there is a downward vertical transport toward the mesosphere. The model shows that odd nitrogen densities at high winter latitudes are entirely controlled by particle precipitation and transport processes.

  5. Theoretical and Empirical Descriptions of Thermospheric Density

    Science.gov (United States)

    Solomon, S. C.; Qian, L.

    2004-12-01

    The longest-term and most accurate overall description the density of the upper thermosphere is provided by analysis of change in the ephemeris of Earth-orbiting satellites. Empirical models of the thermosphere developed in part from these measurements can do a reasonable job of describing thermospheric properties on a climatological basis, but the promise of first-principles global general circulation models of the coupled thermosphere/ionosphere system is that a true high-resolution, predictive capability may ultimately be developed for thermospheric density. However, several issues are encountered when attempting to tune such models so that they accurately represent absolute densities as a function of altitude, and their changes on solar-rotational and solar-cycle time scales. Among these are the crucial ones of getting the heating rates (from both solar and auroral sources) right, getting the cooling rates right, and establishing the appropriate boundary conditions. However, there are several ancillary issues as well, such as the problem of registering a pressure-coordinate model onto an altitude scale, and dealing with possible departures from hydrostatic equilibrium in empirical models. Thus, tuning a theoretical model to match empirical climatology may be difficult, even in the absence of high temporal or spatial variation of the energy sources. We will discuss some of the challenges involved, and show comparisons of simulations using the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) to empirical model estimates of neutral thermosphere density and temperature. We will also show some recent simulations using measured solar irradiance from the TIMED/SEE instrument as input to the TIE-GCM.

  6. Polar heating in Saturn's thermosphere

    Directory of Open Access Journals (Sweden)

    C. G. A. Smith

    2005-10-01

    Full Text Available A 3-D numerical global circulation model of the Kronian thermosphere has been used to investigate the influence of polar heating. The distributions of temperature and winds resulting from a general heat source in the polar regions are described. We show that both the total energy input and its vertical distribution are important to the resulting thermal structure. We find that the form of the topside heating profile is particularly important in determining exospheric temperatures. We compare our results to exospheric temperatures from Voyager occultation measurements (Smith et al., 1983; Festou and Atreya, 1982 and auroral H3+ temperatures from ground-based spectroscopic observations (e.g. Miller et al., 2000. We find that a polar heat source is consistent with both the Smith et al. determination of T~400 K at ~30° N and auroral temperatures. The required heat source is also consistent with recent estimates of the Joule heating rate at Saturn (Cowley et al., 2004. However, our results show that a polar heat source can probably not explain the Festou and Atreya determination of T~800 K at ~4° N and the auroral temperatures simultaneously.

    Keywords. Ionosphere (Planetary ionosphere – Magnetospherica physics (Planetary magnetospheres – Meterology and atmospheric dynamics (Thermospheric dynamics

  7. Thermospheric storms and related ionospheric effects

    International Nuclear Information System (INIS)

    Chandra, S.; Spencer, N.W.

    1976-01-01

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

  8. 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...

  9. Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI): Instrument Design and Calibration

    Science.gov (United States)

    Englert, Christoph R.; Harlander, John M.; Brown, Charles M.; Marr, Kenneth D.; Miller, Ian J.; Stump, J. Eloise; Hancock, Jed; Peterson, James Q.; Kumler, Jay; Morrow, William H.; Mooney, Thomas A.; Ellis, Scott; Mende, Stephen B.; Harris, Stewart E.; Stevens, Michael H.; Makela, Jonathan J.; Harding, Brian J.; Immel, Thomas J.

    2017-10-01

    The Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instrument was built for launch and operation on the NASA Ionospheric Connection Explorer (ICON) mission. The instrument was designed to measure thermospheric horizontal wind velocity profiles and thermospheric temperature in altitude regions between 90 km and 300 km, during day and night. For the wind measurements it uses two perpendicular fields of view pointed at the Earth's limb, observing the Doppler shift of the atomic oxygen red and green lines at 630.0 nm and 557.7 nm wavelength. The wavelength shift is measured using field-widened, temperature compensated Doppler Asymmetric Spatial Heterodyne (DASH) spectrometers, employing low order échelle gratings operating at two different orders for the different atmospheric lines. The temperature measurement is accomplished by a multichannel photometric measurement of the spectral shape of the molecular oxygen A-band around 762 nm wavelength. For each field of view, the signals of the two oxygen lines and the A-band are detected on different regions of a single, cooled, frame transfer charge coupled device (CCD) detector. On-board calibration sources are used to periodically quantify thermal drifts, simultaneously with observing the atmosphere. The MIGHTI requirements, the resulting instrument design and the calibration are described.

  10. Particle precipitaion into the thermosphere (invited review)

    International Nuclear Information System (INIS)

    Reiff, P.H.

    1986-01-01

    A review of research on particle precipitation into the thermosphere is presented. Particle precipitation plays an important role in thermospheric dynamics, often being both the most important ionization source and the most important heat source, comparable to Joule heating rates in the auroral zones and typically exceeding solar ultraviolet as an ionization mechanism in the nightside auroral zones and winter polar caps. Rees (1963) has shown that, roughly speaking, one electron-ion pair is produced by each 35 eV of incident electron energy flux; thus, over half of the incident electron energy flux goes into heating rather than into ionization. Precipitating ions also can produce ionization, also requiring roughly 35 eV per pair; however, since ion energy fluxes are typically much weaker than electron fluxes, they have often been neglected. The particle precipitation into the thermosphere is both an important ionization source and an important heat source; since the globally integrated value can vary over more than a factor of ten, and the instantaneous local rate can vary over nearly three orders of magnitude global, maps of precipitation rates are extremely important for predicting thermospheric weather

  11. Jupiter Thermospheric General Circulation Model (JTGCM): Global Structure and Dynamics Driven by Auroral and Joule Heating

    Science.gov (United States)

    Bougher, S. W.; J. Il. Waite, Jr.; Majeed, T.

    2005-01-01

    A growing multispectral database plus recent Galileo descent measurements are being used to construct a self-consistent picture of the Jupiter thermosphere/ionosphere system. The proper characterization of Jupiter s upper atmosphere, embedded ionosphere, and auroral features requires the examination of underlying processes, including the feedbacks of energetics, neutral-ion dynamics, composition, and magnetospheric coupling. A fully 3-D Jupiter Thermospheric General Circulation Model (JTGCM) has been developed and exercised to address global temperatures, three-component neutral winds, and neutral-ion species distributions. The domain of this JTGCM extends from 20-microbar (capturing hydrocarbon cooling) to 1.0 x 10(exp -4) nbar (including aurora/Joule heating processes). The resulting JTGCM has been fully spun-up and integrated for greater than or equal to40 Jupiter rotations. Results from three JTGCM cases incorporating moderate auroral heating, ion drag, and moderate to strong Joule heating processes are presented. The neutral horizontal winds at ionospheric heights vary from 0.5 km/s to 1.2 km/s, atomic hydrogen is transported equatorward, and auroral exospheric temperatures range from approx.1200-1300 K to above 3000 K, depending on the magnitude of Joule heating. The equatorial temperature profiles from the JTGCM are compared with the measured temperature structure from the Galileo AS1 data set. The best fit to the Galileo data implies that the major energy source for maintaining the equatorial temperatures is due to dynamical heating induced by the low-latitude convergence of the high-latitude-driven thermospheric circulation. Overall, the Jupiter thermosphere/ionosphere system is highly variable and is shown to be strongly dependent on magnetospheric coupling which regulates Joule heating.

  12. Thermospheric Extension of the Quasi 6-day Wave Observed by the TIMED Satellite

    Science.gov (United States)

    Gan, Q.; Oberheide, J.

    2017-12-01

    The quasi 6-day wave is one of the most prevailing planetary waves in the mesosphere and lower thermosphere (MLT) region. Its peak amplitude can attain 20-30 m/s in low-latitude zonal winds at around equinoxes. Consequently, it is anticipated that the 6-day wave can induce not only significantly dynamic effects (via wave-mean flow and wave-wave interactions) in the MLT, but also have significant impacts on the Thermosphere and Ionosphere (T-I). The understanding of the 6-day wave impact on the T-I system has been advanced a lot due to the recent development of whole atmosphere models and new satellite observations. Three pathways were widely proposed to explain the upward coupling due to the 6-day wave: E-region dynamo modulation, dissipation and nonlinear interaction with thermal tides. The current work aims to show a comprehensive pattern of the 6-day wave from the mesosphere up to the thermosphere/ionosphere in neutral fields (temperature, 3-D winds and density) and plasma drifts. To achieve this goal, we carry out the 6-day wave diagnostics by two different means. Firstly, the output of a one-year WACCM+DART run with data assimilation is analyzed to show the global structure of the 6-day wave in the MLT, followed by E-P flux diagnostics to elucidate the 6-day wave source and wave-mean flow interactions. Secondly, we produce observation-based 6-day wave patterns throughout the whole thermosphere by constraining modeled (TIME-GCM) 6-day wave patterns with observed 6-day wave patterns from SABER and TIDI in the MLT region. This allows us to fill the 110-400 km gap between remote sensing and in-situ satellites, and to obtain more realistic 6-day wave plasma drift patterns.

  13. Magnetosphere - Ionosphere - Thermosphere (MIT) Coupling at Jupiter

    Science.gov (United States)

    Yates, J. N.; Ray, L. C.; Achilleos, N.

    2017-12-01

    Jupiter's upper atmospheric temperature is considerably higher than that predicted by Solar Extreme Ultraviolet (EUV) heating alone. Simulations incorporating magnetosphere-ionosphere coupling effects into general circulation models have, to date, struggled to reproduce the observed atmospheric temperatures under simplifying assumptions such as azimuthal symmetry and a spin-aligned dipole magnetic field. Here we present the development of a full three-dimensional thermosphere model coupled in both hemispheres to an axisymmetric magnetosphere model. This new coupled model is based on the two-dimensional MIT model presented in Yates et al., 2014. This coupled model is a critical step towards to the development of a fully coupled 3D MIT model. We discuss and compare the resulting thermospheric flows, energy balance and MI coupling currents to those presented in previous 2D MIT models.

  14. Thermospheric dynamics - A system theory approach

    Science.gov (United States)

    Codrescu, M.; Forbes, J. M.; Roble, R. G.

    1990-01-01

    A system theory approach to thermospheric modeling is developed, based upon a linearization method which is capable of preserving nonlinear features of a dynamical system. The method is tested using a large, nonlinear, time-varying system, namely the thermospheric general circulation model (TGCM) of the National Center for Atmospheric Research. In the linearized version an equivalent system, defined for one of the desired TGCM output variables, is characterized by a set of response functions that is constructed from corresponding quasi-steady state and unit sample response functions. The linearized version of the system runs on a personal computer and produces an approximation of the desired TGCM output field height profile at a given geographic location.

  15. Nature of the Venus thermosphere derived from satellite drag measurements (solicited paper)

    Science.gov (United States)

    Keating, G.; Theriot, M.; Bougher, S.

    2008-09-01

    density, scale height, inferred temperature, pressure, and other parameters as a function of altitude. The risk involved in the orbital decay and accelerometer measurements is minimal. We have not lost any spacecraft orbiting Venus or Mars due to unexpected thermospheric drag effects in over 30 years. The Venus Express accelerometer drag experiment is very similar to accelerometer experiments aboard Mars Global Surveyor, Mars Odyssey, and Mars Reconnaissance Orbiter which orbit Mars. The Venus Express drag measurements of the polar region will allow a global empirical model of the thermosphere to emerge. Previous drag measurements have been made principally near the equator. The experiment may help us understand on a global scale, tides, winds, gravity waves, planetary waves, and the damping of waves. Comparisons will be made between low and high latitude results; between the middle and upper atmosphere; and with other instruments that provide information from current and previous measurements. The character of the sharp temperature gradient near the day/night terminator needs to be studied at all latitudes. The cryosphere we discovered on the nightside needs to be studied at high latitudes. The rotating vortex dipole over the North Pole surrounded by a colder "collar" needs to be analyzed to identify how wave activity extends into the polar thermosphere. We have already discovered super-rotation in the equatorial thermosphere, but we need to study 4-day super-rotation at higher latitudes to obtain a global picture of the thermosphere. The super-rotation may affect escape rates and the evolution of the atmosphere. References: [1] Keating, G. M., et al: Venus Thermosphere and Exosphere: First Satellite Drag Measurements of an Extraterrestrial Atmosphere. Science, Vol. 203, No. 4382, 772-774, Feb. 23, 1979. [2] Keating, G. M. and Bougher, S.W.: Isolation of Major Venus Cooling Mechanism and Implications for Earth and Mars, Journal of Geophysical Research, Vol. 97, 4189

  16. SCANDI – an all-sky Doppler imager for studies of thermospheric spatial structure

    Directory of Open Access Journals (Sweden)

    A. L. Aruliah

    2010-02-01

    Full Text Available A new all-sky Fabry-Perot Interferometer called the Scanning Doppler Imager (SCANDI was built and installed at Longyearbyen in December 2006. Observations have been made of the Doppler shifts and Doppler broadening of the 630 nm airglow and aurora, from which upper thermospheric winds and temperatures are calculated. SCANDI allows measurements over a field-of-view (FOV with a horizontal radius of nearly 600 km for observations at an altitude of 250 km using a time resolution of 8 min. The instrument provides the ability to observe thermospheric spatial structure within a FOV which overlaps that of the EISCAT Svalbard radar and CUTLASS SuperDARN radars. Coordinating with these instruments provides an important opportunity for studying ion-neutral coupling. The all-sky image is divided into several sectors to provide a horizontal spatial resolution of between 100–300 km. This is a powerful extension in observational capability but requires careful calibration and data analysis, as described here. Two observation modes were used: a fixed and a scanning etalon gap. SCANDI results are corroborated using the Longyearbyen single look direction FPI, and ESR measurements of the ion temperatures. The data show thermospheric temperature gradients of a few Kelvins per kilometre, and a great deal of meso-scale variability on spatial scales of several tens of kilometres.

  17. Ionosphere-thermosphere energy budgets for the ICME storms of March 2013 and 2015 estimated with GITM and observational proxies

    Science.gov (United States)

    Verkhoglyadova, O. P.; Meng, X.; Mannucci, A. J.; Mlynczak, M. G.; Hunt, L. A.; Lu, G.

    2017-09-01

    The ionosphere-thermosphere (IT) energy partitioning for the interplanetary coronal mass ejection (ICME) storms of 16-19 March 2013 and 2015 is estimated with the Global Ionosphere-Thermosphere Model (GITM), empirical models and proxies derived from in situ measurements. We focus on auroral heating, Joule heating, and thermospheric cooling. Solar wind data, F10.7, OVATION Prime model and the Weimer 2005 model are used to drive GITM from above. Thermospheric nitric oxide and carbon dioxide cooling emission powers and fluxes are estimated from TIMED/SABER measurements. Assimilative mapping of ionospheric electrodynamics (AMIE) estimations of hemispheric power and Joule heating are presented, based on data from global magnetometers, the AMPERE magnetic field data, SSUSI auroral images, and the SuperDARN radar network. Modeled Joule heating and auroral heating of the IT system are mostly controlled by external driving in the March 2013 and 2015 storms, while NO cooling persists into the storm recovery phase. The total heating in the model is about 1000 GW to 3000 GW. Additionally, we intercompare contributions in selected energy channels for five coronal mass ejection-type storms modeled with GITM. Modeled auroral heating shows reasonable agreement with AMIE hemispheric power and is higher than other observational proxies. Joule heating and infrared cooling are likely underestimated in GITM. We discuss challenges and discrepancies in estimating and global modeling of the IT energy partitioning, especially Joule heating, during geomagnetic storms.

  18. An Observational and Modelling Study of Auroral Upwelling in the Thermosphere

    Science.gov (United States)

    2016-05-05

    finding by Lühr et al. [2004] of a near doubling of the thermospheric density over the geomagnetic cusp region. This was a localised and persistent...throughout the height region 150-200km. From 21:50-21:50 UT there appears to be a reversal to northward followed by a predominantly southward flow until the... Geomagnetic , Seasonal and Solar Cycle Dependence at High Latitudes, J.Atmos.Terr.Physics, 57, 597-609, 1995 (special issue on vertical winds) Aruliah

  19. An Observational and Modeling Study of Auroral Upwelling in the Thermosphere

    Science.gov (United States)

    2016-04-28

    finding by Lühr et al. [2004] of a near doubling of the thermospheric density over the geomagnetic cusp region. This was a localised and persistent...throughout the height region 150-200km. From 21:50-21:50 UT there appears to be a reversal to northward followed by a predominantly southward flow until the... Geomagnetic , Seasonal and Solar Cycle Dependence at High Latitudes, J.Atmos.Terr.Physics, 57, 597-609, 1995 (special issue on vertical winds) Aruliah

  20. The Effect of Sub-Auroral Polarization Streams (SAPS) on Ionosphere and Thermosphere during 2015 St. Patrick's Day storm: Global Ionosphere-Thermosphere Model (GITM) Simulations

    Science.gov (United States)

    Guo, J.; Deng, Y.; Zhang, D.; Lu, Y.; Sheng, C.

    2017-12-01

    Sub-Auroral Polarization Streams (SAPS) are incorporated into the non-hydrostatic Global Ionosphere-Thermosphere Model (GITM), revealing the complex effects on neutral dynamics and ion-neutral coupling processes. The intense westward ion stream could enhance the neutral zonal wind within the SAPS channel. Through neutral dynamics the neutrals then divide into two streams, one turns poleward and the other turns equatorward, forming a two-cell pattern in the SAPS-changed wind. The significant Joule heating induced by SAPS also leads to traveling atmospheric disturbances (TAD) accompanied by traveling ionospheric disturbances (TID), increasing the total electron content (TEC) by 2-8 TECu in the mid-latitude ionosphere. We investigate the potential causes of the reported poleward wind surge during the St. Patrick's Day storm in 2015. It is confirmed that Coriolis force on the westward zonal wind can contribute the poleward wind during post-SAPS interval. In addition, the simulations imply that the sudden decrease of heating rate within auroral oval could result in a TAD propagating equatorward, which could also be responsible for the sudden poleward wind surge. This study highlights the complicated effects of SAPS on ion-neutral coupling and neutral dynamics.

  1. Comparative study of MLT mean winds using MF radars located at ...

    Indian Academy of Sciences (India)

    Medium Frequency Radar, Indian Institute of Geomagnetism, Shivaji University ... Research Laboratory, Indian Institute of Geomagnetism, Tirunelveli 627 011, India. ... paper is to describe mesosphere and lower thermosphere (MLT) wind field.

  2. Origins of the Thermosphere-Ionosphere Semiannual Oscillation: Reformulating the "Thermospheric Spoon" Mechanism

    Science.gov (United States)

    Jones, M.; Emmert, J. T.; Drob, D. P.; Picone, J. M.; Meier, R. R.

    2018-01-01

    We demonstrate how Earth's obliquity generates the global thermosphere-ionosphere (T-I) semiannual oscillation (SAO) in mass density and electron density primarily through seasonally varying large-scale advection of neutral thermospheric constituents, sometimes referred to as the "thermospheric spoon" mechanism (TSM). The National Center for Atmospheric Research thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM) is used to isolate the TSM forcing of this prominent intraannual variation (IAV) and to elucidate the contributions of other processes to the T-I SAO. An ˜30% SAO in globally averaged mass density (relative to its global annual average) at 400 km is reproduced in the TIME-GCM in the absence of seasonally varying eddy diffusion, tropospheric tidal forcing, and gravity wave breaking. Artificially, decreasing the tilt of Earth's rotation axis with respect to the ecliptic plane to 11.75° reduces seasonal variations in insolation and weakens interhemispheric pressure differences at the solstices, thereby damping the global-scale, interhemispheric transport of atomic oxygen (O) and molecular nitrogen in the thermosphere and reducing the simulated global mass density SAO amplitude to ˜10%. Simulated T-I IAVs in mass density and electron density have equinoctial maxima at all latitudes near the F2 region peak; this phasing and its latitude dependence agree well with empirically inferred climatologies. When tropospheric tides and gravity waves are included, simulated IAV amplitudes and their latitudinal dependence also agree well with empirically inferred climatologies. Simulated meridional and vertical transport of O due to the TSM couples to the upper mesospheric circulation, which also contributes to the T-I SAO through O chemistry.

  3. Auroral zone thermospheric dynamics using Fabry-Perot interferometric measurements of the O1 15867 K emission

    International Nuclear Information System (INIS)

    Sica, R.J.

    1985-01-01

    Forty-four nights of thermospheric neutral wind and temperature measurements were obtained from College, Alaska (65 0 invariant latitude) during solar maximum using a ground-based Fabry-Perot interferometer. When averaged by increasing geomagnetic activity, the wind exhibits two main features. First, the general flow pattern poleward and westward in the evening, changing to southward and eastward in the morning, persists with increasing activity. The flow velocity increases and the change in direction occurs earlier in magnetic local time as the geomagnetic activity increases. Second, as the activity increases, the meridional wind pattern shifts equatorward with the auroral oval. Consequently, the low geomagnetic activity average wind pattern in the north is similar to the moderate activity average pattern in the south. The average thermospheric temperature is governed by the geomagnetic activity and by the previous day's 10.7 cm solar flux. The increase in temperature with solar flux is about the same as with auroral activity (approx. = 225 0 K). The dynamical behavior on individual nights highlights the importance of local auroral substorms, which can cause large deviations from both global models and the observed averages. Coupling between the E and F regions is inferred by comparing the bulk motion of the optical aurora and the observed wind. Westward-drifting auroral forms accompany the westward evening zonal wind

  4. Estimating the mass density in the thermosphere with the CYGNSS mission.

    Science.gov (United States)

    Bussy-Virat, C.; Ridley, A. J.

    2017-12-01

    The Cyclone Global Navigation Satellite System (CYGNSS) mission, launched in December 2016, is a constellation of eight satellites orbiting the Earth at 510 km. Its goal is to improve our understanding of rapid hurricane wind intensification. Each CYGNSS satellite uses GPS signals that are reflected off of the ocean's surface to measure the wind. The GPS can also be used to specify the orbit of the satellites quite precisely. The motion of satellites in low Earth orbit are greatly influenced by the neutral density of the surrounding atmosphere through drag. Modeling the neutral density in the upper atmosphere is a major challenge as it involves a comprehensive understanding of the complex coupling between the thermosphere and the ionosphere, the magnetosphere, and the Sun. This is why thermospheric models (such as NRLMSIS, Jacchia-Bowman, HASDM, GITM, or TIEGCM) can only approximate it with a limited accuracy, which decreases during strong geomagnetic events. Because atmospheric drag directly depends on the thermospheric density, it can be estimated applying filtering methods to the trajectories of the CYGNSS observatories. The CYGNSS mission can provide unique results since the constellation of eight satellites enables multiple measurements of the same region at close intervals ( 10 minutes), which can be used to detect short time scale features. Moreover, the CYGNSS spacecraft can be pitched from a low to high drag attitude configuration, which can be used in the filtering methods to improve the accuracy of the atmospheric density estimation. The methodology and the results of this approach applied to the CYGNSS mission will be presented.

  5. Understanding the Effects of Lower Boundary Conditions and Eddy Diffusion on the Ionosphere-Thermosphere System

    Science.gov (United States)

    Malhotra, G.; Ridley, A. J.; Marsh, D. R.; Wu, C.; Paxton, L. J.

    2017-12-01

    The exchange of energy between lower atmospheric regions with the ionosphere-thermosphere (IT) system is not well understood. A number of studies have observed day-to-day and seasonal variabilities in the difference between data and model output of various IT parameters. It is widely speculated that the forcing from the lower atmosphere, variability in weather systems and gravity waves that propagate upward from troposphere into the upper mesosphere and lower thermosphere (MLT) may be responsible for these spatial and temporal variations in the IT region, but their exact nature is unknown. These variabilities can be interpreted in two ways: variations in state (density, temperature, wind) of the upper mesosphere or spatial and temporal changes in the small-scale mixing, or Eddy diffusion that is parameterized within the model.In this study, firstly, we analyze the sensitivity of the thermospheric and ionospheric states - neutral densities, O/N2, total electron content (TEC), peak electron density, and peak electron height - to various lower boundary conditions in the Global Ionosphere Thermosphere Model (GITM). We use WACCM-X and GSWM to drive the lower atmospheric boundary in GITM at 100 km, and compare the results with the current MSIS-driven version of GITM, analyzing which of these simulations match the measurements from GOCE, GUVI, CHAMP, and GPS-derived TEC best. Secondly, we analyze the effect of eddy diffusion in the IT system. The turbulence due to eddy mixing cannot be directly measured and it is a challenge to completely characterize its linear and non-linear effects from other influences, since the eddy diffusion both influences the composition through direct mixing and the temperature structure due to turbulent conduction changes. In this study we input latitudinal and seasonal profiles of eddy diffusion into GITM and then analyze the changes in the thermospheric and ionospheric parameters. These profiles will be derived from both WACC-X simulations

  6. Adaptive regularization

    DEFF Research Database (Denmark)

    Hansen, Lars Kai; Rasmussen, Carl Edward; Svarer, C.

    1994-01-01

    Regularization, e.g., in the form of weight decay, is important for training and optimization of neural network architectures. In this work the authors provide a tool based on asymptotic sampling theory, for iterative estimation of weight decay parameters. The basic idea is to do a gradient desce...

  7. Thermospheric tides simulated by the national center for atmospheric research thermosphere-ionosphere general circulation model at equinox

    International Nuclear Information System (INIS)

    Fesen, C.G.; Roble, R.G.; Ridley, E.C.

    1993-01-01

    The authors use the National Center for Atmospheric Research (NCAR) thermosphere/ionosphere general circulation model (TIGCM) to model tides and dynamics in the thermosphere. This model incorporates the latest advances in the thermosphere general circulation model. Model results emphasized the 70 degree W longitude region to overlap a series of incoherent radar scatter installations. Data and the model are available on data bases. The results of this theoretical modeling are compared with available data, and with prediction of more empirical models. In general there is broad agreement within the comparisons

  8. Ensemble Assimilation Using Three First-Principles Thermospheric Models as a Tool for 72-hour Density and Satellite Drag Forecasts

    Science.gov (United States)

    Hunton, D.; Pilinski, M.; Crowley, G.; Azeem, I.; Fuller-Rowell, T. J.; Matsuo, T.; Fedrizzi, M.; Solomon, S. C.; Qian, L.; Thayer, J. P.; Codrescu, M.

    2014-12-01

    Much as aircraft are affected by the prevailing winds and weather conditions in which they fly, satellites are affected by variability in the density and motion of the near earth space environment. Drastic changes in the neutral density of the thermosphere, caused by geomagnetic storms or other phenomena, result in perturbations of satellite motions through drag on the satellite surfaces. This can lead to difficulties in locating important satellites, temporarily losing track of satellites, and errors when predicting collisions in space. As the population of satellites in Earth orbit grows, higher space-weather prediction accuracy is required for critical missions, such as accurate catalog maintenance, collision avoidance for manned and unmanned space flight, reentry prediction, satellite lifetime prediction, defining on-board fuel requirements, and satellite attitude dynamics. We describe ongoing work to build a comprehensive nowcast and forecast system for neutral density, winds, temperature, composition, and satellite drag. This modeling tool will be called the Atmospheric Density Assimilation Model (ADAM). It will be based on three state-of-the-art coupled models of the thermosphere-ionosphere running in real-time, using assimilative techniques to produce a thermospheric nowcast. It will also produce, in realtime, 72-hour predictions of the global thermosphere-ionosphere system using the nowcast as the initial condition. We will review the requirements for the ADAM system, the underlying full-physics models, the plethora of input options available to drive the models, a feasibility study showing the performance of first-principles models as it pertains to satellite-drag operational needs, and review challenges in designing an assimilative space-weather prediction model. The performance of the ensemble assimilative model is expected to exceed the performance of current empirical and assimilative density models.

  9. Evidence of the Lower Thermospheric Winter-to-Summer Circulation

    Science.gov (United States)

    Qian, L.; Burns, A. G.; Yue, J.

    2017-12-01

    Numerical studies showed that the lower thermospheric winter-to-summer circulation is driven by wave dissipation, and it plays a significant role in trace gas distributions in the mesosphere and lower thermosphere (MLT), and in the composition of the thermosphere. Direct observations of this circulation are difficult. However, it leaves clear signatures in tracer distributions. Recent analysis of CO2 observed by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite showed dynamically driven dense isolines of CO2 at summer high latitudes. We conduct modeling and observational studies to understand the CO2 distribution and circulation patterns in the MLT. We found that there exists maximum vertical gradient of CO2 at summer high latitudes, driven by the convergence of the upwelling of the mesospheric circulation and the downwelling of the lower thermospheric circulation; this maximum vertical gradient of CO2 is located at a higher altitude in the winter hemisphere, driven by the convergence of the upwelling of the lower thermospheric circulation and the downwelling of the solar-driven thermospheric circulation. Based on SABER CO2 distribution, the bottom of the lower thermospheric circulation is located between 95 km and 100 km, and it has a vertical extent of 10 km. Analysis of the SABER CO2 and temperature at summer high latitudes showed that the bottom of this circulation is consistently higher than the mesopause height by 10 km; and its location does not change much between solar maximum and solar minimum.

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

    Directory of Open Access Journals (Sweden)

    V. V. Klimenko

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

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

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

    Directory of Open Access Journals (Sweden)

    V. V. Klimenko

    1998-10-01

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

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

    Science.gov (United States)

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

    2017-12-01

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

  13. The State of the Thermosphere in 2017 as Observed by SABER

    Science.gov (United States)

    Hunt, L. A.; Mlynczak, M. G.; Marshall, B. T.; Russell, J. M., III

    2017-12-01

    Infrared radiative cooling of the thermosphere by carbon dioxide (CO2, 15 μm) and by nitric oxide (NO, 5.3 μm) has been observed for nearly 16 years by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the NASA Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite. SABER has documented dramatic variability in the radiative cooling on timescales ranging from days to the nominal 11-year solar cycle, providing important information about the radiation budget in the upper atmosphere. The effects of Solar Cycle 24 are clearly evident in the infrared radiative cooling of the thermosphere as observed by SABER. The peak NO cooling in SC24 is about one-third less than the maximum seen in SC23 since the beginning of the SABER record in January 2002, while the SC24 CO2 peak is nearly 95% of that in SC23. SC24 has been weakening throughout all of 2017 as measured by the F10.7 index and the sunspot number. Despite this, the radiative cooling by NO and CO2 has not yet reached the low levels of the prior minimum in 2008-2009. This is due to continuing elevated levels of geomagnetic activity as clearly shown by the Ap index. During the years preceding the prior solar minimum, harmonics of the solar rotation period were evident in time series of the NO and CO2 power, and were associated with high speed solar wind streams emanating from coronal holes roughly evenly spaced in solar longitude. Despite a number of large, Earth-facing coronal holes in 2017, periodic features have not yet been observed in spectral/Fourier analysis of the SABER radiative cooling time series. Additional comparisons between solar cycles and with other solar and geomagnetic indicators will also be shown.

  14. Zonal wind observations during a geomagnetic storm

    Science.gov (United States)

    Miller, N. J.; Spencer, N. W.

    1986-01-01

    In situ measurements taken by the Wind and Temperature Spectrometer (WATS) onboard the Dynamics Explorer 2 spacecraft during a geomagnetic storm display zonal wind velocities that are reduced in the corotational direction as the storm intensifies. The data were taken within the altitudes 275 to 475 km in the dusk local time sector equatorward of the auroral region. Characteristic variations in the value of the Dst index of horizontal geomagnetic field strength are used to monitor the storm evolution. The detected global rise in atmospheric gas temperature indicates the development of thermospheric heating. Concurrent with that heating, reductions in corotational wind velocities were measured equatorward of the auroral region. Just after the sudden commencement, while thermospheric heating is intense in both hemispheres, eastward wind velocities in the northern hemisphere show reductions ranging from 500 m/s over high latitudes to 30 m/s over the geomagnetic equator. After 10 hours storm time, while northern thermospheric heating is diminishing, wind velocity reductions, distinct from those initially observed, begin to develop over southern latitudes. In the latter case, velocity reductions range from 300 m/s over the highest southern latitudes to 150 m/s over the geomagnetic equator and extend into the Northern Hemisphere. The observations highlight the interhemispheric asymmetry in the development of storm effects detected as enhanced gas temperatures and reduced eastward wind velocities. Zonal wind reductions over high latitudes can be attributed to the storm induced equatorward spread of westward polar cap plasma convection and the resulting plasma-neutral collisions. However, those collisions are less significant over low latitudes; so zonal wind reductions over low latitudes must be attributed to an equatorward extension of a thermospheric circulation pattern disrupted by high latitude collisions between neutrals transported via eastward winds and ions

  15. Impact of high-latitude energy input on the mid- and low-latitude ionosphere and thermosphere

    Science.gov (United States)

    Lu, G.; Sheng, C.

    2017-12-01

    High-latitude energy input has a profound impact on the ionosphere and thermosphere especially during geomagnetic storms. Intense auroral particle precipitation ionizes neutral gases and modifies ionospheric conductivity; collisions between neutrals and fast-moving ions accelerate the neutral winds and produce Joule frictional heating; and the excess Joule and particle heating causes atmospheric upwelling and changes neutral composition due to the rising of the heavier, molecular-rich air. In addition, impulsive Joule heating launches large-scale gravity waves that propagate equatorward toward middle and low latitudes and even into the opposite hemisphere, altering the mean global circulation of the thermosphere. Furthermore, high-latitude electric field can also directly penetrate to lower latitudes under rapidly changing external conditions, causing prompt ionospheric variations in the mid- and low-latitude regions. To study the effects of high-latitude energy input, we apply the different convection and auroral precipitation patterns based on both empirical models and the AMIE outputs. We investigate how the mid- and low-latitude regions respond to the different specifications of high-latitude energy input. The main purpose of the study is to delineate the various dynamical, electrodynamical, and chemical processes and to determine their relative importance in the resulting ionospheric and thermospheric properties at mid and low latitudes.

  16. Application of the CCD Fabry-Perot Annular Summing Technique to Thermospheric O(1)D.

    Science.gov (United States)

    Coakley, Monica Marie

    1995-01-01

    This work will detail the verification of the advantages of the Fabry-Perot charge coupled device (CCD) annular summing technique, the development of the technique for analysis of daysky spectra, and the implications of the resulting spectra for neutral temperature and wind measurements in the daysky thermosphere. The daysky spectral feature of interest is the bright (1 kilo-Rayleigh) thermospheric (OI) emission at 6300 A which had been observed in the nightsky in order to determine winds and temperatures in the vicinity of the altitude of 250 km. In the daysky, the emission line sits on top of a bright Rayleigh scattered continuum background which significantly complicates the observation. With a triple etalon Fabry-Perot spectrometer, the continuum background can be reduced while maintaining high throughput and high resolution. The inclusion of a CCD camera results in significant savings in integration time over the two more standard scanning photomultiplier systems that have made the same wind and temperature measurements in the past. A comparable CCD system can experience an order of magnitude savings in integration time over a PMT system. Laboratory and field tests which address the advantages and limitations of both the Fabry-Perot CCD annular summing technique and the daysky CCD imaging are included in Chap. 2 and Chap. 3. With a sufficiently large throughput associated with the spectrometer and a CCD detector, rapid observations (~4 minute integrations) can be made. Extraction of the line width and line center from the daysky near-continuum background is complicated compared to the nightsky case, but possible. Methods of fitting the line are included in Chap. 4. The daysky O ^1D temperatures are consistent with a lower average emission height than predicted by models. The data and models are discussed in Chap. 5. Although some discrepancies exist between resulting temperatures and models, the observations indicate the potential for other direct measurements

  17. Reassessment of the thermospheric response to geomagnetic activity at low latitudes

    International Nuclear Information System (INIS)

    Berger, C.; Barlier, F.; Ill, M.

    1988-01-01

    The present study takes advantage of measurements made at low latitudes by the Cactus accelerometer. From such measurements the response of several thermospheric parameters to geomagnetic activity can be simultaneously and reliably retrieved: total density, density scale height, vertical density scale height gradient, temperature, O/N 2 ratio and mean molecular mass. On investigation their behaviour exhibits a diurnal variation, some features of which have not been described, especially in the case of strong geomagnetic storms. In particular, the night scale height response appears to be stronger than the day one while its vertical gradients increase by day and slightly decrease at night. The temperature increase is higher by day while the O/N 2 ratio decreases by day, and increases at night at constant pressure level as well as at fixed height. By day, significant vertical temperature gradients are also found. These results as well as others are analysed in the light of existing theories and compared to the predictions of existing thermospheric models. Strong meridional winds at night, heat transport through thermal conductivity as well as wave dissipation during the day might be factors helping to account for such a behaviour

  18. A Study on the Ionosphere and Thermosphere Interaction Based on NCAR-TIEGCM: Dependence of the Interplanetary Magnetic Field (IMF on the Momentum Forcing in the High-Latitude Lower Thermosphere

    Directory of Open Access Journals (Sweden)

    Young-Sil Kwak

    2005-06-01

    Full Text Available To understand the physical processes that control the high-latitude lower thermospheric dynamics, we quantify the forces that are mainly responsible for maintaining the high-latitude lower thermospheric wind system with the aid of the National Center for Atmospheric Research Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR-TIEGCM. Momentum forcing is statistically analyzed in magnetic coordinates, and its behavior with respect to the magnitude and orientation of the interplanetary magnetic field (IMF is further examined. By subtracting the values with zero IMF from those with non-zero IMF, we obtained the difference winds and forces in the high-latitude lower thermosphere( 0.8 |bar{B}_z| or negative(B_y 0.3125 |bar{B}_y| or negative(B_z 125 km the primary forces that determine the variations of the neutral winds are the pressure gradient, Coriolis and rotational Pedersen ion drag forces; however, at various locations and times significant contributions can be made by the horizontal advection force. On the other hand, at lower altitudes(108-125 km the pressure gradient, Coriolis and non-rotational Hall ion drag forces determine the variations of the neutral winds. At lower altitudes(<108 km it tends to generate a geostrophic motion with the balance between the pressure gradient and Coriolis forces. The northward component of IMF bar{B}_y-dependent average momentum forces act more significantly on the neutral motion except for the ion drag. At lower altitudes(108-125 km for negative IMF-bar{B}_y condition the ion drag force tends to generate a warm clockwise circulation with downward vertical motion associated with the adiabatic compress heating in the polar cap region. For positive IMF-bar{B}_y condition it tends to generate a cold anticlockwise circulation with upward vertical motion associated with the adiabatic expansion cooling in the polar cap region. For negative IMF-bar{B}_z the ion drag force tends to generate a

  19. Acoustic Resonance between Ground and Thermosphere

    Directory of Open Access Journals (Sweden)

    M Matsumura

    2009-04-01

    Full Text Available Ultra-low frequency acoustic waves called "acoustic gravity waves" or "infrasounds" are theoretically expected to resonate between the ground and the thermosphere. This resonance is a very important phenomenon causing the coupling of the solid Earth, neutral atmosphere, and ionospheric plasma. This acoustic resonance, however, has not been confirmed by direct observations. In this study, atmospheric perturbations on the ground and ionospheric disturbances were observed and compared with each other to confirm the existence of resonance. Atmospheric perturbations were observed with a barometer, and ionospheric disturbances were observed using the HF Doppler method. An end point of resonance is in the ionosphere, where conductivity is high and the dynamo effect occurs. Thus, geomagnetic observation is also useful, so the geomagnetic data were compared with other data. Power spectral density was calculated and averaged for each month. Peaks appeared at the theoretically expected resonance frequencies in the pressure and HF Doppler data. The frequencies of the peaks varied with the seasons. This is probably because the vertical temperature profile of the atmosphere varies with the seasons, as does the reflection height of infrasounds. These results indicate that acoustic resonance occurs frequently.

  20. The variability of Joule heating, and its effects on the ionosphere and thermosphere

    Directory of Open Access Journals (Sweden)

    A. S. Rodger

    2001-07-01

    Full Text Available A considerable fraction of the solar wind energy that crosses the magnetopause ends up in the high-latitude thermosphere-ionosphere system as a result of Joule heating, the consequences of which are very significant and global in nature. Often Joule heating calculations use hourly averages of the electric field, rather than the time-varying electric field. This leads to an underestimation of the heating. In this paper, we determine the magnitude of the underestimation of Joule heating by analysing electric field data from the EISCAT Incoherent Scatter Radar, situated at the 67° E magnetic latitude. We find that the underestimation, using hourly-averaged electric field values, is normally ~20%, with an upper value of about 65%. We find that these values are insensitive to changes in solar flux, magnetic activity and magnetic local time, implying that the electric field fluctuations are linear related to the amplitude of the electric field. Assuming that these changes are representative of the entire auroral oval, we then use a coupled ionosphere-thermosphere model to calculate the local changes these underestimations in the heating rate cause to the neutral temperature, mean molecular mass and meridional wind. The changes in each parameter are of the order of a few percent but they result in a reduction in the peak F-region concentration of ~20% in the summer hemisphere at high latitudes, and about half of this level in the winter hemisphere. We suggest that these calculations could be used to add corrections to modelled values of Joule heating.Key words. Ionosphere (eletric fields and currents; ionospheric disturbances; polar ionosphere

  1. 3-Dimensional numerical simulations of the dynamics of the Venusian mesosphere and thermosphere

    Science.gov (United States)

    Tingle, S.; Mueller-Wodarg, I. C.

    2009-12-01

    We present the first results from a new 3-dimensional numerical simulation of the steady state dynamics of the Venusian mesosphere and thermosphere (60-300 km). We have adapted the dynamical core of the Titan thermosphere global circulation model (GCM) [1] to a steady state background atmosphere. Our background atmosphere is derived from a hydrostatic combination of the VTS3 [2] and Venus International Reference Atmosphere (VIRA) [3] empirical models, which are otherwise discontinuous at their 100 km interface. We use 4th order polynomials to link the VTS3 and VIRA thermal profiles and employ hydrostatic balance to derive a consistent density profile. We also present comparisons of our background atmosphere to data from the ESA Venus Express Mission. The thermal structure of the Venusian mesosphere is relatively well documented; however, direct measurements of wind speeds are limited. Venus’ slow rotation results in a negligible Coriolis force. This suggests that the zonal circulation should arise from cyclostrophic balance; where the equatorward component of the centrifugal force balances poleward meridional pressure gradients [4]. The sparseness of direct and in-situ measurements has resulted in the application of cyclostrophic balance to measured thermal profiles to derive wind speeds [5] [6] [7] [8]. However, cyclostrophic balance is only strictly valid at mid latitudes (˜ ± 30-75°) and its applicability to the Venusian mesosphere has not been conclusively demonstrated. Our simulations, by solving the full Navier-Stokes momentum equation, will enable us assess the validity of cyclostrophic balance as a description of mesospheric dynamics. This work is part of an ongoing project to develop the first GCM to encompass the atmosphere from the cloud tops into the thermosphere. When complete, this model will enable self-consistent calculations of the dynamics, energy and composition of the atmosphere. It will thus provide a framework to address many of the

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

    Science.gov (United States)

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

    2017-12-01

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

  3. UNFOLDED REGULAR AND SEMI-REGULAR POLYHEDRA

    Directory of Open Access Journals (Sweden)

    IONIŢĂ Elena

    2015-06-01

    Full Text Available This paper proposes a presentation unfolding regular and semi-regular polyhedra. Regular polyhedra are convex polyhedra whose faces are regular and equal polygons, with the same number of sides, and whose polyhedral angles are also regular and equal. Semi-regular polyhedra are convex polyhedra with regular polygon faces, several types and equal solid angles of the same type. A net of a polyhedron is a collection of edges in the plane which are the unfolded edges of the solid. Modeling and unfolding Platonic and Arhimediene polyhedra will be using 3dsMAX program. This paper is intended as an example of descriptive geometry applications.

  4. Super Dual Auroral Radar Network observations of fluctuations in the spectral distribution of near range meteor echoes in the upper mesosphere and lower thermosphere

    Directory of Open Access Journals (Sweden)

    N. F. Arnold

    2001-04-01

    Full Text Available The Doppler shifts of meteor echoes measured by the SuperDARN HF radar network have been used in several studies to observe neutral winds in the upper mesosphere and lower thermosphere region. In the absence of accurate height information for individual meteors, it has been necessary to assume a statistical mean meteor layer where the variations in altitude were not correlated to changes in the horizontal winds. Observations of spectral width distribution variations made by the radars allow an independent determination of the systematic error in the height. We have investigated the dependence of this distribution on a number of factors including the radar geometry, diurnal and seasonal cycles, variations in solar UV irradiance and geomagnetic activity. Changes in the altitude of the mean meteor layer observed at different radar ranges provide us with some insight into the structure of the upper mesosphere and the lower thermosphere within which the meteors are being ablated. An examination of the spectral widths, as measured by the CUT-LASS Finland radar, in the days preceding and following a Storm Sudden Commencement in April 1997, illustrates how the spectral properties of the observed region can be affected. The variations in the widths were consistent with model calculations of the changes to the temperature profile over this interval. Further refinements in the determination of the spectral width are outlined for future experiments.Key words. Meterology and atmospheric dynamics (middle atmosphere dynamics; thermospheric dynamics; instruments and techniques

  5. Super Dual Auroral Radar Network observations of fluctuations in the spectral distribution of near range meteor echoes in the upper mesosphere and lower thermosphere

    Directory of Open Access Journals (Sweden)

    N. F. Arnold

    Full Text Available The Doppler shifts of meteor echoes measured by the SuperDARN HF radar network have been used in several studies to observe neutral winds in the upper mesosphere and lower thermosphere region. In the absence of accurate height information for individual meteors, it has been necessary to assume a statistical mean meteor layer where the variations in altitude were not correlated to changes in the horizontal winds. Observations of spectral width distribution variations made by the radars allow an independent determination of the systematic error in the height. We have investigated the dependence of this distribution on a number of factors including the radar geometry, diurnal and seasonal cycles, variations in solar UV irradiance and geomagnetic activity. Changes in the altitude of the mean meteor layer observed at different radar ranges provide us with some insight into the structure of the upper mesosphere and the lower thermosphere within which the meteors are being ablated. An examination of the spectral widths, as measured by the CUT-LASS Finland radar, in the days preceding and following a Storm Sudden Commencement in April 1997, illustrates how the spectral properties of the observed region can be affected. The variations in the widths were consistent with model calculations of the changes to the temperature profile over this interval. Further refinements in the determination of the spectral width are outlined for future experiments.

    Key words. Meterology and atmospheric dynamics (middle atmosphere dynamics; thermospheric dynamics; instruments and techniques

  6. A self-consistent derivation of ion drag and Joule heating for atmospheric dynamics in the thermosphere

    Directory of Open Access Journals (Sweden)

    X. Zhu

    2005-11-01

    Full Text Available The thermosphere is subject to additional electric and magnetic forces, not important in the middle and lower atmosphere, due to its partially ionized atmosphere. The effects of charged particles on the neutral atmospheric dynamics are often parameterized by ion drag in the momentum equations and Joule heating in the energy equation. Presented in this paper are a set of more accurate parameterizations for the ion drag and Joule heating for the neutral atmosphere that are functions of the difference between bulk ion velocity and neutral wind. The parameterized expressions also depend on the magnetic field, the Pedersen and Hall conductivities, and the ratio of the ion cyclotron frequency to the ion-neutral collision frequency. The formal relationship between the electromagnetic energy, atmospheric kinetic energy, and Joule heating is illustrated through the conversion terms between these three types of energy. It is shown that there will always be an accompanying conversion of kinetic energy into Joule heating when electromagnetic energy is generated through the dynamo mechanism of the atmospheric neutral wind. Likewise, electromagnetic energy cannot be fully converted into kinetic energy without producing Joule heating in the thermosphere.

  7. Scalar and Vector Spherical Harmonics for Assimilation of Global Datasets in the Ionosphere and Thermosphere

    Science.gov (United States)

    Miladinovich, D.; Datta-Barua, S.; Bust, G. S.; Ramirez, U.

    2017-12-01

    Understanding physical processes during storm time in the ionosphere-thermosphere (IT) system is limited, in part, due to the inability to obtain accurate estimates of IT states on a global scale. One reason for this inability is the sparsity of spatially distributed high quality data sets. Data assimilation is showing promise toward enabling global estimates by blending high quality observational data sets with established climate models. We are continuing development of an algorithm called Estimating Model Parameters for Ionospheric Reverse Engineering (EMPIRE) to enable assimilation of global datasets for storm time estimates of IT drivers. EMPIRE is a data assimilation algorithm that uses a Kalman filtering routine to ingest model and observational data. The EMPIRE algorithm is based on spherical harmonics which provide a spherically symmetric, smooth, continuous, and orthonormal set of basis functions suitable for a spherical domain such as Earth's IT region (200-600 km altitude). Once the basis function coefficients are determined, the newly fitted function represents the disagreement between observational measurements and models. We apply spherical harmonics to study the March 17, 2015 storm. Data sources include Fabry-Perot interferometer neutral wind measurements and global Ionospheric Data Assimilation 4 Dimensional (IDA4D) assimilated total electron content (TEC). Models include Weimer 2000 electric potential, International Geomagnetic Reference Field (IGRF) magnetic field, and Horizontal Wind Model 2014 (HWM14) neutral winds. We present the EMPIRE assimilation results of Earth's electric potential and thermospheric winds. We also compare EMPIRE storm time E cross B ion drift estimates to measured drifts produced from the Super Dual Auroral Radar Network (SuperDARN) and Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) measurement datasets. The analysis from these results will enable the generation of globally assimilated

  8. Coordinate-invariant regularization

    International Nuclear Information System (INIS)

    Halpern, M.B.

    1987-01-01

    A general phase-space framework for coordinate-invariant regularization is given. The development is geometric, with all regularization contained in regularized DeWitt Superstructures on field deformations. Parallel development of invariant coordinate-space regularization is obtained by regularized functional integration of the momenta. As representative examples of the general formulation, the regularized general non-linear sigma model and regularized quantum gravity are discussed. copyright 1987 Academic Press, Inc

  9. Storm time variation of radiative cooling of thermosphere by nitric oxide emission

    Science.gov (United States)

    Krishna, M. V. Sunil; Bag, Tikemani; Bharti, Gaurav

    2016-07-01

    The fundamental vibration-rotation band emission (Δν=1, Δ j=0,± 1) by nitric oxide (NO) at 5.3 µm is one of the most important cooling mechanisms in thermosphere. The collisional vibrational excitation of NO(ν=0) by impact with atomic oxygen is the main source of vibrationally excited nitric oxide. The variation of NO density depends on latitude, longitude and season. The present study aims to understand how the radiative flux gets influenced by the severe geomagnetic storm conditions. The variation of Nitric Oxide (NO) radiative flux exiting thermosphere is studied during the superstorm event of 7-12 November, 2004. The observations of TIMED/SABER suggest a strong anti-correlation with the O/N_2 ratio observed by GUVI during the same period. On a global scale the NO radiative flux showed an enhancement during the main phase on 8 November, 2004, whereas maximum depletion in O/N_2 is observed on 10 November, 2004. Both O/N_2 and NO radiative flux were found to propagate equatorward due to the effect of meridional wind resulting from joule and particle heating in polar region. Larger penetrations is observed in western longitude sectors. These observed variations are effectively connected to the variations in neutral densities. In the equatorial sectors, O/N_2 shows enhancement but almost no variation in radiative flux is observed. The possible reasons for the observed variations in NO radiative emission and O/N_2 ratios are discussed in the light of equator ward increase in the densities and prompt penetration.

  10. Do minor sudden stratospheric warmings in the Southern Hemisphere (SH) impact coupling between stratosphere and mesosphere-lower thermosphere (MLT) like major warmings?

    Science.gov (United States)

    Eswaraiah, S.; Kim, Yong Ha; Liu, Huixin; Ratnam, M. Venkat; Lee, Jaewook

    2017-08-01

    We have investigated the coupling between the stratosphere and mesosphere-lower thermosphere (MLT) in the Southern Hemisphere (SH) during 2010 minor sudden stratospheric warmings (SSWs). Three episodic SSWs were noticed in 2010. Mesospheric zonal winds between 82 and 92 km obtained from King Sejong Station (62.22°S, 58.78°W) meteor radar showed the significant difference from usual trend. The zonal wind reversal in the mesosphere is noticed a week before the associated SSW similar to 2002 major SSW. The mesosphere wind reversal is also noticed in "Specified Dynamics" version of Whole Atmosphere Community Climate Model (SD-WACCM) and Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy (GAIA) simulations. The similar zonal wind weakening/reversal in the lower thermosphere between 100 and 140 km is simulated by GAIA. Further, we observed the mesospheric cooling in consistency with SSWs using Microwave Limb Sounder data. However, the GAIA simulations showed warming between 130 and 140 km after few days of SSW. Thus, the observation and model simulation indicate for the first time that the 2010 minor SSW also affects dynamics of the MLT region over SH in a manner similar to 2002 major SSW.[Figure not available: see fulltext.

  11. Solar rotation effects on the thermospheres of Mars and Earth.

    Science.gov (United States)

    Forbes, Jeffrey M; Bruinsma, Sean; Lemoine, Frank G

    2006-06-02

    The responses of Earth's and Mars' thermospheres to the quasi-periodic (27-day) variation of solar flux due to solar rotation were measured contemporaneously, revealing that this response is twice as large for Earth as for Mars. Per typical 20-unit change in 10.7-centimeter radio flux (used as a proxy for extreme ultraviolet flux) reaching each planet, we found temperature changes of 42.0 +/- 8.0 kelvin and 19.2 +/- 3.6 kelvin for Earth and Mars, respectively. Existing data for Venus indicate values of 3.6 +/- 0.6 kelvin. Our observational result constrains comparative planetary thermosphere simulations and may help resolve existing uncertainties in thermal balance processes, particularly CO2 cooling.

  12. Thermospheric neutral densities derived from Swarm accelerometer and GPS data

    DEFF Research Database (Denmark)

    Doornbos, Eelco; Encarnacao, Joao; van den IJss, Jose

    Over the past years, a lot of effort has been put into characterising and correcting the various disturbance signals that were found in the accelerometer data provided by the Swarm satellites. This effort was first and foremost aimed at the Swarm C along-track axis data, which seems to be the least...... affected and most promising data for scientific use. The goal to make the Swarm C accelerometer along-track axis data ready for further processing into level 2 thermosphere density data has now been accomplished, with the help of information on the satellite motion from the GPS tracking as well...... approach, affects the possibility of determining densities from the accelerometer measurements of the Swarm A and B satellites. We also investigate the possibility of determining crosswind speeds from Swarm data.In the meantime, we have investigated the possibility of deriving thermosphere neutral density...

  13. On the origin of ionospheric sublayers in the lower thermosphere

    Energy Technology Data Exchange (ETDEWEB)

    Shirke, J S; Sridharan, R

    1979-11-01

    Some properties are examined of ionospheric sublayers usually two in number originating at sunrise in the lower thermosphere. The formation of the sublayers is found to be nearly global in nature though they are quickly transported upward over the dip-equatorial region as a result of vertical drifts existing there. The ionization associated with the layers once formed appears to remain constant for over several hours while the ambient ionization exhibits a solar zenith angle dependence. The sublayers at equatorial and low latitudes are often found capable of yielding echoes of radio waves transmitted from ground of frequencies much larger than corresponding to the ambient plasma density. This is shown to be due to generation of gradient type instabilities in these sublayers. The generation of the sublayers themselves is shown to be consistent with the concept of ionization at sunrise of neutral constituents deposited overnight from micrometeorites in the lower thermosphere.

  14. The Michigan Titan Thermospheric General Circulation Model (TTGCM)

    Science.gov (United States)

    Bell, J. M.; Bougher, S. W.; de Lahaye, V.; Waite, J. H.

    2005-12-01

    The Cassini flybys of Titan since late October, 2004 have provided data critical to better understanding its chemical and thermal structures. With this in mind, a 3-D TGCM of Titan's atmosphere from 600km to the exobase (~1450km) has been developed. This paper presents the first results from the partially operational code. Currently, the TTGCM includes static background chemistry (Lebonnois et al 2001, Vervack et al 2004) coupled with thermal conduction routines. The thermosphere remains dominated by solar EUV forcing and HCN rotational cooling, which is calculated by a full line-by-line radiative transfer routine along the lines of Yelle (1991) and Mueller-Wodarg (2000, 2002). In addition, an approximate treatment of magnetospheric heating is explored. This paper illustrates the model's capabilities as well as some initial results from the Titan Thermospheric General Circulation model that will be compared with both the Cassini INMS data and the model of Mueller-Wodarg (2000,2002).

  15. Density variations in the lower thermosphere. Scientific report No. 2

    International Nuclear Information System (INIS)

    Johnson, W.F.

    1974-01-01

    Accelerometer derived thermospheric density data from the LOGACS and SPADES satellites are processed to yield the equivalent density variation at 150 and 160 km respectively. Definite latitudinal and longitudinal variations are found which conflict with Jacchia's 1971 model. Time-latitude analyses are presented of density at a single altitude. The density response to a great geomagnetic storm is nearly the same from 25 0 S to 85 0 N except that a density trough forms just equatorward of the auroral oval. Gravity waves are observed during the storm. The structure and dynamics of the lower thermosphere are far more complex than previous studies indicate. (20 figures, 11 tables, 74 references) (U.S.)

  16. Neutral wind measurements by Fabry-Perot interferometry in Antarctica

    International Nuclear Information System (INIS)

    Stewart, K.D.; Dudeney, J.R.; Rodger, A.S.; Smith, R.W.; Rees, D.

    1986-01-01

    A large-aperture (150 mm), spatially scanned Fabry-Perot Interferometer (FPI) has been deployed at Halley (75.5 o S, 26.8 o W; L=4.2), Antarctica. Thermospheric neutral wind measurements were made by finding the Doppler shift of the OI( 3 P 2 - 1 D 2 ) 630.0 nm emission. This has allowed the first comparison to be made between southern hemisphere ground-based thermospheric wind measurements and the predictions of a three-dimensional, time-dependent thermospheric global circulation model. Geomagnetic and geographic latitude are well separated at Halley, so we may expect a distinct contrast to the dynamic behaviour observed in the more frequently studied northern polar thermosphere. Although the initial results from the experiment are in general agreement with the model, some consistent and significant differences between the observed wind field and that predicted are evident in the morning sector. These may be related to uncertainties in mapping magnetospheric boundaries to ionospheric heights in the southern hemisphere. The intensity of the 630 nm emission has been examined with respect to the maximum plasma frequency of the Es layer using data from the Advanced Ionospheric Sounder at Halley

  17. Vertical circulation and thermospheric composition: a modelling study

    OpenAIRE

    H. Rishbeth; I. C. F. Müller-Wodarg; I. C. F. Müller-Wodarg

    1999-01-01

    The coupled thermosphere-ionosphere-plasmasphere model CTIP is used to study the global three-dimensional circulation and its effect on neutral composition in the midlatitude F-layer. At equinox, the vertical air motion is basically up by day, down by night, and the atomic oxygen/molecular nitrogen [O/N2] concentration ratio is symmetrical about the equator. At solstice there is a summer-to-winter flow of air, with downwelling at subauroral latitudes in winter that produc...

  18. Vertical circulation and thermospheric composition: a modelling study

    Directory of Open Access Journals (Sweden)

    H. Rishbeth

    Full Text Available The coupled thermosphere-ionosphere-plasmasphere model CTIP is used to study the global three-dimensional circulation and its effect on neutral composition in the midlatitude F-layer. At equinox, the vertical air motion is basically up by day, down by night, and the atomic oxygen/molecular nitrogen [O/N2] concentration ratio is symmetrical about the equator. At solstice there is a summer-to-winter flow of air, with downwelling at subauroral latitudes in winter that produces regions of large [O/N2] ratio. Because the thermospheric circulation is influenced by the high-latitude energy inputs, which are related to the geometry of the Earth's magnetic field, the latitude of the downwelling regions varies with longitude. The downwelling regions give rise to large F2-layer electron densities when they are sunlit, but not when they are in darkness, with implications for the distribution of seasonal and semiannual variations of the F2-layer. It is also found that the vertical distributions of O and N2 may depart appreciably from diffusive equilibrium at heights up to about 160 km, especially in the summer hemisphere where there is strong upwelling.

    Atmospheric composition and structure (thermosphere · composition and chemistry · Ionosphere (ionosphere · atmosphere interactions

  19. Developments of STIM, the Saturn Thermosphere Ionosphere Model

    Science.gov (United States)

    Aylward, A. D.; Smith, C. G.; Miller, S.; Millward, G.

    2005-05-01

    The STIM (Saturn Thermosphere Ionosphere Model) model is a joint venture betwen University College London, Imperial College London, Boston University and the University of Arizona to develop a 3-d global circulation model of the Saturnian system - the primary aim being to use this as a tool for interpretation and testing of Cassini data. After initial work producing a basic thermosphere model (Muller-Wodarg et al 2005), examining issues to do with the ionosphere (Moore et al 2005) and examining auroral heating effects (Smith et al 2005), a global coupled ionosphere-plasmasphere has been added to the model. At low latitudes the model calculates ion densities on closed flux tubes passing through the ring plane. At high latitudes it performs self-consistent calculations of Joule heating and ion drag based on the calculated thermospheric and ionospheric parameters. The plasmasphere is complicated for Saturn by the strength of the centrifugal force which can dominate the forces in the outer flux tubes. Studies initially used H+ and H3+ as the principle ions but for the future it will be necessary to look at the consequences of the rings supplying OH or oxygen from ring ice particles. The high-latitude morphology is being refined as Cassini data constrains it. Long-term plans for the STIM development will be discussed.

  20. Vertical circulation and thermospheric composition: a modelling study

    Directory of Open Access Journals (Sweden)

    H. Rishbeth

    1999-06-01

    Full Text Available The coupled thermosphere-ionosphere-plasmasphere model CTIP is used to study the global three-dimensional circulation and its effect on neutral composition in the midlatitude F-layer. At equinox, the vertical air motion is basically up by day, down by night, and the atomic oxygen/molecular nitrogen [O/N2] concentration ratio is symmetrical about the equator. At solstice there is a summer-to-winter flow of air, with downwelling at subauroral latitudes in winter that produces regions of large [O/N2] ratio. Because the thermospheric circulation is influenced by the high-latitude energy inputs, which are related to the geometry of the Earth's magnetic field, the latitude of the downwelling regions varies with longitude. The downwelling regions give rise to large F2-layer electron densities when they are sunlit, but not when they are in darkness, with implications for the distribution of seasonal and semiannual variations of the F2-layer. It is also found that the vertical distributions of O and N2 may depart appreciably from diffusive equilibrium at heights up to about 160 km, especially in the summer hemisphere where there is strong upwelling. Atmospheric composition and structure (thermosphere · composition and chemistry · Ionosphere (ionosphere · atmosphere interactions

  1. Thermospheric mass density variations during geomagnetic storms and a prediction model based on the merging electric field

    Directory of Open Access Journals (Sweden)

    R. Liu

    2010-09-01

    Full Text Available With the help of four years (2002–2005 of CHAMP accelerometer data we have investigated the dependence of low and mid latitude thermospheric density on the merging electric field, Em, during major magnetic storms. Altogether 30 intensive storm events (Dstmin<−100 nT are chosen for a statistical study. In order to achieve a good correlation Em is preconditioned. Contrary to general opinion, Em has to be applied without saturation effect in order to obtain good results for magnetic storms of all activity levels. The memory effect of the thermosphere is accounted for by a weighted integration of Em over the past 3 h. In addition, a lag time of the mass density response to solar wind input of 0 to 4.5 h depending on latitude and local time is considered. A linear model using the preconditioned Em as main controlling parameter for predicting mass density changes during magnetic storms is developed: ρ=0.5 Em + ρamb, where ρamb is based on the mean density during the quiet day before the storm. We show that this simple relation predicts all storm-induced mass density variations at CHAMP altitude fairly well especially if orbital averages are considered.

  2. Thermospheric mass density variations during geomagnetic storms and a prediction model based on the merging electric field

    Science.gov (United States)

    Liu, R.; Lühr, H.; Doornbos, E.; Ma, S.-Y.

    2010-09-01

    With the help of four years (2002-2005) of CHAMP accelerometer data we have investigated the dependence of low and mid latitude thermospheric density on the merging electric field, Em, during major magnetic storms. Altogether 30 intensive storm events (Dstmineffect in order to obtain good results for magnetic storms of all activity levels. The memory effect of the thermosphere is accounted for by a weighted integration of Em over the past 3 h. In addition, a lag time of the mass density response to solar wind input of 0 to 4.5 h depending on latitude and local time is considered. A linear model using the preconditioned color: #000;">Em as main controlling parameter for predicting mass density changes during magnetic storms is developed: ρ=0.5 color: #000;">Em + ρamb, where ρamb is based on the mean density during the quiet day before the storm. We show that this simple relation predicts all storm-induced mass density variations at CHAMP altitude fairly well especially if orbital averages are considered.

  3. Modeling the ionosphere-thermosphere response to a geomagnetic storm using physics-based magnetospheric energy input: OpenGGCM-CTIM results

    Directory of Open Access Journals (Sweden)

    Connor Hyunju Kim

    2016-01-01

    Full Text Available The magnetosphere is a major source of energy for the Earth’s ionosphere and thermosphere (IT system. Current IT models drive the upper atmosphere using empirically calculated magnetospheric energy input. Thus, they do not sufficiently capture the storm-time dynamics, particularly at high latitudes. To improve the prediction capability of IT models, a physics-based magnetospheric input is necessary. Here, we use the Open Global General Circulation Model (OpenGGCM coupled with the Coupled Thermosphere Ionosphere Model (CTIM. OpenGGCM calculates a three-dimensional global magnetosphere and a two-dimensional high-latitude ionosphere by solving resistive magnetohydrodynamic (MHD equations with solar wind input. CTIM calculates a global thermosphere and a high-latitude ionosphere in three dimensions using realistic magnetospheric inputs from the OpenGGCM. We investigate whether the coupled model improves the storm-time IT responses by simulating a geomagnetic storm that is preceded by a strong solar wind pressure front on August 24, 2005. We compare the OpenGGCM-CTIM results with low-earth-orbit satellite observations and with the model results of Coupled Thermosphere-Ionosphere-Plasmasphere electrodynamics (CTIPe. CTIPe is an up-to-date version of CTIM that incorporates more IT dynamics such as a low-latitude ionosphere and a plasmasphere, but uses empirical magnetospheric input. OpenGGCM-CTIM reproduces localized neutral density peaks at ~ 400 km altitude in the high-latitude dayside regions in agreement with in situ observations during the pressure shock and the early phase of the storm. Although CTIPe is in some sense a much superior model than CTIM, it misses these localized enhancements. Unlike the CTIPe empirical input models, OpenGGCM-CTIM more faithfully produces localized increases of both auroral precipitation and ionospheric electric fields near the high-latitude dayside region after the pressure shock and after the storm onset

  4. Evidence of the Lower Thermospheric Winter-to-Summer Circulation From SABER CO2 Observations

    Science.gov (United States)

    Qian, Liying; Burns, Alan; Yue, Jia

    2017-10-01

    Numerical studies have shown that there is a lower thermospheric winter-to-summer circulation that is driven by wave dissipation and that it plays a significant role in trace gas distributions in the mesosphere and lower thermosphere, and in the composition of the thermosphere. However, the characteristics of this circulation are poorly known. Direct observations of it are difficult, but it leaves clear signatures in tracer distributions. The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite has obtained CO2 concentration from 2002 to present. This data set, combined with simulations by the Whole Atmosphere Community Climate Model, provides an unprecedented opportunity to infer the morphology of this circulation in both the summer and winter hemispheres. Our study show that there exists a maximum vertical gradient of CO2 at summer high latitudes, driven by the convergence of the upwelling of the mesospheric circulation and the downwelling of the lower thermospheric circulation; in the winter hemisphere, the maximum vertical gradient of CO2 is located at a higher altitude, driven by the convergence of the upwelling of the lower thermospheric circulation and the downwelling of the solar-driven thermospheric circulation; the bottom of the lower thermospheric circulation is located between 95 km and 100 km, and it has a vertical extent of 10 km. Analysis of the SABER CO2 and temperature at summer high latitudes showed that the bottom of this circulation is consistently higher than the mesopause height by 10 km.

  5. Theoretical model simulations for the global Thermospheric Mapping Study (TMS) periods

    Science.gov (United States)

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

    Theoretical and semiempirical models of the solar UV/EUV and of the geomagnetic driving forces affecting the terrestrial mesosphere and thermosphere have been used to generate a series of representative numerical time-dependent and global models of the thermosphere, for the range of solar and geoamgnetic activity levels which occurred during the three Thermospheric Mapping Study periods. The simulations obtained from these numerical models are compared with observations, and with the results of semiempirical models of the thermosphere. The theoretical models provide a record of the magnitude of the major driving forces which affected the thermosphere during the study periods, and a baseline against which the actual observed structure and dynamics can be compared.

  6. Multiple neutral density measurements in the lower thermosphere with cold-cathode ionization gauges

    Science.gov (United States)

    Lehmacher, G. A.; Gaulden, T. M.; Larsen, M. F.; Craven, J. D.

    2013-01-01

    Cold-cathode ionization gauges were used for rocket-borne measurements of total neutral density and temperature in the aurorally forced lower thermosphere between 90 and 200 km. A commercial gauge was adapted as a low-cost instrument with a spherical antechamber for measurements in molecular flow conditions. Three roll-stabilized payloads on different trajectories each carried two instruments for measurements near the ram flow direction along the respective upleg and downleg segments of a flight path, and six density profiles were obtained within a period of 22 min covering spatial separations up to 200 km. The density profiles were integrated below 125 km to yield temperatures. The mean temperature structure was similar for all six profiles with two mesopause minima near 110 and 101 km, however, for the downleg profiles, the upper minimum was warmer and the lower minimum was colder by 20-30 K indicating significant variability over horizontal scales of 100-200 km. The upper temperature minimum coincided with maximum horizontal winds speeds, exceeding 170 m/s.

  7. Distance-regular graphs

    NARCIS (Netherlands)

    van Dam, Edwin R.; Koolen, Jack H.; Tanaka, Hajime

    2016-01-01

    This is a survey of distance-regular graphs. We present an introduction to distance-regular graphs for the reader who is unfamiliar with the subject, and then give an overview of some developments in the area of distance-regular graphs since the monograph 'BCN'[Brouwer, A.E., Cohen, A.M., Neumaier,

  8. LL-regular grammars

    NARCIS (Netherlands)

    Nijholt, Antinus

    1980-01-01

    Culik II and Cogen introduced the class of LR-regular grammars, an extension of the LR(k) grammars. In this paper we consider an analogous extension of the LL(k) grammars called the LL-regular grammars. The relation of this class of grammars to other classes of grammars will be shown. Any LL-regular

  9. Circulation of the polar thermosphere during geomagnetically quiet and active times as observed by Dynamics Explorer 2

    International Nuclear Information System (INIS)

    McCormac, F.G.; Killeen, T.L.; Thayer, J.P.; Hernandez, G.; Tschan, C.R.; Ponthieu, J.J.; Spencer, N.W.

    1987-01-01

    Neutral wind measurements obtained by instruments on board the Dynamics Explorer 2 (DE 2) spacecraft have been used to study the effects of geomagnetic activity on the circulation of the high-latitude neutral thermosphere for solar maximum conditions during the periods of November 1981 through January 1982 and November 1982 through January 1983. The data have been sorted and ordered according to the two geophysical indices Kp and (auroral electrojet) AE. Simple expressions have been derived which describe (1) the maximum antisunward wind speed in the geomagnetic polar cap, (2) the maximum sunward wind speeds in the dawn and dusk sectors of the auroral oval, and (3) the latitudinal extent of the polar cap antisunward neutral wind as functions of Kp and AE. The results show a positive correlation between the geomagnetic indices and the three characteristic features of the neutral circulation described above. Averaged vector wind fields in geomagnetic coordinates for Kp ≤ 2 and Kp ≥ 4 in both northern and southern hemispheres for the 6 months have been derived from the data. In doing this, a first-order invariance of the neutral wind circulation in geomagnetic coordinates as a function of universal time (UT) was assumed. The results show a two-cell circulation pattern in the northern winter hemisphere for both quiet and active geomagnetic periods. The cell sizes increase with increasing geomagnetic activity. The dusk cell is always dominant. The southern summer hemisphere averages show only the dusk circulation cell for both quiet and active geomagnetic periods. The cell sizes increase with increasing geomagnetic activity. The dusk cell is always dominant. The southern summer hemisphere averages show only the dusk circulation cell for both quiet and active geomagnetic periods. A diminution of this cell occurs for reduced levels of geomagnetic activity

  10. Regular Expression Pocket Reference

    CERN Document Server

    Stubblebine, Tony

    2007-01-01

    This handy little book offers programmers a complete overview of the syntax and semantics of regular expressions that are at the heart of every text-processing application. Ideal as a quick reference, Regular Expression Pocket Reference covers the regular expression APIs for Perl 5.8, Ruby (including some upcoming 1.9 features), Java, PHP, .NET and C#, Python, vi, JavaScript, and the PCRE regular expression libraries. This concise and easy-to-use reference puts a very powerful tool for manipulating text and data right at your fingertips. Composed of a mixture of symbols and text, regular exp

  11. Statistical analysis of thermospheric gravity waves from Fabry-Perot Interferometer measurements of atomic oxygen

    Directory of Open Access Journals (Sweden)

    E. A. K. Ford

    2008-02-01

    Full Text Available Data from the Fabry-Perot Interferometers at KEOPS (Sweden, Sodankylä (Finland, and Svalbard (Norway, have been analysed for gravity wave activity on all the clear nights from 2000 to 2006. A total of 249 nights were available from KEOPS, 133 from Sodankylä and 185 from the Svalbard FPI. A Lomb-Scargle analysis was performed on each of these nights to identify the periods of any wave activity during the night. Comparisons between many nights of data allow the general characteristics of the waves that are present in the high latitude upper thermosphere to be determined. Comparisons were made between the different parameters: the atomic oxygen intensities, the thermospheric winds and temperatures, and for each parameter the distribution of frequencies of the waves was determined. No dependence on the number of waves on geomagnetic activity levels, or position in the solar cycle, was found. All the FPIs have had different detectors at various times, producing different time resolutions of the data, so comparisons between the different years, and between data from different sites, showed how the time resolution determines which waves are observed. In addition to the cutoff due to the Nyquist frequency, poor resolution observations significantly reduce the number of short-period waves (<1 h period that may be detected with confidence. The length of the dataset, which is usually determined by the length of the night, was the main factor influencing the number of long period waves (>5 h detected. Comparisons between the number of gravity waves detected at KEOPS and Sodankylä over all the seasons showed a similar proportion of waves to the number of nights used for both sites, as expected since the two sites are at similar latitudes and therefore locations with respect to the auroral oval, confirming this as a likely source region. Svalbard showed fewer waves with short periods than KEOPS data for a season when both had the same time resolution data

  12. Remote Sensing the Thermosphere's State Using Emissions From Carbon Dioxide and Nitric Oxide

    Science.gov (United States)

    Weimer, D. R.; Mlynczak, M. G.; Doornbos, E.

    2017-12-01

    Measurements of emissions from nitric oxide and carbon dioxide in the thermosphere have strong correlations with properties that are very useful to the determination of thermospheric densities. We have compared emissions measured with the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite with neutral density measurements from the Challenging Mini-satellite Payload (CHAMP), the Gravity Recovery and Climate Experiment (GRACE), the Ocean Circulation Explorer (GOCE), and the three Swarm satellites, spanning a time period of over 15 years. It has been found that nitric oxide emissions match changes in the exospheric temperatures that have been derived from the densities through use of the Naval Reasearch Laboratory Mass Spectrometer, Incoherent Scatter Radar Extended Model (NRLMSISE-00) thermosphere model. Similarly, our results indicate that the carbon dioxide emissions have annual and semiannual oscillations that correlate with changes in the amount of oxygen in the thermosphere, also determined by use of the NRLMSISE-00 model. These annual and semi-annual variations are found to have irregular amplitudes and phases, which make them very difficult to accurately predict. Prediction of exospheric temperatures through the use of geomagnetic indices also tends to be inexact. Therefore, it would be possible and very useful to use measurements of the thermosphere's infrared emissions for real-time tracking of the thermosphere's state, so that more accurate calculations of the density may be obtained.

  13. Characterization of blasts in medium and low thermosphere from infrasonic wave observations

    International Nuclear Information System (INIS)

    Lalande, J.M.

    2012-01-01

    The International Monitoring System (IMS) designed to monitor compliance with the Comprehensive Nuclear Test-Ban Treaty (CTBT) uses four complementary verification methods: seismic, hydro-acoustic, radionuclide and micro-barometric stations spanning the entire globe. Micro-barometric stations record continuously infrasonic waves in the frequency band 0.02-4 Hz. These waves propagate at long-ranges through atmospheric ducts resulting from the natural stratification of atmospheric properties (temperature, density, winds,...) and represent a valuable information to understand atmospheric dynamic until the lower thermosphere. In this thesis, we seek to determine the possible contribution of infra-sound observations for improving current atmospheric specifications. We describe the atmospheric media and its circulation mechanisms as well as the conventional observations used in the development of atmospheric models. A description of the interaction between infrasonic waves and the atmosphere help to understand the interest of micro-barometric measurement compared with conventional observations. To highlight this potential we develop an inverse algorithm in order to estimate atmospheric parameters from infrasonic observations. The forward problem is handled by a ray-tracing algorithm. First-order perturbation equation resulting from perturbation of atmospheric properties, and especially wind parameters, are developed and numerically validated. We then analyse the inverse problem through several numerical experiments in order to show the capabilities and limitations of our algorithm. Results show the suitability of our approach and indicate that infrasonic observations can significantly improve current atmospheric specification at the altitudes of acoustic energy refraction, i.e. around 50 km and between 100 and 120 km. (author)

  14. Geomagnetically conjugate observations of ionospheric and thermospheric variations accompanied with a midnight brightness wave at low latitudes

    Science.gov (United States)

    Fukushima, D.; Shiokawa, K.; Otsuka, Y.; Kubota, M.; Yokoyama, T.; Nishioka, M.; Komonjinda, S.; Yatini, C. Y.

    2014-12-01

    A midnight brightness wave (MBW) is the phenomenon that the OI (630-nm) airglow enhancement propagates poleward once at local midnight. In this study, we first conducted geomagnetically conjugate observations of 630nm airglow for an MBW at conjugate stations. An airglow enhancement which is considered to be an MBW was observed in the 630-nm airglow images at Kototabang, Indonesia (geomagnetic latitude (MLAT): 10.0S) at around local midnight from 1540 to 1730 UT (from 2240 to 2430 LT) on 7 February 2011. This MBW was propagating south-southwestward, which is geomagnetically poleward, with a velocity of 290 m/s. However, similar wave was not observed in the 630-nm airglow images at Chiang Mai, Thailand (MLAT: 8.9N), which is close to being conjugate point of Kototabang. This result indicates that the MBW does not have geomagnetic conjugacy. We simultaneously observed thermospheric neutral winds observed by a co-located Fabry-Perot interferometer at Kototabang. The observed meridional winds turned from northward (geomagnetically equatorward) to southward (geomagnetically poleward) just before the MBW was observed. The bottomside ionospheric heights observed by ionosondes rapidly decreased at Kototabang and slightly increased at Chiang Mai simultaneously with the MBW passage. In the presentation, we discuss the MBW generation by the observed poleward neutral winds at Kototabang, and the cause of the coinciding small height increase at Chiang Mai by the polarization electric field inside the observed MBW at Kototabang.

  15. Regularization by External Variables

    DEFF Research Database (Denmark)

    Bossolini, Elena; Edwards, R.; Glendinning, P. A.

    2016-01-01

    Regularization was a big topic at the 2016 CRM Intensive Research Program on Advances in Nonsmooth Dynamics. There are many open questions concerning well known kinds of regularization (e.g., by smoothing or hysteresis). Here, we propose a framework for an alternative and important kind of regula......Regularization was a big topic at the 2016 CRM Intensive Research Program on Advances in Nonsmooth Dynamics. There are many open questions concerning well known kinds of regularization (e.g., by smoothing or hysteresis). Here, we propose a framework for an alternative and important kind...

  16. Regular expressions cookbook

    CERN Document Server

    Goyvaerts, Jan

    2009-01-01

    This cookbook provides more than 100 recipes to help you crunch data and manipulate text with regular expressions. Every programmer can find uses for regular expressions, but their power doesn't come worry-free. Even seasoned users often suffer from poor performance, false positives, false negatives, or perplexing bugs. Regular Expressions Cookbook offers step-by-step instructions for some of the most common tasks involving this tool, with recipes for C#, Java, JavaScript, Perl, PHP, Python, Ruby, and VB.NET. With this book, you will: Understand the basics of regular expressions through a

  17. Seasonal effects in the ionosphere-thermosphere response to the precipitation and field-aligned current variations in the cusp region

    Directory of Open Access Journals (Sweden)

    A. A. Namgaladze

    Full Text Available The seasonal effects in the thermosphere and ionosphere responses to the precipitating electron flux and field-aligned current variations, of the order of an hour in duration, in the summer and winter cusp regions have been investigated using the global numerical model of the Earth's upper atmosphere. Two variants of the calculations have been performed both for the IMF By < 0. In the first variant, the model input data for the summer and winter precipitating fluxes and field-aligned currents have been taken as geomagnetically symmetric and equal to those used earlier in the calculations for the equinoctial conditions. It has been found that both ionospheric and thermospheric disturbances are more intensive in the winter cusp region due to the lower conductivity of the winter polar cap ionosphere and correspondingly larger electric field variations leading to the larger Joule heating effects in the ion and neutral gas temperature, ion drag effects in the thermospheric winds and ion drift effects in the F2-region electron concentration. In the second variant, the calculations have been performed for the events of 28–29 January, 1992 when precipitations were weaker but the magnetospheric convection was stronger than in the first variant. Geomagnetically asymmetric input data for the summer and winter precipitating fluxes and field-aligned currents have been taken from the patterns derived by combining data obtained from the satellite, radar and ground magnetometer observations for these events. Calculated patterns of the ionospheric convection and thermospheric circulation have been compared with observations and it has been established that calculated patterns of the ionospheric convection for both winter and summer hemispheres are in a good agreement with the observations. Calculated patterns of the thermospheric circulation are in a good agreement with the average circulation for the Southern (summer Hemisphere obtained

  18. Ultraviolet spectrographs for thermospheric and ionospheric remote sensing

    International Nuclear Information System (INIS)

    Dymond, K.F.; McCoy, R.P.

    1993-01-01

    The Naval Research Laboratory (NRL) has been developing far- and extreme-ultraviolet spectrographs for remote sensing the Earth's upper atmosphere and ionosphere. The first of these sensors, called the Special Sensor Ultraviolet Limb Imager (SSULI), will be flying on the Air Force's Defense Meteorological Satellite Program (DMSP) block 5D3 satellites as an operational sensor in the 1997-2010 time frame. A second sensor, called the High-resolution ionospheric and Thermospheric Spectrograph (HITS), will fly in late 1995 on the Air Force Space Test Program's Advanced Research and Global Observation Satellite (ARGOS, also known as P91-1) as part of NRL's High Resolution Airglow and Auroral Spectroscopy (HIRAAS) experiment. Both of these instruments are compact and do not draw much power and would be good candidates for small satellite applications. The instruments and their capabilities are discussed. Possible uses of these instruments in small satellite applications are also presented

  19. Regularities of Multifractal Measures

    Indian Academy of Sciences (India)

    First, we prove the decomposition theorem for the regularities of multifractal Hausdorff measure and packing measure in R R d . This decomposition theorem enables us to split a set into regular and irregular parts, so that we can analyze each separately, and recombine them without affecting density properties. Next, we ...

  20. Stochastic analytic regularization

    International Nuclear Information System (INIS)

    Alfaro, J.

    1984-07-01

    Stochastic regularization is reexamined, pointing out a restriction on its use due to a new type of divergence which is not present in the unregulated theory. Furthermore, we introduce a new form of stochastic regularization which permits the use of a minimal subtraction scheme to define the renormalized Green functions. (author)

  1. The effects of nitric oxide cooling and the photodissociation of molecular oxygen on the thermosphere/ionosphere system over the Argentine Islands

    Directory of Open Access Journals (Sweden)

    G. D. Wells

    1997-03-01

    Full Text Available In the past the global, fully coupled, time-dependent mathematical model of the Earth's thermosphere/ionosphere/plasmasphere (CTIP has been unable to reproduce accurately observed values of the maximum plasma frequency, foF2, at extreme geophysical locations such as the Argentine Islands during the summer solstice where the ionosphere remains in sunlight throughout the day. This is probably because the seasonal dependence of thermospheric cooling by 5.3 µm nitric oxide has been neglected and the photodissociation of O2 and heating rate calculations have been over-simplified. Now we have included an up-to-date calculation of the solar EUV and UV thermospheric heating rate, coupled with a new calculation of a diurnally varying O2 photodissociation rate, in the model. Seasonally dependent 5.3 µm nitric oxide cooling is also included. With these important improvements, it is found that model values of foF2 are in substantially better agreement with observation. The height of the F2-peak is reduced throughout the day, but remains within acceptable limits of values derived from observation, except at around 0600 h LT. We also carry out two studies of the sensitivity of the upper atmosphere to changes in the magnitude of nitric oxide cooling and photodissociation rates. We find that hmF2 increases with increased heating, whilst foF2 falls. The converse is true for an increase in the cooling rate. Similarly increasing the photodissociation rate increases both hmF2 and foF2. These changes are explained in terms of changes in the neutral temperature, composition and neutral wind.

  2. E region neutral winds in the postmidnight diffuse aurora during the atmospheric response in aurora 1 rocket campaign

    International Nuclear Information System (INIS)

    Brinkman, D.G.; Walterscheid, R.L.; Lyons, L.R.

    1995-01-01

    Measured E region neutral winds from the Atmospheric Response in Aurora (ARIA 1) rocket campaign are compared with winds predicted by a high-resolution nonhydrostatic dynamical thermosphere model. The ARIA 1 rockets were launched into the postmidnight diffuse aurora during the recovery phase of a substorm. Simulations have shown that electrodynamical coupling between the auroral ionosphere and the thermosphere was expected to be strong during active diffuse auroral conditions. This is the first time that simulations using the time history of detailed specifications of the magnitude and latitudinal variation of the auroral forcing based on measurements have been compared to simultaneous wind measurements. Model inputs included electron densities derived from ground-based airglow measurements, precipitating electron fluxes measured by the rocket, electron densities measured on the rocket, electric fields derived from magnetometer and satellite ion drift measurements, and large-scale background winds from a thermospheric general circulation model. Our model predicted a strong jet of eastward winds at E region heights. A comparison between model predicted and observed winds showed modest agreement. Above 135 km the model predicted zonal winds with the correct sense, the correct profile shape, and the correct altitude of the peak wind. However, it overpredicted the magnitude of the eastward winds by more than a factor or 2. For the meridional winds the model predicted the general sense of the winds but was unable to predict the structure or strength of the winds seen in the observations. Uncertainties in the magnitude and latitudinal structure of the electric field and in the magnitude of the background winds are the most likely sources of error contributing to the differences between model and observed winds. Between 110 and 135 km the agreement between the model and observations was poor because of a large unmodeled jetlike feature in the observed winds

  3. Geomagnetically conjugate observations of ionospheric and thermospheric variations accompanied by a midnight brightness wave at low latitudes

    Science.gov (United States)

    Fukushima, D.; Shiokawa, K.; Otsuka, Y.; Kubota, M.; Yokoyama, T.; Nishioka, M.; Komonjinda, S.; Yatini, C. Y.

    2017-08-01

    We conducted geomagnetically conjugate observations of 630-nm airglow for a midnight brightness wave (MBW) at Kototabang, Indonesia [geomagnetic latitude (MLAT): 10.0°S], and Chiang Mai, Thailand (MLAT: 8.9°N), which are geomagnetically conjugate points at low latitudes. An airglow enhancement that was considered to be an MBW was observed in OI (630-nm) airglow images at Kototabang around local midnight from 2240 to 2430 LT on February 7, 2011. This MBW propagated south-southwestward, which is geomagnetically poleward, at a velocity of 290 m/s. However, a similar wave was not observed in the 630-nm airglow images at Chiang Mai. This is the first evidence of an MBW that does not have geomagnetic conjugacy, which also implies generation of MBW only in one side of the hemisphere from the equator. We simultaneously observed thermospheric neutral winds observed by a co-located Fabry-Perot interferometer at Kototabang. The observed meridional winds turned from northward (geomagnetically equatorward) to southward (geomagnetically poleward) just before the wave was observed. This indicates that the observed MBW was generated by the poleward winds which push ionospheric plasma down along geomagnetic field lines, thereby increasing the 630-nm airglow intensity. The bottomside ionospheric heights observed by ionosondes rapidly decreased at Kototabang and slightly increased at Chiang Mai. We suggest that the polarization electric field inside the observed MBW is projected to the northern hemisphere, causing the small height increase observed at Chiang Mai. This implies that electromagnetic coupling between hemispheres can occur even though the original disturbance is caused purely by the neutral wind.[Figure not available: see fulltext.

  4. Interhemispheric Asymmetry in the Mesosphere and Lower Thermosphere Observed by SABER/TIMED

    Science.gov (United States)

    Yee, J. H.

    2017-12-01

    In this paper we analyze nearly 15 years of satellite observations of temperature, airglow, and composition in the Mesosphere and Lower Thermosphere (MLT) to quantify their interhemispheric asymmetries ao one can provide quantitative links between observed asymmetries and the spatial and temporal variations of the gravity wave activity. Two processes are believed to be responsible for observed interhemispheric differences in the MLT. The first is the direct radiation effect from the eccentricity of the Earth orbit amd the other is the difference in gravity wave source distribution and filtering due to asymmetries in mean winds of the lower atmosphere. Both processes have been theoretically investigated to explain the observed asymmetry in some of the atmospheric parameters, but not self-consistently in all observed parameters together. In this paper we will show the asymmetry in the time-varying zonal-mean latitudinal structures of temperature, airglow emission rate, and composition observed by TIMED/SABER. We will quantify their interhemispheric asymmetries for different seasons under different solar activity conditions. In addition, temperature measurements will also be used to obtain temporal and spatial morphology of gravity wave potential energies. We will interpret the asymmetry in the observed fields and examine qualitatively their consistency with the two responsible processes, especially the one due to gravity wave filtering process. Our goal is to introduce and to share the spatial and temporal morphologies of all the observed fields to the modeling community so, together self-consistently, they be can be used to gain physical insights into the relative importance of various drivers responsible for the observed asymmetry, especially the role of gravity wave induced eddy drag and mixing, a critical, but least quantitatively understood process.

  5. Sparse structure regularized ranking

    KAUST Repository

    Wang, Jim Jing-Yan; Sun, Yijun; Gao, Xin

    2014-01-01

    Learning ranking scores is critical for the multimedia database retrieval problem. In this paper, we propose a novel ranking score learning algorithm by exploring the sparse structure and using it to regularize ranking scores. To explore the sparse

  6. Regular expression containment

    DEFF Research Database (Denmark)

    Henglein, Fritz; Nielsen, Lasse

    2011-01-01

    We present a new sound and complete axiomatization of regular expression containment. It consists of the conventional axiomatiza- tion of concatenation, alternation, empty set and (the singleton set containing) the empty string as an idempotent semiring, the fixed- point rule E* = 1 + E × E......* for Kleene-star, and a general coin- duction rule as the only additional rule. Our axiomatization gives rise to a natural computational inter- pretation of regular expressions as simple types that represent parse trees, and of containment proofs as coercions. This gives the axiom- atization a Curry......-Howard-style constructive interpretation: Con- tainment proofs do not only certify a language-theoretic contain- ment, but, under our computational interpretation, constructively transform a membership proof of a string in one regular expres- sion into a membership proof of the same string in another regular expression. We...

  7. Supersymmetric dimensional regularization

    International Nuclear Information System (INIS)

    Siegel, W.; Townsend, P.K.; van Nieuwenhuizen, P.

    1980-01-01

    There is a simple modification of dimension regularization which preserves supersymmetry: dimensional reduction to real D < 4, followed by analytic continuation to complex D. In terms of component fields, this means fixing the ranges of all indices on the fields (and therefore the numbers of Fermi and Bose components). For superfields, it means continuing in the dimensionality of x-space while fixing the dimensionality of theta-space. This regularization procedure allows the simple manipulation of spinor derivatives in supergraph calculations. The resulting rules are: (1) First do all algebra exactly as in D = 4; (2) Then do the momentum integrals as in ordinary dimensional regularization. This regularization procedure needs extra rules before one can say that it is consistent. Such extra rules needed for superconformal anomalies are discussed. Problems associated with renormalizability and higher order loops are also discussed

  8. Regularized maximum correntropy machine

    KAUST Repository

    Wang, Jim Jing-Yan; Wang, Yunji; Jing, Bing-Yi; Gao, Xin

    2015-01-01

    In this paper we investigate the usage of regularized correntropy framework for learning of classifiers from noisy labels. The class label predictors learned by minimizing transitional loss functions are sensitive to the noisy and outlying labels of training samples, because the transitional loss functions are equally applied to all the samples. To solve this problem, we propose to learn the class label predictors by maximizing the correntropy between the predicted labels and the true labels of the training samples, under the regularized Maximum Correntropy Criteria (MCC) framework. Moreover, we regularize the predictor parameter to control the complexity of the predictor. The learning problem is formulated by an objective function considering the parameter regularization and MCC simultaneously. By optimizing the objective function alternately, we develop a novel predictor learning algorithm. The experiments on two challenging pattern classification tasks show that it significantly outperforms the machines with transitional loss functions.

  9. Regularized maximum correntropy machine

    KAUST Repository

    Wang, Jim Jing-Yan

    2015-02-12

    In this paper we investigate the usage of regularized correntropy framework for learning of classifiers from noisy labels. The class label predictors learned by minimizing transitional loss functions are sensitive to the noisy and outlying labels of training samples, because the transitional loss functions are equally applied to all the samples. To solve this problem, we propose to learn the class label predictors by maximizing the correntropy between the predicted labels and the true labels of the training samples, under the regularized Maximum Correntropy Criteria (MCC) framework. Moreover, we regularize the predictor parameter to control the complexity of the predictor. The learning problem is formulated by an objective function considering the parameter regularization and MCC simultaneously. By optimizing the objective function alternately, we develop a novel predictor learning algorithm. The experiments on two challenging pattern classification tasks show that it significantly outperforms the machines with transitional loss functions.

  10. How good are remote sensors at measuring extreme winds?

    NARCIS (Netherlands)

    Sathe, A.R.; Courtney, M.; Mann, J.; Wagner, R.

    2011-01-01

    This article describes some preliminary efforts within the SafeWind project, aimed to identify the possible added value of using wind lidars to detect extreme wind events. Exceptionally good performance is now regularly reported in the measurement of the mean wind speed with some wind lidars in flat

  11. Wind energy

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    This chapter discusses the role wind energy may have in the energy future of the US. The topics discussed in the chapter include historical aspects of wind energy use, the wind energy resource, wind energy technology including intermediate-size and small wind turbines and intermittency of wind power, public attitudes toward wind power, and environmental, siting and land use issues

  12. Improving Discoverability Between the Magnetosphere and Ionosphere/Thermosphere Domains

    Science.gov (United States)

    Schaefer, R. K.; Morrison, D.; Potter, M.; Barnes, R. J.; Talaat, E. R.; Sarris, T.

    2016-12-01

    With the advent of the NASA Magnetospheric Multiscale Mission and the Van Allen Probes we have space missions that probe the Earth's magnetosphere and radiation belts. These missions fly at far distances from the Earth in contrast to the larger number of near-Earth satellites. Both of the satellites make in situ measurements. Energetic particles flow along magnetic field lines from these measurement locations down to the ionosphere/thermosphere region. Discovering other data that may be used with these satellites is a difficult and complicated process. To solve this problem we have developed a series of light-weight web services that can provide a new data search capability for the Virtual Ionosphere Thermosphere Mesosphere Observatory (VITMO). The services consist of a database of spacecraft ephemerides and instrument fields of view; an overlap calculator to find times when the fields of view of different instruments intersect; and a magnetic field line tracing service that maps in situ and ground based measurements for a number of magnetic field models and geophysical conditions. These services run in real-time when the user queries for data and allow the non-specialist user to select data that they were previously unable to locate, opening up analysis opportunities beyond the instrument teams and specialists. Each service on their own provides a useful new capability for virtual observatories; operating together they will provide a powerful new search tool. The ephemerides service is being built using the Navigation and Ancillary Information Facility (NAIF) SPICE toolkit (http://naif.jpl.nasa.gov) allowing them to be extended to support any Earth orbiting satellite with the addition of the appropriate SPICE kernels. The overlap calculator uses techniques borrowed from computer graphics to identify overlapping measurements in space and time. The calculator will allow a user defined uncertainty to be selected to allow "near misses" to be found. The magnetic field

  13. Contributions of the Higher Vibrational Levels of Nitric Oxide to the Radiative Cooling of the Thermosphere

    Science.gov (United States)

    Venkataramani, K.; Yonker, J. D.; Bailey, S. M.

    2014-12-01

    The 5.3μm emission from the vibrational levels of nitric oxide (NO) and the 15μm emission from CO2 are known to be the dominant sources of cooling in the thermosphere above 100 km. The 5.3μm emission is primarily produced by the radiative de-excitation of NO from its first vibrational level, which in turn is mainly populated by the collisions of NO with atomic oxygen. However, the reaction of atomic nitrogen (N(4S) and N(2D)) with O2 yields vibrationally excited NO with v>1, resulting in a radiative cascade which produces more than one 5.3μm photon per vibrationally excited NO molecule. This chemiluminescence is approximately 20% in magnitude of the emission produced by thermal collisions. These additional sources of the 5.3μm emission are introduced into a one dimensional photochemical model and the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) to assess their variability with latitude and solar activity, and to also understand their effect on the thermospheric energy budget. The results from the models are compared with data from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) experiment on-board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite, which has been making measurements of the infrared radiative response of the mesosphere and thermosphere to solar inputs since 2002.

  14. Solar Cycle Variation of Upper Thermospheric Temperature Over King Sejong Station, Antarctica

    Science.gov (United States)

    Chung, Jong-Kyun; Won, Young-In; Kim, Yong-Ha; Lee, Bang-Yong; Kim, Jhoon

    2000-12-01

    A ground Fabry-Perot interferometer has been used to measure atomic oxygen nightglow (OI 630.0 nm) from the thermosphere (about 250 km) at King Sejong station (KSS, geographic: 62.22oS, 301.25oE; geomagnetic: 50.65oS, 7.51oE), Antarctica. While numerous studies of the thermosphere have been performed on high latitude using ground-based Fabry-Perot interferometers, the thermospheric measurements in the Southern Hemisphere are relatively new and sparse. Therefore, the nightglow measurements at KSS play an important role in extending the thermospheric studies to the Southern Hemisphere. In this study, we investigated the effects of the geomagnetic and solar activities on the thermospheric neutral temperatures that have been observed at KSS in 1989 and 1997. The measured average temperatures are 1400 K in 1989 and 800 K in 1997, reflecting the influence of the solar activity. The measurements were compared with empirical models, MSIS-86 and semi-empirical model, VSH.

  15. Solar Cycle Variation of Upper Thermospheric Temperature Over King Sejong Station, Antarctica

    Directory of Open Access Journals (Sweden)

    Jong-Kyun Chung

    2000-12-01

    Full Text Available A ground Fabry-Perot interferometer has been used to measure atomic oxygen nightglow (OI 630.0 nm from the thermosphere (about 250 km at King Sejong station (KSS, geographic: 62.22oS, 301.25oE; geomagnetic: 50.65oS, 7.51oE, Antarctica. While numerous studies of the thermosphere have been performed on high latitude using ground-based Fabry-Perot interferometers, the thermospheric measurements in the Southern Hemisphere are relatively new and sparse. Therefore, the nightglow measurements at KSS play an important role in extending the thermospheric studies to the Southern Hemisphere. In this study, we investigated the effects of the geomagnetic and solar activities on the thermospheric neutral temperatures that have been observed at KSS in 1989 and 1997. The measured average temperatures are 1400 K in 1989 and 800 K in 1997, reflecting the influence of the solar activity. The measurements were compared with empirical models, MSIS-86 and semi-empirical model, VSH.

  16. Variations of thermospheric composition according to AE-C data and CTIP modelling

    Directory of Open Access Journals (Sweden)

    H. Rishbeth

    2004-01-01

    Full Text Available Data from the Atmospheric Explorer C satellite, taken at middle and low latitudes in 1975-1978, are used to study latitudinal and month-by-month variations of thermospheric composition. The parameter used is the "compositional Ρ-parameter", related to the neutral atomic oxygen/molecular nitrogen concentration ratio. The midlatitude data show strong winter maxima of the atomic/molecular ratio, which account for the "seasonal anomaly" of the ionospheric F2-layer. When the AE-C data are compared with the empirical MSIS model and the computational CTIP ionosphere-thermosphere model, broadly similar features are found, but the AE-C data give a more molecular thermosphere than do the models, especially CTIP. In particular, CTIP badly overestimates the winter/summer change of composition, more so in the south than in the north. The semiannual variations at the equator and in southern latitudes, shown by CTIP and MSIS, appear more weakly in the AE-C data. Magnetic activity produces a more molecular thermosphere at high latitudes, and at mid-latitudes in summer. Key words. Atmospheric composition and structure (thermosphere – composition and chemistry

  17. Variations of thermospheric composition according to AE-C data and CTIP modelling

    Directory of Open Access Journals (Sweden)

    H. Rishbeth

    2004-01-01

    Full Text Available Data from the Atmospheric Explorer C satellite, taken at middle and low latitudes in 1975-1978, are used to study latitudinal and month-by-month variations of thermospheric composition. The parameter used is the "compositional Ρ-parameter", related to the neutral atomic oxygen/molecular nitrogen concentration ratio. The midlatitude data show strong winter maxima of the atomic/molecular ratio, which account for the "seasonal anomaly" of the ionospheric F2-layer. When the AE-C data are compared with the empirical MSIS model and the computational CTIP ionosphere-thermosphere model, broadly similar features are found, but the AE-C data give a more molecular thermosphere than do the models, especially CTIP. In particular, CTIP badly overestimates the winter/summer change of composition, more so in the south than in the north. The semiannual variations at the equator and in southern latitudes, shown by CTIP and MSIS, appear more weakly in the AE-C data. Magnetic activity produces a more molecular thermosphere at high latitudes, and at mid-latitudes in summer.

    Key words. Atmospheric composition and structure (thermosphere – composition and chemistry

  18. Silicon Chemistry in the Mesosphere and Lower Thermosphere

    Science.gov (United States)

    Plane, John M. C.; Gomez-Martin, Juan Carlos; Feng, Wuhu; Janches, Diego

    2016-01-01

    Silicon is one of the most abundant elements in cosmic dust, and meteoric ablation injects a significant amount of Si into the atmosphere above 80 km. In this study, a new model for silicon chemistry in the mesosphere lower thermosphere is described, based on recent laboratory kinetic studies of Si, SiO,SiO2, and S(exp +). Electronic structure calculations and statistical rate theory are used to show that the likely fate of SiO2 is a two-step hydration to silicic acid (Si(OH)4), which then polymerizes with metal oxides and hydroxides to form meteoric smoke particles. This chemistry is then incorporated into a whole atmosphere chemistry-climate model. The vertical profiles of Si+ and the Si(exp +)Fe(exp +) ratio are shown to be in good agreement with rocket-borne mass spectrometric measurements between 90 and 110 km. Si(exp +) has consistently been observed to be the major meteoric ion around 110 km; this implies that the relative injection rate of Si from meteoric ablation, compared to metals such as Fe and Mg, is significantly larger than expected based on the irrelative chondritic abundances. Finally, the global abundances of SiO and Si(OH)4 show clear evidence of the seasonal meteoric input function, which is much less pronounced in the case of other meteoric species.

  19. Manifold Regularized Reinforcement Learning.

    Science.gov (United States)

    Li, Hongliang; Liu, Derong; Wang, Ding

    2018-04-01

    This paper introduces a novel manifold regularized reinforcement learning scheme for continuous Markov decision processes. Smooth feature representations for value function approximation can be automatically learned using the unsupervised manifold regularization method. The learned features are data-driven, and can be adapted to the geometry of the state space. Furthermore, the scheme provides a direct basis representation extension for novel samples during policy learning and control. The performance of the proposed scheme is evaluated on two benchmark control tasks, i.e., the inverted pendulum and the energy storage problem. Simulation results illustrate the concepts of the proposed scheme and show that it can obtain excellent performance.

  20. Noise from wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Fegeant, Olivier [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Building Sciences

    2002-02-01

    A rapid growth of installed wind power capacity is expected in the next few years. However, the siting of wind turbines on a large scale raises concerns about their environmental impact, notably with respect to noise. To this end, variable speed wind turbines offer a promising solution for applications in densely populated areas like the European countries, as this design would enable an efficient utilisation of the masking effect due to ambient noise. In rural and recreational areas where wind turbines are sited, the ambient noise originates from the action of wind on the vegetation and about the listener's ear (pseudo-noise). It shows a wind speed dependence similar to that of the noise from a variable speed wind turbine and can therefore mask the latter for a wide range of conditions. However, a problem inherent to the design of these machines is their proclivity to pure tone generation, because of the enhanced difficulty of avoiding structural resonances in the mechanical parts. Pure tones are deemed highly annoying and are severely regulated by most noise policies. In relation to this problem, the vibration transmission of structure-borne sound to the tower of the turbine is investigated, in particular when the tower is stiffened at its upper end. Furthermore, since noise annoyance due to wind turbine is mostly a masking issue, the wind-related sources of ambient noise are studied and their masking potentials assessed. With this aim, prediction models for wind-induced vegetation noise and pseudo-noise have been developed. Finally, closely related to the effect of masking, is the difficulty, regularly encountered by local authorities and wind farm developers, to measure noise immission from wind turbines. A new measurement technique has thus been developed in the course of this work. Through improving the signal-to-noise ratio between wind turbine noise and ambient noise, the new technique yields more accurate measurement results.

  1. Non-thermal distribution of O(1D) atoms in the night-time thermosphere

    Science.gov (United States)

    Yee, Jeng-Hwa

    1988-01-01

    The 6300 A O(1D-3P) emission has been used for many years to remotely monitor the thermospheric temperature from the Doppler width of its line profile. The O(1D) atoms in the nighttime thermosphere are initially produced by the dissociative recombination of O2(+) ions with kinetic energy much greater than the thermal energy of the ambient neutrals. The validity of the technique to monitor neutral ambient temperature by measuring O(1D) 6300 A emission depends on the degree of thermalization of the O(1D) atoms. The object of this study is to calculate the velocity distribution of the O(1D) atoms and to examine the effect of nonthermal distribution on the nighttime thermospheric neutral temperature determined.

  2. An equatorial temperature and wind anomaly (ETWA)

    International Nuclear Information System (INIS)

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

    1991-01-01

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

  3. Temporal Variability of Atomic Hydrogen From the Mesopause to the Upper Thermosphere

    Science.gov (United States)

    Qian, Liying; Burns, Alan G.; Solomon, Stan S.; Smith, Anne K.; McInerney, Joseph M.; Hunt, Linda A.; Marsh, Daniel R.; Liu, Hanli; Mlynczak, Martin G.; Vitt, Francis M.

    2018-01-01

    We investigate atomic hydrogen (H) variability from the mesopause to the upper thermosphere, on time scales of solar cycle, seasonal, and diurnal, using measurements made by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere Ionosphere Mesosphere Energetics Dynamics satellite, and simulations by the National Center for Atmospheric Research Whole Atmosphere Community Climate Model-eXtended (WACCM-X). In the mesopause region (85 to 95 km), the seasonal and solar cycle variations of H simulated by WACCM-X are consistent with those from SABER observations: H density is higher in summer than in winter, and slightly higher at solar minimum than at solar maximum. However, mesopause region H density from the Mass-Spectrometer-Incoherent-Scatter (National Research Laboratory Mass-Spectrometer-Incoherent-Scatter 00 (NRLMSISE-00)) empirical model has reversed seasonal variation compared to WACCM-X and SABER. From the mesopause to the upper thermosphere, H density simulated by WACCM-X switches its solar cycle variation twice, and seasonal dependence once, and these changes of solar cycle and seasonal variability occur in the lower thermosphere ( 95 to 130 km), whereas H from NRLMSISE-00 does not change solar cycle and seasonal dependence from the mesopause through the thermosphere. In the upper thermosphere (above 150 km), H density simulated by WACCM-X is higher at solar minimum than at solar maximum, higher in winter than in summer, and also higher during nighttime than daytime. The amplitudes of these variations are on the order of factors of 10, 2, and 2, respectively. This is consistent with NRLMSISE-00.

  4. The effect of energetic electron precipitation on the nitric oxide density in the lower thermosphere

    International Nuclear Information System (INIS)

    Saetre, Camilla

    2006-12-01

    The objective of this thesis has been the study of the chemical effects of the electron precipitation in the upper atmosphere, and mainly the increase of thermospheric nitric oxide (NO). NO plays an important role in the temperature balance for the mesosphere and thermosphere.In this project auroral electron precipitation data, derived from the Polar Ionospheric X-ray Imaging Experiment (PIXIE) and the Ultraviolet Imager (UVI) on board the Polar satellite, have been used together with NO density measurements from the Student Nitric Oxide Explorer (SNOE)

  5. Wind: new wind markets

    International Nuclear Information System (INIS)

    Cameron, A.

    2005-01-01

    The June 2005 edition of 'Wind Force 12' suggests that wind could generate 12% of global electricity requirements by 2020. But what moves a potential market into an emerging one? Geographical factors include a good wind resource, plenty of open space and the ability to get the generated electricity to end-users. A country's political framework is equally important, with fixed price systems, renewable quota systems and political will all playing a part. Some potential wind markets around the world are thought to have the conditions necessary to become key players in the wind industry. The emerging markets in countries such as Australia, Brazil, Canada, France, Japan and the Philippines are highlighted as examples

  6. Diverse Regular Employees and Non-regular Employment (Japanese)

    OpenAIRE

    MORISHIMA Motohiro

    2011-01-01

    Currently there are high expectations for the introduction of policies related to diverse regular employees. These policies are a response to the problem of disparities between regular and non-regular employees (part-time, temporary, contract and other non-regular employees) and will make it more likely that workers can balance work and their private lives while companies benefit from the advantages of regular employment. In this paper, I look at two issues that underlie this discussion. The ...

  7. Sparse structure regularized ranking

    KAUST Repository

    Wang, Jim Jing-Yan

    2014-04-17

    Learning ranking scores is critical for the multimedia database retrieval problem. In this paper, we propose a novel ranking score learning algorithm by exploring the sparse structure and using it to regularize ranking scores. To explore the sparse structure, we assume that each multimedia object could be represented as a sparse linear combination of all other objects, and combination coefficients are regarded as a similarity measure between objects and used to regularize their ranking scores. Moreover, we propose to learn the sparse combination coefficients and the ranking scores simultaneously. A unified objective function is constructed with regard to both the combination coefficients and the ranking scores, and is optimized by an iterative algorithm. Experiments on two multimedia database retrieval data sets demonstrate the significant improvements of the propose algorithm over state-of-the-art ranking score learning algorithms.

  8. 'Regular' and 'emergency' repair

    International Nuclear Information System (INIS)

    Luchnik, N.V.

    1975-01-01

    Experiments on the combined action of radiation and a DNA inhibitor using Crepis roots and on split-dose irradiation of human lymphocytes lead to the conclusion that there are two types of repair. The 'regular' repair takes place twice in each mitotic cycle and ensures the maintenance of genetic stability. The 'emergency' repair is induced at all stages of the mitotic cycle by high levels of injury. (author)

  9. Regularization of divergent integrals

    OpenAIRE

    Felder, Giovanni; Kazhdan, David

    2016-01-01

    We study the Hadamard finite part of divergent integrals of differential forms with singularities on submanifolds. We give formulae for the dependence of the finite part on the choice of regularization and express them in terms of a suitable local residue map. The cases where the submanifold is a complex hypersurface in a complex manifold and where it is a boundary component of a manifold with boundary, arising in string perturbation theory, are treated in more detail.

  10. The effect of breaking gravity waves on the dynamics and chemistry of the mesosphere and lower thermosphere (invited review)

    Science.gov (United States)

    Garcia, R. R.

    1986-01-01

    The influence of breaking gravity waves on the dynamics and chemical composition of the 60 to 110 km region is investigated with a two dimensional model that includes a parameterization of gravity wave momentum deposition and diffusion. The dynamical model is described by Garcia and Solomon (1983) and Solomon and Garcia (1983) and includes a complete chemical scheme for the mesosphere and lower thermosphere. The parameterization of Lindzen (1981) is used to calculate the momentum deposited and the turbulent diffusion produced by the gravity waves. It is found that wave momentum deposition drives a very vigorous mean meridional circulation, produces a very cold summer mesopause and reverse the zonal wind jets above about 85 km. The seasonal variation of the turbulent diffusion coefficient is consistent with the behavior of mesospheric turbulences inferred from MST radar echoes. The large degree of consistency between model results and various types of dynamical and chemical data supports very strongly the hypothesis that breaking gravity waves play a major role in determining the zonally-averaged dynamical and chemical structure of the 60 to 110 km region of the atmosphere.

  11. Regularizing portfolio optimization

    International Nuclear Information System (INIS)

    Still, Susanne; Kondor, Imre

    2010-01-01

    The optimization of large portfolios displays an inherent instability due to estimation error. This poses a fundamental problem, because solutions that are not stable under sample fluctuations may look optimal for a given sample, but are, in effect, very far from optimal with respect to the average risk. In this paper, we approach the problem from the point of view of statistical learning theory. The occurrence of the instability is intimately related to over-fitting, which can be avoided using known regularization methods. We show how regularized portfolio optimization with the expected shortfall as a risk measure is related to support vector regression. The budget constraint dictates a modification. We present the resulting optimization problem and discuss the solution. The L2 norm of the weight vector is used as a regularizer, which corresponds to a diversification 'pressure'. This means that diversification, besides counteracting downward fluctuations in some assets by upward fluctuations in others, is also crucial because it improves the stability of the solution. The approach we provide here allows for the simultaneous treatment of optimization and diversification in one framework that enables the investor to trade off between the two, depending on the size of the available dataset.

  12. Regularizing portfolio optimization

    Science.gov (United States)

    Still, Susanne; Kondor, Imre

    2010-07-01

    The optimization of large portfolios displays an inherent instability due to estimation error. This poses a fundamental problem, because solutions that are not stable under sample fluctuations may look optimal for a given sample, but are, in effect, very far from optimal with respect to the average risk. In this paper, we approach the problem from the point of view of statistical learning theory. The occurrence of the instability is intimately related to over-fitting, which can be avoided using known regularization methods. We show how regularized portfolio optimization with the expected shortfall as a risk measure is related to support vector regression. The budget constraint dictates a modification. We present the resulting optimization problem and discuss the solution. The L2 norm of the weight vector is used as a regularizer, which corresponds to a diversification 'pressure'. This means that diversification, besides counteracting downward fluctuations in some assets by upward fluctuations in others, is also crucial because it improves the stability of the solution. The approach we provide here allows for the simultaneous treatment of optimization and diversification in one framework that enables the investor to trade off between the two, depending on the size of the available dataset.

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

    International Nuclear Information System (INIS)

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

    1988-01-01

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

  14. Regular Single Valued Neutrosophic Hypergraphs

    Directory of Open Access Journals (Sweden)

    Muhammad Aslam Malik

    2016-12-01

    Full Text Available In this paper, we define the regular and totally regular single valued neutrosophic hypergraphs, and discuss the order and size along with properties of regular and totally regular single valued neutrosophic hypergraphs. We also extend work on completeness of single valued neutrosophic hypergraphs.

  15. The geometry of continuum regularization

    International Nuclear Information System (INIS)

    Halpern, M.B.

    1987-03-01

    This lecture is primarily an introduction to coordinate-invariant regularization, a recent advance in the continuum regularization program. In this context, the program is seen as fundamentally geometric, with all regularization contained in regularized DeWitt superstructures on field deformations

  16. 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

  17. Annotation of Regular Polysemy

    DEFF Research Database (Denmark)

    Martinez Alonso, Hector

    Regular polysemy has received a lot of attention from the theory of lexical semantics and from computational linguistics. However, there is no consensus on how to represent the sense of underspecified examples at the token level, namely when annotating or disambiguating senses of metonymic words...... and metonymic. We have conducted an analysis in English, Danish and Spanish. Later on, we have tried to replicate the human judgments by means of unsupervised and semi-supervised sense prediction. The automatic sense-prediction systems have been unable to find empiric evidence for the underspecified sense, even...

  18. Regularity of Minimal Surfaces

    CERN Document Server

    Dierkes, Ulrich; Tromba, Anthony J; Kuster, Albrecht

    2010-01-01

    "Regularity of Minimal Surfaces" begins with a survey of minimal surfaces with free boundaries. Following this, the basic results concerning the boundary behaviour of minimal surfaces and H-surfaces with fixed or free boundaries are studied. In particular, the asymptotic expansions at interior and boundary branch points are derived, leading to general Gauss-Bonnet formulas. Furthermore, gradient estimates and asymptotic expansions for minimal surfaces with only piecewise smooth boundaries are obtained. One of the main features of free boundary value problems for minimal surfaces is t

  19. Regularities of radiation heredity

    International Nuclear Information System (INIS)

    Skakov, M.K.; Melikhov, V.D.

    2001-01-01

    One analyzed regularities of radiation heredity in metals and alloys. One made conclusion about thermodynamically irreversible changes in structure of materials under irradiation. One offers possible ways of heredity transmittance of radiation effects at high-temperature transformations in the materials. Phenomenon of radiation heredity may be turned to practical use to control structure of liquid metal and, respectively, structure of ingot via preliminary radiation treatment of charge. Concentration microheterogeneities in material defect structure induced by preliminary irradiation represent the genetic factor of radiation heredity [ru

  20. Global effect of auroral particle and Joule heating in the undisturbed thermosphere

    Science.gov (United States)

    Hinton, B. B.

    1978-01-01

    From the compositional variations observed with the neutral atmosphere composition experiment on OGO 6 and a simplified model of thermospheric dynamics, global average values of non-EUV heating are deduced. These are 0.19-0.25 mW/sq m for quiet days and 0.44-0.58 mW/sq m for ordinary days.

  1. The MIGHTI Wind Retrieval Algorithm: Description and Verification

    Science.gov (United States)

    Harding, Brian J.; Makela, Jonathan J.; Englert, Christoph R.; Marr, Kenneth D.; Harlander, John M.; England, Scott L.; Immel, Thomas J.

    2017-10-01

    We present an algorithm to retrieve thermospheric wind profiles from measurements by the Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instrument on NASA's Ionospheric Connection Explorer (ICON) mission. MIGHTI measures interferometric limb images of the green and red atomic oxygen emissions at 557.7 nm and 630.0 nm, spanning 90-300 km. The Doppler shift of these emissions represents a remote measurement of the wind at the tangent point of the line of sight. Here we describe the algorithm which uses these images to retrieve altitude profiles of the line-of-sight wind. By combining the measurements from two MIGHTI sensors with perpendicular lines of sight, both components of the vector horizontal wind are retrieved. A comprehensive truth model simulation that is based on TIME-GCM winds and various airglow models is used to determine the accuracy and precision of the MIGHTI data product. Accuracy is limited primarily by spherical asymmetry of the atmosphere over the spatial scale of the limb observation, a fundamental limitation of space-based wind measurements. For 80% of the retrieved wind samples, the accuracy is found to be better than 5.8 m/s (green) and 3.5 m/s (red). As expected, significant errors are found near the day/night boundary and occasionally near the equatorial ionization anomaly, due to significant variations of wind and emission rate along the line of sight. The precision calculation includes pointing uncertainty and shot, read, and dark noise. For average solar minimum conditions, the expected precision meets requirements, ranging from 1.2 to 4.7 m/s.

  2. On the Turbulent Mixing in Horizontal Axis Wind Turbine Wakes

    NARCIS (Netherlands)

    Lignarolo, L.E.M.

    2016-01-01

    The wake flow of a horizontal axis wind turbine is characterised by lower wind speed and higher turbulence than the free-stream conditions. When clustered in large wind farms, wind turbines regularly operate inside the wake of one or more upstream machines. This is a major cause of energy production

  3. Where does the Thermospheric Ionospheric GEospheric Research (TIGER) Program go?

    Science.gov (United States)

    Schmidtke, G.; Avakyan, S. V.; Berdermann, J.; Bothmer, V.; Cessateur, G.; Ciraolo, L.; Didkovsky, L.; Dudok de Wit, T.; Eparvier, F. G.; Gottwald, A.; Haberreiter, M.; Hammer, R.; Jacobi, Ch.; Jakowski, N.; Kretzschmar, M.; Lilensten, J.; Pfeifer, M.; Radicella, S. M.; Schäfer, R.; Schmidt, W.; Solomon, S. C.; Thuillier, G.; Tobiska, W. K.; Wieman, S.; Woods, T. N.

    2015-10-01

    At the 10th Thermospheric Ionospheric GEospheric Research (TIGER/COSPAR) symposium held in Moscow in 2014 the achievements from the start of TIGER in 1998 were summarized. During that period, great progress was made in measuring, understanding, and modeling the highly variable UV-Soft X-ray (XUV) solar spectral irradiance (SSI), and its effects on the upper atmosphere. However, after more than 50 years of work the radiometric accuracy of SSI observation is still an issue and requires further improvement. Based on the extreme ultraviolet (EUV) data from the SOLAR/SolACES, and SDO/EVE instruments, we present a combined data set for the spectral range from 16.5 to 105.5 nm covering a period of 3.5 years from 2011 through mid of 2014. This data set is used in ionospheric modeling of the global Total Electron Content (TEC), and in validating EUV SSI modeling. For further investigations the period of 3.5 years is being extended to about 12 years by including data from SOHO/SEM and TIMED/SEE instruments. Similarly, UV data are used in modeling activities. After summarizing the results, concepts are proposed for future real-time SSI measurements with in-flight calibration as experienced with the ISS SOLAR payload, for the development of a space weather camera for observing and investigating space weather phenomena in real-time, and for providing data sets for SSI and climate modeling. Other planned topics are the investigation of the relationship between solar EUV/UV and visible/near-infrared emissions, the impact of X-rays on the upper atmosphere, the development of solar EUV/UV indices for different applications, and establishing a shared TIGER data system for EUV/UV SSI data distribution and real-time streaming, also taking into account the achievements of the FP7 SOLID (First European SOLar Irradiance Data Exploitation) project. For further progress it is imperative that coordinating activities in this special field of solar-terrestrial relations and solar physics is

  4. First Simultaneous and Common-Volume Lidar Observations of Na and Fe Metals, Temperatures, and Vertical Winds in Antarctica

    Science.gov (United States)

    Chu, X.

    2017-12-01

    A new STAR Na Doppler lidar will be installed to Arrival Heights near McMurdo Station, Antarctica in October 2017. This new lidar will be operated next to an existing Fe Boltzmann lidar to make simultaneous and common-volume measurements of metal Na and Fe layers, neutral temperatures, and vertical winds in the mesosphere and thermosphere, up to nearly 200 km. These measurements will be used to study a variety of science topics, e.g., the meteoric metal layers, wave dynamics, polar mesospheric clouds, constituent and heat fluxes, and cosmic dust. The discoveries of thermospheric neutral Fe layers and persistent gravity waves by the Fe Boltzmann lidar observations has opened a new door to explore the space-atmosphere interactions with ground-based instruments, especially in the least understood but crucially important altitude range of 100-200 km. These neutral metal layers provide excellent tracers for modern resonance lidars to measure the neutral wind and temperature directly. Even more exciting, the neutral metal layers in the thermosphere provide a natural laboratory to test our fundamental understandings of the atmosphere-ionosphere-magnetosphere coupling and processes. This paper will report the first summer results from the simultaneous Na and Fe lidar observations from Antarctica, and highlight important discoveries made by the Fe lidar during its first seven years of campaign at McMurdo. A thermosphere-ionosphere Fe/Fe+ (TIFe) model will be introduced to explain the TIFe layers in Antarctica.

  5. Wind Energy

    International Nuclear Information System (INIS)

    Rodriguez D, J.M.

    1998-01-01

    The general theory of the wind energy conversion systems is presented. The availability of the wind resource in Colombia and the ranges of the speed of the wind in those which is possible economically to use the wind turbines are described. It is continued with a description of the principal technological characteristics of the wind turbines and are split into wind power and wind-powered pumps; and its use in large quantities grouped in wind farms or in autonomous systems. Finally, its costs and its environmental impact are presented

  6. Effective field theory dimensional regularization

    International Nuclear Information System (INIS)

    Lehmann, Dirk; Prezeau, Gary

    2002-01-01

    A Lorentz-covariant regularization scheme for effective field theories with an arbitrary number of propagating heavy and light particles is given. This regularization scheme leaves the low-energy analytic structure of Greens functions intact and preserves all the symmetries of the underlying Lagrangian. The power divergences of regularized loop integrals are controlled by the low-energy kinematic variables. Simple diagrammatic rules are derived for the regularization of arbitrary one-loop graphs and the generalization to higher loops is discussed

  7. Effective field theory dimensional regularization

    Science.gov (United States)

    Lehmann, Dirk; Prézeau, Gary

    2002-01-01

    A Lorentz-covariant regularization scheme for effective field theories with an arbitrary number of propagating heavy and light particles is given. This regularization scheme leaves the low-energy analytic structure of Greens functions intact and preserves all the symmetries of the underlying Lagrangian. The power divergences of regularized loop integrals are controlled by the low-energy kinematic variables. Simple diagrammatic rules are derived for the regularization of arbitrary one-loop graphs and the generalization to higher loops is discussed.

  8. 75 FR 76006 - Regular Meeting

    Science.gov (United States)

    2010-12-07

    ... FARM CREDIT SYSTEM INSURANCE CORPORATION Regular Meeting AGENCY: Farm Credit System Insurance Corporation Board. ACTION: Regular meeting. SUMMARY: Notice is hereby given of the regular meeting of the Farm Credit System Insurance Corporation Board (Board). Date and Time: The meeting of the Board will be held...

  9. Effects of the midnight temperature maximum observed in the thermosphere-ionosphere over the northeast of Brazil

    Science.gov (United States)

    Figueiredo, Cosme Alexandre O. B.; Buriti, Ricardo A.; Paulino, Igo; Meriwether, John W.; Makela, Jonathan J.; Batista, Inez S.; Barros, Diego; Medeiros, Amauri F.

    2017-08-01

    The midnight temperature maximum (MTM) has been observed in the lower thermosphere by two Fabry-Pérot interferometers (FPIs) at São João do Cariri (7.4° S, 36.5° W) and Cajazeiras (6.9° S, 38.6° W) during 2011, when the solar activity was moderate and the solar flux was between 90 and 155 SFU (1 SFU = 10-22 W m-2 Hz-1). The MTM is studied in detail using measurements of neutral temperature, wind and airglow relative intensity of OI630.0 nm (referred to as OI6300), and ionospheric parameters, such as virtual height (h'F), the peak height of the F2 region (hmF2), and critical frequency of the F region (foF2), which were measured by a Digisonde instrument (DPS) at Eusébio (3.9° S, 38.4° W; geomagnetic coordinates 7.31° S, 32.40° E for 2011). The MTM peak was observed mostly along the year, except in May, June, and August. The amplitudes of the MTM varied from 64 ± 46 K in April up to 144 ± 48 K in October. The monthly temperature average showed a phase shift in the MTM peak around 0.25 h in September to 2.5 h in December before midnight. On the other hand, in February, March, and April the MTM peak occurred around midnight. International Reference Ionosphere 2012 (IRI-2012) model was compared to the neutral temperature observations and the IRI-2012 model failed in reproducing the MTM peaks. The zonal component of neutral wind flowed eastward the whole night; regardless of the month and the magnitude of the zonal wind, it was typically within the range of 50 to 150 m s-1 during the early evening. The meridional component of the neutral wind changed its direction over the months: from November to February, the meridional wind in the early evening flowed equatorward with a magnitude between 25 and 100 m s-1; in contrast, during the winter months, the meridional wind flowed to the pole within the range of 0 to -50 m s-1. Our results indicate that the reversal (changes in equator to poleward flow) or abatement of the meridional winds is an important factor in

  10. MIPAS temperature from the stratosphere to the lower thermosphere: Comparison of vM21 with ACE-FTS, MLS, OSIRIS, SABER, SOFIE and lidar measurements

    Directory of Open Access Journals (Sweden)

    M. García-Comas

    2014-11-01

    Full Text Available We present vM21 MIPAS temperatures from the lower stratosphere to the lower thermosphere, which cover all optimized resolution measurements performed by MIPAS in the middle-atmosphere, upper-atmosphere and noctilucent-cloud modes during its lifetime, i.e., from January 2005 to April 2012. The main upgrades with respect to the previous version of MIPAS temperatures (vM11 are the update of the spectroscopic database, the use of a different climatology of atomic oxygen and carbon dioxide, and the improvement in important technical aspects of the retrieval setup (temperature gradient along the line of sight and offset regularizations, apodization accuracy. Additionally, an updated version of ESA-calibrated L1b spectra (5.02/5.06 is used. The vM21 temperatures correct the main systematic errors of the previous version because they provide on average a 1–2 K warmer stratopause and middle mesosphere, and a 6–10 K colder mesopause (except in high-latitude summers and lower thermosphere. These lead to a remarkable improvement in MIPAS comparisons with ACE-FTS, MLS, OSIRIS, SABER, SOFIE and the two Rayleigh lidars at Mauna Loa and Table Mountain, which, with a few specific exceptions, typically exhibit differences smaller than 1 K below 50 km and than 2 K at 50–80 km in spring, autumn and winter at all latitudes, and summer at low to midlatitudes. Differences in the high-latitude summers are typically smaller than 1 K below 50 km, smaller than 2 K at 50–65 km and 5 K at 65–80 km. Differences between MIPAS and the other instruments in the mid-mesosphere are generally negative. MIPAS mesopause is within 4 K of the other instruments measurements, except in the high-latitude summers, when it is within 5–10 K, being warmer there than SABER, MLS and OSIRIS and colder than ACE-FTS and SOFIE. The agreement in the lower thermosphere is typically better than 5 K, except for high latitudes during spring and summer, when MIPAS usually exhibits larger

  11. On the Origins of the Intercorrelations Between Solar Wind Variables

    Science.gov (United States)

    Borovsky, Joseph E.

    2018-01-01

    It is well known that the time variations of the diverse solar wind variables at 1 AU (e.g., solar wind speed, density, proton temperature, electron temperature, magnetic field strength, specific entropy, heavy-ion charge-state densities, and electron strahl intensity) are highly intercorrelated with each other. In correlation studies of the driving of the Earth's magnetosphere-ionosphere-thermosphere system by the solar wind, these solar wind intercorrelations make determining cause and effect very difficult. In this report analyses of solar wind spacecraft measurements and compressible-fluid computer simulations are used to study the origins of the solar wind intercorrelations. Two causes are found: (1) synchronized changes in the values of the solar wind variables as the plasma types of the solar wind are switched by solar rotation and (2) dynamic interactions (compressions and rarefactions) in the solar wind between the Sun and the Earth. These findings provide an incremental increase in the understanding of how the Sun-Earth system operates.

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

    Science.gov (United States)

    2017-12-29

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

  13. Stormtime Magnetosphere-Ionosphere-Thermosphere Interactions and Dynamics

    Science.gov (United States)

    2013-03-13

    discussed the possibility of deriving continuous measurements of Dst using the science grade tri-axial fluxgate magnetometer on the C/NOFS satellite in...Changes in Solar Wind Pressure ..............… ........ 6 3.3. Development of a DST Proxy from DMSP Magnetometer Measurements ............... ........ 7...energetic particle fluxes, electric field and magnetometer measurements from the four spacecraft identified regions at and near the magnetopause where MHD

  14. Selection of regularization parameter for l1-regularized damage detection

    Science.gov (United States)

    Hou, Rongrong; Xia, Yong; Bao, Yuequan; Zhou, Xiaoqing

    2018-06-01

    The l1 regularization technique has been developed for structural health monitoring and damage detection through employing the sparsity condition of structural damage. The regularization parameter, which controls the trade-off between data fidelity and solution size of the regularization problem, exerts a crucial effect on the solution. However, the l1 regularization problem has no closed-form solution, and the regularization parameter is usually selected by experience. This study proposes two strategies of selecting the regularization parameter for the l1-regularized damage detection problem. The first method utilizes the residual and solution norms of the optimization problem and ensures that they are both small. The other method is based on the discrepancy principle, which requires that the variance of the discrepancy between the calculated and measured responses is close to the variance of the measurement noise. The two methods are applied to a cantilever beam and a three-story frame. A range of the regularization parameter, rather than one single value, can be determined. When the regularization parameter in this range is selected, the damage can be accurately identified even for multiple damage scenarios. This range also indicates the sensitivity degree of the damage identification problem to the regularization parameter.

  15. Modeling Study of the Geospace System Response to the Solar Wind Dynamic Pressure Enhancement on 17 March 2015

    Science.gov (United States)

    Ozturk, D. S.; Zou, S.; Ridley, A. J.; Slavin, J. A.

    2018-04-01

    The global magnetosphere-ionosphere-thermosphere system is intrinsically coupled and susceptible to external drivers such as solar wind dynamic pressure enhancements. In order to understand the large-scale dynamic processes in the magnetosphere-ionosphere-thermosphere system due to the compression from the solar wind, the 17 March 2015 sudden commencement was studied in detail using global numerical models. This storm was one of the most geoeffective events of the solar cycle 24 with a minimum Dst of -222 nT. The Wind spacecraft recorded a 10-nPa increment in the solar wind dynamic pressure, while the interplanetary magnetic field BZ became further northward. The University of Michigan Block-Adaptive-Tree Solar wind Roe-type Upwind Scheme global magnetohydrodynamic code was utilized to study the generation and propagation of perturbations associated with the compression of the magnetosphere system. In addition, the high-resolution electric potential and auroral power output from the magnetohydrodynamic model was used to drive the global ionosphere-thermosphere model to investigate the ionosphere-thermosphere system response to pressure enhancement. During the compression, the electric potentials and convection patterns in the polar ionosphere were significantly altered when the preliminary impulse and main impulse field-aligned currents moved from dayside to nightside. As a result of enhanced frictional heating, plasma and neutral temperatures increased at the locations where the flow speeds were enhanced, whereas the electron density dropped at these locations. In particular, the region between the preliminary impulse and main impulse field-aligned currents experienced the most significant heating with 1000-K ion temperature increase and 20-K neutral temperature increase within 2 min. Comparison of the simulation results with the Poker Flat Incoherent Scatter Radar observations showed reasonable agreements despite underestimated magnitudes.

  16. Ensemble manifold regularization.

    Science.gov (United States)

    Geng, Bo; Tao, Dacheng; Xu, Chao; Yang, Linjun; Hua, Xian-Sheng

    2012-06-01

    We propose an automatic approximation of the intrinsic manifold for general semi-supervised learning (SSL) problems. Unfortunately, it is not trivial to define an optimization function to obtain optimal hyperparameters. Usually, cross validation is applied, but it does not necessarily scale up. Other problems derive from the suboptimality incurred by discrete grid search and the overfitting. Therefore, we develop an ensemble manifold regularization (EMR) framework to approximate the intrinsic manifold by combining several initial guesses. Algorithmically, we designed EMR carefully so it 1) learns both the composite manifold and the semi-supervised learner jointly, 2) is fully automatic for learning the intrinsic manifold hyperparameters implicitly, 3) is conditionally optimal for intrinsic manifold approximation under a mild and reasonable assumption, and 4) is scalable for a large number of candidate manifold hyperparameters, from both time and space perspectives. Furthermore, we prove the convergence property of EMR to the deterministic matrix at rate root-n. Extensive experiments over both synthetic and real data sets demonstrate the effectiveness of the proposed framework.

  17. Gravity wave propagation through a large semidiurnal tide and instabilities in the mesosphere and lower thermosphere during the winter 2003 MaCWAVE rocket campaign

    Directory of Open Access Journals (Sweden)

    B. P. Williams

    2006-07-01

    Full Text Available The winter MaCWAVE (Mountain and convective waves ascending vertically rocket campaign took place in January 2003 at Esrange, Sweden and the ALOMAR observatory in Andenes, Norway. The campaign combined balloon, lidar, radar, and rocket measurements to produce full temperature and wind profiles from the ground to 105 km. This paper will investigate gravity wave propagation in the mesosphere and lower thermosphere using data from the Weber sodium lidar on 28–29 January 2003. A very large semidiurnal tide was present in the zonal wind above 80 km that grew to a 90 m/s amplitude at 100 km. The superposition of smaller-scale gravity waves and the tide caused small regions of possible convective or shear instabilities to form along the downward progressing phase fronts of the tide. The gravity waves had periods ranging from the Nyquist period of 30 min up to 4 h, vertical wavelengths ranging from 7 km to more than 20 km, and the frequency spectra had the expected –5/3 slope. The dominant gravity waves had long vertical wavelengths and experienced rapid downward phase progression. The gravity wave variance grew exponentially with height up from 86 to 94 km, consistent with the measured scale height, suggesting that the waves were not dissipated strongly by the tidal gradients and resulting unstable regions in this altitude range.

  18. Extension of the MSIS thermosphere model into the middle and lower atmosphere

    International Nuclear Information System (INIS)

    Hedin, A.E.

    1991-01-01

    The MSIS-86 empirical model has been revised in the lower thermosphere and extended into the mesosphere and lower atmosphere to provide a single analytic model for calculating temperature and density profiles representative of the climatological average for various geophysical conditions. Tabulations from the Handbook for MAP 16 are the primary guide for the lower atmosphere and are supplemented by historical rocket and incoherent scatter data in the upper mesosphere and lower thermosphere. Low-order spherical harmonics and Fourier series are used to describe the major variations throughout the atmosphere including latitude, annual, semiannual, and simplified local time and longitude variations. While month to month details cannot be completely represented, lower atmosphere temperature data are fit to an overall standard deviation of 3 K and pressure to 2%. Comparison with rocket and other data indicates that the model represents current knowledge of the climatological average reasonably well, although there is some conflict as to details near the mesopause

  19. The Effects of a Geomagnetic Storm on Thermospheric Circulation.

    Science.gov (United States)

    1987-01-01

    frequency. .*. p air density. olU 2 Pedersen and Hall conductivities. a P height intergrated Pedersen conductivity. horizontal viscous stress. * east...equations need to be ex- ,n~panded upon. The energy density is: (.2 1 + V2). I~i~iCPT +<V 2 . The horizontal viscous stress, including molecular and...with Z=0 at 80 km and Z=14.4 at 450 km for a total of 49 levels each 0.3 of a scale height apart. Also, the horizontal wind velocity, gas energy

  20. How the effects of winds and electric fields in F2-layer storms vary with latitude and longitude - A theoretical study

    Science.gov (United States)

    Mendillo, M.; He, X.-Q.; Rishbeth, H.

    1992-01-01

    The effects of thermospheric winds and electric fields on the ionospheric F2-layer are controlled by the geometry of the magnetic field, and so vary with latitude and longitude. A simple model of the daytime F2-layer is adopted and the effects at midlatitudes (25-65 deg geographic) of three processes that accompany geomagnetic storms: (1) thermospheric changes due to auroral heating; (2) equatorward winds that tend to cancel the quiet-day poleward winds; and (3) the penetration of magnetospheric electric fields are studied. At +/- 65 deg, the effects of heating and electric fields are strongest in the longitudes toward which the geomagnetic dipole is tilted, i.e., the North American and the South Indian Ocean sectors. Because of the proximity of the geomagnetic equator to the East Asian and South American sectors, the reverse is true at +/- 25 deg.

  1. Lower thermospheric nitric oxide concentrations derived from WINDII observations of the green nightglow continuum at 553.1 nm

    Directory of Open Access Journals (Sweden)

    C. H. A. von Savigny

    1999-11-01

    Full Text Available Vertical profiles of nitric oxide in the altitude range 90 to 105 km are derived from 553 nm nightglow continuum measurements made with the Wind Imaging Interferometer (WINDII on the Upper Atmosphere Research Satellite (UARS. The profiles are derived under the assumption that the continuum emission is due entirely to the NO+O air afterglow reaction. Vertical profiles of the atomic oxygen density, which are required to determine the nitric oxide concentrations, are derived from coordinated WINDII measurements of the atomic oxygen OI 557.7 nm nightglow emission. Data coverage for local solar times ranging from 20 h to 04 h, and latitudes ranging from 42°S to 42°N, is achieved by zonally averaging and binning data obtained on 18 nights during a two-month period extending from mid-November 1992 until mid-January 1993. The derived nitric oxide concentrations are significantly smaller than those obtained from rocket measurements of the airglow continuum but they do compare well with model expectations and nitric oxide densities measured using the resonance fluorescence technique on the Solar Mesosphere Explorer satellite. The near-global coverage of the WINDII observations and the similarities to the nitric oxide global morphology established from other satellite measurements strongly suggests that the NO+O reaction is the major source of the continuum near 553 nm and that there is no compelling reason to invoke additional sources of continuum emission in this immediate spectral region.Key words. Atmospheric composition and structure (airglow and aurora; thermosphere – composition and chemistry; instruments and techniques

  2. Simulations of the Boreal Winter Upper Mesosphere and Lower Thermosphere With Meteorological Specifications in SD-WACCM-X

    Science.gov (United States)

    Sassi, Fabrizio; Siskind, David E.; Tate, Jennifer L.; Liu, Han-Li; Randall, Cora E.

    2018-04-01

    We investigate the benefit of high-altitude nudging in simulations of the structure and short-term variability of the upper mesosphere and lower thermosphere (UMLT) dynamical meteorology during boreal winter, specifically around the time of the January 2009 sudden stratospheric warming. We compare simulations using the Specified Dynamics, Whole Atmosphere Community Climate Model, extended version, nudged using atmospheric specifications generated by the Navy Operational Global Atmospheric Prediction System, Advanced Level Physics High Altitude. Two sets of simulations are carried out: one uses nudging over a vertical domain from 0 to 90 km; the other uses nudging over a vertical domain from 0 to 50 km. The dynamical behavior is diagnosed from ensemble mean and standard deviation of winds, temperature, and zonal accelerations due to resolved and parameterized waves. We show that the dynamical behavior of the UMLT is quite different in the two experiments, with prominent differences in the structure and variability of constituent transport. We compare the results of our numerical experiments to observations of carbon monoxide by the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer to show that the high-altitude nudging is capable of reproducing with high fidelity the observed variability, and traveling planetary waves are a crucial component of the dynamics. The results of this study indicate that to capture the key physical processes that affect short-term variability (defined as the atmospheric behavior within about 10 days of a stratospheric warming) in the UMLT, specification of the atmospheric state in the stratosphere alone is not sufficient, and upper atmospheric specifications are needed.

  3. Numerical modeling study of the momentum deposition of small amplitude gravity waves in the thermosphere

    Energy Technology Data Exchange (ETDEWEB)

    Liu, X. [Chinese Academy of Sciences, Beijing (China). State Key Lab. of Space Weather; Henan Normal Univ., Xinxiang (China). College of Mathematics and Information Science; Xu, J. [Chinese Academy of Sciences, Beijing (China). State Key Lab. of Space Weather; Yue, J. [National Center for Atmospheric Research, Boulder, CO (United States). High Altitude Observatory; Hampton Univ., VA (United States). Atmospheric and Planetary Sciences; Vadas, S.L. [North West Research Associates, Inc., Boulder, CO (United States)

    2013-03-01

    We study the momentum deposition in the thermosphere from the dissipation of small amplitude gravity waves (GWs) within a wave packet using a fully nonlinear two-dimensional compressible numerical model. The model solves the nonlinear propagation and dissipation of a GW packet from the stratosphere into the thermosphere with realistic molecular viscosity and thermal diffusivity for various Prandtl numbers. The numerical simulations are performed for GW packets with initial vertical wavelengths ({lambda}{sub z}) ranging from 5 to 50 km. We show that {lambda}{sub z} decreases in time as a GW packet dissipates in the thermosphere, in agreement with the ray trace results of Vadas and Fritts (2005) (VF05). We also find good agreement for the peak height of the momentum flux (z{sub diss}) between our simulations and VF05 for GWs with initial {lambda}{sub z} {<=} 2{pi}H in an isothermal, windless background, where H is the density scale height.We also confirm that z{sub diss} increases with increasing Prandtl number. We include eddy diffusion in the model, and find that the momentum deposition occurs at lower altitudes and has two separate peaks for GW packets with small initial {lambda}{sub z}. We also simulate GW packets in a non-isothermal atmosphere. The net {lambda}{sub z} profile is a competition between its decrease from viscosity and its increase from the increasing background temperature. We find that the wave packet disperses more in the non-isothermal atmosphere, and causes changes to the momentum flux and {lambda}{sub z} spectra at both early and late times for GW packets with initial {lambda}{sub z} {>=} 10 km. These effects are caused by the increase in T in the thermosphere, and the decrease in T near the mesopause. (orig.)

  4. Solar cycle variability of nonmigrating tides in the infrared cooling of the thermosphere

    Science.gov (United States)

    Nischal, N.; Oberheide, J.; Mlynczak, M. G.; Marsh, D. R.

    2017-12-01

    Nitric Oxide (NO) at 5.3 μm and Carbon dioxide (CO2) at 15 μm are the major infrared emissions responsible for the radiative cooling of the thermosphere. We study the impact of two important diurnal nonmigrating tides, the DE2 and DE3, on NO and CO2 infrared emissions over a complete solar cycle (2002-2013) by (i) analyzing NO and CO2 cooling rate data from SABER and (ii) photochemical modeling using dynamical tides from a thermospheric empirical tidal model, CTMT. Both observed and modeled results show that the NO cooling rate amplitudes for DE2 and DE3 exhibit strong solar cycle dependence. NO 5.3 μm cooling rate tides are relatively unimportant for the infrared energy budget during solar minimum but important during solar maximum. On the other hand DE2 and DE3 in CO2 show comparatively small variability over a solar cycle. CO2 15 μm cooling rate tides remain, to a large extent, constant between solar minimum and maximum. This different responses by NO and CO2 emissions to the DE2 and DE3 during a solar cycle comes form the fact that the collisional reaction rate for NO is highly sensitive to the temperature comparative to that for CO2. Moreover, the solar cycle variability of these nonmigrating tides in thermospheric infrared emissions shows a clear QBO signals substantiating the impact of tropospheric weather system on the energy budget of the thermosphere. The relative contribution from the individual tidal drivers; temperature, density and advection to the observed DE2 and DE3 tides does not vary much over the course of the solar cycle, and this is true for both NO and CO2 emissions.

  5. Partitioning of Electromagnetic Energy Inputs to the Thermosphere during Geomagnetic Disturbances

    Science.gov (United States)

    2012-06-01

    boundary of a local flux tube volume is an equipotential . Figure 4 contains maps of Poynting flux normal to a 500 km altitude surface and maps of height...as a cell quantity throughout its computational volume, we are able to generate maps of the Poynting flux, ⃗ ⃗⃗⃗⃗⃗⃗ , on altitude surfaces at...the top of the thermosphere. We used separate modules to integrate the Poynting flux over this surface to compute the total electromagnetic energy

  6. Venus thermosphere and exosphere - First satellite drag measurements of an extraterrestrial atmosphere

    Science.gov (United States)

    Keating, G. M.; Tolson, R. H.; Hinson, E. W.

    1979-01-01

    Atmospheric drag measurements obtained from the study of the orbital decay of Pioneer Venus I indicate that atomic oxygen predominates in the Venus atmosphere above 160 kilometers. Drag measurements give evidence that conditions characteristic of a planetary thermosphere disappear near sundown, with inferred exospheric temperatures sharply dropping from approximately 300 K to less than 150 K. Observed densities are generally lower than given by theoretical models.

  7. A statistical survey of heat input parameters into the cusp thermosphere

    Science.gov (United States)

    Moen, J. I.; Skjaeveland, A.; Carlson, H. C.

    2017-12-01

    Based on three winters of observational data, we present those ionosphere parameters deemed most critical to realistic space weather ionosphere and thermosphere representation and prediction, in regions impacted by variability in the cusp. The CHAMP spacecraft revealed large variability in cusp thermosphere densities, measuring frequent satellite drag enhancements, up to doublings. The community recognizes a clear need for more realistic representation of plasma flows and electron densities near the cusp. Existing average-value models produce order of magnitude errors in these parameters, resulting in large under estimations of predicted drag. We fill this knowledge gap with statistics-based specification of these key parameters over their range of observed values. The EISCAT Svalbard Radar (ESR) tracks plasma flow Vi , electron density Ne, and electron, ion temperatures Te, Ti , with consecutive 2-3 minute windshield-wipe scans of 1000x500 km areas. This allows mapping the maximum Ti of a large area within or near the cusp with high temporal resolution. In magnetic field-aligned mode the radar can measure high-resolution profiles of these plasma parameters. By deriving statistics for Ne and Ti , we enable derivation of thermosphere heating deposition under background and frictional-drag-dominated magnetic reconnection conditions. We separate our Ne and Ti profiles into quiescent and enhanced states, which are not closely correlated due to the spatial structure of the reconnection foot point. Use of our data-based parameter inputs can make order of magnitude corrections to input data driving thermosphere models, enabling removal of previous two fold drag errors.

  8. Methodological possibilities for using the electron and ion energy balance in thermospheric complex measurements

    International Nuclear Information System (INIS)

    Serafimov, K.B.; Serafimova, M.K.

    1991-01-01

    Combination of ground based measurements for determination of basic thermospheric characteristics is proposed . An expression for the energy transport between components of space plasma is also derived and discussed within the framework of the presented methodology which could be devided into the folowing major sections: 1) application of ionosonde, absorption measurements, TEC-measurements using Faradey radiation or the differential Doppler effect; 2) ground-based airglow measurements; 3) airglow and palsma satelite measurements. 9 refs

  9. Response of the mesosphere-thermosphere-ionosphere system to global change - CAWSES-II contribution

    Czech Academy of Sciences Publication Activity Database

    Laštovička, Jan; Beig, G.; Marsh, R. D.

    2014-01-01

    Roč. 1, 11 November (2014), 21/ 1-21/ 19 ISSN 2197-4284 R&D Projects: GA ČR GAP209/10/1792; GA MŠk LD12070 Institutional support: RVO:68378289 Keywords : mesosphere * thermosphere * ionosphere * long-term trends * climatic change Subject RIV: DG - Athmosphere Sciences, Meteorology http://www.progearthplanetsci.com/content/1/1/21

  10. Adaptive Regularization of Neural Classifiers

    DEFF Research Database (Denmark)

    Andersen, Lars Nonboe; Larsen, Jan; Hansen, Lars Kai

    1997-01-01

    We present a regularization scheme which iteratively adapts the regularization parameters by minimizing the validation error. It is suggested to use the adaptive regularization scheme in conjunction with optimal brain damage pruning to optimize the architecture and to avoid overfitting. Furthermo......, we propose an improved neural classification architecture eliminating an inherent redundancy in the widely used SoftMax classification network. Numerical results demonstrate the viability of the method...

  11. In situ measurements of hydrogen concentration and flux between 160 and 300 km in the thermosphere

    International Nuclear Information System (INIS)

    Breig, E.L.; Hanson, W.B.; Hoffman, J.H.; Kayser, D.C.

    1976-01-01

    Thermospheric concentrations of neutral atomic hydrogen near and below the F peak are directly related to H + , O + and atomic oxygen concentrations through the charge exchange equilibrium that is established between hydrogen and oxygen at these altitudes. This chemical relationship, together with in situ measurements of ionospheric and neutral atmospheric concentrations by instrumentation on board the Atmosphere Explorer C satellite, is utilized to investigate properties of neutral hydrogen at altitudes below 200 km where vertical diffusion strongly affects the hydrogen distribution. Data are discussed for a set of satellite orbits during quiet geomagnetic and solar conditions in February 1974; the resultant altitude variation of the derived hydrogen concentrations applies specifically to early afternoon at low 10 5 atoms/cm 3 is observed for these conditions at 300 km. At lower altitudes the concentration profiles are interpreted in terms of vertical hydrogen flow. The resultant daytime flux in the thermosphere is estimated to be (3.2 +- 1.0) x 10 8 atoms/cm 2 s. The present observations thus support theoretical estimates and model calculations of large hydrogen flow upward from the region below 100 km. They also support the concept of daytime thermospheric loss process of greater magnitude than the traditional evaporative escape mechanism

  12. Evidence for Solar Cycle Influence on the Infrared Energy Budget and Radiative Cooling of the Thermosphere

    Science.gov (United States)

    Mlynczak, Martin G.; Martin-Torres, F. Javier; Marshall, B. Thomas; Thompson, R. Earl; Williams, Joshua; Turpin, TImothy; Kratz, D. P.; Russell, James M.; Woods, Tom; Gordley, Larry L.

    2007-01-01

    We present direct observational evidence for solar cycle influence on the infrared energy budget and radiative cooling of the thermosphere. By analyzing nearly five years of data from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument, we show that the annual mean infrared power radiated by the nitric oxide (NO) molecule at 5.3 m has decreased by a factor of 2.9. This decrease is correlated (r = 0.96) with the decrease in the annual mean F10.7 solar index. Despite the sharp decrease in radiated power (which is equivalent to a decrease in the vertical integrated radiative cooling rate), the variability of the power as given in the standard deviation of the annual means remains approximately constant. A simple relationship is shown to exist between the infrared power radiated by NO and the F10.7 index, thus providing a fundamental relationship between solar activity and the thermospheric cooling rate for use in thermospheric models. The change in NO radiated power is also consistent with changes in absorbed ultraviolet radiation over the same time period.

  13. Properties of the mesosphere and thermosphere and comparison with CIRA 72

    Science.gov (United States)

    Champion, K. S. W.

    Exospheric temperatures of several reference atmosphere are reviewed and a recommendation is made for the exospheric temperature of a proposed mean CIRA. One of the deficiencies of CIRA 72 and other present thermospheric models is the representation of density changes with geomagnetic activity. This deficiency is illustrated with samples of data. The data show the effects of geomagnetic activity, particle precipitation, a solar proton event, and gravity waves. An empirical model developed from the unique AFGL satellite density data bank using multiple linear regression is reviewed. The present model is for low to moderate solar flux and quiet geomagnetic conditions, but it is planned to extend the model to active conditions. Good progress has been made since CIRA 72 was specified in our knowledge and understanding of the properties of the lower thermosphere, although there are still some unresolved problems. The biggest progress has been made in the theory of tidal effects and of particulate energy deposition and of electrojet heating. On the other hand, it is still not possible to define adequately the systematic variations of the lower boundary conditions of thermospheric models. This is due to lack of knowledge of the systematic variations of the structure properties in the 100 to 120 km altitude region and inadequate information on the mesospheric turbulence profile and variations in the turbopause altitude.

  14. Updated Results from the Michigan Titan Thermospheric General Circulation Model (TTGCM)

    Science.gov (United States)

    Bell, J. M.; Bougher, S. W.; de Lahaye, V.; Waite, J. H.; Ridley, A.

    2006-05-01

    This paper presents updated results from the Michigan Titan Thermospheric General Circulation Model (TTGCM) that was recently unveiled in operational form (Bell et al 2005 Spring AGU). Since then, we have incorporated a suite of chemical reactions for the major neutral constituents in Titan's upper atmosphere (N2, CH4). Additionally, some selected minor neutral constituents and major ionic species are also supported in the framework. At this time, HCN, which remains one of the critical thermally active species in the upper atmosphere, remains specified at all altitudes, utilizing profiles derived from recent Cassini-Huygen's measurements. In addition to these improvements, a parallel effort is underway to develop a non-hydrostatic Titan Thermospheric General Circulation Model for further comparisons. In this work, we emphasize the impacts of self-consistent chemistry on the results of the updated TTGCM relative to its frozen chemistry predecessor. Meanwhile, the thermosphere's thermodynamics remains determined by the interplay of solar EUV forcing and HCN rotational cooling, which is calculated by a full line- by-line radiative transfer routine along the lines of Yelle (1991) and Mueller-Wodarg (2000, 2002). In addition to these primary drivers, a treatment of magnetospheric heating is further tested. The model's results will be compared with both the Cassini INMS data and the model of Mueller-Wodarg (2000,2002).

  15. Effect of Thermospheric Neutral Density upon Inner Trapped-belt Proton Flux

    Science.gov (United States)

    Wilson, Thomas L.; Lodhi, M. A. K.; Diaz, Abel B.

    2007-01-01

    We wish to point out that a secular change in the Earth's atmospheric neutral density alters charged-particle lifetime in the inner trapped radiation belts, in addition to the changes recently reported as produced by greenhouse gases. Heretofore, changes in neutral density have been of interest primarily because of their effect on the orbital drag of satellites. We extend this to include the orbital lifetime of charged particles in the lower radiation belts. It is known that the charged-belt population is coupled to the neutral density of the atmosphere through changes induced by solar activity, an effect produced by multiple scattering off neutral and ionized atoms along with ionization loss in the thermosphere where charged and neutral populations interact. It will be shown here that trapped-belt flux J is bivariant in energy E and thermospheric neutral density , as J(E,rho). One can conclude that proton lifetimes in these belts are also directly affected by secular changes in the neutral species populating the Earth s thermosphere. This result is a consequence of an intrinsic property of charged-particle flux, that flux is not merely a function of E but is dependent upon density rho when a background of neutrals is present.

  16. Wavelength Dependence of Solar Flare Irradiation and its Influence on the Thermosphere

    Science.gov (United States)

    Huang, Yanshi; Richmond, Arthur D.; Deng, Yue; Qian, L.; Solomon, S.; Chamberlin, P.

    2012-01-01

    The wavelength dependence of solar flare enhancement is one of the important factors determining how the Thermosphere-Ionosphere (T-I) system response to flares. To investigate the wavelength dependence of solar flare, the Flare Irradiance Spectral Model (FISM) has been run for 34 X-class flares. The results show that the percentage increases of solar irradiance at flare peak comparing to pre-flare condition have a clear wavelength dependence. In the wavelength range between 0 - 195 nm, it can vary from 1% to 10000%. The solar irradiance enhancement is largest ( 1000%) in the XUV range (0 - 25 nm), and is about 100% in EUV range (25 - 120 nm). The influence of different wavebands on the T-I system during the October 28th, 2003 flare (X17.2-class) has also been examined using the latest version of National Center for Atmospheric Research (NCAR) Thermosphere- Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). While the globally integrated solar energy deposition is largest in the 0 - 14 nm waveband, the impact of solar irradiance enhancement on the thermosphere at 400 km is largest for 25 - 105 nm waveband. The effect of 122 - 195 nm is small in magnitude, but it decays slowly.

  17. Effect of geomagnetic storms on the daytime low-latitude thermospheric wave dynamics

    Science.gov (United States)

    Karan, Deepak K.; Pallamraju, Duggirala

    2018-05-01

    The equatorial- and low-latitude thermospheric dynamics is affected by both equatorial electrodynamics and neutral wave dynamics, the relative variation of which is dependent on the prevalent background conditions, which in turn has a seasonal dependence. Depending on the ambient thermospheric conditions, varying effects of the geomagnetic disturbances on the equatorial- and low-latitude thermosphere are observed. To investigate the effect of these disturbances on the equatorial- and low-latitude neutral wave dynamics, daytime airglow emission intensities at OI 557.7 nm, OI 630.0 nm, and OI 777.4 nm are used. These emissions from over a large field-of-view (FOV∼1000) have been obtained using a high resolution slit spectrograph, MISE (Multiwavelength Imaging Spectrograph using Echelle grating), from a low-latitude location, Hyderabad (17.50N, 78.40E; 8.90N MLAT), in India. Variations of the dayglow emission intensities are investigated during three geomagnetic disturbance events that occurred in different seasons. It is seen that the neutral dayglow emission intensities at all the three wavelengths showed different type of variations with the disturbance storm time (Dst) index in different seasons. Even though the dayglow emission intensities over low-latitude regions are sensitive to the variation in the equatorial electric fields, during periods of geomagnetic disturbances, especially in solstices, these are dependent on thermospheric O/N2 values. This shows the dominance of neutral dynamics over electrodynamics in the low-latitude upper atmosphere during geomagnetic disturbances. Further, spectral analyses have been carried out to obtain the zonal scale sizes in the gravity wave regime and their diurnal distributions are compared for geomagnetic quiet and disturbed days. Broadly, the zonal scales seem to be breaking into various scale sizes on days of geomagnetic disturbances when compared to those on quiet days. This contrast in the diurnal distribution of the

  18. 75 FR 53966 - Regular Meeting

    Science.gov (United States)

    2010-09-02

    ... FARM CREDIT SYSTEM INSURANCE CORPORATION Regular Meeting AGENCY: Farm Credit System Insurance Corporation Board. SUMMARY: Notice is hereby given of the regular meeting of the Farm Credit System Insurance Corporation Board (Board). DATE AND TIME: The meeting of the Board will be held at the offices of the Farm...

  19. Online co-regularized algorithms

    NARCIS (Netherlands)

    Ruijter, T. de; Tsivtsivadze, E.; Heskes, T.

    2012-01-01

    We propose an online co-regularized learning algorithm for classification and regression tasks. We demonstrate that by sequentially co-regularizing prediction functions on unlabeled data points, our algorithm provides improved performance in comparison to supervised methods on several UCI benchmarks

  20. Wind energy

    International Nuclear Information System (INIS)

    Kotevski, Darko

    2003-01-01

    Wind is not only free, it is inexhaustible. Wind energy has come a very long way since the prototypes of just 20 years ago. today's wind turbines are state-of-the-art technology - modular and quick to install anywhere where there is sufficient wind potential to provide secure, centralised or distributed generation. It is a global phenomenon, the world's fastest growing energy sector, a clean and effective modern technology that completely avoids pollution and thus reducing the 'green house' effect. (Original)

  1. A ground-base Radar network to access the 3D structure of MLT winds

    Science.gov (United States)

    Stober, G.; Chau, J. L.; Wilhelm, S.; Jacobi, C.

    2016-12-01

    The mesosphere/lower thermosphere (MLT) is a highly variable atmospheric region driven by wave dynamics at various scales including planetary waves, tides and gravity waves. Some of these propagate through the MLT into the thermosphere/ionosphere carrying energy and momentum from the middle atmosphere into the upper atmosphere. To improve our understanding of the wave energetics and momentum transfer during their dissipation it is essential to characterize their space time properties. During the last two years we developed a new experimental approach to access the horizontal structure of wind fields at the MLT using a meteor radar network in Germany, which we called MMARIA - Multi-static Multi-frequency Agile Radar for Investigation of the Atmosphere. The network combines classical backscatter meteor radars and passive forward scatter radio links. We present our preliminary results using up to 7 different active and passive radio links to obtain horizontally resolved wind fields applying a statistical inverse method. The wind fields are retrieved with 15-30 minutes temporal resolution on a grid with 30x30 km horizontal spacing. Depending on the number of observed meteors, we are able to apply the wind field inversion at heights between 84-94 km. The horizontally resolved wind fields provide insights of the typical horizontal gravity wave length and the energy cascade from large scales to small scales. We present first power spectra indicating the transition from the synoptic wave scale to the gravity wave scale.

  2. Electromagnetic energy deposition rate in the polar upper thermosphere derived from the EISCAT Svalbard radar and CUTLASS Finland radar observations

    Directory of Open Access Journals (Sweden)

    H. Fujiwara

    2007-11-01

    Full Text Available From simultaneous observations of the European incoherent scatter Svalbard radar (ESR and the Cooperative UK Twin Located Auroral Sounding System (CUTLASS Finland radar on 9 March 1999, we have derived the height distributions of the thermospheric heating rate at the F region height in association with electromagnetic energy inputs into the dayside polar cap/cusp region. The ESR and CUTLASS radar observations provide the ionospheric parameters with fine time-resolutions of a few minutes. Although the geomagnetic activity was rather moderate (Kp=3+~4, the electric field obtained from the ESR data sometimes shows values exceeding 40 mV/m. The estimated passive energy deposition rates are also larger than 150 W/kg in the upper thermosphere over the ESR site during the period of the enhanced electric field. In addition, enhancements of the Pedersen conductivity also contribute to heating the upper thermosphere, while there is only a small contribution for thermospheric heating from the direct particle heating due to soft particle precipitation in the dayside polar cap/cusp region. In the same period, the CUTLASS observations of the ion drift show the signature of poleward moving pulsed ionospheric flows with a recurrence rate of about 10–20 min. The estimated electromagnetic energy deposition rate shows the existence of the strong heat source in the dayside polar cap/cusp region of the upper thermosphere in association with the dayside magnetospheric phenomena of reconnections and flux transfer events.

  3. Electromagnetic energy deposition rate in the polar upper thermosphere derived from the EISCAT Svalbard radar and CUTLASS Finland radar observations

    Directory of Open Access Journals (Sweden)

    H. Fujiwara

    2007-11-01

    Full Text Available From simultaneous observations of the European incoherent scatter Svalbard radar (ESR and the Cooperative UK Twin Located Auroral Sounding System (CUTLASS Finland radar on 9 March 1999, we have derived the height distributions of the thermospheric heating rate at the F region height in association with electromagnetic energy inputs into the dayside polar cap/cusp region. The ESR and CUTLASS radar observations provide the ionospheric parameters with fine time-resolutions of a few minutes. Although the geomagnetic activity was rather moderate (Kp=3+~4, the electric field obtained from the ESR data sometimes shows values exceeding 40 mV/m. The estimated passive energy deposition rates are also larger than 150 W/kg in the upper thermosphere over the ESR site during the period of the enhanced electric field. In addition, enhancements of the Pedersen conductivity also contribute to heating the upper thermosphere, while there is only a small contribution for thermospheric heating from the direct particle heating due to soft particle precipitation in the dayside polar cap/cusp region. In the same period, the CUTLASS observations of the ion drift show the signature of poleward moving pulsed ionospheric flows with a recurrence rate of about 10–20 min. The estimated electromagnetic energy deposition rate shows the existence of the strong heat source in the dayside polar cap/cusp region of the upper thermosphere in association with the dayside magnetospheric phenomena of reconnections and flux transfer events.

  4. From the Sun to the Earth: impact of the 27-28 May 2003 solar events on the magnetosphere, ionosphere and thermosphere

    Directory of Open Access Journals (Sweden)

    C. Hanuise

    2006-03-01

    Full Text Available During the last week of May 2003, the solar active region AR 10365 produced a large number of flares, several of which were accompanied by Coronal Mass Ejections (CME. Specifically on 27 and 28 May three halo CMEs were observed which had a significant impact on geospace. On 29 May, upon their arrival at the L1 point, in front of the Earth's magnetosphere, two interplanetary shocks and two additional solar wind pressure pulses were recorded by the ACE spacecraft. The interplanetary magnetic field data showed the clear signature of a magnetic cloud passing ACE. In the wake of the successive increases in solar wind pressure, the magnetosphere became strongly compressed and the sub-solar magnetopause moved inside five Earth radii. At low altitudes the increased energy input to the magnetosphere was responsible for a substantial enhancement of Region-1 field-aligned currents. The ionospheric Hall currents also intensified and the entire high-latitude current system moved equatorward by about 10°. Several substorms occurred during this period, some of them - but not all - apparently triggered by the solar wind pressure pulses. The storm's most notable consequences on geospace, including space weather effects, were (1 the expansion of the auroral oval, and aurorae seen at mid latitudes, (2 the significant modification of the total electron content in the sunlight high-latitude ionosphere, (3 the perturbation of radio-wave propagation manifested by HF blackouts and increased GPS signal scintillation, and (4 the heating of the thermosphere, causing increased satellite drag. We discuss the reasons why the May 2003 storm is less intense than the October-November 2003 storms, although several indicators reach similar intensities.

  5. From the Sun to the Earth: impact of the 27-28 May 2003 solar events on the magnetosphere, ionosphere and thermosphere

    Directory of Open Access Journals (Sweden)

    C. Hanuise

    2006-03-01

    Full Text Available During the last week of May 2003, the solar active region AR 10365 produced a large number of flares, several of which were accompanied by Coronal Mass Ejections (CME. Specifically on 27 and 28 May three halo CMEs were observed which had a significant impact on geospace. On 29 May, upon their arrival at the L1 point, in front of the Earth's magnetosphere, two interplanetary shocks and two additional solar wind pressure pulses were recorded by the ACE spacecraft. The interplanetary magnetic field data showed the clear signature of a magnetic cloud passing ACE. In the wake of the successive increases in solar wind pressure, the magnetosphere became strongly compressed and the sub-solar magnetopause moved inside five Earth radii. At low altitudes the increased energy input to the magnetosphere was responsible for a substantial enhancement of Region-1 field-aligned currents. The ionospheric Hall currents also intensified and the entire high-latitude current system moved equatorward by about 10°. Several substorms occurred during this period, some of them - but not all - apparently triggered by the solar wind pressure pulses. The storm's most notable consequences on geospace, including space weather effects, were (1 the expansion of the auroral oval, and aurorae seen at mid latitudes, (2 the significant modification of the total electron content in the sunlight high-latitude ionosphere, (3 the perturbation of radio-wave propagation manifested by HF blackouts and increased GPS signal scintillation, and (4 the heating of the thermosphere, causing increased satellite drag. We discuss the reasons why the May 2003 storm is less intense than the October-November 2003 storms, although several indicators reach similar intensities.

  6. Wind Structure and Wind Loading

    DEFF Research Database (Denmark)

    Brorsen, Michael

    The purpose of this note is to provide a short description of wind, i.e. of the flow in the atmosphere of the Earth and the loading caused by wind on structures. The description comprises: causes to the generation of windhe interaction between wind and the surface of the Earthhe stochastic nature...

  7. Continuum-regularized quantum gravity

    International Nuclear Information System (INIS)

    Chan Huesum; Halpern, M.B.

    1987-01-01

    The recent continuum regularization of d-dimensional Euclidean gravity is generalized to arbitrary power-law measure and studied in some detail as a representative example of coordinate-invariant regularization. The weak-coupling expansion of the theory illustrates a generic geometrization of regularized Schwinger-Dyson rules, generalizing previous rules in flat space and flat superspace. The rules are applied in a non-trivial explicit check of Einstein invariance at one loop: the cosmological counterterm is computed and its contribution is included in a verification that the graviton mass is zero. (orig.)

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

    International Nuclear Information System (INIS)

    Matsushita, S.

    1976-01-01

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

  9. Wind power

    International Nuclear Information System (INIS)

    Gipe, P.

    2007-01-01

    This book is a translation of the edition published in the USA under the title of ''wind power: renewable energy for home, farm and business''. In the wake of mass blackouts and energy crises, wind power remains a largely untapped resource of renewable energy. It is a booming worldwide industry whose technology, under the collective wing of aficionados like author Paul Gipe, is coming of age. Wind Power guides us through the emergent, sometimes daunting discourse on wind technology, giving frank explanations of how to use wind technology wisely and sound advice on how to avoid common mistakes. Since the mid-1970's, Paul Gipe has played a part in nearly every aspect of wind energy development from installing small turbines to promoting wind energy worldwide. As an American proponent of renewable energy, Gipe has earned the acclaim and respect of European energy specialists for years, but his arguments have often fallen on deaf ears at home. Today, the topic of wind power is cropping up everywhere from the beaches of Cape Cod to the Oregon-Washington border, and one wind turbine is capable of producing enough electricity per year to run 200 average American households. Now, Paul Gipe is back to shed light on this increasingly important energy source with a revised edition of Wind Power. Over the course of his career, Paul Gipe has been a proponent, participant, observer, and critic of the wind industry. His experience with wind has given rise to two previous books on the subject, Wind Energy Basics and Wind Power for Home and Business, which have sold over 50,000 copies. Wind Power for Home and Business has become a staple for both homeowners and professionals interested in the subject, and now, with energy prices soaring, interest in wind power is hitting an all-time high. With chapters on output and economics, Wind Power discloses how much you can expect from each method of wind technology, both in terms of energy and financial savings. The book updated models

  10. New regular black hole solutions

    International Nuclear Information System (INIS)

    Lemos, Jose P. S.; Zanchin, Vilson T.

    2011-01-01

    In the present work we consider general relativity coupled to Maxwell's electromagnetism and charged matter. Under the assumption of spherical symmetry, there is a particular class of solutions that correspond to regular charged black holes whose interior region is de Sitter, the exterior region is Reissner-Nordstroem and there is a charged thin-layer in-between the two. The main physical and geometrical properties of such charged regular black holes are analyzed.

  11. Regular variation on measure chains

    Czech Academy of Sciences Publication Activity Database

    Řehák, Pavel; Vitovec, J.

    2010-01-01

    Roč. 72, č. 1 (2010), s. 439-448 ISSN 0362-546X R&D Projects: GA AV ČR KJB100190701 Institutional research plan: CEZ:AV0Z10190503 Keywords : regularly varying function * regularly varying sequence * measure chain * time scale * embedding theorem * representation theorem * second order dynamic equation * asymptotic properties Subject RIV: BA - General Mathematics Impact factor: 1.279, year: 2010 http://www.sciencedirect.com/science/article/pii/S0362546X09008475

  12. Manifold Regularized Correlation Object Tracking

    OpenAIRE

    Hu, Hongwei; Ma, Bo; Shen, Jianbing; Shao, Ling

    2017-01-01

    In this paper, we propose a manifold regularized correlation tracking method with augmented samples. To make better use of the unlabeled data and the manifold structure of the sample space, a manifold regularization-based correlation filter is introduced, which aims to assign similar labels to neighbor samples. Meanwhile, the regression model is learned by exploiting the block-circulant structure of matrices resulting from the augmented translated samples over multiple base samples cropped fr...

  13. On geodesics in low regularity

    Science.gov (United States)

    Sämann, Clemens; Steinbauer, Roland

    2018-02-01

    We consider geodesics in both Riemannian and Lorentzian manifolds with metrics of low regularity. We discuss existence of extremal curves for continuous metrics and present several old and new examples that highlight their subtle interrelation with solutions of the geodesic equations. Then we turn to the initial value problem for geodesics for locally Lipschitz continuous metrics and generalize recent results on existence, regularity and uniqueness of solutions in the sense of Filippov.

  14. Condition Number Regularized Covariance Estimation.

    Science.gov (United States)

    Won, Joong-Ho; Lim, Johan; Kim, Seung-Jean; Rajaratnam, Bala

    2013-06-01

    Estimation of high-dimensional covariance matrices is known to be a difficult problem, has many applications, and is of current interest to the larger statistics community. In many applications including so-called the "large p small n " setting, the estimate of the covariance matrix is required to be not only invertible, but also well-conditioned. Although many regularization schemes attempt to do this, none of them address the ill-conditioning problem directly. In this paper, we propose a maximum likelihood approach, with the direct goal of obtaining a well-conditioned estimator. No sparsity assumption on either the covariance matrix or its inverse are are imposed, thus making our procedure more widely applicable. We demonstrate that the proposed regularization scheme is computationally efficient, yields a type of Steinian shrinkage estimator, and has a natural Bayesian interpretation. We investigate the theoretical properties of the regularized covariance estimator comprehensively, including its regularization path, and proceed to develop an approach that adaptively determines the level of regularization that is required. Finally, we demonstrate the performance of the regularized estimator in decision-theoretic comparisons and in the financial portfolio optimization setting. The proposed approach has desirable properties, and can serve as a competitive procedure, especially when the sample size is small and when a well-conditioned estimator is required.

  15. Condition Number Regularized Covariance Estimation*

    Science.gov (United States)

    Won, Joong-Ho; Lim, Johan; Kim, Seung-Jean; Rajaratnam, Bala

    2012-01-01

    Estimation of high-dimensional covariance matrices is known to be a difficult problem, has many applications, and is of current interest to the larger statistics community. In many applications including so-called the “large p small n” setting, the estimate of the covariance matrix is required to be not only invertible, but also well-conditioned. Although many regularization schemes attempt to do this, none of them address the ill-conditioning problem directly. In this paper, we propose a maximum likelihood approach, with the direct goal of obtaining a well-conditioned estimator. No sparsity assumption on either the covariance matrix or its inverse are are imposed, thus making our procedure more widely applicable. We demonstrate that the proposed regularization scheme is computationally efficient, yields a type of Steinian shrinkage estimator, and has a natural Bayesian interpretation. We investigate the theoretical properties of the regularized covariance estimator comprehensively, including its regularization path, and proceed to develop an approach that adaptively determines the level of regularization that is required. Finally, we demonstrate the performance of the regularized estimator in decision-theoretic comparisons and in the financial portfolio optimization setting. The proposed approach has desirable properties, and can serve as a competitive procedure, especially when the sample size is small and when a well-conditioned estimator is required. PMID:23730197

  16. Solar and magnetospheric forcing of the low latitude thermospheric mass density as observed by CHAMP

    Directory of Open Access Journals (Sweden)

    S. Müller

    2009-05-01

    Full Text Available We have studied the dependence of the thermospheric mass density at equatorial latitudes on the influence of various drivers. This statistical study is based on CHAMP accelerometer measurements. Our aim is to delineate the influences of the different contributions. For the isolation of the effects we make use of a dedicated data selection procedure and/or removal of disturbing effects. In a first step all readings are normalised to an altitude of 400 km. For the investigation of the solar influences only magnetically quiet days (Ap≤15 are considered. The dependence on solar flux can well be described by a linear relation within the flux range F10.7=80–240. The slope is twice as steep on the day side as on the night side. The air density exhibits clear annual and semi-annual variations with maxima at the equinoxes and a pronounced minimum around June solstice. The thermosphere maintains during quiet days a day to night mass density ratio very close to 2, which is independent of solar flux level or season. The magnetospheric input causing thermospheric density enhancement can well be parameterised by the am activity index. The low latitude density responds with a delay to changes of the index by about 3 h on the dayside and 4–5 h on the night side. The magnetospheric forcing causes an additive contribution to the quiet-time density, which is linearly correlated with the am index. The slopes of density increases are the same on the day and night sides. We present quantitative expressions for all the dependences. Our results suggest that all the studied forcing terms can be treated as linear combinations of the respective contribution.

  17. Lower thermospheric neutral densities determined from Soendre Stroemfjord incoherent scatter radar during LTCS 1

    International Nuclear Information System (INIS)

    Reese, K.W.; Johnson, R.M.; Killeen, T.L.

    1991-01-01

    Ion-neutral collision frequencies determined from measurements obtained by the incoherent scatter radar located at Soendre Stroemfjord, Greenland, have been used to derive lower thermospheric neutral densities during the first Lower Thermosphere Coupling Study (LTCS 1), September 21-26, 1987. Periods of Joule and particle heating which might disturb the E region thermal equilibrium were systematically eliminated. The mean profile of neutral density for the period is in good agreement with the mass spectrometer incoherent scatter 1986 (MSIS-86) model between 92 and 104 km. A tendency to overestimate collision frequencies above 105 km may arise from range-smearing effects. The results of a tidal analysis performed on the neutral density between 92 and 109 km show that the amplitudes of the diurnal and semidiurnal components of the tides are approximately equivalent. The observations are generally in better agreement with the MSIS-86 predictions than with the thermosphere-ionosphere general circulation model (TIGCM) simulation of the LTCS 1 interval. The observed phase of the diurnal component is approximately constant with height above 98 km and is in close agreement with the MSIS-86 model phases; however, the TIGCM diurnal phases are shifted by 6-8 hours to later local times. The phase of the semidiurnal tide is in good agreement with predictions of the MSIS-86 model and the TIGCM simulation of this interval, except near 98 km. The observed semidiurnal phase is also consistent with previous high-latitude results (Kirkwood, 1986). The relative amplitude of the observed semidiurnal oscillation is up to 15% larger than that previously observed at the European Incoherent Scatter facility but is consistent with the amplitudes presented in an earlier study of Millstone Hill measurements (Salah, 1974)

  18. Local recurrence after microwave thermosphere ablation of malignant liver tumors: results of a surgical series.

    Science.gov (United States)

    Takahashi, Hideo; Kahramangil, Bora; Berber, Eren

    2018-04-01

    Microwave thermosphere ablation is a new treatment modality that creates spherical ablation zones using a single antenna. This study aims to analyze local recurrence associated with this new treatment modality in patients with malignant liver tumors. This is a prospective clinical study of patients who underwent microwave thermosphere ablation of malignant liver tumors between September 2014 and March 2017. Clinical, operative, and oncologic parameters were analyzed using Kaplan-Meier survival and Cox proportional hazards model. One hundred patients underwent 301 ablations. Ablations were performed laparoscopically in 87 and open in 13 patients. Pathology included neuroendocrine liver metastasis (n = 115), colorectal liver metastasis (n = 100), hepatocellular cancer (n = 21), and other tumor types (n = 65). Ninety-day morbidity was 7% with one not procedure-related mortality. Median follow-up was 16 months with 65% of patients completing at least 12 months of follow-up. The rate of local tumor recurrence rate per lesion was 6.6% (20/301). Local tumor, new hepatic, and extrahepatic recurrences were detected in 15%, 40%, and 40% of patients, respectively. Local recurrence rate per pathology was 12% for both colorectal liver metastasis (12/100) and other metastatic tumors (8/65). No local recurrence was observed to date in the neuroendocrine liver metastasis and in the limited number of patients with hepatocellular cancers. Tumor size >3 cm and tumor type were independent predictors of local recurrence. This is the first study to analyze local recurrence after microwave thermosphere ablation of malignant liver tumors. Short-term local tumor control rate compares favorably with that reported for radiofrequency and other microwave technologies in the literature. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Data-driven Inference and Investigation of Thermosphere Dynamics and Variations

    Science.gov (United States)

    Mehta, P. M.; Linares, R.

    2017-12-01

    This paper presents a methodology for data-driven inference and investigation of thermosphere dynamics and variations. The approach uses data-driven modal analysis to extract the most energetic modes of variations for neutral thermospheric species using proper orthogonal decomposition, where the time-independent modes or basis represent the dynamics and the time-depedent coefficients or amplitudes represent the model parameters. The data-driven modal analysis approach combined with sparse, discrete observations is used to infer amplitues for the dynamic modes and to calibrate the energy content of the system. In this work, two different data-types, namely the number density measurements from TIMED/GUVI and the mass density measurements from CHAMP/GRACE are simultaneously ingested for an accurate and self-consistent specification of the thermosphere. The assimilation process is achieved with a non-linear least squares solver and allows estimation/tuning of the model parameters or amplitudes rather than the driver. In this work, we use the Naval Research Lab's MSIS model to derive the most energetic modes for six different species, He, O, N2, O2, H, and N. We examine the dominant drivers of variations for helium in MSIS and observe that seasonal latitudinal variation accounts for about 80% of the dynamic energy with a strong preference of helium for the winter hemisphere. We also observe enhanced helium presence near the poles at GRACE altitudes during periods of low solar activity (Feb 2007) as previously deduced. We will also examine the storm-time response of helium derived from observations. The results are expected to be useful in tuning/calibration of the physics-based models.

  20. Traveling Atmospheric Disturbances (TADs) in the thermosphere inferred from accelerometer data at three altitudes

    Science.gov (United States)

    Bruinsma, Sean; Forbes, Jeffrey

    2010-05-01

    Densities derived from accelerometer measurements on the GRACE, CHAMP and Air Force/SETA satellites near 490, 390, and 220 km, respectively, are used to elucidate global-scale characteristics of traveling atmospheric disturbances. The accelerometers on the CHAMP and GRACE satellites have made it possible to accumulate near-continuous records of thermosphere density between about 320 and 490 km since May 2001, and July 2002, respectively. They have recorded the response to virtually every significant geomagnetic storm during this period. CHAMP and GRACE are in (near) polar and quasi-circular orbits, sampling 24 hr local time approximately every 4 and 5 months, respectively. These capabilities offer unique opportunities to study the temporal and latitudinal responses of the thermosphere to geomagnetic disturbances. The Air Force/SETA accelerometer data have also been processed, but the analysis is more complicated due to data gaps. Significant and unambiguous TAD activity in the observed response of the thermosphere was detected for about 25 events with CHAMP and GRACE, and less than 10 with SETA. The atmospheric variability is evaluated by de-trending the data, allowing the extraction of specific ranges in horizontal scale, and analyzing density "residuals". The scale of the perturbation is decisive for its lifetime and relative amplitude. Sometimes the disturbances represent wave-like structures propagating far from the source, and these so-called ‘TADs' were detected and described for the May 2003 storm for the first time. Some TADs traveled over the pole into the opposite hemisphere; this was found in both CHAMP and GRACE data. Most TADs propagate equatorward, but poleward propagating TADs have on occasion been detected too. The estimated speeds and amplitudes of the observed TADs, and their dependence on altitude and solar and geomagnetic activity in particular, will be presented in this poster.

  1. Climatology of GW-TIDs in the magnetic equatorial upper thermosphere over India

    Science.gov (United States)

    Manju, G.; Aswathy, R. P.

    2017-11-01

    An analysis of Gravity wave induced travelling ionospheric disturbances (GW-TIDs) in the thermosphere during high and low solar epochs is undertaken using ionosonde data at Trivandrum (8.50N, 770E). Wavelet analysis is performed on the temporal variations of foF2 and the amplitudes of waves present in two period bands of (0.5-1.5) h and (2-4) h are extracted. The real height profiles are generated at 15 min internal for the whole day (for sample days) during high and low solar activity years. The study reveals that the GW-TID activity is significantly greater for solar minimum compared to solar maximum for the period 8.5-17.5 h. Diurnally the GW-TID activity in the (2-4) h period band peaks in the post sunset hours for both high and low solar epochs. For the 0.5-1.5 h period band, the diurnal maximum in GW-TID is occurring in the post sunset hours for high solar epoch while it occurs in the morning hours around 10 h LT for low solar epoch. Seasonally the day time GW-TID activity maximizes (minimizes) for winter (vernal equinox). The post sunset time GW-TID maximizes (minimizes) either for summer/winter (vernal equinox). The other interesting observation is the anti correlation of GW-TID in upper thermosphere with solar activity for day time and the correlation of the same with solar activity in the post sunset hours. The present results for daytime are in agreement with the equatorial daytime GW-TID behaviour reported from CHAMP satellite observations. The GW-TID activity during post sunset time for equatorial region upper thermosphere has not been reported so far.

  2. Observations of Upper Thermospheric Temperatures Using a Ground-Based Optical Instrument at the King Sejong Station, Antarctic

    OpenAIRE

    Jong-Kyun Chung; Young-In Won; Bang Yong Lee; Jhoon Kim

    1998-01-01

    We measured the terrestrial nightglow of OI 6300A in the thermosphere(~250km) using a ground-based Fabry-Perot interferometer at the King Sejong Station, Antarctic from March through September, 1997. The King Sejong Station is located at high latitude geographically (62.22 deg S, 301.25 deg E) but at mid-latitude geomagnetically (50.65 deg S, 7.51 deg E). It is therefore the strategic location to measure the temperatures of the thermosphere in the Southern Hemisphere associated with both sola...

  3. Seasonal Transport in Mars' Mesosphere-Thermosphere revealed by Nitric Oxide nightglow

    Science.gov (United States)

    Royer, E. M.; Stiepen, A.; Schneider, N. M.; Jain, S.; Milby, Z.; Deighan, J.; Gonzalez-Galindo, F.; Bougher, S. W.; Gerard, J. C. M. C.; Stevens, M. H.; Evans, J. S.; Stewart, I. F.; Chaffin, M.; McClintock, B.; Clarke, J. T.; Montmessin, F.; Holsclaw, G.; Lefèvre, F.; Forget, F.; Lo, D.; Hubert, B. A.; Jakosky, B. M.

    2017-12-01

    We analyze the ultraviolet nightglow in the atmosphere of Mars through the Nitric Oxide (NO) δ and γ band emissions observed by the Imaging Ultraviolet Spectrograph (IUVS, McClintock et al., 2015) when the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft is at apoapsis and periapsis. On the dayside thermosphere of Mars, solar extreme ultraviolet radiation dissociates CO2 and N2 molecules. O(3P) and N(4S) atoms are carried by the day-to-night hemispheric transport. They descend in the nightside mesosphere, where they can radiatively recombine to form NO(C2Π). The excited molecules rapidly relax by emitting UV photons in the δ and γ bands. These emissions are thus indicators of the N and O atom fluxes transported from the dayside to Mars' nightside and the descending circulation pattern from the nightside thermosphere to the mesosphere (e.g. Bertaux et al., 2005 ; Bougher et al., 1990 ; Cox et al., 2008 ; Gagné et al., 2013 ; Gérard et al., 2008 ; Stiepen et al., 2015, 2017). A large dataset of nightside disk images and vertical limb scans during southern winter, fall equinox and southern summer conditions have been accumulated since the beginning of the mission. We will present a discussion regarding the variability of the brightness and altitude of the emission with season, geographical position (longitude) and local time and possible interpretation for local and global changes in the mesosphere dynamics. We show the possible impact of atmospheric waves structuring the emission longitudinally and indicating a wave-3 structure in Mars' nightside mesosphere. Quantitative comparison with calculations from the LMD-MGCM (Laboratoire de Météorologie Dynamique-Mars Global Climate Model) show that the model globally reproduces the trends of the NO nightglow emission and its seasonal variation but also indicates large discrepancies (up to a factor 50 fainter in the model) suggesting that the predicted transport is too efficient toward the night winter pole

  4. A comparison of the consequences of thermospheric inertia on Saturn and Earth

    Science.gov (United States)

    Spain, T.; Achilleos, N.; Aruliah, A. L.

    2008-09-01

    ABSTRACT The ionosphere should react near-instantaneously to magnetospheric control via electric fields and particle precipitation. The neutral gas of the thermosphere becomes stirred up through collisions and momentum transfer with the ionospheric plasma, although with a time lag in response because of its much larger population mass [1]. The thermosphere thus responds to magnetospheric drivers with a modulating influence owing to its inertia. This study investigates the effect of thermospheric inertia on the energy drawn from the magnetosphere and redistributed as Joule heating and acceleration of the neutral gas. The decay of ionospheric currents and consequent magnetic perturbations are also studied. The UCL Saturn model [2] and CTIP Earth [3] model will each be used for 2 simulations: the first a steadystate 'quiet' simulation and the second including the representation of a geomagnetic storm lasting for an extended period that is then turned off. For each planet, comparisons will be made between these two simulations for the period immediately following the storm, when the electric field and particle precipitation drivers of the 'storm' simulations have returned to values in accordance with the 'quiet' models. The differences between the steady state and previously active simulations will be purely due to thermospheric inertia [4]. It is anticipated that the response of the Gas Giant will be very different from the Earth due to differences in the size, rotational speed, flow timescales [5] [6] and composition of the respective planetary environments. References [1] Schunk, R. W., 1987, Physica Scripta, T18, pp. 256- 275, doi: 10.1088/0031-8949/1987/T18/026. [2] Smith, C. G. A. and Aylward, A. D. and Millward, G. H. and Miller, S. and Moore, L. E., 2007, Nature, 445 (7126), pp. 399-401. [3] Millward, G. H. and Moffett, R. J. and Quegan, S. and Fuller-Rowell, T. J., 1996, in The STEP Handbook of Ionospheric Models, R.W. Schunk ed., Utah State University. [4

  5. Nonlinear Acoustic Waves Generated by Surface Disturbances and Their Effects on Lower Thermospheric Composition

    Science.gov (United States)

    Pineyro, B.; Snively, J. B.

    2017-12-01

    Recent 1D and 2D nonlinear atmospheric models have provided important insight into acoustic waves generated by seismic events, which may steepen into shocks or saw-tooth trains while also dissipating strongly in the thermosphere [e.g., Chum et al., JGR, 121, 2016; Zettergren et al., JGR, 122, 2017]. Although they have yield results that agree with with observations of ionospheric perturbations, dynamical models for the diffusive and stratified lower thermosphere [e.g., Snively and Pasko, JGR, 113, 2008] often use single gas approximations with height-dependent physical properties (e.g. mean molecular weight, specific heats) that do not vary with time (fixed composition). This approximation is simpler and less computationally expensive than a true multi-fluid model, yet captures the important physical transition between molecular and atomic gases in the lower thermosphere. Models with time-dependent composition and properties have been shown to outperform commonly used models with fixed properties; these time-dependent effects have been included in a one-gas model by adding an advection equation for the molecular weight, finding closer agreement to a true binary-gas model [Walterscheid and Hickey, JGR, 106, 2001 and JGR, 117, 2012]. Here, a one-dimensional nonlinear mass fraction approach to multi-constituent gas modeling, motivated by the results of Walterscheid and Hickey [2001, 2012], is presented. The finite volume method of Bale et al. [SIAM JSC, 24, 2002] is implemented in Clawpack [http://www.clawpack.org; LeVeque, 2002] with a Riemann Solver to solve the Euler Equations including multiple species, defined by their mass fractions, as they undergo advection. Viscous dissipation and thermal conduction are applied via a fractional step method. The model is validated with shock tube problems for two species, and then applied to investigate propagating nonlinear acoustic waves from ground to thermosphere, such as following the 2011 Tohoku Earthquake [e

  6. Geometric continuum regularization of quantum field theory

    International Nuclear Information System (INIS)

    Halpern, M.B.

    1989-01-01

    An overview of the continuum regularization program is given. The program is traced from its roots in stochastic quantization, with emphasis on the examples of regularized gauge theory, the regularized general nonlinear sigma model and regularized quantum gravity. In its coordinate-invariant form, the regularization is seen as entirely geometric: only the supermetric on field deformations is regularized, and the prescription provides universal nonperturbative invariant continuum regularization across all quantum field theory. 54 refs

  7. Observations on Stratospheric-Mesospheric-Thermospheric temperatures using Indian MST radar and co-located LIDAR during Leonid Meteor Shower (LMS

    Directory of Open Access Journals (Sweden)

    R. Selvamurugan

    2002-11-01

    Full Text Available The temporal and height statistics of the occurrence of meteor trails during the Leonid meteor shower revealed the capability of the Indian MST radar to record large numbers of meteor trails. The distribution of radio meteor trails due to a Leonid meteor shower in space and time provided a unique opportunity to construct the height profiles of lower thermospheric temperatures and winds, with good time and height resolution. There was a four-fold increase in the meteor trails observed during the LMS compared to a typical non-shower day. The temperatures were found to be in excellent continuity with the temperature profiles below the radio meteor region derived from the co-located Nd-Yag LIDAR and the maximum height of the temperature profile was extended from the LIDAR to ~110 km. There are, how-ever, some significant differences between the observed profiles and the CIRA-86 model profiles. The first results on the meteor statistics and neutral temperature are presented and discussed below.  Key words. Atmospheric composition and structure (pres-sure, density, and temperature History of geophysics (at-mospheric sciences Meteorology and atmospheric dynamics (middle atmosphere dynamics

  8. Satellite accelerometer measurements of neutral density and winds during geomagnetic storms

    Science.gov (United States)

    Marcos, F. A.; Forbes, J. M.

    1986-01-01

    A new thermospheric wind measurement technique is reported which is based on a Satellite Electrostatic Triaxial Accelerometer (SETA) system capable of accurately measuring accelerations in the satellite's in-track, cross-track and radial directions. Data obtained during two time periods are presented. The first data set describes cross-track winds measured between 170 and 210 km during a 5-day period (25 to 29 March 1979) of mostly high geomagnetic activity. In the second data set, cross-track winds and neutral densities from SETA and exospheric temperatures from the Millstone Hill incoherent scatter radar are examined during an isolated magnetic substorm occurring on 21 March 1979. A polar thermospheric wind circulation consisting of a two cell horizontal convection pattern is reflected in both sets of cross-track acceleration measurements. The density response is highly asymmetric with respect to its day/night behavior. Latitude structures of the density response at successive times following the substorm peak suggest the equatorward propagation of a disturbance with a phase speed between 300 and 600 m/s. A deep depression in the density at high latitudes (less than 70 deg) is evident in conjunction with this phenomenon. The more efficient propagation of the disturbance to lower latitudes during the night is probably due to the midnight surge effect.

  9. A nonlinear dynamics approach for incorporating wind-speed patterns into wind-power project evaluation.

    Science.gov (United States)

    Huffaker, Ray; Bittelli, Marco

    2015-01-01

    Wind-energy production may be expanded beyond regions with high-average wind speeds (such as the Midwest U.S.A.) to sites with lower-average speeds (such as the Southeast U.S.A.) by locating favorable regional matches between natural wind-speed and energy-demand patterns. A critical component of wind-power evaluation is to incorporate wind-speed dynamics reflecting documented diurnal and seasonal behavioral patterns. Conventional probabilistic approaches remove patterns from wind-speed data. These patterns must be restored synthetically before they can be matched with energy-demand patterns. How to accurately restore wind-speed patterns is a vexing problem spurring an expanding line of papers. We propose a paradigm shift in wind power evaluation that employs signal-detection and nonlinear-dynamics techniques to empirically diagnose whether synthetic pattern restoration can be avoided altogether. If the complex behavior of observed wind-speed records is due to nonlinear, low-dimensional, and deterministic system dynamics, then nonlinear dynamics techniques can reconstruct wind-speed dynamics from observed wind-speed data without recourse to conventional probabilistic approaches. In the first study of its kind, we test a nonlinear dynamics approach in an application to Sugarland Wind-the first utility-scale wind project proposed in Florida, USA. We find empirical evidence of a low-dimensional and nonlinear wind-speed attractor characterized by strong temporal patterns that match up well with regular daily and seasonal electricity demand patterns.

  10. Metric regularity and subdifferential calculus

    International Nuclear Information System (INIS)

    Ioffe, A D

    2000-01-01

    The theory of metric regularity is an extension of two classical results: the Lyusternik tangent space theorem and the Graves surjection theorem. Developments in non-smooth analysis in the 1980s and 1990s paved the way for a number of far-reaching extensions of these results. It was also well understood that the phenomena behind the results are of metric origin, not connected with any linear structure. At the same time it became clear that some basic hypotheses of the subdifferential calculus are closely connected with the metric regularity of certain set-valued maps. The survey is devoted to the metric theory of metric regularity and its connection with subdifferential calculus in Banach spaces

  11. Manifold Regularized Correlation Object Tracking.

    Science.gov (United States)

    Hu, Hongwei; Ma, Bo; Shen, Jianbing; Shao, Ling

    2018-05-01

    In this paper, we propose a manifold regularized correlation tracking method with augmented samples. To make better use of the unlabeled data and the manifold structure of the sample space, a manifold regularization-based correlation filter is introduced, which aims to assign similar labels to neighbor samples. Meanwhile, the regression model is learned by exploiting the block-circulant structure of matrices resulting from the augmented translated samples over multiple base samples cropped from both target and nontarget regions. Thus, the final classifier in our method is trained with positive, negative, and unlabeled base samples, which is a semisupervised learning framework. A block optimization strategy is further introduced to learn a manifold regularization-based correlation filter for efficient online tracking. Experiments on two public tracking data sets demonstrate the superior performance of our tracker compared with the state-of-the-art tracking approaches.

  12. Dimensional regularization in configuration space

    International Nuclear Information System (INIS)

    Bollini, C.G.; Giambiagi, J.J.

    1995-09-01

    Dimensional regularization is introduced in configuration space by Fourier transforming in D-dimensions the perturbative momentum space Green functions. For this transformation, Bochner theorem is used, no extra parameters, such as those of Feynman or Bogoliubov-Shirkov are needed for convolutions. The regularized causal functions in x-space have ν-dependent moderated singularities at the origin. They can be multiplied together and Fourier transformed (Bochner) without divergence problems. The usual ultraviolet divergences appear as poles of the resultant functions of ν. Several example are discussed. (author). 9 refs

  13. Regular algebra and finite machines

    CERN Document Server

    Conway, John Horton

    2012-01-01

    World-famous mathematician John H. Conway based this classic text on a 1966 course he taught at Cambridge University. Geared toward graduate students of mathematics, it will also prove a valuable guide to researchers and professional mathematicians.His topics cover Moore's theory of experiments, Kleene's theory of regular events and expressions, Kleene algebras, the differential calculus of events, factors and the factor matrix, and the theory of operators. Additional subjects include event classes and operator classes, some regulator algebras, context-free languages, communicative regular alg

  14. Matrix regularization of 4-manifolds

    OpenAIRE

    Trzetrzelewski, M.

    2012-01-01

    We consider products of two 2-manifolds such as S^2 x S^2, embedded in Euclidean space and show that the corresponding 4-volume preserving diffeomorphism algebra can be approximated by a tensor product SU(N)xSU(N) i.e. functions on a manifold are approximated by the Kronecker product of two SU(N) matrices. A regularization of the 4-sphere is also performed by constructing N^2 x N^2 matrix representations of the 4-algebra (and as a byproduct of the 3-algebra which makes the regularization of S...

  15. Controlling of merging electric field and IMF magnitude on storm-time changes in thermospheric mass density

    Directory of Open Access Journals (Sweden)

    Y. L. Zhou

    2013-01-01

    Full Text Available The controls of merging electrical field, Em, and IMF (interplanetary magnetic field magnitude, B, on the storm-time changes in upper thermospheric mass density are statistically investigated using GRACE accelerometer observations and the OMNI data of solar wind and IMF for 35 great storms during 2002–2006. It reveals the following: (1 The correlation coefficients between the air mass density changes and the parameters of Em and B are generally larger at lower latitudes than at higher latitudes, and larger in noon and midnight sectors than in dawn and dusk. (2 The most likely delay time (MLDT of mass density changes in respect to Em is about 1.5 h (4.5 h at high (low latitudes, having no distinct local time dependence, while it is 6 h at middle latitudes in all the local time sectors except for noon, which is longer than at low latitudes. A similar fact of longer delay time at mid-latitude is also seen for B. The MLDTs for B at various latitudes are all local time dependent distinctly with shorter delay time in noon/midnight sector and larger in dawn/dusk. Despite of widely spread of the delay time, IMF B exhibits still larger correlation coefficients with mass density changes among the interplanetary parameters. (3 The linear control factor of B on the density changes increases for large B, in contrast to somewhat saturation trend for larger Em. (4 The influence of B and Em on the mass densities shows different behavior for different types of storms. The influence intensity of Em is much stronger for CIR-driven than for CME-driven storm, while it is not so distinct for B. On the local time asymmetry of the influence, both Em and B have largest influence at noon sector for CME-driven storms, while an obviously larger intensification of the influence is found in dawn/dusk sector during CIR storms, especially for parameter Em.

  16. Sporadic and Thermospheric Enhanced Sodium Layers Observed by a Lidar Chain over China

    Science.gov (United States)

    Xue, X.

    2013-12-01

    We report the statistical features of sporadic sodium layers (SSLs) and the thermospheric enhanced sodium layers (TeSLs) observed by a lidar chain located at Beijing (40.2N,116.2E), Hefei (31.8N, 117.3E), Wuhan (30.5N, 114.4E), and Haikou (19.5N, 109.1E). The average SSL occurrence rate was approximately 46.0, 12.3, 13.8, and 15.0 hr per SSL at Beijing, Hefei, Wuhan, and Haikou, respectively. However, the TeSLs occurred relatively infrequently and were more likely to appear at low and high latitudinal sites. Both the SSLs and TeSLs at four lidar sites showed evident summer enhancements and correlated well with Es (foEs>4MHz). The co-observations of SSLs at three lidar site pairs, i.e., Hefei -- Beijing, Hefei -- Wuhan and Hefei -- Beijing, indicated that a large-scale SSL extended horizontally for at least a few hundred kilometers and exhibited a tidal-induced modulation. Moreover, the SSLs were better correlated for the Hefei -- Wuhan and Hefei -- Haikou pairs than the Hefei -- Beijing pair, which suggested a difference in the dynamical/chemical process in mesosphere and lower thermosphere (MLT) between the Beijing site and the other sites.

  17. Swarm accelerometer data processing from raw accelerations to thermospheric neutral densities

    DEFF Research Database (Denmark)

    Siemes, Christian; da Encarnacao, Joao de Teixeira; Doornbos, Eelco

    2016-01-01

    The Swarm satellites were launched on November 22, 2013, and carry accelerometers and GPS receivers as part of their scientific payload. The GPS receivers do not only provide the position and time for the magnetic field measurements, but are also used for determining non-gravitational forces like...... in the acceleration measurements of Swarm B. We show the results of each processing stage, highlight the difficulties encountered, and comment on the quality of the thermospheric neutral density data set......., the most prominent being slow temperature-induced bias variations and sudden bias changes. In this paper, we describe the new, improved four-stage processing that is applied for transforming the disturbed acceleration measurements into scientifically valuable thermospheric neutral densities. In the first...... stage, the sudden bias changes in the acceleration measurements are manually removed using a dedicated software tool. The second stage is the calibration of the accelerometer measurements against the non-gravitational accelerations derived from the GPS receiver, which includes the correction...

  18. Laparoscopic microwave thermosphere ablation of malignant liver tumors: an initial clinical evaluation.

    Science.gov (United States)

    Berber, Eren

    2016-02-01

    Microwave ablation (MWA) has been recently recognized as a technology to overcome the limitations of radiofrequency ablation. The aim of the current study was to evaluate the safety and efficacy of a new 2.45-GHz thermosphere MWA system in the treatment of malignant liver tumors. This was a prospective IRB-approved study of 18 patients with malignant liver tumors treated with MWA within a 3-month time period. Tumor sizes and response to MWA were obtained from triphasic liver CT scans done before and after MWA. The ablation zones were assessed for complete tumor response and spherical geometry. There were a total of 18 patients with an average of three tumors measuring 1.4 cm (range 0.2-4). Ablations were performed laparoscopically in all, but three patients who underwent combined liver resection. A single ablation was created in 72% and overlapping ablations in 28% of lesions. Total ablation time per patient was 15.6 ± 1.9 min. There was no morbidity or mortality. At 2-week CT scans, there was 100% tumor destruction, with no residual lesions. Roundness indices A, B and transverse were 1.1, 0.9 and 0.9, respectively, confirming the spherical nature of ablation zones. To the best of our knowledge, this is the first report of a new thermosphere MWA technology in the laparoscopic treatment of malignant liver tumors. The results demonstrate the safety of the technology, with satisfactory spherical ablation zones seen on post-procedural CT scans.

  19. Retrieval of nitric oxide in the mesosphere and lower thermosphere from SCIAMACHY limb spectra

    Directory of Open Access Journals (Sweden)

    S. Bender

    2013-09-01

    Full Text Available We use the ultra-violet (UV spectra in the range 230–300 nm from the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY to retrieve the nitric oxide (NO number densities from atmospheric emissions in the gamma-bands in the mesosphere and lower thermosphere. Using 3-D ray tracing, a 2-D retrieval grid, and regularisation with respect to altitude and latitude, we retrieve a whole semi-orbit simultaneously for the altitude range from 60 to 160 km. We present details of the retrieval algorithm, first results, and initial comparisons to data from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS. Our results agree on average well with MIPAS data and are in line with previously published measurements from other instruments. For the time of available measurements in 2008–2011, we achieve a vertical resolution of 5–10 km in the altitude range 70–140 km and a horizontal resolution of about 9° from 60° S–60° N. With this we have independent measurements of the NO densities in the mesosphere and lower thermosphere with approximately global coverage. This data can be further used to validate climate models or as input for them.

  20. Modeling of Thermospheric Neutral Density Variations in Response to Geomagnetic Forcing using GRACE Accelerometer Data

    Science.gov (United States)

    Calabia, A.; Matsuo, T.; Jin, S.

    2017-12-01

    The upper atmospheric expansion refers to an increase in the temperature and density of Earth's thermosphere due to increased geomagnetic and space weather activities, producing anomalous atmospheric drag on LEO spacecraft. Increased drag decelerates satellites, moving their orbit closer to Earth, decreasing the lifespan of satellites, and making satellite orbit determination difficult. In this study, thermospheric neutral density variations due to geomagnetic forcing are investigated from 10 years (2003-2013) of GRACE's accelerometer-based estimates. In order to isolate the variations produced by geomagnetic forcing, 99.8% of the total variability has been modeled and removed through the parameterization of annual, LST, and solar-flux variations included in the primary Empirical Orthogonal Functions. The residual disturbances of neutral density variations have been investigated further in order to unravel their relationship to several geomagnetic indices and space weather activity indicators. Stronger fluctuations have been found in the southern polar cap, following the dipole-tilt angle variations. While the parameterization of the residual disturbances in terms of Dst index results in the best fit to training data, the use of merging electric field as a predictor leads to the best forecasting performance. An important finding is that modeling of neutral density variations in response geomagnetic forcing can be improved by accounting for the latitude-dependent delay. Our data-driven modeling results are further compared to modeling with TIEGCM.

  1. Wind energy.

    Science.gov (United States)

    Leithead, W E

    2007-04-15

    From its rebirth in the early 1980s, the rate of development of wind energy has been dramatic. Today, other than hydropower, it is the most important of the renewable sources of power. The UK Government and the EU Commission have adopted targets for renewable energy generation of 10 and 12% of consumption, respectively. Much of this, by necessity, must be met by wind energy. The US Department of Energy has set a goal of 6% of electricity supply from wind energy by 2020. For this potential to be fully realized, several aspects, related to public acceptance, and technical issues, related to the expected increase in penetration on the electricity network and the current drive towards larger wind turbines, need to be resolved. Nevertheless, these challenges will be met and wind energy will, very likely, become increasingly important over the next two decades. An overview of the technology is presented.

  2. Global Ionospheric and Thermospheric Effects of the June 2015 Geomagnetic Disturbances : Multi-Instrumental Observations and Modeling

    NARCIS (Netherlands)

    Astafyeva, E; Zakharenkova, I; Huba, J. D.; Doornbos, E.N.; van den IJssel, J.A.A.

    2017-01-01

    By using data from multiple instruments, we investigate ionospheric/thermospheric behavior during the period from 21 to 23 June 2015, when three interplanetary shocks (IS) of different intensities arrived at Earth. The first IS was registered at 16:45 UT on 21 June and caused ~50 nT increase in

  3. Thermospheric mass density variations during geomagnetic storms and a prediction model based on the merging electric field

    NARCIS (Netherlands)

    Liu, R.; Lühr, H.; Doornbos, E.; Ma, S.Y.

    2010-01-01

    With the help of four years (2002–2005) of CHAMP accelerometer data we have investigated the dependence of low and mid latitude thermospheric density on the merging electric field, Em, during major magnetic storms. Altogether 30 intensive storm events (Dstmin

  4. Regularization of Nonmonotone Variational Inequalities

    International Nuclear Information System (INIS)

    Konnov, Igor V.; Ali, M.S.S.; Mazurkevich, E.O.

    2006-01-01

    In this paper we extend the Tikhonov-Browder regularization scheme from monotone to rather a general class of nonmonotone multivalued variational inequalities. We show that their convergence conditions hold for some classes of perfectly and nonperfectly competitive economic equilibrium problems

  5. Lattice regularized chiral perturbation theory

    International Nuclear Information System (INIS)

    Borasoy, Bugra; Lewis, Randy; Ouimet, Pierre-Philippe A.

    2004-01-01

    Chiral perturbation theory can be defined and regularized on a spacetime lattice. A few motivations are discussed here, and an explicit lattice Lagrangian is reviewed. A particular aspect of the connection between lattice chiral perturbation theory and lattice QCD is explored through a study of the Wess-Zumino-Witten term

  6. 76 FR 3629 - Regular Meeting

    Science.gov (United States)

    2011-01-20

    ... Meeting SUMMARY: Notice is hereby given of the regular meeting of the Farm Credit System Insurance Corporation Board (Board). Date and Time: The meeting of the Board will be held at the offices of the Farm... meeting of the Board will be open to the [[Page 3630

  7. Forcing absoluteness and regularity properties

    NARCIS (Netherlands)

    Ikegami, D.

    2010-01-01

    For a large natural class of forcing notions, we prove general equivalence theorems between forcing absoluteness statements, regularity properties, and transcendence properties over L and the core model K. We use our results to answer open questions from set theory of the reals.

  8. Globals of Completely Regular Monoids

    Institute of Scientific and Technical Information of China (English)

    Wu Qian-qian; Gan Ai-ping; Du Xian-kun

    2015-01-01

    An element of a semigroup S is called irreducible if it cannot be expressed as a product of two elements in S both distinct from itself. In this paper we show that the class C of all completely regular monoids with irreducible identity elements satisfies the strong isomorphism property and so it is globally determined.

  9. Fluid queues and regular variation

    NARCIS (Netherlands)

    Boxma, O.J.

    1996-01-01

    This paper considers a fluid queueing system, fed by N independent sources that alternate between silence and activity periods. We assume that the distribution of the activity periods of one or more sources is a regularly varying function of index ¿. We show that its fat tail gives rise to an even

  10. Fluid queues and regular variation

    NARCIS (Netherlands)

    O.J. Boxma (Onno)

    1996-01-01

    textabstractThis paper considers a fluid queueing system, fed by $N$ independent sources that alternate between silence and activity periods. We assume that the distribution of the activity periods of one or more sources is a regularly varying function of index $zeta$. We show that its fat tail

  11. Empirical laws, regularity and necessity

    NARCIS (Netherlands)

    Koningsveld, H.

    1973-01-01

    In this book I have tried to develop an analysis of the concept of an empirical law, an analysis that differs in many ways from the alternative analyse's found in contemporary literature dealing with the subject.

    1 am referring especially to two well-known views, viz. the regularity and

  12. Interval matrices: Regularity generates singularity

    Czech Academy of Sciences Publication Activity Database

    Rohn, Jiří; Shary, S.P.

    2018-01-01

    Roč. 540, 1 March (2018), s. 149-159 ISSN 0024-3795 Institutional support: RVO:67985807 Keywords : interval matrix * regularity * singularity * P-matrix * absolute value equation * diagonally singilarizable matrix Subject RIV: BA - General Mathematics Impact factor: 0.973, year: 2016

  13. Regularization in Matrix Relevance Learning

    NARCIS (Netherlands)

    Schneider, Petra; Bunte, Kerstin; Stiekema, Han; Hammer, Barbara; Villmann, Thomas; Biehl, Michael

    A In this paper, we present a regularization technique to extend recently proposed matrix learning schemes in learning vector quantization (LVQ). These learning algorithms extend the concept of adaptive distance measures in LVQ to the use of relevance matrices. In general, metric learning can

  14. Wind Turbine Power Curve Design for Optimal Power Generation in Wind Farms Considering Wake Effect

    Directory of Open Access Journals (Sweden)

    Jie Tian

    2017-03-01

    Full Text Available In modern wind farms, maximum power point tracking (MPPT is widely implemented. Using the MPPT method, each individual wind turbine is controlled by its pitch angle and tip speed ratio to generate the maximum active power. In a wind farm, the upstream wind turbine may cause power loss to its downstream wind turbines due to the wake effect. According to the wake model, downstream power loss is also determined by the pitch angle and tip speed ratio of the upstream wind turbine. By optimizing the pitch angle and tip speed ratio of each wind turbine, the total active power of the wind farm can be increased. In this paper, the optimal pitch angle and tip speed ratio are selected for each wind turbine by the exhausted search. Considering the estimation error of the wake model, a solution to implement the optimized pitch angle and tip speed ratio is proposed, which is to generate the optimal control curves for each individual wind turbine off-line. In typical wind farms with regular layout, based on the detailed analysis of the influence of pitch angle and tip speed ratio on the total active power of the wind farm by the exhausted search, the optimization is simplified with the reduced computation complexity. By using the optimized control curves, the annual energy production (AEP is increased by 1.03% compared to using the MPPT method in a case-study of a typical eighty-turbine wind farm.

  15. Regular and conformal regular cores for static and rotating solutions

    Energy Technology Data Exchange (ETDEWEB)

    Azreg-Aïnou, Mustapha

    2014-03-07

    Using a new metric for generating rotating solutions, we derive in a general fashion the solution of an imperfect fluid and that of its conformal homolog. We discuss the conditions that the stress–energy tensors and invariant scalars be regular. On classical physical grounds, it is stressed that conformal fluids used as cores for static or rotating solutions are exempt from any malicious behavior in that they are finite and defined everywhere.

  16. Regular and conformal regular cores for static and rotating solutions

    International Nuclear Information System (INIS)

    Azreg-Aïnou, Mustapha

    2014-01-01

    Using a new metric for generating rotating solutions, we derive in a general fashion the solution of an imperfect fluid and that of its conformal homolog. We discuss the conditions that the stress–energy tensors and invariant scalars be regular. On classical physical grounds, it is stressed that conformal fluids used as cores for static or rotating solutions are exempt from any malicious behavior in that they are finite and defined everywhere.

  17. Grid Integration of Offshore Wind | Wind | NREL

    Science.gov (United States)

    Grid Integration of Offshore Wind Grid Integration of Offshore Wind Much can be learned from the existing land-based integration research for handling the variability and uncertainty of the wind resource Arklow Bank offshore wind park consists of seven GE Wind 3.6-MW wind turbines. Integration and

  18. Wind Energy

    Energy Technology Data Exchange (ETDEWEB)

    Beurskens, H.J.M. [SET Analysis, Kievitlaan 26, 1742 AD Schagen (Netherlands); Brand, A.J. [Energy research Centre of the Netherlands ECN, Unit Wind Energy, P.O. Box 1, 1755 ZG Petten (Netherlands)

    2013-02-15

    Over the years, wind energy has become a major source of renewable energy worldwide. The present chapter addresses the wind resource, which is available for exploitation for large-scale electricity production, and its specific physical properties. Furthermore, the technical options available to convert the energy of the air flow into mechanical energy and electricity are described. Specific problems of large-scale integration of wind energy into the grid as well as the present and future market developments are described in this chapter. Finally, environmental aspects are discussed briefly.

  19. World Wind

    Data.gov (United States)

    National Aeronautics and Space Administration — World Wind allows any user to zoom from satellite altitude into any place on Earth, leveraging high resolution LandSat imagery and SRTM elevation data to experience...

  20. Wind power

    International Nuclear Information System (INIS)

    2009-01-01

    At the end of 2008,the European wind power capacity had risen to 65,247 MW which is a 15,1% increase on 2007. The financial crisis does not appear to have any real consequences of the wind power sector's activity in 2008. At the end of 2008 the European Union accommodated 53,9% of the world's wind power capacity. The top ten countries in terms of installed wind capacities are: 1) Usa with 25,388 MW, 2) Germany with 23,903 MW, 3) Spain with 16,740 MW, 4) China with 12,200 MW, 5) India with 9,645 MW, 6) Italy with 3,736 MW, 7) France with 3,542 MW, 8) U.K. with 3,406 MW, 9) Denmark with 3,166 MW and 10) Portugal with 2,862 MW. (A.C.)

  1. Energy functions for regularization algorithms

    Science.gov (United States)

    Delingette, H.; Hebert, M.; Ikeuchi, K.

    1991-01-01

    Regularization techniques are widely used for inverse problem solving in computer vision such as surface reconstruction, edge detection, or optical flow estimation. Energy functions used for regularization algorithms measure how smooth a curve or surface is, and to render acceptable solutions these energies must verify certain properties such as invariance with Euclidean transformations or invariance with parameterization. The notion of smoothness energy is extended here to the notion of a differential stabilizer, and it is shown that to void the systematic underestimation of undercurvature for planar curve fitting, it is necessary that circles be the curves of maximum smoothness. A set of stabilizers is proposed that meet this condition as well as invariance with rotation and parameterization.

  2. Physical model of dimensional regularization

    Energy Technology Data Exchange (ETDEWEB)

    Schonfeld, Jonathan F.

    2016-12-15

    We explicitly construct fractals of dimension 4-ε on which dimensional regularization approximates scalar-field-only quantum-field theory amplitudes. The construction does not require fractals to be Lorentz-invariant in any sense, and we argue that there probably is no Lorentz-invariant fractal of dimension greater than 2. We derive dimensional regularization's power-law screening first for fractals obtained by removing voids from 3-dimensional Euclidean space. The derivation applies techniques from elementary dielectric theory. Surprisingly, fractal geometry by itself does not guarantee the appropriate power-law behavior; boundary conditions at fractal voids also play an important role. We then extend the derivation to 4-dimensional Minkowski space. We comment on generalization to non-scalar fields, and speculate about implications for quantum gravity. (orig.)

  3. Maximum mutual information regularized classification

    KAUST Repository

    Wang, Jim Jing-Yan

    2014-09-07

    In this paper, a novel pattern classification approach is proposed by regularizing the classifier learning to maximize mutual information between the classification response and the true class label. We argue that, with the learned classifier, the uncertainty of the true class label of a data sample should be reduced by knowing its classification response as much as possible. The reduced uncertainty is measured by the mutual information between the classification response and the true class label. To this end, when learning a linear classifier, we propose to maximize the mutual information between classification responses and true class labels of training samples, besides minimizing the classification error and reducing the classifier complexity. An objective function is constructed by modeling mutual information with entropy estimation, and it is optimized by a gradient descend method in an iterative algorithm. Experiments on two real world pattern classification problems show the significant improvements achieved by maximum mutual information regularization.

  4. Maximum mutual information regularized classification

    KAUST Repository

    Wang, Jim Jing-Yan; Wang, Yi; Zhao, Shiguang; Gao, Xin

    2014-01-01

    In this paper, a novel pattern classification approach is proposed by regularizing the classifier learning to maximize mutual information between the classification response and the true class label. We argue that, with the learned classifier, the uncertainty of the true class label of a data sample should be reduced by knowing its classification response as much as possible. The reduced uncertainty is measured by the mutual information between the classification response and the true class label. To this end, when learning a linear classifier, we propose to maximize the mutual information between classification responses and true class labels of training samples, besides minimizing the classification error and reducing the classifier complexity. An objective function is constructed by modeling mutual information with entropy estimation, and it is optimized by a gradient descend method in an iterative algorithm. Experiments on two real world pattern classification problems show the significant improvements achieved by maximum mutual information regularization.

  5. Modeling the solar cycle change in nitric oxide in the thermosphere and upper mesosphere

    International Nuclear Information System (INIS)

    Fuller-Rowell, T.J.

    1993-01-01

    Measurements from the Solar Mesosphere Explorer (SME) satellite have shown that low-latitude nitric oxide densities at 110 km decrease by about a factor of 8 from January 1982 to April 1985. This time period corresponds to the descending phase of the last solar cycle where the monthly smoothed sunspot number decreased from more than 150 to less than 25. In addition, nitric oxide was observed to vary by a factor of 2 over a solar rotation, during high solar activity. A one-dimensional, globally averaged model of the thermosphere and upper mesosphere has been used to study the height distribution of nitric oxide (NO) and its response to changes in the solar extreme ultraviolet radiation (EUV) through the solar cycle and over a solar rotation. The primary source of nitric oxide is the reaction of excited atomic nitrogen, N( 2 D), with molecular oxygen. The atomic nitrogen is created by a number of ion-neutral reactions and by direct dissociation of molecular nitrogen by photons and photoelectrons. The occurrence of the peak nitric oxide density at or below 115 km is a direct consequence of ionization and dissociation of molecular nitrogen by photoelectrons, which are produced by the solar flux below 30.0 nm (XUV). Nitric oxide is shown to vary over the solar cycle by a factor of 7 at low latitudes in the lower thermosphere E region, due to the estimated change in the solar EUV flux, in good agreement with the SME satellite observations. The NO density is shown to be strongly dependent on the temperature profile in the lower thermosphere and accounts for the difference between the current model and previous work. Wavelengths less than 1.8 nm have little impact on the NO profile. A factor of 3 change in solar flux below 5.0 nm at high solar activity produced a factor of 2 change in the peak NO density, consistent with SME observations over a solar rotation; this change also lowered the peak to 100 km, consistent with rocket data. 52 refs., 10 figs., 5 tabs

  6. Regularized strings with extrinsic curvature

    International Nuclear Information System (INIS)

    Ambjoern, J.; Durhuus, B.

    1987-07-01

    We analyze models of discretized string theories, where the path integral over world sheet variables is regularized by summing over triangulated surfaces. The inclusion of curvature in the action is a necessity for the scaling of the string tension. We discuss the physical properties of models with extrinsic curvature terms in the action and show that the string tension vanishes at the critical point where the bare extrinsic curvature coupling tends to infinity. Similar results are derived for models with intrinsic curvature. (orig.)

  7. Circuit complexity of regular languages

    Czech Academy of Sciences Publication Activity Database

    Koucký, Michal

    2009-01-01

    Roč. 45, č. 4 (2009), s. 865-879 ISSN 1432-4350 R&D Projects: GA ČR GP201/07/P276; GA MŠk(CZ) 1M0545 Institutional research plan: CEZ:AV0Z10190503 Keywords : regular languages * circuit complexity * upper and lower bounds Subject RIV: BA - General Mathematics Impact factor: 0.726, year: 2009

  8. Wind power

    Energy Technology Data Exchange (ETDEWEB)

    1979-01-01

    This publication describes some of the technical, economic, safety and institutional considerations involved in the selection, installation and evaluation of a wind generation system. This information is presented, where possible, in practical, non-technical terms. The first four sections provide background information, theory, and general knowledge, while the remaining six sections are of a more specific nature to assist the prospective owner of a wind generator in his calculations and selections. Meteorological information is provided relating to the wind regime in Nova Scotia. The section on cost analysis discusses some of the factors and considerations which must be examined in order to provide a logical comparison between the alternatives of electricity produced from other sources. The final two sections are brief summaries of the regulations and hazards pertaining to the use of wind generators. The cost of wind-generated electricity is high compared to present Nova Scotia Power Corporation rates, even on Sable Island, Nova Scotia's highest wind area. However, it may be observed that Sable Island is one of the areas of Nova Scotia which is not presently supplied through the power grid and, particularly if there was a significant increase in the price of diesel oil, wind-generated electricity may well be the most economical alternative in that area. Generally speaking, however, where a consumer can purchase electricity at the normal domestic rate, wind generators are not economical, and they will not become economical unless there is a great reduction in their cost, an great increase in electricity rates, or both. Includes glossary. 23 figs., 11 tabs.

  9. General inverse problems for regular variation

    DEFF Research Database (Denmark)

    Damek, Ewa; Mikosch, Thomas Valentin; Rosinski, Jan

    2014-01-01

    Regular variation of distributional tails is known to be preserved by various linear transformations of some random structures. An inverse problem for regular variation aims at understanding whether the regular variation of a transformed random object is caused by regular variation of components ...

  10. Full nonlinear treatment of the global thermospheric wind system. Part 1: Mathematical method and analysis of forces

    Science.gov (United States)

    Blum, P. W.; Harris, I.

    1973-01-01

    The equations of horizontal motion of the neutral atmosphere between 120 and 500 km are integrated with the inclusion of all the nonlinear terms of the convective derivative and the viscous forces due to vertical and horizontal velocity gradients. Empirical models of the distribution of neutral and charged particles are assumed to be known. The model of velocities developed is a steady state model. In part 1 the mathematical method used in the integration of the Navier-Stokes equations is described and the various forces are analysed.

  11. The possible effect of solar soft X rays on thermospheric nitric oxide

    International Nuclear Information System (INIS)

    Siskind, D.E.; Barth, C.A.; Cleary, D.D.

    1990-01-01

    A rocket measurement of thermospheric nitric oxide (NO) is used to evaluate the production of odd nitrogen by solar soft X rays (18-50 angstrom). The rocket observation was performed over White Sands Missile Range on November 9, 1981, at 1500 LT for solar maximum conditions (F10.7 = 233). The peak observed NO density was 6.3 x 10 7 cm -3 at 102 km. A photochemical model which included soft X rays was used for comparison with the data. The soft X rays create photoelectrons which lead to enhanced ionization of N 2 and thus increased odd nitrogen production. A good fit to the data was achieved using a soft X ray flux of 0.75 erg cm -2 s -1

  12. An investigation of the solar cycle response of odd-nitrogen in the thermosphere

    Science.gov (United States)

    Rusch, David W.; Solomon, Stanley C.

    1992-01-01

    This annual report covers the first year of funding for the study of the solar cycle variations of odd-nitrogen (N((sup 2)D), N((sup 4)S), NO) in the Earth's thermosphere. The study uses the extensive data base generated by the Atmosphere Explorer (AE) satellites, and the Solar Mesosphere Explorer Satellite. The AE data are being used, for the first time, to define the solar variability effect on the odd-nitrogen species through analysis of the emissions at 520 nano-m from N((sup 2)D) and the emission from O(+)((sup 2)P). Additional AE neutral and ion density data are used to help define and quantify the physical processes controlling the variations. The results from the airglow study will be used in the next two years of this study to explain the solar cycle changes in NO measured by the Solar Mesosphere Explorer.

  13. Secondary gravity waves from momentum deposition in the stratosphere, mesosphere, thermosphere and ionosphere

    Science.gov (United States)

    Vadas, S.

    2017-12-01

    In this paper, we investigate the generation, propagation and effectsof secondary gravity waves (GWs) from momentum deposition in the stratosphere, mesosphere, thermosphere and ionosphere in high-resolution GW-resolving models and in TEC/lidar/redline data. We show that secondary GWs generated from the dissipation of orographic GWs at McMurdo Station in Antarctica play a dominant role in the wave activity over McMurdo in the wintertime mesosphere. These secondary GWs are created in the stratosphere, and have been identified in models and data via their telltale "fishbone" appearance in z-t plots. We also show that secondary GWs from the dissipation of GWs excited by deep convectiongenerate concentric rings in the F-region ionosphere. These model results and data point to the importance of secondary GWs from momentumdeposition in the Earth's atmosphere and ionosphere.

  14. Vibrational-rotational temperature measurement of N2 in the lower thermosphere by the rocket experiment

    Science.gov (United States)

    Kurihara, J.; Oyama, K.; Suzuki, K.; Iwagami, N.

    The vibrational temperature (Tv), the rotational temperature (Tr) and the density of atmospheric N2 between 100 - 150 km were measured in situ by a sounding rocket S310-30, over Kagoshima, Japan at 10:30 UT on February 6, 2002. The main purpose of this rocket experiment is to study the dynamics and the thermal energy budget in the lower thermosphere. N2 was ionized using an electron gun and the emission of the 1st negative bands of N2+ was measured by a sensitive spectrometer. Tv and Tr were determined by fitting the observed spectrum for the simulated spectrum, and the number density was deduced from the intensities of the spectrum. We will report preliminary results of our measurement and discuss the observed thermal structure that indicates the effect of tides and gravity waves.

  15. Thermosphere-ionosphere-mesosphere energetics and dynamics (TIMED). The TIMED mission and science program report of the science definition team. Volume 1: Executive summary

    Science.gov (United States)

    1991-01-01

    A Science Definition Team was established in December 1990 by the Space Physics Division, NASA, to develop a satellite program to conduct research on the energetics, dynamics, and chemistry of the mesosphere and lower thermosphere/ionosphere. This two-volume publication describes the TIMED (Thermosphere-Ionosphere-Mesosphere, Energetics and Dynamics) mission and associated science program. The report outlines the scientific objectives of the mission, the program requirements, and the approach towards meeting these requirements.

  16. Utilizing Probability Distribution Functions and Ensembles to Forecast lonospheric and Thermosphere Space Weather

    Science.gov (United States)

    2016-04-26

    geomagnetic field geometry , zonal wind, meridional wind, high-latitude activity, migrating tides from the lower atmosphere, and solar illumination in...Earth is strongly driven by the solar wind and interplanetary magnetic field (IMF), which are only measured about one hour before they encounter the...Earth’s magnetosphere. This means that it is almost impossible to predict the state of the upper atmosphere without predicting the solar wind and

  17. Characterizing the Meso-scale Plasma Flows in Earth's Coupled Magnetosphere-Ionosphere-Thermosphere System

    Science.gov (United States)

    Gabrielse, C.; Nishimura, T.; Lyons, L. R.; Gallardo-Lacourt, B.; Deng, Y.; McWilliams, K. A.; Ruohoniemi, J. M.

    2017-12-01

    NASA's Heliophysics Decadal Survey put forth several imperative, Key Science Goals. The second goal communicates the urgent need to "Determine the dynamics and coupling of Earth's magnetosphere, ionosphere, and atmosphere and their response to solar and terrestrial inputs...over a range of spatial and temporal scales." Sun-Earth connections (called Space Weather) have strong societal impacts because extreme events can disturb radio communications and satellite operations. The field's current modeling capabilities of such Space Weather phenomena include large-scale, global responses of the Earth's upper atmosphere to various inputs from the Sun, but the meso-scale ( 50-500 km) structures that are much more dynamic and powerful in the coupled system remain uncharacterized. Their influences are thus far poorly understood. We aim to quantify such structures, particularly auroral flows and streamers, in order to create an empirical model of their size, location, speed, and orientation based on activity level (AL index), season, solar cycle (F10.7), interplanetary magnetic field (IMF) inputs, etc. We present a statistical study of meso-scale flow channels in the nightside auroral oval and polar cap using SuperDARN. These results are used to inform global models such as the Global Ionosphere Thermosphere Model (GITM) in order to evaluate the role of meso-scale disturbances on the fully coupled magnetosphere-ionosphere-thermosphere system. Measuring the ionospheric footpoint of magnetospheric fast flows, our analysis technique from the ground also provides a 2D picture of flows and their characteristics during different activity levels that spacecraft alone cannot.

  18. Tropospheric weather influenced by solar wind through atmospheric vertical coupling downward control

    Science.gov (United States)

    Prikryl, Paul; Bruntz, Robert; Tsukijihara, Takumi; Iwao, Koki; Muldrew, Donald B.; Rušin, Vojto; Rybanský, Milan; Turňa, Maroš; Šťastný, Pavel

    2018-06-01

    Occurrence of severe weather in the context of solar wind coupling to the magnetosphere-ionosphere-atmosphere (MIA) system is investigated. It is observed that significant snowfall, wind and heavy rain, particularly if caused by low pressure systems in winter, tend to follow arrivals of high-speed solar wind. Previously published statistical evidence that explosive extratropical cyclones in the northern hemisphere tend to occur within a few days after arrivals of high-speed solar wind streams from coronal holes (Prikryl et al., 2009, 2016) is corroborated for the southern hemisphere. Cases of severe weather events are examined in the context of the magnetosphere-ionosphere-atmosphere (MIA) coupling. Physical mechanism to explain these observations is proposed. The leading edge of high-speed solar wind streams is a locus of large-amplitude magneto-hydrodynamic waves that modulate Joule heating and/or Lorentz forcing of the high-latitude lower thermosphere generating medium-scale atmospheric gravity waves that propagate upward and downward through the atmosphere. Simulations of gravity wave propagation in a model atmosphere using the Transfer Function Model (Mayr et al., 1990) reveal that propagating waves originating in the lower thermosphere can excite a spectrum of gravity waves in the lower atmosphere. In spite of significantly reduced amplitudes but subject to amplification upon reflection in the upper troposphere, these gravity waves can provide a lift of unstable air to release instabilities in the troposphere and initiate convection to form cloud/precipitation bands. It is primarily the energy provided by release of latent heat that leads to intensification of storms. These results indicate that vertical coupling in the atmosphere exerts downward control from solar wind to the lower atmospheric levels influencing tropospheric weather development.

  19. Regularized Statistical Analysis of Anatomy

    DEFF Research Database (Denmark)

    Sjöstrand, Karl

    2007-01-01

    This thesis presents the application and development of regularized methods for the statistical analysis of anatomical structures. Focus is on structure-function relationships in the human brain, such as the connection between early onset of Alzheimer’s disease and shape changes of the corpus...... and mind. Statistics represents a quintessential part of such investigations as they are preluded by a clinical hypothesis that must be verified based on observed data. The massive amounts of image data produced in each examination pose an important and interesting statistical challenge...... efficient algorithms which make the analysis of large data sets feasible, and gives examples of applications....

  20. Regularization methods in Banach spaces

    CERN Document Server

    Schuster, Thomas; Hofmann, Bernd; Kazimierski, Kamil S

    2012-01-01

    Regularization methods aimed at finding stable approximate solutions are a necessary tool to tackle inverse and ill-posed problems. Usually the mathematical model of an inverse problem consists of an operator equation of the first kind and often the associated forward operator acts between Hilbert spaces. However, for numerous problems the reasons for using a Hilbert space setting seem to be based rather on conventions than on an approprimate and realistic model choice, so often a Banach space setting would be closer to reality. Furthermore, sparsity constraints using general Lp-norms or the B

  1. Academic Training Lecture - Regular Programme

    CERN Multimedia

    PH Department

    2011-01-01

    Regular Lecture Programme 9 May 2011 ACT Lectures on Detectors - Inner Tracking Detectors by Pippa Wells (CERN) 10 May 2011 ACT Lectures on Detectors - Calorimeters (2/5) by Philippe Bloch (CERN) 11 May 2011 ACT Lectures on Detectors - Muon systems (3/5) by Kerstin Hoepfner (RWTH Aachen) 12 May 2011 ACT Lectures on Detectors - Particle Identification and Forward Detectors by Peter Krizan (University of Ljubljana and J. Stefan Institute, Ljubljana, Slovenia) 13 May 2011 ACT Lectures on Detectors - Trigger and Data Acquisition (5/5) by Dr. Brian Petersen (CERN) from 11:00 to 12:00 at CERN ( Bldg. 222-R-001 - Filtration Plant )

  2. An Intense Traveling Airglow Front in the Upper Mesosphere-Lower Thermosphere with Characteristic of a Turbulent Bore Observed over Alice Springs, Australia

    Science.gov (United States)

    Walterscheid, R. L.; Hecht, J. H.; Hickey, M. P.; Gelinas, L. J.; Vincent, R. A.; Reid, I. M.; Woithe, J.

    2010-12-01

    The Aerospace Corporation’s Nightglow Imager observed a large step-function change in airglow in the form of a traveling front in the OH and O2 airglow emissions over Alice Springs Australia on February 2, 2003. The front exhibited a stepwise increase of nearly a factor two in the OH brightness and a stepwise decrease in the O2 brightness. The change in brightness in each layer was associated with a strong leading disturbance followed by a train of weak barely visible waves. The OH airglow brightness behind the front was the brightness night for 02 at Alice Springs that we have measured in seven years of observations. The OH brightness was among the five brightest. The event was associated with a strong phase-locked two-day wave (TDW).We have analyzed the stability conditions for the upper mesosphere and lower thermosphere and found that the airglow layers were found in a region of strong ducting. The thermal structure was obtained from combining data from the SABER instrument on the TIMED satellite and the NRLMSISE-00 model. The wind profile was obtained by combining the HWM07 model and MF radar winds from Buckland Park Australia. We found that the TDW-disturbed profile was significantly more effective in supporting a high degree of ducting than a profile based only on HWM07 winds. Dramatic wall events have been interpreted as manifestations of undular bores (e.g., Smith et al. [2003]). Undular bores are nonlinear high Froude number events that must generate an ever increasing train of waves to carry the excess energy away from the bore front. Only a very weak wave train behind the initial disturbance was seen for the Alice Springs event. The form of the amplitude ordering was not typical of a nonlinear wave train. Therefore a bore interpretation requires another means of energy dissipation, namely turbulent dissipation. We suggest that a reasonable interpretation of the observed event is a turbulent bore. We are unaware of any previous event having

  3. Wind Generators

    Science.gov (United States)

    1989-01-01

    When Enerpro, Inc. president, Frank J. Bourbeau, attempted to file a patent on a system for synchronizing a wind generator to the electric utility grid, he discovered Marshall Space Flight Center's Frank Nola's power factor controller. Bourbeau advanced the technology and received a NASA license and a patent for his Auto Synchronous Controller (ASC). The ASC reduces generator "inrush current," which occurs when large generators are abruptly brought on line. It controls voltage so the generator is smoothly connected to the utility grid when it reaches its synchronous speed, protecting the components from inrush current damage. Generator efficiency is also increased in light winds by applying lower than rated voltage. Wind energy is utilized to drive turbines to generate electricity for utility companies.

  4. Wind turbine

    Science.gov (United States)

    Cheney, Jr., Marvin C.

    1982-01-01

    A wind turbine of the type having an airfoil blade (15) mounted on a flexible beam (20) and a pitch governor (55) which selectively, torsionally twists the flexible beam in response to wind turbine speed thereby setting blade pitch, is provided with a limiter (85) which restricts unwanted pitch change at operating speeds due to torsional creep of the flexible beam. The limiter allows twisting of the beam by the governor under excessive wind velocity conditions to orient the blades in stall pitch positions, thereby preventing overspeed operation of the turbine. In the preferred embodiment, the pitch governor comprises a pendulum (65,70) which responds to changing rotor speed by pivotal movement, the limiter comprising a resilient member (90) which engages an end of the pendulum to restrict further movement thereof, and in turn restrict beam creep and unwanted blade pitch misadjustment.

  5. RES: Regularized Stochastic BFGS Algorithm

    Science.gov (United States)

    Mokhtari, Aryan; Ribeiro, Alejandro

    2014-12-01

    RES, a regularized stochastic version of the Broyden-Fletcher-Goldfarb-Shanno (BFGS) quasi-Newton method is proposed to solve convex optimization problems with stochastic objectives. The use of stochastic gradient descent algorithms is widespread, but the number of iterations required to approximate optimal arguments can be prohibitive in high dimensional problems. Application of second order methods, on the other hand, is impracticable because computation of objective function Hessian inverses incurs excessive computational cost. BFGS modifies gradient descent by introducing a Hessian approximation matrix computed from finite gradient differences. RES utilizes stochastic gradients in lieu of deterministic gradients for both, the determination of descent directions and the approximation of the objective function's curvature. Since stochastic gradients can be computed at manageable computational cost RES is realizable and retains the convergence rate advantages of its deterministic counterparts. Convergence results show that lower and upper bounds on the Hessian egeinvalues of the sample functions are sufficient to guarantee convergence to optimal arguments. Numerical experiments showcase reductions in convergence time relative to stochastic gradient descent algorithms and non-regularized stochastic versions of BFGS. An application of RES to the implementation of support vector machines is developed.

  6. Regularized Label Relaxation Linear Regression.

    Science.gov (United States)

    Fang, Xiaozhao; Xu, Yong; Li, Xuelong; Lai, Zhihui; Wong, Wai Keung; Fang, Bingwu

    2018-04-01

    Linear regression (LR) and some of its variants have been widely used for classification problems. Most of these methods assume that during the learning phase, the training samples can be exactly transformed into a strict binary label matrix, which has too little freedom to fit the labels adequately. To address this problem, in this paper, we propose a novel regularized label relaxation LR method, which has the following notable characteristics. First, the proposed method relaxes the strict binary label matrix into a slack variable matrix by introducing a nonnegative label relaxation matrix into LR, which provides more freedom to fit the labels and simultaneously enlarges the margins between different classes as much as possible. Second, the proposed method constructs the class compactness graph based on manifold learning and uses it as the regularization item to avoid the problem of overfitting. The class compactness graph is used to ensure that the samples sharing the same labels can be kept close after they are transformed. Two different algorithms, which are, respectively, based on -norm and -norm loss functions are devised. These two algorithms have compact closed-form solutions in each iteration so that they are easily implemented. Extensive experiments show that these two algorithms outperform the state-of-the-art algorithms in terms of the classification accuracy and running time.

  7. 78 FR 29364 - Exelon Corporation, Exelon Wind 1, LLC, Exelon Wind 2, LLC, Exelon Wind 3, LLC, Exelon Wind 4...

    Science.gov (United States)

    2013-05-20

    ...-005, QF07-55-005, QF07-56-005, QF07-257-004] Exelon Corporation, Exelon Wind 1, LLC, Exelon Wind 2, LLC, Exelon Wind 3, LLC, Exelon Wind 4, LLC, Exelon Wind 5, LLC, Exelon Wind 6, LLC, Exelon Wind 7, LLC, Exelon Wind 8, LLC, Exelon Wind 9, LLC, Exelon Wind 10, LLC, Exelon Wind 11, LLC, High Plains...

  8. The effects of neutral inertia on ionospheric currents in the high-latitude thermosphere following a geomagnetic storm

    International Nuclear Information System (INIS)

    Deng, W.; Killeen, T.L.; Burns, A.G.; Roble, R.G.; Slavin, J.A.; Wharton, L.E.

    1993-01-01

    The authors extend previous work with a National Center for Atmospheric Research (NCAR) thermosphere/ionosphere general circulation model (TIGCM), to study dynamo effects in the high latitude thermosphere. Ionospheric convection can drive neutral currents in much the same pattern by means of ion drag reactions. It has been observed that ion currents established during magnetic storms can induce neutral currents which persist for hours after the end of the storm. Model results have shown that such currents can account for up to 80 percent of the Hall currents in the period immediately following storms. Here this previous work is extended and compared with experimental observations. The authors simulate time dependent Hall currents, field-aligned currents, and electrical power fluxes coupling the magnetosphere and ionosphere. They discuss their results in terms of a loaded magnetosphere, which accounts for the fact that the neutral currents can also induce currents and electric fields in the ionosphere

  9. Remote Sensing Wind and Wind Shear System.

    Science.gov (United States)

    Contents: Remote sensing of wind shear and the theory and development of acoustic doppler; Wind studies; A comparison of methods for the remote detection of winds in the airport environment; Acoustic doppler system development; System calibration; Airport operational tests.

  10. Experimental and numerical study of a 10MW TLP wind turbine in waves and wind

    DEFF Research Database (Denmark)

    Pegalajar Jurado, Antonio Manuel; Hansen, Anders Mandrup; Laugesen, Robert

    2016-01-01

    with the tests by matching key system features, namely the steady thrust curve and the decay tests in water. The calibrated model is used to reproduce the wind-wave climates in the laboratory, including regular and irregular waves, with and without wind. The model predictions are compared to the measured data......This paper presents tests on a 1:60 version of the DTU 10MW wind turbine mounted on a tension leg platform and their numerical reproduction. Both the experimental setup and the numerical model are Froude-scaled, and the dynamic response of the floating wind turbine to wind and waves is compared......, and a good agreement is found for surge and heave, while some discrepancies are observed for pitch, nacelle acceleration and line tension. The addition of wind generally improves the agreement with test results. The aerodynamic damping is identified in both tests and simulations. Finally, the sources...

  11. Resonant dissociation in N2 by electron impact: a source of heating in the thermosphere and auroras

    International Nuclear Information System (INIS)

    Spence, D.; Burrow, P.D.

    1979-01-01

    An electron impact resonant dissociation process, leading to superthermal atom production in molecular nitrogen is described. The maximum cross section for this process is found to be 2.5 x 10 -18 cm 2 at 10 eV. Measurements of scattered electrons indicate a value of -65 to -90 MeV for the electron affinity of N. The possible role of resonant dissociation as a source of heating in the thermosphere and in auroras is discussed

  12. Study of gravity waves propagation in the thermosphere of Mars based on MAVEN/NGIMS density measurements

    Science.gov (United States)

    Vals, M.

    2017-09-01

    We use MAVEN/NGIMS CO2 density measurements to analyse gravity waves in the thermosphere of Mars. In particular the seasonal/latitudinal variability of their amplitude is studied and interpreted. Key background parameters controlling the activity of gravity waves are analysed with the help of the Mars Climate Database (MCD). Gravity waves activity presents a good anti-correlation to the temperature variability retrieved from the MCD. An analysis at pressure levels is ongoing.

  13. Wind energy

    International Nuclear Information System (INIS)

    Portilla S, L.A.

    1995-01-01

    The wind energy or eolic energy is a consequence of solar energy, the one which is absorbed by the atmosphere and is transformed into energy of movement of large bulks of air. In this process the atmosphere acts as the filter to the solar radiation and demotes the ultraviolet beams that result fatal to life in the Earth. The ionosphere is the most external cap and this is ionized by means of absorption process of ultraviolet radiation arising to the Sun. The atmosphere also acts as a trap to the infrared radiation, it that results from the continual process of energetic degradation. In this way, the interaction between Earth - Atmospheres, is behaved as a great greenhouse, maintaining the constant temperatures, including in the dark nights. Processes as the natural convection (that occur by the thermodynamic phenomenon), equatorial calmness, trade winds and against trade winds and global distribution of the air currents are described. The other hand, techniques as the transformation of the wind into energy and its parameters also are shown

  14. Wind power

    International Nuclear Information System (INIS)

    2006-06-01

    This road-map proposes by the Group Total aims to inform the public on the wind power. It presents the principles, the technology takes off, its applications and technology focus, the global market trends and the outlooks and Total commitments in the domain. (A.L.B.)

  15. Wind Energy Japan

    Energy Technology Data Exchange (ETDEWEB)

    Komatsubara, Kazuyo [Embassy of the Kingdom of the Netherlands, Tokyo (Japan)

    2012-06-15

    An overview is given of wind energy in Japan: Background; Wind Energy in Japan; Japanese Wind Energy Industry; Government Supports; Useful Links; Major Japanese Companies; Profiles of Major Japanese Companies; Major Wind Energy Projects in Japan.

  16. Wind energy systems

    Science.gov (United States)

    Stewart, H. J.

    1978-01-01

    A discussion on wind energy systems involved with the DOE wind energy program is presented. Some of the problems associated with wind energy systems are discussed. The cost, efficiency, and structural design of wind energy systems are analyzed.

  17. From inactive to regular jogger

    DEFF Research Database (Denmark)

    Lund-Cramer, Pernille; Brinkmann Løite, Vibeke; Bredahl, Thomas Viskum Gjelstrup

    study was conducted using individual semi-structured interviews on how a successful long-term behavior change had been achieved. Ten informants were purposely selected from participants in the DANO-RUN research project (7 men, 3 women, average age 41.5). Interviews were performed on the basis of Theory...... of Planned Behavior (TPB) and The Transtheoretical Model (TTM). Coding and analysis of interviews were performed using NVivo 10 software. Results TPB: During the behavior change process, the intention to jogging shifted from a focus on weight loss and improved fitness to both physical health, psychological......Title From inactive to regular jogger - a qualitative study of achieved behavioral change among recreational joggers Authors Pernille Lund-Cramer & Vibeke Brinkmann Løite Purpose Despite extensive knowledge of barriers to physical activity, most interventions promoting physical activity have proven...

  18. Tessellating the Sphere with Regular Polygons

    Science.gov (United States)

    Soto-Johnson, Hortensia; Bechthold, Dawn

    2004-01-01

    Tessellations in the Euclidean plane and regular polygons that tessellate the sphere are reviewed. The regular polygons that can possibly tesellate the sphere are spherical triangles, squares and pentagons.

  19. On the equivalence of different regularization methods

    International Nuclear Information System (INIS)

    Brzezowski, S.

    1985-01-01

    The R-circunflex-operation preceded by the regularization procedure is discussed. Some arguments are given, according to which the results may depend on the method of regularization, introduced in order to avoid divergences in perturbation calculations. 10 refs. (author)

  20. The uniqueness of the regularization procedure

    International Nuclear Information System (INIS)

    Brzezowski, S.

    1981-01-01

    On the grounds of the BPHZ procedure, the criteria of correct regularization in perturbation calculations of QFT are given, together with the prescription for dividing the regularized formulas into the finite and infinite parts. (author)

  1. Observations of Upper Thermospheric Temperatures Using a Ground-Based Optical Instrument at the King Sejong Station, Antarctic

    Directory of Open Access Journals (Sweden)

    Jong-Kyun Chung

    1998-06-01

    Full Text Available We measured the terrestrial nightglow of OI 6300A in the thermosphere(~250km using a ground-based Fabry-Perot interferometer at the King Sejong Station, Antarctic from March through September, 1997. The King Sejong Station is located at high latitude geographically (62.22 deg S, 301.25 deg E but at mid-latitude geomagnetically (50.65 deg S, 7.51 deg E. It is therefore the strategic location to measure the temperatures of the thermosphere in the Southern Hemisphere associated with both solar and geomagnetic activities. In this study, we analyzed the observed temperatures in relation to F10.7 and Kp indices to examine the effect of the solar and the geomagnetic activities on high-latitude neutral thermosphere. During the observing period, the solar activity was at its minimum. The measured temperatures are usually in the range between about 600~1000 K with some seasonal variation and are higher than those predicted by semi-empirical model, VSH (Vector Spherical Harmonics and empirical model, MSIS (Mass-Spectrometer-Incoherent-Scatter-86.

  2. Observations of Upper Thermospheric Temperatures Using a Ground-Based Optical Instrument at the King Sejong Station, Antarctic

    Science.gov (United States)

    Chung, Jong-Kyun; Won, Young-In; Lee, Bang Yong; Kim, Jhoon

    1998-06-01

    We measured the terrestrial nightglow of OI 6300A in the thermosphere(~250km) using a ground-based Fabry-Perot interferometer at the King Sejong Station, Antarctic from March through September, 1997. The King Sejong Station is located at high latitude geographically (62.22 deg S, 301.25 deg E) but at mid-latitude geomagnetically (50.65 deg S, 7.51 deg E). It is therefore the strategic location to measure the temperatures of the thermosphere in the Southern Hemisphere associated with both solar and geomagnetic activities. In this study, we analyzed the observed temperatures in relation to F10.7 and Kp indices to examine the effect of the solar and the geomagnetic activities on high-latitude neutral thermosphere. During the observing period, the solar activity was at its minimum. The measured temperatures are usually in the range between about 600~1000 K with some seasonal variation and are higher than those predicted by semi-empirical model, VSH (Vector Spherical Harmonics) and empirical model, MSIS (Mass-Spectrometer-Incoherent-Scatter)-86.

  3. MIPAS observations of longitudinal oscillations in the mesosphere and the lower thermosphere: climatology of odd-parity daily frequency modes

    Directory of Open Access Journals (Sweden)

    M. García-Comas

    2016-09-01

    Full Text Available MIPAS global Sun-synchronous observations are almost fixed in local time. Subtraction of the descending and ascending node measurements at each longitude only includes the longitudinal oscillations with odd daily frequencies nodd from the Sun's perspective at 10:00. Contributions from the background atmosphere, daily-invariant zonal oscillations and tidal modes with even-parity daily frequencies vanish. We have determined longitudinal oscillations in MIPAS temperature with nodd and wavenumber k = 0–4 from the stratosphere to 150 km from April 2007 to March 2012. To our knowledge, this is the first time zonal oscillations in temperature have been derived pole to pole in this altitude range from a single instrument. The major findings are the detection of (1 migrating tides at northern and southern high latitudes; (2 significant k = 1 activity at extratropical and high latitudes, particularly in the Southern Hemisphere; (3 k = 3 and k = 4 eastward-propagating waves that penetrate the lower thermosphere with a significantly larger vertical wavelength than in the mesosphere; and (4 a migrating tide quasi-biennial oscillation in the stratosphere, mesosphere and lower thermosphere. MIPAS global measurements of longitudinal oscillations are useful for testing tide modeling in the mesosphere and lower thermosphere region and as a lower boundary for models extending higher up in the atmosphere.

  4. Simultaneous observations of SAO and QBO in winds, temperature and ozone in the tropical middle atmosphere over Thumba (8.5 N, 77 E)

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Karanam Kishore; Swain, Debadatta; John, Sherine Rachel; Ramkumar, Geetha [Vikram Sarabhai Space Center, Space Physics Laboratory, Thiruvananthapuram (India)

    2011-11-15

    Owing to the importance of middle atmosphere, recently, a Middle Atmospheric Dynamics (MIDAS) program was carried out during the period 2002-2007 at Thumba (8.5 N, 77 E). The measurements under this program, involving regular radiosonde/rocket flights as well as atmospheric radars, provided long period observations of winds and temperature in the middle atmospheric region from which waves and oscillations as well as their forcing mechanisms particularly in the low-latitude middle atmosphere could be analyzed. However, a detailed analysis of the forcing mechanisms remains incomplete due to the lack of important measurements like ozone which is a significant contributor to atmospheric dynamics. Presently, profiles of ozone are available from TIMED/SABER (Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broad Emission Radiometry) satellite globally from about 15 to 100 km, over multiple years since 2002. In this regard, a comprehensive study has been carried out on ozone and its variability at Quasi Biennial Oscillation (QBO) and Semiannual Oscillation (SAO) scales using TIMED/SABER ozone observations during the MIDAS campaign period. Before using the TIMED/SABER ozone measurements, an inter-comparison has been carried out with in situ measurements of ozone obtained under the Southern Hemisphere Additional Ozonesondes (SHADOZ) campaign for the year 2007 at few stations. The inter-comparison showed very good agreement between SABER and ozonesonde derived ozone profiles. After validating the SABER observations, ozone profiles are used extensively to study the QBO and SAO along with temperature and winds in the 20-100 km height region. It is known that the SAO in mesosphere and stratosphere are in opposite phases, but the present study for the first time reports the aspect of opposite phases in the mesosphere itself. Thus, the present work attempts to study the long-period oscillations in stratosphere and mesosphere in ozone

  5. Application of Turchin's method of statistical regularization

    Science.gov (United States)

    Zelenyi, Mikhail; Poliakova, Mariia; Nozik, Alexander; Khudyakov, Alexey

    2018-04-01

    During analysis of experimental data, one usually needs to restore a signal after it has been convoluted with some kind of apparatus function. According to Hadamard's definition this problem is ill-posed and requires regularization to provide sensible results. In this article we describe an implementation of the Turchin's method of statistical regularization based on the Bayesian approach to the regularization strategy.

  6. Regular extensions of some classes of grammars

    NARCIS (Netherlands)

    Nijholt, Antinus

    Culik and Cohen introduced the class of LR-regular grammars, an extension of the LR(k) grammars. In this report we consider the analogous extension of the LL(k) grammers, called the LL-regular grammars. The relations of this class of grammars to other classes of grammars are shown. Every LL-regular

  7. Wind Loads on Structures

    DEFF Research Database (Denmark)

    Dyrbye, Claes; Hansen, Svend Ole

    Wind loads have to be taken into account when designing civil engineering structures. The wind load on structures can be systematised by means of the wind load chain: wind climate (global), terrain (wind at low height), aerodynamic response (wind load to pressure), mechanical response (wind...... pressure to structural response) and design criteria. Starting with an introduction of the wind load chain, the book moves on to meteorological considerations, atmospheric boundary layer, static wind load, dynamic wind load and scaling laws used in wind-tunnel tests. The dynamic wind load covers vibrations...... induced by wind turbulence, vortex shedding, flutter and galloping. The book gives a comprehensive treatment of wind effects on structures and it will be useful for consulting engineers designing wind-sensitive structures. It will also be valuable for students of civil engineering as textbook...

  8. Wavelet analysis on transient behaviour of tidal amplitude fluctuations observed by meteor radar in the lower thermosphere above Bulgaria

    Directory of Open Access Journals (Sweden)

    D. Pancheva

    Full Text Available On the basis of bispectral analysis applied to the hourly data set of neutral wind measured by meteor radar in the MLT region above Bulgaria it was demonstrated that nonlinear processes are frequently and regularly acting in the mesopause region. They contribute significantly to the short-term tidal variability and are apparently responsible for the observed complicated behavior of the tidal characteristics. A Morlet wavelet transform is proposed as a technique for studying nonstationary signals. By simulated data it was revealed that the Morlet wavelet transform is especially convenient for analyzing signals with: (1 a wide range of dominant frequencies which are localized in different time intervals; (2 amplitude and frequency modulated spectral components, and (3 singular, wave-like events, observed in the neutral wind of the MLT region and connected mainly with large-scale disturbances propagated from below. By applying a Morlet wavelet transform to the hourly values of the amplitudes of diurnal and semidiurnal tides the basic oscillations with periods of planetary waves (1.5-20 days, as well as their development in time, are obtained. A cross-wavelet analysis is used to clarify the relation between the tidal and mean neutral wind variability. The results of bispectral analysis indicate which planetary waves participated in the nonlinear coupling with the atmospheric tides, while the results of cross-wavelet analysis outline their time intervals if these interactions are local.

    Key words: Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides - Radio science (nonlinear phenomena

  9. The Effect of Solar Radiation on Molecular Nitrogen Emissions Originating in the Sunlit Thermosphere of Earth.

    Science.gov (United States)

    Hatfield, David Brooke

    The vibrational distribution of N_2 triplet states in the sunlit upper thermosphere of Earth is measured and modeled for the first time. A comparison is made between measured and theoretical limb column emission rates for bands originating from each upper vibrational level of C^3Pi_ u(v) and A^3Sigma_sp {u}{+}(v). The measured column emission rates for the Second Positive (2PG) bands are 3.2 (+/-0.2), 3.2 (+/-0.2) and 0.6 (+0.0,-0.4) kRayleighs for bands originating from C^3Pi_ u(0Kaplan (VK) bands originating from A^3Sigma_sp{u}{+ }(0measured 2PG intensities, but comparisons of predicted A^3Sigma_sp{u }{+}(v) column emissions to measured VK intensities are poor. Despite this discrepancy, the predicted sum of all A^3Sigma_sp {u}{+}(v) emission rates over all v compared well to the sum of measured VK intensities. This implies that the excitation rate into the N_2 triplet states is well understood, but that the cascade mechanisms are not as yet understood sufficiently to use dayglow N_2 band emissions as remote sensing probes of the sunlit thermosphere. The dayglow N_2 emissions are modeled by extending the existing auroral model to include resonance scattering of sunlight and replacing the precipitating auroral electrons with photoelectrons. The effects of solar resonance scattering on the X ^1Sigma_sp{g}{+}, A^3Sigma_sp{u }{+} and B^3Pi _ g states are presented as a function of A^3Sigma_sp{u}{+ } quenching rate. These theoretical predictions have important implications for the analysis of dayglow and auroral emissions. The effect of resonance scattering on the A^3Sigma_sp{u} {+} state is small, and will not be measurable under auroral conditions. This implies that the measured auroral vibrational population of the A^3 Sigma_sp{u}{+} state is valid for sunlit aurora. The population of B ^3Pi_ g(v = O) relative to other B^3Pi_ g(v) states is predicted to be enhanced by sunlight. A novel set of computer variables based on tree structures was created to manage the

  10. VITMO - A Powerful Tool to Improve Discovery in the Magnetospheric and Ionosphere-Thermosphere Domains

    Science.gov (United States)

    Schaefer, R. K.; Morrison, D.; Potter, M.; Stephens, G.; Barnes, R. J.; Talaat, E. R.; Sarris, T.

    2017-12-01

    With the advent of the NASA Magnetospheric Multiscale Mission and the Van Allen Probes we have space missions that probe the Earth's magnetosphere and radiation belts. These missions fly at far distances from the Earth in contrast to the larger number of near-Earth satellites. Both of the satellites make in situ measurements. Energetic particles flow along magnetic field lines from these measurement locations down to the ionosphere/thermosphere region. Discovering other data that may be used with these satellites is a difficult and complicated process. To solve this problem, we have developed a series of light-weight web services that can provide a new data search capability for the Virtual Ionosphere Thermosphere Mesosphere Observatory (VITMO). The services consist of a database of spacecraft ephemerides and instrument fields of view; an overlap calculator to find times when the fields of view of different instruments intersect; and a magnetic field line tracing service that maps in situ and ground based measurements for a number of magnetic field models and geophysical conditions. These services run in real-time when the user queries for data and allow the non-specialist user to select data that they were previously unable to locate, opening up analysis opportunities beyond the instrument teams and specialists, making it easier for future students who come into the field. Each service on their own provides a useful new capability for virtual observatories; operating together they provide a powerful new search tool. The ephemerides service was built using the Navigation and Ancillary Information Facility (NAIF) SPICE toolkit (http://naif.jpl.nasa.gov/naif/index.html) allowing them to be extended to support any Earth orbiting satellite with the addition of the appropriate SPICE kernels. The overlap calculator uses techniques borrowed from computer graphics to identify overlapping measurements in space and time. The calculator will allow a user defined uncertainty

  11. Stellar winds

    International Nuclear Information System (INIS)

    Weymann, R.J.

    1978-01-01

    It is known that a steady outflow of material at comparable rates of mass loss but vastly different speeds is now known to be ubiquitous phenomenon among both the luminous hot stars and the luminous but cool red giants. The flows are probably massive enough in both cases to give rise to significant effects on stellar evolution and the mass balance between stars and the interstellar medium. The possible mechanisms for these phenomena as well as the methods of observation used are described. In particular, the mass-loss processes in stars other than the sun that also involve a steady flow of matter are considered. The evidence for their existence is described, and then the question of whether the process thought to produce the solar wind is also responsible for producing these stellar winds is explored

  12. Class of regular bouncing cosmologies

    Science.gov (United States)

    Vasilić, Milovan

    2017-06-01

    In this paper, I construct a class of everywhere regular geometric sigma models that possess bouncing solutions. Precisely, I show that every bouncing metric can be made a solution of such a model. My previous attempt to do so by employing one scalar field has failed due to the appearance of harmful singularities near the bounce. In this work, I use four scalar fields to construct a class of geometric sigma models which are free of singularities. The models within the class are parametrized by their background geometries. I prove that, whatever background is chosen, the dynamics of its small perturbations is classically stable on the whole time axis. Contrary to what one expects from the structure of the initial Lagrangian, the physics of background fluctuations is found to carry two tensor, two vector, and two scalar degrees of freedom. The graviton mass, which naturally appears in these models, is shown to be several orders of magnitude smaller than its experimental bound. I provide three simple examples to demonstrate how this is done in practice. In particular, I show that graviton mass can be made arbitrarily small.

  13. Wind conditions for wind turbine design

    Energy Technology Data Exchange (ETDEWEB)

    Maribo Pedersen, B.

    1999-04-01

    Delegates from Europe and USA attended the meeting and discussed general aspects of wind conditions for wind turbine design. The subjects and the presented papers covered a very broad range of aspects of wind conditions and related influence on the wind turbine. (EHS)

  14. DYNAMO: a Mars upper atmosphere package for investigating solar wind interaction and escape processes, and mapping Martian fields

    DEFF Research Database (Denmark)

    Chassefiere, E.; Nagy, A.; Mandea, M.

    2004-01-01

    DYNAMO is a small multi-instrument payload aimed at characterizing current atmospheric escape, which is still poorly constrained, and improving gravity and magnetic field representations, in order to better understand the magnetic, geologic and thermal history of Mars. The internal structure...... of periapsis 170 km), and in a lesser extent 2a, offers an unprecedented opportunity to investigate by in situ probing the chemical and dynamical properties of the deep ionosphere, thermosphere, and the interaction between the atmosphere and the solar wind, and therefore the present atmospheric escape rate...

  15. Laparoscopic microwave thermosphere ablation of malignant liver tumors: An analysis of 53 cases.

    Science.gov (United States)

    Zaidi, Nisar; Okoh, Alexis; Yigitbas, Hakan; Yazici, Pinar; Ali, Noaman; Berber, Eren

    2016-02-01

    Microwave thermosphere ablation (MTA) is a new technology that is designed to create spherical zones of ablation using a single antenna. The aim of this study is to assess the results of MTA in a large series of patients. This was a prospective study assessing the use of MTA in patients with malignant liver tumors. The procedures were done mostly laparoscopically and ablation zones created were assessed for completeness of tumor response, spherical geometry and recurrence on tri-phasic CT scans done on follow-up. There were a total of 53 patients with an average of 3 tumors measuring 1.5 cm. Ablations were performed laparoscopically in all but eight patients. Morbidity was 11.3% (n = 6), and mortality zero. On postoperative scans, there was 99.3% tumor destruction. Roundness indices A, B, and transverse were 1.1, 1.0, and 0.9, respectively. At a median follow-up of 4.5 months, incomplete ablation was seen in 1 of 149 lesions treated (0.7%) and local tumor recurrence in 1 lesion (0.7%). The results of this series confirm the safety and feasibility of MTA technology. The 99.3% rate of complete tumor ablation and low rate of local recurrence at short-term follow up are promising. © 2015 Wiley Periodicals, Inc.

  16. Characterizing the Upper Atmosphere of Titan using the Titan Global Ionosphere- Thermosphere Model: Nitrogen and Methane.

    Science.gov (United States)

    Bell, J. M.; Waite, J. H.; Bar-Nun, A.; Bougher, S. W.; Ridley, A. J.; Magee, B.

    2008-12-01

    Recently, a great deal of effort has been put forth to explain the Cassini Ion-Neutral Mass Spectrometer (Waite et al [2004]) in-situ measurements of Titan's upper atmosphere (e.g. Muller-Wodarg [2008], Strobel [2008], Yelle et al [2008]). Currently, the community seems to agree that large amounts of CH4 are escaping from Titan's upper atmosphere at a rate of roughly 2.0 x 1027 molecules of CH4/s (3.33 x 1028 amu/s), representing a significant mass source to the Kronian Magnetosphere. However, such large escape fluxes from Titan are currently not corroborated by measurements onboard the Cassini Spacecraft. Thus, we posit another potential scenario: Aerosol depletion of atmospheric methane. Using the three-dimensional Titan Global Ionosphere-Thermosphere Model (T-GITM) (Bell et al [2008]), we explore the possible removal mechanisms of atmospheric gaseous constituents by these aerosols. Titan simulations are directly compared against Cassini Ion-Neutral Mass Spectrometer in-situ densities of N2 and CH4. From this work, we can then compare and contrast this aerosol depletion scenario against the currently posited hydrodynamic escape scenario, illustrating the merits and shortcomings of both.

  17. Thermospheric mass density model error variance as a function of time scale

    Science.gov (United States)

    Emmert, J. T.; Sutton, E. K.

    2017-12-01

    In the increasingly crowded low-Earth orbit environment, accurate estimation of orbit prediction uncertainties is essential for collision avoidance. Poor characterization of such uncertainty can result in unnecessary and costly avoidance maneuvers (false positives) or disregard of a collision risk (false negatives). Atmospheric drag is a major source of orbit prediction uncertainty, and is particularly challenging to account for because it exerts a cumulative influence on orbital trajectories and is therefore not amenable to representation by a single uncertainty parameter. To address this challenge, we examine the variance of measured accelerometer-derived and orbit-derived mass densities with respect to predictions by thermospheric empirical models, using the data-minus-model variance as a proxy for model uncertainty. Our analysis focuses mainly on the power spectrum of the residuals, and we construct an empirical model of the variance as a function of time scale (from 1 hour to 10 years), altitude, and solar activity. We find that the power spectral density approximately follows a power-law process but with an enhancement near the 27-day solar rotation period. The residual variance increases monotonically with altitude between 250 and 550 km. There are two components to the variance dependence on solar activity: one component is 180 degrees out of phase (largest variance at solar minimum), and the other component lags 2 years behind solar maximum (largest variance in the descending phase of the solar cycle).

  18. Thermospheric/ionospheric disturbances under quiet and magneto-perturbed conditions

    Science.gov (United States)

    Zakharov, Ivan G.; Mozgovaya, O. L.

    2003-04-01

    The basic mechanisms of ionospheric storms (IS) are investigated sufficiently full. Despite of it a quantitative forecast of ionospheric disturbance is not always satisfactory. One of the possible causes can be related to the insufficient account of a background ionospheric. In particualr using electron concentration Ne in the peak of F2-region and total electron content are shown, that the amplitude of a IS positive phase for similar magnetic storms can differ by ~1,5 times. Hence a cause of distinction can be variations in the thermosphere conditions, not reflected by known activity indices. For further research we used the incoherent scatter radar data of the Institute of ionosphere in height range 200-1000 km in the very quiet periods coming to the geomagnetic disturbance. A steady periodic disturbance in Ne during quiet conditions in all heights is established, which can be identified as tidal moda m=6. The amplitude of wave is ~15%, the phase changes with a height. The storm onset leads to an increase of the amplitudes approximately twice without a change in the phase. An ionospheric disturbance in very quiet conditions can lead to additional complicating an ionosphere reaction to magnetic storm.

  19. Analysis of Temperature and Wind Measurements from the TIMED Mission: Comparison with UARS Data

    Science.gov (United States)

    Huang, Frank; Mayr, Hans; Killeen, Tim; Russell, Jim; Reber, Skip

    2004-01-01

    We report on an analysis of temperature and wind data based respectively on measurements with the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) and TIDI (TIMED Doppler Interferometer) instruments on the TIMED (Thermosphere-Ionosphere-Mesosphere-Energetics and Dynamics) mission. Comparisons are made with corresponding results obtained from the HRDI (High Resolution Doppler Imager), MLS (Microwave Limb Sounder) and CLAES (Cryogenic Limb Array Etalon Spectrometer) instruments on the UARS (Upper Atmosphere Research Satellite) spacecraft. The TIMED and UARS instruments have important common and uncommon properties in their sampling of the data as a function local solar time. For comparison between the data from the two satellite missions, we present the derived diurnal tidal and zonal-mean variations of temperature and winds, obtained as functions of season, latitude, and altitude. The observations are also compared with results from the Numerical Spectral Model (NSM).

  20. The necessary distance between large wind farms offshore - study

    DEFF Research Database (Denmark)

    Frandsen, S.; Barthelmie, R.J.; Pryor, S.C.

    2005-01-01

    the new Storpark Analytical Model has been developed and evaluated. As it is often the need for offshore wind farms, the model handles a regular array-geometry with straight rows of wind turbines and equidistantspacing between units in each row and equidistant spacing between rows. Firstly, the case...... with the flow direction being parallel to rows in a rectangular geometry is considered by defining three flow regimes. Secondly, when the flow is not in line withthe main rows, solutions are found for the patterns of wind turbine units emerging corresponding to each wind direction. The model complex......A review of state of the art wake and boundary layer wind farms was conducted. The predictions made for wind recovery distances (that might be used to estimate optimal placing of neighbouring wind farms) range between 2 and 14 km. In order to model thelink between wakes and the boundary layer...

  1. Dynamics in the Modern Upper Atmosphere of Venus: Zonal Wind Transition to Subsolar-to-Antisolar Flow

    Science.gov (United States)

    Livengood, T. A.; Kostiuk, T.; Hewagama, T.; Fast, K. E.

    2017-12-01

    We observed Venus on 19-23 Aug 2010 (UT) to investigate equatorial wind velocities from above the cloud tops through the lower thermosphere. Measurements were made from the NASA Infrared Telescope Facility using the NASA Goddard Space Flight Center Heterodyne Instrument for Planetary Winds and Composition. High-resolution spectra were acquired on a CO2 pressure-broadened absorption feature that probes the lower mesosphere ( 70 km altitude) with a non-LTE core emission of the same transition that probes the lower thermosphere ( 110 km). The resolving power of λ/Δλ≈3×107 determines line-of-sight velocity from Doppler shifts to high precision. The altitude differential between the features enables investigating the transition from zonal wind flow near the cloud tops to subsolar-to-antisolar flow in the thermosphere. The fully-resolved carbon dioxide transition was measured near 952.8808 cm-1 (10.494 µm) rest frequency at the equator with 1 arcsec field-of-view on Venus (24 arcsec diameter) distributed about the central meridian and across the terminator at ±15° intervals in longitude. The non-LTE emission is solar-pumped and appears only on the daylight side, probing subsolar-to-antisolar wind velocity vector flowing radially from the subsolar point through the terminator, which was near the central meridian in these observations and had zero line-of-sight wind projection at the terminator. The velocity of the zonal flow is approximately uniform, with maximum line-of-sight projection at the limb, and can be measured by the frequency of the absorption line on both the daylight and dark side. Variations in Doppler shift between the observable features and the differing angular dependence of the contributing wind phenomena thus provide independent mechanisms to distinguish the dynamical processes at the altitude of each observed spectral feature. Winds up to >100 m/s were determined in previous investigations with uncertainties of order 10 m/s or less.

  2. Wind Power Meteorology

    DEFF Research Database (Denmark)

    Lundtang Petersen, Erik; Mortensen, Niels Gylling; Landberg, Lars

    Wind power meteorology has evolved as an applied science, firmly founded on boundary-layer meteorology, but with strong links to climatology and geography. It concerns itself with three main areas: siting of wind turbines, regional wind resource assessment, and short-term prediction of the wind...... resource. The history, status and perspectives of wind power meteorology are presented, with emphasis on physical considerations and on its practical application. Following a global view of the wind resource, the elements of boundary layer meteorology which are most important for wind energy are reviewed......: wind profiles and shear, turbulence and gust, and extreme winds. The data used in wind power meteorology stem mainly from three sources: onsite wind measurements, the synoptic networks, and the re-analysis projects. Wind climate analysis, wind resource estimation and siting further require a detailed...

  3. Multi-objective genetic algorithm based innovative wind farm layout optimization method

    International Nuclear Information System (INIS)

    Chen, Ying; Li, Hua; He, Bang; Wang, Pengcheng; Jin, Kai

    2015-01-01

    Highlights: • Innovative optimization procedures for both regular and irregular shape wind farm. • Using real wind condition and commercial wind turbine parameters. • Using multiple-objective genetic algorithm optimization method. • Optimize the selection of different wind turbine types and their hub heights. - Abstract: Layout optimization has become one of the critical approaches to increase power output and decrease total cost of a wind farm. Previous researches have applied intelligent algorithms to optimizing the wind farm layout. However, those wind conditions used in most of previous research are simplified and not accurate enough to match the real world wind conditions. In this paper, the authors propose an innovative optimization method based on multi-objective genetic algorithm, and test it with real wind condition and commercial wind turbine parameters. Four case studies are conducted to investigate the number of wind turbines needed in the given wind farm. Different cost models are also considered in the case studies. The results clearly demonstrate that the new method is able to optimize the layout of a given wind farm with real commercial data and wind conditions in both regular and irregular shapes, and achieve a better result by selecting different type and hub height wind turbines.

  4. Adaptive regularization of noisy linear inverse problems

    DEFF Research Database (Denmark)

    Hansen, Lars Kai; Madsen, Kristoffer Hougaard; Lehn-Schiøler, Tue

    2006-01-01

    In the Bayesian modeling framework there is a close relation between regularization and the prior distribution over parameters. For prior distributions in the exponential family, we show that the optimal hyper-parameter, i.e., the optimal strength of regularization, satisfies a simple relation: T......: The expectation of the regularization function, i.e., takes the same value in the posterior and prior distribution. We present three examples: two simulations, and application in fMRI neuroimaging....

  5. Higher derivative regularization and chiral anomaly

    International Nuclear Information System (INIS)

    Nagahama, Yoshinori.

    1985-02-01

    A higher derivative regularization which automatically leads to the consistent chiral anomaly is analyzed in detail. It explicitly breaks all the local gauge symmetry but preserves global chiral symmetry and leads to the chirally symmetric consistent anomaly. This regularization thus clarifies the physics content contained in the consistent anomaly. We also briefly comment on the application of this higher derivative regularization to massless QED. (author)

  6. Regularity effect in prospective memory during aging

    Directory of Open Access Journals (Sweden)

    Geoffrey Blondelle

    2016-10-01

    Full Text Available Background: Regularity effect can affect performance in prospective memory (PM, but little is known on the cognitive processes linked to this effect. Moreover, its impacts with regard to aging remain unknown. To our knowledge, this study is the first to examine regularity effect in PM in a lifespan perspective, with a sample of young, intermediate, and older adults. Objective and design: Our study examined the regularity effect in PM in three groups of participants: 28 young adults (18–30, 16 intermediate adults (40–55, and 25 older adults (65–80. The task, adapted from the Virtual Week, was designed to manipulate the regularity of the various activities of daily life that were to be recalled (regular repeated activities vs. irregular non-repeated activities. We examine the role of several cognitive functions including certain dimensions of executive functions (planning, inhibition, shifting, and binding, short-term memory, and retrospective episodic memory to identify those involved in PM, according to regularity and age. Results: A mixed-design ANOVA showed a main effect of task regularity and an interaction between age and regularity: an age-related difference in PM performances was found for irregular activities (older < young, but not for regular activities. All participants recalled more regular activities than irregular ones with no age effect. It appeared that recalling of regular activities only involved planning for both intermediate and older adults, while recalling of irregular ones were linked to planning, inhibition, short-term memory, binding, and retrospective episodic memory. Conclusion: Taken together, our data suggest that planning capacities seem to play a major role in remembering to perform intended actions with advancing age. Furthermore, the age-PM-paradox may be attenuated when the experimental design is adapted by implementing a familiar context through the use of activities of daily living. The clinical

  7. Regularity effect in prospective memory during aging

    OpenAIRE

    Blondelle, Geoffrey; Hainselin, Mathieu; Gounden, Yannick; Heurley, Laurent; Voisin, Hélène; Megalakaki, Olga; Bressous, Estelle; Quaglino, Véronique

    2016-01-01

    Background: Regularity effect can affect performance in prospective memory (PM), but little is known on the cognitive processes linked to this effect. Moreover, its impacts with regard to aging remain unknown. To our knowledge, this study is the first to examine regularity effect in PM in a lifespan perspective, with a sample of young, intermediate, and older adults.Objective and design: Our study examined the regularity effect in PM in three groups of participants: 28 young adults (18–30), 1...

  8. Wind Energy Basics | NREL

    Science.gov (United States)

    Wind Energy Basics Wind Energy Basics We have been harnessing the wind's energy for hundreds of grinding grain. Today, the windmill's modern equivalent-a wind turbine can use the wind's energy to most energy. At 100 feet (30 meters) or more aboveground, they can take advantage of the faster and

  9. Prospecting for Wind

    Science.gov (United States)

    Swapp, Andy; Schreuders, Paul; Reeve, Edward

    2011-01-01

    Many people use wind to help meet their needs. Over the years, people have been able to harness or capture the wind in many different ways. More recently, people have seen the rebirth of electricity-generating wind turbines. Thus, the age-old argument about technology being either good or bad can also be applied to the wind. The wind can be a…

  10. Careers in Wind Energy

    Science.gov (United States)

    Liming, Drew; Hamilton, James

    2011-01-01

    As a common form of renewable energy, wind power is generating more than just electricity. It is increasingly generating jobs for workers in many different occupations. Many workers are employed on wind farms: areas where groups of wind turbines produce electricity from wind power. Wind farms are frequently located in the midwestern, western, and…

  11. Regularization and error assignment to unfolded distributions

    CERN Document Server

    Zech, Gunter

    2011-01-01

    The commonly used approach to present unfolded data only in graphical formwith the diagonal error depending on the regularization strength is unsatisfac-tory. It does not permit the adjustment of parameters of theories, the exclusionof theories that are admitted by the observed data and does not allow the com-bination of data from different experiments. We propose fixing the regulariza-tion strength by a p-value criterion, indicating the experimental uncertaintiesindependent of the regularization and publishing the unfolded data in additionwithout regularization. These considerations are illustrated with three differentunfolding and smoothing approaches applied to a toy example.

  12. Iterative Regularization with Minimum-Residual Methods

    DEFF Research Database (Denmark)

    Jensen, Toke Koldborg; Hansen, Per Christian

    2007-01-01

    subspaces. We provide a combination of theory and numerical examples, and our analysis confirms the experience that MINRES and MR-II can work as general regularization methods. We also demonstrate theoretically and experimentally that the same is not true, in general, for GMRES and RRGMRES their success......We study the regularization properties of iterative minimum-residual methods applied to discrete ill-posed problems. In these methods, the projection onto the underlying Krylov subspace acts as a regularizer, and the emphasis of this work is on the role played by the basis vectors of these Krylov...... as regularization methods is highly problem dependent....

  13. Iterative regularization with minimum-residual methods

    DEFF Research Database (Denmark)

    Jensen, Toke Koldborg; Hansen, Per Christian

    2006-01-01

    subspaces. We provide a combination of theory and numerical examples, and our analysis confirms the experience that MINRES and MR-II can work as general regularization methods. We also demonstrate theoretically and experimentally that the same is not true, in general, for GMRES and RRGMRES - their success......We study the regularization properties of iterative minimum-residual methods applied to discrete ill-posed problems. In these methods, the projection onto the underlying Krylov subspace acts as a regularizer, and the emphasis of this work is on the role played by the basis vectors of these Krylov...... as regularization methods is highly problem dependent....

  14. Wind energy literature survey no. 34

    DEFF Research Database (Denmark)

    Pavese, Christian

    2015-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawnfrom recent issues of Wind Energy itself and a large number of periodicals including Journal of Wind Engineering andIndustrial Aerodynamics, International Journal of Energy...... Research, Renewable Energy, Energy Sources, Journal of SolarEnergy Engineering, American Institute of Aeronautics and Astronautics Journal, Electric Power Components and Systemsalong with a number of periodicals published by the Institute of Electrical and Electronics Engineers, etc. The list...... is limitedexclusively to journals not specifically devoted to wind energy and its applications. To assist the reader, the list is separatedinto broad categories. Although many papers fit several categories, each paper is listed only once under the categorythought most appropriate. Please note that the inclusion...

  15. Wind Energy literature survey no. 32

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2014-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of Wind Energy itself and a large number of periodicals including the following: Journal of Wind Engineering and Industrial Aerodynamics, International...... Journal of Energy Research, Renewable Energy, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers, and so...... on. The list is limited exclusively to journals not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate...

  16. Wind Energy literature survey no. 31

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2014-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of Wind Energy itself and a large number of periodicals including: Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy...... Research, Renewable Energy, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers, and so on. The list...... is limited exclusively to journals not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note...

  17. Wind energy literature survey no. 33

    DEFF Research Database (Denmark)

    Pavese, Christian

    2014-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of Wind Energy itself and a large number of periodicals, including the following: Journal of Wind Engineering and Industrial Aerodynamics, International...... Journal of Energy Research, Renewable Energy, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers, and so...... on. The list is limited exclusively to journals not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate...

  18. Wind energy in the electric power system

    DEFF Research Database (Denmark)

    Polinder, H.; Peinke, J.; Kramer, O.

    2016-01-01

    have to behave when connected to the power system. In this way, they already incorporate basic ancillary services. However, frequency control is normally not provided as a regular reserve, because this would require reserving parts of the available wind capacity as stand-by capacity. Within R...... in order to guarantee a reliable stable power supply at any instant in time. Substituting these plants with renewable generation units requires the latter to be capable of providing these ancillary services. The state of the art is that grid codes are used to define the way wind turbines and wind farms......&D institutes, such control options were demonstrated and assessed for wind power plant clusters....

  19. Wind energy program overview

    International Nuclear Information System (INIS)

    1992-02-01

    This overview emphasizes the amount of electric power that could be provided by wind power rather than traditional fossil fuels. New wind power markets, advances in technology, technology transfer, and wind resources are some topics covered in this publication

  20. The thermospheric auroral red line polarization: confirmation of detection and first quantitative analysis

    Directory of Open Access Journals (Sweden)

    Moen Joran

    2013-01-01

    Full Text Available The thermospheric atomic oxygen red line is among the brightest in the auroral spectrum. Previous observations in Longyearbyen, Svalbard, indicated that it may be intrinsically polarized, but a possible contamination by light pollution could not be ruled out. During the winter 2010/2011, the polarization of the red line was measured for the first time at the Polish Hornsund polar base without contamination. Two methods of data analysis are presented to compute the degree of linear polarization (DoLP and angle of linear polarization (AoLP: one is based on averaging and the other one on filtering. Results are compared and are in qualitative agreement. For solar zenith angles (SZA larger than 108° (with no contribution from Rayleigh scattering, the DoLP ranges between 2 and 7%. The AoLP is more or less aligned with the direction of the magnetic field line, in agreement with the theoretical predictions of Bommier et al. (2010. However, the AoLP values range between ±20° around this direction, depending on the auroral conditions. Correlations between the polarization parameters and the red line intensity I were considered. The DoLP decreases when I increases, confirming a trend observed during the observations in Longyearbyen. However, for small values of I, DoLP varies within a large range of values, while for large values of I, DoLP is always small. The AoLP also varies with the red line intensity, slightly rotating around the magnetic field line.

  1. Modelling Wind for Wind Farm Layout Optimization Using Joint Distribution of Wind Speed and Wind Direction

    OpenAIRE

    Ju Feng; Wen Zhong Shen

    2015-01-01

    Reliable wind modelling is of crucial importance for wind farm development. The common practice of using sector-wise Weibull distributions has been found inappropriate for wind farm layout optimization. In this study, we propose a simple and easily implementable method to construct joint distributions of wind speed and wind direction, which is based on the parameters of sector-wise Weibull distributions and interpolations between direction sectors. It is applied to the wind measurement data a...

  2. A regularized stationary mean-field game

    KAUST Repository

    Yang, Xianjin

    2016-01-01

    In the thesis, we discuss the existence and numerical approximations of solutions of a regularized mean-field game with a low-order regularization. In the first part, we prove a priori estimates and use the continuation method to obtain the existence of a solution with a positive density. Finally, we introduce the monotone flow method and solve the system numerically.

  3. A regularized stationary mean-field game

    KAUST Repository

    Yang, Xianjin

    2016-04-19

    In the thesis, we discuss the existence and numerical approximations of solutions of a regularized mean-field game with a low-order regularization. In the first part, we prove a priori estimates and use the continuation method to obtain the existence of a solution with a positive density. Finally, we introduce the monotone flow method and solve the system numerically.

  4. On infinite regular and chiral maps

    OpenAIRE

    Arredondo, John A.; Valdez, Camilo Ramírez y Ferrán

    2015-01-01

    We prove that infinite regular and chiral maps take place on surfaces with at most one end. Moreover, we prove that an infinite regular or chiral map on an orientable surface with genus can only be realized on the Loch Ness monster, that is, the topological surface of infinite genus with one end.

  5. From recreational to regular drug use

    DEFF Research Database (Denmark)

    Järvinen, Margaretha; Ravn, Signe

    2011-01-01

    This article analyses the process of going from recreational use to regular and problematic use of illegal drugs. We present a model containing six career contingencies relevant for young people’s progress from recreational to regular drug use: the closing of social networks, changes in forms...

  6. Automating InDesign with Regular Expressions

    CERN Document Server

    Kahrel, Peter

    2006-01-01

    If you need to make automated changes to InDesign documents beyond what basic search and replace can handle, you need regular expressions, and a bit of scripting to make them work. This Short Cut explains both how to write regular expressions, so you can find and replace the right things, and how to use them in InDesign specifically.

  7. Regularization modeling for large-eddy simulation

    NARCIS (Netherlands)

    Geurts, Bernardus J.; Holm, D.D.

    2003-01-01

    A new modeling approach for large-eddy simulation (LES) is obtained by combining a "regularization principle" with an explicit filter and its inversion. This regularization approach allows a systematic derivation of the implied subgrid model, which resolves the closure problem. The central role of

  8. 29 CFR 779.18 - Regular rate.

    Science.gov (United States)

    2010-07-01

    ... employee under subsection (a) or in excess of the employee's normal working hours or regular working hours... Relating to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR STATEMENTS OF GENERAL POLICY OR... not less than one and one-half times their regular rates of pay. Section 7(e) of the Act defines...

  9. Wind farm project economics : value of wind

    Energy Technology Data Exchange (ETDEWEB)

    Bills-Everett, T. [Mainstream Renewable Power, Toronto, ON (Canada)

    2010-07-01

    This PowerPoint presentation discussed methods of increasing the value of wind power projects. Appropriate turbine selection and layout is needed to ensure that wind resources are fully developed. Construction costs have a significant impact on project costs. The world turbine price index has not significantly fluctuated since 2006. Operating costs, and the value of wind power projects, are linked with OPEX fluctuations. Wind power projects can significantly reduce greenhouse gas (GHG) emissions. An increase in wind power capacity will reduce the overall cost of energy produced from wind power. Countries can use wind power as part of a renewable energy portfolio designed to reduce risks related to diminishing petroleum supplies. Wind power will help to ensure a global transition to renewable energy use. tabs., figs.

  10. Wind turbines, is it just wind?

    International Nuclear Information System (INIS)

    Boiteux, M.

    2012-01-01

    The author first outlines that wind energy is not only random, but almost absent in extreme situations when it would be needed (for example and notably, very cold weather without wind). He suggests the association of a gas turbine to each wind turbine, so that the gas turbine will replace non operating wind turbines. He notices that wind turbines are not proximity energy as they were said to be, and that profitability in fact requires tens of grouped giant wind turbines. He also outlines the high cost of construction of grids for the connection of these wind turbines. Thus, he states that wind energy is far from being profitable in the present conditions of electricity tariffs in France

  11. Wind of opportunity

    International Nuclear Information System (INIS)

    Jamieson, Peter

    1999-01-01

    This article traces the move towards the offshore exploitation of wind energy in Europe, and presents information on existing offshore wind energy projects and proposed wind turbine prototypes for offshore operation. The building of the first major offshore wind project at Vindeby, the use of rock socketed monopile foundations for pile drilling and erection of the wind turbines from a mobile jack-up barge, the costs of wind turbines, the fatigue loads on the support structures due to the wind loading, and the offshore wind market in the UK and Europe are discussed. (UK)

  12. Advanced structural wind engineering

    CERN Document Server

    Kareem, Ahsan

    2013-01-01

    This book serves as a textbook for advanced courses as it introduces state-of-the-art information and the latest research results on diverse problems in the structural wind engineering field. The topics include wind climates, design wind speed estimation, bluff body aerodynamics and applications, wind-induced building responses, wind, gust factor approach, wind loads on components and cladding, debris impacts, wind loading codes and standards, computational tools and computational fluid dynamics techniques, habitability to building vibrations, damping in buildings, and suppression of wind-induced vibrations. Graduate students and expert engineers will find the book especially interesting and relevant to their research and work.

  13. A study into the effect of the diurnal tide on the structure of the background mesosphere and thermosphere using the new coupled middle atmosphere and thermosphere (CMAT general circulation model

    Directory of Open Access Journals (Sweden)

    M. J. Harris

    Full Text Available A new coupled middle atmosphere and thermosphere general circulation model has been developed, and some first results are presented. An investigation into the effects of the diurnal tide upon the mean composition, dynamics and energetics was carried out for equinox conditions. Previous studies have shown that tides deplete mean atomic oxygen in the upper mesosphere-lower thermosphere due to an increased recombination in the tidal displaced air parcels. The model runs presented suggest that the mean residual circulation associated with the tidal dissipation also plays an important role. Stronger lower boundary tidal forcing was seen to increase the equatorial local diurnal maximum of atomic oxygen and the associated 0(1S 557.7 nm green line volume emission rates. The changes in the mean background temperature structure were found to correspond to changes in the mean circulation and exothermic chemical heating.

    Key words. Atmospheric composition and structure (middle atmosphere – composition and chemistry Meterology and atmospheric dynamics (middle atmosphere dynamics; waves and tides

  14. A study into the effect of the diurnal tide on the structure of the background mesosphere and thermosphere using the new coupled middle atmosphere and thermosphere (CMAT general circulation model

    Directory of Open Access Journals (Sweden)

    M. J. Harris

    2002-02-01

    Full Text Available A new coupled middle atmosphere and thermosphere general circulation model has been developed, and some first results are presented. An investigation into the effects of the diurnal tide upon the mean composition, dynamics and energetics was carried out for equinox conditions. Previous studies have shown that tides deplete mean atomic oxygen in the upper mesosphere-lower thermosphere due to an increased recombination in the tidal displaced air parcels. The model runs presented suggest that the mean residual circulation associated with the tidal dissipation also plays an important role. Stronger lower boundary tidal forcing was seen to increase the equatorial local diurnal maximum of atomic oxygen and the associated 0(1S 557.7 nm green line volume emission rates. The changes in the mean background temperature structure were found to correspond to changes in the mean circulation and exothermic chemical heating.Key words. Atmospheric composition and structure (middle atmosphere – composition and chemistry Meterology and atmospheric dynamics (middle atmosphere dynamics; waves and tides

  15. An iterative method for Tikhonov regularization with a general linear regularization operator

    NARCIS (Netherlands)

    Hochstenbach, M.E.; Reichel, L.

    2010-01-01

    Tikhonov regularization is one of the most popular approaches to solve discrete ill-posed problems with error-contaminated data. A regularization operator and a suitable value of a regularization parameter have to be chosen. This paper describes an iterative method, based on Golub-Kahan

  16. Multiple graph regularized protein domain ranking

    KAUST Repository

    Wang, Jim Jing-Yan

    2012-11-19

    Background: Protein domain ranking is a fundamental task in structural biology. Most protein domain ranking methods rely on the pairwise comparison of protein domains while neglecting the global manifold structure of the protein domain database. Recently, graph regularized ranking that exploits the global structure of the graph defined by the pairwise similarities has been proposed. However, the existing graph regularized ranking methods are very sensitive to the choice of the graph model and parameters, and this remains a difficult problem for most of the protein domain ranking methods.Results: To tackle this problem, we have developed the Multiple Graph regularized Ranking algorithm, MultiG-Rank. Instead of using a single graph to regularize the ranking scores, MultiG-Rank approximates the intrinsic manifold of protein domain distribution by combining multiple initial graphs for the regularization. Graph weights are learned with ranking scores jointly and automatically, by alternately minimizing an objective function in an iterative algorithm. Experimental results on a subset of the ASTRAL SCOP protein domain database demonstrate that MultiG-Rank achieves a better ranking performance than single graph regularized ranking methods and pairwise similarity based ranking methods.Conclusion: The problem of graph model and parameter selection in graph regularized protein domain ranking can be solved effectively by combining multiple graphs. This aspect of generalization introduces a new frontier in applying multiple graphs to solving protein domain ranking applications. 2012 Wang et al; licensee BioMed Central Ltd.

  17. Multiple graph regularized protein domain ranking

    KAUST Repository

    Wang, Jim Jing-Yan; Bensmail, Halima; Gao, Xin

    2012-01-01

    Background: Protein domain ranking is a fundamental task in structural biology. Most protein domain ranking methods rely on the pairwise comparison of protein domains while neglecting the global manifold structure of the protein domain database. Recently, graph regularized ranking that exploits the global structure of the graph defined by the pairwise similarities has been proposed. However, the existing graph regularized ranking methods are very sensitive to the choice of the graph model and parameters, and this remains a difficult problem for most of the protein domain ranking methods.Results: To tackle this problem, we have developed the Multiple Graph regularized Ranking algorithm, MultiG-Rank. Instead of using a single graph to regularize the ranking scores, MultiG-Rank approximates the intrinsic manifold of protein domain distribution by combining multiple initial graphs for the regularization. Graph weights are learned with ranking scores jointly and automatically, by alternately minimizing an objective function in an iterative algorithm. Experimental results on a subset of the ASTRAL SCOP protein domain database demonstrate that MultiG-Rank achieves a better ranking performance than single graph regularized ranking methods and pairwise similarity based ranking methods.Conclusion: The problem of graph model and parameter selection in graph regularized protein domain ranking can be solved effectively by combining multiple graphs. This aspect of generalization introduces a new frontier in applying multiple graphs to solving protein domain ranking applications. 2012 Wang et al; licensee BioMed Central Ltd.

  18. Hierarchical regular small-world networks

    International Nuclear Information System (INIS)

    Boettcher, Stefan; Goncalves, Bruno; Guclu, Hasan

    2008-01-01

    Two new networks are introduced that resemble small-world properties. These networks are recursively constructed but retain a fixed, regular degree. They possess a unique one-dimensional lattice backbone overlaid by a hierarchical sequence of long-distance links, mixing real-space and small-world features. Both networks, one 3-regular and the other 4-regular, lead to distinct behaviors, as revealed by renormalization group studies. The 3-regular network is planar, has a diameter growing as √N with system size N, and leads to super-diffusion with an exact, anomalous exponent d w = 1.306..., but possesses only a trivial fixed point T c = 0 for the Ising ferromagnet. In turn, the 4-regular network is non-planar, has a diameter growing as ∼2 √(log 2 N 2 ) , exhibits 'ballistic' diffusion (d w = 1), and a non-trivial ferromagnetic transition, T c > 0. It suggests that the 3-regular network is still quite 'geometric', while the 4-regular network qualifies as a true small world with mean-field properties. As an engineering application we discuss synchronization of processors on these networks. (fast track communication)

  19. Multiple graph regularized protein domain ranking.

    Science.gov (United States)

    Wang, Jim Jing-Yan; Bensmail, Halima; Gao, Xin

    2012-11-19

    Protein domain ranking is a fundamental task in structural biology. Most protein domain ranking methods rely on the pairwise comparison of protein domains while neglecting the global manifold structure of the protein domain database. Recently, graph regularized ranking that exploits the global structure of the graph defined by the pairwise similarities has been proposed. However, the existing graph regularized ranking methods are very sensitive to the choice of the graph model and parameters, and this remains a difficult problem for most of the protein domain ranking methods. To tackle this problem, we have developed the Multiple Graph regularized Ranking algorithm, MultiG-Rank. Instead of using a single graph to regularize the ranking scores, MultiG-Rank approximates the intrinsic manifold of protein domain distribution by combining multiple initial graphs for the regularization. Graph weights are learned with ranking scores jointly and automatically, by alternately minimizing an objective function in an iterative algorithm. Experimental results on a subset of the ASTRAL SCOP protein domain database demonstrate that MultiG-Rank achieves a better ranking performance than single graph regularized ranking methods and pairwise similarity based ranking methods. The problem of graph model and parameter selection in graph regularized protein domain ranking can be solved effectively by combining multiple graphs. This aspect of generalization introduces a new frontier in applying multiple graphs to solving protein domain ranking applications.

  20. Coupling regularizes individual units in noisy populations

    International Nuclear Information System (INIS)

    Ly Cheng; Ermentrout, G. Bard

    2010-01-01

    The regularity of a noisy system can modulate in various ways. It is well known that coupling in a population can lower the variability of the entire network; the collective activity is more regular. Here, we show that diffusive (reciprocal) coupling of two simple Ornstein-Uhlenbeck (O-U) processes can regularize the individual, even when it is coupled to a noisier process. In cellular networks, the regularity of individual cells is important when a select few play a significant role. The regularizing effect of coupling surprisingly applies also to general nonlinear noisy oscillators. However, unlike with the O-U process, coupling-induced regularity is robust to different kinds of coupling. With two coupled noisy oscillators, we derive an asymptotic formula assuming weak noise and coupling for the variance of the period (i.e., spike times) that accurately captures this effect. Moreover, we find that reciprocal coupling can regularize the individual period of higher dimensional oscillators such as the Morris-Lecar and Brusselator models, even when coupled to noisier oscillators. Coupling can have a counterintuitive and beneficial effect on noisy systems. These results have implications for the role of connectivity with noisy oscillators and the modulation of variability of individual oscillators.

  1. Multiple graph regularized protein domain ranking

    Directory of Open Access Journals (Sweden)

    Wang Jim

    2012-11-01

    Full Text Available Abstract Background Protein domain ranking is a fundamental task in structural biology. Most protein domain ranking methods rely on the pairwise comparison of protein domains while neglecting the global manifold structure of the protein domain database. Recently, graph regularized ranking that exploits the global structure of the graph defined by the pairwise similarities has been proposed. However, the existing graph regularized ranking methods are very sensitive to the choice of the graph model and parameters, and this remains a difficult problem for most of the protein domain ranking methods. Results To tackle this problem, we have developed the Multiple Graph regularized Ranking algorithm, MultiG-Rank. Instead of using a single graph to regularize the ranking scores, MultiG-Rank approximates the intrinsic manifold of protein domain distribution by combining multiple initial graphs for the regularization. Graph weights are learned with ranking scores jointly and automatically, by alternately minimizing an objective function in an iterative algorithm. Experimental results on a subset of the ASTRAL SCOP protein domain database demonstrate that MultiG-Rank achieves a better ranking performance than single graph regularized ranking methods and pairwise similarity based ranking methods. Conclusion The problem of graph model and parameter selection in graph regularized protein domain ranking can be solved effectively by combining multiple graphs. This aspect of generalization introduces a new frontier in applying multiple graphs to solving protein domain ranking applications.

  2. Scientific challenges in thermosphere-ionosphere forecasting – conclusions from the October 2014 NASA JPL community workshop

    Directory of Open Access Journals (Sweden)

    Mannucci Anthony J.

    2016-01-01

    Full Text Available Interest in forecasting space weather in the thermosphere and ionosphere (T-I led to a community workshop held at NASA’s Jet Propulsion Laboratory in October, 2014. The workshop focus was “Scientific Challenges in Thermosphere-Ionosphere Forecasting” to emphasize that forecasting presumes a sufficiently advanced state of scientific knowledge, yet one that is still evolving. The purpose of the workshop, and this topical issue that arose from the workshop, was to discuss research frontiers that will lead to improved space weather forecasts. Three areas are discussed in some detail in this paper: (1 the role of lower atmosphere forcing in the response of the T-I to geomagnetic disturbances; (2 the significant deposition of energy at polar latitudes during geomagnetic disturbances; and (3 recent developments in understanding the propagation of coronal mass ejections through the heliosphere and prospects for forecasting the north-south component of the interplanetary magnetic field (IMF using observations at the Lagrangian L5 point. We describe other research presented at the workshop that appears in the topical issue. The possibility of establishing a “positive feedback loop” where improved scientific knowledge leads to improved forecasts is described (Siscoe 2006, Space Weather, 4, S01003; Mannucci 2012, Space Weather, 10, S07003.

  3. A study of the terrestrial thermosphere by remote sensing of OI dayglow in the far and extreme ultraviolet

    International Nuclear Information System (INIS)

    Cotton, D.M.

    1991-01-01

    The upper region of the Earth's atmosphere, the thermosphere, is a key part of the coupled solar-terrestrial system. An important method of obtaining information in the this region is through analysis of radiation excited through the interactions of the thermosphere with solar ionizing, extreme and far ultraviolet radiation. This dissertation presents one such study by the remote sensing of OI in the far and extreme ultraviolet dayglow. The research program included the development construction, and flight of a sounding rocket spectrometer to test this current understanding of the excitation and transport mechanisms of the OI 1356, 1304, 1027, and 989 angstrom emissions. This data set was analyzed using current electron and radiative transport models with the purpose of checking the viability of OI remote sensing; that is, whether existing models and input parameters are adequate to predict these detailed measurements. From discrepancies between modeled and measured emissions, inferences about these input parameters were made. Among other things, the data supports a 40% optically thick cascade contribution to the 1304 angstrom emission. From upper lying states corresponding to 1040, 1027 and 989 angstrom about half of this cascade has been accounted for in this study. There is also evidence that the Lyman β airglow from the geo-corona contributes a significant proportion (30-50%) to the OI 1027 angstrom feature. Furthermore, the photoelectron contribution to the 1027 angstrom feature appears to be underestimated in the current models by a factor of 20

  4. Infrasonic attenuation in the upper mesosphere-lower thermosphere: a comparison between Navier-Stokes and Burnett predictions.

    Science.gov (United States)

    Akintunde, Akinjide; Petculescu, Andi

    2014-10-01

    This paper presents the results of a pilot study comparing the use of continuum and non-continuum fluid dynamics to predict infrasound attenuation in the rarefied lower thermosphere. The continuum approach is embodied by the Navier-Stokes equations, while the non-continuum method is implemented via the Burnett equations [Proc. London Math. Soc. 39, 385-430 (1935); 40, 382-435 (1936)]. In the Burnett framework, the coupling between stress tensor and heat flux affects the dispersion equation, leading to an attenuation coefficient smaller than its Navier-Stokes counterpart by amounts of order 0.1 dB/km at 0.1 Hz, 10 dB/km at 1 Hz, and 100 dB/km at 10 Hz. It has been observed that many measured thermospheric arrivals are stronger than current predictions based on continuum mechanics. In this context, the consistently smaller Burnett-based absorption is cautiously encouraging.

  5. Offshore Wind Farm Layout Design Considering Optimized Power Dispatch Strategy

    DEFF Research Database (Denmark)

    Hou, Peng; Hu, Weihao; N. Soltani, Mohsen

    2017-01-01

    Offshore wind farm has drawn more and more attention recently due to its higher energy capacity and more freedom to occupy area. However, the investment is higher. In order to make a cost-effective wind farm, the wind farm layout should be optimized. The wake effect is one of the dominant factors...... leading to energy losses. It is expected that the optimized placement of wind turbines (WT) over a large sea area can lead to the best tradeoff between energy yields and capital investment. This paper proposes a novel way to position offshore WTs for a regular shaped wind farm. In addition to optimizing...... the direction of wind farm placement and the spacing between WTs, the control strategy’s impact on energy yields is also discussed. Since the problem is non-convex and lots of optimization variables are involved, an evolutionary algorithm, the particle swarm optimization algorithm (PSO), is adopted to find...

  6. Ozone-Temperature Diurnal and Longer Term Correlations, in the Lower Thermosphere, Mesosphere and Stratosphere, Based on Measurements from SABER on TIMED

    Science.gov (United States)

    Huang, Frank T.; Mayr, Hans G.; Russell, James M., III; Mlynczak, Martin G.

    2012-01-01

    The analysis of mutual ozone-temperature variations can provide useful information on their interdependencies relative to the photochemistry and dynamics governing their behavior. Previous studies have mostly been based on satellite measurements taken at a fixed local time in the stratosphere and lower mesosphere. For these data, it is shown that the zonal mean ozone amounts and temperatures in the lower stratosphere are mostly positively correlated, while they are mostly negatively correlated in the upper stratosphere and in the lower mesosphere. The negative correlation, due to the dependence of photochemical reaction rates on temperature, indicates that ozone photochemistry is more important than dynamics in determining the ozone amounts. In this study, we provide new results by extending the analysis to include diurnal variations over 24 hrs of local time, and to larger spatial regimes, to include the upper mesosphere and lower thermosphere (MLT). The results are based on measurements by the SABER instrument on the TIMED satellite. For mean variations (i.e., averages over local time and longitude) in the MLT, our results show that there is a sharp reversal in the correlation near 80 km altitude, above which the ozone mixing ratio and temperature are mostly positively correlated, while they are mostly negatively correlated below 80 km. This is consistent with the view that above -80 km, effects due to dynamics are more important compared to photochemistry. For diurnal variations, both the ozone and temperature show phase progressions in local time, as a function of altitude and latitude. For temperature, the phase progression is as expected, as they represent migrating tides. For day time ozone, we also find regular phase progression in local time over the whole altitude range of our analysis, 25 to 105 km, at least for low latitudes. This was not previously known, although phase progressions had been noted by us and by others at lower altitudes. For diurnal

  7. Diagrammatic methods in phase-space regularization

    International Nuclear Information System (INIS)

    Bern, Z.; Halpern, M.B.; California Univ., Berkeley

    1987-11-01

    Using the scalar prototype and gauge theory as the simplest possible examples, diagrammatic methods are developed for the recently proposed phase-space form of continuum regularization. A number of one-loop and all-order applications are given, including general diagrammatic discussions of the nogrowth theorem and the uniqueness of the phase-space stochastic calculus. The approach also generates an alternate derivation of the equivalence of the large-β phase-space regularization to the more conventional coordinate-space regularization. (orig.)

  8. J-regular rings with injectivities

    OpenAIRE

    Shen, Liang

    2010-01-01

    A ring $R$ is called a J-regular ring if R/J(R) is von Neumann regular, where J(R) is the Jacobson radical of R. It is proved that if R is J-regular, then (i) R is right n-injective if and only if every homomorphism from an $n$-generated small right ideal of $R$ to $R_{R}$ can be extended to one from $R_{R}$ to $R_{R}$; (ii) R is right FP-injective if and only if R is right (J, R)-FP-injective. Some known results are improved.

  9. Solar tides in the equatorial upper thermosphere: A comparison between AE-E data and the TIGCM for solstice, solar minimum conditions

    International Nuclear Information System (INIS)

    Burrage, M.D.; Storz, M.F.; Abreu, V.J.; Fesen, C.G.; Roble, R.G.

    1991-01-01

    Equatorial thermospheric tidal temperatures and densities inferred from Atmosphere Explorer E (AE-E) mass spectrometer data are compared with theoretical predictions from the National Center for Atmospheric Research Thermosphere/Ionisphere General Circulation Model (TIGCM) for solar minimum, solstice conditions. The thermospheric diurnal and semidiurnal tides are excited in situ by solar heating and by ion-neutral momentum coupling. Semidiurnal tides are also generated by upward propagating waves excited by heating in the lower atmosphere. The model calculations include all of these sources. The TIGCM reproduces the gross tidal features observed by the satellite, including the midnight temperature anomaly, and the diurnal phases are in good agreement for the densities of atomic oxygen and molecular nitrogen. However, for the neutral temperature, the predicted phases are 1-2 hours earlier than observed. In addition, the diurnal temperature and density amplitudes predicted by the model are considerably weaker than indicated by the AE-E measurements. The semidiurnal variations found in the observations agree well with the model for December solstice but not for June. The present results indicate that upward propagating tides from the lower atmosphere are responsible for at least half of the amplitude of the semidiurnal tide in the upper thermosphere

  10. Τhe observational and empirical thermospheric CO2 and NO power do not exhibit power-law behavior; an indication of their reliability

    Science.gov (United States)

    Varotsos, C. A.; Efstathiou, M. N.

    2018-03-01

    In this paper we investigate the evolution of the energy emitted by CO2 and NO from the Earth's thermosphere on a global scale using both observational and empirically derived data. In the beginning, we analyze the daily power observations of CO2 and NO received from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) equipment on the NASA Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite for the entire period 2002-2016. We then perform the same analysis on the empirical daily power emitted by CO2 and NO that were derived recently from the infrared energy budget of the thermosphere during 1947-2016. The tool used for the analysis of the observational and empirical datasets is the detrended fluctuation analysis, in order to investigate whether the power emitted by CO2 and by NO from the thermosphere exhibits power-law behavior. The results obtained from both observational and empirical data do not support the establishment of the power-law behavior. This conclusion reveals that the empirically derived data are characterized by the same intrinsic properties as those of the observational ones, thus enhancing the validity of their reliability.

  11. Wind engineering in Africa

    NARCIS (Netherlands)

    Wisse, J.A.; Stigter, C.J.

    2007-01-01

    The International Association for Wind Engineering (IAWE) has very few contacts in Africa, the second-largest continent. This paper reviews important wind-related African issues. They all require data on wind climate, which are very sparse in Africa. Wind engineering in Africa can assist in

  12. Generalized regular genus for manifolds with boundary

    Directory of Open Access Journals (Sweden)

    Paola Cristofori

    2003-05-01

    Full Text Available We introduce a generalization of the regular genus, a combinatorial invariant of PL manifolds ([10], which is proved to be strictly related, in dimension three, to generalized Heegaard splittings defined in [12].

  13. Geometric regularizations and dual conifold transitions

    International Nuclear Information System (INIS)

    Landsteiner, Karl; Lazaroiu, Calin I.

    2003-01-01

    We consider a geometric regularization for the class of conifold transitions relating D-brane systems on noncompact Calabi-Yau spaces to certain flux backgrounds. This regularization respects the SL(2,Z) invariance of the flux superpotential, and allows for computation of the relevant periods through the method of Picard-Fuchs equations. The regularized geometry is a noncompact Calabi-Yau which can be viewed as a monodromic fibration, with the nontrivial monodromy being induced by the regulator. It reduces to the original, non-monodromic background when the regulator is removed. Using this regularization, we discuss the simple case of the local conifold, and show how the relevant field-theoretic information can be extracted in this approach. (author)

  14. Satellite observations of middle atmosphere–thermosphere vertical coupling by gravity waves

    Directory of Open Access Journals (Sweden)

    Q. T. Trinh

    2018-03-01

    Full Text Available Atmospheric gravity waves (GWs are essential for the dynamics of the middle atmosphere. Recent studies have shown that these waves are also important for the thermosphere/ionosphere (T/I system. Via vertical coupling, GWs can significantly influence the mean state of the T/I system. However, the penetration of GWs into the T/I system is not fully understood in modeling as well as observations. In the current study, we analyze the correlation between GW momentum fluxes observed in the middle atmosphere (30–90 km and GW-induced perturbations in the T/I. In the middle atmosphere, GW momentum fluxes are derived from temperature observations of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER satellite instrument. In the T/I, GW-induced perturbations are derived from neutral density measured by instruments on the Gravity field and Ocean Circulation Explorer (GOCE and CHAllenging Minisatellite Payload (CHAMP satellites. We find generally positive correlations between horizontal distributions at low altitudes (i.e., below 90 km and horizontal distributions of GW-induced density fluctuations in the T/I (at 200 km and above. Two coupling mechanisms are likely responsible for these positive correlations: (1 fast GWs generated in the troposphere and lower stratosphere can propagate directly to the T/I and (2 primary GWs with their origins in the lower atmosphere dissipate while propagating upwards and generate secondary GWs, which then penetrate up to the T/I and maintain the spatial patterns of GW distributions in the lower atmosphere. The mountain-wave related hotspot over the Andes and Antarctic Peninsula is found clearly in observations of all instruments used in our analysis. Latitude–longitude variations in the summer midlatitudes are also found in observations of all instruments. These variations and strong positive correlations in the summer midlatitudes suggest that GWs with origins related to convection also

  15. Satellite observations of middle atmosphere-thermosphere vertical coupling by gravity waves

    Science.gov (United States)

    Trinh, Quang Thai; Ern, Manfred; Doornbos, Eelco; Preusse, Peter; Riese, Martin

    2018-03-01

    Atmospheric gravity waves (GWs) are essential for the dynamics of the middle atmosphere. Recent studies have shown that these waves are also important for the thermosphere/ionosphere (T/I) system. Via vertical coupling, GWs can significantly influence the mean state of the T/I system. However, the penetration of GWs into the T/I system is not fully understood in modeling as well as observations. In the current study, we analyze the correlation between GW momentum fluxes observed in the middle atmosphere (30-90 km) and GW-induced perturbations in the T/I. In the middle atmosphere, GW momentum fluxes are derived from temperature observations of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite instrument. In the T/I, GW-induced perturbations are derived from neutral density measured by instruments on the Gravity field and Ocean Circulation Explorer (GOCE) and CHAllenging Minisatellite Payload (CHAMP) satellites. We find generally positive correlations between horizontal distributions at low altitudes (i.e., below 90 km) and horizontal distributions of GW-induced density fluctuations in the T/I (at 200 km and above). Two coupling mechanisms are likely responsible for these positive correlations: (1) fast GWs generated in the troposphere and lower stratosphere can propagate directly to the T/I and (2) primary GWs with their origins in the lower atmosphere dissipate while propagating upwards and generate secondary GWs, which then penetrate up to the T/I and maintain the spatial patterns of GW distributions in the lower atmosphere. The mountain-wave related hotspot over the Andes and Antarctic Peninsula is found clearly in observations of all instruments used in our analysis. Latitude-longitude variations in the summer midlatitudes are also found in observations of all instruments. These variations and strong positive correlations in the summer midlatitudes suggest that GWs with origins related to convection also propagate up to the T

  16. Fast and compact regular expression matching

    DEFF Research Database (Denmark)

    Bille, Philip; Farach-Colton, Martin

    2008-01-01

    We study 4 problems in string matching, namely, regular expression matching, approximate regular expression matching, string edit distance, and subsequence indexing, on a standard word RAM model of computation that allows logarithmic-sized words to be manipulated in constant time. We show how...... to improve the space and/or remove a dependency on the alphabet size for each problem using either an improved tabulation technique of an existing algorithm or by combining known algorithms in a new way....

  17. Regular-fat dairy and human health

    DEFF Research Database (Denmark)

    Astrup, Arne; Bradley, Beth H Rice; Brenna, J Thomas

    2016-01-01

    In recent history, some dietary recommendations have treated dairy fat as an unnecessary source of calories and saturated fat in the human diet. These assumptions, however, have recently been brought into question by current research on regular fat dairy products and human health. In an effort to......, cheese and yogurt, can be important components of an overall healthy dietary pattern. Systematic examination of the effects of dietary patterns that include regular-fat milk, cheese and yogurt on human health is warranted....

  18. Deterministic automata for extended regular expressions

    Directory of Open Access Journals (Sweden)

    Syzdykov Mirzakhmet

    2017-12-01

    Full Text Available In this work we present the algorithms to produce deterministic finite automaton (DFA for extended operators in regular expressions like intersection, subtraction and complement. The method like “overriding” of the source NFA(NFA not defined with subset construction rules is used. The past work described only the algorithm for AND-operator (or intersection of regular languages; in this paper the construction for the MINUS-operator (and complement is shown.

  19. Regularities of intermediate adsorption complex relaxation

    International Nuclear Information System (INIS)

    Manukova, L.A.

    1982-01-01

    The experimental data, characterizing the regularities of intermediate adsorption complex relaxation in the polycrystalline Mo-N 2 system at 77 K are given. The method of molecular beam has been used in the investigation. The analytical expressions of change regularity in the relaxation process of full and specific rates - of transition from intermediate state into ''non-reversible'', of desorption into the gas phase and accumUlation of the particles in the intermediate state are obtained

  20. Online Manifold Regularization by Dual Ascending Procedure

    OpenAIRE

    Sun, Boliang; Li, Guohui; Jia, Li; Zhang, Hui

    2013-01-01

    We propose a novel online manifold regularization framework based on the notion of duality in constrained optimization. The Fenchel conjugate of hinge functions is a key to transfer manifold regularization from offline to online in this paper. Our algorithms are derived by gradient ascent in the dual function. For practical purpose, we propose two buffering strategies and two sparse approximations to reduce the computational complexity. Detailed experiments verify the utility of our approache...

  1. Wind power plant

    Energy Technology Data Exchange (ETDEWEB)

    Caneghem, A.E. von

    1975-07-24

    The invention applies to a wind power plant in which the wind is used to drive windmills. The plant consists basically of a vertical tube with a lateral wind entrance opening with windmill on its lower end. On its upper end, the tube carries a nozzle-like top which increases the wind entering the tube by pressure decrease. The wind is thus made suitable for higher outputs. The invention is illustrated by constructional examples.

  2. Wind energy analysis system

    OpenAIRE

    2014-01-01

    M.Ing. (Electrical & Electronic Engineering) One of the most important steps to be taken before a site is to be selected for the extraction of wind energy is the analysis of the energy within the wind on that particular site. No wind energy analysis system exists for the measurement and analysis of wind power. This dissertation documents the design and development of a Wind Energy Analysis System (WEAS). Using a micro-controller based design in conjunction with sensors, WEAS measure, calcu...

  3. Wind power. [electricity generation

    Science.gov (United States)

    Savino, J. M.

    1975-01-01

    A historical background on windmill use, the nature of wind, wind conversion system technology and requirements, the economics of wind power and comparisons with alternative systems, data needs, technology development needs, and an implementation plan for wind energy are presented. Considerable progress took place during the 1950's. Most of the modern windmills feature a wind turbine electricity generator located directly at the top of their rotor towers.

  4. Extreme wind estimate for Hornsea wind farm

    DEFF Research Database (Denmark)

    Larsén, Xiaoli Guo

    The purpose of this study is to provide estimation of the 50-year winds of 10 min and 1-s gust value at hub height of 100 m, as well as the design parameter shear exponent for the Hornsea offshore wind farm. The turbulence intensity required for estimating the gust value is estimated using two...... approaches. One is through the measurements from the wind Doppler lidar, WindCube, which implies serious uncertainty, and the other one is through similarity theory for the atmospheric surface layer where the hub height is likely to belong to during strong storms. The turbulence intensity for storm wind...... strength is taken as 0.1. The shear exponents at several heights were calculated from the measurements. The values at 100 m are less than the limit given by IEC standard for all sectors. The 50-year winds have been calculated from various global reanalysis and analysis products as well as mesoscale models...

  5. Improvements in GRACE Gravity Fields Using Regularization

    Science.gov (United States)

    Save, H.; Bettadpur, S.; Tapley, B. D.

    2008-12-01

    The unconstrained global gravity field models derived from GRACE are susceptible to systematic errors that show up as broad "stripes" aligned in a North-South direction on the global maps of mass flux. These errors are believed to be a consequence of both systematic and random errors in the data that are amplified by the nature of the gravity field inverse problem. These errors impede scientific exploitation of the GRACE data products, and limit the realizable spatial resolution of the GRACE global gravity fields in certain regions. We use regularization techniques to reduce these "stripe" errors in the gravity field products. The regularization criteria are designed such that there is no attenuation of the signal and that the solutions fit the observations as well as an unconstrained solution. We have used a computationally inexpensive method, normally referred to as "L-ribbon", to find the regularization parameter. This paper discusses the characteristics and statistics of a 5-year time-series of regularized gravity field solutions. The solutions show markedly reduced stripes, are of uniformly good quality over time, and leave little or no systematic observation residuals, which is a frequent consequence of signal suppression from regularization. Up to degree 14, the signal in regularized solution shows correlation greater than 0.8 with the un-regularized CSR Release-04 solutions. Signals from large-amplitude and small-spatial extent events - such as the Great Sumatra Andaman Earthquake of 2004 - are visible in the global solutions without using special post-facto error reduction techniques employed previously in the literature. Hydrological signals as small as 5 cm water-layer equivalent in the small river basins, like Indus and Nile for example, are clearly evident, in contrast to noisy estimates from RL04. The residual variability over the oceans relative to a seasonal fit is small except at higher latitudes, and is evident without the need for de-striping or

  6. Wind Energy literature survey no. 20

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2011-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including the following: Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research......, Renewable Energy, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal and Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers. The list is limited exclusively...... to journals not specifi cally devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fi t several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion in the list...

  7. Wind Energy Literature Survey No. 16

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2010-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including: Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research, Renewable...... Energy, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers etc. The list is limited exclusively...... to journals not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion in the list...

  8. Wind Energy literature survey no. 24

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2012-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including the Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research, Renewable...... Energy, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, and Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers, and so on. The list is limited...... exclusively to journals not specifically devoted to wind energy and its applications. For the reader to be assisted, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note...

  9. Wind energy literature survey no. 10

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2008-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including: Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research, Renewable...... Energy, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers etc. The list is limited exclusively...... to journals not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion in the list...

  10. Wind Energy literature survey no. 19

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2011-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research, Renewable Energy......, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers, etc. The list is limited exclusively to journals...... not specifi cally devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fi t several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion in the list...

  11. Wind Energy Literature Survey No. 14

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2009-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including: Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research, Renewable...... Energy, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers etc. The list is limited exclusively...... to journals not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion in the list...

  12. Wind Energy Literature Survey No. 13

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2009-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including: Journal of Wind Engineering & Industrial Aerodynamics, International Journal of Energy Research, Renewable Energy......, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, Electric Power Components and Systems, along with a number of periodicals published by the Institute of Electrical and Electronics Engineers, etc. The list is limited exclusively to journals...... not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion in the list is not an endorsement...

  13. Wind energy literature survey no. 18

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2010-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including: Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research, Renewable...... Energy, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers, etc. The list is limited exclusively...... to journals not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion in the list...

  14. Wind energy literature survey no. 17

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2010-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including: Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research, Renewable...... Energy, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers etc. The list is limited exclusively...... to journals not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion in the list...

  15. Wind energy literature survey no. 11

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2009-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including: Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research, Renewable...... Energy, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers, etc. The list is limited exclusively...... to journals not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion in the list...

  16. Wind Energy literature survey no. 21

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2012-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including the following: Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research......, Renewable Energy, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers and others. The list is limited...... exclusively to journals not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion...

  17. Wind Energy literature survey no. 22

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2012-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including the following: Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research......, Renewable Energy, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers and others. The list is limited...... exclusively to journals not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion...

  18. Wind Energy Literature Survey No. 15

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2010-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including: Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research, Renewable...... Energy, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers etc. The list is limited exclusively...... to journals not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion in the list...

  19. Wind Energy literature survey no. 30

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2013-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research, Renewable Energy......, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers, etc. The list is limited exclusively to journals...... not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion in the list is not an endorsement...

  20. Wind Energy literature survey no. 29

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2013-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including the following: Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research......, Renewable Energy, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal and Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers, etc. The list is limited...... exclusively to journals not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion...

  1. Wind Energy literature survey no. 23

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2012-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including the Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research, Renewable...... Energy, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, and Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers, and so on. The list is limited...... exclusively to journals not specifically devoted to wind energy and its applications. For the reader to be assisted, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note...

  2. Wind Energy literature survey no. 25

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2012-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research, Renewable Energy......, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers and so on. The list is limited exclusively...... to journals not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion in the list...

  3. Wind Energy literature survey no. 28

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2013-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant papers drawn from recent issues of a large number of periodicals including Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research, Renewable Energy......, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal and Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers, etc. The list is limited exclusively to journals...... not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion in the list is not an endorsement...

  4. Wind Energy literature survey no. 27

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2013-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant papers drawn from recent issues of a large number of periodicals including Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research, Renewable Energy......, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal and Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers, etc. The list is limited exclusively to journals...... not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion in the list is not an endorsement...

  5. Wind Energy literature survey no. 12

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2009-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant papers drawn from recent issues of a large number of periodicals including Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research, Renewable Energy......, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal and Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers, etc. The list is limited exclusively to journals...... not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion in the list is not an endorsement...

  6. Wind Energy literature survey no. 26

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian

    2012-01-01

    As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant papers drawn from recent issues of a large number of periodicals including Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research, Renewable Energy......, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal and Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers, etc. The list is limited exclusively to journals...... not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion in the list is not an endorsement...

  7. Utility-sized Madaras wind plants

    Science.gov (United States)

    Whitford, D. H.; Minardi, J. E.

    1981-01-01

    An analysis and technological updating were conducted for the Madaras Rotor Power Plant concept, to determine its ability to compete both technically and economically with horizontal axis wind turbine generators currently under development. The Madaras system uses large cylinders rotating vertically atop each regularly spaced flatcar of a train to propel them, by means of Magnus-effect interaction with the wind, along a circular or oval track. Alternators geared to the wheels of each car generate electrical power, which is transmitted to a power station by a trolley system. The study, consisting of electromechanical design, wind tunnel testing, and performance and cost analyses, shows that utility-sized plants greater than 228 MW in capacity and producing 975,000 kWh/year are feasible. Energy costs for such plants are projected to be between 22% lower and 12% higher than horizontal axis turbine plants of comparable output.

  8. Climatic wind tunnel for wind engineering tasks

    Czech Academy of Sciences Publication Activity Database

    Kuznetsov, Sergeii; Pospíšil, Stanislav; Král, Radomil

    2015-01-01

    Roč. 112, 2-B (2015), s. 303-316 ISSN 1897-628X R&D Projects: GA ČR(CZ) GA14-12892S Keywords : climatic tunnel * wind tunnel * atmospheric boundary layer * flow resistance * wind tunnel contraction Subject RIV: JM - Building Engineering https://suw.biblos.pk.edu.pl/resources/i5/i6/i6/i7/i6/r56676/KuznetsovS_ClimaticWind.pdf

  9. Operational specification and forecasting advances for Dst, LEO thermospheric densities, and aviation radiation dose and dose rate

    Science.gov (United States)

    Tobiska, W. Kent

    Space weather’s effects upon the near-Earth environment are due to dynamic changes in the energy transfer processes from the Sun’s photons, particles, and fields. Of the space environment domains that are affected by space weather, the magnetosphere, thermosphere, and even troposphere are key regions that are affected. Space Environment Technologies (SET) has developed and is producing innovative space weather applications. Key operational systems for providing timely information about the effects of space weather on these domains are SET’s Magnetosphere Alert and Prediction System (MAPS), LEO Alert and Prediction System (LAPS), and Automated Radiation Measurements for Aviation Safety (ARMAS) system. MAPS provides a forecast Dst index out to 6 days through the data-driven, redundant data stream Anemomilos algorithm. Anemomilos uses observational proxies for the magnitude, location, and velocity of solar ejecta events. This forecast index is used by satellite operations to characterize upcoming geomagnetic storms, for example. In addition, an ENLIL/Rice Dst prediction out to several days has also been developed and will be described. LAPS is the SET fully redundant operational system providing recent history, current epoch, and forecast solar and geomagnetic indices for use in operational versions of the JB2008 thermospheric density model. The thermospheric densities produced by that system, driven by the LAPS data, are forecast to 72-hours to provide the global mass densities for satellite operators. ARMAS is a project that has successfully demonstrated the operation of a micro dosimeter on aircraft to capture the real-time radiation environment due to Galactic Cosmic Rays and Solar Energetic Particles. The dose and dose-rates are captured on aircraft, downlinked in real-time via the Iridium satellites, processed on the ground, incorporated into the most recent NAIRAS global radiation climatology data runs, and made available to end users via the web and

  10. Wind Atlas for Egypt

    DEFF Research Database (Denmark)

    The results of a comprehensive, 8-year wind resource assessment programme in Egypt are presented. The objective has been to provide reliable and accurate wind atlas data sets for evaluating the potential wind power output from large electricityproducing wind turbine installations. The regional wind...... climates of Egypt have been determined by two independent methods: a traditional wind atlas based on observations from more than 30 stations all over Egypt, and a numerical wind atlas based on long-term reanalysis data and a mesoscale model (KAMM). The mean absolute error comparing the two methods is about...... 10% for two large-scale KAMM domains covering all of Egypt, and typically about 5% for several smaller-scale regional domains. The numerical wind atlas covers all of Egypt, whereas the meteorological stations are concentrated in six regions. The Wind Atlas for Egypt represents a significant step...

  11. Wind Atlas for Egypt

    DEFF Research Database (Denmark)

    Mortensen, Niels Gylling; Said Said, Usama; Badger, Jake

    2006-01-01

    The results of a comprehensive, 8-year wind resource assessment programme in Egypt are presented. The objective has been to provide reliable and accurate wind atlas data sets for evaluating the potential wind power output from large electricityproducing wind turbine installations. The regional wind...... climates of Egypt have been determined by two independent methods: a traditional wind atlas based on observations from more than 30 stations all over Egypt, and a numerical wind atlas based on long-term reanalysis data and a mesoscale model (KAMM). The mean absolute error comparing the two methods is about...... 10% for two large-scale KAMM domains covering all of Egypt, and typically about 5% for several smaller-scale regional domains. The numerical wind atlas covers all of Egypt, whereas the meteorological stations are concentrated in six regions. The Wind Atlas for Egypt represents a significant step...

  12. 75 FR 23263 - Alta Wind I, LLC; Alta Wind II, LLC; Alta Wind III, LLC; Alta Wind IV, LLC; Alta Wind V, LLC...

    Science.gov (United States)

    2010-05-03

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL10-62-000] Alta Wind I, LLC; Alta Wind II, LLC; Alta Wind III, LLC; Alta Wind IV, LLC; Alta Wind V, LLC; Alta Wind VI, LLC; Alta Wind VII, LLC; Alta Wind VIII, LLC; Alta Windpower Development, LLC; TGP Development Company, LLC...

  13. 77 FR 29633 - Alta Wind VII, LLC, Alta Wind IX, LLC, Alta Wind X, LLC, Alta Wind XI, LLC, Alta Wind XII, LLC...

    Science.gov (United States)

    2012-05-18

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL12-68-000] Alta Wind VII, LLC, Alta Wind IX, LLC, Alta Wind X, LLC, Alta Wind XI, LLC, Alta Wind XII, LLC, Alta Wind XIII, LLC, Alta Wind XIV, LLC, Alta Wind XV, LLC, Alta Windpower Development, LLC, TGP Development Company, LLC...

  14. Diurnal, monthly and seasonal variation of mean winds in the MLT region observed over Kolhapur using MF radar

    Science.gov (United States)

    Sharma, A. K.; Gaikwad, H. P.; Ratnam, M. Venkat; Gurav, O. B.; Ramanjaneyulu, L.; Chavan, G. A.; Sathishkumar, S.

    2018-04-01

    Medium Frequency (MF) radar located at Kolhapur (16.8°N, 74.2°E) has been upgraded in August 2013. Since then continuous measurements of zonal and meridional winds are obtained covering larger altitudes from the Mesosphere and Lower Thermosphere (MLT) region. Diurnal, monthly and seasonal variation of these mean winds is presented in this study using four years (2013-2017) of observations. The percentage occurrence of radar echoes show maximum between 80 and 105 km. The mean meridional wind shows Annual Oscillation (AO) between 80 and 90 km altitudes with pole-ward motion during December solstice and equatorial motion during June solstice. Quasi-biennial oscillation (QBO) with weaker amplitudes are also observed between 90 and 104 km. Zonal winds show semi-annual oscillation (SAO) with westward winds during equinoxes and eastward winds during solstices between 80 and 90 km. AO with eastward winds during December solstice and westward wind in the June solstice is also observed in the mean zonal wind between 100 and 110 km. These results match well with that reported from other latitudes within Indian region between 80 and 90 km. However, above 90 km the results presented here provide true mean background winds for the first time over Indian low latitude region as the present station is away from equatorial electro-jet and are not contaminated by ionospheric processes. Further, the results presented earlier with an old version of this radar are found contaminated due to unknown reasons and are corrected in the present work. This upgraded MF radar together with other MLT radars in the Indian region forms unique network to investigate the vertical and lateral coupling.

  15. Regular Expression Matching and Operational Semantics

    Directory of Open Access Journals (Sweden)

    Asiri Rathnayake

    2011-08-01

    Full Text Available Many programming languages and tools, ranging from grep to the Java String library, contain regular expression matchers. Rather than first translating a regular expression into a deterministic finite automaton, such implementations typically match the regular expression on the fly. Thus they can be seen as virtual machines interpreting the regular expression much as if it were a program with some non-deterministic constructs such as the Kleene star. We formalize this implementation technique for regular expression matching using operational semantics. Specifically, we derive a series of abstract machines, moving from the abstract definition of matching to increasingly realistic machines. First a continuation is added to the operational semantics to describe what remains to be matched after the current expression. Next, we represent the expression as a data structure using pointers, which enables redundant searches to be eliminated via testing for pointer equality. From there, we arrive both at Thompson's lockstep construction and a machine that performs some operations in parallel, suitable for implementation on a large number of cores, such as a GPU. We formalize the parallel machine using process algebra and report some preliminary experiments with an implementation on a graphics processor using CUDA.

  16. Regularities, Natural Patterns and Laws of Nature

    Directory of Open Access Journals (Sweden)

    Stathis Psillos

    2014-02-01

    Full Text Available  The goal of this paper is to sketch an empiricist metaphysics of laws of nature. The key idea is that there are regularities without regularity-enforcers. Differently put, there are natural laws without law-makers of a distinct metaphysical kind. This sketch will rely on the concept of a natural pattern and more significantly on the existence of a network of natural patterns in nature. The relation between a regularity and a pattern will be analysed in terms of mereology.  Here is the road map. In section 2, I will briefly discuss the relation between empiricism and metaphysics, aiming to show that an empiricist metaphysics is possible. In section 3, I will offer arguments against stronger metaphysical views of laws. Then, in section 4 I will motivate nomic objectivism. In section 5, I will address the question ‘what is a regularity?’ and will develop a novel answer to it, based on the notion of a natural pattern. In section 6, I will raise the question: ‘what is a law of nature?’, the answer to which will be: a law of nature is a regularity that is characterised by the unity of a natural pattern.

  17. X-band COSMO-SkyMed wind field retrieval, with application to coastal circulation modeling

    Directory of Open Access Journals (Sweden)

    A. Montuori

    2013-02-01

    Full Text Available In this paper, X-band COSMO-SkyMed© synthetic aperture radar (SAR wind field retrieval is investigated, and the obtained data are used to force a coastal ocean circulation model. The SAR data set consists of 60 X-band Level 1B Multi-Look Ground Detected ScanSAR Huge Region COSMO-SkyMed© SAR data, gathered in the southern Tyrrhenian Sea during the summer and winter seasons of 2010. The SAR-based wind vector field estimation is accomplished by resolving both the SAR-based wind speed and wind direction retrieval problems independently. The sea surface wind speed is retrieved by means of a SAR wind speed algorithm based on the azimuth cut-off procedure, while the sea surface wind direction is provided by means of a SAR wind direction algorithm based on the discrete wavelet transform multi-resolution analysis. The obtained wind fields are compared with ground truth data provided by both ASCAT scatterometer and ECMWF model wind fields. SAR-derived wind vector fields and ECMWF model wind data are used to construct a blended wind product regularly sampled in both space and time, which is then used to force a coastal circulation model of a southern Tyrrhenian coastal area to simulate wind-driven circulation processes. The modeling results show that X-band COSMO-SkyMed© SAR data can be valuable in providing effective wind fields for coastal circulation modeling.

  18. Wind energy information guide

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-04-01

    This book is divided into nine chapters. Chapters 1--8 provide background and annotated references on wind energy research, development, and commercialization. Chapter 9 lists additional sources of printed information and relevant organizations. Four indices provide alphabetical access to authors, organizations, computer models and design tools, and subjects. A list of abbreviations and acronyms is also included. Chapter topics include: introduction; economics of using wind energy; wind energy resources; wind turbine design, development, and testing; applications; environmental issues of wind power; institutional issues; and wind energy systems development.

  19. Arctic wind energy

    Energy Technology Data Exchange (ETDEWEB)

    Peltola, E. [Kemijoki Oy (Finland); Holttinen, H.; Marjaniemi, M. [VTT Energy, Espoo (Finland); Tammelin, B. [Finnish Meteorological Institute, Helsinki (Finland)

    1998-12-31

    Arctic wind energy research was aimed at adapting existing wind technologies to suit the arctic climatic conditions in Lapland. Project research work included meteorological measurements, instrument development, development of a blade heating system for wind turbines, load measurements and modelling of ice induced loads on wind turbines, together with the development of operation and maintenance practices in arctic conditions. As a result the basis now exists for technically feasible and economically viable wind energy production in Lapland. New and marketable products, such as blade heating systems for wind turbines and meteorological sensors for arctic conditions, with substantial export potential, have also been developed. (orig.)

  20. Arctic wind energy

    International Nuclear Information System (INIS)

    Peltola, E.; Holttinen, H.; Marjaniemi, M.; Tammelin, B.

    1998-01-01

    Arctic wind energy research was aimed at adapting existing wind technologies to suit the arctic climatic conditions in Lapland. Project research work included meteorological measurements, instrument development, development of a blade heating system for wind turbines, load measurements and modelling of ice induced loads on wind turbines, together with the development of operation and maintenance practices in arctic conditions. As a result the basis now exists for technically feasible and economically viable wind energy production in Lapland. New and marketable products, such as blade heating systems for wind turbines and meteorological sensors for arctic conditions, with substantial export potential, have also been developed. (orig.)

  1. Wind power today

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-04-01

    This publication highlights initiatives of the US DOE`s Wind Energy Program. 1997 yearly activities are also very briefly summarized. The first article describes a 6-megawatt wind power plant installed in Vermont. Another article summarizes technical advances in wind turbine technology, and describes next-generation utility and small wind turbines in the planning stages. A village power project in Alaska using three 50-kilowatt turbines is described. Very brief summaries of the Federal Wind Energy Program and the National Wind Technology Center are also included in the publication.

  2. Wind Power Career Chat

    Energy Technology Data Exchange (ETDEWEB)

    L. Flowers

    2011-01-01

    This document will teach students about careers in the wind energy industry. Wind energy, both land-based and offshore, is expected to provide thousands of new jobs in the next several decades. Wind energy companies are growing rapidly to meet America's demand for clean, renewable, and domestic energy. These companies need skilled professionals. Wind power careers will require educated people from a variety of areas. Trained and qualified workers manufacture, construct, operate, and manage wind energy facilities. The nation will also need skilled researchers, scientists, and engineers to plan and develop the next generation of wind energy technologies.

  3. Wind and Temperature Spectrometry of the Upper Atmosphere in Low-Earth Orbit

    Science.gov (United States)

    Herrero, Federico

    2011-01-01

    Wind and Temperature Spectrometry (WATS) is a new approach to measure the full wind vector, temperature, and relative densities of major neutral species in the Earth's thermosphere. The method uses an energy-angle spectrometer moving through the tenuous upper atmosphere to measure directly the angular and energy distributions of the air stream that enters the spectrometer. The angular distribution gives the direction of the total velocity of the air entering the spectrometer, and the energy distribution gives the magnitude of the total velocity. The wind velocity vector is uniquely determined since the measured total velocity depends on the wind vector and the orbiting velocity vector. The orbiting spectrometer moves supersonically, Mach 8 or greater, through the air and must point within a few degrees of its orbital velocity vector (the ram direction). Pointing knowledge is critical; for example, pointing errors 0.1 lead to errors of about 10 m/s in the wind. The WATS method may also be applied without modification to measure the ion-drift vector, ion temperature, and relative ion densities of major ionic species in the ionosphere. In such an application it may be called IDTS: Ion-Drift Temperature Spectrometry. A spectrometer-based coordinate system with one axis instantaneously pointing along the ram direction makes it possible to transform the Maxwellian velocity distribution of the air molecules to a Maxwellian energy-angle distribution for the molecular flux entering the spectrometer. This implementation of WATS is called the gas kinetic method (GKM) because it is applied to the case of the Maxwellian distribution. The WATS method follows from the recognition that in a supersonic platform moving at 8,000 m/s, the measurement of small wind velocities in the air on the order of a few 100 m/s and less requires precise knowledge of the angle of incidence of the neutral atoms and molecules. The same is true for the case of ion-drift measurements. WATS also

  4. Is tropospheric weather influenced by solar wind through atmospheric vertical coupling downward control?

    Science.gov (United States)

    Prikryl, Paul; Tsukijihara, Takumi; Iwao, Koki; Muldrew, Donald B.; Bruntz, Robert; Rušin, Vojto; Rybanský, Milan; Turňa, Maroš; Šťastný, Pavel; Pastirčák, Vladimír

    2017-04-01

    More than four decades have passed since a link between solar wind magnetic sector boundary structure and mid-latitude upper tropospheric vorticity was discovered (Wilcox et al., Science, 180, 185-186, 1973). The link has been later confirmed and various physical mechanisms proposed but apart from controversy, little attention has been drawn to these results. To further emphasize their importance we investigate the occurrence of mid-latitude severe weather in the context of solar wind coupling to the magnetosphere-ionosphere-atmosphere (MIA) system. It is observed that significant snowstorms, windstorms and heavy rain, particularly if caused by low pressure systems in winter, tend to follow arrivals of high-speed solar wind. Previously published statistical evidence that explosive extratropical cyclones in the northern hemisphere tend to occur after arrivals of high-speed solar wind streams from coronal holes (Prikryl et al., Ann. Geophys., 27, 1-30, 2009; Prikryl et al., J. Atmos. Sol.-Terr. Phys., 149, 219-231, 2016) is corroborated for the southern hemisphere. A physical mechanism to explain these observations is proposed. The leading edge of high-speed solar wind streams is a locus of large-amplitude magneto-hydrodynamic waves that modulate Joule heating and/or Lorentz forcing of the high-latitude lower thermosphere generating medium-scale atmospheric gravity waves that propagate upward and downward through the atmosphere. Simulations of gravity wave propagation in a model atmosphere using the Transfer Function Model (Mayr et al., Space Sci. Rev., 54, 297-375, 1990) show that propagating waves originating in the thermosphere can excite a spectrum of gravity waves in the lower atmosphere. In spite of significantly reduced amplitudes but subject to amplification upon reflection in the upper troposphere, these gravity waves can provide a lift of unstable air to release instabilities in the troposphere thus initiating convection to form cloud/precipitation bands

  5. Fractional Regularization Term for Variational Image Registration

    Directory of Open Access Journals (Sweden)

    Rafael Verdú-Monedero

    2009-01-01

    Full Text Available Image registration is a widely used task of image analysis with applications in many fields. Its classical formulation and current improvements are given in the spatial domain. In this paper a regularization term based on fractional order derivatives is formulated. This term is defined and implemented in the frequency domain by translating the energy functional into the frequency domain and obtaining the Euler-Lagrange equations which minimize it. The new regularization term leads to a simple formulation and design, being applicable to higher dimensions by using the corresponding multidimensional Fourier transform. The proposed regularization term allows for a real gradual transition from a diffusion registration to a curvature registration which is best suited to some applications and it is not possible in the spatial domain. Results with 3D actual images show the validity of this approach.

  6. Regular non-twisting S-branes

    International Nuclear Information System (INIS)

    Obregon, Octavio; Quevedo, Hernando; Ryan, Michael P.

    2004-01-01

    We construct a family of time and angular dependent, regular S-brane solutions which corresponds to a simple analytical continuation of the Zipoy-Voorhees 4-dimensional vacuum spacetime. The solutions are asymptotically flat and turn out to be free of singularities without requiring a twist in space. They can be considered as the simplest non-singular generalization of the singular S0-brane solution. We analyze the properties of a representative of this family of solutions and show that it resembles to some extent the asymptotic properties of the regular Kerr S-brane. The R-symmetry corresponds, however, to the general lorentzian symmetry. Several generalizations of this regular solution are derived which include a charged S-brane and an additional dilatonic field. (author)

  7. Online Manifold Regularization by Dual Ascending Procedure

    Directory of Open Access Journals (Sweden)

    Boliang Sun

    2013-01-01

    Full Text Available We propose a novel online manifold regularization framework based on the notion of duality in constrained optimization. The Fenchel conjugate of hinge functions is a key to transfer manifold regularization from offline to online in this paper. Our algorithms are derived by gradient ascent in the dual function. For practical purpose, we propose two buffering strategies and two sparse approximations to reduce the computational complexity. Detailed experiments verify the utility of our approaches. An important conclusion is that our online MR algorithms can handle the settings where the target hypothesis is not fixed but drifts with the sequence of examples. We also recap and draw connections to earlier works. This paper paves a way to the design and analysis of online manifold regularization algorithms.

  8. Estimate of the global-scale joule heating rates in the thermosphere due to time mean currents

    International Nuclear Information System (INIS)

    Roble, R.G.; Matsushita, S.

    1975-01-01

    An estimate of the global-scale joule heating rates in the thermosphere is made based on derived global equivalent overhead electric current systems in the dynamo region during geomagnetically quiet and disturbed periods. The equivalent total electric field distribution is calculated from Ohm's law. The global-scale joule heating rates are calculated for various monthly average periods in 1965. The calculated joule heating rates maximize at high latitudes in the early evening and postmidnight sectors. During geomagnetically quiet times the daytime joule heating rates are considerably lower than heating by solar EUV radiation. However, during geomagnetically disturbed periods the estimated joule heating rates increase by an order of magnitude and can locally exceed the solar EUV heating rates. The results show that joule heating is an important and at times the dominant energy source at high latitudes. However, the global mean joule heating rates calculated near solar minimum are generally small compared to the global mean solar EUV heating rates. (auth)

  9. Self-absorption theory applied to rocket measurements of the nitric oxide (1, 0) gamma band in the daytime thermosphere

    Science.gov (United States)

    Eparvier, F. G.; Barth, C. A.

    1992-01-01

    Observations of the UV fluorescent emissions of the NO (1, 0) and (0, 1) gamma bands in the lower-thermospheric dayglow, made with a sounding rocket launched on March 7, 1989 from Poker Flat, Alaska, were analyzed. The resonant (1, 0) gamma band was found to be attenuated below an altitude of about 120 km. A self-absorption model based on Holstein transmission functions was developed for the resonant (1, 0) gamma band under varying conditions of slant column density and temperature and was applied for the conditions of the rocket flight. The results of the model agreed with the measured attenuation of the band, indicating the necessity of including self-absorption theory in the analysis of satellite and rocket limb data of NO.

  10. Some aspects of metallic ion chemistry and dynamics in the mesosphere and thermosphere

    Science.gov (United States)

    Mathews, J. D.

    1987-01-01

    The relationship between the formation of sporadic layers of metallic ion and the dumping of these ions into the upper mesosphere is discussed in terms of the tidal wind, classical (i.e., windshear) and other more complex, perhaps highly nonlinear layer formation mechanisms, and a possible circulation mechanism for these ions. Optical, incoherent scatter radar, rocket, and satellite derived evidence for various layer formation mechanisms and for the metallic ion circulation system is reviewed. The results of simple one dimensional numerical model calculations of sporadic E and intermediate layer formation are presented along with suggestions for more advanced models of intense or blanketing sporadic E. The flux of metallic ions dumped by the tidal wind system into the mesosphere is estimated and compared with estimates of total particle flux of meteoric origin. Possible effects of the metallic ion flux and of meteoric dust on D region ion chemistry are discussed.

  11. Regular transport dynamics produce chaotic travel times.

    Science.gov (United States)

    Villalobos, Jorge; Muñoz, Víctor; Rogan, José; Zarama, Roberto; Johnson, Neil F; Toledo, Benjamín; Valdivia, Juan Alejandro

    2014-06-01

    In the hope of making passenger travel times shorter and more reliable, many cities are introducing dedicated bus lanes (e.g., Bogota, London, Miami). Here we show that chaotic travel times are actually a natural consequence of individual bus function, and hence of public transport systems more generally, i.e., chaotic dynamics emerge even when the route is empty and straight, stops and lights are equidistant and regular, and loading times are negligible. More generally, our findings provide a novel example of chaotic dynamics emerging from a single object following Newton's laws of motion in a regularized one-dimensional system.

  12. Regularity of difference equations on Banach spaces

    CERN Document Server

    Agarwal, Ravi P; Lizama, Carlos

    2014-01-01

    This work introduces readers to the topic of maximal regularity for difference equations. The authors systematically present the method of maximal regularity, outlining basic linear difference equations along with relevant results. They address recent advances in the field, as well as basic semigroup and cosine operator theories in the discrete setting. The authors also identify some open problems that readers may wish to take up for further research. This book is intended for graduate students and researchers in the area of difference equations, particularly those with advance knowledge of and interest in functional analysis.

  13. PET regularization by envelope guided conjugate gradients

    International Nuclear Information System (INIS)

    Kaufman, L.; Neumaier, A.

    1996-01-01

    The authors propose a new way to iteratively solve large scale ill-posed problems and in particular the image reconstruction problem in positron emission tomography by exploiting the relation between Tikhonov regularization and multiobjective optimization to obtain iteratively approximations to the Tikhonov L-curve and its corner. Monitoring the change of the approximate L-curves allows us to adjust the regularization parameter adaptively during a preconditioned conjugate gradient iteration, so that the desired solution can be reconstructed with a small number of iterations

  14. Matrix regularization of embedded 4-manifolds

    International Nuclear Information System (INIS)

    Trzetrzelewski, Maciej

    2012-01-01

    We consider products of two 2-manifolds such as S 2 ×S 2 , embedded in Euclidean space and show that the corresponding 4-volume preserving diffeomorphism algebra can be approximated by a tensor product SU(N)⊗SU(N) i.e. functions on a manifold are approximated by the Kronecker product of two SU(N) matrices. A regularization of the 4-sphere is also performed by constructing N 2 ×N 2 matrix representations of the 4-algebra (and as a byproduct of the 3-algebra which makes the regularization of S 3 also possible).

  15. Thermospheric neutral temperatures derived from charge-exchange produced N{sub 2}{sup +} Meinel (1,0) rotational distributions

    Energy Technology Data Exchange (ETDEWEB)

    Mutiso, C.K.; Zettergren, M.D.; Hughes, J.M.; Sivjee, G.G. [Embry-Riddle Aeronautical Univ., Daytona Beach, FL (United States). Space Physics Research Lab.

    2013-06-01

    Thermalized rotational distributions of neutral and ionized N{sub 2} and O{sub 2} have long been used to determine neutral temperatures (T{sub n}) during auroral conditions. In both bright E-region (or similar 130 km) species provide an exception to this situation. In particular, the charge-exchange reaction O{sup +}({sup 2}D)+N{sub 2}(X) {yields}N{sub 2}{sup +} (A{sup 2}{Pi}{sub u}, {nu}' = 1) + O({sup 3}P) yields thermalized N{sub 2}{sup +} Meinel (1,0) emissions, which, albeit weak, can be used to derive neutral temperatures at altitudes of {proportional_to} 130 km and higher. In this work, we present N{sub 2}{sup +} Meinel (1,0) rotational temperatures and brightnesses obtained at Svalbard, Norway, during various auroral conditions. We calculate T{sub n} at thermospheric altitudes of 130-180 km from thermalized rotational populations of N{sub 2}{sup +} Meinel (1,0); these emissions are excited by soft electron (thermospheric T{sub n} from chargeexchange excited N{sub 2}{sup +} Meinel (1,0) emissions provides an additional means of remotely sensing the neutral atmosphere, although certain limiting conditions are necessary. These include precipitation of low-energy electrons, and a non-sunlit emitting layer. (orig.)

  16. Observations of Infrared Radiative Cooling in the Thermosphere on Daily to Multiyear Timescales from the TIMED/SABER Instrument

    Science.gov (United States)

    Mlynczak, Martin G.; Hunt, Linda A.; Marshall, B. Thomas; Martin-Torres, F. Javier; Mertens, Christopher J.; Russell, James M., III; Remsberg, Ellis E.; Lopez-Puertas, Manuel; Picard, Richard; Winick, Jeremy; hide

    2009-01-01

    We present observations of the infrared radiative cooling by carbon dioxide (CO2) and nitric oxide (NO) in Earth s thermosphere. These data have been taken over a period of 7 years by the SABER instrument on the NASA TIMED satellite and are the dominant radiative cooling mechanisms for the thermosphere. From the SABER observations we derive vertical profiles of radiative cooling rates (W/cu m), radiative fluxes (W/sq m), and radiated power (W). In the period from January 2002 through January 2009 we observe a large decrease in the cooling rates, fluxes, and power consistent with the declining phase of solar cycle. The power radiated by NO during 2008 when the Sun exhibited few sunspots was nearly one order of magnitude smaller than the peak power observed shortly after the mission began. Substantial short-term variability in the infrared emissions is also observed throughout the entire mission duration. Radiative cooling rates and radiative fluxes from NO exhibit fundamentally different latitude dependence than do those from CO2, with the NO fluxes and cooling rates being largest at high latitudes and polar regions. The cooling rates are shown to be derived relatively independent of the collisional and radiative processes that drive the departure from local thermodynamic equilibrium (LTE) in the CO2 15 m and the NO 5.3 m vibration-rotation bands. The observed NO and CO2 cooling rates have been compiled into a separate dataset and represent a climate data record that is available for use in assessments of radiative cooling in upper atmosphere general circulation models.

  17. Validation of the MIPAS CO2 volume mixing ratio in the mesosphere and lower thermosphere and comparison with WACCM simulations

    Science.gov (United States)

    López-Puertas, Manuel; Funke, B.; Jurado-Navarro, Á. A.; García-Comas, M.; Gardini, A.; Boone, C. D.; Rezac, L.; Garcia, R. R.

    2017-08-01

    We present the validation of Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) CO2 daytime concentration in the mesosphere and lower thermosphere by comparing with Atmospheric Chemistry Experiment (ACE) Fourier transform spectrometer and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) data. MIPAS shows a very good agreement with ACE below 100 km with differences of ˜5%. Above 100 km, MIPAS CO2 is generally lower than ACE with differences growing from ˜5% at 100 km to 20-40% near 110-120 km. Part of this disagreement can be explained by the lack of a nonlocal thermodynamic equilibrium correction in ACE. MIPAS also agrees very well (˜5%) with SABER below 100 km. At 90-105 km, MIPAS is generally smaller than SABER by 10-30% in the polar summers. At 100-120 km, MIPAS and SABER CO2 agree within ˜10% during equinox but, for solstice, MIPAS is larger by 10-25%, except near the polar summer. Whole Atmosphere Community Climate Model (WACCM) CO2 shows the major MIPAS features. At 75-100 km, the agreement is very good (˜5%), with maximum differences of ˜10%. At 95-115 km MIPAS CO2 is larger than WACCM by 20-30% in the winter hemisphere but smaller (20-40%) in the summer. Above 95-100 km WACCM generally overestimates MIPAS CO2 by about 20-80% except in the polar summer where underestimates it by 20-40%. MIPAS CO2 favors a large eddy diffusion below 100 km and suggests that the meridional circulation of the lower thermosphere is stronger than in WACCM. The three instruments and WACCM show a clear increase of CO2 with time, more markedly at 90-100 km.

  18. Evolution of wind towards wind turbine

    NARCIS (Netherlands)

    Giyanani, A.H.; Bierbooms, W.A.A.M.; Van Bussel, G.J.W.

    2015-01-01

    Remote sensing of the atmospheric variables with the use of LiDAR is a relatively new technology field for wind resource assessment in wind energy. The validation of LiDAR measurements and comparisons is of high importance for further applications of the data.

  19. Urban Wind Energy

    DEFF Research Database (Denmark)

    Beller, Christina

    important for the implementation of wind energy conversion systems are the macro and micro wind climate, the siting within a micro wind climate and the choice of a wind turbine model most appropriate for the selected site. In the frame of this work, all these important elements are analyzed and a row......New trends e.g. in architecture and urban planning are to reduce energy needs. Several technologies are employed to achieve this, and one of the technologies, not new as such, is wind energy. Wind turbines are installed in cities, both by companies and private persons on both old and new buildings....... However, an overview of the energy content of the wind in cities and how consequently turbines shall be designed for such wind climates is lacking. The objective of the present work is to deliver an objective and fundamental overview of the social, practical and physical conditions relevant...

  20. Leadership Team | Wind | NREL

    Science.gov (United States)

    Leadership Team Leadership Team Learn more about the expertise and technical skills of the wind Initiative and provides leadership in the focus areas of high-fidelity modeling, wind power plant controls