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Sample records for wind auroral zone

  1. Auroral-zone plasma dynamics

    International Nuclear Information System (INIS)

    Gorney, D.J.

    1982-01-01

    Analysis of the USAF S3-3 charged particle data and electric field observations has provided extensive quantitative understanding of the auroral particle acceleration process. The results of an effort to use energetic charged particle observations to probe the altitude profile of auroral electric potential structures by applying adiabatic mapping theory are presented here. In situ energetic charged particle measurements differ from local electric field observations in that charged particles execute dynamic trajectories along the magnetic field lines and retain information on the spatial electric potential distribution in their velocity space distribution function. Although a unique determination of the potential distribution is not possible, basic differences between local or non-local acceleration are readily apparent in the particle observations. Together, the charged particle and electric field measurements have enabled us to form a reasonable picture of the auroral ''inverted-V'' structure which can then be applied to study the nonadiabatic processes that occur in these strong acceleration regions, such as energy scattering of ion and electron beams. Specifically, this study shows that a large scale auroral electric field exists at all times in the evening sector with an altitude distribution that is fairly unstructured at altitudes near and above one earth radius. Significant parallel potential drop is not observed below about 4000 kilometers altitude. At times, however, a substantial portion of the potential drop appears to lie in the low altitude region (4000-10,000 km)

  2. Auroral Electrojet Index Designed to Provide a Global Measure, Hourly Intervals, of Auroral Zone Magnetic Activity

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Auroral Electrojet (AE) index is designed to provide a global quantitative measure of auroral zone magnetic activity produced by enhanced ionospheric currents...

  3. Morphology of auroral zone radio wave scintillation

    International Nuclear Information System (INIS)

    Rino, C.L.; Matthews, S.J.

    1980-01-01

    This paper describes the morphology of midnight sector and morning sector auroral zone scintillation observations made over a two-year period using the Wideband satelite, which is in a sun-synchronous, low-altitude orbit. No definitive seasonal variation was found. The nighttime data showed the highest scintillation ocurrence levels, but significant amounts of morning scintillation were observed. For the most part the scintillation activity followed the general pattern of local magnetic activity. The most prominent feature in the nightime data is a localized amplitude and phase scintillation enhancement at the point where the propagation vector lies within an L shell. A geometrical effect due to a dynamic slab of sheetlike structures in the F region is hypothesized as the source of his enhancement. The data have been sorted by magnetic activity, proximity to local midnight, and season. The general features of the data are in agreement with the accepted morphology of auroral zone scintillation

  4. Auroral Electrojet (AE, AL, AO, AU) - A Global Measure of Auroral Zone Magnetic Activity

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The AE index is derived from geomagnetic variations in the horizontal component observed at selected (10-13) observatories along the auroral zone in the northern...

  5. Auroral Electrojet Index Designed to Provide a Global Measure, l-minute Intervals, of Auroral Zone Magnetic Activity

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Auroral Electrojet index (AE) is designed to provide a global quantitative measure of auroral zone magnetic activity produced by enhanced ionospheric currents...

  6. Auroral Electrojet Indices Designed to Provide a Global Measure, 2.5-Minute Intervals, of Auroral Zone Magnetic Activity

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Auroral Electrojet index (AE) is designed to provide a global quantitative measure of auroral zone magnetic activity produced by enhanced ionospheric currents...

  7. Solar wind control of stratospheric temperatures in Jupiter's auroral regions?

    Science.gov (United States)

    Sinclair, James Andrew; Orton, Glenn; Kasaba, Yasumasa; Sato, Takao M.; Tao, Chihiro; Waite, J. Hunter; Cravens, Thomas; Houston, Stephen; Fletcher, Leigh; Irwin, Patrick; Greathouse, Thomas K.

    2017-10-01

    Auroral emissions are the process through which the interaction of a planet’s atmosphere and its external magnetosphere can be studied. Jupiter exhibits auroral emission at a multitude of wavelengths including the X-ray, ultraviolet and near-infrared. Enhanced emission of CH4 and other stratospheric hydrocarbons is also observed coincident with Jupiter’s shorter-wavelength auroral emission (e.g. Caldwell et al., 1980, Icarus 44, 667-675, Kostiuk et al., 1993, JGR 98, 18823). This indicates that auroral processes modify the thermal structure and composition of the auroral stratosphere. The exact mechanism responsible for this auroral-related heating of the stratosphere has however remained elusive (Sinclair et al., 2017a, Icarus 292, 182-207, Sinclair et al., 2017b, GRL, 44, 5345-5354). We will present an analysis of 7.8-μm images of Jupiter measured by COMICS (Cooled Mid-Infrared Camera and Spectrograph, Kataza et al., 2000, Proc. SPIE(4008), 1144-1152) on the Subaru telescope. These images were acquired on January 11th, 12th, 13th, 14th, February 4, 5th and May 17th, 18th, 19th and 20th in 2017, allowing the daily variability of Jupiter’s auroral-related stratospheric heating to be tracked. Preliminary results suggest lower stratospheric temperatures are directly forced by the solar wind dynamical pressure. The southern auroral hotspot exhibited a significant increase in brightness temperature over a 24-hour period. Over the same time period, a solar wind propagation model (Tao et al. 2005, JGR 110, A11208) predicts a strong increase in the solar wind dynamical pressure at Jupiter.

  8. Double layers do accelerate particles in the auroral zone

    International Nuclear Information System (INIS)

    Borovsky, J.E.

    1992-01-01

    In response to a recent report [D. A. Bryant, R. Bingham, and U. de Angelis, Phys. Rev. Lett. 68, 37 (1991)] that makes the claim that electrostatic fields are weak in the auroral zone and that electrostatic fields cannot accelerate particles, it is pointed out that the evidence for electrostatic fields in the auroral zone is overwhelming and that these electrostatic fields often are accelerating electrons to produce aurora. The literature cited in the article above as evidence against double layers (strong electric fields) is reexamined and is found not to be evidence against double layers

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

    Science.gov (United States)

    Biktash, L.

    2007-08-01

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

  10. The day to night absorption ratio in auroral and subauroral zone riometer measurements during auroral absorption

    International Nuclear Information System (INIS)

    Ranta, H.; Ranta, A.; Rosenberg, T.J.

    1984-01-01

    The day to night ratio of auroral absorption has been studied using data from auroral and subauroral latitudes and by application of different kinds of statistical analyses. Ratios between 0.5 and 3.0 are obtained, depending on the criteria applied to the selection of data. Previous studies obtained similar ratios, but reached different conclusions about the effective solar control of auroral absorption. It is concluded here that evidence of solar control of the day to night ratio of auroral absorption, or the lack thereof, cannot be extracted by these statistical analyses. (author)

  11. Theory of auroral zone PiB pulsation spectra

    International Nuclear Information System (INIS)

    Lysak, R.L.

    1988-01-01

    Changes in the auroral zone current system are often accompanied by magnetic pulsations with periods of about 1 s. These so-called bursts of irregular pulsations (PiB) have been observed both on ground magnetograms and with in situ satellite observations. These pulsations can be understood as excitations of a resonant cavity in the topside ionosphere, where the Alfven speed has a strong gradient due to the exponential decrease of density above the ionosphere. These waves have a frequency which scales as the ratio of the Alfven speed at the ionosphere divided by the ionospheric scale height. For a pure exponential Alfven speed profile, the mode frequencies are related to zeros of the zeroth-order Bessel function. For other profiles of the density, and therefore Alfven speed, the frequencies are not exactly given by the simple theory, but the frequency and mode structure are similar provided the Alfven speed sharply increases above the ionosphere

  12. INTERBALL-Auroral observations of 0.1-12 keV ion gaps in the diffuse auroral zone

    Directory of Open Access Journals (Sweden)

    R. A. Kovrazhkin

    1999-06-01

    Full Text Available We examine ion flux dropouts detected by INTERBALL-Auroral upon traversal of the auroral zone at altitudes of \\sim13 000 up to 20 000 km. These dropouts which we refer to as "gaps", are frequently observed irrespectively of longitudinal sector and appear characteristic of INTERBALL-Auroral ion spectrograms. Whereas some of these gaps display a nearly monoenergetic character (~12 keV, others occur at energies of a few hundreds of eV up to several keV. INTERBALL-Auroral data exhibit the former monoenergetic gap variety essentially in the evening sector. As examined in previous studies, these gaps appear related to transition from particle orbits that are connected with the magnetotail plasma source to closed orbits encircling the Earth. The latter gap variety, which spreads over several hundreds of eV to a few keV is often observed in the dayside magnetosphere. It is argued that such gaps are due to magnetospheric residence times well above the ion lifetime. This interpretation is supported by numerical orbit calculations which reveal extremely large (up to several tens of hours times of flight in a limited energy range as a result of conflicting E × B and gradient-curvature drifts. The characteristic energies obtained numerically depend upon both longitude and latitude and are quite consistent with those measured in-situ.Key words. Magnetospheric physics (auroral phenomena; plasma convection

  13. Studies of currents and electric fields in the auroral zone ionosphere using radar auroral backscatter

    International Nuclear Information System (INIS)

    Greenwald, R.A.

    1980-01-01

    During the 1970s several advances have been made in the understanding of radar aurora. Recent VHF studies have shown that Doppler data obtained from radar auroral backscatter can be used to measure the E-region electron drift velocity, the F-region plasma velocity, and the ionospheric electric field. This type of measurement is particularly valuable when it is made with dual auroral radar systems similar to STARE (Scandinavian Twin Auroral Radar Experiment). Over the past two years STARE has been used to study electric field patterns associated with electrojet and field-aligned currents, magnetospheric convection, the Harang discontinuity, Pc5 micropulsations, and the substorm expansion phase. (Auth.)

  14. Dawn- Dusk Auroral Oval Oscillations Associated with High- Speed Solar Wind

    Science.gov (United States)

    Liou, Kan; Sibeck, David G.

    2018-01-01

    We report evidence of global-scale auroral oval oscillations in the millihertz range, using global auroral images acquired from the Ultraviolet Imager on board the decommissioned Polar satellite and concurrent solar wind measurements. On the basis of two events (15 January 1999 and 6 January 2000) studied, it is found that (1) quasi-periodic auroral oval oscillations (approximately 3 megahertz) can occur when solar wind speeds are high at northward or southward interplanetary magnetic field turning, (2) the oscillation amplitudes range from a few to more than 10 degrees in latitudes, (3) the oscillation frequency is the same for each event irrespective of local time and without any azimuthal phase shift (i.e., propagation), (4) the auroral oscillations occur in phase within both the dawn and dusk sectors but 180 degrees out of phase between the dawn and dusk sectors, and (5) no micropulsations on the ground match the auroral oscillation periods. While solar wind conditions favor the growth of the Kelvin-Helmholtz (K-H) instability on the magnetopause as often suggested, the observed wave characteristics are not consistent with predictions for K-H waves. The in-phase and out-of-phase features found in the dawn-dusk auroral oval oscillations suggest that wiggling motions of the magnetotail associated with fast solar winds might be the direct cause of the global-scale millihertz auroral oval oscillations. Plain Language Summary: We utilize global auroral image data to infer the motion of the magnetosphere and show, for the first time, the entire magnetospheric tail can move east-west in harmony like a windsock flapping in wind. The characteristic period of the flapping motion may be a major source of global long-period ULF (Ultra Low Frequency) waves, adding an extra source of the global mode ULF waves.

  15. Relationship between Alfvén Wave and Quasi-Static Acceleration in Earth's Auroral Zone

    Science.gov (United States)

    Mottez, Fabrice

    2016-02-01

    There are two main categories of acceleration processes in the Earth's auroral zone: those based on quasi-static structures, and those based on Alfvén wave (AW). AWs play a nonnegligible role in the global energy budget of the plasma surrounding the Earth because they participate in auroral acceleration, and because auroral acceleration conveys a large portion of the energy flux across the magnetosphere. Acceleration events by double layers (DLs) and by AW have mostly been investigated separately, but many studies cited in this chapter show that they are not independent: these processes can occur simultaneously, and one process can be the cause of the other. The quasi-simultaneous occurrences of acceleration by AW and by quasi-static structures have been observed predominantly at the polar cap boundary of auroral arc systems, where often new bright arcs develop or intensify.

  16. Substorm related changes in precipitation in the dayside auroral zone – a multi instrument case study

    Directory of Open Access Journals (Sweden)

    A. J. Kavanagh

    Full Text Available A period (08:10–14:40 MLT, 11 February 1997 of enhanced electron density in the D- and E-regions is investigated using EISCAT, IRIS and other complementary instruments. The precipitation is determined to be due to substorm processes occurring close to magnetic midnight. Energetic electrons drift eastward after substorm injection and precipitate in the morning sector. The precipitation is triggered by small pulses in the solar wind pressure, which drive wave particle interactions. The characteristic energy of precipitation is inferred from drift timing on different L-shells and apparently verified by EISCAT measurements. The IMF influence on the precipitation in the auroral zone is also briefly discussed. A large change in the precipitation spectrum is attributed to increased numbers of ions and much reduced electron fluxes. These are detected by a close passing DMSP satellite. The possibility that these ions are from the low latitude boundary layer (LLBL is discussed with reference to structured narrow band Pc1 waves observed by a search coil magnetometer, co-located with IRIS. The intensity of the waves grows with increased distance equatorward of the cusp position (determined by both satellite and HF radar, contrary to expectations if the precipitation is linked to the LLBL. It is suggested that the ion precipitation is, instead, due to the recovery phase of a small geomagnetic storm, following on from very active conditions. The movement of absorption in the later stages of the event is compared with observations of the ionospheric convection velocities. A good agreement is found to exist in this time interval suggesting that E × B drift has become the dominant drift mechanism over the gradient-curvature drift separation of the moving absorption patches observed at the beginning of the morning precipitation event.

    Key words. Ionosphere (auroral ionosphere; particle precipitation Magnetospheric physics (storms and substorms

  17. Substorm related changes in precipitation in the dayside auroral zone – a multi instrument case study

    Directory of Open Access Journals (Sweden)

    A. J. Kavanagh

    2002-09-01

    Full Text Available A period (08:10–14:40 MLT, 11 February 1997 of enhanced electron density in the D- and E-regions is investigated using EISCAT, IRIS and other complementary instruments. The precipitation is determined to be due to substorm processes occurring close to magnetic midnight. Energetic electrons drift eastward after substorm injection and precipitate in the morning sector. The precipitation is triggered by small pulses in the solar wind pressure, which drive wave particle interactions. The characteristic energy of precipitation is inferred from drift timing on different L-shells and apparently verified by EISCAT measurements. The IMF influence on the precipitation in the auroral zone is also briefly discussed. A large change in the precipitation spectrum is attributed to increased numbers of ions and much reduced electron fluxes. These are detected by a close passing DMSP satellite. The possibility that these ions are from the low latitude boundary layer (LLBL is discussed with reference to structured narrow band Pc1 waves observed by a search coil magnetometer, co-located with IRIS. The intensity of the waves grows with increased distance equatorward of the cusp position (determined by both satellite and HF radar, contrary to expectations if the precipitation is linked to the LLBL. It is suggested that the ion precipitation is, instead, due to the recovery phase of a small geomagnetic storm, following on from very active conditions. The movement of absorption in the later stages of the event is compared with observations of the ionospheric convection velocities. A good agreement is found to exist in this time interval suggesting that E × B drift has become the dominant drift mechanism over the gradient-curvature drift separation of the moving absorption patches observed at the beginning of the morning precipitation event.Key words. Ionosphere (auroral ionosphere; particle precipitation Magnetospheric physics (storms and substorms

  18. Observations of auroral zone processes by the Viking satellite

    International Nuclear Information System (INIS)

    Hultqvist, B.

    1989-01-01

    The scientific results of the Viking project obtained up to the spring of 1988 are reviewed. During solar minimum conditions, when Viking was operated, the dayside auroral oval has been found to be the most active part, except during strong substorms and storms. A number of new auroral morphological features have been seen with the imaging experiment onboard Viking. Large-amplitude slow fluctuations of the electric field heat the ionospheric plasma and pump up the magnetic moment of the ionospheric ions so that they may leave the ionosphere. These fluctuations also accelerate ionospheric electrons upwards along the magnetic field lines. The importance of the acceleration of auroral electrons into the atmosphere by magnetic field-aligned potential differences has been confirmed. The first satellite-borne plasma wave interferometer on Viking has made it possible to determine a number of characteristics of the 'weak' double layers, seen first by the S3-3 satellite. A large number of these along the magnetic field lines produce large electric potential differences. Many new results concerning wave-particle interactions have been obtained, of which a few are presented here. (author)

  19. Electron precipitation in the morning sector of the auroral zone

    International Nuclear Information System (INIS)

    Jentsch, V.

    1976-01-01

    Auroral electron precipitation in the morning sector is assumed to be the result of an electromagnetic cyclotron instability of a particle distribution that evolves adiabatically as its constituent electrons drift eastward from a source near midnight. The adiabatic distribution is calculated by using Green's function in various magnetospheric field models, and the corresponding growth rates for whistler mode waves are calculated by the method of Kennel and Petschek (1966). The region of maximum calculated wave growth corresponds spatially and temporally to the region of maximum observed electron precipitation only when the magnetospheric electric field is included realistically in the model

  20. The control of auroral zone dynamics and thermodynamics by the interplanetary magnetic field dawn-dusk (Y) component

    International Nuclear Information System (INIS)

    Sica, R.J.; Hernandez, G.; Emery, B.A.; Roble, R.G.; Smith, R.W.; Rees, M.H.

    1989-01-01

    Previous theoretical and experimental studies have shown that the dawn-dusk component of the interplanetary magnetic field (IMF B y ) expands the classical symmetric two-cell convection pattern toward dusk (B y negative) or toward dawn (B y positive) in the northern hemisphere, altering the ion drag forcing on the neutral atmosphere. Measurements of the neutral dynamics associated with these convection patterns have been presented primarily at magnetic latitudes greater than 70 degree in the polar cap. In this study, nights with coincident IMF measurements have been selected from the extensive four-year auroral zone thermospheric wind and temperature data set derived from Fabry-Perot spectrometer measurements of the Doppler shifts and widths of the O( 1 D) 15,867 cm -1 (630.0 nm) emission from College, Alaska. Averages from 112 nights of measurements from College were also computed using a selection criterion that depended on the previous 2 hours of IMF measurements (case 2). This procedure yielded averages that differed at times from case 1. The wind and temperature averages for both cases show large variations with B y in the auroral zone. The wind averages for B y negative and positive are compared with National Center for Atmospheric Research thermospheric general circulation model predictions that use a B y -dependent model of ionospheric convection. The results for B y negative and positive are compared with National Center for Atmospheric Research thermospheric general circulation model predictions that use a B y -dependent model of ionospheric convection. The results for B y negative compare favorably with the averages, but there are significant differences between model calculations and averages for the B y positive case

  1. A Study of Current Driven Electrostatic Instability on the Auroral Zone

    Directory of Open Access Journals (Sweden)

    S. Y. Kim

    1986-12-01

    Full Text Available According to recent satellite observations, strong ion transverse acceleration to the magnetic field(ion conics has been known. The ion conics may be a result of electrostatic waves frequently observed on the auroral zone. Both linear and nonlinear theory of electrostatic instability driven by an electron current based on 1-dimenstional particle simulation experiment have been considered. From the results of simulation strong ion transverse acceleration has been shown.

  2. Auroral-zone electric fields from DE-1 and -2 at magnetic conjuctions

    International Nuclear Information System (INIS)

    Weimer, D.R.

    1984-01-01

    Nearly simultaneous measurements of auroral zone electric fields are obtained by the Dynamics Explorer spacecraft at altitudes below 900 km and above 4500 km during magnetic conjuctions. The measured electric fields are approximately perpendicular to the magnetic field lines. The north-south meridional electric fields are projected to a common altitude by a mapping function. When plotted as a function of invariant latitude, graphs of the projected electric fields measured by DE-1 and DE-2 show that the large-scale electric field is the same at both altitudes. However, superimposed on the large-scale fields are small-scale features with wavelengths less than 100 km which are larger in magnitude at the higher altitude. Fourier transforms of the electric fields show that the magnitudes depend on wavelength. Outside of the auroral zone the electric field spectrums are nearly identical. But within the auroral zone the spectrums of the high and low altitude electric fields have a ratio which increases with the reciprocal of the wavelength. The small-scale electric field variations are associated with field-aligned currents. These currents are measured with both a plasma instrument and magnetometer on DE-1

  3. Local-time survey of plasma at low altitudes over the auroral zones.

    Science.gov (United States)

    Frank, L. A.; Ackerson, K. L.

    1972-01-01

    Local-time survey of the low-energy proton and electron intensities precipitated into the earth's atmosphere over the auroral zones during periods of magnetic quiescence. This survey was constructed by selecting a typical individual satellite crossing of this region in each of eight local-time sectors from a large library of similar observations with the polar-orbiting satellite Injun 5. The trapping boundary for more-energetic electron intensities, E greater than 45 keV, was found to be a 'natural coordinate' for delineating the boundary between the two major types of lower-energy, 50 less than or equal to E less than or equal to 15,000 eV, electron precipitation commonly observed over the auroral zones at low altitudes. Poleward of this trapping boundary inverted 'V' electron precipitation bands are observed in all local-time sectors. These inverted 'V' electron bands in the evening and midnight sectors are typically more energetic and have greater latitudinal widths than their counterparts in the noon and morning sectors. In general, the main contributors to the electron energy influx into the earth's atmosphere over the auroral zones are the electron inverted 'V' precipitation poleward of the trapping boundary in late evening, the plasma-sheet electron intensities equatorward of this boundary in early morning, and both of these precipitation events near local midnight.

  4. Auroral zone electric fields from DE 1 and 2 at magnetic conjunctions

    Science.gov (United States)

    Weimer, D. R.; Goertz, C. K.; Gurnett, D. A.; Maynard, N. C.; Burch, J. L.

    1985-01-01

    Nearly simultaneous measurements of auroral zone electric fields are obtained by the Dynamics Explorer spacecraft at altitudes below 900 km and above 4,500 km during magnetic conjunctions. The measured electric fields are usually perpendicular to the magnetic field lines. The north-south meridional electric fields are projected to a common altitude by a mapping function which accounts for the convergence of the magnetic field lines. When plotted as a function of invariant latitude, graphs of the projected electric fields measured by both DE-1 and DE-2 show that the large-scale electric field is the same at both altitudes, as expected. Superimposed on the large-scale fields, however, are small-scale features with wavelengths less than 100 km which are larger in magnitude at the higher altitude. Fourier transforms of the electric fields show that the magnitudes depend on wavelength. Outside of the auroral zone the electric field spectrums are nearly identical. But within the auroral zone the high and low altitude electric fields have a ratio which increases with the reciprocal of the wavelength. The small-scale electric field variations are associated with field-aligned currents. These currents are measured with both a plasma instrument and magnetometer on DE-1.

  5. The solar wind plasma density control of night-time auroral particle precipitation

    Directory of Open Access Journals (Sweden)

    V. G. Vorobjev

    2004-03-01

    Full Text Available DMSP F6 and F7 spacecraft observations of the average electron and ion energy, and energy fluxes in different night-time precipitation regions for the whole of 1986 were used to examine the precipitation features associated with solar wind density changes. It was found that during magnetic quietness |AL|<100nT, the enhancement of average ion fluxes was observed at least two times, along with the solar wind plasma density increase from 2 to 24cm–3. More pronounced was the ion flux enhancement that occurred in the b2i–b4s and b4s–b5 regions, which are approximately corresponding to the statistical auroral oval and map to the magnetospheric plasma sheet tailward of the isotropy boundary. The average ion energy decrease of about 2–4kev was registered simultaneously with this ion flux enhancement. The results verify the occurrence of effective penetration of the solar wind plasma into the magnetospheric tail plasma sheet. Key words. Ionosphere (auroral ionosphere, particle precipitation – Magnetospheric physics (solar windmagnetosphere interaction

  6. 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

  7. Investigation of intermittent magnetic flux in the auroral zones with kilometer radiation (AKR)

    International Nuclear Information System (INIS)

    Liu, S.Q.; Li, X.Q.

    2001-01-01

    On the basis of the nonlinear equations for self-generated magnetic fields, it is numerically shown that the magnetic fields self-generated are instable and may collapse, resulting in spatially highly intermittent flux fragment. Numerical results show that the enhanced magnetic flux has a strength about up to 10 -2 Gauss in range about around 250-350 km in auroral zones with kilometric radiation (AKR), which correspond to estimated values in both the strength and characteristic scale by Mckean et al. [J. Geophys. Res. [Oceans] 96, 21055 (1991)

  8. 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

  9. The influence of solar wind on extratropical cyclones – Part 2: A link mediated by auroral atmospheric gravity waves?

    Directory of Open Access Journals (Sweden)

    P. Prikryl

    2009-01-01

    Full Text Available Cases of mesoscale cloud bands in extratropical cyclones are observed a few hours after atmospheric gravity waves (AGWs are launched from the auroral ionosphere. It is suggested that the solar-wind-generated auroral AGWs contribute to processes that release instabilities and initiate slantwise convection thus leading to cloud bands and growth of extratropical cyclones. Also, if the AGWs are ducted to low latitudes, they could influence the development of tropical cyclones. The gravity-wave-induced vertical lift may modulate the slantwise convection by releasing the moist symmetric instability at near-threshold conditions in the warm frontal zone of extratropical cyclones. Latent heat release associated with the mesoscale slantwise convection has been linked to explosive cyclogenesis and severe weather. The circumstantial and statistical evidence of the solar wind influence on extratropical cyclones is further supported by a statistical analysis of high-level clouds (<440 mb extracted from the International Satellite Cloud Climatology Project (ISCCP D1 dataset. A statistically significant response of the high-level cloud area index (HCAI to fast solar wind from coronal holes is found in mid-to-high latitudes during autumn-winter and in low latitudes during spring-summer. In the extratropics, this response of the HCAI to solar wind forcing is consistent with the effect on tropospheric vorticity found by Wilcox et al. (1974 and verified by Prikryl et al. (2009. In the tropics, the observed HCAI response, namely a decrease in HCAI at the arrival of solar wind stream followed by an increase a few days later, is similar to that in the northern and southern mid-to-high latitudes. The amplitude of the response nearly doubles for stream interfaces associated with the interplanetary magnetic field BZ component shifting southward. When the IMF BZ after the stream interface shifts northward, the autumn-winter effect weakens or shifts to lower (mid latitudes

  10. Solitary waves observed in the auroral zone: the Cluster multi-spacecraft perspective

    Directory of Open Access Journals (Sweden)

    J. S. Pickett

    2004-01-01

    Full Text Available We report on recent measurements of solitary waves made by the Wideband Plasma Wave Receiver located on each of the four Cluster spacecraft at 4.5-6.5RE (well above the auroral acceleration region as they cross field lines that map to the auroral zones. These solitary waves are observed in the Wideband data as isolated bipolar and tripolar waveforms. Examples of the two types of pulses are provided. The time durations of the majority of both types of solitary waves observed in this region range from about 0.3 up to 5ms. Their peak-to-peak amplitudes range from about 0.05 up to 20mV/m, with a few reaching up to almost 70mV/m. There is essentially no potential change across the bipolar pulses. There appears to be a small, measurable potential change, up to 0.5V, across the tripolar pulses, which is consistent with weak or hybrid double layers. A limited cross-spacecraft correlation study was carried out in order to identify the same solitary wave on more than one spacecraft. We found no convincing correlations of the bipolar solitary waves. In the two cases of possible correlation of the tripolar pulses, we found that the solitary waves are propagating at several hundred to a few thousand km/s and that they are possibly evolving (growing, decaying as they propagate from one spacecraft to the next. Further, they have a perpendicular (to the magnetic field width of 50km or greater and a parallel width of about 2-5km. We conclude, in general, however, that the Cluster spacecraft at separations along and perpendicular to the local magnetic field direction of tens of km and greater are too large to obtain positive correlations in this region. Looking at the macroscale of the auroral zone at 4.5-6.5RE, we find that the onsets of the broadband electrostatic noise associated with the solitary waves observed in the spectrograms of the WBD data are generally consistent with propagation of the solitary waves up the field lines (away from Earth, or with

  11. Transverse ion energization and low-frequency plasma waves in the mid-altitude auroral zone - A case study

    Science.gov (United States)

    Peterson, W. K.; Shelley, E. G.; Boardsen, S. A.; Gurnett, D. A.; Ledley, B. G.; Sugiura, M.; Moore, T. E.

    1988-01-01

    Evidence of transverse ion energization at altitudes of several earth radii in the auroral zone was reexamined using several hundred hours of high-sensitivity and high-resolution plasma data obtained by the Dynamics Explorer 1 satellite. The data on particle environment encountered at midaltitudes in the auroral zone disclosed rapid variations in the values of total density, thermal structure, and composition of the plasma in the interval measured; the modes of low-frequency plasma waves also varied rapidly. It was not possible to unambiguously identify in these data particle and wave signature of local transverse ion energization; however, many intervals were found where local transverse ion heating was consistent with the observations.

  12. Ion and electron injection in ionosphere and magnetosphere. Application to the parallel electric field measurement in auroral zones

    International Nuclear Information System (INIS)

    Pirre, M.

    1982-11-01

    New methods of measuring parallel electric field in auroral zones are investigated in this thesis. In the studied methods, artificial injection of ions Li + and electrons from a spacecraf is used. Measurements obtained during the ARAKS experiment are also presented. The behaviour of the ionospheric plasma located few hundred meters from a 0,5A electron beam injected in ionosphere from a rocket is studied, together with the behaviour of a Cs plasma artificially injected from the same spacecraft [fr

  13. ''Electron Conic'' Signatures observed in the nightside auroral zone and over the polar cap

    International Nuclear Information System (INIS)

    Menietti, J.D.; Burch, J.L.

    1985-01-01

    A preliminary search of the Dynamics Explorer 1 high-altitude plasma instrument data base has yielded examples of ''electron conic'' signatures. The three example passes show an association with regions of downward electron acceleration and upward ion beams, but this is not true of all the electron conic events. The electron conic signatures are clearly discernible on energy-flux-versus-time color spectrograms as pairs of discrete vertical bands which are symmetric about a pitch angle of approximately 180 0 . One of the examples is a polar cap pass with electron conic signatures observed at invariant latitudes from 84 0 to 75 0 . The other two cases are nightside auroral zone passes in which the regions of detectable electron conics are spatially more confined, covering only about 1 0 in invariant latitude. The conic signatures have been found at energies that range from 50 eV 0 is larger than expected for a loss cone feature. If the electrons conserve the first adiabatic invariant in a dipole magnetic field, and in some cases a parallel electric field, the mirroring altitude varies between about 500 km and 8000 km, which is above the atmospheric loss region. For this reason, and in analogy with the formation of ion conics, we suggest that the conic signatures are produced by heating of the electrons perpendicular to the magnetic field

  14. Offshore Wind Technology Depth Zones

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Coastal bathymetric depth, measured in meters at depth values of: -30, -60, -900 Shallow Zone (0-30m): Technology has been demonstrated on a commercial scale at...

  15. Auroral morphology

    International Nuclear Information System (INIS)

    Deehr, C.S.; Romick, G.J.; Sivjee, G.G.

    1981-01-01

    The aurora is a radiant manifestation of solar particle emissions and their control by intervening electromagnetic fields. The analogy with a television system was first made, we believe, by Elvey, (1958). The latest concepts of solar-terrestrial control are included in description by Akasofu (1979) showing the phosphor screen as the upper atmosphere with an auroral image produced by particles from a source on the sun, modulated by electric and magnetic fields with the magnetohydrodynamic (MDH) generator formed by electrons and protons from the solar wind across the geomagnetic tail as the power supply. Thus, the size and shape of the aurora must reflect all the forces acting in the auroral particles on their way from the sun to the earth. Auroral morphology, therefore, is the study of the occurence of aurora in space and time for the purpose of describing the origin of solar particels and the forces acting upon them between the time of their production on the sun and their loss in the atmosphere. The advantage of using the aurora as a television monitor of this process over any conceivable system of in situ measurements is obvious when one considers the large number of space vehicles which would be necessary to record the information concentrated in the auroral oval which differs in scale with the magnetosphere by perhaps 10 6 . (orig.)

  16. Auroral particles

    International Nuclear Information System (INIS)

    Evans, D.S.

    1987-01-01

    The problems concerning the aurora posed prior to the war are now either solved in principle or were restated in a more fundamental form. The pre-war hypothesis concerning the nature of the auroral particles and their energies was fully confirmed, with the exception that helium and oxygen ions were identified as participating in the auroral particle precipitation in addition to the protons. The nature of the near-Earth energization processes affecting auroral particles was clarified. Charged particle trajectories in various electric field geometries were modeled. The physical problems have now moved from determining the nature and geometry of the electric fields, which accelerate charged particles near the Earth, to accounting for the existence of these electric fields as a natural consequence of the solar wind's interaction with Earth. Ultimately the reward in continuing the work in auroral and magnetospheric particle dynamics will be a deeper understanding of the subtleties of classical electricity and magnetism as applied to situations not blessed with well-defined and invariant geometries

  17. 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)

  18. Transverse ion energization and low-frequency plasma waves in the mid-altitude auroral zone: A case study

    International Nuclear Information System (INIS)

    Peterson, W.K.; Shelley, E.G.; Boardsen, S.A.; Gurnett, D.A.; Ledley, B.G.; Sugiura, M.; Moore, T.E.; Waite, J.H.

    1988-01-01

    The transport of ions from the ionosphere to the magnetosphere requires that ions acquire significant energy in directions both transverse and parallel to the magnetic field. There is a considerable body of experimental evidence that shows that transverse energization occurs over a wide range of altitudes on auroral field lines. Many recent analytical and simulation studies have addressed the microphysics involved in transverse ion energization. There are, however, remarkably few published high-resolution plasma and plasma wave observations obtained in the mid-altitude auroral region available to compare with the analytical and simulation studies. Several hundred hours of high-resolution plasma data obtained from the Dynamics Explorer 1 satellite have been surveyed. A wide variety of plasma environments that are difficult to simply characterize were found. We present here a comprehensive set of high-sensitivity, high-resolution plasma wave, ion, and magnetometer data obtained from an evening auroral zone crossing at r/R/sub E/∼3. The total density, thermal structure, and composition of the plasma in this representative interval varied rapidly, as did the character (mode) of low-frequency plasma waves observed. We did not find an unambiguous particle and wave signature of local transverse ion energization, but we did frequently find intervals where local transverse ion heating was consistent with the observations. We also found a downward flowing ion distribution that occurred simultaneously with a region of intense plasma wave emissions primarily below the lower hybrid resonance frequency. copyright American Geophysical Union 1988

  19. Ulf waves in the auroral zone ionosphere and associated electron precipitation variations

    International Nuclear Information System (INIS)

    Petelski, E.F.; Fahleson, U.; Shawhan, S.D.

    1977-12-01

    On four rocket flights, ULF electric fields were observed in the nighttime auroral oval and in the polar cleft. They had periods between 0.5 and 3 sec, amplitudes from 2 to 30 mV/m, and exhibited left- and right-hand elliptical polarization. Intensifications of these fields often coincided with bursts of energetic electron precipitation which were on occasion modulated with nearly the same period as the fields. The events in the auroral oval were associated with substorms and visual auroral activity. The spectral and polarization properties of the ULF fields suggest that they represented the electric components of Pcl or Pil micropulsations. To model these waves and the concurrent electron flux variations, different mechanisms for wave excitation, electron acceleration, and wave-particle interaction are considered. One likely interpretation attributes the micropulsations to Birkeland current chopping by an unstable double layer located at approximately equal to 1 R(sub)E altitude. It is suggested that the double layer also accelerates the observed electrons, the electron flux variations being due either to the intrinsic variations of the double layer or to its interaction with the micropulsations. Due to the sparcity of parameters measured so far, the models are provisional. A follow-up experiment is proposed to further investigate the problem. (author)

  20. Zoning for Distributed Wind Power - Breaking Down Barriers: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Green, J.; Sagrillo, M.

    2005-08-01

    Zoning regulations for the use of small wind turbines vary from state to state and from one local jurisdiction to the next. This paper examines the zoning experiences of small wind turbine owners, options for local actions, and examples of state and federal limited preemption of local zoning authority as a means of promoting the implementation of new technologies.

  1. Identification of zones of strong wind events in South Africa

    CSIR Research Space (South Africa)

    Goliger, Adam M

    2002-11-01

    Full Text Available This paper summarises the initial stage of development of a wind damage/disaster risk model for South Africa. The aim is to identify the generic zones of various types of strong wind events. The extent of these zones will form the basis...

  2. Analysis of wind energy generation possibilities with various rotor types at disadvantageous wind condition zones

    OpenAIRE

    Bieniek Andrzej

    2017-01-01

    The paper describe possibilities of energy generation using various rotor types but especially with multi-blade wind engine operates in the areas with unfavourable wind condition. The paper presents also wind energy conversion estimation results presented based on proposed solution of multi-blade wind turbine of outer diameter of 4 m. Based on the wind distribution histogram from the disadvantage wind condition zones (city of Basel) and taking into account design and estimated operating index...

  3. D- and E-region effects in the auroral zone during a moderately active 24-h period in July 2005

    Directory of Open Access Journals (Sweden)

    J. K. Hargreaves

    2007-08-01

    Full Text Available The effects of energetic electron precipitation into the auroral region at a time of enhanced solar wind have been investigated during a continuous period of 24 h, using the European Incoherent Scatter (EISCAT radar, an imaging riometer, and particle measurements on an orbiting satellite. The relative effects in the E region (120 km and D region (90 km are found to vary during the day, consistent with a gradual hardening of the incoming electron spectrum from pre-midnight to morning. Whereas the night spectra are single peaked, the daytime spectra are found to be double peaked, suggesting the presence of two distinct populations.

    A comparison between the radiowave absorption observed with the riometer and values estimated from the radar data shows generally good agreement, but with some discrepancies suggesting the occurrence of some small-scale features. The height and thickness of the absorbing region are estimated. Two periods of enhanced precipitation and the related radio absorption, one near magnetic midnight and one in the early morning, are studied in detail, including their horizontal structure and movement of the absorption patches.

    A sharp reduction of electron flux recorded on a POES satellite is related to the edge of an absorption region delineated by the imaging riometer. The observed particle flux is compared with a value deduced from the radar data during the overpass, and found to be in general agreement.

  4. D- and E-region effects in the auroral zone during a moderately active 24-h period in July 2005

    Directory of Open Access Journals (Sweden)

    J. K. Hargreaves

    2007-08-01

    Full Text Available The effects of energetic electron precipitation into the auroral region at a time of enhanced solar wind have been investigated during a continuous period of 24 h, using the European Incoherent Scatter (EISCAT radar, an imaging riometer, and particle measurements on an orbiting satellite. The relative effects in the E region (120 km and D region (90 km are found to vary during the day, consistent with a gradual hardening of the incoming electron spectrum from pre-midnight to morning. Whereas the night spectra are single peaked, the daytime spectra are found to be double peaked, suggesting the presence of two distinct populations. A comparison between the radiowave absorption observed with the riometer and values estimated from the radar data shows generally good agreement, but with some discrepancies suggesting the occurrence of some small-scale features. The height and thickness of the absorbing region are estimated. Two periods of enhanced precipitation and the related radio absorption, one near magnetic midnight and one in the early morning, are studied in detail, including their horizontal structure and movement of the absorption patches. A sharp reduction of electron flux recorded on a POES satellite is related to the edge of an absorption region delineated by the imaging riometer. The observed particle flux is compared with a value deduced from the radar data during the overpass, and found to be in general agreement.

  5. New type of ensemble of quasi-periodic, long-lasting VLF emissions at the auroral zone

    Directory of Open Access Journals (Sweden)

    J. Manninen

    2012-12-01

    Full Text Available A new type of the series of quasi-periodic (QP very low frequency (VLF emissions in frequency range of 1–5 kHz, and not associated with geomagnetic pulsations, has been discovered at auroral latitudes (L = 5.3 during the Finnish VLF campaign (held in December 2011. At least five unusually spectacular events, each with a duration of several hours, have been observed during the night under conditions of quiet geomagnetic activity (Kp = 0–1, although QPs usually occur during the daytime. Contrary to the QP emissions typically occurring during the day, the spectral structure of these QP events represented an extended, complicated sequence of repeated discrete rising VLF signals. Their duration was about 2–3 min each, with the repetition periods ranging from ~1 min to ~10 min. Two such nighttime non-typical events are reported in this paper. The fine structure of the separated QP elements may represent a mixture of the different frequency band signals, which seem to have independent origins. It was found that the periodic signals with lower frequency appear to trigger the strong dispersive upper frequency signals. The temporal dynamics of the spectral structure of the QPs studied were significantly controlled by some disturbances in the solar wind and interplanetary magnetic field (IMF. This finding is very important for future theoretical investigations because the generation mechanism of this new type of QP emissions is not yet understood.

  6. Statistics of Joule heating in the auroral zone and polar cap using Astrid-2 satellite Poynting flux

    Directory of Open Access Journals (Sweden)

    A. Olsson

    2004-12-01

    Full Text Available We make a statistical study of ionospheric Joule heating with the Poynting flux method using six months of Astrid-2/EMMA electric and magnetic field data during 1999 (solar maximum year. For the background magnetic field we use the IGRF model. Our results are in agreement with earlier statistical satellite studies using both the ΣPE2 method and the Poynting flux method. We present a rather comprehensive set of fitted Joule heating formulas expressing the Joule heating in given magnetic local time (MLT and invariant latitude (ILAT range under given solar illumination conditions as a function of the Kp index, the AE index, the Akasofu epsilon parameter and the solar wind kinetic energy flux. The study thus provides improved and more detailed estimates of the statistical Joule heating. Such estimates are necessary building blocks for future quantitative studies of the power budget in the magnetosphere and in the nightside auroral region. Key words. Ionosphere (electric fields and currents; ionosphere-magnetosphere interactions – Magnetospheric physics (magnetospheric configuration and dynamics

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

    International Nuclear Information System (INIS)

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

    1977-01-01

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

  8. Analysis of wind energy generation possibilities with various rotor types at disadvantageous wind condition zones

    Science.gov (United States)

    Bieniek, Andrzej

    2017-10-01

    The paper describe possibilities of energy generation using various rotor types but especially with multi-blade wind engine operates in the areas with unfavourable wind condition. The paper presents also wind energy conversion estimation results presented based on proposed solution of multi-blade wind turbine of outer diameter of 4 m. Based on the wind distribution histogram from the disadvantage wind condition zones (city of Basel) and taking into account design and estimated operating indexes of the considered wind engine rotor an annual energy generation was estimated. Also theoretical energy generation using various types of wind turbines operates at disadvantage wind conditions zones were estimated and compared. The conducted analysis shows that introduction of multi-blade wind rotor instead of the most popular 3- blades or vertical axis rotors results of about 5% better energy generation. Simultaneously there are energy production also at very disadvantages wind condition at wind speed lower then 4 m s-1. Based on considered construction of multi-blade wind engine the rise of rotor mounting height from 10 to 30 m results with more then 300 % better results in terms of electric energy generation.

  9. Analysis of wind energy generation possibilities with various rotor types at disadvantageous wind condition zones

    Directory of Open Access Journals (Sweden)

    Bieniek Andrzej

    2017-01-01

    Full Text Available The paper describe possibilities of energy generation using various rotor types but especially with multi-blade wind engine operates in the areas with unfavourable wind condition. The paper presents also wind energy conversion estimation results presented based on proposed solution of multi-blade wind turbine of outer diameter of 4 m. Based on the wind distribution histogram from the disadvantage wind condition zones (city of Basel and taking into account design and estimated operating indexes of the considered wind engine rotor an annual energy generation was estimated. Also theoretical energy generation using various types of wind turbines operates at disadvantage wind conditions zones were estimated and compared. The conducted analysis shows that introduction of multi-blade wind rotor instead of the most popular 3- blades or vertical axis rotors results of about 5% better energy generation. Simultaneously there are energy production also at very disadvantages wind condition at wind speed lower then 4 ms-1. Based on considered construction of multi-blade wind engine the rise of rotor mounting height from 10 to 30 m results with more then 300 % better results in terms of electric energy generation.

  10. Combined ESR and EISCAT observations of the dayside polar cap and auroral oval during the May 15, 1997 storm

    Directory of Open Access Journals (Sweden)

    H. Liu

    2000-09-01

    Full Text Available The high-latitude ionospheric response to a major magnetic storm on May 15, 1997 is studied and different responses in the polar cap and the auroral oval are highlighted. Depletion of the F2 region electron density occurred in both the polar cap and the auroral zone, but due to different physical processes. The increased recombination rate of O+ ions caused by a strong electric field played a crucial role in the auroral zone. The transport effect, however, especially the strong upward ion flow was also of great importance in the dayside polar cap. During the main phase and the beginning of the recovery phase soft particle precipitation in the polar cap showed a clear relation to the dynamic pressure of the solar wind, with a maximum cross-correlation coefficient of 0.63 at a time lag of 5 min.Key words: Ionosphere (auroral ionosphere; polar ionosphere - Magnetospheric physics (storms and substorms

  11. Complete wave-vector directions of electromagnetic emissions: Application to INTERBALL-2 measurements in the nightside auroral zone

    Czech Academy of Sciences Publication Activity Database

    Santolík, Ondřej; Lefeuvre, F.; Parrot, M.; Rauch, J. L.

    2001-01-01

    Roč. 106, - (2001), s. 13,191-13,201 ISSN 0148-0227 R&D Projects: GA ČR GA205/01/1064 Institutional research plan: CEZ:AV0Z3042911 Keywords : auroral kilometric radiation * wave propagation * analysis techniques Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.609, year: 2001

  12. Strong wind climatic zones in South Africa

    CSIR Research Space (South Africa)

    Kruger, AC

    2010-01-01

    Full Text Available of cold fronts over the southern African subcontinent. Over the eastern and central interior of South Africa annual maximum wind gusts are usually caused by thunderstorm gust fronts during summer, while in the western and southern interior extratropical...

  13. 76 FR 61342 - Foreign-Trade Zone 72 Temporary/Interim Manufacturing Authority Brevini Wind USA, Inc., (Wind...

    Science.gov (United States)

    2011-10-04

    ... DEPARTMENT OF COMMERCE Foreign-Trade Zones Board [Docket T-3-2011] Foreign-Trade Zone 72 Temporary/Interim Manufacturing Authority Brevini Wind USA, Inc., (Wind Turbine Gear Boxes); Notice of Approval On... manufacturing (T/IM) authority, on behalf of Brevini Wind USA, Inc., to manufacture wind turbine gear boxes...

  14. On the formation of auroral arcs

    International Nuclear Information System (INIS)

    Stasiewicz, K.

    1984-04-01

    A new mechanism for auroral arc formation is presented. The characteristic linear shape of auroral arcs is determined by magnetically connected plasma clouds in the distant equatorial magnetosphere. These clouds originate as high speed plasma beams in the magnetotail and in the solar wind. It is found that the free energy for driving an auroral arc is provided by the difference of pressure between the cloud and the ambient plasma. (author)

  15. Generation of auroral kilometric radiation

    International Nuclear Information System (INIS)

    Green, J.L.

    1979-01-01

    Simultaneous observations between the Hawkeye spacecraft in the AKR emission cone and the low altitude polar orbiting spacecraft Triad and AE-D reveal that auroral kilometric radiation (AKR) is correlated with a variety of auroral particle precipitation in the evening to midnight local time sector. It is found that as the AKR intensity increases so does the integrated current sheet intensity of auroral zone field aligned currents observed by Triad of 257 simultaneous observations. Statistically, the linear correlation coefficient between the log of the AKR power flux and the log of the current sheet intensity is 0.57. Auroral kilometric radiation observations from Hawkeye during low altitude (2.0 to 2.5 R/sub E/) auroral zone passes reveal that intense AKR has a low frequency cutoff near the local electron gyrofrequency (f/sub g/ - ) with maximum electric field strengths as large as 12 mV/m. The large electric fields observed near f/sub g/ - are consistent with high altitude observations of AKR using a simple 1/R 2 scaling indicating that the kilometric radiation in or near the average source region is almost completely electromagnetic. The results presented in this study indicate that kilometric radiation is generated by inverted-V electron distribution functions in a direct coupling mechanism between particle energy and R-X mode electromagnetic waves in the region of the auroral zone where f/sub g/ - >> f/sub p/ -

  16. Estimates of the field-aligned current density in current-carrying filaments using auroral zone ground-based observations

    Directory of Open Access Journals (Sweden)

    M. A. Danielides

    Full Text Available We described the ground signatures of dynamic substorm features as observed by the imaging riometer, magnetometers and all-sky camera (ASC at Kilpisjärvi, Finland on 5 and 25 October 1999 during the late evening hours. The magnetometer data was consistent with the motion of up-ward field-aligned currents (FACs associated with absorption patches moving within the field of view of the riometer. We used riometer data in order to estimate the intensity of FACs associated with these local current-carrying filaments. It is shown that during these events, the estimated FAC intensity exceeds a threshold value that corresponds to the excitation of the low-frequency turbulence in the upper ionosphere. As a result, a quasi-oscillating regime of anomalous resistivity on the auroral field lines can give rise to the burst-like electron acceleration responsible for simultaneously observed auroral forms and bursts of Pi1B pulsations.

    Key words. Ionosphere (active experiments; auroral ionosphere; electric fields and currents

  17. 77 FR 55455 - Approval for Manufacturing Authority Foreign-Trade Zone 72, Brevini Wind USA, Inc., (Wind Turbine...

    Science.gov (United States)

    2012-09-10

    ... Authority Foreign-Trade Zone 72, Brevini Wind USA, Inc., (Wind Turbine Gear Boxes), Yorktown, IN Pursuant to... Wind USA, Inc., within FTZ 72 in Yorktown, Indiana (FTZ Docket 54-2011, filed 8-11-2011); Whereas... procedures within FTZ 72 on behalf of Brevini Wind USA, Inc., as described in the application and Federal...

  18. Optimization of offshore wind farm layout in restricted zones

    International Nuclear Information System (INIS)

    Hou, Peng; Hu, Weihao; Chen, Cong; Soltani, Mohsen; Chen, Zhe

    2016-01-01

    In this research, an optimization method for offshore wind farm layout design is proposed. With the purpose of maximizing the energy production of the wind farm, the wind turbine (WT) positions are optimized. Due to the limitations of seabed conditions, marine traffic limitations or shipwrecks, etc., the WTs are expected to be placed outside specific areas. Based on this fact, a restriction zone concept is proposed in this paper and implemented with the penalty function method. In order to find a feasible solution, a recent proposed stochastic algorithm, particle swarm optimization algorithm with multiple adaptive methods (PSO-MAM) is adopted. The simulation results indicate that the proposed method can find a layout which outperforms a baseline layout of a reference wind farm (RWF) by increasing the energy yield by 3.84%. - Highlights: • The offshore restricted area concept is proposed. • The recent developed PSO-MAM algorithm is arranged to optimize the layout. • The penalty function method is adopted to help find the feasible solution. • The optimized layout increases energy yields 3.84% than reference wind farm.

  19. A review of the wind loading zones for flat roofs in code provisions

    NARCIS (Netherlands)

    Geurts, C.P.W.; Kopp, G.A.; Morrison, M.J.

    2013-01-01

    The provisions for wind loads on flat roofs differ considerably between current wind loading standards in different jurisdictions. For a number of major wind loading codes, both the definition of roof zones, and the values applied to determine the wind loads are discussed. This paper concentrates on

  20. Numerical simulation for a vortex street near the poleward boundary of the nighttime auroral oval

    Science.gov (United States)

    Yamamoto, T.

    2012-02-01

    The formation of a vortex street is numerically studied as an aftermath of a transient (≈1 min) depression of the energy density of injected particles. It is basically assumed that the kinetic energies of auroral particles are substantially provided by nonadiabatic acceleration in the tail current sheet. One of the causes of such energy density depression is an outward (away from the Earth) movement of the neutral line because in such situation, a particle passes the acceleration zone for a shorter time interval while it is inwardly transported in the current sheet. The numerical simulation shows that a long chain of many (≥5) vortices can be formed in the nighttime high-latitude auroral oval as a result of the hybrid Kelvin-Helmholtz/Rayleigh-Taylor (KH/RT) instability. The main characteristics of long vortex chains in the simulation such as the short lifetime (≲2 min) and the correlation between wavelength, λ, and arc system width, A, compare well with those of the periodic auroral distortions observed primarily in the high-latitude auroral oval. Specifically, either λ-A relationship from simulation or observation shows a positive correlation between λ and A but with considerable dispersion in λ. Since auroral vortices arising from the hybrid KH/RT instability are not accompanied by significant rotational motions, the magnetic shear instability caused by undulations in the field-aligned current (FAC) sheet could turn the vortices into spirals which wind or unwind in response to increase or decrease of FACs, respectively.

  1. Auroral electron time dispersion

    International Nuclear Information System (INIS)

    Kletzing, C.A.

    1989-01-01

    A sounding rocket flight was launched from Greenland in 1985 to study high latitude, early morning auroral physics. The payload was instrumented with electron and ion detectors, AC and DC electric field experiments, a plasma density experiment, and a magnetometer to measure the ambient field. The rocket was launched during disturbed conditions, when the polar cap was in a contracted state with visible aurora overhead. The electron data contained numerous signatures indicative of time-of-flight energy dispersion characterized by a coherent structure in which lower energy electrons arrived at the rocket after higher energy electrons. A model was constructed to explain this phenomena by the sudden application of a region of parallel electric field along a length of magnetic field line above the rocket. The model incorporates detector response and uses an altitudinal density profile based on auroral zone measurements. Three types of potential structures were tried: linear, quadratic and cubic. Of the three it was found that the cubic (electric field growing in a quadratic manner moving up the field line) produced the best fit to the data. The potential region was found to be approximately 1-2 R e in extent with the lower edge 3000-4000 km away from the rocket. The background electron temperature in the model which produced the best fit to the data was of the order of 15 eV

  2. Characterization of wind velocities in the upstream induction zone of a wind turbine using scanning continuous-wave lidars

    DEFF Research Database (Denmark)

    Simley, Eric; Angelou, Nikolas; Mikkelsen, Torben Krogh

    2016-01-01

    As a wind turbine generates power, induced velocities, lower than the freestream velocity, will be present upstream of the turbine due to perturbation of the flow by the rotor. In this study, the upstream induction zone of a 225kW horizontal axis Vestas V27 wind turbine located at the Danish...... Technical University’s Risø campus is investigated using a scanning Light Detection and Ranging (lidar) system. Three short-range continuous-wave “WindScanner” lidars are positioned in the field around the V27 turbine allowing detection of all three components of the wind velocity vectors within...... the induction zone. The time-averaged mean wind speeds at different locations in the upstream induction zone are measured by scanning a horizontal plane at hub height and a vertical plane centered at the middle of the rotor extending roughly 1.5 rotor diameters (D) upstream of the rotor. Turbulence statistics...

  3. Wind erosion in the Sahelian zone of Niger : processes, models, and control techniques

    NARCIS (Netherlands)

    Sterk, G.

    1997-01-01

    In the Sahelian zone of Niger, severe wind erosion occurs mainly in the first half of the rainy season (May - July), when violent winds preceding thunderstorms result in intense sediment transport. Quantification of this wind erosion is difficult due to a high degree of temporal and spatial

  4. Forecast of auroral activity

    International Nuclear Information System (INIS)

    Lui, A.T.Y.

    2004-01-01

    A new technique is developed to predict auroral activity based on a sample of over 9000 auroral sites identified in global auroral images obtained by an ultraviolet imager on the NASA Polar satellite during a 6-month period. Four attributes of auroral activity sites are utilized in forecasting, namely, the area, the power, and the rates of change in area and power. This new technique is quite accurate, as indicated by the high true skill scores for forecasting three different levels of auroral dissipation during the activity lifetime. The corresponding advanced warning time ranges from 22 to 79 min from low to high dissipation levels

  5. Simultaneous observations of electron spectra in the auroral zone and near the equatorial plane by the DMSP-5D-F2 and GEOS 1 Satellites

    International Nuclear Information System (INIS)

    Townend, M.

    1984-07-01

    Simultaneous observations of differential particle number fluxes in the auroral region by the DMSP-5D-F2 satellite and in the conjugate equatorial plane by GEOS 1, are studied. It is found that spectra in the precipitation region and in the plasma sheet can be similar, both in shape and magnitude. The features of auroral electron precipitation can be determined by the particle characteristics in the conjugate equatorial plane, and dumping of particles occurs without any significant acceleration by electric fields parallel to the Earth's magnetic field. (authors)

  6. Anomalous dc resistivity and double layers in the auroral ionosphere

    International Nuclear Information System (INIS)

    Kindel, J.M.; Barnes, C.; Forslund, D.W.

    1980-01-01

    There are at least four candidate instabilities which might account for anomalous dc rereresistivity in the auroral ionosphere. These are: the ion-acoustic instability, the Buneman instability, the ion-cyclotron instability and double layers. Results are reported of computer simulations of these four instabilities which suggest that double layers are most likely to be responsible for sistivity in the auroral zone

  7. Investigations of auroral dynamics: techniques and results

    International Nuclear Information System (INIS)

    Steen, Aa.

    1988-10-01

    This study is an experimental investigation of the dynamics of the aurora, describing both the systems developed for the optical measurements and the results obtained. It is found that during a auroral arc deformation, a fold travelling eastward along the arc is associated with an enhanced F-region ion temperature of 2700 K, measured by EISCAT, indicative of enhanced ionspheric electric fields. It is shown that for an auroral break-up, the large-scale westward travelling surge (WTS) is the last developed spiral in a sequence of spiral formations. It is proposed that the Kelvin-Helmholtz instability is the responsible process. In another event it is shown that large-amplitude long-lasting pulsations, observed both in ground-based magnetic field and photometer recordings, correspond to strong modulations of the particle intensity at the equatorial orbit (6.6 Re). In this event a gradual transition occurs between pulses classified as Ps6/auroral torches toward pulses with characteristics of substorms. The observations are explained by the Kelvin-Helmholtz instability in a magnetospheric boundary layer. The meridional neutral wind, at about 240 km altitude, is found to be reduced prior to or at the onset of auroral activity. These findings are suggestive of large-scale reconfigurations of the ionspheric electric fields prior to auroral onsets. A new real time triangulation technique developed to determine the altitude of auroral arcs is presented, and an alternative method to analyze incoherent scatter data is discussed. (With 46 refs.) (author)

  8. Wind erosion control with scattered vegetation in the Sahelian zone of Burkina Faso

    NARCIS (Netherlands)

    Leenders, J.K.

    2006-01-01

    The Sahelian zone ofAfricais the region that is globally most subjected to land degradation, with wind erosion being the most important soil degradation process. By using control measures, the negative effects of wind erosion can be reduced. At present, adoption of

  9. Wind Erosion Processes and Control Techniques in the Sahelian Zone of Niger

    NARCIS (Netherlands)

    Sterk, G.; Stroosnijder, L.; Raats, P.A.C.

    1999-01-01

    Wind Erosion Processes and Control Techniques in the Sahelian Zone of Niger G. Sterk, L. Stroosnijder, and P.A.C. Raats Abstract The objective of this paper is to present the main results and conclusions from three years of field research on wind erosion processes and control techniques in the

  10. Optimization of offshore wind farm layout in restricted zones

    DEFF Research Database (Denmark)

    Hou, Peng; Hu, Weihao; Chen, Cong

    2016-01-01

    In this research, an optimization method for offshore wind farm layout design is proposed. With the purpose of maximizing the energy production of the wind farm, the wind turbine (WT) positions are optimized. Due to the limitations of seabed conditions, marine traffic limitations or shipwrecks, etc...... with multiple adaptive methods (PSO-MAM) is adopted. The simulation results indicate that the proposed method can find a layout which outperforms a baseline layout of a reference wind farm (RWF) by increasing the energy yield by 3.84%....

  11. Sounding rocket study of auroral electron precipitation

    International Nuclear Information System (INIS)

    McFadden, J.P.

    1985-01-01

    Measurement of energetic electrons in the auroral zone have proved to be one of the most useful tools in investigating the phenomena of auroral arc formation. This dissertation presents a detailed analysis of the electron data from two sounding rocket campaigns and interprets the measurements in terms of existing auroral models. The Polar Cusp campaign consisted of a single rocket launched from Cape Parry, Canada into the afternoon auroral zone at 1:31:13 UT on January 21, 1982. The results include the measurement of a narrow, magnetic field aligned electron flux at the edge of an arc. This electron precipitation was found to have a remarkably constant 1.2 eV temperature perpendicular to the magnetic field over a 200 to 900 eV energy range. The payload also made simultaneous measurements of both energetic electrons and 3-MHz plasma waves in an auroral arc. Analysis has shown that the waves are propagating in the upper hybrid band and should be generated by a positive slope in the parallel electron distribution. A correlation was found between the 3-MHz waves and small positive slopes in the parallel electron distribution but experimental uncertainties in the electron measurement were large enough to influence the analysis. The BIDARCA campaign consisted of two sounding rockets launched from Poker Flat and Fort Yukon, Alaska at 9:09:00 UT and 9:10:40 UT on February 7, 1984

  12. Combined ESR and EISCAT observations of the dayside polar cap and auroral oval during the May 15, 1997 storm

    Directory of Open Access Journals (Sweden)

    H. Liu

    Full Text Available The high-latitude ionospheric response to a major magnetic storm on May 15, 1997 is studied and different responses in the polar cap and the auroral oval are highlighted. Depletion of the F2 region electron density occurred in both the polar cap and the auroral zone, but due to different physical processes. The increased recombination rate of O+ ions caused by a strong electric field played a crucial role in the auroral zone. The transport effect, however, especially the strong upward ion flow was also of great importance in the dayside polar cap. During the main phase and the beginning of the recovery phase soft particle precipitation in the polar cap showed a clear relation to the dynamic pressure of the solar wind, with a maximum cross-correlation coefficient of 0.63 at a time lag of 5 min.

    Key words: Ionosphere (auroral ionosphere; polar ionosphere - Magnetospheric physics (storms and substorms

  13. Statistics of a parallel Poynting vector in the auroral zone as a function of altitude using Polar EFI and MFE data and Astrid-2 EMMA data

    Directory of Open Access Journals (Sweden)

    P. Janhunen

    2005-07-01

    Full Text Available We study the wave-related (AC and static (DC parallel Poynting vector (Poynting energy flux as a function of altitude in auroral field lines using Polar EFI and MFE data. The study is statistical and contains 5 years of data in the altitude range 5000–30000 km. We verify the low altitude part of the results by comparison with earlier Astrid-2 EMMA Poynting vector statistics at 1000 km altitude. The EMMA data are also used to statistically compensate the Polar results for the missing zonal electric field component. We compare the Poynting vector with previous statistical DMSP satellite data concerning the electron precipitation power. We find that the AC Poynting vector (Alfvén-wave related Poynting vector is statistically not sufficient to power auroral electron precipitation, although it may, for Kp>2, power 25–50% of it. The statistical AC Poynting vector also has a stepwise transition at R=4 RE, so that its amplitude increases with increasing altitude. We suggest that this corresponds to Alfvén waves being in Landau resonance with electrons, so that wave-induced electron acceleration takes place at this altitude range, which was earlier named the Alfvén Resonosphere (ARS. The DC Poynting vector is ~3 times larger than electron precipitation and corresponds mainly to ionospheric Joule heating. In the morning sector (02:00–06:00 MLT we find that the DC Poynting vector has a nontrivial altitude profile such that it decreases by a factor of ~2 when moving upward from 3 to 4 RE radial distance. In other nightside MLT sectors the altitude profile is more uniform. The morning sector nontrivial altitude profile may be due to divergence of the perpendicular Poynting vector field at R=3–4 RE. Keywords. Magnetospheric physics (Auroral phenomena; Magnetosphere-ionosphere interactions – Space plasma physics (Wave-particle interactions

  14. Statistics of a parallel Poynting vector in the auroral zone as a function of altitude using Polar EFI and MFE data and Astrid-2 EMMA data

    Directory of Open Access Journals (Sweden)

    P. Janhunen

    2005-07-01

    Full Text Available We study the wave-related (AC and static (DC parallel Poynting vector (Poynting energy flux as a function of altitude in auroral field lines using Polar EFI and MFE data. The study is statistical and contains 5 years of data in the altitude range 5000–30000 km. We verify the low altitude part of the results by comparison with earlier Astrid-2 EMMA Poynting vector statistics at 1000 km altitude. The EMMA data are also used to statistically compensate the Polar results for the missing zonal electric field component. We compare the Poynting vector with previous statistical DMSP satellite data concerning the electron precipitation power. We find that the AC Poynting vector (Alfvén-wave related Poynting vector is statistically not sufficient to power auroral electron precipitation, although it may, for Kp>2, power 25–50% of it. The statistical AC Poynting vector also has a stepwise transition at R=4 RE, so that its amplitude increases with increasing altitude. We suggest that this corresponds to Alfvén waves being in Landau resonance with electrons, so that wave-induced electron acceleration takes place at this altitude range, which was earlier named the Alfvén Resonosphere (ARS. The DC Poynting vector is ~3 times larger than electron precipitation and corresponds mainly to ionospheric Joule heating. In the morning sector (02:00–06:00 MLT we find that the DC Poynting vector has a nontrivial altitude profile such that it decreases by a factor of ~2 when moving upward from 3 to 4 RE radial distance. In other nightside MLT sectors the altitude profile is more uniform. The morning sector nontrivial altitude profile may be due to divergence of the perpendicular Poynting vector field at R=3–4 RE.

    Keywords. Magnetospheric physics (Auroral phenomena; Magnetosphere-ionosphere interactions – Space plasma physics (Wave-particle interactions

  15. 77 FR 34935 - Foreign-Trade Zone 161; Temporary/Interim Manufacturing Authority; Siemens Energy, Inc., (Wind...

    Science.gov (United States)

    2012-06-12

    ... DEPARTMENT OF COMMERCE Foreign-Trade Zones Board [Docket T-4-2012] Foreign-Trade Zone 161; Temporary/Interim Manufacturing Authority; Siemens Energy, Inc., (Wind Turbine Nacelles and Hubs); Notice of... temporary/interim manufacturing (T/IM) authority, on behalf of Siemens Energy, Inc., to manufacture wind...

  16. Harmonic H+ gyrofrequency structures in auroral hiss observed by high-altitude auroral sounding rockets

    International Nuclear Information System (INIS)

    Kintner, P.M.; Vago, J.; Scales, W.; Yau, A.; Whalen, B.; Arnoldy, R.; Moore, T.

    1991-01-01

    Two recent sounding rocket experiments have yielded VLF wave data with spectral structures ordered by the hydrogen gyrofrequency. The spectral structures occur near and above the lower hybrid frequency in association with auroral hiss. These structures are observed within and near regions of auroral electron precipitation and transverse ion acceleration. They are accompanied by auroral hiss but are anticorrelated with spectral peaks at the lower hybrid frequency. They are typically found above 500 km altitude, have no measureable magnetic component, and are at least occasionally short wavelength (kρ i ≥1). Because the spectral structures appear to be electrostatic, are ordered by the hydrogen gyrofrequency, and are short wavelength, the authors interpret the structures as modes which connect the lower hybrid mode with the hydrogen Bernstein modes. A study of the plasma wave mode structure in the vicinity of the lower hybrid frequency is presented to substantiate this interpretation. The results imply that these waves are a common feature of the auroral zone ionosphere above 500 km altitude and exist any time that auroral hiss exists. The absence of previous satellite abservations of this phenomenon can be explained by Doppler broadening

  17. Assessment of solar and wind energy potentials for three free economic and industrial zones of Iran

    International Nuclear Information System (INIS)

    Mohammadi, Kasra; Mostafaeipour, Ali; Sabzpooshani, Majid

    2014-01-01

    This paper aims to evaluate the potential of renewable energy sources of solar and wind in three free economic and industrial zones of Chabahar, Kish and Salafchegan in Iran. Feasibility of harnessing solar energy was investigated by using key solar parameters like monthly mean global, beam and diffuse solar radiation as well as clearness index. It was found that all locations had great potentials for utilizing different solar energy systems. Additionally, the monthly, seasonal, semi-yearly and yearly optimum tilt angles of south-facing solar surfaces were determined. For all zones, adjusting the tilt angle twice a year or in other words, the semi-yearly tilt adjustment for two periods of warm (April–September) and cold (October–March) were highly recommended, since it offers almost the same level of annual solar energy gain (SEG) as those of monthly and seasonal adjustments. Weibull Distribution Function (WDF) was performed for analyzing the wind potentials at different heights. It was found that Chabahar was not suitable for wind energy development, but Kish and Salafchegan with yearly wind powers of 111.28 W/m 2 and 114.34 W/m 2 , respectively ranked in class 2 which are considered marginal for wind power development. Three different wind turbine models were proposed for Kish and Salafchegan. - Highlights: • Feasibility of solar and wind energy for three locations of Iran was investigated. • All locations were suitable for solar energy utilization. • The optimum tilt angles of solar surfaces were determined. • Chabahar was unsuitable, but Kish and Salafchegan were marginal for wind purpose

  18. Observations pertaining to the generation of auroral kilometric radiation

    International Nuclear Information System (INIS)

    Green, J.L.

    1981-01-01

    Auroral kilometric radiation (AKR) observations that have determined the propagation mode or polarization of the radiation and the detailed intensity distribution of the AKR emission cone are discussed. Attention is also given to correlations between AKR with discrete field-aligned currents. It is noted that these observations have helped to identify the auroral particle population most likely responsible for the generation of AKR and the possible sources of the free energy that drives the instability. Thus far, AKR has not been observed simultaneously with large electrostatic waves. Auroral zone current systems are thought to be intimately involved in the generation of AKR. In particular, the most probable source of energy for AKR is the precipitating inverted-V auroral electron distribution

  19. Auroral Tomography Workshop, Proceedings

    International Nuclear Information System (INIS)

    Steen, Aa.

    1993-08-01

    In ionospheric and atmospheric physics the importance of multi-station imaging has grown as a consequence of the availability of scientific grade CCD cameras with digital output and affordable massive computing power. Tomographic inversion techniques are used in many different areas, e.g. medicine, plasma research and space physics. The tomography workshop was announced to gather a limited group of people interested in auroral tomography or tomographic inversion methods in general. ALIS (Auroral Large Imaging System) is a multi-station ground-based system developed primarily for three-dimensional auroral imaging, however other non-auroral objects can be studied with ALIS, e.g. stratospheric clouds. Several of the contributions in the workshop dealt with problems related to geometries similar to the ALIS-configuration. The Proceedings contain written contributions received either in abstract form or as full papers. The Proceedings also contain contributions intended for the Workshop but not presented due to the absence of the speaker. Separate abstracts have been prepared for 15 of the 17 papers

  20. Midday auroral breakup

    International Nuclear Information System (INIS)

    Sandholt, P.E.; Lybekk, B.; Egeland, A.

    1988-08-01

    Groundbased observations of the midday aurora by all-sky TV and meridian scanning photometers reveal the intermittent occurence of discrete auroral displays within the cusp/cleft. A typical sequence includes the following features: Auroral brightening, near the equatorward boundary of the persistent cusp/cleft arc and subsequent poleward motion of discrete forms through the cusp/cleft region. A strong westward component of auroral motion, both of the individual forms and internal ray structures within these forms, if often observed. At maximum brightness green line intensities of ∼ 10 kR are observed, even within the interval characterized as the midday gap. The duration of the whole sequence is normally less than 10 minutes. During this period the auroral activity moves poleward, in some cases by 3-5 degrees, say from 71 o up to 75 o MLAT. Characteristic ground magnetic signatures are observed, including a ∼ 50 - 100 nT positive deflection in the H-component and a negative Z-component at stations located poleward of the initial brightening. A poleward propagating filamentary Hall current belt associated with the discrete aurora is inferred from the optical and magnetic data. A quantitative estimate shows that the conductivity enhancement, due to electron precipitation in conjunction with northward electric field, roughly accounts for the magnetic deflection on the ground. Series of such events are often observed when the cusp is located at rather low latitudes, say south of 75 o MLAT, presumably associated with negative IMF B z

  1. Detailed Dayside Auroral Morphology as a Function of Local Time for southeast IMF Orientation: Implications for Solar Wind-Magnetosphere Coupling

    National Research Council Canada - National Science Library

    Sandholt, P. E; Farrugia, C. J; Denig, W. F

    2004-01-01

    ...:00 magnetic local time (MLT) and discuss the relationship of this structure to solar wind-magnetosphere interconnection topology and the different stages of evolution of open field lines in the Dungey convection cycle...

  2. Reattachment Zone Characterisation Under Offshore Winds With Flow Separation On The Lee Side Of Coastal Dunes

    Science.gov (United States)

    Delgado-Fernandez, I.; Jackson, D.; Cooper, J. A.; Baas, A. C.; Lynch, K.; Beyers, M.

    2010-12-01

    Airflow separation, lee-side eddies and secondary flows play an essential role on the formation and maintenance of sand dunes. Downstream from dune crests the flow surface layer detaches from the ground and generates an area characterised by turbulent eddies in the dune lee slope (the wake). At some distance downstream from the dune crest, flow separates into a reversed component directed toward the dune toe and an offshore “re-attached” component. This reattachment zone (RZ) has been documented in fluvial and desert environments, wind tunnel experiments and numerical simulations, but not yet characterised in coastal dunes. This study examines the extent and temporal evolution of the RZ and its implications for beach-dune interaction at Magilligan, Northern Ireland. Wind parameters were measured over a profile extending from an 11 m height dune crest towards the beach, covering a total distance of 65 m cross-shore. Data was collected using an array of nine ultrasonic anemometers (UAs) deployed in April-May 2010, as part of a larger experiment to capture airflow data under a range of incident wind velocities and offshore directions. UAs were located along the profile (5 m tower spacing) over the beach, which allowed a detailed examination of the RZ with empirical data. Numerical modelling using Computational Fluid Dynamics (CFD) software was also conducted with input data from anemometer field measurements, running over a surface mesh generated from LiDAR and DGPS surveys. Results demonstrate that there is a wind threshold of approximately 5-6 ms-1 under which no flow separation exists with offshore winds. As wind speed increases over the threshold, a flow reversal area is quickly formed, with the maximum extent of the RZ at approximately 3.5 dune heights (h). The maximum extent of the RZ increases up to 4.5h with stronger wind speeds of 8-10 ms-1 and remains relatively constant as wind speed further increases. This suggests that the spatial extent of the RZ is

  3. Equilibrium motion of quict auroral arcs

    International Nuclear Information System (INIS)

    Lyatskij, V.B.; Leont'ev, S.V.

    1981-01-01

    Ionospheric plasma convection across auroral arc is investigated. It is shown that the existence of plasma area of increased concentration adjoining arc results not only from the arc but also is a factor supporting its existence. Under stable conditions the arc and plasma zone connected to it will move at a velocity different from a velocity of plasma convection. Arc velocity will be higher or lower as compared with convection velocity depending on arc orientation relative to an external electric field. At that the plasma zone is located either in front of or behind aurora polaris [ru

  4. Astrid-2, an advanced microsatellite for auroral research

    Directory of Open Access Journals (Sweden)

    G. T. Marklund

    Full Text Available The successful launch of the Swedish microsatellite Astrid-2 in December 1998 began a new era of auroral research, with advanced microprobes of 30 kg or less used as research tools. Innovative technologies and low-mass solutions were used for the sensors and deployment systems to allow a fairly complete set of scientific instruments within the 10 kg allocated for the scientific payload. A newly developed wire boom deployment system proved to function excellently. During its seven month lifetime Astrid-2 collected more than 26 Gbytes of high-quality data of auroral electric and magnetic fields, and auroral particle and plasma characteristics from approximately 3000 orbits at an inclination of 83° and an altitude of about 1000 km. Scientific results cover a broad range of topics, from the physics of energization of auroral particles to how the magnetosphere responds to the energy input from the solar wind and global magnetic field modelling. The fulfilment of both the technological and the scientific mission objectives has opened entirely new possibilities to carry out low-budget multipoint measurements in near-Earth space.

    Key words. Ionosphere (auroral ionosphere; instruments and techniques – Magnetospheric physics (auroral phenomena

  5. Auroral ionospheric quiet summer time conductances

    International Nuclear Information System (INIS)

    Brekke, A.; Hall, C.

    1988-01-01

    The auroral zone E-region conductivities and conductances have been studied for 7 quiet time summer days. The Hall- and Pedersen conductances are found to follow the solar zenith variations in a rather regular fashion, and empirical formulas for these conductances are obtained. The choice of proper collision frequency models is found to be of great importance when deriving the conductances, and it is argued that some of the different results presented by other authors may be due to different models of the collision frequencies. The Hall- to Pedersen conductance ratios can only be used as an indicator of the energy of the precipitating auroral particles when the contribution from the background solar ionization is subtracted. When this is done this ratio takes much higher values than previously reported

  6. Auroral and sub-auroral phenomena: an electrostatic picture

    Directory of Open Access Journals (Sweden)

    J. De Keyser

    2010-02-01

    Full Text Available Many auroral and sub-auroral phenomena are manifestations of an underlying magnetosphere-ionosphere coupling. In the electrostatic perspective the associated auroral current circuit describes how the generator (often in the magnetosphere is connected to the load (often in the ionosphere through field-aligned currents. The present paper examines the generic properties of the current continuity equation that characterizes the auroral circuit. The physical role of the various elements of the current circuit is illustrated by considering a number of magnetospheric configurations, various auroral current-voltage relations, and different types of behaviour of the ionospheric conductivity. Based on realistic assumptions concerning the current-voltage relation and the ionospheric conductivity, a comprehensive picture of auroral and sub-auroral phenomena is presented, including diffuse aurora, discrete auroral arcs, black aurora, and subauroral ion drift. The electrostatic picture of field-aligned potential differences, field-aligned currents, ionospheric electric fields and plasma drift, and spatial scales for all these phenomena is in qualitative agreement with observations.

  7. V and V Efforts of Auroral Precipitation Models: Preliminary Results

    Science.gov (United States)

    Zheng, Yihua; Kuznetsova, Masha; Rastaetter, Lutz; Hesse, Michael

    2011-01-01

    Auroral precipitation models have been valuable both in terms of space weather applications and space science research. Yet very limited testing has been performed regarding model performance. A variety of auroral models are available, including empirical models that are parameterized by geomagnetic indices or upstream solar wind conditions, now casting models that are based on satellite observations, or those derived from physics-based, coupled global models. In this presentation, we will show our preliminary results regarding V&V efforts of some of the models.

  8. The auroral electron accelerator

    International Nuclear Information System (INIS)

    Bryant, D.A.; Hall, D.S.

    1989-01-01

    A model of the auroral electron acceleration process is presented in which the electrons are accelerated resonantly by lower-hybrid waves. The essentially stochastic acceleration process is approximated for the purposes of computation by a deterministic model involving an empirically derived energy transfer function. The empirical function, which is consistent with all that is known of electron energization by lower-hybrid waves, allows many, possibly all, observed features of the electron distribution to be reproduced. It is suggested that the process occurs widely in both space and laboratory plasmas. (author)

  9. Auroral electron acceleration

    International Nuclear Information System (INIS)

    Bryant, D.A.

    1989-10-01

    Two theories of auroral electron acceleration are discussed. Part 1 examines the currently widely held view that the acceleration is an ordered process in a quasi-static electric field. It is suggested that, although there are many factors seeming to support this theory, the major qualifications and uncertainties that have been identified combine to cast serious doubt over its validity. Part 2 is devoted to a relatively new interpretation in terms of stochastic acceleration in turbulent electric fields. This second theory, which appears to account readily for most known features of the electron distribution function, is considered to provide a more promising approach to this central question in magnetospheric plasma physics. (author)

  10. Dynamic auroral storms on Saturn as observed by the Hubble Space Telescope.

    Science.gov (United States)

    Nichols, J D; Badman, S V; Baines, K H; Brown, R H; Bunce, E J; Clarke, J T; Cowley, S W H; Crary, F J; Dougherty, M K; Gérard, J-C; Grocott, A; Grodent, D; Kurth, W S; Melin, H; Mitchell, D G; Pryor, W R; Stallard, T S

    2014-05-28

    We present observations of significant dynamics within two UV auroral storms observed on Saturn using the Hubble Space Telescope in April/May 2013. Specifically, we discuss bursts of auroral emission observed at the poleward boundary of a solar wind-induced auroral storm, propagating at ∼330% rigid corotation from near ∼01 h LT toward ∼08 h LT. We suggest that these are indicative of ongoing, bursty reconnection of lobe flux in the magnetotail, providing strong evidence that Saturn's auroral storms are caused by large-scale flux closure. We also discuss the later evolution of a similar storm and show that the emission maps to the trailing region of an energetic neutral atom enhancement. We thus identify the auroral form with the upward field-aligned continuity currents flowing into the associated partial ring current.

  11. Upwelling to Outflowing Oxygen Ions at Auroral Latitudes during Quiet Times: Exploiting a New Satellite Database

    Science.gov (United States)

    Redmon, Robert J.

    The mechanisms by which thermal O+ escapes from the top of the ionosphere and into the magnetosphere are not fully understood even with 30 years of active research. This thesis introduces a new database, builds a simulation framework around a thermospheric model and exploits these tools to gain new insights into the study of O+ ion outflows. A dynamic auroral boundary identification system is developed using Defense Meteorological Satellite Program (DMSP) spacecraft observations at 850 km to build a database characterizing the oxygen source region. This database resolves the ambiguity of the expansion and contraction of the auroral zone. Mining this new dataset, new understanding is revealed. We describe the statistical trajectory of the cleft ion fountain return flows over the polar cap as a function of activity and the orientation of the interplanetary magnetic field y-component. A substantial peak in upward moving O+ in the morning hours is discovered. Using published high altitude data we demonstrate that between 850 and 6000 km altitude, O+ is energized predominantly through transverse heating; and acceleration in this altitude region is relatively more important in the cusp than at midnight. We compare data with a thermospheric model to study the effects of solar irradiance, electron precipitation and neutral wind on the distribution of upward O+ at auroral latitudes. EUV irradiance is shown to play a dominant role in establishing a dawn-focused source population of upwelling O+ that is responsible for a pre-noon feature in escaping O+ fluxes. This feature has been corroborated by observations on platforms including the Dynamics Explorer 1 (DE-1), Polar, and Fast Auroral Snapshot SnapshoT (FAST) spacecraft. During quiet times our analysis shows that the neutral wind is more important than electron precipitation in establishing the dayside O+ upwelling distribution. Electron precipitation is found to play a relatively modest role in controlling dayside, and a

  12. Electrodynamics properties of auroral surges

    International Nuclear Information System (INIS)

    Robinson, R.M.; Vondrak, R.R.

    1990-01-01

    The incoherent scatter radar technique provides an excellent means to study the ionization and electric fields associated with auroral precipitation events. One of the most intense and dynamic auroral events is the so-called surge or breakup aurora that accompanies auroral substorms. For their purposes they define a surge as a transient intensification of auroral precipitation that occurs simultaneously with a pronounced negative bay in the ground magnetometer data. They present data obtained during five such events in 1980 and 1981. Prior to the surge, auroral forms move equatorward, develop ray structure, and intensify. The surge is identified by an apparent poleward motion of the aurora producing aurorally associated ionization that extends over several hundred kilometers in latitude. The presurge auroral forms are embedded in a region of northward electric field. The auroral forms that comprise the surge span a region within which the meridional electric field is small and at times southward. A westward electric field is often but not always present within the surge. The behavior of the westward electric field is significantly different from the north-south field, in that sharp spatial gradients are absent even in very disturbed conditions. Although the westward Hall currents are mostly responsible for the negative bays that accompany the surge, at times the westward Pedersen current sustained by the westward electric field can be important. Sudden variations in the H component of the ground magnetogram can be caused by motions of the aurora or by temporal variations in the fields or conductivities. They present a model that simulates the observed changes in electric field and precipitation that accompany surges. The perturbation in the electric field produced by the surge is simulated by adding negative potential in regions of intense precipitation

  13. Characterization of the variability of the South Pacific Convergence Zone using satellite and reanalysis wind products

    Science.gov (United States)

    Kidwell, Autumn; Lee, Tong; Jo, Young-Heon; Yan, Xiao-hai

    2016-04-01

    The South Pacific Convergence Zone (SPCZ), the largest rain band worldwide during austral summer, is important to atmospheric circulation (including cyclone genesis) and ocean circulation. Previous studies of the SPCZ have focused on parameters such as outgoing longwave radiation or precipitation. However, wind convergence is fundamental causing the variations of these parameters. In this study, the SPCZ variability is examined using ocean surface wind products derived from NASA's QuickSCAT (1999-2009) and ESA's ASCAT (2007 onward) satellite scatterometers and ERA-Interim atmospheric reanalysis (1981 onward). From these products, indices were developed to characterize the SPCZ strength, area, and centroid location. Excellent agreement is found in terms of the temporal variations of the indices derived from the satellites and reanalysis wind products, despite some small differences in the time-mean SPCZ strength. The SPCZ strength, area, and centroid latitude have a dominant seasonal cycle. In contrast, the SPCZ centroid longitude is dominated by intraseasonal variability due to the influence by the Madden-Julian Oscillation. The SPCZ indices are all correlated with El Niño-Southern Oscillation indices. Interannual and intraseasonal variations of SPCZ strength during strong El Niño are approximately twice as large as the respective seasonal variations. SPCZ strength depends more on the intensity of El Niño rather than the central- vs. eastern-Pacific type. The longer ERA-Interim product is also used to examine decadal variations of the SPCZ indices. The change from positive to negative Pacific Decadal Oscillation phase around 1999 resulted in a westward shift of the SPCZ centroid longitude, much smaller interannual swing in centroid latitude, and a decrease in SPCZ area. This study improves the understanding of the variations of the SPCZ on multiple time scales and reveals the variations of SPCZ strength not reported previously. The diagnostics analyses can be

  14. Relativistic electron precipitation in the auroral zone

    International Nuclear Information System (INIS)

    Simons, D.J.

    1975-01-01

    The energy spectra and pitch angle distributions of electrons in the energy range 50 keV to 2 MeV have been determined by a solid state electron energy spectrometer during the Relativistic Electron Precipitation (REP) event of 31 May 1972. The experiment was carried aboard a Nike-Cajun sounding rocket as the University of Maryland component of a joint American-Norwegian (NASA-NDRE) ionospheric investigation. The difficulty of determining the expected electron flux prior to the experiment required an instrument with a large dynamic range. The design and theoretical modeling of this instrument is described in great detail. The electron pitch angle distributions are determined from a knowledge of the rocket aspect and the direction in space of the Earth's magnetic field. The electron fluxes during the REP event were highly variable demonstrating correlated energy, flux and pitch angle pulsations with time periods less than one second. Increases in flux were accompanied by marked filling of the loss cone at lower energies (near 50 keV). Drawing upon the quasilinear equations of plasma wave-electron interactions, a theoretical model for the production of relativistic electrons is proposed. A self consistent set of fully relativistic equations for the evolution of the electron distribution function due to the interaction of the electrons with parallel propagating whistler waves is derived in the Appendix. An examination of these equations leads to the conclusion that at comparatively low background electron densities, the anomalous Doppler resonance leads to the acceleration of near relativistic particles. The results of a computer solution of the five coupled integrodifferential quasilinear equations confirms this conclusion

  15. Auroral electron energies

    International Nuclear Information System (INIS)

    McEwan, D.J.; Duncan, C.N.; Montalbetti, R.

    1981-01-01

    Auroral electron characteristic energies determined from ground-based photometer measurements of the ratio of 5577 A OI and 4278 A N 2 + emissions are compared with electron energies measured during two rocket flights into pulsating aurora. Electron spectra with Maxwellian energy distributions were observed in both flights with an increase in characteristic energy during each pulsation. During the first flight on February 15, 1980 values of E 0 ranging from 1.4 keV at pulsation minima to 1.8 keV at pulsation maxima were inferred from the 5577/4278 ratios, in good agreement with rocket measurements. During the second flight on February 23, direct electron energy measurements yielded E 0 values of 1.8 keV rising to 2.1 keV at pulsation maxima. The photometric ratio measurements in this case gave inferred E 0 values about 0.5 keV lower. This apparent discrepancy is considered due to cloud cover which impaired the absolute emission intensity measurements. It is concluded that the 5577/4278 ratio does yield a meaningful measure of the characteristic energy of incoming electrons. This ratio technique, when added to the more sensitive 6300/4278 ratio technique usable in stable auroras can now provide more complete monitoring of electron influx characteristics. (auth)

  16. Observed characteristics of auroral forms

    International Nuclear Information System (INIS)

    Davis, T.N.

    1978-01-01

    Observations indicate that the extended auroral arc is the basic form of the discrete aurora, the brightest and most obvious kind of aurora. Both motions of auroral arcs and their distortions into convoluted forms indicate the presence of shear processes involving substantial charge excesses and magnetic field-aligned currents. Consequently, strong electric fields, both horizontal and vertical, characterize the discrete aurora. The observations of auroral arcs and observations of associated charged-particle fluxes, electric fields and currents fit together into a relatively cohesive description of the auroral arc which is compatible with at least one proposed model of the causative processes. On the other hand, an equally important type of aurora - pulsating aurora - exhibits quite different characteristics which distinguish it from the discrete aurora and which are difficult to interpret satisfactorily in terms of existing proposed models of particle precipitation and excitation of auroral emission. The lack of shearing behavior in the pulsating aurora indicates that substantial electric fields are not associated with it. Transitional forms of auroras exhibit an intermediate degree of shear motion. (Auth.)

  17. Investigation of the Impact of the Upstream Induction Zone on LIDAR Measurement Accuracy for Wind Turbine Control Applications using Large-Eddy Simulation

    International Nuclear Information System (INIS)

    Simley, Eric; Pao, Lucy Y; Gebraad, Pieter; Churchfield, Matthew

    2014-01-01

    Several sources of error exist in lidar measurements for feedforward control of wind turbines including the ability to detect only radial velocities, spatial averaging, and wind evolution. This paper investigates another potential source of error: the upstream induction zone. The induction zone can directly affect lidar measurements and presents an opportunity for further decorrelation between upstream wind and the wind that interacts with the rotor. The impact of the induction zone is investigated using the combined CFD and aeroelastic code SOWFA. Lidar measurements are simulated upstream of a 5 MW turbine rotor and the true wind disturbances are found using a wind speed estimator and turbine outputs. Lidar performance in the absence of an induction zone is determined by simulating lidar measurements and the turbine response using the aeroelastic code FAST with wind inputs taken far upstream of the original turbine location in the SOWFA wind field. Results indicate that while measurement quality strongly depends on the amount of wind evolution, the induction zone has little effect. However, the optimal lidar preview distance and circular scan radius change slightly due to the presence of the induction zone

  18. Plasma line observations in the auroral oval

    International Nuclear Information System (INIS)

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

    1988-01-01

    We report here a series of experiments conducted at the Sondre Stromfjord incoherent scatter radar, aimed at detected enhanced plasma lines associated with midnight sector auroral arcs. Using different receivers, we detected both ion and plasma lines simultaneously. The plasma line signal was recorded with the use of a filter bank of eight frequencies. Plasma lines were found to originate mainly from the topside of the particle-produced E layer. The enhanced plasma lines are sometimes a factor of 100 times larger than the thermal level. Our data show a rapid decay of the plasma lines, however. In some cases, only a 30-s integration time was needed in order to unambiguously detect both upshifted and downshifted lines. The level of the plasma lines reaches values of, for the larger cases, up to 40 0 K above the noise temperature. These are considerably higher than results from prior auroral zone plasma line experiments. In situ observations of enhanced plasma waves in this same region are reported in a companion paper. copyright American Geophysical Union 1988

  19. Correlation between Auroral kilometric radiation and field-aligned currents

    International Nuclear Information System (INIS)

    Green, J.L.; Saflekos, N.A.; Gurnett, D.A.; Potemra, T.A.

    1982-01-01

    Simultaneous observations of field-aligned currents (FAC) and auroral kilometric radiation (AKR) are compared from the polar-orbiting satellites Triad and Hawkeye. The Triad observations were restricted to the evening-to-midnight local time sector (1900 to 0100 hours magnetic local time) in the northern hemisphere. This is the region in which the most intense storms of AKR are believed to originate. The Hawkeye observations were restricted to when the satellite was in the AKR emission cone in the northern hemisphere and at radial distances > or =7R/sub E/ (earth radii) to avoid local propagation cutoff effects. A(R/7R/sub E/) 2 normalization to the power flux measurements of the kilometric radiation from Hawkeye is used to take into account the radial dependence of this radiation and to scale all intensity measurements so that they are independent of Hawkeye's position in the emission cone. Integrated field-aligned current intensities from Triad are determined from the observed transverse magnetic field disturbances. There appears to be a weak correlation between AKR intensity and the integrated current sheet intensity of field-aligned currents. In general, as the intensity of auroral kilometric radiation increases so does the integrated auroral zone current sheet intensity increase. Statistically, the linear correlation coefficient between the log of the AKR power flux and the log of the current sheet intensity is 0.57. During weak AKR bursts ( - 18 W m - 2 Hz - 1 ), Triad always observed weak FAC'S ( - 1 ), and when Triad observed large FAC's (> or =0.6 A m - 1 ), the AKR intensity from Hawkeye was moderately intense (10 - 5 to 10 - 14 W m - 2 Hz - 1 ) to intense (>10 - 14 W m - 2 Hz - 1 ). It is not clear from these preliminary results what the exact role is that auroral zone field-aligned currents play in the generation or amplification of auroral kilometric radiation

  20. Characterization of the variability of the South Pacific Convergence Zone using satellite and reanalysis wind product

    Science.gov (United States)

    Lee, T.; Kidwell, A. N.; Jo, Y. H.; Yan, X. H.

    2016-02-01

    The variability of the South Pacific Convergence Zone (SPCZ) is evaluated using ocean surface wind products derived from the QuickSCAT satellite scatterometer for the period of 1999-2009and ERA-Interim atmospheric reanalysis for the period of 1981-2014. From these products, indices were developed to represent the SPCZ strength, area, and centroid location. Excellent agreement is found between the indices derived from the two wind products during the QuikSCAT period in terms of the spatio-temporal structures of the SPCZ. The longer ERA-Interim product is then used to study the variations of SPCZ properties on intraseasonal, seasonal, interannual, and decadal time scales. The SPCZ strength, area, and centroid latitude have a dominant seasonal cycle. In contrast, the SPCZ centroid longitude is dominated by intraseasonal variability due to the influence by the Madden-Julian Oscillation. The SPCZ indices are all correlated with El Niño-Southern Oscillation indices. Interannual and intraseasonal variations of SPCZ strength during strong El Niño are approximately twice as large as the respective seasonal variations. SPCZ strength depends more on the intensity of El Niño rather than the central- vs. eastern-Pacific type. The change from positive to negative Pacific Decadal Oscillation phase around 1999 results in a westward shift of the SPCZ centroid longitude, much smaller interannual swing in centroid latitude, and a decrease in SPCZ area. This study improves the understanding of the variations of the SPCZ on multiple time scales and reveals the variations of SPCZ strength not reported previously. The diagnostics analyses can be used to evaluate climate models.

  1. Spatial monitoring of auroral emissions

    International Nuclear Information System (INIS)

    Steen, Aa.

    1983-12-01

    A ground based technique to monitor the three-dimensional distribution of auroral emissions is presented. The system is composed of two subsystems. A monochromatic imaging system with digitizing capability monitors the two-dimensional variation of auroral intensity with 50 degree field of view. A second height measuring system obtains in real time the height distribution of the auroral luminosity within the field of view of the imaging system. This paper is a report of the stepwise development of the complete system. The measurements will be carried out in the magnetic meridian plane through the EISCAT-site in Norway and the Kiruna Geophysical Institute. The operation of the optical system will as much as possible be combined with incoherent scatter radar measurements. (author)

  2. First-Generation Jet Propulsion Laboratory "Hockey-Puck" Free-Flying Magnetometers for Distributed In-Situ Multiprobe Measurement of Current Density Filamentation in the Northern Auroral Zone: Enstrophy Mission

    Science.gov (United States)

    Javadi, H.; Blaes, B.; Boehm, M.; Boykins, K.; Gibbs, J.; Goodman, W.; Lieneweg, U.; Lux, J.; Lynch, K.; Narvaez, P.

    2000-01-01

    The sub-orbital rocket mission was a collaborative project between the University of New Hampshire, Cornell University, and the Jet Propulsion Laboratory (JPL) to study filamentation phenomena in the northern Auroral zone. The Enstrophy mission test flies the JPL Free-Flying Magnetometer (FFM) concept. The FFM technology development task has been funded by NASA develop miniaturized, low-power, integrated "sensorcrafts". JPL's role was to design, integrate, test, and deliver four FFMs for deployment from the sounding rocket, allowing a unique determination of curl-B. This provides a direct measurement of magnetic-field-aligned current density along the rocket trajectory. A miniaturized three-axis fluxgate magnetometer was integrated with a 4-channel 22-bit sigma-delta Analog to Digital Converter (ADC), four temperature sensors, digital control electronics, seven (Li-SOCl2) batteries, two (4 deg x 170 deg field of view) sun-sensors, a fan-shaped-beam laser diode beacon, a (16 MHz) stable Temperature Compensated Crystal Oscillator (TCXO) clock, Radio Frequency (RF) communication subsystem, and an antenna for approximately 15 minutes of operation where data was collected continuously and transmitted in three (3) bursts (approximately 26 seconds each) to ground station antennas at Poker Flat, Alaska. FFMs were stowed within two trays onboard the rocket during the rocket launch and were released simultaneously using the spinning action of the rocket at approximately 300 km altitude (approximately 100 sec. into the flight). FFMs were deployed with spin rate of approximately 17 Hz and approximately 3 m/sec linear velocity with respect to the rocket. For testing purposes while the rocket was in the launch pad and during flight prior to release of FFMs from the rocket, commands (such as "power on", "test", "flight", "power off', and clock "Reset" signal) were transmitted via a infrared Light Emitting Diode to an infrared detector in the FFM. Special attention was paid to low

  3. Large scale hydrogen production from wind energy in the Magallanes area for consumption in the central zone of Chile

    International Nuclear Information System (INIS)

    Zolezzi, J.M.; Garay, A.; Reveco, M.

    2010-01-01

    The energy proposal of this research suggests the use of places with abundant wind resources for the production of H 2 on a large scale to be transported and used in the central zone of Chile with the purpose of diversifying the country's energy matrix in order to decrease its dependence on fossil fuels, increase its autonomy, and cover the future increases in energy demand. This research showed that the load factor of the proposed wind park reaches a value of 54.5%, putting in evidence the excellent wind conditions of the zone. This implies that the cost of the electricity produced by the wind park located in the Chilean Patagonia would have a cost of 0.0213 US$ kWh -1 in the year 2030. The low prices of the electricity obtained from the park, thanks to the economy of scale and the huge wind potential, represent a very attractive scenario for the production of H 2 in the future. The study concludes that by the year 2030 the cost of the H 2 generated in Magallanes and transported to the port of Quinteros would be 18.36 US$ MBTU -1 , while by that time the cost of oil would be about 17.241 US$ MBTU -1 , a situation that places H 2 in a very competitive position as a fuel. (author)

  4. Radar probing of the auroral plasma

    International Nuclear Information System (INIS)

    Brekke, A.

    1977-01-01

    The European Incoherent Scatter Radar in the Auroral Zone (EISCAT) is an intereuropean organization planning to install an incoherent scatter radar system in Northern Scandinavia. It is supported by Finland, France, Norway, Great Britain, Sweden and West Germany, and its headquarters is in Kiruna, Sweden. The radar is planned to be operating in 1979. In order to introduce students and young scientists to the incoherent scatter radar technique, a summer school was held in Tromsoe, from 5th to 13th June 1975. In these proceedings an introduction to the basic theory of fluctuations in a plasma is given. Some of the present incoherent scatter radars now in use are presented and special considerations with respect to the planned EISACT facility are discussed. Reviews of some recent results and scientific problems relevant to EISCAT are also presented and finally a presentation of some observational techniques complementary to incoherent scatter radars is included. (Ed.)

  5. The Isinglass Auroral Sounding Rocket Campaign: data synthesis incorporating remote sensing, in situ observations, and modelling

    Science.gov (United States)

    Lynch, K. A.; Clayton, R.; Roberts, T. M.; Hampton, D. L.; Conde, M.; Zettergren, M. D.; Burleigh, M.; Samara, M.; Michell, R.; Grubbs, G. A., II; Lessard, M.; Hysell, D. L.; Varney, R. H.; Reimer, A.

    2017-12-01

    The NASA auroral sounding rocket mission Isinglass was launched from Poker Flat Alaska in winter 2017. This mission consists of two separate multi-payload sounding rockets, over an array of groundbased observations, including radars and filtered cameras. The science goal is to collect two case studies, in two different auroral events, of the gradient scale sizes of auroral disturbances in the ionosphere. Data from the in situ payloads and the groundbased observations will be synthesized and fed into an ionospheric model, and the results will be studied to learn about which scale sizes of ionospheric structuring have significance for magnetosphere-ionosphere auroral coupling. The in situ instrumentation includes thermal ion sensors (at 5 points on the second flight), thermal electron sensors (at 2 points), DC magnetic fields (2 point), DC electric fields (one point, plus the 4 low-resource thermal ion RPA observations of drift on the second flight), and an auroral precipitation sensor (one point). The groundbased array includes filtered auroral imagers, the PFISR and SuperDarn radars, a coherent scatter radar, and a Fabry-Perot interferometer array. The ionospheric model to be used is a 3d electrostatic model including the effects of ionospheric chemistry. One observational and modelling goal for the mission is to move both observations and models of auroral arc systems into the third (along-arc) dimension. Modern assimilative tools combined with multipoint but low-resource observations allow a new view of the auroral ionosphere, that should allow us to learn more about the auroral zone as a coupled system. Conjugate case studies such as the Isinglass rocket flights allow for a test of the models' intepretation by comparing to in situ data. We aim to develop and improve ionospheric models to the point where they can be used to interpret remote sensing data with confidence without the checkpoint of in situ comparison.

  6. Influences on the radius of the auroral oval

    Directory of Open Access Journals (Sweden)

    S. E. Milan

    2009-07-01

    Full Text Available We examine the variation in the radius of the auroral oval, as measured from auroral images gathered by the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE spacecraft, in response to solar wind inputs measured by the Advanced Composition Explorer (ACE spacecraft for the two year interval June 2000 to May 2002. Our main finding is that the oval radius increases when the ring current, as measured by the Sym-H index, is intensified during geomagnetic storms. We discuss our findings within the context of the expanding/contracting polar cap paradigm, in terms of a modification of substorm onset conditions by the magnetic perturbation associated with the ring current.

  7. Investigating the auroral electrojets with low altitude polar orbiting satellites

    DEFF Research Database (Denmark)

    Moretto, T.; Olsen, Nils; Ritter, P.

    2002-01-01

    Three geomagnetic satellite missions currently provide high precision magnetic field measurements from low altitude polar orbiting spacecraft. We demonstrate how these data can be used to determine the intensity and location of the horizontal currents that flow in the ionosphere, predominantly...... to another event for which the combined measurements of the three satellites provide a comprehensive view of the current systems. The analysis hereof reveals some surprising results concerning the connection between solar wind driver and the resulting ionospheric currents. Specifically, preconditioning.......8-0.9) is observed between the amplitudes of the derived currents and the commonly used auroral electro-jet indices based on magnetic measurements at ground. This points to the potential of defining an auroral activity index based on the satellite observations, which could be useful for space weather monitoring...

  8. The location of the open-closed magnetic field line boundary in the dawn sector auroral ionosphere

    Directory of Open Access Journals (Sweden)

    J. A. Wild

    2004-11-01

    Full Text Available As a measure of the degree of coupling between the solar wind-magnetosphere-ionosphere systems, the rate at which the size of the polar cap (the region corresponding to ionospheric termini of open magnetic flux tubes varies is of prime importance. However, a reliable technique by which the extent of the polar cap might be routinely monitored has yet to be developed. Current techniques provide particularly ambiguous indications of the polar cap boundary in the dawn sector. We present a case study of space- and ground-based observations of the dawn-sector auroral zone and attempt to determine the location of the polar cap boundary using multi-wavelength observations of the ultraviolet aurora (made by the IMAGE FUV imager, precipitating particle measurements (recorded by the FAST, DMSP, and Cluster 1 and 3 satellites, and SuperDARN HF radar observations of the ionospheric Doppler spectral width boundary. We conclude that in the dawn sector, during the interval presented, neither the poleward edge of the wideband auroral UV emission (140-180nm nor the Doppler spectral width boundary were trustworthy indicators of the polar cap boundary location, while narrow band UV emissions in the range 130-140nm appear to be much more reliable.

  9. The magnetoionic modes and propagation properties of auroral radio emissions

    International Nuclear Information System (INIS)

    Calvert, W.; Hashimoto, Kozo

    1990-01-01

    The different magnetoionic wave modes which accompany the aurora are identified using DE 1 not only by their appearance on satellite radio spectrograms, but also by concurrent measurements of their wave polarization and arrival directions, and by ray-tracing models of their expected propagation behavior. Of the four possible propagation modes, designated O, X, W, and Z for the ordinary, extraordinary, whistler, and Z modes, respectively, all four are found to occur in the auroral zone, as follows: The most intense, of course, is the well-known auroral kilometric radiation (AKR), which originates primarily in the X mode near the electron cyclotron frequency, but which is frequently also accompanied by a weaker O-mode component from the same location. The next most prominent auroral emission is the W-mode auroral hiss originating from altitudes always well below the DE 1 satellite at frequencies below the local cyclotron frequency. The previously reported Z-mode auroral radiation was also detected, but from sources also below the satellite and at the poleward edge of the cavity, and not from the expected AKR source at the cyclotron frequency. A weaker O-mode component seems to accompany these emissions also, both within the polar cap poleward of the source and inside the cavity, the latter seemingly being guided upward by the cavity's lower plasma densities. Finally, exactly on the source field lines at the poleward edge of the cavity, there also occasionally seems to be localized Z-mode emissions extending from the Z-mode cutoff at quite low frequencies up to and above the plasma frequency

  10. Intensification and deepening of the Arabian Sea oxygen minimum zone in response to increase in Indian monsoon wind intensity

    Science.gov (United States)

    Lachkar, Zouhair; Lévy, Marina; Smith, Shafer

    2018-01-01

    The decline in oxygen supply to the ocean associated with global warming is expected to expand oxygen minimum zones (OMZs). This global trend can be attenuated or amplified by regional processes. In the Arabian Sea, the world's thickest OMZ is highly vulnerable to changes in the Indian monsoon wind. Evidence from paleo-records and future climate projections indicates strong variations of the Indian monsoon wind intensity over climatic timescales. Yet, the response of the OMZ to these wind changes remains poorly understood and its amplitude and timescale unexplored. Here, we investigate the impacts of perturbations in Indian monsoon wind intensity (from -50 to +50 %) on the size and intensity of the Arabian Sea OMZ, and examine the biogeochemical and ecological implications of these changes. To this end, we conducted a series of eddy-resolving simulations of the Arabian Sea using the Regional Ocean Modeling System (ROMS) coupled to a nitrogen-based nutrient-phytoplankton-zooplankton-detritus (NPZD) ecosystem model that includes a representation of the O2 cycle. We show that the Arabian Sea productivity increases and its OMZ expands and deepens in response to monsoon wind intensification. These responses are dominated by the perturbation of the summer monsoon wind, whereas the changes in the winter monsoon wind play a secondary role. While the productivity responds quickly and nearly linearly to wind increase (i.e., on a timescale of years), the OMZ response is much slower (i.e., a timescale of decades). Our analysis reveals that the OMZ expansion at depth is driven by increased oxygen biological consumption, whereas its surface weakening is induced by increased ventilation. The enhanced ventilation favors episodic intrusions of oxic waters in the lower epipelagic zone (100-200 m) of the western and central Arabian Sea, leading to intermittent expansions of marine habitats and a more frequent alternation of hypoxic and oxic conditions there. The increased

  11. Intensification and deepening of the Arabian Sea oxygen minimum zone in response to increase in Indian monsoon wind intensity

    Directory of Open Access Journals (Sweden)

    Z. Lachkar

    2018-01-01

    Full Text Available The decline in oxygen supply to the ocean associated with global warming is expected to expand oxygen minimum zones (OMZs. This global trend can be attenuated or amplified by regional processes. In the Arabian Sea, the world's thickest OMZ is highly vulnerable to changes in the Indian monsoon wind. Evidence from paleo-records and future climate projections indicates strong variations of the Indian monsoon wind intensity over climatic timescales. Yet, the response of the OMZ to these wind changes remains poorly understood and its amplitude and timescale unexplored. Here, we investigate the impacts of perturbations in Indian monsoon wind intensity (from −50 to +50 % on the size and intensity of the Arabian Sea OMZ, and examine the biogeochemical and ecological implications of these changes. To this end, we conducted a series of eddy-resolving simulations of the Arabian Sea using the Regional Ocean Modeling System (ROMS coupled to a nitrogen-based nutrient–phytoplankton–zooplankton–detritus (NPZD ecosystem model that includes a representation of the O2 cycle. We show that the Arabian Sea productivity increases and its OMZ expands and deepens in response to monsoon wind intensification. These responses are dominated by the perturbation of the summer monsoon wind, whereas the changes in the winter monsoon wind play a secondary role. While the productivity responds quickly and nearly linearly to wind increase (i.e., on a timescale of years, the OMZ response is much slower (i.e., a timescale of decades. Our analysis reveals that the OMZ expansion at depth is driven by increased oxygen biological consumption, whereas its surface weakening is induced by increased ventilation. The enhanced ventilation favors episodic intrusions of oxic waters in the lower epipelagic zone (100–200 m of the western and central Arabian Sea, leading to intermittent expansions of marine habitats and a more frequent alternation of hypoxic and oxic conditions there

  12. Joint two-dimensional observations of ground magnetic and ionospheric electric fields associated with auroral zone currents 1. Three-dimensional current flows associated with a substorm-intensified eastward electrojet

    International Nuclear Information System (INIS)

    Baumjohann, W.; Untiedt, J.; Greenwald, R.A.

    1980-01-01

    Two-dimensional distributions of ground magnetic and ionospheric electric fields in the evening sector auroral oval have been simultaneously observed by the Scandinavian Magnetometer Array and the Scandinavian Twin Auroral Radar Experiment (Stare) radars, respectively, on February 15, 1977. They were associated with varying, substorm-intensified, eastward electrojet current systems of the western, middle, and eastern segment of the eastward electrojet. We conclude that the substorm-intensified eastward electroject was a nearly pure Hall current driven by northward electric fields. The observed eastward increase of the current in the western segment of the electrojet was due to a gradual enhancement of the Hall conductivity. Here, the electrojet was fed by a broad sheet of net downward field-aligned current. During one period, the eastern-terminating part of the eastward electrojet diverged up the field lines in a rather local area because of a strong longitudinal decrease in the northward-directed electric field. On another occasion, it diverged northward within the ionosphere and joined the westward-flowing current because of a rotation of the northward electric field with increasing latitude through west- to southward. These two observed mechanisms of current divergence in the region where eastward and westward electrojects coexist may shed some new light on the controversy over the existence of upward field-aligned current flow in the Harang discontinuity

  13. Diffusion in coastal and harbour zones, effects of Waves,Wind and Currents

    Science.gov (United States)

    Diez, M.; Redondo, J. M.

    2009-04-01

    As there are multiple processes at different scales that produce turbulent mixing in the ocean, thus giving a large variation of horizontal eddy diffusivities, we use a direct method to evaluate the influence of different ambient parameters such as wave height and wind on coastal dispersion. Measurements of the diffusivity are made by digital processing of images taken from from video recordings of the sea surface near the coast. The use of image analysis allows to estimate both spatial and temporal characteristics of wave fields, surface circulation and mixing in the surf zone, near Wave breakers and inside Harbours. The study of near-shore dispersion [1], with the added complexity of the interaction between wave fields, longshore currents, turbulence and beach morphology, needs detailed measurements of simple mixing processes to compare the respective influences of forcings at different scales. The measurements include simultaneous time series of waves, currents, wind velocities from the studied area. Cuantitative information from the video images is accomplished using the DigImage video processing system [3], and a frame grabber. The video may be controlled by the computer, allowing, remote control of the processing. Spectral analysis on the images has also used n order to estimate dominant wave periods as well as the dispersion relations of dominant instabilities. The measurements presented here consist mostly on the comarison of difussion coeficients measured by evaluating the spread of blobs of dye (milk) as well as by measuring the separation between different buoys released at the same time. We have used a techniques, developed by Bahia(1997), Diez(1998) and Bezerra(2000)[1-3] to study turbulent diffusion by means of digital processing of images taken from remote sensing and video recordings of the sea surface. The use of image analysis allows to measure variations of several decades in horizontal diffusivity values, the comparison of the diffusivities

  14. VLTI-AMBER Velocity-Resolved Aperture-Synthesis Imaging of Eta Carinae with a Spectral Resolution of 12 000: Studies of the Primary Star Wind and Innermost Wind-Wind Collision Zone

    Science.gov (United States)

    Weigelt, G.; Hofmann, K.-H.; Schertl, D.; Clementel, N.; Corcoran, M. F.; Damineli, A.; de Wit, W.-J.; Grellmann, R.; Groh, J.; Guieu, S.; hide

    2016-01-01

    The mass loss from massive stars is not understood well. Eta Carinae is a unique object for studying the massive stellar wind during the luminous blue variable phase. It is also an eccentric binary with a period of 5.54 yr. The nature of both stars is uncertain, although we know from X-ray studies that there is a wind-wind collision whose properties change with orbital phase. Aims. We want to investigate the structure and kinematics of Car's primary star wind and wind-wind collision zone with a high spatial resolution of approx.6 mas (approx.14 au) and high spectral resolution of R = 12 000. Methods. Observations of Car were carried out with the ESO Very Large Telescope Interferometer (VLTI) and the AMBER instrument between approximately five and seven months before the August 2014 periastron passage. Velocity-resolved aperture-synthesis images were reconstructed from the spectrally dispersed interferograms. Interferometric studies can provide information on the binary orbit, the primary wind, and the wind collision. Results. We present velocity-resolved aperture-synthesis images reconstructed in more than 100 di erent spectral channels distributed across the Br(gamma) 2.166 micron emission line. The intensity distribution of the images strongly depends on wavelength. At wavelengths corresponding to radial velocities of approximately -140 to -376 km/s measured relative to line center, the intensity distribution has a fan-shaped structure. At the velocity of -277 km/s, the position angle of the symmetry axis of the fan is 126. The fan-shaped structure extends approximately 8.0 mas (approx.18:8 au) to the southeast and 5.8 mas (approx.13:6 au) to the northwest, measured along the symmetry axis at the 16% intensity contour. The shape of the intensity distributions suggests that the obtained images are the first direct images of the innermost wind-wind collision zone. Therefore, the observations provide velocity-dependent image structures that can be used to test three

  15. The Detectability of Radio Auroral Emission from Proxima b

    Energy Technology Data Exchange (ETDEWEB)

    Burkhart, Blakesley; Loeb, Abraham [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA (United States)

    2017-11-01

    Magnetically active stars possess stellar winds whose interactions with planetary magnetic fields produce radio auroral emission. We examine the detectability of radio auroral emission from Proxima b, the closest known exosolar planet orbiting our nearest neighboring star, Proxima Centauri. Using the radiometric Bode’s law, we estimate the radio flux produced by the interaction of Proxima Centauri’s stellar wind and Proxima b’s magnetosphere for different planetary magnetic field strengths. For plausible planetary masses, Proxima b could produce radio fluxes of 100 mJy or more in a frequency range of 0.02–3 MHz for planetary magnetic field strengths of 0.007–1 G. According to recent MHD models that vary the orbital parameters of the system, this emission is expected to be highly variable. This variability is due to large fluctuations in the size of Proxima b’s magnetosphere as it crosses the equatorial streamer regions of dense stellar wind and high dynamic pressure. Using the MHD model of Garraffo et al. for the variation of the magnetosphere radius during the orbit, we estimate that the observed radio flux can vary nearly by an order of magnitude over the 11.2-day period of Proxima b. The detailed amplitude variation depends on the stellar wind, orbital, and planetary magnetic field parameters. We discuss observing strategies for proposed future space-based observatories to reach frequencies below the ionospheric cutoff (∼10 MHz), which would be required to detect the signal we investigate.

  16. Mapping auroral activity with Twitter

    Science.gov (United States)

    Case, N. A.; MacDonald, E. A.; Heavner, M.; Tapia, A. H.; Lalone, N.

    2015-05-01

    Twitter is a popular, publicly accessible, social media service that has proven useful in mapping large-scale events in real time. In this study, for the first time, the use of Twitter as a measure of auroral activity is investigated. Peaks in the number of aurora-related tweets are found to frequently coincide with geomagnetic disturbances (detection rate of 91%). Additionally, the number of daily aurora-related tweets is found to strongly correlate with several auroral strength proxies (ravg≈0.7). An examination is made of the bias for location and time of day within Twitter data, and a first-order correction of these effects is presented. Overall, the results suggest that Twitter can provide both specific details about an individual aurora and accurate real-time indication of when, and even from where, an aurora is visible.

  17. Viking investigations of auroral electrodynamical processes

    International Nuclear Information System (INIS)

    Marklund, G.

    1993-01-01

    Recent results from the Viking electric field experiment and their contribution to a better understanding of the aurora and of associated ionosphere-magnetosphere processes are briefly reviewed. The high-resolution electric field data have provided new and important results in a number of different areas, including auroral electrodynamics both on the arc scale size and on the global scale, the auroral acceleration process, the current-voltage relationship, substorms, and the dynamics of the polar cusp. After a short introduction presenting some of the characteristic features of the high-altitude electric field data the remainder of this paper focuses on the role of the electric field in auroral electrodynamics and in the auroral acceleration process. The relationships between the auroral emissions and the associated electric field, current, particle, and conductivity distributions are discussed for both small-scale and large-scale auroral distributions on the basis of results from Viking event studies and from numerical model studies. Particular attention is paid to ionospheric convection and field- aligned current signatures associated with northward interplanetary magnetic field (IMF) auroral distributions, such as the theta aurora or those characterized by extended auroral activity poleward of the classical auroral oval. The role of dc electric fields for the auroral acceleration process has been further investigated and clarified. Intense low-frequency electric field fluctuations (< l Hz) have been shown to play an important role in the auroral acceleration process. In this frequency range the electric field appears static for the electrons but not for the ions, giving rise to a selective acceleration. Estimates of the acceleration potential based on a number of different methods generally show good agreement, providing convincing evidence of the role of dc electric fields in the auroral acceleration process

  18. Relationships between particle precipitation and auroral forms

    International Nuclear Information System (INIS)

    Burch, J.L.; Winningham, J.D.

    1978-01-01

    The present state of knowledge on the relationships between high-latitude particle precipitation and the aurora is reviewed. Attention is focused on the largescale relationships between auroral forms and magnetospheric particle populations, on the relationships between satellite and sounding-rocket measurements, and on the interaction of auroral electrons with the atmosphere. While significant progress is being made in relating the largescale features of the aurora to magnetospheric plasma domains, and in understanding the way in which auroral electrons deposit their energy in the atmosphere, only slight progress has been made in relating satellite data to the small-scale phenomena associated with auroral arcs. (author)

  19. The auroral and ionospheric flow signatures of dual lobe reconnection

    Directory of Open Access Journals (Sweden)

    S. M. Imber

    2006-11-01

    Full Text Available We present the first substantial evidence for the occurrence of dual lobe reconnection from ionospheric flows and auroral signatures. The process of dual lobe reconnection refers to an interplanetary magnetic field line reconnecting with lobe field lines in both the northern and southern hemispheres. Two bursts of sunward plasma flow across the noon portion of the open/closed field line boundary (OCB, indicating magnetic flux closure at the dayside, were observed in SuperDARN radar data during a period of strongly northward IMF. The OCB is identified from spacecraft, radar backscatter, and auroral observations. In order for dual lobe reconnection to take place, we estimate that the interplanetary magnetic field clock angle must be within ±10° of zero (North. The total flux crossing the OCB during each burst is small (1.8% and 0.6% of the flux contained within the polar cap for the two flows. A brightening of the noon portion of the northern auroral oval was observed as the clock angle passed through zero, and is thought to be due to enhanced precipitating particle fluxes due to the occurrence of reconnection at two locations along the field line. The number of solar wind protons captured by the flux closure process was estimated to be ~2.5×1030 (4 tonnes by mass, sufficient to populate the cold, dense plasma sheet observed following this interval.

  20. On the role of magnetic mirroring in the auroral phenomena

    International Nuclear Information System (INIS)

    Lennartsson, W.

    1976-12-01

    On the basis of field and particle observations, it is suggested that a bright auroral display is a part of a magnetosphere-ionosphere current system which is fed by a charge-separation process in the outer magnetosphere (or the solar wind). The upward magnetic-field-aligned current is flowing out of the display, carried mainly by downflowing electrons from the hot-particle populations in the outer magnetosphere (the ambient cold electrons being depleted at high altitudes). As a result of the magnetic mirroring of these downflowing current carriers, a large potential drop is set up along the magnetic field, increasing both the number flux and the kinetic energy of precipitating electrons. It is found that this simple basic model, when combined with wave-particle interactions, may be able to explain a highly diversified selection of auroral particle observations. It may thus be possible to explain both 'inverted-V' events and auroral rays in terms of a static parallel electric field, and the electric field may be compatible with a strongly variable pitch-angle distribution of the precipitating electrons, including distributions peaked at 90 0 as well as 0 0 . This model may also provide a simple explanation of the simultaneous precipitation of electrons and collimated positive ions. (Auth.)

  1. Spatial and temporal variations of wind erosion climatic erosivity in the farming-pastoral zone of Northern China

    Science.gov (United States)

    Yue, Shuping; Yang, Ruixin; Yan, Yechao; Yang, Zhengwei; Wang, Dandan

    2018-03-01

    Wind erosion climatic erosivity is an important parameter to assess the possible effects of climatic conditions on wind erosion. In this paper, the wind erosion climatic factor (C-factor), which was used to quantify the wind erosion climatic erosivity, was calculated for the period 1960-2014 based on monthly meteorological data collected from 101 stations in the farming-pastoral zone of Northern China. The Mann-Kendall (M-K) test, trend analysis, and geostatistical analysis methods were used to explore the spatial and temporal characteristics of the wind erosion climatic erosivity in this region. The result suggests that the annual C-factor, with a maximum of 76.05 in 1969 and a minimum of 26.57 in 2007, has a significant decreasing trend over the past 55 years. Strong seasonality in the C-factor was found, with the highest value in spring, which accounts for a significant proportion of the annual C-factor (41.46%). However, the coefficient of variation of the seasonal C-factor reaches a maximum in winter and a minimum in spring. The mean annual C-factor varies substantially across the region. Areas with high values of the mean annual C-factor (C ≥ 100) are located in Ulanqab and Dingxi, while areas with low values (C ≤ 10) lie in Lanzhou, Linxia, Dingxi, Xining, and Chengde. Spatial analysis on the trend of the C-factor reveals that 81% of the stations show statistically significant decreases at a 90% confidence level. An examination of the concentration ratio of the C-factor shows that the wind erosion climatic erosivity is concentrated in spring, especially in April, which makes this period particularly important for implementing soil conservation measures.

  2. Ecosystem-based management and refining governance of wind energy in the Massachusetts coastal zone: A case study approach

    Science.gov (United States)

    Kumin, Enid C.

    the successful governance of such projects, including any that may involve development of wind energy in the Massachusetts coastal zone or beyond. Three supplemental files of coded data accompany this dissertation.

  3. Wave processes. Auroral kilometer radiowave radiation

    International Nuclear Information System (INIS)

    Safargaleev, V.V.

    1993-01-01

    Characteristics of auroral kilometer radiowave radiation (AKRR) are discussed. AKRR is produced at altitudes 1.5-3 R e (R e is the Earth radius) in the auroral cavity. Electrons at energy 1-15 keV are always observed in AKRR production regions

  4. A Computer Simulation of Auroral Arc Formation.

    Science.gov (United States)

    Wagner, John Scott

    Recent satellite measurements have revealed two intriguing features associated with the formation of auroral arcs. The first is that an auroral arc is produced by a sheet of electrons accelerated along a geomagnetic field -aligned potential drop, and the second is that these electrons carry a field-aligned, upward directed electric current. In order to explain these measurements, a self-consistent, time dependent, computer simulation of auroral arc formation has been developed. The simulation demonstrates for the first time that a stable V-shaped potential structure, called an auroral double layer, develops spontaneously as a result of an ion shielded electron current sheet interacting with a conducting ionosphere. The double layer accelerates current-carrying electrons into the upper atmosphere at auroral energies. The double layer potential depends critically on the drift speed of the current-carrying electrons and on the temperature of the ambient shielding ions. Localized double layers occur near the ionosphere when the geomagnetic field is assumed to be uniform, but when a converging magnetic field is introduced, the double layer becomes extended due to the presence of an additional population of electrons trapped between the magnetic mirror and the double layer potential. The simulated auroral current sheet is subject to auroral curl and fold type deformations due to unstable Kelvin-Helmholtz waves. The previous incompletely understood auroral fold producing mechanism is described.

  5. Plasma mechanizm for auroral kilometer wave radiation

    International Nuclear Information System (INIS)

    Vlasov, V.G.

    1989-01-01

    The linear mechanism of auroral kilometer radiation (AKR) on the Cherenkov resonance is developed. The point is that plasma waves swinged by the electron beam in a dimer auroral plasma cavern on the Cherenkov resonance excercise 100% transformation under conventional and inconventional AKR modes under definite conditions

  6. Wind effects on coastal zone color scanner chlorophyll patterns in the U.S. Mid-Atlantic Bight during spring 1979

    Science.gov (United States)

    Eslinger, David L.; Iverson, Richard L.

    1986-01-01

    Coastal zone color scanner (CZCS) chlorophyll concentration increases in the Mid-Atlantic Bight were associated with high wind speeds in continental shelf waters during March and May 1979. Maximum spring CZCS chlorophyll concentrations occurred during April when the water column was not thermally stratified and were spatially and temporally associated with reductions in wind speed both in onshelf and in offshelf regions. Increased chlorophyll concentrations in offshelf waters were associated with high wind speeds during May when a deep chlorophyll maximum was present. Chlorophyll patchiness was observed on length scales typical of those controlled by biological processes during the April low-wind period but not during March or May when wind speeds were greater. The spring CZCS chlorophyll maximum in the southern portion of the Mid-Atlantic Bight occurred in response to a reduction in mixed layer depth caused by decreased wind speeds and not by increased water column stratification.

  7. Turbulent acceleration of auroral electrons

    International Nuclear Information System (INIS)

    Bryant, D.A.; Cook, A.C.; Wang, Z.-S.; Angelis, U. de; Perry, C.H.

    1991-07-01

    It is shown that the characteristic peak in the auroral electron velocity distribution can be generated stochastically through resonant interactions with lower-hybrid electrostatic turbulence. The peak itself is shown to be a direct consequence of restrictions imposed on reflexion of electron velocities in the frame of reference of individual wave packets by the limitation in group velocity. A Monte-Carlo model demonstrates how the various properties of the acceleration region are reflected in the resultant electron distribution. It is shown, in particular, that the width of the peak is governed by the amplitude of the turbulence, while the amplitude of the peak reflects the column density of wave energy. Electron distributions encountered within three auroral arcs are interpreted to yield order of magnitude estimates of the amplitude and rms electric field of lower-hybrid wave packets. The velocities and frequencies of the resonant waves, the net electric field, the column density of wave energy and the electric-field energy density are also estimated. The results are found to be consistent with available electric-field measurements. A general broadening of the electron distribution caused by less systematic interactions between electrons and wave packets is shown to have a negligible effect on the peak resulting from the reflexion process; it does, though, lead to the creation of a characteristic high-energy tail. (author)

  8. Reconstruction of energetic electron spectra in the upper atmosphere: balloon observations of auroral X-rays coordinated with measurements from the EISCAT radar

    International Nuclear Information System (INIS)

    Olafsson, K.J.

    1990-08-01

    Energetic electron precipitation in the auroral zone has been studied using coordinated auroral X-ray measurements from balloons, altitude profiles of the ionospheric electron density measured by the EISCAT radar above the balloons, and cosmic noise absorption data from the Scandinavian riometer network. The data were obtained during the Coordinated EISCAT and Balloon Observations (CEBO) campaign in August 1984. The energy spectral variations of both the X-ray fluxes and the primary precipitating electrons were examined for two precipitation events in the morning sector. As far as reasonably can be concluded from observations of magnetic activity in the auroral zone, and from the temporal development of the energy spectra, the two precipitation events can be interpreted in the frame of present models of energetic electron precipitation on the mordning side of the auroral zone. 96 refs., 70 figs., 11 tabs

  9. Electron currents associated with an auroral band

    International Nuclear Information System (INIS)

    Spiger, R.J.; Anderson, H.R.

    1975-01-01

    Measurements of electron pitch angle distributions and energy spectra over a broad auroral band were used to calculate net electric current carried by auroral electrons in the vicinity of the band. The particle energy spectrometers were carried by a Nike-Tomahawk rocket launched from Poker Flat, Alaska, at 0722 UT on February 25, 1972. Data are presented which indicate the existence of upward field-aligned currents of electrons in the energy range 0.5-20 keV. The spatial relationship of these currents to visual structure of the auroral arc and the characteristics of the electrons carrying the currents are discussed

  10. Electron currents associated with an auroral band

    Science.gov (United States)

    Spiger, R. J.; Anderson, H. R.

    1975-01-01

    Measurements of electron pitch angle distributions and energy spectra over a broad auroral band were used to calculate net electric current carried by auroral electrons in the vicinity of the band. The particle energy spectrometers were carried by a Nike-Tomahawk rocket launched from Poker Flat, Alaska, at 0722 UT on February 25, 1972. Data are presented which indicate the existence of upward field-aligned currents of electrons in the energy range 0.5-20 keV. The spatial relationship of these currents to visual structure of the auroral arc and the characteristics of the electrons carrying the currents are discussed.

  11. First light from a kilometer-baseline Scintillation Auroral GPS Array.

    Science.gov (United States)

    Datta-Barua, S; Su, Y; Deshpande, K; Miladinovich, D; Bust, G S; Hampton, D; Crowley, G

    2015-05-28

    We introduce and analyze the first data from an array of closely spaced Global Positioning System (GPS) scintillation receivers established in the auroral zone in late 2013 to measure spatial and temporal variations in L band signals at 100-1000 m and subsecond scales. The seven receivers of the Scintillation Auroral GPS Array (SAGA) are sited at Poker Flat Research Range, Alaska. The receivers produce 100 s scintillation indices and 100 Hz carrier phase and raw in-phase and quadrature-phase samples. SAGA is the largest existing array with baseline lengths of the ionospheric diffractive Fresnel scale at L band. With an initial array of five receivers, we identify a period of simultaneous amplitude and phase scintillation. We compare SAGA power and phase data with collocated 630.0 nm all-sky images of an auroral arc and incoherent scatter radar electron precipitation measurements, to illustrate how SAGA can be used in multi-instrument observations for subkilometer-scale studies. A seven-receiver Scintillation Auroral GPS Array (SAGA) is now at Poker Flat, Alaska SAGA is the largest subkilometer array to enable phase/irregularities studies Simultaneous scintillation, auroral arc, and electron precipitation are observed.

  12. Generation of auroral kilometric radiation and the structure of auroral acceleration region

    International Nuclear Information System (INIS)

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

    1980-01-01

    Generation of auroral kilometric radiation (AKR) in the auroral acceleration region is studied. It is shown that auroral kilometric radiation can be generated by the backscattered electrons trapped in the acceleration region via a cyclotron maser process. The parallel electric field in the acceleration region is required to be distributed over 1-2 Rsub(E). The observed AKR frequency spectrum can be used to estimate the altitude range of the auroral acceleration region. The altitudes of the lower and upper boundaries of the acceleration region determined from the AKR data are respectively approximately 2000 and approximately 9000 km. (author)

  13. Ray tracing of auroral Z mode radiation, AKR and auroral hiss

    International Nuclear Information System (INIS)

    Horne, R.B.; Jones, D.; Kimura, I.; Sawada, A.

    1990-01-01

    While observed frequency bandwidths of auroral Z mode radiation cannot be directly accounted for in terms of direct cyclotron maser instability generation, ray tracing in a hot plasma indicates that if the radiation near a plasma frequency lower than the gyrofrequency, the observed bandwidths are explainable in terms of upward propagation away from the earth. An auroral Z-mode generation mechanism is proposed involving mode conversion from O-mode auroral kilometric radiation (AKR) at the plasma frequency, as well as mode conversion from upgoing auroral hiss. Ray tracings in the O mode identify a possible AKR source region along L = 8.55. 11 refs

  14. Assessments of wind-energy potential in selected sites from three geopolitical zones in Nigeria: implications for renewable/sustainable rural electrification.

    Science.gov (United States)

    Okeniyi, Joshua Olusegun; Ohunakin, Olayinka Soledayo; Okeniyi, Elizabeth Toyin

    2015-01-01

    Electricity generation in rural communities is an acute problem militating against socioeconomic well-being of the populace in these communities in developing countries, including Nigeria. In this paper, assessments of wind-energy potential in selected sites from three major geopolitical zones of Nigeria were investigated. For this, daily wind-speed data from Katsina in northern, Warri in southwestern and Calabar in southeastern Nigeria were analysed using the Gumbel and the Weibull probability distributions for assessing wind-energy potential as a renewable/sustainable solution for the country's rural-electrification problems. Results showed that the wind-speed models identified Katsina with higher wind-speed class than both Warri and Calabar that were otherwise identified as low wind-speed sites. However, econometrics of electricity power simulation at different hub heights of low wind-speed turbine systems showed that the cost of electric-power generation in the three study sites was converging to affordable cost per kWh of electric energy from the wind resource at each site. These power simulations identified cost/kWh of electricity generation at Kaduna as €0.0507, at Warri as €0.0774, and at Calabar as €0.0819. These bare positive implications on renewable/sustainable rural electrification in the study sites even as requisite options for promoting utilization of this viable wind-resource energy in the remote communities in the environs of the study sites were suggested.

  15. Assessments of Wind-Energy Potential in Selected Sites from Three Geopolitical Zones in Nigeria: Implications for Renewable/Sustainable Rural Electrification

    Science.gov (United States)

    Okeniyi, Joshua Olusegun; Ohunakin, Olayinka Soledayo; Okeniyi, Elizabeth Toyin

    2015-01-01

    Electricity generation in rural communities is an acute problem militating against socioeconomic well-being of the populace in these communities in developing countries, including Nigeria. In this paper, assessments of wind-energy potential in selected sites from three major geopolitical zones of Nigeria were investigated. For this, daily wind-speed data from Katsina in northern, Warri in southwestern and Calabar in southeastern Nigeria were analysed using the Gumbel and the Weibull probability distributions for assessing wind-energy potential as a renewable/sustainable solution for the country's rural-electrification problems. Results showed that the wind-speed models identified Katsina with higher wind-speed class than both Warri and Calabar that were otherwise identified as low wind-speed sites. However, econometrics of electricity power simulation at different hub heights of low wind-speed turbine systems showed that the cost of electric-power generation in the three study sites was converging to affordable cost per kWh of electric energy from the wind resource at each site. These power simulations identified cost/kWh of electricity generation at Kaduna as €0.0507, at Warri as €0.0774, and at Calabar as €0.0819. These bare positive implications on renewable/sustainable rural electrification in the study sites even as requisite options for promoting utilization of this viable wind-resource energy in the remote communities in the environs of the study sites were suggested. PMID:25879063

  16. Observation of auroral fading before breakup

    International Nuclear Information System (INIS)

    Pellinen, R.J.; Heikkila, W.J.

    1978-02-01

    We have obtained detailed observations of the onset of auroral breakup using a variety of instruments with time resolution of some tens of seconds. Rapid sequences of all-sky photographs, and fast meridian scans by photometers, show that breakup is usually preceded by moderate brightening, followed by fading of the auroral brightness lasting one or two minutes, before the actual breakup itself. At the time of the fading there is a brief darkening of the poleward sky. Often the breakup is preceded by one or more rapid intensifications, each one preceded by local fading. Pseudo-breakups may also occur without the development of a major event. A bonafide breakup may begin on the fading arc, on an adjacent arc, or in an entirely new region nearby. This optical activity is closely correlated with the development of auroral radar echoes, suggesting that variations in the ionospheric and magnetospheric electric and magnetic fields are responsible for the observed auroral variations. Data from the IMS magnetometer network provide some indication of a correlated response by the local auroral and ionospheric current, although this could be partly due to changes in conductivity. Riometer recordings show a slow decrease in ionsperic radio wave absorption over a period of about ten minutes prior to breakup, with the largest decrease essentially to quiet-time values in the region of auroral fading and subsequent breakup. The implications of these observations regarding the trigger mechanism for the expansion phase of a magnetospheric substorm are discussed. (author)

  17. Investigating the auroral electrojets with low altitude polar orbiting satellites

    Directory of Open Access Journals (Sweden)

    T. Moretto

    2002-07-01

    Full Text Available Three geomagnetic satellite missions currently provide high precision magnetic field measurements from low altitude polar orbiting spacecraft. We demonstrate how these data can be used to determine the intensity and location of the horizontal currents that flow in the ionosphere, predominantly in the auroral electrojets. First, we examine the results during a recent geomagnetic storm. The currents derived from two satellites at different altitudes are in very good agreement, which verifies good stability of the method. Further, a very high degree of correlation (correlation coefficients of 0.8–0.9 is observed between the amplitudes of the derived currents and the commonly used auroral electrojet indices based on magnetic measurements at ground. This points to the potential of defining an auroral activity index based on the satellite observations, which could be useful for space weather monitoring. A specific advantage of the satellite observations over the ground-based magnetic measurements is their coverage of the Southern Hemisphere, as well as the Northern. We utilize this in an investigation of the ionospheric currents observed in both polar regions during a period of unusually steady interplanetary magnetic field with a large negative Y-component. A pronounced asymmetry is found between the currents in the two hemispheres, which indicates real inter-hemispheric differences beyond the mirror-asymmetry between hemispheres that earlier studies have revealed. The method is also applied to another event for which the combined measurements of the three satellites provide a comprehensive view of the current systems. The analysis hereof reveals some surprising results concerning the connection between solar wind driver and the resulting ionospheric currents. Specifically, preconditioning of the magnetosphere (history of the interplanetary magnetic field is seen to play an important role, and in the winther hemisphere, it seems to be harder to

  18. Sea state observation in island-sheltered nearshore zone based on in situ intermediate-water wave measurements and NCEP/CFSR wind data

    Digital Repository Service at National Institute of Oceanography (India)

    Dora, G.U.; SanilKumar, V.

    and transformation in and around the offshore islands was analyzed using the wind wave model. 2. Materials and methods As one of the potential fishing zones along the west coast of India, and also as a popular tourist site, Karwar is sheltered by six offshore...

  19. Relationships between the solar wind and the polar cap magnetic activity

    International Nuclear Information System (INIS)

    Berthelier, A.

    1981-01-01

    The influence of solar wind conditions on magnetic activity is described in order to delineate the differences in the response of the magnetic activity to the arrival on the magnetopause of different typical solar wind variations. By determining a new index of local magnetic activity free from seasonal and diurnal effects we put in evidence the dependence of the various effects upon the invariant latitude. Most important results are: (1) the main increase of the magnetic activity does not occur at the same invariant latitude for different interplanetary variations, e.g. peaks of Bz tend to increase magnetic activity mainly in the auroral zones while peaks of B correspond to a uniform increase in magnetic activity over the polar cap and auroral zone; (2) there is a two steps response of magnetic activity to the high speed plasma streams; (3) an increase of magnetic activity is observed for large and northward Bz, which probably indicates that the solar wind-magnetosphere coupling is efficient under these circumstances. The specific influences of the IMF polarity are also briefly reviewed. (orig.)

  20. Statistical study of auroral fragmentation into patches

    Science.gov (United States)

    Hashimoto, Ayumi; Shiokawa, Kazuo; Otsuka, Yuichi; Oyama, Shin-ichiro; Nozawa, Satonori; Hori, Tomoaki; Lester, Mark; Johnsen, Magnar Gullikstad

    2015-08-01

    The study of auroral dynamics is important when considering disturbances of the magnetosphere. Shiokawa et al. (2010, 2014) reported observations of finger-like auroral structures that cause auroral fragmentation. Those structures are probably produced by macroscopic instabilities in the magnetosphere, mainly of the Rayleigh-Taylor type. However, the statistical characteristics of these structures have not yet been investigated. Here based on observations by an all-sky imager at Tromsø (magnetic latitude = 67.1°N), Norway, over three winter seasons, we statistically analyzed the occurrence conditions of 14 large-scale finger-like structures that developed from large-scale auroral regions including arcs and 6 small-scale finger-like structures that developed in auroral patches. The large-scale structures were seen from midnight to dawn local time and usually appeared at the beginning of the substorm recovery phase, near the low-latitude boundary of the auroral region. The small-scale structures were primarily seen at dawn and mainly occurred in the late recovery phase of substorms. The sizes of these large- and small-scale structures mapped in the magnetospheric equatorial plane are usually larger than the gyroradius of 10 keV protons, indicating that the finger-like structures could be caused by magnetohydrodynamic instabilities. However, the scale of small structures is only twice the gyroradius of 10 keV protons, suggesting that finite Larmor radius effects may contribute to the formation of small-scale structures. The eastward propagation velocities of the structures are -40 to +200 m/s and are comparable with those of plasma drift velocities measured by the colocating Super Dual Auroral Radar Network radar.

  1. Auroral pulsations and accompanying VLF emissions

    Directory of Open Access Journals (Sweden)

    V. R. Tagirov

    Full Text Available Results of simultaneous TV observations of pulsating auroral patches and ELF-VLF-emissions in the morning sector carried out in Sodankylä (Finland on February 15, 1991 are presented. Auroral pulsating activity was typical having pulsating patches with characteristic periods of about 7 s. Narrow-band hiss emissions and chorus elements at intervals of 0.3–0.4 s formed the main ELF-VLF activity in the frequency range 1.0–2.5 kHz at the same time. The analysis of auroral images with time resolution of 0.04 s allowed perfectly separate analysis of spatial and temporal variations in the auroral luminosity. Mutual correspondence between the behaviour of the luminous auroral patches and the appearance of ELF noise type hiss emissions and VLF chorus trains was found in two intervals chosen for analysis. While the hiss emissions were associated with the appearance of luminosity inside a limited area close to the zenith, the structured VLF emissions were accompanied by rapid motion of luminosity inside the area. The spatial dimension of the pulsating area was about 45–50 km and luminosity propagated inside it with velocity of about 10–12 kms. We discuss a new approach to explain the 5–15 s auroral pulsation based on the theory of flowing cyclotron maser and relaxation characteristics of ionosphere.

    Key words. Magnetospheric physics (auroral phenomena; magnetosphere-ionosphere interactions · Space plasma physics (wave-particle interactions

  2. Magnetotail phenomena and auroral acceleration

    International Nuclear Information System (INIS)

    Giles, M.J.

    1980-01-01

    It is suggested that localised electrostatic potential wells could be generated in the plasma sheet by large amplitude electrostatic ion cyclotron waves. It is shown from a consideration of a simple one dimensional model that such wells could possess a double structure of oppositely directed fields elongated in longitude. The possibility that the waves could evolve from a turbulent ion wave cascade driven by Earthward streaming protons is discussed and the magnitude of the potentials that could be established in this way is estimated using results for condensed state turbulent equilibria. The projections of these wells along the highly conducting geomagnetic field lines form potential valleys across the field lines in the high latitude auroral plasma. It is shown that these valleys would be of the scale and depth needed to establish electrostatic shocks which would be of sufficient intensity to accelerate electrons to energies comparable to those observed in 'inverted-V' events. Potential wells are formed predominantly in the midnight sector of the plasma sheet and propagate Earthwards. This implies a corresponding equatorwards motion of the valley which, typically, would have a velocity of a few hundred m s -1 . (author)

  3. Comparative studies on control systems for a two-blade variable-speed wind turbine with a speed exclusion zone

    International Nuclear Information System (INIS)

    Yang, Jian; Song, Dongran; Dong, Mi; Chen, Sifan; Zou, Libing; Guerrero, Josep M.

    2016-01-01

    To avoid the coincidence between the tower nature frequency and rotational excitation frequency, a SEZ (speed exclusion zone) must be built for a two-blade wind turbine with a full rated converter. According to the literature, two methods of SEZ-crossing could be adopted. However, none of them have been studied in industrial applications, and their performance remains unclear. Moreover, strategies on power regulation operation are not covered. To fully investigate them, this paper develops two control systems for a two-blade WT (wind turbines) with a SEZ. Because control systems play vital roles in determining the performance of the WT, this paper focuses on comparative studies on their operation strategies and performance. In these strategies, optimal designs are introduced to improve existing SEZ algorithms. Moreover, to perform power regulation outside the SEZ, two operation modes are divided in the proposed down power regulation solutions. The developed control systems’ performance is confirmed by simulations and field tests. Two control systems present similar capabilities of power production and SEZ-bridging. Nevertheless, at the cost of significantly increased tower loads, one captures 1% more energy than the other. Overall consideration must be made for the control system selection for a WT with a SEZ. - Highlights: • Two control systems are developed for a two-blade WT with a SEZ. • Three strategies, that is, power optimization, power limitation and power regulation, are discussed. • Optimal designs are adopted to enhance the WT's SEZ-bridging capability. • Simple but effective power regulation solutions are presented. • Simulation and field test results show that Control System 2 produces 1% more energy at the cost of increased tower loads.

  4. Ground and space observations of medium frequency auroral radio emissions

    Science.gov (United States)

    Broughton, Matthew C.

    The auroral zone is a rich source of natural radio emissions that can be observed in space and at ground-level. By studying these waves, scientists can gain insight into the plasma processes that generate them and use the near-Earth space environment as a large-scale plasma physics laboratory. This thesis uses both ground-level and in situ observations to study two kinds of natural radio emissions. First, we report observations of a new kind of auroral radio emission. The waves have frequencies ranging from 1.3-2.2 MHz, bandwidths ranging from 90-272 kHz, and durations ranging from 16-355 s. Spectral analysis of the waveform data has revealed that the emission has a complex combination of at least three kinds of fine structures. For model auroral electron distributions, calculations indicate that Langmuir waves could be excited at frequencies consistent with observations. The remainder of the thesis discusses auroral medium frequency (MF) burst, an impulsive, broadband natural radio emission observed at ground-level within a few minutes of local substorm onset. LaBelle [2011] proposed that MF burst originates as Langmuir/Z-mode waves on the topside of the ionosphere that subsequently mode convert to L-mode waves and propagate to ground-level. Using continuous waveform measurements and combined observations with the Sondrestrom Incoherent Scatter Radar, we have performed two tests of this mechanism. The results of these tests are consistent with the mechanism described in LaBelle [2011]. A survey of 8,624 half-orbits of the DEMETER spacecraft has revealed 68 observations of bursty MF waves. We have compared the wave properties of these waves to those of MF burst and have found that although it is uncertain, the balance of the evidence suggests that the bursty MF waves observed with DEMETER are the same phenomenon as the ground-level MF burst. Finally, we have used numerical simulations to model both the fine structure of MF burst and to estimate the attenuation the

  5. Theoretical interpretation of upstreaming electrons and elevated conics on auroral field lines

    International Nuclear Information System (INIS)

    Ashour-Abdalla, M.; Schriver, D.

    1989-01-01

    Recent VIKING satellite observations in the auroral zone have shown the association of elevated ion conics (conics with a low energy cutoff above zero) with upward streaming electrons in the presence of low frequency electric field fluctuations. A self-consistent particle simulation was developed which assumed the presence of a steady state electric field on auroral zone field lines capable of accelerating ions up the magnetic field lines. Results from this study show that a low frequency ion-ion two stream instability can be excited. This low frequency instability creates a fluctuating electric field which heats the ions oblique to the magnetic field forming distributions similar to the elevated ion comics. The ion-ion waves also interact resonantly with electrons and accelerates them in the direction of the ion beam

  6. Electrondynamics of the auroral E region

    International Nuclear Information System (INIS)

    Kirkwood, Sheila.

    1990-10-01

    This study concentrates on the signatures of the interaction process seen closest to the Earth - i.e. in the region where the visible aurora is produced. A number of experimental investigations are presented which look at details of the dynamics and electrodynamics of auroral ionisation features in the ionospheric E region. The studies are based primarily on measurement with the EISCAT UHF incoherent scatter radar which is located in northern Scandinavia. Initial calibration of the radar, and some measurements of the properties of the background atmosphere are described first. These are a necessary basis for the detailed studies which follow, which are of two aspects of auroral electrodynamics - substorms and aurorally-associated sporadic E layers. For the substorm studies, all-sky camera observations of the aurora over Scandinavia and ultra-violet images from the Viking satellite are used to identify the auroral forms corresponding to EISCAT measurements. This allows the determination of representative conductivities for the different auroral features which are characteristic of the substorm development. These conductivities are an important input for modelling studies of the electric current systems and have not previously been measured directly. Particle measurements from the Viking satellite are used together with EISCAT to determine the origin of the particles precipitated into the ionosphere during the energy-storage phase prior to the substorm. The sporadic E layers studies address the question of how ion layers and associated neutral sodium layers can be produced by some process which is common in association with auroral activity. Two candidates are considered - gravity waves and electric fields. (author)

  7. Resonant Alfven waves on auroral field lines

    International Nuclear Information System (INIS)

    Chiu, Y.T.

    1987-01-01

    It is shown that resonant Alfven waves on dipole magnetic field geometry and plasma distributions suitable for auroral field lines can be conveniently treated in the theory of Mathieu functions. Resurgent interest in invoking large-scale Alfven waves to structure some elements of auroral electrodynamics calls for interpretation of measured perpendicular electric and magnetic disturbance fields in terms of Alfven waves. The ability to express the resonant eigenmodes in closed form in terms of Mathieu functions allows for convenient tests of the Alfven wave structuring hypothesis. Implications for current vector electric and magnetic disturbance measurements are discussed

  8. Auroral kilometric radiation from transpolar arcs

    International Nuclear Information System (INIS)

    Pederson, B.M.; Pottelette, R.; Eliasson, L.; Murphree, J.S.; Elphinstone, R.D.; Bahnsen, A.; Jespersen, M.

    1992-01-01

    Observations from the Swedish satellite Viking allow the authors to study the relationship between auroral kilometric radiation (AKR) and discrete auroral features. Previous work has shown that AKR generation is most often associated with nightside aurora. They present wave data which show that under certain circumstances the source regions may also occur on discrete features, identified as transpolar arcs. The wave spectrograms detected during crossings or closest approaches to such sources exhibit structures similar to those observed during nightside AKR source crossings. Also, the associated ion beams and trapped conical electron populations with enhanced upward directed loss cones peak at comparable energies (∼1 keV)

  9. Observation and interpretation of particle and electric field measurements inside and adjacent to an active auroral arc

    International Nuclear Information System (INIS)

    Carlson, C.W.; Kelley, M.C.

    1977-01-01

    A Javelin sounding rocket instrumented to measure electric fields, energetic particles, and suprathermal electrons was flown across an auroral display in the late expansion phase of a substorm. Four distinct regions of fields and particles were interpreted here in light of our present understanding of auroral dynamics.r of 10 and resemble fluxes mesured in the equatorial plane during the expansion phase. The hard fluxes in the equatorward zone are further energized and may act as a source for the outer radiation belt as inward convection further energizes them

  10. Space Weather Products and Tools Used in Auroral Monitoring and Forecasting at CCMC/SWRC

    Science.gov (United States)

    Zheng, Yihua; Rastaetter, Lutz

    2015-01-01

    Key points discussed in this chapter are (1) the importance of aurora research to scientific advances and space weather applications, (2) space weather products at CCMC that are relevant to aurora monitoring and forecasting, and (3) the need for more effort from the whole community to achieve a better and long-lead-time forecast of auroral activity. Aurora, as manifestations of solar wind-magnetosphere-ionosphere coupling that occurs in a region of space that is relatively easy to access for sounding rockets, satellites, and other types of observational platforms, serves as a natural laboratory for studying the underlying physics of the complex system. From a space weather application perspective, auroras can cause surface charging of technological assets passing through the region, result in scintillation effects affecting communication and navigation, and cause radar cluttering that hinders military and civilian applications. Indirectly, an aurora and its currents can induce geomagnetically induced currents (GIC) on the ground, which poses major concerns for the wellbeing and operation of power grids, particularly during periods of intense geomagnetic activity. In addition, accurate auroral forecasting is desired for auroral tourism. In this chapter, we first review some of the existing auroral models and discuss past validation efforts. Such efforts are crucial in transitioning a model(s) from research to operations and for further model improvement and development that also benefits scientific endeavors. Then we will focus on products and tools that are used for auroral monitoring and forecasting at the Space Weather Research Center (SWRC). As part of the CCMC (Community Coordinated Modeling Center), SWRC has been providing space weather services since 2010.

  11. Substorm associated radar auroral surges: a statistical study and possible generation model

    Directory of Open Access Journals (Sweden)

    B. A. Shand

    Full Text Available Substorm-associated radar auroral surges (SARAS are a short lived (15–90 minutes and spatially localised (~5° of latitude perturbation of the plasma convection pattern observed within the auroral E-region. The understanding of such phenomena has important ramifications for the investigation of the larger scale plasma convection and ultimately the coupling of the solar wind, magnetosphere and ionosphere system. A statistical investigation is undertaken of SARAS, observed by the Sweden And Britain Radar Experiment (SABRE, in order to provide a more extensive examination of the local time occurrence and propagation characteristics of the events. The statistical analysis has determined a local time occurrence of observations between 1420 MLT and 2200 MLT with a maximum occurrence centred around 1700 MLT. The propagation velocity of the SARAS feature through the SABRE field of view was found to be predominately L-shell aligned with a velocity centred around 1750 m s–1 and within the range 500 m s–1 and 3500 m s–1. This comprehensive examination of the SARAS provides the opportunity to discuss, qualitatively, a possible generation mechanism for SARAS based on a proposed model for the production of a similar phenomenon referred to as sub-auroral ion drifts (SAIDs. The results of the comparison suggests that SARAS may result from a similar geophysical mechanism to that which produces SAID events, but probably occurs at a different time in the evolution of the event.

    Key words. Substorms · Auroral surges · Plasma con-vection · Sub-auroral ion drifts

  12. Mapping of auroral kilometric radiation sources to the aurora

    International Nuclear Information System (INIS)

    Huff, R.L.; Calvert, W.; Craven, J.D.; Frank, L.A.; Gurnett, D.A.

    1988-01-01

    Auroral kilometric radiation (AKR) and optical auroral emissions are observed simultaneously using plasma wave instrumentation and auroral imaging photometers acrried on the DE 1 spacecraft. The DE 1 plasma wave instrument measures the relative phase of signals from orthogonal electric dipole antennas, and from these measurements, apparent source directions can be determined with a high degree of precision. Wave data are analyzed for several strong AKR events, and source directions are determined for several emission frequencies. By assuming that the AKR originates at cyclotron resonant altitudes, a condidate source field line is identified. When the selected source field line is traced down to auroral altitudes on the concurrent DE 1 auroral image, a striking correspondence between the AKR source field line and localized auroral features is produced. The magnetic mapping study provides strong evidence that AKR sources occur on field lines associated with discrete auroral arcs, and it provides confirmation that AKR is generated near the electron cyclotron frequency

  13. Acceleration/heating of plasma on auroral field lines: preliminary results from the Viking satellite

    International Nuclear Information System (INIS)

    Lundin, R.

    1988-01-01

    In this report, a review of the first results obtained from the particle experiment on board the Viking spacecraft will be given. During the first part of the Viking mission, the orbit was suitable for high-altitude measurements (up to ∼ 13500 km) in the dayside oval and the cusp/cleft region. Thus, some emphasis will be put on processes occurring in the dayside auroral region. On the basis of more than 100 Viking traversals of the cusp and cleft it is suggested that these regions can be identified by some regular characteristics in the particle data. The cusp has a continuous presence of solar wind plasma, affected mainly by convection and containing modest plasma energization. Conversely, the cleft is characterized by extensive plasma energization, and strong field aligned current sheets. Temporal injections of solar wind plasma are frequently observed in the cleft. A distinguishing characteristic of the Viking charged particle experiment is the energy and angular resolution. Thus, the fine-structure of narrow particle beams and conical distributions of both electrons and ions can be determined. This enables very detailed studies of the plasma acceleration processes along auroral field lines. Some examples of accelerated plasma populations and their related energy and angular distribution will be presented. The observations are compared with existing theories of auroral plasma heating and acceleration processes

  14. High-frequency and time resolution rocket observations of structured low- and medium-frequency whistler mode emissions in the auroral ionosphere

    Science.gov (United States)

    LaBelle, J.; McAdams, K. L.; Trimpi, M. L.

    High bandwidth electric field waveform measurements on a recent auroral sounding rocket reveal structured whistler mode signals at 400-800 kHz. These are observed intermittently between 300 and 500 km with spectral densities 0-10 dB above the detection threshold of 1.5×10-11V2/m2Hz. The lack of correlation with local particle measurements suggests a remote source. The signals are composed of discrete structures, in one case having bandwidths of about 10 kHz and exhibiting rapid frequency variations of the order of 200 kHz per 100 ms. In one case, emissions near the harmonic of the whistler mode signals are detected simultaneously. Current theories of auroral zone whistler mode emissions have not been applied to explain quantitatively the fine structure of these signals, which resemble auroral kilometric radiation (AKR) rather than auroral hiss.

  15. New look at radar auroral motions

    International Nuclear Information System (INIS)

    Greenwald, R.A.; Ecklund, W.L.

    1975-01-01

    During October 1974, three modifications were temporarily added to the NOAA radar auroral backscatter facility located at Anchorage, Alaska. These modifications included (1) a multiple azimuth antenna system. (2) an on-line computer for processing amplitude and mean Doppler profiles of the radar backscatter, and (3) a 13-baud Barker coder. In combination with the radar these modifications provided data relevant to understanding both the microscopic and the macroscopic nature of the radar aurora. Appreciable structure was often found in the Doppler velocity profiles of radar auroral irregularities. Doppler velocities of nearly 2000 m/s were observed. By combining scatter amplitude profiles and mean Doppler profiles from the five azimuths we have produced contour maps of the scatter intensity and the Doppler velocity. The scatter intensity maps often indicate appreciable temporal and spatial structure in the radar auroral irregularities, corroborating the results of Tsunoda et al. (1974). The mean Doppler contour maps indicate that there is also appreciable temporal and spatial structure in the flow velocities of radar auroral irregularities. At those times when there appears to be large-scale uniformity in the irregularity flow, the Doppler velocity varies with azimuth in a manner that is consistent with a cosine-dependent azimuthal variation

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

    International Nuclear Information System (INIS)

    Monreal M, R.; Llop, C.

    2002-01-01

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

  17. A satellite study of dayside auroral conjugacy

    Directory of Open Access Journals (Sweden)

    H. B. Vo

    Full Text Available A study of dayside auroral conjugacy has been done using the cleft/boundary layer auroral particle boundaries observed by the DMSP-F7 satellite in the southern hemisphere and the global UV auroral images taken by the Viking spacecraft in the northern hemisphere. The 22 events have been studied on the basis of an internal IGRF 1985 magnetic field; it is shown that there is a displacement of up to 4° in latitude from the conjugate points with the northern aurora appearing to be located poleward of the conjugate point. No local time dependence of the north-south auroral location difference was seen. The use of a more realistic magnetic field model for tracing field lines which incorporates the dipole tilt angle and Kp index, the Tsyganenko 1987 long model plus the IGRF 1985 internal magnetic field model, appears to organize the data better. Although with this external plus internal model some tracings did not close in the opposite hemisphere, 70% of those that did indicated satisfactory conjugacy. The study shows that the degree of auroral conjugacy is dependent upon the accuracy of the magnetic field model used to trace to the conjugate point, especially in the dayside region where the field lines can either go to the dayside magnetopause near the subsolar point or sweep all the way back to the flanks of the magnetotail. Also the discrepancy in the latitude of northern and southern aurora can be partially explained by the displacement of the neutral sheet (source region of the aurora by the dipole tilt effect.

  18. A satellite study of dayside auroral conjugacy

    Directory of Open Access Journals (Sweden)

    H. B. Vo

    1995-11-01

    Full Text Available A study of dayside auroral conjugacy has been done using the cleft/boundary layer auroral particle boundaries observed by the DMSP-F7 satellite in the southern hemisphere and the global UV auroral images taken by the Viking spacecraft in the northern hemisphere. The 22 events have been studied on the basis of an internal IGRF 1985 magnetic field; it is shown that there is a displacement of up to 4° in latitude from the conjugate points with the northern aurora appearing to be located poleward of the conjugate point. No local time dependence of the north-south auroral location difference was seen. The use of a more realistic magnetic field model for tracing field lines which incorporates the dipole tilt angle and Kp index, the Tsyganenko 1987 long model plus the IGRF 1985 internal magnetic field model, appears to organize the data better. Although with this external plus internal model some tracings did not close in the opposite hemisphere, 70% of those that did indicated satisfactory conjugacy. The study shows that the degree of auroral conjugacy is dependent upon the accuracy of the magnetic field model used to trace to the conjugate point, especially in the dayside region where the field lines can either go to the dayside magnetopause near the subsolar point or sweep all the way back to the flanks of the magnetotail. Also the discrepancy in the latitude of northern and southern aurora can be partially explained by the displacement of the neutral sheet (source region of the aurora by the dipole tilt effect.

  19. Ring current and auroral electrojets in connection with interplanetary medium parameters during magnetic storm

    Directory of Open Access Journals (Sweden)

    Y. I. Feldstein

    1994-06-01

    Full Text Available The relationship between the auroral electrojet indices (AE and the ring current magnetic field (DR was investigated by observations obtained during the magnetic storm on 1-3 April 1973. During the storm main phase the DR development is accompanied by a shift of the auroral electrojets toward the equator. As a result, the standard AE indices calculated on the basis of data from auroral observatories was substantially lower than the real values (AE'. To determine AE' during the course of a storm main phase data from subauroral magnetic observatories should be used. It is shown that the intensity of the indices (AE' which take into account the shift of the electrojets is increased substantially relative to the standard indices during the storm main phase. AE' values are closely correlated with geoeffective solar wind parameters. A high correlation was obtained between AE' and the energy flux into the ring current during the storm main phase. Analysis of magnetic field variations during intervals with intense southward IMF components demonstrates a decrease of the saturation effect of auroral electrojet currents if subauroral stations magnetic field variations are taken into account. This applies both to case studies and statistical data. The dynamics of the electrojets in connection with the development of the ring current and of magnetospheric substorms can be described by the presence (absence of saturation for minimum (maximum AE index values during a 1-h interval. The ring current magnetic field asymmetry (ASY was calculated as the difference between the maximum and minimum field values along a parallel of latitude at low latitudes. The ASY value is closely correlated with geoeffective solar wind parameters and simultaneously is a more sensitive indicator of IMF Bz variations than the symmetric ring current. ASY increases (decreases faster during the main phase (the recovery phase than DR. The magnetic field decay at low latitudes in the

  20. Secondary contamination of 30-km zone of the Chernobyl atomic electric plant and adjacent territory due to radionuclides carried by ascending wind

    International Nuclear Information System (INIS)

    Garger, E.K.; Gavrilov, V.P.

    1992-01-01

    The territory contaminated with radionuclides as a result of the accident at the Chernobyl atomic electric plant is a surface source of radioactive aerosols carried into the atmosphere by ascending winds. In this connection, a number of problems arise whose solution is important for assessment of the radiation conditions in the atmosphere near the Earth's surface: (1) calculation of the volume concentration of radionuclides and their fallout on the contaminated and neighboring territory and on this basis determine the potentially dangerous contaminated regions; (2) assessment of the secondary contamination of deactivated territories due to ascending winds and transfer of radionuclides; and (3) determination of the size of the protective (buffer) zones around or near populated areas to ensure low volume concentrations of radionuclides during strong winds. In order to calculate the transfer of radionuclides from a surface source, it is necessary to know its dust intensity, which is the vertical turbulent flux of the radionuclides in the atmosphere layer near the ground Q (Ci · m -2 sec -1 ). A quantity frequently used in practice is Q referred to the contamination density of the surface layer c (Ci/m 2 ) and called the wind ascent intensity α = Q/c. As a rule, the radionuclide wind ascent intensity for a plane source with a nonuniform surface and contamination density may depend on the physical characteristics of the surface as well as on those of the radionuclides and also on the space coordinates x, y and on time. In the present study, the wind ascent intensity was determined by gradient measurements of the mean radionuclide concentration, the wind velocity and air temperature; the conditions during the measurements were assumed to correspond to the case of a plane homogeneous, stationary source of a nondepositing admixture

  1. Interferometric phase velocity measurements in the auroral electrojet

    International Nuclear Information System (INIS)

    Labelle, J.; Kinter, P.M.; Kelley, M.C.

    1986-01-01

    A double-probe electric field detector and two spatially separated fixed-bias Langmuir probes were flown on a Taurus-Tomahawk sounding rocket launched from Poker Flat Research Range in March 1982. Interesting wave data have been obtained from about 10 s of the downleg portion of the flight during which the rocket passed through the auroral electrojet. Here the electric field receiver and both density fluctuation (deltan/n) receivers responded to a broad band of turbulence centered at 105 km altitude and at frequencies generally below 4 kHz. Closer examination of the two deltan/n turbulent waveforms reveals that they are correlated, and from the phase difference between the two signals, the phase velocity of the waves in the rocket reference frame is inferred. The magnitude and direction of the observed phase velocity are consistent either with waves which travel at the ion sound speed (Csub(s)) or with waves which travel at the electron drift velocity. The observed phase velocity varies by about 50% over a 5 km altitude range - an effect which probably results from shear in the zonal neutral wind, although unfortunately no simultaneous neutral wind measurements exist to confirm this. (author)

  2. Short-term ecological effects of an offshore wind farm in the Dutch coastal zone; a compilation

    NARCIS (Netherlands)

    Lindeboom, H.J.; Kouwenhoven, H.J.; Bergman, M.J.N.; Bouma, S.; Brasseur, S.; Daan, R.; Fijn, R.C.; de Haan, D.; Dirksen, S.; van Hal, R.; Hille Ris Lambers, R.; ter Hofstede, R.; Krijgsveld, K.L.; Leopold, M.; Scheidat, M.

    2011-01-01

    The number of offshore wind farms is increasing rapidly, leading to questions about the environmental impact of such farms. In the Netherlands, an extensive monitoring programme is being executed at the first offshore wind farm (Offshore Windfarm Egmond aan Zee, OWEZ). This letter compiles the

  3. An Undergraduate Student Instrumentation Project (USIP) to Develop New Instrument Technology to Study the Auroral Ionosphere and Stratospheric Ozone Layer Using Ultralight Balloon Payloads

    Science.gov (United States)

    Nowling, M.; Ahmad, H.; Gamblin, R.; Guala, D.; Hermosillo, D.; Pina, M.; Marrero, E.; Canales, D. R. J.; Cao, J.; Ehteshami, A.; Bering, E. A., III; Lefer, B. L.; Dunbar, B.; Bias, C.; Shahid, S.

    2015-12-01

    This project is currently engaging twelve undergraduate students in the process of developing new technology and instrumentation for use in balloon borne geospace investigations in the auroral zone. Motivation stems from advances in microelectronics and consumer electronic technology. Given the technological innovations over the past 20 years it now possible to develop new instrumentation to study the auroral ionosphere and stratospheric ozone layer using ultralight balloon payloads for less than 6lbs and $3K per payload. The University of Houston Undergraduate Student Instrumentation Project (USIP) team has built ten such payloads for launch using 1500 gm latex weather balloons deployed in Houston, TX, Fairbanks, AK, and as well as zero pressure balloons launched from northern Sweden. The latex balloon project will collect vertical profiles of wind velocity, temperature, electrical conductivity, ozone, and odd nitrogen. This instrument payload will also produce profiles of pressure, electric field, and air-earth electric current. The zero pressure balloons will obtain a suite of geophysical measurements including: DC electric field, electric field and magnetic flux, optical imaging, total electron content of ionosphere via dual-channel GPS, X-ray detection, and infrared/UV spectroscopy. Students flew payloads with different combinations of these instruments to determine which packages are successful. Data collected by these instruments will be useful in understanding the nature of electrodynamic coupling in the upper atmosphere and how the global earth system is changing. Twelve out of the launched fifteen payloads were successfully launched and recovered. Results and best practices learned from lab tests and initial Houston test flights will be discussed.

  4. Experimental study of diffuse auroral precipitations

    International Nuclear Information System (INIS)

    Mouaia, K.

    1983-01-01

    First chapter is devoted to low energy electron precipitation in the evening sector of the auroral magnetosphere, during quiet and disturbed magnetic periods. Four subjects are studied in detail: the latitude distribution of the varied auroral forms and their relations to external magnetosphere; the time coefficients related to precipitations, the form and the dynamic of the diffuse precipitation equatorial frontier; the precipitation effect on the ionosphere concentration. The last part of the chapter shows that the plasma convection in the magnetosphere, associated to wave-particle interactions near the equatorial accounts for the principal characteristics of the evening sector diffuse electronic precipitations. The second chapter deals with subauroral precipitations of low energy ions, after the magnetospheric substorms, in the high latitude regions of the morning sector [fr

  5. The convection electric field in auroral substorms

    DEFF Research Database (Denmark)

    Gjerløv, Jesper Wittendorff; Hoffman, R.A.

    2001-01-01

    Dynamics Explorer 2 (DE 2) electric field and ion drift data are used in a statistical study of the ionospheric convection electric field in bulge-type auroral substorms. Thirty-one individual DE 2 substorm crossings were carefully selected and organized by the use of global auroral images obtained...... this database enabled us to compile a model of the ionospheric convection electric field. The characteristics of the premidnight convection reversal show a pronounced local time dependency. Far west of the surge it is a fairly well defined point reversal or convection shear. Approaching the surge and within...... the surge it is a region of weak electric fields increasing in width toward midnight that separates regions of equatorward and poleward electric fields. Therefore we adopt the term Harang region rather than the Harang discontinuity for the premidnight convection reversal. A relatively narrow convection...

  6. Acceleration of auroral electrons by waves

    International Nuclear Information System (INIS)

    Hall, D.S.

    1983-06-01

    The evolution of the auroral electron distribution function as the electrons traverse a region of plasma turbulence is discussed. Electron measurements are used to illustrate that if the energy densities of the waves associated with the turbulence are distributed in a particular way, various features of the electron distributions can be accounted for by changes in the details of the wave spectra without changes in the overall form. (author)

  7. Statistical study of auroral omega bands

    Directory of Open Access Journals (Sweden)

    N. Partamies

    2017-09-01

    Full Text Available The presence of very few statistical studies on auroral omega bands motivated us to test-use a semi-automatic method for identifying large-scale undulations of the diffuse aurora boundary and to investigate their occurrence. Five identical all-sky cameras with overlapping fields of view provided data for 438 auroral omega-like structures over Fennoscandian Lapland from 1996 to 2007. The results from this set of omega band events agree remarkably well with previous observations of omega band occurrence in magnetic local time (MLT, lifetime, location between the region 1 and 2 field-aligned currents, as well as current density estimates. The average peak emission height of omega forms corresponds to the estimated precipitation energies of a few keV, which experienced no significant change during the events. Analysis of both local and global magnetic indices demonstrates that omega bands are observed during substorm expansion and recovery phases that are more intense than average substorm expansion and recovery phases in the same region. The omega occurrence with respect to the substorm expansion and recovery phases is in a very good agreement with an earlier observed distribution of fast earthward flows in the plasma sheet during expansion and recovery phases. These findings support the theory that omegas are produced by fast earthward flows and auroral streamers, despite the rarity of good conjugate observations.

  8. EISCAT as a tristatic auroral radar

    International Nuclear Information System (INIS)

    Schlegel, K.; Moorcroft, D.R.

    1989-01-01

    The authors have used the European Incoherent Scatter radar (EISCAT) in a mode which allows them to use it as a tristatic auroral radar. Observing at an elevation of less than 10 degree with the Tromsoe beam, they achieved magnetic aspect angles between 4 degree and 6 degree at 105 km altitude and recorded coherent echoes simultaneously from all three sites. The backscattered power for these echoes is up to 3 orders of magnitude higher than typical incoherent scatter echoes. Contrary to most existing auroral radars, they can calibrate the coherent echo strength and thus determine absolute values of the coherent backscatter cross section. Moreover, switching the common volume in short time intervals from E to F region heights, permits the determination of the E x B drift vector almost simultaneously with the E region coherent scattering measurements. This opens unique possibilities to study the E region plasma instabilities and their driving force. The main aim of this paper is to describe the capabilities of EISCAT as an auroral radar and to present and discuss results in terms of coherent backscatter cross sections, coherent spectra shape, irregularity phase velocities, and aspect angle dependence. In forthcoming papers several of these topics will be explored in more detail

  9. New imaging spectrometer for auroral research

    International Nuclear Information System (INIS)

    Rairden, R.; Swenson, G.

    1994-01-01

    A Loral 1024 x 1024 CCD array with 15-micron pixels has been incorporated as the focal plane detector in a new imaging spectrometer for auroral research. The large format low-noise CCD provides excellent dynamic range and signal to noise characteristics with image integration times on the order of 60 seconds using f/1.4 camera optics. Further signal enhancement is achieved through on-CCD pixel binning. In the nominal binned mode the instrument wavelength resolution varies from 15 to 30 angstrom across the 5000 to 8600 angstrom spectral range. Images are acquired and stored digitally on a Macintosh computer. This instrument was operated at a field site in Godhavn, Greenland during the past two winters (1993, 1994) to measure the altitude distribution of the various spectral emissions within auroral arcs. The height resolution on an auroral feature 300 km distant is ∼1 km. Examples of these measurements are presented here in snapshot and summary image formats illustrating the wealth of quantitative information provided by this new imaging spectrometer

  10. A study of auroral activity in the nightside polar cap

    International Nuclear Information System (INIS)

    Wu, Q.

    1989-01-01

    Using various ground observations at South Pole, Antarctica (invariant magnetic latitude -74 degree) and its conjugate point, Frobisher Bay, Canada, the author has studied the following aspects of nightside polar cap auroral activity: the appearance and disappearance of polar cap auroras (diffuse and discrete) associated with substorms and interplanetary magnetic field (IMF) variations; auroral optical emission line intensities; and the seasonal variation of auroral conjugacy. The observations show that the polar cap auroras usually fade away before the expansive phase of a substorm and bright auroral arcs reach high latitude (-74 degree) near the recovery phase. Just before the auroras fade away the discrete polar cap auroral arcs, which are usually on the poleward boundary of the diffuse aurora, intensify for 1 to 2 minutes. The observations also indicate the IMF may have stronger control over polar cap auroral activity than do substorms. A search for energy spectral variation of precipitating electrons using the intensities of 630.0 nm (0) and 427 nm (N 2 + ) auroral emission lines reveals no dramatic changes in the energy spectrum; instead, the data show possible atmospheric scattering and geometric effects on the photometric measurements while the bright auroral arc is moving into the polar cap. The conjugate observations show that the stormtime auroral electrojet current, which is associated with the bright auroral arc, in most cases reaches higher (lower) latitudes in the winter (summer) hemisphere. An asymmetric plasma sheet (with respect to the neutral sheet) is proposed, which expands deeper into the winter lobe, under a tilted geomagnetic dipole. Accordingly, the winter polar cap would have smaller area and the auroral electrojet would be at higher latitude

  11. Ground-based and satellite observations of high-latitude auroral activity in the dusk sector of the auroral oval

    Directory of Open Access Journals (Sweden)

    K. Kauristie

    Full Text Available On 7 December 2000, during 13:30–15:30 UT the MIRACLE all-sky camera at Ny Ålesund observed auroras at high-latitudes (MLAT ~ 76 simultaneously when the Cluster spacecraft were skimming the magnetopause in the same MLT sector (at ~ 16:00–18:00 MLT. The location of the auroras (near the ionospheric convection reversal boundary and the clear correlation between their dynamics and IMF variations suggests their close relationship with R1 currents. Consequently, we can assume that the Cluster spacecraft were making observations in the magnetospheric region associated with the auroras, although exact magnetic conjugacy between the ground-based and satellite observations did not exist. The solar wind variations appeared to control both the behaviour of the auroras and the magnetopause dynamics. Auroral structures were observed at Ny Ålesund especially during periods of negative IMF BZ. In addition, the Cluster spacecraft experienced periodic (T ~ 4 - 6 min encounters between magnetospheric and magnetosheath plasmas. These undulations of the boundary can be interpreted as a consequence of tailward propagating magnetopause surface waves. Simultaneous dusk sector ground-based observations show weak, but discernible magnetic pulsations (Pc 5 and occasionally periodic variations (T ~ 2 - 3 min in the high-latitude auroras. In the dusk sector, Pc 5 activity was stronger and had characteristics that were consistent with a field line resonance type of activity. When IMF BZ stayed positive for a longer period, the auroras were dimmer and the spacecraft stayed at the outer edge of the magnetopause where they observed electromagnetic pulsations with T ~ 1 min. We find these observations interesting especially from the viewpoint of previously presented studies relating poleward-moving high-latitude auroras with pulsation activity and MHD waves propagating at the magnetospheric boundary layers

  12. On the possibility of auroral remote sensing with the Viking ultraviolet imager

    International Nuclear Information System (INIS)

    Steele, D.P.; McEwen, D.J.; Murphree, J.S.

    1992-01-01

    An investigation was carried out to assess the value of ultraviolet auroral images for remote sensing of electron precipitation. The authors compared auroral images, obtained by both cameras of the Viking Ultraviolet Imager during April and early May 1986, with simultaneous measurements of electron precipitation from the DMSP F7 and HiLat satellites at low altitudes above the auroral zone. The electron data were averaged over the image pixels and were used to normalize the imager signals to unit electron energy flux. The resulting quantity, here termed the effective sensitivity, showed large scatter about the mean values for both cameras that tended to mask any energy dependence except a decrease at electron energies above 6 keV. The mean effective sensitivities were 11.3 ± 1.1 digitization numbers (DN)/(erg cm -2 s -1 ) for the Lyman-Birge-Hopfield (LBH) camera and 15.9 ± 2.5 DN/(erg cm -2 s -1 ) for the 1304 camera. The signal ratio in simultaneous images from both cameras was insensitive to electron energy in the two cases examined, consistent with the weak energy dependences of the effective sensitivities. Unusually high LBH camera effective sensitivities of 45-60 DN/(erg cm -2 s -1 ) were obtained during several orbits on May 2 and 3. They conclude that images from either Viking camera may be used to infer the instantaneous distribution of electron energy deposition, with roughly 50% accuracy

  13. Velocity of small-scale auroral ionospheric current systems over ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    a sub-auroral location during magnetically quiet conditions (ΣKp < 10), but attains an auroral position when the ..... ary 1995, the authors thank the expedition leader, .... 6 245–249. Tighe W G and Rostoker G 1981 Characteristics of west-.

  14. Extreme winds and waves for offshore turbines: Coupling atmosphere and wave modeling for design and operation in coastal zones

    DEFF Research Database (Denmark)

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

    modeling for oshore wind farms. This modeling system consists of the atmospheric Weather Research and Forecasting (WRF) model, the wave model SWAN and an interface the Wave Boundary Layer Model WBLM, within the framework of coupled-ocean-atmosphere-wave-sediment transport modeling system COAWST...... (Hereinafter the WRF-WBLM-SWAN model). WBLM is implemented in SWAN, and it calculates stress and kinetic energy budgets in the lowest atmospheric layer where the wave-induced stress is introduced to the atmospheric modeling. WBLM ensures consistent calculation of stress for both the atmospheric and wave......, which can aect the choice of the off-shore wind turbine type. X-WiWa examined various methodologies for wave modeling. The offline coupling system using atmospheric data such as WRF or global reanalysis wind field to the MIKE 21 SW model has been improved with considerations of stability, air density...

  15. Custom auroral electrojet indices calculated by using MANGO value-added services

    Science.gov (United States)

    Bargatze, L. F.; Moore, W. B.; King, T. A.

    2009-12-01

    A set of computational routines called MANGO, Magnetogram Analysis for the Network of Geophysical Observatories, is utilized to calculate customized versions of the auroral electrojet indices, AE, AL, and AU. MANGO is part of an effort to enhance data services available to users of the Heliophysics VxOs, specifically for the Virtual Magnetospheric Observatory (VMO). The MANGO value-added service package is composed of a set of IDL routines that decompose ground magnetic field observations to isolate secular, diurnal, and disturbance variations of magnetic field disturbance, station-by-station. Each MANGO subroutine has been written in modular fashion to allow "plug and play"-style flexibility and each has been designed to account for failure modes and noisy data so that the programs will run to completion producing as much derived data as possible. The capabilities of the MANGO service package will be demonstrated through their application to the study of auroral electrojet current flow during magnetic substorms. Traditionally, the AE indices are calculated by using data from about twelve ground stations located at northern auroral zone latitudes spread longitudinally around the world. Magnetogram data are corrected for secular variation prior to calculating the standard version of the indices but the data are not corrected for diurnal variations. A custom version of the AE indices will be created by using the MANGO routines including a step to subtract diurnal curves from the magnetic field data at each station. The custom AE indices provide more accurate measures of auroral electrojet activity due to isolation of the sunstorm electrojet magnetic field signiture. The improvements in the accuracy of the custom AE indices over the tradition indices are largest during the northern hemisphere summer when the range of diurnal variation reaches its maximum.

  16. Global Coupled Model Studies of The Jovian Upper Atmosphere In Response To Electron Precipitation and Ionospheric Convection Within The Auroral Region.

    Science.gov (United States)

    Millward, G. H.; Miller, S.; Aylward, A. D.

    The Jovian Ionospheric Model (JIM) is a global three-dimensional model of Jupiter's coupled ionosphere and thermosphere, developed at University College London. Re- cently, the model has been used to investigate the atmospheric response to electron precipitation within the high-latitude auroral region. A series of simulations have been performed in which the model atmosphere is subjected to monochromatic precipitat- ing electrons of varying number flux and initial energy and, in addition, to various degrees of ionospheric convection. The auroral ionospheric conductivity which re- sults is shown to be strongly non-linear with respect to the incoming electron energy, with a maximum observed for incident particles of initial energy 60 KeV. Electrons with higher energies penetrate the thermospheric region completely, whilst electrons of lower energy (say 10 keV) produce ionisation at higher levels in the atmosphere which are less less condusive to the creation of ionospheric conductivity. Studies of the thermospheric winds with the auroral region show that zonal winds (around the auroral oval) can attain values of around 70% of the driving zonal ion velocity. Also the results show that these large neutral winds are limited in vertical extent to the region of large ionospheric conductivity, tailing off markedly at altitudes above this. The latest results from this work will be presented, and the implications for Jovian magnetospheric-ionospheric coupling will be discussed.

  17. A theory of auroral hiss and implications on the origin of auroral electrons

    International Nuclear Information System (INIS)

    Swift, D.W.; Kan, J.R.

    1975-01-01

    A theory for auroral hiss is developed based on the existence of a beam of energetic particles that is also believed responsible for the visual aurora. A dispersion relation for electromagnetic waves in a plasma consisting of an electron beam and a background plasma is derived. The Hermitian part of the dispersion relation is assumed to be governed by the denser cold background plasma, whereas the anti-Hermitian part is governed by the electron beam. It is shown that the electron beam can excite an electron whistler mode instability near the resonance cone by the Landau interaction because near the resonance cone the phase velocity of the wave can be made arbitrarily small. The instability can be excited at all frequencies between the lower hybrid resonance and the electron plasma frequencies. The wave normal angles along the resonance curve vary between 0degree and 90degree with respect to the magnetic field. Waves whose wave normal angles are small have the largest growth rates and are most likely to grow to observable amplitudes. Only waves generated within a few degrees of the vertical can reach the ground. The results of the calculations are applied to auroral hiss observations. From the fact that auroral hiss is observed on the ground at frequencies less than 10 kHz it is concluded that at least some of the auroral hiss is generated at altitudes where the ambient electron density is of the order of 1 cm -3 . This suggests that auroral electrons are energized in regions where the ambient density is of the order of 1 cm -3 or less

  18. Computer simulation of auroral kilometric radiation

    International Nuclear Information System (INIS)

    Wagner, J.S.; Tajima, T.; Lee, L.C.; Wu, C.S.

    1983-01-01

    We study the generation of auroral kilometric radiation (AKR) using relativistic, electromagnetic, particle simulations. The AKR source region is modeled by two electron populations in the simulation: a cold (200 eV) Maxwellian component and a hot (5-20 keV) population possessing a loss-cone feature. The loss cone distribution is found to be unstable to the cyclotron maser instability. The fast extraordinary (X-mode) waves dominate the radiation and saturate when resonant particles diffuse into the loss-cone via turbulent scattering of the particles by the amplified X-mode radiation

  19. Local Geomagnetic Indices and the Prediction of Auroral Power

    Science.gov (United States)

    Newell, P. T.; Gjerloev, J. W.

    2014-12-01

    As the number of magnetometer stations and data processing power increases, just how auroral power relates to geomagnetic observations becomes a quantitatively more tractable question. This paper compares Polar UVI auroral power observations during 1997 with a variety of geomagnetic indices. Local time (LT) versions of the SuperMAG auroral electojet (SME) are introduced and examined, along with the corresponding upper and lower envelopes (SMU and SML). Also, the East-West component, BE, is investigated. We also consider whether using any of the local indices is actually better at predicting local auroral power than a single global index. Each index is separated into 24 LT indices based on a sliding 3-h MLT window. The ability to predict - or better reconstruct - auroral power varies greatly with LT, peaking at 1900 MLT, where about 75% of the variance (r2) can be predicted at 1-min cadence. The aurora is fairly predictable from 1700 MLT - 0400 MLT, roughly the region in which substorms occur. Auroral power is poorly predicted from auroral electrojet indices from 0500 MLT - 1500 MLT, with the minima at 1000-1300 MLT. In the region of high predictability, the local variable which works best is BE, in contrast to long-standing expectations. However using global SME is better than any local variable. Auroral power is best predicted by combining global SME with a local index: BE from 1500-0200 MLT, and either SMU or SML from 0300-1400 MLT. In the region of the diffuse aurora, it is better to use a 30 min average than the cotemporaneous 1-min SME value, while from 1500-0200 MLT the cotemporaneous 1-min SME works best, suggesting a more direct physical relationship with the auroral circuit. These results suggest a significant role for discrete auroral currents closing locally with Pedersen currents.

  20. Short-term ecological effects of an offshore wind farm in the Dutch coastal zone. A compilation

    Energy Technology Data Exchange (ETDEWEB)

    Lindeboom, H.J.; Brasseur, S.; Leopold, M.; Scheidat, M. [IMARES, PO Box 167, 1790 AD Den Burg (Netherlands); Kouwenhoven, H.J. [NoordzeeWind, 2e Havenstraat 5b, 1976 CE IJmuiden (Netherlands); Bergman, M.J.N.; Daan, R. [Royal NIOZ, PO Box 59, 1790 AB Den Burg (Netherlands); Bouma, S.; Fijn, R.C.; Dirksen, S.; Krijgsveld, K.L. [Bureau Waardenburg, PO Box 365, 4100 AJ Culemborg (Netherlands); De Haan, D.; Van Hal, R.; Hille Ris Lambers, R.; Ter Hofstede, R. [IMARES, PO Box 68, 1970 AB IJmuiden (Netherlands)

    2011-07-15

    The number of offshore wind farms is increasing rapidly, leading to questions about the environmental impact of such farms. In the Netherlands, an extensive monitoring programme is being executed at the first offshore wind farm (Offshore Windfarm Egmond aan Zee, OWEZ). This letter compiles the short-term (two years) results on a large number of faunal groups obtained so far. Impacts were expected from the new hard substratum, the moving rotor blades, possible underwater noise and the exclusion of fisheries. The results indicate no short-term effects on the benthos in the sandy area between the generators, while the new hard substratum of the monopiles and the scouring protection led to the establishment of new species and new fauna communities. Bivalve recruitment was not impacted by the OWEZ wind farm. Species composition of recruits in OWEZ and the surrounding reference areas is correlated with mud content of the sediment and water depth irrespective the presence of OWEZ. Recruit abundances in OWEZ were correlated with mud content, most likely to be attributed not to the presence of the farm but to the absence of fisheries. The fish community was highly dynamic both in time and space. So far, only minor effects upon fish assemblages especially near the monopiles have been observed. Some fish species, such as cod, seem to find shelter inside the farm. More porpoise clicks were recorded inside the farm than in the reference areas outside the farm. Several bird species seem to avoid the park while others are indifferent or are even attracted. The effects of the wind farm on a highly variable ecosystem are described. Overall, the OWEZ wind farm acts as a new type of habitat with a higher biodiversity of benthic organisms, a possibly increased use of the area by the benthos, fish, marine mammals and some bird species and a decreased use by several other bird species.

  1. Short-term ecological effects of an offshore wind farm in the Dutch coastal zone; a compilation

    Energy Technology Data Exchange (ETDEWEB)

    Lindeboom, H J; Brasseur, S; Leopold, M; Scheidat, M [IMARES, PO Box 167, 1790 AD Den Burg (Netherlands); Kouwenhoven, H J [NoordzeeWind, 2e Havenstraat 5b, 1976 CE IJmuiden (Netherlands); Bergman, M J N; Daan, R [Royal NIOZ, PO Box 59, 1790 AB Den Burg (Netherlands); Bouma, S; Fijn, R C; Dirksen, S; Krijgsveld, K L [Bureau Waardenburg, PO Box 365, 4100 AJ Culemborg (Netherlands); De Haan, D; Van Hal, R; Hille Ris Lambers, R; Ter Hofstede, R, E-mail: han.lindeboom@wur.nl [IMARES, PO Box 68, 1970 AB IJmuiden (Netherlands)

    2011-07-15

    The number of offshore wind farms is increasing rapidly, leading to questions about the environmental impact of such farms. In the Netherlands, an extensive monitoring programme is being executed at the first offshore wind farm (Offshore Windfarm Egmond aan Zee, OWEZ). This letter compiles the short-term (two years) results on a large number of faunal groups obtained so far. Impacts were expected from the new hard substratum, the moving rotor blades, possible underwater noise and the exclusion of fisheries. The results indicate no short-term effects on the benthos in the sandy area between the generators, while the new hard substratum of the monopiles and the scouring protection led to the establishment of new species and new fauna communities. Bivalve recruitment was not impacted by the OWEZ wind farm. Species composition of recruits in OWEZ and the surrounding reference areas is correlated with mud content of the sediment and water depth irrespective the presence of OWEZ. Recruit abundances in OWEZ were correlated with mud content, most likely to be attributed not to the presence of the farm but to the absence of fisheries. The fish community was highly dynamic both in time and space. So far, only minor effects upon fish assemblages especially near the monopiles have been observed. Some fish species, such as cod, seem to find shelter inside the farm. More porpoise clicks were recorded inside the farm than in the reference areas outside the farm. Several bird species seem to avoid the park while others are indifferent or are even attracted. The effects of the wind farm on a highly variable ecosystem are described. Overall, the OWEZ wind farm acts as a new type of habitat with a higher biodiversity of benthic organisms, a possibly increased use of the area by the benthos, fish, marine mammals and some bird species and a decreased use by several other bird species.

  2. Short-term ecological effects of an offshore wind farm in the Dutch coastal zone. A compilation

    International Nuclear Information System (INIS)

    Lindeboom, H.J.; Brasseur, S.; Leopold, M.; Scheidat, M.; Kouwenhoven, H.J.; Bergman, M.J.N.; Daan, R.; Bouma, S.; Fijn, R.C.; Dirksen, S.; Krijgsveld, K.L.; De Haan, D.; Van Hal, R.; Hille Ris Lambers, R.; Ter Hofstede, R.

    2011-01-01

    The number of offshore wind farms is increasing rapidly, leading to questions about the environmental impact of such farms. In the Netherlands, an extensive monitoring programme is being executed at the first offshore wind farm (Offshore Windfarm Egmond aan Zee, OWEZ). This letter compiles the short-term (two years) results on a large number of faunal groups obtained so far. Impacts were expected from the new hard substratum, the moving rotor blades, possible underwater noise and the exclusion of fisheries. The results indicate no short-term effects on the benthos in the sandy area between the generators, while the new hard substratum of the monopiles and the scouring protection led to the establishment of new species and new fauna communities. Bivalve recruitment was not impacted by the OWEZ wind farm. Species composition of recruits in OWEZ and the surrounding reference areas is correlated with mud content of the sediment and water depth irrespective the presence of OWEZ. Recruit abundances in OWEZ were correlated with mud content, most likely to be attributed not to the presence of the farm but to the absence of fisheries. The fish community was highly dynamic both in time and space. So far, only minor effects upon fish assemblages especially near the monopiles have been observed. Some fish species, such as cod, seem to find shelter inside the farm. More porpoise clicks were recorded inside the farm than in the reference areas outside the farm. Several bird species seem to avoid the park while others are indifferent or are even attracted. The effects of the wind farm on a highly variable ecosystem are described. Overall, the OWEZ wind farm acts as a new type of habitat with a higher biodiversity of benthic organisms, a possibly increased use of the area by the benthos, fish, marine mammals and some bird species and a decreased use by several other bird species.

  3. Wideband satellite phase coherent beacon observations at auroral and equatorial latitudes - A review

    International Nuclear Information System (INIS)

    Rino, C.L.; Livingston, R.C.; Cousins, M.D.; Fair, B.C.

    1978-01-01

    This paper presents a brief review of some of the principal results from the first two years of operation of the Wideband satellite which transmits phase-coherent signals from S-band to VHF. The auroral zone data show narrow regions of enhanced scintillation well equatorward of the discrete aurora. Such enhancements can be explained as a purely geometrical effect if the irregularities within the major precipitation regions have a sheet-like structure. Evidence of a localized irregularity source at the poleward boundary of the plasma trough is also found. Model computations are discussed and applied to the interpretation of equatorial data

  4. Large-Scale Structure and Dynamics of the Sub-Auroral Polarization Stream (SAPS)

    Science.gov (United States)

    Baker, J. B. H.; Nishitani, N.; Kunduri, B.; Ruohoniemi, J. M.; Sazykin, S. Y.

    2017-12-01

    The Sub-Auroral Polarization Stream (SAPS) is a narrow channel of high-speed westward ionospheric convection which appears equatorward of the duskside auroral oval during geomagnetically active periods. SAPS is generally thought to occur when the partial ring current intensifies and enhanced region-2 field-aligned currents (FACs) are forced to close across the low conductance region of the mid-latitude ionospheric trough. However, recent studies have suggested SAPS can also occur during non-storm periods, perhaps associated with substorm activity. In this study, we used measurements from mid-latitude SuperDARN radars to examine the large-scale structure and dynamics of SAPS during several geomagnetically active days. Linear correlation analysis applied across all events suggests intensifications of the partial ring current (ASYM-H index) and auroral activity (AL index) are both important driving influences for controlling the SAPS speed. Specifically, SAPS flows increase, on average, by 20-40 m/s per 10 nT of ASYM-H and 10-30 m/s per 100 nT of AL. These dependencies tend to be stronger during the storm recovery phase. There is also a strong local time dependence such that the strength of SAPS flows decrease by 70-80 m/s for each hour of local time moving from dusk to midnight. By contrast, the evidence for direct solar wind control of SAPS speed is much less consistent, with some storms showing strong correlations with the interplanetary electric field components and/or solar wind dynamic pressure, while others do not. These results are discussed in the context of recent simulation results from the Rice Convection Model (RCM).

  5. 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.

  6. Electric field mapping and auroral Birkeland currents

    International Nuclear Information System (INIS)

    Kaufmann, R.L.; Larson, D.J.

    1989-01-01

    Magnetic field lines, electric fields and equipotentials have been mapped throughout the magnetosphere in the vicinity of strong Birkeland currents. It was found that a uniform electric field at either the ionospheric or the equatorial end of a field line can map to a highly structured field at the other end if strong Birkeland currents are located nearby. The initiation of sheet currents of the region 1 - region 2 scale size and intensity resulted in magnetic field line displacements of about 1/2 hour in local time between equatorial and ionospheric end points. As a result, a uniform dawn to dusk electric field at the equator mapped to an ionospheric electric field with strong inward pointing components in the dusk hemisphere. Similar distortions were produced by Birkeland currents associated with narrow east-west-aligned auroral arcs. A specific model for the auroral current system, based on ionospheric measurements during a large substorm, was used to study effects seen during disturbed periods. An iterative procedure was developed to generate a self-consistent current system even in the presence of highly twisted field lines. The measured ionospheric electric field was projected tot he equatorial plane in the presence of the model Birkeland current system. Several physical processes were seen to influence ionospheric and equatorial electric fields, and the associated plasma convection, during a substorm

  7. Bremsstrahlung X rays from Jovian auroral electrons

    International Nuclear Information System (INIS)

    Barbosa, D.D.

    1990-01-01

    The spectrum of X rays from the planet Jupiter is calculated according to an auroral electron beam model. The electrons are assumed to be accelerated by a field-aligned potential drop and penetrate into the atmosphere as a Maxwellian beam of primaries which are scattered, degraded in energy, and merged with a population of ionization secondaries having a power law energy distribution. The soft X rays observed by the Einstein Observatory satelltie are due to bremsstrahlung from the sedondary electrons in the H 2 atmosphere. A good match to the X ray data is obtained if the power law spectral index of the secondary electrons, γ e , is ≅ 2, yielding a power law slope for the photon flux γ X = γ e + 1 ≅ 3. The X ray intensity is best reconciled with a beam of primaries having a characteristic energy 30-100 keV and penetrating the homopause with an auroral energy flux typically of 10-20 ergs cm -2 s -1 but no greater than 50 ergs cm -2 s -1

  8. Cluster in the Auroral Acceleration Region

    Science.gov (United States)

    Pickett, Jolene S.; Fazakerley, Andrew N.; Marklund, Gorun; Dandouras, Iannis; Christopher, Ivar W.; Kistler, Lynn; Lucek, Elizabeth; Masson, Arnaud; Taylor, Matthew G.; Mutel, Robert L.; hide

    2010-01-01

    Due to a fortuitous evolution of the Cluster orbit, the Cluster spacecraft penetrated for the first time in its mission the heart of Earth's auroral acceleration region (AAR) in December 2009 and January 2010. During this time a special AAR campaign was carried out by the various Cluster instrument teams with special support from ESA and NASA facilities. We present some of the first multi-spacecraft observations of the waves, particles and fields made during that campaign. The Cluster spacecraft configuration during these AAR passages was such that it allowed us to explore the differences in the signatures of waves, particles, and fields on the various spacecraft in ways not possible with single spacecraft. For example, one spacecraft was more poleward than the other three (C2), one was at higher altitude (C1), and one of them (0) followed another (C4) through the AAR on approximately the same track but delayed by three minutes. Their separations were generally on the order of a few thousand km or less and occasionally two of them were lying along the same magnetic field line. We will show some of the first analyses of the data obtained during the AAR campaign, where upward and downward current regions, and the waves specifically associated with those regions, as well as the auroral cavities, were observed similarly and differently on the various spacecraft, helping us to explore the spatial, as well as the temporal, aspects of processes occurring in the AAR.

  9. Carl Størmer Auroral Pioneer

    CERN Document Server

    Egeland, Alv

    2013-01-01

    This biography summarizes the seminal contributions to auroral and space science of Carl Størmer (1874 - 1957). He was the first to develop precise photographic methods to calculate heights and morphologies of diverse auroral forms during four solar cycles. Størmer independently devised numerical techniques to determine the trajectories of high-energy charged particles allowed and forbidden in the Earth’s magnetic field. His theoretical analyses explained cosmic ray access to the upper atmosphere, 20 years before they were identified by other scientists. Størmer’s crowning achievement, “The Polar Aurora,” published when he was 81 years old, stands to this day as a regularly cited guide in graduate-level courses on space physics.   The authors present the life of this prodigious scientist in relation to the cultural life of early 20th century in Norway and to the development of the space sciences in the post-Sputnik era.

  10. Enabling Future Large Searches for Exoplanet Auroral Emission with the EPIC Correlator Architecture

    Science.gov (United States)

    Thyagarajan, Nithyanandan; Beardsley, Adam P.; Bowman, Judd D.; Morales, Miguel F.

    2017-05-01

    Extrasolar planets are expected to emit strong ``auroral'' emission at radio frequencies generated by the interaction of the host star's stellar winds with the planet's magnetosphere through electron-cyclotron maser emission. This transient emission lasts a few seconds to days and is almost fully circularly polarized. Detecting this emission in exoplanets is a critical probe of their magnetospheres and thus their interior compositions and habitability. The intensity and detectability of the emission depends on the suitability of many factors to the observing parameters such as the strength of the stellar wind power, the planetary magnetosphere cross-section, the highly beamed and coherent nature of electron-cyclotron emission, and narrow ranges of the planet's orbital phase. Large areas of sky must be surveyed continuously to high sensitivity to detect auroral emission. Next-generation radio telescopes with wide fields of view, large collecting areas and high efficiency are needed for these searches. This poses challenges to traditional correlator architectures whose computational cost scales as the square of the number of antennas. I will present a novel radio aperture synthesis imaging architecture - E-field Parallel Imaging Correlator (EPIC) - whose all-sky and full Stokes imaging capabilities will not only address the aforementioned factors preventing detection but also solve the computational challenges posed by large arrays. Compared to traditional imaging, EPIC is inherently fast and thus presents the unique advantage of probing transient timescales ranging orders of magnitude from tens of microseconds to days at no additional cost.

  11. Validation of a CFD model with a synchronized triple-lidar system in the wind turbine induction zone

    DEFF Research Database (Denmark)

    Meyer Forsting, Alexander Raul; Troldborg, Niels; Murcia Leon, Juan Pablo

    2017-01-01

    and temporal uncertainty of the measurements is quantified and propagated through the data processing. For all velocity components the maximal difference between measurements and model are below 4.5% relative to the average wind speed for most of the validation space. This applies to both mean and standard...... deviation. One rotor radius upstream the difference reaches maximally 1.3% for the axial component....

  12. Cassini UVIS Auroral Observations in 2016 and 2017

    Science.gov (United States)

    Pryor, Wayne R.; Esposito, Larry W.; Jouchoux, Alain; Radioti, Aikaterini; Grodent, Denis; Gustin, Jacques; Gerard, Jean-Claude; Lamy, Laurent; Badman, Sarah; Dyudina, Ulyana A.; Cassini UVIS Team, Cassini VIMS Team, Cassini ISS Team, HST Saturn Auroral Team

    2017-10-01

    In 2016 and 2017, the Cassini Saturn orbiter executed a final series of high-inclination, low-periapsis orbits ideal for studies of Saturn's polar regions. The Cassini Ultraviolet Imaging Spectrograph (UVIS) obtained an extensive set of auroral images, some at the highest spatial resolution obtained during Cassini's long orbital mission (2004-2017). In some cases, two or three spacecraft slews at right angles to the long slit of the spectrograph were required to cover the entire auroral region to form auroral images. We will present selected images from this set showing narrow arcs of emission, more diffuse auroral emissions, multiple auroral arcs in a single image, discrete spots of emission, small scale vortices, large-scale spiral forms, and parallel linear features that appear to cross in places like twisted wires. Some shorter features are transverse to the main auroral arcs, like barbs on a wire. UVIS observations were in some cases simultaneous with auroral observations from the Cassini Imaging Science Subsystem (ISS) the Cassini Visual and Infrared Mapping Spectrometer (VIMS), and the Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS) that will also be presented.

  13. The size of the auroral belt during magnetic storms

    Directory of Open Access Journals (Sweden)

    N. Yokoyama

    1998-05-01

    Full Text Available Using the auroral boundary index derived from DMSP electron precipitation data and the Dst index, changes in the size of the auroral belt during magnetic storms are studied. It is found that the equatorward boundary of the belt at midnight expands equatorward, reaching its lowest latitude about one hour before Dst peaks. This time lag depends very little on storm intensity. It is also shown that during magnetic storms, the energy of the ring current quantified with Dst increases in proportion to Le–3, where Le is the L-value corresponding to the equatorward boundary of the auroral belt designated by the auroral boundary index. This means that the ring current energy is proportional to the ion energy obtained from the earthward shift of the plasma sheet under the conservation of the first adiabatic invariant. The ring current energy is also proportional to Emag, the total magnetic field energy contained in the spherical shell bounded by Le and Leq, where Leq corresponds to the quiet-time location of the auroral precipitation boundary. The ratio of the ring current energy ER to the dipole energy Emag is typically 10%. The ring current leads to magnetosphere inflation as a result of an increase in the equivalent dipole moment.Key words. Ionosphere (Auroral ionosphere · Magnetospheric physics (Auroral phenomena; storms and substorms

  14. Reconstruction of energetic electron spectra in the upper atmosphere: balloon observations of auroral X-rays coordinated with measurements from the Eiscat radar

    International Nuclear Information System (INIS)

    Olafsson, K.J.

    1990-01-01

    Energetic electron precipitation in the auroral zone has been studied using coordinated auroral X-ray measurements from balloons, altitude profiles of the ionospheric electron density measured by the EISCAT radar above the balloons, and cosmic noise absorption data from the Scandinavian riometer network. The data were obtained during the coordinated EISCAT and balloon observation campaign in August 1984. A method by which an estimate of the energy spectrum of precipitating energetic electrons can be obtained from balloon measurements of bremsstrahlung X-rays is described. The energy spectral variation of both the X-ray fluxes and the primary precipitating electrons were examined for two precipitation events in the morning sector. As far as reasonably can be concluded from observations of magnetic activity in the auroral zone, and from the temporal development of the energy spectra, the two precipitation events can be interpreted in the frame of present models of energetic electron precipitation on the morning side of the auroral zone. 96 refs

  15. Auroral omens of the American Civil War

    Science.gov (United States)

    Love, Jeffrey J.

    2014-01-01

    Aurorae are a splendid night-time sight: coruscations of green, purple, and red fluorescent light in the form of gently wafting ribbons, billowing curtains, and flashing rays. Mostly seen at high latitudes, in the north aurorae are often called the northern lights or aurora borealis, and, in the south, the southern lights or aurora australis. The mystery of their cause has historically been the subject of wonder. The folklore and mythology of some far-northern civilizations attributed auroral light to celestial deities. And, in ironic contrast with their heavenly beauty, unusual auroral displays, such as those seen on rare occasions at lower southern latitudes, have sometimes been interpreted as portending unfavorable future events. Today we understand aurorae to be a visual manifestation of the dynamic conditions in the space environment surrounding the earth. Important direct evidence in support of this theory came on September 1, 1859. On that day, an English astronomer named Richard Carrington was situated at his telescope, which was pointed at the sun. While observing and sketching a large group of sunspots, he saw a solar flare—intense patches of white light that were superimposed upon the darker sunspot group and which were illuminated for about a minute. One day later, a magnetic storm was recorded at specially designed observatories in Europe, across Russia, and in India. By many measures, the amplitude of magnetic disturbance was the greatest ever recorded. In the United States, the effects of the Carrington storm could be seen as irregular backand-forth deflections of a few degrees in the magnetized needle of a compass. Rapid magnetic variation also induced electric fields in the earth’s conducting lithosphere, and interfered with the operation of telegraph systems. The Carrington magnetic storm, and an earlier storm that had occurred on August 28, 1859, caused spectacular displays of aurora borealis in the night-time sky over the entire United

  16. Ring current and auroral electrojets in connection with interplanetary medium parameters during magnetic storm

    Directory of Open Access Journals (Sweden)

    Y. I. Feldstein

    Full Text Available The relationship between the auroral electrojet indices (AE and the ring current magnetic field (DR was investigated by observations obtained during the magnetic storm on 1-3 April 1973. During the storm main phase the DR development is accompanied by a shift of the auroral electrojets toward the equator. As a result, the standard AE indices calculated on the basis of data from auroral observatories was substantially lower than the real values (AE'. To determine AE' during the course of a storm main phase data from subauroral magnetic observatories should be used. It is shown that the intensity of the indices (AE' which take into account the shift of the electrojets is increased substantially relative to the standard indices during the storm main phase. AE' values are closely correlated with geoeffective solar wind parameters. A high correlation was obtained between AE' and the energy flux into the ring current during the storm main phase. Analysis of magnetic field variations during intervals with intense southward IMF components demonstrates a decrease of the saturation effect of auroral electrojet currents if subauroral stations magnetic field variations are taken into account. This applies both to case studies and statistical data. The dynamics of the electrojets in connection with the development of the ring current and of magnetospheric substorms can be described by the presence (absence of saturation for minimum (maximum AE index values during a 1-h interval. The ring current magnetic field asymmetry (ASY was calculated as the difference between the maximum and minimum field values along a parallel of latitude at low latitudes. The ASY value is closely correlated with geoeffective solar wind parameters and simultaneously is a more sensitive indicator of IMF Bz variations than the symmetric ring current.

  17. Underwater noise from three types of offshore wind turbines: estimation of impact zones for harbor porpoises and harbor seals.

    Science.gov (United States)

    Tougaard, Jakob; Henriksen, Oluf Damsgaard; Miller, Lee A

    2009-06-01

    Underwater noise was recorded from three different types of wind turbines in Denmark and Sweden (Middelgrunden, Vindeby, and Bockstigen-Valar) during normal operation. Wind turbine noise was only measurable above ambient noise at frequencies below 500 Hz. Total sound pressure level was in the range 109-127 dB re 1 microPa rms, measured at distances between 14 and 20 m from the foundations. The 1/3-octave noise levels were compared with audiograms of harbor seals and harbor porpoises. Maximum 1/3-octave levels were in the range 106-126 dB re 1 microPa rms. Maximum range of audibility was estimated under two extreme assumptions on transmission loss (3 and 9 dB per doubling of distance, respectively). Audibility was low for harbor porpoises extending 20-70 m from the foundation, whereas audibility for harbor seals ranged from less than 100 m to several kilometers. Behavioral reactions of porpoises to the noise appear unlikely except if they are very close to the foundations. However, behavioral reactions from seals cannot be excluded up to distances of a few hundred meters. It is unlikely that the noise reaches dangerous levels at any distance from the turbines and the noise is considered incapable of masking acoustic communication by seals and porpoises.

  18. Theoretical model of polar cap auroral arcs

    International Nuclear Information System (INIS)

    Kan, J.R.; Burke, W.J.; USAF, Bedford, MA)

    1985-01-01

    A theory of the polar cap auroral arcs is proposed under the assumption that the magnetic field reconnection occurs in the cusp region on tail field lines during northward interplanetary magnetic field (IMF) conditions. Requirements of a convection model during northward IMF are enumerated based on observations and fundamental theoretical considerations. The theta aurora can be expected to occur on the closed field lines convecting sunward in the central polar cap, while the less intense regular polar cap arcs can occur either on closed or open field lines. The dynamo region for the polar cap arcs is required to be on closed field lines convecting tailward in the plasma sheet which is magnetically connected to the sunward convection in the central polar cap. 43 references

  19. Auroral nitric oxide concentration and infrared emission

    Science.gov (United States)

    Reidy, W. P.; Degges, T. C.; Hurd, A. G.; Stair, A. T., Jr.; Ulwick, J. C.

    1982-05-01

    Rocket-borne measurements of infrared auroral emission by nitric oxide are analyzed. Four rocket flights provided opportunities to measure 5.3- and 2.7-micron NO emission by means of infrared fixed band radiometers and CVF spectrometers, narrow band photometers, and incident energy spectra on various occasions. Analysis of infrared emission profiles and electron flux data indicates the NO density to be significantly enhanced with respect to midlatitude values. NO emission in the fundamental 5.3-micron band is attributed to resonance excitation by warm earth radiation, collisional excitation primarily by O atoms and chemiluminescence from the reaction of N with O2; with an energy efficiency of 0.015. The overtone band emission at 2.7 microns is accounted for by chemiluminescence produced with an energy efficiency of 0.0054. Total photon yield for the chemiluminescence reaction is estimated to range from 1.2 to 2.4 vibrational quanta per NO molecule.

  20. Influence of strong monsoon winds on the water quality around a marine cage-culture zone in a shallow and semi-enclosed bay in Taiwan.

    Science.gov (United States)

    Huang, Yuan-Chao Angelo; Huang, Shou-Chung; Meng, Pei-Jie; Hsieh, Hernyi Justin; Chen, Chaolun Allen

    2012-04-01

    Influences of marine cage culture and monsoonal disturbances, northeasterly (NE) and southwesterly (SW) monsoons on the proximal marine environment were investigated across a gradient of sites in a semi-enclosed bay, Magong Bay (Penghu Islands, Taiwan). Elevated levels of ammonia produced by the cages were the main pollutant and distinguished the cage-culture and intermediary zones (1000 m away from the cages) from the reference zone in the NE monsoon, indicating currents produced by the strong monsoon may have extended the spread of nutrient-enriched waters without necessarily flushing such effluents outside Magong Bay. Moreover, the levels of chlorophyll-a, dissolved oxygen, and turbidity were distinguishable between two seasons, suggesting that resuspension caused by the NE monsoon winds may also influence the water quality across this bay. It indicated that the impacts of marine cage culture vary as a function of distance, and also in response to seasonal movements of water driven by local climatic occurrences. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. Birkeland current flow in a structured auroral arc

    International Nuclear Information System (INIS)

    Casserly, R.T. Jr.

    1975-01-01

    At 0722 UT on 25 February 1972 a Nike-Tomahawk rocket payload was launched over a structured auroral arc which had a visual intensity of greater than or equal to 40 kR. An array of charged particle detectors measured the auroral electrons and protons in the energy range 0.5-20 keV while a cesium vapor magnetometer made vector magnetic field measurements along the rocket's trajectory. Perturbations in the magnetic field profile are inferred to be the result of a system of two electrojets and a pair of oppositely directed Birkeland currents. Movement and structure in the Birkeland current sheets is shown to be due to the presence of fold motion along the visual auroral band. These results are compared to the observations of the other onboard detectors and discussed in the light of related current auroral research

  2. RFP for the Auroral Multiscale Midex (AMM) Mission star tracker

    DEFF Research Database (Denmark)

    Riis, Troels; Betto, Maurizio; Jørgensen, John Leif

    1999-01-01

    This document is in response to the John Hopkins University - Applied Physics Laboratory RFP for the Auroral Multiscale Midex Mission star tracker.It describes the functionality, the requirements and the performance of the ASC Star Tracker.......This document is in response to the John Hopkins University - Applied Physics Laboratory RFP for the Auroral Multiscale Midex Mission star tracker.It describes the functionality, the requirements and the performance of the ASC Star Tracker....

  3. On geomagnetically-induced currents in the Finnish 400 kV power system by an auroral electrojet current

    International Nuclear Information System (INIS)

    Pirjola, R.; Viljanen, A.

    1989-01-01

    The auroral electrojet current flowing in the ionosphere is modeled by a horizontal east-west line current of infinite length. The earth is described by a simple two-layer model. An expression for the earth-surface electric field, which is thus connected with a geomagnetic disturbance in and near the auroral zone, is given. This electric field is considered as external from the viewpoint of the Finnish 400 kV power system, and the resulting geomagnetically-induced currents (GICs) in the system are computed. In the north, i.e. near the electrojet, GICs may have values even in the order of hundreds of amperes. A comparison to GICs produced by an equivalent spatially-constant external electric field is demonstrated. Sometimes the location of the electrojet is further south. This possibility is studied by letting the line current have several different locations above the Finnish power grid

  4. Evidence in the auroral record for secular solar variability

    International Nuclear Information System (INIS)

    Sicoe, G.L.

    1980-01-01

    The historial record of aurorae is continuous and usefully dense for at least the 2000 years. Revival of interest in the secular variability in solar activity motivates a review of the auroral record. The existence of secular variations in the auroral occurrence frequency has been known since the early 1700's, including the existence of a significant attenuation of auroral activity during the Maunder Minimum. Investigation of secular variations prior to the Maunder Minimum is now possible based on six auroral catalogs that have been published within the last 20 years. The catalogs cover the time period from the fifth century B.C. to the seventeenth century A.D. and combine both oriental and European obsertions. Features corresponding to the previously recognized Medieval Minimum, Medieval Maximum, and the Spoerer Minimum are clearly evident in both oriental and European records. The global synchronicity of anomalies in the auroral occurrence frequency is used to argue that they are caused by changes in the level or state of solar activity. The combined catalogs provide a sufficient number of events in the Middle Ages to resolve a quasi-80-year periodicity in the recorded auroral occurrence frequency. Also in the unusually rich intervals of the Middle Ages, clear quasi-10-year periodicities appear in the recorded occurrence frequency wave from. These are most reasonably interpreted as manifestations of the 11-year solar cycle and indicate that the solar cycle was then operative

  5. Numerical simulation of global formation of auroral arcs

    International Nuclear Information System (INIS)

    Miura, A.; Sato, T.

    1980-01-01

    Global simulation of auroral arcs is performed, based on the feedback theory of auroral arcs (Sato, 1978), for a three-dimensionally coupled ionosphere-magnetosphere system which includes two pairs of large-scale Birkeland currents, large-scale polar cap electric fields, and a day-night asymmetry of the electron density distribution. Simulation results have shown that auroral arcs are formed in the dark sector of the auroral oval, more preferentially in the evening sector. They usually appear in multiples with a shape elongating in the east-west direction, each arc being a couple of thousand kilometers in length and 10 to 40 km in width. A pair of small-scale, upward and downward, Birkeland currents is associated with each arc, the density of which becomes 10 to 200 μA/m 2 at 110-km height, and the intensity of the associated electrojet reaches 5 to 20 kA. Each arc is strongly polarized in the direction of the large-scale northsouth current so that the electric field inside the arc is reduced considerably from its ambient value. What controls the formation of auroral arcs (growing speed, locations, arc width, etc.) is examined in detail. For example, the arc width becomes sharper, as the bounce time of the Alfven wave decreases. The overall structure of auroras is largely dependent upon the large-scale Birkeland current, the electric field, and the electron density distribution in the auroral oval

  6. A Wide Field Auroral Imager (WFAI for low Earth orbit missions

    Directory of Open Access Journals (Sweden)

    N. P. Bannister

    2007-03-01

    Full Text Available A comprehensive understanding of the solar wind interaction with Earth's coupled magnetosphere-ionosphere system requires an ability to observe the charged particle environment and auroral activity from the same platform, generating particle and photon image data which are matched in time and location. While unambiguous identification of the particles giving rise to the aurora requires a Low Earth Orbit satellite, obtaining adequate spatial coverage of aurorae with the relatively limited field of view of current space bourne auroral imaging systems requires much higher orbits. A goal for future satellite missions, therefore, is the development of compact, wide field-of-view optics permitting high spatial and temporal resolution ultraviolet imaging of the aurora from small spacecraft in low polar orbit. Microchannel plate optics offer a method of achieving the required performance. We describe a new, compact instrument design which can observe a wide field-of-view with the required spatial resolution. We report the focusing of 121.6 nm radiation using a spherically-slumped, square-pore microchannel plate with a focal length of 32 mm and an F number of 0.7. Measurements are compared with detailed ray-trace simulations of imaging performance. The angular resolution is 2.7±0.2° for the prototype, corresponding to a footprint ~33 km in diameter for an aurora altitude of 110 km and a spacecraft altitude of 800 km. In preliminary analysis, a more recent optic has demonstrated a full width at half maximum of 5.0±0.3 arcminutes, corresponding to a footprint of ~1 km from the same spacecraft altitude. We further report the imaging properties of a convex microchannel plate detector with planar resistive anode readout; this detector, whose active surface has a radius of curvature of only 100 mm, is shown to meet the spatial resolution and sensitivity requirements of the new wide field auroral imager (WFAI.

  7. Balloon-borne ozonesonde and rocket temperature and wind data gathered during the July 1977 intertropical convergence zone experiment

    Science.gov (United States)

    Schmidlin, F. J.; Kloos, G.

    1979-01-01

    In middle latitudes, it is possible for large concentrations of stratospheric air to be brought down to the tropopause through folds or breaks in the tropopause. The exchange of air from the tropopause into higher altitudes is not well understood. Thus, the ITCZ (Intertropical Convergence Zone) experiment, conducted from July 16 through July 31, 1977, included a series of balloon-borne ozone soundings. The results of these soundings are presented and explain in the vertical exchange of air and provide information on the short vertical scales-of-motion. Rocketsonde data was also gathered in the ITCZ experiment in support of a stratospheric scales-of-motion study. The investigation was to determine whether rocketsonde and satellite information currently used yield information on the stratospheric horizontal wave spectrum and its importance with respect to tropospheric and mesospheric interaction and transport.

  8. Wind tunnel investigation on the retention of air pollutants in three-dimensional recirculation zones in urban areas

    Science.gov (United States)

    Gomes, Marcos Sebastião de Paula; Isnard, André Augusto; Pinto, José Maurício do Carmo

    The article discusses an experimental investigation of turbulent dispersion processes in a typical three-dimensional urban geometry, in reduced scale, in neutrally stable conditions. Wind tunnel experiments were carried out for characterizing the flow and the dispersion of a pollutant around a scaled model (1:400) of a group of eight 10-floor buildings surrounding a square. The situation corresponded to the dispersion of fine inertialess particles released from a line source positioned upstream of the urban geometry. After the sudden interruption of the source generation, the particles persisted in the recirculation cavity between the buildings, with the concentration decaying exponentially with time. This is in accordance with previous works on the dispersion process around bluff bodies of different shapes [e.g., Humphries and Vincent, 1976. An experimental investigation of the detention of airborne smoke in the wake bubble behind a disk. Journal of Fluid Mechanics 73, 453-464; Vincent, 1977. Model experiments on the nature of air pollution transport near buildings. Atmospheric Environment 11, 765-774; Fackrell, 1984. Parameters characterizing dispersion in the near wake of buildings. Journal of Wind Engineering and Industrial Aerodynamics 16, 97-118]. The main parameter in the investigation was the characteristic time constant for the concentration decay. The measurements of the variation in the concentration of the fine particles were performed by means of a photo-detection technique based on the attenuation of light. The velocity fields were evaluated with the particle image velocimetry (PIV) technique. The dimensionless residence time H for the particles ( H= τU/ L, where τ is the time constant for the concentration decay, U the free-stream velocity, and L is a characteristic dimension for the urban geometry, as defined by Humphries and Vincent [1976. An experimental investigation of the detention of airborne smoke in the wake bubble behind a disk. Journal

  9. The size of the auroral belt during magnetic storms

    Directory of Open Access Journals (Sweden)

    N. Yokoyama

    Full Text Available Using the auroral boundary index derived from DMSP electron precipitation data and the Dst index, changes in the size of the auroral belt during magnetic storms are studied. It is found that the equatorward boundary of the belt at midnight expands equatorward, reaching its lowest latitude about one hour before Dst peaks. This time lag depends very little on storm intensity. It is also shown that during magnetic storms, the energy of the ring current quantified with Dst increases in proportion to Le–3, where Le is the L-value corresponding to the equatorward boundary of the auroral belt designated by the auroral boundary index. This means that the ring current energy is proportional to the ion energy obtained from the earthward shift of the plasma sheet under the conservation of the first adiabatic invariant. The ring current energy is also proportional to Emag, the total magnetic field energy contained in the spherical shell bounded by Le and Leq, where Leq corresponds to the quiet-time location of the auroral precipitation boundary. The ratio of the ring current energy ER to the dipole energy Emag is typically 10%. The ring current leads to magnetosphere inflation as a result of an increase in the equivalent dipole moment.

    Key words. Ionosphere (Auroral ionosphere · Magnetospheric physics (Auroral phenomena; storms and substorms

  10. High spatial and spectral resolution measurements of Jupiter's auroral regions using Gemini-North-TEXES

    Science.gov (United States)

    Sinclair, J. A.; Orton, G. S.; Greathouse, T. K.; Lacy, J.; Giles, R.; Fletcher, L. N.; Vogt, M.; Irwin, P. G.

    2017-12-01

    Jupiter exhibits auroral emission at a multitude of wavelengths. Auroral emission at X-ray, ultraviolet and near-infrared wavelengths demonstrate the precipitation of ion and electrons in Jupiter's upper atmosphere, at altitudes exceeding 250 km above the 1-bar level. Enhanced mid-infrared emission of CH4, C2H2, C2H4 and further hydrocarbons is also observed coincident with Jupiter's auroral regions. Retrieval analyses of infrared spectra from IRTF-TEXES (Texas Echelon Cross Echelle Spectrograph on NASA's Infrared Telescope Facility) indicate strong heating at the 1-mbar level and evidence of ion-neutral chemistry, which enriches the abundances of unsaturated hydrocarbons (Sinclair et al., 2017b, doi:10.1002/2017GL073529, Sinclair et al., 2017c (under review)). The extent to which these phenomena in the stratosphere are correlated and coupled physically with the shorter-wavelength auroral emission originating from higher altitudes has been a challenge due to the limited spatial resolution available on the IRTF. Smaller-scale features observed in the near-infrared and ultraviolet emission, such as the main `oval', transient `swirls' and dusk-active regions within the main oval (e.g. Stallard et al., 2014, doi:10.1016/j/Icarus.2015.12.044, Nichols et al., 2017, doi: 10.1002/2017GL073029) are potentially being blurred in the mid-infrared by the diffraction-limited resolution (0.7") of IRTF's 3-metre primary aperture. However, on March 17-19th 2017, we obtained spectral measurements of H2 S(1), CH4, C2H2, C2H4 and C2H6 emission of Jupiter's high latitudes using TEXES on Gemini-North, which has a 8-metre primary aperture. This rare opportunity combines the superior spectral resolving power of TEXES and the high spatial resolution provided by Gemini-North's 8-metre aperture. We will perform a retrieval analyses to determine the 3D distributions of temperature, C2H2, C2H4 and C2H6. The morphology will be compared with near-contemporaneous measurements of H3+ emission from

  11. Response of the auroral electrojet indices to abrupt southward IMF turnings

    Science.gov (United States)

    Gjerloev, J. W.; Hoffman, R. A.; Ohtani, S.; Weygand, J.; Barnes, R.

    2010-05-01

    We present results from a study of the behavior of the auroral electrojet indices following abrupt southward turnings of the IMF Bz. The auroral electrojet indices are calculated from observations made by more than 100 ground based stations provided by the SuperMAG collaborators. Based on three simple criteria we selected 73 events. In each event the interval of analysis started at the time of the IMF Bz southward turning and ended 45 minutes later or at the onset of any abrupt energy unloading event in the magnetosphere, regardless of size. We refer to this period as the "pre-unloading phase". To isolate the dependence of the auroral electrojets on the solar induced ionospheric conductivity during this phase we separated the standard AU/AL indices into two new sets of indices defined by the upper and lower envelope of the north-south component for all sunlit stations (AUs/ALs) and for all stations in darkness (AUd/ALd). Based on events and statistical analyses we can conclude that following a southward turning of the IMF Bz the AUd/ALd indices show no measurable response while the AUs/ALs indices clearly intensify. The intensifications of AUs/ALs are dependent on the intensity of the solar wind driver (as measured by IMF Bz or the Akasofu ɛ parameter). The lack of AUd/ALd response does not depend on the intensity of any subsequent substorm. We find that during these isolated events the ionospheric current system is primarily confined to the sunlit ionosphere. This truncated version of the classical global DP-2 current system suggests that auroral electrojet continuity is not maintained across the terminator. Because of its conductivity dependence on the solar zenith angle, this truncated global current pattern is expected to be highly dependent on UT and season and thus can be asymmetric between hemispheres. Thus we argue that the global two-cell DP-2 current system is not a consequence only of a southward turning of the IMF but requires also the reduction of the

  12. 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

  13. Electric potential differences across auroral generator interfaces

    Directory of Open Access Journals (Sweden)

    J. De Keyser

    2013-02-01

    Full Text Available Strong localized high-altitude auroral electric fields, such as those observed by Cluster, are often associated with magnetospheric interfaces. The type of high-altitude electric field profile (monopolar, bipolar, or more complicated depends on the properties of the plasmas on either side of the interface, as well as on the total electric potential difference across the structure. The present paper explores the role of this cross-field electric potential difference in the situation where the interface is a tangential discontinuity. A self-consistent Vlasov description is used to determine the equilibrium configuration for different values of the transverse potential difference. A major observation is that there exist limits to the potential difference, beyond which no equilibrium configuration of the interface can be sustained. It is further demonstrated how the plasma densities and temperatures affect the type of electric field profile in the transition, with monopolar electric fields appearing primarily when the temperature contrast is large. These findings strongly support the observed association of monopolar fields with the plasma sheet boundary. The role of shear flow tangent to the interface is also examined.

  14. Maximum power flux of auroral kilometric radiation

    International Nuclear Information System (INIS)

    Benson, R.F.; Fainberg, J.

    1991-01-01

    The maximum auroral kilometric radiation (AKR) power flux observed by distant satellites has been increased by more than a factor of 10 from previously reported values. This increase has been achieved by a new data selection criterion and a new analysis of antenna spin modulated signals received by the radio astronomy instrument on ISEE 3. The method relies on selecting AKR events containing signals in the highest-frequency channel (1980, kHz), followed by a careful analysis that effectively increased the instrumental dynamic range by more than 20 dB by making use of the spacecraft antenna gain diagram during a spacecraft rotation. This analysis has allowed the separation of real signals from those created in the receiver by overloading. Many signals having the appearance of AKR harmonic signals were shown to be of spurious origin. During one event, however, real second harmonic AKR signals were detected even though the spacecraft was at a great distance (17 R E ) from Earth. During another event, when the spacecraft was at the orbital distance of the Moon and on the morning side of Earth, the power flux of fundamental AKR was greater than 3 x 10 -13 W m -2 Hz -1 at 360 kHz normalized to a radial distance r of 25 R E assuming the power falls off as r -2 . A comparison of these intense signal levels with the most intense source region values (obtained by ISIS 1 and Viking) suggests that multiple sources were observed by ISEE 3

  15. Auroral kilometric radiation and magnetospheric substorm

    International Nuclear Information System (INIS)

    Morioka, Akira; Oya, Hiroshi

    1980-01-01

    The auroral kilometric radiation (AKR) and its relation to the development of the magnetospheric substorm have been studied based on the data obtained by JIKIKEN (EXOS-B) satellite. The occurrence of AKR is closely correlated to the intense UHR emission outside the plasmapause at the satellite position; the evidence clearly suggests that the development of the field aligned current system is associated with AKR generated at the upward current region and with the UHR emission at the downward current region. The drifting plasma due to the electric field that is generated in the magnetosphere at the moment of the magnetospheric substorm is derived from the frequency change of the plasma waves. The enhancement of the westward electric field in the duskside magnetosphere is detected simultaneously with the appearence of AKR. The altitude of the center of the AKR source region varies with intimate relation to the substorm activity suggesting that the generation of AKR is taking place in the region where the polar ionosphere and the magnetosphere are predominantly coupling through the precipitating or up going particles. From the fine structure of the dynamic spectra of AKR, it is suggested that the source of AKR might be closely related to the double layer type electric field along the magnetic field. (author)

  16. Magnetospheric electric fields and auroral oval

    Science.gov (United States)

    Laakso, Harri; Pedersen, Arne; Craven, John D.; Frank, L. A.

    1992-01-01

    DC electric field variations in a synchronous orbit (GEOS 2) during four substorms in the time sector 19 to 01 LT were investigated. Simultaneously, the imaging photometer on board DE 1 provided auroral images that are also utilized. Substorm onset is defined here as a sudden appearance of large electric fields. During the growth phase, the orientation of the electric field begins to oscillate some 30 min prior to onset. About 10 min before the onset GEOS 2 starts moving into a more tenuous plasma, probably due to a thinning of the current sheet. The onset is followed by a period of 10 to 15 min during which large electric fields occur. This interval can be divided into two intervals. During the first interval, which lasts 4 to 8 min, very large fields of 8 to 20 mV/m are observed, while the second interval contains relatively large fields (2 to 5 mV/m). A few min after the onset, the spacecraft returns to a plasma region of higher electron fluxes which are usually larger than before substorm. Some 30 min after onset, enhanced activity, lasting about 10 min, appears in the electric field. One of the events selected offers a good opportunity to study the formation and development of the Westward Traveling Surge (WST). During the traversal of the leading edge of the WTS (approximately 8 min) a stable wave mode at 5.7 mHz is detected.

  17. Measurements of low energy auroral ions

    International Nuclear Information System (INIS)

    Urban, A.

    1981-01-01

    This paper summarizes ion measurements in the energy range 0.1 to 30 keV observed during the campaigns 'Substorm Phenomena' and 'Porcupine'. For a clear survey of the physical processes during extraordinary events, sometimes ion measurements of higher energies are also taken into account. Generally, the pitch angle distributions were isotropic during all flights except some remarkable events. In general the ion and electron flux intensities correlated, but sometimes revealed a spectral anti-correlation. Acceleration of the ions by an electrostatic field aligned parallel to the magnetic field could be identified accompanied by intense electron precipitation. On the other hand deceleration of the ions was observed in other field-aligned current sheets which are indicated by the electron and magnetic field measurements. Temporal successive monoenergetic ion variations pointed to energy dispersion and to the location of the source region at 9 Rsub(E). Furthermore, ion fluxes higher than those of the electrons were measured at pitch angles parallel to the magnetic field. The integral down-going number and energy flux of the ions contributed to the total particle or energy influx between 65% and less than 7% and did not clearly characterize the geophysical launch conditions or auroral activities. (author)

  18. Axi-symmetric models of auroral current systems in Jupiter's magnetosphere with predictions for the Juno mission

    Directory of Open Access Journals (Sweden)

    S. W. H. Cowley

    2008-12-01

    Full Text Available We develop two related models of magnetosphere-ionosphere coupling in the jovian system by combining previous models defined at ionospheric heights with magnetospheric magnetic models that allow system parameters to be extended appropriately into the magnetosphere. The key feature of the combined models is thus that they allow direct connection to be made between observations in the magnetosphere, particularly of the azimuthal field produced by the magnetosphere-ionosphere coupling currents and the plasma angular velocity, and the auroral response in the ionosphere. The two models are intended to reflect typical steady-state sub-corotation conditions in the jovian magnetosphere, and transient super-corotation produced by sudden major solar wind-induced compressions, respectively. The key simplification of the models is that of axi-symmetry of the field, flow, and currents about the magnetic axis, limiting their validity to radial distances within ~30 RJ of the planet, though the magnetic axis is appropriately tilted relative to the planetary spin axis and rotates with the planet. The first exploration of the jovian polar magnetosphere is planned to be undertaken in 2016–2017 during the NASA New Frontiers Juno mission, with observations of the polar field, plasma, and UV emissions as a major goal. Evaluation of the models along Juno planning orbits thus produces predictive results that may aid in science mission planning. It is shown in particular that the low-altitude near-periapsis polar passes will generally occur underneath the corresponding auroral acceleration regions, thus allowing brief examination of the auroral primaries over intervals of ~1–3 min for the main oval and ~10 s for narrower polar arc structures, while the "lagging" field deflections produced by the auroral current systems on these passes will be ~0.1°, associated with azimuthal fields above the ionosphere of a few hundred nT.

  19. On the formation of auroral arcs and acceleration of auroral electrons

    International Nuclear Information System (INIS)

    Swift, D.W.

    1975-01-01

    It is suggested that the highly structured auroral arc is caused by a current-driven laminar electrostatic shock oblique to the geomagnetic field. Electrons are accelerated by the potential jump associated with the shock. The shock is assumed to be confined to a plane. Self-consistent solutions to the Poisson-Vlasov systems are calculated for the electrostatic potential. A diabatic theory is used to calculate the ion number density in terms of the electrostatic potential and its derivatives. The electrons are assumed to be highly magnetized so they can only move parallel to the magnetic field. Solutions are exhibited for two plasma models: (1) streaming electrons and a two-temperature distribution of ions and (2) streaming electrons and ions and thermal electrons and ions. In the latter model, solutions can be obtained for an arbitrary potential jump across the shock. The shock is identified with the linear electrostatic ion cyclotron wave, and stability of these waves is examined to determine conditions for the formation of oblique shocks. Finally, the theory is discussed in the context of the magnetosphere, and possible model shocks are exhibited and discussed in terms of auroral arc formation

  20. Theory for the asymmetry in the auroral ionization density profile for the generation of auroral infrasonic waves

    International Nuclear Information System (INIS)

    Goodwin, P.A.

    1979-01-01

    Traveling pressure waves with periods from 10 to 100 seconds are generated in the lower ionosphere by auroral electrojet current filaments as they move supersonically in an equatorward direction. The infrasonic waves produced by the auroral motions propagate to the ground as highly directional bow waves that can be detected by infrasonic microphones on the surface. There is an asymmetry in the reception of auroral infrasonic waves (AIW) with respect to whether the auroral arcs are moving equatorward to poleward. In the literature it is suggested that the asymmetry may be due to anisotropic propagation conditions along the acoustic ray path from the E-region, where AIW are produced, to the surface. Some intrinsic property of the AIW generation mechanism itself has also been suggested as a possible explanation. In this thesis anisotropic propagation is eliminated as the cause of the AIW reception asymmetry. Theoretical calculations, beginning with a model of an auroral precipitation region, are presented to show that there can be a significant difference in the transverse ionization density profiles between an auroral arc that is moving equatorward and an arc that is moving poleward, for a given equatorward-directed E-region ambient electric field. The calculation has been accomplished by solving the equations of motion and continuity for the cross-sectional ionization density profile associated with the transverse motion of a filamentary auroral electrojet. Thus, it is shown that there is an asymmetry in the ionization profiles associated with moving arcs, and in their coupling, that is related to the relative direction of motion of the arc with respect to the ambient electric field, and that it is this asymmetry that is probably the cause of the observed AIW reception asymmetry

  1. Offshore wind power system in the Exclusive Economic Zone. Applicability of German property law; Offshore-Windenergieanlagen in der AWZ. Anwendbarkeit des deutschen Sachenrechts

    Energy Technology Data Exchange (ETDEWEB)

    Schulz, Thomas; Glaesner, Michael [Linklaters LLP, Berlin (Germany)

    2013-04-15

    The present article shows how a lack of regulation has led to a certain degree of legal uncertainty as to whether offshore wind power plants located in the German Exclusive Economic Zone are amenable to German property law. For practical purposes this has made it necessary to negotiate project contracts such that the transfer of ownership of individual components is effected while these are still on shore, even if the purchase price has yet to be fully paid. The financing banks have a policy in place of demanding the establishment of a subsidiary which is to receive ownership of the assets. This makes the structure of such contracts a great deal more complicated in terms of corporations law and tax law. The present article summarises the experiences gained by lawyers in these matters, giving an overview of the different legal positions taken on them to date. It shows that the applicability of German property law follows from the law now in force. Aside from this the authors advocate amendments to the relevant IPR norm as a means of reinforcing legal certainty in practice and make a concrete proposal for a clause to this end.

  2. Correlations of auroral kilometric radiation with Birkeland currents

    International Nuclear Information System (INIS)

    Saflekos, N.A.; Carovillano, R.L.; Sheehan, R.E.

    1983-01-01

    This chapter examines auroral kilometric radiation (AKR) in relation to the strength of field-aligned currents (FAC), which represent an energy source stored in the form of magnetic field energy density in the neighborhood of the earth. An attempt is made to find a direct relationship between AKR power flux and optical auroral emissions. Topics considered include correlated Hawkeye and Triad satellite observations and correlated AKR and optical emissions. It is indicated that AKR is electromagnetic radiation in the frequency range of 50 to 500 kHz; AKR is generated at frequencies above the electron plasma frequency and below the electron gyrofrequency; AKR propagates in the Right Hand Extraordinary mode; and AKR may show fine structure in frequency. The principal findings include: distributions of AKR intensity with increasing auroral activity show that although quiet and disturbed auroras are generally accompanied by weak and intense AKR, the moderate auroras are associated with a broad range of AKR power; distributions of AKR intensity with increasing auroral electrojet (AE) index during the expansion phase of a polar magnetic substorm show near maximum levels of AKR power emission; and the maximum AKR power increases with increasing auroral activity and with increasing Birkeland current strength

  3. 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.

  4. Simultaneous rocket and radar measurements of currents in an auroral arc

    International Nuclear Information System (INIS)

    Robinson, R.M.; Bering, E.A.; Vondrak, R.R.; Anderson, H.R.; Cloutier, P.A.

    1981-01-01

    A detailed study of electric field, current and conductivities associated with an auroral arc was made in a coordinated rocket and radar experiment in Alaska on March 9, 1978. The payload, designated 29.007 UE, was launched at 1013 p.m. local time. It penetrated the diffuse aurora on the upleg and at apogee traversed field lines connected to a stable auroral arc of 40 kR intensity. Among the instruments carried by the payload were a vector magnetometer, a set of electrostatic double probes and a set of electron and proton spectrometers. Simultaneous electron density and line-of-sight velocity measurements were made by Chatanika radar operating in an elevation scan mode in the magnetic meridian plane. Both the radar and rocket measurements indicated that the zonal electric field was westward and approximately constant across the arc with a magnitude of about 7 mV/m. Small differences between the rocket and radar zonal electric field measurements indicated the presence of upward drifting ions in the region of the arc. The meridional field was large and northward equatorward of the arc, but negligible within the arc. Conductivities computed from measured fluxes of energetic electrons agreed well with the conductivities derived from the radar measureements of electron density. The electric field and conductivity measurements indicated that the zonal currents were eastward equatorward of the arc and westward within the arc. These electrojet currents agreed well with those inferred from the rocket magnetometer data. Better agreement was obtained when a westward neutral wind was added. The westward wind was also consistent with differences between the rocket and radar meridional electric fields. The meridional currents computed from the electric field measurements were northward over the entire region

  5. Electric field measurements in the auroral E region

    International Nuclear Information System (INIS)

    Mahon, H.P.; Smiddy, M.; Sagalyn, R.C.

    1975-01-01

    Dipole electric field, positive ion and electron densities and temperatures, vehicle potential, and plasma sheath measurements have been made in the auroral E region by means of rockets flown from Fort Churchill, Canada. These results are described and compared over the altitude region 100 to 165 km. On a rocket flight launched on 10 December 1969 during very quiet conditions, adjacent to a stable, low intensity auroral arc, the plasma density and temperatures are found to be high and the electric fields large and steady. Electric field components of the order of -17 mv m -1 to +6 mv m -1 were measured along the Earth's magnetic field. The plasma results indicate that these fields may be contributing to enhanced electron temperatures. On a flight of 9 March 1970 during a large magnetic storm with widespread auroral activity, lower plasma densities and temperatures and much smaller and more erratic electric fields were observed with no significant component parallel to the magnetic field. (auth)

  6. Polarization measurements of auroral kilometric radiation by Dynamics Explorer-1

    International Nuclear Information System (INIS)

    Shawhan, S.D.; Gurnett, D.A.

    1982-01-01

    The plasma wave instrument (PWI) on the Dynamics Explorer-1 has been used to measure polarization of auroral kilometric radiation (AKR) at frequencies of 50 to 400 kHz in both the northern and the southern nightside auroral regions at altitudes of 1 to 3 R/sub E/ above the AKR source regions. The AKR polarization sense is found to be the same as the right hand polarized auroral hiss found in the frequency range of 0.8 to 6.4 kHz. Consequently, these unambiguous direct polarization measurements of AKR lead to the conclusion that AKR escapes the magnetosphere in the R-X mode. Since DE-1 is close to the source region, it can be inferred that AKR is generated predominately in the R-X mode

  7. Solar wind oscillations with a 1.3 year period

    Science.gov (United States)

    Richardson, John D.; Paularena, Karolen I.; Belcher, John W.; Lazarus, Alan J.

    1994-01-01

    The Interplanetary Monitoring Platform 8 (IMP-8) and Voyager 2 spacecraft have recently detected a very strong modulation in the solar wind speed with an approximately 1.3 year period. Combined with evidence from long-term auroral and magnetometer studies, this suggests that fundamental changes in the Sun occur on a roughly 1.3 year time scale.

  8. Radar measurements of the latitudinal variation of auroral ionization

    International Nuclear Information System (INIS)

    Vondrak, R.R.; Baron, M.J.

    1976-01-01

    The Chatanika, Alaska, incoherent scatter radar has been used to measure the spatial variation of auroral ionization. A two-dimensional (altitude, latitude) cross-sectional map of electron densities in the ionosphere is produced by scanning in the geomagnetic meridian plane. The altitutde variation of ionization is used to infer the differential energy distribution of the incident auroral electrons. The latitudinal variation of this energy distribution and the total energy input are obtained by use of the meridian-scanning technique. Examples are shown of observations made during an active aurora

  9. Rocket measurement of auroral partial parallel distribution functions

    Science.gov (United States)

    Lin, C.-A.

    1980-01-01

    The auroral partial parallel distribution functions are obtained by using the observed energy spectra of electrons. The experiment package was launched by a Nike-Tomahawk rocket from Poker Flat, Alaska over a bright auroral band and covered an altitude range of up to 180 km. Calculated partial distribution functions are presented with emphasis on their slopes. The implications of the slopes are discussed. It should be pointed out that the slope of the partial parallel distribution function obtained from one energy spectra will be changed by superposing another energy spectra on it.

  10. Analysis of auroral infrared emissions observed during the ELIAS experiment

    Directory of Open Access Journals (Sweden)

    G. E. Caledonia

    Full Text Available The ELIAS (Earth Limb Infrared Atmospheric Structure experiment was flown from the Poker Flat Research Range, Alaska in 1983 and successfully monitored visible and infrared emissions from an IBC III+ aurora. Measurements were performed in both staring and scanning modes over several hundred seconds. The data for short- and mid-wave infrared regions have been analyzed in terms of auroral excitation of the NO and NO+ vibrational bands. Auroral excitation efficiencies and kinetic implications are presented.

  11. Auroral electron acceleration by lower-hybrid waves

    International Nuclear Information System (INIS)

    Bingham, R.; Bryant, D.A.; Hall, D.S.

    1986-01-01

    Because the particles and electric fields association with inverted-V electron streams do not have the characteristics expected for acceleration by a quasistatic potential difference, the possiblity that the electrons are stochastically accelerated by waves is investigated. It is demonstrated that the lower hybrid waves seen on auroral field lines have the righ properties to account for the electron acceleration. It is further shown that the lower hybrid wave power measured on auroral field lines can be generated by the streaming ions observed at the boundary of the plasma sheet, and that this wave power is sufficient to account for the electron power observed close to the atmosphere. (author)

  12. Climate Wind Power Resources

    Directory of Open Access Journals (Sweden)

    Nana M. Berdzenishvili

    2013-01-01

    Full Text Available Georgia as a whole is characterized by rather rich solar energy resources, which allows to construct alternative power stations in the close proximity to traditional power plants. In this case the use of solar energy is meant. Georgia is divided into 5 zones based on the assessment of wind power resources. The selection of these zones is based on the index of average annual wind speed in the examined area, V> 3 m / s and V> 5 m / s wind speed by the summing duration in the course of the year and V = 0. . . 2 m / s of passive wind by total and continuous duration of these indices per hour.

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

    Directory of Open Access Journals (Sweden)

    S. W. H. Cowley

    2004-04-01

    Full Text Available We consider the flows and currents in Saturn's polar ionosphere which are implied by a three-component picture of large-scale magnetospheric flow driven both by planetary rotation and the solar wind interaction. With increasing radial distance in the equatorial plane, these components consist of a region dominated by planetary rotation where planetary plasma sub-corotates on closed field lines, a surrounding region where planetary plasma is lost down the dusk tail by the stretching out of closed field lines followed by plasmoid formation and pinch-off, as first described for Jupiter by Vasyliunas, and an outer region driven by the interaction with the solar wind, specifically by reconnection at the dayside magnetopause and in the dawn tail, first discussed for Earth by Dungey. The sub-corotating flow on closed field lines in the dayside magnetosphere is constrained by Voyager plasma observations, showing that the plasma angular velocity falls to around half of rigid corotation in the outer magnetosphere, possibly increasing somewhat near the dayside magnetopause, while here we provide theoretical arguments which indicate that the flow should drop to considerably smaller values on open field lines in the polar cap. The implied ionospheric current system requires a four-ring pattern of field-aligned currents, with distributed downward currents on open field lines in the polar cap, a narrow ring of upward current near the boundary of open and closed field lines, and regions of distributed downward and upward current on closed field lines at lower latitudes associated with the transfer of angular momentum from the planetary atmosphere to the sub-corotating planetary magnetospheric plasma. Recent work has shown that the upward current associated with sub-corotation is not sufficiently intense to produce significant auroral acceleration and emission. Here we suggest that the observed auroral oval at Saturn instead corresponds to the ring of upward

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

    Directory of Open Access Journals (Sweden)

    S. W. H. Cowley

    2004-04-01

    Full Text Available We consider the flows and currents in Saturn's polar ionosphere which are implied by a three-component picture of large-scale magnetospheric flow driven both by planetary rotation and the solar wind interaction. With increasing radial distance in the equatorial plane, these components consist of a region dominated by planetary rotation where planetary plasma sub-corotates on closed field lines, a surrounding region where planetary plasma is lost down the dusk tail by the stretching out of closed field lines followed by plasmoid formation and pinch-off, as first described for Jupiter by Vasyliunas, and an outer region driven by the interaction with the solar wind, specifically by reconnection at the dayside magnetopause and in the dawn tail, first discussed for Earth by Dungey. The sub-corotating flow on closed field lines in the dayside magnetosphere is constrained by Voyager plasma observations, showing that the plasma angular velocity falls to around half of rigid corotation in the outer magnetosphere, possibly increasing somewhat near the dayside magnetopause, while here we provide theoretical arguments which indicate that the flow should drop to considerably smaller values on open field lines in the polar cap. The implied ionospheric current system requires a four-ring pattern of field-aligned currents, with distributed downward currents on open field lines in the polar cap, a narrow ring of upward current near the boundary of open and closed field lines, and regions of distributed downward and upward current on closed field lines at lower latitudes associated with the transfer of angular momentum from the planetary atmosphere to the sub-corotating planetary magnetospheric plasma. Recent work has shown that the upward current associated with sub-corotation is not sufficiently intense to produce significant auroral acceleration and emission. Here we suggest that the observed auroral oval at Saturn instead corresponds to the ring of

  15. The distribution of heavy metals and 137Cs in the central part of the Polish maritime zone (Baltic Sea) - the area selected for wind farm acquisition

    Science.gov (United States)

    Zaborska, Agata; Kosakowska, Alicja; Bełdowski, Jacek; Bełdowska, Magdalena; Szubska, Marta; Walkusz-Miotk, Jolanta; Żak, Adam; Ciechanowicz, Agnieszka; Wdowiak, Maciej

    2017-11-01

    Disturbances of the marine sediments that may be induced by offshore wind energy (OWE) construction and functioning may cause reintroduction of contaminants accumulated in the sea bottom over last century. It is thus very important to check in which offshore region of the Polish coast the littlest consequences of the OWE construction may be expected. The area of 9000 km2 in the central part of the Polish economic zone was selected for sediments sampling. In total, sediments from 46 stations were collected by gravity twin corer or geo-vibro corer. Heavy metal (Hg, Pb, Cd, As, Zn, Cu, Cr, Ni, Fe, Mn) concentrations were measured by AAS and ICP-MS while 137 Cs activity concentrations were measured by gamma spectrometer. Sediment accumulation rates were quantified by 210Pb geochronology at 7 stations to follow the history of contaminants accumulation. Study areas located between isobaths of 20 m and 40 m were characterized by the lowest concentration of heavy metals, often below natural environmental background (e.g. Pb = 6.7 - 11.4 μg·g-1, As = 0.3 - 8.4 μg·g-1). The largest contamination by heavy metals (e.g. Pb reached 86.1 μg·g-1 while As = 21.0 μg·g-1) was visible at the outer part of Bornholm Basin and in Słupsk Furrow, the deepest studied regions. Highest accumulation of heavy metals in this area is connected to large fraction of pelite sediments and large proportion of organic matter at those stations. It may be concluded that shallow sandy sediments of the Southern Baltic are unpolluted and appropriate for OWE construction. Deeper sea regions e.g Słupsk Furrow and Bornholm Basin may be regarded as moderately polluted and therefore not recommended for OWE acquisition.

  16. Dynamics of the Solar Wind Electromagnetic Energy Transmission Into Magnetosphere during Large Geomagnetic Storms

    Science.gov (United States)

    Kuznetsova, Tamara; Laptukhov, Alexej; Petrov, Valery

    Causes of the geomagnetic activity (GA) in the report are divided into temporal changes of the solar wind parameters and the changes of the geomagnetic moment orientation relative directions of the solar wind electric and magnetic fields. Based on our previous study we concluded that a reconnection based on determining role of mutual orientation of the solar wind electric field and geomagnetic moment taking into account effects of the Earth's orbital and daily motions is the most effective compared with existing mechanisms. At present a reconnection as paradigma that has applications in broad fields of physics needs analysis of experimental facts to be developed. In terms of reconnection it is important not only mutual orientation of vectors describing physics of interaction region but and reconnection rate which depends from rate of energy flux to those regions where the reconnection is permitted. Applied to magnetosphere these regions first of all are dayside magnetopause and polar caps. Influence of rate of the energy flux to the lobe magnetopause (based on calculations of the Poyting electromagnetic flux component controlling the reconnection rate along the solar wind velocity Pv) on planetary GA (Dst, Kp indices) is investigated at different phases of geomagnetic storms. We study also the rate of energy flux to the polar caps during storms (based on calculations of the Poyting flux vector component along the geomagnetic moment Pm) and its influence on magnetic activity in the polar ionosphere: at the auroral zone (AU,AL indices). Results allow to evaluate contributions of high and low latitude sources of electromagnetic energy to the storm development and also to clear mechanism of the electromagnetic energy transmission from the solar wind to the magnetosphere. We evaluate too power of the solar wind electromagnetic energy during well-known large storms and compare result with power of the energy sources of other geophysical processes (atmosphere, ocean

  17. First results of the Auroral Turbulance II rocket experiment

    DEFF Research Database (Denmark)

    Danielides, M.A.; Ranta, A.; Ivchenco, N.

    1999-01-01

    The Auroral Turbulance II sounding rocket was launched on February 11, 1997 into moderately active nightside aurora from the Poker Flat Research Range, Alaska, US. The experiment consisted of three independent, completely instrumented payloads launched by a single vehicle. The aim of the experiment...

  18. Excitation of low-frequency electrostatic instability on the auroral ...

    African Journals Online (AJOL)

    Low-Frequency Electrostatic Instability That Is Observed By Both Ground Facilities And Satellites Have Been Studied In The Auroral Acceleration Region Consisting Of Hot Precipitating Electron Beam From The Magnetosphere, Cold Background Electron And Ion Beam Moving Upward Away From The Earth Along The ...

  19. Height-integrated conductivity in auroral substorms. 1. Data

    DEFF Research Database (Denmark)

    Gjerløv, Jesper Wittendorff; Hoffman, R.A.

    2000-01-01

    to select substorms which display a typical bulge-type auroral emission pattern and to organize the position of individual DE 2 passes with respect to key features in the emission pattern. The Hall and Pedersen conductances are calculated from electron precipitation data obtained by the low altitude plasma...

  20. Middle-energy electron anisotropies in the auroral region

    Directory of Open Access Journals (Sweden)

    P. Janhunen

    2004-01-01

    Full Text Available Field-aligned anisotropic electron distribution functions of T > T type are observed on auroral field lines at both low and high altitudes. We show that typically the anisotropy is limited to a certain range of energies, often below 1keV, although sometimes extending to slightly higher energies as well. Almost always there is simultaneously an isotropic electron distribution at higher energies. Often the anisotropies are up/down symmetrical, although cases with net upward or downward electron flow also occur. For a statistical analysis of the anisotropies we divide the energy range into low (below 100eV, middle (100eV–1keV and high (above 1keV energies and develop a measure of anisotropy expressed in density units. The statistical magnetic local time and invariant latitude distribution of the middle-energy anisotropies obeys that of the average auroral oval, whereas the distributions of the low and high energy anisotropies are more irregular. This suggests that it is specifically the middle-energy anisotropies that have something to do with auroral processes. The anisotropy magnitude decreases monotonically with altitude, as one would expect, because electrons have high mobility along the magnetic field and thus, the anisotropy properties spread rapidly to different altitudes.

    Key words. Magnetospheric physics (auroral phenomena. Space plasma physics (wave-particle interactions; changed particle motion and acceleration

  1. Velocity of small-scale auroral ionospheric current systems over ...

    Indian Academy of Sciences (India)

    At the latter times, triangulation with 3 uxgate magnetometers located at the vertices of a suitable triangle provides a means of monitoring mobile auroral ionospheric current systems over Maitri. The spacing between the magnetometers is typically kept at 75-200 km, keeping in mind the scale-sizes of ∼100 km for these ...

  2. Atmospheric Pressure and Velocity Fluctuations Near the Auroral Electrojet.

    Science.gov (United States)

    1982-01-15

    various aspects of the atmosphere’s dynamical response to auroral activity have been carried out by Blumen and Hendl (1969), Testud (1970), Francis...Geophys. Res. 80, 2839, 1975. Testud , 3., Gravity waves generated during magnetic substorms, 3. Atmos. Terr. Phys. 32, 1793, 1970. Waco, D. E., A

  3. Auroral-Region Dynamics Determined with the Chatanika Radar.

    Science.gov (United States)

    1982-11-01

    low-latitudes originate in the auroral region [Davis and Da Rosa, 1969; Testud , 1970; Chandra et al., 1979). They may be generated by particle...Ion Composition and Nitric Oxide," Planet. Sp. Sci., 25, 103-116 (1977). Testud , J., "Gravity Waves Generated During Magnetic Substorms," J. Atmos. and

  4. Quasi-periodic latitudinal shift of Saturn's main auroral emission

    Science.gov (United States)

    Roussos, E.; Palmaerts, B.; Grodent, D. C.; Radioti, K.; Krupp, N.; Yao, Z.

    2017-12-01

    The main component of the ultraviolet auroral emissions at Saturn consists in a ring of emission around each pole of the planet. This main ring of emission has been revealed to oscillate by a few degrees in the prenoon-premidnight direction with a period of 10.8h. This auroral oscillation is thought to be induced by a rotating external magnetospheric current system associated with the planetary period oscillations. Here we report, by means of auroral imaging sequences obtained with the Ultraviolet Imaging Spectrograph (UVIS) on board the Cassini spacecraft, the first direct observation of an additional motion of the main emission superimposed to this oscillation. The whole main emission ring exhibits step-like displacements in latitude mainly towards dayside, decoupled from the 10.8h oscillation. These latitude shifts recur around every hour, which is a typical short periodicity at Saturn previously identified in the aurora intensity, in the charged particle fluxes and in the magnetic field. This unique observation directly demonstrates what has been inferred from past in-situ and remote measurements: the 1-hour periodicities reveal a global and fundamental magnetospheric oscillation mode that acts independently of the local magnetospheric conditions. However, the magnetospheric mechanism responsible for these 1-hour auroral shifts is still unknown. It is possible that Alfvén waves inducing hourly magnetic fluctuations might also modify the place where the field-aligned electrons precipitate in the ionosphere and produce the main emission.

  5. Structure of the auroral precipitation region in the dawn sector: relationship to convection reversal boundaries and field-aligned currents

    Directory of Open Access Journals (Sweden)

    Y. I. Feldstein

    2001-05-01

    Full Text Available Abstract. Simultaneous DMSP F7 and Viking satellite measurements of the dawnside high-latitude auroral energy electron and ion precipitation show that the region of the low and middle altitude auroral precipitation consists of three characteristic plasma regimes. The recommendation of the IAGA Working Group IIF/III4 at the IAGA Assembly in Boulder, July 1995 to decouple the nomenclature of ionospheric populations from magnetospheric population is used for their notation. The most equatorial regime is the Diffuse Auroral Zone (DAZ of diffuse spatially unstructured precipitating electrons. It is generated by the plasma injection to the inner magnetosphere in the nightside and the subsequent drift plasma to the dawnside around the Earth. Precipitating particles have a hard spectrum with typical energies of electrons and ions of more than 3 keV. In the DAZ, the ion pitch-angle distribution is anisotropic, with the peak near 90°. The next part is the Auroral Oval (AO, a structured electron regime which closely resembles the poleward portion of the night-side auroral oval. The typical electron energy is several keV, and the ion energy is up to 10 keV. Ion distributions are pre-dominantly isotropic. In some cases, this plasma regime may be absent in the pre-noon sector. Poleward of the Auroral Oval, there is the Soft Small Scale Luminosity (SSSL regime. It is caused by structured electron and ion precipitation with typical electron energy of about 0.3 keV and ion energy of about 1 keV. The connection of these low-altitude regimes with plasma domains of the distant magnetosphere is discussed. For mapping of the plasma regimes to the equatorial plane of the magnetosphere, the empirical model by Tsyganenko (1995 and the conceptual model by Alexeev et al. (1996 are used. The DAZ is mapped along the magnetic field lines to the Remnant Layer (RL, which is located in the outer radiation belt region; the zone of structured electrons and isotropic ion

  6. Structure of the auroral precipitation region in the dawn sector: relationship to convection reversal boundaries and field-aligned currents

    Directory of Open Access Journals (Sweden)

    Y. I. Feldstein

    Full Text Available

    Abstract. Simultaneous DMSP F7 and Viking satellite measurements of the dawnside high-latitude auroral energy electron and ion precipitation show that the region of the low and middle altitude auroral precipitation consists of three characteristic plasma regimes. The recommendation of the IAGA Working Group IIF/III4 at the IAGA Assembly in Boulder, July 1995 to decouple the nomenclature of ionospheric populations from magnetospheric population is used for their notation. The most equatorial regime is the Diffuse Auroral Zone (DAZ of diffuse spatially unstructured precipitating electrons. It is generated by the plasma injection to the inner magnetosphere in the nightside and the subsequent drift plasma to the dawnside around the Earth. Precipitating particles have a hard spectrum with typical energies of electrons and ions of more than 3 keV. In the DAZ, the ion pitch-angle distribution is anisotropic, with the peak near 90°. The next part is the Auroral Oval (AO, a structured electron regime which closely resembles the poleward portion of the night-side auroral oval. The typical electron energy is several keV, and the ion energy is up to 10 keV. Ion distributions are pre-dominantly isotropic. In some cases, this plasma regime may be absent in the pre-noon sector. Poleward of the Auroral Oval, there is the Soft Small Scale Luminosity (SSSL regime. It is caused by structured electron and ion precipitation with typical electron energy of about 0.3 keV and ion energy of about 1 keV. The connection of these low-altitude regimes with plasma domains of the distant magnetosphere is discussed. For mapping of the plasma regimes to the equatorial plane of the magnetosphere, the empirical model by Tsyganenko (1995 and the conceptual model by Alexeev et al. (1996 are used. The DAZ is mapped along the magnetic field lines to the Remnant Layer (RL, which is located in the outer radiation belt region; the zone of structured

  7. Observations of transverse ion acceleration in the topside auroral ionosphere

    International Nuclear Information System (INIS)

    Garbe, G.P.; Arnoldy, R.L.; Moore, T.E.; Kintner, P.M.; Vago, J.L.

    1992-01-01

    Data obtained from a sounding rocket flight which reached an apogee of 927 km and passed through several auroral arcs are reported. During portions of the flight when the rocket was not in an energetic auroral structure, the ion data are fit to a Maxwellian function which yields the plasma parameters. Throughout the middle portion of the flight when above 700 km altitude, ion distributions having a superthermal tail were measured. These ion distributions generally coexisted with a cold thermal core distribution and peaked at pitch angles slightly greater than 90 degree, which identifies them as conic distributions. These ions can be modeled using a bi-Maxwellian distribution function with a perpendicular (to B) temperature about 10 times greater than the parallel temperature of 0.15 eV. When the rocket was immersed in energetic auroral electron precipitation, two other ion distributions were observed. Transversely accelerated ions which represented bulk heating of the ambient population were observed. Transversely accelerated ions which represented bulk heating of the ambient population were observed continuously in these arcs. The characteristic perpendicular energy of the transversely bulk heated ions reached as high as 3 eV compared to typically less than 0.4 eV during nonauroral times. Cold ions flowing down the magnetic field were also continuously observed when the rocket was immersed in auroral electron precipitation and had downward speeds between 3 and 5 km/s. If one balances electric and collisional forces, these speeds translate to an electric field pointing into the atmosphere of magnitude 0.01 mV/m. A close correlation between auroral electron precipitation, measured electrostatic oxygen cyclotron waves, cold downflowing ions and transversely bulk heated ions will be shown

  8. Viking observations at the source region of auroral kilometric radiation

    International Nuclear Information System (INIS)

    Bahnsen, A.; Jespersen, M.; Ungstrup, E.; Pedersen, B.M.; Eliasson, L.; Murphree, J.S.; Elphinstone, R.D.; Blomberg, L.; Holmgren, G.; Zanetti, L.J.

    1989-01-01

    The orbit of the Swedish satellite Viking was optimized for in situ observations of auroral particle acceleration and related phenomena. In a large number of the orbits, auroral kilometric radiation (AKR) was observed, and in approximately 35 orbits the satellite passed through AKR source regions as evidenced by very strong signals at the local electron cyclotron frequency f ce . These sources were found at the poleward edge of the auroral oval at altitudes, from 5,000 to 8,000 km, predominantly in the evening sector. The strong AKR signal has a sharp low-frequency cutoff at or very close to f ce in the source. In addition to AKR, strong broadband electrostatic noise is measured during the source crossings. Energetic (1-15 keV) electrons are always present at and around the AKR sources. Upward directed ion beams of several keV are closely correlated with the source as are strong and variable electric fields, indicating that a region of upward pointing electric field below the observation point is a necessary condition for AKR generation. The plasma density is measured by three independent experiments and it is generally found that the density is low across the whole auroral oval. For some source crossings the three methods agree and show a density depletion (but not always confined to the source region itself), but in many cases the three measurements do not yield consistent results. The magnetic projection of the satellite passes through auroral forms during the source crossings, and the strongest AKR events seem to be connected with kinks in an arc or more complicated structures

  9. Auroral ion acceleration from lower hybrid solitary structures: A summary of sounding rocket observations

    Science.gov (United States)

    Lynch, K. A.; Arnoldy, R. L.; Kintner, P. M.; Schuck, P.; Bonnell, J. W.; Coffey, V.

    In this paper we present a review of sounding rocket observations of the ion acceleration seen in nightside auroral zone lower hybrid solitary structures. Observations from Topaz3, Amicist, and Phaze2 are presented on various spatial scales, including the two-point measurements of the Amicist mission. From this collection of observations we will demonstrate the following characteristics of transverse acceleration of ions (TAI) in lower hybrid solitary structures (LHSS). The ion acceleration process is narrowly confined to 90° pitch angle, in spatially confined regions of up to a few hundred meters across B. The acceleration process does not affect the thermal core of the ambient distribution and does not directly create a measurable effect on the ambient ion population outside the LHSS themselves. This precludes observation with these data of any nonlinear feedback between the ion acceleration and the existence or evolution of the density irregularities on which these LHSS events grow. Within the LHSS region the acceleration process creates a high-energy tail beginning at a few times the thermal ion speed. The ion acceleration events are closely associated with localized wave events. Accelerated ions bursts are also seen without a concurrent observation of a localized wave event, for two possible reasons. In some cases, the pitch angles of the accelerated tail ions are elevated above perpendicular; that is, the acceleration occurred below the observer and the mirror force has begun to act upon the distribution, moving it upward from the source. In other cases, the accelerated ion structure is spatially larger than the wave event structure, and the observation catches only the ion event. The occurrence rate of these ion acceleration events is related to the ambient environment in two ways: its altitude dependence can be modeled with the parameter B2/ne, and it is highest in regions of intense VLF activity. The cumulative ion outflow from these LHSS TAI is

  10. Generation of auroral kilometric radiation in upper hybrid wave-lower hybrid soliton interaction

    International Nuclear Information System (INIS)

    Pottelette, R.; Dubouloz, N.; Treumann, R.A.

    1992-01-01

    Sporadic bursts of auroral kilometric radiation (AKR) associated with strong bursty electrostatic turbulence in the vicinity of the lower hybrid frequency have been frequently recorded in the AKR source region by the Viking satellite. The variation time scale of these emissions is typically 1 s, long enough for lower hybrid waves to grow to amplitudes of several hundred millivolts per meter and to evolve nonlinearly into solitons. On the basis on these observations it is suggested that formation of lower hybrid solitons may play a role in the generation of AKR. A theoretical model is proposed which is based on the direct acceleration of electrons in the combined lower hybrid soliton and upper hybrid wave fields. The solitons act as sporadic, localized antennas allowing for efficient conversions of the electrostatic energy stored in upper hybrid waves into electromagnetic radiation at a frequency above the X mode cutoff. Excitation of lower hybrid waves is due to the presence of energetic electron beams in the auroral zone found to be associated with steep plasma density gradients. Upper hybrid waves can be excited by a population of energetic electrons with loss cone distributions. The power of the electromagnetic radiation obtained is only noticeable in regions where the plasma frequency is less than the electron gyrofrequency. The theory predicts spectral power densities of the order of 10 -11 to 10 -9 W m -2 Hz -1 in the source region, in good agreement with the Viking observations. The sporadic nature of the radiation derives from lower hybrid soliton collapses which occur on ∼1-s time scales

  11. Ancient Norwegian literature in relation to the auroral oval

    International Nuclear Information System (INIS)

    Brekke, A.

    1981-01-01

    The Poetic Edda and The King's Mirror are well preserved Norse documents from the period between 700 and 1300 A.D. The latter states that the aurora was known to people living in Greenland but probably not observed in Norway at about 1200 A.D. The Poetic Edda does not include any decisive evidence for the aurora being known to the Norse scalds in the Viking era. This is a rather surprising fact as the scalds were much inspired by natural phenomena, and in particular occupied by celestial gestalts. In a search for an explanation of this lack of inspiration from the northern lights among the Norse scalds it is maintained that the position and shape of the auroral oval was different in the Viking era from the present day auroral oval. (orig.)

  12. Stormtime Simulations of Sub-Auroral Polarization Streams (SAPS)

    Science.gov (United States)

    Huba, J.; Sazykin, S. Y.; Coster, A. J.

    2017-12-01

    We present simulation results from the self-consistently coupled SAMI3/RCM code on the impact of geomagnetic storms on the ionosphere/plasmasphere system with an emphasis on the development of sub-auroral plasma streams (SAPS). We consider the following storm events: March 31, 2001, March 17, 2013, March 17, 2015, September 3, 2012, and June 23, 2015. We compare and contrast the development of SAPS for these storms. The main results are the development of sub-auroral (< 60 degrees) low-density, high-speed flows (1 - 2 km/s). Additionally, we discuss the impact on plasmaspheric dynamics. We compare our model results to data (e.g., Millstone Hill radar, GPS TEC).

  13. Global auroral imaging instrumentation for the dynamics explorer mission

    International Nuclear Information System (INIS)

    Frank, L.A.; Craven, J.D.; Ackerson, K.L.; English, M.R.; Eather, R.H.; Carovillano, R.L.

    1981-01-01

    The instrumentation for gaining global images of the auroral oval from the high-altitude spacecraft of the Dynamics Explorer Mission is described. Three spin-scan auroral imaging (SAI) photometers are expected to be able to effectively view the dim emissions from earth in the presence of strong stray light sources near their fields-of-view along the sunlit portion of the spacecraft orbit. A special optical design which includes an off-axis parabolic mirror as the focusing element and super-reflecting mirror surfaces is used to minimize the effects of stray light. The rotation of the spacecraft and an instrument scanning mirror provide the two-dimensional array of pixels comprising an image frame. (orig.)

  14. Auroral research in Norway up to the space age

    International Nuclear Information System (INIS)

    Egeland, A.; Brekke, A.

    1986-01-01

    Since Norway is located in and close to the belt of maximum auroral occurrence, this may explain why Norwegian scientists have made such a significant contribution in auroral research. This, however, does not explain why Norwegians have been more active in this field than scientists in our neighboring countries. The same is even true in meteorology. Thus, it seems that Norwegians have concentrated on ''outdoor'' natural sciences. K.O. Birkeland, F.M. Stoermer and L. Vegard were the first to apply precise methods to study aurora and associated phenomena. They were also the first to propose a realistic theory and to calculate the motion of fast electrons from the Sun to the Earth's polar atmosphere. Through their research, these pioneers discovered many new effects and laid the foundation of our present-day exploration of aurora from space

  15. Byers Auto Group: A Case Study Into The Economics, Zoning, and Overall Process of Installing Small Wind Turbines at Two Automotive Dealerships in Ohio (Presentation)

    Energy Technology Data Exchange (ETDEWEB)

    Sinclair, K.; Oteri, F.

    2011-05-01

    This presentation provides the talking points about a case study on the installation of a $600,000 small wind project, the installation process, estimated annual energy production and percentage of energy needs met by the turbines.

  16. Byers Auto Group: A Case Study Into The Economics, Zoning, and Overall Process of Installing Small Wind Turbines at Two Automotive Dealerships in Ohio

    Energy Technology Data Exchange (ETDEWEB)

    Oteri, F.; Sinclair, K.

    2011-11-01

    This paper provides the talking points about a case study on the installation of a $600,000 small wind project, the installation process, estimated annual energy production and percentage of energy needs met by the turbines.

  17. Theoretical and experimental studies relevant to interpretation of auroral emissions. Annual Report

    International Nuclear Information System (INIS)

    Keffer, C.E.

    1992-06-01

    The results obtained in the second year of a three year collaborative effort with MSFC are summarized. A succession of experimental studies was completed to determine the effects of the natural and induced space vehicle environment on the measurement of auroral images from space-based platforms. In addition, a global model which incorporates both auroral and dayglow emission sources is being developed to allow interpretation of measured auroral emissions. A description of work completed on these two tasks is presented

  18. Distribution of auroral surges in the evening sector

    International Nuclear Information System (INIS)

    Kidd, S.R.; Rostoker, G.

    1991-01-01

    Over the past dacades a large statistical data base has been gathered consisting of both ground-based magnetometer and all-sky camera records from which researchers have inferred the distribution of substorm expansive phase events across the nighttime sector. Almost without exception, the activity distribution has been based on single station data acquired over periods of years. However, to truly establish the occurrence frequency of substorm expansive phase events, it is necessary to view the entire nighttime sector instantaneously in the light of evidence which shows that more than one expansive phase disturbance can be in progress across the broad expanse of the evening sector. In this paper, the authors study the distribution of regions of localized auroral luminosity in the poleward portion of the evening sectorauroral oval using images in the ultraviolet portion of the auroral spectrum acquired by the Viking satellite over 9 months in 1986. They find that auroral surge activity peaks in the hour before local magnetic midnight, with the probability of detecting a surge steadily decreasing to 10% of the probability of finding a surge in the hour prior to midnight as one moves westward towards 1,900 MLT. They show that their conclusion is not dependent on the threshold chosen for surge identification over a reasonable portion of the intensity range covered by the Viking imager. They further show that for the interval of several months near sunspot minimum in 1986 there is better than a 90% chance that no surge will be detected in a 1-hour range of magnetic local time if one were to sample that segment of the auroral oval at any arbitrary time

  19. An observation of ionospheric convection and auroral arc motion

    International Nuclear Information System (INIS)

    Doolittle, J.H.; Mende, S.B.; Robinson, R.M.; Swenson, G.R.; Valladares, C.E.

    1990-01-01

    An all-sky imager operated at Sondre Stromfjord, Greenland has been used to make auroral measurements in correlation with data from the incoherent scatter radar. Reviewing the images as movie sequences with an apparent time compression ratio of 60 allows the eye to discern features which are not apparent in the individual frames. The faint 630 nm airglow background lying poleward of the bright auroral oval arcs appears to be structured in the time lapse observations and drifting at a uniform rate. Analysis of the motion of the airglow structures shows excellent agreement with Doppler radar measurement of the ion drift velocities. Electron density profiles derived from the radar data corroborate the existence of high altitude F-region ionization enhancements. The electron temperature in the patches was about 1,000 K and no higher than outside of the patch signifying that the patches were not produced by local soft electron precipitation. According to the radar Doppler data there was a small component of the drift velocity parallel to the arc at either side of the auroral boundary. The sense of those small components was consistent with drifts driven by a convergent electric field which would also produce an up going field aligned current. The larger component of drift velocity perpendicular to the arc appeared to be continuous on either side of the arc. This drift component shows the existence of an electric field parallel to the arc, showing that the arc was not on an equipotential. During the observations the arc moved slowly in the opposite sense to the ion drift, signifying that the auroral arc motion is not driven by the electric field impressed on the atmosphere by the magnetosphere. Calculations of the expected intensity of the 630 nm emissions are in good agreement with the measured intensities of the moving patches

  20. Nonlinear radiation generation processes in the auroral acceleration region

    Directory of Open Access Journals (Sweden)

    R. Pottelette

    2017-11-01

    Full Text Available It is known from laboratory plasma experiments that double layers (DLs radiate in the electromagnetic spectrum; but this is only known qualitatively. In these experiments, it was shown that the electron beam created on the high-potential side of a DL generates nonlinear structures which couple to electromagnetic waves and act as a sender antenna. In the Earth auroral region, observations performed by auroral spacecraft have shown that DLs occur naturally in the source region of intense radio emissions called auroral kilometric radiation (AKR. Very high time-, spatial-, and temporal-resolution measurements are needed in order to characterize waves and particle distributions in the vicinity of DLs, which are moving transient structures. We report observations from the FAST satellite of a localized large-amplitude parallel electric field (∼ 300 mV m−1 recorded at the edges of the auroral density cavity. In agreement with laboratory experiments, on the high-potential side of the DL, elementary radiation events are detected. They occur substantially above the local electron gyrofrequency and are associated with the presence of electron holes. The velocity of these nonlinear structures can be derived from the measurement of the Doppler-shifted AKR frequency spectrum above the electron gyrofrequency. The generated electron holes appear as the nonlinear evolution of electrostatic waves generated by the electron–electron two-stream instability because they propagate at about half the beam velocity. It is pointed out that, in the vicinity of a DL, the shape of the electron distribution gives rise to a significant power recorded in the left-hand polarized ordinary (LO mode.

  1. Coordinated ATS 5 electron flux and simultaneous auroral observations

    International Nuclear Information System (INIS)

    Mende, S.B.; Shelley, E.G.

    1976-01-01

    All-sky camera (ASCA) observations were made at the field line conjugate of the ATS 5 satellite. The field of view of these cameras covered the region of the magnetosphere from L=5 to L=11 at the approximate longitude of the ATS field line conjugate. With this coverage, definite statements can be made concerning the correlation of the auroras observed by the ASCA's and the magnetospheric trapped fluxes. In general, auroral forms are not simply correlated with the synchronous altitude electron fluxes. The presence of hot plasma at the ATS 5 satellite is a necessary but not sufficient condition for the occurrence of local auroras. On quiet days the hot plasma does not penetrate into the magnetosphere far enough to reach the ATS 5 orbit. Under these conditions, no auroras are observed at the field line conjugate, but auroras are usually observed on higher-latitude field lines. On more disturbed days, auroral arcs are observed at lower latitudes when the plasma sheet penetrates into the ATS 5 orbit. There is no general correlation between the intensity of the trapped electron fluxes observed by ATS 5 and the intensity of auroras observed by the ASCA's. Auroral displays exhibit very fast fluctuations, whereas the ATS 5 electron fluxes change on a much slower time scale. However, significant qualitative correlation between the ASCA data and the trapped fluxes is observed when a local plasma injection event occurs near ATS 5. The clearest signature of the injection event is magnetic and is most pronounced as a recovery of a negative bay in the north-south component of the field at the ATS 5. The local injection generally produces structured auroras such as breakup events and sometimes westward-traveling surges. A significant correlation is observed with the intensification of a diffuse uniform glow accompanying the structured auroral activity

  2. Latitudinal and longitudinal dispersion of energetic auroral protons

    Directory of Open Access Journals (Sweden)

    D. A. Lorentzen

    2000-01-01

    Full Text Available Using a collision by collision model from Lorentzen et al., the latitudinal and longitudinal dispersion of single auroral protons are calculated. The proton energies varies from 1 to 50 keV, and are released into the atmosphere at 700 km altitude. The dipole magnetic field has a dip-angle of 8 degrees. Results show that the main dispersion region is at high altitudes (300-350 km and occurs during the first few charge exchange collisions. As the proton travels further down the atmosphere the mean free path becomes smaller, and as a result the spreading effect will not be as pronounced. This means that the first few charge exchange collisions fully determines the width of both the latitudinal and longitudinal dispersion. The volume emission rate was calculated for energies between 1 and 50 keV, and it was found that dayside auroral hydrogen emissions rates were approximately 10 times weaker than nightside emission rates. Simulations were also performed to obtain the dependence of the particle dispersion as a function of initial pitch-angle. It was found that the dispersion varies greatly with initial pitch-angle, and the results are summarized in two tables; a main and an extreme dispersion region.Key words. Ionosphere (auroral ionosphere; · particle precipitation · Space plasma physics · (transport processes

  3. A hybrid simulation model for a stable auroral arc

    Directory of Open Access Journals (Sweden)

    P. Janhunen

    Full Text Available We present a new type of hybrid simulation model, intended to simulate a single stable auroral arc in the latitude/altitude plane. The ionospheric ions are treated as particles, the electrons are assumed to follow a Boltzmann response and the magnetospheric ions are assumed to be so hot that they form a background population unaffected by the electric fields that arise. The system is driven by assumed parallel electron energisation causing a primary negative charge cloud and an associated potential structure to build up. The results show how a closed potential structure and density depletion of an auroral arc build up and how they decay after the driver is turned off. The model also produces upgoing energetic ion beams and predicts strong static perpendicular electric fields to be found in a relatively narrow altitude range (~ 5000–11 000 km.

    Key words. Magnetospheric physics (magnetosphere-ionosphere interactions; auroral phenomena – Space plasma physics (numerical simulation studies

  4. The Auroral Field-aligned Acceleration - Cluster Results

    Science.gov (United States)

    Vaivads, A.; Cluster Auroral Team

    The four Cluster satellites cross the auroral field lines at altitudes well above most of acceleration region. Thus, the orbit is appropriate for studies of the generator side of this region. We consider the energy transport towards the acceleration region and different mechanisms for generating the potential drop. Using data from Cluster we can also for the first time study the dynamics of the generator on a minute scale. We present data from a few auroral field crossings where Cluster are in conjunction with DMSP satellites. We use electric and magnetic field data to estimate electrostatic po- tential along the satellite orbit, Poynting flux as well as the presence of plasma waves. These we can compare with data from particle and wave instruments on Cluster and on low latitude satellites to try to make a consistent picture of the acceleration region formation in these cases. Preliminary results show close agreement both between in- tegrated potential values at Cluster and electron peak energies at DMSP as well as close agreement between the integrated Poynting flux values at Cluster and the elec- tron energy flux at DMSP. At the end we draw a parallels between auroral electron acceleration and electron acceleration at the magnetopause.

  5. E-region echo characteristics governed by auroral arc electrodynamics

    Directory of Open Access Journals (Sweden)

    S. E. Milan

    Full Text Available Observations of a pair of auroral arc features by two imagers, one ground- and one space-based, allows the associated field-aligned current (FAC and electric field structure to be inferred. Simultaneous observations of HF radar echoes provide an insight into the irregularity-generating mechanisms. This is especially interesting for the E-region echoes observed, which form the focus of our analysis, and from which several conclusions can be drawn, summarized as follows. Latitudinal variations in echo characteristics are governed by the FAC and electric field background. Particularly sharp boundaries are found at the edges of auroral arcs. Within regions of auroral luminosity, echoes have Doppler shifts below the ion-acoustic speed and are proportional to the electric field, suggesting scatter from gradient drift waves. Regions of downward FAC are associated with mixed high and low Doppler shift echoes. The high Doppler shift component is greatly in excess of the ion-acoustic speed, but seems to be commensurate with the driving electric field. The low Doppler shift component appears to be much depressed below expectations.

    Key words. Ionosphere (ionospheric irregularities; electric fields and currents

  6. Angular dependent transport of auroral electrons in the upper atmosphere

    International Nuclear Information System (INIS)

    Lummerzheim, D.; Rees, M.H.

    1989-01-01

    The transport of auroral electrons through the upper atmosphere is analyzed. The transport equation is solved using a discrete ordinate method including elastic and inelastic scattering of electrons resulting in changes of pitch angle, and degradation in energy as the electrons penetrate into the atmosphere. The transport equation is solved numerically for the electron intensity as a function of altitude, pitch angle, and energy. In situ measurements of the pitch angle and energy distribution of precipitating electrons over an auroral arc provide boundary conditions for the calculation. The electron spectra from various locations over the aurora present a variety of anisotropic pitch angle distributions and energy spectra. Good agreement is found between the observed backscattered electron energy spectra and model predictions. Differences occur at low energies (below 500 eV) in the structure of the pitch angle distribution. Model calculations were carried out with various different phase functions for elastic and inelastic collisions to attempt changing the angular scattering, but the observed pitch angle distributions remain unexplained. We suggest that mechanisms other than collisional scattering influence the angular distribution of auroral electrons at or below 300 km altitude in the low energy domain. (author)

  7. The Auroral Planetary Imaging and Spectroscopy (APIS) service

    Science.gov (United States)

    Lamy, L.; Prangé, R.; Henry, F.; Le Sidaner, P.

    2015-06-01

    The Auroral Planetary Imaging and Spectroscopy (APIS) service, accessible online, provides an open and interactive access to processed auroral observations of the outer planets and their satellites. Such observations are of interest for a wide community at the interface between planetology, magnetospheric and heliospheric physics. APIS consists of (i) a high level database, built from planetary auroral observations acquired by the Hubble Space Telescope (HST) since 1997 with its mostly used Far-Ultraviolet spectro-imagers, (ii) a dedicated search interface aimed at browsing efficiently this database through relevant conditional search criteria and (iii) the ability to interactively work with the data online through plotting tools developed by the Virtual Observatory (VO) community, such as Aladin and Specview. This service is VO compliant and can therefore also been queried by external search tools of the VO community. The diversity of available data and the capability to sort them out by relevant physical criteria shall in particular facilitate statistical studies, on long-term scales and/or multi-instrumental multi-spectral combined analysis.

  8. Correlated observations of several auroral substorms on February 17, 1971

    International Nuclear Information System (INIS)

    Hones, E.W. Jr.; Akasofu, S.; Wolcott, J.H.; Bame, S.J.; Fairfield, D.H.; Meng, C.

    1976-01-01

    The purpose of this study is to correlate in detail auroral activity with the corresponding disturbances in the magnetotail. The auroral data were recorded by optical instruments aboard an airplane flying over the Arctic Ocean along the Alaska meridian and by the Alaska meridian chain of all-sky cameras. The corresponding magnetotail observations were made by various instruments on Vela 6A and Imp 5; the interplanetary magnetic field was monitored concurrently by Explorer 35 (Imp E). Three successive substorms were observed on February 17, 1971. Each substorm was readily identified by the classical auroral and magnetic signatures which accompanied its onset. The observed variations of plasma and magnetic field in the magnetotail were consistent with the idea that a neutral line formed in the range approx.-12 R/subE/>X/subS//subM/>-18 R/subE/ at the onset of each substorm expansive phase and then moved tailward past X/subS//subM/=-18 R/subE/ some tens of minutes afterward. The Z component of the tail magnetic field decreased rather steadily for a period of 1--21/2 hours after each substorm and until the onset of the next expansive phase, reaching a minimum value just before each onset. This taillike development of the field is more appropriately regarded as the normal evolutionary pattern of variation between substorms than as a 'growth phase' preceding each substorm

  9. Latitudinal and longitudinal dispersion of energetic auroral protons

    Directory of Open Access Journals (Sweden)

    D. A. Lorentzen

    Full Text Available Using a collision by collision model from Lorentzen et al., the latitudinal and longitudinal dispersion of single auroral protons are calculated. The proton energies varies from 1 to 50 keV, and are released into the atmosphere at 700 km altitude. The dipole magnetic field has a dip-angle of 8 degrees. Results show that the main dispersion region is at high altitudes (300-350 km and occurs during the first few charge exchange collisions. As the proton travels further down the atmosphere the mean free path becomes smaller, and as a result the spreading effect will not be as pronounced. This means that the first few charge exchange collisions fully determines the width of both the latitudinal and longitudinal dispersion. The volume emission rate was calculated for energies between 1 and 50 keV, and it was found that dayside auroral hydrogen emissions rates were approximately 10 times weaker than nightside emission rates. Simulations were also performed to obtain the dependence of the particle dispersion as a function of initial pitch-angle. It was found that the dispersion varies greatly with initial pitch-angle, and the results are summarized in two tables; a main and an extreme dispersion region.

    Key words. Ionosphere (auroral ionosphere; · particle precipitation · Space plasma physics · (transport processes

  10. E-region echo characteristics governed by auroral arc electrodynamics

    Directory of Open Access Journals (Sweden)

    S. E. Milan

    2003-07-01

    Full Text Available Observations of a pair of auroral arc features by two imagers, one ground- and one space-based, allows the associated field-aligned current (FAC and electric field structure to be inferred. Simultaneous observations of HF radar echoes provide an insight into the irregularity-generating mechanisms. This is especially interesting for the E-region echoes observed, which form the focus of our analysis, and from which several conclusions can be drawn, summarized as follows. Latitudinal variations in echo characteristics are governed by the FAC and electric field background. Particularly sharp boundaries are found at the edges of auroral arcs. Within regions of auroral luminosity, echoes have Doppler shifts below the ion-acoustic speed and are proportional to the electric field, suggesting scatter from gradient drift waves. Regions of downward FAC are associated with mixed high and low Doppler shift echoes. The high Doppler shift component is greatly in excess of the ion-acoustic speed, but seems to be commensurate with the driving electric field. The low Doppler shift component appears to be much depressed below expectations.Key words. Ionosphere (ionospheric irregularities; electric fields and currents

  11. Particle energization by inertial Alfven wave in auroral ionosphere

    Science.gov (United States)

    Kumar, S.

    2017-12-01

    The role of inertial Alfven wave in auroral acceleration region and in the inertial regime to energize the plasma particles is an interesting field and widely discussed observationally as well as theoretically in recent years. In this work, we present the density perturbations by inertial Alfvén wave (AW) in the auroral ionosphere. We obtain dynamical equations for inertial AW and fast mode of AW using two-fluid model and then solve them numerically in order to analyze the localized structures and cavity formation. The ponderomotive force due to the high frequency inertial AW changes the background density and is believed to be responsible for the wave localization or for the formation of density cavities in auroral ionosphere. These density cavities are believed to be the sites for particle energization. This perturbed density channel grow with time until the modulation instability acquires steady state. We find that the density cavities are accompanied by the high amplitude magnetic fields. The amplitude of the strongest density cavity is estimated as ˜ 0.26n0 (n0 is unperturbed plasma number density). The results presented here are found consistent with the observational studies using FAST spacecraft.

  12. Ionospheric response to variable electric fields in small-scale auroral structures

    Directory of Open Access Journals (Sweden)

    B. S. Lanchester

    1998-10-01

    Full Text Available High time and space resolution optical and radar measurements have revealed the influence of electric fields on E-region electron density profiles in small-scale auroral structures. Large electric fields are present adjacent to auroral filaments produced by monoenergetic electron fluxes. The ionisation profiles measured within and beside the auroral filaments show the effects of plasma convection due to electric fields as well as the consequences of the response time to large and dynamic fluxes of energetic electrons. Without high-resolution optical measurements, the interpretation of the radar data is limited.Key words. Auroral ionosphere · Ionosphere-magnetosphere interactions · EISCAT

  13. Ionospheric response to variable electric fields in small-scale auroral structures

    Directory of Open Access Journals (Sweden)

    B. S. Lanchester

    Full Text Available High time and space resolution optical and radar measurements have revealed the influence of electric fields on E-region electron density profiles in small-scale auroral structures. Large electric fields are present adjacent to auroral filaments produced by monoenergetic electron fluxes. The ionisation profiles measured within and beside the auroral filaments show the effects of plasma convection due to electric fields as well as the consequences of the response time to large and dynamic fluxes of energetic electrons. Without high-resolution optical measurements, the interpretation of the radar data is limited.

    Key words. Auroral ionosphere · Ionosphere-magnetosphere interactions · EISCAT

  14. Generation of auroral hectometer radio emission at the laser cyclotron resonance (ωp≥ωH)

    International Nuclear Information System (INIS)

    Vlasov, V.G.

    1992-01-01

    Generation of auroral hectometer (AHR) and kilometer (AKR) radio emission at a maser cyclotron resonance (MCR) in a relatively dense plasma (ω p ≥ω H ) is theoretically studied. The conclusion is made that availability of two-dimensional small-scale inhomogeneity of plasma density is the basic condition for the AHR generation at the MCR by auroral electron beams. The small-scale inhomogeneity of the auroral plasma, measured on satelites, meets by its parameters the conditions for the generation of auroral radio emission

  15. Wind: French revolutions

    International Nuclear Information System (INIS)

    Jones, C.

    2006-01-01

    Despite having the second best wind resources in Europe after the UK, the wind industry in France lags behind its European counterparts with just 6 W of installed wind capacity per person. The electricity market in France is dominated by the state-owned Electricite de France (EdF) and its nuclear power stations. However, smaller renewable generators are now in theory allowed access to the market and France has transposed the EU renewables directive into national law. The French governement has set a target of generating 10,000 MW of renewable capacity by 2010. The announcement of an increased feed-in tariff and the introduction of 'development zones' (ZDEs) which could allow fast-tracking of planning for wind projects are also expected to boost wind projects. But grid access and adminstrative burdens remain major barriers. In addition, French politicians and local authorities remain committed to nuclear, though encouraged by the European Commission, wind is beginning to gain acceptance; some 325 wind farms (representing 1557 MW of capacity) were approved between February 2004 and January 2005. France is now regarded by the international wind energy sector as a target market. One of France's leading independent wind developers and its only listed wind company, Theolia, is expected to be one of the major beneficiaries of the acceleration of activity in France, though other companies are keen to maximise the opportunities for wind. France currently has only one indigenous manufacturer of wind turbines, but foreign suppliers are winning orders

  16. Ionospheric storms at geophysically-equivalent sites – Part 1: Storm-time patterns for sub-auroral ionospheres

    Directory of Open Access Journals (Sweden)

    M. Mendillo

    2009-04-01

    Full Text Available The systematic study of ionospheric storms has been conducted primarily with groundbased data from the Northern Hemisphere. Significant progress has been made in defining typical morphology patterns at all latitudes; mechanisms have been identified and tested via modeling. At higher mid-latitudes (sites that are typically sub-auroral during non-storm conditions, the processes that change significantly during storms can be of comparable magnitudes, but with different time constants. These include ionospheric plasma dynamics from the penetration of magnetospheric electric fields, enhancements to thermospheric winds due to auroral and Joule heating inputs, disturbance dynamo electrodynamics driven by such winds, and thermospheric composition changes due to the changed circulation patterns. The ~12° tilt of the geomagnetic field axis causes significant longitude effects in all of these processes in the Northern Hemisphere. A complementary series of longitude effects would be expected to occur in the Southern Hemisphere. In this paper we begin a series of studies to investigate the longitudinal-hemispheric similarities and differences in the response of the ionosphere's peak electron density to geomagnetic storms. The ionosonde stations at Wallops Island (VA and Hobart (Tasmania have comparable geographic and geomagnetic latitudes for sub-auroral locations, are situated at longitudes close to that of the dipole tilt, and thus serve as our candidate station-pair choice for studies of ionospheric storms at geophysically-comparable locations. They have an excellent record of observations of the ionospheric penetration frequency (foF2 spanning several solar cycles, and thus are suitable for long-term studies. During solar cycle #20 (1964–1976, 206 geomagnetic storms occurred that had Ap≥30 or Kp≥5 for at least one day of the storm. Our analysis of average storm-time perturbations (percent deviations from the monthly means showed a remarkable

  17. 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

  18. Ionospheric feedback effects on the quasi-stationary coupling between LLBL and postnoon/evening discrete auroral arcs

    Directory of Open Access Journals (Sweden)

    M. M. Echim

    2008-05-01

    Full Text Available We discuss a model for the quasi-stationary coupling between magnetospheric sheared flows in the dusk sector and discrete auroral arcs, previously analyzed for the case of a uniform height-integrated Pedersen conductivity (ΣP. Here we introduce an ionospheric feedback as the variation of ΣP with the energy flux of precipitating magnetospheric electrons (εem. One key-component of the model is the kinetic description of the interface between the duskward LLBL and the plasma sheet that gives the profile of Φm, the magnetospheric electrostatic potential. The velocity shear in the dusk LLBL plays the role of a generator for the auroral circuit closing through Pedersen currents in the auroral ionosphere. The field-aligned current density, j||, and the energy flux of precipitating electrons are given by analytic functions of the field-aligned potential drop, ΔΦ, derived from standard kinetic models of the adiabatic motion of particles. The ionospheric electrostatic potential, Φi (and implicitely ΔΦ is determined from the current continuity equation in the ionosphere. We obtain values of ΔΦ of the order of kilovolt and of j|| of the order of tens of μA/m2 in thin regions of the order of several kilometers at 200 km altitude. The spatial scale is significantly smaller and the peak values of ΔΦ, j|| and εem are higher than in the case of a uniform ΣP. Effects on the postnoon/evening auroral arc electrodynamics due to variations of dusk LLBL and solar wind dynamic and kinetic pressure are discussed. In thin regions (of the order of kilometer embedding the maximum of ΔΦ we evidence a non-linear regime of the current-voltage relationship. The model predicts also that visible arcs form when the velocity shear in LLBL is above a threshold value depending on the generator and ionospheric plasma properties. Brighter arcs are obtained for increased velocity shear in the LLBL; their spatial scale remains virtually unmodified. The field

  19. Ionospheric feedback effects on the quasi-stationary coupling between LLBL and postnoon/evening discrete auroral arcs

    Directory of Open Access Journals (Sweden)

    M. M. Echim

    2008-05-01

    Full Text Available We discuss a model for the quasi-stationary coupling between magnetospheric sheared flows in the dusk sector and discrete auroral arcs, previously analyzed for the case of a uniform height-integrated Pedersen conductivity (ΣP. Here we introduce an ionospheric feedback as the variation of ΣP with the energy flux of precipitating magnetospheric electrons (εem. One key-component of the model is the kinetic description of the interface between the duskward LLBL and the plasma sheet that gives the profile of Φm, the magnetospheric electrostatic potential. The velocity shear in the dusk LLBL plays the role of a generator for the auroral circuit closing through Pedersen currents in the auroral ionosphere. The field-aligned current density, j||, and the energy flux of precipitating electrons are given by analytic functions of the field-aligned potential drop, ΔΦ, derived from standard kinetic models of the adiabatic motion of particles. The ionospheric electrostatic potential, Φi (and implicitely ΔΦ is determined from the current continuity equation in the ionosphere. We obtain values of ΔΦ of the order of kilovolt and of j|| of the order of tens of μA/m2 in thin regions of the order of several kilometers at 200 km altitude. The spatial scale is significantly smaller and the peak values of ΔΦ, j|| and εem are higher than in the case of a uniform ΣP. Effects on the postnoon/evening auroral arc electrodynamics due to variations of dusk LLBL and solar wind dynamic and kinetic pressure are discussed. In thin regions (of the order of kilometer embedding the maximum of ΔΦ we evidence a non-linear regime of the current-voltage relationship. The model predicts also that visible arcs form when the velocity shear in LLBL is above a threshold value depending on the generator and

  20. Plasma structure within poleward-moving cusp/cleft auroral transients: EISCAT Svalbard radar observations and an explanation in terms of large local time extent of events

    Directory of Open Access Journals (Sweden)

    M. Lockwood

    2000-09-01

    Full Text Available We report high-resolution observations of the southward-IMF cusp/cleft ionosphere made on December 16th 1998 by the EISCAT (European incoherent scatter Svalbard radar (ESR, and compare them with observations of dayside auroral luminosity, as seen at a wavelength of 630 nm by a meridian scanning photometer at Ny Ålesund, and of plasma flows, as seen by the CUTLASS (co-operative UK twin location auroral sounding system Finland HF radar. The optical data reveal a series of poleward-moving transient red-line (630 nm enhancements, events that have been associated with bursts in the rate of magnetopause reconnection generating new open flux. The combined observations at this time have strong similarities to predictions of the effects of soft electron precipitation modulated by pulsed reconnection, as made by Davis and Lockwood (1996; however, the effects of rapid zonal flow in the ionosphere, caused by the magnetic curvature force on the newly opened field lines, are found to be a significant additional factor. In particular, it is shown how enhanced plasma loss rates induced by the rapid convection can explain two outstanding anomalies of the 630 nm transients, namely how minima in luminosity form between the poleward-moving events and how events can re-brighten as they move poleward. The observations show how cusp/cleft aurora and transient poleward-moving auroral forms appear in the ESR data and the conditions which cause enhanced 630 nm emission in the transients: they are an important first step in enabling the ESR to identify these features away from the winter solstice when supporting auroral observations are not available.Key words: Ionosphere (polar ionosphere - Magnetospheric physics (magnetopause; cusp and boundary layers; solar wind-magnetosphere interactions

  1. 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

  2. Artificial periodic irregularities in the auroral ionosphere

    Directory of Open Access Journals (Sweden)

    M. T. Rietveld

    1996-12-01

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

  3. On the nature of electromagnetic waves in the vicinity of auroral archs

    International Nuclear Information System (INIS)

    Volokitin, A.S.; Mordovskaya, V.G.

    1988-01-01

    Excitation of kinetic Alfven waves by longitudinal current in the vicinity of auroral arcs is considered in the framework of quasilinear theory. It is shown that experimentally observed low-frequency electromagnetic waves with f<2Hz frequency in the vicinity of uniform auroral arcs represent the Alfven waves, excited at altitudes of three Earth radii and above by longitudinal electric current

  4. How well does wind speed predict air-sea gas transfer in the sea ice zone? A synthesis of radon deficit profiles in the upper water column of the Arctic Ocean

    Science.gov (United States)

    Loose, B.; Kelly, R. P.; Bigdeli, A.; Williams, W.; Krishfield, R.; Rutgers van der Loeff, M.; Moran, S. B.

    2017-05-01

    We present 34 profiles of radon-deficit from the ice-ocean boundary layer of the Beaufort Sea. Including these 34, there are presently 58 published radon-deficit estimates of air-sea gas transfer velocity (k) in the Arctic Ocean; 52 of these estimates were derived from water covered by 10% sea ice or more. The average value of k collected since 2011 is 4.0 ± 1.2 m d-1. This exceeds the quadratic wind speed prediction of weighted kws = 2.85 m d-1 with mean-weighted wind speed of 6.4 m s-1. We show how ice cover changes the mixed-layer radon budget, and yields an "effective gas transfer velocity." We use these 58 estimates to statistically evaluate the suitability of a wind speed parameterization for k, when the ocean surface is ice covered. Whereas the six profiles taken from the open ocean indicate a statistically good fit to wind speed parameterizations, the same parameterizations could not reproduce k from the sea ice zone. We conclude that techniques for estimating k in the open ocean cannot be similarly applied to determine k in the presence of sea ice. The magnitude of k through gaps in the ice may reach high values as ice cover increases, possibly as a result of focused turbulence dissipation at openings in the free surface. These 58 profiles are presently the most complete set of estimates of k across seasons and variable ice cover; as dissolved tracer budgets they reflect air-sea gas exchange with no impact from air-ice gas exchange.

  5. A new method of organizing spectral line intensity ratio fluctuations of auroral emissions

    International Nuclear Information System (INIS)

    Thelin, B.

    1986-02-01

    In this paper a new kind of linearization effect between the atmospheric auroral emissions is presented. The same kind of linearization effect has previously been found in nightglow emissions from photometer measurements and in the spectrochemical field from studies of optical light sources. Linear graphs have been obtained for atomic spectral lines and vibrational bandspectra when the spectral line ratio fluctuations were plotted versus the photon energies of these emissions. This new effect has been studied with a spectrophotometer in auroral emissions, where linear graphs have been obtained on different auroral occasions. By doing such studies of auroral light it is possible to see the importance of the inelastic scattering cross section between electrons - atoms and electrons - molecules. In this way it has shown to be possible to determine the mean energy of the interacting thermal electrons that are active in the different auroral phases. (author)

  6. Correlation between auroral kilometric radiation and inverted v electron precipitation

    International Nuclear Information System (INIS)

    Green, J.L.; Gurnfti, D.A.; Hoffmans, R.A.

    1979-01-01

    Simultaneous observations of energetic electron precipitations and auroral kilometric radiation (AKR) were obtained from the polar orbiting satellites AE-D and Hawkeye. The Hawkeye observations were restricted to periods when the satellite was in the AKR emission cone in the northern hemisphere an at radial distances > or approx. =7 R/sub E/ to avoid local propagation cutoff effects. In addition, the AE-D measurements were restricted to complete passes across the auroral oval in the evening to midnight local time sector (from 20 to 01 hours magnetic local time). This is the local time region where the most intense bursts of AKR are believed to originate. A qualitative survey of AKR and electron precipitation than with plasma sheet precipitation. Quantitatively, a good correlation is found between the AKR intensity and the peak energy of inverted V events. In addition, in the tail of the most field-aligned portion (approx.O 0 pitch angle) of the distribution functions of the inverted V events,systematic changes are indicated as the associated AKR intensity increases. When the AKR power flux is weak ( -17 W/(m 2 Hz)). From a determination of the simultaneous power in the inverted V events and the AKR bursts, the efficiency of converting the charge particle energy into EM radiation increases to a maximum of about 1% for the most intense AKR bursts. However, conversion efficiencies as low as 10 -5 % are also found. There is some evidence which suggests that the tail temperature, T in F (V) of the inverted V events, may play an important role in the efficient generation or amplification of auroral kilometric radiation

  7. Auroral phenomenology and magnetospheric processes earth and other planets

    CERN Document Server

    Keiling, Andreas; Bagenal, Fran; Karlsson, Tomas

    2013-01-01

    Published by the American Geophysical Union as part of the Geophysical Monograph Series. Many of the most basic aspects of the aurora remain unexplained. While in the past terrestrial and planetary auroras have been largely treated in separate books, Auroral Phenomenology and Magnetospheric Processes: Earth and Other Planets takes a holistic approach, treating the aurora as a fundamental process and discussing the phenomenology, physics, and relationship with the respective planetary magnetospheres in one volume. While there are some behaviors common in auroras of the diffe

  8. Altitude variations of ionospheric currents at auroral latitudes

    International Nuclear Information System (INIS)

    Kamide, Y.; Brekke, A.

    1993-01-01

    On the basis of updated EISCAT experiments, the first full derivation of the ionospheric current density of the auroral electrojets at six different altitudes are presented. It is found that current vectors at different altitudes are quite different, although the eastward and westward currents prevail in the evening and morning sectors, respectively, once the currents are integrated over altitude. The eastward electrojet becomes almost northward whilst the westward electrojet becomes almost southward, at the highest altitude, 125 km, in this study. The physical implications of these characteristics are discussed

  9. A detector for high frequency modulation in auroral particle fluxes

    Science.gov (United States)

    Spiger, R. J.; Oehme, D.; Loewenstein, R. F.; Murphree, J.; Anderson, H. R.; Anderson, R.

    1974-01-01

    A high time resolution electron detector has been developed for use in sounding rocket studies of the aurora. The detector is used to look for particle bunching in the range 50 kHz-10 MHz. The design uses an electron multiplier and an onboard frequency spectrum analyzer. By using the onboard analyzer, the data can be transmitted back to ground on a single 93-kHz voltage-controlled oscillator. The detector covers the 50 kHz-10 MHz range six times per second and detects modulation on the order of a new percent of the total electron flux. Spectra are presented for a flight over an auroral arc.

  10. Electron Velocity Shear Instability in the Auroral Ionosphere.

    Science.gov (United States)

    1982-06-25

    function of order .1 ~e y Le’ L 0, Vde - - (ve /2ae) Xn n/ax, Z is the plasma dispersion function and Z’( ) = dZ/d . The ion response X is simply...and 2 current. systems in the auroral ionosphere [lijima and Potemra, 19761 and to electron current return current regions in solar flares [Knight and... SYSTEMS (OS) -TE IS CDP:ES) or.XCCS SYSTE.. ENGLNEERING ORG DIRECTOR WASHINGTON, D.C. 20305 DEFENSE NUCLEAR AGENCY OICY ATTN R. CRAWFORDi,.’, WASHINGTION

  11. Energy of auroral electrons and Z mode generation

    Science.gov (United States)

    Krauss-Varban, D.; Wong, H. K.

    1990-01-01

    The present consideration of Z-mode radiation generation, in light of observational results indicating that the O mode and second-harmonic X-mode emissions can prevail over the X-mode fundamental radiation when suprathermal electron energy is low, gives attention to whether the thermal effect on the Z-mode dispersion can be equally important, and whether the Z-mode can compete for the available free-energy source. It is found that, under suitable circumstances, the growth rate of the Z-mode can be substantial even for low suprathermal auroral electron energies. Growth is generally maximized for propagation perpendicular to the magnetic field.

  12. Investigation of the Representation of OLEs and Terrain Effects Within the Costal Zone in the EDMF Parameterization Scheme: An Airborne Doppler Wind Lidar Perspective

    Science.gov (United States)

    2014-10-20

    This platform relative navigation has been done and is reported in attachment 3. The second step is to compute heat, moisture and momentum fluxes for...Prospecting DWL mode 2° forward stare ~6km surface intercept from 300 m flight level Line-of-Sight wind speed (VLOS) ’ Stacked VLOS ~2m vertical, 50 m...instabilities (non-convective). WY^ Particle probes j* TODWL scanner ^ ^^■^^1 ; ^ ’^^H ^^^immmm CTV Surface Temperature Sensor / iW

  13. Extended period of polar cap auroral display: auroral dynamics and relation to the IMF and the ionospheric convection

    Directory of Open Access Journals (Sweden)

    V. G. Vorobjev

    Full Text Available An unusually extended period (5 h of polar cap auroral display on 3 August 1986 is examined. Auroras have been investigated using ground-based data as well as measurements from the IMP-8 spacecraft in interplanetary space and simultaneous observations from the polar-orbiting satellites Viking and DE-1 in the northern and southern hemispheres, respectively. It is found that visible Sun-aligned arcs are located inside the transpolar band of the θ-aurora observed from the satellite in ultraviolet wavelengths. The transpolar band can contain several Sun-aligned arcs that move inside the band toward the morning or evening side of the auroral oval independent of the direction of the band movement. Intensifications of polar cap auroras with durations of up to about 30 min are observed. No change has been found in either IMF parameters or substorm activity that can be related to these intensifications. The θ-aurora occurred during a 2-h period when the B z-component of the IMF was negative. A tendency is noted for dawnward (duskward displacement of the transpolar band when By>0 (By<0 in the southern hemisphere. Simultaneous observations of auroral ovals during interplanetary Bz<0, By<0 and Bx>0 in both hemispheres and convection patterns for Bz<0 and By<0 have been displayed using satellite and ground-based measurements. It was found that the transpolar band of the -aurora in the sunlit hemisphere was situated in the region of large-scale downward Birkeland currents.

  14. Extended period of polar cap auroral display: auroral dynamics and relation to the IMF and the ionospheric convection

    Directory of Open Access Journals (Sweden)

    V. G. Vorobjev

    1995-08-01

    Full Text Available An unusually extended period (5 h of polar cap auroral display on 3 August 1986 is examined. Auroras have been investigated using ground-based data as well as measurements from the IMP-8 spacecraft in interplanetary space and simultaneous observations from the polar-orbiting satellites Viking and DE-1 in the northern and southern hemispheres, respectively. It is found that visible Sun-aligned arcs are located inside the transpolar band of the θ-aurora observed from the satellite in ultraviolet wavelengths. The transpolar band can contain several Sun-aligned arcs that move inside the band toward the morning or evening side of the auroral oval independent of the direction of the band movement. Intensifications of polar cap auroras with durations of up to about 30 min are observed. No change has been found in either IMF parameters or substorm activity that can be related to these intensifications. The θ-aurora occurred during a 2-h period when the B z-component of the IMF was negative. A tendency is noted for dawnward (duskward displacement of the transpolar band when By>0 (By<0 in the southern hemisphere. Simultaneous observations of auroral ovals during interplanetary Bz<0, By<0 and Bx>0 in both hemispheres and convection patterns for Bz<0 and By<0 have been displayed using satellite and ground-based measurements. It was found that the transpolar band of the -aurora in the sunlit hemisphere was situated in the region of large-scale downward Birkeland currents.

  15. Comparison of ionospheric conductances and auroral luminosities observed simultaneously with the Chatanika radar and the DE 1 auroral imagers

    International Nuclear Information System (INIS)

    Robinson, R.M.; Vondrak, R.R.; Craven, J.D.; Frank, L.A.; Miller, K.

    1989-01-01

    Auroral luminosities at vacuum ultraviolet (VUV) wavelengths are combined with simultaneous and coincident ionospheric electron density measurements made by the Chatanika radar to relate ionospheric conductances to optical emissions. The auroral luminosities are obtained along the magnetic meridian through Chatanika with the auroral imaging photometers on the Dynamics Explorer 1 (DE 1) satellite as the radar scans in the magnetic meridian to measure electron density and conductivity as a function of altitude and latitude. The observations are used to determine an empirical relationship between the luminosities measured at VUV wavelengths and the Hall and Pedersen conductances. Of particular interest is the response of the photometer when using the VUV filter designated 123W. This filter admits the 130.4- and 135.6-nm emissions of atomic oxygen and the Lyman-Birge-Hopfield (LBH) bands of N 2 . Model calculations of the LBH and O I (135.6 nm) contributions to the total measured luminosity indicate that the relation between 123W luminosity and Pedersen conductance is less sensitive to the average energy of the precipitating electrons than the corresponding relation between the Hall conductance and 123W luminosity. This is because both the luminosity and Pedersen conductance decrease with increasing electron energy. The luminosity decreases with increasing energy because the emissions are more strongly absorbed by O 2 above the region of production. The Pedersen conductance decreases with increasing energy because the Pedersen mobility maximizes at an altitude of about 140 km. In contrast, the Hall conductance increases with increasing electron energy, so that the relation between Hall conductance and luminosity depends on the hardness of the precipitation

  16. 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

  17. Generation of the auroral electron velocity distribution by electrostatic turbulence

    International Nuclear Information System (INIS)

    Bryant, D.A.; Cook, A.C.; Wang, Z.-S.; Angelis, U. de; Perry, C.H.

    1991-01-01

    It is shown from first principles that the characteristic peak in the auroral electron velocity distribution can be generated stochastically through resonant interactions with lower-hybrid electrostatic turbulence. The peak itself is shown to be the inevitable consequence of restrictions imposed on random walk in velocity space by the limitation in wave group velocity. A Monte-Carlo model of the process demonstrates how the various properties of the acceleration region are reflected in the resultant electron distribution. It is shown, in particular, that the width of the peak is governed by the amplitude of the turbulence, while the amplitude of the peak reflects the column density of wave energy. Electron distributions encountered within three auroral arcs are interpreted to yield order of magnitude estimates of the amplitude and rms electric field of lower-hybrid wave packets. The velocities and frequencies of the resonant waves, the net electric field, the column density of wave energy and the electric field energy density are also estimated. The results are found to be not inconsistent with available electric-field measurements. (author)

  18. Untangling the Space-Time Ambiguity of Auroral Emissions

    Science.gov (United States)

    Gjerloev, J. W.; Humberset, B.; Michell, R. G.; Samara, M.; Mann, I. R.

    2012-12-01

    In this paper we address the spatiotemporal characteristics of the magnetosphere-ionosphere (M-I) system as observed by an all-sky imager (ASI). We utilize 557.7 nm images obtained by a ground based ASI located under the dark ionosphere (~22 MLT) at Poker Flat, Alaska. The 19 min movie was recorded at 3.31 Hz during continuous moderately intense auroral activity driven by a southward IMF Bz of about -5 nT. We analyze this movie using a simple, yet robust, 2D FFT technique that allows us to determine the scale size dependent variability. When plotting the correlation pattern as a function of scale size and time separation we find a pattern with distinct regions of high and low correlation. Larger scale sizes are found to have longer duration. We interpret this remarkable result as indicative of a M-I system that uses repeatable solutions to transfer energy and momentum from the magnetosphere to the ionosphere. Our findings support the characteristics of the field-aligned currents as determined from multi-point satellite observations (ST-5, Gjerloev et al., Annales Geophysicae, 2011). Two different electromagnetic parameters, auroral emissions and field-aligned currents, display similar characteristics supporting our conclusion that this is indicative of a fundamental behavior of the M-I system.

  19. Electric fields and energetic particle precipitation in an auroral arc

    International Nuclear Information System (INIS)

    Edwards, T.; Bryant, D.A.; Smith, M.J.; Fahleson, U.; Faelthammer, C.G.; Pedersen, A.

    1975-01-01

    Preliminary results are presented from a rocket flight across a single discrete auroral arc extending from early evening to magnetic midnight. The rocket was fired at the end of the growth phase of an isolated auroral substorm. It carried a separating payload to make simultaneous measurements of electrons (0.6 - 25 keV, pitch angle 0 - 60 0 ) at two points. From the main vehicle measurements were also made of ions (same energy range) as well as of the electric field vector and plasma parameters. The electron spectra were hardest towards the centre of the arc, where the peak intensity was at 9.5 keV. The precipitation structure observed was similar to that of an 'inverted V' but on a smaller scale. The electric field was northward south of the arc, southward within the arc and somewhat north of it, then again northward. At the northern edge of the precipitation region the field was very irregular. The field strength reached a maximum of about 50 mV/m some distance north of the arc. The line integral of the electric field across the arc was of the order of a kilovolt, too small to be responsible for the changes observed in the electron energy spectrum. An electric potential distribution, consistent with the results obtained, is present. (Auth.)

  20. Wind speed change regionalization in China (1961–2012

    Directory of Open Access Journals (Sweden)

    Pei-Jun Shi

    2015-06-01

    Full Text Available This research quantitatively recognized the wind speed change using wind speed trend and trend of wind speed variability from 1961 to 2012 and regionalized the wind speed change on a county-level basis. The mean wind speed observation data and linear fitting method were used. The findings suggested that level-I regionalization includes six zones according to wind speed trend value in different regions, viz. Northeast China–North China substantial declining zone, East–Central China declining zone, Southeast China slightly declining zone, Southwest China very slightly declining zone, Northwest China declining zone, and Qinghai–Tibetan Plateau slightly declining zone. Level-II regionalization divides China into twelve regions based on trend of wind speed variability and the level-I regionalization results.

  1. 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

  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. Development of the Near-Earth Magnetotail and the Auroral Arc Associated with Substorm Onset: Evidence for a New Model

    Science.gov (United States)

    Miyashita, Y.; Hiraki, Y.; Angelopoulos, V.; Ieda, A.; Machida, S.

    2015-12-01

    We have studied the time sequence of the development of the near-Earth magnetotail and the auroral arc associated with a substorm onset, using the data from the THEMIS spacecraft and ground-based observatories at high temporal and spatial resolutions. We discuss four steps of the auroral development, linking them to magnetotail changes: the auroral fading, the initial brightening of an auroral onset arc, the enhancement of the wave-like structure, and the poleward expansion. A case study shows that near-Earth magnetic reconnection began at X~-17 RE at least ~3 min before the auroral initial brightening and ~1 min before the auroral fading. Ionospheric large-scale convection also became enhanced just before the auroral fading and before the auroral initial brightening. Then low-frequency waves were amplified in the plasma sheet at X~-10 RE, with the pressure increase due to the arrival of the earthward flow from the near-Earth reconnection site ~20 s before the enhancement of the auroral wave-like structure. Finally, the dipolarization began ~30 s before the auroral poleward expansion. On the basis of the present observations, we suggest that near-Earth magnetic reconnection plays two roles in the substorm triggering. First, it generates a fast earthward flow and Alfvén waves. When the Alfvén waves which propagate much faster than the fast flow reach the ionosphere, large-scale ionospheric convection is enhanced, leading to the auroral initial brightening and subsequent gradual growth of the auroral wave-like structure. Second, when the reconnection-initiated fast flow reaches the near-Earth magnetotail, it promotes rapid growth of an instability, such as the ballooning instability, and the auroral wave-like structure is further enhanced. When the instability grows sufficiently, the dipolarization and the auroral poleward expansion are initiated.

  4. Association between substorm onsets in auroral all-sky images and geomagnetic Pi2pulsations

    Science.gov (United States)

    Miura, T.; Ieda, A.; Teramoto, M.; Kawashima, T.

    2017-12-01

    Substorms are explosive disturbances in the magnetosphere and ionosphere of Earth. Substorm onsets are often identified usingsudden auroral brightenings (auroral breakup) or geomagnetic Pi2 pulsations. These auroral brightenings and Pi2 pulsations aresupposed to occur simultaneously within approximately 1 min of each other. However, as auroral brightenings typically includea two-stage development, this simultaneity is not straightforward. In this study, we clarify the correspondence between Pi2 pulsations and auroral brightenings, including the two-stage development.The first stage of the development is the sudden brightening of an auroral arc near the midnight (initial brightening)and the second stage is the poleward expansion of the auroral arc. We compared all-sky images (3 s resolution) in Canada andgeomagnetic observations (0.5-1 s resolution) in North and Central America, using data from the THEMIS project. In this study,we examined three substorms events that exhibit evidence of the two-stage auroral development. In the first event (4 March 2008), an auroral initial brightening occurred at 0533:57 UT and a poleward expansion was observedat 0538:12 UT (4 min after the initial brightening) in Gillam (magnetic latitude:66.0 °, longitude:333 °, MLT:22.9). In contract,the Pi2 pulsation started at 0539:30 UT, which is closer to the time of the poleward expansion, in Carson City (magnetic latitude:45.0 °, longitude:304 °). and San Juan (magnetic latitude:27.9 °, longitude:6.53 °). Thus, we consider this Pi2 pulsation ascorresponding to the poleward expansion rather than the initial brightening. This correspondence was also seen in the other twoevents, suggesting that it is not exceptional. We interpret that the Pi2 pulsation corresponds to the poleward expansion becauseboth are caused by the magnetic field dipolarization, which is a drastic change that propagates from low- to high-latitude fieldlines.

  5. Rocket measurements of electric fields, electron density and temperature during the three phases of auroral substorms

    International Nuclear Information System (INIS)

    Marklund, G.; Block, L.; Lindqvist, P.-A.

    1979-12-01

    On Jan. 27, 1979, three rocket payloads were launched from Kiruna, Sweden, into different phases of two successive auroral substorms. Among other experiments, the payloads carried the RIT double probe electric field experiments, providing electric field, electron density and temperature data, which are presented here. These are discussed in association with observations of particles, ionospheric drifts (STARE) and electric fields in the equatorial plane (GEOS). The motions of the auroral forms, as obtained from auroral pictures are compared with the E x B/B 2 drifts and the currents calculated from the rocket electric field and density measurements with the equivalent current system deduced from ground based magnetometer data (SMA). (Auth.)

  6. Model county ordinance for wind projects

    Energy Technology Data Exchange (ETDEWEB)

    Bain, D.A. [Oregon Office of Energy, Portland, OR (United States)

    1997-12-31

    Permitting is a crucial step in the development cycle of a wind project and permits affect the timing, cost, location, feasibility, layout, and impacts of wind projects. Counties often have the lead responsibility for permitting yet few have appropriate siting regulations for wind projects. A model ordinance allows a county to quickly adopt appropriate permitting procedures. The model county wind ordinance developed for use by northwest states is generally applicable across the country and counties seeking to adopt siting or zoning regulations for wind will find it a good starting place. The model includes permitting procedures for wind measurement devices and two types of wind systems. Both discretionary and nondiscretionary standards apply to wind systems and a conditional use permit would be issued. The standards, criteria, conditions for approval, and process procedures are defined for each. Adaptation examples for the four northwest states are provided along with a model Wind Resource Overlay Zone.

  7. Distribution of auroral arcs during quiet geomagnetic conditions

    International Nuclear Information System (INIS)

    Lassen, K.; Danielsen, C.

    1989-01-01

    Auroral arcs observed from the Greenland all-sky camera network during quiet intervals (AE 500 eV) and a poleward, low-energy part. Previous studies have shown that the arc pattern is composed of two subpatterns, too, the polar cap are pattern and the oval arc pattern. It is demonstrated that the polar cap arc pattern is situated in the poleward, low-energy part of the precipitation belt, connected to the low-latitude boundary layer, whereas the oval arc pattern is in the equatorial higher energy belt, connected to the plasma sheet. The dividing line between the two arc patterns is associated with the boundary of trapped ≥ 40-keV electrons. The designation polar cap arc pattern is shown to be ambiguous, wherefore it is proposed to replace it by the term high-latitude arc pattern

  8. On the spectrum of the secondary auroral electrons

    International Nuclear Information System (INIS)

    Fung, S.F.; Hoffman, R.A.

    1988-01-01

    We present the results from a statistical study of the spectral characteristics of the (power law portion) secondary electrons associated with inverted-V electron precipitation events. A total of 106 inverted-V events observed at low altitudes ( - /sup γ/ with an averaged γ = 1.85. This spectral parameter is relatively insensitive to the variation of locations of the inverted-V events, but it depends on the primary beam parameters. We compare our results with the predictions and assess the applicabilities of the current theories on the generation of the low-energy auroral power law secondary electrons. Our analysis shows that collisional processes are the dominant source of the secondary electrons. copyright American Geophysical Union 1988

  9. Auroral kilometric radiation source region observations from ISIS 1

    International Nuclear Information System (INIS)

    Benson, R.F.

    1981-01-01

    The ISIS 1 observations of the high-frequency portion of the auroral kilometric radiation (AKR) spectrum are considered, that is, from the minimum frequency encountered for the extraordinary mode cut-off (approximately 450 kHz) to the upper frequency cut-off (approximately 800 kHz). AKR is found to be generated in the extraordinary mode just above the local cutoff frequency and to emanate in a direction that is nearly perpendicular to the magnetic field. It occurs within local depletions of electron density, where the ratio of plasma frequency to cyclotron frequency is below 0.2. The density depletion is restricted to altitudes above approximately 2,000 km, and the upper AKR frequency limit corresponds to the extraordinary cutoff frequency at this altitude

  10. Simultaneous auroral observations described in the historical records of China, Japan and Korea from ancient times to AD 1700

    Directory of Open Access Journals (Sweden)

    D. M. Willis

    Full Text Available Early auroral observations recorded in various oriental histories are examined in order to search for examples of strictly simultaneous and indisputably independent observations of the aurora borealis from spatially separated sites in East Asia. In the period up to ad 1700, only five examples have been found of two or more oriental auroral observations from separate sites on the same night. These occurred during the nights of ad 1101 January 31, ad 1138 October 6, ad 1363 July 30, ad 1582 March 8 and ad 1653 March 2. The independent historical evidence describing observations of mid-latitude auroral displays at more than one site in East Asia on the same night provides virtually incontrovertible proof that auroral displays actually occurred on these five special occasions. This conclusion is corroborated by the good level of agreement between the detailed auroral descriptions recorded in the different oriental histories, which furnish essentially compatible information on both the colour (or colours of each auroral display and its approximate position in the sky. In addition, the occurrence of auroral displays in Europe within two days of auroral displays in East Asia, on two (possibly three out of these five special occasions, suggests that a substantial number of the mid-latitude auroral displays recorded in the oriental histories are associated with intense geomagnetic storms.

    Key words. Magnetospheric physics (auroral phenomena; storms and substorms

  11. Visualizing Space Weather: The Planeterrella Auroral Simulator as a Heliophysics Public Outreach Tool

    Science.gov (United States)

    Masongsong, E. V.; Lilensten, J.; Booth, M. J.; Suri, G.; Heflinger, T. G.; Angelopoulos, V.

    2014-12-01

    The NASA THEMIS and ARTEMIS satellite missions study "space weather," which describes the solar wind influence on Earth's protective magnetic shield, the magnetosphere. Space weather is important to study and predict because it can damage critical GPS and communications satellites, harm space travelers, and even disable our global electrical grid. The Planeterrella is an innovative heliophysics outreach demonstration, expanding public awareness of space weather by visualizing the sun-Earth connection up close and in-person. Using a glass vacuum chamber, two magnetized spheres and a 1kV power supply, the device can simulate plasma configurations of the solar corona, solar wind, Van Allen radiation belts, and auroral ovals, all of which are observable only by satellites. This "aurora in a bottle" is a modernized version of the original Terrella built by Kristian Birkeland in the 1890s to show that the aurora are electrical in nature. Adapted from plans by Lilensten et al. at CNRS-IPAG, the UCLA Planeterrella was completed in Nov. 2013, the second device of its kind in the U.S., and the centerpiece of the THEMIS/ARTEMIS mobile public outreach exhibit. In combination with captivating posters, 3D magnetic field models, dazzling aurora videos and magnetosphere animations, the Planeterrella has already introduced over 1200 people to the electrical link between our sun and the planets. Most visitors had seen solar flare images in the news, however the Planeterrella experience enhanced their appreciation of the dynamic solar wind and its effects on Earth's invisible magnetic field. Most importantly, visitors young and old realized that magnets are not just cool toys or only for powering hybrid car motors and MRIs, they are a fundamental aspect of ongoing life on Earth and are key to the formation and evolution of planets, moons, and stars, extending far beyond our galaxy to other planetary systems throughout the universe. Novel visualizations such as the Planeterrella can

  12. Statistical characterization of the Sub-Auroral Polarization Stream (SAPS)

    Science.gov (United States)

    Kunduri, B.; Baker, J. B.; Ruohoniemi, J. M.; Erickson, P. J.; Coster, A. J.; Oksavik, K.

    2017-12-01

    The Sub-Auroral Polarization Stream (SAPS) is a narrow region of westward directed plasma convection typically observed in the dusk-midnight sector equatorward of the main auroral oval. SAPS plays an important role in mid-latitude space weather dynamics and has a controlling influence on the evolution of large-scale plasma features, such as Storm Enhanced Density (SED) plumes. In this study, data from North American mid-latitude SuperDARN radars collected between January 2011 and December 2014 have been used to compile a database of SAPS events for statistical analysis. We examine the dependence of SAPS velocity magnitude and direction on geomagnetic activity and magnetic local time. The lowest speed limit and electric fields observed during SAPS are discussed and histograms of SAPS velocities for different Dst bins and MLAT-MLT locations are presented. We find significant differences in SAPS characteristics between periods of low and high geomagnetic activity, suggesting that SAPS are driven by different mechanisms during storm and non-storm conditions. To further explore this possibility, we have characterized the SAPS location and peak speed relative to the ionospheric trough specified by GPS Total Electron Content (TEC) data from the MIT Haystack Madrigal database. A particular emphasis is placed on identifying the extent to which the location, structure, and depth of the trough may play a controlling influence on SAPS speeds during storm and non-storm periods. The results are interpreted in terms of the current paradigm for active thermosphere-ionosphere feedback being an important component of SAPS physics.

  13. Interaction of upgoing auroral H+ and O+ beams

    International Nuclear Information System (INIS)

    Kaufmann, R.L.; Ludlow, G.R.; Collin, H.L.; Peterson, W.K.; Burch, J.L.

    1986-01-01

    Data from the S3-3 and DE 1 satellites are analyzed to study the interaction between H + and O + ions in upgoing auroral beams. Every data set analyzed showed some evidence of an interaction. The measured plasma was found to be unstable to a low-frequency electrostatic wave that propagates at an oblique angle to B-arrow-right 0 . A second wave, which can propagate parallel to B-arrow-right 0 , is weakly damped in the plasma studied in most detail. It is likely that the upgoing ion beams generate this parallel wave at lower altitudes. The resulting wave-particle interactions qualitatively can explain most of the features observed in ion distribution functions. H + ions in the low-velocity tail of the H + beam are decelerated and O + ions in the high-velocity tail of the 0 + beam are accelerated through this process. This may explain the occasional observation of O + beams with substantially higher streaming energies than the simultaneously observed H + beams. The wave-particle interactions also can explain the asymmetrical features that regularly are seen in H + and 0 + distribution functions. The wave which was found to be unstable in the measured plasma primarily accelerates 0 + perpendicular to B/sub O/. This process can produce weakly conical 0 + distributions which are characterized by T/sub perpendicular/>T/sub Pi/ rather than by having a peak at 90 0 pitch angle within the acceleration region. In general, the interaction between different ion species in multicomponent beams appears to be a dominant factor in determining the structure of upgoing auroral ions. The same process is likely to be important in a number of other beam-containing space plasmas

  14. Electron cyclotron waves in the presence of parallel electric fields in the Earth's auroral plasma

    Directory of Open Access Journals (Sweden)

    S. Kumar

    1997-01-01

    Full Text Available The electron cyclotron waves that originate at low altitudes (<0.5 RE and observed by ground facilities have been studied in the presence of a weak parallel electric field in auroral magnetoplasma consisting of trapped energetic auroral electrons and cold background electrons of ionospheric origin. The model distribution for auroral trapped electrons is taken as Maxwellian ring distribution. An expression for the growth rate has been obtained in the presence of parallel electric field assuming that the real frequency in the whistler mode is not affected by the presence of the electric field. The results show that waves grow (or damp in amplitude for a parallel (or antiparallel electric field. The influence of the electric field is more pronounced at a shorter wavelength spectrum. An increase in population of energetic electrons increases the growth rate and thus, plays a significant role in the wave excitation process in the auroral regions.

  15. Comparison of auroral ovals from all-sky camera studies and from satellite photographs

    International Nuclear Information System (INIS)

    Bond, F.R.; Akasofu, S.I.

    1979-01-01

    A comparison is made of the statistical auroral ovals determined by all-sky camera photographs with DMSP photographs for different degrees of geomagnetic activity. It is shown that the agreement between them is excellent. (author)

  16. First Application of the Zeeman Technique to Remotely Measure Auroral Electrojet Intensity From Space

    Science.gov (United States)

    Yee, J. H.; Gjerloev, J.; Wu, D.; Schwartz, M. J.

    2017-01-01

    Using the O2 118 GHz spectral radiance measurements obtained by the Microwave Limb Sounder instrument on board the Aura spacecraft, we demonstrate that the Zeeman effect can be used to remotely measure the magnetic field perturbations produced by the auroral electrojet near the Hall current closure altitudes. Our derived current-induced magnetic field perturbations are found to be highly correlated with those coincidently obtained by ground magnetometers. These perturbations are also found to be linearly correlated with auroral electrojet strength. The statistically derived polar maps of our measured magnetic field perturbation reveal a spatial-temporal morphology consistent with that produced by the Hall current during substorms and storms. With today's technology, a constellation of compact, low-power, high spectral-resolution cubesats would have the capability to provide high precision and spatiotemporal magnetic field samplings needed for auroral electrojet measurements to gain insights into the spatiotemporal behavior of the auroral electrojet system.

  17. Field line projections of 6300 AA auroral emissions into the outer magnetosphere

    International Nuclear Information System (INIS)

    Shepherd, M.M.

    1979-07-01

    An empirical magnetospheric model is employed to project auroral intensity boundaries into the magnetosphere. The auroral data are in the form of instantaneous maps of 6300AA emission, acquired with the ISIS-II spacecraft and correspond to fluxes of low energy electrons. These are specific to a particular universal time and date. The magnetospheric model used is a purely empirical one, designed by Mead and Fairfield (1975) from 44.76 x 10 6 magnetic measurements made by 4 IMP satellites. Their model includes the dipole tilt as a variable, and permits selection from four different disturbance levels, so is particularly suited to these data. In a general way, the auroral projections agree with what is expected, giving some confidence in this application of the model. But a number of features appear that were not predicted, and which should permit new insights into the relationship of specific auroral boundaries to the structure of the magnetosphere. (author)

  18. Identification of possible intense historical geomagnetic storms using combined sunspot and auroral observations from East Asia

    Directory of Open Access Journals (Sweden)

    D. M. Willis

    2005-03-01

    Full Text Available Comprehensive catalogues of ancient sunspot and auroral observations from East Asia are used to identify possible intense historical geomagnetic storms in the interval 210 BC-AD 1918. There are about 270 entries in the sunspot catalogue and about 1150 entries in the auroral catalogue. Special databases have been constructed in which the scientific information in these two catalogues is placed in specified fields. For the purposes of this study, an historical geomagnetic storm is defined in terms of an auroral observation that is apparently associated with a particular sunspot observation, in the sense that the auroral observation occurred within several days of the sunspot observation. More precisely, a selection criterion is formulated for the automatic identification of such geomagnetic storms, using the oriental records stored in the sunspot and auroral databases. The selection criterion is based on specific assumptions about the duration of sunspot visibility with the unaided eye, the likely range of heliographic longitudes of an energetic solar feature, and the likely range of transit times for ejected solar plasma to travel from the Sun to the Earth. This selection criterion results in the identification of nineteen putative historical geomagnetic storms, although two of these storms are spurious in the sense that there are two examples of a single sunspot observation being associated with two different auroral observations separated by more than half a (synodic solar rotation period. The literary and scientific reliabilities of the East Asian sunspot and auroral records that define the nineteen historical geomagnetic storms are discussed in detail in a set of appendices. A possible time sequence of events is presented for each geomagnetic storm, including possible dates for both the central meridian passage of the sunspot and the occurrence of the energetic solar feature, as well as likely transit times for the ejected solar plasma

  19. Balloon observations of auroral X-rays at Esrange, Sweden and related phenomena

    OpenAIRE

    Hirasima,Yo; Murakami,Hiroyuki; Okudaira,Kiyoaki; Fujii,Masami; Nishimura,Jun; Yamagami,Takamasa; Ejiri,Masaki; Miyaoka,Hiroshi; Ono,Takayuki; Kodama,Masahiro

    1984-01-01

    Balloon observations of auroral X-rays using different detector systems were carried out twice over Esrange, Sweden, in November and December 1982,in order to examine spatial and temporal characteristics of the energetic component of auroral electrons. One detector is a telescope system consisting of four scintillation counters whose fields of view are different with each other as well as with the viewing directions. It is shown from the first flight carrying the telescope system that a limit...

  20. Manual risk zoning wind turbines. Final version. 3rd updated version May 2013. 3 ed.; Handboek risicozonering windturbines. Eindversie. 3e geactualiseerde versie mei 2013

    Energy Technology Data Exchange (ETDEWEB)

    Faasen, C.J.; Franck, P.A.L.; Taris, A.M.H.W. [DNV KEMA, Arnhem (Netherlands)

    2013-05-15

    The title manual has been drafted to be able to quickly inventory the safety risks of wind turbines, which can speed up the licensing procedures for the installation of wind turbines. Attention is paid to the following categories: building areas, roads, waterways, railroads, industrial areas, underground cables and mains, aboveground cables, power transmission lines, dikes and dams, and telecommunication. For each of these categories the risks are calculated. This is an updated version of the manual which was first published in 2000 and updated in 2005 [Dutch] Dit is een actualisatie van het Handboek uit 2005. Het oorspronkelijke Handboek is in 2000 opgesteld. Het in 2000 verschenen Handboek is door ECN samengesteld in opdracht van Novem (nu: Agentschap NL) met als doel een uniforme methode te bieden voor het uitvoeren van kwantitatieve risicoanalyses en voor het toetsen van de resultaten aan acceptatiecriteria. Dit Handboek bood antwoord op de vraag van zowel projectontwikkelaars als overheden naar een algemeen geldende methode om veiligheidsrisico's van windturbines te berekenen voor diverse omgevingsaspecten. In 2005 is een actualisatie van het Handboek uitgebracht door ECN en KEMA in opdracht van SenterNovem (nu onderdeel van Agentschap NL). Daarin is verder ingegaan op turbines met grotere vermogens en is het Handboek aangevuld met rekenvoorbeelden. Vanwege de verdere ontwikkeling van de windturbinetechnologie, aangepaste wetgeving, het feit dat rekenmodellen verouderd waren en dat diverse infrastructuur steeds vaker gebundeld of geclusterd met windturbines wordt gerealiseerd, is het wenselijk / noodzakelijk de eventuele risico's op een consistente en eenduidige wijze in kaart te brengen. Daarom heeft Agentschap NL in 2012 opdracht gegeven aan DNV KEMA om het Handboek opnieuw te actualiseren. Hierbij zijn de resultaten van het rapport: 'Rekenmethodiek zonering windturbines in relatie tot gas- en elektrische infrastructuur' (2012), dat in

  1. Wind farm array wake losses

    Energy Technology Data Exchange (ETDEWEB)

    Baker, R.W. [Impact Weather, Washougal, WA (United States); McCarthy, E.F. [Wind Economics & Technology, Inc., Martinez, CA (United States)

    1997-12-31

    A wind turbine wake study was conducted in the summer of 1987 at an Altamont Pass wind electric generating facility. The wind speed deficits, turbulence, and power deficits from an array consisting of several rows of wind turbines is discussed. A total of nine different test configurations were evaluated for a downwind spacing ranging from 7 rotor diameters (RD) to 34 RD and a cross wind spacing of 1.3 RD and 2.7 RD. Wake power deficits of 15% were measured at 16 RD and power losses of a few percent were even measurable at 27 RD for the closer cross wind spacing. For several rows of turbines separated by 7-9 RD the wake zones overlapped and formed compound wakes with higher velocity deficits. The wind speed and direction turbulence in the wake was much higher than the ambient turbulence. The results from this study are compared to the findings from other similar field measurements.

  2. Assembling Markets for Wind Power

    DEFF Research Database (Denmark)

    Pallesen, Trine

    hand, as an economic good, wind power is said to suffer from (techno-economic) ‘disabilities’, such as high costs, fluctuating and unpredictable generation, etc. Therefore, because of its performance as a good, it is argued that the survival of wind power in the market is premised on different......This project studies the making of a market for wind power in France. Markets for wind power are often referred to as ‘political markets: On the one hand, wind power has the potential to reduce CO2-emissions and thus stall the effects of electricity generation on climate change; and on the other...... instruments, some of which I will refer to as ‘prosthetic devices’. This thesis inquires into two such prosthetic devices: The feed-in tariff and the wind power development zones (ZDE) as they are negotiated and practiced in France, and also the ways in which they affect the making of markets for wind power....

  3. Pathway and conversion of energy incident on auroral and sub-auroral ionosphere at substorm expansion onset

    Science.gov (United States)

    Ebihara, Y.; Tanaka, T.

    2017-12-01

    One explanation for SAPS/SAID is the poleward ionospheric electric field arising from a pair of Region 1 and Region 2 field-aligned currents (FACs). At substorm expansion onset, the FACs are intensified, resulting in intensification of energy incident on the auroral and sub-auroral ionosphere. Where does the energy comes from? Based on the results obtained by the global magnetohydrodynamics (MHD) simulation, we present energy flow and energy conversion associated with the Region 1 and Region 2 FACs that are intensified at the onset of substorm expansion. The cusp/mantle region transmits electromagnetic energy to almost the entire region of the magnetosphere. A part of electromagnetic energy is stored in the lobe in the growth phase. When reconnection takes place in the near-Earth tail region, the stored energy is released in addition to the continuously supplied one from the cusp/mantle dynamo. Two types of pathways of energy seem to be involved in the generation of the near-Earth dynamo that is associated with FACs at the expansion onset. The first type is related to the earthward fast flow in the plasma sheet. The electromagnetic energy coming from the lobe splits into the thermal energy and the kinetic energy. The kinetic energy is then converted to the thermal energy and the electromagnetic energy, in association of flow braking. The second type is that the plasma coming from the lobe goes into the inner magnetosphere directly. The electromagnetic energy is converted to the thermal energy, followed by the electromagnetic energy at off-equator. The near-Earth dynamo region seems to be embedded in the magnetospheric convection system. In this sense, the expansion onset may be regarded as a sudden, local intensification of the convection.

  4. Correspondence between the ULF wave power spatial distribution and auroral oval boundaries

    Directory of Open Access Journals (Sweden)

    Kozyreva O.V.

    2016-06-01

    Full Text Available The world-wide spatial distribution of the wave power in the Pc5 band during magnetic storms has been compared with auroral oval boundaries. The poleward and equatorward auroral oval boundaries are estimated using either the British Antarctic Survey database containing IMAGE satellite UV observations of the aurora or the OVATION model based on the DMSP particle data. The “epicenter” of the spectral power of broadband Pc5 fluctuations during the storm growth phase is mapped inside the auroral oval. During the storm recovery phase, the spectral power of narrowband Pc5 waves, both in the dawn and dusk sectors, is mapped inside the auroral oval or around its equatorward boundary. This observational result confirms previously reported effects: the spatial/temporal variations of the Pc5 wave power in the morning/pre-noon sector are closely related to the dynamics of the auroral electrojet and magnetospheric field-aligned currents. At the same time, narrowband Pc5 waves demonstrate typical resonant features in the amplitude-phase latitudinal structure. Thus, the location of the auroral oval or its equatorward boundary is the preferred latitude for magnetospheric field-line Alfven resonator excitation. This effect is not taken into account by modern theories of ULF Pc5 waves, but it could be significant for the development of more adequate models.

  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. Auroral zone E-region conductivities during solar minimum derived from EISCAT data

    International Nuclear Information System (INIS)

    Schlegel, K.

    1988-01-01

    From two years of EISCAT data (1985-1986, a period of low solar activity) 8337 E-region conductivity profiles have been calculated as 5-min averages. From these profiles the height of the conductivity maxima for the Hall and Pedersen conductivities (H max ), the height-integrated Hall and Pedersen conductivities and the ratio of both have been computed. Histograms as well as average values of these quantities are displayed as a function of K p and of magnetic local time. The former results showed quantitatively the increase of the conductivities and the decrease of H max with increasing magnetic activity. The latter results revealed that on the average the conductivities are maximal in the early morning hours due to hard particle precipitation, H max being affected both by the solar zenith angle and by particle precipitation. The solar zenith angle dependence of the conductivities is only significant for low K p -values. Latitudinal profiles of the height-integrated conductivities show quantitatively the southward shift of the average conductivity maximum with increasing magnetic activity

  7. SBARMO-79 a multi-balloon campaign in the auroral zone

    International Nuclear Information System (INIS)

    Tanskanen, P.; Kangas, J.; Bjordal, J.; Bronstad, K.; Block, L.P.; Holtet, T.

    1982-01-01

    A joint European International Magnetospheric Study (IMS) balloon campaign was conducted within the framework of the Scientific Ballooning and Radiation Monitoring Organization (SBARMO). The campaign was carried out during the time from May 30 to July 10, 1979. A total of 29 successful balloon launches were made from four launch sites located in Norway and in Finland. The campaign has the objective to provide information for a better understanding of temporal and spatial variations of magnetospheric processes, giving particular attention to the coupling between the magnetosphere and the ionosphere

  8. Effects of the interplanetary conditions on the magnetic activity observed in the southern auroral zone

    International Nuclear Information System (INIS)

    Cazeneuve, H.A.; Tabocchini, H.

    1981-01-01

    The relationship between the interplanetary conditions and the magnetic activity recorded at Belgrano is examined. H-component magnetograms, rheometer records and the concurrent interplanetary data are used. It is found that the geomagnetic activity is generated by the combined effect of a variety of interplanetary conditions. The data distinctly show that each physical entity of the interplanetary medium has a specific and precise role in the development of active periods. The reversal of the IMF polarity appears to be the critical step in the generation of geomagnetic activity. (author)

  9. Magnetic component of narrowband ion cyclotron waves in the auroral zone

    Czech Academy of Sciences Publication Activity Database

    Santolík, Ondřej; Pickett, J. S.; Gurnett, D. A.; Storey, L. R. O.

    2002-01-01

    Roč. 107, A12, 1444 (2002), s. SMP 17-1-17-14, doi: 10.1029/2001JA000146 ISSN 0148-0227 R&D Projects: GA ČR GA205/01/1064 Grant - others:NASA(US) NAG5-7943 Institutional research plan: CEZ:AV0Z3042911; CEZ:MSM 113200004 Keywords : proton-cyclotron frequency * plasma wave instrument * cyclotron waves Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 2.245, year: 2002

  10. Radar observations of auroral zone flows during a multiple-onset substorm

    Directory of Open Access Journals (Sweden)

    J. P. Morelli

    1995-11-01

    Full Text Available We present an analysis of ground magnetic field, ionospheric flow, geosynchronous particle, and interplanetary data during a multiple-onset substorm on 12 April 1988. Our principal results concern the modulations of the ionospheric flow which occur during the impulsive electrojet activations associated with each onset. During the first hour of the disturbance these take place every ~12.5 min and involve the formation of a new intense westward current filament in the premidnight sector, just poleward of the pre-existing extended current system driven by the large-scale flow. These filaments are ~1 h MLT wide (~600 km, and initially expand poleward to a width of ~300 km before contracting equatorward and coalescing with the pre-existing current, generally leaving the latter enhanced in magnitude and/or expanded in latitude. Within the impulsive electrojets the flow is found to be suppressed to values 50–100 m s–1 or less during the first few minutes, before surging equatorward at 0.5–1.0 km s–1 during the phase of rapid coalescence. The implication is that the precipitation-induced Hall conductivity within the impulsive electrojet initially rises to exceed ~100 mho, before decaying over a few minutes. This value compares with Hall conductivities of ~20 mho in the quasi-steady current regions, and a few mho or less in the regions poleward of the electrojets and in the preonset ionosphere. Preliminary evidence has also been found that the flow surges propagate from midnight to the morning sector where they are associated with arrested equatorward motion or poleward contractions of the current system. These observations are discussed in terms of present theoretical paradigms of the global behaviour of fields and flows which occur during substorms.

  11. Ionosphere dynamics in the auroral zone during the magnetic storm of March 17-18, 2015

    Science.gov (United States)

    Blagoveshchensky, D. V.; Sergeeva, M. A.

    2016-11-01

    A comprehensive study of the ionospheric processes encountered during the superstorm which started on March 17th 2015 has been carried out using magnetometer, ionosonde, riometer, ionospheric tomography and an all-sky camera installed in the observatory of Sodankylä, Finland. The storm manifested a number of interesting features. From 12:00 on March 17 there was a significant decrease of critical frequencies foF2 and intensive sporadic Es layers were observed. During the disturbance, there was a lack of variation of the X-component of the magnetic field at times, but the absorption level measured by the riometer was high. A comparison of the electron density distributions for the quiet and disturbed days as shown in the tomography data were very different. Where results were available at the same times, the tomographic foF2 values coincided with the ;real; foF2 values from the ionosonde. Where the ionosonde data was missing due to absorption, the tomographic foF2 values were used instead. The keograms from the all-sky camera showed that during disturbed days the aurorae manifested themselves as bright discrete forms. It was shown that the peaks of absorption due to particle precipitation seen by the riometer coincided in time with the brightenings of aurorae seen on the keograms.

  12. Wind Power in Georgia

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2012-11-01

    Georgia has good wind power potential. Preliminary analyses show that the technical wind power potential in Georgia is good. Meteorological data shows that Georgia has four main areas in Georgia with annual average wind speeds of over 6 m/s and two main areas with 5-6 m/s at 80m. The most promising areas are the high mountain zone of the Great Caucasus, The Kura river valley, The South-Georgian highland and the Southern part of the Georgian Black Sea coast. Czech company Wind Energy Invest has recently signed a Memorandum of Understanding with Georgian authorities for development of the first wind farm in Georgia, a 50MW wind park in Paravani, Southern Georgia, to be completed in 2014. Annual generation is estimated to 170.00 GWh and the investment estimated to 101 million US$. Wind power is suited to balance hydropower in the Georgian electricity sector Electricity generation in Georgia is dominated by hydro power, constituting 88% of total generation in 2009. Limited storage capacity and significant spring and summer peaks in river flows result in an uneven annual generation profile and winter time shortages that are covered by three gas power plants. Wind power is a carbon-free energy source well suited to balance hydropower, as it is available (often strongest) in the winter and can be exported when there is a surplus. Another advantage with wind power is the lead time for the projects; the time from site selection to operation for a wind power park (approximately 2.5 years) is much shorter than for hydro power (often 6-8 years). There is no support system or scheme for renewable sources in Georgia, so wind power has to compete directly with other energy sources and is in most cases more expensive to build than hydro power. In a country and region with rapidly increasing energy demands, the factors described above nevertheless indicate that there is a commercial niche and a role to play for Georgian wind power. Skra: An example of a wind power development

  13. Interactive Auroral Science for Hearing-Impaired Students

    Science.gov (United States)

    Samara, M.; Michell, R. G.; Jahn, J.; Pfeifer, M.; Ibarra, S.; Hampton, D. L.; Powell, D.

    2012-12-01

    Under a NASA E/PO grant, we have partnered with San Antonio's Sunshine Cottage School for Deaf Children to develop a science class experience where students directly interact with scientists and participate in a research-grade space science measurement campaign. The unique aspect of partnering with Sunshine Cottage lies in Sunshine's approach of auditory-verbal communication. Aided by technology (hearing aids, cochlear implants), a diverse student body with students of all levels of hearing loss (moderate through profound) is taught in an entirely auditory-verbal environment at Sunshine Cottage. Bringing these students into early contact with research work can lay the foundation for future careers in the STEM field that normally they might not consider as indicated by the first year of this collaboration where the student response was distinctly positive. Here we report on the first year of those activities, as they related to a ground based imaging approach to exploring the northern lights and from the point of view of the scientists that participated. The major components of that activity included a site visit to SwRI by the students and their teachers, a semester long lab at school utilizing current research tools and a real-time campaign night. The students used a number of diagnostics to first predict and then verify auroral activity. One of the tools used was the MOOSE observatory which is a community resource state of the art observatory comprised of 5 EMCCD imagers in Alaska, established through an NSF MRI grant. We will discuss the approach and lessons learned during the first year of the project and the directions that we will likely take in the second year. Lessons learned from teaching these students space science related topic can be flowed right back into mainstream classroom settings. One other significant and unexpected aspect of this first year was that we were able to connect two groups of students through skype (in the 4th to 5th grades) that

  14. Modeling of Jovian Auroral Polar Ion and Proton Precipitation

    Science.gov (United States)

    Houston, S. J.; Ozak, N. O.; Cravens, T.; Schultz, D. R.; Mauk, B.; Haggerty, D. K.; Young, J. T.

    2017-12-01

    Auroral particle precipitation dominates the chemical and physical environment of the upper atmospheres and ionospheres of the outer planets. Precipitation of energetic electrons from the middle magnetosphere is responsible for the main auroral oval at Jupiter, but energetic electron, proton, and ion precipitation take place in the polar caps. At least some of the ion precipitation is associated with soft X-ray emission with about 1 GW of power. Theoretical modeling has demonstrated that the incident sulfur and oxygen ion energies must exceed about 0.5 MeV/nucleon (u) in order to produce the measured X-ray emission. In this work we present a model of the transport of magnetospheric oxygen ions as they precipitate into Jupiter's polar atmosphere. We have revised and updated the hybrid Monte Carlo model originally developed by Ozak et al., 2010 to model the Jovian X-ray aurora. We now simulate a wider range of incident oxygen ion energies (10 keV/u - 5 MeV/u) and update the collision cross-sections to model the ionization of the atmospheric neutrals. The polar cap location of the emission and magnetosphere-ionosphere coupling both indicate the associated field-aligned currents must originate near the magnetopause or perhaps the distant tail. Secondary electrons produced in the upper atmosphere by ion precipitation could be accelerated upward to relativistic energies due to the same field-aligned potentials responsible for the downward ion acceleration. To further explore this, we simulate the effect of the secondary electrons generated from the heavy ion precipitation. We use a two-stream transport model that computes the secondary electron fluxes, their escape from the atmosphere, and characterization of the H2 Lyman-Werner band emission, including a predicted observable spectrum with the associated color ratio. Our model predicts that escaping electrons have an energy range from 1 eV to 6 keV, H2 band emission rates produced are on the order of 75 kR for an input

  15. On the motion of dayside auroras caused by a solar wind pressure pulse

    Directory of Open Access Journals (Sweden)

    A. Kozlovsky

    2005-02-01

    Full Text Available Global ultraviolet auroral images from the IMAGE satellite were used to investigate the dynamics of the dayside auroral oval responding to a sudden impulse (SI in the solar wind pressure. At the same time, the TV all-sky camera and the EISCAT radar on Svalbard (in the pre-noon sector allowed for detailed investigation of the auroral forms and the ionospheric plasma flow. After the SI, new discrete auroral forms appeared in the poleward part of the auroral oval so that the middle of the dayside oval moved poleward from about 70° to about 73° of the AACGM latitude. This poleward shift first occurred in the 15 MLT sector, then similar shifts were observed in the MLT sectors located more westerly, and eventually the shift was seen in the 6 MLT sector. Thus, the auroral disturbance "propagated" westward (from 15 MLT to 6 MLT at an apparent speed of the order of 7km/s. This motion of the middle of the auroral oval was caused by the redistribution of the luminosity within the oval and was not associated with the corresponding motion of the poleward boundary of the oval. The SI was followed by an increase in the northward plasma convection velocity. Individual auroral forms showed poleward progressions with velocities close to the velocity of the northward plasma convection. The observations indicate firstly a pressure disturbance propagation through the magnetosphere at a velocity of the order of 200km/s which is essentially slower than the velocity of the fast Alfvén (magnetosonic wave, and secondly a potential (curl-free electric field generation behind the front of the propagating disturbance, causing the motion of the auroras. We suggest a physical explanation for the slow propagation of the disturbance through the magnetosphere and a model for the electric field generation. Predictions of the model are supported by the global convection maps produced by the SuperDARN HF radars. Finally, the interchange instability and the eigenmode toroidal

  16. Comprehensive simulation study on local and global development of auroral arcs and field-aligned potentials

    International Nuclear Information System (INIS)

    Watanabe, Tomohiko; Oya, Hiroshi; Watanabe, Kunihiko; Sato, Tetsuya.

    1992-10-01

    Extensive three-dimensional computer simulations of the magnetosphere-ionosphere (M-I) coupling are performed to study self-excitation of auroral arcs with special emphasis on 1) nonlinear evolution of the feedback instability in the M-I coupling system, 2) controlling mechanisms of the auroral arc structure, 3) formation of a field-aligned electric potential structure in association with the development of the feedback instability, and 4) effects of the parallel potential generation on auroral arc development. It is reconfirmed that the feedback instability produces a longitudinally elongated, latitudinally striated structure where the upward field-aligned current and the ionospheric density are locally enhanced. The following important new features are revealed. 1) The global distribution of the striation structure is primarily governed by the magnetospheric convection pattern and the ionospheric density distribution. 2) There appears a significant dawn-dusk asymmetry in the auroral arc formation, even though the apparent geometrical relationship is symmetric. 3) The recombination effect plays a significant role in the global, as well as local, development of the auroral arc structure. The nonlinearity of recombination, in conjunction with the closure of an arc-associated local field-aligned current system, acts to destroy an old arc and creates a new arc in a different but adjacent position. 4) A V-shaped field aligned potential structure is created in association with an auroral arc. Rapid increase in the electron density and the local upward field-aligned current of an arc arises as a result of enhanced ionization by precipitating electrons accelerated by the parallel potential. 5) A drastic oscillatory behavior of appearance and disappearance of auroral arcs is obtained when the ionization effect is strong. The period is primarily given by the Alfven bounce time. (J.P.N.)

  17. Preliminary Observations of Ionospheric Response to an Auroral Driver from the MICA (Magnetosphere-Ionosphere Coupling in the Alfvén Resonator) Sounding Rocket Campaign

    Science.gov (United States)

    Fernandes, P. A.; Lynch, K. A.; Hysell, D. L.; Powell, S.; Miceli, R.; Hampton, D. L.; Ahrns, J.; Lessard, M.; Cohen, I. J.; Moen, J. I.; Bekkeng, T.

    2012-12-01

    The nightside sounding rocket MICA (Magnetosphere-Ionosphere Coupling in the Alfvén Resonator) launched from Poker Flat, AK, on February 19, 2012, and reached an apogee of 325km. MICA was launched into several discrete, localized arcs in the wake of a westward traveling surge. The MICA instrumentation included both in situ and ground based instruments, and was designed to measure the response of the ionosphere to an auroral driver. More specifically, the science goal was to measure response of the ionosphere to a feedback instability in the ionospheric Alfvén resonator. The MICA payload included in situ particle, electric and magnetic field, and GPS instruments. The ground-based array consisted of a multitude of imagers, coherent and incoherent scatter radars, and a Fabry-Perot interferometer. We present observational characteristics of the response of the ionospheric plasma to the auroral drivers inferred from inverting camera data. We compare the measured precipitating electron population to inversions of camera images, which use a transport model to infer a 2D map of the precipitation. Comparisons show that as the payload passes through what appears to be an Alfvénic auroral arc, the in situ electron instrument shows dispersions indicative of Alfvénic activity. We then introduce measurements of the thermal ion distribution, to examine how the auroral arcs drive a response in the ionosphere. The thermal ion data show that the payload potential strengthens as the payload passes through the arc. When including electron density, temperature, and electric field data, we observe times in which the ionospheric environment changes as the precipitation changes, and times during which there is no measured response by the ionosphere. Future work will compare how the ion bulk flow as measured by the thermal ion instrument compares to the ExB drift as measured by the electric field instrument and to the neutral wind measurements from the Fabry-Perot interferometer

  18. Generation of the auroral electron velocity distribution by stochastic acceleration

    International Nuclear Information System (INIS)

    Bryant, D.A.; Cook, A.C.; Wang, Z.-S.; Angelis, U. de.

    1990-07-01

    In a further development of the wave theory of the aurora, it is demonstrated, using a Monte-Carlo numerical model, that the characteristic peak in the auroral electron velocity distribution can be generated stochastically through resonant interactions between an initially monotonic distribution and lower-hybrid electrostatic turbulence. The principal requirement is that the velocity spectrum of resonant waves has a sharp cut-off at high velocity. It is then shown that a cut-off is expected as a natural consequence of the difference between the phase and group velocities of lower-hybrid waves. The possibility is considered that a second peak, sometimes observed at lower velocities, is due to the same statistical mechanism, arising from the damping of waves of low phase velocity. An enhancement of wave intensity is found at higher velocities, where momentum flows preferentially from electrons to waves. The relation between the wave theory and the currently prevailing potential-difference theory emerges clearly from the analysis. (author)

  19. Relationships between interplanetary quantities and the global auroral electrojet index

    International Nuclear Information System (INIS)

    Meloni, A.; Wolfe, A.; Lanzerotti, L.J.

    1982-01-01

    We have studied, using linear cross correlation and multilinear regression analyses, statistical relations between the magnetospheric auroral electrojet intensity index AE and various parameters characterizing the interplanetary plasma and magnetic field. We also consider the recently proposed epsilon parameter as an independent variable. The analyses were carried out separately for twenty-eight days in mid 1975 and for each of five individual magnetic storm intervals that have been previously discussed extensively in the literature. We find that when the interplanetary data set is not distinguished as to the direction of the north-south component B/sub z/, the interplanetary electric field -VB/sub z/ carried to the front of the magnetosphere correlates with AE substantially better than does epsilon. Considering only data during which B/sub z/ is negative gives a slightly better correlation of epsilon with AE than of the electric field with AE. The correlations are valid for the specific storm periods as well as for the unrestricted twenty-eight days of data. Our results suggest that the physical processes involved in energy transfer to the nightside magnetosphere depend upon the direction of the north-south component of the interplanetary magnetic field: the interplanetary electric field plays an important role during northward B/sub z/ and the epsilon parameter and the electric field both provide an indication of energy transfer and substorm activity during southward B/sub z/

  20. Determining the Accuracy of Crowdsourced Tweet Verification for Auroral Research

    Directory of Open Access Journals (Sweden)

    Nathan A. Case

    2016-12-01

    Full Text Available The Aurorasaurus project harnesses volunteer crowdsourcing to identify sightings of an aurora (the “northern/southern lights” posted by citizen scientists on Twitter. Previous studies have demonstrated that aurora sightings can be mined from Twitter with the caveat that there is a large background level of non-sighting tweets, especially during periods of low auroral activity. Aurorasaurus attempts to mitigate this, and thus increase the quality of its Twitter sighting data, by using volunteers to sift through a pre-filtered list of geolocated tweets to verify real-time aurora sightings. In this study, the current implementation of this crowdsourced verification system, including the process of geolocating tweets, is described and its accuracy (which, overall, is found to be 68.4% is determined. The findings suggest that citizen science volunteers are able to accurately filter out unrelated, spam-like, Twitter data but struggle when filtering out somewhat related, yet undesired, data. The citizen scientists particularly struggle with determining the real-time nature of the sightings, so care must be taken when relying on crowdsourced identification.

  1. New DMSP Database of Precipitating Auroral Electrons and Ions.

    Science.gov (United States)

    Redmon, Robert J; Denig, William F; Kilcommons, Liam M; Knipp, Delores J

    2017-08-01

    Since the mid 1970's, the Defense Meteorological Satellite Program (DMSP) spacecraft have operated instruments for monitoring the space environment from low earth orbit. As the program evolved, so to have the measurement capabilities such that modern DMSP spacecraft include a comprehensive suite of instruments providing estimates of precipitating electron and ion fluxes, cold/bulk plasma composition and moments, the geomagnetic field, and optical emissions in the far and extreme ultraviolet. We describe the creation of a new public database of precipitating electrons and ions from the Special Sensor J (SSJ) instrument, complete with original counts, calibrated differential fluxes adjusted for penetrating radiation, estimates of the total kinetic energy flux and characteristic energy, uncertainty estimates, and accurate ephemerides. These are provided in a common and self-describing format that covers 30+ years of DMSP spacecraft from F06 (launched in 1982) through F18 (launched in 2009). This new database is accessible at the National Centers for Environmental Information (NCEI) and the Coordinated Data Analysis Web (CDAWeb). We describe how the new database is being applied to high latitude studies of: the co-location of kinetic and electromagnetic energy inputs, ionospheric conductivity variability, field aligned currents and auroral boundary identification. We anticipate that this new database will support a broad range of space science endeavors from single observatory studies to coordinated system science investigations.

  2. Energy and flux variations across thin auroral arcs

    Directory of Open Access Journals (Sweden)

    H. Dahlgren

    2011-10-01

    Full Text Available Two discrete auroral arc filaments, with widths of less than 1 km, have been analysed using multi-station, multi-monochromatic optical observations from small and medium field-of-view imagers and the EISCAT radar. The energy and flux of the precipitating electrons, volume emission rates and local electric fields in the ionosphere have been determined at high temporal (up to 30 Hz and spatial (down to tens of metres resolution. A new time-dependent inversion model is used to derive energy spectra from EISCAT electron density profiles. The energy and flux are also derived independently from optical emissions combined with ion-chemistry modelling, and a good agreement is found. A robust method to obtain detailed 2-D maps of the average energy and number flux of small scale aurora is presented. The arcs are stretched in the north-south direction, and the lowest energies are found on the western, leading edges of the arcs. The large ionospheric electric fields (250 mV m−1 found from tristatic radar measurements are evidence of strong currents associated with the region close to the optical arcs. The different data sets indicate that the arcs appear on the boundaries between regions with different average energy of diffuse precipitation, caused by pitch-angle scattering. The two thin arcs on these boundaries are found to be related to an increase in number flux (and thus increased energy flux without an increase in energy.

  3. Analytic approach to auroral electron transport and energy degradation

    International Nuclear Information System (INIS)

    Stamnes, K.

    1980-01-01

    The interaction of a beam of auroral electrons with the atmosphere is described by the linear transport equation, encompassing discrete energy loss, multiple scattering, and secondary electrons. A solution to the transport equation provides the electron intensity as a function of altitude, pitch angle (with respect to the geomagnetic field) and energy. A multi-stream (discrete ordinate) approximation to the transport equation is developed. An analytic solution is obtained in this approximation. The computational scheme obtained by combining the present transport code with the energy degradation method of Swartz (1979) conserves energy identically. The theory provides a framework within which angular distributions can be easily calculated and interpreted. Thus, a detailed study of the angular distributions of 'non-absorbed' electrons (i.e., electrons that have lost just a small fraction of their incident energy) reveals a systematic variation with incident angle and energy, and with penetration depth. The present approach also gives simple yet accurate solutions in low order multi-stream approximations. The accuracy of the four-stream approximation is generally within a few per cent, whereas two-stream results for backscattered mean intensities and fluxes are accurate to within 10-15%. (author)

  4. Generation of Z mode radiation by diffuse auroral electron precipitation

    Science.gov (United States)

    Dusenbery, P. B.; Lyons, L. R.

    1985-01-01

    The generation of Z mode waves by diffuse auroral electron precipitation is investigated assuming that a loss cone exists in the upgoing portion of the distribution due to electron interactions with the atmosphere. The waves are generated at frequencies above, but very near, the local electron cyclotron frequency omega(e) and at wave normal angles larger than 90 deg. In agreement with Hewitt et al. (1983), the group velocity is directed downward in regions where the ratio of the upper hybrid frequency omega(pe) to Omega(e) is less than 0.5, so that Z mode waves excited above a satellite propagate toward it and away from the upper hybrid resonance. Z mode waves are excited in a frequency band between Omega(e) and about 1.02 Omega(e), and with maximum growth rates of about 0.001 Omega(e). The amplification length is about 100 km, which allows Z mode waves to grow to the intensities observed by high-altitude satellites.

  5. The EXCEDE spectral artificial auroral experiment: An overview

    International Nuclear Information System (INIS)

    O'Neil, R.R.; Burt, D.A.; Pendleton, W.R.; Stair, A.T.

    1982-01-01

    This chapter investigates the detailed production and loss processes of various excited electronic and vibrational states that result in optical and infrared emissions as energetic primary electrons and their secondaries and all subsequent generation electrons are stopped in the atmosphere. The dosing conditions (primary electron energy, beam power, deposition volume, deposition altitude, and dose duration) in the examined artificial auroral experiment are well controlled and monitored. EXCEDE is a Defense Nuclear Agency and Air Force Geophysics Laboratory program designed to study atmospheric radiative processes resulting from the controlled deposition of energetic electrons from rocketborne electron accelerators. The EXCEDE SPECTRAL payload, launched in 1979, contained a 60 kilowatt (3 kV) electron accelerator, an array of ultraviolet, visible, and cryogenic infrared spectrometers, photometers, and photographic film and video cameras. The extensive set of spectra measured in this experiment will be analyzed to determine production mechanisms for each excited state, to determine electron-induced luminous efficiencies and to determine collisional deactivation rate coefficients in the 72 to 128 km altitude range

  6. H(+) - O(+) two-stream interaction on auroral field lines

    International Nuclear Information System (INIS)

    Bergmann, R.

    1990-01-01

    Upflowing beams of hydrogen, oxygen, and minor ion species, and downward accelerated electrons have been observed above several thousand kilometers altitude on evening auroral field lines. The mechanism for electron and ion acceleration is generally accepted to be the presence of a quasi-static electric field with a component parallel to the earth's magnetic field. The thermal energy of the observed beams is much larger than ionospheric ion temperatures indicating that the beams have been heated as they are accelerated upward. This heating is probably due to a two-stream interaction between beams of different mass ions. The beams gain equal energy in the potential drop and so have different average velocities. Their relative streaming initiates an ion-ion two-stream interaction which then mediates a transfer of energy and momentum between the beams and causes thermalization of each beam. The qualitative evidence that supports this scenario is reviewed. Properties of the two-stream instability are presented in order to demonstrate that a calculation of the evolution of ion beams requires a model that includes field-aligned spatial structure. 26 refs

  7. Parameterization of ionization rate by auroral electron precipitation in Jupiter

    Directory of Open Access Journals (Sweden)

    Y. Hiraki

    2008-02-01

    Full Text Available We simulate auroral electron precipitation into the Jovian atmosphere in which electron multi-directional scattering and energy degradation processes are treated exactly with a Monte Carlo technique. We make a parameterization of the calculated ionization rate of the neutral gas by electron impact in a similar way as used for the Earth's aurora. Our method allows the altitude distribution of the ionization rate to be obtained as a function of an arbitrary initial energy spectrum in the range of 1–200 keV. It also includes incident angle dependence and an arbitrary density distribution of molecular hydrogen. We show that there is little dependence of the estimated ionospheric conductance on atomic species such as H and He. We compare our results with those of recent studies with different electron transport schemes by adapting our parameterization to their atmospheric conditions. We discuss the intrinsic problem of their simplified assumption. The ionospheric conductance, which is important for Jupiter's magnetosphere-ionosphere coupling system, is estimated to vary by a factor depending on the electron energy spectrum based on recent observation and modeling. We discuss this difference through the relation with field-aligned current and electron spectrum.

  8. Parameterization of ionization rate by auroral electron precipitation in Jupiter

    Directory of Open Access Journals (Sweden)

    Y. Hiraki

    2008-02-01

    Full Text Available We simulate auroral electron precipitation into the Jovian atmosphere in which electron multi-directional scattering and energy degradation processes are treated exactly with a Monte Carlo technique. We make a parameterization of the calculated ionization rate of the neutral gas by electron impact in a similar way as used for the Earth's aurora. Our method allows the altitude distribution of the ionization rate to be obtained as a function of an arbitrary initial energy spectrum in the range of 1–200 keV. It also includes incident angle dependence and an arbitrary density distribution of molecular hydrogen. We show that there is little dependence of the estimated ionospheric conductance on atomic species such as H and He. We compare our results with those of recent studies with different electron transport schemes by adapting our parameterization to their atmospheric conditions. We discuss the intrinsic problem of their simplified assumption. The ionospheric conductance, which is important for Jupiter's magnetosphere-ionosphere coupling system, is estimated to vary by a factor depending on the electron energy spectrum based on recent observation and modeling. We discuss this difference through the relation with field-aligned current and electron spectrum.

  9. New DMSP database of precipitating auroral electrons and ions

    Science.gov (United States)

    Redmon, Robert J.; Denig, William F.; Kilcommons, Liam M.; Knipp, Delores J.

    2017-08-01

    Since the mid-1970s, the Defense Meteorological Satellite Program (DMSP) spacecraft have operated instruments for monitoring the space environment from low Earth orbit. As the program evolved, so have the measurement capabilities such that modern DMSP spacecraft include a comprehensive suite of instruments providing estimates of precipitating electron and ion fluxes, cold/bulk plasma composition and moments, the geomagnetic field, and optical emissions in the far and extreme ultraviolet. We describe the creation of a new public database of precipitating electrons and ions from the Special Sensor J (SSJ) instrument, complete with original counts, calibrated differential fluxes adjusted for penetrating radiation, estimates of the total kinetic energy flux and characteristic energy, uncertainty estimates, and accurate ephemerides. These are provided in a common and self-describing format that covers 30+ years of DMSP spacecraft from F06 (launched in 1982) to F18 (launched in 2009). This new database is accessible at the National Centers for Environmental Information and the Coordinated Data Analysis Web. We describe how the new database is being applied to high-latitude studies of the colocation of kinetic and electromagnetic energy inputs, ionospheric conductivity variability, field-aligned currents, and auroral boundary identification. We anticipate that this new database will support a broad range of space science endeavors from single observatory studies to coordinated system science investigations.

  10. Auroral Substorms: Search for Processes Causing the Expansion Phase in Terms of the Electric Current Approach

    Science.gov (United States)

    Akasofu, Syun-Ichi

    2017-10-01

    Auroral substorms are mostly manifestations of dissipative processes of electromagnetic energy. Thus, we consider a sequence of processes consisting of the power supply (dynamo), transmission (currents/circuits) and dissipations (auroral substorms-the end product), namely the electric current line approach. This work confirms quantitatively that after accumulating magnetic energy during the growth phase, the magnetosphere unloads the stored magnetic energy impulsively in order to stabilize itself. This work is based on our result that substorms are caused by two current systems, the directly driven (DD) current system and the unloading system (UL). The most crucial finding in this work is the identification of the UL (unloading) current system which is responsible for the expansion phase. A very tentative sequence of the processes leading to the expansion phase (the generation of the UL current system) is suggested for future discussions. (1) The solar wind-magnetosphere dynamo enhances significantly the plasma sheet current when its power is increased above 10^{18} erg/s (10^{11} w). (2) The magnetosphere accumulates magnetic energy during the growth phase, because the ionosphere cannot dissipate the increasing power because of a low conductivity. As a result, the magnetosphere is inflated, accumulating magnetic energy. (3) When the power reaches 3-5× 10^{18} erg/s (3-5× 10^{11} w) for about one hour and the stored magnetic energy reaches 3-5×10^{22} ergs (10^{15} J), the magnetosphere begins to develop perturbations caused by current instabilities (the current density {≈}3× 10^{-12} A/cm2 and the total current {≈}106 A at 6 Re). As a result, the plasma sheet current is reduced. (4) The magnetosphere is thus deflated. The current reduction causes partial B/partial t > 0 in the main body of the magnetosphere, producing an earthward electric field. As it is transmitted to the ionosphere, it becomes equatorward-directed electric field which drives both

  11. The Effects of Solar Wind Dynamic Pressure Changes on the Substorm Auroras and Energetic Electron Injections on 24 August 2005

    Science.gov (United States)

    Li, L. Y.; Wang, Z. Q.

    2018-01-01

    After the passage of an interplanetary (IP) shock at 06:13 UT on 24 August 2005, the enhancement (>6 nPa) of solar wind dynamic pressure and the southward turning of interplanetary magnetic field (IMF) cause the earthward movement of dayside magnetopause and the drift loss of energetic particles near geosynchronous orbit. The persistent electron drift loss makes the geosynchronous satellites cannot observe the substorm electron injection phenomenon during the two substorm expansion phases (06:57-07:39 UT) on that day. Behind the IP shock, the fluctuations ( 0.5-3 nPa) of solar wind dynamic pressure not only alter the dayside auroral brightness but also cause the entire auroral oval to swing in the day-night direction. However, there is no Pi2 pulsation in the nightside auroral oval during the substorm growth phase from 06:13 to 06:57 UT. During the subsequent two substorm expansion phases, the substorm expansion activities cause the nightside aurora oval brightening from substorm onset site to higher latitudes, and meanwhile, the enhancement (decline) of solar wind dynamic pressure makes the nightside auroral oval move toward the magnetic equator (the magnetic pole). These observations demonstrate that solar wind dynamic pressure changes and substorm expansion activities can jointly control the luminosity and location of the nightside auroral oval when the internal and external disturbances occur simultaneously. During the impact of a strong IP shock, the earthward movement of dayside magnetopause probably causes the disappearance of the substorm electron injections near geosynchronous orbit.

  12. Jupiter's Auroral Energy Input Observed by Hisaki/EXCEED and its Modulations by Io's Volcanic Activity

    Science.gov (United States)

    Tao, C.; Kimura, T.; Tsuchiya, F.; Murakami, G.; Yoshioka, K.; Kita, H.; Yamazaki, A.; Kasaba, Y.; Yoshikawa, I.; Fujimoto, M.

    2016-12-01

    Aurora is an important indicator representing the momentum transfer from the fast-rotating outer planet to the magnetosphere and the energy input into the atmosphere through the magnetosphere-ionosphere coupling. Long-term monitoring of Jupiter's northern aurora was achieved by the Extreme Ultraviolet (EUV) spectrometer called EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics) onboard JAXA's Earth-orbiting planetary space telescope Hisaki until today after its launch in September 2013. We have proceeded the statistical survey of the Jupiter's auroral energy input into the upper atmosphere. The auroral electron energy is estimated using a hydrocarbon color ratio (CR) adopted for the wavelength range of EXCEED, and the emission power in the long wavelength range 138.5-144.8 nm is used as an indicator of total emitted power before hydrocarbon absorption and auroral electron energy flux. Temporal dynamic variation of the auroral intensity was detected when Io's volcanic activity and thus EUV emission from the Io plasma torus are enhanced in the early 2015. Average of the total input power over 80 days increases by 10% with sometimes sporadically more than a factor of 3 upto 7, while the CR indicates the auroral electron energy decrease by 20% during the volcanic event compared to the other period. This indicates much more increase in the current system and Joule heating which contributes heating of the upper atmosphere. We will discuss the impact of this event on the upper atmosphere and ionosphere.

  13. Mapping using the Tsyganenko long magnetospheric model and its relationship to Viking auroral images

    International Nuclear Information System (INIS)

    Elphinstone, R.D.; Hearn, D.; Murphree, J.S.; Cogger, L.L.

    1991-01-01

    The Tsyganenko long magnetospheric model (1987) has been used in conjunction with ultra-violet images taken by the Viking spacecraft to investigate the relationship of the auroral distribution to different magnetospheric regions. The model describes the large-scale structure of the magnetosphere reasonably well for dipole tilt angles near zero, but it appears to break down at higher tilt angles. Even so, a wide variety of auroral configurations can be accurately described by the model. It appears that the open-closed field line boundary is a poor indicator of auroral arc systems with the possible exception of high-latitude polar arcs. The auroral distribution typically called the oval maps to a region in the equatorial plane quite close to the Earth and can be approximately located by mapping the model current density maximum from the equatorial plane into the ionosphere. Although the model may break down along the flanks of the magnetotail, the large-scale auroral distribution generally reflects variations in the near-Earth region and can be modeled quite effectively

  14. VISIONS: Remote Observations of a Spatially-Structured Filamentary Source of Energetic Neutral Atoms near the Polar Cap Boundary During an Auroral Substorm

    Science.gov (United States)

    Collier, Michael R.; Chornay, D.; Clemmons, J.; Keller, J. W.; Klenzing, J.; Kujawski, J.; McLain, J.; Pfaff, R.; Rowland, D.; Zettergren, M.

    2015-01-01

    We report initial results from the VISualizing Ion Outflow via Neutral atom imaging during a Substorm (VISIONS) rocket that flew through and near several regions of enhanced auroral activity and also sensed regions of ion outflow both remotely and directly. The observed neutral atom fluxes were largest at the lower energies and generally higher in the auroral zone than in the polar cap. In this paper, we focus on data from the latter half of the VISIONS trajectory when the rocket traversed the polar cap region. During this period, many of the energetic neutral atom spectra show a peak at 100 electronvolts. Spectra with peaks around 100 electronvolts are also observed in the Electrostatic Ion Analyzer (EIA) data consistent with these ions comprising the source population for the energetic neutral atoms. The EIA observations of this low energy population extend only over a few tens of kilometers. Furthermore, the directionality of the arriving energetic neutral atoms is consistent with either this spatially localized source of energetic ions extending from as low as about 300 kilometers up to above 600 kilometers or a larger source of energetic ions to the southwest.

  15. WIND observations of coherent electrostatic waves in the solar wind

    Directory of Open Access Journals (Sweden)

    A. Mangeney

    1999-03-01

    Full Text Available The time domain sampler (TDS experiment on WIND measures electric and magnetic wave forms with a sampling rate which reaches 120 000 points per second. We analyse here observations made in the solar wind near the Lagrange point L1. In the range of frequencies above the proton plasma frequency fpi and smaller than or of the order of the electron plasma frequency fpe, TDS observed three kinds of electrostatic (e.s. waves: coherent wave packets of Langmuir waves with frequencies f ~ fpe, coherent wave packets with frequencies in the ion acoustic range fpi < f < fpe, and more or less isolated non-sinusoidal spikes lasting less than 1 ms. We confirm that the observed frequency of the low frequency (LF ion acoustic wave packets is dominated by the Doppler effect: the wavelengths are short, 10 to 50 electron Debye lengths λD. The electric field in the isolated electrostatic structures (IES and in the LF wave packets is more or less aligned with the solar wind magnetic field. Across the IES, which have a spatial width of the order of ~ 25λD, there is a small but finite electric potential drop, implying an average electric field generally directed away from the Sun. The IES wave forms, which have not been previously reported in the solar wind, are similar, although with a smaller amplitude, to the weak double layers observed in the auroral regions, and to the electrostatic solitary waves observed in other regions in the magnetosphere. We have also studied the solar wind conditions which favour the occurrence of the three kinds of waves: all these e.s. waves are observed more or less continuously in the whole solar wind (except in the densest regions where a parasite prevents the TDS observations. The type (wave packet or IES of the observed LF waves is mainly determined by the proton temperature and by the direction of the magnetic field, which themselves depend on the latitude of WIND with respect to the heliospheric current sheet.Key words

  16. WIND observations of coherent electrostatic waves in the solar wind

    Directory of Open Access Journals (Sweden)

    A. Mangeney

    Full Text Available The time domain sampler (TDS experiment on WIND measures electric and magnetic wave forms with a sampling rate which reaches 120 000 points per second. We analyse here observations made in the solar wind near the Lagrange point L1. In the range of frequencies above the proton plasma frequency fpi and smaller than or of the order of the electron plasma frequency fpe, TDS observed three kinds of electrostatic (e.s. waves: coherent wave packets of Langmuir waves with frequencies f ~ fpe, coherent wave packets with frequencies in the ion acoustic range fpi < f < fpe, and more or less isolated non-sinusoidal spikes lasting less than 1 ms. We confirm that the observed frequency of the low frequency (LF ion acoustic wave packets is dominated by the Doppler effect: the wavelengths are short, 10 to 50 electron Debye lengths λD. The electric field in the isolated electrostatic structures (IES and in the LF wave packets is more or less aligned with the solar wind magnetic field. Across the IES, which have a spatial width of the order of ~ 25λD, there is a small but finite electric potential drop, implying an average electric field generally directed away from the Sun. The IES wave forms, which have not been previously reported in the solar wind, are similar, although with a smaller amplitude, to the weak double layers observed in the auroral regions, and to the electrostatic solitary waves observed in other regions in the magnetosphere. We have also studied the solar wind conditions which favour the occurrence of the three kinds of waves: all these e.s. waves are observed more or less continuously in the whole solar wind (except in the densest regions where a parasite prevents the TDS observations. The type (wave packet or IES of the observed LF waves is mainly determined

  17. Interconnector capacity allocation in offshore grids with variable wind generation

    DEFF Research Database (Denmark)

    Schröder, Sascha Thorsten

    2013-01-01

    the interconnector capacity should be allocated for wind generation and for international power trading. The main difficulty arises from the stochastic nature of wind generation: in a case with radial connections to the national coast, the wind park owner has the possibility of aggregating the offshore wind park....... It is concluded that treating offshore generation as a single price zone within the interconnector reduces the wind operator’s ability to pool it with other generation. Furthermore, a single offshore price zone between two markets will always receive the lower spot market price of the neighbouring zones, although...

  18. Solar Wind Energy Input during Prolonged, Intense Northward Interplanetary Magnetic Fields: A New Coupling Function

    Science.gov (United States)

    Du, A. M.; Tsurutani, B. T.; Sun, W.

    2012-04-01

    Sudden energy release (ER) events in the midnight sector at auroral zone latitudes during intense (B > 10 nT), long-duration (T > 3 hr), northward (Bz > 0 nT = N) IMF magnetic clouds (MCs) during solar cycle 23 (SC23) have been examined in detail. The MCs with northward-then-southward (NS) IMFs were analyzed separately from MCs with southward-then-northward (SN) configurations. It is found that there is a lack of substorms during the N field intervals of NS clouds. In sharp contrast, ER events do occur during the N field portions of SN MCs. From the above two results it is reasonable to conclude that the latter ER events represent residual energy remaining from the preceding S portions of the SN MCs. We derive a new solar wind-magnetosphere coupling function during northward IMFs: ENIMF = α N-1/12V 7/3B1/2 + β V |Dstmin|. The first term on the right-hand side of the equation represents the energy input via "viscous interaction", and the second term indicates the residual energy stored in the magnetotail. It is empirically found that the magnetosphere/magnetotail can store energy for a maximum of ~ 4 hrs before it has dissipated away. This concept is defining one for ER/substorm energy storage. Our scenario indicates that the rate of solar wind energy injection into the magnetosphere/magnetotail determines the form of energy release into the magnetosphere/ionosphere. This may be more important than the dissipation mechanism itself (in understanding the form of the release). The concept of short-term energy storage is applied for the solar case. It is argued that it may be necessary to identify the rate of energy input into solar magnetic loop systems to be able to predict the occurrence of solar flares.

  19. Records of auroral candidates and sunspots in Rikkokushi, chronicles of ancient Japan from early 7th century to 887

    Science.gov (United States)

    Hayakawa, Hisashi; Iwahashi, Kiyomi; Tamazawa, Harufumi; Ebihara, Yusuke; Kawamura, Akito Davis; Isobe, Hiroaki; Namiki, Katsuko; Shibata, Kazunari

    2017-12-01

    We present the results of the surveys on sunspots and auroral candidates in Rikkokushi, Japanese official histories from the early 7th century to 887, to review the solar and auroral activities. In total, we found one sunspot record and 13 auroral candidates in Rikkokushi. We then examine the records of the sunspots and auroral candidates, compare the auroral candidates with the lunar phase to estimate their reliability, and compare the records of the sunspots and auroral candidates with the contemporary total solar irradiance reconstructed from radioisotope data. We also identify the locations of the observational sites to review possible equatorward expansion of the auroral oval. These discussions suggest a major gap in auroral candidates from the late 7th to early 9th centuries, which includes the candidate of the grand minimum reconstructed from the radioisotope data, a similar tendency as the distributions of sunspot records in contemporary China, and a relatively high magnetic latitude of observational sites with a higher potential for observing aurorae more frequently than at present.

  20. Relative Timing of Substorm-Associated Processes in the Near-Earth Magnetotail and Development of Auroral Onset Arc

    Science.gov (United States)

    Miyashita, Y.; Ieda, A.; Machida, S.; Hiraki, Y.; Angelopoulos, V.; McFadden, J. P.; Auster, H. U.; Mende, S. B.; Donovan, E.; Larson, D. E.

    2014-12-01

    We have studied the relative timing of the processes in the near-Earth magnetotail and development of auroral onset arc at the beginning of the expansion phase, based on substorm events observed by the THEMIS spacecraft and ground-based all-sky imagers. The THEMIS all-sky imagers can observe auroras over a wide area with temporal and spacial resolutions higher than spacecraft-borne cameras. This enables us to investigate the timing of auroral development in more detail than before. A few min after the appearance and intensification of an auroral onset arc, it begins to form wave-like structure. Then auroral poleward expansion begins another few min later. THEMIS magnetotail observations clearly show that magnetic reconnection is initiated at X~-20 Re at least 1-2 min before the intensification of auroral onset arc. Then low-frequency waves are excited in the plasma sheet at X~-10 Re 2 min before dipolarization, which is simultaneous with the formation of auroral wave-like structure. Dipolarization begins at the same time as the auroral poleward expansion. These results suggest that near-Earth magnetic reconnection plays some role in the development of dipolarization and auroral onset arc.

  1. Simulation of auroral current sheet equilibria and associated V-shaped potential structures

    International Nuclear Information System (INIS)

    Singh, N.; Thiemann, H.; Schunk, R.W.

    1983-01-01

    Results from numerical simulations of auroral current sheet equilibrium and associated V-shaped potential structures are presented. It is shown that with allowance for both hot magnetospheric ion and cold ionospheric ion populations, the perpendicular potential drop, assiciated with a non-neutral auroral current sheet is critically controlled by the temperature of the 'heated' ionospheric ions. The heating is caused by the wave turbulence excited by the auroral current sheet. In the presence of heated ionospheric ions, a relatively large variation in the temperature of the hot magnetospheric ion population causes a very small variation in the potential drop thetam. The perpendicular potential drop acts to produce a V-shaped double layer with multiple potential steps parallel to the magnetic field when a zero potential boundary condition is imposed at the ionospheric boundary. Outside the V-shaped potential structure, ionospheric return currents develop self-consistently

  2. Effect of anomalous transport coefficients on the thermal structure of the storm time auroral ionosphere

    International Nuclear Information System (INIS)

    Fontheim, E.G.; Ong, R.S.B.; Roble, R.G.; Mayr, H.G.; Hoegy, W.H.; Baron, M.J.; Wickwar, V.B.

    1978-01-01

    By analyzing an observed storm time auroral electron temperature profile it is shown that anomalous transport effects strongly influence the thermal structure of the disturbed auroral ionosphere. Such anomalous transport effects are a consequence of plasma turbulence, the existence of which has been established by a large number of observations in the auroral ionosphere. The electron and composite ion energy equations are solved with anomalous electron thermal conductivity and parallel electrical resistivity coefficients. The solutions are parameterized with respect to a phenomenological altitude-dependent anomaly coefficient A and are compared with an observed storm time electron temperature profile above Chatanika. The calculated temperature profile for the classical case (A=1)disagrees considerably with the measured profile over most of the altitude range up to 450km. It is shown that an anomaly coefficient with a sharp peak of the order of 10 4 centered aroung the F 2 peak is consistent with observations

  3. Auroral-arc splitting by intrusion of a new convection channel

    Directory of Open Access Journals (Sweden)

    H. U. Frey

    Full Text Available During a run of the Common Programme Three of the EISCAT radar the splitting of an auroral arc was observed by high time-resolution, ground-based cameras when the UHF radar beam was close to the arc. The evening eastward electrojet situation with a large-scale northward ionospheric electric field was disturbed by the intrusion of a convection channel with southward electric field from the east. The interaction of the new convection channel with the auroral arc caused changes in arc brightness and arc splitting, i.e. the creation of a new arc parallel to the pre-existing auroral arc. The event is described as one possibility for the creation of parallel arcs during slightly disturbed magnetic conditions far from the Harang discontinuity.

  4. Auroral-arc splitting by intrusion of a new convection channel

    Directory of Open Access Journals (Sweden)

    H. U. Frey

    1996-12-01

    Full Text Available During a run of the Common Programme Three of the EISCAT radar the splitting of an auroral arc was observed by high time-resolution, ground-based cameras when the UHF radar beam was close to the arc. The evening eastward electrojet situation with a large-scale northward ionospheric electric field was disturbed by the intrusion of a convection channel with southward electric field from the east. The interaction of the new convection channel with the auroral arc caused changes in arc brightness and arc splitting, i.e. the creation of a new arc parallel to the pre-existing auroral arc. The event is described as one possibility for the creation of parallel arcs during slightly disturbed magnetic conditions far from the Harang discontinuity.

  5. Preliminary results of rocket attitude and auroral green line emission rate in the DELTA campaign

    Science.gov (United States)

    Iwagami, Naomoto; Komada, Sayaka; Takahashi, Takao

    2006-09-01

    The attitude of a sounding rocket launched in the DELTA (Dynamics and Energetics of the Lower Thermosphere in Aurora) campaign was determined with IR horizon sensors and geomagnetic sensors. Since the payload was separated into two portions, two sets of attitude sensors were needed. A new IR sensor was developed for the present experiment, and found the zenith-angle of the spin-axis of the rocket with an accuracy of 2°. By combining information obtained by both type of sensors, the absolute attitudes were determined. The auroral green line emission rate was measured by a photometer on board the same rocket launched under active auroral conditions, and the energy flux of the auroral particle precipitation was estimated.

  6. Simultaneous measurements of auroral particles and electric currents by a rocket-borne instrument system - Introductory remarks

    Science.gov (United States)

    Anderson, H. R.; Cloutier, P. A.

    1975-01-01

    A rocket-borne experiment package has been designed to obtain simultaneous in situ measurements of the pitch angle distributions and energy spectra of primary auroral particles, the flux of neutral hydrogen at auroral energies, the electric currents flowing in the vicinity of the auroral arc as determined from vector magnetic data, and the modulation of precipitating electrons in the frequency range 0.5-10 MHz. The experiment package was launched by a Nike-Tomahawk rocket from Poker Flat, Alaska, at 0722 UT on Feb. 25, 1972, over a bright auroral band. This paper is intended to serve as an introduction to the detailed discussion of results given in the companion papers. As such it includes a brief review of the general problem, a discussion of the rocket instrumentation, a delineation of the auroral and geomagnetic conditions at the time of launch, and comments on the overall payload performance.

  7. Simultaneous measurements of auroral particles and electric currents by a rocket-borne instrument system: introductory remarks

    International Nuclear Information System (INIS)

    Anderson, H.R.; Cloutier, P.A.

    1975-01-01

    A rocket-borne experiment package has been designed to obtain simultaneous in situ measurements of the pitch angle distribution and energy spectra of primary auroral particles, the flux of neutral hydrogen at auroral energies, the electric currents flowing in the vicinity of the auroral arc as determined from vector magnetic data, and the modulation of precipitating electrons in the frequency range 0.5-10 MHz. The experiment package was launched by a Nike-Tomahawk rocket from Poker Flat, Alaska, at 0722 UT on February 25, 1972, over a bright auroral band. This paper is intended to serve as an introduction to the detailed discussion of results given in the companion papers. As such it includes a brief review of the general problem, a discussion of the rocket instrumentation, a delineation of the auroral and geomagnetic conditions at the time of launch, and comments on the overall payload performance

  8. 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)

  9. Current-voltage relationship in the auroral particle acceleration region

    Directory of Open Access Journals (Sweden)

    M. Morooka

    2004-11-01

    Full Text Available The current-voltage relationship in the auroral particle acceleration region has been studied statistically by the Akebono (EXOS-D satellite in terms of the charge carriers of the upward field-aligned current. The Akebono satellite often observed field-aligned currents which were significantly larger than the model value predicted by Knight (1973. We compared the upward field-aligned current estimated by three different methods, and found that low-energy electrons often play an important role as additional current carriers, together with the high-energy primary electrons which are expected from Knight's relation. Such additional currents have been observed especially at high and middle altitudes of the particle acceleration region. Some particular features of electron distribution functions, such as "cylindrical distribution functions" and "electron conics", have often been observed coinciding with the additional currents. They indicated time variability of the particle acceleration region. Therefore, we have concluded that the low-energy electrons within the "forbidden" region of electron phase space in the stationary model often contribute to charge carriers of the current because of the rapid time variability of the particle acceleration region. "Cylindrical distribution functions" are expected to be found below the time-varying potential difference. We statistically examined the locations of "cylindrical distribution function", and found that their altitudes are related to the location where the additional currents have been observed. This result is consistent with the idea that the low-energy electrons can also carry significant current when the acceleration region changes in time.

  10. Nonlinear interactions of electromagnetic waves with the auroral ionosphere

    Science.gov (United States)

    Wong, Alfred Y.

    1999-09-01

    The ionosphere provides us with an opportunity to perform plasma experiments in an environment with long confinement times, very large-scale lengths, and no confining walls. The auroral ionosphere with its nearly vertical magnetic field geometry is uniquely endowed with large amount of free energy from electron and ion precipitation along the magnetic field and mega-ampere current across the magnetic field. To take advantage of this giant outdoor laboratory, two facilities HAARP and HIPAS, with frequencies ranging from the radio to optical bands, are now available for active probing of and interaction with this interesting region. The ponderomotive pressures from the self-consistent wave fields have produced significant local perturbations of density and particle distributions at heights where the incident EM frequency matches a plasma resonance. This paper will review theory and experiments covering the nonlinear phenomena of parametric decay instability to wave collapse processes. At HF frequencies plasma lenses can be created by preconditioning pulses to focus what is a normally divergent beam into a high-intensity spot to further enhance nonlinear phenomena. At optical wavelengths a large rotating liquid metal mirror is used to focus laser pulses up to a given height. Such laser pulses are tuned to the same wavelengths of selected atomic and molecular resonances, with resulting large scattering cross sections. Ongoing experiments on dual-site experiments and excitation of ELF waves will be presented. The connection of such basic studies to environmental applications will be discussed. Such applications include the global communication using ELF waves, the ozone depletion and remediation and the control of atmospheric CO2 through the use of ion cyclotron resonant heating.

  11. Interplanetary Shocks Inducing Magnetospheric Supersubstorms (SML < ‑2500 nT): Unusual Auroral Morphologies and Energy Flow

    Science.gov (United States)

    Hajra, Rajkumar; Tsurutani, Bruce T.

    2018-05-01

    We present case studies of two interplanetary shock-induced supersubstorms (SSSs) with extremely high intensities (peak SML ‑4418 and ‑2668 nT) and long durations (∼1.7 and ∼3.1 hr). The events occurred on 2005 January 21 and 2010 April 5, respectively. It is shown that these SSSs have a different auroral evolution than a nominal Akasofu-type substorm. The auroras associated with the SSSs did not have the standard midnight onset and following expansion. Instead, at the time of the SML index peak, the midnight sector was generally devoid of intense auroras, while the most intense auroras were located in the premidnight and postmidnight magnetic local times. Precursor energy input through magnetic reconnection was insufficient to balance the large ionospheric energy dissipation during the SSSs. It is argued that besides the release of stored magnetotail energy during the SSSs, these were powered by additional direct driving through both dayside magnetic reconnection and solar wind ram energy.

  12. The role of magnetic-field-aligned electric fields in auroral acceleration

    International Nuclear Information System (INIS)

    Block, L.P.; Faelthammar, C.G.

    1990-01-01

    Electric field measurements on the Swedish satellite Viking have confirmed and extended earlier observations on S3-3 and provided further evidence of the role of dc electric fields in auroral acceleration processes. On auroral magnetic field lines the electric field is strongly fluctuating both transverse and parallel to the magnetic field. The significance of these fluctuations for the auroral acceleration process is discussed. A definition of dc electric fields is given in terms of their effects on charged particles. Fluctuations below several hertz are experienced as dc by typical auroral electrons if the acceleration length is a few thousand kilometers. For ions the same is true below about 0.1 Hz. The magnetic-field-aligned (as well as the transverse) component of the electric field fluctuations has a maximum below 1 Hz, in a frequency range that appears as dc to the electrons but not to the ions. This allows it to cause a selective acceleration, which may be important in explaining some of the observed characteristics of auroral particle distributions. The electric field observations on Viking support the conclusion that magnetic-field-aligned potential drops play an important role in auroral acceleration, in good agreement with particle observations boht on Viking and on the DE satellites. They also show that a large part, or even all, of the accelerating potential drop may be accounted for by numerous weak (about a volt) electric double layers, in agreement with earlier observations on the S3-3 satellite and with an early theoretical suggestion by L. Block

  13. The optical manifestation of dispersive field-aligned bursts in auroral breakup arcs

    Science.gov (United States)

    Dahlgren, H.; Semeter, J. L.; Marshall, R. A.; Zettergren, M.

    2013-07-01

    High-resolution optical observations of a substorm expansion show dynamic auroral rays with surges of luminosity traveling up the magnetic field lines. Observed in ground-based imagers, this phenomenon has been termed auroral flames, whereas the rocket signatures of the corresponding energy dispersions are more commonly known as field-aligned bursts. In this paper, observations of auroral flames obtained at 50 frames/s with a scientific-grade Complementary Metal Oxide Semiconductor (CMOS) sensor (30° × 30° field of view, 30 m resolution at 120 km) are used to provide insight into the nature of the precipitating electrons similar to high-resolution particle detectors. Thanks to the large field of view and high spatial resolution of this system, it is possible to obtain a first-order estimate of the temporal evolution in altitude of the volume emission rate from a single sensor. The measured volume emission rates are compared with the sum of modeled eigenprofiles obtained for a finite set of electron beams with varying energy provided by the TRANSCAR auroral flux tube model. The energy dispersion signatures within each auroral ray can be analyzed in detail during a fraction of a second. The evolution of energy and flux of the precipitation shows precipitation spanning over a large range of energies, with the characteristic energy dropping from 2.1 keV to 0.87 keV over 0.2 s. Oscillations at 2.4 Hz in the magnetic zenith correspond to the period of the auroral flames, and the acceleration is believed to be due to Alfvenic wave interaction with electrons above the ionosphere.

  14. Influence of Auroral Streamers on Rapid Evolution of Ionospheric SAPS Flows

    Science.gov (United States)

    Gallardo-Lacourt, Bea; Nishimura, Y.; Lyons, L. R.; Mishin, E. V.; Ruohoniemi, J. M.; Donovan, E. F.; Angelopoulos, V.; Nishitani, N.

    2017-12-01

    Subauroral polarization streams (SAPS) often show large, rapid enhancements above their slowly varying component. We present simultaneous observations from ground-based all-sky imagers and flows from the Super Dual Auroral Radar Network radars to investigate the relationship between auroral phenomena and flow enhancement. We first identified auroral streamers approaching the equatorward boundary of the auroral oval to examine how often the subauroral flow increased. We also performed the reverse query starting with subauroral flow enhancements and then evaluated the auroral conditions. In the forward study, 98% of the streamers approaching the equatorward boundary were associated with SAPS flow enhancements reaching 700 m/s and typically hundreds of m/s above background speeds. The reverse study reveals that flow enhancements associated with streamers (60%) and enhanced larger-scale convection (37%) contribute to SAPS flow enhancements. The strong correlation of auroral streamers with rapid evolution (approximately minutes) of SAPS flows suggests that transient fast earthward plasma sheet flows can often lead to westward SAPS flow enhancements in the subauroral region and that such enhancements are far more common than only during substorms because of the much more frequent occurrences of streamers under various geomagnetic conditions. We also found a strong correlation between flow duration and streamer duration and a weak correlation between SAPS flow velocity and streamer intensity. This result suggests that intense flow bursts in the plasma sheet (which correlate with intense streamers) are associated with intense SAPS ionospheric flows perhaps by enhancing the ring current pressure and localized pressure gradients when they are able to penetrate close enough to Earth.

  15. Plasma sheet fast flows and auroral dynamics during substorm: a case study

    Directory of Open Access Journals (Sweden)

    N. L. Borodkova

    2002-03-01

    Full Text Available Interball-1 observations of a substorm development in the mid-tail on 16 December 1998 are compared with the auroral dynamics obtained from the Polar UV imager. Using these data, the relationship between plasma flow directions in the tail and the location of the auroral activation is examined. Main attention is given to tailward and earth-ward plasma flows, interpreted as signatures of a Near Earth Neutral Line (NENL. It is unambiguously shown that in the mid-plasma sheet the flows were directed tailward when the auroral bulge developed equatorward of the spacecraft ionospheric footprint. On the contrary, when active auroras moved poleward of the Interball-1 projection, earthward fast flow bursts were observed. This confirms the concept that the NENL (or flow reversal region is the source of auroras forming the poleward edge of the auroral bulge. The observed earthward flow bursts have all typical signatures of Bursty Bulk Flows (BBFs, described by Angelopolous et al. (1992. These BBFs are related to substorm activations starting at the poleward edge of the expanded auroral bulge. We interpret the BBFs as a result of reconnection pulses occurring tail-ward of Interball-1. In addition, some non-typically observed phenomena were detected in the plasma sheet during this substorm: (i tailward/earthward flows were superimposed on a very strong duskward flow, and (ii wavy structures of both magnetic field and plasma density were registered. The latter observation is probably linked to the filamentary structure of the current sheet.Key words. Magnetospheric physics (auroral phenomena; plasma sheet; storms and substorms

  16. Auroral spectrograph data annals of the international geophysical year, v.25

    CERN Document Server

    Carrigan, Anne; Norman, S J

    1964-01-01

    Annals of the International Geophysical Year, Volume 25: Auroral Spectrograph Data is a five-chapter text that contains tabulations of auroral spectrograph data. The patrol spectrograph built by the Perkin-Elmer Corporation for the Aurora and Airglow Program of the IGY is a high-speed, low-dispersion, automatic instrument designed to photograph spectra of aurora occurring along a given magnetic meridian of the sky. Data from each spectral frame were recorded on an IBM punched card. The data recorded on the cards are printed onto the tabulations in this volume. These tabulations are available

  17. Global auroral conductance distribution due to electron and proton precipitation from IMAGE-FUV observations

    Directory of Open Access Journals (Sweden)

    V. Coumans

    2004-04-01

    Full Text Available The Far Ultraviolet (FUV imaging system on board the IMAGE satellite provides a global view of the north auroral region in three spectral channels, including the SI12 camera sensitive to Doppler shifted Lyman-α emission. FUV images are used to produce instantaneous maps of electron mean energy and energy fluxes for precipitated protons and electrons. We describe a method to calculate ionospheric Hall and Pedersen conductivities induced by auroral proton and electron ionization based on a model of interaction of auroral particles with the atmosphere. Different assumptions on the energy spectral distribution for electrons and protons are compared. Global maps of ionospheric conductances due to instantaneous observation of precipitating protons are calculated. The contribution of auroral protons in the total conductance induced by both types of auroral particles is also evaluated and the importance of proton precipitation is evaluated. This method is well adapted to analyze the time evolution of ionospheric conductances due to precipitating particles over the auroral region or in particular sectors. Results are illustrated with conductance maps of the north polar region obtained during four periods with different activity levels. It is found that the proton contribution to conductance is relatively higher during quiet periods than during substorms. The proton contribution is higher in the period before the onset and strongly decreases during the expansion phase of substorms. During a substorm which occurred on 28 April 2001, a region of strong proton precipitation is observed with SI12 around 14:00MLT at ~75° MLAT. Calculation of conductances in this sector shows that neglecting the protons contribution would produce a large error. We discuss possible effects of the proton precipitation on electron precipitation in auroral arcs. The increase in the ionospheric conductivity, induced by a former proton precipitation can reduce the potential drop

  18. Global auroral conductance distribution due to electron and proton precipitation from IMAGE-FUV observations

    Directory of Open Access Journals (Sweden)

    V. Coumans

    2004-04-01

    Full Text Available The Far Ultraviolet (FUV imaging system on board the IMAGE satellite provides a global view of the north auroral region in three spectral channels, including the SI12 camera sensitive to Doppler shifted Lyman-α emission. FUV images are used to produce instantaneous maps of electron mean energy and energy fluxes for precipitated protons and electrons. We describe a method to calculate ionospheric Hall and Pedersen conductivities induced by auroral proton and electron ionization based on a model of interaction of auroral particles with the atmosphere. Different assumptions on the energy spectral distribution for electrons and protons are compared. Global maps of ionospheric conductances due to instantaneous observation of precipitating protons are calculated. The contribution of auroral protons in the total conductance induced by both types of auroral particles is also evaluated and the importance of proton precipitation is evaluated. This method is well adapted to analyze the time evolution of ionospheric conductances due to precipitating particles over the auroral region or in particular sectors. Results are illustrated with conductance maps of the north polar region obtained during four periods with different activity levels. It is found that the proton contribution to conductance is relatively higher during quiet periods than during substorms. The proton contribution is higher in the period before the onset and strongly decreases during the expansion phase of substorms. During a substorm which occurred on 28 April 2001, a region of strong proton precipitation is observed with SI12 around 14:00MLT at ~75° MLAT. Calculation of conductances in this sector shows that neglecting the protons contribution would produce a large error. We discuss possible effects of the proton precipitation on electron precipitation in auroral arcs. The increase in the ionospheric conductivity, induced by a former proton precipitation can reduce the potential drop

  19. Midday auroral breakup events and related energy and momentum transfer from the magnetosheath

    International Nuclear Information System (INIS)

    Sandholt, P.E.; Lybekk, B.; Egeland, A.; Oguti, T.; Cowley, S.W.

    1989-04-01

    Combined observation by meridan scanning photometers, all-sky auroral TV camera and the EISCAT radar, permitted a detailed analysis of the temporal and spatial development of the midday auroral breakup phenomenon and the related ionospheric ion flow pattern within the 71 o to 75 o invariant latitude radar field of view. The observations reported are considered to be strong evidence of transient reconnection at the dayside magnetopause. Furthermore, the observed relationship between the optical signature and the ion drift observations is found to be consistent with a twin-vortex flow/current pattern in the ionosphere. The geomagnetic signatures are also in accord with this interpretation

  20. Dynamics of night-side auroral oval associated with substorm activity during magnetic storms

    International Nuclear Information System (INIS)

    Tverskaya, L.V.; Tel'tsov, M.V.; Shkol'nikova, S.I.; AN SSSR, Moscow

    1989-01-01

    Data of measurements of precipitated electrons with E=1 keV and longitudinal currents, conducted on INTERCOSMOS-BOLGARIYA-1300 satellite, were used to analyze variations of latitude sizes of the night section of auroral oval during heavy magnetic storm on 1-4.3 1982. Rapid (during ∼ 0.5 h) oval expansion on the night side both to the pole and to the equator at the moment of suddent shift of the west polar electrojet to the equator was revealed. It is shown that the width of the night region of auroral electron precipitation in the process of world magnetic storm development increases during certain substorms

  1. Electric field and electron density thresholds for coherent auroral echo onset

    International Nuclear Information System (INIS)

    Kustov, A.V.; Uspensky, M.V.; Sofko, G.J.; Koehler, J.A.; Jones, G.O.L.; Williams, P.J.S.

    1993-01-01

    The authors study the threshold dependence of electron density and electric field for the observation of coherent auroral echo onset. They make use of Polar Geophysical Institute 83 MHz auroral radar and the EISCAT facility in Scandanavia, to simultaneously get plasma parameter information and coherent scatter observations. They observe an electron density threshold of roughly 2.5x10 11 m -3 for electric fields of 15 - 20 mV/m (near the Farley-Buneman instability threshold). For electric fields of 5 - 10 mV/m echos are not observed for even twice the previous electron density. Echo strength is observed to have other parametric dependences

  2. Spontaneous generation of auroral arcs in a three dimensionally coupled magnetosphere-ionosphere system

    International Nuclear Information System (INIS)

    Watanabe, Kunihiko; Sato, Tetsuya.

    1988-01-01

    This paper presents the first full three-dimensional dynamic simulation of auroral arc formation. The magnetospheric and ionospheric dynamics are represented by one-fluid magnetohydrodynamic equations and two-fluid weakly ionized plasma equations, respectively. The feedback coupling between magnetospheric Alfven waves and ionospheric density waves are self-consistently and three-dimensionally solved. Obtained is a spontaneous generation of longitudinally elongated striations of field-aligned currents and ionospheric electron densities, which compare very well with many features of quiet auroral arcs. (author)

  3. Evaluation of wind energy potential in the south-south geopolitical ...

    African Journals Online (AJOL)

    South geopolitical zone of Nigeria using 10 year wind data obtained at a height of 10m as a possible location for energy generation from wind. The obtained ... Keywords: Mean wind speed, Wind power density, Wind energy, Renewable energy ...

  4. Ground and satellite observations of multiple sun-aligned auroral arcs on the duskside

    Science.gov (United States)

    Hosokawa, K.; Maggiolo, R.; Zhang, Y.; Fear, R. C.; Fontaine, D.; Cumnock, J. A.; Kullen, A.; Milan, S. E.; Kozlovsky, A.; Echim, M.; Shiokawa, K.

    2014-12-01

    Sun-aligned auroral arcs (SAAs) are one of the outstanding phenomena in the high-latitude region during periods of northward interplanetary magnetic field (IMF). Smaller scale SAAs tend to occur either in the duskside or dawnside of the polar cap and are known to drift in the dawn-dusk direction depending on the sign of the IMF By. Studies of SAAs are of particular importance because they represent dynamical characteristics of their source plasma in the magnetosphere, for example in the interaction region between the solar wind and magnetosphere or in the boundary between the plasma sheet and tail lobe. To date, however, very little has been known about the spatial structure and/or temporal evolution of the magnetospheric counterpart of SAAs. In order to gain more comprehensive understanding of the field-aligned plasma transport in the vicinity of SAAs, we have investigated an event of SAAs on November 10, 2005, during which multiple SAAs were detected by a ground-based all-sky camera at Resolute Bay, Canada. During this interval, several SAAs were detached from the duskside oval and moved poleward. The large-scale structure of these arcs was visualized by space-based imagers of TIMED/GUVI and DMSP/SSUSI. In addition to these optical observations, we employ the Cluster satellites to reveal the high-altitude particle signature corresponding to the small-scale SAAs. The ionospheric footprints of the 4 Cluster satellites encountered the SAAs sequentially and observed well correlated enhancements of electron fluxes at weak energies (SAAs. This implies that these ions and electrons were accelerated upward by a quasi-stationary electric field existing in the vicinity of the SAAs and constitute a current system in the magnetosphere-ionosphere coupling system. Ionospheric convection measurement from one of the SuperDARN radars shows an indication that the SAAs are embedded in the lobe cell during northward IMF conditions. In the presentation, we will show the results of

  5. 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...

  6. Offshore winds mapped from satellite remote sensing

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay

    2014-01-01

    the uncertainty on the model results on the offshore wind resource, it is necessary to compare model results with observations. Observations from ground-based wind lidar and satellite remote sensing are the two main technologies that can provide new types of offshore wind data at relatively low cost....... The advantages of microwave satellite remote sensing are 1) horizontal spatial coverage, 2) long data archives and 3) high spatial detail both in the coastal zone and of far-field wind farm wake. Passive microwave ocean wind speed data are available since 1987 with up to 6 observations per day with near...

  7. 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

  8. The Heppner-Maynard Boundary measured by SuperDARN as a proxy for the latitude of the auroral oval

    Science.gov (United States)

    Imber, S. M.; Milan, S. E.; Lester, M.

    2013-02-01

    We present a statistical study relating the latitude of the auroral oval measured by the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) SI-12 proton auroral camera to that of the Heppner-Maynard Boundary (HMB) determined from Super Dual Auroral Radar Network (SuperDARN) data during the period 2000-2002. The HMB represents the latitudinal extent of the ionospheric convection pattern. The oval latitude from the proton auroral images is determined using the method of Milan et al. (2009a), which fits a circle centered on a point 2° duskward and 5° antisunward of the magnetic pole. The auroral latitude at midnight is determined for those images where the concurrent SuperDARN northern hemisphere maps contain more than 200 data points such that the HMB is well-defined. The statistical study comprises over 198,000 two-minute intervals, and we find that the HMB is located on average 2.2° equatorward of the proton auroral latitude. A superposed epoch analysis of over 2500 substorms suggests that the separation between the HMB and the oval latitude increases slightly during periods of high geomagnetic activity. We suggest that during intervals where there are no auroral images available, the HMB latitude and motion could be used as a proxy for that of the aurora, and therefore provide information about motions of the open/closed field line boundary.

  9. A statistical study of ion energization at 1700 km in the auroral region

    Directory of Open Access Journals (Sweden)

    M. Hamrin

    2002-12-01

    Full Text Available We present a comprehensive overview of several potentially relevant causes for the oxygen energization in the auroral region. Data from the Freja satellite near 1700 km altitude are used for an unconditional statistical investigation. The data are obtained in the Northern Hemisphere during 21 months in the declining phase of the solar cycle. The importance of various wave types for the ion energization is statistically studied. We also investigate the correlation of ion heating with precipitating protons, accelerated auroral electrons, suprathermal electron bursts, the electron density variations, Kp index and solar illumination of the nearest conjugate ionosphere. We find that sufficiently strong broad-band ELF waves, electromagnetic ion cyclotron waves, and waves around the lower hybrid frequency are foremost associated with the ion heating. However, magnetosonic waves, with a sharp, lower frequency cutoff just below the proton gyrofrequency, are not found to contribute to the ion heating. In the absence of the first three wave emissions, transversely energized ions are rare. These wave types are approximately equally efficient in heating the ions, but we find that the main source for the heating is broadband ELF waves, since they are most common in the auroral region. We have also observed that the conditions for ion heating are more favourable for smaller ratios of the spectral densities SE /SB of the broadband ELF waves at the oxygen gyrofrequency.Key words. Ionosphere (auroral ionosphere; wave propogation Magnetospheric physics (electric fields

  10. A study of a sector spectrophotometer and auroral O+(2P-2D) emissions

    Science.gov (United States)

    Swenson, G. R.

    1976-01-01

    The metastable O+(2P-2D) auroral emission was investigated. The neighboring OH contaminants and low intensity levels of the emission itself necessitated the evolution of an instrument capable of separating the emission from the contaminants and having a high sensitivity in the wavelength region of interest. A new type of scanning photometer was developed and its properties are discussed. The theoretical aspects of auroral electron interaction with atomic oxygen and the resultant O+(2P-2D) emissions were examined in conjunction with N2(+)1NEG emissions. Ground based measurements of O+(2P-2D) auroral emission intensities were made using the spatial scanning photometer (sector spectrophotometer). Simultaneous measurements of N2(+)1NEG sub 1,0 emission intensity were made in the same field of view using a tilting photometer. Time histories of the ratio of these two emissions made in the magnetic zenith during auroral breakup periods are given. Theories of I sub 7319/I sub 4278 of previous investigators were presented. A rocket measurement of N2(+)1NEG sub 0,0 and O+(2P-2D) emission in aurora was examined in detail and was found to agree with the ground based measurements. Theoretical examination resulted in the deduction of the electron impact efficiency generating O+(2P) and also suggests a large source of O+(2P) at low altitude. A possible source is charge exchange of N+(1S) with OI(3P).

  11. Polarisation of auroral emission lines in the Earth's upper atmosphere : first results and perspectives

    Science.gov (United States)

    Lamy, H.; Barthelemy, M.; Simon Wedlund, C.; Lilensten, J.; Bommier, V.

    2011-12-01

    Polarisation of light is a key observable to provide information about asymmetry or anisotropy within a radiative source. Following the pioneering and controversial work of Duncan in 1959, the polarisation of auroral emission lines in the Earth's upper atmosphere has been overlooked for a long time, even though the red intense auroral line (6300Å) produced by collisional impacts with electrons precipitating along magnetic field lines is a good candidate to search for polarisation. This problem was investigated again by Lilensten et al (2006) and observations were obtained by Lilensten et al (2008) confirming that the red auroral emission line is polarised. More recent measurements obtained by Barthélemy et al (2011) are presented and discussed. The results are compared to predictions of the theoretical work of Bommier et al (2011) and are in good agreement. Following these encouraging results, a new dedicated spectropolarimeter is currently under construction between BIRA-IASB and IPAG to provide simultaneously the polarisation of the red line and of other interesting auroral emission lines such as N2+ 1NG (4278Å), other N2 bands, etc... Perspectives regarding the theoretical polarisation of some of these lines will be presented. The importance of these polarisation measurements in the framework of atmospheric modeling and geomagnetic activity will be discussed.

  12. Superposed epoch analysis of O+ auroral outflow during sawtooth events and substorms

    Science.gov (United States)

    Nowrouzi, N.; Kistler, L. M.; Lund, E. J.; Cai, X.

    2017-12-01

    Sawtooth events are repeated injection of energetic particles at geosynchronous orbit. Studies have shown that 94% of sawtooth events occurred during magnetic storm times. The main factor that causes a sawtooth event is still an open question. Simulations have suggested that heavy ions like O+ may play a role in triggering the injections. One of the sources of the O+ in the Earth's magnetosphere is the nightside aurora. O+ ions coming from the nightside auroral region have direct access to the near-earth magnetotail. A model (Brambles et al. 2013) for interplanetary coronal mass ejection driven sawtooth events found that nightside O+ outflow caused the subsequent teeth of the sawtooth event through a feedback mechanism. This work is a superposed epoch analysis to test whether the observed auroral outflow supports this model. Using FAST spacecraft data from 1997-2007, we examine the auroral O+ outflow as a function of time relative to an injection onset. Then we determine whether the profile of outflow flux of O+ during sawtooth events is different from the outflow observed during isolated substorms. The auroral region boundaries are estimated using the method of (Andersson et al. 2004). Subsequently the O+ outflow flux inside these boundaries are calculated and binned as a function of superposed epoch time for substorms and sawtooth "teeth". In this way, we will determine if sawtooth events do in fact have greater O+ outflow, and if that outflow is predominantly from the nightside, as suggested by the model results.

  13. A Comparative Study of Spectral Auroral Intensity Predictions From Multiple Electron Transport Models

    Science.gov (United States)

    Grubbs, Guy; Michell, Robert; Samara, Marilia; Hampton, Donald; Hecht, James; Solomon, Stanley; Jahn, Jorg-Micha

    2018-01-01

    It is important to routinely examine and update models used to predict auroral emissions resulting from precipitating electrons in Earth's magnetotail. These models are commonly used to invert spectral auroral ground-based images to infer characteristics about incident electron populations when in situ measurements are unavailable. In this work, we examine and compare auroral emission intensities predicted by three commonly used electron transport models using varying electron population characteristics. We then compare model predictions to same-volume in situ electron measurements and ground-based imaging to qualitatively examine modeling prediction error. Initial comparisons showed differences in predictions by the GLobal airglOW (GLOW) model and the other transport models examined. Chemical reaction rates and radiative rates in GLOW were updated using recent publications, and predictions showed better agreement with the other models and the same-volume data, stressing that these rates are important to consider when modeling auroral processes. Predictions by each model exhibit similar behavior for varying atmospheric constants, energies, and energy fluxes. Same-volume electron data and images are highly correlated with predictions by each model, showing that these models can be used to accurately derive electron characteristics and ionospheric parameters based solely on multispectral optical imaging data.

  14. Oxygen auroral transition laser system excited by collisional and photolytic energy transfer

    International Nuclear Information System (INIS)

    Murray, J.R.; Powell, H.T.; Rhodes, C.K.

    1975-06-01

    The properties of laser media involving the auroral transition of atomic oxygen and analogous systems are examined. A discussion of the atomic properties, collisional mechanisms, excitation processes, and collisionally induced radiative phenomena is given. Crossing phenomena play a particularly important role in governing the dynamics of the medium

  15. Jovian longitudinal asymmetry in Io-related and Europa-related auroral hot spots

    International Nuclear Information System (INIS)

    Dessler, A.J.; Chamberlain, J.W.

    1979-01-01

    Jupiter's internal magnetic field is markedly non-dipolar. We propose that Io- or Europa-generated auroral emissions (originating at the foot of either Io's or Europa's magnetic flux tube) are largely restricted to longitudes where Jupiter's ionospheric conductivity is enhanced. Trapped, energetic electrons that drift into Jupiter's atmosphere, in regions where the Jovian magnetic field is anomalously weak, produce the increased conductivity. The longitude range of enchanced auroral hot-spot emissions is thus restricted to an active sector that is determined from dekametric radio emission to lie in the northern hemisphere in the Jovian System III (1965) longitude range of 205 0 +- 30 0 . Relatively weaker auroral hot spots should occur in the southern hemisphere along the mgnetic conjugate trace covering the longitude range of 215 0 +- 55 0 . At other longitudes, the brightness of the hot spot should decrease by at least one order of magnitude. These results, with respect to both brightness and longitude, are in accord with the observations of Jovian auroral hot spots reported by Atreya et al. We show that the northern hemisphere foot of either Io's or Europa's magnetic flux tube was in the preferred longitude range (the active sector) at the time of each observation

  16. On I(5577 Å and I (7620 Å auroral emissions and atomic oxygen densities

    Directory of Open Access Journals (Sweden)

    R. L. Gattinger

    1996-07-01

    Full Text Available A model of auroral electron deposition processes has been developed using Monte Carlo techniques to simulate electron transport and energy loss. The computed differential electron flux and pitch angle were compared with in situ auroral observations to provide a check on the accuracy of the model. As part of the energy loss process, a tally was kept of electronic excitation and ionization of the important atomic and molecular states. The optical emission rates from these excited states were computed and compared with auroral observations of η(3914 Å, η(5577 Å, η(7620 Å and η(N2VK. In particular, the roles played by energy transfer from N2(A3Σ+u and by other processes in the excitation of O(1S and O2(b1Σ+g were investigated in detail. It is concluded that the N2(A3Σ+u mechanism is dominant for the production of OI(5577 Å in the peak emission region of normal aurora, although the production efficiency is much smaller than the measured laboratory value; above 150 km electron impact on atomic oxygen is dominant. Atomic oxygen densities in the range of 0.75±0.25 MSIS-86 [O] were derived from the optical comparisons for auroral latitudes in mid-winter for various levels of solar and magnetic activity.

  17. Observations of the auroral width spectrum at kilometre-scale size

    Directory of Open Access Journals (Sweden)

    N. Partamies

    2010-03-01

    Full Text Available This study examines auroral colour camera data from the Canadian Dense Array Imaging SYstem (DAISY. The Dense Array consists of three imagers with different narrow (compared to all-sky view field-of-view optics. The main scientific motivation arises from an earlier study by Knudsen et al. (2001 who used All-Sky Imager (ASI combined with even earlier TV camera observations (Maggs and Davis, 1968 to suggest that there is a gap in the distribution of auroral arc widths at around 1 km. With DAISY observations we are able to show that the gap is an instrument artifact and due to limited spatial resolution and coverage of commonly used instrumentation, namely ASIs and TV cameras. If the auroral scale size spectrum is indeed continuous, the mechanisms forming these structures should be able to produce all of the different scale sizes. So far, such a single process has not been proposed in the literature and very few models are designed to interact with each other even though the range of their favourable conditions do overlap. All scale-sizes should be considered in the future studies of auroral forms and electron acceleration regions, both in observational and theoretical approaches.

  18. Nonlinear model of short-scale electrodynamics in the auroral ionosphere

    Directory of Open Access Journals (Sweden)

    J.-M. A. Noël

    Full Text Available The optical detection of auroral subarcs a few tens of m wide as well as the direct observation of shears several m/s per m over km to sub km scales by rocket instrumentation both indicate that violent and highly localized electrodynamics can occur at times in the auroral ionosphere over scales 100 m or less in width. These observations as well as the detection of unstable ion-acoustic waves observed by incoherent radars along the geomagnetic field lines has motivated us to develop a detailed time-dependent two-dimensional model of short-scale auroral electrodynamics that uses current continuity, Ohm's law, and 8-moment transport equations for the ions and electrons in the presence of large ambient electric fields to describe wide auroral arcs with sharp edges in response to sharp cut-offs in precipitation (even though it may be possible to describe thin arcs and ultra-thin arcs with our model, we have left such a study for future work. We present the essential elements of this new model and illustrate the model's usefulness with a sample run for which the ambient electric field is 100 mV/m away from the arc and for which electron precipitation cuts off over a region 100 m wide. The sample run demonstrates that parallel current densities of the order of several hundred µA m-2 can be triggered in these circumstances, together with shears several m/s per m in magnitude and parallel electric fields of the order of 0.1 mV/m around 130 km altitude. It also illustrates that the local ionospheric properties like densities, temperature and composition can strongly be affected by the violent localized electrodynamics and vice-versa.

    Key words: Ionosphere (auroral ionosphere, electric fields and currents, ionosphere-magnetosphere interactions

  19. 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.

  20. 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.

  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. Characteristics of merging at the magnetopause inferred from dayside 557.7-nm all-sky images: IMF drivers of poleward moving auroral forms

    Directory of Open Access Journals (Sweden)

    N. C. Maynard

    2006-11-01

    Full Text Available We combine in situ measurements from Cluster with high-resolution 557.7 nm all-sky images from South Pole to investigate the spatial and temporal evolution of merging on the dayside magnetopause. Variations of 557.7 nm emissions were observed at a 6 s cadence at South Pole on 29 April 2003 while significant changes in the Interplanetary Magnetic Field (IMF clock angle were reaching the magnetopause. Electrons energized at merging sites are the probable sources for 557.7 nm cusp emissions. At the same time Cluster was crossing the pre-noon cusp in the Northern Hemisphere. The combined observations confirm results of a previous study that merging events can occur at multiple sites simultaneously and vary asynchronously on time scales of 10 s to 3 min (Maynard et al., 2004. The intensity of the emissions and the merging rate appear to vary with changes in the IMF clock angle, IMF BX and the dynamic pressure of the solar wind. Most poleward moving auroral forms (PMAFs reflect responses to changes in interplanetary medium rather than to local processes. The changes in magnetopause position required by increases in dynamic pressure are mediated by merging and result in the generation of PMAFs. Small (15–20% variations in dynamic pressure of the solar wind are sufficient to launch PMAFs. Changes in IMF BX create magnetic flux compressions and rarefactions in the solar wind. Increases (decreases in IMF BX strengthens |B| near northern (southern hemisphere merging sites thereby enhancing merging rates and triggering PMAFs. When correlating responses in the two hemispheres, the presence of significant IMF BX also requires that different lag-times be applied to ACE measurements acquired ~0.1 AU upstream of Earth. Cluster observations set lag times for merging at Northern Hemisphere sites; post-noon optical emissions set times of Southern Hemisphere merging. All-sky images and magnetohydrodynamic simulations indicate that merging occurs in multiple

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

    Science.gov (United States)

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

    2008-12-01

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

  4. 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.

  5. Astrid-2 and ground-based observations of the auroral bulge in the middle of the nightside convection throat

    Directory of Open Access Journals (Sweden)

    G. T. Marklund

    2001-06-01

    Full Text Available Results concerning the electrodynamics of the nightside auroral bulge are presented based on simultaneous satellite and ground-based observations. The satellite data include Astrid-2 measurements of electric fields, currents and particles from a midnight auroral oval crossing and Polar UVI images of the large-scale auroral distribution. The ground-based observations include STARE and SuperDARN electric fields and magnetic records from the Greenland and MIRACLE magnetometer network, the latter including stations from northern Scandinavia north to Svalbard. At the time of the Astrid-2 crossing the ground-based data reveal intense electrojet activity, both to the east and west of the Astrid-2 trajectory, related to the Polar observations of the auroral bulge but not necessarily to a typical substorm. The energetic electron fluxes measured by Astrid-2 across the auroral oval were generally weak being consistent with a gap observed in the auroral luminosity distribution. The electric field across the oval was directed westward, intensifying close to the poleward boundary followed by a decrease in the polar cap. The combined observations suggests that Astrid-2 was moving close to the separatrix between the dusk and dawn convection cells in a region of low conductivity. The constant westward direction of the electric field across the oval indicates that current continuity was maintained, not by polarisation electric fields (as in a Cowling channel, but solely by localized up- and downward field-aligned currents in good agreement with the Astrid-2 magnetometer data. The absence of a polarisation electric field and thus of an intense westward closure current between the dawn and dusk convection cells is consistent with the relatively weak precipitation and low conductivity in the convection throat. Thus, the Cowling current model is not adequate for describing the electrodynamics of the nightside auroral bulge treated here.Key words. Ionosphere (auroral

  6. Profiling the regional wind power fluctuation in China

    International Nuclear Information System (INIS)

    Yu Dayang; Liang Jun; Han Xueshan; Zhao Jianguo

    2011-01-01

    As China starts to build 6 10-GW wind zones in 5 provinces by 2020, accommodating the wind electricity generated from these large wind zones will be a great challenge for the regional grids. Inadequate wind observing data hinders profiling the wind power fluctuations at the regional grid level. This paper proposed a method to assess the seasonal and diurnal wind power patterns based on the wind speed data from the NASA GEOS-5 DAS system, which provides data to the study of climate processes including the long-term estimates of meteorological quantities. The wind power fluctuations for the 6 largest wind zones in China are presented with both the capacity factor and the megawatt wind power output. The measured hourly wind output in a regional grid is compared to the calculating result to test the analyzing model. To investigate the offsetting effect of dispersed wind farms over large regions, the regional correlations of hourly wind power fluctuations are calculated. The result illustrates the different offsetting effects of minute and hourly fluctuations.

  7. Spectral characteristics of aurorae connected with high-velocity flows of the solar wind from coronal holes

    International Nuclear Information System (INIS)

    Khviyuzova, T.A.; Leont'ev, S.V.

    1997-01-01

    Bright electron aurorae almost always followed by red lower edge occur when the Earth is being passed by high-velocity flows from coronal holes within the auroral range at the night meridian. In contrast to other types of the solar wind the high-velocity flows from coronal holes do not cause the occurrence of A type red polar aurorae, that is, the spectrum of electrons pouring into the Earth atmosphere in these cases is shifted towards higher energies

  8. 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

  9. 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.

  10. Magnetospheric magnetic field modelling for the 2011 and 2012 HST Saturn aurora campaigns – implications for auroral source regions

    Directory of Open Access Journals (Sweden)

    E. S. Belenkaya

    2014-06-01

    Full Text Available A unique set of images of Saturn's northern polar UV aurora was obtained by the Hubble Space Telescope in 2011 and 2012 at times when the Cassini spacecraft was located in the solar wind just upstream of Saturn's bow shock. This rare situation provides an opportunity to use the Kronian paraboloid magnetic field model to examine source locations of the bright auroral features by mapping them along field lines into the magnetosphere, taking account of the interplanetary magnetic field (IMF measured near simultaneously by Cassini. It is found that the persistent dawn arc maps to closed field lines in the dawn to noon sector, with an equatorward edge generally located in the inner part of the ring current, typically at ~ 7 Saturn radii (RS near dawn, and a poleward edge that maps variously between the centre of the ring current and beyond its outer edge at ~ 15 RS, depending on the latitudinal width of the arc. This location, together with a lack of response in properties to the concurrent IMF, suggests a principal connection with ring-current and nightside processes. The higher-latitude patchy auroras observed intermittently near to noon and at later local times extending towards dusk are instead found to straddle the model open–closed field boundary, thus mapping along field lines to the dayside outer magnetosphere and magnetopause. These emissions, which occur preferentially for northward IMF directions, are thus likely associated with reconnection and open-flux production at the magnetopause. One image for southward IMF also exhibits a prominent patch of very high latitude emissions extending poleward of patchy dawn arc emissions in the pre-noon sector. This is found to lie centrally within the region of open model field lines, suggesting an origin in the current system associated with lobe reconnection, similar to that observed in the terrestrial magnetosphere for northward IMF.

  11. QuikSCAT and SSM/I ocean surface winds for wind energy

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Astrup, Poul; Nielsen, Per

    2007-01-01

    -European mid-latitudes and in the Atlantic trade belt zone are compared. Distinct differences are identified and these agree well with independent data from meteorological masts in the two regions. Seven years of twice daily observations from QuikSCAT are used for the offshore wind resource assessment. Wind...

  12. Determining the source region of auroral emissions in the prenoon oval using coordinated Polar BEAR UV-imaging and DMSP particle measurements

    Science.gov (United States)

    Newell, Patrick T.; Meng, CHING-I.; Huffman, Robert E.

    1992-01-01

    The Polar Beacon Experiment and Auroral Research (Polar BEAR) satellite included the capability for imaging the dayside auroral oval in full sunlight at several wavelengths. Particle observations from the DMSP F7 satellite during dayside auroral oval crossings are compared with approximately simultaneous Polar BEAR 1356-A images to determine the magnetospheric source region of the dayside auroral oval. The source region is determined from the DMSP particle data, according to recent work concerning the classification and identification of precipitation source regions. The close DMSP/Polar BEAR coincidences all occur when the former satellite is located between 0945 and 1000 MLT. Instances of auroral arcs mapping to each of several different regions, including the boundary plasma sheet, the low-latitude boundary layer, and the plasma mantle were found. It was determined that about half the time the most prominent auroral arcs are located at the interfaces between distinct plasma regions, at least at the local time studied here.

  13. Rocket and ground-based study of an auroral breakup event

    International Nuclear Information System (INIS)

    Marklund, G.

    1982-02-01

    On 27 January, 1979 the substorm-GEOS rocket S23H was launched from ESRANGE, Kiruna, shortly after the onset of an intense magnetospheric substorm over northern Scandinavia. Rocket electric field and particle observations have been used to calculate ionospheric currents and heating rates. These results are generally consistent with the ground magnetic and optical observations. An important finding emerging from a comparison of this event with a pre-breakup event earlier on this day is that the ionospheric substorm-related electric field could be split up into two parts, namely: 1) an ambient LT dependent field, probably of magnetospheric origin 2) superimposed on this a small-scale electric field associated with the bright auroral structures, being southward for both events. This is shown to have important consequences on the location of the ionospheric currents and the Joule energy discussion relative to the auroral forms. (Author)

  14. Investigation of Io's auroral hiss emissions due to its motion in Jupiter's magnetosphere

    International Nuclear Information System (INIS)

    Moghimi, Mohsen H.

    2012-01-01

    The left-hand side of the auroral hiss emission observed by Galileo has a frequency time profile shaped very similar to the funnel shape observed in the Earth's auroral region. This close similarity indicates that we can use the theory of whistler-mode propagation near the resonance cone to locate the emission source. The general characteristics of the whistler mode are discussed. Then the position of the emission source is investigated using a geometrical method that takes into account the trajectory of Galileo. Initially a point source is assumed. Then the possibility of a sheet source aligned along the magnetic field lines which are tangent to the surface of Io is investigated. Both types of sources show that the whistler mode radiation originates very close to the surface of Io. (research papers)

  15. Radio wave dissipation in turbulent auroral plasma during the precipitation of energetic electrons

    International Nuclear Information System (INIS)

    Mishin, E.V.; Luk'ianova, L.N.; Makarenko, S.F.; Atamaniuk, B.M.

    1992-01-01

    The results of the theoretical analysis of anomalous (collisionless) radio wave absorption in the turbulent auroral ionosphere during the intrusion of energetic electrons (i.e., in aurorae) are presented. The implications of the plasma turbulent layer (PTL) theory are used. It is shown that the dissipation of radio waves with frequencies much higher than the plasma frequency is caused by the nonlinear (combined) scattering in turbulent plasma of the PTL. In the auroral electrojet layer the principal dissipative process for the radio waves with frequencies close to the plasma frequency is O-Z transformation on the field-aligned, small-scale density fluctuations. The typical dissipation decrements are estimated. 26 refs

  16. Electric potential structures of auroral acceleration region border from multi-spacecraft Cluster data

    Science.gov (United States)

    Sadeghi, S.; Emami, M. R.

    2018-04-01

    This paper studies an auroral event using data from three spacecraft of the Cluster mission, one inside and two at the poleward edge of the bottom of the Auroral Acceleration Region (AAR). The study reveals the three-dimensional profile of the region's poleward boundary, showing spatial segmentation of the electric potential structures and their decay in time. It also depicts localized magnetic field variations and field-aligned currents that appear to have remained stable for at least 80 s. Such observations became possible due to the fortuitous motion of the three spacecraft nearly parallel to each other and tangential to the AAR edge, so that the differences and variations can be seen when the spacecraft enter and exit the segmentations, hence revealing their position with respect to the AAR.

  17. Cluster observations and theoretical identification of broadband waves in the auroral region

    Directory of Open Access Journals (Sweden)

    M. Backrud-Ivgren

    2005-12-01

    Full Text Available Broadband waves are common on auroral field lines. We use two different methods to study the polarization of the waves at 10 to 180 Hz observed by the Cluster spacecraft at altitudes of about 4 Earth radii in the nightside auroral region. Observations of electric and magnetic wave fields, together with electron and ion data, are used as input to the methods. We find that much of the wave emissions are consistent with linear waves in homogeneous plasma. Observed waves with a large electric field perpendicular to the geomagnetic field are more common (electrostatic ion cyclotron waves, while ion acoustic waves with a large parallel electric field appear in smaller regions without suprathermal (tens of eV plasma. The regions void of suprathermal plasma are interpreted as parallel potential drops of a few hundred volts.

  18. Auroral ion beams and ion acoustic wave generation by fan instability

    Energy Technology Data Exchange (ETDEWEB)

    Vaivads, A

    1996-04-01

    Satellite observations indicate that efficient energy transport among various plasma particles and between plasma waves and plasma particles is taking place in auroral ion beam regions. These observations show that two characteristic wave types are associated with the auroral ion beam regions: electrostatic hydrogen cyclotron waves with frequencies above hydrogen gyrofrequency, and low frequency waves with frequencies below hydrogen gyrofrequency. We speculate that the low frequency waves can be ion acoustic waves generated through the fan instability. The presence of a cold background ion component is necessary for the onset of this instability. A cold ion component has been directly observed and has been indirectly suggested from observations of solitary wave structures. The wave-particle interaction during the development of the fan instability results in an efficient ion beam heating in the direction perpendicular to the ambient magnetic field. The fan instability development and the ion beam heating is demonstrated in a numerical particle simulation. 23 refs, 16 figs.

  19. Stimulation of auroral kilometric radiation by type III solar radio bursts

    International Nuclear Information System (INIS)

    Calvert, W.

    1981-01-01

    It has been found that the onset of auroral kilometric radiation (AKR) frequently coincides with the arrival of type III solar radio bursts. Although the AKR onsets are usually abrupt and appear to be spontaneous, they sometimes develop from a discrete frequency near the leading edge of a type III burst or sometimes occur at progressively lower frequencies following that edge. From this, and the absence of the related solar electrons in specific cases, it was concluded that the incoming type III waves were sometimes responsible for stimulating auroral kilometric radiation. It was estimated that intense, isolated type III bursts were capable of stimulating AKR roughly one third of the time, and that at least ten percent of the observed AKR onsets could be attributed to these and weaker bursts, including some barely detectable by the ISEE plasma wave receivers

  20. On waves below the local proton gyrofrequency in auroral acceleration regions

    International Nuclear Information System (INIS)

    Gustafsson, G.; Andre, M.; Matson, L.; Koskinen, H.

    1990-01-01

    The Viking wave electric field and density fluctuation measurements together with simultaneous particle observations are used to study waves at frequencies below the local proton gyrofrequency. Such waves were observed during about 20% of nightside auroral field line crossings by Viking at altitudes between 2,000 and 10,000 km. The observations are different from earlier spacecraft observations of similar waves in such a way that the center frequency in about one out of four of the observed events was below the gyrofrequency of singly charged helium, which has not been reported previously. The waves were well correlated with precipitating electrons of energies of a few keV and with VLF auroral hiss. Detailed investigations of simultaneously observed wave emissions, particles, and total densities strongly suggest that secondary peaks at keV energies in the distributions of downgoing electrons can cause the emissions

  1. 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...

  2. 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.)

  3. Different magnetospheric modes: solar wind driving and coupling efficiency

    Directory of Open Access Journals (Sweden)

    N. Partamies

    2009-11-01

    Full Text Available This study describes a systematic statistical comparison of isolated non-storm substorms, steady magnetospheric convection (SMC intervals and sawtooth events. The number of events is approximately the same in each group and the data are taken from about the same years to avoid biasing by different solar cycle phase. The very same superposed epoch analysis is performed for each event group to show the characteristics of ground-based indices (AL, PCN, PC potential, particle injection at the geostationary orbit and the solar wind and IMF parameters. We show that the monthly occurrence of sawtooth events and isolated non-stormtime substorms closely follows maxima of the geomagnetic activity at (or close to the equinoxes. The most strongly solar wind driven event type, sawtooth events, is the least efficient in coupling the solar wind energy to the auroral ionosphere, while SMC periods are associated with the highest coupling ratio (AL/EY. Furthermore, solar wind speed seems to play a key role in determining the type of activity in the magnetosphere. Slow solar wind is capable of maintaining steady convection. During fast solar wind streams the magnetosphere responds with loading–unloading cycles, represented by substorms during moderately active conditions and sawtooth events (or other storm-time activations during geomagnetically active conditions.

  4. 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.

  5. Rocket measurements of X-rays and energetic electrons through an auroral arc

    International Nuclear Information System (INIS)

    Aarsnes, K.; Stadsnes, J.; Soeraas, F.

    1976-01-01

    Preliminary results from rocket measurements on auroral electron precipitation are discussed as far as the spatial structure and time and space variations in the primary electron fluxes are concerned. The analysis demonstrates that there was a good overall correspondence between the X-ray and electron data. By using a well collimated X-ray detector on a spinning rocket, it was possible to get additional information on the overall electron precipitation pattern

  6. Towards a synthesis of substorm electrodynamics: HF radar and auroral observations

    Directory of Open Access Journals (Sweden)

    A. Grocott

    2006-12-01

    Full Text Available At 08:35 UT on 21 November 2004, the onset of an interval of substorm activity was captured in the southern hemisphere by the Far UltraViolet (FUV instrument on board the IMAGE spacecraft. This was accompanied by the onset of Pi2 activity and subsequent magnetic bays, evident in ground magnetic data from both hemispheres. Further intensifications were then observed in both the auroral and ground magnetic data over the following ~3 h. During this interval the fields-of-view of the two southern hemisphere Tasman International Geospace Enviroment Radars (TIGER moved through the evening sector towards midnight. Whilst initially low, the amount of backscatter from TIGER increased considerably during the early stages of the expansion phase such that by ~09:20 UT an enhanced dusk flow cell was clearly evident. During the expansion phase the equatorward portion of this flow cell developed into a narrow high-speed flow channel, indicative of the auroral and sub-auroral flows identified in previous studies (e.g. Freeman et al., 1992; Parkinson et al., 2003. At the same time, higher latitude transient flow features were observed and as the interval progressed the flow reversal region and Harang discontinuity became very well defined. Overall, this study has enabled the spatial and temporal development of many different elements of the substorm process to be resolved and placed within a simple conceptual framework of magnetospheric convection. Specifically, the detailed observations of ionospheric flows have illustrated the complex interplay between substorm electric fields and associated auroral dynamics. They have helped define the distinct nature of different substorm current systems such as the traditional substorm current wedge and the more equatorward currents associated with polarisation electric fields. Additionally, they have revealed a radar signature of nightside reconnection which provides the promise of quantifying nightside reconnection in a

  7. Search for auroral belt Eparallel fields with high-velocity barium ion injections

    International Nuclear Information System (INIS)

    Heppner, J.P.; Ledley, B.G.; Miller, M.L.; Marionni, P.A.; Pongratz, M.B.; Slater, D.W.; Hallinan, T.J.; Rees, D.

    1989-01-01

    Four high-velocity shaped charge Ba + injections were conducted from two Black Brant-10 rockets at collision-free altitudes (770-975 km) over northern Alaska (L = 7.4-10.6) in April 1984 under active auroral and magnetic disturbance (Kp 4+ and 5) conditions. The motions of the Ba + pencil beams from these injections were accurately triangulated to altitudes ranging from 9,000 to 14,000 km from multistation image observations. Well-defined initial conditions and improved software for predicting the unperturbed. E = 0, trajectories in the presence of convection, E perpendicular , fields permitted an accurate detection of changes in the motion which could be attributed to E parallel fields. Large (> 1 keV) potential changes that might be anticipated from double-layer or V-, U- and S-shaped potential structures were not encountered even though the Ba + rays were clearly located on auroral arc flux tubes on at least several occasions and were at various times in close proximity to auroral flux tubes for many minutes. Abnormally intense E perpendicular fields that might also indicate that the above potential structures were also not observed. Transient accelerations and/or decelerations involving magnetic field-aligned energy changes ≤ 375 eV were, however, encountered by each of the seven principal Ba + rays tracked to high altitudes. Acceleration events were only slightly more frequent than deceleration events. Interpretation, taking into account limits on the duration of the events and simultaneous auroral conditions, favors explanation in terms of propagating waves, soliton trains, or other pulse forms provided that the propagation is primarily field-aligned

  8. Production of nitrous oxide in the auroral D and E regions

    Science.gov (United States)

    Zipf, E. C.; Prasad, S. S.

    1980-01-01

    A study of nitrous oxide formation mechanisms indicates that N2O concentrations greater than 10 to the 9th per cu cm could be produced in IBC III aurora or by lower-level activity lasting for many hours, and, in favorable conditions, the N2O concentration could exceed the local nitric oxide density. An upper limit on the globally averaged N2O production rate from auroral activity is estimated at 2 x 10 to the 27th per second.

  9. Storm time dynamics of auroral electrojets: CHAMP observation and the Space Weather Modeling Framework comparison

    Directory of Open Access Journals (Sweden)

    H. Wang

    2008-03-01

    Full Text Available We investigate variations of the location and intensity of auroral currents during two magnetic storm periods based on magnetic field measurements from CHAMP separately for both hemispheres, as well as for the dayside and nightside. The corresponding auroral electrojet current densities are on average enhanced by about a factor of 7 compared to the quiet time current strengths. The nightside westward current densities are on average 1.8 (2.2 times larger than the dayside eastward current densities in the Northern (Southern Hemisphere. Both eastward and westward currents are present during the storm periods with the most intense electrojets appearing during the main phase of the storm, before the ring current maximizes in strength. The eastward and westward electrojet centers can expand to 55° MLat during intense storms, as is observed on 31 March 2001 with Dst=−387 nT. The equatorward shift of auroral currents on the dayside is closely controlled by the southward IMF, while the latitudinal variations on the nightside are better described by the variations of the Dst index. However, the equatorward and poleward motion of the nightside auroral currents occur earlier than the Dst variations. The Space Weather Modeling Framework (SWMF can capture the general dynamics of the storm time current variations. Both the model and the actual data show that the currents tend to saturate when the merging electric field is larger than 10 mV/m. However, the exact prediction of the temporal development of the currents is still not satisfactory.

  10. Storm time dynamics of auroral electrojets: CHAMP observation and the Space Weather Modeling Framework comparison

    Directory of Open Access Journals (Sweden)

    H. Wang

    2008-03-01

    Full Text Available We investigate variations of the location and intensity of auroral currents during two magnetic storm periods based on magnetic field measurements from CHAMP separately for both hemispheres, as well as for the dayside and nightside. The corresponding auroral electrojet current densities are on average enhanced by about a factor of 7 compared to the quiet time current strengths. The nightside westward current densities are on average 1.8 (2.2 times larger than the dayside eastward current densities in the Northern (Southern Hemisphere. Both eastward and westward currents are present during the storm periods with the most intense electrojets appearing during the main phase of the storm, before the ring current maximizes in strength. The eastward and westward electrojet centers can expand to 55° MLat during intense storms, as is observed on 31 March 2001 with Dst=−387 nT. The equatorward shift of auroral currents on the dayside is closely controlled by the southward IMF, while the latitudinal variations on the nightside are better described by the variations of the Dst index. However, the equatorward and poleward motion of the nightside auroral currents occur earlier than the Dst variations. The Space Weather Modeling Framework (SWMF can capture the general dynamics of the storm time current variations. Both the model and the actual data show that the currents tend to saturate when the merging electric field is larger than 10 mV/m. However, the exact prediction of the temporal development of the currents is still not satisfactory.

  11. Electrostatic mode coupling at 2ω/sub UH/: a generation mechanism for auroral kilometric radiation

    International Nuclear Information System (INIS)

    Barbosa, D.D.

    1976-01-01

    The instability of a low density, electron beam drifting along a magnetic field to nearly perpendicular propagating electrostatic waves near the upper hybrid frequency is investigated for application to an auroral environment. It was found that 4 to 10 KeV beams can interact significantly with the background plasma through anomalous cyclotron resonances which extend the range of unstable parallel wave numbers over a large region of wave number space. This region can include a nonconvective hot spot where the group velocity of the unstable waves approaches zero. Positive slope in the total distribution function is not a necessary requirement for instability; the broken symmetry along the field can allow the transfer of beam drift energy to electrostatic wave turbulence. Using Gurnett's (1974) polar ionospheric model for a representative auroral field line modeled as dipolar (L = 8), one infers that certain heights favor generation of enhanced, beamdriven electrostatic turbulence. Those regions are in the vicinity of where ω/sub UH//Ω/sub c/ approx. 3/2 with an excursion from this value depending on beam parameters. We speculate that electrostatic turbulence will heat the background electrons to a limiting temperature such that the instability becomes marginally effective. This limiting temperature is estimated for auroral beam-plasma conditions as 1 to 6 eV. Quasi-linear beam moment equations are developed to compute an upper bound to electrostatic wave amplitudes that can be maintained by the beam. We find that energy densities approaching E 2 /8πnT approx. 1 over auroral scale lengths can result in effective energy transfer from the beam to the plasma

  12. Quasilinear simulation of auroral kilometric radiation by a relativistic Fokker-Planck code

    International Nuclear Information System (INIS)

    Matsuda, Y.

    1991-01-01

    An intense terrestrial radiation called the auroral kilometric radiation (AKR) is believed to be generated by cyclotron maser instability. We study a quasilinear evolution of this instability by means of a two-dimensional relativistic Fokker-Planck code which treats waves and distributions self-consistently, including radiation loss and electron source and sink. We compare the distributions and wave amplitude with spacecraft observations to elucidate physical processes involved. 3 refs., 1 fig

  13. On I(5577 Å and I (7620 Å auroral emissions and atomic oxygen densities

    Directory of Open Access Journals (Sweden)

    R. L. Gattinger

    Full Text Available A model of auroral electron deposition processes has been developed using Monte Carlo techniques to simulate electron transport and energy loss. The computed differential electron flux and pitch angle were compared with in situ auroral observations to provide a check on the accuracy of the model. As part of the energy loss process, a tally was kept of electronic excitation and ionization of the important atomic and molecular states. The optical emission rates from these excited states were computed and compared with auroral observations of η(3914 Å, η(5577 Å, η(7620 Å and η(N2VK. In particular, the roles played by energy transfer from N2(A3Σ+u and by other processes in the excitation of O(1S and O2(b1Σ+g were investigated in detail. It is concluded that the N2(A3Σ+u mechanism is dominant for the production of OI(5577 Å in the peak emission region of normal aurora, although the production efficiency is much smaller than the measured laboratory value; above 150 km electron impact on atomic oxygen is dominant. Atomic oxygen densities in the range of 0.75±0.25 MSIS-86 [O] were derived from the optical comparisons for auroral latitudes in mid-winter for various levels of solar and magnetic activity.

  14. Geographic asymmetries of the Viking auroral distribution: Implications for ionospheric coordinate systems

    International Nuclear Information System (INIS)

    Hearn, D.J.; Elphinstone, R.D.; Murphree, J.S.; Cogger, L.L.

    1993-01-01

    Viking images of the auroral distribution have been used to investigate the relevance of various ionospheric coordinate systems. An important aspect of the large-scale auroral shape is its dependence on the asymmetries of the Earth's internal field. Model predictions of where the aurora occurs, using the equatorial plane's volume current density, agree with observations and imply that the internal field plays a more important role that generally believed. Historically, the belief that the internal field has only small effects seems to stem from the widespread use of the corrected geomagnetic and invariant coordinate systems. These systems involve the mapping of field lines and have advantages in statistical studies and comparisons; less sophisticated systems such as the eccentric dipole coordinate system should be used in individual studies and in studies involving differentiation or integration of some observational parameters. Observations of the auraoral distribution are give to illustrate the universal time, tilt angle, and Kp variability in different coordinate systems and demonstrate that the dominant variability of the aurora is due to internal field asymmetries. A new set of coordinate systems are briefly developed as examples of how to incorporate external field models into studies of auraoral images. It is proposed that the one of these coordinate systems can be used as a test of how well an external field model can match observed auroral distributions. 19 refs., 1 tab

  15. Observations of Magnetosphere-Ionosphere Coupling Processes in Jupiter's Downward Auroral Current Region

    Science.gov (United States)

    Clark, G. B.; Mauk, B.; Allegrini, F.; Bagenal, F.; Bolton, S. J.; Bunce, E. J.; Connerney, J. E. P.; Ebert, R. W.; Gershman, D. J.; Gladstone, R.; Haggerty, D. K.; Hospodarsky, G. B.; Kotsiaros, S.; Kollmann, P.; Kurth, W. S.; Levin, S.; McComas, D. J.; Paranicas, C.; Rymer, A. M.; Saur, J.; Szalay, J. R.; Tetrick, S.; Valek, P. W.

    2017-12-01

    Our view and understanding of Jupiter's auroral regions are ever-changing as Juno continues to map out this region with every auroral pass. For example, since last year's Fall AGU and the release of publications regarding the first perijove orbit, the Juno particles and fields teams have found direct evidence of parallel potential drops in addition to the stochastic broad energy distributions associated with the downward current auroral acceleration region. In this region, which appears to exist in an altitude range of 1.5-3 Jovian radii, the potential drops can reach as high as several megavolts. Associated with these potentials are anti-planetward electron angle beams, energetic ion conics and precipitating protons, oxygen and sulfur. Sometimes the potentials within the downward current region are structured such that they look like the inverted-V type distributions typically found in Earth's upward current region. This is true for both the ion and electron energy distributions. Other times, the parallel potentials appear to be intermittent or spatially structured in a way such that they do not look like the canonical diverging electrostatic potential structure. Furthermore, the parallel potentials vary grossly in spatial/temporal scale, peak voltage and associated parallel current density. Here, we present a comprehensive study of these structures in Jupiter's downward current region focusing on energetic particle measurements from Juno-JEDI.

  16. An empirical determination of the production efficiency for auroral 6300 AA emmission by energetic electrons

    International Nuclear Information System (INIS)

    Winningham, J.D.; Bunn, F.E.; Thirkettle, F.W.; Shepherd, G.G.

    1979-06-01

    Auroral data from the Soft Particle Spectrometer and the Red Line Photometer on the ISIS-2 spacecraft have been selected to form an electron energy flux and optical auroral emission data base. The energy fluxes are stored as integrated fluxes over four energy bands, and the corresponding stored optical emission rates are corrected for airglow and for albedo. Because of the variety of electron energy spectra represented in the data base it was possible to perform a regression analysis that yielded the production efficiency for the production of emission for each of the four bands. While the results of this analysis are interesting to compare with theoretical predictions of 6300 AA excitation processes, these statistical results are not as precise as the comparisons of individual experiments where all parameters, such as the atmospheric composition and temperature profiles are measured. The significance of this approach is that it permits a multiparameter description of an electron energy spectrum, and its relationship to a specific optical emission, by purely empirical means. This is particularly useful in the interpretation of ISIS-2 data from the instruments which provided the results, but should find further application in optical-particle auroral studies. (author)

  17. Particle acceleration and wave emissions associated with the formation of auroral cavities and enhancements

    International Nuclear Information System (INIS)

    Winglee, R.M.; Pritchett, P.L.; Dusenbery, P.B.

    1988-01-01

    Observations from DE 1 and electrostatic particle simulations are combined in an effort to provide a unified model for (nightside) auroral particle acceleration and wave emissions and their association with plasma cavities and enhancements. The observations show that enhanced electron precipitation during inverted-V events is associated with broadband electrostatic bursts (BEB), increased upward field-aligned currents, and density enhancements. These regions are flanked by return current regions where the density is depleted (i.e., by plasma cavities). Perpendicular acceleration of ambient plasma ions can occur in both upward and return current regions. It is shown through the simulations that these processes are integrally related and are not independent of each other. The free energy for the auroral particle acceleration can be provided by energetic ion beams in the plasma sheet boundary layer with nonzero perpendicular energy. The perpendicular energy allows charge separation between the beam ions and costreaming electrons to occur. The resultant space charge fields accelerate electrons on the same field lines as the costreaming electrons downward toward the ionosphere, without the beam ions actually propagating down to auroral altitudes. Ambient plasma electrons on adjacent field lines are accelerated upward, forming a return current

  18. Using spectral characteristics to interpret auroral imaging in the 731.9 nm O+ line

    Directory of Open Access Journals (Sweden)

    H. Dahlgren

    2008-07-01

    Full Text Available Simultaneous observations were made of dynamic aurora during substorm activity on 26 January 2006 with three high spatial and temporal resolution instruments: the ASK (Auroral Structure and Kinetics instrument, SIF (Spectrographic Imaging Facility and ESR (EISCAT Svalbard Radar, all located on Svalbard (78° N, 16.2° E. One of the narrow field of view ASK cameras is designed to detect O+ ion emission at 731.9 nm. From the spectrographic data we have been able to determine the amount of contaminating N2 and OH emission detected in the same filter. This is of great importance to further studies using the ASK instrument, when the O+ ion emission will be used to detect flows and afterglows in active aurora. The ratio of O+ to N2 emission is dependent on the energy spectra of electron precipitation, and was found to be related to changes in the morphology of the small-scale aurora. The ESR measured height profiles of electron densities, which allowed estimates to be made of the energy spectrum of the precipitation during the events studied with optical data from ASK and SIF. It was found that the higher energy precipitation corresponded to discrete and dynamic features, including curls, and low energy precipitation corresponded to auroral signatures that were dominated by rays. The evolution of these changes on time scales of seconds is of importance to theories of auroral acceleration mechanisms.

  19. Two-dimensional quasi-neutral description of particles and fields above discrete auroral arcs

    Science.gov (United States)

    Newman, A. L.; Chiu, Y. T.; Cornwall, J. M.

    1986-01-01

    Models are presented for particle distributions, electric fields and currents in an adiabatic treatment of auroral electrostatic potential distributions in order to describe the quiet-time evening auroral arcs featuring both upward and return currents. The models are consistent with current continuity and charge balance requirements for particle populations controlled by adiabatic invariants and quasi-neutrality in the magnetosphere. The effective energy of the cool electron population is demonstrated to have a significant effect on the latitudinal breadth of the auroral electrostatic potential structure and the extent of the penetration of the accelerating potential into the ionosphere. Another finding is that the energy of any parallel potential drop in the lowest few thousand kilometers of the field line is of the same order of magnitude as the thermal energy of the cool electrons. Additional predictions include density cavities along field lines that support large potential drops, and density enhancements along field lines at the edge of an inverted V with a small potential drop.

  20. Anomalous width variation of rarefactive ion acoustic solitary waves in the context of auroral plasmas

    Directory of Open Access Journals (Sweden)

    S. S. Ghosh

    2004-01-01

    Full Text Available The presence of dynamic, large amplitude solitary waves in the auroral regions of space is well known. Since their velocities are of the order of the ion acoustic speed, they may well be considered as being generated from the nonlinear evolution of ion acoustic waves. However, they do not show the expected width-amplitude correlation for K-dV solitons. Recent POLAR observations have actually revealed that the low altitude rarefactive ion acoustic solitary waves are associated with an increase in the width with increasing amplitude. This indicates that a weakly nonlinear theory is not appropriate to describe the solitary structures in the auroral regions. In the present work, a fully nonlinear analysis based on Sagdeev pseudopotential technique has been adopted for both parallel and oblique propagation of rarefactive solitary waves in a two electron temperature multi-ion plasma. The large amplitude solutions have consistently shown an increase in the width with increasing amplitude. The width-amplitude variation profile of obliquely propagating rarefactive solitary waves in a magnetized plasma have been compared with the recent POLAR observations. The width-amplitude variation pattern is found to fit well with the analytical results. It indicates that a fully nonlinear theory of ion acoustic solitary waves may well explain the observed anomalous width variations of large amplitude structures in the auroral region.

  1. Generation of a auroral kilometer radiowaves at a maser cyclotron resonance

    International Nuclear Information System (INIS)

    Vlasov, V.G.

    1991-01-01

    A linear mechanism of auroral kilometer radiowave (AKR) generation at a maser cyclotron resonance (MCR) in non-homogeneous non-monodimensional plasma is developed. Model distribution functions introduced for longitudinal and transverse electron beasms allow one to obtain x- and o-mode increments in the form of elementary functions. The key concept of work consists in MCR time, taking account of the complex of all processes leading to wave outlet from the MCR. It is shown that MCR time can be sufficient for AKR generation only in certain region of auroral plasma. For x-mode these are such plasma sections where the longitudinal geomagnetic field gradient is compensated by plasma density gradient. O-mode is generated only in those local regions where the plasma density longitudinal gradient is very low. The theoretical minimal width of AKR spectrum line obtained coincides with the minimal measured line width equal to 5Hz. A conclusion is made that the discrete AKR spectrum appears to be the reflection of the auroral plasma inhomogeneous structure

  2. Generation of auroral kilometric radio emission at the cyclotron maser resonance

    International Nuclear Information System (INIS)

    Vlasov, V.G.

    1992-01-01

    A linear mechanism of auroral kilometric radiation (AKR) generation at the maser cyclotron resonance (MCR) in an inhomogeneous multidimensional plasma is developed. The model distribution functions introduced by the author for longitudinal and transverse electron beams allow one to obtain x- and O-mode growth rates in the form of elementary functions. The key idea of the study is the MCR time taking into account all processes leading to the emission of waves from the MCR. It is shown that the MCR time can be sufficient for AKR generation in isolated regions of the auroral plasma. For the X-mode these are the parts of the plasma where the longitudinal gradient of the geomagnetic field is compensated by the plasma density gradient. The O-mode is generated only in those local regions where there is an extremely small longitudinal plasma density gradient. The theoretical minimum width of the AKR spectral line obtained coincides with the minimal measured line width of 5 Hz. It is concluded that the discrete AKR spectrum is related to the inhomogeneous structure of the auroral plasma

  3. Boundary layer plasmas as a source for high-latitude, early afternoon, auroral arcs

    International Nuclear Information System (INIS)

    Lundin, R.; Evans, D.S.

    1985-02-01

    Simultaneous measurements of hot boundary layer plasma from PROGNOZ-7 and particle precipitation from the TIROS/NOAA satellite in nearly magnetically conjugate regions have been used to study the dynamo process responsible for the formation of high latitude, early afternoon, auroral arcs. Characteristic for the PROGNOZ-7 observations in the dayside boundary layer at high latitudes is the frequent occurrence of regions with injected magnetosheath plasma embedded in a 'halo' of antisunward flowing magnetosphere plasma. The injected magnetosheath plasma have several features which indicate that it also acts as a local source of EMF in the boundary layer. The process resembles that of a local MHD dynamo driven by the excess drift velocity of the injected magnetosheath plasma relative to the background magnetospheric plasma. The dynamo region is capable of driving fielc-aligned currents that couple to the ionosphere, where the upward current is associated with the high latitude auroral arcs. We demonstrate that the large-scale morphology as well as the detailed data intercomparison between PROGNOZ-7 and TIROS-N both agree well with a local injection of magnetosheath plasma into the dayside boundary layer as the main dynamo process powering the high-latitude, early afternoon auroral arcs. (Author)

  4. Results based on a correlative study of geomagnetic and radio auroral observations

    International Nuclear Information System (INIS)

    Haldoupis, C.

    The results presented here are from a correlative study of ground based magnetometer data from an auroral station, and STARE radar auroral data from a small ionospheric region located exactly above the magnetometer site. The magnetometer data includes both the horizontal X and Y magnetograms and micropulsation components. The STARE data represents time sequencies of both the echo intensity and irregularity drift velocity (or electric field) vector. The observations used in the analysis are from a reasonably disturbed 16-hour period covering the afternoon, midnight and morning sectors of auroral oval. A close relationship was found to exist between the geomagnetic variations and the backscatter amplitude. The results suggest that the conductivity, rather than the electric field, is the prime agent responsible for the long period modulation observed on both the magnetic signatures and the backscatter intensity. In one case, it was found that conductivity modifications cause direct modulation of direction but not the amplitude of the electric field. The rapid ac-fluctuations seen in the electric field most likely play a role in the generation of Pi-pulsations. (Auth.)

  5. Auroral energy input from energetic electrons and Joule heating at Chatanika

    International Nuclear Information System (INIS)

    Wickwar, V.B.; Baron, M.J.; Sears, R.D.

    1975-01-01

    With the incoherent scatter radar at Chatanika, Alaska, a wide variety of measurements can be made related to the ionosphere, magnetosphere, and neutral atmosphere. A significant parameter is the amount of energy transferred from the magnetosphere into the ionosphere and neutral atmosphere during periods of auroral activity. In this report a procedure is examined whereby the incident energy flux of auroral electrons is ascertained from radar measurements. As part of the process radar-determined fluxes are compared with those ascertained from simultaneous photometric observations at 4278 A. The fluxes obtained by both techniques had similar magnitudes and time variations. If it is assumed that the largest uncertainty in the radar/photometer comparison is the effective recombination coefficient, then that coefficient can also be deduced. A value 3times10 -7 cm 3 /s at about 105 km is found, which is in good agreement with other recent determinations during active auroral conditions. This technique is combined with one to ascertain the Joule heating to determine the energy input from the magnetosphere to the ionosphere in a region localized above the radar on March 22, 1973, in the midnight sector. The energy input is continuous at a significant level, i.e., greater than the 3 ergs/cm 2 that could be delivered by the sun, were it overhead. Moreover, at times, each of these inputs became as great as 30 ergs/cm 2 s

  6. Use of wind energy

    Energy Technology Data Exchange (ETDEWEB)

    Vasil' yeva, I G

    1982-01-01

    Programs on the use of wind energy have been adopted in over 12 countries. The WU of low power is manufactured by over 100 firms. One of the main trends for the use of wind energy currently is water pumping. The cost of operating water pumps with diesel and electric drive has increased and they have become not very accessible for a considerable part of the population in the developing countries. There are now about one million wind pump units (WPU) operating in the world, mainly in the United States, Australia and Argentina. The average power of the WPU is less than or equal to 0.5 kW. A trend is developing wind energy associated with the creation of wind heat units for heat supply of houses. When powerful experimental WEU are operating, the problem was revealed of their influence on the environment. The main difficulties are associated with creating WEU of electromagnetic interference, which in particular, influence the quality of television transmissions. This problem was encountered in operating the WEU P = 200 kW in the United States in Rhode Island. Normal operation of the television receivers was guaranteed with the help of cable network. A method was developed from calculating the zone of interferences which should be used in the future in setting up the WEU. A study was made of the noise from the operating of the WEU. The noise level of the WEU is in limits of permissible, however in direct proximity to the unit, intensive infrasonic fluctuations develop. The most important ecological consequence of building powerful WEU could be the death of nocturnal birds as a result of their colliding with the rotating blades. It is noted that this can be avoided by lighting the WEU.

  7. A joint probability density function of wind speed and direction for wind energy analysis

    International Nuclear Information System (INIS)

    Carta, Jose A.; Ramirez, Penelope; Bueno, Celia

    2008-01-01

    A very flexible joint probability density function of wind speed and direction is presented in this paper for use in wind energy analysis. A method that enables angular-linear distributions to be obtained with specified marginal distributions has been used for this purpose. For the marginal distribution of wind speed we use a singly truncated from below Normal-Weibull mixture distribution. The marginal distribution of wind direction comprises a finite mixture of von Mises distributions. The proposed model is applied in this paper to wind direction and wind speed hourly data recorded at several weather stations located in the Canary Islands (Spain). The suitability of the distributions is judged from the coefficient of determination R 2 . The conclusions reached are that the joint distribution proposed in this paper: (a) can represent unimodal, bimodal and bitangential wind speed frequency distributions, (b) takes into account the frequency of null winds, (c) represents the wind direction regimes in zones with several modes or prevailing wind directions, (d) takes into account the correlation between wind speeds and its directions. It can therefore be used in several tasks involved in the evaluation process of the wind resources available at a potential site. We also conclude that, in the case of the Canary Islands, the proposed model provides better fits in all the cases analysed than those obtained with the models used in the specialised literature on wind energy

  8. Profiles of Wind and Turbulence in the Coastal Atmospheric Boundary Layer of Lake Erie

    KAUST Repository

    Wang, H; Barthelmie, R J; Crippa, P; Doubrawa, P; Pryor, S C

    2014-01-01

    Prediction of wind resource in coastal zones is difficult due to the complexity of flow in the coastal atmospheric boundary layer (CABL). A three week campaign was conducted over Lake Erie in May 2013 to investigate wind characteristics and improve

  9. Wind Speed Pattern in Nigeria (A Case Study of Some Coastal and ...

    African Journals Online (AJOL)

    ADOWIE PERE

    Department of Physics and Solar Energy, Bowen University Iwo, Osun State, Nigeria ... ABSTRACT: In this study, wind speeds were analysed using the daily wind data obtained from Nigeria ..... Selected sites from Three Geopolitical Zones in.

  10. Manual to application of wind energy

    International Nuclear Information System (INIS)

    Pinilla, S. A.

    1995-01-01

    The National Government of Colombia assigned to INEA (Institute of Nuclear Sciences and Alternative Energies), the paper of promotion, diffusion and utilization of sources of energy not - conventional, the one which includes the wind energy. These studies were accomplished mainly in winding zones as the Department La Guajira, area of the Eastern Plains and some sites of mountain chains of the Andes. Internationally, renewable energies utilization is widely used and is included as an important factor in the energetic strategic planning in some countries, where this renewable energy becomes more than 20% to total energy supply. An introduction to the wind energy in some aspects as: the wind resource, global traffic standards of the wind, calculation of the potential of the wind and methods for the calculation of speed measure of the wind are presented. The methodologies for the evaluation of the wind as an energy source, the wind energy technologies, the equipment to wind energy utilization and the implementation of small systems of energy conversion of wind are described

  11. Measurements of auroral particles by means of sounding rockets of mother-daughter type

    International Nuclear Information System (INIS)

    Falck, A.

    1985-11-01

    The scientific objective of the S17 payloads was to study the ionosphere during auroral situations and especially with regards to the local fine structure and a possible separation of spatial and temporal variations of auroral phenomena. The intensities of 8 keV and 2 keV electrons have been measured from one sounding rocket launched into a breakup aurora of moderate activity and from another rocket launched into a very active substorm situation. Both the rockets were of mother-daughter type i.e. had two separated payloads. The general features in the data of different particle energies were very similar over the whole flight time of the rockets. Special events and gradients and well identifiable shapes in the particle intensities were studied to see if the intensity fluctuations obtained from two detectors in one payload or from detectors into separate payloads were time delayed. Such time delays in the particle flux intensities were obvious in both of the rocket measurements and most of these time shifts could be understood as caused by spatial variations in the particle precipitation. In parts of the rocket flights the particle intensity variations were true temporal changes. The time lags between 8 keV and 2 keV electron intensities detected in the same payload, which could be observed and were obtained by crosscorrelation analyses, were in the range less than 0.3 s and most of them less than 0.1 s. If the time differences are assumed to be caused by the velocity dispersion of the particles, the particle data reported here placed the modulation source at a distance of less than 10 000 km from the rocket position. Measurements at the S17-1 mother payload of the electric field have been compared with data of precipitating electrons and low-light-level-TV-recording of the auroral situation. An inverted-V precipitation event was observed and was associated with auroral arcs and with reversals of the measured electric field components implicating the possibility of

  12. Swarm-Aurora: A web-based tool for quickly identifying multi-instrument auroral events

    Science.gov (United States)

    Chaddock, D.; Donovan, E.; Spanswick, E.; Knudsen, D. J.; Frey, H. U.; Kauristie, K.; Partamies, N.; Jackel, B. J.; Gillies, M.; Holmdahl Olsen, P. E.

    2016-12-01

    In recent years there has been a dramatic increase in ground-based auroral imaging systems. These include the continent-wide THEMIS-ASI network, and imagers operated by other programs including GO-Canada, MIRACLE, AGO, OMTI, and more. In the near future, a new Canadian program called TREx will see the deployment of new narrow-band ASIs that will provide multi-wavelength imaging across Western Canada. At the same time, there is an unprecedented fleet of international spacecraft probing geospace at low and high altitudes. We are now in the position to simultaneously observe the magnetospheric drivers of aurora, observe in situ the waves, currents, and particles associated with MI coupling, and the conjugate aurora. Whereas a decade ago, a single magnetic conjunction between one ASI and a low altitude satellite was a relatively rare event, we now have a plethora of triple conjunctions between imagers, low-altitude spacecraft, and near-equatorial magnetospheric probes. But with these riches comes a new level of complexity. It is often difficult to identify the many useful conjunctions for a specific line of inquiry from the multitude of conjunctions where the geospace conditions are often not relevant and/or the imaging is compromised by clouds, moon, or other factors. Swarm-Aurora was designed to facilitate and drive the use of Swarm in situ measurements in auroral science. The project seeks to build a bridge between the Swarm science community, Swarm data, and the complimentary auroral data and community. Swarm-Aurora (http://swarm-aurora.phys.ucalgary.ca) incorporates a web-based tool which provides access to quick-look summary data for a large array of instruments, with Swarm in situ and ground-based ASI data as the primary focus. This web interface allows researchers to quickly and efficiently browse Swarm and ASI data to identify auroral events of interest to them. This allows researchers to be able to easily and quickly identify Swarm overflights of ASIs that

  13. General method for calculating polarization electric fields produced by auroral Cowling mechanism and application examples

    Science.gov (United States)

    Vanhamäki, Heikki; Amm, Olaf; Fujii, Ryo; Yoshikawa, Aki; Ieda, Aki

    2013-04-01

    The Cowling mechanism is characterized by the generation of polarization space charges in the ionosphere in consequence of a partial or total blockage of FAC flowing between the ionosphere and the magnetosphere. Thus a secondary polarization electric field builds up in the ionosphere, which guarantees that the whole (primary + secondary) ionospheric current system is again in balance with the FAC. In the Earth's ionosphere the Cowling mechanism is long known to operate in the equatorial electrojet, and several studies indicate that it is important also in auroral current systems. We present a general method for calculate the secondary polarization electric field, when the ionospheric conductances, the primary (modeled) or the total (measured) electric field, and the Cowling efficiency are given. Here the Cowling efficiency is defined as the fraction of the divergent Hall current canceled by secondary Pedersen current. In contrast to previous studies, our approach is a general solution which is not limited to specific geometrical setups (like an auroral arc), and all parameters may have any kind of spatial dependence. The solution technique is based on spherical elementary current (vector) systems (SECS). This way, we avoid the need to specify explicit boundary conditions for the searched polarization electric field or its potential, which would be required if the problem was solved in a differential equation approach. Instead, we solve an algebraic matrix equation, for which the implicit boundary condition that the divergence of the polarization electric field vanishes outside our analysis area is sufficient. In order to illustrate the effect of Cowling mechanism on ionospheric current systems, we apply our method to two simple models of auroral electrodynamic situations: 1) a mesoscale strong conductance enhancement in the early morning sector within a relatively weak southward primary electric field, 2) a morning sector auroral arc with only a weak conductance

  14. The first full-resolution measurements of Auroral Medium Frequency Burst Emissions

    Science.gov (United States)

    Bunch, N. L.; Labelle, J.; Weatherwax, A.; Hughes, J.

    2008-12-01

    Auroral MF burst is a naturally occurring auroral radio emission which appears unstructured on resolution of previous measurements, is observed in the frequency range of 0.8-4.5 MHz, and has typical amplitudes of around 10-14 V2/m2Hz, and durations of a few minutes. The emission occurs at substorm onset. Since Sept 2006, Dartmouth has operated a broadband (0-5 MHz) interferometer at Toolik Lake, Alaska (68° 38' N, 149° 36' W, 68.51 deg. magnetic latitude), designed for the study of auroral MF burst emissions. Normal operation involves taking snapshots of waveforms from four spaced antennas from which wave spectral and directional information is obtained. However, the experiment can also be run in "continuous mode" whereby the signal from a selected antenna is sampled continuously at 10 M samples/second. A "continuous mode" campaign was run 0800-1200 UT (~2200-0200 MLT) daily from March 21 to April 19, 2008. During this campaign more than twenty auroral MF burst emissions were observed, including three extraordinarily intense examples lasting approximately two minutes each. These observations represent the highest time and frequency resolution data ever collected of MF burst emissions. These data allow us to better characterize the null near twice the electron gyrofrequency identified in previous experiments, since examples of this feature observed during this campaign display a strong null ~50 kHz in bandwidth, with sharp boundaries and occasionally coincident with 2 fce auroral roar. These data also allow us to search for frequency-time structures embedded in MF-burst. One prominent feature appears to be a strong single frequency emission which broadens down to lower frequencies over time, spreading to approximately 500 kHz in bandwidth over ~10 ms. Among other features observed are a diffuse and unstructured emission, as well as what could potentially be several separate emission sources, with multiple emissions occurring simultaneously, appearing as weaker

  15. Conversion from HST ACS and STIS auroral counts into brightness, precipitated power and radiated power for H2 giant planets

    Science.gov (United States)

    Gustin, J.; Bonfond, B.; Grodent, D.; Gerard, J. C.

    2012-09-01

    The STIS and ACS instruments onboard HST are widely used to study the giant planet's aurora. Several assumptions have to be made to convert the instrumental counts into meaningful physical values (type and bandwidth of the filters, definition of the physical units, etc…), but these may significantly differ from one author to another, which makes it difficult to compare the auroral characteristics published in different studies. We present a method to convert the counts obtained in representative ACS and STIS imaging modes / filters used by the auroral scientific community to brightness, precipitated power and radiated power in the ultraviolet (700- 1800 Å). Since hydrocarbon absorption may considerably affect the observed auroral emission, the conversion factors are determined for several attenuation levels. Several properties of the auroral emission have been determined: the fraction of the H2 emission shortward and longward of the HLy-a line is 50.3 % and 49.7 % respectively, the contribution of HLy-a to the total unabsorbed auroral signal has been set to 9.1 % and an input of 1 mW m-2 produces 10 kR of H2 in the Lyman and Werner bands. A first application sets the order of magnitude of Saturn's auroral characteristics in the total UV bandwidth to a brightness of 10 kR and an emitted power of ~2.8 GW. A second application uses published brighnesses of Europa's footprint to determine the current density associated with the Europa auroral spot: 0.21 and 0.045 μA m-2 assuming no hydrocarbon absorption and a color ratio of 2, respectively.

  16. Sound Zones

    DEFF Research Database (Denmark)

    Møller, Martin Bo; Olsen, Martin

    2017-01-01

    Sound zones, i.e. spatially confined regions of individual audio content, can be created by appropriate filtering of the desired audio signals reproduced by an array of loudspeakers. The challenge of designing filters for sound zones is twofold: First, the filtered responses should generate...... an acoustic separation between the control regions. Secondly, the pre- and post-ringing as well as spectral deterioration introduced by the filters should be minimized. The tradeoff between acoustic separation and filter ringing is the focus of this paper. A weighted L2-norm penalty is introduced in the sound...

  17. 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.

  18. 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.

  19. A case study of HF radar spectra and 630.0 nm auroral emission in the pre-midnight sector

    Directory of Open Access Journals (Sweden)

    M. Lester

    2001-03-01

    Full Text Available A comparison of HF radar backscatter observed by the CUTLASS Finland radar, meridian scanning photometer data from Longyearbyen, magnetic field variations from IMAGE stations, and particle precipitation measured by the DMSP F12 spacecraft is presented. The interval under discussion occurred in the pre-midnight local time sector, during a period of weakly northward interplanetary magnetic field. A region of HF backscatter, typically 8 degrees wide, occurred in the field of view of the CUTLASS Finland radar. A well defined gradient in the spectral width parameter was present, with mainly low (< 200 m s - 1 spectral widths in the lower latitude part of the scatter and predominantly large (> 200 ms - 1 spectral widths in the higher latitude part. The relationship between the spectral width and the red line (630.0 nm emission measured by the meridian scanning photometer is considered. The poleward border of the red line emission, which has, in the past, been proposed as being representative of the polar cap boundary, was co-located to within 1° of magnetic latitude with the gradient in spectral width for part of the interval. Statistically, large spectral widths occurred poleward of the red line emission, while small spectral widths occurred within or equatorward of the red line emission. Near simultaneous DMSP particle observations in the 20 eV to 20 keV range indicate that the poleward border of the red line emission and the gradient in spectral width occurred at the same latitude as the transition from auroral oval to polar rain particle energies. We conclude that the large spectral widths were not caused by particle precipitation associated with the auroral oval. There were two periods of special interest when the relationship between the red line and the spectral width broke down. The first of these happened during enhanced red line and green line (557.7 nm emission, with a drop out of the radar scatter and an enhanced, narrow westward

  20. 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...

  1. Relation between Statistics of Radiowave Reception at South Pole Station and Auroral Oval Characteristics: Data and Monte Carlo Simulations

    Science.gov (United States)

    Labelle, J.; Noonan, K.

    2006-12-01

    Despite their remote location, radio receivers at South Pole Station regularly detect AM broadcast band signals propagating from transmitters thousands of kilometers away. Statistical analysis of received radiowave power at South Pole during 2004 and 2005, integrated over the frequency range of AM broadcast stations, reveals a distinctive time-of-day (UT) dependence: a broad maximum in received power centered at 1500 UT corresponds to magnetic daytime; signal levels are lower during magnetic nighttime except for a calculated based on two contributions: daytime D-region absorption and auroral absorption. The latter varies with day of year and magnetic local time in a complex fashion due to the asymmetric shape and varying size of the auroral oval and the offset of South Pole from the geomagnetic pole. The Monte Carlo simulations confirm that the enhanced absorption of AM broadcast signals during magnetic nighttime results from auroral absorption. Furthermore, the simulations predict that a weak (<0.5 dB) peak near magnetic midnight, similar to that observed in the data, arises from including in the statistical data base intervals when the auroral oval is contracted. These results suggest that ground based radio observations at a sufficiently remote high-latitude site such as South Pole may effectively monitor auroral oval characteristics on a statistical basis at least.

  2. 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.

  3. The role of natural E-region plasma turbulence in the enhanced absorption of HF radio waves in the auroral ionosphere:Implications for RF heating of the auroral electrojet

    Directory of Open Access Journals (Sweden)

    T. R. Robinson

    1994-03-01

    Full Text Available Physical processes which affect the absorption of radio waves passing through the auroral E-region when Farley-Buneman irregularities are present are examined. In particular, the question of whether or not it is legitimate to include the anomalous wave-enhanced collision frequency, which has been used successfully to account for the heating effects of Farley-Buneman waves in the auroral E-region, in the usual expression for the radio-wave absorption coefficient is addressed. Effects also considered are those due to wave coupling between electromagnetic waves and high-frequency electrostatic waves in the presence of Farley-Buneman irregularities. The implications for radio-wave heating of the auroral electrojet of these processes are also discussed. In particular, a new theoretical model for calculating the effects of high-power radio-wave heating on the electron temperature in an electrojet containing Farley-Buneman turbulence is presented.

  4. The role of natural E-region plasma turbulence in the enhanced absorption of HF radio waves in the auroral ionosphere:Implications for RF heating of the auroral electrojet

    Directory of Open Access Journals (Sweden)

    T. R. Robinson

    Full Text Available Physical processes which affect the absorption of radio waves passing through the auroral E-region when Farley-Buneman irregularities are present are examined. In particular, the question of whether or not it is legitimate to include the anomalous wave-enhanced collision frequency, which has been used successfully to account for the heating effects of Farley-Buneman waves in the auroral E-region, in the usual expression for the radio-wave absorption coefficient is addressed. Effects also considered are those due to wave coupling between electromagnetic waves and high-frequency electrostatic waves in the presence of Farley-Buneman irregularities. The implications for radio-wave heating of the auroral electrojet of these processes are also discussed. In particular, a new theoretical model for calculating the effects of high-power radio-wave heating on the electron temperature in an electrojet containing Farley-Buneman turbulence is presented.

  5. 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

  6. 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.)

  7. 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.

  8. 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.

  9. Coastal zone

    International Nuclear Information System (INIS)

    2002-01-01

    The report entitled Climate Change Impacts and Adaptation : A Canadian Perspective, presents a summary of research regarding the impacts of climate change on key sectors over the past five years as it relates to Canada. This chapter on the coastal zone focuses on the impact of climate change on Canada's marine and Great Lakes coasts with tips on how to deal with the impacts associated with climate change in sensitive environments. This report is aimed at the sectors that will be most affected by adaptation decisions in the coastal zone, including fisheries, tourism, transportation and water resources. The impact of climate change in the coastal zone may include changes in water levels, wave patterns, storm surges, and thickness of seasonal ice cover. The Intergovernmental Panel on Climate Change projects global average sea level will rise between 9 and 88 centimetres between 1990 to 2100, but not all areas of Canada will experience the same rate of future sea level change. The main physical impact would be shoreline change that could result in a range of biophysical and socio-economic impacts, some beneficial, some negative. The report focuses on issues related to infrastructure and communities in coastal regions. It is noted that appropriate human adaptation will play a vital role in reducing the extent of potential impacts by decreasing the vulnerability of average zone to climate change. The 3 main trends in coastal adaptation include: (1) increase in soft protection, retreat and accommodation, (2) reliance on technology such as geographic information systems to manage information, and (3) awareness of the need for coastal adaptation that is appropriate for local conditions. 61 refs., 7 figs

  10. Observations of intense velocity shear and associated electrostatic waves near an auroral arc

    International Nuclear Information System (INIS)

    Kelley, M.C.; Carlson, C.W.

    1977-01-01

    An intense shear in plasma flow velocity of magnitude 20 (m/s)m -1 has been detected at the edge of an auroral arc. The region of shear appears to display structure with two characteristic scale sizes. The larger structures were of the order of a few kilometers in size and were identified by a deviation of the direction of the charge sheets crossed by the rocket from a direction parallel to the visible arc. As is shown in the companion paper (Carlson and Kelley, 1977), the average (undisturbed) charge sheet was parallel to the arc. These observations are consistent with television studies which often display such structures propagating along the edges of auroral forms. Additional intense irregularities were detected with characteristic wavelengths smaller than the scale size of the shear. The irregularities are discussed in light of the branches of a velocity shear driven instability suggested by several workers: the Kelvin-Helmholtz instability operating at the longest wavelengths and the drift shear instability at the shorter. Neither mode has wavelengths as short as those observed however. A velocity shear mechanism operating at wavelengths short in comparison with the shear scale length, such as those observed here, would be of significant geophysical importance. For example, it could be responsible for production of high-latitude irregularities which exist throughout the polar cap and for the short-wavelength waves responsible for intense 3-m backscatter during equatorial spread F conditions. Since the wavelengths produced by the short-wavelength mode are in the range of typical auroral E region radars, such data must be carefully checked for F region contamination

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

    International Nuclear Information System (INIS)

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

    1984-01-01

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

  12. General solution for calculating polarization electric fields in the auroral ionosphere and application examples

    Science.gov (United States)

    Amm, O.; Fujii, R.; VanhamäKi, H.; Yoshikawa, A.; Ieda, A.

    2013-05-01

    We devise an approach to calculate the polarization electric field in the ionosphere, when the ionospheric conductances, the primary (modeled) or the total (measured) electric field, and the Cowling efficiency are given. In contrast to previous studies, our approach is a general solution which is not limited to specific geometrical setups, and all parameters may have any kind of spatial dependence. The solution technique is based on spherical elementary current (vector) systems (SECS). This way, we avoid the need to specify explicit boundary conditions for the searched polarization electric field of its potential which would be required if the problem was solved in a differential equation approach. Instead, we solve an algebraic matrix equation, and the implicit boundary condition that the divergence of the polarization electric field vanishes outside our analysis area is sufficient. In order to illustrate our theory, we then apply it to two simple models of auroral electrodynamic situations, the first being a mesoscale strong conductance enhancement in the early morning sector within a relatively weak southward primary electric field, and a morning sector auroral arc with only a weak conductance enhancement, but a large southward primary electric field at the poleward flank of the arc. While the significance of the polarization electric field for maximum Cowling efficiency is large for the first case, it is rather minor for the second one. Both models show that the polarization electric field effect may not only change the magnitude of the current systems but also their overall geometry. Furthermore, the polarization electric field may extend into regions where the primary electric field is small, thus even dominating the total electric field in these regions. For the first model case, the total Joule heating integrated over the analysis area decreases by a factor of about 4 for maximum Cowling efficiency as compared to the case of vanishing Cowling efficiency

  13. Multiple current sheets in a double auroral oval observed from the MAGION-2 and MAGION-3 satellites

    Directory of Open Access Journals (Sweden)

    M. Echim

    1997-04-01

    Full Text Available A case is described of multiple current sheets crossed by the MAGION-2 satellite in the near-midnight quieting auroral oval. The data were obtained by the magnetometer experiment onboard. Results show during a quieting period after a preceding substorm, or during an early growth phase of the next substorm, two double-sheet current bands, POLB and EQUB, located at respectively the polar and equatorial borders of the auroral oval separated by about 500 km in latitude. This is consistent with the double-oval structure during recovery introduced by Elphinstone et al. (1995. Within the POLB, the magnetic field data show simultaneous existence of several narrow parallel bipolar current sheets within the upward current branch (at 69.5–70.3° invariant latitude with an adjacent downward current branch at its polar side at (70.5–71.3°. The EQUB was similarly stratified and located at 61.2–63.5° invariant latitude. The narrow current sheets were separated on average by about 35 km and 15 km, respectively, within the POLB and EQUB. A similar case of double-oval current bands with small-scale structuring of their upward current branches during a quieting period is found in the data from the MAGION-3 satellite. These observations contribute to the double-oval structure of the late recovery phase, and add a small-scale structuring of the upward currents producing the auroral arcs in the double- oval pattern, at least for the cases presented here. Other observations of multiple auroral current sheets and theories of auroral arc multiplicity are briefly discussed. It is suggested that multiple X-lines in the distant tail, and/or leakage of energetic particles and FA currents from a series of plasmoids formed during preceding magnetic activity, could be one cause of highly stratified upward FA currents at the polar edge of the quieting double auroral oval.

  14. 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...

  15. Recent Advances in Observations of Ground-level Auroral Kilometric Radiation

    Science.gov (United States)

    Labelle, J. W.; Ritter, J.; Pasternak, S.; Anderson, R. R.; Kojima, H.; Frey, H. U.

    2011-12-01

    Recently LaBelle and Anderson [2011] reported the first definitive observations of AKR at ground level, confirmed through simultaneous measurements on the Geotail spacecraft and at South Pole Station, Antarctica. The initial observations consisted of three examples recorded in 2004. An Antarctic observing site is critical for observing ground level AKR which is obscured by man-made broadcast signals at northern hemisphere locations. Examination of 2008 austral winter radio data from Antarctic Automatic Geophysical Observatories (AGOs) of the Polar Experiment Network for Geospace Upper-atmosphere Investigations (PENGUIn) network and South Pole Station reveals 37 ground level AKR events on 23 different days, 30 of which are confirmed by correlation with AKR observed with the Geotail spacecraft. The location of the Geotail spacecraft appears to be a significant factor enabling coincident measurements. Six of the AKR events are detected at two or three ground-level observatories separated by approximately 500 km, suggesting that the events illuminate an area comparable to a 500-km diameter. For 14 events on ten nights, photometer and all-sky imager data from South Pole and AGOs were examined; in ten cases, locations of auroral arcs could be determined at the times of the events. In eight of those cases, the AKR was detected at observatories poleward of the auroral arcs, and in the other two cases the aurora was approximately overhead at the observatory where AKR was detected. These observations suggest that the AKR signals may be ducted to ground level along magnetic field lines rather than propagating directly from the AKR source region of approximately 5000 km altitude. Correlations between structures in the AKR and intensifications of auroral arcs are occasionally observed but are rare. The ground-level AKR events have a local time distribution similar to that of AKR observed from satellites, peaking in the pre-midnight to midnight sector. This data base of >30

  16. Effects of magnetic storm phases on F layer irregularities below the auroral oval

    International Nuclear Information System (INIS)

    Aarons, J.; Gurgiolo, C.; Rodger, A.S.

    1988-01-01

    Observations of F-layer irregularity development and intensity were obtained between September and October 1981, primarily over subauroral latitudes in the area of the plasmapause. The results reveal the descent of the auroral irregularity region to include subauroral latitudes in the general area of the plasmapause during the main phases of a series of magnetic storms. Irregularities were found primarily at lower latitudes during the subauroral or plasmapause storm. A model for the subauroral irregularities in recovery phases of magnetic storms is proposed in which energy stored in the ring current is slowly released. 27 references

  17. The first year of observations of Jupiter's magnetosphere from Juno's Jovian Auroral Distributions Experiment (JADE)

    Science.gov (United States)

    Valek, P. W.; Allegrini, F.; Angold, N. G.; Bagenal, F.; Bolton, S. J.; Chae, K.; Connerney, J. E. P.; Ebert, R. W.; Gladstone, R.; Kim, T. K. H.; Kurth, W. S.; Levin, S.; Louarn, P.; Loeffler, C. E.; Mauk, B.; McComas, D. J.; Pollock, C. J.; Reno, M. L.; Szalay, J. R.; Thomsen, M. F.; Weidner, S.; Wilson, R. J.

    2017-12-01

    Juno observations of the Jovian plasma environment are made by the Jovian Auroral Distributions Experiment (JADE) which consists of two nearly identical electron sensors - JADE-E - and an ion sensor - JADE-I. JADE-E measures the electron distribution in the range of 100 eV to 100 keV and uses electrostatic deflection to measure the full pitch angle distribution. JADE-I measures the composition separated energy per charge in the range of 10 eV / q to 46 keV / q. The large orbit - apojove 110 Rj, perijove 1.05 Rj - allows JADE to periodically cross through the magnetopause into the magnetosheath, transverse the outer, middle, and inner magnetosphere, and measures the plasma population down to the ionosphere. We present here in situ plasma observations of the Jovian magnetosphere and topside ionosphere made by the JADE instrument during the first year in orbit. Dawn-side crossings of the plasmapause have shown a general dearth of heavy ions except during some intervals at lower magnetic latitudes. Plasma disk crossings in the middle and inner magnetosphere show a mixture of heavy and light ions. During perijove crossings at high latitudes when Juno was connected to the Io torus, JADE-I observed heavy ions with energies consistent with a corotating pickup population. In the auroral regions the core of the electron energy distribution is generally from about 100 eV when on field lines that are connected to the inner plasmasheet, several keVs when connected to the outer plasmasheet, and tens of keVs when Juno is over the polar regions. JADE has observed upward electron beams and upward loss cones, both in the north and south auroral regions, and downward electron beams in the south. Some of the beams are of short duration ( 1 s) implying that the magnetosphere has a very fine spatial and/or temporal structure within the auroral regions. Joint observations with the Waves instrument have demonstrated that the observed loss cone distributions provide sufficient growth rates

  18. Current carrying properties of double layers and low frequency auroral fluctuations

    International Nuclear Information System (INIS)

    Singh, N.; Schunk, R.W.

    1982-01-01

    Numerical simulations showed recurring interruption and recovery of electron and ion currents through double layers. The time period tau of the recurring phenomena is governed by the ion dynamics; for ions with a drift V/sub i/ entering the simulation plasma such that V/sub i/ V/sub ti/ ion-acoustic modes also appear in the electron- and ion-current fluctuations. The electron current fluctuations are governed by the ion current through the Langmuir criterion. It is suggested that some low frequency auroral fluctuations could possibly be explained by current fluctuations through double layers

  19. Auroral vortex street formed by the magnetosphere–ionosphere coupling instability

    Directory of Open Access Journals (Sweden)

    Y. Hiraki

    2015-02-01

    Full Text Available By performing three-dimensional magnetohydrodynamic simulations including Alfvén eigenmode perturbations most unstable to the ionospheric feedback effects, we examined the auroral vortex street that often appears just before substorm onset. We found that an initially placed arc splits, intensifies, and rapidly deforms into a vortex street. We also found that there is a critical convection electric field for growth of the Alfvén eigenmodes. The vortex street is shown to be a consequence of coupling between the magnetospheric Alfvén waves carrying field-aligned currents and the ionospheric density waves driven by Pedersen/Hall currents.

  20. Auroral vortex street formed by the magnetosphere-ionosphere coupling instability

    Science.gov (United States)

    Hiraki, Y.

    2015-02-01

    By performing three-dimensional magnetohydrodynamic simulations including Alfvén eigenmode perturbations most unstable to the ionospheric feedback effects, we examined the auroral vortex street that often appears just before substorm onset. We found that an initially placed arc splits, intensifies, and rapidly deforms into a vortex street. We also found that there is a critical convection electric field for growth of the Alfvén eigenmodes. The vortex street is shown to be a consequence of coupling between the magnetospheric Alfvén waves carrying field-aligned currents and the ionospheric density waves driven by Pedersen/Hall currents.

  1. Ordinary mode auroral kilometric radiation fine structure observed by DE 1

    International Nuclear Information System (INIS)

    Benson, R.F.; Mellott, M.M.; Huff, R.L.; Gurnett, D.A.

    1988-01-01

    The fine structure observed with intense right-hand extraordinary (R-X) mode auroral kilometric radiation (AKR) has received major theoretical attention. Data from the Dynamics Explorer 1 plasma wave instrument indicate that left-hand ordinary (L-O) mode AKR posses similar fine structure. Several theories have been proposed to explain the fine structure of the R-X mode AKR. In order to account for the L-O mode fine structure, these theories will have to be modified to produce the L-O mode directly or will have to rely on mode conversion processes from the R-X to the L-O mode

  2. Interacting Winds in Eclipsing Symbiotic Systems – The Case Study ...

    Indian Academy of Sciences (India)

    produced by the collision of two stellar winds (Vogel 1991, 1993; Girard & Willson ... Therefore, in the nebular environment an energetic zone .... 1b and 1d). .... By applying Kepler's second law, we obtain the time required to cover the corre-.

  3. Seasonal and diurnal dependence of Pc 3-5 magnetic pulsation power at geomagnetically conjugate stations in the auroral zones

    International Nuclear Information System (INIS)

    Saito, Hiroaki; Sato, Natsuo; Tonegawa, Yutaka; Yoshino, Takeo; Saemundsson, T.

    1989-01-01

    Seasonal and diurnal variations of Pc 3-5 magnetic pulsation powers have been examined using 2 years of magnetic data from geomagnetically conjugate stations, Syowa in Antarctica and Husafell and Tjoernes in Iceland. The magnetic pulsation powers are found to be relatively higher at the winter hemisphere station than at the summer station. The pulsations observed during equinox show a diurnal dependence, i.e., that the power density is higher in the geomagnetic morning at the stations in Iceland than at Syowa, and this relationship is reversed in the afternoon. The power density ratio of Pc 3 pulsations between the conjugate stations, which is associated with the seasons and with local time, is higher than that of Pc 5. These characteristics can be attributed to the effects of sunlight in the ionosphere, i.e., Pc 3-5 pulsations are shielded when the waves propagate from the magnetosphere to the ground through the sunlit ionosphere

  4. 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

  5. Latitude dependence of long-term geomagnetic activity and its solar wind drivers

    Energy Technology Data Exchange (ETDEWEB)

    Myllys, M. [Helsinki Univ. (Finland). Dept. of Physics; Partamies, N. [Finnish Meteorological Institute, Helsinki (Finland); University Centre in Svalbard, Longyearbyen (Norway). Dept. of Arctic Geophysics; Juusola, L. [Finnish Meteorological Institute, Helsinki (Finland)

    2015-09-01

    To validate the usage of global indices in studies of geomagnetic activity, we have examined the latitude dependence of geomagnetic variations in Fennoscandia and Svalbard from 1994 to 2010. Daily standard deviation (SD) values of the horizontal magnetic field have been used as a measure of the ground magnetic disturbance level.We found that the timing of the geomagnetic minimum depends on the latitude region: corresponding to the minimum of sunspot cycle 22 (in 1996), the geomagnetic minimum occurred between the geomagnetic latitudes 57-61 in 1996 and at the latitudes 64-67 in 1997, which are the average auroral oval latitudes. During sunspot cycle 23, all latitude regions experienced the minimum in 2009, a year after the sunspot minimum. These timing differences are due to the latitude dependence of the 10 s daily SD on the different solar wind drivers. In the latitude region of 64-67 , the impact of the high-speed solar wind streams (HSSs) on the geomagnetic activity is the most pronounced compared to the other latitude groups, while in the latitude region of 57-61 , the importance of the coronal mass ejections (CMEs) dominates. The geomagnetic activity maxima during ascending solar cycle phases are typically caused by CME activity and occur especially in the oval and sub-auroral regions. The strongest geomagnetic activity occurs during the descending solar cycle phases due to a mixture of CME and HSS activity. Closer to the solar minimum, less severe geomagnetic activity is driven by HSSs and mainly visible in the poleward part of the auroral region. According to our study, however, the timing of the geomagnetic activity minima (and maxima) in different latitude bands is different, due to the relative importance of different solar wind drivers at different latitudes.

  6. Latitude dependence of long-term geomagnetic activity and its solar wind drivers

    International Nuclear Information System (INIS)

    Myllys, M.

    2015-01-01

    To validate the usage of global indices in studies of geomagnetic activity, we have examined the latitude dependence of geomagnetic variations in Fennoscandia and Svalbard from 1994 to 2010. Daily standard deviation (SD) values of the horizontal magnetic field have been used as a measure of the ground magnetic disturbance level.We found that the timing of the geomagnetic minimum depends on the latitude region: corresponding to the minimum of sunspot cycle 22 (in 1996), the geomagnetic minimum occurred between the geomagnetic latitudes 57-61 in 1996 and at the latitudes 64-67 in 1997, which are the average auroral oval latitudes. During sunspot cycle 23, all latitude regions experienced the minimum in 2009, a year after the sunspot minimum. These timing differences are due to the latitude dependence of the 10 s daily SD on the different solar wind drivers. In the latitude region of 64-67 , the impact of the high-speed solar wind streams (HSSs) on the geomagnetic activity is the most pronounced compared to the other latitude groups, while in the latitude region of 57-61 , the importance of the coronal mass ejections (CMEs) dominates. The geomagnetic activity maxima during ascending solar cycle phases are typically caused by CME activity and occur especially in the oval and sub-auroral regions. The strongest geomagnetic activity occurs during the descending solar cycle phases due to a mixture of CME and HSS activity. Closer to the solar minimum, less severe geomagnetic activity is driven by HSSs and mainly visible in the poleward part of the auroral region. According to our study, however, the timing of the geomagnetic activity minima (and maxima) in different latitude bands is different, due to the relative importance of different solar wind drivers at different latitudes.

  7. 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)

  8. M-I coupling across the auroral oval at dusk and midnight. Repetitive substorm activity driven by interplanetary coronal mass ejections (CMEs)

    Energy Technology Data Exchange (ETDEWEB)

    Sandholt, P.E. [Oslo Univ. (Norway). Dept. of Physics; Farrugia, C.J. [New Hampshire Univ., Durham (United Kingdom). Space Science Center; Denig, W.F. [NOAA, Boulder, CO (United States)

    2014-07-01

    We study substorms from two perspectives, i.e., magnetosphere-ionosphere coupling across the auroral oval at dusk and at midnight magnetic local times. By this approach we monitor the activations/expansions of basic elements of the substorm current system (Bostroem type I centered at midnight and Bostroem type II maximizing at dawn and dusk) during the evolution of the substorm activity. Emphasis is placed on the R1 and R2 types of field-aligned current (FAC) coupling across the Harang reversal at dusk. We distinguish between two distinct activity levels in the substorm expansion phase, i.e., an initial transient phase and a persistent phase. These activities/phases are discussed in relation to polar cap convection which is continuously monitored by the polar cap north (PCN) index. The substorm activity we selected occurred during a long interval of continuously strong solar wind forcing at the interplanetary coronal mass ejection passage on 18 August 2003. The advantage of our scientific approach lies in the combination of (i) continuous ground observations of the ionospheric signatures within wide latitude ranges across the auroral oval at dusk and midnight by meridian chain magnetometer data, (ii) 'snapshot' satellite (DMSP F13) observations of FAC/precipitation/ion drift profiles, and (iii) observations of current disruption/near-Earth magnetic field dipolarizations at geostationary altitude. Under the prevailing fortunate circumstances we are able to discriminate between the roles of the dayside and nightside sources of polar cap convection. For the nightside source we distinguish between the roles of inductive and potential electric fields in the two substages of the substorm expansion phase. According to our estimates the observed dipolarization rate (δB{sub z}/δt) and the inferred large spatial scales (in radial and azimuthal dimensions) of the dipolarization process in these strong substorm expansions may lead to 50-100 kV enhancements of the

  9. M–I coupling across the auroral oval at dusk and midnight: repetitive substorm activity driven by interplanetary coronal mass ejections (CMEs

    Directory of Open Access Journals (Sweden)

    P. E. Sandholt

    2014-04-01

    Full Text Available We study substorms from two perspectives, i.e., magnetosphere–ionosphere coupling across the auroral oval at dusk and at midnight magnetic local times. By this approach we monitor the activations/expansions of basic elements of the substorm current system (Bostrøm type I centered at midnight and Bostrøm type II maximizing at dawn and dusk during the evolution of the substorm activity. Emphasis is placed on the R1 and R2 types of field-aligned current (FAC coupling across the Harang reversal at dusk. We distinguish between two distinct activity levels in the substorm expansion phase, i.e., an initial transient phase and a persistent phase. These activities/phases are discussed in relation to polar cap convection which is continuously monitored by the polar cap north (PCN index. The substorm activity we selected occurred during a long interval of continuously strong solar wind forcing at the interplanetary coronal mass ejection passage on 18 August 2003. The advantage of our scientific approach lies in the combination of (i continuous ground observations of the ionospheric signatures within wide latitude ranges across the auroral oval at dusk and midnight by meridian chain magnetometer data, (ii "snapshot" satellite (DMSP F13 observations of FAC/precipitation/ion drift profiles, and (iii observations of current disruption/near-Earth magnetic field dipolarizations at geostationary altitude. Under the prevailing fortunate circumstances we are able to discriminate between the roles of the dayside and nightside sources of polar cap convection. For the nightside source we distinguish between the roles of inductive and potential electric fields in the two substages of the substorm expansion phase. According to our estimates the observed dipolarization rate (δ Bz/δt and the inferred large spatial scales (in radial and azimuthal dimensions of the dipolarization process in these strong substorm expansions may lead to 50–100 kV enhancements of the

  10. Effects of Abrupt Variations of Solar Wind Dynamic Pressure on the High-Latitude Ionosphere

    Directory of Open Access Journals (Sweden)

    Igino Coco

    2011-01-01

    Full Text Available We show the results of a statistical study on the effects in the high-latitude ionosphere of abrupt variations of solar wind dynamic pressure, using Super Dual Auroral Radar Network (SuperDARN data in both hemispheres. We find that, during periods of quiet ionospheric conditions, the amount of radar backscatter increases when a variation in the dynamic pressure occurs, both positive (increase of the pressure and negative (decrease of the pressure. We also investigate the behaviour of the Cross-Polar Cap Potential (CPCP during pressure variations and show preliminary results.

  11. Pulsar Magnetohydrodynamic Winds

    Science.gov (United States)

    Okamoto, Isao; Sigalo, Friday B.

    2006-12-01

    The acceleration and collimation/decollimation of relativistic magnetocentrifugal winds are discussed concerning a cold plasma from a strongly magnetized, rapidly rotating neutron star in a steady axisymmetric state based on ideal magnetohydrodynamics. There exist unipolar inductors associated with the field line angular frequency, α, at the magnetospheric base surface, SB, with a huge potential difference between the poles and the equator, which drive electric current through the pulsar magnetosphere. Any ``current line'' must emanate from one terminal of the unipolar inductor and return to the other, converting the Poynting flux to the kinetic flux of the wind at finite distances. In a plausible field structure satisfying the transfield force-balance equation, the fast surface, SF, must exist somewhere between the subasymptotic and asymptotic domains, i.e., at the innermost point along each field line of the asymptotic domain of \\varpaA2/\\varpi2 ≪ 1, where \\varpiA is the Alfvénic axial distance. The criticality condition at SF yields the Lorentz factor, γF = μ\\varepsilon1/3, and the angular momentum flux, β, as the eigenvalues in terms of the field line angular velocity, α, the mass flux per unit flux tube, η, and one of the Bernoulli integrals, μδ, which are assumed to be specifiable as the boundary conditions at SB. The other Bernoulli integral, μɛ, is related to μδ as μɛ = μδ[1-(α2\\varpiA2/c2)]-1, and both μɛ and \\varpiA2 are eigenvalues to be determined by the criticality condition at SF. Ongoing MHD acceleration is possible in the superfast domain. This fact may be helpful in resolving a discrepancy between the wind theory and the Crab-nebula model. It is argued that the ``anti-collimation theorem'' holds for relativistic winds, based on the curvature of field streamlines determined by the transfield force balance. The ``theorem'' combines with the ``current-closure condition'' as a global condition in the wind zone to produce a

  12. Alfven waves in the auroral ionosphere: A numerical model compared with measurements

    International Nuclear Information System (INIS)

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

    1992-01-01

    The authors solve a linear numerical model of Alfven waves reflecting from the high-latitude ionosphere, both to better understanding the role of the ionosphere in the magnetosphere/ionosphere coupling process and to compare model results with in situ measurements. They use the model to compute the frequency-dependent amplitude and phase relations between the meridional electric and the zonal magnetic fields due to Alfven waves. These relations are compared with measurements taken by an auroral sounding rocket flow in the morningside oval and by the HILAT satellite traversing the oval at local noon. The sounding rocket's trajectory was mostly parallel to the auroral oval, and is measured enhanced fluctuating field energy in regions of electron precipitation. The rocket-measured phase data are in excellent agreement with the Alfven wave model, and the relation between the modeled and the measured by HILAT are related by the height-integrated Pedersen conductivity Σ p , indicating that the measured field fluctuations were due mainly to structured field-aligned current systems. A reason for the relative lack of Alfven wave energy in the HILAT measurements could be the fact that the satellite traveled mostly perpendicular to the oval and therefore quickly traversed narrow regions of electron precipitation and associated wave activity

  13. Initial results form the operation of two argon ion generators in the auroral ionosphere

    International Nuclear Information System (INIS)

    Erlandson, R.E.; Cahill, L.J. Jr.; Pollock, C.J.; Arnoldy, R.L.; Scales, W.A.; Kintner, P.M.

    1987-01-01

    Two argon ion generators were operated during a sounding rocket flight from Sondre Stromfjord, Greenland, on February 10, 1985. The ion generators were flown to investigate ion beam dynamics and beam effects on the ionosphere. The other major purpose of the flight was investigation of auroral electrodynamics as the rocket passed over auroral arcs. One generator emitted an ion beam perpendicular to the magnetic field and the other a beam parallel to the field. Ion detectors, an electric field meter and wave receivers were carried on the main payload to provide diagnostic measurements during the ion beam operations. Seventeen operations of the generators were observed over a 480-s interval before the rocket reentered the atmosphere. There was evidence of heating of the ionosphere around the subpayload during each ion beam emission. Ions of energy 100 to 200 eV, the ion beam energy range, were observed at the main payload during the first seven operations of each generator, with payload separation distances up to 800 m, reaching the main payload from directions appropriate for beam ions. Waves were observed during most of the first seven operations of each beam. Hydrogen, helium and oxygen cyclotron harmonics were observed in some of the perpendicular-beam operations. Waves were weak or absent during the first and third parallel-beam operations at separation distances near 80 and 320 m. In general the waves generated by the parallel beam were weaker than those generated by the perpendicular beam

  14. EISCAT observations of plasma patches at sub-auroral cusp latitudes

    Directory of Open Access Journals (Sweden)

    J. Moen

    2006-09-01

    Full Text Available A sequence of 3 patches of high-density (1012 m−3 cold plasma on a horizontal scale-size of 300–700 km was observed near magnetic noon by the EISCAT VHF radar above Svalbard on 17 December 2001. The patches followed a trajectory towards the cusp inflow region. The combination of radar and all-sky observations demonstrates that the patches must have been segmented equatorward of the cusp/cleft auroral display, and hence their properties had not yet been influenced by cusp particle showers and electrodynamics on open flux tubes. The last patch in the sequence was intersected by radio tomography observations, and was found to be located adjacent to a broader region of the same high electron density further south. The patches occurred under moderately active conditions (Kp=3 and the total electron content (TEC of the high-density plasma was 45 TEC units. The train of patches appeared as a segmentation of the tongue of ionization. The sequence of patches occurred in association with a sequence of flow bursts in the dusk cell return flow. It is proposed that reconnection driven pulsed convection is able to create sub-auroral patches in the region where high density mid-latitude plasma is diverted poleward toward the cusp. It is the downward Birkeland current sheet located at the equatorward boundary of the flow disturbance that represents the actual cutting mechanism.

  15. EISCAT observations of plasma patches at sub-auroral cusp latitudes

    Directory of Open Access Journals (Sweden)

    J. Moen

    2006-09-01

    Full Text Available A sequence of 3 patches of high-density (1012 m−3 cold plasma on a horizontal scale-size of 300–700 km was observed near magnetic noon by the EISCAT VHF radar above Svalbard on 17 December 2001. The patches followed a trajectory towards the cusp inflow region. The combination of radar and all-sky observations demonstrates that the patches must have been segmented equatorward of the cusp/cleft auroral display, and hence their properties had not yet been influenced by cusp particle showers and electrodynamics on open flux tubes. The last patch in the sequence was intersected by radio tomography observations, and was found to be located adjacent to a broader region of the same high electron density further south. The patches occurred under moderately active conditions (Kp=3 and the total electron content (TEC of the high-density plasma was 45 TEC units. The train of patches appeared as a segmentation of the tongue of ionization. The sequence of patches occurred in association with a sequence of flow bursts in the dusk cell return flow. It is proposed that reconnection driven pulsed convection is able to create sub-auroral patches in the region where high density mid-latitude plasma is diverted poleward toward the cusp. It is the downward Birkeland current sheet located at the equatorward boundary of the flow disturbance that represents the actual cutting mechanism.

  16. Auroral particle acceleration by Alfvén waves and ionospheric feedback

    Science.gov (United States)

    Lysak, R. L.; Song, Y.

    2003-12-01

    Recent observations, particularly by Polar and FAST, have indicated that Alfvén waves can directly accelerate auroral electrons. A model for this interaction has been developed that can describe the linear modification of the Alfvén wave profile by the kinetic effects of electrons, including acceleration and heating of the electron population. While many of the heated electrons are accelerated upward into the magnetosphere by the mirror force, a significant fraction of the input Poynting flux due to Alfvén waves can be converted into precipitating electron energy flux. An important aspect of this particle precipitation is that the hot electrons do not arrive at the ionosphere in phase with the field-aligned current, which at ionospheric altitudes is largely carried by cold electrons. This phase shift has direct implications for models of ionospheric feedback that usually assume that the precipitating flux is in phase with the field-aligned current. The effects of quasi-static electric fields can be included in the model, which will introduce new particle populations such as the effects of secondary electrons of ionospheric origin that are reflected by the parallel potential drop. The possible role of Alfvén waves trapped in the ionospheric resonator in creating small-scale auroral structures through feedback and nonlinear interactions will be discussed.

  17. One-Year Observations of Jupiter by the Jovian Infrared Auroral Mapper on Juno

    Science.gov (United States)

    Adriani, A.; Mura, A.; Bolton, S. J.; Connerney, J. E. P.; Levin, S.; Becker, H. N.; Bagenal, F.; Hansen, C. J.; Orton, G.; Gladstone, R.; Kurth, W. S.; Mauk, B.; Valek, P. W.

    2017-12-01

    The Jovian InfraRed Auroral Mapper (JIRAM) [1] on board the Juno [2,3] spacecraft, is equipped with an infrared camera and a spectrometer working in the spectral range 2-5 μm. JIRAM was built to study the infrared aurora of Jupiter as well as to map the planet's atmosphere in the 5 µm spectral region. The spectroscopic observations are used for studying clouds and measuring the abundance of some chemical species that have importance in the atmosphere's chemistry, microphysics and dynamics like water, ammonia and phosphine. During 2017 the instrument will operate during all 7 of Juno's Jupiter flybys. JIRAM has performed several observations of the polar regions of the planet addressing the aurora and the atmosphere. Unprecedented views of the aurora and the polar atmospheric structures have been obtained. We present a survey of the most significant observations that the instrument has performed during the current year. [1] Adriani A. et al., JIRAM, the Jovian Infrared Auroral Mapper. Space Sci. Rew., DOI 10.1007/s11214-014-0094-y, 2014. [2] Bolton S.J. et al., Jupiter's interior and deep atmosphere: The initial pole-to-pole passes with the Juno spacecraft. Science DOI: 10.1126/science.aal2108, 2017. [3] Connerney J. E.P. et al., Jupiter's magnetosphere and aurorae observed by the Juno spacecraft during its first polar orbits. Science, DOI: 10.1126/science.aam5928, 2017.

  18. Auroral lights created by high-power radiowaves in the ionospheric E region

    International Nuclear Information System (INIS)

    Kagan, L M

    2008-01-01

    Artificial auroral lights are optical emissions induced by high-power radiowaves in a manner similar to the creation of natural auroral lights due to precipitation of superthermal electrons. Here the Earth's atmosphere itself plays the role of a plasma laboratory. A high-power radio-transmitter creates superthermal electrons in situ due to radiowave interactions with the ionospheric plasma. Low-altitude (85-125 km) artificial aurora is a relatively rare phenomenon observed for the first time about 10 years ago. Analysis of available observations shows that its intensity and structure, as well as the very possibility of its generation at these altitudes, depend largely on the presence and features of so-called sporadic ionization, best known for its effect on navigation and communication. Thus, all other parameters unchanged, a 20 times increase in the height-extent of sporadic ionization clouds could under certain circumstances result in a 27-fold increase in the intensity of the low-altitude artificial aurora. Understanding the morphology and typical features of sporadic ionization clouds for a given location would allow proper planning of experimental campaigns and noticeably extend our knowledge of the atmosphere and its use for human needs. Equally important is that low-altitude artificial auroras give information about the horizontal structure and dynamics of E-region sporadic ionization, the airglow-source region, the energy of superthermal electrons and perhaps the local atmospheric temperature and water vapor content at 80-90 km

  19. Magnetosphere-ionosphere coupling during periods of extended high auroral activity: a case study

    Directory of Open Access Journals (Sweden)

    S. Liléo

    2008-03-01

    Full Text Available Results are presented from a case study of a plasma boundary crossing by the Cluster spacecraft during an extended period of high auroral activity. The boundary between the magnetotail lobe region of the Southern Hemisphere and the plasma sheet boundary layer, was characterized by intense electric and magnetic field variations, structured upward accelerated ion beams, narrow-scale large field-aligned Poynting fluxes directed upward away from the ionosphere, and a relatively sharp plasma density gradient.

    The observations are shown to be consistent with the concept of a multi-layered boundary with temporal and/or spatial variations in the different layers. H+ and O+ ion beams are seen to be accelerated upwards both by means of a field-aligned electric field and by magnetic pumping caused by large-amplitude and low-frequency electric field fluctuations. The peak energy of the ion beams may here be used as a diagnostic tool for the temporal evolution of the spatial structures, since the temporal changes occur on a time-scale shorter than the times-of-flight of the detected ion species.

    The case study also shows the boundary region to be mainly characterized by a coupling of the detected potential structures to the low ionosphere during the extended period of high auroral activity, as indicated by the intense field-aligned Poynting fluxes directed upward away from the ionosphere.

  20. Magnetosphere-ionosphere coupling during periods of extended high auroral activity: a case study

    Directory of Open Access Journals (Sweden)

    S. Liléo

    2008-03-01

    Full Text Available Results are presented from a case study of a plasma boundary crossing by the Cluster spacecraft during an extended period of high auroral activity. The boundary between the magnetotail lobe region of the Southern Hemisphere and the plasma sheet boundary layer, was characterized by intense electric and magnetic field variations, structured upward accelerated ion beams, narrow-scale large field-aligned Poynting fluxes directed upward away from the ionosphere,