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Sample records for observing field lrc1

  1. Observations of galactic magnetic fields

    NASA Astrophysics Data System (ADS)

    Beck, Rainer

    Magnetic fields are enchored in gas clouds. Field lines are tangled in spiral arms, but highly regular between the arms. The similarity of pitch angles between gaseous and magnetic arms suggests a coupling between the density wave and the magnetic wave. Observations of large-scale patterns in Faraday rotation favour a dynamo origin of the regular fields. Fields in barred galaxies do not reveal the strong shearing shocks observed in the cold gas, but swing smoothly from the upstream region into the bar. Magnetic fields are important for the dynamcis of gas clouds, for the formation of spiral structures, bars and halos, and for mass and angular momentum transport in central regions.

  2. Hinode observations of polar fields

    NASA Astrophysics Data System (ADS)

    Tsuneta, Saku

    The Sun's polar magnetic fields are the direct extension of the global poloidal field, which serves as seed fields for the toroidal fields forming active regions and sunspots. The polar regions are also the source of fast solar wind, and are the final destination of pole-ward meridional flows. We present spectro-polarimetric maps of the vector magnetic fields in the polar region of the Sun that are unprecedented in terms of high spatial resolution, large field of view, and polarimetric precision. These observations were carried out with the Solar Optical Telescope aboard Hinode. More than 100 canopy-like vertical magnetic structures as strong as 1-1.2 kG are scattered in heliographic latitude of 70-90o . They all have the same polarity, consistent with the global polar fields. The temporal-spatial evolution of these kG patches, which are crucial to understanding of their origin, will be reported. In addition to the vertical fields, the polar region appears to be covered with ubiquitous horizontal fields. Chromospheric observations with Hinode indicate that substantial amount of the horizontal fields reach chromosphere. Our observations describe the magnetic landscape of this poorly known region of the solar atmosphere. The polar regions are the source of the fast solar wind channelled along unipolar coronal-hole magnetic fields. We conjecture that the fast solar wind emanates only from the vertical flux tubes (canopies), which also seem to serve as efficient chimneys for Alfven waves to accelerate the solar wind.

  3. Observations of Mercury's magnetic field

    NASA Technical Reports Server (NTRS)

    Ness, N. F.; Behannon, K. W.; Lepping, R. P.; Whang, Y. C.

    1975-01-01

    Magnetic field data obtained by Mariner 10 during the third and final encounter with the planet Mercury on 16 March 1975 were studied. A well developed bow shock and modest magnetosphere, previously observed at first encounter on 29 March 1974, were again observed. In addition, a much stronger magnetic field near closest approach, 400 gamma versus 98 gamma, was observed at an altitude of 327 km and approximately 70 deg north Mercurian latitude. Spherical harmonic analysis of the data provide an estimate of the centered planetary magnetic dipole of 4.7 x 10 to the 22nd power Gauss/cu cm with the axis tilted 12 deg to the rotation axis and in the same sense as Earth's. The interplanetary field was sufficiently different between first and third encounters that in addition to the very large field magnitude observed, it argues strongly against a complex induction process generating the observed planetary field. While a possibility exists that Mercury possesses a remanent field due to magnetization early in its formation, a present day active dynamo seems to be a more likely candidate for its origin.

  4. Review of magnetic field observations.

    NASA Technical Reports Server (NTRS)

    Ness, N. F.

    1972-01-01

    Recent observations in previously unexplored regions of the magnetosphere, particularly in the polar-cusp region, compliment and reinforce emphasis on particle access to the plasma sheet via the polar neutral points. Significant distortions of the geomagnetic field in the polar-cusp region suggest field-aligned currents at large geocentric distances which can be related to low-altitude polar-cap phenomena. Studies of the microstructure of the field reversal region of the plasma sheet embedded in the geomagnetic tail suggest a periodic structure of more complexity than earlier assumed simplified single neutral-line models.

  5. Magnetic field observations in Comet Halley's coma

    NASA Astrophysics Data System (ADS)

    Riedler, W.; Schwingenschuh, K.; Yeroshenko, Ye. G.; Styashkin, V. A.; Russell, C. T.

    1986-05-01

    During the encounter with Comet Halley, the magnetometer (MISCHA) aboard the Vega 1 spacecraft observed an increased level of magnetic field turbulence, resulting from an upstream bow wave. Both Vega spacecraft measured a peak field strength of 70-80 nT and observed draping of magnetic field lines around the cometary obstacle. An unexpected rotation of the magnetic field vector was observed, which may reflect either penetration of magnetic field lines into a diffuse layer related to the contact surface separating the solar-wind and cometary plasma, or the persistence of pre-existing interplanetary field structures.

  6. MMS Observations of Parallel Electric Fields

    NASA Astrophysics Data System (ADS)

    Ergun, R.; Goodrich, K.; Wilder, F. D.; Sturner, A. P.; Holmes, J.; Stawarz, J. E.; Malaspina, D.; Usanova, M.; Torbert, R. B.; Lindqvist, P. A.; Khotyaintsev, Y. V.; Burch, J. L.; Strangeway, R. J.; Russell, C. T.; Pollock, C. J.; Giles, B. L.; Hesse, M.; Goldman, M. V.; Drake, J. F.; Phan, T.; Nakamura, R.

    2015-12-01

    Parallel electric fields are a necessary condition for magnetic reconnection with non-zero guide field and are ultimately accountable for topological reconfiguration of a magnetic field. Parallel electric fields also play a strong role in charged particle acceleration and turbulence. The Magnetospheric Multiscale (MMS) mission targets these three universal plasma processes. The MMS satellites have an accurate three-dimensional electric field measurement, which can identify parallel electric fields as low as 1 mV/m at four adjacent locations. We present preliminary observations of parallel electric fields from MMS and provide an early interpretation of their impact on magnetic reconnection, in particular, where the topological change occurs. We also examine the role of parallel electric fields in particle acceleration. Direct particle acceleration by parallel electric fields is well established in the auroral region. Observations of double layers in by the Van Allan Probes suggest that acceleration by parallel electric fields may be significant in energizing some populations of the radiation belts. THEMIS observations also indicate that some of the largest parallel electric fields are found in regions of strong field-aligned currents associated with turbulence, suggesting a highly non-linear dissipation mechanism. We discuss how the MMS observations extend our understanding of the role of parallel electric fields in some of the most critical processes in the magnetosphere.

  7. Radio observations of the Jovian magnetic field

    NASA Technical Reports Server (NTRS)

    Barrow, C. H.; Carr, T. D.

    1992-01-01

    Radio observations of Jupiter are reviewed and discussed in relation to the planet's magnetic field. Early ground-based decameter- and decimeter-wave observations lead to a first estimate of the magnetic field strength which was subsequently confirmed by space-borne measurements. Decametric, hectometric and decimetric measurements of the Jovian rotation period offer the possibility of detecting a real change in the magnetic field structure within the next few decades. Solar wind control of the radio emission allows inferences to be made concerning the magnetic field and the emission regions at decametric, hectometric and kilometric frequencies. The decametric and the hectometric radiation may originate in hollow-cone emission sources at high (auroral) latitudes on Jupiter. The broad-band kilometric emission appears to originate at the outer edge of the Io torus.

  8. Observations of large transient magnetospheric electric fields

    NASA Technical Reports Server (NTRS)

    Aggson, T. L.; Heppner, J. P.

    1977-01-01

    Transient electric field events were observed with the long, double probe instrumentation carried by the IMP-6 satellite. Nine, clearly defined, exceptionally large amplitude events are presented here. The events are observed in the midnight sector at geocentric distances 3.5 to .5.5 R sub e at middle latitudes within a magnetic L-shell range of 4.8 to 7.5. They usually have a total duration of one to several minutes, with peak power spectra amplitudes occurring at a frequency of about 0.3 Hz. The events occur under magnetically disturbed conditions, and in most cases they can be associated with negative dH/dt excursions at magnetic observatories located near the foot of the magnetic field line intersecting IMP-6. The magnetospheric motions calculated for these electric fields indicated a quasi-stochastical diffusive process rather than the general inward magnetospheric collapsing motion expected during the expansive phases of auroral substorm activity.

  9. CCD observations of old nova fields

    SciTech Connect

    Downes, R.A.; Szkody, P.; Washington Uni., Seattle )

    1989-06-01

    The discovery of CK Vulpeculae (Nova 1670) has prompted a major review of ideas concerning the long-term development of novae. Unfortunately, there are very few recovered novae old enough to provide confirmation (or rejection) of the new hibernation scenario. CCD images of seven old nova fields, and R band photometry for four fields, have been obtained in an attempt to recover these objects in quiescence. A strong candidate for U Leonis, and a possible counterpart for T Bootis, are found. For three other fields, weak candidates have been found. Finding charts and colors are presented for the seven fields observed. The R light curves of U Leo, indicating an orbital period of 192.5 or 385.0 min, are shown. 14 refs.

  10. CCD observations of old nova fields

    NASA Technical Reports Server (NTRS)

    Downes, Ronald A.; Szkody, Paula

    1989-01-01

    The discovery of CK Vulpeculae (Nova 1670) has prompted a major review of ideas concerning the long-term development of novae. Unfortunately, there are very few recovered novae old enough to provide confirmation (or rejection) of the new 'hibernation' scenario. CCD images of seven old nova fields, and R band photometry for four fields, have been obtained in an attempt to recover these objects in quiescence. A strong candidate for U Leonis, and a possible counterpart for T Bootis, are found. For three other fields, weak candidates have been found. Finding charts and colors are presented for the seven fields observed. The R light curves of U Leo, indicating an orbital period of 192.5 or 385.0 min, are shown.

  11. LAMOST observations in the Kepler field

    NASA Astrophysics Data System (ADS)

    De Cat, P.; Fu, J. N.; Yang, X. H.; Ren, A. B.; Frasca, A.; Molenda-Żakowicz, J.; Catanzaro, G.; Gray, R. O.; Corbally, C. J.; Shi, J. R.; Zhang, H. T.; Luo, A. L.

    2015-09-01

    The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) at the Xinglong observatory in China is a new 4-m telescope equipped with 4,000 optical fibers. In 2010, we initiated the LAMOST-Kepler project. We requested to observe the full field-of-view of the nominal Kepler mission with the LAMOST to collect low-resolution spectra for as many objects from the KIC 10 catalogue as possible. So far, 12 of the 14 requested LAMOST fields have been observed resulting in more than 68,000 low-resolution spectra. Our preliminary results show that the stellar parameters derived from the LAMOST spectra are in good agreement with those found in the literature based on high-resolution spectroscopy. The LAMOST data allows to distinguish dwarfs from giants and can provide the projected rotational velocity for very fast rotators.

  12. Gravity Field Recovery with Simulated GOCE Observations

    NASA Astrophysics Data System (ADS)

    Marty, J.; Bruinsma, S.; Balmino, G.; Abrikosov, O.; Foerste, C.; Rothacher, M.

    2005-12-01

    Numerical simulations of the gravity field parameter recovery using the direct method, with satellite positions as pseudo observations instead of simulated GPS Satellite-to-Satellite (SST) tracking data, and with gravity gradients (SGG data), were done and are ongoing in the framework of the European GOCE Gravity Consortium test and validation plan for GOCE mission data processing. This work shows the latest results from the CNES and GFZ software packages, GINS and EPOS, respectively. After the iterative least-squares orbit adjustment procedure has converged to the highest attainable precision level, the gravity field normal equations are computed in a subsequent step. These SST normal equations, representing the long wavelength gravity field signal, are then reduced for arc-dependent parameters (i.e. state vector at epoch, empirical parameters) and cumulated over the entire observation period. Secondly, the gravity gradient measurements (SGG) are processed, taking into account the coloured noise in these data, and yield (high resolution) normal equations. They are combined with the SST normal equations and the gravity field and gradiometer common mode calibration parameters are simultaneously estimated. The coloured noise in the SGG data is based on the latest and realistic gradiometer specifications. The precision in the measurement bandwidth is approximately 3-5 milliEotvos, but rapidly decreasing for lower frequencies. Due to this behaviour, the observation equations have to be filtered in order to obtain the most accurate recovery. The filter algorithm, design and results are presented to considerable detail since this particular step is the key element that will enable the achievement of the GOCE mission objectives from the ground segment point of view.

  13. Wide field camera observations of Baade's Window

    NASA Technical Reports Server (NTRS)

    Holtzman, Jon A.; Light, R. M.; Baum, William A.; Worthey, Guy; Faber, S. M.; Hunter, Deidre A.; O'Neil, Earl J., Jr.; Kreidl, Tobias J.; Groth, E. J.; Westphal, James A.

    1993-01-01

    We have observed a field in Baade's Window using the Wide Field Camera (WFC) of the Hubble Space Telescope (HST) and obtain V- and I-band photometry down to V approximately 22.5. These data go several magnitudes fainter than previously obtained from the ground. The location of the break in the luminosity function suggests that there are a significant number of intermediate age (less than 10 Gyr) stars in the Galactic bulge. This conclusion rests on the assumptions that the extinction towards our field is similar to that seen in other parts of Baade's Window, that the distance to the bulge is approximately 8 kpc, and that we can determine fairly accurate zero points for the HST photometry. Changes in any one of these assumptions could increase the inferred age, but a conspiracy of lower reddening, a shorter distance to the bulge, and/or photometric zero-point errors would be needed to imply a population entirely older than 10 Gyr. We infer an initial mass function slope for the main-sequence stars, and find that it is consistent with that measured in the solar neighborhood; unfortunately, the slope is poorly constrained because we sample only a narrow range of stellar mass and because of uncertainties in the observed luminosity function at the faint end.

  14. Observation of spin Hall effective field

    NASA Astrophysics Data System (ADS)

    Fan, Xin; Wu, Jun; Chen, Yunpeng; Jerry, Matthew; Zhang, Huaiwu; Xiao, John

    2013-03-01

    Recent development in spin Hall driven spin transfer torque has attracted intensive interests1. Liu et. al. has shown that the spin transfer torque induced by the spin Hall effect in a normal metal-ferromagnetic metal bilayer can switch the magnetization of the ferromagnetic layer, which may be a potential candidate for magnetic random access memory2. The switching of the magnetization was primarily attributed to the Slonczewski torque3. We show that besides the Slonczewski torque, the spin Hall effect also produces an effective field that can also facilitate the magnetization reversal. This effective field persists even with a Cu spacer layer, and reduces quickly with the increase of the ferromagnetic layer thickness. The observation of the spin Hall effective field shall have ramification on the understanding of both spin transfer torque and spin Hall effect. 1. K. Ando et. al., Electric manipulation of spin relaxation using the spin Hall effect, Physical Review Letters, 101, 036601 (2008). 2. L. Liu et. al., Spin-Torque Switching with the Giant Spin Hall Effect of Tantalum. Science 336, 555-558 (2012). 3. J. Slonczewski, Current-driven excitation of magnetic multilayers. Journal of Magnetism and Magnetic Materials, 159, L1-L7 (1996).

  15. Interpretation of Solar Magnetic Field Strength Observations

    NASA Astrophysics Data System (ADS)

    Ulrich, R. K.; Bertello, L.; Boyden, J. E.; Webster, L.

    2009-03-01

    This study based on longitudinal Zeeman effect magnetograms and spectral line scans investigates the dependence of solar surface magnetic fields on the spectral line used and the way the line is sampled to estimate the magnetic flux emerging above the solar atmosphere and penetrating to the corona from magnetograms of the Mt. Wilson 150-foot tower synoptic program (MWO). We have compared the synoptic program λ5250 Å line of Fe i to the line of Fe i at λ5233 Å since this latter line has a broad shape with a profile that is nearly linear over a large portion of its wings. The present study uses five pairs of sampling points on the λ5233 Å line. Line profile observations show that the determination of the field strength from the Stokes V parameter or from line bisectors in the circularly polarized line profiles lead to similar dependencies on the spectral sampling of the lines, with the bisector method being the less sensitive. We recommend adoption of the field determined with the line bisector method as the best estimate of the emergent photospheric flux and further recommend the use of a sampling point as close to the line core as is practical. The combination of the line profile measurements and the cross-correlation of fields measured simultaneously with λ5250 Å and λ5233 Å yields a formula for the scale factor δ -1 that multiplies the MWO synoptic magnetic fields. By using ρ as the center-to-limb angle (CLA), a fit to this scale factor is δ -1=4.15-2.82sin 2( ρ). Previously δ -1=4.5-2.5sin 2( ρ) had been used. The new calibration shows that magnetic fields measured by the MDI system on the SOHO spacecraft are equal to 0.619±0.018 times the true value at a center-to-limb position 30°. Berger and Lites (2003, Solar Phys. 213, 213) found this factor to be 0.64±0.013 based on a comparison using the Advanced Stokes Polarimeter.

  16. Hazardous gas model evaluation with field observations

    NASA Astrophysics Data System (ADS)

    Hanna, S. R.; Chang, J. C.; Strimaitis, D. G.

    Fifteen hazardous gas models were evaluated using data from eight field experiments. The models include seven publicly available models (AFTOX, DEGADIS, HEGADAS, HGSYSTEM, INPUFF, OB/DG and SLAB), six proprietary models (AIRTOX, CHARM, FOCUS, GASTAR, PHAST and TRACE), and two "benchmark" analytical models (the Gaussian Plume Model and the analytical approximations to the Britter and McQuaid Workbook nomograms). The field data were divided into three groups—continuous dense gas releases (Burro LNG, Coyote LNG, Desert Tortoise NH 3-gas and aerosols, Goldfish HF-gas and aerosols, and Maplin Sands LNG), continuous passive gas releases (Prairie Grass and Hanford), and instantaneous dense gas releases (Thorney Island freon). The dense gas models that produced the most consistent predictions of plume centerline concentrations across the dense gas data sets are the Britter and McQuaid, CHARM, GASTAR, HEGADAS, HGSYSTEM, PHAST, SLAB and TRACE models, with relative mean biases of about ±30% or less and magnitudes of relative scatter that are about equal to the mean. The dense gas models tended to overpredict the plume widths and underpredict the plume depths by about a factor of two. All models except GASTAR, TRACE, and the area source version of DEGADIS perform fairly well with the continuous passive gas data sets. Some sensitivity studies were also carried out. It was found that three of the more widely used publicly-available dense gas models (DEGADIS, HGSYSTEM and SLAB) predicted increases in concentration of about 70% as roughness length decreased by an order of magnitude for the Desert Tortoise and Goldfish field studies. It was also found that none of the dense gas models that were considered came close to simulating the observed factor of two increase in peak concentrations as averaging time decreased from several minutes to 1 s. Because of their assumption that a concentrated dense gas core existed that was unaffected by variations in averaging time, the dense gas

  17. Field Observations and Interpretations Given New Emphasis.

    ERIC Educational Resources Information Center

    Vick, Timothy D.; Buchwald, C. E.

    1979-01-01

    The quantity of available knowledge has expanded such that the teaching of processes is as important in geology education as the teaching of facts. Field trips must be modified also to conform to this shift in focus. A sample teaching unit at an outcrop illustrates the technique. (RE)

  18. Balloon-borne radiometer profiler: Field observations

    SciTech Connect

    Shaw, W.J.; Whiteman, C.D.; Anderson, G.A.; Alzheimer, J.M.; Hubbe, J.M.; Scott, K.A.

    1995-03-01

    This project involves the development of the capability of making routine soundings of broadband radiative fluxes and radiative flux divergences to heights of 1500m AGL. Described in this document are radiometers carried on a stabilized platform in a harness inserted in the tetherline of a tethered balloon meteriological sounding system. Field test results are given.

  19. Annotated Observations: Field Notes and Reflections

    ERIC Educational Resources Information Center

    Thomas-Fair, Ursula

    2007-01-01

    Purpose: The purpose of this action research presentation is to invite discourse on the intersection of race, gender and instructional decisions in the classrooms of student teachers. The purpose of this study is to also examine the thoughts of a university supervisor during clinical observation with respect to her positionality as a woman of…

  20. Field Research: Learning through the Process of Observation

    ERIC Educational Resources Information Center

    Hartlep, Nicholas Daniel

    2009-01-01

    This paper reports on the process of a participant observation. Its focus is its process, not on what was observed. This report provides the following: (1) an overview of this observation, (2) the purpose of this observation, (3) the site and situation of this observation, (4) two samples of reflective field notes from this observation, and (5) an…

  1. POLAR FIELD REVERSAL OBSERVATIONS WITH HINODE

    SciTech Connect

    Shiota, D.; Tsuneta, S.; Shimojo, M.; Orozco Suarez, D.; Ishikawa, R.; Sako, N.

    2012-07-10

    We have been monitoring yearly variation in the Sun's polar magnetic fields with the Solar Optical Telescope aboard Hinode to record their evolution and expected reversal near the solar maximum. All magnetic patches in the magnetic flux maps are automatically identified to obtain the number density and magnetic flux density as a function of the total magnetic flux per patch. The detected magnetic flux per patch ranges over four orders of magnitude (10{sup 15}-10{sup 20} Mx). The higher end of the magnetic flux in the polar regions is about one order of magnitude larger than that of the quiet Sun, and nearly that of pores. Almost all large patches ({>=}10{sup 18} Mx) have the same polarity, while smaller patches have a fair balance of both polarities. The polarity of the polar region as a whole is consequently determined only by the large magnetic concentrations. A clear decrease in the net flux of the polar region is detected in the slow rising phase of the current solar cycle. The decrease is more rapid in the north polar region than in the south. The decrease in the net flux is caused by a decrease in the number and size of the large flux concentrations as well as the appearance of patches with opposite polarity at lower latitudes. In contrast, we do not see temporal change in the magnetic flux associated with the smaller patches (<10{sup 18} Mx) and that of the horizontal magnetic fields during the years 2008-2012.

  2. Multisatellite Observations of Interplanetary Field Enhancements

    NASA Astrophysics Data System (ADS)

    Russell, C. T.; Weimer, D. R.; Jian, L. K.; Lai, H. R.; Luhmann, J. G.

    2008-12-01

    Interplanetary Field Enhancements (IFEs) are magnetic structures in the solar wind that have a cusp-shaped maximum in the field strength with a strong current sheet often near the central peak. These structures generally last an hour or more. They have a tendency to be seen more often at specific ecliptic longitudes, have been identified on occasion with particular small solar system bodies (asteroid 2201 Oljato and comet 122P/ De Vico) and attributed to the interaction of the solar wind with charged dust. On occasion they are detected nearly simultaneously by several spacecraft. Multispacecraft detection have been made with PVO, Venera-13 and Venera-14; with ISEE 1 and ISEE 3 and more recently with STEREO A and B, ACE and Wind. In this paper we use a delay matching algorithm developed by D. Weimer on the IFE of December 24, 2006 detected by 4 spacecraft. While the IFE is crossing the four spacecraft separated in Y by 90 Re and in X by 160 Re the measured delay was close to the calculated advection time. Along the apparent center line of the event the delay was close to 4 minutes. This event together with previous events are consistent with IFEs being magnetic structures that are convecting outward from the Sun with nearly, but slightly slower than, the solar wind velocity. We need to understand the occurrence rate of such structures and their physical cause because if this hypothesis is true, they may be responsible for accelerating dust out of the inner solar system.

  3. Seismological Field Observation of Mesoscopic Nonlinearity

    NASA Astrophysics Data System (ADS)

    Sens-Schönfelder, Christoph; Gassenmeier, Martina; Eulenfeld, Tom; Tilmann, Frederik; Korn, Michael; Niederleithinger, Ernst

    2016-04-01

    Noise based observations of seismic velocity changes have been made in various environments. We know of seasonal changes of velocities related to ground water or temperature changes, co-seismic changes originating from shaking or stress redistribution and changes related to volcanic activity. Is is often argued that a decrease of velocity is related to the opening of cracks while the closure of cracks leads to a velocity increase if permanent stress changes are invoked. In contrast shaking induced changes are often related to "damage" and subsequent "healing" of the material. The co-seismic decrease and transient recovery of seismic velocities can thus be explained with both - static stress changes or damage/healing processes. This results in ambiguous interpretations of the observations. Here we present the analysis of one particular seismic station in northern Chile that shows very strong and clear velocity changes associated with several earthquakes ranging from Mw=5.3 to Mw=8.1. The fact that we can observe the response to several events of various magnitudes from different directions offers the unique possibility to discern the two possible causative processes. We test the hypothesis, that the velocity changes are related to shaking rather than stress changes by developing an empirical model that is based on the local ground acceleration at the sensor site. The eight year of almost continuous observations of velocity changes are well modeled by a daily drop of the velocity followed by an exponential recovery. Both, the amplitude of the drop as well as the recovery time are proportional to the integrated acceleration at the seismic station. Effects of consecutive days are independent and superimposed resulting in strong changes after earthquakes and constantly increasing velocities during quiet days thereafter. This model describes the continuous observations of the velocity changes solely based on the acceleration time series without individually defined dates

  4. Interplanetary magnetic sector polarity inferred from polar geomagnetic field observations

    NASA Technical Reports Server (NTRS)

    Eriss-Christensen, E.; Lassen, K.; Wilcox, J. M.; Gonzalez, W.; Colburn, D. S.

    1971-01-01

    With the use of a prediction technique it is shown that the polarity (toward or away from the sun) of the interplanetary magnetic field can be reliably inferred from observations of the polar geomagnetic field.

  5. Null fields in the outer Jovian magnetosphere: ULYSSES observations

    NASA Astrophysics Data System (ADS)

    Haynes, P. L.; Balogh, A.; Dougherty, M. K.; Southwood, D. J.; Fazakerley, A.

    1994-03-01

    This paper reports on a magnetic field phenomenon, hereafter referred to as null fields, which were discovered during the inbound pass of the recent flyby of Jupiter by the Ulysses spacecraft. These null fields which were observed in the outer dayside magnetosphere are characterised by brief but sharp decreases of the field magnitude to values less than 1 nT. The nulls are distinguished from the current sheet signatures characteristic of the middle magnetosphere by the fact that the field does not reverse across the event. A field configuration is suggested that accounts for the observed features of the events.

  6. Interplanetary magnetic sector polarity inferred from polar geomagnetic field observations

    NASA Technical Reports Server (NTRS)

    Friis-Christensen, E.; Lassen, K.; Wilcox, J. M.; Gonzalez, W.; Colburn, D. S.

    1971-01-01

    In order to infer the interplanetary sector polarity from polar geomagnetic field diurnal variations, measurements were carried out at Godhavn and Thule (Denmark) Geomagnetic Observatories. The inferred interplanetary sector polarity was compared with the polarity observed at the same time by Explorer 33 and 35 magnetometers. It is shown that the polarity (toward or away from the sun) of the interplanetary magnetic field can be reliably inferred from observations of the polar cap geomagnetic fields.

  7. Reconstructing magnetic fields of spiral galaxies from radiopolarimetric observations

    NASA Astrophysics Data System (ADS)

    Shneider, C.

    2015-12-01

    We live in a magnetic universe with magnetic fields spanning an enormous range of spatial and temporal scales. In particular, magnetic fields at the scale of a galaxy are known as galactic magnetic fields and are the focus of this PhD thesis. These galactic magnetic fields are very important since they affect the dynamics of the interstellar gas as well as the gas distribution. The presence of these magnetic fields induces a certain type of radiation to occur at radio frequencies known as synchrotron radiation. The observed polarization properties of this synchrotron radiation then serves to record the imprint of these magnetic fields. The goal of this thesis has been to infer the structure of the magnetic field across various spatial scales in our own Galaxy as well as the strength and structure of the magnetic field in other galaxies using radiopolarimetric observations.

  8. Computation of solar magnetic fields from photospheric observations

    NASA Technical Reports Server (NTRS)

    Hannakam, L.; Gary, G. A.; Teuber, D. L.

    1984-01-01

    The observational difficulties of obtaining the magnetic field distribution in the chromosphere and corona of the sun has led to methods of extending photospheric magnetic mesurements into the solar atmosphere by mathematical procedures. A new approach to this problem presented here is that a constant alpha force-free field can be uniquely determined from the tangential components of the measured photospheric flux alone. The vector magnetographs now provide measurements of both the solar photospheric tangential and the longitudinal magnetic field. This paper presents derivations for the computation of the solar magnetic field from these type of measurements. The fields considered are assumed to be a constant alpha force-free fields or equivalent, producing vanishing Lorentz forces. Consequently, magnetic field lines and currents are related by a constant and hence show an identical distribution. The magnetic field above simple solar regions are described from the solution of the field equations.

  9. Computation of solar magnetic fields from photospheric observations

    NASA Astrophysics Data System (ADS)

    Hannakam, L.; Gary, G. A.; Teuber, D. L.

    1984-09-01

    The observational difficulties of obtaining the magnetic field distribution in the chromosphere and corona of the sun has led to methods of extending photospheric magnetic mesurements into the solar atmosphere by mathematical procedures. A new approach to this problem presented here is that a constant alpha force-free field can be uniquely determined from the tangential components of the measured photospheric flux alone. The vector magnetographs now provide measurements of both the solar photospheric tangential and the longitudinal magnetic field. This paper presents derivations for the computation of the solar magnetic field from these type of measurements. The fields considered are assumed to be a constant alpha force-free fields or equivalent, producing vanishing Lorentz forces. Consequently, magnetic field lines and currents are related by a constant and hence show an identical distribution. The magnetic field above simple solar regions are described from the solution of the field equations.

  10. Rethinking Field Observations: Strengthening Teacher Education through INFORM

    ERIC Educational Resources Information Center

    Hoyt, Kristin; Terantino, Joe

    2015-01-01

    This article introduces the Instructional Field Observation Rounds Model (INFORM), drawn from the medical profession where resident interns make rounds with experienced physicians, as an alternative approach for conducting classroom observations in pre-service teacher education methods courses. INFORM centers on structured group observations in…

  11. Observations of Strong Magnetic Fields in Nondegenerate Stars

    NASA Astrophysics Data System (ADS)

    Linsky, Jeffrey L.; Schöller, Markus

    2015-10-01

    We review magnetic-field measurements of nondegenerate stars across the Hertzprung-Russell diagram for main sequence, premain sequence, and postmain sequence stars. For stars with complex magnetic-field morphologies, which includes all G-M main sequence stars, the analysis of spectra obtained in polarized vs unpolarized light provides very different magnetic measurements because of the presence or absence of cancellation by oppositely directed magnetic fields within the instrument's spatial resolution. This cancellation can be severe, as indicated by the spatially averaged magnetic field of the Sun viewed as a star. These averaged fields are smaller by a factor of 1000 or more compared to spatially resolved magnetic-field strengths. We explain magnetic-field terms that characterize the fields obtained with different measurement techniques. Magnetic fields typically control the structure of stellar atmospheres in and above the photosphere, the heating rates of stellar chromospheres and coronae, mass and angular momentum loss through stellar winds, chemical peculiarity, and the emission of high energy photons, which is critically important for the evolution of protoplanetary disks and the habitability of exoplanets. Since these effects are governed by the star's magnetic energy, which is proportional to the magnetic-field strength squared and its fractional surface coverage, it is important to measure or reliably infer the true magnetic-field strength and filling factor across a stellar disk. We summarize magnetic-field measurements obtained with the different observing techniques for different types of stars and estimate the highest magnetic-field strengths. We also comment on the different field morphologies observed for stars across the H-R diagram, typically inferred from Zeeman-Doppler imaging and rotational modulation observations,

  12. The Asymmetric Polar Field Reversal - Long Term Observations from WSO

    NASA Astrophysics Data System (ADS)

    Hoeksema, J. T.

    2012-12-01

    The Sun's polar field above 55 degrees in the northern hemisphere is reversing and the southern field may be beginning to weaken. This asymmetry is not unusual and is related to the poleward transport of flux that emerged in the active region bands earlier in the cycle. In the declining phase of Cycle 23 the poles were fairly equal, but the northern field began to decay in early 2009. Prior cycles have behaved differently, as observed by the Wilcox Solar Observatory and elsewhere.

  13. Low frequency radio observations of coronal magnetic field

    NASA Astrophysics Data System (ADS)

    Ramesh, R.; Kathiravan, C.

    2012-07-01

    Magnetic fields play an important role in the dynamics as well as the formation of the structures in the solar corona. Despite its fundamental importance, only a few direct measurements of the coronal magnetic field are available. The existing direct estimates using optical/infrared and radio emissions are limited to the inner corona, i.e., r < 1.2 R , where R is the radius of the Sun. In the outer corona beyond r > 3 R , Faraday rotation observations are used to derive the magnetic field. But due to lack of observational techniques, measurements in the range 1.2 R < r > 3 R (middle corona) are not available until now. As the photosphere, chromosphere, and corona are coupled by the solar magnetic field, the magnetic field strength at these distances is generally obtained by mathematical extrapolation of the observed line-of-sight component of the photospheric magnetic field assuming a potential or force-free model. The Indian Institute of Astrophysics has recently commissioned a radio polarimeter (based on inteferometer techniques) for dedicated obervations of the polarized radio emission from the solar corona. The frequency range of observation is 120-30 MHz which corresponds to a radial distance range of about 1.2-1.8 R. Estimates of weak magnetic fields in the 'undisturbed' Sun (non-flaring sunspot active regions, coronal streamers, etc.) obtained from observations with the above instrument will be presented.

  14. The wireless networking system of Earthquake precursor mobile field observation

    NASA Astrophysics Data System (ADS)

    Wang, C.; Teng, Y.; Wang, X.; Fan, X.; Wang, X.

    2012-12-01

    The mobile field observation network could be real-time, reliably record and transmit large amounts of data, strengthen the physical signal observations in specific regions and specific period, it can improve the monitoring capacity and abnormal tracking capability. According to the features of scatter everywhere, a large number of current earthquake precursor observation measuring points, networking technology is based on wireless broadband accessing McWILL system, the communication system of earthquake precursor mobile field observation would real-time, reliably transmit large amounts of data to the monitoring center from measuring points through the connection about equipment and wireless accessing system, broadband wireless access system and precursor mobile observation management center system, thereby implementing remote instrument monitoring and data transmition. At present, the earthquake precursor field mobile observation network technology has been applied to fluxgate magnetometer array geomagnetic observations of Tianzhu, Xichang,and Xinjiang, it can be real-time monitoring the working status of the observational instruments of large area laid after the last two or three years, large scale field operation. Therefore, it can get geomagnetic field data of the local refinement regions and provide high-quality observational data for impending earthquake tracking forecast. Although, wireless networking technology is very suitable for mobile field observation with the features of simple, flexible networking etc, it also has the phenomenon of packet loss etc when transmitting a large number of observational data due to the wireless relatively weak signal and narrow bandwidth. In view of high sampling rate instruments, this project uses data compression and effectively solves the problem of data transmission packet loss; Control commands, status data and observational data transmission use different priorities and means, which control the packet loss rate within

  15. Observational testing of magnetospheric magnetic field models at geosynchronous orbit

    SciTech Connect

    Weiss, L.A.; Thomsen, M.F.; Reeves, G.D.; McComas, D.J.

    1996-09-01

    Empirical mode which estimate the magnetic field direction and magnitude at any point within the magnetosphere under a variety of conditions play an important role in space weather forecasting. We report here on a number of different studies aimed at quantitatively evaluating these models, and in particular the Tsyganenko T89a model. The models are evaluated in two basic ways: (1) by comparing the range of magnetic field tilt angles observed at geosynchronous orbit with the ranges predicted for the same locations by the models; and (2) by comparing the observed magnetic field mapping between the ionosphere and geosynchronous orbit (using two-satellite magnetic field conjunctions) with the model predictions at the same locations. We find that while the T89a model predicts reasonably well the basic variation in tilt angle with local time and permits a range of field inclinations adequate to encompass the majority of observed angles on the dawn, dusk, and night sides, it is unable to reproduce the range of inclinations on the dayside. The model also predicts a smaller magnetic latitude range of geosynchronous field line footpoints than the observed two-satellite mapping indicate. Together, these results suggest that the next generation of field models should allow a greater range of stretching, especially in local time sectors away from midnight. It is important to note, however, that any increased range should encompass less-stretched configurations: although there are certainly cases where the models are not sufficiently stretched, we find that on average all magnetic field models tested, including T89a, are too stretched. Finally, in investigating how well the observed degree of field stretch was ordered by various magnetospheric indices, we find that the tilt of the field at geosynchronous orbit is a promising candidate for the incorporation into future models.

  16. Direct observations of field-induced assemblies in magnetite ferrofluids

    SciTech Connect

    Mousavi, N. S. Susan; Khapli, Sachin D.; Kumar, Sunil

    2015-03-14

    Evolution of microstructures in magnetite-based ferrofluids with weak dipolar moments (particle size ≤ 10 nm) is studied with an emphasis on examining the effects of particle concentration (ϕ) and magnetic field strength (H) on the structures. Nanoparticles are dispersed in water at three different concentrations, ϕ = 0.15%, 0.48%, and 0.59% (w/v) [g/ml%] and exposed to uniform magnetic fields in the range of H = 0.05–0.42 T. Cryogenic transmission electron microscopy is employed to provide in-situ observations of the field-induced assemblies in such systems. As the magnetic field increases, the Brownian colloids are observed to form randomly distributed chains aligned in the field direction, followed by head-to-tail chain aggregation and then lateral aggregation of chains termed as zippering. By increasing the field in low concentration samples, the number of chains increases, though their length does not change dramatically. Increasing concentration increases the length of the linear particle assemblies in the presence of a fixed external magnetic field. Thickening of the chains due to zippering is observed at relatively high fields. Through a systematic variation of concentration and magnetic field strength, this study shows that both magnetic field strength and change in concentration can strongly influence formation of microstructures even in weak dipolar systems. Additionally, the results of two commonly used support films on electron microscopy grids, continuous carbon and holey carbon films, are compared. Holey carbon film allows us to create local regions of high concentrations that further assist the development of field-induced assemblies. The experimental observations provide a validation of the zippering effect and can be utilized in the development of models for thermophysical properties such as thermal conductivity.

  17. Direct observations of field-induced assemblies in magnetite ferrofluids

    PubMed Central

    Mousavi, N. S. Susan

    2015-01-01

    Evolution of microstructures in magnetite-based ferrofluids with weak dipolar moments (particle size ≤ 10 nm) is studied with an emphasis on examining the effects of particle concentration (ϕ) and magnetic field strength (H) on the structures. Nanoparticles are dispersed in water at three different concentrations, ϕ = 0.15%, 0.48%, and 0.59% (w/v) [g/ml%] and exposed to uniform magnetic fields in the range of H = 0.05–0.42 T. Cryogenic transmission electron microscopy is employed to provide in-situ observations of the field-induced assemblies in such systems. As the magnetic field increases, the Brownian colloids are observed to form randomly distributed chains aligned in the field direction, followed by head-to-tail chain aggregation and then lateral aggregation of chains termed as zippering. By increasing the field in low concentration samples, the number of chains increases, though their length does not change dramatically. Increasing concentration increases the length of the linear particle assemblies in the presence of a fixed external magnetic field. Thickening of the chains due to zippering is observed at relatively high fields. Through a systematic variation of concentration and magnetic field strength, this study shows that both magnetic field strength and change in concentration can strongly influence formation of microstructures even in weak dipolar systems. Additionally, the results of two commonly used support films on electron microscopy grids, continuous carbon and holey carbon films, are compared. Holey carbon film allows us to create local regions of high concentrations that further assist the development of field-induced assemblies. The experimental observations provide a validation of the zippering effect and can be utilized in the development of models for thermophysical properties such as thermal conductivity. PMID:25829566

  18. Direct observations of field-induced assemblies in magnetite ferrofluids

    NASA Astrophysics Data System (ADS)

    Mousavi, N. S. Susan; Khapli, Sachin D.; Kumar, Sunil

    2015-03-01

    Evolution of microstructures in magnetite-based ferrofluids with weak dipolar moments (particle size ≤ 10 nm) is studied with an emphasis on examining the effects of particle concentration (ϕ) and magnetic field strength (H) on the structures. Nanoparticles are dispersed in water at three different concentrations, ϕ = 0.15%, 0.48%, and 0.59% (w/v) [g/ml%] and exposed to uniform magnetic fields in the range of H = 0.05-0.42 T. Cryogenic transmission electron microscopy is employed to provide in-situ observations of the field-induced assemblies in such systems. As the magnetic field increases, the Brownian colloids are observed to form randomly distributed chains aligned in the field direction, followed by head-to-tail chain aggregation and then lateral aggregation of chains termed as zippering. By increasing the field in low concentration samples, the number of chains increases, though their length does not change dramatically. Increasing concentration increases the length of the linear particle assemblies in the presence of a fixed external magnetic field. Thickening of the chains due to zippering is observed at relatively high fields. Through a systematic variation of concentration and magnetic field strength, this study shows that both magnetic field strength and change in concentration can strongly influence formation of microstructures even in weak dipolar systems. Additionally, the results of two commonly used support films on electron microscopy grids, continuous carbon and holey carbon films, are compared. Holey carbon film allows us to create local regions of high concentrations that further assist the development of field-induced assemblies. The experimental observations provide a validation of the zippering effect and can be utilized in the development of models for thermophysical properties such as thermal conductivity.

  19. Injun 5 observations of magnetospheric electric fields and plasma convection

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.

    1971-01-01

    Recent measurements of magnetospheric electric fields with the satellite Injun 5 have provided a comprehensive global survey of plasma convection at low altitudes in the magnetosphere. A persistent feature of these electric field observations is the occurrence of an abrupt reversal in the convection electric field at auroral zone latitudes. The plasma convection velocities associated with these reversals are generally directed east-west, away from the sun on the poleward side of the reversal, and toward the sun on the equatorward side of the reversal. Convection velocities over the polar cap region are normally less than those observed near the reversal region. The electric field reversal is observed to be coincident with the trapping boundary for electrons with energies E greater than 45 keV.

  20. The magnetic field of Saturn - Pioneer 11 observations

    NASA Technical Reports Server (NTRS)

    Acuna, M. H.; Ness, N. F.

    1980-01-01

    The Pioneer 11 high-field fluxgate magnetometer experiment consists of two biaxial fluxgate sensors assemblies and an associated electronics system that is designed to measure fields up to 10 gauss along three orthogonal axes. It was used to provide a higher upper range than that provided by the helium vector magnetometer whose maximum measureable field is only 1.4 gauss. Observations of the intrinsic magnetic field of Saturn measured by the high-field fluxgate magnetometer were found to be much weaker than expected. An analysis of preliminary data combined with the preliminary trajectory yield a model for the main planetary field which is a simple centered dipole. It was determined that the polarity of Saturn is opposite that of Earth, and that the tilt is small, within 2 deg plus or minus 1 deg.

  1. Vector magnetic field observations of flux tube emergence

    NASA Astrophysics Data System (ADS)

    Schmieder, B.; Aulanier, G.; Pariat, E.; Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N.

    2002-10-01

    With Flare Genesis Experiment (FGE), a balloon borne Observatory high spatial and temporal resolution vector magnetograms have been obtained in an emerging active region. The comparison of the observations (FGE and TRACE) with a linear force-free field analysis of the region shows where the region is non-force-free. An analysis of the magnetic topology furnishes insights into the existence of "bald patches" regions (BPs are regions where the vector field is tangential to the boundary (photosphere) along an inversion line). Magnetic reconnection is possible and local heating of the chromopshere is predicted near the BPs. Ellerman bombs (EBs) were found to coincide with few BPs computed from a linear force-free extrapolation of the observed longitudinal field. But when the actual observations of transverse fields were used to identify BPs, then the correspondence with EB positions improved significantly. We conclude that linear force-free extrapolations must be done with the true observed vertical fields, which require the measurement of the three components of the magnetic field.

  2. Cosmic microwave background observables of small field models of inflation

    SciTech Connect

    Ben-Dayan, Ido; Brustein, Ram E-mail: ramyb@bgu.ac.il

    2010-09-01

    We construct a class of single small field models of inflation that can predict, contrary to popular wisdom, an observable gravitational wave signal in the cosmic microwave background anisotropies. The spectral index, its running, the tensor to scalar ratio and the number of e-folds can cover all the parameter space currently allowed by cosmological observations. A unique feature of models in this class is their ability to predict a negative spectral index running in accordance with recent cosmic microwave background observations. We discuss the new class of models from an effective field theory perspective and show that if the dimensionless trilinear coupling is small, as required for consistency, then the observed spectral index running implies a high scale of inflation and hence an observable gravitational wave signal. All the models share a distinct prediction of higher power at smaller scales, making them easy targets for detection.

  3. Magnetic Fields Around the Heliosphere: Theory vs Observations

    NASA Astrophysics Data System (ADS)

    Pogorelov, Nikolai

    2016-07-01

    Voyager in situ measurements of the magnetic field around the heliosphere are the source of invaluable information about the interface between the solar wind (SW) and local interstellar medium (LISM). On the other hand, they are quite challenging for theoretical analysis unless accompanied by remote observations of neutral atoms the Interstellar Boundary Explorer (IBEX) and Ulysses missions. Of particular interest is the fine structure of the heliopause due to its instability and possible magnetic reconnection. Both phenomena may have contributed to the remarkable changes in the galactic and anomalous cosmic ray fluxes observed by Voyager 1 within a one-month period of 2012 after which the spacecraft penetrated into the LISM. Draping of the heliopause by the interstellar magnetic field affects the position of the bright ribbon of enhanced ENA flux observed by IBEX on the celestial sphere and 2-3 kHz radio emission caused by shock propagation through the outer heliosheath observed by Voyager 1. Interstellar magnetic field determines the structure of the bow wave in front of the heliopause. Moreover, magnetic fields define the orientation and shape of the heliotail, the features of which have been observed by IBEX. Recent numerical simulations show that the details of the large-scale interstellar magnetic field modification caused by the presence of the heliotail may be the source of the observed 1-10 TeV cosmic ray anisotropy studied in detail in numerous air shower measurements around the world. In this paper, an overview will be given of the recent theoretical and simulations results describing the magnetic field distribution around the heliosphere. The objective of the talk is to connect observational and theoretical results, and outline challenges that are going to inspire the heliospheric community in the coming years.

  4. Magnetic Field Observations near Mercury: Preliminary Results from Mariner 10.

    PubMed

    Ness, N F; Behannon, K W; Lepping, R P; Whang, Y C; Schatten, K H

    1974-07-12

    Results are presented from a preliminary analysis of data obtained near Mercury on 29 March 1974 by the NASA-GSFC magnetic field experiment on Mariner 10. Rather unexpectedly, a very well-developed, detached bow shock wave, which develops as the super-Alfvénic solar wind interacts with the planet, has been observed. In addition, a magnetosphere-like region, with maximum field strength of 98 gammas at closest approach (704 kilometers altitude), has been observed, contained within boundaries similar to the terrestrial magnetopause. The obstacle deflecting the solar wind flow is global in size, but the origin of the enhanced magnetic field has not yet been uniquely established. The field may be intrinsic to the planet and distorted by interaction with the solar wind. It may also be associated with a complex induction process whereby the planetary interior-atmosphere-ionosphere interacts with the solar wind flow to generate the observed field by a dynamo action. The complete body of data favors the preliminary conclusion that Mercury has an intrinsic magnetic field. If this is correct, it represents a major scientific discovery in planetary magnetism and will have considerable impact on studies of the origin of the solar system. PMID:17810508

  5. Evolution of the dipole geomagnetic field. Observations and models

    NASA Astrophysics Data System (ADS)

    Reshetnyak, M. Yu.; Pavlov, V. E.

    2016-01-01

    The works on paleomagnetic observations of the dipole geomagnetic field, its variations, and reversals in the last 3.5 billion years have been reviewed. It was noted that characteristic field variations are related to the evolution of the convection processes in the liquid core due to the effect of magnetic convection and solid core growth. Works on the geochemistry and energy budget of the Earth's core, the effect of the solid core on convection and the generation of the magnetic field, dynamo models are also considered. We consider how core growth affects the magnetic dipole generation and variations, as well as the possibility of magnetic field generation up to the appearance of the solid core. We also pay attention to the fact that not only the magnetic field but also its configuration and time variations, which are caused by the convection evolution in the core on geological timescales, are important factors for the biosphere.

  6. Training field workers to observe hygiene-related behaviour.

    PubMed

    Oladepo, O; Oyejide, C O; Oke, E A

    1991-01-01

    A study is reported from Nigeria on the training of field workers in the making of structured observations on hygiene-related behaviour with a view to improving the control of diarrhoeal diseases. The programme led to a high degree of consistency in the perception and description of such behaviour by the participants. PMID:1821119

  7. Observations of ionospheric electric fields above atmospheric weather systems

    SciTech Connect

    Farrell, W.M.; Aggson, T.L.; Rodgers, E.B.

    1994-10-01

    The authors report on the observations of a number of quasi-dc electric field events associated with large-scale atmospheric weather formations. The observations were made by the electric field experiment onboard the San Marco D satellite, operational in an equatorial orbit from May to December 1988. Several theoretical studies suggest that electric fields generated by thunderstorms are present at high altitudes in the ionosphere. In spite of such favorable predictions, weather-related events are not often observed since they are relatively weak. The authors report here on a set of likely E field candidates for atmosphere-ionosphere causality, these being observed over the Indonesian Basin, northern South America, and the west coast of Africa; all known sites of atmospheric activity. As they demonstrate, individual events can often be traced to specific active weather features. For example, a number of events were associated with spacecraft passages near Hurricane Joan in mid-October 1988. As a statistical set, the events appear to coincide with the most active regions of atmospheric weather. 31 refs., 11 figs., 1 tab.

  8. Screwworm ecology from field observations to satellite imagery

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Screwworm fly, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae), in its larval stage is a parasite of warm-blooded animals. Screwworm has been successfully eradicated from the United Sates and Central America using the sterile insect technique. Here we present how the field observations o...

  9. Implications of observing and writing field notes through different lenses

    PubMed Central

    Hellesø, Ragnhild; Melby, Line; Hauge, Solveig

    2015-01-01

    Background From a philosophy of science perspective, the literature has posited that different research approaches influence field studies. Studies addressing interdisciplinary research have focused on the challenges of organizing and running interdisciplinary teams, cultural differences between and within disciplines, and constraints in conducting interdisciplinary research. Studies exploring and discussing the process and outcome of transferring observations to notes from an interdisciplinary point of view are not identified. The aim of this paper is to explore the characteristics of field notes created by researchers representing different disciplines and experiences. Methods A case study using a modified dynamic observation method was employed. The analyses were initiated by a researcher who had not been involved in the data collection. The field notes were analyzed using three main steps. Results The structures of both researchers’ field notes were characterized by similarities in their descriptions, but the notes’ foci and analytical levels differed. Conclusion The findings contribute new insights concerning the execution of interdisciplinary observational studies. Our findings demonstrate that entering the field with different lenses produced richer and more varied data, providing a broader platform from which to discuss and interpret a study’s findings. From a theoretical point of view, the findings enable a more nuanced discussion and a conceptual elaboration regarding how observational approaches should be pursued in future studies. On a practical level, the findings show that even if the researchers agree on what the overall focus in the observations should be, differences can occur in both their focus and analytical level throughout the study. PMID:25914543

  10. ACS Flat Field Corrections from Observations of 47 Tucanae

    NASA Astrophysics Data System (ADS)

    Mack, J.; Bohlin, R. C.; Gilliland, R. L.; van der Marel, R.; Blakeslee, J. P.; de Marchi, G.

    2002-12-01

    The uniformity of the WFC and HRC detector response has been assessed using multiple dithered pointings of 47 Tucanae. By placing the same stars over different portions of the detector and measuring relative changes in brightness, low frequency spatial variations in the response of each detector have been measured. The original WFC and HRC laboratory flat fields produce photometric errors of 5 to 18 percent from corner-to-corner. The required low-order correction (L-flat) has been applied to the lab flats, and new flat fields have been delivered for use in the calibration pipeline. Initial results suggest the photometric response for a given star is now the same to 1 for any position in the field of view. As a further test, the improved flat fields are compared with observations of the bright earth at UV wavelengths (F330W) and with skyflats from ERO data at long wavelengths (F775W).

  11. Observations of magnetic field dipolarization during auroral substorm onset

    NASA Astrophysics Data System (ADS)

    Frank, L. A.; Paterson, W. R.; Sigwarth, J. B.; Kokubun, S.

    2000-07-01

    The dynamical behavior of plasmas and magnetic fields in the vicinity of the equatorial crossing of magnetic field lines threading the onset auroral arc is examined for two substorms on November 26, 1997. The locations of the initial brightenings of the auroral arcs were determined with the cameras for visible and far-ultraviolet wavelengths on board the Polar spacecraft. The equatorial positions of the field lines were in the range of radial distances of 8-12RE as computed with models of Earth's global magnetic field. The radial distance of the Geotail spacecraft was 14 RE at a position in the premidnight sector that was 2RE below the current sheet. This spacecraft was embedded in a low-β plasma that was located adjacent to the central hot plasma sheet. For the first substorm, with onset at 1310 UT, no substantial effect was observed in the plasmas and magnetic fields, although the Geotail spacecraft was located only about 2 hours in magnetic local time from the field lines threading the onset auroral arc. For the second substorm onset, at 1354 UT, the spacecraft was positioned within tens of minutes in local time of the position of the magnetic field lines threading the onset auroral arc. This fortuitous spacecraft position in the relatively quiescent plasma and magnetic fields adjacent to the central plasma sheet and within several Earth radii of the position of the onset mechanism allowed determination of the beginning time of the dipolarization of the magnetic fields. This time was simultaneous with the onset brightening of the auroral arc within the approximately 1-min time resolution of the auroral images. The simultaneity of the initial brightening of the auroral arc and of the initiation of the dipolarization of the magnetic field, presumably due to diversion of current from the equatorial current sheet to the ionosphere, provides an important guideline for global dynamical MHD models of Earth's magnetosphere.

  12. THE 2012 HUBBLE ULTRA DEEP FIELD (UDF12): OBSERVATIONAL OVERVIEW

    SciTech Connect

    Koekemoer, Anton M.; Ellis, Richard S.; Schenker, Matthew A.; McLure, Ross J.; Dunlop, James S.; Bowler, Rebecca A. A.; Rogers, Alexander B.; Curtis-Lake, Emma; Cirasuolo, Michele; Wild, V.; Targett, T.; Robertson, Brant E.; Schneider, Evan; Stark, Daniel P.; Ono, Yoshiaki; Ouchi, Masami; Charlot, Stephane; Furlanetto, Steven R.

    2013-11-01

    We present the 2012 Hubble Ultra Deep Field campaign (UDF12), a large 128 orbit Cycle 19 Hubble Space Telescope program aimed at extending previous Wide Field Camera 3 (WFC3)/IR observations of the UDF by quadrupling the exposure time in the F105W filter, imaging in an additional F140W filter, and extending the F160W exposure time by 50%, as well as adding an extremely deep parallel field with the Advanced Camera for Surveys (ACS) in the F814W filter with a total exposure time of 128 orbits. The principal scientific goal of this project is to determine whether galaxies reionized the universe; our observations are designed to provide a robust determination of the star formation density at z ∼> 8, improve measurements of the ultraviolet continuum slope at z ∼ 7-8, facilitate the construction of new samples of z ∼ 9-10 candidates, and enable the detection of sources up to z ∼ 12. For this project we committed to combining these and other WFC3/IR imaging observations of the UDF area into a single homogeneous dataset to provide the deepest near-infrared observations of the sky. In this paper we present the observational overview of the project and describe the procedures used in reducing the data as well as the final products that were produced. We present the details of several special procedures that we implemented to correct calibration issues in the data for both the WFC3/IR observations of the main UDF field and our deep 128 orbit ACS/WFC F814W parallel field image, including treatment for persistence, correction for time-variable sky backgrounds, and astrometric alignment to an accuracy of a few milliarcseconds. We release the full, combined mosaics comprising a single, unified set of mosaics of the UDF, providing the deepest near-infrared blank-field view of the universe currently achievable, reaching magnitudes as deep as AB ∼ 30 mag in the near-infrared, and yielding a legacy dataset on this field.

  13. Possible observation of the isotope effect during field evaporation

    NASA Astrophysics Data System (ADS)

    Golubev, O. L.; Blashenkov, N. M.

    2016-01-01

    The field evaporation of tungsten at high temperatures (T ~ 2000 K) has been studied using a magnetic mass spectrometer equipped with a field ion source. Only low-charge ions (W+2 and W+) have been observed in the course of evaporation for all tungsten isotopes. For singly charged ions only, the number of ions of the heaviest isotope, 186W+, was about one order of magnitude lower than that corresponding to the standard isotope ratio for natural tungsten. An explanation of this anomalous phenomenon is proposed.

  14. Recent Geodynamo Simulations and Observations of the Geomagnetic Field

    NASA Astrophysics Data System (ADS)

    Kono, Masaru; Roberts, Paul H.

    2002-12-01

    In 1995, two groups [, 1995; , 1995a, 1995b] reported results of numerical integrations of fully three-dimensional, fully nonlinear dynamos. Their papers were precursors of a stream of such models that have focused particularly on the geodynamo. They provide us, in unprecedented detail, with spectacular realizations of interesting geomagnetic field behaviors, such as secular variation and even polarity reversals. The proliferation of models has, however, created some confusion and apparently conflicting results. This can be partly attributed to the different ways in which different groups have modeled the core, normalized their equations, defined their dimensionless parameters, chosen their boundary conditions, and selected their energy sources. This has made it difficult to compare the results of different simulations directly. In this paper, we first try, as far as possible, to overcome this difficulty, so that all reported results can be compared on common ground. We then review the results, emphasizing three major topics: (1) onset and evolution of convection, (2) character of the magnetic field generated, and (3) comparison with the observed geomagnetic field. Although there are large differences in the way that the simulations are defined, the magnetic fields that they generate have some surprising similarities. The fields are dominated by the axial dipole. In some models they are most strongly generated in shear layers near the upper and lower boundaries and near the tangent cylinder, an imaginary surface touching the inner core on its equator. Convection rolls occur within which a type of the α effect distorts the toroidal field lines to create poloidal magnetic field. Some features of the models are found to strongly affect the fields that they produce. In particular, the boundary conditions defining the energy flow (e.g., an inhomogeneous heat flux or distribution of buoyancy sources) are very influential and have been extensively studied. They change

  15. Observations of magnetic fields on solar-type stars

    NASA Technical Reports Server (NTRS)

    Marcy, G. W.

    1982-01-01

    Magnetic-field observations were carried out for 29 G and K main-sequence stars. The area covering-factors of magnetic regions tends to be greater in the K dwarfs than in the G dwarfs. However, no spectral-type dependence is found for the field strengths, contrary to predictions that pressure equilibrium with the ambient photospheric gas pressure would determine the surface field strengths. Coronal soft X-ray fluxes from the G and K dwarfs correlate well with the fraction of the stellar surface covered by magnetic regions. The dependence of coronal soft X-ray fluxes on photospheric field strengths is consistent with Stein's predicted generation-rates for Alfven waves. These dependences are inconsistent with the one dynamo model for which a specific prediction is offered. Finally, time variability of magnetic fields is seen on the two active stars that have been extensively monitored. Significant changes in magnetic fields are seen to occur on timescales as short as one day.

  16. Observation of Field-Emission Dependence on Stored Energy

    NASA Astrophysics Data System (ADS)

    Shao, Jiahang; Antipov, Sergey P.; Baryshev, Sergey V.; Chen, Huaibi; Conde, Manoel; Doran, Darrell S.; Gai, Wei; Jing, Chunguang; Liu, Wanming; Power, John; Qiu, Jiaqi; Shi, Jiaru; Wang, Dan; Wang, Faya; Whiteford, Charles E.; Wisniewski, Eric; Xiao, Liling

    2015-12-01

    Field emission from a solid metal surface has been continuously studied for a century over macroscopic to atomic scales. It is general knowledge that, other than the surface properties, the emitted current is governed solely by the applied electric field. A pin cathode has been used to study the dependence of field emission on stored energy in an L -band rf gun. The stored energy was changed by adjusting the axial position (distance between the cathode base and the gun back surface) of the cathode while the applied electric field on the cathode tip is kept constant. A very strong correlation of the field-emission current with the stored energy has been observed. While eliminating all possible interfering sources, an enhancement of the current by a factor of 5 was obtained as the stored energy was increased by a factor of 3. It implies that under certain circumstances a localized field emission may be significantly altered by the global parameters in a system.

  17. Observation of Field-Emission Dependence on Stored Energy.

    PubMed

    Shao, Jiahang; Antipov, Sergey P; Baryshev, Sergey V; Chen, Huaibi; Conde, Manoel; Doran, Darrell S; Gai, Wei; Jing, Chunguang; Liu, Wanming; Power, John; Qiu, Jiaqi; Shi, Jiaru; Wang, Dan; Wang, Faya; Whiteford, Charles E; Wisniewski, Eric; Xiao, Liling

    2015-12-31

    Field emission from a solid metal surface has been continuously studied for a century over macroscopic to atomic scales. It is general knowledge that, other than the surface properties, the emitted current is governed solely by the applied electric field. A pin cathode has been used to study the dependence of field emission on stored energy in an L-band rf gun. The stored energy was changed by adjusting the axial position (distance between the cathode base and the gun back surface) of the cathode while the applied electric field on the cathode tip is kept constant. A very strong correlation of the field-emission current with the stored energy has been observed. While eliminating all possible interfering sources, an enhancement of the current by a factor of 5 was obtained as the stored energy was increased by a factor of 3. It implies that under certain circumstances a localized field emission may be significantly altered by the global parameters in a system. PMID:26764996

  18. An improved proton magnetometer for Earth's magnetic field observation

    NASA Astrophysics Data System (ADS)

    Xiao, Chengyu; Zhang, Shuang; Guo, Xin; Fu, Haoyang

    2015-09-01

    As a precision instrument to measure the earth magnetic field, proton magnetometer is widely used in different fields such as geological survey, buried objects detection and earth field variations. Due to poor signal to noise ratio (SNR) of the system, proton magnetometer suffers from low sensitivity which directly affects the performance. In order to increase the sensitivity, we present an improved proton magnetometer. First, the effect of matching resistance on Q value is discussed to enhance SNR, and high matching resistance has been chosen to improve the Q value of the resonant circuit. Second, noise induced by pre-amplifier is investigated in order to obtain low noise signal, and we adopt the JFET with noise figure less than 0.5dB as the pre-amplifier. Third, by using band-pass filter, low-noise output signal is obtained. Fourth, the method of period measurement based on CPLD is employed to measure frequency of the square wave shaped from the output sinusoidal signal. High precision temperature compensate crystal oscillator (TCXO) has been used to improve the frequency measurement accuracy. Last, experimental data is obtained through field measurements. By calculating the standard deviation, the sensitivity of the improved proton magnetometer is 0.15nT for Earth's magnetic field observation. Experimental results show that the new magnetometer is sensitive to earth field measurement.

  19. Probing the Earth's core with magnetic field observations from Swarm

    NASA Astrophysics Data System (ADS)

    Finlay, Christopher; Olsen, Nils; Kotsiaros, Stavros; Gillet, Nicolas; Tøffner-Clausen, Lars

    2016-07-01

    By far the largest part of the Earth's magnetic field is generated by motions taking place within our planet's liquid metal outer core. Variations of this core-generated field thus provide a unique means of probing the dynamics taking place in the deepest reaches of the Earth. In this contribution we present a new high resolution model of the core-generated magnetic field, and its recent time changes, derived from a dataset that includes more two years of observations from the Swarm mission. Resulting inferences regarding the underlying core flow, its dynamics, and the nature of the geodynamo process will be discussed. The CHAOS-6 geomagnetic field model, covering the interval 1999-2016, is derived from magnetic data collected by the three Swarm missions, as well as the earlier CHAMP and Oersted satellites, and monthly means data collected from 160 ground observatories. Advantage is taken of the constellation aspect of the Swarm mission by ingesting both scalar and vector field differences along-track and across track between the lower pair of Swarm satellites. The internal part of the model consists of a spherical harmonic (SH) expansion, time-dependent for degrees 20 and below. The model coefficients are estimated using a regularized, iteratively reweighted, least squares scheme involving Huber weights. At Earth's surface, CHAOS-6 shows evidence for positive acceleration of the field intensity in 2015 over a broad area around longitude 90deg E that is also seen at ground observatories such as Novosibirsk. At the core surface, we are able to map the secular variation (linear trend in the magnetic field) up to SH degree 16. The radial field acceleration at the core surface in 2015 is found be largest at low latitudes under the India-South East Asia region and under the region of northern South America, as well as at high northern latitudes under Alaska and Siberia. Surprisingly, there is also evidence for some acceleration in the central Pacific region, for example

  20. Mapping the Frontier Fields with Chandra X-ray Observations

    NASA Astrophysics Data System (ADS)

    Jones, Christine

    2015-08-01

    Chandra has observed both the clusters and the parallel fields in four of the Frontier Fields. These observations allow us to dramatically improve our understanding of cluster mergers through the detailed mapping of the hot cluster gas compared with high resolution mass maps and, by mapping the gas temperature and pressure, identify merger shocks. A comparison of the lensing maps and the Chandra images allows us to identify subclusters and determine if these have been stripped of their hot gas. In addition the HST images show unusual galaxies (e.g. jellyfish) whose morphologies may have resulted from interactions with the hot intracluster medium. Finally, we will report on any close pairs of AGN, which are candidates for gravitationally lensed QSOs.

  1. Plasma and field observations of a Pc 5 wave event

    NASA Technical Reports Server (NTRS)

    Waite, J. H.; Gallagher, D. L.; Chappell, C. R.; Chandler, M. O.; Olsen, R. C.; Comfort, R. H.; Johnson, J. F. E.; Peterson, W. K.; Weimer, D.; Shawhan, S. D.

    1986-01-01

    The particle detector and electric field data collected by the Dynamo Explorer 1 on the Pc 5 wave event encounter on July 14, 1982 are presented, yielding a nearly complete picture of the event. The overall structure of the Pc 5 seems to order the event into two distinct halves, suggesting a temporal or spatial variation of the micropulsation. Thermal plasma measurements showed that the dominant ion throughout both lobes was H(+). Significant quantities of He(+), O(+), N(+), and O(2+) were also observed to be present and rotating together in a plane normal to the magnetic field direction, due to the Pc5 E x B drift. The plasma parameters determined for the two lobes were used in theoretical calculations to predict the period of the observed resonance.

  2. Magnetospheric observation of large sub-auroral electric fields

    NASA Technical Reports Server (NTRS)

    Maynard, N. C.; Aggson, T. L.; Heppner, J. P.

    1980-01-01

    An example of large subauroral poleward electric fields similar to those observed on OGO-6, S3-2 and AE-C (SAID) has been found in the magnetosphere near L = 4 and 2300 MLT using ISEE-1 electric field data. The event is located adjacent to and outside the plasmapause and occurs 1 1/2 hours into a substorm. The event is accompaned by a significant penetration of the convection electric field inside the plasmasphere. Data from similar regions on the next orbit occurring near the beginning of a substorm did not exhibit these effects. Recent theoretical models predict SAID to occur in the trough regions, where substorm dynamics force currents to flow in regions of low conductivity. These models provide a first-order interpretation of this phenomena; however, the overal picture is more complex.

  3. Venus Express observations of magnetic field fluctuations in the magnetosheath

    NASA Astrophysics Data System (ADS)

    Du, J.; Wang, C.; Zhang, T. L.; Volwerk, M.; Delva, M.; Baumjohann, W.

    2008-12-01

    Magnetic field fluctuations within a planetary magnetosheath play an important role in the solar wind interaction with the planet, since they can reconfigure the plasma flow and the magnetic field and transfer energy from the bow shock to the lower boundary. Many studies have been presented on the fluctuations in the terrestrial magnetosheath; however, hardly any studies have so far been carried out for Venusian magnetosheath fluctuations, except for Luhmann et al. [1983] and Vörös et al. [2008] who performed some case studies on the magnetosheath fluctuations at Venus. It was shown that the fluctuations are probably convected from the vicinity of the quasi-parallel bow shock along the streamlines. Based on the Venus Express observations in 2006 and 2007, we investigate the spatial distributions of magnetic field fluctuations in the Venus magnetosheath statistically.

  4. MESSENGER observations of induced magnetic fields in Mercury's core

    NASA Astrophysics Data System (ADS)

    Johnson, Catherine L.; Philpott, Lydia C.; Anderson, Brian J.; Korth, Haje; Hauck, Steven A.; Heyner, Daniel; Phillips, Roger J.; Winslow, Reka M.; Solomon, Sean C.

    2016-03-01

    Orbital data from the Magnetometer on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft allow investigation of magnetic fields induced at the top of Mercury's core by time-varying magnetospheric fields. We used 15 Mercury years of observations of the magnetopause position as well as the magnetic field inside the magnetosphere to establish the presence and magnitude of an annual induction signal. Our results indicate an annual change in the internal axial dipole term, g10, of 7.5 to 9.5 nT. For negligible mantle conductivity, the average annual induction signal provides an estimate of Mercury's core radius to within ±90 km, independent of geodetic results. Larger induction signals during extreme events are expected but are challenging to identify because of reconnection-driven erosion. Our results indicate that the magnetopause reaches the dayside planetary surface 1.5-4% of the time.

  5. The magnetic field of Mercury. [Mariner 10 observations

    NASA Technical Reports Server (NTRS)

    Ness, N. F.

    1979-01-01

    Data from Mariner 10 observations of Mercury indicate that there exists an intrinsic magnetic field of the planet, sufficiently strong at present to deflect the solar wind flow around the planet and to form a detached bow shock wave in the super Alfvenic solar wind. Four methods used to analyze the magnetic field data and derive quantitative values for the description of the planetary field include (1) comparison of bow shock and magnetopause relative positions at Mercury to those at Earth; (2) direct spherical harmonic analysis of the data; (3) modeling of the magnetosphere by an image dipole and infinite 2-D current sheet in addition to the planetary field; and (4) scaling of a mathematical model for the terrestrial magnetosphere. The results obtained yield dipole moments ranging from 2.4 to 5.1x10 to the 22d power, with the lower values associated cw cm with certain models using partial quadrupole and octupole terms to improve the least squares fitting of models to observations.

  6. Net field-aligned currents observed by Triad

    NASA Technical Reports Server (NTRS)

    Sugiura, M.; Potemra, T. A.

    1975-01-01

    From the Triad magnetometer observation of a step-like level shift in the east-west component of the magnetic field at 800 km altitude, the existence of a net current flowing into or away from the ionosphere in a current layer was inferred. The current direction is toward the ionosphere on the morning side and away from it on the afternoon side. The field aligned currents observed by Triad are considered as being an important element in the electro-dynamical coupling between the distant magnetosphere and the ionosphere. The current density integrated over the thickness of the layer increases with increasing magnetic activity, but the relation between the current density and Kp in individual cases is not a simple linear relation. An extrapolation of the statistical relation to Kp = 0 indicates existence of a sheet current of order 0.1 amp/m even at extremely quiet times. During periods of higher magnetic activity an integrated current of approximately 1 amp/m and average current density of order 0.000001 amp/sq m are observed. The location and the latitudinal width of the field aligned current layer carrying the net current very roughly agree with those of the region of high electron intensities in the trapping boundary.

  7. Magnetic fields in star-forming regions - Observations

    NASA Technical Reports Server (NTRS)

    Heiles, Carl; Goodman, Alyssa A.; Mckee, Christopher F.; Zweibel, Ellen G.

    1993-01-01

    We review the observational aspects of magnetic fields in dense, star-forming regions. First we discuss ways to observe the field. These include direct methods, which consist of the measurement of both linear and circular polarization of spectral line and continuum radiation; and indirect methods, consisting of the angular distribution of H2O masers on the sky and the measurement of ambipolar diffusion. Next we discuss selected observational results, focusing on detailed discussions of a small number of points rather than a generalized discussion that covers the waterfront. We discuss the Orion/BN-KL region in detail, both on the small and large scales. Next we discuss the derivation of the complete magnetic vector, including both the systematic and fluctuating component, from a large sample of Zeeman and linear polarization measurements for the L204 dark cloud. We examine the virial theorem as it applies to dark clouds in general and one dark cloud, Barnard 1, in particular. We critically discuss the numerous claims for alignment of cloud structural features with the plane-of-the-sky component of the magnetic field, and find that many of these have not been definitively established.

  8. Model Jerks: Insights from Observations and Synthetic Fields

    NASA Astrophysics Data System (ADS)

    Brown, William; Mound, Jonathan; Livermore, Philip; Gillet, Nicolas

    2015-04-01

    The geomagnetic field is generated by the constant motion of the fluid outer core and varies on timescales from months to millions of years. Geomagnetic jerks are rapid changes in the secular variation of Earth's magnetic field, attributed primarily to changing flows near the surface of the outer core. Various generation mechanisms have been suggested for these rapid changes but none have conclusively explained the phenomena. Jerks can be seen in magnetic observatory records over the last 170 years and in satellite data of the last 15 years. This data coverage, spatially limited and/or temporally restricted, makes it difficult to interpret the true character of jerks at the surface or their origins in the core. This leads us to investigate what further insight we can gain from synthetic magnetic fields such as those which are described by modelling stochastic processes. Such fields are not restricted by the temporal smoothing of most magnetic field models and can better represent rapid variations such as jerks. We compare the characteristics of the synthetic fields with those of observatory and satellite data and hence, finding great similarity, study the presence of jerks in stochastic synthetic fields. Synthetic jerks are seen which resemble observed jerks, occurring frequently with regional periodic variations in amplitudes. These synthetic jerks occur without related features in the large scale secular acceleration power at the core-mantle boundary. The flexible spatial and temporal sampling of the models creates a means of validating the robustness of observed features in the real field, which suffer from limited sampling. Results suggest that the distribution of magnetic observatories is sufficient to accurately recover the large scale features of jerks. As such comparisons between jerks seen in observatory and satellite data may be drawn. We further investigate the spectral properties of jerks in the synthetic fields using spherical harmonic analysis with a

  9. Cosmological observables in multi-field inflation with a non-flat field space

    SciTech Connect

    Gao, Xin; Li, Tianjun; Shukla, Pramod E-mail: tli@itp.ac.cn

    2014-10-01

    Using δN formalism, in the context of a generic multi-field inflation driven on a non-flat field space background, we revisit the analytic expressions of the various cosmological observables such as scalar/tensor power spectra, scalar/tensor spectral tilts, non-Gaussianity parameters, tensor-to-scalar ratio, and the various runnings of these observables. In our backward formalism approach, the subsequent expressions of observables automatically include the terms beyond the leading order slow-roll expansion correcting many of the expression at subleading order. To connect our analysis properly with the earlier results, we rederive the (well) known (single field) expressions in the limiting cases of our generic formulae. Further, in the light of PLANCK results, we examine for the compatibility of the consistency relations within the slow-roll regime of a two-field roulette poly-instanton inflation realized in the context of large volume scenarios.

  10. Evolution of Auroral Electric Fields Observed By Cluster

    NASA Astrophysics Data System (ADS)

    Marklund, G.; Cluster Auroral Team

    Cluster observations on nightside auroral field lines are used to study the existence and temporal evolution of quasi-static electric field structures on time scales of min- utes. Results are presented for two events characterized by intense and narrow-scale divergent electric fields. These were encountered at the boundary between the Cen- tral Plasma Sheet and the Plasma Sheet Boundary Layer associated with a large-scale plasma density gradient and a downward field-aligned current. The structures main- tain their bipolar shape but increase in magnitude and width between the crossings by the four spacecraft, each separated by a few minutes in a plane perpendicular to the magnetic field. The perpendicular electric potential calculated for the first event in- creased for about 200 s, following closely the increase in the characteristic energy of the upgoing electron beam. At the time of the last satellite crossing the structure had faded, the energy of the beam was much reduced, and the downward current, main- taining a constant total value throughout the Cluster crossings, was distributed over a much wider region than initially. In this way access was given to a wide collection area of return current electrons. For the other event, the electric field increase was accompanied by a deepening of a density cavity superposed on a larger scale density gradient and a downward field-aligned current that remained roughly constant during the crossings. The divergent structures are likely to represent the high-altitude exten- sion of quasi-static positive potential structures developing on a time scale of several hundred seconds which is comparable to the evacuation time for the return current electrons in the E- and lower F-region. The evolving potential structure and associated hole formation represent a growing load in the return current leg of the auroral current circuit with possible direct impact on the aurora.

  11. Observations of field-aligned density microstructure near the Sun

    NASA Astrophysics Data System (ADS)

    Grall, R. R.; Coles, W. A.; Spangler, S. R.; Sakurai, T.; Harmon, J. K.

    1997-01-01

    Radio scattering observations made with multiple antennas provide a direct measure of the two-dimensional microstructure of the solar wind. Previous multiple antenna observations have shown that the microstructure at scales of the order of 10 km becomes highly field-aligned inside of 6 RS [e.g., Armstrong et al., 1990]. Single antenna observations, which can measure only a radial cut through the microstructure, have shown that scales larger than 1000 km have a Kolmogorov spectrum, whereas the smaller-scale structure has a flatter spectrum and is considerably enhanced above the Kolmogorov ``background'' [e.g., Coles et al., 1991]. Here we present new multiple antenna ``angular broadening'' observations made in 1990 and 1992. These confirm that the microstructure is highly field-aligned near the Sun, they show that it has elliptical symmetry, and they show that the axial ratio changes quite abruptly near 6 RS. We also present simultaneous measurements at 9 RS of the anisotropy on scales of 1 to 30 km and on scales of 200 to 3000 km. Significant anisotropy was seen on the smaller scales but not on the larger scales. This suggests that the process responsible for the anisotropic microstructure is distinct from the larger-scale, more isotropic structure.

  12. Direct observation of the field-stimulated exoemission sites at tungsten surfaces using field ion microscopy

    NASA Astrophysics Data System (ADS)

    Shiota, T.; Umeno, M.; Dohkuni, K.; Tagawa, M.; Ohmae, N.

    2001-05-01

    The spatial distribution of the field-stimulated exoemission (FSEE) from the W tip surface annealed at 800 K for 600 s and the atomic arrangement of the emitting surface were correlated using field ion microscopy (FIM) and field emission microscopy. The FSEE was observed at around the (111) plane of the annealed W tip surface. FIM observation of the annealed W tip revealed the existence of a pyramid-like protrusion at the W(111) surface. From these experimental results, a new emission model of the FSEE was proposed relating to the field-assisted surface structural change. This model deals with the buildup/collapse of the pyramid-like protrusion at the W(111) surface under the effect of negative high electric field. The temperature dependence of the FSEE reported previously [Shiota et al., J. Appl. Phys. 85, 6811 (1999)] was qualitatively explained by this emission model.

  13. Coronal Magnetic Field Measurement Using CME-Driven Shock Observations

    NASA Technical Reports Server (NTRS)

    Gopalswarmy, Nat; Nitta, N.; Yashiro, S.; Makela, P.; Xie, H.; Akiyama, S.

    2012-01-01

    Collisionless shocks form ahead of coronal mass ejections (CMEs) when the CME speed exceeds the Alfven speed of the ambient plasma in the corona and interplanetary medium. The shock stands at a distance from the CME flux rope that depends on the shock Mach number, the geometry of the driver, and the adiabatic index. While the shock ahead of the CME has been observed for a long time in the in situ data, it has been identified recently near the Sun in the coronagraphic and EUV images. Unlike in situ observations, the imaging observations are two dimensional, so one can better discern the CME-shock relationship near the Sun. Gopalswamy and Yashiro demonstrated that the coronal magnetic field can be derived from the shock standoff distance measured in coronagraphic images. The method involves measuring the standoff distance, the radius of curvature of the flux rope, and assuming the value of the adiabatic index and deriving the Alfvenic Mach number. The next step is to derive the Alfvenic Mach number from the measured shock speed and an estimate of the local solar wind speed. The final step involves deriving the magnetic field from the Alfven speed by measuring the local plasma density either from coronagraphic (polarized brightness) images or from the band-splitting of type II radio bursts. In this paper, we derive the combined magnetic field profile from near the Sun to the edge of the LASCO field of view (1.5 to 30 solar radii) and compare it with the current model profiles.

  14. Observational Features of Magnetotail Open Field Line Reconnection

    NASA Astrophysics Data System (ADS)

    Pu, Z.; Mishin, V.; Zhang, H.; Cao, X.; Fu, S.; Xiao, C.; Liu, Z.; Zong, Q.; Wang, X.; Ma, Z.; Lucek, E.; Reme, H.; Dunlop, M.; Escoubet, P.

    2006-12-01

    In the substorm NENL model (McPherron 1991, Baker et al. 1996) and the global synthesis paradigm (Pu et al. 1999, 2001), tail lobe reconnection (TLR) of open field lines is responsible for releasing magnetic energy in the tail to cause the major onset of a number of substorms. Study of the features of TLR in observations is thus of particular interest. This paper reports case studies of a few typical TLR events and statistical results of 39 events observed by Cluster from 2001 to 2003. To show the observational features of TLR, measurements of the magnetic field (B), plasma bulk velocity (V), temperature (T) and number density (N) onboard Cluster four spacecraft are analyzed, in comparison with the data from the world network of the ground-based magnetometers, with the usage of the magnetogram inversion technique MIT-2 (Mishin, 1991). In each event studied MR can be divided into two stages: foregoing plasma sheet MR (PSR) of closed field lines and following TLR. During PSR, the open flux in polar cap ? is continuously accumulated, and T and N remain essentially the same as in the plasma sheet, if spacecraft are not in the center of the plasma sheet. On the other hand, during TLR ? rapidly reduces, and T and N drop off to the level as low as in the lobes. It is seen that the ? starts to decrease almost simultaneously with the appearance of the TLR signatures in Cluster measurements. Quite often TLR occurs quasi-periodically with a period being approximately 2-3 hours. A comparison of observations with simulations is made to get better understanding of the TLR process. *This work is supported by the CNSF Project 40390152, 40536030 and Chinese Fundamental Research Project 2006CB806300.

  15. DMD-based programmable wide field spectrograph for Earth observation

    NASA Astrophysics Data System (ADS)

    Zamkotsian, Frédéric; Lanzoni, Patrick; Liotard, Arnaud; Viard, Thierry; Costes, Vincent; Hébert, Philippe-Jean

    2015-03-01

    In Earth Observation, Universe Observation and Planet Exploration, scientific return could be optimized in future missions using MOEMS devices. In Earth Observation, we propose an innovative reconfigurable instrument, a programmable wide-field spectrograph where both the FOV and the spectrum could be tailored thanks to a 2D micromirror array (MMA). For a linear 1D field of view (FOV), the principle is to use a MMA to select the wavelengths by acting on intensity. This component is placed in the focal plane of a first grating. On the MMA surface, the spatial dimension is along one side of the device and for each spatial point, its spectrum is displayed along the perpendicular direction: each spatial and spectral feature of the 1D FOV is then fully adjustable dynamically and/or programmable. A second stage with an identical grating recomposes the beam after wavelengths selection, leading to an output tailored 1D image. A mock-up has been designed, fabricated and tested. The micromirror array is the largest DMD in 2048 x 1080 mirrors format, with a pitch of 13.68μm. A synthetic linear FOV is generated and typical images have been recorded o at the output focal plane of the instrument. By tailoring the DMD, we could modify successfully each pixel of the input image: for example, it is possible to remove bright objects or, for each spatial pixel, modify the spectral signature. The very promising results obtained on the mock-up of the programmable wide-field spectrograph reveal the efficiency of this new instrument concept for Earth Observation.

  16. Field observations of a debris flow event in the Dolomites

    NASA Astrophysics Data System (ADS)

    Berti, Matteo; Genevois, Rinaldo; Simoni, Alessandro; Tecca, Pia Rosella

    1999-09-01

    A debris flow event occurred in June 1997 in the Dolomites (Eastern Alps, Italy). The phenomenon was directly observed in the field and recorded by a video camera near its initiation area. The debris flow originated shortly after an intense rainstorm (25 mm in 30 min) whose runoff mobilised the loose coarse debris that filled the bottom of the channel in its upper part. The analysis of the steep headwater basin indicates a very short concentration time (9-14 min) that fits the quick hydrological response observed in the field. The debris flow mobilisation was not contemporaneous with the arrival of the peak water discharge in the initiation area probably due to the time required for the saturation of the highly conductive channel-bed material. Channel cross-section measurements taken along the flow channel indicate debris flow peak velocity and discharge ranging from 3.1 to 9.0 m/s and from 23 to 71 m 3/s, respectively. Samples collected immediately after deposition were used to determine the water content and bulk density of the material. Channel scouring, fines enrichment and transported volume increase testify erosion and entrainment of material along the flow channel. Field estimates of the rheological properties based on open channel flow of Bingham fluid indicate a yield strength of 5000±400 Pa and relatively low viscosity (60-326 Pa s), probably due to a high percentage of fines (approx. 30%).

  17. Electric earthquake precursors: from laboratory results to field observations

    NASA Astrophysics Data System (ADS)

    Vallianatos, Filippos; Triantis, Dimos; Tzanis, Andreas; Anastasiadis, Cimon; Stavrakas, Ilias

    The generation of transient electric potential prior to rupture has been demonstrated in a number of laboratory experiments involving both dry and wet rock specimens. Several different electrification effects are responsible for these observations, however, piezoelectricity cannot explain why quartz-free rocks can also generate precursory phenomena and electrokinetic phenomena are normally very weak to produce macro- and megascopic scale effects. Electrification is observed in dry, non-piezoelectric rocks meaning that additional, solid state mechanisms should be responsible. Herein we focus on a promising effect that is ubiquitous during brittle rock failure: the motion of charged edge dislocations (MCD) during crack opening and propagation (microfracturing). We report a series of laboratory experiments on dry marble samples and discuss their possible relationship to field observations of purported electric earthquake precursors (EEP). The experiments confirm the generation of pressure-stimulated currents (PSC) as expected by the MCD model. The PSC was linearly related to the stress rate, so long as the stressed material deformed elastically. Deviation from linearity arose when the applied stress drove the specimen into the plastic deformation range; this effect has been attributed to the dependence of the PSC on the stress rate and, ultimately, to the inverse of the changing (decreasing) Young's modulus. The emitted current appears very intense and non-linear just prior to failure, where massive crack propagation implies massive MCD processes. Repeated cycles of deformation are associated with progressively weaker current emission, indicating the strong dependence of electrification on the residual damage. Overall, the results are consistent with, and render support to the concept of electrification by MCD/microfracturing. Other mechanisms cannot be excluded of course but are rather considered to accompany and supplement the drastic MCD process. The experiments

  18. Observation of anomalous field penetration in collisional, cylindrical ICP discharges

    NASA Astrophysics Data System (ADS)

    Evans, John D.; Chen, Francis F.; Arnush, Donald

    2000-10-01

    Measurements of the radial penetration of RF-generated B-fields are performed in a large diameter cylindrical ICP. A loop antenna surrounds a dome-shaped Pyrex top that sits on top of a magnetic bucket. Rtop=15cm height of top, Rbucket 18cm, bucket height 30cm, N 1011cm-3, Te 3eV, Prf < 1.4kW, Frf = 2-27.12MHz, Po 1-100mT. Field penetration (``skin") depths Lsd are measured in the outer plasma region (r > R/2) that are consistent with collisional skin depth theory. However, in the interior region (r < R/2), non-monotonic radial profiles and interference phenomena that resemble standing wave behavior (e.g. nodes) are observed, where no propagating waves are predicted to occur. Similar phenomena have been observed by other groups [1], but for chambers sizes such that R Lsd. Such observations were explained as manifestations of the anomalous skin effect (ASE), the electromagnetic analog of Debye shielding. However, these phenomena are more apparent as Po (and collisionality) is increased, in apparent contradiction to the predictions of ASE theory. Results of a detailed experimental investigation of interference phenomena under conditions that fall outside of the ASE regime will be presented, as well as a simple physical picture that resolves this apparent paradox. [1]. B. Joye and H. Schneider, Helv. Phys. Acta 51, 804 (1978).

  19. Swarm Observations of Field-Aligned Currents: Case Studies

    NASA Astrophysics Data System (ADS)

    Le, G.; Chi, P. J.; Gjerloev, J. W.; Stolle, C.; Luhr, H.; Park, J.; Rauberg, J.

    2014-12-01

    In this paper, we report the results of a few case studies of multi-point magnetic field measurements of field-aligned currents (FACs) from Swarm constellation mission to understand their temporal and spatial characteristics. During the commissioning phase, the three Swarm spacecraft were in an identical polar orbit with a string-of-pearl configuration with small separations. During the science operational phase (since April, 2014), the three spacecraft were placed in slightly different polar orbits: one spacecraft in a higher altitude orbit (507km x 512km) and two side-by-side in lower altitude orbits (459km x 462km). We analyze a few FAC events in both orbital phases and during periods of active geomagnetic conditions. The multi-point observations enable us to examine the FACs' temporal evolution and separate their temporal and spatial variations.

  20. Multipoint observations of planar interplanetary magnetic field structures

    NASA Technical Reports Server (NTRS)

    Farrugia, C. J.; Lepping, R. P.; Dunlop, M. W.; Elliott, S.; Balogh, A.; Cowley, S. W. H.; Freeman, M. P.; Sibeck, D. G.

    1991-01-01

    IMF data made on November 1, 1984, by three spatially well-separated spacecraft in the solar wind are presented. The IMF measured by each of the spacecraft is found to consist of a multiplicity of structures within which the magnetic field varies in parallel planes. The orientations of these planes at the three spacecraft locations are similar. The planes are inclined at a large angle to the ecliptic, and they lie almost perpendicular to the nominal Parker spiral direction in the ecliptic. Intercomparisons of the measurements at the various spacecraft show that the IMF features at one spacecraft are clearly reproduced at another, with time delays required for signal propagation. From these time delays and the mutual separations of the spacecraft, it is inferred that the structures are convecting with the ambient flow. Simultaneous observations made downstream of the bow shock in the magnetosheath reveal that the magnetosheath magnetic field, too, is planar.

  1. Geomorphology: Perspectives on observation, history, and the field tradition

    NASA Astrophysics Data System (ADS)

    Vitek, John D.

    2013-10-01

    Other than a common interest in form and process, current geomorphologists have little in common with those who established the foundations of this science. Educated people who had an interest in Earth processes during the nineteenth century cannot be compared to the scholars who study geomorphology in the twenty-first century. Whereas Earth has undergone natural change from the beginning of time, the human record of observing and recording processes and changes in the surface Is but a recent phenomena. Observation is the only thread, however, that connects all practitioners of geomorphology through time. As people acquired knowledge related to all aspects of life, technological revolutions, such as the Iron Age, Bronze Age, agricultural revolution, the atomic age, and the digital age, shaped human existence and thought. Technology has greatly changed the power of human observation, including inward to the atomic scale and outward into the realm of space.Books and articles describe how to collect and analyze data but few references document the field experience. Each of us, however, has experienced unique circumstances during field work and we learned from various mentors how to observe. The surface of Earth on which we practice the vocation of geomorphology may not be much different from a hundred years ago but many things about how we collect data, analyze it and disseminate the results have changed. How we function in the field, including what we wear, what we eat, how we get there, and where we choose to collect data, clearly reflects the complexity of the human system on Earth and the processes and forms that arouse our interest. Computers, miniaturization of electronics, satellite communications and observation platforms in space provide access to data to aid in our quest to understand Earth surface processes. Once, people lived closer to nature in primitive shelters in contrast with life in urban environments. But as urban life continues to expand and people

  2. 2010 BLASTPol Observations of Magnetic Fields in Lupus

    NASA Astrophysics Data System (ADS)

    Matthews, Tristan G.

    The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) was created by adding polarimetric capability to the BLAST experiment that was flown in 2003, 2005, and 2006. BLASTPol inherited BLAST's 1.8 m primary and its Herschel/SPIRE heritage focal plane that allows simultaneous observation at 250, 350, and 500 mum. We flew BLASTPol in 2010 and again in 2012. Both were long duration Antarctic flights. The main result presented here is polarimetry of the nearby filamentary dark cloud Lupus I obtained during the 2010 flight. Despite limitations imposed by the effects of a damaged optical component, we were able to clearly detect submillimeter polarization on degree scales. We compare the resulting BLASTPol magnetic field map with a similar map made via optical polarimetry. (The optical data were published in 1998 by J. Rizzo and collaborators.) The two maps partially overlap and are reasonably consistent with one another. We compare these magnetic field maps to the orientations of filaments in Lupus I, and we find that the dominant filament in the cloud is approximately perpendicular to the large-scale field, while secondary filaments appear to run parallel to the magnetic fields in their vicinities. This is similar to what is observed in Serpens South via near-IR polarimetry, and consistent with what is seen in MHD simulations by F. Nakamura and Z. Li. We have performed a similar analysis for Lupus IV and present initial results. The Lupus IV cloud has no clear dominant filament and we make no attempts to interpret these initial findings. Finally, detailed discussions of two of the dominant sources of error in the 2010 data are presented.

  3. Seismostatistical characterization of microseismicity observed at geothermal fields

    NASA Astrophysics Data System (ADS)

    Eto, T.; Asanuma, H.; Adachi, M.; Saeki, K.; Aoyama, K.; Ozeki, H.; Häring, M. O.

    2012-12-01

    Recently, occurrence of felt earthquakes has been recognized as one of the most critical environmental burdens associated with geothermal development. We have taken seismostatistical approach to evaluate characteristics of the microseismicity at geothermal fields to establish realtime and automated monitoring techniques of the reservoir changes and risk assessment of the felt earthquakes. In this study, we have introduced the Epidemic Type Aftershock Sequence (ETAS) model (Ogata, JASA, 1988) to statistically model the time series of occurrences and the magnitude of microseismic events from hydrothermal and EGS fields. Here maximum likelihood estimation has been employed to estimate optimum parameters of the ETAS model. We analyzed microseismic events observed at Yanaizu Nishiyama, one of the largest hydrothermal fields in Japan. In this field, four felt earthquakes with local magnitude larger than 3.0 occurred during production operation since 1996, although no clear correlation between the occurrence of the felt earthquakes and operation to the reservoir has been observed (Asanuma et al., Trans. GRC, 2011). We found that the occurrence rate of primary fluid signals, which are the events triggered by external forcing and have been interpreted to be independent from a series of aftershocks (Hainzl and Ogata, JGR, 2005), correlated to the reinjection rate (Fig. 1). However, no significant change in the other parameters in the ETAS model has been observed. We also analyzed microseismic events observed at Basel EGS site in Switzerland, where some felt earthquakes occurred during and after hydraulic stimulation. The estimated ETAS model demonstrated that there is a correlation between the occurrence rate of primary fluid signals and injection rate. We, however, found that there is limitation to fit the ETAS model to the induced seismic events and new seismostatistical model is required for microseismic reservoir monitoring.ig. 1 A relation among production

  4. Field observations of dilution on the Ipanema Beach outfall.

    PubMed

    Roldão, J; Carvalho, J L; Roberts, P J

    2001-01-01

    Field observations of the Ipanema Beach, Rio de Janeiro, ocean sewage outfall are presented. Measurements of dilution and other wastefield characteristics were obtained by adding dye tracer to the effluent and measuring in-situ. Simultaneous measurements of oceanographic conditions were made by Acoustic Doppler Current Profilers, thermistor strings, and profiling instruments. Four experiments were performed, two during unstratified conditions when the plume was surfacing, and two during conditions of strong stratification when the plume was submerged. The minimum dilution varied from 30 to 130. The measurements reflect the worst case conditions as the campaigns were all made for weak currents. PMID:11443984

  5. Using Clocks and Atomic Interferometry for Gravity Field Observations

    NASA Astrophysics Data System (ADS)

    Müller, Jürgen

    2016-07-01

    New technology developed in the frame of fundamental physics may lead to enhanced capabilities for geodetic applications such as refined observations of the Earth's gravity field. Here, we will present new sensor measurement concepts that apply atomic interferometry for gravimetry and clock measurements for observing potential values. In the first case, gravity anomalies can be determined by observing free-falling atoms (quantum gravimetry). In the second case, highly precise optical clocks can be used to measure differences of the gravity potential over long distances (relativistic geodesy). Principally, also inter-satellite ranging between test masses in space with nanometer accuracy belongs to these novel developments. We will show, how the new measurement concepts are connected to classical geodetic concepts, e.g. geopotential numbers and clock readings. We will illustrate the application of these new methods and their benefit for geodesy, where local and global mass variations can be observed with unforeseen accuracy and resolution, mass variations that reflect processes in the Earth system. We will present a few examples where geodesy will potentially benefit from these developments. Thus, the novel technologies might be applied for defining and realizing height systems in a new way, but also for fast local gravimetric surveys and exploration.

  6. A new approach to observe toroidal magnetic fields of magnetars

    NASA Astrophysics Data System (ADS)

    Murakami, H.; Makishima, K.; Enoto, T.; Nakano, T.; Furuta, Y.; Nakazawa, K.

    2016-06-01

    Over the last decade, observational evidence has amounted that magnetars harbor enormous surface dipole magnetic fields (MFs) of B_{d} = 10^{14-15} {G}. Theoretically, we expect even stronger toroidal MFs B_{t} (e.g., Takiwaki+2009), which is observationally supported by a discovery of low-B_{d} magnetars (e.g., SGR 0418+5729; Rea+2013). Here, we will present a new approach to access B_{t} more directly. {Suzaku} allows us to simultaneously observe a soft thermal component and a distinct hard X-ray tail of magnetars. Extensively analyzing two magnetars, 4U 0142+61 and 1E 1547.0-5408, we found that their hard X-ray pulses suffered from slow phase modulations (Makishima+2014, 2015). This can be interpreted as a manifestation of free precession, under an axial deformation by ˜0.01%. If this effect is attributed to the magnetic stress, B_{t}˜10^{16} G is inferred. We further found that, within 6 years observation of 4U 0142+61, the modulation periods remained constant, while the amplitude gradually increased from < 0.4 to ˜1.3 sec. These results suggest the shift of the hard X-ray emission region (or direction).

  7. {Interball-1 Plasma, Magnetic Field, and Energetic Particle Observations}

    NASA Technical Reports Server (NTRS)

    Sibeck, David G.

    1998-01-01

    Funding from NASA was received in two installments. The first installment supported research using Russian/Czech/Slovak/French Interball-1 plasma, magnetic field, and energetic particles observations in the vicinity of the magnetopause. The second installment provided salary support to review unsolicited proposals to NASA for data recovery and archiving, and also to survey ISTP data provision efforts. Two papers were published under the auspices of the grant. Sibeck et al. reported Interball-1 observations of a wave on the magnetopause with an amplitude in excess of 5 R(sub E), the largest ever reported to date. They attributed the wave to a hot flow anomaly striking the magnetopause and suggested that the hot flow anomaly itself formed during the interaction of an IMF discontinuity with the bow shock. Nemecek et al. used Interball-1's VDP Faraday cup to identify large transient increases in the magnetosheath density. They noted large variations in simultaneous Wind observations of the IMF cone angle, but were unable to establish any relationship between the cone angle variations at Wind and the density variations at Interball-1. Funds from the second installment were used to review over 20 proposals from various researchers in the scientific community who sought NASA support to restore or archive past observations. It also supported a survey of ISTP data provisions which was used as input to a Senior Review of ongoing NASA ISTP programs.

  8. A new approach to observe toroidal magnetic fields of magnetars

    NASA Astrophysics Data System (ADS)

    Murakami, H.; Makishima, K.; Enoto, T.; Nakano, T.; Furuta, Y.; Nakazawa, K.

    2016-06-01

    Over the last decade, observational evidence has amounted that magnetars harbor enormous surface dipole magnetic fields (MFs) of B_{d} = 10^{14-15} {G}. Theoretically, we expect even stronger toroidal MFs B_{t} (e.g., Takiwaki+2009), which is observationally supported by a discovery of low-B_{d} magnetars (e.g., SGR 0418+5729; Rea+2013). Here, we will present a new approach to access B_{t} more directly. Suzaku allows us to simultaneously observe a soft thermal component and a distinct hard X-ray tail of magnetars. Extensively analyzing two magnetars, 4U 0142+61 and 1E 1547.0-5408, we found that their hard X-ray pulses suffered from slow phase modulations (Makishima+2014, 2015). This can be interpreted as a manifestation of free precession, under an axial deformation by ˜0.01%. If this effect is attributed to the magnetic stress, B_{t}˜10^{16} G is inferred. We further found that, within 6 years observation of 4U 0142+61, the modulation periods remained constant, while the amplitude gradually increased from < 0.4 to ˜1.3 sec. These results suggest the shift of the hard X-ray emission region (or direction).

  9. Benefits of “Observer Effects”: Lessons from the Field

    PubMed Central

    Monahan, Torin; Fisher, Jill A.

    2011-01-01

    This paper responds to the criticism that “observer effects” in ethnographic research necessarily bias and therefore invalidate research findings. Instead of aspiring to distance and detachment, some of the greatest strengths of ethnographic research lie in cultivating close ties with others and collaboratively shaping discourses and practices in the field. Informants’ performances – however staged for or influenced by the observer – often reveal profound truths about social and/or cultural phenomena. To make this case, first we mobilize methodological insights from the field of science studies to illustrate the contingency and partiality of all knowledge and to challenge the notion that ethnography is less objective than other research methods. Second, we draw upon our ethnographic projects to illustrate the rich data that can be obtained from “staged performances” by informants. Finally, by detailing a few examples of questionable behavior on the part of informants, we challenge the fallacy that the presence of ethnographers will cause informants to self-censor. PMID:21297880

  10. Field experimental observations of highly graded sediment plumes.

    PubMed

    Jensen, Jacob Hjelmager; Saremi, Sina; Jimenez, Carlos; Hadjioannou, Louis

    2015-06-15

    A field experiment in the waters off the south-eastern coast of Cyprus was carried out to study near-field formation of sediment plumes from dumping. Different loads of sediment were poured into calm and limpid waters one at the time from just above the sea surface. The associated plumes, gravitating towards the seafloor, were filmed simultaneously by four divers situated at different depths in the water column, and facing the plume at different angles. The processes were captured using GoPro-Hero-series cameras. The high-quality underwater footage from near-surface, mid-depth and near-bed positions gives unique insight into the dynamics of the descending plume and near-field dispersion processes, and enables good understanding of flow and sediment transport processes involved from-release-to-deposition of the load in a non-scaled environment. The high resolution images and footages are available through the link provided herein. Observations support the development of a detailed multi-fractional sediment plume model. PMID:25935811

  11. Multicolor Observations of the Hubble Deep Field South

    NASA Astrophysics Data System (ADS)

    Vanzella, Eros; Cristiani, Stefano; Saracco, Paolo; Arnouts, Stephane; Bianchi, Simone; D'Odorico, Sandro; Fontana, Adriano; Giallongo, Emanuele; Grazian, Andrea

    2001-11-01

    We present a deep multicolor (U, B, V, I, Js, H, Ks) catalog of galaxies in the Hubble Deep Field South, based on observations obtained with the HST WFPC2 in 1998 and VLT-ISAAC in 1999. The photometric procedures were tuned to derive a catalog optimized for the estimation of photometric redshifts. In particular we adopted a ``conservative'' detection threshold, which resulted in a list of 1611 objects. The behavior of the observed source counts is in general agreement with the previous results of Casertano et al. in the Hubble Deep Field South and Williams et al. in the Hubble Deep Field North, while the corresponding counts in the Hubble Deep Field North provided by Fernández-Soto, Lanzetta, & Yahil are systematically lower by a factor 1.5 beyond IAB=26. After correcting for the incompleteness of the source counts, the object surface density at IAB<=27.5 is estimated to be 220 arcmin-2, in agreement with the corresponding measure of Volonteri et al. and providing an estimate of the extragalactic background light in the I band consistent with the work of Madau & Pozzetti. The comparison between the median V-I color in the Hubble Deep Field North and South shows a significant difference around IAB~26, possibly due to the presence of large-scale structure at z~1 in the HDF-N. High-redshift galaxy candidates (90 U dropouts and 17 B dropouts) were selected by means of color diagrams, down to a magnitude IAB=27, with a surface density of (21+/-1) and (3.9+/-0.9) arcmin-2, respectively. Eleven extremely red objects [with (I-K)AB>2.7] were selected down to KAB=24, plus three objects whose upper limit to the Ks flux is still compatible with the selection criterion. The corresponding surface density of EROs is (2.5+/-0.8) arcmin-2 [(3.2+/-0.9) arcmin-2 if we include the three Ks upper limits]. They show a remarkably nonuniform spatial distribution and are classified with roughly equal fractions in the categories of elliptical and starburst galaxies.

  12. INTERSTELLAR MAGNETIC FIELDS OBSERVED BY VOYAGER 1 BEYOND THE HELIOPAUSE

    SciTech Connect

    Burlaga, L. F.; Ness, N. F. E-mail: nfnudel@yahoo.com

    2014-11-01

    Voyager 1 (V1) was beyond the heliopause between 2013.00 and 2014.41, where it was making in situ observations of the interstellar magnetic field (ISMF). The average azimuthal angle and elevation angle of the magnetic field B were (λ) = 292.°5 ± 1.°4 and (δ) = 22.°1 ± 1.°2, respectively. The angles λ and δ varied linearly at (1.°4 ± 0.°1) yr{sup –1} and (–1.°1 ± 0.°1) yr{sup –1}, respectively, suggesting that V1 was measuring the draped ISMF around the heliopause. The distributions of hourly averages of λ and δ were Gaussian distributions, with most probable values 292.°5 and 22.°1, and standard deviations (SDs) 1.°3 and 1.°1, respectively. The small SD indicates little or no turbulence transverse to B . An abrupt decrease in B from 0.50 nT on 2013/129.9 to 0.46 nT on 2013/130.6 was observed, possibly associated with a weak reverse shock or magnetoacoustic pressure wave following a burst of electron plasma oscillations. Between 2013/130.6 and 2013/365.3, (B) = 0.464 ± 0.009 nT, (λ) = 292.°6 ± 0.°8, and (δ) = 22.°1 ± 1.°1. The corresponding distribution of hourly averages of B was Gaussian with the most probable value 0.464 nT and σ = 0.009 nT. Since the uncertainty σ corresponds to the instrument and digitization noise, these observations provided an upper limit to the turbulence in the ISMF. The distributions of the hourly increments of B were Gaussian distributions with σ = 0.05 nT, 0.°4, and 0.°4, respectively, indicating that the V1 did not detect evidence of ''intermittent bursts'' of interstellar turbulence.

  13. Field observations using an AOTF polarimetric imaging spectrometer

    NASA Technical Reports Server (NTRS)

    Cheng, Li-Jen; Hamilton, Mike; Mahoney, Colin; Reyes, George

    1993-01-01

    This paper reports preliminary results of recent field observations using a prototype acousto-optic tunable filter (AOTF) polarimetric imaging spectrometer. The data illustrate application potentials for geoscience. The operation principle of this instrument is different from that of current airborne multispectral imaging instruments, such as AVIRIS. The AOTF instrument takes two orthogonally polarized images at a desired wavelength at one time, whereas AVIRIS takes a spectrum over a predetermined wavelength range at one pixel at a time and the image is constructed later. AVIRIS does not have any polarization measuring capability. The AOTF instrument could be a complement tool to AVIRIS. Polarization measurement is a desired capability for many applications in remote sensing. It is well know that natural light is often polarized due to various scattering phenomena in the atmosphere. Also, scattered light from canopies is reported to have a polarized component. To characterize objects of interest correctly requires a remote sensing imaging spectrometer capable of measuring object signal and background radiation in both intensity and polarization so that the characteristics of the object can be determined. The AORF instrument has the capability to do so. The AOTF instrument has other unique properties. For example, it can provide spectral images immediately after the observation. The instrument can also allow observations to be tailored in real time to perform the desired experiments and to collect only required data. Consequently, the performance in each mission can be increased with minimal resources. The prototype instrument was completed in the beginning of this year. A number of outdoor field experiments were performed with the objective to evaluate the capability of this new technology for remote sensing applications and to determine issues for further improvements.

  14. Interplanetary Electric Field Control of Field-Aligned Currents: Polar Magnetometer Observations

    NASA Astrophysics Data System (ADS)

    Fleishman, M.; Russell, C. T.

    2001-05-01

    ACE and Wind measurements of the solar wind velocity and interplanetary magnetic field have been used to calculate the interplanetary electric field during passages of the Polar spacecraft above the southern auroral oval. Periods of the quasi-steady interplanetary electric field have been identified when the Polar spacecraft was transiting the auroral and polar regions both just in front of the terminator above the lit ionosphere and just behind the terminator above the dark ionosphere. The east-west magnetic perturbation observed was then used as a measure of the local field-aligned current density and extrapolated to a common altitude. Independent of whether the interplanetary electric field (IEF) is from dawn to dusk or dusk to dawn a significant field-aligned current always exists. The magnitude of its perturbation field for dusk to dawn IEF is about 180 nT. For dawn to dusk IEF the magnetic perturbation is roughly proportional to the dawn-dusk component of the IEF. The strength of the field-aligned current does not depend on whether the ionosphere under the spacecraft is in sunlight or in darkness.

  15. A magnetospheric field model incorporating the OGO 3 and 5 magnetic field observations.

    NASA Technical Reports Server (NTRS)

    Sugiura, M.; Poros, D. J.

    1973-01-01

    A magnetospheric field model is presented in which the usually assumed toroidal ring current is replaced by a circular disk current of finite thickness that extends from the tail to geocentric distances less than 3 earth radii. The drastic departure of this model from the concept of the conventional ring current lies in that the current is continuous from the tail to the inner magnetosphere. This conceptual change was required to account for the recent results of analysis of the OGO 3 and 5 magnetic field observations. In the present model the cross-tail current flows along circular arcs concentric with the earth and completes circuit via surface currents on the magnetopause. Apart from these return currents in the tail magnetopause, Mead's (1964) model is used for the field from the magnetopause current. The difference scalar field, Delta B, defined as the difference between the scalar field calculated from the present model and the magnitude of the dipole field, is found to be in gross agreement with the observed Delta B.

  16. Observation of synchronized atomic motions in the field ion microscope.

    PubMed

    Rahman, Fhm F; Notte, John A; Livengood, Richard H; Tan, Shida

    2013-03-01

    For over half a century, the field ion microscope (FIM) has been used to visualize atomic structures at the apex of a sharpened needle by way of the ion beams which are created at the most protruding atoms. In this paper we used a conventional FIM to study the emission characteristics of the neon ion beams produced within the FIM. The neon emission pattern is observed to be relatively short lived and subject to temporal and angular fluctuations. The nature of these fluctuations is complex, often with different parts of the emission pattern changing in a synchronized fashion over timescales spanning from milliseconds to a few tens of seconds. In this paper, we characterize the observed instability of the neon emission. We also offer a simple model of adsorbed atom mobility that explains much of these observations. And finally, we present a method by which the stability can be greatly improved so that the produced neon beam can be used effectively for nanomachining applications. PMID:23376401

  17. Observations of field-aligned currents, waves, and electric fields at substorm onset

    NASA Technical Reports Server (NTRS)

    Smits, D. P.; Hughes, W. J.; Cattell, C. A.; Russell, C. T.

    1986-01-01

    Substorm onsets, identified Pi 2 pulsations observed on the Air Force Geophysics Laboratory Magnetometer Network, are studied using magnetometer and electric field data from ISEE 1 as well as magnetometer data from the geosynchronous satellites GOES 2 and 3. The mid-latitude magnetometer data provides the means of both timing and locating the substorm onset so that the spacecraft locations with respect to the substorm current systems are known. During two intervals, each containing several onsets or intensifications, ISEE 1 observed field-aligned current signatures beginning simultaneously with the mid-latitude Pi 2 pulsation. Close to the earth broadband bursts of wave noise were observed in the electric field data whenever field-aligned currents were detected. One onset occurred when ISEE 1 and GOES 2 were on the same field line but in opposite hemispheres. During this onset ISEE 1 and GOES 2 saw magnetic signatures which appear to be due to conjugate field-aligned currents flowing out of the western end of the westward auroral electrojets. The ISEE 1 signature is of a line current moving westward past the spacecraft. During the other interval, ISEE 1 was in the near-tail region near the midnight meridian. Plasma data confirms that the plasma sheet thinned and subsequently expanded at onset. Electric field data shows that the plasma moved in the opposite direction to the plasma sheet boundary as the boundary expanded which implies that there must have been an abundant source of hot plasma present. The plasma motion was towards the center of the plasma sheet and earthwards and consisted of a series of pulses rather than a steady flow.

  18. C/NOFS Observations of AC Electric Field Fields Associated with Equatorial Spread-F

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Liebrecht, C.

    2009-01-01

    The Vector Electric Field Investigation (VEFI) on the C/NOFS equatorial satellite provides a unique data set in which to acquire detailed knowledge of irregularities associated with the equatorial ionosphere and in particular with spread-F depletions. We present vector AC electric field observations, primarily gathered within the ELF band (1 Hz to 250 Hz) on C/NOFS that address a variety of key questions regarding how plasma irregularities, from meter to kilometer scales, are created and evolve. The data will be used to explore the anisotropy/isotropy of the waves, their wavelength and phase velocity, as well as their spectral distributions. When analyzed in conjunction with the driving DC electric fields and detailed plasma number density measurements, the combined data reveal important information concerning the instability mechanisms themselves. We also present high resolution, vector measurements of intense lower hybrid waves that have been detected on numerous occasions by the VEFI burst memory VLF electric field channels.

  19. MAGNETIC FIELDS IN INTERSTELLAR CLOUDS FROM ZEEMAN OBSERVATIONS: INFERENCE OF TOTAL FIELD STRENGTHS BY BAYESIAN ANALYSIS

    SciTech Connect

    Crutcher, Richard M.; Wandelt, Benjamin; Heiles, Carl; Falgarone, Edith

    2010-12-10

    The only direct measurements of interstellar magnetic field strengths depend on the Zeeman effect, which samples the line-of-sight component B{sub z} of the magnetic vector. In this paper, we use a Bayesian approach to analyze the observed probability density function (PDF) of B{sub z} from Zeeman surveys of H I, OH, and CN spectral lines in order to infer a density-dependent stochastic model of the total field strength B in diffuse and molecular clouds. We find that at n < 300 cm{sup -3} (in the diffuse interstellar medium sampled by H I lines), B does not scale with density. This suggests that diffuse clouds are assembled by flows along magnetic field lines, which would increase the density but not the magnetic field strength. We further find strong evidence for B in molecular clouds being randomly distributed between very small values and a maximum that scales with volume density n as B {proportional_to} n {sup 0.65} for n>300 cm{sup -3}, with an uncertainty at the 50% level in the power-law exponent of about {+-}0.05. This break-point density could be interpreted as the average density at which parsec-scale clouds become self-gravitating. Both the uniform PDF of total field strengths and the scaling with density suggest that magnetic fields in molecular clouds are often too weak to dominate the star formation process. The stochasticity of the total field strength B implies that many fields are so weak that the mass/flux ratio in many clouds must be significantly supercritical. A two-thirds power law comes from isotropic contraction of gas too weakly magnetized for the magnetic field to affect the morphology of the collapse. On the other hand, our study does not rule out some clouds having strong magnetic fields with critical mass/flux ratios.

  20. Comparison of St. Lawrence blue whale vocalizations with field observations

    NASA Astrophysics Data System (ADS)

    Berchok, Catherine; Bradley, David; Gabrielson, Thomas; Sears, Richard

    2003-04-01

    During four field seasons from 1998-2001, vocalizations were recorded in the presence of St. Lawrence blue whales using a single omni-directional hydrophone. Both long duration infrasonic calls (~18 Hz, 5-20 s) as well as short duration higher frequency calls (85-25 Hz, ~2 s) were detected and compared with field observations. Two trends were noted. First, the long infrasonic call series were concentrated primarily in the deep (300 m) channel. These call series appear to compare well with blue whale vocalizations recorded by others in the deep open ocean. Second, the shorter audible calls were more evenly distributed over bathymetry and seem to be a form of short distance communication with at least one case occurring during an agonistic interaction. A comparison of these calls with biological parameters such as density of whales in the area, percentages of paired versus single whales, and numbers of males versus females will also be discussed. [Project supported by ARL/PSU, NSF, and the American Museum of Natural History.

  1. Photometric Observations of 6000 Stars in the Cygnus Field

    NASA Technical Reports Server (NTRS)

    Borucki, W.; Caldwell, D.; Koch, D.; Jenkins, J.; Ninkov, Z.

    1999-01-01

    A small photometer to detect transits by extrasolar planets has been assembled and is being tested at Lick Observatory on Mt. Hamilton, California. The Vulcan photometer is constructed from a 30 cm focal length, F/2.5 AeroEktar reconnaissance lens and Photometrics PXL16800 CCD camera. A spectral filter is used to confine the pass band from 480 to 763 mn. It simultaneously monitors 6000 stars brighter than 12th magnitude within a single star field in the galactic plane. When the data are folded and phased to discover low amplitude transits, the relative precision of one-hour samples is about 1 part per thousand (10 x l0(exp -3)) for many of the brighter stars. This precision is sufficient to find jovian-size planets orbiting solar-like stars, which have signal amplitudes from 5 to 30 x l0(exp -3) depending on the inflation of the planet and the size of the star. Based on the frequency of giant inner-planets discovered by Doppler-velocity method, one or two planets should be detectable in a rich star field. The goal of the observations is to obtain the sizes of giant extrasolar planets in short-period orbits and to combine these with masses determined from Doppler velocity measurements to determine the densities of these planets. A further goal is to compare the measured planetary diameters with those predicted from theoretical models. From August 10 through September 30 of 1998, a forty nine square degree field in the Cygnus constellation centered at RA and DEC of 19 hr 47 min, +36 deg 55 min was observed. Useful data were obtained on twenty-nine nights. Nearly fifty stars showed some evidence of transits with periods between 0.3 and 8 days. Most had amplitudes too large to be associated with planetary transits. However, several stars showed low amplitude transits. The data for several transits of each of these two stars have been folded and been folded into 30 minute periods. Only Cygl433 shows any evidence of a flattened bottom that is expected when a small object

  2. Determining degree-day thresholds from field observations

    NASA Astrophysics Data System (ADS)

    Snyder, R. L.; Spano, Donatella; Cesaraccio, Carla; Duce, Pierpaolo

    This paper compares several methods for determining degree-day (°D) threshold temperatures from field observations. Three of the methods use the mean developmental period temperature and simple equations to estimate: (1) the smallest standard deviation in °D, (2) the least standard deviation in days, and (3) a linear regression intercept. Two additional methods use iterations of cumulative °D and threshold temperatures to determine the smallest root mean square error (RMSE). One of the iteration methods uses a linear model and the other uses a single triangle °D calculation method. The method giving the best results was verified by comparing observed and predicted phenological periods using 7 years of kiwifruit data and 10 years of cherry tree data. In general, the iteration method using the single triangle method to calculate °D provided threshold temperatures with the smallest RMSE values. However, the iteration method using a linear °D model also worked well. Simply using a threshold of zero gave predictions that were nearly as good as those obtained using the other two methods. The smallest standard deviation in °D performed the worst. The least standard deviation in days and the regression methods did well sometimes; however, the threshold temperatures were sometimes negative, which does not support the idea that development rates are related to heat units.

  3. Field observations of aye-ayes (Daubentonia madagascariensis) in Madagascar.

    PubMed

    Ancrenaz, M; Lackman-Ancrenaz, I; Mundy, N

    1994-01-01

    Data are presented from a field study of aye-ayes (Daubentonia madagascariensis) in an area of degraded secondary forest in northeast Madagascar. Animals were followed by radiotelemetry for 3 months during the cool dry season, when productivity of the forest is at a minimum. Population density was variable. Male home ranges were larger and overlapped the range of at least 1 female. Male ranges also overlapped, and areas of overlap could be occupied by 2 animals simultaneously. Most of the parties were solitary, but aggregations were observed at feeding sites. All activity was observed during darkness, and aye-ayes were always found to nest singly during the daytime. These patterns conform to those described for other nocturnal solitary prosimians. The aye-ayes showed versatility in their locomotor patterns, enabling them to use all types of supports and forest levels. Dietary diversity was high, although a preference for flower nectar was noted. These results suggest that, despite their anatomical specializations, aye-ayes are able to exploit a wide range of resources within recently degraded forest. This ability seems to allow aye-ayes to remain active throughout the year, unlike certain other nocturnal lemurs which become torpid during the dry season. PMID:7721206

  4. Geopotential Field Anomaly Continuation with Multi-Altitude Observations

    NASA Technical Reports Server (NTRS)

    Kim, Jeong Woo; Kim, Hyung Rae; von Frese, Ralph; Taylor, Patrick; Rangelova, Elena

    2012-01-01

    Conventional gravity and magnetic anomaly continuation invokes the standard Poisson boundary condition of a zero anomaly at an infinite vertical distance from the observation surface. This simple continuation is limited, however, where multiple altitude slices of the anomaly field have been observed. Increasingly, areas are becoming available constrained by multiple boundary conditions from surface, airborne, and satellite surveys. This paper describes the implementation of continuation with multi-altitude boundary conditions in Cartesian and spherical coordinates and investigates the advantages and limitations of these applications. Continuations by EPS (Equivalent Point Source) inversion and the FT (Fourier Transform), as well as by SCHA (Spherical Cap Harmonic Analysis) are considered. These methods were selected because they are especially well suited for analyzing multi-altitude data over finite patches of the earth such as covered by the ADMAP database. In general, continuations constrained by multi-altitude data surfaces are invariably superior to those constrained by a single altitude data surface due to anomaly measurement errors and the non-uniqueness of continuation.

  5. Geopotential Field Anomaly Continuation with Multi-Altitude Observations

    NASA Technical Reports Server (NTRS)

    Kim, Jeong Woo; Kim, Hyung Rae; vonFrese, Ralph; Taylor, Patrick; Rangelova, Elena

    2011-01-01

    Conventional gravity and magnetic anomaly continuation invokes the standard Poisson boundary condition of a zero anomaly at an infinite vertical distance from the observation surface. This simple continuation is limited, however, where multiple altitude slices of the anomaly field have been observed. Increasingly, areas are becoming available constrained by multiple boundary conditions from surface, airborne, and satellite surveys. This paper describes the implementation of continuation with multi-altitude boundary conditions in Cartesian and spherical coordinates and investigates the advantages and limitations of these applications. Continuations by EPS (Equivalent Point Source) inversion and the FT (Fourier Transform), as well as by SCHA (Spherical Cap Harmonic Analysis) are considered. These methods were selected because they are especially well suited for analyzing multi-altitude data over finite patches of the earth such as covered by the ADMAP database. In general, continuations constrained by multi-altitude data surfaces are invariably superior to those constrained by a single altitude data surface due to anomaly measurement errors and the non-uniqueness of continuation.

  6. Cloud atlas for the FIRE Cirrus Intensive Field Observation (IFO)

    NASA Technical Reports Server (NTRS)

    Arking, Albert; Childs, Jeffrey D.; Merritt, John H.; Williams, Sharen L.

    1990-01-01

    An Intensive Field Observation (IFO) of cirrus clouds was conducted over the mid-western U.S. during the period October 13 to November 2, 1986. This activity, part of the First ISCCP Regional Experiment (FIRE), included measurements made from specially deployed instruments on the ground, balloons, and aircraft as well as observations from existing operational and experimental satellites. One of the sets of satellite observations was the radiance measurements made with the 5-channel AVHRR radiometer on the NOAA 9 polar orbiting meteorological satellite. The ground resolution of the measurements at nadir is approx. 1 km. It is these measurements, made once each day at approximately 2:30 p.m. local time, that were used in determining the present cloud atlas. The area covered by the atlas is slightly larger than the area specified for the IFO, in order to be in alignment with the grid that will be used in a forthcoming atlas for the larger, ETO region. The atlas contains four pages of information for each satellite pass. The 1st page of each group shows the distribution of measured radiances in channel 1 (normalized to the incoming solar flux multiplied by the cosine of the solar zenith angle) and in channel 4 for the area as a whole and for each analysis box. The 2nd page shows the images in: channels 1 and 2, channel 3R; and channel 4. The 3rd page shows the retrieved parameters in graphical form for the region as a whole and for each analysis box, where cloud fraction appears as a contour plot with respect to optical thickness and cloudtop temperature. The 4th page provides a statistical summary of the retrieved parameters in numerical form for each analysis box.

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

    SciTech Connect

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

    1991-04-01

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

  8. Earthquake Rupture Complexity Evidence from Field Observations (Invited)

    NASA Astrophysics Data System (ADS)

    Hudnut, K. W.; Fletcher, J. M.; Rockwell, T. K.; Gonzalez-Garcia, J. J.; Teran, O.; Akciz, S. O.

    2010-12-01

    Field observations provide strong evidence for four intriguing aspects of rupture process complexity for the 4 April 2010 El Mayor - Cucapah - Indiviso earthquake. First, the southern “fork” of the rupture exhibits two splays just to the northwest of the event epicenter, both with nearly pure right-lateral faulting. Teleseismic source modeling by others indicates normal slip on deep fault surface preceded the shallow strike-slip faulting, and our field observations from the fork area indicate that the earliest phase of strike-slip faulting did not involve a significant normal faulting component. Second, as rupture propagated to the northwest along the Pescadores fault, slip ended abruptly on this fault and transferred across a complex zone to the Borrego fault (although the Pescadores fault continues farther and would have seemed an easier route to follow). This stepover is called the Puerta Accommodation Zone (PAZ) which extends 11 km along-strike within an elevated portion of the Cucapah massif and accommodates a left step (transpressional) that measures less than 2 km across-strike. Though partly obscured by rockfalls in the steep terrain here, only discontinuous faulting of up to one meter reached the ground surface, yet imagery differencing by others indicates several meters of continuous subsurface slip throughout this section. This 11 km region of reduced and discontinuous slip is one of the longest surface rupture jumps ever observed, with lengthy and continuous surface faulting on either side. The SE end of the stepover coincides spatially with the Canon Rojo embayment where the M7.2 1892 surface rupture propagated onto a second fault forming an abrupt corner in its surface trace. Hence, the surface rupture and slip distribution pattern in 2010 appears to have been influenced by stress changes induced by the 1892 event. Thirdly, from the NW end of the transition section, the Borrego fault continues to the NNW with strong east-down slip obliquity. Along

  9. Field aligned current observations in the polar cusp ionosphere

    NASA Technical Reports Server (NTRS)

    Ledley, B. G.; Farthing, W. H.

    1973-01-01

    Vector magnetic field measurements made during a sounding rocket flight in the polar cusp ionosphere show field fluctuations in the lower F-region which are interpreted as being caused by the payload's passage through a structured field aligned current system. The field aligned currents have a characteristic horizontal scale size of one kilometer. Analysis of one large field fluctuation gives a current density of 0.0001 amp/m sq.

  10. Experimental evidence for seismoelectric observations at field scale

    NASA Astrophysics Data System (ADS)

    Holzhauer, Julia; Yaramanci, Ugur

    2010-05-01

    In the past decades, seismoelectric has concentrated a growing interest as a promising tool for hydrogeophysical studies. Resulting from an electrokinetic coupling in porous saturated media traversed by an acoustic wave, this method could ultimately offer a direct access to various hydraulic parameters ranging from porosity to permeability or fluids conductivity. In some other aspects it also occasionally showed some ability to thin-layer resolution. Within the development of the new test-site Schillerslage with typical north-German geology, consisting of two shallow quaternary aquifers separated by a till layer over cretaceous marl, we tested the observability of the seismoelectric signal along with various conventional (seismic, georadar, geoelectric) and unconventional (magnetic resonance sounding -MRS, spectral induced polarisation -SIP) geophysical methods as well as boreholes analysis. The special focus was on the converted seismoelectric signal, an electromagnetic wave acting as a vertical dipole which should theoretically display on the seismoelectrogram as a horizontal arrival. This converted wave appears when the incident acoustic wave meets a hydraulic discontinuity affecting the pore space in any geometrical or chemical manner. This electromagnetic signal fades out rapidly, due to its dipole nature and its weakness, so that its relevance is restricted to the near surface characterisation. In the given setting, such a wave could either initiate at the water table or originate from an abrupt transition from sand to till. Decision was made to record both seismic and seismoelectric signal concomitantly. To allow the detection of the later signal, the field layout was gradually adjusted. Considering the source, hammer-seismic was chosen for its precision in near surface application and automatic trigger-techniques producing major disturbances in the first 10 ms of the seismoelectrogram were abandoned in favour of manual triggering. To avoid any further noise

  11. Modeling the Jovian magnetic field and its secular variation using all available magnetic field observations

    NASA Astrophysics Data System (ADS)

    Ridley, Victoria A.; Holme, Richard

    2016-03-01

    We present new models of Jupiter's internal magnetic field and secular variation from all available direct measurements from three decades of spacecraft observation. A regularized minimum norm approach allows the creation of smooth, numerically stable models displaying a high degree of structure. External field from the magnetodisk is modeled iteratively for each orbit. Jupiter's inner magnetosphere is highly stable with time, with no evidence for variation with solar activity. We compare two spherical harmonic models, one assuming a field constant in time and a second allowing for linear time variation. Including secular variation improves data fit with fewer additional parameters than increasing field complexity. Our favored solution indicates a ˜0.012% yr-1 increase in Jupiter's dipole magnetic moment from 1973 to 2003; this value is roughly one quarter of that for Earth. Inaccuracies in determination of the planetary reference frame cannot explain all the observed secular variation. Should more structure be allowed in the solutions, we find the northern hemispherical configuration resembles recent models based on satellite auroral footprint locations, and there is also evidence of a possible patch of reversed polar flux seen at the expected depth of the dynamo region, resembling that found at Earth and with implications for the Jovian interior. Finally, using our preferred model, we infer flow dynamics at the top of Jupiter's dynamo source. Though highly speculative, the results produce several gyres with some symmetry about the equator, similar to those seen at Earth's core-mantle boundary, suggesting motion on cylinders aligned with the rotation axis.

  12. Extended field observations of cirrus clouds using a ground-based cloud observing system

    NASA Technical Reports Server (NTRS)

    Ackerman, Thomas P.

    1994-01-01

    The evolution of synoptic-scale dynamics associated with a middle and upper tropospheric cloud event that occurred on 26 November 1991 is examined. The case under consideration occurred during the FIRE CIRRUS-II Intensive Field Observing Period held in Coffeyville, KS during Nov. and Dec., 1991. Using data from the wind profiler demonstration network and a temporally and spatially augmented radiosonde array, emphasis is given to explaining the evolution of the kinematically-derived ageostrophic vertical circulations and correlating the circulation with the forcing of an extensively sampled cloud field. This is facilitated by decomposing the horizontal divergence into its component parts through a natural coordinate representation of the flow. Ageostrophic vertical circulations are inferred and compared to the circulation forcing arising from geostrophic confluence and shearing deformation derived from the Sawyer-Eliassen Equation. It is found that a thermodynamically indirect vertical circulation existed in association with a jet streak exit region. The circulation was displaced to the cyclonic side of the jet axis due to the orientation of the jet exit between a deepening diffluent trough and building ridge. The cloud line formed in the ascending branch of the vertical circulation with the most concentrated cloud development occurring in conjunction with the maximum large-scale vertical motion. The relationship between the large scale dynamics and the parameterization of middle and upper tropospheric clouds in large-scale models is discussed and an example of ice water contents derived from a parameterization forced by the diagnosed vertical motions and observed water vapor contents is presented.

  13. Neotectonic stresses in Fennoscandia: field observations and modelling

    NASA Astrophysics Data System (ADS)

    Pascal, Christophe

    2013-04-01

    The present-day stress state of Fennoscandia is traditionally viewed as the combination of far field sources and residual glacial loading stresses. Investigations were conducted in different regions of Norway with the purpose of detecting and measuring stress-relief features and to derive from them valuable information on the crustal stress state. Stress-relief features are induced by blasting and sudden rock unloading in road construction and quarrying operations and are common in Norway and very likely in other regions of Fennoscandia. Stress relief at the Earth's surface is diagnostic of anomalously high stress levels at shallow depths in the crust and appears to be a characteristic of the formerly glaciated Baltic and Canadian Precambrian shields. The studied stress-relief features are, in general, indicative of NW-SE compression, suggesting ridge-push as the main source of stress. Our derived stress directions are also in excellent agreement with the ones derived from other kinds of stress indicators, including focal mechanisms from deep earthquakes, demonstrating that stress-relief features are valuable for neotectonic research. As a second step we applied numerical modelling techniques to simulate the neotectonic stress field in Fennoscandia with particular emphasis to southern Norway. A numerical method was used to reconstruct the structure of the Fennoscandian lithosphere. The numerical method involves classical steady-state heat equations to derive lithosphere thickness, geotherm and density distribution and, in addition, requires the studied lithosphere to be isostatically compensated at its base. The a priori crustal structure was derived from previous geophysical studies. Undulations of the geoid were used to calibrate the models. Once the density structure of the Fennoscandian lithosphere is reconstructed it is straightforward to quantify its stress state and compare modelling results with existing stress indicators. The modelling suggests that

  14. Field Observations of Soil Moisture Variability across Scales

    NASA Technical Reports Server (NTRS)

    Famiglietti, James S.; Ryu, Dongryeol; Berg, Aaron A.; Rodell, Matthew; Jackson, Thomas J.

    2008-01-01

    In this study, over 36,000 ground-based soil moisture measurements collected during the SGP97, SGP99, SMEX02, and SMEX03 field campaigns were analyzed to characterize the behavior of soil moisture variability across scales. The field campaigns were conducted in Oklahoma and Iowa in the central USA. The Oklahoma study region is sub-humid with moderately rolling topography, while the Iowa study region is humid with low-relief topography. The relationship of soil moisture standard deviation, skewness and the coefficient of variation versus mean moisture content was explored at six distinct extent scales, ranging from 2.5 m to 50 km. Results showed that variability generally increases with extent scale. The standard deviation increased from 0.036 cm3/cm3 at the 2.5-m scale to 0.071 cm3/cm3 at the 50-km scale. The log standard deviation of soil moisture increased linearly with the log extent scale, from 16 m to 1.6 km, indicative of fractal scaling. The soil moisture standard deviation versus mean moisture content exhibited a convex upward relationship at the 800-m and 50-km scales, with maximum values at mean moisture contents of roughly 0.17 cm3/cm3 and 0.19 cm3/cm3, respectively. An empirical model derived from the observed behavior of soil moisture variability was used to estimate uncertainty in the mean moisture content for a fixed number of samples at the 800-m and 50-km scales, as well as the number of ground-truth samples needed to achieve 0.05 cm3/cm3 and 0.03 cm3/cm3 accuracies. The empirical relationships can also be used to parameterize surface soil moisture variations in land surface and hydrological models across a range of scales. To our knowledge, this is the first study to document the behavior of soil moisture variability over this range of extent scales using ground-based measurements. Our results will contribute not only to efficient and reliable satellite validation, but also to better utilization of remotely sensed soil moisture products for

  15. The linear model and experimentally observed resonant field amplification in tokamaks and reversed field pinches

    SciTech Connect

    Pustovitov, V. D.

    2011-01-15

    A review is given of the experimentally observed effects related to the resonant field amplification (RFA) and the Resistive Wall Mode (RWM) instability in tokamaks and reversed field pinches (RFPs). This includes the feedback rotation of RWM in RFX-mod RFP, dependence of the RWM growth rate on the plasma-wall separation observed in JT-60U, appearance of the slowly growing RWM precursors in JT-60U and similar phenomena in other devices. The experimental results are compared with theoretical predictions based on the model comprising the Maxwell equations, Ohm's law for the conducting wall, the boundary conditions and assumption of linear plasma response to the external magnetic perturbations. The model describes the plasma reaction to the error field as essentially depending on two factors: the plasma proximity to the RWM stability threshold and the natural rotation frequency of the plasma mode. The linear response means that these characteristics are determined by the plasma equilibrium parameters only. It is shown that the mentioned effects in different devices under different conditions can be described on a common basis with only assumption that the plasma behaves as a linear system. To extend the range of the model validation, some predictions are derived with proposals for experimental studies of the RFA dynamics.

  16. Coronal Magnetic Fields Derived from Simultaneous Microwave and EUV Observations and Comparison with the Potential Field Model

    NASA Astrophysics Data System (ADS)

    Miyawaki, Shun; iwai, Kazumasa; Shibasaki, Kiyoto; Shiota, Daikou; Nozawa, Satoshi

    2016-02-01

    We estimated the accuracy of coronal magnetic fields derived from radio observations by comparing them to potential field calculations and the differential emission measure measurements using EUV observations. We derived line-of-sight components of the coronal magnetic field from polarization observations of the thermal bremsstrahlung in the NOAA active region 11150, observed around 3:00 UT on 2011 February 3 using the Nobeyama Radioheliograph at 17 GHz. Because the thermal bremsstrahlung intensity at 17 GHz includes both chromospheric and coronal components, we extracted only the coronal component by measuring the coronal emission measure in EUV observations. In addition, we derived only the radio polarization component of the corona by selecting the region of coronal loops and weak magnetic field strength in the chromosphere along the line of sight. The upper limits of the coronal longitudinal magnetic fields were determined as 100-210 G. We also calculated the coronal longitudinal magnetic fields from the potential field extrapolation using the photospheric magnetic field obtained from the Helioseismic and Magnetic Imager. However, the calculated potential fields were certainly smaller than the observed coronal longitudinal magnetic field. This discrepancy between the potential and the observed magnetic field strengths can be explained consistently by two reasons: (1) the underestimation of the coronal emission measure resulting from the limitation of the temperature range of the EUV observations, and (2) the underestimation of the coronal magnetic field resulting from the potential field assumption.

  17. Field Observations of Supraglacial Streams on the Juneau Icefield

    NASA Astrophysics Data System (ADS)

    Zok, A.; Karlstrom, L.; Hood, E. W.; Manga, M.; Wenzel, R.; Kite, E. S.

    2010-12-01

    Each year during the summer, networks of meltwater streams form below the neve line on many glaciers as the ice surface ablates. This supraglacial network forms an integral part of the total glacial hydrologic system, and exhibits many features common to other fluvial systems despite marked differences in the mechanisms and timescales of erosional processes. Here, we discuss field observations of supraglacial streams on the Mendenhall and Llewellyn glaciers on the Juneau Icefield, taken in July and August, 2010. These sites, 960 m apart in elevation and on different sides of the continental divide, exist in different microclimates and are dominated by different terrain features. The Mendenhall site, near the terminus, receives a large yearly rainwater input and exhibits well-developed stream networks dominated by structural control of the underlying ice. In contrast, the Llewellyn site is much drier and near the neve line, with a dense network of streams whose incision dominates the sculpting of the glacial surface. Stream data includes temperature measurements taken with a Distributed Temperature Sensor and HOBO temperature loggers, velocity profiles taken with an Acoustic Doppler Velocimeter, downstream meander migration rates, and the isotopic composition of water samples. We also document the dynamics of streams in the context of the broader supraglacial network by taking detailed GPS surveys of the beds and banks of streams, as well as measuring drainage density and subsurface flow. Finally, we relate these measurements to surface ablation rates and meteorological data gathered from each site. We find distinct diurnal variation in stream water temperature, discharge, and isotopic content. Distributed Temperature Sensor measurements and cross sectional temperature profiles reveal subtle variation in downstream and cross-stream water temperature. Water temperature generally increases downstream where channels tend to be large, and we investigate the contribution

  18. Application of relativistic mean field and effective field theory densities to scattering observables for Ca isotopes

    NASA Astrophysics Data System (ADS)

    Bhuyan, M.; Panda, R. N.; Routray, T. R.; Patra, S. K.

    2010-12-01

    In the framework of relativistic mean field (RMF) theory, we have calculated the density distribution of protons and neutrons for Ca40,42,44,48 with NL3 and G2 parameter sets. The microscopic proton-nucleus optical potentials for p+Ca40,42,44,48 systems are evaluated from the Dirac nucleon-nucleon scattering amplitude and the density of the target nucleus using relativistic-Love-Franey and McNeil-Ray-Wallace parametrizations. We have estimated the scattering observables, such as the elastic differential scattering cross section, analyzing power and the spin observables with the relativistic impulse approximation (RIA). The results have been compared with the experimental data for a few selective cases and we find that the use of density as well as the scattering matrix parametrizations are crucial for the theoretical prediction.

  19. Application of relativistic mean field and effective field theory densities to scattering observables for Ca isotopes

    SciTech Connect

    Bhuyan, M.; Panda, R. N.; Routray, T. R.; Patra, S. K.

    2010-12-15

    In the framework of relativistic mean field (RMF) theory, we have calculated the density distribution of protons and neutrons for {sup 40,42,44,48}Ca with NL3 and G2 parameter sets. The microscopic proton-nucleus optical potentials for p+{sup 40,42,44,48}Ca systems are evaluated from the Dirac nucleon-nucleon scattering amplitude and the density of the target nucleus using relativistic-Love-Franey and McNeil-Ray-Wallace parametrizations. We have estimated the scattering observables, such as the elastic differential scattering cross section, analyzing power and the spin observables with the relativistic impulse approximation (RIA). The results have been compared with the experimental data for a few selective cases and we find that the use of density as well as the scattering matrix parametrizations are crucial for the theoretical prediction.

  20. Field observations of soil moisture variability across scales

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this study, over 36,000 ground-based soil moisture measurements collected during the SGP97, SGP99, SMEX02, and SMEX03 field campaigns were analyzed to characterize the behavior of soil moisture variability across scales. The field campaigns were conducted in Oklahoma and Iowa in the central USA. ...

  1. Field Science Ethnography: Methods For Systematic Observation on an Expedition

    NASA Technical Reports Server (NTRS)

    Clancey, William J.; Clancy, Daniel (Technical Monitor)

    2001-01-01

    The Haughton-Mars expedition is a multidisciplinary project, exploring an impact crater in an extreme environment to determine how people might live and work on Mars. The expedition seeks to understand and field test Mars facilities, crew roles, operations, and computer tools. I combine an ethnographic approach to establish a baseline understanding of how scientists prefer to live and work when relatively unemcumbered, with a participatory design approach of experimenting with procedures and tools in the context of use. This paper focuses on field methods for systematically recording and analyzing the expedition's activities. Systematic photography and time-lapse video are combined with concept mapping to organize and present information. This hybrid approach is generally applicable to the study of modern field expeditions having a dozen or more multidisciplinary participants, spread over a large terrain during multiple field seasons.

  2. Mariner 10 magnetic field observations of the Venus wake

    NASA Technical Reports Server (NTRS)

    Lepping, R. P.; Behannon, K. W.

    1977-01-01

    Magnetic field measurements made over a 21-hour interval during the Mariner 10 encounter with Venus were used to study the down-stream region of the solar wind-Venus interaction over a distance of approximately 100 R sub v. For most of the day before closest approach the spacecraft was located in a sheath-like region which was apparently bounded by planetary bow shock on the outer side and either a planetary wake boundary or transient boundary-like feature on the inner side. The spacecraft made multiple encounters with the wake-like boundary during the 21-hour interval with an increasing frequency as it approached the planet. Each pass into the wake boundary from the sheath region was consistently characterized by a slight decrease in magnetic field magnitude, a marked increase in the frequency and amplitude of field fluctuations, and a systematic clockwise rotation of the field direction when viewed from above the plane of the planet orbit.

  3. Service Learning and Participant Observation: Undergraduate Field Research.

    ERIC Educational Resources Information Center

    White, Timothy J.

    2000-01-01

    Compares the service learning experience of college students to the traditional social science technique of participant observation. Suggests that service learning allows students to test theories through personal observation in a service setting and experience the logic and practice of social research. Uses examples from the Xavier University…

  4. Microspacecraft and Earth observation: Electrical Field (ELF) measurement project

    NASA Technical Reports Server (NTRS)

    1990-01-01

    There is a need for an inexpensive, extensive, long-lasting global electric field measurement system (ELF). The primary performance driver of this mission is the need to measure the attitude of each spacecraft in the Earth's electric field very accurately. In addition, it is necessary to know the electric charge generated by the satellite as it crosses the magnetic field lines (E equals V times B). In order to achieve the desired global coverage, a constellation of about 50 satellites in at least 18 different orbits will be used. To reduce the cost of each satellite, off-the-shelf, proven technology will be used whenever possible. Researchers have set a limit of $500,000 per satellite. Researchers expect the program cost, including the deployment of the entire constellation, to be less than $100 million. The minimum projected mission life is five years.

  5. Observations of interactions between interplanetary and geomagnetic fields

    NASA Technical Reports Server (NTRS)

    Burch, J. L.

    1973-01-01

    Magnetospheric effects associated with variations of the north-south component of the interplanetary magnetic field are examined in light of recent recent experimental and theoretical results. Although the occurrence of magnetospheric substorms is statistically related to periods of southward interplanetary magnetic field, the details of the interaction are not understood. In particular, attempts to separate effects resulting directly from the interaction between the interplanetary and geomagnetic fields from those associated with substorms have produced conflicting results. The transfer of magnetic flux from the dayside to the nightside magnetosphere is evidenced by equatorward motion of the polar cusp and increases of the magnetic energy density in the lobes of the geomagnetic tail. The formation of a macroscopic X-type neutral line at tail distances less than 35 R sub E appears to be a substorm phenomenon.

  6. Convective Systems Observed and Simulated During TRMM Field Campaigns

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Recently completed TRMM field campaigns (TEFLUN1998, SCSMEX-1998, TRMM.LBA-1999, and KWAJEX 1999) have obtained direct measurements of microphysical data associated with convective systems from various geographical locations. These TRMM field experiments were designed to contribute to fundamental understanding of cloud dynamics and microphysics, as well as for validation,, testing assumptions and error estimates of cloud-resolving models, forward radiative transfer models, algorithms used to estimate rainfall statistics and vertical structure of precipitation and latent heating from both surface-based radar and satellites.

  7. Multi-point Magnetic Field Observations of Field-Aligned Currents from Swarm Constellation Mission

    NASA Astrophysics Data System (ADS)

    Le, Guan; Chi, Peter; Lühr, Hermann; Gjerloev, Jesper; Stolle, Claudia; Park, Jaeheung; Rauberg, Jan

    2015-04-01

    In this paper, we report the results of case studies of multi-point magnetic field measurements of field-aligned currents (FACs) from Swarm constellation mission to understand their temporal characteristics and hemispheric asymmetry. For science operations (since April, 2014), the three spacecraft were placed in slightly different polar orbits: Swarm B spacecraft in a higher altitude orbit (507km x 512km) and Swarm A and C side-by-side in lower altitude orbits (459km x 462km). In the beginning of the science operational phase, the longitudinal separations of the orbital planes were small, and Swarm A/C pair and Swarm B were nearly out of phase in the orbit. This unique orbit configuration provides opportunities to study some new features of FACs. Specifically, the Swarm satellites make multiple crossings of a FAC region within a few hours. Such data enable us to study temporal variations in several time scales, from 1 minute up to about 3 hours. Furthermore, the three satellites make nearly simultaneous observations of FACs in northern and southern hemispheres, which provide us an opportunity to study the hemispheric asymmetry.

  8. The magnetic field of saturn: pioneer 11 observations.

    PubMed

    Acuña, M H; Ness, N F

    1980-01-25

    The intrinsic magnetic field of Saturn measured by the high-field fluxgate magnetometer is much weaker than expected. An analysis of preliminary data combined with the preliminary trajectory yield a model for the main planetary field which is a simple centered dipole of moment 0.20 +/- 0.01 gauss-Rs(3) = 4.3 +/- 0.2 x 10(28) gauss-cm(3) (1 Rs = 1 Saturn radius = 60,000 km). The polarity is opposite that of Earth, and, surprisingly, the tilt is small, within 2 degrees +/- 1 degrees of the rotation axis. The equatorial field intensity at the cloud tops is 0.2 gauss, and the polar intensity is 0.56 gauss. The unique moon Titan is expected to be located within the magnetosheath of Saturn or the interplanetary medium about 50 percent of the time because the average subsolar point distance to the magnetosphere is estimated to be 20 Rs, the orbital distance to Titan. PMID:17833558

  9. The radial component of the heliospheric magnetic field: Ulysses observations

    NASA Technical Reports Server (NTRS)

    Smith, E. J.; Tsurutani, B. T.; Balogh, A.; Lepping, R. P.

    1995-01-01

    The radial field component, B(sub R), has been monitored continuously since the Ulysses spacecraft left the ecliptic plane in February 1992 travelling toward the southern pole of the Sun. In order to separate spatial from temporal changes, the Ulysses measurements from 0 to 80 heliographic latitude were compared with in-ecliptic measurements of B(sub R) being made simultaneously by IMP-8. The data revealed essentially the same field strengths and time variations at both locations. The conclusion was drawn that there was no significant latitude gradient in B(sub R) and that the stronger polar cap coronal magnetic fields were being transported equatorward to yield a uniform field in the solar wind. The results contrasted with the predictions of the various source surface models which ignore magnetic stresses within 2.5 solar radii. Since the maximum south latitude was attained in September, 1994, Ulysses has traveled northward toward an ecliptic crossing in March 1995 and onward into the north solar hemisphere. The recent results will be presented and compared with those obtained in the southern hemisphere.

  10. Student Brinkmanship: Some Field Observations, Findings and Questions.

    ERIC Educational Resources Information Center

    Licata, Joseph W.

    The relationship between student brinkmanship, defined as an assertive student behavior which attempts to challenge school authority while avoiding negative sanctions, and classroom social structure in five secondary school classrooms was investigated through a field study. Subjects were 185 students in a small rural high school in Georgia.…

  11. Magnetic Field and Plasma Diagnostics from Coordinated Prominence Observations

    NASA Astrophysics Data System (ADS)

    Schmieder, B.; Levens, P.; Dalmasse, K.; Mein, N.; Mein, P.; Lopez-Ariste, A.; Labrosse, N.; Heinzel, P.

    2016-04-01

    We study the magnetic field in prominences from a statistical point of view, by using THEMIS in the MTR mode, performing spectropolarimetry of the He I D3 line. Combining these measurements with spectroscopic data from IRIS, Hinode/EIS as well as ground-based telescopes, such as the Meudon Solar Tower, we infer the temperature, density, and flow velocities of the plasma. There are a number of open questions that we aim to answer: - What is the general direction of the magnetic field in prominences? Is the model using a single orientation of magnetic field always valid for atypical prominences? %- Does this depend on the location of the filament on the disk (visible in Hα, in He II 304 Å) over an inversion line between weak or strong network ? - Are prominences in a weak environment field dominated by gas pressure? - Measuring the Doppler shifts in Mg II lines (with IRIS) and in Hα can tell us if there are substantial velocities to maintain vertical rotating structures, as has been suggested for tornado-like prominences. We present here some results obtained with different ground-based and space-based instruments in this framework.

  12. The Value of Supplementing Panel Software Reviews with Field Observations.

    ERIC Educational Resources Information Center

    Owston, Ronald D.; Wideman, Herbert H.

    1987-01-01

    Describes study that compared teacher panel reviews of educational software to field test reports to determine the levels of agreement between the two evaluation types. Methods of evaluation are discussed, the York Educational Software Evaluation Scales (YESES) are explained, and the results of the study of 36 software packages are presented.…

  13. Sensor Technology Performance Characteristics- Field and Laboratory Observations

    EPA Science Inventory

    Observed Intangible Performance Characteristics RH and temperature impacts may be significant for some devices Internal battery lifetimes range from 4 to 24 hoursSensor packaging can interfere with accurate measurements (reactivity)Wireless communication protocols are not foolpr...

  14. Space Technology 5 Observations of Auroral Field-Aligned Currents

    NASA Technical Reports Server (NTRS)

    Slavin, James

    2008-01-01

    During its three month long technology validation mission, Space Technology 5 (ST-5) returned high quality multi-point measurements of the near-Earth magnetic field. Its three micro-satellites were launched into a 300 x 4500 km, dawn - dusk, sun synchronous orbit (inclination = 105.60) orbit with a period of 138 min by a Pegasus launch vehicle on March 22, 2006. The spacecraft were maintained in a "pearls on a sting" constellation with controlled spacings ranging from just over 5000 km down to under 50 km. The individual micro-satellites were 48 cm tall octagons with diameters of 50 cm. They were spin-stabilized at approximately 20 rpm at deployment and slowly spun-down to about 15 rpm by the end of the mission. Each spacecraft carried a miniature tri-axial fluxgate magnetometer (MAG) provided by the University of California at Los Angeles mounted at the end of a ultra-low mass 72 cm boom. These data allow, for the first time, the separation of temporal and spatial variations in field-aligned current (FAC) perturbations measured in low-Earth orbit on time scales of 10 sec to 10 min. The constellation measurements are used to directly determine field-aligned current sheet motion, thickness. and current density. Two multi-point methods for the inference of FAC current density that have not previously been possible in low-Earth orbit are demonstrated: 1) the -standard method." based upon s/c velocity, but corrected for FAC current sheet motion. and 2) the "gradiometer method" which uses simultaneous magnetic field measurements at two points with known separation. Future studies will apply these methods to the entire ST-5 data sct and expand to include horizontal ionospheric currents. ULF waves and geomagnetic field gradient analyses.

  15. Space Technology 5 observations of auroral field-aligned currents

    NASA Astrophysics Data System (ADS)

    Slavin, James

    During its three month long technology validation mission, Space Technology 5 (ST-5) returned high quality multi-point measurements of the near-Earth magnetic field. Its three micro-satellites were launched into a 300 x 4500 km, dawn - dusk, sun synchronous orbit (inclination = 105.6o) orbit with a period of 138 min by a Pegasus launch vehicle on March 22, 2006. The spacecraft were maintained in a "pearls on a sting" constellation with controlled spacings ranging from just over 5000 km down to under 50 km. The individual micro-satellites were 48 cm tall octagons with diameters of 50 cm. They were spin-stabilized at approximately 20 rpm at deployment and slowly spun-down to about 15 rpm by the end of the mission. Each spacecraft carried a miniature tri-axial fluxgate magnetometer (MAG) provided by the University of California at Los Angeles mounted at the end of a ultra-low mass 72 cm boom. These data allow, for the first time, the separation of temporal and spatial variations in field-aligned current (FAC) perturbations measured in low-Earth orbit on time scales of 10 sec to 10 min. The constellation measurements are used to directly determine field-aligned current sheet motion, thickness, and current density. Two multi-point methods for the inference of FAC current density that have not previously been possible in low-Earth orbit are demonstrated: 1) the "standard method," based upon s/c velocity, but corrected for FAC current sheet motion, and 2) the "gradiometer method" which uses simultaneous magnetic field measurements at two points with known separation. Future studies will apply these methods to the entire ST-5 data set and expand to include horizontal ionospheric currents, ULF waves and geomagnetic field gradient analyses.

  16. Deep, wide-field, global VLBI observations of the Hubble deep field north (HDF-N) and flanking fields (HFF)

    NASA Astrophysics Data System (ADS)

    Chi, S.; Barthel, P. D.; Garrett, M. A.

    2013-02-01

    Context. Dust is commonly present in weakly radio emitting star-forming galaxies and this dust may obscure the signatures of accreting black holes in these objects. Aims: We aim to uncover weak active galactic nuclei, AGN, in the faint radio source population by means of deep high-resolution radio observations. Methods: VLBI observations with a world-wide array at unparallelled sensitivity are carried out to assess the nature of the faint radio source population in the Hubble deep field north and its flanking fields. Results: Images of twelve compact, AGN-driven radio sources are presented. These represent roughly one quarter of the detectable faint radio source sample. Most, but not all of these low power AGN have X-ray detections. Conclusions: The majority of the faint radio source population must be star-forming galaxies. Faint AGN occur in a variety of (distant) host galaxies, and these are often accompanied by a dust-obscured starburst. Deep, high-resolution VLBI is a unique, powerful technique to assess the occurrence of faint AGN.

  17. Observation of airplane flow fields by natural condensation effects

    NASA Technical Reports Server (NTRS)

    Campbell, James F.; Chambers, Joseph R.; Rumsey, Christopher L.

    1988-01-01

    In-flight condensation patterns can illustrate a variety of airplane flow fields, such as attached and separated flows, vortex flows, and expansion and shock waves. These patterns are a unique source of flow visualization that has not been utilized previously. Condensation patterns at full-scale Reynolds number can provide useful information for researchers experimenting in subscale tunnels. It is also shown that computed values of relative humidity in the local flow field provide an inexpensive way to analyze the qualitative features of the condensation pattern, although a more complete theoretical modeling is necessary to obtain details of the condensation process. Furthermore, the analysis revealed that relative humidity is more sensitive to changes in local static temperature than to changes in pressure.

  18. Microspacecraft and Earth observation: Electrical field (ELF) measurement project

    NASA Technical Reports Server (NTRS)

    Olsen, Tanya; Elkington, Scot; Parker, Scott; Smith, Grover; Shumway, Andrew; Christensen, Craig; Parsa, Mehrdad; Larsen, Layne; Martinez, Ranae; Powell, George

    1990-01-01

    The Utah State University space system design project for 1989 to 1990 focuses on the design of a global electrical field sensing system to be deployed in a constellation of microspacecraft. The design includes the selection of the sensor and the design of the spacecraft, the sensor support subsystems, the launch vehicle interface structure, on board data storage and communications subsystems, and associated ground receiving stations. Optimization of satellite orbits and spacecraft attitude are critical to the overall mapping of the electrical field and, thus, are also included in the project. The spacecraft design incorporates a deployable sensor array (5 m booms) into a spinning oblate platform. Data is taken every 0.1 seconds by the electrical field sensors and stored on-board. An omni-directional antenna communicates with a ground station twice per day to down link the stored data. Wrap-around solar cells cover the exterior of the spacecraft to generate power. Nine Pegasus launches may be used to deploy fifty such satellites to orbits with inclinations greater than 45 deg. Piggyback deployment from other launch vehicles such as the DELTA 2 is also examined.

  19. Microspacecraft and Earth observation: Electrical field (ELF) measurement project

    NASA Astrophysics Data System (ADS)

    Olsen, Tanya; Elkington, Scot; Parker, Scott; Smith, Grover; Shumway, Andrew; Christensen, Craig; Parsa, Mehrdad; Larsen, Layne; Martinez, Ranae; Powell, George

    The Utah State University space system design project for 1989 to 1990 focuses on the design of a global electrical field sensing system to be deployed in a constellation of microspacecraft. The design includes the selection of the sensor and the design of the spacecraft, the sensor support subsystems, the launch vehicle interface structure, on board data storage and communications subsystems, and associated ground receiving stations. Optimization of satellite orbits and spacecraft attitude are critical to the overall mapping of the electrical field and, thus, are also included in the project. The spacecraft design incorporates a deployable sensor array (5 m booms) into a spinning oblate platform. Data is taken every 0.1 seconds by the electrical field sensors and stored on-board. An omni-directional antenna communicates with a ground station twice per day to down link the stored data. Wrap-around solar cells cover the exterior of the spacecraft to generate power. Nine Pegasus launches may be used to deploy fifty such satellites to orbits with inclinations greater than 45 deg. Piggyback deployment from other launch vehicles such as the DELTA 2 is also examined.

  20. Laboratory observation of magnetic field growth driven by shear flow

    SciTech Connect

    Intrator, T. P. Feng, Y.; Sears, J.; Weber, T.; Dorf, L.; Sun, X.

    2014-04-15

    Two magnetic flux ropes that collide and bounce have been characterized in the laboratory. We find screw pinch profiles that include ion flow v{sub i}, magnetic field B, current density J, and plasma pressure. The electron flow v{sub e} can be inferred, allowing the evaluation of the Hall J×B term in a two fluid magnetohydrodynamic Ohm's Law. Flux ropes that are initially cylindrical are mutually attracted and compress each other, which distorts the cylindrical symmetry. Magnetic field is created via the ∇×v{sub e}×B induction term in Ohm's Law where in-plane (perpendicular) shear of parallel flow (along the flux rope) is the dominant feature, along with some dissipation and magnetic reconnection. We predict and measure the growth of a quadrupole out-of-plane magnetic field δB{sub z}. This is a simple and coherent example of a shear flow driven dynamo. There is some similarity with two dimensional reconnection scenarios, which induce a current sheet and thus out-of-plane flow in the third dimension, despite the customary picture that considers flows only in the reconnection plane. These data illustrate a general and deterministic mechanism for large scale sheared flows to acquire smaller scale magnetic features, disordered structure, and possibly turbulence.

  1. VOYAGER OBSERVATIONS OF THE DIFFUSE FAR-ULTRAVIOLET RADIATION FIELD

    SciTech Connect

    Murthy, Jayant; Henry, Richard Conn; Holberg, Jay B.

    2012-03-01

    The two Voyager spacecraft have completed their planetary exploration mission and are now probing the outer realms of the heliosphere. The Voyager ultraviolet spectrometers continued to operate well after the Voyager 2 Neptune encounter in 1989. We present a complete database of diffuse radiation observations made by both Voyagers: a total of 1943 spectra (500-1600 A) scattered throughout the sky. These include observations of dust-scattered starlight, emission lines from the hot interstellar medium, and a number of locations where no diffuse radiation was detected, with the very low upper limit of about 25 photons cm{sup -2} s{sup -1} sr{sup -1} A{sup -1}. Many of these observations were from late in the mission when there was significantly less contribution from interplanetary emission lines and thus less contamination of the interstellar signal.

  2. Nodding Syndrome in Uganda: Field Observations, Challenges and Research Agenda

    PubMed Central

    Feldmeier, Hermann; Komazawa, Osuke; Moji, Kazuhiko

    2014-01-01

    This article summarizes observations made in Northern Uganda and a lecture given at the Nodding Syndrome Workshop in Nagasaki September 2013. The objective of the manuscript is to summarize the current knowledge on nodding syndrome and to provide an agenda for investigations into the epidemiology, pathophysiology, diagnosis and care management of nodding syndrome in Uganda. PMID:25425959

  3. Nodding syndrome in Uganda: field observations, challenges and research agenda.

    PubMed

    Feldmeier, Hermann; Komazawa, Osuke; Moji, Kazuhiko

    2014-06-01

    This article summarizes observations made in Northern Uganda and a lecture given at the Nodding Syndrome Workshop in Nagasaki September 2013. The objective of the manuscript is to summarize the current knowledge on nodding syndrome and to provide an agenda for investigations into the epidemiology, pathophysiology, diagnosis and care management of nodding syndrome in Uganda. PMID:25425959

  4. Programs for the Field Collection of Observational Data.

    ERIC Educational Resources Information Center

    Roberts, William L.; Schill, Loreen G.

    The collection of observational data in natural settings and in real time requires equipment that is light and easily used, and programs that permit rapid and flexible encoding of data. This paper describes a set of four programs for collecting and analyzing continuous time sample, focal-individual data as described by J. Altmann (1974), using a…

  5. Quantifying solar superactive regions with vector magnetic field observations

    NASA Astrophysics Data System (ADS)

    Chen, A. Q.; Wang, J. X.

    2012-07-01

    Context. The vector magnetic field characteristics of superactive regions (SARs) hold the key for understanding why SARs are extremely active and provide the guidance in space weather prediction. Aims: We aim to quantify the characteristics of SARs using the vector magnetograms taken by the Solar Magnetic Field Telescope at Huairou Solar Observatory Station. Methods: The vector magnetic field characteristics of 14 SARs in solar cycles 22 and 23 were analyzed using the following four parameters: 1) the magnetic flux imbalance between opposite polarities; 2) the total photospheric free magnetic energy; 3) the length of the magnetic neutral line with its steep horizontal magnetic gradient; and 4) the area with strong magnetic shear. Furthermore, we selected another eight large and inactive active regions (ARs), which are called fallow ARs (FARs), to compare them with the SARs. Results: We found that most of the SARs have a net magnetic flux higher than 7.0 × 1021 Mx, a total photospheric free magnetic energy higher than 1.0 × 1024 erg cm-1, a magnetic neutral line with a steep horizontal magnetic gradient (≥300 G Mm-1) longer than 30 Mm, and an area with strong magnetic shear (shear angle ≥ 80°) greater than 100 Mm2. In contrast, the values of these parameters for the FARs are mostly very low. The Pearson χ2 test was used to examine the significance of the difference between the SARs and FARs, and the results indicate that these two types of ARs can be fairly distinguished by each of these parameters. The significance levels are 99.55%, 99.98%, 99.98%, and 99.96%, respectively. However, no single parameter can distinguish them perfectly. Therefore we propose a composite index based on these parameters, and find that the distinction between the two types of ARs is also significant with a significance level of 99.96%. These results are useful for a better physical understanding of the SAR and FAR.

  6. Field observations of artificial sand and oil agglomerates

    USGS Publications Warehouse

    Dalyander, Patricia (Soupy); Long, Joseph W.; Plant, Nathaniel G.; McLaughlin, Molly R.; Mickey, Rangley C.

    2015-01-01

    Oil that comes into the surf zone following spills, such as occurred during the 2010 Deepwater Horizon (DWH) blowout, can mix with local sediment to form heavier-than-water sand and oil agglomerates (SOAs), at times in the form of mats a few centimeters thick and tens of meters long. Smaller agglomerates that form in situ or pieces that break off of larger mats, sometimes referred to as surface residual balls (SRBs), range in size from sand-sized grains to patty-shaped pieces several centimeters (cm) in diameter. These mobile SOAs can cause beach oiling for extended periods following the spill, on the scale of years as in the case of DWH. Limited research, including a prior effort by the U.S. Geological Survey (USGS) investigating SOA mobility, alongshore transport, and seafloor interaction using numerical model output, focused on the physical dynamics of SOAs. To address this data gap, we constructed artificial sand and oil agglomerates (aSOAs) with sand and paraffin wax to mimic the size and density of genuine SOAs. These aSOAs were deployed in the nearshore off the coast of St. Petersburg, Florida, during a field experiment to investigate their movement and seafloor interaction. This report presents the methodology for constructing aSOAs and describes the field experiment. Data acquired during the field campaign, including videos and images of aSOA movement in the nearshore (1.5-meter and 0.5-meter water depth) and in the swash zone, are also presented in this report.

  7. Time Series Vegetation Aerodynamic Roughness Fields Estimated from MODIS Observations

    NASA Technical Reports Server (NTRS)

    Borak, Jordan S.; Jasinski, Michael F.; Crago, Richard D.

    2005-01-01

    Most land surface models used today require estimates of aerodynamic roughness length in order to characterize momentum transfer between the surface and atmosphere. The most common method of prescribing roughness is through the use of empirical look-up tables based solely on land cover class. Theoretical approaches that employ satellite-based estimates of canopy density present an attractive alternative to current look-up table approaches based on vegetation cover type that do not account for within-class variability and are oftentimes simplistic with respect to temporal variability. The current research applies Raupach s formulation of momentum aerodynamic roughness to MODIS data on a regional scale in order to estimate seasonally variable roughness and zero-plane displacement height fields using bulk land cover parameters estimated by [Jasinski, M.F., Borak, J., Crago, R., 2005. Bulk surface momentum parameters for satellite-derived vegetation fields. Agric. For. Meteorol. 133, 55-68]. Results indicate promising advances over look-up approaches with respect to characterization of vegetation roughness variability in land surface and atmospheric circulation models.

  8. Relationships between field-aligned currents, electric fields and particle precipitation as observed by dynamics Explorer-2

    NASA Technical Reports Server (NTRS)

    Sugiura, M.; Iyemori, T.; Hoffman, R. A.; Maynard, N. C.; Burch, J. L.; Winningham, J. D.

    1983-01-01

    The relationships between field-aligned currents, electric fields, and particle fluxes are determined using observations from the polar orbiting low-altitude satellite Dynamics Explorer-2. It is shown that the north-south electric field and the east-west magnetic field components are usually highly correlated in the field-aligned current regions. This proportionality observationally proves that the field-aligned current equals the divergence of the height-integrated ionospheric Pedersen current in the meridional plane to a high degree of approximation. As a general rule, in the evening sector the upward field-aligned currents flow in the boundary plasma sheet region and the downward currents flow in the central plasma sheet region. The current densities determined independently from the plasma and magnetic field measurements are compared. Although the current densities deduced from the two methods are in general agreement, the degree and extent of the agreement vary in individual cases.

  9. Relationships between field-aligned currents, electric fields, and particle precipitation as observed by Dynamics Explorer-2

    NASA Technical Reports Server (NTRS)

    Sugiura, M.; Iyemori, T.; Hoffman, R. A.; Maynard, N. C.; Burch, J. L.; Winningham, J. D.

    1984-01-01

    The relationships between field-aligned currents, electric fields, and particle fluxes are determined using observations from the polar orbiting low-altitude satellite Dynamics Explorer-2. It is shown that the north-south electric field and the east-west magnetic field components are usually highly correlated in the field-aligned current regions. This proportionality observationally proves that the field-aligned current equals the divergence of the height-integrated ionospheric Pedersen current in the meridional plane to a high degree of approximation. As a general rule, in the evening sector the upward field-aligned currents flow in the boundary plasma sheet region and the downward currents flow in the central plasma sheet region. The current densities determined independently from the plasma and magnetic field measurements are compared. Although the current densities deduced from the two methods are in general agreement, the degree and extent of the agreement vary in individual cases.

  10. Field Observations of Canopy Flows over Complex Terrain

    NASA Astrophysics Data System (ADS)

    Grant, Eleanor R.; Ross, Andrew N.; Gardiner, Barry A.; Mobbs, Stephen D.

    2015-08-01

    The investigation of airflow over and within forests in complex terrain has been, until recently, limited to a handful of modelling and laboratory studies. Here, we present an observational dataset of airflow measurements inside and above a forest situated on a ridge on the Isle of Arran, Scotland. The spatial coverage of the observations all the way across the ridge makes this a unique dataset. Two case studies of across-ridge flow under near-neutral conditions are presented and compared with recent idealized two-dimensional modelling studies. Changes in the canopy profiles of both mean wind and turbulent quantities across the ridge are broadly consistent with these idealized studies. Flow separation over the lee slope is seen as a ubiquitous feature of the flow. The three-dimensional nature of the terrain and the heterogeneous forest canopy does however lead to significant variations in the flow separation across the ridge, particularly over the less steep western slope. Furthermore, strong directional shear with height in regions of flow separation has a significant impact on the Reynolds stress terms and other turbulent statistics. Also observed is a decrease in the variability of the wind speed over the summit and lee slope, which has not been seen in previous studies. This dataset should provide a valuable resource for validating models of canopy flow over real, complex terrain.

  11. Field Observations of Meteotsunami in Kami-koshiki Island, Japan

    NASA Astrophysics Data System (ADS)

    Asano, T.; Yamashiro, T.; Nishimura, N.

    2012-12-01

    BACKGROUND Meteotsunami; atmospherically induced destructive ocean waves in the tsunami frequency band, are known in Japan by the local term "abiki", literally meaning "net-dragging waves" in Japanese. Large abiki occur in bays and harbors along the west coast of Kyushu almost every year during winter and early spring. On 24-25 February, 2009, Urauchi Bay, located on west coast of Kami-Koshiki Island on the southeast coast of Kyushu, was subjected to a destructive meteotsunami. In this event, a maximum sea surface height of 3.1 m was observed at the inner part of the bay. At least 18 boats capsized and eight houses were flooded. This event surpassed the previous record height for an abiki in Japan: 278 cm in Nagasaki Bay, also located west coast of Kyushu, in 1979. Generally, such an elongated inlet with narrow mouth as Urauchi bay provides calm water conditions even when offshore weather is stormy. Therefore, the area is regarded as a suitable place for the farming of large fish with a high market value. Possible damage to the extensive fish cage system as a result of meteotsunami events is of concern, especially because aquaculture is the main industry in the isolated islands. Forecasting of meteotsunami is a serious request from the local people. AIMS The objectives of the present study are to detect a meteotsunami event in Urauchi Bay and to clarify the meteorological and hydrodynamic conditions related to its occurrence. This work attempts to observe the whole process of a meteotsunami event: generation offshore, resonance while it propagates, and finally amplification in the bay. Observations were conducted over a period of 82 days; 12 January to 4 April, 2010, aiming to record large secondary oscillations. A comprehensive measuring system for sea level, current and barometric pressure fluctuations was deployed covering not only inside and near Urauchi Bay but also further offshore in the vicinity of Mejima in the East China Sea. MAIN RESULTS 1) Large

  12. Observations of vector magnetic fields with a magneto-optic filter

    NASA Technical Reports Server (NTRS)

    Cacciani, Alessandro; Varsik, John; Zirin, Harold

    1990-01-01

    The use of the magnetooptic filter to observe solar magnetic fields in the potassium line at 7699 A is described. The filter has been used in the Big Bear videomagnetograph since October 23. It gives a high sensitivity and dynamic range for longitudnal magnetic fields and enables measurement of transverse magnetic fields using the sigma component. Examples of the observations are presented.

  13. Snowfall Characterization by Field Observation and Atmospheric Sounding

    NASA Astrophysics Data System (ADS)

    Francisco, Dianna M.

    The snowfall rate is related to microphysical and dynamical processes in weather systems and is further specified by choice of measurement time, related to the statistics of individual falling ice crystals. A snowflake is definable as a single ice crystal having long range order in the crystal lattice or as a polycrystalline having a multitude of individual single crystals, frozen together as graupel or held together though interlocking shapes as an aggregate snowflake. Snowflakes are collected on a black cloth, next to a scale, and photographed using a macro magnification. Snowflakes captured at the surface are characterized by their appearance from the habit, shape, size, symmetry, thickness, concentration, and fall of the individual ice crystals and of aggregates. Individual ice crystals are identified, counted, and related to the snowfall rate for a calculation of ice crystal number flux. The snowfall rate is characterized as a concentration and an inferred flux of individual nucleation events, to be related to possible direct nucleation and secondary ice formation (such as rime splintering) aloft. Identifying the number of ice crystals requires a degree of persistence and skill, is not readily automated, and is capable of providing key information on the growth history of ice crystals, not obtainable by other means. Surface data is collected through a surface weather station within one mile of the Observation Site. Atmospheric soundings produced by the National Weather Service, less than two miles distance from the Observation Site, aids in the approximation of the ice crystal's life history.

  14. Integral field observations of damped Lyman-α galaxies

    NASA Astrophysics Data System (ADS)

    Christensen, L.; Sánchez, S. F.; Jahnke, K.; Becker, T.; Kelz, A.; Wisotzki, L.; Roth, M. M.

    2004-02-01

    We report preliminary results from a targeted investigation on quasars containing damped Lyman-α absorption (DLA) lines as well strong metal absorption lines, carried out with the Potsdam Multi Aperture Spectrophotometer (PMAS). We search for line-emitting objects at the same redshift as the absorption lines and close to the line of sight of the QSOs. We have observed and detected the already confirmed absorbing galaxies in Q2233+131 (zabs=3.15) and Q0151+045 (zabs=0.168), while failing to find spectral signatures for the z=0.091 absorber in Q0738+313. From the Q2233+131 DLA galaxy, we have detected extended Lyα emission from an area of 3″×5″.

  15. Quantum gases. Observation of isolated monopoles in a quantum field.

    PubMed

    Ray, M W; Ruokokoski, E; Tiurev, K; Möttönen, M; Hall, D S

    2015-05-01

    Topological defects play important roles throughout nature, appearing in contexts as diverse as cosmology, particle physics, superfluidity, liquid crystals, and metallurgy. Point defects can arise naturally as magnetic monopoles resulting from symmetry breaking in grand unified theories. We devised an experiment to create and detect quantum mechanical analogs of such monopoles in a spin-1 Bose-Einstein condensate. The defects, which were stable on the time scale of our experiments, were identified from spin-resolved images of the condensate density profile that exhibit a characteristic dependence on the choice of quantization axis. Our observations lay the foundation for experimental studies of the dynamics and stability of topological point defects in quantum systems. PMID:25931553

  16. An observation planning algorithm applied to multi-objective astronomical observations and its simulation in COSMOS field

    NASA Astrophysics Data System (ADS)

    Jin, Yi; Gu, Yonggang; Zhai, Chao

    2012-09-01

    Multi-Object Fiber Spectroscopic sky surveys are now booming, such as LAMOST already built by China, BIGBOSS project put forward by the U.S. Lawrence Berkeley National Lab and GTC (Gran Telescopio Canarias) telescope developed by the United States, Mexico and Spain. They all use or will use this approach and each fiber can be moved within a certain area for one astrology target, so observation planning is particularly important for this Sky Surveys. One observation planning algorithm used in multi-objective astronomical observations is developed. It can avoid the collision and interference between the fiber positioning units in the focal plane during the observation in one field of view, and the interested objects can be ovserved in a limited round with the maximize efficiency. Also, the observation simulation can be made for wide field of view through multi-FOV observation. After the observation planning is built ,the simulation is made in COSMOS field using GTC telescope. Interested galaxies, stars and high-redshift LBG galaxies are selected after the removal of the mask area, which may be bright stars. Then 9 FOV simulation is completed and observation efficiency and fiber utilization ratio for every round are given. Otherwise,allocating a certain number of fibers for background sky, giving different weights for different objects and how to move the FOV to improve the overall observation efficiency are discussed.

  17. [Economic assessment, a field between clinical research and observational studies].

    PubMed

    Launois, Robert

    2003-01-01

    Health technology assessments propose to study the differential impact of health interventions in a complex care system which is characterised by the multitude of individual behaviours and the diverse nature of the institutions involved. Current systems for data collection lend themselves poorly to this rigorous analysis of efficacy of treatments in the actual situations where they are used. Randomised trials endeavour to neutralise any parasitic interference which could compromise testing for a causal relationship between the treatment administered and the result obtained. Their methodology which establishes the term ceteris paribus in the principle of good practice lends itself poorly to an analysis of individual behaviour. Observational studies are start from actual treatment situations to describe them as reliably as possible. By definition, however, these assume that the natural course of events is not deviated by any intervention. The absence of an experimental plan increases the likelihood of bias and makes it more difficult to test for causal relationships. They lend themselves poorly to testing for incremental efficacy. The two instruments to be preferred are decisional analysis and quasi-experimental studies. Decisional analysis help to avoid the problems of external validity associated with randomised clinical trials by associating parameters which are extracted from data obtained from everyday practice. Quasi-experimental studies or pragmatic trials are based on the reality of behaviour of the prescriber and his/her patients; their impact on efficacy, quality of life social costs of the disease and of treatments may be identified under normal conditions of use. PMID:12609811

  18. Action video game players and deaf observers have larger Goldmann visual fields.

    PubMed

    Buckley, David; Codina, Charlotte; Bhardwaj, Palvi; Pascalis, Olivier

    2010-03-01

    We used Goldmann kinetic perimetry to compare how training and congenital auditory deprivation may affect the size of the visual field. We measured the ability of action video game players and deaf observers to detect small moving lights at various locations in the central (around 30 degrees from fixation) and peripheral (around 60 degrees ) visual fields. Experiment 1 found that 10 habitual video game players showed significantly larger central and peripheral field areas than 10 controls. In Experiment 2 we found that 13 congenitally deaf observers had significantly larger visual fields than 13 hearing controls for both the peripheral and central fields. Here the greatest differences were found in the lower parts of the fields. Comparison of the two groups showed that whereas VGP players have a more uniform increase in field size in both central and peripheral fields deaf observers show non-uniform increases with greatest increases in lower parts of the visual field. PMID:19962395

  19. Snapshots from deep magma chambers: decoding field observations

    NASA Astrophysics Data System (ADS)

    De Campos, Cristina P.

    2014-05-01

    mingling, between contrasting magmas generated from different sources and depths. When flow patterns from these plutonic structures are compared to those obtained from experiments and numerical modeling, vortex-like systems may be locally recognized with chaotic regions among concentric regular flow cells, separated by major flow shearing zones. These patterns may be in remarkable good agreement with less complex flow patterns obtained for simpler dynamic systems. Differences in the magma supply and flow regimes between distinct plutons, in time and space, depict frozen moments in their evolution and therefore may explain some of the discrepancies in the different hybridization degrees for different complexes. The combination of detailed mapping of flow patterns in the field, numerical modeling and experimental results using natural magmatic products as end-members may provide new insights into the dynamics of magma chambers, specially for shallow chambers in a volcanic environment. Due to high viscosities and non-Newtonian behavior during a long time-interval, the application of fluid dynamics to understanding magmatic processes, especially those taking place in the deep crust, is still a major challenge to Geosciences. Extrapolation for plutonic environments remains therefore a great defiance. This discussion aims to show that it is nevertheless worthwhile.

  20. Observations of Plasma Transient on the Lobe Field Line During the Substorm. Interball Tail Observations on October 3, 1995

    NASA Technical Reports Server (NTRS)

    Avanov, L. A.; Smimov, V. N.; Chandler, M. O.

    2004-01-01

    On October 3, 1995 Interball Tail spacecraft was located on tail lobe field lines. Solar wind conditions monitored by WIND and Getail spacecraft were quiet stable. During the time of operation of SCA-1 plasma spectrometer typical plasma mantle is observed. However, at approx. 15:07 UT strong plasma transient with duration of approx. 10 minutes was detected. We found that magnetic field profile of this plasma transient correlates well with ground based H component of magnetic field measured by Tixie Bay station. Ground base data indicates that this transient is observed during strong substorm. We argue that this transient is probably more dense mantle plasma which can be observed at the Interball Tail location provided that the current on the magnetopause is depressed. This depression probably reflects response of the tail magnetopause to changing of the global current system of the magnetosphere caused by the substorm.

  1. On transient electric fields observed in chemical release experiments by rockets

    NASA Astrophysics Data System (ADS)

    Marklund, G.; Brenning, N.; Holmgren, G.; Haerendel, G.

    1986-06-01

    A large amplitude electric field pulse of 200 mV/m was detected shortly after the explosion of a chemical release in the auroral ionosphere. The central part of the pulse is clearly correlated with an intense layer of swept up ambient particles behind a propagating shockfront. The field is directed towards the center of the expanding ionized cloud, indicative of a polarization electric field source. Expressions for this radial polarization field and the much weaker azimuthal induced electric field are derived from a simple cylindrical model for the field and the expanding neutral cloud. Time profiles of the radial electric field are shown to be in good agreement with observations.

  2. Observations of improved confinement in field reversed configurations sustained by antisymmetric rotating magnetic fields

    SciTech Connect

    Guo, H.Y.; Hoffman, A.L.; Steinhauer, L.C.

    2005-06-15

    Rotating magnetic fields (RMF) have been employed to both form and sustain currents in field reversed configurations (FRC). A major concern about this method has been the fear of opening up magnetic field lines with even small ratios of vacuum RMF B{sub {omega}} to external confinement field B{sub e}. A recently proposed innovation was to use an antisymmetric arrangement of RMF, but vacuum calculations with full RMF penetration showed that very low values of B{sub {omega}}/B{sub e} would still be required to provide field-line closure. Recent comparisons of symmetric and antisymmetric RMF drive on the translation, confinement, and sustainment (TCS) facility [A. L. Hoffman, H. Y. Guo, J. T. Slough et al., Fusion Sci. Technol. 41, 92 (2002)] have shown strong improvements in the basic confinement properties of the FRCs when using antisymmetric drive, even with ratios of B{sub {omega}}/B{sub e} as high as 0.3. This is due to normal standard operation with only partial penetration of the RMF beyond the FRC separatrix. The uniform transverse RMF in vacuum is shielded by the conducting plasma, resulting in a mostly azimuthal field near the FRC separatrix with a very small radial component. Simple numerical calculations using analytical solutions for the partially penetrated antisymmetric RMF, superimposed on Grad-Shafranov solutions for the poloidal FRC fields, show good field-line closure for the TCS experimental conditions. The antisymmetric arrangement also leads to more efficient current drive and improved stabilization of rotational modes.

  3. Guided Field Observations: Variables Related to Preservice Teachers' Knowledge about Effective Primary Reading Instruction

    ERIC Educational Resources Information Center

    Roehrig, Alysia D.; Guidry, Lisa O.; Bodur, Yasar; Guan, Qun; Guo, Ying; Pop, Margareta

    2008-01-01

    Relations between preservice teachers' guided field observations of primary literacy instruction and knowledge about effective beginning reading practices were explored. Preservice teachers (n = 48) participated in a Directed Field Experience course including instruction on and observations of exemplary teaching practices promoting student…

  4. Correlation between magnetic and electric field perturbations in the field-aligned current regions deduced from DE 2 observations

    NASA Technical Reports Server (NTRS)

    Ishii, M.; Sugiura, M.; Iyemori, T.; Slavin, J. A.

    1992-01-01

    The satellite-observed high correlations between magnetic and electric field perturbations in the high-latitude field-aligned current regions are investigated by examining the dependence of the relationship between Delta-B and E on spatial scale, using the electric and magnetic field data obtained by DE 2 in the polar regions. The results are compared with the Pedersen conductivity inferred from the international reference ionosphere model and the Alfven wave velocity calculated from the in situ ion density and magnetic field measurements.

  5. Observation of magnetic field-induced contraction of fission yeast cells using optical projection microscopy

    NASA Astrophysics Data System (ADS)

    Yang, Xi; Beckwith, Andrew; Miller, John; Wood, Lowell

    2004-12-01

    The charges in live cells interact with or produce electric fields, which results in enormous dielectric responses, flexoelectricity, and related phenomena. Here we report on a contraction of Schizosaccharomyces pombe (fission yeast) cells induced by magnetic fields, as observed using a phase-sensitive projection imaging technique. Unlike electric fields, magnetic fields only act on moving charges. The observed behavior is therefore quite remarkable, and may result from a contractile Lorentz force acting on diamagnetic screening currents. This would indicate extremely high intracellular charge mobilities. Besides, we observed a large electro-optic response from fission yeast cells.

  6. Observation of magnetic field-induced contraction of fission yeast cells using optical projection microscopy

    NASA Astrophysics Data System (ADS)

    Yang, Xi; Beckwith, A. W.

    2005-03-01

    The charges in live cells interact with or produce electric fields, which results in enormous dielectric responses, flexoelectricity, and related phenomena. Here we report on a contraction of Schizosaccharomyces pombe (fission yeast) cells induced by magnetic fields, as observed using a phase-sensitive projection imaging technique. Unlike electric fields, magnetic fields only act on moving charges. The observed behavior is therefore quite remarkable, and may result from a contractile Lorentz force acting on diamagnetic screening currents. This would indicate extremely high intracellular charge mobilities. Besides, we observed a large electro-optic response from fission yeast cells.

  7. Observations of the Ion Signatures of Double Merging and the Formation of Newly Closed Field Lines

    NASA Technical Reports Server (NTRS)

    Chandler, Michael O.; Avanov, Levon A.; Craven, Paul D.

    2007-01-01

    Observations from the Polar spacecraft, taken during a period of northward interplanetary magnetic field (IMF) show magnetosheath ions within the magnetosphere with velocity distributions resulting from multiple merging sites along the same field line. The observations from the TIDE instrument show two separate ion energy-time dispersions that are attributed to two widely separated (-20Re) merging sites. Estimates of the initial merging times show that they occurred nearly simultaneously (within 5 minutes.) Along with these populations, cold, ionospheric ions were observed counterstreaming along the field lines. The presence of such ions is evidence that these field lines are connected to the ionosphere on both ends. These results are consistent with the hypothesis that double merging can produce closed field lines populated by solar wind plasma. While the merging sites cannot be unambiguously located, the observations and analyses favor one site poleward of the northern cusp and a second site at low latitudes.

  8. Direct observation of electric field induced pattern formation and particle aggregation in ferrofluids

    SciTech Connect

    Rajnak, Michal; Kopcansky, Peter; Timko, Milan; Petrenko, Viktor I.; Avdeev, Mikhail V.; Ivankov, Olexandr I.; Feoktystov, Artem; Dolnik, Bystrik; Kurimsky, Juraj

    2015-08-17

    Ferrofluids typically respond to magnetic fields and can be manipulated by external magnetic fields. Here, we report on formation of visually observable patterns in a diluted low-polarity ferrofluid exposed to external electric fields. This presents a specific type of ferrofluid structure driven by a combined effect of electrohydrodynamics and electrical body forces. The free charge and permittivity variation are considered to play a key role in the observed phenomenon. The corresponding changes in the ferrofluid structure have been found at nanoscale as well. By small-angle neutron scattering (SANS), we show that the magnetic nanoparticles aggregate in direct current (dc) electric field with a strong dependence on the field intensity. The anisotropic aggregates preferably orient in the direction of the applied electric field. Conducting SANS experiments with alternating current (ac) electric fields of various frequencies, we found a critical frequency triggering the aggregation process. Our experimental study could open future applications of ferrofluids based on insulating liquids.

  9. Direct observation of electric field induced pattern formation and particle aggregation in ferrofluids

    NASA Astrophysics Data System (ADS)

    Rajnak, Michal; Petrenko, Viktor I.; Avdeev, Mikhail V.; Ivankov, Olexandr I.; Feoktystov, Artem; Dolnik, Bystrik; Kurimsky, Juraj; Kopcansky, Peter; Timko, Milan

    2015-08-01

    Ferrofluids typically respond to magnetic fields and can be manipulated by external magnetic fields. Here, we report on formation of visually observable patterns in a diluted low-polarity ferrofluid exposed to external electric fields. This presents a specific type of ferrofluid structure driven by a combined effect of electrohydrodynamics and electrical body forces. The free charge and permittivity variation are considered to play a key role in the observed phenomenon. The corresponding changes in the ferrofluid structure have been found at nanoscale as well. By small-angle neutron scattering (SANS), we show that the magnetic nanoparticles aggregate in direct current (dc) electric field with a strong dependence on the field intensity. The anisotropic aggregates preferably orient in the direction of the applied electric field. Conducting SANS experiments with alternating current (ac) electric fields of various frequencies, we found a critical frequency triggering the aggregation process. Our experimental study could open future applications of ferrofluids based on insulating liquids.

  10. Pioneer 7 observations of plasma flow and field reversal regions in the distant geomagnetic tail

    NASA Technical Reports Server (NTRS)

    Walker, R. C.; Lazarus, A. J.; Villante, U.

    1975-01-01

    The present paper gives the results of an extensive analysis of plasma and magnetic-field data from Pioneer 7 taken in the geomagnetic tail approximately 1000 earth radii downstream from earth. The principal observations are: (1) measurable fluxes of protons in the tail, flowing away from earth, sometimes with a double-peaked velocity distribution; (2) field reversal regions in which the field changes from radial to antiradial by a vector rotation in the north-south plane; and (3) general characteristics of the tail similar to those observed near earth with good correlation between taillike magnetic fields and plasma.

  11. Forcing a Global, Offline Land Surface Modeling System with Observation-Based Fields

    NASA Technical Reports Server (NTRS)

    Rodell, Matthew; Houser, Paul R.; Jambor, U.; Gottschalck, J.; Radakovich, J.; Arsenault, K.; Meng, C.-J.; Mitchell, K. E.

    2002-01-01

    The Global Land Data Assimilation System (GLDAS) drives multiple uncoupled land surface models in order to produce optimal output fields of surface states in near-real time, globally, at 1/4 degree spatial resolution. These fields are then made available for coupled atmospheric model initialization and further research. One of the unique aspects of GLDAS is its ability to ingest both modeled and observation-derived forcing for running global scale land surface models. This paper compares results of runs forced by modeled and observed precipitation and shortwave radiation fields. Differences are examined and the impact of the observations on model skill is assessed.

  12. Field-aligned currents associated with Pc 5 pulsations: STARE and TRIAD observations

    SciTech Connect

    Poulter, E.M.; Nielsen, E.; Potemra, T.A.

    1982-04-01

    The resonance theory for monochromatic Pc 5 micropulsations predicts that the toroidal mode resonance should be accompanied by field-aligned current systems. These currents close via Pedersen current in the ionosphere, and the drifting irregularities observed by the STARE radars are thought to be generated by the associated electric fields. Recent theoretical calculations by Walker (1980) are used to estimate the micropulsation current systems and accompanying magnetic perturbations. STARE radar observations of the pulsation electric field in the ionosphere are then compared with the corresponding magnetic perturbation observed with the TRIAD satellite magnetometer.

  13. Motion of observed structures calculated from multi-point magnetic field measurements: Application to Cluster

    NASA Astrophysics Data System (ADS)

    Shi, Q. Q.; Shen, C.; Dunlop, M. W.; Pu, Z. Y.; Zong, Q.-G.; Liu, Z. X.; Lucek, E.; Balogh, A.

    2006-04-01

    A new method is described which calculates the velocity of observed, quasi-stationary structures at every moment in time from multi-point magnetic field measurements. Once the magnetic gradient tensor G = $\

  14. Nonoptically probing near-field microscopy for the observation of biological living specimens

    NASA Astrophysics Data System (ADS)

    Kawata, Yoshimasa; Murakami, Manabu; Egami, Chikara; Sugihara, Okihiro; Okamoto, Naomichi; Tsuchimori, Masaaki; Watanabe, Osamu; Nakamura, Osamu

    2001-04-01

    We present the observation of living specimens with subwavelength resolution by using the nonoptically probing near-field microscopy we have developed recently. In the near-field microscope, the optical field distributions near the specimens are recorded as the surface topography of a photosensitive film, and the topographical distributions are readout with an atomic-force microscopy. Since the near-field microscope does not require the scanning of a probe tip for illumination or detection or scattering of light, it is possible to observe moving biological specimens and fast phenomena. We demonstrate the observation of a moving paramecium and euglena gracilis with subwavelength resolution. The observation of the nucleus inside a euglena cell was also demonstrated.

  15. Observational estimate of magnetic field and geodynamo parameters under the surface of the Earth's core

    NASA Astrophysics Data System (ADS)

    Starchenko, S. V.

    2015-09-01

    For the first time, estimates (averaged in latitude and longitude) of the radial derivatives of the vortex magnetic field hidden directly under the surface of the Earth's core were obtained on the basis of contemporary determinations of the electric conductivity and systematic observations of the geomagnetic dipole evolution, as well as Faraday's and Ohm's laws. This allows one to formulate the simplest, `almost dipole" model of the vortex field under the core surface and to estimate a characteristic scale of the field measurements, which determines the depth of the adequacy area of the proposed simplest model. According to this estimate, the spatial size of the field (around 60 km) is an order of magnitude less than its typical size, following from an extrapolation of the observable field to the mantle-core boundary. This agrees well with the modern theory of hydromagnetic dynamos of planets, making it possible to refine the typical values of the magnetic field, the convection rate, and specific power, together with other geodynamo parameters, on the basis of known scaling laws and observations. The proposed new approach to determining the surface characteristics of the vortex magnetic field hidden in the interior of a physical object from the observed evolution of the potential field may be used for both astrophysical and engineering objects with an inaccessible current system.

  16. Larmor electric field observed at the Earth's magnetopause by Polar satellite

    SciTech Connect

    Koga, D. Gonzalez, W. D.; Silveira, M. V. D.; Mozer, F. S.; Cardoso, F. R.

    2014-10-15

    We present, for the first time, observational evidence of a kinetic electric field near the X-line associated with asymmetric reconnection at the Earth's dayside magnetopause using Polar observations. On March 29, 2003, Polar satellite detected an asymmetric collisionless reconnection event. This event shows a unipolar Hall electric field signature and a simple deviation from the guide field during the magnetopause crossing, with the absence of an ion plasma jet outflow indicating that the magnetopause crossing was near the X-line. As expected from particle-in-cell simulations by Malakit et al. (Phys. Rev. Lett. 111, 135001 (2013)), an earthward pointing normal electric field appears in the magnetospheric side of the ion diffusion region. The electric field satisfies two necessary conditions for the existence of the finite ion Larmor radius effect: (1) the ion Larmor radius (r{sub g2}) is larger than the distance between the stagnation point and the edge of the ion diffusion region in the strong magnetic field side (δ{sub S2}) and (2) the spatial extent of the kinetic electric field (δ{sub EL}) is of the order of the ion Larmor radius. Furthermore, it is shown that the peak value of the Larmor electric field is comparable to the predicted value. The observation of the Larmor electric field can be valuable in other analyses to show that the crossing occurred near the X-line.

  17. Ulysses Observations of Tripolar Guide-Magnetic Field Perturbations Across Solar Wind Reconnection Exhausts

    NASA Astrophysics Data System (ADS)

    Eriksson, S.; Peng, B.; Markidis, S.; Gosling, J. T.; McComas, D. J.; Lapenta, G.; Newman, D. L.

    2014-12-01

    We report observations from 15 solar wind reconnection exhausts encountered along the Ulysses orbit beyond 4 AU in 1996-1999 and 2002-2005. The events, which lasted between 17 and 45 min, were found at heliospheric latitudes between -36o and 21o with one event detected as high as 58o. All events shared a common characteristic of a tripolar guide-magnetic field perturbation being detected across the observed exhausts. The signature consists of an enhanced guide field magnitude within the exhaust center and two regions of significantly depressed guide-fields adjacent to the center region. The events displayed magnetic field shear angles as low as 37o with a mean of 89o. This corresponds to a strong external guide field relative to the anti-parallel reconnecting component of the magnetic field with a mean ratio of 1.3 and a maximum ratio of 3.1. A 2-D kinetic reconnection simulation for realistic solar wind conditions reveals that tripolar guide fields form at current sheets in the presence of multiple X-lines as two magnetic islands interact with one another for such strong guide fields. The Ulysses observations are also compared with the results of a 3-D kinetic simulation of multiple flux ropes in a strong guide field.

  18. DC Electric Fields and Associated Plasma Drifts Observed with the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Bromund, K.; Rowland, D.

    2009-01-01

    Initial DC electric field observations and associated plasma drifts are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite. We present statistical averages of the vector fields for the first year of operations that include both the zonal and radial components of the resulting E x B plasma flows at low latitudes. Magnetic field data from the VEFI science magnetometer are used to compute the plasma flows. The DC electric field detector reveals zonal and radial electric fields that undergo strong diurnal variations, typically displaying eastward and outward-directed fields during the day and westward and downward-directed fields at night. There is considerable variation in the large scale DC electric field data, in both the daytime and nighttime cases, with enhanced structures typically observed at night. In general, the measured zonal DC electric field amplitudes include excursions that extend within the 0.4 - 2 m V/m range, corresponding to E x B drifts of the order of 30-150 m/s. The average vertical or radial electric fields may exceed the zonal fields in amplitude by a factor of 1.5 to 2. Although the data compare well, in a general sense, with previous satellite observations and statistical patterns of vertical ion drifts, the E x B drifts we report from C/NOFS rarely show a pronounced pre-reversal enhancement after sunset. We attribute this to a combination of extreme solar minimum conditions and the fact that the C/NOFS orbit of 401 by 867 km carries the probes essentially above the lower altitude regions where the wind-driven dynamo might be expected to create enhanced upwards drifts in the early evening. Evidence for wavenumber 4 tidal effects and other longitudinal signatures have been detected and will be presented. We also discuss off-equatorial electric fields and their relation to the ambient plasma density.

  19. On transient electric fields observed in chemical release experiments by rockets

    NASA Astrophysics Data System (ADS)

    Marklund, G.; Brenning, N.; Holmgren, G.; Haerendel, G.

    1987-05-01

    As a follow-up to the successful chemical release experiment Trigger in 1977, the Trigger Optimized Repetition rocket was launched on October 24, 1984. As in the Trigger experiment, a large-amplitude electric field pulse of 200 mV/m was detected shortly after the explosion. The central part of the pulse was found to be clearly correlated with an intense layer of swept up ambient particles behind a propagating shock front. The field was directed toward the center of the expanding ionized cloud, which is indicative of a polarization electric field source. Expressions for this radial polarization field and the much weaker azimuthal-induced electric field are derived from a simple cylindrical model for the field and the expanding neutral cloud. Time profiles of the radial electric field are shown to be in good agreement with observations.

  20. The magnetic field of Jupiter - A comparison of radio astronomy and spacecraft observations

    NASA Technical Reports Server (NTRS)

    Smith, E. J.; Gulkis, S.

    1979-01-01

    The inner magnetic field of Jupiter is characterized on the basis of Pioneer 10 and 11 measurements and earth-based decimetric radio observations. The dipole parameters derived from the two data sets are in good agreement. Problems in reconciling asymmetries observed in the earth-based data and the spacecraft data are discussed. Models of synchrotron emission from arbitrary magnetic field configurations and high-resolution maps of the Jovian radiation belts in all polarizations are needed to further understanding of Jupiter's magnetic field

  1. EXOS D observations of enhanced electric fields during the giant magnetic storm in March 1989

    SciTech Connect

    Okada, T.; Hayakawa, H.; Tsuruda, K.; Nishida, A.; Matsuoka, A.

    1993-09-01

    The authors report the observation of intense electric fields in the magnetosphere at altitudes of 2000 to 6000 km during and after the large magnetic storm on March 13-14, 1989. Such large fields are a manifestation of the inability of convecting plasma bodies from storms to penetrate to the earth. The measurements were made by two sets of double probes on the EXOS D satellite. A sharp peak in the poleward field was observed, with a magnitude of roughly 100 mV/m when projected to ionospheric heights.

  2. Pioneer Venus observations of plasma and field structure in the near wake of Venus

    NASA Technical Reports Server (NTRS)

    Luhmann, J. G.; Russell, C. T.; Brace, L. H.; Knudsen, W. C.; Taylor, H. A.; Scarf, F. L.; Colburn, D. S.; Barnes, A.

    1982-01-01

    Ionospheric plasma density depletions or 'holes' are observed by the Pioneer Venus orbiter in association with radial magnetic fields in the near wake of Venus. This report presents examples of the collected observations of these unexpected features of the Venus nightside ionosphere obtained by the Langmuir probe, magnetometer, ion mass spectrometer, retarding potential analyzer, plasma analyzer, and electric field experiments. The connection between plasma density depletions and temperature changes, changes in ion composition, plasma wave emissions, and magnetic fields with a substantial radial component is illustrated. Mechanisms that may be responsible for the formation and maintenance of holes are suggested.

  3. Relationship of the interplanetary electric field to the high-latitude ionospheric electric field and currents Observations and model simulation

    NASA Technical Reports Server (NTRS)

    Clauer, C. R.; Banks, P. M.

    1986-01-01

    The electrical coupling between the solar wind, magnetosphere, and ionosphere is studied. The coupling is analyzed using observations of high-latitude ion convection measured by the Sondre Stromfjord radar in Greenland and a computer simulation. The computer simulation calculates the ionospheric electric potential distribution for a given configuration of field-aligned currents and conductivity distribution. The technique for measuring F-region in velocities at high time resolution over a large range of latitudes is described. Variations in the currents on ionospheric plasma convection are examined using a model of field-aligned currents linking the solar wind with the dayside, high-latitude ionosphere. The data reveal that high-latitude ionospheric convection patterns, electric fields, and field-aligned currents are dependent on IMF orientation; it is observed that the electric field, which drives the F-region plasma curve, responds within about 14 minutes to IMF variations in the magnetopause. Comparisons of the simulated plasma convection with the ion velocity measurements reveal good correlation between the data.

  4. Comparison of inferred and observed interplanetary magnetic field polarities, 1970-1972

    NASA Technical Reports Server (NTRS)

    Wilcox, J. M.; Svalgaard, L.; Hedgecock, P. C.

    1975-01-01

    The inferred polarity (toward or away from the sun) of the interplanetary magnetic field at earth using polar observations of the geomagnetic field has been compared with spacecraft observations. A list published by Svalgaard (1974) of the inferred field polarities in the period from 1970 to 1972 is found to be correct on 82% of the days. A near real-time (same day) method of inferring the polarity of the interplanetary magnetic field using geomagnetic observations at Vostok and Thule is in use at the NOAA Space Environment Laboratory, Boulder, Colorado. During 1972, this method is found to be correct on 87% of the days. A list of 'well-defined' sector boundaries at earth from 1970 to 1972 is given.

  5. Interplanetary and Interstellar Dust Observed by the Wind/WAVES Electric Field Instrument

    NASA Technical Reports Server (NTRS)

    Malaspina, David; Horanyi, M.; Zaslavsky, A.; Goetz, K.; Wilson, L. B., III; Kersten, K.

    2014-01-01

    Observations of hypervelocity dust particles impacting the Wind spacecraft are reported here for the first time using data from the WindWAVES electric field instrument. A unique combination of rotating spacecraft, amplitude-triggered high-cadence waveform collection, and electric field antenna configuration allow the first direct determination of dust impact direction by any spacecraft using electric field data. Dust flux and impact direction data indicate that the observed dust is approximately micron-sized with both interplanetary and interstellar populations. Nanometer radius dust is not detected by Wind during times when nanometer dust is observed on the STEREO spacecraft and both spacecraft are in close proximity. Determined impact directions suggest that interplanetary dust detected by electric field instruments at 1 AU is dominated by particles on bound trajectories crossing Earths orbit, rather than dust with hyperbolic orbits.

  6. Observations of large scale steady magnetic fields in the dayside Venus ionosphere

    NASA Technical Reports Server (NTRS)

    Luhmann, J. G.; Elphic, R. C.; Russell, C. T.; Mihalov, J. D.; Wolfe, J. H.

    1980-01-01

    Although the dayside ionosphere of Venus is often field-free except for fine-scale features, large-scale steady ionospheric magnetic fields with magnitudes sometimes exceeding 100 gammas are occasionally observed by the Pioneer Venus Orbiter magnetometer. These fields are mainly horizontal and can assume any angle in the horizontal plane. The orientation of the field may change along the spacecraft trajectory. The field magnitude in the upper ionosphere usually shows a distinct minimum near approximately 200 km altitude, but the altitude profile is otherwise arbitrary. With few exceptions, the observations of these large scale fields occur when periapsis is at solar zenith angles less than 50 deg. The occurrence of large-scale fields is often coincident with the observation of high solar wind dynamic pressures by the Pioneer Venus Orbiter plasma analyzer closely following the ionosphere encounter. However, the detection of this phenomenon even during some orbits for which the dynamic pressure is not extraordinarily high suggests that other factors, such as hysteresis effects, must also play a role in determining the occurrence frequency of large-scale magnetic fields in the dayside Venus ionosphere.

  7. Comparison of Electric Fields and Density structures Seen in Simulations and Satellite Observations

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra; Deverapalli, C.; Khazanov, G.

    2005-01-01

    There are now clear observations of large parallel electric fields (E(sub ||)) from Polar and FAST in the auroral upward-current region (UCR). Such fields are associated with large perpendicular electric fields (E(sub perpendicular) and density cavities. The observed features of the fields and density are found to be compatible with their spatial structures seen in a simulated U-shaped potential structure (USPS), consisting of double layers (DL) with obliqueness ranging from zero to 90 degrees from the magnetic field. The spatial and temporal evolution of the USPS, its up and down motions and its striations into thin long potential structures, suggest a variety of signatures in the satellite detection of E(sub ||) and E(sub perpendicular)

  8. Field and thermal plasma observations of ULF pulsations during a magnetically disturbed interval

    NASA Technical Reports Server (NTRS)

    Lin, N.; Engebretson, M. J.; Reinleitner, L. A.; Olson, J. V.; Gallagher, D. L.; Cahill, L. J., Jr.; Slavin, J. A.; Persoon, A. M.

    1992-01-01

    A ULF pulsation event is discussed on the basis of experimental observations of electric and magnetic field measurements as well as particle measurements from the DE 1 spacecraft. The observations were made near the magnetic equator in a space covering a large range of L shells and magnetic latitudes, and comparisons are made to ground observations. Azimuthal oscillations are observed following gradually decaying long-period compressional waves. Weak interaction between magnetic shells indicates that the source is probably weak, and ground data on magnetic pulsations showed strong signals that did not necessarily correspond to the quasisinusoidal pulsations observed in space. Azimuthal pulsations observed by the spacecraft indicate that there was a plasma density gradient beyond the plasmapause. The ULF pulsations were probably affected by changes in the magnetic field and solar-wind dynamic pressure, and their periods are found to be linked to geomagnetic latitude.

  9. Field-aligned currents observed in the vicinity of a moving auroral arc

    NASA Technical Reports Server (NTRS)

    Goertz, C. K.; Bruening, K.

    1984-01-01

    The sounding rocket Porcupine F4 was launched into an auroral arc and the field aligned currents were independently deduced from magnetic field measurements; the horizontal current deduced from the electric field measurements and height integrated conductivity calculations; and measurements of electron fluxes. Above the arc the different methods agree. The magnetosphere acts as generator and the ionosphere as load. North of the arc, the first two methods disagree, possibly due to an Alfven wave carrying the observed magnetic field perturbation. The energy flow is out of the ionosphere. Here the ionosphere acts as generator and the magnetosphere as load.

  10. Field-aligned currents observed in the vicinity of a moving auroral arc

    NASA Astrophysics Data System (ADS)

    Goertz, C. K.; Bruening, K.

    1984-09-01

    The sounding rocket Porcupine F4 was launched into an auroral arc and the field aligned currents were independently deduced from magnetic field measurements; the horizontal current deduced from the electric field measurements and height integrated conductivity calculations; and measurements of electron fluxes. Above the arc the different methods agree. The magnetosphere acts as generator and the ionosphere as load. North of the arc, the first two methods disagree, possibly due to an Alfven wave carrying the observed magnetic field perturbation. The energy flow is out of the ionosphere. Here the ionosphere acts as generator and the magnetosphere as load.

  11. Magnetic Fields in Low-Mass Stars: An Overview of Observational Biases

    NASA Astrophysics Data System (ADS)

    Reiners, Ansgar

    2014-08-01

    Stellar magnetic dynamos are driven by rotation, rapidly rotating stars produce stronger magnetic fields than slowly rotating stars do. The Zeeman effect is the most important indicator of magnetic fields, but Zeeman broadening must be disentangled from other broadening mechanisms, mainly rotation. The relations between rotation and magnetic field generation, between Doppler and Zeeman line broadening, and between rotation, stellar radius, and angular momentum evolution introduce several observational biases that affect our picture of stellar magnetism. In this overview, a few of these relations are explicitly shown, and the currently known distribution of field measurements is presented.

  12. Imaging Analysis of Near-Field Recording Technique for Observation of Biological Specimens

    NASA Astrophysics Data System (ADS)

    Moriguchi, Chihiro; Ohta, Akihiro; Egami, Chikara; Kawata, Yoshimasa; Terakawa, Susumu; Tsuchimori, Masaaki; Watanabe, Osamu

    2006-07-01

    We present an analysis of the properties of an imaging based on a near-field recording technique in comparison with simulation results. In the system, the optical field distributions localized near the specimens are recorded as the surface topographic distributions of a photosensitive film. It is possible to observe both soft and moving specimens, because the system does not require a scanning probe to obtain the observed image. The imaging properties are evaluated using fine structures of paramecium, and we demonstrate that it is possible to observe minute differences of refractive indices.

  13. Solar wind proton reflection by lunar crustal magnetic fields observed at low altitude

    NASA Astrophysics Data System (ADS)

    Nishino, M. N.; Fujimoto, M.; Tsunakawa, H.; Saito, Y.; Yokota, S.; Shibuya, H.; Matsushima, M.; Shimizu, H.; Takahashi, F.

    2012-12-01

    We study interaction between the solar wind flow and lunar crustal magnetic fields observed at lower altitudes by SELENE (Kaguya), predominantly focusing on proton reflection above strong crustal fields. Several studies revealed interaction between the solar wind and the Moon, while detailed observation at low altitude including ion measurements has been hardly reported yet. Previous observations at higher altitude revealed that the solar wind protons are not reflected toward the sun but deflected downstream around the solar wind flow direction. Here we report detailed observations of solar wind proton reflection/deflection observed above South Pole-Aitken (SPA) basin at low altitude (typically, lower than 30 km) and at several solar zenith angles. Above wide crustal fields inside the SPA basin, a large amount of incident solar wind protons are deflected and sometimes reflected to come back sunward; in particular, the sunward proton beams are observed at lower solar zenith angle regions. The reflected/deflected protons at times consist of two (or more-than-two) separate components that have been mirror-reflected at different crustal fields. Our result shows that the mirror reflection of incident protons takes place at the altitude much lower than the spacecraft orbit, and suggests that strong compression of the crustal fields at lower solar zenith angle and at lower altitude by the solar wind dynamic pressure is essential.

  14. Observations of the generation of eastward equatorial electric fields near dawn

    NASA Astrophysics Data System (ADS)

    Kelley, M. C.; Rodrigues, F. S.; Pfaff, R. F.; Klenzing, J.

    2014-09-01

    We report and discuss interesting observations of the variability of electric fields and ionospheric densities near sunrise in the equatorial ionosphere made by instruments onboard the Communications/Navigation Outage Forecasting System (C/NOFS) satellite over six consecutive orbits. Electric field measurements were made by the Vector Electric Field Instrument (VEFI), and ionospheric plasma densities were measured by Planar Langmuir Probe (PLP). The data were obtained on 17 June 2008, a period of solar minimum conditions. Deep depletions in the equatorial plasma density were observed just before sunrise on three orbits, for which one of these depletions was accompanied by a very large eastward electric field associated with the density depletion, as previously described by de La Beaujardière et al. (2009), Su et al. (2009) and Burke et al. (2009). The origin of this large eastward field (positive upward/meridional drift), which occurred when that component of the field is usually small and westward, is thought to be due to a large-scale Rayleigh-Taylor process. On three subsequent orbits, however, a distinctly different, second type of relationship between the electric field and plasma density near dawn was observed. Enhancements of the eastward electric field were also detected, one of them peaking around 3 mV m-1, but they were found to the east (later local time) of pre-dawn density perturbations. These observations represent sunrise enhancements of vertical drifts accompanied by eastward drifts such as those observed by the San Marco satellite (Aggson et al., 1995). Like the San Marco measurements, the enhancements occurred during winter solstice and low solar flux conditions in the Pacific longitude sector. While the evening equatorial ionosphere is believed to present the most dramatic examples of variability, our observations exemplify that the dawn sector can be highly variable as well.

  15. Observational features of field line resonances excited by solar wind pressure variations on 4 September 1984

    NASA Technical Reports Server (NTRS)

    Warnecke, J.; Luehr, H.; Takahashi, K.

    1990-01-01

    The purpose of the study is to establish the most probable excitation mechanism of the magnetic storm occurred after an inverse sudden impulse on September 4, 1984. Geomagnetic pulsations in the Pc5-frequency range observed at magnetometer stations are evaluated. Attention is focused on two events of the enhanced activity: for the first one, conjugate observations on the ground are assessed and then compared with satellite-based observations on adjacent field lines; for the second event two hours later, data from an extended azimuthal range is employed. It is pointed out that the observations are consistent with the theory of filed-line resonance, and may be interpreted as excitations caused by pressure variations in the solar wind. Both magnetopause-surface waves and cavity resonances are excited; the cavity mode drives toroidal field-line oscillations at locations where its frequency matches the resonance frequency of the field lines.

  16. Magnetic fields around evolved stars: further observations of H2O maser polarization

    NASA Astrophysics Data System (ADS)

    Leal-Ferreira, M. L.; Vlemmings, W. H. T.; Kemball, A.; Amiri, N.

    2013-06-01

    Context. A low- or intermediate-mass star is believed to maintain a spherical shape throughout the evolution from the main sequence to the asymptotic giant branch (AGB) phase. However, many post-AGB objects and planetary nebulae exhibit non-spherical symmetry. Several candidates have been suggested as factors that can play a role in this change of morphology, but the problem is still not well understood. Magnetic fields are one of these possible agents. Aims: We aim to detect the magnetic field and infer its properties around four AGB stars using H2O maser observations. The sample we observed consists of the following sources: the semi-regular variable RT Vir, and the Mira variables AP Lyn, IK Tau, and IRC+60370. Methods: We observed the 61,6 -52,3 H2O maser rotational transition in full-polarization mode to determine its linear and circular polarization. Based on the Zeeman effect, one can infer the properties of the magnetic field from the maser polarization analysis. Results: We detected a total of 238 maser features in three of the four observed sources. No masers were found toward AP Lyn. The observed masers are all located between 2.4 and 53.0 AU from the stars. Linear and circular polarization was found in 18 and 11 maser features, respectively. Conclusions: We more than doubled the number of AGB stars in which a magnetic field has been detected from H2O maser polarization. Our results confirm the presence of fields around IK Tau, RT Vir, and IRC+60370. The strength of the field along the line of sight is found to be between 47 and 331 mG in the H2O maser region. Extrapolating this result to the surface of the stars, assuming a toroidal field (∝ r-1), we find magnetic fields of 0.3-6.9 G on the stellar surfaces. If, instead of a toroidal field, we assume a poloidal field (∝ r-2), then the extrapolated magnetic field strength on the stellar surfaces are in the range between 2.2 and ~115 G. Finally, if a dipole field (∝ r-3) is assumed, the field

  17. The quiet Sun magnetic field observed with ZIMPOL on THEMIS. I. The probability density function

    NASA Astrophysics Data System (ADS)

    Bommier, V.; Martínez González, M.; Bianda, M.; Frisch, H.; Asensio Ramos, A.; Gelly, B.; Landi Degl'Innocenti, E.

    2009-11-01

    Context: The quiet Sun magnetic field probability density function (PDF) remains poorly known. Modeling this field also introduces a magnetic filling factor that is also poorly known. With these two quantities, PDF and filling factor, the statistical description of the quiet Sun magnetic field is complex and needs to be clarified. Aims: In the present paper, we propose a procedure that combines direct determinations and inversion results to derive the magnetic field vector and filling factor, and their PDFs. Methods: We used spectro-polarimetric observations taken with the ZIMPOL polarimeter mounted on the THEMIS telescope. The target was a quiet region at disk center. We analyzed the data by means of the UNNOFIT inversion code, with which we inferred the distribution of the mean magnetic field α B, α being the magnetic filling factor. The distribution of α was derived by an independent method, directly from the spectro-polarimetric data. The magnetic field PDF p(B) could then be inferred. By introducing a joint PDF for the filling factor and the magnetic field strength, we have clarified the definition of the PDF of the quiet Sun magnetic field when the latter is assumed not to be volume-filling. Results: The most frequent local average magnetic field strength is found to be 13 G. We find that the magnetic filling factor is related to the magnetic field strength by the simple law α = B_1/B with B1 = 15 G. This result is compatible with the Hanle weak-field determinations, as well as with the stronger field determinations from the Zeeman effect (kGauss field filling 1-2% of space). From linear fits, we obtain the analytical dependence of the magnetic field PDF. Our analysis has also revealed that the magnetic field in the quiet Sun is isotropically distributed in direction. Conclusions: We conclude that the quiet Sun is a complex medium where magnetic fields having different field strengths and filling factors coexist. Further observations with a better

  18. A Method for Observing Soil Re-Deposition and Soil Loss Rates in Large Field Experiments

    NASA Astrophysics Data System (ADS)

    Hsieh, Y. P.; Bugna, G. C.; Nemours, D.

    2014-12-01

    The lack of quality soil erosion field data, which is required for the verification and calibration of soil erosion models, has been one of the serious problems in the soil conservation modeling today. Observing soil erosion of a relatively large field under truly unobstructed runoff conditions has rarely been done and doccumented. Report here is the results of our observation of soil erosion in a 7.3 ha peanut-cotton cropping system in the Mears Farm of Grand Ridge, FL. We used the mesh-pad method to quantify soil loss from the field and soil re-deposition in the field over the cropping season of 2010. The main slope (1-3 %) of the field is about 210 m long. We show that the amount of soil re-deposition was 50-150 times of the soil loss from the slope. The corresponding organic matter, nitrogen, phosphorous and silt and clay contents of the lost soil, however, were 20.9%, 21%, 17.6% and 14.2%, respectively, of the total amounts re-deposited on the slope. The amounts of soil loss predicted by a SWAT model was 10-20 times greater than our observed values. Soil erosion process was quite heterogeneous, as shown by the mesh-pad method, even on a seemingly uniform cultivated field. Soil erosion models need to be verified and calibrated by extensive quality field data in order to improve their performance.

  19. A comparison between maritime field observations and photosimulation for developing and validating visible signature evaluation tools

    NASA Astrophysics Data System (ADS)

    Culpepper, Joanne B.; Wheaton, Vivienne C.; Shao, Q. T.; Furnell, Alistair

    2015-10-01

    Over the past 50 years, the majority of detection models used to assess visible signatures have been developed and validated using static imagery. Some of these models are the German developed CAMAELEON (CAMou age Assessment by Evaluation of Local Energy Spatial Frequency and OrieNtation) model and the U.S. Army's Night Vision and Electronic Sensors Directorate (NVESD) ACQUIRE and TTP (Targeting Task Performance) models. All these models gathered the necessary human observer data for development and validation from static images in photosimulation experiments. In this paper, we compare the results of a field observation trial to a static photosimulation experiment. The probability of detection obtained from the field observation trial was compared to the detection probability obtained from the static photosimulation trial. The comparison showed good correlation between the field trial and the static image photosimulation detection probabilities, where a Spearman correlation coefficient of 0.59 was calculated. The photosimulation detection task was found to be significantly harder than the field observation detection task, suggesting that to use static image photosimulation to develop and validate maritime visible signature evaluation tools may need correction to represent detection in field observations.

  20. Solar coronal and magnetic field observations near the time of the 1988 March 18 solar eclipse

    SciTech Connect

    Sime, D.G.; Fisher, R.R.; Mickey, D.L.

    1988-10-01

    Observations made during the interval March 1-31, 1988, are presented which were designed to provide a synoptic context in which data from the March 18, 1988, total solar eclipse can be interpreted. Daily observations made with the Mark III K-coronameter and the H-alpha prominence monitor at the Mauna Loa Solar Observatory, along with photographic records of the Sun in H-alpha from the flare patrol at Mees Solar Observatory on Haleakala, Maui, are included. Observations of the longitudinal component of the photospheric magnetic field made at Mees Solar Observatory were also gathered around the period of the eclipse. Together with the white-light image of the corona at the eclipse, these coronal and magnetic field observations assembled into synoptic maps for this epoch, are presented. On the basis of these observations, an interpretation of the global density distribution of the corona at the time of the eclipse is constructed. 11 references.

  1. Solar coronal and magnetic field observations near the time of the 1988 March 18 solar eclipse

    NASA Technical Reports Server (NTRS)

    Sime, D. G.; Fisher, R. R.; Mickey, D. L.

    1988-01-01

    Observations made during the interval March 1-31, 1988, are presented which were designed to provide a synoptic context in which data from the March 18, 1988, total solar eclipse can be interpreted. Daily observations made with the Mark III K-coronameter and the H-alpha prominence monitor at the Mauna Loa Solar Observatory, along with photographic records of the Sun in H-alpha from the flare patrol at Mees Solar Observatory on Haleakala, Maui, are included. Observations of the longitudinal component of the photospheric magnetic field made at Mees Solar Observatory were also gathered around the period of the eclipse. Together with the white-light image of the corona at the eclipse, these coronal and magnetic field observations assembled into synoptic maps for this epoch, are presented. On the basis of these observations, an interpretation of the global density distribution of the corona at the time of the eclipse is constructed.

  2. Airborne observations of electric fields around growing and decaying cumulus clouds

    NASA Technical Reports Server (NTRS)

    Giori, K. L.; Nanevicz, J. E.

    1991-01-01

    Airborne electric field data were gathered in an atmospheric electrification study near Cape Canaveral, FL. A Learjet 36A was instrumented with eight electric field meters (mills) and five different particle probes. The local electric field enhancements at each field mill site were determined under lab conditions and verified using in-flight data. The overdetermined system of eight equations (one for each field mill) was solved using a weighted least squares algorithm to compute the magnitude and direction of the ambient electric field. The signal processing system allowed the measured data to be expressed in terms of earth coordinates, regardless of the attitude of the aircraft. Thus, it was possible to take maximum advantage of the Learjet's speed and maneuverability in studying the electric field structure in the vicinity of the clouds. Data gathered while circling just outside the boundary of a growing cumulus cloud show a nonsymmetric pattern of electric field strength. Field intensity grew rapidly over a period of less than 10 minutes. The observed direction of the ambient electric field vector can be explained by an ascending motion of the charge centers of a classic tripole model of a thunderstorm.

  3. Magnetospheric Multiscale Observations of the Electron Diffusion Region of Large Guide Field Magnetic Reconnection.

    PubMed

    Eriksson, S; Wilder, F D; Ergun, R E; Schwartz, S J; Cassak, P A; Burch, J L; Chen, L-J; Torbert, R B; Phan, T D; Lavraud, B; Goodrich, K A; Holmes, J C; Stawarz, J E; Sturner, A P; Malaspina, D M; Usanova, M E; Trattner, K J; Strangeway, R J; Russell, C T; Pollock, C J; Giles, B L; Hesse, M; Lindqvist, P-A; Drake, J F; Shay, M A; Nakamura, R; Marklund, G T

    2016-07-01

    We report observations from the Magnetospheric Multiscale (MMS) satellites of a large guide field magnetic reconnection event. The observations suggest that two of the four MMS spacecraft sampled the electron diffusion region, whereas the other two spacecraft detected the exhaust jet from the event. The guide magnetic field amplitude is approximately 4 times that of the reconnecting field. The event is accompanied by a significant parallel electric field (E_{∥}) that is larger than predicted by simulations. The high-speed (∼300  km/s) crossing of the electron diffusion region limited the data set to one complete electron distribution inside of the electron diffusion region, which shows significant parallel heating. The data suggest that E_{∥} is balanced by a combination of electron inertia and a parallel gradient of the gyrotropic electron pressure. PMID:27419573

  4. Observation of Landau levels on nitrogen-doped flat graphite surfaces without external magnetic fields

    NASA Astrophysics Data System (ADS)

    Kondo, Takahiro; Guo, Donghui; Shikano, Taishi; Suzuki, Tetsuya; Sakurai, Masataka; Okada, Susumu; Nakamura, Junji

    2015-11-01

    Under perpendicular external magnetic fields, two-dimensional carriers exhibit Landau levels (LLs). However, it has recently been reported that LLs have been observed on graphene and graphite surfaces without external magnetic fields being applied. These anomalous LLs have been ascribed primarily to a strain of graphene sheets, leading to in-plane hopping modulation of electrons. Here, we report the observation of the LLs of massive Dirac fermions on atomically flat areas of a nitrogen-doped graphite surface in the absence of external magnetic fields. The corresponding magnetic fields were estimated to be as much as approximately 100 T. The generation of the LLs at the area with negligible strain can be explained by inequivalent hopping of π electrons that takes place at the perimeter of high-potential domains surrounded by positively charged substituted graphitic-nitrogen atoms.

  5. Magnetic field observations as Voyager 1 entered the heliosheath depletion region.

    PubMed

    Burlaga, L F; Ness, N F; Stone, E C

    2013-07-12

    Magnetic fields measured by Voyager 1 (V1) show that the spacecraft crossed the boundary of an unexpected region five times between days 210 and ~238 in 2012. The magnetic field strength B increased across this boundary from ≈0.2 to ≈0.4 nanotesla, and B remained near 0.4 nanotesla until at least day 270, 2012. The strong magnetic fields were associated with unusually low counting rates of >0.5 mega-electron volt per nuclear particle. The direction of B did not change significantly across any of the five boundary crossings; it was very uniform and very close to the spiral magnetic field direction, which was observed throughout the heliosheath. The observations indicate that V1 entered a region of the heliosheath (the heliosheath depletion region), rather than the interstellar medium. PMID:23811226

  6. Observation of Landau levels on nitrogen-doped flat graphite surfaces without external magnetic fields

    PubMed Central

    Kondo, Takahiro; Guo, Donghui; Shikano, Taishi; Suzuki, Tetsuya; Sakurai, Masataka; Okada, Susumu; Nakamura, Junji

    2015-01-01

    Under perpendicular external magnetic fields, two-dimensional carriers exhibit Landau levels (LLs). However, it has recently been reported that LLs have been observed on graphene and graphite surfaces without external magnetic fields being applied. These anomalous LLs have been ascribed primarily to a strain of graphene sheets, leading to in-plane hopping modulation of electrons. Here, we report the observation of the LLs of massive Dirac fermions on atomically flat areas of a nitrogen-doped graphite surface in the absence of external magnetic fields. The corresponding magnetic fields were estimated to be as much as approximately 100 T. The generation of the LLs at the area with negligible strain can be explained by inequivalent hopping of π electrons that takes place at the perimeter of high-potential domains surrounded by positively charged substituted graphitic-nitrogen atoms. PMID:26549618

  7. Magnetospheric Multiscale Observations of the Electron Diffusion Region of Large Guide Field Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Eriksson, S.; Wilder, F. D.; Ergun, R. E.; Schwartz, S. J.; Cassak, P. A.; Burch, J. L.; Chen, L.-J.; Torbert, R. B.; Phan, T. D.; Lavraud, B.; Goodrich, K. A.; Holmes, J. C.; Stawarz, J. E.; Sturner, A. P.; Malaspina, D. M.; Usanova, M. E.; Trattner, K. J.; Strangeway, R. J.; Russell, C. T.; Pollock, C. J.; Giles, B. L.; Hesse, M.; Lindqvist, P.-A.; Drake, J. F.; Shay, M. A.; Nakamura, R.; Marklund, G. T.

    2016-07-01

    We report observations from the Magnetospheric Multiscale (MMS) satellites of a large guide field magnetic reconnection event. The observations suggest that two of the four MMS spacecraft sampled the electron diffusion region, whereas the other two spacecraft detected the exhaust jet from the event. The guide magnetic field amplitude is approximately 4 times that of the reconnecting field. The event is accompanied by a significant parallel electric field (E∥ ) that is larger than predicted by simulations. The high-speed (˜300 km /s ) crossing of the electron diffusion region limited the data set to one complete electron distribution inside of the electron diffusion region, which shows significant parallel heating. The data suggest that E∥ is balanced by a combination of electron inertia and a parallel gradient of the gyrotropic electron pressure.

  8. Electric and magnetic field observations during a substorm on February 24, 1970

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Akasofu, S.-I.

    1974-01-01

    Description of a series of electric field measurements obtained from the Injun 5 satellite and simultaneous magnetic disturbances observed in the interplanetary medium and on the ground during a magnetic substorm. The substorm analyzed took place on Feb. 24, 1970. Prior to the onset of the substorm, a greatly enhanced antisunward plasma flow was observed over the polar cap. The enhanced plasma flow occurred about 30 minutes after a switch in the direction of the interplanetary magnetic field from northward to southward. The electric fields across the polar cap immediately before and during the substorm were essentially unchanged, and it is thus indicated that an enhancement in the ionospheric conductivity rather than the electric field must be responsible for the large increase in the auroral electrojet current during the substorm.

  9. Electric and magnetic field observations during a substorm of 24 February 1970

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Akasofu, S. I.

    1974-01-01

    A series of electric field measurements is reported which was obtained from the Injun 5 satellite along with a simultaneous magnetic disturbance observed in the interplanetary medium and on the ground during a magnetic substorm. The substorm analyzed took place on February 24, 1970. Prior to the onset of the substorm a greatly enhanced anti-sunward plasma flow was observed over the polar cap. The enhanced plasma flow occurred about 30 minutes after a switch in the direction of the interplanetary magnetic field from northward to southward. The electric fields across the polar cap immediately before and during the substorm were essentially unchanged indicating that an enhancement in the ionospheric conductivity rather than the electric field must be responsible for the large increase in the auroral electrojet current during the substorm.

  10. Dynamics of Tachyon Fields and Inflation - Comparison of Analytical and Numerical Results with Observation

    NASA Astrophysics Data System (ADS)

    Milošević, M.; Dimitrijević, D. D.; Djordjević, G. S.; Stojanović, M. D.

    2016-06-01

    The role tachyon fields may play in evolution of early universe is discussed in this paper. We consider the evolution of a flat and homogeneous universe governed by a tachyon scalar field with the DBI-type action and calculate the slow-roll parameters of inflation, scalar spectral index (n), and tensor-scalar ratio (r) for the given potentials. We pay special attention to the inverse power potential, first of all to V(x)˜ x^{-4}, and compare the available results obtained by analytical and numerical methods with those obtained by observation. It is shown that the computed values of the observational parameters and the observed ones are in a good agreement for the high values of the constant X_0. The possibility that influence of the radion field can extend a range of the acceptable values of the constant X_0 to the string theory motivated sector of its values is briefly considered.

  11. Analysis and Modeling of Coronal Holes Observed by CORONAS-1. 1; Morphology and Magnetic Field Configuration

    NASA Technical Reports Server (NTRS)

    Obridko, Vladmir; Formichev, Valery; Kharschiladze, A. F.; Zhitnik, Igor; Slemzin, Vladmir; Hathaway, David H.; Wu, Shi T.

    1998-01-01

    Two low-latitude coronal holes observed by CORONAS-1 in April and June 1994 are analyzed together with magnetic field measurements obtained from Wilcox and Kitt Peak Solar Observatories. To estimate the comparable temperature of these two coronal holes, the YOHKOH observations are also utilized. Using this information, we have constructed three-dimensional magnetic field lines to illustrate the geometrical configuration of these coronal holes. The calculated synoptic maps are used to determine the existence of closed and open field regions of the hole. Finally, we have correlated the characteristics of two coronal holes with observed solar wind speed. We found that the brighter coronal hole has high speed solar wind, and the dimmer coronal hole has low speed solar wind.

  12. A simple model for geomagnetic field excursions and inferences for palaeomagnetic observations

    NASA Astrophysics Data System (ADS)

    Brown, M. C.; Korte, M.

    2016-05-01

    We explore simple excursion scenarios by imposing changes on the axial dipole component of the Holocene geomagnetic field model CALS10k.2 and investigate implications for our understanding of palaeomagnetic observations of excursions. Our findings indicate that globally observed directions of fully opposing polarity are only possible when the axial dipole reverses: linearly decaying the axial dipole to zero and then reestablishing it with the same sign produces a global intensity minimum, but does not produce fully reversed directions globally. Reversing the axial dipole term increases the intensity of the geomagnetic field observed at Earth's surface across the mid-point of the excursion, which results in a double-dip intensity structure during the excursion. Only a limited number of palaeomagnetic records of excursions contain such a double-dip intensity structure. Rather, the maximum directional change is coeval with a geomagnetic field intensity minimum.

  13. A target detection model predicting field observer performance in maritime scenes

    NASA Astrophysics Data System (ADS)

    Culpepper, Joanne B.; Wheaton, Vivienne C.

    2014-10-01

    The U.S. Army's target acquisition models, the ACQUIRE and Target Task Performance (TTP) models, have been employed for many years to assess the performance of thermal infrared sensors. In recent years, ACQUIRE and the TTP models have been adapted to assess the performance of visible sensors. These adaptations have been primarily focused on the performance of an observer viewing a display device. This paper describes an implementation of the TTP model to predict field observer performance in maritime scenes. Predictions of the TTP model implementation were compared to observations of a small watercraft taken in a field trial. In this field trial 11 Australian Navy observers viewed a small watercraft in an open ocean scene. Comparisons of the observed probability of detection to predictions of the TTP model implementation showed the normalised RSS metric overestimated the probability of detection. The normalised Pixel Contrast using a literature value for V50 yielded a correlation of 0.58 between the predicted and observed probability of detection. With a measured value of N50 or V50 for the small watercraft used in this investigation, this implementation of the TTP model may yield stronger correlation with observed probability of detection.

  14. Interpolation of observed rainfall fields for flood forecasting in data poor areas

    NASA Astrophysics Data System (ADS)

    Rogelis Prada, M. C.; Werner, M. G. F.

    2010-09-01

    Observed rainfall fields constitute a crucial input for operational flood forecasting, providing boundary conditions to hydrological models for prediction of flows and levels in relevant forecast points. Such observed fields are derived through interpolation from available observed data from rain gauges. The reliability of the derived rainfall field depends on the density of the gauge network within the basin, as well as on the variability of the rainfall itself, and the interpolation method. In this paper interpolation methods to estimate rainfall fields under data- poor environments are researched, with the derived rainfall fields being used in operational flood warnings. Methods are applied in a small catchment in Bogotá, Colombia. This catchment has a complex climatology, which is strongly influenced by the inter-tropical convergence zone and orographic enhancement. As is common in such catchments in developing countries, the rainfall gauging network is sparse, while the need for reliable rainfall in flood forecasting is high. The extensive high flood risk zones in the lower areas of the catchment, where urbanization processes are characterized by unplanned occupation of areas close to rivers, is common in developing countries. Results show the sensitivity of interpolated rainfall fields to the interpolation methods chosen, and the importance of the use of indicator variables for improving the spatial distribution of interpolated rainfall. The value of these methods in establishing optimal new gauging sites for augmenting the sparse gauge network is demonstrated.

  15. Future missions for observing Earth's changing gravity field: a closed-loop simulation tool

    NASA Astrophysics Data System (ADS)

    Visser, P. N.

    2008-12-01

    The GRACE mission has successfully demonstrated the observation from space of the changing Earth's gravity field at length and time scales of typically 1000 km and 10-30 days, respectively. Many scientific communities strongly advertise the need for continuity of observing Earth's gravity field from space. Moreover, a strong interest is being expressed to have gravity missions that allow a more detailed sampling of the Earth's gravity field both in time and in space. Designing a gravity field mission for the future is a complicated process that involves making many trade-offs, such as trade-offs between spatial, temporal resolution and financial budget. Moreover, it involves the optimization of many parameters, such as orbital parameters (height, inclination), distinction between which gravity sources to observe or correct for (for example are gravity changes due to ocean currents a nuisance or a signal to be retrieved?), observation techniques (low-low satellite-to-satellite tracking, satellite gravity gradiometry, accelerometers), and satellite control systems (drag-free?). A comprehensive tool has been developed and implemented that allows the closed-loop simulation of gravity field retrievals for different satellite mission scenarios. This paper provides a description of this tool. Moreover, its capabilities are demonstrated by a few case studies. Acknowledgments. The research that is being done with the closed-loop simulation tool is partially funded by the European Space Agency (ESA). An important component of the tool is the GEODYN software, kindly provided by NASA Goddard Space Flight Center in Greenbelt, Maryland.

  16. Field trip report: Observations made at Yucca Mountain, Nye County, Nevada. Special report No. 2

    SciTech Connect

    Hill, C.A.

    1993-03-01

    A field trip was made to the Yucca Mountain area on December 5-9, 1992 by Jerry Frazier, Don Livingston, Christine Schluter, Russell Harmon, and Carol Hill. Forty-three separate stops were made and 275 lbs. of rocks were collected during the five days of the field trip. Key localities visited were the Bare Mountains, Yucca Mountain, Calico Hills, Busted Butte, Harper Valley, Red Cliff Gulch, Wahmonie Hills, Crater Flat, and Lathrop Wells Cone. This report only describes field observations made by Carol Hill. Drawings are used rather than photographs because cameras were not permitted on the Nevada Test Site during this trip.

  17. The distant bow shock and magnetotail of Venus - Magnetic field and plasma wave observations

    NASA Technical Reports Server (NTRS)

    Russell, C. T.; Luhmann, J. G.; Elphic, R. C.; Scarf, F. L.

    1981-01-01

    An examination of the magnetic field and plasma wave data obtained by the Pioneer Venus orbiter in the wake region behind Venus discloses a well developed bow shock whose location is similar to that observed on previous missions in contrast to the dayside bow shock. Venus also has a well developed magnetotail in which the field strenght is enhanced over magnetosheath values and in which the magnetic field is aligned approximately with the solar wind direction. The boundary between magnetosheath and magnetotail is also marked by a change in the plasma wave spectrum.

  18. Satellite-borne study of seismic phenomena by low frequency magnetic field observations

    NASA Astrophysics Data System (ADS)

    Schwingenschuh, Konrad; Magnes, Werner; Xuhui, Shen; Wang, Jindong; Pollinger, Andreas; Hagen, Christian; Prattes, Gustav; Eichelberger, Hans-Ulrich; Wolbang, Daniel; Boudjada, Mohammed Y.; Besser, Bruno P.; Rozhnoi, Alexander A.; Zhang, Tielong

    2015-04-01

    A combined scalar-vector magnetic field experiment will be flown on the upcoming CSES mission (China Seismo-Electromagnetic Satellite). Magnetic field data from DC to 30 Hz will be measured with an accuracy of about 10 pT. A fluxgate instrument will provide the 3 magnetic field components and a new type of an optically pumped magnetometer [see Pollinger, 2010] will measure the magnitude of the ambient magnetic field. The satellite will operate in a Sun synchronous polar orbit at an altitude of about 500 km and with an inclination of 97°. We present a model of magnetic field fluctuations in the upper ionosphere based on previous satellite observations and on a model of the lithospheric-atmospheric-ionospheric coupling. Pollinger et al., CDSM-a new scalar magnetometer, EGU General Assembly 2010

  19. Cardiovascular alterations in Macaca monkeys exposed to stationary magnetic fields: experimental observations and theoretical analysis

    SciTech Connect

    Tenforde, T.S.; Gaffey, C.T.; Moyer, B.R.; Budinger, T.F.

    1983-01-01

    Simultaneous measurements were made of the electrocardiogram (ECG) and the intraarterial blood pressure of adult male Macaca monkeys during acute exposure to homogeneous stationary magnetic fields ranging in strength up to 1.5 tesla. An instantaneous, field strength-dependent increase in the ECG signal amplitude at the locus of the T wave was observed in fields greater than 0.1 tesla. The temporal sequence of this signal in the ECG record and its reversibility following termination of the magnetic field exposure are consistent with an earlier suggestion that it arises from a magnetically induced aortic blood flow potential superimposed on the native T-wave signal. No measurable alterations in blood pressure resulted from exposure to fields up to 1.5 tesla. This experimental finding is in agreement with theoretical calculations of the magnetohydrodynamic effect on blood flow in the major arteries of the cardiovascular system. 27 references, 1 figure, 1 table.

  20. Magnetospheric Multiscale Satellites Observations of Parallel Electric Fields Associated with Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Ergun, R. E.; Goodrich, K. A.; Wilder, F. D.; Holmes, J. C.; Stawarz, J. E.; Eriksson, S.; Sturner, A. P.; Malaspina, D. M.; Usanova, M. E.; Torbert, R. B.; Lindqvist, P.-A.; Khotyaintsev, Y.; Burch, J. L.; Strangeway, R. J.; Russell, C. T.; Pollock, C. J.; Giles, B. L.; Hesse, M.; Chen, L. J.; Lapenta, G.; Goldman, M. V.; Newman, D. L.; Schwartz, S. J.; Eastwood, J. P.; Phan, T. D.; Mozer, F. S.; Drake, J.; Shay, M. A.; Cassak, P. A.; Nakamura, R.; Marklund, G.

    2016-06-01

    We report observations from the Magnetospheric Multiscale satellites of parallel electric fields (E∥ ) associated with magnetic reconnection in the subsolar region of the Earth's magnetopause. E∥ events near the electron diffusion region have amplitudes on the order of 100 mV /m , which are significantly larger than those predicted for an antiparallel reconnection electric field. This Letter addresses specific types of E∥ events, which appear as large-amplitude, near unipolar spikes that are associated with tangled, reconnected magnetic fields. These E∥ events are primarily in or near a current layer near the separatrix and are interpreted to be double layers that may be responsible for secondary reconnection in tangled magnetic fields or flux ropes. These results are telling of the three-dimensional nature of magnetopause reconnection and indicate that magnetopause reconnection may be often patchy and/or drive turbulence along the separatrix that results in flux ropes and/or tangled magnetic fields.

  1. Simultaneous observation of the quantization and the interference pattern of a plasmonic near-field

    DOE PAGESBeta

    Piazza, L.; Lummen, T. T. A.; Quiñonez, E.; Murooka, Y.; Reed, B. W.; Barwick, B.; Carbone, F.

    2015-03-02

    Surface plasmon polaritons can confine electromagnetic fields in subwavelength spaces and are of interest for photonics, optical data storage devices and biosensing applications. In analogy to photons, they exhibit wave–particle duality, whose different aspects have recently been observed in separate tailored experiments. Here we demonstrate the ability of ultrafast transmission electron microscopy to simultaneously image both the spatial interference and the quantization of such confined plasmonic fields. Our experiments are accomplished by spatiotemporally overlapping electron and light pulses on a single nanowire suspended on a graphene film. The resulting energy exchange between single electrons and the quanta of the photoinducedmore » near-field is imaged synchronously with its spatial interference pattern. In conclusion, this methodology enables the control and visualization of plasmonic fields at the nanoscale, providing a promising tool for understanding the fundamental properties of confined electromagnetic fields and the development of advanced photonic circuits.« less

  2. Simultaneous observation of the quantization and the interference pattern of a plasmonic near-field

    SciTech Connect

    Piazza, L.; Lummen, T. T. A.; Quiñonez, E.; Murooka, Y.; Reed, B. W.; Barwick, B.; Carbone, F.

    2015-03-02

    Surface plasmon polaritons can confine electromagnetic fields in subwavelength spaces and are of interest for photonics, optical data storage devices and biosensing applications. In analogy to photons, they exhibit wave–particle duality, whose different aspects have recently been observed in separate tailored experiments. Here we demonstrate the ability of ultrafast transmission electron microscopy to simultaneously image both the spatial interference and the quantization of such confined plasmonic fields. Our experiments are accomplished by spatiotemporally overlapping electron and light pulses on a single nanowire suspended on a graphene film. The resulting energy exchange between single electrons and the quanta of the photoinduced near-field is imaged synchronously with its spatial interference pattern. In conclusion, this methodology enables the control and visualization of plasmonic fields at the nanoscale, providing a promising tool for understanding the fundamental properties of confined electromagnetic fields and the development of advanced photonic circuits.

  3. Magnetic fields in Venus nightside ionospheric holes - Collected Pioneer Venus Orbiter magnetometer observations

    NASA Technical Reports Server (NTRS)

    Luhmann, J. G.; Russell, D. S.

    1992-01-01

    The magnetic fields detected by the Pioneer Venus Orbiter (PVO) magnetometer within the electron density depletions called 'holes' in the nightside ionosphere are typically larger and more organized than the fields in the surrounding ionosphere. Moreover, they have substantial sunward/antisunward components which cause them to appear as near-radial fields near the antisolar point. The collection of observations presented here illustrate the variety of appearances of the fields in holes. Some new results which summarize their average properties, their dependence on solar wind conditions, and their lack of geographical control are aslo presented. These results are potentially pertinent to the interpretation of data from the PVO entry at the end of 1992 and from the impending Mars Obsever mission, which will probe the magnetic fields in the low-altitude wake of weakly magnetized Mars.

  4. A quantitative study relating observed shear in photospheric magnetic fields to repeated flaring

    NASA Astrophysics Data System (ADS)

    Hagyard, M. J.; Teuber, D.; West, E. A.; Smith, J. B.

    1984-03-01

    In this paper a quantitative evaluation of the shear in the magnetic field along the neutral line in an active region during an epoch of flare activity is presented. Shear is defined as the angular difference in the photosphere between the potential magnetic field, which fits the boundary conditions imposed by the observed line-of-sight field, and the observed magnetic field. For the active region studied, this angular difference (shear) is non-uniform along the neutral line with maxima occurring at the locations of repeated flare onsets. It is suggested that continued magnetic evolution causes the field's maximum shear to exceed a critical value of shear, resulting in a flare around the site of maximum shear. Evidently, the field at the site of the flare must relax to a state of shear somewhat below the critical value (but still far from potential), with subsequent evolution returning the field to the critical threshold. This inference is drawn because several flares occured at sites of maximum photospheric shear which were persistent in location.

  5. A quantitative study relating observed shear in photospheric magnetic fields to repeated flaring

    NASA Technical Reports Server (NTRS)

    Hagyard, M. J.; Teuber, D.; West, E. A.; Smith, J. B.

    1984-01-01

    In this paper a quantitative evaluation of the shear in the magnetic field along the neutral line in an active region during an epoch of flare activity is presented. Shear is defined as the angular difference in the photosphere between the potential magnetic field, which fits the boundary conditions imposed by the observed line-of-sight field, and the observed magnetic field. For the active region studied, this angular difference (shear) is non-uniform along the neutral line with maxima occurring at the locations of repeated flare onsets. It is suggested that continued magnetic evolution causes the field's maximum shear to exceed a critical value of shear, resulting in a flare around the site of maximum shear. Evidently, the field at the site of the flare must relax to a state of shear somewhat below the critical value (but still far from potential), with subsequent evolution returning the field to the critical threshold. This inference is drawn because several flares occured at sites of maximum photospheric shear which were persistent in location.

  6. The characteristics of quasistatic electric field perturbations observed by DEMETER satellite before large earthquakes

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Shen, X.; Zhao, S.; Yao, Lu; Ouyang, X.; Qian, J.

    2014-01-01

    This paper presents new results after processing the ULF electric field (DC-15 Hz) observed by DEMETER satellite (h = 660-710 km). Typical perturbations were picked up in quasistatic electric field around some large earthquakes in 2010 at first. And then, 27 earthquakes were selected to be analyzed on quasistatic electric field in two seismic regions of Indonesia and Chile at equatorial and middle latitude area respectively. Three-component electric field data related to earthquakes were collected along all the up-orbits (in local nighttime) in a limited distance of 2000 km to the epicenters during 9 days with 7 days before and 1 day after those cases, and totally 57 perturbations were found around them. All the results show that the amplitude of quasistatic electric field perturbations varies from 1.5 to 16 mV/m in the upper ionosphere, mostly smaller than 10 mV/m. And the perturbations were mainly located just over the epicentral area or at the end of seismic faults constructed by a series of earthquakes where electromagnetic emissions may be easily formed during preparation and development processes of seismic sequences. Among all 27 cases, there are 10 earthquakes with perturbations occurring just one day before, which demonstrates the close correlation in time domain between quasistatic electric field in ionosphere and large earthquakes. Finally, combined with in situ observation of plasma parameters, the coupling mechanism of quasistatic electric field in different earth spheres was discussed.

  7. Interaction of solar wind with Mercury and its magnetic field. [as observed by Mariner 10 space probe

    NASA Technical Reports Server (NTRS)

    Ness, N. F.; Behannon, K. W.; Lepping, R. P.; Whang, Y. C.

    1976-01-01

    A brief review is presented of magnetic field and solar wind electron observations by Mariner 10 spacecraft. The intrinsic magnetic field of the planet Mercury and the implications of such a field for the planetary interior are also discussed.

  8. Merged interaction regions and large-scale magnetic field fluctuations during 1991: Voyager 2 observations

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Ness, N. F.

    1994-01-01

    This paper analyzes Voyager 2 observations of the magnetic field between 33.6 AU and 36.2 AU during 1991 when extraordinary events were observed on the Sun and in the heliosphere. The magnetic field strength signal B(t) has the unusual form of two large transient merged interaction regions (MIRs) on a fluctuating background. The two MIRs moved past the spacecraft in 32 days and 18 days, respectively. The mean field strength in each transient MIR was approx. equals 2.6 times the mean field during the remaining part of the year (0.11 nT). Each of the MIRs is related to a fast stream. The magnetic field is strong throughout each stream, suggesting that the strong fields are carried by the streams as well as produced by shock and stream compression. The fluctuations in B(t) during 1991 are not multifractal, and the MIRs cannot be approximated as multifractal clusters of intense magnetic fields. The distribution of the hour-averaged magnetic field strengths is approximately lognormal over 90% of its intermediate range, and it has an exponential tail for B greater than the average magnetic field strength. The elevation angles of B have a normal distribution with a standard deviation of 16 deg +/- 4 deg. The distributions of the azimuthal angles of B in the ranges 1 deg - 180 deg and 180 deg - 360 deg are approximately normal over a more limited range, and non-Gaussian tails associated with nearly radial magnetic fields; the standard deviations are approx. equal to 40 deg. Individual sectors are present throughout most of the interval, even in the MIRs, but there is no recurrent sector pattern. A model of the large-scale fluctuations in 1991 will have to include both determinaistic and statistical factors.

  9. Modular model for Mercury's magnetospheric magnetic field confined within the average observed magnetopause

    NASA Astrophysics Data System (ADS)

    Korth, Haje; Tsyganenko, Nikolai A.; Johnson, Catherine L.; Philpott, Lydia C.; Anderson, Brian J.; Al Asad, Manar M.; Solomon, Sean C.; McNutt, Ralph L.

    2015-06-01

    Accurate knowledge of Mercury's magnetospheric magnetic field is required to understand the sources of the planet's internal field. We present the first model of Mercury's magnetospheric magnetic field confined within a magnetopause shape derived from Magnetometer observations by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft. The field of internal origin is approximated by a dipole of magnitude 190 nT RM3, where RM is Mercury's radius, offset northward by 479 km along the spin axis. External field sources include currents flowing on the magnetopause boundary and in the cross-tail current sheet. The cross-tail current is described by a disk-shaped current near the planet and a sheet current at larger (≳ 5 RM) antisunward distances. The tail currents are constrained by minimizing the root-mean-square (RMS) residual between the model and the magnetic field observed within the magnetosphere. The magnetopause current contributions are derived by shielding the field of each module external to the magnetopause by minimizing the RMS normal component of the magnetic field at the magnetopause. The new model yields improvements over the previously developed paraboloid model in regions that are close to the magnetopause and the nightside magnetic equatorial plane. Magnetic field residuals remain that are distributed systematically over large areas and vary monotonically with magnetic activity. Further advances in empirical descriptions of Mercury's magnetospheric external field will need to account for the dependence of the tail and magnetopause currents on magnetic activity and additional sources within the magnetosphere associated with Birkeland currents and plasma distributions near the dayside magnetopause.

  10. OBSERVATION OF A NON-RADIAL PENUMBRA IN A FLUX EMERGING REGION UNDER CHROMOSPHERIC CANOPY FIELDS

    SciTech Connect

    Lim, Eun-Kyung; Yurchyshyn, Vasyl; Goode, Philip; Cho, Kyung-Suk

    2013-05-20

    The presence of a penumbra is one of the main properties of a mature sunspot, but its formation mechanism has been elusive due to a lack of observations that fully cover the formation process. Utilizing the New Solar Telescope at the Big Bear Solar Observatory, we observed the formation of a partial penumbra for about 7 hr simultaneously at the photospheric (TiO; 7057 A) and the chromospheric (H{alpha} - 1 A) spectral lines with high spatial and temporal resolution. From this uninterrupted, long observing sequence, we found that the formation of the observed penumbra was closely associated with flux emergence under the pre-existing chromospheric canopy fields. Based on this finding, we suggest a possible scenario for penumbra formation in which a penumbra forms when the emerging flux is constrained from continuing to emerge, but rather is trapped at the photospheric level by the overlying chromospheric canopy fields.

  11. Connecting Coronal Holes and Open Magnetic Field via Numerical Modeling and Observations

    NASA Astrophysics Data System (ADS)

    Lowder, Chris; Qui, Jiong; sLeamon, Robert J.; Longcope, Dana

    2015-04-01

    Coronal holes are regions of the Sun's surface that map the footprints of open magnetic field lines traced down from the corona and heliosphere beyond. Without the ability to directly and easily observe coronal magnetic field line structure, mapping their footprint 'dance' throughout the solar cycle is crucial for understanding this open field contribution to space weather. Coronal holes provide just this proxy.Using a combination of SOHO:EIT, SDO:AIA, and STEREO:EUVI A/B extreme ultraviolet (EUV) observations from 1996-2014, coronal holes are automatically detected and characterized throughout this span, enabling long-term solar-cycle-timescale study. In particular, the combination of SDO:AIA and STEREO:EUVI A/B data provides a new viewpoint on understanding coronal hole evolution. As the two STEREO spacecraft drift ahead and behind of the Earth in their orbit, respectively, they are able to peek around the corner and closer to the poles, providing the ability to image nearly the entire solar surface in EUV wavelengths, using SDO data in conjunction. A flux transport model driven by observed bipole data allows for the study and comparison of far-side magnetic field evolution. By combining our numerical models of solar open magnetic field evolution with coronal hole observations, comparison of far-side and polar dynamics becomes possible. Model constraints and boundary conditions are more easily fine-tuned with these global observations. Understanding the dynamics of boundary changes and distribution throughout the solar cycle yields important insight into connecting models of open magnetic field.

  12. Electric field measurements at the magnetopause. I Observation of large convective velocities at rotational magnetopause discontinuities

    NASA Technical Reports Server (NTRS)

    Aggson, T. L.; Maynard, N. C.; Gambardella, P. J.

    1983-01-01

    Large convective electric fields of the order of 10 mV/m (sometimes as high as 22 mV/m) are observed at rotational magnetopause discontinuities. These observations were made with the long cylindrical (179-m base line) probes carried on the ISEE 1 satellite. These electric field observations yield convective velocity magnitudes (equal to the cross product of the vector E and the vector B, the latter divided by the square of the magnitude of B) of the order of 150 km/s. In this format for the convective velocity magnitudes, some of these observations are similar to the high speed plasma velocity observations that were made at the magnetopause with the plasma experiment carried on the ISEE 1 satellite. It is shown that, for many of these magnetopause crossings, there exists a special moving coordinate system where the observed electric fields vanish. Such a unique reference system is often used in theoretical studies of magnetic discontinuities. This special coordinate system does not move at the local plasma velocity but moves instead at a velocity intermediate between the convective velocity and the local Alfven velocity. It is used here as a diagnostic tool for the experimental investigation of rotational discontinuities at the magnetopause.

  13. Radial profile of the inner heliospheric magnetic field as deduced from Faraday rotation observations

    NASA Astrophysics Data System (ADS)

    Mancuso, S.; Garzelli, M. V.

    2013-05-01

    Faraday rotation measures (RMs) of the polarized emission from extragalactic radio sources occulted by the coronal plasma were used to infer the radial profile of the inner heliospheric magnetic field near the solar minimum. By inverting LASCO/SOHO polarized brightness (pB) data taken during the observations in May 1997, we retrieved the electron density distribution along the lines of sight to the sources, which allowed us to separate the two plasma properties that contribute to the observed RMs. By comparing the observed RM values with those theoretically predicted by a power law model of the radial component of the coronal magnetic field using a best-fitting procedure, we found that the radial component of the inner heliospheric magnetic field can be nicely approximated by a power law of the form Br = 3.76 r-2.29 G in a range of heights from about 5 to 14 R⊙. Finally, our analysis suggests that the radial computation of the potential field source surface model from the Wilcox Solar Observatory is the preferred choice near solar minimum assuming a radial field in the photosphere and a source surface located at Rss = 2.5 R⊙.

  14. Constraining magnetic fields morphologies using mid-IR polarization: observations and modeling

    NASA Astrophysics Data System (ADS)

    Zhang, Han; Li, Dan; Pantin, Eric; Telesco, Charles M.

    2016-01-01

    Polarization arises from aligned dust grains in magnetic fields, and thus the direction of polarization can trace the direction of B fields. We present the mid-IR imaging and spectropolarimetry observations made with the GTC's CanariCam of the Herbig Ae star WL 16. WL 16 is embedded in/behind the ρ Ophiuchus molecular cloud with visual extinction of ~31 mag. It exhibits large and extended (~900 AU) emission, which is believed to come from the emission of PAHs and very small dust grains. Uniform polarization vectors from imaging polarization and the absorption-dominated polarization profile from spectropolarimetry consistently indicate a uniform foreground magnetic field oriented at about 30 deg from the North.We also model the predicted polarization patterns expected to arise from different magnetic field morphologies, which can be distinguished by high-resolution observations. As an example, we present the mid-IR polarization modeling of AB Aur, a well-studied Herbig Ae star. We incorporate polarization from dichroic absorption, emission and scattering in the modeling. The observed polarization structures are well reproduced by two components: emissive polarization arising from a poloidal B field and scattering polarization by 0.01-1 μm dust grains.

  15. Modeling electron density, temperature distribution in the solar corona based on solar surface magnetic field observations

    NASA Astrophysics Data System (ADS)

    Lago, A.; Rodríguez, J. M.; Vieira, L.; Coelho Stekel, T. R.; Costa, J. E. R.; Pinto, T. S. N.

    2015-12-01

    Magnetic fields constitute a natural link between the Sun, the Earth and the Heliosphere in general. The solar dynamo action maintains and strengthens the magnetic field in the solar interior. The structure of the solar corona is mostly determined by the configuration and evolution of the magnetic field. While open magnetic field lines carry plasma into the heliosphere, closed field lines confine plasma. Additionally, key physical processes that impact the evolution of Earth's atmosphere on time-scale from days to millennia, such as the soft X-ray and EUV emission, are also determined by the solar magnetic field. However, observations of the solar spectral irradiance are restricted to the last few solar cycles and are subject to large uncertainties. Here we present a physics-based model to reconstruct in near-real time the evolution of the solar EUV emission based on the configuration of the magnetic field imprinted on the solar surface and assuming that the emission lines are optically thin. The structure of the coronal magnetic field is estimated employing a potential field source surface extrapolation based on the synoptic charts. The coronal plasma temperature and density are described by a hydrostatic model. The emission is estimated to employ the CHIANTI database. The performance of the model is compared to the emission observed by EVE instrument on board SDO spacecraft. The preliminary results and uncertainties are discussed in details. Furthermore, we examine the possibility of delivery the reconstruction of the solar spectral irradiance in near-real time using the infrastructure provided by the Brazilian Space weather program (EMBRACE/INPE). This work is partially supported by CNPq/Brazil under the grant agreement no. 140779/2015-9.

  16. High-resolution observations of the polar magnetic fields of the sun

    NASA Technical Reports Server (NTRS)

    Lin, H.; Varsik, J.; Zirin, H.

    1994-01-01

    High-resolution magnetograms of the solar polar region were used for the study of the polar magnetic field. In contrast to low-resolution magnetograph observations which measure the polar magnetic field averaged over a large area, we focused our efforts on the properties of the small magnetic elements in the polar region. Evolution of the filling factor (the ratio of the area occupied by the magnetic elements to the total area) of these magnetic elements, as well as the average magnetic field strength, were studied during the maximum and declining phase of solar cycle 22, from early 1991 to mid-1993. We found that during the sunspot maximum period, the polar regions were occupied by about equal numbers of positive and negative magnetic elements, with equal average field strength. As the solar cycle progresses toward sunspot minimum, the magnetic field elements in the polar region become predominantly of one polarity. The average magnetic field of the dominant polarity elements also increases with the filling factor. In the meanwhile, both the filling factor and the average field strength of the non-dominant polarity elements decrease. The combined effects of the changing filling factors and average field strength produce the observed evolution of the integrated polar flux over the solar cycle. We compared the evolutionary histories of both filling factor and average field strength, for regions of high (70-80 deg) and low (60-70 deg) latitudes. For the south pole, we found no significant evidence of difference in the time of reversal. However, the low-latitude region of the north pole did reverse polarity much earlier than the high-latitude region. It later showed an oscillatory behavior. We suggest this may be caused by the poleward migration of flux from a large active region in 1989 with highly imbalanced flux.

  17. Observer Role and Field Study Knowledge--An Essay Review of Usable Knowledge and SAFARI I.

    ERIC Educational Resources Information Center

    Smith, Louis M.; And Others

    1981-01-01

    A synthesis is presented of the work of Lindblom and Cohen, MacDonald and Walker, and the current authors. The synthesis considers issues in the usefulness of social science theory and research, and how observer roles in qualitative field studies yield multiple kinds of usable knowledge to a variety of audiences. (Author/BW)

  18. Observations of ferrofluid flow under a uniform rotating magnetic field in a spherical cavity

    NASA Astrophysics Data System (ADS)

    Torres-Díaz, Isaac; Rinaldi, Carlos; Khushrushahi, Shahriar; Zahn, Markus

    2012-04-01

    Flow of a ferrofluid in spherical and cylindrical geometries were measured under the influence of a uniform rotating magnetic field produced by two perpendicular spherical coils, a so-called fluxball, excited by quadrature currents. Using an ultrasound velocity profile technique and a commercial oil based ferrofluid (EFH1, Ferrotec) we observed rotational flow around the z-axis. In comparison, the radial component of the flow was found to be negligible. Results show that the magnitude of the azimuthal velocity profile increases as the applied magnetic field amplitude increases. This behavior is also observed for ferrofluid in a cylindrical container placed inside the fluxball cavity and inside a two-pole stator winding. These results indicate that inhomogeneities in the magnetic field produced by slots and finite height of the stator winding used in prior experiments are not the source of previously observed flows produced by a two pole stator winding. The experiments reported here either point to the existence of non-uniform demagnetizing magnetic fields due to the finite height of the cylindrical container, the existence of couple stresses and spin viscosity in ferrofluids, or to the need to develop alternate governing and constitutive equations capable of describing the experimental observations.

  19. FIELD OBSERVATIONS OF THE ECOLOGY AND HABITS OF MANGROVE RIVULUS (RIVULUS MARMORATUS) IN BELIZE AND FLORIDA

    EPA Science Inventory

    This report provides a synopsis of field studies of Rivulus marmaratus from two population surveys of mangrove islands adjacent to the Belize barrier reef and observations made over fifteen years at several sites in south Florida. his small, cryptically colored killifish is the o...

  20. Observations of the longitudinal magnetic field in the transition region and photosphere of a sunspot

    NASA Technical Reports Server (NTRS)

    Henze, W., Jr.; Tandberg-Hanssen, E.; Hagyard, M. J.; West, E. A.; Woodgate, B. E.; Shine, R. A.; Beckers, J. M.; Bruner, M.; Hyder, C. L.; West, E. A.

    1982-01-01

    The Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission spacraft has observed for the first time the longitudinal component of the magnetic field by means of the Zeeman effect in the transition region above a sunspot. The data presented here were obtained on three days in one sunspot, have spatial resolutions of 10 arcsec and 3 arcsec, and yield maximum field strengths greater than 1000 G above the umbrae in the spot. The method of analysis, including a line-width calibration feature used during some of the observations, is described in some detail in an appendix; the line width is required for the determination of the longitudinal magnetic field from the observed circular polarization. The transition region data for one day are compared with photospheric magnetograms from the Marshall Space Flight Center. Vertical gradients of the magnetic field are compared from the two sets of data; the maximum gradients of 0.41 to 0.62 G/km occur above the umbra and agree with or are smaller than values observed previously in the photosphere and low chromosphere.

  1. Viking magnetic and electric field observations of periodic Pc 1 waves: Pearl pulsations

    SciTech Connect

    Erlandson, R.E.; Anderson, B.J.; Zanetti, L.J.

    1992-10-01

    Pearl pulsations, with an average repetition period of 60 s, were recorded using the magnetic and electric field experiments on the polar-orbiting Viking satellite. The wave event occurred on September 30, 1986, during Viking orbit 1212 at 1030 MLT, from L=3.6 to L=4.1, and at an altitude of 13,500 km. Electron density observations obtained from Viking show that the waves were generated at the plasmapause and at lower amplitudes in the plasmasphere. The wave Poynting flux, calculated using the magnetic and electric field, indicated that the waves generally were propagating downward toward the ionosphere, although upward Poynting fluxes were observed. Clear evidence of upward propagating waves, associated with downward propagating waves reflected at the ionosphere, was not observed. Linear convective growth rates suggest that the anisotropic ions which provide the free energy have a perpendicular temperature around 15 keV. The repetition period, calculated using the measured electron density and magnetic field strength at Viking, is consistent with the double-hop transit time for ion cyclotron waves which propagate along field lines from one hemisphere to the other. However, the absence of upward propagating waves packets implies that the upper limit of the wave ionospheric reflection coefficient is on the order of 10 to 20%. Alternative mechanism for producing the observed repetition are also investigated and include a periodic generation model of pearl pulsations at the ion bounce period. 42 refs., 5 figs., 4 tabs.

  2. Horizontal flow fields observed in Hinode G-band images. II. Flow fields in the final stages of sunspot decay

    NASA Astrophysics Data System (ADS)

    Verma, M.; Balthasar, H.; Deng, N.; Liu, C.; Shimizu, T.; Wang, H.; Denker, C.

    2012-02-01

    Context. Generation and dissipation of magnetic fields is a fundamental physical process on the Sun. In comparison to flux emergence and the initial stages of sunspot formation, the demise of sunspots still lacks a comprehensive description. Aims: The evolution of sunspots is most commonly discussed in terms of their intensity and magnetic field. Here, we present additional information about the three-dimensional flow field in the vicinity of sunspots towards the end of their existence. Methods: We present a subset of multi-wavelengths observations obtained with the Japanese Hinode mission, the Solar Dynamics Observatory (SDO), and the Vacuum Tower Telescope (VTT) at Observatorio del Teide, Tenerife, Spain during the time period 2010 November 18-23. Horizontal proper motions were derived from G-band and Ca ii H images, whereas line-of-sight velocities were extracted from VTT echelle Hα λ656.28 nm spectra and Fe i λ630.25 nm spectral data of the Hinode/Spectro-Polarimeter, which also provided three-dimensional magnetic field information. The Helioseismic and Magnetic Imager on board SDO provided continuum images and line-of-sight magnetograms, in addition to the high-resolution observations for the entire disk passage of the active region. Results: We perform a quantitative study of photospheric and chromospheric flow fields in and around decaying sunspots. In one of the trailing sunspots of active region NOAA 11126, we observe moat flow and moving magnetic features (MMFs), even after its penumbra had decayed. We also detect a superpenumbral structure around this pore. We find that MMFs follow well-defined, radial paths from the spot all the way to the border of a supergranular cell surrounding the spot. In contrast, flux emergence near the other sunspot prevents the establishment of similar well ordered flow patterns, which could be discerned around a tiny pore of merely 2 Mm diameter. After the disappearance of the sunspots/pores, a coherent patch of abnormal

  3. Direct Observation of Solar Coronal Magnetic Fields by Vector Tomography of the Coronal Emission Line Polarizations

    NASA Astrophysics Data System (ADS)

    Kramar, M.; Lin, H.; Tomczyk, S.

    2016-03-01

    We present the first direct “observation” of the global-scale, 3D coronal magnetic fields of Carrington Rotation (CR) Cycle 2112 using vector tomographic inversion techniques. The vector tomographic inversion uses measurements of the Fe xiii 10747 Å Hanle effect polarization signals by the Coronal Multichannel Polarimeter (CoMP) and 3D coronal density and temperature derived from scalar tomographic inversion of Solar Terrestrial Relations Observatory (STEREO)/Extreme Ultraviolet Imager (EUVI) coronal emission lines (CELs) intensity images as inputs to derive a coronal magnetic field model that best reproduces the observed polarization signals. While independent verifications of the vector tomography results cannot be performed, we compared the tomography inverted coronal magnetic fields with those constructed by magnetohydrodynamic (MHD) simulations based on observed photospheric magnetic fields of CR 2112 and 2113. We found that the MHD model for CR 2112 is qualitatively consistent with the tomography inverted result for most of the reconstruction domain except for several regions. Particularly, for one of the most noticeable regions, we found that the MHD simulation for CR 2113 predicted a model that more closely resembles the vector tomography inverted magnetic fields. In another case, our tomographic reconstruction predicted an open magnetic field at a region where a coronal hole can be seen directly from a STEREO-B/EUVI image. We discuss the utilities and limitations of the tomographic inversion technique, and present ideas for future developments.

  4. Rocket-borne particle, field, and plasma observations in the cleft region. [ionospheric sounding

    NASA Technical Reports Server (NTRS)

    Ungstrup, E.; Bahnsen, A.; Olesen, J. K.; Primdahl, F.; Spangslev, F.; Heikkila, W. J.; Klumpar, D. M.; Winningham, J. D.; Fahleson, U.; Falthammar, C.-G.

    1975-01-01

    Results are reported for comprehensive observations of magnetic and electric fields together with ambient and suprathermal plasmas above the dayside auroral oval with rocket-borne instrumentation which penetrated the cleft region. Measurements were also obtained equatorward and poleward of the cleft. Convection velocities as inferred from electric-field measurements were generally toward noon equatorward of the cleft and were antisunward over the polar cap. Observations of electron temperatures, electric fields, and low-frequency electrostatic noise provide strong evidence of a plasma instability (Farley-Buneman) in the E-layer associated with the appearance of the 'slant E condition' identified in ground-acquired ionograms. The positions of these measurements relative to that of the cleft were firmly established via the determination of the plasma environment with an electrostatic analyzer.

  5. Modeling of the coseismic electromagnetic fields observed during the 2004 Mw 6.0 Parkfield earthquake

    NASA Astrophysics Data System (ADS)

    Gao, Yongxin; Harris, Jerry M.; Wen, Jian; Huang, Yihe; Twardzik, Cedric; Chen, Xiaofei; Hu, Hengshan

    2016-01-01

    The coseismic electromagnetic signals observed during the 2004 Mw 6 Parkfield earthquake are simulated using electrokinetic theory. By using a finite fault source model obtained via kinematic inversion, we calculate the electric and magnetic responses to the earthquake rupture. The result shows that the synthetic electric signals agree with the observed data for both amplitude and wave shape, especially for early portions of the records (first 9 s) after the earthquake, supporting the electrokinetic effect as the reasonable mechanism for the generation of the coseismic electric fields. More work is needed to explain the magnetic fields and the later portions of the electric fields. Analysis shows that the coseismic electromagnetic (EM) signals are sensitive to both the material properties at the location of the EM sensors and the electrochemical heterogeneity in the vicinity of the EM sensors and can be used to characterize the underground electrochemical properties.

  6. Multisensor Observation and Simulation of Snowfall During the 2003 Wakasa Bay Field Experiment

    NASA Technical Reports Server (NTRS)

    Johnson, Benjamin T.; Petty, Grant W.; Skofronick-Jackson, Gail; Wang, James W.

    2005-01-01

    This research seeks to assess and improve the accuracy of microphysical assumptions used in satellite passive microwave radiative transfer models and retrieval algorithms by exploiting complementary observations from satellite radiometers, such as TRMM/AMSR-E/GPM, and coincident aircraft instruments, such as the next generation precipitation radar (PR-2). We focus in particular on aircraft data obtained during the Wakasa Bay field experiment, Japan 2003, pertaining to surface snowfall events. The observations of vertical profiles of reflectivity and Doppler-derived fall speeds are used in conjunction with the radiometric measurements to identify 1-D profiles of precipitation particle types, sizes, and concentrations that are consistent with the observations.

  7. Coronal structures deduced from photospheric magnetic field and He I lambda 10830 observations

    NASA Technical Reports Server (NTRS)

    Harvey, Karen L.

    1995-01-01

    The National Solar Observatory synoptic program provides an extensive and unique data base of high-resolution full-disk observations of the line-of-sight photospheric magnetic fields and of the He I lambda 10830 equivalent width. These data have been taken nearly daily for more than 21 years since 1974 and provide the opportunity to investigate the behavior of the magnetic fields in the photosphere and those inferred for the corona spanning on the time scales of a day to that of a solar cycle. The intensity of structures observed in He I lambda 10830 are strongly modulated by overlying coronal radiation; areas with low coronal emission are generally brighter in He I lambda 10830, while areas with high coronal emission are darker. For this reason, He I lambda 10830 was selected in the mid-1970's as way to identify and monitor coronal holes, magnetic fields with an open configuration, and the sources of high-speed solar wind streams. The He I lambda 10830 spectroheliograms also show a wide variety of other structures from small-scale, short-lived dark points (less than 30 arc-sec, hours) to the large-scale, long-lived two 'ribbon' flare events that follow the filament eruptions (1000 arc-sec, days). Such structures provide clues about the connections and changes in the large-scale coronal magnetic fields that are rooted in concentrations of magnetic network and active regions in the photosphere. In this paper, what observations of the photospheric magnetic field and He I lambda 10830 can tell us about the short- and long-term evolution of the coronal magnetic fields will be discussed, focussing on the quiet Sun and coronal holes. These data and what we infer from them will be compared with direct observations of the coronal structure from the Yohkoh Soft X-ray Telescope.

  8. EVIDENCE FOR QUASI-ISOTROPIC MAGNETIC FIELDS FROM HINODE QUIET-SUN OBSERVATIONS

    SciTech Connect

    Asensio Ramos, A.

    2009-08-20

    Some recent investigations of spectropolarimetric observations of the Zeeman effect in the Fe I lines at 630 nm carried out with the Hinode solar space telescope have concluded that the strength of the magnetic field vector in the internetwork regions of the quiet Sun is in the hG regime and that its inclination is predominantly horizontal. We critically reconsider the analysis of such observations and carry out a complete Bayesian analysis with the aim of extracting as much information as possible from them, including error bars. We apply the recently developed BAYES-ME code that carries out a complete Bayesian inference for Milne-Eddington atmospheres. The sampling of the posterior distribution function is obtained with a Markov Chain Monte Carlo scheme and the marginal distributions are analyzed in detail. The Kullback-Leibler divergence is used to study the extent to which the observations introduce new information in the inference process resulting in sufficiently constrained parameters. Our analysis clearly shows that only upper limits to the magnetic field strength can be inferred, with fields in the kG regime completely discarded. Furthermore, the noise level present in the analyzed Hinode observations induces a substantial loss of information for constraining the azimuth of the magnetic field. Concerning the inclination of the field, we demonstrate that some information is available to constrain it for those pixels with the largest polarimetric signal. The results also point out that the field in pixels with small polarimetric signals can be nicely reproduced in terms of a quasi-isotropic distribution.

  9. Cone of Darkness: Finding Blank-sky Positions for Multi-object Wide-field Observations

    NASA Astrophysics Data System (ADS)

    Lorente, N. P. F.

    2014-05-01

    We present the Cone of Darkness, an application to automatically configure blank-sky positions for a series of stacked, wide-field observations, such as those carried out by the SAMI instrument on the Anglo-Australian Telescope (AAT). The Sydney-AAO Multi-object Integral field spectrograph (SAMI) uses a plug-plate to mount its 13×61 core imaging fibre bundles (hexabundles) in the optical plane at the telescope's prime focus. To make the most efficient use of each plug-plate, several observing fields are typically stacked to produce a single plate. When choosing blank-sky positions for the observations it is most effective to select these such that one set of 26 holes gives valid sky positions for all fields on the plate. However, when carried out manually this selection process is tedious and includes a significant risk of error. The Cone of Darkness software aims to provide uniform blank-sky position coverage over the field of observation, within the limits set by the distribution of target positions and the chosen input catalogs. This will then facilitate the production of the best representative median sky spectrum for use in sky subtraction. The application, written in C++, is configurable, making it usable for a range of instruments. Given the plate characteristics and the positions of target holes, the software segments the unallocated space on the plate and determines the position which best fits the uniform distribution requirement. This position is checked, for each field, against the selected catalog using a TAP ADQL search. The process is then repeated until the desired number of sky positions is attained.

  10. High-latitude dayside electric fields and currents during strong northward interplanetary magnetic field - Observations and model simulation

    NASA Technical Reports Server (NTRS)

    Clauer, C. Robert; Friis-Christensen, Eigil

    1988-01-01

    On July 23, 1983 the IMF turned strongly northward, becoming about 22 nT for several hours. Using a combined data set of ionospheric convection measurements made by the Sondre Stromfjord incoherent scatter radar and convection inferred from Greenland magnetometer measurements, the onset of the reconfiguration of the high-latitude ionospheric currents is found to occur about 3 min after the northward IMF encounters the magnetopause. The large-scale reconfiguration of currents, however, appears to evolve over a period of about 22 min. These observations and the results of numerical simulations indicate that the dayside polar-cap electric field observed during strong northward IMF is produced by a direct electrical current coupling with the solar wind.

  11. Magnetic-field fluctuations from 0 to 26 Hz observed from a polar-orbiting satellite

    SciTech Connect

    Erlandson, R.E.; Zanetti, L.J.; Potemra, T.A.

    1989-04-01

    The polar orbit of the Viking satellite provides a unique opportunity to obtain observations of magnetic fluctuations at mid-altitudes on the dayside of the magnetosphere and in the polar-cusp region. One type of magnetic-field fluctuation, observed in the dayside magnetosphere, was Pc 1 waves. Pc 1 waves are in the electromagnetic ion-cyclotron mode and are generated by anisotropies in energetic ion distributions. The waves are thought to be generated near the equator and to propagate large distances along magnetic-field lines. Most observations of Pc 1 waves have been obtained near the equator using geosynchronous satellites and on the surface of the earth. The Viking observations provide an opportunity to observe Pc 1 waves at mid-latitudes above the ionosphere and to determine the spectral structure and polarization of the waves. ULF/ELF broadband noise represents a second type of magnetic fluctuation acquired by Viking. This type of magnetic fluctuation was observed at high latitudes near the polar cusp and may be useful in the identification of polar-cusp boundaries. Thirdly, electromagnetic ion-cyclotron waves have also been observed in the polar-cusp region. These waves occur only during an unusually high level of magnetic activity and appear to be generated locally.

  12. Z3 model of Saturns magnetic field and the Pioneer 11 vector helium magnetometer observations

    SciTech Connect

    Connerney, J.E.P.; Acuna, M.H.; Ness, N.F.

    1984-05-01

    Magnetic field observations obtained by the Pioneer 11 vector helium magnetometer are compared with the Z(sub 3) model magnetic field. These Pioneer 11 observations, obtained at close-in radial distances, constitute an important and independent test of the Z(sub 3) zonal harmonic model, which was derived from Voyager 1 and Voyager 2 fluxgate magnetometer observations. Differences between the Pioneer 11 magnetometer and the Z(sub 3) model field are found to be small (approximately 1%) and quantitatively consistent with the expected instrumental accuracy. A detailed examination of these differences in spacecraft payload coordinates shows that they are uniquely associated with the instrument frame of reference and operation. A much improved fit to the Pioneer 11 observations is obtained by rotation of the instrument coordinate system about the spacecraft spin axis by 1.4 degree. With this adjustment, possibly associated with an instrumental phase lag or roll attitude error, the Pioneer 11 vector helium magnetometer observations are fully consistent with the Voyager Z(sub 3) model.

  13. The Z3 model of Saturns magnetic field and the Pioneer 11 vector helium magnetometer observations

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.; Acuna, M. H.; Ness, N. F.

    1984-01-01

    Magnetic field observations obtained by the Pioneer 11 vector helium magnetometer are compared with the Z(sub 3) model magnetic field. These Pioneer 11 observations, obtained at close-in radial distances, constitute an important and independent test of the Z(sub 3) zonal harmonic model, which was derived from Voyager 1 and Voyager 2 fluxgate magnetometer observations. Differences between the Pioneer 11 magnetometer and the Z(sub 3) model field are found to be small (approximately 1%) and quantitatively consistent with the expected instrumental accuracy. A detailed examination of these differences in spacecraft payload coordinates shows that they are uniquely associated with the instrument frame of reference and operation. A much improved fit to the Pioneer 11 observations is obtained by rotation of the instrument coordinate system about the spacecraft spin axis by 1.4 degree. With this adjustment, possibly associated with an instrumental phase lag or roll attitude error, the Pioneer 11 vector helium magnetometer observations are fully consistent with the Voyager Z(sub 3) model.

  14. The Z3 model of Saturn's magnetic field and the Pioneer 11 vector helium magnetometer observations

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.; Acuna, M. H.; Ness, N. F.

    1984-01-01

    Magnetic field observations obtained by the Pioneer 11 vector helium magnetometer are compared with the Z(sub 3) model magnetic field. These Pioneer 11 observations, obtained at close-in radial distances, constitute an important and independent test of the Z(sub 3) zonal harmonic model, which was derived from Voyager 1 and Voyager 2 fluxgate magnetometer observations. Differences between the Pioneer 11 magnetometer and the Z(sub 3) model field are found to be small (approximately 1 percent) and quantitatively consistent with the expected instrumental accuracy. A detailed examination of these differences in spacecraft payload coordinates shows that they are uniquely associated with the instrument frame of reference and operation. A much improved fit to the Pioneer 11 observations is obtained by rotation of the instrument coordinate system about the spacecraft spin axis by 1.4 degree. With this adjustment, possibly associated with an instrumental phase lag or roll attitude error, the Pioneer 11 vector helium magnetometer observations are fully consistent with the Voyager Z(sub 3) model.

  15. Use of Unmanned Aircraft Systems in Observations of Glaciers, Ice Sheets, Sea Ice and Snow Fields

    NASA Astrophysics Data System (ADS)

    Herzfeld Mayer, M. U.

    2015-12-01

    Unmanned Aircraft Systems (UAS) are being used increasingly in observations of the Earth, especially as such UAS become smaller, lighter and hence less expensive. In this paper, we present examples of observations of snow fields, glaciers and ice sheets and of sea ice in the Arctic that have been collected from UAS. We further examine possibilities for instrument miniaturization, using smaller UAS and smaller sensors for collecting data. The quality and type of data is compared to that of satellite observations, observations from manned aircraft and to measurements made during field experiments on the ground. For example, a small UAS can be sent out to observe a sudden event, such as a natural catastrophe, and provide high-resolution imagery, but a satellite has the advantage of providing the same type of data over much of the Earth's surface and for several years, but the data is generally of lower resolution. Data collected on the ground typically have the best control and quality, but the survey area is usually small. Here we compare micro-topographic measurements made on snow fields the Colorado Rocky Mountains with airborne and satellite data.

  16. Observation of self-sustaining relativistic ionization wave launched by a sheath field.

    PubMed

    McCormick, M; Arefiev, A V; Quevedo, H J; Bengtson, R D; Ditmire, T

    2014-01-31

    We present experimental evidence supported by simulations of a relativistic ionization wave launched into a surrounding gas by the sheath field of a plasma filament with high energy electrons. Such a filament is created by irradiating a clustering gas jet with a short pulse laser (115  fs) at a peak intensity of 5×10(17)  W/cm2. We observe an ionization wave propagating radially through the gas for about 2 ps at 0.2-0.5 c after the laser has passed, doubling the initial radius of the filament. The gas is ionized by the sheath field, while the longevity of the wave is explained by a moving field structure that traps the high energy electrons near the boundary, maintaining a strong sheath field despite the significant expansion of the plasma. PMID:24580461

  17. 3D Coronal Magnetic Field Reconstruction Based on Infrared Polarimetric Observations

    NASA Astrophysics Data System (ADS)

    Kramar, M.; Lin, H.; Tomczyk, S.

    2014-12-01

    Measurement of the coronal magnetic field is a crucial ingredient in understanding the nature of solar coronal phenomena at all scales. A significant progress has been recently achieved here with deployment of the Coronal Multichannel Polarimeter (CoMP) of the High Altitude Observatory (HAO). The instrument provides polarization measurements of Fe xiii 10747 A forbidden line emission. The observed polarization are the result of a line-of-sight (LOS) integration through a nonuniform temperature, density and magnetic field distribution. In order resolve the LOS problem and utilize this type of data, the vector tomography method has been developed for 3D reconstruction of the coronal magnetic field. The 3D electron density and temperature, needed as additional input, have been reconstructed by tomography method based on STEREO/EUVI data. We will present the 3D coronal magnetic field and associated 3D curl B, density, and temperature resulted from these inversions.

  18. Observation of thermally driven field-like spin torque in magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Bose, Arnab; Shukla, Amit Kumar; Konishi, Katsunori; Jain, Sourabh; Asam, Nagarjuna; Bhuktare, Swapnil; Singh, Hanuman; Lam, Duc Duong; Fujii, Yuya; Miwa, Shinji; Suzuki, Yoshishige; Tulapurkar, Ashwin A.

    2016-07-01

    We report the thermally driven giant field-like spin-torque in magnetic tunnel junctions (MTJ) on application of heat current from top to bottom. The field-like term is detected by the shift of the magneto-resistance hysteresis loop applying temperature gradient. We observed that the field-like term depends on the magnetic symmetry of the MTJ. In asymmetric structures, with different ferromagnetic materials for free and fixed layers, the field-like term is greatly enhanced. Our results show that a pure spin current density of the order of 109 A/m2 can be produced by creating a 120 mK temperature difference across 0.9 nm thick MgO tunnelling barrier. Our results will be useful for writing MTJ and domain wall-based memories using thermally driven spin torque.

  19. Observations of large scale steady magnetic fields in the nightside Venus ionosphere and near wake

    NASA Technical Reports Server (NTRS)

    Luhmann, J. G.; Elphic, R. C.; Russell, C. T.; Slavin, J. A.; Mihalov, J. D.

    1981-01-01

    Based on an analysis of a large sample of Pioneer Venus Orbiter magnetometer data, characteristics of the magnetic fields near nightside periapsis are discussed. The observations generally indicate a weak average field of less than 10 gammas between 200 km and the periapsis altitude of 150 km, except when (1) the local solar wind dynamic pressure is high or (2) the spacecraft is in a 70 deg wide solar zenith angle range, which includes the midnight meridian and is centered west of it at 1 hr local time. The presence of radial field of alternating sign at low altitudes and in the nightside ionosphere suggests that the antiparallel magnetotail fields can terminate very close to the planet.

  20. Retrieval of Hydrometeor Drop Size Distributions from TRMM Field Campaign Profiler Doppler Velocity Spectra Observations

    NASA Technical Reports Server (NTRS)

    Williams, Christopher R.; Gage, Kenneth S.

    2003-01-01

    Consistent with the original proposal and work plan, this project focused on estimating the raindrop size distributions (DSDs) retrieved from vertically pointing Doppler radar profilers and analyzing the relationship of the retrieved DSDs with the dynamics of the precipitation processes. The first phase of this project focused on developing the model to retrieve the DSD from the observed Doppler velocity spectra. The second phase used this model to perform DSD retrievals from the profiler observations made during the TRMM Ground Validation Field Campaigns of TEFLUN-B, TRMM-LBA, and KWAJEX. The third phase of this project established collaborations with scientists involved with each field campaign in order to validate the profiler DSD estimates and to enable the profiler retrievals to be used in their research. Through these collaborations, the retrieved DSDs were placed into context with the dynamical processes of the observed precipitating cloud systems.

  1. Modeling human target reaching with an adaptive observer implemented with dynamic neural fields.

    PubMed

    Fard, Farzaneh S; Hollensen, Paul; Heinke, Dietmar; Trappenberg, Thomas P

    2015-12-01

    Humans can point fairly accurately to memorized states when closing their eyes despite slow or even missing sensory feedback. It is also common that the arm dynamics changes during development or from injuries. We propose a biologically motivated implementation of an arm controller that includes an adaptive observer. Our implementation is based on the neural field framework, and we show how a path integration mechanism can be trained from few examples. Our results illustrate successful generalization of path integration with a dynamic neural field by which the robotic arm can move in arbitrary directions and velocities. Also, by adapting the strength of the motor effect the observer implicitly learns to compensate an image acquisition delay in the sensory system. Our dynamic implementation of an observer successfully guides the arm toward the target in the dark, and the model produces movements with a bell-shaped velocity profile, consistent with human behavior data. PMID:26559472

  2. Magnetic field observations on DE-A and -B. [Dynamics Explorer A and B satellites

    NASA Technical Reports Server (NTRS)

    Farthing, W. H.; Sugiura, M.; Ledley, B. G.; Cahill, L. J., Jr.

    1981-01-01

    Magnetic field observations are conducted on each of the DE-A and -B satellites by a triaxial fluxgate magnetometer. In the basic mode the instrumental resolution is + or - 1.5 nT; in addition, the DE-A magnetometer has two modes of higher resolution: + or - 0.25 nT and + or - 20 pT. The sampling rate is 16 vector samples per second in all modes. The experiment objectives include observations of field-aligned currents, magnetospheric equatorial currents, and ULF waves. These observations, taking full advantage of the specifically selected orbits of the two spacecraft and of the unique combination of instruments, are performed to achieve a better understanding of the electrodynamic coupling within the atmosphere-ionosphere-magnetosphere system and of wave-particle interactions which contribute to the coupling processes.

  3. Ground Observations of Artificial E Region Field-Aligned Irregularities Over HAARP

    NASA Astrophysics Data System (ADS)

    Nossa, E.; Hysell, D. L.

    2008-12-01

    Heating experiments were performed at HAARP intended to create E region field aligned plasma irregularities (FAIs) at midday in July of 2008 when the critical frequency of the E layer is a maximum. Field-aligned backscatter was observed using a 30 MHz imaging coherent scatter radar located close to Homer, Alaska. Three experiment modes were used, involving 1) heating alternately at zenith and magnetic zenith, 2) heating using triangular power modulation, and 3) heating slightly above and below the second electron gyroharmonic. Strong echoes were observed in all cases. Radar imaging and other diagnostic methods are used to examine the degree to which irregularities can be observed outside the Spitze angle, the possible effects of predonditioning on thermal parametric instability, and the effects of the double resonance on backscatter intensity and irregularity formation.

  4. Lava flow surface textures - SIR-B radar image texture, field observations, and terrain measurements

    NASA Technical Reports Server (NTRS)

    Gaddis, Lisa R.; Mouginis-Mark, Peter J.; Hayashi, Joan N.

    1990-01-01

    SIR-B images, field observations, and small-scale (cm) terrain measurements are used to study lave flow surface textures related to emplacement processes of a single Hawaiian lava flow. Although smooth pahoehoe textures are poorly characterized on the SIR-B data, rougher pahoehoe types and the a'a flow portion show image textures attributed to spatial variations in surface roughness. Field observations of six distinct lava flow textural units are described and used to interpret modes of emplacement. The radar smooth/rough boundary between pahoehoe and a'a occurs at a vertical relief of about 10 cm on this lava flow. While direct observation and measurement most readily yield information related to lava eruption and emplacement processes, analyses of remote sensing data such as those acquired by imaging radars and altimeters can provide a means of quantifying surface texture, identifying the size and distribution of flow components, and delineating textural unit boundaries.

  5. A theory of electron cyclotron waves generated along auroral field lines observed by ground facilities

    NASA Technical Reports Server (NTRS)

    Wu, C. S.; Yoon, Peter H.; Freund, H. P.

    1989-01-01

    A generation mechanism for radio waves in the frequency range 150 - 700 kHz observed by ground facilities is suggested in terms of an electromagnetic electron cyclotron instability driven by auroral electrons. The excited waves can propagate downward along the ambient magnetic field lines and are thus observable with ground facilities. The trapped auroral electrons are supposed to play an important role in the generation process, because they give rise to a thermal anisotropy which consequently leads to the instability. The present work is a natural extension of the theory proposed earlier by Wu et al. (1983) which was discussed in a different context but may be used to explain the observed waves originated at low altitudes. This paper presents a possible wave generation mechanism valid in the entire auroral field-line region of interest.

  6. Geoinformatics and observations of the Earth's magnetic field: The Russian segment

    NASA Astrophysics Data System (ADS)

    Gvishiani, A. D.; Lukianova, R. Yu.

    2015-03-01

    The topical problems of the studies in geomagnetism are discussed. A brief outline of the internal and external magnetic field of the Earth is presented; the state of the art of the network magnetic observations including the ground- and space-based measurements is analyzed. The contribution of the Geophysical Center of the Russian Academy of Sciences (GC RAS) in the investigations of the Earth's magnetic field and development of the national observational segment complying with the highest international quality standards of INTERMAGNET network is demonstrated. The tasks solved by GC RAS in the collection, processing, and analysis of the geomagnetic data are listed. The proposals on updating and improving the system of geomagnetic observations in the Russian Federation are suggested.

  7. The spectral properties of low latitude daytime electric fields inferred from magnetometer observations

    NASA Astrophysics Data System (ADS)

    Nicolls, Michael J.; Kelley, Michael C.; Chau, Jorge L.; Veliz, Oscar; Anderson, David; Anghel, Adela

    2007-07-01

    Four years of magnetometer data from two locations in Peru, one at the equator and one off the equator, have been converted to electric fields and their frequency characteristics (fluctuation spectra) examined. In the frequency range from 0.1 to 30 cycles per hour, the average spectrum monotonically decreases. However, it deviates from a power law in the range 0.3 3 cycles per hour especially for high levels of activity. The integrated power above 0.15 cycles per hour is a strong function of K indicating that much of the fluctuations in the ionospheric equatorial field are of solar wind or magnetospheric origin. This result is in agreement with a previous power spectral study of low, middle, and high latitude fields using radars. The observed field strengths are lower than the ones observed in a previous study using balloon data at middle and high latitudes when the fields are projected to the equatorial plane. Simultaneous interplanetary electric field (IEF) data are compared to the equatorial field to determine how strong a relationship exists and to determine the amplitude and phase of their ratio as a function of frequency—an estimate of the average transfer function of the system. This function displays a bandpass-like form with a peak near 0.5 cycles per hour. This peak and evidence for a ringing of the time domain response suggests a weakly resonant system indicating some capacitance in addition to the inductance of the ring current and the resistance of the ionosphere. Case studies show that application of this function to IEF data yields good results and supports the notion that the response of the equatorial field to long-duration IEF polarities can last for many hours. Application of the function to test inputs such as pulses and triangle waves support this result. At high frequencies, we suggest that mapping of small-scale MHD turbulence is less effective than high frequency related transitions in the IEF.

  8. Cassini SAR, radiometry, scatterometry and altimetry observations of Titan's dune fields

    USGS Publications Warehouse

    Le, Gall A.; Janssen, M.A.; Wye, L.C.; Hayes, A.G.; Radebaugh, J.; Savage, C.; Zebker, H.; Lorenz, R.D.; Lunine, J.I.; Kirk, R.L.; Lopes, R.M.C.; Wall, S.; Callahan, P.; Stofan, E.R.; Farr, Tom

    2011-01-01

    Large expanses of linear dunes cover Titan's equatorial regions. As the Cassini mission continues, more dune fields are becoming unveiled and examined by the microwave radar in all its modes of operation (SAR, radiometry, scatterometry, altimetry) and with an increasing variety of observational geometries. In this paper, we report on Cassini's radar instrument observations of the dune fields mapped through May 2009 and present our key findings in terms of Titan's geology and climate. We estimate that dune fields cover ???12.5% of Titan's surface, which corresponds to an area of ???10millionkm2, roughly the area of the United States. If dune sand-sized particles are mainly composed of solid organics as suggested by VIMS observations (Cassini Visual and Infrared Mapping Spectrometer) and atmospheric modeling and supported by radiometry data, dune fields are the largest known organic reservoir on Titan. Dune regions are, with the exception of the polar lakes and seas, the least reflective and most emissive features on this moon. Interestingly, we also find a latitudinal dependence in the dune field microwave properties: up to a latitude of ???11??, dune fields tend to become less emissive and brighter as one moves northward. Above ???11?? this trend is reversed. The microwave signatures of the dune regions are thought to be primarily controlled by the interdune proportion (relative to that of the dune), roughness and degree of sand cover. In agreement with radiometry and scatterometry observations, SAR images suggest that the fraction of interdunes increases northward up to a latitude of ???14??. In general, scattering from the subsurface (volume scattering and surface scattering from buried interfaces) makes interdunal regions brighter than the dunes. The observed latitudinal trend may therefore also be partially caused by a gradual thinning of the interdunal sand cover or surrounding sand sheets to the north, thus allowing wave penetration in the underlying

  9. Hinode magnetic-field observations of solar flares for exploring the energy storage and trigger mechanisms

    NASA Astrophysics Data System (ADS)

    Shimizu, Toshifumi; Inoue, Satoshi; Kawabata, Yusuke

    2015-08-01

    Solar flares abruptly release the free energy stored as a non-potential magnetic field in the corona and may be accompanied by eruptions of the coronal plasma. Magnetic reconnection is considered as a physical process in which the magnetic energy is converted to kinetic energy, thermal energy, and particle acceleration, but the location of magnetic reconnection is difficult to identify directly because of low emission measure at the reconnection region. We are still lack of observational knowledge on the 3D magnetic configuration and physical conditions for leading to flare trigger. Accurate measurements of vector magnetic fields at the solar photosphere, provided by the Solar Optical Telescope onboard Hinode, help us in exploring how the free energy is stored in the solar atmosphere and how the release of the energy is triggered. This presentation will review the magnetic field configuration and possible candidates for flare trigger primarily based on Hinode observations of some large flare events, which may include X5.4/X1.3 flares on 7 March 2012, X1.2 flare on 7 January 2014 and two M-class flares on 2 February 2014. The 7 March 2012 events were observed in an active region with delta-type sunspots, showing a strong shear in the entire magnetic system. For the sheared magnetic structure, the inclusion of a small-scale trigger field was identified near the polarity inversion line with excitation of a high-speed material flow in the horizontally oriented magnetic field formed nearly in parallel to the polarity inversion line. The observations suggest that gas dynamics at the solar surface play a vital role of leading to the onset of flares. The 7 January 2014 event is an exceptional event which most scientists would not be able to predict its occurrence. The flare unexpectedly happened apart from the sheared magnetic field region. The M-class flares on 2 February 2014 were observed in the magnetic field configuration, in which four magnetic domains were

  10. MAVEN MAG Observations of Magnetic Field Enhancements and Decreases in the Induced Magnetosphere of Mars

    NASA Astrophysics Data System (ADS)

    Soobiah, Y. I. J.; Espley, J. R.; Connerney, J. E. P.; DiBraccio, G. A.; Gruesbeck, J.; Halekas, J. S.; Mitchell, D. L.; McFadden, J. P.; Brain, D. A.; Jakosky, B. M.; Schneider, N. M.; Mazelle, C. X.; Andersson, L.; Ergun, R. E.; Jain, S.; Deighan, J.; McClintock, W. E.

    2015-12-01

    Recent results have shown the occurrence of a large-scale flux rope (enhancement in magnetic field strength and rotation in magnetic field vectors) on the dayside of Mars as associated with a dayside current sheet region forming at the proximity of strong crustal magnetic fields. This dayside current sheet region including the example of the large-scale flux rope occurred when the draped solar wind magnetic field showed a +By component in the MSO frame. All events involved similar anisotropic pitch angle distribution of electrons with low-energy field aligned electrons and higher-energy trapped electrons, indicating either the mixing of trapped magnetosheath electrons with low energy field aligned ionospheric electrons and/or the pitch angle diffusion of ionospheric electrons. During a time of weak draped field, the current sheet region became highly extended and was observed alongside a decrease in magnetic field strength and highly anisotropic plasma indicative of a mirror mode structure or magnetic hole. The occurrence of magnetic decreases or magnetic holes are an established feature of the solar wind and are often found in the terrestrial magnetosheath, and have also been observed near Jupiter, Venus and comets. More recently, mirror mode structures have been reported within the Earth's magnetosphere. The occurrence of the mirror mode instability could result in the excitation of ULF waves and has also been related to Alfvén waves that could cause heating of the local plasma. Hence, both the large-scale flux ropes and mirror mode structures of current sheet regions on the dayside of Mars may have an important role in ionospheric heating and atmospheric escape at Mars. Therefore, using an automated routine we will attempt to search for the occurrence of magnetic field enhancements and magnetic field decreases in measurements of magnetic field by the Mars Atmosphere and Volatile EvolutioN (MAVEN) satellite Magnetometer (MAG) instrument whilst comparing to the

  11. The performance of field scientists undertaking observations of early life fossils while in simulated space suit

    NASA Astrophysics Data System (ADS)

    Willson, D.; Rask, J. C.; George, S. C.; de Leon, P.; Bonaccorsi, R.; Blank, J.; Slocombe, J.; Silburn, K.; Steele, H.; Gargarno, M.; McKay, C. P.

    2014-01-01

    We conducted simulated Apollo Extravehicular Activity's (EVA) at the 3.45 Ga Australian 'Pilbara Dawn of life' (Western Australia) trail with field and non-field scientists using the University of North Dakota's NDX-1 pressurizable space suit to overview the effectiveness of scientist astronauts employing their field observation skills while looking for stromatolite fossil evidence. Off-world scientist astronauts will be faced with space suit limitations in vision, human sense perception, mobility, dexterity, the space suit fit, time limitations, and the psychological fear of death from accidents, causing physical fatigue reducing field science performance. Finding evidence of visible biosignatures for past life such as stromatolite fossils, on Mars, is a very significant discovery. Our preliminary overview trials showed that when in simulated EVAs, 25% stromatolite fossil evidence is missed with more incorrect identifications compared to ground truth surveys but providing quality characterization descriptions becomes less affected by simulated EVA limitations as the science importance of the features increases. Field scientists focused more on capturing high value characterization detail from the rock features whereas non-field scientists focused more on finding many features. We identified technologies and training to improve off-world field science performance. The data collected is also useful for NASA's "EVA performance and crew health" research program requirements but further work will be required to confirm the conclusions.

  12. Electric Field and Lightning Observations in the Core of Category 5 Hurricane Emily

    NASA Technical Reports Server (NTRS)

    Blakeslee, Richard; Mach, Doug M.; Bateman, Monte G.; Bailey, Jeff C.

    2007-01-01

    Significant electric fields and lightning activity associated with Hurricane Emily were observed from a NASA high-altitude ER-2 aircraft on July 17, 2005 while this storm developed as a compact but intense category 5 hurricane in the Caribbean south of Cuba. The electrical measurements were acquired as part of the NASA sponsored Tropical Cloud Systems and Processes (TCSP) experiment. In addition to the electrical measurements, the aircraft's remote sensing instrument complement also included active radars, passive microwave, visible and infrared radiometers, and a temperature sounder providing details on the dynamical, microphysical, and environmental structure, characteristics and development of this intense storm. Cloud-to-ground lightning location data from Vaisala's long range lightning detection network were also acquired and displayed in real-time along with electric fields measured at the aircraft. These data and associated display also supported aircraft guidance and vectoring during the mission. During the observing period, flash rates in excess of 3 to 5 flashes per minute, as well as large electric field and field change values were observed as the storm appeared to undergo periods of intensification, especially in the northwest quadrant in the core eyewall regions. This is in contrast to most hurricanes that tend to be characterized by weak electrification and little or no lightning activity except in the outer rain bands. It should be noted that this storm also had significant lightning associated with its rain bands.

  13. Local magnetic field measurements and fault creep observations on the San Andreas fault

    USGS Publications Warehouse

    Johnston, M.J.S.; Smith, B.E.; Burford, R.O.

    1980-01-01

    Simultaneous creep and magnetic field records have been obtained for more than 60 episodic creep events since early 1974, no clear magnetic transients or offsets, as suggested by Breiner and Kovach (1968), are observed at or up to several days before the occurrence times of these events. Although some patterns of creep onset times at adjacent stations over periods of weeks to months appear to correspond to some periods of longer term change in local magnetic field, these changes do not always occur and other groups of creep events have no corresponding changes in local magnetic field. Changes in stress related to the surface expression of episodic fault creep on the San Andreas fault can be estimated from dislocation models fit to observations of simultaneous strains and tilts at points near the fault. These stress values are generally less than 1 bar. For these stress levels and with the apparent limited extent of surface failure, tectonomagnetic models of creep events indicate that simultaneous observations of related magnetic field variations at detectable levels of a gamma or so are unlikely. Slip at greater depth may occur more smoothly and would load the near-surface material to failure. These data also argue against large-scale dilatant cracking occurring along the region of the fault presently monitored. ?? 1980.

  14. Helicity from observational solar magnetic fields and the relationship with solar activities

    NASA Astrophysics Data System (ADS)

    Zhang, Hongqi

    The helicity is important to present the basic topological configuration of magnetic field trans-ferred form the solar subatmosphere into the interplanetary space. In this talk, the basic configuration of magnetic field and helicity in the solar atmosphere have been discussed in the following: 1) The Hinode high resolution vector magnetograms provide the important infor-mation on the fine features of current helicity density and the possible accumulated process of magnetic helicity in the solar atmosphere. 2) The relationship between the eruption of solar flare-CMEs and helicity transfer from the suntamosphere has be presented based on the analy-sis of photospheric vector magnetograms. 3) The statistical distribution of magnetic field (and helicity) in solar atmosphere and its reversals with solar cycles are presented by means of the observational (vector) magnetograms. As the magnetic fields in the solar surface provides the information on the formation of magnetic field in the solar convection zone, the statistical anal-ysis of the observational magnetic helicity is important for the confirmation of the alpha-effect of the solar dynamo.

  15. Observations of a Newly "Captured" Magnetosheath Field Line: Evidence for "Double Reconnection"

    NASA Technical Reports Server (NTRS)

    Chandler, Michael O.; Avanov, Levon A.; Craven, Paul D.; Mozer, Forrest S.; Moore, Thomas E.

    2007-01-01

    We have begun an investigation of the nature of the low-latitude boundary layer in the mid-altitude cusp region using data from the Polar spacecraft. This region has been routinely sampled for about three months each year for the periods 1999-2001 and 2004-2006. The low-to-mid-energy ion instruments frequently observed dense, magnetosheath-like plasma deep (in terms of distance from the magnetopause and in invariant latitude) in the magnetosphere. One such case, taken during a period of northward interplanetary magnetic field (IMF), shows magnetosheath ions within the magnetosphere with velocity distributions resulting from two separate merging sites along the same field lines. Cold ionospheric ions were also observed counterstreaming along the field lines, evidence that these field lines were closed. These results are consistent with the hypothesis that double merging can produce closed field .lines populated by solar wind plasma. Through the use of individual cases such as this and statistical studies of a broader database we seek to understand the morphology of the LLBL as it projects from the sub-solar region into the cusp. We will present preliminary results of our ongoing study.

  16. Voyager Observations of Magnetic Fields and Cosmic Rays in the Heliosheath

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Ness, N. F.; Stone, E.; McDonald, F. B.

    2011-01-01

    The major features of the profile of greater than 70 MeV/nuc cosmic ray intensity (CRI) observed by Voyager 1 (VI) in the heliosheath from 2005.8-2010.24 are described by the empirical "CR-B" relation as the cumulative effect of variations of the magnetic field strength B. The CRI profile observed by Voyager 2 (V2) from 2008.60 to 2010.28 in the heliosheath is also described by the CR-B relation. On a smaller scale, of the order of a hundred days, a sequence on CRI decreases observed by V 1 during 2006 was interpreted as the effect of a propagating interplanetary shock first interacting with the termination shock, then moving past V1, and finally reflecting from the heliopause and propagating back to V1. Our observations show that the second CRI decrease in this sequence began during the passage of a "Global Merged Interaction Region" (GMIR), 40 days after the arrival of the GMIR and its possible shock. The first and third CRI decreases in the sequence were associated with local enhancements of B. The magnetic field observations associated with the second sequence of 3 cosmic ray intensity decreases observed by V 1 in 2007/2008 are more difficult to reconcile with the scenario of Webber et al. (2009) and the CR-B relation. The discrepancy might indicate the importance of latitudinal effects

  17. Voyager observations of the magnetic field in the heliosheath and the local interstellar medium

    NASA Astrophysics Data System (ADS)

    Burlaga, L.

    2015-09-01

    This paper reviews observations of the magnetic field B in the heliosheath by Voyager 1 (V1) and Voyager 2 (V2) and the recent observations of the LISM by V1. The heliosheath is the region between the termination shock (TS) and the heliopause (HP). The TS was identified by both V1 and V2, and the internal structure of the TS was determined by V2. The radial distance of the TS was 94 AU at V1 and 84 AU at V2, suggesting a global asymmetry of the heliosphere. The average direction of B in the heliosheath is that of the Parker spiral magnetic field, and non-periodic magnetic sectors were observed by V1 and V2. The heliosheath is disturbed and turbulent, particularly just behind the TS, and it is described by the multifractal spectrum, the q-correlation function and the q-Gaussian distribution. The multifractal spectrum in the heliosheath also varies with the solar cycle. Voyager 1 has been in the LISM since at least August 25, 2012, but the nature of the HP and the time of the HP crossing not been determined. The magnetic field direction is close to, but distinguishable from the Parker spiral magnetic field, and its departure from the Parker spiral magnetic field is slowly increasing with distance from the sun. A large pressure pulse and two shocks or pressure waves have been identified in the LISM, presumably generated inside the heliosphere and transmitted through the heliosheath and heliopause. The interstellar magnetic field lines are draped across the heliopause, and B is approximately 0.5 nT. The fluctuations of B are very small but turbulent on scales 1 day to 468 days, with a Kolmogorov spectrum and an injection scale of approximately 10 pc.

  18. Toward the Direct Measurement of Coronal Magnetic Fields: An Airborne Infrared Spectrometer for Eclipse Observations

    NASA Astrophysics Data System (ADS)

    Samra, J.; DeLuca, E. E.; Golub, L.; Cheimets, P.

    2014-12-01

    The solar magnetic field enables the heating of the corona and provides its underlying structure. Energy stored in coronal magnetic fields is released in flares and coronal mass ejections (CME) and provides the ultimate source of energy for space weather. Therefore, direct measurements of the coronal magnetic field have significant potential to enhance understanding of coronal dynamics and improve solar forecasting models. Of particular interest are observations of coronal field lines in the transitional region between closed and open flux systems, providing important information on the origin of the slow solar wind. While current instruments routinely observe only the photospheric and chromospheric magnetic fields, a proposed airborne spectrometer will take a step toward the direct observation of coronal fields by measuring plasma emission in the infrared at high spatial and spectral resolution. The targeted lines are four forbidden magnetic dipole transitions between 2 and 4 μm. The airborne system will consist of a telescope, grating spectrometer, and pointing/stabilization system to be flown on the NSF/NCAR High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) during the August 2017 total solar eclipse. The project incorporates several optical engineering challenges, centered around maintaining adequate spectral and spatial resolution in a compact and inexpensive package and on a moving platform. Design studies are currently underway to examine the tradeoffs between various optical geometries and control strategies for the pointing/stabilization system. The results will be presented and interpreted in terms of the consequences for the scientific questions. In addition, results from a laboratory prototype and simulations of the final system will be presented.

  19. Wide-field direct CCD observations supporting the Astro-1 Space Shuttle mission's Ultraviolet Imaging Telescope

    NASA Technical Reports Server (NTRS)

    Hintzen, Paul; Angione, Ron; Talbert, Freddie; Cheng, K.-P.; Smith, Eric; Stecher, Theodore P.

    1993-01-01

    Wide field direct CCD observations are being obtained to support and complement the vacuum-ultraviolet (VUV) images provided by Astro's Ultraviolet Imaging Telescope (UIT) during a Space Shuttle flight in December 1990. Because of the wide variety of projects addressed by UIT, the fields observed include (1) galactic supernova remnants such as the Cygnus Loop and globular clusters such as Omega Cen and M79; (2) the Magellanic Clouds, M33, M81, and other galaxies in the Local Group; and (3) rich clusters of galaxies, principally the Perseus cluster and Abell 1367. Ground-based observations have been obtained for virtually all of the Astro-1 UIT fields. The optical images allow identification of individual UV sources in each field and provide the long baseline in wavelength necessary for accurate analysis of UV-bright sources. To facilitate use of our optical images for analysis of UIT data and other projects, we plan to archive them, with the UIT images, at the National Space Science Data Center (NSSDC), where they will be universally accessible via anonymous FTP. The UIT, one of three telescopes comprising the Astro spacecraft, is a 38-cm f/9 Ritchey-Chretien telescope on which high quantum efficiency, solar-blind image tubes are used to record VUV images on photographic film. Five filters with passbands centered between 1250A and 2500A provide both VUV colors and a measurement of extinction via the 2200A dust feature. The resulting calibrated VUV pictures are 40 arcminutes in diameter at 2.5 arcseconds resolution. The capabilities of UIT, therefore, complement HST's WFPC: the latter has 40 times greater collecting area, while UIT's usable field has 170 times WFPC's field area.

  20. The alignment of galaxy spin with the shear field in observations

    NASA Astrophysics Data System (ADS)

    Pahwa, Isha; Libeskind, Noam I.; Tempel, Elmo; Hoffman, Yehuda; Tully, R. Brent; Courtois, Hélène M.; Gottlöber, Stefan; Steinmetz, Matthias; Sorce, Jenny G.

    2016-03-01

    Tidal torque theory suggests that galaxies gain angular momentum in the linear stage of structure formation. Such a theory predicts alignments between the spin of haloes and tidal shear field. However, non-linear evolution and angular momentum acquisition may alter this prediction significantly. In this paper, we use a reconstruction of the cosmic shear field from observed peculiar velocities combined with spin axes extracted from galaxies within 115 Mpc (˜8000 km s-1) from 2MASS Redshift Survey (2MRS) catalogue to test whether or not galaxies appear aligned with principal axes of shear field. Although linear reconstructions of the tidal field have looked at similar issues, this is the first such study to examine galaxy alignments with velocity shear field. Ellipticals in the 2MRS sample show a statistically significant alignment with two of the principal axes of the shear field. In general, elliptical galaxies have their short axis aligned with the axis of greatest compression and perpendicular to the axis of slowest compression. Spiral galaxies show no signal. Such an alignment is significantly strengthened when considering only those galaxies that are used in velocity field reconstruction. When examining such a subsample, a weak alignment with the axis of greatest compression emerges for spiral galaxies as well. This result indicates that although velocity field reconstructions still rely on fairly noisy and sparse data, the underlying alignment with shear field is strong enough to be visible even when small numbers of galaxies are considered - especially if those galaxies are used as constraints in the reconstruction.

  1. Predicting wind field in the Bay of Bengal from scatterometer observations using genetic algorithm

    NASA Astrophysics Data System (ADS)

    Sharma, Rashmi; Sarkar, Abhijit; Agarwal, Neeraj; Kumar, Raj; Basu, Sujit

    2007-02-01

    A technique based on genetic algorithm (GA) is applied for predicting wind field in the Bay of Bengal (BOB) using satellite scatterometer observations. Empirical orthogonal function (EOF) analysis is used for compressing the spatial variability into a set of eigenmodes. The time series of each principal component (PC) is subjected to singular spectrum analysis (SSA) and GA is applied to the resulting filtered time series. The forecast PCs are weighted by the spatial eigenmodes for computing forecast wind fields. Predictions made up to 5 days in advance are found to be superior to forecast by persistence method.

  2. Simulation of polarized optical speckle fields: effects of the observation scale on polarimetry.

    PubMed

    Dupont, Jan; Orlik, Xavier

    2016-05-16

    In this paper, we propose the simulation of polarized speckle fields using the Stokes formalism, which allows the description of partially polarized electromagnetic waves. We define a unique parameter which determines the partial decorrelation of the involved fields, allowing to simulate the polarized speckles produced by all types of scatterers, from simple to multiple scatterers. We validate this model by comparison with experimental measurements. We use that simulation model to study the impact of the imaging device parameters on polarimetric measurements: first we emphasize a limit of resolution on retardance measurements, then we study the spatial depolarization, which appears when an observer is measuring any space-variant polarization map. PMID:27409937

  3. Berry's phase in cavity QED: Proposal for observing an effect of field quantization

    SciTech Connect

    Carollo, A.; Santos, M. Franca; Vedral, V.

    2003-06-01

    We propose a feasible experiment to investigate quantum effects in geometric phases, arising when a classical source drives not a single quantum system, but two interacting ones. In particular, we show how to observe a signature of the quantization of the electromagnetic field through a vacuum effect in Berry's phase. To do so, we describe the interaction of an atom and a quantized cavity mode altogether driven by an external quasiclassical field. We also analyze the semiclassical limit recovering the usual Berry's phase results.

  4. Observation of Thermoelectric Currents in High-Field Superconductor-Ferromagnet Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Kolenda, S.; Wolf, M. J.; Beckmann, D.

    2016-03-01

    We report on the experimental observation of spin-dependent thermoelectric currents in superconductor-ferromagnet tunnel junctions in high magnetic fields. The thermoelectric signals are due to a spin-dependent lifting of the particle-hole symmetry, and are found to be in excellent agreement with recent theoretical predictions. The maximum Seebeck coefficient inferred from the data is about -100 μ V /K , much larger than commonly found in metallic structures. Our results directly prove the coupling of spin and heat transport in high-field superconductors.

  5. Observational Signatures and Non-Gaussianities ofGeneral Single Field Inflation

    SciTech Connect

    Chen, Xingang; Huang, Min-xin; Kachru, Shamit; Shiu, Gary

    2006-05-05

    We perform a general study of primordial scalar non-Gaussianities in single field inflationary models. We consider models where the inflaton Lagrangian is an arbitrary function of the scalar field and its first derivative, and the sound speed is arbitrary. We find that under reasonable assumptions, the non-Gaussianity is completely determined by 5 parameters. In special limits of the parameter space, one finds distinctive ''shapes'' of the non-Gaussianity. In models with a small sound speed, several of these shapes would become potentially observable in the near future. Different limits of our formulae recover various previously known results.

  6. Observation of Thermoelectric Currents in High-Field Superconductor-Ferromagnet Tunnel Junctions.

    PubMed

    Kolenda, S; Wolf, M J; Beckmann, D

    2016-03-01

    We report on the experimental observation of spin-dependent thermoelectric currents in superconductor-ferromagnet tunnel junctions in high magnetic fields. The thermoelectric signals are due to a spin-dependent lifting of the particle-hole symmetry, and are found to be in excellent agreement with recent theoretical predictions. The maximum Seebeck coefficient inferred from the data is about -100  μV/K, much larger than commonly found in metallic structures. Our results directly prove the coupling of spin and heat transport in high-field superconductors. PMID:26991193

  7. Field and thermal plasma observations of ULF pulsations during a magnetically disturbed interval

    SciTech Connect

    Lin, N. |; Reinleitner, L.A.

    1992-10-01

    ULF pulsations were observed by DE 1 between 1600 and 1830 UT, October 31, 1982, during a magnetically disturbed interval. Ground observations suggested that the pulsations were excited by a sudden increase in the solar wind velocity and pressure. During the pulsation interval DE 1 traveled near apogee from {minus}55 to {minus}20{degrees} geomagnetic latitude and from L {approximately} 13 to L{approximately}4 at about 0900 LT. The waves observed were azimuthal oscillations preceded by gradually decaying long period compressional waves which lasted for more than 1 hour. Phase relations between magnetic and electric field oscillations and calculated Poynting flux indicate that in the outer magnetosphere (L> 8) DE 1 observed propagating waves which contained strong polodial components, while the quasi-sinusoidal toroidal waves seen later for L<10.3 were standing along field lines. The toroidal waves appeared as four wave packets, each of which corresponded to a region with a distinct plasma distribution. The observed wave periods decreased with L over an extended magnetospheric region. The seemingly weak interaction between magnetic shells suggests that the source was a broadband one. Magnetometer data from several high latitude observatories located near the footpoints of the magnetic shells crossed by DE 1 were also examined. The magnetic pulsations on the ground contained many frequency components, and the waves seen most strongly in space where often not the strongest signals seen on the ground near the same field lines. The broadband nature of the ground pulsations indicates that the stations also detected oscillations of the adjacent field lines. The major frequencies seen at ground stations seemed to be roughly constant for about 2 hours but L dependent. This suggests that the changing periods seen in space by DE 1 were clearly L related and not temporally varying. 42 refs., 16 figs., 3 tabs.

  8. Rocketborne observations of ion convection and electric fields in dayside and nightside visual auroral arcs

    SciTech Connect

    Yau, A.W.; Whalen, B.A.; Creutzberg, F.

    1981-08-01

    We present ionospheric ion convection measurements in a series of four rocket payloads in and near dayside and nightside auroral arcs: one at Cape Parry (75.4/sup 0/N invariant latitude) near 1300 MLT and three at Churchill (70.0/sup 0/N invariant latitude) between 1900 and 2200 MLT. Direct measurements were made of the ionospheric ion velocity distribution function, and the observed ion convection velocities and equivalent convective electric fields were correlated with the energetic particle precipitation, the optical morphology of the aurora, and the topology of the geomagnetic field. Both in the postnoon and premidnight sectors it was observed that (1) equatorward of the region(s) of precipitation the ion flow was predominantly westward, with velocity of about 1 km/s; (2) poleward of the region(s) the flow was predominantly westward, with velocity of about 1 km/s; (2) poleward of the region(s) the flow was predominantly eastward: (3) the change in the flow direction, where observed, occurred near though not exactly at the edges of the precipitation region; (4) the flow inside the precipitation region was lower; (5) the reversal of the ion flow, where observed, occurred on closed magnetic field lines; and (6) the convective electric field typically dropped from 40 to 80 mV/m outside the precipitation region to 10 to 30 mV/m within. In the dayside Cape Perry flight, where quantitative photometric measurements were available, detailed anticorrelation between the ion convection speed and the green line emission intensity was also observed.

  9. Generating wind fields that honour point observations and physical conservation laws

    NASA Astrophysics Data System (ADS)

    Schlabing, Dirk; Bárdossy, András

    2015-04-01

    Wind exhibits a strong spatial and temporal variability. In the application of lake modelling, these features are important for simulating water flows and stratification correctly, as mean and variance of wind speed determine the input of momentum into the lake. This makes a mere interpolation of point measurements an unsuitable method for producing model input. Additionally to concrete point measurements, more subtle aspects of wind fields are to be reproduced. It follows from the fact that wind vectors represent moving air that a wind field has to be divergency-free in order to be mass-conservative. Further, a temporal sequence of wind fields has to comply with the Navier-Stokes equation in order to conserve momentum. All these constraints can be met by representing the conditioned wind field as a linear combination of unconditioned, normally distributed random fields that individually possess the same spatial covariance structuref as observed wind fields. The aim of having the same covariance structure in the conditioned wind field is formulated as an optimization problem with respect to the weights used in the linear combination. With the help of Quadratic Programming (QP) and exploiting the convexity of the problem, feasible solutions can easily be found. In this QP problem, observations become linear constraints. Conservation laws can be incorporated by introducing control volumes in a similar fashion as they are used in fluid mechanics. Budgets of flows through these control volumes become integral conditions in the QP problem. The applicability of the approach will be shown using an artificial example and real-world data measured on shore and on a moving boat on Lake Constance.

  10. Effects of the Observed Meridional Flow Variations since 1996 on the Sun's Polar Fields

    NASA Technical Reports Server (NTRS)

    Hathaway, David H.; Upton, Lisa

    2013-01-01

    The cause of the low and extended minimum in solar activity between Sunspot Cycles 23 and 24 was the small size of Sunspot Cycle 24 itself - small cycles start late and leave behind low minima. Cycle 24 is small because the polar fields produced during Cycle 23 were substantially weaker than those produced during the previous cycles and those (weak) polar fields are the seeds for the activity of the following cycle. The polar fields are produced by the latitudinal transport of magnetic flux that emerged in low-latitude active regions. The polar fields thus depend upon the details of both the flux emergence and the flux transport. We have measured the flux transport flows (differential rotation, meridional flow, and supergranules) since 1996 and find systematic and substantial variation in the meridional flow alone. Here we present experiments using a Surface Flux Transport Model in which magnetic field data from SOHO/MDI and SDO/HMI are assimilated into the model only at latitudes between 45-degrees north and south of the equator (this assures that the details of the active region flux emergence are well represented). This flux is then transported in both longitude and latitude by the observed flows. In one experiment the meridional flow is given by the time averaged (and north-south symmetric) meridional flow profile. In the second experiment the time-varying and north-south asymmetric meridional flow is used. Differences between the observed polar fields and those produced in these two experiments allow us to ascertain the effects of these meridional flow variations on the Sun s polar fields.

  11. Magnetospheric Response to Interplanetary Field Enhancements: Coordinated Space-based and Ground-based Observations

    NASA Astrophysics Data System (ADS)

    Chi, Peter; Russell, Christopher; Lai, Hairong

    2014-05-01

    In general, asteroids, meteoroids and dust do not interact with the plasma structures in the solar system, but after a collision between fast moving bodies the debris cloud contains nanoscale dust particles that are charged and behave like heavy ions. Dusty magnetic clouds are then accelerated to the solar wind speed. While they pose no threat to spacecraft because of the particle size, the coherency imposed by the magnetization of the cloud allows the cloud to interact with the Earth's magnetosphere as well as the plasma in the immediate vicinity of the cloud. We call these clouds Interplanetary Field Enhancements (IFEs). These IFEs are a unique class of interplanetary field structures that feature cusp-shaped increases and decreases in the interplanetary magnetic field and a thin current sheet. The occurrence of IFEs is attributed to the interaction between the solar wind and dust particles produced in inter-bolide collisions. Previous spacecraft observations have confirmed that IFEs move with the solar wind. When IFEs strike the magnetosphere, they may distort the magnetosphere in several possible ways, such as producing a small indentation, a large scale compression, or a glancing blow. In any event if the IFE is slowed by the magnetosphere, the compression of the Earth's field should be seen in the ground-based magnetic records that are continuously recorded. Thus it is important to understand the magnetospheric response to IFE arrival. In this study, we investigate the IFE structure observed by spacecraft upstream of the magnetosphere and the induced magnetic field perturbations observed by networks of ground magnetometers, including the THEMIS, CARISMA, McMAC arrays in North America and the IMAGE array in Europe. We find that, in a well-observed IFE event on December 24, 2006, all ground magnetometer stations observed an impulse at approximately 1217 UT when the IFE was expected to arrive at the Earth's magnetopause. These ground stations spread across many

  12. The study of zonal dynamo electric fields observed by the IPEI on board ROCSAT-1

    NASA Astrophysics Data System (ADS)

    Huang, C. M.; Lin, T. C.

    2014-12-01

    The earth's ionosphere is under direct and indirect influence from the sun. Electric currents, fields and other effects can penetrate into magnetosphere and high latitude ionosphere through magnetic field lines, and into the low latitudes by the disturbance dynamo mechansim, which can lasts for a few hours to a few days, with accumulation of positive charges at the low latitude ionosphere around the midnight. The directions of the corresponding disturbed electric fields are westward in the daytime and eastward in the nighttime, opposite to the normal quiet time condition. A comparison between model results and observed data from the IPEI on board ROCSAT-1 is carried out and presented. There were 23 storm cases with DST indexes lower than -140 from 2000 to 2003. The zonal electric fields, within ±30 degrees in magnetic latitude, are compared at periods one and two days before the storm onset and the time during the storm, which precisely shows the perturbed electric fields at different local times and different magnetic latitudes. Siganificant eastward perturbed electric fields at dawn were found in 17 out of the 23 events. The satellite orbit tracjectories are not suitable or nothing is found for the others.

  13. Observation of magnetic field generation via the Weibel instability in interpenetrating plasma flows

    SciTech Connect

    Huntington, C. M.; Fiuza, F.; Ross, J. S.; Zylstra, A. B.; Drake, R. P.; Froula, D. H.; Gregori, G.; Kugland, N. L.; Kuranz, C. C.; Levy, M. C.; Li, C. K.; Meinecke, J.; Morita, T.; Petrasso, R.; Plechaty, C.; Remington, B. A.; Ryutov, D. D.; Sakawa, Y.; Spitkovsky, A.; Takabe, H.; Park, H.-S.

    2015-01-19

    Collisionless shocks can be produced as a result of strong magnetic fields in a plasma flow, and therefore are common in many astrophysical systems. The Weibel instability is one candidate mechanism for the generation of su fficiently strong fields to create a collisionless shock. Despite their crucial role in astrophysical systems, observation of the magnetic fields produced by Weibel instabilities in experiments has been challenging. Using a proton probe to directly image electromagnetic fields, we present evidence of Weibel-generated magnetic fields that grow in opposing, initially unmagnetized plasma flows from laser-driven laboratory experiments. Three-dimensional particle-in-cell simulations reveal that the instability effi ciently extracts energy from the plasma flows, and that the self-generated magnetic energy reaches a few percent of the total energy in the system. Furthermore, this result demonstrates an experimental platform suitable for the investigation of a wide range of astrophysical phenomena, including collisionless shock formation in supernova remnants, large-scale magnetic field amplification, and the radiation signature from gamma-ray bursts.

  14. Observations of ELF fields near the low-altitude CRRES chemical releases

    SciTech Connect

    Koons, H.C.; Roeder, J.L.

    1995-08-01

    The Combined Release and Radiation Effects Satellite (CRRES) performed a series of seven low altitude chemical releases between September 10, 1990, and August 12, 1991. Immediately following each chemical release, electric and magnetic fields were detected by the extremely low frequency wave analyzer sensors of the Low Altitude Satellite Studies of Ionospheric Irregularities (LASSII) experiment on the spacecraft. The time series and spectra of the two field components are quite similar for each of the releases but vary in detail from release to release. The index of refraction estimated from the ratio of the magnetic field to the electric field is too small by about 2 orders of magnitude for either the right hand wave or the extraordinary wave modes which are the only propagating electromagnetic modes in the detected band above the O+ ion gyrofrequency (about 30 Hz). ELF hiss observed at higher altitudes is found to be propagating in the extraordinary wave mode with the correct index of refraction. This confirms that the intensity measurements are being made correctly by the instrument and that an alternative explanation is required for the signals detected following the chemical releases. The authors show that the waves are primarily electrostatic and that the magnitude of the wave magnetic field is consistent with the transverse magnetic field component of ion acoustic waves.

  15. Finite field of view effects on inversion of limb thermal emission observations. [balloon sounding of stratosphere

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Guo, J.; Conrath, B. J.; Kunde, V. G.; Maguire, W. C.

    1985-01-01

    It is pointed out that the technique of thermal emission spectroscopy provides an effective means for remote sounding of stratospheric temperature structure and constituent distributions. One procedure for measuring the stratospheric infrared spectrum involves the conduction of observations along ray paths tangent to the stratospheric limb. Thermal emission limb tangent observations have certain advantages compared to other types of observations. The techniques for determining temperature and trace gas distributions from limb thermal emission radiances are based on the assumption that the bulk of opacity lies near the tangent point. Ideally, the field of view (FOV) of the observing instrument should be very small. The effect of a finite FOV is to reduce the spatial resolution of the retrieved temperature and constituent profiles. The present investigation is concerned with the effects of the FOV on the inversion of infrared thermal emission measurements for balloon platforms. Attention is given to a convenient method for determining the weighting functions.

  16. The thickness of faults: From laboratory experiments to field scale observations

    NASA Astrophysics Data System (ADS)

    Chambon, G.; Schmittbuhl, J.; Corfdir, A.; Orellana, N.; Diraison, M.; Géraud, Y.

    2006-10-01

    To assess the role of the fault thickness on its mechanical behavior, we first present the results of an experimental modeling of a thick fault core. Our laboratory setup consists in an annular simple shear apparatus in which we can apply very large shear displacements (50 m) to 100 particle thick granular samples. Thanks to a window in the apparatus, pictures of the microstructures can be continuously taken during shear. We observe from a Correlation Image Velocimetry technique that a significant strain field exists outside of the observable shear band. This strain field, though of small magnitude compared to that existing inside the shear band, is very structured and extends in a region much wider than expected from individual static observations (i.e. wider than the directly observable shear band). Moreover, this strain field controls most of the evolution of the shear strength of the fault. We then propose plausible comparisons of our experimental results to geological observations of fault cores in the region of Aigion (Corinth Gulf, Greece). The studied faults indeed display spectacular indurated fault planes lying on weakly cohesive material. Signatures of cementation, clay mineral distribution and porosity profile of one of the studied fault cores are included and discussed in the light of the experimental results. Our observations suggest that the maximum shear strain during earthquakes might occur not in the center, but on the border of the fault cores. It is presumably localized in a transition zone which exhibits a significant cementation owing to a process of mechanical smearing by fine particles. This zone may also act as a very low permeability layer responsible for a channeling of the fluid flow. Such a scheme of progressive multi sub-localizations, is different from classical descriptions of faults and consistent with a layering of the core consisting of separated zones of high strains or large cataclastic flows.

  17. Proto-Type Development of Optical Wide-field Patrol Network and Test Observation

    NASA Astrophysics Data System (ADS)

    Park, J.; Choi, Y.; Jo, J.; Moon, H.; Yim, H.; Park, Y.; Hae, Y.; Park, S.; Choi, J.; Son, J.

    2014-09-01

    We present a prototype system developed for optical satellite tracking and its early test observation results. The main objective of the OWL (Optical Wide-field patroL) network is to get orbital information for Korean domestic satellites using optical means only and to maintain their orbital elements. The network is composed of 5 small wide-field telescopes deployed over the world. Each observing station is operated in fully robotic manner from receiving observation schedule to reporting the result, and controlled by the headquarter located in Daejeon, Korea, where orbit calculation and observation strategy will be determined. We developed a compact telescope system for robotic observation and easy maintenance. The telescope is 0.5m of aperture diameter with Rechey-Cretian configuration and its field of view is 1.1 deg. It is equipped with 4K CCD with 9um pixel size, and its pixel scale is 1.2 arcsec/pixel. A chopper wheel with variable speed is adopted to get more points in a single shot. The CCD camera and all the rotating parts (chopper wheel, de-rotator, and filter wheel) are integrated into one compact component called a wheel station. Each observing station is equipped with a fully automatic dome and heavy duty environment monitoring system. We could get an image every 20 seconds and up to ~100 trail points in a single exposure. Each point is time-tagged by ~1/1000 second precision. For one of best cases, we could estimate satellite position with RMS ~ 0.5km accuracy in the along-track with only 4 exposures (~100 points). The first system was installed at the Mongolian site after completing verification test at the testbed site in Daejeon, Korea. The second and third system will be installed in the end of this year.

  18. Observing the nonequilibrium dynamics of the quantum transverse-field Ising chain in circuit QED.

    PubMed

    Viehmann, Oliver; von Delft, Jan; Marquardt, Florian

    2013-01-18

    We show how a quantum Ising spin chain in a time-dependent transverse magnetic field can be simulated and experimentally probed in the framework of circuit QED with current technology. The proposed setup provides a new platform for observing the nonequilibrium dynamics of interacting many-body systems. We calculate its spectrum to offer a guideline for its initial experimental characterization. We demonstrate that quench dynamics and the propagation of localized excitations can be observed with the proposed setup and discuss further possible applications and modifications of this circuit QED quantum simulator. PMID:23373908

  19. Kilometric radio waves generated along auroral field lines observed by ground facilities - A theoretical model

    NASA Technical Reports Server (NTRS)

    Ziebell, L. F.; Wu, C. S.; Yoon, Peter H.

    1991-01-01

    A theory of generation of radio waves observed by ground-based facilities in the frequency range 150-700 kHz is discussed. This work is a continuation of an earlier discussion (Wu et al., 1989) in which it was proposed that the trapped electrons along the auroral field lines can lead to a cyclotron instability which amplifies the whistler waves observed at ground level. The objective of the present study is to investigate the propagation effect on the wave amplification and to examine whether the proposed mechanism is indeed viable.

  20. Chandra X-ray Observations of Young Clusters. Volume II; Orion Flanking Fields Data

    NASA Technical Reports Server (NTRS)

    Ramirez, Solange V.; Rebull, Luisa; Stauffer, John; Strom, Stephen; Hillenbrand, Lynne; Hearty, Thomas; Kopan, Eugene L.; Pravdo, Steven; Makidon, Russell; Jones, Burton

    2004-01-01

    We present results of Chandra observations of two flanking fields (FFs) in Orion, outside the Orion Nebula Cluster (ONC). The observations were taken with the ACIS-I camera with an exposure time of about 48 ks each field. We present a catalog of 417 sources, which includes X-ray luminosity, optical and infrared photometry, and X-ray variability information. We have found 91 variable sources, 33 of which have a flarelike light curve and 11 of which have a pattern of a steady increase or decrease over a 10 hr period. The optical and infrared photometry for the stars identified as X-ray sources are consistent with most of these objects being pre-main-sequence stars with ages younger than 10 Myr. We present evidence for an age difference among the X-ray-selected samples of NGC 2264, Orion FFs, and ONC, with NGC 2264 being the oldest and ONC being the youngest.

  1. The effect of the interplanetary magnetic field on sidereal variations observed at medium depth underground detectors

    NASA Technical Reports Server (NTRS)

    Humble, J. E.; Fenton, A. G.

    1985-01-01

    It has been known for some years that the intensity variations in sidereal time observed by muon detectors at moderate underground depths are sensitive to the polarity of the interplanetary magnetic field (ipmf) near the Earth. There are differences in the response to these anisotropies as observed in the Norhtern and southern hemispheres. When fully understood, the nature of the anisotropy seems likely to provide information on the 3-dimensional structure of the heliomagnetosphere, its time variations, and its linking with the local interstellar field. The summation harmonic dials for the sidereal diurnal variation during 1958 to 1982 show that there is a strong dependence on whether the ipmf near the Earth is directed outwards from the Sun or inwards it.

  2. High-intensity geomagnetic field 'spike' observed at ca. 3000 cal BP in Texas, USA

    NASA Astrophysics Data System (ADS)

    Bourne, Mark D.; Feinberg, Joshua M.; Stafford, Thomas W.; Waters, Michael R.; Lundelius, Ernest; Forman, Steven L.

    2016-05-01

    By observing the fluctuations in direction and intensity of the Earth's magnetic field through time, we increase our understanding of the fluid motions of the Earth's outer core that sustain the geomagnetic field, the geodynamo. Recent archaeomagnetic studies in the Near East have found extremely rapid increases - 'spikes' - in geomagnetic field intensity at ca. 3000 yr cal BP. These observations have proved problematic for our current understanding of core-flow. However, until now, these geomagnetic spikes had not been observed outside of the Near East, where they have been preserved in metallurgical slag and fired, mud brick walls. We present a new, fully oriented, geomagnetic secular variation and relative palaeointensity (RPI) record for the last 17,000 yr from Hall's Cave, Texas, whose complete, >3.8 m thick sedimentary sequence spans from the present to 16 , 850 ± 110 RC yr BP (Modern to 20,600 cal BP). Within the stable, cool climate of the cave, pedogenic and bioturbation processes are negligible to non-existent, thereby limiting post-depositional physical and geochemical alteration of the magnetic record. The sub-aerial and subterranean setting of the sedimentary sequence in Hall's Cave enabled us to collect oriented palaeomagnetic cubes from a previously excavated stratigraphic section. The palaeomagnetic samples yielded high-quality vectors. An age model for the sequence, determined using 15 AMS 14C-dates on individual bones from microvertebrates, was combined with the palaeomagnetic data to construct a secular variation record. The record is in broad agreement with predictions by Holocene field models for the site's location. However, starting ca. 3000 yr ago, the RPI data indicate an almost four-fold increase in geomagnetic field intensity lasting several hundred years. This record presents well-dated evidence, obtained using conventional techniques, for the existence of a geomagnetic intensity spike in North America that is contemporaneous with the

  3. Magneto-frictional Modeling of Coronal Nonlinear Force-free Fields. II. Application to Observations

    NASA Astrophysics Data System (ADS)

    Guo, Y.; Xia, C.; Keppens, R.

    2016-09-01

    A magneto-frictional module has been implemented and tested in the Message Passing Interface Adaptive Mesh Refinement Versatile Advection Code (MPI-AMRVAC) in the first paper of this series. Here, we apply the magneto-frictional method to observations to demonstrate its applicability in both Cartesian and spherical coordinates, and in uniform and block-adaptive octree grids. We first reconstruct a nonlinear force-free field (NLFFF) on a uniform grid of 1803 cells in Cartesian coordinates, with boundary conditions provided by the vector magnetic field observed by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) at 06:00 UT on 2010 November 11 in active region NOAA 11123. The reconstructed NLFFF successfully reproduces the sheared and twisted field lines and magnetic null points. Next, we adopt a three-level block-adaptive grid to model the same active region with a higher spatial resolution on the bottom boundary and a coarser treatment of regions higher up. The force-free and divergence-free metrics obtained are comparable to the run with a uniform grid, and the reconstructed field topology is also very similar. Finally, a group of active regions, including NOAA 11401, 11402, 11405, and 11407, observed at 03:00 UT on 2012 January 23 by SDO/HMI is modeled with a five-level block-adaptive grid in spherical coordinates, where we reach a local resolution of 0\\buildrel{\\circ}\\over{.} 06 pixel‑1 in an area of 790 Mm × 604 Mm. Local high spatial resolution and a large field of view in NLFFF modeling can be achieved simultaneously in parallel and block-adaptive magneto-frictional relaxations.

  4. Observation of spectrum effect on the measurement of intrinsic error field on EAST

    NASA Astrophysics Data System (ADS)

    Wang, Hui-Hui; Sun, You-Wen; Qian, Jin-Ping; Shi, Tong-Hui; Shen, Biao; Gu, Shuai; Liu, Yue-Qiang; Guo, Wen-Feng; Chu, Nan; He, Kai-Yang; Jia, Man-Ni; Chen, Da-Long; Xue, Min-Min; Ren, Jie; Wang, Yong; Sheng, Zhi-Cai; Xiao, Bing-Jia; Luo, Zheng-Ping; Liu, Yong; Liu, Hai-Qing; Zhao, Hai-Lin; Zeng, Long; Gong, Xian-Zu; Liang, Yun-Feng; Wan, Bao-Nian; The EAST Team

    2016-06-01

    Intrinsic error field on EAST is measured using the ‘compass scan’ technique with different n  =  1 magnetic perturbation coil configurations in ohmically heated discharges. The intrinsic error field measured using a non-resonant dominated spectrum with even connection of the upper and lower resonant magnetic perturbation coils is of the order {{b}r2,1}/{{B}\\text{T}}≃ {{10}-5} and the toroidal phase of intrinsic error field is around {{60}{^\\circ}} . A clear difference between the results using the two coil configurations, resonant and non-resonant dominated spectra, is observed. The ‘resonant’ and ‘non-resonant’ terminology is based on vacuum modeling. The penetration thresholds of the non-resonant dominated cases are much smaller than that of the resonant cases. The difference of penetration thresholds between the resonant and non-resonant cases is reduced by plasma response modeling using the MARS-F code.

  5. Lobe crossing events observed by the Van Allen Probes as tests of magnetic field line mapping

    NASA Astrophysics Data System (ADS)

    Dixon, P.; MacDonald, E.; Grande, M.; Glocer, A.

    2014-04-01

    In this paper we examine a series of lobe crossing events witnessed by the twin Van Allen Probes spacecraft between 0200 and 0515 on November 14th 2012. The events occurred on the flank between 0400 and 0635 local time and at altitudes between 5.6 and 6.2 RE. During the events Dst was less than 100nT with the IMF being strongly southward (Bz = - 15nT) and eastward (By = 20 nT). Other observations at geosynchronous orbit also show lobe crossings at dawn and dusk flanks. These events provide a chance to examine the magnetic field topology in detail and compare it with models. We will show that the spacecraft were in locations with access to the open field lines by comparison to the CRCM + BATS-RUS models as well as comparing spacecraft encounters with the lobe to the predicted magnetic field topology.

  6. Land subsidence caused by the East Mesa geothermal field, California, observed using SAR interferometry

    USGS Publications Warehouse

    Massonnet, D.; Holzer, T.; Vadon, H.

    1997-01-01

    Interferometric combination of pairs of synthetic aperture radar (SAR) images acquired by the ERS-1 satellite maps the deformation field associated with the activity of the East Mesa geothermal plant, located in southern California. SAR interferometry is applied to this flat area without the need of a digital terrain model. Several combinations are used to ascertain the nature of the phenomenon. Short term interferograms reveal surface phase changes on agricultural fields similar to what had been observed previously with SEASAT radar data. Long term (2 years) interferograms allow the study of land subsidence and improve prior knowledge of the displacement field, and agree with existing, sparse levelling data. This example illustrates the power of the interferometric technique for deriving accurate industrial intelligence as well as its potential for legal action, in cases involving environmental damages. Copyright 1997 by the American Geophysical Union.

  7. Field Emission and Consequences as Observed and Simulated for CEBAF Upgrade Cryomodules

    SciTech Connect

    Marhauser, Frank; Johnson, Rolland; Rodriguez, Rodolfo; Degtiarenko, Pavel; Hutton, Andrew; Kharashvili, George; Reece, Charles; Rimmer, Robert

    2013-09-01

    High gamma and neutron radiation levels were monitored at the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Laboratory (JLab) after installation of new cavity cryomodules and initial test runs in the frame of the ongoing 12 GeV upgrade program. The dose rates scaled exponentially with cavity accelerating fields, but were independent of the presence of an electron beam in the accelerator. Hence, field emission (FE) is the source of origin. This has led to concerns regarding the high field operation (100 MV per cryomodule) in the future 12 GeV era. Utilizing supercomputing, novel FE studies have been performed with electrons tracked through a complete cryomodule. It provides a principal understanding of experimental observations as well as ways to mitigate FE as best as practicable by identification of problematic cavities.

  8. Prospects for detection of exoplanet magnetic fields through bow-shock observations during transits

    NASA Astrophysics Data System (ADS)

    Vidotto, A. A.; Jardine, M.; Helling, Ch.

    2011-02-01

    An asymmetry between the ingress and egress times was observed in the near-UV light curve of the transit planet WASP-12b. Such asymmetry led us to suggest that the early ingress in the UV light curve of WASP-12b, compared to the optical observations, is caused by a shock around the planet, and that shocks should be a common feature in transiting systems. Here, we classify all the transiting systems known to date according to their potential for producing shocks that could cause observable light curve asymmetries. We found that 36/92 of known transiting systems would lie above a reasonable detection threshold and that the most promising candidates to present shocks are: WASP-19b, WASP-4b, WASP-18b, CoRoT-7b, HAT-P-7b, CoRoT-1b, TrES-3 and WASP-5b. For prograde planets orbiting outside the corotation radius of fast rotating stars, the shock position, instead of being ahead of the planetary motion as in WASP-12b, trails the planet. In this case, we predict that the light curve of the planet should present a late-egress asymmetry. We show that CoRoT-11b is a potential candidate to host such a behind shock and show a late egress. If observed, these asymmetries can provide constraints on planetary magnetic fields. For instance, for a planet that has a magnetic field intensity similar to Jupiter's field (˜14 G) orbiting a star whose magnetic field is between 1 and 100 G, the stand-off distance between the shock and the planet, which we take to be the size of the planet's magnetosphere, ranges from 1 to 40 planetary radii.

  9. Calculating Coronal Mass Ejection Magnetic Field at 1 AU Using Solar Observables

    NASA Astrophysics Data System (ADS)

    Chen, J.; Kunkel, V.

    2013-12-01

    It is well-established that most major nonrecurrent geomagnetic storms are caused by solar wind structures with long durations of strong southward (Bz < 0) interplanetary magnetic field (IMF). Such geoeffective IMF structures are associated with CME events at the Sun. Unfortunately, neither the duration nor the internal magnetic field vector of the ejecta--the key determinants of geoeffectiveness--is measurable until the observer (e.g., Earth) passes through the ejecta. In this paper, we discuss the quantitative relationships between the ejecta magnetic field at 1 AU and remotely observable solar quantities associated with the eruption of a given CME. In particular, we show that observed CME trajectories (position-time data) within, say, 1/3 AU of the Sun, contain sufficient information to allow the calculation of the ejecta magnetic field (magnitude and components) at 1 AU using the Erupting Flux Rope (EFR) model of CMEs. Furthermore, in order to accurately determine the size and arrival time of the ejecta as seen by a fixed observer at 1 AU (e.g., ACE), it is essential to accurately calculate the three-dimensional geometry of the underlying magnetic structure. Accordingly, we have extended the physics-based EFR model to include a self-consistent calculation of the transverse expansion taking into account the non-symmetric drag coupling between an expanding CME flux rope and the ambient solar wind. The dependence of the minor radius of the flux rope at 1 AU that determines the perceived size of the ejecta on solar quantities is discussed. Work supported by the NRL Base Program.

  10. Observational signatures of sub-Larmor scale magnetic fields in astrophysical objects and HEAD lab experiments

    NASA Astrophysics Data System (ADS)

    Medvedev, Mikhail

    2010-02-01

    An extensive body of studies indicate that small-scale (sub-Larmor-scale) magnetic turbulence are produced at relativistic shocks, in reconnection events and other high-energy density environments. Here we present a general description of radiation produced by relativistic electrons moving in such fields and stress its non-synchrotron spectral characteristics. We illustrate the results with spectral data from gamma-ray burst observations. )

  11. TAOS Project: Searching for Variable Stars in the Selected TAOS Fields and Optical Followup Observations

    NASA Astrophysics Data System (ADS)

    Ngeow, Chow Choong; Chang, D.; Pan, K.; Chung, T.; Koptelova, E.; TAOS Collaboration

    2010-05-01

    The Taiwan-American Occultation Survey (TAOS) project is aimed to find Kuiper Belt Objects (KBO) and measure their size distribution using the occultation technique. The TAOS project employed four 20-inch wide-field (F/1.9, 3 degree-squared FOV) telescopes, equipped with a 2K x 2K CCD, to simultaneously monitor the same patch of the sky. All four TAOS telescopes, which can be operated automatically, were located at the Lulin Observatory in central Taiwan. The TAOS project has been continuously taking data since 2005. In addition of finding KBO, the dense sampling strategy employed in TAOS can also be used to find variable stars. We report the search of variable stars from selected TAOS fields at this Meeting. For example, we found about 50 candidate variables (out of 2600 stars) in TAOS 60 Field (RA: 04h48m00s, DEC: +20d46m20s, with limiting magnitudes about15 mag. at S/N=10), including three previously known variables, using sigma deviation and Stetson's J-index methods. The available data in this field spanned about 150 days in time. However, TAOS observations were conducted using a customized filter. We therefore initiated a followup program to observe and construct the light curves of these candidate variables in the BVRI bands, using the Lulin's One-Meter telescope, Lulin's SLT telescope (16-inch aperture) and 32-inch telescope from the Tenagra II Observatory. The multi-band optical followup observation will help in improving the classification of these candidates, estimate their BVRI mean magnitudes, colors as well as extinction. This will enable a wide range of research in astrophysics for these variables. We also present our preliminary results based on the first season of the followup observations. CCN acknowledges the support from NSC 98-2112-M-008-013-MY3.

  12. Unfolding proteins in an external field: Can we always observe the intermediate states?

    NASA Astrophysics Data System (ADS)

    Lemak, Alexander S.; Lepock, James R.; Chen, Jeff Z.

    2003-03-01

    A protein molecule under the stress of an external denaturing force acting on a terminal end or on the entire molecule is expected to unfold, possibly through a few intermediate stages depending on the magnitude of the denaturing force. We have investigated two protein minimal models under various types of denaturing force fields using the collision molecular-dynamics simulation, in order to critically examine the relationship between the folding pathways observed in different protein denaturing experiments.

  13. Observations of Field Line Resonances by Low-Altitude ST-5 Satellites

    NASA Technical Reports Server (NTRS)

    Le, G.; Chi, P. J.; Strangeway, R. J.; Slavin, J. A.

    2010-01-01

    Space Technology 5 (ST-5) mission is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, and sun synchronous polar orbit with 105.6deg inclination angle. Due to the Earth's rotation and the dipole tilt effect, the spacecraft's dawn-dusk orbit track can reach as low as subauroral latitudes during the course of a day. Whenever the spacecraft traverse across the dayside closed field line region at subauroral latitudes, they frequently observe strong transverse oscillations at 30-200 mHz, or in the Pe 2-3 frequency range. These Pc 2-3 waves appear as wave packets with durations in the order of 5-10 minutes. As the maximum separations of the ST-5 spacecraft are in the order of 10 minutes, the three ST-5 satellites often observe very similar wave packets, implying these wave oscillations occur in a localized region. The coordinated ground-based magnetic observations at the spacecraft footprints, however, do not see waves in the Pc 2- 3 band; instead, the waves appear to be the common Pc 4-5 waves associated with field line resonances. We suggest that this unique Pc 2-3 waves seen by ST-5 are in fact the Doppler-shifted Pc 4-5 waves as a result of rapid traverse of the spacecraft across the resonant field lines azimuthally at low altitudes. The observations with the unique spacecraft dawn-disk orbits at proper altitudes and magnetic latitudes reveal the azimuthal characteristics of field-aligned resonances.

  14. Spontaneous Formation of Closed-Field Torus Equilibrium via Current Jump Observed in an Electron-Cyclotron-Heated Plasma

    SciTech Connect

    Yoshinaga, T.; Uchida, M.; Tanaka, H.; Maekawa, T.

    2006-03-31

    Spontaneous current jump resulting in the formation of closed field equilibrium has been observed in electron-cyclotron-heated toroidal plasmas under steady external fields composed of a toroidal field and a relatively weak vertical field in the low aspect ratio torus experiment device. This bridges the gap between the open field equilibrium maintained by a pressure-driven current in the external field and the closed field equilibrium at a larger current. Experimental results and theoretical analyses suggest a current jump model that is based on the asymmetric electron confinement along the field line appearing upon simultaneous transitions of field topology and equilibrium.

  15. Observation of enhanced field emission properties of Au/TiO2 nanocomposite

    NASA Astrophysics Data System (ADS)

    Patil, Girish P.; Bagal, Vivekanand S.; Suryawanshi, Sachin R.; Late, Dattatray J.; More, Mahendra A.; Chavan, Padmakar G.

    2016-05-01

    Simple and low-cost method of thermal annealing was used to decorate Gold (Au) nanoparticles on aligned TiO2 nanotubes. The aligned TiO2 nanotubes were decorated by Au nanoparticles with an average diameter of 9, 18 and 28 nm (aligned TiO2 nanotubes referred as specimen A and TiO2 nanotubes decorated by Au nanoparticles with average diameter of 9, 18 and 28 nm are referred as specimen B, C and D, respectively). The detailed characterization such as structural, morphological and elemental analysis of TiO2 and Au/TiO2 nanocomposite have been carried out using X-ray diffraction, field emission scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy and Raman spectroscopy. Furthermore, the meticulous comparative field emission characteristics of the aligned TiO2 nanotubes and Au/TiO2 nanocomposite have been performed. The turn-on field defined for the current density of 10 μA/cm2 has been found to be 3.9, 2.8, 3.2 and 3.7 V/μm for specimen A, B, C and D, respectively. The observed low turn-on field of specimen B has been found to be superior than the other semiconducting nanocomposites reported in the literature. The emission current stability over a period of 3 h is found to be better for all the specimens. To the best of our knowledge, a systematic field emission study of Au/TiO2 nanocomposite has not been explored. The observed superior field emission study of Au/TiO2 nanocomposite indicates their possible use in micro/nanoelectronic devices.

  16. Field-aligned currents observed by the OGO 5 and Triad satellites

    NASA Technical Reports Server (NTRS)

    Sugiura, M.

    1975-01-01

    The existence of field-aligned currents in the polar cap boundary layer as a permanent feature of the magnetosphere is investigated. Magnetic field observations from Triad at 800 km altitude and from OGO 5 in the high-altitude magnetosphere are examined. Results indicate that in the morning half of the boundary layer, currents flow into the ionosphere, and that the current direction is reversed in the afternoon half of the layer. The Triad data further indicate that the net current is a maximum near 1500 MLT and that there may be a secondary maximum during early morning hours. According to the Isis 2 electron observations, the locations of these maximums of field-aligned net current roughly match those of two maximums in the isointensity contours for 150 ev electrons. It is proposed that the polar cap boundary current is driven by a current generator in the magnetotail, or ultimately in the solar wind. It is suggested that the large scale field-aligned currents in the polar cap boundary layer are associated with the dominance of protons on the morning side and of electrons on the afternoon side near the poleward edge of the precipitation zone along the auroral oval.

  17. FAST Observations of Acceleration Processes in the Cusp--Evidence for Parallel Electric Fields

    NASA Technical Reports Server (NTRS)

    Pfaff, R. F.. Jr.; Carlson, C.; McFadden, J.; Ergun, R.; Clemmons, J.; Klumpar D.; Strangeway, R.

    1999-01-01

    The existence of precipitating keV ions in the Earth's cusp originating at the magnetosheath provide unique means to test our understanding of particle acceleration and parallel electric fields in the lower altitude acceleration region. On numerous occasions, the FAST (The Fast Auroral Snapshot) spacecraft has encountered the Earth's cusp regions near its apogee of 4175 km which are characterized by their signatures of dispersed keV ion injections. The FAST instruments also reveal a complex microphysics inherent to many, but not all, of the cusp regions encountered by the spacecraft, that include upgoing ion beams and conics, inverted-V electrons, upgoing electron beams, and spikey DC-coupled electric fields and plasma waves. Detailed inspection of the FAST data often show clear modulation of the precipitating magnetosheath ions that indicate that they are affected by local electric potentials. For example, the magnetosheath ion precipitation is sometimes abruptly shut off precisely in regions where downgoing localized inverted-V electrons are observed. Such observations support the existence of a localized process, such as parallel electric fields, above the spacecraft which accelerate the electrons downward and consequently impede the precipitating ion precipitation. Other acceleration events in the cusp are sometimes organized with an apparent cellular structure that suggests Alfven waves or other large-scale phenomena are controlling the localized potentials. We examine several cusp encounters by the FAST satellite where the modulation of energetic session on acceleration particle populations reveals evidence of localized acceleration, most likely by parallel electric fields.

  18. Electric field observations of time constants related to charging and charge neutralization processes in the ionosphere

    NASA Technical Reports Server (NTRS)

    Maynard, N. C.; Evans, D. S.; Troim, J.

    1982-01-01

    The Polar 5 electric field results are reviewed, and the transients from Polar 3 are presented. The phenomena are discussed from the standpoint of space charge. On the basis of the Polar 5 results, the large magnitude of the electric field from Polar 3 is seen as indicating that the observed space charge was probably within a few km or less of the payload. Reference is made to Cole's prediction (1960) that charges in the ionosphere would reach equilibrium with a time constant of the order of a few microsec. The processes involved in the two cases presented here require time constants of the order of ms. If the sheath dimensions are taken to be between 50 and 100 m, which is not considered unreasonable in view of the electric field measurements, then a qualitative estimate of the neutralization time would be the transit time for ions across the sheath. Since the kinetic velocity of a 1-eV proton is approximately 14 m/s, it would traverse the distance in 4 to 8 ms, assuming freedom of movement across magnetic field lines. This is the order of the decay times observed on Polar 5.

  19. Constraints on common envelope magnetic fields from observations of jets in planetary nebulae

    NASA Astrophysics Data System (ADS)

    Tocknell, James; De Marco, Orsola; Wardle, Mark

    2014-04-01

    The common envelope (CE) interaction describes the swallowing of a nearby companion by a growing, evolving star. CEs that take place during the asymptotic giant branch phase of the primary may lead to the formation of a planetary nebula (PN) with a post-CE close binary in the middle. We have used published observations of masses and kinematics of jets in four post-CE PN to infer physical characteristics of the CE interaction. In three of the four systems studied, Abell 63, ETHOS 1 and the Necklace PN, the kinematics indicate that the jets were launched a few thousand years before the CE and we favour a scenario where this happened before Roche lobe overflow, although better models of wind accretion and wind Roche lobe overflow are needed. The magnetic fields inferred to launch pre-CE jets are of the order of a few gauss. In the fourth case, NGC 6778, the kinematics indicate that the jets were launched about 3000 yr after the CE interaction. Magnetic fields of the order of a few hundreds to a few thousands gauss are inferred in this case, approximately in line with predictions of post-CE magnetic fields. However, we remark that in the case of this system, we have not been able to find a reasonable scenario for the formation of the two jet pairs observed: the small orbital separation may preclude the formation of even one accretion disc able to supply the necessary accretion rate to cause the observed jets.

  20. Solar Wind Interaction with Lunar Magnetic Fields: ARTEMIS Observations and Correlations with Surface Properties

    NASA Astrophysics Data System (ADS)

    Halekas, J. S.; Blewett, D. T.; Poppe, A. R.; Brain, D. A.

    2014-12-01

    Lunar magnetic fields, though small in scale and comparatively weak, have surprisingly significant effects on the incoming plasma, and a number of observations suggest that their presence may locally alter the space weathering of the surface. Recent observations from Kaguya and Chandrayaan have shown that lunar magnetic anomalies efficiently reflect incoming solar wind protons, providing substantial shielding of portions of the crust, with potential implications for both space weathering and surface sputtering. The two ARTEMIS probes have made a number of low-altitude (tens of kilometers) passes over regions with moderately strong crustal magnetic fields, at local times both near the sub-solar point and at the terminator. Several such passes occurred over a region of the surface containing unusual albedo markings - or "swirls" - that could indicate a local reduction in space weathering. We investigate the ARTEMIS low-altitude passes in detail, focusing on how the observed reflected protons and other local modifications of charged particle distributions and electromagnetic fields relate to the properties of the surface.

  1. Reconstructing solar magnetic fields from historical observations. I. Renormalized Ca K spectroheliograms and pseudo-magnetograms

    NASA Astrophysics Data System (ADS)

    Pevtsov, Alexei A.; Virtanen, Ilpo; Mursula, Kalevi; Tlatov, Andrey; Bertello, Luca

    2016-01-01

    Aims: The present work is the first in a series of articles that develop a new proxy to represent the evolution of magnetic activity in past solar cycles by combining the information from historical Ca II K line spectroheliograms and sunspot magnetic field measurements. Methods: We use synoptic (Carrington) maps from 1915-1985 that were derived from daily Ca K line observations at Mount Wilson Observatory to identify the chromospheric plages and to create synoptic pseudo-magnetograms. We use historical observations of sunspot magnetic fields from 1917 to the present to assign polarity to pixels situated within plages. The original Ca K spectroheliograms are nonuniform in their brightness, and we develop a novel approach to re-normalize their intensities. Results: We show that a homogeneous long-term series of pseudo-magnetograms can be successfully constructed by combining sunspot field measurements and plages with renormalized intensities. In our tests, about 80% of pixels situated within plages showed the same magnetic polarity as the synoptic magnetograms taken with the Kitt Peak Vacuum Telescope. Finally, we discuss possible approaches to further improve the agreement between observed and pseudo-magnetograms.

  2. Observations of the reappearance of polar coronal holes and the reversal of the polar magnetic field

    NASA Technical Reports Server (NTRS)

    Webb, D. F.; Davis, J. M.; Mcintosh, P. S.

    1984-01-01

    Observational data relating to the evolution of the polar magnetic field around sunspot maximum is examined. Particular emphasis is given to coronal hole observations performed during the last two solar maxima. Long-term averages of the latitudinal dependence of the photospheric magnetic field and the evolutionary pattern of the polar crown filaments are used to trace the poleward motion of the reversal of the large-scale field and are compared to the redevelopment of polar holes. Within the context of phenomenological models of the solar cycle, it is concluded that: (1) the process of polarity reversal and redevelopment of polar holes is discontinuous, with surges of flux of old-cycle polarity interrupting the poleward migration of new-cycle flux; (2) contrary to the Babcock (1961) hypothesis, the polar crown disappears months after the magnetic pole reversal; and (3) the observations support suggestions of a poleward meridional flow around solar maximum that cannot be accounted for by Leighton-type (1964) diffusion.

  3. Validation of EGSIEM gravity field products with globally distributed in situ ocean bottom pressure observations

    NASA Astrophysics Data System (ADS)

    Poropat, Lea; Bergmann-Wolf, Inga; Flechtner, Frank; Dobslaw, Henryk

    2016-04-01

    Time variable global gravity field models that are processed by different research institutions all across Europe are currently compared and subsequently combined within the "European Gravity Field Service for Improved Emergency Management (EGSIEM)" project funded by the European Union. To objectively assess differences between the results from different groups, and also to evaluate the impact of changes in the data processing at an individual institution in preparation of a new data release, a validation of the final GRACE gravity fields against independent observations is required. 
For such a validation, we apply data from a set of globally distributed ocean bottom pressure sensors. The in situ observations have been thoroughly revised for outliers, instrumental drift and jumps, and were additionally reduced for tides. GRACE monthly mean solutions are then validated with the monthly resampled in situ observations. The validation typically concentrates on seasonal to interannual signals, but in case of GRACE-based series with daily sampling available from, e.g., Kalman Smoother Solutions, also sub-monthly signal variability can be assessed.

  4. OBSERVATIONAL EVIDENCE OF CHANGING PHOTOSPHERIC VECTOR MAGNETIC FIELDS ASSOCIATED WITH SOLAR FLARES

    SciTech Connect

    Su, J. T.; Jing, J.; Wang, H. M.; Mao, X. J.; Wang, X. F.; Zhang, H. Q.; Deng, Y. Y.; Guo, J.; Wang, G. P.

    2011-06-01

    Recent observations have provided evidence that the solar photospheric magnetic fields could have rapid and permanent changes in both longitudinal and transverse components associated with major flares. As a result, the Lorentz force (LF) acting on the solar photosphere and solar interior could be perturbed, and the change of LF is always nearly in the downward direction. However, these rapid and permanent changes have not been systematically investigated, yet, using vector magnetograms. In this paper, we analyze photospheric vector magnetograms covering five flares to study the evolution of photospheric magnetic fields. In particular, we investigate two-dimensional spatial distributions of the changing LF. Around the major flaring polarity inversion line, the net change of the LF is directed downward in an area of {approx}10{sup 19} cm{sup 2} for X-class flares. For all events, the white-light observations show that sunspots darken in this location after flares, and magnetic fields become more inclined, which is consistent with the ideas put forward by Hudson et al. and Fisher et al., and observations.

  5. On the motion of electrons in the slow electric field fluctuations observed by Viking

    SciTech Connect

    Hultqvist, B. )

    1991-11-01

    Results are presented of calculations of the motion of electrons in slow, large-amplitude fluctuations of the electric field, which have been observed by means of the Swedish satellite Viking. The E component seen by the ionospheric electrons, entering the acceleration region from below, is assumed to vary along the path of the electrons along the magnetic field lines in the way that Viking recorded along its more or less horizontal path through, or above, the acceleration region. Although this is a simplified model, it is expected to illustrate the effect of the E{parallel} fluctuations on the cold electrons, which enter the acceleration region more realistically than in the earlier, highly simplified model used by hultqvist (1988). The results of the calculations show that temporal variations of E{parallel} of the kind observed by Viking easily can bring the electrons to the top of an acceleration region, which extends 1,000-10,000 km along the magnetic field lines, with energies in the range 100 eV to several keV, as have been observed.

  6. Sediment deposition from Tropical Storm Lee in the upper Chesapeake Bay: field observations and model predictions

    NASA Astrophysics Data System (ADS)

    Palinkas, C. M.; Halka, J. P.; Li, M.; Sanford, L. P.; Cheng, P.

    2012-12-01

    Episodic flood and storm events are important drivers of sediment dynamics in estuarine and marine environments. Event-driven sedimentation has been well-documented by field and modeling studies. Yet, few studies have integrated field observations and modeling results to overcome the limitations inherent in both techniques. A unique opportunity to integrate field observations and model results was provided in late August/early September 2011 with the passage of Hurricane Irene and the remnants of Tropical Storm Lee in the Chesapeake Bay region. These storms differed in their timing, track, and impact on the Bay region - Hurricane Irene was primarily a wind/resuspension event, whereas TS Lee was a hydrological/deposition event, with the second largest discharge of the Susquehanna River on record. Because these two storms occurred within a relatively short period of time, both are potentially represented in the sediment record obtained during rapid-response cruises in September and October 2011. The resulting sediment deposit was recognized in cores using classic flood-sediment signatures (fine grain size, uniform 7Be activity, physical stratification in x-radiographs) and was found to be <4 cm, thickest in the upper Bay. Model runs conducted for TS Lee generally agreed with these estimates. One exception with physical stratification but no 7Be activity appears to be due to extreme wave activity during Hurricane Irene. Integration of observations and modeling in this case greatly improved understanding of the transport and fate of flood sediments in the Chesapeake Bay.

  7. Magnetospheric Multiscale Satellites Observations of Parallel Electric Fields Associated with Magnetic Reconnection.

    PubMed

    Ergun, R E; Goodrich, K A; Wilder, F D; Holmes, J C; Stawarz, J E; Eriksson, S; Sturner, A P; Malaspina, D M; Usanova, M E; Torbert, R B; Lindqvist, P-A; Khotyaintsev, Y; Burch, J L; Strangeway, R J; Russell, C T; Pollock, C J; Giles, B L; Hesse, M; Chen, L J; Lapenta, G; Goldman, M V; Newman, D L; Schwartz, S J; Eastwood, J P; Phan, T D; Mozer, F S; Drake, J; Shay, M A; Cassak, P A; Nakamura, R; Marklund, G

    2016-06-10

    We report observations from the Magnetospheric Multiscale satellites of parallel electric fields (E_{∥}) associated with magnetic reconnection in the subsolar region of the Earth's magnetopause. E_{∥} events near the electron diffusion region have amplitudes on the order of 100  mV/m, which are significantly larger than those predicted for an antiparallel reconnection electric field. This Letter addresses specific types of E_{∥} events, which appear as large-amplitude, near unipolar spikes that are associated with tangled, reconnected magnetic fields. These E_{∥} events are primarily in or near a current layer near the separatrix and are interpreted to be double layers that may be responsible for secondary reconnection in tangled magnetic fields or flux ropes. These results are telling of the three-dimensional nature of magnetopause reconnection and indicate that magnetopause reconnection may be often patchy and/or drive turbulence along the separatrix that results in flux ropes and/or tangled magnetic fields. PMID:27341241

  8. Use of real-time tools to support field operations of NSF's Lower Atmosphere Observing Facilities

    NASA Astrophysics Data System (ADS)

    Daniels, M.; Stossmeister, G.; Johnson, E.; Martin, C.; Webster, C.; Dixon, M.; Maclean, G.

    2012-12-01

    NCAR's Earth Observing Laboratory (EOL) operates Lower Atmosphere Observing Facilities (LAOF) for the scientific community, under sponsorship of the National Science Foundation. In order to obtain the highest quality dataset during field campaigns, real-time decision-making critically depends on the availability of timely data and reliable communications between field operations staff and instrument operators. EOL incorporates the latest technologies to monitor the health of instrumentation, facilitate remote operations of instrumentation and keep project participants abreast of changing conditions in the field. As the availability of bandwidth on mobile communication networks and the capabilities of their associated devices (smart phone, tablets, etc.) improved, so has the ability of researchers to respond to rapidly changing conditions and coordinate ever more detailed measurements from multiple remote fixed, portable and airborne platforms. This presentation will describe several new tools that EOL is making available to project investigators and how these tools are being used in a mobile computing environment to support enhanced data collection during field campaigns. LAOF platforms such as radars, aircraft, sondes, balloons and surface stations all rely on displays of real-time data for their operations. Data from sondes are ingested into the Global Telecommunications System (GTS) for assimilation into regional forecasting models that help guide project operations. Since many of EOL's projects occur around the globe and at the same time instrument complexity has increased, automated monitoring of instrumentation platforms and systems has become essential. Tools are being developed to allow remote instrument control of our suite of observing systems where feasible. The Computing, Data and Software (CDS) Facility of EOL develops and supports a Field Catalog used in field campaigns for nearly two decades. Today, the Field Catalog serves as a hub for the

  9. Intercomparison of surface heat transfer in the Arctic for multiple reanalyses, satellite data and field observations

    NASA Astrophysics Data System (ADS)

    Repina, Irina; Mazilkina, Alexandra; Ivanov, Vladimir

    2015-04-01

    This study evaluated surface heat fluxes from reanalyses (ERAInterim, NCEP/NCAR, ASR) in the Arctic Ocean during summer and fall. Several types of surface conditions are compared: very new ice cover during a period of low temperature, ice-free conditions, ice with leads and melt ponds, pack ice and marginal ice zone. Meteorological and micrometeorological observations were used to validate the temperature profiles and surface heat fluxes in the major reanalyses. We use data from Nansen and Amundsen basins observation system (NABOS) project to evaluate the performance of reanalyses forin the Arctic Ocean. The NABOS field experiment was carried out in the central part of the Arctic and in the eastern Arctic seas during summer and fall period of 2004-2009 and 2013. Compared data arrays are independent and sufficiently detailed to perform trustworthy evaluations. With the explicit treatment of the ice concentration, ERA-Interim generally reproduces the surface heat transfer, while NCEP/NCAR, based on a 55% concentration threshold, shows obvious disagreement with the observations in highly ice-covered and ice-free situations. The spatial and temporal patterns of the resulting flux fields are investigated and compared with those derived from satellite observations such as HOAPS, from blended data such as AOFLUX (in the open water cases). A computation of the sensible heat flux at the surface is formulated on the basis of spatial variations of the surface temperature estimated from satellite data. Based on the comparison of field experiments data, satellite-derived data and reanalysis the causes of underestimation of the values of turbulent heat fluxes in the Arctic modern reanalysis are investigated. Obtained differences are related to the temperature and structural inhomogeneity of the surface and the development of space-organized convection fields. Reanalyses data are sometimes used to calculate the surface heat budgets over polynyas to estimate ice production in

  10. A Cosmic Train Wreck: JVLA Radio Observations of the HST Frontier Fields Cluster Abell 2744

    NASA Astrophysics Data System (ADS)

    Pearce, Connor; Van Weeren, Reinout J.; Jones, Christine; Forman, William R.; Ogrean, Georgiana A.; Andrade-Santos, Felipe; Kraft, Ralph P.; Dawson, William; Brüggen, Marcus; Roediger, Elke; Bulbul, Esra; Mroczkowski, Tony

    2016-01-01

    The galaxy cluster mergers observed in the HST Frontier Fields represent some of the most energetic events in the Universe. Major cluster mergers leave distinct signatures in the ICM in the form of shocks, turbulence, and diffuse cluster radio sources. These diffuse radio sources, so-called radio relics and halos, provide evidence for the acceleration of relativistic particles and the presence of large scale magnetic fields in the ICM. Observations of these halos and relics allow us to (i) study the physics of particle acceleration and its relation with shocks and turbulence in the ICM and (ii) constrain the dynamical evolution of the merger eventsWe present Jansky Very Large Array 1-4 GHz observations of the Frontier cluster Abell 2744. We confirm the presence of the known giant radio halo and radio relic via our deep radio images. Owing to the much greater sensitivity of the JVLA compared to previous observations, we are able to detect a previously unobserved long Mpc-size filament of synchrotron emission to the south west of the cluster core. We also present a radio spectral index image of the diffuse cluster emission to test the origin of the radio relic and halo, related to the underlying particle acceleration mechanism. Finally, we carry out a search for radio emission from the 'jellyfish' galaxies in A2744 to estimate their star formation rate. These highly disturbed galaxies are likely influenced by the cluster merger event, although the precise origin of these galaxies is still being debated.

  11. Use of Observation-Based Aerosol Fields for Detailed Cloud-Scale Modeling Studies

    NASA Astrophysics Data System (ADS)

    Fridlind, A. M.; Vogelmann, A. M.; Ackerman, A. S.; Endo, S.

    2014-12-01

    Within the realm of detailed large-eddy simulation studies with size-resolved microphysics, substantial uncertainties exist regarding the ability of any given model to accurately reproduce basic aspects of cloud microphysics that interact with ambient aerosol properties, such as precipitation formation and evolution. Modeling studies intended to reproduce specific observed cloud fields must also to some degree simplify the complexity of aerosol conditions, and usually lack sufficient measurements to well constrain the most relevant aerosol properties. Here we describe derivation and use of spatiotemporally varying fields of multi-modal aerosol size distributions for 60-hour simulations of boundary-layer clouds observed over Oklahoma during the RACORO campaign. Cases include forced as well as freely convecting shallow clouds, and some warm precipitation. We investigate the sensitivity of simulations to observation-derived aerosol inputs, including hygroscopicity parameter and size distribution properties. Sensitivity is examined in the context of the ability of the simulations to accurately reproduce relevant macrophysical and microphysical cloud properties observed, including droplet size dispersion.

  12. Estimation of Transpiration and Water Use Efficiency Using Satellite and Field Observations

    NASA Technical Reports Server (NTRS)

    Choudhury, Bhaskar J.; Quick, B. E.

    2003-01-01

    Structure and function of terrestrial plant communities bring about intimate relations between water, energy, and carbon exchange between land surface and atmosphere. Total evaporation, which is the sum of transpiration, soil evaporation and evaporation of intercepted water, couples water and energy balance equations. The rate of transpiration, which is the major fraction of total evaporation over most of the terrestrial land surface, is linked to the rate of carbon accumulation because functioning of stomata is optimized by both of these processes. Thus, quantifying the spatial and temporal variations of the transpiration efficiency (which is defined as the ratio of the rate of carbon accumulation and transpiration), and water use efficiency (defined as the ratio of the rate of carbon accumulation and total evaporation), and evaluation of modeling results against observations, are of significant importance in developing a better understanding of land surface processes. An approach has been developed for quantifying spatial and temporal variations of transpiration, and water-use efficiency based on biophysical process-based models, satellite and field observations. Calculations have been done using concurrent meteorological data derived from satellite observations and four dimensional data assimilation for four consecutive years (1987-1990) over an agricultural area in the Northern Great Plains of the US, and compared with field observations within and outside the study area. The paper provides substantive new information about interannual variation, particularly the effect of drought, on the efficiency values at a regional scale.

  13. Plasma and Field Observations at the Day-Side, Equatorial Magnetopause, Boundary Layers and Magnetosphere

    NASA Technical Reports Server (NTRS)

    Chandler, M. O.; Craven, P. D.; Moore, T. E.; Coffey, V. N.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    The Polar spacecraft's orbit has precessed in latitude to an orientation that places it at the dayside magnetopause every 18 hours. In this configuration the various regions near the magnetopause(LLBL, turbulent boundary layer, magnetosphere, and magnetosheath) are sampled with high temporal and spatial resolution. These observational periods-ranging from several minutes to more than two hours-provide an unprecedented look at plasma conditions in these regions. Initial analysis of the low-energy ion data from TIDE reveal plasmaspheric-like ions within the turbulent boundary layer. Within this layer, circularly polarized waves accelerate these ions to 30-40 kilometers per second perpendicular to the local magnetic field. These relatively high velocities allow the H(+) to be observed above the -2V spacecraft potential. They also put the low-density O(+) in the higher-energy, higher sensitivity channels such that densities of order 10e-2 can be observed.

  14. In vivo observation of tree drought response with low-field NMR and neutron imaging

    DOE PAGESBeta

    Malone, Michael W.; Yoder, Jacob; Hunter, James F.; Espy, Michelle A.; Dickman, Lee T.; Nelson, Ron O.; Vogel, Sven C.; Sandin, Henrik J.; Sevanto, Sanna

    2016-05-01

    Using a simple low-field NMR system, we monitored water content in a living tree in a greenhouse over 2 months. By continuously running the system, we observed changes in tree water content on a scale of half an hour. The data showed a diurnal change in water content consistent both with previous NMR and biological observations. Neutron imaging experiments show that our NMR signal is primarily due to water being rapidly transported through the plant, and not to other sources of hydrogen, such as water in cytoplasm, or water in cell walls. After accounting for the role of temperature inmore » the observed NMR signal, we demonstrate a change in the diurnal signal behavior due to simulated drought conditions for the tree. Lastly, these results illustrate the utility of our system to perform noninvasive measurements of tree water content outside of a temperature controlled environment.« less

  15. In vivo Observation of Tree Drought Response with Low-Field NMR and Neutron Imaging

    PubMed Central

    Malone, Michael W.; Yoder, Jacob; Hunter, James F.; Espy, Michelle A.; Dickman, Lee T.; Nelson, Ron O.; Vogel, Sven C.; Sandin, Henrik J.; Sevanto, Sanna

    2016-01-01

    Using a simple low-field NMR system, we monitored water content in a living tree in a greenhouse over 2 months. By continuously running the system, we observed changes in tree water content on a scale of half an hour. The data showed a diurnal change in water content consistent both with previous NMR and biological observations. Neutron imaging experiments show that our NMR signal is primarily due to water being rapidly transported through the plant, and not to other sources of hydrogen, such as water in cytoplasm, or water in cell walls. After accounting for the role of temperature in the observed NMR signal, we demonstrate a change in the diurnal signal behavior due to simulated drought conditions for the tree. These results illustrate the utility of our system to perform noninvasive measurements of tree water content outside of a temperature controlled environment. PMID:27200037

  16. Theoretical interpretation of the observed interplanetary magnetic field radial variation in the outer solar system

    NASA Technical Reports Server (NTRS)

    Suess, S. T.; Thomas, B. T.; Nerney, S. F.

    1985-01-01

    Observations of the azimuthal component of the IMF are evaluated through the use of an MHD model which shows the effect of magnetic flux tubes opening in the outer solar system. It is demonstrated that the inferred meridional transport of magnetic flux is consistent with predictions by the MHD model. The computed azimuthal and radial magnetic flux deficits are almost identical to the observations. It is suggested that the simplest interpretation of the observations is that meridional flows are created by a direct body force on the plasma. This is consistent with the analytic model of Nerney and Suess (1975), in which such flux deficits in the IMF arise naturally from the meridional gradient in the spiralling field.

  17. Radio observations of interplanetary magnetic field structures out of the ecliptic

    NASA Technical Reports Server (NTRS)

    Fitzenreiter, R. J.; Fainberg, J.; Weber, R. R.; Alvarez, H.; Haddock, F. T.; Potter, W. H.

    1976-01-01

    New observations of the out-of-the ecliptic trajectories of type 3 solar radio bursts have been obtained from simultaneous direction finding measurements on two independent satellite experiments, IMP-6 with spin plane in the ecliptic, and RAE-2 with spin plane normal to the ecliptic. Burst exciter trajectories were observed which originated at the active region and then crossed the ecliptic plane at about 0.8 AU. A considerable large scale north-south component of the interplanetary magnetic field is followed by the exciters. The apparent north-south and east-west angular source sizes observed by the two spacecraft are approximately equal, and range from 25 deg at 600 KHz to 110 deg at 80 KHz.

  18. In vivo Observation of Tree Drought Response with Low-Field NMR and Neutron Imaging.

    PubMed

    Malone, Michael W; Yoder, Jacob; Hunter, James F; Espy, Michelle A; Dickman, Lee T; Nelson, Ron O; Vogel, Sven C; Sandin, Henrik J; Sevanto, Sanna

    2016-01-01

    Using a simple low-field NMR system, we monitored water content in a living tree in a greenhouse over 2 months. By continuously running the system, we observed changes in tree water content on a scale of half an hour. The data showed a diurnal change in water content consistent both with previous NMR and biological observations. Neutron imaging experiments show that our NMR signal is primarily due to water being rapidly transported through the plant, and not to other sources of hydrogen, such as water in cytoplasm, or water in cell walls. After accounting for the role of temperature in the observed NMR signal, we demonstrate a change in the diurnal signal behavior due to simulated drought conditions for the tree. These results illustrate the utility of our system to perform noninvasive measurements of tree water content outside of a temperature controlled environment. PMID:27200037

  19. Dust emissions of organic soils observed in the field and laboratory

    NASA Astrophysics Data System (ADS)

    Zobeck, T. M.; Baddock, M. C.; Guo, Z.; Van Pelt, R.; Acosta-Martinez, V.; Tatarko, J.

    2011-12-01

    . In the laboratory wind tunnel, samples with the same ratio of erodible to non-erodible aggregates as the field soils were abraded and dust emissions were observed with the same sampling system as used in the field wind tunnel. In the dust generator, 5 gm samples < 8 mm diameter of each organic soil were rotated in a 50 cm long tube and the dust generated was observed with the GRIMM during a 20 minute run. Comparisons of the field dust emission rates with the laboratory results will be presented.

  20. Voyager 1 observations of the interstellar magnetic field and the transition from the heliosheath

    SciTech Connect

    Burlaga, L. F.; Ness, N. F. E-mail: nfnudel@yahoo.com

    2014-04-01

    Voyager 1 (V1) has been observing interstellar magnetic fields for more than one year beginning ≈2012/209, when V1 crossed a current sheet, a 'CS0' having the structure of a tangential discontinuity. The inclination of this current sheet is consistent with an interstellar magnetic field B draped on a blunt heliopause. Two other current sheets (sector boundaries) were observed at ≈2012/167 and ≈2011/276 with high inclinations (99° ± 10° and 89° ± 10°, respectively). From 2013.0 to ≈2013.6, the difference between the azimuthal angle λ of B from the Parker spiral angle at the latitude 34.°6 of V1 was λ – λ{sub P} = 22° ± 3° and the corresponding difference of the elevation angle δ was δ – δ{sub P} = 23° ± 8°. During 2012, the deviation from the Parker spiral angle was somewhat smaller. The interstellar magnetic field has a 'west to east polarity,' opposite to the direction of planetary motions. The magnitude of B varied smoothly in the range 0.38-0.59 nT with an average B = 0.486 ± 0.045 after 2012/237.7. The transition from heliosheath to interstellar magnetic fields is related to a 'two-step' increase in the cosmic ray intensity observed by V1 from ≈2012.30 to ≈2012.65. The first step increase began near the end of an unusual 'away-polarity' sector, and it reached a plateau when V1 moved into a 'toward-polarity' sector that ended at CS0. The second step increase began slowly after V1 crossed CS0, and it ended abruptly at 2012/237.728.

  1. Observed Enhancement of Reflectivity and Electric Field in Long-Lived Florida Anvils

    NASA Technical Reports Server (NTRS)

    Dye, James E.; Willett, John C.

    2007-01-01

    A study of two long-lived Florida anvils showed that reflectivity greater than 20 dBZ increased in area, thickness and sometimes magnitude at mid-level well downstream of the convective cores. In these same regions electric fields maintained strengths greater than 10 kV m(sup -1) for many tens of minutes and became quite uniform over tens of kilometers. Millimetric aggregates persisted at 9 to 10 km for extended times and distances. Aggregation of ice particles enhanced by strong electric fields might have contributed to reflectivity growth in the early anvil, but is unlikely to explain observations further out in the anvil. The enhanced reflectivity and existence of small, medium and large ice particles far out into the anvil suggest that an updraft was acting, perhaps in weak convective cells formed by instability generated from the evaporation and melting of falling ice particles. We conclude that charge separation must have occurred in these anvils, perhaps at the melting level but also at higher altitudes, in order to maintain fields greater than 10 kV m(sup -1) at 9 to 10 km for extended periods of time over large distances. We speculate that charge separation occurred as a result of ice-ice particle collisions (without supercooled water being present) via either a noninductive or perhaps even an inductive mechanism, given the observed broad ice particle spectra, the strong pre-existing electric fields and the many tens of minutes available for particle interactions. The observations, particularly in the early anvil, show that the charge structure in these anvils was quite complex.

  2. Observed Enhancement of Reflectivity and Electric Field in Long-Lived Florida Anvils

    NASA Technical Reports Server (NTRS)

    Dye, James E.; Willett, John C.

    2007-01-01

    A study of two long-lived Florida anvils showed that reflectivity >20 dBZ increased in area, thickness and sometimes magnitude at mid-level well downstream of the convective cores. In these same regions electric fields maintained strengths >10 kV m1 for many tens of minutes and became quite uniform over tens of kilometers. Millimetric aggregates persisted at 9 to 10 km for extended times and distances. Aggregation of ice particles enhanced by strong electric fields might have contributed to reflectivity growth in the early anvil, but is unlikely to explain observations further out in the anvil. The enhanced reflectivity and existence of small, medium and large ice particles far out into the anvil suggest that an updraft was acting, perhaps in weak convective cells formed by instability generated from the evaporation and melting of falling ice particles. We conclude that charge separation must have occurred in these anvils, perhaps at the melting level but also at higher altitudes, in order to maintain fields >10 kV m 1 at 9 to 10 km for extended periods of time over large distances. We speculate that charge separation occurred as a result of ice-ice particle collisions (without supercooled water being present) via either a non-inductive or perhaps even an inductive mechanism, given the observed broad ice particle spectra, the strong pre-existing electric fields and the many tens of minutes available for particle interactions. The observations, particularly in the early anvil, show that the charge structure in these anvils was quite complex.

  3. An Evaluation of Tropical Cyclogenesis Theories through Intercomparison of Field Experiment Observations

    NASA Astrophysics Data System (ADS)

    Helms, C. N.; Hart, R. E.

    2011-12-01

    The process by which tropical cyclones evolve from loosely organized convective clusters into well organized systems is still poorly understood. A number of theories have been proposed to explain this evolution based on vortex dynamics, adiabatic processes, and diabatic processes. Due to the data sparse location in which many of these systems develop, many studies of tropical cyclogenesis theory are limited to either a few case studies or are forced to rely on simulations to critically evaluate the theories. The recent PREDICT and GRIP field experiments have provided a new opportunity to examine these theories using unusually dense observations. The present study aims at using this new data in conjunction with data from previous field experiments, such as NAMMA, GATE, and TOGA COARE, to evaluate three existing theories: top-down vortex merger (Ritchie and Holland, 1997; Simpson et al., 1997), top-down shower-head (Emanuel, 1993; Bister and Emanuel, 1997), and bottom-up vortex merger (Montgomery and Enagonio, 1998; Enagonio and Montgomery, 2001). Additionally, these observations are used to briefly examine the newer marsupial framework for tropical cyclogenesis in African easterly waves (Dunkerton et al. 2009). The processes associated with each of these theories create unique signatures in wind, vorticity, potential temperature, and humidity fields. Timelines of these fields, created from composited mean dropsonde soundings, are used to determine the system-wide evolution. Further, the temporal evolution of sub-system processes, which are minimized or removed as a result of the compositing process, are identified in isobaric surface plot series. While previous studies have shown that no theory completely explains tropical cyclogenesis, it is hoped that a thorough analysis of these data sets will highlight both consistencies and inconsistencies between theory and observation.

  4. Observed chlorine concentrations during Jack Rabbit I and Lyme Bay field experiments

    NASA Astrophysics Data System (ADS)

    Hanna, Steven; Chang, Joseph; Huq, Pablo

    2016-01-01

    As part of planning for a series of field experiments where large quantities (up to 20 tons) of pressurized liquefied chlorine will be released, observations from previous chlorine field experiments are analyzed to estimate the ranges of chlorine concentrations expected at various downwind distances. In five field experiment days during the summer 2010 Jack Rabbit I (JR I) field trials, up to two tons of chlorine were released and concentrations were observed at distances, x, from 25 to 500 m. In the 1927 Lyme Bay (LB) experiments, there were four days of trials, where 3-10 tons of chlorine were released in about 15 min from the back of a ship. Concentrations were sampled at LB from four ships sailing across the cloud path at downwind distances in the range from about 350 to 3000 m. Thus, the distances from which JR I concentrations were available slightly overlapped the LB distances. One-minute arc-maximum chlorine concentrations, C (g/m3), were analyzed from four JR I trials and two LB trials. Normalized concentrations (Cu/Q) were plotted versus x (m), where u (m/s) is measured wind speed at heights of 2-10 m and Q (g/s) is continuous mass release rate. It is found that the JR I and LB Cu/Q observations smoothly merge with each other and fall along a line with approximate slope of -2 at distances beyond about 200 m (i.e., Cu/Q is proportional to x-2). At x < 200 m, where dense gas effects are more important, the slope is less (about -1.5). Most of the data points are within a factor of two of the "best-fit" line.

  5. Balloon observations of ultra-low-frequency waves in the electric field above the South Pole

    SciTech Connect

    Liao, B.; Benbrrook, J.R.; Bering E.A. III; Byrne, G.J.; Theall, J.R. )

    1988-01-01

    The physics of ultra-low-frequency waves in the magnetosphere, near the cusp and in the polar cap, is important because this region is one where ultra-low-frequency wave energy from the magnetopause can most easily enter the magnetosphere. During the 1985-1986 South Pole balloon campaign, eight stratospheric balloon payloads were launched from Amundsen-Scott Station, South Geographic Pole, Antarctica, to record data on ultra-low-frequency waves. The payloads were instrumented with three-axis double-probe electric field detectors and X-ray scintillation counters. This paper concentrates on the third flight of this series, which was launched at 2205 universal time on 21 December 1985. Good data were received from the payload until the transmitter failed at 0342 universal time on 22 December. During most of the four hours that the balloon was afloat, an intense ultra-low-frequency wave event was in progress. The electric-field data from this period have been examined in detail and compared with magnetic field data, obtained with ground-based fluxgate and induction magnetometers to determine the characteristics of the waves. After float was reached, the electric-field data in figure 1 show large-amplitude, quasi-periodic fluctuations suggesting the presence of intense ultra-low-frequency wave activity. In conclusion, the electric-field signature observed from flight 3 appears to have been essentially an electrostatic event or possibly a short-wavelength hydromagnetic wave with a varying and interesting polarization character. The authors are continuing the analysis of the data to determine the source of the observed ultra-low-frequency waves.

  6. Historical observations of solar wind effects on the high latitude geomagnetic field.

    NASA Astrophysics Data System (ADS)

    Egeland, A.; Deehr, C.

    2012-04-01

    The interplanetary magnetic field (IMF) significantly influences the diurnal variations of the high latitude geomagnetic field with an increased (decreased) horizontal field intensity when the IMF is directed from (towards) the Sun to (from) the Earth. Magnetic observatories at high latitudes were non-existent before the 1920s, but glimpses of the IMF before that time may be extracted from the magnetic observations of Roald Amundsen, who overwintered for two years in the high Canadian arctic to locate the north magnetic dip pole. New analysis of Amundsen's high-quality geomagnetic recordings from 1903 to 1905, yields information about the Earth magnetic field and the solar wind 50 years before it was known to exist. When the H component from the mean diurnal variation is plotted as a function of time for each of the Carrington rotation periods No. 677, 678 and 679 (May, June and July, 1904) the IMF is clearly seen to change direction four times with each 27.3 day rotation. When the days with IMF toward and away from the Sun are separated, a skewed diurnal distribution of the magnetic elements illustrates the overwhelming effect of the IMF during the summer months. Thus, the interactions of the magnetosphere by the solar wind 100 years ago are consistent with the magnitude and variations observed during the space age. In addition, the high latitude diurnal geomagnetic variations support the view that the Svalgaard-Mansurov Effect is associated with the Earth's magnetospheric convection, driven mainly by IMF By. The geomagnetic field (the H-component) is increased when IMF By is positive, but significant reduced when the By-component change direction.

  7. Using MERRA Gridded Innovations for Quantifying Uncertainties in Analysis Fields and Diagnosing Observing System Inhomogeneities

    NASA Technical Reports Server (NTRS)

    da Silva, Arlindo; Redder, Christopher

    2010-01-01

    MERRA is a NASA reanalysis for the satellite era using a major new version of the Goddard Earth Observing System Data Assimilation System Version 5 (GEOS-5). The project focuses on historical analyses of the hydrological cycle on a broad range of weather and climate time scales and places the NASA EOS suite of observations in a climate context. The characterization of uncertainty in reanalysis fields is a commonly requested feature by users of such data. While intercomparison with reference data sets is common practice for ascertaining the realism of the datasets, such studies typically are restricted to long term climatological statistics and seldom provide state dependent measures of the uncertainties involved. In principle, variational data assimilation algorithms have the ability of producing error estimates for the analysis variables (typically surface pressure, winds, temperature, moisture and ozone) consistent with the assumed background and observation error statistics. However, these "perceived error estimates" are expensive to obtain and are limited by the somewhat simplistic errors assumed in the algorithm. The observation minus forecast residuals (innovations) by-product of any assimilation system constitutes a powerful tool for estimating the systematic and random errors in the analysis fields. Unfortunately, such data is usually not readily available with reanalysis products, often requiring the tedious decoding of large datasets and not so-user friendly file formats. With MERRA we have introduced a gridded version of the observations/innovations used in the assimilation process, using the same grid and data formats as the regular datasets. Such dataset empowers the user with the ability of conveniently performing observing system related analysis and error estimates. The scope of this dataset will be briefly described. We will present a systematic analysis of MERRA innovation time series for the conventional observing system, including maximum

  8. A comparison of predicted and observed turbulent wind fields present in natural and internal wind park environments

    SciTech Connect

    Kelly, N D; Wright, A D

    1991-10-01

    This paper assesses the accuracy of simulated wind fields for both the natural flow and that within a wind park environment. The simulated fields are compared with the observed ones in both the time and frequency domains. Actual measurements of the wind fields and the derived kinematic scaling parameters upwind and downwind of a large San Gorgonio Pass wind park are used. The deviations in the modeled wind field from the observed are discussed. 10 refs., 6 figs., 2 tabs.

  9. Constraints on Common Envelope Magnetic Fields from Observations of Jets in Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    De Marco, Orsola; Tocknell, J.; Wardle, M.

    2014-01-01

    The common envelope (CE) interaction describes the swallowing of a nearby companion by a growing, evolving star. CEs that take place during the asymptotic giant branch phase of the primary and may lead to the formation of a planetary nebula (PN) with a post-CE close binary in the middle. We have used published observations of masses and kinematics of jets in four post-CE PN to infer physical characteristics of the CE interaction. In three of the four systems studied, Abell 63, ETHOS 1 and the Necklace PN, the kinematics indicate that the jets were launched a few thousand years before the CE and we favour a scenario where this happened before Roche lobe overflow, although better models of wind accretion and wind Roche lobe overflow are needed. The magnetic fields inferred to launch pre-CE jets are of the order of a few Gauss. In the fourth case, NGC 6778, the kinematics indicate that the jets were launched about 3000 years after the CE interaction. Magnetic fields of the order of a few hundreds to a few thousands Gauss are inferred in this case, approximately in line with predictions of post-CE magnetic fields. However, we remark that in the case of this system, we cannot find a reasonable scenario for the formation of the two jet pairs observed: the small orbital separation would preclude the formation of even one accretion disk able to supply the necessary accretion rate to cause the observed jets. Additional and improved observations of post-CE PN will provide a powerful tool to constrain the CE interaction.

  10. The robustness of using near-UV observations to detect and study exoplanet magnetic fields

    NASA Astrophysics Data System (ADS)

    Turner, J.; Christie, D.; Arras, P.; Johnson, R.

    2015-10-01

    Studying the magnetic fields of exoplanets will allow for the investigation of their formation history, evolution, interior structure, rotation period, atmospheric dynamics, moons, and potential habitability. We previously observed the transits of 16 exoplanets as they crossed the face of their host-star in the near-UV in an attempt to detect their magnetic fields (Turner et al. 2013; Pearson et al. 2014; Turner et al. in press). It was postulated that the magnetic fields of all our targets could be constrained if their near-UV light curves start earlier than in their optical light curves (Vidotto et al. 2011). This effect can be explained by the presence of a bow shock in front of the planet formed by interactions between the stellar coronal material and the planet's magnetosphere. Furthermore, if the shocked material in the magnetosheath is optically thick, it will absorb starlight and cause an early ingress in the near- UV light curve. We do not observe an early ingress in any of our targets (See Figure 1 for an example light curve in our study), but determine upper limits on their magnetic field strengths. All our magnetic field upper limits are well below the predicted magnetic field strengths for hot Jupiters (Reiners & Christensen 2010; Sanchez-Lavega 2004). The upper limits we derived assume that there is an absorbing species in the near-UV. Therefore, our upper limits cannot be trusted if there is no species to cause the absorption. In this study we simulate the atomic physics, chemistry, radiation transport, and dynamics of the plasma characteristics in the vicinity of a hot Jupiter using the widely used radiative transfer code CLOUDY (Ferland et al. 2013). Using CLOUDY we have investigated whether there is an absorption species in the near-UV that can exist to cause an observable early ingress. The number density of hydrogen in the bow shock was varied from 104 - -108 cm-3 and the output spectrum was calculated (Figure 2) and compared to the input

  11. Constraining the Magnetic Fields of Transiting Exoplanets through Ground-based Near-UV Observations

    NASA Astrophysics Data System (ADS)

    Turner, Jake; Smart, B. M.; Pearson, K. A.; Biddle, L. I.; Cates, I. T.; Berube, M.; Thompson, R. M.; Smith, C. W.; Teske, J. K.; Hardegree-Ullman, K. K.; Robertson, A. N.; Crawfod, B. E.; Zellem, R.; Nieberding, M. N.; Raphael, B. A.; Tombleson, R.; Cook, K. L.; Hoglund, S.; Hofmann, R. A.; Jones, C.; Towner, A.; Small, L. C.; Walker-LaFollette, A. M.; Sanford, B.; Griffith, C. C.; Sagan, T.

    2013-10-01

    We observed the primary transits of the exoplanets CoRoT-1b, HAT-P-1b, HAT-P-13b, HAT-P-22b, TrES-2b, TrES-4b, WASP-12b, WASP-33b, WASP-44b, WASP-48b, and WASP77A-b in the near-ultraviolet photometric band in an attempt to detect their magnetic fields and update their planetary parameters. Vidotto et al. (2011) suggest that the magnetic fields of these targets could be constrained if their near-UV light curves show an early ingress compared to their optical light curves, while their egress remain unaffected. We do not observe this effect in any of our targets, however, we have determined an upper limit on their magnetic field strengths. Our results are consistent with observations of TrES-3b and HAT-P-16b which both have had upper limits on their magnetic fields found using this method. We find abnormally low field strengths for all our targets. Due to this result we advocate for follow-up studies on the magnetic fields of all our targets using other detection methods (such as radio emission and magnetic star-planet interactions) and other telescopes capable of achieving a better near-UV cadence to verify our findings and the techniques of Vidotto et al. (2011). We find that the near-UV planetary radii of all our targets are consistent within error of their optical radii. Our data includes the only published near-UV light curves of CoRoT-1b, HAT-P-1b, HAT-P-13b, HAT-P-22b, TrES-2b, TrES-4b, WASP-33b, WASP-44b, WASP-48b, and WASP77A-b. We used an automated reduction pipeline, ExoDRPL, to perform aperture photometry on our data. In addition, we developed a modeling package called EXOMOP that utilizes the Levenberg-Marquardt minimization algorithm to find a least-squares best fit and a differential evolution Markov Chain Monte Carlo algorithm to find the best fit to the light curve. To constrain the red noise in both fitting models we used the residual permutation (rosary bead), time-averaging, and wavelet method.

  12. Constraining the Magnetic Fields of Transiting Exoplanets through Ground-based Near-UV Observations

    NASA Astrophysics Data System (ADS)

    Turner, Jake; Smart, B.; Pearson, K.; Biddle, L. I.; Cates, I.; Berube, M.; Thompson, R.; Smith, C.; Teske, J. K.; Hardegree-Ullman, K.; Robertson, A.; Crawfod, B.; Zellem, R.; Nieberding, M. N.; Raphael, B. A.; Tombleson, R.; Cook, K.; Hoglund, S.; Hofmann, R.; Jones, C.; Towner, A. P.; Small, L.; Walker-LaFollette, A.; Sanford, B.; Sagan, T.

    2014-01-01

    We observed the primary transits of the exoplanets CoRoT-1b, HAT-P-1b, HAT-P-13b, HAT-P-22b, TrES-2b, TrES-4b, WASP-12b, WASP-33b, WASP-44b, WASP-48b, and WASP77A-b in the near-ultraviolet photometric band in an attempt to detect their magnetic fields and update their planetary parameters. Vidotto et al. (2011) suggest that the magnetic fields of these targets could be constrained if their near-UV light curves show an early ingress compared to their optical light curves, while their egress remain unaffected. We do not observe this effect in any of our targets, however, we have determined an upper limit on their magnetic field strengths. Our results are consistent with observations of TrES-3b and HAT-P-16b which both have had upper limits on their magnetic fields found using this method. We find abnormally low field strengths for all our targets. Due to this result we advocate for follow-up studies on the magnetic fields of all our targets using other detection methods (such as radio emission and magnetic star-planet interactions) and other telescopes capable of achieving a better near-UV cadence to verify our findings and the techniques of Vidotto et al. (2011). We find that the near-UV planetary radii of all our targets are consistent within error of their optical radii. Our data includes the only published near-UV light curves of CoRoT-1b, HAT-P-1b, HAT-P-13b, HAT-P-22b, TrES-2b, TrES-4b, WASP-33b, WASP-44b, WASP-48b, and WASP77A-b. We used an automated reduction pipeline, ExoDRPL, to perform aperture photometry on our data. In addition, we developed a modeling package called EXOMOP that utilizes the Levenberg-Marquardt minimization algorithm to find a least-squares best fit and a differential evolution Markov Chain Monte Carlo algorithm to find the best fit to the light curve. To constrain the red noise in both fitting models we used the residual permutation (rosary bead), time-averaging, and wavelet method.

  13. Global control of merging by the interplanetary magnetic field: Cluster observations of dawnside flank magnetopause reconnection

    NASA Astrophysics Data System (ADS)

    Eriksson, S.; Elkington, S. R.; Phan, T. D.; Petrinec, S. M.; RèMe, H.; Dunlop, M. W.; Wiltberger, M.; Balogh, A.; Ergun, R. E.; André, M.

    2004-12-01

    Detailed Cluster observations of flank magnetopause reconnection are presented for two events on the Northern and the Southern Hemispheric dawnside flanks when the interplanetary magnetic field (IMF) clock angle ? = arctan(By/Bz) is within ˜45° of the equatorial plane. The event selection is based on the relative proximity between the Cluster spacecraft 1 position and the predicted magnetospheric sash where antiparallel merging is expected to develop. MHD simulations performed for the two events indicate that the Cluster spacecraft were passing through the MHD sash region in the Northern Hemisphere on 30 June 2001, while crossing the magnetopause equatorward of the Southern Hemispheric sash on 29 May 2001. Accelerated and decelerated plasma flows relative to the magnetosheath velocity were detected by Cluster on both occasions. The Walén test confirms that the observed ΔV is directly correlated with the predicted magnetic field rotation ΔB/? with the expected direction of the normal magnetic field and so we interpret them as speed changes due to magnetic reconnection. The observed directions of ΔV compare very well with the location of the simulated MHD sash relative to Cluster. The magnetic field shear in the locally tangential plane of the magnetopause ranges between 171° and 177° for the 30 June event in good agreement with antiparallel merging at the MHD sash. The corresponding local field shear for the 29 May event is only 144°, either suggesting a component merging site in the direction of the sash or indicating that Cluster is farther away from the location where the neutral line was initially formed as compared with the 30 June event. A comparison between the projected regions of antiparallel and component merging onto the magnetopause and the quasi-steady direction of plasma acceleration detected by Cluster on 29 May and 30 June support the view that the IMF controls the expected global location of magnetic reconnection at limited regions of the

  14. Observation of soil moisture variability in agricultural and grassland field soils using a wireless sensor network

    NASA Astrophysics Data System (ADS)

    Priesack, Eckart; Schuh, Max

    2014-05-01

    Soil moisture dynamics is a key factor of energy and matter exchange between land surface and atmosphere. Therefore long-term observation of temporal and spatial soil moisture variability is important in studying impacts of climate change on terrestrial ecosystems and their possible feedbacks to the atmosphere. Within the framework of the network of terrestrial environmental observatories TERENO we installed at the research farm Scheyern in soils of two fields (of ca. 5 ha size each) the SoilNet wireless sensor network (Biogena et al. 2010). The SoilNet in Scheyern consists of 94 sensor units, 45 for the agricultural field site and 49 for the grassland site. Each sensor unit comprises 6 SPADE sensors, two sensors placed at the depths 10, 30 and 50 cm. The SPADE sensor (sceme.de GmbH, Horn-Bad Meinberg Germany) consists of a TDT sensor to estimate volumetric soil water content from soil electrical permittivity by sending an electromagnetic signal and measuring its propagation time, which depends on the soil dielectric properties and hence on soil water content. Additionally the SPADE sensor contains a temperature sensor (DS18B20). First results obtained from the SoilNet measurements at both fields sites will be presented and discussed. The observed high temporal and spatial variability will be analysed and related to agricultural management and basic soil properties (bulk density, soil texture, organic matter content and soil hydraulic characteristics).

  15. Field-aligned electron density irregularities near 500 km Equator to polar cap topside sounder observations

    NASA Technical Reports Server (NTRS)

    Benson, R. F.

    1985-01-01

    In addition to spread F, evidence for field-aligned electron density irregularities is commonly observed on Alouette 2 topside sounder ionograms recorded near perigee (500 km). This evidence is provided by distinctive signal returns from sounder-generated Z mode waves. At low latitudes these waves become guided in wave ducts caused by field-aligned electron density irregularities and give rise to strong long-duration echoes. At high latitudes, extending well into the polar cap, these Z mode waves (and stimulated electrostatic waves at the plasma frequency) produce a series of vertical bars on the ionogram display as the satellite traverses discrete field-aligned density structures. The radio frequency (RF) noise environment to be expected in the 400 to 500 km altitude region from low to high latitudes was examined by analyzing perigee Alouette 2 topside sounder data. All observed noise bands were scaled on nearly 200 topside sounder ionograms recorded near perigee at low, mid, and high latitude telemetry stations. The minimum and maximum frequencies of each noise band were entered into a data base or computer analysis. The signals of primary interest in the perigee study were found to be sounder-generated.

  16. 2D inverse modeling for potential fields on rugged observation surface using constrained Delaunay triangulation

    NASA Astrophysics Data System (ADS)

    Liu, Shuang; Hu, Xiangyun; Xi, Yufei; Liu, Tianyou

    2015-03-01

    The regular grid discretization is prevalent in the inverse modeling for gravity and magnetic data. However, this subdivision strategy performs lower precision to represent the rugged observation surface. To deal with this problem, we evaluate a non-structured discretization method in which the subsurface with rolling terrain is divided into numbers of Delaunay triangular cells and each mesh has the uniform physical property distributions. The gravity and magnetic anomalies of a complex-shaped anomalous body are represented as the summaries of the single anomaly produced by each triangle field source. When inverting for the potential field data, we specify a minimization objective function composed of data constraints and then use the preconditioned conjugate gradient algorithm to iteratively solve the matrix minimization equations, where the preconditioner is determined by the distances between triangular cells and surface observers. We test our method using synthetic data; all tests return favorable results. In the case studies involving the gravity and magnetic anomalies of the Mengku and Pobei deposits in Xinjiang, northwest China, the inferred magnetite orebodies and ultrabasic rocks distributions are verified by the additional drilling and geological information. The discretization of constrained Delaunay triangulation provides an useful approach of computing and inverting the potential field data on the situations of undulate topography and complicated objects.

  17. TSUBASA (MDS-1) observations of energetic electrons and magnetic field variations in outer radiation belt

    NASA Astrophysics Data System (ADS)

    Nakamura, M.; Matsuoka, H.; Liu, H.; Koshiishi, H.; Koga, K.; Matsumoto, H.; Goka, T.

    2002-12-01

    We have investigated variations of energetic electrons (> 0.4 MeV) and magnetic field in the radiation belt obtained from the Standard DOse Monitor (SDOM) and the MAgnetoMeter (MAM) of the Space Environment Data Acquisition equipment (SEDA) onboard TSUBASA (the Mission Demonstration Test Satellite (MDS)-1) launched on February 4, 2002. Since TSUBASA is operated in the geostationary transfer orbit, it has provided rare opportunities of directly observing near-equatorial radiation belt plasma particles and magnetic field, having already included several large magnetic storms. The energetic electrons in the outer radiation belt are contributors to the total radiation dose deposited in lightly shielded spacecraft electronics for high altitude orbits and are known to have a drastic variability associated with geomagnetic storm and high speed solar wind streams. The abrupt energetic electron flux decreases in the outside of outer radiation belt show characteristic variations of in situ magnetic field. These observations have implications for the possible mechanisms of the depletion and the following recovery and/or buildup of energetic electrons in the outer radiation belt.

  18. Observation of Novel Low-Field FMR modes in Permalloy Antidot Arrays

    NASA Astrophysics Data System (ADS)

    de Long, Lance; Bhat, Vinayak; Farmer, Barry; Woods, Justin; Hastings, Todd; Sklenar, Joseph; Ketterson, John

    2013-03-01

    Permalloy films of thickness 23 nm were patterned with square arrays of square antidots (AD) with feature size D = 120 nm, and lattice constants d = 200, 300, 500 and 700 nm (total sample area = 2 mm x 2mm), using electron beam lithography. Our broad-band (frequencies f = 10 MHz-15 GHz) and narrow-band (9.7 GHz) FMR measurements of even dilute (D/d <<1) AD lattices (ADL) reveal remarkably reproducible absorption spectra in the low-frequency, hysteretic regime in which disordered domain wall (DW) patterns and unsaturated magnetization textures are expected for unpatterned films, but in the present case are strongly affected by the periodic ADL. Other modes in the saturated regime exhibit strong dependence on the angle between the applied DC field H and the ADL axes, as confirmed by our micromagnetic simulations. Novel modes are observed at DC fields above that of the uniform mode, which simulations indicate are localized at AD edges. Other novel modes are observed for DC fields below that of the uniform mode, which simulated power and phase maps indicate are confined to ADL interstices oriented parallel to H. These results show even dilute AD concentrations can effect strong control of DW evolution. Research at Kentucky is supported by U.S. DoE Grant DE-FG02-97ER45653 and NSF Grant EPS-0814194.

  19. STAR FORMATION IN THE CHANDRA DEEP FIELD SOUTH: OBSERVATIONS CONFRONT SIMULATIONS

    SciTech Connect

    Damen, Maaike; Franx, Marijn; Foerster Schreiber, Natascha M.; Labbe, Ivo; Toft, Sune; Van Dokkum, Pieter G.; Wuyts, Stijn

    2009-11-01

    We investigate the star formation history of the universe using FIREWORKS, a multiwavelength survey of the Chandra Deep Field South. We study the evolution of the specific star formation rate (sSFR) with redshift in different mass bins from z = 0 to z approx 3. We find that the sSFR increases with redshift for all masses. The logarithmic increase of the sSFR with redshift is nearly independent of mass, but this cannot yet be verified at the lowest-mass bins at z>0.8, due to incompleteness. We convert the sSFRs to a dimensionless growth rate to facilitate a comparison with a semianalytic galaxy formation model that was implemented on the Millennium Simulation. The model predicts that the growth rates and sSFRs increase similarly with redshift for all masses, consistent with the observations. However, we find that for all masses, the inferred observed growth rates increase more rapidly with redshift than the model predictions. We discuss several possible causes for this discrepancy, ranging from field-to-field variance, conversions to SFR, and shape of the initial mass function. We find that none of these can solve the discrepancy completely. We conclude that the models need to be adapted to produce the steep increase in growth rate between redshift z = 0 and z = 1.

  20. Sprite Initiation Theory Testing Using Lightning Measurements, Optical Observations, and Modeled EM Fields

    NASA Astrophysics Data System (ADS)

    Hu, W.; Cummer, S. A.; Lyons, W. A.

    2006-12-01

    Combining the optical sprite observation data, the ELF/ULF sferic data recorded by our lightning remote sensing system, and an accurate 2D full wave FDTD model including the lightning-related nonlinear processes, we rigorously tested conventional breakdown (CB) theory for sprite initiation by estimating the electric fields above the thunderstorm clouds produced by the causative lightning discharges. First, we selected for this analysis a set of sprite events from the summer of 2004 whose initiation times are well bounded. Then we remotely measured the current moments and charge moment changes of the lightning discharges using the deconvolution technique. The inferred current moments are then used as the input of a 2D FDTD model for lightning-generated electromagnetic field simulations to estimate the high altitude electric field waveforms, which are difficult to measure directly. Finally, we compare the simulated mesospheric electric field to the threshold electric field for conventional breakdown to see whether, according to theory, conventional breakdown (and thus a sprite) would be initiated by that electric field and at what altitude. By analyzing sprites that are both short and long delayed from the source lightning stroke, we compared measurements and theory across a wide range of time scales. The results show that for bright, short-delayed sprites, the measurement-inferred mesospheric electric field, which is enhanced by the ionospheric nonlinearity significantly, agrees within 20% with the threshold electric field for conventional breakdown. The model-predicted sprite initiation altitude is approximately between 79 and 82 km. The charge moment change at the model-predicted sprite initiation time ranges from 360 to 760 C km with an average of 470 C km, which is generally in agreement with the previous measurements of the charge moment changes for sprite initiation. However, for long-delayed sprite events and dimmer sprites, the measurement

  1. DC Electric Fields, Associated Plasma Drifts, and Irregularities Observed on the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Klenzing, J.

    2011-01-01

    Results are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite, a mission designed to understand, model, and forecast the presence of equatorial ionospheric irregularities. The VEFI instrument includes a vector DC electric field detector, a fixed-bias Langmuir probe operating in the ion saturation regime, a flux gate magnetometer, an optical lightning detector, and associated electronics including a burst memory. Compared to data obtained during more active solar conditions, the ambient DC electric fields and their associated E x B drifts are variable and somewhat weak, typically < 1 mV/m. Although average drift directions show similarities to those previously reported, eastward/outward during day and westward/downward at night, this pattern varies significantly with longitude and is not always present. Daytime vertical drifts near the magnetic equator are largest after sunrise, with smaller average velocities after noon. Little or no pre-reversal enhancement in the vertical drift near sunset is observed, attributable to the solar minimum conditions creating a much reduced neutral dynamo at the satellite altitude. The nighttime ionosphere is characterized by larger amplitude, structured electric fields, even where the plasma density appears nearly quiescent. Data from successive orbits reveal that the vertical drifts and plasma density are both clearly organized with longitude. The spread-F density depletions and corresponding electric fields that have been detected thus far have displayed a preponderance to appear between midnight and dawn. Associated with the narrow plasma depletions that are detected are broad spectra of electric field and plasma density irregularities for which a full vector set of measurements is available for detailed study. The VEFI data represents a new set of measurements that are germane to numerous fundamental aspects of the electrodynamics

  2. Observations of photospheric magnetic fields and shear flows in flaring active regions

    NASA Technical Reports Server (NTRS)

    Tarbell, T.; Ferguson, S.; Frank, Z.; Title, A.; Topka, K.

    1988-01-01

    Horizontal flows in the photosphere and subsurface convection zone move the footpoints of coronal magnetic field lines. Magnetic energy to power flares can be stored in the corona if the flows drive the fields far from the potential configuration. Videodisk movies were shown with 0.5 to 1 arcsecond resolution of the following simultaneous observations: green continuum, longitudinal magnetogram, Fe I 5576 A line center (mid-photosphere), H alpha wings, and H alpha line center. The movies show a 90 x 90 arcsecond field of view of an active region at S29, W11. When viewed at speeds of a few thousand times real-time, the photospheric movies clearly show the active region fields being distorted by a remarkable combination of systematic flows and small eruptions of new flux. Magnetic bipoles are emerging over a large area, and the polarities are systematically flowing apart. The horizontal flows were mapped in detail from the continuum movies, and these may be used to predict the future evolution of the region. The horizontal flows are not discernable in H alpha. The H alpha movies strongly suggest reconnection processes in the fibrils joining opposite polarities. When viewed in combination with the magnetic movies, the cause for this evolution is apparent: opposite polarity fields collide and partially cancel, and the fibrils reconnect above the surface. This type of reconnection, driven by subphotospheric flows, complicates the chromospheric and coronal fields, causing visible braiding and twisting of the fibrils. Some of the transient emission events in the fibrils and adjacent plage may also be related.

  3. New Approach for Environmental Monitoring and Plant Observation Using a Light-Field Camera

    NASA Astrophysics Data System (ADS)

    Schima, Robert; Mollenhauer, Hannes; Grenzdörffer, Görres; Merbach, Ines; Lausch, Angela; Dietrich, Peter; Bumberger, Jan

    2015-04-01

    The aim of gaining a better understanding of ecosystems and the processes in nature accentuates the need for observing exactly these processes with a higher temporal and spatial resolution. In the field of environmental monitoring, an inexpensive and field applicable imaging technique to derive three-dimensional information about plants and vegetation would represent a decisive contribution to the understanding of the interactions and dynamics of ecosystems. This is particularly true for the monitoring of plant growth and the frequently mentioned lack of morphological information about the plants, e.g. plant height, vegetation canopy, leaf position or leaf arrangement. Therefore, an innovative and inexpensive light-field (plenoptic) camera, the Lytro LF, and a stereo vision system, based on two industrial cameras, were tested and evaluated as possible measurement tools for the given monitoring purpose. In this instance, the usage of a light field camera offers the promising opportunity of providing three-dimensional information without any additional requirements during the field measurements based on one single shot, which represents a substantial methodological improvement in the area of environmental research and monitoring. Since the Lytro LF was designed as a daily-life consumer camera, it does not support depth or distance estimation or rather an external triggering by default. Therefore, different technical modifications and a calibration routine had to be figured out during the preliminary study. As a result, the used light-field camera was proven suitable as a depth and distance measurement tool with a measuring range of approximately one meter. Consequently, this confirms the assumption that a light field camera holds the potential of being a promising measurement tool for environmental monitoring purposes, especially with regard to a low methodological effort in field. Within the framework of the Global Change Experimental Facility Project, founded by

  4. Visual adaptation: softcopy image contribution to the observer's field of view

    NASA Astrophysics Data System (ADS)

    Toomey, R. J.; Curran, K.; D'Helft, C.; Joyce, M. B.; Stowe, J.; Ryan, J. T.; McEntee, M. F.; Manning, D. J.; Brennan, P. C.

    2008-03-01

    Purpose Detection of low-contrast details is highly dependent on the adaptation state of the eye. It is important therefore that the average luminance of the observer's field of view (FOV) matches those of softcopy radiological images. This study establishes the percentage of FOV filled by workstations at various viewing distances. Methods Five observers stood at viewing distances of 20, 30 and 50cm from a homogenous white surface and were instructed to continuously focus on a fixed object at a height appropriate level. A dark indicator was held at this object and then moved steadily until the observer could no longer perceive it in his/her peripheral vision. This was performed at 0°, 90°, 180° and 270° clockwise from the median sagittal plane. Distances were recorded, radii calculated and observer and mean FOV areas established. These values were then compared with areas of typical high and low specification workstations. Results Individual and mean FOVs were 7660, 15463 and 30075cm2 at viewing distances of 20, 30 and 50cm respectively. High and low specification monitors with respective areas of 1576.25 and 921.25cm2 contributed between 5 to 21% and 3 to 12% respectively to the total FOV depending on observer distance. Limited inter-observer variances were noted. Conclusions Radiology workstations typically comprise between only 3 and 21% of the observer's FOV. This demonstrates the importance of measuring ambient light levels and surface reflection coefficients in order to maximise adaptation and observer's perception of low contrast detail and minimise eye strain.

  5. Initial Venus Express magnetic field observations of the magnetic barrier at solar minimum

    NASA Astrophysics Data System (ADS)

    Zhang, T. L.; Delva, M.; Baumjohann, W.; Volwerk, M.; Russell, C. T.; Barabash, S.; Balikhin, M.; Pope, S.; Glassmeier, K.-H.; Wang, C.; Kudela, K.

    2008-05-01

    Although there is no intrinsic magnetic field at Venus, the convected interplanetary magnetic field piles up to form a magnetic barrier in the dayside inner magnetosheath. In analogy to the Earth's magnetosphere, the magnetic barrier acts as an induced magnetosphere on the dayside and hence as the obstacle to the solar wind. It consists of regions near the planet and its wake for which the magnetic pressure dominates all other pressure contributions. The initial survey performed with the Venus Express magnetic field data indicates a well-defined boundary at the top of the magnetic barrier region. It is clearly identified by a sudden drop in magnetosheath wave activity, and an abrupt and pronounced field draping. It marks the outer boundary of the induced magnetosphere at Venus, and we adopt the name "magnetopause" to address it. The magnitude of the draped field in the inner magnetosheath gradually increases and the magnetopause appears to show no signature in the field strength. This is consistent with PVO observations at solar maximum. A preliminary survey of the 2006 magnetic field data confirms the early PVO radio occultation observations that the ionopause stands at ˜250 km altitude across the entire dayside at solar minimum. The altitude of the magnetopause is much lower than at solar maximum, due to the reduced altitude of the ionopause at large solar zenith angles and the magnetization of the ionosphere. The position of the magnetopause at solar minimum is coincident with the ionopause in the subsolar region. This indicates a sinking of the magnetic barrier into the ionosphere. Nevertheless, it appears that the thickness of the magnetic barrier remains the same at both solar minimum and maximum. We have found that the ionosphere is magnetized ˜95% of the time at solar minimum, compared with 15% at solar maximum. For the 5% when the ionosphere is un-magnetized at solar minimum, the ionopause occurs at a higher location typically only seen during solar

  6. Field-Scale Soil Moisture Observations in Irrigated Agriculture Fields Using the Cosmic-ray Neutron Rover

    NASA Astrophysics Data System (ADS)

    Franz, T. E.; Avery, W. A.; Finkenbiner, C. E.; Wang, T.; Brocca, L.

    2014-12-01

    Approximately 40% of global food production comes from irrigated agriculture. With the increasing demand for food even greater pressures will be placed on water resources within these systems. In this work we aimed to characterize the spatial and temporal patterns of soil moisture at the field-scale (~500 m) using the newly developed cosmic-ray neutron rover near Waco, NE. Here we mapped soil moisture of 144 quarter section fields (a mix of maize, soybean, and natural areas) each week during the 2014 growing season (May to September). The 11 x11 km study domain also contained 3 stationary cosmic-ray neutron probes for independent validation of the rover surveys. Basic statistical analysis of the domain indicated a strong inverted parabolic relationship between the mean and variance of soil moisture. The relationship between the mean and higher order moments were not as strong. Geostatistical analysis indicated the range of the soil moisture semi-variogram was significantly shorter during periods of heavy irrigation as compared to non-irrigated periods. Scaling analysis indicated strong power law behavior between the variance of soil moisture and averaging area with minimal dependence of mean soil moisture on the slope of the power law function. Statistical relationships derived from the rover dataset offer a novel set of observations that will be useful in: 1) calibrating and validating land surface models, 2) calibrating and validating crop models, 3) soil moisture covariance estimates for statistical downscaling of remote sensing products such as SMOS and SMAP, and 4) provide center-pivot scale mean soil moisture data for optimal irrigation timing and volume amounts.

  7. Subsolar magnetopause observation and kinetic simulation of a tripolar guide magnetic field perturbation consistent with a magnetic island

    NASA Astrophysics Data System (ADS)

    Eriksson, S.; Cassak, P. A.; Retinò, A.; Mozer, F. S.

    2016-04-01

    The Polar satellite recorded two reconnection exhausts within 6 min on 1 April 2001 across a subsolar magnetopause that displayed a symmetric plasma density, but different out-of-plane magnetic field signatures for similar solar wind conditions. The first magnetopause crossing displayed a bipolar guide field variation in a weak external guide field consistent with a symmetric Hall field from a single X line. The subsequent crossing represents the first observation of a tripolar guide field perturbation at Earth's magnetopause in a strong guide field. This perturbation consists of a significant guide field enhancement between two narrow guide field depressions. A particle-in-cell simulation for the prevailing conditions across this second event resulted in a magnetic island between two simulated X lines across which a tripolar guide field developed consistent with the observation. The simulated island supports a scenario whereby Polar encountered the asymmetric quadrupole Hall magnetic fields between two X lines for symmetric conditions across the magnetopause.

  8. The Gravity Field, Orientation, and Ephemeris of Mercury from MESSENGER Observations After Three Years in Orbit

    NASA Technical Reports Server (NTRS)

    Mazarico, Erwan M.; Genova, Antonio; Goossens, Sander; Lemoine, Gregory; Neumann, Gregory A.; Zuber, Maria T.; Smith, David E.; Solomon, Sean C.

    2014-01-01

    We have analyzed three years of radio tracking data from the MESSENGER spacecraft in orbit around Mercury and determined the gravity field, planetary orientation, and ephemeris of the innermost planet. With improvements in spatial coverage, force modeling, and data weighting, we refined an earlier global gravity field both in quality and resolution, and we present here a spherical harmonic solution to degree and order 50. In this field, termed HgM005, uncertainties in low-degree coefficients are reduced by an order of magnitude relative to the earlier global field, and we obtained a preliminary value of the tidal Love number k(sub 2) of 0.451+/-0.014. We also estimated Mercury's pole position, and we obtained an obliquity value of 2.06 +/- 0.16 arcmin, in good agreement with analysis of Earth-based radar observations. From our updated rotation period (58.646146 +/- 0.000011 days) and Mercury ephemeris, we verified experimentally the planet's 3: 2 spin-orbit resonance to greater accuracy than previously possible. We present a detailed analysis of the HgM005 covariance matrix, and we describe some near-circular frozen orbits around Mercury that could be advantageous for future exploration.

  9. The gravity field, orientation, and ephemeris of Mercury from MESSENGER observations after three years in orbit

    NASA Astrophysics Data System (ADS)

    Mazarico, Erwan; Genova, Antonio; Goossens, Sander; Lemoine, Frank G.; Neumann, Gregory A.; Zuber, Maria T.; Smith, David E.; Solomon, Sean C.

    2014-12-01

    We have analyzed 3 years of radio tracking data from the MESSENGER spacecraft in orbit around Mercury and determined the gravity field, planetary orientation, and ephemeris of the innermost planet. With improvements in spatial coverage, force modeling, and data weighting, we refined an earlier global gravity field both in quality and resolution, and we present here a spherical harmonic solution to degree and order 50. In this field, termed HgM005, uncertainties in low-degree coefficients are reduced by an order of magnitude relative to earlier global fields, and we obtained a preliminary value of the tidal Love number k2 of 0.451 ± 0.014. We also estimated Mercury's pole position, and we obtained an obliquity value of 2.06 ± 0.16 arcmin, in good agreement with analysis of Earth-based radar observations. From our updated rotation period (58.646146 ± 0.000011 days) and Mercury ephemeris, we verified experimentally the planet's 3:2 spin-orbit resonance to greater accuracy than previously possible. We present a detailed analysis of the HgM005 covariance matrix, and we describe some near-circular frozen orbits around Mercury that could be advantageous for future exploration.

  10. Assessing the GOANNA Visual Field Algorithm Using Artificial Scotoma Generation on Human Observers

    PubMed Central

    Chong, Luke X.; Turpin, Andrew; McKendrick, Allison M.

    2016-01-01

    Purpose To validate the performance of a new perimetric algorithm (Gradient-Oriented Automated Natural Neighbor Approach; GOANNA) in humans using a novel combination of computer simulation and human testing, which we call Artificial Scotoma Generation (ASG). Methods Fifteen healthy observers were recruited. Baseline conventional automated perimetry was performed on the Octopus 900. Visual field sensitivity was measured using two different procedures: GOANNA and Zippy Estimation by Sequential Testing (ZEST). Four different scotoma types were induced in each observer by implementing a novel technique that inserts a step between the algorithm and the perimeter, which in turn alters presentation levels to simulate scotomata in human observers. Accuracy, precision, and unique number of locations tested were measured, with the maximum difference between a location and its neighbors (Max_d) used to stratify results. Results GOANNA sampled significantly more locations than ZEST (paired t-test, P < 0.001), while maintaining comparable test times. Difference plots showed that GOANNA displayed greater accuracy than ZEST when Max_d was in the 10 to 30 dB range (with the exception of Max_d = 20 dB; Wilcoxon, P < 0.001). Similarly, GOANNA demonstrated greater precision than ZEST when Max_d was in the 20 to 30 dB range (Wilcoxon, P < 0.001). Conclusions We have introduced a novel method for assessing accuracy of perimetric algorithms in human observers. Results observed in the current study agreed with the results seen in earlier simulation studies, and thus provide support for performing larger scale clinical trials with GOANNA in the future. Translational Relevance The GOANNA perimetric testing algorithm offers a new paradigm for visual field testing where locations for testing are chosen that target scotoma borders. Further, the ASG methodology used in this paper to assess GOANNA shows promise as a hybrid between computer simulation and patient testing, which may allow more

  11. Viking magnetic and electric field observations of Pc 1 waves at high latitudes

    SciTech Connect

    Erlandson, R.E.; Zanetti, L.J.; Potemra, T.A. ); Block, L.P. ); Holmgren, G. )

    1990-05-01

    Magnetic and electric field fluctuations in the Pc 1 frequency range (0.2-5 Hz) have been observed by the polar-orbiting Viking satellite. The fluctuations, interpreted here as electromagnetic ion cyclotron (EMIC) waves, were observed during 21 of 450 orbits surveyed between 0900 and 1400 MLT, near 3 R{sub E} geocentric altitude, and at invariant latitudes from 59{degree} to 77{degree}. The frequency structure of the waves is investigated, using spectral analysis and by determining the distribution of the wave frequency as a function of invariant latitude. At invariant latitudes from 59{degree} to 72{degree}, EMIC waves were observed in the frequency range below the equatorial He{sup +} gyrofrequency, while from 70{degree} to 77{degree} invariant latitude, EMIC waves were observed in the frequency range above the equatorial He{sup +} gyrofrequency. This latitude structure of the wave frequency is discussed in terms of the linear growth rate dependence of the waves on the heavy ion density, ion anisotropy, and ion energy. The propagation characteristics of these waves were also investigated, using minimum variance analysis and polarization analysis, and by estimating the Poynting flux based on the observed magnetic and electric field. The waves had Poynting vectors directed downward toward Earth and reached magnitudes between 0.01 and 0.1 erg/cm{sup 2} s. The polarization of the waves was found to vary between linear, left-hand, and right-hand as a function of time or latitude. This variation is interpreted as the structure of spatially localized Pc 1 waves at high latitudes above the ionosphere.

  12. Combination of various observation techniques for regional modeling of the gravity field

    NASA Astrophysics Data System (ADS)

    Lieb, Verena; Schmidt, Michael; Dettmering, Denise; Börger, Klaus

    2016-05-01

    Modeling a very broad spectrum of the Earth's gravity field needs observations from various measurement techniques with different spectral sensitivities. Typically, high-resolution regional gravity data are combined with low-resolution global observations. To exploit the gravitational information as optimally as possible, we set up a regional modeling approach using radial spherical basis functions, emphasizing the strengths of various data sets by the flexible combination of high- and middle-resolution terrestrial, airborne, shipborne, and altimetry measurements. The basis functions are defined and located in the region of interest in such a manner, which the highest measure of information of the input data is captured. Any functional of the Earth's gravity field can be derived, as, e.g., quasi-geoid heights or gravity anomalies. Here we present results of a study area in Northern Germany. A comprehensive cross validation to external observation data delivers standard deviations less than 5 cm. Differences to an existing regional quasi-geoid model count on average ±6 cm and proof the plausibility of our solution. The comparison with existing global models reaches higher standard deviations for the more sensitive gravity anomalies as for quasi-geoid heights, showing the additional value of our solution in the high frequency domain. Covering a broad frequency spectrum, our regional models can be used as basis for various applications, such as refinement of global models, national geoid determination, and detection of mass anomalies in the Earth's interior.

  13. Prominence plasma and magnetic field structure - A coordinated observation with IRIS, Hinode and THEMIS

    NASA Astrophysics Data System (ADS)

    Schmieder, Brigitte; Labrosse, Nicolas; Levens, Peter; Lopez Ariste, Arturo

    2016-07-01

    During an international campaign in 2014, utilising both space-based (IRIS and Hinode) and ground-based (THEMIS) instruments, we focused on observing prominences. We compare IRIS observations with those of Hinode (EIS and SOT) in order to build a more complete picture of the prominence structure for a quiescent prominence observed on 15 July 2014, identified to have tornado-like structure. THEMIS provides valuable information on the orientation and strength of the internal magnetic field. Here we find there is almost ubiquitously horizontal field with respect to the local limb, with possibly a turbulent component. The Mg II lines form the majority of our IRIS analysis, with a mixture of reversed and non-reversed profiles present in the prominence spectra. Comparing the differences between the Mg II data from IRIS and the Ca II images from Hinode/SOT provides an intriguing insight into the prominence legs in these channels. We present plasma diagnostics from IRIS, with line of sight velocities of around 10 km/s in either direction along the magnetic loops of material in the front of the prominence, and line widths comparable to those found for prominences by previous authors (e.g. Schmieder et al. 2014). We also take a look into the lines formed at higher, coronal plasma temperatures, as seen by Hinode/EIS, to compare plasma structures at a full range of temperatures.

  14. Sediment deposition from tropical storms in the upper Chesapeake Bay: Field observations and model simulations

    NASA Astrophysics Data System (ADS)

    Palinkas, Cindy M.; Halka, Jeffrey P.; Li, Ming; Sanford, Lawrence P.; Cheng, Peng

    2014-09-01

    Episodic flood and storm events are important drivers of sediment dynamics in estuarine and marine environments. Event-driven sedimentation has been well-documented by field and modeling studies, though both techniques have inherent limitations. A unique opportunity to integrate field observations and model results was provided in late August/early September 2011 with the passage of Hurricane Irene and Tropical Storm Lee in the Chesapeake Bay region. Because these two storms occurred within a relatively short period of time, both are potentially represented in the sediment record obtained during rapid-response cruises in September and October 2011. Associated sediment deposits were recognized in cores using classic flood-sediment signatures (fine grain size, uniform 7Be activity, physical stratification in x-radiographs) and were found to be <4 cm, thickest in the upper Bay. A coupled hydrodynamic-sediment transport model is used to simulate the sediment plume and sediment deposition onto the seabed. The predicted deposition thickness for TS Lee is in general agreement with the observational estimates. One exception with physical stratification but no 7Be activity appears to be due to extreme wave activity during Hurricane Irene. Integration of observations and modeling in this case greatly improved understanding of the transport and fate of flood sediments in the Chesapeake Bay.

  15. Toward Epoch of Reionization Measurements with Wide-Field Radio Observations

    NASA Astrophysics Data System (ADS)

    Morales, Miguel F.; Hewitt, Jacqueline

    2004-11-01

    This paper explores the potential for statistical epoch of reionization (EOR) measurements using wide-field radio observations. New developments in low-frequency radio instrumentation and signal processing allow very sensitive EOR measurements, and the analysis techniques enabled by these advances offer natural ways of separating the EOR signal from the residual foreground emission. This paper introduces the enabling technologies and proposes an analysis technique designed to make optimal use of the capabilities of next-generation low-frequency radio arrays. The observations we propose can directly observe the power spectrum of the EOR using relatively short observations and are significantly more sensitive than other techniques that have been discussed in the literature. For example, in the absence of foreground contamination the measurements we propose would produce five 3 σ power spectrum points in 100 hr of observation with only 4 MHz bandwidth with LOFAR for simple models of the high-redshift 21 cm emission. The challenge of residual foreground removal may be addressed by the symmetries in the three-dimensional (two spatial frequencies and radio frequency) radio interferometric data. These symmetries naturally separate the EOR signal from most classes of residual unsubtracted foreground contamination, including all foreground continuum sources and radio line emission from the Milky Way.

  16. Optical and X-ray observations of the PSR 1913 + 16 field

    NASA Technical Reports Server (NTRS)

    Davidsen, A.; Liebert, J.; Spinrad, H.; Middleditch, J.; Chanan, G.; Mason, K. O.; Sanford, P. W.; Margon, B.

    1975-01-01

    We have obtained medium-resolution spectra in the yellow of seven stars in the error box of the binary radio pulsar PSR 1913 + 16, using the image-tube scanner at the Lick 3-m telescope. None of the objects is spectroscopically abnormal and thus a strong candidate for membership in the system. The data are used to establish the extinction in the field, which is modest for this low galactic latitude. For three of the stars, limits of the order V exceeding 23 mag on optical pulsations with the frequency of the radio pulsar are derived. X-ray observations of the field have been obtained in the 2.5-7.5 keV band, using the UCL experiment aboard OAO Copernicus. No source is detected, with a 2 sigma upper limit on the time-averaged flux of 1.0 times 10 to the -10th power ergs per sq cm per sec.

  17. DMSP F7 observations of a substorm field-aligned current

    NASA Technical Reports Server (NTRS)

    Lopez, R. E.; Spence, H. E.; Meng, C.-I.

    1991-01-01

    Observations are described of a substorm field-aligned current (FAC) system traversed by the DMSP F7 spacecraft just after 0300 UT on April 25, 1985. It is shown that the substorm FAC portion of the current system was located equatorward of the boundary between open and closed field lines. The equatorward boundary of the substorm FAC into the magnetotail was mapped using the Tsyganenko (1987) model, showing that the boundary corresponds to 6.9 earth radii. The result is consistent with the suggestion of Akasofu (1972) and Lopez and Lui (1990) that the region of substorm initiation lies relatively close to the earth and the concept that an essential feature of substorms is the disruption and diversion of the near-earth current sheet.

  18. Laboratory and Field Observations of Microcystis aeruginosa in nearly homogeneous turbulent flows

    NASA Astrophysics Data System (ADS)

    Wilkinson, Anne; Hondzo, Miki; Guala, Michele

    2015-11-01

    Microcystis aeruginosa is a single-celled cyanobacterium, forming large colonies on the surface of freshwater ecosystems during summer, and producing a toxin (microcystin) that in high concentration can be harmful to humans and animals. In addition to water temperature, light and nutrient abundance, fluid motion is also an abiotic environmental factor affecting the growth and metabolism of Microcystis. Systematic investigations in a laboratory bioreactor are paired with field measurements in the lacustrine photic zone from two sites in Lake Minnetonka (MN) to ensure that dissipation levels, water temperature, dissolved oxygen and pH are correctly reproduced under laboratory conditions. Laboratory results for biomass accrual and photosynthetic activity suggest that turbulence levels within the range observed in the field, mediates the metabolism, rather than the cell population growth, of Microcystis aeruginosa. This work was supported by the NSF Graduate Research Fellowship and University of Minnesota start-up funding.

  19. An Explanation for the Observed Spectral Contrast Reduction Between Field and Laboratory Infrared Measurements of Soils

    NASA Astrophysics Data System (ADS)

    Johnson, J. R.; Lucey, P. G.; Horton, K. A.; Williams, T.; Winter, E. M.; Stocker, A. D.

    1996-03-01

    Comparison of emission spectra (7-14 m) of pristine soils in the field with bidirectional reflectance spectra of soils obtained in the laboratory shows that laboratory spectra tend to have less contrast than field spectra. We investigated this phenomenon by measuring emission spectra of both pristine (in situ) and sampled soils (prepared as if for transport to the laboratory). The sampled soils had much less spectral contrast than the pristine soils in the reststrahlen region near 9 m. We hypothesize that this effect is due to a difference in grainsize distribution of the optically active layer (i.e., fine particle coatings). This concept was proposed by Salisbury et al. to explain their observations that soils washed free of small particles adhering to larger grains exhibited greater spectral contrast than unwashed soils. Unrecognized, this phenomenon could influence interpretations of remote sensing data since it is a common practice to use spectra of materials obtained in the laboratory to interpret spectra obtained remotely.

  20. Interaction between Japanese flowering cherry trees and some wild animals observed during physiological experiment in fields

    NASA Technical Reports Server (NTRS)

    Nakamura, Teruko

    2003-01-01

    We have studied the weeping habit of Japanese flowering cherry tree in the field of Tama Forest Science Garden, Forestry and Forest Products Research Institute at the foot of Mt. Takao. Since cherry trees at various age were the materials for our plant physiology experiments, our studies were conducted in the fields where we experienced certain difficulties. Even under such difficult environment that was rather unexpected and uncontrollable, we could obtain fruitful results on the growth of cherry tree, and found them scientifically significant, especially in terms of biological effects of gravity on earth. Moreover, a lot of interesting interactions of cherry trees with various kinds of animals were observed in parallel to the plant physiology.

  1. Harmonically structured ULF pulsations observed by the AMPTE CCE magnetic field experiment

    NASA Technical Reports Server (NTRS)

    Engebretson, M. J.; Zanetti, L. J.; Potemra, T. A.; Acuna, M. H.

    1986-01-01

    Spectrograms of ULF waves in the 0 to 80 mHz frequency range have been prepared from magnetic field data obtained by the elliptically orbiting AMPTE/CCE satellite (with an apogee of approximately 8.8 earth radii). The most prominent feature of these spectrograms (which cover a full 15.6-h orbit) is the presence of harmonically structured, azimuthally polarized pulsations in the outer magnetosphere during daytime hours. The frequencies of these pulsations decrease with increasing radial distance from the earth, indicating that they represent independent resonances of local magnetic flux tubes. The latitudinal structure of these harmonic pulsations, observed as AMPTE/CCE traveled to + or - 16 deg magnetic latitude, is consistent with accepted field line resonance models.

  2. Observations of toroidicity-induced Alfven eigenmodes in a reversed field pinch plasma

    SciTech Connect

    Regnoli, G.; Bergsaaker, H.; Tennfors, E.; Zonca, F.; Martines, E.; Serianni, G.; Spolaore, M.; Vianello, N.; Cecconello, M.; Antoni, V.; Cavazzana, R.; Malmberg, J.-A.

    2005-04-15

    High frequency peaks in the spectra of magnetic field signals have been detected at the edge of Extrap-T2R [P. R. Brunsell, H. Bergsaaker, M. Cecconello, J. R. Drake, R. M. Gravestijn, A. Hedqvist, and J.-A. Malmberg, Plasma Phys. Controlled Fusion, 43, 1457 (2001)]. The measured fluctuation is found to be mainly polarized along the toroidal direction, with high toroidal periodicity n and Alfvenic scaling (f{proportional_to}B/{radical}(m{sub i}n{sub i})). Calculations for a reversed field pinch plasma predict the existence of an edge resonant, high frequency, high-n number toroidicity-induced Alfven eigenmode with the observed frequency scaling. In addition, gas puffing experiments show that edge density fluctuations are responsible for the rapid changes of mode frequency. Finally a coupling with the electron drift turbulence is proposed as drive mechanism for the eigenmode.

  3. Inferring spatial clouds statistics from limited field-of-view, zenith observations

    SciTech Connect

    Sun, C.H.; Thorne, L.R.

    1996-04-01

    Many of the Cloud and Radiation Testbed (CART) measurements produce a time series of zenith observations, but spatial averages are often the desired data product. One possible approach to deriving spatial averages from temporal averages is to invoke Taylor`s hypothesis where and when it is valid. Taylor`s hypothesis states that when the turbulence is small compared with the mean flow, the covariance in time is related to the covariance in space by the speed of the mean flow. For clouds fields, Taylor`s hypothesis would apply when the {open_quotes}local{close_quotes} turbulence is small compared with advective flow (mean wind). The objective of this study is to determine under what conditions Taylor`s hypothesis holds or does not hold true for broken cloud fields.

  4. Observations of electromagnetic fields and plasma flow in hohlraums with proton radiography.

    PubMed

    Li, C K; Séguin, F H; Frenje, J A; Petrasso, R D; Amendt, P A; Town, R P J; Landen, O L; Rygg, J R; Betti, R; Knauer, J P; Meyerhofer, D D; Soures, J M; Back, C A; Kilkenny, J D; Nikroo, A

    2009-05-22

    We report on the first proton radiography of laser-irradiated hohlraums. This experiment, with vacuum gold (Au) hohlraums, resulted in observations of self-generated magnetic fields with peak values approximately 10;{6} G. Time-gated radiographs of monoenergetic protons with discrete energies (15.0 and 3.3 MeV) reveal dynamic pictures of field structures and plasma flow. Near the end of the 1-ns laser drive, a stagnating Au plasma (approximately 10 mg cm;{-3}) forms at the center of the hohlraum. This is a consequence of supersonic, radially directed Au jets (approximately 1000 microm ns;{-1}, approximately Mach 4) that arise from the interaction of laser-driven plasma bubbles expanding into one another. PMID:19519034

  5. Magnetic Field and Plasma Observations at Mars: Initial Results of the Mars Global Surveyor Mission

    PubMed

    Acuña; Connerney; Wasilewski; Lin; Anderson; Carlson; McFadden; Curtis; Mitchell; Reme; Mazelle; Sauvaud; d'Uston; Cros; Medale; Bauer; Cloutier; Mayhew; Winterhalter; Ness

    1998-03-13

    The magnetometer and electron reflectometer investigation (MAG/ER) on the Mars Global Surveyor spacecraft has obtained magnetic field and plasma observations throughout the near-Mars environment, from beyond the influence of Mars to just above the surface (at an altitude of approximately 100 kilometers). The solar wind interaction with Mars is in many ways similar to that at Venus and at an active comet, that is, primarily an ionospheric-atmospheric interaction. No significant planetary magnetic field of global scale has been detected to date (<2 x 10(21) Gauss-cubic centimeter), but here the discovery of multiple magnetic anomalies of small spatial scale in the crust of Mars is reported. PMID:9497279

  6. On the observed hysteresis in field-scale soil moisture variability and its physical controls

    NASA Astrophysics Data System (ADS)

    Mascaro, G.; Vivoni, E. R.

    2016-08-01

    The spatiotemporal variability of soil moisture (θ) has rarely been studied at the field scale across different seasons and sites. Here, we utilized 9 months of θ data in two semiarid ecosystems of North America to investigate the key relationship between the spatial mean (<θ>) and standard deviation (σ θ ) at the field-scale (∼100 m). Analyses revealed a strong seasonal control on the σ θ versus <θ> relation and the existence of hysteretic cycles where wetting and dry-down phases have notably different behavior. Empirical orthogonal functions (EOFs) showed that θ variability depends on two dominant spatial patterns, with time-stable and seasonally varying contributions in time, respectively. Correlations between EOFs and land surface properties also indicated that θ patterns are linked to vegetation (terrain and soil) factors at the site with higher (lower) vegetation cover. These physical controls explained the observed hysteresis cycles, thus confirming interpretations from previous modeling studies for the first time.

  7. Recent changes of the Earth's core derived from satellite observations of magnetic and gravity fields.

    PubMed

    Mandea, Mioara; Panet, Isabelle; Lesur, Vincent; de Viron, Olivier; Diament, Michel; Le Mouël, Jean-Louis

    2012-11-20

    To understand the dynamics of the Earth's fluid, iron-rich outer core, only indirect observations are available. The Earth's magnetic field, originating mainly within the core, and its temporal variations can be used to infer the fluid motion at the top of the core, on a decadal and subdecadal time-scale. Gravity variations resulting from changes in the mass distribution within the Earth may also occur on the same time-scales. Such variations include the signature of the flow inside the core, though they are largely dominated by the water cycle contributions. Our study is based on 8 y of high-resolution, high-accuracy magnetic and gravity satellite data, provided by the CHAMP and GRACE missions. From the newly derived geomagnetic models we have computed the core magnetic field, its temporal variations, and the core flow evolution. From the GRACE CNES/GRGS series of time variable geoid models, we have obtained interannual gravity models by using specifically designed postprocessing techniques. A correlation analysis between the magnetic and gravity series has demonstrated that the interannual changes in the second time derivative of the core magnetic field under a region from the Atlantic to Indian Ocean coincide in phase with changes in the gravity field. The order of magnitude of these changes and proposed correlation are plausible, compatible with a core origin; however, a complete theoretical model remains to be built. Our new results and their broad geophysical significance could be considered when planning new Earth observation space missions and devising more sophisticated Earth's interior models. PMID:23064635

  8. Constraining strength/depth profiles using laboratory experiments and field structural observations

    NASA Astrophysics Data System (ADS)

    Evans, B.

    2012-04-01

    Strength/depth profiles are often used as standard models to constrain treatments of lithosphere-scale geodynamics. Such profiles have virtue because they are motivated by our understanding of inelastic deformation of rocks, and because they can be used in complex numerical calculations. But, by attempting to construct simple, generic mechanical models, often while lacking detailed descriptions of the sub-surface, such treatments may ignore important issues, including spatial heterogeneities in rock composition, in strain displacements, or in other thermodynamic parameters, including temperature, fluid pressure and composition. Further, these profiles usually assume constitutive equations that reflect combinations of a simple yield criterion with steady-state creep. Thus, transient mechanical behavior is neglected. Fortunately, a plethora of recent laboratory, field structural, and computational studies may now be used to shed light on mechanical behavior at a much broader range of temperature, pressure, strain rates, and strain. For example, new experiments provide a description of creep in minerals at pressures greater than 2 GPa, of friction at seismic velocities, and of strains larger than 5. Observations of field microstructures, coupled with mechanical descriptions gleaned from laboratory experiments and theoretical treatments of the thermodynamics and mechanics of deformation, provide important insights into the way that localization occurs in natural shear zones. Finally, Earth scientists have gained an improved understanding of the subtle, yet important, interplay among fluids, transport properties, and rock deformation, which are capable of producing rich patterns of deformation. Among several important and challenging issues that need work is spatial scaling of properties; it is particularly important to consider differences in length scales that are embedded in the various techniques of field and global geophysics, field geology, and experiments. Our

  9. Magnetic Field Observations of Partial Ring Current during Storm Recovery Phase

    NASA Technical Reports Server (NTRS)

    Le, G.; Russell, C. T.; Slavin, J. A.; Lucek, E. A.

    2008-01-01

    We present results of an extensive survey of the magnetic field observations in the inner magnetosphere using 30 years of magnetospheric magnetic field data from Polar, Cluster, ISEE, and AMPTE/CCE missions. The purpose of this study is to understand the magnetic field evolution during the recovery phase of geomagnetic storms, and its implication to the ring current recovery and loss mechanisms of ring current particles. It is now commonly believed that a strong partial ring current is formed during the storm main phase due to the enhanced earthward convection of energetic ions from nightside plasma sheet. But the presence of a strong partial ring current throughout the recovery phase remains controversial. The magnetic field generated by the ring current inflates the inner magnetosphere and causes magnetic field depressions in the equatorial magnetosphere. During the storm recovery phase, we find that the distribution of the equatorial magnetic field depression exhibits similar local time dependence as the ring current distribution obtained from the combined dataset in the earlier study. It shows that a strong partial ring current is a permanent feature throughout the recovery phase. In the early recovery phase, the partial ring current peaks near the dusk terminator as indicated by the peak of the magnetic field depression. As the recovery phase progresses, the partial ring current decays most quickly near the dusk and results in a dusk-to-midnight moving of the peak of the partial ring current. Thus the loss mechanisms work most effectively near the dusk. The magnetic field depression increases the gyroradius of ring current protons to a scale greater or comparable to the thickness of the magnetopause, which increases the chance of ion drift loss near the dusk magnetopause at larger L-shell (L greater than 5). But the drift loss mechanism alone cannot explain the loss of ring current ions especially in the smaller L-shell (L less than 5). The precipitation loss

  10. New Observations of the Heliospheric Magnetic Field from the Voyager Spacecraft

    NASA Technical Reports Server (NTRS)

    Burlaga, Leonard F.

    2007-01-01

    We review recent observations of variations of the heliospheric magnetic field B(t) made by Voyager 1 and 2 (V1 and V2), and we discuss the boundary conditions needed for models to explain the observations. Usually, observations from a spacecraft close to the Sun, such as ACE, WIND or Ulysses are used as input to a time-dependent model. Generally, the predicted profile B(t) can be compared directly with the observed profile only when either V1 or V2 is approximately radially aligned with a near-Sun spacecraft; this happens rarely and only for a brief time interval. The Bastille Day events illustrate this situation. In the absence of radial alignment of the spacecraft it is possible to predict the development of a global structure (a GMIR) with data from ACE or WIND, if they obtain a representative sample the flows that merge to form a GMIR. When latitudinal gradients are small and when there is statistical homogeneity in the azimuthal direction, it is possible to predict the statistical properties of the large-scale fluctuations of B(t) observed by V1 or V2 during a year or so. We illustrate this situation with observations from the recent solar maximum and the declining phase of the solar cycle. Predictions of detailed observations made by V1 and V2 under general conditions (e.g., when there is a large latitudinal gradient) require boundary conditions as a function of time on a surface, such as a Sun-centered sphere with a radius of 1 AU. These conditions can only be provided by global solar observations. We suggest the feasibility of such an approach, using V2 observations for 2005 and 2006. The prediction of observations in the heliosheath requires the solution of the 3-D boundary problem for the supersonic solar wind and propagation of solar wind through the termination shock into the heliosphere. The properties of B(t) observed in the heliosheath have not yet been predicted.

  11. Pulsations in magnetic field and ion flux observed at L = 4. 5 on August 5, 1972

    SciTech Connect

    Engebretson, M.J.; Cahill, L.J. Jr.; Williams, D.J.

    1983-01-01

    After the unusually strong compression of the earth's magnetosphere associated with the August 1972 geomagnetic storm, large amplitude ULF pulsations were observed for several hours in space by Explorer 45 magnetic field and particle instruments near L = 4.5 and at magnetic observatories on the ground over a large range of latitudes. Spectral analysis of Explorer 45 magnetometer data suggests that a compressional mode oscillation coupled to a transverse mode oscillation. Enhancements in amplitude of a 300-s period wave near 0040 UT August 5 coincide with an intensification of 100- to 1000-Hz magnetic and electric field oscillations and with the appearance of enhancements of fluxes of energetic ions. During this period the ion pitch angle distribution in each available energy channel (24--300 keV) followed a periodic sequence, apparently synchronized with the magnetic pulsations, from normal trappping (highest fluxes near 90/sup 0/ and lowest near 0/sup 0/ and 180/sup 0/) to a nearly isotropic particle distribution. During the transitions the particle flux near 90/sup 0/ pitch angle was alternately larger earthward of the satellite (before isotropy) and larger radially outward from the satellite (after isotropy). Intense field-aligned fluxes of lower energy ions (E< or =5 keV) were observed periodically throughout the interval. Possible configurations of the magnetosphere consistent with the wave and particle observations are discussed, the most likely candidate being the presence of a wavelike boundary near the satellite. It is possible that the satellite sensed the low-latitude boundary layer at L = 4.5 during this period of extreme magnetospheric compression.

  12. Paddy field mapping and yield estimation by satellite imagery and in situ observations

    NASA Astrophysics Data System (ADS)

    Oyoshi, K.; Sobue, S.

    2011-12-01

    Since Asian countries are responsible for approximately 90% of the world rice production and consumptions, rice is the most significant cereal crop in Asia. In order to ensure food security and take mitigation strategies or policies to manage food shortages, timely and accurate statistics of rice production are essential. It is time and cost consuming work to create accurate statistics of rice production by ground-based measurements. Hence, satellite remote sensing is expected to contribute food security through the systematic collection of food security related information such as crop growth or yield estimation. In 2011, Japan Aerospace Exploration Agency (JAXA) is collaborating with GISTDA (Geo-Informatics and Space Technology Development Agency, Thailand) in research projects of rice yield estimation by integrating satellite imagery and in situ data. Thailand is one of the largest rice production countries and the largest rice exporting country, therefore rice related statistics are imperative for food security and economy in the country. However, satellite observation by optical sensor in tropics including Thailand is highly limited, because the area is frequently covered by cloud. In contrast, Japanese microwave sensor, namely Phased-Array L-Band Synthetic Aperture Radar (PALSAR) on board Advanced Land Observing Satellite (ALOS) is suitable for monitoring cloudy area such as Southeast Asia, because PALSAR can penetrate clouds and collect land-surface information even if the area is covered by cloud. In this study, rice crop yield over Khon Kaen, northeast part of Thailand was estimated by combining satellite imagery and in-situ observation. This study consists of mainly two parts, paddy field mapping and yield estimation by numerical crop model. First, paddy field areas were detected by integrating PALSAR and AVNIR-2 data. PALSAR imagery has much speckle noise and the border of each landcover is ambiguous compared to that of optical sensor. To overcome this

  13. Observation and analysis of flow field in laser ablation plume of POM

    NASA Astrophysics Data System (ADS)

    Liu, Kefei; Ye, Jifei

    2015-04-01

    When using YAG laser emit strong laser pulses to bombardment solid POM, in the areas of interaction will produce a plume. A shadowgraph photography technique was employed for visualizing temporal evolution of plume. The experiment results show that in the plume flow field, multi-density discontinuities were observed. The plume has a high speed towards laser source, and plume uneven expansion makes the shape and position of discontinuities change. Plume velocity affect the propulsive efficiency, enhance the pulse laser energy can speed up the plume, energy increase to a certain degree of plume speed will reach a steady-state value.

  14. Observations of imposed ordered structures in a dusty plasma at high magnetic field

    NASA Astrophysics Data System (ADS)

    Thomas, Edward; Lynch, Brian; Konopka, Uwe; Merlino, Robert L.; Rosenberg, Marlene

    2015-03-01

    Dusty plasmas have been studied in argon, rf glow discharge plasmas at magnetic fields up to 2 T, where the electrons and ions are strongly magnetized. In this experiment, plasmas are generated between two parallel plate electrodes where the lower, powered electrode is solid and the upper, electrically floating electrode supports a semi-transparent, titanium mesh. We report on the formation of an ordered dusty plasma, where the dust particles form a spatial structure that is aligned to the mesh. We discuss possible mechanisms that may lead to the formation of the "dust grid" and point out potential implications and applications of these observations.

  15. Observations of imposed ordered structures in a dusty plasma at high magnetic field

    SciTech Connect

    Thomas, Edward Lynch, Brian; Konopka, Uwe; Merlino, Robert L.; Rosenberg, Marlene

    2015-03-15

    Dusty plasmas have been studied in argon, rf glow discharge plasmas at magnetic fields up to 2 T, where the electrons and ions are strongly magnetized. In this experiment, plasmas are generated between two parallel plate electrodes where the lower, powered electrode is solid and the upper, electrically floating electrode supports a semi-transparent, titanium mesh. We report on the formation of an ordered dusty plasma, where the dust particles form a spatial structure that is aligned to the mesh. We discuss possible mechanisms that may lead to the formation of the “dust grid” and point out potential implications and applications of these observations.

  16. Spatiotemporal multiplexing method for visual field of view extension in holographic displays with naked eye observation

    NASA Astrophysics Data System (ADS)

    Finke, G.; Kujawińska, M.; Kozacki, T.; Zaperty, W.

    2016-09-01

    In this paper we propose a method which allows to overcome the basic functional problems in holographic displays with naked eye observation caused by delivering too small images visible in narrow viewing angles. The solution is based on combining the spatiotemporal multiplexing method with a 4f optical system. It enables to increase an aperture of a holographic display and extend the angular visual field of view. The applicability of the modified display is evidenced by Wigner distribution analysis of holographic imaging with spatiotemporal multiplexing method and by the experiments performed at the display demonstrator.

  17. Understanding the Interiors of Saturn and Mercury through Magnetic Field Observation and Dynamo Modeling

    NASA Astrophysics Data System (ADS)

    Cao, Hao

    Understanding the interior structure and dynamics of a planet is a key step towards understanding the formation and evolution of a planet. In this thesis, I combine field observation and dynamo modeling to understand planetary interiors. Focus has been put on planets Saturn and Mercury. The Cassini spacecraft has been taking continuous measurements in the Saturnian system since the Saturn orbital insertion in June 2004. Since the Mercury orbital insertion in March 2011, the MESSENGER spacecraft has been examining planet Mercury. After analyzing the close-in portion of the in-situ Cassini magnetometer measurements around Saturn, I find that Saturn's magnetic field features several surprising characteristics. First, Saturn's magnetic field is extremely axisymmetric. We cannot find any consistent departure from axisymmetry, and have put an extremely tight upper bound on the dipole tilt of Saturn: the dipole tilt of Saturn has to be smaller than 0.06 degrees. Second, we find that Saturn's magnetic field is extremely stable with time. Third, we estimated the magnetic moments of Saturn up to degree 5. This is the first magnetic field model for Saturn which goes beyond degree 3. We find that not only Saturn's intrinsic magnetic field is dominated by the axial moments; among these axial moments the odd degree ones dominate. In addition, the first three odd degree axial moments all take the same sign. This sign pattern of Saturn's magnetic moments is in contrast to that of the Earth's magnetic moments which takes alternative signs for the past century. The contrast between the geometries of Saturn's magnetic field and the Earth's magnetic field lead us to propose a dynamo hypothesis which speculates that such differences are caused by structural and dynamical differences inside these two planets. Our dynamo hypothesis for Saturn has two essential ingredients. The first concerns about the existence and size of a central core inside Saturn and its influence on Saturn's dynamo

  18. Validation Of The Earth Observation Land Data Assimilation System By The Field Data Of ESA SPARC Field Campaign

    NASA Astrophysics Data System (ADS)

    Chernetskiy, Maxim; Gomez-Dans, Jose; Lewis, Philip

    2013-12-01

    The Earth Observation Land Data Assimilation System (EO-LDAS) project is uses the weak constraint variational data assimilation (DA) technique for the estimation of land surface parameters and their uncertainties by the remote sensing data. The main goal of the project is to make full use of different sources of optical sensors data, to provide improved estimation of structural and biophysical parameters of land surface. Therefore a software tool - the EO-LDAS prototype - was developed. Within the frame of this work, the possibilities of EO- LDAS have been demonstrated for MERIS/Envisat and CHRIS/Proba data acquired during ESA SPARC 2004 field campaign over an agricultural test-site near Barrax (Spain). We have used a regularization approach and conditions of spatial smoothness in order to better constrain the problem. The EO-LDAS prototype has been used to implement the weak constrain data assimilation (DA) system, to estimate leaf area index (LAI) and Chlorophyll (a + b) concentration as well as their uncertainties.

  19. Modelling field scale water partitioning using on-site observations in sub-Saharan rainfed agriculture

    NASA Astrophysics Data System (ADS)

    Makurira, H.; Savenije, H. H. G.; Uhlenbrook, S.

    2009-08-01

    Smallholder rainfed farming systems generally realise sub-optimal crop yields which are largely attributed to dry spell occurrences during crop growth stages. However, with improved farming practices, it seems possible to significantly increase yield levels even with little and highly variable rainfall. The presented results follow research conducted in the Makanya catchment in northern Tanzania where gross rainfall amounts to less than 400 mm/season which is insufficient to support staple food crops (e.g. maize). Alternative cultivation techniques such as runoff harvesting and in-field micro-storage structures are compared. These techniques aim to reduce soil and nutrient loss from the field but, more importantly, promote in-field infiltration and water retention. Water balance components have been observed in order to study water partitioning processes under different cultivation techniques. Based on rainfall, soil evaporation, transpiration, runoff and soil moisture measurements, a water balance model has been developed to simulate soil moisture variations over the growing season. It appears that about 50% of the diverted water leaves the root zone through deep percolation. Modelling shows that during the field trials the average productive transpiration flow ranged between 1.1-1.4 mm d-1 in the trial plots compared to 0.7-1.0 mm d-1 under traditional tillage practice. Productive transpiration processes accounted for 23-29% while losses to deep percolation accounted for 33-48% of the available water. Conclusions from the research are that the innovations tested are effective in enhancing soil moisture retention at field scale and that diversions allow crop growth moisture conditions to be attained with early rains. It is also concluded that there is more scope for efficient utilisation of the diverted runoff water if storage structures could be installed to regulate water flow to the root zone when required.

  20. Observation of nonuniform structure of the earth's bow shock correlated with interplanetary field orientation.

    NASA Technical Reports Server (NTRS)

    Greenstadt, E. W.

    1972-01-01

    Explorer 33 and 35 magnetometers, on the western and eastern flanks of the earth's bow shock, respectively, observed the boundary concurrently between 0130 and 0430 UT, Oct. 30, 1968. Contrasting shock structures were recorded. Explorer 35 saw a quiet abrupt shock, whereas Explorer 33 saw an irregular noisy boundary with much upstream wave activity. The interplanetary field was roughly in the average archimedean spiral angle and was therefore approximately tangent to the shock at Explorer 35 and normal to the shock at Explorer 33. Gross motions and variable tilting of the aberrated shock probably contributed to the peculiar sequence of shock crossings at the two spacecraft. The observations support a model of the shock in which perpendicular and oblique collisionless structures coexist and form a nonuniform magnetosheath outer boundary.

  1. A system for collecting data on observer preferences in the field using personal data assistants

    NASA Astrophysics Data System (ADS)

    Bennett, John G.; Crile, James

    2003-09-01

    Field tests to compare camouflage patterns rely on collecting data on the preferences of human observers. The director of such tests has been faced with a choice between using pencil-and-paper ballots or using an expensive data collection system based on push buttons wired to personal computers with custom software. In this paper we describe an alternative system that combines the advantages of digital collection with the simplicity of paper ballots. The key ingredients to the system are personal data assistants (PDA's) and database software that runs on a PDA. Specifically, our system makes use of Palm Pilots and the commercial database program thinkDB. Using a stylus, each observer enters his selection of the better camouflage pattern by pushing a radio button on the screen of his Palm Pilot. At the end of the test, the test director uses the Palm HotSync function to transfer the results to a personal computer for analysis.

  2. Shortwave surface radiation network for observing small-scale cloud inhomogeneity fields

    NASA Astrophysics Data System (ADS)

    Lakshmi Madhavan, Bomidi; Kalisch, John; Macke, Andreas

    2016-03-01

    As part of the High Definition Clouds and Precipitation for advancing Climate Prediction Observational Prototype Experiment (HOPE), a high-density network of 99 silicon photodiode pyranometers was set up around Jülich (10 km × 12 km area) from April to July 2013 to capture the small-scale variability of cloud-induced radiation fields at the surface. In this paper, we provide the details of this unique setup of the pyranometer network, data processing, quality control, and uncertainty assessment under variable conditions. Some exemplary days with clear, broken cloudy, and overcast skies were explored to assess the spatiotemporal observations from the network along with other collocated radiation and sky imager measurements available during the HOPE period.

  3. Depth of Field Adaptation for Observation of Microscopic Objects by Using Variable Annular Aperture System

    NASA Astrophysics Data System (ADS)

    Hong, Deokhwa; Cho, Hyungsuck

    2010-11-01

    High magnification optical systems such as microscopes usually suffer from limited depth-of-field (DOF) problem. This hinders efficient observation of microscopic objects and prevents vision based approaches from being applied to automatic micromanipulation tasks. A DOF extension method using variable annular pupil was proposed by the authors' previous publication, and a tradeoff between the depth extension range and image quality was observed. In this article, this tradeoff is numerically analyzed by a proposed wavelet-based image quality measure, and a proper DOF scheme to provide the best image for the given object distribution is proposed. The problem is reduced to finding the optimum pupil division parameter. The experimental results conducted for various imaging conditions with some MEMS objects verify that the system DOF can be adjusted according to their position in depth direction to provide the best visibility.

  4. Shortwave surface radiation budget network for observing small-scale cloud inhomogeneity fields

    NASA Astrophysics Data System (ADS)

    Madhavan, B. L.; Kalisch, J.; Macke, A.

    2015-03-01

    As part of the High Definition Clouds and Precipitation for advancing Climate Prediction Observational Prototype Experiment (HOPE), a high spatial density network of 99 silicon photodiode pyranometers was set up around Jülich (10 km x 12 km area) from April to July 2013, to capture the variability in the radiation field at the surface induced by small-scale cloud inhomogeneity. Each of these autonomously operated pyranometer stations was equipped with weather sensors for simultaneous measurements of ambient air temperature and relative humidity. In this paper, we provide the details of this unique setup of the pyranometer network and the data analysis with initial quality screening procedure we adopted. We also present some exemplary cases consisting of the days with clear, broken cloudy and overcast skies to assess our spatio-temporal observations from the network, and validate their consistency with other collocated radiation measurements available during the HOPE period.

  5. Vibrio viscosus in farmed Atlantic salmon Salmo salar in Scotland: field and experimental observations.

    PubMed

    Bruno, D W; Griffiths, J; Petrie, J; Hastings, T S

    1998-11-30

    Winter mortality occurred in market-sized (2 to 3 kg) Atlantic salmon Salmo salar reared in sea cages in Scottish waters. Many of the fish had skin ulcers. Internally prominent dark-brown petechiae or ecchymotic haemorrhage was observed. Splenomegaly was associated with congestion and widespread necrosis. A Vibrio sp. was isolated from internal organs. Biochemically isolates of the bacterium were similar to a previously described bacterium, Vibrio viscosus, recorded in a phenotypic study from farmed salmon in Norway. This work examines the occurrence of V. viscosus in marine-reared Atlantic salmon for the first time in Scottish waters. An experimental study reproduced the field observations and Koch's postulates were fulfilled. The histopathology associated with natural infection was compared with that in laboratory-infected fish. PMID:9891731

  6. MESSENGER observations of the response of Mercury's magnetosphere to northward and southward interplanetary magnetic fields

    NASA Astrophysics Data System (ADS)

    Slavin, James

    M. H. Acũa (2), B. J. Anderson (3), D. N. Baker (4), M. Benna (2), S. A. Boardsen (1), G. n Gloeckler (5), R. E. Gold (3), G. C. Ho (3), H. Korth (3), S. M. Krimigis (3), S. A. Livi (6), R. L. McNutt Jr. (3), J. M. Raines (5), M. Sarantos (1), D. Schriver (7), S. C. Solomon (8), P. Travnicek (9), and T. H. Zurbuchen (5) (1) Heliophysics Science Division, NASA GSFC, Greenbelt, MD 20771, USA, (2) Solar System Exploration Division, NASA GSFC, Greenbelt, MD 20771, USA, (3) The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA, (4) Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303, USA, (5) Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109, USA (6) Southwest Research Institute, San Antonio, TX 28510, USA, (7) Institute for Geophysics and Planetary Physics, University of California, Los Angeles, CA 90024, USA, (8) Department of Terrestrial Magnetism, Carnegie Institution of Washington, DC 20015, USA, and (9) Institute of Atmospheric Physics, Prague, Czech Republic, 14131 MESSENGER's 14 January 2008 encounter with Mercury has provided new observations of the solar wind interaction with this planet. Here we report initial results concerning this miniature magnetosphere's response to the north-south component of the interplanetary magnetic field (IMF). This is the component of the IMF that is expected to exert the greatest influence over the structure of the magnetopause and the processes responsible for energy transfer into the magnetosphere. The IMF was northward immediately prior to and following the passage of the MESSENGER spacecraft through this small magnetosphere. However, several-minute episodes of southward IMF were observed in the magnetosheath during the inbound portion of the encounter. Evidence for reconnection at the dayside magnetopause in the form of welldeveloped flux transfer events (FTEs) was observed in the magnetosheath following some of

  7. Tsunami damages assessment: vulnerability functions on buildings based on field and earth observation survey.

    NASA Astrophysics Data System (ADS)

    Gauraz, A. L.; Valencia, N.; Koscielny, M.; Guillande, R.; Gardi, A.; Leone, F.; Salaun, T.

    2009-04-01

    The assessment of damages caused by tsunami scenarios on coastal buildings requires using vulnerability matrixes or functions to carry out a relation between the magnitude of the phenomena and the damage expected. These functions represent the probability for a building belonging to a class of vulnerability to suffer from a mean damage level. The physical vulnerability of buildings depends on two parameters: the solicitation level applied by the tsunami on buildings and their resistance capacity. According to the authors after post-tsunami observations (Reese et al. 2007; Ruangrassamee et al. 2006; Leone et al. 2006; Peiris 2006), the level of damage is clearly linked to the water elevation of the inundated areas and the type of observed buildings. Very few works propose relations based on velocity or hydrodynamic pressure of the waves. An approach developed for the estimation of the building vulnerability consists in deriving empirical damage functions starting from field observations. As part of the SCHEMA European Project on the vulnerability assessment for tsunami hazards in the Atlantic and Mediterranean area, vulnerability functions have been elaborated for different classes of buildings in order to produce vulnerability maps for exposed areas with emphasis on extraction of building characteristics using remote sensing data. The damage detection has been carried out by field data collected after the 24 December 2006 tsunami event on the southwest area of Banda Aceh (Sumatra, Thailand) completed by photo-interpretation of satellite images to get representative functions with large population of samples. The building classes consist in several categories depending mainly on the type of construction material (timber/bamboo, traditional brick, reinforced concrete …), the type of structure (beam, pillars, etc) and the number of storeys. The level of damage has been also classified in five categories, from D0 (no damage) to D5 (total destruction). Vulnerability

  8. 30 MHz radar observations of artificial E region field-aligned plasma irregularities

    NASA Astrophysics Data System (ADS)

    Hysell, D. L.

    2008-02-01

    Artificial E region field aligned irregularities (FAIs) have been observed during heating experiments at the HAARP facility using a new 30 MHz coherent scatter radar imager deployed near Homer, Alaska. Irregularities were observed during brief experiments on three quiet days in July and August, 2007, when the daytime E region critical frequency was close to 3 MHz. Irregularities were consistently generated and detected during experiments with O-mode HF pumping on zenith with a 1-min on, 1-min off CW modulation. The scattering cross sections, rise, and fall times of the echoes were observed as well as their spectral properties. Results were found to be mainly in agreement with observations from other mid- and high-latitude sites with some discrepancies. Radar images of the irregularity-filled volume on one case exhibited clear variations in backscatter power and Doppler shift across the volume. The images furthermore show the emergence of a small irregularity-filled region to the south southwest of the main region in the approximate direction of magnetic zenith.

  9. Gravity waves observation of wind field in stratosphere based on a Rayleigh Doppler lidar.

    PubMed

    Zhao, Ruocan; Dou, Xiankang; Sun, Dongsong; Xue, Xianghui; Zheng, Jun; Han, Yuli; Chen, Tingdi; Wang, Guocheng; Zhou, Yingjie

    2016-03-21

    Simultaneous wind and temperature measurements in stratosphere with high time-spatial resolution for gravity waves study are scarce. In this paper we perform wind field gravity waves cases in the stratosphere observed by a mobile Rayleigh Doppler lidar. This lidar system with both wind and temperature measurements were implemented for atmosphere gravity waves research in the altitude region 15-60 km. Observations were carried out for two periods of time: 3 months started from November 4, 2014 in Xinzhou, China (38.425°N,112.729°E) and 2 months started from October 7, 2015 in Jiuquan, China (39.741°N, 98.495°E) . The mesoscale fluctuations of the horizontal wind velocity and the two dimensional spectra analysis of these fluctuations show the presence of dominant oscillatory modes with wavelength of 4-14 km and period of around 10 hours in several cases. The simultaneous temperature observations make it possible to identify gravity wave cases from the relationships between different variables: temperature and horizontal wind. The observed cases demonstrate the Rayleigh Doppler Lidar's capacity to study gravity waves. PMID:27136878

  10. Simulating observations with HARMONI: the integral field spectrograph for the European Extremely Large Telescope

    NASA Astrophysics Data System (ADS)

    Zieleniewski, Simon; Thatte, Niranjan; Kendrew, Sarah; Houghton, Ryan; Tecza, Matthias; Clarke, Fraser; Fusco, Thierry; Swinbank, Mark

    2014-07-01

    With the next generation of extremely large telescopes commencing construction, there is an urgent need for detailed quantitative predictions of the scientific observations that these new telescopes will enable. Most of these new telescopes will have adaptive optics fully integrated with the telescope itself, allowing unprecedented spatial resolution combined with enormous sensitivity. However, the adaptive optics point spread function will be strongly wavelength dependent, requiring detailed simulations that accurately model these variations. We have developed a simulation pipeline for the HARMONI integral field spectrograph, a first light instrument for the European Extremely Large Telescope. The simulator takes high-resolution input data-cubes of astrophysical objects and processes them with accurate atmospheric, telescope and instrumental effects, to produce mock observed cubes for chosen observing parameters. The output cubes represent the result of a perfect data reduc- tion process, enabling a detailed analysis and comparison between input and output, showcasing HARMONI's capabilities. The simulations utilise a detailed knowledge of the telescope's wavelength dependent adaptive op- tics point spread function. We discuss the simulation pipeline and present an early example of the pipeline functionality for simulating observations of high redshift galaxies.

  11. A Reevaluation of Airborne HO(x) Observations from NASA Field Campaigns

    NASA Technical Reports Server (NTRS)

    Olson, Jennifer; Crawford, James H.; Chen, Gao; Brune, William H.; Faloona, Ian C.; Tan, David; Harder, Hartwig; Martinez, Monica

    2006-01-01

    In-situ observations of tropospheric HO(x) (OH and HO2) obtained during four NASA airborne campaigns (SUCCESS, SONEX, PEM-Tropics B and TRACE-P) are reevaluated using the NASA Langley time-dependent photochemical box model. Special attention is given to previously diagnosed discrepancies between observed and predicted HO2 which increase with higher NO(x) levels and at high solar zenith angles. This analysis shows that much of the model discrepancy at high NO(x) during SUCCESS can be attributed to modeling observations at time-scales too long to capture the nonlinearity of HO(x) chemistry under highly variable conditions for NO(x). Discrepancies at high NO(x) during SONEX can be moderated to a large extent by complete use of all available precursor observations. Differences in kinetic rate coefficients and photolysis frequencies available for previous studies versus current recommendations also explain some of the disparity. Each of these causes is shown to exert greater influence with increasing NO(x) due to both the chemical nonlinearity between HO(x) and NO(x) and the increased sensitivity of HO(x) to changes in sources at high NO(x). In contrast, discrepancies at high solar zenith angles will persist until an adequate nighttime source of HO(x) can be identified. It is important to note that this analysis falls short of fully eliminating the issue of discrepancies between observed and predicted HO(x) for high NO(x) environments. These discrepancies are not resolved with the above causes in other data sets from ground-based field studies. Nevertheless, these results highlight important considerations in the application of box models to observationally based predictions of HO(x) radicals.

  12. Structured DC Electric Fields With and Without Associated Plasma Density Gradients Observed with the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Rowland, D.; Klenzing, J.; Freudenreich, H.; Bromund, K.; Liebrecht, C.; Roddy, P.; Hunton, D.

    2009-01-01

    DC electric field observations and associated plasma drifts gathered with the Vector Electric Field Investigation on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite typically reveal considerable variation at large scales (approximately 100's of km), in both daytime and nighttime cases, with enhanced structures usually confined to the nightside. Although such electric field structures are typically associated with plasma density depletions and structures, as observed by the Planar Langmuir Probe on C/NOFS, what is surprising is the number of cases in which large amplitude, structured DC electric fields are observed without a significant plasma density counterpart structure, including their appearance at times when the ambient plasma density appears relatively quiescent. We investigate the relationship of such structured DC electric fields and the ambient plasma density in the C/NOFS satellite measurements observed thus far, taking into account both plasma density depletions and enhancements. We investigate the mapping of the electric fields along magnetic field lines from distant altitudes and latitudes to locations where the density structures, which presumably formed the original seat of the electric fields, are no longer discernible in the observations. In some cases, the electric field structures and spectral characteristics appear to mimic those associated with equatorial spread-F processes, providing important clues to their origins. We examine altitude, seasonal, and longitudinal effects in an effort to establish the origin of such structured DC electric fields observed both with, and without, associated plasma density gradients

  13. Simultaneous observation of ultrafast structural dynamics and transient electrical field by picosecond electron pulses

    NASA Astrophysics Data System (ADS)

    Li, Run-Ze; Zhu, Pengfei; Chen, Long; Chen, Jie; Cao, Jianming; Sheng, Zheng-Ming; Zhang, Jie

    2014-03-01

    Ultrafast electron diffraction and microscopy are very promising methods to study transient structural dynamics with atomic spatial-temporal resolution. However, in these laser-pump electron-probe studies of structural dynamics, a transient electric field induced by laser excitation of the sample could deflect probing electrons, which may eventually leads to a misinterpretation of the diffraction data. Here, picosecond structural dynamics and transient surface electric field evolution, excited by femtosecond laser interaction with a metallic thin film, have been observed simultaneously in real time by ultrashort electron pulses in a transmission configuration. By tracing time dependent changes of electron diffraction and deflection angles, these two processes are found to be significantly different and distinguishable in their temporal behavior. This observation provides an effective approach to extract the otherwise obscured ultrafast structural dynamics and may help to improve the spatiotemporal resolution in ultrafast electron diffraction and microscopy studies. This work was supported by the National Basic Research Program of China and the National Natural Science Foundation of China.

  14. Observations of 3-D Electric Fields and Waves Associated With Reconnection at the Dayside Magnetopause

    NASA Astrophysics Data System (ADS)

    Wilder, F. D.; Ergun, R.; Goodrich, K.; Malaspina, D.; Eriksson, S.; Stawarz, J. E.; Sturner, A. P.; Holmes, J.; Burch, J. L.; Torbert, R. B.; Phan, T.; Le Contel, O.; Goldman, M. V.; Newman, D. L.; Lindqvist, P. A.; Khotyaintsev, Y. V.; Strangeway, R. J.; Russell, C. T.; Giles, B. L.; Pollock, C. J.

    2015-12-01

    The phenomenon of magnetic reconnection, especially at electron scales, is still poorly understood. One process that warrants further investigation is the role of wave phenomenon in mediating magnetic reconnection. Previous observations have shown the presence of electrostatic solitary waves (ESWs) as well as whistler mode waves near the dayside reconnection site. Additionally, recent simulations have suggested that whistler waves might be generated by electron phase space holes associated with ESWs as they propagate along the magnetic separatrix towards the diffusion region. Other observations have shown ESWs with distinct speeds and time scales, suggesting that different instabilities generate the ESWs. NASA's recently launched Magnetospheric Multiscale (MMS) mission presents a unique opportunity to investigate the roles of wave phenomena, such as ESWs and whistlers, in asymmetric reconnection at the dayside magnetopause. We will present 3-D electric and magnetic field data from magnetopause crossings by MMS during its first dayside science phase. Burst mode wave data and electron distributions from all four spacecraft will be analyzed to investigate the origin of these wave phenomena, as well as their impact on the reconnection electric field.

  15. Quiet Sun Magnetic Field Evolution Observed with Hinode SOT and IRIS

    NASA Astrophysics Data System (ADS)

    Fischer, C. E.; Bello González, N.; Rezaei, R.

    2016-04-01

    We study two physical processes that can be commonly observed in the quiet sun and involve temporal evolution of the magnetic field: convective collapse and flux cancellation. The aim is to investigate the response of the chromosphere to the magnetic events in the photosphere below. We have calibrated and aligned a co-spatial and co-temporal 3 hour quiet sun time series observed with the Hinode SOT (Solar Optical Telescope) and the IRIS (Interface Region Imaging Spectrograph) satellites. Convective collapse events are identified in the photosphere by inverting spectropolarimetric data and searching for magnetic field intensification, preceded by a downflow and accompanied by the development of a bright point in Ca II H images. We find a corresponding downflow in the low chromosphere as deduced from IRIS Mg II k and h spectra and an ensuing oscillatory velocity pattern. We use magnetograms in the high photosphere to study pairs of magnetic elements involved in flux cancellation and find an increase in the entire quasi-continuum of the IRIS Mg II k and h spectrum following the flux cancellation process and indicating a substantial energy deposit into the lower atmosphere.

  16. Lena Delta hydrology and geochemistry: long-term hydrological data and recent field observations

    NASA Astrophysics Data System (ADS)

    Fedorova, I.; Chetverova, A.; Bolshiyanov, D.; Makarov, A.; Boike, J.; Heim, B.; Morgenstern, A.; Overduin, P. P.; Wegner, C.; Kashina, V.; Eulenburg, A.; Dobrotina, E.; Sidorina, I.

    2015-01-01

    The Lena River forms one of the largest deltas in the Arctic. We compare two sets of data to reveal new insights into the hydrological, hydrochemical, and geochemical processes within the delta: (i) long-term hydrometric observations at the Khabarova station at the head of the delta from 1951 to 2005; (ii) field hydrological and geochemical observations carried out within the delta since 2002. Periods with differing relative discharge and intensity of fluvial processes were identified from the long-term record of water and sediment discharge. Ice events during spring melt (high water) reconfigured branch channels and probably influenced sediment transport within the delta. Based on summer field measurements during 2005-2012 of discharge and sediment fluxes along main delta channels, both are increased between the apex and the front of the delta. This increase is to a great extent connected with an additional influx of water from tributaries, as well as an increase of suspended and dissolved material released from the ice complex. Summer concentrations of major ion and biogenic substances along the delta branches are partly explained by water sources within the delta, such as thawing ice complex waters, small Lena River branches and estuarine areas.

  17. Field observed relationships between biodiversity and ecosystem functioning during secondary succession in a tropical lowland rainforest

    NASA Astrophysics Data System (ADS)

    Bu, Wensheng; Zang, Runguo; Ding, Yi

    2014-02-01

    The relationship between biodiversity and ecosystem functioning (BEF) is one of the most concerned topics in ecology. However, most of the studies have been conducted in controlled experiments in grasslands, few observational field studies have been carried out in forests. In this paper, we report variations of species diversity, functional diversity and aboveground biomass (AGB) for woody plants (trees and shrubs) along a chronosequence of four successional stages (18-year-old fallow, 30-year-old fallow, 60-year-old fallow, and old-growth forest) in a tropical lowland rainforest recovered after shifting cultivation on Hainan Island, China. Fifty randomly selected sample plots of 20 m × 20 m were investigated in each of the four successional stages. Four functional traits (specific leaf area, wood density, maximum species height and leaf dry matter content) were measured for each woody plants species and the relationships between species/functional diversity and AGB during secondary succession were explored. The results showed that both plant diversity and AGB recovered gradually with the secondary succession. AGB was positively correlated with both species and functional diversity in each stage of succession. Consistent with many controlled experimental results in grasslands, our observational field study confirms that ecosystem functioning is closely related to biodiversity during secondary succession in species rich tropical forests.

  18. Lamost Observations in the Kepler Field. I. Database of Low-resolution Spectra

    NASA Astrophysics Data System (ADS)

    De Cat, P.; Fu, J. N.; Ren, A. B.; Yang, X. H.; Shi, J. R.; Luo, A. L.; Yang, M.; Wang, J. L.; Zhang, H. T.; Shi, H. M.; Zhang, W.; Dong, Subo; Catanzaro, G.; Corbally, C. J.; Frasca, A.; Gray, R. O.; Molenda-Żakowicz, J.; Uytterhoeven, K.; Briquet, M.; Bruntt, H.; Frandsen, S.; Kiss, L.; Kurtz, D. W.; Marconi, M.; Niemczura, E.; Østensen, R. H.; Ripepi, V.; Smalley, B.; Southworth, J.; Szabó, R.; Telting, J. H.; Karoff, C.; Silva Aguirre, V.; Wu, Y.; Hou, Y. H.; Jin, G.; Zhou, X. L.

    2015-09-01

    The nearly continuous light curves with micromagnitude precision provided by the space mission Kepler are revolutionizing our view of pulsating stars. They have revealed a vast sea of low-amplitude pulsation modes that were undetectable from Earth. The long time base of Kepler light curves allows for the accurate determination of the frequencies and amplitudes of pulsation modes needed for in-depth asteroseismic modeling. However, for an asteroseismic study to be successful, the first estimates of stellar parameters need to be known and they cannot be derived from the Kepler photometry itself. The Kepler Input Catalog provides values for the effective temperature, surface gravity, and metallicity, but not always with sufficient accuracy. Moreover, information on the chemical composition and rotation rate is lacking. We are collecting low-resolution spectra for objects in the Kepler field of view with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (lamost, Xinglong observatory, China). All of the requested fields have now been observed at least once. In this paper, we describe those observations and provide a useful database for the whole astronomical community. ) located at the Xinglong observatory, China.

  19. Observing soil water dynamics under two field conditions by a novel sensor system

    NASA Astrophysics Data System (ADS)

    Sheng, W.; Sun, Y.; Schulze Lammers, P.; Schumann, H.; Berg, A.; Shi, C.; Wang, C.

    2011-10-01

    SummarySufficiently available soil water is a basic requirement in agricultural production. Monitoring soil water dynamics (SWD) in the root zone is an optimal approach for managing a crop's growth. This study presents a novel sensor system that simultaneously measures volumetric soil water content (VSWC), apparent electrical conductivity (EC a) and soil temperature at two different soil depths (shallow: 16 cm; deep: 36 cm). For testing its feasibility in the field, two prototypes were installed, one in bare soil and the other in a sugar beet ( Beta vulgaris L.) field in the summer of 2010. Following a sequence of rainfall events randomly distributed over the experimental period, we observed distinct responses from the sensors at each monitored depth in both field conditions. In addition to the multi-parameter measurements, the novel sensor design includes a series of technical advantages such as solar-powered operation, wireless communication, and being relatively easy to install/remove. Thus, the developed wireless sensor system is promising for networked applications in precision farming.

  20. 3-dimensional observations of atmospheric variables during the field campaign COPS

    NASA Astrophysics Data System (ADS)

    Pal, S.; Behrendt, A.; Bauer, H.; Radlach, M.; Riede, A.; Schiller, M.; Wagner, G.

    2008-05-01

    The Convective and Orographically-induced Precipitation Study (COPS) has the aim to advance the quality of forecasts of orographically-induced precipitation in complex terrain. COPS is a Research and Development Project of the World Weather Research Program and considered to be one of the largest field campaigns on quantitative precipitation forecasting that has been performed so far. A network of state-of-the-art active and passive remote sensing systems was combined with in total 10 airborne platforms, Meteosat rapid scans and dense networks of standard meteorological instruments during the three months long field phase (June-August, 2007) in south-western Germany/eastern France to observe atmospheric variables in the three spatial dimensions and in time. By the University of Hohenheim, two novel ground-based mobile scanning lidar systems were deployed: a scanning rotational Raman lidar which provides combined measurements of the field of atmospheric temperature and aerosol optical properties, and a water-vapour differential absorption lidar (DIAL). During COPS, both lidar systems were located at Hornisgrinde, the highest peak of the northern Black Forest together with a large suite of other remote sensing systems. In this contribution we present and discuss highlights of these measurements.

  1. Structures observed on the spot radiance fields during the FIRE experiment

    NASA Technical Reports Server (NTRS)

    Seze, Genevieve; Smith, Leonard; Desbois, Michel

    1990-01-01

    Three Spot images taken during the FIRE experiment on stratocumulus are analyzed. From this high resolution data detailed observations of the true cloud radiance field may be made. The structure and inhomogeneity of these radiance fields hold important implications for the radiation budget, while the fine scale structure in radiance field provides information on cloud dynamics. Wieliki and Welsh, and Parker et al., have quantified the inhomogeneities of the cumulus clouds through a careful examination of the distribution of cloud (and hole) size as functions of an effective cloud diameter and radiance threshold. Cahalan (1988) has compared for different cloud types of (stratocumulus, fair weather cumulus, convective clouds in the ITCZ) the distributions of clouds (and holes) sizes, the relation between the size and the perimeter of these clouds (and holes), and examining the possibility of scale invariance. These results are extended from LANDSAT resolution (57 m and 30 m) to the Spot resolution (10 m) resolution in the case of boundary layer clouds. Particular emphasis is placed on the statistics of zones of high and low reflectivity as a function of a threshold reflectivity.

  2. Giotto magnetic field observations at the outbound quasi-parallel bow shock of Comet Halley

    NASA Technical Reports Server (NTRS)

    Neubauer, F. M.; Glassmeier, K. H.; Acuna, M. H.; Mariani, F.; Musmann, G.

    1990-01-01

    The investigation of the outbound bow shock of Comet Halley using Giotto magnetometer data leads to the following results: the shock is characterized by strong magnetic turbulence associated with an increasing background magnetic field and a change in direction by 60 deg as one goes inward. In HSE-coordinates, the observed normal turned out to be (0.544, - 0.801, 0.249). The thickness of the quasi-parallel shock was 120,000 km. The shock is shown to be a new type of shock transition called a 'draping shock'. In a draping shock with high beta in the transonic transition region, the transonic region is characterized by strong directional variations of the magnetic field. The magnetic turbulence ahead of the shock is characterized by k-vectors parallel or antiparallel to the average field (and, therefore, also to the normal of the quasi-parallel shock) and almost isotropic magnetic turbulence in the shock transition region. A model of the draping shock is proposed which also includes a hypothetical subshock in which the supersonic-subsonic transition is accomplished.

  3. Some experimental observations on circulating currents in a crossed field plasma accelerator

    NASA Technical Reports Server (NTRS)

    Jedlicka, J.; Haacker, J.

    1971-01-01

    Experiments on a thermally ionized argon plasma suggest that applying a Lorentz force by means of orthogonal electric and magnetic fields to an electrically conducting fluid flow imposes necessary but not sufficient conditions for acceleration. There are, in fact, many combinations of current and magnetic field which cause decelerations of the fluid. The deceleration arises from a retarding force which may be larger than the applied Lorentz force. The retarding force causing the deceleration is a consequence of currents circulating completely within the fluid. These currents arise from differences in velocity between the central and wall regions of the duct which interact with the imposed magnetic field to produce differences in induced voltages. The observed physical effects of the circulating currents cause a loss in velocity in the central region of the duct, an increase in thermal energy in the sidewall region, and little change in thermal energy near the electrode wall region. For similar velocity profiles, the adverse effects appear to be related to the product of electrical conductivity and velocity, and performance as an accelerator appears to be controlled by the Hoffman loading parameter (i.e., the ratio of the applied to the induced currents).

  4. Observation of energetic electron confinement in a largely stochastic reversed-field pinch plasma

    NASA Astrophysics Data System (ADS)

    Clayton, D. J.; Chapman, B. E.; O'Connell, R.; Almagri, A. F.; Burke, D. R.; Forest, C. B.; Goetz, J. A.; Kaufman, M. C.; Bonomo, F.; Franz, P.; Gobbin, M.; Piovesan, P.

    2010-01-01

    Runaway electrons with energies >100 keV are observed with the appearance of an m =1 magnetic island in the core of otherwise stochastic Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field-pinch plasmas. The island is associated with the innermost resonant tearing mode, which is usually the largest in the m =1 spectrum. The island appears over a range of mode spectra, from those with a weakly dominant mode to those, referred to as quasi single helicity, with a strongly dominant mode. In a stochastic field, the rate of electron loss increases with electron parallel velocity. Hence, high-energy electrons imply a region of reduced stochasticity. The global energy confinement time is about the same as in plasmas without high-energy electrons or an island in the core. Hence, the region of reduced stochasticity must be localized. Within a numerical reconstruction of the magnetic field topology, high-energy electrons are substantially better confined inside the island, relative to the external region. Therefore, it is deduced that the island provides a region of reduced stochasticity and that the high-energy electrons are generated and well confined within this region.

  5. Structure and Dynamics of the Sub-corotating Region of Saturn's Magnetosphere: Cassini Magnetic Field Observations.

    NASA Astrophysics Data System (ADS)

    Smith, E. J.; Dougherty, M. K.

    2014-12-01

    Measurements of the azimuthal magnetic field component, BΦ, enable the study of the sub-corotating magnetosphere, the associated global current system, the ionospheric Pedersen current, IP, and a comparison with the Cowley-Vasyliunas model. The study is strongly dependent on Cassini's highly elliptical orbits that restrict useful observations to specific orbits and parts of orbits to avoid weak azimuthal fields associated with the magnetopause or other magnetospheric currents. An example is the selection of thirteen identical orbits near 22 +/- 2 hours Local Time and restriction of the data to 4 to 10 Saturn radii. Inferred IP profiles between 10° and 25° ionospheric co-latitude, θi , when averaged, are similar in shape to model predictions with a peak value of 5 million amperes. However, the individual profiles vary significantly, the result of dynamics associated with large-scale motions of the magnetospheric field. The Cowley-Vasyliunas model also relates IP(θi) to magnetospheric rotation rates, ΩS, equivalent to the SKR period, and the sub-corotation rate, ω, and provides a means of estimating ω / ΩS in the night-side magnetosphere as compared to the dayside rotation rates obtained from azimuthal plasma velocity measurements, VΦ. Other carefully- selected orbits extend these results to different ranges in θi and Local Times and provide further values of important magnetospheric parameters and allow additional testing of the model.

  6. Shuttle near-field environmental impacts - Conclusions and observations for launching at other locations

    NASA Technical Reports Server (NTRS)

    Koller, A. M., Jr.; Knott, W. M.

    1985-01-01

    Near field and far field environmental monitoring activities extending from the first launch of the Space Shuttle at the Kennedy Space Center have provided a database from which conclusions can now be drawn for short term, acute effects of launch and, to a lesser degree, long term cumulative effects on the natural environment. Data for the first 15 launches of the Space Shuttle from Kennedy Space Center Pad 39A are analyzed for statistical significance and reduced to graphical presentations of individual and collective disposition isopleths, summarization of observed environmental impacts (e.g., vegetation damage, fish kills), and supporting data from specialized experiments and laboratory analyses. Conclusions are drawn with regard to the near field environment at Pad A, the effects on the lagoonal complex, and the relationships of these data and conclusions to upcoming operations at Complex 39 Pad B where the environment is significantly different. The paper concludes with a subjective evaluation of the likely impacts at Vandenberg Space Launch Complex 6 for the first Shuttle launch next year.

  7. Dynamic Recrystallization in Ice : In-Situ Observation of the Strain Field during Grain Nucleation.

    NASA Astrophysics Data System (ADS)

    Chauve, T.; Montagnat, M.; Tommasi, A.; Vacher, P.

    2014-12-01

    close focus on a triple junction. In particular, we will provide original observations of strain-field evolution associated with the nucleation of new grains and subboundaries close to this triple junction. Associated with post-deformation analyses by AITA and EBSD, these observations enable to follow the strain redistribution due to the nucleation.

  8. Field and LiDAR observations of the Hector Mine California 1999 surface rupture

    NASA Astrophysics Data System (ADS)

    Sousa, F.; Akciz, S. O.; Harvey, J. C.; Hudnut, K. W.; Lynch, D. K.; Scharer, K. M.; Stock, J. M.; Witkosky, R.; Kendrick, K. J.; Wespestad, C.

    2014-12-01

    We report new field- and computer-based investigations of the surface rupture of the October 16, 1999 Hector Mine Earthquake. Since May 2012, in cooperation with the United States Marine Corps Air Ground Combat Center (MCAGCC) at Twentynine Palms, CA, our team has been allowed ground and aerial access to the entire surface rupture. We have focused our new field-based research and imagery analysis along the ~10 kilometer-long maximum slip zone (MSZ) which roughly corresponds to the zone of >4 meter dextral horizontal offset. New data include: 1) a 1 km wide aerial LiDAR survey along the entire surface rupture (@ 10 shots/m2, May 2012, www.opentopography.org); 2) terrestrial LiDAR surveys at 5 sites within the MSZ (@ >1000 shots/m2, April 2014); 3) low altitude aerial photography and ground based photography of the entire MSZ; 4) a ground-truthed database of 87 out of the 94 imagery-based offset measurements made within the MSZ; and 5) a database of 50 new field-based offset measurements made within the MSZ by our team on the ground, 31 of which have also been made on the computer (Ladicaoz) with both the 2000 LiDAR data (@ 0.5 m DEM resolution; Chen et al, in review) and 2012 LiDAR data (@ 35 cm DEM resolution; our team). New results to date include 1) significant variability (> 2 m) in horizontal offsets measured along short distances of the surface rupture (~100 m) within segments of the surface rupture that are localized to a single fault strand; 2) strong dependence of decadal scale fault scarp preservation on local lithology (bedrock vs. alluvial fan vs. fine sediment) and geomorphology (uphill vs. downhill facing scarp); 3) newly observed offset features which were never measured during the post-event field response; 4) newly observed offset features too small to be resolved in airborne LiDAR data (< 1 m); 5) nearly 25% of LiDAR imagery-based measurements that were later ground-truthed were judged by our team to warrant removal from the database due to

  9. Swarm observations of field-aligned currents associated with pulsating auroral patches

    NASA Astrophysics Data System (ADS)

    Gillies, D. M.; Knudsen, D.; Spanswick, E.; Donovan, E.; Burchill, J.; Patrick, M.

    2015-11-01

    We have performed a superposed epoch study of in situ field-aligned currents located near the edges of regions of pulsating aurora observed simultaneously using ground-based optical data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) all-sky imager (ASI) network and magnetometers on board the Swarm satellites. A total of nine traversals of Swarm over regions of pulsating aurora identified using THEMIS ASI were studied. We determined that in the cases where a clear boundary can be identified, strong downward currents are seen just poleward and equatorward of the pulsating patches. A downward current in the range of ~1-6 μA/m2 can be seen just poleward of the boundary. A weaker upward current of ~1-3 μA/m2 is observed throughout the interior of the patch. These observations indicate that currents carried by precipitating electrons within patches could close through horizontal currents and be returned at the edges, in agreement with Oguti and Hayashi (1984) and Hosokawa et al. (2010b). In addition to confirming these earlier results and adding to their statistical significance, the contribution of this study is to quantify the upward and downward current magnitudes, in some cases using two satellites traversing the same pulsating regions. Finally, we compare Swarm's two-satellite field-aligned current product to the single-satellite results and determine that the data product can be compromised in regions of pulsating aurora, a phenomenon that occurs over widespread regions and tends to persist for long periods of time. These results underscore the importance of electrical coupling between the ionosphere and magnetosphere in regions of patchy pulsating aurora.

  10. Moving object detection using motion field constraint with observer motion parameter

    NASA Astrophysics Data System (ADS)

    Suzuki, Hiroki; Ebine, Takumi; Hamada, Nozomu

    1999-10-01

    In this paper we propose a method for detecting moving objects in image sequence observed from a moving platform using optical flow. This problem is difficult because moving observer (i.e. camera) causes apparent motion in the image even for stationary environment. The method can be applied to many situations, such as a robot vision and an obstacle detection for an autonomous vehicle system. We assume that observer motion parameter (translation and rotation) is known and image system is modeled by perspective projection. For the problem, some methods have been proposed, in which the complex logarithm mapping, the estimation of Focus of Expansion and the depth of objects are used. For a given motion parameter of camera, we can formulate motion field constraint (MFC) in the image plane which is satisfied by the relative movement of stationary environment against camera motion. On the other hand, the motion vector in the image plane, which is called motion field, is estimated by the well-known optical flow constraint (OFC). Our main idea is to use the difference between two estimation results. One is the solution of minimizing least squared OFC subjected with MFC, and the other is the solution of that without MFC. For the stationary environment region, the difference between two is small and the difference tends to be large at the moving region. Therefore, the suitable criterion for these values will separate two regions precisely. In our study, two criteria are proposed and are investigated. One criterion uses squared residual of OFC with and without MFC. Another criterion uses directional error between two solutions. The validity of our method is shown through some examples, and the obtained results show the latter criterion gives more accurate estimation than the former one.

  11. Reconciliation of field observations in a North Slope reservoir through pore fluid microvisualizations

    SciTech Connect

    Gamble, I.J.A.; Buller, D.C.; Sinock, K.J.

    1994-12-31

    Log data from a North Slope field indicated particularly high initial water saturations in the major reservoir zone, often in excess of 50%. Despite this, well tests yielded dry oil from the producing intervals, implying that the mobility of the connate water was negligible. A pore fluid microvisualization technique was used to examine the initial distributions of fluids within core samples, in order to reconcile the apparent inconsistencies in the field observations. The amount and distribution of initial water was controlled by the proportion of micro-porosity. Connate water resided primarily within chert, although some was associated with pore-filling kaolinite. This clay mineral was partly water filled and partly oil filled, depending upon the capillary pressure applied to the core sample to acquire S{sub wi}. Very little water was held in a conventional manner as thin films on quartz surfaces. Core flow tests confirmed that mobility of water was essentially zero, even at the highest water saturations. The technique was also used to examine the distributions of fluids at waterflood residual oil saturation. The rock was predominantly water wet in character and classical snap-off of residual oil was observe,d with the oil being trapped as isolated blobs or as multi-pore ganglia. Saturation and distribution of oil after waterflooding was found to depend upon the flow rate and flow regime used. Microvisualizations provide a unique insight into fluid distributions at S{sub wi} and S{sub orw}. For this reservoir renewed confidence in saturations derived from well logs was realized.

  12. Heliosheath magnetic field and plasma observed by Voyager 2 during 2011

    NASA Astrophysics Data System (ADS)

    Burlaga, L. F.; Ness, N. F.; Richardson, J. D.

    2014-08-01

    We discuss magnetic field and plasma observations from Voyager 2 (V2) during 2011, when V2 was beginning to see the effects of increasing solar activity following the solar minimum in 2009. The magnetic field strength (B) profile showed large amplitude fluctuations that can be resolved into a linear increase of B with time and a sinusoidal variation of the period of 86.2 ± 0.8 days. Voyager 2 was in a unipolar region in which the magnetic polarity was directed away from the Sun along the Parker spiral 96% of the time, indicating that V2 was poleward of the heliospheric current sheet throughout most of 2011. The distribution of B was lognormal, but a Gaussian distribution was observed when the linear variation of B was subtracted from the data. The distribution of daily increments of B was a q-Gaussian distribution with q = 1.1 ± 0.1, which is less intermittent than normally observed in the heliosheath. However, the distribution of hourly increments of B was a q-Gaussian distribution with q = 1.5 ± 0.03. The density, temperature, and velocity increased linearly from the beginning of 2011 to approximately day 254. The magnetic and thermal pressure tended to increase throughout the year, but the magnetic pressure dominated most of the time. The counting rate of >70 MeV/nucleon particles increased rapidly during the first 250 days, but it leveled out during the rest of the year when B was stronger. The empirical CR-B relationship describes this behavior.

  13. Modelling field scale water partitioning using on-site observations in sub-Saharan rainfed agriculture

    NASA Astrophysics Data System (ADS)

    Makurira, H.; Savenije, H. H. G.; Uhlenbrook, S.

    2010-04-01

    Smallholder rainfed farming systems generally realise sub-optimal crop yields which are largely attributed to dry spell occurrences during crop growth stages. However, through the introduction of appropriate farming practices, it is possible to substantially increase yield levels even with little and highly variable rainfall. The presented results follow research conducted in the Makanya catchment in northern Tanzania where gross rainfall amounts to less than 400 mm/season which is insufficient to support staple food crops (e.g. maize). The yields from farming system innovations (SIs), which are basically alternative cultivation techniques, are compared against traditional farming practices. The SIs tested in this research are runoff harvesting used in combination with in-field trenches and soil bunds (fanya juus). These SIs aim to reduce soil and nutrient loss from the field and, more importantly, promote in-field infiltration and water retention. Water balance components have been observed in order to study water partitioning processes for the "with" and "without" SI scenarios. Based on rainfall, soil evaporation, transpiration, runoff and soil moisture measurements, a water balance model has been developed to simulate soil moisture variations over the growing season. Simulation results show that, during the field trials, the average productive transpiration flow ranged between 1.1-1.4 mm d-1 in the trial plots compared to 0.7-1.0 mm d-1 under traditional tillage practice. Productive transpiration processes accounted for 23-29% while losses to deep percolation accounted for 33-48% of the available water. The field system has been successfully modelled using the spreadsheet-based water balance 1-D model. Conclusions from the research are that the SIs that were tested are effective in enhancing soil moisture retention at field scale and that diversions allow crop growth moisture conditions to be attained with early rains. From the partitioning analysis, it is also

  14. Comparisons of GCM and Observed Surface Wind Fields over the Tropical Indian and Pacific Oceans.

    NASA Astrophysics Data System (ADS)

    Graham, Nicholas E.; Barnett, Tim P.; Chervin, Robert M.; Schlesinger, Michael E.; Schlese, Ulrich

    1989-03-01

    qualitatively correct, differences in the GCM and observed forcing fields would result in large errors away from the equator. Tests with the Florida State University model of the tropical Pacific, to be reported in a later paper, support this conclusion.Taken together, these findings suggest that while GCMs are capable of reproducing correctly many features of the tropical surface wind fields, discrepancies remain with respect to both the annual cycle and the response to the anomalous SST patterns associated with ENSO. These discrepancies appear to be related, at least in part, to interactions between organized convection and the circulation. To what degree these differences would affect the oceanic component of a coupled model is currently under study.

  15. Time-resolved observation of discrete and continuous magnetohydrodynamic dynamo in the reversed-field pinch edge

    SciTech Connect

    Ji, H.; Almagri, A.F.; Prager, S.C.; Sarff, J.S. )

    1994-08-01

    We report the first experimental verification of the magnetohydrodynamic (MHD) dynamo in the reversed-field pinch (RFP). A burst of MHD dynamo electric field is observed during the sawtooth crash, followed by an increase in the local parallel current in the Madison Symmetric Totus RFP edge. By measuring each term, the parallel MHD mean-field Ohm's law is observed to hold within experimental error bars both between and during sawtooth crashes.

  16. Mid-Continental Intensive Field Campaign Atmospheric CO2 Observations Compared to Forward Models

    NASA Astrophysics Data System (ADS)

    Diaz, L. I.; Davis, K. J.; Miles, N. L.; Richardson, S.; Schuh, A. E.; Denning, A.; Andrews, A. E.; Jacobson, A. R.; Corbin, K.

    2009-12-01

    Two commonly used approaches to study source/sinks of CO2 are the “bottom-up” and the “top-down” methods. Because of the large discrepancies between these approaches, the North America Carbon Program devised the Mid-Continental Intensive field campaign (MCI). The MCI campaign aims at improving the carbon flux estimates of both approaches with a combination of atmospheric transport models, a denser network of in-situ atmospheric CO2 measurements and agricultural inventories. The first step in evaluating and improving inverse models is to compare observed CO2 concentrations and predicted concentrations from forwards models. This study shows a model-data comparison at multiple temporal and spatial scales for the 2007 growing season. In-situ tower-based observations are compared to two different forwards models: NOAA’s Carbon Tracker and CSU’s SiBcrop-RAMS. Observations from two tall towers of the National Oceanic and Atmospheric Administration (NOAA) and five towers of Ring2 PSU network are used for this comparison. The towers are located in an intensively agricultural region of the North American continent. Comparisons to date show that both models predict higher mid-summer concentrations at three sites located in the “corn belt.” Both models have difficulty reproducing the observed monthly-average spatial gradient across these sites. The models also underestimate the maximum observed spatial gradients in daytime, daily-averaged boundary layer concentrations. These results suggest that the rapid photosynthetic rates found in corn are not yet well-simulated in these models, and that these data, when used in inversions, will provide a valuable constraint on regional fluxes.

  17. Phase-field modeling and experimental observation of the irregular interface morphology during directional solidification

    NASA Astrophysics Data System (ADS)

    Guo, Taiming

    Evolution of the complex solid-liquid interface morphology during a solidification process is an important issue in solidification theory since the morphology eventually dictates the final microstructure of the solidified material and therefore the material properties. Significant progress have been made in recent years in the study of the formation and development of regular dendritic growth, while only limited understanding is achieved for the irregular interface patterns observed in many industry processes. This dissertation focuses on the physical mechanisms of the development and transition of various irregular interface patterns, including the tilted dendritic, the seaweed, and the degenerate patterns. Both experimental observations and numerical simulation using the phase field modeling are performed. A special effort is devoted on the effects of the capillary anisotropy and the kinetic anisotropy in the evolution of the interface morphology during solidification. Experimentally, a directional solidification system is constructed to observe in situ the interface morphology by using the transparent organic material succinonitrile. With such a system, both the regular interface patterns (cellular and dendritic) and the irregular interface patterns (seaweed, degenerate and tilted dendritic) are observed. The effects of the temperature gradient and the interface velocity on the development and transition of the irregular interface patterns are investigated. It is found that the interface morphology transits from the seaweed to the tilted dendritic pattern as the interface velocity increases, while the tilted dendritic pattern may transit to the degenerate seaweed pattern as the temperature gradient increases. Under certain conditions, dendrites and seaweed coexist within the same grain. The dynamic transitions among various patterns and the effect of the solidification conditions are examined in detail. Numerically, a 2-D phase field model is developed to

  18. First faint dual-field off-axis observations in optical long baseline interferometry

    SciTech Connect

    Woillez, J.; Wizinowich, P.; Ragland, S.; Akeson, R.; Millan-Gabet, R.; Colavita, M.; Eisner, J.; Monnier, J. D.; Pott, J.-U.

    2014-03-10

    Ground-based long baseline interferometers have long been limited in sensitivity in part by the short integration periods imposed by atmospheric turbulence. The first observation fainter than this limit was performed on 2011 January 22 when the Keck Interferometer observed a K = 11.5 target, about 1 mag fainter than its K = 10.3 atmospherically imposed limit; the currently demonstrated limit is K = 12.5. These observations were made possible by the Dual-Field Phase-Referencing (DFPR) instrument, part of the NSF-funded ASTrometry and phase-Referenced Astronomy project; integration times longer than the turbulence time scale are made possible by its ability to simultaneously measure the real-time effects of the atmosphere on a nearby bright guide star and correct for it on the faint target. We present the implementation of DFPR on the Keck Interferometer. Then, we detail its on-sky performance focusing on the accuracy of the turbulence correction and the resulting fringe contrast stability.

  19. Characterization of Saturn's bow shock: Magnetic field observations of quasi-perpendicular shocks

    NASA Astrophysics Data System (ADS)

    Sulaiman, A. H.; Masters, A.; Dougherty, M. K.

    2016-05-01

    Collisionless shocks vary drastically from terrestrial to astrophysical regimes resulting in radically different characteristics. This poses two complexities. First, separating the influences of these parameters on physical mechanisms such as energy dissipation. Second, correlating observations of shock waves over a wide range of each parameter, enough to span across different regimes. Investigating the latter has been restricted since the majority of studies on shocks at exotic regimes (such as supernova remnants) have been achieved either remotely or via simulations, but rarely by means of in situ observations. Here we present the parameter space of MA bow shock crossings from 2004 to 2014 as observed by the Cassini spacecraft. We find that Saturn's bow shock exhibits characteristics akin to both terrestrial and astrophysical regimes (MA of order 100), which is principally controlled by the upstream magnetic field strength. Moreover, we determined the θBn of each crossing to show that Saturn's (dayside) bow shock is predominantly quasi-perpendicular by virtue of the Parker spiral at 10 AU. Our results suggest a strong dependence on MA in controlling the onset of physical mechanisms in collisionless shocks, particularly nontime stationarity and variability. We anticipate that our comprehensive assessment will yield deeper insight into high MA collisionless shocks and provide a broader scope for understanding the structures and mechanisms of collisionless shocks.

  20. Observations of field-aligned currents, particles, and plasma drift in the polar cusps near solstice

    NASA Technical Reports Server (NTRS)

    Bythrow, P. F.; Potemra, T. A.; Hoffman, R. A.

    1982-01-01

    Magnetic perturbations observed by the TRIAD magnetometer within two hours of an AE-C spacecraft pass provide field-aligned current data, from the same local time in the northern hemisphere, for a study of the polar cusp. The AE-C spinning mode has allowed the use of the Z-axis magnetometer for Birkeland current observations, in conjunction with particle and drift measurements. The average B(z) were found to be 1.9 nT and -1.1 nT during the first two hourly intervals on January 15, 1977. Measurements from the low energy electron experiment revealed intense fluxes of soft, cusp-like 100 eV Maxwellian electrons throughout the prenoon polar cap. The upward directed current can be identified as the dominant cusp current appropriate for B(y) values lower than zero, while the downward directed current, which has the appropriate sign of a dayside region 1 current, is observed to lie entirely within a westerly, antisunward-convecting plasma.

  1. Field observations of the relation between satellite and sea radiances in coastal waters

    NASA Astrophysics Data System (ADS)

    Aas, Eyvind; Sørensen, Kai

    1995-08-01

    Estimates of the different contributions to the satellite radiance above the outer Oslofjord are presented. The contribution from the sea is of the order of 10% of the total signal, and the part due to reflection from the sea surface constitutes 10-20%. The presence of land may increase the satellite radiance up to 4-9%, but such effects, which are probably reduced to 1/e at a distance of 1 km from the coast, cannot be detected in the present measurements. In situ observations of the marine radiance are corrected for shadings by ship and instrument and for varying solar altitude. The average correction for the self-shading effect of the marine instrument becomes 30-50% in these waters. The linear relations between satellite and sea radiances are determined with correlation coefficients of better than 0.95. The observed minimum value of the satellite radiance (or darkest pixel) is not a satisfactory approximation for the atmospheric correction. It is concluded that, in coastal waters and at the present stage, satellite observations have to be combined with field measurements to obtain reliable results.

  2. Magnetic Field Structure of Pressure Balanced Structures from Ulysses High Latitudes Observations

    NASA Technical Reports Server (NTRS)

    Yamauchi, Y.; Suess, S. T.; Sakurai, T.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Ulysses observations showed that pressure balance structures (PBSs) are a common feature in the high-latitude solar winds near the solar minimum. On the other hand, coronal plumes are common in polar coronal holes near the solar minimum. It is therefore considered that the PBSs would be remnants of plumes. Several detailed studies of the PBSs have been made from Ulysses/SWOOPS observations, but study of their magnetic structures has not yet been done. The study of the magnetic structure is important because previous observations and theoretical models of plumes indicate that they are related to the network activity such as magnetic reconnection on the photosphere. We have investigated the magnetic structures of the PBSs with Ulysses magnetometer and SWOOPS data. We have found that magnetic reversals in radial magnetic field take place while the spacecraft passes through most of the PBSs These magnetic reversals have been interpreted as large amplitude Alfv/'enic fluctuations but our results suggest that Ulysses is also traversing current sheets of plasmoids associated with network activity at the base of plumes.

  3. Australian Soil Moisture Field Experiments in Support of Soil Moisture Satellite Observations

    NASA Technical Reports Server (NTRS)

    Kim, Edward; Walker, Jeff; Rudiger, Christopher; Panciera, Rocco

    2010-01-01

    Large-scale field campaigns provide the critical fink between our understanding retrieval algorithms developed at the point scale, and algorithms suitable for satellite applications at vastly larger pixel scales. Retrievals of land parameters must deal with the substantial sub-pixel heterogeneity that is present in most regions. This is particularly the case for soil moisture remote sensing, because of the long microwave wavelengths (L-band) that are optimal. Yet, airborne L-band imagers have generally been large, heavy, and required heavy-lift aircraft resources that are expensive and difficult to schedule. Indeed, US soil moisture campaigns, have been constrained by these factors, and European campaigns have used non-imagers due to instrument and aircraft size constraints. Despite these factors, these campaigns established that large-scale soil moisture remote sensing was possible, laying the groundwork for satellite missions. Starting in 2005, a series of airborne field campaigns have been conducted in Australia: to improve our understanding of soil moisture remote sensing at large scales over heterogeneous areas. These field data have been used to test and refine retrieval algorithms for soil moisture satellite missions, and most recently with the launch of the European Space Agency's Soil Moisture Ocean Salinity (SMOS) mission, to provide validation measurements over a multi-pixel area. The campaigns to date have included a preparatory campaign in 2005, two National Airborne Field Experiments (NAFE), (2005 and 2006), two campaigns to the Simpson Desert (2008 and 2009), and one Australian Airborne Cal/val Experiment for SMOS (AACES), just concluded in the austral spring of 2010. The primary airborne sensor for each campaign has been the Polarimetric L-band Microwave Radiometer (PLMR), a 6-beam pushbroom imager that is small enough to be compatible with light aircraft, greatly facilitating the execution of the series of campaigns, and a key to their success. An

  4. Electric Field Observations of Plasma Convection, Shear, Alfven Waves, and other Phenomena Observed on Sounding Rockets in the Cusp and Boundary Layer

    NASA Technical Reports Server (NTRS)

    Pfaff, R. F.

    2009-01-01

    On December 14,2002, a NASA Black Brant X sounding rocket was launched equatorward from Ny Alesund, Spitzbergen (79 N) into the dayside cusp and subsequently cut across the open/closed field line boundary, reaching an apogee of771 km. The launch occurred during Bz negative conditions with strong By negative that was changing during the flight. SuperDarn (CUTLASS) radar and subsequent model patterns reveal a strong westward/poleward convection, indicating that the rocket traversed a rotational reversal in the afternoon merging cell. The payload returned DC electric and magnetic fields, plasma waves, energetic particle, suprathermal electron and ion, and thermal plasma data. We provide an overview of the main observations and focus on the DC electric field results, comparing the measured E x B plasma drifts in detail with the CUTLASS radar observations of plasma drifts gathered simultaneously in the same volume. The in situ DC electric fields reveal steady poleward flows within the cusp with strong shears at the interface of the closed/open field lines and within the boundary layer. We use the observations to discuss ionospheric signatures of the open/closed character of the cusp/low latitude boundary layer as a function of the IMF. The electric field and plasma density data also reveal the presence of very strong plasma irregularities with a large range of scales (10 m to 10 km) that exist within the open field line cusp region yet disappear when the payload was equatorward of the cusp on closed field lines. These intense low frequency wave observations are consistent with strong scintillations observed on the ground at Ny Alesund during the flight. We present detailed wave characteristics and discuss them in terms of Alfven waves and static irregularities that pervade the cusp region at all altitudes.

  5. Mercury's gravity field and ephemeris after 3 years of MESSENGER orbital observations

    NASA Astrophysics Data System (ADS)

    Genova, Antonio; Mazarico, Erwan; Goossens, Sander J.; Lemoine, Frank G.; Neumann, Gregory A.; Smith, David E.; Zuber, Maria T.; Solomon, Sean C.

    2014-05-01

    18 March 2014 will be the third anniversary of MESSENGER's insertion into orbit about Mercury. The initial orbit was highly eccentric and nearly polar, with a 12-h period and a periapsis at 200 km altitude and ~60°N latitude. The third-body perturbation of the Sun combined with the high eccentricity of the orbit led to a substantial evolution of the periapsis, which drifted slowly northward and reached an altitude of 500 km several times before orbit-corrections maneuvers returned the periapsis altitude to ~200 km. In March 2012, the mission orbital phase was extended for a second year, and the spacecraft transitioned to an 8-h orbit period one month later. A second extended mission started in March 2013, will last for another two years, and will eventually allow observations at very low altitudes (<100 km), starting in September 2014. One of the main mission goals is the determination of the interior structure of Mercury, enabled by a suite of instruments that includes the radio system and a laser altimeter. The X-band tracking system and NASA's Deep Space Network (DSN) were used to determine the gravity field of Mercury. The effective spatial resolution of the gravity field is strongly dependent on latitude, however, because of MESSENGER's eccentric orbit and its high apoapsis over the southern hemisphere (~15,000 km in the first year, ~10,000 km subsequently). The gravity field of the southern hemisphere remains largely unconstrained at short wavelengths, although the global long-wavelength field has been determined robustly. Furthermore, MESSENGER radio tracking data represent an excellent opportunity to improve Mercury's ephemeris. The current knowledge of the orbit of Mercury around the Sun has been mainly defined by direct ranging. Range measurements from the three Mercury flybys and orbital phase of MESSENGER provide a strong data set to measure the motion of Mercury's center of mass. The 1-m range accuracy potentially allows the recovery of the

  6. MAGNETIC FIELD STRENGTH FLUCTUATIONS IN THE HELIOSHEATH: VOYAGER 1 OBSERVATIONS DURING 2009

    SciTech Connect

    Burlaga, L. F.; Ness, N. F. E-mail: nfnudel@yahoo.com

    2012-01-01

    We analyze the ''microscale fluctuations'' of the magnetic field strength B on a scale of several hours observed by Voyager1 (V1) in the heliosheath during 2009. The microscale fluctuations of B range from coherent to stochastic structures. The amplitude of microscale fluctuations of B during 1 day is measured by the standard deviation (SD) of 48 s averages of B. The distribution of the daily values of SD is lognormal. SD(t) from day of year (DOY) 1 to 331, 2009, is very intermittent. SD(t) has a 1/f or 'pink noise' spectrum on scales from 1 to 100 days, and it has a broad multifractal spectrum f({alpha}) with 0.57 {<=} {alpha} {<=} 1.39. The time series of increments SD(t + {tau}) - SD(t) has a pink noise spectrum with {alpha}' = 0.88 {+-} 0.14 on scales from 1 to 100 days. The increments have a Tsallis (q-Gaussian) distribution on scales from 1 to 165 days, with an average q = 1.75 {+-} 0.12. The skewness S and kurtosis K have Gaussian and lognormal distributions, respectively. The largest spikes in K(t) and S(t) are often associated with a change in B across a data gap and with identifiable physical structures. The 'turbulence' observed by V1 during 2009 was weakly compressible on average but still very intermittent, highly variable, and highly compressible at times. The turbulence observed just behind the termination shock by Voyager 2 was twice as strong. These observations place strong constraints on any model of 'turbulence' in the heliosheath.

  7. Magnetic Field Strength Fluctuations in the Heliosheath: Voyager 1 Observations during 2009

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Ness, N. F.

    2011-01-01

    We analyze the "microscale fluctuations" of the magnetic field strength Beta on a scale of several hours observed by Voyager I (VI) in the heliosheath during 2009. The microscale fluctuations of Beta range from coherent to stochastic structures. The amplitude of microscale fluctuations of Beta during 1 day is measured by the standard deviation (SD) of 48 s averages of B. The distribution of the daily values of SD is lognormal. SD(t) from day of year (DOY) I to 331, 2009, is very intermittent. SD(t) has a 1/f or "pink noise" spectrum on scales from I to 100 days, and it has a broad multi fractal spectrum f(alpha) with 0.57 much < alpha much < 1.39. The time series of increments SD(t + r) - SD(t) has a pink noise spectrum with alpha' = 0.88 +/- 0.14 on scales from 1 to 100 days. The increments have a Tsallis (q-Gaussian) distribution on scales from 1 to 165 days, with an average q = 1.75 +/- 0.12. The skewness S and kurtosis K have Gaussian and lognormal distributions, respectively. The largest spikes in K(t) and Set) are often associated with a change in Beta across a data gap and with identifiable physical structures. The "turbulence" observed by VI during 2009 was weakly compressible on average but still very intermittent, highly variable, and highly compressible at times. The turbulence observed just behind the termination shock by Voyager 2 was twice as strong. These observations place strong constraints on any model of "turbulence" in the heliosheath.

  8. Magnetic Field Strength Fluctuations in the Heliosheath: Voyager 1 Observations During 2009

    NASA Technical Reports Server (NTRS)

    Brulaga, L. F.; Ness, N. F.

    2012-01-01

    We analyze the microscale fluctuations of the magnetic field strength B on a scale of several hours observed by Voyager1 (V1) in the heliosheath during 2009. The microscale fluctuations of B range from coherent to stochastic structures. The amplitude of microscale fluctuations of B during 1 day is measured by the standard deviation (SD) of 48 s averages of B. The distribution of the daily values of SD is lognormal. SD(t) from day of year (DOY) 1 to 331, 2009, is very intermittent. SD(t) has a 1/f or "pink noise" spectrum on scales from 1 to 100 days, and it has a broad multifractal spectrum f(alpha) with 0.57 less than or equal to alpha less than or equal to 1.39. The time series of increments SD(t + tau) -- SD(t) has a pink noise spectrum with alpha(1) = 0.88 plus or minus 0.14 on scales from 1 to 100 days. The increments have a Tsallis (q-Gaussian) distribution on scales from 1 to 165 days, with an average q = 1.75 plus or minus 0.12. The skewness S and kurtosis K have Gaussian and lognormal distributions, respectively. The largest spikes in K(t) and S(t) are often associated with a change in B across a data gap and with identifiable physical structures. The "turbulence" observed by V1 during 2009 was weakly compressible on average but still very intermittent, highly variable, and highly compressible at times. The turbulence observed just behind the termination shock by Voyager 2 was twice as strong. These observations place strong constraints on any model of turbulence in the heliosheath.

  9. Radar observations of field-aligned plasma irregularities in the SEEK-2 campaign

    NASA Astrophysics Data System (ADS)

    Saito, S.; Yamamoto, M.; Fukao, S.; Marumoto, M.; Tsunoda, R. T.

    2005-10-01

    During the Sporadic E Experiment over Kyushu 2 (SEEK-2) campaign, field-aligned irregularities (FAIs) associated with midlatitude sporadic-E (Es) layers were observed with two backscatter radars, the Lower Thermosphere Profiler Radar (LTPR) and the Frequency Agile Radar (FAR), which were located 40 km apart in Tanegashima, Japan. We conducted observations of FAI echoes from 31 July to 24 August 2002, and the radar data were used to determine launch timing of two sounding rockets on 3 August 2002. Our comparison of echoes obtained by the LTPR and the FAR revealed that echoes often appeared at the FAR about 10min earlier than they did at the LTPR and were well correlated. This indicates that echoing regions drift with a southward velocity component that maintains the spatial shape. Interferometry observations that were conducted with the LTPR from 3 to 8 August 2002, revealed that the quasi-periodic (QP) striations in the Range-Time-Intensity (RTI) plots were due to the apparent motion of echoing regions across the radar beam including both main and side lobes. In most cases, the echo moved to the east-southeast at an almost constant altitude of 100 110 km, which was along the locus of perpendicularity of the radar line-of-sight to the geomagnetic field line. We found that the QP pattern on the RTI plot reflects the horizontal structure and motion of the (Es layer, and that echoing regions seemed to be in one-dimensionally elongated shapes or in chains of patches. Neutral wind velocities from 75 to 105 km altitude were simultaneously derived with meteor echoes from the LTPR. This is the first time-continuous simultaneous observation FAIs and neutral wind with interferometry measurements. Assuming that the echoing regions were drifting with an ambient neutral wind, we found that the echoing region was aligned east-northeast-west-southwest in eight out of ten QP echo events during the SEEK-2 campaign. A range rate was negative (positive), when a frontal structure of

  10. Chatanika observations of the latitudinal structure of electric fields and particle precipitation on November 21, 1975

    NASA Technical Reports Server (NTRS)

    Wedde, T.; Doupnik, J. R.; Banks, P. M.

    1977-01-01

    By using a new multiposition experimental procedure the incoherent scatter radar facility of Chatanika, Alaska, has been used to obtain detailed latitudinal structure of ion velocities and electric fields in the afternoon and midnight sectors during a period of moderate magnetic disturbance. In particular, the latitudinal and local time structure of the Harang discontinuity has been investigated. In agreement with other observations it is found that the convection flow direction changes from westward through south to eastward over a fairly wide local time range (1-2 hours), the highest latitudes displaying the widest region. The Harang discontinuity encounter is accompanied by an abrupt increase in electron precipitation, the most intense part being located slightly east of the center of the discontinuity. It is suggested that this injection is due to processes closely connected with the discontinuity region itself, rather than to a substorm-related energization.

  11. Spatio-Temporal Dynamics in Collective Frog Choruses Examined by Mathematical Modeling and Field Observations

    NASA Astrophysics Data System (ADS)

    Aihara, Ikkyu; Mizumoto, Takeshi; Otsuka, Takuma; Awano, Hiromitsu; Nagira, Kohei; Okuno, Hiroshi G.; Aihara, Kazuyuki

    2014-01-01

    This paper reports theoretical and experimental studies on spatio-temporal dynamics in the choruses of male Japanese tree frogs. First, we theoretically model their calling times and positions as a system of coupled mobile oscillators. Numerical simulation of the model as well as calculation of the order parameters show that the spatio-temporal dynamics exhibits bistability between two-cluster antisynchronization and wavy antisynchronization, by assuming that the frogs are attracted to the edge of a simple circular breeding site. Second, we change the shape of the breeding site from the circle to rectangles including a straight line, and evaluate the stability of two-cluster and wavy antisynchronization. Numerical simulation shows that two-cluster antisynchronization is more frequently observed than wavy antisynchronization. Finally, we recorded frog choruses at an actual paddy field using our sound-imaging method. Analysis of the video demonstrated a consistent result with the aforementioned simulation: namely, two-cluster antisynchronization was more frequently realized.

  12. Observation of laser-induced field-free permanent planar alignment of molecules

    NASA Astrophysics Data System (ADS)

    Hoque, Md. Z.; Lapert, M.; Hertz, E.; Billard, F.; Sugny, D.; Lavorel, B.; Faucher, O.

    2011-07-01

    Permanent planar alignment of gas-phase linear molecules is achieved by a pair of delayed perpendicularly polarized short laser pulses. The experiment is performed in a supersonic jet, ensuring a relatively high number density of molecules with moderately low rotational temperature. The effect is optically probed on a femtosecond time scale by the use of a third short pulse, enabling a time-resolved birefringence detection performed successively in two perpendicular planes of the laboratory frame. The technique allows for an unambiguous estimation of the molecular planar delocalization produced within the polarization plane of the pulse pair after the turn-off of the field. The measurements are supported by numerical simulations which lead to the quantification of the observed effect and provide more physical insights into the phenomenon.

  13. Observation of correlated electronic decay in expanding clusters triggered by near-infrared fields.

    PubMed

    Schütte, B; Arbeiter, M; Fennel, T; Jabbari, G; Kuleff, A I; Vrakking, M J J; Rouzée, A

    2015-01-01

    When an excited atom is embedded into an environment, novel relaxation pathways can emerge that are absent for isolated atoms. A well-known example is interatomic Coulombic decay, where an excited atom relaxes by transferring its excess energy to another atom in the environment, leading to its ionization. Such processes have been observed in clusters ionized by extreme-ultraviolet and X-ray lasers. Here, we report on a correlated electronic decay process that occurs following nanoplasma formation and Rydberg atom generation in the ionization of clusters by intense, non-resonant infrared laser fields. Relaxation of the Rydberg states and transfer of the available electronic energy to adjacent electrons in Rydberg states or quasifree electrons in the expanding nanoplasma leaves a distinct signature in the electron kinetic energy spectrum. These so far unobserved electron-correlation-driven energy transfer processes may play a significant role in the response of any nano-scale system to intense laser light. PMID:26469997

  14. Cosmology with hybrid expansion law: scalar field reconstruction of cosmic history and observational constraints

    SciTech Connect

    Akarsu, Özgür; Kumar, Suresh; Myrzakulov, R.; Sami, M.; Xu, Lixin E-mail: sukuyd@gmail.com E-mail: samijamia@gmail.com

    2014-01-01

    In this paper, we consider a simple form of expansion history of Universe referred to as the hybrid expansion law - a product of power-law and exponential type of functions. The ansatz by construction mimics the power-law and de Sitter cosmologies as special cases but also provides an elegant description of the transition from deceleration to cosmic acceleration. We point out the Brans-Dicke realization of the cosmic history under consideration. We construct potentials for quintessence, phantom and tachyon fields, which can give rise to the hybrid expansion law in general relativity. We investigate observational constraints on the model with hybrid expansion law applied to late time acceleration as well as to early Universe a la nucleosynthesis.

  15. Spatial characteristics of observed precipitation fields: A catalog of summer storms in Arizona, Volume 1

    NASA Technical Reports Server (NTRS)

    Fennessey, N. M.; Eagleson, P. S.; Qinliang, W.; Rodrigues-Iturbe, I.

    1986-01-01

    Eight years of summer raingage observations are analyzed for a dense, 93 gage, network operated by the U. S. Department of Agriculture, Agricultural Research Service, in their 150 sq km Walnut Gulch catchment near Tucson, Arizona. Storms are defined by the total depths collected at each raingage during the noon to noon period for which there was depth recorded at any of the gages. For each of the resulting 428 storms, the 93 gage depths are interpolated onto a dense grid and the resulting random field is anlyzed. Presented are: storm depth isohyets at 2 mm contour intervals, first three moments of point storm depth, spatial correlation function, spatial variance function, and the spatial distribution of total rainstorm depth.

  16. Observation of correlated electronic decay in expanding clusters triggered by near-infrared fields

    PubMed Central

    Schütte, B.; Arbeiter, M.; Fennel, T.; Jabbari, G.; Kuleff, A.I.; Vrakking, M.J.J.; Rouzée, A.

    2015-01-01

    When an excited atom is embedded into an environment, novel relaxation pathways can emerge that are absent for isolated atoms. A well-known example is interatomic Coulombic decay, where an excited atom relaxes by transferring its excess energy to another atom in the environment, leading to its ionization. Such processes have been observed in clusters ionized by extreme-ultraviolet and X-ray lasers. Here, we report on a correlated electronic decay process that occurs following nanoplasma formation and Rydberg atom generation in the ionization of clusters by intense, non-resonant infrared laser fields. Relaxation of the Rydberg states and transfer of the available electronic energy to adjacent electrons in Rydberg states or quasifree electrons in the expanding nanoplasma leaves a distinct signature in the electron kinetic energy spectrum. These so far unobserved electron-correlation-driven energy transfer processes may play a significant role in the response of any nano-scale system to intense laser light. PMID:26469997

  17. TRANSVERSE COMPONENT OF THE MAGNETIC FIELD IN THE SOLAR PHOTOSPHERE OBSERVED BY SUNRISE

    SciTech Connect

    Danilovic, S.; Beeck, B.; Pietarila, A.; Schuessler, M.; Solanki, S. K.; Barthol, P.; Gandorfer, A.; MartInez Pillet, V.; Bonet, J. A.; Domingo, V.; Berkefeld, T.; Schmidt, W.; Knoelker, M.; Title, A. M.

    2010-11-10

    We present the first observations of the transverse component of a photospheric magnetic field acquired by the imaging magnetograph SUNRISE/IMaX. Using an automated detection method, we obtain statistical properties of 4536 features with significant linear polarization signal. We obtain a rate of occurrence of 7 x 10{sup -4} s{sup -1} arcsec{sup -2}, which is 1-2 orders of magnitude larger than the values reported by previous studies. We show that these features have no characteristic size or lifetime. They appear preferentially at granule boundaries with most of them being caught in downflow lanes at some point. Only a small percentage are entirely and constantly embedded in upflows (16%) or downflows (8%).

  18. New Results from Space and Field Observations on the Aerosol Direct and Indirect Radiative Forcing

    NASA Technical Reports Server (NTRS)

    Kaufman, Yoram J.; Remer, Lorraine; Tanre, Didier; Boucher, Olivier; Chin, Mian; Dubovik, Oleg; Holben, Brent

    2002-01-01

    New space observations from the MODIS instrument on board the Terra satellite and analysis of POLDER data flown on the ADEOS satellite, show in great details the spatial and seasonal variability of the global aerosol system. These spaceborne instruments distinguish fine aerosol from man-made regional pollution and biomass burning from mostly natural coarse dust and sea salt aerosol. E.g. fine regional pollution in and around the Indian sub-continent, Europe and North America; smoke from biomass burning in Southern Africa and Southern America; coarse dust from West Africa and mixed dust pollution and smoke from West and central Africa and East Asia. These regions were also studied extensively in focused field experiments and by the distributed AERONET network. The results generate the first climatologies of the aerosol system, are used to derive the aerosol radiative effects and to estimate the anthropogenic component. The measurements are also used to evaluate each other and constrain aerosol transport models.

  19. Transverse Component of the Magnetic Field in the Solar Photosphere Observed by SUNRISE

    NASA Astrophysics Data System (ADS)

    Danilovic, S.; Beeck, B.; Pietarila, A.; Schüssler, M.; Solanki, S. K.; Martínez Pillet, V.; Bonet, J. A.; del Toro Iniesta, J. C.; Domingo, V.; Barthol, P.; Berkefeld, T.; Gandorfer, A.; Knölker, M.; Schmidt, W.; Title, A. M.

    2010-11-01

    We present the first observations of the transverse component of a photospheric magnetic field acquired by the imaging magnetograph SUNRISE/IMaX. Using an automated detection method, we obtain statistical properties of 4536 features with significant linear polarization signal. We obtain a rate of occurrence of 7 × 10-4 s-1 arcsec-2, which is 1-2 orders of magnitude larger than the values reported by previous studies. We show that these features have no characteristic size or lifetime. They appear preferentially at granule boundaries with most of them being caught in downflow lanes at some point. Only a small percentage are entirely and constantly embedded in upflows (16%) or downflows (8%).

  20. Laboratory and field observations of stress-wave induced changes in oil flow behavior

    SciTech Connect

    Roberts, P. M.; Majer, Ernest Luther; Wooden, W.; Daley, T. M.

    2001-01-01

    We present recent results of laboratory and field experiments designed to validate and quantify the phenomenon of seismically enhanced oil production in marginal reservoirs. Controlled laboratory experiments were performed where mechanical stress oscillations at 100 Hz or less were applied to sandstone cores while flowing oil and/or brine at constant flow rates. Steady-state flow and simulated flooding experiments indicated that stress stimulation causes significant changes in the ability of one fluid to displace the other and on the preference that the rock has for trapping one fluid over the other. For Berea sandstone, which is highly water wet, stress stimulation caused oil production to be impeded during water floods and caused the bulk fluid pressure drop across the core to increase during steady-state simultaneous flow of oil and brine. A possible explanation of these observations is that stimulation caused the core to become more oil wet. Field stimulation tests on producing reservoirs at Lost Hills, California were performed using a downhole fluid pressure pulsation device. Stimulation was applied in one well for 50 days total during July - November 2000. Two groups of producing wells were monitored for changes in oil cut and oil production during the test. A control group of 26 wells displayed an oil-cut increase of 29% and an oil production increase of 26% which are clearly correlated with the stimulation treatment. A larger group of 60 wells showed 11% oil-cut and 17v0 production increases. Similar increases were observed during the October 1999 Hector Mine earthquake, magnitude 7.1, in the Mojave Desert about 230 miles from Lost Hills. Downhole seismic monitoring of the stimulation wavefield is being used to help quantify the frequency range and energy threshold required for effective production enhancement.

  1. Intermittency of magnetic field turbulence: Astrophysical applications of in-situ observations

    NASA Astrophysics Data System (ADS)

    Zelenyi, Lev M.; Bykov, Andrei M.; Uvarov, Yury A.; Artemyev, Anton V.

    2015-08-01

    We briefly review some aspects of magnetic turbulence intermittency observed in space plasmas. Deviation of statistical characteristics of a system (e.g. its high statistical momenta) from the Gaussian can manifest itself as domination of rare large intensity peaks often associated with the intermittency in the system's dynamics. Thirty years ago, Zeldovich stressed the importance of the non-Gaussian appearance of the sharp values of vector and scalar physical parameters in random media as a factor of magnetic field amplification in cosmic structures. Magnetic turbulence is governing the behavior of collisionless plasmas in space and especially the physics of shocks and magnetic reconnections. Clear evidence of intermittent magnetic turbulence was found in recent in-situ spacecraft measurements of magnetic fields in the near-Earth and interplanetary plasma environments. We discuss the potentially promising approaches of incorporating the knowledge gained from spacecraft in-situ measurements into modern models describing plasma dynamics and radiation in various astrophysical systems. As an example, we discuss supernova remnants (SNRs) which are known to be the sources of energy, momentum, chemical elements, and high-energy cosmic rays (CRs) in galaxies. Supernova shocks accelerate charged particles to very high energies and may strongly amplify turbulent magnetic fields via instabilities driven by CRs. Relativistic electrons accelerated in SNRs radiate polarized synchrotron emission in a broad range of frequencies spanning from the radio to gamma-rays. We discuss the effects of intermittency of magnetic turbulence on the images of polarized synchrotron X-ray emission of young SNRs and emission spectra of pulsar wind nebula.

  2. Evaluation of WRF-SFIRE performance with field observations from the FireFlux experiment

    NASA Astrophysics Data System (ADS)

    Kochanski, A. K.; Jenkins, M. A.; Mandel, J.; Beezley, J. D.; Clements, C. B.; Krueger, S.

    2013-08-01

    This study uses in situ measurements collected during the FireFlux field experiment to evaluate and improve the performance of the coupled atmosphere-fire model WRF-SFIRE. The simulation by WRF-SFIRE of the experimental burn shows that WRF-SFIRE is capable of providing realistic head-fire rate of spread and vertical temperature structure of the fire plume, and fire-induced surface flow and vertical velocities within the plume up to 10 m above ground level. The simulation captured the changes in wind speed and direction before, during, and after fire front passage, along with the arrival times of wind speed, temperature, and updraft maxima, at the two instrumented flux towers used in FireFlux. The model overestimated vertical wind speeds and underestimated horizontal wind speeds measured at tower heights above 10 m. It is hypothesized that the limited model spatial resolution led to overestimates of the fire front depth, heat release rate, and updraft speed. However, on the whole, WRF-SFIRE simulated fire plume behavior that is consistent with FireFlux observations. The study suggests optimal experimental pre-planning, design, and execution strategies for future field campaigns that are intended to evaluate and develop further coupled atmosphere-fire models.

  3. SPITZER 70 AND 160 {mu}m OBSERVATIONS OF THE COSMOS FIELD

    SciTech Connect

    Frayer, D. T.; Huynh, M. T.; Bhattacharya, B.; Fadda, D.; Helou, G.; Sanders, D. B.; Le Floc'h, E.; Ilbert, O.; Kartaltepe, J. S.; Lee, N.; Surace, J. A.; Capak, P.; Murphy, E.; Aussel, H.; Salvato, M.; Scoville, N. Z.; Fu, H.; Afonso-Luis, A.; Sargent, M. T.

    2009-11-15

    We present Spitzer 70 and 160 {mu}m observations of the COSMOS Spitzer survey (S-COSMOS). The data processing techniques are discussed for the publicly released products consisting of images and source catalogs. We present accurate 70 and 160 {mu}m source counts of the COSMOS field and find reasonable agreement with measurements in other fields and with model predictions. The previously reported counts for GOODS-North and the extragalactic First Look Survey are updated with the latest calibration, and counts are measured based on the large area SWIRE survey to constrain the bright source counts. We measure an extragalactic confusion noise level of {sigma} {sub c} = 9.4 {+-} 3.3 mJy (q = 5) for the MIPS 160 {mu}m band based on the deep S-COSMOS data and report an updated confusion noise level of {sigma} {sub c} = 0.35 {+-} 0.15 mJy (q = 5) for the MIPS 70 {mu}m band.

  4. Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) observations during several 2013 NASA field campaigns

    NASA Astrophysics Data System (ADS)

    Diner, D. J.; Garay, M. J.; Xu, F.; Kalashnikova, O.; Rheingans, B.; Geier, S.; Val, S.; Bull, M.; Jovanovic, V.; Bruegge, C.; Seidel, F. C.; Daugherty, B.; Chipman, R.; Davis, A.

    2013-12-01

    The Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) is an ultraviolet/visible/near-infrared pushbroom camera mounted on a single-axis gimbal to acquire multiangle imagery over a ×67° along-track range. The instrument flies aboard NASA's high-altitude ER-2 aircraft, and acquires Earth imagery with ~10 m spatial resolution across an 11-km wide swath. Intensity (I) images are obtained in eight spectral bands (355, 380, 445, 470, 555, 660, 865, and 935 nm). Dual photoelastic modulators (PEMs), achromatic quarter-wave plates, and wire-grid polarizers enable imagery of the linear polarization Stokes components Q and U at 470, 660, and 865 nm. The data are used to derive degree of linear polarization (DOLP) and angle of linear polarization (AOLP). Example flight data acquired during various NASA field campaigns in 2013, including the Aerosol-Cloud-Ecosystem (ACE) Polarimeter Definition Experiment (PODEX), Hyperspectral Infrared Imager (HyspIRI), and Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) are presented. Observations of aerosols, low- and mid-level cloud fields, cirrus, and different types of surfaces under clear skies were obtained for a variety of land and ocean targets. Radiance and polarization imagery for several scenes, along with modeling of aerosol, cloud, and surface scattering, are presented to illustrate quantitatively some of the instrument's capabilities. Laboratory and vicarious calibration results are also discussed.

  5. LOFAR 150-MHz observations of the Boötes field: catalogue and source counts

    NASA Astrophysics Data System (ADS)

    Williams, W. L.; van Weeren, R. J.; Röttgering, H. J. A.; Best, P.; Dijkema, T. J.; de Gasperin, F.; Hardcastle, M. J.; Heald, G.; Prandoni, I.; Sabater, J.; Shimwell, T. W.; Tasse, C.; van Bemmel, I. M.; Brüggen, M.; Brunetti, G.; Conway, J. E.; Enßlin, T.; Engels, D.; Falcke, H.; Ferrari, C.; Haverkorn, M.; Jackson, N.; Jarvis, M. J.; Kapińska, A. D.; Mahony, E. K.; Miley, G. K.; Morabito, L. K.; Morganti, R.; Orrú, E.; Retana-Montenegro, E.; Sridhar, S. S.; Toribio, M. C.; White, G. J.; Wise, M. W.; Zwart, J. T. L.

    2016-08-01

    We present the first wide area (19 deg$^2$), deep ($\\approx120-150$ {\\mu}Jy beam$^{-1}$), high resolution ($5.6 \\times 7.4$ arcsec) LOFAR High Band Antenna image of the Bo\\"otes field made at 130-169 MHz. This image is at least an order of magnitude deeper and 3-5 times higher in angular resolution than previously achieved for this field at low frequencies. The observations and data reduction, which includes full direction-dependent calibration, are described here. We present a radio source catalogue containing 6276 sources detected over an area of $19$\\,deg$^2$, with a peak flux density threshold of $5\\sigma$. As the first thorough test of the facet calibration strategy, introduced by van Weeren et al., we investigate the flux and positional accuracy of the catalogue. We present differential source counts that reach an order of magnitude deeper in flux density than previously achieved at these low frequencies, and show flattening at 150 MHz flux densities below 10 mJy associated with the rise of the low flux density star-forming galaxies and radio-quiet AGN.

  6. LOFAR 150-MHz observations of the Boötes field: Catalogue and Source Counts

    NASA Astrophysics Data System (ADS)

    Williams, W. L.; van Weeren, R. J.; Röttgering, H. J. A.; Best, P.; Dijkema, T. J.; de Gasperin, F.; Hardcastle, M. J.; Heald, G.; Prandoni, I.; Sabater, J.; Shimwell, T. W.; Tasse, C.; van Bemmel, I. M.; Brüggen, M.; Brunetti, G.; Conway, J. E.; Enßlin, T.; Engels, D.; Falcke, H.; Ferrari, C.; Haverkorn, M.; Jackson, N.; Jarvis, M. J.; Kapińska, A. D.; Mahony, E. K.; Miley, G. K.; Morabito, L. K.; Morganti, R.; Orrú, E.; Retana-Montenegro, E.; Sridhar, S. S.; Toribio, M. C.; White, G. J.; Wise, M. W.; Zwart, J. T. L.

    2016-05-01

    We present the first wide area (19 deg2), deep (≈120-150 μJy beam-1), high resolution (5.6 × 7.4 arcsec) LOFAR High Band Antenna image of the Boötes field made at 130-169 MHz. This image is at least an order of magnitude deeper and 3 - 5 times higher in angular resolution than previously achieved for this field at low frequencies. The observations and data reduction, which includes full direction-dependent calibration, are described here. We present a radio source catalogue containing 6 276 sources detected over an area of 19 deg2, with a peak flux density threshold of 5σ. As the first thorough test of the facet calibration strategy, introduced by van Weeren et al., we investigate the flux and positional accuracy of the catalogue. We present differential source counts that reach an order of magnitude deeper in flux density than previously achieved at these low frequencies, and show flattening at 150 MHz flux densities below 10 mJy associated with the rise of the low flux density star-forming galaxies and radio-quiet AGN.

  7. Wide-field observations in the SDSS Stripe 82 with the European VLBI Network

    NASA Astrophysics Data System (ADS)

    Cao, H.-M.; Gurvits, L. I.; Yang, J.; Hong, X.-Y.; Frey, S.; Paragi, Z.; Deller, A. T.; Ivezić, Ž.

    2014-07-01

    We observed an area of sky located within the SDSS Stripe 82 field at 1.6 GHz with the European VLBI Network (EVN). There are fifteen mJy/sub-mJy radio sources within the primary beam of a typical 30-m class EVN radio telescope. Our aim was to obtain information on compact radio structures of all VLBI-detectable sources within this primary beam area. The source of particular interest is the recently identified radio quasar J222843.54+011032.2 (J2228+0110) at z = 5.95. The data correlation was performed at the EVN software correlator at JIVE (SFXC). Three targets (J2228+0110, J222851.45+011203.4, J222941.76+011428.5) were detected, all three with position offsets not exceeding the 3σ accuracy of the original low-resolution radio surveys. The detection rate of 20% is consistent with other wide-field VLBI experiments carried out recently (e.g. Middelberg et al. 2013). The project presented here demonstrates the ability of EVN in multiple-phase-centre experiments and paves the way for future large-scale EVN surveys of compact structures in extragalactic radio sources using the multiple-phase-centre VLBI technique.

  8. Response times across the visual field: empirical observations and application to threshold determination.

    PubMed

    McKendrick, Allison M; Denniss, Jonathan; Turpin, Andrew

    2014-08-01

    This study aimed to determine if response times gathered during perimetry can be exploited within a thresholding algorithm to improve the speed and accuracy of the test. Frequency of seeing (FoS) curves were measured at 24 locations across the central 30° of the visual field of 10 subjects using a Method of Constant Stimuli, with response times recorded for each presentation. Spatial locations were interleaved, and built up over multiple 5-min blocks, in order to mimic the attentional conditions of clinical perimetry. FoS curves were fitted to each participant's data for each location, and response times derived as a function of distance-from-threshold normalised to the slope of each FoS curve. This data was then used to derive a function for the probability of observing response times given the distance-from-threshold, and to seed simulations of a new test procedure (BURTO) that exploited the probability function for stimulus placement. Test time and error were then simulated for patients with various false response rates. When compared with a ZEST algorithm, simulations revealed that BURTO was about one presentation per location faster than ZEST, on average, while sacrificing less precision and bias in threshold estimates than simply terminating the ZEST earlier. Despite response times varying considerably for a given individual and their thresholds, response times can be exploited to reduce the number of presentations required in a visual field test without loss of accuracy. PMID:24802595

  9. LOFAR 150-MHz observations of the Boötes field: catalogue and source counts

    NASA Astrophysics Data System (ADS)

    Williams, W. L.; van Weeren, R. J.; Röttgering, H. J. A.; Best, P.; Dijkema, T. J.; de Gasperin, F.; Hardcastle, M. J.; Heald, G.; Prandoni, I.; Sabater, J.; Shimwell, T. W.; Tasse, C.; van Bemmel, I. M.; Brüggen, M.; Brunetti, G.; Conway, J. E.; Enßlin, T.; Engels, D.; Falcke, H.; Ferrari, C.; Haverkorn, M.; Jackson, N.; Jarvis, M. J.; Kapińska, A. D.; Mahony, E. K.; Miley, G. K.; Morabito, L. K.; Morganti, R.; Orrú, E.; Retana-Montenegro, E.; Sridhar, S. S.; Toribio, M. C.; White, G. J.; Wise, M. W.; Zwart, J. T. L.

    2016-08-01

    We present the first wide area (19 deg2), deep (≈120-150 μJy beam-1), high-resolution (5.6 × 7.4 arcsec) LOFAR High Band Antenna image of the Boötes field made at 130-169 MHz. This image is at least an order of magnitude deeper and 3-5 times higher in angular resolution than previously achieved for this field at low frequencies. The observations and data reduction, which includes full direction-dependent calibration, are described here. We present a radio source catalogue containing 6 276 sources detected over an area of 19 deg2, with a peak flux density threshold of 5σ. As the first thorough test of the facet calibration strategy, introduced by van Weeren et al., we investigate the flux and positional accuracy of the catalogue. We present differential source counts that reach an order of magnitude deeper in flux density than previously achieved at these low frequencies, and show flattening at 150-MHz flux densities below 10 mJy associated with the rise of the low flux density star-forming galaxies and radio-quiet AGN.

  10. Tropical Cyclone Precipitation Types and Electrical Field Information Observed by High Altitude Aircraft Instrumentation

    NASA Technical Reports Server (NTRS)

    Hood, Robbie E.; Blakeslee, Richard; Cecil, Daniel; LaFontaine, Frank J.; Heymsfield, Gerald; Marks, Frank

    2004-01-01

    During the 1998 and 200 1 hurricane seasons of the Atlantic Ocean Basin, the Advanced Microwave Precipitation Radiometer (AMPR), the ER-2 Doppler (EDOP) radar, and the Lightning Instrument Package (LIP) were flown aboard the National Aeronautics and Space Administration (NASA) ER-2 high altitude aircraft as part of the Third Convection And Moisture Experiment (CAMEX-3) and the Fourth Convection And Moisture Experiment (CAMEX-4). Several hurricanes and tropical storms were sampled during these experiments. A rainfall screening technique has been developed using AMPR passive microwave observations of these tropical cyclones (TC) collected at frequencies of 10.7, 19.35,37.1, and 85.5 GHz and verified using vertical profiles of EDOP reflectivity and lower altitude horizontal reflectivity scam collected by the National Oceanic and Atmospheric Administration (NOM) P-3 radar. Matching the rainfall classification results with coincident electrical field information collected by the LIP readily identifl convective rain regions within the TC precipitation fields. Strengths and weaknesses of the rainfall classification procedure will be discussed as well as its potential as a real-time analysis tool for monitoring vertical updrafl strength and convective intensity from a remotely operated or uninhabited aerial vehicle.

  11. Field observations of wave-driven circulation over spur and groove formations on a coral reef

    NASA Astrophysics Data System (ADS)

    Rogers, Justin S.; Monismith, Stephen G.; Dunbar, Robert B.; Koweek, David

    2015-01-01

    and groove (SAG) formations are found on the forereefs of many coral reefs worldwide. Modeling results have shown that SAG formations together with shoaling waves induce a nearshore Lagrangian circulation pattern of counter-rotating circulation cells, but these have never been observed in the field. We present results from two separate field studies of SAG formations on Palmyra Atoll which show their effect on waves to be small, but reveal a persistent order 1 cm/s depth-averaged Lagrangian offshore flow over the spur and onshore flow over the grooves. This circulation was stronger for larger, directly incident waves and low alongshore flow conditions, consistent with predictions from modeling. Favorable forcing conditions must be maintained on the order of 1 h to accelerate and develop the SAG circulation cells. The primary cross and alongshore depth-averaged momentum balances were between the pressure gradient, radiation stress gradient, and nonlinear convective terms, and the bottom drag was similar to values found on other reefs. The vertical structure of these circulation cells was previously unknown and the results show a complex horizontal offshore Lagrangian flow over the spurs near the surface driven by alongshore variability in radiation stress gradients. Vertical flow was downward over the spur and upward over the groove, likely driven by alongshore differences in bottom stress and not by vortex forcing.

  12. BLAST OBSERVATIONS OF THE SOUTH ECLIPTIC POLE FIELD: NUMBER COUNTS AND SOURCE CATALOGS

    SciTech Connect

    Valiante, Elisabetta; Braglia, Filiberto G.; Chapin, Edward L.; Halpern, Mark; Marsden, Gaelen; Scott, Douglas; Ade, Peter A. R.; Griffin, Matthew; Hargrave, Peter C.; Mauskopf, Philip; Pascale, Enzo; Bock, James J.; Devlin, Mark J.; Klein, Jeff; Gundersen, Joshua O.; Hughes, David H.; Netterfield, Calvin B.; Olmi, Luca; Patanchon, Guillaume; Rex, Marie

    2010-12-15

    We present results from a survey carried out by the Balloon-borne Large Aperture Submillimeter Telescope (BLAST) on a 9 deg{sup 2} field near the South Ecliptic Pole at 250, 350, and 500 {mu}m. The median 1{sigma} depths of the maps are 36.0, 26.4, and 18.4 mJy, respectively. We apply a statistical method to estimate submillimeter galaxy number counts and find that they are in agreement with other measurements made with the same instrument and with the more recent results from Herschel/SPIRE. Thanks to the large field observed, the new measurements give additional constraints on the bright end of the counts. We identify 132, 89, and 61 sources with S/N {>=}4 at 250, 350, 500 {mu}m, respectively and provide a multi-wavelength combined catalog of 232 sources with a significance {>=}4{sigma} in at least one BLAST band. The new BLAST maps and catalogs are available publicly at http://blastexperiment.info.

  13. Field Observations of Methane Emissions from Unconventional and Conventional Fossil Fuel Exploration

    NASA Astrophysics Data System (ADS)

    Dubey, M.; Lindenmaier, R.; Arata, C.; Costigan, K. R.; Frankenberg, C.; Kort, E. A.; Rahn, T. A.; Henderson, B. G.; Love, S. P.; Aubrey, A. D.

    2013-12-01

    Energy from methane (CH4) has lower carbon dioxide and air pollutant emissions per unit energy produced than coal or oil making it a desirable fossil fuel. Hydraulic fracturing is allowing United States to harvest the nation's abundant domestic shale gas reservoirs to achieve energy independence. However, CH4 is a gas that is hard to contain during mining, processing, transport and end-use. Therefore fugitive CH4 leaks occur that are reported in bottom up inventories by the EPA. Recent targeted field observations at selected plays have provided top down CH4 leak estimates that are larger than the reported EPA inventories. Furthermore, no long-term regional baselines are available to delineate leaks from unconventional mining operations from historical conventional mining. We will report and compare observations of fugitive CH4 leaks from conventional and unconventional mining to understand changes from technology shifts. We will report in situ and regional column measurements of CH4, its isotopologue 13CH4 and ethane (C2H6) at our Four Corners site near Farmington, NM. The region has substantial coal bed methane, conventional oil and gas production, processing and distribution with minimal hydraulic fracturing activity. We observe large enhancements in in situ and regional column CH4 with distinct time dependence. Our in situ 13CH4 observations and remote C2H6/CH4 provide strong evidence of thermogenic sources. Comparisons of WRF-simulations with emissions inventory (Edgar) with our observations show that the fugitive CH4 leaks from conventional mining are 3 times greater than reported. We also compare in situ mobile surveys of fugitive CH4 and 13CH4 leak signals in basins with conventional (San Juan) mining and unconventional (Permian and Powder River) mining. A large number of active and closed wells were sampled in these regions. Furthermore, play scale surveys on public roads allowed us to gain a regional perspective. The composition of atmospheric 13CH4

  14. Initial results on the correlation between the magnetic and electric fields observed from the DE-2 satellite in the field-aligned current regions

    NASA Technical Reports Server (NTRS)

    Sugiura, M.; Maynard, N. C.; Farthing, W. H.; Heppner, J. P.; Ledley, B. G.; Cahill, L. J., Jr.

    1982-01-01

    Initial results of the electric and magnetic field observations from the DE-2 satellite show a remarkably good correlation between the north-south component of the electric field and the east-west component of the magnetic field in many passes of the field-aligned current regions. For a dayside cusp pass on August 15, 1981 the coefficient of correlation between these components was 0.996. A preliminary inspection of the available data from the first 6 months of the DE operation indicates that the similarity between the electric and magnetic field signatures of the field-aligned currents is a commonly observed feature at all local times. This high correlation is interpreted to be an indication that the closure of the field-aligned current is essentially meridional. When the correlation between these components is not good, the closure current is likely to be flowing along the auroral belt. When the correlation between the electric and magnetic fields is high, it is possible to estimate the height-integrated Pedersen conductivity from the observed field components.

  15. A Review of Direct Observation Research within the Past Decade in the Field of Emotional and Behavioral Disorders

    ERIC Educational Resources Information Center

    Adamson, Reesha M.; Wachsmuth, Sean T.

    2014-01-01

    This study reviewed prominent journals within the field of emotional and behavioral disorders to identify direct observation approaches, reported reliability statistics, and key features of direct observation. Selected journals were systematically reviewed for the past 10 years identifying and quantifying specific direct observation systems and…

  16. Mars Infrared Spectroscopy: From Theory and the Laboratory To Field Observations

    NASA Technical Reports Server (NTRS)

    Kirkland, Laurel (Editor); Mustard, John (Editor); McAfee, John (Editor); Hapke, Bruce (Editor); Ramsey, Michael (Editor)

    2002-01-01

    The continuity and timely implementation of the Mars exploration strategy relies heavily on the ability of the planetary community to interpret infrared spectral data. However, the increasing mission rate, data volume, and data variety, combined with the small number of spectroscopists within the planetary community, will require a coordinated community effort for effective and timely interpretation of the newly acquired and planned data sets. Relevant spectroscopic instruments include the 1996 TES, 2001 THEMIS, 2003 Pancam, 2003 Mini-TES, 2003 Mars Express OMEGA, 2003 Mars Express PFS, and 2005 CFUSM. In light of that, leaders of the Mars spectral community met June 4-6 to address the question: What terrestrial theoretical, laboratory, and field studies are most needed to best support timely interpretations of current and planned visible infrared spectrometer data sets, in light of the Mars Program goals? A primary goal of the spectral community is to provide a reservoir of information to enhance and expand the exploration of Mars. Spectroscopy has a long history of providing the fundamental compositional discoveries in the solar system, from atmospheric constituents to surface mineralogy, from earth-based to spacecraft-based observations. However, such spectroscopic compositional discoveries, especially surface mineralogies, have usually come after long periods of detailed integration of remote observations, laboratory analyses, and field measurements. Spectroscopic information of surfaces is particularly complex and often is confounded by interference of broad, overlapping absorption features as well as confusing issues of mixtures, coatings, and grain size effects. Thus some spectroscopic compositional discoveries have come only after many years of research. However, we are entering an era of Mars exploration with missions carrying sophisticated spectrometers launching about every 2 years. It is critical that each mission provide answers to relevant questions

  17. Large-scale interplanetary magnetic fields: Voyager 1 and 2 observations between 1 AU and 9.5 AU

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Klein, L. W.; Lepping, R. P.; Behannon, K. W.

    1984-01-01

    The large-scale radial and temporal variations of the interplanetary magnetic field strength B observed by Voyagers 1 and 2 are discussed. Two components of the magnetic field strength were considered: (1) an average component, B sub zero, based on solar rotation averages, and (2) a fluctuation component, delta B, expressed by 10- or 24-hour averages of B normalized by the best-fit average field for the corresponding time and distance. Observations of the sector structure, interfaces, and shocks are presented to further describe magnetic field strength.

  18. Large-Field CO(J = 1→0) Observations of the Starburst Galaxy M 82

    NASA Astrophysics Data System (ADS)

    Salak, Dragan; Nakai, Naomasa; Miyamoto, Yusuke; Yamauchi, Aya; Tsuru, Takeshi G.

    2013-06-01

    We present large-field (15.7 × 16.9 arcmin2) CO(J = 1→0) observations of the starburst galaxy M 82, at an angular resolution of 22" with the NRO 45-m telescope. The CO emission was detected in the galactic disk, outflow (driven by the galactic wind) up to ˜2 kpc above the galactic plane in the halo, and in tidal streams. The kinematics of the outflow (including CO line splitting) suggests that it has the shape of a cylinder that is diverging outwards. The mass and kinetic energy of the molecular gas outflow are estimated to be (0.26-1.0) × 109 M⊙ and (1-4) × 1056 erg. A clump of CO gas was discovered 3.5 kpc above the galactic plane; it coincides with a dark lane previously found in X-ray observations, and a peak in H I emission. A comparison with H I, hot molecular hydrogen and dust suggests that the molecular gas shows signatures of warm and cool components in the outflow and tidal streams, respectively.

  19. Evaluation of flow direction methods against field observations of overland flow dispersion

    NASA Astrophysics Data System (ADS)

    Orlandini, Stefano; Moretti, Giovanni; Corticelli, Mauro A.; Santangelo, Paolo E.; Capra, Alessandro; Rivola, Riccardo; Albertson, John D.

    2012-10-01

    The D8, D8-LTD, D∞-LTD, D∞, MD∞, and MD8 flow direction methods are evaluated against field observations of overland flow dispersion obtained from novel experimental methods. Thin flows of cold water were released at selected points on a warmer slope and individual overland flow patterns originating from each of these points were observed using a terrestrial laser scanner and a thermal imaging camera. Land microtopography was determined by using laser returns from the dry land surface, whereas overland flow patterns were determined by using either laser returns or infrared emissions from the wetted portions of the land surface. Planar overland flow dispersion is found to play an important role in the region lying immediately downslope of the point source, but attenuates rapidly as flow propagates downslope. In contrast, existing dispersive flow direction methods are found to provide a continued dispersion with distance downslope. Predicted propagation patterns, for all methods considered here, depend critically on the size h of grid cells involved. All methods are found to be poorly sensitive in extremely fine grids (h ≤ 2 cm), and to be poorly specific in coarse grids (h = 2 m). Satisfactory results are, however, obtained in grids having resolutions h that approach the average flow width (50 cm), with the best performances displayed by the MD8 method in the finest grids (5 ≤ h ≤ 20 cm), and by the MD∞, D∞, and D∞-LTD methods in the coarsest grids (20 cm < h ≤ 1 m).

  20. Constraints on the Intergalactic Magnetic Field with Gamma-Ray Observations of Blazars

    NASA Astrophysics Data System (ADS)

    Finke, Justin D.; Reyes, Luis C.; Georganopoulos, Markos; Reynolds, Kaeleigh; Ajello, Marco; Fegan, Stephen J.; McCann, Kevin

    2015-11-01

    Distant BL Lacertae objects emit γ-rays that interact with the extragalactic background light (EBL), creating electron-positron pairs, and reducing the flux measured by ground-based imaging atmospheric Cherenkov telescopes (IACTs) at very-high energies (VHE). These pairs can Compton-scatter the cosmic microwave background, creating a γ-ray signature at slightly lower energies that is observable by the Fermi Large Area Telescope (LAT). This signal is strongly dependent on the intergalactic magnetic field (IGMF) strength (B) and its coherence length (LB). We use IACT spectra taken from the literature for 5 VHE-detected BL Lac objects and combine them with LAT spectra for these sources to constrain these IGMF parameters. Low B values can be ruled out by the constraint that the cascade flux cannot exceed that observed by the LAT. High values of B can be ruled out from the constraint that the EBL-deabsorbed IACT spectrum cannot be greater than the LAT spectrum extrapolated into the VHE band, unless the cascade spectrum contributes a sizable fraction of the LAT flux. We rule out low B values (B ≲ 10-19 G for LB ≥ 1 Mpc) at >5σ in all trials with different EBL models and data selection, except when using >1 GeV spectra and the lowest EBL models. We were not able to constrain high values of B.

  1. Constraints on the Intergalactic Magnetic Field with Gamma-Ray Observations of Blazars

    NASA Astrophysics Data System (ADS)

    Finke, Justin D.; Reyes, Luis C.; Georganopoulos, Markos; Reynolds, Kaeleigh; Ajello, Marco; Fegan, Stephen J.; McCann, Kevin

    2015-11-01

    Distant BL Lacertae objects emit γ-rays that interact with the extragalactic background light (EBL), creating electron–positron pairs, and reducing the flux measured by ground-based imaging atmospheric Cherenkov telescopes (IACTs) at very-high energies (VHE). These pairs can Compton-scatter the cosmic microwave background, creating a γ-ray signature at slightly lower energies that is observable by the Fermi Large Area Telescope (LAT). This signal is strongly dependent on the intergalactic magnetic field (IGMF) strength (B) and its coherence length (LB). We use IACT spectra taken from the literature for 5 VHE-detected BL Lac objects and combine them with LAT spectra for these sources to constrain these IGMF parameters. Low B values can be ruled out by the constraint that the cascade flux cannot exceed that observed by the LAT. High values of B can be ruled out from the constraint that the EBL-deabsorbed IACT spectrum cannot be greater than the LAT spectrum extrapolated into the VHE band, unless the cascade spectrum contributes a sizable fraction of the LAT flux. We rule out low B values (B ≲ 10‑19 G for LB ≥ 1 Mpc) at >5σ in all trials with different EBL models and data selection, except when using >1 GeV spectra and the lowest EBL models. We were not able to constrain high values of B.

  2. Observation of exceptional points in reconfigurable non-Hermitian vector-field holographic lattices.

    PubMed

    Hahn, Choloong; Choi, Youngsun; Yoon, Jae Woong; Song, Seok Ho; Oh, Cha Hwan; Berini, Pierre

    2016-01-01

    Recently, synthetic optical materials represented via non-Hermitian Hamiltonians have attracted significant attention because of their nonorthogonal eigensystems, enabling unidirectionality, nonreciprocity and unconventional beam dynamics. Such systems demand carefully configured complex optical potentials to create skewed vector spaces with a desired metric distortion. In this paper, we report optically generated non-Hermitian photonic lattices with versatile control of real and imaginary sub-lattices. In the proposed method, such lattices are generated by vector-field holographic interference of two elliptically polarized pump beams on azobenzene-doped polymer thin films. We experimentally observe violation of Friedel's law of diffraction, indicating the onset of complex lattice formation. We further create an exact parity-time symmetric lattice to demonstrate totally asymmetric diffraction at the spontaneous symmetry-breaking threshold, referred to as an exceptional point. On this basis, we provide the experimental demonstration of reconfigurable non-Hermitian photonic lattices in the optical domain and observe the purest exceptional point ever reported to date. PMID:27425577

  3. ULF cusp pulsations: Diurnal variations and interplanetary magnetic field correlations with ground-based observations

    SciTech Connect

    McHarg, M.G.; Olson, J.V.; Newell, P.T.

    1995-10-01

    In this paper the authors establish the Pc 5 magnetic pulsation signatures of the cusp and boundary regions for the high-latitude dayside cusp region. These signatures were determined by comparing spectrograms of the magnetic pulsations with optical observations of particle precipitation regions observed at the cusp. The ULF pulsations have a diurnal variation, and a cusp discriminant is proposed using a particular narrow-band feature in the pulsation spectrograms. The statistical distribution of this pattern over a 253-day period resembles the statistical cusp description using particle precipitation data from the Defense Meterological Satellite Program (DMSP). The distribution of the ground-based cusp discriminant is found to peak 1 hour earlier than the DMSP cusp distribution. This offset is due to the interplanetary magnetic field (IMF) being predominantly negative B{sub y} for the period when the data were collected. The authors find the diurnal variations so repeatable that only three main categories have statistically different IMF distributions. The identification of the signatures in the magnetic spectrograms of the boundary regions and central cusp allows the spectrogram to be used as a {open_quotes}time line{close_quotes} that shows when the station passed under different regions of the dayside oval. 36 refs., 11 figs., 1 tab.

  4. Observation of exceptional points in reconfigurable non-Hermitian vector-field holographic lattices

    PubMed Central

    Hahn, Choloong; Choi, Youngsun; Yoon, Jae Woong; Song, Seok Ho; Oh, Cha Hwan; Berini, Pierre

    2016-01-01

    Recently, synthetic optical materials represented via non-Hermitian Hamiltonians have attracted significant attention because of their nonorthogonal eigensystems, enabling unidirectionality, nonreciprocity and unconventional beam dynamics. Such systems demand carefully configured complex optical potentials to create skewed vector spaces with a desired metric distortion. In this paper, we report optically generated non-Hermitian photonic lattices with versatile control of real and imaginary sub-lattices. In the proposed method, such lattices are generated by vector-field holographic interference of two elliptically polarized pump beams on azobenzene-doped polymer thin films. We experimentally observe violation of Friedel's law of diffraction, indicating the onset of complex lattice formation. We further create an exact parity-time symmetric lattice to demonstrate totally asymmetric diffraction at the spontaneous symmetry-breaking threshold, referred to as an exceptional point. On this basis, we provide the experimental demonstration of reconfigurable non-Hermitian photonic lattices in the optical domain and observe the purest exceptional point ever reported to date. PMID:27425577

  5. Fast multicamera video stitching for underwater wide field-of-view observation

    NASA Astrophysics Data System (ADS)

    Li, Qing-Zhong; Zhang, Yang; Zang, Feng-Ni

    2014-03-01

    Underwater robots equipped with a single forward-looking camera usually have a very limited visual range or field-of-view (FOV) due to the light absorption and scattering effects in the underwater environment, which greatly limit their applications for underwater video-based inspection, navigation, and so on. Although underwater robots using multicamera imaging systems can achieve wide FOV of surroundings, parallax distortion and time-consuming stitching computation are encountered, especially for short-distance observation. To overcome these problems, we present a fast multicamera video-stitching algorithm based on adaptive adjustment of image transformation matrix between adjacent images. The proposed method uses a fast and adaptive optimization algorithm to search the optimal parameters of transformation matrix that can minimize the parallax distortion due to short-distance imaging and maximize the matching degree between adjacent overlapping image areas. The advantage of the proposed stitching method lies in that it avoids the complex and time-consuming computations for feature-point extraction and matching. The experimental results show that the proposed method can construct multicamera-based wide FOV video effectively and meets the real-time requirement of wide FOV video observation for both indoor and underwater scenes.

  6. Magnetic field and plasma wave observations in a plasma cloud at Venus

    NASA Technical Reports Server (NTRS)

    Russell, C. T.; Luhmann, J. G.; Elphic, R. C.; Scarf, F. L.; Brace, L. H.

    1982-01-01

    Pioneer Venus magnetic field and plasma wave data are examined in a particularly clear example of a plasma cloud above the Venus ionosphere. The magnetic configuration is suggestive of acceleration of the plasma cloud by magnetic tension. If the plasma is at rest at the subsolar point, it could be accelerated to approximately 90 km/sec by the observed stress at the location of the measurement. This far exceeds the escape velocity and suggests that plasma clouds do form a significant loss mechanism for the Venus ionosphere but does not necessarily indicate that the plasma cloud is detached from the ionosphere proper. The plasma cloud is accompanied by strong plasma wave activity and is significantly hotter than the ionospheric plasma encountered later on the same pass. A loss rate of the order of 2 x 10 to the 25th ions/sec is estimated during this event. The geometry suggested by these observations is one of a ridge of dense cold plasma starting in the subsolar regions and flowing over the poles of the planet. Thus, these plasma clouds may be the planetary analog of cometary tail rays.

  7. First field-based atmospheric observation of the reduction of reactive mercury driven by sunlight