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Sample records for dusk

  1. Stable reconnection at the dusk flank magnetopause

    NASA Astrophysics Data System (ADS)

    Gomez, R. G.; Vines, S. K.; Fuselier, S. A.; Cassak, P. A.; Strangeway, R. J.; Petrinec, S. M.; Burch, J. L.; Trattner, K. J.; Russell, C. T.; Torbert, R. B.; Pollock, C.; Young, D. T.; Lewis, W. S.; Mukherjee, J.

    2016-09-01

    The dusk flank magnetopause was surveyed with instruments on board the Magnetospheric Multiscale (MMS) spacecraft on 28 August 2015 between 13:55 UT and 14:15 UT during a period of persistent southward interplanetary magnetic field (IMF) with varying dawn-dusk component. Plasma measurements (500 eV electrons, > 2 keV ions) revealed the existence of at least one active reconnection region that persisted throughout the interval. The reconnection region convected equatorward despite the poleward and tailward magnetosheath flow, which ranged from slightly sub-Alfvénic to slightly super-Alfvénic throughout the interval. These results suggest that magnetic reconnection moved in response to changes in the IMF clock angle rather than the magnetosheath flow, which is corroborated using predictions of the maximum magnetic shear model.

  2. Dawn-Dusk Asymmetries in Rapidly Rotating Magnetospheres

    NASA Astrophysics Data System (ADS)

    Jia, X.; Kivelson, M.

    2015-12-01

    Spacecraft measurements reveal perplexing dawn-dusk asymmetries of field and plasma properties in the magnetospheres of Saturn and Jupiter. Here we describe a previously unrecognized source of dawn-dusk asymmetry in a rapidly rotating magnetosphere. As plasma rotates from dawn to noon on a dipolarizing flux tube, it flows away from the equator at close to the sound speed. As plasma rotates from noon to dusk on a stretching flux tube, it is accelerated back to the equator by centrifugal acceleration at flow speeds typically smaller than the sound speed. Correspondingly, the plasma sheet remains far thicker in the afternoon than in the morning. Using two magnetohydrodynamic simulations, we analyze the forces that account for flows along and across the field in Saturn's magnetosphere and point out analogous effects at Jupiter. Different radial force balance in the morning and afternoon sectors produces net dusk to dawn flow, or equivalently, a large-scale electric field oriented from post-noon to pre-midnight.

  3. Dawn-dusk asymmetry in the Kelvin-Helmholtz instability at Mercury.

    PubMed

    Paral, Jan; Rankin, Robert

    2013-01-01

    The NASA MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) spacecraft entered orbital phase around Mercury on 18 March 2011. A surprising consistent feature in the data returned is large-scale vortices that form exclusively on the dusk side of the magnetosphere. Here we present global kinetic hybrid simulations that explain these observations. It is shown that vortices are excited by a Kelvin-Helmholtz instability near the subsolar point, which grows convectively along the dusk-side magnetopause. Virtual time series along a track approximating a flyby of the MESSENGER show correspondence with the satellite data; the data contain sawtooth oscillations in plasma density, flow and magnetic field, and exhibit the observed dawn-dusk asymmetry. It is shown that asymmetry between dawn and dusk at Mercury is controlled by the finite gyroradius of ions and by convection electric fields. Mercury's magnetosphere offers a natural laboratory for studying plasma regimes not present in other planetary magnetospheres or the laboratory. PMID:23552060

  4. Dawn-dusk asymmetry in the Kelvin-Helmholtz instability at Mercury.

    PubMed

    Paral, Jan; Rankin, Robert

    2013-01-01

    The NASA MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) spacecraft entered orbital phase around Mercury on 18 March 2011. A surprising consistent feature in the data returned is large-scale vortices that form exclusively on the dusk side of the magnetosphere. Here we present global kinetic hybrid simulations that explain these observations. It is shown that vortices are excited by a Kelvin-Helmholtz instability near the subsolar point, which grows convectively along the dusk-side magnetopause. Virtual time series along a track approximating a flyby of the MESSENGER show correspondence with the satellite data; the data contain sawtooth oscillations in plasma density, flow and magnetic field, and exhibit the observed dawn-dusk asymmetry. It is shown that asymmetry between dawn and dusk at Mercury is controlled by the finite gyroradius of ions and by convection electric fields. Mercury's magnetosphere offers a natural laboratory for studying plasma regimes not present in other planetary magnetospheres or the laboratory.

  5. Dawn-dusk asymmetry of SI-induced transient ionospheric convection

    NASA Astrophysics Data System (ADS)

    Hori, T.; Fujita, S.; Shinbori, A.; Nishitani, N.

    2015-12-01

    A statistical study using a large data set of Super Dual Auroral Radar Network (SuperDARN) observations is conducted for transient ionospheric plasma flows associated with sudden impulses (SI) recorded on ground magnetic field. The global structure of twin vortex-like ionospheric flows is found to be consistent with the twin vortices of ionospheric Hall current deduced by the past geomagnetic field observations. An interesting feature, which is focused on in this study, is that the flow structures show a dawn-dusk asymmetry. One is the difference in flow magnitude of the lower-latitude portion of the flow vortices, which is much clearer for positive SIs. The sunward flow perturbation on the dusk side is significantly larger than that on dawn side. A set of global MHD simulation runs performed by the present study have successfully reproduced the similar asymmetry of the lower-latitude transient flows. The result suggests that ionospheric conductance plays an important role in reproducing this dawn-dusk asymmetry. Another dawn-dusk asymmetry is found for the higher-latitude portion of flow vortices in which a larger flow appears either of dawn or dusk depending on the combination of the polarity of SI and IMF-By. Detailed statistics of the SuperDARN observations reveals that the dawn-dusk asymmetry of flow vortices due to IMF-By appear more clearly during negative SIs, while the flow vortices are more or less symmetric during positive SIs, regardless of IMF-By polarity. On the basis of the upstream observations, we suggest that this particular dawn-dusk asymmetry is caused by the interaction between the pre-existing round convection cell and a pair of the transient convection vortices associated with SIs. The combination of the two convection cell systems has also been reproduced by our MHD simulations.

  6. Dawn-dusk asymmetries in rotating magnetospheres: Lessons from modeling Saturn

    NASA Astrophysics Data System (ADS)

    Jia, Xianzhe; Kivelson, Margaret G.

    2016-02-01

    Spacecraft measurements reveal perplexing dawn-dusk asymmetries of field and plasma properties in the magnetospheres of Saturn and Jupiter. Here we describe a previously unrecognized source of dawn-dusk asymmetry in a rapidly rotating magnetosphere. We analyze two magnetohydrodynamic simulations, focusing on how flows along and across the field vary with local time in Saturn's dayside magnetosphere. As plasma rotates from dawn to noon on a dipolarizing flux tube, it flows away from the equator along the flux tube at roughly half of the sound speed (Cs), the maximum speed at which a bulk plasma can flow along a flux tube into a lower pressure region. As plasma rotates from noon to dusk on a stretching flux tube, the field-aligned component of its centripetal acceleration decreases and it flows back toward the equator at speeds typically smaller than 1/2 Cs. Correspondingly, the plasma sheet remains far thicker and the field less stretched in the afternoon than in the morning. Different radial force balance in the morning and afternoon sectors produce asymmetry in the plasma sheet thickness and a net dusk-to-dawn flow inside of L = 15 or equivalently, a large-scale electric field (E) oriented from postnoon to premidnight, as reported from observations. Morning-afternoon asymmetry analogous to that found at Saturn has been observed at Jupiter, and a noon-midnight component of E cannot be ruled out.

  7. Temporal variations in the dawn and dusk midlatitude trough position-modeled and measured (Ariel 3)

    NASA Technical Reports Server (NTRS)

    Grebowsky, J. M.; Tulunay, Y. K.; Chen, A. J.

    1973-01-01

    The temporal development of the latitudinal position of the 600 km midlatitude electron density trough at dawn and dusk during the period 25-27 May 1967, which encompassed a large magnetic storm, was measured by the RF capacitive probe on the polar orbiting Ariel 3 satellite. The substorm-related changes in the L coordinate of the trough minimum and the point of most rapid change of density gradient on the low latitude side of the trough are similar. Oscillations of the trough position at dusk are in phase with substorm activity whereas movement of the trough at dawn is only apparent with the onset of the large storm. Near dusk there is evidence of structure in the form of a tail-like extension of the plasmasphere at the peak of the storm. Detailed model calculations assuming a spatially invariant equatorial convection E field which varies in step with K sub p index reproduces much of the observed behavior, particularly at dusk, and shows that more than one plasmapause-type transition may be identifiable in the trough region.

  8. Dawn-dusk asymmetry in ionospheric return flows: relationship between flows and Birkeland currents

    NASA Astrophysics Data System (ADS)

    Larson, R.; Anderson, B. J.; Korth, H.; Bodurtha, K. E.; Wilson, G.

    2008-12-01

    Intense duskside ionospheric flows occurring equatorward of the discrete auroral precipitation zone have been attributed to large electric fields resulting from partial ring current injections. In this picture the driver is the ion injection that feeds the Region 2 currents which in turn cause the electric field. Alternatively, one may take the view that the return flow at dusk is favored energetically by the coupled magnetosphere-ionosphere system. In this energetics view, the upward Region 2 at dawn corresponds to discrete aurora and enhanced conductance on closed field lines on the dawn side, whereas the downward Region 2 at dusk does not contribute as substantially to enhancing the duskside conductance. The energy dissipation associated with a given flow is proportional to the conductance. Thus, it is energetically more favorable for the coupled system to send more return flow to the dayside at dusk than at dawn. In this paper we assess whether there is a persistent dawn dusk asymmetry in the return flow relative to the Birkeland current location and intensity. Birkeland currents derived from the Iridium Satellite constellation, augmented with DMSP F13 magnetic field data are used to place DMSP F13 drift meter data in the context of both the global and local Birkeland currents. Using events from the Iridium stable currents database of Anderson et al. (2008), we identified 59 events with high quality drift observations during southward IMF. The events are divided into two ranges of IMF intensity and five IMF clock angle bins. We order the data in latitude relative to the peak Region 1 current density. There is a persistent suppression of the dawn return flows relative to those at dusk regardless of IMF By or IMF intensity. This result indicates that the return flow predominantly occurs through the evening closed field line region, consistent with the above energetics picture of return flow in the coupled system.

  9. Microinjections observed by MMS FEEPS in the dusk to midnight region

    NASA Astrophysics Data System (ADS)

    Fennell, J. F.; Turner, D. L.; Lemon, C. L.; Blake, J. B.; Clemmons, J. H.; Mauk, B. H.; Jaynes, A. N.; Cohen, I. J.; Westlake, J. H.; Baker, D. N.; Craft, J. V.; Spence, H. E.; Reeves, G. D.; Torbert, R. B.; Burch, J. L.; Giles, B. L.; Paterson, W. R.; Strangeway, R. J.

    2016-06-01

    Energetic electron injections are commonly observed in the premidnight to dawn regions in association with substorms. However, successive electron injections are generally separated in time by hours and are rarer in the dusk region of the inner magnetosphere. Early MMS energetic electron data taken in the dusk to premidnight regions above ~9 RE show many clusters of electron injections. These injections of 50-400 keV electrons have energy dispersion signatures indicating that they gradient and curvature drifted from earlier local times. We focus on burst rate data starting near 21:00 UT on 6 August 2015. A cluster of ~40 electron injections occurred in the following 4 h interval. The highest-resolution data showed that the electrons in the injections were trapped and had bidirectional field-aligned angular distributions. These injection clusters are a new phenomenon in this region of the magnetosphere.

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    In the present three-dimensional wind field observations in the dusk auroral oval, the F region winds appear to be at the transition from a clockwise vortex centered at dusk to an antisunward flow at the nightside of the polar cap, while the E region winds seem to be part of a gravity wave with a wind amplitude of 125 m/sec. The wave period is found to be close to three hours, on the basis of the ratio of the magnitude of the wind component normal to the direction of wave propagation to the magnitude parallel to the direction of propagation. The observations show that significant energy resides in the divergent motions that are part of the transient response in the E region, at least in this case.

  11. Light pollution alters the phenology of dawn and dusk singing in common European songbirds.

    PubMed

    Da Silva, Arnaud; Valcu, Mihai; Kempenaers, Bart

    2015-05-01

    Artificial night lighting is expanding globally, but its ecological consequences remain little understood. Animals often use changes in day length as a cue to time seasonal behaviour. Artificial night lighting may influence the perception of day length, and may thus affect both circadian and circannual rhythms. Over a 3.5 month period, from winter to breeding, we recorded daily singing activity of six common songbird species in 12 woodland sites, half of which were affected by street lighting. We previously reported on analyses suggesting that artificial night lighting affects the daily timing of singing in five species. The main aim of this study was to investigate whether the presence of artificial night lighting is also associated with the seasonal occurrence of dawn and dusk singing. We found that in four species dawn and dusk singing developed earlier in the year at sites exposed to light pollution. We also examined the effects of weather conditions and found that rain and low temperatures negatively affected the occurrence of dawn and dusk singing. Our results support the hypothesis that artificial night lighting alters natural seasonal rhythms, independently of other effects of urbanization. The fitness consequences of the observed changes in seasonal timing of behaviour remain unknown.

  12. The effects of selection for early (day) and late (dusk) mating lines of hybrids of Bactrocera tryoni and Bactrocera neohumeralis.

    PubMed

    Meats, A; Pike, N; An, X; Raphael, K; Wang, W Y S

    2003-11-01

    Bactrocera neohumeralis and Bactrocera tryoni are closely related tephritid fruit fly species. B. neohumeralis mates throughout the day (in bright light) and B. tryoni mates at dusk. The two species can also be distinguished by the colour of their calli (prothoracic sclerites) which are brown and yellow, respectively. The F1 hybrids can mate both in bright light just before dusk and during dusk and have calli that are partly brown and partly yellow. The F2 hybrids have a wider range of callus patterns and mating occurs more widely in the day as well as at dusk. We directly selected hybrid stocks for mating time, creating 'early' (day-mating) and 'late' (dusk-mating) lines. As an apparently inadvertent consequence, the two types of line respectively had predominantly brown and predominantly yellow calli and thus came to closely resemble the original two species in both behaviour and appearance. Lines that were evenly selected (half for day and half for dusk) essentially retained the mating pattern of F2 hybrids. Selection for callus colour alone also affected the distribution of mating times in a predictable way. We propose a genetical model to account for the results and discuss them in the light of the apparent maintenance of species integrity in nature. PMID:14686607

  13. Dawn-dusk asymmetry and adiabatic dynamic of the radiation belt electrons during magnetic storm

    NASA Astrophysics Data System (ADS)

    Lazutin, Leonid L.

    2016-09-01

    The changes of the latitudinal profiles of outer belt energetic electrons during magnetic storms are mostly explained by the precipitation into the loss cone caused by VLF and EMIC waves or by the scattering into the magnetopause. In present work, energetic electron dynamics during magnetic storm of August 29-30, 2004 we attributed at most to the adiabatic transformation of the magnetic drift trajectories and Dst effect. This conclusion was based on the analysis of dawn-dusk asymmetry of the electron latitudinal profiles measured by low altitude polar orbiter SERVIS-1 and on the coincidence of pre-storm and after-storm profiles of radiation belt electrons and protons.

  14. Coherent HF radar backscatter from small-scale irregularities in the dusk sector of the subauroral ionosphere

    NASA Technical Reports Server (NTRS)

    Ruohoniemi, J. M.; Greenwald, R. A.; Villain, J.-P.; Baker, K. B.; Newell, P. T.

    1988-01-01

    This paper describes the characteristics of backscatter from decameter-scale ionospheric plasma density irregualarities, observed with an impressive regularity by the Goose Bay (Labrador) high-frequency (HF) radar in the dusk sector of the winter ionosphere, and discusses the relation of the scatter to the midlatitude trough. It is shown that this dusk scatter can be readily distinguished from other types of late afternoon/early evening scatter by the extreme equatorward position of its source region and by the low values of its associated radar Doppler velocities (not above 200 m/s) and spectral widths (not more than 200 m/s). A comparison of the radar observations with nearly simultaneous particle precipitation data obtained with the DMSP F6 satellite demonstrated that the source region of the backscatter lies within the subauroral ionosphere. It is shown that the characteristics of dusk scatter are compatible with the Spiro et al. (1978) model of the electrodynamics of the midlatitude trough.

  15. The Dusk Chorus from an Owl Perspective: Eagle Owls Vocalize When Their White Throat Badge Contrasts Most

    PubMed Central

    Penteriani, Vincenzo; Delgado, Maria del Mar

    2009-01-01

    Background An impressive number of studies have investigated bird vocal displays, and many of them have tried to explain the widespread phenomenon of the so-called dawn and dusk chorus, the sunrise and sunset peaks in bird song output. As many as twelve non-exclusive hypotheses have been proposed to explain why twilight peaks in vocal display might be advantageous; but, even after more than two decades of study, the basis underlying the dusk and dawn chorus is still unclear. Moreover, to date, the majority of studies on this topic have focused on songbirds. Methodology/Principal Findings We investigate here a novel hypothesis on why nocturnal birds with patches of white feathers call at twilight. We propose that white plumage patches and the timing of visual signaling have co-evolved to maximize the effectiveness of social communication such as the dusk chorus. This hypothesis centers on the recent discovery that eagle owls can adopt specific forms of visual signaling and is supported by the observation that adult eagle owls possess a white throat badge that is only visible during vocal displays. By monitoring the calling of eagle owls at dusk, a peak time for bird call output, we found that white throat badges contrasted most with the surrounding background during the owls' twilight chorusing. Conclusions/Significance Crepuscular and nocturnal species appear to have evolved white patches that, shown in association with vocal displays, allow them to communicate in dark surroundings. The evolution of a white badge that operates jointly with call displays at dawn and dusk may be relevant to the eagle owls' social dynamics. Our explanation for the dusk chorus may possibly represent an overlooked but common pattern of signaling among crepuscular and nocturnal birds that combine patches of white feathers with twilight displays. Furthermore, our findings could be relevant to songbirds that breed in dark forest habitats and have contrasting white badges, as well as birds

  16. A simple model describing the nonlinear dynamics of the dusk/dawn asymmetry in the high-latitude thermospheric flow

    NASA Technical Reports Server (NTRS)

    Gundlach, J. P.; Larsen, M. F.; Mikkelsen, I. S.

    1988-01-01

    A simple nonlinear, axisymmetric, shallow-water numerical model has been used to study the asymmetry in the neutral flow between the dusk and dawn sides of the auroral oval. The results indicate that the Coriolis force and the curvature terms are nearly in balance on the evening side and require only a small pressure gradient to effect adjustment. The result is smaller neutral velocities near dawn and larger velocities near dusk than would be the case for a linearized treatment. A consequence is that more gravity wave energy is produced on the morning side than on the evening side.

  17. Distinct sources of particles near the cusp and the dusk flank of the magnetosphere

    NASA Astrophysics Data System (ADS)

    Escoubet, C. P.; Grison, B.; Berchem, J.; Trattner, K. J.; Lavraud, B.; Pitout, F.; Soucek, J.; Richard, R. L.; Laakso, H. E.; Masson, A.; Dunlop, M.; Dandouras, I. S.; Rème, H.; Fazakerley, A. N.; Daly, P. W.

    2015-12-01

    At the magnetopause, the location of the magnetic reconnection sites depends on the orientation of the interplanetary magnetic field (IMF) in the solar wind: on the dayside magnetosphere for an IMF southward, on the lobes for an IMF northward and on the flanks for an IMF in the East-West direction. Since most of observations of reconnection events have sampled a limited region of space simultaneously it is still not yet know if the reconnection line is extended over large regions of the magnetosphere or if is patchy and made of many reconnection lines. We report a Cluster crossing on 5 January 2002 near the exterior cusp on the southern dusk side where we observe multiple sources of reconnection/injections. The IMF was mainly azimuthal (IMF-By around -5 nT), the solar wind speed lower than usual around 280 km/s with the density of order 5 cm-3. The four Cluster spacecraft had an elongated configuration near the magnetopause. C4 was the first spacecraft to enter the cusp around 19:52:04 UT, followed by C2 at 19:52:35 UT, C1 at 19:54:24 UT and C3 at 20:13:15 UT. C4 and C1 observed two ion energy dispersions at 20:10 UT and 20:40 UT and C3 at 20:35 UT and 21:15 UT. Using the time of flight technique on the upgoing and downgoing ions, which leads to energy dispersions, we obtain distances of the ion sources between 14 and 20 RE from the spacecraft. The slope of the ion energy dispersions confirmed these distances. Using Tsyganenko model, we find that these sources are located on the dusk flank, past the terminator. The first injection by C3 is seen at approximately the same time as the 2nd injection on C1 but their sources at the magnetopause were separated by more than 7 RE. This would imply that two distinct sources were active at the same time on the dusk flank of the magnetosphere. In addition, a flow reversal was observed at the magnetopause on C4 which would be an indication that reconnection is also taking place near the exterior cusp quasi-simultaneously. A

  18. A study of ion injections at the dawn and dusk polar edges of the auroral oval

    NASA Astrophysics Data System (ADS)

    Stenuit, H.; Sauvaud, J.-A.; Delcourt, D. C.; Mukai, T.; Kokubun, S.; Fujimoto, M.; Buzulukova, N. Y.; Kovrazhkin, R. A.; Lin, R. P.; Lepping, R. P.

    2001-12-01

    In the auroral dawn and dusk magnetosphere at altitudes of ~2-3RE, three distinct zones of ion and electron precipitation are commonly detected onboard Interball 2, near the polar edge of the auroral oval. From high to low latitudes the satellite encounters (1) magnetosheath/low-latitude boundary layer (LLBL) like plasma (Zone 1), (2) a mixing region with plasma characteristics between LLBL and plasma sheet (Zone 2), and (3) the auroral plasma sheet precipitation (Zone 3). Further equatorward, the satellite crosses the inner plasma sheet characterized by ``ion gaps'' in the morning sector. Inside Zones 1 and 2 impulsive ion injections are often detected. They consist of overlapping energy dispersed structures from about 10 keV down to several hundreds of eV with temperature close to that of the magnetosheath. Using trajectory computations backward in time, these dispersions are shown to be cause by time-of-flight effect from a distant source located close to the equatorial magnetopause. Whereas Zone 1 is located mainly poleward of region 1 (downward field-aligned currents at dawn and upward field-aligned currents at dusk), Zone 2 generally coincides with region 1. It is mainly located on closed field lines, as evidenced from the local detection of bouncing ion clusters. Finally, Zone 3 corresponds with region 2 of upward field-aligned currents. A statistical study of Zone 1 which is present in about 12% of the satellite passes at dawn and dusk reveals that its probability of occurrence seems to be controlled by the interplanetary magnetic field (IMF). That is, it is formed when the IMF has a northward component and tends to be radially directed. Moreover, it is more frequently encountered during periods of enhanced solar wind pressure. Detailed case studies uncover a remarkable correlation between the onsets of individual injections inside Zone 1 and those of pressure pulses in the magnetosheath. Both have a characteristic period of ~200-250 s, similar to that of

  19. Cluster Observations of reconnection along the dusk flank of the magnetosphere

    NASA Astrophysics Data System (ADS)

    Escoubet, C.-Philippe; Grison, Benjamin; Berchem, Jean; Trattner, Karlheinz; Lavraud, Benoit; Pitout, Frederic; Soucek, Jan; Richard, Robert; Laakso, Harri; Masson, Arnaud; Dunlop, Malcolm; Dandouras, Iannis; Reme, Henri; Fazakerley, Andrew; Daly, Patrick

    2015-04-01

    Magnetic reconnection is generally accepted to be the main process that transfers particles and energy from the solar wind to the magnetosphere. The location of the reconnection site depends on the orientation of the interplanetary magnetic field (IMF) in the solar wind: on the dayside magnetosphere for an IMF southward, on the lobes for an IMF northward and on the flanks for an IMF in the East-West direction. Since most of observations of reconnection events have sampled a limited region of space simultaneously it is still not yet know if the reconnection line is extended over large regions of the magnetosphere or if is patchy and made of many reconnection lines. We report a Cluster crossing on 5 January 2002 near the exterior cusp on the southern dusk side where we observe multiple sources of reconnection/injections. The IMF was mainly azimuthal (IMF-By around -5 nT), the solar wind speed lower than usual around 280 km/s with the density of order 5 cm-3. The four Cluster spacecraft had an elongated configuration near the magnetopause. C4 was the first spacecraft to enter the cusp around 19:52:04 UT, followed by C2 at 19:52:35 UT, C1 at 19:54:24 UT and C3 at 20:13:15 UT. C4 and C1 observed two ion energy dispersions at 20:10 UT and 20:40 UT and C3 at 20:35 UT and 21:15 UT. Using the time of flight technique on the upgoing and downgoing ions, which leads to energy dispersions, we obtain distances of the ion sources between 14 and 20 RE from the spacecraft. The slope of the ion energy dispersions confirmed these distances. Using Tsyganenko model, we find that these sources are located on the dusk flank, past the terminator. The first injection by C3 is seen at approximately the same time as the 2nd injection on C1 but their sources at the magnetopause were separated by more than 7 RE. This would imply that two distinct sources were active at the same time on the dusk flank of the magnetosphere. In addition, a flow reversal was observed at the magnetopause on C4

  20. Dawn-Dusk and Interhemispheric Asymmetries in the Magnetospheric Tail Lobes

    NASA Astrophysics Data System (ADS)

    Walsh, Andrew; Haaland, Stein

    2015-04-01

    Dawn-Dusk asymmetries and inter-hemispheric asymmetries are common throughout the solar wind-magnetosphere-ionosphere system, but to date little research has been conducted on the asymmetries that are present in the magnetotail lobes. Here we investigate the extent to which asymmetries in magnetosperic convection (specifically the rotation of the converection pattern towards the premidnight sector) are reflected in the properties of the magnetotail lobe magnetic field, and the cold ion population in the lobes. We employ data from Cluster, Geotail, Double Star and THEMIS taken during intervals of steady southward IMF so asymmetries resulting from IMF BY are minimised. Initial results are suggestive of a higher lobe magnetic field strength in the premidnight sector, consistent with the asymmetric convection pattern and also a higher magnetic field strength in the winter hemisphere.

  1. Dawn and Dusk Set States of the Circadian Oscillator in Sprouting Barley (Hordeum vulgare) Seedlings

    PubMed Central

    Deng, Weiwei; Clausen, Jenni; Boden, Scott; Oliver, Sandra N.; Casao, M. Cristina; Ford, Brett; Anderssen, Robert S.; Trevaskis, Ben

    2015-01-01

    The plant circadian clock is an internal timekeeper that coordinates biological processes with daily changes in the external environment. The transcript levels of clock genes, which oscillate to control circadian outputs, were examined during early seedling development in barley (Hordeum vulgare), a model for temperate cereal crops. Oscillations of clock gene transcript levels do not occur in barley seedlings grown in darkness or constant light but were observed with day-night cycles. A dark-to-light transition influenced transcript levels of some clock genes but triggered only weak oscillations of gene expression, whereas a light-to-dark transition triggered robust oscillations. Single light pulses of 6, 12 or 18 hours induced robust oscillations. The light-to-dark transition was the primary determinant of the timing of subsequent peaks of clock gene expression. After the light-to-dark transition the timing of peak transcript levels of clock gene also varied depending on the length of the preceding light pulse. Thus, a single photoperiod can trigger initiation of photoperiod-dependent circadian rhythms in barley seedlings. Photoperiod-specific rhythms of clock gene expression were observed in two week old barley plants. Changing the timing of dusk altered clock gene expression patterns within a single day, showing that alteration of circadian oscillator behaviour is amongst the most rapid molecular responses to changing photoperiod in barley. A barley EARLY FLOWERING3 mutant, which exhibits rapid photoperiod–insensitive flowering behaviour, does not establish clock rhythms in response to a single photoperiod. The data presented show that dawn and dusk cues are important signals for setting the state of the circadian oscillator during early development of barley and that the circadian oscillator of barley exhibits photoperiod-dependent oscillation states. PMID:26068005

  2. Intensification and fading of auroral arcs in the dusk-midnight sector of the polar cap

    SciTech Connect

    Wu, Q.; Rosenberg, T.J. ); Berkey, F.T. ); Eather, R.H. )

    1991-05-01

    Observations of the aurora from South Pole station (magnetic latitude = {minus}74.2{degree}) have been used to study the intensification and fading of polar arcs observed near the dusk meridian. Most of the cases examined have the following features in common: (1) a preexisting auroral form intensifies for about 10 min; (2) this activation is followed by a pronounced decrease of luminosity; (3) the auroral fade terminates after 30-60 min with the onset of intense aurora which sweeps rapidly overhead. The availability of all-sky camera, auroral electrojet (AE) index and interplanetary magnetic field (IMF) data for some of the cases enables the following additional characterizations of these events. The preexisting form is a Sun- or oval-aligned arc (or part of a multiple arc system) which disappears following the activation; equatorward drift of the arc (or system) accompanies the luminosity change. There is some evidence to suggest that the arc is poleward of the auroral oval. The brief intensification and/or the onset of fading occurs during the growth phase or near the start of the expansive phase of a substorm; termination of the fade is near the maximum in AE and is probably indicative of the beginning of the recovery phase of the substorm. For all three cases for which IMF data were available the onset of fading occurred 20-30 min after B{sub z} turned southward. Sun-aligned arcs are a common feature of the polar cap during northward B{sub z} but disappear during the increasingly disturbed conditions that accompany southward B{sub z}. The present results suggest that brief intensifications of southern hemisphere polar cap arcs near dusk may be linked in part to the sunward orientation of the IMF which favors enhanced electron fluxes in the southern lobe of the magnetotail.

  3. Dawn and Dusk Set States of the Circadian Oscillator in Sprouting Barley (Hordeum vulgare) Seedlings.

    PubMed

    Deng, Weiwei; Clausen, Jenni; Boden, Scott; Oliver, Sandra N; Casao, M Cristina; Ford, Brett; Anderssen, Robert S; Trevaskis, Ben

    2015-01-01

    The plant circadian clock is an internal timekeeper that coordinates biological processes with daily changes in the external environment. The transcript levels of clock genes, which oscillate to control circadian outputs, were examined during early seedling development in barley (Hordeum vulgare), a model for temperate cereal crops. Oscillations of clock gene transcript levels do not occur in barley seedlings grown in darkness or constant light but were observed with day-night cycles. A dark-to-light transition influenced transcript levels of some clock genes but triggered only weak oscillations of gene expression, whereas a light-to-dark transition triggered robust oscillations. Single light pulses of 6, 12 or 18 hours induced robust oscillations. The light-to-dark transition was the primary determinant of the timing of subsequent peaks of clock gene expression. After the light-to-dark transition the timing of peak transcript levels of clock gene also varied depending on the length of the preceding light pulse. Thus, a single photoperiod can trigger initiation of photoperiod-dependent circadian rhythms in barley seedlings. Photoperiod-specific rhythms of clock gene expression were observed in two week old barley plants. Changing the timing of dusk altered clock gene expression patterns within a single day, showing that alteration of circadian oscillator behaviour is amongst the most rapid molecular responses to changing photoperiod in barley. A barley EARLY FLOWERING3 mutant, which exhibits rapid photoperiod-insensitive flowering behaviour, does not establish clock rhythms in response to a single photoperiod. The data presented show that dawn and dusk cues are important signals for setting the state of the circadian oscillator during early development of barley and that the circadian oscillator of barley exhibits photoperiod-dependent oscillation states.

  4. Weak auroral emissions and particle precipitations in the dusk auroral oval

    SciTech Connect

    Ono, T.; Hirasawa, T. ); Ching-I. Meng )

    1989-09-01

    Faint auroral displays in the low-latitude region of the duskside auroral oval were examined by using 5577 A, 6300 A, and 4861 A auroral images from three monochromatic all-sky television cameras at Syowa Station, Antarctica, and simultaneous precipitating auroral particle data obtained by the U.S. Air Force/Defense Meteorological Satellite Program (USAF/DMSP) F6 satellite. In the low-latitude region of the duskside auroral oval, we found three types of auroral displays with weak optical intensity: (1) proton auroras, (2) pulsating auroras, and (3) faint discrete auroral arcs distinct only in the 6300 A emission. In usual cases, the energy input into this region is mostly carried y proton precipitations to produce proton auroras mainly at wavelengths of 4861 A and 5577 A. Pulsating features are sometimes observed in the diffuse auroral region in the dusk sector. Comparing auroral images with the nearly simultaneous data of precipitating auroral particles, we confirmed that the pulsating auroras are associated with the intensification of precipitating electron flux from the central plasma sheet. Furthermore, electrons are the main contributors to the energy input into the duskside auroral oval in this case. We also found that discrete auroras sometimes appeared in the 6300 A images, but not in images at other wavelengths. They appear in the equatorial part of the dusk auroral oval. These 6300 A discrete auroras correspond to weak precipitation spikes of low-energy electrons simultaneously measured by DMSP satellites. The flux and average energy of these electron spikes are about 10{sup 8}/(cm{sup 2} sr s) and 100 eV, respectively. They are intense enough to excite 6300 A emissions but not 5577 A emissions, as detected from the ground observations. {copyright} American Geophysical Union 1989

  5. Dawn-dusk asymmetries in plasma sheet particle distributions and the average behaviour of magnetotail current systems

    NASA Astrophysics Data System (ADS)

    Walsh, A. P.; Forsyth, C.; Owen, C. J.; Fazakerley, A. N.; Dandouras, I. S.

    2011-12-01

    We present the results of a survey of Cluster PEACE and CIS-CODIF data taken in the 2001-2006 tail seasons, building on the work of Walsh et al. (GRL, 2011). We examine the average pitch angle distributions of protons and electrons in the magnetotail as a function of proton plasma beta, restricted to times when the magnetosphere was exposed to steady (on a 3 hour timescale) IMF conditions and focussing in particular on dawn-dusk asymmetries. We confirm that, on average, the 2 component proton plasma sheet exists duskward of the noon-midnight meridian under steady northward IMF. An associated population of cold electrons is also observed. Dawnward of the noon-midnight meridian there are no significant fluxes of the cold component of protons and much reduced fluxes of the cold electron component, implying transport across the dusk magnetopause is the dominant formation mechanism of the two component plasma sheet for both protons and electrons. Under southward IMF, dawn-dusk asymmetries in the protons are controlled by the Y component of the IMF. For the electrons higher fluxes of high energy, field-aligned, particles are observed at dusk than at dawn. This suggests a link to a duskward offset of the tail neutral line and the preferential observation of substorm-related tail signatures in the premidnight sector. We also consider the relationship between the observed particle populations and the average behaviour of the large-scale magnetotail current systems as revealed by the Curlometer.

  6. Solar wind influence on the dawn-dusk asymmetry of the Io plasma torus observed by HISAKI/EXCEED

    NASA Astrophysics Data System (ADS)

    Murakami, G.; Yoshioka, K.; Kimura, T.; Yamazaki, A.; Tsuchiya, F.; Kagitani, M.; Tao, C.; Yoshikawa, I.; Fujimoto, M.

    2014-12-01

    The dawn-dusk asymmetry of the Io plasma torus has been seen by several observations [e.g., Sandel and Broadfoot, 1982; Steffl et al., 2004]. Ip and Goertz [1983] explained this asymmetry can be caused by a dawn-to-dusk electric field in the Jupiter's inner magnetosphere. However, the question what physical process can impose such an electric field deep inside the strong magnetosphere still remains. The long-term monitoring of the Io plasma torus is a key observation to answer this question. The extreme ultraviolet (EUV) spectrometer EXCEED onboard the HISAKI satellite was launched in 2013 and observed the Io plasma torus from December 2013 to March 2014 (75 days). We investigated the temporal variation of the dawn/dusk ratio of EUV brightness. Then we compared it to the solar wind dynamic pressure extrapolated from that observed around Earth by using magnetohydrodynamic (MHD) simulation. As a result we found clear responses of the dawn-dusk asymmetry to rapid increases of the solar wind dynamic pressure. We will present the initial results of this study.

  7. MMS Observations of magnetospheric fast ion flows and magnetic dipolarization near the dusk-meridian flank

    NASA Astrophysics Data System (ADS)

    Pollock, Craig; Chen, Li-Jen; Wang, Shan; Torbert, Roy; Russell, Christopher; Reiff, Patricia; Giles, Barbara; Burch, James

    2016-04-01

    The concept of a magnetic dipolarization front propagating earthward through Earth's magnetotail and accompanied by fast earthward ion flows, both as consequences of magnetic reconnection occurring tail-ward of an observation point, is well known. Examples of this phenomenology have recently been referred to as reconnection fronts. It is less common to imagine similar signature sets in contexts other than the imagined noon-midnight magnetotail configuration. Nevertheless, signatures of 800 km/s earthward ion flows were observed contemporaneously with distinct but temporary increases in the GSE-z component of the magnetic field at a geocentric distance of the order of 10 RE, in the vicinity (but somewhat tail-ward) of Earth's equatorial dusk terminator on August 12, 2015. These observations were obtained using the Fast Plasma Investigation (FPI) and the Fields electric fields experiment on NASA's Magnetospheric Multiscale (MMS) mission. Several interesting questions arise as to the nature of the observed plasma and field signatures and their drivers in cases such as this. To what degree are they analogous to the magnetotail reconnection fronts previously alluded to? And, to the degree that they are, what kind of reconnection geometry can we envision as giving rise to these signatures at such a location? We will present sample observations and discuss their significance from this point of view.

  8. Dusk to dawn activity patterns of anopheline mosquitoes in West Timor and Java, Indonesia.

    PubMed

    Ndoen, Ermi; Wild, Clyde; Dale, Pat; Sipe, Neil; Dale, Mike

    2011-05-01

    Malaria is a serious health issue in Indonesia. We investigated the dusk to dawn anopheline mosquito activity patterns, host-seeking and resting locations in coastal plain, hilly and highland areas in West Timor and Java. Adult mosquitoes were captured landing on humans or resting in houses or animal barns. Data analyzed were: mosquito night-time activities; period of peak activity; night-time activity in specific periods of time and for mosquito resting locations. Eleven species were recorded; data were sparse for some species therefore detailed analyses were performed for four species only. In Java Anopheles vagus was common, with a bimodal pattern of high activity. In West Timor, its activity peaked around midnight. Other species with peak activity around the middle of the night were An. barbirostris and An. subpictus. Most species showed no biting and resting preference for indoors or outdoors, although An. barbirostris preferred indoors in West Timor, but outdoors in Java. An. aconitus and An. annularis preferred resting in human dwellings; An. subpictus and An. vagus preferred resting in animal barns. An. barbirostris preferred resting in human dwellings in West Timor and in animal barns in Java. The information is useful for planning the mosquito control aspect of malaria management. For example, where mosquito species have peak activity at night indoors, bednets and indoor residual spraying should reduce malaria risk, but where mosquitoes are most active outdoors, other options may be more effective.

  9. A DE-1/whistler study of the thermal plasma structure and dynamics in the dusk bulge sector of the magnetosphere

    NASA Technical Reports Server (NTRS)

    Carpenter, D. L.

    1992-01-01

    The objective of this research was to obtain new understanding of the thermal plasma structure and dynamics of the plasmasphere bulge region of the magnetosphere, with special emphasis on the erosion process that results in a reduction in plasmasphere size and on the manner in which erosion leads to the presence of patches of dense plasma in the middle and outer afternoon-dusk magnetosphere. Case studies involving data from the DE 1, GEOS 2, and ISEE 1 satellites and from ground whistler stations Siple, Halley, and Kerguelen were used. A copy of the published paper entitled 'A case study of plasma structure in the dusk sector associated with enhanced magnetospheric convection,' is included.

  10. Multispacecraft study on the dynamics of the dusk-flank magnetosphere under northward IMF: 10-11 January 1997

    NASA Astrophysics Data System (ADS)

    Stenuit, H.; Fujimoto, M.; Fuselier, S. A.; Sauvaud, J.-A.; Wing, S.; Fedorov, A.; Budnik, E.; Savin, S. P.; Trattner, K. J.; Angelopoulos, V.; Bonnell, J.; Phan, T. D.; Mukai, T.; Pedersen, A.

    2002-10-01

    The latter half of the magnetic cloud event on 10-11 January 1997 is studied in the context of the cold-dense plasma sheet. A fortuitous distribution of spacecraft in key regions allows us to relate the plasma sheet status transition with the boundary layer process. When the interplanetary magnetic field (IMF) was strongly northward and the solar wind density returned to a nominal value from an anomalously large one, two spacecraft, Geotail and Interball-Tail, were in the dusk-flank region and detected a change in the plasma sheet status from hot and tenuous to cold and dense. The change seen by these spacecraft making in situ observations is confirmed to be a global feature by DMSP observations at low altitude. Just around this time, Interball-Aurora and Polar were crossing the dusk-auroral oval, monitoring globally the dynamics of the dusk-flank magnetopause at its footpoint. Injection of magnetosheath-like ions was detected by these spacecraft. We try to relate these observations with the processes that transport the magnetosheath plasma onto the magnetospheric field lines. Three candidate processes are discussed, but none of them turn out to be convincing, indicating the need for further study on this issue.

  11. SAR arc observation as the mapping of plasmasphere dusk-bulge during a magnetic storm

    NASA Astrophysics Data System (ADS)

    Ievenko, Igor; Parnikov, Stanislav

    2016-07-01

    The stable auroral red (SAR) arcs are the consequence of interaction of the outer plasmasphere (plasmapause) with energetic ions of the ring current. In this work we analyze the observation of aurorae and SAR arc with the all-sky imager (ASI) at the Yakutsk meridian (130ºE; 200ºE, geom.) during the magnetic storm main phase on March 17, 2015. ASI registers the SAR arc with a maximum of its intensity and the latitude on the westward horizon of station from the start of observations at ~1116 UT during the decrease of magnetic activity after the main phase onset of magnetic storm at ~0630 UT. The measurements of the thermal ion fluxes with ECT HOPE Instrument aboard the Van Allen Probes B satellite at ~1230 UT testify to a plasmapause location on L ~ 3.5 at the meridian ~1825 MLT. The inner boundary of the energetic H+ and O+ ions flux has been registered by the satellite on L ~ 2.8-3.3 at the meridian ~ 1800 MLT at 1210-1220 UT. At this time ASI observes SAR arc up to a meridian 1840 MLT on the westward horizon of station. Further the dynamics of aurorae in the 557.7, 630.0, 470.9 and 486.1 (Hβ) nm emissions owing to sharp changes in the solar wind and during three substorms is observed. We consider differences in the precipitation dynamics of energetic protons and electrons during substorms. It is shown that the SAR arc registered with ASI maps the ring current overlap with the region of plasmasphere dusk-bulge or plume. The research is supported by RFBR grant No 15-05-02372 a.

  12. Dusk-to-nighttime enhancement of mid-latitude NmF2 in local summer: inter-hemispheric asymmetry and solar activity dependence

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Liu, L.; Le, H.; Wan, W.; Zhang, H.

    2015-06-01

    In this paper ionosonde observations in the East Asia-Australia sector were collected to investigate dusk-to-nighttime enhancement of mid-latitude summer NmF2 (maximum electron density of the F2 layer) within the framework of NmF2 diurnal variation. NmF2 were normalized to two solar activity levels to investigate the dependence of the dusk-to-nighttime enhancement on solar activity. The dusk-to-nighttime enhancement of NmF2 is more evident at Northern Hemisphere stations than at Southern Hemisphere stations, with a remarkable latitudinal dependence. The dusk-to-nighttime enhancement shows both increasing and declining trends with solar activity increasing, which is somewhat different from previous conclusions. The difference in the dusk-to-nighttime enhancement between Southern Hemisphere and Northern Hemisphere stations is possibly related to the offset of the geomagnetic axis from the geographic axis. hmF2 (peak height of the F2 layer) diurnal variations show that daytime hmF2 begins to increase much earlier at low solar activity level than at high solar activity level at northern Akita and Wakkanai stations where the dusk-to-nighttime enhancement is more prominent at low solar activity level than at high solar activity level. That implies neutral wind phase is possibly also important for nighttime enhancement.

  13. The dawn-dusk asymmetry of ion density in the dayside magnetosheath and its annual variability measured by THEMIS

    NASA Astrophysics Data System (ADS)

    Dimmock, Andrew P.; Pulkkinen, Tuija I.; Osmane, Adnane; Nykyri, Katariina

    2016-05-01

    The local and global plasma properties in the magnetosheath play a fundamental role in regulating solar wind-magnetosphere coupling processes. However, the magnetosheath is a complex region to characterise as it has been shown theoretically, observationally and through simulations that plasma properties are inhomogeneous, non-isotropic and asymmetric about the Sun-Earth line. To complicate matters, dawn-dusk asymmetries are sensitive to various changes in the upstream conditions on an array of timescales. The present paper focuses exclusively on dawn-dusk asymmetries, in particularly that of ion density. We present a statistical study using THEMIS data of the dawn-dusk asymmetry of ion density in the dayside magnetosheath and its long-term variations between 2009 and 2015. Our data suggest that, in general, the dawn-side densities are higher, and the asymmetry grows from noon towards the terminator. This trend was only observed close to the magnetopause and not in the central magnetosheath. In addition, between 2009 and 2015, the largest asymmetry occurred around 2009 decreasing thereafter. We also concluded that no single parameter such as the Alfvén Mach number, plasma velocity, or the interplanetary magnetic field strength could exclusively account for the observed asymmetry. Interestingly, the dependence on Alfvén Mach number differed between data sets from different time periods. The asymmetry obtained in the THEMIS data set is consistent with previous studies, but the solar cycle dependence was opposite to an analysis based on IMP-8 data. We discuss the physical mechanisms for this asymmetry and its temporal variation. We also put the current results into context with the existing literature in order to relate THEMIS era measurements to those made during earlier solar cycles.

  14. Additional stratifications in the equatorial F region at dawn and dusk during geomagnetic storms: Role of electrodynamics

    NASA Astrophysics Data System (ADS)

    Sreeja, V.; Balan, N.; Ravindran, Sudha; Pant, Tarun Kumar; Sridharan, R.; Bailey, G. J.

    2009-08-01

    The role of electrodynamics in producing additional stratifications in the equatorial F region (F 3 layer) at dawn and dusk during geomagnetic storms is discussed. Two cases of F 3 layer at dawn (0600-0730 LT on 5 October 2000 and 8 December 2000) and one case of F 3 layer at dusk (1600-1730 LT on 5 October 2000) are observed, for the first time, by the digital ionosonde at the equatorial station Trivandrum (8.5°N 77°E dip ˜ 0.5°N) in India. The unusual F 3 layers occurred during the geomagnetic storms and are associated with southward turning of interplanetary magnetic field B z , suggesting that eastward prompt penetration electric field could be the main cause of the F 3 layers. The dawn F 3 layer on 5 October is modeled using the Sheffield University Plasmasphere-Ionosphere Model by using the E × B drift estimated from the real height variation of the ionospheric peak during the morning period. The model qualitatively reproduces the dawn F 3 layer. While the existing F 2 layer rapidly drifts upward and forms the F 3 layer and topside ledge, a new layer forming at lower heights develops into the normal F 2 layer.

  15. Observations of Kelvin-Helmholtz Waves Along the Dusk-Side Boundary of Mercury's Magnetosphere During MESSENGER's Third Flyby

    NASA Technical Reports Server (NTRS)

    Boardsen, Scott A.; Sundberg, Torgjoern; Slavin, James A.; Anderson, Brian J.; Korth, Haje; Solomon, Sean C.; Blomberg, Lars G.

    2010-01-01

    During the third MESSENGER flyby of Mercury on 29 September 2009, 15 crossings of the dusk-side magnetopause were observed in the magnetic field data over a 2-min period, during which the spacecraft traveled a distance of 0.2 R(sub M) (where R(sub M) is Mercury's radius). The quasi-periodic nature of the magnetic field variations during the crossings, the characteristic time separations of approx.16 s between pairs of crossings, and the variations of the magnetopause normal directions indicate that the signals are likely the signature of surface waves highly steepened at their leading edge that arose from the Kelvin-Helmholtz instability. At Earth, the Kelvin- Helmholtz instability is believed to lead to the turbulent transport of solar wind plasma into Earth's plasma sheet. This solar wind entry mechanism could also be important at Mercury. Citation: Boardsen, S. A., T. Sundberg, J. A.Slavin, B. J. Anderson, H. Korth, S. C. Solomon, and L. G. Blomberg (2010), Observations of Kelvin-Helmholtz waves along the dusk-side boundary of Mercury s magnetosphere during MESSENGER's third flyby,

  16. Kelvin-Helmholtz vortices observed by Themis at the dusk side of the magnetopause under southward IMF

    NASA Astrophysics Data System (ADS)

    Qing, Yan Guang; McFadden, James; Parks, George; Shen, Chao; Mozer, Forrest; Chen, professor. Tao; Cai, Chunlin

    Under southward interplanetary magnetic field (IMF), 3 spacecraft of Themis observed several crossings of the magnetopause periodically at the duskside of the magnetopause, with tailward shear flows in the magnetosheath and significant sunward returning flows inside the magnetopause. The observed flow velocity shows rotating features for each of the spacecraft, and periodical enhancements could be seen in the vorticity calculated normal to the 3-point spacecraft plain based on the 3-point velocity measurements. The rotating features of the velocity and the periodic enhancements in the normal vorticity could be considered the evidence of the Kelvin-Helmholtz vortices due to the velocity shear at the dusk side of the magnetopause. The tailward propagation of the vortices along the flank magnetopause could be notable in the time lags from one spacecraft to another, which could be estimated as about 330 km/s, similar to the previous estimate under southward IMF. At the edges of the vortices, enhancements in the magnetic field due to the compression of the magnetic field could be found. By investigating the difference between the observed and convective electric fields, the non-convective electric field of 5-8 mV/m was observed at small scale from electron gyro-radius to ion gyro-radius, some of which consistent with the compression of the magnetic field at the distorted magnetopause. The non-convective electric field might possibly be one of the factors to induce possible reconnection inside the vortices.

  17. The global distribution of the dusk-to-nighttime enhancement of summer NmF2 at solar minimum

    NASA Astrophysics Data System (ADS)

    Chen, Yiding; Liu, Libo; Le, Huijun; Wan, Weixing; Zhang, Hui

    2016-08-01

    In this paper, the dusk-to-nighttime enhancement (DNE) of summer NmF2 was investigated based on Constellation Observing System for Meteorology, Ionosphere, and Climate radio occultation observations at solar minimum. The global distributions of the magnitude and the peak time of the DNE as well as the role of the DNE in NmF2 diurnal cycle were presented. The DNE mainly exists in three regions (one in the Southern Hemisphere and two in the Northern Hemisphere), and its distribution is related to geomagnetic configuration, especially in the Southern Hemisphere. For most DNEs, their peaks correspond to the maxima of NmF2 diurnal cycle. The DNEs are much more prominent in the southern than in the northern summer hemisphere; they last to later nighttime hours, have larger magnitudes, and play more important roles in NmF2 diurnal cycle in the southern than in the northern summer hemisphere. The distribution of the DNE was analyzed in terms of photoionization and the vertical plasma drift induced by neutral winds. The positive geomagnetic declinations and the smaller geomagnetic inclinations at higher geographic latitudes over the South Pacific are crucial for the prominent DNEs in the southern summer hemisphere; they result in larger upward plasma drift at higher latitudes where photoionization is still significant at sunset and evening hours.

  18. Dawn-dusk asymmetry in ion pitch-angle anisotropy in the near-Earth magnetosphere and tail plasma sheet

    NASA Astrophysics Data System (ADS)

    Wang, C.; Zaharia, S. G.; Lyons, L. R.; Angelopoulos, V.

    2012-12-01

    We found a strong dawn-dusk asymmetry in ion pitch-angle anisotropy from spatial distributions statistically determined using THEMIS observations. The asymmetry varies significantly with ion energies and is a result of different processes. The anisotropy of ions below several hundreds eV in the tail plasma sheet (beyond X = 10 Re) and the near-Earth magnetosphere (inside r = 10 Re) is dominantly negative (relatively higher particle fluxes near 0 and 180 degree pitch-angle) and is more strongly negative in the post-midnight sector than the pre-midnight sector. The negative anisotropy is likely caused by field-aligned ionosphere outflow and the post-midnight enhancement is correlated with stronger electron precipitation energy fluxes that create stronger outflow. For ions between 1 to 10 keV in the near-Earth magnetosphere, anisotropy is found to be strongly positive (relatively higher fluxes near 90 degree pitch-angle) in the morning sector while near isotropic in the evening sector. Comparing the fluxes within the region of the positive anisotropy with other MLTs suggests that the positive anisotropy is caused by field-aligned ions not being able to drift as earthward as 90 degree ions. For ions of 10 keV and above, magnetic drift shell splitting results in strongly positive anisotropy on the dayside, while additional magnetopause shadowing causes strongly negative anisotropy in the post-midnight sector.

  19. MHD instability with dawn-dusk symmetry in near-Earth plasma sheet during substorm growth phase*

    NASA Astrophysics Data System (ADS)

    Zhu, P.; Raeder, J.; Hegna, C.; Sovinec, C.

    2010-12-01

    Recent global MHD simulations of March 23, 2007 THEMIS substorm event using the OpenGGCM code have confirmed the presence of both high-ky ballooning modes and zero-ky instabilities in the near-Earth plasma sheet during the substorm growth phase [Raeder et al 2010]. These results are consistent with findings from earlier analyses [Siscoe et al 2009; Zhu et al 2009]. Here ky is the azimuthal wavenumber in the dawn-dusk direction. However, the nature and role of the ky=0 mode, as well as its interaction with the high ky ballooning modes, in the process leading to the expansion onset remain unclear. In this work, we focus on the stability properties of the ky=0 mode. A re-evaluation of the tail-tearing mode criterion by Sitnov and Schindler (2009) suggested that the dipolarization front (DF) structure identified in THEMIS observations [Runov et al 2009] could be tearing-unstable. Linear calculations using the NIMROD code have found a growing tearing mode in a generalized Harris sheet with a DF-like structure, which is also a unique feature closely correlated with the appearance of zero-ky mode in the OpenGGCM simulation. The ideal-MHD energy principle analysis is used to address the question whether the ky=0 mode is an ideal or resistive MHD instability. We further compare the linear and nonlinear tail-tearing mode in NIMROD simulations with the ky=0 mode from OpenGGCM simulations. *Supported by NSF Grants AGS-0902360 and PHY-0821899. References: Raeder, J., P. Zhu, Y.-S. Ge, and G. Siscoe (2010), Tail force imbalance and ballooning instability preceding substorm onset, submitted to J. Geophys. Res. Runov, A., et al. (2009), Geophys. Res. Lett., 36, L14106. Siscoe, G.L., M.M. Kuznetsova, and J. Raeder (2009), Ann. Geophys., 27, 3141. Sitnov, M.I. and K. Schindler (2010), Geophys. Res. Lett., 37, L08102. Zhu, P., J. Raeder, K. Germaschewski, and C.C. Hegna (2009), Ann. Geophys., 27, 1129.

  20. M-I coupling across the auroral oval at dusk and midnight: repetitive substorm activity driven by interplanetary coronal mass ejections (CMEs)

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    We study substorms from two perspectives, i.e., magnetosphere-ionosphere coupling across the auroral oval at dusk and at midnight magnetic local times. By this approach we monitor the activations/expansions of basic elements of the substorm current system (Bostrøm type I centered at midnight and Bostrøm type II maximizing at dawn and dusk) during the evolution of the substorm activity. Emphasis is placed on the R1 and R2 types of field-aligned current (FAC) coupling across the Harang reversal at dusk. We distinguish between two distinct activity levels in the substorm expansion phase, i.e., an initial transient phase and a persistent phase. These activities/phases are discussed in relation to polar cap convection which is continuously monitored by the polar cap north (PCN) index. The substorm activity we selected occurred during a long interval of continuously strong solar wind forcing at the interplanetary coronal mass ejection passage on 18 August 2003. The advantage of our scientific approach lies in the combination of (i) continuous ground observations of the ionospheric signatures within wide latitude ranges across the auroral oval at dusk and midnight by meridian chain magnetometer data, (ii) "snapshot" satellite (DMSP F13) observations of FAC/precipitation/ion drift profiles, and (iii) observations of current disruption/near-Earth magnetic field dipolarizations at geostationary altitude. Under the prevailing fortunate circumstances we are able to discriminate between the roles of the dayside and nightside sources of polar cap convection. For the nightside source we distinguish between the roles of inductive and potential electric fields in the two substages of the substorm expansion phase. According to our estimates the observed dipolarization rate (δ Bz/δt) and the inferred large spatial scales (in radial and azimuthal dimensions) of the dipolarization process in these strong substorm expansions may lead to 50-100 kV enhancements of the cross

  1. Low-Frequency Wave Activity Detected by MMS during Dusk Magnetopause Crossings and its Relation to Heating and Acceleration of Particles

    NASA Astrophysics Data System (ADS)

    Le Contel, O.; Roux, A.; Retino, A.; Mirioni, L.; Sahraoui, F.; Chust, T.; Berthomier, M.; Chasapis, A.; Aunai, N.; Leroy, P.; Alison, D.; Lavraud, B.; Lindqvist, P. A.; Khotyaintsev, Y. V.; Vaivads, A.; Marklund, G. T.; Burch, J. L.; Torbert, R. B.; Moore, T.; Ergun, R. E.; Needell, J.; Chutter, M.; Rau, D.; Dors, I.; Macri, J.; Russell, C. T.; Magnes, W.; Strangeway, R. J.; Bromund, K. R.; Plaschke, F.; Fischer, D.; Leinweber, H. K.; Anderson, B. J.; Nakamura, R.; Argall, M. R.; Le, G.; Slavin, J. A.; Kepko, L.; Baumjohann, W.; Pollock, C. J.; Mauk, B.; Fuselier, S. A.; Goodrich, K.; Wilder, F. D.

    2015-12-01

    Since the 9th of July, the MMS fleet of four satellites have evolved into a tetrahedral configuration with an average inter-satellite distance of 160 km and an apogee of 12 earth radii on the dusk side. In this study we report on ultra-low (1 mHz to ~10 Hz) and very-low (10 Hz to ~ 4 kHz) frequency wave activity measured by the four satellites during several crossings of the dusk equatorial magnetopause. Since the Larmor radius of magnetosheath protons is of the order of 50 km, this inter-satellite distance allows us to investigate in detail the physics of the magnetopause at proton scales including current structures related to Kelvin-Helmholtz instability as well as other energy transfer processes. From wave polarization analysis, we characterize the different types of emissions and discuss different mechanisms of heating and acceleration of particles. In particular, we focus on the electron heating by kinetic Alfvén waves and lower hybrid waves and the electron acceleration by oblique whistler mode waves, which have been suggested as possible mechanisms from previous Cluster and THEMIS measurements.

  2. Actin-based vesicular transport in the first 20 min after dusk is crucial for daily rhabdom synthesis in the compound eye of the grapsid crab Hemigrapsus sanguineus.

    PubMed

    Matsushita, A; Arikawa, K

    1997-09-01

    In the crab Hemigrapsus sanguineus, maintained under a 12 h:12 h light:dark cycle, the amount of vesicular smooth endoplasmic reticulum (vesicular sER) in the photoreceptor cell body increases after the light is turned off. This paper demonstrates that actin filaments in the photoreceptor cell body are involved in the transport of vesicular sER towards the rhabdom. To specify the time of actin contribution to rhabdom synthesis, we disrupted the organization of actin filaments in the cell body with cytochalasin D at various time around dusk. We then measured the rhabdom size and also examined the ultrastructure of the photoreceptor cell body 3 h after extinguishing the light. When cytochalasin D was applied from either 1 h before or immediately after extinguishing the light, the rhabdom size did not increase, whereas vesicular sER accumulated in the cell body. In contrast, cytochalasin D applied to the eyes from 20 min after turning the light off did not inhibit rhabdom synthesis. These results indicate that the first 20 min after the light is turned off is particularly important for the transport of vesicular sER towards the rhabdom by the cell body actin filaments.

  3. Global Plasmaspheric Electron Density Simulations of Pre-dawn and Post-dusk Geomagnetic Events Observed by the Van Allen Probes

    NASA Astrophysics Data System (ADS)

    De Pascuale, S.; Jordanova, V.; Goldstein, J.; Kletzing, C.

    2014-12-01

    We use in situ measurements by the Van Allen Probes (RBSP) to validate a globally applicable plasmaspheric electron density model (RAM-CPL), which is based on ionospheric outflow rates and electric field drivers as proxies for system refilling and erosion respectively. The model is a key component of the RAM-CPL suite in describing the temporal evolution of plasma density in the equatorial plane of the magnetosphere. In addition to considering absolute density values, this study employs a composite definition of the plasmapause boundary as a standard metric for comparison between observations and the model. Because the dynamics of the plasmasphere are governed on different timescales ranging from minutes to days, we consider geomagnetic events for which the RBSP satellites are at conjunction to sample fine-scale density variation as well as large-scale structure. Furthermore, the pre-dawn and post-dusk sectors of the observations provide adequate constraints on the candidate electric field drivers of the plasmasphere. The good agreement attained by the RAM-CPL plasmasphere model can be utilized to predict density conditions in magnetic local time and L-parameter sectors distant from an RBSP orbit of interest. These simulations reproduce plasmapause radial locations to within 0.6 Earth radii (RE) of RBSP observations and we investigate the competing effects of plasmaspheric refilling and erosion on model performance.

  4. Direct observations in the dusk hours of the characteristics of the storm-time ring current particles during the beginning of magnetic storms

    NASA Technical Reports Server (NTRS)

    Smith, P. H.; Hoffman, R. A.

    1973-01-01

    The characteristic features of the initial enhancement of the storm-time ring current particles in the evening hours are consistent with flow patterns resulting from a combination of inward convection, gradient drift, and corotation which carries plasma sheet protons into low L-values near midnight and the higher energy proton component into the plasmasphere and through the evening hours. Data from four magnetic storms during the early life of Explorer 45, when the local time of apogee was in the afternoon and evening hours, show that protons with lower magnetic moments penetrate deeper into the magnetosphere until a low limit, determined by the corotation and gradient drift forces, is reached. Such particle motions produce the stable energy dependent inner boundary of the ring current protons inside the plasmapause in the dusk sector and also provide the mechanism for energy injection into the ring current region. From the analyses of the pitch angle distributions it is evident that charge exchange and wave particle interactions are not the dominant causes of this inner boundary.

  5. The Dusk Flank of Jupiter's Magnetosphere

    NASA Technical Reports Server (NTRS)

    Kurth, W. S.; Gurnett, D. A.; Hospodarsky, G. B.; Farrell, W. M.; Roux, A.; Dougherty, M. K.; Joy, S. P.; Kivelson, M. G.; Walker, R. J.; Crary, F. J.

    2002-01-01

    Limited single-spacecraft observations of Jupiter's magnetopause have been used to infer that the boundary moves inward or outward in response to variations in the dynamic pressure of the solar wind. At Earth, multiple-spacecraft observations have been implemented to understand the physics of how this motion occurs, because they can provide a snapshot of a transient event in progress. Here we present a set of nearly simultaneous two-point measurements of the jovian magnetopause at a time when the jovian magnetopause was in a state of transition from a relatively larger to a relatively smaller size in response to an increase in solar-wind pressure. The response of Jupiter's magnetopause is very similar to that of the Earth, confirming that the understanding built on studies of the Earth's magnetosphere is valid. The data also reveal evidence for a well-developed boundary layer just inside the magnetopause.

  6. The dusk flank of Jupiter's magnetosphere.

    PubMed

    Kurth, W S; Gurnett, D A; Hospodarsky, G B; Farrell, W M; Roux, A; Dougherty, M K; Joy, S P; Kivelson, M G; Walker, R J; Crary, F J; Alexander, C J

    2002-02-28

    Limited single-spacecraft observations of Jupiter's magnetopause have been used to infer that the boundary moves inward or outward in response to variations in the dynamic pressure of the solar wind. At Earth, multiple-spacecraft observations have been implemented to understand the physics of how this motion occurs, because they can provide a snapshot of a transient event in progress. Here we present a set of nearly simultaneous two-point measurements of the jovian magnetopause at a time when the jovian magnetopause was in a state of transition from a relatively larger to a relatively smaller size in response to an increase in solar-wind pressure. The response of Jupiter's magnetopause is very similar to that of the Earth, confirming that the understanding built on studies of the Earth's magnetosphere is valid. The data also reveal evidence for a well-developed boundary layer just inside the magnetopause.

  7. The dusk flank of Jupiter's magnetosphere.

    PubMed

    Kurth, W S; Gurnett, D A; Hospodarsky, G B; Farrell, W M; Roux, A; Dougherty, M K; Joy, S P; Kivelson, M G; Walker, R J; Crary, F J; Alexander, C J

    2002-02-28

    Limited single-spacecraft observations of Jupiter's magnetopause have been used to infer that the boundary moves inward or outward in response to variations in the dynamic pressure of the solar wind. At Earth, multiple-spacecraft observations have been implemented to understand the physics of how this motion occurs, because they can provide a snapshot of a transient event in progress. Here we present a set of nearly simultaneous two-point measurements of the jovian magnetopause at a time when the jovian magnetopause was in a state of transition from a relatively larger to a relatively smaller size in response to an increase in solar-wind pressure. The response of Jupiter's magnetopause is very similar to that of the Earth, confirming that the understanding built on studies of the Earth's magnetosphere is valid. The data also reveal evidence for a well-developed boundary layer just inside the magnetopause. PMID:11875558

  8. Dusk Lighting of Layered Textures in 'Cape Verde'

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Full-shade lighting in the late Martian afternoon helps make details visible in this view of the layered cliff face of the 'Cape Verde' promontory making up part of the rim of Victoria Crater in the Meridiani Planum region of equatorial Mars.

    NASA's Mars Exploration Rover Opportunity used its panoramic camera (Pancam) to shoot the dozens of individual images that have been combined into this mosaic. Opportunity was inside Victoria Crater and near the base of the cliff when it took these images on the 1,579th and 1,580th Martian days, or sols, of the mission (July 2 and 3, 2008).

    Photographing the promontory from this position in Victoria Crater presented challenges for the rover team. The geometry was such that Cape Verde was between the rover and the sun, which could cause a range of negative effects, from glinting off Pancam's dusty lenses to shadowing on the cliff face. The team's solution was to take the images for this mosaic just after the sun disappeared behind the crater rim, at about 5:30 p.m. local solar time. The atmosphere was still lit, but no direct sunlight was illuminating the wall of Cape Verde.

    The result is a high-resolution view of Cape Verde in relatively uniform diffuse sky lighting across the scene.

    Pancam used a clear filter for taking the images for this mosaic. Capturing images in low-light situations was one of the main motivations for including the clear filter among the camera's assortment of filters available for use.

    The face of Cape Verde is about 6 meters (20 feet) tall. Victoria Crater, at about 800 meters (one-half mile) wide, is the largest and deepest crater that Opportunity has visited. It sits more than 5 kilometers (almost 4 miles) away from Opportunity's Eagle Crater landing site. Researchers sent Opportunity into Victoria Crater to study the rock layers exposed inside. The textures seen in the rock layers of Cape Verde suggest that the exposed layers were originally deposited by wind.

  9. Seasonal Differences in the Dusk Equatorial Topside Ionosphere Measured by C/NOFS and DMSP

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    The C/NOFS spacecraft is in a near-equatorial elliptical orbit with an apogee of about 845 km which precesses through all local times over a period of about 66 days. The four operational DMSP spacecraft are in sun-synchronous circular polar orbits at roughly the same altitude as C/NOFS’s apogee. Thus the C/NOFS apogee overlaps with the DMSP duskside orbits every 66 days for a period of about two weeks. This work will present the analysis of three of these overlap periods during the northern winter (roughly December 30, 2008-January 12, 2009), the northern summer (roughly July 14-31, 2009), and one equinox period (roughly March 6-21, 2009) where we will use the combined C/NOFS and DMSP data to show the seasonal changes in ion density, composition, and temperature in the topside ionosphere. This will allow a further validation of the CINDI plasma instruments on C/NOFS as well as establishing a baseline of these geophysical parameters in the topside ionosphere through all seasons during the current extreme solar minimum conditions.

  10. From dusk till dawn: nocturnal and diurnal pollination in the epiphyte Tillandsia heterophylla (Bromeliaceae).

    PubMed

    Aguilar-Rodríguez, P A; Krömer, T; García-Franco, J G; MacSwiney G, M C

    2016-01-01

    In order to compare the effectiveness of diurnal and nocturnal pollinators, we studied the reproductive biology and pollinators of Tillandsia heterophylla E. Morren, an epiphytic tank bromeliad endemic to southeastern Mexico. Since anthesis in T. heterophylla is predominantly nocturnal but lasts until the following day, we hypothesised that this bromeliad would receive visits from both diurnal and nocturnal visitors, but that nocturnal visitors would be the most effective pollinators, since they arrive first to the receptive flower, and that bats would be the most frequent nocturnal visitors, given the characteristics of the nectar. Flowering of T. heterophylla began in May and lasted until July. The species is fully self-compatible, with an anthesis that lasts for ca. 15-16 h. Mean volume of nectar produced per flower was 82.21 μl, with a mean sugar concentration of 6.33%. The highest volume and concentration of nectar were found at 20:00 h, with a subsequent decline in both to almost zero over the following 12-h period. T. heterophylla has a generalist pollination system, since at least four different morphospecies of visitors pollinate its flowers: bats, moths, hummingbirds and bees. Most of the pollinating visits corresponded to bats and took place in the early evening, when stigma receptivity had already begun; making bats the probable pollinator on most occasions. However, diurnal pollinators may be important as a 'fail-safe' system by which to guarantee the pollination of T. heterophylla.

  11. From dusk till dawn: the Arabidopsis thaliana sugar starving responsive network

    PubMed Central

    Arias, Maria C.; Pelletier, Sandra; Hilliou, Frédérique; Wattebled, Fabrice; Renou, Jean-Pierre; D'Hulst, Christophe

    2014-01-01

    Plant growth and development are tightly controlled by photosynthetic carbon availability. The understanding of mechanisms governing carbon partitioning in plants will be a valuable tool in order to satisfy the rising global demand for food and biofuel. The goal of this study was to determine if sugar starvation responses were transcriptionally coordinated in Arabidopsis thaliana. A set of sugar-starvation responsive (SSR) genes was selected to perform a co-expression network analysis. Posteriorly, a guided-gene approach was used to identify the SSR-network from public data and to discover candidate regulators of this network. In order to validate the SSR network, a global transcriptome analysis was realized on three A. thaliana starch-deficient mutants. The starch-deficient phenotype in leaves induces sugar starvation syndrome at the end of the night due to the absence of photosynthesis. Promoter sequences of genes belonging to the SSR-network were analyzed in silico reveling over-represented motifs implicated in light, abscisic acid, and sugar responses. A small cluster of protein encoding genes belonging to different metabolic pathways, including three regulatory proteins, a protein kinase, a transcription factor, and a blue light receptor, were identified as the cornerstones of the SSR co-expression network. In summary, a large transcriptionally coordinated SSR network was identified and was validated with transcriptional data from three starch-deficient mutant lines. Candidate master regulators of this network were point out. PMID:25295047

  12. Statistics of intense dawn-dusk currents in the Earth's magnetotail

    NASA Astrophysics Data System (ADS)

    Artemyev, A. V.; Petrukovich, A. A.; Nakamura, R.; Zelenyi, L. M.

    2015-05-01

    We consider Cluster observations of events with an intense current density (>5 nA/m2) in the magnetotail current sheet. We use measurements by Cluster mission in the central magnetotail (X <- 16 RE, |Y|<10 RE, and |Bx|<10 nT) in the 2003 season when the spacecraft separation was about ˜300 km. For this season, when Cluster can probe very small scale currents, we collect the statistics of observations of strong current densities jy (in GSM coordinate system) and compare curlometer data with plasma parameters. The most intense currents are observed under disturbed conditions (plasma flow vx>300 km/s). We introduce the parameter vD/vTi (where vD=jy/ene, ne is an electron density, and vTi is a proton thermal velocity) and show that cases with vD/vTi˜1 correspond to the most intense currents observed in the vicinity of the reconnection regions. The comparison of electron and proton velocities demonstrates that electron often carry almost the entire current measured by a curlometer technique. The strong electron temperature anisotropy Te∥/Te⊥>1.2 corresponds to large magnitudes of By component of the magnetic field. We conclude that intense current sheets are often characterized by significant (more than 30%) contribution of electron curvature currents to the cross-tail current. The comparison of observations and models shows that the electron anisotropy level is likely controlled by competition of two processes: the electron scattering on fluctuations generated by fire-hose instability and the acceleration in sheared magnetic field configurations. We also suggest that current sheets embedded into the strong plasma flows (vx/vTi>0.1) can be balanced by ion flow anisotropy.

  13. Cluster observations of the dusk flank magnetopause near the sash: Ion dynamics and flow-through reconnection

    NASA Astrophysics Data System (ADS)

    Maynard, Nelson C.; Farrugia, Charles J.; Burke, William J.; Ober, Daniel M.; Mozer, Forrest S.; Rème, Henri; Dunlop, Malcolm; Siebert, Keith D.

    2012-10-01

    Compared to the dayside, dynamics on the flanks of the magnetopause are poorly understood. To help bridge this knowledge gap we analyzed Cluster plasma and field measurements acquired during a 90-min period on 20 November 2003 when Cluster crossed the magnetopause four times in the vicinity of the sash. MHD simulations provide a context for Cluster observations. Crossings were between the magnetosheath and an S-shaped plasma sheet, rather than to the open-field lobes of the magnetotail. Cluster encountered two regions of MHD-breaking differences between perpendicular ion velocities and E × B convection. Ion adiabatic expansion parameter (δi) calculations show that ion gyrotropy was not broken during an episode of strong Alfvén wave activity in the magnetosheath. However, gyrotropy was broken (δi > 1) during the fourth magnetopause crossing. In the magnetosheath, ion guiding-center motion was maintained but inertial effects associated with temporally varying electric fields are probable sources of velocity differences. Regarding the magnetopause crossing, the generalized Ohm's law limits possible sources for breaking ion gyrotropy to inertial forces and/or electron pressure gradients associated with a nearby reconnection event. We suggest that Cluster witnessed effects of a temporally varying and spatially limited, flow-through reconnection event between open mantle field lines from the two polar caps adding new closed flux to the LLBL at the sash. Future modeling of flank dynamics must consider inertial forces as significant drivers at the magnetopause and in the adjacent magnetosheath.

  14. Reed warbler orientation: initiation of nocturnal migratory flights in relation to visibility of celestial cues at dusk.

    PubMed

    Åkesson, S.; Walinder, G.; Karlsson, L.; Ehnbom, S.

    2001-01-01

    We used radiotelemetry to investigate the time of migratory flight initiation relative to available celestial orientation cues and departure direction of a nocturnal passerine migrant, the reed warbler, Acrocephalus scirpaceus, during autumn migration. The study was carried out at Falsterbo, a coastal site in southwest Sweden. The warblers initiated migration from times well after local sunset and well into the night, corresponding to sun elevations between -4 degrees and -35 degrees, coinciding with the occurrence of stars at night. They departed in the expected migratory direction towards south of southwest with a few initiating migration in reverse directions towards northeast to east. Flight directions under overcast conditions (7-8/8) were more scattered than under clear sky conditions (0-4/8). There were fewer clouds on departure nights than on nights when the birds did not initiate migration. For birds staying longer than one night at stopover the horizontal visibility was higher and precipitation was less likely on departure nights than on the previous night. The results show that the visibility of celestial cues, and stars in particular, are important for the decision to initiate migration in reed warblers. However, cloud cover, horizontal visibility and precipitation might be correlated with other weather variables (i.e. wind or air pressure) that are also likely to be important for the decision to migrate. Copyright 2001 The Association for the Study of Animal Behaviour.

  15. Equatorial disc and dawn-dusk currents in the frontside magnetosphere of Jupiter - Pioneer 10 and 11

    NASA Technical Reports Server (NTRS)

    Jones, D. E.; Thomas, B. T.; Melville, J. G., II

    1981-01-01

    Observations by Pioneer 10 and 11 show that the strongest azimuthal fields are observed near the dawn meridian (Pioneer 10) while the weakest occur near the noon meridian (Pioneer 11), suggesting a strong local time dependence for the corresponding radial current system. Modeling studies of the radial component of the field observed by both spacecraft suggest that the corresponding azimuthal current system must also be a strong function of local time. Both the azimuthal and the radial field component signatures exhibit sharp dips and reversals, requiring thin radial and azimuthal current systems. There is also a suggestion that these two current systems either are interacting or are due, at least in part, to the same current. It is suggested that a plausible current model consists of the superposition of a thin, local-time-independent azimuthal current system plus the equatorial portion of a tail-like current system that extends into the dayside magnetosphere.

  16. Melatonin Signal Transduction Pathways Require E-Box-Mediated Transcription of Per1 and Per2 to Reset the SCN Clock at Dusk

    PubMed Central

    Kandalepas, Patty C.; Mitchell, Jennifer W.; Gillette, Martha U.

    2016-01-01

    Melatonin is released from the pineal gland into the circulatory system at night in the absence of light, acting as “hormone of darkness” to the brain and body. Melatonin also can regulate circadian phasing of the suprachiasmatic nucleus (SCN). During the day-to-night transition, melatonin exposure advances intrinsic SCN neural activity rhythms via the melatonin type-2 (MT2) receptor and downstream activation of protein kinase C (PKC). The effects of melatonin on SCN phasing have not been linked to daily changes in the expression of core genes that constitute the molecular framework of the circadian clock. Using real-time RT-PCR, we found that melatonin induces an increase in the expression of two clock genes, Period 1 (Per1) and Period 2 (Per2). This effect occurs at CT 10, when melatonin advances SCN phase, but not at CT 6, when it does not. Using anti-sense oligodeoxynucleotides (α ODNs) to Per 1 and Per 2, as well as to E-box enhancer sequences in the promoters of these genes, we show that their specific induction is necessary for the phase-altering effects of melatonin on SCN neural activity rhythms in the rat. These effects of melatonin on Per1 and Per2 were mediated by PKC. This is unlike day-active non-photic signals that reset the SCN clock by non-PCK signal transduction mechanisms and by decreasing Per1 expression. Rather, this finding extends roles for Per1 and Per2, which are critical to photic phase-resetting, to a nonphotic zeitgeber, melatonin, and suggest that the regulation of these clock gene transcripts is required for clock resetting by diverse regulatory cues. PMID:27362940

  17. Comparison of Dawn and Dusk Precipitating Electron Energy Populations Shortly After the Initial Shock for the January 10th, 1997 Magnetic Cloud

    NASA Technical Reports Server (NTRS)

    Spann, J.; Germany, G.; Swift, W.; Parks, G.; Brittnacher, M.; Elsen, R.

    1997-01-01

    The observed precipitating electron energy between 0130 UT and 0400 UT of January 10 th, 1997, indicates that there is a more energetic precipitating electron population that appears in the auroral oval at 1800-2200 UT at 030) UT. This increase in energy occurs after the initial shock of the magnetic cloud reaches the Earth (0114 UT) and after faint but dynamic polar cap precipitation has been cleared out. The more energetic population is observed to remain rather constant in MLT through the onset of auroral activity (0330 UT) and to the end of the Polar spacecraft apogee pass. Data from the Ultraviolet Imager LBH long and LBH short images are used to quantify the average energy of the precipitating auroral electrons. The Wind spacecraft located about 100 RE upstream monitored the IMF and plasma parameters during the passing of the cloud. The affects of oblique angle viewing are included in the analysis. Suggestions as to the source of this hot electron population will be presented.

  18. Bug Bites and Stings

    MedlinePlus

    ... are most active (dawn and dusk); and apply insect repellent when kids go outside. When in tick country, ... pets to prevent them from being bitten. Use insect repellent when spending time outdoors camping, hiking, etc. Repellents ...

  19. Leishmaniasis

    MedlinePlus

    ... parasitic disease spread by the bite of infected sand flies. There are several different forms of leishmaniasis. The ... prevent the disease is to protect yourself from sand fly bites: Stay indoors from dusk to dawn, when ...

  20. West Nile Virus

    MedlinePlus

    ... appeared in the United States in 1999. Infected mosquitoes spread the virus that causes it. People who ... barrels Stay indoors between dusk and dawn, when mosquitoes are most active Use screens on windows to ...

  1. West Nile Virus

    MedlinePlus

    ... protect themselves from mosquito bites by using mosquito repellent, especially at times when mosquitoes are most active, ... at dusk and dawn. The CDC recommends mosquito repellents that include one of the following ingredients: DEET ( ...

  2. The terrestrial magnetosphere: a half-wave rectifier of the interplanetary electric field.

    PubMed

    Burton, R K; McPherron, R L; Russell, C T

    1975-08-29

    A study of geomagnetic disturbances during 1967 and 1968, for which in situ solar wind observations are available, reveals that the magnetosphere acts as a half-wave rectifier of the interplanetary electric field. The rate of injection of energy into the magnetosphere, as inferred from the strength of the disturbance, is approximately linearly proportional to the component of the electric field from dawn to dusk but is effectively zero if the electricfield has a component from dusk to dawn. PMID:17792538

  3. Ecology of colors of firefly bioluminescence

    SciTech Connect

    Lall, A.B.; Seliger, H.H.; Biggley, W.H.; Lloyd, J.E.

    1980-10-31

    Dark-active North American fireflies emit green bioluminescence and dusk-active species emit yellow, in general. Yellow light and yellow visual spectral sensitivity may be adaptations to increase the signal-to-noise (that is, foliage-reflected ambient light) ratio for sexual signaling during twilight. The peaks of the electroretinogram visual spectral sensitivities of four species tested, two dark- and two dusk-active, correspond with the peak of their bioluminescent emissions.

  4. The terrestrial magnetosphere: a half-wave rectifier of the interplanetary electric field.

    PubMed

    Burton, R K; McPherron, R L; Russell, C T

    1975-08-29

    A study of geomagnetic disturbances during 1967 and 1968, for which in situ solar wind observations are available, reveals that the magnetosphere acts as a half-wave rectifier of the interplanetary electric field. The rate of injection of energy into the magnetosphere, as inferred from the strength of the disturbance, is approximately linearly proportional to the component of the electric field from dawn to dusk but is effectively zero if the electricfield has a component from dusk to dawn.

  5. Cusp geometry in MHD simulations

    NASA Astrophysics Data System (ADS)

    Siscoe, George; Crooker, Nancy; Siebert, Keith; Maynard, Nelson; Weimer, Daniel; White, Willard

    2005-01-01

    The MHD simulations described here show that the latitude of the high-altitude cusp decreases as the IMF swings from North to South, that there is a pronounced dawn dusk asymmetry at high-altitude associated with a dawn dusk component of the IMF, and that at the same time there is also a pronounced dawn dusk asymmetry at low-altitude. The simulations generate a feature that represents what has been called the cleft. It appears as a tail (when the IMF has a By component) attached to the cusp, extending either toward the dawn flank or the dusk flank depending on the dawn dusk orientation of the IMF. This one-sided cleft connects the cusp to the magnetospheric sash. We compare cusp geometry predicted by MHD simulations against published observations based on Hawkeye and DMSP data. Regarding the high-altitude predictions, the comparisons are not definitive, mainly because the observations are incomplete or mutually inconsistent. Regarding the low-altitude prediction of a strong dawn dusk asymmetry, the observations are unambiguous and are in good qualitative agreement with the prediction.

  6. Concerning the Motion of FTEs and Attendant Signatures

    NASA Technical Reports Server (NTRS)

    Sibeck, David G.

    2010-01-01

    We employ the Cooling et al. [2001] model to predict the location, orientation, and motion of flux transfer events (FTEs) generated along finite length component and anti parallel reconnection lines for typical solar wind plasma conditions and various interplanetary magnetic field (IMF) orientations in the plane perpendicular to the SunEarth line at the solstices and equinoxes. For duskward and northward or southward IMF orientations, events formed by component reconnection originate along reconnection curves passing through the sub solar point that tilt from southern dawn to northern dusk. They maintain this orientation as they move either northward into the northern dawn quadrant or southward into the southern dusk quadrant. By contrast, events formed by antiparallel reconnection originate along reconnection curves running from northern dawn to southern dusk in the southern dawn and northern dusk quadrants and maintain these orientations as they move anti sunward into both these quadrants. Although both the component and antiparallel reconnection models can explain previously reported event orientations on the southern dusk magnetopause during intervals of northward and dawn ward IMF orientation, only the component model explains event occurrence near the subsolar magnetopause during intervals when the IMF does not point due southward.

  7. Application of ground-truth for classification and quantification of bird movements on migratory bird habitat initiative sites in southwest Louisiana: final report

    USGS Publications Warehouse

    Barrow, Wylie C.; Baldwin, Michael J.; Randall, Lori A.; Pitre, John; Dudley, Kyle J.

    2013-01-01

    This project was initiated to assess migrating and wintering bird use of lands enrolled in the Natural Resources Conservation Service’s (NRCS) Migratory Bird Habitat Initiative (MBHI). The MBHI program was developed in response to the Deepwater Horizon oil spill in 2010, with the goal of improving/creating habitat for waterbirds affected by the spill. In collaboration with the University of Delaware (UDEL), we used weather surveillance radar data (Sieges 2014), portable marine radar data, thermal infrared images, and visual observations to assess bird use of MBHI easements. Migrating and wintering birds routinely make synchronous flights near dusk (e.g., departure during migration, feeding flights during winter). Weather radars readily detect birds at the onset of these flights and have proven to be useful remote sensing tools for assessing bird-habitat relations during migration and determining the response of wintering waterfowl to wetland restoration (e.g., Wetlands Reserve Program lands). However, ground-truthing is required to identify radar echoes to species or species group. We designed a field study to ground-truth a larger-scale, weather radar assessment of bird use of MBHI sites in southwest Louisiana. We examined seasonal bird use of MBHI fields in fall, winter, and spring of 2011-2012. To assess diurnal use, we conducted total area surveys of MBHI sites in the afternoon, collecting data on bird species composition, abundance, behavior, and habitat use. In the evenings, we quantified bird activity at the MBHI easements and described flight behavior (i.e., birds landing in, departing from, circling, or flying over the MBHI tract). Our field sampling captured the onset of evening flights and spanned the period of collection of the weather radar data analyzed. Pre- and post-dusk surveys were conducted using a portable radar system and a thermal infrared camera. Landbirds, shorebirds, and wading birds were commonly found on MBHI fields during diurnal

  8. Intensity variation of ELF hiss and chorus during isolated substorms

    NASA Technical Reports Server (NTRS)

    Thorne, R. M.; Fiske, K. F.; Church, S. R.; Smith, E. J.

    1974-01-01

    Electromagnetic ELF emissions (100-1000 Hz) observed on the polar-orbiting OGO-6 satellite within three hours of the dawn-dusk meridian consistently exhibit a predictable response to isolated substorm activity. Near dawn, the emissions intensify during the substorm and then subside following the magnetic activity; the waves are most intense at L greater than 4, exhibit considerable structure and have been primarily identified as chorus. At dusk the response is entirely different; the wave intensity falls to background levels during substorm activity but subsequently intensifies, usually reaching levels well in excess of that before the disturbance. The emissions near dusk extend to low L, are relatively featureless, and have been identified as plasmaspheric hiss. These features are interpreted in terms of changes in the drift orbits of outer-zone electrons which cyclotron resonate with ELF waves.

  9. Diurnal activity of soil surface arthropods in agroecosystems: design for an inexpensive time-sorting pitfall trap

    SciTech Connect

    Blumberg, A.Y.; Crossley, D.A. Jr.

    1986-01-01

    The design for an inexpensive time-sorting pitfall trap is presented. The basis of the mechanism is a rotary stepping solenoid powered by lantern batteries. Traps were utilized to sample soil surface arthropods at two hour intervals for five 24 hr periods in 1983. One trap each was placed in conventional tillage (CT) and no-tillage (NT) agroecosystems. Soil arthropod surface activity was greatest in CT on 9 July during the dawn and dusk periods but the data did not indicate other dominant trends. Activity in NT was greatest during dusk on 27 June, but again no other dominant trends were evident. When CT and NT are combined over the sample dates, surface soil arthropod activity peaked during dusk, with a smaller activity peak at dawn. 10 refs., 6 figs.

  10. Effect of the interplanetary magnetic field y component on the high-latitude nightside convection

    NASA Technical Reports Server (NTRS)

    De La Beaujardiere, O.; Wickwar, V. B.; Kelly, J. D.; King, J. H.

    1985-01-01

    Sondrestrom radar observations reveal that the dawn-dusk (By) component of the interplanetary magnetic field (IMF) strongly influences the nightside polar convection. This effect is quite complex. The convection for one orientation of By is not the mirror image of the other orientation. A positive By (i.e., pointing toward dusk) seems to organize the velocities such that, at all local times, they are predominantly westward within the radar field-of-view (approximately 68 deg-to-82 deg invariant latitude). Between dusk and midnight, on one such occasion, sunward flow is observed within the polar cap. In the midnight and dawn sectors, when By is negative, the plasma velocities often appear shifted toward early hours such that large southward velocities are observed about 3 hours before midnight. These are the only times when the predominant velocity component is southward.

  11. The resolution of a magnetic anomaly map expected from GRM data

    NASA Technical Reports Server (NTRS)

    Strangway, D. W.; Arkani-Hamed, J.; Teskey, D. J.; Hood, P. J.

    1985-01-01

    Data from the MAGSAT mission were used to derive a global scalar magnetic anomaly map at an average altitude of about 400 km. It was possible to work with 2 data sets corresponding to dawn and dusk. The anomalies which were repeatable at dawn and at dusk was identified and the error limits of these anomalies were estimated. The repeatable anomalies were downward continued to about 10 km altitude. The anomalies over Canada were correlated quantitatively with bandpass filtered magnetic anomalies derived from aeromagnetic surveys. The close correlation indicates that the repeatable anomalies detected from orbit are due to geological causes. This correlation supports the geological significance of the global anomaly map.

  12. Relationships between behavioral rhythms, plasma corticosterone and hypothalamic circadian rhythms.

    PubMed

    Kafka, M S; Benedito, M A; Steele, L K; Gibson, M J; Zerbe, R L; Jacobowitz, D M; Roth, R H; Zander, K

    1986-01-01

    Circadian rhythms in physiological processes and behaviors were compared with hypothalamic circadian rhythms in norepinephrine (NE) metabolites, adrenergic transmitter receptors, cAMP, cGMP and suprachiasmatic nucleus (SCN) arginine vasopressin (AVP) in a single population of rats under D:D conditions. Eating, drinking and locomotor activity were high during the subjective night (the time when lights were out in L:D) and low during the subjective day (the time when lights were on in L:D). Plasma corticosterone concentration rose at subjective dusk and remained high until subjective dawn. Binding to hypothalamic alpha 1- and beta-adrenergic receptors also peaked during the subjective night. Cyclic cGMP concentration was elevated throughout the 24-hr period except for a trough at dusk, whereas DHPG concentration peaked at dawn. Arginine vasopressin levels in the suprachiasmatic nucleus peaked in the middle of the day. No rhythm was found either in binding to the alpha 2-adrenergic receptor, or in MHPG or cAMP concentration. Behavioral and corticosterone rhythms, therefore, are parallel to rhythms in hypothalamic alpha 1- and beta-receptor binding and NE-release. Cyclic GMP falls only at dusk, suggesting the possibility that cGMP inhibits activity much of the day and that at dusk the inhibition of nocturnal activity is removed. SCN AVP, on the other hand, peaking at 1400 hr, may play a role in the pacemaking function of the SCN that drives these other rhythms.

  13. Remote Observations of Ion Temperatures in the Quiet Time Magnetosphere

    NASA Technical Reports Server (NTRS)

    Keesee, A. M.; Buzulukova, N.; Goldstein, J.; McComas, D. J.; Scime, E. E.; Spence, H.; Fok, M. C.; Tallaksen, K.

    2011-01-01

    Ion temperature analysis of the first energetic neutral atom images of the quiet -time, extended magnetosphere provides evidence of multiple regions of ion heating. This study confirms the existence of a dawn -dusk asymmetry in ion temperature predicted for quiescent magnetospheric conditions by Spence and Kivelson (1993) and demonstrates that it is an inherent magnetospheric feature.

  14. The plasmapause revisited

    NASA Technical Reports Server (NTRS)

    Maynard, N. C.; Gebowsky, J. M.

    1976-01-01

    Saturation of the dc double probe instrument on Explorer 45 was used to identify the plasmapause. A data base was developed to statistically study the average position of the plasmapause over 14.5 hours of magnetic local time under differing magnetic conditions. The afternoon-evening bulge in the L coordinate of the plasmapause versus local time was found centered between 20 and 21 hours MLT during magnetically quiet periods and shifted toward dusk as activity increased, but always post dusk. During quiet periods a bulge in the L coordinate near noon was also seen, which disappeared as activity increased. The average local time distribution plasmapause position during high magnetic activity was irregular in the afternoon region where large scale convection models predict the creation of plasmatails or detached plasma regions from increases in the solar wind induced convection. The results suggest that solar wind induced convection is partially shielded from the dayside. As the intensity of the convection is increased, it more effectively penetrates the dayside, which shifts the post dusk bulge nearer to dusk and eliminates the quiet-time bulge near noon.

  15. The near-earth magnetic field at 1980 determined from Magsat data

    NASA Technical Reports Server (NTRS)

    Langel, R. A.; Estes, R. H.

    1985-01-01

    Data from the Magsat spacecraft for November 1979 through April 1980 and from 91 magnetic observatories for 1978 through 1982 are used to derive a spherical harmonic model of the earth's main magnetic field and its secular variation. Constant coefficients are determined through degree and order 13 and secular variation coefficients through degree and order 10. The first degree external terms and corresponding induced internal terms are given as a function of Dst. Preliminary modeling using separate data sets at dawn and dusk local time showed that the dusk data contains a substantial field contribution from the equatorial electrojet current. The final data set is selected first from dawn data and then augmented by dusk data to achieve a good geographic data distribution for each of three time periods: (1) November/December, 1979; (2) January/February, 1980; (3) March/April, 1980. A correction for the effects of the equatorial electrojet is applied to the dusk data utilized. The solution included calculation of fixed biases, or anomalies, for the observation data.

  16. The near-Earth magnetic field at 1980 determined from MAGSAT data

    NASA Technical Reports Server (NTRS)

    Langel, R. A.; Estes, R. H.

    1984-01-01

    Data from the MAGSAT spacecraft for November 1979 through April 1980 and from 91 magnetic observatories for 1978 through 1982 are used to derive a spherical harmonic model of the Earth's main magnetic field and its secular variation. Constant coefficients are determined through degree and order 13 and secular variation coefficients through degree and order 10. The first degree external terms and corresponding induced internal terms are given as a function of Dst. Preliminary modeling using separate data sets at dawn and dusk local time showed that the dusk data contains a substantial field contribution from the equatorial electrojet current. The final data set is selected first from dawn data and then augmented by dusk data to achieve a good geographic data distribution for each of three time periods: (1) November/December, 1979; (2) January/February; 1980; (3) March/April, 1980. A correction for the effects of the equatorial electrojet is applied to the dusk data utilized. The solution included calculation of fixed biases, or anomalies, for the observation data.

  17. Origin and Evolution of Europa's Oxygen Exosphere

    NASA Astrophysics Data System (ADS)

    Oza, Apurva V.; Leblanc, Francois; Schmidt, Carl; Johnson, Robert E.

    2016-10-01

    Europa's icy surface is constantly bombarded by sulfur and oxygen ions originating from the Io plasma torus. The momentum transferred to molecules in Europa's surface results in the sputtering of water ice, populating a water product exosphere. We simulate Europa's neutral exosphere using a ballistic 3D Monte Carlo routine and find that the O2 exosphere, while global, is not uniformly symmetric in Europa local time. The O2 exosphere, sourced at a rate of ~ 5 kg/s with a disk-averaged column density of NO2 ~ 2.5 x 1014 O2/cm2, preferentially accumulates towards Europa's dusk. These dawn-dusk atmospheric inhomogeneities escalate as the surface-bounded O2 dissociates into an atomic O corona via electron impact. The inhomogeneities persist and evolve throughout the satellite's orbit, implying a diurnal cycle of the exosphere, recently evidenced by a detailed HST oxygen aurorae campaign (Roth et al. 2016). We conclude that the consistently observed 50% increase in FUV auroral emission from dusk to dawn is principally driven by the day-to-night thermal diffusion of O2 coupled with the Coriolis acceleration. This leads to a dawn-to-dusk gradient, peaking at Europa's leading hemisphere. This exospheric oxygen cycle, dependent on both orbital longitude and magnetic latitude, is fundamentally due to the bulk-sputtering vector changing with respect to the subsolar and subjovian points throughout the orbit. In principle, a similar mechanism should be present at other tidally-locked, rapidly orbiting satellite exospheres.

  18. Older Drivers: How Health Affects Driving

    MedlinePlus

    ... see clearly, especially at dawn, dusk, and night. Eyes become more sensitive to glare from headlights, street lights, or the sun, making it difficult to see people, things, and movements outside your direct line of sight. Peripheral vision — the ability to see to the ...

  19. Temporal Links in Daily Activity Patterns between Coral Reef Predators and Their Prey

    PubMed Central

    Bosiger, Yoland J.; McCormick, Mark I.

    2014-01-01

    Few studies have documented the activity patterns of both predators and their common prey over 24 h diel cycles. This study documents the temporal periodicity of two common resident predators of juvenile reef fishes, Cephalopholis cyanostigma (rockcod) and Pseudochromis fuscus (dottyback) and compares these to the activity and foraging pattern of a common prey species, juvenile Pomacentrus moluccensis (lemon damselfish). Detailed observations of activity in the field and using 24 h infrared video in the laboratory revealed that the two predators had very different activity patterns. C. cyanostigma was active over the whole 24 h period, with a peak in feeding strikes at dusk and increased activity at both dawn and dusk, while P. fuscus was not active at night and had its highest strike rates at midday. The activity and foraging pattern of P. moluccensis directly opposes that of C. cyanostigma with individuals reducing strike rate and intraspecific aggression at both dawn and dusk, and reducing distance from shelter and boldness at dusk only. Juveniles examined were just outside the size-selection window of P. fuscus. We suggest that the relatively predictable diel behaviour of coral reef predators results from physiological factors such as visual sensory abilities, circadian rhythmicity, variation in hunting profitability, and predation risk at different times of the day. Our study suggests that the diel periodicity of P. moluccensis behaviour may represent a response to increased predation risk at times when both the ability to efficiently capture food and visually detect predators is reduced. PMID:25354096

  20. Spatial distribution of upstream magnetospheric geq50 keV ions

    NASA Astrophysics Data System (ADS)

    Anagnostopoulos, G. C.; Argyropoulos, G.; Kaliabetsos, G.

    2000-01-01

    We present for the first time a statistical study of geq50 keV ion events of a magnetospheric origin upstream from Earth's bow shock. The statistical analysis of the 50-220 keV ion events observed by the IMP-8 spacecraft shows: (1) a dawn-dusk asymmetry in ion distributions, with most events and lower intensities upstream from the quasi-parallel pre-dawn side (4 LT-6 LT) of the bow shock, (2) highest ion fluxes upstream from the nose/dusk side of the bow shock under an almost radial interplanetary magnetic field (IMF) configuration, and (3) a positive correlation of the ion intensities with the solar wind speed and the index of geomagnetic index Kp, with an average solar wind speed as high as 620 km s-1 and values of the index Kp > 2. The statistical results are consistent with (1) preferential leakage of sim50 keV magnetospheric ions from the dusk magnetopause, (2) nearly scatter free motion of sim50 keV ions within the magnetosheath, and (3) final escape of magnetospheric ions from the quasi-parallel dawn side of the bow shock. An additional statistical analysis of higher energy (290-500 keV) upstream ion events also shows a dawn-dusk asymmetry in the occurrence frequency of these events, with the occurrence frequency ranging between sim16%-sim34% in the upstream region.

  1. The Use of Technology in Literacy Instruction: Implications for Teaching Students from Low Socioeconomic Backgrounds. HBSK 4072, Section 3, Fall 2007

    ERIC Educational Resources Information Center

    Whitney, Jennifer D.

    2007-01-01

    Background: Almost every aspect of modern life is affected in some way by technology. Many people utilize technology from dawn to dusk to communicate; make decisions; reflect, gain, synthesize, evaluate or distribute information, among many other functions. One would be hard pressed to find a single professional, regardless of career field,…

  2. Effect of the Solar UV/EUV Heating on the Intensity and Spatial Distribution of Jupiter's Synchrotron Radiation

    NASA Astrophysics Data System (ADS)

    Kita, Hajime; Misawa, H.; Tsuchiya, F.; Tao, C.; Morioka, A.

    2012-10-01

    Jupiter's synchrotron radiation (JSR) is the emission from relativistic electrons, and it is the most effective probe for remote sensing of Jupiter's radiation belt from the Earth. Recent observations reveal short term variations of JSR with the time scale of days to weeks. Brice and McDonough (1973) proposed that the solar UV/EUV heating for Jupiter's upper atmosphere causes enhancement of total flux density. If such a process occurs at Jupiter, it is also expected that diurnal wind system produces dawn-dusk asymmetry of the JSR brightness distribution. Preceding studies confirmed that the short term variations in total flux density correspond to the solar UV/EUV. However, the effect of solar UV/EUV heating on the brightness distribution has not been confirmed. Hence, the purpose of this study is to confirm the solar UV/EUV heating effect on total flux density and brightness distribution. We made radio imaging analysis using the National Radio Astronomy Observatory (NRAO) archived data of the Very Large Array (VLA) obtained in 2000, and following results were shown. 1, Total flux density varied corresponding to the solar UV/EUV. 2, Dawn side emission was brighter than dusk side emission almost every day. 3, Variations of the dawn-dusk asymmetry did not correspond to the solar UV/EUV. In order to explain the second result, we estimate the diurnal wind velocity from the observed dawn-dusk ratio by using the model brightness distribution of JSR. Estimated neutral wind velocity is 46+/-11 m/s, which reasonably corresponds to the numerical simulation of Jupiter's upper atmosphere. In order to explain the third result, we examined the effect of the global convection electric field driven by tailward outflow of plasma in Jupiter's magnetosphere. As the result, it is suggested that typical fluctuation of the convection electric field strength was enough to cause the observed variations of the dawn-dusk asymmetry.

  3. Characteristics of F-region dynamo currents deduced from CHAMP magnetic field measurements

    NASA Astrophysics Data System (ADS)

    Park, Jaeheung; Lühr, Hermann; Min, Kyoung Wook

    2010-10-01

    Using magnetic field observations of the CHAMP satellite we provide the first comprehensive study of F-region dynamo currents as a function of season, local time, geographic longitude, and solar activity. From bipolar variations of the zonal magnetic field component the density of vertical current driven by the F-region dynamo is deduced. The current strength is smallest around June solstice, which is attributed to a reduced F-region Pedersen conductance caused by a lower electron density and neutral density at that season. During the hours around noon highest current densities are observed. They are flowing downward over the dip equator. A secondary peak of upward currents appears at dusk. The polarity switch occurs between15 and 16 (local time) independent of season. The noontime F-region dynamo current peaks at longitudes connected to the South Atlantic Anomaly, which can be explained by the enhanced conductivity in the region of reduced B field. The F-region current at dusk exhibits no peak in the longitude sector of the South Atlantic Anomaly. At noon, the F-region dynamo currents exhibit a wave 4 longitudinal structure during equinoxes and June solstice. The wave 4 signature becomes weak during December solstice. At dusk the wave 4 signature of F-region dynamo currents is much reduced in all seasons. This behavior can be explained by the DE3 tidal signature in the zonal wind at CHAMP altitude. F-region dynamo currents increase linearly with the solar flux index, F10.7, during both noon and dusk time sectors. The increase in current strength with increasing F10.7 is slightly higher at dusk than at noon.

  4. Application of ground-truth for classification and quantification of bird movements on migratory bird habitat initiative sites in southwest Louisiana: final report

    USGS Publications Warehouse

    Barrow, Wylie C.; Baldwin, Michael J.; Randall, Lori A.; Pitre, John; Dudley, Kyle J.

    2013-01-01

    This project was initiated to assess migrating and wintering bird use of lands enrolled in the Natural Resources Conservation Service’s (NRCS) Migratory Bird Habitat Initiative (MBHI). The MBHI program was developed in response to the Deepwater Horizon oil spill in 2010, with the goal of improving/creating habitat for waterbirds affected by the spill. In collaboration with the University of Delaware (UDEL), we used weather surveillance radar data (Sieges 2014), portable marine radar data, thermal infrared images, and visual observations to assess bird use of MBHI easements. Migrating and wintering birds routinely make synchronous flights near dusk (e.g., departure during migration, feeding flights during winter). Weather radars readily detect birds at the onset of these flights and have proven to be useful remote sensing tools for assessing bird-habitat relations during migration and determining the response of wintering waterfowl to wetland restoration (e.g., Wetlands Reserve Program lands). However, ground-truthing is required to identify radar echoes to species or species group. We designed a field study to ground-truth a larger-scale, weather radar assessment of bird use of MBHI sites in southwest Louisiana. We examined seasonal bird use of MBHI fields in fall, winter, and spring of 2011-2012. To assess diurnal use, we conducted total area surveys of MBHI sites in the afternoon, collecting data on bird species composition, abundance, behavior, and habitat use. In the evenings, we quantified bird activity at the MBHI easements and described flight behavior (i.e., birds landing in, departing from, circling, or flying over the MBHI tract). Our field sampling captured the onset of evening flights and spanned the period of collection of the weather radar data analyzed. Pre- and post-dusk surveys were conducted using a portable radar system and a thermal infrared camera. Landbirds, shorebirds, and wading birds were commonly found on MBHI fields during diurnal

  5. Solar terminator effects on middle- to low-latitude Pi2 pulsations

    NASA Astrophysics Data System (ADS)

    Imajo, Shun; Yoshikawa, Akimasa; Uozumi, Teiji; Ohtani, Shinichi; Nakamizo, Aoi; Demberel, Sodnomsambuu; Shevtsov, Boris Mikhailovich

    2016-08-01

    To clarify the effect of the dawn and dusk terminators on Pi2 pulsations, we statistically analyzed the longitudinal phase and amplitude structures of Pi2 pulsations at middle- to low-latitude stations (GMLat = 5.30°-46.18°) around both the dawn and dusk terminators. Although the H (north-south) component Pi2s were affected by neither the local time (LT) nor the terminator location (at 100 km altitude in the highly conducting E region), some features of the D (east-west) component Pi2s depended on the location of the terminator rather than the LT. The phase reversal of the D component occurred 0.5-1 h after sunrise and 1-2 h before sunset. These phase reversals can be attributed to a change in the contributing currents from field-aligned currents (FACs) on the nightside to the meridional ionospheric currents on the sunlit side of the terminator, and vice versa. The phase reversal of the dawn terminator was more frequent than that of the dusk terminator. The D-to- H amplitude ratio on the dawn side began to increase at sunrise, reaching a peak approximately 2 h after sunrise (the sunward side of the phase reversal region), whereas the ratio on the dusk side reached a peak at sunset (the antisunward side). The dawn-dusk asymmetric features suggest that the magnetic contribution of the nightside FAC relative to the meridional ionospheric current on the dusk side is stronger than that on the dawn side, indicating that the center of Pi2-associated FACs, which probably corresponds to the Pi2 energy source, tends to be shifted duskward on average. Different features and weak sunrise/sunset dependences at the middle-latitude station (Paratunka, GMLat = 46.18°) can be attributed to the larger annual variation in the sunrise/sunset time and a stronger magnetic effect because of closeness from FACs. The D-to- H amplitude ratio decreased with decreasing latitude, suggesting that the azimuthal magnetic field produced by the FACs in darkness and the meridional ionospheric

  6. Radial profile of magnetic field in earth magnetotail current sheet

    NASA Astrophysics Data System (ADS)

    Rong, Zhaojin; Wan, Weixing; Shen, Chao; Petrukovich, Anatoli; Zhang, Tielong; Baumjohann, Wolfgang; Dunlop, Malcolm; Zhang, Yongcun

    2014-05-01

    Knowing the magnetic field distribution in the magnetotail current sheet (CS) is essential for exploring magnetotail dynamics. In this study, using a joint dataset of Cluster/TC-1, the radial profile of the magnetic field in the magnetotail CS with radial distances covering 8 100 nT for active times) and solar wind parameters are statistically surveyed. Our new findings demonstrate that, independent of the activity state, the field strength and Bz component (GSM coordinates) start the monotonous increase prominently as r decreases down to ~11.5RE, which means the dipole field starts to make a significant contribution from there. At least in the surveyed radial range, the Bz component is found to be weaker in the midnight sector and at the dusk flank than that at the dawn flank, displaying a dawn-dusk asymmetry. The occurrence rate of negative Bz during active times also exhibites a similar asymmetric distribution, which implies active dynamics may occur more frequently at midnight and dusk flank. In contrast to quiet intervals, several features can be seen during active times: (1) a local Bz minimum between 10.5dusk region, (2) the Bz component around the midnight region is generally stronger and experiences larger fluctuations, and (3) a sharp positive/negative-excursion of the By component occurrs at the dawn/dusk flank regions inside r<10 RE. The response to solar wind parameters revealed that the Bz component is generally stronger under higher dynamic pressure (Pdy>5 nPa), which may support the dawn-dusk squeezeing effect presented in the case study of Miyashita et al. [2010]. The CS By is generally correlated with the interplanetary magnetic field (IMF) By component, but the correlation is better with higher penetration coefficient (the ratio of CS By to IMF By) when IMF Bz is positive. The implications of the present results are

  7. Radial distribution of magnetic field in earth magnetotail current sheet

    NASA Astrophysics Data System (ADS)

    Rong, Z. J.; Wan, W. X.; Shen, C.; Petrukovich, A. A.; Baumjohann, W.; Dunlop, M. W.; Zhang, Y. C.

    2014-11-01

    Knowing the magnetic field distribution in the magnetotail current sheet (CS) is essential for exploring magnetotail dynamics. In this study, using a joint dataset of Cluster/TC-1, the radial profile of the magnetic field in the magnetotail CS with radial distances covering 8100 nT for active times) and solar wind parameters are statistically surveyed. Our new findings demonstrate that, independent of the activity state, the field strength and Bz component (GSM coordinates) start the monotonic increase prominently as r decreases down to ~11.5RE, which means the dipole field starts to make a significant contribution from there. At least in the surveyed radial range, the Bz component is found to be weaker in the midnight and dusk sectors than that in the dawn sector, displaying a dawn-dusk asymmetry. The occurrence rate of negative Bz in active times also exhibits a similar asymmetric distribution, which implies active dynamics may occur more frequently at midnight and dusk flank. In comparison with that in quiet intervals, several features can be seen in active times: (1) a local Bz minimum between 10.5dusk region, (2) the Bz component around the midnight region is generally stronger and experiences larger fluctuations, and (3) a sharp positive/negative-excursion of the By component occurs at the dawn/dusk flank regions inside r<10RE. The response to solar wind parameters revealed that the Bz component is generally stronger under higher dynamic pressure (Pdy>5 nPa), which may support the dawn-dusk squeezing effect as presented by Miyashita et al. (2010). The CS By is generally correlated with the interplanetary magnetic field (IMF) By component, and the correlation quality is found to be better with higher penetration coefficient (the ratio of CS By to IMF By) when IMF Bz is positive. The implications of the present results are discussed.

  8. Observations of energetic particle escape at the magnetopause: Early results from the MMS Energetic Ion Spectrometer (EIS)

    NASA Astrophysics Data System (ADS)

    Cohen, I. J.; Mauk, B. H.; Anderson, B. J.; Westlake, J. H.; Sibeck, D. G.; Giles, B. L.; Pollock, C. J.; Turner, D. L.; Fennell, J. F.; Blake, J. B.; Clemmons, J. H.; Jaynes, A. N.; Baker, D. N.; Craft, J. V.; Spence, H. E.; Niehof, J. T.; Reeves, G. D.; Torbert, R. B.; Russell, C. T.; Strangeway, R. J.; Magnes, W.; Trattner, K. J.; Fuselier, S. A.; Burch, J. L.

    2016-06-01

    Energetic (greater than tens of keV) magnetospheric particle escape into the magnetosheath occurs commonly, irrespective of conditions that engender reconnection and boundary-normal magnetic fields. A signature observed by the Magnetospheric Multiscale (MMS) mission, simultaneous monohemispheric streaming of multiple species (electrons, H+, Hen+), is reported here as unexpectedly common in the dayside, dusk quadrant of the magnetosheath even though that region is thought to be drift-shadowed from energetic electrons. This signature is sometimes part of a pitch angle distribution evolving from symmetric in the magnetosphere, to asymmetric approaching the magnetopause, to monohemispheric streaming in the magnetosheath. While monohemispheric streaming in the magnetosheath may be possible without a boundary-normal magnetic field, the additional pitch angle depletion, particularly of electrons, on the magnetospheric side requires one. Observations of this signature in the dayside dusk sector imply that the static picture of magnetospheric drift-shadowing is inappropriate for energetic particle dynamics in the outer magnetosphere.

  9. Diel changes in the near-surface biomass of zooplankton and the carbon content of vertical migrants

    NASA Astrophysics Data System (ADS)

    Hays, Graeme C.; Harris, Roger P.; Head, Robert N.

    Zooplankton biomass and the carbon content of vertical migrants were measured in the NE Atlantic (36.5°N, 19.2°W) between 11 and 18 July 1996 as part of the Plankton Reactivity in the Marine Environment (PRIME) programme. The increase in zooplankton biomass near the surface (0-100 m) at night compared to during the day suggested that diel vertical migration was an important feature at this site. For three species of vertically migrant copepods, Pleuromamma pisekii, P. gracilis and P. abdominalis, the carbon content of individuals collected at dusk was significantly less than for individuals collected at dawn, with this reduction being 6.2, 7.3 and 14.8%, respectively. This dawn-dusk reduction in carbon content is consistent with the diel pattern of feeding and fasting exhibited by vertical migrants and supports the suggestion that migrating zooplankton will cause an active export of carbon from the surface layers.

  10. Observation of bow shock protons at the lunar orbit. M.S. Thesis; [particle trajectory analysis of solar protons in the lunar atmosphere

    NASA Technical Reports Server (NTRS)

    Benson, J. L.

    1974-01-01

    Protons with energies ranging from about 500 eV to 3,500 eV were observed by the Suprathermal Ion Detector Experiment (SIDE) on both the dusk and dawn sides of the magnetosphere. On each lunation these particles appeared as a rather continuous phenomenon for 3 to 5 days after crossing from the dawn-side magnetosheath into the solar wind and for about 2 days prior to entering the dusk-side magnetosheath. Data from the SIDE and from the Explorer 35 lunar orbiting magnetometer were analyzed and these data indicated that the transverse ion flows observed by the SIDE in the pre and post bow shock crossing regions of the lunar orbit are due to these deviated solar wind particles. A computer model based on drift trajectories for particles leaving the shock was developed and synthetic particle data produced by this model are in good agreement with the observed data.

  11. Is the sex communication of two pyralid moths, Plodia interpunctella and Ephestia kuehniella, under circadian clock regulation?

    PubMed

    Závodská, Radka; Fexová, Silvie; von Wowern, Germund; Han, Gui-Biao; Dolezel, David; Sauman, Ivo

    2012-06-01

    Females of the Indian meal moth, Plodia interpunctella, and females of the Mediterranean flour month, Ephestia kuehniella (both Lepidoptera: Pyralidae), exhibit daily rhythms in calling behavior. The peak in P. interpunctella calling occurs at dusk, whereas E. kuehniella calls preferentially at dawn. This behavior turned arrhythmic in P. interpunctella females in constant darkness (DD) and remained arrhythmic in constant light (LL), whereas E. kuehniella females showed a persistent rhythm in DD and suppression of the behavior in LL, indicating regulation by a circadian clock mechanism. The rhythm of male locomotor activity corresponded well with the sexual activity of females, reaching the peak at dusk in P. interpunctella and at dawn in E. kuehniella. An immunohistochemical study of the pheromone biosynthesis activating neuropeptide, corazonin, and pigment dispersing factor revealed distinct sets of neurons in the brain-subesophageal complex and in the neurohemal organs of the 2 species.

  12. IMAGE and the Plasmasphere: Model and Data Comparison

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.; Sandel, B.; Ober, D.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    The plasmaspheric environment has been measured through in situ spacecraft since the early 1960's. With these early measurements, modeler's began to build plasmasphere models. A feature that appeared in the models that could not be directly confirmed in the measurements is a 'tail' on the dusk side that extends toward the sun. Convection flow has been assumed to give smooth azimuthal densities, except on the dusk side. The EUV images of the plasmasphere from the IMAGE spacecraft give a global picture, and show the 'tail' to be an extended region rather than density enhancements and also show the plasmasphere, particularly the plasmapause, to be much more dynamic than the models or in situ measurements have indicated. We will show some of the unexpected features and give a possible explanation for them.

  13. Outdoor performance of a motion-sensitive neuron in the blowfly.

    PubMed

    Egelhaaf, M; Grewe, J; Kern, R; Warzecha, A K

    2001-12-01

    We studied an identified motion-sensitive neuron of the blowfly under outdoor conditions. The neuron was stimulated by oscillating the fly in a rural environment. We analysed whether the motion-induced neuronal activity is affected by brightness changes ranging between bright sunlight and dusk. In addition, the relationship between spike rate and ambient temperature was determined. The main results are: (1) The mean spike rate elicited by visual motion is largely independent of brightness changes over several orders of magnitude as they occur as a consequence of positional changes of the sun. Even during dusk the neuron responds strongly and directionally selective to motion. (2) The neuronal spike rate is not significantly affected by short-term brightness changes caused by clouds temporarily occluding the sun. (3) In contrast, the neuronal activity is much affected by changes in ambient temperature.

  14. A statistical study of ion pitch-angle distributions

    NASA Technical Reports Server (NTRS)

    Sibeck, D. G.; Mcentire, R. W.; Lui, A. T. Y.; Krimigis, S. M.

    1987-01-01

    Preliminary results of a statistical study of energetic (34-50 keV) ion pitch-angle distributions (PADs) within 9 Re of earth provide evidence for an orderly pattern consistent with both drift-shell splitting and magnetopause shadowing. Normal ion PADs dominate the dayside and inner magnetosphere. Butterfly PADs typically occur in a narrow belt stretching from dusk to dawn through midnight, where they approach within 6 Re of earth. While those ion butterfly PADs that typically occur on closed drift paths are mainly caused by drift-shell splitting, there is also evidence for magnetopause shadowing in observations of more frequent butterfly PAD occurrence in the outer magnetosphere near dawn than dusk. Isotropic and gradient boundary PADs terminate the tailward extent of the butterfly ion PAD belt.

  15. Possible leakage of energetic particles from the magnetosphere into the upstream region on June 7, 1985

    NASA Technical Reports Server (NTRS)

    Kudela, K.; Sibeck, D. G.; Belian, R. D.; Fischer, S.; Lutsenko, V.

    1990-01-01

    Prognoz 10 observed a series of energetic ion (E not less than 10 KeV) and electron (E not less than 30 KeV) bursts whilst upstream of the dusk bow shock from 2000-2200 UT on June 7, 1985. The particles streamed away from the bow shock along the interplanetary magnetic field (IMF) during periods when the IMF connected the spacecraft to the bow shock/magnetosphere. Both ions and electrons were observed when the IMF connected the spacecraft to the subsolar bow shock, but only ions were observed when the IMF connected the spacecraft to the dusk bow shock. Simultaneous ground and magnetospheric observations are presented which indicate the onset of geomagnetic activity and an increase in magnetospheric energetic particle flux levels just prior to the series of particle bursts observed by Prognoz 10 upstream of the bow shock. The combined observations are consistent with a magnetospheric source for these upstream particle events.

  16. The relationship between the IMF B(y) and the distant tail (150-238 Re) lobe and plasmasheet B(y) fields

    NASA Technical Reports Server (NTRS)

    Tsurutani, B. T.; Smith, E. J.; Jones, D. E.; Lepping, R. P.; Sibeck, D. G.

    1984-01-01

    The relationships between the Solar Magnetospheric (SM) y-component of the interplanetary magnetic field (IMF) and the lobe and plasmasheet magnetic fields have been studied for the two ISEE-3 deep tail passes. It is found that for positive sector IMFs, 13 percent of the interplanetary magnetic field penetrates into the aberrated north-dawn and south-dusk lobe quadrants, and about the same amount in the north-dusk and south-dawn lobe quadrants for negative sector IMFs. For the above cases, field penetration is significantly less for opposite polarity IMFs. The former results are generally consistent with open magnetospheric models, but the latter (the lack of response in certain quadrants) are unexplained by theory at this time. If the magnitude of the plasmasheet B(y) fields are related to plasma pressure anisotropies, very small anisotropies of about 1.01 are expected.

  17. Lunar and daily spawning rhythms of Senegal sole Solea senegalensis.

    PubMed

    Oliveira, C; Dinis, M T; Soares, F; Cabrita, E; Pousão-Ferreira, P; Sánchez-Vázquez, F J

    2009-07-01

    A periodicity of 29 days was observed in spawning rhythms in Senegal sole Solea senegalensis, with an acrophase around the last quarter and the new moon. In both spring and autumn, a very marked nocturnal spawning rhythm was registered, with spawning beginning after dusk and the acrophase occurring around 2300 hours. When the photoperiod was artificially extended (from 10L:14D to 14L:10D), S. senegalensis synchronized to the new photoperiod: spawning took place after the new 'dusk', the beginning gradually shifting from 2100 to 2300 hours and the acrophase from 2325 to 0032 hours. Under continuous light conditions, fish sustained rhythmicity for 2 days, with an acrophase at 2249 hours, which suggested the existence of an endogenous pacemaker controlling the daily spawning rhythm. These findings provided new insights for better understanding the reproductive physiology of this species and for optimizing the timing protocols of egg collection and larvae production in S. senegalensis aquaculture. PMID:20738482

  18. Environmental elements involved in communal roosting in Heliconius butterflies (Lepidoptera: Nymphalidae).

    PubMed

    Salcedo, Christian

    2010-06-01

    Several Heliconius L. butterflies species form nocturnal aggregations in sites with a particular architecture. Roosts are usually formed under relatively dense vegetation mats where dry vines or branches provide a perch for the night. These sites may last for months. To understand the importance of factors related to the expression of Heliconius roosting, data on light, temperature, relative humidity, wind, and use of wing color cues were recorded at H. erato and H. sara roost sites in Costa Rica and Panama in 2008 and 2009. The results show that roost sites offer reduced light conditions at dusk, provide a drier environment compared with its vicinity, and offer protection from wind and rain. Moreover, individuals use wing color recognition under reduced light conditions at dusk to successfully assemble aggregations. These findings provide key information for future experiments to study the use of landmarks, hygrosensitivity, and dim-light eye adaptations in Heliconius navigation to find roost sites.

  19. Comparison of storm-time changes of geomagnetic field at ground and at MAGSAT altitudes, part 3

    NASA Technical Reports Server (NTRS)

    Dejesusparada, N. (Principal Investigator); Kane, R. P.; Trivedi, N. B.

    1982-01-01

    The latitudinal distributions of delta H, delta X, delta Y, and delta Z were studied for quiet and disturbed periods. For quiet periods, the average patterns showed some variations common to dusk and dawn, thus indicating probable ground anomaly. However, there were significant differences too between dusk and dawn, indicating considerable diurnal variation effects. Particularly in delta Y, these effects were large and were symmetric about the dip equator. For disturbed day passes, the quiet day patterns were considered as base levels and the latter were subtracted from the former. The resulting residual latitudinal patterns were, on the average, symmetric about the geographical equator. However, individual passes showed considerable north-south asymmetries, probably indicating meanderings of the central plane of the magnetospheric ring current.

  20. The trans-terminator ion flow in the Venusian ionosphere near solar minimum

    NASA Astrophysics Data System (ADS)

    Wood, Alan; Grande, Manuel; Pryse, Eleri; Whittaker, Ian

    2010-05-01

    The transterminator ion flow in the Venusian ionosphere is primarily driven by a pressure gradient which is caused by photoionisation [1]. At solar maximum this antisunward flow is the principle source of the nightside ionosphere [2]. Around solar minimum the ionopause is located at a lower altitude and it has been suggested that this would severely inhibit the transport process [3,4]. However, it is only within the last few years that extensive in-situ observations of ionospheric plasma under these solar conditions have been conducted. Observations of ions of ionospheric origin conducted by Venus Express throughout one Venus year sampled all local time sectors twice and flew through these sectors in opposing directions half a Venus year apart. These observations, conducted at high latitudes close to the solar terminator, showed asymmetries in both the dawn-dusk and noon-midnight planes. In the dawn-dusk direction greater numbers of ions were observed on the dusk side than on the dawn side. In the noon-midnight plane greater numbers of ions were observed on the dayside, although significant numbers of ions were seen nightward of the terminator. Collectively these observations suggest a nightward ion flow with the dawn-dusk asymmetry resulting from variations in the plasma density in the dayside ionosphere. Observations of the ion energies suggest that this flow has a velocity of ~4 km s-1. References [1] Knudsen et al., Geophys. Res. Letts., 8, 241-244, doi:10.1029/GL008i003p00241, 1981. [2] Knudsen et al., J. Geophys. Res., 85, 7803-7810, doi:10.1016/0273-1177(87)90207-9, 1980. [3] Knudsen et al., J. Geophys. Res., 92, 13,391-13,398, doi:10.1029/JA092iA12p13391, 1987. [4] Spenner et al., J. Geophys. Res., 86, 9170-9178, doi:10.1029/JA086iA11p09170, 1995.

  1. Mapping high-latitude plasma convection with coherent HF radars

    NASA Technical Reports Server (NTRS)

    Ruohoniemi, J. M.; Greenwald, R. A.; Baker, K. B.; Villain, J.-P.; Hanuise, C.

    1989-01-01

    Several methods developed for mapping high-latitude plasma convection with a high-latitude HF radar are described, which utilize coherent backscatter from electron density irregularities at F-region altitudes to observe convective plasma motion. Several examples of two-dimensional convection-velocity maps are presented, showing instances of L-shell-aligned flow in the dusk sector, the reversal of convection near magnetic midnight, and counterstreaming in the dayside cleft.

  2. DE 2 observations of disturbances in the upper atmosphere during a geomagnetic storm

    NASA Technical Reports Server (NTRS)

    Miller, N. J.; Brace, L. H.; Spencer, N. W.; Carignan, G. R.

    1990-01-01

    Results are presented of physical interpretations of a sequence of in situ measurements taken in the midlatitude dusk sector during the geomagnetic storm of November 24, 1982 by instruments on board the DE-2 spacecraft in polar orbit. The results represent the first comparison of nearly simultaneous measurements, obtained at different seasons in a common local time sector, of storm disturbances in dc electric fields, zonal ion convection, zonal winds, gas composition and temperature, and electron density and temperature.

  3. A Critical Time Window for Organismal Interactions in a Pelagic Ecosystem

    PubMed Central

    Benoit-Bird, Kelly J.; McManus, Margaret A.

    2014-01-01

    To measure organismal coherence in a pelagic ecosystem, we used moored sensors to describe the vertical dynamics of each step in the food chain in shelf waters off the west shore of Oahu, Hawaii. Horizontally extensive, intense aggregations of phytoplankton, zooplankton, and micronekton exhibited strong diel patterns in abundance and vertical distribution, resulting in a highly variable potential for interaction amongst trophic levels. Only around dusk did zooplankton layers overlap with phytoplankton layers. Shortly after sunset, micronekton ascended from the deep, aggregating on the island's shelf. Short-lived departures in migration patterns were detected in depth, vertical distribution, density, and total abundance of micronekton when zooplankton layers were present with typical patterns resuming within one hour. Layers of zooplankton began to disappear within 20 minutes of the arrival of micronekton with no layers present after 50 minutes. The effects of zooplankton layers cascaded even further up the food chain, affecting many behaviors of dolphins observed at dusk including their depth, group size, and inter-individual spacing. As a result of these changes in behavior, during a 30-minute window just after dusk, the number of feeding events observed for each dolphin and consequently the feeding time for each individual more than doubled when zooplankton layers were present. Dusk is a critical period for interactions amongst species in this system from phytoplankton to top predators. Our observations that short time windows can drive the structure and function of a complex suite of organisms highlight the importance of explicitly adding a temporal dimension at a scale relevant to individual organisms to our descriptions of heterogeneity in ocean ecosystems. PMID:24844981

  4. On chaotic conductivity in the magnetotail

    NASA Technical Reports Server (NTRS)

    Holland, Daniel L.; Chen, James

    1992-01-01

    The concept of chaotic conductivity and the acceleration of particles due to a constant dawn dusk electric field are studied in a magnetotail-like magnetic field. A test particle simulation is used including the full nonlinear dynamics. It is found that the acceleration process can be understood without invoking chaos and that the cross tail current is determined by the particle dynamics and distributions. It is concluded that in general there is no simple relationship between the electric field and the current.

  5. Distinct sources of injections in the polar cusp observed by Cluster

    NASA Astrophysics Data System (ADS)

    Escoubet, C. Philippe; Reme, Henri; Dunlop, Malcolm; Daly, Patrick; Laakso, Harri; Berchem, Jean; Richard, Robert; Taylor, Matthew; Trattner, Karlheinz; Grison, Benjamin; Dandouras, Iannis; Fazakerley, Andrew; Pitout, Frederic; Masson, Arnaud

    The main process that injects solar wind plasma into the polar cusp is now generally accepted to be magnetic reconnection. Depending on the IMF direction, this process takes place equatorward (for IMF southward), poleward (for IMF northward) or on the dusk or dawn sides (for IMF azimuthal) of the cusp. We report a Cluster crossing on 5 January 2002 near the exterior cusp on the southern dusk side. The IMF was mainly azimuthal (IMF-By around -5 nT), the solar wind speed lower than usual around 280 km/s and the density around 5 cm-3. The four Cluster spacecraft had an elongated configuration near the magnetopause. C4 was the first spacecraft to enter the cusp around 19:52:04 UT, followed by C2 at 19:52:35 UT, C1 at 19:54:24 UT and C3 at 20:13:15 UT. C4 and C1 observed two ion energy dispersions at 20:10 UT and 20:40 UT and C3 at 20:35 UT and 21:15 UT. Using the time of flight technique on the upgoing and downgoing ions in the dispersions, we obtain an altitude of the sources of these ions between 14 and 20 RE. Using Tsyganenko model, these sources are located on the dusk flank, past the terminator. The first injection by C3 is seen at approximately the same time as the 2nd injection on C1 but their sources at the magnetopause were separated by more than 10 RE. This would imply that two distinct sources were active at the same time on the dusk flank of the magnetosphere.

  6. Cluster Observations of Particle Injections in the Exterior Cusp

    NASA Astrophysics Data System (ADS)

    Escoubet, C. P.; Grison, B.; Berchem, J.; Trattner, K. J.; Lavraud, B.; Pitout, F.; Soucek, J.; Richard, R. L.; Laakso, H. E.; Masson, A.; Dunlop, M. W.; Dandouras, I. S.; Reme, H.; Fazakerley, A. N.; Daly, P. W.

    2014-12-01

    The main process that injects solar wind plasma into the polar cusp is now generally accepted to be magnetic reconnection. Depending on the IMF direction, this process takes place equatorward (for IMF southward), poleward (for IMF northward) or on the dusk or dawn sides (for IMF azimuthal) of the cusp. We report a Cluster crossing on 5 January 2002 near the exterior cusp on the southern dusk side. The IMF was mainly azimuthal (IMF-By around -5 nT), the solar wind speed lower than usual around 280 km/s with the density of order 5 cm-3. The four Cluster spacecraft had an elongated configuration near the magnetopause. C4 was the first spacecraft to enter the cusp around 19:52:04 UT, followed by C2 at 19:52:35 UT, C1 at 19:54:24 UT and C3 at 20:13:15 UT. C4 and C1 observed two ion energy dispersions at 20:10 UT and 20:40 UT and C3 at 20:35 UT and 21:15 UT. Using the time of flight technique on the upgoing and downgoing ions, which leads to energy dispersions, we obtain distances of the ion sources between 14 and 20 RE from the spacecraft. Using Tsyganenko model, we find that these sources are located on the dusk flank, past the terminator. The first injection by C3 is seen at approximately the same time as the 2nd injection on C1 but their sources at the magnetopause were separated by more than 7 RE. This would imply that two distinct sources were active at the same time on the dusk flank of the magnetosphere. In addition, a flow reversal was observed at the magnetopause on C4 which would be an indication that reconnection is taking place near the exterior cusp.

  7. The effect of mid-latitude electron precipitation on the geoelectric field

    NASA Technical Reports Server (NTRS)

    Sheldon, W. R.; Benbrook, J. R.; Byrne, G. J.

    1988-01-01

    A simple model is outlined to describe electron precipitation from the population of charged particles trapped in the earth's magnetic field; almost all of the precipitation is shown to occur in the region of the South Atlantic Anomaly. When the effect of a dawn-to-dusk electric field across the magnetosphere is included in the model, a diurnal modulation of the precipitated electron flux is predicted. Experimental evidence which supports the diurnal modulation model is described.

  8. Comparison of storm-time changes of geomagnetic field at ground and MAGSAT altitudes

    NASA Technical Reports Server (NTRS)

    Dejesusparada, N. (Principal Investigator); Kane, R. P.; Trivedi, N. B.

    1982-01-01

    The MAGSAT data for the period Nov. 2-20, 1979 were studied. From the observed H, the HMD predicted by model was subtracted. The residue delta H = H-HMD shows storm-time variations similar to geomagnetic Dst, at least qualitatively. Delta H sub 0, i.e., equatorial values of delta H were studied separately for dusk and dawn and show some differences.

  9. Observation and theory of Pc 5 waves with harmonically related transverse and compressional components

    NASA Technical Reports Server (NTRS)

    Takahashi, K.; Mcentire, R. W.; Cheng, C. Z.; Kistler, L. M.

    1990-01-01

    The properties of 23 magnetic pulsation events observed by the AMPTE CCE spacecraft are studied. These events are selected on the basis of the field magnitude which oscillated at the second harmonic of a simultaneously present transverse oscillation. The events have a second harmonic period of 80-600 s (roughly the Pc 5 range), are observed in cluster in the dawn (0300-0800 magnetic local time, MLT) and dusk (1600-2100 MLT) sectors, and are localized near the magnetic equator. Although the azimuthal wave number estimated from an ion finite Larmor radius effect, is generally large (about 50), there is a marked difference between the events observed in the dawn and dusk sectors. In the dawn sector the waves have low frequencies (1-5 mHz), indicate left-hand polarization with respect to the ambient magnetic field, and propagate eastward with respect to the spacecraft. In the dusk sector the waves have high frequencies (5-15 mHz), indicate right-hand polarization, and propagate westward. It is suggested that the waves are all westward propagating in the plasma rest frame and that local-time-dependent Doppler shift is the reason for the local time dependence of the wave properties.

  10. Comparison of the dynamics and structure of Saturn and Jupiter magnetospheres: camshaft, magnetic anomalies and corotating convection models compared.

    NASA Astrophysics Data System (ADS)

    Southwood, D. J.; Kivelson, M. G.

    Scenarios are presented for the overall flux and mass circulation in the jovian and saturnian magnetospheres It is argued that similar fundamanetal processes underly the dynamical processes at both planets However the differences in parameter regime for the two systems leads to substantial resulting differences in morphology Transport is accomplished from the inner magnetosphere by interchange motion which then feeds into the outer magnetosphere where ballooning driven by centrifugal stress leads to field reconnection and plasma loss It seems likely that Jupiter loses much more material per rotation cycle than Saturn and is possibly much more symmetrically loaded in respect of planetary longitude Material loss and flux return at Jupiter have fixed orientations in local time early evening and morning sector respectively and newly returned flux is probably responsible for the morningside cushion region in the outer magnetosphere At Jupiter the dawn-dusk asymmetry in the current sheet thin in morning thick in afternoon is also a dominant feature At Saturn there seems no evidence of a cushion region flux return is thought to take place sporadically over much of the nightside Although definitive statements about the dusk plasma sheet await the orbit evolution of Cassini a fundamental observational feature in the Saturnian context is a planetary rotation induced magnetic field asymmetry which argues against major dawn-dusk asymmetry We propose the rotational feature could originate from a localized ionospheric magnetic anomaly The

  11. Mapping electrostatic potentials from the ionosphere to the magnetosphere

    NASA Technical Reports Server (NTRS)

    Sojka, J. J.; Foster, J. C.; Banks, P. M.; Doupnik, J. R.

    1983-01-01

    Techniques for mapping observed ionospheric-potential distributions into the magnetosphere are discussed and illustrated using published Millstone Hill and Chatanika incoherent-scatter-radar data. It is shown that the mapping of a given field line to the equator is subject to strong diurnal and seasonal variations (attributed to the combination of internal and tail-current magnetic-field sources at auroral latitudes and the diurnal variation of solar declination in dipole coordinates) and longitude-dependent differences in ionospheric geometry. A mapping based on the tilt-dependent model of Olson and Pfitzer (1977) and using an empirical ionospheric-potential distribution derived from Chatanika plasma-drift measurements produces a relativity uniform magnetospheric electric field in the tail region. The field at 12 earth radii (Re) is found to be between 1 and 2 kV/Re; at the dawn-dusk meridian beyond the plasmasphere it is as high as 5 kV/Re. The plasmasphere is shown to have a dusk bulge in its equipotential structure and to be almost symmetric about the dawn-dusk meridian.

  12. Mapping electrostatic potentials from the ionosphere to the magnetosphere

    NASA Astrophysics Data System (ADS)

    Sojka, J. J.; Foster, J. C.; Banks, P. M.; Doupnik, J. R.

    1983-11-01

    Techniques for mapping observed ionospheric-potential distributions into the magnetosphere are discussed and illustrated using published Millstone Hill and Chatanika incoherent-scatter-radar data. It is shown that the mapping of a given field line to the equator is subject to strong diurnal and seasonal variations (attributed to the combination of internal and tail-current magnetic-field sources at auroral latitudes and the diurnal variation of solar declination in dipole coordinates) and longitude-dependent differences in ionospheric geometry. A mapping based on the tilt-dependent model of Olson and Pfitzer (1977) and using an empirical ionospheric-potential distribution derived from Chatanika plasma-drift measurements produces a relativity uniform magnetospheric electric field in the tail region. The field at 12 earth radii (Re) is found to be between 1 and 2 kV/Re; at the dawn-dusk meridian beyond the plasmasphere it is as high as 5 kV/Re. The plasmasphere is shown to have a dusk bulge in its equipotential structure and to be almost symmetric about the dawn-dusk meridian.

  13. Two encounters with the flank low-latitude boundary layer - Further evidence for closed field topology and investigation of the internal structure

    NASA Technical Reports Server (NTRS)

    Traver, D. P.; Mitchell, D. G.; Williams, D. J.; Frank, L. A.; Huang, C. Y.

    1991-01-01

    The structure of the flank low-latitude boundary layer (LLBL) is examined through differential energy spectra and particle angular anisotropies for traversals of the dawn flank (December 19, 1977) and dusk flank (July 7, 1978) during periods of predominantly northward magnetosheath field orientation. Spectra are presented that were obtained from combined ISEE 1 low-energy-proton and electron-differential-energy-analyzer and medium-energy-particle-instrument data extending over the 200-eV/q to 2-MeV energy range for the plasma sheet, stagnation region, outer LLBL, and magnetosheath regions. The stagnation region and the outer LLBL are each a mixture of plasma-sheet and magnetosheath populations, but the stagnation region contains a relatively higher fraction of plasma sheet particles, consistent with its placement earthward of the outer LLBL. Evidence for energization of thermal electrons appears during the dusk flank crossing. Bidirectional field-aligned ion distributions are observed with typically 5-to-1 enhancement of the flux along the magnetic field during certain portions of the dusk flank crossing.

  14. Magnetic reconnection in Saturn's magnetotail: A comprehensive magnetic field survey

    NASA Astrophysics Data System (ADS)

    Smith, A. W.; Jackman, C. M.; Thomsen, M. F.

    2016-04-01

    Reconnection within planetary magnetotails is responsible for locally energizing particles and changing the magnetic topology. Its role in terms of global magnetospheric dynamics can involve changing the mass and flux content of the magnetosphere. We have identified reconnection related events in spacecraft magnetometer data recorded during Cassini's exploration of Saturn's magnetotail. The events are identified from deflections in the north-south component of the magnetic field, significant above a background level. Data were selected to provide full tail coverage, encompassing the dawn and dusk flanks as well as the deepest midnight orbits. Overall 2094 reconnection related events were identified, with an average rate of 5.0 events per day. The majority of events occur in clusters (within 3 h of other events). We examine changes in this rate in terms of local time and latitude coverage, taking seasonal effects into account. The observed reconnection rate peaks postmidnight with more infrequent but steady loss seen on the dusk flank. We estimate the mass loss from the event catalog and find it to be insufficient to balance the input from the moon Enceladus. Several reasons for this discrepancy are discussed. The reconnection X line location appears to be highly variable, though a statistical separation between events tailward and planetward of the X line is observed at a radial distance of between 20 and 30RS downtail. The small sample size at dawn prevents comprehensive statistical comparison with the dusk flank observations in terms of flux closure.

  15. FORTRAN programs to process Magsat data for lithospheric, external field, and residual core components

    NASA Technical Reports Server (NTRS)

    Alsdorf, Douglas E.; Vonfrese, Ralph R. B.

    1994-01-01

    The FORTRAN programs supplied in this document provide a complete processing package for statistically extracting residual core, external field and lithospheric components in Magsat observations. To process the individual passes: (1) orbits are separated into dawn and dusk local times and by altitude, (2) passes are selected based on the variance of the magnetic field observations after a least-squares fit of the core field is removed from each pass over the study area, and (3) spatially adjacent passes are processed with a Fourier correlation coefficient filter to separate coherent and non-coherent features between neighboring tracks. In the second state of map processing: (1) data from the passes are normalized to a common altitude and gridded into dawn and dusk maps with least squares collocation, (2) dawn and dusk maps are correlated with a Fourier correlation efficient filter to separate coherent and non-coherent features; the coherent features are averaged to produce a total field grid, (3) total field grids from all altitudes are continued to a common altitude, correlation filtered for coherent anomaly features, and subsequently averaged to produce the final total field grid for the study region, and (4) the total field map is differentially reduced to the pole.

  16. Normal vision can compensate for the loss of the circadian clock.

    PubMed

    Schlichting, Matthias; Menegazzi, Pamela; Helfrich-Förster, Charlotte

    2015-09-22

    Circadian clocks are thought to be essential for timing the daily activity of animals, and consequently increase fitness. This view was recently challenged for clock-less fruit flies and mice that exhibited astonishingly normal activity rhythms under outdoor conditions. Compensatory mechanisms appear to enable even clock mutants to live a normal life in nature. Here, we show that gradual daily increases/decreases of light in the laboratory suffice to provoke normally timed sharp morning (M) and evening (E) activity peaks in clock-less flies. We also show that the compound eyes, but not Cryptochrome (CRY), mediate the precise timing of M and E peaks under natural-like conditions, as CRY-less flies do and eyeless flies do not show these sharp peaks independently of a functional clock. Nevertheless, the circadian clock appears critical for anticipating dusk, as well as for inhibiting sharp activity peaks during midnight. Clock-less flies only increase E activity after dusk and not before the beginning of dusk, and respond strongly to twilight exposure in the middle of the night. Furthermore, the circadian clock responds to natural-like light cycles, by slightly broadening Timeless (TIM) abundance in the clock neurons, and this effect is mediated by CRY. PMID:26378222

  17. Label‐free quantitative analysis of the casein kinase 2‐responsive phosphoproteome of the marine minimal model species Ostreococcus tauri

    PubMed Central

    Le Bihan, Thierry; Hindle, Matthew; Martin, Sarah F.; Barrios‐Llerena, Martin E.; Krahmer, Johanna; Kis, Katalin; Millar, Andrew J.

    2015-01-01

    Casein kinase 2 (CK2) is a protein kinase that phosphorylates a plethora of cellular target proteins involved in processes including DNA repair, cell cycle control, and circadian timekeeping. CK2 is functionally conserved across eukaryotes, although the substrate proteins identified in a range of complex tissues are often different. The marine alga Ostreococcus tauri is a unicellular eukaryotic model organism ideally suited to efficiently study generic roles of CK2 in the cellular circadian clock. Overexpression of CK2 leads to a slow circadian rhythm, verifying functional conservation of CK2 in timekeeping. The proteome was analysed in wild‐type and CK2‐overexpressing algae at dawn and dusk, revealing that differential abundance of the global proteome across the day is largely unaffected by overexpression. However, CK2 activity contributed more strongly to timekeeping at dusk than at dawn. The phosphoproteome of a CK2 overexpression line and cells treated with CK2 inhibitor was therefore analysed and compared to control cells at dusk. We report an extensive catalogue of 447 unique CK2‐responsive differential phosphopeptide motifs to inform future studies into CK2 activity in the circadian clock of more complex tissues. All MS data have been deposited in the ProteomeXchange with identifier PXD000975 (http://proteomecentral.proteomexchange.org/dataset/PXD000975). PMID:25930153

  18. Cool night-time temperatures induce the expression of CONSTANS and FLOWERING LOCUS T to regulate flowering in Arabidopsis.

    PubMed

    Kinmonth-Schultz, Hannah A; Tong, Xinran; Lee, Jae; Song, Young Hun; Ito, Shogo; Kim, Soo-Hyung; Imaizumi, Takato

    2016-07-01

    Day length and ambient temperature are major stimuli controlling flowering time. To understand flowering mechanisms in more natural conditions, we explored the effect of daily light and temperature changes on Arabidopsis thaliana. Seedlings were exposed to different day/night temperature and day-length treatments to assess expression changes in flowering genes. Cooler temperature treatments increased CONSTANS (CO) transcript levels at night. Night-time CO induction was diminished in flowering bhlh (fbh)-quadruple mutants. FLOWERING LOCUS T (FT) transcript levels were reduced at dusk, but increased at the end of cooler nights. The dusk suppression, which was alleviated in short vegetative phase (svp) mutants, occurred particularly in younger seedlings, whereas the increase during the night continued over 2 wk. Cooler temperature treatments altered the levels of FLOWERING LOCUS M-β (FLM-β) and FLM-δ splice variants. FT levels correlated strongly with flowering time across treatments. Day/night temperature changes modulate photoperiodic flowering by changing FT accumulation patterns. Cooler night-time temperatures enhance FLOWERING BHLH (FBH)-dependent induction of CO and consequently increase CO protein. When plants are young, cooler temperatures suppress FT at dusk through SHORT VEGETATIVE PHASE (SVP) function, perhaps to suppress precocious flowering. Our results suggest day length and diurnal temperature changes combine to modulate FT and flowering time.

  19. System III variations in apparent distance of Io plasma torus from Jupiter

    NASA Technical Reports Server (NTRS)

    Dessler, A. J.; Sandel, B. R.

    1992-01-01

    System III variations in apparent distance of the Io plasma torus from Jupiter are examined on the basis of data obtained from UVS scans across Jupiter's satellite system. The displacement of the dawn and dusk ansae are found to be unexpectedly complex. The displacements are unequal and both ansae are in motion with the motion of the approaching ansa being the lesser of the two. The radial motions, as measured from either the center of Jupiter or the offset-tilted dipole, are of unequal magnitude and have the System III periodicity. It is concluded that the cross-tail electric field that causes these torus motions is concentrated on the dusk ansa, varied with the System III period, and shows magnetic-anomaly phase control. It is found that the dawn-dust asymmetry in brightness is not explained simply by the cross-tail electric field. It is concluded that there is a heating mechanism that causes the dusk side of the Io plasma torus to be brighter than the dawn side.

  20. Energetic Charged-Particle Phenomena in the Jovian Magnetosphere: First Results from the Ulysses COSPIN Collaboration.

    PubMed

    Simpson, J A; Anglin, J D; Balogh, A; Burrows, J R; Cowley, S W; Ferrando, P; Heber, B; Hynds, R J; Kunow, H; Marsden, R G; McKibben, R B; Müller-Mellin, R; Page, D E; Raviart, A; Sanderson, T R; Staines, K; Wenzel, K P; Wilson, M D; Zhang, M

    1992-09-11

    The Ulysses spacecraft made the first exploration of the region of Jupiter's magnetosphere at high Jovigraphic latitudes ( approximately 37 degrees south) on the dusk side and reached higher magnetic latitudes ( approximately 49 degrees north) on the day side than any previous mission to Jupiter. The cosmic and solar particle investigations (COSPIN) instrumentation achieved a remarkably well integrated set of observations of energetic charged particles in the energy ranges of approximately 1 to 170 megaelectron volts for electrons and 0.3 to 20 megaelectron volts for protons and heavier nuclei. The new findings include (i) an apparent polar cap region in the northern hemisphere in which energetic charged particles following Jovian magnetic field lines may have direct access to the interplanetary medium, (ii) high-energy electron bursts (rise times approximately 17 megaelectron volts) on the dusk side that are apparently associated with field-aligned currents and radio burst emissions, (iii) persistence of the global 10-hour relativistic electron "clock" phenomenon throughout Jupiter's magnetosphere, (iv) on the basis of charged-particle measurements, apparent dragging of magnetic field lines at large radii in the dusk sector toward the tail, and (v) consistent outflow of megaelectron volt electrons and large-scale departures from corotation for nucleons.

  1. Solar wind influence on the Jovian inner magnetosphere observed by Hisaki/EXCEED

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    The dawn-dusk asymmetry of the Io plasma torus has been seen by several observations [e.g., Sandel and Broadfoot, 1982; Steffl et al., 2004]. Ip and Goertz [1983] explained this asymmetry can be caused by a dawn-to-dusk electric field in the Jupiter's inner magnetosphere. However, the question what physical process can impose such an electric field deep inside the strong magnetosphere still remains. The long-term monitoring of the Io plasma torus is a key observation to answer this question. The extreme ultraviolet (EUV) spectrometer EXCEED onboard the Hisaki satellite observed the Io plasma torus continuously during the two periods: from December 2013 to March 2014 and from November 2014 to May 2015. We found clear responses of the dawn-dusk asymmetry to rapid increases of the solar wind dynamic pressure. We statistically analyzed the relations between solar wind and IPT response. Furthermore, we investigated the influence of Io's volcanic activity, detected by Hisaki in January 2015, on the solar wind response of Jovian inner magnetosphere. We will report the initial results of this study.

  2. A numerical modeling study of the interaction between the tides and the circulation forced by high-latitude plasma convection

    SciTech Connect

    Mikkelsen, I.S. ); Larsen, M.F. )

    1991-02-01

    A spectral, time-varying thermospheric general circulation model has been used to study the nonlinear interaction at high latitudes between the tides propagating into the thermosphere from below and the circulation induced by magnetospheric forcing and in situ solar heating. The model is discrete in the vertical with 27 layers spaced by half a scale height. In the horizontal, the fields are expanded in a series of spherical harmonics using a triangular truncation at wave number 31, equivalent to a homogeneous global resolution with a minimum wavelength of 1,270 km. A hypothetical uniform grid point model would require a horizontal spacing of 417 km to describe the same minimum wavelength. In the high-latitude F region the tides affect the dusk vortex of the neutral flow very little, but the dawn vortex is either suppressed or amplified dependent upon the universal time and tidal phase. In the E region neutral flow, both the dusk and dawn vortices are shifted in local time by the tides, again as a function of universal time and tidal phase. At dusk a nonlinear amplification of the sunward winds occurs for certain combination of parameters, and at dawn the winds may be completely suppressed. Below 120 km altitude the magnetospheric forcing creates a single cyclonic vortex which is also sensitive to the high-latitude tidal structure.

  3. 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

  4. Magnetic Field Observations of Partial Ring Current during Storm Recovery Phase

    NASA Technical Reports Server (NTRS)

    Le, Guan; Russell, C. T.; Slavin, J. A.; Lucek, E. A.

    2007-01-01

    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. Our previous work on global ring current distribution [Le et al., 2004] has shown that a significant partial ring current is always present at all Dst levels (regardless of storm phases) even for quiet time ring current. The total current carried by the partial ring current is much stronger than (during stormtime) or at least comparable to (during quiet time) the symmetric ring current. 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

  5. Ionospheric vertical drift response at a mid-latitude station

    NASA Astrophysics Data System (ADS)

    Kouba, Daniel; Koucká Knížová, Petra

    2016-07-01

    Vertical plasma drift data measured at a mid-latitude ionospheric station Pruhonice (50.0 ° N, 14.6 ° E) were collected and analysed for the year 2006, a year of low solar and geomagnetic activity. Hence these data provide insight into the drift behaviour during quiet conditions. The following typical diurnal trend is evident: a significant decay to negative values (downward peak) at dawn; generally less pronounced downward peak at dusk hours. Magnitude of the downward drift varies during the year. Typically it reaches values about 20 ms-1 at dawn hours and 10 ms-1 at dusk hours. Maximum dawn magnitude of about 40 ms-1 has been detected in August. During daytime the vertical drifts increases from the initial small downward drifts to zero drift around noon and to small upward drifts in the afternoon. Night-time drift values display large variability around a near zero vertical drift average. There is a significant trend to larger downward drift values near dawn and a less pronounced decrease of the afternoon upward vertical drifts near sunset. Two regular downward peaks of the drift associated with the dawn and dusk are general characteristics of the analysed data throughout the year 2006. Their seasonal course corresponds to the seasonal course of the sunrise and sunset. The duration of prevailing negative drift velocities forming these peaks and thus the influence of the dawn/dusk on the drift velocity is mostly 1.5-3 h. The dawn effect on vertical drift tends to be larger than the effect of the dusk. The observed magnitude of the sunrise and sunset peaks show significant annual course. The highest variability of the magnitude is seen during winter. High variability is detected till March equinox and again after September equinox. Around solstice, both peaks reaches lowest values. After that, the magnitudes of the drift velocity increase smoothly till maxima in summer (August). The vertical drift velocity course is smooth between June solstice and September

  6. Storm-time Magnetospheric Effects on Electric Fields in the Subauroral Ionosphere

    NASA Astrophysics Data System (ADS)

    Wolf, R. A.; Garner, T. W.; Goldstein, J.; Sazykin, S.; Spiro, R. W.

    2001-12-01

    Although the inner edge of the plasma sheet tends to shield the mid- and low-latitude ionosphere from the full force of magnetospheric convection, the shielding is particularly ineffective during magnetic storms. This talk will review several effects that represent quick responses to magnetospheric drivers, specifically the following: 1. Overshielding and undershielding. The overshielding electric fields, which occur during convection decreases, were predicted theoretically and observed in the post-midnight sector more than twenty years ago. The predicted patterns have been largely confirmed by statistical analysis of radar observations, although it has been necessary to modify the original overshielding idea somewhat to be consistent with the observed strength and duration. Overshielding has also been seen in plasmaspheric observations, most recently by the IMAGE spacecraft. Simulations of the main phase of a large storm predict the sustained presence of an undershielding (direct penetration) eastward electric field in the post-dusk sector, possibly triggering scintillations there. 2. Polarization jets. Simulations indicate that strong ring current injection is accompanied by a several-degree-wide westward-moving jet of plasma in the dusk-midnight quadrant, just equatorward of the auroral zone. These have been observed in recent years from CRRES and Millstone Hill. 3. Interchange-associated electric-field eddies. These are predicted by recent Rice Convection Model simulations and have not, as far as we know, been reported observationally. We predict their occurrence in the early recovery phase of a magnetic storm whose main phase terminates with a strong and sustained northward turning of the interplanetary magnetic field. They should occur in a band roughly 5 degrees wide, just equatorward of the auroral zone, in the dusk-midnight sector.

  7. Ionospheric current contribution to the main impulse of a negative sudden impulse

    NASA Astrophysics Data System (ADS)

    Vichare, Geeta; Rawat, Rahul; Bhaskar, Ankush; Pathan, Bashir M.

    2014-12-01

    The geomagnetic field response to a moderate-amplitude negative sudden impulse (SI-) that occurred on 14 May 2009 at 10:30 UT was examined at 97 geomagnetic observatories situated all over the globe. The response signature contains a contribution from magnetospheric as well as ionospheric currents. The main impulse (MI) is defined as the maximum depression in the observed geomagnetic field. It is observed that for low-to-high latitudes, the amplitude of the MI is larger in the afternoon to post-dusk sector than in the dawn-noon sector, indicating asymmetry in the MI amplitude. We estimated the contribution at various observatories due to the Chapman-Ferraro magnetopause currents using the Tsyganenko model (T01) and subtracted this from the observed MI amplitude to obtain the contribution due to ionospheric currents. It is found that the ionospheric currents contribute significantly to the MI amplitude of moderate SI- even at low-to-mid latitudes and that the contribution is in the same direction as that from the magnetopause currents near dusk and in the opposite direction near dawn. The equivalent current vectors reveal a clockwise (anticlockwise) ionospheric current loop in the afternoon (morning) sector during the MI of the negative pressure impulse. This evidences an ionospheric twin-cell-vortex current system (DP2) due to field-aligned currents (FACs) associated with the dusk-to-dawn convection electric field during the MI of an SI-. We also estimated the magnetic field variation due to prompt penetration electric fields, which is found to be very small at low latitudes in the present case. The studied SI- is not associated with shock, and hence no preliminary reverse impulse was evident. In addition, the summer hemisphere reveals larger MI amplitudes than the winter hemisphere, indicating once again the role of ionospheric currents.

  8. Turbulence in a Global Magnetohydrodynamic Simulation of the Earth's Magnetosphere during Northward and Southward Interplanetary Magnetic Field

    NASA Technical Reports Server (NTRS)

    El-Alaoui, M.; Richard, R. L.; Ashour-Abdalla, M.; Walker, R. J.; Goldstein, M. L.

    2012-01-01

    We report the results of MHD simulations of Earth's magnetosphere for idealized steady solar wind plasma and interplanetary magnetic field (IMF) conditions. The simulations feature purely northward and southward magnetic fields and were designed to study turbulence in the magnetotail plasma sheet. We found that the power spectral densities (PSDs) for both northward and southward IMF had the characteristics of turbulent flow. In both cases, the PSDs showed the three scale ranges expected from theory: the energy-containing scale, the inertial range, and the dissipative range. The results were generally consistent with in-situ observations and theoretical predictions. While the two cases studied, northward and southward IMF, had some similar characteristics, there were significant differences as well. For southward IMF, localized reconnection was the main energy source for the turbulence. For northward IMF, remnant reconnection contributed to driving the turbulence. Boundary waves may also have contributed. In both cases, the PSD slopes had spatial distributions in the dissipative range that reflected the pattern of resistive dissipation. For southward IMF there was a trend toward steeper slopes in the dissipative range with distance down the tail. For northward IMF there was a marked dusk-dawn asymmetry with steeper slopes on the dusk side of the tail. The inertial scale PSDs had a dusk-dawn symmetry during the northward IMF interval with steeper slopes on the dawn side. This asymmetry was not found in the distribution of inertial range slopes for southward IMF. The inertial range PSD slopes were clustered around values close to the theoretical expectation for both northward and southward IMF. In the dissipative range, however, the slopes were broadly distributed and the median values were significantly different, consistent with a different distribution of resistivity.

  9. Earth magnetotail current sheet near and beyond the Lunar orbit

    NASA Astrophysics Data System (ADS)

    Vasko, I.; Petrukovich, A. A.; Artemyev, A.; Nakamura, R.; Zelenyi, L. M.

    2015-12-01

    We analyze the structure of the Earth magnetotail current sheet (CS) in middle, -50 REdusk distributions of the CS parameters: L is about 3000 km at the dusk flank and grows up to 12000 km toward the dawn flank; j0 grows toward the dusk flank by a factor of 2-3; the most intense CSs (with higher vD) are observed near the midnight. We show that ion-scale CSs with the thickness of several ion thermal gyroradii (say less than seven) are observed in middle and distant tail regions in more than 50% of crossings. For observed CSs electrons provide likely the dominant contribution to the current density. We divide the subset into intense and weak CSs (using parameter vD). The weak CSs have thickness of about 20 ion thermal gyroradii and Bz of about 1.5 nT. The intense CSs have thickness of about 3-7 thermal gyroradii and much smaller Bz implying a more stretched field line configuration. For intense CSs velocity vD is larger for larger amplitudes of ion bulk velocity vx that is likely due to larger contribution of Speiser ions. Intense CSs may be responsible for the Bursty Bulk Flow generation in the middle and distant tail regions.

  10. Observations of a unique type of ULF wave by low-altitude Space Technology 5 satellites

    NASA Astrophysics Data System (ADS)

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

    2011-08-01

    We report a unique type of ULF waves observed by low-altitude Space Technology 5 (ST-5) constellation mission. ST-5 is a three-microsatellite constellation deployed into a 300 × 4500 km dawn-dusk and Sun-synchronous polar orbit with 105.6° inclination angle. Because of 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 the dayside closed field line region at subauroral latitudes, they frequently observe strong transverse oscillations at 30-200 mHz, or in the Pc2-3 frequency range. These Pc2-3 waves appear as wave packets with durations in the order of 5-10 min. As the maximum separations of the ST-5 spacecraft are in the order of 10 min, 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 Pc2-3 band; instead, the waves appear to be the common Pc4-5 waves associated with field line resonances. We suggest that these unique Pc2-3 waves seen by ST-5 are in fact the Doppler-shifted Pc4-5 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-dusk orbits at proper altitudes and magnetic latitudes reveal the azimuthal characteristics of field line resonances.

  11. Observations of a Unique Type of ULF Wave by Low-Altitude Space Technology 5 Satellites

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    We report a unique type of ULF waves observed by low-altitude Space Technology 5 (ST-5) constellation mission. ST-5 is a three-microsatellite constellation deployed into a 300 x 4500 km dawn-dusk and Sun-synchronous polar orbit with 105.6deg inclination angle. Because of 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 the dayside closed field line region at subauroral latitudes, they frequently observe strong transverse oscillations at 30-200 mHz, or in the Pc2-3 frequency range. These Pc2-3 waves appear as wave packets with durations in the order of 5-10 min. As the maximum separations of the ST-5 spacecraft are in the order of 10 min, 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 Pc2-3 band; instead, the waves appear to be the common Pc4-5 waves associated with field line resonances. We suggest that these unique Pc2-3 waves seen by ST-5 are in fact the Doppler-shifted Pc4-5 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-dusk orbits at proper altitudes and magnetic latitudes reveal the azimuthal characteristics of field line resonances.

  12. Generation of large-amplitude electric field and subsequent enhancement of O+ ion flux in the inner magnetosphere during substorms

    NASA Astrophysics Data System (ADS)

    Nakayama, Y.; Ebihara, Y.; Tanaka, T.

    2015-06-01

    Energetic O+ ions are rapidly enhanced in the inner magnetosphere because of abrupt intensification of the dawn-to-dusk electric field and significantly contribute to the ring current during substorms. Here we examine the generation mechanism of the dawn-to-dusk electric field that accelerates the O+ ions and the spatial and temporal evolution of the differential flux of the O+ ions by using a test particle simulation in the electric and magnetic fields that are provided by a global magnetohydrodynamics (MHD) simulation. In the MHD simulation, strong dawn-to-dusk electric field appears in the near-Earth tail region by a joint action of the earthward tension force and pileup of magnetic flux near an onset of substorm expansion. The peak of the electric field is ~9-13 mV/m and is located ~1-2 RE earthward of the peak of the plasma bulk speed because of the pileup. O+ ions coming from the lobe are accelerated from ~eV to >100 keV in ~10 min. The reconstructed flux of the O+ ions shows that at ~7 RE near midnight, the flux has a peak near a few tens of keV and the flux below ~10 keV is small. This structure, called a "void" structure, is consistent with the Polar observation and can be regarded as a manifestation of the acceleration of unmagnetized ions perpendicular to the magnetic field. In the inner magnetosphere (at 6.0 RE), reconstructed energy-time spectrograms show the nose dispersion structure that is also consistent with satellite observations.

  13. Strain- and sex-specific differences in daily flight activity and the circadian clock of Anopheles gambiae mosquitoes.

    PubMed

    Rund, Samuel S C; Lee, Samuel J; Bush, Brian R; Duffield, Giles E

    2012-12-01

    Anopheles gambiae, the primary African malaria vector, is currently speciating into two incipient species, the so-called "molecular forms" M and S. While some geographic areas may contain only one form, in many areas both forms are found coexisting, but reproductively isolated. It appears that spatial segregation of mating swarms may contribute significantly to reproductive isolation as in many locales single-form swarms exist almost exclusively even though they are in close geographic proximity. The mechanism causing this spatial segregation is not well understood. Here, we compare the locomotor flight activity of M and S form male and female An. gambiae mosquitoes with the goal of identifying potential strain-specific temporal differences that could potentially serve as a mating barrier. We use an infrared beam break method to monitor flight activity of individual mosquitoes with a minute-to-minute time resolution under both LD cycle and constant dark conditions. We compare daily total flight activity, activity onset, peak in early nocturnal activity, the build up of dusk-related activity, and the free-running circadian period length. Our investigations revealed strain- and sex-specific differences in total daily activity. In both forms, males commenced nightly flight activity earlier than females, and this corresponded with a significantly shorter circadian period length in males compared to females. We note strain-specific differences in this response to dusk as males of the M form have a pronounced build up in flight activity relative to the S form males prior to complete darkness. This is likely driven by a differential response to the decreasing light intensity at dusk. We hypothesize that this behavioral difference could be a temporal factor contributing to the assembly of single-form swarms. PMID:23068991

  14. Observations of Thermospheric Horizontal Winds at Watson Lake, Yukon Territory (lambda=65 Deg N)

    NASA Technical Reports Server (NTRS)

    Niciejewski, R. J.; Killeen, T. L.; Solomon, Stanley C.

    1996-01-01

    Fabry-Perot interferometer observations of the thermospheric O I (6300 A) emission have been conducted from an airglow observatory at a dark field site in the southeastern Yukon Territory, Canada, for the period November 1991 to April 1993. The experiment operated in unattended, remote fashion, has resulted in a substantial data set from which mean neutral winds have been determined. Dependent upon geomagnetic activity, the nocturnal location of the site is either equatorward of the auroral oval or within oval boundaries. The data set is rich enough to permit hourly binning of neutral winds based upon the K(sub p) geomagnetic disturbance index as well as the season. For cases of low geomagnetic activity the averaged vector horizontal neutral wind exhibits the characteristics of a midlatitude site displaying antisunward pressure-gradient-driven winds. As the geomagnetic activity rises in the late afternoon and evening winds slowly rotate sunward in an anticlockwise direction, initially remaining near 100 m/s in speed but eventually increasing to 300 m/s for K(sub p) greater than 5. For the higher levels of activity the observed neutral wind flow pattern resembles a higher-latitude polar cap pattern characterized by ion drag forcing of thermospheric neutral gases. In addition, rotational Coriolis forcing on the dusk side enhances the ion drag forcing, resulting in dusk winds which trace out the clockwise dusk cell plasma flow. On the dawn side the neutral winds also rotate in an anticlockwise direction as the strength of geomagnetic disturbances increase. Since the site is located at a transition latitude between the midlatitude and the polar cap the data set provides a sensitive test for general circulation models which attempt to parameterize the contribution of magnetospheric processes. A comparison with the Vector Spherical Harmonic (VSH) model indicates several regions of poor correspondence for December solstice conditions but reasonable agreement for the

  15. The role of pollinators in maintaining variation in flower colour in the Rocky Mountain columbine, Aquilegia coerulea

    PubMed Central

    Thairu, Margaret W.; Brunet, Johanne

    2015-01-01

    Background and Aims Flower colour varies within and among populations of the Rocky Mountain columbine, Aquilegia coerulea, in conjunction with the abundance of its two major pollinators, hawkmoths and bumble-bees. This study seeks to understand whether the choice of flower colour by these major pollinators can help explain the variation in flower colour observed in A. coerulea populations. Methods Dual choice assays and experimental arrays of blue and white flowers were used to determine the preference of hawkmoths and bumble-bees for flower colour. A test was made to determine whether a differential preference for flower colour, with bumble-bees preferring blue and hawkmoths white flowers, could explain the variation in flower colour. Whether a single pollinator could maintain a flower colour polymorphism was examined by testing to see if preference for a flower colour varied between day and dusk for hawkmoths and whether bumble-bees preferred novel or rare flower colour morphs. Key Results Hawkmoths preferred blue flowers under both day and dusk light conditions. Naïve bumble-bees preferred blue flowers but quickly learned to forage randomly on the two colour morphs when similar rewards were presented in the flowers. Bees quickly learned to associate a flower colour with a pollen reward. Prior experience affected the choice of flower colour by bees, but they did not preferentially visit novel flower colours or rare or common colour morphs. Conclusions Differences in flower colour preference between the two major pollinators could not explain the variation in flower colour observed in A. coerulea. The preference of hawkmoths for flower colour did not change between day and dusk, and bumble-bees did not prefer a novel or a rare flower colour morph. The data therefore suggest that factors other than pollinators may be more likely to affect the flower colour variation observed in A. coerulea. PMID:25808657

  16. Penetration Electric Fields and Inner Magnetosphere Dynamics: A Model and Data Comparison

    NASA Technical Reports Server (NTRS)

    Maynard, Nelson C.

    1998-01-01

    Significant progress has been made on the analysis of the June, 1991 storm. We have completed the analysis of the CRRES and DMSP data sets. We have been able to follow the evolution during the storm of the inner edge of the electric field patterns in the dusk sector and its relation to electron boundaries, ion boundaries and the ring current. Whereas the CRRES data provide radial cuts out through the plasmasphere every I 0 hours, DMSP provides snapshots every orbit of the potential and particle boundaries. Electric field and energetic particle measurements from CRRES and ion drifts and energetic particle measurements from DMSP provide the principal data sets. The combined data set provides high resolution definition of the boundary motions over the phases of the storm. L shell differences between the DMSP and CRRES particle boundaries are easily explained by inflation of the dusk sector by the ring current. The electric field boundaries are typically associated with the ion boundary and the inner edge of the ring current except during rapid increases in the cross-polar cap potential. A significant fraction of the dusk cell potential is found inside the plasmasheet electron inner edge. Twice during the storm this potential exceeded 60 kV. A paper (copy attached) has been prepared (Burke et al., 1998) and submitted to JGR. An invited paper will be presented by Burke at the spring AGU meeting. An abstract has also been submitted to the COSPAR meeting for presentation by Maynard. New simulations have been carried out with the Rice Convection Model for the magnetic storm of June 4-5, 1991, and comparisons have been made with CRRES and DMSP data.

  17. Ion Measurements During Pioneer Venus Reentry: Implications for Solar Cycle Variation of Ion Composition and Dynamics

    NASA Technical Reports Server (NTRS)

    Grebowsky, J. M.; Hartle, R. E.; Kar, J.; Cloutier, P. A.; Taylor, H. A., Jr.; Brace, L. H.

    1993-01-01

    During the final, low solar activity phase of the Pioneer Venus mission, the Orbiter Ion Mass Spectrometer measurements found all ion species, in the midnight-dusk sector, reduced in concentration relative to that observed at solar maximum. Molecular ion species comprised a greater part of the total ion concentration as O(+) and H(+) had the greatest depletions. The nightside ionospheric states were strikingly similar to the isolated solar maximum "disappearing" ionospheres. Both are very dynamic states characterized by a rapidly drifting plasma and 30-100 eV superthermal O(+) ions.

  18. Ion measurements during Pioneer Venus reentry: Implications for solar cycle variation of ion composition and dynamics

    NASA Technical Reports Server (NTRS)

    Grebowsky, J. M.; Hartle, R. E.; Kar, J.; Cloutier, P. A.; Taylor, H. A., Jr.; Brace, L. H.

    1993-01-01

    During the final, low solar activity phase of the Pioneer Venus (PV) mission, the Orbiter Ion Mass Spectrometer (OIMS) measurements found all ion species, in the midnight-dusk sector, reduced in concentration relative to that observed at solar maximum. Molecular ion species comprised a greater part of the total ion concentration as O(+) and H(+) had the greatest depletions. The nightside ionospheric states were strikingly similar to the isolated solar maximum 'disappearing' ionospheres. Both are very dynamic states characterized by a rapidly drifting plasma and 30-100 eV superthermal O(+) ions.

  19. Woodcock feeding habits as related to summer field usage in central Maine

    USGS Publications Warehouse

    Krohn, W.B.

    1970-01-01

    In 1968 and 1969, 60 American woodcock (Philohela minor) were collected before and after alighting on summer fields in central Maine. A comparison of stomach contents from these birds showed that woodcock fed prior to entering fields at dusk. No evidence was found to indicate that any substantial amount of food was eaten by birds remaining on fields throughout the night. In 1968, the availability and abundance of known woodcock foods were measured in 30 soil samples from one field. Few woodcock foods were found in samples located randomly and at flush sites, thus providing no evidence that birds selected sites where soil invertebrates were concentrated.

  20. Relativistic electron precipitation at International Space Station: Space weather monitoring by Calorimetric Electron Telescope

    NASA Astrophysics Data System (ADS)

    Kataoka, Ryuho; Asaoka, Yoichi; Torii, Shoji; Terasawa, Toshio; Ozawa, Shunsuke; Tamura, Tadahisa; Shimizu, Yuki; Akaike, Yosui; Mori, Masaki

    2016-05-01

    The charge detector (CHD) of the Calorimetric Electron Telescope (CALET) on board the International Space Station (ISS) has a huge geometric factor for detecting MeV electrons and is sensitive to relativistic electron precipitation (REP) events. During the first 4 months, CALET CHD observed REP events mainly at the dusk to midnight sector near the plasmapause, where the trapped radiation belt electrons can be efficiently scattered by electromagnetic ion cyclotron (EMIC) waves. Here we show that interesting 5-20 s periodicity regularly exists during the REP events at ISS, which is useful to diagnose the wave-particle interactions associated with the nonlinear wave growth of EMIC-triggered emissions.

  1. Studying internal and external magnetic fields in Japan using MAGSAT data

    NASA Technical Reports Server (NTRS)

    Fukushima, N. (Principal Investigator); Maeda, H.; Yukutake, T.; Tanaka, M.; Oshima, S.; Ogawa, K.; Kawamura, M.; Miyazaki, Y.; Uyeda, S.; Kobayashi, K.

    1980-01-01

    Examination of the total intensity data of CHRONIT on a few paths over Japan and its neighboring sea shows MAGSAT is extremely useful for studying the local magnetic anomaly. In high latitudes, the signatures of field aligned currents are clearly recognized. These include (1) the persistent basic pattern of current flow; (2) the more intense currents in the summer hemisphere than in the winter hemisphere; (3) more fluctuations in current intensities in summer dawn hours; and (4) apparent dawn-dusk asymmetry in the field-aligned current intensity between the north and south polar regions.

  2. A simple model for polar cap convection patterns and generation of theta auroras

    NASA Technical Reports Server (NTRS)

    Lyons, L. R.

    1985-01-01

    An addition of the uniform interplanetary magnetic field and the earth's dipole magnetic field is used to evaluate electric field convection patterns over the polar caps that result from solar wind flow across open geomagnetic field lines. The model also accounts for field-aligned patterns within, and auroral arcs across, the polar cap. The qualitative predictions derived from the model express the electric field magnitudes, aurora intensity, sunward and antisunward flow, and the dusk-side reversal of the convection field in terms of the x and y components of the interplanetary magnetic field.

  3. A model of global convection in Jupiter's magnetosphere

    NASA Astrophysics Data System (ADS)

    Cheng, A. F.; Krimigis, S. M.

    1989-09-01

    Voyager observations of Jupiter's magnetosphere are compared with the planetary wind model in which corotation must break down outside some Alfven critical radius and a centrifugally driven wind outflow must develop. It is found that the model does not agree with the observations. A new global convection model for the Jovian magnetosphere is proposed, based on models of quasi-stationary plasma convection in the earth's magnetosphere. The model predicts a substantial dawn-dusk asymmetry in the structure, dynamics, and plasma composition of the magnetopause and magnetosheath. The model also predicts a region of cross-tail flow in the nightside plasma sheet containing a substantial admixture of solar wind plasma.

  4. Visual systems - The state of the art

    NASA Astrophysics Data System (ADS)

    Shorrock, David

    State-of-the-art, computer-generated image simulator visual systems typically encompass a data base which generates the model of the operating environment, an image generator, and a display system suitable for the applications envisaged. Two basic approaches to such systems are discernible: those employing hybrid raster/calligraphy and those using raster/continuous tone. Attention is presently given to such capabilities and elements of visual displays as texture effects, transparencies, fade level-of-detail management, animation effects, and image generator functions for daylight and night/dusk conditions, as well as prospective developments in this field.

  5. Does Solar Wind also Drive Convection in Jupiter's Magnetosphere?

    NASA Astrophysics Data System (ADS)

    Khurana, K. K.

    2001-05-01

    Using a simple model of magnetic field and plasma velocity, Brice and Ioannidis [1970] showed that the corotation electric field exceeds convection electric field throughout the Jovian magnetosphere. Since that time it has been tacitly assumed that Jupiter's magnetosphere is driven from within. If Brice and Ioannidis conjecture is correct then one would not expect major asymmetries in the field and plasma parameters in the middle magnetosphere of Jupiter. Yet, new field and plasma observations from Galileo and simultaneous auroral observations from HST show that there are large dawn/dusk and day/night asymmetries in many magnetospheric parameters. For example, the magnetic observations show that a partial ring current and an associated Region-2 type field-aligned current system exist in the magnetosphere of Jupiter. In the Earth's magnetosphere it is well known that the region-2 current system is created by the asymmetries imposed by a solar wind driven convection. Thus, we are getting first hints that the solar wind driven convection is important in Jupiter's magnetosphere as well. Other in-situ observations also point to dawn-dusk asymmetries imposed by the solar wind. For example, first order anisotropies in the Energetic Particle Detector show that the plasma is close to corotational on the dawn side but lags behind corotation in the dusk sector. Magnetic field data show that the current sheet is thin and highly organized on the dawn side but thick and disturbed on the dusk side. I will discuss the reasons why Brice and Ioannidis calculation may not be valid. I will show that both the magnetic field and plasma velocity estimates used by Brice and Ioannidis were rather excessive. Using more modern estimates of the field and velocity values I show that the solar wind convection can penetrate as deep as 40 RJ on the dawnside. I will present a new model of convection that invokes in addition to a distant neutral line spanning the whole magnetotail, a near

  6. Managing diabetes during the Muslim fasting month of Ramadan.

    PubMed

    Velayudhan, M

    2012-06-01

    Target blood sugar levels in diabetes are achieved through manipulation of diet, exercise and medication. A change in any one of these three things can skew blood sugar levels and create complications associated with hyperglycemia or hypoglycemia. Fasting during the month of Ramadan is a religious activity that devout Muslims practice whether they are diabetic or not. Since such fasting involves abstinence from food and water for twelve hours or more during the day from dawn to dusk, it is evident that advice regarding exercise and medication will have to be modified during this period.

  7. Magnetic latitude and local time distributions of ionospheric currents during a geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Tsuji, Yuji; Shinbori, Atsuki; Kikuchi, Takashi; Nagatsuma, Tsutomu

    2012-07-01

    In order to clarify the global distribution of ionospheric currents during a geomagnetic storm, we analyzed ground magnetic disturbances from high latitudes to the magnetic equator for the storm on September 7-8, 2002, with the minimum SYM-H value of -168 nT. In this analysis, we investigated magnetic field deviations in the northward component from the SYM-H, as functions of the dipole magnetic latitude (DMLAT) and the magnetic local time (MLT). During the main phase of the storm, the deviations at the low latitudes (10°-35° in DMLAT) were positive/negative in the dawn/dusk (0-9/11-24 h MLT) sector. On the other hand, the deviations at the dayside middle latitudes (35°-55° in DMLAT) were negative/positive in the morning/afternoon (6-12/13-15 h MLT) sector. The local time distribution at the low latitudes may represent the dawn-dusk asymmetry of the storm time ring current, while that at the dayside middle latitudes coincides with the DP2 currents due to the convection electric field associated with the Region 1 field-aligned currents (R1 FACs). All over the nightside middle latitude, the deviations were positive. This implies the direct effect of the R1 FACs through the Biot-Savart's law. At the geomagnetic equator, the eastward and westward electrojets were intensified on the day and nightside, respectively, being caused by the penetrated dawn-to-dusk convection electric field. We found that the MLT distribution of the magnetic deviations during the recovery phase was in opposite sense to that during the main phase at the dayside middle latitudes. The reversed magnetic disturbances must be due to the overshielding electric field associated with the Region 2 field-aligned currents (R2 FACs). Similarly, the deviations at the dayside and nightside equator were reversed, indicating penetration of the dusk-to-dawn overshielding electric field into the equatorial ionosphere. Based on the above results, we propose a current system including the ionospheric currents

  8. Opening the cusp. [using magnetic field topology

    NASA Technical Reports Server (NTRS)

    Crooker, N. U.; Toffoletto, F. R.; Gussenhoven, M. S.

    1991-01-01

    This paper discusses the magnetic field topology (determined by the superposition of dipole, image, and uniform fields) for mapping the cusp to the ionosphere. The model results are compared to both new and published observations and are then used to map the footprint of a flux transfer event caused by a time variation in the merging rate. It is shown that the cusp geometry distorts the field lines mapped from the magnetopause to yield footprints with dawn and dusk protrusions into the region of closed magnetic flux.

  9. Equatorial transport of Saturn's ionosphere as driven by a dust-ring current system

    SciTech Connect

    Ip, W.; Mendis, D.A.

    1983-03-01

    The diurnal modulation of the dust ring current of Saturn's D-ring causes field-aligned Birkeland currents ot flow near the dawn and dusk terminators and close across the mid-latitude ionosphere. One consequence of this current system is the establishment of a global convection pattern in the equatorial outer ionosphere. Outward motion of the dayside ionosheric plasma as well as the corresponding absorption effect of the inner ring system might be one physical cause of the depletion of the ionospheric content of Saturn.

  10. Plasma composition in Jupiter's magnetosphere - Initial results from the Solar Wind Ion Composition Spectrometer

    NASA Technical Reports Server (NTRS)

    Geiss, J.; Gloeckler, G.; Balsiger, H.; Fisk, L. A.; Galvin, A. B.; Gliem, F.; Hamilton, D. C.; Ipavich, F. M.; Livi, S.; Mall, U.

    1992-01-01

    The ion composition in the Jovian environment was investigated with the Solar Wind Ion Composition Spectrometer on board Ulysses. A hot tenuous plasma was observed throughout the outer and middle magnetosphere. In some regions two thermally different components were identified. Oxygen and sulfur ions with several different charge states, from the volcanic satellite Io, make the largest contribution to the mass density of the hot plasma, even at high latitude. Solar wind particles were observed in all regions investigated. Ions from Jupiter's ionosphere were abundant in the middle magnetosphere, particularly in the high-latitude region on the dusk side, which was traversed for the first time.

  11. Central Plasma Sheet Ion Properties as Inferred from Ionospheric Observations

    NASA Technical Reports Server (NTRS)

    Wing, Simon; Newell, Patrick T.

    1998-01-01

    A method of inferring central plasma sheet (CPS) temperature, density, and pressure from ionospheric observations is developed. The advantage of this method over in situ measurements is that the CPS can be studied in its entirely, rather than only in fragments. As a result, for the first time, comprehensive two-dimensional equatorial maps of CPS pressure, density, and temperature within the isotropic plasma sheet are produced. These particle properties are calculated from data taken by the Special Sensor for Precipitating Particles, version 4 (SSJ4) particle instruments onboard DMSP F8, F9, F10, and F11 satellites during the entire year of 1992. Ion spectra occurring in conjunction with electron acceleration events are specifically excluded. Because of the variability of magnetotail stretching, the mapping to the plasma sheet is done using a modified Tsyganenko [1989] magnetic field model (T89) adjusted to agree with the actual magnetotail stretch at observation time. The latter is inferred with a high degree of accuracy (correlation coefficient -0.9) from the latitude of the DMSP b2i boundary (equivalent to the ion isotropy boundary). The results show that temperature, pressure, and density all exhibit dawn-dusk asymmetries unresolved with previous measurements. The ion temperature peaks near the midnight meridian. This peak, which has been associated with bursty bulk flow events, widens in the Y direction with increased activity. The temperature is higher at dusk than at dawn, and this asymmetry increases with decreasing distance from the Earth. In contrast, the density is higher at dawn than at dusk, and there appears to be a density enhancement in the low-latitude boundary layer regions which increases with decreasing magnetic activity. In the near-Earth regions, the pressure is higher at dusk than at dawn, but this asymmetry weakens with increasing distance from the Earth and may even reverse so that at distances X less than approx. 10 to -12 R(sub E

  12. Aspects of Clock Resetting in Flowering of Xanthium 1

    PubMed Central

    Papenfuss, Herbert D.; Salisbury, Frank B.

    1967-01-01

    Flowering is induced in Xanthium strumarium by a single dark period exceeding about 8.3 hours in length (the critical night). To study the mechanism which measures this dark period, plants were placed in growth chambers for about 2 days under constant light and temperature, given a phasing dark period terminated by an intervening light period (1 min to several hrs in duration), and finally a test dark period long enough normally to induce flowering. In some experiments, light interruptions during the test dark period were given to establish the time of maximum sensitivity. If the phasing dark period was less than 5 hours long, its termination by a light flash only broadened the subsequent time of maximum sensitivity to a light flash, but the critical night was delayed. In causing the delay, the end of the intervening light period was acting like the dusk signal which initiated time measurement at the beginning of the phasing dark period. If the phasing dark period was 6 hours or longer, time of maximum sensitivity during the subsequent test dark period was shifted by as much as 10 to 14 hours. In this case the light terminating the phasing dark period acted as a rephaser or a dawn signal. Following a 7.5-hour phasing dark period, intervening light periods of 1 minute to 5 hours did not shift the subsequent time of maximum sensitivity, but with intervening light periods longer than 5 hours, termination of the light acts clearly like a dusk signal. The clock appears to be suspended during intervening light periods longer than 5 to 15 hours. It is restarted by a dusk signal. There is an anomaly with intervening light periods of 10 to 13 hours, following which time of maximum sensitivity is actually less than the usual 8 hours after dusk. Ability of the clock in Xanthium to be rephased, suspended, restarted, or delayed, depending always upon conditions of the experiment, is characteristic of an oscillating timer and may confer upon this plant its ability to respond to

  13. Plasma Composition in Jupiter's Magnetosphere: Initial Results from the Solar Wind Ion Composition Spectrometer.

    PubMed

    Geiss, J; Gloeckler, G; Balsiger, H; Fisk, L A; Galvin, A B; Gliem, F; Hamilton, D C; Ipavich, F M; Livi, S; Mall, U; Ogilvie, K W; von Steiger, R; Wilken, B

    1992-09-11

    The ion composition in the Jovian environment was investigated with the Solar Wind Ion Composition Spectrometer on board Ulysses. A hot tenuous plasma was observed throughout the outer and middle magnetosphere. In some regions two thermally different components were identified. Oxygen and sulfur ions with several different charge states, from the volcanic satellite lo, make the largest contribution to the mass density of the hot plasma, even at high latitude. Solar wind particles were observed in all regions investigated. Ions from Jupiter's ionosphere were abundant in the middle magnetosphere, particularly in the highlatitude region on the dusk side, which was traversed for the first time.

  14. Satellite telemetry and wildlife studies in India: Advantages, options and challenges

    USGS Publications Warehouse

    Javed, S.; Higuchi, H.; Nagendran, Meenakshi; Takekawa, J.Y.

    2003-01-01

    In 1968 and 1969, 60 American woodcock (Philohela minor) were collected before and after alighting on summer fields in central Maine. A comparison of stomach contents from these birds showed that woodcock fed prior to entering fields at dusk. No evidence was found to indicate that any substantial amount of food was eaten by birds remaining on fields throughout the night. In 1968, the availability and abundance of known woodcock foods were measured in 30 soil samples from one field. Few woodcock foods were found in samples located randomly and at flush sites, thus providing no evidence that birds selected sites where soil invertebrates were concentrated.

  15. On the equatorial transport of Saturn's ionosphere as driven by a dust-ring current system

    NASA Astrophysics Data System (ADS)

    Ip, W.-H.; Mendis, D. A.

    1983-03-01

    The diurnal modulation of the dust ring current of Saturn's D-ring causes field-aligned Birkeland currents to flow near the dawn and dusk terminators and close across the mid-latitude ionosphere. One consequence of this current system is the establishment of a global convection pattern in the equatorial outer ionosphere. Outward motion of the dayside ionospheric plasma as well as the corresponding absorption effect of the inner ring system might be one physical cause of the depletion of the ionospheric content of Saturn.

  16. Polarized skylight does not calibrate the compass system of a migratory bat.

    PubMed

    Lindecke, Oliver; Voigt, Christian C; Pētersons, Gunārs; Holland, Richard A

    2015-09-01

    In a recent study, Greif et al. (Greif et al. Nat Commun 5, 4488. (doi:10.1038/ncomms5488)) demonstrated a functional role of polarized light for a bat species confronted with a homing task. These non-migratory bats appeared to calibrate their magnetic compass by using polarized skylight at dusk, yet it is unknown if migratory bats also use these cues for calibration. During autumn migration, we equipped Nathusius' bats, Pipistrellus nathusii, with radio transmitters and tested if experimental animals exposed during dusk to a 90° rotated band of polarized light would head in a different direction compared with control animals. After release, bats of both groups continued their journey in the same direction. This observation argues against the use of a polarization-calibrated magnetic compass by this migratory bat and questions that the ability of using polarized light for navigation is a consistent feature in bats. This finding matches with observations in some passerine birds that used polarized light for calibration of their magnetic compass before but not during migration.

  17. Epithermal Neutron Evidence for a Diurnal Surface Hydration Process in the Moon's High Latitudes

    NASA Technical Reports Server (NTRS)

    McClanahan, T. P.; Mitrofanov, I. G.; Boynton, W. V.; Chin, G.; Parsons, A.; Starr, R. D.; Evans, L. G.; Sanin, A.; Litvak, M.; Livengood, T.

    2015-01-01

    We report evidence from epithermal neutron flux observations that show that the Moon's high latitude surfaces are being actively hydrated, dehydrated and rehydrated in a diurnal cycle. The near-surface hydration is indicated by an enhanced suppression of the lunar epithermal neutron leakage flux on the dayside of the dawn terminator on poleward-facing slopes (PFS). At 0600 to 0800 local-time, hydrogen concentrations within the upper 1 meter of PFS are observed to be maximized relative to equivalent equator-facing slopes (EFS). During the lunar day surface hydrogen concentrations diminish towards dusk and then rebuild overnight. Surface hydration is determined by differential comparison of the averaged EFS to PFS epithermal neutron count rates above +/- 75 deg latitude. At dawn the contrast bias towards PFS is consistent with at least 15 to 25 parts-per-million (ppm) hydrogen that dissipates by dusk. We review several lines of evidence derived from temperature and epithermal neutron data by a correlated analysis of observations from the Lunar Reconnaissance Orbiter's (LRO) Lunar Exploration Neutron Detector (LEND) that were mapped as a function of lunar local-time, Lunar Observing Laser Altimeter (LOLA) topography and Diviner (DLRE) surface temperature.

  18. Polarized skylight does not calibrate the compass system of a migratory bat

    PubMed Central

    Lindecke, Oliver; Voigt, Christian C.; Pētersons, Gunārs; Holland, Richard A.

    2015-01-01

    In a recent study, Greif et al. (Greif et al. Nat Commun 5, 4488. (doi:10.1038/ncomms5488)) demonstrated a functional role of polarized light for a bat species confronted with a homing task. These non-migratory bats appeared to calibrate their magnetic compass by using polarized skylight at dusk, yet it is unknown if migratory bats also use these cues for calibration. During autumn migration, we equipped Nathusius' bats, Pipistrellus nathusii, with radio transmitters and tested if experimental animals exposed during dusk to a 90° rotated band of polarized light would head in a different direction compared with control animals. After release, bats of both groups continued their journey in the same direction. This observation argues against the use of a polarization-calibrated magnetic compass by this migratory bat and questions that the ability of using polarized light for navigation is a consistent feature in bats. This finding matches with observations in some passerine birds that used polarized light for calibration of their magnetic compass before but not during migration. PMID:26382077

  19. Distribution of H2 in the Lunar Exosphere from LAMP Observations

    NASA Astrophysics Data System (ADS)

    Hurley, Dana; Retherford, Kurt; Cook, Jason; Grava, Cesare; Greathouse, Thomas; Gladstone, Randy; Stern, Alan

    2014-11-01

    Hydrogen gas (H2) has been detected in the Moon’s exosphere. It was identified spectrally during the LCROSS impact plume (Gladstone et al., 2010). Then it was found in LAMP data from the nominal exosphere (Stern et al., 2013). We examine the distribution of H2 in the lunar exosphere using a Monte Carlo model and data from the Lyman Alpha Mapping Project (LAMP) FUV imaging spectrograph onboard the Lunar Reconnaissance Orbiter (LRO). LAMP observations made in twilight, i.e., through illuminated exosphere, but with a footprint on the nightside of the Moon, are routinely made with LRO. However, during times when the beta angle of the orbit is close to beta=90°, a great portion of the nightside orbit is in the twilight viewing geometry. Using data from just behind the terminator on the post-dusk and pre-dawn sides, we compile a cumulative spectrum throughout LAMP’s bandpass. A dawn/dusk asymmetry is detected in the H2 abundance. Modeling is used to decipher the release mechanism and source distribution of diatomic hydrogen that best fits the observations. We examine the source rate and the total mass of the H2 exosphere consistent with the observations.

  20. Low-frequency wave activity related to dipolarization fronts detected by MMS in the magnetotail

    NASA Astrophysics Data System (ADS)

    Le Contel, O.; Retino, A.; Breuillard, H.; Mirioni, L.; Roux, A.; Chust, T.; Chasapis, A.; Lavraud, B.; Lindqvist, P. A.; Khotyaintsev, Y. V.; Vaivads, A.; Fu, H.; Marklund, G. T.; Nakamura, R.; Burch, J. L.; Torbert, R. B.; Moore, T. E.; Ergun, R.; Goodrich, K.; Needell, J.; Chutter, M.; Rau, D.; Dors, I.; Russell, C. T.; Magnes, W.; Strangeway, R. J.; Le, G.; Bromund, K. R.; Plaschke, F.; Fischer, D.; Leinweber, H. K.; Anderson, B. J.; Argall, M. R.; Slavin, J. A.; Kepko, L.; Baumjohann, W.; Pollock, C. J.; Mauk, B.; Fuselier, S. A.

    2015-12-01

    Dipolarization fronts are often associated to reconnection jets in the magnetotail current sheet and are sites of important energy dissipation and particle energization. Since the launch on March 12th and until the 9th of July 2015, the MMS constellation has been moving from dawn to dusk in a string of pearls formation. Although particle instruments were rarely operating and only FIELDS instrument suite was often gathering data, the MMS spacecraft have detected numerous dipolarization fronts, in particular on May 15th. Since 9th of July, the MMS evolved into a tetrahedral configuration with an average inter-satellite distance of 160 km and was still able to detect dipolarization fronts in the dusk magnetotail. As the Larmor radius of thermal protons is about 500 km in this region and dipolarization fronts have a typical thickness of the order of the Larmor radius, such a separation allows us to investigate in detail the microphysics of dipolarization fronts. In this study, we focus in particular on low-frequency electromagnetic wave activity related to the fronts and discuss possible mechanisms of particle heating and acceleration both at large scales (string of pearls configuration) and at kinetic scales (tetrahedral configuration).

  1. Observational test of shock drift and Fermi acceleration on a seed particle population upstream of earth's bow shock

    NASA Technical Reports Server (NTRS)

    Anagnostopoulos, G. C.; Sarris, E. T.; Krimigis, S. M.

    1988-01-01

    The efficiency of proposed shock acceleration mechanisms as they operate at the bow shock in the presence of a seed energetic particle population was examined using data from simultaneous observations of energetic solar-origin protons, carried out by the IMP 7 and 8 spacecraft in the vicinity of the quasi-parallel (dawn) and quasi-perpendicular (dusk) regions of the earth's bow shock, respectively. The results of observations (which include acceleration effects in the intensities of the energetic protons with energies as high as 4 MeV observed at the vicinity of the dusk bow shock, but no evidence for any particle acceleration at the energy equal to or above 50 keV at the dawn side of the bow shock) indicate that the acceleration of a seed particle population occurs only at the quasi-perpendicular bow shock through shock drift acceleration and that the major source of observed upstream ion populations is the leakage of magnetospheric ions of energies not less than 50 keV, rather than in situ acceleration.

  2. Woody clockworks: circadian regulation of night-time water use in Eucalyptus globulus.

    PubMed

    Resco de Dios, Víctor; Díaz-Sierra, Rubén; Goulden, Michael L; Barton, Craig V M; Boer, Matthias M; Gessler, Arthur; Ferrio, Juan Pedro; Pfautsch, Sebastian; Tissue, David T

    2013-11-01

    The role of the circadian clock in controlling the metabolism of entire trees has seldom been considered. We tested whether the clock influences nocturnal whole-tree water use. Whole-tree chambers allowed the control of environmental variables (temperature, relative humidity). Night-time stomatal conductance (gs ) and sap flow (Q) were monitored in 6- to 8-m-tall Eucalyptus globulus trees during nights when environmental variables were kept constant, and also when conditions varied with time. Artificial neural networks were used to quantify the relative importance of circadian regulation of gs and Q. Under a constant environment, gs and Q declined from 0 to 6 h after dusk, but increased from 6 to 12 h after dusk. While the initial decline could be attributed to multiple processes, the subsequent increase is most consistent with circadian regulation of gs and Q. We conclude that endogenous regulation of gs is an important driver of night-time Q under natural environmental variability. The proportion of nocturnal Q variation associated with circadian regulation (23-56%) was comparable to that attributed to vapor pressure deficit variation (25-58%). This study contributes to our understanding of the linkages between molecular and cellular processes related to circadian regulation, and whole-tree processes related to ecosystem gas exchange in the field. PMID:23795820

  3. Diurnal lighting patterns and habitat alter opsin expression and colour preferences in a killifish

    PubMed Central

    Johnson, Ashley M.; Stanis, Shannon; Fuller, Rebecca C.

    2013-01-01

    Spatial variation in lighting environments frequently leads to population variation in colour patterns, colour preferences and visual systems. Yet lighting conditions also vary diurnally, and many aspects of visual systems and behaviour vary over this time scale. Here, we use the bluefin killifish (Lucania goodei) to compare how diurnal variation and habitat variation (clear versus tannin-stained water) affect opsin expression and the preference to peck at different-coloured objects. Opsin expression was generally lowest at midnight and dawn, and highest at midday and dusk, and this diurnal variation was many times greater than variation between habitats. Pecking preference was affected by both diurnal and habitat variation but did not correlate with opsin expression. Rather, pecking preference matched lighting conditions, with higher preferences for blue at noon and for red at dawn/dusk, when these wavelengths are comparatively scarce. Similarly, blue pecking preference was higher in tannin-stained water where blue wavelengths are reduced. In conclusion, L. goodei exhibits strong diurnal cycles of opsin expression, but these are not tightly correlated with light intensity or colour. Temporally variable pecking preferences probably result from lighting environment rather than from opsin production. These results may have implications for the colour pattern diversity observed in these fish. PMID:23698009

  4. DMSP F8 observations of the mid-latitude and low-latitude topside ionosphere near solar minimum

    SciTech Connect

    Greenspan, M.E.; Hughes, W.J. |; Burke, W.J.; Rich, F.J.; Heelis, R.A.

    1994-03-01

    The retarding potential analyzer on the DMSP F8 satellite measured ion density, composition, temperature, and ram flow velocity at 840-km altitude near the dawn and dusk meridians close to solar minimum. Nine days of data were selected for study to represent the summer and winter solstices and the autumnal equinox under quiet, moderately active, and disturbed geomagnetic conditions. The observations revealed extensive regions of light-ion dominance along both the dawn and dusk legs of the DMSP F8 orbit. These regions showed seasonal, longitudinal, and geomagnetic control, with light ions commonly predominating in places where the subsatellite ionosphere was relatively cold. Field-aligned plasma flows also were detected. In the morning, ions flowed toward the equator from both sides. In the evening, DMSP F8 detected flows that either diverged away from the equator or were directed toward the northern hemisphere. The effects of diurnal variations in plasma pressure gradients in the ionosphere and plasmasphere, momentum coupling between neutral winds and ions at the feet of field lines, and E {times} B drifts qualitatively explain most features of these composition and velocity measurements. 23 refs., 5 figs., 2 tabs.

  5. Global equatorial ionospheric vertical plasma drifts measured by the AE-E satellite

    SciTech Connect

    Fejer, B.G.; Paula, E.R. de l Heelis, R.A.

    1995-04-01

    Ion drift meter observations from the Atmospheric Explorer E satellite during the period of January 1977 to December 1979 are used to study the dependence of equatorial (dip latitudes {le}7.5{degrees}) F region vertical plasma drifts (east-west electric fields) on solar activity, season, and longitude. The satellite-observed ion drifts show large day-to-day and seasonal variations. Solar cycle effects are most pronounced near the dusk sector with a large increase of the prereversal velocity enhancement from solar minimum to maximum. The diurnal, seasonal, and solar cycle dependence of the longitudinally averaged drifts are consistent with results from the Jicamarca radar except near the June solstice when the AE-E nightime downward velocities are significantly smaller than those observed by the radar. Pronounced presunrise downward drift enhancements are often observed over a large longitudinal range but not in the Peruvian equatorial region. The satellite data indicate that longitudinal variations are largest near the June solstice, particularly near dawn and dusk but are virtually absent during equinox. The longitudinal dependence of the AE-E vertical drifts is consistent with results from ionosonde data. These measurements were also used to develop a description of equatorial F region vertical drifts in four longitudinal sectors. 17 refs., 7 figs.

  6. 3D PIC Simulation of the Magnetosphere during IMF Rotation from North to South: Signatures of Substorm Triggering in the Magnetotail

    NASA Technical Reports Server (NTRS)

    Nishikawa, Ken-Ichi; Cao. D/ S/; Lembege, B.

    2008-01-01

    Three dimensional PIC simulations are performed in order to analyse the dynamics of the magnetotail as the interplanetary magnetic field (IMF) rotates from northward to southward direction. This dynamics reveals to be quite different within meridian/equatorial planes over two successive phases of this rotation. First, as IMF rotates from North to Dawn-Dusk direction, the X-Point (magnetic reconnection) evidenced in the magnetotail (meridian plane) is moving earthward (from x=-35 Re to x=-17.5 ) distance at which it stabilizes. This motion is coupled with the formation of "Crosstail-S" patterns (within the plane perpendicular to the Sun-Earth mine) through the neutral sheet in the nearby magnetotail. Second, as IMF rotates from dawn-dusk to South, the minimum B field region is expanding within the equatorial plane and forms a ring. This two-steps dynamics is analyzed in strong association with the cross field magnetotail current Jy, in order to recover the signatures of substorms triggering.

  7. Coordinated THEMIS and ground-based magnetometer study of ULF wave excitation during a fast solar wind stream

    NASA Astrophysics Data System (ADS)

    Mann, Ian; Rae, Jonathan; Larson, Davin; Glassmeier, Karl-Heinz; Bonnell, J. W.; Kale, Zoe; McFadden, James; Singer, Howard; Angelopoulos, V.; Russell, Christopher; Auster, Uli; Mende, Stephen

    AB: We present results from a study of ULF waves observed during a conjunction between the THEMIS constellation and ground-based magnetometers of the combined CARISMA and THEMIS ground-based observatory (GBO) arrays during a fast solar wind stream in August 2007. Long wavetrain waves in the Pc4 and Pc5 bands were seen across the ground-based arrays during a conjugate overpass of the THEMIS constellation in the dusk magnetosphere over CARISMA on August 8th. The Pc4 waves, also seen on THEMIS, were very monochromatic with many characteristics reminiscent of giant pulsations (Pgs) except that they occurred in the dusk sector. The multiple satellite measurements, including supporting measurements from GOES satellites in this sector, allow characterization of the wavenumbers, spatial scale, and comparison of the widths of the waves on the ground and in space. The monochromatic nature of the Pc4 waves, and their dominant polarization in the D-component on the ground, suggests that they are poloidal Alfven waves perhaps driven by injected ions in the afternoon-side magnetosphere. We use the unique capabilities of the combined THEMIS-GOES constellation, and the extensive ground-based coverage, to address the issue of the source of wave excitation during this high speed stream. Attention is given to internal excitation by energetic ions spectra.

  8. Coordinated THEMIS and ground-based magnetometer study of ULF wave excitation during a fast solar wind stream

    NASA Astrophysics Data System (ADS)

    Mann, I. R.; Rae, I. J.; Glassmeier, K.; Mende, S. B.; Angelopoulos, V.; Auster, U.; Russell, C. T.; Singer, H. J.; Bonnell, J. W.; Mozer, F. S.; Larson, D.; Carlson, C.; McPhadden, J.

    2007-12-01

    We present results from a study of ULF waves observed during a conjunction between the THEMIS constellation and ground-based magnetometers of the combined CARISMA and THEMIS ground-based observatory (GBO) arrays during a fast solar wind stream in August 2007. Long wavetrain waves in the Pc4 and Pc5 bands were seen across the ground-based arrays during a conjugate overpass of the THEMIS constellation in the dusk magnetosphere over CARISMA on August 8th. The Pc4 waves, also seen on THEMIS, were very monochromatic with many characteristics reminiscent of giant pulsations (Pgs) except that they occurred in the dusk sector. The multiple satellite measurements, including supporting measurements from GOES satellites in this sector, allow characterization of the wavenumbers, spatial scale, and comparison of the widths of the waves on the ground and in space. The monochromatic nature of the Pc4 waves, and their dominant polarization in the D-component on the ground, suggests that they are poloidal Alfven waves perhaps driven by injected ions in the afternoon-side magnetosphere. We use the unique capabilities of the combined THEMIS-GOES constellation, and the extensive ground-based coverage, to address the issue of the source of wave excitation during this high speed stream. Attention is given to internal excitation by energetic ions spectra, and drivers at the dayside magnetopause.

  9. Comparison between ionospheric convection vortices and the associated equivalent currents

    NASA Astrophysics Data System (ADS)

    Liang, J.; Benkevitch, L.; Sofko, G. J.; Koustov, A. V.

    2004-12-01

    The equivalent current pattern derived from CANOPUS, NRCAN/GSC and MACCS magnetometers has been compared with the ionospheric convection pattern observed by SuperDARN HF radars. The discrepancies between the equivalent convection (EQC) and the SuperDARN-observed convection (SDC) patterns are explained in terms of the effect of day-night photoionization conductance gradient and the coupling between field-aligned currents (FACs) and ionospheric conductances. In particular, the agreement between the EQC and SDC patterns is usually worse for a counterclockwise convection vortex than for a clockwise cell, but a consistent pattern of discrepancy for counterclockwise convection vortices has been found. We suggest that the discrepancies are due to a downward FAC-conductance coupling process. Since the counterclockwise vortices and clockwise vortices occur predominantly in the dawn and dusk sectors, respectively, in accordance with the usual 2-cell global convection pattern, the asymmetry between the EQC and SDC patterns for counterclockwise vortices and clockwise vortices would naturally lead to a dawn-dusk asymmetry as well. This is revealed by a global statistical study of the deviation of direction between the magnetic equivalent convection and the SuperDARN convection in different time sectors and latitudes. In the dawn sector, the statistical results reveal that, at lower latitudes, the EQC direction deviation is slightly counterclockwise with respect to the SDC direction, whereas the deviation is significantly clockwise at high latitudes. These deviations are consistent with the discrepancy pattern for counterclockwise convection vortices, as found in the individual vortex event studies.

  10. Polarized skylight does not calibrate the compass system of a migratory bat.

    PubMed

    Lindecke, Oliver; Voigt, Christian C; Pētersons, Gunārs; Holland, Richard A

    2015-09-01

    In a recent study, Greif et al. (Greif et al. Nat Commun 5, 4488. (doi:10.1038/ncomms5488)) demonstrated a functional role of polarized light for a bat species confronted with a homing task. These non-migratory bats appeared to calibrate their magnetic compass by using polarized skylight at dusk, yet it is unknown if migratory bats also use these cues for calibration. During autumn migration, we equipped Nathusius' bats, Pipistrellus nathusii, with radio transmitters and tested if experimental animals exposed during dusk to a 90° rotated band of polarized light would head in a different direction compared with control animals. After release, bats of both groups continued their journey in the same direction. This observation argues against the use of a polarization-calibrated magnetic compass by this migratory bat and questions that the ability of using polarized light for navigation is a consistent feature in bats. This finding matches with observations in some passerine birds that used polarized light for calibration of their magnetic compass before but not during migration. PMID:26382077

  11. The global context of the 14 November 2012 storm event

    SciTech Connect

    Hwang, K. -J.; Sibeck, D. G.; Fok, M. -C. H.; Zheng, Y.; Nishimura, Y.; Lee, J. -J.; Glocer, A.; Partamies, N.; Singer, H. J.; Reeves, G. D.; Mitchell, D. G.; Kletzing, C. A.; Onsager, T.

    2015-03-01

    From 2 to 5 UT on 14 November 2012, the Van Allen Probes observed repeated particle flux dropouts during the main phase of a geomagnetic storm as the satellites traversed the post-midnight to dawnside inner magnetosphere. Each flux dropout corresponded to an abrupt change in the magnetic topology, i.e., from a more dipolar configuration to a configuration with magnetic field lines stretched in the dawn-dusk direction. Geosynchronous GOES spacecraft located in the dusk and near-midnight sectors and the LANL constellation with wide local time coverage also observed repeated flux dropouts and stretched field lines with similar occurrence patterns to those of the Van Allen Probe events. THEMIS recorded multiple transient abrupt expansions of the evening-side magnetopause ~20–30 min prior to the sequential Van Allen Probes observations. Ground-based magnetograms and all sky images demonstrate repeatable features in conjunction with the dropouts. We combine the various in-situ and ground-based measurements to define and understand the global spatiotemporal features associated with the dropouts observed by the Van Allen Probes. We discuss various proposed hypotheses for the mechanism that plausibly caused this storm-time dropout event as well as formulate a new hypothesis that explains the combined in-situ and ground-based observations: the earthward motion of magnetic flux ropes containing lobe plasmas that form along an extended magnetotail reconnection line in the near-Earth plasma sheet.

  12. The interaction of a magnetic cloud with the Earth - Ionospheric convection in the Northern and Southern Hemispheres for a wide range of quasi-steady interplanetary magnetic field conditions

    NASA Technical Reports Server (NTRS)

    Freeman, M. P.; Farrugia, C. J.; Burlaga, L. F.; Hairston, M. R.; Greenspan, M. E.; Ruohoniemi, J. M.; Lepping, R. P.

    1993-01-01

    Observations are presented of the ionospheric convection in cross sections of the polar cap and auroral zone as part of the study of the interaction of the Earth's magnetosphere with the magnetic cloud of January 13-15, 1988. For strongly northward IMF, the convection in the Southern Hemisphere is characterized by a two-cell convection pattern comfined to high latitudes with sunward flow over the pole. The strength of the flows is comparable to that later seen under southward IMF. Superimposed on this convection pattern there are clear dawn-dusk asymmetries associated with a one-cell convection component whose sense depends on the polarity of the magnetic cloud's large east-west magnetic field component. When the cloud's magnetic field turns southward, the convection is characterized by a two-cell pattern extending to lower latitude with antisunward flow over the pole. There is no evident interhemispheric difference in the structure and strength of the convection. Superimposed dawn-dusk asymmetries in the flow patterns are observed which are only in part attributable to the east-west component of the magnetic field.

  13. On the IMF BY dependence on polar cap patch exits at night

    NASA Astrophysics Data System (ADS)

    Moen, J.; Hosokawa, K.; Gulbrandsen, N.

    2012-04-01

    Polar cap patches are islands of enhanced F-region electron density within the polar cap. They form near the cusp inflow region at day, transit the polar cap when frozen into twin-cell convection, and finally exit the polar cap at night into the night time auroras. When exiting they change status from patches to blobs. Monitoring the presence of F-region plasma structures and their travel path is essential in order to develop reliable space weather forecasts for the high latitude ionosphere in future. This paper presents a comprehensive study of a sequence of polar cap patches that exit the polar cap. Superimposing satellite images of the auroral oval and all-sky camera observations of airglow patches onto SuperDARN convection maps for an extended time period around magnetic midnight, provides an unparalleled opportunity to examine how plasma exits the polar cap. Under conditions of IMF BY predominantly positive (+5nT) we find that the patches exit both into the oval on the dusk cell pre midnight and on the dusk cell post midnight. This event study concurs with a statistical result also presented. The statistics show that the MLT distribution of patch exits, which is a ~10 hours broad bell shaped function cantered on ~23:30 MLT, is just marginally sensitive to the IMF BY polarity. This makes us conclude that the patches do not memorize on which cell they entered the polar cap.

  14. Plasma and convection reversal boundary motions in the high-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Chen, Y.-J.; Heelis, R. A.; Cumnock, J. A.

    2016-06-01

    In this paper we present a statistical study of the high-latitude ionospheric plasma motion at the convection reversal boundary (CRB) and its dependence on the location of the CRB and the interplanetary magnetic field (IMF) orientation by using the Defense Meteorological Satellite Program (DMSP) F13 and F15 measurements over the period from 2000 to 2007. During periods of stable southward IMF, we find a smaller variability in plasma drifts across the CRB over a 4 h segment in magnetic local time (MLT) around dawn and dusk compared to that for variable IMF. Across these segments, the plasma motion at the CRB is directed poleward at local times closer to local noon and equatorward at local times closer to midnight on both the dawn and dusk sides with a total potential drop ~10 kV, suggesting that the CRB behaves much like an adiaroic line. For variable IMF with no stability constraint, we see a relatively narrow distribution of plasma drifts across the CRB only in the 6-7 h and 17-18 h MLT and equatorward/poleward motions of the CRB when the CRB is located at the highest/lowest latitudes. The smaller local time extent of the adiaroic line for variable IMF (~1 h) may be associated with rotation of the dayside merging gap in local time or local contractions and expansions of the polar cap boundary.

  15. Effects of convection electric field on the distribution of ring current type protons

    NASA Technical Reports Server (NTRS)

    Grebowsky, J. M.; Chen, A. J.

    1975-01-01

    The topology of the boundaries of penetration (or, inversely, the boundaries of the forbidden regions) of 90-deg pitch-angle equatorial protons with energies less than 100 keV are explored for an equatorial convection E-field which is directed in general from dawn to dusk. Due to the dependence of drift path on energy (or magnetic moment), complex structural features are expected in the proton energy spectra detected by satellites since the penetration distance of a proton is not a monotonically increasing or decreasing function of energy. During a storm when the convection E is enhanced, model calculations predict elongations of the forbidden regions analogous to tail extensions of the plasmasphere. Following a reduction in the convection field, spiral-structured forbidden regions can occur. Structural features inherent to large-scale convection field changes may be seen in the nose-like proton spectrograms observed near dusk by instrumentation on Explorer 45. These nose events are modelled by using an electric field model developed originally by Volland (1973). The strength of the field is related to the Kp index through night-time equatorial plasmapause measurements.

  16. Investigation of S3-2 satellite data for local time variation of energetic electron precipitation

    NASA Technical Reports Server (NTRS)

    Robbe, S.; Sheldon, W. R.; Benbrook, J. R.; Bering, E. A.; Vampola, A. L.

    1994-01-01

    Data on precipitating electrons from the S3-2 satellite were investigated for local time variation at four L = 4 stations in the southern hemisphere. The equatorial pitch angles of electrons mirroring at 100 km, assumed to be the edge of the bounce loss cone, are calculated for L = 4 using the International Geomagnetic Reference Field for the epoch of the S3-2 data, along with the variation in mirror altitude per degree of equatorial pitch angle. The largest obstacle to the investigation was uneven sampling in terms of local time for all of the stations. However, this situation was improved upon by the use of S3-2 measurements at the conjugate locations of the four stations which provided additional data on electrons in the southern hemisphere bounce loss cone. Evidence for an effect of the dawn-to-dusk geoelectric field was found at two of the stations, Halley Bay and Siple, in the form of a minimum in electron precipitation at dusk. However, the present study does not completely resolve the question of local time modulation of electron precipitation at L = 4 in the southern hemisphere. Furthermore, while the average precipitation was lowest at the Kerguelen site, as would be expected on the basis of drift loss cone (DLC) theories, the intensity at that site exceeds the level that is expected on the basis of these DLC theories.

  17. Woody clockworks: circadian regulation of night-time water use in Eucalyptus globulus.

    PubMed

    Resco de Dios, Víctor; Díaz-Sierra, Rubén; Goulden, Michael L; Barton, Craig V M; Boer, Matthias M; Gessler, Arthur; Ferrio, Juan Pedro; Pfautsch, Sebastian; Tissue, David T

    2013-11-01

    The role of the circadian clock in controlling the metabolism of entire trees has seldom been considered. We tested whether the clock influences nocturnal whole-tree water use. Whole-tree chambers allowed the control of environmental variables (temperature, relative humidity). Night-time stomatal conductance (gs ) and sap flow (Q) were monitored in 6- to 8-m-tall Eucalyptus globulus trees during nights when environmental variables were kept constant, and also when conditions varied with time. Artificial neural networks were used to quantify the relative importance of circadian regulation of gs and Q. Under a constant environment, gs and Q declined from 0 to 6 h after dusk, but increased from 6 to 12 h after dusk. While the initial decline could be attributed to multiple processes, the subsequent increase is most consistent with circadian regulation of gs and Q. We conclude that endogenous regulation of gs is an important driver of night-time Q under natural environmental variability. The proportion of nocturnal Q variation associated with circadian regulation (23-56%) was comparable to that attributed to vapor pressure deficit variation (25-58%). This study contributes to our understanding of the linkages between molecular and cellular processes related to circadian regulation, and whole-tree processes related to ecosystem gas exchange in the field.

  18. Dynamics of Subauroral Polarization Stream (SAPS) Structures

    NASA Astrophysics Data System (ADS)

    Sazykin, S. Y.; Coster, A. J.; Huba, J.; Ridley, A. J.; Erickson, P. J.; Foster, J. C.; Baker, J. B. H.; Wolf, R.

    2015-12-01

    The Subauroral Polarization Stream (SAPS) flow structures are narrow ionospheric channels of fast (in excess of 100 m/s) westward drift just outside the equatorward edge of the diffuse aurora in the dusk-to-midnight local time sector. Other terms for this phenomenon include subauroral Ion Drift (SAID) events and Polarization Jets. SAPS structures represent a striking departure from the commonly-used two-cell convection pattern. They are thought to arise from the displacement of the downward region-2 Birkeland currents on the dusk side equatorward of the low-latitude boundary of the auroral oval during times of changing high-latitude convection. In this paper, we will use several event simulations with the SAMI3-RCM numerical model (a self-consistent ionosphere-inner magnetosphere model) and RCM-GITM (a self-consistent model of the ionosphere-thermosphere-inner magnetosphere) to analyze the relative roles of changes in the IMF Bz component, ionospheric electron density depletions, and thermospheric modifications in controlling the dynamics of SAPS. Simulation results will be compared to multi-instrument ionospheric observations.

  19. Radar observations of the seasonal migration of brown planthopper (Nilaparvata lugens Stål) in Southern China.

    PubMed

    Qi, H; Jiang, C; Zhang, Y; Yang, X; Cheng, D

    2014-12-01

    The summer and autumn migrations of the brown planthopper (Nilaparvata lugens) were observed in Southern China with a millimetric scanning entomological radar and a searchlight trap supplemented with capture in field cages, field surveys, and dissections of females. Nilaparvata lugens took off at dusk and dawn in summer, but in autumn there was sometimes only a dusk take-off. The variation of the area density of the radar targets indicated that flight durations were about 9-10 h. In summer, planthopper-size targets generally flew below 1800 m above ground level (AGL), although some insects reached 2000 m AGL; in autumn, they flew lower, generally below 1100 m although some insects reached 1700 m AGL. Multiple layer concentrations were seen every night in both summer and autumn. The depths of these layers in autumn were less than in summer. Nilaparvata lugens flew in strong winds; wind shear may be the main factor causing them to accumulate and form dense layers at certain heights. Nilaparvata lugens emigrating in summer from the vicinity of the radar site in the Northeastern Guangxi Zhuang Autonomous Region, and carried by the prevailing southwesterly wind, would have travelled northeastwards and reached Northern Hunan Province. In autumn, with the prevailing northeasterly wind, emigrants would have reached overwintering areas (south of 21°N).

  20. Pineal melatonin and locomotor activity of rats under gradual illuminance transitions.

    PubMed

    Laakso, M L; Leinonen, L; Joutsiniemi, S L; Porkka-Heiskanen, T; Stenberg, D

    1992-10-01

    The locomotor activity and pineal melatonin patterns of adult male rats were compared under two different lighting regimes. The animals were kept 8 days under 12/12 h light/dark cycles with abrupt or slowly decreasing and increasing transitions (twilight periods about 2 h). The onsets of high activity and melatonin rise were phase-locked in the two conditions and related to about half-maximal illuminance level of the gradual dusk. The high activity of the control rats stopped 30-60 min before the abrupt light onset and the rats under the gradual lighting transitions ceased the locomotor activity at about 1 hour before the half-maximal illuminance. The melatonin peak levels were found 4 h before the abrupt lights-on time. Under the slow illuminance transitions the average melatonin peak was related to the illuminance level between maximum and minimum in the morning. Thus, both the melatonin rhythm and the rest-activity rhythm under the gradual dawn and dusk were adjusted according to about half-maximal illuminances in the present conditions.

  1. Twenty-four-hour patterns of pineal melatonin and pituitary and plasma prolactin in male rats under 'natural' and artificial lighting conditions.

    PubMed

    Laakso, M L; Porkka-Heiskanen, T; Alila, A; Peder, M; Johansson, G

    1988-09-01

    Natural lighting differs from usual artificial lighting mainly as follows: it has larger spectral composition, fluctuations of intensity during the day, higher intensity levels during the night (moonlight, starlight), and gradual changes of illuminance at dawn and dusk. The present experiment was performed in order to study whether these features of lighting affect the 24-hour patterns of melatonin and prolactin in male rats. The rats were kept 7 days in 'natural' lighting (sunlight through windows) or in artificial lighting (cool white fluorescent lamps) of similar periodicities (13/11 h light/dark). The samples were collected at 3-hour intervals during a 24-hour period. Pineal melatonin contents, pituitary prolactin contents, and plasma prolactin concentrations were measured radioimmunologically. The nocturnal pineal melatonin contents were higher and the daytime contents lower in natural than in artificial lighting conditions. A corresponding 'strengthening of rhythm' of prolactin was found in natural lighting. A reason for the higher amplitude variation of melatonin in the natural lighting conditions may be the gradual changes of illuminance at dawn and dusk. The different pituitary and plasma prolactin patterns of the rats kept in the two lighting conditions might partly be explained by a stimulatory effect of melatonin on the production and secretion of prolactin, but other regulatory factors had to be involved, too.

  2. Anomalous aspects of magnetosheath flow and of the shape and oscillations of the magnetopause during an interval of strongly northward interplanetary magnetic field

    NASA Technical Reports Server (NTRS)

    Chen, Sheng-Hsien; Kivelson, Margaret G.; Gosling, Jack T.; Walker, Raymond T.; Lazarus, Allan J.

    1992-01-01

    On 15 Feb. 1978, the orientation of the interplanetary magnetic field (IMF) remained steadily northward for more than 12 hours. The ISEE 1 and 2 spacecraft were located near apogee on the dawn side flank of the magnetotail. IMP 8 was almost symmetrically located in the magnetosheath on the dusk flank and IMP 7 was upstream in the solar wind. Using plasma and magnetic field data, we show the following: (1) the magnetosheath flow speed on the flanks of the magnetotail steadily exceeded the solar wind speed by 20 percent; (2) surface waves with approximately a 5-min period and very non-sinusoidal waveform were persistently present on the dawn magnetopause and waves of similar period were present in the dusk magnetosheath; and (3) the magnetotail ceased to flare at an antisunward distance of 15 R(sub E). We propose that the acceleration of the magnetosheath flow is achieved by magnetic tension in the draped field configuration for northward IMF and that the reduction of tail flaring is consistent with a decreased amount of open magnetic flux and a larger standoff distance of the subsolar magnetopause. Results of a three-dimensional magnetohydrodynamic simulation support this phenomenological model.

  3. Spatial Distribution of Rolled up Kelvin-Helmholtz Vortices at Earth's Dayside and Flank Magnetopause

    NASA Technical Reports Server (NTRS)

    Taylor, M. G. G. T.; Hasegawa, H.; Lavraud, B.; Phan, T.; Escoubet, C. P.; Dunlop, M. W.; Bogdanova, Y. V.; Borg, A. L.; Volwerk, M.; Berchem, J.; Constantinescu, O. D.; Eastwood, J. P.; Masson, A.; Laakso, H.; Soucek, J.; Fazakerley, A. N.; Frey, H. U.; Panov, E. V.; Shen, C.; Shi, J. K.; Sibeck, D. G.; Pu, Z. Y.; Wang, J.; Wild, J. A.

    2012-01-01

    The Kelvin-Helmholtz Instability (KHI) can drive waves at the magnetopause. These waves can grow to form rolled-up vortices and facilitate transfer of plasma into the magnetosphere. To investigate the persistence and frequency of such waves at the magnetopause we have carried out a survey of all Double Star 1 magnetopause crossings, using a combination of ion and magnetic field measurements. Using criteria originally used in a Geotail study made by Hasegawa et al. (2006) (forthwith referred to as H2006), 17 candidate events were identified from the entire TC-1 mission (covering 623 orbits where the magnetopause was sampled), a majority of which were on the dayside of the terminator. The relationship between density and shear velocity was then investigated, to identify the predicted signature of a rolled up vortex from H2006 and all 17 events exhibited some level of rolled up behavior. The location of the events had a clear dawn-dusk asymmetry, with 12 (71 %) on the post noon, dusk flank suggesting preferential growth in this region.

  4. Diel variation in ammonia excretion, glutamine levels, and hydration status in two species of terrestrial isopods.

    PubMed

    Wright, Jonathan C; Peña-Peralta, Mariasol

    2005-01-01

    Terrestrial isopods (suborder Oniscidea) excrete most nitrogen diurnally as volatile ammonia, and ammonia-loaded animals accumulate nonessential amino acids, which may constitute the major nocturnal nitrogen pool. This study explored the relationship between ammonia excretion, glutamine storage/mobilization, and water balance, in two sympatric species Ligidium lapetum (section Diplocheta), a hygric species; and Armadillidium vulgare (Section Crinocheta), a xeric species capable of water-vapor absorption (WVA). Ammonia excretion (12-h), tissue glutamine levels, and water contents were measured following field collection of animals at dusk and dawn. In both species, diurnal ammonia excretion exceeded nocturnal excretion four- to fivefold while glutamine levels increased four- to sevenfold during the night. Most glutamine was accumulated in the somatic tissues ("body wall"). While data support the role of glutamine in nocturnal nitrogen storage, potential nitrogen mobilization from glutamine breakdown (162 micromol g(-1) in A. vulgare) exceeds measured ammonia excretion (2.5 micromol g(-1)) over 60-fold. This may serve to generate the high hemolymph ammonia concentrations (and high P(NH3)) seen during volatilization. The energetic cost of ammonia volatilization is discussed in the light of these findings. Mean water contents were similar at dusk and dawn in both species, indicating that diel cycles of water depletion and replenishment were not occurring. PMID:15578188

  5. Kelvin-Helmholtz vortex identification: A survey on Cluster using the magnetopause transition parameter

    NASA Astrophysics Data System (ADS)

    Varsani, Ali; Owen, Christopher J.; Fazakerley, Andrew N.; Taylor, Matthew G. G. T.; Plaschke, Ferdinand; Nakamura, Rumi; Dandouras, Iannis; Carr, Christopher M.

    2016-04-01

    Observations of low density faster than sheath (LDFTS) population at the flank magnetopause are thought to be associated with mixed-up plasma within the Kelvin-Helmholtz vortices. The technique has been previously employed to identify vortices with single-spacecraft such as Geotail observations and Double Star TC-1 spacecraft. However, the abundance of the events identified by LDFTS technique at the dayside magnetopause, and their spatial distribution are not fully in agreement with some simulation which suggest that the dawn flank is a better candidate for KHI vortices. Accordingly, there have been postulations as to whether a thinner magnetopause at the dusk flank, and or velocity patterns in the presence of a plasma depletion layer (PDL), might be responsible for observation of LDFTS where a rolled-up vortex might not be expected. We present a survey of Cluster observations to tackle the understanding of the KHI vortex identification criteria, where two questions are taken into account: 1) Whether the plasma is observed in the boundary layer, and 2) Whether the flow velocity is driven by the KHI only. We utilise the magnetopause transition parameter, to eliminate the arbitrary choice of density, time interval of the observations, and possible presence of the PDL from the LDFTS method. We find that our modified method identifies a more realistic percentage of faster-than-sheath population as candidates for rolled-up vortices. The survey results also show a dawn-dusk asymmetry, with the dawn flank being more favourable for the development of KHI.

  6. Sources of Local Time Asymmetries in Magnetodiscs

    NASA Astrophysics Data System (ADS)

    Arridge, C. S.; Kane, M.; Sergis, N.; Khurana, K. K.; Jackman, C. M.

    2015-04-01

    The rapidly rotating magnetospheres at Jupiter and Saturn contain a near-equatorial thin current sheet over most local times known as the magnetodisc, resembling a wrapped-up magnetotail. The Pioneer, Voyager, Ulysses, Galileo, Cassini and New Horizons spacecraft at Jupiter and Saturn have provided extensive datasets from which to observationally identify local time asymmetries in these magnetodiscs. Imaging in the infrared and ultraviolet from ground- and space-based instruments have also revealed the presence of local time asymmetries in the aurora which therefore must map to local time asymmetries in the magnetosphere. Asymmetries are found in (i) the configuration of the magnetic field and magnetospheric currents, where a thicker disc is found in the noon and dusk sectors; (ii) plasma flows where the plasma flow has local time-dependent radial components; (iii) a thicker plasma sheet in the dusk sector. Many of these features are also reproduced in global MHD simulations. Several models have been developed to interpret these various observations and typically fall into two groups: ones which invoke coupling with the solar wind (via reconnection or viscous processes) and ones which invoke internal rotational processes operating inside an asymmetrical external boundary. In this paper we review these observational in situ findings, review the models which seek to explain them, and highlight open questions and directions for future work.

  7. Radar observations of the seasonal migration of brown planthopper (Nilaparvata lugens Stål) in Southern China.

    PubMed

    Qi, H; Jiang, C; Zhang, Y; Yang, X; Cheng, D

    2014-12-01

    The summer and autumn migrations of the brown planthopper (Nilaparvata lugens) were observed in Southern China with a millimetric scanning entomological radar and a searchlight trap supplemented with capture in field cages, field surveys, and dissections of females. Nilaparvata lugens took off at dusk and dawn in summer, but in autumn there was sometimes only a dusk take-off. The variation of the area density of the radar targets indicated that flight durations were about 9-10 h. In summer, planthopper-size targets generally flew below 1800 m above ground level (AGL), although some insects reached 2000 m AGL; in autumn, they flew lower, generally below 1100 m although some insects reached 1700 m AGL. Multiple layer concentrations were seen every night in both summer and autumn. The depths of these layers in autumn were less than in summer. Nilaparvata lugens flew in strong winds; wind shear may be the main factor causing them to accumulate and form dense layers at certain heights. Nilaparvata lugens emigrating in summer from the vicinity of the radar site in the Northeastern Guangxi Zhuang Autonomous Region, and carried by the prevailing southwesterly wind, would have travelled northeastwards and reached Northern Hunan Province. In autumn, with the prevailing northeasterly wind, emigrants would have reached overwintering areas (south of 21°N). PMID:25229712

  8. The global context of the 14 November 2012 storm event

    NASA Astrophysics Data System (ADS)

    Hwang, K.-J.; Sibeck, D. G.; Fok, M.-C. H.; Zheng, Y.; Nishimura, Y.; Lee, J.-J.; Glocer, A.; Partamies, N.; Singer, H. J.; Reeves, G. D.; Mitchell, D. G.; Kletzing, C. A.; Onsager, T.

    2015-03-01

    From 2 to 5 UT on 14 November 2012, the Van Allen Probes observed repeated particle flux dropouts during the main phase of a geomagnetic storm as the satellites traversed the post-midnight to dawnside inner magnetosphere. Each flux dropout corresponded to an abrupt change in the magnetic topology, i.e., from a more dipolar configuration to a configuration with magnetic field lines stretched in the dawn-dusk direction. Geosynchronous GOES spacecraft located in the dusk and near-midnight sectors and the LANL constellation with wide local time coverage also observed repeated flux dropouts and stretched field lines with similar occurrence patterns to those of the Van Allen Probe events. THEMIS recorded multiple transient abrupt expansions of the evening-side magnetopause ˜20-30 min prior to the sequential Van Allen Probes observations. Ground-based magnetograms and all sky images demonstrate repeatable features in conjunction with the dropouts. We combine the various in situ and ground-based measurements to define and understand the global spatiotemporal features associated with the dropouts observed by the Van Allen Probes. We discuss various proposed hypotheses for the mechanism that plausibly caused this storm-time dropout event as well as formulate a new hypothesis that explains the combined in situ and ground-based observations: the earthward motion of magnetic flux ropes containing lobe plasmas that form along an extended magnetotail reconnection line in the near-Earth plasma sheet.

  9. Effects of the interplanetary magnetic field on the location of the open-closed field line boundary

    NASA Astrophysics Data System (ADS)

    Wang, C.; Wang, J. Y.; Lopez, R. E.; Zhang, L. Q.; Tang, B. B.; Sun, T. R.; Li, H.

    2016-07-01

    Using global magnetohydrodynamic(MHD) simulation, we investigate the effect of the interplanetary magnetic field (IMF) on the location of the open-closed field line boundary(OCB), in particular the duskside and dawnside OCB and their asymmetry. We first model the typical OCB-crossing events on 22 October 2001 and 24 October 2002 observed by DMSP. The MHD model presents a good estimate of OCB location under quasi-steady magnetospheric conditions. We then systemically study the location of the OCB under different IMF conditions. The model results show that the dawnside and duskside OCBs respond differently to IMF conditions when BY is present. An empirical expression describing the relationship between the OCB latitudes and IMF conditions has been obtained. It is found that the IMF conditions play an important role in determining the dawn-dusk OCB asymmetry, which is due to the magnetic reconnection at the dayside magnetopause. The differences between the dawn and dusk OCB latitudes from MHD predictions are in good agreement with the observations.

  10. Distribution of hydrogen and oxygen ion species in the plasmasheet

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Cao, Jinbin; Liu, Wenlong

    2016-07-01

    In this paper, using data obtained by Cluster 4 satellite from 2001 to 2012, we statistically investigate the spatial distributions of H+ and O+ in the magnetotail plasmasheet and their relation with geomagnetic indices. Our work outlines the existence of two regions with enhanced O+ concentration in the tail plasmasheet, one is located in the mid-tail plasmasheet at R > 17 RE, and the other is located near the inner boundary of plasmasheet at R < 10 RE. The existence of the depletion region of O+ between 10 RE < R < 17 RE indicates that the O+ ions in the mid-tail plasmasheet, which come from polar cap, are not likely to be able to make important contribution to the formation of ring current. Both the distributions of density and temperature of O+ ions have a dawn-dusk asymmetry. The number density of O+ during geomagnetic active time (Dst < -20 nT/AE > 200 nT/Kp ⩾ 3) is much larger than that during non-storm time (Dst > -20 nT/AE < 200 nT/Kp < 3). This dawn-dusk asymmetry and the number density of O+ varying with geomagnetic activity apply for both regions (R < 10 RE and R > 17 RE) of O+. Therefore both substorm and enhanced convection provide a large number of O+ ions to the plasmasheet, which makes favorable condition for the growth of the ring current.

  11. Ramadan fasting and patients with renal diseases: A mini review of the literature

    PubMed Central

    Emami-Naini, Afsoon; Roomizadeh, Peyman; Baradaran, Azar; Abedini, Amin; Abtahi, Mohammad

    2013-01-01

    Fasting during the month of Ramadan is one of the five pillars of Islam. During this month, adult Muslims are obligated to refrain from eating and drinking from dawn to dusk. Although based on Islamic principles patients are exempted from fasting, each year, many Muslim patients express their willingness to observe the fast in Ramadan month to respect the cultural customs. There are concerns about the impact of fluid restriction and dehydration during Ramadan fasting for patients with renal diseases. In this study, we reviewed the PubMed, Google Scholar, EBSCO, SCIRUS, Embase, and DOAJ data sources to identify the published studies on the impact of Ramadan fasting on patients with renal diseases. Our review on published reports on renal transplant recipients revealed no injurious effect of Ramadan fasting for the renal graft function. Nearly all studies on this topic suggest that Ramadan fasting is safe when the function of the renal graft is acceptable and stable. Regarding the impact of Ramadan fasting on patients with chronic kidney disease, there is concern about the role of renal hypoperfusion in developing tubular cell injury. Finally, there is controversy between studies about the risk of dehydration in Ramadan in developing renal stones. There are uncertainties about the change in the incidence of renal colic in Ramadan month compared with the other periods of the year. Despite such discrepancies, nearly all studies are in agreement on consuming adequate amounts of water from dusk to dawn to reduce the risk of renal stone formation. PMID:24379850

  12. The global context of the 14 November 2012 storm event

    DOE PAGES

    Hwang, K. -J.; Sibeck, D. G.; Fok, M. -C. H.; Zheng, Y.; Nishimura, Y.; Lee, J. -J.; Glocer, A.; Partamies, N.; Singer, H. J.; Reeves, G. D.; et al

    2015-03-01

    From 2 to 5 UT on 14 November 2012, the Van Allen Probes observed repeated particle flux dropouts during the main phase of a geomagnetic storm as the satellites traversed the post-midnight to dawnside inner magnetosphere. Each flux dropout corresponded to an abrupt change in the magnetic topology, i.e., from a more dipolar configuration to a configuration with magnetic field lines stretched in the dawn-dusk direction. Geosynchronous GOES spacecraft located in the dusk and near-midnight sectors and the LANL constellation with wide local time coverage also observed repeated flux dropouts and stretched field lines with similar occurrence patterns to thosemore » of the Van Allen Probe events. THEMIS recorded multiple transient abrupt expansions of the evening-side magnetopause ~20–30 min prior to the sequential Van Allen Probes observations. Ground-based magnetograms and all sky images demonstrate repeatable features in conjunction with the dropouts. We combine the various in-situ and ground-based measurements to define and understand the global spatiotemporal features associated with the dropouts observed by the Van Allen Probes. We discuss various proposed hypotheses for the mechanism that plausibly caused this storm-time dropout event as well as formulate a new hypothesis that explains the combined in-situ and ground-based observations: the earthward motion of magnetic flux ropes containing lobe plasmas that form along an extended magnetotail reconnection line in the near-Earth plasma sheet.« less

  13. Ulysses at jupiter: an overview of the encounter.

    PubMed

    Smith, E J; Wenzel, K P; Page, D E

    1992-09-11

    In February 1992, the Ulysses spacecraft flew through the giant magnetosphere of Jupiter. The primary objective of the encounter was to use the gravity field of Jupiter to redirect the spacecraft to the sun's polar regions, which will now be traversed in 1994 and 1995. However, the Ulysses scientific investigations were well suited to observations of the Jovian magnetosphere, and the encounter has resulted in a major contribution to our understanding of this complex and dynamic plasma environment. Among the more exciting results are (i) possible entry into the polar cap, (ii) the identification of magnetospheric ions originating from Jupiter's ionosphere, lo, and the solar wind, (iii) observation of longitudinal asymmetries in density and discrete wave-emitting regions of the lo plasma torus, (iv) the presence of counter-streaming ions and electrons, field-aligned currents, and energetic electron and radio bursts in the dusk sector on high-latitude magnetic field lines, and (v) the identification of the direction of the magnetic field in the dusk sector, which is indicative of tailward convection. This overview serves as an introduction to the accompanying reports that present the preliminary scientific findings. Aspects of the encounter that are common to all of the investigations, such as spacecraft capabilities, the flight path past Jupiter, and unique aspects of the encounter, are presented herein.

  14. Magnetic field observations during the ulysses flyby of jupiter.

    PubMed

    Balogh, A; Dougherty, M K; Forsyth, R J; Southwood, D J; Smith, E J; Tsurutani, B T; Murphy, N; Burton, M E

    1992-09-11

    The Jovian flyby of the Ulysses spacecraft presented the opportunity to confirm and complement the findings of the four previous missions that investigated the structure and dynamics of the Jovian magnetosphere and magnetic field, as well as to explore for the first time the high-latitude dusk side of the magnetosphere and its boundary regions. In addition to confirming the general structure of the dayside magnetosphere, the Ulysses magnetic field measurements also showed that the importance of the current sheet dynamics extends well into the middle and outer magnetosphere. On the dusk side, the magnetic field is swept back significantly toward the magnetotail. The importance of current systems, both azimuthal and field-aligned, in determining the configuration of the field has been strongly highlighted by the Ulysses data. No significant changes have been found in the internal planetary field; however, the need to modify the external current densities with respect to previous observations on the inbound pass shows that Jovian magnetic and magnetospheric models are highly sensitive to both the intensity and the structure assumed for the current sheet and to any time dependence that may be assigned to these. The observations show that all boundaries and boundary layers in the magnetosphere have a very complex microstructure. Waves and wave-like structures were observed throughout the magnetosphere; these included the longest lasting mirror-mode wave trains observed in space.

  15. Ramadan fasting and patients with renal diseases: A mini review of the literature.

    PubMed

    Emami-Naini, Afsoon; Roomizadeh, Peyman; Baradaran, Azar; Abedini, Amin; Abtahi, Mohammad

    2013-08-01

    Fasting during the month of Ramadan is one of the five pillars of Islam. During this month, adult Muslims are obligated to refrain from eating and drinking from dawn to dusk. Although based on Islamic principles patients are exempted from fasting, each year, many Muslim patients express their willingness to observe the fast in Ramadan month to respect the cultural customs. There are concerns about the impact of fluid restriction and dehydration during Ramadan fasting for patients with renal diseases. In this study, we reviewed the PubMed, Google Scholar, EBSCO, SCIRUS, Embase, and DOAJ data sources to identify the published studies on the impact of Ramadan fasting on patients with renal diseases. Our review on published reports on renal transplant recipients revealed no injurious effect of Ramadan fasting for the renal graft function. Nearly all studies on this topic suggest that Ramadan fasting is safe when the function of the renal graft is acceptable and stable. Regarding the impact of Ramadan fasting on patients with chronic kidney disease, there is concern about the role of renal hypoperfusion in developing tubular cell injury. Finally, there is controversy between studies about the risk of dehydration in Ramadan in developing renal stones. There are uncertainties about the change in the incidence of renal colic in Ramadan month compared with the other periods of the year. Despite such discrepancies, nearly all studies are in agreement on consuming adequate amounts of water from dusk to dawn to reduce the risk of renal stone formation. PMID:24379850

  16. Vasoactive intestinal polypeptide mediates circadian rhythms in mammalian olfactory bulb and olfaction.

    PubMed

    Miller, Jae-Eun Kang; Granados-Fuentes, Daniel; Wang, Thomas; Marpegan, Luciano; Holy, Timothy E; Herzog, Erik D

    2014-04-23

    Accumulating evidence suggests that the olfactory bulbs (OBs) function as an independent circadian system regulating daily rhythms in olfactory performance. However, the cells and signals in the olfactory system that generate and coordinate these circadian rhythms are unknown. Using real-time imaging of gene expression, we found that the isolated olfactory epithelium and OB, but not the piriform cortex, express similar, sustained circadian rhythms in PERIOD2 (PER2). In vivo, PER2 expression in the OB of mice is circadian, approximately doubling with a peak around subjective dusk. Furthermore, mice exhibit circadian rhythms in odor detection performance with a peak at approximately subjective dusk. We also found that circadian rhythms in gene expression and odor detection performance require vasoactive intestinal polypeptide (VIP) or its receptor VPAC2R. VIP is expressed, in a circadian manner, in interneurons in the external plexiform and periglomerular layers, whereas VPAC2R is expressed in mitral and external tufted cells in the OB. Together, these results indicate that VIP signaling modulates the output from the OB to maintain circadian rhythms in the mammalian olfactory system.

  17. Observations of IMF and seasonal effects in high-latitude convection

    NASA Technical Reports Server (NTRS)

    Ruohoniemi, J. M.; Greenwald, R. A.

    1995-01-01

    Strong interplanetary magnetic field (IMF) and seasonal effects in the convection of nightside ionospheric plasma are described. The findings are based on a statistical analysis of observations made with the Johns Hopkins University/ Applied Physics Lab (JHU/APL) HF radar located at Goose Bay, Labrador. For positive sign of the IMF dusk-dawn component, By greater than 0 the dawn cell is more crescent shaped and the dusk cell more round while for BY less than 0 these pairings of size and shape are reversed. The more extreme crescent /round cell dichotomy is obtained for BY greater than 0. The return flows associated with the crescent-shaped cell dominate at midnight MLT (magnetic local time); the reversal in the zonal velocity in the 67 deg-69 deg lambda (magnetic latitude) interval occurs 2.5 hr earlier in summer than in winter. The maximum effects are obtained on the nightside for the pairings By greater than 0, summer and BY less than 0, winter; the first produces the more structured cell in the morning, the second in the evening, and this cell dominates the return flow at midnight. The difference in the zonal flow reversals for these pairings exceeds 4 hr in MLT.

  18. MESSENGER Orbital Observations of Large-Amplitude Kelvin-Helmholtz Waves at Mercury's Magnetopause

    NASA Technical Reports Server (NTRS)

    Sundberg, Torbjorn; Boardsen, Scott A.; Slavin, James A.; Anderson, Brian J.; Korth, Haje; Zurbuchen, Thomas H.; Raines, Jim M.; Solomon, Sean C.

    2012-01-01

    We present a survey of Kelvi\\ n-Helmholtz (KH) waves at Mercury's magnetopause during MESSENGER's first Mercury year in orb it. The waves were identified on the basis of the well-established sawtooth wave signatures that are associated with non-linear KH vortices at the magnetopause. MESSENGER frequently observed such KH waves in the dayside region of the magnetosphere where the magnetosheath flow velocity is still sub -sonic, which implies that instability growth rates at Mercury's magnetopau are much larger than at Earth. We attribute these greater rates to the limited wave energy dissipation in Mercury's highly resistive regolith. The wave amplitude was often on the order of ' 00 nT or more, and the wave periods were - 10- 20 s. A clear dawn-dusk asymmetry is present in the data, in that all of the observed wave events occurred in the post-noon and dusk-side sectors of the magnetopause. This asymmetry is like ly related to finite Larmor-radius effects and is in agreement with results from particle-in-cell simulations of the instability. The waves were observed almost exclusively during periods when the north-south component of the magnetosheath magnetic field was northward, a pattern similar to that for most terrestrial KH wave events. Accompanying plasma measurements show that the waves were associated with the transport of magnetosheath plasma into the magnetosphere.

  19. Diel variation in ammonia excretion, glutamine levels, and hydration status in two species of terrestrial isopods.

    PubMed

    Wright, Jonathan C; Peña-Peralta, Mariasol

    2005-01-01

    Terrestrial isopods (suborder Oniscidea) excrete most nitrogen diurnally as volatile ammonia, and ammonia-loaded animals accumulate nonessential amino acids, which may constitute the major nocturnal nitrogen pool. This study explored the relationship between ammonia excretion, glutamine storage/mobilization, and water balance, in two sympatric species Ligidium lapetum (section Diplocheta), a hygric species; and Armadillidium vulgare (Section Crinocheta), a xeric species capable of water-vapor absorption (WVA). Ammonia excretion (12-h), tissue glutamine levels, and water contents were measured following field collection of animals at dusk and dawn. In both species, diurnal ammonia excretion exceeded nocturnal excretion four- to fivefold while glutamine levels increased four- to sevenfold during the night. Most glutamine was accumulated in the somatic tissues ("body wall"). While data support the role of glutamine in nocturnal nitrogen storage, potential nitrogen mobilization from glutamine breakdown (162 micromol g(-1) in A. vulgare) exceeds measured ammonia excretion (2.5 micromol g(-1)) over 60-fold. This may serve to generate the high hemolymph ammonia concentrations (and high P(NH3)) seen during volatilization. The energetic cost of ammonia volatilization is discussed in the light of these findings. Mean water contents were similar at dusk and dawn in both species, indicating that diel cycles of water depletion and replenishment were not occurring.

  20. Asymmetric Magnetosphere Deformation Driven by Hot Flow Anomaly(ies)

    NASA Technical Reports Server (NTRS)

    Safrankova, J.; Goncharov, O.; Nemecek, Z.; Prech, L.; Sibeck, D. G.

    2012-01-01

    We present a case study of a large deformation of the magnetopause on November 26, 2008. The investigation is based on observations of five THEMIS spacecraft located at the dawn flank in the magnetosphere and magnetosheath, on Cluster measurements at the dusk magnetosheath, and is supported by ACE solar wind monitoring. The main revelation of our study is that the interaction of the IMF discontinuity with the bow shock creates either one very elongated hot flow anomaly (HFA) or a pair of them that is (are) simultaneously observed at both flanks. Whereas the dusk HFA is weak and does not cause observable deformation of the magnetopause, the pressure variations connected with the dawn HFA lead to a magnetopause displacement by approx. = 5 R(sub E) outward from its nominal position. This is followed by a rapid inward motion of the magnetopause approx. = 4 R(sub E) inward with respect to the model location. The surface deformation is so large that the outermost THEMIS spacecraft was in the magnetosphere, whereas the spacecraft located 9 R(sub E) inbound entered into the magnetosheath at the same time. The whole event lasted about 5 minutes.

  1. Diurnal variations in, and influences on, concentrations of particulate and dissolved arsenic and metals in the mildly alkaline Wallkill River, New Jersey, USA

    USGS Publications Warehouse

    Barringer, J.L.; Wilson, T.P.; Szabo, Z.; Bonin, J.L.; Fischer, J.M.; Smith, N.P.

    2008-01-01

    Diurnal variations in particulate and dissolved As and metal concentrations were observed in mildly alkaline water from a wetlands site on the Wallkill River in northwestern New Jersey. The site, underlain by glacial sediments over dolomite bedrock, is 10 km downstream from a mined area of the Franklin Marble, host to Zn ores, also As and Mn minerals. In mid-September 2005, maxima and minima in dissolved-oxygen-concentration and pH, typically caused by photosynthesis and respiration, occurred at 2000 and 0800 hours. Concentrations of dissolved As (1.52-1.95 ??g/L) peaked at dusk (2000 hours), whereas dissolved Mn and Zn concentrations (76.5-96.9 and 8.55-12.8 ??g/L, respectively) were lowest at dusk and peaked at 1000 hours. These opposing cycles probably reflect sorption and desorption of As (an anion), and Mn and Zn (cations) as pH varied throughout the 24-h period. Doubly-peaked cycles of B, Cl, SO4, and nutrients also were observed; these may result from upstream discharges of septic-system effluent. Both recoverable amd particulate Al, Fe, Mn, and Zn concentrations peaked between 0200 and 0600 hours. The particulate metals cycle, with perturbations at 0400 hours, may be influenced by biological activity. ?? 2007 Springer-Verlag.

  2. Daily rhythms in antennal protein and olfactory sensitivity in the malaria mosquito Anopheles gambiae

    PubMed Central

    Rund, Samuel S. C.; Bonar, Nicolle A.; Champion, Matthew M.; Ghazi, John P.; Houk, Cameron M.; Leming, Matthew T.; Syed, Zainulabeuddin; Duffield, Giles E.

    2013-01-01

    We recently characterized 24-hr daily rhythmic patterns of gene expression in Anopheles gambiae mosquitoes. These include numerous odorant binding proteins (OBPs), soluble odorant carrying proteins enriched in olfactory organs. Here we demonstrate that multiple rhythmically expressed genes including OBPs and takeout proteins, involved in regulating blood feeding behavior, have corresponding rhythmic protein levels as measured by quantitative proteomics. This includes AgamOBP1, previously shown as important to An. gambiae odorant sensing. Further, electrophysiological investigations demonstrate time-of-day specific differences in olfactory sensitivity of antennae to major host-derived odorants. The pre-dusk/dusk peaks in OBPs and takeout gene expression correspond with peak protein abundance at night, and in turn coincide with the time of increased olfactory sensitivity to odorants requiring OBPs and times of increased blood-feeding behavior. This suggests an important role for OBPs in modulating temporal changes in odorant sensitivity, enabling the olfactory system to coordinate with the circadian niche of An. gambiae. PMID:23986098

  3. Diurnal lighting patterns and habitat alter opsin expression and colour preferences in a killifish.

    PubMed

    Johnson, Ashley M; Stanis, Shannon; Fuller, Rebecca C

    2013-07-22

    Spatial variation in lighting environments frequently leads to population variation in colour patterns, colour preferences and visual systems. Yet lighting conditions also vary diurnally, and many aspects of visual systems and behaviour vary over this time scale. Here, we use the bluefin killifish (Lucania goodei) to compare how diurnal variation and habitat variation (clear versus tannin-stained water) affect opsin expression and the preference to peck at different-coloured objects. Opsin expression was generally lowest at midnight and dawn, and highest at midday and dusk, and this diurnal variation was many times greater than variation between habitats. Pecking preference was affected by both diurnal and habitat variation but did not correlate with opsin expression. Rather, pecking preference matched lighting conditions, with higher preferences for blue at noon and for red at dawn/dusk, when these wavelengths are comparatively scarce. Similarly, blue pecking preference was higher in tannin-stained water where blue wavelengths are reduced. In conclusion, L. goodei exhibits strong diurnal cycles of opsin expression, but these are not tightly correlated with light intensity or colour. Temporally variable pecking preferences probably result from lighting environment rather than from opsin production. These results may have implications for the colour pattern diversity observed in these fish.

  4. Evidence for the copepods Acanthocyclops robustus and Mesocyclops edax as competent intermediate hosts for Coelomomyces punctatus during an epizootic in a larval population of the mosquito Anopheles quadrimaculatus.

    PubMed

    Apperson, C S; Federici, B A; Stewart, W; Tarver, F R

    1992-11-01

    Field and laboratory experiments were conducted during an epizootic of Coelomomyces punctatus (Chytridiomycetes: Blastocladiales) in a population of the mosquito Anopheles quadrimaculatus in a North Carolina farm pond to examine the interactions of several potential copepod hosts with the mosquito and fungus. The diel vertical migratory behavior of the copepod species Acanthocyclops robustus, Eucyclops serrulatus, Macrocyclops albidus, and Mesocyclops edax were monitored in relation to infection rates in sentinel mosquito larvae. Mosquito infection occurred primarily around dusk, the same period during which A. robustus and E. serrulatus were most abundant near the surface of the pond. However, exposure of A. robustus, E. serrulatus, M. albidus, M. edax, Microcyclops varicans, and Paracyclops poppei to fungal meiospores in the laboratory showed that only A. robustus and M. edax were competent intermediate hosts for C. punctatus. Laboratory studies of the diel periodicity of gametangial dehiscence in A. robustus and M. edax infected with C. punctatus revealed that gamete release and zygote formation also occurred around dusk. The combined results of the laboratory and field studies on copepod abundance, susceptibility to infection, and periodicity of gametangial dehiscence suggest that A. robustus was the principal intermediate host for C. punctatus during the epizootic, though it is probable that M. edax also contributed importantly to the overall rate of larval infection.

  5. Heavy Ion Effects on Kelvin-Helmholtz Instability: Hybrid Study

    NASA Astrophysics Data System (ADS)

    Burgess, D.; Lin, D.

    2015-12-01

    Kelvin-Helmholtz instability (KHI) is a candidate mechanism for solar wind tansportation into the magnetosphere. The statistical study of Bouhram et al. 2005 has shown that heavy ions could dominate the magnetopause for as much as 30% of the time on the dusk side. Thus the influence of heavy ions in solar wind-magnetosphere coupling should not be neglected. However, the magnetohydrodynamic (MHD) linear theory for KHI does not include any ion effects, and people working on the heavy ion effects have not come to an agreement either. Whether the heavy ions promote or inhibit the KHI still remains not well addressed. With a two-dimensional hybrid model, we investigated the effects of ion mass number on the KHI growth rate, starting from the simplest case of uniform density and uniform magnetic field perpendicular to the shear flow. It is shown that the growth rate of the KHI is lower with a heavier mass number. We try to to derive the linear theory for the kinetic KHI and compare it with the hybrid simulation results. The linear theory with ion effects considered is going to be further verified with varying heavy ion fractions and finite magnetic shear. More implications for the dawn-dusk asymmetry of KHI on planetary magnetopause are desirable when comparing the results of opposite magnetic field directions relative to the flow vorticity.

  6. Machine vision for airport runway identification

    NASA Astrophysics Data System (ADS)

    Schubert, Matthew; Moore, Andrew J.; Dolph, Chester; Woodell, Glenn

    2015-03-01

    For rigid objects and fixed scenes, current machine vision technology is capable of identifying imagery rapidly and with specificity over a modest range of camera viewpoints and scene illumination. We applied that capability to the problem of runway identification using video of sixteen runway approaches at nine locations, subject to two simplifying assumptions. First, by using approach video from just one of the several possible seasonal variations (no snow cover and full foliage), we artificially removed one source of scene variation in this study. Secondly, by not using approach video at dawn and dusk, we limited the study to two illumination variants (day and night). We did allow scene variation due to atmospheric turbidity by using approach video from rainy and foggy days in some daytime approaches. With suitable ensemble statistics to account for temporal continuity in video, we observed high location specificity (<90% Bayesian posterior probability). We also tested repeatability, i.e., identification of a given runway across multiple videos, and observed robust repeatability only if illumination (day vs. night) was the same and approach visibility was good. Both specificity and repeatability degraded in poor weather conditions. The results of this simplified study show that geolocation via real-time comparison of cockpit image sensor video to a database of runway approach imagery is feasible, as long as the database contains imagery from about the same time of day (complete daylight and nighttime, excluding dawn and dusk) and the weather is clear at the time of the flight.

  7. Tidal influence on O(1S) airglow emission rate distributions at the geographic equator as observed by WINDII

    NASA Technical Reports Server (NTRS)

    Shephere, G. G.; Mclandress, C.; Solheim, B. H.

    1995-01-01

    WINDII, the Wind Imaging Interferometer on the Upper Atmosphere Research Satellite, observes winds, temperatures and emission rates in the upper mesosphere and thermosphere. In this paper we report on nighttime observations of the vertical distribution of the O(1S) 557.7 nm emission near the geographic equator for March/April, 1993. The airglow volume emission rate distribution is found to be strongly dependent on local time. Beginning at dusk, an intense airglow emission layer descends from a mean altitude of 95 km, reaching 89 km by midnight after which the emission rapidly decays. Shortly after midnight it reappears weakly at a higher altitude and remains at this level as the emission rate gradually increases towards dawn. This strong local time dependence leads us to conclude that the effect is tidally driven. Comparison with the Forbes (1982a,b) model suggest that total density perturbations and changes in the atomic oxygen mixing ratio may the cause of the changes in emission rate distribution between dusk and midnight. The reappearance of the emission after midnight may be caused by downward winds bringing oxygen-rich air from above.

  8. Ionospheric and magnetospheric plasmapauses'

    NASA Technical Reports Server (NTRS)

    Grebowsky, J. M.; Hoffman, J. H.; Maynard, N. C.

    1977-01-01

    During August 1972, Explorer 45 orbiting near the equatorial plane with an apogee of about 5.2 R sub e traversed magnetic field lines in close proximity to those simultaneously traversed by the topside ionospheric satellite ISIS 2 near dusk in the L range 2-5.4. The locations of the Explorer 45 plasmapause crossings during this month were compared to the latitudinal decreases of the H(+) density observed on ISIS 2 near the same magnetic field lines. The equatorially determined plasmapause field lines typically passed through or poleward of the minimum of the ionospheric light ion trough, with coincident satellite passes occurring for which the L separation between the plasmapause and trough field lines was between 1 and 2. Vertical flows of the H(+) ions in the light ion trough as detected by the magnetic ion mass spectrometer on ISIS were directed upward with velocities between 1 and 2 kilometers/sec near dusk on these passes. These velocities decreased to lower values on the low latitude side of the H(+) trough but did not show any noticeable change across the field lines corresponding to the magnetospheric plasmapause.

  9. Short term variations in Jupiter's synchrotron radiation derived from VLA data analysis

    NASA Astrophysics Data System (ADS)

    Kita, H.; Misawa, H.; Tsuchiya, F.; Morioka, A.

    2011-12-01

    Jupiter's synchrotron radiation (JSR) is the emission from relativistic electrons in the strong magnetic field of the inner magnetosphere, and it is the most effective prove for remote sensing of Jupiter's radiation belt from the Earth. Although JSR has been thought to be stable for a long time, intensive observations for JSR have made after the collisions of comet P/SL9 to Jupiter in 1994, and these observations revealed short term variations of JSR on time scale of days to weeks. However, the mechanisms which cause the short term variations of total flux density and brightness distribution have not been revealed well. In order to reveal the mechanism of short term variations of JSR more precisely, we have made radio image analysis using the NRAO (National Radio Astronomy Observatory) archived data of the VLA [*]. Brice and McDonough [1973, Icarus] proposed a scenario for the short term variations: i.e, the solar UV/EUV heating for Jupiter's upper atmosphere drives neutral wind perturbations and then the induced dynamo electric field leads to enhancement of radial diffusion. It is also suggested that induced dynamo electric field produce dawn-dusk electric potential difference, which cause dawn-dusk asymmetry in electron spatial distribution and emission distribution. So far the following results have been indicated for the short term variations. Miyoshi et al. [1999, GRL] showed that a short term variation event at 2.3GHz is well correlate to solar UV/EUV flux variations. Tsuchiya et al. [2010, Adv. Geosci.] showed that JSR at 325MHz and 785MHz have short term variations. These JSR observations confirmed the existence of the short term variation which is caused by solar UV/EUV. However, the effect of solar UV/EUV heating on the spatial distribution of JSR has never been confirmed, so this study is the first attempt to confirm the solar UV/EUV effect on spatial distribution of JSR. We have selected the data observed from 28th Jan. to 5th Feb. 2000 at 327MHz

  10. Elements of M-I Coupling in Repetitive Substorm Activity Driven by Interplanetary CMEs

    NASA Astrophysics Data System (ADS)

    Farrugia, C. J.; Sandholt, P. E.

    2014-12-01

    By means of case studies we explore key elements of the magnetosphere-ionosphere current system associated with repetitive substorm activity during persistent strong forcing by ICMEs. Our approach consists of a combination of the magnetospheric and ionospheric perspectives on the substorm activity. The first aspect is the near-Earth plasma sheet with its repetitive excitations of the substorm current wedge, as monitored by spacecraft GOES-10 when it traversed the 2100-0300 MLT sector, and its coupling to the westward auroral electrojet (WEJ) centered near midnight during the stable interplanetary (IP) conditions. The second aspect is the excitation of Bostrom type II currents maximizing at dusk and dawn and their associated ionospheric Pedersen current closure giving rise to EEJ (WEJ) events at dusk (dawn). As documented in our study, this aspect is related to the braking phase of Earthward-moving dipolarization fronts-bursty bulk flows. We follow the magnetospheric flow/field events from spacecraft Geotail in the midtail (X = - 11 Re) lobe to geostationary altitude at pre-dawn MLTs (GOES 10). The associated M-I coupling is obtained from ground-satellite conjunctions across the double auroral oval configuration along the meridian at dusk. By this technique we distinguish between ionospheric manifestations in three latitude regimes: (i) auroral oval south, (ii) auroral oval north, and (iii) polar cap. Regime (iii) is characterized by events of enhanced antisunward convection near the polar cap boundary (flow channel events) and in the central polar cap (PCN-index events). The repetitive substorm activity is discussed in the context of the level of IP driving as given by the geoeffective IP electric field (E_KL), magnetotail reconnection (inferred from the PCN-index and spacecraft Wind at X = - 77 Re) and the storm SYM-H index. We distinguish between different variants of the repetitive substorm activity, giving rise to electrojet (AL)-plasma convection (PCN) events

  11. Energetic Neutral Atom Imaging at Low Altitudes from the Swedish Microsatellite Astrid: Images and Spectral Analysis. Paper 1

    NASA Technical Reports Server (NTRS)

    Brandt, Pontus C:son; Barabash, Stas; Norberg, Olle; Lundin, Rickard; Roelof, Rdmond C.; Chase, Christopher J.

    1999-01-01

    Observations of energetic neutral atoms (ENA) in the energy range 26- 52 keV are reported from four occasions during geomagnetically disturbed periods. The data were acquired by the ENA imager flown on the Swedish microsatellite Astrid in a 1000 km circular orbit with 83 deg inclination. The ENA imager separates charged particles from neutrals through an electrostatic deflection system in the energy range between 0.1 and 114 keV. ENA images obtained from vantage points in the polar cap and in the afternoon magnetic local time (MLT) hours looking into the antisunward hemisphere show intense ENA fluxes (approx. 10(exp 4)/sq cm sr s over 26-37 keV) coming from the dusk region and low altitudes (approx. 300 km). The morphology shows no relation to local magnetic field excluding the possibility of charged particle detection. It is concluded that the source of these ENAs are precipitating/mirroring ions from the ring current/trapped radiation interacting with the exobase on auroral L-shells and in the dusk region. The observed ENA fluxes show a relation with Kp and Dst geomagnetic indices. The observed ENA spectrum from a geomagnetic storm on February 8, 1995, is investigated in more detail and compared to the parent ion spectrum obtained by the Defense Meteorological Satellite Project (DMSP) satellite, Fl2, during the same period on L = 6 +/- 2 around dusk. The observed ENA spectral slope is used to derive the parent ion spectral temperature. The derived ion temperatures range is 3.0 - 6.0 keV for H and 4.5 - 8.5 keV for O. The higher of these ion temperatures comes closest in agreement to the extrapolated DMSP spectrum leading us to favor O over H as the species of the detected ENAS. It is shown that the detected ENAs must have been produced at L greater than or equal to 6 to reach the detector without atmospheric attenuation and that the main energy dependence of the ENA spectrum, apart from the parent ion spectrum, is governed by the energy dependence of the charge

  12. The search for Ar in the lunar atmosphere using the Lunar Reconnaissance Orbiter's LAMP instrument.

    NASA Astrophysics Data System (ADS)

    Cook, J. C.; Stern, S. A.; Feldman, P. D.; Gladstone, R.; Retherford, K. D.; Greathouse, T. K.; Grava, C.

    2014-12-01

    The Apollo 17 mass spectrometer, LACE, first measured mass 40 particles in the lunar atmosphere, and over a nine-month period, detected variations correlated with the lunar day (Hoffman et al., 1973, LPSC, 4, 2865). LACE detected a high particle density at dusk (0.6-1.0x104 cm-3), decreasing through the lunar night to a few hundred cm-3, then increasing rapidly before dawn to levels 2-4 times greater than at dusk. No daytime measurements were made due to instrument saturation. Given the LACE measurements' periodic nature, and the Ar abundance in lunar regolith samples (Kaiser, 1972, EPSL, 13, 387), it was concluded that mass 40 was likely due to Ar. Benna et al. (2014, LPSC, 45, 1535) recently reported that the Neutral Mass Spectrometer (NMS) aboard LADEE also detected Ar (mass 40) with similar diurnal profiles. We report on UV spectra of the lunar atmosphere as obtained by the Lunar Reconnaissance Orbiter (LRO). Aboard LRO is the UV-spectrograph, LAMP (Lyman Alpha Mapping Project), spanning the spectral range 575 to 1965 Å. LAMP is typically oriented toward the surface and has been mapping the Moon since September 2009. LAMP also observes the tenuous lunar atmosphere when the surface is in darkness, but the atmospheric column below LRO is illuminated. We have previously used nadir oriented twilight observations to examine the sparse lunar atmosphere (Feldman et al., 2012, Icarus, 221, 854; Cook et al., 2013, Icarus, 225, 681; Stern et al., 2013, Icarus, 226, 1210; Cook & Stern 2014, Icarus, 236, 48). In Cook et al., 2013, we reported an upper limit for Ar of 2.3x104 cm-3. Since then, we have collected additional data and refined our search method by focusing on the regions (near equator) and local times (dawn and dusk) where Ar has been reported previously. We have carefully considered effective area calibration and g-factor accuracies and find these to be unlikely explanations for the order of magnitude differences. We will report new results, which provide much

  13. Hybrid-Kinetic Modelling of Space Plasma with Application to Mercury

    NASA Astrophysics Data System (ADS)

    Paral, Jan

    A planet's magnetosphere is often very dynamic, undergoing large topological changes in response to high speed (˜400km/s) solar wind intervals, coronal mass ejections, and naturally excited plasma wave modes. Plasma waves are very effective at transporting energy throughout the magnetosphere, and are therefore of interest in the context of the coupling between solar wind and magnetosphere. Of relevance to this thesis is Kelvin-Helmholtz macro-instability. Kelvin-Helmholtz instability (KHI) is excited by shear of the flows. KHI is commonly observed at equatorial regions of the magnetopause where fast flowing magnetosheath plasma may interact with slow bulk velocities of magnetospheric plasma. The instability is responsible for exciting shear Alfven waves which (at Earth) may be detected using the ground based magnetometers located at latitude of excited field lines. This thesis uses numerical modelling to understand and to explain the generation and propagation of the KHI in Mercury's magnetosphere. The instability is initiated close to the planet and convectively grows while being transported along the tail. When the wave amplitude reaches a nonlinear stage, the structure of the wave becomes complex due to the wrapping of the plasma into the vortex. A vortex structure is typical for KHI and it is used for identifying the wave in the data from satellites. The instability commonly occurs at the dawn or dusk flank magnetopause (MP) of Earth with approximately the same probability. But the data from NASA's MESSENGER spacecraft, currently in the orbit of the planet Mercury, suggest a strong asymmetry in the observations of KHI. It is shown that the KHI initiated near the subsolar point evolves into large-scale vortices propagating anti-sunward along the dusk-side MP. The simulations are in agreement with the third flyby of the MESSENGER spacecraft, where saw-tooth oscillations in the plasma density, flow, and magnetic field were observed. The observed asymmetry in the

  14. Substorms and polar cap convection: the 10 January 2004 interplanetary CME case

    NASA Astrophysics Data System (ADS)

    Andalsvik, Y.; Sandholt, P. E.; Farrugia, C. J.

    2012-01-01

    The expansion-contraction model of Dungey cell plasma convection has two different convection sources, i.e. reconnections at the magnetopause and in the magnetotail. The spatial-temporal structure of the nightside source is not yet well understood. In this study we shall identify temporal variations in the winter polar cap convection structure during substorm activity under steady interplanetary conditions. Substorm activity (electrojets and particle precipitations) is monitored by excellent ground-satellite DMSP F15 conjunctions in the dusk-premidnight sector. We take advantage of the wide latitudinal coverage of the IMAGE chain of ground magnetometers in Svalbard - Scandinavia - Russia for the purpose of monitoring magnetic deflections associated with polar cap convection and substorm electrojets. These are augmented by direct observations of polar cap convection derived from SuperDARN radars and cross-track ion drift observations during traversals of polar cap along the dusk-dawn meridian by spacecraft DMSP F13. The interval we study is characterized by moderate, stable forcing of the magnetosphere-ionosphere system (EKL = 4.0-4.5 mV m-1; cross polar cap potential (CPCP), Φ (Boyle) = 115 kV) during Earth passage of an interplanetary CME (ICME), choosing an 4-h interval where the magnetic field pointed continuously south-west (Bz < 0; By < 0). The combination of continuous monitoring of ground magnetic deflections and the F13 cross-track ion drift observations in the polar cap allows us to infer the temporal CPCP structure on time scales less than the ~10 min duration of F13 polar cap transits. We arrived at the following estimates of the dayside and nightside contributions to the CPCP (CPCP = CPCP/day + CPCP/night) under two intervals of substorm activity: CPCP/day ~110 kV; CPCP/night ~50 kV (45% CPCP increase during substorms). The temporal CPCP structure during one of the substorm cases resulted in a dawn-dusk convection asymmetry measured by DMSP F13 which

  15. Dipolarization fronts as earthward propagating flux ropes: A three-dimensional global hybrid simulation

    NASA Astrophysics Data System (ADS)

    Lu, S.; Lu, Q.; Lin, Y.; Wang, X.; Ge, Y.; Wang, R.; Zhou, M.; Fu, H.; Huang, C.; Wu, M.; Wang, S.

    2015-12-01

    Dipolarization fronts (DFs) as earthward propagating flux ropes (FRs) in the Earth's magnetotail are presented and investigated with a three-dimensional (3-D) global hybrid simulation for the first time. In the simulation, several small-scale earthward propagating FRs are found to be formed by multiple X-line reconnection in the near-tail. During their earthward propagation, the magnetic field Bz of the FRs becomes highly asymmetric due to the imbalance of the reconnection rates between the multiple X-lines. At the later stage, when the FRs approach the near-Earth dipole-like region, the anti-reconnection between the southward/negative Bz of the FRs and the northward geomagnetic field leads to the erosion of the southward magnetic flux of the FRs, which further aggravates the Bz asymmetry. Eventually, the FRs merge into the near-Earth region through the anti-reconnection. These earthward propagating FRs can fully reproduce the observational features of the DFs, e.g., a sharp enhancement of Bz preceded by a smaller amplitude Bz dip, an earthward flow enhancement, the presence of the electric field components in the normal and dawn-dusk directions, and ion energization. Our results show that the earthward propagating FRs can be used to explain the DFs observed in the magnetotail. The thickness of the DFs is on the order of several ion inertial lengths, and the electric field normal to the front is found to be dominated by the Hall physics. During the earthward propagation from the near-tail to the near-Earth region, the speed of the FR/DFs increases from ~150km/s to ~1000km/s. The FR/DFs can be tilted in the GSM xy plane with respect to the y (dawn-dusk) axis and only extend several RE in this direction. Moreover, the structure and evolution of the FRs/DFs are non-uniform in the dawn-dusk direction, which indicates that the DFs are essentially 3-D.

  16. Penetration of Large Scale Electric Field to Inner Magnetosphere

    NASA Astrophysics Data System (ADS)

    Chen, S. H.; Fok, M. C. H.; Sibeck, D. G.; Wygant, J. R.; Spence, H. E.; Larsen, B.; Reeves, G. D.; Funsten, H. O.

    2015-12-01

    The direct penetration of large scale global electric field to the inner magnetosphere is a critical element in controlling how the background thermal plasma populates within the radiation belts. These plasma populations provide the source of particles and free energy needed for the generation and growth of various plasma waves that, at critical points of resonances in time and phase space, can scatter or energize radiation belt particles to regulate the flux level of the relativistic electrons in the system. At high geomagnetic activity levels, the distribution of large scale electric fields serves as an important indicator of how prevalence of strong wave-particle interactions extend over local times and radial distances. To understand the complex relationship between the global electric fields and thermal plasmas, particularly due to the ionospheric dynamo and the magnetospheric convection effects, and their relations to the geomagnetic activities, we analyze the electric field and cold plasma measurements from Van Allen Probes over more than two years period and simulate a geomagnetic storm event using Coupled Inner Magnetosphere-Ionosphere Model (CIMI). Our statistical analysis of the measurements from Van Allan Probes and CIMI simulations of the March 17, 2013 storm event indicate that: (1) Global dawn-dusk electric field can penetrate the inner magnetosphere inside the inner belt below L~2. (2) Stronger convections occurred in the dusk and midnight sectors than those in the noon and dawn sectors. (3) Strong convections at multiple locations exist at all activity levels but more complex at higher activity levels. (4) At the high activity levels, strongest convections occur in the midnight sectors at larger distances from the Earth and in the dusk sector at closer distances. (5) Two plasma populations of distinct ion temperature isotropies divided at L-Shell ~2, indicating distinct heating mechanisms between inner and outer radiation belts. (6) CIMI

  17. Plasma convection in the nightside magnetosphere of Saturn determined from energetic ion anisotropies

    NASA Astrophysics Data System (ADS)

    Kane, M.; Mitchell, D. G.; Carbary, J. F.; Krimigis, S. M.

    2014-02-01

    The Cassini Ion and Neutral Camera measures intensities of hydrogen and oxygen ions and neutral atoms in the Saturnian magnetosphere and beyond. We use the measured intensity spectrum and anisotropy of energetic hydrogen and oxygen ions to detect, qualify, and quantify plasma convection. We find that the plasma azimuthal convection speed relative to the local rigid corotation speed decreases with radial distance, lagging the planetary rotation rate, and has no significant local time dependences. Plasma in the dusk-midnight quadrant sub-corotates at a large fraction of the rigid corotation speed, with the primary velocity being azimuthal but with a distinct radially outward component. The duskside velocities are similar to those obtained from earlier orbits in the midnight-dawn sector, in contrast to the depressed velocities measured at Jupiter using Energetic Particles Detector measurements on the Galileo spacecraft in the dusk-midnight quadrant. We find significant radial outflow in most of the nightside region. The radial component of the flow decreases with increasing local time in the midnight-dawn sector and reverses as dawn is approached. This and previous results are consistent with a plasma disk undergoing a centrifugally induced expansion as it emerges into the nightside, while maintaining partial rotation with the planet. The magnetodisk expansion continues as plasma rotates across the tail to the dawnside. We do not see evidence in the convection pattern for steady state reconnection in Saturn's magnetotail. The outermost region of the magnetodisk, having undergone expansion upon emerging from the dayside magnetopause confinement, is unlikely to recirculate back into the dayside. We conclude that plasma in the outer magnetodisk [at either planet] rotates from the dayside, expands at the dusk flank, but remains magnetically connected to the respective planet while moving across the tail until it interacts with and is entrained into the dawnside

  18. Multi-point observations of Ion Dispersions near the Exterior Cusp with Cluster

    NASA Astrophysics Data System (ADS)

    Escoubet, C.-Philippe; Grison, Benjamin; Berchem, Jean; Trattner, Kralheinz; Pitout, Frederic; Richard, Robert; Taylor, Matt; Soucek, Jan; Laakso, Harri; Masson, Arnaud; Dunlop, Malcolm; Dandouras, Iannis; Reme, Henri; Fazakerley, Andrew; Daly, Patrick

    2014-05-01

    The exterior cusp is the most external region of the polar magnetosphere in direct contact with the plasma and the magnetic field from the solar wind. Unlike the rest of the magnetopause surface, the exterior cusp is a singular region with small and turbulent magnetic field and where large entry of plasma from solar origin takes place. The main process that injects solar wind plasma into the polar cusp is now generally accepted to be magnetic reconnection. Depending on the IMF direction, this process will take place equatorward (for IMF southward), poleward (for IMF northward) or on the dusk or dawn sides (for IMF azimuthal) of the cusp. We report a Cluster crossing on 5 January 2002 near the exterior cusp on the southern dusk side. The IMF was mainly azimuthal (IMF-By around -5 nT), the solar wind speed lower than usual around 280 km/s and the density around 5 cm-3. The four Cluster spacecraft were still in the "magnetotail" configuration with two perfect tetrahedra of 2000 km around apogee and turning into an elongated configuration near the magnetopause. C4 was the first spacecraft to enter the cusp around 19:52:04 UT, followed by C2 at 19:52:35 UT, C1 at 19:54:24 UT and C3 at 20:13:15 UT. C4 and C1 observed two ion energy dispersions at 20:10 UT and 20:40 UT and C3 at 20:35 UT and 21:15 UT. Using the time of flight technique on the upgoing and downgoing ions in the dispersions, we obtain an altitude of the sources of these ions between 14 and 20 RE. Using Tsyganenko model, these sources are located on the dusk flank, past the terminator. In addition, before entering the cusp, the magnetopause crossing was characterized by a large shear in By and bipolar plasma flows, suggesting that reconnection was taking place near the exterior cusp. We will discuss the extent of the reconnection line along the flank of the magnetopause based on these observations.

  19. An Investigation of Trajectories of Atoms in Mercury's Exosphere

    NASA Astrophysics Data System (ADS)

    Bradley, Eric Todd

    2016-10-01

    Mercury's neutral exosphere consists of atoms or molecules ejected from the surface that are on individual trajectories that may re-impact the surface if there is insufficient energy to escape the gravity of the planet. This is an investigation of how the radiation pressure, orbital acceleration of the planet, and planetary rotation combine together to produce complicated trajectories. Because of Mercury's non-zero eccentricity the planet is not in uniform circular motion, which leads to radial and tangential accelerations that vary throughout the Mercury year. Besides radiation pressure the trajectory of an exospheric atom is affected by the planet accelerating during the time of flight of the atom that 1) causes the atom's position with respect to the ejection point to vary in a manner that is different than if the planet were not accelerating and 2) causes the planet-atom distance to vary in a manner that is different than for a typical ballistic trajectory resulting in variation of the gravitational force that the planet exerts on the atom. These effects are small but persistent and affect where the atom re-impacts the surface, which may lead to asymmetrical distributions of atoms in the surface regolith and exosphere.Preliminary results from simulations of ejected atoms that include 1) radiation pressure that varies with the atom's velocity due to Doppler shifting, 2) radial and tangential accelerations of the planet, and 3) the variation of the planet's gravity on the atom with distance above the planet show that atoms ejected at low energies normal to the surface from the subsolar point re-impact on the dusk side hemisphere of the planet. However atoms ejected at high energies normal to the surface from the subsolar point re-impact on the dawn side hemisphere of the planet. A fraction of atoms ejected normal to the surface from the dawn terminator within an energy range that results in the atom re-impacting and sticking to the night side surface behind the

  20. Equatorial counterelectrojets during geomagnetic storms and their possible dynamos in the magnetosphere

    NASA Astrophysics Data System (ADS)

    Kikuchi, T.; Hashimoto, K. K.; Ebihara, Y.; Tsuji, Y.; Veenadhari, B.; Nishimura, T.; Tanaka, T.; Fujita, S.; Nagatsuma, T.

    2012-12-01

    During the substorm growth phase and storm main phase, the high pressure plasma accumulated in the cusp and mantle regions activates a dynamo for the dawn-to-dusk convection electric field and the Region-1 field-aligned currents (R1 FACs) [Tanaka, 1995]. The electric field and FACs are conveyed by the shear Alfven waves to the polar ionosphere and the electric field extends promptly to low latitude through the Earth-ionosphere waveguide [Kikuchi and Araki, 1979]. The electric field drives the DP2 currents at mid latitudes [Wilson et al., 2001; Tsuji et al., 2012] and intensifies the equatorial electrojet (EEJ) [Kikuchi et al., 1996, 2008]. The convection electric field extends to the inner magnetosphere promptly [Nishimura et al., 2009] and energizes the plasma in the partial ring current region with the help of the gradient and curvature drift [Ebihara and Ejiri, 2000], which in turn works as a dynamo for the dusk-to-dawn electric field and the R2 FACs. The dusk-to-dawn electric field causes the counterelectrojet (CEJ) at the equator when the IMF turns northward [Rastogi, 1975]. The CEJ often appears during substorms [Kobea et al., 2000; Kikuchi et al., 2000]. Both the R1 and R2 FACs are intensified by the substorm expansion, with the R2 FACs strong enough to cause the CEJ [Hashimoto et al., 2011]. The CEJ often occurs during the recovery phase of geomagnetic storms [Kikuchi et al., 2008; Tsuji et al., 2012], while the CEJ also appears during the storm main phase under the relatively stable southward IMF [Fejer et al., 2007; Veenadhari et al., 2010]. In this paper, we analyzed several storm events to identify the dynamo for the stormtime CEJ. The disturbance dynamo is a commonly accepted dynamo for the long lasting stormtime CEJ [Blanc and Richmond, 1980; Fejer and Scherliess 1997]. However, the observed rapid and periodic development of the CEJ should be attributed to the R2 FACs generated in the inner magnetosphere. Based on the magnetometer and radar

  1. Magnetospheric sash dependence on IMF direction

    NASA Astrophysics Data System (ADS)

    Siscoe, G. L.; Erickson, G. M.; Ö Sonnerup, B. U.; Maynard, N. C.; Siebert, K. D.; Weimer, D. R.; White, W. W.

    The magnetospheric sash is a ribbon of weak field shaped like a horseshoe with its open ends adjacent to the north and south dayside, magnetopause cusps and its closed end forming the cross-tail current sheet. The clock angle of the sash in the dawn-dusk meridian plane (as seen from the sun) rotates from 0° to 90° as the clock angle of the interplanetary magnetic field (IMF) rotates from 0° to 180°. We use a global MHD simulation to obtain the sash clock angles for IMF clock angles of 45°, 90°, and 135°. Remarkably, the results are very close to the clock angle of the magnetic null points obtained by superposing a uniform field representing the IMF on a dipole field representing the earth. Contours of magnetic field strength on cross sections perpendicular to the solar wind flow direction show how the sash evolves tailward from the dayside cusps.

  2. Toward a political analysis of the consequences of a world climate change produced by increasing atmospheric carbon dioxide

    SciTech Connect

    Schware, R.

    1980-01-01

    It was Hegel's extraordinarily deep and perceptive insight that mankind is caught up in a drama that cannot be fully understood until it has been played out. The owl of Minewa spreads its wings only with the falling of the dusk. On the more hopeful side is the fact that, although we cannot know the consequences of future interactions between climate and society, we can begin to work toward political solutions and gird ourselves for ominous trends that are now coming into view. The purpose of this paper is to identify one such trend, namely the increase of atmospheric temperatures due to increased carbon dioxide (CO/sub 2/) and lay some initial groundwork for political research related to climate-societal interactions.

  3. Energetic particles in the vicinity of a possible neutral line in the plasma sheet

    NASA Technical Reports Server (NTRS)

    Moebius, E.; Scholer, M.; Hovestadt, D.; Paschmann, G.; Gloeckler, G.

    1983-01-01

    Combined plasma, magnetic field, and energetic particle data obtained from ISEE-1 in the geomagnetic tail during two successive energetic particle burst events are presented. The behavior of protons with energies of more than about 100 keV is very different from that of the 30-100 keV protons which represent the suprathermal tail of the plasma sheet distribution. The more energetic ions appear on a time scale of several minutes following a northward turning of the tail magnetic field. At about the same time the plasma measurements show a velocity of about 200 km/s in the tailward direction. From these results, it is argued that two successive magnetic neutral lines are created well within the plasma sheet and move close to the satellite position in the earthward direction. The extent of the neutral line is then limited to the dusk side of the tail.

  4. Electric field evidence for tailward flow at substorm onset

    NASA Technical Reports Server (NTRS)

    Nishida, A.; Tulunay, Y. K.; Mozer, F. S.; Cattell, C. A.; Hones, E. W., Jr.; Birn, J.

    1983-01-01

    Electric field observations made near the neutral sheet of the magnetotail provide additional support for the view that reconnection occurs in the near-earth region of the tail. Southward turnings of the magnetic field that start at, or shortly after, substorm onsets are accompanied by enhancements in the dawn-to-dusk electric field, resulting in a tailward E x B drift velocity. Both the magnetic and the electric fields in the tailward-flowing plasma are nonuniform and vary with inferred spatial scales of several earth radii in the events examined in this paper. These nonuniformities may be the consequence of the tearing-mode process. The E x B flow was also towards the neutral sheet and away from midnight in the events studied.

  5. Global simulation of EMIC waves in the He+ band for 2001 April 21st storm from RCM-RAM-HOTRAY self-consistent modeling

    NASA Astrophysics Data System (ADS)

    Chen, L.; Thorne, R. M.; Jordanova, V.; Horne, R. B.; Wang, C.

    2009-12-01

    Global distribution of Electromagnetic ion cyclotron (EMIC) wave spectrum in the He+ band is simulated for the 2001 April 21st storm using a self-consistent model, which combines three different codes, the Ring current and atmospheric interaction model (RAM), the Rice Convection Model (RCM), ray tracing code (HOTRAY incorporated with growth rate solver). The ring current H+ provides the source of free energy for EMIC excitation during the storm time, and significant wave gain occurs in the region inside the plume and at the eastward edge of the plume in the dusk sector and pre-midnight sector. The ability of resonating with MeV electrons is also evaluated. Minimum electron resonant energy is generally above 3 MeV. The energetic O+ component of ring current is overestimated in the simulation and thus suppresses significantly on the EMIC waves in the He+. However, the pattern of excitation region basically remains the same.

  6. Mid- and low-latitude prompt-penetration ionospheric zonal plasma drifts

    NASA Astrophysics Data System (ADS)

    Fejer, Bela G.; Scherliess, Ludger

    We have used ion drift observations from the DE-2 satellite to determine the latitudinal variation and the temporal evolution of mid- and low-latitude prompt penetration zonal plasma drifts driven by magnetospheric electric fields. Our results indicate that sudden increases in convection lead to predominantly westward perturbation drifts which decrease equartorwards and have largest amplitudes in the dusk-midnight sector. The diurnal perturbation drift patterns shift to later local times with increasing storm time and decay to new quasi-equilibrium values in about 2 hours, as the ring current readjusts to the new polar cap potential. The daily and latitudinal variations and temporal evolution of the DE-2 prompt penetration drifts are generally in good agreement with predictions from the Rice Convection Model, although the experimental results show larger amplitudes and longer shielding time constants.

  7. Interchange instability in the inner magnetosphere associated with geosynchronous particle flux decreases

    NASA Astrophysics Data System (ADS)

    Sazykin, S.; Wolf, R. A.; Spiro, R. W.; Gombosi, T. I.; De Zeeuw, D. L.; Thomsen, M. F.

    2002-05-01

    We simulate the inner magnetosphere during the magnetic storm of September 25, 1998 using the Rice Convection Model with boundary fluxes estimated from geosynchronous data. Model results indicate development of an interchange-like instability in the dusk-to-midnight sector, producing ripple structures in the plasma density, swirls in the subauroral ionospheric electric field pattern, and undulations near the equatorward edge of the diffuse aurora. We suggest that these disturbances might be observable whenever a strong main-phase ring-current injection is followed by a major, sustained decrease in the plasma energy density at geosynchronous orbit, a circumstance that will also produce rapid decay of the storm-time ring current.

  8. Outer satellite atmospheres: Their extended nature and planetary interactions

    NASA Technical Reports Server (NTRS)

    Smyth, W. H.; Combi, M. R.

    1984-01-01

    Model calculations for the brightness of the sodium cloud in Region A were performed to clarify the role played by the plasma torus sink in producing the east-west intensity asymmetry observed in the sodium D-lines. It was determined that the east-west electric field, proposed by Barbosa and Kievelson (1983) and Ip and Goertz (1983) to explain the dawn-dusk asymmetry in the torus ion emissions measured by the Voyager UVS instrument, could also produce the east-west sodium intensity asymmetry discovered earlier by Bergstralh et al. (1975, 1977). Model results for the directional features of the sodium cloud are also reported. The completion of the development of the Io potassium cloud model, progress in improving the Titan hydrogen torus model, and efforts in developing our model for hydrogen cometary atmospheres are also discussed.

  9. Downstream properties of magnetic flux transfer events. [in magnetosphere

    NASA Technical Reports Server (NTRS)

    Sibeck, D. G.; Siscoe, G. L.

    1984-01-01

    Attention is given to the downstream evolution of the field line tubes known as 'flux transfer events' (FTEs), whose magnetic field and plasma properties are distinct from those of the nearby unmerged magnetosheath and magnetosphere field lines. After the FTE has moved 200 earth radii down the tail, its drained portion reaches 25 earth radii radially outward from the tail boundary. It is suggested that most multiple crossings of the tail boundary observed by spacecraft are encounters with tailward-moving FTEs, thereby explaining both the behavior of boundary normals during multiple crossings and how the sign of the IMF causes the observed dawn-dusk asymmetries in the thickness of the magnetotail boundary layer.

  10. High-Latitude Ionospheric Dynamics During Conditions of Northward IMF

    NASA Technical Reports Server (NTRS)

    Sharber, J. R.

    1996-01-01

    In order to better understand the physical processes operating during conditions of northward interplanetary magnetic field (IMF), in situ measurements from the Dynamics Explorer-2 (low altitude) polar satellite and simultaneous observations from the auroral imager on the Dynamics Explorer-1 (high altitude) satellite were used to investigate the relationships between optical emissions, particle precipitation, and convective flows in the high-latitude ionosphere. Field aligned current and convective flow patterns during IMF north include polar cap arcs, the theta aurora or transpolar arc, and the 'horse-collar' aurora. The initial part of the study concentrated on the electrodynamics of auroral features in the horse-collar aurora, a contracted but thickened emission region in which the dawn and dusk portions can spread to very high latitudes, while the latter part focused on the evolution of one type of IMF north auroral pattern to another, specifically the quiet-time horse-collar pattern to a theta aurora.

  11. Observations of large-scale plasma convection in the magnetosphere with respect to the geomagnetic activity level

    NASA Astrophysics Data System (ADS)

    Stepanov, A. E.; Khalipov, V. L.; Kotova, G. A.; Zabolotskii, M. S.; Golikov, I. A.

    2016-03-01

    The data of the ionospheric observations (the daily f plots) at the Yakutsk meridional chain of ionosondes (Yakutsk-Zhigansk-Batagai-Tixie Bay) with sharp decreases (breaks) in the critical frequency of the regular ionospheric F2 layer ( foF2) are considered. The data for 1968-1983 were analyzed, and the statistics of the foF2 break observations, which indicate that these breaks are mainly registered in equinoctial months and in afternoon and evening hours under moderately disturbed geomagnetic conditions, are presented. Calculations performed using the prognostic model of the high-latitude ionosphere indicate that the critical frequency break position coincides with the equatorial boundary of large-scale plasma convection in the dusk MLT sector.

  12. New Understanding of Mercury's Magnetosphere from MESSENGER'S First Flyby

    NASA Technical Reports Server (NTRS)

    Slavin, James A.; Acuna, Mario H.; Anderson, Brian J.; Baker, Daniel N.; Benna, Mehdi; Gloeckler, George; Gold, Robert E.; Ho, George C.; Killen, M.; Korth, Haje; Krimigis, Stamatios M.; McNutt, Ralph L., Jr.; Raines, James M.; Schriver, David; Somomon, Sean C.; Starr, Richard; Travnicek, Pavel; Zurbuchen, Thomas H.

    2008-01-01

    Observations by the MESSENGER spacecraft on 14 January 2008 have revealed new features of the solar system's smallest planetary magnetosphere. The interplanetary magnetic field orientation was unfavorable for large inputs of energy from the solar wind and no evidence of magnetic substorms, internal magnetic reconnection, or energetic particle acceleration was detected. Large-scale rotations of the magnetic field were measured along the dusk flank of the magnetosphere and ultra-tow frequency waves were frequently observed beginning near closest approach. Outbound the spacecraft encountered two current-sheet boundaries across which the magnetic field intensity decreased in a step-like manner. The outer current sheet is the magnetopause boundary. The inner current sheet is similar in structure, but weaker and -1000 km closer to the planet. Between these two current sheets the magnetic field intensity is depressed by the diamagnetic effect of planetary ions created by the photo-ionization of Mercury's exosphere.

  13. A study of population changes in adult Culex quinquefasciatus Say (Diptera: Culicidae) during a mosquito control programme in Dubai, United Arab Emirates.

    PubMed

    Holmes, P R

    1986-02-01

    The effectiveness of insecticidal control measures on adult Culex quinquefasciatus Say in Dubai, United Arab Emirates, was examined. Direct treatment of the study site with cypermethrin applied as a fog caused a temporary reduction both in total numbers (males and females) and in the proportion of older females. When cypermethrin was applied as an ultra low volume formulation at dusk and dawn numbers of males were greatly reduced, but numbers of females were not affected. It appears that the adulticiding operations had little overall effect on the total numbers or survival rate of females, or breeding success. The oviposition cycle duration was estimated to be two days, with the survival rate per oviposition cycle calculated as 30%. With these values it is thought unlikely that filariasis would be transmitted in Dubai.

  14. Theoretical magnetograms based on quantitative simulation of a magnetospheric substorm

    NASA Technical Reports Server (NTRS)

    Chen, C.-K.; Wolf, R. A.; Karty, J. L.; Harel, M.

    1982-01-01

    Substorm currents derived from the Rice University computer simulation of the September 19, 1976 substorm event are used to compute theoretical magnetograms as a function of universal time for various stations, integrating the Biot-Savart law over a maze of about 2700 wires and bands that carry the ring, Birkeland and horizontal ionospheric currents. A comparison of theoretical results with corresponding observations leads to a claim of general agreement, especially for stations at high and middle magnetic latitudes. Model results suggest that the ground magnetic field perturbations arise from complicated combinations of different kinds of currents, and that magnetic field disturbances due to different but related currents cancel each other out despite the inapplicability of Fukushima's (1973) theorem. It is also found that the dawn-dusk asymmetry in the horizontal magnetic field disturbance component at low latitudes is due to a net downward Birkeland current at noon, a net upward current at midnight, and, generally, antisunward-flowing electrojets.

  15. Adiabatic particle motion in a nearly drift-free magnetic field - Application to the geomagnetic tail

    NASA Technical Reports Server (NTRS)

    Stern, D. P.

    1978-01-01

    An investigation is made of the adiabatic particle motion occurring in an almost drift-free magnetic field. The dependence of the mean drift velocity on the equatorial pitch angle and the variation of the local drift velocity along the trajectories is studied. The fields considered are two-dimensional and resemble the geomagnetic tail. Derivations are presented for instantaneous and average drift velocities, bounce times, longitudinal invariants, and approximations to the adiabatic Hamiltonian. As expected, the mean drift velocity is significantly smaller than the instantaneous drift velocities found at typical points on the trajectory. The slow drift indicates that particles advance in the dawn-dusk direction rather slowly in the plasma sheet of the magnetospheric tail.

  16. Present (unified) and past Polar Cap (PC) index calculations.

    NASA Astrophysics Data System (ADS)

    Stauning, Peter; Troshichev, Oleg; Janzhura, Alexander

    2010-05-01

    The Polar Cap (PC) index was introduced by Troshichev and Andrezen (1985). Index values are derived from polar cap magnetic variations and are mainly related to the intensity of the variable transpolar ionospheric currents. These currents relate to the polar cap antisunward ionospheric plasma convection driven by the dawn-dusk electric field, which in turn is generated by the interaction of the solar wind with the Earth's magnetosphere. Thus the PC index is an important Space Weather parameter. Coefficients to calculate PC index values from polar magnetic variations have been derived by several different procedures in the past. Now, a unified procedure (Troshichev et al., 2005) has been adopted for both the PCN (north) and the PCS (south) index values. The presentation outlines and discusses the principles and the details of the unified procedure, which will be submitted to IAGA for formal approval. The PC index can be made available on-line in real-time for Space Weather applications.

  17. The relationship of total Birkeland currents to the merging electric field

    NASA Technical Reports Server (NTRS)

    Bythrow, P. F.; Potemra, T. A.

    1983-01-01

    Magsat data were used to examine the behavior of Birkeland currents during 1100-2000 UT in consecutive orbits passing near the dawn-dusk meridian. The field was measured with a three-axis fluxgate instrument with a resolution of within 0.5 nT, with the sampling occurring every 1/16th sec. A total of 32 crossings of the Northern Hemisphere auroral zone were available for analysis. The changes in the magnetic readings were correlated more closely with variation in the IMF parameters than to the latitudinal width of the changes. Evidence was found for a relationship between the reconnection electric field and the intensity of the large-scale Birkeland current system. The total conductance of the auroral zone was calculated to be about 18.7 mhos.

  18. Large-scale, near-Earth, magnetic fields from external sources and the corresponding induced internal field

    NASA Technical Reports Server (NTRS)

    Langel, R. A.; Estes, R. H.

    1983-01-01

    Data from MAGSAT analyzed as a function of the Dst index to determine the first degree/order spherical harmonic description of the near-Earth external field and its corresponding induced field. The analysis was done separately for data from dawn and dusk. The MAGSAT data was compared with POGO data. A local time variation of the external field persists even during very quiet magnetic conditions; both a diurnal and 8-hour period are present. A crude estimate of Sq current in the 45 deg geomagnetic latitude range is obtained for 1966 to 1970. The current strength, located in the ionosphere and induced in the Earth, is typical of earlier determinations from surface data, although its maximum is displaced in local time from previous results.

  19. Scalar magnetic anomaly maps of Earth derived from POGO and Magsat data

    NASA Technical Reports Server (NTRS)

    Arkani-Hamed, Jafar; Langel, Robert A.; Purucker, Mike

    1994-01-01

    A new Polar Orbit Geophysical Observatory (POGO) scalar magnetic anomaly map at 400 km altitude is presented which consists of spherical harmonics of degree 15-60. On the basis of the common features of this map with two new Magsat anomaly maps, dawn and dusk, two scalar magnetic anomaly maps of the Earth are presented using two selection criteria with different levels of stringency. These selection criteria suppress the noncrustal components of the original maps by different amounts. The more stringent selection criteria seek to eliminate as much contamination as possible, at the expense of suppressing some anomaly signal. This map is represented by spherical harmonics of degree 15-60. The less stringent selection criteria seek to retain as much crustal signal as possible, at the expense of also retaining some contaminating fields. This map is represented by spherical harmonics of degree 15-65. The resulting two maps are highly correlated with degree correlation coefficients greater than 0.8.

  20. Asymmetric auroral intensities in the Earth's Northern and Southern hemispheres

    NASA Astrophysics Data System (ADS)

    Laundal, K. M.; Østgaard, N.

    2009-07-01

    It is commonly assumed that the aurora borealis (Northern Hemisphere) and aurora australis (Southern Hemisphere) are mirror images of each other because the charged particles causing the aurora follow the magnetic field lines connecting the two hemispheres. The particles are believed to be evenly distributed between the two hemispheres, from the source region in the equatorial plane of the magnetosphere. Although it has been shown that similar auroral features in the opposite hemispheres can be displaced tens of degree in longitude and that seasonal effects can cause differences in global intensity, the overall auroral patterns were still similar. Here we report observations that clearly contradict the common assumption about symmetric aurora: intense spots are seen at dawn in the Northern summer Hemisphere, and at dusk in the Southern winter Hemisphere. The asymmetry is interpreted in terms of inter-hemispheric currents related to seasons, which have been predicted but hitherto had not been seen.

  1. Solar elevation dependent radiosonde temperature bias adjustments back to the 1940s

    NASA Astrophysics Data System (ADS)

    Haimberger, Leopold

    2016-04-01

    The well established RAOBCORE/RICH bias adjustment system for radiosonde temperature records has been enhanced to cope with seasonal changes of solar elevation dependent biases. It is argued that the seasonal cycle of reanalyses is more reliable than that of certain radiosonde types, especially at places where the radiosondes are launched around dawn or dusk, i.e. at high latitudes or near 90E/90W. Furthermore the data set has been extended back to the late 1940s, using JRA-55 and ERA-preSAT background departures as reference. For verification the adjusted data are compared against independent data sets and reanalyses as far as they are available. Suitability of the adjusted data as input for future reanalyses is discussed.

  2. In search of the pathways for light-induced pacemaker resetting in the suprachiasmatic nucleus.

    PubMed

    Meijer, Johanna H; Schwartz, William J

    2003-06-01

    Within the suprachiasmatic nucleus (SCN) of the mammalian hypothalamus is a circadian pacemaker that functions as a clock. Its endogenous period is adjusted to the external 24-h light-dark cycle, primarily by light-induced phase shifts that reset the pacemaker's oscillation. Evidence using a wide variety of neurobiological and molecular genetic tools has elucidated key elements that comprise the visual input pathway for SCN photoentrainment in rodents. Important questions remain regarding the intracellular signals that reset the autoregulatory molecular loop within photoresponsive cells in the SCN's retino-recipient subdivision, as well as the intercellular coupling mechanisms that enable SCN tissue to generate phase shifts of overt behavioral and physiological circadian rhythms such as locomotion and SCN neuronal firing rate. Multiple neurotransmitters, protein kinases, and photoinducible genes add to system complexity, and we still do not fully understand how dawn and dusk light pulses ultimately produce bidirectional, advancing and delaying phase shifts for pacemaker entrainment. PMID:12828281

  3. Solar wind-magnetosphere interaction as simulated by a 3D, EM particle code

    NASA Technical Reports Server (NTRS)

    Buneman, O.; Nishikawa, Ken-Ichi; Neubert, T.

    1993-01-01

    The results of simulating the solar wind-magnetosphere interaction with a three dimensional, electromagnetic (EM) particle code are presented. Hitherto such global simulations were done with magnetohydrodynamic (MHD) codes while lower dimensional particle or hybrid codes served to account for microscopic processes and such transport parameters as have to be introduced ad hoc in MHD. The kinetic model combines macroscopic and microscopic tasks. It relies only on the Maxwell curl equations and the Lorentz equation for particles. The preliminary results are for an unmagnetized solar wind plasma streaming past a dipolar magnetic field. The results show the formation of a bow shock and a magnetotail, the penetration of energetic particles into cusp and radiation belt regions, and dawn to dusk asymmetries.

  4. Solar wind-magnetosphere interaction as simulated by a 3-D EM particle code

    NASA Technical Reports Server (NTRS)

    Buneman, Oscar; Neubert, Torsten; Nishikawa, Ken-Ichi

    1992-01-01

    We present here our first results of simulating the solar wind-magnetosphere interaction with a new three-dimensional electromagnetic particle code. Hitherto such global simulations were done with MHD codes while lower-dimensional particle or hybrid codes served to account for microscopic processes and such transport parameters as have to be introduced ad hoc in MHD. Our kinetic model attempts to combine the macroscopic and microscopic tasks. It relies only on the Maxwell curl equation and the Lorentz equation for particles, which are ideally suited for computers. The preliminary results shown here are for an unmagnetized solar wind plasma streaming past a dipolar magnetic field. The results show the formation of a bow shock and a magnetotail, the penetration of energetic particles into cusp and radiation belt regions, and dawn-dusk asymmetries.

  5. Structure of the martian ionosphere as revealed by the Neutral Gas and Ion Mass Spectrometer during the first two years of the MAVEN mission

    NASA Astrophysics Data System (ADS)

    Benna, Mehdi; Yelle, Roger; Grebowsky, Joseph; Fox, Jane L.; Mahaffy, Paul

    2016-07-01

    We report the results of the observations of the ionosphere of Mars by the Neutral Gas and Ion Mass Spectrometer (NGIMS). These observations were conducted during the first two years of the Mars Atmosphere and Volatile Evolution mission (MAVEN), which also cover a full Martian year. The NGIMS observations revealed the spatial and temporal structures in the density distributions of major and several minor ion species (H_2^+, H_3^+, He^+, O_2^+, C^+, CH^+, N^+, NH^+, O^+, OH^+, H_2O^+, H_3O^+, N_2^+/CO^+, CO^+/HOC^+/N_2H^+, NO^+, HNO^+, O_2^+, HO_2^+, Ar^+, ArH^+, CO_2^+, and OCOH^+). Dusk/dawn and day/night asymmetries in the density distributions were also observed for nearly all ion species. Additionally, NGIMS revealed the presence of a persistent metal layer below 140 km. This layer was accessible for measurement during the MAVEN's "deep-dip" campaigns.

  6. Steepening of waves at the duskside magnetopause

    NASA Astrophysics Data System (ADS)

    Plaschke, F.; Kahr, N.; Fischer, D.; Nakamura, R.; Baumjohann, W.; Magnes, W.; Burch, J. L.; Torbert, R. B.; Russell, C. T.; Giles, B. L.; Strangeway, R. J.; Leinweber, H. K.; Bromund, K. R.; Anderson, B. J.; Le, G.; Chutter, M.; Slavin, J. A.; Kepko, E. L.

    2016-07-01

    Surface waves at the magnetopause flanks typically feature steeper, i.e., more inclined leading (antisunward facing) than trailing (sunward facing) edges. This is expected for Kelvin-Helmholtz instability (KHI) amplified waves. Very rarely, during northward interplanetary magnetic field (IMF) conditions, anomalous/inverse steepening has been observed. The small-scale tetrahedral configuration of the Magnetospheric Multiscale spacecraft and their high time resolution measurements enable us to routinely ascertain magnetopause boundary inclinations during surface wave passage with high accuracy by four-spacecraft timing analysis. At the dusk flank magnetopause, 77%/23% of the analyzed wave intervals exhibit regular/inverse steepening. Inverse steepening happens during northward IMF conditions, as previously reported and, in addition, during intervals of dominant equatorial IMF. Inverse steepening observed under the latter conditions may be due to the absence of KHI or due to instabilities arising from the alignment of flow and magnetic fields in the magnetosheath.

  7. Orbit design for solar and dual satellite occultation measurements of atmospheric constituents

    NASA Technical Reports Server (NTRS)

    Brooks, D. R.; Harrison, E. F.

    1979-01-01

    Two types of satellite based occultation missions are considered for measuring atmospheric constituents. Nominal cases for each type are presented to demonstrate representative solutions to orbit design problems. For the solar occultation mode, large areas of the globe can be covered during a one year mission, but the measurements are limited to local dawn or dusk. For the dual satellite mode, with a laser aboard a second satellite to act as a source, diurnal coverage can be obtained at the expense of more complex systems and mission scenarios. In this mode, orbit pairs are selected which maintain their relative orbit plane geometry while their differing periods drive cyclic patterns of latitude coverage. A simulated one year solar occultation mission is used to illustrate one way of analyzing occultation data by averaging measurements within bands of constant latitude.

  8. Nocturnal activity by diurnal lizards (Sceloporus jarrovi, S. virgatus) eaten by small owls (Glaucidium gnoma, Otus trichopsis)

    USGS Publications Warehouse

    Duncan, W.W.; Gehlbach, F.R.; Middendorf, G. A.

    2003-01-01

    Whiskered screech-owls (Otus trichopsis) and northern pygmy-owls (Glaucidium gnoma) delivered freshly caught Yarrow's spiny lizards (Sceloporus jarrovi) and striped plateau lizards (S. virgatus) to nestlings from dusk to dark in southeastern Arizona. This observation stimulated studies of the prey deliveries by the owls and lizard activity patterns, because the lizards are not known to be nocturnal. Lizards were more frequent prey of both owls than endothermic vertebrates but infrequent compared to arthropods, a pattern in the pygmy-owl that differs from its northern populations. Yarrow's spiny lizard, the most abundant and frequently captured lizard, was most active in the morning but also active in the evening. Striped plateau lizard, the second most abundant and depredated species, had morning and evening peaks of activity. Few lizards, including S. clarki and Urosaurus ornatus, but not Cnemidophorus exsanguis and C. sonorae, were active at or after dark, when relatively few were captured by the owls.

  9. High-resolution multifluid simulations of flux ropes in the Martian magnetosphere

    NASA Astrophysics Data System (ADS)

    Harnett, E. M.

    2009-01-01

    Three-dimensional multifluid simulations of the Martian magnetosphere show the development and dynamics of flux ropes. One flux rope, which is analyzed in detail, initiates at a reconnection region near the dusk terminator and travels tailward with a speed on the order of 40 km s-1. The reconnection region forms close to the planet at an altitude of 700 km. Both the location of the reconnection and energy spectra of the plasma in the reconnection region agree with Mars Global Surveyor observations of reconnection. The largest flux ropes have a spatial extent on the order of 2000 km. Energy spectra taken through the flux ropes show an inverted-V type structure similar to those measured by Mars Express, suggesting that some inverted-V observations may be transits through flux ropes. The simulations indicate that the formation of flux ropes can lead to enhanced loss of heavy ions from the atmosphere.

  10. The substructure of a flux transfer event observed by the MMS spacecraft

    NASA Astrophysics Data System (ADS)

    Hwang, K.-J.; Sibeck, D. G.; Giles, B. L.; Pollock, C. J.; Gershman, D.; Avanov, L.; Paterson, W. R.; Dorelli, J. C.; Ergun, R. E.; Russell, C. T.; Strangeway, R. J.; Mauk, B.; Cohen, I. J.; Torbert, R. B.; Burch, J. L.

    2016-09-01

    On 15 August 2015, MMS (Magnetospheric Multiscale mission), skimming the dusk magnetopause, detected an isolated region of an increased magnetic strength and bipolar Bn, indicating a flux transfer event (FTE). The four spacecraft in a tetrahedron allowed for investigations of the shape and motion of the FTE. In particular, high-resolution particle data facilitated our exploration of FTE substructures and their magnetic connectivity inside and surrounding the FTE. Combined field and plasma observations suggest that the core fields are open, magnetically connected to the northern magnetosphere from which high-energy particles leak; ion "D" distributions characterize the axis of flux ropes that carry old-opened field lines; counterstreaming electrons superposed by parallel-heated components populate the periphery surrounding the FTE; and the interface between the core and draped regions contains a separatrix of newly opened magnetic field lines that emanate from the X line above the FTE.

  11. The GRADIO spaceborne gravity gradiometer: Development and accommodation

    NASA Astrophysics Data System (ADS)

    Bernard, A.

    1989-06-01

    The European ARISTOTELES mission aims at the determination of the Earth's gravity field at short wavelength with a global coverage. Gravity gradient measurements will be achieved during six months by the GRADIO instrument onboard a dedicated satellite in a near dawn-dusk sun-synchronous orbit at an altitude of 200 km. The objective is an accuracy of better than 5 mgals for gravity anomalies, at ground level for blocks of 1 x 1 deg. According to present knowledge of the potential, the recovery of higher spherical harmonics (degree and order greater than 30) is of main importance. This leads to focus on the variations of the measured components T(sub ij) of the gravity gradient tensor, at frequencies greater than 5 x 10(exp -3) Hz. The resolution, required for the gradiometer is 10(exp -2) Eotvos (i.e., 10(exp -11)/s squared) with an averaging time of 4 s.

  12. The GRADIO spaceborne gravity gradiometer: Development and accommodation

    NASA Technical Reports Server (NTRS)

    Bernard, A.

    1989-01-01

    The European ARISTOTELES mission aims at the determination of the Earth's gravity field at short wavelength with a global coverage. Gravity gradient measurements will be achieved during six months by the GRADIO instrument onboard a dedicated satellite in a near dawn-dusk sun-synchronous orbit at an altitude of 200 km. The objective is an accuracy of better than 5 mgals for gravity anomalies, at ground level for blocks of 1 x 1 deg. According to present knowledge of the potential, the recovery of higher spherical harmonics (degree and order greater than 30) is of main importance. This leads to focus on the variations of the measured components T(sub ij) of the gravity gradient tensor, at frequencies greater than 5 x 10(exp -3) Hz. The resolution, required for the gradiometer is 10(exp -2) Eotvos (i.e., 10(exp -11)/s squared) with an averaging time of 4 s.

  13. ARISTOTELES: A European approach for an Earth gravity field recovery mission

    NASA Technical Reports Server (NTRS)

    Benz, R.; Faulks, H.; Langemann, M.

    1989-01-01

    Under contract of the European Space Agency a system study for a spaceborne gravity field recovery mission was performed, covering as a secondary mission objective geodetic point positioning in the cm range as well. It was demonstrated that under the given programmatic constraints including dual launch and a very tight development schedule, a six months gravity field mission in a 200 km near polar, dawn-dusk orbit is adequate to determine gravity anomalies to better than 5 mgal with a spatial resolution of 100 x 100 km half wavelength. This will enable scientists to determine improved spherical harmonic coefficients of the Earth gravity field equation to the order and degree of 180 or better.

  14. ARISTOTELES: A European approach for an Earth gravity field recovery mission

    NASA Astrophysics Data System (ADS)

    Benz, R.; Faulks, H.; Langemann, M.

    1989-06-01

    Under contract of the European Space Agency a system study for a spaceborne gravity field recovery mission was performed, covering as a secondary mission objective geodetic point positioning in the cm range as well. It was demonstrated that under the given programmatic constraints including dual launch and a very tight development schedule, a six months gravity field mission in a 200 km near polar, dawn-dusk orbit is adequate to determine gravity anomalies to better than 5 mgal with a spatial resolution of 100 x 100 km half wavelength. This will enable scientists to determine improved spherical harmonic coefficients of the Earth gravity field equation to the order and degree of 180 or better.

  15. Electromagnetic deep-probing (100-1000 kms) of the Earth's interior from artificial satellites: Constraints on the regional emplacement of crustal resources

    NASA Technical Reports Server (NTRS)

    Hermance, J. F.

    1983-01-01

    The reconnaissance phase of using satellite observtions to studying electromagnetic induction in the solid earth is summarized. Several points are made: (1) satellite data apparently suffer far less from the effects of near surface lateral heterogeneities in the earth than do ground-based data; (2) zonal ionospheric currents during the recovery phase of major magnetic storms appear to be minimal, at least in the dawn and dusk sectors wher MAGSAT was flown; hence the internal contributions that satellites observe during these times is in fact due primarily to induction in the Earth with little or no contribution from ionospheric currents; and (3) the interpretation of satellite data in terms of primitive electromagnetic response functions, while grossly over-simplified, results in a surprisingly well-resolved radius for an equivalent super-conductor representing the conductivity region of the Earth's interior (5,370 + or - 120 km).

  16. Polar aurora and F-layer dynamics studies at Eureka, Canada

    SciTech Connect

    McEwen, D.J.

    1994-12-31

    A polar observatory has been in operation at Eureka (89{degree} north magnetic latitude) since 1990, with two studies centering on the dynamics of polar arcs and F-layer patches. Instrumentation has included all-sky imagers and multichannel scanning photometers. A recent addition has been a turntable photometer mount which permits continuous scanning along the dawn-to-dusk meridian. This is optimum for high resolution studies of sun-aligned auroral arcs and other particle precipitation effects poleward of the auroral oval. F-layer patches (whose optical signatures are typically 100--300 R enhancements in 630 mn emission and lesser 558 nm enhancements) are frequently seen drifting across the pole in an antisunward direction, often in sequences and sometimes recurring through much of the 24-hr period. The instrumentation and results from these studies obtained over the 1993--94 winter are discussed.

  17. Isolated cold plasma regions: Observations and their relation to possible production mechanisms

    NASA Technical Reports Server (NTRS)

    Maynard, N. C.; Chen, A. J.

    1974-01-01

    Regions of enhanced cold plasma, isolated from the main plasmasphere along the Explorer 45 orbit on the equatorial plane, are reported using the sheath induced potentials seen by the electric field experiment. The occurrence of these regions has a strong correlation with negative enhancements of Dst, and their locations are primarily in the noon-dusk quadrant. The data support the concept that changes in large scale convection play a dominant role in the formation of these regions. Plasmatails that are predicted from enhancements of large scale convection electric fields in general define where these regions may be found. More localized processes are necessary to account for the exact configuration and structure seen in these regions and may eventually result in detachment from the main plasmasphere.

  18. Orientation variation of dayside auroral arc alignments obtained from all-sky observation at yellow river station, Svalbard

    NASA Astrophysics Data System (ADS)

    Qiu, Qi; Yang, Hui-Gen; Lu, Quan-Ming; Hu, Ze-Jun; Han, De-Sheng; Wang, Qian

    2016-05-01

    The orientations of dayside auroral arc alignments were calculated for over 40,000 images from all-sky observation at Yellow River Station, Svalbard. For each arc, its "orientation" and "tilt" are defined as the angle the arc alignment makes with the dusk-dawn direction and the local east-west direction, respectively. The mean arc orientation increases linearly with the increasing magnetic local time (MLT). There is a reversal point of the arc tilt located at near 10.5 MLT. Compared with the mean orientation, auroral arc alignment tilts to morning side in the higher latitude and tilts to evening side in the lower latitude in the prenoon sector, whereas it is the opposite in the postnoon sector. We further studied the effects of the interplanetary magnetic field (IMF) on the location of the arc tilt reversal point. We found that the reversal position shifts toward the midday for negative By.

  19. The magnetic topology of the plasmoid flux rope in a MHD-simulation of magnetotail reconnection

    NASA Technical Reports Server (NTRS)

    Birn, J.; Hesse, M.

    1990-01-01

    On the basis of a 3D MHD simulation, the magnetic topology of a plasmoid that forms by a localized reconnection process in a magnetotail configuration (including a net dawn-dusk magnetic field component B sub y N is discussed. As a consequence of B sub y N not equalling 0, the plasmoid assumes a helical flux rope structure rather than an isolated island or bubble structure. Initially all field lines of the plasmoid flux rope remain connected with the earth, while at later times a gradually increasing amount of flux tubes becomes separated, connecting to either the distant boundary or to the flank boundaries. In this stage, topologically different flux tubes become tangled and wrapped around each other, consistent with predictions on the basis of an ad hoc plasmoid model.

  20. Why the Viking descent probes found only one ionospheric layer at Mars

    NASA Astrophysics Data System (ADS)

    Mayyasi, Majd; Mendillo, Michael

    2015-09-01

    Radio wave transmissions from satellites revealed that Mars had two relatively distinct layers of ionization: a maximum electron density near 130 km, and a secondary layer near 110 km. When the Viking descent probes—with their in situ observing capabilities—passed through the ionosphere, the peak electron density was found, with no indication of a secondary layer below. Here we use an ionospheric model to show that profiles of electron density versus height have shapes that favor the detection of two layers at local times near dawn and dusk (where many thousands of radio occultation observations have been made), but that the two layers essentially merge into one during midday hours (when Viking measurements were made). The profile shapes are attributed to ionizing geometry of solar photons and to chemical processes that affect the profile shapes in a way that favors secondary peak formation near sunrise and sunset.

  1. In short photoperiods, human sleep is biphasic.

    PubMed

    Wehr

    1992-06-01

    Results of a photoperiod experiment show that human sleep can be unconsolidated and polyphasic, like the sleep of other animals. When normal individuals were transferred from a conventional 16-h photoperiod to an experimental 10-h photo-period, their sleep episodes expanded and usually divided into two symmetrical bouts, several hours in duration, with a 1-3 h waking interval between them. The durations of nocturnal melatonin secretion and of the nocturnal phase of rising sleepiness (measured in a constant routine protocol) also expanded, indicating that the timing of internal processes that control sleep and melatonin, such as circadian rhythms, had been modified by the change in photoperiod. Previous work suggests that the experimental results could be simulated with dual-oscillators, entrained separately to dawn and dusk, or with a two-process model, having a lowered threshold for sleep-onset during the scotoperiod. PMID:10607034

  2. Longitudinal effects of ionospheric responses to substorms at middle and lower latitudes: a case study

    NASA Astrophysics Data System (ADS)

    Pi, Xiaoqing; Mendillo, Michael; Spalla, Paolo; Anderson, David N.

    1995-08-01

    An ionospheric model is used to simulate total electron content (TEC) disturbance events observed at middle and lower latitude sites near 75°W and 7°E longitudes. Within this longitudinal range, daytime TEC disturbances show patterns that are correlated with substrom activity seen in both auroral electrojet and ring current behavior. In modeling studies of the observed ionospheric effects, both electric field and neutral wind perturbations are examined as possible mechanisms. The morphological features of the required electric field perturbations near drawn and dusk are compared with those at other times to examine the local time characteristics of magnetospheric influence. Large-scale traveling atmospheric disturbances (TADs), an alternative candidate for the disturbance source, are also characterized and compared with known thermospheric behavior.

  3. The large-scale ionospheric electric field - Its variation with magnetic activity and relation to terrestrial kilometric radiation

    NASA Technical Reports Server (NTRS)

    Holzworth, R. H.; Cullers, D. K.; Hudson, M. K.; Berthelier, J.-J.; Fahleson, U. V.; Falthammar, C.-G.; Jalonen, L.; Tanskanen, P.; Kelley, M. C.; Kellogg, P. J.

    1977-01-01

    Four days of simultaneous auroral zone electric field measurements on balloons flown from six sites spanning 180 deg of magnetic longitude have been analyzed. The average electric field behavior during this magnetically quiet epoch is consistent with earlier single-point measurements, although the average auroral zone electric field was more affected by corotation effects than it was during more disturbed times. When these data, which primarily reflect the large-scale (several hundred kilometer) ionospheric electric field, are mapped to the equator, a steady dawn to dusk component is apparent only on the average, while instantaneously the field is quite variable. The ionospheric electric field during isolated substorms is shown to have differing signatures east and west of 2200 LT. A worldwide positive correlation is shown to exist between the auroral zone electric field strength and the intensity of terrestrial kilometric radiation.

  4. Foreshock ions observed behind the Martian bow shock

    NASA Astrophysics Data System (ADS)

    Frahm, R. A.; Yamauchi, M.; Winningham, J. D.; Lundin, R.; Sharber, J. R.; Nilsson, H.; Coates, A. J.

    2016-08-01

    The Mars Express Analyzer of Space Plasmas and Energetic Atoms experiment contains ion and electron instruments for conducting plasma measurements. On January 23, 2012, during in-bound travel of Mars Express in the southern hemisphere of Mars from its dawn side toward periapsis at dusk, the plasma instruments measured foreshock-like ion beams extending from outside the bow shock and into the magnetosphere, continuing to a distance of about a proton gyroradius from the bow shock. These ion beams were mostly protons, were observed to have energies greater than solar wind protons, and were not gyrating, in agreement with reflections of the solar wind proton beam. Furthermore, in the foreshock region the ion energy gradually decreased toward the magnetosheath, in agreement with an acceleration by outward-directed electric field in the bowshock. The observations also suggest that this electric field exists even inside the magnetosheath within the distance of a proton gyroradius from the bow shock.

  5. The influence of the wind in the Schmallenberg virus outbreak in Europe

    NASA Astrophysics Data System (ADS)

    Sedda, Luigi; Rogers, David J.

    2013-11-01

    A model previously developed for the wind-borne spread by midges of bluetongue virus in NW Europe in 2006 is here modified and applied to the spread of Schmallenberg virus in 2011. The model estimates that pregnant animals were infected 113 days before producing malformed young, the commonest symptom of reported infection, and explains the spatial and temporal pattern of infection in 70% of the 3,487 affected farms, most of which were infected by midges arriving through downwind movement (62% of explained infections), or a mixture of downwind and random movements (38% of explained infections), during the period of day (1600-2100 h, i.e. dusk) when these insects are known to be most active. The main difference with Bluetongue is the higher rate of spread of SBV, which has important implications for disease control.

  6. Fabry-Perot Imaging of O III lambda = 5007 Angstrom Emission in the Io Plasma Torus

    NASA Astrophysics Data System (ADS)

    Kueppers, M.; Jockers, K.

    1995-03-01

    In the first week of 1994 April the [O III] 5007 Å line was imaged in the Io plasma torus using the focal reducer camera of the Max-Planck-Institut für Aeronomie attached to the 2.2 m telescope of the European Southern Observatory. The emission was peaked at a Jovicentric distance of 5.8±0.2Rj at a level of 11±6 and 18±8R for the dusk and dawn ansa respectively. Generally the spatial distribution is consistent with Voyager models, but there is some evidence that the 0 111-torus is extended to larger Jovicentric distances than predicted by the model. In contrast to the spectrographic observations of Thomas (1993b) the warm sulphur torus was depressed during the time of our observations indicating that in first order there is no correlation between the presence of 0 III emission and the state of the sulphur torus.

  7. Operation Dominic, Fish Bowl Series. Project Officer's report. Project 9. 1b. Ionospheric wind and diffusion measurements

    SciTech Connect

    Champion, K.; Manring, E.R.

    1985-09-01

    The aim of this project was to measure high-altitude wind velocities and diffusion coefficients in the altitude region between 60 and 150 km. The method involved the ejection of a sodium vapor trail from a Cajun rocket at dust or dawn twilight. The sodium was sunlit, and as a result of emission of resonance radiation, was visible against a darkened background for about 20 minutes. The trail was photographed simultaneously from four different sites, allowing for subsequent triangulation to determine the altitude of various parts of the cloud. A major application of these wind and diffusion data, taken at dusk and dawn following the high-altitude nuclear tests, was to aid in determining the disposition of the nuclear debris.

  8. Correlation between convection electric fields in the nightside magnetosphere and several wave and particle phenomena during two isolated substorms.

    NASA Technical Reports Server (NTRS)

    Carpenter, D. L.; Fraser-Smith, A. C.; Unwin, R. S.; Hones, E. W., Jr.; Heacock, R. R.

    1971-01-01

    Correlation of several magnetoionospheric wave and particle phenomena previously linked observationally to magnetospheric substorms and inferred to involve convection electric fields with whistler measurements of convection activity during two relatively isolated substorms. The events occurred at about 0600 UT on July 15, 1965, and about 0500 UT on Oct. 13, 1965. The correlated phenomena include cross-L inward plasma drifts near midnight within the plasmaphere, diffuse auroral radar echoes observed near the dusk meridian, IPDP micropulsations (intervals of pulsations of diminishing period) in the premidnight sector, apparent contractions and expansions of the plasma sheet at about 20 earth radii in the magnetotail, and Pc 1/Pi 1 micropulsation events near or before midnight. Two new vlf phenomena occurred during the October 13 event - a noise band within the plasmasphere associated with a convecting whistler path, and ?hisslers,' falling-tone auroral-hiss forms repeated at intervals of about 2 sec.

  9. Statistical study of the ULF Pc4-Pc5 range fluctuations in the vicinity of Earth's magnetopause and correlation with the Low Latitude Boundary Layer thickness

    NASA Astrophysics Data System (ADS)

    Nykyri, K.; Dimmock, A. P.

    2016-07-01

    The main generation mechanisms for the Earth's Low Latitude Boundary Layer (LLBL) are considered to be magnetic reconnection, viscous interactions such as Kelvin-Helmholtz instability and associated plasma mixing and diffusion. We have performed a statistical study of the Ultra Low Frequency (ULF) fluctuation power at the Pc4-Pc5 range using ≈6 years of THEMIS measurements of the plasma velocity and magnetic field. The results reveal a clear dawn-dusk asymmetry showing that the fluctuation power is typically more enhanced in the vicinity of the magnetopause downstream of the quasi-parallel shock. The statistical study of the Vx-component of the plasma velocity indicates that the LLBL is also thicker on the dawn-sector. These results may suggest that the physical mechanisms that provide power in the Pc4-Pc5 range are more effective on the dawn-sector and provide a means for a more effective LLBL generation.

  10. The magnetosheath electron population at lunar distance - General features

    NASA Technical Reports Server (NTRS)

    Reiff, P. H.; Reasoner, D. L.

    1975-01-01

    A study was made of the electron population in the earth's magnetosheath at lunar distance. The data used were collected by the Apollo 14 charged particle lunar environment experiment (CPLEE) during four inbound (dusk) and three outbound (dawn) passages of the moon through the magnetosheath. The magnetotail has a diameter of 52 earth radii, while the bow-shock cross section is about 91 earth radii. The average boundary locations computed from the complete data set are consistent with the prediction of fluid dynamics. The electron characteristics for the two least-disturbed passages are presented in detail. An examination of the energy spectra shows that a high-energy (200-2000 eV) tail is superimposed on the expected low-energy (40-200 eV) magnetosheath distribution. It is argued that the high-energy magnetosheath electron population originates at the bow shock, rather than from the plasma sheet.

  11. Statistical mapping of ULF Pc3 velocity fluctuations in the Earth's dayside magnetosheath as a function of solar wind conditions

    NASA Astrophysics Data System (ADS)

    Dimmock, A. P.; Nykyri, K.; Osmane, A.; Pulkkinen, T. I.

    2016-07-01

    In this paper, we present the results of a statistical study of Pc3 velocity fluctuations in the Earth's dayside magnetosheath. There exists a notable dawn-dusk asymmetry, such that velocity fluctuations generally exhibit enhanced spectral power in the magnetosheath downstream of the quasi-parallel shock. The fluctuations in the central magnetosheath and close to bow shock tend to dampen with increasing tail-ward distance while the opposite trend is observed close to the magnetopause. This strongly suggests that velocity shear driven processes such as the Kelvin-Helmholtz instability drive Pc3 flow variations close to the magnetopause as the velocity shear increases with increasing tail-ward distance. We also show strong evidence that Pc3 velocity fluctuations are significantly enhanced during intervals of faster solar wind speeds. We see negligible differences between data collected during northward and southward IMF orientations, but in general, a dawn-favoured asymmetry persists.

  12. Howling at two Minnesota wolf pack summer homesites

    USGS Publications Warehouse

    Harrington, F.H.; Mech, L.D.

    1978-01-01

    Howling sessions were monitored at two Minnesota wolf pack homesites for 2255 h between 29 April and 3 August 1973. All sessions recorded occurred from dusk through early morning, with an evening peak for one pack. Within a night, multiple sessions were grouped temporally, most occurring within an hour of one another. Howling rates for both packs increased throughout the homesite season, with the larger pack howling twice as frequently. The role of howling in both intrapack and interpack contexts was considered. Much of the howling seemed to be involved in the coordination of pack activities. Further, the low frequency and clumped temporal distribution of sessions suggest that howling plays a secondary role in interpack contexts to other modes such as scent marking during the homesite season, but may increase in relative importance once homesites are abandoned and pack travel becomes nomadic.

  13. Studies of the gas tori of Titan and Triton

    NASA Technical Reports Server (NTRS)

    Smyth, William H.

    1995-01-01

    Progress in the development of the model for the circumplanetary distribution of atomic hydrogen in the Saturn system produced by a Titan source is discussed. Because of the action of the solar radiation acceleration and the obliquity of Saturn, the hydrogen distribution is shown to undergo seasonal changes as the planet moves about the Sun. Preliminary model calculations show that for a continuous Titan source, the H distribution is highly asymmetric about the planet and has a density maximum near the dusk side of Saturn, qualitatively similar to the pattern recently deduced by Shemansky and Hall from observations acquired by the UVS instruments aboard the Voyager spacecrafts. The investigation of these Voyager data will be undertaken in the next project year.

  14. Multipoint Observations of Oval-aligned Transpolar Arc Formation

    NASA Astrophysics Data System (ADS)

    Cumnock, J. A.; Le, G.; Zhang, Y.; Slavin, J. A.

    2013-12-01

    We analyze changes in field-aligned currents associated with auroral oval-aligned transpolar arc formation during quiet times on time scales of a few minutes. This is accomplished using observations from the highly accurate multipoint magnetic field measurements provided by the Space Technology 5 mission which consists of three micro-satellites in low Earth orbit. Simultaneous measurements of precipitating particles are provided by three DMSP satellites. We analyze field-aligned currents associated with the dusk oval. For the first time we observe the field-aligned currents associated with the formation of an oval-aligned transpolar arc poleward of the auroral oval which in one case are large compared with the field-aligned currents associated with the auroral oval measured 10 minutes earlier. These events clearly illustrate the dynamic nature of oval-aligned arc formation.

  15. A new plasma regime in the distant geomagnetic tail

    NASA Technical Reports Server (NTRS)

    Hardy, D. A.; Hills, H. K.; Freeman, J. W.

    1975-01-01

    Observations are reported of an extensive region of low-energy plasma particles (LEP) flowing antisunward along the ordered field lines in the lobes of the geomagnetic tail at lunar distances. The flow was detected by three suprathermal ion detectors deployed on the lunar surface during the Apollo 12, 14, and 15 missions. This particle regime is found to be similar to the 'boundary layer' and 'plasma mantle' observed at smaller geocentric distances and to an interior flow region parallel to the magnetopause in the dayside magnetosphere. It is located exterior to the plasma sheet across essentially the entire tail and adjacent to the magnetopause on both the dawn and dusk sides of the magnetosphere. Variations in the integral flux, temperature, and number density are described. It is suggested that this flow and the three similar regimes are simply connected along the inner surface of the magnetopause and are, in fact, the same phenomenon.

  16. Observations of large-amplitude, parallel, electrostatic waves associated with the Kelvin-Helmholtz instability by the magnetospheric multiscale mission

    NASA Astrophysics Data System (ADS)

    Wilder, F. D.; Ergun, R. E.; Schwartz, S. J.; Newman, D. L.; Eriksson, S.; Stawarz, J. E.; Goldman, M. V.; Goodrich, K. A.; Gershman, D. J.; Malaspina, D. M.; Holmes, J. C.; Sturner, A. P.; Burch, J. L.; Torbert, R. B.; Lindqvist, P.-A.; Marklund, G. T.; Khotyaintsev, Y.; Strangeway, R. J.; Russell, C. T.; Pollock, C. J.; Giles, B. L.; Dorrelli, J. C.; Avanov, L. A.; Patterson, W. R.; Plaschke, F.; Magnes, W.

    2016-09-01

    On 8 September 2015, the four Magnetospheric Multiscale spacecraft encountered a Kelvin-Helmholtz unstable magnetopause near the dusk flank. The spacecraft observed periodic compressed current sheets, between which the plasma was turbulent. We present observations of large-amplitude (up to 100 mV/m) oscillations in the electric field. Because these oscillations are purely parallel to the background magnetic field, electrostatic, and below the ion plasma frequency, they are likely to be ion acoustic-like waves. These waves are observed in a turbulent plasma where multiple particle populations are intermittently mixed, including cold electrons with energies less than 10 eV. Stability analysis suggests a cold electron component is necessary for wave growth.

  17. Digital hf radar observations of equatorial spread-F

    SciTech Connect

    Argo, P.E.

    1984-01-01

    Modern digital ionosondes, with both direction finding and doppler capabilities can provide large scale pictures of the Spread-F irregularity regions. A morphological framework has been developed that allows interpretation of the hf radar data. A large scale irregularity structure is found to be nightward of the dusk terminator, stationary in the solar reference frame. As the plasma moves through this foehn-wall-like structure it descends, and irregularities may be generated. Localized upwellings, or bubbles, may be produced, and they drift with the background plasma. The spread-F irregularity region is found to be best characterized as a partly cloudy sky, due to the patchiness of the substructures. 13 references, 16 figures.

  18. Solar maximum ultraviolet spectrometer and polarimeter

    NASA Technical Reports Server (NTRS)

    Tandberg-Hanssen, E.; Woodgate, B. E.; Brandt, J. C.; Chapman, R. D.; Hyder, C. L.; Michalitsianos, A. G.; Shine, R. A.; Athay, R. G.; Beckers, J. M.; Bruner, E. C.

    1979-01-01

    The objectives of the UVSP experiment are to study solar ultraviolet radiations, particularly from flares and active regions, and to measure constituents in the terrestrial atmosphere by the extinction of sunlight at satellite dawn and dusk. The instrument is designed to observe the Sun at a variety of spectral and spatial resolutions in the range from 1150 to 3600 A. A Gregorian telescope with effective focal length of 1.8 m is used to feed a 1 m Ebert-Fastie spectrometer. A polarimeter containing rotatable magnesium fluoride waveplates is included behind the spectrometer entrance slit and will allow all four Stokes parameters to be determined. Velocities on the Sun can also be measured. The instrument is controlled by a computer which can interact with the data stream to modify the observing program. The observing modes, including rasters, spectral scans, velocity measurements, and polarimetry, are also described along with plans for mission operations, data handling, and analysis of the observations.

  19. INSECT FLIGHT. Luminance-dependent visual processing enables moth flight in low light.

    PubMed

    Sponberg, Simon; Dyhr, Jonathan P; Hall, Robert W; Daniel, Thomas L

    2015-06-12

    Animals must operate under an enormous range of light intensities. Nocturnal and twilight flying insects are hypothesized to compensate for dim conditions by integrating light over longer times. This slowing of visual processing would increase light sensitivity but should also reduce movement response times. Using freely hovering moths tracking robotic moving flowers, we showed that the moth's visual processing does slow in dim light. These longer response times are consistent with models of how visual neurons enhance sensitivity at low light intensities, but they could pose a challenge for moths feeding from swaying flowers. Dusk-foraging moths avoid this sensorimotor tradeoff; their nervous systems slow down but not so much as to interfere with their ability to track the movements of real wind-blown flowers.

  20. Observations of the April 2002 Storm Period with TIMED-TIDI

    NASA Astrophysics Data System (ADS)

    Niciejewski, R.; Killeen, T.; Wu, Q.; Skinner, W.; Solomon, S.; Ortland, D.; Kafkalidis, J.; Gell, D.; Gablehouse, D.; Johnson, R.

    2002-12-01

    TIDI is meeting its basic requirement, which is to measure the global wind field in the mesosphere and lower thermosphere, the core study region. Since February 2002, TIDI has been in a routine science data-taking mode. During April 2002, TIMED was positioned at a high beta angle (angle between the plane of the satellite orbit and the Earth-Sun line) resulting in a series of TIDI measurements near the dusk/dawn terminator. The field of view of TIDI allows it to obtain measurements from pole to pole, while the repetition rate of the sky-scanner allows it to obtain several scans within the auroral oval region on each orbit. This paper will discuss TIDI measurements obtained during the April 2002 storm period, including OI (5577\\x8F) intensity data and neutral wind data sets.

  1. Influence of solar wind variability on geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Garrett, H. B.; Dessler, A. J.; Hill, T. W.

    1974-01-01

    A statistical study of solar wind data from the Explorer 33 satellite shows that interplanetary magnetic field irregularities are enhanced in the interaction region where a fast solar wind stream overtakes a slower solar wind stream. Comparison with geomagnetic AE and ap indexes further shows that these interplanetary irregularities enhance the level of geomagnetic disturbances. Thus while substorm occurrence is highly correlated with the dawn-dusk component of the solar wind electric field, the amplitude of the substorms is an increasing function of the variance in the interplanetary field. This result can be interpreted as a capacitative effect of the magnetopause that allows a time-varying solar wind electric field to penetrate the magnetosphere more effectively than a static solar wind electric field.

  2. Evolution of partial ring current ion pitch angle distributions during the main phase of a storm on 17 March 2015

    NASA Astrophysics Data System (ADS)

    Runov, A.; Zhang, X. J.; Angelopoulos, V.

    2016-06-01

    During a severe magnetic storm from 17 to 19 March 2015, three identically instrumented Time History of Events and Macroscale Interactions during Substorms probes crossed the magnetosphere in a string-of-pearls configuration enabling sequential observations of same regions of the magnetosphere with a 2 h time separation. These observations allow us to study the temporal evolution of ion pitch angle distributions (PADs) in the dusk-premidnight sector (between 17 and 20 h magnetic local time) during the storm's main phase. We found that the ion PAD evolved from pancake to isotropic in fewer than 2 h. Analysis of electromagnetic wave spectra revealed the presence of electromagnetic ion cyclotron (EMIC) waves at frequencies below the helium cyclotron frequency. We conclude that the observed pitch angle evolution was due to ion scattering by EMIC waves.

  3. On the azimuthal variation of the equatorial plasmapause

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.; Craven, P. D.; Comfort, R. H.; Moore, T. E.

    1994-01-01

    Previous results of plasmapause position surveys have been synthesized into a comprehensive description of the plasmapause, taken to represent the boundary between diurnal near-corotation and large-scale circulation streamlines that traverse the entire magnetosphere. The result indicates a plasmapause that has a pronounced bulge in the dusk sector, that rotates sunward and shrinks markedly as geomagnetic activity (and presumably magnetospheric convection) increase. The shape of the plasmapause so determined is significantly different from that associated with the simple superposition of sunward flow and corotation, both in its detailed shape and in its varying orientation. The results imply that the magnetospheric circulation departs from a uniform flow field, having a radial dependence with respect to the Earth that is qualitatively consistent with electrostatic shielding of the convection electric field. Also, the results imply the the inner magnetospheric flow field rotates from duskward to dawnward as its intensity increases.

  4. Theory for substorms triggered by sudden reductions in convection

    NASA Technical Reports Server (NTRS)

    Lyons, L. R.

    1996-01-01

    Many substorm expansions are triggered by interplanetary magnetic field changes that reduce magnetospheric convection. This suggests that expansion onsets are a result of a reduction in the large-scale electric field imparted to the magnetosphere from the solar wind. Such a reduction disrupts the inward motion and energization of plasma sheet particles that occur during the growth phase. It is proposed that the resulting magnetic drift of particles and a large dawn to dusk gradient in the ion energies leads to a longitudinally localized reduction in the plasma pressure, and thus, to the current wedge formation. This theory accounts for the rapid development of the expansion phase relative to growth phase, the magnitude of the wedge currents, the speeds of tailward and westward expansion of the current reduction region in the equatorial plane, and the speeds of the poleward and westward motion of active aurora in the ionosphere.

  5. Plasma and electric field boundaries at high and low altitudes on July 29, 1977

    NASA Technical Reports Server (NTRS)

    Fennell, J. F.; Johnson, R. G.; Young, D. T.; Torbert, R. B.; Moore, T. E.

    1982-01-01

    Hot plasma observations at high and low altitudes were compared. The plasma ion composition at high altitudes outside the plasmasphere was 0+. Heavy ions were also observed at low altitudes outside the plasmasphere. It is shown that at times these ions are found well below the plasmapause inside the plasmasphere. Comparisons of the low altitude plasma and dc electric fields show that the outer limits of the plasmasphere is not always corotating at the low L-shells. The corotation boundary, the estimated plasmapause boundary at the boundary of the inner edge of plasma sheet ions were at the same position. The inner edge of plasma sheet electrons is observed at higher latitudes than the plasmasphere boundary during disturbed times. The inner edge of the plasma sheaths shows a strong dawn to dusk asymmetry. At the same time the inner edge of the ring current and plasma sheath also moves to high latitudes reflecting an apparent inflation of the magnetosphere.

  6. Storm-time changes of geomagnetic field at MAGSAT altitudes (325-550 Km) and their comparison with changes at ground locations

    NASA Technical Reports Server (NTRS)

    Parada, N. D. J. (Principal Investigator); Kane, R. P.; Trivedi, N. B.

    1983-01-01

    The values of H, X, Y, Z at MAGSAT altitudes were first expressed as residuals delta H, delta X, delta Y, delta Z after subtracting the model HMD, XMD, YMD, ZMC. The storm-time variations of H showed that delta H (Dusk) was larger (negative) than delta H (Dawn) and occurred earlier, indicating a sort of hysteresis effect. Effects at MAGSAT altitudes were roughly the same (10% accuracy) as at ground, indicating that these effects were mostly of magnetospheric origin. The delta Y component also showed large storm-time changes. The latitudinal distribution of storm-time delta H showed north-south asymmetries varying in nature as the storm progressed. It seems that the central plane of the storm-time magnetospheric ring current undergoes latitudinal meanderings during the course of the storm.

  7. Further determination of the characteristics of magnetospheric plasma vortices with Isee 1 and 2

    NASA Technical Reports Server (NTRS)

    Hones, E. W., Jr.; Bame, S. J.; Asbridge, J. R.; Birn, J.; Paschmann, G.; Sckopke, N.; Haerendel, G.

    1981-01-01

    Further studies of the vortices in magnetospheric plasma flow with the Los Alamos Scientific Laboratory/Max-Planck-Institut (LASL/MPI) fast plasma experiment on Isee 1 and 2 have revealed that the pattern of vortical flow has a wavelength of approximately 20-40 earth radii and moves tailward through the magnetosphere at speeds of several hundred kilometers per second. The tendency toward vorticity pervades the total breadth of the plasma sheet tailward of the dawn-dusk meridian. The sense of rotation of the plasma flow (as viewed from above the ecliptic plane) is clockwise in the morning side of the plasma sheet and counterclockwise in the evening side. The sense of rotation in the morning and evening boundary layers is reversed from that in the contiguous regions of the plasma sheet. The occurrence of vortical flow is independent of the level of geomagnetic activity but is associated with long-period geomagnetic pulsations.

  8. The effects of interplanetary magnetic field orientation on dayside high-latitude ionospheric convection

    NASA Technical Reports Server (NTRS)

    Heelis, R. A.

    1984-01-01

    The Atmosphere Explorer C data base of Northern Hemisphere ionospheric convection signatures at high latitudes is examined during times when the interplanetary magnetic field orientation is relatively stable. It is found that when the interplanetary magnetic field (IMF) has its expected garden hose orientation, the center of a region where the ion flow rotates from sunward to antisunward is displaced from local noon toward dawn irrespective of the sign of By. Poleward of this rotation region, called the cleft, the ion convection is directed toward dawn or dusk depending on whether By is positive or negative, respectively. The observed flow geometry can be explained in terms of a magnetosphere solar wind interaction in which merging is favored in either the prenoon Northern Hemisphere or the prenoon Southern Hemisphere when the IMF has a normal sector structure that is toward or away, respectively.

  9. Evidence for lightning on Venus

    NASA Technical Reports Server (NTRS)

    Strangeway, R. J.

    1992-01-01

    Lightning is an interesting phenomenon both for atmospheric and ionospheric science. At the Earth lightning is generated in regions where there is strong convection. Lightning also requires the generation of large charge-separation electric fields. The energy dissipated in a lightning discharge can, for example, result in chemical reactions that would not normally occur. From an ionospheric point of view, lightning generates a broad spectrum of electromagnetic radiation. This radiation can propagate through the ionosphere as whistler mode waves, and at the Earth the waves propagate to high altitudes in the plasmasphere where they can cause energetic particle precipitation. The atmosphere and ionosphere of Venus are quite different from those on the Earth, and the presence of lightning at Venus has important consequences for our knowledge of why lightning occurs and how the energy is dissipated in the atmosphere and ionosphere. As discussed here, it now appears that lightning occurs in the dusk local time sector at Venus.

  10. Towards developing an analytical procedure of defining the equatorial electrojet for correcting satellite magnetic anomaly data

    NASA Technical Reports Server (NTRS)

    Ravat, Dhananjay; Hinze, William J.

    1991-01-01

    Analysis of the total magnetic intensity MAGSAT data has identified and characterized the variability of ionospheric current effects as reflected in the geomagnetic field as a function of longitude, elevation, and time (daily as well as monthly variations). This analysis verifies previous observations in POGO data and provides important boundary conditions for theoretical studies of ionospheric currents. Furthermore, the observations have led to a procedure to remove these temporal perturbations from lithospheric MAGSAT magnetic anomaly data based on 'along-the-dip-latitude' averages from dawn and dusk data sets grouped according to longitudes, time (months), and elevation. Using this method, high-resolution lithospheric magnetic anomaly maps have been prepared of the earth over a plus or minus 50 deg latitude band. These maps have proven useful in the study of the structures, nature, and processes of the lithosphere.

  11. High latitude f-region drift studies. Technical report, October 1985-September 1986

    SciTech Connect

    Reinisch, B.W.; Buchau, J.; Weber, E.J.; Dozois, C.G.; Bibl, K.

    1986-12-01

    The large-scale, high-latitude ionospheric-convection pattern is driven by the interaction of the solar wind and the interplanetary magnetic field with the earth's magnetosphere. Ground-based digital ionosondes, with spaced receiving antennas, have been developed and deployed at the high latitude stations of Thule, Greenland and Goose Bay, Labrador. Results from these stations demonstrate that the ionospheric convection can be measured for the bottomside ionosphere. Data from Thule consistently show the predominant antisunward convection. The data from Goose Bay indicate the sunward return flows of the polar plasma convection and the switch over when the station rotates from the dusk into the dawn cell. These data also illustrate the potential for systematic study of the convection patterns that is possible with a network of ground-based digital ionosondes.

  12. Early MITHRAS results - The electric field response to substorms

    NASA Astrophysics Data System (ADS)

    de La Beaujardiere, O.; Holt, J.; Nielsen, E.

    1983-12-01

    The MITHRAS data base offers a unique opportunity to observe simultaneously the auroral-zone ion convection pattern with three radars, widely separated in longitude. It is attempted to separate local-time versus universal-time effects in a study of the electric field signature associated with substorms. Preliminary results indicate that this signature is similar at a given local time, regardless of the longitude of the station. In the dawn and dusk sectors the electric field is intensified, whereas around noon and midnight the electric field appears to reverse during a substorm. The potential drop across the polar cap can be estimated from the potential across the auroral oval. The radar data agree well with the relationship found by Reiff and co-workers between the solar wind energy parameter epsilon and the cross-tail potential.

  13. Observations of Field-Aligned Current Spatial and Temporal Variations by Space Technology 5

    NASA Astrophysics Data System (ADS)

    Le, G.; Slavin, J. A.; Strangeway, R. J.; Wang, Y.

    2013-12-01

    In this paper, we report the results of magnetic field measurements of field-aligned currents (FACs) using multi-point magnetic field data from Space Technology 5 (ST-5) mission. ST-5 is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, sun synchronous polar orbit. 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. During the three-month mission duration, the constellation mission returned high quality multi-point measurements of the magnetic field through Earth's dynamic ionospheric current systems over a range of inter-satellite spacing. In this study, we use the ST-5 magnetic field measurements to separate spatial and temporal variations of FACs and to quantify the imbalance between the region 1 (R1) and the region 2 (R2) currents.

  14. Electron dropout echoes induced by interplanetary shock: Van Allen Probes observations

    NASA Astrophysics Data System (ADS)

    Hao, Y. X.; Zong, Q.-G.; Zhou, X.-Z.; Fu, S. Y.; Rankin, R.; Yuan, C.-J.; Lui, A. T. Y.; Spence, H. E.; Blake, J. B.; Baker, D. N.; Reeves, G. D.

    2016-06-01

    On 23 November 2012, a sudden dropout of the relativistic electron flux was observed after an interplanetary shock arrival. The dropout peaks at ˜1 MeV and more than 80% of the electrons disappeared from the drift shell. Van Allen twin Probes observed a sharp electron flux dropout with clear energy dispersion signals. The repeating flux dropout and recovery signatures, or "dropout echoes", constitute a new phenomenon referred to as a "drifting electron dropout" with a limited initial spatial range. The azimuthal range of the dropout is estimated to be on the duskside, from ˜1300 to 0100 LT. We conclude that the shock-induced electron dropout is not caused by the magnetopause shadowing. The dropout and consequent echoes suggest that the radial migration of relativistic electrons is induced by the strong dusk-dawn asymmetric interplanetary shock compression on the magnetosphere.

  15. A comparison of the radio data and model calculations of Jupiter's synchrotron radiation. I - The high energy electron distribution in Jupiter's inner magnetosphere. II - East-west asymmetry in the radiation belts as a function of Jovian longitude

    NASA Technical Reports Server (NTRS)

    De Pater, I.

    1981-01-01

    A comparison has been made between detailed model calculations of Jupiter's synchrotron radiation and the radio data at wavelengths of 6, 21, and 50 cm. The calculations were performed for a Jovian longitude of 200 deg and were based on the multipole field configurations as derived from the Pioneer data. The electron distribution in the inner magnetosphere was derived as a function of energy, pitch angle, and spatial coordinates. In addition, the hot region or east-west asymmetry in the radiation belts is investigated. It is suggested that this asymmetry is due to the combined effect of an overabundance of electrons at jovicentric longitudes of 240-360 deg and the existence of a dusk-to-dawn directed electric field over the inner magnetosphere generated by the wind system in the upper atmosphere.

  16. Mass Transport and Dynamics at Subauroral Latitudes During The March 17, 2013 Storm

    NASA Astrophysics Data System (ADS)

    Erickson, P. J.; Foster, J. C.; Coster, A. J.; Wygant, J. R.; Bonnell, J. W.

    2015-12-01

    During geomagnetic storm periods, plasmasphere erosion carries cold dense plasma of ionospheric origin in a storm-enhanced density plume, extending from dusk toward and through the noontime cusp and dayside magnetopause and back across polar latitudes in a polar tongue of ionization. The March 17, 2013 large storm provided an excellent opportunity to observe these mass transfer processes using a number of ground and in-situ sensors. We examine dusk sector (20 MLT) plasmasphere erosion during the 17 March 2013 storm (Dst ~ 130 nT) using simultaneous, magnetically aligned direct sunward ion flux observations at high altitude by Van Allen Probes RBSP-A (at ~3.0 Re) and at topside ionospheric heights (~840 km) by DMSP F-18, along with direct F region ionospheric observations using the subauroral Millstone Hill incoherent scatter radar system. Plasma erosion occurs at both high and low altitudes where the subauroral polarization stream flow overlaps the outer plasmasphere. At ~20 UT, RBSP-A observed ~1.2E12 m-2 s-1 erosion flux, while DMSP F-18 observed ~2E13 m-2 s-1 sunward flux. We find close similarities at high and low altitudes between the erosion plume in both invariant latitude spatial extent and plasma characteristics. Other incoherent scatter radar facilities at Poker Flat, along with both the mainland Europe and Svalbard EISCAT radars, also have observations available during this period. We use these combined, multi-scale data sets in comparison to model predictions of SAPS, e.g. BATSRUS/RAM, OpenGGCM-RM. We will highlight successes and areas where progress is needed in the quantitative understanding of cold ionospheric origin mass flow through the geospace system and its direct impact on energy coupling to the solar wind.

  17. Low-harmonic magnetosonic waves observed by the Van Allen Probes

    NASA Astrophysics Data System (ADS)

    Posch, J. L.; Engebretson, M. J.; Olson, C. N.; Thaller, S. A.; Breneman, A. W.; Wygant, J. R.; Boardsen, S. A.; Kletzing, C. A.; Smith, C. W.; Reeves, G. D.

    2015-08-01

    Purely compressional electromagnetic waves (fast magnetosonic waves), generated at multiple harmonics of the local proton gyrofrequency, have been observed by various types of satellite instruments (fluxgate and search coil magnetometers and electric field sensors), but most recent studies have used data from search coil sensors, and many have been restricted to high harmonics. We report here on a survey of low-harmonic waves, based on electric and magnetic field data from the Electric Fields and Waves double probe and Electric and Magnetic Field Instrument Suite and Integrated Science fluxgate magnetometer instruments, respectively, on the Van Allen Probes spacecraft during its first full precession through all local times, from 1 October 2012 to 13 July 2014. These waves were observed both inside and outside the plasmapause (PP), at L shells from 2.4 to ~6 (the spacecraft apogee), and in regions with plasma number densities ranging from 10 to >1000 cm-3. Consistent with earlier studies, wave occurrence was sharply peaked near the magnetic equator. Waves appeared at all local times but were more common from noon to dusk, and often occurred within 3 h after substorm injections. Outside the PP occurrence maximized broadly across noon, and inside the PP occurrence maximized in the dusk sector, in an extended plasmasphere. We confirm recent ray-tracing studies showing wave refraction and/or reflection at PP-like boundaries. Comparison with waveform receiver data indicates that in some cases these low-harmonic magnetosonic wave events occurred independently of higher-harmonic waves; this indicates the importance of including this population in future studies of radiation belt dynamics.

  18. Strong IMF By-Related Plasma Convection in the Ionosphere and Cusp Field-Aligned Currents Under Northward IMF Conditions

    NASA Technical Reports Server (NTRS)

    Le, G.; Lu, G.; Strangeway, R. J.; Pfaff, R. F., Jr.; Vondrak, Richard R. (Technical Monitor)

    2001-01-01

    We present in this paper an investigation of IMF-By related plasma convection and cusp field-aligned currents using FAST data and AMIE model during a prolonged interval with large positive IMF By and northward Bz conditions (By/Bz much greater than 1). Using the FAST single trajectory observations to validate the global convection patterns at key times and key locations, we have demonstrated that the AMIE procedure provides a reasonably good description of plasma circulations in the ionosphere during this interval. Our results show that the plasma convection in the ionosphere is consistent with the anti-parallel merging model. When the IMF has a strongly positive By component under northward conditions, we find that the global plasma convection forms two cells oriented nearly along the Sun-earth line in the ionosphere. In the northern hemisphere, the dayside cell has clockwise convection mainly circulating within the polar cap on open field lines. A second cell with counterclockwise convection is located in the nightside circulating across the polar cap boundary, The observed two-cell convection pattern appears to be driven by the reconnection along the anti-parallel merging lines poleward of the cusp extending toward the dusk side when IMF By/Bz much greater than 1. The magnetic tension force on the newly reconnected field lines drives the plasma to move from dusk to dawn in the polar cusp region near the polar cap boundary. The field-aligned currents in the cusp region flow downward into the ionosphere. The return field-aligned currents extend into the polar cap in the center of the dayside convection cell. The field-aligned currents are closed through the Peterson currents in the ionosphere, which flow poleward from the polar cap boundary along the electric field direction.

  19. GPS Based Daily Activity Patterns in European Red Deer and North American Elk (Cervus elaphus): Indication for a Weak Circadian Clock in Ungulates

    PubMed Central

    Ensing, Erik P.; Ciuti, Simone; de Wijs, Freek A. L. M.; Lentferink, Dennis H.; ten Hoedt, André; Boyce, Mark S.; Hut, Roelof A.

    2014-01-01

    Long-term tracking using global positioning systems (GPS) is widely used to study vertebrate movement ecology, including fine-scale habitat selection as well as large-scale migrations. These data have the potential to provide much more information about the behavior and ecology of wild vertebrates: here we explore the potential of using GPS datasets to assess timing of activity in a chronobiological context. We compared two different populations of deer (Cervus elaphus), one in the Netherlands (red deer), the other in Canada (elk). GPS tracking data were used to calculate the speed of the animals as a measure for activity to deduce unbiased daily activity rhythms over prolonged periods of time. Speed proved a valid measure for activity, this being validated by comparing GPS based activity data with head movements recorded by activity sensors, and the use of GPS locations was effective for generating long term chronobiological data. Deer showed crepuscular activity rhythms with activity peaks at sunrise (the Netherlands) or after sunrise (Canada) and at the end of civil twilight at dusk. The deer in Canada were mostly diurnal while the deer in the Netherlands were mostly nocturnal. On an annual scale, Canadian deer were more active during the summer months while deer in the Netherlands were more active during winter. We suggest that these differences were mainly driven by human disturbance (on a daily scale) and local weather (on an annual scale). In both populations, the crepuscular activity peaks in the morning and evening showed a stable timing relative to dawn and dusk twilight throughout the year, but marked periods of daily a-rhythmicity occurred in the individual records. We suggest that this might indicate that (changes in) light levels around twilight elicit a direct behavioral response while the contribution of an internal circadian timing mechanism might be weak or even absent. PMID:25208246

  20. GPS based daily activity patterns in European red deer and North American elk (Cervus elaphus): indication for a weak circadian clock in ungulates.

    PubMed

    Ensing, Erik P; Ciuti, Simone; de Wijs, Freek A L M; Lentferink, Dennis H; Ten Hoedt, André; Boyce, Mark S; Hut, Roelof A

    2014-01-01

    Long-term tracking using global positioning systems (GPS) is widely used to study vertebrate movement ecology, including fine-scale habitat selection as well as large-scale migrations. These data have the potential to provide much more information about the behavior and ecology of wild vertebrates: here we explore the potential of using GPS datasets to assess timing of activity in a chronobiological context. We compared two different populations of deer (Cervus elaphus), one in the Netherlands (red deer), the other in Canada (elk). GPS tracking data were used to calculate the speed of the animals as a measure for activity to deduce unbiased daily activity rhythms over prolonged periods of time. Speed proved a valid measure for activity, this being validated by comparing GPS based activity data with head movements recorded by activity sensors, and the use of GPS locations was effective for generating long term chronobiological data. Deer showed crepuscular activity rhythms with activity peaks at sunrise (the Netherlands) or after sunrise (Canada) and at the end of civil twilight at dusk. The deer in Canada were mostly diurnal while the deer in the Netherlands were mostly nocturnal. On an annual scale, Canadian deer were more active during the summer months while deer in the Netherlands were more active during winter. We suggest that these differences were mainly driven by human disturbance (on a daily scale) and local weather (on an annual scale). In both populations, the crepuscular activity peaks in the morning and evening showed a stable timing relative to dawn and dusk twilight throughout the year, but marked periods of daily a-rhythmicity occurred in the individual records. We suggest that this might indicate that (changes in) light levels around twilight elicit a direct behavioral response while the contribution of an internal circadian timing mechanism might be weak or even absent. PMID:25208246

  1. The use of automated bioacoustic recorders to replace human wildlife surveys: an example using nightjars.

    PubMed

    Zwart, Mieke C; Baker, Andrew; McGowan, Philip J K; Whittingham, Mark J

    2014-01-01

    To be able to monitor and protect endangered species, we need accurate information on their numbers and where they live. Survey methods using automated bioacoustic recorders offer significant promise, especially for species whose behaviour or ecology reduces their detectability during traditional surveys, such as the European nightjar. In this study we examined the utility of automated bioacoustic recorders and the associated classification software as a way to survey for wildlife, using the nightjar as an example. We compared traditional human surveys with results obtained from bioacoustic recorders. When we compared these two methods using the recordings made at the same time as the human surveys, we found that recorders were better at detecting nightjars. However, in practice fieldworkers are likely to deploy recorders for extended periods to make best use of them. Our comparison of this practical approach with human surveys revealed that recorders were significantly better at detecting nightjars than human surveyors: recorders detected nightjars during 19 of 22 survey periods, while surveyors detected nightjars on only six of these occasions. In addition, there was no correlation between the amount of vocalisation captured by the acoustic recorders and the abundance of nightjars as recorded by human surveyors. The data obtained from the recorders revealed that nightjars were most active just before dawn and just after dusk, and least active during the middle of the night. As a result, we found that recording at both dusk and dawn or only at dawn would give reasonably high levels of detection while significantly reducing recording time, preserving battery life. Our analyses suggest that automated bioacoustic recorders could increase the detection of other species, particularly those that are known to be difficult to detect using traditional survey methods. The accuracy of detection is especially important when the data are used to inform conservation. PMID

  2. The thalamic intergeniculate leaflet modulates photoperiod responsiveness in Siberian hamsters.

    PubMed

    Freeman, David A; Dhandapani, Krishnan M; Goldman, Bruce D

    2004-11-26

    Siberian hamsters are seasonal breeders that use changes in day length to synchronize their reproductive effort with those times of the year most favorable for successful reproduction. The ability of Siberian hamsters to measure and respond to changes in day length depends upon accurate photoentrainment of the circadian clock in the suprachiasmatic nucleus (SCN) of the hypothalamus. Two pathways have been characterized through which entraining stimuli reach the SCN: the retinohypothalamic tract (RHT), which transmits light information from the retinae, and the geniculohypothalamic tract (GHT) from the intergeniculate leaflet of the thalamus (IGL), which is involved in transmitting both photic and nonphotic cues. Ablating the IGL/GHT results in only modest alterations in entrainment to static day lengths and fails to interfere with seasonal responses induced by transfer from static long day to static short day lengths. Because several studies suggest that the IGL may be involved in tracking the time of dusk and dawn, we sought to determine whether an intact IGL is necessary for hamsters to respond to a simulated natural photoperiod (SNP) in which the time of dusk and dawn gradually changes in a pattern approximating the rate of change in day length that occurs during autumn at the latitude this species inhabits in nature. The results indicate that neurochemical lesions of the IGL alter both the pattern of circadian entrainment and photoperiodic responsiveness of Siberian hamsters to an SNP. Both intact and IGL-lesioned hamsters exhibited testicular regression in shortening day lengths, but only IGL-intact hamsters exhibited seasonal pelage molt.

  3. GPS based daily activity patterns in European red deer and North American elk (Cervus elaphus): indication for a weak circadian clock in ungulates.

    PubMed

    Ensing, Erik P; Ciuti, Simone; de Wijs, Freek A L M; Lentferink, Dennis H; Ten Hoedt, André; Boyce, Mark S; Hut, Roelof A

    2014-01-01

    Long-term tracking using global positioning systems (GPS) is widely used to study vertebrate movement ecology, including fine-scale habitat selection as well as large-scale migrations. These data have the potential to provide much more information about the behavior and ecology of wild vertebrates: here we explore the potential of using GPS datasets to assess timing of activity in a chronobiological context. We compared two different populations of deer (Cervus elaphus), one in the Netherlands (red deer), the other in Canada (elk). GPS tracking data were used to calculate the speed of the animals as a measure for activity to deduce unbiased daily activity rhythms over prolonged periods of time. Speed proved a valid measure for activity, this being validated by comparing GPS based activity data with head movements recorded by activity sensors, and the use of GPS locations was effective for generating long term chronobiological data. Deer showed crepuscular activity rhythms with activity peaks at sunrise (the Netherlands) or after sunrise (Canada) and at the end of civil twilight at dusk. The deer in Canada were mostly diurnal while the deer in the Netherlands were mostly nocturnal. On an annual scale, Canadian deer were more active during the summer months while deer in the Netherlands were more active during winter. We suggest that these differences were mainly driven by human disturbance (on a daily scale) and local weather (on an annual scale). In both populations, the crepuscular activity peaks in the morning and evening showed a stable timing relative to dawn and dusk twilight throughout the year, but marked periods of daily a-rhythmicity occurred in the individual records. We suggest that this might indicate that (changes in) light levels around twilight elicit a direct behavioral response while the contribution of an internal circadian timing mechanism might be weak or even absent.

  4. Multispecies spawning sites for fishes on a low-latitude coral reef: spatial and temporal patterns.

    PubMed

    Claydon, J A B; McCormick, M I; Jones, G P

    2014-04-01

    Spawning sites used by one or more species were located by intensively searching nearshore coral reefs of Kimbe Bay (New Britain, Papua New Guinea). Once identified, the spawning sites were surveyed repeatedly within fixed 5 m radius circular areas, for  > 2000 h of observations ranging from before dawn to after dusk spanning 190 days between July 2001 and May 2004. A total of 38 spawning sites were identified on the seven study reefs distributed at an average of one site every 60 m of reef edge. Pelagic spawning was observed in 41 fish species from six families. On three intensively studied reefs, all 17 spawning sites identified were used by at least three species, with a maximum of 30 different species observed spawning at a single site. Spawning was observed during every month of the study, on all days of the lunar month, at all states of the tide and at most hours of the day studied. Nevertheless, the majority of species were observed spawning on proportionately more days from December to April, on more days around the new moon and in association with higher tides. The strongest temporal association, however, was with species-specific diel spawning times spanning < 3 h for most species. While dawn spawning, afternoon spawning and dusk spawning species were differentiated, the time of spawning for the striated surgeonfish Ctenochaetus striatus also differed significantly among sites. The large number of species spawning at the same restricted locations during predictable times suggests that these sites are extremely important on this low-latitude coral reef.

  5. Response of the incompressible ionosphere to the compression of the magnetosphere during the geomagnetic sudden commencements

    NASA Astrophysics Data System (ADS)

    Kikuchi, T.; Hashimoto, K. K.; Tomizawa, I.; Ebihara, Y.; Nishimura, Y.; Araki, T.; Shinbori, A.; Veenadhari, B.; Tanaka, T.; Nagatsuma, T.

    2016-02-01

    The ionospheric plasma in midlatitude moves upward/downward during the geomagnetic sudden commencement causing the HF Doppler frequency changes; SCF (+ -) and (- +) on the dayside and nightside, respectively, except for the SCF (+ -) in the evening as found by Kikuchi et al. (1985). Although the preliminary and main frequency deviations (PFD, MFD) of the SCF have been attributed to the dusk-to-dawn and dawn-to-dusk potential electric fields, there still remain questions if the positive PFD can be caused by the compressional magnetohydrodynamic (MHD) wave and what causes the evening anomaly of the SCF. With the HF Doppler sounder, we show that the dayside ionosphere moves upward toward the Sun during the main impulse (MI) of the SC, when the compressional wave is supposed to push the ionosphere downward. The motion of the ionosphere is shown to be correlated with the equatorial electrojet, matching the potential electric field transmitted with the ionospheric currents from the polar ionosphere. We confirmed that the electric field of the compressional wave is severely suppressed by the conducting ionosphere and reproduced the SC electric fields using the global MHD simulation in which the potential solver is employed. The model calculations well reproduced the preliminary impulse and MI electric fields and their evening anomaly. It is suggested that the electric potential is transmitted from the polar ionosphere to the equator by the zeroth-order transverse magnetic (TM0) mode waves in the Earth-ionosphere waveguide. The near-instantaneous transmission of the electric potential leads to instantaneous global response of the incompressible ionosphere.

  6. Seasonal abundance & role of predominant Japanese encephalitis vectors Culex tritaeniorhynchus & Cx. gelidus Theobald in Cuddalore district, Tamil Nadu

    PubMed Central

    Ramesh, D.; Muniaraj, M.; Samuel, P. Philip; Thenmozhi, V.; Venkatesh, A.; Nagaraj, J.; Tyagi, B.K.

    2015-01-01

    Background & objectives: Japanese encephalitis (JE) is the leading cause of viral encephalitis in Asia. The first major JE outbreak occurred in 1978 and since 1981 several outbreaks had been reported in the Cuddalore district (erstwhile South Arcot), Tamil Nadu, India. Entomological monitoring was carried out during January 2010 - March 2013, to determine the seasonal abundance and transmission dynamics of the vectors of JE virus, with emphasis on the role of Culex tritaeniorhynchus and Cx. gelidus. Methods: Mosquito collections were carried out fortnightly during dusk hours in three villages viz. Soundara Solapuram, Pennadam, Erappavur of Cuddalore district. Mosquitoes were collected during dusk for a period of one hour in and around the cattle sheds using oral aspirator and torch light. The collected mosquitoes were later identified and pooled to detect JE virus (JEV) infection by enzyme linked immunosorbent assay (ELISA). Results: A total of 46,343 mosquitoes comprising of 25 species and six genera were collected. Species composition included viz, Cx. tritaeniorhynchus (46.26%), Cx. gelidus (43.12%) and other species (10.62%). A total of 17,678 specimens (403 pools) of Cx. gelidus and 14,358 specimens (309 pools) of Cx. tritaeniorhynchus were tested, of which 12 pools of Cx. gelidus and 14 pools of Cx. tritaeniorhynchus were positive for JE virus antigen. The climatic factors were negatively correlated with minimum infection rate (MIR) for both the species, except mean temperature (P<0.05) for Cx. gelidus. Interpretation & conclusions: High abundance of Cx. tritaeniorhynchus and Cx. gelidus was observed compared to other mosquito species in the study area. Detection of JEV antigen in the two species confirmed the maintenance of virus. Appropriate vector control measures need to be taken to reduce the vector abundance. PMID:26905238

  7. A Statistical Study of Plasmaspheric Plumes and Ionospheric Outflows Observed at the Dayside Magnetopause

    NASA Astrophysics Data System (ADS)

    Lee, S. H.; Zhang, H.; Zong, Q. G.; Otto, A.; Rème, H.; Liebert, E.

    2015-12-01

    The low-energy and dense plasma originated from the ionosphere has often been observed in the dayside magnetosphere and may play an important role in the dynamics of the dayside magnetopause. We present a statistical study of the plasmaspheric plumes and the ionospheric outflows observed by the Cluster spacecraft near the dayside magnetopause from 2007 to 2009. The plasmaspheric plumes were identified by the low-energy ions (< 1 keV) which have 90° pitch angle distributions from the CIS/HIA instrument onboard Cluster in the magnetosphere. The ionospheric outflows were characterized by uni- or bi-directional field-aligned pitch angle distributions with low-energy ions observed in the dayside magnetosphere. 43 (10%) plasmaspheric plume events and 32 (7%) ionospheric outflow events were detected during 442 dayside magnetopause crossings. The occurrence rate of the plume at the duskside is significantly higher than that at the dawnside, indicating that the plasmaspheric plumes may lead to a dawn-dusk asymmetry of the dayside reconnection. The occurrence rate of the outflow shows a weak dawn-dusk asymmetry. We investigated how the plasmaspheric plume and ionospheric outflow's occurrence rates depend on geomagnetic activity and solar wind/IMF conditions. It is found that the plume events prefer to occur during moderate geomagnetic activity (Kp = 3, -30 ≤ Dst < -10 nT), while the ionospheric outflow events do not occur when Kp = 0 and their occurrence rate does not have a clear Dst dependence. It is also found that the plume events tend to occur during southward IMF (duskward solar wind electric field). In contrast, the ionospheric outflows prefer to occur during northward IMF (dawnward solar wind electric field). Finally, the occurrence rates of both plumes and outflows increase with increasing solar wind dynamic pressure.

  8. 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.

  9. Space Technology 5 (ST-5) Observations of the Imbalance of Region 1 and 2 Field-Aligned Currents

    NASA Technical Reports Server (NTRS)

    Le, Guan

    2010-01-01

    Space Technology 5 (ST-5) is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, sun-synchronous polar orbit from March 22 to June 21, 2006, for technology validations. In this study, we use the in-situ magnetic field observations from Space Technology 5 mission to quantify the imbalance of Region 1 (R1) and Region 2 (R2) currents. During the three-month duration of the ST5 mission, geomagnetic conditions range from quiet to moderately active. We find that the R1 current intensity is consistently stronger than the R2 current intensity both for the dawnside and the duskside large-scale field-aligned current system. The net currents flowing into (out of) the ionosphere in the dawnside (duskside) are in the order of 5% of the total RI currents. We also find that the net currents flowing into or out of the ionosphere are controlled by the solar wind-magnetosphere interaction in the same way as the field-aligned currents themselves are. Since the net currents due to the imbalance of the R1 and R2 currents require that their closure currents flow across the polar cap from dawn to dusk as Pedersen currents, our results indicate that the total amount of the cross-polar cap Pedersen currents is in the order of approx. 0.1 MA. This study, although with a very limited dataset, is one of the first attempts to quantify the cross-polar cap Pedersen currents. Given the importance of the Joule heating due to Pedersen currents to the high-latitude ionospheric electrodynamics, quantifying the cross-polar cap Pedersen currents and associated Joule heating is needed for developing models of the magnetosphere-ionosphere coupling.

  10. Observations of a Unique Type of ULF Waves by Low-altitude ST-5 Satellites

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    We report a unique type of ULF waves observed by low-altitude Space Technology 5 (ST-5) constellation mission. ST-5 is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, and sun synchronous polar orbit with 105.6° inclination angle. Even though the spacecraft are in a high-inclination orbit, the combined effects of the Earth’s rotation and dipole tilt allow the spacecraft’s dawn-dusk orbit track to reach subauroral latitudes on the day side. 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 Pc 2-3 frequency range. These Pc 2-3 waves appear as wave packets with durations of the order of 5-10 minutes. As the maximum separations of the ST-5 spacecraft are around 10 minutes, the three ST-5 satellites often observe very similar wave packets, implying these wave oscillations occur in a localized region. 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 high azimuthal wave number Pc 4-5 waves Doppler-shifted to higher frequencies by the rapid traverse of the spacecraft across the resonant field lines azimuthally at low altitudes. These unique low altitude observations, where the spacecraft motion is mainly azimuthal at subauroral latitudes, reveal the azimuthal wave-number characteristics of the field-aligned resonance signals.

  11. Observations of a unique type of ULF waves by low-altitude ST-5 satellites

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

    We report a unique type of ULF waves observed by low-altitude Space Technology 5 (ST-5) constellation mission. ST-5 is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, and sun synchronous polar orbit with 105.6° 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 Pc 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.

  12. 3D kinetic picture of magnetotail explosions and characteristic auroral features prior to and after substorm onset

    NASA Astrophysics Data System (ADS)

    Sitnov, M. I.; Merkin, V. G.; Motoba, T.

    2015-12-01

    Recent findings in theory, observations and 3D particle-in-cell simulations of magnetotail explosions reveal a complex picture of reconnection, buoyancy and flapping motions, which have interesting correlations with the auroral morphology. First, the formation of the tailward Bz gradient as a theoretical prerequisite for tearing, ballooning/interchange and flapping instabilities is consistent with the structure of the pre-onset quiet arc and the associated deep minimum of Bz. Another distinctive pre-onset feature, equatorward extension of the auroral oval in the late growth phase, is conventionally associated with earthward motion of the inner edge of the plasma sheet. However, if open magnetic flux saturates in the late growth phase, it may also be treated as a signature of magnetic flux accumulation tailward of the Bz minimum, which is also favorable for the tail plasma sheet instabilities. 3D PIC simulations of similar magnetotail equilibria with a tailward Bz gradient show spontaneous formation of earthward flows led by dipolarization fronts. They are structured in the dawn-dusk direction on the ion inertial scale, consistent with the minimum scales of the observed auroral beads. At the same time, simulations show the formation of a new X-line in the wake of the dipolarization front with no significant spatial modulation in the dawn-dusk direction suggesting smooth profiles of the substorm current wedge as well as poleward parts of auroral streamers. Flapping motions, which also grow at the dipolarization front, extend beyond it, up to the new X-line region. To understand auroral manifestations of tail structures in our simulations we investigate the plasma moments at the plasma sheet boundary.

  13. Observations of a Unique Type of ULF Waves by Low-altitude ST5 Satellites

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

    We report a unique type of ULF waves observed by low-altitude Space Technology 5 (ST5) constellation mission. ST5 is a three micro-satellite constellation deployed into a 300 x 4500 lan, dawn-dusk, and sun synchronous polar orbit with 105.6 inclination angle. Even though the spacecraft are in a high-inclination orbit, the combined effects of the Earth's rotation and dipole tilt allow the spacecraft's dawn-dusk orbit track to reach subauroral latitudes on the day side. Whenever the spacecraft traverse across the dayside closed field line region at sub auroral latitudes they frequently observe strong transverse oscillations at 30-200 mHz, or in the Pc 2-3 frequency range. These Pc 2-3 waves appear as wave packets with durations of the order of 5-10 minutes. As the maximum separations of the ST5 spacecraft are around 10 minutes, the three ST5 satellites often observe very similar wave packets, implying these wave oscillations occur in a localized region. 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 ST5 are in fact high azimuthal wave number Pc 4-5 waves Doppler-shifted to higher frequencies by the rapid traverse of the spacecraft across the resonant field lines azimuthally at low altitudes. These unique low altitude observations, where the spacecraft motion is mainly azimuthal at subauroral latitudes, reveal the azimuthal wave-number characteristics of the field-aligned resonance signals.

  14. Sulfur Oxidation, Microbes And Acidity In A Mine Tailings Lake

    NASA Astrophysics Data System (ADS)

    Warren, L. A.; Bernier, L.

    2003-12-01

    Disposal of tailings (waste rock) aqueously is a common approach at mine sites to minimize oxidation of the associated sulfur minerals (pyrrhotite, pyrite) and the associated generation of acidity that accompanies this process. The study site, Moose Lake, receives tailings runoff at a nickel mine in Northern Ontario, which has rendered the lake highly acidic (surface pH values less than 3.5) with high metal loads and on-going acid export to off-site, downstream systems. To investigate the potential influence of microbial processes for acid generation, as well as characterizing any attendant influences for metal behaviour, the biogeochemistry of Moose Lake was characterized on a seasonal and a diel basis during the summer of 2002. Physico-chemical profiles were used to identify the area of strong redox gradient across the thermocline (typically 1 to 2 metres across this zone) on each sampling day. Samples at five depths within this redox gradient, were then collected for Fe3+/Fe2+, SO42-/H2S, metal and microbial samples, in addition to more highly resolved Hydrolab profiling. Samples were collected both during the lighted portion of the day (10am-12pm) and at dusk (6pm-8pm) to evaluate any contributions to S and Fe cycling attributed to photosynthetic activity. Results indicate a clear seasonal increase in acidity in the upper waters of the lake: pH values dropped from 3.19 in May to 2.90 in September. Further, a strong diel trend of increasing acidity (lower pH) from mid morning to dusk was also observed for each sampling period. Biotic control on S processes appears to be important associated with the thermocline region of the lake, whilst surficial processes occurring in the upper one to three meters are more consistent with a dominant abiotic control. Both pathways contribute to acidity generation, however the controls and rates differ. These results and implications for mitigation strategies will be presented.

  15. Discontinuous ammonia excretion and glutamine storage in littoral Oniscidea (Crustacea: Isopoda): testing tidal and circadian models.

    PubMed

    Nakamura, Maya; Wright, Jonathan C

    2013-01-01

    A key evolutionary development facilitating land colonization in terrestrial isopods (Isopoda: Oniscidea) is the intermittent liberation of waste nitrogen as volatile ammonia. Intermittent ammonia release exploits glutamine (Gln) as an intermediary nitrogen store. Here, we explore the relationship between temporal patterns of ammonia release and Gln accumulation in three littoral oniscideans from Southern California. Results are interpreted in terms of water availability, habitat, activity patterns, and ancestry. A two-way experimental design was used to test whether ammonia excretion and Gln accumulation follow a tidal or diel periodicity. Ammonia excretion was studied in the laboratory using chambers with or without available seawater and using an acid trap to collect volatile ammonia. Ligia occidentalis releases ammonia directly into seawater and accumulates Gln during low tide (48.9 ± 6.5 μmol g⁻¹ at low tide, 24.1 ± 3.0 μmol g⁻¹ at high tide), indicating that excretion is tidally constrained. Alloniscus perconvexus and Tylos punctatus can excrete ammonia directly into seawater or utilize volatilization. Both species burrow in sand by day and show a diel excretory pattern, accumulating Gln nocturnally (31.8 ± 2.7 μmol g⁻¹ at dawn and 21.8 ± 2.3 μmol g⁻¹ at dusk for A. perconvexus; 85.7 ± 15.1 μmol g⁻¹ at dawn and 25.4 ± 2.9 μmol g⁻¹ at dusk for T. punctatus) and liberating ammonia diurnally. Glutaminase shows higher activity in terrestrial (0.54-0.86 U g⁻¹) compared to intertidal (0.25-0.31 U g⁻¹) species, consistent with the need to generate high PNH₃ for volatilization. The predominant isoform in Armadillidium vulgare is phosphate dependent and maleate independent; phosphate is a plausible regulator in vivo. PMID:22836297

  16. Host-seeking activity and avian host preferences of mosquitoes associated with West Nile virus transmission in the northeastern U.S.A.

    USGS Publications Warehouse

    Suom, Channsotha; Ginsberg, Howard S.; Bernick, Andrew; Klein, Coby; Buckley, P.A.; Salvatore, Christa; LeBrun, Roger A.

    2010-01-01

    Mosquito host-seeking activity was studied using a custom-designed trap to explore: (1) at which time interval of the night adult mosquito abatement would be most effective, and (2) if there exists an avian-specific host-seeking preference. Overnight trials using traps baited with dry ice showed that Aedes taeniorhynchus (Wiedemann) was most active at dusk and was then captured throughout the night. In contrast, Culex spp. (Cx. pipiens (Linnaeus) and Cx. restuans (Theobald) delayed most activity until about two h after dusk and were then captured through the night. This pattern suggests that management activities directed at adult Culex spp. would be most effective if initiated well after sunset. Mosquito capture rates in traps baited with birds in net bags were significantly greater than those with empty net bags, indicating that mosquitoes were attracted to the birds and not incidentally being sucked in by the custom trap's strong fan motor (Wilcoxon matched-pairs signed-ranks test, n = 24, t = 30, p 2 = 0.21, p = 0.02). Trials with paired traps that contained different native bird species showed that Gray Catbirds, Dumatella carolinensis, attracted more mosquitoes than the heavier Northern Cardinals, Cardinalis cardinalis (paired samples t-test, t = 2.58, df = 7, p = 0.04). However, attractiveness did not differ substantially among bird species, and Gray Catbirds did not attract more mosquitoes than all other birds combined as a group. American Robins, Turdus migratorius (n = 4) were comparable in attractiveness to other bird species, but not enough American Robins were captured for a comprehensive study of mosquito avian preference.

  17. A comparison of 2 techniques for estimating deer density

    USGS Publications Warehouse

    Robbins, C.S.

    1977-01-01

    We applied mark-resight and area-conversion methods to estimate deer abundance at a 2,862-ha area in and surrounding the Gettysburg National Military Park and Eisenhower National Historic Site during 1987-1991. One observer in each of 11 compartments counted marked and unmarked deer during 65-75 minutes at dusk during 3 counts in each of April and November. Use of radio-collars and vinyl collars provided a complete inventory of marked deer in the population prior to the counts. We sighted 54% of the marked deer during April 1987 and 1988, and 43% of the marked deer during November 1987 and 1988. Mean number of deer counted increased from 427 in April 1987 to 582 in April 1991, and increased from 467 in November 1987 to 662 in November 1990. Herd size during April, based on the mark-resight method, increased from approximately 700-1,400 from 1987-1991, whereas the estimates for November indicated an increase from 983 for 1987 to 1,592 for 1990. Given the large proportion of open area and the extensive road system throughout the study area, we concluded that the sighting probability for marked and unmarked deer was fairly similar. We believe that the mark-resight method was better suited to our study than the area-conversion method because deer were not evenly distributed between areas suitable and unsuitable for sighting within open and forested areas. The assumption of equal distribution is required by the area-conversion method. Deer marked for the mark-resight method also helped reduce double counting during the dusk surveys.

  18. Multi-Scale Kelvin-Helmholtz Vortices Along Mercury's Magnetopause

    NASA Astrophysics Data System (ADS)

    Gershman, D. J.; Raines, J. M.; Slavin, J. A.; Zurbuchen, T.; Sundberg, T.; Boardsen, S. A.; Anderson, B. J.; Korth, H.; Solomon, S. C.

    2014-12-01

    Data from the Fast Imaging Plasma Spectrometer (FIPS) and Magnetometer (MAG) sensors on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft have revealed stark differences in the Kelvin-Helmholtz (K-H) instability at Mercury compared with that at Earth. Although K-H vortices have been documented in planetary magnetospheres at the interface of magnetosheath and magnetospheric plasmas, such features at Mercury have been observed exclusively on the dusk side. From a survey of 58 K-H events, we find that these vortices have two distinct sets of behavior separated by the dusk terminator. On the dayside, the wave frequencies measured by MAG are nearly constant at ~0.025 Hz (~40 s period) under a variety of magnetosheath conditions, whereas the wave frequency measured on the nightside is correlated with the strength of the magnetic field near the magnetopause and matches the local Na+ gyrofrequency. The polarization of these waves inside the magnetosphere is distinctly right-handed, consistent with non-linear roll-up of K-H vortices as opposed to the left-handed ion-cyclotron wave mode. During these events, measurements from FIPS reveal strong (~30%) concentrations of Na+ in the nightside plasma sheet adjacent to the magnetopause. The keV energies of these planetary ions provide them with gyroradii that are ~500-1000 km, a scale at which a kinetic description of the K-H instability may be appropriate at Mercury. These data suggest a transition from fluid-scale to kinetic scale K-H vortices from day to night along Mercury's duskside magnetopause.

  19. Magnetic reconnection in Saturn's magnetotail: A comprehensive magnetic field survey.

    NASA Astrophysics Data System (ADS)

    Smith, A. W.; Jackman, C. M.; Thomsen, M. F.; Dougherty, M. K.

    2015-10-01

    Magnetic reconnection is a fundamental process throughout the solar system, significantly shaping and modulating the magnetospheres of the magnetized planets. Within planetary magnetotails reconnection can be responsible for energizing particles and potentially changing the total flux and mass contained within the magnetosphere. The Kronian magnetosphere is thought to be a middle ground between the rotationally dominated Jovian magnetosphere and the solar wind driven terrestrial magnetosphere. However, previous studies have not been able to find a statistical reconnection x-line, as has been possible at both Jupiter and Earth. Additionally the standard picture of magnetotail reconnection at Saturn, developed by Cowley et al. [2004], suggests a potential asymmetry between the dawn and dusk flanks, caused by different reconnection processes dominating. This work centers on the development of an algorithm designed to find reconnection related events in spacecraft magnetometer data, aiming to reduce the bias that manual searches could inherently introduce, thereby ensuring the validity of any statistical analysis. The algorithm primarily identifies the reconnection related events from deflections in the north-south component of the magnetic field, allowing an almost uninterrupted in-situ search (when the spacecraft is situated within the magnetotail). The new catalogue of candidate reconnection events, produced by the algorithm, enables a more complete statistical view of reconnection in the Kronian magnetotail. Well-studied data encompassing the deep magnetotail and dawn flank (particularly from orbits in 2006) were used to train the algorithm and develop reasonable criteria. The algorithm was then applied to data encompassing the dusk flank (including orbits from 2009, for which plasma data have been examined by Thomsen et al. [2014]). This combination enables a robust, and global, comparison of reconnection rates, signatures and properties in the Kronian magnetotail.

  20. The Interplay between Carbon Availability and Growth in Different Zones of the Growing Maize Leaf1[OPEN

    PubMed Central

    Arrivault, Stéphanie; Lohse, Marc A.; Feil, Regina; Krohn, Nicole; Encke, Beatrice; Nunes-Nesi, Adriano; Fernie, Alisdair R.; Stitt, Mark

    2016-01-01

    Plants assimilate carbon in their photosynthetic tissues in the light. However, carbon is required during the night and in nonphotosynthetic organs. It is therefore essential that plants manage their carbon resources spatially and temporally and coordinate growth with carbon availability. In growing maize (Zea mays) leaf blades, a defined developmental gradient facilitates analyses in the cell division, elongation, and mature zones. We investigated the responses of the metabolome and transcriptome and polysome loading, as a qualitative proxy for protein synthesis, at dusk, dawn, and 6, 14, and 24 h into an extended night, and tracked whole-leaf elongation over this time course. Starch and sugars are depleted by dawn in the mature zone, but only after an extension of the night in the elongation and division zones. Sucrose (Suc) recovers partially between 14 and 24 h into the extended night in the growth zones, but not the mature zone. The global metabolome and transcriptome track these zone-specific changes in Suc. Leaf elongation and polysome loading in the growth zones also remain high at dawn, decrease between 6 and 14 h into the extended night, and then partially recover, indicating that growth processes are determined by local carbon status. The level of Suc-signaling metabolite trehalose-6-phosphate, and the trehalose-6-phosphate:Suc ratio are much higher in growth than mature zones at dusk and dawn but fall in the extended night. Candidate genes were identified by searching for transcripts that show characteristic temporal response patterns or contrasting responses to carbon starvation in growth and mature zones. PMID:27582314

  1. Observations of purely compressional waves in the upper ULF band observed by the Van Allen Probes

    NASA Astrophysics Data System (ADS)

    Posch, J. L.; Engebretson, M. J.; Johnson, J.; Kim, E. H.; Thaller, S. A.; Wygant, J. R.; Kletzing, C.; Smith, C. W.; Reeves, G. D.

    2014-12-01

    Purely compressional electromagnetic waves, also denoted fast magnetosonic waves, equatorial noise, and ion Bernstein modes, can both heat thermal protons and accelerate electrons up to relativistic energies. These waves have been observed both in the near-equatorial region in the inner magnetosphere and in the plasma sheet boundary layer. Although these waves have been observed by various types of satellite instruments (DC and AC magnetometers and electric field sensors), most recent studies have used data from AC sensors, and many have been restricted to frequencies above ~50 Hz. We report here on a survey of ~200 of these waves, based on DC electric and magnetic field data from the EFW double probe and EMFISIS fluxgate magnetometer instruments, respectively, on the Van Allen Probes spacecraft during its first two years of operation. The high sampling rate of these instruments makes it possible to extend observational studies of the lower frequency population of such waves to lower L shells than any previous study. These waves, often with multiple harmonics of the local proton gyrofrequency, were observed both inside and outside the plasmapause, in regions with plasma number densities ranging from 10 to >1000 cm-3. Wave occurrence was sharply peaked near the magnetic equator and occurred at L shells from below 2 to ~6 (the spacecraft apogee). Waves appeared at all local times but were more common from noon to dusk. Outside the plasmapause, occurrence maximized broadly across noon. Inside the plasmapause, occurrence maximized in the dusk sector, in an extended plasmasphere. Every event occurred in association with a positive gradient in the HOPE omnidirectional proton flux in the range between 2 keV and 10 keV. The Poynting vector, determined for 8 events, was in all cases directed transverse to B, but with variable azimuth, consistent with earlier models and observations.

  2. The hot plasma environment at jupiter: ulysses results.

    PubMed

    Lanzerotti, L J; Armstrong, T P; Gold, R E; Anderson, K A; Krimigis, S M; Lin, R P; Pick, M; Roelof, E C; Sarris, E T; Simnett, G M; Maclennan, C G; Choo, H T; Tappin, S J

    1992-09-11

    Measurements of the hot plasma environment during the Ulysses flyby of Jupiter have revealed several new discoveries related to this large rotating astrophysical system. The Jovian magnetosphere was found by Ulysses to be very extended, with the day-side magnetopause located at approximately 105 Jupiter radii. The heavy ion (sulfur, oxygen, and sodium) population in the day-side magnetosphere increased sharply at approximately 86 Jupiter radii. This is somewhat more extended than the "inner" magnetosphere boundary region identified by the Voyager hot plasma measurements. In the day-side magnetosphere, the ion fluxes have the anisotropy direction expected for corotation with the planet, with the magnitude of the anisotropy increasing when the spacecraft becomes more immersed in the hot plasma sheet. The relative abundances of sulfur, oxygen, and sodium to helium decreased somewhat with decreasing radial distance from the planet on the day-side, which suggests that the abundances of the Jupiter-derived species are dependent on latitude. In the dusk-side, high-latitude region, intense fluxes of counter-streaming ions and electrons were discovered from the edge of the plasma sheet to the dusk-side magnetopause. These beams of electrons and ions were found to be very tightly aligned with the magnetic field and to be superimposed on a time- and space-variable isotropic hot plasma background. The currents carried by the measured hot plasma particles are typically approximately 1.6 x 10(-4) microamperes per square meter or approximately 8 x 10(5) amperes per squared Jupiter radius throughout the high-latitude magnetosphere volume. It is likely that the intense particle beams discovered at high Jovian latitudes produce auroras in the polar caps of the planet. PMID:17776161

  3. Polarization patterns of the twilight sky

    NASA Astrophysics Data System (ADS)

    Cronin, Thomas W.; Warrant, Eric J.; Greiner, Birgit

    2005-08-01

    Although natural light sources produce depolarized light, patterns of partially linearly polarized light appear in the sky due to scattering from air molecules, dust, and aerosols. Many animals, including bees and ants, orient themselves to patterns of polarization that are present in daytime skies, when the intensity is high and skylight polarization is strong and predictable. The halicitid bee Megalopta genalis inhabits rainforests in Central America. Unlike typical bees, it forages before sunrise and after sunset, when light intensities under the forest canopy are very low, and must find its way to food sources and return to its nest in visually challenging circumstances. An important cue for the orientation could be patterns of polarization in the twilight sky. Therefore, we used a calibrated digital camera to image skylight polarization in an overhead patch of sky, 87.6° across, before dawn on Barro Colorado Island in Panama, where the bees are found. We simultaneously measured the spectral properties of polarized light in a cloudless patch of sky 15° across centered on the zenith. We also performed full-sky imaging of polarization before dawn and after dusk on Lizard Island in Australia, another tropical island. During twilight, celestial polarized light occurs in a wide band stretching perpendicular to the location of the hidden sun and reaching typical degrees of polarization near 80% at wavelengths >600 nm. This pattern appears about 45 minutes before local sunrise or disappears 45 minutes after local sunset (about 20 minutes after the onset of astronomical twilight at dawn, or before its end at dusk) and extends with little change through the entire twilight period. Such a strong and reliable orientation cue could be used for flight orientation by any animal with polarization sensitivity that navigates during twilight.

  4. Storm-enhanced plasma density and polar tongue of ionization development during the 15 May 2005 superstorm

    NASA Astrophysics Data System (ADS)

    Horvath, Ildiko; Lovell, Brian C.

    2015-06-01

    We investigate the ionosphere's global response to the 15 May 2005 superstorm in terms of storm evolution and ionospheric electrodynamics. Our aim is to study the global distribution of plasma and the resultant large-scale ionospheric features including the equatorial ionization anomaly (EIA), storm-enhanced density (SED), and polar tongue of ionization (TOI). We have combined multi-instrument ionospheric data, solar and terrestrial magnetic data, and polar convection maps. Results reveal the prompt penetration of the interplanetary electric field to the polar region and then to the equator with a dusk-to-dawn polarity during the initial phase and with a dawn-to-dusk polarity during the main phase. This drove during the initial phase a weak eastward equatorial electrojet (EEJ) in the American sector at nighttime and a weak westward EEJ in the Indian-Australian sector at daytime. During the main phase, these EEJs intensified and changed polarities. SED and polar TOI development was observed prior to and during the initial phase at evening-premidnight hours over North America and during the main phase in the south at afternoon-evening hours in the Australian sector. During the main phase and early in the recovery phase, the EIA-SED structure was well formed in the Asian longitude sector. Then, polar TOI development was absent in the north because of the long distance from the magnetic pole but was supported in the south because of the closeness of daytime cusp and magnetic pole. Thus, the EIA-SED-TOI structure developed twice but each time in a different longitude sector and with different characteristics.

  5. The Use of Automated Bioacoustic Recorders to Replace Human Wildlife Surveys: An Example Using Nightjars

    PubMed Central

    Zwart, Mieke C.; Baker, Andrew

    2014-01-01

    To be able to monitor and protect endangered species, we need accurate information on their numbers and where they live. Survey methods using automated bioacoustic recorders offer significant promise, especially for species whose behaviour or ecology reduces their detectability during traditional surveys, such as the European nightjar. In this study we examined the utility of automated bioacoustic recorders and the associated classification software as a way to survey for wildlife, using the nightjar as an example. We compared traditional human surveys with results obtained from bioacoustic recorders. When we compared these two methods using the recordings made at the same time as the human surveys, we found that recorders were better at detecting nightjars. However, in practice fieldworkers are likely to deploy recorders for extended periods to make best use of them. Our comparison of this practical approach with human surveys revealed that recorders were significantly better at detecting nightjars than human surveyors: recorders detected nightjars during 19 of 22 survey periods, while surveyors detected nightjars on only six of these occasions. In addition, there was no correlation between the amount of vocalisation captured by the acoustic recorders and the abundance of nightjars as recorded by human surveyors. The data obtained from the recorders revealed that nightjars were most active just before dawn and just after dusk, and least active during the middle of the night. As a result, we found that recording at both dusk and dawn or only at dawn would give reasonably high levels of detection while significantly reducing recording time, preserving battery life. Our analyses suggest that automated bioacoustic recorders could increase the detection of other species, particularly those that are known to be difficult to detect using traditional survey methods. The accuracy of detection is especially important when the data are used to inform conservation. PMID

  6. How does a carnivore guild utilise a substantial but unpredictable anthropogenic food source? Scavenging on hunter-shot ungulate carcasses by wild dogs/dingoes, red foxes and feral cats in south-eastern Australia revealed by camera traps.

    PubMed

    Forsyth, David M; Woodford, Luke; Moloney, Paul D; Hampton, Jordan O; Woolnough, Andrew P; Tucker, Mark

    2014-01-01

    There is much interest in understanding how anthropogenic food resources subsidise carnivore populations. Carcasses of hunter-shot ungulates are a potentially substantial food source for mammalian carnivores. The sambar deer (Rusa unicolor) is a large (≥ 150 kg) exotic ungulate that can be hunted throughout the year in south-eastern Australia, and hunters are not required to remove or bury carcasses. We investigated how wild dogs/dingoes and their hybrids (Canis lupus familiaris/dingo), red foxes (Vulpes vulpes) and feral cats (Felis catus) utilised sambar deer carcasses during the peak hunting seasons (i.e. winter and spring). We placed carcasses at 1-km intervals along each of six transects that extended 4-km into forest from farm boundaries. Visits to carcasses were monitored using camera traps, and the rate of change in edible biomass estimated at ∼ 14-day intervals. Wild dogs and foxes fed on 70% and 60% of 30 carcasses, respectively, but feral cats seldom (10%) fed on carcasses. Spatial and temporal patterns of visits to carcasses were consistent with the hypothesis that foxes avoid wild dogs. Wild dog activity peaked at carcasses 2 and 3 km from farms, a likely legacy of wild dog control, whereas fox activity peaked at carcasses 0 and 4 km from farms. Wild dog activity peaked at dawn and dusk, whereas nearly all fox activity occurred after dusk and before dawn. Neither wild dogs nor foxes remained at carcasses for long periods and the amount of feeding activity by either species was a less important predictor of the loss of edible biomass than season. Reasons for the low impacts of wild dogs and foxes on sambar deer carcass biomass include the spatially and temporally unpredictable distribution of carcasses in the landscape, the rapid rate of edible biomass decomposition in warm periods, low wild dog densities and the availability of alternative food resources. PMID:24918425

  7. The Spatial Distribution of the Io Plasma Torus

    NASA Astrophysics Data System (ADS)

    Herbert, F.; Schneider, N. M.; Dessler, A. J.

    2004-11-01

    Ground-based coronographic images of the Io plasma torus in S+ 6371Å emission have been pseudo-tomographically deconvolved from their inherent line-of-sight integration, yielding estimates of their three-dimensional (3D) S+ density distributions with spatial resolution of ˜0.05RJ By interpreting this derived time-dependent structure we can infer some of the characteristics of torus formation mechanisms. For example, the dawn-to-dusk electric field in the torus region of Jupiter's magnetosphere causes the warm outer torus (including the ``ribbon'' feature) and the outer edge of the cold torus (which is the innermost region of the torus) to move closer to Jupiter by ˜0.3RJ as the torus plasma rotates from the dawn region to dusk. Although this electric field is often approximated as spatially uniform, the initial analyses of these and other observations (Dessler and Sandel, GRL 19:2099, 1992; Schneider and Trauger, ApJ 450:450, 1995) implied a variation of the field strength with subsolar magnetic longitude. Now, preliminary results of our analyses of these observations imply differential motion between the inner and outer edges of the cold torus, indicating that the field strength varies spatially as well, appearing at times to diminish at the inner edge of the cold torus. Such behavior can result from a process known as magnetospheric ``shielding'', which has been noted in the magnetospheres of Earth and possibly Uranus, but this would be the first instance where it has been seen at Jupiter. This and other anomalies of torus structure, such as the difference in magnetic latitudes of the warm and cold tori and the large gap between them, will be discussed at the meeting. This work was supported by NASA under grants NAG5-12944 and 9079 (Geospace Sciences Program) and NAG5-8952 (Planetary Atmospheres Program).

  8. The Spatial Distribution of the Io Plasma Torus

    NASA Astrophysics Data System (ADS)

    Herbert, F.; Schneider, N. M.; Dessler, A. J.

    2004-12-01

    Ground-based coronographic images of the Io plasma torus in S+~6371Å emission have been pseudo-tomographically deconvolved from their inherent line-of-sight integration, yielding estimates of their three-dimensional (3D) S+ density distributions with spatial resolution of ˜0.05RJ. By interpreting this derived time-dependent structure we can infer some of the characteristics of torus formation mechanisms. For example, the dawn-to-dusk electric field in the torus region of Jupiter's magnetosphere causes the warm outer torus (including the ``ribbon'' feature) and the outer edge of the cold torus (which is the innermost region of the torus) to move closer to Jupiter by ˜0.3RJ as the torus plasma rotates from the dawn region to dusk. Although this electric field is often approximated as spatially uniform, the initial analyses of these and other observations (Dessler and Sandel, GRL 19:2099, 1992; Schneider and Trauger, ApJ 450:450, 1995) implied a variation of the field strength with subsolar magnetic longitude. Now, preliminary results of our analyses of these observations imply differential motion between the inner and outer edges of the cold torus, indicating that the field strength varies spatially as well, appearing at times to diminish at the inner edge of the cold torus. Such behavior can result from a process known as magnetospheric ``shielding'', which has been noted in the magnetospheres of Earth and possibly Uranus but this would be the first instance where it has been seen at Jupiter. This and other anomalies of torus structure, such as the difference in magnetic latitudes of the warm and cold tori and the large gap between them, will be discussed at the meeting. This work was supported by NASA under grants NAG5-12944 and 9079 (Geospace Sciences Program) and NAG5-8952 (Planetary Atmospheres Program).

  9. How Does a Carnivore Guild Utilise a Substantial but Unpredictable Anthropogenic Food Source? Scavenging on Hunter-Shot Ungulate Carcasses by Wild Dogs/Dingoes, Red Foxes and Feral Cats in South-Eastern Australia Revealed by Camera Traps

    PubMed Central

    Forsyth, David M.; Woodford, Luke; Moloney, Paul D.; Hampton, Jordan O.; Woolnough, Andrew P.; Tucker, Mark

    2014-01-01

    There is much interest in understanding how anthropogenic food resources subsidise carnivore populations. Carcasses of hunter-shot ungulates are a potentially substantial food source for mammalian carnivores. The sambar deer (Rusa unicolor) is a large (≥150 kg) exotic ungulate that can be hunted throughout the year in south-eastern Australia, and hunters are not required to remove or bury carcasses. We investigated how wild dogs/dingoes and their hybrids (Canis lupus familiaris/dingo), red foxes (Vulpes vulpes) and feral cats (Felis catus) utilised sambar deer carcasses during the peak hunting seasons (i.e. winter and spring). We placed carcasses at 1-km intervals along each of six transects that extended 4-km into forest from farm boundaries. Visits to carcasses were monitored using camera traps, and the rate of change in edible biomass estimated at ∼14-day intervals. Wild dogs and foxes fed on 70% and 60% of 30 carcasses, respectively, but feral cats seldom (10%) fed on carcasses. Spatial and temporal patterns of visits to carcasses were consistent with the hypothesis that foxes avoid wild dogs. Wild dog activity peaked at carcasses 2 and 3 km from farms, a likely legacy of wild dog control, whereas fox activity peaked at carcasses 0 and 4 km from farms. Wild dog activity peaked at dawn and dusk, whereas nearly all fox activity occurred after dusk and before dawn. Neither wild dogs nor foxes remained at carcasses for long periods and the amount of feeding activity by either species was a less important predictor of the loss of edible biomass than season. Reasons for the low impacts of wild dogs and foxes on sambar deer carcass biomass include the spatially and temporally unpredictable distribution of carcasses in the landscape, the rapid rate of edible biomass decomposition in warm periods, low wild dog densities and the availability of alternative food resources. PMID:24918425

  10. The hot plasma environment at jupiter: ulysses results.

    PubMed

    Lanzerotti, L J; Armstrong, T P; Gold, R E; Anderson, K A; Krimigis, S M; Lin, R P; Pick, M; Roelof, E C; Sarris, E T; Simnett, G M; Maclennan, C G; Choo, H T; Tappin, S J

    1992-09-11

    Measurements of the hot plasma environment during the Ulysses flyby of Jupiter have revealed several new discoveries related to this large rotating astrophysical system. The Jovian magnetosphere was found by Ulysses to be very extended, with the day-side magnetopause located at approximately 105 Jupiter radii. The heavy ion (sulfur, oxygen, and sodium) population in the day-side magnetosphere increased sharply at approximately 86 Jupiter radii. This is somewhat more extended than the "inner" magnetosphere boundary region identified by the Voyager hot plasma measurements. In the day-side magnetosphere, the ion fluxes have the anisotropy direction expected for corotation with the planet, with the magnitude of the anisotropy increasing when the spacecraft becomes more immersed in the hot plasma sheet. The relative abundances of sulfur, oxygen, and sodium to helium decreased somewhat with decreasing radial distance from the planet on the day-side, which suggests that the abundances of the Jupiter-derived species are dependent on latitude. In the dusk-side, high-latitude region, intense fluxes of counter-streaming ions and electrons were discovered from the edge of the plasma sheet to the dusk-side magnetopause. These beams of electrons and ions were found to be very tightly aligned with the magnetic field and to be superimposed on a time- and space-variable isotropic hot plasma background. The currents carried by the measured hot plasma particles are typically approximately 1.6 x 10(-4) microamperes per square meter or approximately 8 x 10(5) amperes per squared Jupiter radius throughout the high-latitude magnetosphere volume. It is likely that the intense particle beams discovered at high Jovian latitudes produce auroras in the polar caps of the planet.

  11. Spatial Dynamics and Expanded Vertical Niche of Blue Sharks in Oceanographic Fronts Reveal Habitat Targets for Conservation

    PubMed Central

    Queiroz, Nuno; Humphries, Nicolas E.; Noble, Leslie R.; Santos, António M.; Sims, David W.

    2012-01-01

    Dramatic population declines among species of pelagic shark as a result of overfishing have been reported, with some species now at a fraction of their historical biomass. Advanced telemetry techniques enable tracking of spatial dynamics and behaviour, providing fundamental information on habitat preferences of threatened species to aid conservation. We tracked movements of the highest pelagic fisheries by-catch species, the blue shark Prionace glauca, in the North-east Atlantic using pop-off satellite-linked archival tags to determine the degree of space use linked to habitat and to examine vertical niche. Overall, blue sharks moved south-west of tagging sites (English Channel; southern Portugal), exhibiting pronounced site fidelity correlated with localized productive frontal areas, with estimated space-use patterns being significantly different from that of random walks. Tracked female sharks displayed behavioural variability in diel depth preferences, both within and between individuals. Diel depth use ranged from normal DVM (nDVM; dawn descent, dusk ascent), to reverse DVM (rDVM; dawn ascent, dusk descent), to behavioural patterns where no diel differences were apparent. Results showed that blue sharks occupy some of the most productive marine zones for extended periods and structure diel activity patterns across multiple spatio-temporal scales in response to particular habitat types. In so doing, sharks occupied an extraordinarily broad vertical depth range for their size (1.0–2.0 m fork length), from the surface into the bathypelagic realm (max. dive depth, 1160 m). The space-use patterns of blue sharks indicated they spend much of the time in areas where pelagic longlining activities are often highest, and in depth zones where these fisheries particularly target other species, which could account for the rapid declines recently reported for blue sharks in many parts of the world's oceans. Our results provide habitat targets for blue shark conservation

  12. Spatial dynamics and expanded vertical niche of blue sharks in oceanographic fronts reveal habitat targets for conservation.

    PubMed

    Queiroz, Nuno; Humphries, Nicolas E; Noble, Leslie R; Santos, António M; Sims, David W

    2012-01-01

    Dramatic population declines among species of pelagic shark as a result of overfishing have been reported, with some species now at a fraction of their historical biomass. Advanced telemetry techniques enable tracking of spatial dynamics and behaviour, providing fundamental information on habitat preferences of threatened species to aid conservation. We tracked movements of the highest pelagic fisheries by-catch species, the blue shark Prionace glauca, in the North-east Atlantic using pop-off satellite-linked archival tags to determine the degree of space use linked to habitat and to examine vertical niche. Overall, blue sharks moved south-west of tagging sites (English Channel; southern Portugal), exhibiting pronounced site fidelity correlated with localized productive frontal areas, with estimated space-use patterns being significantly different from that of random walks. Tracked female sharks displayed behavioural variability in diel depth preferences, both within and between individuals. Diel depth use ranged from normal DVM (nDVM; dawn descent, dusk ascent), to reverse DVM (rDVM; dawn ascent, dusk descent), to behavioural patterns where no diel differences were apparent. Results showed that blue sharks occupy some of the most productive marine zones for extended periods and structure diel activity patterns across multiple spatio-temporal scales in response to particular habitat types. In so doing, sharks occupied an extraordinarily broad vertical depth range for their size (1.0-2.0 m fork length), from the surface into the bathypelagic realm (max. dive depth, 1160 m). The space-use patterns of blue sharks indicated they spend much of the time in areas where pelagic longlining activities are often highest, and in depth zones where these fisheries particularly target other species, which could account for the rapid declines recently reported for blue sharks in many parts of the world's oceans. Our results provide habitat targets for blue shark conservation that

  13. Cluster Observations of Ion Dispersions near the Exterior Cusp

    NASA Astrophysics Data System (ADS)

    Escoubet, C.; Grison, B.; Berchem, J.; Trattner, K. J.; Pitout, F.; Richard, R. L.; Taylor, M. G.; Laakso, H. E.; Masson, A.; Dunlop, M. W.; Dandouras, I. S.; Reme, H.; Fazakerley, A. N.; Daly, P. W.

    2013-12-01

    The cusps are the places where the Earth's magnetic field lines, connected to the inner side of the magnetopause, converge. It is therefore the place where signatures of processes occurring near the subsolar point, in the tail lobes, as well as near the dawn and dusk flanks are observed. The main process that injects solar wind plasma into the polar cusp is now generally accepted to be magnetic reconnection. Depending on the IMF direction, this process will take place equatorward (for IMF southward), poleward (for IMF northward) or on the side (for IMF azimuthal) of the cusp. We report a Cluster crossing on 5 January 2002 near the exterior cusp on the southern dusk side. The IMF was mainly azimuthal (IMF-By around -5 nT), the solar wind speed around 280 km/s and the density around 5 cm-3. The four Cluster spacecraft were still in the "magnetotail" configuration with two perfect tetrahedra of 2000 km around apogee and turning into an elongated configuration near the magnetopause. C4 was the first spacecraft to enter the cusp around 19:52:04 UT, followed by C2 at 19:52:35 UT, C1 at 19:54:24 UT and C3 at 20:13:15 UT. C4 and C1 observed two ion energy dispersions at 20:10 UT and 20:40 UT and C3 at 20:35 UT and 21:15 UT. We will investigate the origin of the injections forming the dispersions and if these can be explained by the reconnection between the interplanetary magnetic field and the Earth's magnetic field.

  14. How does a carnivore guild utilise a substantial but unpredictable anthropogenic food source? Scavenging on hunter-shot ungulate carcasses by wild dogs/dingoes, red foxes and feral cats in south-eastern Australia revealed by camera traps.

    PubMed

    Forsyth, David M; Woodford, Luke; Moloney, Paul D; Hampton, Jordan O; Woolnough, Andrew P; Tucker, Mark

    2014-01-01

    There is much interest in understanding how anthropogenic food resources subsidise carnivore populations. Carcasses of hunter-shot ungulates are a potentially substantial food source for mammalian carnivores. The sambar deer (Rusa unicolor) is a large (≥ 150 kg) exotic ungulate that can be hunted throughout the year in south-eastern Australia, and hunters are not required to remove or bury carcasses. We investigated how wild dogs/dingoes and their hybrids (Canis lupus familiaris/dingo), red foxes (Vulpes vulpes) and feral cats (Felis catus) utilised sambar deer carcasses during the peak hunting seasons (i.e. winter and spring). We placed carcasses at 1-km intervals along each of six transects that extended 4-km into forest from farm boundaries. Visits to carcasses were monitored using camera traps, and the rate of change in edible biomass estimated at ∼ 14-day intervals. Wild dogs and foxes fed on 70% and 60% of 30 carcasses, respectively, but feral cats seldom (10%) fed on carcasses. Spatial and temporal patterns of visits to carcasses were consistent with the hypothesis that foxes avoid wild dogs. Wild dog activity peaked at carcasses 2 and 3 km from farms, a likely legacy of wild dog control, whereas fox activity peaked at carcasses 0 and 4 km from farms. Wild dog activity peaked at dawn and dusk, whereas nearly all fox activity occurred after dusk and before dawn. Neither wild dogs nor foxes remained at carcasses for long periods and the amount of feeding activity by either species was a less important predictor of the loss of edible biomass than season. Reasons for the low impacts of wild dogs and foxes on sambar deer carcass biomass include the spatially and temporally unpredictable distribution of carcasses in the landscape, the rapid rate of edible biomass decomposition in warm periods, low wild dog densities and the availability of alternative food resources.

  15. Observations of a Unique Type of ULF Waves by Low-Latitude Space Technology 5 Mission

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    We report a unique type of ULF waves observed by low-altitude Space Technology 5 (ST-5) constellation mission. ST-5 is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, and sun synchronous polar orbit with 105.6 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 sub auroral latitudes during the course of a day. Whenever the spacecraft traverse across the dayside closed field line region at sub auroral latitudes, they frequently observe strong transverse oscillations at 30-200 mHz, or in the Pc 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 these 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.

  16. Observations of a Unique Type of ULF Waves by Low-Latitude Space Technology 5 Mission

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    We report a unique type of ULF waves observed by low-altitude Space Technology 5 (ST-5) constellation mission. ST-5 is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, and sun synchronous polar orbit with 105.6 degree 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 sub auroral latitudes, they frequently observe strong transverse oscillations at 30-200 mHz, or in the Pc 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 these 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.

  17. Observations of a Unique Type of ULF Waves by Low-Latitude Space Technology 5 Satellites

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    We report a unique type of ULF waves observed by low-altitude Space Technology 5 (ST-5) constellation mission. ST-5 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 Pc 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.

  18. Observations of a Unique Type of ULF Waves by Low-Latitude Space Technology Five Mission

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    We report a unique type of ULF waves observed by low-altitude Space Technology 5 (ST-5) constellation mission. ST-5 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 Pc 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 these 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.

  19. Discontinuous ammonia excretion and glutamine storage in littoral Oniscidea (Crustacea: Isopoda): testing tidal and circadian models.

    PubMed

    Nakamura, Maya; Wright, Jonathan C

    2013-01-01

    A key evolutionary development facilitating land colonization in terrestrial isopods (Isopoda: Oniscidea) is the intermittent liberation of waste nitrogen as volatile ammonia. Intermittent ammonia release exploits glutamine (Gln) as an intermediary nitrogen store. Here, we explore the relationship between temporal patterns of ammonia release and Gln accumulation in three littoral oniscideans from Southern California. Results are interpreted in terms of water availability, habitat, activity patterns, and ancestry. A two-way experimental design was used to test whether ammonia excretion and Gln accumulation follow a tidal or diel periodicity. Ammonia excretion was studied in the laboratory using chambers with or without available seawater and using an acid trap to collect volatile ammonia. Ligia occidentalis releases ammonia directly into seawater and accumulates Gln during low tide (48.9 ± 6.5 μmol g⁻¹ at low tide, 24.1 ± 3.0 μmol g⁻¹ at high tide), indicating that excretion is tidally constrained. Alloniscus perconvexus and Tylos punctatus can excrete ammonia directly into seawater or utilize volatilization. Both species burrow in sand by day and show a diel excretory pattern, accumulating Gln nocturnally (31.8 ± 2.7 μmol g⁻¹ at dawn and 21.8 ± 2.3 μmol g⁻¹ at dusk for A. perconvexus; 85.7 ± 15.1 μmol g⁻¹ at dawn and 25.4 ± 2.9 μmol g⁻¹ at dusk for T. punctatus) and liberating ammonia diurnally. Glutaminase shows higher activity in terrestrial (0.54-0.86 U g⁻¹) compared to intertidal (0.25-0.31 U g⁻¹) species, consistent with the need to generate high PNH₃ for volatilization. The predominant isoform in Armadillidium vulgare is phosphate dependent and maleate independent; phosphate is a plausible regulator in vivo.

  20. Spatial dynamics and expanded vertical niche of blue sharks in oceanographic fronts reveal habitat targets for conservation.

    PubMed

    Queiroz, Nuno; Humphries, Nicolas E; Noble, Leslie R; Santos, António M; Sims, David W

    2012-01-01

    Dramatic population declines among species of pelagic shark as a result of overfishing have been reported, with some species now at a fraction of their historical biomass. Advanced telemetry techniques enable tracking of spatial dynamics and behaviour, providing fundamental information on habitat preferences of threatened species to aid conservation. We tracked movements of the highest pelagic fisheries by-catch species, the blue shark Prionace glauca, in the North-east Atlantic using pop-off satellite-linked archival tags to determine the degree of space use linked to habitat and to examine vertical niche. Overall, blue sharks moved south-west of tagging sites (English Channel; southern Portugal), exhibiting pronounced site fidelity correlated with localized productive frontal areas, with estimated space-use patterns being significantly different from that of random walks. Tracked female sharks displayed behavioural variability in diel depth preferences, both within and between individuals. Diel depth use ranged from normal DVM (nDVM; dawn descent, dusk ascent), to reverse DVM (rDVM; dawn ascent, dusk descent), to behavioural patterns where no diel differences were apparent. Results showed that blue sharks occupy some of the most productive marine zones for extended periods and structure diel activity patterns across multiple spatio-temporal scales in response to particular habitat types. In so doing, sharks occupied an extraordinarily broad vertical depth range for their size (1.0-2.0 m fork length), from the surface into the bathypelagic realm (max. dive depth, 1160 m). The space-use patterns of blue sharks indicated they spend much of the time in areas where pelagic longlining activities are often highest, and in depth zones where these fisheries particularly target other species, which could account for the rapid declines recently reported for blue sharks in many parts of the world's oceans. Our results provide habitat targets for blue shark conservation that

  1. Variation of surface electric field during geomagnetic disturbed period at Maitri, Antarctica

    NASA Astrophysics Data System (ADS)

    Victor, N. Jeni; Panneerselvam, C.; Anil Kumar, C. P.

    2015-12-01

    The paper discusses on the variations of the atmospheric vertical electric field measured at sub-auroral station Maitri (70∘75'S, 11∘75'E), and polar station Vostok (78.5∘S, 107∘E) during the geomagnetic disturbances on 25-26 January 2006. Diurnal variation of surface electric field measured at Maitri shows a similar variation with worldwide thunderstorm activity, whereas the departure of the field is observed during disturbed periods. This part of the field corresponds to the magnetospheric/ionospheric (an additional generator in the polar regions) voltage generators. Solar wind parameters and planetary indices represent the temporal variation of the disturbances, and digital fluxgate magnetometer variation continuously monitored to trace the auroral movement at Maitri. We have observed that the electrojet movement leaves its signature on vertical and horizontal components of the DFM in addition; the study infers the position of auroral current wedge with respect to Maitri. To exhibit the auroral oval, OVATION model is obtained with the aid of DMSP satellite and UV measurements. It is noted that the Maitri is almost within the auroral oval during the periods of disturbances. To examine the simultaneous changes in the vertical electric field associated with this magnetic disturbance, the dawn-dusk potential is studied for every UT hours; the potential was obtained from Weimer model and SuperDARN radar. The comparison reveals the plausible situation for the superposition of dawn-dusk potential on surface electric field over Maitri. This observation also shows that the superposition may not be consistent with the phase of the electrojet. Comparison of surface electric field at Maitri and Vostok shows that the parallel variation exhibits with each other, but during the period of geomagnetic disturbances, the influence is not much discerned at Vostok.

  2. Observations of IMF and seasonal effects in high-latitude convection

    SciTech Connect

    Ruohoniemi, J.M.; Greenwald, R.A.

    1995-05-01

    The authors describe strong interplanetary magnetic field (IMF) and seasonal effects in the convection of nightside ionospheric plasma. The findings are based on a statistical analysis of observations made with the JHU/APL HF radar located at Goose Bay, Labrador. For positive sign of the IMF dawn-dusk component, i.e., B{sub y}>0, the dawn cell is more crescent-shaped and the dusk cell more round while for B{sub y}<0 these pairings of size and shape are reversed. The more extreme crescent/round cell dichotomy is obtained for B{sub y}>0. The return flows associated with the crescent-shaped cell dominate at midnight MLT (Magnetic Local Time); the reversal in the zonal velocity in the 67{degrees}-69{degrees}{Lambda} (magnetic latitude) interval occurs 2 1/2 hr earlier for B{sub y}>0. The seasonal dependence of nightside convection resembles in important respects the B{sub y} dependence. Greater latitudinal velocity shears occur in the morning/afternoon sector for summer/winter and the return flow of this sector dominates at midnight. The zonal flow reversal occurs 2 1/2 hr earlier in summer than in winter. The maximum effects are obtained on the nightside for the pairings [B{sub y}>0, summer] and [B{sub y}<0, winter]; the first produces the more structured cell in the morning, the second in the evening, and this cell dominates the return flow at midnight. The difference in the zonal flow reversals for these pairings exceeds 4 hr in MLT. 15 refs., 4 figs.

  3. Reconstructing the magnetosphere from data using radial basis functions

    NASA Astrophysics Data System (ADS)

    Andreeva, Varvara A.; Tsyganenko, Nikolai A.

    2016-03-01

    A new method is proposed to derive from data magnetospheric magnetic field configurations without any a priori assumptions on the geometry of electric currents. The approach utilizes large sets of archived satellite data and uses an advanced technique to represent the field as a sum of toroidal and poloidal parts, whose generating potentials Ψ1 and Ψ2 are expanded into series of radial basis functions (RBFs) with their nodes regularly distributed over the 3-D modeling domain. The method was tested by reconstructing the inner and high-latitude field within geocentric distances up to 12RE on the basis of magnetometer data of Geotail, Polar, Cluster, Time History of Events and Macroscale Interactions during Substorms, and Van Allen space probes, taken during 1995-2015. Four characteristic states of the magnetosphere before and during a disturbance have been modeled: a quiet prestorm period, storm deepening phase with progressively decreasing SYM-H index, the storm maximum around the negative peak of SYM-H, and the recovery phase. Fitting the RBF model to data faithfully resolved contributions to the total magnetic field from all principal sources, including the westward and eastward ring current, the tail current, diamagnetic currents associated with the polar cusps, and the large-scale effect of the field-aligned currents. For two main phase conditions, the model field exhibited a strong dawn-dusk asymmetry of the low-latitude magnetic depression, extending to low altitudes and partly spreading sunward from the terminator plane in the dusk sector. The RBF model was found to resolve even finer details, such as the bifurcation of the innermost tail current. The method can be further developed into a powerful tool for data-based studies of the magnetospheric currents.

  4. Observation of Neutral Sodium above Mercury During the Transit of November 8, 2006

    NASA Astrophysics Data System (ADS)

    Potter, Andrew E.; Killen, R. M.; Reardon, K. P.; Bida, T. A.

    2012-10-01

    We mapped the absorption of sunlight by sodium vapor in the exosphere of Mercury during the transit of Mercury on November 8, 2006, using the IBIS Interferometric BIdimensional Spectrometer at the Dunn solar telescope operated by the National Solar Observatory at Sunspot, New Mexico. The measurements were reduced to line-of-sight equivalent widths for absorption at the sodium D2 line, and mapped in thirty degree increments around the shadow of Mercury. We observed north and south polar enhancements of sodium absorption. The sodium absorptions fell off exponentially with altitude up to about 600 km, and we analyzed the altitude distributions to determine surface densities, zenith column densities, temperatures and scale heights for sodium. The average surface concentration of sodium atoms was about 900 atoms/cm3, and the average zenith column density was 0.8 x 1010 atoms/cm2. The average temperature was about 1100 K, with excursions to 1750 and 700 K. The 2003 transit was observed by Schleicher et al. [2004], using instrumentation similar to that employed for this research. They reported the appearance of a streamer-like feature extending a thousand kilometers above the north polar region, and a similar but smaller feature above the south polar region. Our observations did not detect similar features. They observed considerably more sodium absorption over the dawn terminator than over the dusk terminator. In contrast, we observed slightly larger sodium absorption on the dawn relative to the dusk side. The difference might be due to the slow advance of the dawn terminator at during the 2006 transit (0.13 degrees/day) relative to the 2003 transit (3.27 degrees/day). Reference Schleicher, H.; Wiedemann, G.; Wöhl, H.; Berkefeld, T.; Soltau, D. (2004), Detection of neutral sodium above Mercury during the transit on 2003 May 7. Astronomy and Astrophysics, 425, 1119-1124

  5. Kelvin Helmholtz Instability at the Equatorial Magnetotail Boundary: MHD Simulation and Comparison with Geotail Observations

    NASA Technical Reports Server (NTRS)

    Fairfield, Donald H.; Otto, A.

    1999-01-01

    On March 24, 1995 the Geotail spacecraft observed large fluctuations of the magnetic field and plasma properties in the Low Latitude Boundary Layer (LLBL) about 15 R(sub E) tailward of the dusk meridian. Although the magnetospheric and the magnetosheath field were strongly northward, the B(sub z) component showed strong short duration fluctuations in which B(sub z) could even reach negative values. We have used two-dimensional magnetohydrodynamic simulations with magnetospheric and magnetosheath input parameters specifically chosen for this. Geotail event to identify the processes which cause the observed boundary properties. It is shown that these fluctuations can be explained by the Kelvin-Helmholtz instability if the k vector of the instability has a component along the magnetic field direction. The simulation results show many of the characteristic properties of the Geotail observations. In particular, the quasi-periodic strong fluctuations are well explained by satellite crossings through the Kelvin-Helmholtz vortices. It is illustrated how the interior structure of the Kelvin-Helmholtz vortices leads to the rapid fluctuations in the Geotail observations. Our results suggest an average Kelvin-Helmholtz wavelength of about 5 R(sub E) with a vortex size of close to 2 R(sub E) for an average repetition time of 2.5 minutes. The growth time for these waves implies a source region of about 10 to 16 R(sub E) upstream from the location of the Geotail spacecraft (i.e., near the dusk meridian). The results also indicate a considerable mass transport of magnetosheath material into the magnetosphere by magnetic reconnection in the Kelvin-Helmholtz vortices.

  6. Characteristics of enhanced convection electric field in the inner magnetosphere associated with sudden commencements observed by the Akebono Satellite

    NASA Astrophysics Data System (ADS)

    Shinbori, Atsuki; Nishimura, Yukitoshi; Kikuchi, Takashi; Araki, Tohru; Matsuoka, Ayako; Tsuji, Yuji

    In order to investigate the characteristics of a sudden enhancement of dawn-to-dusk convection electric field in the inner magnetosphere and plasmasphere associated with sudden commence-ments (SCs), we have analyzed the electric field data of the Akebono satellite observation data within a period from March 1989 to January 1996. For 300 SC events which are identified as an abrupt increase of the SYM-H index with its amplitude and time variation of more than 5 nT within 10 minutes, respectively, the electric field data showed an abrupt change of intensity as well as direction within a few minutes in the inner magnetosphere and plasmasphere (L¡10) at the onset of SCs. The temporal variations of the electric field indicate an impulsive signature with its amplitude range from 0.2 [mV/m] to 38 [mV/m] corresponding to a sudden increase of the ambient magnetic field associated with the compression of the magnetosphere due to an abrupt increase of solar wind dynamic pressure. The initial excursion of the electric field during 153 SCs tends to be directed westward in the inner magnetosphere and plasmasphere (L¡5.0). From this result, it can be concluded that the westward electric field in these regions is inductive field which leads to a wavefront of the fast mode waves propagating to the nighttime plasmasphere. The amplitude does not show a clear dependence on magnetic local time as has been observed at the geostationary orbit [Schmidt and Pedersen, 1987]. One of the most interesting results from the present study is that a DC offset of the Ey component of the electric field appears after the initial electric field impulse associated with SCs. This variation of the Ey field corresponds to an enhancement of the magnetospheric convection electric field which is potential field. The intensity of the Ey field gradually increases by 0.3-2.4 [mV/m] about 1-2 minutes after the onset of the initial electric field impulse. From the statistical analysis result of the enhanced

  7. Effects of bilateral and unilateral laser ocular exposure in humans

    NASA Astrophysics Data System (ADS)

    Stamper, David A.; Lund, David J.; Molchany, Jerome W.; Stuck, Bruce E.

    2003-06-01

    INTRODUCTION: The amount of visual disruption experienced by individuals exposed to a visible laser source at levels, which are below that, which will damage the cornea or retina will depend on laser exposure parameters and task demands. Previous work has evaluated the effects of wavelength, duration, ambient light level, and target variables. One factor that has not received attention is monocular vs. binocular exposure. Whether the exposure is monocular or binocular may alter pupil dynamics, eyelid closure, and ultimately affect visual performance. METHODS: In this study 10 males and females were exposed to 0.1 and 3.0 sec laser flashes while tracking a dynamic target at 0.28 deg/sec through a scope that was capable of selecting binocular or monocular viewing. Bright (430 nits) and dawn/dusk (4.3 nits) ambient light conditions were simulated using ND filters. A collimated 514.5 nm argon laser beam produced corneal radiant exposures of 0.16 and 1.0 mJ/cm2 for the 0.1 and 3.0 sec conditions respectively. For each flash trial total time off target and maximum absolute error scores were calculated. Eye response (changes in pupil diameter) was assessed by evaluation of videotape from an IR eye camera. Tracking error scores (total time off target) were calculated for each flash trial. RESULTS: Analysis of variance results for the total time off target scores found all three main factors (light level, exposure duration, and monocular/binocular to be significant. Earlier studies have previously shown dawn/dusk flash exposures be more disruptive than bright light trials. Also three sec exposures were more disruptive than one sec exposures. Finally, monocular exposures produced significantly higher error scores than did binocular exposures. For the pupil diameters the post-flash diameters were significantly smaller that the pre-flash diameters and monocular diameters larger that binocular pupil sizes. SUMMARY: The Total Time Off Target error scores for the monocular

  8. Differential expression of melanopsin mRNA and protein in Brown Norwegian rats.

    PubMed

    Hannibal, Jens; Georg, Birgitte; Fahrenkrug, Jan

    2013-01-01

    Melanopsin is expressed in a subpopulation of retinal ganglion cells rendering these cells intrinsically photosensitive (ipRGCs). The ipRGCs are the primary RGCs mediating light entrainment of the circadian clock and control of the pupillary light reflex, light regulated melatonin secretion and negative masking behaviour. Previous studies have demonstrated that melanopsin expression in albino rats is regulated by light and darkness. The present study was undertaken to study the influence of light and darkness during the circadian day and after extended periods of constant light and darkness on melanopsin expression in the pigmented retina of the Brown Norwegian rat (Rattus norvegicus). The diurnal and circadian expressions were examined in retinal extracts from rats euthanized every 4 h during a 24 h light/dark (LD) and a 24 h dark cycle (DD) using quantitative real-time PCR and Western blotting. To study whether light regulates melanopsin expression, rats were sacrificed after being placed in either constant light (LL) or darkness for 3 or 21 d. Flat mount retinas from animals kept during either LL or DD were also examined by immunohistochemistry. Melanopsin mRNA expression displayed a significant rhythmic change during the LD cycle with peak expression around dusk and nadir at dawn. Melanopsin protein also changed over the LD cycle with peak expression at the end of the night and nadir at dusk. Rhythmic expression of melanopsin mRNA but not melanopsin protein was found in constant darkness. After 3 or 21 d in either LL or DD melanopsin mRNA expression was unaltered. Melanopsin protein was at the same high level after 3 and 21 d in DD, whereas a significant decrease was found after prolonging the light period for 3 or 21 d. The change in melanopsin protein was primarily due to change in immunoreactivity in the dendritic processes. In conclusion we found that light and darkness are important for regulation of melanopsin protein expression whereas input from a

  9. Multi-instrument study of the Jovian radio emissions triggered by solar wind shocks and inferred magnetospheric subcorotation rates

    NASA Astrophysics Data System (ADS)

    Hess, S. L. G.; Echer, E.; Zarka, P.; Lamy, L.; Delamere, P. A.

    2014-09-01

    The influence of solar wind conditions on the Jovian auroral radio emissions has long been debated, mostly because it has always been difficult to get accurate solar wind and radio observations at the same time. We present here a study of Jupiter's radio emissions compared to solar wind conditions using radio (RPWS) and magnetic (MAG) data from the Cassini spacecraft from October to December 2000, just before its flyby of Jupiter. The spacecraft was then in the solar wind and could record both the radio emissions coming from the Jovian magnetosphere and the solar wind magnetic field (IMF). With these data, we found a good correspondence between the arrival of interplanetary shocks at Jupiter and the occurrence of radio storms. Our results confirm those from the previous studies showing that fast forward shocks (FFS) trigger mostly dusk emissions, whereas fast reverse shocks (FRS) trigger both dawn and dusk emissions. FFS-triggered emissions are found to occur 10-30 h after the shock arrival when the IMF is weak (below 2 nT), and quasi-immediately after shock arrival when the IMF is strong (above 2 nT). FRS-triggered emissions are found to occur quasi-immediately even when the IMF is weak. We show and discuss in depth the characteristic morphologies of the radio emissions related to each type of shock and their implications. We also used simultaneous radio observations from the ground-based Nançay decameter array and from the Galileo radio instrument (PWS). From the comparison of these measurements with Cassini's, we deduce the regions where the radio storms occur, as well as the radio source subcorotation rates. We show that FFS-triggered emissions onset happens in a sector of local time centered around 15:00 LT, and that all the shock-triggered radio sources sub-corotate with a subcorotation rate of ~50% when the IMF is below 2 nT and of ~80% when it is above 2 nT. These rates could correspond to the extended and compressed states of the Jovian magnetosphere.

  10. Ion heat flux and energy transport near the magnetotail neutral sheet

    NASA Astrophysics Data System (ADS)

    Kaufmann, Richard L.; Paterson, William R.

    2008-05-01

    Ten-year averages of energy transport rates near the neutral sheet showed that the enthalpy flux density or thermal energy term QT = (5/2)PV was the largest, where P is the isotropic pressure and V is the bulk flow velocity. The ion heat flux, qi, was the next largest term. Sorting data using a magnetic flux transport parameter showed that qi could become dominant during periods of slow flow. Both qi and the ion bulk velocity Vi were duskward on the dusk side of the neutral sheet. This relationship is characteristic of cross-tail drift and a heat flux that can be attributed to the energy dependent gradient and curvature drifts. The qi and Vi vectors often pointed in different directions on the dawn side. The x component of qi on the dawn side pointed tailward, suggesting entry through the magnetopause of a suprathermal ion component. On the dusk side the qix plots that were sorted using a magnetic flux transport parameter showed evidence of plasma sheet reconnection. The long-term averaged x component of QT pointed earthward almost everywhere in the neutral sheet, and was attributed to periods of very fast plasma flow. The cross-tail component of QT was separated into two contributions. One part of QTy involved a common drift away from midnight during both earthward and tailward fast flows. This feature suggests that thermal energy and plasma flow from the outer plasma sheet toward the neutral sheet near midnight, and then toward the flanks. The other part of QTy involved a differential duskward drift during fast earthward flows and a dawnward drift during fast tailward flows. The incremental E fields that would produce such convection point tailward during the fastest earthward flows and earthward during the fastest tailward flows. The dependencies of Vi, qi and QT on the interplanetary magnetic field (IMF) clock angle also were studied. Both Vi and QT were reduced when the IMF was northward and the neutral sheet plasma became cold and dense. However, no

  11. Differences in timing of mating swarms in sympatric populations of Anopheles coluzzii and Anopheles gambiae s.s. (formerly An. gambiae M and S molecular forms) in Burkina Faso, West Africa

    PubMed Central

    2013-01-01

    Background The M and S molecular forms of Anopheles gambiae s.s. Giles appear to have speciated in West Africa and the M form is now formally named An. coluzzii Coetzee & Wilkerson sp.n. and the S form retains the nominotypical name (abbreviated here to An. gambiae). Reproductive isolation is thought to be the main barrier to hybridisation; even though both species are found in the same mating swarms, hybrid fertilisations in copulae have not been found in the study area. The aim of the study, therefore, was to determine whether differences in circadian and/or environmental control over the timing of swarming in the two species contribute to reproductive isolation. Methods The timing of male swarming in these species was recorded four nights per month over four years at five swarming sites in each of two villages. The timing of the start and end of swarming, and the concurrent environmental parameters, temperature, humidity and light intensity, were recorded for n = 20 swarms/month/species. The timing of 'spontaneous’ activity at dusk of individual An. coluzzii and An. gambiae males was video-recorded in an actograph outdoors for 21 nights. Results Of the environmental parameters considered, swarming was most strongly correlated with sunset (r2 > 0.946). Anopheles gambiae started and stopped swarming earlier than An. coluzzii (3:35 ± 0:68 min:sec and 4:51 ± 1:21, respectively), and the mean duration of swarming was 23:37 ± 0:33 for An. gambiae and 21:39 ± 0:33 for An. coluzzii. Accordingly, in principle, whenever both species swarm over the same marker, a mean of 15.3 ± 3.1% of An. gambiae swarming would occur before An. coluzzii males arrived, and 19.5 ± 4.55% of An. coluzzii swarming would occurred after An. gambiae males had stopped swarming. These results are consistent with the finding that An. gambiae males became active in the actograph 09:35 ± 00:22 min:sec earlier than An. coluzzii males. Conclusions The

  12. Evolution of flux ropes in the magnetotail: A three-dimensional global hybrid simulation

    NASA Astrophysics Data System (ADS)

    Lu, S.; Lin, Y.; Lu, Q. M.; Wang, X. Y.; Wang, R. S.; Huang, C.; Wu, M. Y.; Wang, S.

    2015-05-01

    Flux ropes in the Earth's magnetotail are widely believed to play a crucial role in energy transport during substorms and the generation of energetic particles. Previous kinetic simulations are limited to the local-scale regime, and thus cannot be used to study the structure associated with the geomagnetic field and the global-scale evolution of the flux ropes. Here, the evolution of flux ropes in the magnetotail under a steady southward interplanetary magnetic field are studied with a newly developed three-dimensional global hybrid simulation model for dynamics ranging from the ion Larmor radius to the global convection time scales. Magnetic reconnection with multiple X-lines is found to take place in the near-tail current sheet at geocentric solar magnetospheric distances x = - 30 R E ˜ - 15 R E around the equatorial plane ( z = 0 ). The magnetotail reconnection layer is turbulent, with a nonuniform structure and unsteady evolution, and exhibits properties of typical collisionless fast reconnection with the Hall effect. A number of small-scale flux ropes are generated through the multiple X-line reconnection. The diameter of the flux ropes is several R E , and the spatial scale of the flux ropes in the dawn-dusk direction is on the order of several R E and does not extend across the entire section of the magnetotail, contrary to previous models and MHD simulation results and showing the importance of the three-dimensional effects. The nonuniform and unsteady multiple X-line reconnection with particle kinetic effects leads to various kinds of flux rope evolution: The small-scale flux ropes propagate earthward or tailward after formation, and eventually merge into the near-Earth region or the mid-/distant-tail plasmoid, respectively. During the propagation, some of the flux ropes can be tilted in the geocentric solar magnetospheric ( x , y ) plane with respect to the y (dawn-dusk) axis. Coalescence between flux ropes is also observed. At the same time, the

  13. Carbon Isotope Discrimination in Leaves of C3 Plants

    NASA Astrophysics Data System (ADS)

    Cuntz, M.; Gleixner, G.

    2009-04-01

    Carbon isotope composition is regarded as a powerful tool in understanding carbon cycling, both as a tracer and as a process recorder. However, accurate predictions of, for example, partitioning the net carbon flux into its components or obtaining climate information from tree rings, requires a good understanding of plant metabolism and related isotopic fractionations. Mechanistic models have concentrated largely on photosynthetic pathways and their isotopic composition. This cannot be said for respiratory processes. The mechanistic models of leaf isotope discrimination hence do not describe dawn, dusk and night very realistically or not at all. A new steady-state approach of the carbon isotope distribution in glucose potentially addresses the time of twilight and night (Tcherkez et al. 2004). Here, a new model of 13C discrimination in leaves of C3 plants is presented. The model is based on the steady-state approach of Tcherkez et al. (2004) but with much reduced complexity while retaining its general characteristics. In addition, the model introduces some new concepts such as a day-length dependent starch synthesis, night-length dependent starch degradation, energy-driven biosynthesis rates, and continuous leaf discrimination calculation for the whole diel cycle. It is therefore well adapted for biosphere-atmosphere exchange studies. The model predicts enriched sucrose and starch pools in the leaf compared to assimilated CO2. Biosynthesis on the other hand acts as the sink of the remaining, depleted carbon. The model calculates slightly different absolute starch compositions from the Tcherkez et al. (2004) model but this depends on chosen fractionation factors. The greatest difference between the two models is during dawn, dusk and night. For example, while Tcherkez et al. has changing phloem sucrose isotope composition during night, the model here predicts constant sucrose export composition. Observations seem to support rather constant phloem isotope composition

  14. Strong ion energization by electromagnetic fluctuations in plasmoid-like magnetic structures.

    NASA Astrophysics Data System (ADS)

    Grigorenko, Elena

    2016-04-01

    Numerous studies based on data from many magnetospheric missions reported the observations of energetic ions with energies of hundreds of keV in the Earth magnetotail. The acceleration of charged particles to energies exceeding the potential drop across the tail can be produced by strong inductive electric fields generated in the course of transient processes related to changes of the magnetic field topology: e.g., magnetic reconnection, dipolarization, magnetic turbulence, and so on. The observations of energetic ion flows by Cluster/RAPID instruments in the near-Earth tail show the increase of H+, He+, and O+ fluxes in the energy range ≥130 keV during the periods of the tailward flows. The hardening of ion spectra is observed inside the plasmoid-like magnetic structures propagating tailward through the Cluster spacecraft. Simultaneously, the low-frequency electromagnetic fluctuations were observed in such structures. The analysis of 37 events demonstrated that the following factors are favorable for the ion energization: (1) the spatial scale of a plasmoid should exceed the thermal gyroradius of a given ion component in the plasmoid neutral plane; (2) the Power Spectral Density (PSD) of the magnetic fluctuations near the gyrofrequency of a particular ion component should exceed ~ 50.0 nT2/Hz for oxygen ions; while the energization of He+ and H+ takes place for much lower values of the PSD. The kinetic analysis of ion dynamics in the plasmoid-like magnetic configurations with the superimposed electromagnetic fluctuations similar to the observed ones confirms the importance of ion resonant interactions with the low-frequency electromagnetic fluctuations for ion energization inside plasmoids. The analysis also show that to be strongly accelerated ions do not need to pass a large distance in the duskward direction and the effective energization can be reached even at the localized source. Thus, ion acceleration by the electromagnetic fluctuations may smear the dawn-dusk

  15. ULF Waves and Diffusive Radial Transport of Charged Particles

    NASA Astrophysics Data System (ADS)

    Ali, Ashar Fawad

    field data from the Radiation Belt Storm Probes (RBSP) to compute the electric and the magnetic component of the radial diffusion coefficient using the Fei et al. [2006] formulation. We conclude that contrary to prior notions, the electric component is dominant in driving radial diffusion of charged particles in the Earth's inner magnetosphere instead of the magnetic component. The electric component can be up to two orders of magnitude larger than the magnetic component. In addition, we see that ULF wave power in both the electric and the magnetic fields has a clear dependence on Kp with wave power decreasing as radial distance decreases. For both fields, the noon sectors generally contain more ULF wave power than the dawn, dusk, and the midnight magnetic local time (MLT) sectors. There is no significant difference between ULF wave power in the dawn, dusk, and the midnight sectors.

  16. Calcium in Mercury's Exosphere: Modeling MESSENGER Data

    NASA Astrophysics Data System (ADS)

    Burger, M. H.; Killen, R. M.; McClintock, W. E.; Merkel, A. W.; Vervack, R. J.; Sarantos, M.; Sprague, A. L.

    2011-12-01

    Mercury is surrounded by a surface-bounded exosphere known to contain hydrogen, sodium, potassium, calcium, and magnesium. Because the exosphere is collisionless, its composition represents a balance of active source and loss processes. The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft has made high-spatial-resolution observations of sodium, calcium, and magnesium near Mercury's surface and in the extended, anti-sunward direction. The most striking feature of these data is the substantial differences among species, which was detected during three close flybys of the planet and has been persistantly present during MESSENGER's orbital phase. Our modeling demonstrates that these differences are not because of post-ejection dynamics such as differences in photo-ionization rate and radiation pressure, but rather result from differences in the source mechanisms and regions on the surface from which each species is ejected. The observations of calcium have revealed a strong dawn/dusk asymmetry, with the abundance over the dawn hemisphere substantially greater than that on the dusk side. To understand this asymmetry, we use a Monte Carlo model of Mercury's exosphere that we developed to track the motions of exospheric neutrals under the influence of gravity and radiation pressure. In this model, Ca atoms can be ejected directly from the surface or produced by ejection of CaO followed by dissociation to produce Ca and O. Particles are removed from the system if they stick to the surface or escape from the model region of interest (within 15 Mercury radii). Photoionization reduces the final weighting given to each particle when simulating the Ca radiance. Data from the flybys are consistent with a high temperature (~1-2 x 104 K) source of atomic Ca concentrated over the dawn hemisphere. Such a high temperature resutls from dissociation of CaO in a near

  17. Dynamics of the Landmark and Current Parameters of the Equatorial Electrojet Over India

    NASA Astrophysics Data System (ADS)

    Rabiu, A.; Onwumechili, C. A.; Nagarajan, N.; Yumoto, K.

    2013-12-01

    For the first time the five parameters required to fully describe Onwumechili's composite thick current shell model format of equatorial electrojet have been evaluated from a single autonomous set of ground data at solar minimum. The thick current shell model, which takes into account the vertical ionospheric currents, permits both the width and the thickness of the jet to be determined simultaneously. The mean annual values of the electrojet parameters evaluated over India sector are: the peak intensity of the forward current at its centre, 62.97 × 2.73 A/km; the peak intensity of the return current, 19.43 × 2.49 A/km; the ratio of the peak return to the peak forward current intensity, 0.312 × 0.052; the total forward current flowing between the current foci, 19.01 × 1.74 kA; half of the latitudinal width or the focal distance from the current centre, 2.7 × 0.18 degrees; the distance of the peak return current location from the current centre, 5.31 × 0.19 degrees; the half thickness of the peak current density, 0.063 × 0.003 degrees; the latitudinal extent of the current from its centre, 9.25 × 2. 08 degrees; and the dip latitude of the electrojet centre -0.190 × 0.003 degrees. The dip latitude of the center of EEJ exhibits a consistent northward migration towards the dip equator from the rising of the jet at dawn from an annual average of -0.193 degrees to about -0.186 degrees at about 1100, thus becoming closer to the dip equator at the peak intensity period of the jet after which it begins to recede southward towards the dusk. The electrojet becomes more (less) intensified as the centre of the electrojet moves northwards (southwards) towards (away from) the dip equator. The diurnal variation of the thickness of the EEJ is opposite that of its current intensity and half width. The thickness of equatorial electrojet EEJ exhibits a consistent diurnal variation such that it decreases from about 0.066 degrees at dawn to the minimum at about 1100 hr LT and

  18. On the Release of Energetic Electrons from the Jovian Magnetosphere: Evidence for a Low Latitude Cusp

    NASA Astrophysics Data System (ADS)

    Jones, D. E.; Murphy, N.

    2001-12-01

    Magnetic field data from Pioneers 10 and 11 have been used to develop a model magnetosphere for Jupiter consisting of an offset, tilted planetary dipole, a bent and twisted current disc represented by an array of concentric current rings, a dayside tail-like dusk-dawn current sheet, and an image dipole (Jones et al, 1980; Jones et al., 1981, Thomas and Jones, 1984). Such a model also fits the Ulysses magnetic field data as well (Jones et al., 1993). In all cases, the magnetosphere has a low latitude cusp. In this paper we compare the model magnetosphere shape and cusp location with the location of periodic energetic particle bursts observed by outbound Pioneer 11 (Fillius, 1976). It is found that the observed peaks occur very near the model cusp field lines, suggesting that this is where energetic particles leave the magnetosphere to propagate on interplanetary magnetic field lines connecting Jupiter with the sun (Conlon et al., 1974). Moiroka and Tsuchiya (1996) have found that the release of energetic electrons is controlled by the solar wind at Jupiter, as expected if they are released at the cusps. D.L. Chenette, T. F. Conlon, and J. A. Simpson, Bursts of relativistic electrons from Jupiter observed in interplanetary space with the time variations of the planetary rotation period, J. Geophys. Res., 79, 3551-3558, 1974 D. E. Jones, J. G. Melville II, and M. L. Blake, Modeling Jupiter's current disc: Pioneer 10 outbound, J. Geophys. Res., 85, 3329, 1980. D. E. Jones, B. T. Thomas, Equatorial disk and dawn-dusk currents in the frontside magnetosphere of Jupiter: Pioneers 10 and 11, J. Geophys. Res., 86, 1738, 1981. B. T. Thomas and D. E. Jones, Modeling Jupiter's magnetospheric currents using Pioneer data: Evidence for a low-latitude cusp, J. Geophys. Res., 89, 6663, 1984. D. E. Jones, E. J. Smith, N. Murphy, D. Winterhalter, A. Balogh, and D. J. Southwood, A model Jovian magnetospheric current system based upon magnetic field data obtained by the Ulysses helium

  19. Comparing Local-Time and Storm-Phase Distributions of EMIC Waves Observed by Van Allen Probes A, GOES-13, and Halley, Antarctica

    NASA Astrophysics Data System (ADS)

    Ohnsted, M.; Engebretson, M. J.; Posch, J. L.; Lessard, M.; Singer, H. J.; Kletzing, C.; Smith, C. W.; Horne, R. B.

    2015-12-01

    Electromagnetic ion cyclotron (EMIC) waves are expected to be highly efficient in depleting the ring current and in removing outer radiation belt electrons. However, the distribution of these waves in subauroral regions has not been well characterized. In this study we present 0-5 Hz magnetic field data from the Van Allen Probes A (RBSP A) spacecraft (in elliptical equatorial orbit with apogee at 5.8 RE), 0-1 Hz data from GOES-13 (in geosynchronous orbit), and 0-5 Hz data from Halley, Antarctica (L ~4.6), during the first full local-time precession of the Van Allen Probes from October 2012 through July 2014. The considerably different hourly local time vs. L distributions observed point to distinct locations and geomagnetic activity-dependent patterns of EMIC wave activity. GOES-13 wave occurrences exhibited a broad peak in the noon-to-dusk sector. He+ band events peaked near dusk, while H+ band waves peaked near noon, with a secondary peak centered near dawn. More EMIC waves occurred during storm main phase in the He+ band (5%) than in the H+ band (1%), and 80% and 89% of the He+ and H+ band waves, respectively, occurred under late storm recovery or quiet conditions. During all storm phases the local time occurrence patterns of < 0.4 Hz and 0.4-1.0 Hz events at Halley resembled those of He+ and H+ band waves, respectively, at GOES-13. The relatively few wave events at Halley with f > 1.0 Hz occurred at all local times, but with a modest, broad peak near dawn. Roughly 90% of both the 1570 Halley events < 1.0 Hz and the 142 Halley events > 1.0 Hz occurred during late storm recovery and quiet conditions. Events during compressions at GOES-13 (10%), Halley (6%), and RBSP A (6%) peaked near local noon, but with a secondary peak near midnight. Waves observed by RBSP A were distributed rather evenly in local time in all L shell ranges between 3 and 6, and the percentage occurring during late storm recovery or quiet conditions was only 65%. We interpret the difference in

  20. A Case Study in Leveraging Major Science at Low Cost: Development of Large Scale Birkeland Currents Determined from AMPERE

    NASA Astrophysics Data System (ADS)

    Anderson, B. J.; Dyrud, L. P.; Korth, H.; Waters, C. L.; Green, D. L.; Barnes, R. J.

    2011-12-01

    The Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) uses the constellation of Iridium Communications satellites in 780-km-altitude, circular, polar orbits to monitor the global Birkeland currents with a nine-minute cadence. This allows us to follow the development of these currents through transitions from quiescent conditions to moderate driving as indicated by rotations of the interplanetary magnetic field (IMF) from northward to southward. AMPERE data are available beginning on October 2009 for development testing purposes and for continuous science observations starting in June 2010. Data are processed in 10-minute windows stepped by two minutes to derive global Birkeland currents with a minimum intensity of 0.2 mirco-A/m2. A transition event ocurred on 24 February 2010, which illustrates one type of systematic behavior found. As measured by ACE at the first Langrangian point, L1, the IMF was northward and sunward from 1300 to 1420 UT with a BZ component of +2 to +3 nT. At 1420 UT, the IMF began rotating southward reaching -2 to -3 nT by 1510 UT. At Earth, the first enhancement in Birkeland currents occurs at 1524-1534 UT on the dayside, reflecting reconnection driven convection associated with the positive IMF BY that persisted through the event. The dayside currents continued to intensify through 1540-1550 UT and extended from mid-morning to dusk. At 1542-1552 UT, isolated nightside currents appear at midnight and are localized in latitude and longitude, extending less than one hour pre or post-midnight. Ten minutes later the nightside currents expand to most of the nighside and merge with the dayside system. The nightside currents then continue to intensify, first near midnight and expand toward both dawn and dusk, resulting in a fully formed classic Region 1/Region 2 current system by 1640-1650 UT. The results indicate that dayside reconnection drives both Region-1 and Region-2-sense currents, whereas the nightside currents

  1. A Double-Disruption Substorm Model - The Growth Phase

    NASA Astrophysics Data System (ADS)

    Sofko, G. J.; McWilliams, K. A.; Hussey, G. C.

    2014-12-01

    When the IMF turns from Bz- to Bz+, dayside merging forms open lobe field lines at low latitudes. These lobe lines are populated with shocked solar wind and dayside magnetospheric plasma from the reconnection inflow. As those lobe flux tubes pass tailward over the polar caps, they are also populated with outflow from the north and south polar cap ionospheres. As the lobe lines move tailward, they acquire a convex curvature that blocks the westward-flowing cross-tail current (XTJ). This constitutes the first stage of XTJ disruption, and it begins less than 10 min after the frontside merging.The disrupted XTJ closes dawn-to-dusk in the transition plasmasheet (TPS), where it produces a downward FAC to the ionosphere. This causes the proton arc, which is seen for the period from about 10 - 80 min after frontside merging begins at time t=0. The lobe lines eventually reconnect well downtail at about t=30 minutes. The middle section that closes the lobe lines has concave curvature and is called the Neutral Sheet (NSh). The resulting stretched field lines thus have a central NSh which separates the two convex-curvature regions to the north and south, regions which are called the Disruption Zones (DZs); the overall combination of the NDZ, NSh and SDZ is called the Stretched Plasmasheet (SPS). As the SPS continues to grow and the stretched lines are pulled earthward to relieve the magnetic tension, the filling of the NSh occurs both from the DTNL with the higher energy magnetospheric particle population on the lobe lines, but eventually also at about 25 earth radii when the polar cap ionospheric outflow (PCO) component finally reaches the NSh. A NSh FAC system forms, from which electrons flow down to the auroral ionosphere to create the pre-onset arc, starting at about t=65 min. At the same time, the Lyons-Speiser mechanism is initiated in the inner NSh, causing the PCO ions to become trapped and accelerated in the inner NSh region. Eventually, when the SPS grows earthward

  2. Investigation of solar wind dependence of the plasma sheet based on long-term Geotail/LEP data evaluation

    NASA Astrophysics Data System (ADS)

    Saeki, R.; Seki, K.; Saito, Y.; Shinohara, I.; Miyashita, Y.; Imada, S.; Machida, S.

    2014-12-01

    It is observationally known that the plasma density and temperature in plasma sheet are significantly changed by solar wind conditions [e.g., Terasawa et al., 1997]. Thus it is considered that the plasma sheet plasma is originated from the solar wind, and several entry mechanisms have been suggested. When the interplanetary magnetic field (IMF) is southward, the solar wind plasma enters the plasma sheet mainly through magnetic reconnection at the dayside magnetopause. In contrast, for the northward IMF, the double-lobe reconnection [Song et al., 1999], abnormal diffusion [Johnson and Cheng., 1997], and plasma mixing through the Kelvin-Helmholtz instability caused by viscous interaction [Hasegawa et al., 2004] have been proposed. Relative contribution of each process is, however, far from understood. In the present study, we use magnetotail observations by the Geotail spacecraft at radial distances of 10-32 Re during 12-year period from 1995 to 2006 to investigate properties of the plasma sheet. We conducted a statistical analysis with calibrated LEP-EA [Mukai et al., 1994] ion and electron data. We selected central plasma sheet observations and derived electron and ion temperature and density using the same method and criteria as Terasawa et al. [1997]. In addition, OMNI solar-wind data are used. The results show that the plasma sheet density (both ion and electron temperatures) has a good correlation with the solar wind density (kinetic energy) over the whole solar cycle. We find clear dawn-dusk asymmetry in the temperature ratio Ti/Te, i.e., the average Ti/Te is higher on the duskside than the dawn. The density also shows the dawn-dusk asymmetry and higher on the duskside than on the dawnside. A previous study by Wang et al. [2012] showed that Ti/Te is high (typically 5-10) in the magnetosheath. The statistical results, therefore, suggest that the shocked solar wind plasma can easily enter the duskside plasma sheet rather than the dawnside. We will discuss the

  3. Calcium in Mercury's Exosphere: Modeling MESSENGER Data

    NASA Technical Reports Server (NTRS)

    Burger, Matthew H.; Killen, Rosemary M.; McClintock, William E.; Merkel, Aimee; Vervack, Ronald J.; Sarantos, Menelaos; Sprague, Ann L.

    2011-01-01

    Mercury is surrounded by a surface-bounded exosphere comprised of atomic species including hydrogen, sodium, potassium, calcium, magnesium, and likely oxygen. Because it is collisionless. the exosphere's composition represents a balance of the active source and loss processes. The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) on the MErcury Surface. Space ENvironment. GEochemistry. and Ranging (MESSENGER) spacecraft has made high spatial-resolution observations of sodium, calcium, and magnesium near Mercury's surface and in the extended, anti-sunward direction. The most striking feature of these data has been the substantial differences in the spatial distribution of each species, Our modeling demonstrates that these differences cannot be due to post-ejection dynamics such as differences in photo-ionization rate and radiation pressure. but instead point to differences in the source mechanisms and regions on the surface from which each is ejected. The observations of calcium have revealed a strong dawn/dusk asymmetry. with the abundance over the dawn hemisphere significantly greater than over the dusk. To understand this asymmetry, we use a Monte Carlo model of Mercury's exosphere that we developed to track the motions of exospheric neutrals under the influence of gravity and radiation pressure. Ca atoms can be ejected directly from the surface or produced in a molecular exosphere (e.g., one consisting of CaO). Particles are removed from the system if they stick to the surface or escape from the model region of interest (within 15 Mercury radii). Photoionization reduces the final weighting given to each particle when simulating the Ca radiance. Preliminary results suggest a high temperature ( I-2x 10(exp 4) K) source of atomic Ca concentrated over the dawn hemisphere. The high temperature is consistent with the dissociation of CaO in a near-surface exosphere with scale height <= 100 km, which imparts 2 eV to the freshly produced Ca atom. This

  4. Effects of bed net use, female size, and plant abundance on the first meal choice (blood vs sugar) of the malaria mosquito Anopheles gambiae

    PubMed Central

    2012-01-01

    Background The purpose of this study was to determine whether the sugar-or-blood meal choice of Anopheles gambiae females one day after emergence is influenced by blood-host presence and accessibility, nectariferous plant abundance, and female size. This tested the hypothesis that the initial meal of female An. gambiae is sugar, even when a blood host is available throughout the night, and, if not, whether the use of a bed net diverts mosquitoes to sugar sources. Methods Females and males <1-day post-emergence were released in a mesocosm. Overnight they had access to either one or six Senna didymobotrya plants. Simultaneously they had access to a human blood host, either for 8 h or for only 30 min at dusk and dawn (the remainder of the night being excluded by an untreated bed net). In a third situation, the blood host was not present. All mosquitoes were collected in the morning. Their wing lengths, an indicator of pre-meal energetic state, were measured, and their meal choice was determined by the presence of midgut blood and of fructose. Results Female sugar feeding after emergence was facultative. When a blood host was accessible for 8 h per night, 92% contained blood, and only 3.7% contained sugar. Even with the use of a bed net, 78% managed to obtain a blood meal during the 30 min of accessibility at dusk or dawn, but 14% of females were now fructose-positive. In the absence of a blood host, and when either one or six plants were available, a total of 21.7% and 23.6% of females and 30.8% and 43.5% of males contained fructose, respectively. Feeding on both sugar and blood was more likely with bed net use and with greater plant abundance. Further, mosquitoes that fed on both resources were more often small and had taken a sugar meal earlier than the blood meal. The abundance of sugar hosts also affected the probability of sugar feeding by males and the amount of fructose obtained by both males and females. Conclusion Even in an abundance of potential sugar

  5. Evolution of flux ropes in the magnetotail: A three-dimensional global hybrid simulation

    SciTech Connect

    Lu, S.; Lin, Y.; Wang, X. Y.; Lu, Q. M. Huang, C.; Wu, M. Y.; Wang, S.; Wang, R. S.

    2015-05-15

    Flux ropes in the Earth's magnetotail are widely believed to play a crucial role in energy transport during substorms and the generation of energetic particles. Previous kinetic simulations are limited to the local-scale regime, and thus cannot be used to study the structure associated with the geomagnetic field and the global-scale evolution of the flux ropes. Here, the evolution of flux ropes in the magnetotail under a steady southward interplanetary magnetic field are studied with a newly developed three-dimensional global hybrid simulation model for dynamics ranging from the ion Larmor radius to the global convection time scales. Magnetic reconnection with multiple X-lines is found to take place in the near-tail current sheet at geocentric solar magnetospheric distances x=−30R{sub E}∼−15R{sub E} around the equatorial plane (z=0). The magnetotail reconnection layer is turbulent, with a nonuniform structure and unsteady evolution, and exhibits properties of typical collisionless fast reconnection with the Hall effect. A number of small-scale flux ropes are generated through the multiple X-line reconnection. The diameter of the flux ropes is several R{sub E}, and the spatial scale of the flux ropes in the dawn-dusk direction is on the order of several R{sub E} and does not extend across the entire section of the magnetotail, contrary to previous models and MHD simulation results and showing the importance of the three-dimensional effects. The nonuniform and unsteady multiple X-line reconnection with particle kinetic effects leads to various kinds of flux rope evolution: The small-scale flux ropes propagate earthward or tailward after formation, and eventually merge into the near-Earth region or the mid-/distant-tail plasmoid, respectively. During the propagation, some of the flux ropes can be tilted in the geocentric solar magnetospheric (x,y) plane with respect to the y (dawn-dusk) axis. Coalescence between flux ropes is also observed. At the same time, the

  6. Spike firing pattern of output neurons of the Limulus circadian clock.

    PubMed

    Liu, Jiahui S; Passaglia, Christopher L

    2011-08-01

    The lateral eyes of the horseshoe crab (Limulus polyphemus) show a daily rhythm in visual sensitivity that is mediated by efferent nerve signals from a circadian clock in the crab's brain. How these signals communicate circadian messages is not known for this or other animals. Here the authors describe in quantitative detail the spike firing pattern of clock output neurons in living horseshoe crabs and discuss its possible significance to clock organization and function. Efferent fiber spike trains were recorded extracellularly for several hours to days, and in some cases, the electroretinogram was simultaneously acquired to monitor eye sensitivity. Statistical features of single- and multifiber recordings were characterized via interval distribution, serial correlation, and power spectral analysis. The authors report that efferent feedback to the eyes has several scales of temporal structure, consisting of multicellular bursts of spikes that group into clusters and packets of clusters that repeat throughout the night and disappear during the day. Except near dusk and dawn, the bursts occur every 1 to 2 sec in clusters of 10 to 30 bursts separated by a minute or two of silence. Within a burst, each output neuron typically fires a single spike with a preferred order, and intervals between bursts and clusters are positively correlated in length. The authors also report that efferent activity is strongly modulated by light at night and that just a brief flash has lasting impact on clock output. The multilayered firing pattern is likely important for driving circadian rhythms in the eye and other target organs. PMID:21775292

  7. Energetic neutral atom imaging with the Polar CEPPAD/IPS instrument: Initial forward modeling results

    SciTech Connect

    Henderson, M.G.; Reeves, G.D.; Moore, K.R.; Spence, H.E.; Jorgensen, A.M.; Fennell, J.F.; Blake, J.B.; Roelof, E.C.

    1997-12-31

    Although the primary function of the CEP-PAD/IPS instrument on Polar is the measurement of energetic ions in-situ, it has also proven to be a very capable Energetic neutral Atom (ENA) imager. Raw ENA images are currently being constructed on a routine basis with a temporal resolution of minutes during both active and quiet times. However, while analyses of these images by themselves provide much information on the spatial distribution and dynamics of the energetic ion population in the ring current, detailed modeling is required to extract the actual ion distributions. In this paper, the authors present the initial results of forward modeling an IPS ENA image obtained during a small geo-magnetic storm on June 9, 1997. The equatorial ion distribution inferred with this technique reproduces the expected large noon/midnight and dawn/dusk asymmetries. The limitations of the model are discussed and a number of modifications to the basic forward modeling technique are proposed which should significantly improve its performance in future studies.

  8. Diel vertical migration and feeding rhythm of copepods under sea ice at Saroma-ko Lagoon

    NASA Astrophysics Data System (ADS)

    Saito, Hiroaki; Hattori, Hiroshi

    1997-02-01

    Diel vertical migration and feeding rhythm of copepods were investigated in Saroma-ko Lagoon, Japan, one of the southernmost areas covered by seasonal sea ice in the Northern Hemisphere. Copepods were collected under sea ice every 4 h for 24 h at five depths (0, 1, 3, 6 and 9 m from the under-surface of the sea ice) to examine their density and ingestion rate. Distinct changes in the vertical distribution and ingestion rate of copepods were observed at dusk, when they migrated upward from the near-bottom layer to the food-abundant sub-ice layer. However, most copepods left the food-abundant sub-ice layer by midnight and reached near bottom again before sunrise. The ingestion rates of copepods increased after sunset throughout the water column as in areas without ice cover. The ingestion rates at the food-poor near-bottom layer were higher than those during the day in the food-abundant sub-ice layer. The estimated grazing rate by zooplankton, predominately copepods, was between 0.056 and 0.08% of the chlorophyll standing stock in the water column per day. This estimate is lower than that observed under Arctic sea ice, due to the lower biomass of copepods under sea ice at Saroma-ko Lagoon.

  9. Lunar tidal effects in the electrodynamics of the low-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Tracy, Brian D.

    We used extensive measurements made by the Jicamarca Unattended Long-Term Investigations of the Ionosphere and Atmosphere (JULIA) and Incoherent Scatter Radar (ISR) systems at Jicamarca, Peru during geomagnetic quiet conditions to determine the climatologies of lunar tidal effects on equatorial vertical plasma drifts. We use, for the first time, the expectation maximization (EM) algorithm to derive the amplitudes and phases of the semimonthly and monthly lunar tidal perturbations. Our results indicate, as expected, lunar tidal effects can significantly modulate the equatorial plasma drifts. The local time and seasonal dependent phase progression has been studied in much more detail than previously and has shown to have significant variations from the average value. The semimonthly drift amplitudes are largest during December solstice and smallest during June solstice during the day, and almost season independent at night. The monthly lunar tidal amplitudes are season independent during the day, while nighttime monthly amplitudes are largest and smallest in December solstice and autumnal equinox, respectively. The monthly and semimonthly amplitudes decrease from early morning to afternoon and evening to morning with moderate to large increases near dusk and dawn. We also examined these perturbation drifts during periods of sudden stratospheric warmings (SSWs). Our results show, for the first time, the enhancements of the lunar semimonthly tidal effects associated with SSWs to occur at night, as well as during the day. Our results also indicate during SSWs, monthly tidal effects are not enhanced as strongly as the semimonthly effects.

  10. Lobe cell convection and polar cap precipitation

    NASA Astrophysics Data System (ADS)

    Eriksson, S.; Peria, W. J.; Bonnell, J. W.; Su, Y.-J.; Ergun, R. E.; Tung, Y.-K.; Parks, G. K.; Carlson, C. W.

    2003-05-01

    The characteristic electric and magnetic field signature of lobe cells as observed by the low-altitude FAST satellite in 55 dawn-dusk passes are compared with Polar ultraviolet images of polar cap auroral activity. Initial results from 34 events of UV image coverage suggest that there is an intimate coupling between the sunward convection flow of the lobe cell and transpolar auroral arcs or diffuse polar cap precipitation in ˜62% of these cases. However, in some cases where the field signatures are suggestive of lobe cell convection, there is no detectable particle precipitation either in Polar UVI or the FAST data sets. Moreover, the presence of lobe cells coincide with UV data intensifications in the premidnight 2000-2400 MLT sector and/or the postnoon 1500 MLT region in ˜59% of all cases with UVI coverage. The magnetic local time dependence of the lobe cells and polar cap precipitation on the interplanetary magnetic field (IMF) are examined using the upstream Wind monitor. The relative importance of the IMF By and Bz components are investigated and compared with the predictions of the antiparallel merging model and strongly suggests a connection with the magnetospheric sash, as is further implied by the mapping of magnetic field lines using the [2002] (T01) model. It was also noted that a majority of lobe cell events occurred during enhanced AE index substorm-like conditions and that generally stronger AE indices are measured for stronger IMF By magnitudes during these events.

  11. Environmental influences on patterns of vertical movement and site fidelity of grey reef sharks (Carcharhinus amblyrhynchos) at aggregation sites.

    PubMed

    Vianna, Gabriel M S; Meekan, Mark G; Meeuwig, Jessica J; Speed, Conrad W

    2013-01-01

    We used acoustic telemetry to describe the patterns of vertical movement, site fidelity and residency of grey reef sharks (Carcharhinus amblyrhynchos) on the outer slope of coral reefs in Palau, Micronesia, over a period of two years and nine months. We tagged 39 sharks (mostly adult females) of which 31 were detected regularly throughout the study. Sharks displayed strong inter-annual residency with greater attendance at monitored sites during summer than winter months. More individuals were detected during the day than at night. Mean depths of tagged sharks increased from 35 m in winter to 60 m in spring following an increase in water temperature at 60 m, with maximum mean depths attained when water temperatures at 60 m stabilised around 29°C. Sharks descended to greater depths and used a wider range of depths around the time of the full moon. There were also crepuscular cycles in mean depth, with sharks moving into shallower waters at dawn and dusk each day. We suggest that daily, lunar and seasonal cycles in vertical movement and residency are strategies for optimising both energetic budgets and foraging behaviour. Cyclical patterns of movement in response to environmental variables might affect the susceptibility of reef sharks to fishing, a consideration that should be taken into account in the implementation of conservation strategies.

  12. Assessment of alternative mating strategies in Anopheles gambiae: Does mating occur indoors?

    PubMed Central

    Dao, Adama; Adamou, Abdoulaye; Yaro, Alpha Seydou; Maïga, Hamidou Moussa; Kassogue, Yaya; Traoré, Sékou Fantamady; Lehmann, Tovi

    2016-01-01

    Mating in Anopheles gambiae has been observed only in outdoor swarms. Here we evaluate if mating also occurs indoors. Mark release recapture of virgin males and females in natural houses showed that mating occurred over a single day even when mosquitoes can leave the house through exit traps and without adaptation to laboratory conditions. In these experiments, insemination rate in the M molecular form of An. gambiae (and An. arabiensis) was higher than that of the S form (15% vs. 6%). Under these conditions, smaller females of the M form mated more frequently than larger females of that form. Sampling mosquitoes throughout the day showed that both sexes enter houses around sunrise and leave around sunset, staying indoors together from dawn to dusk. In an area dominated by the M form, the daily rate of insemination in samples from exit traps was approximately 5% higher than in those from entry traps, implying that mating occurred indoors. Importantly, frequency of cross mating between the molecular forms was as high as that between members of the same form, indicating that indoors - assortative mating breaks down. Altogether, these results suggest that indoor mating is an alternative mating strategy of the M molecular form of An. gambiae. Because naturally occurring mating couples have not yet been observed indoors, this conclusion awaits validation. PMID:18714863

  13. Doppler micro sense and avoid radar

    NASA Astrophysics Data System (ADS)

    Gorwara, Ashok; Molchanov, Pavlo; Asmolova, Olga

    2015-10-01

    There is a need for small Sense and Avoid (SAA) systems for small and micro Unmanned Aerial Systems (UAS) to avoid collisions with obstacles and other aircraft. The proposed SAA systems will give drones the ability to "see" close up and give them the agility to maneuver through tight areas. Doppler radar is proposed for use in this sense and avoid system because in contrast to optical or infrared (IR) systems Doppler can work in more harsh conditions such as at dusk, and in rain and snow. And in contrast to ultrasound based systems, Doppler can better sense small sized obstacles such as wires and it can provide a sensing range from a few inches to several miles. An SAA systems comprised of Doppler radar modules and an array of directional antennas that are distributed around the perimeter of the drone can cover the entire sky. These modules are designed so that they can provide the direction to the obstacle and simultaneously generate an alarm signal if the obstacle enters within the SAA system's adjustable "Protection Border". The alarm signal alerts the drone's autopilot to automatically initiate an avoidance maneuver. A series of Doppler radar modules with different ranges, angles of view and transmitting power have been designed for drones of different sizes and applications. The proposed Doppler radar micro SAA system has simple circuitry, works from a 5 volt source and has low power consumption. It is light weight, inexpensive and it can be used for a variety of small unmanned aircraft.

  14. MESSENGER observations of energetic electron acceleration in Mercury's magnetotail

    NASA Astrophysics Data System (ADS)

    Dewey, Ryan; Slavin, James A.; Baker, Daniel; Raines, Jim; Lawrence, David

    2016-10-01

    Energetic particle bursts within Mercury's magnetosphere have been a source of curiosity and controversy since Mariner 10's flybys. Unfortunately, instrumental effects prevent an unambiguous determination of species, flux, and energy spectrum for the Mariner 10 events. MESSENGER data taken by the Energetic Particle Spectrometer (EPS) have now shown that these energetic particle bursts are composed entirely of electrons. EPS made directional measurements of these electrons from ~30 to 300 keV at 3 s resolution, and while the energy of these electrons sometimes exceeded 200 keV, the energy distributions usually exhibited a cutoff near 100 keV. The Gamma Ray Spectrometer (GRS) has also provided measurements of these electron events, at higher time resolution (10 ms) and energetic threshold (> 50 keV) compared to EPS. We focus on GRS electron events near the plasma sheet in Mercury's magnetotail to identify reconnection-associated acceleration mechanisms. We present observations of acceleration associated with dipolarization events (betratron acceleration), flux ropes (Fermi acceleration), and tail loading/unloading (X-line acceleration). We find that the most common source of energetic electron events in Mercury's magnetosphere are dipolarization events similar to those first observed by Mariner 10. Further, a significant dawn-dusk asymmetry is found with dipolarization-associated energetic particle bursts being more common on the dawn side of the magnetotail.

  15. Fast O(sup +) ion flow observed around Venus at low altitudes

    SciTech Connect

    Kasprzak, W.T.; Niemann, H.B.

    1988-12-01

    The Pioneer Venus Orbiter Neutral Mass Spectrometer (ONMS) has observed fast O(+) ions with an energy exceeding 40 eV in the spacecraft reference frame. The orbit of the spacecraft is nearly polar with periapsis near the equator. The ONMS is mounted at an angle to the spin axis which, in turn, is perpendicular to the ecliptic plane. From the spin modulated data the direction of the ion flow in that plane can be determined. Data from the first 11 diurnal cycles (orbits 1 to 2475) are vector averaged in order to display the general flow pattern. Plots of the averaged data are presented. On the dayside and near the terminators, where fast O(+) is observed near the ionopause, the directions are more or less parallel to the planet's surface with evidence of an asymmetry about the Sun-Venus line. On the nightside below 2000 km and near the equator there is a preferred dawn to dusk direction while at higher altitudes (lower solar zenith angles and higher latitudes) the flow direction is more antisunward. The averaged flux for this time period is 8x10 to the 5th/sq cm/s with a maximum of 5x10 to the 8th.

  16. Effects of The Encounter of A Solar Energetic Particle Event With Mercury

    NASA Astrophysics Data System (ADS)

    Leblanc, F.; Luhmann, J. G.; Johnson, R. E.; Chassefiere, E.

    In this work, we use a typical Solar Energetic Particles event observed at the Earth orbit and scaled to Mercury's orbit. We follow these energetic particles inside the Hermean magnetosphere. The model for the magnetosphere is deduced from Tsyga- nenko's Earth model (Tsyganenko, JGR 1996) extrapolated to Mercury following the measurements of the Hermean magnetosphere made by Mariner 10 (Luhmann et al., JGR 1998). For each of the four main species of ions which usually composed a SEP event, that is H+, He2+, O7+ and C6+, and for the electrons we follow inside the Her- mean magnetosphere thousands of particles launched from the magnetopause as far as either they leave the Hermean magnetosphere or reach the Hermean surface. From this calculation, we deduce the lifetime of these particles inside the magnetosphere and therefore confirm the existence of transfer radial ion and electron pockets (Luh- mann DPS 2001). We also estimate the flux of energetic particles reaching the surface in particular with respect to the Interplanetary Magnetic Field. We then calculate the importance of such encounter among the processes which contribute to generate the Hermean sodium neutral exosphere (Potter et al. 1986). We show in particular that most of the unexplained casual characteristics of this exosphere - peaks of emission on North and South daylight hemispheres (Killen et al. JGR 2001) and dawn/dusk asymmetries (Sprague et al. JGR 1998) - can be explained by such a type of encounter.

  17. Asymmetries in the location of the Venus ionopause

    NASA Technical Reports Server (NTRS)

    Phillips, J. L.; Luhmann, J. G.; Knudsen, W. C.; Brace, L. H.

    1988-01-01

    Four large data sets of Venus ionopause observations, based on different definitions and observations by Pioneer Venus Orbiter field and particle instruments, are compared. Regardless of the definition chosen, the ionopause is observed to be higher on average at dawn than at dusk. The results of an empirical ionosphere model and a data analysis technique which minimizes orbital bias are combined to show that most or all of this asymmetry results from the effects of orbital bias and uneven sampling of solar wind conditions. However, an additional asymmetry is found in which the ionopause is displaced in the direction opposite to the motional electric field of the solar wind. This effect is attributed to asymmetric pickup of exospheric ions by the electric and magnetic fields in the magnetosheath. This ion pickup interpretation can be understood in terms of a previous observed magnetosheath magnetic field asymmetry. Quantitative analysis indicates that the transverse momentum imparted by the solar plasma to pickup particles in their initial gyration is transmitted by the magnetosheath magnetic field to the ionosphere boundary.

  18. Large-amplitude electric fields in the inner magnetosphere: Van Allen Probes observations of subauroral polarization streams

    NASA Astrophysics Data System (ADS)

    Califf, S.; Li, X.; Wolf, R. A.; Zhao, H.; Jaynes, A. N.; Wilder, F. D.; Malaspina, D. M.; Redmon, R.

    2016-06-01

    The subauroral polarization stream (SAPS) is an important magnetosphere-ionosphere (MI) coupling phenomenon that impacts a range of particle populations in the inner magnetosphere. SAPS studies often emphasize ionospheric signatures of fast westward flows, but the equatorial magnetosphere is also affected through strong radial electric fields in the dusk sector. This study focuses on a period of steady southward interplanetary magnetic field (IMF) during the 29 June 2013 geomagnetic storm where the Van Allen Probes observe a region of intense electric fields near the plasmapause over multiple consecutive outbound duskside passes. We show that the large-amplitude electric fields near the equatorial plane are consistent with SAPS by investigating the relationship between plasma sheet ion and electron boundaries, associated field-aligned currents, and the spatial location of the electric fields. By incorporating high-inclination DMSP data we demonstrate the spatial and temporal variability of the SAPS region, and we suggest that discrete, earthward propagating injections are driving the observed strong electric fields at low L shells in the equatorial magnetosphere. We also show the relationship between SAPS and plasmasphere erosion, as well as a possible correlation with flux enhancements for 100s keV electrons.

  19. Spatial distribution of magnetic fluctuation power with period 40 to 600 s in the magnetosphere observed by THEMIS

    NASA Astrophysics Data System (ADS)

    Wang, Guoqiang; Zhang, Tielong; Ge, Yasong

    2016-04-01

    Ultralow frequency (ULF) fluctuations are ubiquitous in the magnetosphere and have significant influence on the energetic particle transport. We use Time History of Events and Macroscale Interactions During Substorms (THEMIS) data to give the spatial distribution of the Pi2/Pc4- and Pc5-band magnetic fluctuation amplitude near the magnetic equator in the magnetosphere. Statistical results can be summarized as follows: (1) Strong ULF fluctuations are common in the magnetotail plasma sheet; The amplitude of all three components of magnetic fluctuations decreases with decreasing radial distance; (2) During periods of high AE index, fluctuations can propagate toward the Earth as far as the data cutoff in the nightside of the magnetosphere, and the amplitude of magnetic fluctuations is clearly stronger near the dusk sector of the synchronous orbit than that near the dawn sector, suggesting that the substorm particle injection has significant contribution to these fluctuations; (3) Intense compressional Pc5-band magnetic fluctuations are a persistent feature near two flanks of the magnetosphere. Clear peaks of the compressional Pi2/Pc4-band magnetic fluctuation power near two flanks can be found during periods of fast solar wind, while the power of compressional Pi2/Pc4-band fluctuations is weak when the solar wind is slow. (4) Solar wind dynamic pressure and its variations can globally affect the ULF fluctuation power in the magnetosphere. Magnetic fluctuations near the noon side can penetrate from the magnetopause to the synchronous orbit or inner when solar wind pressure variations are large.

  20. A radar study of emigratory flight and layer formation by insects at dawn over southern Britain.

    PubMed

    Reynolds, D R; Smith, A D; Chapman, J W

    2008-02-01

    Radar observations have consistently shown that high-altitude migratory flight in insects generally occurs after mass take-off at dusk or after take-off over a more extended period during the day (in association with the growth of atmospheric convection). In this paper, we focus on a less-studied third category of emigration - the 'dawn take-off' - as recorded by insect-monitoring radars during the summer months in southern England. In particular, we describe occasions when dawn emigrants formed notable layer concentrations centred at altitudes ranging from ca. 240 m to 700 m above ground, very probably due to the insects responding to local temperature maxima in the atmosphere, such as the tops of inversions. After persisting for several hours through the early morning, the layers eventually merged into the insect activity building up later in the morning (from 06.00-08.00 h onwards) in conjunction with the development of daytime convection. The species forming the dawn layers have not been positively identified, but their masses lay predominantly in the 16-32 mg range, and they evidently formed a fauna quite distinct from that in flight during the previous night. The displacement and common orientation (mutual alignment) characteristics of the migrants are described.

  1. Seasonal variation in daily activity patterns of free-ranging European ground squirrels (Spermophilus citellus).

    PubMed

    Everts, Lammina G; Strijkstra, Arjen M; Hut, Roelof A; Hoffmann, Ilse E; Millesi, Eva

    2004-01-01

    Daily aboveground activity of European ground squirrels (Spermophilus citellus) in their natural habitat was recorded with a visual scanning procedure during the active seasons of 1992 and 1993. Activity patterns were analyzed with respect to time of year and to the animal's reproductive state. Aboveground activity started on average 3.9 h (SD 0.6 h, n = 37 days) after civil twilight at dawn and ended on average 3.2 h (SD 0.9 h, n = 37 days) before civil twilight at dusk. Between onset and offset of activity, 54% was spent aboveground, of which 73% was spent foraging. Activity patterns were influenced by photoperiod, rainfall, and by reproductive state. During mating, reproductively active males started activity earlier than females and reproductively inactive males. For females, time spent foraging was high during lactation. The midpoint of daily activity was at 12:16 h (SD 0.37 h, n = 37 days). Activity patterns of European ground squirrels thus appear robustly positioned in the middle of the photoperiod. PMID:15129824

  2. Habitat use by squirrel monkeys (Saimiri oerstedi) in Costa Rica.

    PubMed

    Boinski, S

    1987-01-01

    This paper analyses movement patterns, habitat preferences, activity schedules, and dispersion of troop members in squirrel monkeys (Saimiri oerstedi) in relation to seasonal changes in food abundance in a Costa Rican tropical wet forest. Secondary forest was the preferred habitat and use of primary forest and late successional forest was limited primarily to seasons when food availability was low. Range area differed between seasons, varying from 79 to 110 ha, and totaling 176 ha over 11 months. The number of hectares used, hourly rate of group movement, and proportion of time spent foraging each season were all negatively related to relative food abundance. There was a tendency to spend less time in foraging activities in the middle of the day and to spend more time exclusively in travel at dawn and dusk. In all seasons dispersion was least when the troop was travelling and it was generally greatest during seasons of low food abundance. Measures of the allocation of time by the troop to food-related activities and the extent of troop dispersion each season were consistent with estimates based on behavior sampling of individuals. PMID:3504420

  3. Candle light-style OLED: a plausibly human-friendly safe night light

    NASA Astrophysics Data System (ADS)

    Jou, Jwo-Huei; Chen, Po-Wei; Hsieh, Chun-Yu; Wang, Ching-Chiun; Chen, Chien-Chih; Tung, F.-C.; Chen, Szu-Hao; Wang, Yi-Shan

    2013-09-01

    Candles emit sensationally-warm light with a very-low color-temperature, comparatively most suitable for use at night. In response to the need for such a human-friendly night light, we demonstrate the employment of a high number of candle light complementary organic emitters to generate mimic candle light based on organic light emitting diode (OLED). One resultant candle light-style OLED shows a very-high color rendering index, with an efficacy at least 300 times that of candles or twice that of an incandescent bulb. The device can be fabricated, for example, by using four candle light complementary emitters, namely: red, yellow, green, and sky-blue phosphorescent dyes, vacuum-deposited into two emission layers, separated by a nano-layer of carrier modulation material to maximize both the desirable very-high color rendering index and energy efficiency, while keeping the blue emission very low and red emission high to obtain the desirable low color temperature. With different layer structures, the OLEDs can also show color tunable between that of candle light and dusk-hue. Importantly, a romantic sensation giving and supposedly physiologically-friendly candle light-style emission can hence be driven by electricity in lieu of the hydrocarbon-burning and greenhouse gas releasing candles that were invented 5,000 years ago.

  4. Compound eyes and retinal information processing in miniature dipteran species match their specific ecological demands.

    PubMed

    Gonzalez-Bellido, Paloma T; Wardill, Trevor J; Juusola, Mikko

    2011-03-01

    The compound eye of insects imposes a tradeoff between resolution and sensitivity, which should exacerbate with diminishing eye size. Tiny lenses are thought to deliver poor acuity because of diffraction; nevertheless, miniature insects have visual systems that allow a myriad of lifestyles. Here, we investigate whether size constraints result in an archetypal eye design shared between miniature dipterans by comparing the visual performance of the fruit fly Drosophila and the killer fly Coenosia. These closely related species have neural superposition eyes and similar body lengths (3 to 4 mm), but Coenosia is a diurnal aerial predator, whereas slow-flying Drosophila is most active at dawn and dusk. Using in vivo intracellular recordings and EM, we report unique adaptations in the form and function of their photoreceptors that are reflective of their distinct lifestyles. We find that although these species have similar lenses and optical properties, Coenosia photoreceptors have three- to fourfold higher spatial resolution and rate of information transfer than Drosophila. The higher performance in Coenosia mostly results from dramatically diminished light sensors, or rhabdomeres, which reduce pixel size and optical cross-talk between photoreceptors and incorporate accelerated phototransduction reactions. Furthermore, we identify local specializations in the Coenosia eye, consistent with an acute zone and its predatory lifestyle. These results demonstrate how the flexible architecture of miniature compound eyes can evolve to match information processing with ecological demands.

  5. Dynamic characteristics of Prochlorococcus and Synechococcus consumption by bacterivorous nanoflagellates.

    PubMed

    Christaki, U; Courties, C; Karayanni, H; Giannakourou, A; Maravelias, C; Kormas, K Ar; Lebaron, P

    2002-04-01

    We compared the characteristics of ingestion of Prochlorococcus and Synechococcus by the marine heterotrophic nanoflagellate Pseudobodo sp. and by a mixed nanoflagellate culture (around 3 microm in size) obtained from an open sea oligotrophic area. Maximum ingestion rate on Synechococcus (2.7 Syn flagellate(-1) h(-1)) was reached at concentrations of 5 x 10(5) Syn mL(-1) and decreased between 6 x 10(5) and 1.5 x 10(6) Syn mL(-1). In order to validate laboratory data, one set of data on Synechococcus grazing was obtained during a field study in the oligotrophic northeastern Mediterranean Sea. Ingestion rates by heterotrophic nanoflagellates were related to Synechococcus abundance in the water, and the feeding rate showed a clear diel rhythm with consumption being highest during the night, declining during the day hours, and being lowest at dusk. Ingestion rates on Prochlorococcus increased linearly for the whole range of prey density used (i.e., from 1 x 10(3) to 3 x 10(6) Proc mL(-1)), with maximum ingestion of 6.7 Proc flagellate(-1) h(-1). However, for prey concentrations in the range of 10(3)-10(5), which are usually encountered in aquatic systems, ingestion rates were significantly less than on Synechococcus. In our experiments, both Prochlorococcus and Synechococcus proved to be poor food items for support of nanoflagellate growth.

  6. Effects of Lactobacilli and lactose on Salmonella typhimurium colonisation and microbial fermentation in the crop of the young turkey.

    PubMed

    Cutler, S A; Rasmussen, M A; Hensley, M J; Wilhelms, K W; Griffith, R W; Scanes, C G

    2005-12-01

    1. Three experiments were performed to examine the effects of Lactobacilli and lactose on microbial fermentation and Salmonella enterica serovar Typhimurium colonisation in the crop of the young turkey. 2. The following carboxylic acids were detected in the crop ingesta: formic, acetic, butyric, lactic, valeric, caproic, oxalic, phenyl acetic, succinic and fumaric; propionic, isobutyric and isovaleric acids were not detectable. 3. At the beginning of the night, there were considerable quantities of ingesta in the crop of young turkeys. During the scotophase, there were progressive reductions in the contents and pH. Moreover, there were linear increases in the concentration of lactic, valeric and caproic acids (by approximately 7-fold over 8 h). Much smaller changes in crop pH were observed in the study where dietary treatments of Lactobacilli were not included. 4. Chronic addition of lactose or Lactobacilli to the diet exerted modest effects on the carboxylic acid concentration in the crop contents but did not consistently influence colonisation of the crop by Salmonella enterica serovar Typhimurium. 5. Young turkeys confine eating to the hours of illumination (photophase) with a peak in consumption prior to the subjective dusk.

  7. Light and clock expression of the Neurospora clock gene frequency is differentially driven by but dependent on WHITE COLLAR-2.

    PubMed Central

    Collett, Michael A; Garceau, Norm; Dunlap, Jay C; Loros, Jennifer J

    2002-01-01

    Visible light is thought to reset the Neurospora circadian clock by acting through heterodimers of the WHITE COLLAR-1 and WHITE COLLAR-2 proteins to induce transcription of the frequency gene. To characterize this photic entrainment we examined frq expression in constant light, under which condition the mRNA and protein of this clock gene were strongly induced. In continuous illumination FRQ accumulated in a highly phosphorylated state similar to that seen at subjective dusk, the time at which a step from constant light to darkness sets the clock. Examination of frq expression in several wc-2 mutant alleles surprisingly revealed differential regulation when frq expression was compared between constant light, following a light pulse, and darkness (clock-driven expression). Construction of a wc-2 null strain then demonstrated that WC-2 is absolutely required for both light and clock-driven frq expression, in contrast to previous expectations based on presumptive nulls containing altered Zn-finger function. Additionally, we found that frq light signal transduction differs from that of other light-regulated genes. Thus clock and light-driven frq expression is differentially regulated by, but dependent on, WC-2. PMID:11805052

  8. Rax : developmental and daily expression patterns in the rat pineal gland and retina.

    PubMed

    Rohde, Kristian; Klein, David C; Møller, Morten; Rath, Martin F

    2011-09-01

    Retina and anterior neural fold homeobox (Rax) gene encodes a transcription factor essential for vertebrate eye development. Recent microarray studies indicate that Rax is expressed in the adult rat pineal gland and retina. The present study reveals that Rax expression levels in the rat change significantly during retinal development with a peak occurring at embryonic day 18, whereas Rax expression in the pineal is relatively delayed and not detectable until embryonic day 20. In both tissues, Rax is expressed throughout postnatal development into adulthood. In the mature rat pineal gland, the abundance of Rax transcripts increases 2-fold during the light period with a peak occurring at dusk. These findings are consistent with the evidence that Rax is of functional importance in eye development and suggest a role of Rax in the developing pineal gland. In addition, it would appear possible that Rax contributes to phenotype maintenance in the mature retina and pineal gland and may facilitate 24-h changes in the pineal transcriptome.

  9. Diurnal, seasonal and interannual variability of carbon isotope discrimination at the canopy level in response to environmental factors in a boreal forest ecosystem.

    PubMed

    Chen, Baozhang; Chen, Jing M

    2007-10-01

    Accurate estimation of temporal and spatial variations in photosynthetic discrimination of 13C is critical to carbon cycle research. In this study, a combined ecosystem-boundary layer isotope model, which was satisfactorily validated against intensive campaign data, was used to explore the temporal variability of carbon discrimination in response to environmental driving factors in a boreal ecosystem in the vicinity of Fraserdale Tower, Ontario, Canada (49 degrees 52'30''N, 81 degrees 34'12''W). A 14 year (1990-1996 and 1998-2004) hourly CO2 concentration and meteorological record measured on this tower was used for this purpose. The 14 year mean yearly diurnal amplitude of canopy-level discrimination Delta(canopy) was computed to be 2.8 +/- 0.5 per thousand, and the overall diurnal cycle showed that the greatest Delta(canopy) values occurred at dawn and dusk, while the minima generally appeared in mid-afternoon. The average annual Delta(canopy) varied from 18.3 to 19.7 per thousand with the 14 year average of 19 +/- 0.4 per thousand. The overall seasonality of Delta(canopy) showed a gradually increasing trend from leaf emergence in May-September and with a slight decrease at the end of the growing season in October. Delta(canopy) was negatively correlated to vapour pressure deficit and air temperature across hourly to decadal timescales. A strong climatic control on stomatal regulation of ecosystem isotope discrimination was found in this study. PMID:17727414

  10. Do phosphine resistance genes influence movement and dispersal under starvation?

    PubMed

    Kaur, Ramandeep; Ebert, Paul R; Walter, Gimme H; Swain, Anthony J; Schlipalius, David I

    2013-10-01

    Phosphine resistance alleles might be expected to negatively affect energy demanding activities such as walking and flying, because of the inverse relationship between phosphine resistance and respiration. We used an activity monitoring system to quantify walking of Rhyzopertha dominica (F.) and a flight chamber to estimate their propensity for flight initiation. No significant difference in the duration of walking was observed between the strongly resistant, weakly resistant, and susceptible strains of R. dominica we tested, and females walked significantly more than males regardless of genotype. The walking activity monitor revealed no pattern of movement across the day and no particular time of peak activity despite reports of peak activity of R. dominica and Tribolium castaneum (Herbst) under field conditions during dawn and dusk. Flight initiation was significantly higher for all strains at 28 degrees C and 55% relative humidity than at 25, 30, 32, and 35 degrees C in the first 24 h of placing beetles in the flight chamber. Food deprivation and genotype had no significant effect on flight initiation. Our results suggest that known resistance alleles in R. dominica do not affect insect mobility and should therefore not inhibit the dispersal of resistant insects in the field.

  11. Day-night variations in malate concentration, osmotic pressure, and hydrostatic pressure in Cereus validus

    SciTech Connect

    Luettge, U.; Nobel, P.S.

    1984-07-01

    Malate concentration and stem osmotic pressure concomitantly increase during nighttime CO/sub 2/ fixation and then decrease during the daytime in the obligate Crassulacean acid metabolism (CAM) plant, Cereus validus (Cactaceae). Changes in malate osmotic pressure calculated using the Van't Hoff relation match the changes in stem osmotic pressure, indicating that changes in malate level affected the water relations of the succulent stems. In contrast to stem osmotic pressure, stem water potential showed little day-night changes, suggesting that changes in cellular hydrostatic pressure occurred. This was corroborated by direct measurements of hydrostatic pressure using the Juelich pressure probe where a small oil-filled micropipette is inserted directly into chlorenchyma cells, which indicated a 4-fold increase in hydrostatic pressure from dusk to dawn. A transient increase of hydrostatic pressure at the beginning of the dark period was correlated with a short period of stomatal closing between afternoon and nighttime CO/sub 2/ fixation, suggesting that the rather complex hydrostatic pressure patterns could be explained by an interplay between the effects of transpiration and malate levels. A second CAM plant, Agave deserti, showed similar day-night changes in hydrostatic pressure in its succulent leaves. It is concluded that, in addition to the inverted stomatal rhythm, the oscillations of malate markedly affect osmotic pressures and hence water relations of CAM plants. 13 references, 4 figures.

  12. Longitudinal frequency variation of long-lasting EMIC Pc1-Pc2 waves localized in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Kim, K.-H.; Shiokawa, K.; Mann, I. R.; Park, J.-S.; Kwon, H.-J.; Hyun, K.; Jin, H.; Connors, M.

    2016-02-01

    Long-lasting (> 20 h) electromagnetic ion cyclotron (EMIC) Pc1-Pc2 waves were observed by the Athabasca (L =˜ 4.6) induction magnetometer and Canadian Array for Realtime Investigations of Magnetic Activity (L =˜ 4-6) fluxgate magnetometers on 5 April 2007. These waves showed a systematic frequency change with local time, the minimum frequency near dusk, and the maximum frequency near dawn. Assuming the plasmapause as a potential source region of the waves, we estimated the plasmapause location from localized proton enhancement (LPE) events observed at NOAA-Polar Orbiting Environmental Satellites and METOP-2 satellites. We found that the longitudinal frequency variation of EMIC waves has a clear correlation with the estimated plasmapause location and that the waves are in the frequency band between the equatorial helium and oxygen gyrofrequencies at the estimated plasmapause. With our analysis results we suggest that the LPE events are caused by wave-particle interaction with the helium band EMIC waves generated near the plasmapause.

  13. Magnetic field power spectra and magnetic radial diffusion coefficients using CRRES magnetometer data

    NASA Astrophysics Data System (ADS)

    Ali, Ashar F.; Elkington, Scot R.; Tu, Weichao; Ozeke, Louis G.; Chan, Anthony A.; Friedel, Reiner H. W.

    2015-02-01

    We used the fluxgate magnetometer data from Combined Release and Radiation Effects Satellite (CRRES) to estimate the power spectral density (PSD) of the compressional component of the geomagnetic field in the ˜1 mHz to ˜8 mHz range. We conclude that magnetic wave power is generally higher in the noon sector for quiet times with no significant difference between the dawn, dusk, and the midnight sectors. However, during high Kp activity, the noon sector is not necessarily dominant anymore. The magnetic PSDs have a very distinct dependence on Kp. In addition, the PSDs appear to have a weak dependence on McIlwain parameter L with power slightly increasing as L increases. The magnetic wave PSDs are used along with the Fei et al. (2006) formulation to compute DLLB[CRRES] as a function of L and Kp. The L dependence of DLLB[CRRES] is systematically studied and is shown to depend on Kp. More significantly, we conclude that DLLEis the dominant term driving radial diffusion, typically exceeding DLLB by 1-2 orders of magnitude.

  14. Infectious Disease and Grouping Patterns in Mule Deer

    PubMed Central

    2016-01-01

    Infectious disease dynamics are determined, to a great extent, by the social structure of the host. We evaluated sociality, or the tendency to form groups, in Rocky Mountain mule deer (Odocoileus hemionus hemionus) from a chronic wasting disease (CWD) endemic area in Saskatchewan, Canada, to better understand factors that may affect disease transmission. Using group size data collected on 365 radio-collared mule deer (2008–2013), we built a generalized linear mixed model (GLMM) to evaluate whether factors such as CWD status, season, habitat and time of day, predicted group occurrence. Then, we built another GLMM to determine factors associated with group size. Finally, we used 3 measures of group size (typical, mean and median group sizes) to quantify levels of sociality. We found that mule deer showing clinical signs of CWD were less likely to be reported in groups than clinically healthy deer after accounting for time of day, habitat, and month of observation. Mule deer groups were much more likely to occur in February and March than in July. Mixed-sex groups in early gestation were larger than any other group type in any season. Groups were largest and most likely to occur at dawn and dusk, and in open habitats, such as cropland. We discuss the implication of these results with respect to sociobiology and CWD transmission dynamics. PMID:27007808

  15. Plasma Boundary Locations as Measured Simultaneously by Rosetta and Mars Express

    NASA Astrophysics Data System (ADS)

    Edberg, Niklas; Eriksson, A. I.; Auster, U.; Barabash, S.; Boesswetter, A.; Brain, D. A.; Carr, C. M.; Cowley, S. W. H.; Cupido, E.; Fränz, M.; Glassmeier, K.; Goldstein, R.; Lester, M.; Lundin, R.; Modolo, R.; Nilsson, H.; Richter, I.; Samara, M.; Trotignon, J.

    2008-09-01

    We present the first two-spacecraft simultaneous observations of the Martian bow shock (BS) and magnetic pileup boundary (MPB), obtained by the plasma instruments onboard Rosetta and Mars Express during the Rosetta Mars flyby on February 25, 2007. We compare the positions of these two boundaries with models based on previous measurements by Mars Global Surveyor. The BS is found to be compressed despite a low solar wind dynamical pressure whereas the MPB is found at its average position. We also show the result of a single case study of the effects of extreme solar wind conditions on the location of the above boundaries. A long-lasting ( 24 hours) solar wind structure with high magnetic field strength and variability as well as high solar wind density and velocity is observed in Rosetta (far downtail of Mars) and Mars Express (close to the terminator) data simultaneously. The fortunate orbital configuration of Mars Express at this time makes it possible to observe how the BS and MPB becomes asymmetric during the passage of this solar wind structure: the BS and MPB observed in the southern/dawn hemisphere is found significantly further out than in the northern/dusk hemisphere.

  16. He Bulge Detection by MAVEN Neutral Gas and Ion Mass Spectrometer (NGIMS) in the Upper Atmosphere of Mars

    NASA Astrophysics Data System (ADS)

    Elrod, Meredith; Bougher, Stephen; Benna, Mehdi; Yelle, Roger; Jakosky, Bruce; Bell, Jared; Mahaffy, Paul; Stone, Shane

    2016-07-01

    Studies of the Venusian atmospheres have demonstrated enhanced He densities at high latitudes and on the night-side detections. To determine if Mars has a similar enhanced He 'bulge' in the same region, we compared several periapsis passes from night to dayside. The first six weeks of the MAVEN prime mission had periapsis at high latitudes on the night-side, followed by the next three months at mid latitudes on the dayside moving to low latitudes on the night-side. In addition to its normal orbit, which has a periapsis of approximately 150 km, MAVEN conducts a few deep dip orbits where the spacecraft has a periapsis closer to 125km. The first deep dip was at dusk at mid latitudes, the second at noon at the equator, with the third going from dawn to night in the southern hemisphere. Initial analysis of the Neutral Gas and Ion Mass Spectrometer (NGIMS) closed source data from all orbits with good pointing revealed an enhanced He density on the night-side orbits and a decreased He density on the dayside. This enhancement of He demonstrates a bulge at Mars that will continue to be explored over the course of the mission.

  17. He Bulge Detection by MAVEN Neutral Gas and Ion Mass Spectrometer (NGIMS) in the Upper Atmosphere of Mars

    NASA Astrophysics Data System (ADS)

    Stone, S. W.; Elrod, M. K.; Mahaffy, P. R.; Benna, M.; Bell, J. M.; Bougher, S. W.; Yelle, R. V.; Jakosky, B. M.

    2015-12-01

    Studies of the Venusian atmospheres have demonstrated enhanced He densities at high latitudes and on the night-side detections. To determine if Mars has a similar enhanced He 'bulge' in the same region, we compared several periapsis passes from night to dayside. The first six weeks of the MAVEN prime mission had periapsis at high latitudes on the night-side, followed by the next three months at mid latitudes on the dayside moving to low latitudes on the night-side. In addition to its normal orbit, which has a periapsis of approximately 150 km, MAVEN conducts a few deep dip orbits where the spacecraft has a periapsis closer to 125km. The first deep dip was at dusk at mid latitudes, the second at noon at the equator, with the third going from dawn to night in the southern hemisphere. Initial analysis of the Neutral Gas and Ion Mass Spectrometer (NGIMS) closed source data from all orbits with good pointing revealed an enhanced He density on the night-side orbits and a decreased He density on the dayside. This enhancement of He demonstrates a bulge at Mars that will continue to be explored over the course of the mission.

  18. He Bulge Detection by MAVEN Neutral Gas and Ion Mass Spectrometer (NGIMS) in the Upper Atmosphere of Mars

    NASA Astrophysics Data System (ADS)

    Elrod, Meredith K.; Mahaffy, Paul R.; Yelle, Roger; Stone, Shane; Benna, Mehdi; Jakowski, Bruce

    2015-11-01

    Studies of the Venusian atmospheres have demonstrated enhanced He densities at high latitudes and on the night-side detections. To determine if Mars has a similar enhanced He ‘bulge’ in the same region, we compared several periapsis passes from night to dayside. The first six weeks of the MAVEN prime mission had periapsis at high latitudes on the night-side, followed by the next three months at mid latitudes on the dayside moving to low latitudes on the night-side. In addition to its normal orbit, which has a periapsis of approximately 150 km, MAVEN conducts a few deep dip orbits where the spacecraft has a periapsis closer to 125km. The first deep dip was at dusk at mid latitudes, the second at noon at the equator, with the third going from dawn to night in the southern hemisphere. Initial analysis of the Neutral Gas and Ion Mass Spectrometer (NGIMS) closed source data from all orbits with good pointing revealed an enhanced He density on the night-side orbits and a decreased He density on the dayside. This enhancement of He demonstrates a bulge at Mars that will continue to be explored over the course of the mission.

  19. Awareness of dengue and practice of dengue control among the semi-urban community: a cross sectional survey.

    PubMed

    Naing, Cho; Ren, Wong Yih; Man, Chan Yuk; Fern, Koh Pei; Qiqi, Chua; Ning, Choo Ning; Ee, Clarice Wong Syun

    2011-12-01

    Primary prevention is the most effective measure in dengue prevention and control. The objectives were (i) to determine the level of knowledge and practice of dengue control amongst the study community, and (ii) to explore the factors affecting practice of dengue control in the study area. A cross-sectional study was conducted in a semi-urban Town of Malaysia, using a structured questionnaire covering sociodemography, knowledge related to dengue, knowledge related to Aedes mosquito and preventive measures against the disease. For comparison of survey responses, chi-square test was applied for categorical data. To explore the factors affecting the practice of dengue control, a linear regression model was introduced. Almost all of the respondents (95%) had heard about dengue. Overall, misconceptions of dengue transmission were identified and the practice of dengue control in the study population was insufficient. About half (50.5%) had misconceptions that Aedes can breed in dirty water and the preferred biting time is dusk or sunset (45.6%). Only 44.5% of the households surveyed had covered their water containers properly. Significant associations were found between knowledge scores of dengue and age (P = 0.001), education level (P = 0.001), marital status (P = 0.012), and occupation (P = 0.007). In regression analysis, only the knowledge of dengue was significantly and positively associated with practice on dengue control. A future study with larger samples and more variables to assess the knowledge, attitudes and practices of dengue control is recommended.

  20. Radar studies of midlatitude ionospheric plasma drifts

    NASA Astrophysics Data System (ADS)

    Scherliess, L.; Fejer, B. G.; Holt, J.; Goncharenko, L.; Amory-Mazaudier, C.; Buonsanto, M. J.

    2001-02-01

    We use incoherent scatter radar measurements from Millstone Hill and Saint Santin to study the midlatitude F region electrodynamic plasma drifts during geomagnetically quiet and active periods. We present initially a local time, season, and solar flux dependent analytical model of the quiet time zonal and meridional E×B drifts over these stations. We discuss, for the first time, the Saint Santin drift patterns during solar maximum. We have used these quiet time models to extract the geomagnetic perturbation drifts which were modeled as a function of the time history of the auroral electrojet indices. Our results illustrate the evolution of the disturbance drifts driven by the combined effects of prompt penetration and longer lasting perturbation electric fields. The meridional electrodynamic disturbance drifts have largest amplitudes in the midnight-noon sector. The zonal drifts are predominantly westward, with largest amplitudes in the dusk-midnight sector and, following a decrease in the high-latitude convection, they decay more slowly than the meridional drifts. The prompt penetration and steady state zonal disturbance drifts derived from radar measurements are in good agreement with results obtained from both the ion drift meter data on board the Dynamics Explorer 2 (DE 2) satellite and from the Rice Convection Model.

  1. Magnetosphere-Ionosphere Coupling at Subauroral Latitudes (Invited)

    NASA Astrophysics Data System (ADS)

    Sazykin, S.; Spiro, R. W.; Wolf, R. A.; Song, Y.; Toffoletto, F.

    2010-12-01

    On the night side of the inner magnetosphere and the conjugate ionosphere, there is a region where boundaries of several plasma populations of different origins and energy regimes (the plasmapause, the equatorward edge of the auroral oval, and the inner edge of the ring current) approximately coincide or overlap. This region is highly complex and dynamic. The magnetospheric hot plasmas and ionospheric-plasmaspheric cold populations are coupled through convection electric fields and auroral particle precipitation. Both convection (electric field) patterns and plasma densities are observed to be structured during geomagnetic disturbances, with Subauroral Polarization Streams (SAPS) near the auroral oval and plasma plumes (particularly prominent in TEC maps) extending to lower latitudes and in MLT from the nightside toward the afternoon sector. In this paper, we present an initial attempt to explain the causes of the observed ionospheric storm-time plasma structuring at mid and sub-auroral latitudes through self-consistent simulations using the Rice Convection Model. Specifically, we model the structure and longitudinal/UT dependence of SAPS structures in the duskside ionosphere, and how they may be related to meridional electron density transport postulated to be responsible for large storm-time TEC structuring in the afternoon-to-dusk MLT sector.

  2. Dynamics of midlatitude light ion trough and plasmatails. [from data obtained on OGO-4

    NASA Technical Reports Server (NTRS)

    Chen, A. J.; Grebowsky, J. M.; Taylor, H. A., Jr.

    1973-01-01

    Light ion trough measurements near midnight made by the RF ion mass spectrometer on OGO-4 operating in the high resolution mode in Feb. 1968 reveal the existence of irregular structure on the low latitude side of the midlatitude trough. Using two different relations between the equatorial convection electric field, assumed spatially invariant and directed from dawn to dusk, and Kp (one based on plasmapause measurements, the other on polar cap E field measurements) a model development was made of the outer plasmasphere. The model calculations produced multiple plasmatail extensions of the plasmasphere which compare favorably with the observed irregularities. Due to magnetic local time differences between the Northern and Southern Hemisphere along OGO's orbit, the time dependent irregularity structure observed is not symmetrical about the equator. The model development produces an outer plasmasphere boundary location which varies similarly to the observed minimum density point of the light ion trough. However the measurements are not extensive enough to yield conclusive proof that one of the electric field models is better than the other.

  3. High-latitude proton precipitation and light ion density profiles during the magnetic storm initial phase.

    NASA Technical Reports Server (NTRS)

    Burch, J. L.

    1973-01-01

    Measurements of precipitating protons and light ion densities by experiments on Ogo 4 indicate that widespread proton precipitation occurs in predawn hours during the magnetic storm initial phase from the latitude of the high-latitude ion trough, or plasmapause, up to latitudes greater than 75 deg. A softening of the proton spectrum is apparent as the plasmapause is approached. The separation of the low-latitude precipitation boundaries for 7.3-keV and 23.8-keV protons is less than about 1 deg, compared with a 3.6-deg separation that has been computed by using the formulas of Gendrin and Eather and Carovillano. Consideration of probable proton drift morphology leads to the conclusion that protons are injected in predawn hours, widespread precipitation occurring in the region outside the plasmapause. Protons less energetic than 7 keV drift eastward, whereas the more energetic protons drift westward, producing the observed dawn-dusk asymmetry for the lower-energy protons.

  4. The measurement of cold ion densities in the plasma trough. [in magnetosphere

    NASA Technical Reports Server (NTRS)

    Harris, K. K.

    1974-01-01

    The cold ion density in the plasma trough region is an important fundamental parameter in the currently proposed mechanisms to describe magnetospheric dynamics. Direct in situ measurements of the cold ion density are generally difficult owing to uncertainties in vehicle potentials and ion temperatures. It is shown that the light ion mass spectrometer from Ogo 5 was very successful in acquiring these data and that vehicle potentials appear not to have been a prohibitive factor. The cold ion plasma trough data show a great deal of variability, indicating a strong dependence on the state of the convection electric field; consequently, average values of cold ion densities in the plasma trough may be significantly different from the actual time-dependent values. The local time plot of plasma trough densities at L = 7 for data acquired over a 1-year period shows the anticipated increase in cold ion density during the daytime and the expected decrease in cold ion density during dusk and early nighttime.

  5. Temporal organization of an anuran acoustic community in a Taiwanese subtropical forest

    USGS Publications Warehouse

    Hsu, M.-Y.; Kam, Y.-C.; Fellers, G.M.

    2006-01-01

    We recorded anuran vocalizations in each of four habitats at Lien Hua Chih Field Station, Taiwan, between July 2000 and July 2001. For each 27 biweekly sample, eight recorders taped calls for 1 min out of every 11 between the hours of 17:00 and 07:00. We obtained 11 481 recordings with calls, and identified 21 503 frogs or groups of frogs. These included 20 species, with an average of 10.4??3.5 species calling each night. Some species called year round, others called in the spring and summer, and a third group called only in the fall and winter. The number of species calling and the maximum calling intensity were correlated with both rainfall and air temperature. The nightly pattern of calling varied among species. Most species called continuously throughout the night, whereas some had a peak right after dusk. A few species had different nightly calling patterns in different habitats. Both Rana limnocharis and Rana kuhlii changed their calling pattern in the presence of large choruses of other anuran species. ?? 2006 The Authors.

  6. A statistical study of Pc 1-2 magnetic pulsations in the equatorial magnetosphere. I - Equatorial occurrence distributions. II - Wave properties

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    AMPTE CCE magnetic field data from a period spanning a complete local time revolution of the satellite orbit major axis are used to examine the occurrence distribution of transverse narrowband Pc 1-2 emissions in the equatorial magnetosphere from L = 3.5 to L = 9 at all local times. Three examples are presented to illustrate the properties of events occurring at dawn, noon, and dusk. The early afternoon outer magnetosphere is found to be the dominant site for electromagnetic ion cyclotron wave occurrence. Pc 1-2 exhibited a radial structure with a gap between high- and low-L events. The example intervals indicate that a significant local time variation of wave properties may exist. Distributions are presented of narrowband Pc 1-2 frequency, ellipticity, normalized frequency and spectral power vs local time, L, and magnetic latitude, using the data base of more than 9000 events obtained from AMPTE CCE magnetometer data. Events occurring in the region 0300-0900 MLT, L greater than 7 are distinctly different from the remainder of Pc 1-2. The unique features of this population are linear polarization at all latitudes and high normalized frequency, 0.4 to 0.5 on average.

  7. Solar Wind Effects on Plasma Density Depletions: C/NOFS Results with Related Observations from DMSP

    NASA Astrophysics Data System (ADS)

    Burke, W. J.; Gentile, L. C.; Roddy, P. A.; Retterer, J. M.; Wilson, G. R.; de La Beaujardiere, O.; Su, Y.

    2010-12-01

    Before C/NOFS, the prevailing wisdom was that equatorial plasma bubbles (EPBs) were primarily a post-sunset phenomenon. Changes in the ionosphere after sunset create conditions favorable for instability formation as polarization electric fields increase near the terminator. Plasma irregularities that develop in the bottomside of the F-layer grow into large depletions that rise rapidly into the topside ionosphere. By two hours in local time after sunset the initial upward drift of the ionosphere reverses suppressing further development of instabilities. Tsunoda’s [1985] seasonal-longitudinal model predicted that EPB rates should peak near times when the equatorial declination and the dusk terminator are closely aligned. Under these conditions E-layer conductance vanishes at both ends of flux tubes simultaneously, allowing EPBs to grow most rapidly. We validated this model during the recent solar maximum. In this unusual solar minimum, however, C/NOFS has encountered very few post-sunset depletions. They commonly appear between local midnight and dawn. We trace the energy flow from the Sun to the Earth to demonstrate that C/NOFS measurements are providing key insights into the dynamics of the Ionosphere-Thermosphere system. Results suggest that systematic effects of solar wind / IMF on dynamics of equatorial plasmas and electric fields may allow long-term alerts about impending ionospheric disturbances that lead to scintillation activity. Reference: Tsunoda, R. T. (1985), J. Geophys. Res., 90, 447.

  8. Daily Activity and Nest Occupation Patterns of Fox Squirrels (Sciurus niger) throughout the Year

    PubMed Central

    Wassmer, Thomas; Refinetti, Roberto

    2016-01-01

    The authors investigated the general activity and nest occupation patterns of fox squirrels in a natural setting using temperature-sensitive data loggers that measure activity as changes in the microenvironment of the animal. Data were obtained from 25 distinct preparations, upon 14 unique squirrels, totaling 1385 recording days. The animals were clearly diurnal, with a predominantly unimodal activity pattern, although individual squirrels occasionally exhibited bimodal patterns, particularly in the spring and summer. Even during the short days of winter (9 hours of light), the squirrels typically left the nest after dawn and returned before dusk, spending only about 7 hours out of the nest each day. Although the duration of the daily active phase did not change with the seasons, the squirrels exited the nest earlier in the day when the days became longer in the summer and exited the nest later in the day when the days became shorter in the winter, thus tracking dawn along the seasons. During the few hours spent outside the nest each day, fox squirrels seemed to spend most of the time sitting or lying. These findings suggest that fox squirrels may have adopted a slow life history strategy that involves long periods of rest on trees and short periods of ground activity each day. PMID:26963918

  9. Geotail Measurements Compared with the Motions of High-Latitude Auroral Boundaries during Two Substorms

    NASA Technical Reports Server (NTRS)

    Maynard, N. C.; Burke, W. J.; Erickson, G. M.; Nakamura, M.; Mukai, T.; Kokubun, S.; Yamamoto, T.; Jacobsen, B.; Egeland, A.; Samson, J. C.; Weimer, D. R.; Reeves, G. D.; Luhr, H.

    1997-01-01

    Geotail plasma and field measurements at -95 R(sub E) are compared with extensive ground-based, near-Earth, and geosynchronous measurements to study relationships between auroral activity and magnetotail dynamics during the expansion phases of two substorms. The studied intervals are representative of intermittent, moderate activity. The behavior of the aurora and the observed effects at Geotail for both events are harmonized by the concept of the activation of near-Earth X lines (NEXL) after substorm onsets, with subsequent discharges of one or more plasmoids down the magnetotail. The plasmoids must be viewed as three-dimensional structures which are spatially limited in the dawn-dusk direction. Also, reconnection at the NEXL must proceed at variable rates on closed magnetic field lines for significant times before beginning to reconnect lobe flux. This implies that the plasma sheet in the near-Earth magnetotail is relatively thick in comparison with an embedded current sheet and that both the NEXL and distant X line can be active simultaneously. Until reconnection at the NEXL engages lobe flux, the distant X line maintains control of the poleward auroral boundary. If the NEXL remains active after reaching the lobe, the auroral boundary can move poleward explosively. The dynamics of high-latitude aurora in the midnight region thus provides a means for monitoring these processes and indicating when significant lobe flux reconnects at the NEXL.

  10. Direct observations of the full Dungey convection cycle in the polar ionosphere for southward interplanetary magnetic field conditions

    NASA Astrophysics Data System (ADS)

    Zhang, Q.-H.; Lockwood, M.; Foster, J. C.; Zhang, S.-R.; Zhang, B.-C.; McCrea, I. W.; Moen, J.; Lester, M.; Ruohoniemi, J. M.

    2015-06-01

    Tracking the formation and full evolution of polar cap ionization patches in the polar ionosphere, we directly observe the full Dungey convection cycle for southward interplanetary magnetic field (IMF) conditions. This enables us to study how the Dungey cycle influences the patches' evolution. The patches were initially segmented from the dayside storm enhanced density plume at the equatorward edge of the cusp, by the expansion and contraction of the polar cap boundary due to pulsed dayside magnetopause reconnection, as indicated by in situ Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations. Convection led to the patches entering the polar cap and being transported antisunward, while being continuously monitored by the globally distributed arrays of GPS receivers and Super Dual Auroral Radar Network radars. Changes in convection over time resulted in the patches following a range of trajectories, each of which differed somewhat from the classical twin-cell convection streamlines. Pulsed nightside reconnection, occurring as part of the magnetospheric substorm cycle, modulated the exit of the patches from the polar cap, as confirmed by coordinated observations of the magnetometer at Tromsø and European Incoherent Scatter Tromsø UHF radar. After exiting the polar cap, the patches broke up into a number of plasma blobs and returned sunward in the auroral return flow of the dawn and/or dusk convection cell. The full circulation time was about 3 h.

  11. Gravity wave-induced variability of the middle thermosphere

    NASA Astrophysics Data System (ADS)

    Forbes, Jeffrey M.; Bruinsma, Sean L.; Doornbos, Eelco; Zhang, Xiaoli

    2016-07-01

    Contemporary theory, modeling, and first-principles simulations indicate that dissipation of gravity waves (GW) plays an important role in modifying the mean circulation, thermal structure, and composition of the thermosphere. GW can propagate into the thermosphere from various sources in the lower atmosphere, deposit energy, and momentum into the thermosphere, and thereby modify its mean circulation, thermal structure and composition. However, measurements that verify or constrain predictions of GW propagation well into the thermosphere, especially on a global basis, are extremely limited. In this paper total mass densities and cross-track winds between 230 and 280 km derived from accelerometer measurements on the Gravity Field and Ocean Circulation Earth Explorer (GOCE) satellite between November 2009 and October 2013 are used to reveal the global morphology of horizontal structures between 128 km and 640 km, which are assumed to mainly reflect the presence of GW. The zonal-mean RMS variability at these scales is quantified in terms of seasonal-latitudinal dependences and dawn-dusk differences, which are interpreted in terms of current theoretical and modeling results. Little evidence is found for any longitude variability that can be attributed to specific source regions, except at high latitudes where polar/auroral sources and magnetic control dominate and near the Andes and the Antarctic Peninsula during local winter.

  12. Saw-tooth substorms: inconsistency of repetitive bay-like magnetic disturbances with behavior of aurora

    NASA Astrophysics Data System (ADS)

    Troshichev, Oleg; Stauning, Peter; Liou, Kan; Reeves, Geoffrey

    The relationships between the magnetic disturbances in the auroral zone, aurora dynamics and particles injections at the geostationary orbit have been analyzed in detail for 62 repetitive bay-like magnetic disturbances (sawtooth substorms). It is shown that lack of the auroral breakup is typical of the powerful repetitive bay-like disturbances, unlike the isolated ("classi-cal") magnetospheric substorms. In case of sawtooth substorms the aurora in the oval usually demonstrates high activity well before (up to few hours) the magnetic disturbance onset. One of the distinguishing features of the auroral activity is the double oval structure, which is most noticeable near the dusk meridian. The close relation of the auroral behavior to the parti-cle injections at geostationary orbit breaks down. The conclusion is made, that the powerful repetitive bay-like magnetic disturbances display that kind of disturbance, which is regulated by the ionospheric electric field variations unlike to the isolated ("classical") substorms strongly related to the varying auroral particle precipitation.

  13. Quarter wave field line resonances: variation with latitude

    NASA Astrophysics Data System (ADS)

    Menk, Frederick; Obana, Yuki; Waters, Colin; Sciffer, Murray; Yoshikawa, Akimasa; Yoshikawa, Ichiro; Moldwin, Mark; Mann, Ian; Boteler, David

    When for a particular field line there is a strong asymmetry in conductivity at conjugate ionospheres, quarter wavelength mode eigenoscillations may be sustained instead of the more usual half-wave oscillations. We have studied the latitudinal distribution of such quarter-wave mode standing Alfvén waves. The diurnal variation of the local field line eigenfrequency was examined for L=1.7-5.1 using cross-phase analysis of geomagnetic data from the MEASURE, CANMOS, and CARISMA arrays in North America. The detected eigenfrequencies for L=2-3.1 were remarkably low near the dawn and dusk terminator, when one end of a field line was sunlit and the other end was in darkness. However, the eigenfrequencies for L¡2 and L¿3.1 did not exhibit this extraordinary low frequency trend. These results suggest that quarter-wave modes were localized to the middle latitude region. We will discuss why this occurs and in particular why quarter wave modes were not generated at high latitudes even though the ionospheric conditions were strongly asymmetric there.

  14. Magnetopause shadowing effects on the GEO flux dropout during a very weak magnetic storm: RBE results

    NASA Astrophysics Data System (ADS)

    Hwang, J.; Choi, E.; Park, J.; Kim, K.; Lee, D.; Fok, M. H.; Usanova, M.

    2013-12-01

    We investigate a geosynchronous flux dropout event during a weak storm of which Sym-H minimum value is -37 nT on November 7, 2008. During this event period, two dropouts are observed by GOES observation. Interestingly we found that there is local time dependence by THEMIS SST observation such that the GEO flux dropout starts first from noon-dusk MLT and recovers from midnight-dawn MLT in a few hundreds of keV electrons. This tendency is confirmed with RBE simulation results for both lower and higher energies' electrons; a few hundreds of keV and ~Me V. There is no observed atmospheric precipitation during the first dropout period and there are just negligible atmospheric precipitations during the second dropout by all available NOAA POES satellites' observations. We also check wave activities can provide the indirect proof of the atmospheric precipitation through wave-particle interactions, Chorus wave power from THEMIS exists just only during the second dropout period. EMIC waves do not appear from THEMIS observations while ground observations by CARISMA network show that there are clear EMIC waves during both dropouts. Finally we conclude that the first dropout event is caused by purely magnetopause shadowing effect and the second one might be the result of the combination of magnetopause shadowing and atmospheric precipitation into the earth's atmosphere by wave-particle interaction.

  15. A case study on the GEO flux dropout during a weak geomagnetic storm of November 7, 2008: RBE results

    NASA Astrophysics Data System (ADS)

    Hwang, Junga; Choi, Enjin; Park, Jong-Sun; Kim, Kyung-Chan; Lee, Dae-Young; Fok, Mei-Ching; Usanova, Maria

    2014-05-01

    We investigate a geosynchronous flux dropout event during a weak storm of which Sym-H minimum value is -37 nT on November 7, 2008. During this event period, two dropouts are observed by GOES observation. Interestingly we found that there is local time dependence by THEMIS SST observation such that the GEO flux dropout starts first from noon-dusk MLT and recovers from midnight-dawn MLT in a few hundreds of keV electrons. This tendency is confirmed with RBE simulation results for both lower and higher energies' electrons; a few hundreds of keV and ~Me V. There is no observed atmospheric precipitation during the first dropout period and there are just negligible atmospheric precipitations during the second dropout by all available NOAA POES satellites' observations. We also check wave activities can provide the indirect proof of the atmospheric precipitation through wave-particle interactions, Chorus wave power from THEMIS exists just only during the second dropout period. EMIC waves do not appear from THEMIS observations while ground observations by CARISMA network show that there are clear EMIC waves during both dropouts. Finally we conclude that the first dropout event is caused by purely magnetopause shadowing effect and the second one might be the result of the combination of magnetopause shadowing and atmospheric precipitation into the earth's atmosphere by wave-particle interaction.

  16. Empirical ground-based characterization of ULF wave power: Towards a ULF wave index

    NASA Astrophysics Data System (ADS)

    Rae, Jonathan; Pahud, Danielle; Amalraj, Valantina; Mann, Ian; Murphy, Kyle

    Ultra-Low Frequency (ULF) waves are believed to play an important role in the dynamics of the outer radiation belt electrons following geomagnetic storms. The energisation mechanism is thought to be the adiabatic radial transport of electrons inward into regions of higher magnetic field strength, through violation of the third invariant. This transport is generally thought to be diffusive in nature and can be characterised by a diffusion coefficient which is dependent on the ULF wave power. The CARISMA magnetometer network (www.carisma.ca) has been in operation since 1986 and thus has an uninterrupted database of ground magnetic observations throughout nearly two solar cycles. Using this database, we present a statistical characterisation of Pc5 ULF power as a function of magnetic local time (MLT), and solar wind speed. We examine the power across L-shells spanning the outer radiation belts between 4.2 and 7.9, using data from the "Churchill Line" stations. We demonstrate the solar wind speed dependence of Pc5 ULF wave power as a function of MLT and L-shell. It is suggested that the dawn-dusk asymmetry of ULF waves observed on the ground is determined by the Parker spiral angle. We address the statistical dependence of ULF wave power as a function of IMF angle. Finally, we present results of median ULF wave power during CIR and CME storms in order to address the solar wind drivers potentially responsible for ULF-wave driven radial diffusion of radiation belt electrons.

  17. Statistical study on the characterization of ULF Pulsations in the Inner Magnetosphere by THEMIS

    NASA Astrophysics Data System (ADS)

    Liu, W.; Sarris, T.; Liu, X.; Elkington, S. R.; Ergun, R.; Kabin, K.; Rankin, R.; Angelopoulos, V.; Bonnell, J.; Glassmeier, K.; Auster, U.

    2008-12-01

    ULF pulsations (2~25 mHz) have significant influence on the transport of energetic particles trapped in the outer radiation belt, which have drift frequencies comparable to this range. However recent studies indicate that not all classes of ULF waves are equally important for radiation belt electron acceleration. For example, simulations suggest that electrons could be adiabatically accelerated through a drift-resonance interaction with either azimuthal (toroidal) mode or radial (poloidal) mode ULF waves. THEMIS electric field observations provide a good opportunity to study and fully characterize the features of the ULF pulsations in the inner magnetosphere. The ULF polarization study by Sarris et al [2008] focuses on the observations made by one THEMIS probe during its out-bound pass on September 4th, 2007. Here we will present the statistical studies of the polarizations of ULF pulsations, based on the spin-fit electric and magnetic field data from July 2007 to June 2008, with full local time coverage. Through this global coverage, ULF polarizations are characterized at different regions, in terms of radial distance and local times. Preliminary analysis indicates that the polarizations of electric field pulsation are more radial in dawn/dusk sectors and more azimuthal in noon/midnight sectors.

  18. Nighttime foraging by deep diving echolocating odontocetes off the Hawaiian islands of Kauai and Ni'ihau as determined by passive acoustic monitors.

    PubMed

    Au, Whitlow W L; Giorli, Giacomo; Chen, Jessica; Copeland, Adrienne; Lammers, Marc; Richlen, Michael; Jarvis, Susan; Morrissey, Ronald; Moretti, David; Klinck, Holger

    2013-05-01

    Remote autonomous ecological acoustic recorders (EARs) were deployed in deep waters at five locations around the island of Kauai and one in waters off Ni'ihau in the main Hawaiian island chain. The EARs were moored to the bottom at depths between 400 and 800 m. The data acquisition sampling rate was 80 kHz and acoustic signals were recorded for 30 s every 5 min to conserve battery power and disk space. The acoustic data were analyzed with the M3R (Marine Mammal Monitoring on Navy Ranges) software, an energy-ratio-mapping algorithm developed at Oregon State University and custom MATLAB programs. A variety of deep diving odontocetes, including pilot whales, Risso's dolphins, sperm whales, spinner and pan-tropical spotted dolphins, and beaked whales were detected at all sites. Foraging activity typically began to increase after dusk, peaked in the middle of the night and began to decrease toward dawn. Between 70% and 84% of biosonar clicks were detected at night. At present it is not clear why some of the known deep diving species, such as sperm whales and beaked whales, concentrate their foraging efforts at night. PMID:23654414

  19. Jupiter's deep magnetotail boundary layer

    NASA Astrophysics Data System (ADS)

    Nicolaou, G.; McComas, D. J.; Bagenal, F.; Elliott, H. A.; Ebert, R. W.

    2015-06-01

    In 2007 the New Horizons (NH) spacecraft flew by Jupiter for a gravity assist en route to Pluto. After closest approach on day of year (DOY) 58, 2007, NH followed a tailward trajectory that provided a unique opportunity to explore the deep jovian magnetotail and the surrounding magnetosheath. After DOY 132, 16 magnetopause crossings were observed between 1654 and 2429 Jupiter radii (Rj) along the dusk flank tailward of the planet. In some cases the crossings were identified as rapid transitions from the magnetotail to the magnetosheath and vice versa. In other cases a boundary layer was observed just inside the magnetopause. Solar Wind Around Pluto (SWAP) is an instrument on board NH that obtained spectra of low energy ions during the flyby period. We use a forward model including the SWAP instrument response to derive plasma parameters (density, temperature and velocity) which best reproduce the observations. We also vary the plasma parameters in our model in order to fit the observations more accurately on occasions where the measurements exhibit significant variability. We compare the properties of the plasma in the boundary layer with those of the magnetosheath plasma derived in our earlier work. We attempt to estimate the magnetic field in the boundary layer assuming pressure balance between it and the magnetosheath. Finally, we investigate several possible scenarios to assess if magnetopause movement and structure could cause the variations seen in the data.

  20. Japanese Magsat Team. A: Crustal structure near Japan and its Antarctic Station. B: Electric currents and hydromagnetic waves in the ionosphere and the magnetosphere

    NASA Technical Reports Server (NTRS)

    Fukushima, N.; Maeda, H.; Yukutake, T.; Tanaka, M.; Oshima, S.; Ogawa, K.; Kawamura, M.; Miyzaki, Y.; Uyeda, S.; Kobayashi, K. (Principal Investigator)

    1981-01-01

    Efforts continue in compiling tapes which contain vector and scalar data decimated at an interval of 0.5 sec, together with time and position data. A map of the total force field anomaly around Japan was developed which shows a negative magnetic anomaly in the Okhotsk Sea. Examination of vector residuals from the MGST model shows that the total force perturbation is almost ascribable to the perturbation parallel to the main geomagnetic field and that the contribution from the perturbation transverse to the main field to the total force perturbation is negligibly small. The influences of ionospheric current with equatorial electroject and of the magnetospheric field aligned current on the dawn-dusk asymmetry of daily geomagnetic variations are being considered. The total amount of electric current flowing through the plane of the Magsat orbit loop was calculated by direct application of Maxwell's equation. Results show that the total electric current is 1 to 5 ampheres, and the current direction is either sunward or antisunward.

  1. Ka Band Objects: Observation and Monitoring (KaBOOM)

    NASA Astrophysics Data System (ADS)

    Geldzahler, B.

    2012-09-01

    NASA has embarked on a path that will enable the implementation of a high power, high resolution X/Ka band radar system using widely spaced 12m antennas to better track and characterize near Earth objects and orbital debris. This radar system also has applications for cost effective space situational awareness. We shall demonstrate Ka band coherent uplink arraying with real-time atmospheric compensation using three 12m antennas at the Kennedy Space Center (KSC). Our proposed radar system can complement and supplement the activities of the Space Fence. The proposed radar array has the advantages of filling the gap between dusk and dawn and offers the possibility of high range resolution (4 cm) and high spatial resolution (?10 cm at GEO) when used in a VLBI mode. KSC was chosen because [a] of reduced implementation costs, [b] there is a lot of water vapor in the air (not Ka band friendly), and [c] the test satellites have a low elevation adding more attenuation and turbulence to the demonstration. If Ka band coherent uplink arraying can be made to work at KSC, it will work anywhere. We expect to rebaseline X-band in 2013, and demonstrate Ka band uplink arraying in 2014.

  2. Domestication effects on behavioural synchronization and individual distances in chickens (Gallus gallus).

    PubMed

    Eklund, Beatrix; Jensen, Per

    2011-02-01

    Behavioural synchrony (allelomimetic behaviour), and inter-individual distances are aspects of social and anti-predator strategies which may have been affected by domestication. Chickens are known to adjust synchronization and inter-individual distances depending on behaviour. We hypothesized that White Leghorn (WL) chickens would show less synchronized behaviour than the ancestor, the red jungle fowl (RJF). Sixty birds, 15 female and 15 male WL and the same number of RJF (28 weeks old) were studied in groups of three in furnished pens (1 m×2 m) for 24 consecutive hours per group, following 24 h of habituation. Video tapes covering 4 h per group (dawn, 9-10 am, 1-2 pm and dusk) were analysed. Red junglefowl perched significantly more, but there were no breed effects on the frequency or daily rhythm of any other activities, or on average inter-individual distances. Red junglefowl were more synchronized during perching and a tendency for the same was found for social behaviour. After performance of the two most synchronized behaviours, perching and comfort behaviour, individual distance increased more for RJF than WL. According to this study domestication of chickens appears not to have significantly altered the relative frequencies of different activities or average inter-individual distances, but have caused some changes in behavioural synchronization and maintenance of activity-specific inter-individual distances in chickens. The changes may indicate an adaptive response to captivity and domestication. PMID:21187131

  3. Efficacy of light-traps in sampling malaria vectors in different ecological zones in central India.

    PubMed

    Singh, N; Mishra, A K

    1997-03-01

    This preliminary field study was designed chiefly to test the efficiency of the light-trap as a tool for sampling malaria vectors, in tribal villages located in different ecological settings in comparison with indoor resting collections as an alternative method. Anopheles culicifacies, a known malaria vector, was the most prevalent species in the study villages and more than 80% of trap catches were obtained before midnight with peak activity during dusk. Reproductive status of trapped specimens revealed proportional representations of unfed, freshly fed, and gravid females. Another vector, An. fluviatilis was found in small numbers by both the methods. Thus the trap could give a reliable and unbiased sample of vector population. Seven species were abundant in the light-trap catches while only four in the indoor resting collections indicates the usefulness of the light-trap for sampling exophilic species. The study revealed that light-traps did not have any bias in favor of any particular species. The method may be useful for assessing the night time densities of different species or the fluctuation of a species at different dates and village to village variations. Light-traps could be used for sampling both endophilic and exophilic anophelines. PMID:9322305

  4. PCH1 integrates circadian and light-signaling pathways to control photoperiod-responsive growth in Arabidopsis

    PubMed Central

    Huang, He; Yoo, Chan Yul; Bindbeutel, Rebecca; Goldsworthy, Jessica; Tielking, Allison; Alvarez, Sophie; Naldrett, Michael J; Evans, Bradley S; Chen, Meng; Nusinow, Dmitri A

    2016-01-01

    Plants react to seasonal change in day length through altering physiology and development. Factors that function to harmonize growth with photoperiod are poorly understood. Here we characterize a new protein that associates with both circadian clock and photoreceptor components, named PHOTOPERIODIC CONTROL OF HYPOCOTYL1 (PCH1). pch1 seedlings have overly elongated hypocotyls specifically under short days while constitutive expression of PCH1 shortens hypocotyls independent of day length. PCH1 peaks at dusk, binds phytochrome B (phyB) in a red light-dependent manner, and co-localizes with phyB into photobodies. PCH1 is necessary and sufficient to promote the biogenesis of large photobodies to maintain an active phyB pool after light exposure, potentiating red-light signaling and prolonging memory of prior illumination. Manipulating PCH1 alters PHYTOCHROME INTERACTING FACTOR 4 levels and regulates light-responsive gene expression. Thus, PCH1 is a new factor that regulates photoperiod-responsive growth by integrating the clock with light perception pathways through modulating daily phyB-signaling. DOI: http://dx.doi.org/10.7554/eLife.13292.001 PMID:26839287

  5. Solar wind - magnetosphere coupling efficiency during ejecta and sheath region driven geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Myllys, Minna; Kilpua, Emilia; Lavraud, Benoit

    2016-04-01

    We have investigated the effect of key solar wind driving parameters on solar wind- magnetosphere coupling efficiency during sheath and magnetic cloud driven storms. The particular focus of the study was on the coupling efficiency dependence with Alfven Mach number (MA). The efficiency has been estimated using the dawn-dusk component of the interplanetary electric field (EY), Newell and Borovsky functions as a proxy for the energy inflow and the polar cap potential (PCN), auroral electrojet (AE) and SYM-H indices as the measure of the energy output. We have also performed a time delay analysis between the input parameters and the geomagnetic indices. We demonstrate that the PCN index distinctively shows both a MA dependent saturation and a MA-independent saturation, pointing to the existence of at least two underlying physical mechanisms for the saturation of the index. By contrast, we show that the AE index saturates, but that the saturation of this index is independent of the solar wind MA. Finally we find that the SYM-H index does not seem to saturate and that the absence of saturation is independent of the MA regime.

  6. Comparison of Polar Cap (PC) index calculations.

    NASA Astrophysics Data System (ADS)

    Stauning, P.

    2012-04-01

    The Polar Cap (PC) index introduced by Troshichev and Andrezen (1985) is derived from polar magnetic variations and is mainly a measure of the intensity of the transpolar ionospheric currents. These currents relate to the polar cap antisunward ionospheric plasma convection driven by the dawn-dusk electric field, which in turn is generated by the interaction of the solar wind with the Earth's magnetosphere. Coefficients to calculate PCN and PCS index values from polar magnetic variations recorded at Thule and Vostok, respectively, have been derived by several different procedures in the past. The first published set of coefficients for Thule was derived by Vennerstrøm, 1991 and is still in use for calculations of PCN index values by DTU Space. Errors in the program used to calculate index values were corrected in 1999 and again in 2001. In 2005 DMI adopted a unified procedure proposed by Troshichev for calculations of the PCN index. Thus there exists 4 different series of PCN index values. Similarly, at AARI three different sets of coefficients have been used to calculate PCS indices in the past. The presentation discusses the principal differences between the various PC index procedures and provides comparisons between index values derived from the same magnetic data sets using the different procedures. Examples from published papers are examined to illustrate the differences.

  7. The Polar Cap index: A critical review of methods and a new approach

    NASA Astrophysics Data System (ADS)

    Stauning, Peter

    2013-08-01

    The Polar Cap (PC) index introduced by Troshichev and Andrezen (1985) is derived from polar magnetic variations and is mainly a measure of the intensity of the transpolar ionospheric currents. These currents relate to the polar cap antisunward ionospheric plasma convection driven by the dawn-dusk electric fields, which in turn are generated by the interaction of the solar wind with the Earth's magnetosphere. Coefficients to calculate PCN and PCS index values from polar magnetic variations recorded at Thule and Vostok, respectively, have been derived by several different procedures in the past. The PCN index is found in seven different versions while the PCS index is found in five different versions in past publications. Recent publications (in 2011 and 2012) still convey three different PCN and two different PCS indices. The presentation here discusses the principal differences between the various PC index procedures and provides comparisons between coefficient and index values derived using the different procedures. Finally, a new approach to define a simplified PC index procedure is outlined.

  8. The Polar Cap (PC) index. A critical review of methods and a new approach.

    NASA Astrophysics Data System (ADS)

    Stauning, Peter

    2013-04-01

    The Polar Cap (PC) index introduced by Troshichev and Andrezen (1985) is derived from polar magnetic variations and is mainly a measure of the intensity of the transpolar ionospheric currents. These currents relate to the polar cap antisunward ionospheric plasma convection driven by the dawn-dusk electric field, which in turn is generated by the interaction of the solar wind with the Earth's magnetosphere. Coefficients to calculate PCN and PCS index values from polar magnetic variations recorded at Thule and Vostok, respectively, have been derived by several different procedures in the past. Approval of a final PC index procedure is pending at the International Association for Geomagnetism and Aeronomy (IAGA) for a decision possibly at the General Assembly in 2013. The presentation discusses the principal differences between the various PC index procedures and provides comparisons between coefficient and index values derived using the different procedures. It will be demonstrated that depending on the procedure, PC index values derived in the past, and used in many publications, may differ substantially although the same basic geomagnetic data were used. Finally, a new approach to define a unified PC index procedure, built from the best elements of the three different current versions, is outlined.

  9. THE NEAR VICINITY OF THE BLACK HOLE AT THE CORE OF GALAXY NGC 4261 - ARTIST CONCEPT

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This is an illustration of how the night sky might look to a dweller in the core of galaxy NGC 4261, which harbors an 800-light-year-wide disk of dust and 1.2 billion-solar-mass black hole. This imaginary view is from a hypothetical planet inside the dust dusk, looking toward the black hole. The black hole's white-hot glow from super-heated gas is reddened by intervening dust. A 'lighthouse beam' from the hot accretion disk around the black hole, along with invisible radio jets, radiates above and below the hole at right angles to the dark dust disk encircling the hole. This dark, dusty disk bisects the sky, blocking out light from the star behind it, and reddening starlight traveling near it by optical scattering - much in the same way the sunlight turns red at sunset by scatter from dust in our atmosphere. The imaginary planet, and surrounding stars, are destined to be swallowed by the black hole, and material in the disk spirals into its gravitational abyss. Illustration by J. Gitlin (Space Telescope Science Institute)

  10. Low-level water vapor fields from the VAS split-window channels at 11 and 12 microns

    NASA Technical Reports Server (NTRS)

    Chesters, D.; Uccellini, L. W.; Robinson, W.

    1983-01-01

    Originally, the VAS split window channels were designed to use the differential water vapor absorption between 11 and 12 microns to estimate sea surface temperature by correcting for the radiometric losses caused by atmospheric moisture. It is shown that it is possible to reverse the procedure in order to estimate the vertically integrated low level moisture content with the background surface (skin) temperature removed, even over the bright, complex background of the land. Because the lower troposphere's water vapor content is an important factor in convective instability, the derived fields are of considerable value to mesoscale meteorology. Moisture patterns are available as quantitative fields (centimeters of precipitable water) at full VAS resolution (as fine as 7 kilometers horizontal resolution every 15 minutes), and are readily converted to image format for false color movies. The technique, demonstrated with GOES-5, uses a sequence of split window radiances taken once every 3 hours from dawn to dusk over the Eastern and Central United States. The algorithm is calibrated with the morning radiosonde sites embedded within the first VAS radiance field; then, entire moisture fields are calculated at all five observation times. Cloud contamination is removed by rejecting any pixel having a radiance less than the atmospheric brightness determined at the radiosonde sites.

  11. Photic and pineal modulation of food anticipatory circadian activity rhythms in rodents.

    PubMed

    Patton, Danica F; Parfyonov, Maksim; Gourmelen, Sylviane; Opiol, Hanna; Pavlovski, Ilya; Marchant, Elliott G; Challet, Etienne; Mistlberger, Ralph E

    2013-01-01

    Restricted daily feeding schedules entrain circadian oscillators that generate food anticipatory activity (FAA) rhythms in nocturnal rodents. The location of food-entrainable oscillators (FEOs) necessary for FAA remains uncertain. The most common procedure for inducing circadian FAA is to limit food access to a few hours in the middle of the light period, when activity levels are normally low. Although light at night suppresses activity (negative masking) in nocturnal rodents, it does not prevent the expression of daytime FAA. Nonetheless, light could reduce the duration or magnitude of FAA. If so, then neural or genetic ablations designed to identify components of the food-entrainable circadian system could alter the expression of FAA by affecting behavioral responses to light. To assess the plausibility of light as a potential mediating variable in studies of FAA mechanisms, we quantified FAA in rats and mice alternately maintained in a standard full photoperiod (12h of light/day) and in a skeleton photoperiod (two 60 min light pulses simulating dawn and dusk). In both species, FAA was significantly and reversibly enhanced in the skeleton photoperiod compared to the full photoperiod. In a third experiment, FAA was found to be significantly attenuated in rats by pinealectomy, a procedure that has been reported to enhance some effects of light on behavioral circadian rhythms. These results indicate that procedures affecting behavioral responses to light can significantly alter the magnitude of food anticipatory rhythms in rodents.

  12. Fourier analysis of polar cap electric field and current distributions

    NASA Technical Reports Server (NTRS)

    Barbosa, D. D.

    1984-01-01

    A theoretical study of high-latitude electric fields and currents, using analytic Fourier analysis methods, is conducted. A two-dimensional planar model of the ionosphere with an enhanced conductivity auroral belt and field-aligned currents at the edges is employed. Two separate topics are treated. A field-aligned current element near the cusp region of the polar cap is included to investigate the modifications to the convection pattern by the east-west component of the interplanetary magnetic field. It is shown that a sizable one-cell structure is induced near the cusp which diverts equipotential contours to the dawnside or duskside, depending on the sign of the cusp current. This produces characteristic dawn-dusk asymmetries to the electric field that have been previously observed over the polar cap. The second topic is concerned with the electric field configuration obtained in the limit of perfect shielding, where the field is totally excluded equatorward of the auroral oval. When realistic field-aligned current distributions are used, the result is to produce severely distorted, crescent-shaped equipotential contours over the cap. Exact, analytic formulae applicable to this case are also provided.

  13. Pollination ecology of Agave macroacantha (Agavaceae) in a Mexican tropical desert. I. Floral biology and pollination mechanisms.

    PubMed

    Arizaga, S; Ezcurra, E; Peters, E; de Arellano, F R; Vega, E

    2000-07-01

    In a study of sexual reproduction in long-lived semelparous plants, we observed Agave macroacantha in the tropical desert of Tehuacán-Cuicatlán, Mexico, describing duration of flowering, flower phenology, and nectar production patterns. We also performed two manipulative experiments evaluating (a) the seed production efficiency of different crossing systems (selfing, cross-pollination, apomixis, and control), and (b) the effect of different pollinators (diurnal exposure to pollinators, nocturnal exposure, exclusion, and control) on the seeds produced. Flowering occurred from early May to late July and had a mean duration of 29 days in the individual rosettes. The flowers were protandrous; anthesis occurred in the afternoon of the third day after floral opening, and the pistils matured in the afternoon of the fifth day. The stigmas remained receptive from dusk to the following morning. Pollination was mostly allogamous. Nectar was produced principally during the night, from the first stages of floral aperture until the stigmas wilted and flowering ceased. The flowers were visited during the day by hymenoptera, butterflies, and hummingbirds and during the night by bats and moths. Only the nocturnal visitors, however, were successful pollinators. Agave macroacantha is extremely dependent on nocturnal pollinators for its reproductive success.

  14. Plasma structuring in the polar cap

    SciTech Connect

    Basu, S.; Basu, S.; Weber, E.J.; Bishop, G.J.

    1990-01-01

    Propagation experiments providing scintillation, total electron content and drift data in the field of view of an all-sky imager near the magnetic polar in Greenland are utilized to investigate the manner in which ionospheric plasma becomes structured within the polar cap. It is found that under IMF Bz southward conditions, large scale ionization patches which are convected through the dayside cusp into the polar cap get continually structured. The structuring occurs through the ExB gradient drift instability process which operates through an interaction between the antisunward plasma convection in the neutral rest frame and large scale plasma density gradients that exist at the edges of the ionization patches. It is shown that with the increase of solar activity the strength of the irregularities integrated through the ionosphere is greatly increased. Under the IMF Bz northward conditions, the plasma structuring occurs around the polar cap arcs in the presence of inhomogeneous electric field or disordered plasma convection. In that case, the irregularity generation is caused by the competing processes of non-linear Kelvin-Helmholtz instability driven by sheared plasma flows and the gradient drift instability process which operates in the presence of dawn-dusk motion of arc structures. The integrated strength of this class of irregularities also exhibits marked increase with increasing solar activity presumably because the ambient plasma density over the polar cap is enhanced.

  15. Local time variations of high-energy plasmaspheric ion pitch angle distributions

    DOE PAGES

    Sarno-Smith, Lois K.; Liemohn, Michael W.; Skoug, Ruth M.; Larsen, Brian Arthur; Moldwin, Mark B.; Katus, Roxanne M.; Wygant, John R.

    2016-07-05

    Recent observations from the Van Allen Probes Helium Oxygen Proton Electron (HOPE) instrument revealed a persistent depletion in the 1–10 eV ion population in the postmidnight sector during quiet times in the 2 < L < 3 region. This study explores the source of this ion depletion by developing an algorithm to classify 26 months of pitch angle distributions measured by the HOPE instrument. We correct the HOPE low energy fluxes for spacecraft potential using measurements from the Electric Field and Waves (EFW) instrument. A high percentage of low count pitch angle distributions is found in the postmidnight sector coupledmore » with a low percentage of ion distributions peaked perpendicular to the field line. A peak in loss cone distributions in the dusk sector is also observed. Here, these results characterize the nature of the dearth of the near 90° pitch angle 1–10 eV ion population in the near-Earth postmidnight sector. This study also shows, for the first time, low-energy HOPE differential number fluxes corrected for spacecraft potential and 1–10 eV H+ fluxes at different levels of geomagnetic activity.« less

  16. Flower color-flower scent associations in polymorphic Hesperis matronalis (Brassicaceae).

    PubMed

    Majetic, Cassie J; Raguso, Robert A; Tonsor, Stephen J; Ashman, Tia-Lynn

    2007-03-01

    Floral scent emission rate and composition of purple and white flower color morphs of Hesperis matronalis (Brassicaceae) were determined for two populations and, for each, at two times of day using dynamic headspace collection and GC-MS. The floral volatile compounds identified for this species fell into two main categories, terpenoids and aromatics. Principal component analysis of 30 compounds demonstrated that both color morphs emitted more scent at dusk than at dawn. Color morphs varied in chemical composition of scent, but this differed between populations. The white morphs exhibited significant differences between populations, while the purple morphs did not. In the white morphs, one population contains color-scent associations that match expectations from classical pollination syndrome theory, where the flowers have aromatic scents, which are expected to maximize night-flying moth pollinator attraction; in the second population, white morphs were strongly associated with terpenoid compounds. The potential impact that pollinators, conserved biosynthetic pathways, and the genetics of small colonizing populations may have in determining population-specific associations between floral color and floral scent are discussed.

  17. The mouse liver displays daily rhythms in the metabolism of phospholipids and in the activity of lipid synthesizing enzymes.

    PubMed

    Gorné, Lucas D; Acosta-Rodríguez, Victoria A; Pasquaré, Susana J; Salvador, Gabriela A; Giusto, Norma M; Guido, Mario Eduardo

    2015-02-01

    The circadian system involves central and peripheral oscillators regulating temporally biochemical processes including lipid metabolism; their disruption leads to severe metabolic diseases (obesity, diabetes, etc). Here, we investigated the temporal regulation of glycerophospholipid (GPL) synthesis in mouse liver, a well-known peripheral oscillator. Mice were synchronized to a 12:12 h light-dark (LD) cycle and then released to constant darkness with food ad libitum. Livers collected at different times exhibited a daily rhythmicity in some individual GPL content with highest levels during the subjective day. The activity of GPL-synthesizing/remodeling enzymes: phosphatidate phosphohydrolase 1 (PAP-1/lipin) and lysophospholipid acyltransferases (LPLATs) also displayed significant variations, with higher levels during the subjective day and at dusk. We evaluated the temporal regulation of expression and activity of phosphatidylcholine (PC) synthesizing enzymes. PC is mainly synthesized through the Kennedy pathway with Choline Kinase (ChoK) as a key regulatory enzyme or through the phosphatidylethanolamine (PE) N-methyltransferase (PEMT) pathway. The PC/PE content ratio exhibited a daily variation with lowest levels at night, while ChoKα and PEMT mRNA expression displayed maximal levels at nocturnal phases. Our results demonstrate that mouse liver GPL metabolism oscillates rhythmically with a precise temporal control in the expression and/or activity of specific enzymes.

  18. Effects of Ontogeny, Diel Rhythms, and Environmental Variation on the Adrenocortical Physiology of Semialtricial Black Kites (Milvus migrans).

    PubMed

    López-Jiménez, Lidia; Blas, Julio; Tanferna, Alessandro; Cabezas, Sonia; Marchant, Tracy; Hiraldo, Fernando; Sergio, Fabrizio

    2016-01-01

    We examined whether hypothalamic-pituitary-adrenal axis activity in the nestlings of a semialtricial raptor, the black kite (Milvus migrans), varied with advancing age, throughout the day, and in response to a number of socioecological factors presumed to affect allostatic load. Both baseline corticosterone (CORT) titers and maximum CORT levels during 30 min of handling and restraint augmented across all sampled ages, suggesting that nestlings' energetic demands and capacity to respond to perturbations increase progressively throughout development. CORT secretion also peaked in the early morning, reached minimum levels in the central hours of the day, and increased again before dusk, suggesting a possible role of CORT in the regulation of activity-inactivity patterns. Finally, nestlings raised in a year of low marsh inundation, implying lower food availability and heightened allostatic loads, exhibited higher adrenocortical responsiveness to stress than nestlings raised in years of intermediate or high flooding. The nondetectable effect of other socioecological variables, such as territory quality, temperature, or brood order, suggests that parents may be able to buffer their nestlings from adverse environmental conditions or that the effect of such factors may have been obscured by selective mortality operating before sampling. We propose that future studies increase the simultaneous use of complementary techniques (fecal sampling, feather analysis) to reach firmer and more comprehensive conclusions, especially for planning the management and conservation of sensitive species. PMID:27153131

  19. Storytelling and Science Under the Stars

    NASA Astrophysics Data System (ADS)

    Haggard, Daryl

    2013-01-01

    This summer the Aspen Center for Physics and the Aspen Science Center collaborated with a small team of astrophysicists to host a joint stargazing, storytelling, ask an astronomer, and ice cream social event. The team consisted of staff members from the ACP and the ASC, four visting professional astrophysicists, and professional storytellers from the international organization "Spellbinders" (including the two founders). The event kicked off with liquid nitrogen ice cream making, which was a big hit with the more than 150 people in attendance. At dusk we divided into 4 groups and teams of two (a Spellbinder and an astrophysicist) circulated from group to group telling stories about the sky from all over the world, and answering questions about planets, stars, galaxies, and black holes. Three small telescopes focused on Saturn and lines formed after it finally got dark. I'll discuss how we put this event together, why it is important to join science and culture in order to engage the public, and how fantastic the stars are for creating this union.

  20. Infectious Disease and Grouping Patterns in Mule Deer.

    PubMed

    Mejía Salazar, María Fernanda; Waldner, Cheryl; Stookey, Joseph; Bollinger, Trent K

    2016-01-01

    Infectious disease dynamics are determined, to a great extent, by the social structure of the host. We evaluated sociality, or the tendency to form groups, in Rocky Mountain mule deer (Odocoileus hemionus hemionus) from a chronic wasting disease (CWD) endemic area in Saskatchewan, Canada, to better understand factors that may affect disease transmission. Using group size data collected on 365 radio-collared mule deer (2008-2013), we built a generalized linear mixed model (GLMM) to evaluate whether factors such as CWD status, season, habitat and time of day, predicted group occurrence. Then, we built another GLMM to determine factors associated with group size. Finally, we used 3 measures of group size (typical, mean and median group sizes) to quantify levels of sociality. We found that mule deer showing clinical signs of CWD were less likely to be reported in groups than clinically healthy deer after accounting for time of day, habitat, and month of observation. Mule deer groups were much more likely to occur in February and March than in July. Mixed-sex groups in early gestation were larger than any other group type in any season. Groups were largest and most likely to occur at dawn and dusk, and in open habitats, such as cropland. We discuss the implication of these results with respect to sociobiology and CWD transmission dynamics. PMID:27007808

  1. First joint in situ and global observations of the medium-energy oxygen and hydrogen in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Valek, P. W.; Goldstein, J.; Jahn, J.-M.; McComas, D. J.; Spence, H. E.

    2015-09-01

    We present the first simultaneous observations of the in situ ions and global Energetic Neutral Atom (ENA) images of the composition-separated, medium-energy (~1-50 keV) particle populations of the inner magnetosphere. The ENA emissions are mapped into L shell/magnetic local time space based on the exospheric density along the line of sight (LOS). The ENA measurement can then be scaled to determine an average ion flux along a given LOS. The in situ ion flux tends to be larger than the scaled ENAs at the same local time. This indicates that the ion population is more concentrated in the Van Allen Probes orbital plane than distributed along the Two Wide-angle Imaging Neutral-atom Spectrometers LOS. For the large storm of 14 November 2012, we observe that the concentration of O (in situ ions and ENAs) increases during the storm's main phase with a relatively larger increase than H. The ratio of the O+/H+ can be measured both from the in situ observations and from the ENA images. During the main phase, this O+/H+ increase is initially seen near midnight, but when the storm reaches its peak value the O+/H+ ratio increases across all local times, with the largest at dusk and dawn.

  2. Energetic Neutral Atom Imaging with the POLAR CEPPAD/ IPS Instrument : Initial Forward Modeling Results

    NASA Technical Reports Server (NTRS)

    Henderson, M. G.; Reeves, G. D.; Moore, K. R.; Spence, H. E.; Jorgensen, A. M.; Fennell, J. F.; Blake, J. B.; Roelof, E. C.

    1999-01-01

    Although the primary function of the CEPPAD/IPS instrument on Polar is the measurement of energetic ions in-situ, it has also proven to be a very capable Energetic Neutral Atom (ENA) imager. Raw ENA images are currently being constructed on a routine basis with a temporal resolution of minutes during both active and quiet times. However, while analyses of these images by themselves provide much information on the spatial distribution and dynamics of the energetic ion population in the ring current. detailed modeling is required to extract the actual ion distributions. In this paper. we present the initial results of forward modeling an IPS ENA image obtained during a small geo-magnetic storm on June 9, 1997. The equatorial ion distribution inferred with this technique reproduces the expected large noon/midnight and dawn/dusk asymmetries. The limitations of the model are discussed and a number of modifications to the basic forward modeling technique are proposed which should significantly improve its performance in future studies.

  3. Energetic Neutral Atom Imaging at Low Altitudes from the Swedish Microsatellite Astrid: Extraction of the Equatorial Ion Distribution. Paper 2

    NASA Technical Reports Server (NTRS)

    Brandt, Pontus C:son; Barabash, Stas; Roelof, Edmond C.; Chase, Christopher J.

    1999-01-01

    Energetic neutral atom (ENA) images obtained by the ENA imager on- board the Astrid satellite in the polar cap at 1000 km during a moderate magnetic storm (Dst greater than or equal to 80 nT) on 8 February 1995 are simulated using a parameterized model of the equatorial ion distribution and a six-component Chamberlain exo-sphere with parameters from the MSISE-90 model. By changing the ion parameters until a matching ENA image is obtained one can extract the equatorial ion distribution. Four consecutive images from different view points several of minutes apart are simulated assuming H(+) and O(+), respectively, as parent ions. The optimal set of parameters is extracted by minimizing the chi(exp 2) difference between simulated and observed ENA image using Powell's minimization algorithm. The optimal equatorial model ion distribution consists of O(+) peaked in around dusk. The lower intensity of fluxes obtained from vantage points closer to the pole is an effect of the loss cone of the parent ion distribution being empty.

  4. First In-Orbit Experience of TerraSAR-X Flight Dynamics Operations

    NASA Technical Reports Server (NTRS)

    Kahle, R.; Kazeminejad, B.; Kirschner, M.; Yoon, Y.; Kiehling, R.; D'Amico, S.

    2007-01-01

    TerraSAR-X is an advanced synthetic aperture radar satellite system for scientific and commercial applications that is realized in a public-private partnership between the German Aerospace Center (DLR) and the Astrium GmbH. TerraSAR-X was launched at June 15, 2007 on top of a Russian DNEPR-1 rocket into a 514 km sun-synchronous dusk-dawn orbit with an 11-day repeat cycle and will be operated for a period of at least 5 years during which it will provide high resolution SAR-data in the X-band. Due to the objectives of the interferometric campaigns the satellite has to comply to tight orbit control requirements, which are formulated in the form of a 250 m toroidal tube around a pre-flight determined reference trajectory (see [1] for details). The acquisition of the reference orbit was one of the main and key activities during the Launch and Early Orbit Phase (LEOP) and had to compensate for both injection errors and spacecraft safe mode attitude control thruster activities. The paper summarizes the activities of GSOC flight dynamics team during both LEOP and early Commissioning Phase, where the main tasks have been 1) the first-acquisition support via angle-tracking and GPS-based orbit determination, 2) maneuver planning for target orbit acquisition and maintenance, and 3) precise orbit and attitude determination for SAR processing support. Furthermore, a presentation on the achieved results and encountered problems will be addressed.

  5. Acute Suppressive and Long-Term Phase Modulation Actions of Orexin on the Mammalian Circadian Clock

    PubMed Central

    Belle, Mino D.C.; Hughes, Alun T.L.; Bechtold, David A.; Cunningham, Peter; Pierucci, Massimo; Burdakov, Denis

    2014-01-01

    Circadian and homeostatic neural circuits organize the temporal architecture of physiology and behavior, but knowledge of their interactions is imperfect. For example, neurons containing the neuropeptide orexin homeostatically control arousal and appetitive states, while neurons in the suprachiasmatic nuclei (SCN) function as the brain's master circadian clock. The SCN regulates orexin neurons so that they are much more active during the circadian night than the circadian day, but it is unclear whether the orexin neurons reciprocally regulate the SCN clock. Here we show both orexinergic innervation and expression of genes encoding orexin receptors (OX1 and OX2) in the mouse SCN, with OX1 being upregulated at dusk. Remarkably, we find through in vitro physiological recordings that orexin predominantly suppresses mouse SCN Period1 (Per1)-EGFP-expressing clock cells. The mechanisms underpinning these suppressions vary across the circadian cycle, from presynaptic modulation of inhibitory GABAergic signaling during the day to directly activating leak K+ currents at night. Orexin also augments the SCN clock-resetting effects of neuropeptide Y (NPY), another neurochemical correlate of arousal, and potentiates NPY's inhibition of SCN Per1-EGFP cells. These results build on emerging literature that challenge the widely held view that orexin signaling is exclusively excitatory and suggest new mechanisms for avoiding conflicts between circadian clock signals and homeostatic cues in the brain. PMID:24599460

  6. Environmental and lunar cues are predictive of the timing of river entry and spawning-site arrival in lake sturgeon Acipenser fulvescens.

    PubMed

    Forsythe, P S; Scribner, K T; Crossman, J A; Ragavendran, A; Baker, E A; Davis, C; Smith, K K

    2012-07-01

    The associations were quantified between daily and interannual variation in the timing of a closed population of lake sturgeon Acipenser fulvescens migration and arrival at spawning sites with stream environmental and lunar covariates. Spawning data were gathered from 1262 fish in Black Lake, Michigan 2001 to 2008 and by video monitoring 2000 to 2002. Sex-specific variation in responses to external cues was also tested. Results showed that a greater number of individuals initiated migration from lake to riverine habitats at dawn and dusk relative to other times of the day. Current and lagged effects of water temperature and river discharge, and periods in the lunar cycle were important variables in models quantifying movements into the river and timing of adult arrival at spawning sites. Different suites of covariates were predictive of A. fulverscens responses during different periods of the spawning season. The timing of initiation of migration and spawning, and the importance of covariates to the timing of these events, did not differ between sexes. Stream flow and temperature covaried with other variables including day length and the lunar cycle. Anthropogenic disruption of relationships among variables may mean that environmental cues may no longer reliably convey information for Acipenseriformes and other migratory fishes. PMID:22747803

  7. It's not black or white-on the range of vision and echolocation in echolocating bats.

    PubMed

    Boonman, Arjan; Bar-On, Yinon; Cvikel, Noam; Yovel, Yossi

    2013-01-01

    Around 1000 species of bats in the world use echolocation to navigate, orient, and detect insect prey. Many of these bats emerge from their roost at dusk and start foraging when there is still light available. It is however unclear in what way and to which extent navigation, or even prey detection in these bats is aided by vision. Here we compare the echolocation and visual detection ranges of two such species of bats which rely on different foraging strategies (Rhinopoma microphyllum and Pipistrellus kuhlii). We find that echolocation is better than vision for detecting small insects even in intermediate light levels (1-10 lux), while vision is advantageous for monitoring far-away landscape elements in both species. We thus hypothesize that, bats constantly integrate information acquired by the two sensory modalities. We suggest that during evolution, echolocation was refined to detect increasingly small targets in conjunction with using vision. To do so, the ability to hear ultrasonic sound is a prerequisite which was readily available in small mammals, but absent in many other animal groups. The ability to exploit ultrasound to detect very small targets, such as insects, has opened up a large nocturnal niche to bats and may have spurred diversification in both echolocation and foraging tactics. PMID:24065924

  8. It's not black or white—on the range of vision and echolocation in echolocating bats

    PubMed Central

    Boonman, Arjan; Bar-On, Yinon; Cvikel, Noam; Yovel, Yossi

    2013-01-01

    Around 1000 species of bats in the world use echolocation to navigate, orient, and detect insect prey. Many of these bats emerge from their roost at dusk and start foraging when there is still light available. It is however unclear in what way and to which extent navigation, or even prey detection in these bats is aided by vision. Here we compare the echolocation and visual detection ranges of two such species of bats which rely on different foraging strategies (Rhinopoma microphyllum and Pipistrellus kuhlii). We find that echolocation is better than vision for detecting small insects even in intermediate light levels (1–10 lux), while vision is advantageous for monitoring far-away landscape elements in both species. We thus hypothesize that, bats constantly integrate information acquired by the two sensory modalities. We suggest that during evolution, echolocation was refined to detect increasingly small targets in conjunction with using vision. To do so, the ability to hear ultrasonic sound is a prerequisite which was readily available in small mammals, but absent in many other animal groups. The ability to exploit ultrasound to detect very small targets, such as insects, has opened up a large nocturnal niche to bats and may have spurred diversification in both echolocation and foraging tactics. PMID:24065924

  9. Infectious Disease and Grouping Patterns in Mule Deer.

    PubMed

    Mejía Salazar, María Fernanda; Waldner, Cheryl; Stookey, Joseph; Bollinger, Trent K

    2016-01-01

    Infectious disease dynamics are determined, to a great extent, by the social structure of the host. We evaluated sociality, or the tendency to form groups, in Rocky Mountain mule deer (Odocoileus hemionus hemionus) from a chronic wasting disease (CWD) endemic area in Saskatchewan, Canada, to better understand factors that may affect disease transmission. Using group size data collected on 365 radio-collared mule deer (2008-2013), we built a generalized linear mixed model (GLMM) to evaluate whether factors such as CWD status, season, habitat and time of day, predicted group occurrence. Then, we built another GLMM to determine factors associated with group size. Finally, we used 3 measures of group size (typical, mean and median group sizes) to quantify levels of sociality. We found that mule deer showing clinical signs of CWD were less likely to be reported in groups than clinically healthy deer after accounting for time of day, habitat, and month of observation. Mule deer groups were much more likely to occur in February and March than in July. Mixed-sex groups in early gestation were larger than any other group type in any season. Groups were largest and most likely to occur at dawn and dusk, and in open habitats, such as cropland. We discuss the implication of these results with respect to sociobiology and CWD transmission dynamics.

  10. Effects of square-wave and simulated natural light-dark cycles on hamster circadian rhythms

    NASA Technical Reports Server (NTRS)

    Tang, I. H.; Murakami, D. M.; Fuller, C. A.

    1999-01-01

    Circadian rhythms of activity (Act) and body temperature (Tb) were recorded from male Syrian hamsters under square-wave (LDSq) and simulated natural (LDSN, with dawn and dusk transitions) light-dark cycles. Light intensity and data sampling were under the synchronized control of a laboratory computer. Changes in reactive and predictive onsets and offsets for the circadian rhythms of Act and Tb were examined in both lighting conditions. The reactive Act onset occurred 1.1 h earlier (P < 0.01) in LDSN than in LDSq and had a longer alpha-period (1.7 h; P < 0.05). The reactive Tb onset was 0.7 h earlier (P < 0.01) in LDSN. In LDSN, the predictive Act onset advanced by 0.3 h (P < 0.05), whereas the Tb predictive onset remained the same as in LDSq. The phase angle difference between Act and Tb predictive onsets decreased by 0.9 h (P < 0.05) in LDSN, but the offsets of both measures remained unchanged. In this study, animals exhibited different circadian entrainment characteristics under LDSq and LDSN, suggesting that gradual and abrupt transitions between light and dark may provide different temporal cues.

  11. A statistical study of EMIC waves observed by Cluster: 2. Associated plasma conditions

    DOE PAGES

    Allen, R. C.; Zhang, J. -C.; Kistler, L. M.; Spence, H. E.; Lin, R. -L.; Klecker, B.; Dunlop, M. W.; Andre, M.; Jordanova, Vania Koleva

    2016-07-19

    This is the second in a pair of papers discussing a statistical study of electromagnetic ion cyclotron (EMIC) waves detected during 10 years (2001–2010) of Cluster observations. In the first paper, an analysis of EMIC wave properties (i.e., wave power, polarization, normal angle, and wave propagation angle) is presented in both the magnetic latitude (MLAT)-distance as well as magnetic local time (MLT)-L frames. In addition, this paper focuses on the distribution of EMIC wave-associated plasma conditions as well as two EMIC wave generation proxies (the electron plasma frequency to gyrofrequency ratio proxy and the linear theory proxy) in these samemore » frames. Based on the distributions of hot H+ anisotropy, electron and hot H+ density measurements, hot H+ parallel plasma beta, and the calculated wave generation proxies, three source regions of EMIC waves appear to exist: (1) the well-known overlap between cold plasmaspheric or plume populations with hot anisotropic ring current populations in the postnoon to dusk MLT region; (2) regions all along the dayside magnetosphere at high L shells related to dayside magnetospheric compression and drift shell splitting; and (3) off-equator regions possibly associated with the Shabansky orbits in the dayside magnetosphere.« less

  12. Observation of 'Band' Structures in Spacecraft Observations of Inner Magnetosphere Plasma Electrons

    NASA Astrophysics Data System (ADS)

    Mohan Narasimhan, Kirthika; Fazakerley, Andrew; Milhaljcic, Branislav; Grimald, Sandrine; Dandouras, Iannis; Owen, Chris

    2013-04-01

    In previous studies, several authors have reported inner magnetosphere observations of proton distributions confined to narrow energy bands in the range of 1-25 keV. These structures have been known as "nose structures", with reference to their appearance in energy-time spectrograms and are known as "bands" if they are observed for extended periods of time. These proton structures have been studied quite extensively with multiple mechanisms proposed for their formation, not all of which apply for electrons. We examine Double-Star TC1 PEACE electron data recorded in the inner magnetosphere (L<15) near the equatorial plane to see if these features are also observed in the electron energy spectra. These "bands" also appear in electron spectrograms, spanning an energy range of 0.2-30 keV, and are shown to occur predominantly towards the dayside and dusk sectors. We also see multiple bands in some instances. We investigate the properties of these multi-banded structures and carry out a statistical survey analysing them as a function of geomagnetic activity, looking at both the Kp and Auroral Indices, in an attempt to explain their presence.

  13. Diurnal, seasonal and interannual variability of carbon isotope discrimination at the canopy level in response to environmental factors in a boreal forest ecosystem.

    PubMed

    Chen, Baozhang; Chen, Jing M

    2007-10-01

    Accurate estimation of temporal and spatial variations in photosynthetic discrimination of 13C is critical to carbon cycle research. In this study, a combined ecosystem-boundary layer isotope model, which was satisfactorily validated against intensive campaign data, was used to explore the temporal variability of carbon discrimination in response to environmental driving factors in a boreal ecosystem in the vicinity of Fraserdale Tower, Ontario, Canada (49 degrees 52'30''N, 81 degrees 34'12''W). A 14 year (1990-1996 and 1998-2004) hourly CO2 concentration and meteorological record measured on this tower was used for this purpose. The 14 year mean yearly diurnal amplitude of canopy-level discrimination Delta(canopy) was computed to be 2.8 +/- 0.5 per thousand, and the overall diurnal cycle showed that the greatest Delta(canopy) values occurred at dawn and dusk, while the minima generally appeared in mid-afternoon. The average annual Delta(canopy) varied from 18.3 to 19.7 per thousand with the 14 year average of 19 +/- 0.4 per thousand. The overall seasonality of Delta(canopy) showed a gradually increasing trend from leaf emergence in May-September and with a slight decrease at the end of the growing season in October. Delta(canopy) was negatively correlated to vapour pressure deficit and air temperature across hourly to decadal timescales. A strong climatic control on stomatal regulation of ecosystem isotope discrimination was found in this study.

  14. Magnetospheric convection strength inferred from inner edge of the electron plasma sheet and its relation to the polar cap potential drop

    NASA Astrophysics Data System (ADS)

    Jiang, F.; Kivelson, M. G.; Walker, R. J.; Khurana, K. K.; Angelopoulos, V.

    2010-12-01

    The sharp inner edge of the nightside electron plasma sheet observed by the THEMIS spacecraft is shown to provide a measure of the effective convection strength that transports plasma sheet plasma into the inner magnetosphere. The effective convection strength is characterized by the difference of potential between the magnetopause terminators at dawn and at dusk. We have surveyed inner boundary crossings of the electron plasma sheet measured by three THEMIS probes on orbits from Nov. 2007 to Apr. 2009. The values of the convection electric potential are inferred from the locations of the inner edge for different energy channels using a steady-state drift boundary model with a dipole magnetic field and a Volland-Stern electric field. When plotted against the solar wind electric field ( ), the convection electric potential is found to have a quasi-linear relationship with the driving solar wind electric field for the range of values tested (meaningful statistics only for Esw < 1.5 mV/m). Reasonably good agreement is found between the convection electric potential and the polar-cap potential drop calculated from model of Boyle et al. [1997] when the degree of shielding in the Volland-Stern potential is selected as gamma=1.5.

  15. Foraging movements of Audouin’s gull (Larus audouinii) in the Ebro Delta, NW Mediterranean: A preliminary satellite-tracking study

    NASA Astrophysics Data System (ADS)

    Christel, Isadora; Navarro, Joan; del Castillo, Marcos; Cama, Albert; Ferrer, Xavier

    2012-01-01

    A knowledge of the foraging strategies of marine predators is essential to understand the intrinsic factors controlling their distribution, abundance and their ecological function within the marine ecosystem. Here, we investigated for the first time the foraging movements and activity patterns of Audouin's gull Larus audouinii by using satellite-tracking data from eight breeding adults in the main colony of the species worldwide (Ebro Delta, NW Mediterranean). Tagged gulls foraged in the marine area close to the breeding colony (62% of foraging locations) and in the terrestrial area of the Ebro Delta (mainly rice fields; 38% of foraging locations). The foraging activity patterns changed significantly throughout the day; lower from dusk through the first half of the night (19-1 h; 32% of active locations) and higher during the rest of the day (1-19 h; 75.5 ± 4.3% of active locations). These results confirm the foraging plasticity of this seabird and, based on previous information about the dietary habits of this species, we hypothesize how its time-dependent activity patterns and habitat use could be associated with variations in the availability of marine food resources (e.g. diel vertical migrations of pelagic fish) and the exploitation of terrestrial resources (e.g. American crayfish Procambarus clarkii).

  16. Convection of Plasmaspheric Plasma into the Outer Magnetosphere and Boundary Layer Region: Initial Results

    NASA Technical Reports Server (NTRS)

    Ober, Daniel M.; Horwitz, J. L.; Gallagher, D. L.

    1998-01-01

    We present initial results on the modeling of the circulation of plasmaspheric- origin plasma into the outer magnetosphere and low-latitude boundary layer (LLBL), using a dynamic global core plasma model (DGCPM). The DGCPM includes the influences of spatially and temporally varying convection and refilling processes to calculate the equatorial core plasma density distribution throughout the magnetosphere. We have developed an initial description of the electric and magnetic field structures in the outer magnetosphere region. The purpose of this paper is to examine both the losses of plasmaspheric-origin plasma into the magnetopause boundary layer and the convection of this plasma that remains trapped on closed magnetic field lines. For the LLBL electric and magnetic structures we have adopted here, the plasmaspheric plasma reaching the outer magnetosphere is diverted anti-sunward primarily along the dusk flank. These plasmas reach X = -15 R(sub E) in the LLBL approximately 3.2 hours after the initial enhancement of convection and continues to populate the LLBL for 12 hours as the convection electric field diminishes.

  17. Significance of color, calories, and climate to the visual ecology of catarrhines.

    PubMed

    Dominy, Nathaniel J; Lucas, Peter W

    2004-03-01

    Here we describe correlations among visual ecology and the physiochemical properties of fruits and leaves consumed by four species of catarrhine primate: Cercopithecus ascanius, Colobus guereza, Pan troglodytes, and Piliocolobus badius. Collectively, their diet was diverse, with each species relying on fruits and leaves to different extents. The mean chromaticity of both foods, as perceived by the green-red and yellow-blue signals that catarrhines decode, was distinct from background foliage. However, selection on the basis of color was evident only for leaves. Primates consumed leaves with higher green-red values than the leaves they avoided-sensory mechanism that correlated with key nutritional variables, such as increased protein and reduced toughness. Moreover, the monkeys ingested leaves near dusk, when reddish targets may be more salient. Similar patterns were never observed with respect to edible fruits, the chromaticities of which did not differ from unconsumed fruits or correlate with nutritional properties. We also found that primate biomass is higher in seasonal sites. We conclude that these findings are consistent with the notion that routine trichromatic vision evolved in a context where seasonal folivory was pivotal to survival. PMID:15027092

  18. The statistical relationship between magnetosheath ion temperatures and magnetic field perturbations throughout the dayside magnetosheath.

    NASA Astrophysics Data System (ADS)

    Dimmock, Andrew; Osmane, Adnane; Pulkkinen, Tuija; Nykyri, Katariina

    2016-04-01

    The magnetosheath layer functions as an interface between interplanetary and near Earth space. As a result, the magnetosheath plasma properties dictate the efficiency and occurrence of processes which regulate the energy and momentum transport to the inner magnetosphere. Two (and possibly correlated) magnetosheath plasma properties which may play a significant role are ion temperatures and magnetic field perturbations; both of which comfortably exceed their solar wind counterparts. It has been proposed that magnetic field fluctuations, particularly those close to ion gyro-scales, can heat ions. In some cases, especially close to the magnetopause, these may facilitate diffusive plasma transport via kinetic Alfvén waves. The results presented here describe a statistical study using THEMIS and OMNI data between 2008 through 2015 in which we study the statistical relationship between magnetosheath ion temperatures and magnetic field variations over Pc 1-5 scale lengths. We show that higher amplitude fluctuations behind the quasi-parallel shock can produce higher ion temperatures subsequently driving a dawn-dusk asymmetry. We will also determine which scale/s are more effective at driving higher temperatures. We ascertain whether this relationship varies with spatial location, and if there are any global implications.

  19. Regulation of floral scent production in petunia revealed by targeted metabolomics.

    PubMed

    Verdonk, Julian C; Ric de Vos, C H; Verhoeven, Harrie A; Haring, Michel A; van Tunen, Arjen J; Schuurink, Robert C

    2003-03-01

    Petunia hybrida line W115 (Mitchell) has large white flowers that produce a pleasant fragrance. By applying solid phase micro extraction (SPME) techniques coupled to GC-MS analysis, volatile emission was monitored in vivo using a targeted metabolomics approach. Mature flowers released predominantly benzenoid compounds of which benzaldehyde, phenylacetaldehyde, methylbenzoate, phenylethylalcohol, iso-eugenol and benzylbenzoate were most abundant. This emission had a circadian rhythm reaching its maximum at dusk. During petal limb expansion two sesquiterpenes were emitted by the petunia flowers, tentatively identified as germacrene D and cadina-3,9-diene. In vitro analysis showed that the petal limbs and stigma were the main producers of the benzenoids and sesquiterpenes, respectively. Moreover, comparison of in vivo and in vitro analysis indicated that volatiles were not stored during periods of low emission but rather were synthesized de novo. DNA-microarray analysis revealed that genes of the pathways leading to the production of volatile benzenoids were upregulated late during the day, preceding the increase of volatile emission. RNA-gel blot analyses confirmed that the levels of phenylalanine ammonia lyase (PAL) and S-adenosyl methionine (SAM) synthase transcripts increased towards the evening. Our results suggest that the circadian production of volatile benzenoids in petunia W115 is, at least partly, regulated at the transcript level.

  20. Red-Light Initiated Decomposition of α-Hydroxy Methylperoxy Radical in the Presence of Organic and Inorganic Acids: Implications for the HOx Formation in the Lower Stratosphere.

    PubMed

    Kumar, Manoj; Francisco, Joseph S

    2016-05-01

    Theoretical calculations have been carried out to investigate the gas-phase decomposition of α-hydroxy methylperoxy (HOCH2(OO)) radical in the absence and presence of formic acid, acetic acid, nitric acid, and sulfuric acid. The HOCH2(OO) radical decomposition represents a new source of the HOx radical in troposphere. The results suggest that sulfuric acid will be more effective than other acids in catalyzing the peroxy radical decomposition. However, the significant stability of prereaction and postreaction complexes in all the bimolecular reactions implies a new photomechanism for the acid-mediated decomposition of the HOCH2(OO) radical that involves the visible or near IR overtone excitation of the OH stretching modes or electronic excitation of the O-O peroxy moiety in the acid-bound radical. This new overtone or electronic excitation-based photomechanism for the peroxy radical decomposition may provide useful insight into the missing photolytic source of the HOx at high solar zenith angles corresponding to the dawn or dusk photochemistry. PMID:27070960

  1. Satellite-Based Technologies in Use for Extreme Nocturnal Mountain Rescue Operations: a Synergetic Approach Applying Geophysical Principles

    NASA Astrophysics Data System (ADS)

    Buchroithner, Manfred F.; Ehlert, Guido; Hetze, Bernd; Kohlschmidt, Horst; Prechtel, Nikolas

    2014-06-01

    Mountain-rescue operations require rapid response whilst also ensuring the security of the rescue teams. Rescuing people in a big rock-face is even more difficult if night or fog prevent sight. The paper presents a technical solution to optimally support, under these aggravated conditions, the location of the casualties and the navigation of the rescue team(s) in a rock-face from a coordination station. In doing so, standard components like a smartphones with GPS functionality, a data communication on a client-server basis and VR visualisation software have been adapted to the specific requirements. Remote support of the navigation in steep rocky terrain requires a highly accurate wall model which permits the local experts of the coordination station to dependably estimate geometry and structure of the rock along the rescue route and to convey necessary directives to the retrieval team. Based on terrestrial laser-scans from different locations, such a model has been generated for the mighty Dachstein South Face (Austria) and texturised with digital photographs. Over a twelve-month period, a transdisciplinary team of the Dresden University of Technology (Informatics, Electrical Engineering, Cartography) developed and integrated the various technical modules of the mountain-rescue support-system (digital rock-face model, optimised GPS data transmission between mobile device, server and client, data filtering, and dynamic visualisation component). In summer 2011 the proper functioning of the prototype was demonstrated in a rescue exercise under foggy dusk conditions.

  2. On the Azimuthal Variation of Core Plasma in the Equatorial Magnetosphere

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.; Craven, P. D.; Comfort, R. H.; Moore, T. E.

    1995-01-01

    Previous results of plasmapause position surveys have been synthesized into a description of the underlying global distribution of plasmasphere-like or core plasma densities unique to a steady state magnetosphere. Under these steady conditions, the boundary between high- and low-density regions is taken to represent the boundary between diurnal near-corotation and large-scale circulation streamlines that traverse the entire magnetosphere. Results indicate a boundary that has a pronounced bulge in the dusk sector that is rotated westward and markedly reduced in size at increased levels of geomagnetic activity (and presumably magnetospheric convection). The derived profile is empirical confirmation of an underlying 'tear drop' distribution of core plasma, which is valid only for prolonged steady conditions and is somewhat different from that associated with the simple superposition of sunward flow and corotation, both in its detailed shape and in its varying orientation. Variation away from the tear drop profile suggests that magnetospheric circulation departs from a uniform flow field, having a radial dependence with respect to the Earth that is qualitatively consistent with electrostatic shielding of the convection electric field and which is rotated westward at increased levels of geophysical activity.

  3. Auroral electron beams - Electric currents and energy sources

    NASA Astrophysics Data System (ADS)

    Kaufmann, R. L.

    1981-09-01

    The energy sources, electric equipotentials and electric currents associated with auroral electron acceleration observed during rocket flight 18:152 are discussed. Steep flow gradients at the interface between the convection boundary layer and the plasma sheet are considered as the probable source of energy for dayside and dawn and dusk auroras, while it is suggested that the cross tail potential drop may provide an energy source for some midnight auroras. Birkeland currents that flow along distorted field lines are shown possibly to be important in the mechanism that produces U-shaped equipotentials in the ionosphere, as well as unexpected jumps in ionospheric or magnetotail currents and unusual electric fields and plasma drift in the magnetotail. The production of equipotential structures under oppositely directed higher-altitude electric fields is discussed, and it is pointed out that cold ionospheric plasma can enter the structure in a cusp-shaped region where fields are weak. The rocket data reveals that the sudden change in conductivity at the edge of the bright arc and the constancy of the electric field produce sudden changes in the Hall and Pedersen currents. It is concluded that current continuity is satisfied primarily by east-west changes in the electric field or conductivity.

  4. The energy expenditure of Iranian agricultural workers.

    PubMed

    Brun, T A; Geissler, C A; Mirbagheri, I; Hormozdiary, H; Bastani, J; Hedayat, H

    1979-10-01

    The energy cost of agricultural and standard activities and the daily energy expenditure of male agricultural workers were measured during different seasons in Iranian villages to assess the validity of past and present Food and Agricultural Organization recommended energy allowances for that population. Studies included low income farmers in a village representative of those around the central desert where harvesting takes place under conditions of extreme summer heat. Measurements were also made during the Moslem fasting period when no food may be eaten between dawn and dusk. Energy cost of typical activities was measured by indirect calorimetry using the Max-Planck respirometer and daily energy expenditure was assessed using these figures combined with a diary of activities throughout the 24-hr period. Results of individual activity values are compared with other published figures. Comparison of daily energy expenditure of fasting subjects and nonfasting after Ramazan showed no significant difference. No significant difference was found between values of standardized activities at high summer temperatures and moderate temperatures. Mean values of daily energy expenditure during winter when activity is low are around 2600 kcal/day and for the other seasons of high activity 3400 kcal/day. These figures suggest that past and present Food and Agricultural Organization standards are low for this population. PMID:484535

  5. Community metabolism in shallow coral reef and seagrass ecosystems, lower Florida Keys

    USGS Publications Warehouse

    Turk, Daniela; Yates, Kimberly K.; Vega-Rodriguez, Maria; Toro-Farmer, Gerardo; L'Esperance, Chris; Melo, Nelson; Ramsewak, Deanesch; Estrada, S. Cerdeira; Muller-Karger, Frank E.; Herwitz, Stan R.; McGillis, Wade

    2016-01-01

    Diurnal variation of net community production (NEP) and net community calcification (NEC) were measured in coral reef and seagrass biomes during October 2012 in the lower Florida Keys using a mesocosm enclosure and the oxygen gradient flux technique. Seagrass and coral reef sites showed diurnal variations of NEP and NEC, with positive values at near-seafloor light levels >100–300 µEinstein m-2 s-1. During daylight hours, we detected an average NEP of 12.3 and 8.6 mmol O2 m-2 h-1 at the seagrass and coral reef site, respectively. At night, NEP at the seagrass site was relatively constant, while on the coral reef, net respiration was highest immediately after dusk and decreased during the rest of the night. At the seagrass site, NEC values ranged from 0.20 g CaCO3 m-2 h-1 during daylight to -0.15 g CaCO3 m-2 h-1 at night, and from 0.17 to -0.10 g CaCO3 m-2 h-1 at the coral reef site. There were no significant differences in pH and aragonite saturation states (Ωar) between the seagrass and coral reef sites. Decrease in light levels during thunderstorms significantly decreased NEP, transforming the system from net autotrophic to net heterotrophic.

  6. Properties of daytime long-period pulsations during magnetospheric storm commencement

    NASA Astrophysics Data System (ADS)

    Klibanova, Yu. Yu.; Mishin, V. V.; Tsegmed, B.; Moiseev, A. V.

    2016-07-01

    Long-period geomagnetic pulsations during the SSC of July 14, 2012, are studied. The prenoon longitudinal sector (09:20-11:30) MLT, from the boundaries of which pulsations propagate azimuthally onto the dawn and dusk sides with an opposite polarization direction and increased amplitude, has been distinguished. The position of this sector relative to noon (a shift to the dawn side) depends on the front azimuthal inclination. It has been found that the polarization direction reverses in going from low (<30°) to middle/subauroral (≥50°) latitudes on the entire dayside. The geomagnetic pulsations mainly fluctuate near the f 1 = 2.9 and f 2 = 4.4 mHz frequencies. Fluctuations with frequency f 1, which coincide with the fluctuation frequency of the IMF x component, predominate at the polar cap latitudes (the open field line region) in the form of rapidly attenuating impulses and at low latitudes with a much smaller amplitude. Fluctuations with frequency f 2 are globally registered at all latitudes in the dayside sector below the magnetopause projection as a train of several fluctuations. It is assumed that fluctuations with frequency f 1 penetrate from the solar wind, and fluctuations with frequency f 2 are radial magnetopause oscillations.

  7. Magnetospheric Multiscale Mission observations and non-force free modeling of a flux transfer event immersed in a super-Alfvénic flow

    NASA Astrophysics Data System (ADS)

    Farrugia, C. J.; Lavraud, B.; Torbert, R. B.; Argall, M.; Kacem, I.; Yu, W.; Alm, L.; Burch, J.; Russell, C. T.; Shuster, J.; Dorelli, J.; Eastwood, J. P.; Ergun, R. E.; Fuselier, S.; Gershman, D.; Giles, B. L.; Khotyaintsev, Y. V.; Lindqvist, P. A.; Matsui, H.; Marklund, G. T.; Phan, T. D.; Paulson, K.; Pollock, C.; Strangeway, R. J.

    2016-06-01

    We analyze plasma, magnetic field, and electric field data for a flux transfer event (FTE) to highlight improvements in our understanding of these transient reconnection signatures resulting from high-resolution data. The ˜20 s long, reverse FTE, which occurred south of the geomagnetic equator near dusk, was immersed in super-Alfvénic flow. The field line twist is illustrated by the behavior of flows parallel/perpendicular to the magnetic field. Four-spacecraft timing and energetic particle pitch angle anisotropies indicate a flux rope (FR) connected to the Northern Hemisphere and moving southeast. The flow forces evidently overcame the magnetic tension. The high-speed flows inside the FR were different from those outside. The external flows were perpendicular to the field as expected for draping of the external field around the FR. Modeling the FR analytically, we adopt a non-force free approach since the current perpendicular to the field is nonzero. It reproduces many features of the observations.

  8. The noon and midnight mid-latitude trough as seen by Ariel 4

    NASA Technical Reports Server (NTRS)

    Tulunay, Y. K.; Grebowsky, J. M.

    1978-01-01

    The electron density data returned by the polar orbiting satellites Ariel 3 and Ariel 4 revealed that the midlatitude trough is one of the distinct large-scale features of the ionosphere at about 550 km. Recent work (e.g., Tulunay and Grebowsky, 1975) on the data included the investigation of the temporal development of the latitudinal position of the midlatitude electron density trough at dawn and dusk during the large magnetic storms of May 1967 and May 1972. Model calculations which assumed that the equatorial convection E-field varies in step with the Kp index reproduced on the average the observed behavior. In the present paper, trough observations made at noon and midnight during the period, 12-21 December 1971 which encompassed a relatively large magnetic storm are discussed. In this context, model calculations have been employed as a guide of average approximations of the actual situation in predicting the plasmapause location. It is also shown that the trough observed on the noon passes is not generally plasmapause-related as the nightside troughs are expected to be.

  9. The ecology of elk in an arid environment: An overview of the Hanford elk project

    SciTech Connect

    McCorquodale, S.M . Wildlife Resource Management); Eberhardt, L.E. )

    1990-08-01

    We studied elk (Cerves elaphus) in Washington's shrub-steppe region from 1982 to the present. The population originated from a small number of colonizers that took up residence on the Hanford Site in winter 1972--73. Rapid population growth was facilitated by high reproductive and survival rates. Elk showed strong preferences for bedding in sagebrush (Artemisia tridentata) stands, the only vegetative cover available. Foraging elk typically selected previously burned habitats that no longer supported sagebrush. Elk limited their major diurnal activity, favoring dusk-to-dawn foraging with relatively high nocturnal activity levels. Elk diets were dominated by grasses from winter through early summer and by forbs during the summer drought period. High reproductive success and survival and superior antler growth relative to elk occupying more mesic environments suggested that these elk were effectively utilizing the shrub-steppe environment. Mild, short winters in the shrub-steppe were hypothesized to contribute to reduced winter energy deficits common in temperate herbivores, partly facilitating the observed high fitness. We also hypothesize that in the absence of a significant overstory, the proportion of the range of these elk that would be considered foraging habitat exceeded that typical of elk occupying coniferous forests. Thus, the quantity of foraging areas may have compensated for reduced productivity typical of this region. 29 refs., 3 figs., 2 tabs.

  10. Tail lobe ion composition at energies of 0.1 to 16 keV/e: Evidence for mass-dependent density gradients

    NASA Technical Reports Server (NTRS)

    Lennartsson, O. W.

    1994-01-01

    A large set of energetic (0.1- to 16-keV/e) ion composition data from the central magnetotail, obtained by the International Sun Earth Explorer (ISEE) 1 spacecraft between 10 and 23 R(sub E) from Earth, is sorted according to measured total ion beta value, in order to investigate whether bulk properties of different ions vary in different ways between plasma sheet and lobes, as suggested by a comparison of certain experimental and theoretical results in the literature. Despite inevitable difficulties with extracting statistically valid data at very low beta (10(exp -2) or lower), the results seem to support a recent theoretical model suggesting that lighter ions have a steeper density gradient than heavier ions, especially when comparing H(+) ions with O(+) ions. The results also indicate that ion velocity distributions are fairly isotropic even at low beta, at least those of H(+) ions, although field-aligned flows are common. The results are evaluated in the context of plasma transport and are found to lend some support to the notion that tail lobe convection may be directed inward from the dawn and dusk flanks.

  11. Vocalisation Repertoire of Female Bluefin Gurnard (Chelidonichthys kumu) in Captivity: Sound Structure, Context and Vocal Activity

    PubMed Central

    Radford, Craig A.; Ghazali, Shahriman M.; Montgomery, John C.; Jeffs, Andrew G.

    2016-01-01

    Fish vocalisation is often a major component of underwater soundscapes. Therefore, interpretation of these soundscapes requires an understanding of the vocalisation characteristics of common soniferous fish species. This study of captive female bluefin gurnard, Chelidonichthys kumu, aims to formally characterise their vocalisation sounds and daily pattern of sound production. Four types of sound were produced and characterised, twice as many as previously reported in this species. These sounds fit two aural categories; grunt and growl, the mean peak frequencies for which ranged between 129 to 215 Hz. This species vocalized throughout the 24 hour period at an average rate of (18.5 ± 2.0 sounds fish-1 h-1) with an increase in vocalization rate at dawn and dusk. Competitive feeding did not elevate vocalisation as has been found in other gurnard species. Bluefin gurnard are common in coastal waters of New Zealand, Australia and Japan and, given their vocalization rate, are likely to be significant contributors to ambient underwater soundscape in these areas. PMID:26890124

  12. Body size limits dim-light foraging activity in stingless bees (Apidae: Meliponini).

    PubMed

    Streinzer, Martin; Huber, Werner; Spaethe, Johannes

    2016-10-01

    Stingless bees constitute a species-rich tribe of tropical and subtropical eusocial Apidae that act as important pollinators for flowering plants. Many foraging tasks rely on vision, e.g. spatial orientation and detection of food sources and nest entrances. Meliponini workers are usually small, which sets limits on eye morphology and thus quality of vision. Limitations are expected both on acuity, and thus on the ability to detect objects from a distance, as well as on sensitivity, and thus on the foraging time window at dusk and dawn. In this study, we determined light intensity thresholds for flight under dim light conditions in eight stingless bee species in relation to body size in a Neotropical lowland rainforest. Species varied in body size (0.8-1.7 mm thorax-width), and we found a strong negative correlation with light intensity thresholds (0.1-79 lx). Further, we measured eye size, ocelli diameter, ommatidia number, and facet diameter. All parameters significantly correlated with body size. A disproportionately low light intensity threshold in the minute Trigonisca pipioli, together with a large eye parameter P eye suggests specific adaptations to circumvent the optical constraints imposed by the small body size. We discuss the implications of body size in bees on foraging behavior. PMID:27495990

  13. Arabidopsis coordinates the diurnal regulation of carbon allocation and growth across a wide range of photoperiods.

    PubMed

    Sulpice, Ronan; Flis, Anna; Ivakov, Alexander A; Apelt, Federico; Krohn, Nicole; Encke, Beatrice; Abel, Christin; Feil, Regina; Lunn, John E; Stitt, Mark

    2014-01-01

    In short photoperiods, plants accumulate starch more rapidly in the light and degrade it more slowly at night, ensuring that their starch reserves last until dawn. To investigate the accompanying changes in the timing of growth, Arabidopsis was grown in a range of photoperiods and analyzed for rosette biomass, photosynthesis, respiration, ribosome abundance, polysome loading, starch, and over 40 metabolites at dawn and dusk. The data set was used to model growth rates in the daytime and night, and to identify metabolites that correlate with growth. Modeled growth rates and polysome loading were high in the daytime and at night in long photoperiods, but decreased at night in short photoperiods. Ribosome abundance was similar in all photoperiods. It is discussed how the amount of starch accumulated in the light period, the length of the night, and maintenance costs interact to constrain growth at night in short photoperiods, and alter the strategy for optimizing ribosome use. Significant correlations were found in the daytime and the night between growth rates and the levels of the sugar-signal trehalose 6-phosphate and the amino acid biosynthesis intermediate shikimate, identifying these metabolites as hubs in a network that coordinates growth with diurnal changes in the carbon supply.

  14. Quantification of Overnight Movement of Birch (Betula pendula) Branches and Foliage with Short Interval Terrestrial Laser Scanning.

    PubMed

    Puttonen, Eetu; Briese, Christian; Mandlburger, Gottfried; Wieser, Martin; Pfennigbauer, Martin; Zlinszky, András; Pfeifer, Norbert

    2016-01-01

    The goal of the study was to determine circadian movements of silver birch (Petula Bendula) branches and foliage detected with terrestrial laser scanning (TLS). The study consisted of two geographically separate experiments conducted in Finland and in Austria. Both experiments were carried out at the same time of the year and under similar outdoor conditions. Experiments consisted of 14 (Finland) and 77 (Austria) individual laser scans taken between sunset and sunrise. The resulting point clouds were used in creating a time series of branch movements. In the Finnish data, the vertical movement of the whole tree crown was monitored due to low volumetric point density. In the Austrian data, movements of manually selected representative points on branches were monitored. The movements were monitored from dusk until morning hours in order to avoid daytime wind effects. The results indicated that height deciles of the Finnish birch crown had vertical movements between -10.0 and 5.0 cm compared to the situation at sunset. In the Austrian data, the maximum detected representative point movement was 10.0 cm. The temporal development of the movements followed a highly similar pattern in both experiments, with the maximum movements occurring about an hour and a half before (Austria) or around (Finland) sunrise. The results demonstrate the potential of terrestrial laser scanning measurements in support of chronobiology.

  15. Modeling of the quasi-steady magnetotail

    SciTech Connect

    Birn, J. ); Schindler, K. )

    1989-01-01

    The three-dimensional theory of the quiet magnetotail is reviewed and updated. The most advanced formulation of the theory allows one to solve the magnetohydrodynamic (MHD) equations including field-aligned flow by reduction to a set of ordinary differential equations and an ordinary integral. These solutions represent lowest order solutions of an asymptotic expansion of the MHD equations for small electric field and weak time dependence. Applications to the magnetotail configuration are presented, which include the following properties in a self-consistent way: Flaring of the tail in y and z, associated with the presence of B{sub y} and B{sub z}; variation of plasma sheet and current sheet thickness with x and y, associated with variations of B{sub z}; field-aligned currents at the boundary between plasma sheet and lobes with the signature of region 1'' currents, i.e., toward the Earth on the dawn side and away on the dusk side, associated with the decrease of the tail flaring with distance from the Earth; net cross-tail magnetic field. Particular steady models with field-aligned flow demonstrate the important role of the flow in allowing or producing configurations with a transition from a thick closed plasma sheet to a much thinner distant open current sheet and for the possibility of thick plasmoids propagating in near equilibrium through the thin distant current sheet.

  16. On the nature of the plasma sheet boundary layer

    SciTech Connect

    Hones, E.W. Jr. Los Alamos National Lab., NM )

    1990-01-01

    The regions of the plasma sheet adjacent to the north and south lobes of the magnetotail have been described by many experimenters as locations of beams of energetic ions and fast-moving plasma directed primarily earthward and tailward along magnetic field lines. Measurements taken as satellites passed through one or the other of these boundary layers have frequently revealed near-earth mirroring of ions and a vertical segregation of velocities of both earthward-moving and mirroring ions with the fastest ions being found nearest the lobe-plasma sheet interface. These are features expected for particles from a distant tail source {bar E} {times} {bar B} drifting in a dawn-to-dusk electric field and are consistent with the source being a magnetic reconnection region. The plasma sheet boundary layers are thus understood as separatrix layers, bounded at their lobeward surfaces by the separatrices from the distant neutral line. This paper will review the observations that support this interpretation. 10 refs., 7 figs.

  17. The Role of Localized Inductive Electric Fields in Electron Injections Around Dipolarizing Flux Bundles

    NASA Astrophysics Data System (ADS)

    Gabrielse, C.; Harris, C.; Angelopoulos, V.; Runov, A.

    2015-12-01

    We study energetic electron injections using an analytical model that describes self-consistent electric and magnetic field perturbations of a transient, localized dipolarizing flux bundle (DFB). This simple model can reproduce most injection signatures at multiple locations simultaneously, reaffirming earlier findings that an earthward-traveling DFB can both transport and accelerate electrons to suprathermal energies, and can thus be considered as the primary driver of short-lived (~<10 min) injections. We find that energetic electron drift paths are greatly influenced by the sharp magnetic field gradients around the localized DFB. If the gradients are weak the energetic electrons initiating at reconnection will drift out of the flow channel such that the observed injection is comprised mostly of plasma sheet electrons. However, if the duskward magnetic field gradients on the DFB's dawn flank are strong they can cause electrons to drift further earthward from the reconnection site than due to E x B alone. Similarly, strong dawnward magnetic field gradients on the DFB's dusk flank can extract energetic electrons from the inner magnetosphere out to the plasma sheet, where they can either be recirculated earthward or remain at higher L-shells. Therefore, the source of electrons observed during injection depends sensitively on the spacecraft location relative to the DFB and on the DFB's properties.

  18. Saturn's northern auroras as observed using the Hubble Space Telescope

    NASA Astrophysics Data System (ADS)

    Nichols, J. D.; Badman, S. V.; Bunce, E. J.; Clarke, J. T.; Cowley, S. W. H.; Hunt, G. J.; Provan, G.

    2016-01-01

    We discuss the features of Saturn's northern FUV auroras as observed during a program of Hubble Space Telescope observations which executed over 2011-2013 and culminated, along with Cassini observations, in a comprehensive multi-spectral observing campaign. Our 2011-2013 observations of the northern aurora are also compared with those from our 2007-2008 observation of the southern aurora. We show that the variety of morphologies of the northern auroras is broadly consistent with the southern, and determine the statistical equatorward and poleward boundary locations. We find that our boundaries are overall consistent with previous observations, although a modest poleward displacement of the poleward boundaries is due to the increased prevalence of poleward auroral patches in the noon and afternoon sectors during this program, likely due to the solar wind interaction. We also show that the northern auroral oval oscillates with the northern planetary period oscillation (PPO) phase in an elongated ellipse with semi-major axis ∼1.6° oriented along the post-dawn/post-dusk direction. We further show that the northern auroras exhibit dawn-side brightenings at zero northern magnetic PPO phase, although there is mixed evidence of auroral emissions fixed in the rotating frame of the northern PPO current system, such that overall the dependence of the auroras on northern magnetic phase is somewhat weak.

  19. Energetic O+ and H+ Ions in the Plasma Sheet: Implications for the Transport of Ionospheric Ions

    NASA Technical Reports Server (NTRS)

    Ohtani, S.; Nose, M.; Christon, S. P.; Lui, A. T.

    2011-01-01

    The present study statistically examines the characteristics of energetic ions in the plasma sheet using the Geotail/Energetic Particle and Ion Composition data. An emphasis is placed on the O+ ions, and the characteristics of the H+ ions are used as references. The following is a summary of the results. (1) The average O+ energy is lower during solar maximum and higher during solar minimum. A similar tendency is also found for the average H+ energy, but only for geomagnetically active times; (2) The O+ -to -H+ ratios of number and energy densities are several times higher during solar maximum than during solar minimum; (3) The average H+ and O+ energies and the O+ -to -H+ ratios of number and energy densities all increase with geomagnetic activity. The differences among different solar phases not only persist but also increase with increasing geomagnetic activity; (4) Whereas the average H+ energy increases toward Earth, the average O+ energy decreases toward Earth. The average energy increases toward dusk for both the H+ and O+ ions; (5) The O+ -to -H+ ratios of number and energy densities increase toward Earth during all solar phases, but most clearly during solar maximum. These results suggest that the solar illumination enhances the ionospheric outflow more effectively with increasing geomagnetic activity and that a significant portion of the O+ ions is transported directly from the ionosphere to the near ]Earth region rather than through the distant tail.

  20. Convection of Plasmaspheric Plasma into the Outer Magnetosphere and Boundary Layer Region: Initial Results

    NASA Technical Reports Server (NTRS)

    Ober, Daniel M.; Horwitz, J. L.

    1998-01-01

    We present initial results on the modeling of the circulation of plasmaspheric-origin plasma into the outer magnetosphere and low-latitude boundary layer (LLBL), using a dynamic global core plasma model (DGCPM). The DGCPM includes the influences of spatially and temporally varying convection and refilling processes to calculate the equatorial core plasma density distribution throughout the magnetosphere. We have developed an initial description of the electric and magnetic field structures in the outer magnetosphere region. The purpose of this paper is to examine both the losses of plasmaspheric-origin plasma into the magnetopause boundary layer and the convection of this plasma that remains trapped on closed magnetic field lines. For the LLBL electric and magnetic structures we have adopted here, the plasmaspheric plasma reaching the outer magnetosphere is diverted anti-sunward primarily along the dusk flank. These plasmas reach X= -15 R(sub E) in the LLBL approximately 3.2 hours after the initial enhancement of convection and continues to populate the LLBL for 12 hours as the convection electric field diminishes.

  1. Space Technology 5 (ST-5) Multipoint Observations of Temporal and Spatial Variability of Field-Aligned Currents

    NASA Technical Reports Server (NTRS)

    Le, Guan

    2010-01-01

    Space Technology 5 (ST-5) is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, sun-synchronous polar orbit from March 22 to June 21, 2006, for technology validations. In this paper, we present a study of the temporal variability of field-aligned currents using multi-point magnetic field measurements from ST5. The data demonstrate that mesoscale current structures are commonly embedded within large-scale field-aligned current sheets. The meso-scale current structures are very dynamic with highly variable current density and/or polarity in time scales of about 10 min. They exhibit large temporal variations during both quiet and disturbed times in such time scales. On the other hand, the data also shown that the time scales for the currents to be relatively stable are about 1 min for meso-scale currents and about 10 min for large scale current sheets. These temporal features are obviously associated with dynamic variations of their particle carriers (mainly electrons) as they respond to the variations of the parallel electric field in auroral acceleration region. The characteristic time scales for the temporal variability of meso-scale field-aligned currents are found to be consistent with those of auroral parallel electric field.

  2. Space Technology 5 (ST-5) Observations of Field-Aligned Currents: Temporal Variability

    NASA Technical Reports Server (NTRS)

    Le, Guan

    2010-01-01

    Space Technology 5 (ST-5) is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, sun-synchronous polar orbit from March 22 to June 21, 2006, for technology validations. In this paper, we present a study of the temporal variability of field-aligned currents using multi-point magnetic field measurements from STS. The data demonstrate that masoscale current structures are commonly embedded within large-scale field-aligned current sheets. The meso-scale current structures are very dynamic with highly variable current density and/or polarity in time scales of about 10 min. They exhibit large temporal variations during both quiet and disturbed times in such time scales. On the other hand, the data also shown that the time scales for the currents to be relatively stable are about I min for meso-scale currents and about 10 min for large scale current sheets. These temporal features are obviously associated with dynamic variations of their particle carriers (mainly electrons) as they respond to the variations of the parallel electric field in auroral acceleration region. The characteristic time scales for the temporal variability of meso-scale field-aligned currents are found to be consistent with those of auroral parallel electric field.

  3. Space Technology 5 multi-point measurements of near-Earth magnetic fields: Initial results

    NASA Astrophysics Data System (ADS)

    Slavin, J. A.; Le, G.; Strangeway, R. J.; Wang, Y.; Boardsen, S. A.; Moldwin, M. B.; Spence, H. E.

    2008-01-01

    The Space Technology 5 (ST-5) mission successfully placed three micro-satellites in a 300 × 4500 km dawn-dusk orbit on 22 March 2006. Each spacecraft carried a boom-mounted vector fluxgate magnetometer that returned highly sensitive and accurate measurements of the geomagnetic field. 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. In doing so, we demonstrate two multi-point methods for the inference of FAC current density that have not previously been possible in low-Earth orbit: 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 geomagnetic field gradient analyses as well as field-aligned and ionospheric currents.

  4. Along-track gradients from ST-5: Improving magnetic and thermal models of the lithosphere

    NASA Astrophysics Data System (ADS)

    Sabaka, T. J.; Le, G.

    2006-12-01

    The three-satellite ST-5 mission collected vector magnetic field observations in a string-of-pearls configuration at low (300+ km) altitudes over selected regions at mid and high-northern latitudes in early (March-June) 2006. The spin-stabilized, polar-orbiting satellites flew in the dawn-dusk meridian, and utilized miniature, high-quality, UCLA fluxgate magnetometers that were mounted on a novel boom. The mission was not designed to do geomagnetism, and contained no absolute magnetometer, no GPS, and no star camera. This technology demonstration mission tested a new miniature but high resolution sun sensor that was utilized for the despinning of the magnetic field observations (0.1 degree accuracy). Satellite location was estimated by tracking, and enhanced via post-processing to accuracies of about 0.1 km. Many of the magnetic field observations were collected in magnetically quiet times. After pre- and in-flight calibrations of this spinner, the along-track gradient of the total field derived from two of the three satellites was calculated, and exhibited favorable comparisons with the Comprehensive model (CM4) of the near-Earth magnetic field. CM4 was developed from high resolution geomagnetic field satellites such as CHAMP, Orsted, and Magsat. We utilize the gradient data to construct a model of the lithospheric magnetic field in several N-S bands of dense ST-5 coverage, and illustrate how these models can be used to improve magnetic and thermal models of the lithosphere.

  5. A simulation study of the thermosphere mass density response to substorms using GITM

    NASA Astrophysics Data System (ADS)

    Liu, Xianjing; Ridley, Aaron

    2015-09-01

    The temporal and spatial variations of the thermospheric mass density during a series of idealized substorms were investigated using the Global Ionosphere Thermosphere Model (GITM). The maximum mass density perturbation of an idealized substorm with a peak variation of hemispheric power (HP) of 50 GW and interplanetary magnetic field (IMF) Bz of -2 nT was ~14% about 50 min after the substorm onset in the nightside sector of the auroral zone. The mass density response to different types of energy input has a strong local time dependence, with the mass density perturbation due to only an IMF Bz variation peaking in the dusk sector and the density perturbation due to only HP variation peaks in the nightside sector. Simulations with IMF Bz changes only and HP changes only showed that the system behaves slightly nonlinearly when both IMF and HP variations are included (a maximum of 6% of the nonlinearity) and that the nonlinearity grows with energy input. The neutral gas heating rate due to Joule heating was of same magnitude as the heating rate due to precipitation, but the majority of the temperature enhancement due to the heating due to precipitation occurs at lower altitude as compared to the auroral heating. About 110 min after onset, a negative mass density perturbation (~-5%) occurred in the night sector, which was consistent with the mass density measurement of the CHAMP satellite.

  6. Red-Light Initiated Decomposition of α-Hydroxy Methylperoxy Radical in the Presence of Organic and Inorganic Acids: Implications for the HOx Formation in the Lower Stratosphere.

    PubMed

    Kumar, Manoj; Francisco, Joseph S

    2016-05-01

    Theoretical calculations have been carried out to investigate the gas-phase decomposition of α-hydroxy methylperoxy (HOCH2(OO)) radical in the absence and presence of formic acid, acetic acid, nitric acid, and sulfuric acid. The HOCH2(OO) radical decomposition represents a new source of the HOx radical in troposphere. The results suggest that sulfuric acid will be more effective than other acids in catalyzing the peroxy radical decomposition. However, the significant stability of prereaction and postreaction complexes in all the bimolecular reactions implies a new photomechanism for the acid-mediated decomposition of the HOCH2(OO) radical that involves the visible or near IR overtone excitation of the OH stretching modes or electronic excitation of the O-O peroxy moiety in the acid-bound radical. This new overtone or electronic excitation-based photomechanism for the peroxy radical decomposition may provide useful insight into the missing photolytic source of the HOx at high solar zenith angles corresponding to the dawn or dusk photochemistry.

  7. Sunglint Detection for Unmanned and Automated Platforms

    PubMed Central

    Garaba, Shungudzemwoyo Pascal; Schulz, Jan; Wernand, Marcel Robert; Zielinski, Oliver

    2012-01-01

    We present an empirical quality control protocol for above-water radiometric sampling focussing on identifying sunglint situations. Using hyperspectral radiometers, measurements were taken on an automated and unmanned seaborne platform in northwest European shelf seas. In parallel, a camera system was used to capture sea surface and sky images of the investigated points. The quality control consists of meteorological flags, to mask dusk, dawn, precipitation and low light conditions, utilizing incoming solar irradiance (ES) spectra. Using 629 from a total of 3,121 spectral measurements that passed the test conditions of the meteorological flagging, a new sunglint flag was developed. To predict sunglint conspicuous in the simultaneously available sea surface images a sunglint image detection algorithm was developed and implemented. Applying this algorithm, two sets of data, one with (having too much or detectable white pixels or sunglint) and one without sunglint (having least visible/detectable white pixel or sunglint), were derived. To identify the most effective sunglint flagging criteria we evaluated the spectral characteristics of these two data sets using water leaving radiance (LW) and remote sensing reflectance (RRS). Spectral conditions satisfying ‘mean LW (700–950 nm) < 2 mW·m−2·nm−1·Sr−1’ or alternatively ‘minimum RRS (700–950 nm) < 0.010 Sr−1’, mask most measurements affected by sunglint, providing an efficient empirical flagging of sunglint in automated quality control.

  8. TIME FOR COFFEE controls root meristem size by changes in auxin accumulation in Arabidopsis

    PubMed Central

    Lu, Ying-Tang

    2014-01-01

    Roots play important roles in plant survival and productivity as they not only anchor the plants in the soil but are also the primary organ for the uptake of nutrients from the outside. The growth and development of roots depend on the specification and maintenance of the root meristem. Here, we report a previously unknown role of TIME FOR COFFEE (TIC) in controlling root meristem size in Arabidopsis. The results showed that loss of function of TIC reduced root meristem length and cell number by decreasing the competence of meristematic cells to divide. This was due to the repressed expression of PIN genes for decreased acropetal auxin transport in tic-2, leading to low auxin accumulation in the roots responsible for reduced root meristem, which was verified by exogenous application of indole-3-acetic acid. Downregulated expression of PLETHORA1 (PLT1) and PLT2, key transcription factors in mediating the patterning of the root stem cell niche, was also assayed in tic-2. Similar results were obtained with tic-2 and wild-type plants at either dawn or dusk. We also suggested that the MYC2-mediated jasmonic acid signalling pathway may not be involved in the regulation of TIC in controlling the root meristem. Taken together, these results suggest that TIC functions in an auxin–PLTs loop for maintenance of post-embryonic root meristem. PMID:24277277

  9. Avoidance of overheating and selection for both hair loss and bipedality in hominins

    PubMed Central

    Ruxton, Graeme D.; Wilkinson, David M.

    2011-01-01

    Two frequently debated aspects of hominin evolution are the development of upright bipedal stance and reduction in body hair. It has long been argued, on the basis of heat-balance models, that thermoregulation might have been important in the evolution of both of these traits. Previous models were based on a stationary individual standing in direct sunlight; here we extend this approach to consider a walking hominin, having argued that walking is more thermally challenging than remaining still. Further, stationary activities may be more compatible with shade seeking than activities (such as foraging) involving travel across the landscape. Our model predictions suggest that upright stance probably evolved for nonthermoregulatory reasons. However, the thermoregulatory explanation for hair loss was supported. Specifically, we postulate progressive hair loss being selected and this allowing individuals to be active in hot, open environments initially around dusk and dawn without overheating. Then, as our ancestors’ hair loss increased and sweating ability improved over evolutionary time, the fraction of the day when they could remain active in such environments extended. Our model suggests that only when hair loss and sweating ability reach near-modern human levels could hominins have been active in the heat of the day in hot, open environments. PMID:22160694

  10. Dispersal behavior of adult snow melt mosquitoes in the Upper Rhine Valley, Germany.

    PubMed

    Schäfer, M; Storch, V; Kaiser, A; Beck, M; Becker, N

    1997-06-01

    The dispersal behavior of female snow melt mosquitoes was studied in two forests in Rhineland-Palatinate, Germany, from April to August 1993. Both CDC-light-traps and human bait collections were used to collect mosquitoes. Sampling sites were chosen along a west-east and a north-south transect in treated and untreated parts of a forest with a village in its center. Around this settlement, breeding sites within a radius of 1.5 to 2.5 km were treated. It could be shown that this buffer zone is sufficient to prevent a nuisance caused by snow melt mosquitoes in the village. The results lead to the conclusion that snow melt mosquitoes do not regularly migrate over large distances but stay near their breeding sites. In a detailed study of the behavior of Aedes rusticus, it could be observed that these mosquitoes were resting in the interior of the forest during daytime and leaving it with increasing dusk up to 50 m from the forest edge. A comparison of landing rate counts near a row of trees and in the open field showed higher activity near the row of trees indicating visual orientation of the mosquitoes. Although the Ae. rusticus females left the forest regularly, no nuisance occurred in nearby villages. The treatment of breeding sites near settlements appeared to be sufficient to prevent a nuisance caused by the snow melt mosquitoes.

  11. Armigeres subalbatus colonization of damaged pit latrines: a nuisance and potential health risk to residents of resettlement villages in Laos.

    PubMed

    Hiscox, A; Hirooka, R; Vongphayloth, K; Hill, N; Lindsay, S W; Grandadam, M; Brey, P T

    2016-03-01

    During the resettlement of 6500 persons living around the Nam Theun 2 hydroelectric project in Laos, more than 1200 pour-flush latrines were constructed. To assess the role of these latrines as productive larval habitats for mosquitoes, entomological investigations using Centers for Disease Control (CDC) light traps, visual inspection and emergence trapping were carried out in over 300 latrines during the rainy seasons of 2008-2010. Armigeres subalbatus (Diptera: Culicidae) were nine times more likely to be found in latrines (mean catch: 3.09) than in adjacent bedrooms (mean catch: 0.37) [odds ratio (OR) 9.08, 95% confidence interval (CI) 6.74-15.11] and mosquitoes were active in and around 59% of latrines at dusk. Armigeres subalbatus was strongly associated with latrines with damaged or improperly sealed septic tank covers (OR 5.44, 95% CI 2.02-14.67; P < 0.001). Armigeres subalbatus is a nuisance biter and a putative vector of Japanese encephalitis and dengue viruses. Dengue virus serotype 3 was identified from a single pool of non-blood-fed female A. subalbatus using reverse transcription polymerase chain reaction. Maintaining a good seal around septic tanks by covering them with a layer of soil is a simple intervention to block mosquito exit/entry and contribute to vector control in resettlement villages. The scale-up of this simple, cheap intervention would have global impact in preventing the colonization of septic tanks by nuisance biting and disease-transmitting mosquitoes. PMID:26508317

  12. Vocalisation Repertoire of Female Bluefin Gurnard (Chelidonichthys kumu) in Captivity: Sound Structure, Context and Vocal Activity.

    PubMed

    Radford, Craig A; Ghazali, Shahriman M; Montgomery, John C; Jeffs, Andrew G

    2016-01-01

    Fish vocalisation is often a major component of underwater soundscapes. Therefore, interpretation of these soundscapes requires an understanding of the vocalisation characteristics of common soniferous fish species. This study of captive female bluefin gurnard, Chelidonichthys kumu, aims to formally characterise their vocalisation sounds and daily pattern of sound production. Four types of sound were produced and characterised, twice as many as previously reported in this species. These sounds fit two aural categories; grunt and growl, the mean peak frequencies for which ranged between 129 to 215 Hz. This species vocalized throughout the 24 hour period at an average rate of (18.5 ± 2.0 sounds fish-1 h-1) with an increase in vocalization rate at dawn and dusk. Competitive feeding did not elevate vocalisation as has been found in other gurnard species. Bluefin gurnard are common in coastal waters of New Zealand, Australia and Japan and, given their vocalization rate, are likely to be significant contributors to ambient underwater soundscape in these areas. PMID:26890124

  13. Diel Drift Patterns and Spatio-temporal Distribution of Macroinvertebrates in the Blanco River, Texas: A Groundwater Dominated Stream Subject to Intermittent Flow

    NASA Astrophysics Data System (ADS)

    Pendergrass, D. R.; Arsuffi, T. L.

    2005-05-01

    The Blanco River is a relatively pristine karst stream in central Texas and designated a conservation target by The Nature Conservancy. It is fed primarily by groundwater in the upper reaches and dominated by runoff and intermittency downstream. The spatial and temporal structure of macroinvertebrates in the Blanco River was assessed with seasonal Hess and d-net samples during 2003-2004 and three diel drift samples from May to October 2004. Our downstream site showed a 47% drop in diversity, but comparable abundances to up- and mid-stream sites. Ephemeropteran and trichopteran taxa (e.g. Tricorythodes and Cheumatopsyche) comprised about 60% of drift and benthic samples alike, however, non-insect taxa were nearly absent from the drift. Some taxa not present in the benthic samples were present in the drift. Post-dusk and pre-dawn peaks in diel drift were discerned. No strong seasonal patterns were detected which may be attributable to an unusually wet year and asynchronous, multivoltinous life cycles associated with mild seasonality in subtropical regions. The Blanco River's historically variable hydrological regime may be further exacerbated by long-term flow alteration associated with increasing anthropogenic development and could alter the composition and distribution of macroinvertebrate assemblages.

  14. Swimming behavior of the spoon worm Urechis unicinctus (Annelida, Echiura).

    PubMed

    Abe, Hirokazu; Sato-Okoshi, Waka; Tanaka, Masaatsu; Okoshi, Kenji; Teramoto, Wataru; Kondoh, Tomohiko; Nishitani, Goh; Endo, Yoshinari

    2014-06-01

    Large numbers of swimming and stranding Urechis unicinctus were observed at night during low tide in Sasuhama, Miyagi Prefecture, northeastern Japan, during the periods from January to February in 2012 and 2013. Worms did not drift passively but swam actively, therefore hinting at a certain purpose for such behavior. As trochophore larvae of U. unicinctus were observed to occur simultaneously in the plankton, we infer the possibility that this is an event of reproductive swarming. Anatomical observations of both swimming and stranding U. unicinctus showed that none of the specimens had gametes, which may suggest that these were completely spent after spawning. Urechis unicinctus seemed to begin swimming after dusk and the observed swimming behavior occurred during the evening ebb tide throughout the night low tide during winter time. Stranding U. unicinctus have long been known in Japan and have been attributed to sea storms. The present study shows for the first time the possibility that U. unicinctus swims in order to reproduce at night and that this swimming behavior is closely linked to the stranding of U. unicinctus individuals.

  15. Kinetic effects on the Kelvin-Helmholtz instability in ion-to-magnetohydrodynamic scale transverse velocity shear layers: Particle simulations.

    PubMed

    Nakamura, T K M; Hasegawa, H; Shinohara, I

    2010-04-01

    Ion-to-magnetohydrodynamic scale physics of the transverse velocity shear layer and associated Kelvin-Helmholtz instability (KHI) in a homogeneous, collisionless plasma are investigated by means of full particle simulations. The shear layer is broadened to reach a kinetic equilibrium when its initial thickness is close to the gyrodiameter of ions crossing the layer, namely, of ion-kinetic scale. The broadened thickness is larger in B⋅Ω<0 case than in B⋅Ω>0 case, where Ω is the vorticity at the layer. This is because the convective electric field, which points out of (into) the layer for B⋅Ω<0 (B⋅Ω>0), extends (reduces) the gyrodiameters. Since the kinetic equilibrium is established before the KHI onset, the KHI growth rate depends on the broadened thickness. In the saturation phase of the KHI, the ion vortex flow is strengthened (weakened) for B⋅Ω<0 (B⋅Ω>0), due to ion centrifugal drift along the rotational plasma flow. In ion inertial scale vortices, this drift effect is crucial in altering the ion vortex size. These results indicate that the KHI at Mercury-like ion-scale magnetospheric boundaries could show clear dawn-dusk asymmetries in both its linear and nonlinear growth.

  16. Context-dependent reproductive isolation mediated by floral scent and color.

    PubMed

    Bischoff, Mascha; Raguso, Robert A; Jürgens, Andreas; Campbell, Diane R

    2015-01-01

    Reproductive isolation due to pollinator behavior is considered a key mode of speciation in flowering plants. Although floral scent is thought to mediate pollinator behavior, little is known about its effects on pollinator attraction and floral visitation in the wild. We used field experiments with wild hawkmoths and laboratory experiments with naïve hawkmoths to investigate attraction to and probing of flowers in response to indole, a volatile emitted by Ipomopsis tenuituba but not its close relative I. aggregata, both alone and in combination with floral color differences. We demonstrated that indole attracts wild hawkmoths to flowers, but has little effect on the rate at which those attracted moths probe flowers. In contrast, white flower color did not influence hawkmoth attraction in the field, but caused more attracted moths to probe flowers. Thus, the moths require both scent and high visual contrast, in that order, to feed at flowers at dusk. Their preference for indole-scented flowers is innate, but species-specific preference is mitigated by previous experience and plant spatial patterning. This context-dependent behavior helps explain why these Ipomopsis species show geographical variation in the extent of hybridization and may potentially explain formation of hybrid bridges in other systems of hawkmoth-pollinated plants.

  17. The effect of different solar wind parameters upon significant relativistic electron flux dropouts in the magnetosphere

    NASA Astrophysics Data System (ADS)

    Gao, Xinliang; Li, Wen; Bortnik, Jacob; Thorne, Richard M.; Lu, Quanming; Ma, Qianli; Tao, Xin; Wang, Shui

    2015-06-01

    Superposed epoch analyses were performed on 193 significant relativistic electron flux dropout events, in order to study the roles of different solar wind parameters in driving the depletion of relativistic electrons, using ~16 years of data from the POES and GOES missions, and the OMNIWEB solar wind database. We find that the solar wind dynamic pressure and interplanetary magnetic field (IMF) Bz play key roles in causing the relativistic electron flux dropouts, but also that either large solar wind dynamic pressure or strong southward IMF Bz by itself is capable of producing the significant depletion of relativistic electrons. The relativistic electron flux dropouts occur not only when the magnetopause is compressed closer to the Earth but also when the magnetopause is located very far (> ~10 RE). Importantly, our results show that in addition to the large solar wind dynamic pressure, which pushes the magnetopause inward strongly and causes the electrons to escape from the magnetosphere, relativistic electrons can also be scattered into the loss cone and precipitate into the Earth's atmosphere during periods of strong southward IMF Bz, which preferentially provides a source of free energy for electromagnetic ion cyclotron (EMIC) wave excitation. This is supported by the fact that the strongest electron precipitation into the atmosphere is found in the dusk sector, where EMIC waves are typically observed in the high-density plasmasphere or plume and cause efficient electron precipitation down to ~1 MeV.

  18. The Effect of Different Solar Wind Parameters upon Significant Relativistic Electron Flux Dropouts in the Magnetosphere

    NASA Astrophysics Data System (ADS)

    Gao, X.; Li, W.; Bortnik, J.; Thorne, R. M.; Lu, Q.

    2015-12-01

    Superposed epoch analyses were performed on 193 significant relativistic electron flux dropout events, in order to study the roles of different solar wind parameters in driving the depletion of relativistic electrons, using ~16 years of data from the POES and GOES missions, and the OMNIWEB solar wind database. We find that the solar wind dynamic pressure and IMF Bz play key roles in causing the relativistic electron flux dropouts, but also that either large solar wind dynamic pressure or strong southward IMF Bz by itself is capable of producing the significant depletion of relativistic electrons. The relativistic electron flux dropouts occur not only when the magnetopause is compressed closer to the Earth, but also when the magnetopause is located very far (> ~10 RE). Importantly, our results show that in addition to the large solar wind dynamic pressure, which pushes the magnetopause inward strongly and causes the electrons to escape from the magnetosphere, relativistic electrons can also be scattered into the loss cone and precipitate into the Earth's atmosphere during periods of strong southward IMF Bz, which preferentially provides a source of free energy for electromagnetic ion cyclotron (EMIC) wave excitation. This is supported by the fact that the strongest electron precipitation into the atmosphere is found in the dusk sector, where EMIC waves are typically observed in the high-density plasmasphere or plume and cause efficient electron precipitation down to ~ 1 MeV.

  19. Modeling the magnetospheric X-ray emission from solar wind charge exchange with verification from XMM-Newton observations

    NASA Astrophysics Data System (ADS)

    Whittaker, Ian C.; Sembay, Steve; Carter, Jennifer A.; Read, Andrew M.; Milan, Steve E.; Palmroth, Minna

    2016-05-01

    An MHD-based model of terrestrial solar wind charge exchange (SWCX) is created and compared to 19 case study observations in the 0.5-0.7 keV emission band taken from the European Photon Imaging Cameras on board XMM-Newton. This model incorporates the Global Unified Magnetosphere-Ionosphere Coupling Simulation-4 MHD code and produces an X-ray emission datacube from O7+ and O8+ emission lines around the Earth using in situ solar wind parameters as the model input. This study details the modeling process and shows that fixing the oxygen abundances to a constant value reduces the variance when comparing to the observations, at the cost of a small accuracy decrease in some cases. Using the ACE oxygen data returns a wide ranging accuracy, providing excellent correlation in a few cases and poor/anticorrelation in others. The sources of error for any user wishing to simulate terrestrial SWCX using an MHD model are described here and include mask position, hydrogen to oxygen ratio in the solar wind, and charge state abundances. A dawn-dusk asymmetry is also found, similar to the results of empirical modeling. Using constant oxygen parameters, magnitudes approximately double that of the observed count rates are returned. A high accuracy is determined between the model and observations when comparing the count rate difference between enhanced SWCX and quiescent periods.

  20. The Surf Zone Ichthyoplankton Adjacent to an Intermittently Open Estuary, with Evidence of Recruitment during Marine Overwash Events

    NASA Astrophysics Data System (ADS)

    Cowley, P. D.; Whitfield, A. K.; Bell, K. N. I.

    2001-03-01

    The composition, structure and seasonality of ichthyoplankton in the surf zone adjacent to the mouth of the intermittently open East Kleinemonde Estuary (33°32'S, 27°03'E) were investigated over a period of 2 years. Altogether 451 fishes, representing at least 21 taxa from 14 families, were collected. The assemblage was dominated by postflexion larvae of euryhaline marine species that are dependent on estuaries as nursery areas. The sparid Rhabdosargus holubi was the most abundant taxon and constituted more than 77% of the total catch. A distinct modal size class was identified for R. holubi , while the mean individual size of this and other abundant taxa was comparable to the observed recruitment size range reported from a wide variety of estuarine nursery habitats in southern Africa. Periodic regression analyses revealed significant peaks in abundance of larval R. holubi during late winter (August), at down and dusk, at new and full moon (spring tides), and on the flood stage of the tidal cycle. Evidence for estuarine immigration during marine overwash events (surging rough seas that enter the estuary) is provided by (1) the stranding of postflexion larvae in the region of the closed estuary mouth following these events, and (2) back extrapolation from length modes within the estuary to coincide with such an event. The advantages and disadvantages of such a recruitment strategy are discussed.