The Role of the Upper Atmosphere for Dawn-Dusk and Interhemispheric Differences in the Coupled Magnetosphere-Ionosphere-Thermosphere System

NASA Astrophysics Data System (ADS)

Foerster, M.; Doornbos, E.; Haaland, S.

2016-12-01

Solar wind and IMF interaction with the geomagnetic field sets up a large-scale plasma circulation in the Earth's magnetosphere and the magnetically tightly connected ionosphere. The ionospheric ExB ion drift at polar latitudes accelerates the neutral gas as a nondivergent momentum source primarily in force balance with pressure gradients, while the neutral upper thermosphere circulation is essentially modified by apparent forces due to Earth's rotation (Coriolis and centrifugal forces) as well as advection and viscous forces. The apparent forces affect the dawn and dusk side asymmetrically, favouring a large dusk-side neutral wind vortex, while the non-dipolar portions of the Earth's magnetic field constitute significant hemispheric differences in magnetic flux and field configurations that lead to essential interhemispheric differences of the ion-neutral interaction. We present statistical studies of both the high-latitude ionospheric convection and the upper thermospheric circulation patterns based on measurements of the electron drift instrument (EDI) on board the Cluster satellites and by the accelerometer on board the CHAMP, GOCE, and Swarm spacecraft, respectively.

Reconciling the Dawn-Dusk Asymmetry in Mercury’s Exosphere with the Micrometeoroid Impact Directionality

NASA Astrophysics Data System (ADS)

Pokorný, Petr; Sarantos, Menelaos; Janches, Diego

2017-06-01

Combining dynamical models of dust from Jupiter-family comets and Halley-type comets, we demonstrate that the seasonal variation of the dust/meteoroid environment at Mercury is responsible for producing the dawn-dusk asymmetry in Mercury’s exosphere observed by the MESSENGER spacecraft. Our latest models, calibrated recently from ground-based and space-borne measurements, provide unprecedented statistics that enable us to study the longitudinal and latitudinal distribution of meteoroids impacting Mercury’s surface. We predict that the micrometeoroid impact vaporization source is expected to undergo significant motion on Mercury’s surface toward the nightside during Mercury’s approach to aphelion and toward the dayside when the planet is approaching the Sun.

On the Occurrence of Magnetic Reconnection Along the Dawn and Dusk Magnetopause

NASA Astrophysics Data System (ADS)

Petrinec, S. M.; Burch, J. L.; Fuselier, S. A.; Trattner, K. J.; Gomez, R. G.; Giles, B. L.; Pollock, C.; Russell, C. T.; Strangeway, R. J.

2017-12-01

Magnetic reconnection is recognized as the primary process by which bulk solar wind plasma is able to enter the magnetosphere. The amount of plasma and energy transport is affected by the reconnection rate along the reconnection line as well as the spatial extent of the reconnection line. These parameters are in turn influenced by parameters such as the orientation of the interplanetary magnetic field (IMF), the dipole tilt angle of the Earth, and the local change in plasma beta between the magnetosheath and magnetosphere. Local variations of magnetosheath parameters are influenced by the character of the standing bow shock upstream of the observing location; i.e., there is greater variation downstream of the quasi-parallel shock than downstream of the quasi-perpendicular shock. Observations from the MMS mission are used to examine the occurrence of quasi-steady magnetic reconnection along the dawn and dusk regions of the magnetopause, and to determine the influence of local magnetosheath variations on the characteristics of the extended reconnection line.

Relationship between electron field-aligned anisotropy and dawn-dusk magnetic field: Nine years of Cluster observations in the Earth magnetotail

NASA Astrophysics Data System (ADS)

Yushkov, E.; Petrukovich, A.; Artemyev, A.; Nakamura, R.

2017-09-01

We investigate the distribution and possible origins of thermal anisotropic electrons in the Earth's magnetotail, using 9 years of Cluster observations. We mainly focus on relation between electron anisotropy and Bz and By magnetic field components (in GSM coordinates). The anisotropy of electron population is characterized by temperature ratio T∥/T⊥ and by the maximum of phase space density ratio F∥/F⊥ (∥ and ⊥ are relative to the background magnetic field). The population identified by large F∥/F⊥ is organized as short-time (dozens of seconds) bursts with enhanced F∥ and can be observed even in the plasma sheet with small T∥/T⊥. The thermal anisotropy T∥/T⊥ is larger for time intervals characterized by stronger Bz and By: the strong By corresponds to the T∥/T⊥ peak around the magnetotail neutral plane Bx=0, whereas the strong Bz corresponds to larger T∥/T⊥ with a flat profile across the magnetotail. There is a dawn-dusk asymmetry: large T∥/T⊥ corresponds mostly to strong Bz at the dusk flank and to strong By at the dawn flank. Using these differences of the electron anisotropy dependence on By and Bz, we discuss two possible mechanisms responsible for the anisotropy formation.

Formation of Dawn-Dusk Asymmetry in Earth's Magnetotail Thin Current Sheet: A Three-Dimensional Particle-In-Cell Simulation

NASA Astrophysics Data System (ADS)

Lu, San; Pritchett, P. L.; Angelopoulos, V.; Artemyev, A. V.

2018-04-01

Using a three-dimensional particle-in-cell simulation, we investigate the formation of dawn-dusk asymmetry in Earth's magnetotail. The magnetotail current sheet is compressed by an external driving electric field down to a thickness on the order of ion kinetic scales. In the resultant thin current sheet (TCS) where the magnetic field line curvature radius is much smaller than ion gyroradius, a significant portion of the ions becomes unmagnetized and decoupled from the magnetized electrons, giving rise to a Hall electric field Ez and an additional cross-tail current jy caused by the unmagnetized ions being unable to comove with the electrons in the Hall electric field. The Hall electric field transports via E × B drift magnetic flux and magnetized plasma dawnward, causing a reduction of the current sheet thickness and the normal magnetic field Bz on the duskside. This leads to an even stronger Hall effect (stronger jy and Ez) in the duskside TCS. Thus, due to the internal kinetic effects in the TCS, namely, the Hall effect and the associated dawnward E × B drift, the magnetotail dawn-dusk asymmetry forms in a short time without any global, long-term effects. The duskside preference of reconnection and associated dynamic phenomena (such as substorm onsets, dipolarizing flux bundles, fast flows, energetic particle injections, and flux ropes), which has been pervasively observed by spacecraft in the past 20 years, can thus be explained as a consequence of this TCS asymmetry.

Ionospheric control of the dawn-dusk asymmetry of the Mars magnetotail current sheet

NASA Astrophysics Data System (ADS)

Liemohn, Michael W.; Xu, Shaosui; Dong, Chuanfei; Bougher, Stephen W.; Johnson, Blake C.; Ilie, Raluca; De Zeeuw, Darren L.

2017-06-01

is not directly behind the planet but rather shifted toward the dawn or dusk direction. It is shown here that one factor controlling the location of the current sheet is the dayside ionosphere. At solar maximum, the ionosphere is dense, the magnetic field slips easily by the planet, and the current sheet is shifted toward dawn. At solar minimum, the ionosphere is relatively weak, the magnetic field slippage is slowed down, and the current sheet shifts toward dusk.

The Wonder and Enrichment of Teaching Wright Morris's "A Fight between a White Boy and a Black Boy in the Dusk of a Fall Afternoon in Omaha, Nebraska."

ERIC Educational Resources Information Center

McCaffrey, Jerrine

2001-01-01

Outlines a teaching method for Wright Morris's "A Fight Between a White Boy and a Black Boy in the Dusk of a Fall Afternoon in Omaha, Nebraska." Proposes that the story provides and opportunity to introduce stream-of-consciousness writing and to convey the significance of memory recall. (PM)

Varying and unchanging whiteness on the wings of dusk-active and shade-inhabiting Carystoides escalantei butterflies.

PubMed

Ge, Dengteng; Wu, Gaoxiang; Yang, Lili; Kim, Hye-Na; Hallwachs, Winnie; Burns, John M; Janzen, Daniel H; Yang, Shu

2017-07-11

Whiteness, although frequently apparent on the wings, legs, antennae, or bodies of many species of moths and butterflies, along with other colors and shades, has often escaped our attention. Here, we investigate the nanostructure and microstructure of white spots on the wings of Carystoides escalantei , a dusk-active and shade-inhabiting Costa Rican rain forest butterfly (Hesperiidae). On both males and females, two types of whiteness occur: angle dependent (dull or bright) and angle independent, which differ in the microstructure, orientation, and associated properties of their scales. Some spots on the male wings are absent from the female wings. Whether the angle-dependent whiteness is bright or dull depends on the observation directions. The angle-dependent scales also show enhanced retro-reflection. We speculate that the biological functions and evolution of Carystoides spot patterns, scale structures, and their varying whiteness are adaptations to butterfly's low light habitat and to airflow experienced on the wing base vs. wing tip.

An extended study of the low-latitude boundary layer on the dawn and dusk flanks of the magnetosphere

NASA Technical Reports Server (NTRS)

Mitchell, D. G.; Kutchko, F.; Williams, D. J.; Eastman, T. E.; Frank, L. A.

1987-01-01

The characteristics and structure of the low-latitude boundary layer (LLBL) have been studied for 66 ISEE 1 passes through the LLBL region. The dawn and dusk LLBL are on closed magnetic field lines for northward magnetosheath and/or IMF (M/IMF), and are on both closed and open field lines for southward M/IMF. For southward M/IMF, the regions of open LLBL field lines lie adjacent to the magnetopause and outside the closed LLBL. The LLBL is thicker (thinner) for northward (southward) M/IMF. With distance away from the subsolar magnetosphere, the LLBL becomes thicker for northward M/IMF and more variable in thickness for southward M/IMF. No dependence of LLBL thickness or electric field on geomagnetic activity is seen in these data. The LLBL electric field is a few millivolts per meter with a apparent upper limit of about 10 mV/m. The field captures magnetospherically drifting particles and propels them tailward.

Dawn-dusk asymmetry induced by the Parker spiral angle in the plasma dynamics around comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Behar, E.; Tabone, B.; Nilsson, H.

2018-05-01

When interacting, the solar wind and the ionised atmosphere of a comet exchange energy and momentum. Our aim is to understand the influence of the average Parker spiral configuration of the solar wind magnetic field on this interaction. We compare the theoretical expectations of an analytical generalised gyromotion with Rosetta observations at comet 67P/Churyumov-Gerasimenko. A statistical approach allows one to overcome the lack of upstream solar wind measurement. We find that additionally to their acceleration along (for cometary pick-up ions) or against (for solar wind ions) the upstream electric field orientation and sense, the cometary pick-up ions are drifting towards the dawn side of the coma, while the solar wind ions are drifting towards the dusk side of the coma, independent of the heliocentric distance. The dynamics of the interaction is not taking place in a plane, as often assumed in previous works.

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.

SAPS-associated explosive brightening on the dusk-side: A new type of onset-like disturbance: A new type of onset-like disturbance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henderson, M. G.; Morley, S. K.; Kepko, L. E.

Quasi-periodic energetic particle injections have been observed at geosynchronous orbit on the dusk-side during a steady magnetospheric convection event. Here, we examine high resolution auroral imager data and ground magnetometer data associated with the first of these injections and conclude that it was not associated with classical substorm signatures. It is proposed that these injections are caused by the explosive non-linear growth of a shear-flow-ballooning instability in the region where sub-auroral polarization streams (SAPS) also occur. It is suggested that interchange will occur preferentially in the low-conductivity SAPS region since the magnetic Richardson number is lowest there and the ‘line-tying’more » effect will also be least stabilizing there. We also propose that the observed particle injection signatures and auroral morphology constitute a new type of SAPS-associated explosive ‘onset-like’ disturbance that can occur during intervals of strong convection.« less

SAPS-associated explosive brightening on the dusk-side: A new type of onset-like disturbance: A new type of onset-like disturbance

DOE PAGES

Henderson, M. G.; Morley, S. K.; Kepko, L. E.

2017-12-06

Quasi-periodic energetic particle injections have been observed at geosynchronous orbit on the dusk-side during a steady magnetospheric convection event. Here, we examine high resolution auroral imager data and ground magnetometer data associated with the first of these injections and conclude that it was not associated with classical substorm signatures. It is proposed that these injections are caused by the explosive non-linear growth of a shear-flow-ballooning instability in the region where sub-auroral polarization streams (SAPS) also occur. It is suggested that interchange will occur preferentially in the low-conductivity SAPS region since the magnetic Richardson number is lowest there and the ‘line-tying’more » effect will also be least stabilizing there. We also propose that the observed particle injection signatures and auroral morphology constitute a new type of SAPS-associated explosive ‘onset-like’ disturbance that can occur during intervals of strong convection.« less

Control of the Polarity of the Interplanetary Magnetic Field on the Dawn-Dusk Symmetry of the Magnetopause

NASA Astrophysics Data System (ADS)

Shue, J.; Jhuang, B.; Song, P.; Safrankova, J.; Nemecek, Z.; Russell, C. T.; Chen, S.

2008-12-01

The solar wind dynamic pressure is reduced when the solar wind flows around the magnetosphere due to the diversion of the flows. The magnetopause is the boundary where the reduced dynamic pressure is balanced with the magnetic pressure of the compressed magnetosphere by the solar wind. The size and shape of the magnetopause have long been considered among the most important parameters in Solar Terrestrial physics. Previous models of the size and shape of the magnetopause often assumed the axis- symmetry of the magnetopause with respect to the Sun-Earth line. With a large number of magnetopause crossings by ISEE-1 and -2, AMPTE/IRM, Hawkeye, Geotail, Interball-1, and Magion-4, we are able to consider the asymmetry of the magnetopuase. In the Shue et al. [1997] model, the magnetopause was modeled by two parameters, r0 and alpha, representing the subsolar standoff distance and the flaring level of the magnetopause, respectively. Parameter alpha was assumed to be independent of phi in the Shue et al. [1997] model, where phi is the angle between the Z axis and the mapping of the radial vector of the magnetopause on the YZ plane. In the present study we allow alpha to be a function of phi. We separate crossings with different phis and fit them in each bin to the new functional form proposed by Shue et al. [1997]. We find that the magnetopause is symmetric in the dawn-dusk direction for northward IMF. However, its size on the dawnside becomes larger when the IMF is southward. The function of alpha in terms of phi can be combined with the 2-D Shue et al. [1997] model into a 3-D magnetopause model. (Shue, J.-H., J. K. Chao, H. C. Fu, C. T. Russell, P. Song, K. K. Khurana, and H. J. Singer, A new functional form to study the solar wind control of the magnetopause size and shape, J. Geophys. Res., 102, 9497, 1997.)

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.

Dusk in the South

NASA Image and Video Library

2013-12-23

Slipping into shadow, the south polar vortex at Saturn's moon Titan still stands out against the orange and blue haze layers that are characteristic of Titan's atmosphere. Images like this, from NASA's Cassini spacecraft, lead scientists to conclude that the polar vortex clouds form at a much higher altitude -- where sunlight can still reach -- than the lower-altitude surrounding haze. This view looks towards the trailing hemisphere of Titan (3,200 miles or 5,150 kilometers across). North on Titan is up and rotated 17 degrees to the left. Images taken using red, green and blue spectral filters were combined to create this natural-color view. The image was taken with the Cassini spacecraft narrow-angle camera on July 30, 2013. The view was acquired at a distance of approximately 895,000 miles (1.441 million kilometers) from Titan. Image scale is 5 miles (9 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA17177

Non-parametric entrainment by natural twilight in the microchiropteran bat, Hipposideros speoris inside a cave.

PubMed

Joshi, D S; Vanlalnghaka, C

2005-01-01

The study aimed to determine the influence of repeated natural dawn and dusk twilight pulses in entraining the circadian flight activity rhythm of the microchiropteran bat, Hipposideros speoris, free-running in constant darkness in a natural cave. The bats were exposed to repeated dawn or dusk twilight pulses at eight circadian phases. All bats exposed to dawn twilight pulses were entrained by advancing transients, and the stable entrainment was reached when the onset of activity occurred about 12 h before the lights-on of the pulses, irrespective of the initial phase at which the bats were exposed to twilight. All bats exposed to dusk twilight pulses, however, were entrained by delaying transients, and the stable entrainment was reached when the onset of activity occurred about 1.6 h after the lights-on of the pulses. The entrainment caused by dawn and dusk twilight pulses is discussed in the context of the postulated two photoreceptors: the short wavelength sensitive (S) photoreceptors mediating entrainment via dusk twilight, and the medium wavelength sensitive (M) photoreceptors mediating entrainment via dawn twilight.

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

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.

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.

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.

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.

Asymmetric Kelvin-Helmholtz Instability at Jupiter's Magnetopause Boundary: Implications for Corotation-Dominated Systems

NASA Astrophysics Data System (ADS)

Zhang, B.; Delamere, P. A.; Ma, X.; Burkholder, B.; Wiltberger, M.; Lyon, J. G.; Merkin, V. G.; Sorathia, K. A.

2018-01-01

The multifluid Lyon-Fedder-Mobarry (MFLFM) global magnetosphere model is used to study the interactions between solar wind and rapidly rotating, internally driven Jupiter magnetosphere. The MFLFM model is the first global simulation of Jupiter magnetosphere that captures the Kelvin-Helmholtz instability (KHI) in the critically important subsolar region. Observations indicate that Kelvin-Helmholtz vortices are found predominantly in the dusk sector. Our simulations explain that this distribution is driven by the growth of KHI modes in the prenoon and subsolar region (e.g., >10 local time) that are advected by magnetospheric flows to the dusk sector. The period of density fluctuations at the dusk terminator flank (18 magnetic local time, MLT) is roughly 1.4 h compared with 7.2 h at the dawn flank (6 MLT). Although the simulations are only performed using parameters of the Jupiter's magnetosphere, the results may also have implications for solar wind-magnetosphere interactions at other corotation-dominated systems such as Saturn. For instance, the simulated average azimuthal speed of magnetosheath flows exhibit significant dawn-dusk asymmetry, consistent with recent observations at Saturn. The results are particularly relevant for the ongoing Juno mission and the analysis of dawnside magnetopause boundary crossings for other planetary missions.

First results from the ionospheric radio occultations of Saturn by the Cassini spacecraft

NASA Astrophysics Data System (ADS)

Nagy, Andrew F.; Kliore, Arvydas J.; Marouf, Essam; French, Richard; Flasar, Michael; Rappaport, Nicole J.; Anabtawi, Aseel; Asmar, Sami W.; Johnston, Douglas; Barbinis, Elias; Goltz, Gene; Fleischman, Don

2006-06-01

The first set of near-equatorial occultations of the Saturn ionosphere was obtained by the Cassini spacecraft between May and September of 2005. The occultations occurred at near-equatorial latitudes, between 10°N and 10°S, at solar zenith angles from about 84° to 96°. The entry observations correspond to dusk conditions and the exit ones to dawn. An initial look at the data indicates that the average peak densities are lower and the peak altitude higher at dawn than at dusk, possibly the result of ionospheric decay during the night hours. There are also significant differences between individual dawn and dusk occultations; the initial thought is that this variation must be connected to changes in the water inflow into the upper atmosphere and/or variations in the particle impact ionization rates.

From Cosmic Dusk till Dawn with RELICS

NASA Astrophysics Data System (ADS)

Bradac, Marusa

When did galaxies start forming stars? What is the role of distant galaxies in galaxy formation models and the epoch of reionization? What are the conditions in typical lowmass, star-forming galaxies at z 4? Why is galaxy evolution dependent on environment? Recent observations indicate several critical puzzles in studies that address these questions. Chief among these, galaxies might have started forming stars earlier than previously thought (<400Myr after the Big Bang) and their star formation history differs from what is predicted from simulations. Furthermore, the details of the mechanisms that regulate star formation and morphological transformation in dense environments are still unknown. To solve these puzzles of galaxy evolution, we will use 41 galaxy clusters from the RELICS program (Reionization Lensing Cluster Survey) that are among the most powerful cosmic telescopes. Their magnification will allow us to study stellar properties of a large number of galaxies all the way to the reionization era. Accurate knowledge of stellar masses, ages, and star formation rates (SFRs) requires measuring both rest-frame UV and optical light, which only Spitzer can probe at z>0.5-11 for a sufficiently large sample of typical galaxies. This program will combine Spitzer imaging from two large programs, Director Discretionary Time (DDT) and the SRELICS program led by the PI.The main challenge in a study such as this is the capability to perform reliable photometry in crowded fields. Our team recently helped develop TPHOT, which is a much improved and much faster version of previously available codes. TPHOT is specifically designed to extract fluxes in crowded fields with very different PSFs. We will combine Spitzer photometry with ground based imaging and spectroscopy to obtain robust measurements of galaxy star formation rates, stellar masses, and stellar ages. This program will be a crucial legacy complement to previous Spitzer/IRAC deep blank field surveys and cluster studies, and will open up new parameter space by probing intrinsically fainter objects than most current surveys with a significantly improved sample variance over deep field surveys. It will allow us to study the properties (e.g. SFRs and stellar masses) of a large number of galaxies (200 at z=6-10), thus meeting our goal of reconstructing the cosmic SFR density with sufficient precision to better understand the role of galaxies in the reionization process. We will measure the presence (or absence) of established stellar populations with Spitzer for the largest sample to date. Furthermore this proposal will allow us to study the SFRs of the intrinsically faint (and magnified) intermediate redshift (z 4) galaxies, as well as the stellar mass function of z=0.3-0.7 galaxy members of our cluster sample, thereby expanding our understanding of star formation from reionization to the epoch of galaxy formation and dense environments. Many of the science goals of this proposal are main science drivers for JWST. Due to magnification our effective depth and resolution match those of the JWST blank fields and affords us a sneak preview of JWST sources with Spitzer now. This program will thus provide a valuable test-bed for simulations, observation planning and source selection just in time for JWST Cycle 1.

Dog and Cat Interactions in a Remote Aboriginal Community.

PubMed

Kennedy, Brooke; Brown, Wendy Y; Vernes, Karl; Körtner, Gerhard; Butler, James R A

2018-04-26

This study examined dog and cat demographics, roaming behaviours, and interspecific interactions in a remote Aboriginal island community using multiple methods. Our results revealed temporal differences between the roaming behaviours of dogs, cats, and wildlife. Dogs showed crepuscular behaviour, being active around dawn (5:30 a.m. to 9:30 a.m.) and dusk (6:00 p.m. and 11:35 p.m.). The majority of cats were active between dawn (6:30 a.m.) and dusk (7:30 p.m.) and travelled shorter distances than dogs. However, some cats were also observed roaming between dusk and dawn, and were likely to be hunting since flightless wildlife were also recorded on our remote-sensing cameras during this time. These baseline data provide evidence to suggest that new management programs are needed to reduce the number of roaming cats and therefore their potential impacts on native wildlife. Collaborations between Aboriginal owners and other stakeholders is necessary to design innovative and effective animal management and policy on the island.

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.

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.

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.

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.

Distribution of larval fishes related to potential navigation impacts on the upper Mississippi River, pool 7

USGS Publications Warehouse

Holland, L.E.; Sylvester, J.R.

1983-01-01

Ichthyoplankton samples were collected twice monthly during spring and summer 1981 from a variety of habitats in Navigation Pool 7 of the upper Mississippi River. Larval-fish distributions in the pool and variations in those distributions were analyzed relative to potential impacts of increased commercial navigation. Although as many as 66 species of adults have been found in the area (33 considered common), only 17 taxa were identified from our collections. In April and May, most larvae were collected in main-channel and main-channel-border areas next to major expanses of shallow backwaters. White bass Morone chrysops, yellow perch Perca flavescens, and crappies Pomoxis spp. were predominant. Numerous catostomids also were taken. In June and July, most larvae were taken in the lower pool. Freshwater drum Aplodinotus grunniens and gizzard shad Dorosoma cepedianum predominated in these samples, which also included many cyprinids and centrarchids. Diel patterns of abundance varied with species and sampling location. Freshwater drums were more abundant near the surface at midnight than during the day. Common carp Cyprinus carpio were most abundant in collections at dusk, whereas all other cyprinids were most abundant at dusk and dawn. Numbers of gizzard shad also increased slightly at dusk. Total numbers of larvae collected were greatest at dusk in main-channel and main-channel-border samples; backwater areas produced the greatest catches at midnight and dawn. Seasonal, spatial, diel, and species-specific variations in larval fish abundances significantly influenced the proportion of the community potentially vulnerable to increased boat traffic through Pool 7.

The Magnetic Local Time Distribution of Energetic Electrons in the Radiation Belt Region

NASA Astrophysics Data System (ADS)

Allison, H. J.

2017-12-01

Using fourteen years of electron flux data from the National Oceanic and Atmospheric Administration Polar Operational Environmental Satellites (POES), a statistical study of the magnetic local time (MLT) distribution of the electron population is performed across a range of activity levels, defined by AE, AE*, Kp, solar wind velocity (Vsw), and VswBz. Three electron energies (>30, >100, and >300 keV) are considered. Dawn-dusk flux asymmetries larger than order of magnitude were observed for >30 and >100 keV electrons. For >300 keV electrons, dawn-dusk asymmetries were primarily due to a decrease in the average dusk-side flux beyond L* ˜ 4.5 that arose with increasing activity. For the >30 keV population, substorm injections enhance the dawn-side flux, which may not reach the dusk-side as the electrons can be on open drift paths and lost to the magnetopause. The asymmetries in the >300 keV population are attributed to the combination of magnetopause shadowing and >300 keV electron injections by large electric fields. We suggest that 3D radiation belt models could set the minimum energy boundary (Emin) to 30 keV or above at L* ˜6 during periods of low activity. However, for more moderate conditions, Emin should be larger than 100 keV and, for very extreme activities, ˜300 keV. Our observations show the extent that in-situ electron flux readings may vary during active periods due to the MLT of the satellite and highlight the importance of 4D radiation belt models to fully understand radiation belt processes.

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

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

A critical time window for organismal interactions in a pelagic ecosystem.

PubMed

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.

The Extent to Which Dayside Reconnection Drives Field-Aligned Currents During Substorms

NASA Astrophysics Data System (ADS)

Forsyth, C.; Shortt, M. W.; Coxon, J.; Rae, J.; Freeman, M. P.; Kalmoni, N. M. E.; Jackman, C. M.; Anderson, B. J.

2016-12-01

Field-aligned currents, also known as Birkeland currents, are the agents by which energy and momentum is transferred to the ionosphere from the magnetosphere and solar wind. In order to understand this coupling, it is necessary to analyze the variations in these current systems with respect to the main energy sources of the solar wind and substorms. In this study, we perform a superposed epoch analysis of field-aligned currents determined by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) project with respect to substorm expansion phase onsets identified using the Substorm Onsets and Phases from Indices of the Electrojet (SOPHIE) technique. We examine the total upward and downward currents separately in the noon, dusk, dawn and midnight sectors. Our results show that the dusk and dawn currents have up to a 66% linear correlated with the dayside reconnection rate estimated from solar wind measurements, whereas the noon and midnight currents are not. The noon currents show little or no variation throughout the substorm cycle. The midnight currents follows the dusk currents up to 20 min before onset, after which the midnight current increases more rapidly and exponentially. At substorm onset, the exponential growth rate increases. While the midnight field-aligned currents grow exponentially after substorm onset, the auroral indices vary with a 1/6th power law. Overall, our results show that the growth and decay rates of the Region 1 and 2 current systems, which are strongest at dawn and dusk, are directly driven by the solar wind, whereas the growth and decay rates of the substorm current system, which are dominant at midnight, act independently of the upstream driver.

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.

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

NASA Astrophysics Data System (ADS)

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

1990-02-01

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.

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.

Hopkins Ultraviolet Telescope determination of the Io torus electron temperature

NASA Technical Reports Server (NTRS)

Hall, D. T.; Bednar, C. J.; Durrance, S. T.; Feldman, P. D.; Mcgrath, M. A.; Moos, H. W.; Strobel, D. F.

1994-01-01

Sulfur ion emissions from the Io plasma torus observed by the Hopkins Ultraviolet Telescope (HUT) in 1990 December have been analyzed to determine the effective temperature of the exciting electrons. Spectra were obtained with a long slit that extended from 3.1 to 8.7 Jupiter radii R(sub J) on both dawn and dusk torus ansae. The average temperature of electrons exciting S(2+) emissions from the dawn ansa is (4800 +/- 2400) K lower than on the dusk ansa, a dawn-dusk asymmetry comparable in both sign and magnitude to that measured by the Voyager Ultraviolet Spectrograph (UVS) experiment. Emissions from S(2+) ions are generated in a source region with electron temperatures in the range 32,000-56,000 K; S(3+) ion emissions are excited by electrons that average 20,000-40,000 K hotter. This distinct difference suggests that the S(3+) emission source region is spatially separate from the S(2+) source region. Estimated relative aperture filling factors suggest that the S(3+) emissions originate from a region more extended out of the centrifugal plane than the S(2+) emissions.

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.

Normal vision can compensate for the loss of the circadian clock

PubMed Central

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

2015-01-01

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

Energy storage and dissipation in the magnetotail during substorms. I - Particle simulations. II - MHD simulations

NASA Technical Reports Server (NTRS)

Winglee, R. M.; Steinolfson, R. S.

1993-01-01

2D electromagnetic particle simulations are used to investigate the dynamics of the tail during development of substorms under the influence of the pressure in the magnetospheric boundary layer and the dawn-to-dusk electric field. It is shown that pressure pulses result in thinning of the tail current sheet as the magnetic field becomes pinched near the region where the pressure pulse is applied. The pinching leads to the tailward flow of the current sheet plasma and the eventual formation and injection of a plasmoid. Surges in the dawn-to-dusk electric field cause plasma on the flanks to convect into the center of the current sheet, thereby thinning the current sheet. The pressure in the magnetospheric boundary laser is coupled to the dawn-to-dusk electric field through the conductivity of the tail. Changes in the predicted evolution of the magnetosphere during substorms due to changes in the resistivity are investigated under the assumption that MHD theory provides a suitable representation of the global or large-scale evolution of the magnetotail to changes in the solar wind and to reconnection at the dayside magnetopause. It is shown that the overall evolution of the magnetosphere is about the same for three different resistivity distributions with plasmoid formation and ejection in each case.

Relationship between PC index and magnetospheric field-aligned currents measured by Swarm satellites

NASA Astrophysics Data System (ADS)

Troshichev, O.; Sormakov, D.; Behlke, R.

2018-03-01

The relationship between the magnetospheric field-aligned currents (FAC) monitored by the Swarm satellites and the magnetic activity PC index (which is a proxy of the solar wind energy incoming into the magnetosphere) is examined. It is shown that current intensities measured in the R1 and R2 FAC layers at the poleward and equtorward boundaries of the auroral oval are well correlated, the R2 currents being evidently secondary in relation to R1 currents and correlation in the dawn and dusk oval sectors being better than in the noon and night sectors. There is evident relationship between the PC index and the intensity of field-aligned currents in the R1 dawn and dusk layers: increase of FAC intensity in the course of substorm development is accompanied by increasing the PC index values. Correlation between PC and FAC intensities in the R2 dawn and dusk layers is also observed, but it is much weaker. No correlation is observed between PC and field-aligned currents in the midnight as well as in the noon sectors ahead of the substorm expansion phase. The results are indicative of the R1 field-aligned currents as a driver of the polar cap magnetic activity (PC index) and currents in the R2 layer.

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.

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

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.

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.

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. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Auditory sensitivity of an acoustic parasitoid (Emblemasoma sp., Sarcophagidae, Diptera) and the calling behavior of potential hosts

PubMed Central

Farris, H.E.; Oshinsky, M.; Forrest, T.G.; Hoy, R.R.

2009-01-01

Using field broadcasts of model male calling songs, we tested whether Tibicen pruinosa and T. chloromera (Homoptera: Cicadidae) are candidate hosts for acoustic parasitoid flies. The model calling song of T. pruinosa attracted 90% of the flies (Sarcophagidae: Emblemasoma sp.; all larvapositing females) when broadcast simultaneously with the model T. chloromera song, a phonotactic bias reconfirmed in single song playbacks. In paired broadcasts of model T. pruinosa songs with different relative amplitudes (3 dB or 6 dB), significantly more flies were attracted to the more powerful song, a result consistent with the responses predicted by a model proposed by Forrest and Raspet [1994]. Using intracellular recordings and dye injections, we characterized the sensitivity of auditory units in sound-trapped flies. Intracellular recordings from six auditory units (5 interneurons, 1 afferent) revealed best sensitivity for frequencies near 3-4 kHz, matching the predominant spectral components of the calling songs of both species of cicada. Interestingly, although flies could be attracted to T. pruinosa broadcasts throughout the day, hourly censuses of singing males revealed that calling occurred exclusively at dusk. Furthermore, the duration of the dusk chorus in T. pruinosa was significantly shorter than the midday chorus of the less attractive song of T. chloromera. We propose that the tight temporal aggregation of the dusk chorus time could function to reduce risk from attracted parasitoids. PMID:18560209

Passive ranging redundancy reduction in diurnal weather conditions

NASA Astrophysics Data System (ADS)

Cha, Jae H.; Abbott, A. Lynn; Szu, Harold H.

2013-05-01

Ambiguity in binocular ranging (David Marr's paradox) may be resolved by using two eyes moving from side to side behind an optical bench while integrating multiple views. Moving a head from left to right with one eye closed can also help resolve the foreground and background range uncertainty. That empirical experiment implies redundancy in image data, which may be reduced by adopting a 3-D camera imaging model to perform compressive sensing. Here, the compressive sensing concept is examined from the perspective of redundancy reduction in images subject to diurnal and weather variations for the purpose of resolving range uncertainty at all weather conditions such as the dawn or dusk, the daytime with different light level or the nighttime at different spectral band. As an example, a scenario at an intersection of a country road at dawn/dusk is discussed where the location of the traffic signs needs to be resolved by passive ranging to answer whether it is located on the same side of the road or the opposite side, which is under the influence of temporal light/color level variation. A spectral band extrapolation via application of Lagrange Constrained Neural Network (LCNN) learning algorithm is discussed to address lost color restoration at dawn/dusk. A numerical simulation is illustrated along with the code example.

The role of the large scale convection electric field in erosion of the plasmasphere during moderate and strong storms

NASA Astrophysics Data System (ADS)

Thaller, S. A.; Wygant, J. R.; Cattell, C. A.; Breneman, A. W.; Bonnell, J. W.; Kletzing, C.; De Pascuale, S.; Kurth, W. S.; Hospodarsky, G. B.; Bounds, S. R.

2015-12-01

The Van Allen Probes offer the first opportunity to investigate the response of the plasmasphere to the enhancement and penetration of the large scale duskward convection electric field in different magnetic local time (MLT) sectors. Using electric field measurements and estimates of the cold plasma density from the Van Allen Probes' Electric Fields and Waves (EFW) instrument, we study erosion of the plasmasphere during moderate and strong geomagnetic storms. We present the electric field and density data both on an orbit by orbit basis and synoptically, showing the behavior of the convection electric field and plasmasphere over a period of months. The data indicate that the large scale duskward electric field penetrates deep (L shell < 3) into the inner magnetosphere on both the dusk and dawn sides, but that the plasmasphere response on the dusk and dawn sides differ. In particular, significant (~2 orders of magnitude) decreases in the cold plasma density occur on the dawn side within hours of the onset of enhanced duskward electric field. In contrast, on the dusk side, the plasmapause is located at higher L shell than it is on the dawn side. In some cases, in the post-noon sector, cold plasma density enhancements accompany duskward electric field enhancements for the first orbit after the electric field enchantment, consistent with a duskside, sunward flowing, drainage plume.

Leishmaniasis

MedlinePlus

... who study birds), other people who do research outdoors at night, and soldiers are examples of people ... air-conditioned areas as much as possible. Avoid outdoor activities, especially from dusk to dawn, when sand ...

Joule heating at high latitudes

NASA Technical Reports Server (NTRS)

Foster, J. C.; St.-Maurice, J.-P.; Abreu, V. J.

1983-01-01

Calculations based on simultaneous observations of the electric field magnitude, and individual measurements of ion drift velocity and particle precipitation, over the lifetime of the AE-C satellite, are used to determine high latitude Joule heating. Conductivities produced by an averaged seasonal illumination were included with those calculated from particle precipitation. It is found that high latitude Joule heating occurs in an approximately oval pattern, and consists of dayside cleft, dawn and dusk sunward convection, and night sector heating regions. On average, heating in the cleft and dawn-dusk regions contributes the largest heat input, and there is no apparent difference between hemispheres for similar seasons. Joule heat input is 50 percent greater in summer than in winter, due primarily to the greater conductivity caused by solar production.

A study of the electric field in an open magnetospheric model

NASA Technical Reports Server (NTRS)

Stern, D. P.

1973-01-01

Recently, Svalgaard and Heppner reported two separate features of the polar electromagnetic field that correlate with the dawn-dusk component of the interplanetary magnetic field. This work attempts to explain these findings in terms of properties of the open magnetosphere. The topology and qualitative properties of the open magnetosphere are first studied by means of a simple model, consisting of a dipole in a constant field. Many such properties are found to depend on the separation line, a curve connecting neutral points and separating different field line regimes. In the simple model it turns out that the electric field in the central polar cap tends to point from dawn to dusk for a wide variety of external fields, but, near the boundary of the polar cap, electric equipotentials are deformed into crescents.

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

PubMed

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 30 R S downtail. The small sample size at dawn prevents comprehensive statistical comparison with the dusk flank observations in terms of flux closure.

Endogenous modulation of human visual cortex activity improves perception at twilight.

PubMed

Cordani, Lorenzo; Tagliazucchi, Enzo; Vetter, Céline; Hassemer, Christian; Roenneberg, Till; Stehle, Jörg H; Kell, Christian A

2018-04-10

Perception, particularly in the visual domain, is drastically influenced by rhythmic changes in ambient lighting conditions. Anticipation of daylight changes by the circadian system is critical for survival. However, the neural bases of time-of-day-dependent modulation in human perception are not yet understood. We used fMRI to study brain dynamics during resting-state and close-to-threshold visual perception repeatedly at six times of the day. Here we report that resting-state signal variance drops endogenously at times coinciding with dawn and dusk, notably in sensory cortices only. In parallel, perception-related signal variance in visual cortices decreases and correlates negatively with detection performance, identifying an anticipatory mechanism that compensates for the deteriorated visual signal quality at dawn and dusk. Generally, our findings imply that decreases in spontaneous neural activity improve close-to-threshold perception.

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.

Ground-Based Observation of Mercury's Sodium at Haleakala Observatory in 2013–2017

NASA Astrophysics Data System (ADS)

Kameda, S.; Kagitani, M.

2018-05-01

In this study, daily variation in Mercury's sodium exosphere was observed at the Haleakala Observatory in Hawaii. We confirmed the seasonal variation of the column density of sodium atoms over the dawn side differs from that over the dusk side.

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

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

Aerial Refueling Test Methods

DTIC Science & Technology

2015-04-13

and receiver optimal lighting configuration should be determined and evaluated in dusk, twilight and full dark lunar illumination periods. Degraded...should consist of sunset to nautical twilight . These conditions provide poor illumination for visible cameras, but high for IR ones.  Night conditions

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.

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.

Observation of relativistic electron loss induced by EMIC waves in the outer radiation belt: Arase and PWING induction magnetometer array collaboration

NASA Astrophysics Data System (ADS)

Kurita, S.; Yoshizumi, M.; Kazuo, S.; Higashio, N.; Mitani, T.; Takashima, T.; Matsuoka, A.; Teramoto, M.; Shinohara, I.

2017-12-01

EMIC waves are generated by temperature anisotropy of energetic ions near the magnetic equator and satellite observations show that the waves tend to be observed on the dusk side and noon side magnetosphere. EMIC waves can propagate from the magnetosphere to the ground and they are observed by ground-based magnetometers as Pc1 pulsation. It has been pointed out that EMIC waves can resonate with relativistic electrons through anomalous cyclotron resonance, and cause strong pitch angle scattering of radiation belt electrons. It has been considered that precipitation loss of relativistic electrons by pitch angle scattering induced by EMIC waves is an important loss mechanism of radiation belt electrons. We report on the observation of relativistic electron loss observed by the Arase satellite on the dawn side magnetosphere during a geomagnetic disturbance, which is likely to be related to an EMIC wave activity. During the event, the EMIC wave activity in conjunction with the relativistic electron loss is identified from observation by the ground-based induction magnetometer array deployed by the PWING project. The magnetometer array observation reveals that EMIC waves are distributed in the wide magnetic local time range from the dusk to midnight sector. It is suggested that drifting relativistic electrons are scattered into the loss cone by the EMIC waves on the dusk to midnight sector before they arrive at the Arase satellite located on the dawn side. We will discuss the impact of loss caused by EMIC wave-induced precipitation loss on the overall flux variation of radiation belt electrons during the geomagnetic disturbance.

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.

Local time dependence of the thermal structure in the Venusian equatorial region revealed by Akatsuki radio occultation measurements

NASA Astrophysics Data System (ADS)

Ando, H.; Fukuhara, T.; Takagi, M.; Imamura, T.; Sugimoto, N.; Sagawa, H.

2017-12-01

The radio occultation technique is one of the most useful methods to retrieve vertical temperature profiles in planetary atmospheres. Ultra-Stable Oscillator (USO) onboard Venus Climate Orbiter, Akatsuki, enables us to investigate the thermal structure of the Venus atmosphere between about 40-90 km levels. It is expected that 35 temperature profiles will be obtained by the radio occultation measurements of Akatsuki until August 2017. Static stability derived from the temperature profiles shows its local time dependence above the cloud top level at low-latitudes equatorward of 25˚. The vertical profiles of the static stability in the dawn and dusk regions have maxima at 77 km and 82 km levels, respectively. A general circulation model (GCM) for the Venus atmosphere (AFES-Venus) reproduced the thermal structures above the cloud top qualitatively consistent with the radio occultation measurements; the maxima of the static stability are seen both in the dawn and dusk regions, and the local maximum of the static stability in the dusk region is located at a highler level than in the dawn region. Comparing the thermal structures between the radio occultation measurements and the GCM results, it is suggested that the distribution of the static stability above the cloud top could be strongly affected by the diurnal tide. The thermal tide influences on the thermal structure as well as atmospheric motions above the cloud level. In addition, it is shown that zonally averaged zonal wind at about 80 km altitude could be roughly estimated from the radio occultation measurements using the dispersion relation of the internal gravity wave.

An assessment of the need for changes in Virginia law concerning headlamp usage.

DOT National Transportation Integrated Search

1979-01-01

An evaluation was made of the need for changes in Virginia law concerning headlamp usage during periods of dusk and dawn and at times of limited visibility. At the present time motorists are required to turn on the headlamps of their vehicles one-hal...

West Nile Virus

MedlinePlus

... at risk. There are no specific vaccines or treatments for human WNV disease. The best way to avoid WNV is to prevent mosquito bites: Use insect repellent Get rid of mosquito breeding sites by emptying standing water from flower pots, buckets or barrels Stay indoors between dusk ...

Magnetosphere-ionosphere coupling during substorm onset

NASA Technical Reports Server (NTRS)

Maynard, N. C.; Burke, W. J.; Erickson, G. M.; Basinka, E. M.; Yahnin, A. G.

1996-01-01

Through the analysis of a combination of CRRES satellite measurements and ground-based measurements, an empirical scenario was developed for the onset of substorms. The process develops from ripples at the inner edge of the plasma sheet associated with dusk to dawn excursions of the electric field, prior to the beginning of dipolarization. The importance of Poynting flux is considered. Substorms develop when significant amounts of energy flow in both directions with the second cycle stronger than the initial cycle. Pseudobreakups occur when the energy flowing in both directions is weak or out of phase. The observations indicate that the dusk to dawn excursions of the cross-tail electric field correlate with changes in currents and particle energies observed by CRRES, and with ultra low frequency wave activity observed on the ground. Magnetic signatures of field aligned current filaments, associated with the substorm current wedge were observed to be initiated by the process.

Coincident observations of ionospheric troughs and the equatorial plasmapause

NASA Technical Reports Server (NTRS)

Grebowsky, J. M.; Maynard, N. C.; Tulunay, Y. K.; Lanzerotti, L. J.

1976-01-01

Electron-density observations made in the topside ionosphere by the Ariel 4 and Isis 2 satellites are examined in conjunction with results obtained by Explorer 45 when it traversed the near-equatorial plasmapause with one hour (both UT and MLT) of the Ariel and Isis traversals of the same L coordinate. Both dusk and night observations are analyzed, and an attempt is made to show that depressions in ionospheric electron density occur in the vicinity of the plasmapause field line. It is concluded that the electron distributions observed in the electron-density troughs at 550 km near dusk by Ariel and at 1400 km near midnight by Isis do not always parallel variations in the light-ion distribution inferred from the Explorer plasmapause traversals and that there appears to be no specific feature of the main ionospheric trough which can be used to identify the plasmapause field line except in a statistical sense.

Observations of Energetic Particle Escape at the Magnetopause: Early Results from the MMS Energetic Ion Spectrometer (EIS)

NASA Technical Reports Server (NTRS)

Cohen, I. J.; Mauk, B. H.; Anderson, B. J.; Westlake, J. H.; Sibeck, David Gary; Giles, Barbara L.; Pollock, C. J.; Turner, D. L.; Fennell, J. F.; Blake, J. B.;

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.

The inner edge of the plasma sheet and the diffuse aurora

NASA Technical Reports Server (NTRS)

Fairfield, D. H.; Vinas, A. F.

1983-01-01

Three dimensional measurements from the ISEE-1 low energy electron spectrometer are used to map the location of the inner edge of the plasma sheet and study the anisotropies in the electron distribution function associated with this boundary. Lower energy plasma sheet electrons have inner edges closer to the Earth than higher energies with the separations at different energies being larger near dawn and after dusk than at midnight. Lowest energy inner edges are frequently located adjacent to the plasmapause in the dawn hemisphere but are often separated from it in the dusk hemisphere by a gap of at least several Re. The energy dispersion is minimal in the afternoon quadrant where the inner edge is near the magnetopause and frequently oscillating on a time scale of minutes. The location of the inner edge is probably determined primarily by the motion of electrons in the existing electric and magnetic fields rather than by strong diffusion as has sometimes been supposed.

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

Dynamical injections as the source of near geostationary quiet time particle spatial boundaries

NASA Technical Reports Server (NTRS)

Mauk, B. H.; Meng, C. I.

1983-01-01

The question whether the noon-dusk feature is a manifestation of the spatial structures that should arise from quasi-stationary convection is examined. The key consideration here is whether the energy dispersion of the feature can be explained. It is shown that the observed energy dispersion cannot be attributed to the standard stationary convection configurations, either perturbed or unperturbed. It is also demonstrated, using a detailed computer simulation, that the nighttime, double-spiral-shaped injection boundary (used previously to reproduce the fast changing nighttime features) is successful at reproducing the noon-dusk feature by allowing the particles to evolve for periods of 12 to 36 hours after the injection. It is stressed that the portion of the injection boundary responsible for the feature looks very different from the standard convection boundaries configuration. Conclusions are offered concerning the importance of quasi-stationary convection as the mechanism by which the near geostationary regions are populated.

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

State Regulation of Heliport Design

DTIC Science & Technology

2001-05-01

Arpt Lgt Sked: Dusk-Dawn 81. Schedule for beacon; if lights on different from beacon list as a remark. If no beacon list light schedule. 82. Unicorn ...continued importance of hospital heliports and the rapidly growing use of instrument approach/departure procedures at such sites, is it appropriate

Diurnal flight response of the walnut twig beetle, Pityophthorus juglandis, to pheromone-baited traps in two northern California walnut habitats

Treesearch

Steven J. Seybold; Jennifer A. King; Daren R. Harris; Lori J. Nelson; Shakeeb M. Hamud; Yigen. Chen

2012-01-01

The diurnal flight response of the walnut twig beetle, Pityophthorus juglandis Blackman (Coleoptera: Scolytidae), was assessed during two seasonal periods at two sites in northern California. Males and females flew primarily at dusk in response to aggregation pheromone-baited traps during late June/early July, and the percentage of beetles that...

How Tiny Collisions Shape Mercury

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-07-01

If space rocks are unpleasant to encounter, space dust isnt much better. Mercurys cratered surface tells of billions of years of meteoroid impacts but its thin atmosphere is what reveals its collisional history with smaller impactors. Now new research is providing a better understanding of what were seeing.Micrometeoroids Ho!The inner solar system is bombarded by micrometeoroids, tiny particles of dust (on the scale of a tenth of a millimeter) emitted by asteroids and comets as they make their closest approach to the Sun. This dust doesnt penetrateEarths layers of atmosphere, but the innermost planet of our solar system, Mercury, doesnt have this convenient cushioning.Just as Mercury is affected by the impacts of large meteoroids, its also shaped by the many smaller-scale impacts it experiences. These tiny collisions are thought to vaporize atoms and molecules from the planets surface, which quickly dissociate. This process adds metals to Mercurys exosphere, the planets extremely tenuous atmosphere.Modeling PopulationsDistribution of the directions from which meteoroids originate before impacting Mercurys surface, as averaged over its entire orbit. Local time of 12 hr corresponds to the Sun-facing side. A significant asymmetry is seen between the dawn (6 hrs) and dusk (18 hrs) rates. [Pokorn et al. 2017]The metal distribution in the exosphere provides a way for us to measure the effect of micrometeoroid impacts on Mercury but this only works if we have accurate models of the process. A team of scientists led by Petr Pokorn (The Catholic University of America and NASA Goddard SFC) has now worked to improve our picture of micrometeoroid impact vaporization on Mercury.Pokorn and collaborators argue that two meteoroid populations Jupiter-family comets (short-period) and Halley-type comets (long-period) contribute the dust for the majority of micrometeoroid impacts on Mercury. The authors model the dynamics and evolution of these two populations, reproducing the

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,…

The magnetospheric lobe at geosynchronous orbit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomsen, M.F.; Bame, S.J.; McComas, D.J.

1994-09-01

On rare occasions, satellites at geosynchronous altitude enter the magnetospheric lobe, characterized by extremely low ion fluxes between 1 eV and 40 keV and electron fluxes above a few hundred eV. One year of plasma observations from two simultaneously operating spacecraft at synchronous orbit is surveyed for lobe encounters. A total of 34 full encounters and 56 apparent near encounters are identified, corresponding to {approximately}0.06% of the total observation time. Unlike energetic particle (E>40 keV) dropouts studied earlier, there is a strong tendency for the lobe encounters to occur postmidnight, as late as 07 local time. The two spacecraft encountermore » the lobe with different rates and in different seasons. These occurrence properties are not simply explicable in terms of the orbital geometry in either the solar magnetic or the geocentric solar magnetospheric coordinate system. A composite coordinate system which previously organized more energetic particle dropouts is somewhat more successful in organizing the lobe encounters, suggesting that solar wind distortion of the magnetic equatorial plane away from the dipole location and toward the antisolar direction may be largely responsible for these dropouts. The authors results further suggest that this distortion persists even sunward of the dawn-dusk terminator. However, a simple dawn-dusk symmetric distortion does not fully account for all the seasonal and local time asymmetries in the occurrence of the lobe encounters; thus there is probably an additional dawn-dusk asymmetry in the distorted field. The lobe encounters are strongly associated with magnetospheric activity and tend to occur in association with rare magnetosheath encounters at synchronous orbit. It thus appears that the presence of the lobe at geosynchronous orbit is the result of major, probably asymmetric modifications of the magnetospheric field geometry in times of strong disturbance. 19 refs., 7 figs., 1 tab.« less

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

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

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.

Observations of subauroral ionospheric dynamics during SED plume passage at Millstone Hill

NASA Astrophysics Data System (ADS)

Zhang, S.; Erickson, P. J.; Coster, A. J.

2017-12-01

Storm enhanced density (SED) is a characteristic ionospheric storm time structure, with a significant plasma density enhancement in a narrow zone. SED structures often (but not always) span the continental US with a base in the US northeast at the afternoon and dusk sector, extending westward or northwest into the high latitude dayside cusp region. It is a typical and repeatable space weather phenomenon occurring during the main phase of magnetic storms with intensity ranging from active to disturbed levels. Observations of stormtime ionospheric density enhancement at subauroral latitudes have a long history, and were termed the 'dusk effect' until relatively recently, when dense networks of GNSS receivers have allowed us to view this structure with much finer spatial and temporal resolution. The formation of a SED plume is a topic under intensive community investigation, but in general it is believed that stormtime ionospheric dynamics and processes within the coupling magnetosphere-ionosphere-thermosphere system are responsible. For instance, poleward and sunward plasma drifts at the edge of the expanded dusk sector high-latitude convection can be important. Subauroral polarization stream (SAPS) are often observed at the poleward edge of the SED plume where ionospheric conductivity is low. SAPS is a huge westward ion flow that can convect ionospheric plasma from the afternoon or evening sector where solar photoionization production is waning, creating low density or density troughs. Stormtime penetration electric fields also exist, creating enhanced low and mid latitude upward ion drifts that move ionospheric plasma upward from the low altitude region where they are produced. This provides another important ionization source to contribute to maintaining the SED plume. This paper will provide analysis of the relative strength of these factors by using joint datasets of current geospace storm events obtained with the Millstone Hill incoherent scatter radar, GNSS

Chapter 12: Daily Patterns of Marbled Murrelet Activity at Inland Sites

Treesearch

Nancy L. Naslund; Brian P. O’Donnell

1995-01-01

Patterns in the daily activity of Marbled Murrelets (Brachyramphus marmoratus) at inland sites has been studied throughout their range from California to Alaska. Murrelets are most active at inland sites around dawn, and to a lesser degree, at dusk. Throughout their range, peak levels of activity (detections) occur in the hour around dawn, but...

Synchronous Crepuscular Flight of Female Asian Gypsy Moths: Relationships of Light Intensity and Ambient and Body Temperatures

Treesearch

Ralph E. Charlton; Ring T. Carde; William E. Wallner; William E. Wallner

1999-01-01

Female gypsy moths (Lymantria dispar) of Asian heritage studied in central Siberia and Germany exhibit a highly synchronous flight at dusk, after light intensity falls to about 2 lux. This critical light intensity sets the timing of flight behaviors independent of ambient temperature. Flight follows several minutes of preflight wing fanning during which females in...

Abnormal evening vertical plasma drift and effects on ESF and EIA over Brazil-South Atlantic sector during the 30 October 2003 superstorm

NASA Astrophysics Data System (ADS)

Abdu, M. A.; de Paula, E. R.; Batista, I. S.; Reinisch, B. W.; Matsuoka, M. T.; Camargo, P. O.; Veliz, O.; Denardini, C. M.; Sobral, J. H. A.; Kherani, E. A.; de Siqueira, P. M.

2008-07-01

Equatorial F region vertical plasma drifts, spread F and anomaly responses, in the south American longitude sector during the superstorm of 30 October 2003, are analyzed using data from an array of instruments consisting of Digisondes, a VHF radar, GPS TEC and scintillation receivers in Brazil, and a Digisonde and a magnetometer in Jicamarca, Peru. Prompt penetrating eastward electric field of abnormally large intensity drove the F layer plasma up at a velocity ˜1200 ms-1 during post dusk hours in the eastern sector over Brazil. The equatorial anomaly was intensified and expanded poleward while the development of spread F/plasma bubble irregularities and GPS signal scintillations were weaker than their quiet time intensity. Significantly weaker F region response over Jicamarca presented a striking difference in the intensity of prompt penetration electric field between Peru and eastern longitudes of Brazil. The enhanced post dusk sector vertical drift over Brazil is attributed to electro-dynamics effects arising energetic particle precipitation in the South Atlantic Magnetic Anomaly (SAMA). These extraordinary results and their longitudinal differences are presented and discussed in this paper.

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

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. © 2015 The Author(s).

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.;

Low-energy plasma observations at synchronous orbit

NASA Technical Reports Server (NTRS)

Lennartsson, W.; Reasoner, D. L.

1978-01-01

The University of California at San Diego Auroral Particles Experiment on the ATS 6 satellite in synchronous orbit has detected a low-energy plasma population which is separate and distinct from both the ring current and the plasma sheet populations. The density and temperature of this low-energy population are highly variable, with temperatures in the range kT = 1-30 eV and densities ranging from less than 1 per cu cm to more than 10 per cu cm. The occurrence of a dense low-energy plasma is most likely in the afternoon and dusk local time sectors, whereas n greater than 1 per cu cm is seen in the local night sector only during magnetically quiet periods. These observations suggest that this plasma is the outer zone of the plasmasphere. During magnetically active periods this low-energy plasma is often observed flowing sunward. In the dusk sector, strong sunward plasma flow is often observed for 1-2 hours prior to the onset of a substorm-associated particle injection.

The magnetic field of the equatorial magnetotail from 10 to 40 earth radii

NASA Technical Reports Server (NTRS)

Fairfield, D. H.

1986-01-01

A statistical study of IMP 6, 7, and 8 magnetotail magnetic field measurements near the equatorial plane reveals new information about various aspects of magnetospheric structure. More magnetic flux crosses the equatorial plane on the dawn and dusk flanks of the tail than near midnight, but no evidence is found for a dependence on the interplanetary magnetic field sector polarity. Field magnitudes within 3 earth radii of the equatorial plane near dawn are more than twice as large as those near dusk for Xsm = -20 to -10 earth radii. The frequency of occurrence of southward fields is greatest near midnight, and such fields are seen almost twice as often for Xsm = -20 to -10 earth radii as for Xsm beyond -20 earth radii. This latter result supports the idea that the midnight region of the tail between 10 and 20 is a special location where neutral lines are particularly apt to form. Such a neutral line will approach nearest the earth in the midnight and premidnight region, where substorms are thought to have their onset.

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.

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.

Northern Saw-whet Owls (Aegolius acadicus) captured at Cape May Point, NJ, 1980-1994: comparison of two capture techniques

Treesearch

Katharine E. Duffy; Patrick E. Matheny

1997-01-01

During autumn migration 1980-1994, 1,270 Northern Saw-whet Owls (Aegolius acadicus) (NSWO) were captured and banded at Cape May Point, NJ. From 1980-1988, captures were effected by passive mist-netting. From 1989-1994, an audiolure (NSWO territorial song broadcast loudly from dusk to dawn in the trapping area) was used to enhance capture rate. 638...

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.

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.

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.

Ionospheric convection signatures observed by DE 2 during northward interplanetary magnetic field

NASA Technical Reports Server (NTRS)

Heelis, R. A.; Hanson, W. B.; Reiff, P. H.; Winningham, J. D.

1986-01-01

Observations of the ionospheric convection signature at high latitudes are examined during periods of prolonged northward interplanetary magnetic field (IMF). The data from Dynamics Explorer 2 show that a four-cell convection pattern can frequently be observed in a region that is displaced to the sunward side of the dawn-dusk meridian regardless of season. In the eclipsed ionosphere, extremely structured or turbulent flow exists with no identifiable connection to a more coherent pattern that may simultaneously exist in the dayside region. The two highest-latitude convection cells that form part of the coherent dayside pattern show a dependence on the y component of the IMF. This dependence is such that a clockwise circulating cell displaced toward dawn dominates the high-latitude region when B(Y) is positive. Anti-clockwise circulation displaced toward dusk dominates the highest latitudes when B(Y) is negative. Examination of the simultaneously observed energetic particle environment suggests that both open and closed field lines may be associated with the high-latitude convection cells. On occasions these entire cells can exist on open field lines. The existence of closed field lines in regions of sunward flow is also apparent in the data.

Take-Off Time of the First Generation of the Overwintering Small Brown Planthopper, Laodelphax striatellus in the Temperate Zone in East Asia

PubMed Central

Sanada-Morimura, Sachiyo; Otuka, Akira; Matsumura, Masaya; Etoh, Tomoki; Zhu, Yeqin; Zhou, Yijun; Zhang, Gufeng

2015-01-01

Overseas migration of the small brown planthopper, Laodelphax striatellus (Fallén), occurs during the winter wheat harvest season in East Asia. Knowing the take-off time of emigrating L. striatellus is crucial for predicting such migrations with a simulation technique because winds, carriers of migratory insects, change continuously. Several methods were used in China and Japan from late May to early June 2012 and again in 2013 to identify the precise timing of take-off. These methods included: a tow net trap mounted to a pole at 10 m above the ground, a helicopter-towed net trap, and a canopy trap (which also had video monitoring) set over wheat plants. Laodelphax striatellus emigrated from wheat fields mainly in the early evening, before dusk. The insects also emigrated during the daytime but rarely emigrated at dawn, showing a pattern that is unlike the bimodal emigration at dusk and dawn of two other rice planthoppers, the brown planthopper, Nilaparvata lugens (Stål), and the white-backed planthopper, Sogatella furcifera (Horváth). There was no significant difference in the temporal pattern of take-off behavior between females and males of Japanese L. striatellus populations. PMID:25780936

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.

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.

SAPS/SAID revisited: A causal relation to the substorm current wedge

NASA Astrophysics Data System (ADS)

Mishin, Evgeny; Nishimura, Yukitoshi; Foster, John

2017-08-01

We present multispacecraft observations of enhanced flow/electric field channels in the inner magnetosphere and conjugate subauroral ionosphere, i.e., subauroral polarization streams (SAPS) near dusk and subauroral ion drifts (SAID) near midnight. The channels collocate with ring current (RC) injections lagging the onset of substorms by a few to ˜20 min, i.e., significantly shorter than the gradient-curvature drift time of tens of keV ions. The time lag is of the order of the propagation time of reconnection-injected hot plasma jets to the premidnight plasmasphere and the substorm current wedge (SCW) to dusk. The observations confirm and expand on the previous results on the SAID features that negate the paradigm of voltage and current generators. Fast-time duskside SAPS/RC injections appear intimately related to a two-loop circuit of the substorm current wedge (SCW2L). We suggest that the poleward electric field inherent in the SCW2L circuit, which demands closure of the Region 1 and Region 2 sense field-aligned currents via meridional currents, is the ultimate cause of fast RC injections and SAPS on the duskside.

SAID/SAPS Revisited: A Causal Relation to the Substorm Current Wedge

NASA Astrophysics Data System (ADS)

Mishin, E. V.

2017-12-01

We present multi-spacecraft observations of enhanced flow/electric field channels in the inner magnetosphere and conjugate subauroral ionosphere, i.e., subauroral polarization streams (SAPS) near dusk and subauroral ion drifts (SAID) near midnight. The channels collocate with ring current (RC) injections lagging the onset of substorms by a few to ˜20 minutes, i.e., significantly shorter than the gradient-curvature drift time of tens of keV ions. The time lag is of the order of the propagation time of reconnection-injected hot plasma jets to the premidnight plasmasphere and the substorm current wedge (SCW) to dusk. The observations confirm and expand on the previous results on the SAID features that negate the paradigm of voltage and current generators. Fast-time duskside SAPS/RC injections appear intimately related to a two-loop circuit of the substorm current wedge (SCW2L). We suggest that the poleward electric field inherent in the SCW2L circuit, which demands closure of the Region 1- and Region 2-sense field-aligned currents via meridional currents, is the ultimate cause of fast RC injections and SAPS on the duskside.

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.

Extreme ultraviolet explorer satellite observation of Jupiter's Io plasma torus

NASA Technical Reports Server (NTRS)

Hall, D. T; Gladstone, G. R.; Moos, H. W.; Bagenal, F.; Clarke, J. T.; Feldman, P. D.; Mcgrath, M. A.; Schneider, N. M.; Shemansky, D. E.; Strobel, D. F.

1994-01-01

We present the first Extreme Ultraviolet Explorer (EUVE) satellite observation of the Jupiter system, obtained during the 2 day period 1993 March 30 through April 1, which shows a rich emission-line spectrum from the Io plasma torus spanning wavelengths 370 to 735 A. The emission features correspond primarily to known multiplets of oxygen and sulfur ions, but a blended feature near 372 A is a plausible Na II transition. The summed detected energy flux of (7.2 +/- 0.2) x 10(exp -11) ergs/sq cm(s) corresponds to a radiated power of approximately equal to 4 x 10(exp 11) W in this spectral range. All ansa emissions show a distinct dawn-dusk brightness asymmetry and the measured dusk/dawn ratio of the bright S III lambda-680 feature is 2.3 +/- 0.3, significantly larger than the ratio measured by the Voyager spacecraft ultraviolet (UV) instruments. A preliminary estimate of ion partitioning indicates that the oxygen/sulfur ion ratio is approximately equal to 2, compared to the value approximately equal to 1.3 measured by Voyager, and that (Na(+))/(e) greater than 0.01.

Diagnosis at dusk: malignant hypertension and phaeochromocytoma in a 6-year-old girl.

PubMed

Corcoran, John; Bird, Chris; Side, Lucy; Lakhoo, Kokila; Ryan, Fiona

2008-02-01

Phaeochromocytoma is a rare catecholamine-secreting tumour that may arise at any age, but is particularly unusual in childhood. The case of a 6-year-old girl who presented with a prolonged history of general malaise, headaches and abdominal pain is reported. On examination, she was noted to have malignant hypertension. Subsequent imaging of the abdomen demonstrated a left adrenal mass, with the diagnosis of phaeochromocytoma being confirmed by serial raised urinary metanephrines. Sympathetic blockade was established prior to definitive surgical treatment, resulting in complete resolution of the patient's symptoms and hypertension. Genetic screening of the family has since identified a previously undocumented missense mutation in the patient's VHL gene. The case raises the importance of routine measurement of blood pressure in all paediatric patients regardless of age, presentation or other factors.

Southeast Asia Report

DTIC Science & Technology

1987-03-16

evening, those in charge of the companies report their activities to the battalion committee. At dusk at 1900 hours each unit gets together for...organizational apparatuses of our sectors and echelons are too cumbersome and their effectiveness is low. Because cadres are not appropriately...emphasized initially in 1986. Many sectors and localities have tried very hard to apply technical innovations; expand their joint ventures and

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

PubMed

Thairu, Margaret W; Brunet, Johanne

2015-05-01

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. 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. 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. 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. Published by Oxford University Press on behalf of the Annals of Botany Company 2015. This work is written by (a) US Government

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

NASA Astrophysics Data System (ADS)

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

2014-06-01

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

Investigating Perturbation Electric Fields and Their Effects on the Coupled Low-, Mid- and High-latitude Ionosphere

DTIC Science & Technology

2015-08-14

stream (SAPS) E field had been strong. During these E field events, the repeated development of equatorial ionization anomaly ( EIA ), storm-enhanced...density (SED) bulge and SED plume occurred in those longitude sectors that covered the local dusk-midnight hours. Thus, a well-formed EIA - SED...Observational results and CTIPe simulated wind vector maps suggest that 1) the enhanced growth of the EIA transported solar produced plasma to the

Don't go with the Flow: An Invitation to Magnetosheath and Foreshock Studies

NASA Technical Reports Server (NTRS)

Sibeck, D. G.

2010-01-01

This talk reviews the predictions of gasdynamic, magnetohydrodynamic, and kinetic models for the magnetosheath and foreshock and compares these predictions with observations by the recent Cluster and THEMIS missions. Topics of interest include: the depletion layer, dawn/dusk asymmetries, the transmission of solar wind discontinuities, the formation of hot flow anomalies and cavities in the foreshock, and flows accelerated by field-line tension. We conclude by discussing opportunities for magnetosheath imaging.

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.

Large-scale irregularities of the winter polar topside ionosphere according to data from Swarm satellites

NASA Astrophysics Data System (ADS)

Lukianova, R. Yu.; Bogoutdinov, Sh. R.

2017-11-01

An analysis of the electron density measurements ( Ne) along the flyby trajectories over the high-latitude region of the Northern Hemisphere under winter conditions in 2014 and 2016 has shown that the main large-scale structure observed by Swarm satellites is the tongue of ionization (TOI). At the maximum of the solar cycle ( F 10.7 = 160), the average value of Ne in the TOI region at an altitude of 500 km was 8 × 104 cm-3. Two years later, at F 10.7 = 100, Ne 5 × 104 cm-3 and Ne 2.5 × 104 cm-3 were observed at altitudes of 470 and 530 km, respectively. During the dominance of the azimuthal component of the interplanetary magnetic field, the TOI has been observed mainly on the dawn or dusk side depending on the sign of B y . Simultaneous observations of the convective plasma drift velocity in the polar cap show the transpolar flow drift to the dawn ( B y < 0) or dusk side ( B y < 0). Observations and numerical simulation of the Ne distribution have confirmed the significant role of the electric field of the magnetospheric convection in the generation of large-scale irregularities in the polar ionosphere.

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

The bat-bird-bug battle: daily flight activity of insects and their predators over a rice field revealed by high-resolution Scheimpflug Lidar

NASA Astrophysics Data System (ADS)

Malmqvist, Elin; Jansson, Samuel; Zhu, Shiming; Li, Wansha; Svanberg, Katarina; Svanberg, Sune; Rydell, Jens; Song, Ziwei; Bood, Joakim; Brydegaard, Mikkel; Åkesson, Susanne

2018-04-01

We present the results of, to our knowledge, the first Lidar study applied to continuous and simultaneous monitoring of aerial insects, bats and birds. It illustrates how common patterns of flight activity, e.g. insect swarming around twilight, depend on predation risk and other constraints acting on the faunal components. Flight activity was monitored over a rice field in China during one week in July 2016, using a high-resolution Scheimpflug Lidar system. The monitored Lidar transect was about 520 m long and covered approximately 2.5 m3. The observed biomass spectrum was bimodal, and targets were separated into insects and vertebrates in a categorization supported by visual observations. Peak flight activity occurred at dusk and dawn, with a 37 min time difference between the bat and insect peaks. Hence, bats started to feed in declining insect activity after dusk and stopped before the rise in activity before dawn. A similar time difference between insects and birds may have occurred, but it was not obvious, perhaps because birds were relatively scarce. Our observations are consistent with the hypothesis that flight activity of bats is constrained by predation in bright light, and that crepuscular insects exploit this constraint by swarming near to sunset/sunrise to minimize predation from bats.

Hot-blooded singers: endothermy facilitates crepuscular signaling in African platypleurine cicadas (Hemiptera: Cicadidae: Platypleura spp.).

PubMed

Sanborn, Allen F; Villet, Martin H; Phillips, Polly K

2003-07-01

The cicada genus Platypleura has a wide distribution across Africa and southern Asia. We describe endothermic thermoregulation in four South African species that show crepuscular signaling behavior. This is the first evidence of thermoregulation in platypleurine cicadas. Field measurements of body temperature ( T(b)) show that these animals regulate T(b) through endogenous heat production. Maximum T(b) measured was 22.1 degrees C above ambient temperature during calling activity at dusk. The mean T(b) during dusk activity did not differ from the mean T(b) during diurnal activity. A unique behavior for cicadas, a temperature-dependent telescoping pulsation of the abdomen, was observed in the laboratory during endogenous warm-up. This behavior is part of a unique method of heat generation in endothermic cicadas. Males generally call from trunks and branches within the canopy and appear to use endothermy even when the sun is available to elevate T(b). Endothermy may provide the cicadas with the advantage of decreasing predation and acoustic competition by permitting calling from perches that most complement their cryptic coloration patterns and that ectotherms cannot use due to thermal constraints. In addition, endothermy may permit calling activity during crepuscular hours when atmospheric conditions are optimal for acoustic communication and predation risks are minimal.

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

NASA Astrophysics Data System (ADS)

Barringer, Julia L.; Wilson, Timothy P.; Szabo, Zoltan; Bonin, Jennifer L.; Fischer, Jeffrey M.; Smith, Nicholas 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 μg/L) peaked at dusk (2000 hours), whereas dissolved Mn and Zn concentrations (76.5-96.9 and 8.55-12.8 μg/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.

Defense Meteorological Satellite Program Data in Dynamic Auroral Boundary Coordinates: New insights into Polar Cap and Auroral Dynamics

NASA Astrophysics Data System (ADS)

Knipp, D.

2016-12-01

Using reprocessed (Level-2) data from the Defense Meteorology Satellite Program magnetometer (SSM) and particle precipitation (SSJ) instruments we determine the boundaries of the central plasma sheet auroral oval, and then consider the relative locations and intensities of field aligned currents. Large-scale field-aligned currents (FAC) are determined using the Minimum Variance Analysis technique, and their influence is then removed from the magnetic perturbations allowing us to estimate intensity and scale-size of the smaller-scale currents. When sorted by dynamic auroral boundary coordinates we find that large- scale Region 1 (R1) FAC are often within the polar cap and Region 2 (R2) FAC show a strong dawn-dusk asymmetry (as in Ohtani et al., 2010). We find that mesoscale FAC are stronger in the summer and are most consistently present in the vicinity of dawnside (downward) R1 FAC. Further, mesoscale FAC are confined to auroral latitudes and above on the dawnside, but can be subaroural on the dusk side. Hotspots of mesoscale FAC occur in pre-midnight regions especially during summer. Finally, we show how this information can be combined with measurements from above and below the ionosphere-thermosphere to help explain significant perturbations in polar cap dynamics.

Drift resonance and stability of the Io plasma torus

NASA Astrophysics Data System (ADS)

Zhan, Jie; Hill, T. W.

2000-03-01

The observed local time asymmetry of the Io plasma torus is generally attributed to the presence of a persistent dawn-to-dusk electric field in the Jovian magnetosphere. The local time asymmetry is modulated at the System 3 rotation period of Jupiter's magnetic field, suggesting that the dawn-to-dusk electric field may be similarly modulated. We argue that such a System 3 modulation would have a profound disruptive effect on the observed torus structure if the torus were to corotate at exactly the System 3 rate: the torus would be a resonantly forced harmonic oscillator, and would disintegrate in a few rotation periods, contrary to observations. This destabilizing effect is independent of, and in addition to, the more familiar effect of the centrifugal interchange instability, which is also capable of disrupting the torus in a few rotation periods in the absence of other effects. We conclude that the observed (few percent) corotation lag of the torus is essential to preserving the observed long-lived torus structure by detuning the resonant frequency (the torus drift frequency) relative to the forcing frequency (System 3). A possible outcome of this confinement mechanism is a residual radial oscillation of the torus at the beat period (~10 days) between System 3 and the torus drift period.

Ion and electron Kappa distribution functions in the plasma sheet.

NASA Astrophysics Data System (ADS)

Moya, P. S.; Stepanova, M. V.; Espinoza, C.; Antonova, E. E.; Valdivia, J. A.

2017-12-01

We present a study of ion and electron flux spectra in the Earth's plasma sheet using kappa distribution functions. Satellite data from the THEMIS mission were collected for thousands of crossings through the plasma sheet, between 7 and 35 Re and during the years 2008-2009. The events were separated according to the geomagnetic activity at the time. Our results show the distribution of the kappa index and characteristic energies across the plasma sheet and its evolution with distance to Earth for quiet times and for the substorm expansion and recovery phases. For the ions, it is observed that the kappa values tend to decrease outwards and that this effect is more significant in the dusk sector, where the smallest values are found for distances beyond 15 Re. The main effect of the substorms appears as an enhancement of this behavior. The electrons show a much more homogeneous distribution in quiet times, with a mild tendency for larger kappa values at larger distances. During substorms, the kappa values tend to equalize and appear very homogenous during expansion. However, they exhibit a significant increase in the dusk sector during the recovery substorm phase. Finally, we observe that the characteristic energy of the particles during substorms increases and concentrate at distances less than 15 Re.

Molecular Basis of Circadian Photoreception

DTIC Science & Technology

2006-06-30

dusk transitions . For example, proper circadian entrainment permits animals to inhabit precise “temporal niches” that minimize exposure to predation...into the spectral sensitivity of any unidentified circadian photoreceptors. Such a study in the golden hamster (Mesocricetus auratus) indicated a...0.05–0.3mM GTP-Tris; (280–300 mOsm, pH 7.3). Liquid junction potentials (-14mV) were corrected. In darkness, most cells had series resistance ᝺MΩ

Second harmonic poloidal waves observed by Van Allen Probes in the dusk-midnight sector

DOE PAGES

Min, Kyungguk; Takahashi, Kazue; Ukhorskiy, Aleksandr Y.; ...

2017-02-24

This paper presents observations of ultralow-frequency (ULF) waves from Van Allen Probes. The event that generated the ULF waves occurred 2 days after a minor geomagnetic storm during a geomagnetically quiet time. Narrowband pulsations with a frequency of about 7 mHz with moderate amplitudes were registered in the premidnight sector when Probe A was passing through an enhanced density region near geosynchronous orbit. Probe B, which passed through the region earlier, did not detect the narrowband pulsations but only broadband noise. Despite the single-spacecraft measurements, we were able to determine various wave properties. We find that the observed waves aremore » a second harmonic poloidal mode propagating westward with an azimuthal wave number estimated to be ~100; the magnetic field fluctuations have a finite compressional component due to small but finite plasma beta (~0.1); the energetic proton fluxes in the energy ranging from above 10 keV to about 100 keV exhibit pulsations with the same frequency as the poloidal mode and energy-dependent phase delays relative to the azimuthal component of the electric field, providing evidence for drift-bounce resonance; and the second harmonic poloidal mode may have been excited via the drift-bounce resonance mechanism with free energy fed by the inward radial gradient of ~80 keV protons. Here, we show that the wave active region is where the plume overlaps the outer edge of ring current and suggest that this region can have a wide longitudinal extent near geosynchronous orbit.« less

Second harmonic poloidal waves observed by Van Allen Probes in the dusk-midnight sector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Min, Kyungguk; Takahashi, Kazue; Ukhorskiy, Aleksandr Y.

This paper presents observations of ultralow-frequency (ULF) waves from Van Allen Probes. The event that generated the ULF waves occurred 2 days after a minor geomagnetic storm during a geomagnetically quiet time. Narrowband pulsations with a frequency of about 7 mHz with moderate amplitudes were registered in the premidnight sector when Probe A was passing through an enhanced density region near geosynchronous orbit. Probe B, which passed through the region earlier, did not detect the narrowband pulsations but only broadband noise. Despite the single-spacecraft measurements, we were able to determine various wave properties. We find that the observed waves aremore » a second harmonic poloidal mode propagating westward with an azimuthal wave number estimated to be ~100; the magnetic field fluctuations have a finite compressional component due to small but finite plasma beta (~0.1); the energetic proton fluxes in the energy ranging from above 10 keV to about 100 keV exhibit pulsations with the same frequency as the poloidal mode and energy-dependent phase delays relative to the azimuthal component of the electric field, providing evidence for drift-bounce resonance; and the second harmonic poloidal mode may have been excited via the drift-bounce resonance mechanism with free energy fed by the inward radial gradient of ~80 keV protons. Here, we show that the wave active region is where the plume overlaps the outer edge of ring current and suggest that this region can have a wide longitudinal extent near geosynchronous orbit.« less

Ionosphere of Venus - First observations of the dayside ion composition near dawn and dusk

NASA Technical Reports Server (NTRS)

Taylor, H. A., Jr.; Brinton, H. C.; Bauer, S. J.; Hartle, R. E.; Donahue, T. M.; Cloutier, P. A.; Michel, F. C.; Daniell, R. E., Jr.; Blackwell, B. H.

1979-01-01

Independent Bennett radio-frequency ion mass spectrometers on the Pioneer Venus bus and orbiter spacecraft obtained in situ measurements of the composition of the ionosphere of Venus. The spectrometer on the bus explored the dawn region while the spectrometer on the orbiter explored the duskside region. Information on the ion composition in the topside, the lower ionosphere, and the upper ionosphere is presented. Below the O(+) peak near 200 km, the ions are found to exhibit scale heights consistent with a neutral gas temperature of about 180 K near the terminator. In the upper ionosphere, scale heights of all species reflect the effects of plasma transport.

Ionosphere of venus: first observations of the dayside ion composition near dawn and dusk.

PubMed

Taylor, H A; Brinton, H C; Bauer, S J; Hartle, R E; Donahue, T M; Cloutier, P A; Michel, F C; Daniell, R E; Blackwell, B H

1979-02-23

The first in situ measurements of the composition of the ionosphere of Venus are provided by independent Bennett radio-frequency ion mass spectrometers on the Pioneer Venus bits and orbiter spacecraft, exploring the dawn and duskside regions, respectively. An extensive composition of ion species, rich in oxygen, nitrogen, and carbon chemistry is idenitified. The dominant topside ion is O(+), with C(+), N(+), H(+), and He(+) as prominent secondary ions. In the lower ionosphere, the ionzization peak or F(1) layer near 150 kilometers reaches a concentration of about 5 x l0(3) ions per cubic centimeter, and is composed of the dominant molecular ion, O(2)(+), with NO(+), CO(+), and CO(2)(+), constituting less than 10 percent of the total. Below the O(+) peak near 200 kilometers, the ions exhibit scale heights consistent with a neutral gas temperature of about 180 K near the terminator. In the upper ionosphere, scale heights of all species reflect the effects of plasma transport, which lifts the composition upward to the often abrupt ionopause, or thermal ion boundary, which is observed to vary in height between 250 to 1800 kilometers, in response to solar wind dynamics.

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. © 2015 German Botanical Society and The Royal Botanical Society of the Netherlands.

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

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.

Impact of Feed Delivery Pattern on Aerial Particulate Matter and Behavior of Feedlot Cattle.

PubMed

Mitloehner, Frank M; Dailey, Jeff W; Morrow, Julie L; McGlone, John J

2017-03-01

Fine particulate matter with less than 2.5 microns diameter (PM 2.5 ) generated by cattle in feedlots is an environmental pollutant and a potential human and animal health issue. The objective of this study was to determine if a feeding schedule affects cattle behaviors that promote PM 2.5 in a commercial feedlot. The study used 2813 crossbred steers housed in 14 adjacent pens at a large-scale commercial West Texas feedlot. Treatments were conventional feeding at 0700, 1000, and 1200 (CON) or feeding at 0700, 1000, and 1830 (ALT), the latter feeding time coincided with dusk. A mobile behavior lab was used to quantify behaviors of steers that were associated with generation of PM 2.5 (e.g., fighting, mounting of peers, and increased locomotion). PM 2.5 samplers measured respirable particles with a mass median diameter ≤2.5 μm (PM 2.5 ) every 15 min over a period of 7 d in April and May. Simultaneously, the ambient temperature, humidity, wind speed and direction, precipitation, air pressure, and solar radiation were measured with a weather station. Elevated downwind PM 2.5 concentrations were measured at dusk, when cattle that were fed according to the ALT vs. the CON feeding schedule, demonstrated less PM 2.5 -generating behaviors ( p < 0.05). At dusk, steers on ALT vs. CON feeding schedules ate or were waiting to eat (standing in second row behind feeding cattle) at much greater rates ( p < 0.05). Upwind PM 2.5 concentrations were similar between the treatments. Downwind PM 2.5 concentrations averaged over 24 h were lower from ALT compared with CON pens (0.072 vs. 0.115 mg/m³, p < 0.01). However, dry matter intake (DMI) was less ( p < 0.05), and average daily gain (ADG) tended to be less ( p < 0.1) in cattle that were fed according to the ALT vs. the CON feeding schedules, whereas feed efficiency (aka gain to feed, G:F) was not affected. Although ALT feeding may pose a challenge in feed delivery and labor scheduling, cattle exhibited fewer PM 2.5 -generating

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

Energetic neutral atom imaging at low altitudes from the Swedish microsatellite Astrid: Images and spectral analysis

NASA Astrophysics Data System (ADS)

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

1999-02-01

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° 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 (~104(cm2srs)-1 over 26-37 keV) coming from the dusk region and low altitudes (~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, F12, 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>=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 exchange cross section between ions and exospheric oxygen.

AF-Geospace User’s Manual Version 2.5.1 and Version 2.51P

DTIC Science & Technology

2012-08-01

system of the grid. The choices are: GEOC: Geocentric coordinate system: The Z axis is aligned with the north rotational pole, the X axis pierces...the Greenwich Meridian on the equator (0 o Long, 0 o Lat), and the Y axis is minus the cross-product of X and Z. GSM: Geocentric solar magnetospheric...handed system and is positive towards dusk. GEI: Geocentric equatorial inertial coordinate system: The Z axis is the same as for the geocentric

Medical Effects and Dosimetric Data from Nuclear Tests at the Semipalatinsk Test Site

DTIC Science & Technology

2006-06-01

fi bromyoma 8 10 4 Posthysterectomy changes (radical hys- terectomy for cancer) 5 7 2 Displaced sex organs 3 11 7 Uterine prolapse and varicose...dust, of diffi culty in breathing, and eye irritation. The skies were overcast and dusk fell; the cattle were restless, and howling dogs , their...11 Chronic adnexitis 32 54 42 Cervicitis 19 32 17 Endocervicitis 6 16 6 Fibrocystic changes of the ovary 4 5 -- Cervical canal polyps 2 2 6 Uterine

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.

Modeling ionospheric pre-reversal enhancement and plasma bubble growth rate using data assimilation

NASA Astrophysics Data System (ADS)

Rajesh, P. K.; Lin, C. C. H.; Chen, C. H.; Matsuo, T.

2017-12-01

We report that assimilating total electron content (TEC) into a coupled thermosphere-ionosphere model by using the ensemble Kalman filter results in improved specification and forecast of eastward pre-reversal enhancement (PRE) electric field (E-field). Through data assimilation, the ionospheric plasma density, thermospheric winds, temperature and compositions are adjusted simultaneously. The improvement of dusk-side PRE E-field over the prior state is achieved primarily by intensification of eastward neutral wind. The improved E-field promotes a stronger plasma fountain and deepens the equatorial trough. As a result, the horizontal gradients of Pedersen conductivity and eastward wind are increased due to greater zonal electron density gradient and smaller ion drag at dusk, respectively. Such modifications provide preferable conditions and obtain a strengthened PRE magnitude closer to the observation. The adjustment of PRE E-field is enabled through self-consistent thermosphere and ionosphere coupling processes captured in the model. The assimilative outputs are further utilized to calculate the flux tube integrated Rayleigh-Taylor instability growth rate during March 2015 for investigation of global plasma bubble occurrence. Significant improvements in the calculated growth rates could be achieved because of the improved update of zonal electric field in the data assimilation forecast. The results suggest that realistic estimate or prediction of plasma bubble occurrence could be feasible by taking advantage of the data assimilation approach adopted in this work.

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.

Timescales Of The Influence Of IMF Clock Angle In Controlling The Characteristics Of Magnetospheric Dynamics

NASA Astrophysics Data System (ADS)

Grocott, A.; Milan, S. E.

2013-12-01

We exploit a database of high-latitude ionospheric electric potential patterns, derived from radar observations of plasma convection in the northern hemisphere from the years 2000 - 2006, to investigate the timescales of interplanetary magnetic field (IMF) penetration into the magnetosphere. We parameterise the convection observations by IMF clock angle, θ (the angle between geocentric solar magnetic (GSM) north and the projection of the IMF vector onto the GSM Y-Z plane), and by an IMF timescale, τB (the length of time that a similar clock angle has been maintained prior to the convection observations being made). We find that the nature of the ionospheric convection changes with IMF clock angle, as expected from previous time-averaged studies, and that for τB ~ 30 mins the convection patterns closely resemble their time-averaged counterparts. However, we also find that for certain IMF clock angles, in particular those with a northward BZ component and significant BY (dusk-dawn) component, the patterns evolve with increasing τB to less resemble their time-averaged counterparts, showing a marked enhancement in dusk-dawn asymmetry as τB approaches 10 hours. We discuss these findings in terms of the effects of the persistent penetration of a quasi-steady IMF into the magnetosphere, and its implications for understanding different modes of magnetospheric dynamics.

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).

F-region and Topside Plasma Response During Geomagnetic Storms

NASA Astrophysics Data System (ADS)

Fuller-Rowell, T. J.; Fedrizzi, M.; Maruyama, N.; Richards, P.; Fang, T. W.; Codrescu, M.

2015-12-01

The noon to dusk mid-latitudes sector appears to be a preferred region for substantial rise in plasma density during elevated geomagnetic activity. Previous the plasma density increase in this sector was referred to as the "dusk effect" and more recently the "storm enhanced density". Certainly in some longitude sectors, if the increase in magnetospheric convection occurs at the appropriate Universal Time, the activity does not need to be particularly strong to produce a significant increase in plasma content, such as during the February 27th 2014 event when Kp reached only 6 but there was substantial loss of the FAA WAAS system. The March 2015 St. Patrick's Day storm was considerably more intense with respect to Kp and Dst, and different in timing and duration, so the response and longitude sectors affected were quite different. Numerical simulation of the St. Patrick's Day storm with a coupled thermosphere-ionosphere model (CTIPe) and a stand-alone ionosphere-plasmasphere code (IPE) can be used to understand the physical processes in the plasma and neutral response. In particular the focus is on the vertical distribution of the plasma from the F-region to the topside. The models can be used to assess the impact of electric fields, meridional neutral winds, and solar illumination aiding plasma buildup and storage, neutral composition creating depletions, and magnetospheric convection creating structure.

Electron Dropout Echoes Induced by Interplanetary Shock: A Statistical Study

NASA Astrophysics Data System (ADS)

Liu, Z.; Zong, Q.; Hao, Y.; Zhou, X.; Ma, X.; Liu, Y.

2017-12-01

"Electron dropout echo" as indicated by repeated moderate dropout and recovery signatures of the flux of energetic electron in the out radiation belt region has been investigated systematically. The electron dropout and its echoes are usually found for higher energy (> 300 keV) channels fluxes, whereas the flux enhancements are obvious for lower energy electrons simultaneously after the interplanetary shock arrives at the Earth's geosynchronous orbit. 104 dropout echo events have been found from 215 interplanetary shock events from 1998 to 2007 based on LANL satellite data. In analogy to substorm injections, these 104 events could be naturally divided into two categories: dispersionless (49 events) or dispersive (55 events) according to the energy dispersion of the initial dropout. It is found that locations of dispersionless events are distributed mainly in the duskside magnetosphere. Further, the obtained locations derived from dispersive events with the time-of-flight technique of the initial dropout regions are mainly located at the duskside as well. Statistical studies have shown that the effect of shock normal, interplanetary magnetic field Bz and solar wind dynamic pressure may be insignificant to these electron dropout events. We suggest that the electric field impulse induced by the IP shock produces a more pronounced inward migration of electrons at the dusk side, resulting in the observed dusk-side moderate dropout of electron flux and its consequent echoes.

Using soundscapes to detect variable degrees of human influence on tropical forests in Papua New Guinea.

PubMed

Burivalova, Zuzana; Towsey, Michael; Boucher, Tim; Truskinger, Anthony; Apelis, Cosmas; Roe, Paul; Game, Edward T

2018-02-01

There is global concern about tropical forest degradation, in part, because of the associated loss of biodiversity. Communities and indigenous people play a fundamental role in tropical forest management and are often efficient at preventing forest degradation. However, monitoring changes in biodiversity due to degradation, especially at a scale appropriate to local tropical forest management, is plagued by difficulties, including the need for expert training, inconsistencies across observers, and lack of baseline or reference data. We used a new biodiversity remote-sensing technology, the recording of soundscapes, to test whether the acoustic saturation of a tropical forest in Papua New Guinea decreases as land-use intensity by the communities that manage the forest increases. We sampled soundscapes continuously for 24 hours at 34 sites in different land-use zones of 3 communities. Land-use zones where forest cover was fully retained had significantly higher soundscape saturation during peak acoustic activity times (i.e., dawn and dusk chorus) compared with land-use types with fragmented forest cover. We conclude that, in Papua New Guinea, the relatively simple measure of soundscape saturation may provide a cheap, objective, reproducible, and effective tool for monitoring tropical forest deviation from an intact state, particularly if it is used to detect the presence of intact dawn and dusk choruses. © 2017 The Authors. Conservation Biology published by Wiley Periodicals, Inc. on behalf of Society for Conservation Biology.

Medical Effects and Dosimetric Data from Nuclear Tests at Semipalatinsk

DTIC Science & Technology

2006-10-01

5 7 2 Displaced sex organs 3 11 7 Uterine prolapse and varicose labial veins 5 7 7 Total 130 273 119 The colpitis observed in middle-aged women was...breathing, and eye irritation. The skies were overcast and dusk fell; the cattle were restless, and howling dogs , their tails between their legs, would...Fibrocystic changes of the ovary 4 5 -- Cervical canal polyps 2 2 6 Uterine fi bromyoma 8 10 4 Posthysterectomy changes (radical hys- terectomy for cancer

Medical Effects and Dosimetric Data from Nuclear Tests at the Semipalatinsk Test Site

DTIC Science & Technology

2006-10-01

5 7 2 Displaced sex organs 3 11 7 Uterine prolapse and varicose labial veins 5 7 7 Total 130 273 119 The colpitis observed in middle-aged women was...breathing, and eye irritation. The skies were overcast and dusk fell; the cattle were restless, and howling dogs , their tails between their legs, would...Fibrocystic changes of the ovary 4 5 -- Cervical canal polyps 2 2 6 Uterine fi bromyoma 8 10 4 Posthysterectomy changes (radical hys- terectomy for cancer

Two Observed Consequences of Penetration Electric Fields

DTIC Science & Technology

2008-10-11

satellites are three- axis stabilized spacecraft that fly in circular. Sun -synchronous, polar ( inclination 98.7 ) orbits at an altitude of ~840km. The...350 km. The orbital period was —10 h. CRRES was spin stabilized at a rate of 2 rpm. Its spin axis always pointed within 15 of the Sun . The line of...satellites with flight designations 10 and higher, orbital ascending nodes are on the dusk side of the Earth . Thus, during the Halloween storm DMSP

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.

Space-based pseudo-fixed latitude observation mode based on the characteristics of geosynchronous orbit belt

NASA Astrophysics Data System (ADS)

Hu, Yun-peng; Chen, Lei; Huang, Jian-yu

2017-08-01

The US Lincoln Laboratory proved that space-based visible (SBV) observation is efficient to observe space objects, especially Geosynchronous Orbit (GEO) objects. After that, SBV observation plays an important role in the space surveillance. In this paper, a novel space-based observation mode is designed to observe all the GEO objects in a relatively short time. A low earth orbit (LEO) satellite, especially a dawn-dusk sun-synchronous orbit satellite, is useful for space-based observation. Thus, the observation mode for GEO objects is based on a dawn-dusk sun-synchronous orbit satellite. It is found that the Pinch Point (PP) regions proposed by the US Lincoln Laboratory are spreading based on the analysis of the evolution principles of GEO objects. As the PP regions becoming more and more widely in the future, many strategies based on it may not be efficient any more. Hence, the key point of the space-based observation strategy design for GEO objects should be emphasized on the whole GEO belt as far as possible. The pseudo-fixed latitude observation mode is proposed in this paper based on the characteristics of GEO belt. Unlike classical space-based observation modes, pseudo-fixed latitude observation mode makes use of the one-dimensional attitude adjustment of the observation satellite. The pseudo-fixed latitude observation mode is more reliable and simple in engineering, compared with the gazing observation mode which needs to adjust the attitude from the two dimensions. It includes two types of attitude adjustment, i.e. daily and continuous attitude adjustment. Therefore, the pseudo-fixed latitude observation mode has two characteristics. In a day, the latitude of the observation region is fixed and the scanning region is about a rectangle, while the latitude of the observation region centre changes each day in a long term based on a daily strategy. The capabilities of a pseudo-fixed latitude observation instrument with a 98° dawn-dusk sun-synchronous orbit are

Radial and azimuthal distribution of Io's oxygen neutral cloud observed by Hisaki/EXCEED

NASA Astrophysics Data System (ADS)

Koga, R.; Tsuchiya, F.; Kagitani, M.; Sakanoi, T.; Yoneda, M.; Yoshikawa, I.; Yoshioka, K.; Murakami, G.; Yamazaki, A.; Kimura, T.; Smith, H. T.

2017-12-01

We report the spatial distributions of oxygen neural cloud surrounding Jupiter's moon Io and along Io's orbit observed by the HISAKI satellite. Atomic oxygen and sulfur in Io's atmosphere escape from the exobase and move to corona (< 5.8 Io radii, the boundary where Jupiter's gravity begins to dominate) and neutral clouds (> 5.8 Io radii) mainly due to atmospheric sputtering. Io plasma torus is formed by ionization of these atoms by electron impact and charge exchange processes. It is essential to examine the dominant source of Io plasma torus, particularly in the vicinity of Io (<5.8 Io radii; atmosphere and corona) or the region away from Io (>5.8 Io radii; extended neutral clouds). The spatial distribution of oxygen and sulfur neutral clouds is important to understand the source. The extreme ultraviolet spectrometer called EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics) installed on the Hisaki satellite observed Io plasma torus continuously in 2014-2015, and we carried out the monitoring of the distribution of atomic oxygen emission at 130.4 nm. The emission averaged over the distance range of 4.5-6.5 Jovian radii on the dawn and dusk sides strongly depends on the Io phase angle (IPA), and has a emission peak between IPA of 60-90 degrees on the dawn side, and between 240-270 degrees on the dusk side, respectively. It also shows the asymmetry with respect to Io's position: the intensity averaged for IPA 60-90 degrees (13.3 Rayleighs (R)) is 1.2 times greater than that for IPA 90-120 degrees (11.1 R) on the dawn side. The similar tendency is found on the dusk side. Weak atomic oxygen emission (4 R) uniformly distributes in every IPA. We also examined the radial distribution of the oxygen neutral cloud during the same period and found the emission peak near Io's orbit with decreasing the intensity toward 8.0 Jupiter radii. The results show the high density component of the oxygen neutral cloud is concentrated around Io and extends mainly toward

DC and AC Electric Field Measurements by Spin-Plane Double Probes Onboard MMS

NASA Astrophysics Data System (ADS)

Lindqvist, P. A.; Marklund, G. T.; Khotyaintsev, Y. V.; Ergun, R. E.; Goodrich, K.; Torbert, R. B.; Argall, M. R.; Nakamura, R.

2015-12-01

The four spacecraft of the NASA Magnetospheric Multiscale mission (MMS) were launched on 12 March 2015 into a 1.2 x 12 Re equatorial orbit to study energy conversion processes in Earth's magnetosphere. After a 5-month commissioning period the first scientific phase starts on 1 September as the orbit enters the dusk magnetopause region. The Spin-plane Double Probe electric field instrument (SDP), part of the electric and magnetic fields instrument suite FIELDS, measures the electric field in the range 0.3 - 500 mV/m with a continuous time resolution up to 8192 samples/s. The instrument features adjustable bias currents and guard voltages to optimize the measurement performance. SDP also measures the spacecraft potential, which can be controlled by the Active Spacecraft Potential Control (ASPOC) ion emitter, and under certain conditions can be used to determine plasma density. We present observations of DC and AC electric fields in different plasma regions covered by MMS since launch including the night side flow braking region, reconnection regions at the dusk and dayside magnetopause, and in the magnetosheath. We compare the electric field measurements by SDP to other, independent determinations of the electric field, in particular by the Electron Drift Instrument (EDI), in order to assess the accuracy of the electric field measurement under different plasma conditions. We also study the influence of the currents emitted by ASPOC and EDI on the SDP measurements.

The global context of the 14 November 2012 storm event

DOE PAGES

Hwang, K. -J.; Sibeck, D. G.; Fok, M. -C. H.; ...

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

Fragaria vesca CONSTANS controls photoperiodic flowering and vegetative development.

PubMed

Kurokura, Takeshi; Samad, Samia; Koskela, Elli; Mouhu, Katriina; Hytönen, Timo

2017-10-13

According to the external coincidence model, photoperiodic flowering occurs when CONSTANS (CO) mRNA expression coincides with light in the afternoon of long days (LDs), leading to the activation of FLOWERING LOCUS T (FT). CO has evolved in Brassicaceae from other Group Ia CO-like (COL) proteins which do not control photoperiodic flowering in Arabidopsis. COLs in other species have evolved different functions as floral activators or even as repressors. To understand photoperiodic development in the perennial rosaceous model species woodland strawberry, we functionally characterized FvCO, the only Group Ia COL in its genome. We demonstrate that FvCO has a major role in the photoperiodic control of flowering and vegetative reproduction through runners. FvCO is needed to generate a bimodal rhythm of FvFT1 which encodes a floral activator in the LD accession Hawaii-4: a sharp FvCO expression peak at dawn is followed by the FvFT1 morning peak in LDs indicating possible direct regulation, but additional factors that may include FvGI and FvFKF1 are probably needed to schedule the second FvFT1 peak around dusk. These results demonstrate that although FvCO and FvFT1 play major roles in photoperiodic development, the CO-based external coincidence around dusk is not fully applicable to the woodland strawberry. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

SAID-SAPS Paradigm: Beliefs and Reality

NASA Astrophysics Data System (ADS)

Mishin, E. V.

2016-12-01

Enhanced westward flows are the dominant feature of the plasma convection in the perturbed subauroral geospace. These include latitudinally-narrow "polarization jets" (PJ) or "subauroral ion drifts" (SAID) observed mainly in the premidnight MLT sector and broad flow channels on the duskside. The generic term "sub-auroral polarization streams" (SAPS) was introduced to unite both (narrow and broad) flows, taking for granted that their underlying mechanisms are quite similar, if not the same. The concept of voltage and current generators is believed to explain the SAPS major features. The generator paradigm treats hot, ≥1 keV, plasma sheet (PS) particles as single (test) particles driven by the dawn-to-dusk and co-rotation electric fields and gradient-curvature drift disregarding charge neutrality and concomitant polarization fields, inherent in slow plasma processes. In this approach, the inner boundary of the hot ion trajectories on the duskside extends earthward of that of the PS electrons by some distance increasing toward dusk. However, magnetically conjugate observations in the evening sector reveal that the generator paradigm fails to explain the substorm SAID features and that they are rather explained in terms of a short-circuiting of substorm-injected hot plasma jets over the plasmapause. This report presents multispacecraft magnetically conjugate observations of substorm-enhanced flows on the duskside showing that their features are hardly compatible with the (test particle) generator paradigm. It is suggested that they are causally related to the two-loop system of the westward traveling surge.

A multipoint study of a substorm occurring on 7 December, 1992, and its theoretical implications

NASA Astrophysics Data System (ADS)

Fox, N. J.; Cowley, S. W. H.; Davda, V. N.; Enno, G.; Friis-Christensen, E.; Greenwald, R. A.; Hairston, M. R.; Lester, M.; Lockwood, M.; Lühr, H.; Milling, D. K.; Murphree, J. S.; Pinnock, M.; Reeves, G. D.

1999-11-01

On 7 December 1992, a moderate substorm was observed by a variety of satellites and ground-based instruments. Ionospheric flows were monitored near dusk by the Goose Bay HF radar and near midnight by the EISCAT radar. The observed flows are compared here with magnetometer observations by the IMAGE array in Scandinavia and the two Greenland chains, the auroral distribution observed by Freja and the substorm cycle observations by the SABRE radar, the SAMNET magnetometer array and LANL geosynchronous satellites. Data from Galileo Earth-encounter II are used to estimate the IMF Bz component. The data presented show that the substorm onset electrojet at midnight was confined to closed field lines equatorward of the pre-existing convection reversal boundaries observed in the dusk and midnight regions. No evidence of substantial closure of open flux was detected following this substorm onset. Indeed the convection reversal boundary on the duskside continued to expand equatorward after onset due to the continued presence of strong southward IMF, such that growth and expansion phase features were simultaneously present. Clear indications of closure of open flux were not observed until a subsequent substorm intensification 25 min after the initial onset. After this time, the substorm auroral bulge in the nightside hours propagated well poleward of the pre-existing convection reversal boundary, and strong flow perturbations were observed by the Goose Bay radar, indicative of flows driven by reconnection in the tail.

Occurrence rate of dipolarization fronts in the plasma sheet: Cluster observations

NASA Astrophysics Data System (ADS)

Xiao, Sudong; Zhang, Tielong; Wang, Guoqiang; Volwerk, Martin; Ge, Yasong; Schmid, Daniel; Nakamura, Rumi; Baumjohann, Wolfgang; Plaschke, Ferdinand

2017-08-01

We investigate the occurrence rate of dipolarization fronts (DFs) in the plasma sheet by taking full advantage of all four Cluster satellites (C1-4) from years 2001 to 2009. In total, we select 466 joint-observation DF events, in which 318, 282, 254, and 236 DFs are observed by C1, C2, C3, and C4, respectively. Our findings are as follows: (1) the maximum occurrence rate is ˜ 15.3 events per day at X ˜ 15 RE in the XY plane, and the average occurrence rate is ˜ 5.4 events per day over the whole observation period; (2) the occurrence rate on the dusk side of the plasma sheet is larger and decreases with increasing BXY/BLobe; (3) the occurrence rate within |Y| < 6 RE increases gradually from X ≈ -19 to -15 RE and then decreases from X ≈ -15 to -10 RE; (4) the occurrence rate when AE > 200 nT is much larger than that when AE < 200 nT, indicating that DFs preferentially occur during high geomagnetic activity. The magnetic pileup and earthward and duskward ion flows could contribute to the increases in the occurrence rate from X ≈ -19 to -15 RE. We suggest that both geomagnetic activity and multiple DFs contribute to the high occurrence rate of the DFs. In addition, the finite length of the DF in the dawn-dusk direction can affect the chance that a satellite observes the DF.

The NUCLEAR FACTOR-CONSTANS complex antagonizes Polycomb repression to de-repress FLOWERING LOCUS T expression in response to inductive long days in Arabidopsis.

PubMed

Luo, Xiao; Gao, Zheng; Wang, Yizhong; Chen, Zhijuan; Zhang, Wenju; Huang, Jirong; Yu, Hao; He, Yuehui

2018-07-01

Many plants sense the seasonal cues, day length or photoperiod changes, to align the timing of the developmental transition to flowering with changing seasons for reproductive success. Inductive day lengths through the photoperiod pathway induce the expression of FLOWERING LOCUS T (FT) or FT relatives that encode a major mobile florigen to promote flowering. In Arabidopsis thaliana, under inductive long days the photoperiod pathway output CONSTANS (CO) accumulates toward the end of the day, and associates with the B and C subunits of Nuclear Factor Y (NF-Y) to form the NF-CO complex that acts to promote FT expression near dusk, whereas Polycomb group (PcG) proteins function to silence FT expression. How NF-CO acts to antagonize the function of PcG proteins to regulate FT expression remains unclear. Here, we show that the NF-CO complex bound to the proximal FT promoter, through chromatin looping, acts in concert with an NF-Y complex bound to a distal enhancer to reduce the levels of PcG proteins, including both Polycomb repressive complex 1 (PRC1) and PRC2 at the FT promoter, leading to a relieving of Polycomb silencing and thus FT de-repression near dusk. Thus, our study provides molecular insights on how the 'active' photoperiod pathway and the 'repressive' Polycomb silencing system interact to control temporal FT expression, conferring the long-day induction of flowering in Arabidopsis. © 2018 The Authors The Plant Journal © 2018 John Wiley & Sons Ltd.

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.

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.

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.

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

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.

A Description of Local Time Asymmetries in the Kronian Current Sheet

NASA Astrophysics Data System (ADS)

Nickerson, J. S.; Hansen, K. C.; Gombosi, T. I.

2012-12-01

Cassini observations imply that Saturn's magnetospheric current sheet is displaced northward above the rotational equator [C.S. Arridge et al., Warping of Saturn's magnetospheric and magnetotail current sheets, Journal of Geophysical Research, Vol. 113, August 2008]. Arridge et al. show that this hinging of the current sheet above the equator occurs over the noon, midnight, and dawn local time sectors. They present an azimuthally independent model to describe this paraboloid-like geometry. We have used our global MHD model, BATS-R-US/SWMF, to study Saturn's magnetospheric current sheet under various solar wind dynamic pressure and solar zenith angle conditions. We show that under reasonable conditions the current sheet does take on the basic shape of the Arridge model in the noon, midnight, and dawn sectors. However, the hinging distance parameter used in the Arridge model is not a constant and does in fact vary in Saturn local time. We recommend that the Arridge model should be adjusted to account for this azimuthal dependence. Arridge et al. does not discuss the shape of the current sheet in the dusk sector due to an absence of data but does presume that the current sheet will assume the same geometry in this region. On the contrary, our model shows that this is not the case. On the dusk side the current sheet hinges (aggressively) southward and cannot be accounted for by the Arridge model. We will present results from our simulations showing the deviation from axisymmetry and the general behavior of the current sheet under different conditions.

Effect of an MLT dependent electron loss rate on the magnetosphere-ionosphere coupling

NASA Astrophysics Data System (ADS)

Gkioulidou, Matina; Wang, Chih-Ping; Wing, Simon; Lyons, Larry R.; Wolf, Richard A.; Hsu, Tung-Shin

2012-11-01

As plasma sheet electrons drift earthward, they get scattered into the loss cone due to wave-particle interactions and the resulting precipitation produces auroral conductance. Realistic electron loss is thus important for modeling the magnetosphere - ionosphere (M-I) coupling and the degree of plasma sheet electron penetration into the inner magnetosphere. In order to evaluate the significance of electron loss, we used the Rice Convection Model (RCM) coupled with a force-balanced magnetic field to simulate plasma sheet transport under different electron loss rates and under self-consistent electric and magnetic field. We used different magnitudes of i) strong pitch angle diffusion everywhere electron loss rate (strong rate) and ii) a more realistic loss rate with its MLT dependence determined by wave activity (MLT rate). We found that electron pressure under the MLT rate is larger compared to the strong rate inside L ∼ 12 RE. The dawn-dusk asymmetry in the precipitating electron energy flux under the MLT rate, with much higher energy flux at dawn than at dusk, agrees better with statistical DMSP observations. High-energy electrons inside L ∼ 8 RE can remain there for many hours under the MLT rate, while those under the strong rate get lost within minutes. Under the MLT rate, the remaining electrons cause higher conductance at lower latitudes; thus after a convection enhancement, the shielding of the convection electric field is less efficient, and as a result, the ion plasma sheet penetrates further earthward into the inner magnetosphere than under the strong rate.

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

The magnetic local time distribution of energetic electrons in the radiation belt region

NASA Astrophysics Data System (ADS)

Allison, Hayley J.; Horne, Richard B.; Glauert, Sarah A.; Zanna, Giulio Del

2017-08-01

Using 14 years of electron flux data from the National Oceanic and Atmospheric Administration Polar Operational Environmental Satellites, a statistical study of the magnetic local time (MLT) distribution of the electron population is performed across a range of activity levels, defined by AE, AE*, Kp, solar wind velocity (Vsw), and VswBz. Three electron energies (>30, >100, and >300 keV) are considered. Dawn-dusk flux asymmetries larger than order of magnitude were observed for >30 and >100 keV electrons. For >300 keV electrons, dawn-dusk asymmetries were primarily due to a decrease in the average duskside flux beyond L* ˜ 4.5 that arose with increasing activity. For the >30 keV population, substorm injections enhance the dawnside flux, which may not reach the duskside as the electrons can be on open drift paths and lost to the magnetopause. The asymmetries in the >300 keV population are attributed to the combination of magnetopause shadowing and >300 keV electron injections by large electric fields. We suggest that 3-D radiation belt models could set the minimum energy boundary (Emin) to 30 keV or above at L* ˜ 6 during periods of low activity. However, for more moderate conditions, Emin should be larger than 100 keV and, for very extreme activities, ˜300 keV. Our observations show the extent that in situ electron flux readings may vary during active periods due to the MLT of the satellite and highlight the importance of 4-D radiation belt models to fully understand radiation belt processes.

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.

A comparison of 2 techniques for estimating deer density

USGS Publications Warehouse

Storm, G.L.; Cottam, D.F.; Yahner, R.H.; Nichols, J.D.

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.

Local time distribution of the SSC-associated HF-Doppler frequency shifts

NASA Technical Reports Server (NTRS)

Kikuchi, T.; Sugiuchi, H.; Ishimine, T.

1985-01-01

The HF-Doppler frequency shift observed at the storm's sudden commencement is composed of a frequency increase (+) and decrease (-), and classified into four types, SCF(+ -), SCF(- +), SCF(+) and SCF(-). Since the latter two types are special cases of the former two types, two different kinds of electrical field exist in the F region and cause the ExB drift motion of plasma. HUANG (1976) interpreted the frequency increase of SCF(+ -) as due to the westward induction electric field proportional to delta H/ delta t and the succeeding frequency decrease due to the eastward conduction electric field which produces ionospheric currents responsible for the magnetic increase on the ground. In spite of his success in interpreting the SCF(+ -), some other interpretations are needed for the explanation of the whole set of SCF's, particularly SCF(- +). Local time distributions of the SCF's are derived from 41 SCF's which are observed on the HF standard signal (JJY) as received in Okinawa (path length =1600 km) and Kokubunji (60 km). It is shown that the SCF(+ -) appears mainly during the day, whereas the SCF(- +) is observed during the night. The results indicate that the preliminary frequency shift (+) of SCF(+ -) and (-) of SCF(- +) is caused by a westward electric field in the dayside hemisphere, while by an eastward electric field in the nightside hemisphere. The main frequency shift (-) of SCF(+ -) and (+) of SCF(- +) is caused by the reversed electric field. Consequently, the preliminary frequency shift is caused by the dusk-to-dawn electric field, while the main frequency shift by the dawn-to-dusk electric field.

The Morphology of the Solar Wind Magnetic Field Draping on the Dayside of Mars and Its Variability

NASA Astrophysics Data System (ADS)

Fang, Xiaohua; Ma, Yingjuan; Luhmann, Janet; Dong, Yaxue; Brain, David; Hurley, Dana; Dong, Chuanfei; Lee, Christina O.; Jakosky, Bruce

2018-04-01

The magnetic field draping pattern in the magnetosheath of Mars is of interest for what it tells us about both the solar wind interaction with the Mars obstacle and the use of the field measured there as a proxy for the upstream interplanetary magnetic field (IMF) clock angle. We apply a time-dependent, global magnetohydrodynamic model toward quantifying the spatial and temporal variations of the magnetic field draping direction on the Martian dayside above 500-km altitude. The magnetic field and plasma are self-consistently solved over one Mars rotation period, with the dynamics of the field morphology considered as the result of the rotation of the crustal field orientation. Our results show how the magnetic field direction on the plane perpendicular to the solar wind flow direction gradually departs from the IMF as the solar wind penetrates toward the obstacle and into the tail region. This clock angle departure occurs mainly inside the magnetic pileup region and tailward of the terminator plane, exhibiting significant dawn-dusk and north-south asymmetries. Inside the dayside sheath region, the field direction has the greatest departure from the IMF-perpendicular component direction downstream of the quasi-parallel bow shock, which for the nominal Parker spiral is over the dawn quadrant. Thus, the best region to obtain an IMF clock angle proxy is within the dayside magnetosheath at sufficiently high altitudes, particularly over subsolar and dusk sectors. Our results illustrate that the crustal field has only a mild influence on the magnetic field draping direction within the magnetosheath region.

Characteristics of Seasonal Variation and Solar Activity Dependence of the Geomagnetic Solar Quiet Daily Variation

NASA Astrophysics Data System (ADS)

Shinbori, Atsuki; Koyama, Yukinobu; Nosé, Masahito; Hori, Tomoaki; Otsuka, Yuichi

2017-10-01

Characteristics of seasonal variation and solar activity dependence of the X and Y components of the geomagnetic solar quiet (Sq) daily variation at Memambetsu in midlatitudes and Guam near the equator have been investigated using long-term geomagnetic field data with 1 h time resolution from 1957 to 2016. The monthly mean Sq variation in the X and Y components (Sq-X and Sq-Y) shows a clear seasonal variation and solar activity dependence. The amplitude of seasonal variation increases significantly during high solar activities and is proportional to the solar F10.7 index. The pattern of the seasonal variation is quite different between Sq-X and Sq-Y. The result of the correlation analysis between the solar F10.7 index and the Sq-X and Sq-Y shows an almost linear relationship, but the slope of the linear fitted line varies as a function of local time and month. This implies that the sensitivity of Sq-X and Sq-Y to the solar activity is different for different local times and seasons. The pattern of the local time and seasonal variations of Sq-Y at Guam shows good agreement with that of a magnetic field produced by interhemispheric field-aligned currents (FACs), which flow from the summer to winter hemispheres in the dawn and dusk sectors and from the winter to summer hemispheres in the prenoon to afternoon sectors. The direction of the interhemispheric FAC in the dusk sector is opposite to the concept of Fukushima's model.

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.

Energetic electron bursts in the plasma sheet and their relation with BBFs

NASA Astrophysics Data System (ADS)

Duan, A. Y.; Cao, J. B.; Dunlop, M.; Wang, Z. Q.

2014-11-01

We studied energetic electron bursts (EEBs) (40-250 keV) in the plasma sheet (PS) and their relation to bursty bulk flows (BBFs) using the data recorded by Cluster from 2001 to 2009. The EEBs in the PS can be classified into four types. Three types of EEBs are dispersionless, including EEBs accompanied with BBFs (V > 250 km/s) but without dipolarization front (DF); EEBs accompanied with both dipolarization front (DF) and BBF; and EEBs accompanied with DF and fast flow with V < 250 km/s. One type of EEB, i.e., EEBs not accompanied with BBFs and DFs, is dispersed. The energetic electrons (40-130 keV) can be easily transported earthward by BBFs due to the strong dawn-dusk electric field embedded in BBFs. The DFs in BBFs can produce energetic electrons (40 to 250 keV). For the EEBs with DF and BBFs, the superposed epoch analyses show that the increase of energetic electron flux has two phases: gradual increase phase before DF and rapid increase phase concurrent with DF. In the PS around x = -18 RE, 60%-70% of EEBs are accompanied with BBFs, indicating that although hitherto there have been various acceleration mechanisms of energetic electrons, most of the energetic electrons in the PS are related with magnetic reconnection, and they are produced either directly by magnetic reconnection or indirectly by the DFs within BBFs. In the BBF's braking region of -12 RE < x < -10 RE, 20% of EEBs are accompanied with BBFs. The corresponding ratio between EEBs and BBFs shows a dawn-dusk asymmetry.

Electric fields in the plasma sheet and plasma sheet boundary layer

NASA Technical Reports Server (NTRS)

Pedersen, A.; Cattell, C. A.; Faelthammar, C. G.; Knott, K.; Lindqvist, P. A.; Manka, R. H.; Mozer, F. S.

1984-01-01

Data from the spherical double probe electric-field experiment on ISEE-1 were used to study plasmasheet/lobe boundary crossings during substorms, identified by plasma measurements and by using the electric field probes as a reference for measurements of the spacecraft potential. There are strong electric fields, with a dominant dawn-to-dusk component, throughout the boundary layer outside the plasmasheet for contracting and expanding motions of the plasmasheet and for different magnetic field directions. Characteristic amplitudes and durations are 5 to 10 mV/m and 5 to 15 min. The corresponding E x B vectors are always towards the plasmasheet.

Structure of the plasmapause from ISEE 1 low-energy ion and plasma wave observations

NASA Technical Reports Server (NTRS)

Nagai, T.; Horwitz, J. L.; Anderson, R. R.; Chappell, C. R.

1985-01-01

Low-energy ion pitch angle distributions are compared with plasma density profiles in the near-earth magnetosphere using ISEE 1 observations. The classical plasmapause determined by the sharp density gradient is not always observed in the dayside region, whereas there almost always exists the ion pitch angle distribution transition from cold, isotropic to warm, bidirectional, field-aligned distributions. In the nightside region the plasmapause density gradient is typically found, and it normally coincides with the ion pitch angle distribution transition. The sunward motion of the plasma is found in the outer part of the 'plasmaspheric' plasma in the dusk bulge region.

A storm time, Pc 5 event observed in the outer magnetosphere by ISEE 1 and 2 - Wave properties

NASA Technical Reports Server (NTRS)

Greenstadt, E. W.; Scarf, F. L.; Mcpherron, R. L.; Anderson, R. R.

1986-01-01

The properties of the waves composing a classical storm time Pc 5 event, recorded by the satellite pair ISEE 1,2 during an inbound nearly equatorial pass in the dusk sector on August 21-22, 1978, are described. On the basis of these observations it is concluded that the events of the August 21-22 pass resulted from a combination of sources, namely, distant wideband excitation and ion drift instability, plus a coupling of wave modes. It is suggested that the observed phenomenon was a radial cross section of the type of event reported by Barfield et al. (1972).

Parallel Electric Field on Auroral Magnetic Field Lines.

NASA Astrophysics Data System (ADS)

Yeh, Huey-Ching Betty

1982-03-01

The interaction of Birkeland (magnetic-field-aligned) current carriers and the Earth's magnetic field results in electrostatic potential drops along magnetic field lines. The statistical distributions of the field-aligned potential difference (phi)(,(PARLL)) were determined from the energy spectra of electron inverted "V" events observed at ionospheric altitude for different conditions of geomagnetic activity as indicated by the AE index. Data of 1270 electron inverted "V"'s were obtained from Low-Energy Electron measurements of the Atmosphere Explorer-C and -D Satellite (despun mode) in the interval January 1974-April 1976. In general, (phi)(,(PARLL)) is largest in the dusk to pre-midnight sector, smaller in the post-midnight to dawn sector, and smallest in the near noon sector during quiet and disturbed geomagnetic conditions; there is a steady dusk-dawn-noon asymmetry of the global (phi)(,(PARLL)) distribution. As the geomagnetic activity level increases, the (phi)(,(PARLL)) pattern expands to lower invariant latitudes, and the magnitude of (phi)(,(PARLL)) in the 13-24 magnetic local time sector increases significantly. The spatial structure and intensity variation of the global (phi)(,(PARLL)) distribution are statistically more variable, and the magnitudes of (phi)(,(PARLL)) have smaller correlation with the AE-index, in the post-midnight to dawn sector. A strong correlation is found to exist between upward Birkeland current systems and global parallel potential drops, and between auroral electron precipitation patterns and parallel potential drops, regarding their mophology, their intensity and their dependence of geomagnetic activity. An analysis of the fine-scale simultaneous current-voltage relationship for upward Birkeland currents in Region 1 shows that typical field-aligned potential drops are consistent with model predictions based on linear acceleration of the charge carriers through an electrostatic potential drop along convergent magnetic field

Plasmasphere dynamics in the duskside bulge region: A new look at old topic

NASA Technical Reports Server (NTRS)

Carpenter, D. L.; Giles, B. L.; Chappell, C. R.; Decreau, P. M. E.; Anderson, R. R.; Persoon, A. M.; Smith, A. J.; Corcuff, Y.; Canu, P.

1993-01-01

Data acquired during several multiday periods in 1982 at ground stations Siple, Halley, and Kerguelen and on satellites Dynamics Explorer 1, International Sun Earth Explorer 1, and GEOS 2 have been used to investigate thermal plasma structure and dynamics in the duskside plasmasphere bulge region of the Earth. The distribution of thermal plasma in the dusk bulge sector is difficult to describe realistically, in part because of the time integral manner in which the thermal plasma distribution depends upon on the effects of bulk cross-B flow and interchange plasma flows along B. While relatively simple MHD models can be useful for qualitatively predicting certain effects of enhanced convection on a quiet plasmasphere, such as an initial sunward entrainment of the outer regions, they are of limited value in predicting the duskside thermal plasma structures that are observed. Furthermore, use of such models can be misleading if one fails to realize that they do not address the question of the formation of the steep plasmapause profile or provide for a possible role of instabilities or other irreversible processes in plasmapause formation. Our specific findings, which are based both upon the present case studies and upon earlier work, include the following: (1) during active periods the plasmasphere appears to become divided into two entities, a main plasmasphere and a duskside bulge region. (2) in the aftermath of an increase in convection activity, the main plasmasphere tends (from a statistical point of view) to become roughly circular in equatorial cross section, with only a slight bulge at dusk; (3) the abrupt westward edge of the duskside bulge observed from whistlers represents a state in the evolution of sunward extending streamers; (4) in the aftermath of a weak magnetic storm, 10 to 30% of the plasma 'removed' from the outer plasmasphere appears to remain in the afternoon-dusk sector beyond the main plasmasphere. (5) outlying dense plasma structures may

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.

Effects of electric field methods on modeling the midlatitude ionospheric electrodynamics and inner magnetosphere dynamics

DOE PAGES

Yu, Yiqun; Jordanova, Vania Koleva; Ridley, Aaron J.; ...

2017-05-10

Here, we report a self-consistent electric field coupling between the midlatitude ionospheric electrodynamics and inner magnetosphere dynamics represented in a kinetic ring current model. This implementation in the model features another self-consistency in addition to its already existing self-consistent magnetic field coupling with plasma. The model is therefore named as Ring current-Atmosphere interaction Model with Self-Consistent magnetic (B) and electric (E) fields, or RAM-SCB-E. With this new model, we explore, by comparing with previously employed empirical Weimer potential, the impact of using self-consistent electric fields on the modeling of storm time global electric potential distribution, plasma sheet particle injection, andmore » the subauroral polarization streams (SAPS) which heavily rely on the coupled interplay between the inner magnetosphere and midlatitude ionosphere. We find the following phenomena in the self-consistent model: (1) The spatially localized enhancement of electric field is produced within 2.5 < L < 4 during geomagnetic active time in the dusk-premidnight sector, with a similar dynamic penetration as found in statistical observations. (2) The electric potential contours show more substantial skewing toward the postmidnight than the Weimer potential, suggesting the resistance on the particles from directly injecting toward the low-L region. (3) The proton flux indeed indicates that the plasma sheet inner boundary at the dusk-premidnight sector is located further away from the Earth than in the Weimer potential, and a “tongue” of low-energy protons extends eastward toward the dawn, leading to the Harang reversal. (4) SAPS are reproduced in the subauroral region, and their magnitude and latitudinal width are in reasonable agreement with data.« less

Comparing simulated and observed EMIC wave amplitudes using in situ Van Allen Probes’ measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saikin, A. A.; Jordanova, Vania Koleva; Zhang, J. C.

In this study, we perform a statistical study calculating electromagnetic ion cyclotron (EMIC) wave amplitudes based off in situ plasma measurements taken by the Van Allen Probes’ (1.1–5.8 R e) Helium, Oxygen, Proton, Electron (HOPE) instrument. Calculated wave amplitudes are compared to EMIC waves observed by the Electric and Magnetic Field Instrument Suite and Integrated Science on board the Van Allen Probes during the same period. The survey covers a 22-month period (1 November 2012 to 31 August 2014), a full Van Allen Probe magnetic local time (MLT) precession. The linear theory proxy was used to identify EMIC wave eventsmore » with plasma conditions favorable for EMIC wave excitation. Two hundred and thirty-two EMIC wave events (103 H +-band and 129 He +-band) were selected for this comparison. Nearly all events selected are observed beyond L = 4. Results show that calculated wave amplitudes exclusively using the in situ HOPE measurements produce amplitudes too low compared to the observed EMIC wave amplitudes. Hot proton anisotropy (Ahp) distributions are asymmetric in MLT within the inner (L < 7) magnetosphere with peak (minimum) A hp, ~0.81 to 1.00 (~0.62), observed in the dawn (dusk), 0000 < MLT ≤ 1200 (1200 < MLT ≤ 2400), sectors. Measurements of A hp are found to decrease in the presence of EMIC wave activity. A hp amplification factors are determined and vary with respect to EMIC wave-band and MLT. Lastly, He +-band events generally require double (quadruple) the measured A hp for the dawn (dusk) sector to reproduce the observed EMIC wave amplitudes.« less

Effects of electric field methods on modeling the midlatitude ionospheric electrodynamics and inner magnetosphere dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Yiqun; Jordanova, Vania Koleva; Ridley, Aaron J.

Here, we report a self-consistent electric field coupling between the midlatitude ionospheric electrodynamics and inner magnetosphere dynamics represented in a kinetic ring current model. This implementation in the model features another self-consistency in addition to its already existing self-consistent magnetic field coupling with plasma. The model is therefore named as Ring current-Atmosphere interaction Model with Self-Consistent magnetic (B) and electric (E) fields, or RAM-SCB-E. With this new model, we explore, by comparing with previously employed empirical Weimer potential, the impact of using self-consistent electric fields on the modeling of storm time global electric potential distribution, plasma sheet particle injection, andmore » the subauroral polarization streams (SAPS) which heavily rely on the coupled interplay between the inner magnetosphere and midlatitude ionosphere. We find the following phenomena in the self-consistent model: (1) The spatially localized enhancement of electric field is produced within 2.5 < L < 4 during geomagnetic active time in the dusk-premidnight sector, with a similar dynamic penetration as found in statistical observations. (2) The electric potential contours show more substantial skewing toward the postmidnight than the Weimer potential, suggesting the resistance on the particles from directly injecting toward the low-L region. (3) The proton flux indeed indicates that the plasma sheet inner boundary at the dusk-premidnight sector is located further away from the Earth than in the Weimer potential, and a “tongue” of low-energy protons extends eastward toward the dawn, leading to the Harang reversal. (4) SAPS are reproduced in the subauroral region, and their magnitude and latitudinal width are in reasonable agreement with data.« less

Multiscale Currents Observed by MMS in the Flow Braking Region

NASA Astrophysics Data System (ADS)

Nakamura, Rumi; Varsani, Ali; Genestreti, Kevin J.; Le Contel, Olivier; Nakamura, Takuma; Baumjohann, Wolfgang; Nagai, Tsugunobu; Artemyev, Anton; Birn, Joachim; Sergeev, Victor A.; Apatenkov, Sergey; Ergun, Robert E.; Fuselier, Stephen A.; Gershman, Daniel J.; Giles, Barbara J.; Khotyaintsev, Yuri V.; Lindqvist, Per-Arne; Magnes, Werner; Mauk, Barry; Petrukovich, Anatoli; Russell, Christopher T.; Stawarz, Julia; Strangeway, Robert J.; Anderson, Brian; Burch, James L.; Bromund, Ken R.; Cohen, Ian; Fischer, David; Jaynes, Allison; Kepko, Laurence; Le, Guan; Plaschke, Ferdinand; Reeves, Geoff; Singer, Howard J.; Slavin, James A.; Torbert, Roy B.; Turner, Drew L.

2018-02-01

We present characteristics of current layers in the off-equatorial near-Earth plasma sheet boundary observed with high time-resolution measurements from the Magnetospheric Multiscale mission during an intense substorm associated with multiple dipolarizations. The four Magnetospheric Multiscale spacecraft, separated by distances of about 50 km, were located in the southern hemisphere in the dusk portion of a substorm current wedge. They observed fast flow disturbances (up to about 500 km/s), most intense in the dawn-dusk direction. Field-aligned currents were observed initially within the expanding plasma sheet, where the flow and field disturbances showed the distinct pattern expected in the braking region of localized flows. Subsequently, intense thin field-aligned current layers were detected at the inner boundary of equatorward moving flux tubes together with Earthward streaming hot ions. Intense Hall current layers were found adjacent to the field-aligned currents. In particular, we found a Hall current structure in the vicinity of the Earthward streaming ion jet that consisted of mixed ion components, that is, hot unmagnetized ions, cold E × B drifting ions, and magnetized electrons. Our observations show that both the near-Earth plasma jet diversion and the thin Hall current layers formed around the reconnection jet boundary are the sites where diversion of the perpendicular currents take place that contribute to the observed field-aligned current pattern as predicted by simulations of reconnection jets. Hence, multiscale structure of flow braking is preserved in the field-aligned currents in the off-equatorial plasma sheet and is also translated to ionosphere to become a part of the substorm field-aligned current system.

The causes of the hardest electron precipitation events seen with SAMPEX

NASA Astrophysics Data System (ADS)

Smith, David M.; Casavant, Eric P.; Comess, Max D.; Liang, Xinqing; Bowers, Gregory S.; Selesnick, Richard S.; Clausen, Lasse B. N.; Millan, Robyn M.; Sample, John G.

2016-09-01

We studied the geomagnetic, plasmaspheric, and solar wind context of relativistic electron precipitation (REP) events seen with the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX), Proton Electron Telescope (PET) to derive an exponential folding energy E0 for each event. Events with E0< 400 keV peak near midnight, and with increasing E0, the peak magnetic local time (MLT) moves earlier but never peaks as early as the MLT distribution of electromagnetic ion cyclotron (EMIC) waves in the outer belt, and a distinct component near midnight remains. Events with E0>750 keV near dusk (1400 < MLT < 2000) show correlations with solar wind dynamic pressure and proton density, AE index, negative Dst index, and an extended plasmasphere, all supporting an EMIC wave interpretation. Events with 500 keV 500 keV ("hard REP"), we estimate that roughly 45% of the whole population has the distributions of geomagnetic and solar wind parameters associated with EMIC waves, while 55% does not. We hypothesize that the latter events may be caused by current sheet scattering (CSS), which can be mistaken for EMIC wave scattering in that both simultaneously precipitate MeV electrons and keV protons. Since a large number of MeV electrons are lost in the near-midnight hard REP events, and in the large number of E0< 400 keV events that show no dusk-like peak at all, we conclude that CSS should be studied further as a possibly important loss channel for MeV electrons.

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. © 2014 The Fisheries Society of the British Isles.

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.

The Interplay between Carbon Availability and Growth in Different Zones of the Growing Maize Leaf.

PubMed

Czedik-Eysenberg, Angelika; Arrivault, Stéphanie; Lohse, Marc A; Feil, Regina; Krohn, Nicole; Encke, Beatrice; Nunes-Nesi, Adriano; Fernie, Alisdair R; Lunn, John E; Sulpice, Ronan; Stitt, Mark

2016-10-01

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. © 2016 American Society of Plant Biologists. All Rights Reserved.

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.

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.

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.

Multiscale Currents Observed by MMS in the Flow Braking Region.

PubMed

Nakamura, Rumi; Varsani, Ali; Genestreti, Kevin J; Le Contel, Olivier; Nakamura, Takuma; Baumjohann, Wolfgang; Nagai, Tsugunobu; Artemyev, Anton; Birn, Joachim; Sergeev, Victor A; Apatenkov, Sergey; Ergun, Robert E; Fuselier, Stephen A; Gershman, Daniel J; Giles, Barbara J; Khotyaintsev, Yuri V; Lindqvist, Per-Arne; Magnes, Werner; Mauk, Barry; Petrukovich, Anatoli; Russell, Christopher T; Stawarz, Julia; Strangeway, Robert J; Anderson, Brian; Burch, James L; Bromund, Ken R; Cohen, Ian; Fischer, David; Jaynes, Allison; Kepko, Laurence; Le, Guan; Plaschke, Ferdinand; Reeves, Geoff; Singer, Howard J; Slavin, James A; Torbert, Roy B; Turner, Drew L

2018-02-01

We present characteristics of current layers in the off-equatorial near-Earth plasma sheet boundary observed with high time-resolution measurements from the Magnetospheric Multiscale mission during an intense substorm associated with multiple dipolarizations. The four Magnetospheric Multiscale spacecraft, separated by distances of about 50 km, were located in the southern hemisphere in the dusk portion of a substorm current wedge. They observed fast flow disturbances (up to about 500 km/s), most intense in the dawn-dusk direction. Field-aligned currents were observed initially within the expanding plasma sheet, where the flow and field disturbances showed the distinct pattern expected in the braking region of localized flows. Subsequently, intense thin field-aligned current layers were detected at the inner boundary of equatorward moving flux tubes together with Earthward streaming hot ions. Intense Hall current layers were found adjacent to the field-aligned currents. In particular, we found a Hall current structure in the vicinity of the Earthward streaming ion jet that consisted of mixed ion components, that is, hot unmagnetized ions, cold E × B drifting ions, and magnetized electrons. Our observations show that both the near-Earth plasma jet diversion and the thin Hall current layers formed around the reconnection jet boundary are the sites where diversion of the perpendicular currents take place that contribute to the observed field-aligned current pattern as predicted by simulations of reconnection jets. Hence, multiscale structure of flow braking is preserved in the field-aligned currents in the off-equatorial plasma sheet and is also translated to ionosphere to become a part of the substorm field-aligned current system.

Comparing simulated and observed EMIC wave amplitudes using in situ Van Allen Probes’ measurements

DOE PAGES

Saikin, A. A.; Jordanova, Vania Koleva; Zhang, J. C.; ...

2018-02-02

In this study, we perform a statistical study calculating electromagnetic ion cyclotron (EMIC) wave amplitudes based off in situ plasma measurements taken by the Van Allen Probes’ (1.1–5.8 R e) Helium, Oxygen, Proton, Electron (HOPE) instrument. Calculated wave amplitudes are compared to EMIC waves observed by the Electric and Magnetic Field Instrument Suite and Integrated Science on board the Van Allen Probes during the same period. The survey covers a 22-month period (1 November 2012 to 31 August 2014), a full Van Allen Probe magnetic local time (MLT) precession. The linear theory proxy was used to identify EMIC wave eventsmore » with plasma conditions favorable for EMIC wave excitation. Two hundred and thirty-two EMIC wave events (103 H +-band and 129 He +-band) were selected for this comparison. Nearly all events selected are observed beyond L = 4. Results show that calculated wave amplitudes exclusively using the in situ HOPE measurements produce amplitudes too low compared to the observed EMIC wave amplitudes. Hot proton anisotropy (Ahp) distributions are asymmetric in MLT within the inner (L < 7) magnetosphere with peak (minimum) A hp, ~0.81 to 1.00 (~0.62), observed in the dawn (dusk), 0000 < MLT ≤ 1200 (1200 < MLT ≤ 2400), sectors. Measurements of A hp are found to decrease in the presence of EMIC wave activity. A hp amplification factors are determined and vary with respect to EMIC wave-band and MLT. Lastly, He +-band events generally require double (quadruple) the measured A hp for the dawn (dusk) sector to reproduce the observed EMIC wave amplitudes.« less

Effects of electric field methods on modeling the midlatitude ionospheric electrodynamics and inner magnetosphere dynamics

NASA Astrophysics Data System (ADS)

Yu, Yiqun; Jordanova, Vania K.; Ridley, Aaron J.; Toth, Gabor; Heelis, Roderick

2017-05-01

We report a self-consistent electric field coupling between the midlatitude ionospheric electrodynamics and inner magnetosphere dynamics represented in a kinetic ring current model. This implementation in the model features another self-consistency in addition to its already existing self-consistent magnetic field coupling with plasma. The model is therefore named as Ring current-Atmosphere interaction Model with Self-Consistent magnetic (B) and electric (E) fields, or RAM-SCB-E. With this new model, we explore, by comparing with previously employed empirical Weimer potential, the impact of using self-consistent electric fields on the modeling of storm time global electric potential distribution, plasma sheet particle injection, and the subauroral polarization streams (SAPS) which heavily rely on the coupled interplay between the inner magnetosphere and midlatitude ionosphere. We find the following phenomena in the self-consistent model: (1) The spatially localized enhancement of electric field is produced within 2.5 < L < 4 during geomagnetic active time in the dusk-premidnight sector, with a similar dynamic penetration as found in statistical observations. (2) The electric potential contours show more substantial skewing toward the postmidnight than the Weimer potential, suggesting the resistance on the particles from directly injecting toward the low-L region. (3) The proton flux indeed indicates that the plasma sheet inner boundary at the dusk-premidnight sector is located further away from the Earth than in the Weimer potential, and a "tongue" of low-energy protons extends eastward toward the dawn, leading to the Harang reversal. (4) SAPS are reproduced in the subauroral region, and their magnitude and latitudinal width are in reasonable agreement with data.

Ramadan fasting and dental treatment considerations: a review.

PubMed

Shaeesta, Khaleelahmed Bhavikatti; Prabhuji, M Lv; Shruthi, J R

2015-01-01

During the sacred month of Ramadan, Muslims abstain from the consumption of food from dawn until dusk. Extended fasting hours produce changes in the body's metabolism during this period. A majority of the population who fast also restrict themselves from undergoing dental treatments due to a fear of breaking the fast. Even among health professionals, a certain amount of uncertainty prevails about the implications of treating a patient who is fasting. To help clinicians carry out safe and effective treatment without hampering a patient's religious beliefs, the present article focuses on the effect of Ramadan fasting on the body's metabolism and the ramifications for treatment aspects, including medications and dental procedures.

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.

Particle orbits in model current sheet with a nonzero B(y) component

NASA Technical Reports Server (NTRS)

Zhu, Zhongwei; Parks, George

1993-01-01

The problem of charged particle motions in magnetotaillike model current sheets is revisited with the inclusion of a nonzero dawn-dusk magnetic field component. Three cases are examined considering both trapped and escaped orbits. The results show that a nonzero B(y) component disturbs the particle orbits by destroying orbit symmetry in the phase space about the z = 0 plane. It also changes the bounce frequency of particle orbits. The presence of B(y) thus modifies the Speiser orbits, particularly near the ejection phase. The process of ejected particle such as ejection direction, ejection velocity, and pitch angles are shown to depend on the sign of the charge.

Asymmetry of nonlinear interactions of solar MHD discontinuities with the bow shock

NASA Astrophysics Data System (ADS)

Grib, S. A.; Pushkar, E. A.

2006-07-01

Oblique interaction between the solar fast shock wave, which is a typical nonstationary strong discontinuity in the interplanetary space, and the bow shock front upstream of an Earth-type planetary magnetosphere is studied. Attention has been paid to the qualitative and quantitative (with respect to the proton density distribution) dawn-dusk (or morning-evening) asymmetry of the discontinuities refracted into the magnetosheath, which originates in the ecliptic plane on different sides of the Sun-Earth line. The results under discussion have been corroborated experimentally by the gas-kinetic pattern of the bow-shock front and the WIND and ISEE 3 spacecraft measurements of the plasma density.

Migration and survival of Atlantic salmon Salmo salar smolts in a large natural lake.

PubMed

Kennedy, R J; Rosell, R; Millane, M; Doherty, D; Allen, M

2018-06-08

An investigation with acoustic telemetry of the passage of Salmo salar smolts through a large natural lake found heavy mortality occurred at the river-to-lake confluences (mean 31 . 2 % km -1 ), but was lower in the main body of the lake (mean 2 . 4 % km -1 ). Predation was a significant pressure on emigrating smolts as tagged pike Esox lucius aggregated at river-to-lake confluences during the peak of the smolt run. Tagged smolts mainly emmigrated into the lake in the late evening after dusk, possibly as a predator-avoidance behaviour. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

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.

Entomological investigations into an epidemic of Japanese encephalitis (JE) in northern districts of West Bengal, India (2011-2012).

PubMed

Mariappan, T; Samuel, P Philip; Thenmozhi, V; Paramasivan, R; Sharma, Puran Kumar; Biswas, Asit Kumar; Tyagi, B K

2014-05-01

Japanese encephalitis (JE) is one of the most important arboviral diseases of human beings with outbreaks in many parts of Southeast Asia including India. We present the entomological findings of an outbreak occurred in northern part of West Bengal during 2011-2012 with special emphasis on the role of JE vectors in different seasons. Adult mosquito collections were made with the help of mouth aspirators, aided by flash lights during day time resting inside human and animal habitations as indoor, and resting outside field grasses, bushes, underneath of culverts and bridges as outdoor, and in and around the pig enclosures and cattle sheds during dusk period in JE affected villages from Cooch Behar, Dakshin Dinajpur, Darjeeling and Jalpaiguri districts in North West Bengal. In all study villages, a long handled with enamel bowl dipper was used to obtain immature stages of mosquitoes from various breeding habitats. A total of 19 different types of mosquito breeding habitats were examined for vectors of JE. From these habitats, 23.7 per cent were positive for breeding during the study period. Overall, nine different species were recorded through emergence, but none was positive for JE virus when subjected for detection of virus. Adult mosquitoes of more than 50 per cent of the potential JE vector species obtained through dusk and the rest through indoor and outdoor collections in all seasons. Altogether, 27 different species were recorded. Most of these were JE vectors. Our results showed that in addition to Cx. vishnui subgroup, detection of JE virus antigen in Cx. quinquefasciatus indicated the possible maintenance of JE virus in nature through poor vector mosquitoes throughout the year. Since, all potential vector species reported elsewhere in India were also found in this region and fluctuated in density in different seasons, a proper integrated vector control programme needs to be implemented to control JE transmission.

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.

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

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.

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.

Climatology of the inter-hemispheric field-aligned currents system over the Nigeria ionosphere

NASA Astrophysics Data System (ADS)

Bolaji, O. S.; Rabiu, A. B.; Oyeyemi, E. O.; Yumoto, K.

2012-11-01

Records of the declination (D) magnetic field data for the year 2009 from the Magnetic Data Acquisition System (MAGDAS) facilities at University of Ilorin were employed for this work. From the minutes value of the D-component, the deduced hourly values of the D-component (Sq(QD)) were used to estimate its diurnal (Sq(D)) values with the most five quietest days identified. The monthly mean (MSq(D)) of the most five quietest days and their seasonal (SSq(D)) variabilities were investigated. The inter-hemispheric field aligned currents (IHFACs) exhibit downward and upward inter-hemispheric field-aligned sheet current that appears as a pair at all local times of the Sq(D), MSq(D), and SSq(D) variations. From these variabilities, the IHFACs were observed to flow from the winter to summer hemisphere during noon and dusk sector and flowing in opposite direction during the dawn sector. The Sq(D) variability patterns that were observed in May, June, August September are gentle compared to the disturbed variabilities in January, February, March and November. The highest positive (˜1.7 arc-min) and negative (˜-2.7 arc min) MSq(D) maxima values were observed in August during the dawn and noon sectors respectively. These values indicated that the IHFACs flow in August is strongly southbound (positive) and northbound (negative) in the dawn and noon sectors respectively. Dusk-side IHFACs as can be observed by MAGDAS are weakly northbound in all the seasons. The direction of IHFACs does not flip at the equinoxes but in June and November and does not become largest at solstices but in August. The IHFACs was observed to exhibit longitudinal variability, which indicated that larger amplitude of winter-to-summer IHFACs is observed to be greater in June solstice (northbound/negative IHFACs) than in the December solstice (southbound/positive IHFACs) during the noon sector.

Adjustments in CAM and enzymatic scavenging of H2O2 in juvenile plants of the epiphytic bromeliad Guzmania monostachia as affected by drought and rewatering.

PubMed

Carvalho, Victória; Abreu, Maria E; Mercier, Helenice; Nievola, Catarina C

2017-04-01

Juvenile plants of epiphytes such as bromeliads are highly prone to dehydration under drought conditions. It is likely that young epiphytes evolved mostly metabolic strategies to resist drought, which may include the plastic modulation of the enzymatic antioxidant system and crassulacean acid metabolism (CAM). Few studies have investigated such strategies in juvenile epiphytes, although such research is important to understand how these plants might face drought intensification derived from potential climatic alterations. The epiphytic CAM bromeliad Guzmania monostachia (L.) Rusby ex Mez var. monostachia is known to have plastic responses to drought, but no reports have focused on the metabolism of juvenile plants to drought and recovery. Hence, we aimed to verify how juvenile G. monostachia plants adjust malate (indicative of CAM), H 2 O 2 content and enzymatic scavenging in response to drought (eight days without irrigation) and rewatering (six days of irrigation post-drought). Interestingly, drought decreased H 2 O 2 content and activities of superoxide dismutase, catalase (CAT) and ascorbate peroxidase (APX) in the pre-dusk period, although glutathione reductase (GR) and CAM activity increased. Rewatering restored H 2 O 2 , but activities of APX, CAT and GR exceeded pre-stress levels in the pre-dusk and/or pre-dawn periods. Results suggest that recovery from a first drought redefines the homeostatic balance of H 2 O 2 scavenging, in which rewatered plants stimulate the enzymatic antioxidant system while drought-exposed plants intensify CAM activity to regulate H 2 O 2 content, a photosynthetic pathway known to prevent oxidative stress. Such data show that young G. monostachia plants adjust CAM and H 2 O 2 scavenging to adapt to water availability. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

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.

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.

Evolution of convection vortices associated with sudden impulses observed by SuperDARN

NASA Astrophysics Data System (ADS)

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

2014-12-01

Spatial evolution of transient ionospheric convection induced by sudden impulses (SIs) recorded by ground magnetometers is studied statistically by using SuperDARN (SD) data. An advantage of using SD data instead of ground magnetic fields is that ionospheric flows measured by the radars are not virtually biased by the spatially-varying ionospheric conductance or the magnetospheric currents. First we surveyed the Sym-H index for Jan., 2007 to Dec., 2012 to identify SI events with a peak amplitude |dSym-H| greater than 10 nT. Next we searched all SD data over the northern hemisphere during the SI events for ionospheric backscatters which give us the light-of-sight velocity of horizontal ionospheric flows. For each SI event, the collected ionospheric flow data were sorted into the four periods: the pre-SI period, the pre-Main Impulse (MI), middle-MI, and post-MI periods. In the present study, we examine the differences in flow velocity between the pre-SI period and the three MI periods to clarify how ionospheric flows change in association with SIs. As a result, the ionospheric flow shifts eastward on the dusk side and westward on the dawn side at the higher latitudes during positive SIs (SI+), while it shows a roughly westward/eastward shift on the dusk/dawn side, respectively, during negative SIs (SI-). These polarities of flow shifts are basically consistent with the higher latitude portions of the DP current for the MI phase as shown by Araki [1994] and Araki and Nagano [1988]. In terms of temporal evolution, the SI-induced transient flows remain slightly longer for SI- than for SI+. These findings suggest that the compression and expansion of the magnetosphere affect in different manners the magnetosphere-ionosphere coupled convection system.

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.

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.

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.

Relationship of Topside Ionospheric Ion Outflows to Auroral Forms and Precipitations, Plasma Waves, and Convection Observed by POLAR

NASA Technical Reports Server (NTRS)

Hirahara, M.; Horwitz, J. L.; Moore, T. E.; Germany, G. A.; Spann, J. F.; Peterson, W. K.; Shelley, E. G.; Chandler, M. O.; Giles, B. L.; Craven, P. D.;

Application of a global magnetospheric-ionospheric current model for dayside and terminator Pi2 pulsations

NASA Astrophysics Data System (ADS)

Imajo, S.; Yoshikawa, A.; Uozumi, T.; Ohtani, S.; Nakamizo, A.; Chi, P. J.

2017-12-01

Pi2 magnetic oscillations on the dayside are considered to be produced by the ionospheric current that is driven by Pi2-associated electric fields from the high-latitude region, but this idea has not been quantitatively tested. The present study numerically tested the magnetospheric-ionospheric current system for Pi2 consisting of field-aligned currents (FACs) localized in the nightside auroral region, the perpendicular magnetospheric current flowing in the azimuthal direction, and horizontal ionospheric currents driven by the FACs. We calculated the spatial distribution of the ground magnetic field produced by these currents using the Biot-Savart law in a stationary state. The calculated magnetic field reproduced the observational features reported by previous studies; (1) the sense of the H component does not change a wide range of local time sectors at low latitudes; (2) the amplitude of the H component on the dayside is enhanced at the equator; (3) The D component reverses its phase near the dawn and dusk terminators; (4) the meridian of the D-component phase reversal near the dusk terminator is shifted more sunward than that near the dawn terminator; (5) the amplitude of the D component in the morning is larger than that in the early evening. We also derived the global distributions of observed equivalent currents for two Pi2 events. The spatial patterns of dayside equivalent currents were similar to the spatial pattern of numerically derived equivalent currents. The results indicate that the oscillation of the magnetospheric-ionospheric current system is a plausible explanation of Pi2s on the dayside and near the terminator. These results are included in an accepted paper by Imajo et al. [2017JGR, DOI: 10.1002/2017JA024246].

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.

Field aligned current study during the solar declining- extreme minimum of 23 solar cycle

NASA Astrophysics Data System (ADS)

Nepolian, Jeni Victor; Kumar, Anil; C, Panneerselvam

Field Aligned Current (FAC) density study has been carried out during the solar declining phase from 2004 to 2006 of the 23rd solar cycle and the ambient terrestrial magnetic field of the extended minimum period of 2008 and 2009. We mainly depended on CHAMP satellite data (http://isdc.gfz-potsdam.de/) for computing the FAC density with backup of IGRF-10 model. The study indicates that, the FAC is controlled by quasi-viscous processes occurring at the flank of the earth’s magnetosphere. The dawn-dusk conventional pattern enhanced during disturbed days. The intensity of R1 current system is higher than the R2 current system. Detailed results will be discussed in the conference.

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.

Observations of Large-Amplitude, Parallel, Electrostatic Waves Associated with the Kelvin-Helmholtz Instability by the Magnetospheric Multiscale Mission

NASA Technical Reports Server (NTRS)

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.;

Acceleration mechanisms for energetic particles in the earth's magnetosphere

NASA Technical Reports Server (NTRS)

Schiferl, S.; Fan, C. Y.; Hsieh, K. C.; Erickson, K. N.; Gloeckler, G.

1982-01-01

By analyzing data on energetic particle fluxes measured simultaneously with detector systems on several earth satellites, signatures of different acceleration mechanisms for these particles were searched for. One of the samples is an event observed on ATS-6 and IMP-7. IMP-7 was in the dusk quarter at 38 earth radii while ATS-6 was located at local midnight at a distance of 6.6 earth radii. Although the flux variations as observed on the two spacecraft both showed 1.5 min periodicity, there was a 40-second time lag with IMP-7 behind. The results indicate that the particles are accelerated by magnetic field line annihilation, with the x-point located at about 10 earth radii.

KSC-2011-1867

NASA Image and Video Library

2011-02-25

CAPE CANAVERAL, Fla. -- Dusk descends on the Freedom Star, one of NASA's solid rocket booster retrieval ships stationed in the Atlantic Ocean, to recover the right spent booster after it splashed down following space shuttle Discovery's final launch. The shuttle’s two solid rocket booster casings and associated flight hardware are recovered in the Atlantic Ocean after every launch by Freedom Star and Liberty Star. The boosters impact the Atlantic about seven minutes after liftoff and the retrieval ships are stationed about 10 miles from the impact area at the time of splashdown. After the spent segments are processed, they will be transported to Utah, where they will be refurbished and stored, if needed. Photo credit: NASA/Frank Michaux

The Development of Laminated Armor

DTIC Science & Technology

1948-09-27

U.S. Army Ramie Sea Island Mills, Inc. Ramie-Rayon Sea Island Mills, Ilc. Inconel Fabric (006R260R13) Metal Tex Co. -4- Inconel Fabric (00R21OMl6...Plies .02 U.D. Glass Mat 3111-44 4 Plies .02 IT.D. Glass Mat f 110 90 100 1 Ply Nylon Dusk(13 Oz.) I Ply 00R260R13 2-l/4# Inconel 2 Puiem Nylon Duck(13 Oz...13 Oz.) 1 Ply O07R210M16 2-1/4# Inconel 2 Pl•es Nylon Duck(13 Oz.) I Ply 007R210MI( ?-1/4# Inconel 1 Ply Nylon Duck(13 Oz.) 4 Plies .02 U.D. Mlass Mat

Near Earth Current Meander (Necm) Model of Substorms

NASA Astrophysics Data System (ADS)

Heikkila, W. J.; Chen, T.; Liu, Z. X.; Pu, Z. Y.; Pellinen, R. J.; Pulkkinen, T. I.

2001-01-01

We propose that the appropriate instability to trigger a substorm is a tailward meander (in the equatorial plane) of the strong current filament that develops during the growth phase. From this single assumption follows the entire sequence of events for a substorm. The main particle acceleration mechanism in the plasma sheet is curvature drift with a dawn-dusk electric field, leading to the production of auroral arcs. Eventually the curvature becomes so high that the ions cannot negotiate the sharp turn at the field-reversal region, locally, at a certain time. The particle motion becomes chaotic, causing a local outward meander of the cross-tail current. An induction electric field is produced by Lenz's law, E^ind=-∂A/∂t. An outward meander with B_z>0 will cause E×B flow everywhere out from the disturbance; this reaction is a macroscopic instability which we designate the electromotive instability. The response of the plasma is through charge separation and a scalar potential, E^es=-∇φ. Both types of electric fields have components parallel to B in a realistic magnetic field. For MHD theory to hold the net E_∥ must be small; this usually seems to happen (because MHD often does hold), but not always. Part of the response is the formation of field-aligned currents producing the well-known substorm current diversion. This is a direct result of a strong E_∥^ind (the cause) needed to overcome the mirror force of the current carriers; this enables charge separation to produce an opposing electrostatic field E_∥^es (the effect). Satellite data confirm the reality of a strong E_∥ in the plasma sheet by counter-streaming of electrons and ions, and by the inverse ion time dispersion, up to several 100 keV. The electron precipitation is associated with the westward traveling surge (WTS) and the ion with omega (Ω) bands, respectively. However, with zero curl, E^es cannot modify the emf ɛ=∮E.dl=-dΦ^M/dt of the inductive electric field E^ind (a property of

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

NASA Technical Reports Server (NTRS)

Kane, R. P.; Trivedi, N. B.

1981-01-01

Computations concerning variations of the geomagnetic field at MAGSAT altitudes were investigated. Using MAGSAT data for the X, Y, and Z components of the geomagnetic field, a computer conversion to yield the H component was performed. Two methods of determining delta H normalized to a constant geocentric distance R sub 0 = 6800 were investigated, and the utility of elta H at times of magnetic storms was considered. Delta H at a geographical latitude of 0 at dawn and dusk, the standard Dst, and K sub p histograms were plotted and compared. Magnetic anomalies are considered. Examination of data from the majority of the 400 passes of MAGSAT considered show a reasonable delta H versus latitude variation. Discrepancies in values are discussed.

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.

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

NASA Technical Reports Server (NTRS)

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

1985-01-01

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.

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.

Geomagnetic storms of cycle 24 and their solar sources

NASA Astrophysics Data System (ADS)

Watari, Shinichi

2017-05-01

Solar activity of cycle 24 following the deep minimum between cycle 23 and cycle 24 is the weakest one since cycle 14 (1902-1913). Geomagnetic activity is also low in cycle 24. We show that this low geomagnetic activity is caused by the weak dawn-to-dusk solar wind electric field ( E d-d) and that the occurrence rate of E d-d > 5 mV/m decreased in the interval from 2013 to 2014. We picked up seventeen geomagnetic storms with the minimum Dst index of less than -100 nT and identified their solar sources in cycle 24 (2009-2015). It is shown that the relatively slow coronal mass ejections contributed to the geomagnetic storms in cycle 24.

Anisotropic pitch angle distribution of 50 eV to 50 keV particles at synchronous altitude.

NASA Technical Reports Server (NTRS)

Deforest, S. E.; Mcilwain, C. F.

1972-01-01

At times, the electron pitch angle distributions at synchronous orbit have been observed to be highly anisotropic. In the local morning region, distributions concentrated near 90 deg are often observed in particles of less than approximately 2000 V. This anisotropy decreases with increasing energy from 1 keV to the detector's limit at 50 keV. The time development of anisotropy is consistent with production by pitch angle scattering processes which are not effective on electrons with small velocities parallel to the magnetic field. Another type of distribution has been observed with the low-energy (below 1000 V) electrons concentrated parallel and antiparallel to the magnetic field. These distributions are only seen in the dusk sector, but this may be an orbital artifact.

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.

Entomological investigations into an epidemic of Japanese encephalitis (JE) in northern districts of West Bengal, India (2011-2012)

PubMed Central

Mariappan, T.; Samuel, P. Philip; Thenmozhi, V.; Paramasivan, R.; Sharma, Puran Kumar; Biswas, Asit Kumar; Tyagi, B.K.

2014-01-01

Background & objectives: Japanese encephalitis (JE) is one of the most important arboviral diseases of human beings with outbreaks in many parts of Southeast Asia including India. We present the entomological findings of an outbreak occurred in northern part of West Bengal during 2011-2012 with special emphasis on the role of JE vectors in different seasons. Methods: Adult mosquito collections were made with the help of mouth aspirators, aided by flash lights during day time resting inside human and animal habitations as indoor, and resting outside field grasses, bushes, underneath of culverts and bridges as outdoor, and in and around the pig enclosures and cattle sheds during dusk period in JE affected villages from Cooch Behar, Dakshin Dinajpur, Darjeeling and Jalpaiguri districts in North West Bengal. In all study villages, a long handled with enamel bowl dipper was used to obtain immature stages of mosquitoes from various breeding habitats. Results: A total of 19 different types of mosquito breeding habitats were examined for vectors of JE. From these habitats, 23.7 per cent were positive for breeding during the study period. Overall, nine different species were recorded through emergence, but none was positive for JE virus when subjected for detection of virus. Adult mosquitoes of more than 50 per cent of the potential JE vector species obtained through dusk and the rest through indoor and outdoor collections in all seasons. Altogether, 27 different species were recorded. Most of these were JE vectors. Interpretation & conclusions: Our results showed that in addition to Cx. vishnui subgroup, detection of JE virus antigen in Cx. quinquefasciatus indicated the possible maintenance of JE virus in nature through poor vector mosquitoes throughout the year. Since, all potential vector species reported elsewhere in India were also found in this region and fluctuated in density in different seasons, a proper integrated vector control programme needs to be implemented

Effect of an MLT dependent electron loss rate on the inner magnetosphere electrodynamics and plasma sheet penetration to the ring current region

NASA Astrophysics Data System (ADS)

Gkioulidou, M.; Wang, C.; Wing, S.; Lyons, L. R.; Wolf, R. A.; Hsu, T.

2012-12-01

Transport of plasma sheet particles into the ring current region is strongly affected by the penetrating convection electric field, which is the result of the large-scale magnetosphere-ionosphere (M-I) electromagnetic coupling. One of the main factors controlling this coupling is the ionospheric conductance. As plasma sheet electrons drift earthward, they get scattered into the loss cone due to wave-particle interactions and precipitate to the ionosphere, producing auroral conductance. Realistic electron loss is thus important for modeling the (M-I) coupling and penetration of plasma sheet into the inner magnetosphere. To evaluate the significance of electron loss rate, we used the Rice Convection Model (RCM) coupled with a force-balanced magnetic field to simulate plasma sheet transport under different electron loss rates and under self-consistent electric and magnetic field. The plasma sheet ion and electron sources for the simulations are based on the Geotail observations. Two major rates are used: different portions of i) strong pitch-angle diffusion everywhere electron loss rate (strong rate) and ii) a more realistic loss rate with its MLT dependence determined by wave activity (MLT rate). We found that the dawn-dusk asymmetry in the precipitating electron energy flux under the MLT rate, with much higher energy flux at dawn than at dusk, agrees better with statistical DMSP observations. Electrons trapped inside L ~ 8 RE can remain there for many hours under the MLT rate, while those under the strong rate get lost within minutes. Compared with the strong rate, the remaining electrons under the MLT rate cause higher conductance at lower latitudes, allowing for less efficient electric field shielding to convection enhancement, thus further earthward penetration of the plasma sheet into the inner magnetosphere. Therefore, our simulation results indicate that the electron loss rate can significantly affect the electrodynamics of the ring current region. Development

The diel vertical migration patterns and individual swimming behavior of overwintering sprat Sprattus sprattus

NASA Astrophysics Data System (ADS)

Solberg, Ingrid; Kaartvedt, Stein

2017-02-01

We addressed the behavioral patterns and DVM dynamics of sprat overwintering in a Norwegian fjord (150 m) with increasing hypoxia by depth. An upward-facing echosounder deployed at the bottom and cabled to shore provided 4 months of continuous acoustic data. This enabled detailed studies of individual behavior, specifically allowing assessment of individual vertical migrations at dusk and dawn in relation to light, analysis of so-called rise-and-sink swimming, and investigation of the sprat' swimming activity and behavior in severely hypoxic waters. Field campaigns supplemented the acoustic studies. The acoustic records showed that the main habitat for sprat was the upper ∼65 m where oxygen concentrations were ⩾0.7 mL O2 L-1. The sprat schooled at ∼50 m during daytime and initiated an upward migration about 1 h prior to sunset. While some sprat migrated to surface waters, other individuals interrupted the ascent when at ∼20-30 m, and returned to deeper waters ∼20-50 min after sunset. Sprat at depth was on average larger, yet individuals made excursions to- and from upper layers. Sprat were swimming in a "rise and sink" pattern at depth, likely related to negative buoyancy. Short-term dives into waters with less than 0.45 mL O2 L-1 were interpreted as feeding forays for abundant overwintering Calanus spp. The deep group of sprat initiated a dawn ascent less than 1 h before sunrise, ending at 20-30 m where they formed schools. They subsequently returned to deeper waters about ∼20 min prior to sunrise. Measurements of surface light intensities indicated that the sprat experienced lower light levels in upper waters at dawn than at dusk. The vertical swimming speed varied significantly between the behavioral tasks. The mixed DVM patterns and dynamic nocturnal behavior of sprat persisted throughout winter, likely shaped by individual strategies involving optimized feeding and predator avoidance, as well as relating to temperature, hypoxia and negative

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

Electron Acceleration in the Magnetotail during Substorms in Semi-Global PIC Simulations

NASA Astrophysics Data System (ADS)

Richard, R. L.; Schriver, D.; Ashour-Abdalla, M.; El-Alaoui, M.; Lapenta, G.; Walker, R. J.

2015-12-01

To understand the acceleration of electrons during a substorm reconnection event we have applied a semi-global particle in cell (PIC) simulation box embedded within a global magnetohydrodynamic (MHD) simulation of Earth's magnetosphere for an event on February 15, 2008. The MHD results were used to populate the PIC simulation and to set the boundary conditions. In the magnetotail we found that a series of dipolarizations formed due to unsteady reconnection. We also found that the most energetic electrons were in the separatrices far from the x-point. We attributed the acceleration to a streaming instability in the separatrices. To further understand electron acceleration we have applied the large scale kinetic (LSK) technique in which tens- to hundreds- of thousands of electrons are followed within the electric and magnetic fields from the PIC simulations., Electrons are already included in the PIC simulation, but the LSK simulations will allow selected individual particles to be followed and analyzed. Initially we performed electron LSK calculations in a two dimensional version of the PIC simulation in which electrons were allowed to move in the ignorable cross tail direction. These LSK calculations showed that electrons gained energy primarily for two reasons: (1) acceleration by the average dawn to dusk electric field and (2) acceleration by intense but localized electric field structures. The overall electron transport was more dawnward than duskward due to the average electric field. At the same time electrons typically moved away from the reconnection region in both the earthward and tailward directions. Superimposed on this large-scale transport was motion in both the dusk and dawn directions across the tail because of the electric field structures, which were particularly intense in the separatrices. LSK calculations are now being carried out by using the full three-dimensional magnetic and electric fields from the PIC simulation and these results will be

Cluster observations of band-limited Pc 1 waves associated with streaming H+ and O+ ions in the high-altitude plasma mantle

NASA Astrophysics Data System (ADS)

Engebretson, M. J.; Kahlstorf, C. R. G.; Murr, D. L.; Posch, J. L.; Keiling, A.; Lavraud, B.; Rème, H.; Lessard, M. R.; Kim, E.-H.; Johnson, J. R.; Dombeck, J.; Grison, B.; Robert, P.; Glassmeier, K.-H.; Décréau, P. M. E.

2012-10-01

Bursts of band-limited Pc 1 waves (0.2 to ˜1.0 Hz) with normalized frequency f/fH+ ˜ 0.5 have been observed by the Cluster spacecraft during many passes through the high-latitude plasma mantle. These transverse, left-hand polarized waves are associated with regions of H+ and O+ ions streaming away from Earth along magnetic field lines at the same velocity (˜140 km/s). Waves were observed only when H+ fluxes increased by factors of 10-1000 and energies of both ion species increased by factors of up to 10. We present two satellite-ground conjunctions to demonstrate the high latitude localization of these waves and their ability to reach the polar ionosphere and two extended examples of waves and associated ion distribution functions near the southern dusk flank magnetopause. We also present the results of a search for all such events during Cluster's 2002 and 2003 passages through the magnetotail, with orbital precession covering dawn to dusk on Earth's night side (June through December). A total of 46 events (band-limited Pc 1-2 waves accompanied by a sustained population of streaming H+ and O+ ions, separated by at least 12 min) were observed on 29 days. The waves were generally associated with intervals of southward IMF Bz and/or large IMF By (times of active cusp reconnection), and often but not always occurred during the main phase or early recovery phase of magnetic storms. Analysis of selected events shows that the waves are associated with large H+ temperature anisotropy, and that the waves propagate opposite to the direction of the streaming ions. A wave instability analysis using the WHAMP code confirms that the generation of these waves, via the ion cyclotron instability, is basically consistent with known physics. Their extended region of wave growth is likely, however, to reach tailward significantly beyond the Cluster orbit.

Externally-Driven Onset of Localized Magnetic Reconnection in a Magnetotail Configuration

NASA Astrophysics Data System (ADS)

Pritchett, P. L.; Lu, S.

2017-12-01

In observations of the nightside auroral arcs and ionospheric currents, the onset or breakup phase of a substorm is sharply defined in time and is highly localized in space. Attempts to understand this localization in terms of the onset of localized magnetic reconnection have generally been unsuccessful. Thus, a y-localized driving convection electric field Ey applied at the lobe boundaries spreads out before it reaches the equatorial plane and results only in 2-D reconnection. In this work, the response of a magnetotail equilibrium containing a dipole magnetic field and plasma sheet regions to the imposition of a longitudinally-limited, high-latitude driving electric field is investigated using 3-D particle-in-cell simulations. The initial response involves a reduction in the equatorial Bz field that is then followed by the development of a dawn-dusk asymmetric current sheet relative to the meridian plane of the driving field. The key feature is the presence of a dusk-side Hall electric field Ez that drives magnetic flux dawnward and thus further reduces the Bz field on the duskward side. The net result is that Bz is driven through zero in a localized region on the duskward side, leading to the onset of localized reconnection and the emergence of magnetic flux ropes. The cross-tail extent of the reconnection expands but remains limited to ˜30di, where di is the ion inertia length. The dissipation E' \\cdot J is peaked along the finite X line, with a load region (negative E' \\cdot J) forming tailward of this region. The particle energy spectra in the downtail region show shoulders for the ions in the energy range ˜3-8Eth (Eth is the initial thermal energy) and extended tails for the electrons in the range ˜10-20Eth. These results demonstrate the ability of a high-latitude disturbance that may be connected to dayside flow channels [Nishimura et al., 2014] to initiate localized magnetic reconnection in the magnetotail.

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

Geostrophic adjustment in a shallow-water numerical model as it relates to thermospheric dynamics

NASA Technical Reports Server (NTRS)

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

1986-01-01

The theory of geostrophic adjustment and its application to the dynamics of the high latitude thermosphere have been discussed in previous papers based on a linearized treatment of the fluid dynamical equations. However, a linearized treatment is only valid for small Rossby numbers given by Ro = V/fL, where V is the wind speed, f is the local value of the Coriolis parameter, and L is a characteristic horizontal scale for the flow. For typical values in the auroral zone, the approximation is not reasonable for wind speeds greater than 25 m/s or so. A shallow-water (one layer) model was developed that includes the spherical geometry and full nonlinear dynamics in the momentum equations in order to isolate the effects of the nonlinearities on the adjustment process. A belt of accelerated winds between 60 deg and 70 deg latitude was used as the initial condition. The adjustment process was found to proceed as expected from the linear formulation, but that an asymmetry between the response for an eastward and westward flow results from the nonlineawr curvature (centrifugal) terms. In general, the amplitude of an eastward flowing wind will be less after adjustment than a westward wind. For instance, if the initial wind velocity is 300 m/s, the linearized theory predicts a final wind speed of 240 m/s, regardless of the flow direction. However, the nonlinear curvature terms modify the response and produce a final wind speed of only 200 m/s for an initial eastward wind and a final wind speed of almost 300 m/s for an initial westward flow direction. Also, less gravity wave energy is produced by the adjustment of the westward flow than by the adjustment of the eastward flow. The implications are that the response of the thermosphere should be significantly different on the dawn and dusk sides of the auroral oval. Larger flow velocities would be expected on the dusk side since the plasma will accelerate the flow in a westward direction in that sector.

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

Three-dimensional magnetosheath plasma ion distributions from 200 eV to 2 MeV

NASA Technical Reports Server (NTRS)

Williams, D. J.; Mitchell, D. G.; Frank, L. A.; Eastman, T. E.

1988-01-01

This paper presents initial measurements, made with ISEE 1 plasma and energetic-particle instruments, of the three-dimensional magnetosheath plasma ion flow and the spectrum over the energy range of 200 eV to 2 MeV, obtained on two magnetosheath traversals, one on the dawn (December 19, 1977) and the other on the dusk (July 7, 1978) flanks of the magnetosphere. The data suggest that the magnetosheath plasma ion population often consisted of a shocked solar wind component, of energy not greater than 5 keV, and a magnetospheric high-energy (not below 5 keV) component. The shocked solar wind component generally behaved independently of the magnetic field direction, indicating that the magnetic field was carried along in the bulk plasma flow. The high-energy tail was highly modulated by the magnetic field.

Colonization of Anopheles pseudopunctipennis from Mexico.

PubMed

Villarreal, C; Arredondo-Jiménez, J I; Rodriguez, M H; Ulloa, A

1998-12-01

Two colonies of Anopheles pseudopunctipennis, Tapachula and Abasolo strains, were established under laboratory conditions with a thermoperiod (29 degrees C during the day; 24 degrees C during the night) and artificial dusk. To stimulate mating, a light beam from a flashlight was shone on the cage shortly after lights off. This procedure was repeated for the first 6 mosquito generations (parental to F6) and thereafter light stimulation was unnecessary for mating. The Tapachula colony has been maintained for 24 generations in 24 months, with insemination rates in females > 80% since the F3, and a monthly production of 30,000 pupae since the F7. Using the same procedure, the Abasolo colony from northeastern Mexico has been maintained for 13 generations in 14 months, with insemination rates of 26-52%.

Earth observation

NASA Image and Video Library

2014-08-31

ISS040-E-113700 (31 Aug. 2014) --- This panorama view, photographed by an Expedition 40 crew member on the International Space Station, shows tan-colored dust of a major dust storm obscuring the Persian Gulf and the its northern shoreline. Strong north winds often blow in summer, churning up dust from the entire length of the desert surfaces of the Tigris and Euphrates valleys (top left). Dust partly obscures the hundreds of kilometers of Iraq’s light-green agricultural lands along these rivers (left). A line of thunderstorms is being set off by the Zagros Mountains of Iran (right), with the setting sun casting long shadows from the thunderheads. Space station crews see sixteen sunrises and sunsets every day from low Earth orbit. Here the crew captured dusk in a darkening Iranian landscape (right).

Ionospheric plasma cloud dynamics

NASA Technical Reports Server (NTRS)

1976-01-01

Measurements of the thermospheric neutral wind and ionospheric drift made at Eglin AFB, Florida and Kwajalein Atoll are discussed. The neutral wind measurements at Eglin had little variation over a period of four years for moderate magnetic activity (Kp 4); the ionospheric drifts are small. Evidence is presented that indicates that increased magnetic activity has a significant effect on the neutral wind magnitude and direction at this midlatitude station. The neutral wind at dusk near the equator is generally small although in one case out of seven it was significantly larger. It is described how observations of large barium releases can be used to infer the degree of electrodynamic coupling of ion clouds to the background ionosphere. Evidence is presented that indicates that large barium releases are coupled to the conjugate ionosphere at midlatitudes.

Low altitude, one centimeter, space debris search at Lincoln Laboratory's (M.I.T.) experimental test system

NASA Technical Reports Server (NTRS)

Taff, L. G.; Beatty, D. E.; Yakutis, A. J.; Randall, P. M. S.

1985-01-01

The majority of work performed by the Lincoln Laboratory's Space Surveillance Group, at the request of NASA, to define the near-earth population of man-made debris is summarized. Electrooptical devices, each with a 1.2 deg FOV, were employed at the GEODSS facility in New Mexico. Details of the equipment calibration and alignment procedures are discussed, together with implementation of a synchronized time code for computer controlled videotaping of the imagery. Parallax and angular speed data served as bases for distinguishing between man-made debris and meteoroids. The best visibility was obtained in dawn and dusk twilight conditions at elevation ranges of 300-2000 km. Tables are provided of altitudinal density distribution of debris. It is noted that the program also yielded an extensive data base on meteoroid rates.

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.

Plasmasphere Response: Tutorial and Review of Recent Imaging Results

NASA Astrophysics Data System (ADS)

Goldstein, J.

2006-06-01

The plasmasphere is the cold, dense innermost region of the magnetosphere that is populated by upflow of ionospheric plasma along geomagnetic field lines. Driven directly by dayside magnetopause reconnection, enhanced sunward convection erodes the outer layers of the plasmasphere. Erosion causes the plasmasphere outer boundary, the plasmapause, to move inward on the nightside and outward on the dayside to form plumes of dense plasma extending sunward into the outer magnetosphere. Coupling between the inner magnetosphere and ionosphere can significantly modify the convection field, either enhancing sunward flows near dusk or shielding them on the night side. The plasmaspheric configuration plays a crucial role in the inner magnetosphere; wave-particle interactions inside the plasmasphere can cause scattering and loss of warmer space plasmas such as the ring current and radiation belts.

Regulation of assimilate partitioning by daylength and spectral quality

DOE Office of Scientific and Technical Information (OSTI.GOV)

Britz, S.J.

1994-12-31

Photosynthesis is the process by which plants utilize light energy to assimilate and transform carbon dioxide into products that support growth and development. The preceding review provides an excellent summary of photosynthetic mechanisms and diurnal patterns of carbon metabolism with emphasis on the importance of gradual changes in photosynthetically-active radiation at dawn and dusk. In addition to these direct effects of irradiance, there are indirect effects of light period duration and spectral quality on carbohydrate metabolism and assimilate partitioning. Both daylength and spectral quality trigger developmental phenomena such as flowering (e.g., photoperiodism) and shade avoidance responses, but their effects onmore » partitioning of photoassimilates in leaves are less well known. Moreover, the adaptive significance to the plants of such effects is sometimes not clear.« less

Optical Fiber Illumination System for visual flight simulation

NASA Technical Reports Server (NTRS)

Hollow, R. H.

1981-01-01

An electronically controlled lighting system simulating runway, aircraft carrier, and landing aid lights for flight simulations is described. The various colored lights that would be visible to a pilot by day, at dusk, or at night are duplicated at the distances the lights would normally become visible. Plastic optical fiber illuminators using tungsten halogen lights are distributed behind the model. The tips of the fibers of illuminators simulating runway lights are bevelled in order that they may be seen from long distances and at low angles. Fibers representing taxiway lights are pointed and polished for omni-directional visibility. The electronic intensity controls, which can be operated either manually or remotely, regulate the intensity of the lights to simulate changes in distance. A dichronic mirror, infrared filter system is used to maintain color integrity.

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.

Non-linear three dimensional spectral model of the Venusian thermosphere with super-rotation. I - Formulation and numerical technique. II - Temperature, composition and winds

NASA Technical Reports Server (NTRS)

Stevens-Rayburn, D. R.; Mengel, J. G.; Harris, I.; Mayr, H. G.

1989-01-01

A three-dimensional spectral model for the Venusion thermosphere is presented which uses spherical harmonics to represent the horizontal variations in longitude and latitude and which uses Fourier harmonics to represent the LT variations due to atmospheric rotation. A differencing scheme with tridiagonal block elimination is used to perform the height integration. Quadratic nonlinearities are taken into account. In the second part, numerical results obtained with the model are shown to reproduce the observed broad daytime maxima in CO2 and CO and the significantly larger values at dawn than at dusk. It is found that the diurnal variations in He are most sensitive to thermospheric superrotation, and that, given a globally uniform atmosphere as input, larger heating rates yield a larger temperature contrast between day and night.

Interplanetary magnetic field dependency of stable Sun-aligned polar cap arcs

NASA Technical Reports Server (NTRS)

Valladares, C. E.; Carlson, H. C., Jr.; Fukui, K.

1994-01-01

This is the first analysis, using a statistically significant data set, of the morphological dependence of the presence, orientation, and motion of stable sun-aligned polar cap arcs upon the vector interplanetary magnetic field (IMF). For the one winter season analyzed we had 1392 all-sky 630.0-nm images of 2-min resolution containing a total of 150 polar cap arcs, all with corresponding values of the IMF as measured by International Monitoring Platform (IMP) 8 or International Sun Earth Explorer (ISEE) 2. After demonstrating an unbiased data set with smooth normal distributions of events versus the dimensions of time, space, and IMF component, we examine IMF dependencies of the properties of the optical arcs. A well-defined dependence for B(sub z) is found for the presence/absence of stable Sun-aligned polar cap arcs. Consistent with previous statistical studies, the probability of observing polar cap aurora steadily increases for larger positive values of B(sub z), and linearly decreases when B(sub z) becomes more negative. The probability of observing Sun-aligned arcs within the polar cap is determined to vary sharply as a function of the arc location; arcs were observed 40% of the time on the dawnside and only 10% on the duskside. This implies an overall probability of at least 40% for the whole polar cap. 20% of the arcs were observed during 'southward IMF conditions,' but in fact under closer inspection were found to have been formed under northward IMF conditions; these 'residual' positive B(sub z) arcs ha d a delayed residence time in the polar cap of about what would be expected after a north to south transition of B(sub z). A firm dependence on B(sub y) is also found for both the orientation and the dawn-dusk direction of motion of the arcs. All the arcs are Sun-aligned to a first approximation, but present deviations from this orientation, depending primarily upon the location of the arc in corrected geomagnetic (CG) coordinates. The arcs populating the

Policies of inclusion: immigrants, disease, dependency, and American immigration policy at the dawn and dusk of the 20th century.

PubMed

Fairchild, Amy L

2004-04-01

The racial politics of immigration have punctuated national discussions about immigration at different periods in US history, particularly when concerns about losing an American way of life or American population have coincided with concerns about infectious diseases. Nevertheless, the main theme running through American immigration policy is one of inclusion. The United States has historically been a nation reliant on immigrant labor and, accordingly, the most consequential public policies regarding immigration have responded to disease and its economic burdens by seeking to control the behavior of immigrants within our borders rather than excluding immigrants at our borders.

KSC-2010-4817

NASA Image and Video Library

2010-09-22

CAPE CANAVERAL, Fla. -- This view at dusk from the stern of Freedom Star, one of NASA's solid rocket booster retrieval ships, shows the Pegasus Barge carrying the Space Shuttle Program's last external fuel tank, ET-122, as it is transported to NASA's Kennedy Space Center in Florida. The tank will travel 900 miles by sea before being offloaded and moved to Kennedy's Vehicle Assembly Building where it will be integrated to space shuttle Endeavour for the STS-134 mission to the International Space Station. The tank, which is the largest element of the space shuttle stack, was damaged during Hurricane Katrina in August 2005 and restored to flight configuration by Lockheed Martin Space Systems Company employees. STS-134, targeted to launch Feb. 2011, currently is scheduled to be the last mission in the Space Shuttle Program. Photo credit: NASA/Kim Shiflett

Celestial polarization patterns during twilight.

PubMed

Cronin, Thomas W; Warrant, Eric J; Greiner, Birgit

2006-08-01

Scattering of sunlight produces patterns of partially linearly polarized light in the sky throughout the day, and similar patterns appear at night when the Moon is bright. We studied celestial polarization patterns during the period of twilight, when the Sun is below the horizon, determining the degree and orientation of the polarized-light field and its changes before sunrise and after sunset. 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. In the tropics, this pattern appears approximately 1 h before local sunrise or disappears approximately 1 h after local sunset (within 10 min. after the onset of astronomical twilight at dawn, or before its end at dusk) and extends with little change through the entire twilight period.

NASA's Ship-Aircraft Bio-Optical Research (SABOR)

NASA Image and Video Library

2017-12-08

Instruments Overboard On July 26, 2014, scientists worked past dusk to prepare and deploy the optical instruments and ocean water sensors during NASA's SABOR experiment. NASA's Ship-Aircraft Bio-Optical Research (SABOR) experiment is a coordinated ship and aircraft observation campaign off the Atlantic coast of the United States, an effort to advance space-based capabilities for monitoring microscopic plants that form the base of the marine food chain. Read more: 1.usa.gov/WWRVzj Credit: NASA/SABOR/Wayne Slade, Sequoia Scientific . NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

PDF-modulated visual inputs and cryptochrome define diurnal behavior in Drosophila.

PubMed

Cusumano, Paola; Klarsfeld, André; Chélot, Elisabeth; Picot, Marie; Richier, Benjamin; Rouyer, François

2009-11-01

Morning and evening circadian oscillators control the bimodal activity of Drosophila in light-dark cycles. The lateral neurons evening oscillator (LN-EO) is important for promoting diurnal activity at dusk. We found that the LN-EO autonomously synchronized to light-dark cycles through either the cryptochrome (CRY) that it expressed or the visual system. In conditions in which CRY was not activated, flies depleted for pigment-dispersing factor (PDF) or its receptor lost the evening activity and displayed reversed PER oscillations in the LN-EO. Rescue experiments indicated that normal PER cycling and the presence of evening activity relied on PDF secretion from the large ventral lateral neurons and PDF receptor function in the LN-EO. The LN-EO thus integrates light inputs and PDF signaling to control Drosophila diurnal behavior, revealing a new clock-independent function for PDF.

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.

Local time dependence of turbulent magnetic fields in Saturn's magnetodisc

NASA Astrophysics Data System (ADS)

Kaminker, V.; Delamere, P. A.; Ng, C. S.; Dennis, T.; Otto, A.; Ma, X.

2017-04-01

Net plasma transport in magnetodiscs around giant planets is outward. Observations of plasma temperature have shown that the expanding plasma is heating nonadiabatically during this process. Turbulence has been suggested as a source of heating. However, the mechanism and distribution of magnetic fluctuations in giant magnetospheres are poorly understood. In this study we attempt to quantify the radial and local time dependence of fluctuating magnetic field signatures that are suggestive of turbulence, quantifying the fluctuations in terms of a plasma heating rate density. In addition, the inferred heating rate density is correlated with magnetic field configurations that include azimuthal bend forward/back and magnitude of the equatorial normal component of magnetic field relative to the dipole. We find a significant local time dependence in magnetic fluctuations that is consistent with flux transport triggered in the subsolar and dusk sectors due to magnetodisc reconnection.

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).

SAPS effects on thermospheric winds during the 17 March 2013 storm

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

An analysis of howling response parameters useful for wolf pack censusing

USGS Publications Warehouse

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

1982-01-01

Gray wolves (Canis lupus) were studied from April-1972 through April 1974 in the Superior National Forest in northeastern Minnesota by radio-tracking and simulated howling. Based on replies during 217 of 456 howling sessions, the following recommendations were derived for using simulated howling as a census technique: (1) the best times of day are dusk and night; (2) July, August, and September are the best months; (3) precipitation and winds greater than 12 km/hour should be aVQided; (4) a sequence of 5 single howls should be used, alternating 'flat' and 'breaking' howls; (5) trials should be repeated 3 times at about 2-minute intervals with the first trial at lower volume; and (6) the trial series should be repeated on 3 nights as close to each other as possible. Two censuses are described: a saturation census and a sampling census.

A mysterious dust clump in a disk around an evolved binary star system.

PubMed

Jura, M; Turner, J

1998-09-10

The discovery of planets in orbit around the pulsar PSR1257+12 shows that planets may form around post-main-sequence stars. Other evolved stars, such as HD44179 (an evolved star which is part of the binary system that has expelled the gas and dust that make the Red Rectangle nebula), possess gravitationally bound orbiting dust disks. It is possible that planets might form from gravitational collapse in such disks. Here we report high-angular-resolution observations at millimetre and submillimetre wavelengths of the dusk disk associated with the Red Rectangle. We find a dust clump with an estimated mass near that of Jupiter in the outer region of the disk. The clump is larger than our Solar System, and far beyond where planet formation would normally be expected, so its nature is at present unclear.

Development of anti-slip sustainable tiles from agricultural waste

NASA Astrophysics Data System (ADS)

Zulkefli, Zainordin Firdaus; Zainol, Mohd Remy Rozainy Mohd Arif; Osman, Norhayati

2017-04-01

In general of 80% the human activities is located in the building. Buildings constructed should be in line with full functions and optimum safety features. Aspects to be emphasized is the slip on the floor of the building. The selection of tiles must have anti-slip characteristics and achieve standard strength stress. This study is conducted to develop anti-slip tiles modification using agricultural waste. The material used is agricultural waste such rice husks, palm fibre and saw dusk mixed into the clay and then baked at a temperature of 900-1185 C °. Agricultural waste mixture ratio is 5%, 10% and 15%. The samples of tiles are produced for experiments. The results of agricultural waste tiles show that the strength is higher than standard strength, the water absorption less than standard tiles and pendulum value test is exceeds 36.

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.

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.

Impact of Feed Delivery Pattern on Aerial Particulate Matter and Behavior of Feedlot Cattle †

PubMed Central

Mitloehner, Frank M.; Dailey, Jeff W.; Morrow, Julie L.; McGlone, John J.

2017-01-01

Simple Summary Fine particulate matter (with less than 2.5 microns diameter; aka PM2.5) are a human and animal health concern because they can carry microbes and chemicals into the lungs. Particulate matter (PM) in general emitted from cattle feedlots can reach high concentrations. When feedlot cattle were given an altered feeding schedule (ALT) that more closely reflected their biological feeding times compared with conventional morning feeding (CON), PM2.5 generation at peak times was substantially lowered. Average daily generation of PM2.5 was decreased by 37% when cattle behavior was redirected away from PM-generating behaviors and toward evening feeding behaviors. Behavioral problems such as agonistic (i.e., aggressive) and bulling (i.e., mounting each other) behaviors also were reduced several fold among ALT compared with CON cattle. Intake of feed was less and daily body weight gain tended to be less with the altered feeding schedule while efficiency of feed utilization was not affected. Although ALT may pose a challenge in feed delivery and labor scheduling, cattle had fewer behavioral problems and reduced PM2.5 generation when feed delivery times matched with the natural drive to eat in a crepuscular pattern. Abstract Fine particulate matter with less than 2.5 microns diameter (PM2.5) generated by cattle in feedlots is an environmental pollutant and a potential human and animal health issue. The objective of this study was to determine if a feeding schedule affects cattle behaviors that promote PM2.5 in a commercial feedlot. The study used 2813 crossbred steers housed in 14 adjacent pens at a large-scale commercial West Texas feedlot. Treatments were conventional feeding at 0700, 1000, and 1200 (CON) or feeding at 0700, 1000, and 1830 (ALT), the latter feeding time coincided with dusk. A mobile behavior lab was used to quantify behaviors of steers that were associated with generation of PM2.5 (e.g., fighting, mounting of peers, and increased locomotion

Statistical survey of pitch angle distributions in core (0-50 eV) ions from Dynamics Explorer 1: Outflow in the auroral zone, polar cap, and cusp

NASA Technical Reports Server (NTRS)

Giles, B. L.; Chappell, C. R.; Moore, T. E.; Comfort, R. H.; Waite, J. H., Jr.

1994-01-01

Core (0-50 eV) ion pitch angle measurements from the retarding ion mass spectrometer on Dynamics Explorer 1 are examined with respect to magnetic disturbance, invariant latitude, magnetic local time, and altitude for ions H(+), He(+), O(+), M/Z = 2 (D(+) or He(++)), and O(++). Included are outflow events in the auroral zone, polar cap, and cusp, separated into altitude regions below and above 3 R(sub E). In addition to the customary division into beam, conic, and upwelling distributions, the high-latitude observations fall into three categories corresponding to ion bulk speeds that are (1) less than, (2) comparable to, or (3) faster than that of the spacecraft. This separation, along with the altitude partition, serves to identify conditions under which ionospheric source ions are gravita- tionally bound and when they are more energetic and able to escape to the outer magnetosphere. Features of the cleft ion fountain inferred from single event studies are clearly identifiable in the statistical results. In addition, it is found that the dayside pre-noon cleft is a dayside afternoon cleft, or auroral zone, becomes an additional source for increased activity. The auroral oval as a whole appears to be a steady source of escape velocity H(+), a steady source of escape velocity He(+) ions for the dusk sector, and a source of escape velocity heavy ions for dusk local times primarily during increased activity. The polar cap above the auroral zone is a consistent source of low-energy ions, although only the lighter mass particles appear to have sufficient velocity, on average, to escape to higher altitudes. The observations support two concepts for outflow: (1) The cleft ion fountain consists of ionospheric plasma of 1-20 eV energy streaming upward into the magnetosphere where high-latitude convection electric fields cause poleward dispersion. (2) The auroral ion fountain involves field-aligned beams which flow out along auroral latitude field lines; and, in addition, for

Evolution of flux ropes in the magnetotail: A three-dimensional global hybrid simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, S.; State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing; Lin, Y.

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 withmore » 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

Dst and a map of average equivalent ring current: 1958-2007

NASA Astrophysics Data System (ADS)

Love, J. J.

2008-12-01

midnight and noon, but rather between dawn and dusk, with greatest mean disturbance occurring at dusk. As a result, proposed corrections to Dst for magnetopause and tail currents might be reasonably reconsidered.

Hypothesis driven single cell dual oscillator mathematical model of circadian rhythms

PubMed Central

S, Shiju

2017-01-01

Molecular mechanisms responsible for 24 h circadian oscillations, entrainment to external cues, encoding of day length and the time-of-day effects have been well studied experimentally. However, it is still debated from the molecular network point of view whether each cell in suprachiasmatic nuclei harbors two molecular oscillators, where one tracks dawn and the other tracks dusk activities. A single cell dual morning and evening oscillator was proposed by Daan et al., based on the molecular network that has two sets of similar non-redundant per1/cry1 and per2/cry2 circadian genes and each can independently maintain their endogenous oscillations. Understanding of dual oscillator dynamics in a single cell at molecular level may provide insight about the circadian mechanisms that encodes day length variations and its response to external zeitgebers. We present here a realistic dual oscillator model of circadian rhythms based on the series of hypotheses proposed by Daan et al., in which they conjectured that the circadian genes per1/cry1 track dawn while per2/cry2 tracks dusk and they together constitute the morning and evening oscillators (dual oscillator). Their hypothesis also provides explanations about the encoding of day length in terms of molecular mechanisms of per/cry expression. We frame a minimal mathematical model with the assumption that per1 acts a morning oscillator and per2 acts as an evening oscillator and to support and interpret this assumption we fit the model to the experimental data of per1/per2 circadian temporal dynamics, phase response curves (PRC's), and entrainment phenomena under various light-dark conditions. We also capture different patterns of splitting phenomena by coupling two single cell dual oscillators with neuropeptides vasoactive intestinal polypeptide (VIP) and arginine vasopressin (AVP) as the coupling agents and provide interpretation for the occurrence of splitting in terms of ME oscillators, though they are not required to

Hypothesis driven single cell dual oscillator mathematical model of circadian rhythms.

PubMed

S, Shiju; Sriram, K

2017-01-01

Molecular mechanisms responsible for 24 h circadian oscillations, entrainment to external cues, encoding of day length and the time-of-day effects have been well studied experimentally. However, it is still debated from the molecular network point of view whether each cell in suprachiasmatic nuclei harbors two molecular oscillators, where one tracks dawn and the other tracks dusk activities. A single cell dual morning and evening oscillator was proposed by Daan et al., based on the molecular network that has two sets of similar non-redundant per1/cry1 and per2/cry2 circadian genes and each can independently maintain their endogenous oscillations. Understanding of dual oscillator dynamics in a single cell at molecular level may provide insight about the circadian mechanisms that encodes day length variations and its response to external zeitgebers. We present here a realistic dual oscillator model of circadian rhythms based on the series of hypotheses proposed by Daan et al., in which they conjectured that the circadian genes per1/cry1 track dawn while per2/cry2 tracks dusk and they together constitute the morning and evening oscillators (dual oscillator). Their hypothesis also provides explanations about the encoding of day length in terms of molecular mechanisms of per/cry expression. We frame a minimal mathematical model with the assumption that per1 acts a morning oscillator and per2 acts as an evening oscillator and to support and interpret this assumption we fit the model to the experimental data of per1/per2 circadian temporal dynamics, phase response curves (PRC's), and entrainment phenomena under various light-dark conditions. We also capture different patterns of splitting phenomena by coupling two single cell dual oscillators with neuropeptides vasoactive intestinal polypeptide (VIP) and arginine vasopressin (AVP) as the coupling agents and provide interpretation for the occurrence of splitting in terms of ME oscillators, though they are not required to

A study of the storm event on October 21-22, 1999 by the MHD simulation

NASA Astrophysics Data System (ADS)

Park, K. S.; Ogino, T.

2006-05-01

We carried out a high resolution three-dimensional magnetohydrodynamic (MHD) simulation of the interac-tionbetween the solar wind and the Earth's magnetosphere during a strong magnetic storm on October 21-22, 1999. The input to the simulation was from WIND solar wind observations. As the IMF is strongly south-ward(-20 nT to -30 nT) for 6 hours, the geomagnetic field lines in the dayside magnetopause are eroded to the geosynchronous orbit (GEO) region by reconnection. The associated magnetic flux is transferred from thedayside magnetosphere to the tail. The reconnection region still appears near GEO region on the dayside magne-topause,even though the IMF Bz component becomes small or northward, because of the influence of the strong IMF By (30 nT). IMF lines can successively reconnect with the naked and large geomagnetic field line in the dayside flank regions. Thus, the cross polar cap potential is maintained to be large value and convection in the ionosphere is enhanced. The cross polar cap potential is governed by IMF By as well as Bz (φ ~ 250 kV for Bz ~ -20 nT and φ ~ 300 kV for Bz ~ -30 nT), and it saturates during the strong southward IMF. A large energy flux enters the ionosphere at very low latitudes (50°) and the inner edge of the plasma sheet becomes very close to the Earth (X = -3.2 RE) for a strong magnetic storms. The open-closed boundary extends to 60° latitudes on the nightside, 72° on the dayside, 62° on dawn, and 66° on dusk. Enhanced energy flux appears at low latitudes (50°) on the nightside in simulation. Moreover, the energy flux in the dusk region (19 MLT) appears down to 55° latitude in simulation, which is consistent with the low latitude boundary of the 0.02-20 keV particles detected by TED of the NOAA-15. A convective electric field, which is penetrating to the Earth-side of the NENL, is almost comparable to that of the solar wind. The present MHD simulation study give reasonable results even for extreme conditions and thereby its

Energized Oxygen : Speiser Current Sheet Bifurcation

NASA Astrophysics Data System (ADS)

George, D. E.; Jahn, J. M.

2017-12-01

A single population of energized Oxygen (O+) is shown to produce a cross-tail bifurcated current sheet in 2.5D PIC simulations of the magnetotail without the influence of magnetic reconnection. Treatment of oxygen in simulations of space plasmas, specifically a magnetotail current sheet, has been limited to thermal energies despite observations of and mechanisms which explain energized ions. We performed simulations of a homogeneous oxygen background, that has been energized in a physically appropriate manner, to study the behavior of current sheets and magnetic reconnection, specifically their bifurcation. This work uses a 2.5D explicit Particle-In-a-Cell (PIC) code to investigate the dynamics of energized heavy ions as they stream Dawn-to-Dusk in the magnetotail current sheet. We present a simulation study dealing with the response of a current sheet system to energized oxygen ions. We establish a, well known and studied, 2-species GEM Challenge Harris current sheet as a starting point. This system is known to eventually evolve and produce magnetic reconnection upon thinning of the current sheet. We added a uniform distribution of thermal O+ to the background. This 3-species system is also known to eventually evolve and produce magnetic reconnection. We add one additional variable to the system by providing an initial duskward velocity to energize the O+. We also traced individual particle motion within the PIC simulation. Three main results are shown. First, energized dawn- dusk streaming ions are clearly seen to exhibit sustained Speiser motion. Second, a single population of heavy ions clearly produces a stable bifurcated current sheet. Third, magnetic reconnection is not required to produce the bifurcated current sheet. Finally a bifurcated current sheet is compatible with the Harris current sheet model. This work is the first step in a series of investigations aimed at studying the effects of energized heavy ions on magnetic reconnection. This work differs

Natural changes in light interact with circadian regulation at promoters to control gene expression in cyanobacteria

PubMed Central

2017-01-01

The circadian clock interacts with other regulatory pathways to tune physiology to predictable daily changes and unexpected environmental fluctuations. However, the complexity of circadian clocks in higher organisms has prevented a clear understanding of how natural environmental conditions affect circadian clocks and their physiological outputs. Here, we dissect the interaction between circadian regulation and responses to fluctuating light in the cyanobacterium Synechococcus elongatus. We demonstrate that natural changes in light intensity substantially affect the expression of hundreds of circadian-clock-controlled genes, many of which are involved in key steps of metabolism. These changes in expression arise from circadian and light-responsive control of RNA polymerase recruitment to promoters by a network of transcription factors including RpaA and RpaB. Using phenomenological modeling constrained by our data, we reveal simple principles that underlie the small number of stereotyped responses of dusk circadian genes to changes in light. PMID:29239721

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;

Development of large-scale Birkeland currents determined from the Active Magnetosphere and Planetary Electrodynamics Response Experiment

DOE PAGES

Anderson, B. J.; Korth, H.; Waters, C. L.; ...

2014-05-07

The Active Magnetosphere and Planetary Electrodynamics Response Experiment uses magnetic field data from the Iridium constellation to derive the global Birkeland current distribution every 10 min. We examine cases in which the interplanetary magnetic field (IMF) rotated from northward to southward resulting in onsets of the Birkeland currents. Dayside Region 1/2 currents, totaling ~25% of the final current, appear within 20 min of the IMF southward turning and remain steady. In the onset of nightside currents occurs 40 to 70 min after the dayside currents appear. Afterwards, the currents intensify at dawn, dusk, and on the dayside, yielding a fullymore » formed Region 1/2 system ~30 min after the nightside onset. Our results imply that the dayside Birkeland currents are driven by magnetopause reconnection, and the remainder of the system forms as magnetospheric return flows start and progress sunward, ultimately closing the Dungey convection cycle.« less

Rise and fall: two sides of a coin of middle aged women's perceptions of reproductive: a qualitative study.

PubMed

Reyhani, Mitra; Kazemi, Ashraf; Keshvari, Mahrokh

2018-02-02

The present study was conducted to determine the perceptions of middle-aged women of reproductive changes. The present study was a qualitative research with a content analysis approach. The participants were 30 middle-aged women whose perceptions of reproductive changes had been collected on in-depth semi-structured interviews. The data were analyzed using the Graneheim and Lundman's inductive content analysis method. The main themes extracted from the data were a sense of "fall" and "the beginning of a new life cycle." A feeling of fall was formed from the subthemes "deterioration of youth," "the dusk of femininity," and "fade-out of the gender roles." The theme "beginning of a new life cycle" was formed from the subthemes of "acceptance," "sophistication," and "maturity." Middle-aged women had a wide range of emotions experienced from the reproductive changes ranging from a feeling of decline to that of excellence and rise.

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.

Steepening of Waves at the Duskside Magnetopause

NASA Technical Reports Server (NTRS)

Plaschke, F.; Kahr, N.; Fischer, D.; Nakamura, R.; Baumjohann, W.; Magnes, W.; Burch, J. L.; Torbert, R.; Russell, C. T.; Giles, B. L.;

The Substructure of a Flux Transfer Event Observed by the MMS Spacecraft

NASA Technical Reports Server (NTRS)

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.; Russel, C. T.;

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

DOE PAGES

Hao, Y. X.; Zong, Q. -G.; Zhou, X. -Z.; ...

2016-06-07

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 then concludemore » that the shock-induced electron dropout is not caused by the magnetopause shadowing. Furthermore, 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.« less

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.

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.

Penetration of the Interplanetary Magnetic Field B(sub y) into Earth's Plasma Sheet

NASA Technical Reports Server (NTRS)

Hau, L.-N.; Erickson, G. M.

1995-01-01

There has been considerable recent interest in the relationship between the cross-tail magnetic field component B(sub y) and tail dynamics. The purpose of this paper is to give an overall description of the penetration of the interplanetary magnetic field (IMF) B(sub y) into the near-Earth plasma sheet. We show that plasma sheet B(sub y) may be generated by the differential shear motion of field lines and enhanced by flux tube compression. The latter mechanism leads to a B(sub y) analogue of the pressure-balance inconsistency as flux tubes move from the far tail toward the Earth. The growth of B(sub y), however, may be limited by the dawn-dusk asymmetry in the shear velocity as a result of plasma sheet tilting. B(sub y) penetration into the plasma sheet implies field-aligned currents flowing between hemispheres. These currents together with the IMF B(sub y) related mantle field-aligned currents effectively shield the lobe from the IMF B(sub y).

Numerical solution of the geoelectrodynamic problem

NASA Technical Reports Server (NTRS)

Cain, Joseph C.

1990-01-01

The primary goal is to understand the sources of the near-Earth ambient magnetic field as observed by recent spacecraft surveys and surface variational magnetic observations so as to determine the electrical properties of the crust and upper mantle. Also included is the structure and changes on a short time scale of the core field which must be separated and identified. The Magsat data collection interval provides an opportunity to compare the vector field projections of ionospheric currents computed from surface data above the ionosphere as does the POGO data for scalar projections. The limitation of Magsat is its sun-synchronous orbit, which only sampled low latitudes at dawn and dusk, whereas POGO, though only making observations of the scalar field, sampled all local times. Magsat operated at a lower altitude than POGO (down to 350 km) whereas the orbits of the three POGO spacecraft ranged up to 1500 km and were never lower than about 400 km.

Saturn's ionosphere: Inferred electron densities

NASA Technical Reports Server (NTRS)

Kaiser, M. L.; Desch, M. D.; Connerney, J. E. P.

1983-01-01

During the two Voyager encounters with Saturn, radio bursts were detected which appear to have originated from atmospheric lightning storms. Although these bursts generally extended over frequencies from as low as 100 kHz to the upper detection limit of the instrument, 40 MHz, they often exhibited a sharp but variable low frequency cutoff below which bursts were not detected. We interpret the variable low-frequency extent of these bursts to be due to the reflection of the radio waves as they propagate through an ionosphere which varies with local time. We obtain estimates of electron densities at a variety of latitude and local time locations. These compare well with the dawn and dusk densitis measured by the Pioneer 11 Voyager Radio Science investigations, and with model predictions for dayside densities. However, we infer a two-order-of-magnitude diurnal variation of electron density, which had not been anticipated by theoretical models of Saturn's ionosphere, and an equally dramatic extinction of ionospheric electron density by Saturn's rings.

Larval fish collected from sound-scattering layers in an offshore tropical area.

PubMed

Castro, M S; Bonecker, A C T

2017-12-01

The composition of the larval fish assemblage in the sound-scattering layer of the continental shelf waters off the coast of south-eastern Brazil (12 and 22° S), a research project that is part of the Brazilian programme Avaliação do Potencial Sustentável de Recursos Vivos na Zona Econômica Exclusiva (REVIZEE), is described. Samples were collected during daylight hours and at dusk at five oceanographic stations in the winter of 1999 using an Isaacs-Kidd Midwater Trawl (IKMT). The oceanographic stations were chosen based on the detection of plankton layers by acoustic observation. A total of 2192 larval fish were identified, comprising 52 families and 62 species. Maurolicus stehmanni (Sternoptychidae) was the most abundant species found within the study area, comprising 18·5% of all identified larvae, followed by Psilotris celsus (Gobiidae) at 10·9%. © 2017 The Fisheries Society of the British Isles.

Autoreceptor Modulation of Peptide/Neurotransmitter Co-release from PDF Neurons Determines Allocation of Circadian Activity in Drosophila

PubMed Central

Choi, Charles; Cao, Guan; Tanenhaus, Anne K.; McCarthy, Ellena v.; Jung, Misun; Schleyer, William; Shang, Yuhua; Rosbash, Michael; Yin, Jerry C.P.; Nitabach, Michael N.

2012-01-01

Drosophila melanogaster flies concentrate behavioral activity around dawn and dusk. This organization of daily activity is controlled by central circadian clock neurons, including the lateral ventral pacemaker neurons (LNvs) that secrete the neuropeptide PDF (Pigment Dispersing Factor). Previous studies have demonstrated the requirement for PDF signaling to PDF receptor (PDFR)-expressing dorsal clock neurons in organizing circadian activity. While LNvs also express functional PDFR, the role of these autoreceptors has remained enigmatic. Here we show that (1) PDFR activation in LNvs shifts the balance of circadian activity from evening to morning, similar to behavioral responses to summer-like environmental conditions and (2) this shift is mediated by stimulation of the Ga,s-cAMP pathway and a consequent change in PDF/neurotransmitter co-release from the LNvs. These results suggest a novel mechanism for environmental control of the allocation of circadian activity and provide new general insight into the role of neuropeptide autoreceptors in behavioral control circuits. PMID:22938867

A Cold-Pole Enhancement in Mercury’s Sodium Exosphere

PubMed Central

Cassidy, Timothy A.; McClintock, William E.; Killen, Rosemary M.; Sarantos, Menelaos; Merkel, Aimee W.; Vervack, Ronald J.; Burger, Matthew H.

2018-01-01

The Ultraviolet and Visible Spectrometer (UVVS) component of the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) on the MESSENGER spacecraft characterized the local-time distribution of the sodium exosphere over the course of its orbital mission. The observations show that the sodium exosphere is enhanced above Mercury’s cold-pole longitudes. Based on previously published sodium exosphere models we infer that these regions act as nightside surface reservoirs, temporary sinks to the exosphere that collect sodium atoms transported anti-sunward. The reservoirs are revealed as exospheric enhancements when they are exposed to sunlight. As in the models the reservoir is depleted as the cold poles rotate from dawn to dusk, but unlike the models the depletion is only partial. The persistence of the reservoir means that it could, over the course of geologically long periods of time, contribute to an increase in the bulk concentration of sodium near the cold-pole longitudes. PMID:29720774

Ionospheric hot spot at high latitudes

NASA Technical Reports Server (NTRS)

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

1982-01-01

Schunk and Raitt (1980) and Sojka et al. (1981) have developed a model of the convecting high-latitude ionosphere in order to determine the extent to which various chemical and transport processes affect the ion composition and electron density at F-region altitudes. The numerical model produces time-dependent, three-dimensional ion density distributions for the ions NO(+), O2(+), N2(+), O(+), N(+), and He(+). Recently, the high-latitude ionospheric model has been improved by including thermal conduction and diffusion-thermal heat flow terms. Schunk and Sojka (1982) have studied the ion temperature variations in the daytime high-latitude F-region. In the present study, a time-dependent three-dimensional ion temperature distribution is obtained for the high-latitude ionosphere for an asymmetric convection electric field pattern with enhanced flow in the dusk sector of the polar region. It is shown that such a convection pattern produces a hot spot in the ion temperature distribution which coincides with the location of the strong convection cell.

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.

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.

A study of the electric field in an open magnetospheric model

NASA Technical Reports Server (NTRS)

Stern, D. P.

1972-01-01

The qualitative properties of an open magnetosphere and its electric field are examined and compared to a simple model of a dipole in a constant field and to actual observations. Many of these properties are found to depend on the separatrix, a curve connecting neutral points and separating different field-line regimes. In the simple model, the electric field in the central polar cap tends to point from dawn to dusk for a wide choice of external fields. Near the boundary of the polar cap electric equipotentials curve and become crescent-shaped, which may explain the correlation of polar magnetic variations with the azimuthal component of the interplanetary magnetic field, reported by Svalgaard. Modifications expected to occur in the actual magnetosphere are also investigated: in particular, it appears that bending of equipotentials may be reduced by cross-field flow during the merging of field lines and that open field lines connected to the polar caps emerge from a long and narrow slot extending along the tail.

Magnetospheric Multiscale Mission Observations and Non-Force Free Modeling of a Flux Transfer Event Immersed in a Super-Alfvenic Flow

NASA Technical Reports Server (NTRS)

Farrugia, C. J.; Lavraud, B.; Torbert, R. B.; Argall, M.; Kacem, I.; Yu, W.; Alm, L.; Burch, J.; Russell, C. T.; Shuster, J.;

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.

Photosynthetic physiology and biomass partitioning in the model diatom Phaeodactylum tricornutum grown in a sinusoidal light regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jallet, Denis; Caballero, Michael A.; Gallina, Alessandra A.

Photosynthetic microbes respond to changing light environments to balance photosynthetic process with light induced damage and photoinhibition. There have been very few characterizations of photosynthetic physiology or biomass partitioning during the day in mass culture. Understanding the constraints on photosynthetic efficiency and biomass accumulation are necessary for engineering superior strains or cultivation methods. We observed the photosynthetic physiology of nutrient replete Phaeodactylum tricornutum growing in light environments that mimic those found in rapidly mixing, outdoor, low biomass photobioreactors. We found little evidence for photoinhibition or non-photochemical quenching in situ, suggesting photosynthesis remains highly efficient throughout the day. Cells doubled theirmore » organic carbon from dawn to dusk and a small percentage – around 20% – of this carbon was allocated to carbohydrates or triacylglycerol. We thus conclude that the self-shading provided by dense culturing of P. tricornutum inhibits the induction of photodamage, and energy dissipation processes that would otherwise lower productivity in an outdoor photobioreactor.« less

Photosynthetic physiology and biomass partitioning in the model diatom Phaeodactylum tricornutum grown in a sinusoidal light regime

DOE PAGES

Jallet, Denis; Caballero, Michael A.; Gallina, Alessandra A.; ...

2016-06-11

Photosynthetic microbes respond to changing light environments to balance photosynthetic process with light induced damage and photoinhibition. There have been very few characterizations of photosynthetic physiology or biomass partitioning during the day in mass culture. Understanding the constraints on photosynthetic efficiency and biomass accumulation are necessary for engineering superior strains or cultivation methods. We observed the photosynthetic physiology of nutrient replete Phaeodactylum tricornutum growing in light environments that mimic those found in rapidly mixing, outdoor, low biomass photobioreactors. We found little evidence for photoinhibition or non-photochemical quenching in situ, suggesting photosynthesis remains highly efficient throughout the day. Cells doubled theirmore » organic carbon from dawn to dusk and a small percentage – around 20% – of this carbon was allocated to carbohydrates or triacylglycerol. We thus conclude that the self-shading provided by dense culturing of P. tricornutum inhibits the induction of photodamage, and energy dissipation processes that would otherwise lower productivity in an outdoor photobioreactor.« less

A Study of Transport in the Near-Earth Plasma Sheet During A Substorm Using Time-Dependent Large Scale Kinetics

NASA Technical Reports Server (NTRS)

El-Alaoui, M.; Ashour-Abdalla, M.; Raeder, J.; Frank, L. A.; Paterson, W. R.

1998-01-01

In this study we investigate the transport of H+ ions that made up the complex ion distribution function observed by the Geotail spacecraft at 0740 UT on November 24, 1996. This ion distribution function, observed by Geotail at approximately 20 R(sub E) downtail, was used to initialize a time-dependent large-scale kinetic (LSK) calculation of the trajectories of 75,000 ions forward in time. Time-dependent magnetic and electric fields were obtained from a global magnetohydrodynamic (MHD) simulation of the magnetosphere and its interaction with the solar wind and the interplanetary magnetic field (IMF) as observed during the interval of the observation of the distribution function. Our calculations indicate that the particles observed by Geotail were scattered across the equatorial plane by the multiple interactions with the current sheet and then convected sunward. They were energized by the dawn-dusk electric field during their transport from Geotail location and ultimately were lost at the ionospheric boundary or into the magnetopause.

Dawn Auroral Breakup at Saturn Initiated by Auroral Arcs: UVIS/Cassini Beginning of Grand Finale Phase

NASA Astrophysics Data System (ADS)

Radioti, A.; Grodent, D.; Yao, Z. H.; Gérard, J.-C.; Badman, S. V.; Pryor, W.; Bonfond, B.

2017-12-01

We present Cassini auroral observations obtained on 11 November 2016 with the Ultraviolet Imaging Spectrograph at the beginning of the F-ring orbits and the Grand Finale phase of the mission. The spacecraft made a close approach to Saturn's southern pole and offered a remarkable view of the dayside and nightside aurora. With this sequence we identify, for the first time, the presence of dusk/midnight arcs, which are azimuthally spread from high to low latitudes, suggesting that their source region extends from the outer to middle/inner magnetosphere. The observed arcs could be auroral manifestations of plasma flows propagating toward the planet from the magnetotail, similar to terrestrial "auroral streamers." During the sequence the dawn auroral region brightens and expands poleward. We suggest that the dawn auroral breakup results from a combination of plasma instability and global-scale magnetic field reconfiguration, which is initiated by plasma flows propagating toward the planet. Alternatively, the dawn auroral enhancement could be triggered by tail magnetic reconnection.

Analysis of HF interference with application to digital communications

NASA Astrophysics Data System (ADS)

Gott, G. F.; Dutta, S.; Doany, P.

1983-08-01

Recent observations of HF spectral occupancy and the design of devices to overcome the effects of interference on digital communications are reported. Spectral occupancy was determined at a resolution bandwidth of 100 Hz in 50-kHz bands, corresponding to the optimum working frequency over 1000 km, at noon, midnight, dawn, and dusk; and the data are analyzed in terms of congestion and voice-band availability. The implications for DPSK, frequency-exchange FSK, and frequency-diversity FSK data-transmission systems are discussed. The findings were used in the design of three improved diversity combiners (Dutta, 1977), which were tested over a 140-km range and found to reduce interference-related losses. Even better results are predicted for a sixth-order diversity modem with a sophisticated hopping scheme, now under development. Preliminary congestion spectra for the entire HF band, obtained with a calibrated active vertical antenna at noon and midnight of the summer and winter solstices in 1980, are presented.

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 J.; Lazarus, Allan J.

1993-01-01

On February 15, 1978, the orientation of the IMF remained steadily northward for more than 12 hours. Using plasma and magnetic field data from ISEE 1 and 2, IMP 8, and IMP 7, we show that (1) the magnetosheath flow speed on the flanks of the magnetotail steadily exceeded the solar wind speed by 20 percent, (2) surface waves of about 5-min period and very nonsinusoidal 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 earth radii. We propose that the acceleration of the magnetosheath flow is achieved by magnetic tension in the draped field configuration for northward IMP; 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 3D MHD simulation support this phenomenological model.

Large-Scale Structure of Subauroral Polarization Streams During the Main Phase of a Severe Geomagnetic Storm

NASA Astrophysics Data System (ADS)

He, Fei; Zhang, Xiao-Xin; Wang, Wenbin; Liu, Libo; Ren, Zhi-Peng; Yue, Xinan; Hu, Lianhuan; Wan, Weixing; Wang, Hui

2018-04-01

In this study, we present multisatellite observations of the large-scale structures of subauroral polarization streams (SAPS) during the main phase of a severe geomagnetic storm that occurred on 31 March 2001. Observations by the Defense Meteorological Satellite Program F12 to F15 satellites indicate that the SAPS were first generated around the dusk sector at the beginning of the main phase. The SAPS channel then expanded toward the midnight sector and moved to lower latitudes as the main phase progressed. The peak velocity, latitudinal width, latitudinal alignment, and longitudinal span of the SAPS channel were highly dynamic during the storm main phase. The large westward velocities of the SAPS were located in the region of low electron densities, associated with low ionospheric conductivity. The large-scale structures of the SAPS also corresponded closely to those of the region-2 field-aligned currents, which were mainly determined by the azimuthal pressure gradient of the ring current.

Night firing range performance following photorefractive keratectomy and laser in situ keratomileusis.

PubMed

Bower, Kraig S; Burka, Jenna M; Subramanian, Prem S; Stutzman, Richard D; Mines, Michael J; Rabin, Jeff C

2006-06-01

To investigate the effect of laser refractive surgery on night weapons firing. Firing range performance was measured at baseline and postoperatively following photorefractive keratectomy and laser in situ keratomileusis. Subjects fired the M-16A2 rifle with night vision goggles (NVG) at starlight, and with iron sight (simulated dusk). Scores, before and after surgery, were compared for both conditions. No subject was able to acquire the target using iron sight without correction before surgery. After surgery, the scores without correction (95.9 +/- 4.7) matched the preoperative scores with correction (94.3 +/- 4.0; p = 0.324). Uncorrected NVG scores after surgery (96.4 +/- 3.1) exceeded the corrected scores before surgery (91.4 +/- 10.2), but this trend was not statistically significant (p = 0.063). Night weapon firing with both the iron sight and the NVG sight improved after surgery. This study supports the operational benefits of refractive surgery in the military.

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.

ISEE-1 and 2 observations of field-aligned currents in the distant midnight magnetosphere

NASA Technical Reports Server (NTRS)

Elphic, R. C.; Kelly, T. J.; Russell, C. T.

1985-01-01

Magnetic field measurements obtained in the nightside magnetosphere by the co-orbiting ISEE-1 and 2 spacecraft have been examined for signatures of field-aligned currents (FAC). Such currents are found on the boundary of the plasma sheet both when the plasma sheet is expanding and when it is thinning. Evidence is often found for the existence of waves on the plasma sheet boundary, leading to multiple crossings of the FAC sheet. At times the boundary layer FAC sheet orientation is nearly parallel to the X-Z GSM plane, suggesting 'protrusions' of plasma sheet into the lobes. The boundary layer current polarity is, as expected, into the ionosphere in the midnight to dawn local time sector, and outward near dusk. Current sheet thicknesses and velocities are essentially independent of plasma sheet expansion or thinning, having typical values of 1500 km and 20-40 km/s respectively. Characteristic boundary layer current densities are about 10 nanoamps per square meter.

Statistical results from 10 years of Cassini Langmuir probe plasma measurements

NASA Astrophysics Data System (ADS)

Holmberg, M.; Shebanits, O.; Wahlund, J. E.; Morooka, M.; Andre, N.

2016-12-01

We use a new analysis method to obtain 10 years of Cassini RPWS Langmuir probe (LP) measurements to study the structure and dynamics of the inner plasma disk of Saturn. The LP plasma density measurements show good agreement with electron densities derived from the RPWS electric field power spectra and confirms and/or improves a number of previous findings about the structure of the plasma disk. E.g., the Enceladus plume is detected as a localised density maximum at the orbit of Enceladus, but the peak density of the inner plasma disk, excluding Enceladus plume passages, is located closer to 4.7 Rs. No density peaks are recorded at the orbits of the moons Mimas, Tethys, Dione, and Rhea. We confirm the previously detected plasma density dayside/nightside asymmetry, which is likely due to a particle drift in the dusk to dawn direction. Presented is also the LP result on the seasonal dependence of the plasma disk within Enceladus' orbit.

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.

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

Rax: Developmental and Daily Expression Patterns in the Rat Pineal Gland and Retina

PubMed Central

Rohde, Kristian; Klein, David C.; Møller, Morten; Rath, Martin F.

2011-01-01

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 (E) 18, whereas Rax expression in the pineal is relatively delayed and not detectable until E20. 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. PMID:21749377

The time variation of atomic oxygen emission around Io during a volcanic event observed with Hisaki/EXCEED

NASA Astrophysics Data System (ADS)

Koga, Ryoichi; Tsuchiya, Fuminori; Kagitani, Masato; Sakanoi, Takeshi; Yoneda, Mizuki; Yoshioka, Kazuo; Kimura, Tomoki; Murakami, Go; Yamazaki, Atsushi; Yoshikawa, Ichiro; Smith, H. Todd

2018-01-01

Io has an atmosphere produced by volcanism and sublimation of frosts deposited around active volcanoes. However, the time variation of atomic oxygen escaping Io's atmosphere is not well known. In this paper, we show a significant increase in atomic oxygen around Io during a volcanic event. Brightening of Io's extended sodium nebula was observed in the spring of 2015. We used the Hisaki satellite to investigate the time variation of atomic oxygen emission around Io during the same period. This investigation reveals that the duration of atomic oxygen brightness increases from a volcanically quiet level to a maximum level during the same approximate time period of 30 days as the observed sodium brightness. On the other hand, the recovery of the atomic oxygen brightness from the maximum to the quiet level (60 days) was longer than that of the sodium nebula decreasing (40 days). Additionally, a dawn-dusk asymmetry of the atomic oxygen emission is observed.

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.

Particle Fluxes Over a Ponderosa Pine Plantation

NASA Astrophysics Data System (ADS)

Baker, B.; Goldstein, A.

2006-12-01

Atmospheric aerosols can affect visibility, climate, and health. Particle fluxes were measured continuously over a 15 year-old ponderosa pine plantation in the foothills of the Sierra Nevada from mid July to the end of September in the year 2005. Air at this field site is affected by both biogenic emissions from the dense forests of the surrounding area and by urban pollution transported from the Sacramento valley. It is believed that fluxes of very reactive hydrocarbons from plants to the atmosphere have an impact on the production and growth of atmospheric particles at this site. Two condensation particle counters (CPCs) were located near the top of a 12 m measurement tower, several meters above the top of the tree canopy. Particle count data was collected at 10 Hz and particle fluxes were determined using the eddy covariance method. A set of diffusion screens was added to the inlet of one of the CPCs such that the lower particle size limit for detection was increased to a diameter of approximately 40 nm. The other CPC counted particles with minimum diameters of 3 nm. Particle concentrations showed a distinct diurnal pattern with minimum daily average concentrations of 2000 particles cm-3 occurring at dawn, and average daily maximum concentrations of 5700 particles cm-3 occurring at dusk. The evening increase of particle number corresponded to the arrival of polluted air from the Sacramento region. During the day, deposition of particles to the forest canopy (daytime average of 5.8x106 particles m-2 s-1 was generally observed. Concentrations and fluxes of particles under 40 nm could be examined by subtracting the data of one CPC from the other. On average, the fraction of particles under 40 nm increased from less than 20% at dawn to more than 50% at dusk; indicating that air coming from the Sacramento region was enriched in smaller, newly formed aerosol. Daily average deposition fluxes of particles under 40 nm were 1.0x107 particles m-2 s-1. Much of this flux was

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

The Topology and Properties of Mercury's Tail Current Sheet

NASA Astrophysics Data System (ADS)

Al Asad, M.; Johnson, C.; Philpott, L. C.

2017-12-01

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft orbited Mercury from March 2011 until April 2015, measuring the vector magnetic field inside and outside the magnetosphere. MESSENGER repeatedly encountered the tail current sheet (TCS) on the nightside of the planet. We examined 1s magnetic field data within 20 minutes of the magnetic equator position on 2435 orbit to characterize the shape and properties of Mercury's TCS and investigate its response to solar wind conditions. Identification of the TCS from vector magnetic field data used the following criteria: (1) a rapid rotation in the field direction from anti-sunward in the southern tail lobe to sunward in the northern lobe, accompanied by (2) a decrease in the field magnitude and (3) an increase in field variability. The current sheet was encountered on 606 orbits allowing the probability of encountering the tail current sheet in the equatorial plane to be mapped. Orbits on which the TCS was identified were binned spatially and superposed epoch analysis used to determine the field magnitude at the edge of the TCS, from which its time-averaged 3D shape was extracted. The TCS has an inner edge at 1.5 RM downtail in the midnight plane with a thickness of 0.34 RM, extends to the observation limit of 2.8 RM, decreasing in thickness to 0.28 RM. The thickness of the TCS increases in the dawn/dusk directions to 0.7 RM at 1.8 RM downtail and ± 1.5 RM from the noon-midnight plane and it warps towards the planet in the dawn/dusk directions. No strong correlations were found between the time-averaged shape and position of the TCS and solar wind conditions such as the solar wind ram pressure and the magnetic disturbance index, nor with parameters that control these conditions such as heliocentric distance. However, it is likely that the TCS does respond to these conditions on time scales too short to be characterized with MESSENGER data. In addition to mapping the shape of the

Graded-Index Optics are Matched to Optical Geometry in the Superposition Eyes of Scarab Beetles

NASA Astrophysics Data System (ADS)

McIntyre, P.; Caveney, S.

1985-11-01

range. Differences in the eye design are related to when the beetles fly at dusk. Flight experiments comparing two of the species show that the species with the higher value for M and corresponding lower sensitivity, initiates and terminates its flight earlier in the dusk than the other species with 2.8 times the sensitivity.

Observations of the Early Evening Boundary-Layer Transition Using a Small Unmanned Aerial System

NASA Astrophysics Data System (ADS)

Bonin, Timothy; Chilson, Phillip; Zielke, Brett; Fedorovich, Evgeni

2013-01-01

The evolution of the lower portion of the planetary boundary layer is investigated using the Small Multifunction Research and Teaching Sonde (SMARTSonde), an unmanned aerial vehicle developed at the University of Oklahoma. The study focuses on the lowest 200 m of the atmosphere, where the most noticeable thermodynamic changes occur during the day. Between October 2010 and February 2011, a series of flights was conducted during the evening hours on several days to examine the vertical structure of the lower boundary layer. Data from a nearby Oklahoma Mesonet tower was used to supplement the vertical profiles of temperature, humidity, and pressure, which were collected approximately every 30 min, starting 2 h before sunset and continuing until dusk. From the profiles, sensible and latent heat fluxes were estimated. These fluxes were used to diagnose the portion of the boundary layer that was most affected by the early evening transition. During the transition period, a shallow cool and moist layer near the ground was formed, and as the evening progressed the cooling affected an increasingly shallower layer just above the surface.

2001 Mars Odyssey THEMIS: Thermophysics at a New Local Time

NASA Astrophysics Data System (ADS)

Hamilton, V. E.; Christensen, P. R.

2017-12-01

During its sixth extended mission, the 2001 Mars Odyssey transitioned to a new, rarely-seen, post-sunset (morning daylight) local time designed to reduce stress on the spacecraft. Since then, Thermal Emission Imaging System (THEMIS) observations have provided an unprecedented opportunity to investigate dynamic phenomena in the atmosphere and on the surface. In this new local time ( 6:45 am/pm) orbit, Odyssey's camera is acquiring expanded diurnal thermal imaging coverage, providing insight into surface texture, layering, and ice content, as well as dynamic, temperature-dependent surface, atmospheric, and polar processes. New THEMIS observations at dawn and dusk local times are filling major gaps in current knowledge about the diurnal variation of clouds, hazes and surface frost. In this presentation, we will highlight some of these data and discuss the unique scientific results that can be obtained from Mars Odyssey THEMIS observations, including: insights into potential past and present habitability of Mars, the processes and history of climate, the nature and evolution of geologic processes, and aspects of the environment relevant to future human exploration.

Twilight helium 10,830-A calculations and observations. [in upper atmosphere

NASA Technical Reports Server (NTRS)

Tinsley, B. A.; Christensen, A. B.

1976-01-01

The 10,830-A column emission rates from metastable He(2 3S) atoms in the upper atmosphere are calculated and compared with other calculations and observations. It is shown that the calculated emission rates agree well with the observed emission rates provided that the cross sections for loss of He(2 3S) by Penning ionization on atomic oxygen is near 5 A 2 and not 44 A 2 as previously measured. It is assumed that the local and conjugate photoelectron fluxes above 300 km are about double those calculated. The dawn/dusk intensity ratio observed in New Mexico, Brazil and Peru is accounted for by changes in the ambient thermal electron concentration in Brazil and Peru and by changes in plasmasphere opacity to conjugate point electrons for New Mexico and to some extent for Brazil. The rate at which He-4 would escape from the earth if sufficient energy were imparted to the He-4 atoms during the Penning reaction was recalculated and found to be inadequate by an order of magnitude to balance the terrestrial production.

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.

Saturn's ionosphere - Inferred electron densities

NASA Technical Reports Server (NTRS)

Kaiser, M. L.; Desch, M. D.; Connerney, J. E. P.

1984-01-01

During the two Voyager encounters with Saturn, radio bursts were detected which appear to have originated from atmospheric lightning storms. Although these bursts generally extended over frequencies from as low as 100 kHz to the upper detection limit of the instrument, 40 MHz, they often exhibited a sharp but variable low frequency cutoff below which bursts were not detected. We interpret the variable low-frequency extent of these bursts to be due to the reflection of the radio waves as they propagate through an ionosphere which varies with local time. We obtain estimates of electron densities at a variety of latitude and local time locations. These compare well with the dawn and dusk densities measured by the Pioneer 11 Voyager Radio Science investigations, and with model predictions for dayside densities. However, we infer a two-order-of-magnitude diurnal variation of electron density, which had not been anticipated by theoretical models of Saturn's ionosphere, and an equally dramatic extinction of ionospheric electron density by Saturn's rings. Previously announced in STAR as N84-17102

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

Autoreceptor control of peptide/neurotransmitter corelease from PDF neurons determines allocation of circadian activity in drosophila.

PubMed

Choi, Charles; Cao, Guan; Tanenhaus, Anne K; McCarthy, Ellena V; Jung, Misun; Schleyer, William; Shang, Yuhua; Rosbash, Michael; Yin, Jerry C P; Nitabach, Michael N

2012-08-30

Drosophila melanogaster flies concentrate behavioral activity around dawn and dusk. This organization of daily activity is controlled by central circadian clock neurons, including the lateral-ventral pacemaker neurons (LN(v)s) that secrete the neuropeptide PDF (pigment dispersing factor). Previous studies have demonstrated the requirement for PDF signaling to PDF receptor (PDFR)-expressing dorsal clock neurons in organizing circadian activity. Although LN(v)s also express functional PDFR, the role of these autoreceptors has remained enigmatic. Here, we show that (1) PDFR activation in LN(v)s shifts the balance of circadian activity from evening to morning, similar to behavioral responses to summer-like environmental conditions, and (2) this shift is mediated by stimulation of the Gα,s-cAMP pathway and a consequent change in PDF/neurotransmitter corelease from the LN(v)s. These results suggest another mechanism for environmental control of the allocation of circadian activity and provide new general insight into the role of neuropeptide autoreceptors in behavioral control circuits. Copyright © 2012 The Authors. Published by Elsevier Inc. All rights reserved.

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.

Modeling Magnetotail Ion Distributions with Global Magnetohydrodynamic and Ion Trajectory Calculations

NASA Technical Reports Server (NTRS)

El-Alaoui, M.; Ashour-Abdalla, M.; Raeder, J.; Peroomian, V.; Frank, L. A.; Paterson, W. R.; Bosqued, J. M.

1998-01-01

On February 9, 1995, the Comprehensive Plasma Instrumentation (CPI) on the Geotail spacecraft observed a complex, structured ion distribution function near the magnetotail midplane at x approximately -30 R(sub E). On this same day the Wind spacecraft observed a quiet solar wind and an interplanetary magnetic field (IMF) that was northward for more than five hours, and an IMF B(sub y) component with a magnitude comparable to that of the RAF B(sub z) component. In this study, we determined the sources of the ions in this distribution function by following approximately 90,000 ion trajectories backward in time, using the time-dependent electric and magnetic fields obtained from a global MHD simulation. The Wind observations were used as input for the MHD model. The ion distribution function observed by Geotail at 1347 UT was found to consist primarily of particles from the dawn side low latitude boundary layer (LLBL) and from the dusk side LLBL; fewer than 2% of the particles originated in the ionosphere.

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.

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.

Comment on 'Observations of reconnection of interplanetary and lobe magnetic field lines at the high-latitude magnetopause' by J.T. Gosling, M.F. Thomsen, S.J. Bame, R.C. Elphic, and C.T. Russell

NASA Technical Reports Server (NTRS)

Belen'kaia, Elena

1993-01-01

Comment is presented on the results of measurements, reported by Gosling et al. (1991), that were made on ISEE in the vicinity of the high-latitude dusk magnetopause near the terminator plane, at a time when the local magnetosheath and tail lobe magnetic fields were nearly oppositely directed. The character of the observed plasma flowing both tailward and sunward within the high-latitude magnetopause current layer presented real evidence for the local reconnection process. Gosling et al. argued that this process may be a manifestation of different global magnetospheric topology structures. In the comment, a global magnetospheric convection pattern is constructed for the northward IMF and for the case of a large azimuthal component of the IMF with small Bz, irrespective of its sign. The suggested scheme provides a simple explanation for the observed sunward convection in the polar caps both for the northward and for strong By with small Bz. According to the present model, for the magnetosheath field at 2300 UT on June 11, 1978, the reconnection between the open field lines appears at the northern neutral point.

Dynamics Explorer measurements of particles, fields, and plasma drifts over a horse-collar auroral pattern

NASA Technical Reports Server (NTRS)

Sharber, J. R.; Hones, E. W., Jr.; Heelis, R. A.; Craven, J. D.; Frank, L. A.; Maynard, N. C.; Slavin, J. A.; Birn, J.

1992-01-01

As shown from ground-based measurements and satellite-borne imagers, one type of global auroral pattern characteristic of quiet (usually northward IMF) intervals is that of a contracted but thickened emission region in which the dawn and dusk portions can spread poleward to very high latitudes, (the type of a pattern referred to as a 'horse-collar' aurora by Hones et al., 1989). In this report we use a DE data set to examine a case in which this horse-collar pattern was observed by the DE-1 auroral imager while at the same time the DE-2, at lower altitude, measured precipitating particles, electric and magnetic fields, and plasma drifts. There is close agreement between the optical signatures and the particle precipitation patterns. The particle, plasma, and field measurements made along the satellite track and the 2-D perspective of the imager provide a means of determining the configuration of convective flows in the high-latitude ionosphere during this interval of northward IMF. Recent mapping studies are used to relate the low-altitude observations to possible magnetospheric source regions.

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. © 2011 The Authors. Journal of Neurochemistry © 2011 International Society for Neurochemistry.

Diel resource partitioning among juvenile Atlantic Salmon, Brown Trout, and Rainbow Trout during summer

USGS Publications Warehouse

Johnson, James H.; McKenna, James E.

2015-01-01

Interspecific partitioning of food and habitat resources has been widely studied in stream salmonids. Most studies have examined resource partitioning between two native species or between a native species and one that has been introduced. In this study we examine the diel feeding ecology and habitat use of three species of juvenile salmonids (i.e., Atlantic Salmon Salmo salar, Brown Trout Salmo trutta, and Rainbow Trout Oncorhynchus mykiss) in a tributary of Skaneateles Lake, New York. Subyearling Brown Trout and Rainbow Trout fed more heavily from the drift than the benthos, whereas subyearling Atlantic Salmon fed more from the benthos than either species of trout. Feeding activity of Atlantic Salmon and Rainbow Trout was similar, with both species increasing feeding at dusk, whereas Brown Trout had no discernable feeding peak or trough. Habitat availability was important in determining site-specific habitat use by juvenile salmonids. Habitat selection was greater during the day than at night. The intrastream, diel, intraspecific, and interspecific variation we observed in salmonid habitat use in Grout Brook illustrates the difficulty of acquiring habitat use information for widespread management applications.

The ionization cone, obscured nucleus, and gaseous outflow in NGC 3281 - A prototypical Seyfert 2 galaxy?

NASA Technical Reports Server (NTRS)

Storchi-Bergmann, Thaisa; Wilson, Andrew S.; Baldwin, Jack A.

1992-01-01

Narrow-band images and long-slit spectroscopy of the central region of the highly inclined Seyfert galaxy NGC 3281 are presented. The image of the continuum-subtracted forbidden 4959 emission line shows a very clear conical morphology for the high-excitation gas. A possible similar structure can also be seen on the other side of the nucleus, but is dimmed by patchy obscuration in the dusk. The continuum images and long-slit spectroscopy are used to derive and map the extinction in the inner regions of NGC 3281; heavy obscuration is found along the present line of sight to the apex of the cone, suggesting that the true nucleus is located at the apex and is obscured. Low-resolution long-slit spectra are used to study the stellar population, which is found to be old, uniform within 2.5 kpc of the nucleus, and typical of the bulges of early-type galaxies. It is suggested that NGC3281 may be another example of a 'hidden' Seyfert 1, even though there is no direct evidence for a broad-line region in this particular galaxy.

Penetration electric fields: A Volland Stern approach

NASA Astrophysics Data System (ADS)

Burke, William J.

2007-07-01

This paper reformulates the Volland Stern model, separating contributions from corotation and convection to predict electric field penetration of the inner magnetosphere using data from the Advanced Composition Explorer (ACE) satellite. In the absence of shielding, the model electric field is EVS=ΦPC/2LYRE, where ΦPC is the polar cap potential and 2LYRE is the width of the magnetosphere along the dawn dusk meridian. ΦPC is estimated from the interplanetary electric field (IEF) and the dynamic pressure of the solar wind (PSW); values of LY were approximated using PSW and simple force-balance considerations. ACE measurements on 16 17 April 2002 were then used to calculate EVS for comparison with the eastward electric field component (EJφ) detected by the incoherent scatter radar at Jicamarca, Peru. While the interplanetary magnetic field (IMF) was southward, the model predicted observed ratios of EVS/IEF. During intervals of northward IMF, EJφ turned westward suggesting that a northward IMF BZ system of field-aligned currents affected the electrodynamics of the dayside ionosphere on rapid time scales.

Competitive interactions between walleye (Sander vitreus) and smallmouth bass (Micropterus dolomieu) under various controlled conditions

USGS Publications Warehouse

Wuellner, M.R.; Graeb, B.D.S.; Willis, D.W.; Galster, B.J.; Selch, T.M.; Chipps, S.R.

2011-01-01

The range of smallmouth bass (Micropterus dolomieu) is expanding northward, creating new interactions with native predators, including walleye (Sander vitreus). We used a series of experiments to investigate competition between walleye (WAE) and smallmouth bass (SMB) at different life stages and light conditions, identified behaviors that allowed one fish to outcompete another, and evaluated whether prey switching mitigated competitive interactions. Juvenile and adult SMB appeared to outcompete WAE when fed during the daytime; neither species dominated when fed near dusk. Attack rates and capture efficiencies of both species were similar with an intra- or interspecific competitor, but SMB often exploited prey before the competitor had a chance to feed (exploitative competition) or displayed agonistic behaviors toward a potential competitor (interference competition). Prey selectivity of WAE or SMB did not differ when by themselves or with a potential competitor. These results indicate that SMB could outcompete WAE under limiting prey conditions due to the aggressive nature of SMB, but resources may be partitioned at least along a temporal scale. ?? 2011 Taylor & Francis.

Field-aligned currents, convection electric fields, and ULF-ELF waves in the cusp

NASA Technical Reports Server (NTRS)

Saflekos, N. A.; Potemra, T. A.; Kintner, P. M., Jr.; Green, J. L.

1979-01-01

Nearly simultaneous observations from the Triad and Hawkeye satellites over the Southern Hemisphere, at low altitudes near the noon meridian and close to the usual polar cusp latitudes, show that in and near the polar cusp there exist several relationships between field-aligned currents (FACs), convection electric fields, ULF-ELF magnetic noise, broadband electrostatic noise and interplanetary magnetic fields. The most important findings are (1) the FACs directed into the ionosphere in the noon-to-dusk local time sector and directed away from the ionosphere in the noon-to-dawn local time sector and identified as region-1 permanent FACs (Iijima and Potemra, 1976a) and are located equatorward of the regions of antisunward (westward) convection; (2) the observations are consistent with a two-cell convection pattern symmetric in one case (throat positioned at noon) and asymmetric in another (throat located in a sector on the forenoon side in juxtaposition to the region of strong convection on the afternoon side); and (3) fine-structure FACs are responsible for the generation of ULF-ELF noise in the polar cusp.

Insect abundance over Chinese rice fields in relation to environmental parameters, studied with a polarization-sensitive CW near-IR lidar system

NASA Astrophysics Data System (ADS)

Zhu, Shiming; Malmqvist, Elin; Li, Wansha; Jansson, Samuel; Li, Yiyun; Duan, Zheng; Svanberg, Katarina; Feng, Hongqiang; Song, Ziwei; Zhao, Guangyu; Brydegaard, Mikkel; Svanberg, Sune

2017-07-01

Effective monitoring of flying insects is of major societal importance in view of the role of insects as indispensable pollinators, destructive disease vectors and economically devastating agricultural pests. The present paper reports on monitoring of flying agricultural pests using a continuous-wave lidar system in a rice-field location in Southern China. Using a Scheimpflug arrangement, range resolution over several 100 m long observational paths was achieved. The system operates with two perpendicularly polarized near-infrared lasers, which are activated intermittently, and back-scattered radiation from insects was recorded by a linear array detector placed after a linear polarizer. Our polarization sensitive system was used to monitor the flying insect diurnal activity and also the influence of changes in weather conditions, e.g., the occurrence of rain. Activity strongly peaked at dusk and rose again, although to a lower extent, just before dawn. At the onset of rainfall, a strong increase in insect counts occurred which was interpreted as the rain-induced bringing down of high-altitude migrant insects.

Investigation of low energy space plasma

NASA Technical Reports Server (NTRS)

Comfort, R. H.; Horwitz, J. L.

1986-01-01

A statistical study of 1982 data for occurrences of equatorially trapped plasma has been extended. The previous survey, which utilized only the MSFC summary fiche, has been supplemented with the GSFC summary fiche, which has had the effect of substantially improving the late 1982 coverage. It was found that in the post midnight region (1 - 3 LT), the trapped plasma is limited to + or - 5 degrees magnetic latitude, while in the early afternoon (13-15 LT), latitude ranges as high as + or 30 degrees are found. This survey has provided a link to earlier ATS-6 and ISEE studies of pancake distributions. Although the most energetic, and most anisotopic plasmas are trapped within a few degrees of the equator, the results of these equatorial interactions extend substantially along the magnetic field line in the afternoon and dusk region and these high latitude extensions were previously studied by the Huntsville group. Results of this study were incorporated into a revision of the equatorial ion paper, which has been resubmitted and accepted for publication.

On the average configuration of the geomagnetic tail

NASA Technical Reports Server (NTRS)

Fairfield, D. H.

1978-01-01

Over 3000 hours of IMP-6 magnetic field data obtained between 20 and 33 R sub E in the geomagnetic tail have been used in a statistical study of the tail configuration. A distribution of 2.5 minute averages of B sub Z as a function of position across the tail reveals that more flux crosses the equatorial plane near the dawn and dusk flanks than near midnight. The tail field projected in the solar magnetospheric equatorial plane deviates from the X axis due to flaring and solar wind aberration by an angle alpha = -0.9 y sub SM - 1.7 where Y sub SM is in earth radii and alpha is in degrees. After removing these effects the Y component of the tail field is found to depend on interplanetary sector structure. During an away sector the B sub Y component of the tail field is on average 0.5 gamma greater than that during a toward sector, a result that is true in both tail lobes and is independent of location across the tail.

Fear of darkness, the full moon and the nocturnal ecology of African lions.

PubMed

Packer, Craig; Swanson, Alexandra; Ikanda, Dennis; Kushnir, Hadas

2011-01-01

Nocturnal carnivores are widely believed to have played an important role in human evolution, driving the need for night-time shelter, the control of fire and our innate fear of darkness. However, no empirical data are available on the effects of darkness on the risks of predation in humans. We performed an extensive analysis of predatory behavior across the lunar cycle on the largest dataset of lion attacks ever assembled and found that African lions are as sensitive to moonlight when hunting humans as when hunting herbivores and that lions are most dangerous to humans when the moon is faint or below the horizon. At night, people are most active between dusk and 10:00 pm, thus most lion attacks occur in the first weeks following the full moon (when the moon rises at least an hour after sunset). Consequently, the full moon is a reliable indicator of impending danger, perhaps helping to explain why the full moon has been the subject of so many myths and misconceptions.

Is motivation important to brook trout passage through culverts?

USGS Publications Warehouse

Goerig, Elsa; Castro-Santos, Theodore R.

2017-01-01

Culverts can restrict movement of stream-dwelling fish. Motivation to enter and ascend these structures is an essential precursor for successful passage. However, motivation is challenging to quantify. Here, we use attempt rate to assess motivation of 447 brook trout (Salvelinus fontinalis) entering three culverts under a range of hydraulic, environmental, and biological conditions. A passive integrated transponder system allowed for the identification of passage attempts and success of individual fish. Attempt rate was quantified using time-to-event analysis allowing for time-varying covariates and recurrent events. Attempt rate was greatest during the spawning period, at elevated discharge, at dusk, and for longer fish. It decreased during the day and with increasing number of conspecifics downstream of the culvert. Results also show a positive correlation between elevated motivation and successful passage. This study enhances understanding of factors influencing brook trout motivation to ascend culverts and shows that attempt rate is a dynamic phenomenon, variable over time and among individuals. It also presents methods that could be used to investigate other species’ motivation to pass natural or anthropogenic barriers.

MHD simulation of the shock wave event on October 24, 2003

NASA Astrophysics Data System (ADS)

Ogino, T.; Kajiwara, Y.; Nakao, M.; Park, K. S.; Fukazawa, K.; Yi, Y.

2007-11-01

A three-dimensional global MHD simulation of the interaction between the solar wind and the Earth's magnetosphere has been executed to study the shock wave event on space weather problem on October 24, 2003, when an abnormal operation happened in a satellite for Environment Observation Technology, ADEOS-II (Midori-II). Characteristic features of the event are the long duration of southward IMF, arrival of a strong shock wave, then large variation of IMF By from negative to positive for about 15 min duration. In the simulation, the shock wave compresses the magnetosphere for southward IMF and a hot plasma was injected around the geosynchronous orbit from plasma sheet. During the interval when IMF By changes from negative to positive, the magnitude of IMF extremely decreases to bring attenuation of magnetic reconnection. The open-closed boundary shrinks in the polar cap and the transient expansion of the magnetic field lines occurs to imply enhancement of particle precipitation. The reconnection site moves from dawn to dusk in the dayside magnetopause and a narrow cockscomb closed field region is formed in the high latitude tail.

Quasi-periodic 1-hour pulsations in the Saturn's outer magnetosphere

NASA Astrophysics Data System (ADS)

Rusaitis, L.; Khurana, K. K.; Walker, R. J.; Kivelson, M.

2017-12-01

Pulsations in the Saturn's magnetic field and particle fluxes of approximately 1-hour periodicity have been frequently detected in the outer Saturnian magnetosphere by the Cassini spacecraft since 2004. These particle and magnetic field enhancements have been typically observed more often in the dusk sector of the planet, and mid to high latitudes. We investigate nearly 200 of these events as detected by the magnetometer and the Cassini Low-Energy Magnetospheric Measurement System detector (LEMMS) data during the 2004-2015 time frame to characterize these pulsations and suggest their origin. The mechanism needed to produce these observed enhancements needs to permit the acceleration of the energetic electrons to a few MeV and a variable periodicity of enhancements from 40 to 90 minutes. We examine the relation of the oscillations to the periodic power modulations in Saturn kilometric radiation (SKR), using the SKR phase model of Kurth et al. [2007] and Provan et al. [2011]. Finally, we show that similar pulsations can also be observed at 2.5-D MHD simulations of Saturn's magnetosphere.

Uplift of Ionospheric Oxygen Ions During Extreme Magnetic Storms

NASA Technical Reports Server (NTRS)

Tsurutani, Bruce T.; Mannucci, Anthony J.; Verkhoglyadova, Olga P.; Huba, Joseph; Lakhina, Gurbax S.

2013-01-01

Research reported earlier in literature was conducted relating to estimation of the ionospheric electrical field, which may have occurred during the September 1859 Carrington geomagnetic storm event, with regard to modern-day consequences. In this research, the NRL SAMI2 ionospheric code has been modified and applied the estimated electric field to the dayside ionosphere. The modeling was done at 15-minute time increments to track the general ionospheric changes. Although it has been known that magnetospheric electric fields get down into the ionosphere, it has been only in the last ten years that scientists have discovered that intense magnetic storm electric fields do also. On the dayside, these dawn-to-dusk directed electric fields lift the plasma (electrons and ions) up to higher altitudes and latitudes. As plasma is removed from lower altitudes, solar UV creates new plasma, so the total plasma in the ionosphere is increased several-fold. Thus, this complex process creates super-dense plasmas at high altitudes (from 700 to 1,000 km and higher).

A statistical study of the THEMIS satellite data for plasma sheet electrons carrying auroral upward field-aligned currents

NASA Astrophysics Data System (ADS)

Lee, S.; Shiokawa, K.; McFadden, J. P.

2010-12-01

-aligned potential difference, particularly during active time (AE > 100 nT). On the other hand, in the dusk side outer magnetosphere (source of the region 1), electron density and temperature are small, thus the thermal current is much smaller than the typical auroral current suggested by Iijima and Potemra (JGR, 1976). From this result, we suppose that electron acceleration is necessary on the dusk side region 1 upward field-aligned current. Our preliminary result, however, does not consider contamination of the radiation belt particles into the ESA data that is apparent inside 9 Re. In the presentation, we show the results with removal of the radiation belt particle contamination.

Local time variations of high-energy plasmaspheric ion pitch angle distributions

DOE PAGES

Sarno-Smith, Lois K.; Liemohn, Michael W.; Skoug, Ruth M.; ...

2016-07-01

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

Optical observations on the CRIT-II Critical Ionization Velocity Experiment

NASA Technical Reports Server (NTRS)

Stenbaek-Nielsen, H. C.; Wescott, E. M.; Haerendel, G.; Valenzuela, A.

1990-01-01

A rocket borne Critical Ionization Velocity (CIV0 experiment was carried out from Wallops Island at dusk on May 4, 1989. Two barium shaped charges were released below the solar terminator (to prevent photoionization) at altitudes near 400 km. The ambient ionospheric electron density was 50,000/cu cm. The neutral barium jet was directed upward and at an angle of nominally 45 degrees to B which gives approximately 3 x 10 to the 23rd neutrals with super critical velocity. Ions created by a CIV process in the region of the neutral jet would travel up along B into sunlight where they can be detected optically. Well defined ion clouds (max. brightness 750 R) were observed in both releases. An ionization rate of 0.8 percent/sec (125 sec ionization time constant) can account for the observed ion cloud near the release field line, but the ionization rate falls off with increasing distance from the release. It is concluded that a CIV process was present in the neutral jet out to about 50 km from the release, which is significantly further than allowed by current theories.

Ring Current Dynamics in Moderate and Strong Storms: Comparative Analysis of TWINS and IMAGE/HENA Data with the Comprehensive Ring Current Model

NASA Technical Reports Server (NTRS)

Buzulukova, N.; Fok, M.-C.; Goldstein, J.; Valek, P.; McComas, D. J.; Brandt, P. C.

2010-01-01

We present a comparative study of ring current dynamics during strong and moderate storms. The ring current during the strong storm is studied with IMAGE/HENA data near the solar cycle maximum in 2000. The ring current during the moderate storm is studied using energetic neutral atom (ENA) data from the Two Wide-Angle Imaging Neutral- Atom Spectrometers (TWINS) mission during the solar minimum in 2008. For both storms, the local time distributions of ENA emissions show signatures of postmidnight enhancement (PME) during the main phases. To model the ring current and ENA emissions, we use the Comprehensive Ring Current Model (CRCM). CRCM results show that the main-phase ring current pressure peaks in the premidnight-dusk sector, while the most intense CRCM-simulated ENA emissions show PME signatures. We analyze two factors to explain this difference: the dependence of charge-exchange cross section on energy and pitch angle distributions of ring current. We find that the IMF By effect (twisting of the convection pattern due to By) is not needed to form the PME. Additionally, the PME is more pronounced for the strong storm, although relative shielding and hence electric field skewing is well developed for both events.

A statistical study of EMIC waves observed by Cluster: 2. Associated plasma conditions

NASA Astrophysics Data System (ADS)

Allen, R. C.; Zhang, J.-C.; Kistler, L. M.; Spence, H. E.; Lin, R.-L.; Klecker, B.; Dunlop, M. W.; André, M.; Jordanova, V. K.

2016-07-01

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. 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 same 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.

Colour As a Signal for Entraining the Mammalian Circadian Clock

PubMed Central

Walmsley, Lauren; Hanna, Lydia; Mouland, Josh; Martial, Franck; West, Alexander; Smedley, Andrew R.; Bechtold, David A.; Webb, Ann R.; Lucas, Robert J.; Brown, Timothy M.

2015-01-01

Twilight is characterised by changes in both quantity (“irradiance”) and quality (“colour”) of light. Animals use the variation in irradiance to adjust their internal circadian clocks, aligning their behaviour and physiology with the solar cycle. However, it is currently unknown whether changes in colour also contribute to this entrainment process. Using environmental measurements, we show here that mammalian blue–yellow colour discrimination provides a more reliable method of tracking twilight progression than simply measuring irradiance. We next use electrophysiological recordings to demonstrate that neurons in the mouse suprachiasmatic circadian clock display the cone-dependent spectral opponency required to make use of this information. Thus, our data show that some clock neurons are highly sensitive to changes in spectral composition occurring over twilight and that this input dictates their response to changes in irradiance. Finally, using mice housed under photoperiods with simulated dawn/dusk transitions, we confirm that spectral changes occurring during twilight are required for appropriate circadian alignment under natural conditions. Together, these data reveal a new sensory mechanism for telling time of day that would be available to any mammalian species capable of chromatic vision. PMID:25884537

Diel resource partitioning among juvenile Atlantic Salmon, Brown Trout, and Rainbow Trout during summer

USGS Publications Warehouse

Johnson, James H.; McKenna, James E.

2015-01-01

Interspecific partitioning of food and habitat resources has been widely studied in stream salmonids. Most studies have examined resource partitioning between two native species or between a native species and one that has been introduced. In this study we examine the diel feeding ecology and habitat use of three species of juvenile salmonids (i.e., Atlantic Salmon Salmo salar, Brown Trout Salmo trutta, and Rainbow Trout Oncorhynchus mykiss) in a tributary of Skaneateles Lake, New York. Subyearling Brown Trout and Rainbow Trout fed more heavily from the drift than the benthos, whereas subyearling Atlantic Salmon fed more from the benthos than either species of trout. Feeding activity of Atlantic Salmon and Rainbow Trout was similar, with both species increasing feeding at dusk, whereas Brown Trout had no discernable feeding peak or trough. Habitat availability was important in determining site-specific habitat use by juvenile salmonids. Habitat selection was greater during the day than at night. The intrastream, diel, intraspecific, and interspecific variation we observed in salmonid habitat use in Grout Brook illustrates the difficulty of acquiring habitat use information for widespread management applications.

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.

Distribution of energetic oxygen and hydrogen in the near-Earth plasma sheet

NASA Astrophysics Data System (ADS)

Kronberg, E. A.; Grigorenko, E. E.; Haaland, S. E.; Daly, P. W.; Delcourt, D. C.; Luo, H.; Kistler, L. M.; Dandouras, I.

2015-05-01

The spatial distributions of different ion species are useful indicators for plasma sheet dynamics. In this statistical study based on 7 years of Cluster observations, we establish the spatial distributions of oxygen ions and protons at energies from 274 to 955 keV, depending on geomagnetic and solar wind (SW) conditions. Compared with protons, the distribution of energetic oxygen has stronger dawn-dusk asymmetry in response to changes in the geomagnetic activity. When the interplanetary magnetic field (IMF) is directed southward, the oxygen ions show significant acceleration in the tail plasma sheet. Changes in the SW dynamic pressure (Pdyn) affect the oxygen and proton intensities in the same way. The energetic protons show significant intensity increases at the near-Earth duskside during disturbed geomagnetic conditions, enhanced SW Pdyn, and southward IMF, implying there location of effective inductive acceleration mechanisms and a strong duskward drift due to the increase of the magnetic field gradient in the near-Earth tail. Higher losses of energetic ions are observed in the dayside plasma sheet under disturbed geomagnetic conditions and enhanced SW Pdyn. These observations are in agreement with theoretical models.

Migration timing of female kokanee salmon Oncorhynchus nerka: diel patterns and effects of maturation state.

PubMed

Warren, M A; Morbey, Y E

2012-09-01

Diel patterns of migration and migration speed were compared between reproductive timing phenotypes in female kokanee salmon Oncorhynchus nerka. Females of varying degrees of reproductive maturation were captured on their migration route to the Meadow Creek Spawning Channel (British Columbia, Canada), were tagged with passive-integrated transponders (PIT tags) and were subsequently monitored with stationary receivers. Females showed crepuscular migration timing, with approximately equal detections at dawn and dusk. In particular, peaks of movement were associated with the appearance of the sun over the mountains in the east and the disappearance of the sun over the mountains in the west. Over 25 m, migration speed was 1·0 body lengths (measured as fork length; L(F)) s(-1) and did not depend on maturation state. Over 3 km, migration speed was much slower (0·2-0·3 L(F) s(-1)) than over the short distance, with less mature females migrating more slowly than more mature females. Less mature females appeared to be in less of a hurry to reach breeding areas compared with more mature females. © 2012 The Authors. Journal of Fish Biology © 2012 The Fisheries Society of the British Isles.

Characteristics of high-latitude precursor flows ahead of dipolarization fronts

NASA Astrophysics Data System (ADS)

Li, Jia-Zheng; Zhou, Xu-Zhi; Runov, Andrei; Angelopoulos, Vassilis; Liu, Jiang; Pan, Dong-Xiao; Zong, Qiu-Gang

2017-05-01

Dipolarization fronts (DFs), earthward propagating structures in the magnetotail current sheet characterized by sharp enhancements of northward magnetic field, are capable of converting electromagnetic energy into particle kinetic energy. The ions previously accelerated and reflected at the DFs can contribute to plasma flows ahead of the fronts, which have been identified as DF precursor flows in both the near-equatorial plasma sheet and far from it, near the plasma sheet boundary. Using observations from the THEMIS (Time History of Events and Macroscale Interactions during Substorms) spacecraft, we show that the earthward particle and energy flux enhancements ahead of DFs are statistically larger farther away from the neutral sheet (at high latitudes) than in the near-equatorial region. High-latitude particle and energy fluxes on the DF dawnside are found to be significantly greater than those on the duskside, which is opposite to the dawn-dusk asymmetries previously found near the equatorial region. Using forward and backward tracing test-particle simulations, we then explain and reproduce the observed latitude-dependent characteristics of DF precursor flows, providing a better understanding of ion dynamics associated with dipolarization fronts.

Dayside ionospheric convection changes in response to long-period interplanetary magnetic field oscillations - Determination of the ionospheric phase velocity

NASA Technical Reports Server (NTRS)

Saunders, M. A.; Freeman, M. P.; Southwood, D. J.; Cowley, S. W.; Lockwood, M.; Samson, J. C.; Farrugia, C. J.; Hughes, T. J.

1992-01-01

Ground magnetic field perturbations recorded by the CANOPUS magnetometer network in the 7 to 13 MLT sector are used to examine how reconfigurations of the dayside polar ionospheric flow take place in response to north-south changes of the IMF. During the 6-h interval in question, IMF Bz oscillates between +/- 7 nT with about a 1-h period. Corresponding variations in the ground magnetic disturbance are observed which we infer are due to changes in ionospheric flow. Cross correlation of the data obtained from two ground stations at 73.5 deg magnetic latitude, but separated by about 2 hours in MLT, shows that changes in the flow are initiated in the prenoon sector (about 10 MLT) and then spread outward toward dawn and dusk with a phase speed of about 5 km/s over the longitude range about 8 to 12 MLT, slowing to about 2 km/s outside this range. Cross correlating the data from these ground stations with IMP 8 IMF Bz records produces a MLT variation in the ground response delay relative to the IMF which is compatible with these deduced phase speeds.

Impact of the storm-time plasma sheet ion composition on the ring current energy density

NASA Astrophysics Data System (ADS)

Mouikis, C.; Kistler, L. M.; Petrinec, S. M.; Fuselier, S. A.; Cohen, I.

2017-12-01

The adiabatic inward transport of the night-side near-earth ( 6 Re) hot plasma sheet is the dominant contributor to the ring current pressure during storm times. During storm times, the plasma sheet composition in the 6 - 12 Re tail region changes due to O+ entry from the lobes (from the cusp) and the direct feeding from the night side auroral region. In addition, at substorm onset the plasma sheet O+ ions can be preferentially accelerated. We use MMS and observations during two magnetic storms, 5/8/2016 and 7/16/2017, to monitor the composition changes and energization in the 6 - 12 Re plasma sheet region. For both storms the MMS apogee was in the tail. In addition, we use subsequent Van Allen Probe observations (with apogee in the dawn and dusk respectively) to test if the 6-12 Re plasma sheet, observed by MMS, is a sufficient source of the O+ in the ring current. For this we will compare the phase space density (PSD) of the plasma sheet source population and the PSD of the inner magnetosphere at constant magnetic moment values as used in Kistler et al., [2016].

Design and Testing of a Novel, Protective Human-Baited Tent Trap for the Collection of Anthropophilic Disease Vectors

PubMed Central

KRAJACICH, BENJAMIN J.; SLADE, JEREMIAH R.; MULLIGAN, ROBERT T.; LABRECQUE, BRENDAN; KOBYLINSKI, KEVIN C.; GRAY, MEG; KUKLINSKI, WOJTEK S.; BURTON, TIMOTHY A.; SEAMAN, JONATHAN A.; SYLLA, MASSAMBA; FOY, BRIAN D.

2014-01-01

Currently, there exists a deficit of safe, active trapping methods for the collection of host-seeking Anopheles and other disease-causing arthropod vectors. The gold-standard approach for mosquito collection is that of human landing catch (HLC), in which an individual exposes bare skin to possibly infected vectors. Here, we present the development of a new method for mosquito collection, the Infoscitex tent, which uses modern tent materials coupled with a novel trap design. This provides an efficacious, a non-labor-intensive, and a safe method for vector collection. In these initial studies, we found it collected an average of 27.7 Anophelesgambiae s.l. per trap per night in rural villages in southeastern Senegal, and 43.8 Culex group V per trap per night in the semiurban town of Kedougou, Senegal. In direct comparisons with HLC, the tent was not statistically different for collection of Culex quinquefasciatus in crepuscular sampling, but was significantly less efficacious at trapping the highly motile dusk-biter Aedes aegypti. These studies suggest that the Infoscitex tent is a viable and safe alternative to HLC for Anopheles and Culex sampling in areas of high vector-borne disease infection risk. PMID:24605476

The Roles of Magnetosphere-Ionosphere Coupling on Ring Current development: Comparison of TWINS Measurements and CIMI Simulations for the 7-10 September 2015 Geomagnetic Storm

NASA Astrophysics Data System (ADS)

Edmond, J. A.; Hill, S. C.; Xu, H.; Perez, J. D.; Fok, M. C. H.; Goldstein, J.; McComas, D. J.; Valek, P. W.

2017-12-01

The Two Wide-Angle Imaging Neutral-Atom Spectrometers (TWINS) mission obtained energetic neutral atom (ENA) images during a 4 day storm on 7-10 September 2015. The storm has two separate SYM/H minima, so we divide the storm into four intervals: first main phase, first recovery phase, second main phase, and second recovery phase. Simulations with the Comprehensive Inner Magnetosphere-Ionosphere Model (CIMI) are compared and contrasted with the TWINS observations. We find good agreement in most aspects of the storm. E. G. (1) the location of the ion pressure peaks are most often in the dusk-midnight sector, (2) the pitch angle distributions at the pressure peaks most often display perpendicular anisotropy, and (3) the energy spectra at the pressure peaks have similar maximum energies. There are, however, some exceptions to these general features. We describe and interpret these notable events. We also have examined particle paths determined from the CIMI model simulations to assist in the interpretation of the notable events.In this poster, we focus upon the features of the CIMI simulations with a self-consistent electric field and with the semi-empirical Weimer electric potential in relationship to the TWINS observations.

Using DNA barcodes to identify a bird involved in a birdstrike at a Chinese airport.

PubMed

Yang, Rong; Wu, Xiaobing; Yan, Peng; Li, Xiaoqiang

2010-10-01

One day at dusk in August, 200X, an airplane was struck by a bird at a Chinese airport (M Airport). After a careful check, some blades of the plane's engine were found to be out of shape and a few feathers and some bloodstains were found in the air intake of the engine. In order to know which species of bird was involved in the birdstrike, firstly we extracted DNA from the bloodstains; secondly, the DNA barcode (portion of COI gene) of the unknown species was amplified by PCR method; thirdly, sequence divergences (K2P differences) of the DNA barcode between the unknown species and a library of 59 common bird species distributed at the airport area were analyzed. Furthermore, a neighbor-joining (NJ) tree based on COI barcodes was created to provide graphic representation of sequence divergences among the species to confirm the identification. The result showed that red-rumped swallow (Hirundo daurica) was involved in the birdstrike incident. Some suggestions to avoid birdstrikes caused by red-rumped swallows were given to the administrative department of M Airport to ensure flying safety.

Crres Observations of Particle Flux Dropout Events

NASA Technical Reports Server (NTRS)

Fennell, J.; Roeder, J.; Spence, H.; Singer, H.; Korth, A.; Grande, M.; Vampola, A.

1999-01-01

The complete disappearance of energetic electrons was observed by CRRES in the near geosynchronous region in 7.5% of the orbits examined. These total flux dropouts were defined by the fluxes rapidly dropping to levels below the sensitivity of the MEA energetic electron spectrometer on the CRRES satellite. They were separated into those that were only energetic electron dropouts and those that were associated with energetic ion and plasma dropouts. Approximately 20% of the events showed dropouts of 0 particle fluxes, and these were usually coincident with large increases in the local magnetic intensity and signatures of strong current systems. The energetic particle instruments and magnetometer on CRRES provide a detailed picture of the particle and field responses to these unusual conditions. Both the local morning and dusk events were associated with strong azimuthal (eastward) and radial changes in the magnetic field indicative of a strong current system approaching and sometimes crossing the CRRES position at the time of the flux dropouts. The direction of the field changes and the details of particle observations are consistent with CRRES passing through the plasma sheet boundary layer and entering the tail lobe for a significant number of the events.

A surface transporter family conveys the trypanosome differentiation signal.

PubMed

Dean, Samuel; Marchetti, Rosa; Kirk, Kiaran; Matthews, Keith R

2009-05-14

Microbial pathogens use environmental cues to trigger the developmental events needed to infect mammalian hosts or transmit to disease vectors. The parasites causing African sleeping sickness respond to citrate or cis-aconitate (CCA) to initiate life-cycle development when transmitted to their tsetse fly vector. This requires hypersensitization of the parasites to CCA by exposure to low temperature, conditions encountered after tsetse fly feeding at dusk or dawn. Here we identify a carboxylate-transporter family, PAD (proteins associated with differentiation), required for perception of this differentiation signal. Consistent with predictions for the response of trypanosomes to CCA, PAD proteins are expressed on the surface of the transmission-competent 'stumpy-form' parasites in the bloodstream, and at least one member is thermoregulated, showing elevated expression and surface access at low temperature. Moreover, RNA-interference-mediated ablation of PAD expression diminishes CCA-induced differentiation and eliminates CCA hypersensitivity under cold-shock conditions. As well as being molecular transducers of the differentiation signal in these parasites, PAD proteins provide the first example of a surface marker able to discriminate the transmission stage of trypanosomes in their mammalian host.

Ion-Scale Wave Properties and Enhanced Ion Heating across the Magnetopause during Kelvin-Helmholtz Instability

NASA Astrophysics Data System (ADS)

Nykyri, K.; Moore, T.; Dimmock, A. P.

2017-12-01

In the Earth's magnetosphere, the magnetotail plasma sheet ions are much hotter than in the shocked solar wind. On the dawn-sector, the cold-component ions are more abundant and hotter by 30-40 percent when compared to the dusk sector. Recent statistical studies of the flank magnetopause and magnetosheath have shown that the level of temperature asymmetry of the magnetosheath is unable to account for this, so additional physical mechanisms must be at play, either at the magnetopause or plasma sheet that contribute to this asymmetry. In this study, we perform a statistical analysis on the ion-scale wave properties in the three main plasma regimes common to flank magnetopause boundary crossings when the boundary is unstable to KHI: hot and tenuous magnetospheric, cold and dense magnetosheath and mixed [Hasegawa 2004 et al., 2004]. These statistics of ion-scale wave properties are compared to observations of fast magnetosonic wave modes that have recently been linked to Kelvin-Helmholtz vortex centered ion heating [Moore et al., 2016]. The statistical analysis shows that during KH events there is enhanced non-adiabatic heating calculated during (temporal) ion scale wave intervals when compared to non-KH events.

Magsat - A new satellite to survey the earth's magnetic field

NASA Technical Reports Server (NTRS)

Mobley, F. F.; Eckard, L. D.; Fountain, G. H.; Ousley, G. W.

1980-01-01

The Magsat satellite was launched on Oct. 30, 1979 into a sun-synchronous dawn-dusk orbit, of 97 deg inclination, 350 km perigee, and 550 km apogee. It contains a precision vector magnetometer and a cesium-vapor scalar magnetometer at the end of a 6-m long graphite epoxy scissors boom. The magnetometers are accurate to 2 nanotesla. A pair of star cameras are used to define the body orientation to 10 arc sec rms. An 'attitude transfer system' measures the orientation of the magnetometer sensors relative to the star cameras to approximately 5 arc sec rms. The satellite position is determined to 70 meters rms by Doppler tracking. The overall objective is to determine each component of the earth's vector magnetic field to an accuracy of 6 nanotesla rms. The Magsat satellite gathers a complete picture of the earth's magnetic field every 12 hours. The vector components are sampled 16 times per second with a resolution of 0.5 nanotesla. The data will be used by the U.S. Geological Survey to prepare 1980 world magnetic field charts and to detect large-scale magnetic anomalies in the earth's crust for use in planning resource exploration strategy.

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.

Anthropophilic biting behaviour of Anopheles (Kerteszia) neivai Howard, Dyar & Knab associated with Fishermen’s activities in a malaria-endemic area in the Colombian Pacific

PubMed Central

Escovar, Jesús Eduardo; González, Ranulfo; Quiñones, Martha Lucía

2013-01-01

On the southwest Pacific Coast of Colombia, a field study was initiated to determine the human-vector association between Anopheles (Kerteszia) neivai and fishermen, including their nearby houses. Mosquitoes were collected over 24-h periods from mangrove swamps, marshlands and fishing vessels in three locations, as well as in and around the houses of fishermen. A total of 6,382 mosquitoes were collected. An. neivai was most abundant in mangroves and fishing canoes (90.8%), while Anopheles albimanus was found indoors (82%) and outdoors (73%). One An. neivai and one An. albimanus collected during fishing activities in canoes were positive for Plasmodium vivax , whereas one female An. neivai collected in a mangrove was positive for P. vivax . In the mangroves and fishing canoes, An. neivai demonstrated biting activity throughout the day, peaking between 06:00 pm-07:00 pm and there were two minor peaks at dusk and dawn. These peaks coincided with fishing activities in the marshlands and mangroves, a situation that places the fishermen at risk of contracting malaria when they are performing their daily activities. It is recommended that protective measures be implemented to reduce the risk that fishermen will contract malaria. PMID:24402159

Space Technology 5 Multi-point Measurements of Near-Earth Magnetic Fields: Initial Results

NASA Technical Reports Server (NTRS)

Slavin, James A.; Le, G.; Strangeway, R. L.; Wang, Y.; Boardsen, S.A.; Moldwin, M. B.; Spence, H. E.

2007-01-01

The Space Technology 5 (ST-5) mission successfully placed three micro-satellites in a 300 x 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 approximately 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.

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.

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.

A Computational Method to Quantify Fly Circadian Activity.

PubMed

Lazopulo, Andrey; Syed, Sheyum

2017-10-28

In most animals and plants, circadian clocks orchestrate behavioral and molecular processes and synchronize them to the daily light-dark cycle. Fundamental mechanisms that underlie this temporal control are widely studied using the fruit fly Drosophila melanogaster as a model organism. In flies, the clock is typically studied by analyzing multiday locomotor recording. Such a recording shows a complex bimodal pattern with two peaks of activity: a morning peak that happens around dawn, and an evening peak that happens around dusk. These two peaks together form a waveform that is very different from sinusoidal oscillations observed in clock genes, suggesting that mechanisms in addition to the clock have profound effects in producing the observed patterns in behavioral data. Here we provide instructions on using a recently developed computational method that mathematically describes temporal patterns in fly activity. The method fits activity data with a model waveform that consists of four exponential terms and nine independent parameters that fully describe the shape and size of the morning and evening peaks of activity. The extracted parameters can help elucidate the kinetic mechanisms of substrates that underlie the commonly observed bimodal activity patterns in fly locomotor rhythms.

Van Allen Probes Measurements of Energetic Particle Deep Penetration Into the Low L Region (L < 4) During the Storm on 8 April 2016

NASA Astrophysics Data System (ADS)

Zhao, H.; Baker, D. N.; Califf, S.; Li, X.; Jaynes, A. N.; Leonard, T.; Kanekal, S. G.; Blake, J. B.; Fennell, J. F.; Claudepierre, S. G.; Turner, D. L.; Reeves, G. D.; Spence, H. E.

2017-12-01

Using measurements from the Van Allen Probes, a penetration event of tens to hundreds of keV electrons and tens of keV protons into the low L shells (L < 4) is studied. Timing and magnetic local time (MLT) differences of energetic particle deep penetration are unveiled and underlying physical processes are examined. During this event, both proton and electron penetrations are MLT asymmetric. The observed MLT difference of proton penetration is consistent with convection of plasma sheet protons, suggesting enhanced convection during geomagnetic active times to be the cause of energetic proton deep penetration during this event. The observed MLT difference of tens to hundreds of keV electron penetration is completely different from tens of keV protons and cannot be well explained by inward radial diffusion, convection of plasma sheet electrons, or transport of trapped electrons by enhanced convection electric field represented by the Volland-Stern model or a uniform dawn-dusk electric field model based on the electric field measurements. It suggests that the underlying physical mechanism responsible for energetic electron deep penetration, which is very important for fully understanding energetic electron dynamics in the low L shells, should be MLT localized.

Temperature and evaporative water loss of leaf-sitting frogs: the role of reflection spectra

PubMed Central

Blount, Chris; Dickinson, Mark

2016-01-01

ABSTRACT The near infrared reflection peak in some frogs has been speculated to be either for enhancing crypticity, or to help them with thermoregulation. The theoretical background for the thermoregulatory processes has been established before, but little consideration has been given to the contribution from the frogs' reflection spectra differences. In this investigation, the reflection spectra from a range of different species of frogs were taken and combined with precise surface area measurements of frogs and an approximation to the mass transfer coefficient of agar frog models. These were then used to simulate the temperature and water evaporation in anurans with and without the near infrared reflective peak. We have shown that the presence of the near infrared reflection peak can contribute significantly to the temperature and evaporative water loss of a frog. The significance of the steady-state temperature differences between frogs with and without the near infrared reflection peak is discussed in a realistic and an extreme scenario. Temperature differences of up to 3.2°C were found, and the rehydration period was increased by up to 16.7%, although this does not reduce the number of rehydration events between dawn and dusk. PMID:27793832

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.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bishop, James K.B.; Wood, Todd

Three Carbon Explorer (CE) floats profiling to kilometer depths in the Southern Ocean tracked dawn-dusk variations of mixing/stratification, particulate organic carbon (POC), and light scattering and sedimentation at 100, 250, and 800 m continuously from January 2002 to April 2003. Data were analyzed in conjunction with contemporaneous satellite winds and chlorophyll and derived subsurface light fields. The CE deployed at 66{sup o}S 172{sup o}W operated in the ice edge zone in absence of light. Two CEs deployed at 55{sup o}S 172{sup o}W recorded wintertime mixing to {approx}400 m, yet observed very different bloom dynamics and sedimentation the following spring. Fourmore » hypotheses are explored. The strongest is that shallow transient stratification of the deep winter mixed layer to shallower than photosynthetic critical depth occurred more frequently in the non-bloom/higher sedimentation case. The lower particle export to 800 m under the bloom was hypothesized to be due to higher interception of sinking carbon by a relatively starved over wintering zooplankton population. In the Southern Ocean surface phytoplankton biomass may counter indicate particle flux at kilometer depths.« less

Anthropophilic biting behaviour of Anopheles (Kerteszia) neivai Howard, Dyar & Knab associated with Fishermen's activities in a malaria-endemic area in the Colombian Pacific.

PubMed

Escovar, Jesús Eduardo; González, Ranulfo; Quiñones, Martha Lucía

2013-12-01

On the southwest Pacific Coast of Colombia, a field study was initiated to determine the human-vector association between Anopheles (Kerteszia) neivai and fishermen, including their nearby houses. Mosquitoes were collected over 24-h periods from mangrove swamps, marshlands and fishing vessels in three locations, as well as in and around the houses of fishermen. A total of 6,382 mosquitoes were collected. An. neivai was most abundant in mangroves and fishing canoes (90.8%), while Anopheles albimanus was found indoors (82%) and outdoors (73%). One An. neivai and one An. albimanus collected during fishing activities in canoes were positive for Plasmodium vivax , whereas one female An. neivai collected in a mangrove was positive for P. vivax . In the mangroves and fishing canoes, An. neivai demonstrated biting activity throughout the day, peaking between 06:00 pm-07:00 pm and there were two minor peaks at dusk and dawn. These peaks coincided with fishing activities in the marshlands and mangroves, a situation that places the fishermen at risk of contracting malaria when they are performing their daily activities. It is recommended that protective measures be implemented to reduce the risk that fishermen will contract malaria.

Fields of rice: health hazards for women and unborn children.

PubMed

Batliwala, S

1988-01-01

A death information study, to determine why the infant mortality rate failed to fall below 75/1000, was begun in January 1982, after 9 years of accomplishments by the rural health research project in Raigad district of coastal Maharashtra. All data were collected by 27 female rural health workers, some of whom were illiterate but received help from villagers. Death records included name, sex, age, date and time of death, and cause of death or symptoms before death. In the 0-6 age group, 64% of the deaths were girls. 80% of the dead children were infant deaths, and of these, 75% were neonatal, suggesting the influence of prenatal, obstetric and postnatal factors and maternal nutrition. The majority were related to premature and low birth weight babies. Another striking observation was that 40% of all infant deaths occurred in July-October, and 50% of these were stillbirths and premature births. July and August are the months when all women (and no men) work transplanting rice seedlings. This work is done by bending or squatting from dawn to dusk. Thus, rice culture must be considered an occupational hazard for women in late pregnancy.

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.

Statistical survey on the magnetic structure in magnetotail current sheets

NASA Astrophysics Data System (ADS)

Rong, Z. J.; Wan, W. X.; Shen, C.; Li, X.; Dunlop, M. W.; Petrukovich, A. A.; Zhang, T. L.; Lucek, E.

2011-09-01

On the basis of the multipoint magnetic observations of Cluster in the region 15-19 RE downtail, the magnetic field structure in magnetotail current sheet (CS) center is statistically surveyed. It is found that the By component (in GSM coordinates) is distributed mainly within ∣By∣ < 5nT, while the Bz component is mostly positive and distributes mainly within 1˜10 nT. The plane of the magnetic field lines (MFLs) is mostly vertical to the equatorial plane, with the radius of curvature (Rc) of the MFLs being directed earthward and the binormal (perpendicular to the curvature and magnetic field direction) being directed azimuthally westward. The curvature radius of MFLs reaches a minimum, Rc,min, at the CS center and is larger than the corresponding local half thickness of the neutral sheet, h. Statistically, it is found that the overall surface of the CS, with the normal pointing basically along the south-north direction, can be approximated to be a plane parallel to equatorial plane, although the local CS may be flapping and is frequently tilted to the equatorial plane. The tilted CS (normal inclined to the equatorial plane) is apt to be observed near both flanks and is mainly associated with the slippage of magnetic flux tubes. It is statistically verified that the minimum curvature radius, Rc,min, half thickness of neutral sheet, h, and the slipping angle of MFLs, δ, in the CS satisfies h = Rc,min cosδ. The current density, with a mean strength of 4-8 nA/m2, basically flows azimuthally and tangentially to the surface of the CS, from dawn side to the dusk side. There is an obvious dawn-dusk asymmetry of CS, however. For magnetic local times (MLT) ˜21:00-˜01:00, the CS is relatively thinner; the minimum curvature radius of MFLs, Rc,min (0.6-1 RE) and the half-thickness of neutral sheet, h (0.2-0.4 RE), are relatively smaller, and Bz (3-5 nT) and the minimum magnetic field, Bmin (5-7 nT), are weaker. It is also found that negative Bz has a higher probability

Field-aligned currents onboard the Intercosmos Bulgaria-1300 satellite in comparison with modeled FAC

NASA Astrophysics Data System (ADS)

Danov, Dimitar

2008-02-01

The statistical field-aligned current (FAC) distribution has been demonstrated by [Iijima, T., Potemra, T.A., 1976. The amplitude distribution of field-aligned currents at northern high latitudes observed by Triad. Journal of Geophysical Research 81(13), 2165-2174] and many other authors. The large-scale (LS) FACs have been described by different empirical/statistical models [Feldstein, Ya. I., Levitin, A.E., 1986. Solar wind control of electric fields and currents in the ionosphere. Journal of Geomagnetism and Geoelectricity 38, 1143; Papitashvili, V.O., Rich, F.J., Heinemann, M.A., Hairston, M.R., 1999. Parameterization of the Defense Meteorological Satellite Program ionospheric electrostatic potentials by the interplanetary magnetic field strength and direction. Journal of Geophysical Research 104, 177-184; Papitashvili, V.O., Christiansen, F., Neubert, T., 2002. A new model of field-aligned currents derived from high-precision satellite magnetic field data. Geophysical Research Letters, 29(14), 1683, doi:10.1029/2001GL014207; Tsyganenko, N.A., 2001. A model of the near magnetosphere with a dawn-dusk asymetry (I. Mathematical structure). Journal of Geophysical Research 107(A8), doi:10.1029/2001JA000219; Weimer, D.R., 1996a. A new model for prediction of ionospheric electric potentials as a function of the IMF. In: Snowmass'96 Online Poster Session; Weimer, D.R., 1996b. Substorm influence on the ionospheric convection patterns. In: Snowmass'96 Online Poster Session; Weimer, D.R., 2001. Maps of ionospheric field-aligned currents as a function of the interplanetary magnetic field derived from Dynamic Explorer 2 data. Journal of Geophysical Research 106, 12,889-12,902; Weimer, D.R., 2005. Improved ionospheric electrodynamic models and application to calculating Joule heating rates. Journal of Geophysical Research 110, A05306, doi:10.1029/2004JA010884]. In the present work, we compare two cases of LS FAC obtained from magnetic field measurements onboard the

Large enhancements in low latitude total electron content during 15 May 2005 geomagnetic storm in Indian zone

NASA Astrophysics Data System (ADS)

Dashora, N.; Sharma, S.; Dabas, R. S.; Alex, S.; Pandey, R.

2009-05-01

Results pertaining to the response of the equatorial and low latitude ionosphere to a major geomagnetic storm that occurred on 15 May 2005 are presented. These results are also the first from the Indian zone in terms of (i) GPS derived total electron content (TEC) variations following the storm (ii) Local low latitude electrodynamics response to penetration of high latitude convection electric field (iii) effect of storm induced traveling atmospheric disturbances (TAD's) on GPS-TEC in equatorial ionization anomaly (EIA) zone. Data set comprising of ionospheric TEC obtained from GPS measurements, ionograms from an EIA zone station, New Delhi (Geog. Lat. 28.42° N, Geog. Long. 77.21° E), ground based magnetometers in equatorial and low latitude stations and solar wind data obtained from Advanced Composition Explorer (ACE) has been used in the present study. GPS receivers located at Udaipur (Geog. Lat. 24.73° N, Geog. Long. 73.73° E) and Hyderabad (Geog. Lat. 17.33° N, Geog. Long. 78.47° E) have been used for wider spatial coverage in the Indian zone. Storm induced features in vertical TEC (VTEC) have been obtained comparing them with the mean VTEC of quiet days. Variations in solar wind parameters, as obtained from ACE and in the SYM-H index, indicate that the storm commenced on 15 May 2005 at 02:39 UT. The main phase of the storm commenced at 06:00 UT on 15 May with a sudden southward turning of the Z-component of interplanetary magnetic field (IMF-Bz) and subsequent decrease in SYM-H index. The dawn-to-dusk convection electric field of high latitude origin penetrated to low and equatorial latitudes simultaneously as corroborated by the magnetometer data from the Indian zone. Subsequent northward turning of the IMF-Bz, and the penetration of the dusk-to-dawn electric field over the dip equator is also discernible. Response of the low latitude ionosphere to this storm may be characterized in terms of (i) enhanced background level of VTEC as compared to the mean

A circadian gene expression atlas in mammals: implications for biology and medicine.

PubMed

Zhang, Ray; Lahens, Nicholas F; Ballance, Heather I; Hughes, Michael E; Hogenesch, John B

2014-11-11

To characterize the role of the circadian clock in mouse physiology and behavior, we used RNA-seq and DNA arrays to quantify the transcriptomes of 12 mouse organs over time. We found 43% of all protein coding genes showed circadian rhythms in transcription somewhere in the body, largely in an organ-specific manner. In most organs, we noticed the expression of many oscillating genes peaked during transcriptional "rush hours" preceding dawn and dusk. Looking at the genomic landscape of rhythmic genes, we saw that they clustered together, were longer, and had more spliceforms than nonoscillating genes. Systems-level analysis revealed intricate rhythmic orchestration of gene pathways throughout the body. We also found oscillations in the expression of more than 1,000 known and novel noncoding RNAs (ncRNAs). Supporting their potential role in mediating clock function, ncRNAs conserved between mouse and human showed rhythmic expression in similar proportions as protein coding genes. Importantly, we also found that the majority of best-selling drugs and World Health Organization essential medicines directly target the products of rhythmic genes. Many of these drugs have short half-lives and may benefit from timed dosage. In sum, this study highlights critical, systemic, and surprising roles of the mammalian circadian clock and provides a blueprint for advancement in chronotherapy.

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.

Plasma convection and ion beam generation in the plasma sheet boundary layer

NASA Technical Reports Server (NTRS)

Moghaddam-Taaheri, E.; Goertz, C. K.; Smith, R. A.

1991-01-01

Because of the dawn-dusk electric field E(dd), plasma in the magnetotail convects from the lobe toward the central plasma sheet (CPS). In the absence of space or velocity diffusion due to plasma turbulence, convection would yield a steady state distribution function f = V exp (-2/3) g(v exp 2 V exp 2/3), where V is the flux tube volume. Starting with such a distribution function and a plasma beta which varies from beta greater than 1 in the CPS to beta much smaller than 1 in the lobe, the evolution of the ion distribution function was studied considering the combined effects of ion diffusion by kinetic Alfven waves (KAW) in the ULF frequency range (1-10 mHz) and convection due to E(dd) x B drift in the plasma sheet boundary layer (PSBL) and outer central plasma sheet (OCPS). The results show that, during the early stages after launching the KAWs, a beamlike ion distribution forms in the PSBL and at the same time the plasma density and temperature decrease in the OCPS. Following this stage, ions in the beams convect toward the CPS resulting in an increase of the plasma temperature in the OCPS.

Space Technology 5 Multi-Point Observations of Temporal Variability of Field-Aligned Currents

NASA Technical Reports Server (NTRS)

Le, Guan; Wang, Yongli; Slavin, James A.; Strangeway, Robert J.

2008-01-01

Space Technology 5 (ST5) 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 meso-scale 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 approximately 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 approximately 1 min for meso-scale currents and approximately 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.

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.

Space Technology 5 Multi-point Observations of Field-aligned Currents: Temporal Variability of Meso-Scale Structures

NASA Technical Reports Server (NTRS)

Le, Guan; Wang, Yongli; Slavin, James A.; Strangeway, Robert J.

2007-01-01

Space Technology 5 (ST5) 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 meso-scale 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 - 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 approx. 1 min for meso-scale currents and approx. 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.

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.

A statistical study of EMIC waves observed by Cluster: 2. Associated plasma conditions

DOE PAGES

Allen, R. C.; Zhang, J. -C.; Kistler, L. M.; ...

2016-07-01

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

A statistical study of EMIC waves observed by Cluster: 2. Associated plasma conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allen, R. C.; Zhang, J. -C.; Kistler, L. M.

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

Preliminary study of Malaysian fruit bats species diversity in Lenggong Livestock Breeding Center, Perak: Potential risk of spill over infection

PubMed Central

Mikail, Muhammed; Putra, T. A. Tengku Rinalfi; Suri, Arshad Siti; Hezmee, Mohd Noor Mohd; Marina, M. T.

2017-01-01

Aim: Farms that are neighboring wildlife sanctuaries are at risk of spillover infection from wildlife, and the objective of this research is to examine the species diversity of Malaysian fruit bats in livestock farm in determining the possible risk of spill over infection to livestock. Materials and Methods: Fifty individual fruit bats were captured using six mists net, from May to July 2017. The nets were set at dusk (1830 h) as bats emerge for foraging and monitored at every 30-min intervals throughout the night until dawn when they returned to the roost. The nets were closed for the day until next night, and captured bats were identified to species levels. Results: All the captured bats were mega chiropterans, and Cynopterus brachyotis was the highest captured species, representing 40% of the total capture. Shannon–Weiner index is 2.80, and Simpson index is 0.2. Our result suggests that there is a degree of species dominance with low diversity in Lenggong Livestock Breeding Center. Conclusion: We concluded that fruit bats are indeed, encroaching livestock areas and the species identified could be a potential source of infection to susceptible livestock. Hence, an active surveillance should be embarked on farms that border wildlife sanctuaries. PMID:29263588

Polarization transition between sunlit and moonlit skies with possible implications for animal orientation and Viking navigation: anomalous celestial twilight polarization at partial moon.

PubMed

Barta, András; Farkas, Alexandra; Száz, Dénes; Egri, Ádám; Barta, Pál; Kovács, József; Csák, Balázs; Jankovics, István; Szabó, Gyula; Horváth, Gábor

2014-08-10

Using full-sky imaging polarimetry, we measured the celestial distribution of polarization during sunset and sunrise at partial (78% and 72%) and full (100%) moon in the red (650 nm), green (550 nm), and blue (450 nm) parts of the spectrum. We investigated the temporal change of the patterns of degree p and angle α of linear polarization of sunlit and moonlit skies at dusk and dawn. We describe here the position change of the neutral points of sky polarization, and present video clips about the celestial polarization transition at moonlit twilight. We found that at partial moon and at a medium latitude (47° 15.481' N) during this transition there is a relatively short (10-20 min) period when (i) the maximum of p of skylight decreases, and (ii) from the celestial α pattern neither the solar-antisolar nor the lunar-antilunar meridian can be unambiguously determined. These meridians can serve as reference directions of animal orientation and Viking navigation based on sky polarization. The possible influence of these atmospheric optical phenomena during the polarization transition between sunlit and moonlit skies on the orientation of polarization-sensitive crepuscular/nocturnal animals and the hypothesized navigation of sunstone-aided Viking seafarers is discussed.

Twilight and photoperiod affect behavioral entrainment in the house mouse (Mus musculus).

PubMed

Comas, M; Hut, R A

2009-10-01

The effect of twilight transitions on entrainment of C57BL/6JOlaHsd mice (Mus musculus) was studied using light-dark cycles of different photoperiods (6, 12, and 18 h) and twilight transitions of different durations (0, 1, and 2 h). Phase angle differences of the onset, center of gravity, and offset of activity, activity duration (alpha), as well as free-running period (tau) in continuous darkness were analyzed. The main finding was that for all conditions the onset of activity was close to dusk or lights-off except for the short photoperiod with 2 h of twilight where activity onset was on average 5.3 (SEM 1.07) h after lights-off. This finding contrasts with the results of Boulos and Macchi for Syrian hamsters where a 5.9-h earlier activity onset was observed when similar photoperiod and twilight conditions are compared with a rectangular LD cycle. The authors suggest the opposite effects of 2 h of twilight in the 2 species may be related to their different free-running periods under DD conditions following entrainment to short photoperiod with 2-h twilight conditions. Since the authors observed larger variation in phase angle of entrainment in longer twilight conditions, twilight does not necessarily form a stronger zeitgeber.

Twilight dominates over moonlight in adjusting Drosophila's activity pattern.

PubMed

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

2015-04-01

Light is the most important zeitgeber for the synchronization of the Drosophila melanogaster circadian clock. In nature, there is twilight, and the nights are rarely completely dark, a fact that is usually disregarded in lab experiments. Recent studies showed contrary effects of simulated twilight and moonlight on fly locomotor activity, with twilight shifting morning and evening activity into the day and moonlight shifting it into the night. A currently unanswered question is, what may happen to locomotor activity when flies are exposed to more natural conditions in which both moonlight and twilight are simulated? Our data demonstrate that flies are able to integrate twilight and moonlight. However, twilight seems to dominate over moonlight as both, morning and evening activity peaks, take place at dawn or at dusk, respectively, and not during the night. Furthermore, nocturnal activity decreases in the presence of twilight. The compound eyes are essential for this behavior, and by investigating different photoreceptor mutants, we unraveled the importance of photoreceptor cells 7 and 8 for wild-type phases of the activity peaks. To adjust nocturnal activity levels to a wild-type manner, all photoreceptor cells work together in a complex way, with rhodopsin 6 having a prominent role. © 2015 The Author(s).

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

Bat Hunting and Bat-Human Interactions in Bangladeshi Villages: Implications for Zoonotic Disease Transmission and Bat Conservation.

PubMed

Openshaw, J J; Hegde, S; Sazzad, H M S; Khan, S U; Hossain, M J; Epstein, J H; Daszak, P; Gurley, E S; Luby, S P

2017-08-01

Bats are an important reservoir for emerging zoonotic pathogens. Close human-bat interactions, including the sharing of living spaces and hunting and butchering of bats for food and medicines, may lead to spillover of zoonotic disease into human populations. We used bat exposure and environmental data gathered from 207 Bangladeshi villages to characterize bat exposures and hunting in Bangladesh. Eleven percent of households reported having a bat roost near their homes, 65% reported seeing bats flying over their households at dusk, and 31% reported seeing bats inside their compounds or courtyard areas. Twenty percent of households reported that members had at least daily exposure to bats. Bat hunting occurred in 49% of the villages surveyed and was more likely to occur in households that reported nearby bat roosts (adjusted prevalence ratio [aPR] 2.3, 95% CI 1.1-4.9) and villages located in north-west (aPR 7.5, 95% CI 2.5-23.0) and south-west (aPR 6.8, 95% CI 2.1-21.6) regions. Our results suggest high exposure to bats and widespread hunting throughout Bangladesh. This has implications for both zoonotic disease spillover and bat conservation. © 2016 Blackwell Verlag GmbH.

The quiet evening auroral arc and the structure of the growth phase near-Earth plasma sheet

NASA Astrophysics Data System (ADS)

Coroniti, F. V.; Pritchett, P. L.

2014-03-01

The plasma pressure and current configuration of the near-Earth plasma sheet that creates and sustains the quiet evening auroral arc during the growth phase of magnetospheric substorms is investigated. We propose that the quiet evening arc (QEA) connects to the thin near-Earth current sheet, which forms during the development of the growth phase enhancement of convection. The current sheet's large polarization electric fields are shielded from the ionosphere by an Inverted-V parallel potential drop, thereby producing the electron precipitation responsible for the arc's luminosity. The QEA is located in the plasma sheet region of maximal radial pressure gradient and, in the east-west direction, follows the vanishing of the approximately dawn-dusk-directed gradient or fold in the plasma pressure. In the evening sector, the boundary between the Region1 and Region 2 current systems occurs where the pressure maximizes (approximately radial gradient of the pressure vanishes) and where the approximately radial gradient of the magnetic flux tube volume also vanishes in an inflection region. The proposed intricate balance of plasma sheet pressure and currents may well be very sensitive to disruption by the arrival of equatorward traveling auroral streamers and their associated earthward traveling dipolarization fronts.

The occurrence, spatial distribution, and wave properties of hydrogen-, helium-, and oxygen-band EMIC waves observed by the Van Allen Probes

NASA Astrophysics Data System (ADS)

Saikin, A.; Zhang, J.; Allen, R. C.; Smith, C. W.; Kistler, L. M.; Spence, H. E.; Torbert, R. B.; Kletzing, C.; Jordanova, V.

2014-12-01

Electromagnetic ion cyclotron (EMIC) waves play an important role in the overall dynamics of the Earth's magnetosphere, including the energization and loss of particles. We perform a statistical study of EMIC waves detected by the Van Allen Probes mission to investigate their occurrence, spatial distribution, and properties (e.g., wave power, normal angle, and ellipticity). Magnetic field measurements from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) onboard Van Allen Probes are used to identify EMIC wave events from the beginning of the mission (September, 2012) to the present. EMIC waves are examined in hydrogen, helium and oxygen bands. So far, about 280 EMIC wave events have been identified over the three different bands. Preliminary results show that hydrogen-band EMIC waves have been primarily observed in the dusk sector, while helium-band EMIC waves have been observed in all Magnetic Local Times (MLTs). Particularly, the Van Allen Probes provide a better resolution of lower frequencies (0.2-0.9 Hz), within which oxygen-band EMIC waves can occur in the inner magnetosphere. This allows us to obtain better insight into the characteristics of this previously largely unavailable band of EMIC waves, and allows for comparisons amongst EMIC waves in different bands.

VRILLE Controls PDF Neuropeptide Accumulation and Arborization Rhythms in Small Ventrolateral Neurons to Drive Rhythmic Behavior in Drosophila.

PubMed

Gunawardhana, Kushan L; Hardin, Paul E

2017-11-20

In Drosophila, the circadian clock is comprised of transcriptional feedback loops that control rhythmic gene expression responsible for daily rhythms in physiology, metabolism, and behavior. The core feedback loop, which employs CLOCK-CYCLE (CLK-CYC) activators and PERIOD-TIMELESS (PER-TIM) repressors to drive rhythmic transcription peaking at dusk, is required for circadian timekeeping and overt behavioral rhythms. CLK-CYC also activates an interlocked feedback loop, which uses the PAR DOMAIN PROTEIN 1ε (PDP1ε) activator and the VRILLE (VRI) repressor to drive rhythmic transcription peaking at dawn. Although Pdp1ε mutants disrupt activity rhythms without eliminating clock function, whether vri is required for clock function and/or output is not known. Using a conditionally inactivatable transgene to rescue vri developmental lethality, we show that clock function persists after vri inactivation but that activity rhythms are abolished. The inactivation of vri disrupts multiple output pathways thought to be important for activity rhythms, including PDF accumulation and arborization rhythms in the small ventrolateral neuron (sLN v ) dorsal projection. These results demonstrate that vri acts as a key regulator of clock output and suggest that the primary function of the interlocked feedback loop in Drosophila is to drive rhythmic transcription required for overt rhythms. Copyright © 2017 Elsevier Ltd. All rights reserved.

On the origin of the 1-hour pulsations in the Saturn's magnetosphere

NASA Astrophysics Data System (ADS)

Rusaitis, L.; Walker, R. J.; Khurana, K. K.; Kivelson, M.

2016-12-01

The quasi-periodic pulsations of approximately 1-hour periodicity in the magnetic field and particle fluxes have been regularly detected in the outer Saturnian magnetosphere by the Cassini spacecraft since the orbital insertion in 2004 [Palmaerts, 2016; Roussos, 2016]. In this study we focus on the Cassini's magnetometer (MAG) and the Cassini Plasma Spectrometer (CAPS) data from the July 1st, 2004 to June 4th, 2012 (when the CAPS instrument was turned off). Throughout this 8-year period we find over 130 pulsation events in the MAG data, ranging in periodicity from 40 to 90 minutes, and having a typical amplitude of 0.5-1nT in the transverse (φ ) direction. The pulsations typically last 4-6 hours before decaying, and occur both in the dawn and dusk sectors during the crossings of the outer magnetosphere. We study the pulsations in the azimuthal magnetic field as signatures for the periodic enhancements detected in the CAPS data in the plasma temperature and densities. Additionally, we investigate a high temporal resolution 3-D MHD simulation of Saturn's magnetosphere to look for the signatures of these pulsations at the equivalent positions, and use the simulation results to suggest their physical origin and the triggering mechanism by varying the solar wind parameters.

Generation of EMIC Waves and Effects on Particle Precipitation During a Solar Wind Pressure Intensification with Bz > 0

NASA Astrophysics Data System (ADS)

Lessard, M.; Engebretson, M. J.; Spence, H. E.; Paulson, K. W.; Halford, A. J.; Millan, R. M.; Rodger, C. J.; Hendry, A.

2017-12-01

During geomagnetic storms, solar wind energy couples to the magnetosphere and drives the generation of electromagnetic ion cyclotron (EMIC) waves, which can then scatter energetic electrons and ions from the radiation belts. In the event described in this paper, the interplanetary magnetic field remained northward throughout the duration, a condition unfavorable for solar wind energy coupling through low latitude reconnection. While this resulted in SYM/H remaining positive, pressure fluctuations were directly transferred into and then propagated throughout the magnetosphere, generating EMIC waves on global scales. The generation mechanism presumably involved the development of temperature anisotropies via perpendicular pressure perturbations, as evidenced by strong correlations between the pressure variations and the intensifications of the waves globally. Electron precipitation was recorded by the BARREL balloons, although it did not have the same widespread signatures as the waves and, in fact, appears to have been quite patchy in character. Observations from Van Allen Probe-A (RBSP-A) satellite (at post midnight local time), showed clear butterfly distributions and it may be possible that the EMIC waves contributed to the development of these distribution functions. Ion precipitation was also recorded by the Polar-orbiting Operational Environmental Satellite (POES) satellites, though tended to be confined to the dawn-dusk meridians.

Immunity, Life and Dancing Starlings: A Physician's Perspective.

PubMed

Bercovich, Dani; Goodman, Geoffrey; Gershwin, M Eric

2016-08-01

Immune function is the most basic physiological process in humans and indeed throughout the animal kingdom. Interestingly, the vast majority of textbooks of physiology do not include a chapter on immunity. Our species survival is dependent on the diversity of the immune response and the ability for antigen presentation and effector mechanisms to be enormously promiscuous. As physicians, we are likely all too aware of how brief our life span is and the myriad of diseases and events that shorten it. It is not surprising that we question where our life comes from and our relationship within the universe. Many hypotheses have been offered regarding the likelihood that intelligent life exists elsewhere. We propose that such issues be discussed in the context of basic biologic observations on earth, such as the sight of a dense flock of tens of thousands of starlings maneuvering in rapid twists and turns at dusk before settling in trees for the night. The mathematical likelihood for life elsewhere was proposed by Frank Drake in a classic equation whose 'thesis' has stimulated the search for alien civilizations and the nature of life. A fundamental gap in this equation is the presence of a diverse immune response, a feature essential for survival of Life, presumably also extra-terrestrially.

How wide in magnetic local time is the cusp? An event study

NASA Astrophysics Data System (ADS)

Maynard, N. C.; Weber, E. J.; Weimer, D. R.; Moen, J.; Onsager, T.; Heelis, R. A.; Egeland, A.

1997-03-01

A unique pass of the DMSP F11 satellite, longitudinally cutting through the cusp and mantle, combined with simultaneous optical measurements of the dayside cusp from Svalbard has been used to determine the width in local time of the cusp. We have shown from this event study that the cusp was at least 3.7 hours wide in magnetic local time. These measurements provide a lower limit for the cusp width. The observed cusp optical emissions are relatively constant, considering the processes which lead to the 630.0 nm emissions, and require precipitating electron flux to be added each minute during the DMSP pass throughout the local time extent observed by the imaging photometer and probably over the whole extent of the cusp defined by DMSP data. We conclude that the electron fluxes which produce the cusp aurora are from a process which must have been operable sometime during each minute but could have had both temporal and spatial variations. The measured width along with models of cusp precipitation provide the rationale to conclude that the region of flux tube opening in the dayside merging process involves the whole frontside magnetopause and can extend beyond the dawn-dusk terminator. The merging process for this event was found to be continuous, although spatially and temporally variable.

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.

Daily Activity and Nest Occupation Patterns of Fox Squirrels (Sciurus niger) throughout the Year.

PubMed

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.

Believable Characters

NASA Astrophysics Data System (ADS)

El-Nasr, Magy Seif; Bishko, Leslie; Zammitto, Veronica; Nixon, Michael; Vasiliakos, Athanasios V.; Wei, Huaxin

The interactive entertainment industry is one of the fastest growing industries in the world. In 1996, the U.S. entertainment software industry reported 2.6 billion in sales revenue, this figure has more than tripled in 2007 yielding 9.5 billion in revenues [1]. In addition, gamers, the target market for interactive entertainment products, are now reaching beyond the traditional 8-34 year old male to include women, Hispanics, and African Americans [2]. This trend has been observed in several markets, including Japan, China, Korea, and India, who has just published their first international AAA title (defined as high quality games with high budget), a 3D third person action game: Ghajini - The Game [3]. The topic of believable characters is becoming a central issue when designing and developing games for today's game industry. While narrative and character were considered secondary to game mechanics, games are currently evolving to integrate characters, narrative, and drama as part of their design. One can see this pattern through the emergence of games like Assassin's Creed (published by Ubisoft 2008), Hotel Dusk (published by Nintendo 2007), and Prince of Persia series (published by Ubisoft), which emphasized character and narrative as part of their design.

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.

A statistical study of single crest phenomenon in the equatorial ionospheric anomaly region using Swarm A satellite

NASA Astrophysics Data System (ADS)

Fathy, Adel; Ghamry, Essam

2017-03-01

Though the Equatorial Ionospheric Anomaly (EIA) is represented by two crests within ±15° latitude, a single crest is also observed in the entire ionosphere. Few studies have addressed single crest phenomena. A statistical study of 2237 single crest phenomenon from the in situ electron density measurements of Swarm A satellite was investigated during December 2013-December 2015. Our analysis focused on local time, seasonal, and both geographic and geomagnetic latitudinal variations. Our results show the following observations: 1 - The maximum number of events peaks mainly in the dayside region around 0800-1200 LT and these occur mainly within the magnetic equator. 2 - The maximum amplitude of the single crests take place most prominently during equinoxes. 3 - The majority of single crests occur in the northern hemisphere. 4 - The seasonal distribution of the events shows that the summer events are located further from the magnetic equator in the northern hemisphere and shift their locations into the southern hemisphere in winter, while spring events are centered along the magnetic equator. 5 - Dayside single crest events appear close to the magnetic equator and more centered on the equator in winter season. 6 - Dawn, night and dusk side events reverse their location from northern hemisphere in summer to southern hemisphere in winter.

Simulation Studies for a Space-Based CO2 Lidar Mission

NASA Technical Reports Server (NTRS)

Kawa, S. R.; Mao, J.; Abshire, J. B.; Collatz, G. J.; Sun, X.; Weaver, C. J.

2010-01-01

We report results of initial space mission simulation studies for a laser-based, atmospheric CO2 sounder, which are based on real-time carbon cycle process modelling and data analysis. The mission concept corresponds to the Active Sensing of CO2 Emissions over Nights, Days and Seasons (ASCENDS) recommended by the US National Academy of Sciences' Decadal Survey. As a pre-requisite for meaningful quantitative evaluation, we employ a CO2 model that has representative spatial and temporal gradients across a wide range of scales. In addition, a relatively complete description of the atmospheric and surface state is obtained from meteorological data assimilation and satellite measurements. We use radiative transfer calculations, an instrument model with representative errors and a simple retrieval approach to quantify errors in 'measured' CO2 distributions, which are a function of mission and instrument design specifications along with the atmospheric/surface state. Uncertainty estimates based on the current instrument design point indicate that a CO2 laser sounder can provide data consistent with ASCENDS requirements and will significantly enhance our ability to address carbon cycle science questions. Test of a dawn/dusk orbit deployment, however, shows that diurnal differences in CO2 column abundance, indicative of plant photosynthesis and respiration fluxes, will be difficult to detect

Geomagnetic responses to the solar wind and the solar activity

NASA Technical Reports Server (NTRS)

Svalgaard, L.

1975-01-01

Following some historical notes, the formation of the magnetosphere and the magnetospheric tail is discussed. The importance of electric fields is stressed and the magnetospheric convection of plasma and magnetic field lines under the influence of large-scale magnetospheric electric fields is outlined. Ionospheric electric fields and currents are intimately related to electric fields and currents in the magnetosphere and the strong coupling between the two regions is discussed. The energy input of the solar wind to the magnetosphere and upper atmosphere is discussed in terms of the reconnection model where interplanetary magnetic field lines merge or connect with the terrestrial field on the sunward side of the magnetosphere. The merged field lines are then stretched behind earth to form the magnetotail so that kinetic energy from the solar wind is converted into magnetic energy in the field lines in the tail. Localized collapses of the crosstail current, which is driven by the large-scale dawn/dusk electric field in the magnetosphere, divert part of this current along geomagnetic field lines to the ionosphere, causing substorms with auroral activity and magnetic disturbances. The collapses also inject plasma into the radiation belts and build up a ring current. Frequent collapses in rapid succession constitute the geomagnetic storm.

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.

Differences in competitive ability for the occupancy of shelters in triatomines.

PubMed

Zacharias, C A; Minoli, S A; Manrique, G

2017-09-01

Triatomines (Hemiptera: Reduviidae: Triatominae) are nocturnal blood-sucking insects. During daylight hours they remain in an akinetic state inside their shelters, whereas at dusk they become active and move outside. When they are outside their shelters during the photophase, triatomines are vulnerable to diurnal predators and the period just before dawn is critical to their survival. This work analyses the existence of competitive interactions involved in the occupancy of shelters by triatomines. Behavioural assays were performed in which nymphs of different stages, nutritional status or species were released in an experimental arena containing a space-limited artificial shelter. The proportions of individuals occupying the shelter during the photophase were quantified to estimate the competitive abilities of each stage and species. Intraspecific comparisons showed higher levels of shelter occupancy for fourth over fifth instars and fed over unfed nymphs of Triatoma infestans. Interspecific comparisons showed higher rates of shelter occupancy for Triatoma sordida in comparison with T. infestans, and for T. infestans over Rhodnius prolixus. Arrival order was also relevant to determining shelter occupancy levels: early arrival was advantageous in comparison with later arrival. The study of intra- and interspecific competitive interactions for shelter occupancy provides relevant information about colonization and recolonization processes in the natural environments of triatomines. © 2017 The Royal Entomological Society.

Unusual Observations during the December 2006 Solar Energetic Particle Events within an Interplanetary Coronal Mass Ejection at 1 AU

NASA Astrophysics Data System (ADS)

Mulligan, T.; Blake, J. B.; Mewaldt, R. A.; Leske, R. A.

2008-08-01

In mid December 2006 several flares on the Sun occurred in rapid succession, spawning several CMEs and bathing the Earth in multiple solar energetic particle (SEP) events. One such SEP event occurring on December 14 was observed at the Earth just as an interplanetary CME (ICME) from a previous flare on December 13 was transiting the Earth. Although solar wind observations during this time show typical energetic proton fluxes from the prior SEP event and IP shock driven ahead of the ICME, as the ICME passes the Earth unusual energetic particle signatures are observed. Measurements from ACE, Wind, and STEREO show proton flux variations at energies ranging from ~3 MeV up to greater than 70 MeV. Energetic electron signatures from ACE show similar variations. Within the Earth's magnetosphere Polar HIST also sees these proton flux variations at energies greater than 10 MeV while crossing open field lines in the southern polar cap. Although no such variation in the energetic proton flux is observed at the GOES 11 spacecraft in geosynchronous orbit near the subsolar region, differential fluxes observed at GOES 11 and GOES 12 in the 15-40 MeV energy range do show some variability, indicating the signature is observable near dawn and dusk.

Effects of Auroral Potential Drops on Field-Aligned Currents and Nightside Reconnection Dynamos

NASA Astrophysics Data System (ADS)

Lotko, W.; Xi, S.; Zhang, B.; Wiltberger, M. J.; Lyon, J.

2016-12-01

The reaction of the magnetosphere-ionosphere system to dynamic auroral potential drops is investigated using the Lyon-Fedder-Mobarry global model and, for the first time in a global simulation, including the dissipative load of field-aligned potential drops in the low-altitude boundary condition. This extra load reduces the demand for field-aligned current (j||) from nightside reconnection dynamos. The system adapts by forcing the nightside x-line closer to Earth to reduce current lensing (j||/B = constant) at the ionosphere, with the plasma sheet undergoing additional contraction during substorm recovery and steady magnetospheric convection. For steady and moderate solar wind driving and with constant ionospheric conductance, the cross-polar cap potential and hemispheric field-aligned current are lower by approximately the ratio of the peak field-aligned potential drop to the cross polar cap potential (10-15%) when potential drops are included. Hemispheric ionospheric Joule dissipation is less by 8%, while the area-integrated, average work done on the fluid by the reconnecting magnetotail field increases by 50% within |y| < 8 RE. Effects on the nightside plasma sheet include: (1) an average x-line 4 RE closer to Earth; (2) a 12% higher mean reconnection rate; and (3) dawn-dusk asymmetry in reconnection with a 17% higher rate in the premidnight sector.

Effects of auroral potential drops on plasma sheet dynamics

NASA Astrophysics Data System (ADS)

Xi, Sheng; Lotko, William; Zhang, Binzheng; Wiltberger, Michael; Lyon, John

2016-11-01

The reaction of the magnetosphere-ionosphere system to dynamic auroral potential drops is investigated using the Lyon-Fedder-Mobarry global model including, for the first time in a global simulation, the dissipative load of field-aligned potential drops in the low-altitude boundary condition. This extra load reduces the field-aligned current (j||) supplied by nightside reconnection dynamos. The system adapts by forcing the nightside X line closer to Earth, with a corresponding reduction in current lensing (j||/B = constant) at the ionosphere and additional contraction of the plasma sheet during substorm recovery and steady magnetospheric convection. For steady and moderate solar wind driving and with constant ionospheric conductance, the cross polar cap potential and hemispheric field-aligned current are lower by approximately the ratio of the peak field-aligned potential drop to the cross polar cap potential (10-15%) when potential drops are included. Hemispheric ionospheric Joule dissipation is less by 8%, while the area-integrated, average work done on the fluid by the reconnecting magnetotail field increases by 50% within |y| < 8 RE. Effects on the nightside plasma sheet include (1) an average X line 4 RE closer to Earth; (2) a 12% higher mean reconnection rate; and (3) dawn-dusk asymmetry in reconnection with a 17% higher rate in the premidnight sector.

Measurement of hydrogen peroxide and organic hydroperoxide concentrations during autumn in Beijing, China.

PubMed

Zhang, Qingyu; Liu, Jiaoyu; He, Youjiang; Yang, Jiaying; Gao, Jian; Liu, Houfeng; Tang, Wei; Chen, Yizhen; Fan, Wenhao; Chen, Xuan; Chai, Fahe; Hatakeyama, Shiro

2018-02-01

Gaseous peroxides play important roles in atmospheric chemistry. To understand the pathways of the formation and removal of peroxides, atmospheric peroxide concentrations and their controlling factors were measured from 7:00 to 20:00 in September, October, and November 2013 at a heavily trafficked residential site in Beijing, China, with average concentrations of hydrogen peroxide (H 2 O 2 ) and methyl hydroperoxide (MHP) at 0.55ppb and 0.063ppb, respectively. H 2 O 2 concentrations were higher in the afternoon and lower in the morning and evening, while MHP concentrations did not exhibit a regular diurnal pattern. Both H 2 O 2 and MHP concentrations increased at dusk in most cases. Both peroxides displayed monthly variations with higher concentrations in September. These results suggested that photochemical activity was the main controlling factor on variations of H 2 O 2 concentrations during the measurement period. Increasing concentrations of volatile organic compounds emitted by motor vehicles were important contributors to H 2 O 2 and MHP enrichment. High levels of H 2 O 2 and MHP concentrations which occurred during the measurement period probably resulted from the transport of a polluted air mass with high water vapor content passing over the Bohai Bay, China. Copyright © 2017. Published by Elsevier B.V.

Diet and feeding ecology of invasive icefish Neosalanx taihuensis in Erhai Lake, a Chinese plateau mesoeutrophicated lake

NASA Astrophysics Data System (ADS)

Hu, Cuilin; Guo, Longgen; Wang, Shengrui

2015-03-01

A comprehensive study of the invasive icefish Neosalanx taihuensis feeding ecology in Erhai Lake was conducted from November 2009 to October 2010. Prey items in the guts of the icefish sampled varied significantly according to season. This finding suggests a relationship between fluctuations in available prey in the environment and selective feeding by icefish. N. taihuensis preferred large-sized zooplankton, such as Daphnia and calanoids. Additionally, the gut fullness values differed significantly ( P<0.001) among sampling times. To compare the values at different times, samples were taken over a 24 h period every 2 months for the entire year. The feeding activities of the fish were concentrated either in the morning (8:00) and/or at dusk (20:00), except in September 2010. This finding can be explained primarily by the variation in optimum light intensity. Daily N. taihuensis zooplankton consumption varied significantly, both diurnally and among seasons. The daily consumption values ranged from 0.089 to 0.237 g (wet weight) per 100 g wet fish weight in temperatures between 11.50°C and 24.68°C. This is the first report of diel feeding periodicity and daily food consumption of icefish in their invaded ecosystems.

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.

Impact on Space-Based Navigation Systems of Large Magnetic Storm-Driven Nighttime Flows in the Mid-latitude Ionosphere

NASA Astrophysics Data System (ADS)

Basu, S.; Makela, J.; Doherty, P.; Wright, J.; Coster, A.

2008-05-01

Multi-technique ground and space-based studies conducted during the intense magnetic storm of 7-8 November 2004 yielded a hitherto little-recognized means of impacting space-based navigation systems such as the Federal Aviation Administration's Wide Area Augmentation System (WAAS) that operates in the North American sector. During this superstorm, no appreciable storm-enhanced density gradients were observed. Rather the mid-latitude region was enveloped by the auroral oval and the ionospheric trough within which the sub auroral polarization stream (SAPS) was confined during the local dusk to nighttime hours. This shows that such processes can partially disable GPS-based navigation systems for many hours even in the absence of appreciable TEC gradients, provided an intense flow channel is present in the ionosphere during nighttime hours, as revealed by DMSP and Dynasonde drift results. The competing effects of irregularity amplitude ΔN/N, the background F-region density and the magnitude of SAPS or auroral convection are discussed in establishing the extent of the region of impact on the WAAS system. In order to provide inputs to operational space weather models, the current GPS network used for measuring the total electron content in North America and elsewhere should be augmented by instruments that can measure ionospheric drifts.

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.

Energetic electron acceleration and injection during dipolarization events in Mercury's magnetotail

NASA Astrophysics Data System (ADS)

Dewey, R. M.; Slavin, J. A.; Raines, J. M.; Baker, D. N.; Lawrence, D. J.

2017-12-01

MESSENGER frequently observed bursts of energetic electrons (>10 keV to 300 keV) within Mercury's miniature terrestrial-like magnetosphere. These bursts are observed most often in the post-midnight sector near the magnetic equator, suggestive of the acceleration and injection of electrons from the magnetotail and their eastward drift about the planet. We use the Gamma-Ray Spectrometer's high-time resolution (10 ms) energetic electron measurements to examine the relationship between energetic electron injections and magnetospheric dynamics in Mercury's magnetotail. We find that these electron injections were observed most frequently in association with magnetic field dipolarization. Between March 2013 and April 2015, we identified 2976 magnetotail electron events of which 538 were coincident with the leading edge of a dipolarization event. These dipolarization fronts were detected on the basis of their rapid ( 2 s) increase in the northward component of the tail magnetic field (ΔBz 30 nT), which typically persists for 10 s. We find electrons experience brief, yet intense, betatron and Fermi acceleration during these dipolarization events, reaching energies 160 keV and contributing to nightside precipitation. Dipolarization events, and subsequently, the electron acceleration associated with them, display a strong dawn-dusk asymmetry, suggestive of a post-midnight maximum in magnetotail reconnection.

Magnetosphere and ionosphere response to a positive-negative pulse pair of solar wind dynamic pressure

NASA Astrophysics Data System (ADS)

Tian, A.; Degeling, A. W.

2017-12-01

Simulations and observations had shown that single positive/negative solar wind dynamic pressure pulse would excite geomagnetic impulsive events along with ionosphere and/or magnetosphere vortices which are connected by field aligned currents(FACs). In this work, a large scale ( 9min) magnetic hole event in solar wind provided us with the opportunity to study the effects of positive-negative pulse pair (△p/p 1) on the magnetosphere and ionosphere. During the magnetic hole event, two traveling convection vortices (TCVs, anti-sunward) first in anticlockwise then in clockwise rotation were detected by geomagnetic stations located along the 10:30MLT meridian. At the same time, another pair of ionospheric vortices azimuthally seen up to 3 MLT first in clockwise then in counter-clockwise rotation were also appeared in the afternoon sector( 14MLT) and centered at 75 MLAT without obvious tailward propagation feature. The duskside vortices were also confirmed in SuperDARN radar data. We simulated the process of magnetosphere struck by a positive-negative pulse pair and it shows that a pair of reversed flow vortices in the magnetosphere equatorial plane appeared which may provide FACs for the vortices observed in ionosphere. Dawn dusk asymmetry of the vortices as well as the global geomagnetism perturbation characteristics were also discussed.

Observations of subauroral ion drift (SAID) occurrence statistics and associated ionospheric conditions measured by the Defense Meteorological Satellite Program (DMSP) and Dynamics Explorer 2 (DE-2).

NASA Astrophysics Data System (ADS)

Landry, R. G.; Anderson, P. C.

2017-12-01

Subauroral ion drifts (SAID) are a phenomenon sometimes observed in the subauroral ionosphere in dusk to post-midnight magnetic local time sectors during magnetically active periods characterized by strong poleward electric fields that drive westward ion drifts greater than 1 km/s. SAIDs typically will span 1-2 degrees magnetic latitude and several hours in magnetic local time. SAIDs are often observed colocated with the midlatitude trough. The strong electric field can act to reduce the ionospheric conductivity further through enhanced recombination and vertical transport. The theory that SAIDs are generated by ionospheric Pedersen currents fed by ring current driven field-aligned currents (FAC) requires the decreased conductance associated with the midlatitude trough to produce the latitudinally narrow, large amplitude SAID electric field. Using Dynamics Explorer 2 (DE 2) plasma measurements of SAIDs from altitudes of 200 to 1000 km, we investigate the statistical variation of the ionospheric composition, temperature, and vertical ion drifts as a function of altitude. Using Defense Meteorological Satellite Program (DMSP) measurements from 1987-2012, we extend the empirical study at the DMSP altitude of 830 km to investigate how season, longitude, and any ionospheric preconditioning before SAID formation affect the likelihood of SAID occurrence and coincidence with FACs and ion density troughs.

Patterns and Processes in Nocturnal and Crepuscular Pollination Services.

PubMed

Borges, Renee M; Somanathan, Hema; Kelber, Almut

2016-12-01

Night, dawn, and dusk have abiotic features that differ from the day. Illumination, wind speeds, turbulence, and temperatures are lower while humidity may be higher at night. Nocturnal pollination occurred in 30% of angiosperm families across 68% of orders, 97% of families with C3, two-thirds of families with crassulacean acid metabolism (CAM), and 71% dicot families with C4 photosynthesis. Despite its widespread occurence, nocturnal pollination occurs in more families with xerophytic adaptations than helophytes or mesophytes, suggesting that nocturnal flowering is primarily an adaptation to water stress since flowering is a water-intensive process. We propose the arid or water stress hypothesis for nocturnal flowering suggesting that plants facing water stress in a habitat (e.g., deserts) or a habitat stratum (e.g., upper canopy for epiphytes) gain a selective advantage by nocturnal flowering by reducing water loss through evapotranspiration, leading to larger flowers that provide more nectar or other resources, to support pollinators with higher rewards. Contrary to the wide taxonomic occurrence of nocturnal flowering, few animal taxa serve as nocturnal pollinators. We discuss the sensory and physiological abilities that enable pollinator movement, navigation, and detection of flowers within the nocturnal temporal niche and present a unified framework for investigation of nocturnal flowering and pollination.

Fauna and Geographical Distribution of Scorpions in Ilam Province, South Western Iran.

PubMed

Sharifinia, Narges; Gowhari, Iman; Hoseiny-Rad, Manijeh; Aivazi, Ali Ashraf

2017-06-01

Scorpions' stings and their own mortalities place them among the most important health and medical problems. The dreadful features and especially their poisonous stings are considered a major cause of human stress and abhorrence/phobia. The current study aimed to study the scorpion fauna of Ilam Province, south western Iran in order to manage scorpionism related problems. In this field-laboratory investigation during March 2014 to February 2015, different parts of Ilam Province were surveyed. Nine sampling parts were selected based on geographical situation, scorpionism reports, weather, flora, and local data. Capturing scorpion was done employing a black light, and a long forceps from dusk to midnight. The collected scorpions were placed to 70% ethyl alcohol. All specimens were determined based on the valid taxonomic keys, furthermore their sexes were studied. Out of the 391 collected scorpions, 11 species were identified as follows: Hottentotta saulcyi , Mesobuthus eupeus , Compsobuthus matthiesseni , Razianus zarudnyi , Hemiscorpius lepturus , Androctonus crassicauda , Orthochirus iranus , Odontobuthus bidentatus , Buthacus macrocentrus , Scorpio maurus , and Polisius persicus . Eleven species of Buthidae, Scorpionidae and Hemiscorpiidae families from high risk areas were identified. Despite the low surface of the province, such different species reveals a diverse scorpion fauna that, in turn, shows good and suitable habits of scorpions, as considered by health staff.

Dancing in the dark: darkness as a signal in plants.

PubMed

Seluzicki, Adam; Burko, Yogev; Chory, Joanne

2017-11-01

Daily cycles of light and dark provide an organizing principle and temporal constraints under which life on Earth evolved. While light is often the focus of plant studies, it is only half the story. Plants continuously adjust to their surroundings, taking both dawn and dusk as cues to organize their growth, development and metabolism to appropriate times of day. In this review, we examine the effects of darkness on plant physiology and growth. We describe the similarities and differences between seedlings grown in the dark versus those grown in light-dark cycles, and the evolution of etiolated growth. We discuss the integration of the circadian clock into other processes, looking carefully at the points of contact between clock genes and growth-promoting gene-regulatory networks in temporal gating of growth. We also examine daily starch accumulation and degradation, and the possible contribution of dark-specific metabolic controls in regulating energy and growth. Examining these studies together reveals a complex and continuous balancing act, with many signals, dark included, contributing information and guiding the plant through its life cycle. The extraordinary interconnection between light and dark is manifest during cycles of day and night and during seedling emergence above versus below the soil surface. © 2017 John Wiley & Sons Ltd.

Fast Flows in the Magnetotail and Energetic Particle Transport: Multiscale Coupling in the Magnetosphere

NASA Astrophysics Data System (ADS)

Lin, Y.; Wang, X.; Fok, M. C. H.; Buzulukova, N.; Perez, J. D.; Chen, L. J.

2017-12-01

The interaction between the Earth's inner and outer magnetospheric regions associated with the tail fast flows is calculated by coupling the Auburn 3-D global hybrid simulation code (ANGIE3D) to the Comprehensive Inner Magnetosphere/Ionosphere (CIMI) model. The global hybrid code solves fully kinetic equations governing the ions and a fluid model for electrons in the self-consistent electromagnetic field of the dayside and night side outer magnetosphere. In the integrated computation model, the hybrid simulation provides the CIMI model with field data in the CIMI 3-D domain and particle data at its boundary, and the transport in the inner magnetosphere is calculated by the CIMI model. By joining the two existing codes, effects of the solar wind on particle transport through the outer magnetosphere into the inner magnetosphere are investigated. Our simulation shows that fast flows and flux ropes are localized transients in the magnetotail plasma sheet and their overall structures have a dawn-dusk asymmetry. Strong perpendicular ion heating is found at the fast flow braking, which affects the earthward transport of entropy-depleted bubbles. We report on the impacts from the temperature anisotropy and non-Maxwellian ion distributions associated with the fast flows on the ring current and the convection electric field.

Outbreak of pulmonary histoplasmosis involving a group of four Polish travellers returning from Ecuador.

PubMed

Kajfasz, Piotr; Basiak, Wojciech

2012-01-01

Exploring caves is, without doubt, a very exciting adventure; however, it carries some dangers. Three of four travellers were admitted to hospital with lung changes after returning from Ecuador, successively. Epidemiological studies revealed that the travellers visited caves infested by bats, and had contact with bats' guano. They gave a history of fever, fatigue, myalgia, dry cough, and chest pain during the stay or just after returning from Ecuador. In two patients, symptoms persisted in mild nature. Chest X-ray films showed diffuse nodules (coin-like lesions) in the lungs in each case. Histoplasmosis was taken into consideration. Differential diagnosis included paragonimiasis, pulmonary tuberculosis, and pulmonary infection of other causes. Direct examination of sputum was negative. Cultures were negative. Final diagnosis was made on epidemiological histories, as well as typical radiological changes, and was supported by positive tests for antibodies to Histoplasma capsulatum. Immunodiffusion test (ID), complement fixation test (CFTs), and Western blot test were positive. In two cases antifungal treatment was established. Ketoconazole followed by Itraconazole were used. Persons who are going to explore caves should be equipped with anti-dusk masks to prevent pulmonary histoplasmosis. The threat of Histoplasma capsulatum infection in bat-inhabited caves should be emphasized to travellers and also to physicians.

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).

Contradiction and Complacency Shape Attitudes towards the Toll of Roads on Wildlife

PubMed Central

Ramp, Daniel; Wilson, Vanessa K.; Croft, David B.

2016-01-01

Simple Summary Mitigating the toll of roads on wildlife can become difficult when awareness and exposure does not result in willingness to change driving behaviour. Using a self-reporting questionnaire, we found that while most drivers view wildlife vehicle collisions as a serious issue, increasing exposure to collisions decreased this attitude and it did not translate into willingness to adopt additional mitigation strategies. In addition, despite most respondents stating they routinely drive slower when collision risk is high (at dusk and dawn), our assessment of driving trends via traffic speeds suggested this sentiment was not generally adhered to. We suggest that competing priorities and complacency when risk to people is low may adversely affect willingness to prevent collisions. Abstract Most people in the world now live in cities. Urbanisation simultaneously isolates people from nature and contributes to biodiversity decline. As cities expand, suburban development and the road infrastructure to support them widens their impact on wildlife. Even so, urban communities, especially those on the peri-urban fringe, endeavour to support biodiversity through wildlife friendly gardens, green spaces and corridors, and conservation estates. On one hand, many who live on city fringes do so because they enjoy proximity to nature, however, the ever increasing intrusion of roads leads to conflict with wildlife. Trauma (usually fatal) to wildlife and (usually emotional and financial) to people ensues. Exposure to this trauma, therefore, should inform attitudes towards wildlife vehicle collisions (WVC) and be linked to willingness to reduce risk of further WVC. While there is good anecdotal evidence for this response, competing priorities and better understanding of the likelihood of human injury or fatalities, as opposed to wildlife fatalities, may confound this trend. In this paper we sought to explore this relationship with a quantitative study of driver behaviour and

Seasonal variation of temporal niche in wild owl monkeys (Aotus azarai azarai) of the Argentinean Chaco: a matter of masking?

PubMed

Erkert, Hans G; Fernandez-Duque, Eduardo; Rotundo, Marcelo; Scheideler, Angelika

2012-07-01

Among the more than 40 genera of anthropoid primates (monkeys, apes, and humans), only the South American owl monkeys, genus Aotus, are nocturnal. However, the southernmostly distributed species, Aotus azarai azarai, of the Gran Chaco may show considerable amounts of its 24-h activity during bright daylight. Due to seasonal changes in the duration of photophase and climatic parameters in their subtropical habitat, the timing and pattern of their daily activity are expected to show significant seasonal variation. By quantitative long-term activity recordings with Actiwatch AW4 accelerometer data logger devices of 10 wild owl monkeys inhabiting a gallery forest in Formosa, Argentina, the authors analyzed the seasonal variation in the temporal niche and activity pattern resulting from entrainment and masking of the circadian activity rhythm by seasonally and diurnally varying environmental factors. The owl monkeys always displayed a distinct bimodal activity pattern, with prominent activity bouts and peaks during dusk and dawn. Their activity rhythm showed distinct lunar and seasonal variations in the timing and daily pattern. During the summer, the monkeys showed predominantly crepuscular/nocturnal behavior, and a crepuscular/cathemeral activity pattern with similar diurnal and nocturnal activity levels during the cold winter months. The peak times of the evening and morning activity bouts were more closely related to the times of sunset and sunrise, respectively, than activity-onset and -offset. Obviously, they were better circadian markers for the phase position of the entrained activity rhythm than activity-onset and -offset, which were subject to more masking effects of environmental and/or internal factors. Total daily activity was lowest during the two coldest lunar months, and almost twice as high during the warmest months. Nighttime (21:00-06:00 h) and daytime (09:00-18:00 h) activity varied significantly across the year, but in an opposite manner. Highest

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.

Observation of Neutral Sodium Above Mercury During the Transit of November 8, 2006

NASA Technical Reports Server (NTRS)

Potter, A. E.; Killen, R. M.; Reardon, Kevin P.; Bida, T. A.

2013-01-01

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 around the shadow of Mercury. The sodium absorption fell off exponentially with altitude up to about 600 km. However there were regions around north and south polar-regions where relatively uniform sodium absorptions extended above 1000 km. We corrected the 0-600 km altitude profiles for seeing blur using the measured point spread function. Analysis of the corrected altitude distributions yielded surface densities, zenith column densities, temperatures and scale heights for sodium all around the planet. Sodium absorption on the dawn side equatorial terminator was less than on the dusk side, different from previous observations of the relative absorption levels. We also determined Earthward velocities for sodium atoms, and line widths for the absorptions. Earthward velocities resulting from radiation pressure on sodium averaged 0.8 km/s, smaller than a prediction of 1.5 km/s. Most line widths were in the range of 20 mA after correction for instrumental broadening, corresponding to temperatures in the range of 1000 K.

Simulated Prompt Acceleration of Multi-MeV Electrons by the 17 March 2015 Interplanetary Shock

NASA Astrophysics Data System (ADS)

Hudson, Mary; Jaynes, Allison; Kress, Brian; Li, Zhao; Patel, Maulik; Shen, Xiao-Chen; Thaller, Scott; Wiltberger, Michael; Wygant, John

2017-10-01

Prompt enhancement of relativistic electron flux at L = 3-5 has been reported from Van Allen Probes Relativistic Electron Proton Telescope (REPT) measurements associated with the 17 March 2015 interplanetary shock compression of the dayside magnetosphere. Acceleration by ˜1 MeV is inferred on less than a drift timescale as seen in prior shock compression events, which launch a magnetosonic azimuthal electric field impulse tailward. This impulse propagates from the dayside around the flanks accelerating electrons in drift resonance at the dusk flank. Such longitudinally localized acceleration events produce a drift echo signature which was seen at >1 MeV energy on both Van Allen Probe spacecraft, with sustained observations by Probe B outbound at L = 5 at 2100 MLT at the time of impulse arrival, measured by the Electric Fields and Waves instrument. MHD test particle simulations are presented which reproduce drift echo features observed in the REPT measurements at Probe B, including the energy and pitch angle dependence of drift echoes observed. While the flux enhancement was short lived for this event due to subsequent inward motion of the magnetopause, stronger events with larger electric field impulses, as observed in March 1991 and the Halloween 2003 storm, produce enhancements which can be quantified by the inward radial transport and energization determined by the induction electric field resulting from dayside compression.

Multispacecraft Observations and 3D Structure of Electromagnetic Electron Phase-Space Holes

NASA Astrophysics Data System (ADS)

Holmes, J.; Ahmadi, N.; Ergun, R.; Wilder, F. D.; Newman, D. L.; Le Contel, O.; Torbert, R. B.; Burch, J. L.

2017-12-01

Electron phase-space holes are nonlinear plasma structures characterized by a unipolar trapping potential with a radial electric field. They commonly form from beam instabilities and other turbulent processes in many plasma environments. Due to their strong fields and long lifetimes, it has been hypothesized that phase-space holes can carry energy over long distances, contribute to large-scale currents, and accelerate individual particles to high energies. With electromagnetic field measurements at high cadence and precision on more than two spacecraft, we can compare the real 3D structure of electron phase-space holes to the models suggested by Andersson et al. (2009) and Treumann and Baumjohann (2012). In this case study, we consider a train of correlated electron phase-space holes observed by all four MMS spacecraft on the dusk flank within the magnetosphere. A number of the holes appear to pass directly through the 7 km tetrahedron formation. We use this data to compute the holes' phase velocity vector relative to the background magnetic field, and quantify their internal currents and associated magnetic moments. For these weak magnetic signatures, we find that the contribution from internal E×B0 currents is comparable to the v×E effect. This study will be interesting to compare with MMS observations in the magnetotail, which are expected to capture large, semi-relativistic phase-space holes with a strong magnetic component.

Environmental Influences on Patterns of Vertical Movement and Site Fidelity of Grey Reef Sharks (Carcharhinus amblyrhynchos) at Aggregation Sites

PubMed Central

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. PMID:23593193

Emergence periodicity of Phlebotomus argentipes annandale and brunetti (Diptera: psychodidae): A laboratory study.

PubMed

Dinesh, D S; Singh, A; Kumar, V; Kesari, S; Kumar, A J; Kishore, K; Roy, S P; Bhattacharya, S K; Das, P

2009-12-01

Phlebotomus argentipes Annandale and Brunetti (Diptera: Psychodidae) is the vector for visceral leishmaniasis in India. The aspects of its biology such as feeding and man vector contact are associated with emergence periodicity of the adult. Hence, the present study was made to find out the actual emergence period of P. argentipes. Wild caught P. argentipes were confined in the rearing pots inside laboratory. The newly emerged adults were collected at hourly intervals and released in to separate polythene bags and were held at 4°C till death. Sand flies were segregated sex-wise after the death under a microscope. The emergence of adult was observed throughout the day. However, the male preferred dawn emergence and the female the dusk. Two peaks of emergence were found in a day; first one in the morning (0900h) and the second one in the evening (1800h). The ratio of both sexes was found to be about equal. The emergence of adult was found to be 77% out of total eggs laid, which was completed within 7-10 days from the 1st day of emergence under laboratory conditions (25°C to 31°C and 70% to 75% relative humidity). This study has important bearings to find out the actual time for personal protection against biting of sand flies to prevent the transmission of Kala-azar.

Modeling Io's Sublimation-Driven Atmosphere: Gas Dynamics and Radiation Emission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walker, Andrew C.; Goldstein, David B.; Varghese, Philip L.

2008-12-31

Io's sublimation-driven atmosphere is modeled using the direct simulation Monte Carlo method. These rarefied gas dynamics simulations improve upon earlier models by using a three-dimensional domain encompassing the entire planet computed in parallel. The effects of plasma impact heating, planetary rotation, and inhomogeneous surface frost are investigated. Circumplanetary flow is predicted to develop from the warm subsolar region toward the colder night-side. The non-equilibrium thermal structure of the atmosphere, including vibrational and rotational temperatures, is also presented. Io's rotation leads to an asymmetric surface temperature distribution which is found to strengthen circumplanetary flow near the dusk terminator. Plasma heating ismore » found to significantly inflate the atmosphere on both day- and night-sides. The plasma energy flux also causes high temperatures at high altitudes but permits relatively cooler temperatures at low altitudes near the dense subsolar point due to plasma energy depletion. To validate the atmospheric model, a radiative transfer model was developed utilizing the backward Monte Carlo method. The model allows the calculation of the atmospheric radiation from emitting/absorbing and scattering gas using an arbitrary scattering law and an arbitrary surface reflectivity. The model calculates the spectra in the {nu}{sub 2} vibrational band of SO{sub 2} which are then compared to the observational data.« less

The Effects of High Frequency ULF Wave Activity on the Spectral Characteristics of Coherent HF Radar Returns

NASA Astrophysics Data System (ADS)

Wright, D. M.; Yeoman, T. K.; Woodfield, E. E.

2003-12-01

It is now a common practice to employ ground-based radars in order to distinguish between those regions of the Earth's upper atmosphere which are magnetically conjugate to open and closed field lines. Radar returns from ionospheric irregularities inside the polar cap and cusp regions generally exhibit large spectral widths in contrast to those which exist on closed field lines at lower latitudes. It has been suggested that the so-called Spectral Width Boundary (SWB) might act as a proxy for the open-closed field line boundary (OCFLB), which would then be an invaluable tool for investigating reconnection rates in the magnetosphere. The exact cause of the increased spectral widths observed at very high latitudes is still subject to considerable debate. Several mechanisms have been proposed. This paper compares a dusk-sector interval of coherent HF radar data with measurements made by an induction coil magnetometer located at Tromso, Norway (66° N geomagnetic). On this occasion, a series of transient regions of radar backscatter exhibiting large spectral widths are accompanied by increases in spectral power of ULF waves in the Pc1-2 frequency band. These observations would then, seem to support the possibility that high frequency magnetospheric wave activity at least contribute to the observed spectral characteristics and that such wave activity might play a significant role in the cusp and polar cap ionospheres.

Weberized Mumford-Shah Model with Bose-Einstein Photon Noise

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen Jianhong, E-mail: jhshen@math.umn.edu; Jung, Yoon-Mo

Human vision works equally well in a large dynamic range of light intensities, from only a few photons to typical midday sunlight. Contributing to such remarkable flexibility is a famous law in perceptual (both visual and aural) psychology and psychophysics known as Weber's Law. The current paper develops a new segmentation model based on the integration of Weber's Law and the celebrated Mumford-Shah segmentation model (Comm. Pure Appl. Math., vol. 42, pp. 577-685, 1989). Explained in detail are issues concerning why the classical Mumford-Shah model lacks light adaptivity, and why its 'weberized' version can more faithfully reflect human vision's superiormore » segmentation capability in a variety of illuminance conditions from dawn to dusk. It is also argued that the popular Gaussian noise model is physically inappropriate for the weberization procedure. As a result, the intrinsic thermal noise of photon ensembles is introduced based on Bose and Einstein's distributions in quantum statistics, which turns out to be compatible with weberization both analytically and computationally. The current paper focuses on both the theory and computation of the weberized Mumford-Shah model with Bose-Einstein noise. In particular, Ambrosio-Tortorelli's {gamma}-convergence approximation theory is adapted (Boll. Un. Mat. Ital. B, vol. 6, pp. 105-123, 1992), and stable numerical algorithms are developed for the associated pair ofnonlinear Euler-Lagrange PDEs.« less

The ability to entrain to long photoperiods differs between 3 Drosophila melanogaster wild-type strains and is modified by twilight simulation.

PubMed

Rieger, Dirk; Peschel, Nicolai; Dusik, Verena; Glotz, Silvia; Helfrich-Förster, Charlotte

2012-02-01

The ability to adapt to different environmental conditions including seasonal changes is a key feature of the circadian clock. Here, we compared the ability of 3 Drosophila melanogaster wild-type strains to adapt rhythmic activity to long photoperiods simulated in the laboratory. Fruit flies are predominantly crepuscular with activity bouts in the morning (M) and evening (E). The M peak follows dawn and the E peak follows dusk when the photoperiod is extended. We show that this ability is restricted to a certain extension of the phase angle between M and E peaks, such that the E peak does not delay beyond a certain phase under long days. We demonstrate that this ability is significantly improved by simulated twilight and that it depends additionally on the genetic background and the ambient temperature. At 20 °C, the laboratory strain CantonS had the most flexible phase angle between M and E peaks, a Northern wild-type strain had an intermediate one, and a Southern wild-type strain had the lowest flexibility. Furthermore, we found that the 3 strains differed in clock light sensitivity, with the CantonS and the Northern strains more light sensitive than the Southern strain. These results are generally in accord with the recently discovered polymorphisms in the timeless gene (tim) that affect clock light sensitivity.

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

Artificial ionospheric modification: The Metal Oxide Space Cloud experiment

NASA Astrophysics Data System (ADS)

Caton, Ronald G.; Pedersen, Todd R.; Groves, Keith M.; Hines, Jack; Cannon, Paul S.; Jackson-Booth, Natasha; Parris, Richard T.; Holmes, Jeffrey M.; Su, Yi-Jiun; Mishin, Evgeny V.; Roddy, Patrick A.; Viggiano, Albert A.; Shuman, Nicholas S.; Ard, Shaun G.; Bernhardt, Paul A.; Siefring, Carl L.; Retterer, John; Kudeki, Erhan; Reyes, Pablo M.

2017-05-01

Clouds of vaporized samarium (Sm) were released during sounding rocket flights from the Reagan Test Site, Kwajalein Atoll in May 2013 as part of the Metal Oxide Space Cloud (MOSC) experiment. A network of ground-based sensors observed the resulting clouds from five locations in the Republic of the Marshall Islands. Of primary interest was an examination of the extent to which a tailored radio frequency (RF) propagation environment could be generated through artificial ionospheric modification. The MOSC experiment consisted of launches near dusk on two separate evenings each releasing 6 kg of Sm vapor at altitudes near 170 km and 180 km. Localized plasma clouds were generated through a combination of photoionization and chemi-ionization (Sm + O → SmO+ + e-) processes producing signatures visible in optical sensors, incoherent scatter radar, and in high-frequency (HF) diagnostics. Here we present an overview of the experiment payloads, document the flight characteristics, and describe the experimental measurements conducted throughout the 2 week launch window. Multi-instrument analysis including incoherent scatter observations, HF soundings, RF beacon measurements, and optical data provided the opportunity for a comprehensive characterization of the physical, spectral, and plasma density composition of the artificial plasma clouds as a function of space and time. A series of companion papers submitted along with this experimental overview provide more detail on the individual elements for interested readers.

TCP4-dependent induction of CONSTANS transcription requires GIGANTEA in photoperiodic flowering in Arabidopsis

PubMed Central

Shim, Jae Sung; Song, Yong Hun; Laboy Cintrón, Dianne; Koyama, Tomotsugu; Ohme-Takagi, Masaru; Pruneda-Paz, Jose L.; Kay, Steve A.; MacCoss, Michael J.

2017-01-01

Photoperiod is one of the most reliable environmental cues for plants to regulate flowering timing. In Arabidopsis thaliana, CONSTANS (CO) transcription factor plays a central role in regulating photoperiodic flowering. In contrast to posttranslational regulation of CO protein, still little was known about CO transcriptional regulation. Here we show that the CINCINNATA (CIN) clade of class II TEOSINTE BRANCHED 1/ CYCLOIDEA/ PROLIFERATING CELL NUCLEAR ANTIGEN FACTOR (TCP) proteins act as CO activators. Our yeast one-hybrid analysis revealed that class II CIN-TCPs, including TCP4, bind to the CO promoter. TCP4 induces CO expression around dusk by directly associating with the CO promoter in vivo. In addition, TCP4 binds to another flowering regulator, GIGANTEA (GI), in the nucleus, and induces CO expression in a GI-dependent manner. The physical association of TCP4 with the CO promoter was reduced in the gi mutant, suggesting that GI may enhance the DNA-binding ability of TCP4. Our tandem affinity purification coupled with mass spectrometry (TAP-MS) analysis identified all class II CIN-TCPs as the components of the in vivo TCP4 complex, and the gi mutant did not alter the composition of the TCP4 complex. Taken together, our results demonstrate a novel function of CIN-TCPs as photoperiodic flowering regulators, which may contribute to coordinating plant development with flowering regulation. PMID:28628608

TCP4-dependent induction of CONSTANS transcription requires GIGANTEA in photoperiodic flowering in Arabidopsis.

PubMed

Kubota, Akane; Ito, Shogo; Shim, Jae Sung; Johnson, Richard S; Song, Yong Hun; Breton, Ghislain; Goralogia, Greg S; Kwon, Michael S; Laboy Cintrón, Dianne; Koyama, Tomotsugu; Ohme-Takagi, Masaru; Pruneda-Paz, Jose L; Kay, Steve A; MacCoss, Michael J; Imaizumi, Takato

2017-06-01

Photoperiod is one of the most reliable environmental cues for plants to regulate flowering timing. In Arabidopsis thaliana, CONSTANS (CO) transcription factor plays a central role in regulating photoperiodic flowering. In contrast to posttranslational regulation of CO protein, still little was known about CO transcriptional regulation. Here we show that the CINCINNATA (CIN) clade of class II TEOSINTE BRANCHED 1/ CYCLOIDEA/ PROLIFERATING CELL NUCLEAR ANTIGEN FACTOR (TCP) proteins act as CO activators. Our yeast one-hybrid analysis revealed that class II CIN-TCPs, including TCP4, bind to the CO promoter. TCP4 induces CO expression around dusk by directly associating with the CO promoter in vivo. In addition, TCP4 binds to another flowering regulator, GIGANTEA (GI), in the nucleus, and induces CO expression in a GI-dependent manner. The physical association of TCP4 with the CO promoter was reduced in the gi mutant, suggesting that GI may enhance the DNA-binding ability of TCP4. Our tandem affinity purification coupled with mass spectrometry (TAP-MS) analysis identified all class II CIN-TCPs as the components of the in vivo TCP4 complex, and the gi mutant did not alter the composition of the TCP4 complex. Taken together, our results demonstrate a novel function of CIN-TCPs as photoperiodic flowering regulators, which may contribute to coordinating plant development with flowering regulation.

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.

The Warm Plasma Composition in the Inner Magnetosphere during 2012–2015

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jahn, J. M.; Goldstein, J.; Reeves, Geoffrey D.

Ionospheric heavy ions play an important role in the dynamics of Earth's magnetosphere. The greater mass and gyro radius of ionospheric oxygen differentiates its behavior from protons at the same energies. Oxygen may have an impact on tail reconnection processes, and it can at least temporarily dominate the energy content of the ring current during geomagnetic storms. At sub-keV energies, multi-species ion populations in the inner magnetosphere form the warm plasma cloak, occupying the energy range between the plasmasphere and the ring current. Lastly, cold lighter ions from the mid-latitude ionosphere create the co-rotating plasmasphere whose outer regions can interactmore » with the plasma cloak, plasma sheet, ring current, and outer electron belt. Here in this paper we present a statistical view of warm, cloak-like ion populations in the inner magnetosphere, contrasting in particular the warm plasma composition during quiet and active times. We study the relative abundances and absolute densities of warm plasma measured by the Van Allen Probes, whose two spacecraft cover the inner magnetosphere from plasmaspheric altitudes close to Earth to just inside geostationary orbit. We observe that warm (>30 eV) oxygen is most abundant closer to the plasmasphere boundary whereas warm hydrogen dominates closer to geostationary orbit. Warm helium is usually a minor constituent, but shows a noticeable enhancement in the near-Earth dusk sector.« less

Getting back to nature: a reality check for experiments in controlled environments.

PubMed

Annunziata, Maria Grazia; Apelt, Federico; Carillo, Petronia; Krause, Ursula; Feil, Regina; Mengin, Virginie; Lauxmann, Martin A; Köhl, Karin; Nikoloski, Zoran; Stitt, Mark; Lunn, John E; Raines, Christine

2017-07-20

Irradiance from sunlight changes in a sinusoidal manner during the day, with irregular fluctuations due to clouds, and light-dark shifts at dawn and dusk are gradual. Experiments in controlled environments typically expose plants to constant irradiance during the day and abrupt light-dark transitions. To compare the effects on metabolism of sunlight versus artificial light regimes, Arabidopsis thaliana plants were grown in a naturally illuminated greenhouse around the vernal equinox, and in controlled environment chambers with a 12-h photoperiod and either constant or sinusoidal light profiles, using either white fluorescent tubes or light-emitting diodes (LEDs) tuned to a sunlight-like spectrum as the light source. Rosettes were sampled throughout a 24-h diurnal cycle for metabolite analysis. The diurnal metabolite profiles revealed that carbon and nitrogen metabolism differed significantly between sunlight and artificial light conditions. The variability of sunlight within and between days could be a factor underlying these differences. Pairwise comparisons of the artificial light sources (fluorescent versus LED) or the light profiles (constant versus sinusoidal) showed much smaller differences. The data indicate that energy-efficient LED lighting is an acceptable alternative to fluorescent lights, but results obtained from plants grown with either type of artificial lighting might not be representative of natural conditions. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Implications of Circadian Rhythm in Dopamine and Mood Regulation.

PubMed

Kim, Jeongah; Jang, Sangwon; Choe, Han Kyoung; Chung, Sooyoung; Son, Gi Hoon; Kim, Kyungjin

2017-07-31

Mammalian physiology and behavior are regulated by an internal time-keeping system, referred to as circadian rhythm. The circadian timing system has a hierarchical organization composed of the master clock in the suprachiasmatic nucleus (SCN) and local clocks in extra-SCN brain regions and peripheral organs. The circadian clock molecular mechanism involves a network of transcription-translation feedback loops. In addition to the clinical association between circadian rhythm disruption and mood disorders, recent studies have suggested a molecular link between mood regulation and circadian rhythm. Specifically, genetic deletion of the circadian nuclear receptor Rev-erbα induces mania-like behavior caused by increased midbrain dopaminergic (DAergic) tone at dusk. The association between circadian rhythm and emotion-related behaviors can be applied to pathological conditions, including neurodegenerative diseases. In Parkinson's disease (PD), DAergic neurons in the substantia nigra pars compacta progressively degenerate leading to motor dysfunction. Patients with PD also exhibit non-motor symptoms, including sleep disorder and neuropsychiatric disorders. Thus, it is important to understand the mechanisms that link the molecular circadian clock and brain machinery in the regulation of emotional behaviors and related midbrain DAergic neuronal circuits in healthy and pathological states. This review summarizes the current literature regarding the association between circadian rhythm and mood regulation from a chronobiological perspective, and may provide insight into therapeutic approaches to target psychiatric symptoms in neurodegenerative diseases involving circadian rhythm dysfunction.

Modelling bidirectional fluxes of methanol and acetaldehyde with the FORCAsT canopy exchange model

DOE PAGES

Ashworth, Kirsti; Chung, Serena H.; McKinney, Karena A.; ...

2016-12-15

Here, the FORCAsT canopy exchange model was used to investigate the underlying mechanisms governing foliage emissions of methanol and acetaldehyde, two short chain oxygenated volatile organic compounds ubiquitous in the troposphere and known to have strong biogenic sources, at a northern mid-latitude forest site. The explicit representation of the vegetation canopy within the model allowed us to test the hypothesis that stomatal conductance regulates emissions of these compounds to an extent that its influence is observable at the ecosystem scale, a process not currently considered in regional- or global-scale atmospheric chemistry models. Here, we found that FORCAsT could only reproducemore » the magnitude and diurnal profiles of methanol and acetaldehyde fluxes measured at the top of the forest canopy at Harvard Forest if light-dependent emissions were introduced to the model. With the inclusion of such emissions, FORCAsT was able to successfully simulate the observed bidirectional exchange of methanol and acetaldehyde. Although we found evidence that stomatal conductance influences methanol fluxes and concentrations at scales beyond the leaf level, particularly at dawn and dusk, we were able to adequately capture ecosystem exchange without the addition of stomatal control to the standard parameterisations of foliage emissions, suggesting that ecosystem fluxes can be well enough represented by the emissions models currently used.« less

A critical examination of the dual system theory in Ostrinia nubilalis.

PubMed

Skopik, S D; Takeda, M; Holyoke, C W

1981-11-01

Beck's dual system theory (DST) is examined theoretically and experimentally by investigating the oviposition rhythm of Ostrinia nubilalis and its entrainment by light cycles. Several well-known circadian phenomena are not accounted for by the DST. 1) It does not generate transient cycles when light pulses fall during the advance portion of the circadian cycle. This is also reflected in DST-predicted phase-response curves (PRC's) for both Drosophila pseudoobscura and O. nubilalis. Steady-state phase advances are predicted to occur on day 1 after the light pulses by the DST, not several cycles later as has been observed in many cases. 2) It does not account for the observation that the magnitude of a phase shift (delta phi) is often a function of pulse duration of both delays and advances. The DST predicts the same + delta phi, for example, for a 0.5-h and a 6.0-h light pulse beginning 5.0 h after dusk. 3) The DST does not accurately predict steady-state phase relationships between the light cycle and the gating oscillation (P-system) in non-24-h light cycles. 4) The driver (S-system) is given the property of being temperature sensitive whereas the driven rhythm (P-system) is temperature compensated. This is contrary to accumulated data suggesting that the circadian pacemaker is temperature compensated.

Effects of melatonin on 2-deoxy-(1-/sup 14/C)glucose uptake within rat suprachiasmatic nucleus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cassone, V.M.; Roberts, M.H.; Moore, R.Y.

Previously, we have demonstrated that metabolic activity, shown by autoradiographic determination of 2-deoxy-(1-/sup 14/C)glucose (2-DG) uptake, within the rat hypothalamic suprachiasmatic nuclei (SCN) was inhibited by subcutaneous injection of 1 mg/kg melatonin. To determine whether this effect was specific to a particular time of day, the effects of melatonin on 2-DG uptake were studied in several hypothalamic areas, including the SCN, supraoptic nuclei (SON), lateral hypothalamic area (LHA), and anterior hypothalamic area (AHA) every 4 h throughout the circadian day. In a second experiment, the effects of different melatonin doses were studied at the time of day at which melatoninmore » had its maximal effect to determine the dose-response relationship of melatonin-induced inhibition of SCN 2-DG uptake. The data indicate that melatonin inhibited 2-DG uptake in the SCN alone at one time of day, primarily at circadian time (CT) 6 and CT10, 2-6 h before subjective dusk, and secondarily at CT22, just before subjective dawn. This effect was dose dependent with a 50% effective dose of 1.49 +/- 2.30 micrograms/kg. The temporal and dose-response characteristics of these effects are similar to those characterizing the entraining effects of melatonin on circadian patterns of locomotion and drinking.« less

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.

3D ion-scale dynamics of BBFs and their associated emissions in Earth's magnetotail using 3D hybrid simulations and MMS multi-spacecraft observations

NASA Astrophysics Data System (ADS)

Breuillard, H.; Aunai, N.; Le Contel, O.; Catapano, F.; Alexandrova, A.; Retino, A.; Cozzani, G.; Gershman, D. J.; Giles, B. L.; Khotyaintsev, Y. V.; Lindqvist, P. A.; Ergun, R.; Strangeway, R. J.; Russell, C. T.; Magnes, W.; Plaschke, F.; Nakamura, R.; Fuselier, S. A.; Turner, D. L.; Schwartz, S. J.; Torbert, R. B.; Burch, J.

2017-12-01

Transient and localized jets of hot plasma, also known as Bursty Bulk Flows (BBFs), play a crucial role in Earth's magnetotail dynamics because the energy input from the solar wind is partly dissipated in their vicinity, notably in their embedded dipolarization front (DF). This dissipation is in the form of strong low-frequency waves that can heat and accelerate energetic particles up to the high-latitude plasma sheet. The ion-scale dynamics of BBFs have been revealed by the Cluster and THEMIS multi-spacecraft missions. However, the dynamics of BBF propagation in the magnetotail are still under debate due to instrumental limitations and spacecraft separation distances, as well as simulation limitations. The NASA/MMS fleet, which features unprecedented high time resolution instruments and four spacecraft separated by kinetic-scale distances, has also shown recently that the DF normal dynamics and its associated emissions are below the ion gyroradius scale in this region. Large variations in the dawn-dusk direction were also observed. However, most of large-scale simulations are using the MHD approach and are assumed 2D in the XZ plane. Thus, in this study we take advantage of both multi-spacecraft observations by MMS and large-scale 3D hybrid simulations to investigate the 3D dynamics of BBFs and their associated emissions at ion-scale in Earth's magnetotail, and their impact on particle heating and acceleration.

Day-night variations in malate concentration, osmotic pressure, and hydrostatic pressure in Cereus validus

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 smallmore » 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.« less

Survival of Flux Transfer Event (FTE) Flux Ropes Far Along the Tail Magnetopause

NASA Technical Reports Server (NTRS)

Eastwood, J. P.; Phan, T. D.; Fear, R. C.; Sibeck, D. G.; Angelopoulos, V.; Oieroset, M.; Shay, M. A.

2012-01-01

During intervals of southward IMF, magnetic reconnection can result in the formation of flux transfer events (FTEs) on the dayside magnetopause which travel along the magnetopause in the anti-sunward direction. Of particular interest is their fate and the role they play transporting solar wind plasma into the magnetosphere. We present the discovery of FTEs far along the distant tail magnetopause (x = 67 Earth radii) using data from ARTEMIS on the dusk flank magnetopause under southward/duskward IMF conditions. The identification of several events is further supported by excellent fits to a force-free flux rope model. The axis of each structure is principally north-south, i.e., perpendicular to the Sun-Earth line. Simultaneous observations by THEMIS on the dayside magnetopause indicate that FTEs are being produced there, although perhaps 2-4 times smaller in size. The convection time from the dayside magnetopause to ARTEMIS is 30 min, and the FTEs have a flux content comparable to those typically observed on the dayside magnetopause, indicating that these features are in quasi-equilibrium as they are convected downtail. By considering the relative orientations of the FTEs observed by THEMIS and ARTEMIS, the magnetic field geometry is consistent with the FTEs being produced on the dayside magnetopause along an extended X-line in the presence of IMF By and bending as they are convected to the flanks.

Roosting behavior of premigratory Dunlins (Calidris alpina)

USGS Publications Warehouse

Handel, Colleen M.; Gill, Robert E.

1992-01-01

We studied roosting behavior of Dunlins (Calidris alpina) during late summer along the coast of the Yukon-Kuskokwim Delta, Alaska, in relation to tidal cycle, time of day, time of season, and occurrence of predators. Within Angyoyaravak Bay, peak populations of 70,000-100,000 Dunlins occur each year. The major diurnal roost sites were adjacent to intertidal feeding areas, provided an unobstructed view of predators, and were close to shallow waters used for bathing. At one site studied intensively, roosting flocks formed at high water consistently during the day but rarely at night. On about 75% of the days, Dunlins also came to the roost at dawn and dusk when the tide was low. The size of the roosting flock, the length of time birds spent at the roost site, and behavior at the roost site were highly variable throughout the season and significantly affected by both tide level and time of day. Roosting behavior changed significantly between early and late August, as Dunlins underwent heavy wing and body molt, and began premigratory fattening. The reaction of Dunlins to potential predators, the formation of roosting flocks in response to light cues, and seasonal changes in social behavior at the roost site suggested that communal roosting behavior may be related not only to the risk of predation but also to behavior during migration.

Circadian behaviour of Tectus (Trochus) niloticus in the southwest Pacific inferred from accelerometry.

PubMed

Jolivet, Aurélie; Chauvaud, Laurent; Thébault, Julien; Robson, Anthony A; Dumas, Pascal; Amos, George; Lorrain, Anne

2015-01-01

Behaviour and time spent active and inactive are key factors in animal ecology, with important consequences for bioenergetics. For the first time, here, we equipped the gastropod Tectus (= Trochus) niloticus with accelerometers to describe activity rhythms at two sites in the Southwest Pacific with different temperature regimes: New Caledonia and Vanuatu. Based on a 24-hour cycle, T. niloticus activity began at dusk and gradually stopped during the night, before sunrise. This nocturnal behaviour was characterised by short (duration <30 s), low intensity (acceleration < 0.12 ɡ) movements and was probably associated with foraging behaviour. We assumed that activity ceased once the animal was satiated. Our analysis of two size groups in Vanuatu (80-90 mm vs. 120-140 mm, basal shell diameter) revealed a size effect; smaller specimens displayed greater activity, reflected by more intense and longer movements while migrating at night toward the edge of the reef. This nocturnal behaviour is not uncommon for grazing gastropods and is mainly associated with attempting to avoid visual predators whilst feeding. The use of accelerometers coupled with light and temperature sensors provided detailed information on topshell behaviour and physiology under natural conditions. These data provide a foundation for identifying potential changes in the fine-scale behaviour of T. niloticus in response to environmental changes, which is essential in animal ecology and stock conservation.

Prey Capture Behavior in an Arboreal African Ponerine Ant

PubMed Central

Dejean, Alain

2011-01-01

I studied the predatory behavior of Platythyrea conradti, an arboreal ponerine ant, whereas most species in this subfamily are ground-dwelling. The workers, which hunt solitarily only around dusk, are able to capture a wide range of prey, including termites and agile, nocturnal insects as well as diurnal insects that are inactive at that moment of the Nyctemeron, resting on tree branches or under leaves. Prey are captured very rapidly, and the antennal palpation used by ground-dwelling ponerine species is reduced to a simple contact; stinging occurs immediately thereafter. The venom has an instant, violent effect as even large prey (up to 30 times the weight of a worker) never struggled after being stung. Only small prey are not stung. Workers retrieve their prey, even large items, singly. To capture termite workers and soldiers defending their nest entrances, ant workers crouch and fold their antennae backward. In their role as guards, the termites face the crouching ants and end up by rolling onto their backs, their legs batting the air. This is likely due to volatile secretions produced by the ants' mandibular gland. The same behavior is used against competing ants, including territorially-dominant arboreal species that retreat further and further away, so that the P. conradti finally drive them from large, sugary food sources. PMID:21589941

Ionospheric convection driven by NBZ currents

NASA Technical Reports Server (NTRS)

Rasmussen, C. E.; Schunk, R. W.

1987-01-01

Computer simulations of Birkeland currents and electric fields in the polar ionosphere during periods of northward IMF were conducted. When the IMF z component is northward, an additional current system, called the NBZ current system, is present in the polar cap. These simulations show the effect of the addition of NBZ currents on ionospheric convection, particularly in the polar cap. When the total current in the NBZ system is roughly 25 to 50 percent of the net region 1 and 2 currents, convection in the central portion of the polar cap reverses direction and turns sunward. This creates a pattern of four-cell convection with two small cells located in the polar cap, rotating in an opposite direction from the larger cells. When the Birkeland currents are fixed (constant current source), the electric field is reduced in regions of relatively high conductivity, which affects the pattern of ionospheric convection. Day-night asymmetries in conductivity change convection in such a way that the two polar-cap cells are located within the large dusk cell. When ionospheric convection is fixed (constant voltage source), Birkeland currents are increased in regions of relatively high conductivity. Ionospheric currents, which flow horizontally to close the Birkeland currents, are changed appreciably by the NBZ current system. The principal effect is an increase in ionospheric current in the polar cap.

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.

Medium-Scale Traveling Ionospheric Disturbances Observed by Detrended Total Electron Content Maps Over Brazil

NASA Astrophysics Data System (ADS)

Figueiredo, C. A. O. B.; Takahashi, H.; Wrasse, C. M.; Otsuka, Y.; Shiokawa, K.; Barros, D.

2018-03-01

A ground-based network of Global Navigation Satellite Systems receivers has been used to monitor medium-scale traveling ionospheric disturbances (MSTIDs). MSTIDs were studied using total electron content perturbation maps and keograms over south-southeast of Brazil during the period from December 2012 to February 2016. In total, 826 MSTIDs were observed mainly in daytime, thus presenting median values of horizontal wavelength, period, and horizontal phase velocity of 452 ± 107 km, 24 ± 4 min. and 323 ± 81 m/s, respectively. The direction of propagation varies on the season: during the winter (June-August), the waves preferentially propagated to north-northeast, while in the other seasons the waves propagated to other directions. The anisotropy observed in the MSTID propagation direction could be associated with the region of the gravity wave generation that takes place in the troposphere. We also found that the MSTIDs were observed most frequently during the daytime, between 11 and 15 local time in winter and near to dusk solar terminator (17-19 local time) in the other seasons. Furthermore, the occurrence of MSTIDs was higher in winter. We suggest that atmospheric gravity waves in the thermosphere, mesosphere, and troposphere could play an important role in generating the MSTIDs and the propagation direction may depend on location of the wave sources.

The effects of an interplanetary shock on the high-latitude ionospheric convection during an IMF By-dominated period

NASA Astrophysics Data System (ADS)

Coco, I.; Amata, E.; Marcucci, M. F.; Ambrosino, D.; Villain, J.-P.; Hanuise, C.

2008-09-01

On 6 January 1998 an interplanetary shock hit the magnetosphere around 14:15 UT and caused a reconfiguration of the northern high-latitude ionospheric convection. We use SuperDARN, spacecraft and ground magnetometer data to study such reconfiguration. We find that the shock front was tilted towards the morning flank of the magnetosphere, while the Interplanetary Magnetic Field (IMF) was By-dominated, with By<0, IMF Bz>0 and |By|>>Bz. As expected, the magnetospheric compression started at the first impact point of the shock on the magnetopause causing an increase of the Chapman-Ferraro current from dawn to dusk and yielding an increase of the geomagnetic field at the geostationary orbit and on the ground. Moreover, the high-latitude magnetometer data show vortical structures clearly related to the interaction of the shock with the magnetosphere-ionosphere system. In this context, the SuperDARN convection maps show that at very high latitudes above the northern Cusp and in the morning sector, intense sunward convection fluxes appear, well correlated in time with the SI arrival, having a signature typical for Bz>0 dominated lobe reconnection. We suggest that in this case the dynamic pressure increase associated to the shock plays a role in favouring the setting up of a new lobe merging line albeit |By|>>Bz≥0.

Penetration of Magnetosheath Plasma into Dayside Magnetosphere: 1. Density, Velocity, and Rotation

NASA Technical Reports Server (NTRS)

Lyatsky, Wladislaw; Pollock, Craig; Goldstein, Melvyn L.; Lyatsky, Sonya; Avanov, Levon Albert

2016-01-01

In this study, we examine a large number of plasma structures (filaments), observed with the Cluster spacecraft during 2 years (2007-2008) in the dayside magnetosphere but consisting of magnetosheath plasma. To reduce the effects observed in the cusp regions and on magnetosphere flanks, we consider these events predominantly inside the narrow cone less than 30 about the subsolar point. Two important features of these filaments are (i) their stable antisunward (earthward) motion inside the magnetosphere, whereas the ambient magnetospheric plasma moves usually in the opposite direction (sunward), and (ii) between these filaments and the magnetopause, there is a region of magnetospheric plasma, which separates these filaments from the magnetosheath. The stable earthward motion of these magnetopause show the possible disconnection of these filaments from the magnetosheath, as suggested earlier by many researchers. The results also show that these events cannot be a result of back-and-forth motions of magnetopause position or surface waves propagating on the magnetopause. Another important feature of these filaments is their rotation about the filament axis, which might be a result of their passage through the velocity shear on magnetopause boundary. After crossing the velocity shear, the filaments get a rotational velocity, which has opposite directions in the noon-dusk and noon-dawn sectors. This rotation velocity may be an important factor, supporting the stability of these filaments and providing their motion into the magnetosphere.

Acceleration of Magnetospheric Relativistic Electrons by Ultra-Low Frequency Waves: A Comparison between Two Cases Observed by Cluster and LANL Satellites

NASA Technical Reports Server (NTRS)

Shao, X.; Fung, S. F.; Tan, L. C.; Sharma, A. S.

2010-01-01

Understanding the origin and acceleration of magnetospheric relativistic electrons (MREs) in the Earth's radiation belt during geomagnetic storms is an important subject and yet one of outstanding questions in space physics. It has been statistically suggested that during geomagnetic storms, ultra-low-frequency (ULF) Pc-5 wave activities in the magnetosphere are correlated with order of magnitude increase of MRE fluxes in the outer radiation belt. Yet, physical and observational understandings of resonant interactions between ULF waves and MREs remain minimum. In this paper, we show two events during storms on September 25, 2001 and November 25, 2001, the solar wind speeds in both cases were > 500 km/s while Cluster observations indicate presence of strong ULF waves in the magnetosphere at noon and dusk, respectively, during a approx. 3-hour period. MRE observations by the Los Alamos (LANL) spacecraft show a quadrupling of 1.1-1.5 MeV electron fluxes in the September 25, 2001 event, but only a negligible increase in the November 2.5, 2001 event. We present a detailed comparison between these two events. Our results suggest that the effectiveness of MRE acceleration during the September 25, 2001 event can be attributed to the compressional wave mode with strong ULF wave activities and the physical origin of MRE acceleration depends more on the distribution of toroidal and poloidal ULF waves in the outer radiation belt.

The Warm Plasma Composition in the Inner Magnetosphere during 2012–2015

DOE PAGES

Jahn, J. M.; Goldstein, J.; Reeves, Geoffrey D.; ...

2017-09-11

Ionospheric heavy ions play an important role in the dynamics of Earth's magnetosphere. The greater mass and gyro radius of ionospheric oxygen differentiates its behavior from protons at the same energies. Oxygen may have an impact on tail reconnection processes, and it can at least temporarily dominate the energy content of the ring current during geomagnetic storms. At sub-keV energies, multi-species ion populations in the inner magnetosphere form the warm plasma cloak, occupying the energy range between the plasmasphere and the ring current. Lastly, cold lighter ions from the mid-latitude ionosphere create the co-rotating plasmasphere whose outer regions can interactmore » with the plasma cloak, plasma sheet, ring current, and outer electron belt. Here in this paper we present a statistical view of warm, cloak-like ion populations in the inner magnetosphere, contrasting in particular the warm plasma composition during quiet and active times. We study the relative abundances and absolute densities of warm plasma measured by the Van Allen Probes, whose two spacecraft cover the inner magnetosphere from plasmaspheric altitudes close to Earth to just inside geostationary orbit. We observe that warm (>30 eV) oxygen is most abundant closer to the plasmasphere boundary whereas warm hydrogen dominates closer to geostationary orbit. Warm helium is usually a minor constituent, but shows a noticeable enhancement in the near-Earth dusk sector.« less

Asymmetry of the Mars Ionosphere Boundary Altitude during a Solar Energetic Particle Event

NASA Astrophysics Data System (ADS)

Frahm, R. A.; Elliott, H. A.; Winningham, J. D.; Sharber, J. R.; DeForest, C. E.; Howard, T. A.; Kallio, E. J.; McKenna-Lawlor, S.; Duru, F.; Morgan, D. D.; Coates, A. J.; Odstrcil, D.; Lundin, R. N.; Futaana, Y.; Barabash, S. V.

2013-12-01

The Electron Spectrometer (ELS) and the Ion Mass Spectrometer (IMA) from the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) experiment on the ESA's Mars Express (MEx) spacecraft have been used to study a Solar Energetic Particle (SEP) event associated with a Class X solar flare on on January 27, 2012. Arrival of the SEP at Mars about 46 minutes later is observed as an increase in the background of these plasma instruments. The background counts were observed to increase sharply, followed by a gradual decrease that lasted for about 4 days. During this time, ELS and IMA also recorded passages across the Martian ionospheric boundary on the dusk side of the planet, twice during each MEx orbit. The altitude of the ionospheric boundary was thereby found to have behaved differently in the northern and southern hemispheres. The boundary increased in altitude in each hemisphere with a time delay as the flare pumped energy into the Mars system. After reaching peak altitude, the ionospheric boundary returned to its original configuration faster in the northern than in the southern hemisphere. This suggests that the main difference between the northern and southern hemispheres at Mars, namely the presence in the south of crustal magnetic fields, is responsible for the dissipation of the energy input at a slower rate in the southern than in the northern hemisphere.

Cross-scale transport processes in the three-dimensional Kelvin-Helmholtz instability

NASA Astrophysics Data System (ADS)

Delamere, P. A.; Burkholder, B. L.; Ma, X.; Nykyri, K.

2017-12-01

The Kelvin-Helmholtz (KH) instability is a crucial aspect of the solar wind interaction with the giant magnetospheres. Rapid internal rotation of the magnetodisc produces conditions favorable for the growth of KH vortices along much of the equatorial magnetopause boundary. Pronounced dawn/dusk asymmetries at Jupiter and Saturn indicate a robust interaction with the solar wind. Using three-dimensional hybrid simulations we investigate the transport processes associated with the flow shear-driven KH instability. Of particular importance is small-scale and intermittent reconnection generated by the twisting of the magnetic field into configurations with antiparallel components. In three-dimensions strong guide field reconnection can occur even for initially parallel magnetic field configurations. Often the twisting motion leads to pairs of reconnection sites that can operate asynchronously, generating intermittent open flux and Maxwell stresses at the magnetopause boundary. We quantify the generation of open flux using field line tracing methods, determine the Reynolds and Maxwell stresses, and evaluate the mass transport as functions of magnetic shear, velocity shear, electron pressure and plasma beta. These results are compared with magnetohydrodynamic simulations (Ma et al., 2017). In addition, we present preliminary results for the role of cross-scale coupling processes, from fluid to ion scales. In particular, we characterize small-scale waves and the their role in mixing, diffusing and heating plasma at the magnetopause boundary.

Global Magnetospheric Response to an Interplanetary Shock: THEMIS Observations

NASA Technical Reports Server (NTRS)

Zhang, Hui; Sibeck, David G.; Zong, Q.-G.; McFadden, James P.; Larson, Davin; Glassmeier, K.-H.; Angelopoulos, V.

2011-01-01

We investigate the global response of geospace plasma environment to an interplanetary shock at approx. 0224 UT on May 28, 2008 from multiple THEMIS spacecraft observations in the magnetosheath (THEMIS B and C) and the mid-afternoon (THEMIS A) and dusk magnetosphere (THEMIS D and E). The interaction of the transmitted interplanetary shock with the magnetosphere has global effects. Consequently, it can affect geospace plasma significantly. After interacting with the bow shock, the interplanetary shock transmitted a fast shock and a discontinuity which propagated through the magnetosheath toward the Earth at speeds of 300 km/s and 137 km/s respectively. THEMIS A observations indicate that the plasmaspheric plume changed significantly by the interplanetary shock impact. The plasmaspheric plume density increased rapidly from 10 to 100/ cubic cm in 4 min and the ion distribution changed from isotropic to strongly anisotropic distribution. Electromagnetic ion cyclotron (EMIC) waves observed by THEMIS A are most likely excited by the anisotropic ion distributions caused by the interplanetary shock impact. To our best knowledge, this is the first direct observation of the plasmaspheric plume response to an interplanetary shock's impact. THEMIS A, but not D or E, observed a plasmaspheric plume in the dayside magnetosphere. Multiple spacecraft observations indicate that the dawn-side edge of the plasmaspheric plume was located between THEMIS A and D (or E).

Energetic particle penetrations into the inner magnetosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

Data from Explorer 45 (S/sup 3/- A) instruments have revealed characteristics of magnetospheric storm or substorm time energetic particle enhancements in the inner magnetosphere (L< or approx. =5). The properties of the ion 'nose' structure in the dusk hemisphere are examined in detail. A statistical study of the local time dependence of noses places the highest probability of occurrence around 2000 MLT, but hey can be observed even near the noon meridian. It also appears that most noses are not isolated events but will appear on successive passes. A geoelectric field enhancement corresponding to a minimum value of AE ofmore » about 205 ..gamma.. seems to be required to convect the particles within the apogee of Explorer 45. The dynamical behavior of the nose characteristics observed along successive orbits is then explained quantitatively by the time-dependent convection theory in a Volland-Stern type geoelectric field (..gamma..=2). These calculations of adiabatic charged particle motions are also applied to expalin the energy spectra and dispersion in penetration distances for both electrons and ions observed in the postmidnight to morning hours. Finally, useful descriptions are given of the dispersion properties of particles penetrating the inter magnetosphere at all local times as a function of time after a sudden enhancement of the geoelectric field.« less

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.;

Quasi-stagnant plasmoid in the middle tail - A new preexpansion phase phenomenon. [in magnetosphere

NASA Technical Reports Server (NTRS)

Nishida, A.; Terasawa, T.; Scholer, M.; Bame, S. J.; Zwickl, R. D.; Gloeckler, G.; Smith, E. J.

1986-01-01

From the analysis of ISEE 3 data it is found that a plasmoid is sometimes formed in the middle tail outside the intervals of the substorm expansion phase. This plasmoid is produced by reconnection at the X-type neutral line, which is located earthward of the distant neutral line but beyond the substorm-associated near-tail neutral line, and it is almost stagnant in that the associated flow speed is less than 300 km/s. The blocking effect of the distant neutral line is the most probable reason for the slow movement. The quasi-stagnant plasmoid is observed at x = -60 to - 100 earth radii for a duration of a few tens of minutes, and in about one half of the cases it is followed by the fast tailward streaming. The onset of this streaming tends to coincide with the onset of the substorm expansion phase, and this probably occurs when the reconnection at the middle-tail neutral line comes close to processing the last closed field line. Intensification of the dawn-to-dusk electric field that causes the mantle plasma to reach the plasma sheet boundary closer to the earth is suggested as the reason for the formation of the middle-tail neutral line earthward of the distant neutral line. The effects on the energetic particle flux and relation to the near-tail reconnection are also discussed.

The location and rate of occurrence of near-Earth magnetotail reconnection as observed by Cluster and Geotail

NASA Astrophysics Data System (ADS)

Genestreti, K. J.; Fuselier, S. A.; Goldstein, J.; Nagai, T.; Eastwood, J. P.

2014-12-01

A statistical characterization of the location and rate of occurrence of magnetic reconnection in the near-Earth magnetotail is performed by analyzing the set of ion diffusion region (DR) observations made by the Cluster and Geotail spacecraft during solar maximum and the declining phase. The occurrence rate is analyzed in terms of its dependence on both XGSM* and YGSM* (where coordinates are in the solar wind aberrated geocentric solar magnetospheric system). Within the limits of the statistics available to this study, we find the purely XGSM* -dependent occurrence rate to be roughly constant over a large portion of the near-Earth magnetotail. In contrast, we find the purely YGSM* -dependent occurrence rate to be biased towards dusk with a local maximum between 0RE ≤YGSM* ≤ 5RE. The YGSM* -dependent occurrence rate is then used to construct a quasi-2D formulation of the DR occurrence rate, which has explicit dependence on XGSM* and implicit dependence on YGSM*. The quasi-2D occurrence rate is then used to examine the predicted ephemeris of the Magnetospheric MultiScale (MMS) spacecraft. We estimate that, during its near-Earth magnetotail survey phase, MMS will likely observe 11±4 DR events. • The occurrence rate of events is calculated as a function of XGSM and YGSM. • The occurrence rate is used to estimate the number of events MMS will observe.

ULF waves associated with enhanced subauroral proton precipitation

NASA Astrophysics Data System (ADS)

Immel, Thomas J.; Mende, S. B.; Frey, H. U.; Patel, J.; Bonnell, J. W.; Engebretson, M. J.; Fuselier, S. A.

Several types of sub-auroral proton precipitation events have been identified using the Spectrographic Imager (SI) onboard the NASA-IMAGE satellite, including dayside subauroral proton flashes and detached proton arcs in the dusk sector. These have been observed at various levels of geomagnetic activity and solar wind conditions and the mechanism driving the precipitation has often been assumed to be scattering of protons into the loss cone by enhancement of ion-cyclotron waves in the interaction of the thermal plasmaspheric populations and more energetic ring current particles. Indeed, recent investigation of the detached arcs using the MPA instruments aboard the LANL geosynchronous satellites has shown there are nearly always heightened densities of cold plasma on high-altitude field lines which map down directly to the sub-auroral precipitation. If the ion-cyclotron instability is a causative mechanism, the enhancement of wave activity at ion-cyclotron frequencies should be measurable. It is here reported that magnetic pulsations in the Pc1 range occur in the vicinity of each of 4 detached arcs observed in 2000-2002, though with widely varying signatures. Additionally, longer period pulsations in the Pc5 ranges are also observed in the vicinity of the arcs, leading to the conclusion that a bounce-resonance of ring-current protons with the azimuthal Pc5 wave structure may also contribute to the detached precipitation.

Effects of Convection Electric Fields on Modeled Plasmaspheric Densities and ccc Temperatures

NASA Technical Reports Server (NTRS)

Comfort, Richard H.; Richards, Phil G.; Liao, Jin-Hua; Craven, Paul D.

1998-01-01

This paper examines the effects of convection electric fields on plasmaspheric H+, O+, He+, and N+ densities and electron and ion temperatures. These effects are studied with the aid of the Field Line Interhemispheric Plasma (FLIP) model, which has recently been extended to include the effects of ExB drifts. The FLIP model solves the continuity and momentum equations for the major ion species as well as the energy equations for ions and electrons along entire drifting flux tubes from 100 km altitude in the northern hemisphere to 100 km altitude in the southern hemisphere. Electron heating in the ionosphere and plasmasphere is provided by the solution of two-stream equations for photoelectrons. The dawn-dusk electric field imposed by the solar wind causes changes in plasmaspheric density and temperature as the plasma drifts onto flux tubes having different volumes. In an idealized convection model, outward drifts in the afternoon cause decreases in the plasmasphere density and temperature while inward drifts in the evening cause increases in plasmasphere density and temperature. In this paper we examine the effects of convection electric fields on the rate of refilling of flux tubes and investigate the hypothesis that convection electric fields are responsible for the unusually high evening electron temperatures and the post-midnight density maxima often observed in the winter ionosphere above Millstone Hill.

Equatorial measurement of SAID electric fields and relation with the plasmapause location

NASA Astrophysics Data System (ADS)

Nishimura, Y.; Wygant, J.; Ono, T.; Iizima, M.; Kumamoto, A.; Brautigam, D.; Rich, F.

2007-12-01

In order to investigate the equatorial source of subauroral ion drifts (SAID) and its association with the plasmapause position, multi-spacecraft measurements of SAID are presented using the CRRES, Akebono, and DMSP. Direct measurement of the convection electric field and plasmapause density close to the equator is measured by the electric field instrument onboard the CRRES satellite, and the plasmasheet electrons and low energy part of the ring current ions are measured by the low energy plasma instrument. The CRRES satellite is on the dusk inner magnetosphere, and the DMSP-F8 and Akebono satellites are approximately on the same field line. Associated with a substorm onset at 16:40 UT on February 20, 1991, the DMSP-F8 satellite at 19 MLT measures SAID with a maximum westward velocity of 1,500 m/s. The CRRES satellite is on outbound in the inner magnetosphere at ~21 MLT and ~5 RE at the onset of the substorm. It measures increase of DC electric field with 0.4 mV/m in the plasmasphere just after the substorm onset. Thirty minutes later, injection of ring current ions are observed in the plasmasphere with Bz decrease. After the crossing of the plasmapause, the electric field increases to 0.8 mV/m. At the same time, the spacecraft enters the plasmasheet, and the DC electric field disappears. The same time sequence is also identified in other SAID events detected on the dusk inner magnetosphere. The above CRRES measurement indicates that DC electric field is intensified in a narrow region between the ring current and electron plasmasheet after the onset of the substorm. Although the E*B drift points sunward in this region, this region with enhanced electric field is filled with plasmaspheric plasma without abrupt density change. The position where the convection electric field is equal to the corotation electric field locates inside the plasmapause. The plasmapause coincides with inner edge of the plasmasheet. This association suggests that the plasmaspheric plasma is

(2E,6Z,9Z)-2,6,9-Pentadecatrienal as a Male-Produced Aggregation-Sex Pheromone of the Cerambycid Beetle Elaphidion mucronatum.

PubMed

Millar, Jocelyn G; Mitchell, Robert F; Meier, Linnea R; Johnson, Todd D; Mongold-Diers, Judith A; Hanks, Lawrence M

2017-12-01

An increasing body of evidence suggests that the volatile pheromones of cerambycid beetles are much more diverse in structure than previously hypothesized. Here, we describe the identification, synthesis, and field testing of (2E,6Z,9Z)-2,6,9-pentadecatrienal as a male-produced aggregation-sex pheromone of the cerambycid Elaphidion mucronatum (Say) (subfamily Cerambycinae, tribe Elaphidiini). This novel structure is unlike any previously described cerambycid pheromone, and in field bioassays attracted only this species. Males produced about 9 μg of pheromone per 24 h period, and, in field trials, lures loaded with 10, 25, and 100 mg of synthetic pheromone attracted beetles of both sexes, whereas lures loaded with 1 mg of pheromone or less were not significantly attractive. Other typical cerambycine pheromones such as 3-hydroxy-2-hexanone, syn-2,3-hexanediol, and anti-2,3-hexanediol were not attractive to E. mucronatum, and when combined with (2E,6Z,9Z)-2,6,9-pentadecatrienal, the former two compounds appeared to inhibit attraction. Unexpectedly, adults of the cerambycine Xylotrechus colonus (F.) were attracted in significant numbers to a blend of 3-hydroxyhexan-2-one and (2E,6Z,9Z)-2,6,9-pentadecatrienal, even though there is no evidence that this species produces the latter compound. From timed pheromone trap catches, adults of E. mucronatum were determined to be active from dusk until shortly after midnight.

The Characteristic Pitch Angle Distributions of 1 eV to 600 keV Protons Near the Equator Based On Van Allen Probes Observations

DOE PAGES

Yue, Chao; Bortnik, Jacob; Thorne, Richard M.; ...

2017-08-31

Understanding the source and loss processes of various plasma populations is greatly aided by having accurate knowledge of their pitch angle distributions (PADs). Here we statistically analyze ~1 eV to 600 keV hydrogen (H+) PADs near the geomagnetic equator in the inner magnetosphere based on Van Allen Probes measurements, to comprehensively investigate how the H+ PADs vary with different energies, magnetic local times (MLTs), L shells, and geomagnetic conditions. Our survey clearly indicates four distinct populations with different PADs: a pancake distribution of the plasmaspheric H+ at low L shells except for dawn sector; a bidirectional field-aligned distribution of themore » warm plasma cloak; pancake or isotropic distributions of ring current H+; radiation belt particles show pancake, butterfly, and isotropic distributions depending on their energy, MLT, and L shell. Meanwhile, the pancake distribution of ring current H+ moves to lower energies as shell increases, which is primarily caused by adiabatic transport. Furthermore, energetic H+ (>10 keV) PADs become more isotropic following the substorm injections, indicating wave-particle interactions. The radiation belt H+ butterfly distributions are identified in a narrow energy range of 100 < E < 400 keV at large L ( L > 5), which are less significant during quiet times and extend from dusk to dawn sector through midnight during substorms. In conclusion, the different PADs near the equator provide clues of the underlying physical processes that produce the dynamics of these different populations.« less

The Characteristic Pitch Angle Distributions of 1 eV to 600 keV Protons Near the Equator Based On Van Allen Probes Observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yue, Chao; Bortnik, Jacob; Thorne, Richard M.

Understanding the source and loss processes of various plasma populations is greatly aided by having accurate knowledge of their pitch angle distributions (PADs). Here we statistically analyze ~1 eV to 600 keV hydrogen (H+) PADs near the geomagnetic equator in the inner magnetosphere based on Van Allen Probes measurements, to comprehensively investigate how the H+ PADs vary with different energies, magnetic local times (MLTs), L shells, and geomagnetic conditions. Our survey clearly indicates four distinct populations with different PADs: a pancake distribution of the plasmaspheric H+ at low L shells except for dawn sector; a bidirectional field-aligned distribution of themore » warm plasma cloak; pancake or isotropic distributions of ring current H+; radiation belt particles show pancake, butterfly, and isotropic distributions depending on their energy, MLT, and L shell. Meanwhile, the pancake distribution of ring current H+ moves to lower energies as shell increases, which is primarily caused by adiabatic transport. Furthermore, energetic H+ (>10 keV) PADs become more isotropic following the substorm injections, indicating wave-particle interactions. The radiation belt H+ butterfly distributions are identified in a narrow energy range of 100 < E < 400 keV at large L ( L > 5), which are less significant during quiet times and extend from dusk to dawn sector through midnight during substorms. In conclusion, the different PADs near the equator provide clues of the underlying physical processes that produce the dynamics of these different populations.« less

Evidence for Radiative Recombination of O+ Ions as a Significant Source of O 844.6 nm Emission Excitation

NASA Astrophysics Data System (ADS)

Waldrop, L.; Kerr, R. B.; Huang, Y.

2018-04-01

Photoelectron (PE) impact on ground-state O(3P) atoms is well known as a major source of twilight 844.6 nm emission in the midlatitude thermosphere. Knowledge of the PE flux can be used to infer thermospheric oxygen density, [O], from photometric measurements of 844.6 nm airglow, provided that PE impact is the dominant process generating the observed emission. During several spring observational campaigns at Arecibo Observatory, however, we have observed significant 844.6 nm emission throughout the night, which is unlikely to arise from PE impact excitation which requires solar illumination of either the local or geomagnetically conjugate thermosphere. Here we show that radiative recombination (RR) of O+ ions is likely responsible for the observed nighttime emission, based on model predictions of electron and O+ ion density and temperature by the Incoherent Scatter Radar Ionosphere Model. The calculated emission brightness produced by O + RR exhibits good agreement with the airglow data, in that both decay approximately monotonically throughout the night at similar rates. We conclude that the conventional assumption of a pure PE impact source is most likely to be invalid during dusk twilight, when RR-generated emission is most significant. Estimation of [O] from measurements of 844.6 nm emission demands isolation of the PE impact source via coincident estimation of the RR source, and the effective cross section for RR-generated emission is found here to be consistent with optically thin conditions.

It's like night and day: Diel net-effects on Cercopagidae densities in the Laurentian Great Lakes

USGS Publications Warehouse

Armenio, Patricia M.; Bunnell, David B.; Adams, Jean V.; Watson, Nicole M.; Woelmer, Whitney

2017-01-01

In the Laurentian Great Lakes, zooplankters are often sampled using standard ≤153 μm mesh nets without regard to the time of day they are collected. We sampled Cercopagidae during 2013–2014 in northern Lake Huron during day, dusk, and night using two different nets (a 0.5 m wide 153 μm mesh “standard” net and a 0.75 m wide 285 μm mesh “Bythotrephes” net) to determine if there were any differences in their sampled densities. Bythotrephes densities with the standard net were approximately 2.07-fold greater when captured at night than during the day. No time of day bias occurred with the Bythotrephes net. Nighttime Bythotrephes densities did not differ between the two net types. Cercopagis densities did not vary with net type or the time of day in this study, but future work should revisit this result given our low sample size and the low occurrence of Cercopagis in Lake Huron. To reduce bias and calculate accurate density estimates, Cercopagidae should be sampled at night if using a standard net or any time of day with the Bythotrephes net. Given the large impact of invasive predatory cladocerans Bythotrephes longimanus and Cercopagis pengoi on food webs since their invasion in the Laurentian Great Lakes in the 1980s, proper estimation of their densities is essential.

Time-lag and Correlation between ACE and RBSPICE Injection Event Observations during Storm Times

NASA Astrophysics Data System (ADS)

Madanian, H.; Patterson, J. D.; Manweiler, J. W.; Soto-chavez, A. R.; Gerrard, A. J.; Lanzerotti, L. J.

2017-12-01

The Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) on the Van Allen Probes mission measures energetic charged particles [ 20 keV to 1 MeV] in the inner magnetosphere and ring current. During geomagnetic storms, injections of energetic ions into the ring current change the ion population and produce geomagnetic field depressions on Earth's surface. We analyzed the magnetic field strength and particle composition in the interplanetary medium measured by instruments on the Advanced Composition Explorer (ACE) spacecraft near the inner Lagrangian point. The Electron, Proton, and Alpha Monitor-Low Energy Magnetic Spectrometer (EPAM-LEMS) sensor on ACE measures energetic particles [ 50 keV to 5 MeV] in the interplanetary space. The SYM-H index is utilized to classify the storm events by magnitude and to select more than 60 storm events between 2013 and 2017. We cross-compared ACE observations at storm times, with the RBSPICE ion measurements at dusk to midnight magnetic local time and over the 3-6 L-shell range. We report on the relative composition of the solar particles and the relative composition of the inner magnetospheric hot plasma during storm times. The data correlation is accomplished by shifting the observation time from ACE to RBSPICE using the solar wind velocity at the time of the observation. We will discuss time lags between storm onset at the magnetopause and injection events measured for each storm.

Raman lidar water vapor profiling over Warsaw, Poland

NASA Astrophysics Data System (ADS)

Stachlewska, Iwona S.; Costa-Surós, Montserrat; Althausen, Dietrich

2017-09-01

Water vapor mixing ratio and relative humidity profiles were derived from the multi-wavelength Raman PollyXT lidar at the EARLINET site in Warsaw, using the Rayleigh molecular extinction calculation based on atmospheric temperature and pressure from three different sources: i) the standard atmosphere US 62, ii) the Global Data Assimilation System (GDAS) model output, and iii) the WMO 12374 radiosoundings launched at Legionowo. With each method, 136 midnight relative humidity profiles were obtained for lidar observations from July 2013 to August 2015. Comparisons of these profiles showed in favor of the latter method (iii), but it also indicated that the other two data sources could replace it, if necessary. Such use was demonstrated for an automated retrieval of water vapor mixing ratio from dusk until dawn on 19/20 March 2015; a case study related to an advection of biomass burning aerosol from forest fires over Ukraine. Additionally, an algorithm that applies thresholds to the radiosounding relative humidity profiles to estimate macro-physical cloud vertical structure was used for the first time on the Raman lidar relative humidity profiles. The results, based on a subset of 66 profiles, indicate that below 6 km cloud bases/tops can be successfully obtained in 53% and 76% cases from lidar and radiosounding profiles, respectively. Finally, a contribution of the lidar derived mean relative humidity to cloudy conditions within the range of 0.8 to 6.2 km, in comparison to clear-sky conditions, was estimated.