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Sample records for northward imf conditions

  1. Latitudinal electron precipitation patterns during large and small IMF magnitudes for northward IMF conditions

    NASA Technical Reports Server (NTRS)

    Makita, K.; Meng, C.-I.; Akasofu, S.-I.

    1988-01-01

    It is demonstrated that there are distinct differences in the electron precipitation patterns (or the polar cap size), geomagnetic activity, and field-aligned currents in the highest-latitude region for small and large IMF B(z) values when the IMF B(z) component is positive. First, during periods of weakly northward IMF, there is a distinct area in the highest-latitude region in which the electron precipitation is absent except for the polar rain. By contrast, during strongly northward IMF, the entire polar region is often filled with burst-type soft electron precipitations. Second, geomagnetic disturbances and field-aligned-current intensities in the highest-latitude region are less during a weak IMF B(z) condition than those during a strongly northward IMF B(z) condition. Geomagnetic activity in the auroral zone for both conditions is absent or very weak.

  2. 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.

  3. Relation of PC index to magnetic disturbances developing under conditions of northward IMF

    NASA Astrophysics Data System (ADS)

    Podorozhkina, N.; Sormakov, D.; Troshichev, O.

    2012-04-01

    Substorms and storms occurring under conditions of northward IMF (BZN) are commonly examined as "extraordinary events" since they are developed when the efficiency of the interplanetary electric field EY = vBZS (Reiff and Luhmann, 1986) falls to zero. Examination of these events demonstrates that all of them occur, like to ordinary substorms and storms, under conditions that are necessary and sufficient for development of substorms (PC ≥ 1.5 mV/m) and storms ( >2 mV/m). The specified values of the PC index testify that the magnetosphere is affected by the intense interplanetary electric field EKL=vBTsin2θ/2 (Kan and Lee, 1979), where BT is the IMF tangential component and θ is an angle between BT component and the geomagnetic Z-axis. The principal difference between coupling functions EY and EKL lies in the fact that EKL function includes the IMF azimuthal (BY) component. As BY increases relative to BZ, the difference between electric fields EY and EKL quickly grows, and the value of EKL field can be as large as 5-10 mV/m even under conditions of northward IMF orientation, when EY reaches to zero. The same situation is valid for substorms triggered by sharp northward turning of the IMF BZ component following the prolonged period of southward IMF influence. Examination of these substorms demonstrates that they are initiated by increase of coupling function EKL and that the substorm sudden onsets were preceded by the PC index growth. Consistency between the IMF northward turning and substorm sudden onset in these cases is coincidence that explains why substorm are only occasionally initiated by the IMF northward turning. Thus, the "extraordinary" storms and substorms occurring under conditions of ineffective northward IMF component turned out to be events nothing out of the ordinary, if examining them in relation to proper coupling function (EKL) and monitoring them by the PC index.

  4. The Distant Magnetotail Under Long Duration, Very Northward IMF Conditions: October 22-24, 2003

    NASA Technical Reports Server (NTRS)

    Fairfield, Donald H.; Oieroset, M.; Raeder, J.; Lepping, R. P.; Newell, P. T.; Wind, S.

    2006-01-01

    A unique 32 hour interval of very northward Interplanetary Magnetic Field (IMF) on October 22-24, 2003 created a exceptionally thick cold dense magnetotail plasma sheet, a small polar cap and accompanying small tail lobe. These features were detected by the Cluster DMSP and FAST spacecraft and modeled by a global simulation as described in papers by Oieroset et al. (2005) and Li et al. (2005). During the same interval the Wind spacecraft was passing through the center of the magnetotail about 130 Re downstream of Earth. Wind results will be described that reveal a very unusual magnetotail characterized by (1) continual tailward flow of 200-400 km/s with densities in the range 0.2-3/cc, both of whch are clearly less than those expected in the magnetosheath, (2) a mostly northward Bz but with a predominant Bx field component with sign reversals indicating crossings between the two hemispheres of the tail, and (3) velocity waves superposed on the downstream flow with peak-to-peak amplitudes of 100 to 200 km/s, periods of 10 to 20 minutes and clockwise polarization. Low altitude DMSP and Fast measurements reveal an auroral oval with enhanced latitudinal thickness and a small polar cap filled with structured precipitzting electrons and few ions. A new global MHD simulation of the event exhibits a highly elliptical tail of diminished cross-section at 130 Re with major axis aligned with the northward IMF. The tail current sheet also tends to be aligned in a north-south direction with the two tail hemispheres to the east and west with their polarities depending on prior history of the IMF. The simulation appears to be consistent with many, but not all, of the observations. High latitude cusp reconnection and subsequent downtail flow of closed field lines may explain the tail structure, but the waves are more likely due to the Kelvin-Helmholtz instability often thought to occur during northward IMF conditions.

  5. 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.

  6. Auroral Substorms during Prolonged Northward IMF

    NASA Astrophysics Data System (ADS)

    Du, Aimin

    Multiple observations by satellites and ground-based magnetometers identify the occurrence of substorm events during prolonged northward interplanetary magnetic field (IMF). The func-tion, as an expression of the solar wind energy flow, and the energy dissipation in the ionosphere (UI) are calculated during substorm periods. The delay time of the UI to the function and UI for seven substorm events with AL values of -231 -1500 nT under northward IMF condition are 45 95 min with a mean value of 70.86 min. For comparison, 23 substorm events with the AL index of -316 -1685 nT under southward IMF condition are detected to have the delay time of 21 66 min with a mean value of 42.04 min. The longer delay time for substorms during northward IMF can be presumably attributed to the contribution of IMF By component to merging between IMF and the Earth's magnetic field. A tendency of the decrease of the delay time with increasing absolute values of IMF By is noted. Acknowledgement: This work is supported by NSFC(40774086).

  7. Magnetic substorms and northward IMF turning

    NASA Astrophysics Data System (ADS)

    Troshichev, Oleg; Podorozhkina, Nataly

    To determine the relation of the northward IMF turnings to substorm sudden onsets, we separated all events with sharp northward IMF turnings observed in years of solar maximum (1999-2002) and solar minimum (2007-2008). The events (N=261) have been classified in 5 groups in accordance with average magnetic activity in auroral zone (low, moderate or high levels of AL index) at unchanged or slightly changed PC index and with dynamics of PC (steady distinct growth or distinct decline) at arbitrary values of AL index. Statistical analysis of relationships between the IMF turning and changes of PC and AL indices has been fulfilled separately for each of 5 classes. Results of the analysis showed that, irrespective of geophysical conditions and solar activity epoch, the magnetic activity in the polar caps and in the auroral zone demonstrate no response to the sudden northward IMF turning, if the moment of northward turning is taken as a key date. Sharp increases of magnetic disturbance in the auroral zone are observed only under conditions of the growing PC index and statistically they are related to moment of the PC index exceeding the threshold level (~1.5 mV/m), not to northward turnings timed, as a rule, after the moment of sudden onset. Magnetic disturbances observed in these cases in the auroral zone (magnetic substorms) are guided by behavior of the PC index, like to ordinary magnetic substorms or substorms developed under conditions of the prolonged northward IMF impact on the magnetosphere. The evident inconsistency between the sharp IMF changes measured outside of the magnetosphere and behavior of the ground-based PC index, the latter determining the substorm development, provides an additional argument in favor of the PC index as a ground-based proxy of the solar wind energy that entered into magnetosphere.

  8. An evidence for prompt electric field disturbance driven by changes in the solar wind density under northward IMF Bz condition

    NASA Astrophysics Data System (ADS)

    Rout, Diptiranjan; Chakrabarty, D.; Sekar, R.; Reeves, G. D.; Ruohoniemi, J. M.; Pant, Tarun K.; Veenadhari, B.; Shiokawa, K.

    2016-05-01

    Before the onset of a geomagnetic storm on 22 January 2012 (Ap = 24), an enhancement in solar wind number density from 10/cm3 to 22/cm3 during 0440-0510 UT under northward interplanetary magnetic field (IMF Bz) condition is shown to have enhanced the high-latitude ionospheric convection and also caused variations in the geomagnetic field globally. Conspicuous changes in ΔX are observed not only at longitudinally separated low-latitude stations over Indian (prenoon), South American (midnight), Japanese (afternoon), Pacific (afternoon) and African (morning) sectors but also at latitudinally separated stations located over high and middle latitudes. The latitudinal variation of the amplitude of the ΔX during 0440-0510 UT is shown to be consistent with the characteristics of prompt penetration electric field disturbances. Most importantly, the density pulse event caused enhancements in the equatorial electrojet strength and the peak height of the F layer (hmF2) over the Indian dip equatorial sector. Further, the concomitant enhancements in electrojet current and F layer movement over the dip equator observed during this space weather event suggest a common driver of prompt electric field disturbance at this time. Such simultaneous variations are found to be absent during magnetically quiet days. In absence of significant change in solar wind velocity and magnetospheric substorm activity, these observations point toward perceptible prompt electric field disturbance over the dip equator driven by the overcompression of the magnetosphere by solar wind density enhancement.

  9. Impact of Magnetic Draping, Convection, and Field Line Tying on Magnetopause Reconnection Under Northward IMF

    NASA Technical Reports Server (NTRS)

    Wendel, Deirdre E.; Reiff, Patricia H.; Goldstein, Melvyn L.

    2010-01-01

    We simulate a northward IMF cusp reconnection event at the magnetopause using the OpenGGCM resistive MHD code. The ACE input data, solar wind parameters, and dipole tilt belong to a 2002 reconnection event observed by IMAGE and Cluster. Based on a fully three-dimensional skeleton separators, nulls, and parallel electric fields, we show magnetic draping, convection, ionospheric field line tying play a role in producing a series of locally reconnecting nulls with flux ropes. The flux ropes in the cusp along the global separator line of symmetry. In 2D projection, the flux ropes the appearance of a tearing mode with a series of 'x's' and 'o's' but bearing a kind of 'guide field' that exists only within the magnetopause. The reconnecting field lines in the string of ropes involve IMF and both open and closed Earth magnetic field lines. The observed magnetic geometry reproduces the findings of a superposed epoch impact parameter study derived from the Cluster magnetometer data for the same event. The observed geometry has repercussions for spacecraft observations of cusp reconnection and for the imposed boundary conditions reconnection simulations.

  10. Separator reconnection at the magnetopause for predominantly northward and southward IMF: Techniques and results

    NASA Astrophysics Data System (ADS)

    Glocer, A.; Dorelli, J.; Toth, G.; Komar, C. M.; Cassak, P. A.

    2016-01-01

    In this work, we demonstrate how to track magnetic separators in three-dimensional simulated magnetic fields with or without magnetic nulls, apply these techniques to enhance our understanding of reconnection at the magnetopause. We present three methods for locating magnetic separators and apply them to 3-D resistive MHD simulations of the Earth's magnetosphere using the Block-Adaptive-Tree Solar-wind Roe-type Upwind Scheme code. The techniques for finding separators and determining the reconnection rate are insensitive to interplanetary magnetic field (IMF) clock angle and can in principle be applied to any magnetospheric model. Moreover, the techniques have a number of advantages over prior separator finding techniques applied to the magnetosphere. The present work examines cases of high and low resistivity for two clock angles. We go beyond previous work examine the separator during Flux Transfer Events (FTEs). Our analysis of reconnection on the magnetopause yields a number of interesting conclusions: Reconnection occurs all along the separator even during predominately northward IMF cases. Multiple separators form in low-resistivity conditions, and in the region of an FTE the separator splits into distinct branches. Moreover, the local contribution to the reconnection rate, as determined by the local parallel electric field, drops in the vicinity of the FTE with respect to the value when there are none.

  11. Extreme Poynting Flux Depostion in the Polar Cap and Polar Cap Boundary Regions During Northward IMF

    NASA Astrophysics Data System (ADS)

    Knipp, D.; Kilcommons, L. M.; Cook, M. R.; Larson, T.; Redmon, R. J.

    2015-12-01

    We investigate several intervals of prolonged northward Interplanetary Magnetic Field (IMF) and describe the correlation between strong Poynting flux and the transverse components of the IMF. We primarily focus on Summer events in each hemisphere when the polar regions are sunlit. During northward IMF the magnetic reconnection regions can form tailward of the magnetic cusp. Using data from the Defense Meteorological Satellite Program (DMSP) F13, F15 and F16 spacecraft we looked for and found areas of strong Poynting flux over the magnetic polar cap regions. Values ranging from 20 mW/m^2 to 140 mW/m^2 were measured in narrow channels, showing that there can be significant energy transport to small concentrated regions at very high latitudes. An example of an event from 2001 is shown in the attached image. We also show where these events occur with respect to the dynamic polar cap boundary and discuss the implications of this extreme Poynting flux for other aspects of polar thermodynamics and electrodynamics.

  12. Characteristics of penetration electric fields to the equatorial ionosphere during southward and northward IMF turnings

    NASA Astrophysics Data System (ADS)

    Bhaskar, Ankush; Vichare, Geeta

    2013-07-01

    The signatures of abrupt turnings of the vertical component of the interplanetary magnetic field (IMF), Bz, can be seen at equatorial latitudes through the prompt transmission of high-latitude electric fields to the lower latitudes, called as prompt penetration electric field (PPE). The present work studies the signatures of PPE in daytime equatorial electrojet (EEJ) index derived in the Indian sector during 2001-2005. The signatures are observed in polar (PCN index) and equatorial (EEJ index) ionosphere almost instantaneously (<1 min). The communication time of 12±6 min is observed between bow shock nose and the equatorial ionosphere, and it is found to have inverse relationship with radial component of solar wind velocity during southward and northward Bz turnings which might indicate magnetosphere crossing time scale by solar wind. Ionospheric reconfiguration time during southward turnings shows inverse relationship with solar wind flow in contrast to northward turnings with "no relationship," indicating differences in underlying physical mechanisms during both turnings. We observe no local time dependence (within 06-18 h) in conductivity-corrected EEJ signatures associated with Bz turnings. Regression analysis between conductivity-corrected EEJ and interplanetary electric field shows higher efficiency during northward turnings. However, further analysis investigating the effect of actual orientation of Bz indicates that the magnitude of northward Bz does not have influence on the ionospheric signatures. It is noticed that the response signatures are mainly controlled by the magnitudes of southward Bz. Thus, the present study signifies the role of inner magnetospheric shielding electric field in addition to ceasing of convection during northward turnings.

  13. Observations of a transient event in the subsolar magnetosheath during strongly northward IMF

    NASA Astrophysics Data System (ADS)

    Dias Silveira, M. V.; Sibeck, D. G.; Gonzalez, W. D.; Koga, D.

    2013-12-01

    We present multipoint THEMIS observation of a transient event in the subsolar magnetosheath on July 10, 2007. The event exhibits some features of a flux transfer event, such as a bipolar variation in the magnetic field component normal to the nominal magnetopause centered on a peak in the total magnetic field strength. Four THEMIS spacecraft were in the magnetosheath and one in the magnetosphere. Timing analysis and the absence of flow perturbation suggest that the event is a small scale structure (~0.12 Re in the direction of the flow) moving with the background magnetosheath flow. Despite the inferred small size of the event, THC and THD both observed large amplitude (~40 nT) bipolar magnetic field signatures normal to the nominal magnetopause. Nearby spacecraft THE (only 0.2 Re further outward in the Xgsm direction) observed no significant magnetic field perturbation. Neither did THB or THA, located further away in the magnetosheath and magnetosphere, respectively. During the event, the IMF was strongly northward (approximately 20nT), which does not favor subsolar magnetic reconnection. Inside the structure, the magnetic field briefly rotates 90° away from northward to dawnward. Ions stream antiparallel to the magnetic field in the magnetosheath, parallel to the magnetic field in the event.

  14. Investigation of a rare event where the polar ionospheric reverse convection potential does not saturate during a period of extreme northward IMF solar wind driving

    NASA Astrophysics Data System (ADS)

    Clauer, C. Robert; Xu, Zhonghua; Maimaiti, M.; Ruohoneimi, J. Michael; Scales, Wayne; Hartinger, Michael D.; Nicolls, Michael J.; Kaeppler, Stephen; Wilder, Frederick D.; Lopez, Ramon E.

    2016-06-01

    A variety of statistical studies have shown that the ionospheric polar potential produced by solar wind-magnetosphere-ionosphere coupling is linear for weak to moderate solar wind driving but becomes nonlinear during periods of very strong driving. It has been shown that this applies to the two-cell convection potential that develops during southward interplanetary magnetic field (IMF) and also to the reverse convection cells that develop during northward IMF. This has been described as polar potential saturation, and it appears to begin when the driving solar wind electric field becomes greater than 3 mV/m. Utilizing measurements from the Resolute Incoherent Scatter Radar (RISR-N), we examine ionospheric data near local noon within the reverse convection cells that developed during a period of very strong northward interplanetary magnetic field (IMF) on 12 September 2014. During this period we measure the electric field within the throat of the reverse convection cells to be near 150 mV/m at a time when the IMF is nearly 28 nT northward. This is far in excess of the 30-40 mV/m expected for polar potential saturation of the reverse convection cells. In fact, the development of the electric field responds linearly to the IMF Bz component throughout this period of extreme driving. The conditions in the solar wind show the solar wind velocity near 600 km/s, number density near 20 ions/cm3, and the Alfvén velocity about 75 km/s giving an Alfvén Mach number of 8. A search of several years of solar wind data shows that these values occur together 0.035% of the time. These conditions imply a high plasma β in the magnetosheath. We believe that condition of high β along with high mass density and a strong merging electric field in the magnetosheath are the significant parameters that produce the linear driving of the ionospheric electric field during this unusual period of extreme solar wind conditions. A discussion of current theories to account for cross-polar cap

  15. Connection between high-latitude arcs and the low-latitude boundary layer during periods of northward IMF

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    High-latitude auroral arcs are a typical feature of periods of northward IMF. They consist in thin and elongated optical emission similar to discrete auroral arcs but located in the polar ionosphere. Their formation mechanism and the magnetospheric regions to which they are connected are still not well understood. On November 10, 2005, high-latitude arcs were detected by an all-sky camera at Resolute Bay in Canada and by the TIMED/GUVI and DMSP/SUSIE space-based imagers. These observations indicate that they were detaching from the duskside auroral oval and then drifting poleward while pointing in the cusp direction. The same day, the Cluster spacecraft were flying in the dawn-dusk direction from the lobe region at altitudes ~5 RE to the magnetospheric equatorial plane at geocentric distances ~19 RE. Cluster observations reveal the presence of field-aligned acceleration regions above the polar ionosphere associated with the high-latitude arcs detected by the imagers. We analyze Cluster particle observations from the lobe region to the duskside magnetopause. In the high-latitude arcs region, Cluster detects upgoing ions and precipitating electrons accelerated by a quasi-static electric field. These accelerated particles coexist with plasmasheet-like plasma embedded in the lobe region. A comparison between the 4 Cluster spacecraft electron measurements for the most poleward arc reveals that the plasmasheet-like electron population is vanishing on a time scale of a few minutes while the plasmasheet-like ion population doesn't display any temporal evolution. The most equatorward arc is separated from the auroral oval by a "transition" region where weak fluxes of ions with plasmasheet like temperatures are detected. Then the Cluster spacecraft cross the plasmasheet until they reach the low-latitude boundary layer (LLBL) characterized by a mixture of plasmasheet and magnetosheath plasma. The "transition" region and the LLBL are magnetically connected. Using Cluster

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

    NASA Astrophysics Data System (ADS)

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

    2002-10-01

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

  17. Separator reconnection at Earth's dayside magnetopause under generic northward interplanetary magnetic field conditions

    NASA Astrophysics Data System (ADS)

    Dorelli, John C.; Bhattacharjee, Amitava; Raeder, Joachim

    2007-02-01

    We investigate the global properties of magnetic reconnection at the dayside terrestrial magnetopause under generic northward interplanetary magnetic field (IMF) conditions. In particular, we consider a zero dipole tilt case where the y and z components of the IMF (in GSM coordinates) are equal in magnitude, using three-dimensional resistive magnetohydrodynamics (MHD) simulations to address the following questions: (1) What is the geometry of the dayside X line? (2) How is current density distributed over the magnetopause surface? Using a technique described by Geene (1992) to track the magnetic nulls in the system, we identify the dayside X line as a magnetic separator line, a segment of a magnetic field line which extends across the dayside magnetopause, terminating in the cusps. We demonstrate that the separator line is the intersection of two separatrix surfaces which define volumes containing topologically distinct field lines. Parallel current density, proportional to the parallel electric field in our resistive MHD simulations, is distributed in a broad, thin sheet which extends across the separator line and terminates in the cusps. Thus separator reconnection at the dayside magnetopause displays features of both antiparallel (near the cusp nulls) and component (near the subsolar separator line) reconnection. We discuss some implications of our results for spacecraft observations of reconnection signatures.

  18. A global MHD simulation study of the vortices at the magnetosphere boundary under the southward IMF condition

    NASA Astrophysics Data System (ADS)

    Park, K.; Ogino, T.; Lee, D.; Walker, R. J.; Kim, K.

    2013-12-01

    One of the significant problems in magnetospheric physics concerns the nature and properties of the processes which occur at the magnetopause boundary; in particular how energy, momentum, and plasma the magnetosphere receives from the solar wind. Basic processes are magnetic reconnection [Dungey, 1961] and viscouslike interaction, such as Kelvin-Helmholtz instability [Dungey 1955, Miura, 1984] and pressure-pulse driven [Sibeck et al. 1989]. In generally, magnetic reconnection occurs efficiently when the IMF is southward and the rate is largest where the magnetosheath magnetic field is antiparallel to the geomagnetic field. [Sonnerup, 1974; Crooker, 1979; Luhmann et al., 1984; Park et al., 2006, 2009]. The Kelvin-Helmholtz instability is driven by the velocity shear at the boundary, which occur frequently when the IMF is northward. Also variation of the magnetic field and the plasma properties is reported to be quasi-periodic with 2-3min [Otto and Fairfield, 2000] and period of vortex train with 3 to 4 minutes by global MHD simulation [Ogino, 2011]. The pressure-pulse is driven by the solar wind. And the observations of the magnetospheric magnetic field response show quasi-periodic with a period of 8 minutes [Sibeck et al., 1989; Kivelson and Chen, 1995]. There have been few studies of the vortices in the magnetospheric boundary under southward IMF condition. However it is not easy to find the generation mechanism and characteristic for vortices in complicated 3-dimensional space. Thus we have performed global MHD simulation for the steady solar wind and southward IMF conditions. From the simulation results, we find that the vortex occurs at R= 11.7Re (IMF Bz = -2 nT) and R= 10.2Re (IMF Bz = -10 nT) in the dayside magnetopause boundary. Also the vortex rotates counterclockwise in duskside magnetopause (clockwise in dawnside) and propagates tailward. Across the vortex, magnetic field and plasma properties clearly show quasi-periodic fluctuations with a period of 8

  19. Ion and neutral polar winds for northward interplanetary magnetic field conditions

    NASA Astrophysics Data System (ADS)

    Gardner, Larry C.; Schunk, Robert W.

    2006-08-01

    The coupling of the ionosphere/magnetosphere system at high-latitudes is dependent in part upon the transport of neutral atoms from the ionosphere to the magnetosphere, and visa versa. The neutral atoms that flow between the ionosphere and the magnetosphere are neutral stream atoms that are produced in charge exchange reactions between the ions in the polar wind and the background thermal and geocoronal atoms. The characteristics of these neutral stream particles are highly dependent upon the ions in the polar cap. The ions are convected across the polar cap due to convection electric fields, and thus the neutral stream particles are also indirectly affected by the convection electric fields due to charge exchange. The horizontal flow of neutral stream particles, therefore, shows a general anti-sunward motion during periods of southward interplanetary magnetic field (IMF), and a general sunward flow across the magnetic pole during times of northward IMF. The vertical fluxes of these neutral stream particles depend upon several processes, including the heat input due to precipitating electrons, the vertical velocity of the ions involved in the charge exchange reactions that produce the neutral stream particles, and the time history of neutral stream particles in the high-latitude region.

  20. 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.

  1. Influence of Geomagnetic and IMF conditions on High Latitude Upper Atmospheric winds and Temperatures

    NASA Astrophysics Data System (ADS)

    Dhadly, M. S.; Conde, M.; Emmert, J. T.

    2015-12-01

    We analyzed the climatological behavior of upper atmospheric winds (horizontal and vertical) and temperatures above Alaska by combining line-of-sight Doppler shifts of 630 nm optical emissions recorded during the 2011 and 2012 winters using a ground based all-sky wavelength scanning Doppler Fabry-Perot interferometer (SDI) located at Poker Flat (65.12N, 147.47W). The wide field of view covered a large geographic region above Alaska. This field was divided in software into multiple zones (115 used here), allowing independent spectra to be sampled from many directions simultaneously. As a result, it is capable of recording the wind field's spatial variations over a wide geographic region with high spatial resolution, and to resolve these variations over time. Although such climatological studies have been performed previously using satellites, models, and narrow field Fabry-Perot interferometers, there are no published climatological studies of thermospheric winds and temperatures using either SDI data or any other technique with comparable geographic coverage and resolution. Wind summary dial plots were produced to depict the climatology of the horizontal winds and temperatures for different geomagnetic conditions and orientation of interplanetary magnetic field (IMF). Results show that horizontal winds and temperatures had a strong dependence on geospace activity and orientation of IMF. The latitudinal shears in horizontal winds were stronger when geomagnetic conditions were active compared to the latitudinal shears for quiet conditions. Also, shears appeared earlier over Poker Flat when geomagnetic conditions were active. The latitudinal shears showed more dependence on IMF when geomagnetic conditions were active than they did during quieter conditions. F-region temperatures were higher under active geomagnetic conditions than during quiet conditions. They were also observed to be higher in pre-magnetic midnight sector (duskside) than they were post

  2. Multi-Fault Detection of Rolling Element Bearings under Harsh Working Condition Using IMF-Based Adaptive Envelope Order Analysis

    PubMed Central

    Zhao, Ming; Lin, Jing; Xu, Xiaoqiang; Li, Xuejun

    2014-01-01

    When operating under harsh condition (e.g., time-varying speed and load, large shocks), the vibration signals of rolling element bearings are always manifested as low signal noise ratio, non-stationary statistical parameters, which cause difficulties for current diagnostic methods. As such, an IMF-based adaptive envelope order analysis (IMF-AEOA) is proposed for bearing fault detection under such conditions. This approach is established through combining the ensemble empirical mode decomposition (EEMD), envelope order tracking and fault sensitive analysis. In this scheme, EEMD provides an effective way to adaptively decompose the raw vibration signal into IMFs with different frequency bands. The envelope order tracking is further employed to transform the envelope of each IMF to angular domain to eliminate the spectral smearing induced by speed variation, which makes the bearing characteristic frequencies more clear and discernible in the envelope order spectrum. Finally, a fault sensitive matrix is established to select the optimal IMF containing the richest diagnostic information for final decision making. The effectiveness of IMF-AEOA is validated by simulated signal and experimental data from locomotive bearings. The result shows that IMF-AEOA could accurately identify both single and multiple faults of bearing even under time-varying rotating speed and large extraneous shocks. PMID:25353982

  3. Global Auroral Energy Deposition during Substorm Onset Compared with Local Time and Solar Wind IMF Conditions

    NASA Technical Reports Server (NTRS)

    Spann, J. F.; Brittnacher, M.; Fillingim, M. O.; Germany, G. A.; Parks, G. K.

    1998-01-01

    The global images made by the Ultraviolet Imager (UVI) aboard the IASTP/Polar Satellite are used to derive the global auroral energy deposited in the ionosphere resulting from electron precipitation. During a substorm onset, the energy deposited and its location in local time are compared to the solar wind IMF conditions. Previously, insitu measurements of low orbiting satellites have made precipitating particle measurements along the spacecraft track and global images of the auroral zone, without the ability to quantify energy parameters, have been available. However, usage of the high temporal, spatial, and spectral resolution of consecutive UVI images enables quantitative measurement of the energy deposited in the ionosphere not previously available on a global scale. Data over an extended period beginning in January 1997 will be presented.

  4. A Small Postmidnight Substorm During IMF Bz+ and By+ Conditions -- Joint Optical, Radar, Magnetic and Satellite Observations

    NASA Astrophysics Data System (ADS)

    Liang, J.; Sofko, G.; Donovan, E.; Greenwald, R.

    2002-12-01

    Multi-instrument observations of a small postmidnight substorm event during a period of IMF dominated by Bz+ and By+ conditions on October 9, 2000, showed the substorm structure with high time resolution. Three optical intensifications and Pi2 bursts occurred. The last and strongest Pi2 burst was associated with an expansive phase (EP) onset, characterized by a 100 nT magnetic bay at Fort Churchill and an auroral breakup in which the 630 nm emissions moved poleward about 2.5 degrees. About 11 minutes after the first EP onset, a second stage of auroral brightening occurred. For each of the three initial optical intensifications, there was an eastward-moving discrete azimuthal structure. SuperDARN HF radar line-of-sight velocity measurements revealed eastward electric fields within each Pi2 wave train. The observations are interpreted as resulting from the drift-Alfven-ballooning (DAB) mode instability at near-geosynchronous orbit (NGO) locations. Within the NGO drift waves, regions of charge separation led to electric fields and field-aligned currents (FACs) of alternating direction. The ionospheric reflection of Alfven wave energy likely generated the Pi2 pulsations observed on the ground. The multi-instrument ground observations agree quite well with the substorm onset scenario based upon CRRES satellite observations by Erickson et al. [2000]. There was a single, relatively confined (~4 hour in MLT) counterclockwise convection cell during the growth phase and EP onset. A clearly defined vortex at its center defined the center of the downward FAC. This vortex, initially northward of the optical aurora, moved eastward and then suddenly southward just prior to the EP onset. At that time, the FAC structure was typical of the substorm current wedge (SCW). Reasons for the convection cell motion and SCW development are discussed. Erickson, G. M., N. C. Maynard, W. J. Burke, G. R. Wilson, and M. A. Heinemann, Electromagnetics of substorm onsets in the near

  5. Proton Aurora Dynamics in Response to the IMF and Solar Wind Variations

    NASA Technical Reports Server (NTRS)

    Chang, S.; Mende, S.; Frey, H.; Gallagher, D. L.; Lepping, R. P.; Six, N. Frank (Technical Monitor)

    2002-01-01

    On May 23, 2000, proton auroras observed by IMAGE (Imager for Magnetopause to Aurora Global Exploration) FUV (Far Ultraviolet) on the dayside were very dynamic. Auroral pattern in the cusp is well correlated with Interplanetary Magnetic Field (IMF) and solar wind parameters. When IMF were northward, cusp proton aurora appeared at high latitude poleward from the auroral oval. A high-latitude proton aurora brightened after solar wind ion temperature increased and it disappeared after IMF turned southward. Under the southward IMF condition, auroral activity occurred only in the dayside auroral oval. As IMF $B_z$ reverted to northward, cusp proton aurora reappeared at high latitude. The magnetic local time of the cusp proton aurora changes with the IMF $B_y$ polarity, consistent with previous reports. These results suggest an upstream source of the high-latitude cusp proton aurora for this event. One possible explanation is that bow shock energetic ions are transported into the cusp via the high-latitude magnetic merging process to induce optical emissions in the ionosphere.

  6. Temporal evolutions of the solar wind conditions at 1 AU prior to the near-Earth X lines in the tail: Superposed epoch analysis

    NASA Astrophysics Data System (ADS)

    Zhang, L. Q.; Dai, L.; Baumjohann, W.; Lui, A. T. Y.; Wang, C.; Rème, H.; Dunlop, M. W.

    2016-08-01

    Utilizing conjunction observations of the Geotail and ACE satellites from 1998 to 2005, we investigated the temporal evolutions of the solar wind conditions prior to the formation of X lines in the near-Earth magnetotail. We first show the statistical properties of Bz, By, density, and velocity of the solar wind related to the 374 tail X line events. A superposed epoch analysis is performed to study the temporal evolutions of the solar wind conditions 5 h prior to the tail X lines. The solar wind conditions for tail X lines during southward interplanetary magnetic field (IMF) (SW-IMF) and northward IMF (NW-IMF) are analyzed. The main results are as follows: (1) For events classified as SW-IMF, near-Earth X line observations in the magnetosphere are preceded by ~2 h intervals of southward IMF; (2) for events classified as NW-IMF, the northward IMF orientation preceding near-Earth X line observations lasts ~ 40 min.

  7. Shift of the magnetopause reconnection line to the winter hemisphere under southward IMF conditions: Geotail and MMS observations

    NASA Astrophysics Data System (ADS)

    Kitamura, N.; Hasegawa, H.; Saito, Y.; Shinohara, I.; Yokota, S.; Nagai, T.; Pollock, C. J.; Giles, B. L.; Moore, T. E.; Dorelli, J. C.; Gershman, D. J.; Avanov, L. A.; Paterson, W. R.; Coffey, V. N.; Chandler, M. O.; Sauvaud, J. A.; Lavraud, B.; Torbert, R. B.; Russell, C. T.; Strangeway, R. J.; Burch, J. L.

    2016-06-01

    At 02:13 UT on 18 November 2015 when the geomagnetic dipole was tilted by -27°, the MMS spacecraft observed southward reconnection jets near the subsolar magnetopause under southward and dawnward interplanetary magnetic field conditions. Based on four-spacecraft estimations of the magnetic field direction near the separatrix and the motion and direction of the current sheet, the location of the reconnection line was estimated to be ~1.8 RE or further northward of MMS. The Geotail spacecraft at GSM Z~1.4 RE also observed southward reconnection jets at the dawnside magnetopause 30-40 min later. The estimated reconnection line location was northward of GSM Z~2 RE. This crossing occurred when MMS observed purely southward magnetic fields in the magnetosheath. The simultaneous observations are thus consistent with the hypothesis that the dayside magnetopause reconnection line shifts from the subsolar point toward the northern (winter) hemisphere due to the effect of geomagnetic dipole tilt.

  8. IMF draping around the geotail - IMP 8 observations

    NASA Technical Reports Server (NTRS)

    Kaymaz, Zerefsan; Siscoe, George; Luhmann, Janet G.

    1992-01-01

    The draping pattern for the full range of IMF directions is mapped in the GSM yz-plane using a large data set for studying magnetic field draping around the tail. Based on the maps, it is concluded that the dominant pattern is draping as found by Ohtani and Kokubun (1991) and Sanchez and Siscoe (1990). A new finding is that the draping pattern is rotated relative to the plane formed by the IMF and the aberrated x-axis, with the degree of rotation varying from zero for strongly northward and southward IMF to a peak of 17 deg for moderately southward IMF. It is also found that the tail radius is bigger for southward IMF than for northward IMF.

  9. Seasonal variations in the diet and foraging behaviour of dunlins Calidris alpina in a south European estuary: improved feeding conditions for northward migrants.

    PubMed

    Martins, Ricardo C; Catry, Teresa; Santos, Carlos D; Palmeirim, Jorge M; Granadeiro, José P

    2013-01-01

    During the annual cycle, migratory waders may face strikingly different feeding conditions as they move between breeding areas and wintering grounds. Thus, it is of crucial importance that they rapidly adjust their behaviour and diet to benefit from peaks of prey abundance, in particular during migration, when they need to accumulate energy at a fast pace. In this study, we compared foraging behaviour and diet of wintering and northward migrating dunlins in the Tagus estuary, Portugal, by video-recording foraging birds and analysing their droppings. We also estimated energy intake rates and analysed variations in prey availability, including those that were active at the sediment surface. Wintering and northward migrating dunlins showed clearly different foraging behaviour and diet. In winter, birds predominantly adopted a tactile foraging technique (probing), mainly used to search for small buried bivalves, with some visual surface pecking to collect gastropods and crop bivalve siphons. Contrastingly, in spring dunlins generally used a visual foraging strategy, mostly to consume worms, but also bivalve siphons and shrimps. From winter to spring, we found a marked increase both in the biomass of invertebrate prey in the sediment and in the surface activity of worms and siphons. The combination of these two factors, together with the availability of shrimps in spring, most likely explains the changes in the diet and foraging behaviour of dunlins. Northward migrating birds took advantage from the improved feeding conditions in spring, achieving 65% higher energy intake rates as compared with wintering birds. Building on these results and on known daily activity budgets for this species, our results suggest that Tagus estuary provides high-quality feeding conditions for birds during their stopovers, enabling high fattening rates. These findings show that this large wetland plays a key role as a stopover site for migratory waders within the East Atlantic Flyway. PMID

  10. Seasonal Variations in the Diet and Foraging Behaviour of Dunlins Calidris alpina in a South European Estuary: Improved Feeding Conditions for Northward Migrants

    PubMed Central

    Martins, Ricardo C.; Catry, Teresa; Santos, Carlos D.; Palmeirim, Jorge M.; Granadeiro, José P.

    2013-01-01

    During the annual cycle, migratory waders may face strikingly different feeding conditions as they move between breeding areas and wintering grounds. Thus, it is of crucial importance that they rapidly adjust their behaviour and diet to benefit from peaks of prey abundance, in particular during migration, when they need to accumulate energy at a fast pace. In this study, we compared foraging behaviour and diet of wintering and northward migrating dunlins in the Tagus estuary, Portugal, by video-recording foraging birds and analysing their droppings. We also estimated energy intake rates and analysed variations in prey availability, including those that were active at the sediment surface. Wintering and northward migrating dunlins showed clearly different foraging behaviour and diet. In winter, birds predominantly adopted a tactile foraging technique (probing), mainly used to search for small buried bivalves, with some visual surface pecking to collect gastropods and crop bivalve siphons. Contrastingly, in spring dunlins generally used a visual foraging strategy, mostly to consume worms, but also bivalve siphons and shrimps. From winter to spring, we found a marked increase both in the biomass of invertebrate prey in the sediment and in the surface activity of worms and siphons. The combination of these two factors, together with the availability of shrimps in spring, most likely explains the changes in the diet and foraging behaviour of dunlins. Northward migrating birds took advantage from the improved feeding conditions in spring, achieving 65% higher energy intake rates as compared with wintering birds. Building on these results and on known daily activity budgets for this species, our results suggest that Tagus estuary provides high-quality feeding conditions for birds during their stopovers, enabling high fattening rates. These findings show that this large wetland plays a key role as a stopover site for migratory waders within the East Atlantic Flyway. PMID

  11. Simulation of the geospace response to a sudden change in IMF orientation.

    NASA Astrophysics Data System (ADS)

    Lopez, R. E.; Pham, K. H.; Wiltberger, M. J.

    2015-12-01

    We have conducted simulations of the response of the geospace system to a sudden change in the orientation of the interplanetary magnetic field (IMF) using the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic code. Specifically, we have explored a sudden change in the IMF orientation from an extended period during which it was steady northward, to a steady southward IMF. The change in the IMF orientation first causes a reversal in the direction of the bow shock current, which launches a fast mode wave that propagates through the system, causing changes in the overall current pattern even before the southward IMF arrives at the dayside magnetopause to initiate low latitude merging. When the southward IMF does arrive at the magnetopause, the preceding northward IMF in the solar wind flow is still driving high latitude merging poleward of the cusp. Even when the two-cell convection pattern in the ionosphere becomes the dominant convection, the LFM results show that there is still some remnant of the high latitude reverse cell convection that is associated with northward IMF that had previously merged with the geomagnetic field and which takes some time to be cleared out of the system. We will present a detailed account of the timescales and changes in the magnetic topologies, current systems, magnetospheric plasma flows, and ionospheric potential patterns associated with the transition from northward to southward IMF. We will also discuss the implications of these findings for understanding the effect of transient changes in IMF orientations.

  12. Magnetic reconnection due to Kelvin-Helmholtz waves at the magnetopause during northward interplanetary magnetic field

    NASA Astrophysics Data System (ADS)

    Li, Wenya; André, Mats; Khotyaintsey, Yuri; Vaivads, Andris; Graham, Daniel; Wang, Chi; Tang, Binbin; Burch, James; Lindqvist, Per-Arne; Ergun, Robert; Torbert, Roy; Magnes, Werner; Russell, Christopher; Giles, Barbara; Pollock, Craig

    2016-04-01

    The Kelvin-Helmholtz (K-H) instability is predominantly excited during northward interplanetary magnetic field (IMF), and reconnection due to K-H waves has been suggested to break the frozen-in condition and transport solar wind plasma into the magnetosphere. We investigated the magnetopause boundaries of a K-H wave case observed by the new Magnetospheric Multiscale (MMS) mission, and found ion jets in the trailing edges of the K-H waves along both the positive and negative directions relative to the magnetosheath ion flow. The ion jets satisfy the Walen test. The high-energy magnetospheric electrons are observed on the magnetosheath side of the jets, and the pitch angle distributions are consistent with the magnetic field configuration of both positive and negative jets. The magnetosheath ions mix with magnetosphere ions on the magnetospheric side of the jets, and there are flat-top electron distributions near the jets. We concluded that these observations are unambiguous pieces of evidence for reconnection due to K-H waves during northward IMF.

  13. Properties of Kelvin-Helmholtz waves at the magnetopause under northward interplanetary magnetic field: Statistical study

    NASA Astrophysics Data System (ADS)

    Lin, Dong; Wang, Chi; Li, Wenya; Tang, Binbin; Guo, Xiaocheng; Peng, Zhong

    2014-09-01

    We search the plasma and magnetic field data of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes B and C during 2008 and 2009 for observation evidences of the Kelvin-Helmholtz instability (KHI). Fourteen KHI events with rolled-up vortices are identified under the northward interplanetary magnetic field (IMF) at the low-latitude boundary layer (LLBL). We collect another 42 events reported from the observations of the Geotail, Double Star TC-1, and Cluster for a statistical study of the KH wave properties. All the 56 rolled-up KH wave events are quantitatively characterized by the dominant period, phase velocity, and the wavelength. We further explore the relationship between the KH wave period and the solar wind velocity (VSW) and the IMF clock angle. It is found that the KH period tends to be shorter under a higher VSW, and longer with a larger IMF clock angle. The spatial distribution of the KH wavelength shows a longitudinal growth with increasing distance from the subsolar point along the flank magnetopause. The statistical results provide new insights for the development of KH waves and their connection with the interplanetary conditions and deepen our understanding of the KHI at the magnetopause.

  14. Asymmetrical response of dayside ion precipitation to a large rotation of the IMF

    NASA Astrophysics Data System (ADS)

    Berchem, J.; Richard, R. L.; Escoubet, C. P.; Wing, S.; Pitout, F.

    2016-01-01

    We have carried out global magnetohydrodynamics (MHD) simulations together with large-scale kinetic simulations to investigate the response of the dayside magnetospheric ion precipitation to a large rotation (135°) of the interplanetary magnetic field (IMF). The study uses simplified global MHD model (no dipole tilt and constant ionospheric conductance) and idealized solar wind conditions where the IMF rotates smoothly from a southward toward a northward direction (BX = 0) to clearly identify the effects of the impact of the discontinuity on the magnetopause. Results of the global simulations reveal that a strong north-south asymmetry develops in the pattern of precipitating ions during the interaction of the IMF rotation with the magnetopause. For a counterclockwise IMF rotation from its original southward direction (BY < 0), a spot of high-energy particle injections occurs in the Northern Hemisphere but not in the Southern Hemisphere. The spot moves poleward and dawnward as the interacting field rotates. In that case, reconnection is found close to the poleward edge of the northern cusp, while it occurs farther tailward in the Southern Hemisphere. Tracing magnetic field lines shows an asymmetry in the tilt of the cusps and indicates that the draping and subsequent double reconnection of newly opened field lines from the Southern Hemisphere over the dayside magnetosphere cause the symmetry breaking. The reverse north-south asymmetry is found for a clockwise IMF rotation from its original southward direction (BY > 0). Trends observed in the ion dispersions predicted from the simulations are in good agreement with Cluster observations of the midaltitude northern cusp, which motivated the study.

  15. Response of the Reverse Convection to Sharp IMF Turnings

    NASA Astrophysics Data System (ADS)

    Taguchi, S.; Tawara, A.; Hairston, M. R.; Slavin, J. A.; Le, G.; Matzka, J.; Stolle, C.

    2014-12-01

    How strongly the dayside high-latitude convection is controlled by the orientation of the IMF for periods of the steady IMF is well established. However, the nature of the transition that the convection makes when the IMF changes sharply is still not fully understood. In the present paper, we report the characteristics of the transient nature of the reverse convection on the basis of observations from multi-spacecraft and ground magnetometer stations. During a period of northward IMF on 22 April 2006 the magnetic field observations from three ST-5 spacecraft identified distribution change in the polar cap field-aligned current which responds to a quick IMF turning from the purely northward orientation to the duskward orientation. At this time ST-5 flew over one of the Greenland magnetometer stations located near 1200 MLT. The analysis of the ground magnetic perturbations shows that the field-aligned current distribution, which is closely related to the reverse convection pattern, was changing gradually during about 10 min before reaching a steady state. When the steady state was going on, the IMF changed sharply from the duskward orientation to the dawnward orientation. Immediately after this IMF turning, three DMSP spacecraft (F13, F15, and F16) traversed the dayside polar cap in the northern hemisphere. The ion drift observation indicates that the polar cap convection changed from the clockwise circulation to the counter-clockwise circulation during about 10 min. The data from the Greenland magnetometer stations show that a transient state, i.e., deformation or reduction of the clockwise circulation started in the near-noon and postnoon sectors almost simultaneously when the ion drift consisting of the clockwise circulation is still seen in the prenoon polar cap by the DMSP spacecraft. We discuss the changing global patterns that occurred over the whole dayside polar cap during the course of the 10-min transient state for both cases.

  16. DC and Wave Electric Fields and Other Plasma Parameters Observed on Two Sounding Rockets in the Dark Cusp during IMF Bz North and South Conditions

    NASA Technical Reports Server (NTRS)

    Pfaff, R. F.; Acuna, M.; Bounds, S.; Farrell, W.; Freudenreich, W.; Lepping, R.; Vondrak, R.; Maynard, N. C.; Moen, J.; Egeland, A.

    1999-01-01

    Two Black Brant IX sounding rockets were launched into the dark, dayside cusp near magnetic noon on December 2 and 3, 1997, from Ny Alesund, Spitzbergen at 79 deg N reaching altitudes of about 450 km. Real-time ground-based and Wind IMF data were used to determine the launch conditions. The first launch, with Bz north conditions, crossed into and back out of an open field region with merging poleward of the projected trajectory. The second flight, into Bz south conditions, was timed to coincide with an enhancement in the merging rate from a increase in the negative Bz, while the DMSP Fl 3 satellite was situated slightly to the north of the rocket trajectory. Each payload returned DC electric and magnetic fields, plasma waves, energetic particles, photometer data, and thermal plasma data. Data from both flights will be shown, with an emphasis on the DC electric field results. In particular, the data gathered on December 2, 1997 will be used to discuss ionospheric signatures of merging and the open/closed character of the the cusp/low latitude boundary layer. In contrast, the data gathered on December 3, 1997 shows evidence of pulsed electric field structures which will be examined in the context of cusp plasma entry processes. Both data sets returned a rich variety of plasma waves, as well as optical emissions and thermal plasma data.

  17. DC and Wave Electric Fields and Other Plasma Parameters Observed on Two Sounding Rockets in the Dark Cusp During IMF Bz North and South Conditions

    NASA Technical Reports Server (NTRS)

    Pfaff, R. F.; Acuna, M.; Bounds, S.; Farrell, W.; Freudenreich, H.; Lepping, R.; Vondrak, R.; Maynard, N. C.; Moen, J.; Egeland, A.

    1997-01-01

    Two Black Brant IX sounding rockets were launched into the dark, dayside cusp near magnetic noon on December 2 and 3, 1997, from Ny Alesund, Spitzbergen at 79 N reaching altitudes of approximately 450 km. Real-time ground-based and Wind IMF data were used to determine the launch conditions. The first launch, with Bz north conditions, crossed into and back out of an open field region with merging poleward of the projected trajectory. The second flight, into Bz south conditions, was timed to coincide with an enhancement in the merging rate from a increase in the negative Bz, while the DMSP F13 satellite was situated slightly to the north of the rocket trajectory. Each payload returned DC electric and magnetic fields, plasma waves, energetic particles, photometer data, and thermal plasma data. Data from both flights will be shown, with an emphasis on the DC electric field results. In particular, the data gathered on December 2, 1997 will be used to discuss ionospheric signatures of merging and the open/closed character of the the cusp/low latitude boundary layer. In contrast, the data gathered on December 3, 1997 shows evidence of pulsed electric field structures which will be examined in the context of cusp plasma entry processes. Both data sets returned a rich variety of plasma waves, as well as optical emissions and thermal plasma data.

  18. DC and Wave Electric Fields and Other Plasma Parameters Observed on Two Sounding Rockets in the Dark Cusp during IMF BZ North and South Conditions

    NASA Technical Reports Server (NTRS)

    Pfaff, R. F.; Bounds, S.; Acuna, M.; Maynard, N. C.; Moen, J.; Egeland, A.; Holtet, J.; Maseide, K.; Sandholt, P. E.; Soraas, F.

    1999-01-01

    Two Black Brant IX sounding rockets were launched into the dark, dayside cusp near magnetic noon on December 2 and 3, 1997, from Ny Alesund, Spitzbergen at 79degN reaching altitudes of approximately 450 km. Real-time ground-based and Wind (interplanetary magnetic field) IMF data were used to determine the launch conditions. The first launch, with Bz north conditions, crossed into and back out of an open field region with merging poleward of the projected trajectory. The second flight, into Bz south conditions, was timed to coincide with an enhancement in the merging rate from a increase in the negative Bz, while the (Defense Meteorological Satellite Program) DMSP F13 satellite was situated slightly to the north of the rocket trajectory. Each payload returned DC electric and magnetic fields, plasma waves, energetic particles, photometer data, and thermal plasma data. Data from both flights will be shown, with an emphasis on the DC electric field results. In particular, the data gathered on December 2, 1997 will be used to discuss ionospheric signatures of merging and the open/closed character of the the cusp/low latitude boundary layer. In contrast, the data gathered on December 3, 1997 shows evidence of pulsed electric field structures which will be examined in the context of cusp plasma entry processes. Both data sets returned a rich variety of plasma waves, as well as optical emissions and thermal plasma data.

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

    NASA Technical Reports Server (NTRS)

    Clauer, C. Robert; Friis-Christensen, Eigil

    1988-01-01

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

  20. Extreme Driving of Reverse Convection During Strongly Northward Interplanetary Magnetic Field

    NASA Astrophysics Data System (ADS)

    Clauer, C. R.; Xu, Z.; Hartinger, M.; Maimaiti, M.; Ruohoniemi, J. M.; Scales, W.; Nicolls, M. J.; Wilder, F. D.

    2015-12-01

    A variety of statistical studies have shown that the ionospheric polar potential produced by solar wind - magnetosphere - ionosphere coupling is linear for weak to moderate solar wind driving, but becomes non-linear during periods of very strong driving. It has been shown that this applies to the two-cell convection potential that develops during southward interplanetary magnetic field (IMF) and also to the reverse convection cells that develop during northward IMF. This has been described as polar potential saturation and it appears to begin when the driving solar wind electric field becomes greater than 3 mV/m. It has also been shown that the summer ionospheric electric field saturates at about the same value (20 mV/m) for both northward or southward IMF. Recent measurements of the high latitude convection on September 12 - 13, 2014 using the Resolute Incoherent Scatter Radar during periods of large northward IMF show ionospheric electric fields varying between 56 mV/m and 156 mV/m within the dayside reverse convection cells. There is no indication of saturation during these periods of very strong driving. A second set of observations during June 22-24, 2015 of a CME interaction with the Earth's magnetosphere that also produced large northward IMF during the time period when RISR could measure the dayside reverse convection is also investigated. Factors beyond the strength of the driving electric field must play a role in the process that produces polar potential saturation, at least for the case of reverse convection. Results of an investigation of these additional factors will be discussed.

  1. Rapid response of the plasmasphere to changes in the solar wind and IMF: Global plasmapause electric field measurements by IMAGE EUV, and simulation with the Rice MSM.

    NASA Astrophysics Data System (ADS)

    Goldstein, J.; Wolf, R. A.; Sandel, B. R.; Forrester, W. T.; Gallager, D. L.; Reiff, P. H.; Spiro, R.

    2002-05-01

    Images recorded by the extreme ultraviolet (EUV) instrument on the IMAGE satellite very often show a well-defined and identifiable plasmapause; dynamic changes in the shape and location of this plasmapause can be tracked by EUV with 10-minute time resolution. For some time, it has been established that the plasmapause moves in response to changes in the global magnetospheric convection field, which in turn is driven by solar wind dynamic pressure and interplanetary magnetic field (IMF) orientation. A handful of time histories recorded by EUV show the plasmapause moving radially inward or outward. Comparison of the EUV-observed plasmapause time development with IMF orientation in these cases shows that the plasmapause responds rapidly (within 25 to 30 minutes) to sudden changes in the IMF Bz polarity. A change to southward Bz enhances magnetospheric convection, causing visible inward motion of the nightside plasmapause. A change to northward Bz seems to trigger an overshielding condition, producing outward motion of the nightside plasmapause. In general the plasmapause motion (inward and outward) seems to be concentrated most strongly in the post-midnight sector, with a lesser concentration at pre-noon MLT. This spatial character is consistent with simulation results of the Rice Magnetospheric Specification Model (MSM). The overall picture, from both observation and simulation, is that the plasmapause location is very responsive to changes in the solar wind and IMF conditions.

  2. Impact of the IMF rotation on the cusp dynamics on the dayside: Global 3D PIC simulations

    NASA Astrophysics Data System (ADS)

    Huang, Z.; Cai, D.; Lembege, B.; Nishikawa, K.-I.

    The dynamics of the cusp region is analyzed with a new version of a global three-dimensional full particle simulation with changing the interplanetary magnetic field IMF direction progressively from northward to duskward then duskward to southward With the initial northward IMF bands of weak magnetic field sash form poleward of the cusp at high latitudes in each hemisphere and at high altitudes these sashes are located approximately around the pole axis As the IMF rotates duskward these sashes move toward the equator within opposite quadrants Then as the duskward-oriented IMF continue to rotate toward southward these sashes move further and reach the dayside magnetopause at the equator During the progressive rotation of the IMF from northward to duskward i the sash region widens towards lower latitudes banana-shape and with the duskward IMF ii the size of the banana-shape region becomes minimum and its location stops around a maximum deviation of 45degree from the polar axis It should be noted that the sashes are extended from the dayside to the nightside tailward The motion of the sashes is also analyzed during the IMF rotation form duskward to southward

  3. The Myth of the IMF

    NASA Astrophysics Data System (ADS)

    Melnick, J.

    2009-11-01

    The Myth of Science is the idea that complex phenomena in Nature can be reduced to a set of equations based on the fundamental laws of physics. The Myth of the IMF is the notion that the observed distribution of stellar masses at birth (the IMF) can and must be explained by any successful theory of star formation. In this contribution I argue that the IMF is the result of the complex evolution of the interstellar medium in galaxies, and that as such the IMF preserves very little information, if any, about the detailed physics of star formation. Trying to infer the physics of star formation from the IMF is like trying to understand the personality of Beethoven from the power-spectrum of the Ninth Symphony!

  4. The Earth's magnetosphere is 165 R(sub E) long: Self-consistent currents, convection, magnetospheric structure, and processes for northward interplanetary magnetic field

    NASA Technical Reports Server (NTRS)

    Fedder, J. A.; Lyon, J. G.

    1995-01-01

    The subject of this paper is a self-consistent, magnetohydrodynamic numerical realization for the Earth's magnetosphere which is in a quasi-steady dynamic equilibrium for a due northward interplanetary magnetic field (IMF). Although a few hours of steady northward IMF are required for this asymptotic state to be set up, it should still be of considerable theoretical interest because it constitutes a 'ground state' for the solar wind-magnetosphere interaction. Moreover, particular features of this ground state magnetosphere should be observable even under less extreme solar wind conditions. Certain characteristics of this magnetosphere, namely, NBZ Birkeland currents, four-cell ionospheric convection, a relatively weak cross-polar potential, and a prominent flow boundary layer, are widely expected. Other characteristics, such as no open tail lobes, no Earth-connected magnetic flux beyond 155 R(sub E) downstream, magnetic merging in a closed topology at the cusps, and a 'tadpole' shaped magnetospheric boundary, might not be expected. In this paper, we will present the evidence for this unusual but interesting magnetospheric equilibrium. We will also discuss our present understanding of this singular state.

  5. IMF dependence of high-latitude thermospheric wind pattern derived from CHAMP cross-track measurements

    NASA Astrophysics Data System (ADS)

    Förster, M.; Rentz, S.; Köhler, W.; Liu, H.; Haaland, S. E.

    2008-06-01

    Neutral thermospheric wind pattern at high latitudes obtained from cross-track acceleration measurements of the CHAMP satellite above both North and South polar regions are statistically analyzed in their dependence on the Interplanetary Magnetic Field (IMF) direction in the GSM y-z plane (clock angle). We compare this dependency with magnetospheric convection pattern obtained from the Cluster EDI plasma drift measurements under the same sorting conditions. The IMF-dependency shows some similarity with the corresponding high-latitude plasma convection insofar that the larger-scale convection cells, in particular the round-shaped dusk cell for ByIMF+ (ByIMF-) conditions at the Northern (Southern) Hemisphere, leave their marks on the dominant general transpolar wind circulation from the dayside to the nightside. The direction of the transpolar circulation is generally deflected toward a duskward flow, in particular in the evening to nighttime sector. The degree of deflection correlates with the IMF clock angle. It is larger for ByIMF+ than for ByIMF- and is systematically larger (~5°) and appear less structured at the Southern Hemisphere compared with the Northern. Thermospheric cross-polar wind amplitudes are largest for BzIMF-/ByIMF- conditions at the Northern Hemisphere, but for BzIMF-/ByIMF+ conditions at the Southern because the magnetospheric convection is in favour of largest wind accelerations over the polar cap under these conditions. The overall variance of the thermospheric wind magnitude at Southern high latitudes is larger than for the Northern. This is probably due to a larger "stirring effect" at the Southern Hemisphere because of the larger distance between the geographic and geomagnetic frameworks.

  6. The First in situ Observation of Kelvin-Helmholtz Waves at High-Latitude Magnetopause during Strongly Dawnward Interplanetary Magnetic Field Conditions

    NASA Technical Reports Server (NTRS)

    Hwang, K.-J.; Goldstein, M. L.; Kuznetsova, M. M.; Wang, Y.; Vinas, A. F.; Sibeck, D. G.

    2012-01-01

    We report the first in situ observation of high-latitude magnetopause (near the northern duskward cusp) Kelvin-Helmholtz waves (KHW) by Cluster on January 12, 2003, under strongly dawnward interplanetary magnetic field (IMF) conditions. The fluctuations unstable to Kelvin-Helmholtz instability (KHI) are found to propagate mostly tailward, i.e., along the direction almost 90 deg. to both the magnetosheath and geomagnetic fields, which lowers the threshold of the KHI. The magnetic configuration across the boundary layer near the northern duskward cusp region during dawnward IMF is similar to that in the low-latitude boundary layer under northward IMF, in that (1) both magnetosheath and magnetospheric fields across the local boundary layer constitute the lowest magnetic shear and (2) the tailward propagation of the KHW is perpendicular to both fields. Approximately 3-hour-long periods of the KHW during dawnward IMF are followed by the rapid expansion of the dayside magnetosphere associated with the passage of an IMF discontinuity that characterizes an abrupt change in IMF cone angle, Phi = acos (B(sub x) / absolute value of Beta), from approx. 90 to approx. 10. Cluster, which was on its outbound trajectory, continued observing the boundary waves at the northern evening-side magnetopause during sunward IMF conditions following the passage of the IMF discontinuity. By comparing the signatures of boundary fluctuations before and after the IMF discontinuity, we report that the frequencies of the most unstable KH modes increased after the discontinuity passed. This result demonstrates that differences in IMF orientations (especially in f) are associated with the properties of KHW at the high-latitude magnetopause due to variations in thickness of the boundary layer, and/or width of the KH-unstable band on the surface of the dayside magnetopause.

  7. Particle entry into the inner magnetosphere during duskward IMF By: Global three-dimensional electromagnetic full particle simulations

    NASA Astrophysics Data System (ADS)

    Cai, D.; Yan, X. Y.; Nishikawa, K.-I.; Lembege, B.

    2006-06-01

    The change of the interplanetary magnetic field (IMF) direction from northward to duskward has an important impact on the inner magnetosphere. This impact is analyzed with the help of a new parallel version of the global three-dimensional full particle simulation code. For northward IMF, bands of weak magnetic field (sash) form poleward of the cusp at high latitudes in each hemisphere. These sashes move to the equator (within opposite quadrants) as the IMF rotates duskward and merge into one another to form the characteristic ``Crosstail-S'' within the neutral sheet of the magnetotail. These macroscopic magnetic patterns (sashes and Crosstail-S) evidenced herein are in a good agreement with results of previous 3D MHD simulations and experimental observations. Moreover, the analysis of particle fluxes shows that ``sashes'' and ``Crosstail-S'' act as magnetic groove to facilitate the entry and injection of magnetosheath particles into the inner magnetosphere. Injected particles are accelerated after the IMF changes its direction from northward to duskward.

  8. Super dual auroral radar network radar imaging of dayside high-latitude convection under northward interplanetary magnetic field: Toward resolving the distorted two-cell versus multicell controversy

    NASA Astrophysics Data System (ADS)

    Greenwald, R. A.; Bristow, W. A.; Sofko, G. J.; Senior, C.; Cerisier, J.-C.; Szabo, A.

    1995-10-01

    Data from the Kapuskasing and Saskatoon radars of the evolving Super Dual Auroral Radar Network (SuperDARN) HF radar network have been analyzed to study the two-dimensional structure and dynamics of dayside high-latitude ionospheric convection under northward interplanetary magnetic field (IMF) conditions. A period extending from 1600 to 2030 UT (~0900-1330 MLT) on January 10, 1994, was examined. During this interval, magnetic field data were available from the IMP 8 satellite and indicated moderately stable northward IMF conditions. For the first few hours of observation the By component of the IMF was positive, reasonably steady, and approximately twice the magnitude of Bz. During this interval, the high-latitude convection images obtained with the SuperDARN radars were very similar to the distorted two-cell convection maps for positive By as presented by Heppner and Maynard (1987). At ~1840 UT, a decrease in By in association with an increase in Bz, led to an extended period with By~Bz. During this second interval the convection patterns were highly variable and even chaotic. Finally, a sharp decrease in the By component at 1914 UT, probably in association with a rotational discontinuity in the solar wind, led to an extended period with By<

  9. IMF Prediction with Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Bieber, J. W.; Evenson, P. A.; Kuwabara, T.; Pei, C.

    2013-12-01

    Cosmic rays impacting Earth have passed through and interacted with the interplanetary magnetic field (IMF) surrounding Earth, and in some sense they carry information on the three-dimensional structure of that field. This work uses neutron monitor data in an effort to extract that information and use it to predict the future behavior of the IMF, especially the north-south component (Bz) which is so crucial in determining geomagnetic activity. We consider 161 events from a published list of interplanetary coronal mass ejections and compare hourly averages of the predicted field with the actual field measured later. We find that the percentage of events with 'good' predictions of Bz (in the sense of having a positive correlation between the prediction and the subsequent measurement) varies from about 85% for predictions 1 hour into the future to about 60% for predictions 4 hours into the future. We present several ideas for how the method might be improved in future implementations. Supported by NASA grant NNX08AQ01G and NSF grant ANT-0739620.

  10. The financial crisis and global health: the International Monetary Fund's (IMF) policy response.

    PubMed

    Ruckert, Arne; Labonté, Ronald

    2013-09-01

    In this article, we interrogate the policy response of the International Monetary Fund (IMF) to the global financial crisis, and discuss the likely global health implications, especially in low-income countries. In doing so, we ask if the IMF has meaningfully loosened its fiscal deficit targets in light of the economic challenges posed by the financial crisis and adjusted its macro-economic policy advice to this new reality; or has the rhetoric of counter-cyclical spending failed to translate into additional fiscal space for IMF loan-recipient countries, with negative health consequences? To answer these questions, we assess several post-crisis IMF lending agreements with countries requiring financial assistance, and draw upon recent academic studies and civil society reports examining policy conditionalities still being prescribed by the IMF. We also reference recent studies examining the health impacts of these conditionalities. We demonstrate that while the IMF has been somewhat more flexible in its crisis response than in previous episodes of financial upheaval, there has been no meaningful rethinking in the application of dominant neoliberal macro-economic policies. After showing some flexibility in the initial crisis response, the IMF is pushing for excessive contraction in most low and middle-income countries. We conclude that there remains a wide gap between the rhetoric and the reality of the IMF's policy and programming advice, with negative implications for global health. PMID:22504946

  11. The financial crisis and global health: the International Monetary Fund's (IMF) policy response.

    PubMed

    Ruckert, Arne; Labonté, Ronald

    2013-09-01

    In this article, we interrogate the policy response of the International Monetary Fund (IMF) to the global financial crisis, and discuss the likely global health implications, especially in low-income countries. In doing so, we ask if the IMF has meaningfully loosened its fiscal deficit targets in light of the economic challenges posed by the financial crisis and adjusted its macro-economic policy advice to this new reality; or has the rhetoric of counter-cyclical spending failed to translate into additional fiscal space for IMF loan-recipient countries, with negative health consequences? To answer these questions, we assess several post-crisis IMF lending agreements with countries requiring financial assistance, and draw upon recent academic studies and civil society reports examining policy conditionalities still being prescribed by the IMF. We also reference recent studies examining the health impacts of these conditionalities. We demonstrate that while the IMF has been somewhat more flexible in its crisis response than in previous episodes of financial upheaval, there has been no meaningful rethinking in the application of dominant neoliberal macro-economic policies. After showing some flexibility in the initial crisis response, the IMF is pushing for excessive contraction in most low and middle-income countries. We conclude that there remains a wide gap between the rhetoric and the reality of the IMF's policy and programming advice, with negative implications for global health.

  12. Particle entry through "Sash" groove simulated by Global 3D Electromagnetic Particle code with duskward IMF By

    NASA Astrophysics Data System (ADS)

    Yan, X.; Cai, D.; Nishikawa, K.; Lembege, B.

    2004-12-01

    We made our efforts to parallelize the global 3D HPF Electromagnetic particle model (EMPM) for several years and have also reported our meaningful simulation results that revealed the essential physics involved in interaction of the solar wind with the Earth's magnetosphere using this EMPM (Nishikawa et al., 1995; Nishikawa, 1997, 1998a, b, 2001, 2002) in our PC cluster and supercomputer(D.S. Cai et al., 2001, 2003). Sash patterns and related phenomena have been observed and reported in some satellite observations (Fujumoto et al. 1997; Maynard, 2001), and have motivated 3D MHD simulations (White and al., 1998). We also investigated it with our global 3D parallelized HPF EMPM with dawnward IMF By (K.-I. Nishikawa, 1998) and recently new simulation with dusk-ward IMF By was accomplished in the new VPP5000 supercomputer. In the new simulations performed on the new VPP5000 supercomputer of Tsukuba University, we used larger domain size, 305×205×205, smaller grid size (Δ ), 0.5R E(the radium of the Earth), more total particle number, 220,000,000 (about 8 pairs per cell). At first, we run this code until we get the so-called quasi-stationary status; After the quasi-stationary status was established, we applied a northward IMF (B z=0.2), and then wait until the IMF arrives around the magnetopuase. After the arrival of IMF, we begin to change the IMF from northward to duskward (IMF B y=-0.2). The results revealed that the groove structure at the day-side magnetopause, that causes particle entry into inner magnetosphere and the cross structure or S-structure at near magneto-tail are formed. Moreover, in contrast with MHD simulations, kinetic characteristic of this event is also analyzed self-consistently with this simulation. The new simulation provides new and more detailed insights for the observed sash event.

  13. Enhanced Thermospheric Density: The Roles of East-West and Northward Interplanetary Magnetic Field

    NASA Astrophysics Data System (ADS)

    Knipp, D. J.; Drake, K. A.; Lei, J.; Crowley, G.

    2009-12-01

    During 2005 solar EUV energy input to the thermosphere waned as Solar Cycle 23 declined. The reduction allowed a clearer delineation of episodic density disturbances caused by geomagnetic storms. We show new views of these disturbances based on Poynting flux calculations from the Defense Meteorological Satellite Program (DMSP) F-series satellites, as well as from 1) accelerometer data from polar orbiting satellites, 2) the assimilative mapping of ionospheric electrodynamics (AMIE) procedure and 3) the Thermospheric Ionospheric Electrodynamic General Circulation Model (TIEGCM). The new Poynting flux estimates and TIEGCM results allow us to trace the origins of disturbances that are poorly specified by ground indices. In particular we find that intervals of enhanced northward Interplanetary Magnetic Field (IMF) combined with strong east-west components of the IMF allow significant electromagnetic energy input into localized dayside regions of the high-latitude thermosphere. In some cases this energy deposition is consistent with IMF-geomagnetic field merging tailward of the Earth’s magnetic cusps. In other cases the energy is deposited in the vicinity of an extremely narrow convection throat. This mode of interaction provides little energy to the magnetotail; and instead concentrates the energy in the dayside thermosphere. We discuss the solar cycle variability of this type of interaction. as well as compare the relative value of Poynting flux and particle energy deposition for such events.

  14. MESSENGER observations of the response of Mercury's magnetosphere to northward and southward interplanetary magnetic fields

    NASA Astrophysics Data System (ADS)

    Slavin, James

    M. H. Acũa (2), B. J. Anderson (3), D. N. Baker (4), M. Benna (2), S. A. Boardsen (1), G. n Gloeckler (5), R. E. Gold (3), G. C. Ho (3), H. Korth (3), S. M. Krimigis (3), S. A. Livi (6), R. L. McNutt Jr. (3), J. M. Raines (5), M. Sarantos (1), D. Schriver (7), S. C. Solomon (8), P. Travnicek (9), and T. H. Zurbuchen (5) (1) Heliophysics Science Division, NASA GSFC, Greenbelt, MD 20771, USA, (2) Solar System Exploration Division, NASA GSFC, Greenbelt, MD 20771, USA, (3) The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA, (4) Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303, USA, (5) Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109, USA (6) Southwest Research Institute, San Antonio, TX 28510, USA, (7) Institute for Geophysics and Planetary Physics, University of California, Los Angeles, CA 90024, USA, (8) Department of Terrestrial Magnetism, Carnegie Institution of Washington, DC 20015, USA, and (9) Institute of Atmospheric Physics, Prague, Czech Republic, 14131 MESSENGER's 14 January 2008 encounter with Mercury has provided new observations of the solar wind interaction with this planet. Here we report initial results concerning this miniature magnetosphere's response to the north-south component of the interplanetary magnetic field (IMF). This is the component of the IMF that is expected to exert the greatest influence over the structure of the magnetopause and the processes responsible for energy transfer into the magnetosphere. The IMF was northward immediately prior to and following the passage of the MESSENGER spacecraft through this small magnetosphere. However, several-minute episodes of southward IMF were observed in the magnetosheath during the inbound portion of the encounter. Evidence for reconnection at the dayside magnetopause in the form of welldeveloped flux transfer events (FTEs) was observed in the magnetosheath following some of

  15. IMF-lending programs and suicide mortality.

    PubMed

    Goulas, Eleftherios; Zervoyianni, Athina

    2016-03-01

    While the economic consequences of IMF programs have been extensively analyzed in the literature, much less is known about how key welfare indicators, including suicide-mortality rates, correlate with countries' participation in such programs. This paper examines the impact of IMF lending on suicide mortality, using data from 30 developing and transition countries that received non-concessionary IMF loans during 1991-2008. Our results support the hypothesis of a positive causal relationship between suicide mortality and participation in IMF programs but reveal no systematic suicide-increasing effect from the size of IMF loans. This holds after accounting for self-selection into programs, resulting from the endogeneity of a country's decision to resort to the IMF for funding, and after controlling for standard socio-economic influences on suicidal behaviour. In particular, we find a positive aggregate suicide-mortality differential due to IMF-program participation of between 4 and 14 percentage points. We also find that the positive association between suicides and program participation is stronger and more robust among males. Comparing age groups, individuals belonging to the age group 45-to-64 exhibit the highest increase in suicide due to program-participation, which amounts to over 18 percentage points. Overall, our results imply that when countries are exposed to IMF programs in an attempt to resolve their economic problems, social-safety nets need to be designed to protect the adversely-affected part of the population. PMID:26874823

  16. Acceleration and injection of particles inside the magnetosphere changes during duskward IMF By: statistical approach

    NASA Astrophysics Data System (ADS)

    Yan, X.; Cai, D.; Lembege, B.; Nishikawa, K.

    2005-12-01

    The change of the interplanetary magnetic field (IMF) direction from northward to duskward has an important impact on the inner magnetosphere as analyzed in a recent paper [Yan et al, GRL, to appear] . This impact is analyzed with the help of a new parallel version of the global three-dimensional full particle simulation. As the newly duskward-oriented IMF interacts with the magnetosphere, bands of weak magnetic field (sash) move to the equator (within opposite quadrants), reach lower latitude and merge into each other to form characteristic ``Crosstail-S" structures within the neutral sheet of the magnetotail. The analysis of particle fluxes shows that ``sashs" and ``Crosstail-S" act as magnetic groove to facilitate the entry and injection of magnetosheath particles into the inner magnetosphere. Injected particles are accelerated after the IMF changes its direction from northward to duskward. Characteristic times associated to the changes of the particle dynamics are estimated from the simulations. These informations are thought to be helpful as pre-signatures announcing the triggering of magnetic substorms.

  17. North-south asymmetry of the high-latitude thermospheric density: IMF BY effect

    NASA Astrophysics Data System (ADS)

    Yamazaki, Yosuke; Kosch, Michael J.; Sutton, Eric K.

    2015-01-01

    Previous studies have established that the y component of the interplanetary magnetic field (IMF By) plays a role in the north-south asymmetry of the high-latitude plasma convection and wind. The effect of the positive/negative IMF By in the Northern Hemisphere resembles the effect that the negative/positive IMF By would have in the Southern Hemisphere. In this study, we demonstrate that the IMF By effect can also contribute to the hemispheric asymmetry of the thermospheric density. We use high-accuracy air drag measurements from the CHAllenging Minisatellite Payload (CHAMP) satellite and SuperMAG AE index during the period 2001-2006 to examine the response of the high-latitude thermospheric density to geomagnetic activity. Our statistical analysis reveals that the density response at 400 km is greater in the Southern Hemisphere under positive IMF By conditions, and greater in the Northern Hemisphere under negative IMF By conditions. The results suggest that the IMF By effect needs to be taken into account in upper atmospheric modeling for an accurate description of high-latitude densities during periods of enhanced geomagnetic activity.

  18. Impact of the IMF rotation on the cusp dynamics on the dayside: Global 3D PIC simulations

    NASA Astrophysics Data System (ADS)

    Tao, W.; Cai, D.; Lembege, B.; Nishikawa, K.

    2005-12-01

    The dynamics of the cusp region as the interplanetary magnetic field (IMF) progressively changes its direction from northward to duskward is analysed with a new version of a global three-dimensional full particle simulation. For northward IMF, bands of weak magnetic field (sash) form poleward of the cusp at high latitudes in each hemisphere (and at high altitudes); these sashs are centered approximately around the pole axis. However, as the newly duskward-oriented IMF approaches and interacts with the magnetosphere, these sashs move to the equator (within opposite quadrants). During the progressive rotation of the IMF, this motion is decomposed in the plane perpendicular to the solar wind as follows: (i) the "sash" region widens towards lower latitudes ("banana-shape"), and (ii) the size of the "banana-shape" region strongly shrinks and its location stabilizes around a maximum deviation of 45?. In addition, this motion is observed both on the day and the night sides where sashs are simultaneously observed. Characteristic time and space scales of the cusp motion are indicated, in order to be compare with results deduced from previous MHD simulations. Changes of local reconnection in the cusp region are analysed.

  19. Quasi-continuous reconnection accompanied by FTEs during IMF Bz ≈ 0 nT observed by Double Star TC-1 at the dawnside magnetopause

    NASA Astrophysics Data System (ADS)

    Yan, Guang Qing; Mozer, Forrest S.; Phan, Tai; Shen, Chao; Chen, Tao; Bogdanova, Yulia V.; Rème, Henri; Carr, Chris; Liu, Zhen Xing

    2016-07-01

    During a one-hour interval of interplanetary magnetic field (IMF) Bz ≈ 0 nT, the equatorial spacecraft Double Star TC-1 encountered the dawn flank magnetopause many times at the magnetic local time (MLT) of about 08:00 and the latitude of about -27°. During each encounter, reconnection jets were observed with their velocities up to more than 500 km/s, significantly higher than the background flow in the magnetosheath. The fast flows match the theoretical prediction of Alfvénic acceleration well. The medium temperature and density of ions in the boundary layer indicate the open magnetic field topology inside this layer. The mainly southward and tailward flows of the plasma jets alongside with the negative slopes of the Walén test indicate that the spacecraft was located south of the reconnection site, consistent with both anti-parallel and component reconnection models. The accelerated flows were observed lasting for about one hour, with some modulations by the oscillations of the magnetopause, but no reversals in the direction of Vz were found during the interval. The significantly enhanced flows in the boundary layer compared to the adjacent magnetosheath indicate that the reconnection was quasi-continuously active at the magnetopause northward of the spacecraft under such IMF conditions. At the same time, the bipolar signatures in BN with enhancements of the magnetic field indicate the occurrence of the Flux Transfer Events (FTEs). The observed reconnection was quasi-continuous, whereas the simultaneously accompanied FTEs were time-dependent under the IMF Bz ≈ 0 nT. For this event, however, it is not possible to identify whether the reconnection was anti-parallel or component because the TC-1 was far away from the reconnection site.

  20. The IMF of Globular Clusters

    NASA Astrophysics Data System (ADS)

    De Marchi, G.; Paresce, F.

    1999-12-01

    Accurate luminosity functions (LF) for a dozen globular clusters have now been measured at or just beyond their half-light radius using HST. They span almost the entire cluster main sequence below 0.75 MO. All these clusters exhibit LF that rise continuously from an absolute I magnitude MI 6 to a peak at MI 8.5-9 and then drop with increasing MI. Transformation of the LF into mass functions (MF) by means of the most recent mass luminosity relations that are consistent with all presently available data on the physical properties of low mass, low metallicity stars shows that all the LF observed so far can be obtained from MF having the shape of a log-normal distribution with characteristic mass mc=0.33 +/- 0.03 MO and standard deviation sigma =1.81 +/- 0.19. In particular, the LF of the four clusters in the sample that extend well beyond the peak luminosity down to close to the Hydrogen burning limit (NGC6341, NGC6397, NGC6752, and NGC6809) can only be reproduced by such distributions and not by a single power-law in the 0.1 - 0.6 MO range. After correction for the effects of mass segregation, the variation of the ratio of the number of higher to lower mass stars with cluster mass or any simple orbital parameter or the expected time to disruption recently computed for these clusters shows no statistically significant trend over a range of this last parameter of more than a factor of 100. We conclude that the global MF of these clusters have not been measurably modified by evaporation and tidal interactions with the Galaxy and, thus, should reflect the initial distribution of stellar masses. Since the log-normal function that we find is also very similar to the one obtained independently for much younger clusters and to the form expected theoretically, the implication seems to be unavoidable that it represents the true stellar IMF for this type of stars in this mass range.

  1. Magnetospheric sash dependence on IMF direction

    NASA Astrophysics Data System (ADS)

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

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

  2. 3. VIEW NORTHWARD FROM 51 N. THIRD ST. TO 63 ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. VIEW NORTHWARD FROM 51 N. THIRD ST. TO 63 N. THIRD ST. (FROM RIGHT TO LEFT). WEST (FRONT) FACADES, LOOKING NORTHEAST - North Third Street Area Study, 17-63 North Third Street (Commercial Buildings), Philadelphia, Philadelphia County, PA

  3. 3D Global PIC simulation of Alfvenic transition layers at the cusp outer boundary during IMF rotations from north to south

    NASA Astrophysics Data System (ADS)

    Cai, D. S.; Lembege, B.; Esmaeili, A.; Nishikawa, K.

    2013-12-01

    Statistical experimental observations of the cusp boundaries from CLUSTER mission made by Lavraud et al. (2005) have clearly evidenced the presence of a transition layer inside the magnetosheath near the outer boundary of the cusp. This layer characterized by Log(MA)~ 1 allows a transition from super-Alfvenic to sub-Alfvenic bulk flow from the exterior to the interior side of the outer cusp and has been mainly observed experimentally under northward interplanetary magnetic field (IMF). The role of this layer is important in order to understand the flow variations (and later the entry and precipitation of particles) when penetrating the outer boundary of the cusp. In order to analyze this layer, a large 3D PIC simulation of the global solar wind-terrestrial magnetosphere interaction have been performed, and the attention has been focused on the cusp region and its nearby surrounding during IMF rotation from north to south. Present results retrieve quite well the presence of this layer within the meridian plane for exactly northward IMF, but its location differs in the sense that it is located slightly below the X reconnection region associated to the nearby magnetopause (above the outer boundary of the cusp). In order to clarify this question, an extensive study has been performed as follows: (i) a 3D mapping of this transition layer in order to analyze more precisely the thickness, the location and the spatial extension of this layer on the magnetosphere flanks for a fixed Northward IMF configuration; (ii) a parametric study in order to analyze the impact of the IMF rotation from north to south on the persistence and the main features of this transition layer. The locations of this transition layer slightly radially expand and shrink during the IMF rotation and the thickness of the layer increases during the rotation. We show how these transition layers render the flow from super to sub Alfvenic and allow the particles enter into the magnetic cusp region. Alfven

  4. Simultaneous conjugate observations of dynamic variations in high-latitude dayside convection due to changes in IMF By

    NASA Technical Reports Server (NTRS)

    Greenwald, R. A.; Baker, K. B.; Ruohoniemi, J. M.; Dudeney, J. R.; Pinnock, M.; Mattin, N.; Leonard, J. M.; Lepping, R. P.

    1990-01-01

    Data from two conjugate HF radars currently operating at Goose Bay (Labrador) and the Halley Station (Antarctica), obtained for a single 45-min period about local noon on April 22, 1988, were used to study the near-instantaneous conjugate two-dimensional patterns of plasma convection in the vicinity of the cusp. In particular, the response of these plasma convection patterns to changes in the By component of the IMF was examined. Results indicate that, under quasi-stationary IMF conditions, the conjugate convection patterns are quite similar to the synthesized patterns of Heppner and Maynard (1987) and that the patterns respond rapidly to changes in the IMF By component. Results also show that transitions between convection states begin to occur within minutes of the time that an IMF state change is incident on the magnetospheric boundary, and that the convection reconfigurations expand poleward, completely filling the field of view of an HF radar within 6 min of the time of onset.

  5. Observations of draping plasma accelerations in the magnetosheath under IMF Bz North

    NASA Astrophysics Data System (ADS)

    Harris, B. S.; Farrugia, C. J.

    2011-12-01

    Accelerations in the magnetosheath due to draping of the Interplanetary Magnetic Field (IMF) around the magnetosphere is a rich topic of renewed interest. Here, we study these draping events in the first statistical study of draping related accelerations in the magnetosheath. We present a methodology to unambiguously identify draping related accelerations from reconnection, and present several case studies of 34 identified events. To discourage reconnection, we focus on the IMF Bz northward phase of ICMEs identified by Cane and Richardson [2010] from 1997-2010, and spacecraft that are low in the ecliptic plane to avoid reconnection at high latitudes. We study the effect of upstream MA and Magnetic Local Time (MLT) on the ratio at which the magnetosheath speeds exceed the speed of the solar wind, and compare with theory. We find that the ratio of magnetosheath speed to speed of the solar wind increases with decreasing MA, and show the suggested positional dependance along the magnetopause of this ratio with respect to the east-west terminator as well as global trends.

  6. The IMF at intermediate masses from Galactic Cepheids

    NASA Astrophysics Data System (ADS)

    Mor, R.; Robin, A. C.; Figueras, F.; Lemasle, B.

    2014-07-01

    Aims: To constrain the Initial Mass Function (IMF) of the Galactic young (<1 Gyr) thin Disc population using Cepheids. Methods: We have optimized the flexibility of the new Besançon Galaxy Model (Czekaj 2014) to simulate magnitude and distance complete samples of young intermediate mass stars assuming different IMFs and Star Formation Histories (SFH). Comparing the simulated synthetic catalogues with the observational data we studied which IMF reproduces better the observational number of Cepheids in the Galactic thin Disc. We analysed three different IMF: (1) Salpeter, (2) Kroupa-Haywood and (3) Haywood-Robin IMFs with a decreasing SFH from Aumer & Binney (2009). Results: For the first time the Besançon Galaxy Model is used to characterize the galactic Cepheids. We found that for most of the cases the Salpeter IMF overestimates the number of observed Cepheids and Haywood-Robin IMF underestimates it. The Kroupa-Haywood IMF, with a slope α = 3.2, is the one that best reproduces the observed Cepheids. From the comparison of the predicted and observed number of Cepheids up to V = 12, we point that the model might underestimate the scale height of the young population. Conclusions: In agreement with Kroupa & Weidner (2003) our study shows that the Salpeter IMF (α = 2.35) overestimates the star counts in the range 4 ≤ M/M⊙≤ 10 and supports the idea that the slope of the intermediate and massive stars IMF is steeper than the Salpeter IMF. The poster can be found online at: https://gaia.ub.edu/Twiki/pub/GREATITNFC/ProgramFinalconference/Poster_R._Mor_Great.pdf.

  7. The Role of Stratiform and Convective heating in modifying the northward phase propagation of Monsoon Intraseasonal Oscillation

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, R.; Goswami, B.; Sahai, A. K.

    2009-12-01

    In this study, contribution of stratiform and convective rain rate to total rain rate during different phases of the northward propagating boreal summer monsoon Intraseasonal Oscillation (ISO) is brought out using the TRMM data. Two new insights have emerged from this analysis as shown in Fig.1. It may be noted from Fig.1 that the convective component seems to grow and decay in situ during evolution of active/break phases, the northward propagation of the monsoon ISO is contributed by organized movement of the stratiform component. Further, the trade mark meridional dipole pattern of total rainfall between monsoon trough zone (MTZ) and equatorial Indian Ocean (EIO) also arises largely from contribution stratiform anomalies. The northward propagation of the monsoon intraseasonal oscillation is known to be due to the anomalous response of the atmosphere to heating in the presence of mean easterly vertical shear. Modification of vertical profile of heating due to contribution from stratiform rain could influence the northward propagation of monsoon ISO. We test this using a simple dynamical model known as PUMA (Portable Unified Model of Atmosphere) developed by University of Hamburg, Germany to study the response of the ‘convective’ and ‘stratiform’ heating profiles on the modification of the mean condition which facilitates the northward propagation. Such modification in the large scale response (e.g. vertical shear, barotropic vorticity) seen clearly to be related with the structure of the heating profile (convective or stratiform). The presence of stratiform heating favors the northward phase propagation of monsoon ISO. These results underline the importance simulating the partitioning of convective and stratiform rain by cumulous parameterization in climate models if they have to get the space-time structure of the summer ISOs correctly. Fig. 1 Figure showing the northward propagation of total (top), convective (middle) and stratiform (bottom) rainrate

  8. Role of Ocean-Atmosphere Interaction on Northward Propagation of Boreal Summer Monsoon Intraseasonal Oscillations

    NASA Astrophysics Data System (ADS)

    Sharmila, S.; Pillai, P.; Joseph, S.; Mathew, R.; Krishna, R.; Chattopadhyay, R.; Abhilash, S.; Sahai, A. K.; Goswami, B.

    2013-12-01

    CFSv2, the lead-lag relationship between the atmospheric fluxes, SST and convection are maintained, while such lead-lag is unrealistic in the uncoupled simulations. This leads to the conclusion that high frequent and interactive ocean-atmosphere coupling is a necessary and crucial condition for reproducing the realistic northward propagation of MISO in this particular model.

  9. Particle entry through sash in the magnetopause with a dawndard IMF as simulated by a 3-D EM particle code

    NASA Astrophysics Data System (ADS)

    Cai, D.; Yan, X.; Lembege, B.; Nishikawa, K.

    2003-12-01

    We report a new progress in the long-term effort to represent the global interaction of the solar wind with the Earth's magnetosphere using a three-dimensional electromagnetic particle code with the improved resolutions using the HPF Tristan code. After a quasi-steady state is established with an unmagnetized solar wind we gradually switch on a northward interplanetary magnetic field (IMF), which causes a magnetic reconnection at the nightside cusps and the magnetosphere to be depolarized. In the case that the northward IMF is switched gradually to dawnward, there is no signature of reconnection in the near-Earth magnetotail as in the case with the southward turning. On the contrary analysis of magnetic fields in the magnetopause confirms a signature of magnetic reconnection at both the dawnside and duskside. And the plasma sheet in the near-Earth magnetotail clearly thins as in the case of southward turning. Arrival of dawnward IMF to the magnetopause creates a reconnection groove which cause particle entry into the deep region of the magnetosphere via field lines that go near the magnetopause. This deep connection is more fully recognized tailward of Earth. The flank weak-field fan joins onto the plasma sheet and the current sheet to form a geometrical feature called the cross-tail S that structurally integrates the magnetopause and the tail interior. This structure contributes to direct plasma entry between the magnetosheath to the inner magnetosphere and plasma sheet, in which the entry process heats the magnetosheath plasma to plasma sheet temperatures. These phenomena have been found by Cluster observations. Further investigation with Cluster observations will provide new insights for unsolved problems such as hot flow anomalies (HFAs), substorms, and storm-substorm relationship. 3-D movies with sash structure will be presented at the meeting.

  10. How chemistry influences cloud structure, star formation, and the IMF

    NASA Astrophysics Data System (ADS)

    Hocuk, S.; Cazaux, S.; Spaans, M.; Caselli, P.

    2016-03-01

    In the earliest phases of star-forming clouds, stable molecular species, such as CO, are important coolants in the gas phase. Depletion of these molecules on dust surfaces affects the thermal balance of molecular clouds and with that their whole evolution. For the first time, we study the effect of grain surface chemistry (GSC) on star formation and its impact on the initial mass function (IMF). We follow a contracting translucent cloud in which we treat the gas-grain chemical interplay in detail, including the process of freeze-out. We perform 3D hydrodynamical simulations under three different conditions, a pure gas-phase model, a freeze-out model, and a complete chemistry model. The models display different thermal evolution during cloud collapse as also indicated in Hocuk, Cazaux & Spaans, but to a lesser degree because of a different dust temperature treatment, which is more accurate for cloud cores. The equation of state (EOS) of the gas becomes softer with CO freeze-out and the results show that at the onset of star formation, the cloud retains its evolution history such that the number of formed stars differ (by 7 per cent) between the three models. While the stellar mass distribution results in a different IMF when we consider pure freeze-out, with the complete treatment of the GSC, the divergence from a pure gas-phase model is minimal. We find that the impact of freeze-out is balanced by the non-thermal processes; chemical and photodesorption. We also find an average filament width of 0.12 pc (±0.03 pc), and speculate that this may be a result from the changes in the EOS caused by the gas-dust thermal coupling. We conclude that GSC plays a big role in the chemical composition of molecular clouds and that surface processes are needed to accurately interpret observations, however, that GSC does not have a significant impact as far as star formation and the IMF is concerned.

  11. 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.

  12. IMF Dependence of High-Latitude Thermospheric Wind Pattern Derived from CHAMP Cross-Track Accelerometer Data and the Corresponding Magnetospheric Convection from Cluster EDI Measurements

    NASA Astrophysics Data System (ADS)

    Foerster, Matthias; Haaland, Stein E.; Rentz, Stefanie; Liu, Huixin

    Neutral thermospheric wind pattern at high latitudes obtained from cross-track acceleration measurements of the CHAMP satellite above both North and South polar regions are statistically analyzed in their dependence on the Interplanetary Magnetic Field (IMF) direction in the GSM y-z plane (clock angle). We compare this dependency with magnetospheric convection pattern using 1-min-averages of Cluster/EDI electric drift observations and the same IMF and solar wind sorting conditions. The spatially distributed Cluster/EDI measurements are mapped to a the common reference level at ionospheric F-region heights in a magnetic latitude/MLT grid. We obtained both regular thermospheric wind and plasma drift pattern according to the various IMF conditions. The IMF-dependency shows some similarity with the corresponding high-latitude plasma convection insofar that the larger-scale convection cells, in particular the round-shaped dusk cell for IMF By+ (By-) conditions at the Northern (Southern) Hemisphere, leave their marks on the dominant general transpolar wind circulation from the dayside to the nightside. The direction of the transpolar circulation is generally deflected toward a duskward flow, in particular in the evening to nighttime sector. The degree of deflection correlates with the IMF clock angle. It is larger for IMF By+ than for Byand is systematically larger (about 5 deg) and appear less structured at the Southern Hemisphere compared with the Northern. Thermospheric cross-polar wind amplitudes are largest for IMF Bz-/Byconditions (corresponding to sector 5) at the Northern Hemisphere, but for IMF Bz-/By+ conditions (sector 3) at the Southern because the magnetospheric convection is in favour of largest wind accelerations over the polar cap under these conditions. The overall variance of the thermospheric wind magnitude at Southern high latitudes is larger than for the Northern. This is probably due to a larger "stirring effect" at the Southern Hemisphere because

  13. Thermospheric Neutral Density Responses to Changes in IMF Sector Polarity

    NASA Astrophysics Data System (ADS)

    Kwak, Y.; Kim, K.; Forbes, J.; Lee, S.

    2008-12-01

    The thermospheric density is important not only for satellite orbital tracking, but also in understanding the thermosphere-ionosphere coupling process as well. Thermospheric density variations are controlled by various sources such as Joule/particle heating, Lorentz force, thermal expansion, upwelling and horizontal wind circulation. These sources are directly or indirectly associated with the direction and/or strength of the interplanetary magnetic field (IMF). That is, there is an intimate relationship between IMF variation and thermospheric density variation. In order to examine how thermospheric density variations are influenced on the orientation and/or strength of the IMF, we used total mass density around 400 km, derived from the high- accuracy accelerometer on board the Challenging Minisatellite Payload (CHAMP) spacecraft, in 2003 when the IMF exhibited a well-defined sector polarity change with a ~27-day periodicity; directed toward the Sun (i.e., +Bx and -By) and away the Sun (-Bx and +By). It has been known that the IMF By in GSE coordinates makes a positive or negative IMF Bz offset in GSM coordinate. We discuss whether the thermospheric total mass density from CHAMP changes with the IMF sector polarity.

  14. IMF polarity effects on the equatorial ionospheric F-region

    SciTech Connect

    Sastri, J.H.

    1985-01-01

    An exploratory study is made of the influence, during the equinoxes, of the interplanetary magnetic field (IMF) sector structure on the ionospheric F-region using ionosonde data from several equatorial stations for a 3-yr period around the 19th sunspot cycle maximum. It is found that, compared with days having positive IMF polarity, the post-sunset increase of h'F near the dip equator and the depth of the equatorial ionization anomaly (EIA) are reduced during the vernal equinox and enhanced during the autumnal equinox on days with negative IMF polarity. Similar trends are also noted in the data for the 20th sunspot cycle maximum, but with reduced amplitude. The systematic changes in the F-region characteristics suggest a modification of the equatorial zonal electric fields in association with the IMF polarity-related changes in the semi-annual variation of geomagnetic activity. 24 references.

  15. Coldness triggers northward flight in remigrant monarch butterflies.

    PubMed

    Guerra, Patrick A; Reppert, Steven M

    2013-03-01

    Each fall, eastern North American monarch butterflies (Danaus plexippus) migrate from their northern range to their overwintering grounds in central Mexico. Fall migrants are in reproductive diapause, and they use a time-compensated sun compass to navigate during the long journey south. Eye-sensed directional cues from the daylight sky (e.g., the horizontal or azimuthal position of the sun) are integrated in the sun compass in the midbrain central complex region. Sun compass output is time compensated by circadian clocks in the antennae so that fall migrants can maintain a fixed flight direction south. In the spring, the same migrants remigrate northward to the southern United States to initiate the northern leg of the migration cycle. Here we show that spring remigrants also use an antenna-dependent time-compensated sun compass to direct their northward flight. Remarkably, fall migrants prematurely exposed to overwintering-like coldness reverse their flight orientation to the north. The temperature microenvironment at the overwintering site is essential for successful completion of the migration cycle, because without cold exposure, aged migrants continue to orient south. Our discovery that coldness triggers the northward flight direction in spring remigrants solves one of the long-standing mysteries of the monarch migration.

  16. Microbial responses to southward and northward Cambisol soil transplant.

    PubMed

    Wang, Mengmeng; Liu, Shanshan; Wang, Feng; Sun, Bo; Zhou, Jizhong; Yang, Yunfeng

    2015-12-01

    Soil transplant serves as a proxy to simulate climate changes. Recently, we have shown that southward transplant of black soil and northward transplant of red soil altered soil microbial communities and biogeochemical variables. However, fundamental differences in soil types have prevented direct comparison between southward and northward transplants. To tackle it, herein we report an analysis of microbial communities of Cambisol soil in an agriculture field after 4 years of adaptation to southward and northward soil transplants over large transects. Analysis of bare fallow soils revealed concurrent increase in microbial functional diversity and coarse-scale taxonomic diversity at both transplanted sites, as detected by GeoChip 3.0 and DGGE, respectively. Furthermore, a correlation between microbial functional diversity and taxonomic diversity was detected, which was masked in maize cropped soils. Mean annual temperature, soil moisture, and nitrate (NO3 ¯-N) showed strong correlations with microbial communities. In addition, abundances of ammonium-oxidizing genes (amoA) and denitrification genes were correlated with nitrification capacity and NO3 ¯-N contents, suggesting that microbial responses to soil transplant could alter microbe-mediated biogeochemical cycle at the ecosystem level.

  17. The effects of IMF sector boundary crossings on the induced magnetosphere of Venus

    NASA Astrophysics Data System (ADS)

    Vech, D.; Stenberg, G.; Nilsson, H.; Edberg, N. J. T.; Opitz, A.; Szegő, K.; Zhang, T. L.; Futaana, Y.

    2015-10-01

    The induced planetary magnetosphere is the result of the interaction between the streaming solar wind plasma and an unmagnetized planetary body with an ionosphere acting as an obstacle. The structure of the induced magnetosphere highly depends on the upstream solar wind parameters including the direction and magnitude of the Interplanetary Magnetic Field (IMF). (e.g. Zhang et al., 2009; Masunaga et al., 2011). Not only the upstream conditions but also temporal variations of the upstream conditions are expected to cause changes in the structure of induced magnetospheres. For example, Niedner and Brandt [1978] reported that the cometary ion tail was lost due to reconnection after an IMF sector boundary crossing. Edberg et al. [2011] studied the effects of Interplanetary Coronal Mass Ejections (ICME) and Co-rotating Interaction Regions (CIR) at Venus. They suggested that the change in the magnetic field polarity during IMF sector boundary crossings contribute to an increased ion outflow. In addition, they speculated that this might be due to dayside magnetic reconnection. In this study we aim to understand the effects of the varying upstream conditions on the Venusian induced magnetosphere. Using the entire Venus Express/ASPERA-4 and MAG datasets, we first produce the spatial distribution of ions in the plasma environment of Venus during ICME and CIR passages together with that during the average condition. In addition to ICME/CIR passages, we focus on the Heliospheric Current Sheet (HCS) crossings, which can also change the polarity of the induced magnetosphere. By comparing HCS events and ICME/CIR events, we may be able to distinguish the contribution of IMF polarity change on the Venusian induced magnetosphere, because the solar wind is less disturbed during HCS events. We will compare the signatures associated with the sector boundary crossings found at the magnetotail of Venus with that is previously reported from comet studies.

  18. The effect of a northward shift in the southern hemisphere westerlies on the global ocean

    NASA Astrophysics Data System (ADS)

    Sijp, Willem P.; England, Matthew H.

    2008-10-01

    We examine the effect of a northward shift in the position of the southern hemisphere subpolar westerly winds (SWWs) on the vertical and horizontal distribution of temperature and salinity in the world ocean. A northward shift of the SWWs causes a latitudinal contraction of the subpolar gyres in the southern hemisphere (SH). In the Indian and Pacific, this leads to subsurface warming in the subtropical thermocline. As the southern margins of the gyres move into latitudes characterised by warmer surface air temperature (SAT), the layers at mid-depth below 400 m depth become ventilated by warmer water. We characterize the approximation of the ventilated thermocline in our coarse resolution model using a set of passive tracer experiments, and illustrate how the northward shift in the SWWs causes an equatorward shift in the latitude of origin of water ventilating layers deeper than 400 m in the Indian and Pacific, leaving the total surface ventilation of the upper 1200 m unchanged. In contrast, the latitudinal constraint on the Antarctic Circumpolar Current posed by the Drake Passage causes a cooling and freshening throughout the Atlantic thermocline; here, subsurface thermocline water originates from higher latitudes under the wind shift. On longer timescales Atlantic cooling and freshening is reinforced by a reduction in North Atlantic Deep Water (NADW) formation and surface salinification of the Indian and Pacific Oceans. In effect, the latitude of zero wind stress curl in the SWWs regulates the relative importance of the “cold water route” via the Drake Passage and the “warm water route” associated with thermocline water exchange via the Indian Ocean. Thus, a more northward location of the SWWs corresponds with a reduced salinity contrast between the Indian/ Pacific Oceans and the Atlantic. This results in reduced NADW formation. Also, a more northward location of the SWWs facilitates the injection of cool fresh Antarctic Intermediate Water into the South

  19. Investigation of Solar Wind Coupling to the High-Latitude Ionospheric Reverse Convection Electric Field during Large Positive IMF Bz

    NASA Astrophysics Data System (ADS)

    Clauer, C. R.; Deshpande, K.; Xu, Z.; Hartinger, M.; Weimer, D. R.; Nicolls, M. J.

    2015-12-01

    An empirical determination of the coupling function between the solar wind dynamo electric field and the high latitude ionospheric electric field is possible using the Weiner filter technique. We investigate the response of the high latitude reverse convection electric field measured by the Resolute Incoherent Scatter Radar (RISR) during periods of large northward IMF for two CME-related events 12-13 September 2014 and 22 - 23 June 2015. The technique provides the most general linear coupling function including frequency response and time delays. We find that the solar wind is strongly coupled to the high latitude reverse convection electric field. We discuss the details of this coupling as it relates to various parameters that may influence the coupling efficiency, such as solar wind mach number, plasma beta, ionospheric Pederson conductivity, etc.

  20. Simulated orbits of heavy planetary ions at Mars for different IMF configurations

    NASA Astrophysics Data System (ADS)

    Curry, Shannon; Luhmann, Janet; Livi, Roberto; Hara, Takuya; Dong, Chuanfei; Ma, Yingjuan; McFadden, James; Bougher, Stephen

    2014-11-01

    We present simulated detections of O+, O2+ and CO2+ ions at Mars along a virtual orbit in the Mars space environment. Planetary pick-up ions are formed through the direct interaction of the solar wind with the neutral upper atmosphere, causing the newly created ions to be picked up and accelerated by the background convective electric field. Because previous missions such as Mars Global Surveyor (MGS) and Mars Express (MEX) have not been able to measure the interplanetary magnetic field (IMF) components simultaneously with plasma measurements, the response of heavy planetary pick-up ions to changes in the IMF has not been well characterized. Using a steady-state multi-species MHD model to provide the background electric and magnetic fields, the Mars Test Particle (MTP) simulation can trace each of these particles along field lines in near-Mars space and construct virtual ion detections from a spacecraft orbit. Specifically, we will present energy-time spectrograms and velocity space distributions (VSDs) for a selection of orbits during different IMF configurations and solar cycle conditions. These simulated orbits have broader implications for how to measure ion escape. Using individual particle traces, the origin and trajectories of different ion populations can be analyzed in order to assess how and where they contribute to the total atmospheric escape rate, which is a major objective of the upcoming MAVEN mission.

  1. The IMF as a function of supersonic turbulence

    NASA Astrophysics Data System (ADS)

    Bertelli Motta, C.; Clark, P. C.; Glover, S. C. O.; Klessen, R. S.; Pasquali, A.

    2016-08-01

    Recent studies seem to suggest that the stellar initial mass function (IMF) in early-type galaxies might be different from a classical Kroupa or Chabrier IMF, i.e. contain a larger fraction of the total mass in low-mass stars. From a theoretical point of view, supersonic turbulence has been the subject of interest in many analytical theories proposing a strong correlation with the characteristic mass of the core mass function (CMF) in star forming regions, and as a consequence with the stellar IMF. Performing two suites of smoothed particles hydrodynamics (SPH) simulations with different mass resolutions, we aim at testing the effects of variations in the turbulent properties of a dense, star forming molecular cloud on the shape of the system mass function in different density regimes. While analytical theories predict a shift of the peak of the CMF towards lower masses with increasing velocity dispersion of the cloud, we observe in the low-density regime the opposite trend, with high Mach numbers giving rise to a top-heavy mass distribution. For the high-density regime we do not find any trend correlating the Mach number with the characteristic mass of the resulting IMF, implying that the dynamics of protostellar accretion discs and fragmentation on small scales is not strongly affected by turbulence driven at the scale of the cloud. Furthermore, we suggest that a significant fraction of dense cores are disrupted by turbulence before stars can be formed in their interior through gravitational collapse. Although this particular study has limitations in its numerical resolution, we suggest that our results, along with those from other studies, cast doubt on the turbulent fragmentation models on the IMF that simply map the CMF to the IMF.

  2. The IMF as a function of supersonic turbulence

    NASA Astrophysics Data System (ADS)

    Bertelli Motta, C.; Clark, P. C.; Glover, S. C. O.; Klessen, R. S.; Pasquali, A.

    2016-11-01

    Recent studies seem to suggest that the stellar initial mass function (IMF) in early-type galaxies might be different from a classical Kroupa or Chabrier IMF, i.e. contain a larger fraction of the total mass in low-mass stars. From a theoretical point of view, supersonic turbulence has been the subject of interest in many analytical theories proposing a strong correlation with the characteristic mass of the core mass function (CMF) in star-forming regions, and as a consequence with the stellar IMF. Performing two suites of smoothed particle hydrodynamics (SPH) simulations with different mass resolutions, we aim at testing the effects of variations in the turbulent properties of a dense, star-forming molecular cloud on the shape of the system mass function in different density regimes. While analytical theories predict a shift of the peak of the CMF towards lower masses with increasing velocity dispersion of the cloud, we observe in the low-density regime the opposite trend, with high Mach numbers giving rise to a top-heavy mass distribution. For the high-density regime we do not find any trend correlating the Mach number with the characteristic mass of the resulting IMF, implying that the dynamics of protostellar accretion discs and fragmentation on small scales is not strongly affected by turbulence driven at the scale of the cloud. Furthermore, we suggest that a significant fraction of dense cores are disrupted by turbulence before stars can be formed in their interior through gravitational collapse. Although this particular study has limitations in its numerical resolution, we suggest that our results, along with those from other studies, cast doubt on the turbulent fragmentation models on the IMF that simply map the CMF to the IMF.

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

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

  4. Role of ocean-atmosphere interaction on northward propagation of Indian summer monsoon intra-seasonal oscillations (MISO)

    NASA Astrophysics Data System (ADS)

    Sharmila, S.; Pillai, P. A.; Joseph, S.; Roxy, M.; Krishna, R. P. M.; Chattopadhyay, R.; Abhilash, S.; Sahai, A. K.; Goswami, B. N.

    2013-09-01

    active’ ocean. In CFSv2, the lead-lag relationship between the atmospheric fluxes, SST and convection are maintained, while such lead-lag is unrealistic in the uncoupled simulations. This leads to the conclusion that high frequent and interactive ocean-atmosphere coupling is a necessary and crucial condition for reproducing the realistic northward propagation of MISO in this particular model.

  5. Possible density dependent local variations in the IMF

    NASA Astrophysics Data System (ADS)

    Kavila, Indulekha; George, Babitha

    2015-08-01

    Variations in the IMF have been reported within open clusters (signifying mass segregation), between globular clusters, within galaxies and between galaxies. Most stars are considered to form in a clustered mode. However, the surface density of YSO's shows a wide range and it is also considered that stars form in the clustered mode only at the peaks of the surface density. The bound cluster formation efficiency in galaxies is observed to be correlated with the Star Formation Rate density which itself is seen to be correlated with the gas surface density by the Kennicutt Schmidt law.Observationally, dense cores in molecular clouds - which go on to produce stars - have a mass spectrum that is broadly consistent with a Salpeter slope of -1.35 at the high mass end. In simulations of clouds with Gaussian fluctuations it is seen that the mass spectrum of peaks which collapse are approximately log-normal, peaking roughly at the average Jeans' mass in the cloud. We explore a possible way in which the IMF could depend on the local gas density. The extent of the variations that can be caused by such a dependence is explored. The IMFs of the sample clusters that are generated are compared with the IMFs of observed clusters and also against radial trends reported in galaxies.

  6. ON THE IMF IN A TRIGGERED STAR FORMATION CONTEXT

    SciTech Connect

    Zhou, Tingtao; Huang, Chelsea X.; Lin, D. N. C.; Gritschneder, Matthias

    2015-07-20

    The origin of the stellar initial mass function (IMF) is a fundamental issue in the theory of star formation. It is generally fit with a composite power law. Some clues on the progenitors can be found in dense starless cores that have a core mass function (CMF) with a similar shape. In the low-mass end, these mass functions increase with mass, albeit the sample may be somewhat incomplete; in the high-mass end, the mass functions decrease with mass. There is an offset in the turn-over mass between the two mass distributions. The stellar mass for the IMF peak is lower than the corresponding core mass for the CMF peak in the Pipe Nebula by about a factor of three. Smaller offsets are found between the IMF and the CMFs in other nebulae. We suggest that the offset is likely induced during a starburst episode of global star formation which is triggered by the formation of a few O/B stars in the multi-phase media, which naturally emerged through the onset of thermal instability in the cloud-core formation process. We consider the scenario that the ignition of a few massive stars photoionizes the warm medium between the cores, increases the external pressure, reduces their Bonnor–Ebert mass, and triggers the collapse of some previously stable cores. We quantitatively reproduce the IMF in the low-mass end with the assumption of additional rotational fragmentation.

  7. Modern yields per stellar generation: the effect of the IMF

    NASA Astrophysics Data System (ADS)

    Vincenzo, F.; Matteucci, F.; Belfiore, F.; Maiolino, R.

    2016-02-01

    Gaseous and stellar metallicities in galaxies are nowadays routinely used to constrain the evolutionary processes in galaxies. This requires the knowledge of the average yield per stellar generation, yZ, i.e. the quantity of metals that a stellar population releases into the interstellar medium (ISM), which is generally assumed to be a fixed fiducial value. Deviations of the observed metallicity from the expected value of yZ are used to quantify the effect of outflows or inflows of gas, or even as evidence for biased metallicity calibrations or inaccurate metallicity diagnostics. Here, we show that y_{Z} depends significantly on the initial mass function (IMF), varying by up to a factor larger than three, for the range of IMFs typically adopted in various studies. Varying the upper mass cutoff of the IMF implies a further variation of yZ by an additional factor that can be larger than two. These effects, along with the variation of the gas mass fraction restored into the ISM by supernovae (R, which also depends on the IMF), may yield to deceiving results, if not properly taken into account. In particular, metallicities that are often considered unusually high can actually be explained in terms of yield associated with commonly adopted IMFs such as the Kroupa or Chabrier. We provide our results for two different sets of stellar yields (both affected by specific limitations) finding that the uncertainty introduced by this assumption can be as large as ˜0.2 dex. Finally, we show that yZ is not substantially affected by the initial stellar metallicity as long as Z > 10-3 Z⊙.

  8. Statistical Comparison of a Southern Auroral Electrojet Index with Northern Hemisphere AE Indices as a Function of Solar Wind and IMF

    NASA Astrophysics Data System (ADS)

    Boudouridis, A.; Weygand, J. M.; Zesta, E.

    2014-12-01

    A Southern Auroral Electrojet (SAE) index has been recently constructed using seven Antarctica magnetometer stations. It has been compared for case studies with the standard Auroral Electrojet (AE) index, and a near-conjugate to the southern stations Northern Auroral Electrojet (NAE) index. Both similarities and differences with the Northern Hemisphere indices have been detected, and they reveal information about the conjugacy of geomagnetic disturbances. In this work we compare the three indices statistically as a function of the accompanying solar wind (SW) and Interplanetary Magnetic Field (IMF) conditions to further explore conjugacy issues. We use 274 days of common north/south data presence between December 2005 and August 2010. We calculate the cross correlation coefficients and differences between all three pairs, AE-SAE, NAE-SAE, and AE-NAE. We estimate the effect of the SW/IMF conditions on the index correlations and differences using three groups of data: 1) the entire data set, 2) periods when there is no station in the Southern Hemisphere located within the 20-02 Magnetic Local Time (MLT) sector where substorms occur, and 3) separately for the four different seasons. We consider the following SW/IMF quantities: IMF By, Bz, clock angle θ = tan-1(|By|/Bz), coupling parameter sin2(θ/2), SW dynamic pressure, density, velocity, and electric field. We find that high north-south correlation coefficients are more common during strong SW/IMF driving, e.g., southward IMF, high IMF |By|, high SW dynamic pressure, high SW electric field, and high θ and sin2(θ/2). All the above studies are also conducted for the index differences instead of their correlations. We find that the index differences are higher for higher SW/IMF driving, suggesting that the SAE index follows the northern indices trend, but has in general lower values than either the standard AE or the conjugate NAE index. The MLT study shows that the number of high AE/SAE correlations is slightly

  9. Investigating the low-mass slope and possible turnover in the LMC IMF

    NASA Astrophysics Data System (ADS)

    Gennaro, Mario

    2014-10-01

    We propose to derive the Initial Mass Function (IMF) of the field population of the Large Magellanic Cloud (LMC) down to 0.2 solar masses, probing the mass regime where the characteristic IMF turnover is observed in our Galaxy. The power of the HST, using the WFC3 IR channel, is necessary to obtain photometric mass estimates for the faint, cool, dwarf stars with masses below the expected IMF turnover point. Only by probing the IMF down to such masses, it will be possible to clearly distinguish between a bottom-heavy or bottom-light IMF in the LMC. Recent studies, using the deepest available observations for the Small Magellanic Cloud, cannot find clear evidence of a turnover in the IMF for this galaxy, suggesting a bottom-heavy IMF in contrast to the Milky Way. A similar study of the LMC is needed to confirm a possible dependence of the low-mass IMF with galactic environment. Studies of giant ellipticals have recently challenged the picture of a universal IMF, and suggest an enviromental dependence of the IMF, with the most massive galaxies having a larger fraction of low mass stars and no IMF turnover. A study of possible IMF variations from resolved stellar populations in nearby galaxies is of great importance in sheding light on this issue. Our simple approach, using direct evidence from basic star counts, is much less prone to systematic errors with respect to studies of more distant objects which have to rely on the observations of integrated properties.

  10. Auroral Substorm Time Scales: Seasonal and IMF Variations

    NASA Technical Reports Server (NTRS)

    Chua, D.; Parks, G. K.; Brittnacher, M.; Germany, G. A.; Spann, J. F.; Six, N. Frank (Technical Monitor)

    2002-01-01

    The time scales and phases of auroral substorm, activity are quantied in this study using the hemispheric power computed from Polar Ultraviolet Imager (UVI) images. We have applied this technique to several hundred substorm events and we are able to quantify how the characterist act, of substorms vary with season and IMF Bz orientation. We show that substorm time scales vary more strongly with season than with IMF Bz orientation. The recovery time for substorm. activity is well ordered by whether or not the nightside oral zone is sunlit. The recovery time scales for substorms occurring in the winter and equinox periods are similar and are both roughly a factor of two longer than in summer when the auroral oval is sunlit. Our results support the hypothesis that the ionosphere plays an active role in governing the dynamics of the aurora.

  11. How Radiation Feedback Affects Fragmentation and the IMF

    NASA Astrophysics Data System (ADS)

    Krumholz, M. R.

    2011-06-01

    The stellar initial mass function (IMF) is determined by a process of fragmentation and accretion in the opaque, dense center of a giant molecular cloud. This environment effectively traps radiation from newborn stars, and the interaction between the gas and the radiation is the dominant feature controlling the thermodynamics and in some extreme cases the bulk motion of the gas. Not surprisingly, radiation feedback therefore plays a dominant role in determining how gas fragments to produce the IMF. In this contribution I focus on simulations exploring two radiative effects particularly relevant to the formation of massive stars: suppression of fragmentation by radiative heating, and interruption of accretion by radiation pressure. Contrary to past theoretical expectations, simulations show that the former is a dominant effect that may ultimately control when and where massive stars form, while the latter does not appear to have a significant effect on stellar masses.

  12. ZFIRE Survey: Studying the IMF at z~2

    NASA Astrophysics Data System (ADS)

    Nanayakkara, Themiya

    2015-08-01

    The development of sensitive Near Infra-Red instruments has made it possible to study the galaxy properties at z~2, just 3Gy after the Big Bang. This is expected to be the time period where galaxies are actively star forming and evolving rapidly to form the massive galaxies that are observed in our local neighborhood.As a part of the ZFIRE survey we used the MOSFIRE on Keck to study environment, metallicity and ISM properties of galaxies at these redshifts. This allowed us to spectroscopically confirm the highest redshift cluster found so far.In my talk I will present results of the first ever attempt to constrain the Initial Mass Function (IMF) of galaxies at these redshifts using a cluster and a field sample. We have investigated the degeneracy between the star formation histories and the IMF to make strong constrains on the stellar mass distribution of these galaxies using synthetic stellar spectra. Our results will demonstrate the possibility of the universality of the IMF as a function of time and environment.

  13. Venus ionopause 'clouds' and IMF sector boundaries

    NASA Astrophysics Data System (ADS)

    Luhmann, Janet G.; Russell, C. T.; Wei, Hanying; Ma, Yingjuan; Zhang, Tielong; McEnulty, T.

    Disconnected or partially connected structures observed by the PVO Langmuir Probe near the ionopause of Venus were called 'clouds' by Brace et al. (1980). These authors speculated that the loss of atmosphere represented by these features could be significant compared to other loss processes. Russell et al. (1982) subsequently showed that the clouds occurred together with sharp rotations in the magnetic field. They suggested that the extreme draping of the interplanetary field that occurs near the ionopause at the draping poles could exert JxB forces sufficient to pull the ionospheric plasma in the cloud tailward and out into the heliosphere. But in 1991, Ong et al. demonstrated via analysis of many clouds that they are not generally seen in the polar regions of the draped magnetosheath field. Instead they occur at times when the interplanetary magnetic field undergoes a sudden rotation, as in interplanetary field sector boundaries. We discuss the statistics of such rotations at the orbit of Venus and their frequency as a function of solar cycle. Whether they enable or enhance escape or not requires simulation studies, but this study calls attention to the potential importance of time dependent external conditions.

  14. Field-aligned currents in the polar cap at small IMF Bz and By inferred from SuperDARN radar observations

    NASA Astrophysics Data System (ADS)

    Kustov, A. V.; Lyatsky, W. B.; Sofko, G. J.; Xu, L.

    2000-01-01

    Routine SuperDARN observations of the ionospheric plasma convection and field-aligned currents (FACs) in the high-latitude ionosphere are used to study current systems established at small interplanetary magnetic field (IMF) Bz and By. By statistical averaging of available data sets we show that under this IMF condition the ionospheric convection pattern consists of two (evening and morning) convection cells that are similar in shape. The flow intensity inside the central polar cap is noticeably depressed so that plasma entering the polar cap flows around its border, predominantly along the lines of equal magnetic latitude, so that the convection cells are of a crescent-like shape. This global pattern of plasma flow is associated with the effect of the region 0 field-aligned currents coexisting with the region 1 and region 2 field-aligned currents. SuperDARN observations of FACs for individual events support this conclusion. FACs were derived by analyzing the vorticity of the SuperDARN convection maps. We show that region 0 currents for small IMF Bz and By can exist in time sectors way off the magnetic noon. Thus radar observations support earlier findings from satellite magnetometer measurements of the region 0 current system at high latitudes during both the prenoon and afternoon at small IMF intensities. Because the region 0 FACs occur during small IMF intensities, it is suggested that quasi-viscous processes play a role in their generation.

  15. Windsock memory COnditioned RAM (CO-RAM) pressure effect: Forced reconnection in the Earth's magnetotail

    NASA Astrophysics Data System (ADS)

    Vörös, Z.; Facskó, G.; Khodachenko, M.; Honkonen, I.; Janhunen, P.; Palmroth, M.

    2014-08-01

    Magnetic reconnection (MR) is a key physical concept explaining the addition of magnetic flux to the magnetotail and closed flux lines back-motion to the dayside magnetosphere. This scenario elaborated by Dungey (1963) can explain many aspects of solar wind-magnetosphere interaction processes, including substorms. However, neither the Dungey model nor its numerous modifications were able to explain fully the onset conditions for MR in the tail. In this paper, we introduce new onset conditions for forced MR in the tail. We call our scenario the "windsock memory conditioned ram pressure effect." Our nonflux transfer-associated forcing is introduced by a combination of the large-scale windsock motions exhibiting memory effects and solar wind dynamic pressure actions on the nightside magnetopause during northward oriented interplanetary magnetic field (IMF). Using global MHD Grand Unified Magnetosphere Ionosphere Coupling Simulation version 4 simulation results, upstream data from Wind, magnetosheath data from Cluster 1 and distant tail data from the two-probe Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun mission, we show that the simultaneous occurrence of vertical windsock motions of the magnetotail and enhanced solar wind dynamic pressure introduces strong nightside disturbances, including enhanced electric fields and persistent vertical cross-tail shear flows. These perturbations, associated with a stream interaction region in the solar wind, drive MR in the tail during episodes of northward oriented interplanetary magnetic field (IMF). We detect MR indirectly, observing plasmoids in the tail and ground-based signatures of earthward moving fast flows. We also consider the application to solar system planets and close-in exoplanets, where the proposed scenario can elucidate some new aspects of solar/stellar wind-magnetosphere interactions.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  17. The Turbulent ISM of Galaxies 10 Gyrs ago: Star Formation, Gas Accretion, and IMF

    NASA Astrophysics Data System (ADS)

    Le Tiran, Loïc; Lehnert, Matthew D.

    2011-12-01

    The utilization of integral-field spectroscopy has led us to a new understanding of the physical conditions in galaxies within the first few billion years after the Big Bang. In this proceedings, we analyze observations of ~50 massive galaxies as seen as they were 10 Gyrs ago using SINFONI from the ESO-VLT. We show that the large line width they exhibit can be explained by the intense mechanical energy output from the young stars. We also study the influence of cold gas accretion upon these galaxies: We show that an unrealistic amount of shocked gas would be needed in order to explain the Hα emission from these galaxies through shocks from gas accretion with velocity about the Hα line widths of these galaxies. We also use DEEP2 photometric measurements for a sub-sample of 10 of these galaxies to evaluate their ratio of Hα to FUV flux as a function of their Hα and R-band luminosity surface brightnesses. Our data suggests that perhaps their initial mass function (IMF) is flatter than Salpeter at the high mass end, as has been suggested recently for some local galaxies. It may be that high turbulence is responsible for skewing the IMF towards more massive stars as suggested by some theories of star-formation. Much work is however needed to accredit this hypothesis.

  18. IMF sector behavior estimated from geomagnetic data at South Pole

    SciTech Connect

    Matsushita, S.; Xu, W.h.

    1981-05-01

    IMF sector behavior which has previously been estimated from the geomagnetic data at Godhavn is confirmed by study of the data at South Pole for 1959--1970 with the same estimation technique, taking the difference between northern and southern hemispheres into consideration. A method to improve (about 18%) the agreement between assigned and actual sector structures by study of the data at the two stations is suggested. Geomagnetic disturbance effects on sector estimation are discussed, and reversed sector effects in winter are given special emphasis.

  19. Strong gravitational lensing and the stellar IMF of early-type galaxies

    NASA Astrophysics Data System (ADS)

    Leier, Dominik; Ferreras, Ignacio; Saha, Prasenjit; Charlot, Stéphane; Bruzual, Gustavo; La Barbera, Francesco

    2016-07-01

    Systematic variations of the initial mass function (IMF) in early-type galaxies, and their connection with possible drivers such as velocity dispersion or metallicity, have been much debated in recent years. Strong lensing over galaxy scales combined with photometric and spectroscopic data provides a powerful method to constrain the stellar mass-to-light ratio and hence the functional form of the IMF. We combine photometric and spectroscopic constraints from the latest set of population synthesis models of Charlot & Bruzual, including a varying IMF, with a non-parametric analysis of the lens masses of 18 ETGs from the SLACS survey, with velocity dispersions in the range 200-300 km s-1. We find that very bottom-heavy IMFs are excluded. However, the upper limit to the bimodal IMF slope (μ ≲ 2.2, accounting for a dark matter fraction of 20-30 per cent, where μ = 1.3 corresponds to a Kroupa-like IMF) is compatible at the 1σ level with constraints imposed by gravity-sensitive line strengths. A two-segment power-law parametrization of the IMF (Salpeter-like for high masses) is more constrained (Γ ≲ 1.5, where Γ is the power index at low masses) but requires a dark matter contribution of ≳25 per cent to reconcile the results with a Salpeter IMF. For a standard Milky Way-like IMF to be applicable, a significant dark matter contribution is required within 1Re. Our results reveal a large range of allowed IMF slopes, which, when interpreted as intrinsic scatter in the IMF properties of ETGs, could explain the recent results of Smith et al., who find Milky Way-like IMF normalizations in a few massive lensing ETGs.

  20. Superposed epoch analysis of vertical plasma flow and its relationship with FACs as observed by DMSP and CHAMP: IMF By and Bx dependence

    NASA Astrophysics Data System (ADS)

    Kervalishvili, Guram; Lühr, Hermann

    2016-04-01

    This study presents results of a superposed epoch analysis (SEA) method applied to vertical plasma flow and large-scale field aligned currents (FACs) in the Northern Hemisphere cusp region. Our study is based on DMSP (F13 and F15) and CHAMP satellite observations during the years 2001-2005. Interplanetary magnetic field (IMF) data were taken from the NASA/GSFC's OMNI online database. The dependence on IMF By and Bx component orientation is investigated, while the absolute amplitude of IMF Bz is selected to be less than 2 nT. Seasonal variations are also investigated with seasons defined as follows: local winter (1 January ± 65 days), combined equinoxes (1 April and 1 October ± 32 days), and local summer (1 July ± 65 days). The reference time and location for the SEA method are taken from the vertical ion velocity peaks (> 100 m/s for upflow and <-100 m/s for downflow) detected by DMSP in the northern cusp region. Our analyses were performed in the magnetic latitude (MLat) and local time (MLT) coordinate system. In general the vertical plasma downflow is weaker than the upflow. This product, ion density times velocity, shows no dependence on the IMF By orientation, while its value increases towards local summer. The ion density is low in winter and increases towards local summer, while the vertical velocity is much higher in local winter than during equinoxes or local summer. The event number distribution (in MLat-MLT frame) of vertical ion velocity peaks shows no significant dependence on the given conditions. In case of large-scale FACs a clear dependence on IMF By orientation and local season emerges from SEA analysis. Similarly to the vertical plasma upflow, the amplitude of large-scale FACs is also increasing towards local summer. Large-scale FACs show an IMF By dependent regular pattern for upflow cases and no regular pattern for downflow cases in all considered cases.

  1. Relationship between the observed and modeled modulation of the dayside ionospheric convection by the IMF B{sub y} component

    SciTech Connect

    Papitashvili, V.O.; Clauer, C.R.; Levitin, A.E.

    1995-05-01

    The Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN) electrodynamic model (IZMEM) provides global patterns of polar ionospheric potential and is parameterized by the interplanetary magnetic field (IMF). Given IMF conditions measured by an upstream satellite, the model yields a good global approximation to the polar ionospheric convection patterns assuming the proper time delay. While the model assumes static patterns and is based upon statistical regression analysis of high-latitude magnetometer data, it can furnish an appropriate global context within which to examine time-varying phenomena. The authors use the IZMEM model to further develop their understanding of the coordinated analysis of Greenland radar, riometer, and magnetometer data on August 2, 1991, which is one of the geospace environment modeling program intervals. The event is characterized by geomagnetic pulsations observed near local magnetic noon, having a 25-min period and poleward phase propagation. A modulation of the intensity and orientation of the convection electric field is observed by the Sondrestrom incoherent scatter radar. Modeled global convection patterns show striking agreement with observations in the area covered by the radar field of view. The authors interpret observed phenomena as a direct ground-based evidence of the IMF B{sub y} component reconnection at the dayside magnetopause. 31 refs., 6 figs.

  2. Case Study of Solar Wind and IMF Influence on Ionospheric Outflow

    NASA Technical Reports Server (NTRS)

    Elliott, H. A.; Comfort, R. H.; Craven, P. D.; Chandler, M. O.; Moore, T. E.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    We examine ionospheric outflows in the high attitude magnetospheric polar cap during the POLAR satellite's apogee on 04/19/96 using the TIDE instrument. The pass has a fairly constant flux of H+ which is similar to many other passes, but there is a large amount of O+ present. The elevated levels of O+ may be due both to the geophysical conditions during the apogee pass (Kp=5) and prior to the pass. When the outflows for many high altitude polar cap passes are analyzed the O+ density correlates well with the dynamic pressure. There are several aspects of this pass which are interesting besides the abundance of O+ relative to H+. In this pass both the H+ and O+ outflow velocity correlate with both the solar wind speed and Interplanetary Magnetic Field (IMF) Bx. The geophysical conditions are such that the solar wind speed and IMF Bx are highly correlated with each other. For this case the dynamic pressure of the solar wind is fairly constant and has an average value of about 2.5 nPa which is typical for the solar wind, but the average solar wind speed is about 695 km/s which is greater than 450 km/s which is typical for the solar wind at I AU. The ion outflow measurements themselves are interrelated. The H+ density and parallel speed are anticorrelated which results in the constant flux. The 0+ density does not have as large of a anticorrelation with its parallel speed as H+ does with its parallel speed.

  3. The dependence of the IMF on the density- temperature relation of pre-stellar gas

    NASA Astrophysics Data System (ADS)

    Kitsionas, S.; Whitworth, A. P.; Klessen, R. S.; Jappsen, A.-K.

    It has been recently shown by several authors that fragmentation of pre-stellar gas (i.e. at densities from 10^4 to 10^10 particles cm^-3 and temperatures of order 10-30K) depends on the gas thermodynamics much more than it was anticipated in earlier studies, in which only an isothermal behaviour has been assumed for the gas. We shall review the results of a number of numerical hydrodynamic simulations (e.g. Li et al. 2003, Jappsen et al. 2005, Bonnell et al. 2006) in which departure from isothermality has been attempted by employing a polytropic equation of state (eos) with exponent different from unity. In particular, in these studies it has been shown that the dominant fragmentation scale of pre-stellar gas, and hence the peak of the initial mass function (IMF), depends on a polytropic exponent that changes value at a critical density. Furthermore, this critical density depends on the gas metallicity and fundamental constants rather than on initial conditions, thus allowing for the first time to infer theoretically the notion of a universal IMF (at least for its low-mass end). We shall subsequently present two test cases in which such an equation of state has been used in the context of smoothed particle hydrodynamic (SPH) numerical simulations. In the first case star formation is triggered by means of low-mass clump collisions. These calculations have shown that clump collisions can be a relatively efficient mechanism for the formation of solar mass protostars and their lower mass companions (efficiency greater or of order 20%; Kitsionas & Whitworth 2006). In the second case, the use of a polytropic eos with an exponent varying according to the metallicity of starburst regions (Spaans & Silk 2000, 2005) is shown to be sufficient to obtain a top heavy IMF similar to that observed e.g. in the Galactic centre (Klessen, Spaans & Jappsen 2006). These are preliminary results in the direction of revisiting earlier calculations that were resolving the opacity limit for

  4. Arctic Amplification and the Northward shift of a new Greenland melting record

    NASA Astrophysics Data System (ADS)

    Tedesco, Marco; Mote, Thomas; Fettweis, Xavier; Hanna, Edward; Booth, James; Jeyaratnam, Jeyavinoth; Datta, Rajashree; Briggs, Kate

    2016-04-01

    Large-scale atmospheric circulation controls the mass and energy balance of the Greenland ice sheet through its impact on radiative budget, runoff and accumulation. Using reanalysis data and the outputs of a regional climate model, here we show that the persistence of an exceptional atmospheric ridge, centred over the Arctic Ocean was responsible for a northward shift of surface melting records over Greenland, and for increased accumulation in the south during the summer of 2015. Concurrently, new records of mean monthly zonal winds at 500 hPa and of the maximum latitude of ridge peaks of the 5700±50 m isohypse over the Arctic were also set. An unprecedented (1948 - 2015) and sustained jet stream easterly flow promoted enhanced runoff, increased surface temperatures and decreased albedo in northern Greenland, while inhibiting melting in the south. The exceptional 2015 summer Arctic atmospheric conditions are consistent with the anticipated effects of Arctic Amplification, including slower zonal winds and increased jet stream wave amplitude. Properly addressing the impact of Arctic Amplification on surface runoff of the Greenland ice sheet is crucial for rigorously quantifying its contribution to current and future sea level rise, and the relative impact of freshwater discharge on the surrounding ocean.

  5. Response of reverse convection to fast IMF transitions

    NASA Astrophysics Data System (ADS)

    Taguchi, S.; Tawara, A.; Hairston, M. R.; Slavin, J. A.; Le, G.; Matzka, J.; Stolle, C.

    2015-05-01

    The nature of the transition that high-latitude reverse convection makes in response to fast interplanetary magnetic field (IMF) changes is investigated using observations from multiple spacecraft and a ground magnetometer array. We focused on two fast IMF-transition events on 22 April 2006. Immediately after the first event, three ST5 spacecraft identified a clear change in the distribution of the polar cap field-aligned current. Coordinate observations with the Greenland magnetometer chain showed that the near-noon Hall current distribution, which is closely related to the polar cap field-aligned current or reverse convection, was in a transition state for about 10 min. For the second event, the Greenland magnetic perturbations also showed that a transition state occurred in the near-noon sector for 10-15 min. Three DMSP spacecraft that traversed the polar cap provided evidence showing that variations of the ground magnetic perturbations were produced by the transition from clockwise plasma circulation to the anticlockwise circulation over the polar cap. A simple calculation based on the Biot-Savart law shows that the near-noon transition state is consistent with the approach of a new convection region to the near-noon sector at the speed of 0.5-1 km s-1, which is coupled with the moving away of the old convection region at a similar speed. For the higher-latitude sunward flow region, it is found that the convection takes a transition state almost simultaneously (within 1 min) with that in the near-noon sector, i.e., quasi-instantaneous response.

  6. Influence of IMF Rotation on the Magnetic Field Depression in the Magnetosheath: A Kinetic View

    NASA Astrophysics Data System (ADS)

    Tsubouchi, K.; Terasawa, T.

    2001-12-01

    Numerical simulations using a one-dimensional hybrid code are performed to investigate how the particle kinetic process determines the magnetosheath structure when the upstream solar wind carries the IMF rotation. It is known from the conventional MHD theory that the interaction of such an IMF disturbance with the bow shock leads to the formation of the diamagnetic structure (density enhancement and magnetic field depression) in the downstream, the edges of which correspond to the excited slow, or intermediate, shock waves. However, the downstream plasma has strong anisotropy (energy imbalance between the component parallel and perpendicular to the magnetic field) in the quasi-perpendicular shock regime; which enables the mirror instability to grow, for instance. Thus the present kinetic approach is essential for the precise understanding of the resultant magnetosheath structure. The most significant result (different from MHD view) is that the rotating magnetic field which passes through the shock rapidly modifies the directional energy distribution of ions in the downstream. Stronger energy of the perpendicular component turns to contribute to the substantial parallel heating in the field rotation. Such ion isotropization shows the net increase of the total thermal pressure which makes the reduction of the magnetic field to maintain the pressure balance. Inside this field rotation region, a large amount of particles with v∥ ~ 0 are accumulated. This process can be considered as an analogy of the physics in the mirror instability. However, the condition for the instability is immediately suppressed when particles experience the field rotation, so that the resultant structure is stably convected in the downstream. Geotail magnetosheath observation is compared to the simulation results.

  7. Are Unusual Solar Wind Conditions in SC23-24 Triggering Changes in the Geospace Response to High Speed Streams? (Invited)

    NASA Astrophysics Data System (ADS)

    Kozyra, J. U.; Brandt, P. C.; Buzulukova, N.; de Zeeuw, D.; Fok, M. H.; Frey, H. U.; Gibson, S. E.; Ilie, R.; Liemohn, M. W.; Mende, S. B.; Paxton, L. J.; Rastaetter, L.; Ridley, A. J.; Thomsen, M. F.

    2009-12-01

    In the descent to solar minimum in solar cycle 23-24, the high-speed streams (HSS) were faster and longer lived than previous cycles but the average IMF was weaker and the average solar wind density lower than ever before recorded upstream of the Earth. A simulation of high speed stream activity on 22-24 January 2005 using the BATS-R-US MHD model with embedded Rice Convection Model driven by solar wind inputs indicates that, at least for this event, the interaction between high speed streams and the magnetosphere has been modified by these unusual solar wind conditions. Northward IMF in the HSS drove the periodic capture of solar wind/magnetosheath plasma in the dayside magnetosphere due to high-latitude reconnection. At times of observed strong periodic auroral activity, a significant IMF By component produced a magnetospheric sash configuration in the simulations in which fingers of enhanced plasma beta were associated with strong field-aligned currents linking to the nightside auroral region. In agreement with the simulations, IMAGE HENA observed low energy (less than tens of keV) hydrogen energetic neutral atoms peaking on the dayside for the 3-days of the high speed stream activity. IMAGE FUV and TIMED GUVI observed periodic auroral activations during the HSS that resembled poleward boundary intensifications (PBIs) rather than the periodic substorms typically associated with HSS. The locations of the observed PBIs in the southern hemisphere were consistent with the high-beta fingers in the near-Earth plasma sheet predicted by the simulation. Particle injection signatures at LANL geosynchronous satellites accompanied the PBIs. To our knowledge, these results provide the first evidence in support of the role of northward IMF in HSS interactions. Based on these results, a study of energetic neutral atom images from TWINS and IMAGE HENA along with observations from other missions in the Heliophysics System Observatory is underway to determine if these

  8. A Northward Shift of the North Atlantic Ocean Intertropical Convergence Zone in Response to Summertime Saharan Dust Outbreaks

    NASA Technical Reports Server (NTRS)

    Wilcox, Eric M.; Lau, K. M.; Kim, Kyu-Myong

    2010-01-01

    The influence on the summertime North Atlantic Ocean inter-tropical convergence zone (ITCZ) of Saharan dust outbreaks is explored using nine years of continuous satellite observations and atmospheric reanalysis products. During dust outbreak events rainfall along the ITCZ shifts northward by 1 to 4 degrees latitude. Dust outbreaks coincide with warmer lower-tropospheric temperatures compared to low dust conditions, which is attributable to advection of the warm Saharan Air Layer, enhanced subtropical subsidence, and radiative heating of dust. The enhanced positive meridional temperature gradient coincident with dust outbreaks is accompanied by an acceleration of the easterly winds on the n011h side of the African Easterly Jet (AEJ). The center of the positive vorticity region south of the AEJ moves north drawing the center of low-level convergence and ITCZ rainfall northward with it. The enhanced precipitation on the north side of the ITCZ occurs in spite of widespread sea surface temperature cooling north of the ITCZ owing to reduced surface solar insolation by dust scattering.

  9. Gradient in the IMF slope and Sodium abundance of M87 with MUSE

    NASA Astrophysics Data System (ADS)

    Spiniello, C.; Sarzi, M.; Krajnovic, D.

    2016-06-01

    We present evidence for a radial variation of the stellar initial mass function IMF) in the giant elliptical NGC~4486 based on integral-field MUSE data acquired during the first Science Verification run for this instrument. A steepening of the low-mass end of the IMF towards the centre of this galaxy is necessary to explain the increasing strength of several of the optical IMF sensitive features introduced by Spiniello et al., which we observe in high-quality spectra extracted in annular apertures. The need for a varying slope of the IMF emerges when the strength of these IMF-sensitive features, together with that other classical Lick indices mostly sensitive to stellar metallicity and the bundance of α-elements, are fitted with the state-of-the-art stellar population models from Conroy & van Dokkum and Vazdekis et al., which we modified in order to allow variations in IMF slope, metallicity and α-elements abundance. More specifically, adopting 13-Gyr-old, single-age stellar population models and an unimodal IMF we find that the slope of the latter increases from x=1.8 to x=2.6 in the central 25 arcsec of NGC~4486. Varying IMF accompanied by a metallicity gradient, whereas the abundance of α-element appears constant throughout the MUSE field of view. We found metallicity and α-element abundance gradients perfectly consistent with the literature. A sodium over-abundance is necessary (according to CvD12 models) at all the distances (for all the apertures) and a slight gradient of increasing [Na/Fe] ratio towards the center can be inferred. However, in order to completely break the degeneracies between Na-abundance, total metallicity and IMF variation a more detailed investigation that includes the redder NaI line is required.

  10. NORTHWARD EXPANSION OF A MARINE PARASITE: TESTING THE ROLE OF TEMPERATURE ADAPTATION

    EPA Science Inventory

    The known range of the eastern oyster (Crassostrea virginica) parasite, Perkinsus marinus, expanded into the northeastern United States in the early 1990s. We used both in vitro and in vivo data to test the hypothesis that the northward expansion was associated with a low-tempera...

  11. Polar, Cluster and SuperDARN Evidence for High-Latitude Merging during Southward IMF: Temporal/Spatial Evolution

    NASA Technical Reports Server (NTRS)

    Maynard, N. C.; Ober, D. M.; Burke, W. J.; Scudder, J. D.; Lester, M.; Dunlap, M.; Wild, J. A.; Grocott, A.; Farrugia, C. J.; Lund, E. J.; Russell, C. T.

    2003-01-01

    Magnetic merging on the dayside magnetopause often occurs at high latitudes. Polar measured fluxes of accelerated ions and wave Poynting vectors while skimming the subsolar magnetopause. The measurements indicate that their source was located to the north of the spacecraft, well removed from expected component merging sites. This represents the first use of wave Poynting flux as a merging discriminator at the magnetopause. We argue that wave Poynting vectors, like accelerated particle fluxes and the Walen tests, are necessary, but not sufficient, conditions, for identifying merging events. The Polar data are complemented with nearly simultaneous measurements from Cluster in the northern cusp, with correlated observations from the SuperDARN radar, to show that the locations and rates of merging vary. Magnetohydrodynamic (MHD) simulations are used to place the measurements into a global context. The MHD simulations confirm the existence of a high-latitude merging site and suggest that Polar and SuperDARN observed effects are attributable to both exhaust regions of a temporally varying X-line. A survey of 13 merging events places the location at high latitudes whenever the interplanetary magnetic field (IMF) clock angle is less than approximately 150 degrees. While inferred high-latitude merging sites favor the antiparallel merging hypothesis, our data alone cannot exclude the possible existence of a guide field. Merging can even move away from equatorial latitudes when the IMF has a strong southward component. MHD simulations suggest that this happens when the dipole tilt angle increases or when IMF B(sub X) increases the effective dipole tilt.

  12. Dark matter and IMF normalization in Virgo dwarf early-type galaxies

    NASA Astrophysics Data System (ADS)

    Tortora, C.; La Barbera, F.; Napolitano, N. R.

    2016-01-01

    In this work, we analyse the dark matter (DM) fraction, fDM, and mass-to-light ratio mismatch parameter, δIMF (computed with respect to a Milky Way-like initial mass function), for a sample of 39 dwarf early-type galaxies in the Virgo cluster. Both fDM and δIMF are estimated within the central (one effective radius) galaxy regions, with a Jeans dynamical analysis that relies on galaxy velocity dispersions, structural parameters, and stellar mass-to-light ratios from the SMAKCED survey. In this first attempt to constrain, simultaneously, the initial mass function (IMF) normalization and the DM content, we explore the impact of different assumptions on the DM model profile. On average, for an Navarro, Frenk & White (NFW) profile, the δIMF is consistent with a Chabrier-like normalization ({δ _IMF}˜ 1), with {f_DM}˜ 0.35. One of the main results of this work is that for at least a few systems the δIMF are heavier than the Milky Way-like value (i.e. either top- or bottom-heavy). When introducing tangential anisotropy, larger δIMF and smaller fDM are derived. Adopting a steeper concentration-mass relation than that from simulations, we find lower δIMF ( ≲ 1) and larger fDM. A constant M/L profile with null fDM gives the heaviest δIMF (˜2). In the MONDian framework, we find consistent results to those for our reference NFW model. If confirmed, the large scatter of δIMF for dEs would provide (further) evidence for a non-universal IMF in early-type systems. On average, our reference fDM estimates are consistent with those found for low-σe (˜ 100 km s^{-1}) early-type galaxies (ETGs). Furthermore, we find fDM consistent with values from the SMAKCED survey, and find a double-value behaviour of fDM with stellar mass, which mirrors the trend of dynamical M/L and global star formation efficiency (from abundance matching estimates) with mass.

  13. Implications of a variable IMF for the interpretation of observations of galaxy populations

    NASA Astrophysics Data System (ADS)

    Clauwens, Bart; Schaye, Joop; Franx, Marijn

    2016-11-01

    We investigate the effect of a metallicity-dependent stellar initial mass function (IMF), as deduced observationally by Martín-Navarro et al., on the inferred stellar masses and star formation rates (SFRs) of a representative sample of 186 886 SDSS galaxies. Relative to a Chabrier IMF, for which we show the implied masses to be close to minimal, the inferred masses increase in both the low- and high-metallicity regimes due to the addition of stellar remnants and dwarf stars, respectively. The resulting galaxy stellar mass function (GSMF) shifts towards higher masses by 0.5 dex, without affecting the high-mass slope (and thus the need for effective quenching). The implied low-redshift SFR density increases by an order of magnitude. However, these results depend strongly on the assumed IMF parametrization, which is not directly constrained by the observations. Varying the low-end IMF slope instead of the high-end IMF slope, while maintaining the same dwarf-to-giant ratio, results in a much more modest GSMF shift of 0.2 dex and a 10 per cent increase in the SFR density relative to the Chabrier IMF. A bottom-heavy IMF during the late, metal-rich evolutionary stage of a galaxy would help explain the rapid quenching and the bimodality in the galaxy population by on the one hand making galaxies less quenched (due to the continued formation of dwarf stars) and on the other hand reducing the gas consumption time-scale. We conclude that the implications of the observational evidence for a variable IMF could vary from absolutely dramatic to mild but significant.

  14. The influence of IMF on the lower ionosphere plasma in high and middle latitudes

    NASA Technical Reports Server (NTRS)

    Bremer, J.

    1989-01-01

    As shown by ground-based absorption measurements, the lower ionospheric plasma is markedly controlled by the structure of the IMF. Whereas in high auroral and subauroral latitudes this effect is very pronounced, in midlatitudes its influence is less important. A comparison of these results with satellite data of the IMF and the solar wind speed confirms the important role of these components, not only during special events but also for the normal state of the ionospheric D region plasma.

  15. Association of consecutive Pi2-Ps6 band pulsations with earthward fast flows in the plasma sheet in response to IMF variations

    NASA Astrophysics Data System (ADS)

    Cheng, Ching-Chang; Mann, Ian R.; Baumjohann, Wolfgang

    2014-05-01

    On 11 March 2009, the H component had four consecutive bay-like variations accompanied by positive and negative deflections in the D component across the Atlantic like those affected by the substorm current wedge formation. A train of pulsations with a frequency range 2-10 mHz (referred to as Pi2-Ps6 band), sensed by Time History of Events and Macroscale Interactions during Substorms (THEMIS)/Canadian Array for Real-time Investigations of Magnetic Activity (CARISMA) magnetometers, had clearly three consecutive Pi2s followed by a Ps6 at low latitudes, but first Pi2 and then Ps6 at high latitudes mixed with large-amplitude Ps6 at midlatitudes. The geostationary orbit magnetometers sensed similar magnetic perturbations. THEMIS probes first observed earthward fast flows, magnetic dipolarizations, and modulated energetic particle fluxes at ~ XGSM -9.2 RE, then at ~ XGSM -7.5 RE for Pi2 and at ~ XGSM -18.0 RE only for Ps6. They appeared during a very quiet period for northward interplanetary magnetic field (IMF) with a clock angle variation of low to high and then low. The H spectrum shows two harmonic frequencies ~2-4 mHz and ~8-10 mHz but the D spectrum one dominant frequency ~2-4 mHz. Pi2 can result from a combination of fast magnetospheric and plasmaspheric cavity resonances and Ps6 from a fast magnetospheric cavity resonance. The surface waves at the interface separating braking earthward fast flows from the ambient plasma convection region could lead to large-amplitude Ps6 at midlatitudes. Hence, consecutive Pi2-Ps6 band pulsations can be associated with earthward fast flows in the plasma sheet, expectedly driven by magnetotail reconnection, respectively, in the near-Earth region and the distant Earth one in response to IMF variations as in the two-neutral-point model.

  16. High-altitude Cusp Precipitation for Different IMF Orientations

    NASA Astrophysics Data System (ADS)

    Nemecek, Z.; Safrankova, J.; Simunek, J.

    2005-12-01

    Reconnection is the most important process in the magnetospheric physics. Dayside reconnection of interplanetary and terrestrial magnetic fields supplies the magnetosphere with a huge amount of the solar wind plasma that is then released due to reconnection occurring in the tail. In spite of its principal importance, reconnection is still understood insufficiently. The main problem is probably connected with the fact that both MHD and kinetic processes are equally important for its initialization and further development. Experimental investigations are difficult because reconnection spots are limited in space and time and a probability that a spacecraft is located in appropriate time at a right position is very low. However, all possible places where magnetopause reconnection can occur are magnetically connected to the cusp and thus the plasma proceeding along reconnected magnetic field lines brings information on reconnection. As observed by the various spacecraft at both low and high altitudes, a cusp precipitation is often characterized by ion energy dispersion. During southward IMF, ion energy falls with increasing magnetic latitudes due to the convection electric field operating as a velocity filter on particles from the injection point to the observation point. The high-energy ions rapidly reach lower latitudes and the lower-energy ions appear later at higher latitudes. By contrast, if reconnection takes place in the tail lobes, the high-energy ions quickly reach higher latitudes, whereas the low-energy ions are convected to lower latitudes and thus the ion energy-latitude dispersion signifies the boundary of open and closed magnetic field lines. We are presenting case studies of crossings of the cusp region at high altitudes which reveal that both spatial and temporal changes should be taken into account for an explanation of the observed features. Moreover, our study shows that the cusp can be supplied from two simultaneously operating reconnection sites

  17. The Turbulent ISM of Galaxies about 10 Gyrs Ago: An Impact on their IMF?

    NASA Astrophysics Data System (ADS)

    Le Tiran, L.; Lehnert, M. D.

    2011-06-01

    The utilization of integral-field spectroscopy has led us to a new understanding of the physical conditions in galaxies within the first few billion years after the Big Bang. The combination of the kinematics and emission line diagnostics is a powerful technique to discern the physical processes that are at work in distant galaxies. In these proceedings, we present observations of 10 massive galaxies as seen as they were 9 Gyrs ago using SINFONI from the ESO-VLT, combined with photometry from the DEEP2 Survey. We first portray a brief picture of the physical conditions in the warm ionized medium of these galaxies; they exhibit complex morphologies, high star formation and are so pressure dominated they are likely to drive winds and high turbulence. Moreover, their ratio of Hα to FUV flux to their R-band luminosity surface brightnesses indicates that perhaps their initial mass function is flatter than Salpeter at the high mass end, as has been suggested recently for some local galaxies. It may be that high turbulence is responsible for skewing the IMF towards more massive stars as suggested by some theories of star-formation.

  18. Modelling the Northward Expansion of Culicoides sonorensis (Diptera: Ceratopogonidae) under Future Climate Scenarios.

    PubMed

    Zuliani, Anna; Massolo, Alessandro; Lysyk, Timothy; Johnson, Gregory; Marshall, Shawn; Berger, Kathryn; Cork, Susan Catherine

    2015-01-01

    Climate change is affecting the distribution of pathogens and their arthropod vectors worldwide, particularly at northern latitudes. The distribution of Culicoides sonorensis (Diptera: Ceratopogonidae) plays a key role in affecting the emergence and spread of significant vector borne diseases such as Bluetongue (BT) and Epizootic Hemorrhagic Disease (EHD) at the border between USA and Canada. We used 50 presence points for C. sonorensis collected in Montana (USA) and south-central Alberta (Canada) between 2002 and 2012, together with monthly climatic and environmental predictors to develop a series of alternative maximum entropy distribution models. The best distribution model under current climatic conditions was selected through the Akaike Information Criterion, and included four predictors: Vapour Pressure Deficit of July, standard deviation of Elevation, Land Cover and mean Precipitation of May. This model was then projected into three climate change scenarios adopted by the IPCC in its 5th assessment report and defined as Representative Concentration Pathways (RCP) 2.6, 4.5 and 8.5. Climate change data for each predictor and each RCP were calculated for two time points pooling decadal data around each one of them: 2030 (2021-2040) and 2050 (2041-2060). Our projections showed that the areas predicted to be at moderate-high probability of C. sonorensis occurrence would increase from the baseline scenario to 2030 and from 2030 to 2050 for each RCP. The projection also indicated that the current northern limit of C. sonorensis distribution is expected to move northwards to above 53°N. This may indicate an increased risk of Culicoides-borne diseases occurrence over the next decades, particularly at the USA-Canada border, as a result of changes which favor C. sonorensis presence when associated to other factors (i.e. host and pathogen factors). Recent observations of EHD outbreaks in northern Montana and southern Alberta supported our projections and considerations

  19. Modelling the Northward Expansion of Culicoides sonorensis (Diptera: Ceratopogonidae) under Future Climate Scenarios

    PubMed Central

    Lysyk, Timothy; Johnson, Gregory; Marshall, Shawn; Berger, Kathryn; Cork, Susan Catherine

    2015-01-01

    Climate change is affecting the distribution of pathogens and their arthropod vectors worldwide, particularly at northern latitudes. The distribution of Culicoides sonorensis (Diptera: Ceratopogonidae) plays a key role in affecting the emergence and spread of significant vector borne diseases such as Bluetongue (BT) and Epizootic Hemorrhagic Disease (EHD) at the border between USA and Canada. We used 50 presence points for C. sonorensis collected in Montana (USA) and south-central Alberta (Canada) between 2002 and 2012, together with monthly climatic and environmental predictors to develop a series of alternative maximum entropy distribution models. The best distribution model under current climatic conditions was selected through the Akaike Information Criterion, and included four predictors: Vapour Pressure Deficit of July, standard deviation of Elevation, Land Cover and mean Precipitation of May. This model was then projected into three climate change scenarios adopted by the IPCC in its 5th assessment report and defined as Representative Concentration Pathways (RCP) 2.6, 4.5 and 8.5. Climate change data for each predictor and each RCP were calculated for two time points pooling decadal data around each one of them: 2030 (2021–2040) and 2050 (2041–2060). Our projections showed that the areas predicted to be at moderate-high probability of C. sonorensis occurrence would increase from the baseline scenario to 2030 and from 2030 to 2050 for each RCP. The projection also indicated that the current northern limit of C. sonorensis distribution is expected to move northwards to above 53°N. This may indicate an increased risk of Culicoides-borne diseases occurrence over the next decades, particularly at the USA-Canada border, as a result of changes which favor C. sonorensis presence when associated to other factors (i.e. host and pathogen factors). Recent observations of EHD outbreaks in northern Montana and southern Alberta supported our projections and

  20. High-time resolution measurements of upstream magnetic field and plasma conditions during flux transfer events at the Earth's dayside magnetopause

    NASA Technical Reports Server (NTRS)

    Jacob, Jamey D.; Carrell, Cynthia

    1993-01-01

    We present preliminary results of a study of upstream magnetic field and plasma conditions measured by IRM during flux transfer events observed at the Earth's magnetopause by CCE. This study was designed to determine the importance of various upstream factors in the formation of bipolar magnetic field signatures called flux transfer events (FTEs). Six FTE encounters were examined. In three cases, the two satellites were on similar magnetic field lines. Preliminary investigation showed that fluctuations occurred in the Bz component of the interplanetary magnetic field (IMF) resulting in a southward field preceding the FTE in all three of these cases. In two of these cases, the changes were characterized by a distinct rotation from a strong southward to a strong northward field. There were also accompanying changes in the dynamic and thermal pressure in the solar wind immediately before the FTE was encountered. Examination of the 3D plasma distributions showed that these pulses were due to the addition of energetic upstreaming foreshock particles. There were no consistent changes in either Bz or the plasma pressure at IRM for the three events when the satellites were not connected by the IMF.

  1. Limits to northward drift of the Paleocene Cantwell Formation, central Alaska.

    USGS Publications Warehouse

    Hillhouse, J.W.; Gromme, C.S.

    1982-01-01

    Volcanic rocks of the Paleocene Cantwell Formation in central Alaska apparently originated at a paleolatitude of 83oN (alpha 95 = 9.7o), as indicated by paleomagnetic results. When compared with the Paleocene pole for the North American craton, the 95% confidence limits of the results suggest that terranes N of the Denali fault have moved no more than 550km northward relative to the North American craton since Paleocene time.-Authors

  2. On the driving forces of the Pangea breakup and northward drift of the Indian subcontinent

    NASA Astrophysics Data System (ADS)

    Yoshida, Masaki; Hamano, Yozo

    2015-04-01

    During the breakup of the supercontinent Pangea, the Indian subcontinent became isolated from the southern part of Pangea, called Gondwanaland, at around 130 Ma, moved northwards, and eventually collided with Eurasia to form the Himalayas at around 40-50 Ma. The reason why the Indian subcontinent moved at such a high speed of up to c. 20 cm/yr remains a controversial issue in geodynamics. Here, numerical simulation of 3-D spherical mantle convection with an Earth-like Rayleigh number is reported, considering the assembly of highly viscous continental blocks with the configuration of Pangea, to determine the geodynamic mechanisms of the Pangea breakup, the subsequent continental drift, and the high-speed northward drift of the Indian subcontinent. Our numerical simulations approximately reproduced the process of continental drift from the breakup of Pangea at 200 Ma to the present-day continental distribution. These simulations revealed that a major factor in the northward drift of the Indian subcontinent was the large-scale cold mantle downwelling that developed spontaneously in the North Tethys Ocean, attributed to the overall shape of Pangea. The strong lateral mantle flow caused by the high-temperature anomaly beneath Pangea, due to the thermal insulation effect, enhanced the acceleration of the Indian subcontinent during the early stage of the Pangea breakup. The large-scale hot upwelling plumes from the lower mantle, initially located under Africa, might have contributed to the formation of the large-scale cold mantle downwelling in the North Tethys Ocean. References: [1] Yoshida, M., Effects of various lithospheric yield stresses and different mantle-heating modes on the breakup of the Pangea supercontinent, Geophys. Res. Lett., 41(9), 3060-3067, doi:10.1002/2014GL060023, 2014. [2] Yoshida, M. and Y. Hamano, Pangea breakup and northward drift of the Indian subcontinent reproduced by a numerical model of mantle convection, Submitted to Scientific Reports, 2015

  3. Polar cap response to the solar wind density jump under constant southward IMF

    NASA Astrophysics Data System (ADS)

    Belenkaya, E. S.; Kalegaev, V. V.; Blokhina, M. S.

    2014-11-01

    Sharp changes of the solar wind parameters determining the dynamic pressure jump lead to strong magnetosphere-ionosphere disturbances. Here the effect on the Earth's ionospheric high latitudes of the solar wind dynamic pressure pulse caused only by the increase of the interplanetary plasma density under southward constant IMF is considered. We investigate reaction of the cross-polar cap potential on the increase of AL index and/or jump of the solar wind density. It is found that for the case of 10 January 1997 the main contribution to the polar cap potential drop increase gave the growth of AL index relative to the input of the solar wind density jump. We also study the influence of the solar wind density increase on the crosspolar cap potential for the quiet magnetospheric conditions. It occurred that the polar cap potential difference decreases with the great increase of the interplanetary plasma density. For the disturbed magnetosphere the main role in the polar cap potential drop increase plays increase of AL. Thus, we found the change of the cross-polar cap potential due to the AL index variations and/or the solar wind density drop even in a case when the interplanetary electric field is constant.

  4. The nonlinear response of the polar cap potential under southward IMF: A statistical view

    NASA Astrophysics Data System (ADS)

    Wilder, F. D.; Clauer, C. R.; Baker, J. B. H.; Cousins, E. P.; Hairston, M. R.

    2011-12-01

    We report the results of an investigation into the effect of solar wind properties on the saturation of the polar cap potential (CPCP) during periods of strongly southward IMF. We use propagated solar wind data to search for periods between 1998 and 2007 when the interplanetary electric field is stable for more than 50 min and placed further conditions on the availability of SuperDARN and DMSP velocity data. CPCP values are calculated from these data sets and various fits of the polar cap potential to the interplanetary electric field (IEF) are compared. It is found that the trend is nonlinear, with a square root function fitting better than a straight line, and that the CPCP does not appear to exhibit asymptotic behavior. The nonlinearity of the CPCP is then correlated with various interplanetary parameters to test the various models of polar cap potential saturation. It is also found that the deviation of the CPCP from a linear fit has statistically significant correlation with solar wind Alfvènic Mach number and no significant correlation with solar wind dynamic pressure.

  5. Large-Scale Structures in Earth Foreshock Waves during Radial IMF

    NASA Astrophysics Data System (ADS)

    Ganse, Urs; Pfau-Kempf, Yann; Hoilijoki, Sanni; von Alfthan, Sebastian; Palmroth, Minna; Vainio, Rami

    2016-04-01

    Wave instabilities in the foreshock region of Earth's bow shock lead to formation of magnetic field and density fluctuations, commonly observed by spacecraft as 30-second waves. These waves are oblique to the interplanetary magnetic field, with the mechanism leading to oblique propagation still under discussion. Using the VLASIATOR (http://vlasiator.fmi.fi) global hybrid-Vlasov simulation code, we performed runs of radial and near-radial IMF conditions and were able to reproduce the development of these oblique foreshock wave instabilities, revealing a peculiar global structure, in which waves with different wave-vector directions are arranged around central spines, which are spatially offset from the bow shock's nose. We present analysis of the waves' growth behaviour and combine them with artificial observations, comparing to in-situ spacecraft data. Furthermore, we employed a test particle approach to investigate the formation mechanism of the instabilities' large-scale structure, and found that a coupling between the microphysics of wave-particle interaction and global-scale shock and foreshock geometry is essential to explain them.

  6. VizieR Online Data Catalog: Gamma Vel cluster membership and IMF (Prisinzano+, 2016)

    NASA Astrophysics Data System (ADS)

    Prisinzano, L.; Damiani, F.; Micela, G.; Jeffries, R. D.; Franciosini, E.; Sacco, G. G.; Frasca, A.; Klutsch, A.; Lanzafame, A.; Alfaro, E. J.; Biazzo, K.; Bonito, R.; Bragaglia, A.; Caramazza, M.; Vallenari, A.; Carraro, G.; Costado, M. T.; Flaccomio, E.; Jofre, P.; Lardo, C.; Monaco, L.; Morbidelli, L.; Mowlavi, N.; Pancino, E.; Randich, S.; Zaggia, S.

    2016-04-01

    We derived a list as complete as possible of confirmed members of the young open cluster Gamma Velorum, with the aim of deriving general cluster properties such as the IMF. We used all available spectroscopic membership indicators within the Gaia-ESO public archive, based on spectra acquired with FLAMES a the VLT using the GIRAFFE intermediate-resolution spectrograph. In addition, we used literature photometry and X-ray data. For each membership criterion, we derived the most complete list of candidate cluster members. Then, we considered photometry, gravity, and radial velocities as necessary conditions for selecting a subsample of candidates whose membership was confirmed by using the lithium and Halpha lines and X-rays as youth indicators. Table 5 lists the fundamental parameters of the confirmed and possible members in Gamma Velorum, i.e. photometry, radial velocities, equivalent widths of the lithium line, the Halpha activity index, the X-ray flag, the gravity gamma index and the stellar masses. Finally the binarity and membership flags are given. (1 data file).

  7. Response of Saturn's Current Sheet Structure to Changes in the Solar Wind Dynamic Pressure and IMF

    NASA Astrophysics Data System (ADS)

    Hansen, K. C.; Jia, X.; Gombosi, T. I.

    2010-12-01

    Using our global MHD model of Saturn’s magnetosphere, we investigate the location, shape and motion of Saturn’s current sheet under a variety of situations. Our global MHD model self consistently treats the entire magnetosphere and includes magnetospheric plasma sources from a major disk-like source from Enceladus and the rings and a secondary toroidal plasma source from Titan. The model produces solutions which are not constrained to be symmetric therefore the results are quite useful in trying to extend previous models that have been generated using Cassini data. Because we can carefully control the inputs to our MHD model, we do not have to worry about separating variations due to local time, varying upstream conditions, spacecraft motion or changes in the mass loading rate that often make interpreting the data complicated. We will present results for both steady state, as well as time varying solar wind conditions. Simulations with constant solar wind conditions allow us to study the effect that upsteam dynamic pressure has on both the shape and size of the current sheet. In addition, we will present results from simulations that include sudden changes in the solar wind dynamics pressure as well as the IMF direction. These simulations will allow us to study the current sheet response and to look for features such as current sheet flapping. Our previous studies have shown that the current sheet in our model does in fact reproduce the “bowl-like” behavior expect at most local times. However, at dusk, the current sheet is often quite warped. We will examine the cause of this warping and under what conditions it occurs.

  8. Spatially resolved variations of the IMF mass normalisation in early-type galaxies as probed by molecular gas kinematics

    NASA Astrophysics Data System (ADS)

    Davis, Timothy A.; McDermid, Richard M.

    2016-09-01

    We here present the first spatially-resolved study of the IMF in external galaxies derived using a dynamical tracer of the mass-to-light ratio. We use the kinematics of relaxed molecular gas discs in seven early-type galaxies (ETGs) selected from the ATLAS3D survey to dynamically determine mass-to-light ratio (M/L) gradients. These M/L gradients are not very strong in the inner parts of these objects, and galaxies that do show variations are those with the highest specific star formation rates. Stellar population parameters derived from star formation histories are then used in order to estimate the stellar initial mass function function (IMF) mismatch parameter, and shed light on its variation within ETGs. Some of our target objects require a light IMF, otherwise their stellar population masses would be greater than their dynamical masses. In contrast, other systems seem to require heavier IMFs to explain their gas kinematics. Our analysis again confirms that IMF variation seems to be occurring within massive ETGs. We find good agreement between our IMF normalisations derived using molecular gas kinematics and those derived using other techniques. Despite this, we do not see find any correlation between the IMF normalisation and galaxy dynamical properties or stellar population parameters, either locally or globally. In the future larger studies which use molecules as tracers of galaxy dynamics can be used to help us disentangle the root cause of IMF variation.

  9. More-frequent extreme northward shifts of eastern Indian Ocean tropical convergence under greenhouse warming.

    PubMed

    Weller, Evan; Cai, Wenju; Min, Seung-Ki; Wu, Lixin; Ashok, Karumuri; Yamagata, Toshio

    2014-08-15

    The Intertropical Convergence Zone (ITCZ) in the tropical eastern Indian Ocean exhibits strong interannual variability, often co-occurring with positive Indian Ocean Dipole (pIOD) events. During what we identify as an extreme ITCZ event, a drastic northward shift of atmospheric convection coincides with an anomalously strong north-minus-south sea surface temperature (SST) gradient over the eastern equatorial Indian Ocean. Such shifts lead to severe droughts over the maritime continent and surrounding islands but also devastating floods in southern parts of the Indian subcontinent. Understanding future changes of the ITCZ is therefore of major scientific and socioeconomic interest. Here we find a more-than-doubling in the frequency of extreme ITCZ events under greenhouse warming, estimated from climate models participating in the Coupled Model Intercomparison Project phase 5 that are able to simulate such events. The increase is due to a mean state change with an enhanced north-minus-south SST gradient and a weakened Walker Circulation, facilitating smaller perturbations to shift the ITCZ northwards.

  10. [Effects of typhoon 'Haitang' airflow field on the northward migration route of rice brown planthopper].

    PubMed

    Wang, Cui-Hua; Zhai, Bao-Ping; Bao, Yun-Xuan

    2009-10-01

    Based on GIS, GrADS, and HYSPLIT-4.8 model, this paper analyzed the daily light-trap catches of rice brown planthopper at 42 pest monitoring stations of 10 provinces in China, the wind field on 850 hPa isobaric surface, and the migration tracks of rice brown planthopper at 20 pest monitoring stations during the occurrence of 0505 typhoon 'Haitang' from 19th to 21st July, 2005. After its landing on China, the typhoon 'Haitang' changed the southwest air flow, a flow which leads the northward migration of rice brown planthopper, and made the wind field converge in the southwest of the typhoon and swerve in larger areas. Accordingly, the northward migration of the rice brown planthopper was stopped, and the airborne populations were forced to descend in some areas. The shear line area nearby 850 hPa isobaric surface was the concentration and deposition area of the rice brown planthopper. There would be a mass migration area in the warm airflow shear area in the southeast of typhoon during the collapse of the typhoon. After the whole typhoon landed, the southwest airflow rebuilt, and a mass rice brown planthopper migrated to the north.

  11. Northward expansion of paddy rice in northeastern Asia during 2000-2014

    NASA Astrophysics Data System (ADS)

    Dong, J.; Xiao, X.; Zhang, G.; Menarguez, M. A.; Choi, C. Y.; Qin, Y.; Luo, P.; Zhang, Y.; Moore, B.

    2016-04-01

    Paddy rice in monsoon Asia plays an important role in global food security and climate change. Here we documented annual dynamics of paddy rice areas in the northern frontier of Asia, including northeastern (NE) China, North Korea, South Korea, and Japan, from 2000 to 2014 through analysis of satellite images. The paddy rice area has increased by 120% (2.5 to 5.5 million ha) in NE China, in comparison to a decrease in South Korea and Japan, and the paddy rice centroid shifted northward from 41.16°N to 43.70°N (~310 km) in this period. Market, technology, policy, and climate together drove the rice expansion in NE China. The increased use of greenhouse nurseries, improved rice cultivars, agricultural subsidy policy, and a rising rice price generally promoted northward paddy rice expansion. The potential effects of large rice expansion on climate change and ecosystem services should be paid more attention to in the future.

  12. SuperDARN Cross Polar Cap Potential: Correlation with the IMF and solar wind parameters

    NASA Astrophysics Data System (ADS)

    Mori, D.; Koustov, A. V.; Colville, K.; Jayachandran, P. T.

    2011-12-01

    Cross Polar Cap Potential (CPCP) is one of the core parameters provided by the SuperDARN network on a regular basis. The CPCP is estimated from individual convection maps built for every 1-2 min. We show that the SuperDARN CPCPs are highly "quantized" around values "prescribed" by the startup convection model and significantly depart from those values only if the number of convection vectors on a map exceeds 200-300. We show that with an increase of the plasma convection speed in the polar cap (as measured by the CADI ionosonde at Resolute Bay) the CPCP shows "saturation" effect for velocities above ~ 500 m/s. We relate the effect to progressively increased underestimation of the separation between the dawn and dusk convection foci in the process of CPCP derivation. We also show that, although the HF radar velocities are generally in agreement with CADI ExB measurements, significant mixed scatter on the dayside supplies low-velocity data (velocities well below the values given by the startup convection model) to the fitting procedure that might also affect the CPCP estimates. For densely enough convection maps and for weakly- or moderately-driven solar wind conditions, the SuperDARN data should be of satisfactory quality. By considering one full year of SuperDARN CPCP data (2000) and splitting them according to 3 seasons, we illustrate the CPCP almost linear dependence on the IMF Bz and By and the interplanetary electric field. Weak CPCP dependencies upon the solar wind pressure, Alfven Mach number and Alfven speed are found. The CPCP data show best correlation with coupling function introduced by Lyatsky et al. (2007) and they agree best with the recent theory by Kivelson and Ridley (2010), although discrepancies are significant.

  13. Non Equilibrated IMF Emission in Heavy Ion Collisions around the Fermi Energy

    NASA Astrophysics Data System (ADS)

    Piantelli, S.; Bidini, L.; Bini, M.; Casini, G.; Maurenzig, P. R.; Olmi, A.; Pasquali, G.; Poggi, G.; Poggi, S.; Stefanini, A. A.; Taccetti, N.

    2001-11-01

    The first experimental data obtained with the FIASCO setup for the reaction 116Sn+93Nb at 29.5AMeV confirm the existence of a midvelocity emission of LCPs and IMFs that may come from the neck rupture during the first phase of the reaction

  14. Impact of the uncertainties of the ISM when studying the IMF at intermediate masses

    NASA Astrophysics Data System (ADS)

    Mor, R.; Robin, A. C.; Lemasle, B.; Figueras, F.

    We evaluate the impact of the uncertainties in the 3D structure of the Interstellar Medium (ISM) when studying the Initial Mass Function (IMF) at intermediate masses using classical Galactic Cepheids. For that we use the Besan\\c{c}on Galaxy Model (BGM, \\citealt{Robin2003} and \\citealt{Czekaj2014}) and assume different IMFs and different interstellar structure maps to simulate magnitude limited samples of young intermediate mass stars. As our strategy to derive the IMF is based on star counts (in proceedings \\cite{Mor2015} and Mor et al. 2016 in prep.), we quantify the differences in star counts by comparing the whole-sky simulations with Tycho-2 catalogue up to V_T=11 and using Healpix maps. Moreover we compare simulations with different extinction models up to Gaia magnitude G=20. As expected, larger discrepancies between simulations and observations are found in the Galactic Plane, showing that the interstellar extinction in the plane is one of the major source of uncertainty in our study. We show how even with the uncertainties due to the ISM we are able to distinguish between different IMFs.

  15. Transpolar auroras, their particle precipitation, and IMF B sub y component

    SciTech Connect

    Makita, K. ); Meng, C.I. ); Akasofu, S.I. )

    1991-08-01

    Transpolar auroras, their associated particle precipitation, and their occurrence with respect to the IMF B{sub y} polarity are examined on the basis of DMSP F6 auroral images and the corresponding particle data. It is found that the transpolar arcs are located in the poleward edge of the soft particle precipitation region extending from either the dawn or dusk part of the auroral oval precipitation; they are not embedded in the polar rain region. This finding suggests that the transpolar arcs are located along the poleward boundary of the closed field line region (or the equatorward boundary of the open region) as suggested by Meng. Further, the appearance of the extended precipitation region from the oval depends on the polarity of the IMF B{sub y}, in the northern hemisphere morning sector for IMF B{sub y} < 0 or in the evening sector for IMF B{sub y} > 0. In general, the precipitating particle flux in the extended precipitation region is not high enough to produce appreciable luminosity. Thus only the transpolar arcs (associated with relatively intense precipitation) near the poleward boundary tend to become much more luminous, forming the so-called theta aurora.

  16. MOND and IMF variations in early-type galaxies from ATLAS3D

    NASA Astrophysics Data System (ADS)

    Tortora, C.; Romanowsky, A. J.; Cardone, V. F.; Napolitano, N. R.; Jetzer, Ph.

    2014-02-01

    Modified Newtonian Dynamics (MOND) represents a phenomenological alternative to dark matter (DM) for the missing mass problem in galaxies and clusters of galaxies. We analyse the central regions of a local sample of ˜220 early-type galaxies from the ATLAS3D survey, to see if the data can be reproduced without recourse to DM. We estimate dynamical masses in the MOND context through Jeans analysis and compare to ATLAS3D stellar masses from stellar population synthesis. We find that the observed stellar mass-velocity dispersion relation is steeper than expected assuming MOND with a fixed stellar initial mass function (IMF) and a standard value for the acceleration parameter a0. Turning from the space of observables to model space (a) fixing the IMF, a universal value for a0 cannot be fitted, while, (b) fixing a0 and leaving the IMF free to vary, we find that it is `lighter' (Chabrier like) for low-dispersion galaxies and `heavier' (Salpeter like) for high dispersions. This MOND-based trend matches inferences from Newtonian dynamics with DM and from the detailed analysis of spectral absorption lines, adding to the converging lines of evidence for a systematically varying IMF.

  17. A Vortical Dawn Flank Boundary Layer for Near-Radial IMF: Wind Observations on 24 October 2001

    NASA Technical Reports Server (NTRS)

    Farrugia, C. J.; Gratton, F. T.; Gnavi, G.; Torbert, R. B.; Wilson, Lynn B., III

    2014-01-01

    We present an example of a boundary layer tailward of the dawn terminator which is entirely populated by rolled-up flow vortices. Observations were made by Wind on 24 October 2001 as the spacecraft moved across the region at the X plane approximately equal to -13 Earth radii. Interplanetary conditions were steady with a near-radial interplanetary magnetic field (IMF). Approximately 15 vortices were observed over the 1.5 hours duration of Wind's crossing, each lasting approximately 5 min. The rolling up is inferred from the presence of a hot tenuous plasma being accelerated to speeds higher than in the adjoining magnetosheath, a circumstance which has been shown to be a reliable signature of this in single-spacecraft observations. A blob of cold dense plasma was entrained in each vortex, at whose leading edge abrupt polarity changes of field and velocity components at current sheets were regularly observed. In the frame of the average boundary layer velocity, the dense blobs were moving predominantly sunward and their scale size along the X plane was approximately 7.4 Earth radii. Inquiring into the generation mechanism of the vortices, we analyze the stability of the boundary layer to sheared flows using compressible magnetohydrodynamic Kelvin-Helmholtz theory with continuous profiles for the physical quantities. We input parameters from (i) the exact theory of magnetosheath flow under aligned solar wind field and flow vectors near the terminator and (ii) the Wind data. It is shown that the configuration is indeed Kelvin-Helmholtz (KH) unstable. This is the first reported example of KH-unstable waves at the magnetopause under a radial IMF.

  18. Northward migration of the eastern Himalayan syntaxis revealed by OSL thermochronometry.

    PubMed

    King, Georgina E; Herman, Frédéric; Guralnik, Benny

    2016-08-19

    Erosion influences the dynamical evolution of mountains. However, evidence for the impact of surface processes on tectonics mostly relies on the circumstantial coincidence of rugged topography, high stream power, erosion, and rock uplift. Using the optically stimulated luminescence (OSL) thermochronometry technique, we quantified the spatial and temporal exhumation of the eastern Himalayan syntaxis. We found increasing exhumation rates within the past million years at the northeast end of the Namche Barwa-Gyala Peri dome. These observations imply headward propagation of erosion in the Parlung River, suggesting that the locus of high exhumation has migrated northward. Although surface processes influence exhumation rates, they do not necessarily engage in a feedback that sets the location of tectonic deformation. PMID:27540169

  19. Northward migration of the eastern Himalayan syntaxis revealed by OSL thermochronometry

    NASA Astrophysics Data System (ADS)

    King, Georgina E.; Herman, Frédéric; Guralnik, Benny

    2016-08-01

    Erosion influences the dynamical evolution of mountains. However, evidence for the impact of surface processes on tectonics mostly relies on the circumstantial coincidence of rugged topography, high stream power, erosion, and rock uplift. Using the optically stimulated luminescence (OSL) thermochronometry technique, we quantified the spatial and temporal exhumation of the eastern Himalayan syntaxis. We found increasing exhumation rates within the past million years at the northeast end of the Namche Barwa-Gyala Peri dome. These observations imply headward propagation of erosion in the Parlung River, suggesting that the locus of high exhumation has migrated northward. Although surface processes influence exhumation rates, they do not necessarily engage in a feedback that sets the location of tectonic deformation.

  20. Northward migration of the eastern Himalayan syntaxis revealed by OSL thermochronometry.

    PubMed

    King, Georgina E; Herman, Frédéric; Guralnik, Benny

    2016-08-19

    Erosion influences the dynamical evolution of mountains. However, evidence for the impact of surface processes on tectonics mostly relies on the circumstantial coincidence of rugged topography, high stream power, erosion, and rock uplift. Using the optically stimulated luminescence (OSL) thermochronometry technique, we quantified the spatial and temporal exhumation of the eastern Himalayan syntaxis. We found increasing exhumation rates within the past million years at the northeast end of the Namche Barwa-Gyala Peri dome. These observations imply headward propagation of erosion in the Parlung River, suggesting that the locus of high exhumation has migrated northward. Although surface processes influence exhumation rates, they do not necessarily engage in a feedback that sets the location of tectonic deformation.

  1. Ring Current Decay During Northward Turnings of The Interplanetary Magnetic Field

    NASA Astrophysics Data System (ADS)

    Monreal MacMahon, R.; Llop, C.; Miranda, R.

    The ring current formation and energization is thought to be the main consequence of geomagnetic storms and its strength is characterized by the Dst index which evolu- tion satisfies a simple and well-known differential equation introduced by Burton et al. (1975). Since then, several attempts and approaches have been done to study the evolution of the ring current whether introducing discrete values or continuous func- tions for the decay time involved. In this work, we study the character of the recovery phase of magnetic storms in response to well defined northward turnings of the inter- planetary magnetic field using our functional form of the decay time of ring current particles introduced previously.

  2. Northward shifts of the distributions of Spanish reptiles in association with climate change.

    PubMed

    Moreno-Rueda, Gregorio; Pleguezuelos, Juan M; Pizarro, Manuel; Montori, Albert

    2012-04-01

    It is predicted that climate change will drive extinctions of some reptiles and that the number of these extinctions will depend on whether reptiles are able to change their distribution. Whether the latitudinal distribution of reptiles may change in response to increases in temperature is unknown. We used data on reptile distributions collected during the 20th century to analyze whether changes in the distributions of reptiles in Spain are associated with increases in temperature. We controlled for biases in sampling effort and found a mean, statistically significant, northward shift of the northern extent of reptile distributions of about 15.2 km from 1940-1975 to 1991-2005. The southern extent of the distributions did not change significantly. Thus, our results suggest that the latitudinal distributions of reptiles may be changing in response to climate change.

  3. Structure of the Outer Cusp and Sources of the Cusp Precipitation during Intervals of a Horizontal IMF

    NASA Technical Reports Server (NTRS)

    Nemecek, Z.; Safrankova, J.; Prech, L.; Simunek, J.; Sauvaud, J.-A.; Fedorov, A.; Stenuit, H.; Fuselier, S. A.; Savin, S.; Zelenyi, L.

    2003-01-01

    The cusp represents a place where the magnetosheath plasma can directly penetrate into the magnetosphere. Since the main transport processes are connected with merging of the interplanetary and magnetospheric field lines, the interplanetary magnetic field (IMF) Orientation plays a decisive role in the formation of the high-altitude cusp. The importance of the sign of the IMF Bz component for this process was suggested about 40 years ago and later it was documented by many experimental investigations. However, situations when IMF Bz is the major IMF component are rather rare. The structure of the cusp during periods of a small IMF BZ is generally unknown, probably due to the fully 3-D nature of the interaction. The present case study reveals the importance of horizontal IMF components on the global magnetospheric configuration as well as on small-scale processes at the cusp-magnetosheath interface. We have used simultaneous measurements of several spacecraft (ISTP program) operating in different regions of interplanetary space and two closely spaced satellites (INTERBALL-1/MAGION- 4) crossing the cusp-magnetosheath boundary to show the connection between the short- and large-scale phenomena. In the northern hemisphere, observations suggest a presence of two spots of cusp-like precipitation supplied by reconnection occurring simultaneously in both hemispheres. A source of this bifurcation is the positive IMF By component further enhanced by the field draping in the magnetosheath. This magnetic field component shifts the entry point far away from the local noon but in opposite sense in either hemisphere.

  4. EVIDENCE FOR A CONSTANT IMF IN EARLY-TYPE GALAXIES BASED ON THEIR X-RAY BINARY POPULATIONS

    NASA Astrophysics Data System (ADS)

    Zepf, Stephen E.; Maccarone, T. J.; Kundu, A.; Gonzalez, A. H.; Lehmer, B.; Maraston, C.

    2014-01-01

    A number of recent studies have proposed that the stellar initial mass function (IMF) of early type galaxies varies systematically as a function of galaxy mass, with higher mass galaxies having steeper IMFs. These steeper IMFs have more low-mass stars relative to the number of high mass stars, and therefore naturally result in proportionally fewer neutron stars and black holes. In this paper, we specifically predict the variation in the number of black holes and neutron stars in early type galaxies based on the IMF variation required to reproduce the observed mass-to-light ratio trends with galaxy mass. We then test whether such variations are observed by studying the field low-mass X-ray binary populations (LMXBs) of nearby early-type galaxies. These binaries are field neutron stars or black holes accreting from a low-mass donor star. We specifically compare the number of field LMXBs per K-band light in a well-studied sample of elliptical galaxies, and use this result to distinguish between an invariant IMF and one that is Kroupa/Chabrier-like at low masses and steeper at high masses. We discuss how these observations constrain the possible forms of the IMF variations and how future Chandra observations can enable sharper tests of the IMF.

  5. Evaluating Asian Monsoon Northward Propagation Mechanisms in the ERA-interim Reanalysis and SP-CCSM

    NASA Astrophysics Data System (ADS)

    DeMott, C.; Stan, C.; Randall, D.

    2012-04-01

    Equatorial tropical convection is dominated by the eastward-propagating Madden-Julian Oscillation (MJO). During boreal summer months, MJO convection also acquires a northward component to its propagation, which results in the intraseasonal "active" and "break" periods of the Asian monsoon. Northward propagation (NP) may results from air-sea coupling and/or from the interaction of convection, particularly that associated with equatorial Rossby (ER) waves, and environmental easterly shear that develops as low-level winds shift from northeasterly to southwesterly during the summer months. Several studies have proposed specific mechanisms for NP, but no consensus exists as to which mechanisms are dominant, or even present, in observations. This study evaluates the presence and impact of NP mechanisms on the Asian monsoon as observed in the ERA-Interim reanalysis and in the super-paramaterized CCSM (SP-CCSM). We evaluate the following mechanisms: 1) surface temperature destabilization, 2) SST gradient-induced boundary layer convergence, 3) the easterly shear mechanism of Jiang et al. (2004), 4) boundary layer moisture advection, and 5) tropospheric vorticity advection. Comparison of the relative impacts of these myriad mechanisms is accomplished by computing an index of each mechanism, and regressing normalized indices onto ISO-filtered OLR anomalies at several lead/lag times. Indices with high regression coefficients are considered to be important to NP. We conclude that many mechanisms contribute to NP in the Asian monsoon, but are dominated by boundary layer moisture advection and the easterly shear mechanism. Air-sea coupling effects are secondary to atmospheric dynamic mechanisms. The distribution and relative contribution of mechanisms in SP-CCSM is remarkably similar to those in the reanalysis, and emphasize the need for both realistic basic states of wind and moisture, as well as robust tropical equatorial waves.

  6. GPS Evidence for Northward Motion of the Sinai Block: Implications for E. Mediterranean Tectonics

    NASA Astrophysics Data System (ADS)

    Mahmoud, S.; Reilinger, R. E.; McClusky, S.; Vernant, P.; Tealeb, A.

    2004-12-01

    We present GPS yearly survey-mode observations for the period 1997 to 2003 at 12 sites within and adjacent to the Sinai Peninsula to constrain motion of the Sinai Block. Sites in the Sinai Peninsula show northerly motion relative to Africa (Nubian plate) at an average rate of 1.5 +/- 1 mm/yr north and -0.8 +/- 1 mm/yr west (1 sigma). While there is some variability, 11 of 12 sites show northerly motion strongly suggesting that the Sinai as a whole is moving northward relative to Nubia. Continuous IGS GPS sites in Israel, west of the Dead Sea fault (greater than 45 km from the fault trace and outside the main zone of elastic strain accumulation) show a similar northerly sense of motion relative to Africa (~ 2.7 +/- 1mm/yr north and -0.9 +/- 1 mm/yr west), suggesting that the entire Sinai Block south of Lebanon is characterized by northward translation relative to Africa. Using an elastic block model we estimate slip rates for the Gulf of Aqaba - southern Dead Sea fault system of 5.1 +/- 0.7 mm/yr, left lateral, and along the Gulf of Suez of 3.0 +/- 0.5 mm/yr left lateral. Present-day opening of the Gulf of Suez is less than 1 mm/yr. This block model provides a quantitative, kinematic explanation for the first order, present-day tectonic character of the easternmost Mediterranean, including the Dead Sea fault system, the Gulf of Suez, and the Cyprus Arc.

  7. Geomagnetic response to IMF and solar wind over different latitudes

    NASA Astrophysics Data System (ADS)

    Aslam, A. M.; Tripathi, Sharad Chandra; Mansoori, Azad Ahmad; Waheed, Malik Abdul

    2016-07-01

    In this paper a study on the response of geomagnetic field characteristics to the solar wind variation during three solar cycles (SC 21, SC 22, SC 23) have been conducted in a long term scale. The difference in the response of two different latitudinal characteristic indices has been investigated. For the purpose we have considered the high latitude index AE and the mid-latitude aa index and both gives the knowledge about the perturbations in the geomagnetic field conditions. Eventually we can infer the idea about the ionospheric current system changes in response to the solar wind conditions. The variation found in the AE and aa indices have been found to follow a 11 year cycle as similar to the sunspot variation. Also the correlation between the annual means of the solar wind parameters velocity V, magnetic filed B and the composite parameters BV and BV ^{2 } have been calculated . A difference was found between the correlations obtained for the AE and aa indices. We could also see that the difference in correlation follows a cyclic pattern i.e. the large difference is found during the solar maxima while a small difference is observed during the minima.

  8. Longitude and IMF By Effects on Stormtime Low-Latitude Prompt-Penetration Electric Fields

    NASA Astrophysics Data System (ADS)

    Spiro, R. W.; Sazykin, S.; Song, Y.; Toffoletto, F.; Wolf, R. A.

    2010-12-01

    During geomagnetically disturbed periods, transient large-scale electric fields of magnetospheric origin, known as prompt penetration electric fields, are known to strongly affect ionospheric dynamics. We examine storm-associated prompt-penetration electric fields in the low-latitude ionosphere using a recently reformulated version of the Rice Convection Model (RCM), a numerical model of the inner magnetosphere and its coupling to the ionosphere. This reformulated version of the RCM was designed to accept an arbitrary intrinsic geomagnetic field and to represent the lack of symmetry in the magnetospheric magnetic field due to the partial penetration of IMF By. In this study we assume an IGRF internal magnetic field together with an event-driven storm-time Tsyganenko external field to investigate the longitudinal dependence of the prompt penetration electric field pattern and the effects of IMF By penetration.

  9. Is coverage a factor in non-Gaussianity of IMF parameters?

    SciTech Connect

    Ahluwalia, H.S.; Fikani, M.M.

    1995-06-01

    Recently, Feynman and Ruzmaikin showed that IMF parameters for the 1973 to 1990 period are not log-normally distributed as previously suggested by Burlaga and King for the data obtained over a shorter time period (1963-75). They studied the first four moments, namely: mean, variance, skewness, and kurtosis. For a Gaussian distribution, moments higher than the variance should vanish. In particular, Feynman and Ruzmaikin obtained very high values of kurtosis during some periods of their analysis. The authors note that the coverage for IMF parameters is very uneven for the period analyzed by them, ranging from less than 40% to greater than 80%. So a question arises as to whether the amount of coverage is a factor in their analysis. The authors decided to test this for the B{sub z} component of IMF, since it is an effective geoactive parameter for short term disturbances. Like them, the authors used 1-hour averaged data available on the Omnitape. They studied the scatter plots of the annual mean values of B{sub z}(nT) and its kurtosis versus the percent coverage for the year. They obtain a correlation coefficient of 0.48 and 0.42 respectively for the 1973-90 period. The probability for a chance occurrence of these correlation coefficients for 18 pair of points is less than 8%. As a rough measure of skewness, the authors determined the percent asymmetry between the areas of the histograms representing the distributions of the positive and the negative values of B{sub z} and studied its correlation with the coverage for the year. This analysis yields a correlation coefficient of 0.41. When they extended the analysis for the whole period for which IMF data are available (1963-93) the corresponding correlation coefficients are 0.59, 0.14, and 0.42. These findings will be presented and discussed.

  10. Is coverage a factor in non-Gaussianity of IMF parameters?

    NASA Technical Reports Server (NTRS)

    Ahluwalia, H. S.; Fikani, M. M.

    1995-01-01

    Recently, Feynman and Ruzmaikin (1994) showed that IMF parameters for the 1973 to 1990 period are not log-normally distributed as previously suggested by Burlaga and King (1979) for the data obtained over a shorter time period (1963-75). They studied the first four moments, namely: mean, variance, skewness, and kurtosis. For a Gaussian distribution, moments higher than the variance should vanish. In particular, Feynman and Ruzmaikin obtained very high values of kurtosis during some periods of their analysis. We note that the coverage for IMF parameters is very uneven for the period analyzed by them, ranging from less than 40% to greater than 80%. So a question arises as to whether the amount of coverage is a factor in their analysis. We decided to test this for the B(sub z) component of IMF, since it is an effective geoactive parameter for short term disturbances. Like them, we used 1-hour averaged data available on the Omnitape. We studied the scatter plots of the annual mean values of B(sub z)(nT) and its kurtosis versus the percent coverage for the year. We obtain a correlation coefficient of 0.48 and 0.42 respectively for the 1973-90 period. The probability for a chance occurrence of these correlation coefficients for 18 pair of points is less than 8%. As a rough measure of skewness, we determined the percent asymmetry between the areas of the histograms representing the distributions of the positive and the negative values of B(sub z) and studied its correlation with the coverage for the year. This analysis yields a correlation coefficient of 0.41 When we extended the analysis for the whole period for which IMF data are available (1963-93) the corresponding correlation coefficients are 0.59, 0.14, and 0.42. Our findings will be presented and discussed

  11. Abundance ratios and IMF slopes in the dwarf elliptical galaxy NGC 1396 with MUSE

    NASA Astrophysics Data System (ADS)

    Mentz, J. J.; La Barbera, F.; Peletier, R. F.; Falcón-Barroso, J.; Lisker, T.; van de Ven, G.; Loubser, S. I.; Hilker, M.; Sánchez-Janssen, R.; Napolitano, N.; Cantiello, M.; Capaccioli, M.; Norris, M.; Paolillo, M.; Smith, R.; Beasley, M. A.; Lyubenova, M.; Munoz, R.; Puzia, T.

    2016-08-01

    Deep observations of the dwarf elliptical (dE) galaxy NGC 1396 (MV = -16.60, Mass ˜4 × 108 M⊙), located in the Fornax cluster, have been performed with the VLT/ MUSE spectrograph in the wavelength region from 4750 - 9350 Å. In this paper we present a stellar population analysis studying chemical abundances, the star formation history (SFH) and the stellar initial mass function (IMF) as a function of galacto-centric distance. Different, independent ways to analyse the stellar populations result in a luminosity-weighted age of ˜ 6 Gyr and a metallicity [Fe/H]˜ -0.4, similar to other dEs of similar mass. We find unusually overabundant values of [Ca/Fe] ˜+0.1, and under-abundant Sodium, with [Na/Fe] values around -0.1, while [Mg/Fe] is overabundant at all radii, increasing from ˜+0.1 in the centre to ˜+0.2 dex. We notice a significant metallicity and age gradient within this dwarf galaxy. To constrain the stellar IMF of NGC 1396, we find that the IMF of NGC 1396 is consistent with either a Kroupa-like or a top-heavy distribution, while a bottom-heavy IMF is firmly ruled out. An analysis of the abundance ratios, and a comparison with galaxies in the Local Group, shows that the chemical enrichment history of NGC 1396 is similar to the Galactic disc, with an extended star formation history. This would be the case if the galaxy originated from a LMC-sized dwarf galaxy progenitor, which would lose its gas while falling into the Fornax cluster.

  12. Slow modes in the Hermean magnetosphere: Effect of the solar wind hydrodynamic parameters and IMF orientation

    NASA Astrophysics Data System (ADS)

    Varela, J.; Pantellini, F.; Moncuquet, M.

    2016-06-01

    The aim of this study is to simulate the slow mode structures in the Hermean magnetosphere. We use a single fluid MHD model and a multipolar expansion of the Northward displaced Hermean magnetic field, to perform simulations with different solar wind parameters to foreseen the most favorable configuration for the formation of slow modes, attending to the solar wind density, velocity, temperature and the interplanetary magnetic field orientation. If the interplanetary magnetic field is aligned with the Mercury-Sun direction, the magnetic axis of Mercury in the Northward direction or the planet orbital plane, slow mode structures are observed nearby the South pole. If the orientation is in the Sun-Mercury or Northward directions, slow mode structures are observed nearby the North pole, but smaller compared with the structures near the South pole. Increasing the density or the solar wind velocity avoids the formation of slow modes structures, not observed for a dynamic pressure larger than 6.25 ·10-9 Pa in the case of a Northward interplanetary magnetic field orientation, due to the enhancement of the bow shock compression. If the solar wind temperature increases, the slow mode structures are wider because the sonic Mach number is smaller and the bow shock is less compressed.

  13. Structural adjustment and public spending on health: evidence from IMF programs in low-income countries.

    PubMed

    Kentikelenis, Alexander E; Stubbs, Thomas H; King, Lawrence P

    2015-02-01

    The relationship between health policy in low-income countries (LICs) and structural adjustment programs devised by the International Monetary Fund (IMF) has been the subject of intense controversy over past decades. While the influence of the IMF on health policy can operate through various pathways, one main link is via public spending on health. The IMF has claimed that its programs enhance government spending for health, and that a number of innovations have been introduced to enable borrowing countries to protect health spending from broader austerity measures. Critics have pointed to adverse effects of Fund programs on health spending or to systematic underfunding that does not allow LICs to address health needs. We examine the effects of Fund programs on government expenditures on health in low-income countries using data for the period 1985-2009. We find that Fund programs are associated with higher health expenditures only in Sub-Saharan African LICs, which historically spent less than any other region. This relationship turns negative in LICs in other regions. We outline the implications of these findings for health policy in a development context. PMID:25576997

  14. The IMF in galaxy clusters: What is needed to account for high metal production?

    NASA Astrophysics Data System (ADS)

    Morsony, Brian; Heath, Caitlin; Workman, Jared

    2015-08-01

    The gas in galaxy clusters is enriched in metal, typically to about 30% of solar metallicity. However, stars a relatively rare in clusters, meaning that the amount of metal produced per star is about 3 times as much as in the Milky Way. We set out to determine what changes to standard star formation are needed to reproduce the observed metal enhancement. Modifications include expanding the IMF to high mass (>130 M_sun) stars and including metal production from pair-instability supernovae, using an enhanced type-Ia SN rate, and using various modifications of the IMF to make it more top-heavy. For each set of assumptions, we use theoretical nucleosynthesis models to calculate the expected total metal yield per mass of star formation, and to predict the relative abundances of different elements. Including pair-instability supernovae will dramatically increase the amount of metal produced, and, combined with a slightly flatter IMF, can lead to 3 times the metal production per solar mass of star formation, along with an increase abundance of intermediate-mass elements.

  15. Cloning and Expression of SFRP5 in Tibetan Chicken and its Relationship with IMF Deposition.

    PubMed

    Li, Qian; Zuo, Lu-Lu; Lin, Ya-Qiu; Xu, Ya-Ou; Zhu, Jiang-Jiang; Liao, Hong-Hai; Lin, Sen; Xiong, Xian-Rong; Wang, Yong

    2016-10-01

    Secreted frizzled related protein 5 (SFRP5), an anti-inflammatory adipokine, is relevant to the adipocyte differentiation. In order to clarify its role in regulating intramuscular fat (IMF) deposition in Tibetan chicken, the full-length sequence of the Tibetan chicken SFRP5 gene was cloned. The relative expression of SFRP5 gene was detected using quantitative RT-PCR in various tissues of 154 days old Tibetan chicken, as well as in breast muscle, thigh muscle, and adipose tissue at different growth stages. The results showed that SFRP5 gene was expressed in all examined tissues but highly enriched in adipose tissue. Temporal expression profile showed that the expression of SFRP5 was gradually decreased in breast muscle, but was fluctuated in thigh muscle and adipose tissue with the growth of Tibetan chicken. Furthermore, correlation analysis demonstrated that the expression of SFRP5 in breast muscle, thigh muscle and adipose tissue was correlated with IMF content at different levels. The results indicated that Tibetan chicken SFRP5 is involved in IMF deposition.

  16. Cloning and Expression of SFRP5 in Tibetan Chicken and its Relationship with IMF Deposition.

    PubMed

    Li, Qian; Zuo, Lu-Lu; Lin, Ya-Qiu; Xu, Ya-Ou; Zhu, Jiang-Jiang; Liao, Hong-Hai; Lin, Sen; Xiong, Xian-Rong; Wang, Yong

    2016-10-01

    Secreted frizzled related protein 5 (SFRP5), an anti-inflammatory adipokine, is relevant to the adipocyte differentiation. In order to clarify its role in regulating intramuscular fat (IMF) deposition in Tibetan chicken, the full-length sequence of the Tibetan chicken SFRP5 gene was cloned. The relative expression of SFRP5 gene was detected using quantitative RT-PCR in various tissues of 154 days old Tibetan chicken, as well as in breast muscle, thigh muscle, and adipose tissue at different growth stages. The results showed that SFRP5 gene was expressed in all examined tissues but highly enriched in adipose tissue. Temporal expression profile showed that the expression of SFRP5 was gradually decreased in breast muscle, but was fluctuated in thigh muscle and adipose tissue with the growth of Tibetan chicken. Furthermore, correlation analysis demonstrated that the expression of SFRP5 in breast muscle, thigh muscle and adipose tissue was correlated with IMF content at different levels. The results indicated that Tibetan chicken SFRP5 is involved in IMF deposition. PMID:27565866

  17. Structural adjustment and public spending on health: evidence from IMF programs in low-income countries.

    PubMed

    Kentikelenis, Alexander E; Stubbs, Thomas H; King, Lawrence P

    2015-02-01

    The relationship between health policy in low-income countries (LICs) and structural adjustment programs devised by the International Monetary Fund (IMF) has been the subject of intense controversy over past decades. While the influence of the IMF on health policy can operate through various pathways, one main link is via public spending on health. The IMF has claimed that its programs enhance government spending for health, and that a number of innovations have been introduced to enable borrowing countries to protect health spending from broader austerity measures. Critics have pointed to adverse effects of Fund programs on health spending or to systematic underfunding that does not allow LICs to address health needs. We examine the effects of Fund programs on government expenditures on health in low-income countries using data for the period 1985-2009. We find that Fund programs are associated with higher health expenditures only in Sub-Saharan African LICs, which historically spent less than any other region. This relationship turns negative in LICs in other regions. We outline the implications of these findings for health policy in a development context.

  18. On the Effect of IMF Turning on Ion Dynamics at Mercury

    NASA Technical Reports Server (NTRS)

    Delcourt, D. C.; Moore, T. E.; Fok, M.-C. H.

    2011-01-01

    We investigate the effect of a rotation of the Interplanetary Magnetic Field (IMF) on the transport of magnetospheric ion populations at Mercury. We focus on ions of planetary origin and investigate their large-scale circulation using three-dimensional single-particle simulations. We show that a nonzero Bx component of the IMF leads to a pronounced asymmetry in the overall circulation pattern . In particular, we demonstrate that the centrifugal acceleration due to curvature of the E x B drift paths is more pronounced in one hemisphere than the other, leading to filling of the magnetospheric lobes and plasma sheet with more or less energetic material depending upon the hemisphere of origin. Using a time-varying electric and magnetic field model, we investigate the response of ions to rapid (a few tens of seconds) re-orientation of the IMF. We show that, for ions with gyroperiods comparable to the field variation time scale, the inductive electric field should lead to significant nonadiabatic energization, up to several hundreds of eVs or a few keVs. It thus appears that IMP turning at Mercury should lead to localized loading of the magnetosphere with energetic material of planetary origin (e.g., Na+).

  19. Pathway seesaw of the northward warm water transport in the Japan/East Sea

    NASA Astrophysics Data System (ADS)

    Trusenkova, Olga

    The Japan/East Sea stretched out in the meridional direction can be divided into the subtropical and subarctic areas separated by the Subarctic Front. The hydrographic regime is strongly controlled by the throughflow transport of subtropical water entering the Sea in the Korea Strait. It was established from empirical analysis of infrared satellite imagery that warm water is advected northward along both western and eastern coasts by mean currents and chains of mesoscale eddies (Nikitin et al., 2002; Lobanov et al., 2007; Nikitin, 2007). The purpose of this study is to determine statistical patterns associated with these pathways and determine characteristic time scales. To this end, we use AVISO 0.25 degree gridded weekly sea level anomalies (SLA) for the period from October 1992 onwards, eddy kinetic energy (EKE) computed from SLA, and 0.25 degree gridded Merged Satellite and In Situ Data Global Daily Sea Surface Temperature (SST) product by the Japan Meteorological Agency for the period from October 1993 onwards. Multivariate analysis of SST, SLA, and EKE made it possible to detect the east - west seesaw in the Japan/East Sea. On average, sea level and temperature gradients are largest across the Subarctic Front and the eastern part of the Sea is warmer than the western area. In the positive phase of the west - east seesaw (late summer on the seasonal time scale), the entire western Sea is even colder than average, SLA is negative there, and EKE is decreased in the northwestern area off North Korea and Primorye (Russia). SLA and SST anomalies are positive along the eastern coast, while EKE is increased in the southwestern and eastern Sea. The warm water is advected northward within the Tsushima Warm Current (TWC) and then westward towards the Primorye coast, with the TWC western branch originating in the area off the southern Hokkaido Island. In the negative phase, SLA and SST are positive in the western Sea and EKE is increased in the northwestern area off

  20. Long-period irregular pulsations under the conditions of a quiet magnetosphere

    NASA Astrophysics Data System (ADS)

    Kurazhkovskaya, N. A.; Klain, B. I.; Lavrov, I. P.

    2016-05-01

    Simultaneous observations of high-latitude long-period irregular pulsations at frequencies of 2.0-6.0 mHz ( ipcl) and magnetic field disturbances in the solar wind plasma at low geomagnetic activity ( Kp ~ 0) have been studied. The 1-s data on the magnetic field registration at Godhavn (GDH) high-latitude observatory and the 1-min data on the solar wind plasma and IMF parameters for 2011-2013 were used in an analysis. Ipcl (irregular pulsations continuous, long), which were observed against a background of the IMF Bz reorientation from northward to southward, have been analyzed. In this case other solar wind plasma and IMF parameters, such as velocity V, density n, solar wind dynamic pressure P = ρ V 2 (ρ is plasma density), and strength magnitude B, were relatively stable. The effect of the IMF Bz variation rate on the ipcl spectral composition and intensity has been studied. It was established that the ipcl spectral density reaches its maximum (~10-20 min) after IMF Bz sign reversal in a predominant number of cases. It was detected that the ipcl average frequency ( f) is linearly related to the IMF Bz variation rate (Δ Bz/Δ t). It was shown that the dependence of f on Δ Bz/Δ t is controlled by the α = arctan( By/ Bx) angle value responsible for the MHD discontinuity type at the front boundary of magnetosphere. The results made it possible to assume that the formation of the observed ipcl spectrum, which is related to the IMF Bz reorientation, is caused by solar wind plasma turbulence, which promotes the development of current sheet instability and surface wave amplification at the magnetopause.

  1. Wind effects on prey availability: How northward migrating waders use brackish and hypersaline lagoons in the sivash, Ukraine

    NASA Astrophysics Data System (ADS)

    Verkuil, Yvonne; Koolhaas, Anita; Van Der Winden, Jan

    Large numbers of waders migrating northward in spring use the Sivash, a large system of shallow, brackish and hypersaline lagoons in the Black Sea and Azov Sea region (Ukraine). The bottoms of these lagoons are often uncovered by the wind. Hence, for waders the time and space available for feeding depend on wind conditions. In hypersaline lagoons the benthic and pelagic fauna was very poor, consisting mainly of chironomid larvae (0.19 g AFDM·m -2) and brine shrimps Artemia salina, respectively. Brine shrimp abundance was correlated with salinity, wind force, wind direction and water depth. Dunlin Calidris alpina and curlew sandpiper Calidris ferruginea were the only species feeding on brine shrimp. As brine shrimp densities are higher in deeper water, smaller waders such as broad-billed sandpipers Limicola falcinellus are too short-legged to reach exploitable densities of brine shrimp. In brackish lagoons the benthic and pelagic fauna was rich, consisting of polychaetes, bivalves, gastropods, chironomid larvae, isopods and amphipods (8.9 to 30.5 g AFDM·m -2), but there were no brine shrimps. Prey biomass increased with the distance from the coast, being highest on the site that was most frequently inundated. Dunlin, broad-billed sandpiper and grey plover Pluvialis squatarola were the most abundant birds in the brackish lagoon. Due to the effects of wind-tides only a small area was usually available as a feeding site. Gammarus insensibilis was the alternative prey resource in the water layer, and their density varied with wind direction in the same way as brine shrimp. Curlew sandpipers and dunlins in the hypersaline lagoons and broad-billed sandpipers in the brackish lagoons often changed feeding sites, probably following the variation in prey availability. Only because of the large size and variety of lagoons are waders in the Sivash always able to find good feeding sites.

  2. Cross section through the Toa Baja drillsite: Evidence for northward change in Late Eocene deformation intensity

    SciTech Connect

    Larue, D.K. ); Berrong, B. )

    1991-03-01

    A 55 km geologic cross section through the Toa Baja Drillsite, generated by integrating geologic mapping data from the foothills of the Central Mountains of Puerto Rico with onshore and offshore multichannel seismic reflection data, provides an opportunity to examine in profile from the arc interior northward to within 40 km of the current trench slope break. Three structural divisions are recognized. In the foothills of Puerto Rico, Cretaceous and Eocene rocks are separated by transpressional strike-slip faults. In the vicinity of the Toa Baja drillsite where both seismic reflection and borehole data are available, Eocene rocks, deformed by thrust faults, .ie above a lower unit, interpreted to be of Cretaceous age. Offshore, north of the drilling site, seismic reflections suggest Eocene rocks onlap structural basement, thought to be Cretaceous rocks, and both units appear only slightly deformed. All Eocene and Eocene ( ) rocks are overlain by little deformed Oligocene to Recent rocks. From south to north, or from the arc massif interior toward the present-day trench, there is an apparent decrease in amount of Late Eocene to Middle Oligocene strike-slip and shortening deformation. Deformation events occurred mostly in the arc-interior and were not directly associated with the plate boundary which was probably near the Puerto Rico Trench.

  3. [Northward shift in faunal diversity is a general pattern of evolution of the phanerozoic marine biota].

    PubMed

    Naĭmark, E B; Markov, A V

    2010-01-01

    The analysis of two global databases on spatio-temporal distribution of fossil marine animal genera (Sepkoski's compendium and The Paleobiology Database) has revealed the presence of the latitudinal diversity gradient (LDG) in the marine realm throughout the Phanerozoic. Within each time interval, LDG is characterized by two parameters: the latitudinal position of peak diversity and the steepness of monotonous decline of diversity with increasing distance from the zone of the highest diversity. During the Phanerozoic, peak diversity has drifted gradually from the tropics and subtropics of the Southern hemisphere into northern midlatitudes. The shift in peak diversity is not likely to be an artifact of incompleteness of the fossil record or uneven sampling of different regions. The shift proceeded in a stepwise manner, with periods of relatively fast changes separated by longer periods of little or no change. The latitudinal shift in peak diversity was probably due to a combination of several causes: tectonic (northward shift in the latitudinal distribution of continental shelf area), climatic (as demonstrated by the fact that peak diversity tended to occur near equator during the cold epochs and in midlatitudes during the warm epochs), and historical ("evolutionary inertia" of local faunas). PMID:21061643

  4. Paleomagnetic evidence from land-based and ODP cores for clockwise rotation and northward translation of the Phillippine Sea plate

    SciTech Connect

    Cisowski, S.M.; Fuller, M.; Haston, R.B.; Koyama, M. )

    1990-06-01

    On-land and deep-sea core paleomagnetic data have been collected from around the Philippine Sea plate. Data from the Palau islands suggest 70{degree} of clockwise rotation and northward translation since the mid-Oligocene. The authors interpret this rotation as a rotation of the West Philippine Sea basin as a whole. New paleomagnetic data from Guam indicate 70{degree} of clockwise rotation and northward translation since the early Oligocene. Although Eocene results have been previously quoted, the new data suggest that there is no reliable Eocene data from Guam. New data from Saipan suggest 50-60{degree} of clockwise rotation since the Late Eocene and 20{degree} of clockwise rotation since the mid-Miocene, along with northward translation. During ODP Leg 126, a new technique utilizing the formation microscanner logging tool was employed to obtain orientated drill cores from the Bonin forearc basin. Preliminary results indicate that 70-110{degree} of clockwise rotation has occurred there since the mid-Oligocene. Inclination studies on cores from ODP Legs 125 and 126 along with the on-land paleomagnetic data support 15{degree} of northward translation of the Philippine Sea plate since the mid-Oligocene. The consistent clockwise rotations found around the Philippine Sea plate suggest that the entire plate, including the Bonin and Mariana arcs, has rotated more than 50{degree} since the mid-Oligocene. The similarity of Oligocene results from the Bonin forearc and Guam suggest that little or no relative rotation has occurred between these two points. This implies that the shape of the Mariana arc is probably not due to rotational deformation. The northward translation and clockwise rotation of the Philippine Sea plate established oblique subduction along the proto-Philippine margin, which could account for the 600 km of subducted slab beneath the eastern Celebes Sea.

  5. Structure of the Outer Cusp and Sources of the Cusp Precipitation during Intervals of a Horizontal IMF

    NASA Technical Reports Server (NTRS)

    Berchem, Jean; Nemecek, Z.; Safrankova, J.; Prech, L.; Simunek, J.; Sauvaud, J.-A.; Fedorov, A.; Stenuit, H.; Fuselier, S. A.; Savin, S.; Zelenyi, L.

    2003-01-01

    The cusp represents a place where the magnetosheath plasma can directly penetrate into the magnetosphere. Since the main transport processes are connected with merging of the interplanetary and magnetospheric field lines: the interplanetary magnetic field (IMF) Orientation plays a decisive role in the formation of the high-altitude cusp. The importance of the sign of the IMF B(sub Z) component for this process was suggested about 40 years ago and later it was documented by many experimental investigations. However, situations when IMF Bz is the major IMF component are rather rare. The structure of the cusp during periods of a small IMF B(sub Z) is generally unknown, probably due to the fully 3-D nature of the interaction. The present case study reveals the importance of horizontal IMF components on the global magnetospheric configuration as well as on small-scale processes at the cusp-magnetosheath interface. We have used simultaneous measurements of several spacecraft (ISTP program) operating in different regions of interplanetary space and two closely spaced satellites (INTERBALL-1/MAGION-4) crossing the cusp-magnetosheath boundary to show the connection between the short- and large-scale phenomena. In the northern hemisphere, observations suggest a presence of two spots of cusp-like precipitation supplied by reconnection occurring simultaneously in both hemispheres. A source of this bifurcation is the positive IMF B(sub y) component further enhanced by the field draping in the magnetosheath. This magnetic field component shifts the entry point far away from the local noon but in opposite sense in either hemisphere. The cusp represents a place where the magnetosheath plasma can directly

  6. ULF foreshock under radial IMF: THEMIS observations and global kinetic simulation Vlasiator results compared

    NASA Astrophysics Data System (ADS)

    Palmroth, Minna; Rami, Vainio; Archer, Martin; Hietala, Heli; Afanasiev, Alexandr; Kempf, Yann; Hoilijoki, Sanni; von Alfthan, Sebastian

    2015-04-01

    For decades, a certain type of ultra low frequency waves with a period of about 30 seconds have been observed in the Earth's quasi-parallel foreshock. These waves, with a wavelength of about an Earth radius, are compressive and propagate with an average angle of 20 degrees with respect of the interplanetary magnetic field (IMF). The latter property has caused trouble to scientists as the growth rate for the instability causing the waves is maximized along the magnetic field. So far, these waves have been characterized by single or multi-spacecraft methods and 2-dimensional hybrid-PIC simulations, which have not fully reproduced the wave properties. Vlasiator is a newly developed, global hybrid-Vlasov simulation, which solves the six-dimensional phase space utilising the Vlasov equation for protons, while electrons are a charge-neutralising fluid. The outcome of the simulation is a global reproduction of ion-scale physics in a holistic manner where the generation of physical features can be followed in time and their consequences can be quantitatively characterised. Vlasiator produces the ion distribution functions and the related kinetic physics in unprecedented detail, in the global scale magnetospheric scale with a resolution of a couple of hundred kilometres in the ordinary space and 20 km/s in the velocity space. We run Vlasiator under a radial IMF in five dimensions consisting of the three-dimensional velocity space embedded in the ecliptic plane. We observe the generation of the 30-second ULF waves, and characterize their evolution and physical properties in time. We compare the results both to THEMIS observations and to the quasi-linear theory. We find that Vlasiator reproduces the foreshock ULF waves in all reported observational aspects, i.e., they are of the observed size in wavelength and period, they are compressive and propagate obliquely to the IMF. In particular, we discuss the issues related to the long-standing question of oblique propagation.

  7. Relationship between the IMF magnitude and Pc 3 magnetic pulsations in the magnetosphere

    NASA Technical Reports Server (NTRS)

    Yumoto, K.; Saito, T.; Tsurutani, B. T.; Smith, E. J.; Akasofu, S.-I.

    1984-01-01

    The relationships between the IMF magnitude and pulsation frequencies in the Pc 3-4 range simultaneously observed both at synchronous orbit and at low latitudes on the ground are statistically described. A theoretical discussion is given on how these observations can be interpreted in terms of the characteristic frequency of compressional Pc 3-4 magnetic pulsations in the magnetosphere, based on the well-established ion cyclotron resonance mechanism between magnetosonic mode of low-frequency upstream waves and narrowly reflected ion beams in the earth's foreshock.

  8. THE STELLAR INITIAL MASS FUNCTION OF ULTRA-FAINT DWARF GALAXIES: EVIDENCE FOR IMF VARIATIONS WITH GALACTIC ENVIRONMENT

    SciTech Connect

    Geha, Marla; Brown, Thomas M.; Tumlinson, Jason; Kalirai, Jason S.; Avila, Roberto J.; Ferguson, Henry C.; Simon, Joshua D.; Kirby, Evan N.; VandenBerg, Don A.; Munoz, Ricardo R.; Guhathakurta, Puragra E-mail: tbrown@stsci.edu

    2013-07-01

    We present constraints on the stellar initial mass function (IMF) in two ultra-faint dwarf (UFD) galaxies, Hercules and Leo IV, based on deep Hubble Space Telescope Advanced Camera for Surveys imaging. The Hercules and Leo IV galaxies are extremely low luminosity (M{sub V} = -6.2, -5.5), metal-poor (([Fe/H]) = -2.4, -2.5) systems that have old stellar populations (>11 Gyr). Because they have long relaxation times, we can directly measure the low-mass stellar IMF by counting stars below the main-sequence turnoff without correcting for dynamical evolution. Over the stellar mass range probed by our data, 0.52-0.77 M{sub Sun }, the IMF is best fit by a power-law slope of {alpha}= 1.2{sub -0.5}{sup +0.4} for Hercules and {alpha} = 1.3 {+-} 0.8 for Leo IV. For Hercules, the IMF slope is more shallow than a Salpeter ({alpha} = 2.35) IMF at the 5.8{sigma} level, and a Kroupa ({alpha} = 2.3 above 0.5 M{sub Sun }) IMF slope at 5.4{sigma} level. We simultaneously fit for the binary fraction, f{sub binary}, finding f{sub binary}= 0.47{sup +0.16}{sub -0.14} for Hercules, and 0.47{sup +0.37}{sub -0.17} for Leo IV. The UFD binary fractions are consistent with that inferred for Milky Way stars in the same mass range, despite very different metallicities. In contrast, the IMF slopes in the UFDs are shallower than other galactic environments. In the mass range 0.5-0.8 M{sub Sun }, we see a trend across the handful of galaxies with directly measured IMFs such that the power-law slopes become shallower (more bottom-light) with decreasing galactic velocity dispersion and metallicity. This trend is qualitatively consistent with results in elliptical galaxies inferred via indirect methods and is direct evidence for IMF variations with galactic environment.

  9. Solar Flare and IMF Sector Structure Effects in the Lower Ionosphere

    NASA Technical Reports Server (NTRS)

    Lastovicka, J.

    1984-01-01

    About 1% of all sudden ionospheric disturbances (SIDs) observed at the Panska Ves Observatory (Czechoslovakia), were found to be not of solar-XUV origin. Among them, the very rare SWF events (observed at L = 2.4) of corpuscular origin are the most interesting. The IMF sector structure effects in the midlatitude lower ionosphere are minor in comparison with effects of solar flares, geomagnetic storms, etc. There are two basic types of effects. The first type is a disturbance, best developed in geomagnetic activity, and observed in the night-time ionosphere. It can be interpreted as a response to sector structure related changes of geomagnetic (= magnetospheric) activity. The other type is best developed in the tropospheric vorticity area index and is also observed in the day-time ionosphere in winter. This effect is quietening in the ionosphere as well as troposphere. While the occurrence of the former type is persistent in time, the latter is severely diminished in some periods. All the stratosphere, the 10-mb level temperature and height above Berlin-Tempelhof do not display any observable IMF section structure effect.

  10. Observations of magnetospheric substorms occurring with no apparent solar wind/IMF trigger

    SciTech Connect

    Henderson, M.G.; Reeves, G.D.; Belian, R.D.; Murphree, J.S.

    1996-03-01

    An outstanding topic in magnetospheric physics is whether substorms are always externally triggered by disturbances in either the interplanetary magnetic field or solar wind, or whether they can also occur solely as the result of an internal magnetospheric instability. Over the past decade, arguments have been made on both sides of this issue. Horwitz and McPherron have shown examples of substorm onsets which they claimed were not externally triggered. However, as pointed out by Lyons, there are several problems associated with these studies that make their results somewhat inconclusive. In particular, in the McPherron et al. study, fluctuations in the B{sub y} component were not considered as possible triggers. Furthermore, Lyons suggests that the sharp decreases in the AL index during intervals of steady IMF/solar wind, are not substorms at all but rather that they are just enhancements of the convection driven DP2 current system that are often observed to occur during steady magnetospheric convection events. In the present study, we utilize a much more comprehensive dataset (consisting of particle data from the Los Alamos energetic particle detectors at geosynchronous orbit, IMP 8 magnetometer and plasma data, Viking UV auroral imager data, mid-latitude Pi2 pulsation data, ground magnetometer data and ISEE1 magnetic field and energetic particle data) to show as unambiguously as possible that typical substorms can indeed occur in the absence of an identifiable trigger in the solar wind/IMF.

  11. Solar flare and IMF sector structure effects in the lower ionosphere

    SciTech Connect

    Lastovicka, J.

    1984-05-01

    About 1% of all sudden ionospheric disturbances (SIDs) observed at the Panska Ves Observatory (Czechoslovakia), were found to be not of solar-XUV origin. Among them, the very rare SWF events (observed at L 2.4) of corpuscular origin are the most interesting. The IMF sector structure effects in the midlatitude lower ionosphere are minor in comparison with effects of solar flares, geomagnetic storms, etc. There are two basic types of effects. The first type is a disturbance, best developed in geomagnetic activity, and observed in the night-time ionosphere. It can be interpreted as a response to sector structure related changes of geomagnetic (magnetospheric) activity. The other type is best developed in the tropospheric vorticity area index and is also observed in the day-time ionosphere in winter. This effect is quietening in the ionosphere as well as troposphere. While the occurrence of the former type is persistent in time, the latter is severely diminished in some periods. All the stratosphere, the 10-mb level temperature and height above Berlin-Tempelhof do not display any observable IMF section structure effect.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  13. Does the IMF vary with galaxy mass? The X-ray binary population of a key galaxy, NGC7457

    NASA Astrophysics Data System (ADS)

    Peacock, Mark

    2014-09-01

    We propose a 100ksec observation of NGC7457. The primary goal of this observation is to test for variations in the initial mass function (IMF). Many recent studies have proposed that the IMF varies systematically as a function of early-type galaxy mass. This has potentially dramatic consequences and must to be confirmed. The number of LMXBs in a galaxy (per stellar luminosity) can be used to provide an independent test of this hypothesis (see Peacock et al. 2014). Unfortunately, only galaxies with intermediate to high masses currently have the data needed to perform this test. The proposed observation of the elliptical galaxy NGC7457 will detect an order of magnitude more LMXBs in a low mass galaxy - hence providing the crucial constraint needed to significantly test for a variable IMF.

  14. Ionospheric convection inferred from interplanetary magnetic field-dependent Birkeland currents

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    Computer simulations of ionospheric convection have been performed, combining empirical models of Birkeland currents with a model of ionospheric conductivity in order to investigate IMF-dependent convection characteristics. Birkeland currents representing conditions in the northern polar cap of the negative IMF By component are used. Two possibilities are considered: (1) the morning cell shifting into the polar cap as the IMF turns northward, and this cell and a distorted evening cell providing for sunward flow in the polar cap; and (2) the existence of a three-cell pattern when the IMF is strongly northward.

  15. Large Scale Earth's Bow Shock with Northern IMF as Simulated by PIC Code in Parallel with MHD Model

    NASA Astrophysics Data System (ADS)

    Baraka, Suleiman

    2016-06-01

    In this paper, we propose a 3D kinetic model (particle-in-cell, PIC) for the description of the large scale Earth's bow shock. The proposed version is stable and does not require huge or extensive computer resources. Because PIC simulations work with scaled plasma and field parameters, we also propose to validate our code by comparing its results with the available MHD simulations under same scaled solar wind (SW) and (IMF) conditions. We report new results from the two models. In both codes the Earth's bow shock position is found to be ≈14.8 R E along the Sun-Earth line, and ≈29 R E on the dusk side. Those findings are consistent with past in situ observations. Both simulations reproduce the theoretical jump conditions at the shock. However, the PIC code density and temperature distributions are inflated and slightly shifted sunward when compared to the MHD results. Kinetic electron motions and reflected ions upstream may cause this sunward shift. Species distributions in the foreshock region are depicted within the transition of the shock (measured ≈2 c/ ω pi for Θ Bn = 90° and M MS = 4.7) and in the downstream. The size of the foot jump in the magnetic field at the shock is measured to be (1.7 c/ ω pi ). In the foreshocked region, the thermal velocity is found equal to 213 km s-1 at 15 R E and is equal to 63 km s -1 at 12 R E (magnetosheath region). Despite the large cell size of the current version of the PIC code, it is powerful to retain macrostructure of planets magnetospheres in very short time, thus it can be used for pedagogical test purposes. It is also likely complementary with MHD to deepen our understanding of the large scale magnetosphere.

  16. Pressure balance across the magnetopause: Global MHD results

    NASA Astrophysics Data System (ADS)

    Lu, J. Y.; Wang, M.; Kabin, K.; Zhao, J. S.; Liu, Z.-Q.; Zhao, M. X.; Li, G.

    2015-02-01

    The equilibrium magnetopause location on the dayside is determined by the balance of pressure forces. In this paper we use a physics-based global magnetohydrodynamic (MHD) to examine contributions of different terms to this balance. We calculate the total pressure, as well as thermal and magnetic pressures just inside and just outside the magnetopause. Our results show that (1) the total pressure just outside the magnetopause is enhanced with the increasing of BZ in both northward and southward interplanetary magnetic field (IMF). For southward IMF the thermal pressure is dominant in the total pressure while the magnetic pressure is dominant for northward IMF when BZ is not small (BZ > 5 nT). For southward IMF larger solar wind dynamic pressure further enhances thermal pressure near the magnetopause while for northward IMF the dynamic pressure is more effectively converted to the magnetic pressure; (2) the thermal pressure just outside the magnetopause is significantly enhanced with the increasing southward IMF as compared to the northward IMF case. However, this enhanced thermal pressure is not the only reason for the well-known earthward displacement of the magnetopause under southward IMF conditions. The dayside magnetic reconnection for southward IMF dramatically decreases magnetic pressure just inside the magnetopause. The combination of these two factors explains the Earthward motion of the magnetopause for southward IMF.

  17. Comparison Between Vortices Created and Evolving During Fixed and Dynamic Solar Wind Conditions

    NASA Technical Reports Server (NTRS)

    Collado-Vega, Yaireska M.; Kessel, R. L.; Sibeck, David Gary; Kalb, V. L.; Boller, R. A.; Rastaetter, L.

    2013-01-01

    We employ Magnetohydrodynamic (MHD) simulations to examine the creation and evolution of plasma vortices within the Earth's magnetosphere for steady solar wind plasma conditions. Very few vortices form during intervals of such solar wind conditions. Those that do remain in fixed positions for long periods (often hours) and exhibit rotation axes that point primarily in the x or y direction, parallel (or antiparallel) to the local magnetospheric magnetic field direction. Occasionally, the orientation of the axes rotates from the x direction to another direction. We compare our results with simulations previously done for unsteady solar wind conditions. By contrast, these vortices that form during intervals of varying solar wind conditions exhibit durations ranging from seconds (in the case of those with axes in the x or y direction) to minutes (in the case of those with axes in the z direction) and convect antisunward. The local-time dependent sense of rotation seen in these previously reported vortices suggests an interpretation in terms of the Kelvin-Helmholtz instability. For steady conditions, the biggest vortices developed on the dayside (about 6R(E) in diameter), had their rotation axes aligned with the y direction and had the longest periods of duration. We attribute these vortices to the flows set up by reconnection on the high latitude magnetopause during intervals of northward Interplanetary Magnetic Field (IMF) orientation. This is the first time that vortices due to high-latitude reconnection have been visualized. The model also successfully predicts the principal characteristics of previously reported plasma vortices within the magnetosphere, namely their dimension, flow velocities, and durations.

  18. Evolution of the Global Aurora During Positive IMP Bz and Varying IMP By Conditions

    NASA Technical Reports Server (NTRS)

    Cumnock, J. A.; Sharber, J. R.; Heelis. R. A.; Hairston, M. R.; Carven, J. D.

    1997-01-01

    The DE 1 imaging instrumentation provides a full view of the entire auroral oval every 12 min for several hours during each orbit. We examined five examples of global evolution of the aurora that occurred during the northern hemisphere winter of 1981-1982 when the z component of the interplanetary magnetic field was positive and the y component was changing sign. Evolution of an expanded auroral emission region into a theta aurora appears to require a change in the sign of By during northward interplanetary magnetic field (IMF). Theta aurora are formed both from expanded duskside emission regions (By changes from positive to negative) and dawnside emission regions (By changes from negative to positive), however the dawnside-originating and duskside-originating evolutions are not mirror images. The persistence of a theta aurora after its formation suggests that there may be no clear relationship between the theta aurora pattern and the instantaneous configuration of the IMF.

  19. Variation in the statistical properties of IMF direction fluctuations during the 22-year solar magnetic cycle

    NASA Astrophysics Data System (ADS)

    Erofeev, D. V.

    2014-12-01

    The variation in the IMF direction distribution during the 22-year solar magnetic cycle has been studied. Data obtained in near-Earth orbits and measurements in the heliospheric regions located far from the Earth, performed with the Helios and Ulysses spacecraft devices, have been analyzed. It has been found that the correlation between the azimuth and magnetic field fluctuations is statistically significant in the low-latitude heliospheric region at heliocentric distances of 0.3-5.4 AU, and the sign of this correlation reverses at a change in the polar solar magnetic field orientation. In the polar zones of the heliosphere outside the latitudinal extension of the heliospheric current sheet, the angle correlation coefficient rapidly decreases with increasing heliographic latitude. The angle correlation sign reversal during the 22-year cycle is accompanied by a change of the asymmetry sign of the magnetic field inclination distribution.

  20. Statistical Properties of the Solar Wind and IMF at 1 AU

    NASA Astrophysics Data System (ADS)

    McPherron, R. L.

    2006-12-01

    During the declining phase of the solar cycle the evolution of the solar magnetic field produces large regions of unipolar magnetic field that create coronal holes and are the sources of high speed solar wind streams. These streams overtake and interact with slow solar wind emitted from the equatorial belt of closed magnetic field lines. These interaction regions corotate (CIR) with the Sun and sweep across the Earth once per solar rotation. Inside a CIR the properties of the solar wind are well organized by time relative to the interface between the two streams (epoch time). We have compiled lists of stream interfaces in solar cycle #22 (1994- 1996) and in cycle #23 (2003-2005) and used them to study the systematic properties of the solar wind and interplanetary magnetic field at 1 AU. We present the results as dynamic cumulative probability distributions (cdf) for different variables and as traces of the quartiles of these distributions as function of epoch time. We find that the solar wind is highly organized relative to the stream interface and therefore that geomagnetic activity driven by this wind is organized as well. This systematic behavior provides the basis for probabilistic forecasting by air mass climatology. If one can predict the arrival of a stream interface then within certain limits one can predict the probability that various measures of geomagnetic activity will lie within a given range. We also find that the climatology of the solar wind as measured at the Earth has a semiannual variation as a consequence of two different effects: the axial effect that causes the Earth to be at high or low heliographic latitude near equinoxes and the Rosenberg-Coleman (R-C) effect which states that the fraction of time the Earth samples a particular polarity of the IMF is dominated by the polar magnetic field of the Sun emanating from the hemisphere in which the Earth is located. A third phenomenon the Russell-McPherron (R-M) effect is important for the Earth

  1. Investigating [X/Fe], IMF, and compositeness in integrated-light models

    NASA Astrophysics Data System (ADS)

    Tang, Baitian; Worthey, Guy

    2015-01-01

    Modelling elliptical galaxy integrated-light characteristics with old, metal-rich stellar populations is a common and promising way to study these distant objects. However, different model parameters may change the characteristics in a similar way, causing degeneracy, e.g., the age-metallicity degeneracy. Here, we investigate several under-appreciated effects with the evolving Worthey models, and discuss their detectabilities.We model composite stellar populations with realistic abundance distribution functions (ADFs), tracking the trends of individual elements as a function of overall heavy element abundance as observed in MW bulge stars in addition to solar neighborhood stars. Comparing bulge versus elliptical galaxies, Fe, Ti, and Mg trend about the same for both but C, Na, and Ca seem irreconcilably different.Exploring the behavior of abundance compositeness leads to the concepts of ``red lean'' where a narrower ADF appears more metal rich than a wide one, and ``red spread'' where the spectral difference between wide and narrow ADFs increases as the ADF peak is moved to more metal-rich values. The prospects of measuring the width of the ADF of an old stellar population were investigated and seem bright using UV to IR photometry.Next, we try to disentangle the effects of 1) low-mass cut-off; 2) IMF slope; and 3) AGB strength in several IMF-sensitive indices and NIR colors. In most of the NIR-optical colors, varying low-mass cut-off and AGB strength leads to about 0.03 mag drift, which is comparable to the observable limits. Using a mix of photometric and spectral absorption indices (e.g. [MgFe], Wing-Ford, V-K, and B-V) degeneracy can be lifted, although at an observationally challenging amplitude. We go on to include ADF width and abundance ratio effects, and discuss the accuracy of disentangling multiple effects from integrated-light measurements.

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

    SciTech Connect

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

    1995-05-01

    The authors describe strong interplanetary magnetic field (IMF) and seasonal effects in the convection of nightside ionospheric plasma. The findings are based on a statistical analysis of observations made with the JHU/APL HF radar located at Goose Bay, Labrador. For positive sign of the IMF dawn-dusk component, i.e., B{sub y}>0, the dawn cell is more crescent-shaped and the dusk cell more round while for B{sub y}<0 these pairings of size and shape are reversed. The more extreme crescent/round cell dichotomy is obtained for B{sub y}>0. The return flows associated with the crescent-shaped cell dominate at midnight MLT (Magnetic Local Time); the reversal in the zonal velocity in the 67{degrees}-69{degrees}{Lambda} (magnetic latitude) interval occurs 2 1/2 hr earlier for B{sub y}>0. The seasonal dependence of nightside convection resembles in important respects the B{sub y} dependence. Greater latitudinal velocity shears occur in the morning/afternoon sector for summer/winter and the return flow of this sector dominates at midnight. The zonal flow reversal occurs 2 1/2 hr earlier in summer than in winter. The maximum effects are obtained on the nightside for the pairings [B{sub y}>0, summer] and [B{sub y}<0, winter]; the first produces the more structured cell in the morning, the second in the evening, and this cell dominates the return flow at midnight. The difference in the zonal flow reversals for these pairings exceeds 4 hr in MLT. 15 refs., 4 figs.

  3. Fluctuation spectroscopy with the ACS ramp filters: a new way to measure the IMF in elliptical galaxies

    NASA Astrophysics Data System (ADS)

    van Dokkum, Pieter

    2014-10-01

    Images of old stellar populations show pixel-to-pixel fluctuations due to Poisson variations in the number of giant stars. These surface brightness fluctuations can be used to study the spectra of stars as a function of their luminosity, by obtaining differential spectroscopy of pixels with high and low fluctuations. If the average number of stars per pixel is sufficiently low, there will be individual pixels that have almost no light from luminous giants, providing sightlines that are dominated by main sequence stars. In this regime the observed spectral response is strongly dependent on the number of cool, low mass stars, and hence the stellar initial mass function (IMF). We propose to observe the nearest elliptical galaxy, Centaurus A, through four narrowband ACS ramp filters tuned to the 0.8 - 0.9 micron range. From the relation between ACS narrowband indices and the amplitude of the surface brightness fluctuation we will be able to obtain quantitative constraints on the IMF from 0.1-1 Solar masses, and distinguish between a Kroupa-like IMF or a bottom-heavy, Salpeter-like IMF, with ~5 sigma significance. We have demonstrated the feasibility of the technique used in this proposal in a Cycle 19 program, where we used the same observational strategy to measure the properties of luminous giants in the Virgo galaxy NGC 4472.

  4. Northward extension of Carolina slate belt stratigraphy and structure, South-Central Virginia: Results from geologic mapping

    USGS Publications Warehouse

    Hackley, P.C.; Peper, J.D.; Burton, W.C.; Horton, J.W.

    2007-01-01

    Geologic mapping in south-central Virginia demonstrates that the stratigraphy and structure of the Carolina slate belt extend northward across a steep thermal gradient into upper amphibolite-facies correlative gneiss and schist. The Neoproterozoic greenschist-facies Hyco, Aaron, and Virgilina Formations were traced northward from their type localities near Virgilina, Virginia, along a simple, upright, northeast-trending isoclinal syncline. This syncline is called the Dryburg syncline and is a northern extension of the more complex Virgilina synclinorium. Progressively higher-grade equivalents of the Hyco and Aaron Formations were mapped northward along the axial trace of the refolded and westwardly-overturned Dryburg syncline through the Keysville and Green Bay 7.5-minute quadrangles, and across the northern end of the Carolina slate belt as interpreted on previous geologic maps. Hyco rocks, including felsic metatuff, metawacke, and amphibolite, become gneisses upgrade with areas of local anatexis and the segregation of granitic melt into leucosomes with biotite selvages. Phyllite of the Aaron Formation becomes garnet-bearing mica schist. Aaron Formation rocks disconformably overlie the primarily felsic volcanic and volcaniclastic rocks of the Hyco Formation as evidenced by repeated truncation of internal contacts within the Hyco on both limbs of the Dryburg syncline at the Aaron-Hyco contact. East-northeast-trending isograds, defined successively by the first appearance of garnet, then kyanite ?? staurolite in sufficiently aluminous rocks, are superposed on the stratigraphic units and synclinal structure at moderate to high angles to strike. The textural distinction between gneisses and identifiable sedimentary structures occurs near the kyanite ?? staurolite-in isograd. Development of the steep thermal gradient and regional penetrative fabric is interpreted to result from emplacement of the Goochland terrane adjacent to the northern end of the slate belt during

  5. Radial Trends in IMF-sensitive Absorption Features in Two Early-type Galaxies: Evidence for Abundance-driven Gradients

    NASA Astrophysics Data System (ADS)

    McConnell, Nicholas J.; Lu, Jessica R.; Mann, Andrew W.

    2016-04-01

    Samples of early-type galaxies show a correlation between stellar velocity dispersion and the stellar initial mass function (IMF) as inferred from gravity-sensitive absorption lines in the galaxies’ central regions. To search for spatial variations in the IMF, we have observed two early-type galaxies with Keck/LRIS and measured radial gradients in the strengths of absorption features from 4000-5500 Å and 8000-10000 Å. We present spatially resolved measurements of the dwarf-sensitive spectral indices {Na} {{I}} (8190 Å) and Wing-Ford {{FeH}} (9915 Å), as well as indices for species of H, C2, CN, Mg, Ca, {{TiO}}, and Fe. Our measurements show a metallicity gradient in both objects, and Mg/Fe consistent with a shallow gradient in α-enhancement, matching widely observed trends for massive early-type galaxies. The {Na} {{I}} index and the CN1 index at 4160 Å exhibit significantly steeper gradients, with a break at r˜ 0.1 {r}{{eff}} (r˜ 300 pc). Inside this radius, {Na} {{I}} strength increases sharply toward the galaxy center, consistent with a rapid central rise in [Na/Fe]. In contrast, the ratio of the {{FeH}} to Fe index strength decreases toward the galaxy center. This behavior cannot be reproduced by a steepening IMF inside of 0.1 {r}{{eff}} if the IMF is a single power law. While gradients in the mass function above ˜ 0.4 {M}⊙ may occur, exceptional care is required to disentangle these IMF variations from the extreme variations in individual element abundances near the galaxies’ centers.

  6. Pangea breakup and northward drift of the Indian subcontinent reproduced by a numerical model of mantle convection.

    PubMed

    Yoshida, Masaki; Hamano, Yozo

    2015-01-01

    Since around 200 Ma, the most notable event in the process of the breakup of Pangea has been the high speed (up to 20 cm yr(-1)) of the northward drift of the Indian subcontinent. Our numerical simulations of 3-D spherical mantle convection approximately reproduced the process of continental drift from the breakup of Pangea at 200 Ma to the present-day continental distribution. These simulations revealed that a major factor in the northward drift of the Indian subcontinent was the large-scale cold mantle downwelling that developed spontaneously in the North Tethys Ocean, attributed to the overall shape of Pangea. The strong lateral mantle flow caused by the high-temperature anomaly beneath Pangea, due to the thermal insulation effect, enhanced the acceleration of the Indian subcontinent during the early stage of the Pangea breakup. The large-scale hot upwelling plumes from the lower mantle, initially located under Africa, might have contributed to the formation of the large-scale cold mantle downwelling in the North Tethys Ocean. PMID:25673102

  7. Pangea breakup and northward drift of the Indian subcontinent reproduced by a numerical model of mantle convection.

    PubMed

    Yoshida, Masaki; Hamano, Yozo

    2015-02-12

    Since around 200 Ma, the most notable event in the process of the breakup of Pangea has been the high speed (up to 20 cm yr(-1)) of the northward drift of the Indian subcontinent. Our numerical simulations of 3-D spherical mantle convection approximately reproduced the process of continental drift from the breakup of Pangea at 200 Ma to the present-day continental distribution. These simulations revealed that a major factor in the northward drift of the Indian subcontinent was the large-scale cold mantle downwelling that developed spontaneously in the North Tethys Ocean, attributed to the overall shape of Pangea. The strong lateral mantle flow caused by the high-temperature anomaly beneath Pangea, due to the thermal insulation effect, enhanced the acceleration of the Indian subcontinent during the early stage of the Pangea breakup. The large-scale hot upwelling plumes from the lower mantle, initially located under Africa, might have contributed to the formation of the large-scale cold mantle downwelling in the North Tethys Ocean.

  8. Pangea breakup and northward drift of the Indian subcontinent reproduced by a numerical model of mantle convection

    NASA Astrophysics Data System (ADS)

    Yoshida, Masaki; Hamano, Yozo

    2015-02-01

    Since around 200 Ma, the most notable event in the process of the breakup of Pangea has been the high speed (up to 20 cm yr-1) of the northward drift of the Indian subcontinent. Our numerical simulations of 3-D spherical mantle convection approximately reproduced the process of continental drift from the breakup of Pangea at 200 Ma to the present-day continental distribution. These simulations revealed that a major factor in the northward drift of the Indian subcontinent was the large-scale cold mantle downwelling that developed spontaneously in the North Tethys Ocean, attributed to the overall shape of Pangea. The strong lateral mantle flow caused by the high-temperature anomaly beneath Pangea, due to the thermal insulation effect, enhanced the acceleration of the Indian subcontinent during the early stage of the Pangea breakup. The large-scale hot upwelling plumes from the lower mantle, initially located under Africa, might have contributed to the formation of the large-scale cold mantle downwelling in the North Tethys Ocean.

  9. Pangea breakup and northward drift of the Indian subcontinent reproduced by a numerical model of mantle convection

    PubMed Central

    Yoshida, Masaki; Hamano, Yozo

    2015-01-01

    Since around 200 Ma, the most notable event in the process of the breakup of Pangea has been the high speed (up to 20 cm yr−1) of the northward drift of the Indian subcontinent. Our numerical simulations of 3-D spherical mantle convection approximately reproduced the process of continental drift from the breakup of Pangea at 200 Ma to the present-day continental distribution. These simulations revealed that a major factor in the northward drift of the Indian subcontinent was the large-scale cold mantle downwelling that developed spontaneously in the North Tethys Ocean, attributed to the overall shape of Pangea. The strong lateral mantle flow caused by the high-temperature anomaly beneath Pangea, due to the thermal insulation effect, enhanced the acceleration of the Indian subcontinent during the early stage of the Pangea breakup. The large-scale hot upwelling plumes from the lower mantle, initially located under Africa, might have contributed to the formation of the large-scale cold mantle downwelling in the North Tethys Ocean. PMID:25673102

  10. Moisture dynamics of the northward and eastward propagating boreal summer intraseasonal oscillations: possible role of tropical Indo-west Pacific SST and circulation

    NASA Astrophysics Data System (ADS)

    Pillai, Prasanth A.; Sahai, A. K.

    2016-08-01

    Boreal summer intraseasonal oscillation (BSISO) has complex spatial structure due to the co-existence of equatorial eastward and off-equatorial northward propagation in the equatorial Indian Ocean. As a result, equatorial Indian Ocean convection has simultaneous northward and eastward (NE), northward only (N-only) and eastward only (E-only) propagations. It is well established that the convection propagates in the direction of increasing moist static energy (MSE). The moisture and MSE budget analysis reveals that the horizontal advection of anomalous MSE contributes to positive MSE tendency, which is in agreement with the horizontal advection of column integrated moisture anomaly. Northward movement of warm SST and the anomalous moisture advected by zonal wind are the major initiative for the northward propagation of convection from the equatorial Indian Ocean in both NE and N-only category. At the same time warm SST anomaly in the equatorial west Pacific along with moisture advection caused by anomalous meridional wind is important for the equatorial eastward branch of NE propagation. As these anomalies in the west Pacific moves northward, equatorial Indian Ocean convection establishes over the equatorial west Pacific. The absence of these processes confines the BSISO in northward direction for N-only category. In the case of E-only movement, warm SST anomaly and moisture advection by zonal component of wind causes the eastward propagation of convection. Boundary layer moisture convergence always remains east of convection center in E-only propagation, while it coincides with convection centre in other two categories. Thus the present study concludes that the difference in underlying SST and atmospheric circulation in tropical Indo-west Pacific oceanic regions encourage the differential propagation of BSISO convection through moisture dynamics.

  11. Paleomagnetic and geologic data indicating 2500 km of northward displacement for the Salinian and related terranes, California

    NASA Astrophysics Data System (ADS)

    Champion, D. E.; Howell, D. G.; Gromme, C. S.

    1984-09-01

    Results of a pair of paleomagnetic studies of sedimentary rocks in the Salinian terrane of westernmost California indicate a northward displacement of about 2500 km since Cretaceous time. Stratigraphic relations suggest that the Salinian terrane became amalgamated with several others by the Late Cretaceous and all underwent the same northward translation. This composite terrane (allochthon) became sutured to cratonal North America by early Tertiary time. One paleomagnetic study involved Upper Cretaceous turbidites of the Pigeon Point Formation. Fine-grained, thin-bedded turbidites yielded the most reliable results, whereas medium- to coarse-grained sandstones are not always stably magnetized. Contorted layers resulting from soft sediment deformation usually gave directional results parallel to those of undeformed sedimentary layers, thereby implying a postdepositional remanence process. There is no indication of inclination error or other processes affecting the fidelity of the remanent magnetization. Paleomagnetic results from four separate locations in the Pigeon Point Formation gave positive fold tests and mean inclination values near 36°. A mean geomagnetic latitude calculated from these results is 21.2°±5.3°, much more southerly than the value of 46.5°±2.3° calculated for Pigeon Point using paleomagnetic pole data from Late Cretaceous rocks from cratonic North America. Declination values are not antipodal for normal and reversed polarity sites. Analysis of depositional current directions from sandstone beds of the same outcrops shows that the difference is the result of Neogene rotations of small crustal blocks adjacent to the San Gregorio fault. In a sequence of Paleocene turbidites that crop out at Point San Pedro, four sample localities yielded positive fold tests with mean inclination values near -40°. Declination values, however, were spread over a range between 230° and 320°. Comparison with depositional current directions from the same

  12. Magnetospheric convection observed between 0600 and 2100 LT Solar wind and IMF dependence

    SciTech Connect

    Baumjohann, W.; Haerendel, G.

    1985-07-01

    Baumjohann et al. (1985) have used GEOS 2 electron gun data to construct average patterns of dayside magnetospheric convection for different levels of magnetic activity. It was found that the synchronous orbit electric field is influenced by both solar wind and ionospheric wind dynamo action. However, it was not possible to decide what fraction of the dawn-to-dusk electric field attributed to a solar wind source was caused by each of the two known solar wind dynamo processes, including viscous interaction and dayside merging. In the present investigation, the GEOS 2 electron gun measurements used in the earlier study are also employed. The data were averaged over one UT hour and combined with solar wind plasma (bulk velocity and proton density) and Interplanetary Magnetic Field (IMF) data. A regression analysis was conducted, taking into account viscous-like interaction, and dayside merging. It is concluded that weak merging electric fields of the order of 0.3 mV/m do exist at the dayside magnetopause even during very quiet times. 37 references.

  13. Understanding the mechanisms behind the West African Monsoon northward extension during Mid-Holocene

    NASA Astrophysics Data System (ADS)

    Gaetani, Marco; Messori, Gabriele; Zhang, Qiong; Flamant, Cyrille; Evan, Amato T.; Pausata, Francesco S. R.

    2016-04-01

    Understanding the West African monsoon (WAM) dynamics in the mid-Holocene (MH) is a crucial issue in climate modelling, because numerical models typically fail to reproduce the extensive precipitation suggested by proxy evidence. This discrepancy is largely due to unrealistic imposed land surface cover and aerosols. Numerical experiments are conducted by imposing a "green Sahara", along with a reduced dust concentration in the atmosphere, coherently with the MH environment in the region, and the atmospheric dynamics response and impact on precipitation are investigated. The response of the WAM system to the imposed conditions shows a dramatic augmentation of the precipitation across West Africa up to the Mediterranean coast. This follows a substantial reorganization of the regional circulation, with some monsoonal circulation features (Saharan heat low, African easterly jet, African easterly waves) weakened in favour of deep convection development over land. The simulated response is dominated by land cover changes, and the reduction in dust concentration further enhances the changes induced by the "green Sahara". The intensity and meridional extent of the WAM is fully consistent with proxy evidence. The results for the MH WAM present important implications for understanding future climate scenarios in the region, in the perspective of projected wetter conditions in West Africa.

  14. Y-Chromosome evidence for a northward migration of modern humans into Eastern Asia during the last Ice Age.

    PubMed

    Su, B; Xiao, J; Underhill, P; Deka, R; Zhang, W; Akey, J; Huang, W; Shen, D; Lu, D; Luo, J; Chu, J; Tan, J; Shen, P; Davis, R; Cavalli-Sforza, L; Chakraborty, R; Xiong, M; Du, R; Oefner, P; Chen, Z; Jin, L

    1999-12-01

    The timing and nature of the arrival and the subsequent expansion of modern humans into eastern Asia remains controversial. Using Y-chromosome biallelic markers, we investigated the ancient human-migration patterns in eastern Asia. Our data indicate that southern populations in eastern Asia are much more polymorphic than northern populations, which have only a subset of the southern haplotypes. This pattern indicates that the first settlement of modern humans in eastern Asia occurred in mainland Southeast Asia during the last Ice Age, coinciding with the absence of human fossils in eastern Asia, 50,000-100,000 years ago. After the initial peopling, a great northward migration extended into northern China and Siberia.

  15. Genetic evidence of an East Asian origin and paleolithic northward migration of Y-chromosome haplogroup N.

    PubMed

    Shi, Hong; Qi, Xuebin; Zhong, Hua; Peng, Yi; Zhang, Xiaoming; Ma, Runlin Z; Su, Bing

    2013-01-01

    The Y-chromosome haplogroup N-M231 (Hg N) is distributed widely in eastern and central Asia, Siberia, as well as in eastern and northern Europe. Previous studies suggested a counterclockwise prehistoric migration of Hg N from eastern Asia to eastern and northern Europe. However, the root of this Y chromosome lineage and its detailed dispersal pattern across eastern Asia are still unclear. We analyzed haplogroup profiles and phylogeographic patterns of 1,570 Hg N individuals from 20,826 males in 359 populations across Eurasia. We first genotyped 6,371 males from 169 populations in China and Cambodia, and generated data of 360 Hg N individuals, and then combined published data on 1,210 Hg N individuals from Japanese, Southeast Asian, Siberian, European and Central Asian populations. The results showed that the sub-haplogroups of Hg N have a distinct geographical distribution. The highest Y-STR diversity of the ancestral Hg N sub-haplogroups was observed in the southern part of mainland East Asia, and further phylogeographic analyses supports an origin of Hg N in southern China. Combined with previous data, we propose that the early northward dispersal of Hg N started from southern China about 21 thousand years ago (kya), expanding into northern China 12-18 kya, and reaching further north to Siberia about 12-14 kya before a population expansion and westward migration into Central Asia and eastern/northern Europe around 8.0-10.0 kya. This northward migration of Hg N likewise coincides with retreating ice sheets after the Last Glacial Maximum (22-18 kya) in mainland East Asia.

  16. Genetic Evidence of an East Asian Origin and Paleolithic Northward Migration of Y-chromosome Haplogroup N

    PubMed Central

    Peng, Yi; Zhang, Xiaoming; Ma, Runlin Z.; Su, Bing

    2013-01-01

    The Y-chromosome haplogroup N-M231 (Hg N) is distributed widely in eastern and central Asia, Siberia, as well as in eastern and northern Europe. Previous studies suggested a counterclockwise prehistoric migration of Hg N from eastern Asia to eastern and northern Europe. However, the root of this Y chromosome lineage and its detailed dispersal pattern across eastern Asia are still unclear. We analyzed haplogroup profiles and phylogeographic patterns of 1,570 Hg N individuals from 20,826 males in 359 populations across Eurasia. We first genotyped 6,371 males from 169 populations in China and Cambodia, and generated data of 360 Hg N individuals, and then combined published data on 1,210 Hg N individuals from Japanese, Southeast Asian, Siberian, European and Central Asian populations. The results showed that the sub-haplogroups of Hg N have a distinct geographical distribution. The highest Y-STR diversity of the ancestral Hg N sub-haplogroups was observed in the southern part of mainland East Asia, and further phylogeographic analyses supports an origin of Hg N in southern China. Combined with previous data, we propose that the early northward dispersal of Hg N started from southern China about 21 thousand years ago (kya), expanding into northern China 12–18 kya, and reaching further north to Siberia about 12–14 kya before a population expansion and westward migration into Central Asia and eastern/northern Europe around 8.0–10.0 kya. This northward migration of Hg N likewise coincides with retreating ice sheets after the Last Glacial Maximum (22–18 kya) in mainland East Asia. PMID:23840409

  17. Rapid Northward Spread of a Zooxanthellate Coral Enhanced by Artificial Structures and Sea Warming in the Western Mediterranean

    PubMed Central

    Serrano, Eduard; Coma, Rafel; Ribes, Marta; Weitzmann, Boris; García, María; Ballesteros, Enric

    2013-01-01

    The hermatypic coral Oculina patagonica can drive a compositional shift in shallow water benthic marine communities in the northwestern Mediterranean. Here, we analyze a long-term, large-scale observational dataset to characterize the dynamics of the species' recent northward range shift along the coast of Catalonia and examine the main factors that could have influenced this spread. The variation in the distributional range of Oculina patagonica was examined by monitoring 223 locations including natural and artificial habitats along >400 km of coastline over the last 19 years (1992–2010). Abundance of the species increased from being present in one location in 1992 to occur on 19% of the locations in 2010, and exhibited an acceleration of its spreading over time driven by the join action of neighborhood and long-distance dispersal. However, the pattern of spread diverged between artificial and natural habitats. A short lag phase and a high slope on the exponential phase characterized the temporal pattern of spread on artificial habitats in contrast to that observed on natural ones. Northward expansion has occurred at the fastest rate (22 km year−1) reported for a coral species thus far, which is sufficiently fast to cope with certain climate warming predictions. The pattern of spread suggests that this process is mediated by the interplay of (i) the availability of open space provided by artificial habitats, (ii) the seawater temperature increase with the subsequent extension of the growth period, and (iii) the particular biological features of O. patagonica (current high growth rates, early reproduction, and survival to low temperature and in polluted areas). These results are indicative of an ongoing fundamental modification of temperate shallow water assemblages, which is consistent with the predictions indicating that the Mediterranean Sea is one of the most sensitive regions to global change. PMID:23341904

  18. The IMF in NGC6611: the environmental influence on the formation of low-mass stars and brown dwarfs

    NASA Astrophysics Data System (ADS)

    Oliveira, Joana

    2005-07-01

    We propose to use HST with ACS and NICMOS to survey the central area of the young {2 Myr} cluster NGC6611 in the Eagle Nebula, with the goal of constructing the low-mass and substellar Initial Mass Function {IMF}. We plan to obtain deep images in I {F775W} and Z {F850LP} with ACS/WFC, and deep images in J {F110W} and H {F160W} for 25 NICMOS/NIC2 fields within the 202" x 202" ACS/WFC field. Using a proven technique based on the use of IZJH color-magnitude and color-color diagrams to identify and determine the masses of the low-mass pre-main sequence cluster members, we are thus able to construct the IMF down to masses of 0.02-0.03 Msun. With an intense ionizing radiation field but a relatively low density, NGC6611 provides a unique laboratory in which to test the importance of photoevaporation and density on the formation of low-mass stars and brown dwarfs, through comparison with the IMFs determined for the different environments in the Orion Nebular Cluster, Taurus and IC348. This will not only offer substantial new insight into the physics of star formation, but also have important ramifications for estimating the global star formation rates at high redshift, the efficiency of galactic chemical evolution and the contribution of sub-stellar mass objects to the baryonic dark matter content of the Universe.

  19. Role of imf orientation in the precipitation of solar wind ions into the upper atmosphere of venus.

    NASA Astrophysics Data System (ADS)

    Talha, Madeeha; Stenberg, Gabriella

    2016-07-01

    Analyzer of Space Plasma and Energetic Atoms (ASPERA-4) is used to study the precipitation of solar wind ions (H+ and He2+) into the upper atmosphere of Venus for the period of April 2006 to December 2007 as representative of solar minimum. Precipitation cases are selected and analyzed for the orbits having extreme Interplanetary Magnetic Field (IMF) orientations: IMF perpendicular to the solar wind direction (IMFperp) and IMF aligned with the solar wind direction (IMFpll ). Large number of precipitation behind terminator (nightside) is observed for IMFpll as compared to IMFperp while the reverse trend is noted for the precipitation into the dayside. This is turn favour the presence and absence of magnetic barrier (MB) for IMFperp and IMFpll respectively, as less transport to the nightside and more ions escape from dayside ionosphere during IMFperp contribute for the formation of MB. Contribution in the proton flux by both orientations in the ionosphere and in the transition region is same i.e., 104cm

  20. 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.

  1. The Non-universality of the Low-mass End of the IMF is Robust against the Choice of SSP Model

    NASA Astrophysics Data System (ADS)

    Spiniello, C.; Trager, S. C.; Koopmans, L. V. E.

    2015-04-01

    We perform a direct comparison of two state-of-the art single stellar population (SSP) models that have been used to demonstrate the non-universality of the low-mass end of the initial mass function (IMF) slope. The two public versions of the SSP models are restricted to either solar abundance patterns or solar metallicity, too restrictive if one aims to disentangle elemental enhancements, metallicity changes, and IMF variations in massive early-type galaxies (ETGs) with star formation histories different from those in the solar neighborhood. We define response functions (to metallicity and α-abundance) to extend the parameter space for each set of models. We compare these extended models with a sample of Sloan Digital Sky Survey (SDSS) ETG spectra with varying velocity dispersions. We measure equivalent widths of optical IMF-sensitive stellar features to examine the effect of the underlying model assumptions and ingredients, such as stellar libraries or isochrones, on the inference of the IMF slope down to ∼0.1 M⊙. We demonstrate that the steepening of the low-mass end of the IMF based on a non-degenerate set of spectroscopic optical indicators is robust against the choice of the stellar population model. Although the models agree in a relative sense (i.e., both imply more bottom-heavy IMFs for more massive systems), we find non-negligible differences in the absolute values of the IMF slope inferred at each velocity dispersion by using the two different models. In particular, we find large inconsistencies in the quantitative predictions of the IMF slope variations and abundance patterns when sodium lines are used. We investigate the possible reasons for these inconsistencies.

  2. THE NON-UNIVERSALITY OF THE LOW-MASS END OF THE IMF IS ROBUST AGAINST THE CHOICE OF SSP MODEL

    SciTech Connect

    Spiniello, C.; Trager, S. C.; Koopmans, L. V. E.

    2015-04-20

    We perform a direct comparison of two state-of-the art single stellar population (SSP) models that have been used to demonstrate the non-universality of the low-mass end of the initial mass function (IMF) slope. The two public versions of the SSP models are restricted to either solar abundance patterns or solar metallicity, too restrictive if one aims to disentangle elemental enhancements, metallicity changes, and IMF variations in massive early-type galaxies (ETGs) with star formation histories different from those in the solar neighborhood. We define response functions (to metallicity and α-abundance) to extend the parameter space for each set of models. We compare these extended models with a sample of Sloan Digital Sky Survey (SDSS) ETG spectra with varying velocity dispersions. We measure equivalent widths of optical IMF-sensitive stellar features to examine the effect of the underlying model assumptions and ingredients, such as stellar libraries or isochrones, on the inference of the IMF slope down to ∼0.1 M{sub ⊙}. We demonstrate that the steepening of the low-mass end of the IMF based on a non-degenerate set of spectroscopic optical indicators is robust against the choice of the stellar population model. Although the models agree in a relative sense (i.e., both imply more bottom-heavy IMFs for more massive systems), we find non-negligible differences in the absolute values of the IMF slope inferred at each velocity dispersion by using the two different models. In particular, we find large inconsistencies in the quantitative predictions of the IMF slope variations and abundance patterns when sodium lines are used. We investigate the possible reasons for these inconsistencies.

  3. Oxygen abundance in local disk and bulge: chemical evolution with a strictly universal IMF

    NASA Astrophysics Data System (ADS)

    Caimmi, R.; Milanese, E.

    2009-09-01

    This paper has two parts: one about observational constraints related to the empirical differential oxygen abundance distribution (EDOD), and the other about inhomogeneous models of chemical evolution, in particular the theoretical differential oxygen abundance distribution (TDOD). In the first part, the EDOD is deduced from subsamples related to two different samples involving (i) N=532 solar neighbourhood (SN) stars within the range, -1.5<[Fe/H]<0.5, for which the oxygen abundance has been determined both in presence and in absence of the local thermodynamical equilibrium (LTE) approximation (Ramirez et al. in Astron. Astrophys. 465:271, 2007); and (ii) N=64 SN thick disk, SN thin disk, and bulge K-giant stars within the range, -1.7<[Fe/H]<0.5, for which the oxygen abundance has been determined (Melendez et al. in Astron. Astrophys. 484:L21, 2008). A comparison is made with previous results implying use of [O/H]-[Fe/H] empirical relations (Caimmi in Astron. Nachr. 322:241, 2001b; New Astron. 12:289, 2007) related to (iii) 372 SN halo subdwarfs (Ryan and Norris in Astron. J. 101:1865, 1991); and (iv) 268 K-giant bulge stars (Sadler et al. in Astron. J. 112:171, 1996). The EDOD of the SN thick + thin disk is determined by weighting the mass, for assumed SN thick to thin disk mass ratio within the range, 0.1-0.9. In the second part, inhomogeneous models of chemical evolution for the SN thick disk, the SN thin disk, the SN thick + thin disk, the SN halo, and the bulge, are computed assuming the instantaneous recycling approximation. The EDOD data are fitted, to an acceptable extent, by their TDOD counterparts with the exception of the thin or thick + thin disk, where two additional restrictions are needed: (i) still undetected, low-oxygen abundance thin disk stars exist, and (ii) a single oxygen overabundant star is removed from a thin disk subsample. In any case, the (assumed power-law) stellar initial mass function (IMF) is universal but gas can be inhibited from

  4. Kelvin-Helmholtz Instability at Earth's magnetopause: THEMIS Observations and OpenGGCM Simulations

    NASA Astrophysics Data System (ADS)

    Kavosi, Shiva

    Magnetic reconnection is believed to be the dominant process by which solar wind plasma enters the magnetosphere. However, for periods of northward interplanetary magnetic field (IMF) reconnection is less likely at the dayside magnetopause, and Kelvin--Helmholtz (KH) waves may be important agents for plasma entry and for the excitation of ultra-low-frequency (ULF) waves. The relative importance of KH waves is controversial because no statistical data on their occurrence frequency exists. Here we survey seven years of in-situ data from the NASA THEMIS (Time History of Events and Macro scale Interactions during Substorms) mission in order to create a database of magnetopause crossings throughout the entire mission in motivation to investigate the occurrence rate of KH waves at the Earth's magnetopause. Our analysis, using very conservative criteria to positively identify KH waves, has shown that KH waves at the Earth's magnetopause are ubiquitous and are present approximately 19% of the time regardless of the solar wind conditions. This occurrence frequency is much higher than has been previously thought and suggests that KH waves may be more important for plasma transport across the magnetopause, and frequently drive magnetospheric ULF waves. Our statistical analysis shows that the occurrence rate of KH waves increases with solar wind speed, Alfven Mach number, and number density, but is mostly independent of IMF magnitude. The occurrence rate increases with the IMF cone angle and maximizes at zero clock angle at about 35% for near northward IMF, and about 10% under southward IMF conditions. Although the occurrence rate under southward IMF is significantly higher than previously detected, it is still approximately four times less than the occurrence rate under northward IMF. The previous study suggested that the irregular and temporally intermittent structure of KH waves due to dynamically active sub solar behavior under southward IMF condition may explain the

  5. Climatology of Vertical Ion Velocity and its Relationship with Large-scale FAC Based on DMSP and CHAMP Observations: Seasonal and IMF By Dependence

    NASA Astrophysics Data System (ADS)

    Luhr, H.; Kervalishvili, G.

    2015-12-01

    In this study we present climatology of vertical ion drift and its relationship with large-scale field-aligned current (LSFAC) in the Northern Hemisphere cusp region using the superposed epoch analysis (SEA) method. The dependence on the interplanetary magnetic field (IMF) Bycomponent orientation and the local season is also investigated. The three local seasons of 130 days each are defined as follows: local winter (1 January ± 65 days), combined equinoxes (1 April and 1 October ± 32 days), and local summer (1 July ± 65 days). Our results are based on DMSP (F13 and F15) and CHAMP satellite observations and NASA/GSFC's OMNI online data set during the years 2001-2005. The time and location of the vertical ion velocity peaks (> 100 m/s for upflow and <-100 m/s for downflow) in the cusp region are used as reference parameters (time and location of the event) for the SEA method. Event number distribution based on the ion velocity peaks shows no significant variations for IMF By component orientation and local season. Corresponding averaged profiles of total magnetic field Bt and IMF components, taken for flow events from both DMSP satellites and all seasons together, also show no differences in temporal variations (only negligible changes in amplitude) between upflow and downflow events. There is no systematic sign change related to flow direction in any of the three IMF components and IMF Bz is always negative. IMF By and Bz components are peaking about half an hour before the event for all considered cases. The main findings of our SEA analysis, can be summarized as follows: Vertical plasma flow, taken for both DMSP satellites together, shows no dependence on IMF By component orientation. Its amplitude is increasing towards local summer. Vertical plasma velocity is much higher in winter than during combined equinox or summer. It seems the ion density is low in winter and increases towards local summer. The plasma upflow is generally stronger than the downflow in

  6. Northward migration of the Cascadia forearc in the northwestern U.S. and implications for subduction deformation

    USGS Publications Warehouse

    Wells, R.E.; Simpson, R.W.

    2001-01-01

    Geologic and paleomagnetic data from the Cascadia forearc indicate long-term northward migration and clockwise rotation of an Oregon coastal block with respect to North America. Paleomagnetic rotation of coastal Oregon is linked by a Klamath Mountains pole to geodetically and geologically determined motion of the Sierra Nevada block to derive a new Oregon Coast-North America (OC-NA) pole of rotation and velocity field. This long-term velocity field, which is independent of Pacific Northwest GPS data, is interpreted to be the result of Basin-Range extension and Pacific-North America dextral shear. The resulting Oregon Coast pole compares favorably to those derived solely from GPS data, although uncertainties are large. Subtracting the long-term motion from forearc GPS velocities reveals ENE motion with respect to an OC reference frame that is parallel to the direction of Juan de Fuca-OC convergence and decreases inland. We interpret this to be largely the result of subduction-related deformation. The adjusted mean GPS velocities are generally subparallel to those predicted from elastic dislocation models for Cascadia, but more definitive interpretations await refinement of the present large uncertainty in the Sierra Nevada block motion. Copyright ?? The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences.

  7. Strong modulations on the Bay of Bengal monsoon onset vortex by the first northward-propagating intra-seasonal oscillation

    NASA Astrophysics Data System (ADS)

    Li, Kuiping; Li, Zhi; Yang, Yang; Xiang, Baoqiang; Liu, Yanliang; Yu, Weidong

    2016-07-01

    Monsoon onset vortex (OV) in the form of tropical cyclone is often observed in the pre-monsoon period and contributes to the subsequent abrupt establishment of summer monsoon over the Bay of Bengal (BoB). It is identified here that all historical OVs occurred during the convection-enhanced phase of the first northward-propagating intra-seasonal oscillation (FNISO). The individual contributions from the four large scale environmental fields associated with the intra-seasonal variations to the cyclone genesis are diagnosed with the aid of the genesis potential index. The significant moistening of mid-level atmosphere, which is embedded in the FNISO convection-enhanced phase, is shown to be the primary factor leading to the cyclone genesis. The water vapor budget analysis is further done to understand the governing process for the mid-level humidity increase. It is clearly seen that the vertical advection process, dominated by the anomalous vertical advection of the mean vertical water vapor gradient, plays the critical role. Hence the OVs are shown to be strongly modulated by FNISOs, both of which are important elements of the complex story of the BoB monsoon onset.

  8. Remagnetization and northward coastwise transport of Franciscan Complex rocks, northern California: a reinterpretation of the paleomagnetic data

    USGS Publications Warehouse

    Hagstru, J.T.

    1990-01-01

    Previous paleomagnetic studies of accreted oceanic rocks within the Franciscan Complex of northern California have concluded that these rocks originated far to the south of their present positions with respect to the North American continent. However, the plate motions implied by some of these paleomagnetic data are problematic (e.g., exceptional plate velocities), and uniform-polarity magnetizations in almost all of these rocks indicate the possibility of remagnetization. In this paper, Franciscan rocks in northern California are reinterpreted as having been remagnetized prior to accretion-related deformation. Paleolatitudes of subduction and remagnetization in the northern hemisphere (12?? to 33??) appear to be inversely proportional to age of accretion (middle Cretaceous to Oligocene) for the Franciscan rocks. Subsequent northward displacements (800 to 3700 km) and clockwise rotations (56?? and 154??) of these rocks inferred from the paleomagnetic data are consistent with potential displacements along the western margin of North America during late Mesozoic and Cenozoic time calculated using examples of modern subduction zones and current plate reconstruction models. -from Author

  9. A new research of the current sheet and Field aligned current system: IMF, Solar Wind influence? MLT dependence?

    NASA Astrophysics Data System (ADS)

    Yang, J.

    2015-12-01

    Field-aligned current systems (FACs) are the dominant process by which energy and momentum are transported between the magnetosphere and the ionosphere-thermosphere system. Both large- and small-scale FACs have been observed in the auroral zone and the current sheets have complicated spatial and temporal variations. However, It is argued that while the intensity of currents varies from event to event, the basic pattern will be maintained or not. We present a statistical study of the temporal and spatial characteristics of FACs using Swarm satellite, and show the IMF, Solar Wind influence and the MLT dependence of the FACs.

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

    NASA Astrophysics Data System (ADS)

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

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

  11. AE index forecast at different time scales through an ANN algorithm based on L1 IMF and plasma measurements

    NASA Astrophysics Data System (ADS)

    Pallocchia, G.; Amata, E.; Consolini, G.; Marcucci, M. F.; Bertello, I.

    2008-02-01

    The AE index is known to have two main components, one directly driven by the solar wind and the other related to the magnetotail unloading process. As regards the role played by the IMF and solar wind parameters, recently several authors used artificial neural networks (ANN) to forecast AE from solar wind data. Following this track, in this paper we present a study of the AE forecast at different time scales, from 5 min to 1 h, in order to check whether the performance of the ANN prediction varies significantly as a function of the AE time resolution.The study is based on a new ANN Elman network with Bz (in GSM) and Vx as inputs, one hidden layer containing four neurons, four context units and one output neuron. We find that the forecast AE values, during disturbed AE periods, result to be always smaller than the experimental values; on the other hand, the algorithm performance improves as the time scale increases, i.e. the total standard deviation (calculated over a test data set) between the forecast and the Kyoto AE decreases as the averaging time increases. Under the hypothesis that this decrease follows an exponential law, we find that the 1 h scale normalised standard deviation is 0.975, very close to the asymptotic value of 0.95 for an infinite averaging time. We interpret our results in the sense that the unloading component of the AE variations cannot be predicted from IMF and solar wind parameters only.

  12. Probing the Low-Mass End of the IMF in Star-Forming Regions: AWIRCam/CFHT Survey

    NASA Astrophysics Data System (ADS)

    Alves de Oliveira, Catarina; Moraux, Estelle; Bouvier, Jerôme; Burgess, Andrew; Bouy, Hervé; Marmo, Chiara; Hudelot, Patrick

    One of the most attempted goals of star formation theories is to determine the dominant process by which brown dwarfs form and the implications of the environment on its outcome. Current theories must be able to reproduce not only the observed shape of the IMF, but predict observable properties of clusters such as multiplicity, mass segregation, frequency and sizes of discs, accretion, etc. The new observational frontier is therefore the detection and characterization of very low mass objects in star forming regions, to confront model predictions from numerical simulations of the collapse of molecular clouds to the observed properties of YSOs. This is the main driver behind a WIRCam large program that has been conducted at CFHT to detect BD with masses between 1 and 30 Jupiter masses in a sample of 6 young clusters. I will present the main results obtained so far for the ρ Ophiuchi molecular cloud and IC 348, where a spectroscopic follow-up of many of these candidates is being conducted using several facilities (TNG, GTC, NTT, VLT, Gemini) to ascertain their spectral types and masses, and ultimately, to construct the low-mass end of the IMF for those star forming regions.

  13. External versus internal triggering of substorms: An information-theoretical approach

    NASA Astrophysics Data System (ADS)

    Johnson, Jay R.; Wing, Simon

    2014-08-01

    The role of external triggering of substorms through northward turning of the interplanetary magnetic field has been examined in a number of recent studies. While Hsu and McPherron (2002, 2004) argue that the strong association between external triggers defined by Lyons et al. (1997) and substorm onsets could be responsible for most substorms, Morley and Freeman (2007) argue that the association between northward interplanetary magnetic field (IMF) turnings and substorm onsets are coincidental rather than causal, because the same external triggers are also closely associated with an artificial list of substorm onsets generated with the Minimal Substorm Model, which has no requirement of northward IMF turning. We examine an expanded list of substorms using conditional redundancy, an entropy-based measure of conditional dependency, to examine whether northward IMF turning as an external trigger provides any additional information about substorm onset beyond knowing that there has been a period of sustained loading of energy flux (southward IMF). Our analysis reveals that only a few percent additional information is provided by the northward turning criterion, which is consistent with the statistics of surrogate data sets of external triggers constructed to coincide with 2% of substorms. We therefore conclude that northward turning of the IMF is, in general, coincidentally, rather than causally, associated with substorm onsets.

  14. Hall-MHD simulations of the magnetosphere-northward solar wind interface : the Kelvin-Helmholtz instability as an entry mechanism for the solar wind through mixing and reconnections

    NASA Astrophysics Data System (ADS)

    Leroy, Matthieu; Keppens, Rony

    2016-04-01

    The transfer of matter from the solar-wind to the Earth's magnetosphere during southward solar wind is mostly well understood but the processes governing the same phenomenon during northward solar wind remains to be fully apprehended. Numerous numerical studies have investigated the topic with many interesting results but most of these were considering two-dimensional situations with simplified magnetic configuration and often neglecting the inhomogeneities for the sake of clarity. Given the typical parameters at the magnetosphere-solar wind interface, the situation must be considered in the frame of Hall-MHD, due to the fact that the current layers widths and the gradient lengths can be in the order of the ion inertial length. As a consequence of Hall-MHD creating a third vector component from two planar ones, and also because magnetic perturbations can affect the field configuration at a distance in all directions and not only locally, three-dimensional treatment is necessary. In this spirit three-dimensional simulations of a configuration approaching the conditions leading to the development of Kelvin-Helmholtz instabilities at the flank of the magnetosphere during northward oriented solar-wind are performed as means to study the entry of solar-wind matter into Earth's magnetic field. In the scope of assessing the effect of the Hall-term in the physical processes, the simulations are also performed in the MHD frame. Furthermore the influence of the density and velocity jump through the shear layer on the rate of mass entering the magnetosphere is explored. Indeed, depending on the exact values of the physical quantities, the Kelvin-Helmholtz instability may have to compete with secondary instabilities and the non-linear phase may exhibit vortex merging and large-scale structures reorganisation, creating very different mixing layers, or generate different reconnection sites, locally and at a distance. These different configurations may have discernible signatures

  15. Model and observation comparison of the universal time and IMF by dependence of the ionospheric polar hole

    NASA Technical Reports Server (NTRS)

    Sojka, J. J.; Schunk, R. W.; Hoegy, W. R.; Grebowsky, J. M.

    1991-01-01

    The polar ionospheric F-region often exhibits regions of marked density depletion. These depletions have been observed by a variety of polar orbiting ionospheric satellites over a full range of solar cycle, season, magnetic activity, and universal time (UT). An empirical model of these observations has recently been developed to describe the polar depletion dependence on these parameters. Specifically, the dependence has been defined as a function of F10.7 (solar), summer or winter, Kp (magnetic), and UT. Polar cap depletions have also been predicted /1, 2/ and are, hence, present in physical models of the high latitude ionosphere. Using the Utah State University Time Dependent Ionospheric Model (TDIM) the predicted polar depletion characteristics are compared with those described by the above empirical model. In addition, the TDIM is used to predict the IMF By dependence of the polar hole feature.

  16. IMF, SFR and stellar depletion in the local Galactic plane, based on improved Hipparcos samples of single stars

    NASA Astrophysics Data System (ADS)

    Dawson, S. A.; Schröder, K.-P.

    2010-05-01

    We have used the recently reduced Hipparcos data and the Washington Double Star catalogue to derive two volume- and magnitude-limited samples of single stars in the Galactic plane. The star count method has been used to compare synthetic to empirical samples of stars within both the main sequence and the evolved regions of the Hertzsprung-Russell diagram. Corrections have been made for unrecognized binaries and the residual incompleteness of the Hipparcos catalogue. Two methods of binary reduction have been compared, a flat 71 per cent binary fraction (including multiples) and a mass-dependent binary fraction, which decreases with primary mass from 71 to 57 per cent. A semi-empirical relation between the vertical scaleheight and stellar age has been derived from kinematic data provided by the OSACA data base. This relation is used to prescribe the loss of stellar content vertically from the plane due to heating. When employing the fixed binary ratio, we find that the best fit is provided by a Scalo initial mass function (IMF) with an exponent of 1.85 +/- 0.15, together with an average Galactic thin-disc star formation rate (SFR) of 618(+/-15) starsMyr-1kpc-3 with 1211(+/-30)MsolarMyr-1kpc-3 for single stars with M* > 0.9Msolar. The application of the mass-dependent variable binary ratio yields more single stars at lower mass and hence a steeper (Γ = 2.2,..., 2.3) IMF and an increased SFR.

  17. What physics determines the peak of the IMF? Insights from the structure of cores in radiation-magnetohydrodynamic simulations

    NASA Astrophysics Data System (ADS)

    Krumholz, Mark R.; Myers, Andrew T.; Klein, Richard I.; McKee, Christopher F.

    2016-08-01

    As star-forming clouds collapse, the gas within them fragments to ever-smaller masses. Naively one might expect this process to continue down to the smallest mass that is able to radiate away its binding energy on a dynamical time-scale, the opacity limit for fragmentation, at ˜0.01 M⊙. However, the observed peak of the initial mass function (IMF) lies a factor of 20-30 higher in mass, suggesting that some other mechanism halts fragmentation before the opacity limit is reached. In this paper we analyse radiation-magnetohydrodynamic simulations of star cluster formation in typical Milky Way environments in order to determine what physical process limits fragmentation in them. We examine the regions in the vicinity of stars that form in the simulations to determine the amounts of mass that are prevented from fragmenting by thermal and magnetic pressure. We show that, on small scales, thermal pressure enhanced by stellar radiation heating is the dominant mechanism limiting the ability of the gas to further fragment. In the brown dwarf mass regime, ˜0.01 M⊙, the typical object that forms in the simulations is surrounded by gas whose mass is several times its own that is unable to escape or fragment, and instead is likely to accrete. This mechanism explains why ˜0.01 M⊙ objects are rare: unless an outside agent intervenes (e.g. a shock strips away the gas around them), they will grow by accreting the warmed gas around them. In contrast, by the time stars grow to masses of ˜0.2 M⊙, the mass of heated gas is only tens of percent of the central star mass, too small to alter its final mass by a large factor. This naturally explains why the IMF peak is at ˜0.2 M⊙.

  18. Spectroscopy of brown dwarf candidates in IC 348 and the determination of its substellar IMF down to planetary masses

    NASA Astrophysics Data System (ADS)

    Alves de Oliveira, C.; Moraux, E.; Bouvier, J.; Duchêne, G.; Bouy, H.; Maschberger, T.; Hudelot, P.

    2013-01-01

    Context. Brown dwarfs represent a sizable fraction of the stellar content of our Galaxy and populate the transition between the stellar and planetary mass regime. There is, however, no agreement on the processes responsible for their formation. Aims: We have conducted a large survey of the young, nearby cluster IC 348, to uncover its low-mass brown dwarf population and have studied the cluster properties in the substellar regime. Methods: Deep optical and near-IR images taken with MegaCam and WIRCam at the Canada-France-Hawaii Telescope (CFHT) were used to select photometric candidate members. A spectroscopic follow-up of a large fraction of the candidates was conducted to assess their youth and membership. Results: We confirmed spectroscopically 16 new members of the IC 348 cluster, including 13 brown dwarfs, contributing significantly to the substellar census of the cluster, where only 30 brown dwarfs were previously known. Five of the new members have a L0 spectral type, the latest-type objects found to date in this cluster. At 3 Myr, evolutionary models estimate these brown dwarfs to have a mass of ~13 MJup. Combining the new members with previous census of the cluster, we constructed the initial mass function (IMF) complete down to 13 MJup. Conclusions: The IMF of IC 348 is well fitted by a log-normal function and we do not see evidence for variations of the mass function down to planetary masses when compared to other young clusters. Based on observations obtained with WIRCam, a joint project of CFHT, Taiwan, Korea, Canada, France, and MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institute National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

  19. Tectonic and climatic control on river profiles for rivers draining northwards from the Pamir and Kunlun (Central Asia).

    NASA Astrophysics Data System (ADS)

    Brookfield, M. E.

    2004-12-01

    - Oligocene collisions of India with magmatic arcs south of Asia can be followed in some detail in the Pakistan Himalaya though not in the Indian Himalaya. d) The river profiles and courses can be directly related to the major tectonic development of the arc, modified by the influence of Quaternary climatic change (Molnar and England, 1990). The main drainage divide is along the crest of the fundamentally Mesozoic Hindu Kush and Karakoram ranges and extensions. Despite the late Cenozoic uplift of the Pamir, only the Pyandzh river cuts across the Pamir range in a course that corresponds with a geophysical but not a geological boundary. The rest of the rivers, with a few exceptions, tend to run in valleys parallel to the arc, except to the west and east. To the west, in northern Afghanistan the rivers still run northward from the westward extension of the Hindu Kush. To the east the main rivers have headwaters far within the Tibetan plateau and cut, with incredibly steep gradients across the Kun Lun and related ranges - testifying to the latest Tertiary development of this range. REFERENCES Brookfield, 1998. The evolution of the great river systems of southern Asia during the Cenozoic India-Asia collision: rivers draining southwards. Geomorphology, 22: 285-312. Dewey, J.F., Cande, S. and Pitman III, W.C., 1989. Tectonic evolution of the India/Eurasia collision zone. Eclogae geologica Helvetica, 82: 717-734. England, P. and Molnar, P., 1990. Surface uplift, uplift of rocks and exhumation of rocks. Geology, 18: 1173-1177. Molnar, P. and England, P., 1990. Late Cenozoic uplift of mountain ranges and global climatic change: chicken or egg? Nature, 346: 29-34.

  20. Spread-F during the magnetic storm of 22 January 2004 at low latitudes: Effect of IMF-Bz in relation to local sunset time

    NASA Astrophysics Data System (ADS)

    Rastogi, R. G.; Chandra, H.; Janardhan, P.; Hoang, Thai Lan; Condori, Louis; Pant, T. K.; Prasad, D. S. V. V. D.; Reinisch, B.

    2014-08-01

    The paper describes the results of spread-F at low latitude stations around the world during the magnetic storm starting at 0130 UT on 22 January 2004. The storm can be divided into two phases, first phase up to 1000 UT when interplanetary magnetic field IMF-Bz was highly fluctuating around a small positive value and the second phase after a sudden large southward turning of IMF-Bz at 1030 UT. The first phase produced strong spread-F at Jicamarca, Sao Luis, and Ascension Island and caused complete inhibition of spread-F at Thumba and Waltair in India. It generated weak spread-F at Ho Chi Minh City in Vietnam and strong spread-F at Hainan and Chung Li. The strong spread-F at Hainan and Chung Li were caused by the positive IMF-Bz during the first phase of the storm and not by the negative pulse of IMF-Bz at 1000 UT.

  1. The SL2S Galaxy-scale Lens Sample. V. Dark Matter Halos and Stellar IMF of Massive Early-type Galaxies Out to Redshift 0.8

    NASA Astrophysics Data System (ADS)

    Sonnenfeld, Alessandro; Treu, Tommaso; Marshall, Philip J.; Suyu, Sherry H.; Gavazzi, Raphaël; Auger, Matthew W.; Nipoti, Carlo

    2015-02-01

    We investigate the cosmic evolution of the internal structure of massive early-type galaxies over half of the age of the universe. We perform a joint lensing and stellar dynamics analysis of a sample of 81 strong lenses from the Strong Lensing Legacy Survey and Sloan ACS Lens Survey and combine the results with a hierarchical Bayesian inference method to measure the distribution of dark matter mass and stellar initial mass function (IMF) across the population of massive early-type galaxies. Lensing selection effects are taken into account. We find that the dark matter mass projected within the inner 5 kpc increases for increasing redshift, decreases for increasing stellar mass density, but is roughly constant along the evolutionary tracks of early-type galaxies. The average dark matter slope is consistent with that of a Navarro-Frenk-White profile, but is not well constrained. The stellar IMF normalization is close to a Salpeter IMF at log M * = 11.5 and scales strongly with increasing stellar mass. No dependence of the IMF on redshift or stellar mass density is detected. The anti-correlation between dark matter mass and stellar mass density supports the idea of mergers being more frequent in more massive dark matter halos.

  2. Detecting the Gender Dimension of the Choice of the Teaching Profession Prior to the Economic Crisis and IMF (International Monetary Fund) Memorandum in Greece--A Case Study

    ERIC Educational Resources Information Center

    Asimaki, Anna; Vergidis, Dimitris K.

    2013-01-01

    The purpose of this research paper is the investigation of, and the sociological approach to, and interpretation of the attitudes of male and female students in the University Department of Primary Education (U.D.P.E.) at the University of Patras in Greece, before the enforcement of the IMF Memorandum, concerning the choice of the teaching…

  3. THE SL2S GALAXY-SCALE LENS SAMPLE. V. DARK MATTER HALOS AND STELLAR IMF OF MASSIVE EARLY-TYPE GALAXIES OUT TO REDSHIFT 0.8

    SciTech Connect

    Sonnenfeld, Alessandro; Treu, Tommaso; Marshall, Philip J.; Suyu, Sherry H.; Gavazzi, Raphaël; Auger, Matthew W.; Nipoti, Carlo

    2015-02-20

    We investigate the cosmic evolution of the internal structure of massive early-type galaxies over half of the age of the universe. We perform a joint lensing and stellar dynamics analysis of a sample of 81 strong lenses from the Strong Lensing Legacy Survey and Sloan ACS Lens Survey and combine the results with a hierarchical Bayesian inference method to measure the distribution of dark matter mass and stellar initial mass function (IMF) across the population of massive early-type galaxies. Lensing selection effects are taken into account. We find that the dark matter mass projected within the inner 5 kpc increases for increasing redshift, decreases for increasing stellar mass density, but is roughly constant along the evolutionary tracks of early-type galaxies. The average dark matter slope is consistent with that of a Navarro-Frenk-White profile, but is not well constrained. The stellar IMF normalization is close to a Salpeter IMF at log M {sub *} = 11.5 and scales strongly with increasing stellar mass. No dependence of the IMF on redshift or stellar mass density is detected. The anti-correlation between dark matter mass and stellar mass density supports the idea of mergers being more frequent in more massive dark matter halos.

  4. East flank of the Sibumasu block in NW Thailand and Myanmar and its possible northward continuation into Yunnan: a review and suggested tectono-stratigraphic interpretation

    NASA Astrophysics Data System (ADS)

    Ridd, Michael F.

    2015-05-01

    The east flank of the Sibumasu block was a passive continental margin, and in NW Thailand is marked by the absence of the autochthonous Middle Permian-Triassic platform carbonates which are widespread across the rest of Sibumasu further west. Instead, the carbonates are represented by hemipelagic cherts, mudstones and sandstones including turbidites. During the northward drift of Sibumasu, following its Early Permian rifting from Gondwana, an accretionary complex was present where Palaeotethyan pelagic rocks as old as Devonian were subducted beneath the Sukhothai volcanic arc. At the time of Sibumasu's collision with the Sukhothai arc, beginning in the Middle Triassic, the accretionary complex was thrust westwards across the east flank of Sibumasu. It is suggested that in the Late Triassic the thrust pile which had been the accretionary complex underwent erosion and was the source of terrigenous clastic rocks deposited further west in a foredeep basin. The boundary of Sibumasu's east flank with the Permo-Triassic carbonate platform further west is the arcuate Mae Ping-Nam Teng Fault system. Notwithstanding later Cenozoic strike-slip displacement, those faults (as well as the Mae Yuam Fault) are interpreted to have had an earlier history of westward-directed Indosinian thrusting. Northwards in Myanmar and Yunnan the Sibumasu Permo-Triassic carbonate shelf continues as the Shan Plateau and Baoshan Block. The east flank is represented by the Changning-Menglian Belt, and the Palaeotethys 'cryptic suture' in Thailand possibly joins with the Lancangjiang Suture.

  5. Dichothermal layer deepening in relation with halocline depth change associated with northward shrinkage of North Pacific western subarctic gyre in early 2000s

    NASA Astrophysics Data System (ADS)

    Nagano, Akira; Wakita, Masahide; Watanabe, Shuichi

    2016-02-01

    In the western subarctic North Pacific, a wind-driven cyclonic circulation, called the western subarctic gyre (WSAG), exists. We examined year-to-year changes of the gyre and hydrographic structures, applying the altimetry-based gravest empirical mode (AGEM) method to hydrographic and altimetric sea surface height (SSH) data, and relation to the in situ variation of the temperature minimum layer, i.e., the dichothermal layer, depth at station K2 (47∘ N, 160∘ E). The AGEM-based geostrophic volume transport and the streamfunction of the WSAG in the top 1000-dbar layer show that the gyre changes substantially. From the late 1990s to the mid-2000s, the gyre shrunk northward. Due to the shrinkage, the halocline bottom, which is equivalent to the top of the main pycnocline, deepens at K2 outside the central part of the gyre. The downward displacement of the dichothermal layer at K2 was found to be significantly related to that of the underlying halocline due to the northward shrinkage of the WSAG.

  6. Paleomagnetism of basaltic basement rocks from IODP Hole C0012A, Exp. 322: Constraints on age, northward migration and rotation of Shikoku Basin

    NASA Astrophysics Data System (ADS)

    Oda, H.; Yamamoto, Y.; Lin, W.; Ishizuka, O.; Zhao, X.; Wu, H.; Torii, M.

    2012-12-01

    The Integrated Ocean Drilling Program Expedition 322 penetrated sediment-basement boundary and recovered successive cores from basaltic basement at Site C0012 near the crest of the Kashinosaki Knoll in the Shikoku Basin. Paleomagnetic measurements were conducted on 29 samples to understand the polarity of magnetization, paleolatitude and tectonic rotation. Paleomagnetic samples suffer from drilling induced remanent magnetization (DIRM), however, alternating field demagnetization at 10 mT was enough to remove DIRM to extract characteristic remanent magnetization (ChRM). Paleomagnetic measurements show that the ChRM has reversed polarity and the magnetic anomaly at the site could be correlated to anomaly C6Ar (20.7-21.1Ma). Average inclination was obtained from 21 samples and paleolatitude was calculated as 26.5±5.5°N suggesting the northward latitudinal translation of 688±611 km since the formation of the seafloor, which is consistent with the northward latitudinal shift of Philippine Sea Plate (Yamazaki et al., 2010). Reconstruction of tectonic rotation was also attempted by using viscous remanent magnetization (VRM) acquired during Brunhes Chron. VRM components were extracted as intersections of great circles from overlapping DIRM and ChRM. The rotation angle could be calculated as 0.6±16.7° clockwise suggesting that the drilled site did not experience detectable rotation since the formation of the Shikoku Basin.

  7. Fault geometry and cumulative offsets in the central Coast Ranges, California: Evidence for northward increasing slip along the San Gregorio-San Simeon-Hosgri fault

    USGS Publications Warehouse

    Langenheim, V.E.; Jachens, R.C.; Graymer, R.W.; Colgan, J.P.; Wentworth, C.M.; Stanley, R.G.

    2012-01-01

    Estimates of the dip, depth extent, and amount of cumulative displacement along the major faults in the central California Coast Ranges are controversial. We use detailed aeromagnetic data to estimate these parameters for the San Gregorio–San Simeon–Hosgri and other faults. The recently acquired aeromagnetic data provide an areally consistent data set that crosses the onshore-offshore transition without disruption, which is particularly important for the mostly offshore San Gregorio–San Simeon–Hosgri fault. Our modeling, constrained by exposed geology and in some cases, drill-hole and seismic-reflection data, indicates that the San Gregorio–San Simeon–Hosgri and Reliz-Rinconada faults dip steeply throughout the seismogenic crust. Deviations from steep dips may result from local fault interactions, transfer of slip between faults, or overprinting by transpression since the late Miocene. Given that such faults are consistent with predominantly strike-slip displacement, we correlate geophysical anomalies offset by these faults to estimate cumulative displacements. We find a northward increase in right-lateral displacement along the San Gregorio–San Simeon–Hosgri fault that is mimicked by Quaternary slip rates. Although overall slip rates have decreased over the lifetime of the fault, the pattern of slip has not changed. Northward increase in right-lateral displacement is balanced in part by slip added by faults, such as the Reliz-Rinconada, Oceanic–West Huasna, and (speculatively) Santa Ynez River faults to the east.

  8. From Stars to Super-Planets: The Low-Mass IMF in the Young Cluster IC348

    NASA Technical Reports Server (NTRS)

    Najita, Joan R.; Tiede, Glenn P.; Carr, John S.

    2000-01-01

    We investigate the low-mass population of the young cluster IC348 down to the deuterium-burning limit, a fiducial boundary between brown dwarf and planetary mass objects, using a new and innovative method for the spectral classification of late-type objects. Using photometric indices, constructed from HST/NICMOS narrow-band imaging, that measure the strength of the 1.9 micron water band, we determine the spectral type and reddening for every M-type star in the field, thereby separating cluster members from the interloper population. Due to the efficiency of our spectral classification technique, our study is complete from approximately 0.7 solar mass to 0.015 solar mass. The mass function derived for the cluster in this interval, dN/d log M alpha M(sup 0.5), is similar to that obtained for the Pleiades, but appears significantly more abundant in brown dwarfs than the mass function for companions to nearby sun-like stars. This provides compelling observational evidence for different formation and evolutionary histories for substellar objects formed in isolation vs. as companions. Because our determination of the IMF is complete to very low masses, we can place interesting constraints on the role of physical processes such as fragmentation in the star and planet formation process and the fraction of dark matter in the Galactic halo that resides in substellar objects.

  9. Bifurcation and Hysteresis of the Magnetospheric Structure with a varying Southward IMF: Field Topology and Global Three-dimensional Full Particle Simulations

    NASA Technical Reports Server (NTRS)

    Cai, DongSheng; Tao, Weinfeng; Yan, Xiaoyang; Lembege, Bertrand; Nishikawa, Ken-Ichi

    2007-01-01

    Using a three-dimensional full electromagnetic particle model (EMPM), we have performed global simulations of the interaction between the solar wind and the terrestrial magnetosphere, and have investigated its asymptotic stability. The distance between the dayside magnetopause subsolar point and the Earth center, R(sub mp) is measured, as the intensity of southward IMF |B(sub z)| is slowly varying. Based on the field topology theory, one analyzes the variation of R(sub mp) as a reference index of the dynamics of this interaction, when IMF |B(sub z)| successively increases and decreases to its original value. Two striking results are observed. First, as the IMF |B(sub z)| increases above a critical value, the variation of R(sub mp) suddenly changes (so called 'bifurcation' process in field topology). Above this critical value, the overall magnetic field topology changes drastically and is identified as being the signature of magnetic reconnection at the subsolar point on the magnetopause. Second, this subsolar point recovers its original location R(sub mp) by following different paths as the IMF |B(sub z)| value increases (from zero to a maximum fixed value) and decreases (from this maximum to zero) passing through some critical values. These different paths are the signature of 'hysteresis' effect, and are characteristic of the so-called 'subcritical-type' bifurcation. This hysteresis signature indicates that dissipation processes take place via an energy transfer from the solar wind to the magnetosphere by some irreversible way, which leads to a drastic change in the magnetospheric field topology. This hysteresis is interpreted herein as a consequence of the magnetic reconnection taking place at the dayside magnetopause. The field topology reveals to be a very powerful tool to analyze the signatures of three-dimensional magnetic reconnection without the obligation for determining the mechanisms responsible for, and the consequences of the reconnection on the

  10. How the IMF By induces a By component in the closed magnetosphere and how it leads to asymmetric currents and convection patterns in the two hemispheres

    NASA Astrophysics Data System (ADS)

    Tenfjord, P.; Østgaard, N.; Snekvik, K.; Laundal, K. M.; Reistad, J. P.; Haaland, S.; Milan, S. E.

    2015-11-01

    We used the Lyon-Fedder-Mobarry global magnetohydrodynamics model to study the effects of the interplanetary magnetic field (IMF) By component on the coupling between the solar wind and magnetosphere-ionosphere system. When the IMF reconnects with the terrestrial magnetic field with IMF By≠0, flux transport is asymmetrically distributed between the two hemispheres. We describe how By is induced in the closed magnetosphere on both the dayside and nightside and present the governing equations. The magnetosphere imposes asymmetric forces on the ionosphere, and the effects on the ionospheric flow are characterized by distorted convection cell patterns, often referred to as "banana" and "orange" cell patterns. The flux asymmetrically added to the lobes results in a nonuniform induced By in the closed magnetosphere. By including the dynamics of the system, we introduce a mechanism that predicts asymmetric Birkeland currents at conjugate foot points. Asymmetric Birkeland currents are created as a consequence of y directed tension contained in the return flow. Associated with these currents, we expect fast localized ionospheric azimuthal flows present in one hemisphere but not necessarily in the other. We also present current density measurements from Active Magnetosphere and Planetary Electrodynamics Response Experiment that are consistent with this picture. We argue that the induced By produces asymmetrical Birkeland currents as a consequence of asymmetric stress balance between the hemispheres. Such an asymmetry will also lead to asymmetrical foot points and asymmetries in the azimuthal flow in the ionosphere. These phenomena should therefore be treated in a unified way.

  11. Northward laramide thrusting in the quitovac region, northwestern sonora, mexico: Implications for the juxtaposition of paleoproterozoic basement blocks and the mojave-sonora megashear hypothesis

    USGS Publications Warehouse

    Iriondo, A.; Martinez-Torres, L. M.; Kunk, M.J.; Atkinson, W.W.; Premo, W.R.; McIntosh, W.C.

    2005-01-01

    Restoration of 12%-30% Basin and Range extension allows direct interpretation of ductile fabrics associated with a stack of Laramide thrust faults in the Quito- vac region in northwestern Sonora. The inferred direction of displacement of these thrusts varies gradually from N63??W to N23??E and is interpreted to represent a clockwise rotation of the direction of Laramide thrusting through time. The thrust faults represent a piggy-back sequence of thrusting propagating north, toward the foreland. The average direction and sense of displacement of the thrusts is N18??W, and the cumulative 45 km of estimated northward-directed displacement corresponds to ???86% of shortening. ?? 2005 Geological Society of America.

  12. A case study of Ionospheric storm effects during long-lasting southward IMF Bz driven geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Liu, J., Sr.

    2014-12-01

    Multiple instrumental observations including GPS TEC, foF2 and hmF2 from ionosondes, vertical ion drift measurements from C/NOFS, magnetometer data and far-ultraviolet airglow measured by TIMED/GUVI are used to investigate the profound ionospheric disturbances at mid- and low-latitudes during the 14-17 July 2012 geomagnetic storm event, which was featured by prolonged southward interplanetary geomagnetic field component for about 30 hours below -10 nT. In the East Asian/Australian sector, latitudinal profile of TEC variations in the main phase were characterized by three bands of increments and separated by weak depressions in the Equatorial Ionospheric Anomaly (EIA) crest regions, which were caused by the combined effects of disturbance dynamo electric fields (DDEF) and equatorward neutral winds. In the recovery phase, strong inhibition of EIA occurred and the summer crest of EIA disappeared on 16 July due to the combined effects of intrusion of neutral composition disturbance zone as shown by the TIME/GUVI O/N2 measurements and long-lasting daytime westward DDEF inferred from the equatorial electric electrojet (EEJ) observations. The transit time of DDEF over the dip equator from westward to eastward is around 2200 LT. In the American longitude, the salient ionospheric disturbances in the summer hemisphere were characterized by daytime periodical intrusion of negative phase for three consecutive days in the recovery phase, preceded by storm enhanced density (SED) plume in the initial phase. In addition, multiple short-lived prompt penetration electric fields (PPEF) appeared during stable southward IMF Bz in the recovery phase and were responsible for enhanced the EIA and equatorial ionospheric uplift around sunset.

  13. Fitness consequences of northward dispersal as possible adaptation to climate change, using experimental translocation of a migratory passerine.

    PubMed

    Burger, Claudia; Nord, Andreas; Nilsson, Jan-Åke; Gilot-Fromont, Emmanuelle; Both, Christiaan

    2013-01-01

    Climate change leads to rapid, differential changes in phenology across trophic levels, often resulting in temporal mismatches between predators and their prey. If a species cannot easily adjust its timing, it can adapt by choosing a new breeding location with a later phenology of its prey. In this study, we experimentally investigated whether long-distance dispersal to northern breeding grounds with a later phenology could be a feasible process to restore the match between timing of breeding and peak food abundance and thus improve reproductive success. Here, we report the successful translocation of pied flycatchers (Ficedula hypoleuca) to natural breeding sites 560 km to the Northeast. We expected translocated birds to have a fitness advantage with respect to environmental phenology, but to potentially pay costs through the lack of other locally adapted traits. Translocated individuals started egg laying 11 days earlier than northern control birds, which were translocated only within the northern site. The number of fledglings produced was somewhat lower in translocated birds, compared to northern controls, and fledglings were in lower body condition. Translocated individuals were performing not significantly different to control birds that remained at the original southern site. The lack of advantage of the translocated individuals most likely resulted from the exceptionally cold spring in which the experiment was carried out. Our results, however, suggest that pied flycatchers can successfully introduce their early breeding phenotype after dispersing to more northern areas, and thus that adaptation through dispersal is a viable option for populations that get locally maladapted through climate change.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  15. Evolution of the Rodgers Creek–Maacama right-lateral fault system and associated basins east of the northward-migrating Mendocino Triple Junction, northern California

    USGS Publications Warehouse

    McLaughlin, Robert J.; Sarna-Wojcicki, Andrei M.; Wagner, David L.; Fleck, Robert J.; Langenheim, V.E.; Jachens, Robert C.; Clahan, Kevin; Allen, James R.

    2012-01-01

    The Rodgers Creek–Maacama fault system in the northern California Coast Ranges (United States) takes up substantial right-lateral motion within the wide transform boundary between the Pacific and North American plates, over a slab window that has opened northward beneath the Coast Ranges. The fault system evolved in several right steps and splays preceded and accompanied by extension, volcanism, and strike-slip basin development. Fault and basin geometries have changed with time, in places with younger basins and faults overprinting older structures. Along-strike and successional changes in fault and basin geometry at the southern end of the fault system probably are adjustments to frequent fault zone reorganizations in response to Mendocino Triple Junction migration and northward transit of a major releasing bend in the northern San Andreas fault. The earliest Rodgers Creek fault zone displacement is interpreted to have occurred ca. 7 Ma along extensional basin-forming faults that splayed northwest from a west-northwest proto-Hayward fault zone, opening a transtensional basin west of Santa Rosa. After ca. 5 Ma, the early transtensional basin was compressed and extensional faults were reactivated as thrusts that uplifted the northeast side of the basin. After ca. 2.78 Ma, the Rodgers Creek fault zone again splayed from the earlier extensional and thrust faults to steeper dipping faults with more north-northwest orientations. In conjunction with the changes in orientation and slip mode, the Rodgers Creek fault zone dextral slip rate increased from ∼2–4 mm/yr 7–3 Ma, to 5–8 mm/yr after 3 Ma. The Maacama fault zone is shown from several data sets to have initiated ca. 3.2 Ma and has slipped right-laterally at ∼5–8 mm/yr since its initiation. The initial Maacama fault zone splayed northeastward from the south end of the Rodgers Creek fault zone, accompanied by the opening of several strike-slip basins, some of which were later uplifted and compressed

  16. Boundary Layer Formation in the Magnetotail: Geotail Observations and Comparisons with a Global MHD Simulation

    NASA Technical Reports Server (NTRS)

    Raeder, J.; Berchem, J.; Ashour-Abdalla, M.; Frank, L. A.; Paterson, W. R.; Ackerson, K. L.; Kokubun, S.; Yamamoto, T.; Slavin, J. A.

    1997-01-01

    We present Geotail plasma and field observations from the middle magnetotail near X(sub GSE) = -46 R(sub E) for the time period 1400 to 1800 UT on December 14, 1994. During that period, the Wind satellite monitored the solar wind plasma and interplanetary magnetic field (IMF) upstream of the bow shock. The IMF was northward and the plasma parameters near average. Geotail observed slow tailward flows and a northward field. The plasma and field parameters indicate that Geotail is either in the plasma sheet or in a boundary layer. We used the Wind solar wind plasma and IMF data as input for a global simulation of that time interval. Comparison of the simulation results with the observational data show very good overall agreement of the magnitudes of the plasma and field parameters. In particular, the simulation reproduces the slow tailward flows and northward field found at Geotail. Small scale temporal, variations are less well reproduced. The simulation shows the formation of a broad boundary layer (which we call tail flank boundary layer, TFBL) that consists of closed flux which is formed by magnetic magnetic reconnection of IMF and lobe field lines. The simulation results indicate that Geotail is located very close to the TFBL and may have entered the TFBL proper. We show that the TFBL plays an important role in energy transport from the solar wind into the magnetosphere during northward IMF conditions.

  17. The effect of the changing polarity and neutral sheet of the IMF on the cosmic ray diurnal anisotropy at neutron monitor energies

    NASA Technical Reports Server (NTRS)

    Van Staden, M. L.; Potgieter, M. S.

    1991-01-01

    A drift with a simulated wavy neutral sheet have been used to study the effects of the reversal of the solar magnetic field every 11 years and the changes in the waviness of the heliospheric neutral sheet, corresponding to changes in solar activity, on the diurnal anisotropy at an energy of 20 GeV. The results indicate that the long-term behavior of the diurnal anisotropy, especially the phase shift from one solar minimum period to another, which seems to depend on the polarity of the IMF, has a theoretical explanation in the drift picture of the modulation of cosmic rays in the heliosphere.

  18. Intertidal biofilm distribution underpins differential tide-following behavior of two sandpiper species (Calidris mauri and Calidris alpina) during northward migration

    NASA Astrophysics Data System (ADS)

    Jiménez, Ariam; Elner, Robert W.; Favaro, Corinna; Rickards, Karen; Ydenberg, Ronald C.

    2015-03-01

    The discovery that some shorebird species graze heavily on biofilm adds importance to elucidating coastal processes controlling biofilm, as well as impetus to better understand patterns of shorebird use of intertidal flats. Western sandpipers (Calidris mauri) and dunlin (Calidris alpina) stopover in the hundreds of thousands on the Fraser River estuary, British Columbia, Canada, during northward migration to breeding areas. Western sandpipers show greater modification of tongue and bill morphology for biofilm feeding than dunlin, and their diet includes more biofilm. Therefore, we hypothesized that these congeners differentially use the intertidal area. A tide following index (TFI) was used to describe their distributions in the upper intertidal during ebbing tides. Also, we assessed sediment grain size, biofilm (= microphytobenthic or MPB) biomass and invertebrate abundance. Foraging dunlin closely followed the ebbing tide line, exploiting the upper intertidal only as the tide retreated through this area. In contrast, western sandpipers were less prone to follow the tide, and spent more time in the upper intertidal. Microphytobenthic biomass and sediment water content were highest in the upper intertidal, indicating greater biofilm availability for shorebirds in the first 350 m from shore. Invertebrate density did not differ between sections of the upper intertidal. Overall, western sandpiper behaviour and distribution more closely matched MPB biofilm availability than invertebrate availability. Conservation of sandpipers should consider physical processes, such as tides and currents, which maintain the availability of biofilm, a critical food source during global migration.

  19. A Trend in the Northward Transport of Saharan Dust and Its Links to the Trend in North Atlantic Tropical Cyclone Energy

    NASA Astrophysics Data System (ADS)

    Wong, S.; Dessler, A. E.; Mahowald, N.; Colarco, P.; da Silva, A.

    2007-05-01

    During late spring and early fall, Saharan dust is transported toward the tropical North Atlantic Ocean by African easterly waves. The warm and dry anomalies associated with the Saharan dust, the Saharan air layer, can suppress the tropical cyclone (TC) activity over the tropical North Atlantic Ocean. On the other hand, it is well known that increasing sea surface temperatures (SSTs) over the tropical North Atlantic Ocean is responsible for the increasing tropical cyclone intensity in the last two decades. In this study, we analyze two 27-year simulations (MATCH and GEOS-4) of dust transport over the tropical North Atlantic Ocean using, respectively, NCEP reanalysis and GMAO assimilated winds and temperatures for 1979-2005. We evaluate the trends in the transport of Saharan dust together with the trends in surface temperatures and TC energy over the North Atlantic Ocean. We find that the increasing trend in TC energy has a spatial pattern similar to the trend in covective available potential energy (CAPE), which is further related to both increasing trends in sea surface temperatures and in northward transport of Saharan dust over the North Atlantic Ocean.

  20. Hyalomma ticks on northward migrating birds in southern Spain: Implications for the risk of entry of Crimean-Congo haemorrhagic fever virus to Great Britain.

    PubMed

    England, Marion E; Phipps, Paul; Medlock, Jolyon M; Atkinson, Peter M; Atkinson, Barry; Hewson, Roger; Gale, Paul

    2016-06-01

    Crimean-Congo haemorrhagic fever virus (CCHFV) is a zoonotic virus transmitted by Hyalomma ticks, the immature stages of which may be carried by migratory birds. In this study, a total of 12 Hyalomma ticks were recovered from five of 228 migratory birds trapped in Spring, 2012 in southern Spain along the East Atlantic flyway. All collected ticks tested negative for CCHFV. While most birds had zero Hyalomma ticks, two individuals had four and five ticks each and the statistical distribution of Hyalomma tick counts per bird is over-dispersed compared to the Poisson distribution, demonstrating the need for intensive sampling studies to avoid underestimating the total number of ticks. Rates of tick exchange on migratory birds during their northwards migration will affect the probability that a Hyalomma tick entering Great Britain is positive for CCHFV. Drawing on published data, evidence is presented that the latitude of a European country affects the probability of entry of Hyalomma ticks on wild birds. Further data on Hyalomma infestation rates and tick exchange rates are required along the East Atlantic flyway to further our understanding of the origin of Hyalomma ticks (i.e., Africa or southern Europe) and hence the probability of entry of CCHFV into GB. PMID:27232135

  1. Howthe IMF By induces a By component in the closed magnetosphere and how it leads to asymmetric currents and convection patterns in the two hemispheres

    NASA Astrophysics Data System (ADS)

    Tenfjord, Paul; Østgaard, Nikolai; Snekvik, Kristian; Reistad, Jone; Magnus Laundal, Karl; Haaland, Stein; Milan, Steve

    2016-04-01

    We describe the effects of the interplanetary magnetic field (IMF) By component on the coupling between the solar wind and magnetosphere-ionosphere system using AMPERE observations and MHD simulations. We show how By is induced on closed magnetospheric field lines on both the dayside and nightside. The magnetosphere imposes asymmetric forces on the ionosphere, and the effects on the ionospheric flow are characterized by distorted convection cell patterns, often referred to as "banana" and "orange" cell patterns. The flux asymmetrically added to the lobes results in a nonuniform induced By in the closed magnetosphere. We present a mechanism that predicts asymmetric Birkeland currents at conjugate foot points. Asymmetric Birkeland currents are created as a consequence of y directed tension contained in the return flow. Associated with these currents, we expect aurora and fast localized ionospheric azimuthal flows present in one hemisphere but not necessarily in the other. We present a statistical study where we show that these processes should occur on timescales of about 30 minutes after the IMF By has arrived at the magnetopause. We also present an event with simultaneous global imaging of the aurora and SuperDARN measurements from both hemisphere. The event is interpreted as an example of the of the proposed asymmetric current mechanism.

  2. Ground-based observations of ion/neutral coupling at Thule and Qanaq, Greenland

    NASA Technical Reports Server (NTRS)

    Thayer, J. P.; Crowley, G.; Niciejewski, R. J.; Killeen, T. L.; Buchau, J.; Reinisch, B. W.

    1995-01-01

    During December 1988, 24 hours of darkness and clear sky conditions permitted continuous observations of the O I(6300 A) airglow by a Fabry-Perot interferometer located at Thule Air Base, Greenland. Thus a continuous record of the F region neutral winds was obtained for that month. During this same time period, a digital ionosonde located at Qanaq, Greenland (110 km north of Thule Air Base), was in operation measuring electron density profiles and F region ion drifts. This combination of ground-based observations allowed the investigation of ion/neutral coupling at a temporal resolution of about 15 min. Interplanetary magnetic field (IMF) data from the IMP 8 satellite were also available from December 16 to 24 and indicated intervals of B(sub z) northward IMF conditions during this period. Here we investigate the observed response of the neutral wind to convection changes in the ion drift inside the polar cap for southward and northward IMF B(sub z) conditions. In particular, we establish a control day illustrating the typical antisunward neutral wind and ion drift patterns observed for southward B(sub z) over Thule and Qanaq, and we compare it with observations made when the IMF B(sub z) is directed northward. The observations during periods of northward B(sub z) display sunward directed ion drifts over the polar cap accompanied by decreasing antisunward directed neutral winds. We investigate these times of northward B(sub z) further and demonstrate that the ion drag term alone cannot describe the observed response in the neutral wind during northward IMF.

  3. Steepening of waves at the duskside magnetopause

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  4. A Tree-Ring Based Reconstruction (1725-present) of the Position of the Summer North Atlantic Jet Shows a 20th Century Northward Shift

    NASA Astrophysics Data System (ADS)

    Trouet, V.; Babst, F.

    2014-12-01

    The position and strength of the Northern Hemisphere polar jet are important modulators of mid-latitude weather extremes and the societal, ecosystem, and economic damage related to them. The position of the North Atlantic jet (NAJ) controls the location of the Atlantic storm track and anomalies in the NAJ position have been related to temperature and precipitation extremes over Europe. In summer, a southern NAJ regime can result in floods in the British Isles (BRIT) and increasing odds of heat waves in the northeastern Mediterranean (NEMED). Variability in the amplitude and speed of the Northern Hemisphere jet stream is hotly debated as a potential mechanism linking recent mid-latitude weather extremes to anthropogenic warming. However, the hypothesis of jet stream variability as a possible mechanism linking Arctic amplification to mid-latitude weather extremes is largely based on data sets with limited temporal extent that do not warrant robust results from a statistical significance perspective. Here, we combined two summer temperature-sensitive tree-ring records from BRIT and NEMED to reconstruct interannual variability in the latitudinal position of the summer NAJ back to 1725. The two well-replicated temperature proxies counter-correlate significantly over the full period and thus illustrate the temperature dipole generated by anomalous NAJ positions. Positive extremes in the NAJ reconstruction correspond to heatwaves recorded in the historical Central England temperature record and negative extremes correspond to reconstructed fire years in Greece. The reconstruction shows a northward shift in the latitudinal NAJ position since the 1930s that is most pronounced in the northern NAJ extremes, suggesting a more frequent occurrence of BRIT hot summers in the 20th century compared to previous centuries.

  5. Fundamental Aspects of External Triggers and Non-Triggers of Substorm Particle Injections, and Implications on Sawtooth Events and Repetitive Substorms

    NASA Astrophysics Data System (ADS)

    Lee, D.; Lyons, L.; Reeves, G.

    2005-12-01

    It is important to understand what specific types of solar wind disturbances lead to a substorm and what other specific types do not. The types of solar wind disturbances include a variation in either IMF or dynamic pressure or a combination of simultaneous variations in both. We used observations of geosynchronous particle fluxes at energies of tens to hundreds of keV and found the following features. (1) A northward turning of the IMF is found to trigger the typical substorm injection as well known already. The injection front is wider when it is triggered by a northward turning under a strongly southward IMF condition. (2) The effect by the northward turning can however be cancelled out by a simultaneous increase of the IMF By magnitude and/or a simultaneous decrease of the dynamic pressure, leading to no substorm. (3) Generally a pressure increase leads to a compression effect which appears as flux increase or decrease or even no change, depending on the radial profile of the particle distribution at constant adiabatic invariants. This compression effect can be different between different MLTs and different particle species. (4) However, a pressure increase under strongly southward IMF conditions leads to not only the typical compression effect but also a nightside substorm injection, i.e., a two-mode response. (5) This pressure-induced substorm injection can however be cancelled out by a simultaneous (further) decrease of the already-southward IMF and/or by a simultaneous increase of the IMF By magnitude. (6) In addition, the effects by a simultaneous increase of both IMF Bz and dynamic pressure add up to lead to a substorm injection accompanied by the typical compression effect, while no substorm injection is expected by a pressure decrease or a decrease of the IMF Bz or a simultaneous decrease of both. We suggest that a substorm injection is triggered only by a variation or a combination of variations that results in a convection reduction within the inner

  6. The SLUGGS survey: breaking degeneracies between dark matter, anisotropy and the IMF using globular cluster subpopulations in the giant elliptical NGC 5846

    NASA Astrophysics Data System (ADS)

    Napolitano, Nicola R.; Pota, Vincenzo; Romanowsky, Aaron J.; Forbes, Duncan A.; Brodie, Jean P.; Foster, Caroline

    2014-03-01

    We study the mass and anisotropy distribution of the giant elliptical galaxy NGC 5846 using stars, as well as the red and blue globular cluster (GC) subpopulations. We break degeneracies in the dynamical models by taking advantage of the different phase space distributions of the two GC subpopulations to unambiguously constrain the mass of the galaxy and the anisotropy of the GC system. Red GCs show the same spatial distribution and behaviour as the starlight, whereas blue GCs have a shallower density profile, a larger velocity dispersion and a lower kurtosis, all of which suggest a different orbital distribution. We use a dispersion-kurtosis Jeans analysis and find that the solutions of separate analyses for the two GC subpopulations overlap in the halo parameter space. The solution converges on a massive dark matter halo, consistent with expectations from Λ cold dark matter (ΛCDM) and 7-year Wilkinson Microwave Anisotropy Probe (WMAP7) cosmology in terms of virial mass (log MDM ˜ 13.3 M⊙) and concentration (cvir ˜ 8). This is the first such analysis that solves the dynamics of the different GC subpopulations in a self-consistent manner. Our method improves the uncertainties on the halo parameter determination by a factor of 2 and opens new avenues for the use of elliptical galaxy dynamics as tests of predictions from cosmological simulations. The implied stellar mass-to-light ratio derived from the dynamical modelling is fully consistent with a Salpeter initial mass function (IMF) and rules out a bottom light IMF. The different GC subpopulations show markedly distinct orbital distributions at large radii, with red GCs having an anisotropy parameter β˜0.4 outside ˜ 3 Re (Re is the effective radius), and the blue GCs having β˜0.15 at the same radii, while centrally ( ˜ 1 Re) they are both isotropic. We discuss the implications of our findings within the two-phase formation scenario for early-type galaxies.

  7. Link between the northward extension of Great Sumatra Fault and continental rifting in the Andaman Sea: new results from seismic reflection studies

    NASA Astrophysics Data System (ADS)

    Singh, S. C.; Moeremans, R. E.; McArdle, J.; Johansen, K.

    2012-12-01

    The Great Sumatra Fault (GSF) traverses the main land Sumatra from Sunda Strait in the southeast to Banda Aceh in the northwest for about 1900 km, and defines the present day plate boundary between the Sunda Plate in the north and Burmese Sliver Plate in the south. It is formed due to the oblique subduction of the Indo-Australian Plate beneath the Sunda Plate. It has been well studied on land but is poorly studied north of Banda Aceh in the Andaman Sea. Its study is further complicated by the presence of volcanic arc in its vicinity and its interaction with the West Andaman Fault (WAF) further north. Here we present deep seismic reflection images along the northward extension of the GSF over 700 km until it joins the Andaman Spreading Centre and interpret these images in the light of earthquake, gravity and bathymetry data. We find that the GSF has two strands between Banda Aceh and Nicobar Island: a transpression in the south and a deep narrow active rift basin in the north dotted with volcanoes in the center, suggesting that the volcanic arc is coincident with the rifting. Further north of Nicobar Island, an active strike-slip fault cuts through a deep rifted basin until its intersection with Andaman Sea Spreading Centre. The volcanic arc lies just east of the basin. The western margin of this basin seems to be a rifted continental margin, tilted westward flooring the Andaman-Nicobar forearc basin, which was once a part of Malaya Peninsula, suggesting that a significant parts of the Andaman-Nicobar forearc system is underlain by the Sunda continental crust. The Andaman-Nicobar forearc basin is bounded in the west by backthrusts, similar to the West Andaman and Mentawai faults bounding the Aceh and Mentawai forearc basins in the south. The cluster of seismicity after the 2004 great Andaman-Sumatra earthquake just north of Nicobar Island coincides with the intersection of two NW-SE and N-S trending strike-slip fault systems. Some of hypocentre of these earthquakes

  8. Where East Africa and the Levant Are Climatically Connected: An Alternative View of the Northward Shifts of Either the ITCZ and/or the Indian Summer Monsoon

    NASA Astrophysics Data System (ADS)

    Enzel, Y.; Kushnir, Y.; Quade, J.

    2014-12-01

    Lake levels in basins in areas bordering northern Arabian Sea have been used to reconstruct regional paleohydrological patterns through lake-level statuses. For the early-middle Holocene, dramatic increases in regional rainfall have been proposed. These rainfall changes are commonly thought to be associated with an intensified Indian summer monsoon (ISM) and a large northward shift in the latitude of the boreal summer ITCZ over the Indian Ocean; this shift was proposed to reach latitudes as far north as the Levant. However, the ISM currently forces total summer drought not rains, in the Levant and neighboring deserts, including Arabia. The drought is due to large-scale air subsidence forced by the ISM and dries the region except in southernmost Arabia, where topography lifts air and produces orographic rain. This Arabian summer drought is assisted by increased upwelling that limits rainfall inland. How large the actual changes in paleohydrology were in the Arabian Peninsula? If not the ISM, what are the real causes of these changes? We summarize paleohydrologic information from Arabia and revisit the paleolake status of all lacustrine-like deposits and their basins in Arabia. From reinterpretation of these data and sedimentology and fauna, we conclude that these basins were occupied by shallow marsh environments, not lakes. Consequently, the paleohydrologic changes required to support restricted wetland versus lakes were much smaller. These conclusions are supported by the temporal and spatial distribution of other paleoenvironmental indicators such as pollen and speleothems. They indicate that (a) rainfall changes were very small in the heart of and northern Arabia, and (b) that these changes were only at the elevated edges of southwestern, southern, and southeastern Arabian Peninsula, where it rains at present, mainly due to orographic effects on precipitation in the presence of increased moisture supply. We propose that (a) latitudinal and slight inland impact

  9. Comet Halley remote plasma tail observations and in situ solar wind properties - Vega-1/2 IMF/plasma observations and ground-based optical observations from 1 December 1985 to 1 May 1986

    NASA Technical Reports Server (NTRS)

    Delva, Magda; Schwingenschuh, Konrad; Niedner, Malcolm B.; Gringauz, Konstantin I.

    1991-01-01

    General features of the solar wind plasma and the interplanetary magnetic field (IMF) are studied for the time period of December 1, 1985 - May 1, 1986. Characteristics studied include corotating events, shocks, and sector boundaries in the IMF. For the same period, Comet Halley was near its perihelion and many ground-based observations of the plasma tail were made. They show interesting events such as tail substorms and disconnection events where the whole distant plasma tail seems to be disrupted from the part that is still attached to the cometary head. Several mechanisms have been produced to explain the cause of these events. The correlation between the IMF sector boundaries measured by Vega and the observed disconnection events are studied, noting that such a correlation would support the dayside reconnection explanation. It is found that only in 50 percent of the considered events does a correlation between these two phenomena exist. For the other cases, a sector boundary of the IMF sweeping over the comet cannot explain the occurrence of disruptions of the main plasma tail.

  10. SIMILARITY BETWEEN THE C{sup 18}O (J = 1-0) CORE MASS FUNCTION AND THE INITIAL MASS FUNCTION (IMF) IN THE S140 REGION

    SciTech Connect

    Ikeda, Norio; Kitamura, Yoshimi

    2011-05-10

    We present the results of C{sup 18}O(J = 1-0) mapping observations of a 20' x 18' area in the Lynds 1204 molecular cloud associated with the Sharpless 2-140 (S140) H II region. The C{sup 18}O cube ({alpha}-{delta}-v{sub LSR}) data show that there are three clumps of sizes {approx}1 pc in the region. Two of these have peculiar redshifted velocity components at their edges, which can be interpreted as the results of the interaction between the cloud and the Cepheus Bubble. From the C{sup 18}O cube data, clumpfind identified 123 C{sup 18}O cores, which have mean radius, velocity width in FWHM, and LTE mass of 0.36 {+-} 0.07 pc, 0.37 {+-} 0.09 km s{sup -1}, and 41 {+-} 29 M{sub sun}, respectively. Considering the uncertainty in the C{sup 18}O abundance, all the cores in S140 are most likely to be gravitationally bound. We derived a C{sup 18}O core mass function (CMF), which shows a power-law-like behavior above a turnover at 30 M{sub sun}. The best-fit power-law index of -2.1 {+-} 0.2 is quite consistent with that of the initial mass function (IMF) and the C{sup 18}O CMF in the OMC-1 region as found by Ikeda and Kitamura. Kramer et al. estimated the power-law index of -1.65 in S140 from the C{sup 18}O(J = 2-1) data, which is inconsistent with this study. The C{sup 18}O(J = 2-1) data are spatially limited to the central part of the cloud and are likely to be biased toward high-mass cores, leading to the flatter CMF. Consequently, this study and our previous study strongly support that the power-law form of the IMF has already been determined at the density of {approx}< 10{sup 3}-10{sup 4} cm{sup -3}, traced by the C{sup 18}O(J = 1-0) line.

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  13. The quiet time polar cap: DE 1 observations and conceptual model

    SciTech Connect

    Burch, J.L. ); Saflekos, N.A. ); Gurnett, D.A.; Frank, L.A. ); Craven, J.D. )

    1992-12-01

    Auroral activity increases over the polar caps during quiet times, which are associated with northward interplanetary magnetic field (IMF) components. Polar cap auroras (Sun-aligned arcs, theta auroras, and horse collar auroras) occur under these conditions. DE 1 data have provided partial characterization of these events. A conceptual northward IMF merging model containing lobe cells, merging cells, and viscous cells is shown to be consistent with the observations. As the IMF becomes more northward, the polar arc configuration changes from the horse collar pattern to the theta aurora pattern in the model, and this is shown to be generally true for the set of published data on these phenomena. The model involves dayside merging both at high latitudes on open field lines and at lower latitudes on closed field lines. The ratio between the merged flux produced by the high-latitude merging to that produced by the lower-latitude merging increases as the IMF becomes more northward. Two types of open field lines, equator-crossing and non-equator-crossing, are produced by the higher- and lower-latitude merging, respectively. The equator-crossing field lines have a strong azimuthal component of convection as they flow around the magnetopause, while the non-equator-crossing field lines can convect more or less directly across the polar cap, leading to an antisunward flow channel across the central polar cap. This antisunward flow region grows as the IMF becomes less northward, causing dual polar cap arcs to spread out into the horse collar configuration.

  14. Testing alternative tectono-stratigraphic interpretations of the Late Palaeozoic-Early Mesozoic Karakaya Complex in NW Turkey: support for an accretionary origin related to northward subduction of Palaeotethys

    NASA Astrophysics Data System (ADS)

    Robertson, Alastair; Ustaömer, Timur

    2010-05-01

    The mainly Permian-Triassic rocks of the Karakaya Complex exposed E-W across Turkey are critical to reconstruction of Tethys in the E Mediterranean region. Their origin remains controversial with both stratigraphic layer-cake and accretionary-type settings being advocated. Suggested tectonic settings range from back-arc rift, to accretionary prism- related to either northward or southward subduction. To test alternatives we have studied the contact relations and the internal fabric of each of the main litho-tectonic units making up the Karakaya Complex and related "basement" in nine outcrop areas across NW Turkey, also taking account of existing chemical and dating evidence. Our results show that the Karakaya Complex was assembled by regional-scale thrust faulting without evidence of layer cake-type stratigraphical contacts, or even of deformed sedimentary contacts separating the major lithotectonic units. In several areas (e.g. Havran) the outcrops of meta-siliciclastic sediments of presumed Palaeozoic-age (~Kalabak Unit) are locally cut by Early-Mid Devonian granites. These outcrops represent one or more high-level crustal imbricates made up of basement rocks together with depositionally overlying U. Triassic siliciclastic rocks. Evidence from structurally lower, high pressure-low temperature Karakaya rocks (~Nilüfer Unit) reveals an imbricated, mainly volcaniclastic-carbonate sequence. Both these relatively high-grade Karakaya rocks and the structurally overlying, lower-grade Karakaya rocks (i.e. Çal and Ortaoba units) are interpreted as tectonically emplaced accretionary melange rather than sedimentary "olistostromes". MOR-type basalts (Ortaoba Unit) are locally overlain by red ribbon radiolarites that then pass upwards into feldspar-rich siliciclastics. Triassic oceanic crust and oceanic siliceous sediments were overlain by terrigenous turbidites derived from the north (Sakarya continent), followed by tectonic accretion at a subduction trench bordering the

  15. Submillimeter Galaxies at z ~ 2: Evidence for Major Mergers and Constraints on Lifetimes, IMF, and CO-H2 Conversion Factor

    NASA Astrophysics Data System (ADS)

    Tacconi, L. J.; Genzel, R.; Smail, I.; Neri, R.; Chapman, S. C.; Ivison, R. J.; Blain, A.; Cox, P.; Omont, A.; Bertoldi, F.; Greve, T.; Förster Schreiber, N. M.; Genel, S.; Lutz, D.; Swinbank, A. M.; Shapley, A. E.; Erb, D. K.; Cimatti, A.; Daddi, E.; Baker, A. J.

    2008-06-01

    We report subarcsecond resolution IRAM PdBI millimeter CO interferometry of four z ~ 2 submillimeter galaxies (SMGs), and sensitive CO(3-2) flux limits toward three z ~ 2 UV/optically selected star-forming galaxies. The new data reveal for the first time spatially resolved CO gas kinematics in the observed SMGs. Two of the SMGs show double or multiple morphologies, with complex, disturbed gas motions. The other two SMGs exhibit CO velocity gradients of ~500 km s-1 across <=0.2'' (1.6 kpc) diameter regions, suggesting that the star-forming gas is in compact, rotating disks. Our data provide compelling evidence that these SMGs represent extreme, short-lived "maximum" star-forming events in highly dissipative mergers of gas-rich galaxies. The resulting high-mass surface and volume densities of SMGs are similar to those of compact quiescent galaxies in the same redshift range and much higher than those in local spheroids. From the ratio of the comoving volume densities of SMGs and quiescent galaxies in the same mass and redshift ranges, and from the comparison of gas exhaustion timescales and stellar ages, we estimate that the SMG phase duration is about 100 Myr. Our analysis of SMGs and optically/UV selected high-redshift star-forming galaxies supports a "universal" Chabrier IMF as being valid over the star-forming history of these galaxies. We find that the 12CO luminosity to total gas mass conversion factors at z ~ 2-3 are probably similar to those assumed at z ~ 0. The implied gas fractions in our sample galaxies range from 20% to 50%. Based on observations obtained at the IRAM Plateau de Bure Interferometer (PdBI). IRAM is funded by the Centre National de la Recherché Scientifique (France), the Max-Planck Gesellschaft (Germany), and the Instituto Geografico Nacional (Spain).

  16. Cosmic Rays during Intense Geomagnetic Conditions and their Solar / Interplanetary features

    NASA Astrophysics Data System (ADS)

    Kaushik, Subhash Chandra

    In this study we discuss the behavior of cosmic rays during the phase of highly intense or ultra intense geomagnetic storms, as shocks driven by energetic coronal mass ejections (CME’s) and other interplanetary (IP) transients are mainly responsible for initiating large and intense geomagnetic storms. Observational results indicate that galactic cosmic rays (CR) coming from deep surface interact with these abnormal solar and IP conditions and suffer modulation effects. In this paper a systematic study has been performed to analyze the CRI variation during super storms i.e. very intense geomagnetic storms with Dst index ≥ -300 nT. The neutron monitor data of three stations Oulu (Rc = 0.77 GV), Climax (Rc = 2.97 GV) and Huancayo (Rc = 13.01 GV) well distributed over different latitudes and hourly values of IMF parameters derived from satellite observations near Earth IP medium from OMNI Data base is used for the period spanning over solar cycles 20, 21, 22 and 23. It is found that AP and AE indices show rise before the forward turnings of IMF, while the Dst index shows a classic storm time decrease. The analysis indicates that the magnitude of all the responses depends on BZ component of IMF being well correlated with solar maximum and minimum periods. Transient decrease in cosmic ray intensity with slow recovery is observed during the storm phase duration.

  17. 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.

  18. Structured subauroral polarization streams and related auroral undulations occurring on the storm day of 21 January 2005

    NASA Astrophysics Data System (ADS)

    Horvath, Ildiko; Lovell, Brian C.

    2016-02-01

    We investigate structured subauroral polarization streams (SAPS) and their impacts on the midlatitude trough and auroral regions during the 21-22 January 2005 geomagnetic storm. This was a storm with two sudden commencements occurring under varying interplanetary magnetic field (IMF) conditions and three main phases, two of them unfolding during northward IMF. Its onset at ~1700 UT allowed us to investigate SAPS wave structures (WS) and their impacts during the local evening hours under both southward and northward IMF conditions in the American sector. Results suggest that during southward IMF, SAPS-WS might be related with standing (toroidal) Alfven waves and structured most intensively the stagnation trough. During northward IMF, the trough was created by SAPS electric (E) field effects only and became less structured by SAPS-WS that were of Alfvenic origin. Auroral wave structures and undulations occurred in the structured and unstructured oval regions, respectively, and triggered the subauroral region's response to produce SAPS-WS. Spectrogram images (only one shown) confirmed ring current injections implying magnetotail reconnections during the four SAPS-WS events investigated. Periodic tail connections are also evidenced by the periodic increases seen in both the solar wind-magnetosphere coupling function (ɛ) and the energy input efficiency. Finally, we conclude for the time period investigated that (1) the nature of SAPS-WS was informative of IMF orientation, (2) plasma stagnation enhanced SAPS E field and SAPS-WS development, and (3) more efficient energy input into the magnetosphere contributed to the better development of auroral undulations and SAPS-WS.

  19. Imager for Mars Pathfinder (IMF)

    NASA Technical Reports Server (NTRS)

    Smith, Peter H.

    1994-01-01

    The IMP camera is a near-surface sensing experiment with many capabilities beyond those normally associated with an imager. It is fully pointable in both elevation and azimuth with a protected, stowed position looking straight down. Stereo separation is provided with two optical paths; each has a 12-position filter wheel. The primary function of the camera, strongly tied to mission success, is to take a color panorama of the surrounding terrain. IMP requires approximately 120 images to give a complete downward hemisphere from the deployed position. IMP provides the geologist, and everyone else, a view of the local morphology with millimeter-tometer-scale resolution over a broad area. In addition to the general morphology of the scale, IMP has a large compliment of specially chosen filters to aid in both the identification of the mineral types and their degree of weathering.

  20. MERGER RATES OF DOUBLE NEUTRON STARS AND STELLAR ORIGIN BLACK HOLES: THE IMPACT OF INITIAL CONDITIONS ON BINARY EVOLUTION PREDICTIONS

    SciTech Connect

    Mink, S. E. de; Belczynski, K. E-mail: kbelczyn@astrouw.edu.pl

    2015-11-20

    The initial mass function (IMF), binary fraction, and distributions of binary parameters (mass ratios, separations, and eccentricities) are indispensable inputs for simulations of stellar populations. It is often claimed that these are poorly constrained, significantly affecting evolutionary predictions. Recently, dedicated observing campaigns have provided new constraints on the initial conditions for massive stars. Findings include a larger close binary fraction and a stronger preference for very tight systems. We investigate the impact on the predicted merger rates of neutron stars and black holes. Despite the changes with previous assumptions, we only find an increase of less than a factor of 2 (insignificant compared with evolutionary uncertainties of typically a factor of 10–100). We further show that the uncertainties in the new initial binary properties do not significantly affect (within a factor of 2) our predictions of double compact object merger rates. An exception is the uncertainty in IMF (variations by a factor of 6 up and down). No significant changes in the distributions of final component masses, mass ratios, chirp masses, and delay times are found. We conclude that the predictions are, for practical purposes, robust against uncertainties in the initial conditions concerning binary parameters, with the exception of the IMF. This eliminates an important layer of the many uncertain assumptions affecting the predictions of merger detection rates with the gravitational wave detectors aLIGO/aVirgo.

  1. Merger Rates of Double Neutron Stars and Stellar Origin Black Holes: The Impact of Initial Conditions on Binary Evolution Predictions

    NASA Astrophysics Data System (ADS)

    de Mink, S. E.; Belczynski, K.

    2015-11-01

    The initial mass function (IMF), binary fraction, and distributions of binary parameters (mass ratios, separations, and eccentricities) are indispensable inputs for simulations of stellar populations. It is often claimed that these are poorly constrained, significantly affecting evolutionary predictions. Recently, dedicated observing campaigns have provided new constraints on the initial conditions for massive stars. Findings include a larger close binary fraction and a stronger preference for very tight systems. We investigate the impact on the predicted merger rates of neutron stars and black holes. Despite the changes with previous assumptions, we only find an increase of less than a factor of 2 (insignificant compared with evolutionary uncertainties of typically a factor of 10–100). We further show that the uncertainties in the new initial binary properties do not significantly affect (within a factor of 2) our predictions of double compact object merger rates. An exception is the uncertainty in IMF (variations by a factor of 6 up and down). No significant changes in the distributions of final component masses, mass ratios, chirp masses, and delay times are found. We conclude that the predictions are, for practical purposes, robust against uncertainties in the initial conditions concerning binary parameters, with the exception of the IMF. This eliminates an important layer of the many uncertain assumptions affecting the predictions of merger detection rates with the gravitational wave detectors aLIGO/aVirgo.

  2. Comparative analysis of dayside magnetic reconnection models in global magnetosphere simulations

    NASA Astrophysics Data System (ADS)

    Komar, C. M.; Fermo, R. L.; Cassak, P. A.

    2015-01-01

    We test and compare a number of existing models predicting the location of magnetic reconnection at Earth's dayside magnetopause for various solar wind conditions. We employ robust image processing techniques to determine the locations where each model predicts reconnection to occur. The predictions are then compared to the magnetic separators, the magnetic field lines separating different magnetic topologies. The predictions are tested in distinct high-resolution simulations with interplanetary magnetic field (IMF) clock angles ranging from 30 to 165° in global magnetohydrodynamic simulations using the three-dimensional Block Adaptive Tree Solarwind Roe-type Upwind Scheme code with a uniform resistivity, although the described techniques can be generally applied to any self-consistent magnetosphere code. Additional simulations are carried out to test location model dependence on IMF strength and dipole tilt. We find that most of the models match large portions of the magnetic separators when the IMF has a southward component, with the models saying reconnection occurs where the local reconnection rate and reconnection outflow speed are maximized performing best. When the IMF has a northward component, none of the models tested faithfully map the entire magnetic separator, but the maximum magnetic shear model is the best at mapping the separator in the cusp region where reconnection has been observed. Predictions for some models with northward IMF orientations improve after accounting for plasma flow shear parallel to the reconnecting components of the magnetic fields. Implications for observations are discussed.

  3. Northward range expansion requires synchronization of both overwintering behaviour and physiology with photoperiod in the invasive Colorado potato beetle (Leptinotarsa decemlineata).

    PubMed

    Lehmann, Philipp; Lyytinen, Anne; Piiroinen, Saija; Lindström, Leena

    2014-09-01

    Photoperiodic phenological adaptations are prevalent in many organisms living in seasonal environments. As both photoperiod and growth season length change with latitude, species undergoing latitudinal range expansion often need to synchronize their life cycle with a changing photoperiod and growth season length. Since adaptive synchronization often involves a large number of time-consuming genetic changes, behavioural plasticity might be a faster way to adjust to novel conditions. We compared behavioural and physiological traits in overwintering (diapause) preparation in three latitudinally different European Colorado potato beetle (Leptinotarsa decemlineata) populations reared under two photoperiods. Our aim was to study whether behavioural plasticity could play a role in rapid range expansion into seasonal environments. Our results show that while burrowing into the soil occurred in the southernmost studied population also under a non-diapause-inducing long photoperiod, the storage lipid content of these beetles was very low compared to the northern populations. However, similar behavioural plasticity was not found in the northern populations. Furthermore, the strongest suppression of energy metabolism was seen in pre-diapause beetles from the northernmost population. These results could indicate accelerated diapause preparation and possibly energetic adjustments due to temporal constraints imposed by a shorter, northern, growth season. Our results indicate that behavioural plasticity in burrowing may have facilitated initial range expansion of L. decemlineata in Europe. However, long-term persistence at high latitudes has required synchronization of burrowing behaviour with physiological traits. The results underline that eco-physiological life-history traits of insects, such as diapause, should be included in studies on range expansion. PMID:25012598

  4. Breeding on the leading edge of a northward range expansion: differences in morphology and the stress response in the arctic Gambel's white-crowned sparrow.

    PubMed

    Krause, Jesse S; Chmura, Helen E; Pérez, Jonathan H; Quach, Lisa N; Asmus, Ashley; Word, Karen R; McGuigan, Michaela A; Sweet, Shannan K; Meddle, Simone L; Gough, Laura; Boelman, Natalie; Wingfield, John C

    2016-01-01

    Individuals at the forefront of a range shift are likely to exhibit phenotypic traits that distinguish them from the population breeding within the historic range. Recent studies have examined morphological, physiological and behavioral phenotypes of individuals at the edge of their range. Several studies have found differences in the hypothalamic-pituitary-adrenal (HPA) axis activity in response to acute restraint stress in individuals at the range limits. HPA axis activation leads to elevations in glucocorticoids that regulate physiology and behavior. Here we compare the hormonal profiles and morphometrics from Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii) breeding at the northern limit of the population's range to those birds breeding within the historic population range. Birds breeding at the northern limit experienced a harsher environment with colder temperatures; however, we found no differences in arthropod prey biomass between the northern limit and more southern (historic) sites. Males at the northern limit had higher body condition scores (mass corrected for body size) compared to individuals within the historic range, but no differences were found in beak and tarsus lengths, wing chord, muscle profile or fat stores. In males during the pre-parental stage, before breeding commenced, HPA axis activity was elevated in birds at the northern limit of the range, but no differences were found during the parental or molt stages. Females showed no differences in HPA axis activity during the parental stage. This study suggests that "pioneering" individuals at the limits of their breeding range exhibit physiology and morphology that are distinct from individuals within the historic range. PMID:26423267

  5. Northward range expansion requires synchronization of both overwintering behaviour and physiology with photoperiod in the invasive Colorado potato beetle (Leptinotarsa decemlineata).

    PubMed

    Lehmann, Philipp; Lyytinen, Anne; Piiroinen, Saija; Lindström, Leena

    2014-09-01

    Photoperiodic phenological adaptations are prevalent in many organisms living in seasonal environments. As both photoperiod and growth season length change with latitude, species undergoing latitudinal range expansion often need to synchronize their life cycle with a changing photoperiod and growth season length. Since adaptive synchronization often involves a large number of time-consuming genetic changes, behavioural plasticity might be a faster way to adjust to novel conditions. We compared behavioural and physiological traits in overwintering (diapause) preparation in three latitudinally different European Colorado potato beetle (Leptinotarsa decemlineata) populations reared under two photoperiods. Our aim was to study whether behavioural plasticity could play a role in rapid range expansion into seasonal environments. Our results show that while burrowing into the soil occurred in the southernmost studied population also under a non-diapause-inducing long photoperiod, the storage lipid content of these beetles was very low compared to the northern populations. However, similar behavioural plasticity was not found in the northern populations. Furthermore, the strongest suppression of energy metabolism was seen in pre-diapause beetles from the northernmost population. These results could indicate accelerated diapause preparation and possibly energetic adjustments due to temporal constraints imposed by a shorter, northern, growth season. Our results indicate that behavioural plasticity in burrowing may have facilitated initial range expansion of L. decemlineata in Europe. However, long-term persistence at high latitudes has required synchronization of burrowing behaviour with physiological traits. The results underline that eco-physiological life-history traits of insects, such as diapause, should be included in studies on range expansion.

  6. Breeding on the leading edge of a northward range expansion: differences in morphology and the stress response in the arctic Gambel's white-crowned sparrow.

    PubMed

    Krause, Jesse S; Chmura, Helen E; Pérez, Jonathan H; Quach, Lisa N; Asmus, Ashley; Word, Karen R; McGuigan, Michaela A; Sweet, Shannan K; Meddle, Simone L; Gough, Laura; Boelman, Natalie; Wingfield, John C

    2016-01-01

    Individuals at the forefront of a range shift are likely to exhibit phenotypic traits that distinguish them from the population breeding within the historic range. Recent studies have examined morphological, physiological and behavioral phenotypes of individuals at the edge of their range. Several studies have found differences in the hypothalamic-pituitary-adrenal (HPA) axis activity in response to acute restraint stress in individuals at the range limits. HPA axis activation leads to elevations in glucocorticoids that regulate physiology and behavior. Here we compare the hormonal profiles and morphometrics from Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii) breeding at the northern limit of the population's range to those birds breeding within the historic population range. Birds breeding at the northern limit experienced a harsher environment with colder temperatures; however, we found no differences in arthropod prey biomass between the northern limit and more southern (historic) sites. Males at the northern limit had higher body condition scores (mass corrected for body size) compared to individuals within the historic range, but no differences were found in beak and tarsus lengths, wing chord, muscle profile or fat stores. In males during the pre-parental stage, before breeding commenced, HPA axis activity was elevated in birds at the northern limit of the range, but no differences were found during the parental or molt stages. Females showed no differences in HPA axis activity during the parental stage. This study suggests that "pioneering" individuals at the limits of their breeding range exhibit physiology and morphology that are distinct from individuals within the historic range.

  7. Solar Wind Influence on the Oxygen Content of Ion Outflow in the High Altitude Polar Cap During Solar Minimum Conditions

    NASA Technical Reports Server (NTRS)

    Elliott, Heather A.; Comfort, Richard H.; Craven, Paul D.; Chandler, Michael O.; Moore, Thomas E.

    2000-01-01

    We correlate solar wind and IMF properties with the properties of O(+) and H(+) in the polar cap in early 1996 during solar minimum conditions at altitudes between 5.5 and 8.9 Re geocentric using the Thermal Ion Dynamics Experiment (TIDE) on the POLAR satellite. Throughout the high altitude polar cap, we observe H(+) to be more abundant than O(+). H(+) is a significant fraction of both the ionosphere and the solar wind, and O(+) is not a significant species in the solar wind. O(+) is the major species in the ionosphere so the faction of O(+) present in the magnetosphere is commonly used as a measure of the ionospheric contribution to the magnetosphere. For these reasons, 0+ is of primary interest in this study. We observe O(+) to be most abundant at lower latitudes when the solar wind speed is low (and low Kp), and at higher solar wind speeds (and high Kp) O(+) is observed across most of the polar cap. We also find that O(+) density and parallel flux are well organized by solar wind dynamic pressure; they both increase with solar wind dynamic pressure. H(+) is not as highly correlated with solar wind and IMF parameters, but H(+) density and parallel flux have some negative correlation with IMF By, and some positive correlation with VswBIMF. In this solar minimum data set, H(+) is dominant so that contributions of this plasma to the plasma sheet would have a very low O(+) to H(+) ratio.

  8. Concerning the Motion and Orientation of Flux Transfer Events Produced by Component and Antiparallel Reconnection

    NASA Technical Reports Server (NTRS)

    Sibeck, D. G.; Lin, R.-Q.

    2011-01-01

    We employ the Cooling et al. (2001) model to predict the location, orientation, motion, and signatures of flux transfer events (FTEs) generated at the solstices and equinoxes along extended subsolar component and high ]latitude antiparallel reconnection curves for typical solar wind plasma conditions and various interplanetary magnetic field (IMF) strengths and directions. In general, events generated by the two mechanisms maintain the strikingly different orientations they begin with as they move toward the terminator in opposite pairs of magnetopause quadrants. The curves along which events generated by component reconnection form bow toward the winter cusp. Events generated by antiparallel reconnection form on the equatorial magnetopause during intervals of strongly southward IMF orientation during the equinoxes, form in the winter hemisphere and only reach the dayside equatorial magnetopause during the solstices when the IMF strength is very large and the IMF points strongly southward, never reach the equatorial dayside magnetopause when the IMF has a substantial dawnward or duskward component, and never reach the equatorial flank magnetopause during intervals of northward and dawnward or duskward IMF orientation. Magnetosheath magnetic fields typically have strong components transverse to events generated by component reconnection but only weak components transverse to the axes of events generated by antiparallel reconnection. As a result, much stronger bipolar magnetic field signatures normal to the nominal magnetopause should accompany events generated by component reconnection. The results presented in this paper suggest that events generated by component reconnection predominate on the dayside equatorial and flank magnetopause for most solar wind conditions.

  9. View Northward from Spirit's Winter Roost

    NASA Technical Reports Server (NTRS)

    2006-01-01

    One part of the research program that NASA's Mars Exploration Rover Spirit is conducting while sitting at a favorable location for wintertime solar energy is the most detailed panorama yet taken on the surface of Mars. This view is a partial preliminary product from the continuing work on the full image, which will be called the 'McMurdo Panorama.'

    Spirit's panoramic camera (Pancam) began taking exposures for the McMurdo Panorama on the rover's 814th Martian day (April 18, 2006). The rover has accumulated more than 900 exposures for this panorama so far, through all of the Pancam mineralogy filters and using little or no image compression. Even with a tilt toward the winter sun, the amount of energy available daily is small, so the job will still take one to two more months to complete.

    This portion of the work in progress looks toward the north. 'Husband Hill,' which Spirit was climbing a year ago, is on the horizon near the center. 'Home Plate' is a between that hill and the rover's current position. Wheel tracks imprinted when Spirit drove south from Home Plate can be seen crossing the middle distance of the image from the center to the right.

    This is an approximate true-color rendering combining exposures taken through three of the panoramic camera's filters. The filters used are centered on wavelengths of 750 nanometers, 530 nanometers and 430 nanometers.

  10. ISEE 1 and 2 observation of the oscillating magnetopause

    NASA Technical Reports Server (NTRS)

    Song, PU; Elphic, R. C.; Russell, C. T.

    1988-01-01

    The ISEE 1 and 2 magnetometer data for 10 years between October 1977 and September 1987 were used to identify magnetopause crossings that occurred in this period in the northward, horizontal, and southward IMFs and to determine the dependence of the oscillation amplitude of surface waves with periods greater than about 2 min on latitude, local time, and the direction of the IMF. The IMP 8 and ISEE 3 data were used to determine the IMF in the geocentric solar magnetosphere coordinates during the crossings. More than 1000 magnetopause passes were identified, with half of them with multiple crossings. The number of crossings per pass and the inferred average amplitude of the oscillation under southward conditions were nearly three times higher than under northward conditions. The amplitude increased with increasing angle from the subsolar point, when under southward, but not when under northward, conditions. The results suggest that the Kelvin-Helmholtz instability plays a very minor role in causing the surface waves on the dayside magnetopause.

  11. Field-Aligned Current Sheet Motion and Its Correlation with Solar Wind Conditions and Geomagnetic Activities

    NASA Astrophysics Data System (ADS)

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

    2008-05-01

    Field-aligned currents (FACs) are the currents flowing into and out of the ionosphere which connect to the magnetosphere. They provide an essential linkage between the solar wind - magnetosphere system and the ionosphere, and the understanding of these currents is important for global magnetosphere dynamics and space weather prediction. The three spacecraft ST-5 constellation provides an unprecedented opportunity to study in situ FAC dynamics in time scales (10 sec to 10 min) that can not be achieved previously with single spacecraft studies or large-spaced conjugate spacecraft studies. In this study, we use the magnetic field observations during the whole ST-5 mission and their corresponding solar wind conditions to study the dependence of FAC current sheet motion and intensity on solar wind conditions. FAC peak current densities show very good correlations with some solar wind parameters, including IMF Bz, dynamic pressure, Ey, and some IMF angles, but not with other parameters. Instant FAC speeds show generally much weaker dependence on solar wind conditions comparing to FAC peak current densities. This obvious uncorrelation between FAC peak current densities and speeds implies that FAC peak current densities are more consistently controlled by solar wind conditions and geomagnetic activities, while FAC speeds are more oscillatory, sometimes with higher speeds during quieter times and lower speeds during more turbulent times.

  12. Chromosomal Conditions

    MedlinePlus

    ... 150 babies is born with a chromosomal condition. Down syndrome is an example of a chromosomal condition. Because ... all pregnant women be offered prenatal tests for Down syndrome and other chromosomal conditions. A screening test is ...

  13. Dynamical ejections of massive stars from young star clusters under diverse initial conditions

    NASA Astrophysics Data System (ADS)

    Oh, Seungkyung; Kroupa, Pavel

    2016-05-01

    We study the effects that initial conditions of star clusters and their massive star population have on dynamical ejections of massive stars from star clusters up to an age of 3 Myr. We use a large set of direct N-body calculations for moderately massive star clusters (Mecl ≈ 103.5 M⊙). We vary the initial conditions of the calculations, such as the initial half-mass radius of the clusters, initial binary populations for massive stars and initial mass segregation. We find that the initial density is the most influential parameter for the ejection fraction of the massive systems. The clusters with an initial half-mass radius rh(0) of 0.1 (0.3) pc can eject up to 50% (30)% of their O-star systems on average, while initially larger (rh(0) = 0.8 pc) clusters, that is, lower density clusters, eject hardly any OB stars (at most ≈ 4.5%). When the binaries are composed of two stars of similar mass, the ejections are most effective. Most of the models show that the average ejection fraction decreases with decreasing stellar mass. For clusters that are efficient at ejecting O stars, the mass function of the ejected stars is top-heavy compared to the given initial mass function (IMF), while the mass function of stars that remain in the cluster becomes slightly steeper (top-light) than the IMF. The top-light mass functions of stars in 3 Myr old clusters in our N-body models agree well with the mean mass function of young intermediate-mass clusters in M 31, as reported previously. This implies that the IMF of the observed young clusters is the canonical IMF. We show that the multiplicity fraction of the ejected massive stars can be as high as ≈ 60%, that massive high-order multiple systems can be dynamically ejected, and that high-order multiples become common especially in the cluster. We also discuss binary populations of the ejected massive systems. Clusters that are initially not mass-segregated begin ejecting massive stars after a time delay that is caused by mass

  14. Future changes in atmospheric condition for the baiu under RCP scenarios

    NASA Astrophysics Data System (ADS)

    Okada, Y.; Takemi, T.; Ishikawa, H.

    2015-12-01

    This study focuses on atmospheric circulation fields during the baiu in Japan with global warming projection experimental data conducted using a 20-km mesh global atmospheric model (MRI-AGCM3.2) under Representative Concentration Pathways (RCP) scenarios. This model also used 4 different sea surface temperature (SST) initial conditions. Support of this dataset is provided by the Meteorological Research Institute (MRI). The baiu front indicated by the north-south gradient of moist static energy moves northward in present-day climate, whereas this northward shift in future climate simulations is very slow during May and June. In future late baiu season, the baiu front stays in the northern part of Japan even in August. As a result, the rich water vapor is transported around western Japan and the daily precipitation amount will increase in August. This northward shift of baiu front is associated with the westward expansion of the enhanced the North Pacific subtropical high (NPSH) into Japan region. However, the convective activity around northwest Pacific Ocean is inactive and is unlikely to occur convective jump (CJ). These models show that the weak trough exists in upper troposphere around Japan. Therefore, the cold advection stays in the northern part of Japan during June. In July, the front due to the strengthening of the NPSH moves northward, and then it stays until August. This feature is often found between the clustered SSTs, Cluster 2 and 3. The mean field of future August also show the inflow of rich water vapor content to Japan islands. In this model, the extreme rainfall suggested tends to almost increase over the Japan islands during future summer. This work was conducted under the Program for Risk Information on Climate Change supported by the Ministry of Education, Culture, Sports, Science, and Technology-Japan (MEXT).

  15. ISTP Solar Maximum Extended Science Program

    NASA Technical Reports Server (NTRS)

    Ashour-Abdalla, Maha; Curtis, Steven (Technical Monitor)

    2002-01-01

    We have studied the entry of solar energetic particles (SEPS) into the magnetosphere by following particles in the time dependent magnetic and electric field from global magnetohydrodynamic (MHD) simulations of the magnetosphere. The MHD simulations can either be for idealized interplanetary magnetic field (IMF) conditions, or for upstream conditions measured by spacecraft. An important part of the analysis is understanding the response of the magnetosphere to the IMF conditions. In the idealized case, the MHD simulation included a steady interplanetary magnetic field (IMF) B(sub x), velocity and density, while the B(sub y) and B(sub z) components were varied from southward IMF to dawnward and finally to northward IMF. We launched more than ten million protons, as well as about 1 million He-3 ions and a few thousand electrons upstream of the magnetosphere into the solar wind. They were initialized using a kappa distribution, which is a power law distribution with a power law coefficient of 1.5 at high energies. The particles had energies between 0. 1 and 50 MeV. The particles were run in time dependent MHD fields that were advanced in time as the particles moved through the system.

  16. Reconnection versus Kelvin-Helmholtz instability in magnetospheric energy transfer - ISEE observations

    NASA Technical Reports Server (NTRS)

    Song, PU; Elphic, R. C.; Russell, C. T.

    1990-01-01

    Examination of multiple magnetopause crossings observed with the magnetometers on ISEE 1 and 2 makes it possible to determine the amplitude of the oscillation of surface waves on the magnetopause with periods greater than about 2 min and its dependence on latitude, local time, and the direction of the IMF. The magnetopause is more oscillatory for southward IMF than for northward IMF. When the IMF is southward, the amplitude of the oscillation increases with increasing angle from the subsolar point, which suggests that reconnection-related phenomena can generate surface waves on the magnetopause. When the IMF is northward, the oscillation does not grow with distance from the subsolar point, which is contrary to the expected growth of the Kelvin-Helmholtz (K-H) instability. It is also found that solar-wind pressure fluctuations may cause all of the observed boundary oscillations for northward IMF.

  17. Concerning the Occurrence Pattern of Flux Transfer Events on the Dayside Magnetopause

    NASA Technical Reports Server (NTRS)

    Sibeck, D. G.

    2009-01-01

    We present an analytical model for the magnetic field perturbations associated with flux transfer events (FTEs) on the dayside magnetopause as a function of the shear between the magnetosheath and magnetospheric magnetic fields and the ratio of their strengths. We assume that the events are produced by component reconnection along subsolar reconnection lines with tilts that depend upon the orientation of the interplanetary magnetic field (IMF), and show that the amplitudes of the perturbations generated during southward IMF greatly exceed those during northward IMF As a result, even if the distributions of magnetic reconnection burst durations/event dimensions are identical during periods of northward and southward IMF orientation, events occurring for southward IMF orientations must predominate in surveys of dayside events. Two factors may restore the balance between events occurring for northward and southward IMF orientations on the flanks of the magnetosphere. Events generated on the dayside magnetopause during periods of southward IMF move poleward, while those generated during periods of northward IMF slip dawnward or duskward towards the flanks. Due to differing event and magnetospheric magnetic field orientations, events that produce weak signatures on the dayside magnetopause during intervals of northward IMF orientation may produce strong signatures on the flanks.

  18. Field-Aligned Current Dynamics and Its Correlation with Solar Wind Conditions and Geomagnetic Activities From Space Technology 5 Observations

    NASA Astrophysics Data System (ADS)

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

    Field-aligned currents (FACs) are the currents flowing into and out of the ionosphere which connect to the magnetosphere. They provide an essential linkage between the solar wind - magnetosphere system and the ionosphere, and the understanding of these currents is important for global magnetosphere dynamics and space weather prediction. The three spacecraft ST-5 constellation provides an unprecedented opportunity to study in situ FAC dynamics in time scales (10 sec to 10 min) that can not be achieved previously with single spacecraft studies or large-spaced conjugate spacecraft studies. In this study, we use the magnetic field observations during the whole ST-5 mission to study the dependence of FAC current sheet motion and intensity on solar wind conditions. FAC peak current densities show very good correlations with some solar wind parameters, including IMF Bz, dynamic pressure, Ey, and some IMF angles, but not with other parameters. Instant FAC speeds show generally much weaker dependence on solar wind conditions comparing to FAC peak current densities. This obvious uncorrelation between FAC peak current densities and speeds implies that FAC peak current densities are more consistently controlled by solar wind conditions and geomagnetic activities, while FAC speeds are more oscillatory, sometimes with higher speeds during quieter times and lower speeds during more turbulent times. Detailed examination of FAC current sheet speed during two major storms in the ST-5 mission will also be given to illustrate the temporal evolution of the FAC dynamics with geomagnetic storm.

  19. Observational Evidence that Magnetosheath Plasma Parameters are Prominent in Determining Cross Polar Cap Potential Saturation

    NASA Astrophysics Data System (ADS)

    Clauer, Robert; Xu, Zhonghua; Hartinger, Michael; Ruohoniemi, Michael; Scales, Wayne; Maimaiti, Maimaitirebike; Nicolls, Michael; Wilder, Rick; Lopez, Ramon

    2016-04-01

    A variety of statistical studies have shown that the ionospheric polar potential produced by solar wind - magnetosphere - ionosphere coupling is linear for weak to moderate solar wind driving, but becomes non-linear during periods of very strong driving. It has been shown that this applies to the two-cell convection potential that develops during southward interplanetary magnetic field (IMF) and also to the reverse convection cells that develop during northward IMF. This has been described as polar potential saturation and it appears to begin when the driving solar wind electric field becomes greater than 3 mV/m. It has also been shown that the summer ionospheric electric field saturates at about the same value (20 mV/m) for both northward or southward IMF. Recent measurements of the high latitude convection on September 12 - 13, 2014 using the Resolute Incoherent Scatter Radar during periods of large northward IMF show ionospheric electric fields varying between 56 mV/m and 156 mV/m within the dayside reverse convection cells. There is no indication of saturation during these periods of very strong driving. We believe that the extremely rare conditions in the solar wind that produce extreme driving while also producing a high plasma beta in the magnetosheath provide the best explanation for the lack of potential saturation of the reverse convection cells. That is to say, the conditions in the magnetosheath that contribute to enhancing or limiting reconnection are most important in determining cross polar cap potential saturation. This research was supported at Virginia Tech by National Science Foundation Grant AGS-1216373.

  20. High-latitude magnetic reconnection in sub-Alfvénic flow: Interball tail observations on May 29, 1996

    NASA Astrophysics Data System (ADS)

    Avanov, L. A.; Fuselier, S. A.; Vaisberg, O. L.

    2001-12-01

    The Interball Tail spacecraft crossed the high-latitude magnetopause near the cusp region under northward interplanetary magnetic field (IMF) conditions on May 29, 1996, with magnetic local time and magnetic latitude of ~7.3 hours and ~65.4°, respectively. Under these IMF conditions the Interball Tail spacecraft observed quasi-steady reconnection in progress and evidence for a relatively stable reconnection site at high latitudes. Sunward plasma flow observed by Interball Tail and a determination of the tangential stress balance indicated that reconnection was occurring poleward of the Earth's magnetic cusp, above the space-craft's location. At these high latitudes the gasdynamic model of the solar wind/magnetosphere interaction indicates that the magnetosheath flow should be super-Alfvénic, and therefore that the reconnection site should have propagated tailward. However, the spacecraft observed sub-Alfvénic flow in the magnetosheath region adjacent to the magnetopause current layer near the reconnection site indicating that the reconnection site may have moved in the sunward direction. These observations suggest that the region of sub-Alfvénic flow and stable, quasi-steady reconnection extend to very high latitudes under northward IMF conditions. It is shown that the thickness of the magnetopause current layer for this event (estimated as ~1600 km) is consistent with that found for reconnection at the dayside magnetopause.

  1. Global MHD simulation of magnetic erosion and flux transport

    NASA Astrophysics Data System (ADS)

    Lopez, R. E.; Wiltberger, M. J.

    2001-05-01

    It has long been known that when the Interplanetary Magnetic Field (IMF) turns from a northward orientation to a southward orientation that the dayside magnetopause moves earthward. This phenomenon is termed "magnetic erosion". Simultaneously, the nightside magnetopause flaring angle changes as the flux removed from the dayside is added to the nightside. A simple picture of erosion is an "onion-peeling" model, in which a newly merged field line is transported by the solar wind to the nightside and the dayside magnetopause is now one field line closer to the Earth. This model however ignores pressure balance considerations, and in fact the agent of erosion is the Region 1 current system. In this presentation we present an analysis of several MHD simulations, driven with real IMF conditions, in which the IMF switched from northward to southward producing erosion. We will show that the increasing Region 1 current system produced a perturbation that reduces the dayside field magnitude, causing the pressure balance condition to be satisfied closer to Earth, while simultaneously increasing the nightside magnetic flux. The increased flaring angle causes the nightside field magnitude to increase as well due to pressure balance considerations.

  2. The Impact of Boreal Summer Intra-Seasonal Oscillation on the development of extremely wet and dry condition in South Asian Summer Monsoon

    NASA Astrophysics Data System (ADS)

    Minamide, M.; Ahmad, S.; Koike, T.

    2014-12-01

    Boreal Summer Intra-seasonal Oscillation (BSISO) is known to have a strong impact on the development of drought in South Asian Summer Monsoon (SASM). Our research found that in 6 of 8 past extremely wet / dry SASM years, monsoonal precipitation tendency dynamically reversed during May to July, associated with BSISO (figure). Since the predictability of BSISO is greatly limited, the perturbation associated with BSISO could be the main causality of the difficulty in seasonal prediction. Careful analysis on the atmospheric condition in 2002 and 2003, which are extremely dry / wet year with seasonal dynamical change of precipitation tendency, revealed that BSISO influenced on the development of both extremely dry and wet rainy season. The key factor of the influence of BSISO on the development of wet/dry atmospheric condition is the difference in the northward propagating activity of BSISO. Though it is already known that northward propagation of BSISO active (phase 1-4) phase depends on the environmental atmospheric condition [Jiang et al., 2004; Wheeler and Hendon, 2004], break (phase 5-8) phase northward propagating activity is also revealed to be different between various environment. In 2002, both of active and break convection of BSISO contributed to the development of dry condition. Both of those phases created convergence over Pakistan and north India (SASM region) in the upper troposphere. On the other hand, the opposite effect was caused by the BSISO of 2003. In order to show the generality of this impact of BSISO, theoretical analysis and carefully designed numerical experiment with Weather Research and Forecasting model (WRF) were conducted. We created a convection which shares common characteristics with BSISO by the forcing of sea surface temperature (SST). Further analysis revealed that northward propagation of BSISO differs depending on strong (weak) vertical shear of wind and with plenty (meagerness) of specific humidity in planetary boundary layer

  3. Winning Conditions?

    PubMed

    Green, Esther; Moody, Lesley

    2015-01-01

    The authors of the paper, "The Patient Experience in Ontario 2020: What is Possible?", framed both the current state as well as the future of what patient experience might look like in five years. To ensure intention is catalyzed into meaningful change to improve experience and outcomes, we suggest four winning conditions. The first is to change the language; patients are people too, irrespective of their disease or illness; person-centred is inclusive language and ought to be the focus. The second condition is focused on leaders who play a critical role to establish, build and embed person-centred within the organization. The third and fourth winning conditions are building the evidence base and using effective and meaningful engagement, moving beyond advice, to partnership, respectively. Person-centred care is not the flavour of the month, it is here to stay. Ontarians are important actors in the system not only as users of the system but owners as well. To those who might argue that it is costly to do this work, what are the costs to not engage? Are we satisfied not only as administrators, and clinicians, but as patients at some point, to maintain the status quo? PMID:26888319

  4. On the IMF of first stars

    SciTech Connect

    Susa, H.; Tominaga, N.; Hasegawa, K.

    2014-05-02

    We investigate the formation of the first stars in 60 minihalos found in cosmological simulations, utilizing radiation hydrodynamics simulations. We find ∼70% of the halos host multiple stellar system, while the rest of them have single stars. The stellar mass found in our simulations is in the range of 0.5M{sub ⊙} < M < 300M{sub ⊙}, peaking at several tens of Msun. We do not find that the mass spectrum do not have significant dependence on the formation redshifts and the spin parameters of parent minihalos.

  5. A comparison of Flux transfer events' motion determined by deHoffmann-Teller technique with the Cooling model

    NASA Astrophysics Data System (ADS)

    Dias Silveira, M. V.; Sibeck, D. G.; Gonzalez, W.; Koga, D.

    2015-12-01

    Flux transfer events (FTEs) are considered as a result of transient magnetic reconnection and are often observed in the vicinity of the Earth's magnetopause. The FTEs are responsible for transfer of mass, energy and momentum between solar wind and magnetosphere. According to FTE generation models and in situ observations, FTEs are formed in the subsolar region when the interplanetary magnetic field (IMF) is southward while for northward IMF they should be formed in the polar cap regions. In the present study it is analyzed 58 FTE events observed by the THEMIS spacecraft. First of all, the deHoffmann-Teller technique is employed to determine the local FTE velocity and direction. Then, these parameters (velocity and direction) are compared with those predicted by the Cooling model which has largely been employed to estimate the motion of reconnected flux tubes over a modeled magnetopause under specific solar wind conditions. The calculated deHoffmann-Teller velocity and direction indicate that FTEs observed at the flanks of magnetosphere (|YGSM|≥10 Re) move antisunward and dawn/duskward. For intermediate longitudes (|YGSM|<10 Re) a combination of dusk/dawnward and southward motions is found for the present study. The comparison between the calculated FTEs' velocity/direction and those predicted by the Cooling model presents a good agreement. It is also found that 12 FTE events were observed in the equatorial region during northward IMF.

  6. Operant Conditioning

    PubMed Central

    Staddon, J. E. R.; Cerutti, D. T.

    2005-01-01

    Operant behavior is behavior “controlled” by its consequences. In practice, operant conditioning is the study of reversible behavior maintained by reinforcement schedules. We review empirical studies and theoretical approaches to two large classes of operant behavior: interval timing and choice. We discuss cognitive versus behavioral approaches to timing, the “gap” experiment and its implications, proportional timing and Weber's law, temporal dynamics and linear waiting, and the problem of simple chain-interval schedules. We review the long history of research on operant choice: the matching law, its extensions and problems, concurrent chain schedules, and self-control. We point out how linear waiting may be involved in timing, choice, and reinforcement schedules generally. There are prospects for a unified approach to all these areas. PMID:12415075

  7. Direct determination of IMF BY-related cusp current systems, using SuperDARN radar and multiple ground magnetometer data: A link to theory on cusp current origin

    NASA Astrophysics Data System (ADS)

    Amm, O.; Engebretson, M. J.; Greenwald, R. A.; Lühr, H.; Moretto, T.

    1999-08-01

    We analyze an ionospheric ``enhanced convection event'' in the cusp on November 13, 1996, at 1900 UT, by using data of the SuperDARN radar, and of the IMAGE, Greenland, MACCS and CANOPUS magnetometer arrays; and from other magnetometer stations. The event occurs ~20 minutes after a transition of the IMF BY component from positive to negative and an associated reconfiguration of the ionospheric electric potential pattern. The data allow an instantaneous two-dimensional view of the event in terms of the ionospheric electric and ground magnetic field. The ``method of characteristics'' is used to obtain distributions of ionospheric conductances, actual ionospheric currents, and field-aligned currents (FACs) for the interval under study. Our results show that the region of enhanced convection observed by the radar is associated with a region of low conductances, ranging only slightly above the UV conductance values. However, owing to the strongly enhanced electric field, it produces enhanced westward flowing Hall and southward flowing Pedersen currents. At the northern and southern borders of the enhanced convection region, sheets of downward and upward FACs are observed, respectively, with magnitudes of around 0.5 A/km2. The geometry of the current system resembles a DPY current system [Friis-Christensen and Wilhjelm, 1975]. Using our results, we test alternative theories on cusp current origin that lead to different predictions of the relative location of the cusp current system with respect to the open-closed field line boundary. The location of this boundary is inferred from DMSP F10 satellite data. The center of our resulting current system is located clearly poleward of the open-closed field line boundary, thus favoring the idea of Lee et al. [1985] that the cusp FACs are caused by a rotational discontinuity of the magnetic field at the magnetopause. In contrast, the idea of Clauer and Banks [1986] that a mapping of the solar wind EZ component to the ionosphere is

  8. Reconstruction of Geomagnetic activity and near-Earth interplanetary conditions over the past 167 years.

    NASA Astrophysics Data System (ADS)

    Lockwood, Mike; Nevanlinna, Heikki; Barnard, Luke; Owens, Mat; Harrison, Giles; Rouillard, Alexis; Scott, Chris; Vokhmyanin, Mikhail; Ponyavin, Dmitri; Sokolov, Sergey

    2014-05-01

    Records of geomagnetic activity have previously been used to reconstruct the conditions in near-Earth space, such as the interplanetary magnetic field (IMF), solar wind speed (Vsw) and open solar flux (OSF). Reliable geomagnetic activity records exist back until the mid-1800's, and these data provide one of the few means of inferring variations in the conditions in near-Earth space before the advent of the space age. However, there are challenges in using geomagnetic activity records to reconstruct interplanetary conditions. In particular it is necessary to ensure, as best as is possible, the homogeneity and reliability of any geomagnetic indices used. This becomes increasingly difficult further back in history, as both the quality of the data and the number of observing stations decreases. A new geomagnetic activity index, the IDV(1D) index, is presented, which is designed to be as homogeneous in its construction as possible (Lockwood et al. 2013a). This is achieved by only combining data that, by virtue of the locations of the source observatories used, have similar responses to solar wind and IMF variations. IDV(1d) employs many of the principles of the IDV index (Svalgaard and Cliver (2010)), inspired by the u index of Bartels (1932). The index uses interdiurnal variation data from Helsinki for 1845- 1890 and 1893-1896 and from Eskdalemuir from 1911 to the present. The gaps are filled using data from the Potsdam (1891-1892 and 1897-1907) and the nearby Seddin observatories (1908-1910) and intercalibration achieved using the Potsdam-Seddin sequence. The index is compared with independent, early data from European-sector stations, as well as the composite u index and the IDV index. Agreement is found to be extremely good in most cases. IDV(1D) does not suffer from the poor homogeneity of the IDV index, and is more highly correlated with the IMF, consequently it yields a more reliable reconstruction (Lockwood et al 2013b). For completeness, we use 4 different

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  10. Simulation of Theoretical Most-Extreme Geomagnetic Sudden Commencements

    NASA Astrophysics Data System (ADS)

    Welling, Daniel; Love, Jeffrey; Wiltberger, Michael; Rigler, Erin; Gombosi, Tamas

    2016-04-01

    We report results from a numerical simulation of geomagnetic sudden commencements driven by solar wind conditions given by theoretical-limit extreme coronal-mass ejections (CMEs) estimated by Tsurutani and Lakhina [2014]. The CME characteristics at Earth are a step function that jumps from typical quiet values to 2700 km/s flow speed and a magnetic field magnitude of 127 nT. These values are used to drive three coupled models: a global magnetohydrodynamic (MHD) magnetospheric model (BATS-R-US), a ring current model (the Rice Convection Model, RCM), and a height-integrated ionospheric electrodynamics model (the Ridley Ionosphere Model, RIM), all coupled together using the Space Weather Modeling Framework (SWMF). Additionally, simulations from the Lyon-Fedder-Mobarry MHD model are performed for comparison. The commencement is simulated with both purely northward and southward IMF orientations. Low-latitude ground-level geomagnetic variations, both B and dB/dt, are estimated in response to the storm sudden commencement. For a northward interplanetary magnetic field (IMF) storm, the combined models predict a maximum sudden commencement response, Dst-equivalent of +200 nT and a maximum local dB/dt of ~200nT/s. While this positive Dst response is driven mainly by magnetopause currents, complicated and dynamic Birkeland current patterns also develop, which drive the strong dB/dt responses at high latitude. For southward IMF conditions, erosion of dayside magnetic flux allows magnetopause currents to approach much closer to the Earth, leading to a stronger terrestrial response (Dst-equivalent of +250 nT). Further, high latitude signals from Region 1 Birkeland currents move to lower latitudes during the southward IMF case, increasing the risk to populated areas around the globe. Results inform fundamental understanding of solar-terrestrial interaction and benchmark estimates for induction hazards of interest to the electric-power grid industry.

  11. MESSENGER Observations of Mercury's Dynamic Magnetosphere

    NASA Technical Reports Server (NTRS)

    Slavin, James A.

    2009-01-01

    MESSENGER's 14 January and 6 October 2008 encounters with Mercury have provided new measurements dynamic variations in the coupled atmosphere magnetosphere system. The two flybys took place under very different interplanetary magnetic field (IMF) conditions. The northward IMF during the first encounter produced a very quiet, stable magnetosphere. Neutral sodium atoms and photo-ions were observed to high altitudes ; > 2000 km, even in the subsolar region demonstrating the important role played by more energetic neutral atom production processes such as sputtering. Consistent with predictions of magnetospheric models for northward IMF, the neutral atmosphere was observed to have its strongest sources in the high latitude northern hemisphere for the first flyby. The southward IMF for the second encounter revealed a highly dynamic magnetosphere. Reconnection between the interplanetary and planetary magnetic fields is known to control the rate of energy transfer from the solar wind and to drive magnetospheric convection. The MESSENGER magnetic field measurements revealed that the rate at which interplanetary magnetic fields were reconnecting to planetary fields was a factor of 10 greater than is usually observed at Earth. This extremely high reconnection results in a large magnetic field component normal to the magnetopause and the formation of flux transfer events that are much larger relative to the size of the forward magnetosphere than is observed at Earth. The resulting magnetospheric configuration allows the solar wind access to much of the dayside surface of the Mercury. This widespread impingement of the solar wind on Mercury's surface is a likely source of the less structured sodium exosphere imaged during the second flyby and quite possibly the high degree of exospheric temporal variability observed by ground-based telescopes.

  12. View Northward from Spirit's Winter Roost (False Color)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    One part of the research program that NASA's Mars Exploration Rover Spirit is conducting while sitting at a favorable location for wintertime solar energy is the most detailed panorama yet taken on the surface of Mars. This view is a partial preliminary product from the continuing work on the full image, which will be called the 'McMurdo Panorama.'

    Spirit's panoramic camera (Pancam) began taking exposures for the McMurdo Panorama on the rover's 814th Martian day (April 18, 2006). The rover has accumulated more than 900 exposures for this panorama so far, through all of the Pancam mineralogy filters and using little or no image compression. Even with a tilt toward the winter sun, the amount of energy available daily is small, so the job will still take one to two more months to complete.

    This portion of the work in progress looks toward the north. 'Husband Hill,' which Spirit was climbing a year ago, is on the horizon near the center. 'Home Plate' is a between that hill and the rover's current position. Wheel tracks imprinted when Spirit drove south from Home Plate can be seen crossing the middle distance of the image from the center to the right.

    This view is presented in false color to emphasize differences among rock and soil materials. It combines exposures taken through three of the panoramic camera's filters, centered on wavelengths of 750 nanometers, 530 nanometers and 430 nanometers.

  13. Preliminary assessment of aridity conditions in the Iberian Peninsula

    NASA Astrophysics Data System (ADS)

    Andrade, C.; Corte-Real, J. A.

    2016-06-01

    Aridity is one of the key elements characterizing the climate of a region, having a severe impact on human activities. Aiming at assessing aridity conditions in the Iberian Peninsula, the spatial distribution of the UNEP aridity index is analyzed during the period 1901-2012. Gridded precipitation and potential evapotranspiration datasets are used on a monthly basis. Results show that the southern half of Iberia is particularly vulnerable to water stress and hence to desertification processes. In particular, the UNEP aridity index reveals an increase and northward extension of the semi-arid regime in the Iberian Peninsula between 1901 and 2012. More than 50% of the north and western territory have experienced humid/sub-humid conditions, while the other regions underwent semi-arid settings. Results also reveal that climate was subjected to spatial and temporal variabilities with an overall statistically significant (at a 95% confidence level) trend to aridification in the south-easternmost and central regions. The remaining territory of the Iberian Peninsula does not reveal statistically significant trends.

  14. Allergic Skin Conditions

    MedlinePlus

    American Academy of Allergy Asthma & Immunology Menu Search Main navigation Skip to content Conditions & Treatments Allergies Asthma Primary Immunodeficiency Disease Related Conditions Drug Guide Conditions Dictionary Just ...

  15. Simultaneous backward conditioned inhibition and mediated conditioning.

    PubMed

    Graham, Steven; Jie, Hans Lee; Chan, Hui-Minn; McLaren, I P L; Wills, Andy J

    2011-04-01

    Demonstrations of retrospective revaluation suggest that remembered stimuli undergo a reduction in association with the unconditioned stimulus (US) present during learning. Conversely, demonstrations of mediated conditioning in flavor-conditioning experiments with rats suggest that remembered stimuli undergo an increase in association with the US present during learning. In a food allergy prediction task with 23 undergraduates, we demonstrated simultaneous backward conditioned inhibition and mediated conditioning effects. These results are compatible with the hypothesis that the direction of change (decrease or increase) in associative strength depends on whether the remembered stimulus was of a different category (conditioned stimulus/antecedent) or the same category (US/outcome) as the presented US. PMID:21319913

  16. A critical note on the IAGA-endorsed Polar Cap index procedure: effects of solar wind sector structure and reverse polar convection

    NASA Astrophysics Data System (ADS)

    Stauning, P.

    2015-11-01

    The International Association of Geomagnetism and Aeronomy (IAGA) has recently endorsed a new Polar Cap (PC) index version to supersede the previous seven different versions of the PCN (North) index and the five different PCS (South) index versions. However, the new PC index has some adverse features which should be known and taken into account by users of the index. It uses in its derivation procedure an "effective" quiet day level (QDC) composed of a "basic" QDC and an added solar wind sector term related to the azimuthal component (By) of the interplanetary magnetic field (IMF). The added IMF By-related terms may introduce unjustified contributions to the PC index of more than 2 index units (mV m-1). Furthermore, cases of reverse convection during strong northward IMF Bz (NBZ) conditions included in the database for calculation of index coefficients can cause unjustified index enhancements of 0.5-1 mV m-1 during calm conditions, reduction of index values by more than 20 % during disturbed conditions, and inconsistencies between index coefficients and index values for the northern and southern polar caps. The aim here is to specify these adverse features and quantify their effects, and to suggest alternative steps for future modifications of the index procedure.

  17. A statistical study of plasmaspheric plumes and ionospheric outflows observed at the dayside magnetopause

    NASA Astrophysics Data System (ADS)

    Lee, S. H.; Zhang, H.; Zong, Q.-G.; Otto, A.; Rème, H.; Liebert, E.

    2016-01-01

    We present a statistical study of plasmaspheric plumes and ionospheric outflows observed by the Cluster spacecraft near the dayside magnetopause. Plasmaspheric plumes are identified when the low-energy ions (<1 keV) with ˜90° pitch angle distributions are observed by the Cluster Ion Spectrometer/Hot Ion Analyzer instrument. The ionospheric outflows are characterized by unidirectional or bidirectional field-aligned pitch angle distributions of low-energy ions observed in the dayside magnetosphere. Forty-three (10%) plasmaspheric plume events and 32 (7%) ionospheric outflow events were detected out of the 442 times that C3 crossed the dayside magnetopause between 2007 and 2009. The occurrence rate of plumes at duskside is significantly higher than that at dawnside. The occurrence rate of outflows shows a weak dawn-dusk asymmetry. We investigate the dependence of the occurrence rates of plumes and ionospheric outflows on geomagnetic activity and on solar wind/interplanetary magnetic field (IMF) conditions. The plume events tend to occur during southward IMF (duskward solar wind electric field) and moderate geomagnetic activity (Kp = 3,-30≤Dst <- 10 nT). However, the ionospheric outflow events tend to occur during northward IMF (dawnward solar wind electric field). The ionospheric outflows do not occur when Kp = 0, and the occurrence rate of the ionospheric outflows does not have a clear Dst dependence. Seventy-five percent (46%) of the outflows are observed in the duskside for negative (positive) IMF By. Conversely, 54% (25%) of the outflows are observed in the dawnside for positive (negative) IMF By. Finally, the occurrence rates of both plumes and outflows increase with solar wind dynamic pressure.

  18. Early Pavlovian conditioning impairs later Pavlovian conditioning.

    PubMed

    Lariviere, N A; Spear, N E

    1996-11-01

    Four experiments tested the effects in the rat of very early experience with stimuli to be used later for Pavlovian conditioning. Beginning on postnatal Day 12, prior to the development of substantial detection and effective perception of visual and auditory stimuli, rats were given five daily experiences with either lights or tones and a footshock known to be an effective unconditioned stimulus at these ages. Twenty-four hours after the last of these experiences, pairings of either the light or tone and the unconditioned stimulus were given with parameters established to yield a moderate degree of conditioning in untreated preweanlings (Experiment 1). Experiment 2 determined that early experience with paired or unpaired presentations of either the light or tone and the unconditioned stimulus resulted in a failure to condition to these same lights or tones on postnatal Day 17, although nontreated pups from the same litters conditioned quite effectively. Experiment 3 determined that this early conditioning experience with either paired or unpaired presentations of the lights or tones and the unconditioned stimulus yielded impaired conditioning on postnatal Day 17 in the alternative sensory modality as well, although again nontreated siblings conditioned quite effectively. Experiment 4 replicated the results of each of Experiments 2 and 3 and determined in addition that despite the impairment in conditioning that resulted from early paired or unpaired experience with the stimuli of conditioning, early experience with the individual stimuli of conditioning-with only the CS, the US, or the context-did not result in a similar impairment in conditioning. Although the results were unexpected, they may be understood in part in terms of intersensory competition during development, and there is precedent in the literature for similar interfering effects of early learning on later learning in a variety of species.

  19. The evolution of high-latitude field-aligned currents and magnetospheric dynamics in response to solar wind drivers

    NASA Astrophysics Data System (ADS)

    Bogdanova, Yulia; Vennerstrøm, Susanne; Wild, James; Korth, Haje; Lühr, Hermann; Wing, Simon; Pitout, Frederic

    2016-04-01

    While the statistical behaviour of the solar wind-magnetosphere-ionosphere system is well defined by the Dungey cycle, questions remain on the behaviour of this coupled system during extreme conditions, for example during magnetic storms or periods with long lasting northward IMF, and on how, and how fast, the system reacts to abrupt changes in the solar wind driver. Field-aligned currents play a crucial role in the dynamics of this coupled system as they provide connectivity between different regions and act as channels for energy and momentum transfer. These currents have been investigated in the last decade thanks to observations from low-orbiting satellites, such as CHAMP, Ørsted, DMSP, and the Iridium constellation. However, many previous studies concentrated on the statistical behavior of the current systems or measurements from individual observatories. In this paper we will employ data from Swarm, AMPERE, DMSP, Cluster, SuperDARN and SuperMAG to perform a multi-point study of high-latitude field-aligned current systems evolution and properties and magnetospheric dynamics in response to the solar wind driver, concentrating on the intervals of changes in the IMF orientation and extreme IMF and solar wind conditions.

  20. A theory of substorms: Onset and subsidence

    SciTech Connect

    Kan, J.R.; Zhu, L.; Akasofu, S.I. )

    1988-06-01

    It is shown by a computer simulation study of the magnetosphere-ionosphere (M-I) coupling that an enhanced magnetospheric convection can lead to auroral substorm onset in about 40 min after a southward turning of IMF. The simulation results show that the enhanced M-I coupling can produce intense upward field-aligned currents in the midnight sector near the poleward boundary of a high-conductance belt associated with the diffuse auroral precipitation. Two necessary conditions for substorm onset are that (1) the polar cap potential must exceed a certain value and (2) the convection reversal region must overlap with the poleward gradient of the diffuse auroral conductance in the ionosphere in the midnight sector. The matching ensures that the divergence of the Pedersen current colocates with the divergence of the Hall current to maximize the upward field-aligned current near the poleward boundary of the diffuse aurora in the midnight sector for substorm onset. Without the matching, the auroral brightening would not occur, even if the electrojets are appreciable. Substorm subsides when one of the two necessary conditions is no longer satisfied. This can occur owing either to a northward turning of the IMF or weakening of Alfven shielding due to substorm enhancement of the ionospheric conductance during a prolonged southward IMF.

  1. Chinese Conditionals and the Theory of Conditionals.

    ERIC Educational Resources Information Center

    Chierchia, Gennaro

    2000-01-01

    Summarizes the main features of discourse representation theory, situation-based approaches, and dynamic semantics, and discusses the role the novelty condition plays in each of them, providing the main theoretical coordinates against which to try an assessment of the role of the Chinese conditional and a proposal put forth by Chang and Huang…

  2. The Role of Flux Transfer Events in Solar Wind-Magnetosphere Coupling

    NASA Technical Reports Server (NTRS)

    Dorelli, John C.

    2009-01-01

    Recent global MHD simulations of Flux Transfer Events (FTE's)[Dorelli and Bhattachar ee, JGR, 114, 2009] demonstrate that they are topologically complex flux ropes which extend large distances away from the subsolar magnetopause. Thus, FTE's represent a significant perturbation to the magnetopause magnetic field topology. Specifically, prior to the formation of the first FTE of the simulation, the dayside magnetopause has a relatively simple topology consisting of a single magnetic separator draping northward (even for southward IMF) over the dayside magnetopause (in a manner similar to the "overdraping" which occurs under northward IMF conditions). After the first FTE forms, however, the magnetopause becomes topologically more complex, consisting of multiple separators and braided flux domains. One consequence of this topological complexity is that open flux tubes have direct access to the magnetosphere near the subsolar region (such direct access is not possible during steady separator reconnection). Since the magnetopause topology affects the mapping of the solar wind electric field to the magnetosphere, an interesting question arises: What is the effect of FTE generation on the global magnetospheric convection pattern? In this talk, we address this question by exploring the differences between magnetospheric and ionospheric convection before and after the formation of the first FTE of the simulation.

  3. Dark polar ionosphere: Progress and future challenges

    SciTech Connect

    Carlson, H.C. Jr.

    1994-01-01

    Since the end of the 1970s, we have seen enormous progress in our understanding of the polar ionosphere and its structuring. With this benchmark issue of Radio Science it is appropriate to reflect briefly on that passage and some key questions that lie ahead. The discussion here will concentrate on the winter hemisphere, in keeping with the conditions under which most of the data studied to date have been gathered. The polar ionosphere alternates between two states, depending on whether the interplanetary magnetic field (IMF) is southward or northward. The former state is characterized by approximately 100-1000 km islands of enhanced F region plasma, originating in sunlit upper midlatitudes, entering and traversing the polar cap. They become highly structured and produce severe scintillation. Despite much progress on the source, evolution, and ultimate fate of this polar plasma, we remain challenged by the process(es) which chop entering plasma into such islands. For northward IMF we have learned much about the near-Earth processes determining the character of polar cap arcs, velocity structure and electrodynamics, and energetics. A remaining challenge is to relate these structures to the topology and driving physical processes in the magnetosphere and solar wind. Here we sketch the principles behind the progress and the context of several key problem areas ahead.

  4. REACH. Air Conditioning Units.

    ERIC Educational Resources Information Center

    Garrison, Joe; And Others

    As a part of the REACH (Refrigeration, Electro-Mechanical, Air-Conditioning, Heating) electromechanical cluster, this student manual contains individualized instructional units in the area of air conditioning. The instructional units focus on air conditioning fundamentals, window air conditioning, system and installation, troubleshooting and…

  5. Heliospheric and Geomagnetic Modulation of Galactic Cosmic Ray under Quiet and disturbed interplanetary conditions during Solar cycle 20-23.

    NASA Astrophysics Data System (ADS)

    Kalu, F. D.

    2015-12-01

    The modulation of galactic cosmic rays (GCR) within the heliosphere leads to a reduction in the GCR count rates during period of high solar activity and conversely. Data from three geomagnetic observatories and three Neutron monitors (in close proximity to the geomagnetic stations) have been studied. The monthly residuals of the geomagnetic field components with respect to quiet time conditions from these three stations have been computed and compared with the cosmic ray count rates. The modulations of the GCR during quiet and disturbed interplanetary conditions have been investigated with a view to better understand the role of the global merged interaction regions and coronal mass ejections to the GCR modulation. From first-order partial correlation, we found that removing the influence of the total IMF-B, (especially during quiet conditions), and the influence of SW dynamic pressure (during disturbed conditions) generally enhances the correlation of the residual geomagnetic field with the GCR significantly. The influence of the more subtle parameters like speed, Bz component and proton density were masked by these dominant parameters. Results from this work are important for the modeling of long term GCR variability.

  6. Heliospheric and geomagnetic modulation of galactic cosmic rays under quiet and disturbed interplanetary conditions during solar cycles 20-23

    NASA Astrophysics Data System (ADS)

    Chukwudi Okpala, Kingsley

    2015-08-01

    The modulation of galactic cosmic rays (GCR) within the heliosphere leads to a reduction in the GCR count rates during period of high solar activity and conversely. Data from three geomagnetic observatories and three Neutron monitors (in close proximity to the geomagnetic stations) have been studied. The monthly residuals of the geomagnetic field components with respect to quiet time conditions from these three stations have been computed and compared with the cosmic ray count rates. The modulations of the GCR during quiet and disturbed interplanetary conditions have been investigated with a view to better understand the role of the global merged interaction regions and intense magnetic fields to the GCR modulation. From first-order partial correlation, we found that removing the influence of the total IMF-B, (especially during quiet conditions) and the influence of SW dynamic pressure (during disturbed conditions) generally enhances the correlation of the residual geomagnetic field with the GCR significantly. The influence of the more subtle parameters like speed, Bz component and proton density were masked by these dominant parameters. Results from this work are important for the modeling of long term GCR variability.

  7. Magnetopause Boundary Standoff Position Changes and Its Time-Dependent Response to Solar Wind Conditions: Models and Observations

    NASA Astrophysics Data System (ADS)

    Collado-Vega, Y. M.; Sibeck, D. G.; Rastaetter, L.

    2015-12-01

    The Earth's magnetopause is the boundary that separates the solar wind and the Earth's magnetosphere. Its location as a function of solar wind conditions has been estimated via theory, simulation, and empirical models. This presentation compares magnetopause standoff locations determined by all these methods. We use the Run-On-Request capabilities available from the Community Coordinated Modeling Center (CCMC) at NASA Goddard Space Flight Center, specifically the BATS-R-US, OpenGGCM, LFM and GUMICS global physics-based MHD models. The simulated magnetopause standoff positions and response time to the solar wind changes will then be compared with the results obtained using empirical models (e.g. Shue et al. 1998), and to individual THEMIS, Cluster and the Geotail magnetopause crossing observations. We also inspect times of extreme solar wind conditions when magnetopause crossings have been observed by the GOES satellites. Rigorous analysis/comparison of observations with models is critical in determining the performance of the models used to capture magnetospheric dynamics. We will also identify which types of solar wind conditions lead to significant differences between the models. Preliminary results show that there can be significant discrepancies between magnetopause locations predicted by different global MHD models. The discrepancies are seen, for example, during increases in solar wind dynamic pressure and sharp changes in the IMF Bz component. Preliminary results also indicate that during nominal background solar wind conditions models do agree with the observed magnetopause locations.

  8. Thermal structure and melting conditions associated with `hot' subduction: Implications from thermobarometry of Garibaldi belt basalts, northern Cascadia Subduction System

    NASA Astrophysics Data System (ADS)

    Green, N. L.

    2005-12-01

    The northern Cascadia margin of North America is the classic example of a "hot" subduction system. The downgoing Juan de Fuca plate decreases in age from ca. 10 m.y. off the central Washington coast to less than 5 m.y. off central Vancouver Island; beneath the Garibaldi volcanic belt (GVB) 250 km east of the convergent margin, inferred age of the oceanic lithosphere decreases northward from ca. 22 m.y to 13 m.y. Primitive and near-primitive mafic lavas, which primarily occur trenchward of the GVB volcanic front, range northward from high-Al olivine tholeiites, Mg-andesites and LILE- and LREE-enriched calc-alkaline basalts at Glacier Peak, through transitional basalts in the Cheakamus Valley to alkali olivine basalts and trachybasalts at Meager Mountain, Salal Glacier and Bridge River. The more northerly GVB basaltic magmas show the least evidence of slab-derived components in their source regions. Application of various olivine-melt and pyroxene-melt thermobarometers to GVB basalts indicates a general increase in magmatic temperatures from 1150-1200 C in Mount Baker and Glacier Peak basalts to 1225-1300 C in Bridge River and Salal Glacier lavas. Fe-Ti oxide thermobarometry suggests that northernmost basalts equilibrated under oxygen fugacities conditions between QFM and NNO, whereas Glacier Peak lavas equilibrated at higher oxygen fugacities (ca. 1 log unit above NNO). Estimated P and T conditions of mantle segregation suggest that GVB basalts ascended from increasingly greater depths northward along the volcanic arc. Similar variation is indicated by calculated P-T of basalt equilibrations with both Mg- and Fe-rich peridotite mineral assemblages, based on diopside and albite activity-composition relations. Estimated mantle equilibration temperatures correlate positively with some HFSE abundances (e.g., Hf), but negatively with those of fluid mobile elements (e.g., Cs and B). These relationships are considered in terms of the influence of slab thermal structure on

  9. Ionospheric Current Systems Under Magnetic Cloud Condition

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Rostoker, G.; Sun, W.; Du, A.; Lui, T.

    2005-12-01

    During magnetic clouds the solar wind has properties of low plasma beta, intense magnetic field, smooth north-south (or south-north) magnetic field polarity reversals, and a general absence of Alfven waves and discontinuities. The earth's magnetospheric and ionospheric convection velocities significantly increase during periods of southward IMF within magnetic clouds. At high latitudes, a two-cell convection pattern develops that can be quantitatively described by the DP2 equivalent current system. Under certain circumstances, "sawtooth" events occur featuring quasi-periodic substorm expansion phase activity in which westward electrojets (i.e., equivalent DP1 current) appear in the midnight sector in association with each substorm expansion phase. By studying the April 18, 2002 "sawtooth" event, we show how the DP2 and DP1 current systems develop during a smooth southward IMF interval within the magnetic cloud. With an absence of external triggering, the occurrence of quasi-periodic substorm expansion onsets suggests that this "sawtooth" event may be a result of magnetospheric self-regulation. We also discuss the corresponding energy transfer from the magnetotail where the tail magnetic field intensity is seen to vary quasi-periodically.

  10. Baseball-specific conditioning.

    PubMed

    Rhea, Matthew R; Bunker, Derek

    2009-09-01

    Baseball demands speed, power, and quickness. To perform at a high level, and avoid injuries that are common among baseball players, an evaluation of current trends in strength and conditioning practices is helpful. Based on the demands of the sport and the injury risks, qualified strength and conditioning professionals can develop effective baseball-specific conditioning programs. This commentary briefly covers historical aspects of baseball conditioning, recent injury trends, current practices among elite baseball professionals, and provides suggestions for future improvements in training.

  11. Magnetohydrodynamic Characteristic Boundary Conditions

    NASA Astrophysics Data System (ADS)

    Schaffenberger, Werner; Stein, R.

    2009-05-01

    We implemented MHD characteristic boundary conditions for a non-ideal plasma in the "stagger-code" (Gudiksen and Nordlund, 2005, ApJ 618, 1020). The aim of these boundary conditions is to reduce reflection at the boundaries which is important for the simulation of wave propagation. We present some test simulations of propagating waves demonstrating the capability of these boundary conditions.

  12. Inflation of Conditional Predictions

    ERIC Educational Resources Information Center

    Koriat, Asher; Fiedler, Klaus; Bjork, Robert A.

    2006-01-01

    The authors report 7 experiments indicating that conditional predictions--the assessed probability that a certain outcome will occur given a certain condition--tend to be markedly inflated. The results suggest that this inflation derives in part from backward activation in which the target outcome highlights aspects of the condition that are…

  13. Evidence for multiple ejecta: April 7-11, 1997, ISTP Sun-Earth connection event

    NASA Astrophysics Data System (ADS)

    Berdichevsky, D.; Bougeret, J.-L.; Delaboudinière, J.-P.; Fox, N.; Kaiser, M.; Lepping, R.; Michels, D.; Plunkett, S.; Reames, D.; Reiner, M.; Richardson, I.; Rostoker, G.; Steinberg, J.; Thompson, B.; von Rosenvinge, T.

    Evidence is presented that the enhanced geomagnetic activity, on April 10-11, 1997, was caused by one of two ejecta that left the Sun at ≈ 14 UT on April 7. This ejecta was not directly detected at the Earth. The evidence for this interpretation is based on WIND spacecraft observations in the solar wind (SW). It is consistent with: (i) measured velocities of the coronal mass ejections from the SOHO coronagraph; (ii) the initial propagation speed of the shock generated in this event, estimation from type II radio burst observations from the WAVES instrument on WIND, and (iii) the time profile of energetic ions observed by EPACT on WIND. This locally unobserved ejecta (moving at 600 to 700 kms-1) generated a fast shock which accelerated ions to several tens of MeV/amu. The inferred passage of the first ejecta close to Earth (on April 10 to 11) is based on the observation of an interplanetary shock (IS) ahead of a field and plasma compressional region where the draping of the SW flow and possibly the changes in the direction of the IMF are consistent with a location northward of a faster ejecta. This ejecta was responsible for disturbed SW conditions including approximately ten hours of southward orientation of the interplanetary magnetic field (IMF) and a ram pressure many times above normal. The slower moving ejecta was directed toward Earth and was observed with WIND from about 0550 until 1500 UT on April 11. It had a strong northward IMF and produced density enhancements which elevated the ram pressure to more than four times above normal.

  14. [Conditioning mechanisms and psychoneuroimmunology].

    PubMed

    Stockhorst, Ursula; Klosterhalfen, Sibylle

    2005-01-01

    This chapter deals with the role of conditioning principles in psychoneuroimmunology (PNI). We will first describe the paradigms of classical and instrumental conditioning and classify immune parameters that are subject to conditioning (chapter 1). So far, PNI research mainly uses classical (or Pavlovian) conditioning. We will summarize some of the paradigmatic studies, mainly animal studies (chapter 2) and also describe studies that support the clinical relevance of classical conditioning, i. e., in the pharmacological treatment of autoimmune diseases, transplantation and tumor chemotherapy (chapter 3). A study of our group on anticipatory immunomodulation in pediatric cancer patients is reported. Mechanisms mediating conditioned immunomodulation are summarized (chapter 4). We also describe studies that analyze the impact of instrumental conditioning contingencies on immune functioning (chapter 5). Finally, research perspectives are summarized (chapter 6).

  15. Statistical Dependence of the Large-Scale Birkeland Currents on Solar Wind Parameters

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

    Since February 1999, distributions of the large-scale field-aligned Birkeland currents have been derived continuously from magnetic perturbations measured globally by the Iridium constellation of satellites. In a statistical study, over 1500 two-hour intervals (5% of the data) were identified for which the currents were stable to within at least 45% overlap between successive hours, corresponding to conditions in the solar wind were sufficiently stable to obtain reliable Birkeland currents. Organized by the interplanetary magnetic field (IMF) clock angle, the statistical current distributions show familiar Regrion-1 and Region-2 currents for southward IMF, NBZ currents for northward IMF, and a continuous distortion of the currents with IMF clock angle consistent with changes in the location of outflow from magnetopause reconnection (Anderson et al. 2008). Here we extend the statistical analysis to examine the dependence of the large-scale Birkeland currents on solar wind electric field in the plane normal to the Earth-Sun line, Eyz, to assess the sensitivity to the strength of the solar wind dynamo, Alfvén Mach number to assess the influence of dayside reconnection mass loading, and dynamic pressure to investigate the dependence on ram pressure. The current intensities are first corrected for variations in EUV-produced ionospheric conductance, normalizing the current densities to zero dipole tilt conditions. Findings include: (1) with increasing solar wind electric field the large-scale Birkeland currents shift duskward and expand equatorward, and the total current intensifies; (2) the total current intensifies with increasing solar wind dynamic pressure by 0.4 MA/nPa; (3) the total current intensifies with increasing Alfvén Mach number by 0.07 MA per unit Alfvén Mach number change. The analysis and implications are discussed.

  16. Imaging the development of the cold dense plasma sheet

    NASA Astrophysics Data System (ADS)

    Fuselier, S. A.; Dayeh, M. A.; Livadiotis, G.; McComas, D. J.; Ogasawara, K.; Valek, P.; Funsten, H. O.; Petrinec, S. M.

    2015-10-01

    The Interstellar Boundary Explorer (IBEX) frequently images the Earth's magnetosphere in Energetic Neutral Atoms (ENAs). In May 2013, there was an extended period of northward interplanetary magnetic field (IMF) while IBEX was imaging the Earth's magnetotail. During this period, IBEX imaged the development of the cold plasma sheet between about 15 and 20 Earth radii (RE) down the tail from the Earth. The ENA fluxes changed in both amplitude and average energy during this development. In addition, the plasma sheet may have thickened. At the end of the interval, the IMF turned southward and ENA fluxes decreased. The thickening of the plasma sheet suggests that the plasma in this region increases in both density and volume as it develops during extended periods of northward IMF. The decrease in the ENA flux suggests thinning of the plasma sheet and loss of plasma associated with the IMF turning.

  17. Numerical simulation of the subsolar magnetopause current layer in the sun-earth meridian plane

    NASA Technical Reports Server (NTRS)

    Okuda, H.

    1993-01-01

    The formation and stability of the magnetopause current layer near the subsolar point in the sun-earth meridian plane are examined using a 2D electromagnetic particle simulation. For the case of zero IMF, the simulation results show that the current layer remains stable and is essentially the same as in the 1D simulation. The width of the current layer is given by the electron-ion hybrid gyroradius which is much smaller than the ion gyroradius. The current layer is found to remain stable for the northward IMF as well. As in the 1D simulation, the jump of the magnetic field at the current layer for the northward IMF remains small. For the southward IMF, collisionless magnetic reconnection is found to develop, leading to the formation of magnetic islands and density peaking within the current layer.

  18. Winter Conditions Correlate with Phytophthora alni Subspecies Distribution in Southern Sweden.

    PubMed

    Redondo, Miguel A; Boberg, Johanna; Olsson, Christer H B; Oliva, Jonàs

    2015-09-01

    During the last century, the number of forest pathogen invasions has increased substantially. Environmental variables can play a crucial role in determining the establishment of invasive species. The objective of the present work was to determine the correlation between winter climatic conditions and distribution of two subspecies of the invasive forest pathogen Phytophthora alni: P. alni subspp. alni and uniformis killing black alder (Alnus glutinosa) in southern Sweden. It is known from laboratory experiments that P. alni subsp. alni is more pathogenic than P. alni subsp. uniformis, and that P. alni subsp. alni is sensitive to low temperatures and long frost periods. By studying the distribution of these two subspecies at the northern limit of the host species, we could investigate whether winter conditions can affect the geographical distribution of P. alni subsp. alni spreading northward. Sixteen major river systems of southern Sweden were systematically surveyed and isolations were performed from active cankers. The distribution of the two studied subspecies was highly correlated with winter temperature and duration of periods with heavy frost. While P. alni subsp. uniformis covered the whole range of temperatures of the host, P. alni subsp. alni was recovered in areas subjected to milder winter temperatures and shorter frost periods. Our observations suggest that winter conditions can play an important role in limiting P. alni subsp. alni establishment in cold locations, thus affecting the distribution of the different subspecies of P. alni in boreal regions.

  19. Context and Pavlovian conditioning.

    PubMed

    Landeira-Fernandez, J

    1996-02-01

    Procedurally, learning has to occur in a context. Several lines of evidence suggest that contextual stimuli actively affect learning and expression of the conditional response. The experimental context can become associated with the unconditional stimulus (US), especially when the US is presented in a context in the absence of a discrete conditional stimulus (CS). Moreover, context can modulate CS-US associations. Finally, it appears that context can become associated with the CS when it is presented before the CS-US training. The purpose of the present paper is to review some of the relevant literature that considers the context as an important feature of Pavlovian conditioning and to discuss some of the main learning theories that incorporate the context into their theoretical framework. The paper starts by mentioning historical positions that considered context an important variable in conditioning and then describes how the approach to contextual conditioning changed with the modern study of Pavlovian conditioning. Various forms of measurement of context conditioning are presented and the associative strength attached to context in several experimental paradigms is examined. The possible functions that context may acquire during conditioning are pointed out and related to major learning theories. Moreover, the effect of certain neurological manipulations on context conditioning is presented and these results are discussed in terms of possible functions that the context might acquire during Pavlovian conditioning. It is concluded that contextual stimuli acquire different functions during normal conditioning. A procedure in which animals are exposed to an aversive US immediately after they are placed in the experimental context is suggested as a useful control for the study of context conditioning.

  20. Common skin conditions.

    PubMed Central

    Ridley, M.; Safranek, M.

    1992-01-01

    Four common conditions: acne, psoriasis, eczema and urticaria are considered. Guidance is given on appropriate topical and systematic treatment for the different types and degrees of these conditions, with notes on management in general and criteria for referral to hospital outpatient departments. Where there are different types of the condition, with varying aetiology, for example in urticaria and eczema, management of the common types is outlined. PMID:1345156

  1. Nonbirefringence conditions for spacetime

    SciTech Connect

    Itin, Yakov

    2005-10-15

    Within the axiomatic premetric approach to classical electrodynamics, we derive under which covariant conditions the quartic Fresnel surface represents a unique light cone without birefringence in vacuum.

  2. Condition Assessment Information System

    2002-09-16

    CAIS2000 records, tracks and cost maintenance deficiencies associated with condition assessments of real property assets. Cost information is available for 39,000 items in the currenht RS Means, Facilities Construction Manual. These costs can, in turn, be rolled by by asset to produce the summary condition of an asset or site.

  3. Air-Conditioning Mechanic.

    ERIC Educational Resources Information Center

    Marine Corps Inst., Washington, DC.

    This student guide, one of a series of correspondence training courses designed to improve the job performance of members of the Marine Corps, deals with the skills needed by air conditioning mechanics. Addressed in the four chapters, or lessons, of the manual are the following topics: principles of air conditioning, refrigeration components as…

  4. CONDITIONAL DISTANCE CORRELATION

    PubMed Central

    Wang, Xueqin; Pan, Wenliang; Hu, Wenhao; Tian, Yuan; Zhang, Heping

    2015-01-01

    Statistical inference on conditional dependence is essential in many fields including genetic association studies and graphical models. The classic measures focus on linear conditional correlations, and are incapable of characterizing non-linear conditional relationship including non-monotonic relationship. To overcome this limitation, we introduces a nonparametric measure of conditional dependence for multivariate random variables with arbitrary dimensions. Our measure possesses the necessary and intuitive properties as a correlation index. Briefly, it is zero almost surely if and only if two multivariate random variables are conditionally independent given a third random variable. More importantly, the sample version of this measure can be expressed elegantly as the root of a V or U-process with random kernels and has desirable theoretical properties. Based on the sample version, we propose a test for conditional independence, which is proven to be more powerful than some recently developed tests through our numerical simulations. The advantage of our test is even greater when the relationship between the multivariate random variables given the third random variable cannot be expressed in a linear or monotonic function of one random variable versus the other. We also show that the sample measure is consistent and weakly convergent, and the test statistic is asymptotically normal. By applying our test in a real data analysis, we are able to identify two conditionally associated gene expressions, which otherwise cannot be revealed. Thus, our measure of conditional dependence is not only an ideal concept, but also has important practical utility. PMID:26877569

  5. Sheltered Living Conditions.

    ERIC Educational Resources Information Center

    Netherland's Central Society for Rehabilitation, The Hague.

    Resulting from a study conducted by the Advisory Housing Committee of the Dutch Society for Rehabilitation, the report describes housing conditions and possibilities for the physically handicapped in the Netherlands. Four categories of sheltered living conditions are described and analyzed: residential centers, supervised residential centers,…

  6. NATIONAL COASTAL CONDITION REPORT

    EPA Science Inventory

    The National Coastal Condition report compiles several available data sets from different agencies and areas of the country and summarizes them to present a broad baseline picture of the condition of coastal waters. Although data sets presented in this report do not cover all coa...

  7. Solar Wind Influence on the Oxygen Content of Ion Outflow in the High-Altitude Polar Cap During Solar Minimum Conditions

    NASA Technical Reports Server (NTRS)

    Elliott, H. A.; Comfort, R. H.; Craven, P. D.; Chandler, M. O.; Moore, T. E.

    2001-01-01

    We correlate solar wind and interplanetary magnetic field (IMF) properties with the properties of O(+) and H(+) during early 1996 (solar minimum) at altitudes between 5.5 and 8.9 R(sub E) geocentric using the Thermal Ion Dynamics Experiment (TIDE) on the Polar satellite. Throughout the high-altitude polar cap we observe H(+) to be more abundant than O(+). O(+) is found to be more abundant at lower latitudes when the solar wind speed is low (and Kp is low), while at higher solar wind speeds (and high Kp), O(+) is observed across most of the polar cap. The O(+) density and parallel flux are well organized by solar wind dynamic pressure, both increasing with solar wind dynamic pressure. Both the O(+) density and parallel flux have positive correlations with both V(sub SW)B(sub IMF) and E(sub SW). No correlation is found between O(+) density and IMF Bz, although a nonlinear relationship with IMF By is observed, possibly due to a strong linear correlation with the dynamic pressure. H(+) is not as highly correlated with solar wind and IMF parameters, although H(+) density and parallel flux are negatively correlated with IMF By and positively correlated with both V(sub SW)B(sub IMF) and E(sub SW). In this solar minimum data set, H(+) is dominant, so that contributions of this plasma to the plasma sheet would have very low O(+) to H(+) ratios.

  8. Systematizing semishortening conditions

    NASA Astrophysics Data System (ADS)

    Ju, C.-Y.; Siegel, W.

    2014-12-01

    We rederive semishortening conditions for four-dimensional superconformal field theory with a different approach. These conditions have similar patterns that can be generalized to weaker constraints, including all those of Dolan and Osborn [Ann. Phys. (Amsterdam) 307, 41 (2003)]. In particular, for the case of N =4 super-Yang-Mills theory formulated in projective superspace, we find constraints for all Bogomol'nyi-Prasad-Sommerfield operators. We also give an example how constraints can be found from known ones. These constraints are a subset of our maximal set of semishortening conditions.

  9. A case study of the response of the magnetosphere to changes in the interplanetary medium

    NASA Technical Reports Server (NTRS)

    Rostoker, G.; Baumjohann, W.; Russell, C. T.

    1983-01-01

    A detailed analysis of world-wide ground based magnetometer data is presented, together with information on the plasma and magnetic field properties of the interplanetary medium and magnetosheath obtained from the ISEE 1 and 2 and IMP 8 spacecraft. The event concerned exhibited an interval of relatively stable southward IMF followed by a sharp northward turning. It is pointed out that during the interval of southward IMF there were occasional transient northward turnings with significant substorm expansive phase activity appearing to be triggered by these transient northward turnings. The final northward turning of the IMF was linked with an episode of strong magnetospheric substorm expansive phase activity after which the level of high latitude magnetic activity declined to a low level. Evidence is presented indicating that the driven system auroral electrojets begin to decay at the time of the northward turning of the IMF, even as the substorm expansive phase activity is initiated in the midnight sector. The collapse of the substorm current wedge during the final decay of high latitude activity is described in some detail, and it is shown that this collapse occurs progressively from east to west in a series of impulsive episodes.

  10. Etiquette of Verbal Conditioning

    ERIC Educational Resources Information Center

    Denner, Bruce

    1970-01-01

    Explores role of ambiguity in producing verbal conditioning by using two E types and two S types. Six college students were assigned to "crafty Es. Results revealed that certain types of ambiguity increase verbal compliance. (Author)

  11. Operant Conditioning and Education.

    ERIC Educational Resources Information Center

    de Noronha, Mario

    A case study of a learning disabled 8-year-old with behavior disturbancs is presented to highlight the use of operant conditioning in cutting down educational costs and easing the teacher's class management problems. (CL)

  12. Skin Conditions during Pregnancy

    MedlinePlus

    ... during pregnancy? • What is pruritic urticarial papules and plaques of pregnancy (PUPPP)? • What is prurigo of pregnancy? • ... itchy skin. What is pruritic urticarial papules and plaques of pregnancy (PUPPP)? In this condition, small, red ...

  13. Common Childhood Orthopedic Conditions

    MedlinePlus

    ... Ones & When? Smart School Lunches Emmy-Nominated Video "Cerebral Palsy: Shannon's Story" 5 Things to Know About Zika & ... might be linked to other conditions, such as cerebral palsy, muscle weakness disorders, autism, or other nervous system ...

  14. Aerobic Conditioning Class.

    ERIC Educational Resources Information Center

    Johnson, Neil R.

    1980-01-01

    An aerobic exercise class that focuses on the conditioning of the cardiovascular and muscular systems is presented. Students complete data cards on heart rate, pulse, and exercises to be completed during the forty minute course. (CJ)

  15. Lung Diseases and Conditions

    MedlinePlus

    ... Share this page from the NHLBI on Twitter. Lung Diseases and Conditions Breathing is a complex process. ... your bronchial tubes ( bronchitis ) or deep in your lungs ( pneumonia ). These infections cause a buildup of mucus ...

  16. Pavement condition data analysis

    SciTech Connect

    Zaniewski, J.P.; Hudson, S.W.; Hudson, W.R.

    1987-07-01

    This paper describes a computer methodology for analyzing pavement condition data to define inputs for pavement management systems. This system of programs was developed during a Federal Highway Administration research project. In the project, eight state highway departments were studied to determine the types of pavement condition data collected, procedures used for collecting data, the inputs to the states' pavement management systems, and computer programs used by the states to analyze raw pavement condition data. Several of the programs were assembled into the Method for Analyzing Pavement Condition, MAPCON, during a project performed at Pennsylvania State University. These and other existing or new programs (a total of 18) were identified, tested, modified, and incorporated onto a MS/DOS microcomputer system. MAPCON guides the user through selection of analysis method, raw data entry, and data analysis.

  17. Climatic Conditions in Classrooms.

    ERIC Educational Resources Information Center

    Kevan, Simon M.; Howes, John D.

    1980-01-01

    Presents an overview of research on the ways in which classroom thermal environment, lighting conditions, ion state, and electromagnetic and air pollution affect learning and the performance of students and teachers. (SJL)

  18. 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.

  19. Conditional data watchpoint management

    DOEpatents

    Burdick, Dean Joseph; Vaidyanathan, Basu

    2010-08-24

    A method, system and computer program product for managing a conditional data watchpoint in a set of instructions being traced is shown in accordance with illustrative embodiments. In one particular embodiment, the method comprises initializing a conditional data watchpoint and determining the watchpoint has been encountered. Upon that determination, examining a current instruction context associated with the encountered watchpoint prior to completion of the current instruction execution, further determining a first action responsive to a positive context examination; otherwise, determining a second action.

  20. Power supply conditioning circuit

    NASA Technical Reports Server (NTRS)

    Primas, Lori E. (Inventor); Loveland, Rohan C. (Inventor)

    1988-01-01

    A conditioning circuit is provided with a constant current diode in series with a zener diode, the former having a high dynamic impedance and the latter a low dynamic impedance. The constant current diode can receive an input voltage with PARD. In conjunction with the zener diode fixed to a ground, a voltage divider is provided which can give an output voltage whose PARD was significantly reduced. The conditioning circuit is effective down to dc.

  1. Paired microfossil evidence for a delayed development of fully marine surface water conditions in the Nordic seas during the Last interglacial (MIS 5e)

    NASA Astrophysics Data System (ADS)

    van Nieuwenhove, N.; Bauch, H. A.; Kandiano, E. S.

    2010-12-01

    Dinoflagellate cyst (dinocyst) and foraminiferal records of sediment cores from The Vøring and Iceland Plateau and south of the Fram Strait were used to reconstruct the evolution of the surface circulation in the Nordic seas during the last interglacial (Marine Isotopic Stage or MIS 5e). The location of the cores, under the modern pathway of the warm Norwegian Atlantic Current (NwAC) and within the mixing zone of the NwAC and the cold East Greenland Current (EGC), allows to reconstruct the spreading of inflowing North Atlantic surface waters across the Nordic seas during the climate progression of MIS 5e. The microfossil records, supported by stable isotope and IRD data, reveal that during the first ~6000 years of MIS 5e a more pronounced stratification and seasonality existed in the eastern Nordic seas, presumably as a result of long-lasting deglacial effects. Thus, the northward heat flux was reduced during this time in this area. It was only during late MIS 5e, and when IRD-input into the eastern Nordic seas had come to a halt, that the northward flow of warm Atlantic water masses intensified so that interglacial conditions became also eminent in the surface waters south of the Fram Strait. Our data further suggest that the stronger NwAC of late MIS 5e entailed an intensification of the EGC. While this brought comparatively colder conditions towards the Iceland Plateau it was also the only time when proper, that is fully marine, warm interglacial surface conditions co-existed in the eastern Nordic seas.

  2. Chemical conditioning of sludge.

    PubMed

    Novak, J T; Park, C

    2004-01-01

    With all the advances made in understanding the structure and composition of sewage sludges, chemical conditioning remains a trial and error process, both with regard to the type and dose of conditioner needed. Recent studies at Virginia Tech have found that biological floc consists of two types of biopolymer, material associated with iron and aluminium and material associated with calcium and magnesium. These materials behave differently when sludges undergo digestion. This results in very different material being released into solution during digestion and very different conditioning requirements. This study shows that the primary materials released during anaerobic digestion are proteins and coagulation of the colloidal protein fraction in solution is the primary mechanism for conditioning. For aerobically digested sludges, both proteins and polysaccharides make up the colloid fraction, which interferes with dewatering. This research also shows that the effectiveness of the digestion process as characterized by volatile solids destruction is directly related to the chemical dose required for conditioning. That is, as the solids destruction increases, the conditioning chemical requirement also increases. Well digested sludges dewater more poorly and require more conditioning chemical than those with less volatile solids destruction. PMID:15259940

  3. Causal conditionals and counterfactuals

    PubMed Central

    Frosch, Caren A.; Byrne, Ruth M.J.

    2012-01-01

    Causal counterfactuals e.g., ‘if the ignition key had been turned then the car would have started’ and causal conditionals e.g., ‘if the ignition key was turned then the car started’ are understood by thinking about multiple possibilities of different sorts, as shown in six experiments using converging evidence from three different types of measures. Experiments 1a and 1b showed that conditionals that comprise enabling causes, e.g., ‘if the ignition key was turned then the car started’ primed people to read quickly conjunctions referring to the possibility of the enabler occurring without the outcome, e.g., ‘the ignition key was turned and the car did not start’. Experiments 2a and 2b showed that people paraphrased causal conditionals by using causal or temporal connectives (because, when), whereas they paraphrased causal counterfactuals by using subjunctive constructions (had…would have). Experiments 3a and 3b showed that people made different inferences from counterfactuals presented with enabling conditions compared to none. The implications of the results for alternative theories of conditionals are discussed. PMID:22858874

  4. Choice and conditioned reinforcement.

    PubMed

    Fantino, E; Freed, D; Preston, R A; Williams, W A

    1991-03-01

    A potential weakness of one formulation of delay-reduction theory is its failure to include a term for rate of conditioned reinforcement, that is, the rate at which the terminal-link stimuli occur in concurrent-chains schedules. The present studies assessed whether or not rate of conditioned reinforcement has an independent effect upon choice. Pigeons responded on either modified concurrent-chains schedules or on comparable concurrent-tandem schedules. The initial link was shortened on only one of two concurrent-chains schedules and on only one of two corresponding concurrent-tandem schedules. This manipulation increased rate of conditioned reinforcement sharply in the chain but not in the tandem schedule. According to a formulation of delay-reduction theory, when the outcomes chosen (the terminal links) are equal, as in Experiment 1, choice should depend only on rate of primary reinforcement; thus, choice should be equivalent for the tandem and chain schedules despite a large difference in rate of conditioned reinforcement. When the outcomes chosen are unequal, however, as in Experiment 2, choice should depend upon both rate of primary reinforcement and relative signaled delay reduction; thus, larger preferences should occur in the chain than in the tandem schedules. These predictions were confirmed, suggesting that increasing the rate of conditioned reinforcement on concurrent-chains schedules may have no independent effect on choice.

  5. Latitudinal Dependence of the Radial IMF Component - Interplanetary Imprint

    NASA Technical Reports Server (NTRS)

    Suess, S. T.; Smith, E. J.; Phillips, J.; Goldstein, B. E.; Nerney, S.

    1996-01-01

    Ulysses measurements have confirmed that there is no significant gradient with respect to heliomagnetic latitude in the radial component, B(sub r,), of the interplanetary magnetic field. There are two processes responsible for this observation. In the corona, the plasma beta is much less than 1, except directly above streamers, so both longitudinal and latitudinal (meridional) gradients in field strength will relax, due to the transverse magnetic pressure gradient force, as the solar wind carries magnetic flux away from the Sun. This happens so quickly that the field is essentially uniform by 5 solar radius. Beyond 10 solar radius, beta is greater than 1 and it is possible for a meridional thermal pressure gradient to redistribute magnetic flux - an effect apparently absent in Ulysses and earlier ICE and Interplanetary Magnetic Physics (IMP) data. We discuss this second effect here, showing that its absence is mainly due to the perpendicular part of the anisotropic thermal pressure gradient in the interplanetary medium being too small to drive significant meridional transport between the Sun and approx. 4 AU. This is done using a linear analytic estimate of meridional transport. The first effect was discussed in an earlier paper.

  6. Mugabe: victim of the IMF and World Bank?

    PubMed

    Moore, J L

    2000-06-01

    This paper discusses the role of President Robert Mugabe on the economic crisis in Zimbabwe. It is noted that President Mugabe adopted the Economic Structural Adjustment Programme in 1990. The introduction of this program had more to do with the demands of major exporters, such as White farmers and multinational companies, and the demise of socialist thinking than with any high ideals of altruism. As part of the market strategy, the government removed food subsidies, deregulated the exchange rate, and increased education and health fees. Such moves contributed to the existing crisis in the country, in which access to fertile land has become a matter of survival for many of the 7 million people caught within overcrowded and environmentally degraded communal lands.

  7. Anomalous plasma diffusion and the magnetopause boundary layer

    NASA Technical Reports Server (NTRS)

    Treumann, Rudolf A.; Labelle, James; Haerendel, Gerhard; Pottelette, Raymond

    1992-01-01

    An overview of the current state of anomalous diffusion research at the magnetopause and its role in the formation of the magnetopause boundary layer is presented. Plasma wave measurements in the boundary layer indicate that most of the relevant unstable wave modes contribute negligibly to the diffusion process at the magnetopause under magnetically undisturbed northward IMF conditions. The most promising instability is the lower hybrid drift instability, which may yield diffusion coefficients of the right order if the highest measured wave intensities are assumed. It is concluded that global stationary diffusion due to wave-particle interactions does not take place at the magnetopause. Microscopic wave-particle interaction and anomalous diffusion may contribute to locally break the MD frozen-in conditions and help in transporting large amounts of magnetosheath plasma across the magnetospheric boundary.

  8. Conditional E-Cash

    NASA Astrophysics Data System (ADS)

    Shi, Larry; Carbunar, Bogdan; Sion, Radu

    We introduce a novel conditional e-cash protocol allowing future anonymous cashing of bank-issued e-money only upon the satisfaction of an agreed-upon public condition. Payers are able to remunerate payees for services that depend on future, yet to be determined outcomes of events. Once payment complete, any double-spending attempt by the payer will reveal its identity; no double-spending by the payee is possible. Payers can not be linked to payees or to ongoing or past transactions. The flow of cash within the system is thus both correct and anonymous. We discuss several applications of conditional e-cash including online trading of financial securities, prediction markets, and betting systems.

  9. Universal signal conditioning amplifier

    NASA Technical Reports Server (NTRS)

    Larson, William E.; Hallberg, Carl; Medelius, Pedro J.

    1994-01-01

    Engineers at NASA's Kennedy Space Center have designed a signal conditioning amplifier which automatically matches itself to almost any kind of transducer. The product, called Universal Signal Conditioning Amplifier (USCA), uses state-of-the-art technologies to deliver high accuracy measurements. USCA's features which can be either programmable or automated include: voltage, current, or pulsed excitation, unlimited resolution gain, digital filtering and both analog and digital output. USCA will be used at Kennedy Space Center's launch pads for environmental measurements such as vibrations, strains, temperatures and overpressures. USCA is presently being commercialized through a co-funded agreement between NASA, the State of Florida, and Loral Test and Information Systems, Inc.

  10. Mineralogy under extreme conditions

    SciTech Connect

    Shu, Jinfu

    2012-02-07

    We have performed measurements of minerals based on the synchrotron source for single crystal and powder X-ray diffraction, inelastic scattering, spectroscopy and radiography by using diamond anvil cells. We investigated the properties of iron (Fe), iron-magnesium oxides (Fe, Mg)O, silica(SiO{sub 2}), iron-magnesium silicates (Fe, Mg)SiO{sub 3} under simulated high pressure-high temperature extreme conditions of the Earth's crust, upper mantle, low mantle, core-mantle boundary, outer core, and inner core. The results provide a new window on the investigation of the mineral properties at Earth's conditions.

  11. Simulation of interplanetary magnetic field B{sub y} penetration into the magnetotail

    SciTech Connect

    Guo, Jiuling; Shen, Chao; Liu, Zhenxing

    2014-07-15

    Based on our global 3D magnetospheric MHD simulation model, we investigate the phenomena and physical mechanism of the B{sub y} component of the interplanetary magnetic field (IMF) penetrating into the magnetotail. We find that the dayside reconnected magnetic field lines move to the magnetotail, get added to the lobe fields, and are dragged in the IMF direction. However, the B{sub y} component in the plasma sheet mainly originates from the tilt and relative slippage of the south and north lobes caused by plasma convection, which results in the original B{sub z} component in the plasma sheet rotating into a B{sub y} component. Our research also shows that the penetration effect of plasma sheet B{sub y} from the IMF B{sub y} during periods of northward IMF is larger than that during periods of southward IMF.

  12. Flow-Through Reconnection 3: The General Case

    NASA Astrophysics Data System (ADS)

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

    2001-05-01

    This talk covers "flow-through reconnection," FTR, for the general IMF case as represented by a duskward IMF (IMF clock angle = 90 degrees). For the general IMF case, FTR occurs in the magnetospheric sash where the magnetic separatrix has its null point. Reconnection occurs all along the separatrix, from one null point across the dayside magnetopause to the null point in the other hemisphere. We show that the null point in the sash is stationary even though plasma is flowing through it tailward in excess of 200 km/s. In this case the sash acts as the long, narrow tongue of very weak field, described for the northward and southward IMF cases, within which the dissipation electric field exceeds the motional electric field. This case illustrates that the horn of the northward IMF case, the tongue of the southward IMF case, and the sash of the general case have the same function: to enable FTR when the magnetosphere is faced with the problem of operating sites of magnetic reconnection away from a stagnation point. This talk will also demonstrate how streamlines of the Poynting vector can be used to define the reconnection line along the magnetopause.

  13. Operant Conditioning - Token Economy.

    ERIC Educational Resources Information Center

    Montgomery, Jacqueline; McBurney, Raymond D.

    Described is an Operant Conditioning-Token Economy Program, teaching patients to be responsible for their own behavior, to make choices, and to be motivated to change. The program was instigated with mentally ill patients in a state hospital and was later used with institutionalized mentally handicapped groups. After two years, only four of the…

  14. Teachers and Operant Conditioning.

    ERIC Educational Resources Information Center

    Frey, Sherman

    A survey was conducted of 406 elementary, middle, and secondary school teachers to determine their understanding, acceptance, and use of the principle of operant conditioning. The treatment of data was by percent and chi square analysis primarily according to sex, experience, degree, and position. Subjects reported that a) they believed that the…

  15. Workplace Conditions. Brief

    ERIC Educational Resources Information Center

    National Education Association Research Department, 2006

    2006-01-01

    This brief describes workplace conditions in "learning centered" schools, where practices are consistent with recent research knowledge about learning and its contexts. Its purpose is to support fundamental, long-term change by offering a vision of best practice for educators to consider, discuss, and adapt to their circumstances. It summarizes…

  16. Expectation and conditioning

    NASA Astrophysics Data System (ADS)

    Coster, Adelle C. F.; Alstrøm, Preben

    2001-02-01

    We present a dynamical model that embodies both classical and instrumental conditioning paradigms in the same framework. The model is based on the formation of expectations of stimuli and of rewards. The expectations of stimuli are formed in a recurrent process called expectation learning in which one activity pattern evokes another. The expectation of rewards or punishments (motivation) is modelled using reinforcement learning.

  17. Impacts of sociopolitical conditions

    NASA Technical Reports Server (NTRS)

    Finney, Ben R.

    1992-01-01

    Space development scenarios and the choice of technologies to carry them out depend upon the future social, economic, and political factors. A brief discussion concerning the impact of sociopolitical conditions on space exploration is presented. Some of the topics mentioned include: space weapons/warfare, international cooperation, NASA's Search for Extraterrestrial Intelligence (SETI) Program, and superpower rivelry.

  18. Effective Conditions for Learning

    ERIC Educational Resources Information Center

    Ball, Barbara; Ball, Derek

    2007-01-01

    In this article, the authors respond to four 2006 "Mathematics Teaching" articles by Paul Andrews and Judy Sayers comparing conditions for learning mathematics in England and in four other European countries. They reflect on what might be done with English education, and with English mathematics education in particular. They challenge Andrews' and…

  19. Preventing Secondary Conditions.

    ERIC Educational Resources Information Center

    Pope, Andrew M.

    1992-01-01

    This paper presents the Institute of Medicine model of the dynamic nature of the disabling process of both primary disabilities and secondary conditions, and the interaction of that process with risk factors and quality of life. The components of a comprehensive disability prevention program are discussed. (Author/JDD)

  20. Turbulent transport of cold and dense solar wind plasma into the magnetosphere by 3-D evolution of the Kelvin-Helmholtz instability

    NASA Astrophysics Data System (ADS)

    Matsumoto, Y.; Seki, K.

    2006-12-01

    An appearance of cold and dense plasma at the geosynchronous orbit is one of the characteristic natures after a prolonged northward IMF duration. This cold dense material can contribute to the enhancement of the ring current density, which results a further declination of Dst. Therefore investigating the origin, path and fate of the cold dense plasma is important to understand how it preconditions the magnetosphere during a quiet interval before storm [Borovsky and Steinberg, 2006]. Observational evidences have shown that the cold dense material builds up during the northward IMF intervals in the flanks of the magnetosphere [e.g., Wing and Newell, 2002] which is referred to as the low latitude boundary layer (LLBL). The entry process of the solar wind plasma into the magnetosphere during the northward IMF conditions has been controversial in contrast to the Dungey's reconnection model for the southward IMF cases. The major candidate processes are the double lobe reconnection model [Song et al., 1999], in which newly closed magnetic field lines on the dayside magnetopause capture the solar wind plasma, and the turbulent transport by the Kelvin-Helmholtz instability (KHI) driven by the fast solar wind flow. We have studied the solar wind entry process by the KHI. Matsumoto and Hoshino [2004, 2006] showed by 2- D MHD and full particle simulation studies that the strong flow turbulence is a natural consequence of the nonlinear development of the KHI through the secondary Rayleigh-Taylor instability, if there is a large density difference between the two media. The mechanism is fundamentally two-dimensional and therefore we term it the 2-D secondary instability. They also showed that the turbulent development greatly contributes to the solar wind plasma transport deep into the magnetosphere. Based on the previous 2-D studies, the 3-D nonlinear evolution of the KHI is studied by performing MHD simulation. Starting with a uniform background field configuration and a

  1. HELIOSPHERIC ASYMMETRIES AND 2-3 kHz RADIO EMISSION UNDER STRONG INTERSTELLAR MAGNETIC FIELD CONDITIONS

    SciTech Connect

    Pogorelov, Nikolai V.; Heerikhuisen, Jacob; Zank, Gary P.; Mitchell, Jeremy J.; Cairns, Iver H.

    2009-04-10

    We discuss the asymmetry of the major heliospheric discontinuities obtained from the analysis of three-dimensional modeling of the solar wind interaction with the local interstellar medium (LISM). The flow of charged particles is governed by the ideal MHD equations and the transport of neutral particles is described by the Boltzmann equation. The emphasis is on the asymmetries of the termination shock (TS) and the heliopause under the combined action of the interstellar and interplanetary magnetic fields (ISMF and IMF) in the presence of neutral hydrogen atoms. It is shown that an ISMF of a strength greater than 4 {mu}G can account for the 10 AU difference in the TS heliocentric distances observed by the Voyager 1 and Voyager 2 spacecraft. We analyze the deflection of neutral hydrogen flow from its original direction in the unperturbed LISM and conclude that it remains within the range measured in the SOHO SWAN experiment. The impact is analyzed of a strong ISMF on the 2-3 kHz radio emission observed by the Voyager spacecraft, using new estimates of the radio emission conditions.

  2. Direct observations of the full Dungey convection cycle in the polar ionosphere for southward interplanetary magnetic field conditions

    NASA Astrophysics Data System (ADS)

    Zhang, Q.-H.; Lockwood, M.; Foster, J. C.; Zhang, S.-R.; Zhang, B.-C.; McCrea, I. W.; Moen, J.; Lester, M.; Ruohoniemi, J. M.

    2015-06-01

    Tracking the formation and full evolution of polar cap ionization patches in the polar ionosphere, we directly observe the full Dungey convection cycle for southward interplanetary magnetic field (IMF) conditions. This enables us to study how the Dungey cycle influences the patches' evolution. The patches were initially segmented from the dayside storm enhanced density plume at the equatorward edge of the cusp, by the expansion and contraction of the polar cap boundary due to pulsed dayside magnetopause reconnection, as indicated by in situ Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations. Convection led to the patches entering the polar cap and being transported antisunward, while being continuously monitored by the globally distributed arrays of GPS receivers and Super Dual Auroral Radar Network radars. Changes in convection over time resulted in the patches following a range of trajectories, each of which differed somewhat from the classical twin-cell convection streamlines. Pulsed nightside reconnection, occurring as part of the magnetospheric substorm cycle, modulated the exit of the patches from the polar cap, as confirmed by coordinated observations of the magnetometer at Tromsø and European Incoherent Scatter Tromsø UHF radar. After exiting the polar cap, the patches broke up into a number of plasma blobs and returned sunward in the auroral return flow of the dawn and/or dusk convection cell. The full circulation time was about 3 h.

  3. Tracking Biological and Ecosystem Responses to Changing Environmental Conditions in the Pacific Arctic

    NASA Astrophysics Data System (ADS)

    Grebmeier, J. M.; Cooper, L. W.; Frey, K. E.; Moore, S. E.

    2014-12-01

    Changing seasonal sea ice conditions and seawater temperatures strongly influence biological processes and marine ecosystems at high latitudes. In the Pacific Arctic, persistent regions termed "hotspots", are localized areas with high benthic macroinfaunal biomass that have been documented over four decades (see Figure). These regions are now being more formally tracked to relate physical forcing and ecosystem response as an Arctic Distributed Biological Observatory (DBO) supported by the US National Ocean Policy Implementation Plan and international partners. These hotspots are important foraging areas for upper trophic level benthic feeders, such as marine mammals and seabirds. South of St. Lawrence Island (SLI) in the northern Bering Sea, benthic feeding spectacled eiders, bearded seals and walruses are important winter consumers of infauna, such as bivalves and polychaetes. Gray whales have historically been a major summer consumer of benthic amphipods in the Chirikov Basin to the north of SLI, although summertime sightings of gray whales declined in the Chirikov from the 1980s up until at least 2002. The SE Chukchi Sea hotspot, as are the other hotspots, is maintained by export of high chlorophyll a that is produced locally as well as advected by water masses transiting northward through the system. Both walrus and gray whales are known to forage in this hotspot seasonally on high biomass levels of benthic prey. Notably the center of the highest benthic biomass regions has shifted northward in three of the DBO hotspots in recent years. This has coincided with changing sediment grain size, an indicator of current speed, and is also likely a response to changes in primary production in the region. Studies of these broad biological responses to changing physical drivers have been facilitated through development of the DBO cooperative effort by both US and international scientists. The DBO includes a series of coordinated, multi-trophic level observations that

  4. Stability Behaviour of the Atlantic Thermohaline Circulation Under Different Climate Conditions: The Thermal Component

    NASA Astrophysics Data System (ADS)

    Knorr, G.; Eichinger, R.; Lohmann, G.; Prange, M.; Barker, S.

    2010-05-01

    During the Last Glacial Maximum the Atlantic Thermohaline Circulation (THC) was characterized by a southward shift of the North Atlantic deep water (NADW) formation sites and a relatively shallow NADW- overturning cell, compared to the present mode of operation. Furthermore, abrupt climate events during the last glacial are associated with rapid changes in the THC and accompanying changes of the inter-hemispheric northward oceanic heat transport. Using an interhemispheric box model of the Atlantic THC, coupled to a moist energy balance model of the atmosphere we present a new approach, which is based on the assumption that a completely sea ice covered North Atlantic would inhibit the generation of deep water. Therefore we introduce a dependence of the overturning strength from the sea ice extent in the North Atlantic. This approach can be viewed as a loss of efficiency of the inter-hemispheric density gradient in driving the overturning with cooler climate conditions. The transition from the present day climate to a colder climate forces the Atlantic THC to collapse in an intermediate climate state. This change in the stability behaviour is a consequence of the model response to gradual changes in the outgoing infra-red radiation at the top of the atmosphere. At cooler climate states the increasing atmosphere-ocean temperature contrast and associated ocean heat loss dominates the insulating effect of sea ice on North Atlantic temperature and promotes a sea ice growth. This effect is amplified by a weaker overturning circulation and decreased northward oceanic heat transport, which leads to a positive feedback loop and the existence of multiple equilibria in an intermediate climate state. Based on the reduction of the system to key variables governing the stability, we will also discuss the internal and structural stability of the system with the aid of numerical and analytical solutions to gain a deeper understanding of the underlying dynamics. A comparison with

  5. Power supply conditioning circuit

    NASA Technical Reports Server (NTRS)

    Primas, L. E.; Loveland, R.

    1987-01-01

    A power supply conditioning circuit that can reduce Periodic and Random Deviations (PARD) on the output voltages of dc power supplies to -150 dBV from dc to several KHz with no measurable periodic deviations is described. The PARD for a typical commercial low noise power supply is -74 dBV for frequencies above 20 Hz and is often much worse at frequencies below 20 Hz. The power supply conditioning circuit described here relies on the large differences in the dynamic impedances of a constant current diode and a zener diode to establish a dc voltage with low PARD. Power supplies with low PARD are especially important in circuitry involving ultrastable frequencies for the Deep Space Network.

  6. Quantum conditional operations

    NASA Astrophysics Data System (ADS)

    Bisio, Alessandro; Dall'Arno, Michele; Perinotti, Paolo

    2016-08-01

    An essential element of classical computation is the "if-then" construct, that accepts a control bit and an arbitrary gate, and provides conditional execution of the gate depending on the value of the controlling bit. On the other hand, quantum theory prevents the existence of an analogous universal construct accepting a control qubit and an arbitrary quantum gate as its input. Nevertheless, there are controllable sets of quantum gates for which such a construct exists. Here we provide a necessary and sufficient condition for a set of unitary transformations to be controllable, and we give a complete characterization of controllable sets in the two-dimensional case. This result reveals an interesting connection between the problem of controllability and the problem of extracting information from an unknown quantum gate while using it.

  7. Conditional statistical model building

    NASA Astrophysics Data System (ADS)

    Hansen, Mads Fogtmann; Hansen, Michael Sass; Larsen, Rasmus

    2008-03-01

    We present a new statistical deformation model suited for parameterized grids with different resolutions. Our method models the covariances between multiple grid levels explicitly, and allows for very efficient fitting of the model to data on multiple scales. The model is validated on a data set consisting of 62 annotated MR images of Corpus Callosum. One fifth of the data set was used as a training set, which was non-rigidly registered to each other without a shape prior. From the non-rigidly registered training set a shape prior was constructed by performing principal component analysis on each grid level and using the results to construct a conditional shape model, conditioning the finer parameters with the coarser grid levels. The remaining shapes were registered with the constructed shape prior. The dice measures for the registration without prior and the registration with a prior were 0.875 +/- 0.042 and 0.8615 +/- 0.051, respectively.

  8. High voltage pulse conditioning

    DOEpatents

    Springfield, Ray M.; Wheat, Jr., Robert M.

    1990-01-01

    Apparatus for conditioning high voltage pulses from particle accelerators in order to shorten the rise times of the pulses. Flashover switches in the cathode stalk of the transmission line hold off conduction for a determinable period of time, reflecting the early portion of the pulses. Diodes upstream of the switches divert energy into the magnetic and electrostatic storage of the capacitance and inductance inherent to the transmission line until the switches close.

  9. Fuel gas conditioning process

    DOEpatents

    Lokhandwala, Kaaeid A.

    2000-01-01

    A process for conditioning natural gas containing C.sub.3+ hydrocarbons and/or acid gas, so that it can be used as combustion fuel to run gas-powered equipment, including compressors, in the gas field or the gas processing plant. Compared with prior art processes, the invention creates lesser quantities of low-pressure gas per unit volume of fuel gas produced. Optionally, the process can also produce an NGL product.

  10. Cyclone-induced rapid creation of extreme Antarctic sea ice conditions

    PubMed Central

    Wang, Zhaomin; Turner, John; Sun, Bo; Li, Bingrui; Liu, Chengyan

    2014-01-01

    Two polar vessels, Akademik Shokalskiy and Xuelong, were trapped by thick sea ice in the Antarctic coastal region just to the west of 144°E and between 66.5°S and 67°S in late December 2013. This event demonstrated the rapid establishment of extreme Antarctic sea ice conditions on synoptic time scales. The event was associated with cyclones that developed at lower latitudes. Near the event site, cyclone-enhanced strong southeasterly katabatic winds drove large westward drifts of ice floes. In addition, the cyclones also gave southward ice drift. The arrival and grounding of Iceberg B9B in Commonwealth Bay in March 2011 led to the growth of fast ice around it, forming a northward protruding barrier. This barrier blocked the westward ice drift and hence aided sea ice consolidation on its eastern side. Similar cyclone-induced events have occurred at this site in the past after the grounding of Iceberg B9B. Future events may be predictable on synoptic time scales, if cyclone-induced strong wind events can be predicted. PMID:24937550

  11. Cyclone-induced rapid creation of extreme Antarctic sea ice conditions.

    PubMed

    Wang, Zhaomin; Turner, John; Sun, Bo; Li, Bingrui; Liu, Chengyan

    2014-01-01

    Two polar vessels, Akademik Shokalskiy and Xuelong, were trapped by thick sea ice in the Antarctic coastal region just to the west of 144°E and between 66.5°S and 67°S in late December 2013. This event demonstrated the rapid establishment of extreme Antarctic sea ice conditions on synoptic time scales. The event was associated with cyclones that developed at lower latitudes. Near the event site, cyclone-enhanced strong southeasterly katabatic winds drove large westward drifts of ice floes. In addition, the cyclones also gave southward ice drift. The arrival and grounding of Iceberg B9B in Commonwealth Bay in March 2011 led to the growth of fast ice around it, forming a northward protruding barrier. This barrier blocked the westward ice drift and hence aided sea ice consolidation on its eastern side. Similar cyclone-induced events have occurred at this site in the past after the grounding of Iceberg B9B. Future events may be predictable on synoptic time scales, if cyclone-induced strong wind events can be predicted.

  12. Modern California current system and radiolarian responses to normal (anti-El Nino) conditions

    SciTech Connect

    Casey, R.E.; Carson, T.L.; Weinheimer, A.L.

    1986-04-01

    The modern California Current is a relatively wide, slow, southward flow of cold, low-salinity water subject to considerable seasonal upwelling and other seasonal and supraseasonal perturbations. The radiolarian fauna contained within these waters reflects the parameters and perturbations common to eastern boundary currents. Radiolarian faunas characteristic of the California Current (subarctic and transitional waters), the offshore gyre (North Pacific anticyclonic subtropical gyre), the eastern tropical Pacific, and underlying intermediate and deep waters have been documented and characterized. During normal (anti-El Nino) conditions within the California Current system, the following physical oceanographic changes (and their characteristic radiolarian responses) occur. Spring and summer are dominated by the strongest southerly flow of the California Current - with high-standing crops of subarctic and transitional radiolarians in the core of that current - whose core is seaward of the southern California continental borderland. Spring and summer are also periods of strongest upwelling, with deeper radiolarians appearing at or near the surface. During fall and into winter, the California Current slows and a coastal countercurrent, the Davidson Current, develops. Radiolarians indicate that a much reduced core of the California Current swings in over the southern California continental borderland, and that faunas from the south are brought northward near the shore.

  13. Coccolithophore species as indicators of surface oceanographic conditions in the vicinity of Azores islands

    NASA Astrophysics Data System (ADS)

    Silva, A.; Brotas, V.; Valente, A.; Sá, C.; Diniz, T.; Patarra, R. F.; Álvaro, N. V.; Neto, A. I.

    2013-02-01

    During summer 2008 and spring 2009, surface oceanographic surveys were carried out around three islands of the Azores archipelago (Terceira, São Miguel and Santa Maria) to assess the phytoplankton distribution and associated physico-chemical processes. The Azores archipelago is a major feature in the biogeochemical North Atlantic Subtropical Gyre (NAST) province although its influence on the productivity of the surrounding ocean is poorly known. Surface phytoplankton was studied by microscopy and HPLC (High Precision Liquid Chromatography). The mean values for biomass proxy Chlorophyll a (Chla) ranged from 0.04 to 0.55 μg L-1 (Chla maximum = 0.86 μg L-1) and coccolithophores were the most abundant group, followed by small flagellates, Cyanobacteria, diatoms and dinoflagellates being the least abundant group. The distribution of phytoplankton and coccolithophore species in particular presented seasonal differences and was consistent with the nearshore influence of warm subtropical waters from the south Azores current and colder subpolar waters from the north. The satellite-derived circulation patterns showed southward cold water intrusions off Terceira and northward warm water intrusions off Santa Maria. The warmer waters signal was confirmed by the subtropical coccolithophore assemblage, being Discosphaera tubifera a constant presence under these conditions. The regions of enhanced biomass, either resulting from northern cooler waters or from island induced processes, were characterized by the presence of Emiliania huxleyi. Diatoms and dinoflagellates indicated coastal and regional processes of nutrient enrichment and areas of physical stability, respectively.

  14. Earth's collision with a solar filament on 21 January 2005: Overview

    NASA Astrophysics Data System (ADS)

    Kozyra, J. U.; Manchester, W. B.; Escoubet, C. P.; Lepri, S. T.; Liemohn, M. W.; Gonzalez, W. D.; Thomsen, M. W.; Tsurutani, B. T.

    2013-10-01

    21 January 2005, one of the fastest interplanetary coronal mass ejections (ICME) of solar cycle 23, containing exceptionally dense plasma directly behind the sheath, hit the magnetosphere. We show from charge-state analysis that this material was a piece of the erupting solar filament and further, based on comparisons to the simulation of a fast CME, that the unusual location of the filament material was a consequence of three processes. As the ICME decelerated, the momentum of the dense filament material caused it to push through the flux rope toward the nose. Diverging nonradial flows in front of the filament moved magnetic flux to the sides of the ICME. At the same time, reconnection between the leading edge of the ICME and the sheath magnetic fields worked to peel away the outer layers of the flux rope creating a remnant flux rope and a trailing region of newly opened magnetic field lines. These processes combined to move the filament material into direct contact with the ICME sheath region. Within 1 h after impact and under northward interplanetary magnetic field (IMF) conditions, a cold dense plasma sheet formed within the magnetosphere from the filament material. Dense plasma sheet material continued to move through the magnetosphere for more than 6 h as the filament passed by the Earth. Densities were high enough to produce strong diamagnetic stretching of the magnetotail despite the northward IMF conditions and low levels of magnetic activity. The disruptions from the filament collision are linked to an array of unusual features throughout the magnetosphere, ionosphere, and atmosphere. These results raise questions about whether rare collisions with solar filaments may, under the right conditions, be a factor in producing even more extreme events.

  15. A Case Study in Leveraging Major Science at Low Cost: Development of Large Scale Birkeland Currents Determined from AMPERE

    NASA Astrophysics Data System (ADS)

    Anderson, B. J.; Dyrud, L. P.; Korth, H.; Waters, C. L.; Green, D. L.; Barnes, R. J.

    2011-12-01

    The Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) uses the constellation of Iridium Communications satellites in 780-km-altitude, circular, polar orbits to monitor the global Birkeland currents with a nine-minute cadence. This allows us to follow the development of these currents through transitions from quiescent conditions to moderate driving as indicated by rotations of the interplanetary magnetic field (IMF) from northward to southward. AMPERE data are available beginning on October 2009 for development testing purposes and for continuous science observations starting in June 2010. Data are processed in 10-minute windows stepped by two minutes to derive global Birkeland currents with a minimum intensity of 0.2 mirco-A/m2. A transition event ocurred on 24 February 2010, which illustrates one type of systematic behavior found. As measured by ACE at the first Langrangian point, L1, the IMF was northward and sunward from 1300 to 1420 UT with a BZ component of +2 to +3 nT. At 1420 UT, the IMF began rotating southward reaching -2 to -3 nT by 1510 UT. At Earth, the first enhancement in Birkeland currents occurs at 1524-1534 UT on the dayside, reflecting reconnection driven convection associated with the positive IMF BY that persisted through the event. The dayside currents continued to intensify through 1540-1550 UT and extended from mid-morning to dusk. At 1542-1552 UT, isolated nightside currents appear at midnight and are localized in latitude and longitude, extending less than one hour pre or post-midnight. Ten minutes later the nightside currents expand to most of the nighside and merge with the dayside system. The nightside currents then continue to intensify, first near midnight and expand toward both dawn and dusk, resulting in a fully formed classic Region 1/Region 2 current system by 1640-1650 UT. The results indicate that dayside reconnection drives both Region-1 and Region-2-sense currents, whereas the nightside currents

  16. Cosmic rays, conditions in interplanetary space and geomagnetic variations during solar cycles 19-24

    NASA Astrophysics Data System (ADS)

    Biktash, Lilia

    2016-07-01

    We have studied conditions in interplanetary space, which can have an influence on galactic and solar cosmic rays (CRs). In this connection the solar wind and interplanetary magnetic field parameters and CRs variations have been compared with geomagnetic activity represented by the equatorial Dst and Kp indices beginning from 1955 to the end 2015. The indices are in common practice in the solar wind-magnetosphere-ionosphere interaction studies and they are the final product of this interaction. The important drivers in interplanetary medium which have effect on cosmic rays as CMEs (coronal mass ejections) and CIRs (corotating interaction regions) undergo very strong changes during their propagation to the Earth. Correlation of sunspot numbers and long-term variations of cosmic rays do not adequately reflect peculiarities concerned with the solar wind arrival to 1 AU also. Moreover records of in situ space measurements of the IMF and most other indicators of solar activity cover only a few decades and have a lot of gaps for calculations of long-term variations. Because of this, in such investigations, the geomagnetic indices have some inestimable advantage as continuous series other the solar wind measurements. We have compared the yearly average variations of the indices and of the solar wind parameters with cosmic ray data from Moscow, Climax, Halekala and Oulu neutron monitors during the 20-24 solar cycles. During the descending phases of the solar cycles the long-lasting solar wind high speed streams occurred frequently and were the primary contributors to the recurrent Dst variations and had effects on cosmic rays variations. We show that long-term Dst and Kp variations in these solar cycles were correlated with cosmic ray count rates and can be used for prediction of CR variations. Climate change in connection with evolution of CRs variations is discussed.

  17. Formation of Polar Ionospheric Tongue of Ionization during Minor Geomagnetic Disturbed Conditions

    NASA Astrophysics Data System (ADS)

    Liu, J.; Wang, W.; Burns, A. G.; Yue, X.; Zhang, S.; Zhang, Y.

    2015-12-01

    Previous investigations of ionospheric storm-enhanced density (SED) and tongue of ionization (TOI) focused mostly on the behavior of TOI during intense geomagnetic storms. Little attention has been paid to the spatial and temporal variations of TOI during weak to moderate geomagnetic disturbed conditions. we investigate the source and development of TOI during a moderate geomagnetic storm on 14 October 2012.Multi-instrumental observations including GPS total electron content (TEC), Defense Meteorological SatelliteProgram(DMSP) in situ measured total ion concentration and ion drift velocity, SuperDARN measured polar ionconvection patterns, and electron density profiles from the Poker Flat Incoherent Scatter Radar (PFISR) have been utilized in the current analysis. GPS TEC maps show salient TOI structures persisting for about 5 h over high latitudes of North America on 14 October 2012 in the later recovery phase of the storm when the magnitudes of IMF By and Bz were less than 5 nT. The PFISR electron density profiles indicate that the extra ionization for TEC enhancements mainly occurred in the topside ionosphere with no obvious changes in the bottom side ionosphere and vertical plasma drifts. Additionally, there were no signatures of penetration electric fields in the equatorial electrojet data and upward ion drifts at high latitudes. At the same time, strong subauroral polarization streams with ion drift speeds exceeding 2.5 km/s carried sunward fluxes and migrated toward lower latitudes for about 5° based on the DMSP cross-track driftmeasurements. Based on those measurements,we postulate that the combined effects of initial build-up of ionization at midlatitudes through daytime production of ionization and equatorward (or less poleward than normal daytime) neutral wind reducing downward diffusion along the inclined filed lines, and an expanded polar ion convection pattern and its associated horizontal plasma transport are important in the formation of the TOI.

  18. Formation of polar ionospheric tongue of ionization during minor geomagnetic disturbed conditions

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Nakamura, Takuji; Liu, Libo; Wang, Wenbin; Balan, Nanan; Nishiyama, Takanori; Hairston, Marc R.; Thomas, E. G.

    2015-08-01

    Previous investigations of ionospheric storm-enhanced density (SED) and tongue of ionization (TOI) focused mostly on the behavior of TOI during intense geomagnetic storms. Little attention has been paid to the spatial and temporal variations of TOI during weak to moderate geomagnetic disturbed conditions. In this paper we investigate the source and development of TOI during a moderate geomagnetic storm on 14 October 2012. Multi-instrumental observations including GPS total electron content (TEC), Defense Meteorological Satellite Program (DMSP) in situ measured total ion concentration and ion drift velocity, SuperDARN measured polar ion convection patterns, and electron density profiles from the Poker Flat Incoherent Scatter Radar (PFISR) have been utilized in the current analysis. GPS TEC maps show salient TOI structures persisting for about 5 h over high latitudes of North America on 14 October 2012 in the later recovery phase of the storm when the magnitudes of IMF By and Bz were less than 5 nT. The PFISR electron density profiles indicate that the extra ionization for TEC enhancements mainly occurred in the topside ionosphere with no obvious changes in the bottomside ionosphere and vertical plasma drifts. Additionally, there were no signatures of penetration electric fields in the equatorial electrojet data and upward ion drifts at high latitudes. At the same time, strong subauroral polarization streams with ion drift speeds exceeding 2.5 km/s carried sunward fluxes and migrated toward lower latitudes for about 5° based on the DMSP cross-track drift measurements. Based on those measurements, we postulate that the combined effects of initial build-up of ionization at midlatitudes through daytime production of ionization and equatorward (or less poleward than normal daytime) neutral wind reducing downward diffusion along the inclined filed lines, and an expanded polar ion convection pattern and its associated horizontal plasma transport are important in the

  19. ON THE INITIAL CONDITIONS FOR STAR FORMATION AND THE INITIAL MASS FUNCTION

    SciTech Connect

    Elmegreen, Bruce G.

    2011-04-10

    Density probability distribution functions (PDFs) for turbulent self-gravitating clouds should be convolutions of the local log-normal PDF, which depends on the local average density {rho}{sub ave} and Mach number M, and the PDFs for {rho}{sub ave} and M, which depend on the overall cloud structure. When self-gravity drives a cloud to increased central density, the total PDF develops an extended tail. If there is a critical density or column density for star formation, then the fraction of the local mass exceeding this threshold becomes higher near the cloud center. These elements of cloud structure should be in place before significant star formation begins. Then the efficiency is high so that bound clusters form rapidly, and the stellar initial mass function (IMF) has an imprint in the gas before destructive radiation from young stars can erase it. The IMF could arise from a power-law distribution of mass for cloud structure. These structures should form stars down to the thermal Jeans mass M{sub J} at each density in excess of a threshold. The high-density tail of the PDF, combined with additional fragmentation in each star-forming core, extends the IMF into the brown dwarf regime. The core fragmentation process is distinct from the cloud structuring process and introduces an independent core fragmentation mass function (CFMF). The CFMF would show up primarily below the IMF peak.

  20. Mining Conditional Phosphorylation Motifs.

    PubMed

    Liu, Xiaoqing; Wu, Jun; Gong, Haipeng; Deng, Shengchun; He, Zengyou

    2014-01-01

    Phosphorylation motifs represent position-specific amino acid patterns around the phosphorylation sites in the set of phosphopeptides. Several algorithms have been proposed to uncover phosphorylation motifs, whereas the problem of efficiently discovering a set of significant motifs with sufficiently high coverage and non-redundancy still remains unsolved. Here we present a novel notion called conditional phosphorylation motifs. Through this new concept, the motifs whose over-expressiveness mainly benefits from its constituting parts can be filtered out effectively. To discover conditional phosphorylation motifs, we propose an algorithm called C-Motif for a non-redundant identification of significant phosphorylation motifs. C-Motif is implemented under the Apriori framework, and it tests the statistical significance together with the frequency of candidate motifs in a single stage. Experiments demonstrate that C-Motif outperforms some current algorithms such as MMFPh and Motif-All in terms of coverage and non-redundancy of the results and efficiency of the execution. The source code of C-Motif is available at: https://sourceforge. net/projects/cmotif/. PMID:26356863

  1. Terrestrial Myriametric Radio Burst Observed by IMAGE and Geotail Satellites

    NASA Technical Reports Server (NTRS)

    Fung, Shing F.; Hashimoto, KoZo; Kojima, Hirotsugu; Boardson, Scott A.; Garcia, Leonard N.; Matsumoto, Hiroshi; Green, James L.; Reinisch, Bodo W.

    2013-01-01

    We report the simultaneous detection of a terrestrial myriametric radio burst (TMRB) by IMAGE and Geotail on 19 August 2001. The TMRB was confined in time (0830-1006 UT) and frequency (12-50kHz). Comparisons with all known nonthermal myriametric radiation components reveal that the TMRB might be a distinct radiation with a source that is unrelated to the previously known radiation. Considerations of beaming from spin-modulation analysis and observing satellite and source locations suggest that the TMRB may have a fan beamlike radiation pattern emitted by a discrete, dayside source located along the poleward edge of magnetospheric cusp field lines. TMRB responsiveness to IMF Bz and By orientations suggests that a possible source of the TMRB could be due to dayside magnetic reconnection instigated by northward interplanetary field condition.

  2. Childhood Eye Diseases and Conditions

    MedlinePlus

    ... and Conditions Nov. 01, 2013 The importance of vision screening There are many eye conditions and diseases ... child’s vision. Focus and alignment disorders that affect vision If any of the following conditions is suspected, ...

  3. How Are Genetic Conditions Diagnosed?

    MedlinePlus

    ... Consultation How are genetic conditions diagnosed? How are genetic conditions diagnosed? A doctor may suspect a diagnosis ... and advocacy resources. For more information about diagnosing genetic conditions: Genetics Home Reference provides information about genetic ...

  4. Remote Ischemic Conditioning

    PubMed Central

    Heusch, Gerd; Bøtker, Hans Erik; Przyklenk, Karin; Redington, Andrew; Yellon, Derek

    2014-01-01

    In remote ischemic conditioning (RIC) brief, reversible episodes of ischemia with reperfusion in one vascular bed, tissue or organ confer a global protective phenotype and render remote tissues and organs resistant to ischemia/reperfusion injury. The peripheral stimulus can be chemical, mechanical or electrical and involves activation of peripheral sensory nerves. The signal transfer to the heart or other organs is through neuronal and humoral communications. Protection can be transferred, even across species, with plasma-derived dialysate and involves nitric oxide, stromal derived factor-1α, microRNA-144, but also other, not yet identified factors. Intracardiac signal transduction involves: adenosine, bradykinin, cytokines, and chemokines, which activate specific receptors; intracellular kinases; and mitochondrial function. RIC by repeated brief inflation/deflation of a blood pressure cuff protects against endothelial dysfunction and myocardial injury in percutaneous coronary interventions, coronary artery bypass grafting and reperfused acute myocardial infarction. RIC is safe and effective, noninvasive, easily feasible and inexpensive. PMID:25593060

  5. Explaining Verification Conditions

    NASA Technical Reports Server (NTRS)

    Deney, Ewen; Fischer, Bernd

    2006-01-01

    The Hoare approach to program verification relies on the construction and discharge of verification conditions (VCs) but offers no support to trace, analyze, and understand the VCs themselves. We describe a systematic extension of the Hoare rules by labels so that the calculus itself can be used to build up explanations of the VCs. The labels are maintained through the different processing steps and rendered as natural language explanations. The explanations can easily be customized and can capture different aspects of the VCs; here, we focus on their structure and purpose. The approach is fully declarative and the generated explanations are based only on an analysis of the labels rather than directly on the logical meaning of the underlying VCs or their proofs. Keywords: program verification, Hoare calculus, traceability.

  6. Conditional sterility in plants

    DOEpatents

    Meagher, Richard B.; McKinney, Elizabeth; Kim, Tehryung

    2010-02-23

    The present disclosure provides methods, recombinant DNA molecules, recombinant host cells containing the DNA molecules, and transgenic plant cells, plant tissue and plants which contain and express at least one antisense or interference RNA specific for a thiamine biosynthetic coding sequence or a thiamine binding protein or a thiamine-degrading protein, wherein the RNA or thiamine binding protein is expressed under the regulatory control of a transcription regulatory sequence which directs expression in male and/or female reproductive tissue. These transgenic plants are conditionally sterile; i.e., they are fertile only in the presence of exogenous thiamine. Such plants are especially appropriate for use in the seed industry or in the environment, for example, for use in revegetation of contaminated soils or phytoremediation, especially when those transgenic plants also contain and express one or more chimeric genes which confer resistance to contaminants.

  7. Signal conditioning system

    NASA Technical Reports Server (NTRS)

    Zahzah, Mohamad (Inventor); Korkosz, Gregory J. (Inventor); Bohr, Gerald (Inventor)

    2000-01-01

    A current-driven signal conditioning system comprising a first terminal, a second terminal, a strain gauge, and an instrumentation amplifier is disclosed. The strain gauge is adapted to measure a deformation of a structure and to generate a resistance which corresponds to the measured deformation. The instrumentation amplifier is adapted to be connected between the first terminal and the second terminal. The instrumentation amplifier is further adapted to be connected to the strain gauge and to place an output current on the second terminal. The output current is proportional to the resistance generated by the strain gauge. An output resister is coupled between the strain gauge and the second terminal, and a capacitor is coupled between the resister and the first terminal. A zenor diode is coupled between the first terminal and the strain gauge, and a diode is also coupled between the first terminal and the strain gauge.

  8. Multi-Sensor Data Fusion Identification for Shearer Cutting Conditions Based on Parallel Quasi-Newton Neural Networks and the Dempster-Shafer Theory

    PubMed Central

    Si, Lei; Wang, Zhongbin; Liu, Xinhua; Tan, Chao; Xu, Jing; Zheng, Kehong

    2015-01-01

    In order to efficiently and accurately identify the cutting condition of a shearer, this paper proposed an intelligent multi-sensor data fusion identification method using the parallel quasi-Newton neural network (PQN-NN) and the Dempster-Shafer (DS) theory. The vibration acceleration signals and current signal of six cutting conditions were collected from a self-designed experimental system and some special state features were extracted from the intrinsic mode functions (IMFs) based on the ensemble empirical mode decomposition (EEMD). In the experiment, three classifiers were trained and tested by the selected features of the measured data, and the DS theory was used to combine the identification results of three single classifiers. Furthermore, some comparisons with other methods were carried out. The experimental results indicate that the proposed method performs with higher detection accuracy and credibility than the competing algorithms. Finally, an industrial application example in the fully mechanized coal mining face was demonstrated to specify the effect of the proposed system. PMID:26580620

  9. Multi-Sensor Data Fusion Identification for Shearer Cutting Conditions Based on Parallel Quasi-Newton Neural Networks and the Dempster-Shafer Theory.

    PubMed

    Si, Lei; Wang, Zhongbin; Liu, Xinhua; Tan, Chao; Xu, Jing; Zheng, Kehong

    2015-11-13

    In order to efficiently and accurately identify the cutting condition of a shearer, this paper proposed an intelligent multi-sensor data fusion identification method using the parallel quasi-Newton neural network (PQN-NN) and the Dempster-Shafer (DS) theory. The vibration acceleration signals and current signal of six cutting conditions were collected from a self-designed experimental system and some special state features were extracted from the intrinsic mode functions (IMFs) based on the ensemble empirical mode decomposition (EEMD). In the experiment, three classifiers were trained and tested by the selected features of the measured data, and the DS theory was used to combine the identification results of three single classifiers. Furthermore, some comparisons with other methods were carried out. The experimental results indicate that the proposed method performs with higher detection accuracy and credibility than the competing algorithms. Finally, an industrial application example in the fully mechanized coal mining face was demonstrated to specify the effect of the proposed system.

  10. Initial Cladding Condition

    SciTech Connect

    E. Siegmann

    2000-08-22

    The purpose of this analysis is to describe the condition of commercial Zircaloy clad fuel as it is received at the Yucca Mountain Project (YMP) site. Most commercial nuclear fuel is encased in Zircaloy cladding. This analysis is developed to describe cladding degradation from the expected failure modes. This includes reactor operation impacts including incipient failures, potential degradation after reactor operation during spent fuel storage in pool and dry storage and impacts due to transportation. Degradation modes include cladding creep, and delayed hydride cracking during dry storage and transportation. Mechanical stresses from fuel handling and transportation vibrations are also included. This Analysis and Model Report (AMR) does not address any potential damage to assemblies that might occur at the YMP surface facilities. Ranges and uncertainties have been defined. This analysis will be the initial boundary condition for the analysis of cladding degradation inside the repository. In accordance with AP-2.13Q, ''Technical Product Development Planning'', a work plan (CRWMS M&O 2000c) was developed, issued, and utilized in the preparation of this document. There are constraints, caveats and limitations to this analysis. This cladding degradation analysis is based on commercial Pressurized Water Reactor (PWR) fuel with Zircaloy cladding but is applicable to Boiling Water Reactor (BWR) fuel. Reactor operating experience for both PWRs and BWRs is used to establish fuel reliability from reactor operation. It is limited to fuel exposed to normal operation and anticipated operational occurrences (i.e. events which are anticipated to occur within a reactor lifetime), and not to fuel that has been exposed to severe accidents. Fuel burnup projections have been limited to the current commercial reactor licensing environment with restrictions on fuel enrichment, oxide coating thickness and rod plenum pressures. The information provided in this analysis will be used in

  11. Magnetic conditioning in superfluid

    SciTech Connect

    Caspi, S.

    1988-08-01

    Improvements in superconducting magnet technology have reduced to a handful the number of training quenches typical of dipole magnets. The number of training quenches in long (17 m) and short (1--2 m) SSC magnets are now about the same (operating at 6.6 tesla and 4.4 K). Yet the steps necessary to totally eliminate training are in the future RandD plans for magnet construction and conductor motion prevention. The accepted hypothesis is that Lorentz forces and poor mechanical properties of superconducting cables are the cause of conductor motion. Conductor motion reduces the stored energy in the cable by converting it into heat. The small amount of heat generated (millijoules) during motion is usually enough to quench the magnet when it is close to short sample. During training, the magnet performance normally improves with the number of quenches. It is not the quench itself that improves magnet performance but rather the fact that once conductor motion has occurred it will probably not repeat itself unless subjected to higher forces. Conditioning is a process that enables the magnet to reduce its stored energy without causing a premature quench. During the conditioning process the magnet is further cooled from its operating temperature of 4.4 K to 1.8 K by converting He I into He II. As a result the magnet is placed in a state where it has excess stability as well as excellent heat transfer capabilities. Although this does not eliminate motion, if the magnet is now cycled to /approximately/10% above its operating field at 4.4 K (which is above short sample) the excess stability should be enough to prevent quenching and reduce the probability of conductor motion and training once the magnet has been warmed back up to its operating temperature of 4.4 K. 3 refs., 5 figs.

  12. Verbal Conditioning and Therapeutic Change

    ERIC Educational Resources Information Center

    Lapuc, Paul S.; Harmatz, Morton G.

    1970-01-01

    Investigates the generalization of verbal conditioning effects to postconditioning personality and behavioral measures. Results demonstrated conditioning and generalization to some of the personality measures. (Author)

  13. Plasma structuring in the polar cap

    SciTech Connect

    Basu, S.; Basu, S.; Weber, E.J.; Bishop, G.J.

    1990-01-01

    Propagation experiments providing scintillation, total electron content and drift data in the field of view of an all-sky imager near the magnetic polar in Greenland are utilized to investigate the manner in which ionospheric plasma becomes structured within the polar cap. It is found that under IMF Bz southward conditions, large scale ionization patches which are convected through the dayside cusp into the polar cap get continually structured. The structuring occurs through the ExB gradient drift instability process which operates through an interaction between the antisunward plasma convection in the neutral rest frame and large scale plasma density gradients that exist at the edges of the ionization patches. It is shown that with the increase of solar activity the strength of the irregularities integrated through the ionosphere is greatly increased. Under the IMF Bz northward conditions, the plasma structuring occurs around the polar cap arcs in the presence of inhomogeneous electric field or disordered plasma convection. In that case, the irregularity generation is caused by the competing processes of non-linear Kelvin-Helmholtz instability driven by sheared plasma flows and the gradient drift instability process which operates in the presence of dawn-dusk motion of arc structures. The integrated strength of this class of irregularities also exhibits marked increase with increasing solar activity presumably because the ambient plasma density over the polar cap is enhanced.

  14. Flue gas conditioning today

    SciTech Connect

    Southam, B.J.; Coe, E.L. Jr.

    1995-12-01

    Many relatively small electrostatic precipitators (ESP`s) exist which collect fly ash at remarkably high efficiencies and have been tested consistently at correspondingly high migration velocities. But the majority of the world`s coal supplies produce ashes which are collected at much lower migration velocities for a given efficiency and therefore require correspondingly large specific collection areas to achieve acceptable results. Early trials of flue gas conditioning (FGC) showed benefits in maximizing ESP performance and minimizing expense which justified continued experimentation. Trials of several dozen ways of doing it wrong eventually developed a set of reliable rules for doing it right. One result is that the use of sulfur trioxide (SO{sub 3}) for adjustment of the resistivity of fly ash from low sulfur coal has been widely applied and has become an automatically accepted part of the option of burning low sulfur coal for compliance with the Clean Air Act of l990 in the U.S.A. Currently, over 100,000 MW of generating capacity is using FGC, and it is estimated that approximately 45,800 MW will utilize coal-switching with FGC for Clean Air Act emission compliance. Guarantees that this equipment will be available to operate at least 98 percent of the time it is called upon are routinely fulfilled.

  15. Universal Signal Conditioning Amplifier

    NASA Technical Reports Server (NTRS)

    Kinney, Frank

    1997-01-01

    The Technological Research and Development Authority (TRDA) and NASA-KSC entered into a cooperative agreement in March of 1994 to achieve the utilization and commercialization of a technology development for benefiting both the Space Program and U.S. industry on a "dual-use basis". The technology involved in this transfer is a new, unique Universal Conditioning Amplifier (USCA) used in connection with various types of transducers. The project was initiated in partnership with I-Net Corporation, Lockheed Martin Telemetry & Instrumentation (formerly Loral Test and Information Systems) and Brevard Community College. The project consists of designing, miniaturizing, manufacturing, and testing an existing prototype of USCA that was developed for NASA-KSC by the I-Net Corporation. The USCA is a rugged and field-installable self (or remotely)- programmable amplifier that works in combination with a tag random access memory (RAM) attached to various types of transducers. This summary report comprises performance evaluations, TRDA partnership tasks, a project summary, project milestones and results.

  16. Thermal condition of Surtsey

    NASA Astrophysics Data System (ADS)

    Stefansson, V.; Axelsson, G.; Sigurdsson, O.; Gudmundsson, G.; Steingrimsson, B.

    1985-12-01

    The island Surtsey was created by a submarine volcanic eruption which started on the 14th of November 1963, 21 km southwest of the Westman Islands. Volcanic activity continued in this area for nearly 4 years. During the summer of 1979 a 181 m deep continuously cored borehole was drilled on the Surtsey island. Several temperature profiles have been measured in the hole since 1979. The results of these temperature measurements are used as the basis for a discussion of the thermal condition of Surtsey. The hypothesis that intrusions rather than pillow lavas are responsible for the excess heat content of Surtsey is favored. It is found that the 13 m thick discontinuous dike complex, observed in the drill core, is sufficient to explain the excess heat content in the vicinity of the borehole and the shape of the temperature profiles recorded. It is demonstrated that the heat transfer in Surtsey has been dominated by hydrothermal convection and that the system is vapor dominated above sea level. It is estimated that the permeability of a 40 m thick section of altered tuff below sea level is 4.1 × 10 -13 m 2, while the permeability of the unaltered tuff above sea level is estimated as 1.2 × 10 -10 m 2.

  17. Universal signal conditioning amplifier

    NASA Technical Reports Server (NTRS)

    Medelius, Pedro J.; Hallberg, Carl; Cecil, Jim

    1994-01-01

    A state-of-the-art instrumentation amplifier capable of being used with most types of transducers has been developed at the Kennedy Space Center. This Universal Signal Conditioning Amplifier (USCA) can eliminate costly measurement setup item and troubleshooting, improve system reliability and provide more accurate data than conventional amplifiers. The USCA can configure itself for maximum resolution and accuracy based on information read from a RAM chip attached to each transducer. Excitation voltages or current are also automatically configured. The amplifier uses both analog and digital state-of-the-art technology with analog-to-digital conversion performed in the early stages in order to minimize errors introduced by offset and gain drifts in the analog components. A dynamic temperature compensation scheme has been designed to achieve and maintain 12-bit accuracy of the amplifier from 0 to 70 C. The digital signal processing section allows the implementation of digital filters up to 511th order. The amplifier can also perform real-time linearizations up to fourth order while processing data at a rate of 23.438 kS/s. Both digital and analog outputs are available from the amplifier.

  18. The Probabilities of Conditionals Revisited

    ERIC Educational Resources Information Center

    Douven, Igor; Verbrugge, Sara

    2013-01-01

    According to what is now commonly referred to as "the Equation" in the literature on indicative conditionals, the probability of any indicative conditional equals the probability of its consequent of the conditional given the antecedent of the conditional. Philosophers widely agree in their assessment that the triviality arguments of…

  19. The Probability of Causal Conditionals

    ERIC Educational Resources Information Center

    Over, David E.; Hadjichristidis, Constantinos; Evans, Jonathan St. B. T.; Handley, Simon J.; Sloman, Steven A.

    2007-01-01

    Conditionals in natural language are central to reasoning and decision making. A theoretical proposal called the Ramsey test implies the conditional probability hypothesis: that the subjective probability of a natural language conditional, P(if p then q), is the conditional subjective probability, P(q [such that] p). We report three experiments on…

  20. Assessing the planet's condition.

    PubMed

    Brown, L R

    1990-01-01

    The destruction of the environment has accelerated since the Earth Day of 1970, the world's population has increased by another 1.6 billion, and over 500 million acres of forest have been lost. Carbon dioxide levels, greenhouse gases, and chlorofluorocarbons have increased in the atmosphere with evidence that global warming has started. The ozone hole has appeared, acid rain has destroyed forests, air pollution in major northern hemisphere cities has worsened, and species are disappearing, while toxic chemicals have been dumped indiscriminately. World grain production has fallen while population has increased. In Europe 14 countries have stabilized their population, and Japan, France, and Finland are on the way to zero growth. Reduction of high fertility in 1/2 could halt the deterioration of living conditions. Japan and China achieved this within a decade. Energy efficiency has to be attained; US cars still consume too much gas. Solar energy with photovoltaic cells to provide power, fuel alcohol from plants, and solar thermal power plants have potential. Semiarid regions, such as northern Africa, could become major producers of solar energy. Various measures are mandatory to cut down on waste: to recycle paper bags, to use standardized glasses for beverages, and to utilize scrap metal in electric arc steel furnaces. Reforestation is also on the agenda, as major deforestation has occurred in the Brazilian Amazon region, in India, and in Europe because of acid rain. Australia's national plan envisions planting 1 billion trees, and the US project is of similar magnitude during the 1990s. Only the US has succeeded in erosion control and topsoil stabilization when it converted erodible cropland into grassland or woodland during 1986-90.

  1. Assessing the planet's condition.

    PubMed

    Brown, L R

    1990-01-01

    The destruction of the environment has accelerated since the Earth Day of 1970, the world's population has increased by another 1.6 billion, and over 500 million acres of forest have been lost. Carbon dioxide levels, greenhouse gases, and chlorofluorocarbons have increased in the atmosphere with evidence that global warming has started. The ozone hole has appeared, acid rain has destroyed forests, air pollution in major northern hemisphere cities has worsened, and species are disappearing, while toxic chemicals have been dumped indiscriminately. World grain production has fallen while population has increased. In Europe 14 countries have stabilized their population, and Japan, France, and Finland are on the way to zero growth. Reduction of high fertility in 1/2 could halt the deterioration of living conditions. Japan and China achieved this within a decade. Energy efficiency has to be attained; US cars still consume too much gas. Solar energy with photovoltaic cells to provide power, fuel alcohol from plants, and solar thermal power plants have potential. Semiarid regions, such as northern Africa, could become major producers of solar energy. Various measures are mandatory to cut down on waste: to recycle paper bags, to use standardized glasses for beverages, and to utilize scrap metal in electric arc steel furnaces. Reforestation is also on the agenda, as major deforestation has occurred in the Brazilian Amazon region, in India, and in Europe because of acid rain. Australia's national plan envisions planting 1 billion trees, and the US project is of similar magnitude during the 1990s. Only the US has succeeded in erosion control and topsoil stabilization when it converted erodible cropland into grassland or woodland during 1986-90. PMID:12285798

  2. The dynamic cusp

    NASA Technical Reports Server (NTRS)

    Potemra, T. A.; Erlandson, R. E.; Zanetti, L. J.; Arnoldy, R. L.; Woch, J.; Friis-Christensen, E.

    1992-01-01

    Results of a study of satellite and ground-based data acquired near the dayside cusp during a period when the IMF was inferred to have a strong northward component are presented. The presence of Pc 1 bursts, Pc 4-5 pulsations, and a tailward traveling twin vortex pattern of ionospheric convection suggests that the magnetosphere may have been temporarily compressed. Magnetic field data acquired at a synchronous altitude from GOES 5 and on the ground from Huanacayo support this suggestion. Plasma with ion dispersion characteristics associated with a cusp during southward IMF was detected by Viking over a 3.5-deg range of latitude. The presence of standing Alfven waves and ring current ions suggests that this 'cusplike' plasma was observed on closed geomagnetic field lines. It is suggested that the magnetosphere, during a northward IMF, is temporarily compressed by a solar wind pressure enhancement that produces the Pc 1 bursts, Pc 4-5 pulsations, and ionospheric vortices.

  3. Joule heating hot spot at high latitudes in the afternoon sector

    NASA Astrophysics Data System (ADS)

    Cai, L.; Aikio, A. T.; Milan, S. E.

    2016-07-01

    The afternoon Joule heating hot spot has been studied statistically by using the EISCAT Svalbard Radar (ESR) measurements at 75.4° Corrected Geomagnetic latitude (CGMLAT) and the OMNI solar wind data base. For a small subset of events, the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) field-aligned current distributions have been available. The main results are as follows. Afternoon Joule heating hot spots are associated with high values of ionospheric electric fields and slightly enhanced Pedersen conductances. The Joule heating hot spot values are larger in summer than in winter, which can be explained by the higher Pedersen conductances during summer than winter. The afternoon Joule heating hot spots are located close to the reversals of the large-scale field-aligned current systems. The most common location is close to the Region 1/Region 2 boundary and those events are associated with sunward convecting F region plasma. In a few cases, the hot spots take place close to the Region 1/Region 0 boundary and then the ionospheric plasma is convecting antisunward. The hot spots may occur both during slow (<450 km/s) and high (>450 km/s) speed solar wind conditions. During slow-speed solar wind events, the dominant interplanetary magnetic field (IMF) direction is southward, which is the general requirement for the low-latitude magnetic merging at the dayside magnetopause. During high-speed solar wind, also northward IMF conditions appear, but those are associated with large values of the IMF |By| component, making again the dayside magnetopause merging possible. Finally, the measured afternoon hot spot Joule heating rates are not a linear function of the solar wind energy coupling function.

  4. Conditioned stimulus determinants of conditioned response form in Pavlovian fear conditioning.

    PubMed

    Kim, S D; Rivers, S; Bevins, R A; Ayres, J J

    1996-01-01

    Four experiments using barpress conditioned suppression in rats found that tone evoked more freezing (immobility) than did light. Still, tone and light appeared to have similar conditioned value as assessed by suppression in Experiments 1, 2, and 3, and by blocking, second-order conditioning, and overconditioning assays in Experiments 1, 2, and 3, respectively. Experiment 4 arranged for tone to evoke less suppression than light but more freezing. Results suggest that in fear conditioning, the nature of the conditioned stimulus affects the form of conditioned responding (strong vs. weak freezing). This conclusion extends one drawn by P. C. Holland (1977) on the basis of his work in appetitive conditioning.

  5. Oceanographic Conditions Limit the Spread of a Marine Invader along Southern African Shores.

    PubMed

    Assis, Jorge; Zupan, Mirta; Nicastro, Katy R; Zardi, Gerardo I; McQuaid, Christopher D; Serrão, Ester A

    2015-01-01

    Invasive species can affect the function and structure of natural ecological communities, hence understanding and predicting their potential for spreading is a major ecological challenge. Once established in a new region, the spread of invasive species is largely controlled by their dispersal capacity, local environmental conditions and species interactions. The mussel Mytilus galloprovincialis is native to the Mediterranean and is the most successful marine invader in southern Africa. Its distribution there has expanded rapidly and extensively since the 1970s, however, over the last decade its spread has ceased. In this study, we coupled broad scale field surveys, Ecological Niche Modelling (ENM) and Lagrangian Particle Simulations (LPS) to assess the current invaded distribution of M. galloprovincialis in southern Africa and to evaluate what prevents further spread of this species. Results showed that all environmentally suitable habitats in southern Africa have been occupied by the species. This includes rocky shores between Rocky Point in Namibia and East London in South Africa (approx. 2800 km) and these limits coincide with the steep transitions between cool-temperate and subtropical-warmer climates, on both west and southeast African coasts. On the west coast, simulations of drifting larvae almost entirely followed the northward and offshore direction of the Benguela current, creating a clear dispersal barrier by advecting larvae away from the coast. On the southeast coast, nearshore currents give larvae the potential to move eastwards, against the prevalent Agulhas current and beyond the present distributional limit, however environmental conditions prevent the establishment of the species. The transition between the cooler and warmer water regimes is therefore the main factor limiting the northern spread on the southeast coast; however, biotic interactions with native fauna may also play an important role. PMID:26114766

  6. Oceanographic Conditions Limit the Spread of a Marine Invader along Southern African Shores

    PubMed Central

    Nicastro, Katy R.; Zardi, Gerardo I.; McQuaid, Christopher D.; Serrão, Ester A.

    2015-01-01

    Invasive species can affect the function and structure of natural ecological communities, hence understanding and predicting their potential for spreading is a major ecological challenge. Once established in a new region, the spread of invasive species is largely controlled by their dispersal capacity, local environmental conditions and species interactions. The mussel Mytilus galloprovincialis is native to the Mediterranean and is the most successful marine invader in southern Africa. Its distribution there has expanded rapidly and extensively since the 1970s, however, over the last decade its spread has ceased. In this study, we coupled broad scale field surveys, Ecological Niche Modelling (ENM) and Lagrangian Particle Simulations (LPS) to assess the current invaded distribution of M. galloprovincialis in southern Africa and to evaluate what prevents further spread of this species. Results showed that all environmentally suitable habitats in southern Africa have been occupied by the species. This includes rocky shores between Rocky Point in Namibia and East London in South Africa (approx. 2800 km) and these limits coincide with the steep transitions between cool-temperate and subtropical-warmer climates, on both west and southeast African coasts. On the west coast, simulations of drifting larvae almost entirely followed the northward and offshore direction of the Benguela current, creating a clear dispersal barrier by advecting larvae away from the coast. On the southeast coast, nearshore currents give larvae the potential to move eastwards, against the prevalent Agulhas current and beyond the present distributional limit, however environmental conditions prevent the establishment of the species. The transition between the cooler and warmer water regimes is therefore the main factor limiting the northern spread on the southeast coast; however, biotic interactions with native fauna may also play an important role. PMID:26114766

  7. MHD Flow Visualization of Magnetopause and Polar Cusps Vortices

    NASA Technical Reports Server (NTRS)

    Collado-Vega, Y. M.; Kessel, R. L.; Shao, X.; Boller, R. A.

    2007-01-01

    Detailed analysis of Wind, Geotail, and Cluster data shows how magnetopause boundary and polar cusps vortices associated with high speed streams can be a carrier of energy flux to the Earth's magnetosphere. For our analysis time interval, March 29 . - April 5 2002, the Interplanetary Magnetic Field (IMF) is primarily northward and MHD simulations of vortices along the flanks within nine hours of the time interval suggest that a Kelvin Helmholtz (KH) instability is likely present. Vortices were classified by solar wind input provided by the Wind satellite located 70-80 RE upstream from Earth. We present statistics for a total of 304 vortices found near the ecliptic plane on the magnetopause flanks, 273 with northward IMF and 31 with southward IMF. The vortices generated under northward IMF were more driven into the dawnside than into the duskside, being substantially more ordered on the duskside. Most of the vortices were large in scale, up to 10 RE, and with a rotation axis closely aligned with the Z(sub GSE) direction. They rotated preferentially clockwise on the dawnside, and. counter-clockwise on the duskside. Those generated under southward IMF were less ordered, fewer in number, and also smaller in diameter. Significant vortex activity occurred on the nightside region of the magnetosphere for these southward cases in contrast to the northward IMF cases on which most of the activity was driven onto the magnetopause flanks. Magnetopause crossings seen by the Geotail spacecraft for the time interval were analyzed and compared with the MHD simulation to validate our results. Vortices over the polar cusps are also being analyzed and the simulation results will be compared to the multi-point measurements of the four Cluster satellites.

  8. MHD Flow Visualization of Magnetopause and Polar Cusps Vortices

    NASA Technical Reports Server (NTRS)

    Collado-Vega, Y. M.; Kessel, R. L.; Shao, X.; Boller, R. A.

    2006-01-01

    Detailed analysis of Wind, Geotail, and Cluster data shows how magnetopause boundary and polar cusps vortices associated with high speed streams can be a carrier of energy flux to the Earth s magnetosphere. For our analysis time interval, March 29 . - April 5 2002, the Interplanetary Magnetic Field (IMF) is primarily northward and MHD simulations of vortices along the flanks within nine hours of the time interval suggest that a Kelvin Helmholtz (KH) instability is likely present. Vortices were classified by solar wind input provided by the Wind satellite located 70-80 RE upstream from Earth. We present statistics for a total of 304 vortices found near the ecliptic plane on the magnetopause flanks, 273 with northward IMF and 31 with southward IMF. The vortices generated under northward IMF were more driven into the dawnside than into the duskside, being substantially more ordered on the duskside. Most of the vortices were large in scale, up to 10 RE, and with a rotation axis closely aligned with the ZGSE direction. They rotated preferentially clockwise on the dawnside, and. counter-clockwise on the duskside. Those generated under southward IMF were less ordered, fewer in number, and also smaller in diameter. Significant vortex activity occurred on the nightside region of the magnetosphere for these southward cases in contrast to the northward IMF cases on which most of the activity was driven onto the magnetopause flanks. Magnetopause crossings seen by the Geotail spacecraft for the time interval were analyzed and compared with the MHD simulation to validate our results. Vortices over the polar cusps are also being analyzed and the simulation results will be compared to the multi-point measurements of the four Cluster satellites.

  9. South Pole all-sky imager observations of dayside aurora activity induced by a solar wind dynamic pressure enhancement

    NASA Astrophysics Data System (ADS)

    Motoba, T.; Kadokura, A.; Ebihara, Y.; Sato, N.

    2008-12-01

    Ground observations of the optical aurora in the dayside cusp region have the distinct advantages of continuity of coverage and sufficient temporal-spatial sensitivity to monitor dayside signatures of solar wind/magnetosphere/ionosphere interaction mechanisms. The South Pole Station (SP, geomagnetic latitude (GMLat) = -74.3 degs, magnetic local time = UT-3.5 h) in Antarctica is a unique place for dayside aurora observations during austral winter season. We present the detailed features of enhancements of dayside aurora activity induced by a sudden increase in the solar wind dynamic pressure (Psw), using a ground-based all-sky imager (ASI) at SP. The interplanetary magnetic field (IMF) was northward during the Psw enhancement. Just after the arrival of the Psw enhancement on the Earth"fs magnetosphere, the 557.7 nm aurora activity on the dayside is suddenly intensified almost in the whole field of view of ASI. Further a few minutes later, the intensity of the auroral emissions shows a maximum, and then decays within about 5 minutes. Even after decay of the transient aurora activity at lower latitudes, the newly formed auroral emissions from the dayside cusp to the polar cap (GMLat -76 to -80 degs) develop during the Psw enhancement lasting about an hour. The polar aurora intensifications seem to be associated with lobe reconnection under the northward IMF conditions as well as the Psw enhancement. In this talk, two cases have been studied and the possible generation mechanisms will be discussed by comparing the ASI data at SP with other instruments.

  10. Organizational Conditions of Teacher Learning.

    ERIC Educational Resources Information Center

    Bassler, Otto; Hoover-Dempsey, Kathy

    1986-01-01

    This research examined 1,213 elementary school teachers' perceptions of the school organizational conditions that provide the greatest opportunities for professional development. Ten workplace conditions were analyzed. Results are presented. (Author/MT)

  11. CLASSICAL CONDITIONING AND PAIN: CONDITIONED ANALGESIA AND HYPERALGESIA

    PubMed Central

    Miguez, Gonzalo; Laborda, Mario A.; Miller, Ralph R.

    2013-01-01

    This article reviews situations in which stimuli produce an increase or a decrease in nociceptive responses through basic associative processes and provides an associative account of such changes. Specifically, the literature suggests that cues associated with stress can produce conditioned analgesia or conditioned hyperalgesia, depending on the properties of the conditioned stimulus (e.g., contextual cues and audiovisual cues vs. gustatory and olfactory cues, respectively) and the proprieties of the unconditioned stimulus (e.g., appetitive, aversive, or analgesic, respectively). When such cues are associated with reducers of exogenous pain (e.g., opiates), they typically increase sensitivity to pain. Overall, the evidence concerning conditioned stress-induced analgesia, conditioned hyperalagesia, conditioned tolerance to morphine, and conditioned reduction of morphine analgesia suggests that selective associations between stimuli underlie changes in pain sensitivity. PMID:24269884

  12. Classical conditioning and pain: conditioned analgesia and hyperalgesia.

    PubMed

    Miguez, Gonzalo; Laborda, Mario A; Miller, Ralph R

    2014-01-01

    This article reviews situations in which stimuli produce an increase or a decrease in nociceptive responses through basic associative processes and provides an associative account of such changes. Specifically, the literature suggests that cues associated with stress can produce conditioned analgesia or conditioned hyperalgesia, depending on the properties of the conditioned stimulus (e.g., contextual cues and audiovisual cues vs. gustatory and olfactory cues, respectively) and the proprieties of the unconditioned stimulus (e.g., appetitive, aversive, or analgesic, respectively). When such cues are associated with reducers of exogenous pain (e.g., opiates), they typically increase sensitivity to pain. Overall, the evidence concerning conditioned stress-induced analgesia, conditioned hyperalagesia, conditioned tolerance to morphine, and conditioned reduction of morphine analgesia suggests that selective associations between stimuli underlie changes in pain sensitivity.

  13. Global hybrid simulations of the ion foreshock

    NASA Astrophysics Data System (ADS)

    Omidi, N.; Blanco-Cano, X.; Sibeck, D.; Russell, C.

    2005-12-01

    The ion foreshock is a dynamic region with many linear and nonlinear plasma processes which lead to a variety of observables such as ion beams, ULF waves and cavity structures. Local spacecraft observations and theory/simulation studies have investigated many individual processes in the foreshock. Global hybrid (kinetic ions, fluid electrons) simulations of the bow shock and associated foreshock provide a collective picture of these processes and how they interact together. These simulations also allow us to understand how the structure of the foreshock and the processes contained in it vary as a function of solar wind conditions such as, the direction of the interplanetary magnetic field (IMF). In this talk, results from global hybrid simulations of the ion foreshock, for northward, southward, radial and intermediate IMF directions are presented and the differences and similarities discussed. Emphasis will be on the origin, evolution and consequences of 30 second sinusoidal waves and shocklets, various ion beam populations, as well as, foreshock cavities. In addition, issues regarding the coupling between the foreshock, bow shock, magnetosheath and the magnetopause are discussed. This coupling has direct impact on the nature of solar wind magnetosphere interaction and involves processes propagating in both directions. Namely, it is demonstrated that foreshock phenomenon influence processes at the magnetopause and visa-versa where reconnection at the magnetopause directly modifies ion foreshock structure and dynamics.

  14. Magnetosheath influence on solar wind - magnetosphere coupling

    NASA Astrophysics Data System (ADS)

    Pulkkinen, Tuija; Kilpua, Emilia; Dimmock, Andrew; Myllys, Minna; Osmane, Adnane; Nykyri, Katariina; Lakka, Antti

    2016-07-01

    We have shown that the solar wind - magnetosphere - ionosphere coupling is different during due northward IMF from that during due southward IMF, and that the Poynting flux at the magnetopause is not a simple function of the upstream solar wind conditions upstream of the bow shock. These results are indicative of multiple transport processes taking place on various temporal and spatial scales, and therefore more detailed analysis is required to identify these mechanisms and quantify their contributions to solar wind - magnetosphere coupling. We combine the OMNI, IMAGE and THEMIS observations to statistically examine the properties incident at the magnetopause in the quasi-perpendicular and quasi-parallel shock sides separately. We use local and global MHD simulations to examine the energy and plasma transport properties across the bow shock, in the magnetosheath, and across the magnetopause. We focus especially on the anomalously quiet period during the deep solar minimum in 2008-2010, comparing the results with steady but stronger drivers during magnetic cloud events.

  15. Operant Conditioning for Special Educators.

    ERIC Educational Resources Information Center

    Pedrini, Bonnie C.; Pedrini, D. T.

    The paper briefly explains operant conditioning as it pertains to special educators. Operant conditioning is thought to be an efficient method for modifying student behavior. Using the B. F. Skinner frame of reference, operant conditioning is said to include behavior modification and therapy, programed instruction, and computer assisted and…

  16. Teacher Working Conditions that Matter

    ERIC Educational Resources Information Center

    Leithwood, Ken; McAdie, Pat

    2007-01-01

    To advance understanding of the issues concerning teachers' working conditions, the Elementary Teachers' Federation of Ontario commissioned one of the authors to do an analytical review of literature on teachers' working conditions. This resulted in the publication, "Teacher Working Conditions That Matter: Evidence for Change." The framework for…

  17. Teaching and Demonstrating Classical Conditioning.

    ERIC Educational Resources Information Center

    Sparrow, John; Fernald, Peter

    1989-01-01

    Discusses classroom demonstrations of classical conditioning and notes tendencies to misrepresent Pavlov's procedures. Describes the design and construction of the conditioner that is used for demonstrating classical conditioning. Relates how students experience conditioning, generalization, extinction, discrimination, and spontaneous recovery.…

  18. Serotonin and conditioning: focus on Pavlovian psychostimulant drug conditioning.

    PubMed

    Carey, Robert J; Damianopoulos, Ernest N

    2015-04-01

    Serotonin containing neurons are located in nuclei deep in the brainstem and send axons throughout the central nervous system from the spinal cord to the cerebral cortex. The vast scope of these connections and interactions enable serotonin and serotonin analogs to have profound effects upon sensory/motor processes. In that conditioning represents a neuroplastic process that leads to new sensory/motor connections, it is apparent that the serotonin system has the potential for a critical role in conditioning. In this article we review the basics of conditioning as well as the serotonergic system and point up the number of non-associative ways in which manipulations of serotonin neurotransmission have an impact upon conditioning. We focus upon psychostimulant drug conditioning and review the contribution of drug stimuli in the use of serotonin drugs to investigate drug conditioning and the important impact drug stimuli can have on conditioning by introducing new sensory stimuli that can create or mask a CS. We also review the ways in which experimental manipulations of serotonin can disrupt conditioned behavioral effects but not the associative processes in conditioning. In addition, we propose the use of the recently developed memory re-consolidation model of conditioning as an approach to assess the possible role of serotonin in associative processes without the complexities of performance effects related to serotonin treatment induced alterations in sensory/motor systems.

  19. Evolution of the current system during solar wind pressure pulses based on aurora and magnetometer observations

    NASA Astrophysics Data System (ADS)

    Nishimura, Yukitoshi; Kikuchi, Takashi; Ebihara, Yusuke; Yoshikawa, Akimasa; Imajo, Shun; Li, Wen; Utada, Hisashi

    2016-08-01

    We investigated evolution of ionospheric currents during sudden commencements using a ground magnetometer network in conjunction with an all-sky imager, which has the advantage of locating field-aligned currents much more accurately than ground magnetometers. Preliminary (PI) and main (MI) impulse currents showed two-cell patterns propagating antisunward, particularly during a southward interplanetary magnetic field (IMF). Although this overall pattern is consistent with the Araki (solar wind sources of magnetospheric ultra-low-frequency waves. Geophysical monograph series, vol 81. AGU, Washington, DC, pp 183-200, 1994. doi: 10.1029/GM081p0183) model, we found several interesting features. The PI and MI currents in some events were highly asymmetric with respect to the noon-midnight meridian; the post-noon sector did not show any notable PI signal, but only had an MI starting earlier than the pre-noon MI. Not only equivalent currents but also aurora and equatorial magnetometer data supported the much weaker PI response. We suggest that interplanetary shocks impacting away from the subsolar point caused the asymmetric current pattern. Additionally, even when PI currents form in both pre- and post-noon sectors, they can initiate and disappear at different timings. The PI currents did not immediately disappear but coexisted with the MI currents for the first few minutes of the MI. During a southward IMF, the MI currents formed equatorward of a preexisting DP-2, indicating that the MI currents are a separate structure from a preexisting DP-2. In contrast, the MI currents under a northward IMF were essentially an intensification of a preexisting DP-2. The magnetometer and imager combination has been shown to be a powerful means for tracing evolution of ionospheric currents, and we showed various types of ionospheric responses under different upstream conditions.

  20. A Statistical Study of Plasmaspheric Plumes and Ionospheric Outflows Observed at the Dayside Magnetopause

    NASA Astrophysics Data System (ADS)

    Lee, S. H.; Zhang, H.; Zong, Q. G.; Otto, A.; Rème, H.; Liebert, E.

    2015-12-01

    The low-energy and dense plasma originated from the ionosphere has often been observed in the dayside magnetosphere and may play an important role in the dynamics of the dayside magnetopause. We present a statistical study of the plasmaspheric plumes and the ionospheric outflows observed by the Cluster spacecraft near the dayside magnetopause from 2007 to 2009. The plasmaspheric plumes were identified by the low-energy ions (< 1 keV) which have 90° pitch angle distributions from the CIS/HIA instrument onboard Cluster in the magnetosphere. The ionospheric outflows were characterized by uni- or bi-directional field-aligned pitch angle distributions with low-energy ions observed in the dayside magnetosphere. 43 (10%) plasmaspheric plume events and 32 (7%) ionospheric outflow events were detected during 442 dayside magnetopause crossings. The occurrence rate of the plume at the duskside is significantly higher than that at the dawnside, indicating that the plasmaspheric plumes may lead to a dawn-dusk asymmetry of the dayside reconnection. The occurrence rate of the outflow shows a weak dawn-dusk asymmetry. We investigated how the plasmaspheric plume and ionospheric outflow's occurrence rates depend on geomagnetic activity and solar wind/IMF conditions. It is found that the plume events prefer to occur during moderate geomagnetic activity (Kp = 3, -30 ≤ Dst < -10 nT), while the ionospheric outflow events do not occur when Kp = 0 and their occurrence rate does not have a clear Dst dependence. It is also found that the plume events tend to occur during southward IMF (duskward solar wind electric field). In contrast, the ionospheric outflows prefer to occur during northward IMF (dawnward solar wind electric field). Finally, the occurrence rates of both plumes and outflows increase with increasing solar wind dynamic pressure.

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

    SciTech Connect

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

    1991-05-01

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

  2. Extended slow-roll conditions and rapid-roll conditions

    SciTech Connect

    Chiba, Takeshi; Yamaguchi, Masahide E-mail: gucci@phys.aoyama.ac.jp

    2008-10-15

    We derive slow-roll conditions for a scalar field which is non-minimally coupled with gravity in a consistent manner and express spectral indices of scalar/tensor perturbations in terms of the slow-roll parameters. The conformal invariance of the curvature perturbation is proved without linear approximations. Rapid-roll conditions are also derived, and the relation with the slow-roll conditions is discussed.

  3. Sensitivity to masked conditioned stimuli predicts conditioned response magnitude under masked conditions

    PubMed Central

    Cornwell, Brian R.; Echiverri, Aileen M.; Grillon, Christian

    2009-01-01

    Expression of conditioned fear has been reported to be independent of perceptual awareness of conditioned stimuli (CSs). Previous studies have been criticized, however, for not adequately assessing perceptual awareness. We fear-conditioned participants to one of two symbols and measured skin conductance responses to dichoptically masked and unmasked CSs. Participants also performed a target detection task and sensitivity (d′) to the masked conditioned stimuli (CS+, CS−) was measured. Results showed that sensitivity under masking conditions was related to conditioned responses to masked CSs but not unmasked CSs. Thus, a strong relationship between expression of conditioned fear and awareness of the CS+ emerges when the latter is assessed by signal detection methods. Without consensus on how awareness should be defined, these findings bring balance to previous studies that have typically used less sensitive assessments of awareness. PMID:17433097

  4. Extinction in human fear conditioning.

    PubMed

    Hermans, Dirk; Craske, Michelle G; Mineka, Susan; Lovibond, Peter F

    2006-08-15

    Although most extinction research is conducted in animal laboratories, the study of extinction learning in human fear conditioning has gained increasing attention over the last decade. The most important findings from human fear extinction are reviewed in this article. Specifically, we review experimental investigations of the impact of conditioned inhibitors, conditioned exciters, context renewal, and reinstatement on fear extinction in human samples. We discuss data from laboratory studies of the extinction of aversively conditioned stimuli, as well as results from experimental clinical work with fearful or anxious individuals. We present directions for future research, in particular the need for further investigation of differences between animal and human conditioning outcomes, and research examining the role of both automatic and higher-order cognitive processes in human conditioning and extinction.

  5. How People Interpret Conditionals: Shifts toward the Conditional Event

    ERIC Educational Resources Information Center

    Fugard, Andrew J. B.; Pfeifer, Niki; Mayerhofer, Bastian; Kleiter, Gernot D.

    2011-01-01

    We investigated how people interpret conditionals and how stable their interpretation is over a long series of trials. Participants were shown the colored patterns on each side of a 6-sided die and were asked how sure they were that a conditional holds of the side landing upward when the die is randomly thrown. Participants were presented with 71…

  6. Polarity in Conditionals and Conditional-Like Constructions

    ERIC Educational Resources Information Center

    Hsieh, I-Ta Chris

    2012-01-01

    This dissertation concerns the distribution of negative polarity items (henceforth, NPIs) in conditionals and conditional-like constructions. NPIs include words such as any and ever and idioms such as "give a damn" and "lift a finger"; these expressions have only a limited distribution. In this dissertation, the distribution of…

  7. Demand Characteristics in Classical Verbal Conditioning and Attitude Conditioning Studies.

    ERIC Educational Resources Information Center

    McGinley, Hugh

    This paper is a draft for the American Psychological Association Symposium on the conditioning of verbal behavior and attitudes. The author presents the results of several studies he conducted in the classical conditioning of meaning and attitude. These studies attempt to control the measurement effects created by extraneous variables operating on…

  8. Conditional entropy of ordinal patterns

    NASA Astrophysics Data System (ADS)

    Unakafov, Anton M.; Keller, Karsten

    2014-02-01

    In this paper we investigate a quantity called conditional entropy of ordinal patterns, akin to the permutation entropy. The conditional entropy of ordinal patterns describes the average diversity of the ordinal patterns succeeding a given ordinal pattern. We observe that this quantity provides a good estimation of the Kolmogorov-Sinai entropy in many cases. In particular, the conditional entropy of ordinal patterns of a finite order coincides with the Kolmogorov-Sinai entropy for periodic dynamics and for Markov shifts over a binary alphabet. Finally, the conditional entropy of ordinal patterns is computationally simple and thus can be well applied to real-world data.

  9. FPC conditioning cart at BNL

    SciTech Connect

    Xu, W.; Ben-Zvi, I.; Altinbas, F.Z.; Belomestnykh, S.; Burrill, A.; Cole, M.; Deonarine, J.; Jamilkowski, J.; Kayran, D.; Laloudakis, N.; Masi Jr, L.; McIntyre, G.; Pate, D.; Philips, D.; Seda, T.; Steszyn, A.; Tallerico, T.; Todd, R.; Weiss, D.; White, G.; Zaltsman, A.

    2011-03-28

    The 703 MHz superconducting gun for the BNL Energy Recovery Linac (ERL) prototype has two fundamental power couplers (FPCs), and each of them will deliver up to 500 kW of CW RF power. In order to prepare the couplers for high power RF service and process multipacting, the FPCs should be conditioned prior to installation into the gun cryomodule. A conditioning cart based test stand, which includes a vacuum pumping system, controllable bake-out system, diagnostics, interlocks and data log system has been designed, constructed and commissioned by collaboration of BNL and AES. This paper presents FPC conditioning cart systems and the conditioning process.

  10. Storm surges in the Mediterranean Sea: Variability and trends under future climatic conditions

    NASA Astrophysics Data System (ADS)

    Androulidakis, Yannis S.; Kombiadou, Katerina D.; Makris, Christos V.; Baltikas, Vassilis N.; Krestenitis, Yannis N.

    2015-09-01

    The trends of storm surge extremes in the Mediterranean Sea for a period of 150 years (1951-2100) are explored, using a high-resolution storm surge model. Numerical simulations are forced by the output of regional climate simulations with RegCM3, which uses IPCC's historical data on greenhouse gasses emissions for the (past) period 1951-2000, and IPCC's A1B climate scenario for the (future) period 2001-2100. Comparisons between observations and modeling results show good agreement and confirm the ability of our model to estimate the response of the sea surface to future climatic conditions. We investigate the future trends, the variability and frequency of local extremes and the main forcing mechanisms that can induce strong surges in the Mediterranean region. Our results support that there is a general decreasing trend in storminess under the considered climate scenario, mostly related to the frequency of local peaks and the duration and spatial coverage of the storm surges. The northward shift in the location of storm tracks is a possible reason for this storminess attenuation, especially over areas where the main driving factor of extreme events is the inverted barometer effect. However, the magnitudes of sea surface elevation extremes may increase in several Mediterranean sub-regions, i.e., Southern Adriatic, Balearic and Tyrrhenian Seas, during the 21st century. There are clear distinctions in the contributions of winds and pressure fields to the sea level height for various regions of the Mediterranean Sea, as well as on the seasonal variability of extreme values; the Aegean and Adriatic Seas are characteristic examples, where high surges are predicted to be mainly induced by low pressure systems and favorable winds, respectively.

  11. Hydrogeology and ground-water-quality conditions at the Emporia- Lyon County Landfill, eastern Kansas, 1988

    USGS Publications Warehouse

    Myers, N.C.; Bigsby, P.R.

    1990-01-01

    Hydrogeology and water-quality conditions at the Emporia-Lyon County Landfill, eastern Kansas, were investigated from April 1988 through April 1989. Potentiometric-surface maps indicated groundwater movement from the northeast and northwest towards the landfill and then south through the landfill to the Cottonwood River. The maps indicate that during periods of low groundwater levels, groundwater flows northward in the north-west part of the landfill, which may have been induced by water withdrawal from wells north of the landfill or by water ponded in waste lagoons south and west of the landfill. Chemical analysis of water samples from monitoring wells upgradient and downgradient of the landfill indicate calcium bicarbonate to be the dominant water type. No inorganic or organic chemical concentrations exceeded Kansas or Federal primary drinking-water standards. Kansas secondary drinking-water standards were equaled or exceeded, however, in water from some or all wells for total hardness, dissolved solids, iron, and manganese. Water from one upgradient well contained larger concentrations of dissolved oxygen and nitrate, and smaller concentrations of bicarbonate, alkalinity, ammonia, arsenic, iron, and manganese as compared to all other monitoring wells. Results of this investigation indicate that groundwater quality downgradient of well MW-2 has increased concentrations of some inorganic and organic compounds. Due to the industrial nature of the area and the changing directions of groundwater flow, it is not clear what the source of these compounds might be. Long-term monitoring, additional wells, and access to nearby waste lagoons and waste-lagoon monitoring wells would help define the sources of increased inorganic and organic compounds. (USGS)

  12. Reconstructing coastal environmental condition in the eastern Norwegian Sea by means of Arctica islandica sclerochronological records

    NASA Astrophysics Data System (ADS)

    Trofimova, Tamara; Andersson, Carin

    2015-04-01

    Paleo archives are fundament in improving our knowledge of the natural climate variability. Established marine proxy records for the ocean, especially for high latitudes, are both sparsely distributed and are poorly resolved in time. The identification and development of new archives and proxies for studying key ocean processes at annual to sub-annual resolution that can extend the marine instrumental record is therefore a clear priority for marine climate science. The bivalve species Arctica islandica is a unique paleoclimatic archive with an exceptional longevity combined with high temporal resolution, due to accretion of annual growth increments. The aim of this study is to use sclerochronological records of A. islandica to extend instrumental hydrographic records and increase our understanding of a variability of a Norwegian Coastal Current (NCC). The NCC transports warm, low-salinity water northwards, which eventually plays role for the Arctic halocline. Moreover, previous investigations showed the connection of properties and variability of the NCC with catches of commercially valuable fishes. The knowledge of the variability of the NCC is also essential for possible future prediction climate conditions and fish stock variability in the region. In this study we use shells of Arctica islandica collected off the coast of Eggum (Lofoten, Norway). The material was obtained from the depth 5-10 m by dredging along the seabed and by means of scuba divers. We examine the growth patterns of living and subfossil shells. Ongoing work mainly focuses on the construction of a composite growth chronology based on increment-width time series. The results we will compare with existing time series of the environment and climatic parameters to determine the controlling factors and test the applicability of growth chronology in a climate reconstruction. Furthermore, we will perform geochemical analyses of the stable isotope composition (δ18O and δ13C) in shell carbonate to

  13. Entanglement conditions and polynomial identities

    SciTech Connect

    Shchukin, E.

    2011-11-15

    We develop a rather general approach to entanglement characterization based on convexity properties and polynomial identities. This approach is applied to obtain simple and efficient entanglement conditions that work equally well in both discrete as well as continuous-variable environments. Examples of violations of our conditions are presented.

  14. Matching and Conditioned Reinforcement Rate

    ERIC Educational Resources Information Center

    Shahan, Timothy A.; Podlesnik, Christopher A.; Jimenez-Gomez, Corina

    2006-01-01

    Attempts to examine the effects of variations in relative conditioned reinforcement rate on choice have been confounded by changes in rates of primary reinforcement or changes in the value of the conditioned reinforcer. To avoid these problems, this experiment used concurrent observing responses to examine sensitivity of choice to relative…

  15. Operant conditioning in redwinged blackbirds.

    PubMed

    Bastian, C W; Hothersall, D

    1970-09-01

    An operant conditioning technique for use with passerine birds is described. Two redwinged blackbirds were successfully conditioned to perch-hop for food reinforcement. Continuous reinforcement and fixed-ratio schedules involving substantial ratio requirements were used to maintain this response. The behavior of the two redwinged blackbirds was comparable to that of more conventional organisms working on similar schedules of reinforcement.

  16. The National Wetland Condition Assessment

    EPA Science Inventory

    The first National Wetland Condition Assessment (NWCA) was conducted in 2011 by the US Environmental Protection Agency (USEPA). Vegetation, algae, soil, water chemistry,and hydrologic data were collected at each of 1138 sites across the contiguous US. Ecological condition was ass...

  17. Trace fear conditioning in mice.

    PubMed

    Lugo, Joaquin N; Smith, Gregory D; Holley, Andrew J

    2014-03-20

    In this experiment we present a technique to measure learning and memory. In the trace fear conditioning protocol presented here there are five pairings between a neutral stimulus and an unconditioned stimulus. There is a 20 sec trace period that separates each conditioning trial. On the following day freezing is measured during presentation of the conditioned stimulus (CS) and trace period. On the third day there is an 8 min test to measure contextual memory. The representative results are from mice that were presented with the aversive unconditioned stimulus (shock) compared to mice that received the tone presentations without the unconditioned stimulus. Trace fear conditioning has been successfully used to detect subtle learning and memory deficits and enhancements in mice that are not found with other fear conditioning methods. This type of fear conditioning is believed to be dependent upon connections between the medial prefrontal cortex and the hippocampus. One current controversy is whether this method is believed to be amygdala-independent. Therefore, other fear conditioning testing is needed to examine amygdala-dependent learning and memory effects, such as through the delay fear conditioning.

  18. Conditional Logic and Primary Children.

    ERIC Educational Resources Information Center

    Ennis, Robert H.

    Conditional logic, as interpreted in this paper, means deductive logic characterized by "if-then" statements. This study sought to investigate the knowledge of conditional logic possessed by primary children and to test their readiness to learn such concepts. Ninety students were designated the experimental group and participated in a 15-week…

  19. Study of the cofactor conditions: Conditions of supercompatibility between phases

    NASA Astrophysics Data System (ADS)

    Chen, Xian; Srivastava, Vijay; Dabade, Vivekanand; James, Richard D.

    2013-12-01

    The cofactor conditions, introduced in James and Zhang(2005), are conditions of compatibility between phases in martensitic materials. They consist of three subconditions: (i) the condition that the middle principal stretch of the transformation stretch tensor U is unity (λ2=1), (ii) the condition a·Ucof(U2-I)n=0, where the vectors a and n are certain vectors arising in the specification of the twin system, and (iii) the inequality trU2+det U2-(1/4)|a|2|n|2≥2. Together, these conditions are necessary and sufficient for the equations of the crystallographic theory of martensite to be satisfied for the given twin system but for any volume fraction f of the twins, 0≤f≤1. This contrasts sharply with the generic solutions of the crystallographic theory which have at most two such volume fractions for a given twin system of the form f* and 1-f*. In this paper we simplify the form of the cofactor conditions, we give their specific forms for various symmetries and twin types, we clarify the extent to which the satisfaction of the cofactor conditions for one twin system implies its satisfaction for other twin systems. In particular, we prove that the satisfaction of the cofactor conditions for either Type I or Type II twins implies that there are solutions of the crystallographic theory using these twins that have no elastic transition layer. We show that the latter further implies macroscopically curved, transition-layer-free austenite/martensite interfaces for Type I twins, and planar transition-layer-free interfaces for Type II twins which nevertheless permit significant flexibility (many deformations) of the martensite. We identify some real material systems nearly satisfying the cofactor conditions. Overall, the cofactor conditions are shown to dramatically increase the number of deformations possible in austenite/martensite mixtures without the presence of elastic energy needed for coexistence. In the context of earlier work that links the special case λ2

  20. Serotonin in fear conditioning processes.

    PubMed

    Bauer, Elizabeth P

    2015-01-15

    This review describes the latest developments in our understanding of how the serotonergic system modulates Pavlovian fear conditioning, fear expression and fear extinction. These different phases of classical fear conditioning involve coordinated interactions between the extended amygdala, hippocampus and prefrontal cortices. Here, I first define the different stages of learning involved in cued and context fear conditioning and describe the neural circuits underlying these processes. The serotonergic system can be manipulated by administering serotonin receptor agonists and antagonists, as well as selective serotonin reuptake inhibitors (SSRIs), and these can have significant effects on emotional learning and memory. Moreover, variations in serotonergic genes can influence fear conditioning and extinction processes, and can underlie differential responses to pharmacological manipulations. This research has considerable translational significance as imbalances in the serotonergic system have been linked to anxiety and depression, while abnormalities in the mechanisms of conditioned fear contribute to anxiety disorders.

  1. Redox Conditions and Related Color Change in Eastern Equatorial Pacific Sediments: IODP Site U1334

    NASA Astrophysics Data System (ADS)

    Kordesch, W. E.; Gussone, N. C.; Hathorne, E. C.; Kimoto, K.; Delaney, M. L.

    2011-12-01

    This study was prompted by a 65 m thick brown-green color change in deep-sea sediments of IODP Site U1334 (0-38 Ma, 4799 m water depth) that corresponds to its equatorial crossing (caused by the Northward movement of the pacific plate). Green sediment is a visual indicator of reducing conditions in sediment due to enhanced organic matter deposition and burial. Here we use geochemical redox indicators to characterize the effect of equatorial upwelling on bottom water. The modern redox signal is captured in porewater profiles (nitrate, manganese, iron, sulfate) while trace metal Enrichment Factors (EF) in bulk sediment (manganese, uranium, molybdenum, rhenium) normalized to the detrital component (titanium) record redox state at burial. To measure export productivity we also measure biogenic barium. Porewater profiles reveal suboxic diagenesis; profiles follow the expected sequence of nitrate, manganese oxide, and iron oxide reduction with increasing depth. Constant sulfate (~28 μM) implies anoxia has not occurred. Bulk sediment Mn EF are enriched (EF > 1) throughout the record (Mn EF = 15-200) while U and Mo enrichment corresponds to green color and equatorial proximity (U EF = 4-19; Mo EF = 0-7). Constant Mn enrichment implies continuous oxygenation. Uranium and Mo enrichment near the equator represents suboxic conditions also seen in the porewater. Low Re concentrations (below detection) provide additional evidence against anoxia. A comparison of Mn EF from total digestions to samples treated with an additional reductive cleaning step distinguishes between Mn-oxides and Mn-carbonates, indicating oxygenated and reducing conditions respectively. Mn-carbonate occurrence agrees with U and Mo EF; conditions were more reducing near the equator. Bio-Ba shows significant variability over this interval (22-99 mmol g-1). Our geochemical results indicate that bottom waters became suboxic at the equator as a result of equatorial upwelling-influenced increases in organic

  2. From Early Holocene to Neoglacial conditions - Multiproxy evidence for stepwise cooling in the Arctic Gateway

    NASA Astrophysics Data System (ADS)

    Werner, K.; Müller, J.; Hass, H.; Spielhagen, R. F.

    2012-12-01

    Two high-resolution sediment sequences from the Western Svalbard margin covering the last ca. 10.000 years were studied in order to derive information on the Holocene variability of heat transport to the Arctic Ocean and fluctuations in the position of the marginal ice zone. The Fram Strait, often referred to as the Arctic Gateway, is the only deep-water passage for Atlantic-derived water masses to enter the Arctic Ocean. Northward advection of relatively warm and saline Atlantic Water masses keeps the eastern Fram Strait ice-free all year and controls the Arctic Ocean's heat budget. We investigated geochemical, micropaleontological, and sedimentological parameters with centennial to multidecadal time resolution at two sites which are located today beneath the Atlantic Water-bearing inner and outer West Spitsbergen Current. Records of planktic and benthic foraminiferal stable isotopes and planktic foraminifer assemblages clearly reveal distinct variations between climatically warmer and colder intervals throughout this period. Strong fluctuations in stable isotope data of the subpolar planktic foraminifer species Turborotalita quinqueloba infer strong variability of summer sea surface conditions probably caused by variable extent of the upper mixed layer and the sea ice margin. Planktic foraminifer fauna imply a stepwise transition from deglacial/Early Holocene to modern-like conditions. Superimposed on the generally strong heat transport to the Arctic Ocean during the Early to Mid-Holocene are repeated short-term coolings such as the 8.2 ka event. Past sea ice conditions were studied by means of the sea ice proxy IP25 and ice rafted detritus and document increasing occurrence of sea ice and/or icebergs since the Mid-Holocene, culminating in the so-called 'neoglaciation' trend. The Late Holocene Neoglacial phase was in particular characterized by the dominance of the cold water-indicating planktic foraminifer species Neogloboquadrina pachyderma. Consistent with the

  3. SIPEX 2012: Extreme sea-ice and atmospheric conditions off East Antarctica

    NASA Astrophysics Data System (ADS)

    Heil, P.; Stammerjohn, S.; Reid, P.; Massom, R. A.; Hutchings, J. K.

    2016-09-01

    In 2012, Antarctic sea-ice coverage was marked by weak annual-mean climate anomalies that consisted of opposing anomalies early and late in the year (some setting new records) which were interspersed by near-average conditions for most of the austral autumn and winter. Here, we investigate the ocean-ice-atmosphere system off East Antarctica, prior to and during the Sea Ice Physics and Ecosystems eXperiment [SIPEX] 2012, by exploring relationships between atmospheric and oceanic forcing together with the sea-ice and snow characteristics. During August and September 2012, just prior to SIPEX 2012, atmospheric circulation over the Southern Ocean was near-average, setting up the ocean-ice-atmosphere system for near-average conditions. However, below-average surface pressure and temperature as well as strengthened circumpolar winds prevailed during June and July 2012. This led to a new record (19.48×106 km2) in maximum Antarctic sea-ice extent recorded in late September. In contrast to the weak circum-Antarctic conditions, the East Antarctic sector (including the SIPEX 2012 region) experienced positive sea-ice extent and concentration anomalies during most of 2012, coincident with negative atmospheric pressure and sea-surface temperature anomalies. Heavily deformed sea ice appeared to be associated with intensified wind stress due to increased cyclonicity as well as an increased influx of sea ice from the east. This increased westward ice flux is likely linked to the break-up of nearly 80% of the Mertz Glacier Tongue in 2010, which strongly modified the coastal configuration and hence the width of the westward coastal current. Combined with favourable atmospheric conditions the associated changed coastal configuration allowed more sea ice to remain within the coastal current at the expense of a reduced northward flow in the region around 141°-145°E. In addition a westward propagating positive anomaly of sea-ice extent from the western Ross Sea during austral winter

  4. Barotropic eastward currents in the western Gulf of Lion, north-western Mediterranean Sea, during stratified conditions

    NASA Astrophysics Data System (ADS)

    Petrenko, A.; Dufau, C.; Estournel, C.

    2008-11-01

    The circulation of the Gulf of Lion, a large continental shelf north of the western basin of the Mediterranean Sea, is complex and highly variable. During stratified conditions, unexpected barotropic eastward currents can be detected, mostly in the western part of the gulf. Care is given to retrieve inertial oscillations when necessary. The primitive-equation free-surface model Symphonie is used to investigate the processes which can generate and influence these eastward currents. Three main wind forcing create these barotropic eastward currents: northwesterlies channelled in the western part of the gulf, northwesterlies and north winds both homogeneous throughout the gulf. In the first case, the wind stress curl of the channeled northwesterlies generates an elongated cyclonic circulation in the western part of the Gulf of Lion. The southern part of this cyclonic circulation is a barotropic eastward current, detected west of longitude 4.5°E. In the second case, a homogeneous northwesterly wind creates an intrusion of the along-slope geostrophic current on the shelf, generating a strong coastal jet going northward above Cap Creus. In stratified conditions, intrusion at this western end of the continental shelf only occurs during this type of wind forcing. The coastal jet goes north then detaches itself from the coast and goes eastward, north of the 100 m isobath. In the third case, a homogeneous north wind creates an eastward current which occupies the whole shelf north of latitude 43°N. The first two cases are studied in more details since cruise data corroborate the model simulations. The striking characteristic of these eastward currents is that they are barotropic despite the stratified conditions. Otherwise, their amplitude and exact locations are slightly different for the different cases of circulation. These eastward currents probably have an impact on the residence time of water masses in the Gulf of Lion, and hence on the total water budget of the gulf

  5. Saltier sea surface water conditions recorded by multiple mid-Holocene corals in the northern South China Sea

    NASA Astrophysics Data System (ADS)

    Guo, Yangrui; Deng, Wenfeng; Chen, Xuefei; Wei, Gangjian; Yu, Kefu; Zhao, Jian-xin

    2016-08-01

    The typical features of the mid-Holocene can be used to better understand present-day climate conditions and the potential trends of future climate change. The surface conditions, including sea surface temperature (SST) and sea surface salinity (SSS), of the South China Sea (SCS) are largely controlled by the East Asian monsoon system. Surface water conditions reconstructed from coral proxies can be used to study the evolution of the East Asian monsoon during the mid-Holocene. However, there are some discrepancies among existing coral-based studies regarding whether the mid-Holocene sea surface water was much saltier than the present day surface waters. Based on paired Sr/Ca and δ18O of modern and three fossil corals, this paper reconstructs the patterns of seasonal variation in SSS during the mid-Holocene in the northern SCS. The Δδ18O records (a proxy for SSS) derived from the three fossil corals were all heavier than that from the modern coral, which suggests the presence of more saline surface waters during the mid-Holocene in the northern SCS. These results are consistent with previous studies based on records reconstructed from coral and foraminifera, as well as from numerical simulations. Reduced rainfall caused by the strengthened Asian Monsoon and/or the northward shift of the intertropical convergence zone during the mid-Holocene would explain the increased salinity of the surface waters of the northern SCS. The findings presented here clarify the discrepancies among previous studies and confirm the existence of saltier surface waters in the northern SCS during the mid-Holocene.

  6. Conceptual Conditioning: Mechanisms Mediating Conditioning Effects on Pain.

    PubMed

    Jepma, Marieke; Wager, Tor D

    2015-11-01

    Classical conditioning can profoundly modify subsequent pain responses, but the mechanisms that drive this effect are unresolved. In pain-conditioning studies, cues are typically conditioned to primary aversive reinforcers; hence, subsequent pain modulation could reflect learned precognitive associations (i.e., those involving neural plasticity independent of expectations and other forms of conceptual thought) or conceptual expectancies. We isolated conceptual contributions using a thermal pain-conditioning procedure in which different conditioned stimulus (CS) cues were repeatedly paired with symbolic representations of high and low noxious heat. In a subsequent test phase, identical noxious stimuli evoked larger skin conductance responses (SCRs) and pain ratings when preceded by CS cues associated with high temperature than by those associated with low temperature. These effects were mediated by participants' self-reported expectancies. CS cues associated with high temperature also evoked larger anticipatory SCRs than did CS cues associated with low temperature, but larger anticipatory SCRs predicted smaller subsequent heat-evoked SCRs. These results provide novel evidence that conditioned modulation of pain physiology can be acquired through purely conceptual processes, and that self-reported expectancies and physiological threat responses have opposing effects on pain.

  7. Defeasible reasoning with legal conditionals.

    PubMed

    Gazzo Castañeda, Lupita Estefania; Knauff, Markus

    2016-04-01

    Valid conclusions can be defeated if people can think of conditions that prevent the consequent to occur although the antecedent is given. The goal of the present research was to investigate how people consider these conditions when reasoning with legal conditionals such as "If a person kills another human, then this person should be punished for manslaughter." In Experiments 1 and 2 legal conditionals were presented to participants together with exculpatory circumstances, i.e., counterexamples. The participants' task was to decide whether they would adhere to the legal conditional rule and punish the offender. Participants were either lawyers (i.e., advanced law students and graduate lawyers) or legal laypeople. We found that laypeople often ignore exculpatory circumstances and adhere to the conditional rule when offences evoked high levels of moral outrage. Lawyers did not show this effect. In Experiment 3 laypeople showed difficulties even when asked to simply imagine exculpatory circumstances for highly morally outrageous offences. Results provide new evidence for the role of emotions--like moral outrage--in the consideration of counterexamples to legal conditionals. PMID:26689704

  8. Compatibility Conditions of Structural Mechanics

    NASA Technical Reports Server (NTRS)

    Patnaik, Surya N.; Coroneos, Rula M.; Hopkins, Dale A.

    1999-01-01

    The theory of elasticity has camouflaged a deficiency in the compatibility formulation since 1860. In structures the ad hoc compatibility conditions through virtual "cuts" and closing "gaps" are not parallel to the strain formulation in elasticity. This deficiency in the compatibility conditions has prevented the development of a direct stress determination method in structures and in elasticity. We have addressed this deficiency and attempted to unify the theory of compatibility. This work has led to the development of the integrated force method for structures and the completed Beltrami-Michell formulation for elasticity. The improved accuracy observed in the solution of numerical examples by the integrated force method can be attributed to the compliance of the compatibility conditions. Using the compatibility conditions allows mapping of variables and facile movement among different structural analysis formulations. This paper reviews and illustrates the requirement of compatibility in structures and in elasticity. It also describes the generation of the conditions and quantifies the benefits of their use. The traditional analysis methods and available solutions (which have been obtained bypassing the missed conditions) should be verified for compliance of the compatibility conditions.

  9. Quantitative modeling of the magnetic field configuration associated with the theta aurora

    NASA Astrophysics Data System (ADS)

    Naehr, S. M.; Toffoletto, F. R.

    2004-07-01

    The relationships among the interplanetary magnetic field (IMF), the global magnetospheric configuration, and the polar cap configuration known as the theta aurora are explored, using simulations generated by the Rice Field Model and the BATSRUS global MHD model. Two phenomena that have been linked to theta auroras are examined: a "convection gap," or region of zero magnetic normal component on the magnetopause, associated with antiparallel merging during periods of steady, predominantly northward IMF, and a reconfiguration of the tail lobe and plasma sheet twist following abrupt IMF rotations. It is found that (1) the convection gap does not produce configurations consistent with the theta aurora, (2) large-angle rotations of the IMF produce partial bifurcations of the open-closed boundary and tail lobes and field-aligned current patterns that are consistent with the theta aurora, (3) reconfiguration of the plasma sheet during IMF rotations, rather than relocation of the merging line, is critical to the development of theta aurora-like configurations, (4) a sufficient magnetotail length, longer than produced in MHD simulations but consistent with the Rice Field Model, can account for the observed duration and velocity of theta auroras created by a single IMF rotation, (5) multiple IMF rotations do not significantly affect the duration of the theta configuration but may lead to multiple transpolar arcs.

  10. The Eastern California Shear Zone as the northward extension of the southern San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Thatcher, W.; Savage, J. C.; Simpson, R. W.

    2016-04-01

    Cluster analysis offers an agnostic way to organize and explore features of the current GPS velocity field without reference to geologic information or physical models using information only contained in the velocity field itself. We have used cluster analysis of the Southern California Global Positioning System (GPS) velocity field to determine the partitioning of Pacific-North America relative motion onto major regional faults. Our results indicate the large-scale kinematics of the region is best described with two boundaries of high velocity gradient, one centered on the Coachella section of the San Andreas Fault and the Eastern California Shear Zone and the other defined by the San Jacinto Fault south of Cajon Pass and the San Andreas Fault farther north. The ~120 km long strand of the San Andreas between Cajon Pass and Coachella Valley (often termed the San Bernardino and San Gorgonio sections) is thus currently of secondary importance and carries lesser amounts of slip over most or all of its length. We show these first order results are present in maps of the smoothed GPS velocity field itself. They are also generally consistent with currently available, loosely bounded geologic and geodetic fault slip rate estimates that alone do not provide useful constraints on the large-scale partitioning we show here. Our analysis does not preclude the existence of smaller blocks and more block boundaries in Southern California. However, attempts to identify smaller blocks along and adjacent to the San Gorgonio section were not successful.

  11. The Eastern California Shear Zone as the northward extension of the southern San Andreas Fault

    USGS Publications Warehouse

    Thatcher, Wayne R.; Savage, James C.; Simpson, Robert W.

    2016-01-01

    Cluster analysis offers an agnostic way to organize and explore features of the current GPS velocity field without reference to geologic information or physical models using information only contained in the velocity field itself. We have used cluster analysis of the Southern California Global Positioning System (GPS) velocity field to determine the partitioning of Pacific-North America relative motion onto major regional faults. Our results indicate the large-scale kinematics of the region is best described with two boundaries of high velocity gradient, one centered on the Coachella section of the San Andreas Fault and the Eastern California Shear Zone and the other defined by the San Jacinto Fault south of Cajon Pass and the San Andreas Fault farther north. The ~120 km long strand of the San Andreas between Cajon Pass and Coachella Valley (often termed the San Bernardino and San Gorgonio sections) is thus currently of secondary importance and carries lesser amounts of slip over most or all of its length. We show these first order results are present in maps of the smoothed GPS velocity field itself. They are also generally consistent with currently available, loosely bounded geologic and geodetic fault slip rate estimates that alone do not provide useful constraints on the large-scale partitioning we show here. Our analysis does not preclude the existence of smaller blocks and more block boundaries in Southern California. However, attempts to identify smaller blocks along and adjacent to the San Gorgonio section were not successful.

  12. Phylogeographic structure and northward range expansion in the barnacle Chthamalus fragilis

    PubMed Central

    Bukša, Filip; Bockrath, Katherine; Wares, John P.; Pineda, Jesús

    2015-01-01

    The barnacle Chthamalus fragilis is found along the US Atlantic seaboard historically from the Chesapeake Bay southward, and in the Gulf of Mexico. It appeared in New England circa 1900 coincident with warming temperatures, and is now a conspicuous member of rocky intertidal communities extending through the northern shore of Cape Cod, Massachusetts. The origin of northern C. fragilis is debated. It may have spread to New England from the northern end of its historic range through larval transport by ocean currents, possibly mediated by the construction of piers, marinas, and other anthropogenic structures that provided new hard substrate habitat. Alternatively, it may have been introduced by fouling on ships originating farther south in its historic distribution. Here we examine mitochondrial cytochrome c oxidase I sequence diversity and the distribution of mitochondrial haplotypes of C. fragilis from 11 localities ranging from Cape Cod, to Tampa Bay, Florida. We found significant genetic structure between northern and southern populations. Phylogenetic analysis revealed three well-supported reciprocally monophyletic haplogroups, including one haplogroup that is restricted to New England and Virginia populations. While the distances between clades do not suggest cryptic speciation, selection and dispersal barriers may be driving the observed structure. Our data are consistent with an expansion of C. fragilis from the northern end of its mid-19th century range into Massachusetts. PMID:25945315

  13. Middle Miocene kinematic shift in northeastern Tibet from collision-related northward growth to eastward contraction

    NASA Astrophysics Data System (ADS)

    Lease, R. O.; Burbank, D. W.; Hough, B. G.; Clark, M. K.; Zhang, H.; Farley, K. A.; Wang, Z.

    2009-12-01

    Variations in the direction and timing of range growth demonstrate how India-Asia convergence was manifest in northeastern Tibet (near 36°N, 103°E) throughout the Cenozoic. We detect a >45° change in shortening direction in middle Miocene time by examining thermochronological relief transects from contractional ranges in combination with stratigraphic successions from adjacent foreland basins. Apatite (U-Th)/He and fission track age-elevation relationships suggest an onset of rapid exhumation in the north-directed Laji Shan at ~23 Ma. Rapid exhumation of the adjacent east-directed Jishi Shan, however, did not commence until ~12 Ma. Furthermore, diachronous Miocene range growth is expressed in the subsidence, provenance, and paleoclimatic records from magnetostratigraphically dated sections in adjacent Xunhua and Linxia basins. Emergence of the north-directed Laji Shan is highlighted in Xunhua basin by a doubling of sediment accumulation rates between 24 and 22 Ma, enhanced flexural loading from 25 to 22 Ma, and the introduction of proximal alluvial facies at 20.7 Ma that detrital zircon U/Pb age spectra show were sourced from basement terranes within the Laji Shan. In contrast, growth of the east-directed Jishi Shan is expressed by an acceleration in Xunhua accumulation rates between 12 and 9 Ma and a doubling of detrital zircons derived from Jishi Shan sources by 11.5 Ma in Linxia. Additionally, the divergence of Linxia and Xunhua oxygen isotopic values signals topographic isolation of these two basins by surface uplift of the intervening Jishi Shan by 11 Ma. Together these diverse observations document a middle Miocene change in the kinematic style of plateau growth from initial north-directed contraction along a trajectory that mimicked the India-Asia collision to later east-directed contraction. This kinematic shift in northeastern Tibet coincides with expansion of the plateau margin in southeastern Tibet, as well as the onset of normal faulting in the high-elevation plateau interior, and may suggest a common geodynamic cause.

  14. Tracing the Origin and Northward Dissemination Dynamics of HIV-1 Subtype C in Brazil

    PubMed Central

    Delatorre, Edson; Couto-Fernandez, José C.; Guimarães, Monick Lindenmayer; Vaz Cardoso, Ludimila Paula; de Alcantara, Keila Correia; Martins de Araújo Stefani, Mariane; Romero, Hector; Freire, Caio C. M.; Iamarino, Atila; de A Zanotto, Paolo M.; Morgado, Mariza G.; Bello, Gonzalo

    2013-01-01

    Previous studies indicate that the HIV-1 subtype C epidemic in southern Brazil was initiated by the introduction of a single founder strain probably originating from east Africa. However, the exact country of origin of such a founder strain as well as the origin of the subtype C viruses detected outside the Brazilian southern region remains unknown. HIV-1 subtype C pol sequences isolated in the southern, southeastern and central-western Brazilian regions (n = 209) were compared with a large number (n ~ 2,000) of subtype C pol sequences of African origin. Maximum-likelihood analyses revealed that most HIV-1 subtype C Brazilian sequences branched in a single monophyletic clade (CBR-I), nested within a larger monophyletic lineage characteristic of east Africa. Bayesian analyses indicate that the CBR-I clade most probably originated in Burundi and was introduced into the Paraná state (southern region) around the middle 1970s, after which it rapidly disseminated to neighboring regions. The states of Paraná and Santa Catarina have been the most important hubs of subtype C dissemination, and routine travel and spatial accessibility seems to have been the major driving forces of this process. Five additional introductions of HIV-1 subtype C strains probably originated in eastern (n = 2), southern (n = 2) and central (n = 1) African countries were detected in the Rio de Janeiro state (southeastern region). These results indicate a continuous influx of HIV-1 subtype C strains of African origin into Brazil and also unveil the existence of unrecognized transmission networks linking this country to east Africa. PMID:24069269

  15. Phylogeographic structure and northward range expansion in the barnacle Chthamalus fragilis.

    PubMed

    Govindarajan, Annette F; Bukša, Filip; Bockrath, Katherine; Wares, John P; Pineda, Jesús

    2015-01-01

    The barnacle Chthamalus fragilis is found along the US Atlantic seaboard historically from the Chesapeake Bay southward, and in the Gulf of Mexico. It appeared in New England circa 1900 coincident with warming temperatures, and is now a conspicuous member of rocky intertidal communities extending through the northern shore of Cape Cod, Massachusetts. The origin of northern C. fragilis is debated. It may have spread to New England from the northern end of its historic range through larval transport by ocean currents, possibly mediated by the construction of piers, marinas, and other anthropogenic structures that provided new hard substrate habitat. Alternatively, it may have been introduced by fouling on ships originating farther south in its historic distribution. Here we examine mitochondrial cytochrome c oxidase I sequence diversity and the distribution of mitochondrial haplotypes of C. fragilis from 11 localities ranging from Cape Cod, to Tampa Bay, Florida. We found significant genetic structure between northern and southern populations. Phylogenetic analysis revealed three well-supported reciprocally monophyletic haplogroups, including one haplogroup that is restricted to New England and Virginia populations. While the distances between clades do not suggest cryptic speciation, selection and dispersal barriers may be driving the observed structure. Our data are consistent with an expansion of C. fragilis from the northern end of its mid-19th century range into Massachusetts. PMID:25945315

  16. Paleozoic paleomagnetism and northward drift of the Alexander Terrane, southeastern Alaska

    NASA Astrophysics Data System (ADS)

    van Der Voo, Rob; Jones, Meridee; Gromme, C. Sherman; Eberlein, G. Donald; Churkin, Michael, Jr.

    1980-10-01

    Paleozoic limestone, graywacke, sandstone, milestone, red beds and volcanic rocks of the Alexander terrane, southeastern Alaska, have yielded six paleomagnetic pole positions after thermal and alternating-field demagnetization. These poles are from sample groups of late Middle Ordovician, Late Ordovician, Devonian, Late Devonian, and early and late Carboniferous age. To test various tectonic models for the structural development of this part of western North America, the paleomagnetic results are compared to those for the North American craton. It is found that the observed inclination and declination values deviate significantly from the values predicted for the present-day position of the Alexander terrane (55.5N, 133.5W). Better matching can be obtained for a paleoposition of the terrane at about 40N, 120W, in the present position of western Nevada and northeastern California. In addition, an in situ 25° clockwise rotation of the terrane is required to restore it to its original position.

  17. GALIC: Galaxy initial conditions construction

    NASA Astrophysics Data System (ADS)

    Yurin, Denis; Springel, Volker

    2014-08-01

    GalIC (GALaxy Initial Conditions) is an implementation of an iterative method to construct steady state composite halo-disk-bulge galaxy models with prescribed density distribution and velocity anisotropy that can be used as initial conditions for N-body simulations. The code is parallelized for distributed memory based on MPI. While running, GalIC produces "snapshot files" that can be used as initial conditions files. GalIC supports the three file formats ('type1' format, the slightly improved 'type2' format, and an HDF5 format) of the GADGET (ascl:0003.001) code for its output snapshot files.

  18. Mass-based condition measures and their relationship with fitness: in what condition is condition?

    PubMed Central

    Barnett, Craig A.; Suzuki, Toshitaka N.; Sakaluk, Scott K.; Thompson, Charles F.

    2015-01-01

    Mass or body-size measures of ‘condition’ are of central importance to the study of ecology and evolution, and it is often assumed that differences in condition measures are positively and linearly related to fitness. Using examples drawn from ecological studies, we show that indices of condition frequently are unlikely to be related to fitness in a linear fashion. Researchers need to be more explicit in acknowledging the limitations of mass-based condition measures and accept that, under some circumstances, they may not relate to fitness as traditionally assumed. Any relationship between a particular condition measure and fitness should first be empirically validated before condition is used as a proxy for fitness. In the absence of such evidence, researchers should explicitly acknowledge that assuming such a relationship may be unrealistic. PMID:26019406

  19. FTEs: Theory, Simulation, and Observations

    NASA Technical Reports Server (NTRS)

    Siebeck, David G.; Zhang, H.

    2011-01-01

    Flux transfer events (FTEs) are ropes of interconnected magnetosheath and magnetospheric magnetic field lines generated by bursty reconnection at the dayside magnetopause. Theory predicts that the combined pressure gradient and magnetic curvature forces should determine the speed at which the events move and the locations where they can be observed. We present results indicating that events form on the dayside magnetopause for both northward and southward IMF orientations, but that the events for northward IMF orientations exhibit far weaker signatures until they reach the magnetospheric flanks and argue that this is consistent with observations indicating that events on the dayside tend to occur for southward IMF orientations, but those on the flank do not. We show that the component and antiparallel reconnection models predict events in strikingly different quadrants outside the flanks of the magnetotail.Observations of events in all four quadrants indicate that both models are required. The motion of events inferred from multispacecraft timing during periods of northward IMF orientation is generally consistent with the component reconnection model.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    the SAAs are embedded in the lobe cell during northward IMF conditions. In the presentation, we will show the results of detailed comparison between the ground-based radio and optical signatures of the SAAs and those obtained by the Cluster spacecraft at magnetospheric altitudes.

  1. Plant Condition Remote Monitoring Technique

    NASA Technical Reports Server (NTRS)

    Fotedar, L. K.; Krishen, K.

    1996-01-01

    This paper summarizes the results of a radiation transfer study conducted on houseplants using controlled environmental conditions. These conditions included: (1) air and soil temperature; (2) incident and reflected radiation; and (3) soil moisture. The reflectance, transmittance, and emittance measurements were conducted in six spectral bands: microwave, red, yellow, green, violet and infrared, over a period of three years. Measurements were taken on both healthy and diseased plants. The data was collected on plants under various conditions which included: variation in plant bio-mass, diurnal variation, changes in plant pathological conditions (including changes in water content), different plant types, various disease types, and incident light wavelength or color. Analysis of this data was performed to yield an algorithm for plant disease from the remotely sensed data.

  2. Conditioning biomass for microbial growth

    DOEpatents

    Bodie, Elizabeth A; England, George

    2015-03-31

    The present invention relates to methods for improving the yield of microbial processes that use lignocellulose biomass as a nutrient source. The methods comprise conditioning a composition comprising lignocellulose biomass with an enzyme composition that comprises a phenol oxidizing enzyme. The conditioned composition can support a higher rate of growth of microorganisms in a process. In one embodiment, a laccase composition is used to condition lignocellulose biomass derived from non-woody plants, such as corn and sugar cane. The invention also encompasses methods for culturing microorganisms that are sensitive to inhibitory compounds in lignocellulose biomass. The invention further provides methods of making a product by culturing the production microorganisms in conditioned lignocellulose biomass.

  3. 8 Conditions for Motivated Learning

    ERIC Educational Resources Information Center

    Cushman, Kathleen

    2014-01-01

    The author interviewed hundreds of adolescents about what makes them interested in learning, in and out of school. The result is a formula hinging on creating eight conditions that spur kids to take active, motivated roles in their own learning.

  4. 76 FR 14600 - Dental Conditions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-17

    ... examination to be needed, and Application for treatment is received within 180 days of discharge, and A VA... treatment of periodontal disease or calculus, unless the condition meets regulatory eligibility criteria....

  5. Matching and conditioned reinforcement rate.

    PubMed

    Shahan, Timothy A; Podlesnik, Christopher A; Jimenez-Gomez, Corina

    2006-03-01

    Attempts to examine the effects of variations in relative conditioned reinforcement rate on choice have been confounded by changes in rates of primary reinforcement or changes in the value of the conditioned reinforcer. To avoid these problems, this experiment used concurrent observing responses to examine sensitivity of choice to relative conditioned reinforcement rate. In the absence of observing responses, unsignaled periods of food delivery on a variable-interval 90-s schedule alternated with extinction on a center key (i.e., a mixed schedule was in effect). Two concurrently available observing responses produced 15-s access to a stimulus differentially associated with the schedule of food delivery (S+). The relative rate of S+ deliveries arranged by independent variable-interval schedules for the two observing responses varied across conditions. The relation between the ratio of observing responses and the ratio of S+ deliveries was well described by the generalized matching law, despite the absence of changes in the rate of food delivery. In addition, the value of the S+ deliveries likely remained constant across conditions because the ratio of S+ to mixed schedule food deliveries remained constant. Assuming that S+ deliveries serve as conditioned reinforcers, these findings are consistent with the functional similarity between primary and conditioned reinforcers suggested by general choice theories based on the concatenated matching law (e.g., contextual choice and hyperbolic value-added models). These findings are inconsistent with delay reduction theory, which has no terms for the effects of rate of conditioned reinforcement in the absence of changes in rate of primary reinforcement.

  6. [Early Development under Microgravity Conditions].

    PubMed

    Ogneva, I V

    2015-01-01

    The review is devoted to various aspects of early development under the space flight conditions. The different possible cell mechanosensors are considered. Structural and functional changes in the cells, predominantly, in non-muscle ones, were discussed. The results of the different experiments with the embryos of fish, amphibians, birds and mammals under microgravity conditions are shown discussing possible reasons for the development of morphological changes. PMID:26591615

  7. Blood circulation under weightless conditions

    NASA Technical Reports Server (NTRS)

    Kasyan, I. I.; Kopanev, V. I.; Yazdovskiy, V. I.

    1975-01-01

    Biomedical data obtained on men and animals during weightlessness conditions establish instabilities in pulse rate and blood circulation that smooth out in proportion to adaptation to the weightless condition. The unusual slowness of recovery of pulse rate to initial values after space flight stress is attributed to biological simulation of hormonal shifts and discharge of humoral substances into the blood that prevent a rapid recovery of some biological indicators to initial values.

  8. Air conditioning and refrigeration engineering

    SciTech Connect

    Kreith, F.

    1999-12-01

    This book supplies the basics of design, from selecting the optimum system and equipment to preparing the drawings and specifications. It discusses the four phases of preparing a project: gathering information, developing alternatives, evaluating alternatives, and selling the best solution. In addition, the author breaks down the responsibilities of the engineer design documents, computer aided design, and government codes and standards. It provides you with an easy reference to all aspects of the topic. This resource addresses the most current areas of interest, such as computer aided design and drafting, desiccant air conditioning and energy conservation. It is a thorough and convenient guide to air conditioning and refrigeration engineering. Contents include: introduction; psychrometrics; air-conditioning processes and cycles; refrigerants and refrigeration cycles; outdoor design conditions and indoor design criteria; load calculations; air handling units and packaged units; refrigeration components and evaporative coolers; water systems; heating systems; refrigeration systems; thermal storage system; air system basics; absorption systems; air-conditioning systems and selection; and desiccant dehumidification and air-conditioning.

  9. Initial conditions for bubble universes

    NASA Astrophysics Data System (ADS)

    McInnes, Brett

    2008-06-01

    The “bubble universes” of Coleman and De Luccia play a crucial role in string cosmology. Since our own Universe is supposed to be of this kind, bubble cosmology should supply definite answers to the long-standing questions regarding cosmological initial conditions. In particular, it must explain how an initial singularity is avoided, and also how the initial conditions for inflation were established. I argue that the simplest nonanthropic approach to these problems involves a requirement that the spatial sections defined by distinguished bubble observers should not be allowed to have arbitrarily small volumes. Casimir energy is a popular candidate for a quantum effect which can ensure this, but (because it violates energy conditions) there is a danger that it could lead to nonperturbative instabilities in string theory. I make a simple proposal for the initial conditions of a bubble universe, and show that my proposal ensures that the system is nonperturbatively stable. Thus, low-entropy conditions can be established at the beginning of a bubble universe without violating the second law of thermodynamics and without leading to instability in string theory. These conditions are inherited from the ambient spacetime.

  10. Precursor Environmental Conditions Associated with the Termination of Madden-Julian Oscillation Events

    NASA Astrophysics Data System (ADS)

    Stachnik, J. P.; Waliser, D. E.; Majda, A.

    2014-12-01

    Current generations of global climate models continue to struggle with simulating many of the observed features of the Madden-Julian oscillation (MJO) and suffer from low skill regarding initiation forecasts. While recent work has focused on those mechanisms thought to be important for MJO initiation, fewer studies have examined the large-scale conditions associated with quiescent periods of the MJO and the decay of existing events. Understanding these mechanisms may provide a valuable context toward improving simulations of MJO initiation and propagation in climate and operational weather forecast models. This study presents an analysis of the precursor environmental conditions related to the termination of MJO events. A simple climatology is created using a real-time MJO monitoring index, documenting the locations and frequencies of MJO decay. Lead-lag composites of several atmospheric variables including temperature, moisture, and intraseasonal wind anomalies are generated from three reanalyses. Long-term, lower tropospheric moisture deficits over the local domain best identify terminating events over the Indian Ocean, with a northward shift of the Intertropical Convergence Zone (ITCZ) and corresponding lead times as much as 20 days prior to MJO decay. Statistically significant differences are also identified more than 10 days in advance of MJO termination events in the west Pacific, though the vertical velocity and moisture anomalies are more symmetric about the equator. We also present results for those MJOs that terminate over the maritime continent. Unlike the Indian Ocean and west Pacific, the likelihood of an MJO to cross the maritime continent appears related to its own intensity, rather than the upstream environmental conditions, with only the strongest MJOs propagating into the warm pool region. Finally, a budget analysis is performed on the three-dimensional moisture advection equation in order to better elucidate what time-scales and physical

  11. MESSENGER Observation of Mercury's Magnetopause: Structure and Dynamics

    NASA Technical Reports Server (NTRS)

    Slavin, J. A.; Acuna, M. H.; Anderson, B. J.; Baker, D. N.; Benna, M.; Boardsen, S. A.; Gloeckler, G.; Gold, R. E.; Ho, G. C.; Korth, H.; Krimigis, S. M.; Livi, S. A.; McNutt, R. L., Jr.; Raines, J. M.; Sarantos, M.; Schriver, D.; Solomon, S. C.; Travnicek, P.

    2008-01-01

    MESSENGER'S 14 January 2008 encounter with Mercury has provided new observations of the magnetopause of this small magnetosphere, particularly concerning the effect of the direction of the interplanetary magnetic field (IMF) on the structure and dynamics of this boundary. The IMF was northward immediately prior to and following the passage of the MESSENGER spacecraft through Mercury's magnetosphere. However, several-minute episodes of southward IMF were observed in the magnetosheath during the inbound portion of the encounter. Evidence for reconnection at the dayside magnetopause in the form of well-developed flux transfer events (FTEs) was observed in the magnetosheath following some of these southward-B, intervals. The inbound magnetopause crossing seen in the magnetic field measurements is consistent with a transition from the magnetosheath into the plasma sheet. Immediately following MESSENGER'S entry into the magnetosphere, rotational perturbations in the magnetic field similar to those seen at the Earth in association with large-scale plasma sheet vortices driven by Kelvin-Helmholtz waves along the magnetotail boundary at the Earth were observed. The outbound magnetopause occurred during northward IMF B(sub z) and had the characteristics of a tangential discontinuity. These new observations by MESSENGER may be combined and compared with the magnetopause measurements collected by Mariner 10 to derive new understanding of the response of Mercury's magnetopause to IMF direction and its effect on the rate of solar wind energy and mass input to this small magnetosphere.

  12. Monetary effects on fear conditioning.

    PubMed

    Qu, Chen; Zhang, Aiyi; Chen, Qishan

    2013-04-01

    Previous research has found that the loss of money as a negative secondary reinforcer was as effective as a primary reinforcer during fear conditioning. The purpose of the present study was to explore the effect of monetary gain as a positive secondary reinforcer in fear conditioning. Participants were assigned to a high-reward group or low-reward group. Three kinds of squares prompting non-compensation shock, compensation shock, and no shock were presented. Skin conductance responses (SCRs) and self-ratings were recorded. The results revealed that (a) both SCRs and self-ratings in the compensation shock condition were lower than in the non-compensation shock condition, suggesting that money might block the learning stage of fear conditioning; and (b) a higher ratio of fear reduction was present in self-rating when compared to SCRs, suggesting that people might overstate the utility of money, subjectively. Monetary effects, the effects of different amounts of money, and the differences between subjective and physiological levels are discussed.

  13. Conditioned sounds enhance visual processing.

    PubMed

    Leo, Fabrizio; Noppeney, Uta

    2014-01-01

    This psychophysics study investigated whether prior auditory conditioning influences how a sound interacts with visual perception. In the conditioning phase, subjects were presented with three pure tones ( =  conditioned stimuli, CS) that were paired with positive, negative or neutral unconditioned stimuli. As unconditioned reinforcers we employed pictures (highly pleasant, unpleasant and neutral) or monetary outcomes (+50 euro cents, -50 cents, 0 cents). In the subsequent visual selective attention paradigm, subjects were presented with near-threshold Gabors displayed in their left or right hemifield. Critically, the Gabors were presented in synchrony with one of the conditioned sounds. Subjects discriminated whether the Gabors were presented in their left or right hemifields. Participants determined the location more accurately when the Gabors were presented in synchrony with positive relative to neutral sounds irrespective of reinforcer type. Thus, previously rewarded relative to neutral sounds increased the bottom-up salience of the visual Gabors. Our results are the first demonstration that prior auditory conditioning is a potent mechanism to modulate the effect of sounds on visual perception.

  14. Enhanced flue gas conditioning study

    SciTech Connect

    Miller, S.J.; Laudal, D.L.

    1991-11-01

    Many electrostatic precipitators (ESPS) do not achieve acceptable particulate removal efficiencies because of high-resistivity ash. One method to improve ESP performance is to employ chemical conditioning agents to reduce fly ash resistivity. Widely used agents include sulfur trioxide (SO[sub 3]) and ammonia, which are sometimes used simultaneously. For some fly ashes, that have a low affinity for SO[sub 3], conditioning with SO[sub 3] alone is not adequate to reduce resistivity without excessive amounts of SO[sub 3] exiting the stack. In such cases, the use of ammonia in addition to SO[sub 3] may reduce the amount of required SO[sub 3] and prevent the emission of excess SO[sub 3] out of the stack. The general objective of the work was to test enhanced flue gas conditioning methods to improve the performance of ESPS. Specific objectives were to (1) verify the relationship between the required SO[sub 3] injection rates to maintain the desired fly ash resistivity and temperature for four coals, (2) verify that dual conditioning with both ammonia and SO[sub 3] promotes SO[sub 3] utilization and allows for resistivity modification with moderate SO[sub 3] injection rates, and (3) verify the effectiveness and practicality of an enhanced flue gas conditioning (EFGC) method. The EFGC method is a proprietary development of Wahlco, Inc.

  15. Conditioned Sounds Enhance Visual Processing

    PubMed Central

    Leo, Fabrizio; Noppeney, Uta

    2014-01-01

    This psychophysics study investigated whether prior auditory conditioning influences how a sound interacts with visual perception. In the conditioning phase, subjects were presented with three pure tones ( =  conditioned stimuli, CS) that were paired with positive, negative or neutral unconditioned stimuli. As unconditioned reinforcers we employed pictures (highly pleasant, unpleasant and neutral) or monetary outcomes (+50 euro cents, −50 cents, 0 cents). In the subsequent visual selective attention paradigm, subjects were presented with near-threshold Gabors displayed in their left or right hemifield. Critically, the Gabors were presented in synchrony with one of the conditioned sounds. Subjects discriminated whether the Gabors were presented in their left or right hemifields. Participants determined the location more accurately when the Gabors were presented in synchrony with positive relative to neutral sounds irrespective of reinforcer type. Thus, previously rewarded relative to neutral sounds increased the bottom-up salience of the visual Gabors. Our results are the first demonstration that prior auditory conditioning is a potent mechanism to modulate the effect of sounds on visual perception. PMID:25192387

  16. Conditioning across the duration of a backward conditioned stimulus.

    PubMed

    Romaniuk, C B; Williams, D A

    2000-10-01

    Five conditioned suppression experiments examined the extent to which an appetitively motivated lever-press response can be punished by different components of a backward conditioned stimulus (CS). Using a 0-s unconditioned stimulus (US)-CS interval, Experiments 1 and 2 showed that the initial 3 s of a normally 30-s backward CS served as a more effective punisher than the CS as a whole. Experiment 3 found no such effect if the US-CS interval were 3 s rather than 0 s. Experiments 4A and 4B found that if the US-CS interval were 0 s, the initial part of the backward CS acquired excitatory properties although the CS as a whole passed a summation test for conditioned inhibition. By contrast, the 3-s US-CS interval supported inhibitory conditioning across the whole duration of the backward CS. Taken together, these findings support a modified version of Wagner's sometimes opponent process model, which suggests that different components of a backward CS become either excitatory or inhibitory depending on the components' temporal proximity to the US. PMID:11056885

  17. Condition with Caution: Think Thrice Before Conditioning. (Rough Draft).

    ERIC Educational Resources Information Center

    Katz, Lilian G.

    1971-01-01

    Innovative models for education are often quickly adopted. Behavior modification, or operant conditioning, is an example of a technique which has been widely used because, when properly applied in the classroom, it "works." However, the application of a technique should be carefully thought through in terms of the meaning of the behavior in…

  18. Oil Analysis and Condition Monitoring

    NASA Astrophysics Data System (ADS)

    Toms, A.; Toms, L.

    Lubricants are essential and expensive components of machine systems needing sampling, analysis and monitoring. Monitoring can be either performance testing or oil condition monitoring. Knowledge of the system's critical failure modes is essential for cost-effective oil and machinery monitoring. Contamination occurs by water, fuel, glycol, dirt, wrong oil, metal particulate, soot, oil degradation and additive depletion. Oil test methods include in situ or laboratory FT-IR, electronic particle counting, elemental metal measurement, X-ray fluorescence, viscosity, gas chromatography, water determination and RULER®. Condition monitoring data must be managed by storage, analysis and interpretation. Status levels must be established from the database and reported upon for individual and sequential runs of samples as condition indicators.

  19. Conditioned Reinforcement and Response Strength

    PubMed Central

    Shahan, Timothy A

    2010-01-01

    Stimuli associated with primary reinforcers appear themselves to acquire the capacity to strengthen behavior. This paper reviews research on the strengthening effects of conditioned reinforcers within the context of contemporary quantitative choice theories and behavioral momentum theory. Based partially on the finding that variations in parameters of conditioned reinforcement appear not to affect response strength as measured by resistance to change, long-standing assertions that conditioned reinforcers do not strengthen behavior in a reinforcement-like fashion are considered. A signposts or means-to-an-end account is explored and appears to provide a plausible alternative interpretation of the effects of stimuli associated with primary reinforcers. Related suggestions that primary reinforcers also might not have their effects via a strengthening process are explored and found to be worthy of serious consideration. PMID:20885815

  20. Diffusions conditioned on occupation measures

    NASA Astrophysics Data System (ADS)

    Angeletti, Florian; Touchette, Hugo

    2016-02-01

    A Markov process fluctuating away from its typical behavior can be represented in the long-time limit by another Markov process, called the effective or driven process, having the same stationary states as the original process conditioned on the fluctuation observed. We construct here this driven process for diffusions spending an atypical fraction of their evolution in some region of state space, corresponding mathematically to stochastic differential equations conditioned on occupation measures. As an illustration, we consider the Langevin equation conditioned on staying for a fraction of time in different intervals of the real line, including the positive half-line which leads to a generalization of the Brownian meander problem. Other applications related to quasi-stationary distributions, metastable states, noisy chemical reactions, queues, and random walks are discussed.

  1. Quantum Measurement and Initial Conditions

    NASA Astrophysics Data System (ADS)

    Stoica, Ovidiu Cristinel

    2016-03-01

    Quantum measurement finds the observed system in a collapsed state, rather than in the state predicted by the Schrödinger equation. Yet there is a relatively spread opinion that the wavefunction collapse can be explained by unitary evolution (for instance in the decoherence approach, if we take into account the environment). In this article it is proven a mathematical result which severely restricts the initial conditions for which measurements have definite outcomes, if pure unitary evolution is assumed. This no-go theorem remains true even if we take the environment into account. The result does not forbid a unitary description of the measurement process, it only shows that such a description is possible only for very restricted initial conditions. The existence of such restrictions of the initial conditions can be understood in the four-dimensional block universe perspective, as a requirement of global self-consistency of the solutions of the Schrödinger equation.

  2. Conditioned reinforcement and response strength.

    PubMed

    Shahan, Timothy A

    2010-03-01

    Stimuli associated with primary reinforcers appear themselves to acquire the capacity to strengthen behavior. This paper reviews research on the strengthening effects of conditioned reinforcers within the context of contemporary quantitative choice theories and behavioral momentum theory. Based partially on the finding that variations in parameters of conditioned reinforcement appear not to affect response strength as measured by resistance to change, long-standing assertions that conditioned reinforcers do not strengthen behavior in a reinforcement-like fashion are considered. A signposts or means-to-an-end account is explored and appears to provide a plausible alternative interpretation of the effects of stimuli associated with primary reinforcers. Related suggestions that primary reinforcers also might not have their effects via a strengthening process are explored and found to be worthy of serious consideration.

  3. Structural lubricity under ambient conditions

    PubMed Central

    Cihan, Ebru; İpek, Semran; Durgun, Engin; Baykara, Mehmet Z.

    2016-01-01

    Despite its fundamental importance, physical mechanisms that govern friction are poorly understood. While a state of ultra-low friction, termed structural lubricity, is expected for any clean, atomically flat interface consisting of two different materials with incommensurate structures, some associated predictions could only be quantitatively confirmed under ultra-high vacuum (UHV) conditions so far. Here, we report structurally lubric sliding under ambient conditions at mesoscopic (∼4,000–130,000 nm2) interfaces formed by gold islands on graphite. Ab initio calculations reveal that the gold–graphite interface is expected to remain largely free from contaminant molecules, leading to structurally lubric sliding. The experiments reported here demonstrate the potential for practical lubrication schemes for micro- and nano-electromechanical systems, which would mainly rely on an atomic-scale structural mismatch between the slider and substrate components, via the utilization of material systems featuring clean, atomically flat interfaces under ambient conditions. PMID:27350035

  4. Eckart−Sayvetz conditions revisited

    SciTech Connect

    Szalay, Viktor

    2014-06-21

    It is shown that vibrational displacements satisfying the Eckart−Sayvetz conditions can be constructed by projection of unconstrained displacements. This result has a number of interesting direct and indirect ramifications: (i) The normal coordinates corresponding to an electronic state or an isotopologue of a molecule are transformed to those of another state or isotopologue by a linear and, in general, non-orthogonal transformation. (ii) Novel interpretation of axis switching. (iii) One may enhance the separation of rotational-large-amplitude internal motions and the vibrational motions beyond that offered by the standard use of the Eckart−Sayvetz conditions. (iv) The rotational-vibrational Hamiltonian given in terms of curvilinear internal coordinates may be derived with elementary mathematical tools while taking into account the Eckart conditions with or without enhancement.

  5. Motor activity under weightless conditions

    NASA Technical Reports Server (NTRS)

    Kasyan, I. I.; Kopanev, V. I.; Cherepakhin, M. A.; Yuganov, Y. M.

    1975-01-01

    The material presented on the motor activity under weightless conditions (brief and long) leads to the conclusion that it is not significantly disrupted, if those being examined are secured at the workplaces. Some discoordination of movement, moderately expressed disruption of the precision of reproduction of assigned muscular forces, etc., were observed. Motor disorders decrease significantly in proportion to the length of stay under weightless conditions. This apparently takes place, as a consequence of formation of a new functional system, adequate to the conditions of weightlessness. Tests on intact and labyrinthectomized animals have demonstrated that signaling from the inner ear receptors is superfluous in weightlessness, since it promotes the onset of disruptions in the combined work of the position analyzers.

  6. Conditioned reinforcement and response strength.

    PubMed

    Shahan, Timothy A

    2010-03-01

    Stimuli associated with primary reinforcers appear themselves to acquire the capacity to strengthen behavior. This paper reviews research on the strengthening effects of conditioned reinforcers within the context of contemporary quantitative choice theories and behavioral momentum theory. Based partially on the finding that variations in parameters of conditioned reinforcement appear not to affect response strength as measured by resistance to change, long-standing assertions that conditioned reinforcers do not strengthen behavior in a reinforcement-like fashion are considered. A signposts or means-to-an-end account is explored and appears to provide a plausible alternative interpretation of the effects of stimuli associated with primary reinforcers. Related suggestions that primary reinforcers also might not have their effects via a strengthening process are explored and found to be worthy of serious consideration. PMID:20885815

  7. Structural lubricity under ambient conditions

    NASA Astrophysics Data System (ADS)

    Cihan, Ebru; Ipek, Semran; Durgun, Engin; Baykara, Mehmet Z.

    2016-06-01

    Despite its fundamental importance, physical mechanisms that govern friction are poorly understood. While a state of ultra-low friction, termed structural lubricity, is expected for any clean, atomically flat interface consisting of two different materials with incommensurate structures, some associated predictions could only be quantitatively confirmed under ultra-high vacuum (UHV) conditions so far. Here, we report structurally lubric sliding under ambient conditions at mesoscopic (~4,000-130,000 nm2) interfaces formed by gold islands on graphite. Ab initio calculations reveal that the gold-graphite interface is expected to remain largely free from contaminant molecules, leading to structurally lubric sliding. The experiments reported here demonstrate the potential for practical lubrication schemes for micro- and nano-electromechanical systems, which would mainly rely on an atomic-scale structural mismatch between the slider and substrate components, via the utilization of material systems featuring clean, atomically flat interfaces under ambient conditions.

  8. Structural lubricity under ambient conditions.

    PubMed

    Cihan, Ebru; İpek, Semran; Durgun, Engin; Baykara, Mehmet Z

    2016-01-01

    Despite its fundamental importance, physical mechanisms that govern friction are poorly understood. While a state of ultra-low friction, termed structural lubricity, is expected for any clean, atomically flat interface consisting of two different materials with incommensurate structures, some associated predictions could only be quantitatively confirmed under ultra-high vacuum (UHV) conditions so far. Here, we report structurally lubric sliding under ambient conditions at mesoscopic (∼4,000-130,000 nm(2)) interfaces formed by gold islands on graphite. Ab initio calculations reveal that the gold-graphite interface is expected to remain largely free from contaminant molecules, leading to structurally lubric sliding. The experiments reported here demonstrate the potential for practical lubrication schemes for micro- and nano-electromechanical systems, which would mainly rely on an atomic-scale structural mismatch between the slider and substrate components, via the utilization of material systems featuring clean, atomically flat interfaces under ambient conditions. PMID:27350035

  9. Initial conditions and quantum cosmology

    NASA Technical Reports Server (NTRS)

    Hartle, James B.

    1987-01-01

    A theory of initial conditions is necessary for a complete explanation of the presently observed large scale structural features of the universe, and a quantum theory of cosmology is probably needed for its formulation. The kinematics of quantum cosmology are reviewed, and some candidates for a law of initial conditions are discussed. The proposal that the quantum state of a closed universe is the natural analog of the ground state for closed cosmologies and is specified by a Euclidean sum over histories is sketched. When implemented in simple models, this proposal is consistent with the most important large-scale observations.

  10. Real-time streamflow conditions

    USGS Publications Warehouse

    Graczyk, David J.; Gebert, Warren A.

    1996-01-01

    Would you like to know streamflow conditions before you go fishing in Wisconsin or in more distant locations? Real-time streamflow data throughout Wisconsin and the United States are available on the Internet from the U.S. Geological Survey. You can see if the stream you are interested in fishing is high due to recent rain or low because of an extended dry spell. Flow conditions at more than 100 stream-gaging stations located throughout Wisconsin can be viewed by accessing the Wisconsin District Home Page at: http://wwwdwimdn.er.usgs.gov

  11. Making chromosome abnormalities treatable conditions.

    PubMed

    Cody, Jannine DeMars; Hale, Daniel Esten

    2015-09-01

    Individuals affected by the classic chromosome deletion syndromes which were first identified at the beginning of the genetic age, are now positioned to benefit from genomic advances. This issue highlights five of these conditions (4p-, 5p-, 11q-, 18p-, and 18q-). It focuses on the increased in understanding of the molecular underpinnings and envisions how these can be transformed into effective treatments. While it is scientifically exciting to see the phenotypic manifestations of hemizygosity being increasingly understood at the molecular and cellular level, it is even more amazing to consider that we are now on the road to making chromosome abnormalities treatable conditions.

  12. Heat pipe thermal conditioning panel

    NASA Technical Reports Server (NTRS)

    Saaski, E. W.; Loose, J. D.; Mccoy, K. E.

    1974-01-01

    Thermal control of electronic hardware and experiments on future space vehicles is critical to proper functioning and long life. Thermal conditioning panels (cold plates) are a baseline control technique in current conceptual studies. Heat generating components mounted on the panels are typically cooled by fluid flowing through integral channels within the panel. However, replacing the pumped fluid coolant loop within the panel with heat pipes offers attractive advantages in weight, reliability, and installation. This report describes the development and fabrication of two large 0.76 x 0.76 m heat pipe thermal conditioning panels to verify performance and establish the design concept.

  13. Extreme Conditions Modeling Workshop Report

    SciTech Connect

    Coe, R. G.; Neary, V. S.; Lawson, M. J.; Yu, Y.; Weber, J.

    2014-07-01

    Sandia National Laboratories (SNL) and the National Renewable Energy Laboratory (NREL) hosted the Wave Energy Converter (WEC) Extreme Conditions Modeling (ECM) Workshop in Albuquerque, NM on May 13th-14th, 2014. The objective of the workshop was to review the current state of knowledge on how to model WECs in extreme conditions (e.g. hurricanes and other large storms) and to suggest how U.S. Department of Energy (DOE) and national laboratory resources could be used to improve ECM methods for the benefit of the wave energy industry.

  14. Associations in Human Instrumental Conditioning

    ERIC Educational Resources Information Center

    Gamez, A. Matias; Rosas, Juan M.

    2007-01-01

    Four experiments were conducted to study the contents of human instrumental conditioning. Experiment 1 found positive transfer between a discriminative stimulus (S[superscript D] and an instrumental response (R) that shared the outcome (O) with the response that was originally trained with the S[superscript D], showing the formation of an…

  15. How Cells Endure Extreme Conditions

    SciTech Connect

    2009-01-01

    One of natures most gripping feats of survival is now better understood. For the first time, Berkeley Lab scientists observed the chemical changes in individual cells that enable them to survive in conditions that should kill them. http://newscenter.lbl.gov/feature-stories/2009/07/07/cells-endure-extremes/

  16. Auditory Temporal Conditioning in Neonates.

    ERIC Educational Resources Information Center

    Franz, W. K.; And Others

    Twenty normal newborns, approximately 36 hours old, were tested using an auditory temporal conditioning paradigm which consisted of a slow rise, 75 db tone played for five seconds every 25 seconds, ten times. Responses to the tones were measured by instantaneous, beat-to-beat heartrate; and the test trial was designated as the 2 1/2-second period…

  17. Condition Number Regularized Covariance Estimation*

    PubMed Central

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

    2012-01-01

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

  18. Conditions for Developing Communicative Competence

    ERIC Educational Resources Information Center

    Zascerinska, Jelena

    2010-01-01

    Introduction. Individuals need communicative competence for personal fulfillment and development, active citizenship, social inclusion and employment. Materials and Methods. The meaning of the key concepts of "communicative competence" and "opportunities" is studied within the search for conditions to develop. Conclusion. The theoretical findings…

  19. NATIONAL COASTAL CONDITION REPORT II

    EPA Science Inventory

    The purpose of EPA's National Coastal Assessment (NCA) program is to estimate the status and trends of the condition of the nation's coastal resources on state, regional and national scales. During 1999-2003, 100% of the nation's estuarine waters were representatively sampled at ...

  20. NATIONAL COASTAL CONDITION REPORT IV

    EPA Science Inventory

    The National Coastal Condition Report IV (NCCR IV) is the fourth in a series of environmental assessments of U.S. coastal waters and the Great Lakes. The report includes assessments of all the nation’s estuaries in the contiguous 48 states and Puerto Rico, south-eastern Alaska, ...