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Sample records for corotation resonance rossby

  1. On resonant Rossby-Haurwitz triads

    NASA Astrophysics Data System (ADS)

    Lynch, Peter

    2009-05-01

    The dynamics of non-divergent flow on a rotating sphere are described by the conservation of absolute vorticity. The analytical study of the non-linear barotropic vorticity equation is greatly facilitated by the expansion of the solution in spherical harmonics and truncation at low order. The normal modes are the well-known Rossby-Haurwitz (RH) waves, which represent the natural oscillations of the system. Triads of RH waves, which satisfy conditions for resonance, are of critical importance for the distribution of energy in the atmosphere. We show how non-linear interactions of resonant RH triads may result in dynamic instability of large-scale components. We also demonstrate a mathematical equivalence between the equations for an orographically forced triad and a simple mechanical system, the forced-damped swinging spring. This equivalence yields insight concerning the bounded response to a constant forcing in the absence of damping. An examination of triad interactions in atmospheric reanalysis data would be of great interest.

  2. A Rossby whistle: A resonant basin mode observed in the Caribbean Sea

    NASA Astrophysics Data System (ADS)

    Hughes, Chris W.; Williams, Joanne; Hibbert, Angela; Boening, Carmen; Oram, James

    2016-07-01

    We show that an important source of coastal sea level variability around the Caribbean Sea is a resonant basin mode. The mode consists of a baroclinic Rossby wave which propagates westward across the basin and is rapidly returned to the east along the southern boundary as coastal shelf waves. Almost two wavelengths of the Rossby wave fit across the basin, and it has a period of 120 days. The porous boundary of the Caribbean Sea results in this mode exciting a mass exchange with the wider ocean, leading to a dominant mode of bottom pressure variability which is almost uniform over the Grenada, Venezuela, and Colombia basins and has a sharp spectral peak at 120 day period. As the Rossby waves have been shown to be excited by instability of the Caribbean Current, this resonant mode is dynamically equivalent to the operation of a whistle.

  3. Rossby wave resonance in the presence of a nonlinear critical layer

    NASA Astrophysics Data System (ADS)

    Ritchie, Harold

    1985-01-01

    The behavior of Rossby waves on a shear flow in the presence of a nonlinear critical layer is studied, with particular emphasis on the role played by the critical layer in a Rossby wave resonance mechanism. Previous steady analyses are extended to the resonant case and it is found that the forced wave dominates the solution, provided the flow configuration is not resonant for the higher harmonics induced by the critical layer. Numerical simulations for the forced initial value problem show that the solution evolves towards the analysed steady state when conditions are resonant for the forced wave, and demonstrate some of the complications that arise when they are resonant for higher harmonics. In relating the initial value and steady problems, it is argued that the time dependent solution does not require the large mean flow distortion that Haberman (1972) found to be necessary outside the critical layer in the steady case.

  4. F Ring Core Stability: Corotation Resonance Plus Antiresonance

    NASA Astrophysics Data System (ADS)

    Cuzzi, Jeffrey N.; Marouf, Essam; French, Richard; Jacobson, Robert

    2014-11-01

    The decades-or-longer stability of the narrow F Ring core in a sea of orbital chaos appears to be due to an unusual combination of traditional corotation resonance and a novel kind of “antiresonance”. At a series of specific locations in the F Ring region, apse precession between synodic encounters with Prometheus allows semimajor axis perturbations to promptly cancel before significant orbital period changes can occur (Cuzzi et al. 2014, Icarus 232, 157-175). This cancellation fails for particles that encounter Prometheus when it is near its apoapse, especially during periods of antialignment of its apse with that of the F Ring. At these times, the strength of the semimajor axis perturbation is large (tens of km) and highly nonsinusoidal in encounter longitude, making it impossible to cancel promptly on a subsequent encounter and leading to chaotic orbital diffusion. Only particles that consistently encounter Prometheus away from its apoapse can use antiresonance to maintain stable orbits, implying that the true mean motion nF of the stable core must be defined by a corotational resonance of the form nF = nP-κP/m, where (nP, κP) are Prometheus’ mean motion and epicycle frequency. To test this hypothesis we used the fact that Cassini RSS occultations only sporadically detect a “massive” F Ring core, composed of several-cm-and-larger particles. We regressed the inertial longitudes of 24 Cassini RSS (and VGR) detections and 43 nondetections to a common epoch, using a comb of candidate nP, and then folded them modulo the anticipated m-number of the corotational resonance (Prometheus m=110 outer CER), to see if clustering appears. We find the “true F Ring core” is actually arranged in a series of short longitudinal arcs separated by nearly empty longitudes, orbiting at a well determined semimajor axis of 140222.4km (from 2005-2012 at least). Small particles seen by imaging and stellar occultations spread quickly in azimuth and obscure this clumpy

  5. F Ring Core Stability: Corotation Resonance Plus Antiresonance

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey N.; Marouf, Essam; French, Richard; Jacobson, Robert

    2014-01-01

    The decades-or-longer stability of the narrow F Ring core in a sea of orbital chaos appears to be due to an unusual combination of traditional corotation resonance and a novel kind of "antiresonance". At a series of specific locations in the F Ring region, apse precession between synodic encounters with Prometheus allows semimajor axis perturbations to promptly cancel before significant orbital period changes can occur. This cancellation fails for particles that encounter Prometheus when it is near its apoapse, especially during periods of antialignment of its apse with that of the F Ring. At these times, the strength of the semimajor axis perturbation is large (tens of km) and highly nonsinusoidal in encounter longitude, making it impossible to cancel promptly on a subsequent encounter and leading to chaotic orbital diffusion. Only particles that consistently encounter Prometheus away from its apoapse can use antiresonance to maintain stable orbits, implying that the true mean motion nF of the stable core must be defined by a corotational resonance of the form nF = nP(-kappa)P/m, where (nP, kappaP) are Prometheus' mean motion and epicycle frequency. To test this hypothesis we used the fact that Cassini RSS occultations only sporadically detect a "massive" F Ring core, composed of several-cm-and-larger particles. We regressed the inertial longitudes of 24 Cassini RSS (and VGR) detections and 43 nondetections to a common epoch, using a comb of candidate nP, and then folded them modulo the anticipated m-number of the corotational resonance (Prometheus m = 110 outer CER), to see if clustering appears. We find the "true F Ring core" is actually arranged in a series of short longitudinal arcs separated by nearly empty longitudes, orbiting at a well determined semimajor axis of 140222.4 km (from 2005-2012 at least). Small particles seen by imaging and stellar occultations spread quickly in azimuth and obscure this clumpy structure. Small chaotic variations in the mean

  6. The Rossby whistle: A resonant basin mode in the Caribbean Sea.

    NASA Astrophysics Data System (ADS)

    Hughes, Christopher W.; Williams, Joanne; Hibbert, Angela; Boening, Carmen; Oram, James

    2016-04-01

    We present a a leaky, resonant Rossby basin mode in the Caribbean Sea, excited by instability of the Caribbean Current. The mode is seen at the surface as westward-propagating Rossby waves with period 120 days, but it is most distinctive in ocean bottom pressure where it is seen in both observations and in a wide variety of ocean models. This bottom pressure mode is a product of the leakiness of the basin, which allows for mass exchange with the surrounding ocean. The mode is found to dominate sea level variability on parts of the South American coast.

  7. The role of the corotation resonance in the secular evolution of disks of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Lépine, J. R. D.; Scarano, S., Jr.; Barros, D. A.; Junqueira, T. C.; Dias, W. S.; Andrievsky, S.

    2014-10-01

    The corotation resonance plays an important role in the evolution of the disks of spiral galaxies, and in particular, of our Galaxy. Its effect on the chemical abundance gradients is even a tool to estimate the age of the present spiral arm structure, which we find to be long-lived, contrary to a recent common belief. The metallicity gradients usually decrease in the inner regions and become flat or rising at larger radii. In several galaxies, including the Milky Way, one observes not only a change in the slope of the abundance gradient, but also an abrupt step in metallicity at corotation. This step is because the corotation resonance separates the disk of a galaxy in two regions (inside corotation and outside corotation) which are isolated one from the other, so that the two sides evolve in an independent way. The barrier between the two regions is the result of the flow of gas in opposite directions on the two sides and by the ring-shaped void of gas observed at corotation. We investigated a sample of galaxies, which have a known corotation radius, and for which there are measurements of abundance gradients of Oxygen available in the literature. A very good correlation is found between corotation radii and the radii at which there is a break in the slope of the gradients. Besides this, an independent effect of corotation is a minimum of star formation associated with the minimum velocity at which the interstellar gas feeds the spiral arms (seen as potential wells and star-formation machines). Still another effect is the scattering of stars by the resonance, which causes their migration to different galactic radii.

  8. Complete classification of discrete resonant Rossby/drift wave triads on periodic domains

    NASA Astrophysics Data System (ADS)

    Bustamante, Miguel D.; Hayat, Umar

    2013-09-01

    We consider the set of Diophantine equations that arise in the context of the partial differential equation called "barotropic vorticity equation" on periodic domains, when nonlinear wave interactions are studied to leading order in the amplitudes. The solutions to this set of Diophantine equations are of interest in atmosphere (Rossby waves) and Tokamak plasmas (drift waves), because they provide the values of the spectral wavevectors that interact resonantly via three-wave interactions. These wavenumbers come in "triads", i.e., groups of three wavevectors. We provide the full solution to the Diophantine equations in the physically sensible limit when the Rossby deformation radius is infinite. The method is completely new, and relies on mapping the unknown variables via rational transformations, first to rational points on elliptic curves and surfaces, and from there to rational points on quadratic forms of "Minkowski" type (such as the familiar space-time in special relativity). Classical methods invented centuries ago by Fermat, Euler, Lagrange, Minkowski, are used to classify all solutions to our original Diophantine equations, thus providing a computational method to generate numerically all the resonant triads in the system. Computationally speaking, our method has a clear advantage over brute-force numerical search: on a 10,0002 grid, the brute-force search would take 15 years using optimised C codes on a cluster, whereas our method takes about 40 min using a laptop. Moreover, the method is extended to generate so-called quasi-resonant triads, which are defined by relaxing the resonant condition on the frequencies, allowing for a small mismatch. Quasi-resonant triads' distribution in wavevector space is robust with respect to physical perturbations, unlike resonant triads' distribution. Therefore, the extended method is really valuable in practical terms. We show that the set of quasi-resonant triads form an intricate network of connected triads, forming

  9. Percolation transition in the kinematics of nonlinear resonance broadening in Charney-Hasegawa-Mima model of Rossby wave turbulence

    NASA Astrophysics Data System (ADS)

    Harris, Jamie; Connaughton, Colm; Bustamante, Miguel D.

    2013-08-01

    We study the kinematics of nonlinear resonance broadening of interacting Rossby waves as modelled by the Charney-Hasegawa-Mima equation on a biperiodic domain. We focus on the set of wave modes which can interact quasi-resonantly at a particular level of resonance broadening and aim to characterize how the structure of this set changes as the level of resonance broadening is varied. The commonly held view that resonance broadening can be thought of as a thickening of the resonant manifold is misleading. We show that in fact the set of modes corresponding to a single quasi-resonant triad has a non-trivial structure and that its area in fact diverges for a finite degree of broadening. We also study the connectivity of the network of modes which is generated when quasi-resonant triads share common modes. This network has been argued to form the backbone for energy transfer in Rossby wave turbulence. We show that this network undergoes a percolation transition when the level of resonance broadening exceeds a critical value. Below this critical value, the largest connected component of the quasi-resonant network contains a negligible fraction of the total number of modes in the system whereas above this critical value a finite fraction of the total number of modes in the system are contained in the largest connected component. We argue that this percolation transition should correspond to the transition to turbulence in the system.

  10. Coupling between corotation and Lindblad resonances in the presence of secular precession rates

    NASA Astrophysics Data System (ADS)

    El Moutamid, Maryame; Sicardy, Bruno; Renner, Stéfan

    2014-03-01

    We investigate the dynamics of two satellites with masses and orbiting a massive central planet in a common plane, near a first order mean motion resonance ( m integer). We consider only the resonant terms of first order in eccentricity in the disturbing potential of the satellites, plus the secular terms causing the orbital apsidal precessions. We obtain a two-degrees-of-freedom system, associated with the two critical resonant angles and , where and are the mean longitude and longitude of periapsis of , respectively, and where the primed quantities apply to . We consider the special case where (restricted problem). The symmetry between the two angles and is then broken, leading to two different kinds of resonances, classically referred to as corotation eccentric resonance (CER) and Lindblad eccentric Resonance (LER), respectively. We write the four reduced equations of motion near the CER and LER, that form what we call the CoraLin model. This model depends upon only two dimensionless parameters that control the dynamics of the system: the distance between the CER and LER, and a forcing parameter that includes both the mass and the orbital eccentricity of the disturbing satellite. Three regimes are found: for the system is integrable, for of order unity, it exhibits prominent chaotic regions, while for large compared to 2, the behavior of the system is regular and can be qualitatively described using simple adiabatic invariant arguments. We apply this model to three recently discovered small Saturnian satellites dynamically linked to Mimas through first order mean motion resonances: Aegaeon, Methone and Anthe. Poincaré surfaces of section reveal the dynamical structure of each orbit, and their proximity to chaotic regions. This work may be useful to explore various scenarii of resonant capture for those satellites.

  11. Rossby rip currents

    NASA Astrophysics Data System (ADS)

    Marshall, David P.; Vogel, Bendix; Zhai, Xiaoming

    2013-08-01

    Oceanic Rossby waves and eddies flux energy and fluid westward, the latter through the Stokes drift or bolus transport. While the wave energy is largely dissipated at the western boundary, mass conservation requires that the fluid be returned offshore through Rossby rip currents. The form and magnitude of these rip currents are investigated through linear Rossby wave theory, a nonlinear numerical model, and analysis of sea surface height satellite observations. The net eastward volume transport by Rossby rip currents over the global ocean is estimated to be of order 10 Sv (1 Sv ≡106 m3 s-1). In an eddying ocean, both the westward Stokes drift and eastward rip currents can assume the form of banded quasi-zonal jets.

  12. Global observations of ocean Rossby waves

    SciTech Connect

    Chelton, D.B.; Schlax, M.G.

    1996-04-12

    Rossby waves play a critical role in the transient adjustment of ocean circulation to changes in large-scale atmospheric forcing. The TOPEX/POSEIDON satellite altimeter has detected Rossby waves throughout much of the world ocean from sea level signals with {approx_lt} 10-centimeters amplitude and {approx_lt} 500-kilometer wavelength. Outside of the tropics Rossby waves are abruptly amplified by major topographic features. Analysis of 3 years of data reveals discrepancies between observed and theoretical Rossby wave phase speeds that indicate that the standard theory for free, linear Rossby waves in an incomplete description of the observed waves. 32 refs., 5 figs.

  13. Large-scale drift and Rossby wave turbulence

    NASA Astrophysics Data System (ADS)

    Harper, K. L.; Nazarenko, S. V.

    2016-08-01

    We study drift/Rossby wave turbulence described by the large-scale limit of the Charney–Hasegawa–Mima equation. We define the zonal and meridional regions as Z:= \\{{k} :| {k}y| \\gt \\sqrt{3}{k}x\\} and M:= \\{{k} :| {k}y| \\lt \\sqrt{3}{k}x\\} respectively, where {k}=({k}x,{k}y) is in a plane perpendicular to the magnetic field such that k x is along the isopycnals and k y is along the plasma density gradient. We prove that the only types of resonant triads allowed are M≤ftrightarrow M+Z and Z≤ftrightarrow Z+Z. Therefore, if the spectrum of weak large-scale drift/Rossby turbulence is initially in Z it will remain in Z indefinitely. We present a generalised Fjørtoft’s argument to find transfer directions for the quadratic invariants in the two-dimensional {k}-space. Using direct numerical simulations, we test and confirm our theoretical predictions for weak large-scale drift/Rossby turbulence, and establish qualitative differences with cases when turbulence is strong. We demonstrate that the qualitative features of the large-scale limit survive when the typical turbulent scale is only moderately greater than the Larmor/Rossby radius.

  14. Rossby waves and cascade phenomena

    NASA Astrophysics Data System (ADS)

    Reshetnyak, M. Yu.

    2012-09-01

    Nonlinear triad interactions in the Navier-Stokes equation describing quasi-geostrophic thermal convection in a spherical layer are considered. The analysis provides an insight into the nature of kinetic energy transfer across the spectrum and allows us to assess the degree of nonlocality in the energy transfer. The distinguishing feature of the spherical problem is the emergence of the Rossby waves, which cause nonlocal redistribution of energy in the system. The results of this study are compared with their counterparts for the plane model.

  15. COROT telescope development

    NASA Astrophysics Data System (ADS)

    Viard, Thierry; Bodin, Pierre; Magnan, Alain

    2004-06-01

    COROTEL is the telescope of the future COROT satellite which aims at measuring stellar flux variations very accurately. To perform this mission, COROTEL has to be very well protected against straylight (from Sun and Earth) and must be very stable with time. Thanks to its high experience in this field, Alcatel Space has proposed an original optical concept associated with a high performance baffle. From 2001, the LAM (Laboratoire d'Astrophysique de Marseille, CNRS) has placed the telescope development contract to Alcatel Space and is presently almost finished. Based on relevant material and efficient thermal control design, COROTEL should meet its ambitious performance and bring to scientific community for the first time precious data coming from stars and their possible companions.

  16. The COROT Archive at LAEFF

    NASA Astrophysics Data System (ADS)

    Velasco, Almudena; Gutiérrez, Raúl; Solano, Enrique; García-Torres, Miguel; López, Mauro; Sarro, Luis Manuel

    We describe here the main capabilities of the COROT archive. The archive (http://sdc.laeff.inta.es/corotfa/jsp/searchform.jsp), managed at LAEFF in the framework of the Spanish Virtual Observatory (http://svo.laeff.inta.es), has been developed following the standards and requirements defined by IVOA (http://www.ivoa.net). The COROT archive at LAEFF will be publicly available by the end of 2008.

  17. Rossby Wave Instability in Astrophysical Disks

    NASA Astrophysics Data System (ADS)

    Lovelace, Richard; Li, Hui

    2014-10-01

    A brief review is given of the Rossby wave instability in astrophysical disks. In non-self-gravitating discs, around for example a newly forming stars, the instability can be triggered by an axisymmetric bump at some radius r0 in the disk surface mass-density. It gives rise to exponentially growing non-axisymmetric perturbation (proportional to Exp[im ϕ], m = 1,2,...) in the vicinity of r0 consisting of anticyclonic vortices. These vortices are regions of high pressure and consequently act to trap dust particles which in turn can facilitate planetesimal growth in protoplanetary disks. The Rossby vortices in the disks around stars and black holes may cause the observed quasi-periodic modulations of the disk's thermal emission. Stirling Colgate's long standing interest in all types of vortices - particularly tornados - had an important part in stimulating the research on the Rossby wave instability.

  18. Rossby rogons in atmosphere and in the solar photosphere

    NASA Astrophysics Data System (ADS)

    Misra, A. P.; Shukla, P. K.

    2012-12-01

    The generation of Rossby rogue waves (Rossby rogons), as well as the excitation of bright and dark Rossby envelpe solitons are demonstrated on the basis of the modulational instability (MI) of a coherent Rossby wave packet. The evolution of an amplitude-modulated Rossby wave packet is governed by a one-dimensional (1D) nonlinear Schrödinger equation (NLSE). The latter is used to study the amplitude modulation of Rossby wave packets for fluids in Earth's atmosphere and in the solar photosphere. It is found that an ampitude-modulated Rossby wave packet becomes stable (unstable) against quasi-stationary, long-wavelength (in comparision with the Rossby wavelength) perturbations, when the carrier Rossby wave number satisfies k2 < 1/2 or \\sqrt {2}+1 (k2 > 3 or 1/2). It is also shown that a Rossby rogon or a bright Rossby envelope soliton may be excited in the shallow-water approximation for the Rossby waves in solar photosphere. However, the excitation of small- or large-scale perturbations may be possible for magnetized plasmas in the ionosphereic E-layer.

  19. NONLINEAR DYNAMICS OF MAGNETOHYDRODYNAMIC ROSSBY WAVES AND THE CYCLIC NATURE OF SOLAR MAGNETIC ACTIVITY

    SciTech Connect

    Raphaldini, Breno; Raupp, Carlos F. M. E-mail: carlos.raupp@iag.usp.br

    2015-01-20

    The solar dynamo is known to be associated with several periodicities, with the nearly 11/22 yr cycle being the most pronounced one. Even though these quasiperiodic variations of solar activity have been attributed to the underlying dynamo action in the Sun's interior, a fundamental theoretical description of these cycles is still elusive. Here, we present a new possible direction in understanding the Sun's cycles based on resonant nonlinear interactions among magnetohydrodynamic (MHD) Rossby waves. The WKB theory for dispersive waves is applied to magnetohydrodynamic shallow-water equations describing the dynamics of the solar tachocline, and the reduced dynamics of a resonant triad composed of MHD Rossby waves embedded in constant toroidal magnetic field is analyzed. In the conservative case, the wave amplitudes evolve periodically in time, with periods on the order of the dominant solar activity timescale (∼11 yr). In addition, the presence of linear forcings representative of either convection or instabilities of meridionally varying background states appears to be crucial in balancing dissipation and thus sustaining the periodic oscillations of wave amplitudes associated with resonant triad interactions. Examination of the linear theory of MHD Rossby waves embedded in a latitudinally varying mean flow demonstrates that MHD Rossby waves propagate toward the equator in a waveguide from –35° to 35° in latitude, showing a remarkable resemblance to the structure of the butterfly diagram of the solar activity. Therefore, we argue that resonant nonlinear magnetohydrodynamic Rossby wave interactions might significantly contribute to the observed cycles of magnetic solar activity.

  20. Solar Rossby Wave 'Hills' Identified As Supergranules

    NASA Technical Reports Server (NTRS)

    Williams, P. E.; Hathaway, David H.; Cuntz, M.

    2007-01-01

    We explore the nature of 'hills' observed on the solar surface which had previously been attributed to Rossby waves. We investigate the sol ar hills phenomenon by analyzing the output from a synthetic model ba sed solely on the observed solar photospheric convection spectrum. We show that the characteristics of these hills can be explained by the corrugation of the surface produced by the radial flows of the conve ction. The hills in our simulations are dominated by supergranules, a well-known component of solar convection. Rossby waves have been predicted to exist within the Sun and may play an important role in the d ynamics of the solar interior, including the Sun's differential rotat ion and magnetic dynamo. Our study suggests, however, that the hills observed at the solar limb do not confirm the existence of solar Ross by waves.

  1. The Hilsch Tube, Rossby Vortices, and a Carnot Engine: Angular Momentum Transport in Astrophysics

    NASA Astrophysics Data System (ADS)

    Beckley, Howard F.; Klein, B.; Milburn, M.; Schindel, P.; Westpfahl, D. J.; Teare, S.; Li, H.; Colgate, S. A.

    2008-05-01

    We are attempting to demonstrate that the common laboratory vortex or Hilsch tube is a paradigm for the angular momentum transport by Rossby vortices in Keplerian accretion disks, either in super massive black hole formation or in star formation. Near supersonic rotating flow is induced in a cylinder by gas pressure injected through a tangential nozzle in a typical Ranque vortex or Hilsch tube. The gas exits through both an on-axis hole and a peripheral radially-aligned hole. The surprising result, demonstrated in hundreds of class rooms, is that one of the exit gas streams is hot and the other is cold. Depressing is that the typical explanation is given in terms of a "Maxwell daemon” that separates hot molecules from cold molecules, just as is the basis of any perpetual motion machine that violates the second law of thermodynamics. Instead we believe that the rotational flow is unstable to the formation of Rossby vortices that co-rotate with the azimuthal flow and act like semi-ridged turbine vanes. These quasi-vanes act like a Carnot turbine engine to the flow that escapes on axis and is therefore cooled by doing work. With the resulting free-energy, the vortices accelerate the peripheral flow which in turn becomes hot by friction with the cylinder wall. As a first step we expect to demonstrate that a free-running turbine, where metal vanes form the Carnot engine, will demonstrate the temperature effect. Such a suggestive result may lead to funding of time-dependent Schlerian photography of a vortex tube that can demonstrate the formation and pressure distribution of the Rossby vortices and coherent transport of angular momentum. This work is supported by a cooperative agreement between the New Mexico Institute of Mining and Technology, the University of California, Los Alamos National Laboratory, and the U.S. Dept. of Energy.

  2. Counterpropagating Rossby waves in confined plane wakes

    NASA Astrophysics Data System (ADS)

    Biancofiore, L.; Gallaire, F.

    2012-07-01

    In the present work, we revisit the temporal and the spatio-temporal stability of confined plane wakes under the perspective of the counterpropagating Rossby waves (CRWs). Within the context of broken line velocity profiles, each vorticity discontinuity can be associated to a counterpropagating Rossby wave. In the case of a wake modeled by a broken line profile, the interaction of two CRWs is shown to originate in a shear instability. Following this description, we first recover the stability results obtained by Juniper [J. Fluid Mech. 590, 163-185 (2007)], 10.1017/S0022112007007975 and Biancofiore and Gallaire [Phys. Fluids 23, 034103 (2011)], 10.1063/1.3554764 by means of the classical normal mode analysis. In this manner, we propose an explanation of the stabilizing influence of the confinement on the temporal stability properties. The CRW description further allows us to propose a new interpretation of the counterintuitive spatio-temporal destabilization in wake flows at moderate confinement noticed by Juniper [J. Fluid Mech. 565, 171-195 (2006)], 10.1017/S0022112006001558: it is well predicted by the mean group velocity of the uncoupled CRWs.

  3. Do eddies ride on Rossby waves?

    NASA Astrophysics Data System (ADS)

    Polito, Paulo S.; Sato, Olga T.

    2015-08-01

    Both vortices and baroclinic Rossby waves show up as westward-propagating features in the sea surface height anomaly (SSHA) records when displayed in the form of zonal-temporal or Hovmöller diagrams. A chain of filters was used to separate the SSHA into orthogonal components. Each of the filtered components was then reassembled as a set of maps. In the maps of individual components, we clearly see westward propagating Rossby waves. Our most striking findings are: (i) limited within their critical latitudes, the wave extrema coincide with a significant number of vortices; (ii) eddy-wave coincidence occurs at a preferred latitude that depends on the wave period; (iii) among the vortices that, at some point of their existence coincide with a wave, a relatively large percentage of them remained their whole lifetime with the wave, and (iv) a mechanism is proposed to explain why eddies tend to remain over the wave extrema (crests and troughs). Our answer to the title question is: yes, they often do.

  4. Counterpropagating Rossby waves in confined plane wakes

    PubMed Central

    Biancofiore, L.; Gallaire, F.

    2012-01-01

    In the present work, we revisit the temporal and the spatio-temporal stability of confined plane wakes under the perspective of the counterpropagating Rossby waves (CRWs). Within the context of broken line velocity profiles, each vorticity discontinuity can be associated to a counterpropagating Rossby wave. In the case of a wake modeled by a broken line profile, the interaction of two CRWs is shown to originate in a shear instability. Following this description, we first recover the stability results obtained by Juniper [J. Fluid Mech. 590, 163–185 (2007)]10.1017/S0022112007007975 and Biancofiore and Gallaire [Phys. Fluids 23, 034103 (2011)]10.1063/1.3554764 by means of the classical normal mode analysis. In this manner, we propose an explanation of the stabilizing influence of the confinement on the temporal stability properties. The CRW description further allows us to propose a new interpretation of the counterintuitive spatio-temporal destabilization in wake flows at moderate confinement noticed by Juniper [J. Fluid Mech. 565, 171–195 (2006)]10.1017/S0022112006001558: it is well predicted by the mean group velocity of the uncoupled CRWs. PMID:22865998

  5. Counterpropagating Rossby waves in confined plane wakes.

    PubMed

    Biancofiore, L; Gallaire, F

    2012-07-01

    In the present work, we revisit the temporal and the spatio-temporal stability of confined plane wakes under the perspective of the counterpropagating Rossby waves (CRWs). Within the context of broken line velocity profiles, each vorticity discontinuity can be associated to a counterpropagating Rossby wave. In the case of a wake modeled by a broken line profile, the interaction of two CRWs is shown to originate in a shear instability. Following this description, we first recover the stability results obtained by Juniper [J. Fluid Mech. 590, 163-185 (2007)]10.1017/S0022112007007975 and Biancofiore and Gallaire [Phys. Fluids 23, 034103 (2011)]10.1063/1.3554764 by means of the classical normal mode analysis. In this manner, we propose an explanation of the stabilizing influence of the confinement on the temporal stability properties. The CRW description further allows us to propose a new interpretation of the counterintuitive spatio-temporal destabilization in wake flows at moderate confinement noticed by Juniper [J. Fluid Mech. 565, 171-195 (2006)]10.1017/S0022112006001558: it is well predicted by the mean group velocity of the uncoupled CRWs. PMID:22865998

  6. Inertia-gravity wave radiation from the merging of two co-rotating vortices in the f-plane shallow water system

    SciTech Connect

    Sugimoto, Norihiko

    2015-12-15

    Inertia-gravity wave radiation from the merging of two co-rotating vortices is investigated numerically in a rotating shallow water system in order to focus on cyclone–anticyclone asymmetry at different values of the Rossby number (Ro). A numerical study is conducted on a model using a spectral method in an unbounded domain to estimate the gravity wave flux with high accuracy. Continuous gravity wave radiation is observed in three stages of vortical flows: co-rotating of the vortices, merging of the vortices, and unsteady motion of the merged vortex. A cyclone–anticyclone asymmetry appears at all stages at smaller Ro (≤20). Gravity waves from anticyclones are always larger than those from cyclones and have a local maximum at smaller Ro (∼2) compared with that for an idealized case of a co-rotating vortex pair with a constant rotation rate. The source originating in the Coriolis acceleration has a key role in cyclone–anticyclone asymmetry in gravity waves. An additional important factor is that at later stages, the merged axisymmetric anticyclone rotates faster than the elliptical cyclone due to the effect of the Rossby deformation radius, since a rotation rate higher than the inertial cutoff frequency is required to radiate gravity waves.

  7. Inertia-gravity wave radiation from the merging of two co-rotating vortices in the f-plane shallow water system

    NASA Astrophysics Data System (ADS)

    Sugimoto, Norihiko

    2015-12-01

    Inertia-gravity wave radiation from the merging of two co-rotating vortices is investigated numerically in a rotating shallow water system in order to focus on cyclone-anticyclone asymmetry at different values of the Rossby number (Ro). A numerical study is conducted on a model using a spectral method in an unbounded domain to estimate the gravity wave flux with high accuracy. Continuous gravity wave radiation is observed in three stages of vortical flows: co-rotating of the vortices, merging of the vortices, and unsteady motion of the merged vortex. A cyclone-anticyclone asymmetry appears at all stages at smaller Ro (≤20). Gravity waves from anticyclones are always larger than those from cyclones and have a local maximum at smaller Ro (˜2) compared with that for an idealized case of a co-rotating vortex pair with a constant rotation rate. The source originating in the Coriolis acceleration has a key role in cyclone-anticyclone asymmetry in gravity waves. An additional important factor is that at later stages, the merged axisymmetric anticyclone rotates faster than the elliptical cyclone due to the effect of the Rossby deformation radius, since a rotation rate higher than the inertial cutoff frequency is required to radiate gravity waves.

  8. The seasonal cycle of boreal Rossby wave breaking processes

    NASA Astrophysics Data System (ADS)

    Peters, D. H.; Schneidereit, A.; Gabriel, A.

    2010-12-01

    In a changing climate coupling processes between the atmospheric layers play an important role. For example, the changing zonally asymmetric ozone distribution of the stratosphere has an influence on the strength and position of stratospheric jet streams as well as on the upper tropospheric large-scale flow characteristics and teleconnection patterns. The radiative influence of zonally asymmetric ozone forcing on model dynamics was investigated by ensemble runs of the GCM ECHAM5. Induced by the zonally asymmetric forcing we identified a strong polar vortex shift which was connected to changes of regions of Rossby wave breaking and storm track activity. In the extratropics, Rossby waves play an important role in determining the jet streams of the polar front, especially in the upper troposphere and lower stratosphere region. It is known that events of poleward breaking Rossby waves are often observed over the North Atlantic-European or Eastern Pacific region in wintertime. In this study we investigate the seasonal influence of the observed background flow in the upper troposphere on poleward Rossby wave breaking events and the link to severe weather in a changing climate. The seasonal cycle of events of poleward breaking Rossby waves for the 1980s and 1990s has been revealed with ECMWF Reanalysis data (ERA-40). We found that the different, diffluent and confluent, large-scale flow structure determine the occurrence rate of Rossby wave breaking events. These events are differentiated into four breaking types: cyclonically (poleward or equatorward) and anticyclonically (poleward or equatorward). Especially we focused on the seasonal behavior of these four breaking types. We found a strong seasonal dependence with major poleward breaking events in winter and minor in summer time. Further, with SGCM experiments we could show that the seasonal changing zonally varying large-scale flow explains mainly the seasonal variation of poleward Rossby wave breaking events

  9. The stability of Rossby waves in a stratified shear fluid

    NASA Astrophysics Data System (ADS)

    Tan, Benkui

    1990-11-01

    An investigation is undertaken of the stability of linear Rossby waves in a stratified shear fluid by means of a qualitative theory employing ordinary differential equations. It is noted that, while the basic current has no detectable shear, the Rossby waves are always stable. If the basic current possesses only horizontal shear, the unstable criterion for waves takes one form, but it takes entirely another in the case where the basic current possesses only vertical shear.

  10. ROSSBY WAVE INSTABILITY IN LOCALLY ISOTHERMAL AND POLYTROPIC DISKS: THREE-DIMENSIONAL LINEAR CALCULATIONS

    SciTech Connect

    Lin, Min-Kai

    2012-07-20

    Numerical calculations of the linear Rossby wave instability (RWI) in global three-dimensional (3D) disks are presented. The linearized fluid equations are solved for vertically stratified, radially structured disks with either a locally isothermal or polytropic equation of state, by decomposing the vertical dependence of the perturbed hydrodynamic quantities into Hermite and Gegenbauer polynomials, respectively. It is confirmed that the RWI operates in 3D. For perturbations with vertical dependence assumed above, there is little difference in growth rates between 3D and two-dimensional (2D) calculations. Comparison between 2D and 3D solutions of this type suggests the RWI is predominantly a 2D instability and that 3D effects, such as vertical motion, can be interpreted as a perturbative consequence of the dominant 2D flow. The vertical flow around corotation, where vortex formation is expected, is examined. In locally isothermal disks, the expected vortex center remains in approximate vertical hydrostatic equilibrium. For polytropic disks, the vortex center has positive vertical velocity, whose magnitude increases with decreasing polytropic index n.

  11. Large Rossby number flows in Cozumel Channel

    NASA Astrophysics Data System (ADS)

    Ochoa, J.; Candela, J.; Sheinbaum, J.; Badan, A.

    2003-04-01

    The Caribbean Current flows to the west impinging the Yucatan coast south of Cozumel Island, then, most of its flow turns north, surrounds the island and continues towards the Yucatan Straits. About 4 Sv in the mean pass between the Yucatan coast and the Cozumel Island; through the Cozumel Channel, where subinertial currents exhibit large ageostrophic fluctuations [Chavez et. al. (2003)]. This channel is about 18 km wide, 50 km long, 400 m deep, and 70 km southwest of the Yucatan Straits. The curvature and latitude of the Caribbean Current on its approach to the Yucatan coast vary significantly. Observations with two upward-looking ADCPs, 8.6 km from each other, closely aligned with the mean current at the channel's axis and entrance, allow robust estimations of the current speed (U), direction and curvature (|R|-1). A signed Rossby number (Uf-1R-1), where f is the Coriolis parameter, is readily available as a function of time. The positive/negative curvature is defined by the cyclonic/anticyclonic turn. The currents observations along with pressure measurements at both sides of the channel produce evidence that favor the bend of the current as the cause of the ageostrophic fluctuations. Another possible cause for the ageostrophic fluctuations is the passage of eddies within the channel. We test the gradient wind balance between the currents and pressure observations. A very low frequency component on the seasonal time scale and high frequency fluctuations (superinercial) do not adjust to this balance, only the intermediate frequency variations show a clear equilibrium of centripetal (i.e. due to curvature) plus Coriolis accelerations against the pressure gradient perpendicular to the velocity. The conjecture is that the ageostrophic fluctuations occur when the bend and approach of the Caribbean Current is just south of Cozumel Island, thus influencing all its entrance. When the current impinges the coast further south, the flow, with a longer path to transit

  12. The Roles of Tidal Evolution and Evaporative Mass Loss in the Origin of CoRoT-7 b

    NASA Technical Reports Server (NTRS)

    Jackson, Brian; Miller, Neil; Barnes, Rory; Raymond, Sean N.; Fortney, Jonathan J.; Greenberg, Richard

    2010-01-01

    CoRoT-7 b is the first confirmed rocky exoplanet, but, with an orbital semimajor axis of 0.0172 au, its origins may be unlike any rocky planet in our Solar System. In this study, we consider the roles of tidal evolution and evaporative mass loss in CoRoT-7 b's history, which together have modified the planet's mass and orbit. If CoRoT-7 b has always been a rocky body, evaporation may have driven off almost half its original mass, but the mass loss may depend sensitively on the extent of tidal decay of its orbit. As tides caused CoRoT-7 b's orbit to decay, they brought the planet closer to its host star, thereby enhancing the mass loss rate. Such a large mass loss also suggests the possibility that CoRoT-7 b began as a gas giant planet and had its original atmosphere completely evaporated. In this case, we find that CoRoT-7 b's original mass probably did not exceed 200 Earth masses (about two-third of a Jupiter mass). Tides raised on the host star by the planet may have significantly reduced the orbital semimajor axis, perhaps causing the planet to migrate through mean-motion resonances with the other planet in the system, CoRoT-7 c. The coupling between tidal evolution and mass loss may be important not only for CoRoT-7 b but also for other close-in exoplanets, and future studies of mass loss and orbital evolution may provide insight into the origin and fate of close-in planets, both rocky and gaseous.

  13. Free and forced Rossby normal modes in a rectangular gulf of arbitrary orientation

    NASA Astrophysics Data System (ADS)

    Graef, Federico

    2016-09-01

    A free Rossby normal mode in a rectangular gulf of arbitrary orientation is constructed by considering the reflection of a Rossby mode in a channel at the head of the gulf. Therefore, it is the superposition of four Rossby waves in an otherwise unbounded ocean with the same frequency and wavenumbers perpendicular to the gulf axis whose difference is equal to 2mπ/W, where m is a positive integer and W the gulf's width. The lower (or higher) modes with small m (or large m) are oscillatory (evanescent) in the coordinate along the gulf; these are elucidated geometrically. However for oceanographically realistic parameter values, most of the modes are evanescent. When the gulf is forced at the mouth with a single Fourier component, the response is in general an infinite sum of modes that are needed to match the value of the streamfunction at the gulf's entrance. The dominant mode of the response is the resonant one, which corresponds to forcing with a frequency ω and wavenumber normal to the gulf axis η appropriate to a gulf mode: η =- β sin α/(2ω) ± Mπ/W, where α is the angle between the gulf's axis and the eastern direction (+ve clockwise) and M the resonant's mode number. For zonal gulfs ω drops out of the resonance condition. For the special cases η = 0 in which the free surface goes up and down at the mouth with no flow through it, or a flow with a sinusoidal profile, resonant modes can get excited for very specific frequencies (only for non-zonal gulfs in the η = 0 case). The resonant mode is around the annual frequency for a wide range of gulf orientations α ∈ [40°, 130°] or α ∈ [220°, 310°] and gulf widths between 150 and 200 km; these include the Gulf of California and the Adriatic Sea. If η is imaginary, i.e. a flow with an exponential profile, there is no resonance. In general less modes get excited if the gulf is zonally oriented.

  14. The Hadley and Rossby regimes in a spherical atmosphere

    NASA Technical Reports Server (NTRS)

    Feldstein, S. B.; Clark, J. H. E.

    1985-01-01

    The properties of the steady Hadley and Rossby regimes for a thermally forced rotating fluid on a sphere are studied. The two layer modified geostrophic model is employed which allows for thermal advection by the divergent wind and time dependent static stability. Heating processes are parameterized using the Newtonian approximation and Rayleigh friction is accounted for. The equations are transformed to spectral form using spherical harmonics and then truncated retaining a simple axisymmetric state and initial, one wave. A time independent Hadley circulation is obtained which is neutral to axisymmetric disturbances but unstable to wave like perturbations for intermediate values of the meridional temperature gradient, indicating the existence of both an upper and lower symmetric Hadley regime. An analytical solution for the steady Rossby circulation is determined for values of the meridional temperature gradient where the Hadley regime is unstable. Linear perturbation theory is used to show that within the steady Rossby regime two or more waves cannot exist simultaneously.

  15. Midlatitude Rossby wave forcing of equatorial Kelvin waves

    NASA Astrophysics Data System (ADS)

    Biello, J. A.; Kiladis, G. N.; Back, A.

    2015-12-01

    Observations strongly suggest that convectively coupled Kelvin waves can be generated by extratropical wave activity. This mechanism is particularly efficient over Australia, where wave activity appears immediately after the extratropical Rossby waves propagate into the region during the Austral winter. This interaction occurs where the zonal wind is strongly sheared both in the meridional and vertical directions. In order to understand this phenomenon the authors study the linear primitive equations in the presence of barotropic and baroclinic shear and the dispersion characteristics of the sheared Matsuno modes are calculated. Depending on the shear strength, the waves are stable or unstable and can be categorized into three groups. First there are the classical Matsuno modes modified by shear. Second there are extratropical "free" Rossby waves. Third, there are Rossby waves meridionally confined to the shear layer - these latter modes can be unstable, or stable and part of the continuous spectrum. In examples where the zonal winds are barotropically and baroclinically stable, we show that a continuous spectrum of Rossby waves exists. If the zonal winds are strong enough, the Rossby waves in the continuous spectrum have an equatorial signature exactly like the Matsuno Kelvin wave - despite the fact that, in these examples, the Matsuno Kelvin wave also exists on its own and that all modes are stable. For stronger shears, these continuous spectrum modes become unstable. Although the appear similar to Sakai's Rossby/Kelvin instability, their existence arises from a completely different phenomenon. The Sakai instability requires the frequency of a stable equatorial Rossby mode to coincide with the stable Kelvin wave frequency in order for the two modes to create a stable/unstable pair. Our results show that unstable Rossby waves need only have their frequencies Doppler shifted to that of the Kelvin wave frequency by the underlying shear in order that they acquire a

  16. Rossby wave Green's functions in an azimuthal wind

    NASA Astrophysics Data System (ADS)

    Webb, G. M.; Duba, C. T.; Hu, Q.

    2016-05-01

    Green's functions for Rossby waves in an azimuthal wind are obtained, in which the stream-function $\\psi$ depends on $r$, $\\phi$ and $t$, where $r$ is cylindrical radius and $\\phi$ is the azimuthal angle in the $\\beta$-plane relative to the easterly direction, in which the $x$-axis points east and the $y$-axis points north. The Rossby wave Green's function with no wind is obtained using Fourier transform methods, and is related to the previously known Green's function obtained for this case, which has a different but equivalent form to the Green's function obtained in the present paper. We emphasize the role of the wave eikonal solution, which plays an important role in the form of the solution. The corresponding Green's function for a rotating wind with azimuthal wind velocity ${\\bf u}=\\Omega r{\\bf e}_\\phi$ ($\\Omega=$const.) is also obtained by Fourier methods, in which the advective rotation operator in position space is transformed to a rotation operator in ${\\bf k}$ transform space. The finite Rossby deformation radius is included in the analysis. The physical characteristics of the Green's functions are delineated and applications are discussed. In the limit as $\\Omega\\to 0$, the rotating wind Green's function reduces to the Rossby wave Green function with no wind.

  17. Rossby solitary vortices, on giant planets and in the laboratory.

    PubMed

    Nezlin, Mikhail V.

    1994-06-01

    This is a review of laboratory experiments with a layer of shallow water having a free surface and rotating together with a vessel of parabolic form. Such a (rather original) setup has allowed one to create Rossby solitary vortex for the first time. The latter is an anticyclonic Rossby vortex not subjected to dispersive spread owing to its compensation by the nonlinearity of KdV type. By its structural, collisional, and other properties, including clear-cut cyclonic-anticyclonic asymmetry, it may be considered as a physical prototype of the large-scale long-lived anticyclonic Rossby vortices like the Great Red Spot of Jupiter or the Great Dark Spot of Neptune (this remarkable vortex was discovered by the spacecraft Voyager-2 during its farewell to the Solar System) and other vortices dominating in the atmospheres of giant planets and created by the unstable zonal flows. It has been shown that the vortex under study is a long-lived entity provided it satisfies "antitwisting condition," i.e., it has rather large amplitude (at which it rotates more quickly than it propagates and thereby carries the trapped fluid). In this case, it is not subjected to the "twisting" deformation and may be ascribed by the generalized Charney-Obukhov equation for Rossby vortices on shallow water with a free surface. The results of creating the vortex under consideration by the different methods have been compared with the results obtained by other authors in the experiments on shear-flow generation of Rossby vortices. PMID:12780099

  18. Corotation of an intermittent solar wind source

    NASA Technical Reports Server (NTRS)

    Croft, T. A.

    1972-01-01

    The measured electron content of the solar wind in mid-1970 exhibited a region of relatively high electron density that reappeared at intervals of about 27.8 days. It is shown that the repeating event cannot be reconciled with the concept of a long-enduring steady flow, even though the recurrence period is close to the rotation period of the sun. This evidence of transients is inferred from the short duration of each appearance of the interval of higher density; each should last for roughly one corotation interval if it is caused by a steady stream. The radio path was approximately 0.8 AU long, and the corotation interval exceeded 3 days. Other aspects of the content data patterns support the view that such transient events are common in the solar wind. The mid-1970 repeating event is an unusually good example of the intermittent character of flow regions in the solar wind that fluctuate on a time scale of days but endure as identifiable regions for many months. A sputtering corotating source of thin solar plasma streams could explain this series of events; it could also be explained in terms of a stream that is steady in density and speed but undulating north-south so that it passes into and out of the 0.8 AU radio path in a matter of a day or less.

  19. Linear corotation torques in non-barotropic disks

    SciTech Connect

    Tsang, David

    2014-02-20

    A fully analytic expression for the linear corotation torque to first order in eccentricity for planets in non-barotropic protoplanetary disks is derived, taking into account the effect of disk entropy gradients. This torque formula is applicable to both the co-orbital, corotation torques and the non-co-orbital, corotation torques—for planets in orbits with non-zero eccentricity—in disks where the thermal diffusivity and viscosity are sufficient to maintain the linearity of these interactions. While the co-orbital, corotation torque is important for migration of planets in Type I migration, the non-co-orbital, corotation torque plays an important role in the eccentricity evolution of giant planets that have opened gaps in the disk. The presence of an entropy gradient in the disk can significantly modify the corotation torque in both these cases.

  20. The instability of finite amplitude Rossby waves on the infinite beta-plane

    NASA Astrophysics Data System (ADS)

    Anderson, Jeffrey L.

    The normal mode instability problem for a stationary Rossby wave of finite amplitude and arbitrary orientation is examined on the infinite beta-plane using a Floquet technique. A survey of the instability problem as a function of the basic state wave amplitude and wave orientation is presented. In the large amplitude case, two modes of instability are found, while in the small amplitude case, a family of resonant interactions can completely describe the Floquet results. For intermediate values of amplitude, a combination of the large and small amplitude limits can explain the instabilities. For the range of greatest geophysical interest, two physically distinct unstable modes of approximately equal growth rate are available for certain values of the basic state wave orientation. Relevance to geophysical flows and the instability problem on the sphere are discussed briefly.

  1. Theoretical evolution of Rossby number for solar analog stars

    NASA Astrophysics Data System (ADS)

    Castro, Matthieu; Duarte, Tharcísyo; do Nascimento, José Dias

    2014-08-01

    Magnetic fields of late-type stars are presumably generated by a dynamo mechanism at the interface layer between the radiative interior and the outer convective zone. The Rossby number, which is related to the dynamo process, shows an observational correlation with activity. It represents the ratio between the rotation period of the star and the local convective turnover time. The former is well determined from observations but the latter is estimated by an empirical iterated function depending on the color index (B-V) and the mixing-length parameter. We computed the theoretical Rossby number of stellar models with the TGEC code, and analyze its evolution with time during the main sequence. We estimated a function for the local convective turnover time corresponding to a mixing-length parameter inferred from a solar model, and compare our results to the estimated Rossby number of 33 solar analogs and twins, observed with the spectropolarimeters ESPaDOnS@CFHT and Narval@LBT.

  2. Dynamics of vortex Rossby waves in tropical cyclones

    NASA Astrophysics Data System (ADS)

    Nikitina, Lidia

    This thesis describes an analytical study of vortex Rossby waves in tropical cyclones. Observational analyses of hurricanes in the tropical atmosphere indicate the existence of spiral rainbands which propagate outwards from the eye and affect the structure and intensity of the hurricane. These disturbances may be described as vortex Rossby waves. The aim of this research is to study the propagation of vortex Rossby waves in tropical cyclones and wave-mean-flow interactions near the critical radius where the mean flow angular velocity matches the phase speed of the waves. Depending on the wave magnitude, the problem can be linear or nonlinear. Analytical techniques including Laplace transforms, multiple scaling and asymptotic expansions are used to obtain approximate solutions of the governing linear and nonlinear equations. In this study we carry out asymptotic analyses to examine the evolution of the interactions near the critical radius in some two-dimensional configurations on an f-plane and a beta-plane. The results are used to explain some features of the tropical cyclone's development, namely, the change of angular wind in the critical layer, the secondary eyewall formation and the eyewall dynamics.

  3. Anisotropy and corotation of galactic cosmic rays.

    PubMed

    Amenomori, M; Ayabe, S; Bi, X J; Chen, D; Cui, S W; Danzengluobu; Ding, L K; Ding, X H; Feng, C F; Feng, Zhaoyang; Feng, Z Y; Gao, X Y; Geng, Q X; Guo, H W; He, H H; He, M; Hibino, K; Hotta, N; Hu, Haibing; Hu, H B; Huang, J; Huang, Q; Jia, H Y; Kajino, F; Kasahara, K; Katayose, Y; Kato, C; Kawata, K; Labaciren; Le, G M; Li, A F; Li, J Y; Lou, Y-Q; Lu, H; Lu, S L; Meng, X R; Mizutani, K; Mu, J; Munakata, K; Nagai, A; Nanjo, H; Nishizawa, M; Ohnishi, M; Ohta, I; Onuma, H; Ouchi, T; Ozawa, S; Ren, J R; Saito, T; Saito, T Y; Sakata, M; Sako, T K; Sasaki, T; Shibata, M; Shiomi, A; Shirai, T; Sugimoto, H; Takita, M; Tan, Y H; Tateyama, N; Torii, S; Tsuchiya, H; Udo, S; Wang, B; Wang, H; Wang, X; Wang, Y G; Wu, H R; Xue, L; Yamamoto, Y; Yan, C T; Yang, X C; Yasue, S; Ye, Z H; Yu, G C; Yuan, A F; Yuda, T; Zhang, H M; Zhang, J L; Zhang, N J; Zhang, X Y; Zhang, Y; Zhang, Yi; Zhaxisangzhu; Zhou, X X

    2006-10-20

    The intensity of Galactic cosmic rays is nearly isotropic because of the influence of magnetic fields in the Milky Way. Here, we present two-dimensional high-precision anisotropy measurement for energies from a few to several hundred teraelectronvolts (TeV), using the large data sample of the Tibet Air Shower Arrays. Besides revealing finer details of the known anisotropies, a new component of Galactic cosmic ray anisotropy in sidereal time is uncovered around the Cygnus region direction. For cosmic-ray energies up to a few hundred TeV, all components of anisotropies fade away, showing a corotation of Galactic cosmic rays with the local Galactic magnetic environment. These results have broad implications for a comprehensive understanding of cosmic rays, supernovae, magnetic fields, and heliospheric and Galactic dynamic environments. PMID:17053141

  4. From CoRoT 102899501 to the Sun. A time evolution model of chromospheric activity on the main sequence

    NASA Astrophysics Data System (ADS)

    Gondoin, P.; Gandolfi, D.; Fridlund, M.; Frasca, A.; Guenther, E. W.; Hatzes, A.; Deeg, H. J.; Parviainen, H.; Eigmüller, P.; Deleuil, M.

    2012-12-01

    Aims: The present study reports measurements of the rotation period of a young solar analogue, estimates of its surface coverage by photospheric starspots and of its chromospheric activity level, and derivations of its evolutionary status. Detailed observations of many young solar-type stars, such as the one reported in the present paper, provide insight into rotation and magnetic properties that may have prevailed on the Sun in its early evolution. Methods: Using a model based on the rotational modulation of the visibility of active regions, we analysed the high-accuracy CoRoT lightcurve of the active star CoRoT 102899501. Spectroscopic follow-up observations were used to derive its fundamental parameters. We compared the chromospheric activity level of Corot 102899501 with the R'HK index distribution vs age established on a large sample of solar-type dwarfs in open clusters. We also compared the chromospheric activity level of this young star with a model of chromospheric activity evolution established by combining relationships between the R'HK index and the Rossby number with a recent model of stellar rotation evolution on the main sequence. Results: We measure the spot coverage of the stellar surface as a function of time and find evidence for a tentative increase from 5 - 14% at the beginning of the observing run to 13-29% 35 days later. A high level of magnetic activity on Corot 102899501 is corroborated by a strong emission in the Balmer and Ca ii H and K lines (R'HK ~ -4). The starspots used as tracers of the star rotation constrain the rotation period to 1.625 ± 0.002 days and do not show evidence for differential rotation. The effective temperature (Teff = 5180 ± 80 K), surface gravity (log g = 4.35 ± 0.1), and metallicity ([M/H] = 0.05 ± 0.07 dex) indicate that the object is located near the evolutionary track of a 1.09 ± 0.12 M⊙ pre-main sequence star at an age of 23 ± 10 Myr. This value is consistent with the "gyro-age" of about 8-25 Myr

  5. Classification of CoRoT Exoplanet Light Curves

    NASA Astrophysics Data System (ADS)

    Sarro, L. M.; Debosscher, J.; Aerts, C.

    2006-11-01

    We describe the methodology developed for the classification of the exoplanet light curves to be assembled by the CoRoT space mission. A supervised classification method will be used to deliver the N3 data products to the CoRoT Additional Programme community. Unsupervised classification will also be performed, but at a later stage of the mission. In the current paper, we provide the class definitions and attributes under consideration for the fast supervised classification. These definitions and attributes will be improved after each long run of CoRoT.

  6. Tilted Rossby-wave critical layers in stratified atmospheres

    NASA Astrophysics Data System (ADS)

    Parham, Frederick Melvin, Jr.

    The quasigeostrophic potential vorticity equations linearized about a zonal mean flow, which describe Rossby waves, become singular at the critical level where the mean flow equals the wave's phase velocity. The Wentzel-Kramer-Brillouin solution describes a superposition of two eigenmodes, each of which has meridional structure corresponding to that of Dickenson's (1968) two-dimensional solutions. Rossby waves in a continuously stratified atmosphere are studied whose basic state zonal winds vary over large meridional scales. Again, WKB is used. The linearized potential vorticity equation is separable to lowest order. The WKB analysis applies to the outer solution. The inner solution, which provides a condition on the jump in the derivative of the outer solution across the critical line, depends on whether the critical line is desingularized by damping or by weak nonlinearity. Using the results on the matching across the critical line, the vertical structure eigenfunctions and eigenvalues are calculated for low critical layer heights with the basic state as given in the Charney model. Asymptotic values of the eigenvalues are also calculated as the critical height approaches zero or infinity. Finally, the eigenfunctions and eigenvalues are used to calculate the structure of waves on a basic state with a region of easterly winds surrounded by westerlies. The assumption of constant N makes it possible to compute the wave-forced change in the mean flow by means of modified Bessel functions.

  7. Assuring the Legacy of the CoRoT Planets

    NASA Astrophysics Data System (ADS)

    Deeg, H. J.; Klagyivik, P.; Alonso, R.; Hoyer, S.

    2015-09-01

    For the long-lasting impact of CoRoT's planet findings, precise knowledge of the times of their transits is of vital importance for any future observing campaigns. Here we give the motivation and first results of a systematic revisit of the transits of most CoRoT planets to refine their ephemeris. As secondary objectives, more precise planet characterisations, from period or transit shape variations on/and from use of a well-defined passband may be obtained.

  8. Distribution of refractory and volatile elements in CoRoT exoplanet host stars

    NASA Astrophysics Data System (ADS)

    Chavero, C.; de La Reza, R.; Domingos, R. C.; Drake, N. A.; Pereira, C. B.; Winter, O. C.

    2010-07-01

    The relative distribution of abundances of refractory, intermediate, and volatile elements in stars with planets can be an important tool for investigating the internal migration of a giant planet. This migration can lead to the accretion of planetesimals and the selective enrichment of the star with these elements. We report on a spectroscopic determination of the atmospheric parameters and chemical abundances of the parent stars in transiting planets CoRoT-2b and CoRoT-4b. Adding data for CoRoT-3 and CoRoT-5 from the literature, we find a flat distribution of the relative abundances as a function of their condensation temperatures. For CoRoT-2, the relatively high lithium abundance and intensity of its Li i resonance line permit us to propose an age of 120 Myr, making this star one of the youngest stars with planets to date. We introduce a new methodology to investigate a relation between the abundances of these stars and the internal migration of their planets. By simulating the internal migration of a planet in a disk formed only by planetesimals, we are able, for the first time, to separate the stellar fractions of refractory, intermediate, and volatile rich planetesimals accreting onto the central star. Intermediate and volatile element fractions enriching the star are similar and much larger than those of pure refractory ones. This result is opposite to what has been considered in the literature for the accreting self-enrichment processes of stars with planets. We also show that these results are highly dependent on the model adopted for the disk distribution regions in terms of refractory, intermediate, and also volatile elements and other parameters considered. We note however, that this self-enrichment mechanism is only efficient during the first 20-30 Myr or later in the lifetime of the disk when the surface convection layers of the central star for the first time attain its minimum size configuration. Based on observations made with the 2.2 m telescope

  9. Weak nonlinear coupling of Rossby-Haurwitz waves

    NASA Astrophysics Data System (ADS)

    Becker, G.

    1986-11-01

    The Rossby-Haurwitz waves as solutions of the linearized free barotropic vorticity equation in a spherical coordinate system are in good agreement with the observed ultralong planetary waves of the troposphere. Within an antisymmetric basic flow, as in the middle atmosphere, the solutions become unstable because of mathematical singularities, called 'critical latitudes'. Therefore the nonlinear advection terms have to be considered in such a case. Analytical solutions of a corresponding spectral truncated model demonstrate the weak interaction between the mean flow and the ultralong waves of zonal wavenumbers one to three. The time structures of the planetary waves change from periodic oscillations via vacillations to turbulent character with increasing initial amplitudes. Finally the spectral model is extended by the waves of wavenumber four. The numerical solutions for the periods of the planetary waves within tropospheric and stratospheric basic flow configurations agree with observations.

  10. Discovery Of A Rossby Wave In Jupiter's South Equatorial Region

    NASA Technical Reports Server (NTRS)

    Simon-Miller, Amy A.; Choi, D. S.; Rogers, J. H.; Gierasch, P. J.

    2012-01-01

    A detailed study of the chevron-shaped dark spots on the strong southern equatorial wind jet near 7.5 deg S planetographic latitude shows variations in velocity with longitude and time. The chevrons move with velocities near the maximum wind jet velocity of approx.140 m/s, as deduced by the history of velocities at this latitude and the magnitude of the symmetric wind jet near 7 deg N latitude. Their repetitive nature is consistent with an inertia-gravity wave (n = 75-100) with phase speed up to 25 m/s, relative to the local flow, but the identity of this wave mode is not well constrained. However, high spatial resolution movies from Cassini images show that the chevrons oscillate in latitude with a approx.7-day period. This oscillating motion has a wavelength of approx.20 deg and a speed of approx.100 m/s, following a pattern similar to that seen in the Rossby wave plumes of the North Equatorial Zone, and possibly reinforced by it, though they are not perfectly in phase. The transient anticyclonic South Equatorial Disturbance (SED) may be a similar wave feature, but moves at slower velocity. All data show chevron latitude variability, but it is unclear if this Rossby wave is present during other epochs, without time series movies that fully delineate it. In the presence of multiple wave modes, the difference in dominant cloud appearance between 7 deg N and 7.5 deg S may be due to the presence of the Great Red Spot, either through changes in stratification and stability or by acting as a wave boundary.

  11. Discovery Of A Rossby Wave In Jupiter's South Equatorial Region

    NASA Astrophysics Data System (ADS)

    Simon-Miller, Amy A.; Choi, D. S.; Rogers, J. H.; Gierasch, P. J.

    2012-10-01

    A detailed study of the chevron-shaped dark spots on the strong southern equatorial wind jet near 7.5 deg S planetographic latitude shows variations in velocity with longitude and time. The chevrons move with velocities near the maximum wind jet velocity of 140 m/s, as deduced by the history of velocities at this latitude and the magnitude of the symmetric wind jet near 7 deg N latitude. Their repetitive nature is consistent with an inertia-gravity wave (n = 75-100) with phase speed up to 25 m/s, relative to the local flow, but the identity of this wave mode is not well constrained. However, high spatial resolution movies from Cassini images show that the chevrons oscillate in latitude with a 7-day period. This oscillating motion has a wavelength of 20 deg and a speed of 100 m/s, following a pattern similar to that seen in the Rossby wave plumes of the North Equatorial Zone, and possibly reinforced by it, though they are not perfectly in phase. The transient anticyclonic South Equatorial Disturbance (SED) may be a similar wave feature, but moves at slower velocity. All data show chevron latitude variability, but it is unclear if this Rossby wave is present during other epochs, without time series movies that fully delineate it. In the presence of multiple wave modes, the difference in dominant cloud appearance between 7 deg N and 7.5 deg S may be due to the presence of the Great Red Spot, either through changes in stratification and stability or by acting as a wave boundary.

  12. Stellar cycles from photometric data: CoRoT stars

    NASA Astrophysics Data System (ADS)

    Ferreira Lopes, C. E.; Leão, I. C.; de Freitas, D. B.; Canto Martins, B. L.; Catelan, M.; De Medeiros, J. R.

    2015-11-01

    Context. Until a few years ago, the amplitude variation in the photometric data had been explored to a limited extent mainly because of time resolution and photometric sensitivity limitations. This investigation is now possible thanks to the Kepler and CoRoT databases which provide a unique set of data for studying the nature of stellar variability cycles. Aims: The present study characterizes the amplitude variation in a sample of main-sequence stars with light curves collected using CoRoT exofield CCDs. Methods: We analyze potential stellar activity cycles by studying the variability amplitude over small boxes. The cycle periods and amplitudes were computed based on the Lomb-Scargle periodogram, harmonic fits, and visual inspection. As a first application of our approach, we considered the photometric data for 16 CoRoT FGK main sequence stars, revisited during the IRa01, LRa01 and LRa06 CoRoT runs. Results: The 16 CoRoT stars appear to follow the empirical relations between activity cycle periods (Pcyc) and the rotation period (Prot) found by previous works. In addition to the so-called A (active) and I (inactive) sequences previously identified, there is a possible third sequence, here named S (short-cycles) sequence. However, recovery fractions estimated from simulations suggest that only a half of our sample has confident cycle measurements. Therefore, more study is needed to verify our results, and Kepler data will clearly be useful for such a study. Overall, our procedure provides a key tool for exploring the CoRoT and Kepler databases to identify and characterize stellar cycle variability. The CoRoT space mission was developed and is operated by the French space agency CNES, with the participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain.

  13. Oceanic Rossby Waves Acting As a ``Hay Rake'' for Ecosystem Floating By-Products

    NASA Astrophysics Data System (ADS)

    Dandonneau, Yves; Vega, Andres; Loisel, Hubert; du Penhoat, Yves; Menkes, Christophe

    2003-11-01

    Recent satellite observations of Rossby waves and chlorophyll anomalies propagating in subtropical gyres have suggested that wave-induced upwelling could stimulate photosynthesis. Instead, we show that chlorophyll maxima are located in abnormally warm water, in Rossby wave-induced convergences. This excludes inputs of nutrients from deeper water. We argue that the sea color anomalies are not caused by chlorophyll but by floating particles evolved from the ecosystem and accumulated by Rossby waves, acting as ``marine hay rakes,'' in convergence zones. Such processes may be determinant for the distribution of living organisms in oligotrophic areas.

  14. CoRoT data reduction by example

    NASA Astrophysics Data System (ADS)

    Weingrill, J.

    2015-02-01

    Data reduction techniques published so far for the CoRoT N2 data product were targeted primarily on the detection of extrasolar planets. Since the whole dataset has been released, specific algorithms are required to process the lightcurves from CoRoT correctly. Though only unflagged datapoints must be chosen for scientific processing, some flags might be reconsidered. The reduction of data along with improving the signal-to-noise ratio can be achieved by applying a one dimensional drizzle algorithm. Gaps can be filled by linear interpolated data without harming the frequency spectrum. Magnitudes derived from the CoRoT color channels might be used to derive additional information about the targets. Depending on the needs, various filters in the frequency domain remove either the red noise background or high frequency noise. The autocorrelation function or the least squares periodogram are appropriate methods to identify periodic signals. The methods described here are not strictly limited to CoRoT data but may also be applied on Kepler data or the upcoming PLATO mission. The CoRoT space mission, launched on 2006 December 27, has been developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA (RSSD and Science Programme), Germany and Spain.

  15. Equatorward shift of annual Rossby waves in the Equatorial Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Ma, Xiao; Sun, Che

    2016-01-01

    Annual Rossby wave is a key component of the ENSO phenomenon in the equatorial Pacific Ocean. Due to the paucity and seasonal bias in historical hydrographic data, previous studies on equatorial Rossby waves only gave qualitative description. The accumulation of Argo measurements in recent years has greatly alleviated the data problem. In this study, seasonal variation of the equatorial Pacific Ocean is examined with annual harmonic analysis of Argo gridded data. Results show that strong seasonal signal is present in the western equatorial Pacific and explains more than 50% of the thermal variance below 500 m. Lag-correlation tracing further shows that this sub-thermocline seasonal signal originates from the eastern equatorial Pacific via downward and southwestward propagation of annual Rossby waves. Possible mechanisms for the equatorward shift of Rossby wave path are also discussed.

  16. Dust-trapping Rossby vortices in protoplanetary disks

    NASA Astrophysics Data System (ADS)

    Meheut, H.; Meliani, Z.; Varniere, P.; Benz, W.

    2012-09-01

    Context. One of the most challenging steps in planet formation theory is the one leading to the formation of planetesimals of kilometre size. A promising scenario involves the existence of vortices able to concentrate a large amount of dust and grains in their centres. Up to now this scenario has mostly been studied in 2D razor thin disks. A 3D study including, simultaneously, the formation and resulting dust concentration of the vortices with vertical settling, is still missing. Aims: The Rossby wave instability self-consistently forms 3D vortices, which have the unique quality of presenting a large-scale vertical velocity in their centre. Here we aim to study how this newly discovered effect can alter the dynamic evolution of the dust. Methods: We performed global 3D simulations of the RWI in a radially and vertically stratified disk using the code MPI-AMRVAC. After the growth phase of the instability, the gas and solid phases are modelled by a bi-fluid approach, where the dust is considered as a fluid without pressure. Both the drag force of the gas on the dust and the back reaction of the dust on the gas are included. Multiple grain sizes from 1 mm to 5 cm are used with a constant density distribution. Results: We obtain in a short timescale a high concentration of the largest grains in the vortices. Indeed, in 3 rotations the dust-to-gas density ratio grows from 10-2 to unity leading to a concentration of mass up to that of Mars in one vortex. The presence of the radial drift is also at the origin of a dust pile-up at the radius of the vortices. Lastly, the vertical velocity of the gas in the vortex causes the sedimentation process to be reversed, the mm size dust is lifted and higher concentrations are obtained in the upper layer than in the midplane. Conclusions: The Rossby wave instability is a promising mechanism for planetesimal formation, and the results presented here can be of particular interest in the context of future observations of protoplanetary

  17. Investigation of Rossby-number similarity in the neutral boundary layer using large-eddy simulation

    SciTech Connect

    Ohmstede, W.D.; Cederwall, R.T.; Meyers, R.E.

    1988-01-01

    One special case of particular interest, especially to theoreticians, is the steady-state, horizontally homogeneous, autobarotropic (PLB), hereafter referred to as the neutral boundary layer (NBL). The NBL is in fact a 'rare' atmospheric phenomenon, generally associated with high-wind situations. Nevertheless, there is a disproportionate interest in this problem because Rossby-number similarity theory provides a sound approach for addressing this issue. Rossby-number similarity theory has rather wide acceptance, but because of the rarity of the 'true' NBL state, there remains an inadequate experimental database for quantifying constants associated with the Rossby-number similarity concept. Although it remains a controversial issue, it has been proposed that large-eddy simulation (LES) is an alternative to physical experimentation for obtaining basic atmospherc 'data'. The objective of the study reported here is to investigate Rossby-number similarity in the NBL using LES. Previous studies have not addressed Rossby-number similarity explicitly, although they made use of it in the interpretation of their results. The intent is to calculate several sets of NBL solutions that are ambiguous relative to the their respective Rossby numbers and compare the results for similarity, or the lack of it. 14 refs., 1 fig.

  18. Extratropical anticyclonic Rossby wave breaking and Indian summer monsoon failure

    NASA Astrophysics Data System (ADS)

    Samanta, Dhrubajyoti; Dash, M. K.; Goswami, B. N.; Pandey, P. C.

    2016-03-01

    Interactions between midlatitude disturbances and the monsoonal circulation are significant for the Indian summer monsoon (ISM) rainfall. This paper presents examples of monsoon-midlatitude linkage through anticyclonic Rossby wave breaking (RWB) over West Asia during June, July and August of the years 1998-2010. RWB events over West Asia are identified by the inversion of the potential vorticity air mass at three different isentropic levels (340, 350, and 360 K) using daily NCEP-NCAR reanalysis. It is observed that RWB took place over West Asia before/during breaks in the ISM. Further, these events occur on the anticyclonic shear side of the subtropical jet, where the gradient of the zonal wind is found to be high. RWB is responsible for the southward movement of high potential vorticity air from the westerly jet, leading to the formation of a blocking high over the Arabian region. In turn, this blocking high advects and causes the descent of upper tropospheric cold and dry air towards Central India. Such an air mass with low moist static energy inhibits deep monsoonal convection and thereby leads to a dry spell. In fact, we find that RWB induced blocking over West Asia to be one of the major causes of dry spell/break episodes in ISM. Additionally, the presence of cold air over Central India reduces the north-south thermal contrast over the monsoon region thereby modifying the local Hadley circulation over the region.

  19. Revisiting the Rossby Haurwitz wave test case with contour advection

    NASA Astrophysics Data System (ADS)

    Smith, Robert K.; Dritschel, David G.

    2006-09-01

    This paper re-examines a basic test case used for spherical shallow-water numerical models, and underscores the need for accurate, high resolution models of atmospheric and ocean dynamics. The Rossby-Haurwitz test case, first proposed by Williamson et al. [D.L. Williamson, J.B. Drake, J.J. Hack, R. Jakob, P.N. Swarztrauber, A standard test set for numerical approximations to the shallow-water equations on the sphere, J. Comput. Phys. (1992) 221-224], has been examined using a wide variety of shallow-water models in previous papers. Here, two contour-advective semi-Lagrangian (CASL) models are considered, and results are compared with previous test results. We go further by modifying this test case in a simple way to initiate a rapid breakdown of the basic wave state. This breakdown is accompanied by the formation of sharp potential vorticity gradients (fronts), placing far greater demands on the numerics than the original test case does. We also go further by examining other dynamical fields besides the height and potential vorticity, to assess how well the models deal with gravity waves. Such waves are sensitive to the presence or not of sharp potential vorticity gradients, as well as to numerical parameter settings. In particular, large time steps (convenient for semi-Lagrangian schemes) can seriously affect gravity waves but can also have an adverse impact on the primary fields of height and velocity. These problems are exacerbated by a poor resolution of potential vorticity gradients.

  20. Aspect ratio effects on revolving wings with Rossby number consideration.

    PubMed

    Lee, Y J; Lua, K B; Lim, T T

    2016-01-01

    Numerical simulations have been conducted to investigate the effect of aspect ratio (AR) on the mean lift generation of a revolving flat rectangular wing. The purpose of the study is to address some discrepancies reported in the literature regarding the influence of AR on mean lift coefficient. Here, we consider a range of AR from 1 to 10 and Rossby number (Ro) from 0.58 to 7.57, and our results show that different degrees of coupling between AR and Ro yield different trends of a mean lift coefficient with respect to increasing AR. The choice of reference velocity for the normalisation of mean lift forces also has a significant effect on the perceived AR effect. By isolating the effect of Ro, we found that higher AR produces higher mean lift coefficient until it plateaus at a sufficiently high AR. This finding is consistent with conventional fixed wing aerodynamics. Additionally, our results show that increasing AR reduces the three-dimensional wing tip effect and is beneficial to mean lift generation while higher Ro increases leading-edge vortex instability, which is detrimental to mean lift generation. Therefore, mean lift generation on revolving wings is dictated by the competition between these two factors, which represent two fundamentally independent phenomena. PMID:27608653

  1. Transiting exoplanets from the CoRoT space mission⋆. XXVIII. CoRoT-33b, an object in the brown dwarf desert with 2:3 commensurability with its host star

    NASA Astrophysics Data System (ADS)

    Csizmadia, Sz.; Hatzes, A.; Gandolfi, D.; Deleuil, M.; Bouchy, F.; Fridlund, M.; Szabados, L.; Parviainen, H.; Cabrera, J.; Aigrain, S.; Alonso, R.; Almenara, J.-M.; Baglin, A.; Bordé, P.; Bonomo, A. S.; Deeg, H. J.; Díaz, R. F.; Erikson, A.; Ferraz-Mello, S.; Tadeu dos Santos, M.; Guenther, E. W.; Guillot, T.; Grziwa, S.; Hébrard, G.; Klagyivik, P.; Ollivier, M.; Pätzold, M.; Rauer, H.; Rouan, D.; Santerne, A.; Schneider, J.; Mazeh, T.; Wuchterl, G.; Carpano, S.; Ofir, A.

    2015-12-01

    We report the detection of a rare transiting brown dwarf with a mass of 59 MJup and radius of 1.1 RJup around the metal-rich, [Fe/H] = +0.44, G9V star CoRoT-33. The orbit is eccentric (e = 0.07) with a period of 5.82 d. The companion, CoRoT-33b, is thus a new member in the so-called brown dwarf desert. The orbital period is within 3% to a 3:2 resonance with the rotational period of the star. CoRoT-33b may be an important test case for tidal evolution studies. The true frequency of brown dwarfs close to their host stars (P< 10 d) is estimated to be approximately 0.2% which is about six times smaller than the frequency of hot Jupiters in the same period range. We suspect that the frequency of brown dwarfs declines faster with decreasing period than that of giant planets. The CoRoT space mission, launched on December 27th 2006, has been developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA (RSSD and Science Programme), Germany and Spain. Based on observations made with HARPS (High Accuracy Radial velocity Planet Searcher) spectrograph on the 3.6-m European Organisation for Astronomical Research in the Southern Hemisphere telescope at La Silla Observatory, Chile (ESO program 188.C-0779).Based on observations obtained with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, in time allocated by the Spanish Time Allocation Committee (CAT).

  2. Decrease of the Atmospheric Co-Rotation with Height

    ERIC Educational Resources Information Center

    Membrado, M.; Pacheco, A. F.

    2010-01-01

    Considering our atmosphere as a steady viscous gaseous envelope that co-rotates with the Earth, we obtain a solution for the form in which this induced rotational effect decreases as a function of the distances to the centre of the Earth and to the rotation axis. (Contains 1 figure.)

  3. Asteroseismology of OB stars with CoRoT

    NASA Astrophysics Data System (ADS)

    Degroote, P.; Aerts, C.; Samadi, R.; Miglio, A.; Briquet, M.; Auvergne, M.; Baglin, A.; Baudin, F.; Catala, C.; Michel, E.

    2010-12-01

    The CoRoT satellite is revolutionizing the photometric study of massive O-type and B-type stars. During its long runs, CoRoT observed the entire main sequence B star domain, from typical hot β Cep stars, via cooler hybrid p- and g-mode pulsators to the SPB stars near the edge of the instability strip. CoRoT lowers the sensitivity barrier from the typical mmag-precision reached from the ground, to the μmag-level reached from space. Within the wealth of detected and identified pulsation modes, relations have been found in the form of multiplets, combination of frequencies, and frequency- and period spacings. This wealth of observational evidence is finally providing strong constraints to test current models of the internal structure and pulsations of hot stars. Aside from the expected opacity driven modes with infinite lifetime, other unexpected types of variability are detected in massive stars, such as modes of stochastic nature. The simultaneous observation of all these light curve characteristics implies a challenge for both observational asteroseismology and stellar modelling. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain.

  4. The Superposition of Eastward and Westward Rossby Waves in Response to Localized Forcing

    NASA Astrophysics Data System (ADS)

    Shaman, J. L.; Tziperman, E.

    2015-12-01

    Rossby waves are a principal form of atmospheric communication between disparate parts of the climate system. These planetary waves are typically excited by diabatic or orographic forcing and can be subject to considerable downstream modification. Due to differences in wave properties, including vertical structure, phase speed and group velocity, Rossby waves exhibit a wide range of behaviors. Here we demonstrate the combined effects of eastward propagating stationary barotropic Rossby waves and westward propagating very low zonal wavenumber stationary barotropic Rossby waves on the atmospheric response to wintertime El Niño convective forcing over the tropical Pacific. Experiments are conducted using the Community Atmospheric Model 4.0 in which both diabatic forcing over the Pacific and localized relaxation outside the forcing region are applied. The localized relaxation is used to dampen Rossby wave propagation to either the west or east of the forcing region and isolate the alternate direction signal. Wave responses match theoretical expectations and clarify that observed downstream stationary responses to diabatic forcing result from the superposition of planetary wave signals emanating in alternate directions.

  5. Can a minimalist model of wind forced baroclinic Rossby waves produce reasonable results?

    NASA Astrophysics Data System (ADS)

    Watanabe, Wandrey B.; Polito, Paulo S.; da Silveira, Ilson C. A.

    2016-04-01

    The linear theory predicts that Rossby waves are the large scale mechanism of adjustment to perturbations of the geophysical fluid. Satellite measurements of sea level anomaly (SLA) provided sturdy evidence of the existence of these waves. Recent studies suggest that the variability in the altimeter records is mostly due to mesoscale nonlinear eddies and challenges the original interpretation of westward propagating features as Rossby waves. The objective of this work is to test whether a classic linear dynamic model is a reasonable explanation for the observed SLA. A linear-reduced gravity non-dispersive Rossby wave model is used to estimate the SLA forced by direct and remote wind stress. Correlations between model results and observations are up to 0.88. The best agreement is in the tropical region of all ocean basins. These correlations decrease towards insignificance in mid-latitudes. The relative contributions of eastern boundary (remote) forcing and local wind forcing in the generation of Rossby waves are also estimated and suggest that the main wave forming mechanism is the remote forcing. Results suggest that linear long baroclinic Rossby wave dynamics explain a significant part of the SLA annual variability at least in the tropical oceans.

  6. Reflection of annual Rossby waves at the maritime western boundary of the tropical Pacific

    NASA Technical Reports Server (NTRS)

    White, Warren B.; Graham, Nicholas; Tai, C.-K.

    1990-01-01

    Results are presented of an examination of altimetric sea level time series from the first 17 months of the Geosat Geodetic Mission. The examination provides the first direct evidence of the Rossby wave reflection process operating in both hemispheres at the maritime western boundary of the tropical Pacific, in regard to annual Rossby activity. It is demonstrated that the Philippines in the Northern Hemisphere and the Solomon, the Bismarck, and the New Guinea islands in the Southern Hemisphere reflected the incident baroclinic Rossby wave activity of the one-year period, generating equatorial Kelvin wave activity that emanated from the maritime western boundary of the tropical Pacific, conducting the annual baroclinic signal along the equator into the eastern equatorial Pacific.

  7. THE MASS OF CoRoT-7b

    SciTech Connect

    Hatzes, Artie P.; Wuchterl, Guenther; Fridlund, Malcolm; Gandolfi, Davide; Nachmani, Gil; Mazeh, Tsevi; Valencia, Diana; Hebrard, Guillaume; Borde, Pascal; Carone, Ludmila; Paetzold, Martin; Udry, Stephane; Bouchy, Francois; Deleuil, Magali; Moutou, Claire; Barge, Pierre; Deeg, Hans; Tingley, Brandon; Dvorak, Rudolf; Ferraz-Mello, Sylvio E-mail: malcolm.fridlund@esa.int; and others

    2011-12-10

    The mass of CoRoT-7b, the first transiting super-Earth exoplanet, is still a subject of debate. A wide range of masses have been reported in the literature ranging from as high as 8 M{sub Circled-Plus} to as low as 2.3 M{sub Circled-Plus }. This range in mass is largely due to the activity level of the star that contributes a significant amount of radial velocity (RV) 'jitter' and how the various methods correct this jitter. Although most mass determinations give a density consistent with a rocky planet, the lower value permits a bulk composition that can be up to 50% water. We present an analysis of the CoRoT-7b RV measurements that uses very few and simple assumptions in treating the activity signal. By analyzing those RV data for which multiple measurements were made in a given night, we remove the activity related RV contribution without any a priori model. We argue that the contribution of activity to the final RV curve is negligible and that the K-amplitude due to the planet is well constrained. This yields a mass of 7.42 {+-} 1.21 M{sub Circled-Plus} and a mean density of {rho} = 10.4 {+-} 1.8 gm cm{sup -3}. CoRoT-7b is similar in mass and radius to the second rocky planet to be discovered, Kepler-10b, and within the errors they have identical bulk densities-they are virtual twins. These bulk densities lie close to the density-radius relationship for terrestrial planets similar to what is seen for Mercury. CoRoT-7b and Kepler-10b may have an internal structure more like Mercury than the Earth.

  8. Energetic particle acceleration at corotating interaction regions: Ulysses results

    SciTech Connect

    Desai, M.I.; Marsden, R.G.; Sanderson, T.R.; Gosling, J.T.

    1997-07-01

    We present here statistical properties of energetic ions (tilde 1 MeV) accelerated by corotating interaction regions observed at the Ulysses spacecraft. We have correlated the tilde 1 MeV proton intensity measured near the trailing edges of the interaction regions with their compression ratio. We interpret our results in terms of the plasma conditions experienced at Ulysses and identify a likely source of the low energy seed particles accelerated at the interaction regions.

  9. CoRoT space photometry of seven Cepheids

    NASA Astrophysics Data System (ADS)

    Poretti, E.; Le Borgne, J. F.; Rainer, M.; Baglin, A.; Benkő, J. M.; Debosscher, J.; Weiss, W. W.

    2015-11-01

    A few Galactic classical Cepheids were observed in the programmes of space missions as Coriolis, MOST, and Kepler. An appealing opportunity was to detect additional non-radial modes, thus opening the possibility to perform asteroseismic studies and making the pulsational content of Galactic Cepheids more similar to that of Magellanic Clouds ones. However, only hints of cycle-to-cycle variations were found, without any strict periodicity. In this context the potential of the CoRoT exoplanetary data base was not fully exploited despite the wide area covered on the Galactic plane. Therefore, we investigated all the candidate Cepheids pointed out by the automatic classification of the CoRoT curves. At the end, we could identify seven bona fide Cepheids. The light curves were investigated to remove some instrumental effects. The frequency analysis was particularly delicate since these small effects can be enhanced by the large amplitude, resulting in the presence of significant, but spurious, peaks in the power spectrum. Indeed, the careful evaluation of a very attracting peak in the spectra of CoRoT 0102618121 allowed us to certify its spurious origin. Once that the instrumental effects were properly removed, no additional mode was detected. On the other hand, cycle-to-cycle variations of the Fourier parameters were observed, but very small and always within ±3σ. Among the seven Cepheids, there are two Pop. I first-overtone pulsators, four Pop. I fundamental mode pulsators, and one Pop. II star. The CoRoT colours allowed us to measure that times of maximum brightness occur a little earlier (about 0.01 period) at short wavelengths than at long ones.

  10. The Mass of CoRoT-7b

    NASA Astrophysics Data System (ADS)

    Hatzes, Artie P.; Fridlund, Malcolm; Nachmani, Gil; Mazeh, Tsevi; Valencia, Diana; Hébrard, Guillaume; Carone, Ludmila; Pätzold, Martin; Udry, Stephane; Bouchy, Francois; Deleuil, Magali; Moutou, Claire; Barge, Pierre; Bordé, Pascal; Deeg, Hans; Tingley, Brandon; Dvorak, Rudolf; Gandolfi, Davide; Ferraz-Mello, Sylvio; Wuchterl, Günther; Guenther, Eike; Guillot, Tristan; Rauer, Heike; Erikson, Anders; Cabrera, Juan; Csizmadia, Szilard; Léger, Alain; Lammer, Helmut; Weingrill, Jörg; Queloz, Didier; Alonso, Roi; Rouan, Daniel; Schneider, Jean

    2011-12-01

    The mass of CoRoT-7b, the first transiting super-Earth exoplanet, is still a subject of debate. A wide range of masses have been reported in the literature ranging from as high as 8 M ⊕ to as low as 2.3 M ⊕. This range in mass is largely due to the activity level of the star that contributes a significant amount of radial velocity (RV) "jitter" and how the various methods correct this jitter. Although most mass determinations give a density consistent with a rocky planet, the lower value permits a bulk composition that can be up to 50% water. We present an analysis of the CoRoT-7b RV measurements that uses very few and simple assumptions in treating the activity signal. By analyzing those RV data for which multiple measurements were made in a given night, we remove the activity related RV contribution without any a priori model. We argue that the contribution of activity to the final RV curve is negligible and that the K-amplitude due to the planet is well constrained. This yields a mass of 7.42 ± 1.21 M ⊕ and a mean density of ρ = 10.4 ± 1.8 gm cm-3. CoRoT-7b is similar in mass and radius to the second rocky planet to be discovered, Kepler-10b, and within the errors they have identical bulk densities—they are virtual twins. These bulk densities lie close to the density-radius relationship for terrestrial planets similar to what is seen for Mercury. CoRoT-7b and Kepler-10b may have an internal structure more like Mercury than the Earth.

  11. Testing a Method of Detecting a Magnetic Field of Transiting Hot-Jupiter CoRot-1b

    NASA Astrophysics Data System (ADS)

    Biddle, Lauren I.; Turner, J.; Pearson, K.; Teske, J.

    2013-06-01

    In October of 2011 and December of 2012, exoplanet CoRot-1b was observed on the Steward Observatory 61” Kuiper Telescope using the Bessel-U filter to detect a possible magnetic field. In addition, the primary transit of CoRoT-1b was observed January 29, 2012 and February 2, 2012 using the medium resolution spectrograph on the 6.5 meter MMT Observatory. It is suggested by Vidotto et. al. (2011), that it is possible to detect a magnetic field of a transiting exoplanet in the near-UV photometric band by comparing asymmetry between the ingress and egress of the light curve. This effect is believed to be caused by a bow shock being formed in front of the planet as it transverses through the coronal plasma of its host star. CoRot-1b is a candidate for demonstrating this effect. We do not observe an early ingress in our near-UV broad-band light curves from the 61" Kuiper Telescope. We find an unexpected upper limit of 0.087-1.4 Gauss for the magnetic field strength of CoRoT-1b. This result is consistent with the near-UV observations by Turner et al. 2013 of another exoplanet predicted to show this effect, TrES-3b. It was suggested Vidotto et al 2011 and the finding of Turner et al. 2013 that an early near-UV might only happen at certain spectral resonance lines. Our observations from the MMT observatory hope to shed light on this possibly. Our spectral observations can constrain the composition of a possible bowshock and also investigate potential molecular features in the atmosphere of CoRoT-1b. To find the best fit to the light curves we used a modeling package called EXOMOP that uses the analytic equations of Mandel & Agol (2002) to generate a model transit, the Levenberg-Marquardt non-linear least squares minimization algorithm to find the best fit, the bootstrap Monte Carlo technique to calculate robust errors of the fitted parameters, and the residual permutation “rosary bead” method to access the importance of red noise. Several other parameters to confirm

  12. Corotating pressure waves without streams in the solar wind

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.

    1983-01-01

    Voyager 1 and 2 magnetic field and plasma data are presented which demonstrate the existence of large scale, corotating, non-linear pressure waves between 2 AU and 4 AU that are not accompanied by fast streams. The pressure waves are presumed to be generated by corotating streams near the Sun. For two of the three pressure waves that are discussed, the absence of a stream is probably a real, physical effect, viz., a consequence of deceleration of the stream by the associated compression wave. For the third pressure wave, the apparent absence of a stream may be a geometrical effect; it is likely that the stream was at latitudes just above those of the spacecraft, while the associated shocks and compression wave extended over a broader range of latitudes so that they could be observed by the spacecraft. It is suggested that the development of large-scale non-linear pressure waves at the expense of the kinetic energy of streams produces a qualitative change in the solar wind in the outer heliosphere. Within a few AU the quasi-stationary solar wind structure is determined by corotating streams whose structure is determined by the boundary conditions near the Sun.

  13. First imaging of corotating interaction regions using the STEREO spacecraft

    NASA Astrophysics Data System (ADS)

    Rouillard, A. P.; Davies, J. A.; Forsyth, R. J.; Rees, A.; Davis, C. J.; Harrison, R. A.; Lockwood, M.; Bewsher, D.; Crothers, S. R.; Eyles, C. J.; Hapgood, M.; Perry, C. H.

    2008-05-01

    Plasma parcels are observed propagating from the Sun out to the large coronal heights monitored by the Heliospheric Imagers (HI) instruments onboard the NASA STEREO spacecraft during September 2007. The source region of these out-flowing parcels is found to corotate with the Sun and to be rooted near the western boundary of an equatorial coronal hole. These plasma enhancements evolve during their propagation through the HI cameras' fields of view and only becoming fully developed in the outer camera field of view. We provide evidence that HI is observing the formation of a Corotating Interaction Region (CIR) where fast solar wind from the equatorial coronal hole is interacting with the slow solar wind of the streamer belt located on the western edge of that coronal hole. A dense plasma parcel is also observed near the footpoint of the observed CIR at a distance less than 0.1AU from the Sun where fast wind would have not had time to catch up slow wind. We suggest that this low-lying plasma enhancement is a plasma parcel which has been disconnected from a helmet streamer and subsequently becomes embedded inside the corotating interaction region.

  14. Reflection of interannual Rossby waves at the maritime western boundary of the tropical Pacific

    NASA Astrophysics Data System (ADS)

    White, Warren B.; Tai, Chang-Kou

    1992-09-01

    The reflection of interannual Rossby waves over a 2.7-year period (i.e., November 1986 to August 1989) is examined in the western tropical Pacific utilizing altimetric sea level observations from the Geosat Exact Repeat Mission. In 1987 this reflection process generates upwelling Kelvin waves that tended to limit the growth of the 1986-1987 El Niño in the eastern equatorial Pacific. Two-dimensional autocorrelation and spectral analyses verify the existence of westward traveling Rossby waves in both the equatorial and off-equatorial domains, and eastward propagating Kelvin waves in the equatorial domain. Extended empirical orthogonal function (EEOF) analysis characterizes the time-space evolutionary behavior of the Rossby wave reflection process, extending from the El Niño in 1986-1987 toward the anti-El Niño in 1988-1989. Both the Philippines Archipelago in the northern hemisphere and the Solomon Archipelago/Bismarck Archipelago/New Guinea complex in the southern hemisphere appear to reflect incident Rossby waves, with maximum amplitude near 8°N and 8°S, generating Kelvin waves in the equatorial wave guide that conduct the anomalous signal eastward along the equator. This apparent reflection process is examined in terms of the linear theory, with sea level phase information in the northern hemisphere at the western boundary (130°W) expanded in terms of the Kelvin and symmetric Rossby meridional wave modes. These modes are formed as weighted sums of parabolic cylinder functions. This procedure, operating under the constraint that the reflection process occurred according to linear theory, determines the percent contribution that each incident Rossby wave mode amplitude has upon the amplitude of the reflected Kelvin wave. This percentage changed little over the evolution of the EEOF pattern. The amplitude of the first-mode Rossby wave (i.e., mode 2) accounts for most of the Kelvin wave amplitude (i.e., 70-80%), with the higher-mode Rossby wave amplitudes (i

  15. Planetary transit candidates in the CoRoT LRa01 field

    NASA Astrophysics Data System (ADS)

    Carone, L.; Gandolfi, D.; Cabrera, J.; Hatzes, A. P.; Deeg, H. J.; Csizmadia, Sz.; Pätzold, M.; Weingrill, J.; Aigrain, S.; Alonso, R.; Alapini, A.; Almenara, J.-M.; Auvergne, M.; Baglin, A.; Barge, P.; Bonomo, A. S.; Bordé, P.; Bouchy, F.; Bruntt, H.; Carpano, S.; Cochran, W. D.; Deleuil, M.; Díaz, R. F.; Dreizler, S.; Dvorak, R.; Eislöffel, J.; Eigmüller, P.; Endl, M.; Erikson, A.; Ferraz-Mello, S.; Fridlund, M.; Gazzano, J.-C.; Gibson, N.; Gillon, M.; Gondoin, P.; Grziwa, S.; Günther, E. W.; Guillot, T.; Hartmann, M.; Havel, M.; Hébrard, G.; Jorda, L.; Kabath, P.; Léger, A.; Llebaria, A.; Lammer, H.; Lovis, C.; MacQueen, P. J.; Mayor, M.; Mazeh, T.; Moutou, C.; Nortmann, L.; Ofir, A.; Ollivier, M.; Parviainen, H.; Pepe, F.; Pont, F.; Queloz, D.; Rabus, M.; Rauer, H.; Régulo, C.; Renner, S.; de La Reza, R.; Rouan, D.; Santerne, A.; Samuel, B.; Schneider, J.; Shporer, A.; Stecklum, B.; Tal-Or, L.; Tingley, B.; Udry, S.; Wuchterl, G.

    2012-02-01

    Context. CoRoT is a pioneering space mission whose primary goals are stellar seismology and extrasolar planets search. Its surveys of large stellar fields generate numerous planetary candidates whose lightcurves have transit-like features. An extensive analytical and observational follow-up effort is undertaken to classify these candidates. Aims: We present the list of planetary transit candidates from the CoRoT LRa01 star field in the Monoceros constellation toward the Galactic anti-center direction. The CoRoT observations of LRa01 lasted from 24 October 2007 to 3 March 2008. Methods: We acquired and analyzed 7470 chromatic and 3938 monochromatic lightcurves. Instrumental noise and stellar variability were treated with several filtering tools by different teams from the CoRoT community. Different transit search algorithms were applied to the lightcurves. Results: Fifty-one stars were classified as planetary transit candidates in LRa01. Thirty-seven (i.e., 73% of all candidates) are "good" planetary candidates based on photometric analysis only. Thirty-two (i.e., 87% of the "good" candidates) have been followed-up. At the time of writing twenty-two cases were solved and five planets were discovered: three transiting hot-Jupiters (CoRoT-5b, CoRoT-12b, and CoRoT-21b), the first terrestrial transiting planet (CoRoT-7b), and another planet in the same system (CoRoT-7c, detected by radial velocity survey only). Evidence of another non-transiting planet in the CoRoT-7 system, namely CoRoT-7d, was recently found as well. The CoRoT space mission, launched on December 27, 2006, has been developed and is operated by CNES, with contributions of Austria, Belgium, Brazil, ESA (RSSD and Science Program), Germany and Spain.

  16. Resonance

    NASA Astrophysics Data System (ADS)

    Perozzi, E.; Murdin, P.

    2000-11-01

    A resonance in CELESTIAL MECHANICS occurs when some of the quantities characterizing the motion of two or more celestial bodies can be considered as commensurable, i.e. their ratio is close to an integer fraction. In a simplified form, this can be expressed as ...

  17. Rossby wave radiation by an eddy on a beta-plane: Experiments with laboratory altimetry

    SciTech Connect

    Zhang, Y.; Afanasyev, Y. D.

    2015-07-15

    Results from the laboratory experiments on the evolution of vortices (eddies) generated in a rotating tank with topographic β-effect are presented. The focus of the experiments is on the far-field flow which contains Rossby waves emitted by travelling vortices. The surface elevation and velocity fields are measured by the altimetric imaging velocimetry. The experiments are supplemented by shallow water numerical simulations as well as a linear theory which describes the Rossby wave radiation by travelling vortices. The cyclonic vortices observed in the experiments travel to the northwest and continuously radiate Rossby waves. Measurements show that initially axisymmetric vortices develop a dipolar component which enables them to perform translational motion. A pattern of alternating zonal jets to the west of the vortex is created by Rossby waves with approximately zonal crests. Energy spectra of the flows in the wavenumber space indicate that a wavenumber similar to that introduced by Rhines for turbulent flows on the β-plane can be introduced here. The wavenumber is based on the translational speed of a vortex rather than on the root-mean-square velocity of a turbulent flow. The comparison between the experiments and numerical simulations demonstrates that evolving vortices also emit inertial waves. While these essentially three-dimensional non-hydrostatic waves can be observed in the altimetric data, they are not accounted for in the shallow water simulations.

  18. Reflection of annual Rossby waves at the maritime western boundary of the tropical Pacific

    NASA Astrophysics Data System (ADS)

    White, Warren B.; Graham, Nicholas; Tai, C.-K.

    1990-03-01

    In this study the examination of altimetric sea level time series from the first 17 months of the Geosat Geodetic Mission provides the first evidence of the Rossby wave reflection process operating at the maritime western boundary of the tropical Pacific in both the northern and southern hemispheres. In an earlier study, Tai et al. (1989) analyzed altimetric sea level time series derived from crossover differences during the first 17 months of the Geosat Geodetic Mission from April 1985 to September 1986, finding statistically significant agreement with in situ measurements of sea level differences (i.e., island sea level and relative dynamic height), In the present study, two-dimensional spectral analysis verified the existence of both off-equatorial baroclinic Rossby wave activity and equatorial baroclinic Kelvin wave activity in the altimetric sea level data set, establishing also that the annual cycle dominated the variability over this 17-month period. Next, extended empirical orthogonal function analysis (Graham et al., 1987) determined the evolutionary behavior of the readjustment process that occurred in the sea surface topography on the annual cycle over this 17-month period. Both the Philippines archipelago in the northern hemisphere and the Solomon archipelago-Bismarck archipelago-New Guinea complex in the southern hemisphere were found to reflect incident baroclinic Rossby wave activity of 1-year period, particularly manifested in the October-April transition, generating equatorial Kelvin wave activity that conducted the annual signal along the equatorial waveguide into the eastern equatorial Pacific. At the eastern boundary of South America, reflection of the incident equatorial Kelvin wave activity was associated with coastal Kelvin wave activity and equatorial-trapped Rossby wave activity in the equatorial waveguide, the latter propagating back to the west. However, the equatorial-trapped Rossby wave activity thus generated was not observed to

  19. Testing a Method of Detecting a Magnetic Field of Transiting Hot-Jupiter CoRot-1b

    NASA Astrophysics Data System (ADS)

    Biddle, Lauren; Turner, J.; Pearson, K.; Teske, J.

    2013-10-01

    In October of 2011 and December of 2012, exoplanet CoRot-1b was observed on the Steward Observatory 1.55m Kuiper Telescope using the Bessel-U filter to detect a possible magnetic field. It is suggested by Vidotto et. al. (2011), that it is possible to detect a magnetic field of a transiting exoplanet in the near-UV photometric band by comparing asymmetry between the ingress and egress of the light curve. This effect is believed to be caused by a bow shock being formed in front of a closely orbiting planet as it transverses through the coronal plasma of its host star. CoRot-1b is a candidate for demonstrating this effect. We do not observe an early ingress in our near-UV broad-band light curves from the 61" Kuiper Telescope. We find an unexpected upper limit of 0.087-1.4 Gauss for the magnetic field strength of CoRoT-1b. This result is consistent with the near-UV observations by Turner et al. (2013) of another exoplanet predicted to show this effect, TrES-3b. It was suggested by Vidotto et al. (2011) and the finding of Turner et al. (2013) that an early ingress observed in the near-UV might only happen at certain spectral resonance lines. To find the best fit to the light curves we used a modeling package called EXOMOP that uses the analytic equations of Mandel & Agol (2002) to generate a model transit, the Levenberg-Marquardt non-linear least squares minimization algorithm to find the best fit, the bootstrap Monte Carlo technique to calculate robust errors of the fitted parameters, and the residual permutation “rosary bead” method to access the importance of red noise. Several other parameters to confirm and amend can be derived from the light curve including the planet’s mass, radius, density, surface gravity, distance, and orbital inclination.

  20. Latitude dependence of co-rotating shock acceleration

    NASA Technical Reports Server (NTRS)

    Gold, R. E.; Lanzerotti, L. J.; Maclennan, C. G.; Krimigis, S. M.

    1985-01-01

    Energetic particle observations in the outer heliosphere (approx 12 A. U.) by the LECP instruments on the Voyager 1 and Voyager 2 spacecraft are discussed that show a definite latitude dependence of the number and intensity of particle enhancements produced by corotating interplanetary regions during an interval when no solar energetic particle events were observed. The particle enhancements are fewer in number and less intense at higher (approx 20 deg.) heliolatitudes. However, the similar spectral shapes of the accelerated particles at the two spacecraft indicate that the acceleration process is the same at the two latitudes, but less intense at the higher latitude.

  1. Departure from corotation of the Io plasma torus - Local plasma production

    NASA Technical Reports Server (NTRS)

    Pontius, D. H., Jr.; Hill, T. W.

    1982-01-01

    The departure of the Jovian magnetosphere from rigid corotation is adequately explained by outward plasma transport at distances where L is greater than approximately 10. The departure of 5% observed in the Io plasma torus, however, is too large to be accounted for simply by plasma transport. Local plasma production is proposed as the main factor determining the corotation lag in the torus. The outward pick-up current provided by ionization of neutral atoms is calculated and related to the current produced in the ionosphere by the corotation lag. This leads to an expression giving the corotation lag of the torus as a function of radial distance. Charge transfer is found to be an important process, allowing the majority of the torus mass to be ejected from the magnetosphere in a neutral state. Thus, the mass loading rate is found to be several times that inferred from examination of the corotation lag associated with outward plasma transport.

  2. Magnetic activity of the star Corot-Exo-2a

    NASA Astrophysics Data System (ADS)

    Savanov, I. S.

    2010-05-01

    Continuous photometric observations of the young active solar-type star Corot-Exo-2a using the “Corot” space telescope obtained over 142 days were used to analyze the star’s surface temperature inhomogeneities and to monitor their continuous evolution. This analysis was based on the iPH code, which reconstructs the distribution of temperature inhomogeneities on the surface of a star based on its light curve in a two-temperature approximation. We identified five time intervals in the positions of active areas, with corresponding flip-flop events, interpreted as activity periods. Their durations were between 55 and 15 days. The time scale for the active-longitude flip-flops of Corot-Exo-2a is a few tens of days, rather than years, as for other stars studied earlier. We detected motions of the active longitudes, possibly indicating differential rotation of the star. The phenomenon of flip-flops in the positions of active longitudes has a complex character. This is the first case apart fromthe Sun where we are able to follow the appearance and development of temperature inhomogeneities on a stellar surface in such detail. We determined typical timescales for variations of the activity parameter of the star in the ranges 17-20, 28-32, 33-38, and 51-55 days, which characterize changes of the brightness variation amplitude, the spotted surface area, positions of active areas, and brightness variations.

  3. DIRECT OBSERVATION OF A COROTATING INTERACTION REGION BY THREE SPACECRAFT

    SciTech Connect

    Tappin, S. J. Howard, T. A

    2009-09-10

    White-light observations of interplanetary disturbances have been dominated by interplanetary coronal mass ejections (ICMEs). This is because the other type of disturbance, the corotating interaction region (CIR), has proved difficult to detect using white-light imagers. Recently, a number of papers have appeared presenting CIR observations using the Solar Terrestrial Relations Observatory (STEREO) Heliospheric Imagers (HIs), but have mostly only focused on a single spacecraft and imager. In this paper, we present observations of a single CIR that was observed by all three current white-light heliospheric imagers (SMEI and both STEREO HIs), as well as the in situ instruments on both STEREO satellites and ACE. We begin with a discussion of the geometry of the CIR structure, and show how the apparent leading edge structure is expected to change as it corotates relative to the observer. We use these calculations to predict elongation-time profiles for CIRs of different speeds for each of the imagers, and also to predict the arrival times at the in situ instruments. We show that although all three measured different parts, they combine to produce a self-consistent picture of the CIR. Finally, we offer some thoughts on why CIRs have proved so difficult to detect in white-light heliospheric images.

  4. PRE-DISCOVERY OBSERVATIONS OF CoRoT-1b AND CoRoT-2b WITH THE BEST SURVEY

    SciTech Connect

    Rauer, H.; Erikson, A.; Kabath, P.; Hedelt, P.; Csizmadia, Sz.; Paris, P. v.; Renner, S.; Titz, R.; Voss, H.; Boer, M.; Tournois, G.; Carone, L.; Eigmueller, P.

    2010-01-15

    The Berlin Exoplanet Search Telescope (BEST) wide-angle telescope installed at the Observatoire de Haute-Provence and operated in remote control from Berlin by the Institut fuer Planetenforschung, DLR, has observed the CoRoT target fields prior to the mission. The resulting archive of stellar photometric light curves is used to search for deep transit events announced during CoRoT's alarm mode to aid in fast photometric confirmation of these events. The 'initial run' field of CoRoT (IRa01) was observed with BEST in 2006 November and December for 12 nights. The first 'long run' field (LRc01) was observed from 2005 June to September for 35 nights. After standard CCD data reduction, aperture photometry has been performed using the ISIS image subtraction method. About 30,000 light curves were obtained in each field. Transits of the first detected planets by the CoRoT mission, CoRoT-1b and CoRoT-2b, were found in archived data of the BEST survey and their light curves are presented here. Such detections provide useful information at the early stage of the organization of follow-up observations of satellite alarm-mode planet candidates. In addition, no period change was found over {approx}4 years between the first BEST observation and last available transit observations.

  5. The role of resonances in the evolution of galactic disks

    NASA Astrophysics Data System (ADS)

    Lepine, Jacques; Scarano, Sergio; Andrievsky, Sergei; de Barros, Douglas A.; Junqueira, Thiago C.

    2015-03-01

    Resonances play an important role in the evolution of the disks of spiral galaxies, and in particular in the chemical abundance evolution. The dominant effect is that of corotation; this effect can be even used as a tool to estimate the age of the present spiral arm pattern, which are usually found to be long-lived, contrary to a recent common belief. We investigated a sample of galaxies for which the corotation radius is known and for which there are available in the literature measurements of abundance gradients for Oxygen. A very good correlation is found between corotation radii and the radii at which there is a break in the slope of the gradients. The gradients are usually decreasing in the inner regions and become flat or rising at larger radii. In several galaxies, including the Milky Way, one observes not only a change in the slope of the abundance gradient, but also an abrupt step in metallicity, at corotation. This step is due to the fact that corotation separates the disk of a galaxy in two regions (inside corotation and outside corotation) which are isolated one from the other, so that the two sides evolve in an independent way. The barrier between the two regions is produced by the flow of gas in opposite directions in the two sides and by the ring-shaped void of gas observed at corotation. Besides this, an independent effect of corotation is a minimum of star formation associated with the minimum velocity at which the spiral arms (seen as potential wells) are fed with interstellar gas. Still another effect is the scattering of stars by the resonance, which causes their migration to different galactic radii. Other resonances, like 4:1, have properties almost opposite to corotation; they stimulate star-formation, and tend to gather the stars in the resonant orbit, instead of scattering them out, as shown by numerical simulations. Due to this property, one can see arms which have the shape of resonant stellar orbits, which depart from logarithmic spirals.

  6. Rossby-Khantadze electromagnetic planetary vortical motions in the ionospheric E-layer

    NASA Astrophysics Data System (ADS)

    Kaladze, T. D.; Tsamalashvili, L. V.; Kahlon, L. Z.

    2011-12-01

    It is shown that in the earth's conductive ionospheric E-region, large-scale ultra low-frequency Rossby and Khantadze electromagnetic waves can propagate. Along with the prevalent effect of Hall conductivity for these waves, the latitudinal inhomogeneity of both the earth's angular velocity and the geomagnetic field becomes essential. Action of these effects leads to the coupled propagation of electromagnetic Rossby and Khantadze modes. Linear propagation properties of these waves are given in detail. It is shown that the waves lose the dispersing property for large values of wave numbers. Corresponding nonlinear solitary vortical structures are constructed. Conditions for such self-organization are given. It is shown that nonlinear large-scale vortices generate the stronger pulses of the geomagnetic field than the corresponding linear waves. Previous investigations are revised.

  7. The role of toroidal magnetic field on the Rossby wave instability

    NASA Astrophysics Data System (ADS)

    Gholipour, Mahmoud; Nejad-Asghar, Mohsen

    2015-05-01

    In the accretion discs, the toroidal magnetic fields and viscous stresses are directly connected to each other, because generation of the large-scale toroidal magnetic fields are produced by the magnetohydrodynamic (MHD) turbulence. Gholipour & Nejad-Asghar have recently shown that the effect of high turbulent viscosity on the Rossby wave instability (RWI) is important, while the effect of low turbulent viscosity can be ignored. In this paper, in addition of turbulent viscosity, we investigate the role of toroidal magnetic field on the non-axisymmetric RWI in the self-gravitating accretion discs. We use a numerical method to investigate stable and unstable modes. The results show that the perturbations of Rossby waves will be damped by both the viscosity and toroidal magnetic field, while the magnetic diffusivity acts vice versa. Also, occurrence of RWI depends on the turbulent magnetic Prandtl number (i.e. ratio of the turbulent viscosity to the turbulent magnetic diffusivity).

  8. Long-Range Radiation of Barotropic Rossby Waves from the Equatorial Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Farrar, J. T.; Durland, T.

    2014-12-01

    Analysis of sea-surface height (SSH) anomalies from satellite altimetry shows variability throughout the North Pacific that is coherent with Tropical Instability Waves. In the tropics (10N-20N) this variability has regular phase patterns that are consistent with barotropic Rossby waves having northward energy propagation (Farrar, J. Phys. Oceanogr., 2011). Further north, the phase patterns become confused and the variance decreases, but hot spots of coherent variability reemerge in the Gulf of Alaska and south of the Aleutian Islands. Ray-tracing calculations and comparisons with numerical simulations support the conclusion that this remote (and seemingly isolated) variability can indeed be attributed to barotropic Rossby waves generated near the equator and undergoing bathymetric refraction as they propagate northward.

  9. (2+1)-dimensional dissipation nonlinear Schrödinger equation for envelope Rossby solitary waves and chirp effect

    NASA Astrophysics Data System (ADS)

    Jin-Yuan, Li; Nian-Qiao, Fang; Ji, Zhang; Yu-Long, Xue; Xue-Mu, Wang; Xiao-Bo, Yuan

    2016-04-01

    In the past few decades, the (1+1)-dimensional nonlinear Schrödinger (NLS) equation had been derived for envelope Rossby solitary waves in a line by employing the perturbation expansion method. But, with the development of theory, we note that the (1+1)-dimensional model cannot reflect the evolution of envelope Rossby solitary waves in a plane. In this paper, by constructing a new (2+1)-dimensional multiscale transform, we derive the (2+1)-dimensional dissipation nonlinear Schrödinger equation (DNLS) to describe envelope Rossby solitary waves under the influence of dissipation which propagate in a plane. Especially, the previous researches about envelope Rossby solitary waves were established in the zonal area and could not be applied directly to the spherical earth, while we adopt the plane polar coordinate and overcome the problem. By theoretical analyses, the conservation laws of (2+1)-dimensional envelope Rossby solitary waves as well as their variation under the influence of dissipation are studied. Finally, the one-soliton and two-soliton solutions of the (2+1)-dimensional NLS equation are obtained with the Hirota method. Based on these solutions, by virtue of the chirp concept from fiber soliton communication, the chirp effect of envelope Rossby solitary waves is discussed, and the related impact factors of the chirp effect are given. Project supported by the National Natural Science Foundation of China (Grant No. 41406018).

  10. Generalized Investigation of the Rotation-Activity Relation: Favoring Rotation Period instead of Rossby Number

    NASA Astrophysics Data System (ADS)

    Reiners, A.; Schüssler, M.; Passegger, V. M.

    2014-10-01

    Magnetic activity in Sun-like and low-mass stars causes X-ray coronal emission which is stronger for more rapidly rotating stars. This relation is often interpreted in terms of the Rossby number, i.e., the ratio of rotation period to convective overturn time. We reconsider this interpretation on the basis of the observed X-ray emission and rotation periods of 821 stars with masses below 1.4 M ⊙. A generalized analysis of the relation between X-ray luminosity normalized by bolometric luminosity, L X/L bol, and combinations of rotational period, P, and stellar radius, R, shows that the Rossby formulation does not provide the solution with minimal scatter. Instead, we find that the relation L X/L bolvpropP -2 R -4 optimally describes the non-saturated fraction of the stars. This relation is equivalent to L XvpropP -2, indicating that the rotation period alone determines the total X-ray emission. Since L X is directly related to the magnetic flux at the stellar surface, this means that the surface flux is determined solely by the star's rotation and is independent of other stellar parameters. While a formulation in terms of a Rossby number would be consistent with these results if the convective overturn time scales exactly as L_bol-1/2, our generalized approach emphasizes the need to test a broader range of mechanisms for dynamo action in cool stars.

  11. Suppression of Atlantic Tropical Cyclone Activity by Extratropical Rossby Wave Breaking

    NASA Astrophysics Data System (ADS)

    Zhang, G.; Wang, Z.

    2014-12-01

    With warm SST anomalies in the tropical Atlantic and cold SST anomalies in the East Pacific, the reduced Atlantic tropical cyclone activity from August to early September in 2013 was a surprise to the hurricane community. Our analyses suggest that the suppressed storm activity can be attributed to the frequent occurrence of dry air in the middle to upper troposphere along with strong vertical wind shear. Such unfavorable conditions are directly related to the equatorward propagation and breaking of midlatitude Rossby waves, which lead to the equatorward intrusions of cold and dry extratropical air. Further examination suggests the active anti-cyclonic Rossby wave breaking and frequent equatorward intrusions of extratropical air in August 2013 were associated with changes of the midlatitude jet stream (i.e., acceleration, eastward extension and greater strain rate). The EOF analysis of 200-hPa zonal wind identifies a recurrent mode of interannual variability over Atlantic, which is associated with the variations of the intensity and zonal extent of the mid-latitude jet. This mode is found significantly correlated to Atlantic hurricane frequency in August, with a coefficient higher than the Nino3.4 index and comparable to the (relative) SST of Major Development Region (MDR). Our analyses thus emphasize the extratropical impacts on Atlantic tropical cyclones via the Rossby wave breaking. This physical link is missing in most statistical and hybrid forecast schemes and may help explain the seasonal prediction bust in 2013.

  12. On the seasonal distribution on Rossby wave breaking and their impact on weather variables

    NASA Astrophysics Data System (ADS)

    Schneidereit, Andrea; Peters, Dieter

    2014-05-01

    Rossby wave breaking on tropopause level is determined by the objective method according to Gabriel and Peters (2007). This method assumes that during the irreversible meridional overturning of potential vorticity contours the meridional component of the wave activity flux reaches its maximum value. According to the background flow, two different types of anticyclonic and two different types of cyclonic Rossby wave breaking can be distinguished. Analyzing seasonal cycle of the re-analysis data of the ECMWF, ERA-Interim, showing that the mean distributions of RWB events result mainly from the winter. Evaluating the composite distribution of precipitation and wind, reveal all four types are related with a special precipitation distribution. On the example of poleward anticyclonic RWB events, RWB-P2, a region can be identified where also the generation of inertia-gravity waves is possible. This region is located on the exit part of the breaking induced jet streak. A GCM model study with zonal mean ozone and added zonally asymmetric ozone in stratosphere was performed. The induced radiative changes in the stratosphere are causing changes of the location of Rossby wave breaking events in the upper troposphere. This results from the changing background flow in the lower stratosphere, which induce more diffluence over the eastern North Atlantic. As a result, the distribution of RWB-P2 events is shifted significantly westwards.

  13. Barotropic and baroclinic instability of Rossby waves on the infinite beta-plane

    NASA Astrophysics Data System (ADS)

    Anderson, Jeffrey L.

    The normal mode instability problem for a stationary Rossby wave of finite amplitude and arbitrary orientation in a two-level model with zonal mean shear in the vertical is examined on the infinite beta-plane using a Floquet technique. The results are compared to the instability of a finite amplitude stationary Rossby wave in a barotropic model. The instability of the barotropic model linearized about the upper level flow of the stationary two-level Rossby wave is also examined; forcing must be introduced to the barotropic equations in this case to balance the time tendency of the basic state. The instabilities of the three models are compared in an attempt to address two questions. First, are the barotropic instabilities related to any of the two-level model instabilities? Second, what are the consequences of introducing forcing in the stability problem? It is found that the barotropic models accurately reproduce those instabilities of the two-level model that have a nearly barotropic structure; these are not necessarily low-frequency instabilities. The introduction of forcing is found to have a significant impact on the barotropic instabilities. Special emphasis is placed on parameter ranges judged to be analogous to the mid-latitude atmosphere. Possible relevance of the results to geophysical flows and the instability problem on the sphere are discussed.

  14. Observations of rossby wave propagation in the Northeast Atlantic with topex/poseidon altimetry

    NASA Astrophysics Data System (ADS)

    Cipollini, P.; Cromwell, D.; Quartly, G. D.

    1998-11-01

    A technique is described to observe Rossby waves in the oceans using altimeter data, which makes use of longitude/time diagrams of sea surface height anomalies at a given latitude, relying on the zonal propagation of those waves. By means of the Fast Fourier and Radon Transforms of the longitude/time diagrams it is possible to locate the spectral components corresponding to wave propagation and to give an approximate estimation of some of their characteristics such as their height and speed. The results obtained by using data from the TOPEX/POSEIDON radar altimeters in the Northeast Atlantic highlight a narrow `preferred' zonal band of propagation for Rossby waves around 33°-34° N. The speeds of the dominant signals at different latitudes have been computed both in Fourier space and in Radon space: they are in good agreement with the prediction of a revised theory of Rossby wave propagation, which has recently been introduced to explain the discrepancy between observed wave speeds and the speeds computed from the classical theory.

  15. Inhomogeneous closure and statistical mechanics for Rossby wave turbulence over topography

    NASA Astrophysics Data System (ADS)

    Frederiksen, Jorgen S.; O'Kane, Terence J.

    2005-09-01

    The quasi-diagonal direct interaction approximation (QDIA) closure theory is formulated for the interaction of mean fields, Rossby waves and inhomogeneous turbulence over topography on a generalized beta-plane. An additional small term, corresponding to the solid-body rotation vorticity on the sphere, is included in the barotropic equation and it is shown that this results in a one-to-one correspondence between the dynamical equations, Rossby wave dispersion relations, nonlinear stability criteria and canonical equilibrium theory on the generalized beta-plane and on the sphere. The dynamics, kinetic energy spectra, mean field structures and mean streamfunction tendencies contributed by transient eddies are compared with the ensemble-averaged results from direct numerical simulations (DNS) at moderate resolution. A series of numerical experiments is performed to examine the generation of Rossby waves when eastward large-scale flows impinge on a conical mountain in the presence of moderate to strong two-dimensional turbulence. The ensemble predictability of northern hemisphere flows in 10-day forecasts is also examined on a generalized beta-plane. In all cases, the QDIA closure is found to be in very good agreement with the statistics of DNS except in situations of strong turbulence and weak mean fields where ensemble-averaged DNS fails to predict mean field amplitudes correctly owing to sampling problems even with as many as 1800 ensemble members.

  16. Role of SST meridional structure in coupling the Kelvin and Rossby waves of the intraseasonal oscillation

    NASA Astrophysics Data System (ADS)

    Liu, Fei; Huang, Gang; Yan, Mi

    2015-08-01

    The intraseasonal oscillation (ISO) is one of the most important modes of the tropical atmosphere, which influences global livelihood of hundreds of millions of people. The meridional structure of sea surface temperature (SST) has been found to be important for the ISO simulation in general circulation models (GCMs). Using a theoretical frictional skeleton model for the ISO, we investigate the effects of different SST structures on the ISO in this study. The model results show that the observed Madden-Julian oscillation (MJO), boreal summer ISO (BSISO) and quasi-biweekly oscillation can be simulated in this model with different SST structures. The Ekman pumping of the boundary layer associated with equatorially trapped SST favors the growth of eastward propagating Kelvin waves and prefers the fast eastward propagating signal. A broad SST provides a strong instability source for the Rossby waves, which will slow down the MJO. In the boreal summer, the high SST center in the off-equatorial region can trigger strong off-equatorial moisture pumping from the boundary layer, which enhances the Rossby waves and can simulate the northwest-southeast tilted rain band associated with the BSISO. When the Rossby component overwhelms the Kelvin component, the low-frequency westward component of the BSISO and the higher-frequency quasi-biweekly oscillation can be simulated.

  17. The CoRoT transit candidate catalog

    NASA Astrophysics Data System (ADS)

    Aigrain, S.; Deleuil, M.

    2013-09-01

    We present a full catalog of all the candidate transiting planets identified by the CoRoT space mission during its first 5 years of operations, including homogeneously derived transit parameters, validation diagnostics and a summary of the outcome of follow-up observations, where available.The catalog includes confirmed planets, clear false alarms (mainly blended or grazing eclipsing binaries), but also dozens of unconfirmed cases, where the follow-up was either inconclusive (hot stars, fast rotators) or incomplete (owing to limited telescope time and the relatively faint nature of the CoRoT targets). The catalog is intended primarily as a resource for the community, for example as a starting point for completeness and population studies. The candidate detection and selection processes have evolved significantly over the course of the mission. Several teams independently analyse the light curves from each observing run, searching for transits and providing ranked candidate lists, which are subsequently merged and ranked manually. This enables the use of some specialist methods, which are better suited to the detection of only certain types of transits, but makes it difficult to provide an overall assessment of the sensitivity of the mission to transits of different depths and periods. However, we note the transit search methods used by the different teams have gradually converged since launch, and there are now fewer teams actively involved in the transit search, with more overlap between the resulting candidate lists. For each CoRoT observing run, one team member coordinates the selection of candidates for followup, with input from the other team members. The set of criteria used to perform this selection have also evolved over the years, becoming more homogeneous. In particular, the light curve fitting tools used to produce the transit parameters and other diagnostics, which are included in the present catalog, are now routinely used to validate candidates and

  18. VizieR Online Data Catalog: CoRoT observation log (N2-4.4) (CoRoT 2016)

    NASA Astrophysics Data System (ADS)

    COROT Team

    2014-03-01

    CoRoT, a space astronomy mission, has measured photometric micro-variability of stars from minutes to months (up to 150 days) with a high duty cycle (more than 90%). The mission was led by CNES in association with four French laboratories and 7 participating countries and agencies (Austria, Belgium, Brazil, Germany, Spain, and the ESA Science Programme). The satellite was composed of a PROTEUS platform (the 3rd in the series) and a unique instrument: a stellar rapid photometer. It was launched on December 27th 2006 by a Soyuz Rocket, from Bakonour. The mission has lasted almost 6 years (the nominal 3-year duration and a 3-year extension) and has observed more than 160 000 stars. It stopped sending data on November 2nd 2012. Two regions of the sky were accessible for long period of time: circles of 10 degrees centered on the equator around alpha=06:50 and alpha=18:50. They were called the CoRoT eyes: the "anticenter" and the "center eye" (as they are approximately in these directions). Each pointing covers 1.4x2.8 square degrees within one of those CoRoT eyes. The original scientific objectives were focussed on the study of stellar pulsations (asteroseismology) to probe the internal structure of stars, and the detection of small exoplanets through their "transit" in front of their host star, and the measurement of their size. This lead to introduce two modes of observations, working simultaneously: - The "bright star" mode dedicated to very precise seismology of a small sample of bright and closeby stars - The "faint star" mode, observing a very large number of stars at the same time, to detect transits, which are rare events, as they imply the alignment of the star, the planet and the observer. The large amount of data gathered in this mode turned out to be extremely fruitful for many topics of stellar physics. Beyond these two initial objectives, CoRoT data revealed stellar variability associated with various other phenomena: granulation, rotational modulation by

  19. VizieR Online Data Catalog: CoRoT observation log (N2-4.4) (CoRoT 2016)

    NASA Astrophysics Data System (ADS)

    COROT Team

    2014-03-01

    CoRoT, a space astronomy mission, has measured photometric micro-variability of stars from minutes to months (up to 150 days) with a high duty cycle (more than 90%). The mission was led by CNES in association with four French laboratories and 7 participating countries and agencies (Austria, Belgium, Brazil, Germany, Spain, and the ESA Science Programme). The satellite was composed of a PROTEUS platform (the 3rd in the series) and a unique instrument: a stellar rapid photometer. It was launched on December 27th 2006 by a Soyuz Rocket, from Bakonour. The mission has lasted almost 6 years (the nominal 3-year duration and a 3-year extension) and has observed more than 160 000 stars. It stopped sending data on November 2nd 2012. Two regions of the sky were accessible for long period of time: circles of 10 degrees centered on the equator around alpha=06:50 and alpha=18:50. They were called the CoRoT eyes: the "anticenter" and the "center eye" (as they are approximately in these directions). Each pointing covers 1.4x2.8 square degrees within one of those CoRoT eyes. The original scientific objectives were focussed on the study of stellar pulsations (asteroseismology) to probe the internal structure of stars, and the detection of small exoplanets through their "transit” in front of their host star, and the measurement of their size. This lead to introduce two modes of observations, working simultaneously: - The “bright star” mode dedicated to very precise seismology of a small sample of bright and closeby stars - The “faint star” mode, observing a very large number of stars at the same time, to detect transits, which are rare events, as they imply the alignment of the star, the planet and the observer. The large amount of data gathered in this mode turned out to be extremely fruitful for many topics of stellar physics. Beyond these two initial objectives, CoRoT data revealed stellar variability associated

  20. The high-energy environment in the super-Earth system CoRoT-7

    NASA Astrophysics Data System (ADS)

    Poppenhaeger, K.; Czesla, S.; Schröter, S.; Lalitha, S.; Kashyap, V.; Schmitt, J. H. M. M.

    2012-05-01

    High-energy irradiation of exoplanets has been identified to be a key influence on the stability of these planets' atmospheres. So far, irradiation-driven mass-loss has been observed only in two Hot Jupiters, and the observational data remain even more sparse in the super-Earth regime. We present an investigation of the high-energy emission in the CoRoT-7 system, which hosts the first known transiting super-Earth. To characterize the high-energy XUV radiation field into which the rocky planets CoRoT-7b and CoRoT-7c are immersed, we analyzed a 25 ks XMM-Newton observation of the host star. Our analysis yields the first clear (3.5σ) X-ray detection of CoRoT-7. We determine a coronal temperature of ≈ 3 MK and an X-ray luminosity of 3 × 1028 erg s-1. The level of XUV irradiation on CoRoT-7b amounts to ≈37 000 erg cm-2 s-1. Current theories for planetary evaporation can only provide an order-of-magnitude estimate for the planetary mass loss; assuming that CoRoT-7b has formed as a rocky planet, we estimate that CoRoT-7b evaporates at a rate of about 1.3 × 1011 g s-1 and has lost ≈4-10 earth masses in total.

  1. GAUDI: A Preparatory Archive for the COROT Mission

    NASA Astrophysics Data System (ADS)

    Solano, E.; Catala, C.; Garrido, R.; Poretti, E.; Janot-Pacheco, E.; Gutiérrez, R.; González, R.; Mantegazza, L.; Neiner, C.; Fremat, Y.; Charpinet, S.; Weiss, W.; Amado, P. J.; Rainer, M.; Tsymbal, V.; Lyashko, D.; Ballereau, D.; Bouret, J. C.; Hua, T.; Katz, D.; Lignières, F.; Lüftinger, T.; Mittermayer, P.; Nesvacil, N.; Soubiran, C.; van't Veer-Menneret, C.; Goupil, M. J.; Costa, V.; Rolland, A.; Antonello, E.; Bossi, M.; Buzzoni, A.; Rodrigo, C.; Aerts, C.; Butler, C. J.; Guenther, E.; Hatzes, A.

    2005-01-01

    The GAUDI database (Ground-based Asteroseismology Uniform Database Interface) is a preparatory archive for the COROT (Convection, Rotation, and Planetary Transits) mission developed at the Laboratorio de Astrofísica Espacial y Física Fundamental (Laboratory for Space Astrophysics and Theoretical Physics, Spain). Its intention is to make the ground-based observations obtained in preparation of the asteroseismology program available in a simple and efficient way. It contains spectroscopic and photometric data together with inferred physical parameters for more than 1500 objects gathered since 1998 January 1998 in 6 years of observational campaigns. In this paper, the main functions and characteristics of the system are described. Based on observations collected at La Silla (ESO proposals 67.D-0169, 69.D-0166, and 70.D-0110), Telescopio Nazionale Galileo (proposal 6-20-068), Observatoire de Haute-Provence, the South African Astronomical Observatory, Tautenburg Observatory, and Sierra Nevada Observatory.

  2. Effects of corotating interaction regions on ULYSSES high energy particles

    SciTech Connect

    Droege, W.; Kunow, H.; Raviart, A.

    1995-09-01

    Since June 1992 the Kiel Electron Telescope on board ULYSSES measures variations of more than 10% in the fluxes of high energy H and He showing a periodicity of about 26 days in coincidence with the passage of corotating interaction regions. (CIR). At low energies MeV protons are accelerated at the shocks of the CIRs. These effects are observed up to high southern latitudes, where the signature of a CIR is no longer visible in plasma or magnetic field data. After passing over the south polar cap ULYSSES has now returned to the solar equator and climbs up to the north pole. In this paper we study the relative intensity variations with latitude and the latitude dependence at solar distances smaller than ever studied before.

  3. Transiting exoplanets from the CoRoT space mission. XXVI. CoRoT-24: a transiting multiplanet system

    NASA Astrophysics Data System (ADS)

    Alonso, R.; Moutou, C.; Endl, M.; Almenara, J.-M.; Guenther, E. W.; Deleuil, M.; Hatzes, A.; Aigrain, S.; Auvergne, M.; Baglin, A.; Barge, P.; Bonomo, A. S.; Bordé, P.; Bouchy, F.; Cavarroc, C.; Cabrera, J.; Carpano, S.; Csizmadia, Sz.; Cochran, W. D.; Deeg, H. J.; Díaz, R. F.; Dvorak, R.; Erikson, A.; Ferraz-Mello, S.; Fridlund, M.; Fruth, T.; Gandolfi, D.; Gillon, M.; Grziwa, S.; Guillot, T.; Hébrard, G.; Jorda, L.; Léger, A.; Lammer, H.; Lovis, C.; MacQueen, P. J.; Mazeh, T.; Ofir, A.; Ollivier, M.; Pasternacki, T.; Pätzold, M.; Queloz, D.; Rauer, H.; Rouan, D.; Santerne, A.; Schneider, J.; Tadeu dos Santos, M.; Tingley, B.; Titz-Weider, R.; Weingrill, J.; Wuchterl, G.

    2014-07-01

    We present the discovery of a candidate multiply transiting system, the first one found in the CoRoT mission. Two transit-like features with periods of 5.11 and 11.76 d are detected in the CoRoT light curve around a main sequence K1V star of r = 15.1. If the features are due to transiting planets around the same star, these would correspond to objects of 3.7 ± 0.4 and 5.0 ± 0.5 R⊕ , respectively. Several radial velocities serve to provide an upper limit of 5.7 M⊕ for the 5.11 d signal and to tentatively measure a mass of 28+11-11 M⊕ for the object transiting with a 11.76 d period. These measurements imply low density objects, with a significant gaseous envelope. The detailed analysis of the photometric and spectroscopic data serves to estimate the probability that the observations are caused by transiting Neptune-sized planets as much as over 26 times higher than a blend scenario involving only one transiting planet and as much as over 900 times higher than a scenario involving two blends and no planets. The radial velocities show a long-term modulation that might be attributed to a 1.5 MJup planet orbiting at 1.8 AU from the host, but more data are required to determine the precise orbital parameters of this companion. The CoRoT space mission, launched on 27 December 2006, has been developed and is operated by the CNES, with the contribution of Austria, Belgium, Brazil, ESA (RSSD and Science Program), Germany, and Spain. Some of the observations were made with the HARPS spectrograph at ESO La Silla Observatory (184.C-0639) and with the HIRES spectrograph at the Keck Telescope (N035Hr, N143Hr 260 and N095Hr). Partly based on observations obtained at ESO Paranal Observatory, Chile (086.C-0235(A) and B).Tables 2-4 and Fig. 12 are available in electronic form at http://www.aanda.org

  4. Expected Performance of the CoRoT Planet Search from Light Curve Beauty Contests

    NASA Astrophysics Data System (ADS)

    Moutou, C.; Aigrain, S.; Almenara, J.; Alonso, R.; Auvergne, M.; Barge, P.; Blouin, D.; Borde, P.; Cabrera, J.; Carone, L.; Cautain, R.; Deeg, H.; Erikson, A.; Fressin, F.; Guis, V.; Leger, A.; Guterman, P.; Irwin, M.; Kabath, P.; Lanza, A.; Maceroni, C.; Mazeh, T.; Ollivier, M.; Pont, F.; Paetzold, M.; Queloz, D.; Rauer, H.; Rouan, D.; Schneider, J.; Tamuz, O.; Voss, H.; Zucker, S.

    2007-07-01

    The CoRoT space mission, scheduled for launch in December 2006, has two primary science goals: asteroseismology and the detection of planetary transits, the latter being the subject of this contribution. Given its expected photometric performance and its 150 day observing window, CoRoT will detect planets with periods up to 75 days and radii down to 2 Earth radii. To prepare for the data analysis and evaluate the detection limits of the mission, a number of blind exercises to detect planets in simulated light curves have been carried out within the CoRoT exoplanet community, and their results to date are summarized here.

  5. WARM SPITZER PHOTOMETRY OF THE TRANSITING EXOPLANETS CoRoT-1 AND CoRoT-2 AT SECONDARY ECLIPSE

    SciTech Connect

    Deming, Drake; Knutson, Heather; Agol, Eric; Cowan, Nicolas B.; Desert, Jean-Michel; Charbonneau, David; Burrows, Adam; Fortney, Jonathan J.; Laughlin, Gregory; Langton, Jonathan; Showman, Adam P.; Lewis, Nikole K.

    2011-01-10

    We measure secondary eclipses of the hot giant exoplanets CoRoT-1 at 3.6 and 4.5 {mu}m, and CoRoT-2 at 3.6 {mu}m, both using Warm Spitzer. We find that the Warm Spitzer mission is working very well for exoplanet science. For consistency of our analysis we also re-analyze archival cryogenic Spitzer data for secondary eclipses of CoRoT-2 at 4.5 and 8 {mu}m. We compare the total data for both planets, including optical eclipse measurements by the CoRoT mission, and ground-based eclipse measurements at 2 {mu}m, to existing models. Both planets exhibit stronger eclipses at 4.5 than at 3.6 {mu}m, which is often indicative of an atmospheric temperature inversion. The spectrum of CoRoT-1 is best reproduced by a 2460 K blackbody, due either to a high altitude layer that strongly absorbs stellar irradiance, or an isothermal region in the planetary atmosphere. The spectrum of CoRoT-2 is unusual because the 8 {mu}m contrast is anomalously low. Non-inverted atmospheres could potentially produce the CoRoT-2 spectrum if the planet exhibits line emission from CO at 4.5 {mu}m, caused by tidal-induced mass loss. However, the viability of that hypothesis is questionable because the emitting region cannot be more than about 30% larger than the planet's transit radius, based on the ingress and egress times at eclipse. An alternative possibility to account for the spectrum of CoRoT-2 is an additional opacity source that acts strongly at wavelengths less than 5 {mu}m, heating the upper atmosphere while allowing the deeper atmosphere seen at 8 {mu}m to remain cooler. We obtain a similar result as Gillon et al. for the phase of the secondary eclipse of CoRoT-2, implying an eccentric orbit with e cos({omega}) = -0.0030 {+-} 0.0004.

  6. Transiting exoplanets from the CoRoT space mission. XXV. CoRoT-27b: a massive and dense planet on a short-period orbit

    NASA Astrophysics Data System (ADS)

    Parviainen, H.; Gandolfi, D.; Deleuil, M.; Moutou, C.; Deeg, H. J.; Ferraz-Mello, S.; Samuel, B.; Csizmadia, Sz.; Pasternacki, T.; Wuchterl, G.; Havel, M.; Fridlund, M.; Angus, R.; Tingley, B.; Grziwa, S.; Korth, J.; Aigrain, S.; Almenara, J. M.; Alonso, R.; Baglin, A.; Barros, S. C. C.; Bordé, P.; Bouchy, F.; Cabrera, J.; Díaz, R. F.; Dvorak, R.; Erikson, A.; Guillot, T.; Hatzes, A.; Hébrard, G.; Mazeh, T.; Montagnier, G.; Ofir, A.; Ollivier, M.; Pätzold, M.; Rauer, H.; Rouan, D.; Santerne, A.; Schneider, J.

    2014-02-01

    Aims: We report the discovery of a massive and dense transiting planet CoRoT-27b on a 3.58-day orbit around a 4.2 Gyr-old G2 star. The planet candidate was identified from the CoRoT photometry, and was confirmed as a planet with ground-based spectroscopy. Methods: The confirmation of the planet candidate is based on radial velocity observations combined with imaging to rule out blends. The characterisation of the planet and its host star was carried out using a Bayesian approach where all the data (CoRoT photometry, radial velocities, and spectroscopic characterisation of the star) are used jointly. The Bayesian analysis included a study whether the assumption of white normally distributed noise holds for the CoRoT photometry and whether the use of a non-normal noise distribution offers advantages in parameter estimation and model selection. Results: CoRoT-27b has a mass of 10.39 ± 0.55MJup, a radius of 1.01 ± 0.04RJup, a mean density of 12.6-1.67+1.92g cm-3, and an effective temperature of 1500 ± 130 K. The planet orbits around its host star, a 4.2 Gyr-old G2-star with a mass M⋆ = 1.06M⊙ and a radius R⋆ = 1.05R⊙, on a 0.048 ± 0.007 AU orbit of 3.58 days. The radial velocity observations allow us to exclude highly eccentric orbits, namely, e < 0.065 with 99% confidence. Given its high mass and density, theoretical modelling of CoRoT-27b is demanding. We identify two solutions with heavy element mass fractions of 0.11 ± 0.08M⊕ and 0.07 ± 0.06M⊕, but even solutions void of heavy elements cannot be excluded. We carry out a secondary eclipse search from the CoRoT photometry using a method based on Bayesian model selection, but conclude that the noise level is too high to detect eclipses shallower than 9% of the transit depth. Using a non-normal noise model was shown not to affect the parameter estimation results, but led to significant improvement in the sensitivity of the model selection process. The CoRoT space mission, launched on December 27, 2006

  7. CoRoT-7b: SUPER-EARTH OR SUPER-Io?

    SciTech Connect

    Barnes, Rory; Kaib, Nathan A.; Raymond, Sean N.; Greenberg, Richard; Jackson, Brian

    2010-02-01

    CoRoT-7b, a planet about 70% larger than the Earth orbiting a Sun-like star, is the first-discovered rocky exoplanet, and hence has been dubbed a 'super-Earth'. Some initial studies suggested that since the planet is so close to its host star, it receives enough insolation to partially melt its surface. However, these past studies failed to take into consideration the role that tides may play in this system. Even if the planet's eccentricity has always been zero, we show that tidal decay of the semimajor axis could have been large enough that the planet formed on a wider orbit which received less insolation. Moreover, CoRoT-7b could be tidally heated at a rate that dominates its geophysics and drives extreme volcanism. In this case, CoRoT-7b is a 'super-Io' that, like Jupiter's volcanic moon, is dominated by volcanism and rapid resurfacing. Such heating could occur with an eccentricity of just 10{sup -5}. This small value could be driven by CoRoT-7c if its own eccentricity is larger than {approx}10{sup -4}. CoRoT-7b may be the first of a class of planetary super-Ios likely to be revealed by the CoRoT and Kepler spacecraft.

  8. Planets and Stellar Activity: Hide and Seek in the CoRoT-7 system

    NASA Astrophysics Data System (ADS)

    Haywood, R. D.; Cameron, A. C.; Queloz, D.; Barros, S. C. C.; Deleuil, M.; Fares, R.; Gillon, M.; Hatzes, A.; Lanza, A. F.; Lovis, C.; Moutou, C.; Pepe, F.; Pollacco, D.; Santerne, A.; Ségransan, D.; Unruh, Y.

    2014-01-01

    Since the discovery of the transiting Super-Earth CoRoT-7b, several investigations have been made of the number and precise masses of planets present in the system, but they all yield different results, owing to the star's high level of activity. Radial velocity (RV) variations induced by stellar activity therefore need to be modelled and removed to allow a reliable detection of all planets in the system. We re-observed CoRoT-7 in January 2012 with both HARPS and the CoRoT satellite, so that we now have the benefit of simultaneous RV and photometric data. We fitted the off-transit variations in the CoRoT lightcurve using a harmonic decomposition similar to that implemented in Queloz et al. (2009). This fit was then used to model the stellar RV contribution, according to the methods described by Aigrain et al. (2011). This model was incorporated into a Monte Carlo Markov Chain in order to make a precise determination of the orbits of CoRoT-7b and CoRoT-7c. We also assess the evidence for the presence of one or two additional planetary companions.

  9. CoRoT-7b: Super-Earth or Super-Io?

    NASA Astrophysics Data System (ADS)

    Barnes, Rory; Raymond, Sean N.; Greenberg, Richard; Jackson, Brian; Kaib, Nathan A.

    2010-02-01

    CoRoT-7b, a planet about 70% larger than the Earth orbiting a Sun-like star, is the first-discovered rocky exoplanet, and hence has been dubbed a "super-Earth." Some initial studies suggested that since the planet is so close to its host star, it receives enough insolation to partially melt its surface. However, these past studies failed to take into consideration the role that tides may play in this system. Even if the planet's eccentricity has always been zero, we show that tidal decay of the semimajor axis could have been large enough that the planet formed on a wider orbit which received less insolation. Moreover, CoRoT-7b could be tidally heated at a rate that dominates its geophysics and drives extreme volcanism. In this case, CoRoT-7b is a "super-Io" that, like Jupiter's volcanic moon, is dominated by volcanism and rapid resurfacing. Such heating could occur with an eccentricity of just 10-5. This small value could be driven by CoRoT-7c if its own eccentricity is larger than ~10-4. CoRoT-7b may be the first of a class of planetary super-Ios likely to be revealed by the CoRoT and Kepler spacecraft.

  10. Generalized investigation of the rotation-activity relation: favoring rotation period instead of Rossby number

    SciTech Connect

    Reiners, A.; Passegger, V. M.; Schüssler, M.

    2014-10-20

    Magnetic activity in Sun-like and low-mass stars causes X-ray coronal emission which is stronger for more rapidly rotating stars. This relation is often interpreted in terms of the Rossby number, i.e., the ratio of rotation period to convective overturn time. We reconsider this interpretation on the basis of the observed X-ray emission and rotation periods of 821 stars with masses below 1.4 M {sub ☉}. A generalized analysis of the relation between X-ray luminosity normalized by bolometric luminosity, L {sub X}/L {sub bol}, and combinations of rotational period, P, and stellar radius, R, shows that the Rossby formulation does not provide the solution with minimal scatter. Instead, we find that the relation L {sub X}/L {sub bol}∝P {sup –2} R {sup –4} optimally describes the non-saturated fraction of the stars. This relation is equivalent to L {sub X}∝P {sup –2}, indicating that the rotation period alone determines the total X-ray emission. Since L {sub X} is directly related to the magnetic flux at the stellar surface, this means that the surface flux is determined solely by the star's rotation and is independent of other stellar parameters. While a formulation in terms of a Rossby number would be consistent with these results if the convective overturn time scales exactly as L{sub bol}{sup −1/2}, our generalized approach emphasizes the need to test a broader range of mechanisms for dynamo action in cool stars.

  11. The Effect of Surface Topography on the Nonlinear Dynamics of Rossby Waves

    NASA Technical Reports Server (NTRS)

    Abarzhi, S. I.; Desjardins, O.; Pitsch, H.

    2003-01-01

    Boussinesq convection in rotating systems attracts a sustained attention of the fluid dynamics community, because it has intricate non-linear dynamics (Cross & Hohenberg 1993) and plays an important role in geophysical and astrophysical applications, such as the motion of the liquid outer core of Earth, the Red Spot in Jupiter, the giant cells in the Sun etc. (Alridge et al. 1990). A fundamental distinction between the real geo- and astrophysical problems and the idealized laboratory studies is that natural systems are inhomogeneous (Alridge et al. 1990). Heterogeneities modulate the flow and influence significantly the dynamics of convective patterns (Alridge et al. 1990; Hide 1971). The effect of modulations on pattern formation and transition to turbulence in Boussinesq convection is far from being completely understood (Cross & Hohenberg 1993; Aranson & Kramer 2002). It is generally accepted that in the liquid outer core of the Earth the transport of the angular momentum and internal heat occurs via thermal Rossby waves (Zhang et al. 2001; Kuang & Bloxham 1999). These waves been visualized in laboratory experiments in rotating liquid-filled spheres and concentric spherical shells (Zhang et al. 2001; Kuang & Bloxham 1999). The basic dynamical features of Rossby waves have been reproduced in a cylindrical annulus, a system much simpler than the spherical ones (Busse & Or 1986; Or & Busse 1987). For convection in a cylindrical annulus, the fluid motion is two-dimensional, and gravity is replaced by a centrifugal force, (Busse & Or 1986; Or & Busse 1987). Hide (1971) has suggested that the momentum and heat transport in the core might be influenced significantly by so-called bumps, which are heterogeneities on the mantle-core boundary. To model the effect of surface topography on the transport of momentum and energy in the liquid outer core of the Earth, Bell & Soward (1996), Herrmann & Busse (1998) and Westerburg & Busse (2001) have studied the nonlinear dynamics

  12. Shear flow driven Rossby-Khantadze electromagnetic planetary vortices in the ionospheric E-layer

    NASA Astrophysics Data System (ADS)

    Kaladze, T. D.; Kahlon, L. Z.; Horton, W.; Pokhotelov, O.; Onishchenko, O.

    2014-04-01

    A system of equations describing the nonlinear interaction of coupled Rossby-Khantadze electromagnetic waves with a sheared zonal flow in the Earth's ionospheric E-layer is obtained. For the linear regime the corresponding region of phase velocities is analyzed and the appropriate stability condition of zonal flow is deduced. It is shown that the sheared zonal flow may excite solitary vortical structures in the form of a row of counter-rotating vortices whose amplitudes decrease with the increase of the zonal flow parameter. This conclusion is consistent with the stabilizing idea of a sheared zonal flow. The possibility of an intense magnetic-field generation is shown.

  13. Nonaxisymmetric Rossby vortex instability with toroidal magnetic fields in structured disks

    SciTech Connect

    Yu, Cong; Li, Hui

    2009-01-01

    We investigate the global nonaxisymmetric Rossby vortex instability (RVI) in a differentially rotating, compressible magnetized accretion disk with radial density structures. Equilibrium magnetic fields are assumed to have only the toroidal component. Using linear theory analysis, we show that the density structure can be unstable to nonaxisymmetric modes. We find that, for the magnetic field profiles we have studied, magnetic fields always provide a stabilizing effect to the unstable RVI modes. We discuss the physical mechanism of this stabilizing effect. The threshold and properties of the unstable modes are also discussed in detail. In addition, we present linear stability results for the global magnetorotational instability when the disk is compressible.

  14. Conservation laws of wave action and potential enstrophy for Rossby waves in a stratified atmosphere

    NASA Technical Reports Server (NTRS)

    Straus, D. M.

    1983-01-01

    The evolution of wave energy, enstrophy, and wave motion for atmospheric Rossby waves in a variable mean flow are discussed from a theoretical and pedagogic standpoint. In the absence of mean flow gradients, the wave energy density satisfies a local conservation law, with the appropriate flow velocity being the group velocity. In the presence of mean flow variations, wave energy is not conserved, but wave action is, provided the mean flow is independent of longitude. Wave enstrophy is conserved for arbitrary variations of the mean flow. Connections with Eiiassen-Palm flux are also discussed.

  15. Conservation laws of wave action and potential enstrophy for Rossby waves in a stratified atmosphere

    NASA Technical Reports Server (NTRS)

    Straus, D. M.

    1983-01-01

    The evolution of wave energy, enstrophy, and wave motion for atmospheric Rossby waves in a variable mean flow are discussed from a theoretical and pedagogic standpoint. In the absence of mean flow gradients, the wave energy density satisfies a local conservation law, with the appropriate flow velocity being the group velocity. In the presence of mean flow variations, wave energy is not conserved, but wave action is, provided the mean flow is independent of longitude. Wave enstrophy is conserved for arbitrary variations of the mean flow. Connections with Eliassen-Palm flux are also discussed.

  16. Corotation lag limit on mass-loss rate from Io

    NASA Technical Reports Server (NTRS)

    Huang, T. S.; Siscoe, G. L.

    1987-01-01

    Considering rapid escape of H2O from Io during an early hot evolutionary epoch, an H2O plasma torus is constructed by balancing dissociation and ionization products against centrifugally driven diffusion, including for the first time the effects of corotation lag resulting from mass loading. Two fundamental limits are found as the mass injection rate increases: (1) an 'ignition' limit of 1.1 x 10 to the 6th kg/s, beyond which the torus cannot ionize itself and photoionization dominates; and (2) the ultimate mass loading limit of 1.3 x 10 to the 7th kg/s, which occurs when neutrals newly created by charge exchange and recombination cannot leave the torus, thereby bringing magnetospherically driven transport to a halt. Connecting this limit with the variations of Io's temperature in its early evolution epoch gives an estimate of the upper limit on the total mass loss from Io, about 3.0 x 10 to the 20th kg (for high-opacity nebula) and about 8.9 x 10 to the 20th kg (for low-opacity nebula). These limits correspond to eroding 8 km and 22 km of H2O from the surface. It is concluded that compared to the other Galilean satellites, Io was created basically dry.

  17. Effects of corotating interaction regions on Ulysses high energy particles

    SciTech Connect

    Droege, W.; Kunow, H.; Heber, B.; Mueller-Mellin, R.; Sierks, H.; Wibberenz, G.; Raviart, A.; Ducros, R.; Ferrando, P.; Rastoin, C.; Gosling, J.T.

    1996-07-01

    We investigate the intensity variation of low energy ({approximately}6{endash}23MeV/N) heliospheric ions and of galactic protons (250{endash}2200 MeV) observed by the Kiel Electron Telescope onboard the Ulysses spacecraft associated with Corotating Interaction Regions (CIR) from mid-1992 to end of June 1995. This period covers Ulysses{close_quote} transit to high southern latitudes, the south polar pass, return to the solar equator and ascent to the north pole up to 70{degree}. We find that the flux of high energy protons exhibits a periodicity of about 26 days with a relative intensity variation of 10{percent}. At latitudes below {approximately}50{degree} the recurrent variations of galactic protons are in coincidence with the passage of CIRs and enhancements of low energies protons and alpha particles which are accelerated at the shocks of the CIRs. The modulation of galactic protons is observed up to high southern latitudes, where the signatures of a CIR are no longer visible in plasma or magnetic field data. The periodicity does not depend on latitude and its phase apparently remains constant during Ulysses{close_quote} pass over the south pole as well as through the solar equator. {copyright} {ital 1996 American Institute of Physics.}

  18. Suprathermal helium associated with corotating interaction regions: A case study

    NASA Astrophysics Data System (ADS)

    Yu, J.; Berger, L.; Wimmer-Schweingruber, R. F.; Hilchenbach, M.; Kallenbach, R.; Klecker, B.; Guo, J.

    2016-03-01

    Enhancements of suprathermal particles observed at 1AU often can be related to Corotating Interaction Regions (CIRs). The compression regions associated with CIRs and their driven shocks which typically form at a few AU distance to the Sun can efficiently accelerate particles. If accelerated at the trailing edge of a CIR these particles can travel sunward along the ambient magnetic field and thus enhanced fluxes can be observed even if the acceleration region has passed over the spacecraft. We have analysed a CIR that has been observed at L1 by ACE/SWICS and SOHO/CELIAS/STOF on days 207 and 208 in 2003. The combination of SWICS and STOF data allowed us to study suprathermal Helium ranging from its onset at solar wind bulk energies up to 330 keV/nuc. Here we present our results for the temporal evolution of the flux, energy spectra and the He+/He++ ratio. In particular we present observational evidence for a turnover of the energy spectra at lower energies after the CIR passage which has been theoretically predicted but never been observed so far.

  19. Effects of corotating interaction regions on Ulysses high energy particles

    SciTech Connect

    Droege, W.; Kunow, H.; Heber, B.; Mueller-Mellin, R.; Sierks, H.; Wibberenz, G.; Raviart, A.; Ducros, R.; Ferrando, P.; Rastoin, C.; Paizis, C.; Gosling, J. T.

    1996-07-20

    We investigate the intensity variation of low energy ({approx}6-23 MeV/N) heliospheric ions and of galactic protons (250-2200 MeV) observed by the Kiel Electron Telescope onboard the Ulysses spacecraft associated with Corotating Interaction Regions (CIR) from mid-1992 to end of June 1995. This period covers Ulysses' transit to high southern latitudes, the south polar pass, return to the solar equator and ascent to the north pole up to 70 deg. We find that the flux of high energy protons exhibits a periodicity of about 26 days with a relative intensity variation of 10%. At latitudes below {approx}50 deg. the recurrent variations of galactic protons are in coincidence with the passage of CIRs and enhancements of low energies protons and alpha particles which are accelerated at the shocks of the CIRs. The modulation of galactic protons is observed up to high southern latitudes, where the signatures of a CIR are no longer visible in plasma or magnetic field data. The periodicity does not depend on latitude and its phase apparently remains constant during Ulysses' pass over the south pole as well as through the solar equator.

  20. HELIUM ION ANISOTROPIES IN COROTATING INTERACTION REGIONS AT 1 AU

    SciTech Connect

    Ebert, R. W.; Desai, M. I.; Dayeh, M. A.; Mason, G. M.

    2012-08-01

    We investigated the first-order flow anisotropies in the solar wind frame of {approx}0.06-0.95 MeV nucleon{sup -1} He ions during three corotating interaction region (CIR)-associated particle intensity enhancements observed at 1 AU by Wind, examining CIRs with (1) a reverse shock, (2) a well-formed compression region, and (3) a weak compression region. We identified anti-sunward flows in the compression region downstream of the CIR trailing edge in the events with a reverse shock and well-formed compression that transitioned to sunward flows across and upstream of this boundary. These observations suggest that the trailing edge is organizing the He ion flows and is a local source for the particles in these events, this source being inside 1 AU prior to the trailing edge arrival and beyond 1 AU after its passage. The event with the weak compression region had predominantly sunward flows throughout, indicating that the source of the He ions was beyond 1 AU. These observations provide compelling evidence that He ions at 1 AU can be accelerated to suprathermal energies at the CIR trailing edge in events where the compression region is well formed.

  1. Energetic Particles and Upstream Waves at Co-rotating Shocks

    NASA Astrophysics Data System (ADS)

    Smith, Edward J.; Zhou, Xiaoyan

    2010-03-01

    We report a study of energetic ion acceleration at shocks bounding co-rotating interaction regions (CIRs). Archived data obtained by Ulysses magnetic field, solar wind and energetic particle investigations at low latitude CIRs have been assembled and analyzed. The statistical relations between various properties of 22 Forward shocks, energetic particles and upstream heliospheric magnetic field fluctuations are presented. No statistically significant correlations are found between the shock compression ratio, r, or the particle intensity, jp, or the energetic particle spectral index, s, and the shock normal-upstream field angle, θBn. Furthermore, a theoretical relation between the particle spectral index and shock compression is not consistent with the observed values of s and r. The particle intensities are poorly correlated with the power in upstream heliospheric magnetic field fluctuations contrary to our preliminary study of fewer shocks. We conclude that many of the expectations of Diffusive Shock Theory are not supported by this data set but it is too early to decide whether some key measurement is missing or the theory needs reconsideration.

  2. VizieR Online Data Catalog: Fourier analysis of HD 49330 CoRoT light curve (Huat+, 2009)

    NASA Astrophysics Data System (ADS)

    Huat, A.-L.; Hubert, A.-M.; Baudin, F.; Floquet, M.; Neiner, C.; Fremat, Y.; Gutierrez-Soto, J.; Andrade, L.; de Batz, B.; Diago, P. D.; Emilio, M.; Espinosa, F. Lara; Fabregat, J.; Janot-Pacheco, E.; Leroy, B.; Martayan, C.; Semaan, T.; Suso, J.; Auvergne, M.; Catala, C.; Michel, E.; Samadi, R.

    2009-09-01

    This work analyses the high precision photometric light curve obtained for the CoRoT target HD49330 (B0.5 IVe) which was observed during 136.886 days with a sample of 32s. During the CoRoT run the star underwent an outburst often observed in hot Be star. The CoRoT light curve was analysed using Fourier methods and non-linear least square fitting. (5 data files).

  3. Abrupt Cooling and the Oceanic Rossby Wave Observed during CINDY2011

    NASA Astrophysics Data System (ADS)

    Seiki, A.; Katsumata, M.; Horii, T.; Hasegawa, T.; Richards, K. J.; Yoneyama, K.; Shirooka, R.

    2012-12-01

    Cooperative Indian Ocean experiment on intraseasonal variability in the Year 2011 (CINDY 2011) was conducted to capture atmospheric and oceanic characteristics of the Madden-Julian Oscillation (MJO) in the central Indian Ocean. During CINDY, the research vessel MIRAI basically stayed at 8°S, 80.5°E from 1 October to 28 November 2011. Intraseasonal convection associated with MJO was organized in the central Indian Ocean twice in late October and late November during the period. In the southern hemisphere, however, it was weak and lagged the northern one by a week in the October and November events, respectively. In the middle of November, both sea surface temperature (SST) and mixed layer temperature decreased suddenly when cold low salinity water intruded in the surface layer around the MIRAI. This intrusion was accompanied by a surface current change from southwestward to northwestward associated with the passage of the downwelling Rossby wave. Advective cooling is shown to play an important role in the heat budget of the mixed layer. This is an interesting result because the associated downwelling Rossby wave is usually considered to increase SST. In addition, the cooling is suggested to suppress the convection, resulting in the lagged convective onset in the south Indian Ocean in late November.

  4. Propagation of Rossby-Khantadze Electromagnetic Planetary Waves in the Ionospheric E-Layer

    NASA Astrophysics Data System (ADS)

    Futatani, S.; Kaladze, T.; Horton, W.; Benkadda, S.

    2013-10-01

    Nonlinear vortex propagation of electromagnetic coupled Rossby and Khantadze planetary waves in the weakly ionized E-layer of the ionosphere are investigated with numerical simulations. For each k-vector the linear dispersion relation has two eigenmodes corresponding to the slow magnetized Rossby wave and the fast magnetic Khantadze wave. Both waves propagate westward with speeds of order 10-20 m/s for the slow wave and of order 500-1000 km/s for the fast wave. We show that for finite amplitudes there are dipole solitary vortex structures emitted from general initial conditions. These structures are the neutrally stable, nonlinear states that avoid radiating waves by propagating faster than the corresponding linear wave speeds. The condition for these coherent structures to occur is that their amplitudes be such that the nonlinear convection around the core of the disturbance is faster that the linear wave speed for the corresponding dominant Fourier components of the initial disturbance. The presence of the solitary vortex states are indicative of an initial strong disturbance such that arising from a solar storm, a tectonic plate movements or volcanic eruptions. Supported by NSF Grant 0964692 to the University of Texas at Austin; PIIM/CNRS at Aix-Marseille University, and by IMeRA Grant for Advanced Research.

  5. Nonlinear propagation of Rossby-Khantadze electromagnetic planetary waves in the ionospheric E-layer

    NASA Astrophysics Data System (ADS)

    Futatani, S.; Horton, W.; Kaladze, T. D.

    2013-10-01

    Nonlinear vortex propagation of electromagnetic coupled Rossby and Khantadze planetary waves in the weakly ionized ionospheric E-layer is investigated with numerical simulations. Large scale, finite amplitude vortex structures are launched as initial conditions at low, mid, and high latitudes. For each k-vector the linear dispersion relation has two eigenmodes corresponding to the slow magnetized Rossby wave and the fast magnetic Khantadze wave. Both waves propagate westward with local speeds of the order of 10-20 m/s for the slow wave and of the order of 500-1000 km/s for the fast wave. We show that for finite amplitudes there are dipole solitary structures emitted from the initial conditions. These structures are neutrally stable, nonlinear states that avoid radiating waves by propagating faster than the corresponding linear wave speeds. The condition for these coherent structures to occur is that their amplitudes are such that the nonlinear convection around the core of the disturbance is faster than the linear wave speed for the corresponding dominant Fourier components of the initial disturbance. The presence of the solitary vortex states is indicative of an initial strong disturbance such as that from a solar storm or a tectonic plate movement. We show that for generic, large amplitude initial disturbances both slow and fast vortex structures propagate out of the initial structure.

  6. A new model for algebraic Rossby solitary waves in rotation fluid and its solution

    NASA Astrophysics Data System (ADS)

    Chen, Yao-Deng; Yang, Hong-Wei; Gao, Yu-Fang; Yin, Bao-Shu; Feng, Xing-Ru

    2015-09-01

    A generalized Boussinesq equation that includes the dissipation effect is derived to describe a kind of algebraic Rossby solitary waves in a rotating fluid by employing perturbation expansions and stretching transformations of time and space. Using this equation, the conservation laws of algebraic Rossby solitary waves are discussed. It is found that the mass, the momentum, the energy, and the velocity of center of gravity of the algebraic solitary waves are conserved in the propagation process. Finally, the analytical solution of the equation is generated. Based on the analytical solution, the properties of the algebraic solitary waves and the dissipation effect are discussed. The results point out that, similar to classic solitary waves, the dissipation can cause the amplitude and the speed of solitary waves to decrease; however, unlike classic solitary waves, the algebraic solitary waves can split during propagation and the decrease of the detuning parameter can accelerate the occurrence of the solitary waves fission phenomenon. Project supported by the Shandong Provincial Key Laboratory of Marine Ecology and Environment and Disaster Prevention and Mitigation Project, China (Grant No. 2012010), the National Natural Science Foundation of China (Grant Nos. 41205082 and 41476019), the Special Funds for Theoretical Physics of the National Natural Science Foundation of China (Grant No. 11447205), and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), China.

  7. Nonlinear propagation of Rossby-Khantadze electromagnetic planetary waves in the ionospheric E-layer

    SciTech Connect

    Futatani, S.; Horton, W.; Kaladze, T. D.

    2013-10-15

    Nonlinear vortex propagation of electromagnetic coupled Rossby and Khantadze planetary waves in the weakly ionized ionospheric E-layer is investigated with numerical simulations. Large scale, finite amplitude vortex structures are launched as initial conditions at low, mid, and high latitudes. For each k-vector the linear dispersion relation has two eigenmodes corresponding to the slow magnetized Rossby wave and the fast magnetic Khantadze wave. Both waves propagate westward with local speeds of the order of 10–20 m/s for the slow wave and of the order of 500–1000 km/s for the fast wave. We show that for finite amplitudes there are dipole solitary structures emitted from the initial conditions. These structures are neutrally stable, nonlinear states that avoid radiating waves by propagating faster than the corresponding linear wave speeds. The condition for these coherent structures to occur is that their amplitudes are such that the nonlinear convection around the core of the disturbance is faster than the linear wave speed for the corresponding dominant Fourier components of the initial disturbance. The presence of the solitary vortex states is indicative of an initial strong disturbance such as that from a solar storm or a tectonic plate movement. We show that for generic, large amplitude initial disturbances both slow and fast vortex structures propagate out of the initial structure.

  8. QUASI-BIENNIAL OSCILLATIONS IN THE SOLAR TACHOCLINE CAUSED BY MAGNETIC ROSSBY WAVE INSTABILITIES

    SciTech Connect

    Zaqarashvili, Teimuraz V.; Carbonell, Marc; Oliver, Ramon; Ballester, Jose Luis E-mail: marc.carbonell@uib.e E-mail: joseluis.ballester@uib.e

    2010-11-20

    Quasi-biennial oscillations (QBOs) are frequently observed in solar activity indices. However, no clear physical mechanism for the observed variations has been suggested so far. Here, we study the stability of magnetic Rossby waves in the solar tachocline using the shallow water magnetohydrodynamic approximation. Our analysis shows that the combination of typical differential rotation and a toroidal magnetic field with a strength of {>=}10{sup 5} G triggers the instability of the m = 1 magnetic Rossby wave harmonic with a period of {approx}2 years. This harmonic is antisymmetric with respect to the equator and its period (and growth rate) depends on the differential rotation parameters and magnetic field strength. The oscillations may cause a periodic magnetic flux emergence at the solar surface and consequently may lead to the observed QBO in solar activity features. The period of QBOs may change throughout a cycle, and from cycle to cycle, due to variations of the mean magnetic field and differential rotation in the tachocline.

  9. Transiting exoplanets from the CoRoT space mission. XXIV. CoRoT-25b and CoRoT-26b: two low-density giant planets

    NASA Astrophysics Data System (ADS)

    Almenara, J. M.; Bouchy, F.; Gaulme, P.; Deleuil, M.; Havel, M.; Gandolfi, D.; Deeg, H. J.; Wuchterl, G.; Guillot, T.; Gardes, B.; Pasternacki, T.; Aigrain, S.; Alonso, R.; Auvergne, M.; Baglin, A.; Bonomo, A. S.; Bordé, P.; Cabrera, J.; Carpano, S.; Cochran, W. D.; Csizmadia, Sz.; Damiani, C.; Diaz, R. F.; Dvorak, R.; Endl, M.; Erikson, A.; Ferraz-Mello, S.; Fridlund, M.; Hébrard, G.; Gillon, M.; Guenther, E.; Hatzes, A.; Léger, A.; Lammer, H.; MacQueen, P. J.; Mazeh, T.; Moutou, C.; Ollivier, M.; Ofir, A.; Pätzold, M.; Parviainen, H.; Queloz, D.; Rauer, H.; Rouan, D.; Santerne, A.; Samuel, B.; Schneider, J.; Tal-Or, L.; Tingley, B.; Weingrill, J.

    2013-07-01

    We report the discovery of two transiting exoplanets, CoRoT-25b and CoRoT-26b, both of low density, one of which is in the Saturn mass-regime. For each star, ground-based complementary observations through optical photometry and radial velocity measurements secured the planetary nature of the transiting body and allowed us to fully characterize them. For CoRoT-25b we found a planetary mass of 0.27 ± 0.04 MJup, a radius of 1.08-0.10+0.3 RJup and hence a mean density of 0.15-0.06+0.15 g cm-3. The planet orbits an F9 main-sequence star in a 4.86-day period, that has a V magnitude of 15.0, solar metallicity, and an age of 4.5-2.0+1.8-Gyr. CoRoT-26b orbits a slightly evolved G5 star of 9.06 ± 1.5-Gyr age in a 4.20-day period that hassolar metallicity and a V magnitude of 15.8. With a mass of 0.52 ± 0.05 MJup, a radius of 1.26-0.07+0.13 RJup, and a mean density of 0.28-0.07+0.09 g cm-3, it belongs to the low-mass hot-Jupiter population. Planetary evolution models allowed us to estimate a core mass of a few tens of Earth mass for the two planets with heavy-element mass fractions of 0.52-0.15+0.08 and 0.26-0.08+0.05, respectively, assuming that a small fraction of the incoming flux is dissipated at the center of the planet. In addition, these models indicate that CoRoT-26b is anomalously large compared with what standard models could account for, indicating that dissipation from stellar heating could cause this size. The CoRoT space mission, launched on December 27th 2006, has been developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA (RSSD and Science Programme), Germany and Spain. Partly based on observations obtained at the European Southern Observatory at Paranal and La Silla, Chile in programs 083.C-0690(A), 184.C-0639.

  10. Resonance trapping in the primordial solar nebula - The case of a Stokes drag dissipation

    NASA Astrophysics Data System (ADS)

    Beauge, C.; Ferraz-Mello, S.

    1993-06-01

    An analytical and numerical study is conducted of the orbital evolution of solid particles in a gas-rich planetary nebula, in the presence of a planetary embryo, for the case of a Stokes drag. The equations of the averaged model for the motion of particles in resonance with the embryo have allowed corotation and libration solutions to be obtained for a wide range of drag coefficient values, thereby clarifying the role played by secular resonances. Effective resonance capture is shown by the numerical simulations for both librations and corotations.

  11. Particle acceleration at corotating interaction regions in the heliosphere

    SciTech Connect

    Tsubouchi, K.

    2014-11-01

    Hybrid simulations are performed to investigate the dynamics of both solar wind protons and interplanetary pickup ions (PUIs) around the corotating interaction region (CIR). The one-dimensional system is applied in order to focus on processes in the direction of CIR propagation. The CIR is bounded by forward and reverse shocks, which are responsible for particle acceleration. The effective acceleration of solar wind protons takes place when the reverse shock (fast wind side) favors a quasi-parallel regime. The diffusive process accounts for this acceleration, and particles can gain energy in a suprathermal range (on the order of 10 keV). In contrast, the PUI acceleration around the shock differs from the conventional model in which the motional electric field along the shock surface accelerates particles. Owing to their large gyroradius, PUIs can gyrate between the upstream and downstream, several proton inertial lengths away from the shock. This 'cross-shock' gyration results in a net velocity increase in the field-aligned component, indicating that the magnetic mirror force is responsible for acceleration. The PUIs that remain in the vicinity of the shock for a long duration (tens of gyroperiods) gain much energy and are reflected back toward the upstream. These reflected energetic PUIs move back and forth along the magnetic field between a pair of CIRs that are magnetically connected. The PUIs are repeatedly accelerated in each reflection, leading to a maximum energy gain close to 100 keV. This mechanism can be evaluated in terms of 'preacceleration' for the generation of anomalous cosmic rays.

  12. Data Analysis Provenance: Use Case for Exoplanet Search in CoRoT Database

    NASA Astrophysics Data System (ADS)

    de Souza, L.; Salete Marcon Gomes Vaz, M.; Emílio, M.; Ferreira da Rocha, J. C.; Janot Pacheco, E.; Carlos Boufleur, R.

    2012-09-01

    CoRoT (COnvection Rotation and Planetary Transits) is a mission led by the French national space agency CNES, in collaboration with Austria, Spain, Germany, Belgium and Brazil. The mission priority is dedicated to exoplanet search and stellar seismology. CoRoT light curves database became public after one year of their delivery to the CoRoT Co-Is, following the CoRoT data policy. The CoRoT archive contains thousands of light curves in FITS format. Several exoplanet search algorithms require detrend algorithms to remove both stellar and instrumental signal, improving the chance to detect a transit. Different detrend and transit detection algorithms can be applied to the same database. Tracking the origin of the information and how the data was derived in each level in the data analysis process is essential to allow sharing, reuse, reprocessing and further analysis. This work aims at applying a formalized and codified knowledge model by means of domain ontology. It allows to enrich the data analysis with semantic and standardization. It holds the provenance information in the database for a posteriori recovers by humans or software agents.

  13. Revisiting the transits of CoRoT-7b at a lower activity level

    NASA Astrophysics Data System (ADS)

    Barros, S. C. C.; Almenara, J. M.; Deleuil, M.; Diaz, R. F.; Csizmadia, Sz.; Cabrera, J.; Chaintreuil, S.; Collier Cameron, A.; Hatzes, A.; Haywood, R.; Lanza, A. F.; Aigrain, S.; Alonso, R.; Bordé, P.; Bouchy, F.; Deeg, H. J.; Erikson, A.; Fridlund, M.; Grziwa, S.; Gandolfi, D.; Guillot, T.; Guenther, E.; Leger, A.; Moutou, C.; Ollivier, M.; Pasternacki, T.; Pätzold, M.; Rauer, H.; Rouan, D.; Santerne, A.; Schneider, J.; Wuchterl, G.

    2014-09-01

    The first super-Earth with measured radius discovered was CoRoT-7b and it has opened the new field of rocky exoplanet characterisation. To better understand this interesting system, new observations were taken with the CoRoT satellite. During this run 90 new transits were obtained in the imagette mode. These were analysed together with the previous 151 transits obtained in the discovery run and HARPS radial velocity observations to derive accurate system parameters. A difference is found in the posterior probability distribution of the transit parameters between the previous CoRoT run (LRa01) and the new run (LRa06). We propose that this is due to an extra noise component in the previous CoRoT run suspected of being transit spot occultation events. These lead to the mean transit shape becoming V-shaped. We show that the extra noise component is dominant at low stellar flux levels and reject these transits in the final analysis. We obtained a planetary radius, Rp = 1.585 ± 0.064 R⊕ , in agreement with previous estimates. Combining the planetary radius with the new mass estimates results in a planetary density of 1.19 ± 0.27 ρ⊕ which is consistent with a rocky composition. The CoRoT-7 system remains an excellent test bed for the effects of activity in the derivation of planetary parameters in the shallow transit regime.

  14. The relation of objectively detected Rossby-Wave-Trains and extratropical cyclones in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Schuster, Mareike; Kirchner, Ingo; Lorenz, Philip; Ulbrich, Uwe; Will, Andreas

    2014-05-01

    Our current interest and topic of this poster is the relation of Rossby-Wave-Trains (RWTs) and cyclones in the North Atlantic. Northern Hemisphere extra-tropical cyclones, especially those systems that occur in winter, are known to have high socioeconomic impacts, e.g. through high windspeed and large amounts of precipitation. Recently, a specific interest in Rossby-Wave-Trains has arisen. Long lived RWTs have been shown to be precursors for extreme events and they may impact the predictability of mid-latitude weather systems. We therefore apply automated schemes for the identification of RWTs and cyclones, respectively and relate their characteristics, with the focus of the impact for European climate. Evaluating reanalysis and model data of historical runs, we aim to identify possible spatio-temporal connections between these objectively identified RWTs and cyclones. As our project "MesoTel", which is presented here, is part of a decadal prediction initiative from the German Federal Ministry of Education and Research called "MiKlip", we are additionally investigating the decadal variability of RWTs & cyclones within reanalyses and MiKlip simulations. Our long-term goal is to improve the predictability of seasonal means for Europe through a Two-Way-Nested (TWN) model setup. For this TWN model setup, the regional climate model COSMO-CLM (CCLM) is nested into the atmosphere-ocean general circulation model ECHAM6/MPI-OM (MPI-ESM) in order to investigate the feedback of the meso-scales on the large scales and vice versa. Focus is laid on the development and propagation of synoptic systems (e.g. Rossby Wave Trains and cyclones) that are affecting Europe. The Two-Way-Nested region, thus the CCLM domain, covers Central America and the North Atlantic (CANA) and therefore includes the Gulf stream region, whose prevalent strong meridional SST gradients favor the development of perturbations which then propagate downstream, commonly develop into extra-tropical cyclones and

  15. Onset and Forecast of the 1994-1995 El Nino Event: Equatorial Rossby Wave Reflection Evidenced by TOPEX/POSEIDON

    NASA Technical Reports Server (NTRS)

    Boulanger, Jean-Phillipe; Fu, L. L.; Perigaud, C.

    1996-01-01

    We found evidence in TOPEX/POSEIDON sea level data that equatorial first meridionsl mode Rossby waves reflected at the Pacific western boundary into Kelvin waves during the January-july 1994 period prior to the 1994-1995 El Nino event.

  16. Short-scale convection and long-scale deformationally unstable Rossby wave in a rotating fluid layer heated from below

    NASA Astrophysics Data System (ADS)

    Tikhomolov, Evgeniy

    1996-12-01

    A rotating fluid layer, heated from below, with a deformable upper and nondeformable lower stress free surfaces is considered in the Boussinesq approximation. The system of the differential equations that governs the long-scale Rossby waves and short-scale convection is obtained in the rapid-rotation approximation. Long-scale flows are unstable due to heating and deformation of the upper surface. The neutral stability curves for Rossby waves and convection are obtained for linearized version of the equations. In a slightly supercritical regime the amplitude equations for convection and Rossby waves are derived by the use of the method of multiscale expansions. The properties of the amplitude equations are discussed. The existence of the two weakly supercritical stationary convection regimes is shown by numerical integration of the equations in the rapid-rotation approximation. In one of them, the amplitude of short-scale convection is modulated due to long-scale deformation of the upper surface associated with the excitation of the Rossby wave. In the other regime, the presence of deformation gives rise to alternating regions with and without convection.

  17. Validation of the smallest CoRoT candidates using PASTIS

    NASA Astrophysics Data System (ADS)

    Díaz, R. F.; Almenara, J. M.; Santerne, A.; Moutou, C.; Lethuillier, A.; Deleuil, M.; Bouchy, F.; Hébrard, G.; Montagnier, G.

    2013-09-01

    The majority of the smallest transiting planet candidates detected by CoRoT could not be directly confirmed by a dynamical measurement of their mass. This is due mainly to the faintness of the typical stars observed by CoRoT and to the small reflex motion induced by low-mass planets on their host stars. These candidates have traditionally being labeled as "unresolved", and virtually forgotten in the hope that the new generation of ultra-precise spectrographs installed in large telescopes would permit their confirmation. A way out of this problem is to statistically validate these candidates. In this talk, I will present PASTIS, the validation tool developed in Marseille that is being used to study the CoRoT unresolved candidates.

  18. Transport out of the lower stratospheric Arctic vortex by Rossby wave breaking

    NASA Technical Reports Server (NTRS)

    Waugh, D. W.; Plumb, R. A.; Atkinson, R. J.; Schoeberl, M. R.; Lait, L. R.; Newman, P. A.; Loewenstein, M.; Toohey, D. W.; Avallone, L. M.; Webster, C. R.

    1994-01-01

    The fine-scale structure in lower stratospheric tracer transport during the period of the two Arctic Airborne Stratospheric Expeditions (January and February 1989; December 1991 to March 1992) is investigated using contour advection with surgery calculations. These calculations show that Rossby wave breaking is an ongoing occurrence during these periods and that air is ejected from the polar vortex in the form of long filamentary structures. There is good qualitative agreement between these filaments and measurements of chemical tracers taken aboard the NASA ER-2 aircraft. The ejected air generally remains filamentary and is stretched and mixed with midlatitude air as it is wrapped around the vortex. This process transfers vortex air into midlatitudes and also produces a narrow region of fine-scale filaments surrounding the polar vortex. Among other things, this makes it difficult to define a vortex edge. The calculations also show that strong stirring can occur inside as well as outside the vortex.

  19. Rossby normal modes in nonuniform background configurations. I Simple fields. II - Equinox and solstice conditions

    NASA Technical Reports Server (NTRS)

    Salby, M. L.

    1981-01-01

    An investigation is conducted regarding the influence of mean field variations on the realization of planetary normal modes, taking into account the mode response and structure in the presence of simple background nonuniformities. It is found that mean field variations have the combined effect of depressing, shifting, and broadening the characteristic response of Rossby normal modes. While nonuniformities in both the mean wind and temperature fields contribute to the reduction in peak response, the former are primarily responsible for translation and spectral broadening. An investigation is conducted to determine which modes may be realized in actual atmospheric configurations and which may be identified. For both the equinox and solstice configurations, response peaks corresponding to all of the first four modes of wavenumbers 1, 2, and 3 are readily visible above the noise.

  20. Long-Time Sustainability of Rossby Wave Instability in Protoplanetary Disks with Dead Zone

    NASA Astrophysics Data System (ADS)

    Li, S.; Li, H.

    2015-10-01

    We have run 2D simulations to investigate the generation and sustainability of Rossby wave instability (RWI) in proto-planetary disks with constant viscosity and for disks with low viscosity regions (dead zone). For the constant viscosity case, the development of RWI requires a low viscosity and life time of the RWI is short. We also find that the vortex, when it migrates, does so much faster than the disk's viscous drift rate. For disks with dead zone case, a much larger viscosity can be used and the RWI vortex can be sustained for a long time, even the life time of the disk, depending on the width and depth of the dead zone. For a narrow dead zone, the vortex depicts a periodic pattern with a period inversely proportional to the viscosity. If the dead-zone width exceeds some threshold, the periodicity of the RWI disappears.

  1. Observations of planetary mixed Rossby-gravity waves in the upper stratosphere

    NASA Technical Reports Server (NTRS)

    Randel, William J.; Boville, Byron A.; Gille, John C.

    1990-01-01

    Observational evidence is presented for planetary scale (zonal wave number 1-2) mixed Rossby-gravity (MRG) waves in the equatorial upper stratosphere (35-50 km). These waves are detected in LIMS measurements as coherently propagating temperature maxima of amplitude 0.1-0.3 K, which are antisymmetric (out of phase) about the equator, centered near 10-15 deg north and south latitude. These features have vertical wavelengths of order 10-15 km, periods near 2-3 days, and zonal phase velocities close to 200 m/s. Both eastward and westward propagating waves are found, and the observed vertical wavelengths and meridional structures are in good agreement with the MRG dispersion relation. Theoretical estimates of the zonal accelerations attributable to these waves suggest they do not contribute substantially to the zonal momentum balance in the middle atmosphere.

  2. Rossby vortex simulation on a paraboloidal coordinate system using the lattice Boltzmann method.

    PubMed

    Yu, H; Zhao, K

    2001-11-01

    In this paper, we apply our compressible lattice Boltzmann model to a rotating parabolic coordinate system to simulate Rossby vortices emerging in a layer of shallow water flowing zonally in a rotating paraboloidal vessel. By introducing a scaling factor, nonuniform curvilinear mesh can be mapped to a flat uniform mesh and then normal lattice Boltzmann method works. Since the mass per unit area on the two-dimensional (2D) surface varies with the thickness of the water layer, the 2D flow seems to be "compressible" and our compressible model is applied. Simulation solutions meet with the experimental observations qualitatively. Based on this research, quantitative solutions and many natural phenomena simulations in planetary atmospheres, oceans, and magnetized plasma, such as the famous Jovian Giant Red Spot, the Galactic Spiral-vortex, the Gulf Stream, and the Kuroshio Current, etc., can be expected. PMID:11736137

  3. Planets and stellar activity: hide and seek in the CoRoT-7 system

    NASA Astrophysics Data System (ADS)

    Haywood, R. D.; Collier Cameron, A.; Queloz, D.; Barros, S. C. C.; Deleuil, M.; Fares, R.; Gillon, M.; Lanza, A. F.; Lovis, C.; Moutou, C.; Pepe, F.; Pollacco, D.; Santerne, A.; Ségransan, D.; Unruh, Y. C.

    2014-09-01

    Since the discovery of the transiting super-Earth CoRoT-7b, several investigations have yielded different results for the number and masses of planets present in the system, mainly owing to the star's high level of activity. We re-observed CoRoT-7 in 2012 January with both HARPS and CoRoT, so that we now have the benefit of simultaneous radial-velocity and photometric data. This allows us to use the off-transit variations in the star's light curve to estimate the radial-velocity variations induced by the suppression of convective blueshift and the flux blocked by starspots. To account for activity-related effects in the radial velocities which do not have a photometric signature, we also include an additional activity term in the radial-velocity model, which we treat as a Gaussian process with the same covariance properties (and hence the same frequency structure) as the light curve. Our model was incorporated into a Monte Carlo Markov Chain in order to make a precise determination of the orbits of CoRoT-7b and CoRoT-7c. We measure the masses of planets b and c to be 4.73 ± 0.95 and 13.56 ± 1.08 M⊕, respectively. The density of CoRoT-7b is (6.61 ± 1.72)(Rp/1.58 R⊕)-3 g cm-3, which is compatible with a rocky composition. We search for evidence of an additional planet d, identified by previous authors with a period close to 9 d. We are not able to confirm the existence of a planet with this orbital period, which is close to the second harmonic of the stellar rotation at ˜7.9 d. Using Bayesian model selection, we find that a model with two planets plus activity-induced variations is most favoured.

  4. Abrupt cooling associated with the oceanic Rossby wave and lateral advection during CINDY2011

    NASA Astrophysics Data System (ADS)

    Seiki, Ayako; Katsumata, Masaki; Horii, Takanori; Hasegawa, Takuya; Richards, Kelvin J.; Yoneyama, Kunio; Shirooka, Ryuichi

    2013-10-01

    The cooperative Indian Ocean experiment on intraseasonal variability in the Year 2011 (CINDY2011) was conducted to capture atmospheric and oceanic characteristics of the Madden-Julian Oscillation (MJO) in the central Indian Ocean from late 2011 to early 2012. During CINDY2011, the research vessel (R/V) MIRAI stayed at 8°S, 80.5°E for two months during the special observing period (SOP). Intraseasonal convection associated with the MJO was organized in the central Indian Ocean in late October and late November during the SOP. In the middle of November, both sea surface temperature (SST) and mixed layer temperature decreased suddenly when cold low salinity water intruded into the upper layer around the R/V MIRAI. This intrusion was accompanied by a surface current change from southwestward to westward/west-northwestward associated with the passage of the annual oceanic downwelling Rossby wave. The mixed layer heat budget analysis shows that horizontal advection plays an important role in the abrupt cooling whereas the net surface heat flux cannot account for the cooling. This is an interesting result because the associated downwelling Rossby wave is usually considered to increase SST through a reduction of entrainment cooling. In addition, for the second MJO event convection was activated around 20 November over the central north and equatorial Indian Ocean but not in the south. It is suggested that the cooler surface waters (as seen at the location of the R/V MIRAI) tended to suppress the initial atmospheric convection, resulting in the lagged convective onset in the end of November over the central south Indian Ocean.

  5. Long-term observations of transport, eddies, and Rossby waves in the Mozambique Channel

    NASA Astrophysics Data System (ADS)

    Harlander, U.; Ridderinkhof, H.; Schouten, M. W.; de Ruijter, W. P. M.

    2009-02-01

    Data from an array of current meter moorings covering a period of two and a half years are used to estimate the varying transport through the Mozambique Channel. The total transport during this period is small (8.6 · 106 m3 s-1 or 8.6 Sv southward). Below 1200 m the transport is weak but a prominent deep western boundary undercurrent with cores at 1700 and 2200 m is found that transports 1.5 Sv to the north. The transport shows a large temporal variability, and neither a continuous upper layer western boundary current nor a continuous deep undercurrent is found. The variability in the upper layer is dominated by a period of 68 days and results mainly from eddies that migrate southward through the Mozambique Channel. In addition to this southward propagation, a westward-propagating signal is evident from a space-time diagram of the throughflow. The signal is interpreted as a Mozambique Channel Rossby normal mode. This interpretation is consistent with results from a Principal Oscillation Pattern Analysis (that estimates normal modes from the data) and a quasi-geostrophic channel model. A detailed inspection of a single "eddy event" shows that a precursor of an anticyclone is a strong southward current along the Madagascar coast that propagates westward to the center of the Channel. During the westward propagation, the current becomes unstable inducing an anticyclone. This scenario connects the westward-propagating mode with the eddy growth and explains the coincidence of the eddy and Rossby mode frequency. Still, the type of instability that leads to eddy growth could not be determined yet.

  6. Transiting exoplanets from the CoRoT space mission. XXVII. CoRoT-28b, a planet orbiting an evolved star, and CoRoT-29b, a planet showing an asymmetric transit

    NASA Astrophysics Data System (ADS)

    Cabrera, J.; Csizmadia, Sz.; Montagnier, G.; Fridlund, M.; Ammler-von Eiff, M.; Chaintreuil, S.; Damiani, C.; Deleuil, M.; Ferraz-Mello, S.; Ferrigno, A.; Gandolfi, D.; Guillot, T.; Guenther, E. W.; Hatzes, A.; Hébrard, G.; Klagyivik, P.; Parviainen, H.; Pasternacki, Th.; Pätzold, M.; Sebastian, D.; Tadeu dos Santos, M.; Wuchterl, G.; Aigrain, S.; Alonso, R.; Almenara, J.-M.; Armstrong, J. D.; Auvergne, M.; Baglin, A.; Barge, P.; Barros, S. C. C.; Bonomo, A. S.; Bordé, P.; Bouchy, F.; Carpano, S.; Chaffey, C.; Deeg, H. J.; Díaz, R. F.; Dvorak, R.; Erikson, A.; Grziwa, S.; Korth, J.; Lammer, H.; Lindsay, C.; Mazeh, T.; Moutou, C.; Ofir, A.; Ollivier, M.; Pallé, E.; Rauer, H.; Rouan, D.; Samuel, B.; Santerne, A.; Schneider, J.

    2015-07-01

    Context. We present the discovery of two transiting extrasolar planets by the satellite CoRoT. Aims: We aim at a characterization of the planetary bulk parameters, which allow us to further investigate the formation and evolution of the planetary systems and the main properties of the host stars. Methods: We used the transit light curve to characterize the planetary parameters relative to the stellar parameters. The analysis of HARPS spectra established the planetary nature of the detections, providing their masses. Further photometric and spectroscopic ground-based observations provided stellar parameters (log g, Teff, v sin i) to characterize the host stars. Our model takes the geometry of the transit to constrain the stellar density into account, which when linked to stellar evolutionary models, determines the bulk parameters of the star. Because of the asymmetric shape of the light curve of one of the planets, we had to include the possibility in our model that the stellar surface was not strictly spherical. Results: We present the planetary parameters of CoRoT-28b, a Jupiter-sized planet (mass 0.484 ± 0.087 MJup; radius 0.955 ± 0.066 RJup) orbiting an evolved star with an orbital period of 5.208 51 ± 0.000 38 days, and CoRoT-29b, another Jupiter-sized planet (mass 0.85 ± 0.20 MJup; radius 0.90 ± 0.16 RJup) orbiting an oblate star with an orbital period of 2.850 570 ± 0.000 006 days. The reason behind the asymmetry of the transit shape is not understood at this point. Conclusions: These two new planetary systems have very interesting properties and deserve further study, particularly in the case of the star CoRoT-29. The CoRoT space mission, launched on December 27th 2006, was developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA (RSSD and Science Programme), Germany, and Spain. Based on observations obtained with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland

  7. The legacy of CoRoT and Kepler on the physics of stellar evolution

    NASA Astrophysics Data System (ADS)

    Chaplin, William

    2015-08-01

    It is a golden era for stellar astrophysics studies, driven by new satellite observations of unprecedented quality and scope. In this talk I will review advances in our understanding that have followed from asteroseismic studies with CoRoT and Kepler data, not only for stellar evolution theory but also in respect of the legacy for exoplanet and Galactic stellar population studies. I will also highlight the huge amount of work that remains to be performed to fully exploit the CoRoT and Kepler databases, and look to ongoing studies with K2, and the future promise of the NASA TESS and ESA PLATO Missions.

  8. Multiple star systems observed with CoRoT and Kepler

    NASA Astrophysics Data System (ADS)

    Southworth, John

    2015-09-01

    The CoRoT and Kepler satellites were the first space platforms designed to perform high-precision photometry for a large number of stars. Multiple systems display a wide variety of photometric variability, making them natural benefactors of these missions. I review the work arising from CoRoT and Kepler observations of multiple systems, with particular emphasis on eclipsing binaries containing giant stars, pulsators, triple eclipses and/or low-mass stars. Many more results remain untapped in the data archives of these missions, and the future holds the promise of K2, TESS and PLATO.

  9. How to separate the low amplitude delta Scuti variation in CoRoT data unambigousely?

    NASA Astrophysics Data System (ADS)

    Benko, Jozsef M.; Paparo, Margit

    2015-08-01

    Rich regular frequency patterns were found in the Fourier spectra of low-amplitude Delta Scuti stars observed by CoRoT satellite. The CoRoT observations are, however, influenced by the disturbing effect of the SAA. The effect is marginal for high amplitude variable stars but it could be dangerous in the case of low amplitude variables, especially if the frequency range of the intrinsic variation overlaps the instrumental frequencies. Systematic tests were carried out both on synthetic and real data. Our aim was to determine a limit amplitude above which we were sure that the frequency pattern belonged to the stars.

  10. Consistent linearization of the element-independent corotational formulation for the structural analysis of general shells

    NASA Technical Reports Server (NTRS)

    Rankin, C. C.

    1988-01-01

    A consistent linearization is provided for the element-dependent corotational formulation, providing the proper first and second variation of the strain energy. As a result, the warping problem that has plagued flat elements has been overcome, with beneficial effects carried over to linear solutions. True Newton quadratic convergence has been restored to the Structural Analysis of General Shells (STAGS) code for conservative loading using the full corotational implementation. Some implications for general finite element analysis are discussed, including what effect the automatic frame invariance provided by this work might have on the development of new, improved elements.

  11. Dissipative Dynamics of a Corotating Vortex Pair in a Bose-Einstein Condensate

    NASA Astrophysics Data System (ADS)

    Kwon, Woo Jin; Moon, Geol; Seo, Sang Won; Kim, Minseok; Lee, Moosong; Han, Jeong Ho; Shin, Yong-Il

    2015-05-01

    We report on the long-time evolution of a corotating vortex pair in a highly oblate Bose-Einstein Condensate at finite temperature. We generate a doubly charged vortex in a condensate by a phase imprinting method using a magnetic quadrupole field and measure the temporal evolution of the inter-vortex distance between corotating vortices. We find that the vortex separation monotonically increases over the hold time and its increasing rate is almost linearly proportional to the temperature of the system. We discuss the thermal damping on the vortex motion in a condensate.

  12. Transiting exoplanets from the CoRoT space mission. VIII. CoRoT-7b: the first super-Earth with measured radius

    NASA Astrophysics Data System (ADS)

    Léger, A.; Rouan, D.; Schneider, J.; Barge, P.; Fridlund, M.; Samuel, B.; Ollivier, M.; Guenther, E.; Deleuil, M.; Deeg, H. J.; Auvergne, M.; Alonso, R.; Aigrain, S.; Alapini, A.; Almenara, J. M.; Baglin, A.; Barbieri, M.; Bruntt, H.; Bordé, P.; Bouchy, F.; Cabrera, J.; Catala, C.; Carone, L.; Carpano, S.; Csizmadia, Sz.; Dvorak, R.; Erikson, A.; Ferraz-Mello, S.; Foing, B.; Fressin, F.; Gandolfi, D.; Gillon, M.; Gondoin, Ph.; Grasset, O.; Guillot, T.; Hatzes, A.; Hébrard, G.; Jorda, L.; Lammer, H.; Llebaria, A.; Loeillet, B.; Mayor, M.; Mazeh, T.; Moutou, C.; Pätzold, M.; Pont, F.; Queloz, D.; Rauer, H.; Renner, S.; Samadi, R.; Shporer, A.; Sotin, Ch.; Tingley, B.; Wuchterl, G.; Adda, M.; Agogu, P.; Appourchaux, T.; Ballans, H.; Baron, P.; Beaufort, T.; Bellenger, R.; Berlin, R.; Bernardi, P.; Blouin, D.; Baudin, F.; Bodin, P.; Boisnard, L.; Boit, L.; Bonneau, F.; Borzeix, S.; Briet, R.; Buey, J.-T.; Butler, B.; Cailleau, D.; Cautain, R.; Chabaud, P.-Y.; Chaintreuil, S.; Chiavassa, F.; Costes, V.; Cuna Parrho, V.; de Oliveira Fialho, F.; Decaudin, M.; Defise, J.-M.; Djalal, S.; Epstein, G.; Exil, G.-E.; Fauré, C.; Fenouillet, T.; Gaboriaud, A.; Gallic, A.; Gamet, P.; Gavalda, P.; Grolleau, E.; Gruneisen, R.; Gueguen, L.; Guis, V.; Guivarc'h, V.; Guterman, P.; Hallouard, D.; Hasiba, J.; Heuripeau, F.; Huntzinger, G.; Hustaix, H.; Imad, C.; Imbert, C.; Johlander, B.; Jouret, M.; Journoud, P.; Karioty, F.; Kerjean, L.; Lafaille, V.; Lafond, L.; Lam-Trong, T.; Landiech, P.; Lapeyrere, V.; Larqué, T.; Laudet, P.; Lautier, N.; Lecann, H.; Lefevre, L.; Leruyet, B.; Levacher, P.; Magnan, A.; Mazy, E.; Mertens, F.; Mesnager, J.-M.; Meunier, J.-C.; Michel, J.-P.; Monjoin, W.; Naudet, D.; Nguyen-Kim, K.; Orcesi, J.-L.; Ottacher, H.; Perez, R.; Peter, G.; Plasson, P.; Plesseria, J.-Y.; Pontet, B.; Pradines, A.; Quentin, C.; Reynaud, J.-L.; Rolland, G.; Rollenhagen, F.; Romagnan, R.; Russ, N.; Schmidt, R.; Schwartz, N.; Sebbag, I.; Sedes, G.; Smit, H.; Steller, M. B.; Sunter, W.; Surace, C.; Tello, M.; Tiphène, D.; Toulouse, P.; Ulmer, B.; Vandermarcq, O.; Vergnault, E.; Vuillemin, A.; Zanatta, P.

    2009-10-01

    Aims: We report the discovery of very shallow (Δ F/F ≈ 3.4× 10-4), periodic dips in the light curve of an active V = 11.7 G9V star observed by the CoRoT satellite, which we interpret as caused by a transiting companion. We describe the 3-colour CoRoT data and complementary ground-based observations that support the planetary nature of the companion. Methods: We used CoRoT colours information, good angular resolution ground-based photometric observations in- and out- of transit, adaptive optics imaging, near-infrared spectroscopy, and preliminary results from radial velocity measurements, to test the diluted eclipsing binary scenarios. The parameters of the host star were derived from optical spectra, which were then combined with the CoRoT light curve to derive parameters of the companion. Results: We examined all conceivable cases of false positives carefully, and all the tests support the planetary hypothesis. Blends with separation >0.40´´or triple systems are almost excluded with a 8 × 10-4 risk left. We conclude that, inasmuch we have been exhaustive, we have discovered a planetary companion, named CoRoT-7b, for which we derive a period of 0.853 59 ± 3 × 10-5 day and a radius of Rp = 1.68 ± 0.09 R_Earth. Analysis of preliminary radial velocity data yields an upper limit of 21 M_Earth for the companion mass, supporting the finding. Conclusions: CoRoT-7b is very likely the first Super-Earth with a measured radius. This object illustrates what will probably become a common situation with missions such as Kepler, namely the need to establish the planetary origin of transits in the absence of a firm radial velocity detection and mass measurement. The composition of CoRoT-7b remains loosely constrained without a precise mass. A very high surface temperature on its irradiated face, ≈1800-2600 K at the substellar point, and a very low one, ≈50 K, on its dark face assuming no atmosphere, have been derived. The CoRoT space mission, launched on 27

  13. Transiting exoplanets from the CoRoT space mission. XVIII. CoRoT-18b: a massive hot Jupiter on a prograde, nearly aligned orbit

    NASA Astrophysics Data System (ADS)

    Hébrard, G.; Evans, T. M.; Alonso, R.; Fridlund, M.; Ofir, A.; Aigrain, S.; Guillot, T.; Almenara, J. M.; Auvergne, M.; Baglin, A.; Barge, P.; Bonomo, A. S.; Bordé, P.; Bouchy, F.; Cabrera, J.; Carone, L.; Carpano, S.; Cavarroc, C.; Csizmadia, Sz.; Deeg, H. J.; Deleuil, M.; Díaz, R. F.; Dvorak, R.; Erikson, A.; Ferraz-Mello, S.; Gandolfi, D.; Gibson, N.; Gillon, M.; Guenther, E.; Hatzes, A.; Havel, M.; Jorda, L.; Lammer, H.; Léger, A.; Llebaria, A.; Mazeh, T.; Moutou, C.; Ollivier, M.; Parviainen, H.; Pätzold, M.; Queloz, D.; Rauer, H.; Rouan, D.; Santerne, A.; Schneider, J.; Tingley, B.; Wuchterl, G.

    2011-09-01

    We report the detection of CoRoT-18b, a massive hot Jupiter transiting in front of its host star with a period of 1.9000693 ± 0.0000028 days. This planet was discovered thanks to photometric data secured with the CoRoT satellite combined with spectroscopic and photometric ground-based follow-up observations. The planet has a mass Mp = 3.47 ± 0.38 MJup, a radius Rp = 1.31 ± 0.18 RJup, and a density ρp = 2.2 ± 0.8 g cm-3. It orbits a G9V star with a mass M⋆ = 0.95 ± 0.15 M⊙, a radius R⋆ = 1.00 ± 0.13 R⊙, and arotation period Prot = 5.4 ± 0.4 days. The age of the system remains uncertain, with stellar evolution models pointing either to a few tens Ma or several Ga, while gyrochronology and lithium abundance point towards ages of a few hundred Ma. This mismatch potentially points to a problem in our understanding of the evolution of young stars, with possibly significant implications for stellar physics and the interpretation of inferred sizes of exoplanets around young stars. We detected the Rossiter-McLaughlin anomaly in the CoRoT-18 system thanks to the spectroscopic observation of a transit. We measured the obliquity ψ = 20° ± 20° (sky-projected value λ = -10° ± 20°), indicating that the planet orbits in the same way as the star is rotating and that this prograde orbit is nearly aligned with the stellar equator. The CoRoT space mission, launched on 2006 December 27, has been developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA (RSSD and Science Programme), Germany and Spain.Table 2 is available in electronic form at http://www.aanda.org

  14. Transiting exoplanets from the CoRoT space mission. XXIII. CoRoT-21b: a doomed large Jupiter around a faint subgiant star

    NASA Astrophysics Data System (ADS)

    Pätzold, M.; Endl, M.; Csizmadia, Sz.; Gandolfi, D.; Jorda, L.; Grziwa, S.; Carone, L.; Pasternacki, T.; Aigrain, S.; Almenara, J. M.; Alonso, R.; Auvergne, M.; Baglin, A.; Barge, P.; Bonomo, A. S.; Bordé, P.; Bouchy, F.; Cabrera, J.; Cavarroc, C.; Cochran, W. B.; Deleuil, M.; Deeg, H. J.; Díaz, R.; Dvorak, R.; Erikson, A.; Ferraz-Mello, S.; Fridlund, M.; Gillon, M.; Guillot, T.; Hatzes, A.; Hébrard, G.; Léger, A.; Llebaria, A.; Lammer, H.; MacQueen, P. J.; Mazeh, T.; Moutou, C.; Ofir, A.; Ollivier, M.; Parviainen, H.; Queloz, D.; Rauer, H.; Rouan, D.; Santerne, A.; Schneider, J.; Tingley, B.; Weingrill, J.; Wuchterl, G.

    2012-09-01

    CoRoT-21, a F8IV star of magnitude V = 16 mag, was observed by the space telescope CoRoT during the Long Run 01 (LRa01) in the first winter field (constellation Monoceros) from October 2007 to March 2008. Transits were discovered during the light curve processing. Radial velocity follow-up observations, however, were performed mainly by the 10-m Keck telescope in January 2010. The companion CoRoT-21b is a Jupiter-like planet of 2.26 ± 0.33 Jupiter masses and 1.30 ± 0.14 Jupiter radii in an circular orbit of semi-major axis 0.0417 ± 0.0011 AU and an orbital period of 2.72474 ± 0.00014 days. The planetary bulk density is (1.36 ± 0.48) × 103 kg m-3, very similar to the bulk density of Jupiter, and follows an M1/3 - R relation like Jupiter. The F8IV star is a sub-giant star of 1.29 ± 0.09 solar masses and 1.95 ± 0.2 solar radii. The star and the planet exchange extremetidal forces that will lead to orbital decay and extreme spin-up of the stellar rotation within 800 Myr if the stellar dissipation is Q∗/k2∗ ≤ 107. The CoRoT space mission, launched on December 27th 2006, has been developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA (RSSD and Science Programme), Germany and Spain.

  15. Transiting exoplanets from the CoRoT space mission. XX. CoRoT-20b: A very high density, high eccentricity transiting giant planet

    NASA Astrophysics Data System (ADS)

    Deleuil, M.; Bonomo, A. S.; Ferraz-Mello, S.; Erikson, A.; Bouchy, F.; Havel, M.; Aigrain, S.; Almenara, J.-M.; Alonso, R.; Auvergne, M.; Baglin, A.; Barge, P.; Bordé, P.; Bruntt, H.; Cabrera, J.; Carpano, S.; Cavarroc, C.; Csizmadia, Sz.; Damiani, C.; Deeg, H. J.; Dvorak, R.; Fridlund, M.; Hébrard, G.; Gandolfi, D.; Gillon, M.; Guenther, E.; Guillot, T.; Hatzes, A.; Jorda, L.; Léger, A.; Lammer, H.; Mazeh, T.; Moutou, C.; Ollivier, M.; Ofir, A.; Parviainen, H.; Queloz, D.; Rauer, H.; Rodríguez, A.; Rouan, D.; Santerne, A.; Schneider, J.; Tal-Or, L.; Tingley, B.; Weingrill, J.; Wuchterl, G.

    2012-02-01

    We report the discovery by the CoRoT space mission of a new giant planet, CoRoT-20b. The planet has a mass of 4.24 ± 0.23 MJup and a radius of 0.84 ± 0.04 RJup. With a mean density of 8.87 ± 1.10 g cm-3, it is among the most compact planets known so far. Evolutionary models for the planet suggest a mass of heavy elements of the order of 800 M⊕ if embedded in a central core, requiring a revision either of the planet formation models or both planet evolution and structure models. We note however that smaller amounts of heavy elements are expected by more realistic models in which they are mixed throughout the envelope. The planet orbits a G-type star with an orbital period of 9.24 days and an eccentricity of 0.56.The star's projected rotational velocity is vsini = 4.5 ± 1.0 km s-1, corresponding to a spin period of 11.5 ± 3.1 days if its axis of rotation is perpendicular to the orbital plane. In the framework of Darwinian theories and neglecting stellar magnetic breaking, we calculate the tidal evolution of the system and show that CoRoT-20b is presently one of the very few Darwin-stable planets that is evolving toward a triple synchronous state with equality of the orbital, planetary and stellar spin periods. The CoRoT space mission, launched on December 27th 2006, has been developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA (RSSD and Science Programme), Germany, and Spain.

  16. Spectral characterization and differential rotation study of active CoRoT stars

    NASA Astrophysics Data System (ADS)

    Nagel, E.; Czesla, S.; Schmitt, J. H. M. M.

    2016-05-01

    The CoRoT space telescope observed nearly 160 000 light curves. Among the most outstanding is that of the young, active planet host star CoRoT-2A. In addition to deep planetary transits, the light curve of CoRoT-2A shows strong rotational variability and a superimposed beating pattern. To study the stars that produce such an intriguing pattern of photometric variability, we identified a sample of eight stars with rotation periods between 0.8 and 11 days and photometric variability amplitudes of up to 7.5%, showing a similar CoRoT light curve. We also obtained high-resolution follow-up spectroscopy with TNG/SARG and carried out a spectral analysis with SME and MOOG. We find that the color dependence of the light curves is consistent with rotational modulation due to starspots and that latitudinal differential rotation provides a viable explanation for the light curves, although starspot evolution is also expected to play an important role. Our MOOG and SME spectral analyses provide consistent results, showing that the targets are dwarf stars with spectral types between F and mid-K. Detectable Li i absorption in four of the targets confirms a low age of 100-400 Myr also deduced from gyrochronology. Our study indicates that the photometric beating phenomenon is likely attributable to differential rotation in fast-rotating stars with outer convection zones.

  17. Transiting exoplanets from the CoRoT space mission . XIX. CoRoT-23b: a dense hot Jupiter on an eccentric orbit

    NASA Astrophysics Data System (ADS)

    Rouan, D.; Parviainen, H.; Moutou, C.; Deleuil, M.; Fridlund, M.; Ofir, A.; Havel, M.; Aigrain, S.; Alonso, R.; Auvergne, M.; Baglin, A.; Barge, P.; Bonomo, A. S.; Bordé, P.; Bouchy, F.; Cabrera, J.; Cavarroc, C.; Csizmadia, Sz.; Deeg, H. J.; Diaz, R. F.; Dvorak, R.; Erikson, A.; Ferraz-Mello, S.; Gandolfi, D.; Gillon, M.; Guillot, T.; Hatzes, A.; Hébrard, G.; Jorda, L.; Léger, A.; Llebaria, A.; Lammer, H.; Lovis, C.; Mazeh, T.; Ollivier, M.; Pätzold, M.; Queloz, D.; Rauer, H.; Samuel, B.; Santerne, A.; Schneider, J.; Tingley, B.; Wuchterl, G.

    2012-01-01

    We report the detection of CoRoT-23b, a hot Jupiter transiting in front of its host star with a period of 3.6314 ± 0.0001 days. This planet was discovered thanks to photometric data secured with the CoRoT satellite, combined with spectroscopic radial velocity (RV) measurements. A photometric search for possible background eclipsing binaries conducted at CFHT and OGS concluded with a very low risk of false positives. The usual techniques of combining RV and transit data simultaneously were used to derive stellar and planetary parameters. The planet has a mass of Mp = 2.8 ± 0.3 MJup, a radius of Rpl= 1.05 ± 0.13RJup, a density of ≈ 3 g cm-3. RV data also clearly reveal a nonzero eccentricity of e = 0.16 ± 0.02. The planet orbits a mature G0 main sequence star of V = 15.5 mag, with a mass M⋆ = 1.14 ± 0.08 M⊙, a radius R ⋆ = 1. 61 ± 0.18 R⊙ and quasi-solarabundances. The age of the system is evaluated to be 7 Gyr, not far from the transition to subgiant, in agreement with the rather large stellar radius. The two features of a significant eccentricity of the orbit and of a fairly high density are fairly uncommon for a hot Jupiter. The high density is, however, consistent with a model of contraction of a planet at this mass, given the age of the system. On the other hand, at such an age, circularization is expected to be completed. In fact, we show that for this planetary mass and orbital distance, any initial eccentricity should not totally vanish after 7 Gyr, as long as the tidal quality factor Qp is more than a few 105, a value that is the lower bound of the usually expected range. Even if CoRoT-23b features a density and an eccentricity that are atypical of a hot Jupiter, it is thus not an enigmatic object. The CoRoT space mission, launched on 27 December 2006, has been developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA, Germany, and Spain. First CoRoT data are available to the public from the CoRoT archive: http://idoc-corot

  18. Long-Term Tracking of Corotating Density Structures Using Heliospheric Imaging

    NASA Astrophysics Data System (ADS)

    Plotnikov, I.; Rouillard, A. P.; Davies, J. A.; Bothmer, V.; Eastwood, J. P.; Gallagher, P.; Harrison, R. A.; Kilpua, E.; Möstl, C.; Perry, C. H.; Rodriguez, L.; Lavraud, B.; Génot, V.; Pinto, R. F.; Sanchez-Diaz, E.

    2016-08-01

    The systematic monitoring of the solar wind in high-cadence and high-resolution heliospheric images taken by the Solar-Terrestrial Relation Observatory (STEREO) spacecraft permits the study of the spatial and temporal evolution of variable solar wind flows from the Sun out to 1 AU, and beyond. As part of the EU Framework 7 (FP7) Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS) project, we have generated a catalog listing the properties of 190 corotating structures well-observed in images taken by the Heliospheric Imager (HI) instruments onboard STEREO-A (ST-A). Based on this catalog, we present here one of very few long-term analyses of solar wind structures advected by the background solar wind. We concentrate on the subset of plasma density structures clearly identified inside corotating structures. This analysis confirms that most of the corotating density structures detected by the heliospheric imagers comprises a series of density inhomogeneities advected by the slow solar wind that eventually become entrained by stream interaction regions. We have derived the spatial-temporal evolution of each of these corotating density structures by using a well-established fitting technique. The mean radial propagation speed of the corotating structures is found to be 311 ±31 km s^{-1}. Such a low mean value corresponds to the terminal speed of the slow solar wind rather than the speed of stream interfaces, which is typically intermediate between the slow and fast solar wind speeds ({˜} 400 km s^{-1}). Using our fitting technique, we predicted the arrival time of each corotating density structure at different probes in the inner heliosphere. We find that our derived speeds are systematically lower by {˜} 100 km s^{-1} than those measured in situ at the predicted impact times. Moreover, for cases when a stream interaction region is clearly detected in situ at the estimated impact time, we find that our derived speeds are lower than the speed of the

  19. Noise properties of the CoRoT data. A planet-finding perspective

    NASA Astrophysics Data System (ADS)

    Aigrain, S.; Pont, F.; Fressin, F.; Alapini, A.; Alonso, R.; Auvergne, M.; Barbieri, M.; Barge, P.; Bordé, P.; Bouchy, F.; Deeg, H.; de La Reza, R.; Deleuil, M.; Dvorak, R.; Erikson, A.; Fridlund, M.; Gondoin, P.; Guterman, P.; Jorda, L.; Lammer, H.; Léger, A.; Llebaria, A.; Magain, P.; Mazeh, T.; Moutou, C.; Ollivier, M.; Pätzold, M.; Queloz, D.; Rauer, H.; Rouan, D.; Schneider, J.; Wuchter, G.; Zucker, S.

    2009-10-01

    In this short paper, we study the photometric precision of stellar light curves obtained by the CoRoT satellite in its planet-finding channel, with a particular emphasis on the time scales characteristic of planetary transits. Together with other articles in the same issue of this journal, it forms an attempt to provide the building blocks for a statistical interpretation of the CoRoT planet and eclipsing binary catch to date. After pre-processing the light curves so as to minimise long-term variations and outliers, we measure the scatter of the light curves in the first three CoRoT runs lasting more than 1 month, using an iterative non-linear filter to isolate signal on the time scales of interest. The behaviour of the noise on 2 h time scales is described well by a power-law with index 0.25 in R-magnitude, ranging from 0.1 mmag at R=11.5 to 1 mmag at R=16, which is close to the pre-launch specification, though still a factor 2-3 above the photon noise due to residual jitter noise and hot pixel events. There is evidence of slight degradation in the performance over time. We find clear evidence of enhanced variability on hour time scales (at the level of 0.5 mmag) in stars identified as likely giants from their R magnitude and B-V colour, which represent approximately 60 and 20% of the observed population in the directions of Aquila and Monoceros, respectively. On the other hand, median correlated noise levels over 2 h for dwarf stars are extremely low, reaching 0.05 mmag at the bright end. The CoRoT space mission, launched on December 27, 2006, has been developed and is operated by the CNES, with the contribution of Austria, Belgium, Brazil, ESA, Germany, and Spain. CoRoT data become publicly available one year after release to the Co-Is of the mission from the CoRoT archive: http://idoc-corot.ias.u-psud.fr/.

  20. Long-Term Tracking of Corotating Density Structures Using Heliospheric Imaging

    NASA Astrophysics Data System (ADS)

    Plotnikov, I.; Rouillard, A. P.; Davies, J. A.; Bothmer, V.; Eastwood, J. P.; Gallagher, P.; Harrison, R. A.; Kilpua, E.; Möstl, C.; Perry, C. H.; Rodriguez, L.; Lavraud, B.; Génot, V.; Pinto, R. F.; Sanchez-Diaz, E.

    2016-06-01

    The systematic monitoring of the solar wind in high-cadence and high-resolution heliospheric images taken by the Solar-Terrestrial Relation Observatory (STEREO) spacecraft permits the study of the spatial and temporal evolution of variable solar wind flows from the Sun out to 1 AU, and beyond. As part of the EU Framework 7 (FP7) Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS) project, we have generated a catalog listing the properties of 190 corotating structures well-observed in images taken by the Heliospheric Imager (HI) instruments onboard STEREO-A (ST-A). Based on this catalog, we present here one of very few long-term analyses of solar wind structures advected by the background solar wind. We concentrate on the subset of plasma density structures clearly identified inside corotating structures. This analysis confirms that most of the corotating density structures detected by the heliospheric imagers comprises a series of density inhomogeneities advected by the slow solar wind that eventually become entrained by stream interaction regions. We have derived the spatial-temporal evolution of each of these corotating density structures by using a well-established fitting technique. The mean radial propagation speed of the corotating structures is found to be 311 ±31 km s^{-1}. Such a low mean value corresponds to the terminal speed of the slow solar wind rather than the speed of stream interfaces, which is typically intermediate between the slow and fast solar wind speeds ( {˜} 400 km s^{-1}). Using our fitting technique, we predicted the arrival time of each corotating density structure at different probes in the inner heliosphere. We find that our derived speeds are systematically lower by {˜} 100 km s^{-1} than those measured in situ at the predicted impact times. Moreover, for cases when a stream interaction region is clearly detected in situ at the estimated impact time, we find that our derived speeds are lower than the speed of the

  1. Detection of Rossby Waves in Multi-Parameters in Multi-Mission Satellite Observations and HYCOM Simulations in the Indian Ocean

    NASA Technical Reports Server (NTRS)

    Subrahmanyam, Bulusu; Heffner, David M.; Cromwell, David; Shriver, Jay F.

    2009-01-01

    Rossby waves are difficult to detect with in situ methods. However, as we show in this paper, they can be clearly identified in multi-parameters in multi-mission satellite observations of sea surface height (SSH), sea surface temperature (SST) and ocean color observations of chlorophyll-a (chl-a), as well as 1/12-deg global HYbrid Coordinate Ocean Model (HYCOM) simulations of SSH, SST and sea surface salinity (SSS) in the Indian Ocean. While the surface structure of Rossby waves can be elucidated from comparisons of the signal in different sea surface parameters, models are needed to gain direct information about how these waves affect the ocean at depth. The first three baroclinic modes of the Rossby waves are inferred from the Fast Fourier Transform (FFT), and two-dimensional Radon Transform (2D RT). At many latitudes the first and second baroclinic mode Rossby wave phase speeds from satellite observations and model parameters are identified.

  2. First observational Evidence of Rossby Wave Signatures in Spectral Aerosol Optical Depths over Central Himalayas

    NASA Astrophysics Data System (ADS)

    Devulapalli, P. V.; Kondapalli, N. K.; Krishna, S.; Ratnam, M.; Naja, M. K.; Kishore, R.

    2013-12-01

    retrieved AOD (550nm). These signatures are also observed in background winds with westward propagation at a speed of ~ 2ms-1. Further, the Hovmoller diagram obtained from MODIS AOD also showed westward propagation through the observational site, re-confirming that these modulations are associated with Rossby waves of extra-tropical region. It is shown that inclusion of the Rossby wave modulation can cause an additional warming of ~ 4.07×0.98 Wm-2 over Central Himalayan region. The present study finds important implications in terms of wave induced dynamics of aerosols which have immense impact on atmospheric radiative forcing.

  3. The transport of angular momentum by gravitational instabilities and Rossby vortices in accretion disks

    NASA Astrophysics Data System (ADS)

    Currier, Nathaniel W.

    We propose a model for the birth of spiral galaxies and the supermassive black holes (SMBHs) at their centers. It all starts when a galaxy-mass gas condensation collapses to ~ 200 × the background density. It experiences weak tidal torques from similar condensations, which establish its spin parameter l. It forms a Lyman-a (Lya) cloud, then undergoes an inviscid, angular-momentum- preserving collapse to a Mestel disk with a flat rotation curve (FRCD). A FRCD has v ~ const, M Rossby vortex instability (RVI). Both mechanisms transport angular momentum coherently, so they easily dominate turbulent mechanisms wherever the disk is thin. The popular magneto-rotational instability (MRI) is semi-coherent, but it's not required for our model, so we leave it for further study. We use a 2-D Eulerian hydro code to simulate the SGI and RVI in both FRCDs and Keplerian disks. We explore the triggers of these instabilities, namely, the Toomre parameter Q in SGI-unstable FRCDs and pressure jumps in RVI-unstable Keplerian disks. We confirm that Q [Special characters omitted.] 1 triggers the SGI in FRCDs and that D P/P [Special characters omitted.] 5 generates robust Rossby vortices in Keplerian disks. We also find that these instabilities interact in the transition region between these two types of disks. We relate all this to our self-consistent model

  4. Excitation of zonal flow and magnetic field by Rossby-Khantadze electromagnetic planetary waves in the ionospheric E-layer

    NASA Astrophysics Data System (ADS)

    Kaladze, T. D.; Kahlon, L. Z.; Tsamalashvili, L. V.

    2012-02-01

    Nonlinear dynamics of Rossby-Khantadze electromagnetic planetary waves in the weakly ionized ionospheric E-layer is investigated. Along with the prevalent effect of Hall conductivity for these waves, the latitudinal inhomogeneity of both the Earth's angular velocity and the geomagnetic field becomes essential. It is shown that such short wavelength turbulence of Rossby-Khantadze waves is unstable with respect to the excitation of low-frequency and large-scale perturbations of the zonal flow and magnetic field. The nonlinear mechanism of the instability is driven by the advection of vorticity, leading to the inverse energy cascade toward the longer wavelength. The growth rate of the corresponding instability is found. It is shown that the generation of the intense mean magnetic field is caused by the latitudinal gradient of the geomagnetic field.

  5. VizieR Online Data Catalog: Planetary transit candidates in CoRoT LRa01 field (Carone+, 2012)

    NASA Astrophysics Data System (ADS)

    Carone, L.; Gandolfi, D.; Cabrera, J.; Hatzes, A. P.; Deeg, H. J.; Csizmadia, Sz.; Paetzold, M.; Weingrill, J.; Aigrain, S.; Alonso, R.; Alapini, A.; Almenara, J.-M.; Auvergne, M.; Baglin, A.; Barge, P.; Bonomo, A. S.; Borde, P.; Bouchy, F.; Bruntt, H.; Carpano, S.; Cochran, W. D.; Deleuil, M.; Diaz, R. F.; Dreizler, S.; Dvorak, R.; Eisloeffel, J.; Eigmueller, P.; Endl, M.; Erikson, A.; Ferraz-Mello, S.; Fridlund, M.; Gazzano, J.-C.; Gibson, N.; Gillon, M.; Gondoin, P.; Grziwa, S.; Guenther, E. W.; Guillot, T.; Hartmann, M.; Havel, M.; Hebrard, G.; Jorda, L.; Kabath, P.; Leger, A.; Llebaria, A.; Lammer, H.; Lovis, C.; MacQueen, P. J.; Mayor, M.; Mazeh, T.; Moutou, C.; Nortmann, L.; Ofir, A.; Ollivier, M.; Parviainen, H.; Pepe, F.; Pont, F.; Queloz, D.; Rabus, M.; Rauer, H.; Regulo, C.; Renner, S.; de La, Reza R.; Rouan, D.; Santerne, A.; Samuel, B.; Schneider, J.; Shporer, A.; Stecklum, B.; Tal-Or, L.; Tingley, B.; Udry, S.; Wuchterl, G.

    2012-04-01

    We present the list of planetary transit candidates from the CoRoT LRa01 star field in the Monoceros constellation toward the Galactic anti-center direction. The CoRoT observations of LRa01 lasted from 24 October 2007 to 3 March 2008. We acquired and analyzed 7470 chromatic and 3938 monochromatic lightcurves. Instrumental noise and stellar variability were treated with several filtering tools by different teams from the CoRoT community. Different transit search algorithms were applied to the lightcurves. (4 data files).

  6. The Rossby Centre Regional Atmospheric Climate Model part II: application to the Arctic climate.

    PubMed

    Jones, Colin G; Wyser, Klaus; Ullerstig, Anders; Willén, Ulrika

    2004-06-01

    The Rossby Centre regional climate model (RCA2) has been integrated over the Arctic Ocean as part of the international ARCMIP project. Results have been compared to observations derived from the SHEBA data set. The standard RCA2 model overpredicts cloud cover and downwelling longwave radiation, during the Arctic winter. This error was improved by introducing a new cloud parameterization, which significantly improves the annual cycle of cloud cover. Compensating biases between clear sky downwelling longwave radiation and longwave radiation emitted from cloud base were identified. Modifications have been introduced to the model radiation scheme that more accurately treat solar radiation interaction with ice crystals. This leads to a more realistic representation of cloud-solar radiation interaction. The clear sky portion of the model radiation code transmits too much solar radiation through the atmosphere, producing a positive bias at the top of the frequent boundary layer clouds. A realistic treatment of the temporally evolving albedo, of both sea-ice and snow, appears crucial for an accurate simulation of the net surface energy budget. Likewise, inclusion of a prognostic snow-surface temperature seems necessary, to accurately simulate near-surface thermodynamic processes in the Arctic. PMID:15264599

  7. Rossby wave energy dispersion from tropical cyclone in zonal basic flows

    NASA Astrophysics Data System (ADS)

    Shi, Wenli; Fei, Jianfang; Huang, Xiaogang; Liu, Yudi; Ma, Zhanhong; Yang, Lu

    2016-04-01

    This study investigates tropical cyclone energy dispersion under horizontally sheared flows using a nonlinear barotropic model. In addition to common patterns, unusual features of Rossby wave trains are also found in flows with constant vorticity and vorticity gradients. In terms of the direction of the energy dispersion, the wave train can rotate clockwise and elongate southwestward under anticyclonic circulation (ASH), which contributes to the reenhancement of the tropical cyclone (TC). The wave train even splits into two obvious wavelike trains in flows with a southward vorticity gradient (WSH). Energy dispersed from TCs varies over time, and variations in the intensity of the wave train components typically occur in two stages. Wave-activity flux diagnosis and ray tracing calculations are extended to the frame that moves along with the TC to reveal the concrete progress of wave propagation. The direction of the wave-activity flux is primarily determined by the combination of the basic flow and the TC velocity. Along the flux, the distribution of pseudomomentum effectively illustrates the development of wave trains, particularly the rotation and split of wave propagation. Ray tracing involves the quantitative tracing of wave features along rays, which effectively coincide with the wave train regimes. Flows of a constant shear (parabolic meridional variation) produce linear (nonlinear) wave number variations. For the split wave trains, the real and complex wave number waves move along divergent trajectories and are responsible for different energy dispersion ducts.

  8. Persistent and energetic bottom-trapped topographic Rossby waves observed in the southern South China Sea

    NASA Astrophysics Data System (ADS)

    Shu, Yeqiang; Xue, Huijie; Wang, Dongxiao; Chai, Fei; Xie, Qiang; Cai, Shuqun; Chen, Rongyu; Chen, Ju; Li, Jian; He, Yunkai

    2016-04-01

    Energetic fluctuations with periods of 9–14 days below a depth of 1400 m were observed in the southern South China Sea (SCS) from 5 years of direct measurements. We interpreted such fluctuations as topographic Rossby waves (TRWs) because they obey the dispersion relation. The TRWs persisted from May 24, 2009 to August 23, 2013, and their bottom current speed with a maximum of ~10 cm/s was one order of magnitude greater than the mean current and comparable to the tidal currents near the bottom. The bottom-trapped TRWs had an approximate trapping depth of 325 m and reference wavelength of ~82 km, which were likely excited by eddies above. Upper layer current speed that peaked approximately every 2 months could offer the energy sources for the persistent TRWs in the southern SCS. Energetic bottom-trapped TRWs may have a comparable role in deep circulation to tides in areas with complex topography.

  9. Persistent and energetic bottom-trapped topographic Rossby waves observed in the southern South China Sea

    PubMed Central

    Shu, Yeqiang; Xue, Huijie; Wang, Dongxiao; Chai, Fei; Xie, Qiang; Cai, Shuqun; Chen, Rongyu; Chen, Ju; Li, Jian; He, Yunkai

    2016-01-01

    Energetic fluctuations with periods of 9–14 days below a depth of 1400 m were observed in the southern South China Sea (SCS) from 5 years of direct measurements. We interpreted such fluctuations as topographic Rossby waves (TRWs) because they obey the dispersion relation. The TRWs persisted from May 24, 2009 to August 23, 2013, and their bottom current speed with a maximum of ~10 cm/s was one order of magnitude greater than the mean current and comparable to the tidal currents near the bottom. The bottom-trapped TRWs had an approximate trapping depth of 325 m and reference wavelength of ~82 km, which were likely excited by eddies above. Upper layer current speed that peaked approximately every 2 months could offer the energy sources for the persistent TRWs in the southern SCS. Energetic bottom-trapped TRWs may have a comparable role in deep circulation to tides in areas with complex topography. PMID:27075644

  10. Atmospheric Transport and Mixing linked to Rossby Wave Breaking in GFDL Dynamical Core

    NASA Astrophysics Data System (ADS)

    Liu, C.; Barnes, E. A.

    2015-12-01

    Atmospheric transport and mixing plays an important role in the global energy balance and the distribution of health-related chemical constituents. Previous studies suggest a close linkage between large-scale transport and Rossby wave breaking (RWB). In this work, we use the GFDL spectral dynamical core to investigate this relationship and study the response of RWB-related transport in different climate scenarios. In a standard control run, we quantify the contribution of RWB to the total transport and mixing of an idealized tracer. In addition, we divide the contribution further into the two types of RWB - anticyclonic wave breaking (AWB) and cyclonic wave breaking (CWB) -- and contrast their efficiency at transport and mixing. Our results are compared to a previous study in which the transport ability of the two types of RWB is studied for individual baroclinic wave life-cycles. In a series of sensitivity runs, we study the response of RWB-related transport and mixing to various states of the jet streams. The responses of the mean strength, frequency, and the efficiency of RWB-related transport are documented and the implications for the transport and mixing in a warmer climate are discussed.

  11. Penetration of nonlinear Rossby eddies into South China Sea evidenced by cruise data

    NASA Astrophysics Data System (ADS)

    Hu, Jianyu; Zheng, Quanan; Sun, Zhenyu; Tai, Chang-Kuo

    2012-03-01

    From the analyses of the cruise conductivity-temperature-depth profiler and acoustic Doppler current profiler data combined with simultaneous satellite altimeter data and Argo float profiling data, this paper provides evidence for the nonlinear Rossby eddies (NREs) penetrating through the Kuroshio and the Luzon Strait and entering the South China Sea (SCS). A high-salinity water prism in the subsurface layer west of the Luzon Strait was observed in January 2010. The salty prism centered at around 21°N and 118°E has a salinity higher than 34.8 and co-locates with an anticyclonic eddy with a diameter of about 150 km. The water properties of the salty prism are close to those of the Northwest Pacific (NWP) water. The time series of altimeter data and Argo float profiling data indicate that the anticyclonic eddy originates from an NRE that propagates westward from the NWP. The eddy penetrates the Luzon Strait at a speed of about 0.6 m s-1 because of the effects of the narrow strait and the Kuroshio-eddy interaction and carries the high-salinity subsurface water from the NWP into the northern SCS.

  12. Persistent and energetic bottom-trapped topographic Rossby waves observed in the southern South China Sea.

    PubMed

    Shu, Yeqiang; Xue, Huijie; Wang, Dongxiao; Chai, Fei; Xie, Qiang; Cai, Shuqun; Chen, Rongyu; Chen, Ju; Li, Jian; He, Yunkai

    2016-01-01

    Energetic fluctuations with periods of 9-14 days below a depth of 1400 m were observed in the southern South China Sea (SCS) from 5 years of direct measurements. We interpreted such fluctuations as topographic Rossby waves (TRWs) because they obey the dispersion relation. The TRWs persisted from May 24, 2009 to August 23, 2013, and their bottom current speed with a maximum of ~10 cm/s was one order of magnitude greater than the mean current and comparable to the tidal currents near the bottom. The bottom-trapped TRWs had an approximate trapping depth of 325 m and reference wavelength of ~82 km, which were likely excited by eddies above. Upper layer current speed that peaked approximately every 2 months could offer the energy sources for the persistent TRWs in the southern SCS. Energetic bottom-trapped TRWs may have a comparable role in deep circulation to tides in areas with complex topography. PMID:27075644

  13. A Possible Rossby Wave Instability Origin for the Flares in Sagittarius A*

    NASA Astrophysics Data System (ADS)

    Tagger, Michel; Melia, Fulvio

    2006-01-01

    In recent years, near-IR and X-ray flares have been detected from the Galaxy's central radio point source, Sagittarius A* (Sgr A*), believed to be an ~3×106 Msolar supermassive black hole. In some cases, the transient emission appears to be modulated with a (quasi-)periodic oscillation (QPO) of ~17-20 minutes. The implied ~3rS size of the emitter (where rS≡2GM/c2 is the Schwarzschild radius) points to an instability-possibly induced by accretion-near the marginally stable orbit (MSO) of a slowly spinning object. But Sgr A* is not accreting via a large, ``standard'' disk; instead, the low-density environment surrounding it apparently feeds the black hole with low angular momentum clumps of plasma that circularize within ~(10-300)rS and merge onto a compact, hot disk. In this Letter, we follow the evolution of the disk following such an event, and we show that a Rossby wave instability, particularly in its magnetohydrodynamic (MHD) form, grows rapidly and produces a period of enhanced accretion lasting several hours. Both the amplitude of this response and its duration match the observed flare characteristics rather well.

  14. Transiting exoplanets from the CoRoT space mission. XVII. The hot Jupiter CoRoT-17b: a very old planet

    NASA Astrophysics Data System (ADS)

    Csizmadia, Sz.; Moutou, C.; Deleuil, M.; Cabrera, J.; Fridlund, M.; Gandolfi, D.; Aigrain, S.; Alonso, R.; Almenara, J.-M.; Auvergne, M.; Baglin, A.; Barge, P.; Bonomo, A. S.; Bordé, P.; Bouchy, F.; Bruntt, H.; Carone, L.; Carpano, S.; Cavarroc, C.; Cochran, W.; Deeg, H. J.; Díaz, R. F.; Dvorak, R.; Endl, M.; Erikson, A.; Ferraz-Mello, S.; Fruth, Th.; Gazzano, J.-C.; Gillon, M.; Guenther, E. W.; Guillot, T.; Hatzes, A.; Havel, M.; Hébrard, G.; Jehin, E.; Jorda, L.; Léger, A.; Llebaria, A.; Lammer, H.; Lovis, C.; MacQueen, P. J.; Mazeh, T.; Ollivier, M.; Pätzold, M.; Queloz, D.; Rauer, H.; Rouan, D.; Santerne, A.; Schneider, J.; Tingley, B.; Titz-Weider, R.; Wuchterl, G.

    2011-07-01

    We report on the discovery of a hot Jupiter-type exoplanet, CoRoT-17b, detected by the CoRoT satellite. It has a mass of 2.43 ± 0.30 MJup and a radius of 1.02 ± 0.07 RJup, while its mean density is 2.82 ± 0.38 g/cm3. CoRoT-17b is in a circular orbit with a period of 3.7681 ± 0.0003 days. The host star is an old (10.7 ± 1.0 Gyr) main-sequence star, which makes it an intriguing object for planetary evolution studies. The planet's internal composition is not well constrained and can range from pure H/He to one that can contain ~380 earth masses of heavier elements. The CoRoT space mission, launched on December 27th 2006, has been developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA (RSSD and Science Programme), Germany and Spain. Part of the observations were obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. Based on observations made with HARPS spectrograph on the 3.6-m European Organisation for Astronomical Research in the Southern Hemisphere telescope at La Silla Observatory, Chile (ESO program 184.C-0639). Based on observations made with the IAC80 telescope operated on the island of Tenerife by the Instituto de Astrofísica de Canarias in the Spanish Observatorio del Teide. Part of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

  15. VizieR Online Data Catalog: Algorithm for correcting CoRoT raw light curves (Mislis+, 2010)

    NASA Astrophysics Data System (ADS)

    Mislis, D.; Schmitt, J. H. M. M.; Carone, L.; Guenther, E. W.; Patzold, M.

    2010-10-01

    Requirements : gfortran (or g77, ifort) compiler Input Files : The input files sould be raw CoRoT txt files (http://idoc-corot.ias.u-psud.fr/index.jsp) with names CoRoT*.txt Run the cda by typing C>: ./cda.csh (code and data sould be in the same directory) Output files : CDA creates one ascii output file with name - CoRoT*.R.cor for R filter (2 data files).

  16. Stellar parameters for stars of the CoRoT exoplanet field

    NASA Astrophysics Data System (ADS)

    Cortés, C.; Maciel, S. C.; Vieira, S.; Ferreira Lopes, C. E.; Leão, I. C.; de Oliveira, G. P.; Correia, C.; Canto Martins, B. L.; Catelan, M.; De Medeiros, J. R.

    2015-09-01

    Context. Spectroscopic observations represent a fundamental step in the physical characterization of stars and, in particular, in the precise location of stars in the HR diagram. Rotation is also a key parameter, impacting stellar properties and evolution, which modulates the interior and manifests itself on the surface of stars. To date, the lack of analysis based on large samples has prevented our understanding of the real impact of stellar parameters and rotation on the stellar evolution as well as on the behavior of surface abundances. The space missions, CoRoT and Kepler, are providing us with rotation periods for thousands of stars, thus enabling a robust assessment of the behavior of rotation for different populations and evolutionary stages. For these reasons, the follow-up programs are fundamental to increasing the returns of these space missions. An analysis that combines spectroscopic data and rotation/modulation periods obtained from these space missions provides the basis for establishing the evolutionary behavior of the angular momentum of solar-like stars at different evolutionary stages, and the relation of rotation with other relevant physical and chemical parameters. Aims: To support the computation and evolutionary interpretation of periods associated with the rotational modulation, oscillations, and variability of stars located in the CoRoT fields, we are conducting a spectroscopic survey for stars located in the fields already observed by the satellite. These observations allow us to compute physical and chemical parameters for our stellar sample. Methods: Using spectroscopic observations obtained with UVES/VLT and Hydra/Blanco, and based on standard analysis techniques, we computed physical and chemical parameters (Teff, log (g), [Fe/H], vmic, vrad, vsin (i), and A(Li)) for a large sample of CoRoT targets. Results: We provide physical and chemical parameters for a sample comprised of 138 CoRoT targets. Our analysis shows the stars in our

  17. Corotating MeV/amu ion enhancements at 1 AU or less from 1978 to 1986

    NASA Technical Reports Server (NTRS)

    Richardson, I. G.; Barbier, L. M.; Reames, D. V.; Von Rosenvinge, T. T.

    1993-01-01

    The properties of MeV/amu ions in 64 corotating streams at and inside 1 AU associated with corotating high-speed streams from 1978 to 1986 during presolar maximum to near solar minimum conditions are discussed. Around 50 percent of the streams include significant ion intensity enhancements not associated with solar particle events or traveling interplanetary shocks. The ions stream nearly along the E x B drift direction in the spacecraft frame, corresponding to a weak sunward field-aligned streaming in the solar wind frame. The sunward streaming is consistent with particle acceleration in the outer heliosphere followed by diffusion into the inner heliosphere. The ion intensity is not correlated with the stream solar wind speed or with the increase in solar wind speed at the leading edge of the high-speed stream, suggesting that the local shock strength alone may not play a dominant role in determining the intensity.

  18. Global regularity for the 2D Oldroyd-B model in the corotational case

    NASA Astrophysics Data System (ADS)

    Ye, Zhuan; Xu, Xiaojing

    2016-09-01

    This paper is dedicated to the Oldroyd-B model with fractional dissipation $(-\\Delta)^{\\alpha}\\tau$ for any $\\alpha>0$. We establish the global smooth solutions to the Oldroyd-B model in the corotational case with arbitrarily small fractional powers of the Laplacian in two spatial dimensions. The methods described here are quite different from the tedious iterative approach used in recent paper \\cite{XY}. Moreover, in the Appendix we provide some a priori estimates to the Oldroyd-B model in the critical case which may be useful and of interest for future improvement. Finally, the global regularity to to the Oldroyd-B model in the corotational case with $-\\Delta u$ replaced by $(-\\Delta)^{\\gamma}u$ for $\\gamma>1$ are also collected in the Appendix. Therefore our result is more closer to the resolution of the well-known global regularity issue on the critical 2D Oldroyd-B model.

  19. VizieR Online Data Catalog: CoRoT 105906206 frequencies analysis (da Silva+, 2014)

    NASA Astrophysics Data System (ADS)

    da Silva, R.; Maceroni, C.; Gandolfi, D.; Lehmann, H.; Hatzes, A. P.

    2014-03-01

    The file frequenc.dat contains the table with 220 frequencies, amplitudes, and phases, together with their uncertainties, derived for the light curve of CoRoT 105906206 with pulsations only (after subtracting the best binary model). The uncertainties are the formal values computed using equations (4), (10), and (11) of Montgomery & O'Donoghue (1999DSSN...13...28M). (1 data file).

  20. Observed departure of the Io plasma torus from rigid corotation with Jupiter

    NASA Technical Reports Server (NTRS)

    Brown, R. A.

    1983-01-01

    A study of forbidden S II red doublet spectra indicates that the Io plasma torus at 5.9 Jupiter radii does not corotate rigidly with Jupiter. The lag is found to be 6 percent + or 4 percent, where the variability range, not the uncertainty, is indicated. Comparison with existing models indicates the lag may be due primarily to ion creation in the Io torus.

  1. A rotating Michelson interferometer from the co-rotating point of view

    NASA Astrophysics Data System (ADS)

    Maraner, Paolo

    2016-06-01

    The phase shift induced by a uniform rotation in a Michelson interferometer is re-derived in the geometrical framework of the coordinate-free formalism of general relativity from the co-rotating point of view. The effect is second order in the ratio of the interferometer's speed to the speed of light and further suppressed by the ratio of the length of the interferometer's arms to the radius of rotation. The relation of the effect to gravitational time dilation is discussed.

  2. THE FUTURE OF THE SUN: AN EVOLVED SOLAR TWIN REVEALED BY CoRoT

    SciTech Connect

    Do Nascimento, J.-D. Jr.; Da Costa, J. S.; Castro, M.; Takeda, Y.; Melendez, J.

    2013-07-10

    The question of whether the Sun is peculiar within the class of solar-type stars has been the subject of active investigation over the past three decades. Although several solar twins have been found with stellar parameters similar to those of the Sun (albeit in a range of Li abundances and with somewhat different compositions), their rotation periods are unknown, except for 18 Sco, which is younger than the Sun and with a rotation period shorter than solar. It is difficult to obtain rotation periods for stars of solar age from ground-based observations, as a low-activity level implies a shallow rotational modulation of their light curves. CoRoT has provided space-based long time series from which the rotation periods of solar twins as old as the Sun could be estimated. Based on high-signal-to-noise, high-resolution spectroscopic observations gathered at the Subaru Telescope, we show that the star CoRoT ID 102684698 is a somewhat evolved solar twin with a low Li abundance. Its rotation period is 29 {+-} 5 days, compatible with its age (6.7 Gyr) and low lithium content, A{sub Li} {approx}< 0.85 dex. Interestingly, our CoRoT solar twin seems to have enhanced abundances of the refractory elements with respect to the Sun, a typical characteristic of most nearby twins. With a magnitude V {approx_equal} 14.1, ID 102684698 is the first solar twin revealed by CoRoT, the farthest field solar twin so far known, and the only solar twin older than the Sun for which a rotation period has been determined.

  3. The Transit Detection Algorithm DST and its application to CoRoT and Kepler data

    NASA Astrophysics Data System (ADS)

    Cabrera, J.; Rauer, H.; Erikson, A.; Csizmadia, S.

    2011-10-01

    Transit detection algorithms are mathematical tools used to detect the presence of planets in the photometric data of transit surveys. Space missions are exploring the parameter space of transit surveys towards small planets where classical algorithms do not perform optimally, either due to the low signal to noise ratio of the signal or to its non-periodic characteristics. We present an algorithm addressing these challenges and its performance in an application to CoRoT and Kepler data.

  4. Rossby wave instability and long-term evolution of dead zones in protoplanetary discs

    NASA Astrophysics Data System (ADS)

    Miranda, Ryan; Lai, Dong; Méheut, Héloïse

    2016-04-01

    The physical mechanism of angular momentum transport in poorly ionized regions of protoplanetary discs, the dead zones (DZs), is not understood. The presence of a DZ naturally leads to conditions susceptible to the Rossby wave instability (RWI), which produces vortices and spiral density waves that may revive the DZ and be responsible for observed large-scale disc structures. We present a series of two-dimensional hydrodynamic simulations to investigate the role of the RWI in DZs, including its impact on the long-term evolution of the disc and its morphology. The non-linear RWI can generate Reynolds stresses (effective α parameter) as large as 0.01-0.05 in the DZ, helping to sustain quasi-steady accretion throughout the disc. It also produces novel disc morphologies, including azimuthal asymmetries with m = 1, 2, and atypical vortex shapes. The angular momentum transport strength and morphology are most sensitive to two parameters: the radial extent of the DZ and the disc viscosity. The largest Reynolds stresses are produced when the radial extent of the DZ is less than its distance to the central star. Such narrow DZs lead to a single vortex or two coherent antipodal vortices in the quasi-steady state. The edges of wider DZs evolve separately, resulting in two independent vortices and reduced angular momentum transport efficiency. In either case, we find that, because of the Reynolds stresses generated by the non-linear RWI, gravitational instability is unlikely to play a role in angular momentum transport across the DZ, unless the accretion rate is sufficiently high.

  5. On the mechanism of self gravitating Rossby interfacial waves in proto-stellar accretion discs

    NASA Astrophysics Data System (ADS)

    Yellin-Bergovoy, Ron; Heifetz, Eyal; Umurhan, Orkan M.

    2016-05-01

    The dynamical response of edge waves under the influence of self-gravity is examined in an idealized two-dimensional model of a proto-stellar disc, characterized in steady state as a rotating vertically infinite cylinder of fluid with constant density except for a single density interface at some radius r0. The fluid in basic state is prescribed to rotate with a Keplerian profile $\\Omega_k(r)\\sim r^{-3/2}$ modified by some additional azimuthal sheared flow. A linear analysis shows that there are two azimuthally propagating edge waves, kin to the familiar Rossby waves and surface gravity waves in terrestrial studies, which move opposite to one another with respect to the local basic state rotation rate at the interface. Instability only occurs if the radial pressure gradient is opposite to that of the density jump (unstably stratified) where self-gravity acts as a wave stabilizer irrespective of the stratification of the system. The propagation properties of the waves are discussed in detail in the language of vorticity edge waves. The roles of both Boussinesq and non-Boussinesq effects upon the stability and propagation of these waves with and without the inclusion of self-gravity are then quantified. The dynamics involved with self-gravity non- Boussinesq effect is shown to be a source of vorticity production where there is a jump in the basic state density, in addition, self-gravity also alters the dynamics via the radial main pressure gradient, which is a Boussinesq effect . Further applications of these mechanical insights are presented in the conclusion including the ways in which multiple density jumps or gaps may or may not be stable.

  6. North and South Atlantic Bidecadal SL variability: Rossby Waves, AMOC fingerprints and Regime Shifts

    NASA Astrophysics Data System (ADS)

    Vianna, M. L.; Menezes, V. V.

    2014-12-01

    The relationship between the North and South Atlantic bidecadal sea level (SL) oscillations in the twentieth century (1908-2008) is investigated using SODA 2.2.4 reanalysis and 102 monthly mean SL time series from TG stations provided by PSMSL. Bidecadal SL signal extraction was done using our method of subjectively choosing groupings of space-time data into non-overlapping period bands by use of Singular Spectrum Analysis (SSA)/ Maximum Entropy Method (MEM) analysis. A CEOF analysis of the SODA bidecadal band shows dominance of 22-24 year periods. Propagating bidecadal mode expansions were then determined through this analysis, which gives two principal modes. The first mode is dominant from 1915 to 1965 and the second from 1970 onward. The amplitude variabilities obtained suggests the presence of regime shifts, which coincide in time with shifts actually observed in European climate and South African lobster fisheries. The first mode is characterized by states with North and South Atlantic subtropical gyres in phase, while tropical and subpolar regions are in opposite phase relative to them. The second mode is characterized by the subpolar gyre and North subtropical gyre almost in quadrature, with North and South subtropical gyres out of phase. The evolution mechanism of this latter mode is related to east-west density contrasts and westward propagating Rossby waves. These waves show phase speeds dominated by geostrophic self-advection of density anomalies relative to the mean meridional density gradient as known from previous studies, but are shown to be additionally influenced by bottom topography. The oscillations caused by these waves are shown to have phase differences (quadrature in the North Atlantic) with regional indices of bidecadal AMOC oscillations. A number of SL-AMOC fingerprints are also reviewed, and a new eastern equatorial fingerprint is proposed.

  7. Extreme Moisture Transport into the Arctic Linked to Rossby Wave Breaking

    NASA Astrophysics Data System (ADS)

    Liu, C.; Barnes, E. A.

    2014-12-01

    Water vapor plays an important role in the energetics of the Arctic. We demonstrate that the bulk of the poleward moisture transport by transients across 60N is driven by extreme transport events. These events are shown to be closely related to two types of Rossby wave breaking (RWB) - anticyclonic wave breaking (AWB) and cyclonic wave breaking (CWB). Using a RWB tracking algorithm, we determine that these two types can account for 47% of the total poleward moisture transport by transients across 60∘^circN in winter and 37% in summer. Additional analysis suggests that the seasonality of this RWB-related moisture transport is determined equally by the strength of RWB transport, and the frequency of RWB occurrence. The seasonality of RWB occurrence is, in turn, dictated by the seasonal variation of the latitude of the jet-streams - AWB (CWB) related transport occurs more frequently when the jet is shifted poleward (equatorward). The interannual variability of RWB-related transport across 60N in winter is shown to be strongly influenced by climate variability captured by ENSO and the NAO. In the positive (negative) phase of ENSO, AWB transports less (more) moisture through the Bering Strait and CWB transports more (less) through Canada. In the positive (negative) phase of the NAO, AWB transports more (less) moisture through the Norwegian Sea and CWB transports less (more) along the west coast of Greenland. These results highlight how low-frequency climate variability outside of the polar region can influence Arctic water vapor by modulating extreme synoptic transport events.

  8. Extreme moisture transport into the Arctic linked to Rossby wave breaking

    NASA Astrophysics Data System (ADS)

    Liu, Chengji; Barnes, Elizabeth A.

    2015-05-01

    The transport of moisture into the Arctic is tightly connected to midlatitude dynamics. We show that the bulk of the transient poleward moisture transport across 60°N is driven by extreme transport (fluxes greater than the 90th percentile) events. We demonstrate that these events are closely related to the two types of Rossby wave breaking (RWB)-anticyclonic wave breaking (AWB) and cyclonic wave breaking (CWB). Using a RWB tracking algorithm, we determine that RWB can account for approximately 68% of the extreme poleward moisture transport by transients across 60°N in winter and 56% in summer. Additional analysis suggests that the seasonality of such RWB-related moisture transport is determined approximately equally by (1) the magnitude of transport (which is largely a function of the background moisture gradient) and (2) the frequency of RWB occurrence. The seasonality of RWB occurrence is, in turn, tied to the seasonal variation of the latitude of the jet streams-AWB-related (CWB-related) transport occurs more frequently when the jet is shifted poleward (equatorward). The interannual variability of RWB-related transport across 60°N in winter is shown to be strongly influenced by climate variability captured by the El Niño/Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). In the positive (negative) phase of ENSO, AWB transports less (more) moisture through the Bering Strait and CWB transports more (less) through western Canada. In the positive (negative) phase of the NAO, AWB transports more (less) moisture through the Norwegian Sea and CWB transports less (more) along the west coast of Greenland. These results highlight that low-frequency climate variability outside of the polar regions can influence the Arctic water vapor by modulating extreme synoptic transport events.

  9. A theoretical perspective on the ultra-compact systems of CoRoT and Kepler

    NASA Astrophysics Data System (ADS)

    Wuchterl, G.

    2011-10-01

    CoRoT and Kepler discovered closely spaced short period planetary systems. We investigate into the physics of these systems by combining an approach that was developed for the CoRoT mission to determine the distributions of planetary masses and radii based on a minimum number of basic physical principles with the classical approach of Hill-exclusion volumes to estimate dynamical stability. We discuss to what extent the discovered systems can be understood as a random draw from the theoretical mass and/or radius distributions with Hill-exclusion stability as a constraint. We point to the bi-modality of the theoretical planetary mass-function as a key factor in shaping the architecture of the presently known systems. Given the first-time availability of new high-resolution epoch-of observation theoretical radius distributions for the entire present period sensitivity of CoRoT and Keplerreleases, we take the opportunity to confront the various radius anomalies — 'styrofoam' planets, inflated Jupiters and Neptunes — to our statistical approach.

  10. THE CoRoT DISCOVERY OF A UNIQUE TRIPLE-MODE CEPHEID IN THE GALAXY

    SciTech Connect

    Poretti, E.; Baglin, A.; Weiss, W. W.

    2014-11-10

    The exploitation of the CoRoT treasure of stars observed in the exoplanetary field allowed the detection of a unusual triple-mode Cepheid in the Milky Way, CoRoT 0223989566. The two modes with the largest amplitudes and a period ratio of 0.80 are identified with the first (P {sub 1} = 1.29 days) and second (P {sub 2} = 1.03 days) radial overtones. The third period, which has the smallest amplitude but is able to produce combination terms with the other two, is the longest one (P {sub 3} = 1.89 days). The ratio of 0.68 between the first-overtone period and the third period is the unusual feature. Its identification with the fundamental radial or a nonradial mode is discussed with respect to similar cases in the Magellanic Clouds. In both cases, the period triplet and the respective ratios make the star unique in our Galaxy. The distance derived from the period-luminosity relation and the galactic coordinates put CoRoT 0223989566 in the metal-rich environment of the ''outer arm'' of the Milky Way.

  11. Uncovering the planets and stellar activity of CoRoT-7 using only radial velocities

    NASA Astrophysics Data System (ADS)

    Faria, J. P.; Haywood, R. D.; Brewer, B. J.; Figueira, P.; Oshagh, M.; Santerne, A.; Santos, N. C.

    2016-04-01

    Stellar activity can induce signals in the radial velocities of stars, complicating the detection of orbiting low-mass planets. We present a method to determine the number of planetary signals present in radial-velocity datasets of active stars, using only radial-velocity observations. Instead of considering separate fits with different number of planets, we use a birth-death Markov chain Monte Carlo algorithm to infer the posterior distribution for the number of planets in a single run. In a natural way, the marginal distributions for the orbital parameters of all planets are also inferred. This method is applied to HARPS data of CoRoT-7. We confidently recover the orbits of both CoRoT-7b and CoRoT-7c although the data show evidence for the presence of additional signals. All data and software presented in this article are available online at http://https://github.com/j-faria/exoBD-CoRoT7

  12. The CoRoT Discovery of a Unique Triple-mode Cepheid in the Galaxy

    NASA Astrophysics Data System (ADS)

    Poretti, E.; Baglin, A.; Weiss, W. W.

    2014-11-01

    The exploitation of the CoRoT treasure of stars observed in the exoplanetary field allowed the detection of a unusual triple-mode Cepheid in the Milky Way, CoRoT 0223989566. The two modes with the largest amplitudes and a period ratio of 0.80 are identified with the first (P 1 = 1.29 days) and second (P 2 = 1.03 days) radial overtones. The third period, which has the smallest amplitude but is able to produce combination terms with the other two, is the longest one (P 3 = 1.89 days). The ratio of 0.68 between the first-overtone period and the third period is the unusual feature. Its identification with the fundamental radial or a nonradial mode is discussed with respect to similar cases in the Magellanic Clouds. In both cases, the period triplet and the respective ratios make the star unique in our Galaxy. The distance derived from the period-luminosity relation and the galactic coordinates put CoRoT 0223989566 in the metal-rich environment of the "outer arm" of the Milky Way.

  13. BEER analysis of Kepler and CoRoT light curves. III. Spectroscopic confirmation of seventy new beaming binaries discovered in CoRoT light curves

    NASA Astrophysics Data System (ADS)

    Tal-Or, L.; Faigler, S.; Mazeh, T.

    2015-08-01

    Context. The BEER algorithm searches stellar light curves for the BEaming, Ellipsoidal, and Reflection photometric modulations that are caused by a short-period companion. These three effects are typically of very low amplitude and can mainly be detected in light curves from space-based photometers. Unlike eclipsing binaries, these effects are not limited to edge-on inclinations. Aims: Applying the algorithm to wide-field photometric surveys such as CoRoT and Kepler offers an opportunity to better understand the statistical properties of short-period binaries. It also widens the window for detecting intrinsically rare systems, such as short-period brown-dwarf and massive-planetary companions to main-sequence stars. Methods: Applying the search to the first five long-run center CoRoT fields, we identified 481 non-eclipsing candidates with periodic flux amplitudes of 0.5-87 mmag. Optimizing the Anglo-Australian-Telescope pointing coordinates and the AAOmega fiber-allocations with dedicated softwares, we acquired six spectra for 231 candidates and seven spectra for another 50 candidates in a seven-night campaign. Analysis of the red-arm AAOmega spectra, which covered the range of 8342-8842 Å, yielded a radial-velocity precision of ~1 km s-1. Spectra containing lines of more than one star were analyzed with the two-dimensional correlation algorithm TODCOR. Results: The measured radial velocities confirmed the binarity of seventy of the BEER candidates - 45 single-line binaries, 18 double-line binaries, and 7 diluted binaries. We show that red giants introduce a major source of false candidates and demonstrate a way to improve BEER's performance in extracting higher fidelity samples from future searches of CoRoT light curves. The periods of the confirmed binaries span a range of 0.3-10 days and show a rise in the number of binaries per ΔlogP toward longer periods. The estimated mass ratios of the double-line binaries and the mass ratios assigned to the single

  14. An Analytic Model for Buoyancy Resonances in Protoplanetary Disks

    NASA Astrophysics Data System (ADS)

    Lubow, Stephen H.; Zhu, Zhaohuan

    2014-04-01

    Zhu et al. found in three-dimensional shearing box simulations a new form of planet-disk interaction that they attributed to a vertical buoyancy resonance in the disk. We describe an analytic linear model for this interaction. We adopt a simplified model involving azimuthal forcing that produces the resonance and permits an analytic description of its structure. We derive an analytic expression for the buoyancy torque and show that the vertical torque distribution agrees well with the results of the Athena simulations and a Fourier method for linear numerical calculations carried out with the same forcing. The buoyancy resonance differs from the classic Lindblad and corotation resonances in that the resonance lies along tilted planes. Its width depends on damping effects and is independent of the gas sound speed. The resonance does not excite propagating waves. At a given large azimuthal wavenumber ky > h -1 (for disk thickness h), the buoyancy resonance exerts a torque over a region that lies radially closer to the corotation radius than the Lindblad resonance. Because the torque is localized to the region of excitation, it is potentially subject to the effects of nonlinear saturation. In addition, the torque can be reduced by the effects of radiative heat transfer between the resonant region and its surroundings. For each azimuthal wavenumber, the resonance establishes a large scale density wave pattern in a plane within the disk.

  15. An analytic model for buoyancy resonances in protoplanetary disks

    SciTech Connect

    Lubow, Stephen H.; Zhu, Zhaohuan E-mail: zhzhu@astro.princeton.edu

    2014-04-10

    Zhu et al. found in three-dimensional shearing box simulations a new form of planet-disk interaction that they attributed to a vertical buoyancy resonance in the disk. We describe an analytic linear model for this interaction. We adopt a simplified model involving azimuthal forcing that produces the resonance and permits an analytic description of its structure. We derive an analytic expression for the buoyancy torque and show that the vertical torque distribution agrees well with the results of the Athena simulations and a Fourier method for linear numerical calculations carried out with the same forcing. The buoyancy resonance differs from the classic Lindblad and corotation resonances in that the resonance lies along tilted planes. Its width depends on damping effects and is independent of the gas sound speed. The resonance does not excite propagating waves. At a given large azimuthal wavenumber k{sub y} > h {sup –1} (for disk thickness h), the buoyancy resonance exerts a torque over a region that lies radially closer to the corotation radius than the Lindblad resonance. Because the torque is localized to the region of excitation, it is potentially subject to the effects of nonlinear saturation. In addition, the torque can be reduced by the effects of radiative heat transfer between the resonant region and its surroundings. For each azimuthal wavenumber, the resonance establishes a large scale density wave pattern in a plane within the disk.

  16. Constraints on the exosphere of CoRoT-7b

    NASA Astrophysics Data System (ADS)

    Guenther, E. W.; Cabrera, J.; Erikson, A.; Fridlund, M.; Lammer, H.; Mura, A.; Rauer, H.; Schneider, J.; Tulej, M.; von Paris, Ph.; Wurz, P.

    2011-01-01

    Context. The small radius and high density of CoRoT-7b implies that this transiting planet belongs to a different species than all transiting planets previously found. Current models suggest that this is the first transiting rocky planet found outside the solar system. Given that the planet orbits a solar-like star at a distance of only 4.5 R*, it is expected that material released from its surface may then form an exosphere. Aims: We constrain the properties of the exosphere by observing the planet in- and out-of-transit. Detecting the exosphere of CoRoT-7b would for the first time allow us to study the material originating in the surface of a rocky extrasolar planet. We scan the entire optical spectrum for any lines originating from the planet, focusing particularly on spectral lines such as those detected in Mercury and Io in our solar system. Methods: Since lines originating in the exosphere are expected to be narrow, we observed CoRoT-7b at high resolution with UVES on the VLT. By subtracting the two spectra from each other, we search for emission and absorption lines originating in the exosphere of CoRoT-7b. Results: In the first step, we focus on Ca I, Ca II, and Na, because these lines have been detected in Mercury. Since the signal-to-noise ratio (S/N) of the spectra is as high as 300, we derive firm upper limits for the flux-range between 1.6 × 10-18 and 3.2 × 10-18 W m-2. For CaO, we find an upper limit of 10-17 W m-2. We also search for emission lines originating in the plasma torus fed by volcanic activity and derive upper limits for these lines. In the whole spectrum we finally try to identify other lines originating in the planet. Conclusions: Except for CaO, the upper limits derived correspond to 2-6 × 10-6 L*, demonstrating the capability of UVES to detect very weak lines. Our observations certainly exclude the extreme interpretations of data for CoRoT-7b, such as an exosphere that emits 2000 times as brightly as Mercury. Based on observations

  17. Study of HD 169392A observed by CoRoT and HARPS

    NASA Astrophysics Data System (ADS)

    Mathur, S.; Bruntt, H.; Catala, C.; Benomar, O.; Davies, G. R.; García, R. A.; Salabert, D.; Ballot, J.; Mosser, B.; Régulo, C.; Chaplin, W. J.; Elsworth, Y.; Handberg, R.; Hekker, S.; Mantegazza, L.; Michel, E.; Poretti, E.; Rainer, M.; Roxburgh, I. W.; Samadi, R.; Stȩślicki, M.; Uytterhoeven, K.; Verner, G. A.; Auvergne, M.; Baglin, A.; Barceló Forteza, S.; Baudin, F.; Roca Cortés, T.

    2013-01-01

    Context. The results obtained by asteroseismology with data from space missions such as CoRoT and Kepler are providing new insights into stellar evolution. After five years of observations, CoRoT is continuing to provide high-quality data and we here present an analysis of the CoRoT observations of the double star HD 169392, complemented by ground-based spectroscopic observations. Aims: This work aims at characterising the fundamental parameters of the two stars, their chemical composition, the acoustic-mode global parameters including their individual frequencies, and their dynamics. Methods: We analysed HARPS observations of the two stars to derive their chemical compositions. Several methods were used and compared to determine the global properties of stars' acoustic modes and their individual frequencies from the photometric data of CoRoT. Results: The new spectroscopic observations and archival astrometric values suggest that HD 169392 is a weakly bound wide binary system. We obtained spectroscopic parameters for both components which suggest that they originate from the same interstellar cloud. However, only the signature of oscillation modes of HD 169392 A was measured; the signal-to-noise ratio of the modes in HD 169392B is too low to allow any confident detection. For HD 169392 A we were able to extract parameters of modes for ℓ = 0, 1, 2, and 3. The analysis of splittings and inclination angle gives two possible solutions: one with with splittings and inclination angles of 0.4-1.0 μHz and 20 - 40°, the other with 0.2-0.5 μHz and 55-86°. Modelling this star using the Asteroseismic Modeling Portal (AMP) gives a mass of 1.15 ± 0.01 M⊙, a radius of 1.88 ± 0.02 R⊙, and an age of 4.33 ± 0.12 Gyr. The uncertainties come from estimated errors on the observables but do not include uncertainties on the surface layer correction or the physics of stellar models. The CoRoT space mission, launched on December 27 2006, has been developed and is operated by

  18. HD 50844: a new look at δ Scuti stars from CoRoT space photometry

    NASA Astrophysics Data System (ADS)

    Poretti, E.; Michel, E.; Garrido, R.; Lefèvre, L.; Mantegazza, L.; Rainer, M.; Rodríguez, E.; Uytterhoeven, K.; Amado, P. J.; Martín-Ruiz, S.; Moya, A.; Niemczura, E.; Suárez, J. C.; Zima, W.; Baglin, A.; Auvergne, M.; Baudin, F.; Catala, C.; Samadi, R.; Alvarez, M.; Mathias, P.; Paparò, M.; Pápics, P.; Plachy, E.

    2009-10-01

    Context: Aims: This work presents the results obtained by CoRoT on HD 50844, the only δ Sct star observed in the CoRoT initial run (57.6 d). The aim of these CoRoT observations was to investigate and characterize for the first time the pulsational behaviour of a δ Sct star, when observed at a level of precision and with a much better duty cycle than from the ground. Methods: The 140 016 datapoints were analysed using independent approaches (SigSpec software and different iterative sine-wave fittings) and several checks performed (splitting of the timeseries in different subsets, investigation of the residual light curves and spectra). A level of 10-5 mag was reached in the amplitude spectra of the CoRoT timeseries. The space monitoring was complemented by ground-based high-resolution spectroscopy, which allowed the mode identification of 30 terms. Results: The frequency analysis of the CoRoT timeseries revealed hundreds of terms in the frequency range 0-30 d-1. All the cross-checks confirmed this new result. The initial guess that δ Sct stars have a very rich frequency content is confirmed. The spectroscopic mode identification gives theoretical support since very high-degree modes (up to ℓ=14) are identified. We also prove that cancellation effects are not sufficient in removing the flux variations associated to these modes at the noise level of the CoRoT measurements. The ground-based observations indicate that HD 50844 is an evolved star that is slightly underabundant in heavy elements, located on the Terminal Age Main Sequence. Probably due to this unfavourable evolutionary status, no clear regular distribution is observed in the frequency set. The predominant term (f_1=6.92 d-1) has been identified as the fundamental radial mode combining ground-based photometric and spectroscopic data. Conclusions: The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programmes, Austria

  19. Warm Season Subseasonal Variability and Climate Extremes in the Northern Hemisphere: The Role of Stationary Rossby Waves

    NASA Technical Reports Server (NTRS)

    Schubert, Siegfried; Wang, Hailan; Suarez, Max

    2010-01-01

    This study examines the nature of boreal summer subseasonal atmospheric variability based on the new NASA Modern-Era Retrospective analysis for Research and Applications (MERRA) for the period 1979-2010. An analysis of the June, July and August subseasonal 250hPa v-wind anomalies shows distinct Rossby wave-like structures that appear to be guided by the mean jets. On monthly subseasonal time scales, the leading waves (the first 10 rotated empirical orthogonal functions or REOFs of the 250hPa v-wind) explain about 50% of the Northern Hemisphere vwind variability, and account for more than 30% (60%) of the precipitation (surface temperature) variability over a number of regions of the northern middle and high latitudes, including the U.S. northern Great Plains, parts of Canada, Europe, and Russia. The first REOF in particular, consists of a Rossby wave that extends across northern Eurasia where it is a dominant contributor to monthly surface temperature and precipitation variability, and played an important role in the 2003 European and 2010 Russian heat waves. While primarily subseasonal in nature, the Rossby waves can at times have a substantial seasonal mean component. This is exemplified by REOF 4 which played a major role in the development of the most intense anomalies of the U.S. 1988 drought (during June) and the 1993 flooding (during July), though differed in the latter event by also making an important contribution to the seasonal mean anomalies. A stationary wave model (SWM) is used to reproduce some of the basic features of the observed waves and provide insight into the nature of the forcing. In particular, the responses to a set of idealized forcing functions are used to map the optimal forcing patterns of the leading waves. Also, experiments to reproduce the observed waves with the SWM using MERRA-based estimates of the forcing indicate that the wave forcing is dominated by sub-monthly vorticity transients.

  20. Using a new algorithm to track mixed-Rossby gravity waves (MRG) waves in reanalysis data

    NASA Astrophysics Data System (ADS)

    Au-Yeung, A. Y. M.; Tam, C. Y.

    2015-12-01

    A new algorithm has been developed to track westward travelling mixed-Rossby gravity waves (MRG) waves in the western Pacific based on the theoretical meridional wind structure stated in the shallow water equation (SWE) solutions. Applied to space-time filtered (period=3 to 8 days and wavenumber =-20 to 0), asymmetric meridional wind data at the 850hPa level from the NCEP CFS reanalysis, the algorithm finds locations with Gaussian-shaped meridional wind structure stated in SWE solutions through space and time. Two groups of MRG waves were found: one with higher wavenumber (11) and another one with lower-wavenumber (6). Moreover, the MRG waves show very different dispersive properties and occurrence behavior in the western and eastern equatorial Pacific. While both groups appear in the western Pacific, mainly 6 waves were found in the eastern Pacific. The fact that both 6 and 11 waves appear in the western Pacific agrees with past discussions on the co-existence of MRG waves and tropical-disturbance type (TD-type) waves. Also, the high wavenumber wave activities mainly appear west of the dateline, meaning that some triggering process may have taken place there. Northwestward wave train movement was found west of 140E in the low-level wind composites. On the other hand, negative correlation between meridional wind and temperature (negative) found in the vertical composites indicates downward vertical wave activity flux prior to the occurrences of MRG waves. Finally, in the western Pacific, kinetic energy energetics suggests that energy source of transient eddies is from the confluent background flow and also the zonal wind shear terms in the western Pacific. Overall, our method provides a way to identify the MRG waves instantaneously; in contrast, most of the methods employed in the past (e.g., spectral analysis or lag correlation/regression) are based on aggregates of data and they can only examine wave properties averaged over a certain period of time. Since MRG

  1. CoRoT light curves of Blazhko RR Lyrae stars. Evidence of a strong correlation between phase and amplitude modulations of CoRoT ID 0105288363

    NASA Astrophysics Data System (ADS)

    Chadid, M.; Perini, C.; Bono, G.; Auvergne, M.; Baglin, A.; Weiss, W. W.; Deboscher, J.

    2011-03-01

    Context. The CoRoT - Convection Rotation and planetary Transits - space mission provides a unique opportunity to monitor RR Lyrae stars with excellent time-sampling, unprecedented photometric precision, and a long time base of 150 days. Aims: The pulsation characteristics of RR Lyrae stars rely on robust physics, but we still lack a firm quantitative understanding of the physical mechanisms driving the Blazhko modulation and the long-term changes in their pulsation behavior. We use the high-precision space data of an unknown RR Lyrae star CoRoT ID 0105288363 observed during a second long run centered on the Galaxy - LRc02 -, to improve our understanding of the pulsation properties of RR Lyrae stars. Methods: The CoRoT data were corrected using a jump and trend filtering code. We applied different period-finding techniques including Period04, MuFrAn, PDM, and SigSpec. Amplitude and phase modulation were investigated using an analytical function method as well as traditional O-C diagrams. Results: For the first time, we detect significant cycle-to-cycle changes in the Blazhko modulation, which appear to be analogous to those predicted by Stothers - owing to the suppression of turbulent convection - to explain this phenomenon. We discuss the clear correlations between the phase and the amplitude of the bump, and the skewness and acuteness of the light curve during different Blazhko cycles. We find that these quantities are strongly anticorrelated with the fundamental pulsation period. This provides a strong support to the slow convective cycle model suggested by Stothers. We also detect a long-term modulation period in the maximum brightness spectrum. A more extended coverage of the long-term modulation is required to constrain its period. Seventh-order side peaks of the pulsation multiplet structure are also visible with the left-side peak amplitudes being higher than those of the right. This has never previously been detected. Future theoretical investigations are

  2. CoRoT-7b: Convection in a Tidally Locked Planet

    NASA Astrophysics Data System (ADS)

    Noack, Lena; Stamenkovic, Vlada; Wagner, Frank W.; Sohl, Frank; Breuer, Doris

    2010-05-01

    The number of terrestrial extrasolar planets found in the past few years is increasing rapidly. Some have masses ranging from 2 to 10 Earth masses, and the habitability of these planets is widely discussed in the planetary community. Due to observational limitations we will mostly be able to observe planets that are very close to its host star, resulting in a potentially tidally locked orbit. Our goal is to investigate if such planets can be habitable at all. But to do so, we first have to understand the convection behaviour of such planets. In this work we model the mantle convection of the recently discovered exoplanet CoRoT-7b [1], which is a planet believed to be tidally locked. The extreme intense insolation in the vicinity of its host star heats the day-side of CoRoT-7b, leading to surface temperatures about 2000 Kelvin higher than on the night-side [1]. CoRoT-7b is about 5 times more massive than the Earth and predominantly composed of dry silicate rock similar to Earth's Moon. A central iron core, if present, would be relatively small [2] with a core mass fraction of no more than 15 wt%. The mantle convection is modelled in a spherical shell [3] using a temperature- and pressure-dependent viscosity. We use a radioactive heat source density similar to present Earth. Coriolis forces are neglected and we assume that CoRoT-7b has no atmosphere. The results show that the lower mantle above the core-mantle boundary is in a more sluggish convection regime as a consequence of the viscosity increase with pressure. Depending on the strength of the viscosity increase, even a so-called low-lid [4] can form and conductive heat transport dominates from the core to the upper part of the mantle. The thermal state of such a deeply situated, conductive lower mantle of CoRoT-7b is not much influenced by the strongly laterally varying surface temperature. However, the temperatures of the upper convecting mantle are found to strongly vary from one side of the planet to the

  3. Development of corotational formulated FEM for application to 30m class large deployable reflector

    NASA Astrophysics Data System (ADS)

    Ozawa, Satoru; Fujiwara, Yuuichi; Tsujihata, Akio

    2010-06-01

    JAXA, Japan Aerospace Exploration Agency, is now developing a corotational formulated finite element analysis method and its software "Origami/ETS" for the development of 30m class large deployable reflectors. For the reason that the deployable reflector is composed of beams, cables and mesh, this analysis method is generalized for finite elements with multiple nodes, which are commonly used in linear finite element analyses. The large displacement and rotation are taken into account by the corotational formulation. The tangent stiffness matrix for finite elements with multiple nodes is obtained as follows; the geometric stiffness matrix of two node elements is derived by taking variation of the element's corotational matrix from the virtual work of finite elements with large displacement; similarly the geometric stiffness matrix for three node elements is derived; as the extension of two and three node element theories, the geometric stiffness matrix for multiple node elements is derived; with the geometric stiffness matrix for multiple node elements, the tangent stiffness matrix is obtained. The analysis method is applied for the deployment analysis and static structural analysis of the 30m class large deployable reflector. In the deployment analysis, it is confirmed that this method stably analyzes the deployment motion from the deployment configuration to the stowed configuration of the reflector. In the static analysis, it is confirmed that the mesh structure is analyzed successfully. The 30m class large deployable reflector is now still being developed and is about to undergo several tests with its prototypes. This analysis method will be used in the tests and verifications of the reflector.

  4. MOST detects corotating bright spots on the mid-O-type giant ξ Persei

    NASA Astrophysics Data System (ADS)

    Ramiaramanantsoa, Tahina; Moffat, Anthony F. J.; Chené, André-Nicolas; Richardson, Noel D.; Henrichs, Huib F.; Desforges, Sébastien; Antoci, Victoria; Rowe, Jason F.; Matthews, Jaymie M.; Kuschnig, Rainer; Weiss, Werner W.; Sasselov, Dimitar; Rucinski, Slavek M.; Guenther, David B.

    2014-06-01

    We have used the MOST (Microvariability and Oscillations of STars) microsatellite to obtain four weeks of contiguous high-precision broad-band visual photometry of the O7.5III(n)((f)) star ξ Persei in 2011 November. This star is well known from previous work to show prominent DACs (discrete absorption components) on time-scales of about 2 d from UV spectroscopy and non-radial pulsation with one (l = 3) p-mode oscillation with a period of 3.5 h from optical spectroscopy. Our MOST-orbit (101.4 min) binned photometry fails to reveal any periodic light variations above the 0.1 mmag 3σ noise level for periods of a few hours, while several prominent Fourier peaks emerge at the 1 mmag level in the two-day period range. These longer period variations are unlikely due to pulsations, including gravity modes. From our simulations based upon a simple spot model, we deduce that we are seeing the photometric modulation of several corotating bright spots on the stellar surface. In our model, the starting times (random) and lifetimes (up to several rotations) vary from one spot to another yet all spots rotate at the same period of 4.18 d, the best-estimated rotation period of the star. This is the first convincing reported case of corotating bright spots on an O star, with important implications for drivers of the DACs (resulting from corotating interaction regions) with possible bright-spot generation via a breakout at the surface of a global magnetic field generated by a subsurface convection zone.

  5. Presenting new exoplanet candidates for the CoRoT chromatic light curves

    NASA Astrophysics Data System (ADS)

    Boufleur, Rodrigo; Emilio, Marcelo; Andrade, Laerte; Janot-Pacheco, Eduardo; De La Reza, Ramiro

    2015-08-01

    One of the most promising topics of modern Astronomy is the discovery and characterization of extrasolar planets due to its importance for the comprehension of planetary formation and evolution. Missions like MOST (Microvariability and Oscillations of Stars Telescope) (Walker et al., 2003) and especially the satellites dedicated to the search for exoplanets CoRoT (Convection, Rotation and planetary Transits) (Baglin et al., 1998) and Kepler (Borucki et al., 2003) produced a great amount of data and together account for hundreds of new discoveries. An important source of error in the search for planets with light curves obtained from space observatories are the displacements occuring in the data due to external causes. This artificial charge generation phenomenon associated with the data is mainly caused by the impact of high energy particles onto the CCD (Pinheiro da Silva et al. 2008), although other sources of error, not as well known also need to be taken into account. So, an effective analysis of the light curves depends a lot on the mechanisms employed to deal with these phenomena. To perform our research, we developed and applied a different method to fix the light curves, the CDAM (Corot Detrend Algorithm Modified), inspired by the work of Mislis et al. (2012). The paradigms were obtained using the BLS method (Kovács et al., 2002). After a semiautomatic pre-analysis associated with a visual inspection of the planetary transits signatures, we obtained dozens of exoplanet candidates in very good agreement with the literature and also new unpublished cases. We present the study results and characterization of the new cases for the chromatic channel public light curves of the CoRoT satellite.

  6. A 6-node co-rotational triangular elasto-plastic shell element

    NASA Astrophysics Data System (ADS)

    Li, Zhongxue; Xiang, Yu; Izzuddin, Bassam A.; Vu-Quoc, Loc; Zhuo, Xin; Zhang, Chuanjie

    2015-05-01

    A 6-node co-rotational triangular elasto-plastic shell element is developed. The local coordinate system of the element is defined by the vectors directing from one vertex to the other two vertices and their cross product. Based on such a co-rotational framework, the element rigid-body rotations are excluded in calculating the local nodal variables from the global nodal variables. The two smallest components of each nodal orientation vector are defined as rotational variables, resulting in the desired additive property for all nodal variables in a nonlinear incremental solution procedure. Different from other existing co-rotational finite element formulations, both the element tangent stiffness matrices in the local and in the global coordinate systems are symmetric owing to the commutativity of the nodal variables in calculating the second derivatives of the strain energy with respect to the local nodal variables and, through chain differentiation, with respect to the global nodal variables. For elasto-plastic analysis, the Maxwell-Huber-Hencky-von Mises yield criterion is employed together with the backward-Euler return-mapping method for the evaluation of the elasto-plastic stress state, where a consistent tangent modulus matrix is employed. To overcome locking problems, the assumed linear membrane strains and shear strains are obtained by using the line integration method proposed by MacNeal, and the assumed higher-order membrane strains are obtained by enforcing the stationarity of the mixed displacement-strain canonical functional, these assumed strains are then employed to replace the corresponding conforming strains. The reliability and convergence of the present 6-node triangular shell element formulation are verified through two elastic plate patch tests as well as two elastic and five elasto-plastic plate/shell problems undergoing large displacements and large rotations.

  7. Transiting exoplanets from the CoRoT space mission. XIV. CoRoT-11b: a transiting massive ``hot-Jupiter'' in a prograde orbit around a rapidly rotating F-type star

    NASA Astrophysics Data System (ADS)

    Gandolfi, D.; Hébrard, G.; Alonso, R.; Deleuil, M.; Guenther, E. W.; Fridlund, M.; Endl, M.; Eigmüller, P.; Csizmadia, Sz.; Havel, M.; Aigrain, S.; Auvergne, M.; Baglin, A.; Barge, P.; Bonomo, A. S.; Bordé, P.; Bouchy, F.; Bruntt, H.; Cabrera, J.; Carpano, S.; Carone, L.; Cochran, W. D.; Deeg, H. J.; Dvorak, R.; Eislöffel, J.; Erikson, A.; Ferraz-Mello, S.; Gazzano, J.-C.; Gibson, N. B.; Gillon, M.; Gondoin, P.; Guillot, T.; Hartmann, M.; Hatzes, A.; Jorda, L.; Kabath, P.; Léger, A.; Llebaria, A.; Lammer, H.; MacQueen, P. J.; Mayor, M.; Mazeh, T.; Moutou, C.; Ollivier, M.; Pätzold, M.; Pepe, F.; Queloz, D.; Rauer, H.; Rouan, D.; Samuel, B.; Schneider, J.; Stecklum, B.; Tingley, B.; Udry, S.; Wuchterl, G.

    2010-12-01

    The CoRoT exoplanet science team announces the discovery of CoRoT-11b, a fairly massive hot-Jupiter transiting a V = 12.9 mag F6 dwarf star (M_* = 1.27±0.05 M⊙, R_* = 1.37±0.03 R⊙, Teff = 6440±120 K), with an orbital period of P = 2.994329±0.000011 days and semi-major axis a = 0.0436±0.005 AU. The detection of part of the radial velocity anomaly caused by the Rossiter-McLaughlin effect shows that the transit-like events detected by CoRoT are caused by a planet-sized transiting object in a prograde orbit. The relatively high projected rotational velocity of the star (v sin i = 40±5 km s-1) places CoRoT-11 among the most rapidly rotating planet host stars discovered so far. With a planetary mass of Mp = 2.33±0.34 MJup and radius Rp =1.43±0.03 RJup, the resulting mean density of CoRoT-11b (ρp = 0.99±0.15 g/cm3) can be explained with a model for an inflated hydrogen-planet with a solar composition and a high level of energy dissipation in its interior. The CoRoT space mission, launched on 2006 December 27, has been developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA (RSSD and Science Programme), Germany and Spain.

  8. Rotation period distribution of CoRoT and Kepler Sun-like stars

    NASA Astrophysics Data System (ADS)

    Leão, I. C.; Pasquini, L.; Ferreira Lopes, C. E.; Neves, V.; Valcarce, A. A. R.; de Oliveira, L. L. A.; Freire da Silva, D.; de Freitas, D. B.; Canto Martins, B. L.; Janot-Pacheco, E.; Baglin, A.; De Medeiros, J. R.

    2015-10-01

    Aims: We study the distribution of the photometric rotation period (Prot), which is a direct measurement of the surface rotation at active latitudes, for three subsamples of Sun-like stars: one from CoRoT data and two from Kepler data. For this purpose, we identify the main populations of these samples and interpret their main biases specifically for a comparison with the solar Prot. Methods: Prot and variability amplitude (A) measurements were obtained from public CoRoT and Kepler catalogs, which were combined with public data of physical parameters. Because these samples are subject to selection effects, we computed synthetic samples with simulated biases to compare with observations, particularly around the location of the Sun in the Hertzsprung-Russel (HR) diagram. Publicly available theoretical grids and empirical relations were used to combine physical parameters with Prot and A. Biases were simulated by performing cutoffs on the physical and rotational parameters in the same way as in each observed sample. A crucial cutoff is related with the detectability of the rotational modulation, which strongly depends on A. Results: The synthetic samples explain the observed Prot distributions of Sun-like stars as having two main populations: one of young objects (group I, with ages younger than ~1 Gyr) and another of main-sequence and evolved stars (group II, with ages older than ~1 Gyr). The proportions of groups I and II in relation to the total number of stars range within 64-84% and 16-36%, respectively. Hence, young objects abound in the distributions, producing the effect of observing a high number of short periods around the location of the Sun in the HR diagram. Differences in the Prot distributions between the CoRoT and Kepler Sun-like samples may be associated with different Galactic populations. Overall, the synthetic distribution around the solar period agrees with observations, which suggests that the solar rotation is normal with respect to Sun

  9. Modelling Flow and Heat Transfer in Co-Rotating Twin-Screw Extruders

    NASA Astrophysics Data System (ADS)

    Teixeira, C.; Faria, R.; Covas, J. A.; Gaspar-Cunha, A.

    2007-04-01

    This work presents a modelling routine of co-rotating twin-screw extrusion, from hopper to die. The program accounts for a sequence of individual stages linked together by boundary conditions, namely starve-fed solids conveying, solids conveying under pressure, delay, melting, melt conveying without pressure and melt conveying under pressure. It predicts the evolution along the screw and die of temperature, shear rate, residence time, viscosity, mechanical power consumption, pressure and fill ratio. The results obtained showed adequate sensitivity to changes in operating conditions and screw geometry and are in agreement with current theoretical and experimental knowledge.

  10. Affirmation of triggered Jovian radio emissions and their attribution to corotating radio lasers

    NASA Technical Reports Server (NTRS)

    Calvert, W.

    1985-01-01

    It is argued that the original statistical evidence for the existence of triggered radio emissions and corotating radio lasers on Jupiter remains valid notwithstanding the critique of Desch and Kaiser (1985). The Voyager radio spectrograms used to identify the triggered emissions are analyzed and the results are discussed. It is shown that the critique by Desch and Kaiser is unjustified because it is not based on the original event criteria, i.e., the correlation between the occurrence of Jovian auroral kilometric radiation and fast-drift type III solar bursts in the same frequency.

  11. Zonal Wave Number 2 Rossby Wave (3.5-day oscillation) Over The Martian Lower Atmosphere

    NASA Astrophysics Data System (ADS)

    Ghosh, P.; Thokuluwa, R. K.

    2013-12-01

    to get decreasing monotonously to the statistically significant lowest power of 20 K^2 in the height of 450 Pascal level. Similar to the 0-30E longitude region, there is no significant wave in all the heights above the 450 Pascal level. The 190-230 E region shows similar wave characteristics (both the power and height structure) as observed for the 0-30 E region. This would indicate that the here reporting 3.5 day wave might be associated with eastward propagating (observed the zonal phase speed of ~0.5 days per 30 degree longitude) wave number 2 Rossby wave as the wave shows similar characteristics in the two longitude regions of 0-30E and 190-230 E with the longitudinal interval of 180 degrees. Peculiarly, in the 250-280 E region, the wave shows maximum power (120 K^2) in the two heights of 550 and 700 Pascal levels. As a further support for the zonal wave number 2 structure, there is no significant 3.5-day oscillation in all the height levels in the 290-320 E longitude region which is similar to what observed in the 35-60E longitude sector. A detailed investigation of this 3.5 day oscillation will be presented also for other periods of different years.

  12. Optical and mechanical design of a straylight rejection baffle for CoRoT

    NASA Astrophysics Data System (ADS)

    Plesseria, Jean-Yves; Mazy, Emmanuel; Defise, Jean-Marc; Rochus, Pierre; Lemmens, Els; Vrancken, Davy

    2003-11-01

    The COROT mission is part of the program "Petites Missions" of CNES (French space agency). It implies international cooperation between France, Belgium, Germany, Austria, Spain and the European Space Agency (ESA). COROT aims to perform astroseismology measurements and to detect exoplanets. Long duration observations of stars will be used to detect periodic variations with an afocal telescope followed by a dioptric objective and 4 CCDs. Due to the orbit of the spacecraft (low altitude polar orbit) and even if the observation are performed in a direction perpendicular to orbit plane, the measurements can be disturbed by the straylight reflected on the earth (albedo) that can generate periodic perturbation. CSL is in charge of the design and procurement, with the help of Belgian industries, of a baffle and its protective cover that will be mounted on top of the afocal entrance telescope. The requirements are very stringent from the optical point of view as well as from the mechanical point of view. The rejection of the baffle must be of the order of 1013 for field angles above 20 degrees while the allocated mass is 19 kilograms.

  13. Physical state of the deep interior of the CoRoT-7b exoplanet

    NASA Astrophysics Data System (ADS)

    Wagner, Frank W.; Sohl, Frank; Rückriemen, Tina; Rauer, Heike

    2011-11-01

    The present study takes the CoRoT-7b exoplanet as an analogue for massive terrestrial planets to investigate conditions, under which intrinsic magnetic fields could be sustained in liquid cores. We examine the effect of depth-dependent transport parameters (e.g., activation volume of mantle rock) on a planet's thermal structure and the related heat flux across the core mantle boundary. For terrestrial planets more massive than the Earth, our calculations suggest that a substantial part of the lowermost mantle is in a sluggish convective regime, primarily due to pressure effects on viscosity. Hence, we find substantially higher core temperatures than previously reported from parameterized convection models. We also discuss the effect of melting point depression in the presence of impurities (e.g., sulfur) in iron-rich cores and compare corresponding melting relations to the calculated thermal structure. Since impurity effects become less important at the elevated pressure and temperature conditions prevalent in the deep interior of CoRoT-7b, iron-rich cores are likely solid, implying that a self-sustained magnetic field would be absent.

  14. Structure and Dynamics of the Sub-corotating Region of Saturn's Magnetosphere: Cassini Magnetic Field Observations.

    NASA Astrophysics Data System (ADS)

    Smith, E. J.; Dougherty, M. K.

    2014-12-01

    Measurements of the azimuthal magnetic field component, BΦ, enable the study of the sub-corotating magnetosphere, the associated global current system, the ionospheric Pedersen current, IP, and a comparison with the Cowley-Vasyliunas model. The study is strongly dependent on Cassini's highly elliptical orbits that restrict useful observations to specific orbits and parts of orbits to avoid weak azimuthal fields associated with the magnetopause or other magnetospheric currents. An example is the selection of thirteen identical orbits near 22 +/- 2 hours Local Time and restriction of the data to 4 to 10 Saturn radii. Inferred IP profiles between 10° and 25° ionospheric co-latitude, θi , when averaged, are similar in shape to model predictions with a peak value of 5 million amperes. However, the individual profiles vary significantly, the result of dynamics associated with large-scale motions of the magnetospheric field. The Cowley-Vasyliunas model also relates IP(θi) to magnetospheric rotation rates, ΩS, equivalent to the SKR period, and the sub-corotation rate, ω, and provides a means of estimating ω / ΩS in the night-side magnetosphere as compared to the dayside rotation rates obtained from azimuthal plasma velocity measurements, VΦ. Other carefully- selected orbits extend these results to different ranges in θi and Local Times and provide further values of important magnetospheric parameters and allow additional testing of the model.

  15. Modeling transport of energetic particles in corotating interaction regions: A case study

    NASA Astrophysics Data System (ADS)

    Zhao, Lulu; Li, Gang; Ebert, R. W.; Dayeh, M. A.; Desai, M. I.; Mason, G. M.; Wu, Z.; Chen, Y.

    2016-01-01

    We investigate energetic particle transport in corotating interaction regions (CIRs) through a case study. The CIR event we study occurred on 8 February 2008 and was observed by both the Advanced Composition Explorer (ACE) and the twin Solar TErrestrial RElations Observatory (STEREO) B spacecraft. An in situ reverse shock was observed by STEREO B (1.0 AU) but not ACE (0.98 AU). Using STEREO B observations and assuming the CIR structure does not vary significantly in the corotating frame, we estimate the shock location at later times for both the STEREO B and ACE observations. Further assuming the accelerated particle spectral shape at the shock does not vary with shock location, we calculate the particle differential intensities as observed by ACE and STEREO B at two different times by solving the focused transport equation using a Monte Carlo simulation. We assume that particles move along Parker's field and experience no cross-field diffusion. We find that the modulation of sub-MeV/nucleon particles is significant. To obtain reasonable comparisons between the simulations and the observations by both ACE and STEREO B, one has to assume that the CIR shock can accelerate more particles at a larger heliocentric distance than at a smaller heliocentric distance.

  16. Solar Wind Interaction with Comet 67P/C-G: Impact of Corotating Interaction Regions

    NASA Astrophysics Data System (ADS)

    Edberg, N. J. T.; Eriksson, A. I.; Odelstad, E.; Vigren, E.; Burch, J. L.; Carr, C.; Cupido, E.; Glassmeier, K. H.; Goldstein, R.; Halekas, J. S.; Pierre, H.; Lebreton, J. P.; Mandt, K.; Mokashi, P.; Nemeth, Z.; Nilsson, H.; Ramstad, R.; Richter, I.; Stenberg Wieser, G.

    2015-12-01

    We present observations from the Rosetta Plasma Consortium (RPC) of impacts of corotating interaction regions (CIRs) on comet 67P. Corotating interaction regions build up in the solar wind when slow flow is caught up by faster flow. A pressure pulse is then formed, which propagates outward in interplanetary space and impacts on e.g. planets, moons and comet in its path. In the interval October to December 2014 four such CIRs are traced from Earth (using ACE) to Mars (using Mars Express and MAVEN) and to comet 67P (using Rosetta). As the CIRs impact on the cometary coma the ionospheric low-energy plasma density in the ionosphere increases by roughly one order of magnitude in the first three events. The increased density is possibly caused by sweeping up of more upstream plasma in combination with increased impact ionization and charge exchange processes. Increased fluxes of ~100 eV electrons are observed concurrently and the magnetic field strength typically doubles as more interplanetary magnetic field piles up around of the comet.

  17. Implications of the Corotation Theorem on the MRI in Axial Symmetry

    NASA Astrophysics Data System (ADS)

    Montani, G.; Cianfrani, F.; Pugliese, D.

    2016-08-01

    We analyze the linear stability of an axially symmetric ideal plasma disk, embedded in a magnetic field and endowed with a differential rotation. This study is performed by adopting the magnetic flux function as the fundamental dynamical variable, in order to outline the role played by the corotation theorem on the linear mode structure. Using some specific assumptions (e.g., plasma incompressibility and propagation of the perturbations along the background magnetic field), we select the Alfvénic nature of the magnetorotational instability, and, in the geometric optics limit, we determine the dispersion relation describing the linear spectrum. We show how the implementation of the corotation theorem (valid for the background configuration) on the linear dynamics produces the cancellation of the vertical derivative of the disk angular velocity (we check such a feature also in the standard vector formalism to facilitate comparison with previous literature, in both the axisymmetric and three-dimensional cases). As a result, we clarify that the unstable modes have, for a stratified disk, the same morphology, proper of a thin-disk profile, and the z-dependence has a simple parametric role.

  18. The variability behaviour of CoRoT M-giant stars⋆

    NASA Astrophysics Data System (ADS)

    Ferreira Lopes, C. E.; Neves, V.; Leão, I. C.; de Freitas, D. B.; Canto Martins, B. L.; da Costa, A. D.; Paz-Chinchón, F.; Das Chagas, M. L.; Baglin, A.; Janot-Pacheco, E.; De Medeiros, J. R.

    2015-11-01

    Context. For six years the Convection, Rotation, and planetary Transits (CoRoT) space mission has been acquiring photometric data from more than 100 000 point sources towards and directly opposite the inner and outer regions of the Galaxy. The high temporal resolution of the CoRoT data, combined with the wide time span of the observations, enabled the study of short- and long-time variations in unprecedented detail. Aims: The aim of this work is to study the variability and evolutionary behaviour of M-giant stars using CoRot data. Methods: From the initial sample of 2534 stars classified as M giants in the CoRoT databases, we selected 1428 targets that exhibit well defined variability, by visual inspection. Then, we defined three catalogues: C1 - stars with Teff< 4200 K and LCs displaying semi-sinusoidal signatures; C2 - rotating variable candidates with Teff> 4200 K; C3 - long-period variable candidates (with LCs showing a variability period up to the total time span of the observations). The variability period and amplitude of C1 stars were computed using Lomb-Scargle and harmonic fit methods. Finally, we used C1 and C3 stars to study the variability behaviour of M-giant stars. Results: The trends found in the V-I vs. J-K colour-colour diagram are in agreement with standard empirical calibrations for M giants. The sources located towards the inner regions of the Galaxy are distributed throughout the diagram, while the majority of the stars towards the outer regions of the Galaxy are spread between the calibrations of M giants and the predicted position for carbon stars. The stars classified as supergiants follow a different sequence from the one found for giant stars. We also performed a Kolmogorov-Smirnov (KS) test of the period and amplitude of stars towards the inner and outer regions of the Galaxy. We obtained a low probability that the two samples came from the same parent distribution. The observed behaviour of the period-amplitude and period

  19. Rossby-Khantadze Electromagnetic Planetary Waves Driven by Sheared Zonal Winds in the E-Layer Ionosphere

    NASA Astrophysics Data System (ADS)

    Futatani, S.; Horton, W.; Kahlon, L. Z.; Kaladze, T.

    2014-10-01

    Nonlinear simulations are carried out for planetary scale [ >1000 km] electromagnetic Rossby and Khantadze planetary waves in the presence of a sheared zonal flow in the weakly ionized ionospheric E-layer. A variety of sheared flow profiles are studied. We shown that the nonlinear dynamics with the sheared zonal flows provides an energy source into the vortex structures. The energy transfer through the Reynolds stress tensor produces growth of the stable vortices under a variety of conditions. The energy accumulation breaks the vortex structure into multiple species according to the non-uniformity of profile of the external zonal shear flows. S. Futatani, W. Horton, T. D. Kaladze, Phys. Plasmas 20, 102903 (2013). T. D. Kaladze, L. Z. Kahlon, W. Horton. O Pokhotelov, and O. Onishenchenko, EPL 106, A05302 (2014).

  20. Rossby-Khantadze electromagnetic planetary waves driven by sheared zonal winds in the E-layer ionosphere

    NASA Astrophysics Data System (ADS)

    Futatani, S.; Horton, W.; Kahlon, L. Z.; Kaladze, T. D.

    2015-01-01

    Nonlinear simulations of electromagnetic Rossby and Khantadze planetary waves in the presence of a shearless and sheared zonal flows in the weakly ionized ionospheric E-layer are carried out. The simulations show that the nonlinear action of the vortex structures keeps the solitary character in the presence of shearless zonal winds as well as the ideal solutions of solitary vortex in the absence of zonal winds. In the presence of sheared zonal winds, the zonal flows result in breaking into separate multiple smaller pieces. A passively convected scalar field is shown to clarify the transport associated with the vortices. The work shows that the zonal shear flows provide an energy source into the vortex structure according to the shear rate of the zonal winds.

  1. Observations by GLORIA of stirring and mixing in the UTLS following Rossby wave breaking in winter 2015/2016

    NASA Astrophysics Data System (ADS)

    Ungermann, Joern; Friedl-Vallon, Felix; Höpfner, Michael; Preusse, Peter; Riese, Martin

    2016-04-01

    The Gimbaled Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an airborne infrared limb-imager combining a 2-D infrared detector with a Fourier transform spectrometer. It was operated aboard the German Gulfstream G550 research aircraft HALO during a series of simultaneous campaigns (POLSTRACC, SALSA, GWLCYCLE, GWEX) during the winter of 2015/2016 over Europe and the Arctic. This poster shows a set of GLORIA observations and analyses of 2-D trace gas cross-sections in the extratropical upper troposphere / lower stratosphere (UTLS). The spatially highly-resolved temperature, H2O, O3 and HNO3 data reveal an intricate layered structure in the extratropical Transition Layer (exTL). This heterogeneous structure was caused by Rossby wave breaking and is similar to the state found during previous measurements in summer 2012 over Europe. This study presents first analyses of the stirring and stratosphere-troposphere-exchange by means of backward-trajectory calculation.

  2. Rossby-Khantadze electromagnetic planetary waves driven by sheared zonal winds in the E-layer ionosphere

    SciTech Connect

    Futatani, S.; Horton, W.; Kahlon, L. Z.; Kaladze, T. D.

    2015-01-15

    Nonlinear simulations of electromagnetic Rossby and Khantadze planetary waves in the presence of a shearless and sheared zonal flows in the weakly ionized ionospheric E-layer are carried out. The simulations show that the nonlinear action of the vortex structures keeps the solitary character in the presence of shearless zonal winds as well as the ideal solutions of solitary vortex in the absence of zonal winds. In the presence of sheared zonal winds, the zonal flows result in breaking into separate multiple smaller pieces. A passively convected scalar field is shown to clarify the transport associated with the vortices. The work shows that the zonal shear flows provide an energy source into the vortex structure according to the shear rate of the zonal winds.

  3. Transiting exoplanets from the CoRoT space mission. XXI. CoRoT-19b: a low density planet orbiting an old inactive F9V-star

    NASA Astrophysics Data System (ADS)

    Guenther, E. W.; Díaz, R. F.; Gazzano, J.-C.; Mazeh, T.; Rouan, D.; Gibson, N.; Csizmadia, Sz.; Aigrain, S.; Alonso, R.; Almenara, J. M.; Auvergne, M.; Baglin, A.; Barge, P.; Bonomo, A. S.; Bordé, P.; Bouchy, F.; Bruntt, H.; Cabrera, J.; Carone, L.; Carpano, S.; Cavarroc, C.; Deeg, H. J.; Deleuil, M.; Dreizler, S.; Dvorak, R.; Erikson, A.; Ferraz-Mello, S.; Fridlund, M.; Gandolfi, D.; Gillon, M.; Guillot, T.; Hatzes, A.; Havel, M.; Hébrard, G.; Jehin, E.; Jorda, L.; Lammer, H.; Léger, A.; Moutou, C.; Nortmann, L.; Ollivier, M.; Ofir, A.; Pasternacki, Th.; Pätzold, M.; Parviainen, H.; Queloz, D.; Rauer, H.; Samuel, B.; Santerne, A.; Schneider, J.; Tal-Or, L.; Tingley, B.; Weingrill, J.; Wuchterl, G.

    2012-01-01

    Context. Observations of transiting extrasolar planets are of key importance to our understanding of planets because their mass, radius, and mass density can be determined. These measurements indicate that planets of similar mass can have very different radii. For low-density planets, it is generally assumed that they are inflated owing to their proximity to the host-star. To determine the causes of this inflation, it is necessary to obtain a statistically significant sample of planets with precisely measured masses and radii. Aims: The CoRoT space mission allows us to achieve a very high photometric accuracy. By combining CoRoT data with high-precision radial velocity measurements, we derive precise planetary radii and masses. We report the discovery of CoRoT-19b, a gas-giant planet transiting an old, inactive F9V-type star with a period of four days. Methods: After excluding alternative physical configurations mimicking a planetary transit signal, we determine the radius and mass of the planet by combining CoRoT photometry with high-resolution spectroscopy obtained with the echelle spectrographs SOPHIE, HARPS, FIES, and SANDIFORD. To improve the precision of its ephemeris and the epoch, we observed additional transits with the TRAPPIST and Euler telescopes. Using HARPS spectra obtained during the transit, we then determine the projected angle between the spin of the star and the orbit of the planet. Results: We find that the host star of CoRoT-19b is an inactive F9V-type star close to the end of its main-sequence life. The host star has a mass M∗ = 1.21 ± 0.05 M⊙ and radius R∗ = 1.65 ± 0.04 R⊙. The planet has a mass of MP = 1.11 ± 0.06 MJup and radius of RP = 1.29 ± 0.03 RJup. The resulting bulk density is only ρ = 0.71 ± 0.06 g cm-3, which is much lower than that for Jupiter. Conclusions: The exoplanet CoRoT-19b is an example of a giant planet of almost the same mass as Jupiter but a ≈30% larger radius. The CoRoT space mission, launched on

  4. Transiting exoplanets from the CoRoT space mission. XXII. CoRoT-16b: a hot Jupiter with a hint of eccentricity around a faint solar-like star

    NASA Astrophysics Data System (ADS)

    Ollivier, M.; Gillon, M.; Santerne, A.; Wuchterl, G.; Havel, M.; Bruntt, H.; Bordé, P.; Pasternacki, T.; Endl, M.; Gandolfi, D.; Aigrain, S.; Almenara, J. M.; Alonso, R.; Auvergne, M.; Baglin, A.; Barge, P.; Bonomo, A. S.; Bouchy, F.; Cabrera, J.; Carone, L.; Carpano, S.; Cavarroc, C.; Cochran, W. D.; Csizmadia, Sz.; Deeg, H. J.; Deleuil, M.; Diaz, R. F.; Dvorak, R.; Erikson, A.; Ferraz-Mello, S.; Fridlund, M.; Gazzano, J.-C.; Grziwa, S.; Guenther, E.; Guillot, T.; Guterman, P.; Hatzes, A.; Hébrard, G.; Lammer, H.; Léger, A.; Lovis, C.; MacQueen, P. J.; Mayor, M.; Mazeh, T.; Moutou, C.; Ofir, A.; Pätzold, M.; Queloz, D.; Rauer, H.; Rouan, D.; Samuel, B.; Schneider, J.; Tadeu dos Santos, M.; Tal-Or, L.; Tingley, B.; Weingrill, J.

    2012-05-01

    Aims: We report the discovery of CoRoT-16b, a low density hot jupiter that orbits a faint G5V star (mV = 15.63) in 5.3523 ± 0.0002 days with slight eccentricity. A fit of the data with no a priori assumptions on the orbit leads to an eccentricity of 0.33 ± 0.1. We discuss this value and also derive the mass and radius of the planet. Methods: We analyse the photometric transit curve of CoRoT-16 given by the CoRoT satellite, and radial velocity data from the HARPS and HIRES spectrometers. A combined analysis using a Markov chain Monte Carlo algorithm is used to get the system parameters. Results: CoRoT-16b is a 0.535 -0.083/+0.085 MJ, 1.17 -0.14/+0.16 RJ hot Jupiter with a density of 0.44 -0.14/+0.21 g cm-3. Despite its short orbital distance (0.0618 ± 0.0015 AU) and the age of the parent star (6.73 ± 2.8 Gyr), the planet orbit exhibits significantly non-zero eccentricity. This is very uncommon for this type of objects as tidal effects tend to circularise the orbit. This value is discussed taking into account the characteristics of the star and the observation accuracy. The CoRoT space mission, launched on December 27, 2006, has been developed and is operated by the CNES with the contribution of Austria, Belgium, Brasil, ESA, Germany, and Spain.Observations made with the HARPS spectrograph at ESO La Silla Observatory (HARPS programs 083.C-0186 and 184.C-0639) and the HIRES spectrograph at the Keck Observatory (NASA-Keck programs N035Hr, N143Hr and N095Hr).

  5. Finest light curve details, physical parameters, and period fluctuations of CoRoT RR Lyrae stars

    NASA Astrophysics Data System (ADS)

    Benkő, J. M.; Szabó, R.; Derekas, A.; Sódor, Á.

    2016-08-01

    The CoRoT satellite supplied the scientific community with a huge data base of variable stars. Among them the RR Lyrae stars have intensively been discussed in numerous papers in the last few years, but the latest runs have not been checked to find RR Lyrae stars up to now. Our main goal was to fill this gap and complete the CoRoT RR Lyrae sample. We found nine unstudied RR Lyrae stars. Seven of them are new discoveries. We identified three new Blazhko stars. The Blazhko effect shows non-strictly repetitive nature for all stars. The frequency spectrum of the Blazhko star CoRoT 104948132 contains second overtone frequency with the highest known period ratio. The harmonic amplitude and phase declines with the harmonic order were studied for non-Blazhko stars. We found a period dependent but similar shape amplitude decline for all stars. We discovered significant random period fluctuation for one of the two oversampled target, CM Ori. After a successful transformation of the CoRoT band parameters to the Johnson V values we estimated the basic physical properties such as mass, luminosity, metallicity. The sample can be divided into two subgroups with respect to the metallicity but otherwise the physical parameters are in the canonical range of RR Lyrae stars.

  6. VizieR Online Data Catalog: Stellar parameters for CoRoT exoplanet field stars (Cortes+, 2015)

    NASA Astrophysics Data System (ADS)

    Cortes, C.; Maciel, S. C.; Vieira, S.; Ferreira Lopes, C. E.; Leao, I. C.; de Oliveira, G. P.; Correia, C.; Canto Martins, B. L.; Catelan, M.; de Medeiros, J. R.

    2016-08-01

    The present stellar sample is composed of 138 stars of spectral types F, G, and K, with visual magnitudes V between 10 to 14, located in two exoplanet fields observed by CoRoT, namely the Galactic center (LRc01: Long Run Center 01) and the Galactic anticenter (LRa01: Long Run Anticenter 01) fields. (4 data files).

  7. Accretion dynamics and disk evolution in NGC 2264: a study based on CoRoT photometric observations

    NASA Astrophysics Data System (ADS)

    Alencar, S. H. P.; Teixeira, P. S.; Guimarães, M. M.; McGinnis, P. T.; Gameiro, J. F.; Bouvier, J.; Aigrain, S.; Flaccomio, E.; Favata, F.

    2010-09-01

    Context. The young cluster NGC 2264 was observed with the CoRoT satellite for 23 days uninterruptedly in March 2008 with unprecedented photometric accuracy. We present the first results of our analysis of the accreting population belonging to the cluster as observed by CoRoT. Aims: We search for possible light curve variability of the same nature as that observed in the classical T Tauri star AA Tau, which was attributed to a magnetically controlled inner disk warp. The inner warp dynamics is supposed to be directly associated with the interaction between the stellar magnetic field and the inner disk region. Methods: We analyzed the CoRoT light curves of 83 previously known classical T Tauri stars that belong to NGC 2264 classifying them according to their light-curve morphology. We also studied the CoRoT light-curve morphology as a function of a Spitzer-based classification of the star-disk systems. Results: The classification derived on the basis of the CoRoT light-curve morphology agrees very well with the Spitzer IRAC-based classification of the systems. The percentage of AA Tau-like light curves decreases as the inner disk dissipates, from 40% ± 10% in systems with thick inner disks to 36% ± 16% in systems with anemic disks and zero in naked photosphere systems. Indeed, 91% ± 29% of the CTTS with naked photospheres exhibit pure spot-like variability, while only 18% ± 7% of the thick disk systems do so, presumably those seen at low inclination and thus free of variable obscuration. Conclusions: AA Tau-like light curves are found to be fairly common, with a frequency of at least ~30 to 40% in young stars with inner dusty disks. The temporal evolution of the light curves indicates that the structure of the inner disk warp, located close to the corotation radius and responsible for the obscuration episodes, varies over a timescale of a few (~1-3) rotational periods. This probably reflects the highly dynamical nature of the star-disk magnetospheric interaction

  8. The evolution of corotating stream fronts near the ecliptic plane in the inner solar system, 1. Two-dimensional fronts

    SciTech Connect

    Pizzo, V.J. )

    1989-07-01

    Numerical models of corotating solar wind flows have enjoyed considerable success in simulating the evolution of shocks and corotating interaction regions (CIRs) in the region beyond 1 AU, but their performance with respect to stream fronts located nearer the Sun has been somewhat disappointing. In particular, they tend to predict erroneously that corotating shock pairs should occur relatively frequently within 1 AU, given the sort of sharp boundaries between slow and fast flows observed at stream fronts near 0.3 AU by Helios. We use an existing two-dimensional MHD numerical model for corotating flow in the supersonic, superalfvenic solar wind to show that the predictions of premature shock pair formation are due to improper specification of flow conditions on the initial surface (inner boundary) used as the starting point in such models. This faulty initialization leads to the generation of a physically extraneous strong compression along the stream interface just outside the initial surface, which results in the appearance of evolutionary artifacts (like spurious discontinuities) further on in the solution. We describe an initialization scheme incorporating flow conditions more appropriate to stream fronts near the Sun and demonstrate that it produces the smooth initial behavior expected on physical grounds. Thus free of the evolutionary artifacts, we see that the shear flow at the stream interface approximately balances the kinematic steepening near the Sun, which for typical input conditions keeps the corotating shock pair from forming before about 1.5 AU. We describe the criteria for shock formation in terms of the interface dynamics and show that the steepening process cannot be treated even approximately with conventional kinematic techniques. In a subsequent paper we investigate how the three-dimensional geometry of the stream front affects the dynamical evolution and the resulting CIR structure.

  9. Mirroring of fast solar flare electrons on a downstream corotating interaction region

    NASA Technical Reports Server (NTRS)

    Anderson, K. A.; Sommers, J.; Lin, R. P.; Pick, M.; Chaizy, P.; Murphy, N.; Smith, E. J.; Phillips, J. L.

    1995-01-01

    We discuss an example of confinement of fast solar electrons by a discrete solar wind-interplanetary magnetic field structure on February 22, 1991. The structure is about 190,000 km in width and is clearly defined by changes in the direction of the magnetic field at the Ulysses spacecraft. This structure carries electrons moving toward the Sun as well as away from the Sun. A loss cone in the angular distribution of the fast electrons shows that mirroring, presumably magnetic, takes place downstream from the spacecraft. Following passage of this narrow structure, the return flux vanishes for 21 min after which time the mirroring resumes and persists for several hours. We identify the enhanced magnetic field region lying downstream from the Ulysses spacecraft that is responsible for the mirroring to be a corotating stream interaction region. Backstreaming suprathermal electron measurements by the Los Alamos National Laboratory plasma experiment on the Ulysses spacecraft support this interpretation.

  10. A three-dimensional model of corotating streams in the solar wind. 1: Theoretical foundations

    NASA Technical Reports Server (NTRS)

    Pizzo, V. J.

    1978-01-01

    The theoretical and mathematical background pertinent to the study of steady, corotating solar wind structure in all three spatial dimensions (3-D) is discussed. The dynamical evolution of the plasma in interplanetary space (defined as the region beyond roughly 35 solar radii where the flow is supersonic) is approximately described by the nonlinear, single fluid, polytropic (magneto-) hydrodynamic equations. Efficient numerical techniques for solving this complex system of coupled, hyperbolic partial differential equations are outlined. The formulation is inviscid and nonmagnetic, but methods allow for the potential inclusion of both features with only modest modifications. One simple, highly idealized, hydrodynamic model stream is examined to illustrate the fundamental processes involved in the 3-D dynamics of stream evolution. Spatial variations in the rotational stream interaction mechanism were found to produce small nonradial flows on a global scale that lead to the transport of mass, energy, and momentum away from regions of relative compression and into regions of relative rarefaction.

  11. Numerical study of mixed convection between two corotating symmetrically heated disks

    SciTech Connect

    Soong, C.Y.; Yan, W.M. Hua Fan Inst. of Technology, Taipei )

    1993-03-01

    This article is concerned with a numerical study of mixed convection between two symmetrically heated corotating disks. Both thermal boundary conditions of constant wall temperature and uniform heat flux are considered. By applying the boundary-layer approximation and a linear relation for density variation in centrifugal force term, the governing equations reduce to a Boussinesq system of parabolic nature. The spatially developing flow and heat transfer are studied numerically. The effects of centrifugal buoyancy, Coriolis force, radial through-flow, and wall-heating on the flow structure and heat transfer performance are examined in detail. The results reveal that the centrifugal buoyancy, which was ignored in prior studies, is indeed a significant effect in this class of rotating flows. 19 refs.

  12. Angular velocity of gravitational radiation from precessing binaries and the corotating frame

    NASA Astrophysics Data System (ADS)

    Boyle, Michael

    2013-05-01

    This paper defines an angular velocity for time-dependent functions on the sphere and applies it to gravitational waveforms from compact binaries. Because it is geometrically meaningful and has a clear physical motivation, the angular velocity is uniquely useful in helping to solve an important—and largely ignored—problem in models of compact binaries: the inverse problem of deducing the physical parameters of a system from the gravitational waves alone. It is also used to define the corotating frame of the waveform. When decomposed in this frame, the waveform has no rotational dynamics and is therefore as slowly evolving as possible. The resulting simplifications lead to straightforward methods for accurately comparing waveforms and constructing hybrids. As formulated in this paper, the methods can be applied robustly to both precessing and nonprecessing waveforms, providing a clear, comprehensive, and consistent framework for waveform analysis. Explicit implementations of all these methods are provided in accompanying computer code.

  13. Mirroring of fast solar flare electrons on a downstream corotating interaction region

    SciTech Connect

    Anderson, K.A.; Sommers, J.; Lin, R.P.; Pick, M.; Chaizy, P.; Murphy, N.; Smith, E.J.; Phillips, J.L.

    1995-01-01

    The authors discuss an example of confinement of fast solar electrons by a discrete solar wind-interplanetary magnetic field structure on February 22, 1991. The structure is about 190,000 km in width and is clearly defined by changes in the direction of the magnetic field at the Ulysses spacecraft. This structure carries electrons moving toward the Sun as well as away from the Sun. A loss cone in the angular distribution of the fast electrons shows that mirroring, presumably magnetic, takes place downstream from the spacecraft. Following passage of this narrow structure, the return flux vanishes for 21 min after which time the mirroring resumes and persists for several hours. The authors identify the enhanced magnetic field region lying downstream from the Ulysses spacecraft that is responsible for the mirroring to be a corotating stream interaction region. Backstreaming suprathermal electron measurements by the Los Alamos National Laboratory plasma experiment on the Ulysses spacecraft support this interpretation. 12 refs., 9 figs.

  14. Shock acceleration of energetic particles in corotating interaction regions in the solar wind

    SciTech Connect

    Fisk, L.A.; Lee, M.A.

    1980-04-15

    A simple shock model for the acceleration of energetic particles in corotating interaction regions (CIRs) in the solar wind is presented. Particles are accelerated at the forward and reverse shocks which bound the CIR by being compressed between the shock fronts and magnetic irregularities upstream from the shocks, or by being compressed between upstream irregularities and those downstream from the shocks. Particles also suffer adiabatic deceleration in the expanding solar wind, an effect not included in previous shock models for acceleration in CIRs. The model is able to account for the observed exponential spectra at Earth, the observed behavior of the spectra with radial distance, the observed radial gradients in the intensity, and the observed differences in the intensity and spectra at the forward and reverse shocks.

  15. Structure of a Magnetic Decrease Observed in a Corotating Interaction Region

    NASA Astrophysics Data System (ADS)

    Lee, Ensang; Parks, George K.

    2016-02-01

    Magnetic decreases are often observed in various regions of interplanetary space. Many studies are devoted to reveal the physical nature and generation mechanism of the magnetic decreases, but still we do not fully understand magnetic decreases. In this study, we investigate the structure of a magnetic decrease observed in a corotating interaction region using multi-spacecraft measurements. We use three spacecraft, ACE, Cluster, and Wind, which were widely separated in the x- and y-directions in the geocentric solar ecliptic (GSE) coordinates. The boundaries of the magnetic decrease are the same at the three locations and can be identified as tangential discontinuities. A notable feature is that the magnetic decrease has very large dimension, ≳268 R_{E}, along the boundary, which is much larger than the size, ˜6 R_{E}, along the normal direction. This suggests that the magnetic decrease has a shape of a long, thin rod or a wide slab.

  16. The Domain of δ Scuti Stars: First CoRoT IRa01 Results

    NASA Astrophysics Data System (ADS)

    Kaiser, Alexander; Weiss, Werner; Guenther, Eike; Balaguer, Lola; Maceroni, Carla; Ribas, Ignasi

    2009-09-01

    We present the first results of determing the δ Scuti population observed with CoRoT during the Initial Run (IRa01). From more than 10000 stars observed continuously in the exoplanet-channel during 58 days, 397 stars show pulsation in the δ Scuti domain. For 39 of the 397 stars low resolution classification spectra and Strömgren uvby photometry were available; thus fundamental parameters like effective temperature and surface gravity could be derived. Classical Fourier techniques and least squares multi-sine fits were applied to identify the pulsation frequencies. For additional 90 stars a pair of radial modes were found and by comparing with pulsation models it was possible to estimate the corresponding fundamental parameters.

  17. The CoRoT and Kepler Revolution in Stellar Variability Studies

    NASA Astrophysics Data System (ADS)

    Degroote, Pieter; Debosscher, Jonas

    2012-04-01

    Space-based observations of variable stars have revolutionized the field of variability studies. Dedicated satellites such as the CoRoT and Kepler missions have duty cycles which are unachievable from the ground, and effectively solve many of the aliasing problems prevalent in ground-based observation campaigns. Moreover, the location above the Earth's atmosphere eliminates a major source of scatter prevalent in observations from the ground. These two major improvements in instrumentation have triggered significant increases in our knowledge of the stars, but in order to reap the full benefits they are also obliging the community to adopt more efficient techniques for handling, analysing and interpreting the vast amounts of new, high-precision data in an effective yet comprehensive manner. This workshop heard an outline of the history and development of asteroseismology, and descriptions of the two space missions (CoRoT and Kepler) which have been foremost in accelerating those recent developments. Informal discussions on numerous points peppered the proceedings, and involved the whole audience at times. The conclusions which the workshop reached have been distilled into a list of seven recommendations (Section 5) for the asteroseismology community to study and absorb. In fact, while addressing activities (such as stellar classification or analysing and modelling light curves) that could be regarded as specific to the community in question, the recommendations include advice on matters such as improving communication, incorporating trans-disciplinary knowledge and involving the non-scientific public that are broad enough to serve as guidelines for the astrophysical community at large.

  18. The CoRoT chemical peculiar target star HD 49310

    NASA Astrophysics Data System (ADS)

    Paunzen, E.; Fröhlich, H.-E.; Netopil, M.; Weiss, W. W.; Lüftinger, T.

    2015-02-01

    Context. The magnetic chemically peculiar (CP) stars of the upper main sequence are well-suited laboratories for investigating the influence of local magnetic fields on the stellar surface because they produce inhomogeneities (spots) that can be investigated in detail as the star rotates. Aims: We studied the inhomogeneous surface structure of the CP2 star HD 49310 based on high-quality CoRoT photometry obtained during 25 days. The data have nearly no gaps. This analysis is similar to a spectroscopic Doppler-imaging analysis, but it is not a tomographic method. Methods: We performed detailed light-curve fitting in terms of stationary circular bright spots. Furthermore, we derived astrophysical parameters with which we located HD 49310 within the Hertzsprung-Russell diagram. We also investigated the possible connection of this star to the nearby young open cluster NGC 2264. Results: With a Bayesian technique, we produced a surface map that shows six bright spots. After removing some artefacts, the residuals of the observed and synthetic photometric data are ± 0.123 mmag. The rotational period of the star is P = 1.91909 ± 0.00001 days. Our photometric observations therefore cover about 13 full rotational cycles. Three spots are very large with diameters of ≃ 40deg. The spots are brighter by 40% than the unperturbed stellar photosphere. Conclusions: HD 49310 is a classical silicon (CP2) star with a mass of about 3 M⊙. It is not a member of NGC 2264. Our analysis shows the potential of using high-quality photometric data to analyse the surface structure of CP stars. A comprehensive analysis of similar archival data, preferrably from space missions, would contribute significantly to our understanding of surface phenomena of CP stars and their temporal evolution. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain.

  19. The CoRoT satellite in flight: description and performance

    NASA Astrophysics Data System (ADS)

    Auvergne, M.; Bodin, P.; Boisnard, L.; Buey, J.-T.; Chaintreuil, S.; Epstein, G.; Jouret, M.; Lam-Trong, T.; Levacher, P.; Magnan, A.; Perez, R.; Plasson, P.; Plesseria, J.; Peter, G.; Steller, M.; Tiphène, D.; Baglin, A.; Agogué, P.; Appourchaux, T.; Barbet, D.; Beaufort, T.; Bellenger, R.; Berlin, R.; Bernardi, P.; Blouin, D.; Boumier, P.; Bonneau, F.; Briet, R.; Butler, B.; Cautain, R.; Chiavassa, F.; Costes, V.; Cuvilho, J.; Cunha-Parro, V.; de Oliveira Fialho, F.; Decaudin, M.; Defise, J.-M.; Djalal, S.; Docclo, A.; Drummond, R.; Dupuis, O.; Exil, G.; Fauré, C.; Gaboriaud, A.; Gamet, P.; Gavalda, P.; Grolleau, E.; Gueguen, L.; Guivarc'h, V.; Guterman, P.; Hasiba, J.; Huntzinger, G.; Hustaix, H.; Imbert, C.; Jeanville, G.; Johlander, B.; Jorda, L.; Journoud, P.; Karioty, F.; Kerjean, L.; Lafond, L.; Lapeyrere, V.; Landiech, P.; Larqué, T.; Laudet, P.; Le Merrer, J.; Leporati, L.; Leruyet, B.; Levieuge, B.; Llebaria, A.; Martin, L.; Mazy, E.; Mesnager, J.-M.; Michel, J.-P.; Moalic, J.-P.; Monjoin, W.; Naudet, D.; Neukirchner, S.; Nguyen-Kim, K.; Ollivier, M.; Orcesi, J.-L.; Ottacher, H.; Oulali, A.; Parisot, J.; Perruchot, S.; Piacentino, A.; Pinheiro da Silva, L.; Platzer, J.; Pontet, B.; Pradines, A.; Quentin, C.; Rohbeck, U.; Rolland, G.; Rollenhagen, F.; Romagnan, R.; Russ, N.; Samadi, R.; Schmidt, R.; Schwartz, N.; Sebbag, I.; Smit, H.; Sunter, W.; Tello, M.; Toulouse, P.; Ulmer, B.; Vandermarcq, O.; Vergnault, E.; Wallner, R.; Waultier, G.; Zanatta, P.

    2009-10-01

    Context: CoRoT is a space telescope dedicated to stellar seismology and the search for extrasolar planets. The mission is led by the CNES in association with French laboratories and has a large international participation. The European Space Agency (ESA), Austria, Belgium, and Germany contribute to the payload, and Spain and Brazil contribute to the ground segment. Development of the spacecraft, which is based on a PROTEUS low earth orbit (LEO) recurrent platform, commenced in October 2000, and the satellite was launched on December 27, 2006. Aims: The instrument and platform characteristics prior to launch have been described in ESA publication (SP-1306). In the present paper we explain the behaviour in flight, based on raw and corrected data. Methods: Five runs have been completed since January 2007. The data used here are essentially those acquired during the commissioning phase and from a long run that lasted 146 days. These enable us to give a complete overview of the instrument and platform behaviour for all environmental conditions. The ground based data processing is not described in detail because the most important method has been published elsewhere. Results: We show that the performance specifications are easily satisfied when the environmental conditions are favourable. Most of the perturbations, hence data corrections, are related to LEO perturbations: high energy particles inside the South Atlantic Anomaly (SAA), eclipses and temperature variations, and line of sight fluctuations due to the attitude control system. Straylight due to the reflected light from the earth, which is controlled by the telescope and baffle design, appears to be negligible. The CoRoT space mission, launched on December 27th 2006, has been developed and is operated by CNES, with contributions from Austria, Belgium, Brazil, ESA, Germany and Spain. Four French laboratories associated with the CNRS (LESIA, LAM, IAS, OMP) collaborate with CNES on the satellite development. The

  20. The extreme physical properties of the CoRoT-7b super-Earth

    NASA Astrophysics Data System (ADS)

    Léger, A.; Grasset, O.; Fegley, B.; Codron, F.; Albarede, A. F.; Barge, P.; Barnes, R.; Cance, P.; Carpy, S.; Catalano, F.; Cavarroc, C.; Demangeon, O.; Ferraz-Mello, S.; Gabor, P.; Grießmeier, J.-M.; Leibacher, J.; Libourel, G.; Maurin, A.-S.; Raymond, S. N.; Rouan, D.; Samuel, B.; Schaefer, L.; Schneider, J.; Schuller, P. A.; Selsis, F.; Sotin, C.

    2011-05-01

    The search for rocky exoplanets plays an important role in our quest for extra-terrestrial life. Here, we discuss the extreme physical properties possible for the first characterised rocky super-Earth, CoRoT-7b ( R pl = 1.58 ± 0.10 R Earth, M pl = 6.9 ± 1.2 M Earth). It is extremely close to its star ( a = 0.0171 AU = 4.48 R st), with its spin and orbital rotation likely synchronised. The comparison of its location in the ( M pl, R pl) plane with the predictions of planetary models for different compositions points to an Earth-like composition, even if the error bars of the measured quantities and the partial degeneracy of the models prevent a definitive conclusion. The proximity to its star provides an additional constraint on the model. It implies a high extreme-UV flux and particle wind, and the corresponding efficient erosion of the planetary atmosphere especially for volatile species including water. Consequently, we make the working hypothesis that the planet is rocky with no volatiles in its atmosphere, and derive the physical properties that result. As a consequence, the atmosphere is made of rocky vapours with a very low pressure ( P ⩽ 1.5 Pa), no cloud can be sustained, and no thermalisation of the planet is expected. The dayside is very hot (2474 ± 71 K at the sub-stellar point) while the nightside is very cold (50-75 K). The sub-stellar point is as hot as the tungsten filament of an incandescent bulb, resulting in the melting and distillation of silicate rocks and the formation of a lava ocean. These possible features of CoRoT-7b could be common to many small and hot planets, including the recently discovered Kepler-10b. They define a new class of objects that we propose to name " Lava-ocean planets".

  1. The Berlin Exoplanet Search Telescope II Catalog of Variable Stars. II. Characterization of the CoRoT SRc02 Field

    NASA Astrophysics Data System (ADS)

    Klagyivik, P.; Csizmadia, Sz.; Pasternacki, T.; Cabrera, J.; Chini, R.; Eigmüller, P.; Erikson, A.; Fruth, T.; Kabath, P.; Lemke, R.; Murphy, M.; Rauer, H.; Titz-Weider, R.

    2016-05-01

    Time-series photometry of the CoRoT field SRc02 was obtained by the Berlin Exoplanet Search Telescope II (BEST II) in 2009. The main aim was to conduct a ground-based follow-up of the CoRoT field in order to detect variable stars with better spatial resolution than what can be achieved with the CoRoT Space Telescope. A total of 1846 variable stars were detected, of which only 30 have been previously known. For nine eclipsing binaries the stellar parameters were determined by modeling their light curves.

  2. Rossby and drift wave turbulence and zonal flows: The Charney-Hasegawa-Mima model and its extensions

    NASA Astrophysics Data System (ADS)

    Connaughton, Colm; Nazarenko, Sergey; Quinn, Brenda

    2015-12-01

    A detailed study of the Charney-Hasegawa-Mima model and its extensions is presented. These simple nonlinear partial differential equations suggested for both Rossby waves in the atmosphere and drift waves in a magnetically-confined plasma, exhibit some remarkable and nontrivial properties, which in their qualitative form, survive in more realistic and complicated models. As such, they form a conceptual basis for understanding the turbulence and zonal flow dynamics in real plasma and geophysical systems. Two idealised scenarios of generation of zonal flows by small-scale turbulence are explored: a modulational instability and turbulent cascades. A detailed study of the generation of zonal flows by the modulational instability reveals that the dynamics of this zonal flow generation mechanism differ widely depending on the initial degree of nonlinearity. The jets in the strongly nonlinear case further roll up into vortex streets and saturate, while for the weaker nonlinearities, the growth of the unstable mode reverses and the system oscillates between a dominant jet, which is slightly inclined to the zonal direction, and a dominant primary wave. A numerical proof is provided for the extra invariant in Rossby and drift wave turbulence-zonostrophy. While the theoretical derivations of this invariant stem from the wave kinetic equation which assumes weak wave amplitudes, it is shown to be relatively well-conserved for higher nonlinearities also. Together with the energy and enstrophy, these three invariants cascade into anisotropic sectors in the k-space as predicted by the Fjørtoft argument. The cascades are characterised by the zonostrophy pushing the energy to the zonal scales. A small scale instability forcing applied to the model has demonstrated the well-known drift wave-zonal flow feedback loop. The drift wave turbulence is generated from this primary instability. The zonal flows are then excited by either one of the generation mechanisms, extracting energy from

  3. Evidence of Boundary Reflection of Kelvin and First-Mode Rossby Waves from Topex/Poseidon Sea Level Data

    NASA Technical Reports Server (NTRS)

    Boulanger, Jean-Philippe; Fu, Lee-Lueng

    1996-01-01

    The TOPEX/POSEIDON sea level data lead to new opportunities to investigate some theoretical mechanisms suggested to be involved in the El Nino-Southern Oscillation phenomenon in the tropical Pacific ocean. In particular, we are interested in studying the western boundary reflection, a process crucial for the delayed action oscillator theory, by using the TOPEX/POSEIDON data from November 1992 to May 1995. We first projected the sea level data onto Kelvin and first-mode Ross waves. Then we estimated the contribution of wind forcing to these waves by using a single baroclinic mode simple wave model forced by the ERS-1 wind data. Wave propagation was clearly observed with amplitudes well explained by the wind forcing in the ocean interior. Evidence of wave reflection was detected at both the western and eastern boundaries of the tropical Pacific ocean. At the eastern boundary, Kelvin waves were seen to reflect as first-mode Rossby waves during the entire period. The reflection efficiency (in terms of wave amplitude) of the South American coasts was estimated to be 80% of that of an infinite meridional wall. At the western boundary, reflection was observed in April-August 1993, in January-June 1994, and, later, in December 1994 to February 1995. Although the general roles of these reflection events in the variability observed in the equatorial Pacific ocean are not clear, the data suggest that the reflections in January-June 1994 have played a role in the onset of the warm conditions observed in late 1994 to early 1995. Indeed, during the January-June 1994 period, as strong downwelling first-mode Rossby waves reflected into downwelling Kelvin waves, easterly wind and cold sea surface temperature anomalies located near the date line weakened and eventually reversed in June-July 1994. The presence of the warm anomalies near the date line then favored convection and westerly wind anomalies that triggered strong downwelling Kelvin waves propagating throughout the basin

  4. Zonal flows and magnetic fields driven by large-amplitude Rossby-Alfvén-Khantadze waves in the E-layer ionosphere

    NASA Astrophysics Data System (ADS)

    Kaladze, T. D.; Horton, W.; Kahlon, L. Z.; Pokhotelov, O.; Onishchenko, O.

    2013-12-01

    waves and vortices in the weakly ionized ionospheric E layer are dominated by the Hall conductivity that couples the Rossby and Alfvén dynamics giving rise to what are called Rossby-Alfvén-Khantadze electromagnetic structures. At finite amplitudes we show that the nonlinearities in the dynamics generate sheared zonal-flow velocities and zonal magnetic field fluctuations. The zonal-flow mechanism is based on the parametric excitation of the zonal variations through three-wave mode coupling in the planetary-scale waves. The coupled dynamics of the nonlinear 3-D incompressible flows and the magnetic field fluctuations are derived and used to derive the structure and growth rates for the zonal flows and zonal magnetic fields. Large-amplitude planetary waves are shown to drive up magnetic fluctuations up to 100 nT.

  5. Temporal Spectral Analysis of Be stars observed with CoRoT satellite

    NASA Astrophysics Data System (ADS)

    Emilio, Marcelo; Janot Pacheco, Eduardo; Andrade, Laerte

    . Nevertheless, to measure frequencies with great accuracy in stars requires both high photometric precision and high time-frequency resolution. The CoRoT (Convection, Rotation and planetary Transits) satellite opens for the first time in history the possibility of fulfilling this goal. CoRoT is an experiment of astronomy dedicated to seismology and the detection of extrasolar planet transits. It was launched on December 2006 in an inertial polar orbit at an altitude of 897 mathrm{km}. The instrument is fed by a phi=27 textrm{cm} telescope. Its scientific program is three-fold consisting of: (1) The seismology core program (SISMO), which concerns the seismic study of ˜10 bright (6CoRoT ID 102761769 observed by CoRoT satellite. We found two close frequencies related to the .CoRoT ID 102761769 star. They are 2.465 c d(-1) (28.5 mathrm{mu Hz}) and 2.441 c d(-1) (28.2 mathrm{mu Hz}). The precision to which those frequencies were found is 0.018 c d(-1) (0.2 mathrm{mu Hz}). The projected stellar rotation was estimated to be 120 km s(-1) from the Fourier transform of spectral lines. If CoRoT-ID 102761769 is a typical Galactic Be star it rotates near the critical velocity. The critical rotation frequency of a typical B5-6 star is about 3.5 c d(-1) (40.5 mathrm{mu Hz}), which implies that the above frequencies are really caused by stellar pulsations rather than star's rotation. HD 171219 frequencies 1.113, 1.130, 1.146 c * d(-1) form a triplet with the

  6. Feature-based verification of synoptic-scale Rossby wave breaking in the ECHAM5-HAM model

    NASA Astrophysics Data System (ADS)

    Béguin, A.; Martius, O.; Sprenger, M.; Spichtinger, P.; Folini, D.; Werlni, H.

    2010-09-01

    Breaking synoptic-scale Rossby waves (RWB) are central to the daily weather evolution of the extratropics and subtropics and for the meridional transport of chemical constituents and momentum. Synoptic-scale RWB events are manifest as elongated and narrow structures in the tropopause level potential vorticity (PV) field. A feature-based verification approach is used to assess the representation of these structures in present day climate simulations carried out with the ECHAM5-HAM climate model with different resolutions (T42L19, T63L31 and T106L31) in comparison to the ERA-40 data set. The algorithm extracts RWB objects from the tropopause-level PV field and allows verifying the frequency of occurrence of RWB objects. The model captures the location of the RWB frequency maxima in the northern hemisphere well in all resolutions. However, in the T42L19 simulation the frequency of events is underestimated in the entire northern hemisphere by 28% (averaged over all seasons and grid-points). The higher-resolution simulations capture the overall frequency of RWB much better, with a fairly small improvement from the T63L31 to the T106L31 run. In the higher-resolution simulations significant differences to the ERA-40 data are regionally confined and vary with the season. The most striking feature is that the model overestimates the frequency of RWB in the subtropical Atlantic in all seasons except for spring.

  7. Retrograde rotation of the large-scale flow in turbulent rotating Rayleigh-Benard convection with high Rossby number

    NASA Astrophysics Data System (ADS)

    Zhong, Jin-Qiang; Li, Hui-Min; Wang, Xue-Ying

    2015-11-01

    We present measurements of the azimuthal orientation θ (t) of the large-scale circulation (LSC) for turbulent Rayleigh-Bénard convection in the presence of week rotations Ω . Linear retrograde rotations of the LSC circulating plane are observed over the entire Rossby-number range (1 <= Ro <= 300) studied. When the Ro increases, the ratio of the retrograde rotation rate, γ = - < . θ > / Ω remains nearly a constant 0.12 in the range of (1 <= Ro <= 80) and starts to increases when Ro > 80 . When Ro ~= 300 , γ approaches a value of 0.36 close to the prediction from previous theoretical models. In a background of linear rotations, erratic changes in θ (t) accompanied by decreasing in the LSC amplitude δ are observed. These small- δ events give rise to the increasing γ with very high Ro numbers (80 <= Ro <= 300). In this range, the diffusivity of θ is proportional to δ-2 . Moreover, the occurrence frequency of the small- δ events, and their average duration are independent on Ro. We propose a model to include additional viscous damping for the LSC azimuthal motion due to turbulent viscosity and provide theoretical interpretations of the experimental results. Work supported by NSFC Grant No. 11202151.

  8. The coupling of mixed Rossby-gravity waves with diabatic heating during the TRMM-KWAJEX field campaign

    NASA Astrophysics Data System (ADS)

    Wang, Xiaocong; Zhang, Minghua

    2015-10-01

    Composite dynamic and thermodynamic structures of mixed Rossby-gravity (MRG) waves are presented with their coupling with diabatic heating and moisture sources/sinks, using Tropical Rainfall Measuring Mission-Kwajalein Experiment (TRMM-KWAJEX) field campaign data. A significant departure of convectively coupled waves from dry waves exists in the phases of wave component: maximum low-level wind convergence is accompanied by midtropospheric divergence and upper tropospheric convergence that is preceded by increase of moisture in the boundary layer. These phases correspond to surface turbulent transport, shallow and midlevel convections that cause moistening and heating of the lower and middle troposphere. They are followed by deep convection with maximum heating centered in the upper troposphere. The deep convective heating evolves to stratiform-like upper tropospheric heating and lower tropospheric cooling that precedes the quick demise of convection. Such a structure on convectively coupled MRG waves is summarized by four phases, which sheds lights on how tropical waves are coupled with convective processes in all their phases.

  9. From Land-surface Snow Cover To Routed River Discharge In The Rossby Centre Regional Climate Model

    NASA Astrophysics Data System (ADS)

    Samuelsson, P.; Gollvik, S.; Graham, L. P.; Bringfelt, B.

    The purpose of a land-surface scheme (LSS) in a coupled atmosphere- land-ocean model system is in general to provide the atmosphere with correct turbulent and radia- tion fluxes and to provide the routing scheme with correct water runoff flux. ``Correct" includes both amounts and time distributions. Snow is a very important process to con- sider in a LSS used for simulations at high latitudes. Snow has extreme radiation and heat transfer properties and it accumulates water during the winter season. Therefore, both amount and distribution of snow have to be carefully simulated. The LSS in the Rossby Centre Regional Climate Model (RCA) separates snow storage on open land and in forest. Both storages are single-layered, include liquid water and use the en- ergy balance to solve for time changes in temperature and water storage. The runoff generated from i.e. snow melt in each grid cell is used in a routing scheme to produce river discharge for the ocean model. The routing scheme is based on the hydrological HBV model which means that it is separately calibrated for each individual sub-basin. Validations of snow cover and river discharge simulations will be presented.

  10. Transiting exoplanets from the CoRoT space mission Resolving the nature of transit candidates for the LRa03 and SRa03 fields

    NASA Astrophysics Data System (ADS)

    Cavarroc, C.; Moutou, C.; Gandolfi, D.; Tingley, B.; Ollivier, M.; Aigrain, S.; Alonso, R.; Almenara, J.-M.; Auvergne, M.; Baglin, A.; Barge, P.; Bonomo, A. S.; Bordé, P.; Bouchy, F.; Cabrera, J.; Carpano, S.; Carone, L.; Cochran, W. D.; Csizmadia, S.; Deeg, H. J.; Deleuil, M.; Díaz, R. F.; Dvorak, R.; Endl, M.; Erikson, A.; Fridlund, M.; Gillon, M.; Guenther, E. W.; Guillot, T.; Hatzes, A.; Hébrard, G.; Jorda, L.; Léger, A.; Lammer, H.; Lev, T.-O.; Lovis, C.; MacQueen, P. J.; Mazeh, T.; Ofir, A.; Parviainen, H.; Pasternacki, T.; Pätzold, M.; Queloz, D.; Rauer, H.; Rouan, D.; Samuel, B.; Santerne, A.; Schneider, J.; Weingrill, J.; Wuchterl, G.

    2012-02-01

    CoRoT is a space telescope which aims at studying internal structure of stars and detecting extrasolar planets. We present here a list of transits detected in the light curves of stars observed by CoRoT in two fields in the anti-center direction: the LRa03 one observed during 148 days from 3 October 2009 to 1 March 2010 followed by the SRa03 one from the 5 March 2010 to the 29 March 2010 during 25 days. 5329 light curves for the LRa03 field and 4169 for the SRa03 field were analyzed by the detection team of CoRoT. Then some of the selected exoplanetary candidates have been followed up from the ground. In the LRa03 field, 19 exoplanet candidates have been found, 8 remain unsolved. No secured planet has been found yet. In the SRa03 field, there were 11 exoplanetary candidates among which 6 cases remain unsolved and 3 planets have been found: CoRoT-18b, CoRoT-19b, CoRoT-20b.

  11. VizieR Online Data Catalog: GTC transit light curves of CoRoT-29b (Palle+, 2016)

    NASA Astrophysics Data System (ADS)

    Palle, E.; Chen, G.; Alonso, R.; Nowak, G.; Deeg, H.; Cabrera, J.; Murgas, F.; Parviainen, H.; Nortmann, L.; Hoyer, S.; Prieto-Arranz, J.; Nespral, D.; Cabrera Lavers, A.; Iro, N.

    2016-04-01

    2 transit light curves of the hot Jupiter CoRoT-29b obtained on the nights of 2014/7/31 and 2015/7/8 using the OSIRIS instrument at the 10.4-m GTC telescope. The light curves have been integrated over the bandpass of 515-915nm, where the wavelength range of 755-765 nm has been excluded due to presence of strong telluric O2 absorption. (2 data files).

  12. CoRoT-22 b: a validated 4.9 R⊕ exoplanet in 10-d orbit

    NASA Astrophysics Data System (ADS)

    Moutou, C.; Almenara, J. M.; Díaz, R. F.; Alonso, R.; Deleuil, M.; Guenther, E.; Pasternacki, T.; Aigrain, S.; Baglin, A.; Barge, P.; Bonomo, A. S.; Bordé, P.; Bouchy, F.; Cabrera, J.; Carpano, S.; Cochran, W. D.; Csizmadia, Sz.; Deeg, H. J.; Dvorak, R.; Endl, M.; Erikson, A.; Ferraz-Mello, S.; Fridlund, M.; Gandolfi, D.; Guillot, T.; Hatzes, A.; Hébrard, G.; Lovis, C.; Lammer, H.; MacQueen, P. J.; Mazeh, T.; Ofir, A.; Ollivier, M.; Pätzold, M.; Rauer, H.; Rouan, D.; Santerne, A.; Schneider, J.; Tingley, B.; Wuchterl, G.

    2014-11-01

    The CoRoT satellite has provided high-precision photometric light curves for more than 163 000 stars and found several hundreds of transiting systems compatible with a planetary scenario. If ground-based velocimetric observations are the best way to identify the actual planets among many possible configurations of eclipsing binary systems, recent transit surveys have shown that it is not always within reach of the radial-velocity detection limits. In this paper, we present a transiting exoplanet candidate discovered by CoRoT whose nature cannot be established from ground-based observations, and where extensive analyses are used to validate the planet scenario. They are based on observing constraints from radial-velocity spectroscopy, adaptive optics imaging and the CoRoT transit shape, as well as from priors on stellar populations, planet and multiple stellar systems frequency. We use the fully Bayesian approach developed in the PASTIS (Planet Analysis and Small Transit Investigation Software) analysis software, and conclude that the planet scenario is at least 1400 times more probable than any other false-positive scenario. The primary star is a metallic solar-like dwarf, with Ms = 1.099 ± 0.049 M⊙ and Rs = 1.136^{+0.038}_{-0.090} R⊙. The validated planet has a radius of Rp = 4.88^{+0.17}_{-0.39} R⊕ and mass less than 49 M⊕. Its mean density is smaller than 2.56 g cm-3 and orbital period is 9.7566 ± 0.0012 d. This object, called CoRoT-22 b, adds to a large number of validated Kepler planets. These planets do not have a proper measurement of the mass but allow statistical characterization of exoplanets population.

  13. Long Wave Resonance in Tropical Oceans and Implications on Climate: The Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Pinault, Jean-Louis

    2016-06-01

    The dynamics of the tropical Pacific can be understood satisfactorily by invoking the coupling between the basin modes of 1-, 4- and 8-year average periods. The annual quasi-stationary wave (QSW) is a first baroclinic-mode, fourth meridional-mode Rossby wave resonantly forced by easterlies. The quadrennial QSW is built up from a first baroclinic-mode Kelvin wave and a first baroclinic-mode, first meridional-mode Rossby wave equatorially trapped and two off-equatorial Rossby waves, their dovetailing forming a resonantly forced wave (RFW). The 8-year period QSW is a replica of the quadrennial QSW for the second-baroclinic mode. The coupling between basin modes results from the merging of modulated currents both in the western part of the North Equatorial Counter Current and along the South Equatorial Current. Consequently, a sub-harmonic mode locking occurs, which means that the average period of QSWs is 1-, 4- and 8-year exactly. The quadrennial sub-harmonic is subject to two modes of forcing. One results from coupling with the annual QSW that produces a Kelvin wave at the origin of transfer of the warm waters from the western part of the basin to the central-eastern Pacific. The other is induced by El Niño and La Niña that self-sustain the sub-harmonic by stimulating the Rossby wave accompanying the westward recession of the QSW at a critical stage of its evolution. The interpretation of ENSO from the coupling of different basin modes allows predicting and estimating the amplitude of El Niño events a few months before they become mature from the accelerations of the geostrophic component of the North Equatorial Counter Current.

  14. Long Wave Resonance in Tropical Oceans and Implications on Climate: The Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Pinault, Jean-Louis

    2015-12-01

    The dynamics of the tropical Pacific can be understood satisfactorily by invoking the coupling between the basin modes of 1-, 4- and 8-year average periods. The annual quasi-stationary wave (QSW) is a first baroclinic-mode, fourth meridional-mode Rossby wave resonantly forced by easterlies. The quadrennial QSW is built up from a first baroclinic-mode Kelvin wave and a first baroclinic-mode, first meridional-mode Rossby wave equatorially trapped and two off-equatorial Rossby waves, their dovetailing forming a resonantly forced wave (RFW). The 8-year period QSW is a replica of the quadrennial QSW for the second-baroclinic mode. The coupling between basin modes results from the merging of modulated currents both in the western part of the North Equatorial Counter Current and along the South Equatorial Current. Consequently, a sub-harmonic mode locking occurs, which means that the average period of QSWs is 1-, 4- and 8-year exactly. The quadrennial sub-harmonic is subject to two modes of forcing. One results from coupling with the annual QSW that produces a Kelvin wave at the origin of transfer of the warm waters from the western part of the basin to the central-eastern Pacific. The other is induced by El Niño and La Niña that self-sustain the sub-harmonic by stimulating the Rossby wave accompanying the westward recession of the QSW at a critical stage of its evolution. The interpretation of ENSO from the coupling of different basin modes allows predicting and estimating the amplitude of El Niño events a few months before they become mature from the accelerations of the geostrophic component of the North Equatorial Counter Current.

  15. Dynamic Young Stars and their Disks: A Temporal View of NGC 2264 with Spitzer and CoRoT

    NASA Astrophysics Data System (ADS)

    Cody, Ann Marie; Stauffer, John; Bouvier, Jèrôme

    2014-01-01

    Variability is a signature feature of young stars. Among the well known light curve phenomena are periodic variations attributed to surface spots and irregular changes associated with accretion or circumstellar disk material. While decades of photometric monitoring have provided a framework for classifying young star variability, we still know surprisingly little about its underlying mechanisms and connections to the surrounding disks. In the past few years, dedicated photometric monitoring campaigns from the ground and space have revolutionized our view of young stars in the time domain. We present a selection of optical and infrared time series from several recent campaigns, highlighting the Coordinated Synoptic Investigation of NGC 2264 ("CSI 2264")- a joint30-day effort with the Spitzer, CoRoT, and MOST telescopes. The extraordinary photometric precision, high cadence, and long time baseline of these observations is now enabling correlation of variability properties at very different wavelengths, corresponding to locations from the stellar surface to the inner 0.1 AU of the disk. We present some results of the CSI 2264 program, including new classes of optical/infrared behavior. Further efforts to tie observed variability features to physical models will provide insights into the inner disk environment at a time when planet formation may be underway. Based on data from the Spitzer and CoRoT missions. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA-s RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain.

  16. Mode width fitting with a simple Bayesian approach. Application to CoRoT targets HD 181420 and HD 49933

    NASA Astrophysics Data System (ADS)

    Gaulme, P.; Appourchaux, T.; Boumier, P.

    2009-10-01

    Aims: We investigate the asteroseismology of two solar-like targets as observed with the CoRoT satellite, with particular attention paid to the mode fitting. HD 181420 and HD 49933 are typical CoRoT solar-like targets (156 and 60-day runs). The low signal-to-noise ratio (SNR) of about 3{-}10 prevents us from unambiguously identifying the individual oscillation modes. In particular, convergence problems appear at the edges of the oscillation spectrum. Methods: We apply a Bayesian approach to the analysis of these data. We compare the global fitting of the power spectra obtained by the classical maximum likelihood (MLE) and the maximum a posteriori (MAP) estimators. Results: We examine the impact of the choice of the priors upon the fitted parameters. We also propose to reduce the number of free parameters in the fitting, by replacing the individual estimate of mode height associated with each overtone by a continuous function of frequency (Gaussian profile). Conclusions: The MAP appears as a powerful tool to constrain the global fits, but it must be used carefully and only with reliable priors. The mode width of the stars increases with the frequency over all the oscillation spectrum. The CoRoT space mission, launched on 2006 December 27, was developed and is operated by the CNES, with participation of the Science Programs of ESA, ESA's RSSD, Austria, Belgium, Brazil, Germany and Spain.

  17. Locating the open-closed boundary during the passage of a corotating interaction region

    NASA Astrophysics Data System (ADS)

    Urban, K. D.; Gerrard, A. J.; Lanzerotti, L. J.; Weatherwax, A. T.

    2014-12-01

    During the 2007-2009 solar quiet period there existed a unique opportunity to study the synoptic variability of the open-closed boundary (OCB) using data provided by fluxgate magnetometers located at South Pole, McMurdo, and from a network of Automatic Geophysical Observatories distributed across the Antarctic continent. In Urban et al [2011], this synoptic variability was analyzed during a geomagnetic quiet period of early August 2008 and excellent (>83%) agreement was found between the experimental observations and the BATSRUS space weather model. In this paper we discuss the OCB's synoptic behavior under the forcing of a geomagnetic storm driven by a corotating interaction region and again compare these results to predictions made with different versions of BATSRUS model runs. Strictly adhering to the method developed in Urban et al [2011], we show only weak agreement between the experimental data and model during this geomagnetically-active time, independent of the model resolution and the incorporation of the Rice Convection Model. Given that a potential source of disagreement could be from the rigidity of the original open/closed field line determination technique itself (developed for geomagnetic quiescence), we adapt the technique to variations in local time and geomagnetic activity; any remaining discrepancies between the data and the model are investigated with DMSP spacecraft-determined boundary data.

  18. Corotating Interaction Regions as Seen by the STEREO Heliospheric Imagers 2007 - 2010

    NASA Astrophysics Data System (ADS)

    Conlon, T. M.; Milan, S. E.; Davies, J. A.; Williams, A. O.

    2015-08-01

    NASA's Solar Terrestrial Relations Observatory (STEREO) mission has coincided with a pronounced solar minimum. This allowed for easier detection of corotating interaction regions (CIRs). CIRs are formed by the interaction between fast and slow solar-wind streams ejected from source regions on the solar surface that rotate with the Sun. High-density plasma blobs that have become entrained at the stream interface can be tracked out to large elongations in data from the Heliospheric Imager (HI) instruments onboard STEREO. These blobs act as tracers of the CIR itself such that their HI signatures can be used to estimate CIR source location and radial speed. We estimate the kinematic properties of solar-wind transients associated with 40 CIRs detected by the HI instrument onboard the STEREO-A spacecraft between 2007 and 2010. We identify in-situ signatures of these transients at L1 using the Advanced Composition Explorer (ACE) and compare the in-situ parameters with the HI results. We note that solar-wind transients associated with CIRs appear to travel at or close to the slow solar-wind speed preceding the event as measured in situ. We also highlight limitations in the commonly used analysis techniques of solar-wind transients by considering variability in the solar wind.

  19. Galactic Cosmic-Ray Intensity Modulation by Corotating Interaction Region Stream Interfaces at 1 au

    NASA Astrophysics Data System (ADS)

    Guo, X.; Florinski, V.

    2016-07-01

    We present a new model that couples galactic cosmic-ray (GCR) propagation with magnetic turbulence transport and the MHD background evolution in the heliosphere. The model is applied to the problem of the formation of corotating interaction regions (CIRs) during the last solar minimum from the period between 2007 and 2009. The numerical model simultaneously calculates the large-scale supersonic solar wind properties and its small-scale turbulent content from 0.3 au to the termination shock. Cosmic rays are then transported through the background, and thus computed, with diffusion coefficients derived from the solar wind turbulent properties, using a stochastic Parker approach. Our results demonstrate that GCR variations depend on the ratio of diffusion coefficients in the fast and slow solar winds. Stream interfaces inside the CIRs always lead to depressions of the GCR intensity. On the other hand, heliospheric current sheet (HCS) crossings do not appreciably affect GCR intensities in the model, which is consistent with the two observations under quiet solar wind conditions. Therefore, variations in diffusion coefficients associated with CIR stream interfaces are more important for GCR propagation than the drift effects of the HCS during a negative solar minimum.

  20. Investigation of Galactic Cosmic Rays Modulation by the Corotating Interaction Regions

    NASA Astrophysics Data System (ADS)

    Guo, X.; Florinski, V. A.

    2014-12-01

    Corotating interaction regions (CIRs) are produced as a result of the interaction between fast and slowsolar-wind streams, and quite ubiquitous in every region of the heliosphere. Observations shown thatthe stream interfaces of CIRs between fast and slow solar wind streams and the leading edges of CIRsare responsible for the depressions of galactic cosmic rays (GCRs) intensity. Based on the well knownlocal-scale expansion of the ideal MHD conservation law and the developed global MHD model ofCIRs in the heliosphere, we perform the numerical investigation of the transport and turbulence of thesolar wind fluctuation in CIRs. Turbulent energy density and correlation length distribution throughoutthe heliosphere are presented, and further in turn used to compute the mean free path and perpendiculardiffusion coefficient of energetic particles. We attempt to use the plasma background from the globalMHD simulations and the transport coefficients in our existing stochastic cosmic-ray transport code tonumerically solve the Parker transport equation for GCRs. The modulated GCR spectrum from Voyager2 observations near the termination shock was used at the external boundary condition. The computedGCR spectral features and temporal profiles at any given location was directly compared withobservations by spacecraft based cosmic-ray detectors and neutron monitors on the ground, which willgreatly enhance our understanding of the physics of GCR modulation by the CIRs in heliosphere.

  1. Vortex dynamics studies in supersonic flow: Merging of co-rotating streamwise vortices

    NASA Astrophysics Data System (ADS)

    Maddalena, L.; Vergine, F.; Crisanti, M.

    2014-04-01

    For air-breathing propulsion systems intended for flight at very high Mach numbers, combustion is carried out at supersonic velocities and the process is mixing limited. Substantial increase in mixing rates can be obtained by fuel injection strategies centered on generating selected modes of supersonic, streamwise vortex interactions. Despite the recognized importance, and potential of the role of streamwise vortices for supersonic mixing enhancement, only few fundamental studies on their dynamics and interactions have been conducted, leaving the field largely unexplored. A reduced order model that allows the dynamics of complex, interacting, supersonic vortical structures to be investigated, is presented in this work. The prediction of the evolution of mutually interacting streamwise vortices represents an enabling element for the initiation of an effective, systematic experimental study of selected cases of interest, and is an important step toward the design of new fuel injection strategies for supersonic combustors. The case presented in this work is centered on a merging process of co-rotating vortices, and the subsequent evolution of a system composed of two counter-rotating vortex pairs. This interaction was studied, initially, with the proposed model, and was chosen for the peculiarity of the resulting morphology of the vorticity field. These results were used to design an experimental investigation with the intent to target the same specific complex flow physics. The experiment revealed the same peculiar features encountered in the simulation.

  2. Flow between a stationary and a rotating disk shrouded by a co-rotating cylinder

    NASA Astrophysics Data System (ADS)

    Lopez, J. M.

    1996-10-01

    Boundary layers on stationary and rotating disks have received much attention since von Kármán's [Z. Angew. Math. Mech. 1, 233 (1921)] and Bödewadt's [Z. Angew. Math. Mech. 20, 241 (1940)] studies of the cases with disks of infinite radius. Theoretical treatments have focused on similarity treatments leading to conflicting ideas about existence and uniqueness, and where self-similar solutions exist, whether they are physically realizable. The coupling between the boundary layer flows and the interior flow between them, while being of practical importance in a variety of situations such as turbomachinery and ocean circulations, is not well understood. Here, a numerical treatment of the axisymmetric Navier-Stokes equations, together with some experiments for the case of finite stationary and rotating disks bounded by a co-rotating sidewall is presented. We show that in the long time limit, solutions are steady and essentially self-similar. Yet the transients are not. In particular, axisymmetric waves propagate in the stationary disk boundary layer when the vortex lines entering the boundary layer develop inflection points, and there are subsequent eruptions of vortical flow out of the boundary layer deep into the interior at large Reynolds numbers.

  3. Corotating interaction regions during the recent solar minimum: The power and limitations of global MHD modeling

    NASA Astrophysics Data System (ADS)

    Riley, Pete; Linker, Jon A.; Lionello, R.; Mikic, Z.

    2012-07-01

    The declining phase of solar activity cycle 23 has provided an unprecedented opportunity to study the evolution and properties of corotating interaction regions (CIRs) during unique and relatively steady conditions. The absence of significant transient activity has allowed modelers to test ambient solar wind models, but has also challenged them to reproduce structure that was qualitatively different than had been observed previously (at least within the space era). In this study, we present and analyze global magnetohydrodynamic (MHD) solutions of the inner heliosphere (from 1RS to 1 AU) for several intervals defined as part of a Center for Integrated Space weather Modeling (CISM) interdisciplinary campaign study, and, in particular, Carrington rotation 2060. We compare in situ measurements from ACE and STEREO A and B with the model results to illustrate both the capabilities and limitations of current numerical techniques. We show that, overall, the models do capture the essential structural features of the solar wind for specific time periods; however, there are times when the models and observations diverge. We describe, and, to some extent assess the sources of error in the modeling chain from the input photospheric magnetograms to the numerical schemes used to propagate structure through the heliosphere, and speculate on how they may be resolved, or at least mitigated in the future.

  4. Modeling interstellar pickup ion distributions in corotating interaction regions inside 1 AU

    NASA Astrophysics Data System (ADS)

    Chen, J. H.; Schwadron, N. A.; Möbius, E.; Gorby, M.

    2015-11-01

    We present a modeling study of interstellar pickup ion (PUI) distributions in corotating interaction regions (CIRs). We consider gradual compressions associated with CIRs formed when fast speed streams overtake slower streams in the inner heliosphere. For the analysis, we adopt a simplified magnetohydrodynamic model of a CIR. The Energetic Particle Radiation Environment Module, a parallelized particle numerical kinetic code, is used to model PUI distributions using the focused transport equation, including adiabatic cooling/heating, adiabatic focusing, and parallel and perpendicular diffusion. The continuous injection of PUIs is handled as a source term with a ring distribution in velocity space that is produced from the local neutral density obtained from a hot model of the interstellar neutral gas. The simulated distributions exhibit a harder spectrum in the compression region and a softer spectrum in the rarefaction region than that in undisturbed solar wind. As an additional result, a v-5 power law tail distribution above the PUI cutoff speed (a knee in the distribution) emerges for a particular velocity gradient in the CIR. The tail above the PUI cutoff is sensitive to the CIR velocity gradient, and in one observational case studied, this relationship adequately explains the observed spectrum from 2 to 4 times the solar wind speed. This suggests that the velocity gradient associated with the CIR formation can efficiently create a seed population of PUIs before a shock forms even without stochastic acceleration. Thus, local CIR compressions without shocks may play a significant role in the acceleration process as suggested previously.

  5. Observations of energetic particles between a pair of corotating interaction regions

    SciTech Connect

    Wu, Z.; Chen, Y.; Tang, C. L.; Li, G.; Zhao, L. L.; Ebert, R. W.; Desai, M. I.; Mason, G. M.; Lavraud, B.; Sauvaud, J.; Zhao, L.; Landi, E.; Liu, Y. C.-M.; Guo, F.

    2014-01-20

    We report observations of the acceleration and trapping of energetic ions and electrons between a pair of corotating interaction regions (CIRs). The event occurred in Carrington Rotation 2060. Observed by the STEREO-B spacecraft, the two CIRs were separated by less than 5 days. In contrast to other CIR events, the fluxes of the energetic ions and electrons in this event reached their maxima between the trailing edge of the first CIR and the leading edge of the second CIR. The radial magnetic field (B{sub r} ) reversed its sense and the anisotropy of the flux also changed from Sunward to anti-Sunward between the two CIRs. Furthermore, there was an extended period of counterstreaming suprathermal electrons between the two CIRs. Similar observations for this event were also obtained with the Advanced Composition Explorer and STEREO-A. We conjecture that these observations were due to a U-shaped, large-scale magnetic field topology connecting the reverse shock of the first CIR and the forward shock of the second CIR. Such a disconnected U-shaped magnetic field topology may have formed due to magnetic reconnection in the upper corona.

  6. SOLAR CYCLE ABUNDANCE VARIATIONS IN COROTATING INTERACTION REGIONS: EVIDENCE FOR A SUPRATHERMAL ION SEED POPULATION

    SciTech Connect

    Mason, G. M.; Desai, M. I.; Li, G.

    2012-04-01

    We have surveyed the heavy ion composition of corotating interaction regions (CIRs) over the recent solar minimum and combined this with our earlier survey to cover the 1998-2011 period encompassing a full solar cycle and onset of the new cycle. We find that the solar minimum CIR intensities and spectral forms are similar to those in active periods, indicating that the basic acceleration mechanism does not vary with solar activity for energies below a few MeV nucleon{sup -1}. However, the heavy ion abundances show a clear correlation with sunspot number, where heavy ions are more enhanced during active periods. Over the mass range He-Fe, the enhancement is organized by a power law in Q/M with exponent -1.9, with Fe/O varying by a factor of {approx}6. During solar minimum CIR Fe/O was {approx}0.05, well below the corresponding solar wind ratio. Previous studies have shown that rare ions (He{sup +}, {sup 3}He) enhanced in CIRs come from the suprathermal ion pool. The observations presented here extend this evidence, indicating that in addition to rare He{sup +} and {sup 3}He the CIR major heavy ion species are accelerated out of the suprathermal ion pool, not the bulk solar wind.

  7. THE THREE-DIMENSIONAL MORPHOLOGY OF A COROTATING INTERACTION REGION IN THE INNER HELIOSPHERE

    SciTech Connect

    Wood, B. E.; Howard, R. A.; Thernisien, A.; Socker, D. G. E-mail: russ.howard@nrl.navy.mil E-mail: dennis.socker@nrl.navy.mil

    2010-01-10

    In its three years of operation, the HI2 imagers on the two Solar TErrestrial RElations Observatory (STEREO) spacecraft have imaged many corotating interaction regions (CIRs) in the interplanetary medium, allowing the study of their three-dimensional (3D) morphology. Using an entirely empirical analysis technique, we construct a 3D model of one CIR, which is able to reproduce the general appearance and evolution of the CIR in HI2 images. The model CIR is also consistent with in situ data. Its curvature is compatible with the observed speed of the slow wind that is acting as the barrier for the fast wind piling up against it, and the width of the model CIR is consistent with the duration of the observed density pulse. Perpendicular to the equatorial plane, the model CIR has a parabolic shape that maps beautifully back to a bifurcated streamer observed at the Sun, which surrounds a coronal hole. This implies that this particular CIR is due to fast wind emanating from low latitudes that is impinging against slow wind in overlying streamers.

  8. Abundance and Source Population of Suprathermal Heavy Ions in Corotating Interaction Regions

    NASA Astrophysics Data System (ADS)

    Jensema, R. J.; Desai, M. I.; Broiles, T. W.; Dayeh, M. A.

    2015-12-01

    In this study we analyze the abundances of suprathermal heavy ions in 75 Corotating Interaction Region (CIR) events between January 1st 1995 and December 31st 2008. We correlate the heavy ion abundances in these CIRs with those measured in the solar wind and suprathermal populations upstream of these events. Our analysis reveals that the CIR suprathermal heavy ion abundances vary by nearly two orders of magnitude over the solar activity cycle, with higher abundances (e.g., Fe/O) occurring during solar maximum and depleted values occurring during solar minimum. The abundances are also energy dependent, with larger abundances at higher energies, particularly during solar maximum. Following the method used by Mason et al. 2008, we correlate the CIR abundances with the corresponding solar wind and suprathermal values measured during 6-hour intervals for upstream periods spanning 10 days prior to the start of each CIR event. This correlation reveals that suprathermal heavy ions are better correlated with upstream suprathermal abundances measured at the same energy compared with the solar wind heavy ion abundances. Using the 6-hour averaging method, we also identified timeframes of maximum correlation between the CIR and the upstream suprathermal abundances, and find that the time of maximum correlation depends on the energy of the suprathermal ions. We discuss the implications of these results in terms of previous studies of CIR and suprathermal particles, and CIR seed populations and acceleration mechanisms.

  9. Relativistic electron flux dropouts in the outer radiation belt associated with corotating interaction regions

    NASA Astrophysics Data System (ADS)

    Yuan, C.-J.; Zong, Q.-G.; Wan, W.-X.; Zhang, H.; Du, A.-M.

    2015-09-01

    Understanding how the relativistic electron fluxes drop out in the outer radiation belt under different conditions is of great importance. To investigate which mechanisms may affect the dropouts under different solar wind conditions, 1.5-6.0 MeV electron flux dropout events associated with 223 corotating interaction regions (CIRs) from 1994 to 2003 are studied using the observations of Solar, Anomalous, Magnetospheric Particle Explorer satellite. According to the superposed epoch analysis, it is found that high solar wind dynamic pressure with the peak median value of about 7 nPa is corresponding to the dropout of the median of the radiation belt content (RBC) index to 20% of the level before stream interface arrival, whereas low dynamic pressure with the peak median value of about 3 nPa is related to the dropout of the median of RBC index to 40% of the level before stream interface arrival. Furthermore, the influences of Russell-McPherron effect with respect to interplanetary magnetic field orientation on dropouts are considered. It is pointed out that under positive Russell-McPherron effect (+RM effect) condition, the median of RBC index can drop to 23% of the level before stream interface arrival, while for negative Russell-McPherron effect (-RM effect) events, the median of RBC index only drops to 37% of the level before stream interface arrival. From the evolution of phase space density profiles, the effect of +RM on dropouts can be through nonadiabatic loss.

  10. Perpendicular Transport of Low-Energy Corotating Interaction Region--associated Nuclei

    NASA Astrophysics Data System (ADS)

    Dwyer, J. R.; Mason, G. M.; Mazur, J. E.; Jokipii, J. R.; von Rosenvinge, T. T.; Lepping, R. P.

    1997-11-01

    We present compelling observational evidence for substantial transport of energetic charged particles across the local average magnetic field. Using data from the STEP/EPACT instrument on board the Wind spacecraft, we find that during three intense corotating interaction region (CIR) events, for periods greater than 12 hr, the observed anisotropy of the particle intensity at 1 AU is often directed at a significant angle to the measured magnetic field direction, which implies significant transport across the local magnetic field. A simple diffusion model is found to fit the three events very well with a large inferred κ⊥/κ∥. For example, for 80-154 keV nucleon-1 helium, we find that κ⊥/κ∥=1.47+/-0.07, κ⊥/κ∥=0.13+/-0.02, and κ⊥/κ∥=0.45+/-0.05 for the most intense periods of the three events. We believe that this is the first direct, quantitative measurement in space of large cross-field particle transport, utilizing simultaneous measurements of the streaming particle flux, the solar wind velocity and the magnetic field direction.

  11. New code for quasiequilibrium initial data of binary neutron stars: Corotating, irrotational, and slowly spinning systems

    NASA Astrophysics Data System (ADS)

    Tsokaros, Antonios; UryÅ«, Kōji; Rezzolla, Luciano

    2015-05-01

    We present the extension of our cocal—Compact Object CALculator—code to compute general-relativistic initial data for binary compact-star systems. In particular, we construct quasiequilibrium initial data for equal-mass binaries with spins that are either aligned or antialigned with the orbital angular momentum. The Isenberg-Wilson-Mathews formalism is adopted and the constraint equations are solved using the representation formula with a suitable choice of a Green's function. We validate the new code with solutions for equal-mass binaries and explore its capabilities for a wide range of compactnesses, from a white dwarf binary with compactness ˜1 0-4, up to a highly relativistic neutron-star binary with compactness ˜0.22 . We also present a comparison with corotating and irrotational quasiequilibrium sequences from the spectral code lorene [Taniguchi and Gourgoulhon, Phys. Rev. D 66, 104019 (2002)] and with different compactness, showing that the results from the two codes agree to a precision of the order of 0.05%. Finally, we present equilibria for spinning configurations with a nuclear-physics equation of state in a piecewise polytropic representation.

  12. Identifying the upper atmosphere structure of the inflated hot sub-Neptune CoRoT-24b

    NASA Astrophysics Data System (ADS)

    Juvan, Ines; Lammer, Helmut; Erkaev, Nikolai V.; Fossati, Luca; Cubillos, Patricio E.; Guenther, Eike; Odert, Petra; Kislyakova, Kristina G.; Lendl, Monika

    2016-04-01

    The CoRoT satellite mission discovered two Neptune-type planets, CoRoT-24b and CoRoT-24c, with observed transit radii of ≈3.7REarth and ≈4.9REarth and masses of ≤5.7MEarth and ≈28MEarth, respectively. From the deduced low mean densities it can be expected that their planetary cores are most likely surrounded by H2 dominated envelopes. While having very similar radii, the outer planet CoRoT-24c is at least 4.9 times more massive than its neighbour, indicating that their atmospheres can be fundamentally different. Therefore, we have investigated the upper atmosphere structure and escape rates of these two planets. We applied a hydrodynamic upper atmosphere model including heating by absorption of stellar extreme ultraviolet and X-ray (XUV) radiation, under the assumption that the observed transit radius RT is produced by Rayleigh scattering and H2-H2 collision absorption in a pure hydrogen atmosphere. This corresponds to a pressure level near 1 bar. We find an unsustainably high hydrodynamic escape rate of 1.6 × 1011 g/s for the atmosphere of CoRoT-24b. If real, such high atmospheric escape would lead to substantial mass loss from the planetary atmosphere, shrinking it to ≈2.2REarth within ≈4 Myr, which is inconsistent with the old age of the system. The solution to this discrepancy is that the observed transit radius RT must be 30-60% larger than the actual planetary radius at the 1 bar pressure level. We suggest that the observed transit radius RT is produced by absorption through scattering processes due to high altitude clouds or hazes. The Kepler satellite has discovered similar close-in low-density Neptune-type planets. We propose that it is very likely that the observed transit radii for the vast majority of these planets also differ from their actual planetary radii at the 1 bar pressure level. This would introduce a systematic bias in the measured radii and has dramatic implications in the determination of the mass-radius relation and for planet

  13. Resonances and resonance widths

    SciTech Connect

    Collins, T.

    1986-05-01

    Two-dimensional betatron resonances are much more important than their simple one-dimensional counterparts and exhibit a strong dependence on the betatron phase advance per cell. A practical definition of ''width'' is expanded upon in order to display these relations in tables. A primarily pedagogical introduction is given to explain the tables, and also to encourage a wider capability for deriving resonance behavior and wider use of ''designer'' resonances.

  14. SPITZER INFRARED OBSERVATIONS AND INDEPENDENT VALIDATION OF THE TRANSITING SUPER-EARTH CoRoT-7 b

    SciTech Connect

    Fressin, Francois; Torres, Guillermo; Charbonneau, David; Pont, Frederic; Knutson, Heather A.; Mazeh, Tsevi; Aigrain, Suzanne; Fridlund, Malcolm; Guillot, Tristan; Rauer, Heike

    2012-01-20

    The detection and characterization of the first transiting super-Earth, CoRoT-7 b, has required an unprecedented effort in terms of telescope time and analysis. Although the star does display a radial-velocity signal at the period of the planet, this has been difficult to disentangle from the intrinsic stellar variability and pinning down the velocity amplitude has been very challenging. As a result, the precise value of the mass of the planet-and even the extent to which it can be considered to be confirmed-has been debated in the recent literature, with six mass measurements published so far based on the same spectroscopic observations, ranging from about 2 to 8 Earth masses. Here we report on an independent validation of the planet discovery using one of the fundamental properties of a transit signal: its achromaticity. We observed four transits of CoRoT-7 b at 4.5 {mu}m and 8.0 {mu}m with the Infrared Array Camera (IRAC) on board the Spitzer Space Telescope in order to determine whether the depth of the transit signal in the near-infrared is consistent with that observed in the CoRoT bandpass, as expected for a planet. We detected the transit and found an average depth of 0.426 {+-} 0.115 mmag at 4.5 {mu}m, which is in good agreement with the depth of 0.350 {+-} 0.011 mmag (ignoring limb darkening) found by CoRoT. The observations at 8.0 {mu}m did not yield a significant detection. The 4.5 {mu}m observations place important constraints on the kinds of astrophysical false positives that could mimic the signal. Combining this with additional constraints reported earlier, we performed an exhaustive exploration of possible blend scenarios for CoRoT-7 b using the BLENDER technique. We are able to rule out the vast majority of false positives, and the remaining ones are found to be much less likely than a true transiting planet. We thus validate CoRoT-7 b as a bona fide planet with a very high degree of confidence, independently of any radial-velocity information

  15. Rocky super-Earth interiors. Structure and internal dynamics of CoRoT-7b and Kepler-10b

    NASA Astrophysics Data System (ADS)

    Wagner, F. W.; Tosi, N.; Sohl, F.; Rauer, H.; Spohn, T.

    2012-05-01

    Aims: We present interior structure models of the recently discovered exoplanets CoRoT-7b and Kepler-10b addressing their bulk compositions, present thermal states, and internal dynamics. We investigate how mantle convection patterns are influenced by the depth-dependence of thermodynamic parameters (e.g., thermal expansivity and conductivity) caused by the extended pressure and temperature ranges within rocky super-Earths. Methods: To model the interior of rocky exoplanets, we construct a four-layer structural model solving the mass and energy balance equations in conjunction with a generalized Rydberg equation of state providing the radial density distribution within each layer. The present thermal state is calculated according to a modified mixing-length approach for highly viscous fluids. Furthermore, the obtained internal structure is used to carry out two-dimensional convection simulations to visualize the mantle convection pattern within massive exoplanets such as CoRoT-7b and Kepler-10b. Results: Both CoRoT-7b and Kepler-10b most likely have large iron cores and a bulk composition similar to that of Mercury. For a planetary radius of Rp = (1.58 ± 0.10) R⊕, a revised total mass of Mp = (7.42 ± 1.21) M⊕, and the existence of a third planet in the CoRoT-7 planetary system, calculations suggest that an iron core of 64 wt-% and a silicate mantle of 36 wt-% is produced owing to the relatively high average compressed density of ρavg = (10.4 ± 1.8) g cm-3. Kepler-10b's planetary radius and total mass yield an iron core of 59.5 wt-%, which complements the silicate mantle of 40.5 wt-%. An enhanced radiogenic heating rate owing to CoRoT-7b's young age (1.2-2.3 Gyr) raises the radial distribution of temperature by only a few hundred Kelvin, but reduces the viscosity by an order of magnitude. The planform of mantle convection is found to be strongly modified for depth-dependent material properties, with hot plumes rising across the whole mantle and cold slabs

  16. Genesis of twin tropical cyclones as revealed by a global mesoscale model: The role of mixed Rossby gravity waves

    NASA Astrophysics Data System (ADS)

    Shen, Bo-Wen; Tao, Wei-Kuo; Lin, Yuh-Lang; Laing, Arlene

    2012-07-01

    In this study, it is proposed that twin tropical cyclones (TCs), Kesiny and 01A, in May 2002 formed in association with the scale interactions of three gyres that appeared as a convectively coupled mixed Rossby gravity (ccMRG) wave during an active phase of the Madden-Julian Oscillation (MJO). This is shown by analyzing observational data, including NCEP reanalysis data and METEOSAT 7 IR satellite imagery, and performing numerical simulations using a global mesoscale model. A 10-day control run is initialized at 0000 UTC 1 May 2002 with grid-scale condensation but no sub-grid cumulus parameterizations. The ccMRG wave was identified as encompassing two developing and one non-developing gyres, the first two of which intensified and evolved into the twin TCs. The control run is able to reproduce the evolution of the ccMRG wave and thus the formation of the twin TCs about two and five days in advance as well as their subsequent intensity evolution and movement within an 8-10 day period. Five additional 10-day sensitivity experiments with different model configurations are conducted to help understand the interaction of the three gyres, leading to the formation of the TCs. These experiments suggest the improved lead time in the control run may be attributed to the realistic simulation of the ccMRG wave with the following processes: (1) wave deepening (intensification) associated with a reduction in wavelength and/or the intensification of individual gyres, (2) poleward movement of gyres that may be associated with boundary layer processes, (3) realistic simulation of moist processes at regional scales in association with each of the gyres, and (4) the vertical phasing of low- and mid-level cyclonic circulations associated with a specific gyre.

  17. Genesis of Twin Tropical Cyclones as Revealed by a Global Mesoscale Model: The Role of Mixed Rossby Gravity Waves

    NASA Technical Reports Server (NTRS)

    Shen, Bo-Wen; Tao, Wei-Kuo; Lin, Yuh-Lang; Laing, Arlene

    2012-01-01

    In this study, it is proposed that twin tropical cyclones (TCs), Kesiny and 01A, in May 2002 formed in association with the scale interactions of three gyres that appeared as a convectively coupled mixed Rossby gravity (ccMRG) wave during an active phase of the Madden-Julian Oscillation (MJO). This is shown by analyzing observational data, including NCEP reanalysis data and METEOSAT 7 IR satellite imagery, and performing numerical simulations using a global mesoscale model. A 10-day control run is initialized at 0000 UTC 1 May 2002 with grid-scale condensation but no sub-grid cumulus parameterizations. The ccMRG wave was identified as encompassing two developing and one non-developing gyres, the first two of which intensified and evolved into the twin TCs. The control run is able to reproduce the evolution of the ccMRG wave and thus the formation of the twin TCs about two and five days in advance as well as their subsequent intensity evolution and movement within an 8-10 day period. Five additional 10-day sensitivity experiments with different model configurations are conducted to help understand the interaction of the three gyres, leading to the formation of the TCs. These experiments suggest the improved lead time in the control run may be attributed to the realistic simulation of the ccMRG wave with the following processes: (1) wave deepening (intensification) associated with a reduction in wavelength and/or the intensification of individual gyres, (2) poleward movement of gyres that may be associated with boundary layer processes, (3) realistic simulation of moist processes at regional scales in association with each of the gyres, and (4) the vertical phasing of low- and mid-level cyclonic circulations associated with a specific gyre.

  18. Derivation of baroclinic Ertel—Rossby invariant-based thermally-coupled vorticity equation in moist flow

    NASA Astrophysics Data System (ADS)

    Yang, Shuai; Gao, Shou-Ting

    2014-11-01

    For the potential vorticity (PV) invariant, there is a PV-based complete-form vorticity equation, which we use heuristically in the present paper to answer the following question: for the Ertel—Rossby invariant (ERI), is there a corresponding vorticity tendency equation? Such an ERI-based thermally-coupled vorticity equation is derived and discussed in detail in this study. From the obtained new vorticity equation, the vertical vorticity change is constrained by the vertical velocity term, the term associated with the slope of the generalized momentum surface, the term related to the horizontal vorticity change, and the baroclinic or solenoid term. It explicitly includes both the dynamical and thermodynamic factors' influence on the vorticity change. For the ERI itself, besides the traditional PV term, the ERI also includes the moisture factor, which is excluded in dry ERI, and the term related to the gradients of pressure, kinetic energy, and potential energy that reflects the fast-manifold property. Therefore, it is more complete to describe the fast motions off the slow manifold for severe weather than the PV term. These advantages are naturally handed on and inherited by the ERI-based thermally-coupled vorticity equation. Then the ERI-based thermally-coupled vorticity equation is further transformed and compared with the traditional vorticity equation. The main difference between the two equations is the term which describes the contribution of the solenoid term to the vertical vorticity development. In a barotropic flow, the solenoid term disappears, then the ERI-based thermally-coupled vorticity equation can regress to the traditional vorticity equation.

  19. The East Atlantic - West Russia Teleconnection in the North Atlantic: Climate Impact and Relation to Rossby Wave Propagation

    NASA Technical Reports Server (NTRS)

    Lim, Young-Kwon

    2014-01-01

    Large-scale winter teleconnection of the East Atlantic - West Russia (EA-WR) over the Atlantic and surrounding regions is examined in order to quantify its impacts on temperature and precipitation and identify the physical mechanisms responsible for its existence. A rotated empirical orthogonal function (REOF) analysis of the upper-tropospheric monthly height field captures successfully the EA-WR pattern and its interannual variation, with the North Atlantic Oscillation as the first mode. EA-WRs climate impact extends from eastern North America to Eurasia. The positive (negative) EA-WR produces positive (negative) temperature anomalies over the eastern US, western Europe and Russia east of Caspian Sea, with negative (positive) anomalies over eastern Canada, eastern Europe including Ural Mountains and the Middle East. These anomalies are largely explained by lower-tropospheric temperature advections. Positive (negative) precipitation anomalies are found over the mid-latitude Atlantic and central Russia around 60E, where lower-level cyclonic (anticyclonic) circulation anomaly is dominant. The eastern Canada and the western Europe are characterized by negative (positive) precipitation anomalies.The EA-WR is found to be closely associated with Rossby wave propagation. Wave activity fluxes show that it is strongly tied to large-scale stationary waves. Furthermore, a stationary wave model (SWM) forced with vorticity transients in the mid-latitude Atlantic (approximately 40N) or diabatic heat source over the subtropical Atlantic near the Caribbean Sea produces well-organized EA-WR-like wave patterns, respectively. Sensitivity tests with the SWM indicate improvement in the simulation of the EA-WR when the mean state is modified to have a positive NAO component that enhances upper-level westerlies between 40-60N.

  20. ROSSBY WAVE INSTABILITY AT DEAD ZONE BOUNDARIES IN THREE-DIMENSIONAL RESISTIVE MAGNETOHYDRODYNAMICAL GLOBAL MODELS OF PROTOPLANETARY DISKS

    SciTech Connect

    Lyra, Wladimir; Mac Low, Mordecai-Mark E-mail: mordecai@amnh.org

    2012-09-01

    It has been suggested that the transition between magnetorotationally active and dead zones in protoplanetary disks should be prone to the excitation of vortices via Rossby wave instability (RWI). However, the only numerical evidence for this has come from alpha disk models, where the magnetic field evolution is not followed, and the effect of turbulence is parameterized by Laplacian viscosity. We aim to establish the phenomenology of the flow in the transition in three-dimensional resistive-magnetohydrodynamical models. We model the transition by a sharp jump in resistivity, as expected in the inner dead zone boundary, using the PENCIL CODE to simulate the flow. We find that vortices are readily excited in the dead side of the transition. We measure the mass accretion rate finding similar levels of Reynolds stress at the dead and active zones, at the {alpha} Almost-Equal-To 10{sup -2} level. The vortex sits in a pressure maximum and does not migrate, surviving until the end of the simulation. A pressure maximum in the active zone also triggers the RWI. The magnetized vortex that results should be disrupted by parasitical magneto-elliptic instabilities, yet it subsists in high resolution. This suggests that either the parasitic modes are still numerically damped or that the RWI supplies vorticity faster than they can destroy it. We conclude that the resistive transition between the active and dead zones in the inner regions of protoplanetary disks, if sharp enough, can indeed excite vortices via RWI. Our results lend credence to previous works that relied on the alpha-disk approximation, and caution against the use of overly reduced azimuthal coverage on modeling this transition.

  1. Mean flow-storm track relationship and Rossby wave breaking in two types of El-Niño

    NASA Astrophysics Data System (ADS)

    Liu, Chengji; Ren, Xuejuan; Yang, Xiuqun

    2014-01-01

    The features of large-scale circulation, storm tracks and the dynamical relationship between them were examined by investigating Rossby wave breaking (RWB) processes associated with Eastern Pacific (EP) and Central Pacific (CP) El-Niño. During EP El-Niño, the geopotential height anomaly at 500 hPa (Z500) exhibits a Pacific-North America (PNA) pattern. During CP El-Niño, the Z500 anomaly shows a north positive-south negative pattern over the North Pacific. The anomalous distributions of baroclinicity and storm track are consistent with those of upper-level zonal wind for both EP and CP El-Niño, suggesting impacts of mean flow on storm track variability. Anticyclonic wave breaking (AWB) occurs less frequently in EP El-Niño years, while cyclonic wave breaking (CWB) occurs more frequently in CP El-Niño years over the North Pacific sector. Outside the North Pacific, more CWB events occur over North America during EP El-Niño. When AWB events occur less frequently over the North Pacific during EP El-Niño, Z500 decreases locally and the zonal wind is strengthened (weakened) to the south (north). This is because AWB events reflect a monopole high anomaly at the centroid of breaking events. When CWB events occur more frequently over the North Pacific under CP El-Niño conditions, and over North America under EP El-Niño condition, Z500 increases (decreases) to the northeast (southwest), since CWB events are related to a northeast-southwest dipole Z500 anomaly. The anomalous RWB events act to invigorate and reinforce the circulation anomalies over the North Pacific-North America region linked with the two types of El-Niño.

  2. Genesis of Twin Tropical Cyclones as Revealed by a Global Mesoscale Model: The Role of Mixed Rossby Gravity Waves

    NASA Technical Reports Server (NTRS)

    Shen, Bo-Wen; Tao, Wei-Kuo; Lin, Yuh-Lang; Laing, Arlene

    2012-01-01

    In this study, it is proposed that twin tropical cyclones (TCs), Kesiny and 01A, in May 2002 formed in association with the scale interactions of three gyres that appeared as a convectively-coupled mixed Rossby gravity (ccMRG) wave during an active phase of the Madden-Julian Oscillation (MJO). This is shown by analyzing observational data and performing simulations using a global mesoscale model. A 10-day control run is initialized at 0000 UTC 1 May 2002 with grid-scale condensation but no cumulus parameterizations. The ccMRG wave was identified as encompassing two developing and one non-developing gyres, the first two of which intensified and evolved into the twin TCs. The control run is able to reproduce the evolution of the ccMRG wave and the formation of the twin TCs about two and five days in advance as well as their subsequent intensity evolution and movement within an 8-10 day period. Five additional 10-day sensitivity experiments with different model configurations are conducted to help understand the interaction of the three gyres. These experiments suggest the improved lead time in the control run may be attributed to the realistic simulation of the ccMRG wave with the following processes: (I) wave deepening associated with wave shortening and/or the intensification of individual gyres, (2) poleward movement of gyres that may be associated with bOlll1dary layer processes, (3) realistic simulation of moist processes at regional scales in association with each of the gyres, and (4) the vertical phasing of low- and mid-level cyclonic circulations associated with a specific gyre.

  3. Polarimetric modeling of corotating interaction regions threading massive-star winds

    NASA Astrophysics Data System (ADS)

    Ignace, Richard; St-Louis, Nicole; Proulx-Giraldeau, Félix

    2015-03-01

    Context. Massive star winds are complex radiation-hydrodynamic (sometimes magnetohydrodynamic) outflows that are propelled by their enormously strong luminosities. The winds are often found to be structured and variable, but can also display periodic or quasi-periodic behavior in a variety of wind diagnostics. Aims: The regular variations observed in putatively single stars, especially in UV wind lines, have often been attributed to corotating interaction regions (CIRs) like those seen in the solar wind. We present light curves for variable polarization from winds with CIR structures. Methods: We develop a model for a time-independent CIR based on a kinematical description. Assuming optically thin electron scattering, we explore the range of polarimetric light curves that result as the curvature, latitude, and number of CIRs are varied. Results: We find that a diverse array of variable polarizations result from an exploration of cases. The net polarization from an unresolved source is weighted more toward the inner radii of the wind. Given that most massive stars have relatively fast winds compared to their rotation speeds, CIRs tend to be conical at inner radii, transitioning to a spiral shape at a few to several stellar radii in the wind. Conclusions: Winds with a single CIR structure lead to easily identifiable polarization signatures. By contrast allowing for multiple CIRs, all emerging from a range of azimuth and latitude positions at the star, can yield complex polarimetric behavior. Although our model is based on some simplifying assumptions, it produces qualitative behavior that we expect to be robust, and this has allowed us to explore a wide range of CIR configurations that will prove useful for interpreting polarimetric data. Appendix A is available in electronic form at http://www.aanda.org

  4. SHOCK ACCELERATION OF PARTICLES IN THE NONSTATIONARY EVOLUTION OF COROTATING INTERACTION REGIONS

    SciTech Connect

    Tsubouchi, K.

    2011-10-20

    One-dimensional hybrid simulations are used to investigate the particle energization process during the nonstationary evolution of corotating interaction regions (CIRs) in the heliosphere. The simulation model, where fast and slow solar wind streams interact with each other, allows the formation of a pair (forward/reverse) of shocks at the CIR boundaries and the stream interface interior, which prevents the interchange of both streams. While both shocks are quasi-perpendicular and are not capable of accelerating thermal particles (hundreds of eV) up to a suprathermal energy (tens to hundreds of keV) in the early phase of their development, the reverse shock in the fast wind experiences a transition to a quasi-parallel regime in the later phase. The quasi-parallel reverse shock can efficiently accelerate particles to the suprathermal range. The different timescale of the adiabatic expansion between the fast and slow wind leads to a transition of the shock geometry that can take place more easily in the reverse shock than in the forward shock, where the magnetic field in the fast wind remains more radial to the propagation direction than in the slow wind. The difference in the acceleration efficiency between these shocks follows a well-known observed asymmetry in the profile of the energetic particle fluxes, where the larger intensity increases more in the reverse shock than in the forward shock. The present results suggest that the solar wind thermal plasma, as well as interstellar pickup ions, can contribute to the composition of energetic particles associated with the CIRs.

  5. Solar wind interaction with comet 67P: Impacts of corotating interaction regions

    NASA Astrophysics Data System (ADS)

    Edberg, N. J. T.; Eriksson, A. I.; Odelstad, E.; Vigren, E.; Andrews, D. J.; Johansson, F.; Burch, J. L.; Carr, C. M.; Cupido, E.; Glassmeier, K.-H.; Goldstein, R.; Halekas, J. S.; Henri, P.; Koenders, C.; Mandt, K.; Mokashi, P.; Nemeth, Z.; Nilsson, H.; Ramstad, R.; Richter, I.; Wieser, G. Stenberg

    2016-02-01

    We present observations from the Rosetta Plasma Consortium of the effects of stormy solar wind on comet 67P/Churyumov-Gerasimenko. Four corotating interaction regions (CIRs), where the first event has possibly merged with a coronal mass ejection, are traced from Earth via Mars (using Mars Express and Mars Atmosphere and Volatile EvolutioN mission) to comet 67P from October to December 2014. When the comet is 3.1-2.7 AU from the Sun and the neutral outgassing rate ˜1025-1026 s-1, the CIRs significantly influence the cometary plasma environment at altitudes down to 10-30 km. The ionospheric low-energy (˜5 eV) plasma density increases significantly in all events, by a factor of >2 in events 1 and 2 but less in events 3 and 4. The spacecraft potential drops below -20 V upon impact when the flux of electrons increases. The increased density is likely caused by compression of the plasma environment, increased particle impact ionization, and possibly charge exchange processes and acceleration of mass-loaded plasma back to the comet ionosphere. During all events, the fluxes of suprathermal (˜10-100 eV) electrons increase significantly, suggesting that the heating mechanism of these electrons is coupled to the solar wind energy input. At impact the magnetic field strength in the coma increases by a factor of 2-5 as more interplanetary magnetic field piles up around the comet. During two CIR impact events, we observe possible plasma boundaries forming, or moving past Rosetta, as the strong solar wind compresses the cometary plasma environment. We also discuss the possibility of seeing some signatures of the ionospheric response to tail disconnection events.

  6. DO COROTATING INTERACTION REGION ASSOCIATED SHOCKS SURVIVE WHEN THEY PROPAGATE INTO THE HELIOSHEATH?

    SciTech Connect

    Provornikova, E.; Opher, M.; Izmodenov, V.; Toth, G. E-mail: mopher@bu.edu E-mail: gtoth@umich.edu

    2012-09-10

    During the solar minimum at the distance of 42-52 AU from the Sun, Voyager 2 observed recurrent sharp, shock-like increases in the solar wind speed that look very much like forward shocks (Lazarus et al.). The shocks were produced by corotating interaction regions (CIRs) that originated near the Sun. After the termination shock (TS) crossing in 2007, Voyager 2 entered the heliosheath and has been observing the plasma emanated during the recent solar minima. Measurements show high variable flow, but there were no shocks detected in the heliosheath. When CIR-driven shocks propagate to the outer heliosphere, their structure changes due to collision and merging processes of CIRs. In this Letter, we explore an effect of the merging of CIRs on the structure of CIR-associated shocks. We use a three-dimensional MHD model to study the outward propagation of the shocks with characteristics similar to those observed by Voyager 2 at {approx}45 AU (Lazarus et al. 1999). We show that due to merging of CIRs (1) reverse shocks disappear, (2) forward shocks become weaker due to interaction with rarefaction regions from preceding CIRs, and (3) forward shocks significantly weaken in the heliosheath. Merged CIRs produce compression regions in the heliosheath with small fluctuations of plasma parameters. Amplitudes of the fluctuations diminish as they propagate deeper in the sheath. We conclude that interaction of shocks and rarefaction regions could be one of the explanations, why shocks produced by CIRs are not observed in the heliosheath by Voyager 2 while they were frequently observed upstream the TS.

  7. Particle acceleration at corotating interaction regions in the three-dimensional heliosphere

    SciTech Connect

    Desai, M.I.; Marsden, R.G.; Sanderson, T.R.; Balogh, A.; Forsyth, R.J.; Gosling, J.T.

    1998-02-01

    We have investigated the relationship between the energetic ({approximately}1MeV) proton intensity (J) and the magnetic compression ratio (C) measured at the trailing edges of corotating interaction regions observed at Ulysses. In general, our results show that the proton intensity was well correlated with the compression ratio, provided that the seed intensity remained constant, consistent with predictions of the Fermi model. Specifically, our results indicate that particles were accelerated to above {approximately}1MeV in energy at or near the trailing edges of the compression regions observed in the midlatitude southern heliosphere, irrespective of whether the bounding reverse shocks were present or not. On the basis of this, we conclude that shock acceleration is probably not the only mechanism by which particles are accelerated to above {approximately}1MeV in energy at compression or interaction regions (CIRs). On the basis of magnetic field measurements obtained near the trailing edges of several midlatitude CIRs, we propose that particles could have been accelerated via the Fermi mechanism by being scattered back and forth across the trailing edges of the compression regions by large-amplitude Alfv{acute e}n waves. Our results also show that the proton intensity was well correlated with the compression ratio during low solar activity periods but was essentially independent of C during periods of high solar activity. We suggest that the correlation between J and C was not observed during solar active periods because of significant variations in the seed intensity that result from sporadic contributions from transient solar events. In contrast, the correlation was observable during quiescent periods probably because contributions from transients had decreased dramatically, which allowed the CIRs to accelerate particles out of a seed population whose intensity remained relatively unperturbed. {copyright} 1998 American Geophysical Union

  8. STEREO Observations of Suprathermal Corotating Interaction Region Ions in the Helium Focusing Cone

    NASA Astrophysics Data System (ADS)

    Bucik, R.; Mall, U.; Korth, A.; Mason, G. M.; Klecker, B.

    2011-12-01

    Interstellar pickup He+ contributes about ~25% of the total He population in corotating interaction regions (CIRs). It has been known that He+ pickup ion density shows annual variations due to gravitational focusing of the Sun. However, the variations in the CIR energetic ions reflecting the temporal changes in the He+ pickup ions remain unproven. In this work we examine the elemental composition and energy spectra of the 0.1 - 1 MeV/nucleon heavy ions accelerated in CIRs. For the investigations we use data from the SIT (Suprathermal Ion Telescope) instruments on board the two STEREO spacecraft (S/C) acquired over the extended minimum phase of Solar Cycle 23 from January 2007 to December 2010. The two STEREO S/C are well separated in heliolongitude, and enter the helium focusing cone at different times. During the investigated period instruments on STEREO observed more than 70 CIR events, allowing one to study CIR ion abundances during solar minimum conditions with unprecedented high statistics. The observations reveal annual variations of relative ion abundances in the CIRs during the 2007-2008 period. In 2010 the elemental composition in CIRs were influenced by solar energetic particle events. We find that the CIR He/H and He/O ratios were enhanced in the period of the focusing cone traversals. By combining the SIT observations with the solar wind plasma observations from the PLASTIC instrument on the STEREO S/C we discuss the correlations between the energy spectral slopes of the suprathermal heavy ions and the He+ pickup ion count rates. In the investigated period the solar wind was dominated by stably recurring CIRs. This could lead to more uniform particle injection and acceleration conditions in the CIRs, making it possible to see the signatures of the focusing cone in the energetic ion population.

  9. The Effect of Tropospheric Jet Latitude on Rossby Wave Breaking and on Coupling between the Stratospheric Polar Vortex and the Troposphere

    NASA Astrophysics Data System (ADS)

    Garfinkel, Chaim; Waugh, Darryn; Gerber, Edwin

    2014-05-01

    A dry General Circulation Model is used to investigate how the latitude of the tropospheric jet affects (1) coupling between the stratospheric polar vortex and the extratropical tropospheric circulation, and (2) Rossby wave breaking. The tropospheric response to an identical stratospheric vortex configuration is shown to be strongest for a jet centered near 40° and weaker for jets near either 30° or 50° by more than a factor of three. Stratosphere-focused mechanisms based on stratospheric potential vorticity inversion, eddy phase speed, and planetary wave reflection, as well as arguments based on tropospheric eddy heat flux and zonal length scale, appear to be incapable of explaining the differences in the magnitude of the jet shift. In contrast, arguments based purely on tropospheric variability involving the strength of eddy-zonal mean flow feedbacks and jet persistence, and related changes in the synoptic eddy momentum flux, appear to explain this effect. The dependence of coupling between the stratospheric polar vortex and the troposphere on tropospheric jet latitude found here is consistent with (1) the observed variability in the North Atlantic and the North Pacific, and (2) the trend in the Southern Hemisphere as projected by comprehensive models. The shift in wavebreaking per degree latitude of jet shift is then compared for three different sources of jet movement: the baroclinic forcing imposed by the equator-to-pole temperature gradient, the imposition of a stratospheric polar vortex, and the internal variability of the mid-latitude eddy driven jet. It is demonstrated that all three sources of jet movement produce a similar change in Rossby wave breaking frequency per degree of jet shift. Hence, it is difficult (if not impossible) to isolate the ultimate cause behind the shift in Rossby wave breaking in response to the two external forcings.

  10. The three dimensional structure of corotating interaction regions and modeling of the heavy ion sensor

    NASA Astrophysics Data System (ADS)

    Broiles, Thomas W.

    Corotating Interaction Regions (CIRs) are compression regions that form in interplanetary space at the interfaces between slow and fast solar wind streams. This dissertation studies the three-dimensional orientation of planar magnetic structures within CIRs near Earth, how their orientation evolves, and the implications for the structure and properties of parent coronal holes. This dissertation also shows our work of modeling the response of the Heavy Ion Sensor (HIS) for the Solar Orbiter mission. We will discuss the methods and results of each chapter below. In Chapter 2, we have surveyed the properties of 153 co-rotating interaction regions (CIRs) observed at 1 AU from January, 1995 through December, 2008. We identified that 74 of the 153 CIRs contain planar magnetic structures (PMSs). For planar and non-planar CIRs, we compared distributions of the bulk plasma and magnetic field parameters. Our identification of CIRs and their features yields the following results: (1) The thermal, magnetic, and dynamic pressures within CIRs are strongly correlated. (2) There is no statistical difference between planar and non-planar CIRs in the distributions and correlations between bulk plasma and magnetic field parameters. (3) The mean observed CIR azimuthal tilt is within 1 sigma of the predicted Parker spiral at 1 AU, while the mean meridional tilt is about 20°. (4) The meridional tilt of CIRs changes from one solar rotation to the next, with no relationship between successive reoccurrences. (5) The meridional tilt of CIRs in the ecliptic is not ordered by the magnetic field polarity of the parent coronal hole. (6) Although solar wind deflection is a function of CIR shape and speed, the relationship is not in agreement with that predicted by Lee [2000]. We conclude the following: (1) PMSs in CIRs are not caused by a unique characteristic in the local plasma or magnetic field. (2) The lack of relationship between CIR tilt and its parent coronal hole suggests that coronal

  11. Identifying the `true' radius of the hot sub-Neptune CoRoT-24b by mass-loss modelling

    NASA Astrophysics Data System (ADS)

    Lammer, H.; Erkaev, N. V.; Fossati, L.; Juvan, I.; Odert, P.; Cubillos, P. E.; Guenther, E.; Kislyakova, K. G.; Johnstone, C. P.; Lüftinger, T.; Güdel, M.

    2016-09-01

    For the hot exoplanets CoRoT-24b and CoRoT-24c, observations have provided transit radii RT of 3.7 ± 0.4R⊕ and 4.9 ± 0.5R⊕, and masses of ≤5.7M⊕ and 28 ± 11M⊕, respectively. We study their upper atmosphere structure and escape applying an hydrodynamic model. Assuming RT ≈ RPL, where RPL is the planetary radius at the pressure of 100 mbar, we obtained for CoRoT-24b unrealistically high thermally driven hydrodynamic escape rates. This is due to the planet's high temperature and low gravity, independent of the stellar EUV flux. Such high escape rates could last only for <100 Myr, while RPL shrinks till the escape rate becomes less than or equal to the maximum possible EUV-driven escape rate. For CoRoT-24b, RPL must be therefore located at ≈1.9-2.2R⊕ and high altitude hazes/clouds possibly extinct the light at RT. Our analysis constraints also the planet's mass to be 5-5.7M⊕. For CoRoT-24c, RPL and RT lie too close together to be distinguished in the same way. Similar differences between RPL and RT may be present also for other hot, low-density sub-Neptunes.

  12. High Rossby-wave activity in austral winter 2002: Modulation of the general circulation of the MLT during the MaCWAVE/MIDAS northern summer program

    NASA Astrophysics Data System (ADS)

    Becker, E.; Müllemann, A.; Lübken, F.-J.; Körnich, H.; Hoffmann, P.; Rapp, M.

    2004-10-01

    The seasonally and zonally averaged effects of the anomalously strong Rossby-wave activity in austral winter 2002 are estimated by a sensitivity experiment using an idealized general circulation model. The approach focuses on the modulation of gravity-wave saturation via the altered mean winds in the mesosphere and MLT. In the northern summer MLT the effects consist of increased vertical gradients of the mean zonal wind and temperature, as well as downward shifts of the residual circulation and the gravity wave-induced frictional heating. All these signals agree reasonably with observations obtained during the MaCWAVE/MIDAS program 2002.

  13. Stochastic gravito-inertial modes discovered by CoRoT in the hot Be star HD 51452

    NASA Astrophysics Data System (ADS)

    Neiner, C.; Floquet, M.; Samadi, R.; Espinosa Lara, F.; Frémat, Y.; Mathis, S.; Leroy, B.; de Batz, B.; Rainer, M.; Poretti, E.; Mathias, P.; Guarro Fló, J.; Buil, C.; Ribeiro, J.; Alecian, E.; Andrade, L.; Briquet, M.; Diago, P. D.; Emilio, M.; Fabregat, J.; Gutiérrez-Soto, J.; Hubert, A.-M.; Janot-Pacheco, E.; Martayan, C.; Semaan, T.; Suso, J.; Zorec, J.

    2012-10-01

    Context. Be stars are rapidly rotating stars with a circumstellar decretion disk. They usually undergo pressure and/or gravity pulsation modes excited by the κ-mechanism, i.e. an effect of the opacity of iron-peak elements in the envelope of the star. In the Milky Way, p-modes are observed in stars that are hotter than or equal to the B3 spectral type, while g-modes are observed at the B2 spectral type and cooler. Aims: We observed a B0IVe star, HD 51452, with the high-precision, high-cadence photometric CoRoT satellite and high-resolution, ground-based HARPS and SOPHIE spectrographs to study its pulsations in great detail. We also used the lower resolution spectra available in the BeSS database. Methods: We analyzed the CoRoT and spectroscopic data with several methods: Clean-NG, FreqFind, and a sliding window method. We also analyzed spectral quantities, such as the violet over red (V/R) emission variations, to obtain information about the variation in the circumstellar environment. We calculated a stellar structure model with the ESTER code to test the various interpretation of the results. Results: We detect 189 frequencies of variations in the CoRoT light curve in the range between 0 and 4.5 c d-1. The main frequencies are also recovered in the spectroscopic data. In particular we find that HD 51452 undergoes gravito-inertial modes that are not in the domain of those excited by the κ-mechanism. We propose that these are stochastic modes excited in the convective zones and that at least some of them are a multiplet of r-modes (i.e. subinertial modes mainly driven by the Coriolis acceleration). Stochastically excited gravito-inertial modes had never been observed in any star, and theory predicted that their very low amplitudes would be undetectable even with CoRoT. We suggest that the amplitudes are enhanced in HD 51452 because of the very rapid stellar rotation. In addition, we find that the amplitude variations of these modes are related to the occurrence of

  14. Could CoRoT-7b and Kepler-10b be remnants of evaporated gas or ice giants?

    PubMed Central

    Leitzinger, M.; Odert, P.; Kulikov, Yu.N.; Lammer, H.; Wuchterl, G.; Penz, T.; Guarcello, M.G.; Micela, G.; Khodachenko, M.L.; Weingrill, J.; Hanslmeier, A.; Biernat, H.K.; Schneider, J.

    2011-01-01

    We present thermal mass loss calculations over evolutionary time scales for the investigation if the smallest transiting rocky exoplanets CoRoT-7b (∼1.68REarth) and Kepler-10b (∼1.416REarth) could be remnants of an initially more massive hydrogen-rich gas giant or a hot Neptune-class exoplanet. We apply a thermal mass loss formula which yields results that are comparable to hydrodynamic loss models. Our approach considers the effect of the Roche lobe, realistic heating efficiencies and a radius scaling law derived from observations of hot Jupiters. We study the influence of the mean planetary density on the thermal mass loss by placing hypothetical exoplanets with the characteristics of Jupiter, Saturn, Neptune, and Uranus to the orbital location of CoRoT-7b at 0.017 AU and Kepler-10b at 0.01684 AU and assuming that these planets orbit a K- or G-type host star. Our findings indicate that hydrogen-rich gas giants within the mass domain of Saturn or Jupiter cannot thermally lose such an amount of mass that CoRoT-7b and Kepler-10b would result in a rocky residue. Moreover, our calculations show that the present time mass of both rocky exoplanets can be neither a result of evaporation of a hydrogen envelope of a “Hot Neptune” nor a “Hot Uranus”-class object. Depending on the initial density and mass, these planets most likely were always rocky planets which could lose a thin hydrogen envelope, but not cores of thermally evaporated initially much more massive and larger objects. PMID:21969736

  15. Observações no âmbito dos "additional programs" do satélite COROT

    NASA Astrophysics Data System (ADS)

    Janot Pacheco, E.

    2003-08-01

    O satélite Fraco-europeu COROT fará fotometria de altissima precisão (pretende-se atingir uma parte em um milhão), grande campo (3x3 graus) e por longos períodos, de duas regiões pré-determinadas do céu, com 10 graus de raio. Suas finalidades básicas serão estudos em sismologia estelar e a procura de exoplanetas. A comunidade astronômica brasileira participará dessa missão espacial, com direitos iguais aos dos parceiros europeus. Isso se deve a que o satélite utilizará a estação de recepção de dados de Natal (INPE), 5 a 6 brasileiros participarão das equipes de software e cientistas do país atuarão na fase de pré-lançamento. Apresentamos nesta comunicação sugestões para a preparação de propostas de observações com COROT, no âmbito dos Programas Adicionais, que contemplam outros projetos que não de sismologia ou exoplanetas. As últimas definições técnicas e decisões tomadas na 4th Corot Week de junho último serão igualmente apresentadas, em particular quanto às regiões de observação escolhidas e quanto aos procedimentos a seguir para se propor observações.

  16. Could CoRoT-7b and Kepler-10b be remnants of evaporated gas or ice giants?

    PubMed

    Leitzinger, M; Odert, P; Kulikov, Yu N; Lammer, H; Wuchterl, G; Penz, T; Guarcello, M G; Micela, G; Khodachenko, M L; Weingrill, J; Hanslmeier, A; Biernat, H K; Schneider, J

    2011-10-01

    We present thermal mass loss calculations over evolutionary time scales for the investigation if the smallest transiting rocky exoplanets CoRoT-7b (∼1.68REarth) and Kepler-10b (∼1.416REarth) could be remnants of an initially more massive hydrogen-rich gas giant or a hot Neptune-class exoplanet. We apply a thermal mass loss formula which yields results that are comparable to hydrodynamic loss models. Our approach considers the effect of the Roche lobe, realistic heating efficiencies and a radius scaling law derived from observations of hot Jupiters. We study the influence of the mean planetary density on the thermal mass loss by placing hypothetical exoplanets with the characteristics of Jupiter, Saturn, Neptune, and Uranus to the orbital location of CoRoT-7b at 0.017 AU and Kepler-10b at 0.01684 AU and assuming that these planets orbit a K- or G-type host star. Our findings indicate that hydrogen-rich gas giants within the mass domain of Saturn or Jupiter cannot thermally lose such an amount of mass that CoRoT-7b and Kepler-10b would result in a rocky residue. Moreover, our calculations show that the present time mass of both rocky exoplanets can be neither a result of evaporation of a hydrogen envelope of a "Hot Neptune" nor a "Hot Uranus"-class object. Depending on the initial density and mass, these planets most likely were always rocky planets which could lose a thin hydrogen envelope, but not cores of thermally evaporated initially much more massive and larger objects. PMID:21969736

  17. Displaced narrow absorption components in the spectra of mass-losing OB stars - Indications of corotating interaction regions?

    NASA Technical Reports Server (NTRS)

    Mullan, D. J.

    1986-01-01

    The discovery of displaced narrow components (DNCs) in an increasingly large number of stars of various spectral types suggests that an explanation of these features may contribute significantly to understanding of winds from stars of all types. The reported properties of DNCs are summarized here with a view to evaluating one particular scenario for DNC formation which involves corotating interaction regions (CIRs) in the stellar wind. The relevant features of the CIR scenario are summarized, and the extent to which DNC properties support the CIR scenario is discussed.

  18. Seventy new non-eclipsing BEER binaries discovered in CoRoT lightcurves and confirmed by RVs from AAOmega

    NASA Astrophysics Data System (ADS)

    Tal-Or, Lev; Faigler, Simchon; Mazeh, Tsevi

    2015-09-01

    We applied the BEER algorithm to the CoRoT lightcurves from the first five LRc fields and identified 481 non-eclipsing BEER candidates with periodic lightcurve modulations and amplitudes of 0.5 - 87 mmag. Medium-resolution spectra of 281 candidates were obtained in a seven-night AAOmega radial-velocity (RV) campaign, with a precision of ˜ 1 km/s. The RVs confirmed the binarity of 70 of the BEER candidates, with periods of 0.3 - 10 days.

  19. VizieR Online Data Catalog: Planetary transit candidates in CoRoT SRc01 field (Erikson+, 2012)

    NASA Astrophysics Data System (ADS)

    Erikson, A.; Santerne, A.; Renner, S.; Barge, P.; Aigrain, S.; Alapini, A.; Almenara, J.-M.; Alonso, R.; Auvergne, M.; Baglin, A.; Benz, W.; Bonomo, A. S.; Borde, P.; Bouchy, F.; Bruntt, H.; Cabrera, J.; Carone, L.; Carpano, S.; Csizmadia, Sz.; Deleuil, M.; Deeg, H. J.; Diaz, R. F.; Dvorak, R.; Ferraz-Mello, S.; Fridlund, M.; Gandolfi, D.; Gazzano, J.-C.; Gillon, M.; Guenther, E. W.; Guillot, T.; Hatzes, A.; Hebrard, G.; Jorda, L.; Lammer, H.; Leger, A.; Llebaria, A.; Mayor, M.; Mazeh, T.; Moutou, C.; Ollivier, M.; Ofir, A.; Paetzold, M.; Pepe, F.; Pont, F.; Queloz, D.; Rabus, M.; Rauer, H.; Regulo, C.; Rouan, D.; Samuel, B.; Schneider, J.; Shporer, A.; Tingley, B.; Udry, S.; Wuchterl, G.

    2012-04-01

    Among the acquired data, we analyzed those for 1269 sources in the chromatic bands and 5705 in the monochromatic band. Instrumental noise and the stellar variability were treated with several detrending tools, to which several transit-search algorithms were subsequently applied. Fifty-one sources were classified as planetary transit candidates and 26 were followed up with ground-based observations. Until now, no planet has been detected in the CoRoT data from the SRc01 field. (1 data file).

  20. Observed distribution functions of H, He, C, O, and Fe in corotating energetic particle streams: Implications for interplanetary acceleration and propagation

    NASA Technical Reports Server (NTRS)

    Gloeckler, G.; Hovestadt, D.; Fisk, L. A.

    1979-01-01

    Distribution functions for H, He, C, O, and Fe derived from our IMP 8 measurements of approximately 0.15 to approximately 8 MeV/nucleon particles in three corotating streams observed near earth are shown to have a simple exponential dependence on the particle speed. The e-folding speed, v sub o, is typically 0.01c, is found to be the same for the distribution functions of all elements examined, and varies little from one corotating event to the next. The relative abundances of energetic particles in these events resemble most closely the solar coronal composition and, thus, presumably that of the solar wind. These results may imply that the acceleration of these particles, which occurs in corotating interaction regions at several AU from the sun, is by a statistical process.

  1. Changing risks of resonance in extreme weather events for higher atmospheric greenhouse gas concentrations

    NASA Astrophysics Data System (ADS)

    Huntingford, Chris; Mitchell, Dann; Osprey, Scott

    2015-04-01

    A recent paper by Petoukhov et al (2013) demonstrates that many of the recent major extreme events in the NH may have been caused by resonant conditions driving very high meridional winds around slowly moving centres-of-action. Besides high amplitudes of planetary wave numbers 6,7 and 8, additional features are identified through 4 further conditions that trigger system resonance. These make the potential for high amplitude waves more likely as well as the possibility of more persistent events. A concern is that human-induced climate change could create conditions more conducive to tropospheric Rossby wave resonance, thereby forcing any periods of extreme weather to become more commonplace and longer lasting. Whilst the CMIP5 ensemble provides much information on expected changes, to fully address changing probabilities of extreme event occurrence - which by definition are relatively rare - is, though, best approached through a massive ensemble modeling framework. The climateprediction-dot-net citizen-science massive ensemble GCM modeling framework provides order 104 simulations for sea-surface temperature, sea-ice extent and atmospheric gas composition representative of both pre-industrial and contemporary conditions. Here we present what these families of simulations imply in terms of the changing likelihood of conditions for mid-latitude resonance, and implications for amplitudes of Rossby waves

  2. CoRoT 101186644: A transiting low-mass dense M-dwarf on an eccentric 20.7-day period orbit around a late F-star. Discovered in the CoRoT lightcurves

    NASA Astrophysics Data System (ADS)

    Tal-Or, L.; Mazeh, T.; Alonso, R.; Bouchy, F.; Cabrera, J.; Deeg, H. J.; Deleuil, M.; Faigler, S.; Fridlund, M.; Hébrard, G.; Moutou, C.; Santerne, A.; Tingley, B.

    2013-05-01

    We present the study of the CoRoT transiting planet candidate 101186644, also named LRc01_E1_4780. Analysis of the CoRoT lightcurve and the HARPS spectroscopic follow-up observations of this faint (mV = 16) candidate revealed an eclipsing binary composed of a late F-type primary (Teff = 6090 ± 200 K) and a low-mass, dense late M-dwarf secondary on an eccentric (e = 0.4) orbit with a period of ~20.7 days. The M-dwarf has a mass of 0.096 ± 0.011 M⊙, and a radius of 0.104-0.006+0.026 R⊙, which possibly makes it the smallest and densest late M-dwarf reported so far. Unlike the claim that theoretical models predict radii that are 5-15% smaller than measured for low-mass stars, this one seems to have a radius that is consistent and might even be below the radius predicted by theoretical models. Based on observations made with the 1-m telescope at the Wise Observatory, Israel, the Swiss 1.2-m Leonhard Euler telescope at La Silla Observatory, Chile, the IAC-80 telescope at the Observatory del Teide, Canarias, Spain, and the 3.6-m telescope at La Silla Observatory (ESO), Chile (program 184.C-0639).

  3. Generation of zonal flow and magnetic field by coupled Rossby-Alfvén-Khantadze waves in the Earth's ionospheric E-layer

    NASA Astrophysics Data System (ADS)

    Kaladze, T. D.; Horton, W.; Kahlon, L. Z.; Pokhotelov, O.; Onishchenko, O.

    2013-12-01

    It is shown that in the Earth's weakly ionized ionospheric E-layer with the dominant Hall conductivity, a new type of coupled Rossby-Alfvén-Khantadze (CRAK) electromagnetic (EM) planetary waves, attributable by the latitudinal inhomogeneity of both the Earth's Coriolis parameter and the geomagnetic field, can exist. Under such coupling, a new type of dispersive Alfvén waves is revealed. The generation of a sheared zonal flow and a magnetic field by CRAK EM planetary waves is investigated. The nonlinear mechanism of the instability is based on the parametric excitation of a zonal flow by interacting four waves, leading to the inverse energy cascade in the direction of a longer wavelength. A three-dimensional (3D) set of coupled equations describing the nonlinear interaction of pumping CRAK waves and zonal flow is derived. The growth rate of the corresponding instability and the conditions for driving them are determined. It is found that the growth rate is mainly stipulated by Rossby waves but the generation of the intense mean magnetic field is caused by Alfvén waves.

  4. Dynamics of the Coupled Moist Kelvin-Rossby Wave on an Equatorial -Plane.

    NASA Astrophysics Data System (ADS)

    Wang, Bin; Rui, Hualan

    1990-02-01

    A simple theoretical analysis on the stability of a resting tropical atmosphere to semigeostrophic perturbations is given using a free atmosphere-boundary layer coupled model on an equatorial -plane.An unstable mode emerges when sea surface temperature is higher than a critical value. The growing mode is a moist Kelvin wave modified through coupling with a Rossby wave of the lowest meridional index. The modified Rossby modes, however, remain damped even for high SST. The unstable mode selection can be explained in terms of wave energy generation due to the latent heating induced by frictional moisture convergence.The horizontal mode-coupling has profound impacts on wave instability. It favors the amplification of long planetary-scale waves, slows down eastward propagation, and suppresses unrealistically fast growth of the uncoupled moist Kelvin mode by creating substantial meridional flows. These effects make the coupled unstable mode more resemble observed equatorial intraseasonal disturbances.The results also demonstrate that when maximum SST moves from the equator to 7.5°N, the growth rate of the unstable wave is significantly reduced, suggesting that the annual march of the `thermal equator' and associated convective heating is likely responsible for annual variations of the equatorial 40-50 day wave activity.

  5. VARIATIONS OF THE MUON FLUX AT SEA LEVEL ASSOCIATED WITH INTERPLANETARY ICMEs AND COROTATING INTERACTION REGIONS

    SciTech Connect

    Augusto, C. R. A.; Kopenkin, V.; Navia, C. E.; Tsui, K. H.; Shigueoka, H.; Fauth, A. C.; Kemp, E.; Manganote, E. J. T.; Leigui de Oliveira, M. A.; Miranda, P.; Ticona, R.; Velarde, A.

    2012-11-10

    We present the results of an ongoing survey on the association between the muon flux variation at ground level (3 m above sea level) registered by the Tupi telescopes (Niteri-Brazil, 22.{sup 0}9S, 43.{sup 0}2W, 3 m) and the Earth-directed transient disturbances in the interplanetary medium propagating from the Sun (such as coronal mass ejections (CME), and corotating interaction regions (CIRs)). Their location inside the South Atlantic Anomaly region enables the muon telescopes to achieve a low rigidity of response to primary and secondary charged particles. The present study is primarily based on experimental events obtained by the Tupi telescopes in the period from 2010 August to 2011 December. This time period corresponds to the rising phase of solar cycle 24. The Tupi events are studied in correlation with data obtained by space-borne detectors (SOHO, ACE, GOES). Identification of interplanetary structures and associated solar activity was based on the nomenclature and definitions given by the satellite observations, including an incomplete list of possible interplanetary shocks observed by the CELIAS/MTOF Proton Monitor on the Solar and Heliospheric Observatory (SOHO) spacecraft. Among 29 experimental events reported in the present analysis, there are 15 possibly associated with the CMEs and sheaths, and 3 events with the CIRs (forward or reverse shocks); the origin of the remaining 11 events has not been determined by the satellite detectors. We compare the observed time (delayed or anticipated) of the muon excess (positive or negative) signal on Earth (the Tupi telescopes) with the trigger time of the interplanetary disturbances registered by the satellites located at Lagrange point L1 (SOHO and ACE). The temporal correlation of the observed ground-based events with solar transient events detected by spacecraft suggests a real physical connection between them. We found that the majority of observed events detected by the Tupi experiment were delayed in

  6. WR 110: A Single Wolf-Rayet Star with Corotating Interaction Regions in its Wind?

    NASA Astrophysics Data System (ADS)

    Chené, A.-N.; Moffat, A. F. J.; Cameron, C.; Fahed, R.; Gamen, R. C.; Lefèvre, L.; Rowe, J. F.; St-louis, N.; Muntean, V.; De La Chevrotière, A.; Guenther, D. B.; Kuschnig, R.; Matthews, J. M.; Rucinski, S. M.; Sasselov, D.; Weiss, W. W.

    2011-07-01

    A 30 day contiguous photometric run with the Microvariability and Oscillations of STars (MOST) satellite on the WN5-6b star WR 110 (HD 165688) reveals a fundamental periodicity of P = 4.08 ± 0.55 days along with a number of harmonics at periods P/n, with n ≈ 2, 3, 4, 5, and 6, and a few other possible stray periodicities and/or stochastic variability on timescales longer than about a day. Spectroscopic radial velocity studies fail to reveal any plausible companion with a period in this range. Therefore, we conjecture that the observed light-curve cusps of amplitude ~0.01 mag that recur at a 4.08 day timescale may arise in the inner parts, or at the base, of a corotating interaction region (CIR) seen in emission as it rotates around with the star at constant angular velocity. The hard X-ray component seen in WR 110 could then be a result of a high velocity component of the CIR shock interacting with the ambient wind at several stellar radii. Given that most hot, luminous stars showing CIRs have two CIR arms, it is possible that either the fundamental period is 8.2 days or, more likely in the case of WR 110, there is indeed a second weaker CIR arm for P = 4.08 days, that occurs ~two-thirds of a rotation period after the main CIR. If this interpretation is correct, WR 110 therefore joins the ranks with three other single WR stars, all WN, with confirmed CIR rotation periods (WR 1, WR 6, and WR 134), albeit with WR 110 having by far the lowest amplitude photometric modulation. This illustrates the power of being able to secure intense, continuous high-precision photometry from space-based platforms such as MOST. It also opens the door to revealing low-amplitude photometric variations in other WN stars, where previous attempts have failed. If all WN stars have CIRs at some level, this could be important for revealing sources of magnetism or pulsation in addition to rotation periods. Based on data from the MOST satellite, a Canadian Space Agency mission, jointly

  7. WR 110: A SINGLE WOLF-RAYET STAR WITH COROTATING INTERACTION REGIONS IN ITS WIND?

    SciTech Connect

    Chene, A.-N.; Moffat, A. F. J.; Fahed, R.; St-louis, N.; Muntean, V.; Chevrotiere, A. De La; Cameron, C.; Matthews, J. M.; Gamen, R. C.; Rowe, J. F.; Guenther, D. B.; Kuschnig, R.; Weiss, W. W.; Rucinski, S. M.; Sasselov, D. E-mail: moffat@astro.umontreal.ca

    2011-07-01

    A 30 day contiguous photometric run with the Microvariability and Oscillations of STars (MOST) satellite on the WN5-6b star WR 110 (HD 165688) reveals a fundamental periodicity of P = 4.08 {+-} 0.55 days along with a number of harmonics at periods P/n, with n {approx} 2, 3, 4, 5, and 6, and a few other possible stray periodicities and/or stochastic variability on timescales longer than about a day. Spectroscopic radial velocity studies fail to reveal any plausible companion with a period in this range. Therefore, we conjecture that the observed light-curve cusps of amplitude {approx}0.01 mag that recur at a 4.08 day timescale may arise in the inner parts, or at the base, of a corotating interaction region (CIR) seen in emission as it rotates around with the star at constant angular velocity. The hard X-ray component seen in WR 110 could then be a result of a high velocity component of the CIR shock interacting with the ambient wind at several stellar radii. Given that most hot, luminous stars showing CIRs have two CIR arms, it is possible that either the fundamental period is 8.2 days or, more likely in the case of WR 110, there is indeed a second weaker CIR arm for P = 4.08 days, that occurs {approx}two-thirds of a rotation period after the main CIR. If this interpretation is correct, WR 110 therefore joins the ranks with three other single WR stars, all WN, with confirmed CIR rotation periods (WR 1, WR 6, and WR 134), albeit with WR 110 having by far the lowest amplitude photometric modulation. This illustrates the power of being able to secure intense, continuous high-precision photometry from space-based platforms such as MOST. It also opens the door to revealing low-amplitude photometric variations in other WN stars, where previous attempts have failed. If all WN stars have CIRs at some level, this could be important for revealing sources of magnetism or pulsation in addition to rotation periods.

  8. Measurements of H(+), He(2+), and He(+), in Corotating Interaction Regions at 1 AU

    NASA Astrophysics Data System (ADS)

    Chotoo, Kancham

    Using the Supra-Thermal Ion Composition Spectrometer (STICS) from the SMS experiment on the WIND spacecraft, measurements of H+, He2+, and He+ were made during two corotating interacting regions (CIRs) at 1 AU. The unique energy range of STICS (6-198 keV/e) allowed simultaneous observation of the pre- and post-accelerated ions. These observations gave important clues about the source population, injection, acceleration mechanism, and ion transport in CIRs. The abundance of He2+ relative to H+ in the velocity range 2.5-6.0 times the solar wind velocity, VSW, (5-90 keV/amu) was between 0.11-0.18, which is more than double the solar wind values. However, the same ratio was observed in the suprathermal tail above 1.4 VSW in the spacecraft frame or above ~0.4 VSW in the solar wind frame. This suggests that the H+ and He2+ ions are injected equally into the CIR acceleration process from the suprathermal tail of the solar wind. At 1 AU the H+ and He2+ ions are primarily from the solar wind, but the He+ ions are interstellar pickup ions. The He+/He2+ ratio at 1 AU was ~0.15 for the same velocity range as above. However, this ratio was greater than 1.0 at 4.5 AU as measured previously (Gloeckler et al., 1994). This shows that the relative contribution of the pickup He+ ions to the seed population increases with radial distance away from the Sun. By combining data from three separate sensors on WIND (SMS-MASS, SMS-STICS, and EPACT-STEP), the extended helium distribution was presented for solar wind ions (~1 keV/amu) through energetic particles up to ~1 MeV/amu. The distribution covered 14 orders of magnitude in phase space density. This is the first time such an extended helium distribution is being reported at any radial distance. Using the Fisk and Lee (1980) model to fit the data between ~10-1000 keV/amu, the energetic particles were found to originate from 1.0-1.2 AU and not from beyond 2 AU, as is conventional believed. Anisotropy measurements were made using STICS for

  9. The Rossiter-McLaughlin effect of CoRoT-3b and HD 189733b

    NASA Astrophysics Data System (ADS)

    Triaud, A. H. M. J.; Queloz, D.; Bouchy, F.; Moutou, C.; Collier Cameron, A.; Claret, A.; Barge, P.; Benz, W.; Deleuil, M.; Guillot, T.; Hébrard, G.; Lecavelier Des Étangs, A.; Lovis, C.; Mayor, M.; Pepe, F.; Udry, S.

    2009-10-01

    We present radial-velocity sequences acquired during three transits of the exoplanet HD 189733b and one transit of CoRoT-3b. We applied a combined Markov-chain Monte-Carlo analysis of spectroscopic and photometric data on these stars, to determine a full set of system parameters including the projected spin-orbit misalignment angle of HD 189733b to an unprecedented precision via the Rossiter-McLaughlin effect: β = 0.85 circ + 0.32 ~- 0.28. This small but non-zero inclination of the planetary orbit is important to understand the origin of the system. On CoRoT-3b, results seem to point towards a non-zero inclination as well with β=37.6circ + 10.0 ~-22.3, but this remains marginal. Systematic effects due to non-Gaussian cross-correlation functions appear to be the main cause of significant residuals that prevent an accurate determination of the projected stellar rotation velocity V sin(I) for both stars. Using observations with the Harps spectrograph from the ESO 3.6 m installed at La Silla, Chile, under the allocated programmes 072.C-0488(E) and 079.C-0828(A). The data is publicly available in electronic form at the CDS. Tables 3 and 4 are only available in electronic form at http://www.aanda.org

  10. GROUND-BASED NEAR-INFRARED OBSERVATIONS OF THE SECONDARY ECLIPSE OF CoRoT-2b

    SciTech Connect

    Alonso, R.; Deeg, H. J.; Rabus, M.; Kabath, P.

    2010-04-15

    We present the results of a ground-based search for the secondary eclipse of the 3.3 M {sub Jup} transiting planet CoRoT-2b. We performed near-infrared photometry using the LIRIS instrument on the 4.2 m William Herschel Telescope, in the H and K{sub s} filters. We monitored the star around two expected secondary eclipses in two nights under very good observing conditions. For the depth of the secondary eclipse, in the H band we found a 3{sigma} upper limit of 0.17%, whereas we detected a tentative eclipse with a depth of 0.16% {+-} 0.09% in the K{sub s} band. These depths can be translated into brightness temperatures of T{sub H} < 2250 K and T{sub K{sub s}}= 1890{sup +260}{sub -350} K, which indicate an inefficient re-distribution of the incident stellar flux from the planet's day side to its night side. Our results are in agreement with the CoRoT optical measurement (Alonso et al.) and with Spitzer 4.5 and 8 {mu}m results (Gillon et al.)

  11. GROUND-BASED DETECTIONS OF THERMAL EMISSION FROM CoRoT-1b AND WASP-12b

    SciTech Connect

    Zhao Ming; Swain, Mark R.; Monnier, John D.; Barman, Travis; Hinkley, Sasha

    2012-01-10

    We report a new detection of the H-band thermal emission of CoRoT-1b and two confirmation detections of the Ks-band thermal emission of WASP-12b at secondary eclipses. The H-band measurement of CoRoT-1b shows an eclipse depth of 0.145% {+-} 0.049% with a 3{sigma} percentile between 0.033% and 0.235%. This depth is consistent with the previous conclusions that the planet has an isothermal region with inefficient heat transport from day side to night side, and has a dayside thermal inversion layer at high altitude. The two Ks-band detections of WASP-12b show a joint eclipse depth of 0.299% {+-} 0.065%. This result agrees with the measurement of Croll and collaborators, providing independent confirmation of their measurement. The repeatability of the WASP-12b measurements also validates our data analysis method. Our measurements, in addition to a number of previous results made with other telescopes, demonstrate that ground-based observations are becoming widely available for characterization of atmospheres of hot Jupiters.

  12. Low-amplitude rotational modulation rather than pulsations in the CoRoT B-type supergiant HD 46769

    NASA Astrophysics Data System (ADS)

    Aerts, C.; Simón-Díaz, S.; Catala, C.; Neiner, C.; Briquet, M.; Castro, N.; Schmid, V. S.; Scardia, M.; Rainer, M.; Poretti, E.; Pápics, P. I.; Degroote, P.; Bloemen, S.; Østensen, R. H.; Auvergne, M.; Baglin, A.; Baudin, F.; Michel, E.; Samadi, R.

    2013-09-01

    Aims: We aim to detect and interpret photometric and spectroscopic variability of the bright CoRoT B-type supergiant target HD 46769 (V = 5.79). We also attempt to detect a magnetic field in the target. Methods: We analyse a 23-day oversampled CoRoT light curve after detrending and spectroscopic follow-up data using standard Fourier analysis and phase dispersion minimization methods. We determine the fundamental parameters of the star, as well as its abundances from the most prominent spectral lines. We perform a Monte Carlo analysis of spectropolarimetric data to obtain an upper limit of the polar magnetic field, assuming a dipole field. Results: In the CoRoT data, we detect a dominant period of 4.84 d with an amplitude of 87 ppm and some of its (sub-)multiples. Given the shape of the phase-folded light curve and the absence of binary motion, we interpret the dominant variability in terms of rotational modulation, with a rotation period of 9.69 d. Subtraction of the rotational modulation signal does not reveal any sign of pulsations. Our results are consistent with the absence of variability in the Hipparcos light curve. The spectroscopy leads to a projected rotational velocity of 72 ± 2 km s-1 and does not reveal periodic variability or the need to invoke macroturbulent line broadening. No signature of a magnetic field is detected in our data. A field stronger than ~500 G at the poles can be excluded, unless the possible non-detected field were more complex than dipolar. Conclusions: The absence of pulsations and macroturbulence of this evolved B-type supergiant is placed into the context of instability computations and of observed variability of evolved B-type stars. Based on CoRoT space-based photometric data; the CoRoT space mission was developed and operated by the French space agency CNES, with the participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain. Based on observations collected at La Silla Observatory, ESO

  13. Transiting exoplanets from the CoRoT space mission . XIII. CoRoT-13b: a dense hot Jupiter in transit around a star with solar metallicity and super-solar lithium content

    NASA Astrophysics Data System (ADS)

    Cabrera, J.; Bruntt, H.; Ollivier, M.; Díaz, R. F.; Csizmadia, Sz.; Aigrain, S.; Alonso, R.; Almenara, J.-M.; Auvergne, M.; Baglin, A.; Barge, P.; Bonomo, A. S.; Bordé, P.; Bouchy, F.; Carone, L.; Carpano, S.; Deleuil, M.; Deeg, H. J.; Dvorak, R.; Erikson, A.; Ferraz-Mello, S.; Fridlund, M.; Gandolfi, D.; Gazzano, J.-C.; Gillon, M.; Guenther, E. W.; Guillot, T.; Hatzes, A.; Havel, M.; Hébrard, G.; Jorda, L.; Léger, A.; Llebaria, A.; Lammer, H.; Lovis, C.; Mazeh, T.; Moutou, C.; Ofir, A.; von Paris, P.; Pätzold, M.; Queloz, D.; Rauer, H.; Rouan, D.; Santerne, A.; Schneider, J.; Tingley, B.; Titz-Weider, R.; Wuchterl, G.

    2010-11-01

    We announce the discovery of the transiting planet CoRoT-13b. Ground-based follow-up in CFHT and IAC80 confirmed CoRoT's observations. The mass of the planet was measured with the HARPS spectrograph and the properties of the host star were obtained analyzing HIRES spectra from the Keck telescope. It is a hot Jupiter-like planet with an orbital period of 4.04 days, 1.3 Jupiter masses, 0.9 Jupiter radii, and a density of 2.34 g cm-3. It orbits a G0V star with T_eff = 5 945 K, M* = 1.09 M⊙, R_* = 1.01 R⊙, solar metallicity, a lithium content of + 1.45 dex, and an estimated age of between 0.12 and 3.15 Gyr. The lithium abundance of the star is consistent with its effective temperature, activity level, and age range derived from the stellar analysis. The density of the planet is extreme for its mass, implies that heavy elements are present with a mass of between about 140 and 300 {M}⊕. The CoRoT space mission, launched on December 27th 2006, has been developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA (RSSD and Science Programme), Germany and Spain. Part of the observations were obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. Based on observations made with HARPS spectrograph on the 3.6-m European Organisation for Astronomical Research in the Southern Hemisphere telescope at La Silla Observatory, Chile (ESO program 184.C-0639). Based on observations made with the IAC80 telescope operated on the island of Tenerife by the Instituto de Astrofísica de Canarias in the Spanish Observatorio del Teide. Part of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics

  14. Evolution of the multiscale statistical properties of corotating streams from 1 to 95 AU

    NASA Astrophysics Data System (ADS)

    Burlaga, L. F.; Wang, C.; Richardson, J. D.; Ness, N. F.

    2003-07-01

    This paper discusses the multiscale structure of the large-scale speed fluctuations between 1 and 95 AU during the declining phase of the solar cycle, when corotating streams are dominant structures close to the Sun. A deterministic, multifluid, one-dimensional MHD model with the WIND data at 1 AU during 1995 as input was used to compute the time series of daily averages of speed, V(ti), with a length on the order of 1 year at R = 5, 10, … 95 AU, from which we calculated various statistical functions describing the solar wind speed. The probability distribution functions (PDFs) of the running speed differences dVn(ti) were calculated at scales τ from 1 to 64 days. The theoretical PDFs at 50 AU have the same qualitative forms as those observed by Voyager 2 (V2) between 46 and 49 AU. The theoretical PDF at a scale of 1 day at 15 AU agrees with the corresponding PDF observed by V2 between 13 and 16 AU. With increasing distance from the Sun, the width of the predicted PDF with τ = 1 decreases and the tail becomes more prominent. The standard deviation of dVn(ti) at various R computed from the model, SD(τ, R), decreases nearly exponentially with increasing R, and it is consistent with the observations of SD(τ, R) made by V2 near 15 and 50 AU. The skewness at a scale of 1 day increases almost linearly with R beyond ≈35 AU, but it shows structure between 5 and 35 AU; it is consistent with the observations of V2 near 15 and 50 AU. The theoretical power spectral density of the speed fluctuations, PSD(f, R), agrees with the observations of V2 near 15 and 50 AU. For frequencies f > 8.5 × 10-7 Hz, PSD(f, R) ∝ f-s(R). The observed and predicted s are ≤-2 beyond 40 AU, consistent with the jump-ramp structure of V(t) in the distant heliosphere. We predict that the PDF for τ = 1 which will be observed by V2 at 70 AU in 2003 will have a core whose width is only ≈5 km/s and a tail extending up to 60 km/s that represents the major jumps in the speed profile. The

  15. BEER Analysis of Kepler and CoRoT Light Curves III. Sixty New Non-Eclipsing BEER Binaries Discovered in CoRoT Light Curves Confirmed by RVs from AAOmega

    NASA Astrophysics Data System (ADS)

    Tal-Or, L.; Faigler, S.; Mazeh, T.

    2015-07-01

    We have applied the BEER algorithm (Faigler& Mazeh 2011) to the CoRoT white-light curves from the first five LRc fields. We have found 491 non-eclipsing BEER candidates with periodic photometric modulations and amplitudes of 0.5-80 mmag. Medium-resolution spectra of 281 candidates were obtained in a seven-night AAOmega radial-velocity (RV) campaign, with a precision of ˜1 km s-1. The RVs confirmed the binarity of at least 60 of the BEER candidates, with RV semi-amplitudes ranging from 6 to 115 km s-1, and periods from 0.3 to 10 days. We detected an F-type star that may possibly have a brown dwarf companion in a 0.7-day period orbit.

  16. Transiting exoplanets from the CoRoT space mission . VI. CoRoT-Exo-3b: the first secure inhabitant of the brown-dwarf desert

    NASA Astrophysics Data System (ADS)

    Deleuil, M.; Deeg, H. J.; Alonso, R.; Bouchy, F.; Rouan, D.; Auvergne, M.; Baglin, A.; Aigrain, S.; Almenara, J. M.; Barbieri, M.; Barge, P.; Bruntt, H.; Bordé, P.; Collier Cameron, A.; Csizmadia, Sz.; de La Reza, R.; Dvorak, R.; Erikson, A.; Fridlund, M.; Gandolfi, D.; Gillon, M.; Guenther, E.; Guillot, T.; Hatzes, A.; Hébrard, G.; Jorda, L.; Lammer, H.; Léger, A.; Llebaria, A.; Loeillet, B.; Mayor, M.; Mazeh, T.; Moutou, C.; Ollivier, M.; Pätzold, M.; Pont, F.; Queloz, D.; Rauer, H.; Schneider, J.; Shporer, A.; Wuchterl, G.; Zucker, S.

    2008-12-01

    Context: The CoRoT space mission routinely provides high-precision photometric measurements of thousands of stars that have been continuously observed for months. Aims: The discovery and characterization of the first very massive transiting planetary companion with a short orbital period is reported. Methods: A series of 34 transits was detected in the CoRoT light curve of an F3V star, observed from May to October 2007 for 152 days. The radius was accurately determined and the mass derived for this new transiting, thanks to the combined analysis of the light curve and complementary ground-based observations: high-precision radial-velocity measurements, on-off photometry, and high signal-to-noise spectroscopic observations. Results: CoRoT-Exo-3b has a radius of 1.01 ± 0.07 R_Jup and transits around its F3-type primary every 4.26 days in a synchronous orbit. Its mass of 21.66 ± 1.0 M_Jup, density of 26.4 ± 5.6 g cm-3, and surface gravity of logg = 4.72 clearly distinguish it from the regular close-in planet population, making it the most intriguing transiting substellar object discovered so far. Conclusions: With the current data, the nature of CoRoT-Exo-3b is ambiguous, as it could either be a low-mass brown-dwarf or a member of a new class of “superplanets”. Its discovery may help constrain the evolution of close-in planets and brown-dwarfs better. Finally, CoRoT-Exo-3b confirms the trend that massive transiting giant planets (M ≥ 4 M_Jup) are found preferentially around more massive stars than the Sun. The CoRoT space mission, launched on December 27th 2006, has been developed and is operating by CNES, with the contribution of Austria, Belgium, Brasil, ESA, Germany and Spain. The first CoRoT data will be available to the public in February 2009 from the CoRoT archive: http://idoc-corot.ias.u-psud.fr/ Table of the COROT photometry is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb

  17. A new model of resonance in the winter stratosphere

    NASA Technical Reports Server (NTRS)

    Haynes, P. H.

    1985-01-01

    It is generally accepted that the planetary waves observed in the winter stratosphere are primarily a response to dynamical forcing from the troposphere. Nevertheless, the mechanism by which wave amplitudes sometimes become larger remains uncertain. It is possible that anomalously large waves in the stratosphere might simply be the result of anomalously large tropospheric forcing. However, it has also been suggested that they are a response to a stratospheric-tropospheric cavity being in a near-resonant configuration. It has been suggested that nonlinear self-tuning effects could play an important role in the behavior of such a cavity. Self-tuning may occur when a system starts to one side of resonance, such that the mean-state change induced by growing waves brings the system closer to resonance. A new model of the stratospheric cavity is introduced and is then used to re-examine the possibility of wave growth in the real atmosphere and in atmospheric models due to self-tuning effects. The new model is based on the picture of the winter-time stratosphere which has been revealed by the observations of Ertel's potential vorticity, Q. Isentropic maps of Q show two rather distinct regions, the first containing the circumpolar vortex, where gradients of Q are large and Rossby waves may propagate easily. Surrounding this is a second, low-latitude region where the gradients are generally weak and where, because the Eulerian-mean flow is comparable with their phase speed, Rossby waves must be continually breaking. As the waves are observed to grow the relative sizes of these two regions change in time. This leads to the interesting possibility that self-tuning, mainly due to irreversible changes in the size of the polar vortex, is taking place.

  18. A 0.8-2.4 μm Transmission spectrum of the hot Jupiter CoRoT-1b

    SciTech Connect

    Schlawin, E.; Herter, T.; Zhao, M.; Teske, J. K.

    2014-03-01

    Hot Jupiters with brightness temperatures ≳2000 K can have TiO and VO molecules as gaseous species in their atmospheres. The TiO and VO molecules can potentially induce temperature inversions in hot Jupiter atmospheres and also have an observable signature of large optical to infrared transit depth ratios. Previous transmission spectra of very hot Jupiters have shown a lack of TiO and VO, but only in planets that also appear to lack temperature inversions. We measure the transmission spectrum of CoRoT-1b, a hot Jupiter that was predicted to have a temperature inversion potentially due to significant TiO and VO in its atmosphere. We employ the multi-object spectroscopy method using the SpeX and MORIS instruments on the Infrared Telescope Facility (IRTF) and the Gaussian process method to model red noise. By using a simultaneous reference star on the slit for calibration and a wide slit to minimize slit losses, we achieve transit depth precision of 0.03%-0.09%, comparable to the atmospheric scale height but detect no statistically significant molecular features. We combine our IRTF data with optical CoRoT transmission measurements to search for differences in the optical and near-infrared absorption that would arise from TiO/VO. Our IRTF spectrum and the CoRoT photometry disfavor a TiO/VO-rich spectrum for CoRoT-1b, suggesting that the atmosphere has another absorber that could create a temperature inversion or that the blackbody-like emission from the planet is due to a spectroscopically flat cloud, dust, or haze layer that smoothes out molecular features in both CoRoT-1b's emission and transmission spectra. This system represents the faintest planet hosting star (K = 12.2) with a measured planetary transmission spectrum.

  19. Gravity and Rossby Wave Signatures in the Tropical Troposphere and Lower Stratosphere Based on Southern Hemisphere Additional Ozonesondes (SHADOZ), 1998-2007

    NASA Technical Reports Server (NTRS)

    Thompson, Anne M.; Allen, Amber L.; Lee, Sukyoung; Miller, Sonya K.; Witte, Jacquelyn C.

    2011-01-01

    Prior investigations attempted to determine the relative influence of advection and convective processes on ozone and water vapor distributions in the tropical tropopause layer (TTL) through analyses of tracers, related physical parameters (e.g., outgoing long-wave radiation, precipitable water, and temperature), or with models. In this study, stable laminae in Southern Hemisphere Additional Ozonesonde Network (SHADOZ) ozone profIles from 1998 to 2007 are interpreted in terms of gravity waves (GW) or Rossby waves (RW) that are identified with vertical and quasi-horizontal displacements, respectively. Using the method of Pierce and Grant (1998) as applied by Thompson et al. (2007a, 2007b, 2010, 2011), amplitudes and frequencies in ozone laminae are compared among representative SHADOZ sites over Africa and the Pacific, Indian, and Atlantic oceans. GW signals maximize in the TTL and lower stratosphere. Depending on site and season, GW are identified in up to 90% of the soundings. GW are most prevalent over the Pacific and eastern Indian oceans, a distribution consistent with vertically propagating equatorial Kelvin waves. Ozone laminae from RW occur more often below the tropical tropopause and with lower frequency 20%). Gravity wave and Rossby wave indices (GWI, RWI) are formulated to facilitate analysis of interannual variability of wave signatures among sites. GWI is positively correlated with a standard ENSO (El Nino-Southern Oscillation) index over American Samoa (14degS, 171degW) and negatively correlated at Watukosek, Java (7.5degS, 114degE), Kuala Lumpur (3degN, 102degE), and Ascension Island (80degS, 15degW). Generally, the responses of GW and RW to ENSO are consistent with prior studies.

  20. Distribution function representation of energy spectra of H, He, C, O and Fe in corotating particle streams

    NASA Technical Reports Server (NTRS)

    Gloeckler, G.; Ipavich, F. M.; Mason, G. M.; Hovestadt, D.

    1980-01-01

    From an analysis of nine corotating events observed near 1 AU during the 1974-1976 solar minimum, the spectral parameters for H, He, C, O and Fe and relative abundances of these elements and of Ne, Mg, Si, and S-Ca were determined. The distribution functions of H, He, O and Fe are well represented by an exponential in particle speed over the energy range of the measurements from 0.3 to 5 MeV/nucleon. The composition resembles that of the solar corona, particularly in the O/C ratio which is 0.95 + or - 0.19, and the He/H and He/Ne ratios are similar to the respective ratios in the solar wind. The results are consistent with interplanetary statistical acceleration of these particles out of the high-energy tail of the high-speed solar wind.

  1. VizieR Online Data Catalog: Limb-darkening for CoRoT, Kepler, Spitzer. II. (Claret+, 2013)

    NASA Astrophysics Data System (ADS)

    Claret, A.; Hauschildt, P. H.; Witte, S.

    2013-02-01

    We present an extension of our investigations on limb-darkening coefficients computed with spherical symmetrical PHOENIX models. The models investigated in this paper cover the range 5000K<=Teff<=10000K and complete our previous studies of low effective temperatures computed with the same code. The limb-darkening coefficients are computed for the transmission curves of the Kepler, CoRoT, and Spitzer space missions and the Stroemgren, Johnson-Cousins, Sloan, and 2MASS passbands. These computations were performed by adopting the least-squares method. We have used six laws to describe the specific intensity distribution: linear, quadratic, square root, logarithmic, exponential, and a general law with four terms. The computations are presented for the solar chemical composition and cover the range 3.0<=logg<=5.5. The adopted microturbulent velocity and the mixing-length parameter are 2.0km/s and 2.0. (17 data files).

  2. A three-dimensional model of co-rotating streams in the solar wind. 2: Hydrodynamic streams

    NASA Technical Reports Server (NTRS)

    Pizzo, V. J.

    1979-01-01

    Theoretical aspects of corotating solar wind dynamics on a global scale are explored by means of numerical simulations executed with a nonlinear, inviscid, adiabatic, single-fluid, three-dimensional (3-D) hydrodynamic formulation. A simple, hypothetical 3-D stream structure is defined on a source surface located at 35 solar radius and carefully documents its evolution to 1 AU under the influence of solar rotation. By manipulating the structure of this prototype configuration at the source surface, it is possible to elucidate the factors most strongly affecting stream evolution: (1) the intrinsic correlations among density, temperature, and velocity existing near the source; (2) the amplitude of the stream; (3) the longitudinal breadth of the stream; (4) the latitudinal breadth of the stream; and (5) the heliographic latitude of the centroid of the stream.

  3. Comprehensive Characterization of CoRoT-2b and XO-1b with Keck/MOSFIRE

    NASA Astrophysics Data System (ADS)

    Mandell, Avi

    2014-02-01

    We propose observations of the transiting exoplanets CoRoT-2b and XO-1b with Keck/MOSFIRE in the K-band. We will observe both the thermal emission spectrum of each planet obtained at secondary eclipse as well as a transmission spectrum obtained when the planet is in transit, which will allow us to constrain (1) the overall temperature structure of the dayside atmosphere, including the presence of a thermal inversion, (2) the chemical composition of the atmosphere, both on the dayside as well as at the day-night terminator. We will also use the additional observing time on our four nights to observe other ancillary exoplanet targets.

  4. On the differences in element abundances of energetic ions from corotating events and from large solar events

    NASA Technical Reports Server (NTRS)

    Reames, D. V.; Richardson, I. G.; Barbier, L. M.

    1991-01-01

    The abundances of energetic ions accelerated from high-speed solar wind streams by shock waves formed at corotating interaction regions (CIRs) where high-speed streams overtake the lower-speed solar wind are examined. The observed element abundances appear to represent those of the high-speed solar wind, unmodified by the shock acceleration. These abundances, relative to those in the solar photosphere, are organized by the first ionization potential (FIP) of the ions in a way that is different from the FIP effect commonly used to describe differences between abundances in the solar photosphere and those in the solar corona, solar energetic particles (SEPs), and the low-speed solar wind. In contrast, the FIP effect of the ion abundances in the CIR events is characterized by a smaller amplitude of the differences between high-FIP and low-FIP ions and by elevated abundances of He, C, and S.

  5. A corotational flat triangular element for large strain analysis of thin shells with application to soft biological tissues

    NASA Astrophysics Data System (ADS)

    Caselli, Federica; Bisegna, Paolo

    2014-09-01

    A flat triangular element for the nonlinear analysis of thin shells is presented. The formulation relies on (i) a polar decomposition based corotational framework and (ii) a core-element kinematic description adopting the multiplicative superposition of membrane and bending actions. The resulting element is a refined yet simple three-node displacement-based triangle accounting for thickness extensibility and initial shell curvature, and equipped with a fully consistent tangent stiffness. Numerical tests involving shell structures made of rubber-like materials or fibred biological tissues show the effectiveness of the proposed element and its suitability to problems characterized by large displacements, large rotations, large membrane strains and bending. A Matlab toolkit implementing the present formulation is provided as supplementary material.

  6. Diagnostics of corotating interaction regions with the kinetic properties of iron ions as determined with STEREO/PLASTIC

    NASA Astrophysics Data System (ADS)

    Bochsler, P.; Lee, M. A.; Karrer, R.; Jian, L. K.; Ellis, L.; Farrugia, C. J.; Galvin, A. B.; Kistler, L. M.; Kucharek, H.; Möbius, E.; Popecki, M. A.; Simunac, K. D. C.; Blush, L. M.; Daoudi, H.; Wurz, P.; Klecker, B.; Wimmer-Schweingruber, R. F.; Thompson, B.; Luhmann, J. G.; Russell, C. T.; Opitz, A.

    2010-02-01

    STEREO/PLASTIC determines three-dimensional distributions of solar wind iron ions with unprecedented time resolution. Typically 300 to 1000 counts are registered within each 5 min time interval. For the present study we use the information contained in these distributions to characterize CIRs (Corotating Interaction Regions) in two test cases. We perform a consistency test for both the derived physical parameters and for the analytical model of CIRs of Lee (2000). At 1 AU we find that apart from compositional changes the most indicative parameter for marking the time when a CIR passes a spacecraft is the angular deflection of the flow vector of particles. Changes in particle densities and the changes in magnitudes of speeds are apparently less reliable indicators of stream interfaces.

  7. The B0.5 IVe CoRoT target HD 49330. II. Spectroscopic ground-based observations

    NASA Astrophysics Data System (ADS)

    Floquet, M.; Hubert, A.-M.; Huat, A.-L.; Frémat, Y.; Janot-Pacheco, E.; Gutiérrez-Soto, J.; Neiner, C.; de Batz, B.; Leroy, B.; Poretti, E.; Amado, P.; Catala, C.; Rainer, M.; Diaz, D.; Uytterhoeven, K.; Andrade, L.; Diago, P. D.; Emilio, M.; Espinosa Lara, F.; Fabregat, J.; Martayan, C.; Semaan, T.; Suso, J.

    2009-10-01

    Context: We present spectroscopic ground-based observations of the early Be star HD 49330 obtained simultaneously with the CoRoT-LRA1 run just before the burst observed in the CoRoT data. Aims: Ground-based spectroscopic observations of the early Be star HD 49330 obtained during the precursor phase and just before the start of an outburst allow us to disantangle stellar and circumstellar contributions and identify modes of stellar pulsations in this rapidly rotating star. Methods: Time series analysis (TSA) is performed on photospheric line profiles of He I and Si III by means of the least squares method. Results: We find two main frequencies f1 = 11.86 c d-1 and f2 = 16.89 c d-1 which can be associated with high order p-mode pulsations. We also detect a frequency f3 = 1.51 c d-1 which can be associated with a low order g-mode. Moreover we show that the stellar line profile variability changed over the spectroscopic run. These results are in agreement with the results of the CoRoT data analysis, as shown in Huat et al. (2009). Conclusions: Our study of mid- and short-term spectroscopic variability allows the identification of p- and g-modes in HD 49330. It also allows us to display changes in the line profile variability before the start of an outburst. This brings new constraints for the seimic modelling of this star. Based on observations made with ESO Telescopes at La Silla Observatory under the ESO Large Programme: LP178.D-0361, and on data collected with the TBL at Pic du Midi Observatory (France).

  8. The GTC exoplanet transit spectroscopy survey. III. No asymmetries in the transit of CoRoT-29b

    NASA Astrophysics Data System (ADS)

    Pallé, E.; Chen, G.; Alonso, R.; Nowak, G.; Deeg, H.; Cabrera, J.; Murgas, F.; Parviainen, H.; Nortmann, L.; Hoyer, S.; Prieto-Arranz, J.; Nespral, D.; Cabrera Lavers, A.; Iro, N.

    2016-04-01

    Context. The launch of the exoplanet space missions obtaining exquisite photometry from space has resulted in the discovery of thousands of planetary systems with very different physical properties and architectures. Among them, the exoplanet CoRoT-29b was identified in the light curves the mission obtained in summer 2011, and presented an asymmetric transit light curve, which was tentatively explained via the effects of gravity darkening. Aims: Transits of CoRoT-29b are measured with precision photometry, to characterize the reported asymmetry in their transit shape. Methods: Using the OSIRIS spectrograph at the 10-m GTC telescope, we perform spectro-photometric differential observations, which allow us to both calculate a high-accuracy photometric light curve, and a study of the color-dependence of the transit. Results: After careful data analysis, we find that the previously reported asymmetry is not present in either of two transits, observed in July 2014 and July 2015 with high photometric precisions of 300 ppm over 5 min. Due to the relative faintness of the star, we do not reach the precision necessary to perform transmission spectroscopy of its atmosphere, but we see no signs of color-dependency of the transit depth or duration. Conclusions: We conclude that the previously reported asymmetry may have been a time-dependent phenomenon, which did not occur in more recent epochs. Alternatively, instrumental effects in the discovery data may need to be reconsidered. Light curves are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/589/A62

  9. Models of red giants in the CoRoT asteroseismology fields combining asteroseismic and spectroscopic constraints

    NASA Astrophysics Data System (ADS)

    Lagarde, N.; Miglio, A.; Eggenberger, P.; Morel, T.; Montalbán, J.; Mosser, B.; Rodrigues, T. S.; Girardi, L.; Rainer, M.; Poretti, E.; Barban, C.; Hekker, S.; Kallinger, T.; Valentini, M.; Carrier, F.; Hareter, M.; Mantegazza, L.; Elsworth, Y.; Michel, E.; Baglin, A.

    2015-08-01

    Context. The availability of asteroseismic constraints for a large sample of red giant stars from the CoRoT and Kepler missions paves the way for various statistical studies of the seismic properties of stellar populations. Aims: We use a detailed spectroscopic study of 19 CoRoT red giant stars to compare theoretical stellar evolution models to observations of the open cluster NGC 6633 and field stars. Methods: In order to explore the effects of rotation-induced mixing and thermohaline instability, we compare surface abundances of carbon isotopic ratio and lithium with stellar evolution predictions. These chemicals are sensitive to extra-mixing on the red giant branch. Results: We estimate mass, radius, and distance for each star using the seismic constraints. We note that the Hipparcos and seismic distances are different. However, the uncertainties are such that this may not be significant. Although the seismic distances for the cluster members are self consistent they are somewhat larger than the Hipparcos distance. This is an issue that should be considered elsewhere. Models including thermohaline instability and rotation-induced mixing, together with the seismically determined masses can explain the chemical properties of red giant targets. However, with this sample of stars we cannot perform stringent tests of the current stellar models. Tighter constraints on the physics of the models would require the measurement of the core and surface rotation rates, and of the period spacing of gravity-dominated mixed modes. A larger number of stars with longer times series, as provided by Kepler or expected with Plato, would help ensemble asteroseismology.

  10. Spitzer Secondary Eclipse Observations of Hot-Jupiters WASP-26b and CoRoT-1b

    NASA Astrophysics Data System (ADS)

    DeLarme, Emerson; Harrington, Joseph; Cubillos, Patricio; Blecic, Jasmina; Foster, Andrew SD; Garland, Justin; Foster, AJ; Collier Cameron, Andrew

    2015-11-01

    WASP-26b is a hot-Jupiter planet that orbits an early G star every 2.7566 days at a distance of 0.03985 AU. Using the Spitzer Space Telescope in 2010 as a part of the Spitzer Exoplanet Target of Opportunity program (program 60003) we observed two secondary eclipses of the planet, one in the 3.6 μm channel on 7 September and one in the 4.5 μm channel on 3 August. We also reanalize archival Spitzer data of CoRoT-1b, which is another hot Jupiter orbiting a G star every 1.5089686 days at a distance of 0.0254 AU, in the 3.6 and 4.5 μm channels. The eclipse depths for WASP-26b are 0.00117 ± 0.00012 and 0.001507 ± 0.00016, for the 3.6 and 4.5 μm channels respectively. The eclipse depths for CoRoT-1b are 0.0047 ± 0.0003 and 0.0046 ± 0.0004 respecitvely. We also refine their orbits using our own secondary eclipse measurements in combination with external radial-velocity and transit observations from both professional and amateur observers. Using our Bayesian Atmostpheric Radiative Transfer code, we characterize the atmospheres of these planets. Spitzer is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. This work was supported by NASA Planetary Atmospheres grant NNX12AI69G and NASA Astrophysics Data Analysis Program grant NNX13AF38G. Blecic holds a NASA Earth and Space Science Fellowship.

  11. The GTC exoplanet transit spectroscopy survey. III. No asymmetries in the transit of CoRoT-29b

    NASA Astrophysics Data System (ADS)

    Pallé, E.; Chen, G.; Alonso, R.; Nowak, G.; Deeg, H.; Cabrera, J.; Murgas, F.; Parviainen, H.; Nortmann, L.; Hoyer, S.; Prieto-Arranz, J.; Nespral, D.; Cabrera Lavers, A.; Iro, N.

    2016-05-01

    Context. The launch of the exoplanet space missions obtaining exquisite photometry from space has resulted in the discovery of thousands of planetary systems with very different physical properties and architectures. Among them, the exoplanet CoRoT-29b was identified in the light curves the mission obtained in summer 2011, and presented an asymmetric transit light curve, which was tentatively explained via the effects of gravity darkening. Aims: Transits of CoRoT-29b are measured with precision photometry, to characterize the reported asymmetry in their transit shape. Methods: Using the OSIRIS spectrograph at the 10-m GTC telescope, we perform spectro-photometric differential observations, which allow us to both calculate a high-accuracy photometric light curve, and a study of the color-dependence of the transit. Results: After careful data analysis, we find that the previously reported asymmetry is not present in either of two transits, observed in July 2014 and July 2015 with high photometric precisions of 300 ppm over 5 min. Due to the relative faintness of the star, we do not reach the precision necessary to perform transmission spectroscopy of its atmosphere, but we see no signs of color-dependency of the transit depth or duration. Conclusions: We conclude that the previously reported asymmetry may have been a time-dependent phenomenon, which did not occur in more recent epochs. Alternatively, instrumental effects in the discovery data may need to be reconsidered. Light curves are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/589/A62

  12. Discovery of a magnetic field in the CoRoT hybrid B-type pulsator HD 43317

    NASA Astrophysics Data System (ADS)

    Briquet, M.; Neiner, C.; Leroy, B.; Pápics, P. I.; MiMeS Collaboration

    2013-09-01

    Context. A promising way of testing the impact of a magnetic field on internal mixing (core overshooting, internal rotation) in main-sequence B-type stars is to perform asteroseismic studies of a sample of magnetic pulsators. Aims: The CoRoT satellite revealed that the B3IV star HD 43317 is a hybrid SPB/β Cep-type pulsator that has a wealth of pulsational constraints on which one can perform a seismic modelling, in particular, probing the extent of its convective core and mixing processes. Moreover, indirect indicators of a magnetic field in the star were observed: rotational modulation due to chemical or temperature spots and X-ray emission. Our goal was to directly investigate the field in HD 43317 and, if it is magnetic, to characterise it. Methods: We collected data with the Narval spectropolarimeter installed at Télescope Bernard Lyot (TBL, Pic du Midi, France) and applied the least-squares deconvolution technique to measure the circular polarisation of the light emitted from HD 43317. We modelled the longitudinal field measurements directly with a dipole. Results: Zeeman signatures in the Stokes V profiles of HD 43317 are clearly detected and rotationally modulated, which proves that this star exhibits an oblique magnetic field. The modulation with the rotation period deduced from the CoRoT light curve is also confirmed, and we found a field strength at the poles of about 1 kG. Our result must be taken into account in future seismic modelling work of this star. Based on observations obtained using the Narval spectropolarimeter at the Observatoire du Pic du Midi (France), which is operated by the Institut National des Sciences de l'Univers (INSU).

  13. Analysis of Secondary Eclipse Observations of Hot-Jupiters WASP-26b and CoRoT-1b

    NASA Astrophysics Data System (ADS)

    DeLarme, Emerson; Harrington, Joseph; Cubillos, Patricio; Blecic, Jasmina; Foster, Andrew S.; Garland, Justin; Foster, Austin James; Cameron, Andrew

    2016-01-01

    WASP-26b is a hot-Jupiter planet that orbits an early G star every 2.7566 days at a distance of 0.03985 AU. Using the Spitzer Space Telescope in 2010 as a part of the Spitzer Exoplanet Target of Opportunity program (program 60003) we observed two secondary eclipses of the planet, one in the 3.6 μm channel on 7 September and one in the 4.5 μm channel on 3 August. We also reanalize archival Spitzer data of CoRoT-1b, which is another hot Jupiter orbiting a G star every 1.5089686 days at a distance of 0.0254 AU, in the 3.6 and 4.5 μm channels. The eclipse depths for WASP-26b are 0.00117 ± 0.00012 and 0.001507 ± 0.00016, for the 3.6 and 4.5 μm channels respectively. The eclipse depths for CoRoT-1b are 0.0047 ± 0.0003 and 0.0046 ± 0.0004 respecitvely. We also refine their orbits using our own secondary eclipse measurements in combination with external radial-velocity and transit observations from both professional and amateur observers. Using our Bayesian Atmostpheric Radiative Transfer code, we characterize the atmospheres of these planets. Spitzer is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. This work was supported by NASA Planetary Atmospheres grant NNX12AI69G and NASA Astrophysics Data Analysis Program grant NNX13AF38G. Blecic holds a NASA Earth and Space Science Fellowship.

  14. Charged dust dynamics - Orbital resonance due to planetary shadows

    NASA Technical Reports Server (NTRS)

    Horanyi, M.; Burns, J. A.

    1991-01-01

    The dynamics of a weakly charged dust grain orbiting in the equatorial plane of a planet surrounded by a rigidly corotating magnetospehre is examined. It is shown that an introduction of an effectilve 1D potential causes a perturbation due to electrostatic forces, which induces a motion of the pericenter, similar to the effect of the planetary oblateness. A case is examined where the charge varies periodically due to the modulation of the photoelectron current occurring as the grain enters and leaves the planetary shadow, causing the electromagnetic perturbation to resonate with the orbital period and to modify the size and eccentricity of the orbit. This effect is demonstrated both numerically and analytically for small grains comprising the Jovian ring, showing that their resulting changes are periodic, and their amplitude is much larger than that of the periodic changes due to light-pressure perturbation or the secular changes due to resonant charge variations that develop over a comparable time span.

  15. Resonances of low orders in the planetary system of HD37124

    NASA Astrophysics Data System (ADS)

    Baluev, Roman V.

    2008-12-01

    The full set of published radial velocity data (52 measurements from Keck + 58 ones from ELODIE + 17 ones from CORALIE) for the star HD37124 is analysed. Two families of dynamically stable high-eccentricity orbital solutions for the planetary system are found. In the first one, the outer planets c and d are trapped in the 2/1 mean-motion resonance. The second family of solutions corresponds to the 5/2 mean-motion resonance between these planets. In both families, the planets are locked in (or close to) an apsidal corotation resonance. In the case of the 2/1 MMR, it is an asymmetric apsidal corotation (with the difference between the longitudes of periastra Δ ω ~ 60°), whereas in the case of the 5/2 MMR it is a symmetric antialigned one (Δ ω = 180°). It remains also possible that the two outer planets are not trapped in an orbital resonance. Then their orbital eccentricities should be relatively small (less than, say, 0.15) and the ratio of their orbital periods is unlikely to exceed 2.3 - 2.5.

  16. Resonant excitation of density waves in Saturn's rings

    NASA Astrophysics Data System (ADS)

    Griv, Evgeny

    1996-06-01

    The dynamics of regions in the Saturnian ring system with rare collisions between particles, that is, Ω 2≫ν c2, where Ω is the orbital angular frequency and νc the collision frequency, is considered. According to observations, such low optical depth regions can be found in the C ring, the inner portions of the B ring and the A ring. Kinetic theory with the Vlasov and Poisson equations is used to obtain the eigen-frequencies of oscillations propagating in the plane of the system. In the considered case of rare collisions the resulting kinetic equation for the perturbed distribution function can be solved by successive approximations, neglecting the effect of binary particle collisions in the zeroth-order approximation. An oscillating instability of the kinetic type is discussed. This instability of a particulate disk is similar to the magneto-drift instability first discovered by Krall and Rosenbluth ( Physics Fluids6, 254-265, 1963) in a nonuniform magnetic plasma, and belongs to the class of microinstabilities of an inhomogeneous plasma. The cause of the oscillating instability in Saturn's rings is a resonant interaction of drifting particles with nonaxisymmetric Jeans-stable waves at the corotation. The waves that may be produced by the corotation-resonance interaction represent non-radial normal modes of the gravitationally stable disk modified by a particle drift. It is shown that density waves are effectively excited at this resonance: the growth rate of the mode of maximum instability is large, Im ω∗˜Ω. The resonant excitation of density waves investigated in the present paper may be proposed as the cause of the irregular, small-scale ˜ 100 m structure in regions of low optical depth in Saturn's rings. It is suggested that Cassini spacecraft high-resolution images of low optical depth regions will show this kind of structure.

  17. The γ Doradus CoRoT target HD 49434. I. Results from the ground-based campaign

    NASA Astrophysics Data System (ADS)

    Uytterhoeven, K.; Mathias, P.; Poretti, E.; Rainer, M.; Martín-Ruiz, S.; Rodríguez, E.; Amado, P. J.; Le Contel, D.; Jankov, S.; Niemczura, E.; Pollard, K. R.; Brunsden, E.; Paparó, M.; Costa, V.; Valtier, J.-C.; Garrido, R.; Suárez, J. C.; Kilmartin, P. M.; Chapellier, E.; Rodríguez-López, C.; Marin, A. J.; Aceituno, F. J.; Casanova, V.; Rolland, A.; Olivares, I.

    2008-10-01

    Context: We present an extensive ground-based photometric and spectroscopic campaign of the γ Dor CoRoT target HD 49434. This campaign was a preparatory step of the CoRoT satellite observations, which occurred between October 2007 and March 2008. Aims: With satellite data, detection of low-degree pulsation modes only is achievable, and, as no filters are available, with poor identification. Ground-based data promise eventually to identify additional modes and provide extra input for the identification: spectroscopic data allows the detection of high-degree modes and an estimate of the azimuthal number m. We attempt to detect and identify as many pulsation modes as possible from the ground-based dataset of the γ Dor star HD 49434, and anticipate the CoRoT results. Methods: We searched for frequencies in the multi-colour variations, the pixel-to-pixel variations across the line profiles, and the moments variations in a large dataset, consisting of both multi-colour photometric and spectroscopic data from different observatories, using different frequency analysis methods. We performed a tentative mode identification of the spectroscopic frequencies using the Moment Method and the Intensity Period Search Method. We also completed an abundance analysis. Results: The frequency analysis clearly indicates the presence of four frequencies in the 0.2-1.7 d-1 interval, as well as six frequencies in the 5-12 d-1 domain. The low frequencies are typical of γ Dor variables, while the high frequencies are common to δ Sct pulsators. We propose that the frequency 2.666 d-1 is the rotational frequency. All modes, for which an identification was possible, appear to be high-degree modes (3 ≤ ell ≤ 8). We did not find evidence for a possible binary nature of the star HD 49434. The element abundances that we derived are consistent with values obtained in previous analyses. Conclusions: We classify the γ Dor star HD 49434 as a hybrid pulsator, which pulsates simultaneously in p

  18. Coupled orbital and spin evolution of the CoRoT-7 two-planet system using a Maxwell viscoelastic rheology

    NASA Astrophysics Data System (ADS)

    Rodríguez, A.; Callegari, N.; Correia, A. C. M.

    2016-09-01

    We investigate the orbital and rotational evolution of the CoRoT-7 two-planet system, assuming that the innermost planet behaves like a Maxwell body. We numerically resolve the coupled differential equations governing the instantaneous deformation of the inner planet together with the orbital motion of the system. We show that, depending on the relaxation time for the deformation of the planet, the orbital evolution has two distinct behaviours: for relaxation times shorter than the orbital period, we reproduce the results from classic tidal theories, for which the eccentricity is always damped. However, for longer relaxation times, the eccentricity of the inner orbit is secularly excited and can grow to high values. This mechanism provides an explanation for the present high eccentricity observed for CoRoT-7 b, as well as for other close-in super-Earths in multiple planetary systems.

  19. Periodic Variations in Ultraviolet Spectral Lines of the B0.5 Ib Star HD 64760: Evidence for Corotating Wind Streams Rooted in Surface Variations

    NASA Astrophysics Data System (ADS)

    Owocki, Stanley P.; Cranmer, Steven R.; Fullerton, Alexander W.

    1995-11-01

    We discuss recently observed periodic modulations in the UV wind lines of the B-type supergiant HD 64760, with a focus on the peculiar, upwardly bowed shape seen in isoflux contours of the absorption variations plotted against velocity and time. We show that this qualitative impression of bowed contours is quantitatively confirmed by a peak in the phase for the associated periodic variation at very nearly the same line position as the apparent bow minimum. The bowed shape is significant because it indicates that wind variations evolve both blueward and redward, i.e., toward both larger and smaller line-of-sight velocities. We show here, however, that these characteristics arise naturally from absorption by strictly accelerating corotating wind streams seen in projection against the stellar disk. The quite good agreement obtained with the observed profile variations provides strong evidence for corotating stream modulations in this wind.

  20. The magnetic Bp star 36 Lyncis. II. A spectroscopic analysis of its co-rotating disk

    NASA Astrophysics Data System (ADS)

    Smith, M. A.; Wade, G. A.; Bohlender, D. A.; Bolton, C. T.

    2006-11-01

    We report on the physical properties of the disk-like structure of B8 IIIp star 36 Lyncis from line syntheses of phase-resolved, high resolution spectra obtained from the International Ultraviolet Explorer archives and from newly obtained ground-based spectra of the Hα absorption profile. This disk is highly inclined to the rotational axis and betrays its existence every half rotation cycle as one of two opposing sectors pass in front of the star. Although the disk absorption spectrum is at least ten times too weak to be visible in optical iron lines during these occultations, its properties can be readily examined in a large number of UV "iron curtain" lines because of their higher opacities. The UV Fe II and Fe III lines in particular permit a determination of the disk temperature: 7500±500 K and a column density of 3-1.5+3×1020 cm-2. The analysis of the variations of the UV resonance lines brings out some interesting details about the radiative properties of the disks: (1) they are optically thick in the C IV and Si IV doublets, (2) the range of excitation of the UV resonance lines is larger at the primary occultation (φ = 0.00) than at the secondary one, and (3) the relative strengths of the absorption peaks for the two occultations varies substantially from line to line. We have modeled the absorptions of the UV C IV resonance and Hα absorptions by means of a simulated disk with opaque and translucent components. Our simulations suggest that a gap separates the star and the inner edge of the disk. The disk extends radially out to ≥10 R*. The disk scale height perpendicular to the plane is ≈1 R*. However, the sector causing the primary occultation is about four times thicker than the opposite sector. The C IV scattering region extends to a larger height than the Hα region does, probably because it results from shock heating far from the cooler disk plane.

  1. Constraining magnetic-activity modulations in three solar-like stars observed by CoRoT and NARVAL

    NASA Astrophysics Data System (ADS)

    Mathur, S.; García, R. A.; Morgenthaler, A.; Salabert, D.; Petit, P.; Ballot, J.; Régulo, C.; Catala, C.

    2013-02-01

    Context. Stellar activity cycles are the manifestation of dynamo process running in the stellar interiors. They have been observed from years to decades thanks to the measurement of stellar magnetic proxies on the surface of the stars, such as the chromospheric and X-ray emissions, and to the measurement of the magnetic field with spectropolarimetry. However, all of these measurements rely on external features that cannot be visible during, for example, a Maunder-type minimum. With the advent of long observations provided by space asteroseismic missions, it has been possible to penetrate the stars and study their properties. Moreover, the acoustic-mode properties are also perturbed by the presence of these dynamos. Aims: We track the temporal variations of the amplitudes and frequencies of acoustic modes allowing us to search for signature of magnetic activity cycles, as has already been done in the Sun and in the CoRoT target HD 49933. Methods: We used asteroseimic tools and more classical spectroscopic measurements performed with the NARVAL spectropolarimeter to check that there are hints of any activity cycle in three solar-like stars observed continuously for more than 117 days by the CoRoT satellite: HD 49385, HD 181420, and HD 52265. To consider that we have found a hint of magnetic activity in a star we require finding a change in the amplitude of the p modes that should be anti-correlated with a change in their frequency shifts, as well as a change in the spectroscopic observations in the same direction as the asteroseismic data. Results: Our analysis gives very small variation in the seismic parameters preventing us from detecting any magnetic modulation. However, we are able to provide a lower limit of any magnetic-activity change in the three stars that should be longer than 120 days, which is the length of the time series. Moreover we computed the upper limit for the line-of-sight magnetic field component being 1, 3, and 0.6 G for HD 49385, HD 181420

  2. Seismic and spectroscopic characterization of the solar-like pulsating CoRoT target HD 49385

    NASA Astrophysics Data System (ADS)

    Deheuvels, S.; Bruntt, H.; Michel, E.; Barban, C.; Verner, G.; Régulo, C.; Mosser, B.; Mathur, S.; Gaulme, P.; Garcia, R. A.; Boumier, P.; Appourchaux, T.; Samadi, R.; Catala, C.; Baudin, F.; Baglin, A.; Auvergne, M.; Roxburgh, I. W.; Pérez Hernández, F.

    2010-06-01

    Context. The star HD 49385 is the first G-type solar-like pulsator observed in the seismology field of the space telescope CoRoT. The satellite collected 137 days of high-precision photometric data on this star, confirming that it presents solar-like oscillations. HD 49385 was also observed in spectroscopy with the NARVAL spectrograph in January 2009. Aims: Our goal is to characterize HD 49385 using both spectroscopic and seismic data. Methods: The fundamental stellar parameters of HD 49385 are derived with the semi-automatic software VWA, and the projected rotational velocity is estimated by fitting synthetic profiles to isolated lines in the observed spectrum. A maximum likelihood estimation is used to determine the parameters of the observed p modes. We perform a global fit, in which modes are fitted simultaneously over nine radial orders, with degrees ranging from ℓ = 0 to ℓ = 3 (36 individual modes). Results: Precise estimates of the atmospheric parameters (Teff, [M/H], log g) and of the ν sin i of HD 49385 are obtained. The seismic analysis of the star leads to a clear identification of the modes for degrees ℓ = 0,1,2. Around the maximum of the signal (ν ≃ 1013 μHz), some peaks are found significant and compatible with the expected characteristics of ℓ = 3 modes. Our fit yields robust estimates of the frequencies, linewidths and amplitudes of the modes. We find amplitudes of ~5.6 ± 0.8 ppm for radial modes at the maximum of the signal. The lifetimes of the modes range from one day (at high frequency) to a bit more than two days (at low frequency). Significant peaks are found outside the identified ridges and are fitted. They are attributed to mixed modes. Based on data obtained from the CoRoT (Convection, Rotation and planetary Transits) space mission, developed by the French Space agency CNES in collaboration with the Science Programs of ESA, Austria, Belgium, Brazil, Germany and Spain.Based on data obtained using the Télescope Bernard Lyot at

  3. Rossby-wave driven stirring of the UTLS - a detailed view on the intricately layered structure by the 3-D imaging limb-sounder GLORIA

    NASA Astrophysics Data System (ADS)

    Ungermann, J.; Friedl-Vallon, F.; Hoepfner, M.; Oelhaf, H.; Preusse, P.; Riese, M.

    2014-12-01

    The Gimballed Limb Radiance Imager of the Atmosphere (GLORIA) is a new instrument that combines a classical Fourier transform spectrometer (FTS) with a 2-D detector array. Imaging allows the spatial sampling to be improved by up to an order of magnitude when compared to a limb scanning instrument. GLORIA is designed to operate on various high altitude research platforms. The instrument is a joint development of the German Helmholtz Large Research Facilities Karlsruhe Institute of Technology (KIT) and Research Centre Juelich (FZJ). GLORIA builds upon the heritage of KIT and FZJ in developing and operating IR limb sounders (MIPAS, CRISTA). In Summer 2012, GLORIA was an integral part of the first large missions for the German research aircraft HALO dedicated to atmospheric research, TACTS and ESMVAL. The data span latitudes from 80°N to 65°S and include several tomographic flight patterns that allow the 3-D reconstruction of observed air masses. We provide an overview of the heterogeneous structure of the upper troposphere/lower stratosphere (UTLS) as observed over Europe. Retrieved water vapor and ozone are used to identify the tropospheric or stratospheric character of air masses and can thus be used to visualize the multi-species 2-D (and partly 3-D) chemical structure of the UTLS. A highly intricate structure is found consisting often of fine-scale layers extending only several hundred meters in the vertical. These horizontally large-scale structures are thus below the typical vertical resolution of current chemistry climate models. Trajectory studies reveal the origin of the filaments to be Rossby wave-breaking events over the Pacific and Atlantic that cause tropical air stemming from the general area of the Asian monsoon to be mixed across the jet-stream into the subtropical lowermost stratosphere. These results demonstrate a rich spatial structure of the UTLS region at the subtropical jet, where the tropopause break is perturbed by breaking Rossby waves. The

  4. Comet-like tail-formation of exospheres of hot rocky exoplanets: Possible implications for CoRoT-7b

    NASA Astrophysics Data System (ADS)

    Mura, A.; Wurz, P.; Schneider, J.; Lammer, H.; Grießmeier, J.-M.; Khodachenko, M. L.; Weingrill, J.; Guenther, E.; Cabrera, J.; Erikson, A.; Fridlund, M.; Milillo, A.; Rauer, H.; von Paris, Ph.

    2011-01-01

    In this study, the interaction of stellar wind plasma with the exosphere and possibly with the planetary magnetospheric environment of close-in rocky exoplanets is investigated. In particular, we focus on the "super-Earth" CoRoT-7b, which has been recently discovered by the CoRoT space observatory. The physical properties of such a planet, with an orbital distance of about 0.017 AU from its host star, may most likely resemble a big and more massive Mercury-type planet in the sense that it most likely releases its surface elements into space. Based on the present knowledge of CoRoT-7b and drawing on the analogy to Solar System planets, we use numerical models to simulate exospheric and magnetospheric distributions of different particle populations, among which are neutral sodium and ionised calcium and magnesium. We find that, for most species, the atmospheric loss rate in such an extreme environment can be very high, so that a neutral and an ionised tail of escaping particles will form. Depending on the planetary composition we postulate the presence of a sodium tail, similar to that of Mercury but shorter due to the shorter Na lifetime, and of an extended magnetospheric distribution of ionised calcium or magnesium. The feasibility of observation of such populations is also discussed.

  5. SMEI 3D RECONSTRUCTION OF A CORONAL MASS EJECTION INTERACTING WITH A COROTATING SOLAR WIND DENSITY ENHANCEMENT: THE 2008 APRIL 26 CME

    SciTech Connect

    Jackson, B. V.; Buffington, A.; Hick, P. P.; Clover, J. M.; Bisi, M. M.; Webb, D. F.

    2010-12-01

    The Solar Mass Ejection Imager (SMEI) has recorded the brightness responses of hundreds of interplanetary coronal mass ejections (CMEs) in the interplanetary medium. Using a three-dimensional (3D) reconstruction technique that derives its perspective views from outward-flowing solar wind, analysis of SMEI data has revealed the shapes, extents, and masses of CMEs. Here, for the first time, and using SMEI data, we report on the 3D reconstruction of a CME that intersects a corotating region marked by a curved density enhancement in the ecliptic. Both the CME and the corotating region are reconstructed and demonstrate that the CME disrupts the otherwise regular density pattern of the corotating material. Most of the dense CME material passes north of the ecliptic and east of the Sun-Earth line: thus, in situ measurements in the ecliptic near Earth and at the Solar-TErrestrial RElations Observatory Behind spacecraft show the CME as a minor density increase in the solar wind. The mass of the dense portion of the CME is consistent with that measured by the Large Angle Spectrometric Coronagraph on board the Solar and Heliospheric Observatory spacecraft, and is comparable to the masses of many other three-dimensionally reconstructed solar wind features at 1 AU observed in SMEI 3D reconstructions.

  6. Optical resonator

    NASA Technical Reports Server (NTRS)

    Taghavi-Larigani, Shervin (Inventor); Vanzyl, Jakob J. (Inventor); Yariv, Amnon (Inventor)

    2006-01-01

    The invention discloses a semi-ring Fabry-Perot (SRFP) optical resonator structure comprising a medium including an edge forming a reflective facet and a waveguide within the medium, the waveguide having opposing ends formed by the reflective facet. The performance of the SRFP resonator can be further enhanced by including a Mach-Zehnder interferometer in the waveguide on one side of the gain medium. The optical resonator can be employed in a variety of optical devices. Laser structures using at least one SRFP resonator are disclosed where the resonators are disposed on opposite sides of a gain medium. Other laser structures employing one or more resonators on one side of a gain region are also disclosed.

  7. Resonance scraping

    SciTech Connect

    Collins, T.

    1986-06-01

    Protons lost in a ring leave at a few preferred locations, determined by some non-linear property of the dipoles. This paper suggests taking control of lost protons by beating the magnets at their own game - by means of a designed resonance used as a beam scraper. It is a study of suitable resonances, including estimates of the required multipole element strengths. The appropriate resonances are two-dimensional. A large number of figures is included.

  8. Oscillations and resonances in electrostatically supported dust rings

    SciTech Connect

    Melandsoe, F.; Havnes, O. )

    1991-04-01

    The authors show that planetary dust rings which are electrostatically supported, i.e., the ring thickness is determined by a balance between the component of gravity toward the central plane and the expanding electrostatic force on the dust, will oscillate if the ambient plasma conditions are changed. The oscillation frequency of tenuous clouds is found analytically to be {radical}3 times the local Kepler frequency. This is confirmed by numerical results which also show that the oscillation frequency decreases for denser rings. While a tenuous ring has one oscillation frequency throughout, the different parts of a dense ring, e.g., the central density and ring edge position, oscillate with different frequencies. The oscillations become increasingly complex for denser rings. They have concentrated on tenuous rings and looked for resonances between the oscillation frequency {radical}3 {Omega}{sub K} and other naturally occurring frequencies in a ring system. They have investigated the consequences if magnetospheric corotating plasma is not symmetric in azimuth. This can lead to resonances with the vertical dust profile oscillaitons of orbiting dust rings. They determine the major resonance distances around Jupiter and Saturn and find striking coincidences with features in both ring systems which indicate that such resonances may have effects beyond that of simply uncreasing the thickness of a ring at a resonance distance.

  9. FUNDAMENTAL PROPERTIES OF STARS USING ASTEROSEISMOLOGY FROM KEPLER AND CoRoT AND INTERFEROMETRY FROM THE CHARA ARRAY

    SciTech Connect

    Huber, D.; Ireland, M. J.; Bedding, T. R.; Maestro, V.; White, T. R.; Brandao, I. M.; Sousa, S. G.; Cunha, M. S.; Piau, L.; Bruntt, H.; Aguirre, V. Silva; Christensen-Dalsgaard, J.; Casagrande, L.; Molenda-Zakowicz, J.; Barclay, T.; De Ridder, J.; Farrington, C. D.; Frasca, A.; and others

    2012-11-20

    We present results of a long-baseline interferometry campaign using the PAVO beam combiner at the CHARA Array to measure the angular sizes of five main-sequence stars, one subgiant and four red giant stars for which solar-like oscillations have been detected by either Kepler or CoRoT. By combining interferometric angular diameters, Hipparcos parallaxes, asteroseismic densities, bolometric fluxes, and high-resolution spectroscopy, we derive a full set of near-model-independent fundamental properties for the sample. We first use these properties to test asteroseismic scaling relations for the frequency of maximum power ({nu}{sub max}) and the large frequency separation ({Delta}{nu}). We find excellent agreement within the observational uncertainties, and empirically show that simple estimates of asteroseismic radii for main-sequence stars are accurate to {approx}< 4%. We furthermore find good agreement of our measured effective temperatures with spectroscopic and photometric estimates with mean deviations for stars between T {sub eff} = 4600-6200 K of -22 {+-} 32 K (with a scatter of 97 K) and -58 {+-} 31 K (with a scatter of 93 K), respectively. Finally, we present a first comparison with evolutionary models, and find differences between observed and theoretical properties for the metal-rich main-sequence star HD 173701. We conclude that the constraints presented in this study will have strong potential for testing stellar model physics, in particular when combined with detailed modeling of individual oscillation frequencies.

  10. Photometric detections of secondary and primary transits of extra-solar planet CoRoT-1b

    NASA Astrophysics Data System (ADS)

    Gibson, Stephanie

    The goal of this project is to determine the observational limitations of photometrically detecting secondary eclipses of exoplanets from a 0.6-meter ground-based telescope and to place constraints on the planet's thermal properties. Secondary eclipses have been successfully measured via space-based telescopes such as the Spitzer Space Telescope. Time on space-based telescopes is limited and highly competitive. Smaller, ground-based telescopes are more common and thus it is easier for observers to schedule large blocks of time on these telescopes. These smaller telescopes also can observe exoplanets in the z' band on which the planets' thermal emission begins to become significant and would be more useful for building up large samples of data. A primary transit in B, V, and z' filters and a secondary transit in the z' filter of CoRoT-1b are analyzed in this thesis. Constraints on the planet's temperature, albedo and energy transports can be found from analysis of these transits.

  11. VizieR Online Data Catalog: Limb-darkening for CoRoT, Kepler, Spitzer (Claret+, 2012)

    NASA Astrophysics Data System (ADS)

    Claret, A.; Hauschildt, P. H.; Witte, S.

    2012-09-01

    The knowledge of how the specific intensity is distributed over the stellar disk is crucial for interpreting the light curves of extrasolar transiting planets, double-lined eclipsing binaries, and other astrophysical phenomena. To provide theoretical inputs for light curve modelling codes, we present new calculations of limb-darkening coefficients for the spherically symmetric PHOENIX models. The limb-darkening coefficients were computed by covering the transmission curves of Kepler, CoRoT, and Spitzer space missions, as well as the passbands of the Stromgren, Johnson-Cousins, Sloan, and 2MASS. These computations adopted the least-square method. In addition, we also calculated the linear and bi-parametric approximations by adopting the flux conservation method as an additional tool for estimating the theoretical error bars in the limb-darkening coefficients. Six laws were used to describe the specific intensity distribution: linear, quadratic, square root, logarithmic, exponential, and a more general one with 4 terms. The computations are presented for the solar chemical composition, with logg varying between 2.5 and 5.5 and effective temperatures between 1500K-4800K. The adopted Microturbulent velocity and the mixing-length parameters are 2.0km/s and 2.0, respectively. Model are for solar metallicity. (17 data files).

  12. Corotational nonlinear analyses of laminated shell structures using a 4-node quadrilateral flat shell element with drilling stiffness

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Sun, Qin

    2014-06-01

    A new 4-node quadrilateral flat shell element is developed for geometrically nonlinear analyses of thin and moderately thick laminated shell structures. The flat shell element is constructed by combining a quadrilateral area coordinate method (QAC) based membrane element AGQ6-II, and a Timoshenko beam function (TBF) method based shear deformable plate bending element ARS-Q12. In order to model folded plates and connect with beam elements, the drilling stiffness is added to the element stiffness matrix based on the mixed variational principle. The transverse shear rigidity matrix, based on the first-order shear deformation theory (FSDT), for the laminated composite plate is evaluated using the transverse equilibrium conditions, while the shear correction factors are not needed. The conventional TBF methods are also modified to efficiently calculate the element stiffness for laminate. The new shell element is extended to large deflection and post-buckling analyses of isotropic and laminated composite shells based on the element independent corotational formulation. Numerical results show that the present shell element has an excellent numerical performance for the test examples, and is applicable to stiffened plates.

  13. Exploring the sources of p-mode frequency shifts in the CoRoT target HD 49933

    NASA Astrophysics Data System (ADS)

    Liu, Zhi-E.; Bi, Shao-Lan; Yang, Wu-Ming; Li, Tan-Da; Liu, Kang; Tian, Zhi-Jia; Ge, Zhi-Shuai; Yu, Jie

    2014-06-01

    Oscillations of the solar-like star HD 49933 have been thoroughly observed by CoRot. Two dozen frequency shifts, which are closely related to the change in magnetic activity, have been measured. To explore the effects of magnetic activity on frequency shifts, we calculate frequency shifts for the radial and l = 1 p-modes of HD 49933 with the general variational method, which evaluates the shifts using a spatial integral of the product of a kernel and some sources. The theoretical frequency shifts reproduce the observation well. The magnitudes and positions of the sources are determined according to a χ2 criterion. We predict the source that contributes to both the l = 0 and l = 1 modes is located 0.48 - 0.62 Mm below the surface of the star. In addition, based on the assumption that A0 is proportional to the change in the MgII activity index ΔiMgII, we obtain that the change in MgII index between the minimum and maximum of the cycle during the period of HD 49933 is about 0.665. The magnitude of the frequency shifts compared to the Sun already demonstrates that HD 49933 is much more active than the Sun, which is further confirmed in this paper. Furthermore, our calculation of the frequency shifts for l = 1 modes indicates the variation of turbulent velocity in the stellar convective zone may be an important source for the l = 1 shifts.

  14. Study of the geoeffectiveness of coronal mass ejections, corotating interaction regions and their associated structures observed during Solar Cycle 23

    NASA Astrophysics Data System (ADS)

    Badruddin, A.; Falak, Z.

    2016-08-01

    The interplanetary coronal mass ejections (ICMEs) and the corotating interaction regions (CIRs) are the two most important structures of the interplanetary medium affecting the Earth and the near-Earth space environment. We study the solar wind-magnetosphere coupling during the passage of ICMEs and CIRs, in the Solar Cycle 23 (Jan. 1995-Dec. 2009), and their relative geoeffectiveness. We utilize the timings of different features of these structures, their arrival and duration. As geomagnetic parameter, we utilize high time resolution data of Dst and AE indices. In addition to these geomagnetic indices, we utilize the simultaneous and similar time resolution data of interplanetary plasma and field, namely, solar wind velocity, interplanetary magnetic field, its north-south component and dawn-dusk electric field. We apply the method of superposed epoch analysis. Utilizing the properties of various structures during the passage of ICMEs and CIRs, and variations observed in plasma and field parameters during their passage along with the simultaneous changes observed in geomagnetic parameters, we identify the interplanetary conditions, plasma/field parameters and their relative importance in solar wind-magnetosphere coupling. Geospace consequences of ICMEs and CIRs, and the implications of these results for solar wind-magnetosphere coupling are discussed.

  15. Observations of corotating solar wind structures at radio sounding by signals of the Rosetta and Mars Express spacecraft

    NASA Astrophysics Data System (ADS)

    Efimov, A. I.; Lukanina, L. A.; Samoznaev, L. N.; Chashei, I. V.; Bird, M. K.; Pätzold, M.

    2016-05-01

    In the implementation of the space projects Rosetta and Mars Express, a large-scale series of experiments has been carried out on radio sounding circumsolar plasma by decimeter ( S-band) and centimeter ( X-band) signals of the Rosetta comet probe (from October 3 to October 31, 2010) and the Mars Express satellite of Mars (from December 25, 2010 to March 27, 2011). It was found that in the phase of ingress the spacecraft behind the Sun, the intensity of the frequency fluctuations increases in accordance with a power function whose argument is the solar offset distance of radio ray path, and when the spacecraft is removed from the Sun (the egress phase), frequency fluctuations are reduced. Periodic strong increases in the fluctuation level, exceeding by a factor of 3-12 the background values of this value determined by the regular radial dependences, are imposed on the regular dependences. It was found that increasing the fluctuations of radio waves alternates with the periodicity m × T or n × T, where m = 1/2, n = 1, and T is the synodic period of the Sun's rotation ( T ≈ 27 days). It was shown that the corotating structures associated with the interaction regions of different speed fluxes are formed in the area of solar wind acceleration and at distances of 6-20 solar radii already have a quasi-stationary character.

  16. The optimization of Blister Disk geometry for mixing performance in co-rotating twin-screw extruder

    NASA Astrophysics Data System (ADS)

    Matsumoto, Koki; Kayamori, Natsuki; Tanaka, Tatsuya; Arao, Yoshihiko

    2015-05-01

    Extensional flow has been taken notice as the more efficient solution for improving the dispersion of nanocomposites than shear flow. One of the production processes of nanocomposites is melt extrusion with co-rotating twin-screw extruder (TSE) which is superior in terms of productivity and mixing performance. Then, we focused on "Blister Disk" which had many small holes for generating the extensional flow. However, the influences on the mixing performance by changing the geometry of Blister Disk have not been investigated as far as we know. Therefore, the objective of this study is the optimization of Blister Disk geometry (e.g. hole numbers, hole diameter and disk length) for improving the dispersion of nanocomposites. Primary, the extensional flow state was investigated at the Blister Disk with FEM analysis. Secondly, to validate the simulation results experimentally, the polypropylene reinforced multi-walled carbon nanotube (PP/CNT nanocomposite) was used as the model of nanocomposite, and the dispersion state of CNT was investigated by morphological observation. As the result of these experiments, the better dispersion state of CNT was obtained as total permeation area and shorter hole length of Blister Disk was smaller because extensional and shear stress were increased.

  17. Counterstreaming suprathermal electron events upstream of corotating shocks in the solar wind beyond [approximately]2 AU: Ulysses

    SciTech Connect

    Gosling, J.T.; Bame, S.J.; Feldman, W.C.; Mcomas, D.J.; Phillips, J.L. ); Goldstein, B.E. )

    1993-11-05

    Enhanced fluxes of suprathermal electrons are commonly observed upstream of corotating forward and reverse shocks in the solar wind at heliocentric distances beyond [approximately]2 AU by the Los Alamos plasma experiment on Ulysses. The average duration of these events, which are most intense immediately upstream from the shocks and which fade with increasing distance from them, is [approximately]2.4 days near 5 AU. These events are caused by the leakage of shock-heated electrons into the upstream region. The upstream regions of these shocks face back toward the SUN along the interplanetary magnetic field, so these leaked electrons commonly counterstream relative to the normal solar wind electron heat flux. The observations suggest that conservation of magnetic moment and scattering typically limit the sunward propagation of these electrons as beams to field-aligned distances of [approximately]15 AU. Although it seems unlikely that these shock-associated events are an important source of counterstreaming events near 1 AU, remnants of the backstreaming beams may contribute importantly to the diffuse solar wind halo electron population there. 13 refs., 3 figs.

  18. On the origin of the MeV energy nucleon flux associated with CIRs. [plasma interaction regions corotating with sun

    NASA Technical Reports Server (NTRS)

    Christon, S. P.

    1981-01-01

    Measurements of recurrent enhancements of interplanetary nucleon flux in the MeV energy range are presented and interpreted. The features recur at the solar rotation period in association with stream-stream plasma interaction regions corotating with the sun. At distances from the sun less than 1 AU, the maximum intensities of the hydrogen and helium components increase with increasing distance between 300%/AU and 600%/AU. A model is proposed which predicts the acceleration of nuclei from keV plasma energies to MeV energies by means of transit time damping of magnetosonic waves as solar wind plasma flows from the sun. Numerical solutions of the transport equation are derived to demonstrate that the model does not reproduce radial variations of hydrogen and helium fluxes, and estimates are made of the radial diffusive mean free path. Finally, the observations are found to be consistent with nucleon acceleration at the CIR shocks beyond 1 AU with subsequent diffusion toward the sun.

  19. Spot modelling of periodic weak-line T Tauri stars observed by CoRoT in NGC 2264

    NASA Astrophysics Data System (ADS)

    Lanza, A. F.; Flaccomio, E.; Messina, S.; Micela, G.; Pagano, I.; Leto, G.

    2016-08-01

    Context. The space telescope CoRoT has provided light curves of T Tauri stars belonging to the star-forming region of NGC 2264 with unprecedented continuity and precision in the framework of a coordinated multi-wavelength observational project. Aims: We perform spot modelling of the optical light curves of five weak-line T Tauri stars whose variability is dominated by starspots. Methods: We apply two-spot and evolving single-spot models in the framework of a Bayesian Markov chain Monte Carlo approach to derive the a posteriori distributions of the starspot parameters and the inclination of the star rotation axis. We focus on the rotation periods of the spots that can provide evidence for differential rotation in those stars. Results: We find meaningful results in the case of three stars with an inclination higher than 50° and a slow variation of the light curve amplitude. The relative difference of the spot rotation periods ranges from 0.02 to 0.05 that is 3-10 times larger than the amplitude of the differential rotation found in similar stars with Doppler imaging techniques. Conclusions: We conclude that the intrinsic starspot evolution, although very slow, has a significant impact on the determination of the differential rotation by means of our spot modelling approach. We estimate typical timescales for the evolution of the starspot pattern between ~20 and ~50 rotation periods in our stars.

  20. Analysis of Solar Wind Plasma Properties of Co-Rotating Interaction Regions at Mars with MSL/RAD

    NASA Astrophysics Data System (ADS)

    Lohf, H.; Kohler, J.; Zeitlin, C. J.; Ehresmann, B.; Guo, J.; Wimmer-Schweingruber, R. F.; Hassler, D.; Reitz, G.; Posner, A.; Heber, B.; Appel, J. K.; Matthiae, D.; Brinza, D. E.; Weigle, E.; Böttcher, S. I.; Burmeister, S.; Martin-Garcia, C.; Boehm, E.; Rafkin, S. C.; Kahanpää, H.; Martín-Torres, J.; Zorzano, M. P.

    2014-12-01

    The measurements of the Radiation Assessment Detector (RAD) onboard Mars Science Laboratory's rover Curiosity have given us the very first opportunity to evaluate the radiation environment on the surface of Mars, which consists mostly of Galactic Cosmic Rays (GCRs) and secondary particles created in the Martian Atmosphere. The solar wind can have an influence on the modulation of the GCR, e.g. when the fast solar wind (~ 750 km/s) interacts with the slow solar wind (~ 400 km/s) at so-called Stream Interaction Regions (SIRs) resulting in an enhancement of the local magnetic field which could affect the shielding of GCRs. SIRs often occur periodically as Co-rotating Interaction Regions (CIRs) which may-be observed at Mars as a decrease in the radiation data measured by MSL/RAD. Considering the difference of the Earth-Mars orbit, we correlate these in-situ radiation data at Mars with the solar wind properties measured by spacecrafts at 1 AU, with the aim to eventually determine the solar wind properties at Mars based on MSL/RAD measurements.

  1. Counterstreaming suprathermal electron events upstream of corotating shocks in the solar wind beyond approximately 2 AU: Ulysses

    NASA Technical Reports Server (NTRS)

    Gosling, J. T.; Bame, S. J.; Feldman, W. C.; Mccomas, D. J.; Phillips, J. L.; Goldstein, B. E.

    1993-01-01

    Enhanced fluxes of suprathermal electrons are commonly observed upstream of corotating forward and reverse shocks in the solar wind at heliocentric distances beyond approximately 2 AU by the Los Alamos plasma experiment on Ulysses. The average duration of these events, which are most intense immediately upstream from the shocks and which fade with increasing distance from them, is approximately 2.4 days near 5 AU. These events are caused by the leakage of shock-heated electrons into the upstream region. The upstream regions of these shocks face back toward the Sun along the interplanetary magnetic field, so these leaked electrons commonly counterstream relative to the normal solar wind electron heat flux. The observations suggest that conservation of magnetic moment and scattering typically limit the sunward propagation of these electrons as beams to field-aligned distances of approximately 15 AU. Although it seems unlikely that these shock-associated events are an important source of counterstreaming events near 1 AU, remnants of the backstreaming beams may contribute importantly to the diffuse solar wind halo electron population there.

  2. Field-Aligned Currents in Saturn's Southern Nightside Magnetosphere: Sub-Corotation and Planetary Period Oscillation Currents

    NASA Astrophysics Data System (ADS)

    Hunt, G. J.; Cowley, S. W. H.; Provan, G.; Bunce, E. J.; Alexeev, I. I.; Belenkaya, E. S.; Kalegaev, V. V.; Dougherty, M. K.; Coates, A. J.

    2014-12-01

    We have investigated azimuthal magnetic field data showing the presence of field-aligned current sheets on 31 similar Cassini passes during the 2008 interval of near polar orbits across Saturn's southern post-midnight auroral region at radial distances ~3-5 RS. The currents are found to be strongly modulated in magnitude, form, and position by the phase of the southern planetary period oscillations (PPOs). We separate currents independent of PPO phase from PPO-related currents, by exploiting the expected anti-symmetry of the latter with respect to PPO phase. The PPO-independent current system is thought to be associated mainly with sub-corotation of magnetospheric plasma, and consists of a weak distributed downward current over the whole polar region, enhanced downward currents in a layer mapping to the outer magnetosphere where the ionospheric conductivity is elevated, and a main upward-directed current layer ~2° wide centered at ~18° co-latitude with respect to the southern pole carrying ~2.5 MA per radian of azimuth. The latter current maps to the main region of the hot plasma in Saturn's magnetosphere and is co-located with Saturn's main UV oval in this hemisphere and local time sector. No major currents are detected mapping to the inner equatorial magnetosphere ~4-8 RS dominated by cool Enceladus plasma. The PPO-related currents map to the inner part of the hot plasma region at ~18°-20° co-latitude, and carry rotating upward and downward currents peaking at ~1.7 MA rad-1. The co-latitude of the current layers is also modulated by 1° amplitude in the PPO cycle, with maximum equatorward and poleward excursions adjacent to maximum upward and downward PPO currents, respectively. It is shown that this phasing requires the current system to be driven upward from the planetary atmosphere rather than downward from the magnetosphere.

  3. THE DISCOVERY OF A STRONG MAGNETIC FIELD AND COROTATING MAGNETOSPHERE IN THE HELIUM-WEAK STAR HD 176582

    SciTech Connect

    Bohlender, David A.; Monin, Dmitry

    2011-05-15

    We report the detection of a strong, reversing magnetic field and variable H{alpha} emission in the bright helium-weak star HD 176582 (HR 7185). Spectrum, magnetic, and photometric variability of the star are all consistent with a precisely determined period of 1.5819840 {+-} 0.0000030 days which we assume to be the rotation period of the star. From the magnetic field curve, and assuming a simple dipolar field geometry, we derive a polar field strength of approximately 7 kG and a lower limit of 52 deg. for the inclination of the rotation axis. However, based on the behavior of the H{alpha} emission, we adopt a large inclination angle of 85 deg. and this leads to a large magnetic obliquity of 77{sup 0}. The H{alpha} emission arises from two distinct regions located at the intersections of the magnetic and rotation equators and which corotate with the star at a distance of about 3.5 R{sub *} above its surface. We estimate that the emitting regions have radial and meridional sizes on the order of 2 R{sub *} and azimuthal extents (perpendicular to the magnetic equator) of less than approximately 0.6 R{sub *}. HD 176582 therefore appears to show many of the cool magnetospheric phenomena as that displayed by other magnetic helium-weak and helium-strong stars such as the prototypical helium-strong star {sigma} Ori E. The observations are consistent with current models of magnetically confined winds and rigidly rotating magnetospheres for magnetic Bp stars.

  4. A modeling study on the effects of MJO and equatorial Rossby waves on tropical cyclone genesis over the western North Pacific in June 2004

    NASA Astrophysics Data System (ADS)

    Ching, Lin; Sui, Chung-Hsiung; Yang, Ming-Jen; Lin, Pay-Liam

    2015-12-01

    This study investigates the influence of the Madden Julian oscillations (MJO) and equatorial Rossby (ER) waves on tropical cyclone (TC) formation in western Pacific during June 2004 through one control and three wave experiments for each of the five TCs. The control experiment reasonably simulates the formation of five TCs. In the corresponding wave experiments, the MJO, ER waves, and both the MJO and ER waves are removed, from the initial fields and lateral boundary conditions, respectively. The differences of simulated TC intensity between the control and corresponding wave experiments provide a quantitative assessment of the relative contribution of each wave to TC formation. In the wave experiments with the MJO removed, three of the five TCs are weakened, and the remaining two (TC A and B) grow stronger due to an altered background flow that steered the TCs into more favorable oceanic regions. For the wave experiments with ER waves removed, three of the five simulated TCs become weaker (TC A, C, and E). TC D develops into a tropical storm because of a dominant influence from active synoptic-scale disturbance. The results indicate that both the MJO and ER waves have an important modulating effect on TC formation. In addition to the influence from the MJO, ER and synoptic-scale waves, local processes may dominate in TC formation; for the example of TC B, none of the waves positively influence the formation in significant ways. The present modeling approach provides a quantitative assessment of the relative contribution of tropical wave disturbances to TC formation.

  5. Effects of moisture feedback in a frictional coupled Kelvin-Rossby wave model and implication in the Madden-Julian oscillation dynamics

    NASA Astrophysics Data System (ADS)

    Liu, Fei; Wang, Bin

    2016-03-01

    The authors extend the original frictional wave dynamics and implement the moisture feedback (MF) to explore the effects of planetary boundary layer (PBL) process and the MF on the Madden-Julian Oscillation (MJO). This new system develops the original frictional wave dynamics by including the moisture tendency term (or the MF mode), along with a parameterized precipitation based on the Betts-Miller scheme. The linear instability analysis of this model provides solutions to elucidate the behaviors of the "pure" frictional convergence (FC) mode and the "pure" MF mode, respectively, as well as the behaviors of the combined FC-MF mode or the dynamical moisture mode. These results show that without the PBL frictional moisture convergence, the MF mode is nearly stationary and damped. Not only does the PBL frictional feedback make the damping MF mode grow with preferred planetary scale but it also enables the nearly stationary MF mode to move eastward slowly, resulting in an oscillation with a period of 30-90 days. This finding suggests the important role of the frictional feedback in generating eastward propagating unstable modes and selecting the preferred planetary scales. The MF process slows down the eastward-propagating short-wave FC mode by delaying the occurrence of deep convection and by enhancing the Rossby wave component. However, the longest wave (wavenumber one) is insensitive to the MF or the convective adjustment time, indicating that the unstable longest wave is primarily controlled by PBL frictional feedback process. Implications of these theoretical results in MJO simulation in general circulation models are discussed.

  6. Modulation of equatorial Pacific westerly/easterly wind events by the Madden-Julian oscillation and convectively-coupled Rossby waves

    NASA Astrophysics Data System (ADS)

    Puy, Martin; Vialard, J.; Lengaigne, M.; Guilyardi, E.

    2016-04-01

    Synoptic wind events in the equatorial Pacific strongly influence the El Niño/Southern Oscillation (ENSO) evolution. This paper characterizes the spatio-temporal distribution of Easterly (EWEs) and Westerly Wind Events (WWEs) and quantifies their relationship with intraseasonal and interannual large-scale climate variability. We unambiguously demonstrate that the Madden-Julian Oscillation (MJO) and Convectively-coupled Rossby Waves (CRW) modulate both WWEs and EWEs occurrence probability. 86 % of WWEs occur within convective MJO and/or CRW phases and 83 % of EWEs occur within the suppressed phase of MJO and/or CRW. 41 % of WWEs and 26 % of EWEs are in particular associated with the combined occurrence of a CRW/MJO, far more than what would be expected from a random distribution (3 %). Wind events embedded within MJO phases also have a stronger impact on the ocean, due to a tendency to have a larger amplitude, zonal extent and longer duration. These findings are robust irrespective of the wind events and MJO/CRW detection methods. While WWEs and EWEs behave rather symmetrically with respect to MJO/CRW activity, the impact of ENSO on wind events is asymmetrical. The WWEs occurrence probability indeed increases when the warm pool is displaced eastward during El Niño events, an increase that can partly be related to interannual modulation of the MJO/CRW activity in the western Pacific. On the other hand, the EWEs modulation by ENSO is less robust, and strongly depends on the wind event detection method. The consequences of these results for ENSO predictability are discussed.

  7. The power of low-resolution spectroscopy: On the spectral classification of planet candidates in the ground-based CoRoT follow-up

    NASA Astrophysics Data System (ADS)

    Ammler-von Eiff, M.; Sebastian, D.; Guenther, E. W.; Stecklum, B.; Cabrera, J.

    2015-02-01

    Planetary transits detected by the CoRoT mission can be mimicked by a low-mass star in orbit around a giant star. Spectral classification helps to identify the giant stars and also early-type stars which are often excluded from further follow-up. We study the potential and the limitations of low-resolution spectroscopy to improve the photometric spectral types of CoRoT candidates. In particular, we want to study the influence of the signal-to-noise ratio (SNR) of the target spectrum in a quantitative way. We built an own template library and investigate whether a template library from the literature is able to reproduce the classifications. Including previous photometric estimates, we show how the additional spectroscopic information improves the constraints on spectral type. Low-resolution spectroscopy (R≈ 1000) of 42 CoRoT targets covering a wide range in SNR (1-437) and of 149 templates was obtained in 2012-2013 with the Nasmyth spectrograph at the Tautenburg 2 m telescope. Spectral types have been derived automatically by comparing with the observed template spectra. The classification has been repeated with the external CFLIB library. The spectral class obtained with the external library agrees within a few sub-classes when the target spectrum has a SNR of about 100 at least. While the photometric spectral type can deviate by an entire spectral class, the photometric luminosity classification is as close as a spectroscopic classification with the external library. A low SNR of the target spectrum limits the attainable accuracy of classification more strongly than the use of external templates or photometry. Furthermore we found that low-resolution reconnaissance spectroscopy ensures that good planet candidates are kept that would otherwise be discarded based on photometric spectral type alone.

  8. A study of the performance of the transit detection tool DST in space-based surveys. Application of the CoRoT pipeline to Kepler data

    NASA Astrophysics Data System (ADS)

    Cabrera, J.; Csizmadia, Sz.; Erikson, A.; Rauer, H.; Kirste, S.

    2012-12-01

    Context. Transit detection algorithms are mathematical tools used for detecting planets in the photometric data of transit surveys. In this work we study their application to space-based surveys. Aims: Space missions are exploring the parameter space of the transit surveys where classical algorithms do not perform optimally, either because of the challenging signal-to-noise ratio of the signal or its non-periodic characteristics. We have developed an algorithm addressing these challenges for the mission CoRoT. Here we extend the application to the data from the space mission Kepler. We aim at understanding the performances of algorithms in different data sets. Methods: We built a simple analytical model of the transit signal and developed a strategy for the search that improves the detection performance for transiting planets. We analyzed Kepler data with a set of stellar activity filtering and transit detection tools from the CoRoT community that are designed for the search of transiting planets. Results: We present a new algorithm and its performances compared to one of the most widely used techniques in the literature using CoRoT data. Additionally, we analyzed Kepler data corresponding to quarter Q1 and compare our results with the most recent list of planetary candidates from the Kepler survey. We found candidates that went unnoticed by the Kepler team when analyzing longer data sets. We study the impact of instrumental features on the production of false alarms and false positives. These results show that the analysis of space mission data advocates the use of complementary detrending and transit detection tools also for future space-based transit surveys such as PLATO.

  9. CoRoT's view of newly discovered B-star pulsators: results for 358 candidate B pulsators from the initial run's exoplanet field data

    NASA Astrophysics Data System (ADS)

    Degroote, P.; Aerts, C.; Ollivier, M.; Miglio, A.; Debosscher, J.; Cuypers, J.; Briquet, M.; Montalbán, J.; Thoul, A.; Noels, A.; De Cat, P.; Balaguer-Núñez, L.; Maceroni, C.; Ribas, I.; Auvergne, M.; Baglin, A.; Deleuil, M.; Weiss, W. W.; Jorda, L.; Baudin, F.; Samadi, R.

    2009-10-01

    Context: We search for new variable B-type pulsators in the CoRoT data assembled primarily for planet detection, as part of CoRoT's additional programme. Aims: We aim to explore the properties of newly discovered B-type pulsators from the uninterrupted CoRoT space-based photometry and to compare them with known members of the β Cep and slowly pulsating B star (SPB) classes. Methods: We developed automated data analysis tools that include algorithms for jump correction, light-curve detrending, frequency detection, frequency combination search, and for frequency and period spacing searches. Results: Besides numerous new, classical, slowly pulsating B stars, we find evidence for a new class of low-amplitude B-type pulsators between the SPB and δ Sct instability strips, with a very broad range of frequencies and low amplitudes, as well as several slowly pulsating B stars with residual excess power at frequencies typically a factor three above their expected g-mode frequencies. Conclusions: The frequency data we obtained for numerous new B-type pulsators represent an appropriate starting point for further theoretical analyses of these stars, once their effective temperature, gravity, rotation velocity, and abundances will be derived spectroscopically in the framework of an ongoing FLAMES survey at the VLT. The CoRoT space mission was developed and is operated by the French space agency CNES, with the participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain. All frequency tables, including the identification of combination frequencies, are only available as online material. Frequency Tables are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/506/471 Bâtiment 121, 91405, Orsay Cedex, France. Postdoctoral Researcher, Fonds de la Recherche Scientifique - FNRS, Belgium. Postdoctoral Fellow of the Fund for Scientific Research

  10. The periodic and chaotic regimes of motion in the exoplanet 2/1 mean-motion resonance

    NASA Astrophysics Data System (ADS)

    Michtchenko, T. A.; Ferraz-Mello, S.; Beaugé, C.

    We present the dynamical structure of the phase space of the planar plane- tary 2/1 mean-motion resonance (MMR). Inside the resonant domain, there exist two families of periodic orbits, one associated to the librational mo- tion of the critical angle (-family) and the other related to the circulatory motion of the angle between the pericentres (-family). The well-known apsidal corotation resonances (ACR) appear at the intersections of these families. A complex web of secondary resonances exists also for low ec- centricities, whose strengths and positions are dependent on the individual masses and spatial scale of the system. Depending on initial conditions, a resonant system is found in one of the two topologically different states, referred to as internal and external resonances. The internal resonance is characterized by symmetric ACR and its resonant angle is 2 2 - 1 - 1 , where i and i stand for the planetary mean longitudes and longitudes of pericentre, respectively. In contrast, the external resonance is characterized by asymmetric ACR and the resonant angle is 2 2 - 1 - 2 . We show that systems with more massive outer planets always envolve inside inter- nal resonances. The limit case is the well-known asteroidal resonances with Jupiter. At variance, systems with more massive inner planets may evolve in either internal or external resonances; the internal resonances are typical for low-to-moderate eccentricity configurations, whereas the external ones for high eccentricity configurations of the systems. In the limit case, anal- ogous to Kuiper belt objects in resonances with Neptune, the systems are always in the external resonances characterized by asymmetric equilibria.

  11. DETECTABILITY AND ERROR ESTIMATION IN ORBITAL FITS OF RESONANT EXTRASOLAR PLANETS

    SciTech Connect

    Giuppone, C. A.; Beauge, C.; Tadeu dos Santos, M.; Ferraz-Mello, S.; Michtchenko, T. A.

    2009-07-10

    We estimate the conditions for detectability of two planets in a 2/1 mean-motion resonance from radial velocity data, as a function of their masses, number of observations and the signal-to-noise ratio. Even for a data set of the order of 100 observations and standard deviations of the order of a few meters per second, we find that Jovian-size resonant planets are difficult to detect if the masses of the planets differ by a factor larger than {approx}4. This is consistent with the present population of real exosystems in the 2/1 commensurability, most of which have resonant pairs with similar minimum masses, and could indicate that many other resonant systems exist, but are currently beyond the detectability limit. Furthermore, we analyze the error distribution in masses and orbital elements of orbital fits from synthetic data sets for resonant planets in the 2/1 commensurability. For various mass ratios and number of data points we find that the eccentricity of the outer planet is systematically overestimated, although the inner planet's eccentricity suffers a much smaller effect. If the initial conditions correspond to small-amplitude oscillations around stable apsidal corotation resonances, the amplitudes estimated from the orbital fits are biased toward larger amplitudes, in accordance to results found in real resonant extrasolar systems.

  12. Discrete resonances

    NASA Astrophysics Data System (ADS)

    Vivaldi, Franco

    2015-12-01

    The concept of resonance has been instrumental to the study of Hamiltonian systems with divided phase space. One can also define such systems over discrete spaces, which have a finite or countable number of points, but in this new setting the notion of resonance must be re-considered from scratch. I review some recent developments in the area of arithmetic dynamics which outline some salient features of linear and nonlinear stable (elliptic) orbits over a discrete space, and also underline the difficulties that emerge in their analysis.

  13. Discrete resonances

    NASA Astrophysics Data System (ADS)

    Vivaldi, Franco

    The concept of resonance has been instrumental to the study of Hamiltonian systems with divided phase space. One can also define such systems over discrete spaces, which have a finite or countable number of points, but in this new setting the notion of resonance must be re-considered from scratch. I review some recent developments in the area of arithmetic dynamics which outline some salient features of linear and nonlinear stable (elliptic) orbits over a discrete space, and also underline the difficulties that emerge in their analysis.

  14. Laser Resonator

    NASA Technical Reports Server (NTRS)

    Harper, L. L. (Inventor)

    1983-01-01

    An optical resonator cavity configuration has a unitary mirror with oppositely directed convex and concave reflective surfaces disposed into one fold and concertedly reversing both ends of a beam propagating from a laser rod disposed between two total internal reflection prisms. The optical components are rigidly positioned with perpendicularly crossed virtual rooflines by a compact optical bed. The rooflines of the internal reflection prisms, are arranged perpendicularly to the axis of the laser beam and to the optical axes of the optical resonator components.

  15. Major Geomagnetic Storms (Dst less than or equal to -100 nT) Generated by Corotating Interaction Regions

    NASA Technical Reports Server (NTRS)

    Richardson, I. G.; Webb, D. F.; Zhang, J.; Berdichevsky, B. D.; Biesecker, D. A.; Kasper, J. C.; Kataoka, R.; Steinberg, J. T.; Thompson, B. J.; Wu, C.-C.; Zhukov, A. N.

    2006-01-01

    Seventy-nine major geomagnetic storms (minimum Dst less than or equal to -100 nT) observed in 1996 to 2004 were the focus of a Living with a Star Coordinated Data-Analysis Workshop (CDAW) in March, 2005. In 9 cases, the storm driver appears to have been purely a corotating interaction region (CIR) without any contribution from coronal mass ejection-related material (interplanetary coronal mass ejections, ICMEs). These storms were generated by structures within CIRs located both before and/or after the stream interface that included persistently southward magnetic fields for intervals of several hours. We compare their geomagnetic effects with those of 159 CIRs observed during 1996 - 2005. The major storms form the extreme tail of a continuous distribution of CIR geoeffectiveness which peaks at Dst approx. -40 nT but is subject to a prominent seasonal variation of - 40 nT which is ordered by the spring and fall equinoxes and the solar wind magnetic field direction towards or away from the Sun. The O'Brien and McPherron [2000] equations, which estimate Dst by integrating the incident solar wind electric field and incorporating a ring current loss term, largely account for the variation in storm size. They tend to underestimate the size of the larger CIR-associated storms by Dst approx. 20 nT. This suggests that injection into the ring current may be more efficient than expected in such storms. Four of the nine major storms in 1996 - 2004 occurred during a period of less than three solar rotations in September - November, 2002, also the time of maximum mean IMF and solar magnetic field intensity during the current solar cycle. The maximum CIR-storm strength found in our sample of events, plus additional 23 probable CIR-associated Dst less than or equal to -100 nT storms in 1972 - 1995, is (Dst = -161 nT). This is consistent with the maximum storm strength (Dst approx. -180 nT) expected from the O'Brien and McPherron equations for the typical range of solar wind

  16. Solar-wind turbulence and shear: a superposed-epoch analysis of corotating interaction regions at 1 AU

    SciTech Connect

    Borovsky, Joseph E; Denton, Michael H

    2009-01-01

    A superposed-epoch analysis of ACE and OMNI2 measurements is performed on 27 corotating interaction regions (CIRs) in 2003-2008, with the zero epoch taken to be the stream interface as determined by the maximum of the plasma vorticity. The structure of CIRs is investigated. When the flow measurements are rotated into the local-Parker-spiral coordinate system the shear is seen to be abrupt and intense, with vorticities on the order of 10{sup -5}-10{sup -4} sec{sup -1}. Converging flows perpendicular to the stream interface are seen in the local-Parker-spiral coordinate system and about half of the CIRs show a layer of divergent rebound flow away from the stream interface. Arguments indicate that any spreading of turbulence away from the region where it is produced is limited to about 10{sup 6} km, which is very small compared with the thickness of a CrR. Analysis of the turbulence across the CrRs is performed. When possible, the effects of discontinuities are removed from the data. Fluctuation amplitudes, the Alfvenicity, and the level of Alfvenic correlations all vary smoothly across the CrR. The Alfven ratio exhibits a decrease at the shear zone of the stream interface. Fourier analysis of 4.5-hr subintervals of ACE data is performed and the results are superposed averaged as an ensemble of realizations. The spectral slopes of the velocity, magnetic-field, and total-energy fluctuations vary smoothly across the CIR. The total-energy spectral slope is {approx} 3/2 in the slow and fast wind and in the CrRs. Analysis of the Elsasser inward-outward fluctuations shows a smooth transition across the CrR from an inward-outward balance in the slow wind to an outward dominance in the fast wind. A number of signatures of turbulence driving at the shear zone are sought (entropy change, turbulence amplitude, Alfvenicity, Alfven ratio, spectral slopes, in-out nature): none show evidence of driving of turbulence by shear.

  17. Multiple, Distant (40 deg) in situ Observations of a Magnetic Cloud and a Corotating Interaction Region Complex

    NASA Astrophysics Data System (ADS)

    Farrugia, C. J.; Berdichevsky, D. B.; Moestl, C.; Galvin, A. B.; Leitner, M.; Popecki, M.; Simunac, K. D.; Opitz, A.; Lavraud, B.; Ogilvie, K.; Veronig, A.; Temmer, M.; Luhmann, J. G.; Sauvaud, J.

    2010-12-01

    We report a comprehensive analysis of in situ observations made by Wind and the STEREO probes (STA, STB) of a complex interaction between a magnetic cloud (MC) and a corotating interaction region (CIR) occurring near the heliospheric current sheet (HCS) on November 19-21, 2007. The probes were separated by 0.7 AU (~40 deg) with a spread in heliographic latitudes (4.8, 2.2, and -0.4 deg for STB, Wind and STA, respectively). We employ data from the MFI, SWE and 3DP instruments on Wind, and the PLASTIC and IMPACT suites on STEREO. STB, located east of Earth, observed a forward shock followed by signatures of a MC. The MC took the role of the HCS in that the polarity of the interplanetary magnetic field (IMF) on exit was the reverse of that on entry. A passage through a plasma sheet is observed. Along the Sun-Earth line Wind observed a stream interface (SI) between a forward and a reverse shock. A MC, compressed by the CIR, was entrained in this. STA, located 20 deg to the west of Earth, saw a MC which was not preceded by a shock. A SI trailed the transient. The shocks are examined using various methods and from this it is concluded that the forward shock at Wind - but not at STB - was driven by the MC. Examining the MC by Grad-Shafranov reconstruction, we find evidence of a double-flux rope structure at Wind and STA and possibly also at STB. The orientations are at variance with the notion of a large-scale flux tube being observed at the three spacecraft. We find consistency of this with the directional properties of the solar wind "strahl" electrons. We examine aspects of the geomagnetic response and find a double-dip storm corresponding to the two interplanetary triggers. The minimum Dst phase was prolonged and the geoffects were intensified due to the interaction. We conclude that while the formation of compound streams is a common feature of interplanetary space, understanding their components when CIRs are involved is a complicated matter needing numerical

  18. Multiple, distant (40°) in situ observations of a magnetic cloud and a corotating interaction region complex

    NASA Astrophysics Data System (ADS)

    Farrugia, C. J.; Berdichevsky, D. B.; Möstl, C.; Galvin, A. B.; Leitner, M.; Popecki, M. A.; Simunac, K. D. C.; Opitz, A.; Lavraud, B.; Ogilvie, K. W.; Veronig, A. M.; Temmer, M.; Luhmann, J. G.; Sauvaud, J. A.

    2011-06-01

    We report a comprehensive analysis of in situ observations made by Wind and the STEREO probes (STA, STB) of a complex interaction between a magnetic cloud (MC) and a corotating interaction region (CIR) occurring near the heliospheric current sheet (HCS) on November 19-21, 2007. The probes were separated by 0.7 AU (˜40∘) with a spread in heliographic latitudes (4.8,° 2.2,° and -0.4,° for STB, Wind and STA, respectively). We employ data from the MFI, SWE and 3DP instruments on Wind, and the PLASTIC and IMPACT suites on STEREO. STB, located east of Earth, observed a forward shock followed by signatures of a MC. The MC took the role of the HCS in that the polarity of the interplanetary magnetic field (IMF) on exit was the reverse of that on entry. A passage through a plasma sheet was observed. Along the Sun-Earth line Wind observed a stream interface (SI) between a forward and a reverse shock. A MC, compressed by the CIR, was entrained in this. STA, located 20° to the west of Earth, saw a MC which was not preceded by a shock. A SI trailed the transient. The shocks are examined using various methods and from this it is concluded that the forward shock at Wind—but not at STB—was driven by the MC. Examining the MC by Grad-Shafranov reconstruction, we find evidence of a double-flux rope structure at Wind and STA and possibly also at STB. The orientations are at variance with the notion of a large-scale flux tube being observed at the three spacecraft. We find consistency of this with the directional properties of the solar wind "strahl" electrons. We examine aspects of the geomagnetic response and find a double-dip storm corresponding to the two interplanetary triggers. The minimum Dst phase was prolonged and the geoeffects were intensified due to the interaction. We conclude that while the formation of compound streams is a common feature of interplanetary space, understanding their components when CIRs are involved is a complicated matter needing numerical

  19. Effects of Complex Interplanetary Structures on the Dynamics of the Earth's Outer Radiation Belt During the 16-30 September 2014 Period: II) Corotating Solar Wind Stream

    NASA Astrophysics Data System (ADS)

    Souza, V. M. C. E. S.; Da Silva, L. A.; Sibeck, D. G.; Alves, L. R.; Jauer, P. R.; Dias Silveira, M. V.; Medeiros, C.; Marchezi, J.; Rockenbach, M.; Baker, D. N.; Kletzing, C.; Kanekal, S. G.; Georgiou, M.; Mendes, O., Jr.; Dal Lago, A.; Vieira, L. E. A.

    2015-12-01

    We present a case study describing the dynamics of the outer radiation belt for two different solar wind conditions. First, we discuss a dropout of outer belt energetic electron fluxes corresponding to the arrival of an interplanetary coronal mass ejection (ICME) followed by a corotating stream in September 2014. Second, we discuss the reformation of the outer radiation belt that began on September 22nd. We find that the arrival of the ICME and the corotating interaction region that preceded the stream cause a long-duration (many day) dropout of high-energy electrons. The recovery in radiation belt fluxes only begins when the high-speed stream begins to develop IMF Bz fluctuations and auroral activity resumes. Furthermore, during periods in which several consecutive solar wind structures appear, the first structure primes the outer radiation belt prior to the interaction of the subsequent solar wind structures with the magnetosphere. Consequently, the evolution of the outer radiation belt through the solar cycle is significantly affected by the dominant structure of each phase of the cycle. We use energetic electron and magnetic field observations provided by the Van Allen Probes, THEMIS, and GOES missions.

  20. Models of red giants in the CoRoT asteroseismology fields combining asteroseismic and spectroscopic constraints - The open cluster NGC 6633 and field stars-

    NASA Astrophysics Data System (ADS)

    Lagarde, Nadège; Miglio, Andrea; Eggenberger, Patrick; Morel, Thierry; Montalbàn, Josefina; Mosser, Benoit

    2015-08-01

    The availability of asteroseismic constraints for a large sample of red giant stars from the CoRoT and Kepler missions paves the way for various statistical studies of the seismic properties of stellar populations.We use the first detailed spectroscopic study of CoRoT red-giant stars (Morel et al 2014) to compare theoretical stellar evolution models to observations of the open cluster NGC 6633 and field stars.In order to explore the effects of rotation-induced mixing and thermohaline instability, we compare surface abundances of carbon isotopic ratio and lithium with stellar evolution predictions. These chemicals are sensitive to extra-mixing on the red-giant branch.We estimate mass, radius, and distance for each star using the seismic constraints. We note that the Hipparcos and seismic distances are different. However, the uncertainties are such that this may not be significant. Although the seismic distances for the cluster members are self consistent they are somewhat larger than the Hipparcos distance. This is an issue that should be considered elsewhere. Models including thermohaline instability and rotation-induced mixing, together with the seismically determined masses can explain the chemical properties of red-giants targets. Tighter constraints on the physics of the models would be possible if there were detailed knowledge of the core rotation rate and the asymptotic period spacing.

  1. The silicate and carbon-rich models of CoRoT-7b, Kepler-9d and Kepler-10b

    NASA Astrophysics Data System (ADS)

    Gong, Yan-Xiang; Zhou, Ji-Lin

    2012-06-01

    Possible bulk compositions of the super-Earth exoplanets CoRoT-7b, Kepler-9d, and Kepler-10b are investigated by applying a commonly used silicate model and a non-standard carbon model. Their internal structures are deduced using a suitable equation of state for the materials. The degeneracy problems of their compositions can be partly overcome, based on the fact that all three planets are extremely close to their host stars. By analyzing the numerical results, we conclude: 1) the iron core of CoRoT-7b is not more than 27% of its total mass within 1σ mass-radius error bars, so an Earth-like composition is less likely, but its carbon rich model can be compatible with an Earth-like core/mantle mass fraction; 2) Kepler-10b is more likely to have a Mercury-like composition, with its old age implying that its high iron content may be a result of strong solar wind or giant impact; 3) the transiting-only super-Earth Kepler-9d is also discussed. Combining its possible composition with the formation theory, we can place some constraints on its mass and bulk composition.

  2. IMPROVED VARIABLE STAR SEARCH IN LARGE PHOTOMETRIC DATA SETS: NEW VARIABLES IN CoRoT FIELD LRa02 DETECTED BY BEST II

    SciTech Connect

    Fruth, T.; Cabrera, J.; Csizmadia, Sz.; Eigmueller, P.; Erikson, A.; Kirste, S.; Pasternacki, T.; Rauer, H.; Titz-Weider, R.; Kabath, P.; Chini, R.; Lemke, R.; Murphy, M.

    2012-06-15

    The CoRoT field LRa02 has been observed with the Berlin Exoplanet Search Telescope II (BEST II) during the southern summer 2007/2008. A first analysis of stellar variability led to the publication of 345 newly discovered variable stars. Now, a deeper analysis of this data set was used to optimize the variability search procedure. Several methods and parameters have been tested in order to improve the selection process compared to the widely used J index for variability ranking. This paper describes an empirical approach to treat systematic trends in photometric data based upon the analysis of variance statistics that can significantly decrease the rate of false detections. Finally, the process of reanalysis and method improvement has virtually doubled the number of variable stars compared to the first analysis by Kabath et al. A supplementary catalog of 272 previously unknown periodic variables plus 52 stars with suspected variability is presented. Improved ephemerides are given for 19 known variables in the field. In addition, the BEST II results are compared with CoRoT data and its automatic variability classification.

  3. CoRoT LRa02_E2_0121: Neptune-size planet candidate turns into a hierarchical triple system with a giant primary

    NASA Astrophysics Data System (ADS)

    Tal-Or, L.; Santerne, A.; Mazeh, T.; Bouchy, F.; Moutou, C.; Alonso, R.; Gandolfi, D.; Aigrain, S.; Auvergne, M.; Barge, P.; Bonomo, A. S.; Bordé, P.; Deeg, H.; Ferraz-Mello, S.; Deleuil, M.; Dvorak, R.; Erikson, A.; Fridlund, M.; Gillon, M.; Guenther, E. W.; Guillot, T.; Hatzes, A.; Jorda, L.; Lammer, H.; Léger, A.; Llebaria, A.; Ollivier, M.; Pätzold, M.; Queloz, D.; Rauer, H.; Rouan, D.; Tsodikovich, Y.; Wuchterl, G.

    2011-10-01

    This paper presents the case of CoRoT LRa02_E2_0121, which was initially classified as a Neptune-size transiting-planet candidate on a relatively wide orbit of 36.3 days. Follow-up observations were performed with UVES, Sandiford, SOPHIE, and HARPS. These observations revealed a faint companion in the spectra. To find the true nature of the system we derived the radial velocities of the faint companion using TODMOR - a two-dimensional correlation technique, applied to the SOPHIE spectra. Modeling the lightcurve with EBAS we discovered a secondary eclipse with a depth of ~0.07%, indicating a diluted eclipsing binary. Combined MCMC modeling of the lightcurve and the radial velocities suggested that CoRoT LRa02_E2_0121 is a hierarchical triple system with an evolved G-type primary and an A-type:F-type grazing eclipsing binary. Such triple systems are difficult to discover. Based on observations made with the 1.93-m telescope at Observatoire de Haute-Provence (CNRS), France, the 3.6-m telescope at La Silla Observatory (ESO), Chile (program 184.C-0639), the VLT at Paranal Observatory (ESO), Chile (program 083.C-0690), and the 2.1-m Otto Struve telescope at McDonald Observatory, Texas, USA.

  4. Improved Variable Star Search in Large Photometric Data Sets: New Variables in CoRoT Field LRa02 Detected by BEST II

    NASA Astrophysics Data System (ADS)

    Fruth, T.; Kabath, P.; Cabrera, J.; Chini, R.; Csizmadia, Sz.; Eigmüller, P.; Erikson, A.; Kirste, S.; Lemke, R.; Murphy, M.; Pasternacki, T.; Rauer, H.; Titz-Weider, R.

    2012-06-01

    The CoRoT field LRa02 has been observed with the Berlin Exoplanet Search Telescope II (BEST II) during the southern summer 2007/2008. A first analysis of stellar variability led to the publication of 345 newly discovered variable stars. Now, a deeper analysis of this data set was used to optimize the variability search procedure. Several methods and parameters have been tested in order to improve the selection process compared to the widely used J index for variability ranking. This paper describes an empirical approach to treat systematic trends in photometric data based upon the analysis of variance statistics that can significantly decrease the rate of false detections. Finally, the process of reanalysis and method improvement has virtually doubled the number of variable stars compared to the first analysis by Kabath et al. A supplementary catalog of 272 previously unknown periodic variables plus 52 stars with suspected variability is presented. Improved ephemerides are given for 19 known variables in the field. In addition, the BEST II results are compared with CoRoT data and its automatic variability classification.

  5. An in-depth study of HD 174966 with CoRoT photometry and HARPS spectroscopy. Large separation as a new observable for δ Scuti stars

    NASA Astrophysics Data System (ADS)

    García Hernández, A.; Moya, A.; Michel, E.; Suárez, J. C.; Poretti, E.; Martín-Ruíz, S.; Amado, P. J.; Garrido, R.; Rodríguez, E.; Rainer, M.; Uytterhoeven, K.; Rodrigo, C.; Solano, E.; Rodón, J. R.; Mathias, P.; Rolland, A.; Auvergne, M.; Baglin, A.; Baudin, F.; Catala, C.; Samadi, R.

    2013-11-01

    Aims: The aim of this work was to use a multi-approach technique to derive the most accurate values possible of the physical parameters of the δ Sct star HD 174966, which was observed with the CoRoT satellite. In addition, we searched for a periodic pattern in the frequency spectra with the goal of using it to determine the mean density of the star. Methods: First, we extracted the frequency content from the CoRoT light curve. Then, we derived the physical parameters of HD 174966 and carried a mode identification out from the spectroscopic and photometric observations. We used this information to look for the models fulfilling all the conditions and discussed the inaccuracies of the method because of the rotation effects. In a final step, we searched for patterns in the frequency set using a Fourier transform, discussed its origin, and studied the possibility of using the periodicity to obtain information about the physical parameters of the star. Results: A total of 185 peaks were obtained from the Fourier analysis of the CoRoT light curve, all of which were reliable pulsating frequencies. From the spectroscopic observations, 18 oscillation modes were detected and identified, and the inclination angle (62.5°-17.5+7.5) and the rotational velocity of the star (142 km s-1) were estimated. From the multi-colour photometric observations, only three frequencies were detected that correspond to the main ones in the CoRoT light curve. We looked for periodicities within the 185 frequencies and found a quasiperiodic pattern Δν ~ 64 μHz. Using the inclination angle, the rotational velocity, and an Echelle diagram (showing a double comb outside the asymptotic regime), we concluded that the periodicity corresponds to a large separation structure. The quasiperiodic pattern allowed us to discriminate models from a grid. As a result, the value of the mean density is achieved with a 6% uncertainty. So, the Δν pattern could be used as a new observable for A-F type stars. The

  6. Large-scale vapor transport of remotely evaporated seawater by a Rossby wave response to typhoon forcing during the Baiu/Meiyu season as revealed by the JRA-55 reanalysis

    NASA Astrophysics Data System (ADS)

    Kudo, Tadasuke; Kawamura, Ryuichi; Hirata, Hidetaka; Ichiyanagi, Kimpei; Tanoue, Masahiro; Yoshimura, Kei

    2014-07-01

    The modulation of large-scale moisture transport from the tropics into East Asia in response to typhoon-induced heating during the mature stage of the Baiu/Meiyu season is investigated using the Japanese 55-year reanalysis (JRA-55), aided by a Rayleigh-type global isotope circulation model (ICM). We highlighted the typhoons that migrate northward along the western periphery of the North Pacific subtropical high and approach the vicinity of Japan. Anomalous anticyclonic circulations to the northeast and southeast of typhoons and cyclonic circulation to their west become evident as they migrate toward Japan, which could be interpreted as a Rossby wave response to typhoon heating. These resultant anomalous circulation patterns form moisture conveyor belt (MCB) stretching from the South Asian monsoon region to East Asia via the confluence region between the monsoon westerlies and central Pacific easterlies. The ICM results confirm that the well-defined nature of the MCB leads to penetration of the Indian Ocean, South China Sea, Philippine Sea, and Pacific Ocean water vapors into western Japan. The typhoons have the potential to accumulate large amounts of moisture from distant tropical oceans through the interaction of their Rossby wave response with the background flow. In the case of a typical typhoon, the total precipitable water around the typhoon center as it approaches Japan is maintained by the moisture supply from distant oceans rather than from the underlying ocean, which indirectly leads to the occurrence of heavy rainfall over western Japan.

  7. Resonant behavior of dielectric objects (electrostatic resonances).

    PubMed

    Fredkin, D R; Mayergoyz, I D

    2003-12-19

    Resonant behavior of dielectric objects occurs at certain frequencies for which the object permittivity is negative and the free-space wavelength is large in comparison with the object dimensions. Unique physical features of these resonances are studied and a novel technique for the calculation of resonance values of permittivity, and hence resonance frequencies, is proposed. Scale invariance of resonance frequencies, unusually strong orthogonality properties of resonance modes, and a two-dimensional phenomenon of "twin" spectra are reported. The paper concludes with brief discussions of optical controllability of these resonances in semiconductor nanoparticles and a plausible, electrostatic resonance based, mechanism for nucleation and formation of ball lightning. PMID:14754117

  8. Stochastic charging of dust grains in planetary rings: Diffusion rates and their effects on Lorentz resonances

    NASA Technical Reports Server (NTRS)

    Schaffer, L.; Burns, J. A.

    1995-01-01

    Dust grains in planetary rings acquire stochastically fluctuating electric charges as they orbit through any corotating magnetospheric plasma. Here we investigate the nature of this stochastic charging and calculate its effect on the Lorentz resonance (LR). First we model grain charging as a Markov process, where the transition probabilities are identified as the ensemble-averaged charging fluxes due to plasma pickup and photoemission. We determine the distribution function P(t;N), giving the probability that a grain has N excess charges at time t. The autocorrelation function tau(sub q) for the strochastic charge process can be approximated by a Fokker-Planck treatment of the evolution equations for P(t; N). We calculate the mean square response to the stochastic fluctuations in the Lorentz force. We find that transport in phase space is very small compared to the resonant increase in amplitudes due to the mean charge, over the timescale that the oscillator is resonantly pumped up. Therefore the stochastic charge variations cannot break the resonant interaction; locally, the Lorentz resonance is a robust mechanism for the shaping of etheral dust ring systems. Slightly stronger bounds on plasma parameters are required when we consider the longer transit times between Lorentz resonances.

  9. Variability in the CoRoT photometry of three hot O-type stars. HD 46223, HD 46150, and HD 46966

    NASA Astrophysics Data System (ADS)

    Blomme, R.; Mahy, L.; Catala, C.; Cuypers, J.; Gosset, E.; Godart, M.; Montalban, J.; Ventura, P.; Rauw, G.; Morel, T.; Degroote, P.; Aerts, C.; Noels, A.; Michel, E.; Baudin, F.; Baglin, A.; Auvergne, M.; Samadi, R.

    2011-09-01

    Context. The detection of pulsational frequencies in stellar photometry is required as input for asteroseismological modelling. The second short run (SRa02) of the CoRoT mission has provided photometric data of unprecedented quality and time-coverage for a number of O-type stars. Aims: We analyse the CoRoT data corresponding to three hot O-type stars, describing the properties of their light curves and search for pulsational frequencies, which we then compare to theoretical model predictions. Methods: We determine the amplitude spectrum of the data, using the Lomb-Scargle and a multifrequency HMM-like technique. Frequencies are extracted by prewhitening, and their significance is evaluated under the assumption that the light curve is dominated by red noise. We search for harmonics, linear combinations, and regular spacings among these frequencies. We use simulations with the same time sampling as the data as a powerful tool to judge the significance of our results. From the theoretical point of view, we use the MAD non-adiabatic pulsation code to determine the expected frequencies of excited modes. Results: A substantial number of frequencies is listed, but none can be convincingly identified as being connected to pulsations. The amplitude spectrum is dominated by red noise. Theoretical modelling shows that all three O-type stars can have excited modes, but the relation between the theoretical frequencies and the observed spectrum is not obvious. Conclusions: The dominant red noise component in the hot O-type stars studied here clearly points to a different origin than the pulsations seen in cooler O stars. The physical cause of this red noise is unclear, but we speculate on the possibility of sub-surface convection, granulation, or stellar wind inhomogeneities being responsible. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany and Spain

  10. The CoRoT star ID 100866999: a hybrid γ Doradus-δ Scuti star in an eclipsing binary system

    NASA Astrophysics Data System (ADS)

    Chapellier, E.; Mathias, P.

    2013-08-01

    Context. The presence of g- and p-modes allows testing stellar models from the core to the envelope. Moreover, binarity in an eclipsing system constrains the physical parameters of the pulsating star. Aims: CoRot ID 100866999 is a relatively large-amplitude hybrid γ Doradus-δ Scuti star with two clearly distinct frequency domains. The large number of detected frequencies allows a detailed study of the interaction between them. In addition, we can derive the fundamental parameters of both components from the study of the eclipsing light curve. Methods: After removing the eclipsing phases, we analyzed the data with the Period04 package up to a signal-to-noise ratio S/N = 4. The light curve was then prewhitened with these oscillation frequencies to derive the fundamental parameters of the two components. Results: The eclipsing light curve analysis results in a (1.8+1.1) M⊙ system, both components being main sequence stars. We detect 124 frequencies related to luminosity variations of the primary. They are present in two well-separated domains: 89 frequencies in the interval [0.30;3.64] d-1 and 35 in the interval [14.57; 33.96] d-1. There are 22 γ Doradus frequencies separated by a constant period interval ΔP = 0.03493 d. These frequencies correspond to a series of g-modes of degree ℓ = 1 with successive radial orders k. We identify 21 linear combinations between the first nine γ Doradus frequencies. The δ Scuti domain is dominated by a large-amplitude frequency F = 16.9803 d-1. The eight first γ Doradus frequencies fi are present with much lower amplitude in the δ Scuti domain as F ± fi. These interactions between g- and p-modes confirm the phenomenon we detected in another CoRoT star. The amplitude and the phase of the main frequency F shows a double-wave modulation along the orbital phase, giving rise to series of combination frequencies. Such combination frequencies are also detected, with lower amplitude, for the first γ Doradus modes. The CoRoT

  11. If It's Resonance, What is Resonating?

    ERIC Educational Resources Information Center

    Kerber, Robert C.

    2006-01-01

    The phenomenon under the name "resonance," which, is based on the mathematical analogy between mechanical resonance and the behavior of wave functions in quantum mechanical exchange phenomena was described. The resonating system does not have a structure intermediate between those involved in the resonance, but instead a structure which is further…

  12. OBSERVATIONS OF BINARY STARS WITH THE DIFFERENTIAL SPECKLE SURVEY INSTRUMENT. IV. OBSERVATIONS OF KEPLER, CoRoT, AND HIPPARCOS STARS FROM THE GEMINI NORTH TELESCOPE

    SciTech Connect

    Horch, Elliott P.; Howell, Steve B.; Everett, Mark E.; Ciardi, David R. E-mail: steve.b.howell@nasa.gov E-mail: ciardi@ipac.caltech.edu

    2012-12-01

    We present the results of 71 speckle observations of binary and unresolved stars, most of which were observed with the DSSI speckle camera at the Gemini North Telescope in 2012 July. The main purpose of the run was to obtain diffraction-limited images of high-priority targets for the Kepler and CoRoT missions, but in addition, we observed a number of close binary stars where the resolution limit of Gemini was used to better determine orbital parameters and/or confirm results obtained at or below the diffraction limit of smaller telescopes. Five new binaries and one triple system were discovered, and first orbits are calculated for other two systems. Several systems are discussed in detail.

  13. In-flight measurements of propeller blade deformation on a VUT100 cobra aeroplane using a co-rotating camera system

    NASA Astrophysics Data System (ADS)

    Boden, F.; Stasicki, B.; Szypuła, M.; Ružička, P.; Tvrdik, Z.; Ludwikowski, K.

    2016-07-01

    Knowledge of propeller or rotor blade behaviour under real operating conditions is crucial for optimizing the performance of a propeller or rotor system. A team of researchers, technicians and engineers from Avia Propeller, DLR, EVEKTOR and HARDsoft developed a rotating stereo camera system dedicated to in-flight blade deformation measurements. The whole system, co-rotating with the propeller at its full speed and hence exposed to high centrifugal forces and strong vibration, had been successfully tested on an EVEKTOR VUT 100 COBRA aeroplane in Kunovice (CZ) within the project AIM2—advanced in-flight measurement techniques funded by the European Commission (contract no. 266107). This paper will describe the work, starting from drawing the first sketch of the system up to performing the successful flight test. Apart from a description of the measurement hardware and the applied IPCT method, the paper will give some impressions of the flight test activities and discuss the results obtained from the measurements.

  14. A Tale of Two Exoplanets: the Inflated Atmospheres of the Hot Jupiters HD 189733 b and CoRoT-2 b

    NASA Astrophysics Data System (ADS)

    Poppenhaeger, K.; Wolk, Scott J.; Schmitt, J. H. M. M.

    2015-01-01

    Planets in close orbits around their host stars are subject to strong irradiation. High-energy irradiation, originating from the stellar corona and chromosphere, is mainly responsible for the evaporation of exoplanetary atmospheres. We have conducted multiple X-ray observations of transiting exoplanets in short orbits to determine the extent and heating of their outer planetary atmospheres. In the case of HD 189733 b, we find a surprisingly deep transit profile in X-rays, indicating an atmosphere extending out to 1.75 optical planetary radii. The X-ray opacity of those high-altitude layers points towards large densities or high metallicity. We preliminarily report on observations of the Hot Jupiter CoRoT-2 b from our Large Program with XMM-Newton, which was conducted recently. In addition, we present results on how exoplanets may alter the evolution of stellar activity through tidal interaction.

  15. VARIABILITY SURVEY IN THE CoRoT SRa01 FIELD: IMPLICATIONS OF ECLIPSING BINARY DISTRIBUTION ON CLUSTER FORMATION IN NGC 2264

    SciTech Connect

    Klagyivik, P.; Csizmadia, Sz.; Pasternacki, T.; Fruth, T.; Erikson, A.; Cabrera, J.; Eigmueller, P.; Kirste, S.; Rauer, H.; Titz-Weider, R.; Chini, R.; Lemke, R.; Kabath, P.; Murphy, M.

    2013-08-10

    Time-series photometry of the CoRoT field SRa01 was carried out with the Berlin Exoplanet Search Telescope II in 2008/2009. A total of 1161 variable stars were detected, of which 241 were previously known and 920 are newly found. Several new, variable young stellar objects have been discovered. The study of the spatial distribution of eclipsing binaries revealed the higher relative frequency of Algols toward the center of the young open cluster NGC 2264. In general Algol frequency obeys an isotropic distribution of their angular momentum vectors, except inside the cluster, where a specific orientation of the inclinations is the case. We suggest that we see the orbital plane of the binaries almost edge-on.

  16. Regular frequency patterns in the young δ Scuti star HD 261711 observed by the CoRoT and MOST satellites

    NASA Astrophysics Data System (ADS)

    Zwintz, K.; Fossati, L.; Guenther, D. B.; Ryabchikova, T.; Baglin, A.; Themessl, N.; Barnes, T. G.; Matthews, J. M.; Auvergne, M.; Bohlender, D.; Chaintreuil, S.; Kuschnig, R.; Moffat, A. F. J.; Rowe, J. F.; Rucinski, S. M.; Sasselov, D.; Weiss, W. W.

    2013-04-01

    Context. The internal structure of pre-main-sequence (PMS) stars is poorly constrained at present. This could change significantly through high-quality asteroseismological observations of a sample of such stars. Aims: We concentrate on an asteroseismological study of HD 261711, a rather hot δ Scuti-type pulsating member of the young open cluster NGC 2264 located at the blue border of the instability region. HD 261711 was discovered to be a PMS δ Scuti star using the time series photometry obtained by the MOST satellite in 2006. Methods: High-precision, time-series photometry of HD 261711 was obtained by the MOST and CoRoT satellites in four separate new observing runs that are put into context with the star's fundamental atmospheric parameters obtained from spectroscopy. Frequency Analysis was performed using Period04. The spectral analysis was performed using equivalent widths and spectral synthesis. Results: With the new MOST data set from 2011/12 and the two CoRoT light curves from 2008 and 2011/12, the δ Scuti variability was confirmed and regular groups of frequencies were discovered. The two pulsation frequencies identified in the data from the first MOST observing run in 2006 are confirmed and 23 new δ Scuti-type frequencies were discovered using the CoRoT data. Weighted average frequencies for each group were determined and are related to l = 0 and l = 1 p-modes. Evidence for amplitude modulation of the frequencies in two groups is seen. The effective temperature (Teff) was derived to be 8600 ± 200 K, log g is 4.1 ± 0.2, and the projected rotational velocity (υsini) is 53 ± 1 km s-1. Using our Teff value and the radius of 1.8 ± 0.5 R⊙ derived from spectral energy distribution (SED) fitting, we get a luminosity log L/L⊙ of 1.20 ± 0.14 which agrees well to the seismologically determined values of 1.65 R⊙ and, hence, a log L/L⊙ of 1.13. The radial velocity of 14 ± 2 km s-1 we derived for HD 261711, confirms the star's membership to NGC 2264

  17. Variability Survey in the CoRoT SRa01 Field: Implications of Eclipsing Binary Distribution on Cluster Formation in NGC 2264

    NASA Astrophysics Data System (ADS)

    Klagyivik, P.; Csizmadia, Sz.; Pasternacki, T.; Fruth, T.; Erikson, A.; Cabrera, J.; Chini, R.; Eigmüller, P.; Kabath, P.; Kirste, S.; Lemke, R.; Murphy, M.; Rauer, H.; Titz-Weider, R.

    2013-08-01

    Time-series photometry of the CoRoT field SRa01 was carried out with the Berlin Exoplanet Search Telescope II in 2008/2009. A total of 1161 variable stars were detected, of which 241 were previously known and 920 are newly found. Several new, variable young stellar objects have been discovered. The study of the spatial distribution of eclipsing binaries revealed the higher relative frequency of Algols toward the center of the young open cluster NGC 2264. In general Algol frequency obeys an isotropic distribution of their angular momentum vectors, except inside the cluster, where a specific orientation of the inclinations is the case. We suggest that we see the orbital plane of the binaries almost edge-on.

  18. BENEFITS OF GROUND-BASED PHOTOMETRIC FOLLOW-UP FOR TRANSITING EXTRASOLAR PLANETS DISCOVERED WITH KEPLER AND CoRoT

    SciTech Connect

    Colon, Knicole D.; Ford, Eric B.

    2009-09-20

    Currently, over 40 transiting planets have been discovered by ground-based photometric surveys, and space-based missions such as Kepler and CoRoT are expected to detect hundreds more. Follow-up photometric observations from the ground will play an important role in constraining both orbital and physical parameters for newly discovered planets, especially those with small radii (R{sub p} {approx}< 4R{sub +}) and/or intermediate-to-long orbital periods (P{approx}> 30 days). Here, we simulate transit light curves (LCs) from Kepler-like photometry and ground-based observations in the near-infrared (NIR) to determine how jointly modeling space-based and ground-based LCs can improve measurements of the transit duration and planet-star radius ratio. We find that adding observations of at least one ground-based transit to space-based observations can significantly improve the accuracy for measuring the transit duration and planet-star radius ratio of small planets (R{sub p} {approx}< 4R{sub +}) in long-period ({approx}1 year) orbits, largely thanks to the reduced effect of limb darkening in the NIR. We also demonstrate that multiple ground-based observations are needed to gain a substantial improvement in the measurement accuracy for small planets with short orbital periods ({approx}3 days). Finally, we consider the role that higher ground-based precisions will play in constraining parameter measurements for typical Kepler targets. Our results can help inform the priorities of transit follow-up programs (including both primary and secondary transit of planets discovered with Kepler and CoRoT), leading to improved constraints for transit durations, planet sizes, and orbital eccentricities.

  19. Resonant instability in two-dimensional vortex arrays

    NASA Astrophysics Data System (ADS)

    Luzzatto-Fegiz, Paolo; Williamson, Charles H. K.

    2011-11-01

    In this work, we examine conditions for the development of an oscillatory instability in two-dimensional vortex arrays. By building on the theory of Krein signatures for Hamiltonian systems, and considering constraints owing to impulse conservation, we show that a resonant instability (developing through coalescence of two eigenvalues) cannot occur for one or two vortices. We illustrate this deduction by examining available linear stability results for one or two vortices. Our work indicates that a resonant instability may, however, occur for three or more vortices. For these more complex flows, we propose a simple model, based on an elliptical vortex representation, to detect the onset of an oscillatory instability. We provide an example in support of our theory by examining three co-rotating vortices, for which we also perform a linear stability analysis. The stability boundary in our model is in good agreement with the full stability calculation. In addition, we show that eigenmodes associated with an overall rotation or an overall displacement of the vortices always have eigenvalues equal to zero and +/- iΩ , respectively, where Ω is the angular velocity of the array. These results, for overall rotation and displacement modes, can also be used to immediately check the accuracy of a detailed stability calculation.

  20. Self-gravity, Resonances, and Orbital Diffusion in Stellar Disks

    NASA Astrophysics Data System (ADS)

    Fouvry, Jean-Baptiste; Binney, James; Pichon, Christophe

    2015-06-01

    Fluctuations in a stellar system's gravitational field cause the orbits of stars to evolve. The resulting evolution of the system can be computed with the orbit-averaged Fokker-Planck equation once the diffusion tensor is known. We present the formalism that enables one to compute the diffusion tensor from a given source of noise in the gravitational field when the system's dynamical response to that noise is included. In the case of a cool stellar disk we are able to reduce the computation of the diffusion tensor to a one-dimensional integral. We implement this formula for a tapered Mestel disk that is exposed to shot noise and find that we are able to explain analytically the principal features of a numerical simulation of such a disk. In particular the formation of narrow ridges of enhanced density in action space is recovered. As the disk's value of Toomre's Q is reduced and the disk becomes more responsive, there is a transition from a regime of heating in the inner regions of the disk through the inner Lindblad resonance to one of radial migration of near-circular orbits via the corotation resonance in the intermediate regions of the disk. The formalism developed here provides the ideal framework in which to study the long-term evolution of all kinds of stellar disks.

  1. Record Balkan floods of 2014 linked to planetary wave resonance.

    PubMed

    Stadtherr, Lisa; Coumou, Dim; Petoukhov, Vladimir; Petri, Stefan; Rahmstorf, Stefan

    2016-04-01

    In May 2014, the Balkans were hit by a Vb-type cyclone that brought disastrous flooding and severe damage to Bosnia and Herzegovina, Serbia, and Croatia. Vb cyclones migrate from the Mediterranean, where they absorb warm and moist air, to the north, often causing flooding in central/eastern Europe. Extreme rainfall events are increasing on a global scale, and both thermodynamic and dynamical mechanisms play a role. Where thermodynamic aspects are generally well understood, there is large uncertainty associated with current and future changes in dynamics. We study the climatic and meteorological factors that influenced the catastrophic flooding in the Balkans, where we focus on large-scale circulation. We show that the Vb cyclone was unusually stationary, bringing extreme rainfall for several consecutive days, and that this situation was likely linked to a quasi-stationary circumglobal Rossby wave train. We provide evidence that this quasi-stationary wave was amplified by wave resonance. Statistical analysis of daily spring rainfall over the Balkan region reveals significant upward trends over 1950-2014, especially in the high quantiles relevant for flooding events. These changes cannot be explained by simple thermodynamic arguments, and we thus argue that dynamical processes likely played a role in increasing flood risks over the Balkans. PMID:27152340

  2. Record Balkan floods of 2014 linked to planetary wave resonance

    PubMed Central

    Stadtherr, Lisa; Coumou, Dim; Petoukhov, Vladimir; Petri, Stefan; Rahmstorf, Stefan

    2016-01-01

    In May 2014, the Balkans were hit by a Vb-type cyclone that brought disastrous flooding and severe damage to Bosnia and Herzegovina, Serbia, and Croatia. Vb cyclones migrate from the Mediterranean, where they absorb warm and moist air, to the north, often causing flooding in central/eastern Europe. Extreme rainfall events are increasing on a global scale, and both thermodynamic and dynamical mechanisms play a role. Where thermodynamic aspects are generally well understood, there is large uncertainty associated with current and future changes in dynamics. We study the climatic and meteorological factors that influenced the catastrophic flooding in the Balkans, where we focus on large-scale circulation. We show that the Vb cyclone was unusually stationary, bringing extreme rainfall for several consecutive days, and that this situation was likely linked to a quasi-stationary circumglobal Rossby wave train. We provide evidence that this quasi-stationary wave was amplified by wave resonance. Statistical analysis of daily spring rainfall over the Balkan region reveals significant upward trends over 1950–2014, especially in the high quantiles relevant for flooding events. These changes cannot be explained by simple thermodynamic arguments, and we thus argue that dynamical processes likely played a role in increasing flood risks over the Balkans. PMID:27152340

  3. Regenerative feedback resonant circuit

    DOEpatents

    Jones, A. Mark; Kelly, James F.; McCloy, John S.; McMakin, Douglas L.

    2014-09-02

    A regenerative feedback resonant circuit for measuring a transient response in a loop is disclosed. The circuit includes an amplifier for generating a signal in the loop. The circuit further includes a resonator having a resonant cavity and a material located within the cavity. The signal sent into the resonator produces a resonant frequency. A variation of the resonant frequency due to perturbations in electromagnetic properties of the material is measured.

  4. Resonant generation and energetics of wind-forced near-inertial motions in a submesoscale jet

    NASA Astrophysics Data System (ADS)

    Whitt, D. B.; Thomas, L. N.

    2014-12-01

    Theory and numerical simulations are used to study the resonant generation and energetics of inertial oscillations in a unidirectional, laterally-sheared ocean current forced by oscillatory winds. The analysis applies to submesoscale geostrophic flows with Rossby numbers, Rog, that are of order one. In this case, the local resonant forcing frequency for inertial oscillations is modified from the Coriolis frequency f to the effective Coriolis frequency F=f(1+Rog)1/2. In addition, the resonant inertial velocity response is elliptical, not circular, because the oscillation periodically exchanges energy with the geostrophic flow via shear production. With damping, the energy exchange becomes permanent, but its magnitude and sign depend strongly on the angle of the oscillatory wind vector relative to the geostrophic flow. However, for an ocean forced by an isotropic distribution of wind directions, the response averaged over all wind angles results in a net extraction of energy from the geostrophic flow that scales as the wind-work on the inertial motions times Rog2 for Rog <<1. For Rog ~ 1, this sink of kinetic energy for the circulation preferentially damps geostrophic flows with anticyclonic vorticity and thus could contribute towards shaping the positively-skewed vorticity distribution observed in the upper ocean.

  5. Seismic modelling of the late Be stars HD 181231 and HD 175869 observed with CoRoT: a laboratory for mixing processes

    NASA Astrophysics Data System (ADS)

    Neiner, C.; Mathis, S.; Saio, H.; Lovekin, C.; Eggenberger, P.; Lee, U.

    2012-03-01

    Context. HD 181231 and HD 175869 are two late rapidly rotating Be stars, which have been observed using high-precision photometry with the CoRoT satellite during about five consecutive months and 27 consecutive days, respectively. An analysis of their light curves, by Neiner and collaborators and Gutiérrez-Soto and collaborators respectively, showed that several independent pulsation g-modes are present in these stars. Fundamental parameters have also been determined by these authors using spectroscopy. Aims: We aim to model these results to infer seismic properties of HD 181231 and HD 175869, and constrain internal transport processes of rapidly rotating massive stars. Methods: We used an adiabatic (NRO) and a non-adiabatic (Tohoku) oscillation code that accounts for the combined action of Coriolis and centrifugal accelerations on stellar pulsations as needed for rapid rotator modelling. We coupled these codes with a 2D (ROTORC) stellar structure model to take the rotational deformation of the star into account. The action of transport processes was parametrised with the mixing parameter αov, which represents the "non-standard" extension of the convective core, and determined by matching observed pulsation frequencies assuming a single star evolution scenario. In a second step, we used (Geneva) evolution models to evaluate the contribution of the secular rotational transport and mixing processes in the radiative envelope. A Monte Carlo analysis of spectropolarimetric data was also performed to examine the role of a potential fossil magnetic field. Finally, based on state-of-the-art modelling of penetrative convection and internal waves, we unravelled their respective contribution to the needed "non-standard" mixing. Results: We find that extra mixing of αov = 0.3-0.35Hp is needed in HD 181231 and HD 175869 to match the observed frequencies with those of prograde sectoral g-modes. We also detect the possible presence of r-modes. We investigated the respective

  6. Polar summer mesospheric extreme horizontal drift speeds during interplanetary corotating interaction regions (CIRs) and high-speed solar wind streams: Coupling between the solar wind and the mesosphere

    NASA Astrophysics Data System (ADS)

    Lee, Young-Sook; Kirkwood, Sheila; Kwak, Young-Sil; Kim, Kyung-Chan; Shepherd, Gordon G.

    2014-05-01

    We report the observation of echo extreme horizontal drift speed (EEHS, ≥ 300 m s-1) during polar mesospheric (80-90 km) summer echoes (PMSEs) by the VHF (52 MHz) radar at Esrange, Sweden, in years of 2006 and 2008. The EEHS occur in PMSEs as correlated with high-speed solar wind streams (HSSs), observed at least once in 12-17% of all hours of observation for the two summers. The EEHS rate peaks occur either during high solar wind speed in the early part of the PMSE season or during the arrival of interplanetary corotating interaction regions (CIRs) followed by peaks in PMSE occurrence rate after 1-4 days, in the latter part of the 2006 summer. The cause of EEHS rate peaks is likely under the competition between the interval of the CIR and HSS passage over the magnetosphere. A candidate process in producing EEHS is suggested to be localized strong electric field, which is caused by solar wind energy transfer from the interaction of CIR and HSS with the magnetosphere in a sequential manner. We suggest that EEHS are created by strong electric field, estimated as > 10-30 V m-1 at 85 km altitude, exceeding the mesospheric breakdown threshold field.

  7. Corotating interaction regions and the 27 day variation of galactic cosmic rays intensity at 1 AU during the cycle 23/24 solar minimum

    NASA Astrophysics Data System (ADS)

    Guo, X.; Florinski, V.

    2014-04-01

    We investigate the formation and evolution of corotating interaction regions (CIRs) in the solar wind and their effects on galactic cosmic rays (GCR) during the recent solar cycle 23/24 solar minimum. The output from a three-dimensional MHD model serves as background for kinetic time-dependent simulations of GCR transport based on the Parker equation. The results show that the CIR forward/reverse shock pairs or compression/rarefaction regions play important roles in the transport of GCR particles and directly control the observed 27 day periodic intensity variations. We find that stream interfaces (SIs) in CIRs and the heliospheric current sheet (HCS) are both closely associated with the GCR depression onset, in agreement with the observations at 1 AU. The HCS is more important when its tilt angle becomes small during the declining phase of the solar minimum, while the passages of SIs control the onset of GCR depressions for larger HCS tilt angles. The mechanism of GCR intensity variation near 1 AU can be explained through an interplay between the effects of particle drift and diffusion. The simulated plasma background and GCR intensity are compared with the observations from spacecraft and a neutron monitor on the ground, to find good qualitative agreement. Evidently, CIRs had a substantial modulational effect on GCR during the recent solar minimum.

  8. The influence of Corotating Interaction Region (CIR) driven geomagnetic storms on the development of equatorial plasma bubbles (EPBs) over wide range of longitudes

    NASA Astrophysics Data System (ADS)

    Tulasi Ram, S.; Kumar, Sandeep; Su, S.-Y.; Veenadhari, B.; Ravindran, Sudha

    2015-01-01

    Recurrent high speed solar wind streams from coronal holes on the Sun are more frequent and Geoeffective during the declining phase of solar cycle which interact with the ambient solar wind leading the formation of Corotating Interaction Regions (CIRs) in the interplanetary medium. These CIR-High Speed Stream (HSS) structures of enhanced density and magnetic fields, when they impinge up on the Earth's magnetosphere, can cause recurrent geomagnetic storms in the Geospace environment. In this study, we investigate the influence of two CIR-driven recurrent geomagnetic storms on the equatorial and low-latitude ionosphere in the context of the development of equatorial plasma bubbles over Indian and Asian longitudes. The results consistently indicate that prompt penetration of eastward electric fields into equatorial and low-latitudes under southward IMF Bz can occur even during the CIR-driven storms. Further, the penetration of eastward electric fields augments the evening pre-reversal enhancement and triggers the development of EPBs over wide longitudinal sectors where the local post-sunset hours coincide with the main phase of the storm. Similar results that are consistently observed during both the CIR-driven geomagnetic storms are reported and discussed in this paper.

  9. Cavity- and waveguide-resonators in electron paramagnetic resonance, nuclear magnetic resonance, and magnetic resonance imaging.

    PubMed

    Webb, Andrew

    2014-11-01

    Cavity resonators are widely used in electron paramagnetic resonance, very high field magnetic resonance microimaging and also in high field human imaging. The basic principles and designs of different forms of cavity resonators including rectangular, cylindrical, re-entrant, cavity magnetrons, toroidal cavities and dielectric resonators are reviewed. Applications in EPR and MRI are summarized, and finally the topic of traveling wave MRI using the magnet bore as a waveguide is discussed. PMID:25456314

  10. Magnetic resonance of slotted circular cylinder resonators

    NASA Astrophysics Data System (ADS)

    Du, Junjie; Liu, Shiyang; Lin, Zhifang; Chui, S. T.

    2008-07-01

    By a rigorous full-wave approach, a systemic study is made on the magnetic resonance of slotted circular cylinder resonators (SCCRs) made of a perfect conductor for the lossless case. This is a two-dimensional analog of the split-ring resonator and may serve as an alternative type of essential constituent of electromagnetic metamaterials. It is found that the resonance frequency can be modulated by changing the geometrical parameters and the dielectrics filling in the cavity and the slot. An approximate empirical expression is presented for magnetic resonance frequency of SCCRs from the viewpoint of an L-C circuit system. Finally, it is demonstrated that the SCCR structure can be miniaturized to less than 1/150 resonant wavelength in size with the dielectrics available currently.

  11. Integral resonator gyroscope

    NASA Technical Reports Server (NTRS)

    Shcheglov, Kirill V. (Inventor); Challoner, A. Dorian (Inventor); Hayworth, Ken J. (Inventor); Wiberg, Dean V. (Inventor); Yee, Karl Y. (Inventor)

    2008-01-01

    The present invention discloses an inertial sensor having an integral resonator. A typical sensor comprises a planar mechanical resonator for sensing motion of the inertial sensor and a case for housing the resonator. The resonator and a wall of the case are defined through an etching process. A typical method of producing the resonator includes etching a baseplate, bonding a wafer to the etched baseplate, through etching the wafer to form a planar mechanical resonator and the wall of the case and bonding an end cap wafer to the wall to complete the case.

  12. Secular resonant dressed orbital diffusion - II. Application to an isolated self-similar tepid galactic disc

    NASA Astrophysics Data System (ADS)

    Fouvry, Jean-Baptiste; Pichon, Christophe

    2015-05-01

    The main orbital signatures of the secular evolution of an isolated self-gravitating stellar Mestel disc are recovered using a dressed Fokker-Planck formalism in angle-action variables. The shot-noise-driven formation of narrow ridges of resonant orbits is recovered in the WKB limit of tightly wound transient spirals, for a tepid Toomre-stable tapered disc. The relative effect of the bulge, the halo, the disc temperature and the spectral properties of the shot noise are investigated in turn. For such galactic discs all elements seem to impact the locus and direction of the ridge. For instance, when the halo mass is decreased, we observe a transition between a regime of heating in the inner regions of the disc through the inner Lindblad resonance to a regime of radial migration of quasi-circular orbits via the corotation resonance in the outer part of the disc. The dressed secular formalism captures both the nature of collisionless systems (via their natural frequencies and susceptibility), and their nurture via the structure of the external perturbing power spectrum. Hence it provides the ideal framework in which to study their long-term evolution.

  13. Neutron resonance averaging

    SciTech Connect

    Chrien, R.E.

    1986-10-01

    The principles of resonance averaging as applied to neutron capture reactions are described. Several illustrations of resonance averaging to problems of nuclear structure and the distribution of radiative strength in nuclei are provided. 30 refs., 12 figs.

  14. Nanomechanical resonance detector

    DOEpatents

    Grossman, Jeffrey C; Zettl, Alexander K

    2013-10-29

    An embodiment of a nanomechanical frequency detector includes a support structure and a plurality of elongated nanostructures coupled to the support structure. Each of the elongated nanostructures has a particular resonant frequency. The plurality of elongated nanostructures has a range of resonant frequencies. An embodiment of a method of identifying an object includes introducing the object to the nanomechanical resonance detector. A resonant response by at least one of the elongated nanostructures of the nanomechanical resonance detector indicates a vibrational mode of the object. An embodiment of a method of identifying a molecular species of the present invention includes introducing the molecular species to the nanomechanical resonance detector. A resonant response by at least one of the elongated nanostructures of the nanomechanical resonance detector indicates a vibrational mode of the molecular species.

  15. Asteroseismology for "à la carte" stellar age-dating and weighing. Age and mass of the CoRoT exoplanet host HD 52265

    NASA Astrophysics Data System (ADS)

    Lebreton, Y.; Goupil, M. J.

    2014-09-01

    Context. In the context of the space missions CoRoT, Kepler, Gaia, TESS, and PLATO, precise and accurate stellar ages, masses, and radii are of paramount importance. For instance, they are crucial for constraining scenarii of planetary formation and evolution. Aims: We aim at quantifying how detailed stellar modelling can improve the accuracy and precision on age and mass of individual stars. To that end, we adopt a multifaceted approach where we carefully examine how the number of observational constraints as well as the uncertainties on observations and on model input physics affect the results of age-dating and weighing. Methods: We modelled in detail the exoplanet host-star HD 52265, a main-sequence, solar-like oscillator that CoRoT observed for four months. We considered different sets of observational constraints (Hertzsprung-Russell data, metallicity, various sets of seismic constraints). For each case, we determined the age, mass, and properties of HD 52265 inferred from stellar models, and we quantified the impact of the model input physics and free parameters. We also compared model ages with ages derived by empirical methods or Hertzsprung-Russell diagram inversion. Results: For our case study HD 52265, our seismic analysis provides an age A = 2.10-2.54 Gyr, a mass M = 1.14-1.32 M⊙, and a radius R = 1.30-1.34 R⊙, which corresponds to age, mass, and radius uncertainties of ~10, ~7, and ~1.5 per cent, respectively. These uncertainties account for observational errors and current state-of-the-art stellar model uncertainties. Our seismic study also provides constraints on surface convection properties through the mixing-length, which we find to be 12-15 per cent lower than the solar value. On the other hand, because of helium-mass degeneracy, the initial helium abundance is determined modulo the mass value. Finally, we evaluate the seismic mass of the exoplanet to be Mpsini = 1.17-1.26 MJupiter, much more precise than what can be derived by Hertzsprung

  16. Ionospheric VTEC and thermospheric infrared emission dynamics during corotating interaction region and high-speed stream intervals at solar minimum: 25 March to 26 April 2008

    NASA Astrophysics Data System (ADS)

    Verkhoglyadova, O. P.; Tsurutani, B. T.; Mannucci, A. J.; Mlynczak, M. G.; Hunt, L. A.; Komjathy, A.; Runge, T.

    2011-09-01

    We analyze a portion of the Whole Heliospheric Interval from 25 March to 26 April 2008 to identify the ionospheric and thermospheric responses to high-speed solar wind streams. This period during solar sunspot minimum is of moderate geomagnetic activity (with the minimum Dst ˜ -50 nT) with enhanced auroral activity seen in High-Intensity Long-Duration Continuous Auroral Activity events. The solar wind data show several corotating interaction regions (CIRs) and recurrent high-speed streams (HSSs). Using the infrared emission data obtained with Sounding of the Atmosphere using Broadband Emission Radiometry on Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics, we identify a distinct relationship between the infrared emission irradiated from the thermosphere and CIR-HSS intervals. Specifically, zonal flux of NO infrared radiation correlates well with AE indices. The most pronounced effects are found at high latitudes. We used Jet Propulsion Laboratory Global Ionospheric Maps (GIMs) software and the GPS total electron content (TEC) database to calculate the vertical total electron content (VTEC) and construct GIMs. It is shown that VTEC intensifies during HSSs periods. To illustrate the point, dynamics of daytime VTEC averaged over different latitude bands are presented. These results are compared to quiet time observations to contrast variations associated with geomagnetic activity. Data analyses show fast, global, and continuous ionospheric responses to external solar wind forcing. The largest variations are found in low-latitude (between -30° and 30°) VTEC. In conclusion, we suggest that CIRs/HSSs are external drivers for both thermospheric and ionospheric phenomena during the solar sunspot minimum. We discuss both prompt penetration electric fields and disturbance dynamos as possible mechanisms responsible for the observed VTEC effects. It is clear that efficient heliospheric-magnetospheric-ionospheric-thermospheric coupling occurs during CIR

  17. COROTATING INTERACTION REGION ASSOCIATED SUPRATHERMAL HELIUM ION ENHANCEMENTS AT 1 AU: EVIDENCE FOR LOCAL ACCELERATION AT THE COMPRESSION REGION TRAILING EDGE

    SciTech Connect

    Ebert, R. W.; Dayeh, M. A.; Desai, M. I.; Mason, G. M.

    2012-04-10

    We examined the temporal profiles and peak intensities for 73 corotating interaction region (CIR)-associated suprathermal ({approx}0.1-8 MeV nucleon{sup -1}) helium (He) ion enhancements identified at STEREO-A, STEREO-B, and/or Advanced Composition Explorer between 2007 and 2010. We found that in most events the peak He intensity times were well organized by the CIR compression region trailing edge, regardless of whether or not a reverse shock was present. Out of these events, 19% had their 0.193 MeV nucleon{sup -1} He intensities peak within 1 hr and 50% within 4.75 hr of the CIR trailing edge, the distribution having a 1{sigma} value of 7.3 hr. Events with a 0.193 MeV nucleon{sup -1} He intensity peak time within 1{sigma} of the CIR trailing edge showed a positive correlation between the {approx}0.1 and 0.8 MeV nucleon{sup -1} He peak intensities and magnetic compression ratios in events both with and without a reverse shock. The peak intensities in all other events showed little to moderate correlation between these parameters. Our results provide evidence that some fraction of the CIR-associated <0.8 MeV nucleon{sup -1} He intensity enhancements observed at 1 AU are locally driven. We suggest an extended source for the CIR-associated energetic particles observed at 1 AU where the MeV particles are likely accelerated at CIR-driven shocks beyond Earth orbit.

  18. Galaxies Probing Galaxies at High Resolution: Co-rotating Gas Associated with a Milky Way Analog at z=0.4

    NASA Astrophysics Data System (ADS)

    Diamond-Stanic, Aleksandar M.; Coil, Alison L.; Moustakas, John; Tremonti, Christy A.; Sell, Paul H.; Mendez, Alexander J.; Hickox, Ryan C.; Rudnick, Greg H.

    2016-06-01

    We present results on gas flows in the halo of a Milky-Way-like galaxy at z = 0.413 based on high-resolution spectroscopy of a background galaxy. This is the first study of circumgalactic gas at high spectral resolution toward an extended background source (i.e., a galaxy rather than a quasar). Using long-slit spectroscopy of the foreground galaxy, we observe spatially extended Hα emission with a circular rotation velocity {v}{circ}≈ 270 km s‑1. Using echelle spectroscopy of the background galaxy, we detect {Mg} {{ii}} and {Fe} {{ii}} absorption lines at an impact parameter ρ =27 kpc that are blueshifted from systemic in the sense of the foreground galaxy’s rotation. The strongest absorber ({{{EW}}}2796=0.90 Å) has an estimated column density ({N}{{H}}≥slant {10}19 cm‑2) and line-of-sight velocity dispersion (σ =17 km s‑1) that are consistent with the observed properties of extended {{H}} {{i}} disks in the local universe. Our analysis of the rotation curve also suggests that this r≈ 30 {{kpc}} gaseous disk is warped with respect to the stellar disk. In addition, we detect two weak {Mg} {{ii}} absorbers in the halo with small velocity dispersions (σ \\lt 10 km s‑1). While the exact geometry is unclear, one component is consistent with an extraplanar gas cloud near the disk–halo interface that is co-rotating with the disk, and the other is consistent with a tidal feature similar to the Magellanic Stream. We can place lower limits on the cloud sizes (l\\gt 0.4 kpc) for these absorbers given the extended nature of the background source. We discuss the implications of these results for models of the geometry and kinematics of gas in the circumgalactic medium.

  19. Eddy viscosity and flow properties of the solar wind: Co-rotating interaction regions, coronal-mass-ejection sheaths, and solar-wind/magnetosphere coupling

    SciTech Connect

    Borovsky, Joseph E.

    2006-05-15

    The coefficient of magnetohydrodynamic (MHD) eddy viscosity of the turbulent solar wind is calculated to be {nu}{sub eddy}{approx_equal}1.3x10{sup 17} cm{sup 2}/s: this coefficient is appropriate for velocity shears with scale thicknesses larger than the {approx}10{sup 6} km correlation length of the solar-wind turbulence. The coefficient of MHD eddy viscosity is calculated again accounting for the action of smaller-scale turbulent eddies on smaller scale velocity shears in the solar wind. This eddy viscosity is quantitatively tested with spacecraft observations of shear flows in co-rotating interaction regions (CIRs) and in coronal-mass-ejection (CME) sheaths and ejecta. It is found that the large-scale ({approx}10{sup 7} km) shear of the CIR fractures into intense narrow ({approx}10{sup 5} km) slip zones between slabs of differently magnetized plasma. Similarly, it is found that the large-scale shear of CME sheaths also fracture into intense narrow slip zones between parcels of differently magnetized plasma. Using the solar-wind eddy-viscosity coefficient to calculate vorticity-diffusion time scales and comparing those time scales with the {approx}100-h age of the solar-wind plasma at 1 AU, it is found that the slip zones are much narrower than eddy-viscosity theory says they should be. Thus, our concept of MHD eddy viscosity fails testing. For the freestream turbulence effect in solar-wind magnetosphere coupling, the eddy-viscous force of the solar wind on the Earth's magnetosphere is rederived accounting for the action of turbulent eddies smaller than the correlation length, along with other corrections. The improved derivation of the solar-wind driver function for the turbulence effect fails to yield higher correlation coefficients between measurements of the solar-wind driver and measurements of the response of the Earth's magnetosphere.

  20. The emergent 1.1-1.7 μm spectrum of the exoplanet COROT-2B as measured using the Hubble space telescope

    SciTech Connect

    Wilkins, Ashlee N.; Deming, Drake; Madhusudhan, Nikku; Burrows, Adam; Knutson, Heather; McCullough, Peter; Ranjan, Sukrit

    2014-03-10

    We have used Hubble/WFC3 and the G141 grism to measure the secondary eclipse of the transiting, very hot Jupiter CoRoT-2b in the 1.1-1.7 μm spectral region. We find an eclipse depth averaged over this band equal to 395{sub −45}{sup +69} parts per million, equivalent to a blackbody temperature of 1788 ± 18 K. We study and characterize several WFC3 instrumental effects, especially the 'hook' phenomenon described by Deming et al. We use data from several transiting exoplanet systems to find a quantitative relation between the amplitude of the hook and the exposure level of a given pixel. Although the uncertainties in this relation are too large to allow us to develop an empirical correction for our data, our study provides a useful guide for optimizing exposure levels in future WFC3 observations. We derive the planet's spectrum using a differential method. The planet-to-star contrast increases to longer wavelength within the WFC3 bandpass, but without water absorption or emission to a 3σ limit of 85 ppm. The slope of the WFC3 spectrum is significantly less than the slope of the best-fit blackbody. We compare all existing eclipse data for this planet to a blackbody spectrum, and to spectra from both solar abundance and carbon-rich (C/O = 1) models. A blackbody spectrum is an acceptable fit to the full data set. Extra continuous opacity due to clouds or haze, and flattened temperature profiles, are strong candidates to produce quasi-blackbody spectra, and to account for the amplitude of the optical eclipses. Our results show ambiguous evidence for a temperature inversion in this planet.

  1. Analysis of a coronal mass ejection and corotating interaction region as they travel from the Sun passing Venus, Earth, Mars, and Saturn

    NASA Astrophysics Data System (ADS)

    Prise, A. J.; Harra, L. K.; Matthews, S. A.; Arridge, C. S.; Achilleos, N.

    2015-03-01

    During June 2010 a good alignment in the solar system between Venus, STEREO-B, Mars, and Saturn provided an excellent opportunity to study the propagation of a coronal mass ejection (CME) and closely occurring corotating interaction region (CIR) from the Sun to Saturn. The CME erupted from the Sun at 01:30 UT on 20 June 2010,with v≈ 600 km s-1, as observed by STEREO-B, Solar Dynamics Observatory, and SOHO/Large Angle and Spectrometric Coronagraph. It arrived at Venus over 2 days later, some 3.5 days after a CIR is also detected here. The CIR was also observed at STEREO-B and Mars, prior to the arrival of the CME. The CME is not directed earthward, but the CIR is detected here less than 2 days after its arrival at Mars. Around a month later, a strong compression of the Saturn magnetosphere is observed by Cassini, consistent with the scenario that the CME and CIR have merged into a single solar transient. The arrival times of both the CME and the CIR at different locations were predicted using the ENLIL solar wind model. The arrival time of the CME at Venus, STEREO-B, and Mars is predicted to within 20 h of its actual detection, but the predictions for the CIR showed greater differences from observations, all over 1.5 days early. More accurate predictions for the CIR were found by extrapolating the travel time between different locations using the arrival times and speeds detected by STEREO-B and ACE. We discuss the implications of these results for understanding the propagation of solar transients.

  2. An Inexpensive Resonance Demonstration

    ERIC Educational Resources Information Center

    Dukes, Phillip

    2005-01-01

    The phenomenon of resonance is applicable to almost every branch of physics. Without resonance, there wouldn't be televisions or stereos, or even swings on the playground. However, resonance also has undesirable side effects such as irritating noises in the car and the catastrophic events such as helicopters flying apart. In this article, the…

  3. Magnetic Resonance Imaging (MRI)

    MedlinePlus

    ... How Can I Help a Friend Who Cuts? Magnetic Resonance Imaging (MRI) KidsHealth > For Teens > Magnetic Resonance Imaging (MRI) Print A A A Text Size What's ... Exam Safety Getting Your Results What Is MRI? Magnetic resonance imaging (MRI) is a type of safe, painless testing ...

  4. Nuclear Magnetic Resonance

    NASA Astrophysics Data System (ADS)

    Andrew, E. R.

    2009-06-01

    Author's preface; 1. Introduction; 2. Basic theory; 3. Experimental methods; 4. Measurement of nuclear properties and general physical applications; 5. Nuclear magnetic resonance in liquids and gases; 6. Nuclear magnetic resonance in non-metallic solids; 7. Nuclear magnetic resonance in metals; 8. Quadrupole effects; Appendices 1-6; Glossary of symbols; Bibliography and author index; Subject index.

  5. Monitoring a high-amplitude δ Scuti star for 152 days: discovery of 12 additional modes and modulation effects in the light curve of CoRoT 101155310

    NASA Astrophysics Data System (ADS)

    Poretti, E.; Rainer, M.; Weiss, W. W.; Bognár, Zs.; Moya, A.; Niemczura, E.; Suárez, J. C.; Auvergne, M.; Baglin, A.; Baudin, F.; Benkő, J. M.; Debosscher, J.; Garrido, R.; Mantegazza, L.; Paparó, M.

    2011-04-01

    Aims: The detection of small-amplitude nonradial modes in high-amplitude δ Sct (HADS) variables has been very elusive until at least five of them were detected in the light curve of V974 Oph obtained from ground-based observations. The combination of radial and nonradial modes has a high asteroseismic potential, thanks to the strong constraints we can put in the modelling. The continuous monitoring of ASAS 192647-0030.0 ≡ CoRoT 101155310 (P = 0.1258 d, V = 13.4) ensured from space by the CoRoT (COnvection, ROtation and planetary Transits) mission constitutes a unique opportunity to exploit such potential. Methods: The 22270 CoRoT measurements were performed in the chromatic mode. They span 152 d and cover 1208 consecutive cycles. After the correction for one jump and the long-term drift, the level of the noise turned out to be 29 μmag. The phase shifts and amplitude ratios of the coloured CoRoT data, the HARPS spectra, and the period-luminosity relation were used to determine a self-consistent physical model. In turn, it allowed us to model the oscillation spectrum, also giving feedback on the internal structure of the star. Results: In addition to the fundamental radial mode f1 = 7.949 d-1 with harmonics up to 10f1, we detected 12 independent terms. Linear combinations were also found and the light curve was solved by means of 61 frequencies (smallest amplitude 0.10 mmag). The newest result is the detection of a periodic modulation of the f1 mode (triplets at ± 0.193 d-1 centred on f1 and 2f1), discussed as a rotational effect or as an extension of the Blazhko effect to HADS stars. The physical model suggests that CoRoT 101155310 is an evolved star, with a slight subsolar metallic abundance, close to the terminal age main sequence. All the 12 additional terms are identified with mixed modes in the predicted overstable region. The CoRoT space mission was developed and is operated by the French space agency CNES, with the participation of ESA's RSSD and Science

  6. Ovenized microelectromechanical system (MEMS) resonator

    SciTech Connect

    Olsson, Roy H; Wojciechowski, Kenneth; Kim, Bongsang

    2014-03-11

    An ovenized micro-electro-mechanical system (MEMS) resonator including: a substantially thermally isolated mechanical resonator cavity; a mechanical oscillator coupled to the mechanical resonator cavity; and a heating element formed on the mechanical resonator cavity.

  7. CSI 2264: Simultaneous Optical and Infrared Light Curves of Young Disk-bearing Stars in NGC 2264 with CoRoT and Spitzer—Evidence for Multiple Origins of Variability

    NASA Astrophysics Data System (ADS)

    Cody, Ann Marie; Stauffer, John; Baglin, Annie; Micela, Giuseppina; Rebull, Luisa M.; Flaccomio, Ettore; Morales-Calderón, María; Aigrain, Suzanne; Bouvier, Jèrôme; Hillenbrand, Lynne A.; Gutermuth, Robert; Song, Inseok; Turner, Neal; Alencar, Silvia H. P.; Zwintz, Konstanze; Plavchan, Peter; Carpenter, John; Findeisen, Krzysztof; Carey, Sean; Terebey, Susan; Hartmann, Lee; Calvet, Nuria; Teixeira, Paula; Vrba, Frederick J.; Wolk, Scott; Covey, Kevin; Poppenhaeger, Katja; Günther, Hans Moritz; Forbrich, Jan; Whitney, Barbara; Affer, Laura; Herbst, William; Hora, Joseph; Barrado, David; Holtzman, Jon; Marchis, Franck; Wood, Kenneth; Medeiros Guimarães, Marcelo; Lillo Box, Jorge; Gillen, Ed; McQuillan, Amy; Espaillat, Catherine; Allen, Lori; D'Alessio, Paola; Favata, Fabio

    2014-04-01

    We present the Coordinated Synoptic Investigation of NGC 2264, a continuous 30 day multi-wavelength photometric monitoring campaign on more than 1000 young cluster members using 16 telescopes. The unprecedented combination of multi-wavelength, high-precision, high-cadence, and long-duration data opens a new window into the time domain behavior of young stellar objects. Here we provide an overview of the observations, focusing on results from Spitzer and CoRoT. The highlight of this work is detailed analysis of 162 classical T Tauri stars for which we can probe optical and mid-infrared flux variations to 1% amplitudes and sub-hour timescales. We present a morphological variability census and then use metrics of periodicity, stochasticity, and symmetry to statistically separate the light curves into seven distinct classes, which we suggest represent different physical processes and geometric effects. We provide distributions of the characteristic timescales and amplitudes and assess the fractional representation within each class. The largest category (>20%) are optical "dippers" with discrete fading events lasting ~1-5 days. The degree of correlation between the optical and infrared light curves is positive but weak; notably, the independently assigned optical and infrared morphology classes tend to be different for the same object. Assessment of flux variation behavior with respect to (circum)stellar properties reveals correlations of variability parameters with Hα emission and with effective temperature. Overall, our results point to multiple origins of young star variability, including circumstellar obscuration events, hot spots on the star and/or disk, accretion bursts, and rapid structural changes in the inner disk. Based on data from the Spitzer and CoRoT missions. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain.

  8. Optical Helmholtz resonators

    NASA Astrophysics Data System (ADS)

    Chevalier, Paul; Bouchon, Patrick; Haïdar, Riad; Pardo, Fabrice

    2014-08-01

    Helmholtz resonators are widely used acoustic components able to select a single frequency. Here, based on an analogy between acoustics and electromagnetism wave equations, we present an electromagnetic 2D Helmholtz resonator made of a metallic slit-box structure. At the resonance, the light is funneled in the λ/800 apertures, and is subsequently absorbed in the cavity. As in acoustics, there is no higher order of resonance, which is an appealing feature for applications such as photodetection or thermal emission. Eventually, we demonstrate that the slit is of capacitive nature while the box behaves inductively. We derive an analytical formula for the resonance wavelength, which does not rely on wave propagation and therefore does not depend on the permittivity of the material filling the box. Besides, in contrast with half-wavelength resonators, the resonance wavelength can be engineered by both the slit aspect ratio and the box area.

  9. Magnetic resonance energy and topological resonance energy.

    PubMed

    Aihara, Jun-Ichi

    2016-04-28

    Ring-current diamagnetism of a polycyclic π-system is closely associated with thermodynamic stability due to the individual circuits. Magnetic resonance energy (MRE), derived from the ring-current diamagnetic susceptibility, was explored in conjunction with graph-theoretically defined topological resonance energy (TRE). For many aromatic molecules, MRE is highly correlative with TRE with a correlation coefficient of 0.996. For all π-systems studied, MRE has the same sign as TRE. The only trouble with MRE may be that some antiaromatic and non-alternant species exhibit unusually large MRE-to-TRE ratios. This kind of difficulty can in principle be overcome by prior geometry-optimisation or by changing spin multiplicity. Apart from the semi-empirical resonance-theory resonance energy, MRE is considered as the first aromatic stabilisation energy (ASE) defined without referring to any hypothetical polyene reference. PMID:26878709

  10. Resonance splitting in gyrotropic ring resonators.

    PubMed

    Jalas, Dirk; Petrov, Alexander; Krause, Michael; Hampe, Jan; Eich, Manfred

    2010-10-15

    We present the theoretical concept of an optical isolator based on resonance splitting in a silicon ring resonator covered with a magneto-optical polymer cladding. For this task, a perturbation method is derived for the modes in the cylindrical coordinate system. A polymer magneto-optical cladding causing a 0.01 amplitude of the off-diagonal element of the dielectric tensor is assumed. It is shown that the derived resonance splitting of the clockwise and counterclockwise modes increases for smaller ring radii. For the ring with a radius of approximately 1.5μm, a 29GHz splitting is demonstrated. An integrated optical isolator with a 10μm geometrical footprint is proposed based on a critically coupled ring resonator. PMID:20967092

  11. Comparative orbital evolution of transient Uranian co-orbitals: exploring the role of ephemeral multibody mean motion resonances

    NASA Astrophysics Data System (ADS)

    de la Fuente Marcos, C.; de la Fuente Marcos, R.

    2014-07-01

    Uranus has three known co-orbitals: 83982 Crantor (2002 GO9), 2010 EU65 and 2011 QF99. All of them were captured in their current resonant state relatively recently. Here, we perform a comparative analysis of the orbital evolution of these transient co-orbitals to understand better how they got captured in the first place and what makes them dynamically unstable. We also look for additional temporary Uranian co-orbital candidates among known objects. Our N-body simulations show that the long-term stability of 2011 QF99 is controlled by Jupiter and Neptune; it briefly enters the 1:7 mean motion resonance with Jupiter and the 2:1 with Neptune before becoming a Trojan and prior to leaving its tadpole orbit. During these ephemeral two-body mean motion resonance episodes, apsidal corotation resonances are also observed. For known co-orbitals, Saturn is the current source of the main destabilizing force but this is not enough to eject a minor body from the 1:1 commensurability with Uranus. These objects must enter mean motion resonances with Jupiter and Neptune in order to be captured or become passing Centaurs. Asteroid 2010 EU65, a probable visitor from the Oort cloud, may have been stable for several Myr due to its comparatively low eccentricity. Additionally, we propose 2002 VG131 as the first transient quasi-satellite candidate of Uranus. Asteroid 1999 HD12 may signal the edge of Uranus' co-orbital region. Transient Uranian co-orbitals are often submitted to complex multibody ephemeral mean motion resonances that trigger the switching between resonant co-orbital states, making them dynamically unstable. In addition, we show that the orbital properties and discovery circumstances of known objects can be used to outline a practical strategy by which additional Uranus' co-orbitals may be found.

  12. The effect of solar flares, coronal mass ejections, and co-rotating interaction regions on the Venusian 557.7 nm oxygen green line

    NASA Astrophysics Data System (ADS)

    Gray, Candace L.; Chanover, Nancy; Slanger, Tom; Molaverdikhani, Karan; Peter, Kerstin; Häusler, Bernd; Tellmann, Silvia; Pätzold, Martin; Witasse, Olivier; Blelly, Pierre-Louis; Collinson, Glyn

    2015-11-01

    The Venusian 557.7nm OI (1S - 1D) (oxygen green line) nightglow emission is known to be highly temporally variable. The reason for this variability is unknown. We propose that the emission is due to electron precipitation from intense solar storms. For my dissertation, I observed the Venusian green line after solar flares, coronal mass ejections (CMEs), and co-rotating interaction regions from December 2010 to April 2015 using the high resolution Astrophysical Research Consortium Echelle Spectrograph on the Apache Point Observatory 3.5-m telescope. Combining these observation with all other published observations, we find that the strongest detections occur after CME impacts and we conclude electron precipitation is required to produce green line emission. We do not detect emission from the 630.0nm OI (1D - 3P) oxygen red line for any observation.In an effort to determine the emitting altitude, thereby constraining the possible emission processes responsible for green line emission, and quantify the electron energy and flux entering the Venusian nightside, we conducted analyses of space-based observations of the Venusian nightglow and ionosphere collected by the Venus Express (VEX) spacecraft. We were unable to detect the green line but confirmed that electron energy and flux increases after CME impacts.In order to determine the effect of storm condition electron precipitation on the Venusian green line, we modeled the Venusian ionosphere using the TRANSCAR model (a 1-D magnetohydrodynamic ionospheric model that simulates auroral emission from electron precipitation) by applying observed electron energies and fluxes. We found that electron energy plays a primary role in producing increased green line emission in the Venusian ionosphere.Based on observation and modeling results, we conclude that the Venusian green line is an auroral-type emission that occurs after solar storms with the largest intensities observed after CMEs. Post-CME electron fluxes and energies

  13. A SYSTEMATIC SEARCH FOR COROTATING INTERACTION REGIONS IN APPARENTLY SINGLE GALACTIC WOLF-RAYET STARS. II. A GLOBAL VIEW OF THE WIND VARIABILITY

    SciTech Connect

    Chene, A.-N.; St-Louis, N. E-mail: stlouis@astro.umontreal.ca

    2011-08-01

    This study is the second part of a survey searching for large-scale spectroscopic variability in apparently single Wolf-Rayet (WR) stars. In a previous paper (Paper I), we described and characterized the spectroscopic variability level of 25 WR stars observable from the northern hemisphere and found 3 new candidates presenting large-scale wind variability, potentially originating from large-scale structures named corotating interaction regions (CIRs). In this second paper, we discuss an additional 39 stars observable from the southern hemisphere. For each star in our sample, we obtained 4-5 high-resolution spectra with a signal-to-noise ratio of {approx}100 and determined its variability level using the approach described in Paper I. In total, 10 new stars are found to show large-scale spectral variability of which 7 present CIR-type changes (WR 8, WR 44, WR55, WR 58, WR 61, WR 63, WR 100). Of the remaining stars, 20 were found to show small-amplitude changes and 9 were found to show no spectral variability as far as can be concluded from the data on hand. Also, we discuss the spectroscopic variability level of all single galactic WR stars that are brighter than v {approx} 12.5, and some WR stars with 12.5 < v {<=} 13.5, i.e., all the stars presented in our two papers and four more stars for which spectra have already been published in the literature. We find that 23/68 stars (33.8%) present large-scale variability, but only 12/54 stars ({approx}22.1%) are potentially of CIR type. Also, we find that 31/68 stars (45.6%) only show small-scale variability, most likely due to clumping in the wind. Finally, no spectral variability is detected based on the data on hand for 14/68 (20.6%) stars. Interestingly, the variability with the highest amplitude also has the widest mean velocity dispersion.

  14. A study of concentrated acid hydrolysis conversion of lignocellulosic materials to sugars using a co-rotating twin-screw reactor extruder and plug flow reactor

    NASA Astrophysics Data System (ADS)

    Miller, William Scott

    Concerns about the ability of petroleum to continue supplying ever increasing global energy demands, at a price capable of generating continued economic growth, have spurred innovative research in the field of alternative energy. One alternative energy option that has the ability to provide long-term sustainable energy supplies for the global energy market is the conversion of lignocellulosic materials, via acid hydrolysis, to fermentable sugars for the production of fuel grade ethanol. This research demonstrates the ability of a co-rotating twin-screw reactor extruder and plug flow reactor to continuously convert lignocellulosic materials to fermentable sugars using high temperature concentrated acid hydrolysis. In addition to demonstrating continuous operation of the two-stage concentrated acid hydrolysis system, a number of design of experiments were conducted to model the twin-screw performance and maximize its ability to effectively solubilize lignocellulosic feedstocks in the high shear, elevated temperature, concentrated acid environment. These studies produced a base case twin-screw operating condition used to generate a standard extrudate composition for an extensive high temperature acid hydrolysis batch reactor kinetic modeling study. In this study a number of nonlinear and linear regression analyses were undertaken so that the concentration of less resistant cellulose, or the amount of solublilized extrudate cellulose, resistant cellulose, or non-solubilized extrudate cellulose, glucose, and decomposition products could be obtained as a function of time, temperature, and acid concentration. This study demonstrated that the theoretical cellulose conversion of 51% was limited by the amount of solubilized polysaccharides that could be produced in the twin-screw pretreatment. Further experimentation, showing twin-screw pretreatment lignocellulosic versatility, produced nearly identical results as the southern yellow pine sawdust experiments that were

  15. Excitonic surface lattice resonances

    NASA Astrophysics Data System (ADS)

    Humphrey, A. D.; Gentile, M. J.; Barnes, W. L.

    2016-08-01

    Electromagnetic resonances are important in controlling light at the nanoscale. The most studied such resonance is the surface plasmon resonance that is associated with metallic nanostructures. Here we explore an alternative resonance, the surface exciton-polariton resonance, one based on excitonic molecular materials. Our study is based on analytical and numerical modelling. We show that periodic arrays of suitable molecular nanoparticles may support surface lattice resonances that arise as a result of coherent interactions between the particles. Our results demonstrate that excitonic molecular materials are an interesting alternative to metals for nanophotonics; they offer the prospect of both fabrication based on supramolecular chemistry and optical functionality arising from the way the properties of such materials may be controlled with light.

  16. Large mode radius resonators

    NASA Technical Reports Server (NTRS)

    Harris, Michael R.

    1987-01-01

    Resonator configurations permitting operation with large mode radius while maintaining good transverse mode discrimination are considered. Stable resonators incorporating an intracavity telescope and unstable resonator geometries utilizing an output coupler with a Gaussian reflectivity profile are shown to enable large radius single mode laser operation. Results of heterodyne studies of pulsed CO2 lasers with large (11mm e sup-2 radius) fundamental mode sizes are presented demonstrating minimal frequency sweeping in accordance with the theory of laser-induced medium perturbations.

  17. Dynamics of the 3/1 planetary mean-motion resonance: an application to the HD60532 b-c planetary system

    NASA Astrophysics Data System (ADS)

    Alves, A. J.; Michtchenko, T. A.; Tadeu dos Santos, M.

    2016-03-01

    In this paper, we use a semi-analytical approach to analyze the global structure of the phase space of the planar planetary 3/1 mean-motion resonance. The case where the outer planet is more massive than its inner companion is considered. We show that the resonant dynamics can be described using two fundamental parameters, the total angular momentum and the spacing parameter. The topology of the Hamiltonian function describing the resonant behaviour is investigated on a large domain of the phase space without time-expensive numerical integrations of the equations of motion, and without any restriction on the magnitude of the planetary eccentricities. The families of the Apsidal Corotation Resonances (ACR) parameterized by the planetary mass ratio are obtained and their stability is analyzed. The main dynamical features in the domains around the ACR are also investigated in detail by means of spectral analysis techniques, which allow us to detect the regions of different regimes of motion of resonant systems. The construction of dynamical maps for various values of the total angular momentum shows the evolution of domains of stable motion with the eccentricities, identifying possible configurations suitable for exoplanetary systems.

  18. Quasi-resonant circulation regimes and hemispheric synchronization of extreme weather in boreal summer

    PubMed Central

    Coumou, Dim; Petoukhov, Vladimir; Rahmstorf, Stefan; Petri, Stefan; Schellnhuber, Hans Joachim

    2014-01-01

    The recent decade has seen an exceptional number of high-impact summer extremes in the Northern Hemisphere midlatitudes. Many of these events were associated with anomalous jet stream circulation patterns characterized by persistent high-amplitude quasi-stationary Rossby waves. Two mechanisms have recently been proposed that could provoke such patterns: (i) a weakening of the zonal mean jets and (ii) an amplification of quasi-stationary waves by resonance between free and forced waves in midlatitude waveguides. Based upon spectral analysis of the midtroposphere wind field, we show that the persistent jet stream patterns were, in the first place, due to an amplification of quasi-stationary waves with zonal wave numbers 6–8. However, we also detect a weakening of the zonal mean jet during these events; thus both mechanisms appear to be important. Furthermore, we demonstrate that the anomalous circulation regimes lead to persistent surface weather conditions and therefore to midlatitude synchronization of extreme heat and rainfall events on monthly timescales. The recent cluster of resonance events has resulted in a statistically significant increase in the frequency of high-amplitude quasi-stationary waves of wave numbers 7 and 8 in July and August. We show that this is a robust finding that holds for different pressure levels and reanalysis products. We argue that recent rapid warming in the Arctic and associated changes in the zonal mean zonal wind have created favorable conditions for double jet formation in the extratropics, which promotes the development of resonant flow regimes. PMID:25114245

  19. The resonator handbook

    NASA Technical Reports Server (NTRS)

    Cook, Jerry D.; Zhou, Shiliang

    1993-01-01

    The purpose of this work is to extend resonator theory into the region in which the planar mirror is quite small. Results of the theoretical description are then extended to resonator design and experimental arrangements as discussed in further sections of this work. Finally, a discussion of dielectric measurements for small samples is included as a specific application of this work.

  20. Resonances in heavy systems

    SciTech Connect

    Betts, R.R.

    1983-01-01

    The experimental situation for the study of resonances in heavy-ion collisions is reviewed, with emphasis on the heaviest systems. New data are presented which show some of the systematics of this phenomenon. The narrow resonance structures are established as a feature of the nuclear structure of the composite system rather than a purely entrance channel effect.

  1. The Concept of Resonance

    ERIC Educational Resources Information Center

    Truhlar, Donald G.

    2007-01-01

    A general example of a delocalization system associated with a higher energy than the localized one, which suggests that it is wrong to consider delocalization as equivalent to resonance stabilization, is presented. The meaning of resonance energy as it appears in valence bond theory is described as the lowering of the calculated ground-state…

  2. Unstable optical resonators.

    PubMed

    Kahn, W K

    1966-03-01

    A technique, firmly based on a development from ray optics, is presented for calculating the loss due to the finite sizes of curved mirrors when these form an unstable optical resonator. If paraxial rays launched within such a resonator are confined near the resonator axis, the resonator is termed stable; otherwise it is termed unstable, and is known to have high losses. Siegman has recently presented a geometrical method, brilliantly constructed ad hoc, for calculating these losses in unstable resonators, and indicated where these might be advantageous in laser application. The ray optical theory presented here, which employs the concept of ray modes in an equivalent beam waveguide, is shown to yield results equivalent to those of Siegman for all cases considered by him. However, being derived from conventional ray optics, the validity of the formulas is independently established, and these formulas are immediately applicable to re-entrant resonators and resonators containing inhomogeneous media. The fractional loss per resonator pass is equal to 1-|lambda(2)|, where |lambda(2)| < this 1 is an eigenvalue of the transfer matrix T, representing the corresponding ray transformation. PMID:20048863

  3. Resonant snubber inverter

    DOEpatents

    Lai, J.S.; Young, R.W. Sr.; Chen, D.; Scudiere, M.B.; Ott, G.W. Jr.; White, C.P.; McKeever, J.W.

    1997-06-24

    A resonant, snubber-based, soft switching, inverter circuit achieves lossless switching during dc-to-ac power conversion and power conditioning with minimum component count and size. Current is supplied to the resonant snubber branches solely by the main inverter switches. Component count and size are reduced by use of a single semiconductor switch in the resonant snubber branches. Component count is also reduced by maximizing the use of stray capacitances of the main switches as parallel resonant capacitors. Resonance charging and discharging of the parallel capacitances allows lossless, zero voltage switching. In one embodiment, circuit component size and count are minimized while achieving lossless, zero voltage switching within a three-phase inverter. 14 figs.

  4. Narrowband resonant transmitter

    DOEpatents

    Hutchinson, Donald P.; Simpson, Marcus L.; Simpson, John T.

    2004-06-29

    A transverse-longitudinal integrated optical resonator (TLIR) is disclosed which includes a waveguide, a first and a second subwavelength resonant grating in the waveguide, and at least one photonic band gap resonant structure (PBG) in the waveguide. The PBG is positioned between the first and second subwavelength resonant gratings. An electro-optic waveguide material may be used to permit tuning the TLIR and to permit the TLIR to perform signal modulation and switching. The TLIR may be positioned on a bulk substrate die with one or more electronic and optical devices and may be communicably connected to the same. A method for fabricating a TLIR including fabricating a broadband reflective grating is disclosed. A method for tuning the TLIR's transmission resonance wavelength is also disclosed.

  5. Resonant snubber inverter

    DOEpatents

    Lai, Jih-Sheng; Young, Sr., Robert W.; Chen, Daoshen; Scudiere, Matthew B.; Ott, Jr., George W.; White, Clifford P.; McKeever, John W.

    1997-01-01

    A resonant, snubber-based, soft switching, inverter circuit achieves lossless switching during dc-to-ac power conversion and power conditioning with minimum component count and size. Current is supplied to the resonant snubber branches solely by the main inverter switches. Component count and size are reduced by use of a single semiconductor switch in the resonant snubber branches. Component count is also reduced by maximizing the use of stray capacitances of the main switches as parallel resonant capacitors. Resonance charging and discharging of the parallel capacitances allows lossless, zero voltage switching. In one embodiment, circuit component size and count are minimized while achieving lossless, zero voltage switching within a three-phase inverter.

  6. Possible solution to the riddle of HD 82943 multiplanet system: the three-planet resonance 1:2:5?

    NASA Astrophysics Data System (ADS)

    Baluev, Roman V.; Beaugé, Cristian

    2014-03-01

    We carry out a new analysis of the published radial velocity data for the planet-hosting star HD 82943. We include the recent Keck/HIRES measurements as well as the aged but much more numerous CORALIE data. We find that the CORALIE radial velocity measurements are polluted by a systematic annual variation which affected the robustness of many previous results. We show that after purging this variation, the residuals still contain a clear signature of an additional ˜1100 d periodicity. The latter variation leaves significant hints in all three independent radial velocity subsets that we analysed: the CORALIE data, the Keck data acquired prior to a hardware upgrade and the Keck data taken after the upgrade. We mainly treat this variation as a signature of a third planet in the system, although we cannot rule out other interpretations, such as long-term stellar activity. We find it easy to naturally obtain a stable three-planet radial velocity fit close to the three-planet mean-motion resonance 1:2:5, with the two main planets (those in the 1:2 resonance) in an aligned apsidal corotation. The dynamical status of the third planet is still uncertain: it may reside in as well as slightly out of the 5:2 resonance. We obtain the value of about 1075 d for its orbital period and ˜0.3MJup for its minimum mass, while the eccentric parameters are uncertain.

  7. The atypical generation mechanism of Titan's Schumann resonance

    NASA Astrophysics Data System (ADS)

    Béghin, Christian

    2014-03-01

    The observation of a presumed Schumann resonance (SR) during the landing of the Huygens Probe in Titan's atmosphere on January 2005 was subsequently reported and interpreted by Béghin et al. (2007, 2009, 2010, 2012) as being generated through the interaction of Saturn's magnetosphere with Titan's ionosphere rather than from the lightning activity that prevails on Earth. Beyond this atypical behavior, the existence of a single mode instead of the usual multimodal structure of terrestrial SRs and a comprehensive analysis of the physical generation mechanism remained to be investigated. The purpose of the present work is to draw up the baselines of a global model reconciling the Huygens data and the proposed generation mechanism. Based upon relevant observations obtained after several tenths of Titan's flybys by the Cassini orbiter, the modeling involves macro plasma physics processes as well as a global analysis of the mechanisms at the moon's scale. The clue to the SR's generation mechanism is shown to be the low-frequency modulation of the Pedersen current sheets that are induced in the ionopause region by the corotating Saturn's magnetosphere. The modulation principle involves a wave coupling between the ion-acoustic instabilities driven by the longitudinal current sheets and the electromagnetic quasi-transverse whistler mode. The spectral distribution of the sole second eigenmode seen by the Huygens Probe is found to comply with the ionopause plasma parameters measured by Cassini during the bipolar configuration of Titan-Saturn interaction that is thought to have occurred during the probe descent in the atmosphere.

  8. LABCOM resonator Phase 3

    SciTech Connect

    Keres, L.J.

    1990-11-01

    The purpose of this project was to develop quartz crystal resonator designs, production processes, and test capabilities for 5-MHz, 6.2-MHz, and 10-MHz resonators for Tactical Miniature Crystal Oscillator (TMXO) applications. GE Neutron Devices (GEND) established and demonstrated the capability to produce and test quartz crystal resonators for use in the TMXO developed by the US Army ERADCOM (now LABCOM). The goals in this project were based on the ERADCOM statement of work. The scope of work indicated that the resonator production facilities for this project would not be completely independent, but that they would be supported in part by equipment and processes in place at GEND used in US Department of Energy (DOE) work. In addition, provisions for production test equipment or or eventual technology transfer costs to a commercial supplier were clearly excluded from the scope of work. The demonstrated technical capability of the deep-etched blank design is feasible and practical. It can be manufactured in quantity with reasonable yield, and its performance is readily predictable. The ceramic flatpack is a very strong package with excellent hermeticity. The four-point mount supports the crystal to reasonable shock levels and does not perturb the resonator's natural frequency-temperature behavior. The package can be sealed with excellent yields. The high-temperature, high-vacuum processing developed for the TMXO resonator, including bonding the piezoid to its mount with conductive polyimide adhesive, is consistent with precision resonator fabrication. 1 fig., 6 tabs.

  9. Modelling resonant planetary systems

    NASA Astrophysics Data System (ADS)

    Emel'yanenko, V.

    2012-09-01

    Many discovered multi-planet systems are in meanmotion resonances. The aim of this work is to study dynamical processes leading to the formation of resonant configurations on the basis of a unified model described earlier [1]. The model includes gravitational interactions of planets and migration of planets due to the presence of a gas disc. For the observed systems 24 Sex, HD 37124, HD 73526, HD 82943, HD 128311, HD 160691, Kepler 9, NN Ser with planets moving in the 2:1 resonance, it is shown that the capture in this resonance occurs at very wide ranges of parameters of both type I and type II migration. Conditions of migration leading to the formation of the resonant systems HD 45364 и HD 200964 (3:2 and 4:3, respectively) are obtained. Formation scenarios are studied for the systems HD 102272, HD 108874, HD 181433, HD 202206 with planets in high order resonances. We discuss also how gravitational interactions of planets and planetesimal discs lead to the breakup of resonant configurations and the formation of systems similar to the 47 UMa system.

  10. Spin resonance strength calculations

    SciTech Connect

    Courant,E.D.

    2008-10-06

    In calculating the strengths of depolarizing resonances it may be convenient to reformulate the equations of spin motion in a coordinate system based on the actual trajectory of the particle, as introduced by Kondratenko, rather than the conventional one based on a reference orbit. It is shown that resonance strengths calculated by the conventional and the revised formalisms are identical. Resonances induced by radiofrequency dipoles or solenoids are also treated; with rf dipoles it is essential to consider not only the direct effect of the dipole but also the contribution from oscillations induced by it.

  11. Tunable multiwalled nanotube resonator

    DOEpatents

    Zettl, Alex K.; Jensen, Kenneth J.; Girit, Caglar; Mickelson, William E.; Grossman, Jeffrey C.

    2011-03-29

    A tunable nanoscale resonator has potential applications in precise mass, force, position, and frequency measurement. One embodiment of this device consists of a specially prepared multiwalled carbon nanotube (MWNT) suspended between a metal electrode and a mobile, piezoelectrically controlled contact. By harnessing a unique telescoping ability of MWNTs, one may controllably slide an inner nanotube core from its outer nanotube casing, effectively changing its length and thereby changing the tuning of its resonance frequency. Resonant energy transfer may be used with a nanoresonator to detect molecules at a specific target oscillation frequency, without the use of a chemical label, to provide label-free chemical species detection.

  12. Tunable multiwalled nanotube resonator

    DOEpatents

    Jensen, Kenneth J; Girit, Caglar O; Mickelson, William E; Zettl, Alexander K; Grossman, Jeffrey C

    2013-11-05

    A tunable nanoscale resonator has potential applications in precise mass, force, position, and frequency measurement. One embodiment of this device consists of a specially prepared multiwalled carbon nanotube (MWNT) suspended between a metal electrode and a mobile, piezoelectrically controlled contact. By harnessing a unique telescoping ability of MWNTs, one may controllably slide an inner nanotube core from its outer nanotube casing, effectively changing its length and thereby changing the tuning of its resonance frequency. Resonant energy transfer may be used with a nanoresonator to detect molecules at a specific target oscillation frequency, without the use of a chemical label, to provide label-free chemical species detection.

  13. Micro-machined resonator

    DOEpatents

    Godshall, N.A.; Koehler, D.R.; Liang, A.Y.; Smith, B.K.

    1993-03-30

    A micro-machined resonator, typically quartz, with upper and lower micro-machinable support members, or covers, having etched wells which may be lined with conductive electrode material, between the support members is a quartz resonator having an energy trapping quartz mesa capacitively coupled to the electrode through a diaphragm; the quartz resonator is supported by either micro-machined cantilever springs or by thin layers extending over the surfaces of the support. If the diaphragm is rigid, clock applications are available, and if the diaphragm is resilient, then transducer applications can be achieved. Either the thin support layers or the conductive electrode material can be integral with the diaphragm. In any event, the covers are bonded to form a hermetic seal and the interior volume may be filled with a gas or may be evacuated. In addition, one or both of the covers may include oscillator and interface circuitry for the resonator.

  14. Micro-machined resonator

    DOEpatents

    Godshall, Ned A.; Koehler, Dale R.; Liang, Alan Y.; Smith, Bradley K.

    1993-01-01

    A micro-machined resonator, typically quartz, with upper and lower micro-machinable support members, or covers, having etched wells which may be lined with conductive electrode material, between the support members is a quartz resonator having an energy trapping quartz mesa capacitively coupled to the electrode through a diaphragm; the quartz resonator is supported by either micro-machined cantilever springs or by thin layers extending over the surfaces of the support. If the diaphragm is rigid, clock applications are available, and if the diaphragm is resilient, then transducer applications can be achieved. Either the thin support layers or the conductive electrode material can be integral with the diaphragm. In any event, the covers are bonded to form a hermetic seal and the interior volume may be filled with a gas or may be evacuated. In addition, one or both of the covers may include oscillator and interface circuitry for the resonator.

  15. Resonances in QCD

    NASA Astrophysics Data System (ADS)

    Lutz, Matthias F. M.; Lange, Jens Sören; Pennington, Michael; Bettoni, Diego; Brambilla, Nora; Crede, Volker; Eidelman, Simon; Gillitzer, Albrecht; Gradl, Wolfgang; Lang, Christian B.; Metag, Volker; Nakano, Takashi; Nieves, Juan; Neubert, Sebastian; Oka, Makoto; Olsen, Stephen L.; Pappagallo, Marco; Paul, Stephan; Pelizäus, Marc; Pilloni, Alessandro; Prencipe, Elisabetta; Ritman, Jim; Ryan, Sinead; Thoma, Ulrike; Uwer, Ulrich; Weise, Wolfram

    2016-04-01

    We report on the EMMI Rapid Reaction Task Force meeting 'Resonances in QCD', which took place at GSI October 12-14, 2015. A group of 26 people met to discuss the physics of resonances in QCD. The aim of the meeting was defined by the following three key questions: What is needed to understand the physics of resonances in QCD? Where does QCD lead us to expect resonances with exotic quantum numbers? What experimental efforts are required to arrive at a coherent picture? For light mesons and baryons only those with up, down and strange quark content were considered. For heavy-light and heavy-heavy meson systems, those with charm quarks were the focus. This document summarizes the discussions by the participants, which in turn led to the coherent conclusions we present here.

  16. Resonances in Positronium Hydride

    NASA Technical Reports Server (NTRS)

    DiRienzi, Joseph; Drachman, Richard J.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    We re-examine the problem of calculating the positions and widths of the lowest-lying resonances in the Ps + H scattering system which consists of two electrons, one positron and one proton. The first of these resonances, for L=0, was found by the methods of complex rotation and stabilization, and later described as a Feshbach resonance lying close to a bound state in the closed-channel e (+) + H (-) system. Recently, results for the L=1 and 2 scattering states were published, and it was found, surprisingly, that there is a larae shift in the positions of these resonances. In this work we repeat the analysis for L=1 and find an unexpected explanation for the shift.

  17. Resonant ultrasound spectroscopy

    DOEpatents

    Migliori, Albert

    1991-01-01

    A resonant ultrasound spectroscopy method provides a unique characterization of an object for use in distinguishing similar objects having physical differences greater than a predetermined tolerance. A resonant response spectrum is obtained for a reference object by placing excitation and detection transducers at any accessible location on the object. The spectrum is analyzed to determine the number of resonant response peaks in a predetermined frequency interval. The distribution of the resonance frequencies is then characterized in a manner effective to form a unique signature of the object. In one characterization, a small frequency interval is defined and stepped though the spectrum frequency range. Subsequent objects are similarly characterized where the characterizations serve as signatures effective to distinguish objects that differ from the reference object by more than the predetermined tolerance.

  18. Cylindrical laser resonator

    DOEpatents

    Casperson, Lee W.

    1976-02-24

    The properties of an improved class of lasers is presented. In one configuration of these lasers the radiation propagates radially within the amplifying medium, resulting in high fields and symmetric illumination at the resonator axis. Thus there is a strong focusing of energy at the axis of the resonator. In a second configuration the radiation propagates back and forth in a tubular region of space.

  19. Injector with integrated resonator

    SciTech Connect

    Johnson, Thomas Edward; Ziminsky, Willy Steve; York, William David; Stevenson, Christian Xavier

    2014-07-29

    The system may include a turbine engine. The turbine engine may include a fuel nozzle. The fuel nozzle may include an air path. The fuel nozzle may also include a fuel path such that the fuel nozzle is in communication with a combustion zone of the turbine engine. Furthermore, the fuel nozzle may include a resonator. The resonator may be disposed in the fuel nozzle directly adjacent to the combustion zone.

  20. Hexagonal quartz resonator

    DOEpatents

    Peters, Roswell D. M.

    1982-01-01

    A generally flat, relatively thin AT-cut piezoelectric resonator element structured to minimize the force-frequency effect when mounted and energized in a housing. The resonator is in the form of an equilateral hexagon with the X crystallographic axis of the crystal passing through one set of opposing corners with mounting being effected at an adjacent set of corners respectively .+-.60.degree. away from the X axis which thereby results in a substantially zero frequency shift of the operating frequency.

  1. Resonant dielectric metamaterials

    SciTech Connect

    Loui, Hung; Carroll, James; Clem, Paul G; Sinclair, Michael B

    2014-12-02

    A resonant dielectric metamaterial comprises a first and a second set of dielectric scattering particles (e.g., spheres) having different permittivities arranged in a cubic array. The array can be an ordered or randomized array of particles. The resonant dielectric metamaterials are low-loss 3D isotropic materials with negative permittivity and permeability. Such isotropic double negative materials offer polarization and direction independent electromagnetic wave propagation.

  2. Plasmofluidic Disk Resonators

    PubMed Central

    Kwon, Min-Suk; Ku, Bonwoo; Kim, Yonghan

    2016-01-01

    Waveguide-coupled silicon ring or disk resonators have been used for optical signal processing and sensing. Large-scale integration of optical devices demands continuous reduction in their footprints, and ultimately they need to be replaced by silicon-based plasmonic resonators. However, few waveguide-coupled silicon-based plasmonic resonators have been realized until now. Moreover, fluid cannot interact effectively with them since their resonance modes are strongly confined in solid regions. To solve this problem, this paper reports realized plasmofluidic disk resonators (PDRs). The PDR consists of a submicrometer radius silicon disk and metal laterally surrounding the disk with a 30-nm-wide channel in between. The channel is filled with fluid, and the resonance mode of the PDR is strongly confined in the fluid. The PDR coupled to a metal-insulator-silicon-insulator-metal waveguide is implemented by using standard complementary metal oxide semiconductor technology. If the refractive index of the fluid increases by 0.141, the transmission spectrum of the waveguide coupled to the PDR of radius 0.9 μm red-shifts by 30 nm. The PDR can be used as a refractive index sensor requiring a very small amount of analyte. Plus, the PDR filled with liquid crystal may be an ultracompact intensity modulator which is effectively controlled by small driving voltage. PMID:26979929

  3. Plasmofluidic Disk Resonators

    NASA Astrophysics Data System (ADS)

    Kwon, Min-Suk; Ku, Bonwoo; Kim, Yonghan

    2016-03-01

    Waveguide-coupled silicon ring or disk resonators have been used for optical signal processing and sensing. Large-scale integration of optical devices demands continuous reduction in their footprints, and ultimately they need to be replaced by silicon-based plasmonic resonators. However, few waveguide-coupled silicon-based plasmonic resonators have been realized until now. Moreover, fluid cannot interact effectively with them since their resonance modes are strongly confined in solid regions. To solve this problem, this paper reports realized plasmofluidic disk resonators (PDRs). The PDR consists of a submicrometer radius silicon disk and metal laterally surrounding the disk with a 30-nm-wide channel in between. The channel is filled with fluid, and the resonance mode of the PDR is strongly confined in the fluid. The PDR coupled to a metal-insulator-silicon-insulator-metal waveguide is implemented by using standard complementary metal oxide semiconductor technology. If the refractive index of the fluid increases by 0.141, the transmission spectrum of the waveguide coupled to the PDR of radius 0.9 μm red-shifts by 30 nm. The PDR can be used as a refractive index sensor requiring a very small amount of analyte. Plus, the PDR filled with liquid crystal may be an ultracompact intensity modulator which is effectively controlled by small driving voltage.

  4. Resonant nonlinear ultrasound spectroscopy

    DOEpatents

    Johnson, Paul A.; TenCate, James A.; Guyer, Robert A.; Van Den Abeele, Koen E. A.

    2001-01-01

    Components with defects are identified from the response to strains applied at acoustic and ultrasound frequencies. The relative resonance frequency shift .vertline..DELTA..function./.function..sub.0.vertline., is determined as a function of applied strain amplitude for an acceptable component, where .function..sub.0 is the frequency of the resonance peak at the lowest amplitude of applied strain and .DELTA..function. is the frequency shift of the resonance peak of a selected mode to determine a reference relationship. Then, the relative resonance frequency shift .vertline..DELTA..function./.function..sub.0 is determined as a function of applied strain for a component under test, where fo .function..sub.0 the frequency of the resonance peak at the lowest amplitude of applied strain and .DELTA..function. is the frequency shift of the resonance peak to determine a quality test relationship. The reference relationship is compared with the quality test relationship to determine the presence of defects in the component under test.

  5. Tunable Resonant Scanners

    NASA Astrophysics Data System (ADS)

    Montagu, Jean I.

    1987-01-01

    The most attractive features of resonant scanners are high reliability and eternal life as well as extremely low wobble and jitter. Power consumption is also low, electronic drive is simple, and the device is capable of handling large beams. All of these features are delivered at a low cost in a small package. The resonant scanner's use in numerous high precision applications, however, has been limited because of the difficulty in controlling its phase and resonant frequency. This paper introduces the concept of tunable/controllable resonant scanners, discusses their features, and offers a number of tuning techniques. It describes two angular scanner designs and presents data on tunable range and life tests. It also reviews applications for these new tunable resonant scanners that preserve the desirable features of earlier models while removing the old problems with synchronization or time base flexibility. The three major types of raster scanning applications where the tunable resonant scanner may be of benefit are: 1. In systems with multiple time bases such as multiple scanner networks or with scanners keyed to a common clock (the line frequency or data source) or a machine with multiple resonant scanners. A typical application is image and text transmission, also a printer with a large data base where a buffer is uneconomical. 2. In systems sharing data processing or laser equipment for reasons of cost or capacity, typically multiple work station manufacturing processes or graphic processes. 3. In systems with extremely precise time bases where the frequency stability of conventional scanners cannot be relied upon.

  6. Resonant ultrasound spectrometer

    DOEpatents

    Migliori, Albert; Visscher, William M.; Fisk, Zachary

    1990-01-01

    An ultrasound resonant spectrometer determines the resonant frequency spectrum of a rectangular parallelepiped sample of a high dissipation material over an expected resonant response frequency range. A sample holder structure grips corners of the sample between piezoelectric drive and receive transducers. Each transducer is mounted on a membrane for only weakly coupling the transducer to the holder structure and operatively contacts a material effective to remove system resonant responses at the transducer from the expected response range. i.e., either a material such as diamond to move the response frequencies above the range or a damping powder to preclude response within the range. A square-law detector amplifier receives the response signal and retransmits the signal on an isolated shield of connecting cabling to remove cabling capacitive effects. The amplifier also provides a substantially frequency independently voltage divider with the receive transducer. The spectrometer is extremely sensitive to enable low amplitude resonance to be detected for use in calculating the elastic constants of the high dissipation sample.

  7. MACHINERY RESONANCE AND DRILLING

    SciTech Connect

    Leishear, R.; Fowley, M.

    2010-01-23

    New developments in vibration analysis better explain machinery resonance, through an example of drill bit chattering during machining of rusted steel. The vibration of an operating drill motor was measured, the natural frequency of an attached spring was measured, and the two frequencies were compared to show that the system was resonant. For resonance to occur, one of the natural frequencies of a structural component must be excited by a cyclic force of the same frequency. In this case, the frequency of drill bit chattering due to motor rotation equaled the spring frequency (cycles per second), and the system was unstable. A soft rust coating on the steel to be drilled permitted chattering to start at the drill bit tip, and the bit oscillated on and off of the surface, which increased the wear rate of the drill bit. This resonant condition is typically referred to as a motor critical speed. The analysis presented here quantifies the vibration associated with this particular critical speed problem, using novel techniques to describe resonance.

  8. Resonances in Positronium Hydride

    NASA Technical Reports Server (NTRS)

    Drachman, Richard J.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    Recently, Ho and his colleagues have calculated the positions and widths of a series of resonances in the Ps+H scattering system, using the complex -rotation method and have compared them with estimates that I made many years ago using a quite different technique. I assumed that the resonance mechanism was the existence in the rearrangement channel [e+ + H-] of an infinite series of perturbed Coulomb bound states. Although these must be broadened and shifted by coupling with the open scattering channel, I expected them to lie very close to the actual resonance positions. To verify this, I did a model calculation for S-waves, including the coupling, and found that the first two resonances were not shifted very far from their unperturbed position. The new, detailed calculation agrees with this result, but when the P-wave was examined it was found, surprisingly, that the lowest resonance indeed moved up in energy by a large amount. With the help of Joseph DiRienzi of the College of Notre Dame of Maryland I am now extending the old calculation to P- and D-waves, in an attempt to understand this unexpected energy shift. Results will be presented at the Workshop.

  9. Collider Signal I :. Resonance

    NASA Astrophysics Data System (ADS)

    Tait, Tim M. P.

    2010-08-01

    These TASI lectures were part of the summer school in 2008 and cover the collider signal associated with resonances in models of physics beyond the Standard Model. I begin with a review of the Z boson, one of the best-studied resonances in particle physics, and review how the Breit-Wigner form of the propagator emerges in perturbation theory and discuss the narrow width approximation. I review how the LEP and SLAC experiments could use the kinematics of Z events to learn about fermion couplings to the Z. I then make a brief survey of models of physics beyond the Standard Model which predict resonances, and discuss some of the LHC observables which we can use to discover and identify the nature of the BSM physics. I finish up with a discussion of the linear moose that one can use for an effective theory description of a massive color octet vector particle.

  10. Three-pion resonances

    NASA Astrophysics Data System (ADS)

    Garcilazo, H.; Mathelitsch, L.

    1994-03-01

    We investigate the continuum three-pion problem within a relativistic three-body model that takes into account the ππ S and P waves. The dynamical input of the two-body subsystem is given by separable potentials, which yield a good fit to the ππ scattering data and resonance parameters up to a two-body invariant mass of 900MeV. We introduce a parameter ν expressing the ambiguity in the reduction of a fully relativistic theory to a three-dimensional one. The masses and widths of the ω, a 1(1260), and π(1300) mesons, which decay predominantly into three pions, are reasonably well described by our model. The h 1(1170) meson, however, which also decays into three pions, cannot be explained as a three-pion resonance. Some πρ Argand diagrams are shown in those channels where resonances exist.

  11. Quartz resonator processing system

    DOEpatents

    Peters, Roswell D. M.

    1983-01-01

    Disclosed is a single chamber ultra-high vacuum processing system for the oduction of hermetically sealed quartz resonators wherein electrode metallization and sealing are carried out along with cleaning and bake-out without any air exposure between the processing steps. The system includes a common vacuum chamber in which is located a rotatable wheel-like member which is adapted to move a plurality of individual component sets of a flat pack resonator unit past discretely located processing stations in said chamber whereupon electrode deposition takes place followed by the placement of ceramic covers over a frame containing a resonator element and then to a sealing stage where a pair of hydraulic rams including heating elements effect a metallized bonding of the covers to the frame.

  12. Magnetostrictive resonance excitation

    DOEpatents

    Schwarz, Ricardo B.; Kuokkala, Veli-Tapani

    1992-01-01

    The resonance frequency spectrum of a magnetostrictive sample is remotely determined by exciting the magnetostrictive property with an oscillating magnetic field. The permeability of a magnetostrictive material and concomitant coupling with a detection coil varies with the strain in the material whereby resonance responses of the sample can be readily detected. A suitable sample may be a magnetostrictive material or some other material having at least one side coated with a magnetostrictive material. When the sample is a suitable shape, i.e., a cube, rectangular parallelepiped, solid sphere or spherical shell, the elastic moduli or the material can be analytically determined from the measured resonance frequency spectrum. No mechanical transducers are required and the sample excitation is obtained without contact with the sample, leading to highly reproducible results and a measurement capability over a wide temperature range, e.g. from liquid nitrogen temperature to the Curie temperature of the magnetostrictive material.

  13. Physics of Sports: Resonances

    NASA Astrophysics Data System (ADS)

    Browning, David

    2000-04-01

    When force is applied by an athlete to sports equipment resonances can occur. Just a few examples are: the ringing of a spiked volleyball, the strumming of a golf club shaft during a swing, and multiple modes induced in an aluminum baseball bat when striking a ball. Resonances produce acoustic waves which, if conditions are favorable, can be detected off the playing field. This can provide a means to evaluate athletic performance during game conditions. Results are given from the use of a simple hand-held acoustic detector - by a spectator sitting in the stands - to determine how hard volleyballs were spiked during college and high school games.

  14. Method for resonant measurement

    DOEpatents

    Rhodes, G.W.; Migliori, A.; Dixon, R.D.

    1996-03-05

    A method of measurement of objects to determine object flaws, Poisson`s ratio ({sigma}) and shear modulus ({mu}) is shown and described. First, the frequency for expected degenerate responses is determined for one or more input frequencies and then splitting of degenerate resonant modes are observed to identify the presence of flaws in the object. Poisson`s ratio and the shear modulus can be determined by identification of resonances dependent only on the shear modulus, and then using that shear modulus to find Poisson`s ratio using other modes dependent on both the shear modulus and Poisson`s ratio. 1 fig.

  15. Magnetic resonance annual, 1988

    SciTech Connect

    Kressel, H.Y.

    1987-01-01

    This book features reviews of high-resolution MRI of the knee, MRI of the normal and ischmeic hip, MRI of the heart, and temporomandibular joint imaging, as well as thorough discussion on artifacts in magnetic resonance imaging. Contributors consider the clinical applications of gadolinium-DTPA in magnetic resonance imaging and the clinical use of partial saturation and saturation recovery sequences. Timely reports assess the current status of rapid MRI and describe a new rapid gated cine MRI technique. Also included is an analysis of cerebrospinal fluid flow effects during MRI of the central nervous system.

  16. Pygmy resonances and nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Tsoneva, Nadia; Lenske, Horst

    2015-05-01

    A microscopic theoretical approach based on a self-consistent density functional theory for the nuclear ground state and QRPA formalism extended with multi-phonon degrees of freedom for the nuclear excited states is implemented in investigations of new low-energy modes called pygmy resonances. Advantage of the method is the unified description of low-energy multiphonon excitations, pygmy resonances and core polarization effects. This is found of crucial importance for the understanding of the fine structure of nuclear response functions at low energies. Aspects of the precise knowledge of nuclear response functions around the neutron threshold are discussed in a connection to nucleosynthesis.

  17. Method for resonant measurement

    DOEpatents

    Rhodes, George W.; Migliori, Albert; Dixon, Raymond D.

    1996-01-01

    A method of measurement of objects to determine object flaws, Poisson's ratio (.sigma.) and shear modulus (.mu.) is shown and described. First, the frequency for expected degenerate responses is determined for one or more input frequencies and then splitting of degenerate resonant modes are observed to identify the presence of flaws in the object. Poisson's ratio and the shear modulus can be determined by identification of resonances dependent only on the shear modulus, and then using that shear modulus to find Poisson's ratio using other modes dependent on both the shear modulus and Poisson's ratio.

  18. Field resonance propulsion concept

    NASA Technical Reports Server (NTRS)

    Holt, A. C.

    1979-01-01

    A propulsion concept was developed based on a proposed resonance between coherent, pulsed electromagnetic wave forms, and gravitational wave forms (or space-time metrics). Using this concept a spacecraft propulsion system potentially capable of galactic and intergalactic travel without prohibitive travel times was designed. The propulsion system utilizes recent research associated with magnetic field line merging, hydromagnetic wave effects, free-electron lasers, laser generation of megagauss fields, and special structural and containment metals. The research required to determine potential, field resonance characteristics and to evaluate various aspects of the spacecraft propulsion design is described.

  19. Hexagonal quartz resonator

    DOEpatents

    Peters, R.D.M.

    1982-11-02

    A generally flat, relatively thin AT-cut piezoelectric resonator element structured to minimize the force-frequency effect when mounted and energized in a housing. The resonator is in the form of an equilateral hexagon with the X crystallographic axis of the crystal passing through one set of opposing corners with mounting being effected at an adjacent set of corners respectively [+-]60[degree] away from the X axis which thereby results in a substantially zero frequency shift of the operating frequency. 3 figs.

  20. Resonant optical gun.

    PubMed

    Maslov, A V; Bakunov, M I

    2014-05-01

    We propose a concept of a structure-a resonant optical gun-to realize an efficient propulsion of dielectric microparticles by light forces. The structure is based on a waveguide in which a reversal of the electromagnetic momentum flow of the incident mode is realized by exciting a whispering gallery resonance in the microparticle. The propelling force can reach the value up to the theoretical maximum of twice the momentum flow of the initial wave. The force density oscillates along the particle periphery and has very large amplitude. PMID:24784113

  1. Surface waves in a square container due to its resonant horizontal elliptic motion

    NASA Astrophysics Data System (ADS)

    Funakoshi, Mitsuaki; Hiramitsu, Ai

    2015-11-01

    Surface waves in a square container due to its resonant horizontal elliptic or linear motion are investigated theoretically. The motion of the container is characterized by the ratio, expressed as tan ϕ , of the length of the minor axis to the length of the major axis of its elliptic orbit, and by the angle θ between the directions of the major axis and one of its sidewalls. Using the reductive perturbation method, nonlinear time evolution equations for the complex amplitudes of two degenerate modes excited by this motion are derived with the inclusion of linear damping. When tan ϕ is small, for any θ these equations have two kinds of stable stationary solutions corresponding to regular co-rotating waves whose direction of rotation is the same as that of the container, and regular counter-rotating waves of the opposite direction of rotation. As tan ϕ increases to one, the region of forcing frequency in which stable regular counter-rotating waves are observed shrinks and then disappears for any θ. Solutions with chaotic or periodic slow variations in amplitude and phase of excited surface waves are also obtained for forcing frequencies where no stable stationary solutions exist.

  2. Micromachined double resonator

    NASA Technical Reports Server (NTRS)

    Gutierrez, Roman (Inventor); Tang, Tony K. (Inventor); Shcheglov, Kirill (Inventor)

    2002-01-01

    A micromachined resonator mountable to an external support structure has a proof mass coupled to a base structure by a first spring structure, the base structure having a plurality of electrodes, and a second spring structure coupling the base structure to the external support structure.

  3. Magnetic resonance imaging

    SciTech Connect

    Stark, D.D.; Bradley, W.G. Jr.

    1988-01-01

    The authors present a review of magnetic resonance imaging. Many topics are explored from instrumentation, spectroscopy, blood flow and sodium imaging to detailed clinical applications such as the differential diagnosis of multiple sclerosis or adrenal adenoma. The emphasis throughout is on descriptions of normal multiplanar anatomy and pathology as displayed by MRI.

  4. Proton resonance spectroscopy

    SciTech Connect

    Shriner, J.F. Jr.

    1991-11-01

    This report discusses the following topics: Complete Level Scheme for {sup 30}P; A Search for Resonances Suitable for Tests of Detailed-Balance Violation; The Fourier Transform as a Tool for Detecting Chaos; Entrance Channel Correlations in p + {sup 27}Al; The Parity Dependence of Level Densities in {sup 49}V; and A Computer Program for the Calculation of Angular Momentum Coupling.

  5. Magnetic Resonance Annual, 1985

    SciTech Connect

    Kressel, H.Y.

    1985-01-01

    The inaugural volume of Magnetic Resonance Annual includes reviews of MRI of the posterior fossa, cerebral neoplasms, and the cardiovascular and genitourinary systems. A chapter on contrast materials outlines the mechanisms of paramagnetic contrast enhancement and highlights several promising contrast agents.

  6. Double resonator cantilever accelerometer

    DOEpatents

    Koehler, Dale R.

    1984-01-01

    A digital quartz accelerometer includes a pair of spaced double-ended tuning forks fastened at one end to a base and at the other end through a spacer mass. Transverse movement of the resonator members stresses one and compresses the other, providing a differential frequency output which is indicative of acceleration.

  7. Double resonator cantilever accelerometer

    DOEpatents

    Koehler, D.R.

    1982-09-23

    A digital quartz accelerometer includes a pair of spaced double-ended tuning forks fastened at one end to a base and at the other end through a spacer mass. Transverse movement of the resonator members stresses one and compresses the other, providing a differential frequency output which is indicative of acceleration.

  8. Single spin magnetic resonance

    NASA Astrophysics Data System (ADS)

    Wrachtrup, Jörg; Finkler, Amit

    2016-08-01

    Different approaches have improved the sensitivity of either electron or nuclear magnetic resonance to the single spin level. For optical detection it has essentially become routine to observe a single electron spin or nuclear spin. Typically, the systems in use are carefully designed to allow for single spin detection and manipulation, and of those systems, diamond spin defects rank very high, being so robust that they can be addressed, read out and coherently controlled even under ambient conditions and in a versatile set of nanostructures. This renders them as a new type of sensor, which has been shown to detect single electron and nuclear spins among other quantities like force, pressure and temperature. Adapting pulse sequences from classic NMR and EPR, and combined with high resolution optical microscopy, proximity to the target sample and nanoscale size, the diamond sensors have the potential to constitute a new class of magnetic resonance detectors with single spin sensitivity. As diamond sensors can be operated under ambient conditions, they offer potential application across a multitude of disciplines. Here we review the different existing techniques for magnetic resonance, with a focus on diamond defect spin sensors, showing their potential as versatile sensors for ultra-sensitive magnetic resonance with nanoscale spatial resolution.

  9. Magnetoelectric resonance engine

    SciTech Connect

    Moscrip, W.M.

    1992-09-15

    This patent describes a magnetoelectric resonance thermal machine. It comprises a reciprocating, multiple-piston, Alpha-type Stirling-cycle mechanical assembly; an electronic quadrature phase-lock circuit; an ancillary external energy and mass transfer subsystem; and a master microcomputer control system.

  10. Single spin magnetic resonance.

    PubMed

    Wrachtrup, Jörg; Finkler, Amit

    2016-08-01

    Different approaches have improved the sensitivity of either electron or nuclear magnetic resonance to the single spin level. For optical detection it has essentially become routine to observe a single electron spin or nuclear spin. Typically, the systems in use are carefully designed to allow for single spin detection and manipulation, and of those systems, diamond spin defects rank very high, being so robust that they can be addressed, read out and coherently controlled even under ambient conditions and in a versatile set of nanostructures. This renders them as a new type of sensor, which has been shown to detect single electron and nuclear spins among other quantities like force, pressure and temperature. Adapting pulse sequences from classic NMR and EPR, and combined with high resolution optical microscopy, proximity to the target sample and nanoscale size, the diamond sensors have the potential to constitute a new class of magnetic resonance detectors with single spin sensitivity. As diamond sensors can be operated under ambient conditions, they offer potential application across a multitude of disciplines. Here we review the different existing techniques for magnetic resonance, with a focus on diamond defect spin sensors, showing their potential as versatile sensors for ultra-sensitive magnetic resonance with nanoscale spatial resolution. PMID:27378060

  11. Resonance Ionization, Mass Spectrometry.

    ERIC Educational Resources Information Center

    Young, J. P.; And Others

    1989-01-01

    Discussed is an analytical technique that uses photons from lasers to resonantly excite an electron from some initial state of a gaseous atom through various excited states of the atom or molecule. Described are the apparatus, some analytical applications, and the precision and accuracy of the technique. Lists 26 references. (CW)

  12. RESONANT CAVITY EXCITATION SYSTEM

    DOEpatents

    Baker, W.R.

    1959-08-01

    A cavity excitation circuit is described for rapidly building up and maintaining high-level oscillations in a resonant cavity. The circuit overcomes oscillation buildup slowing effects such as ion locking in the cavity by providing for the selective application of an amplified accelerating drive signal to the main cavity exciting oscillator during oscillation buildup and a direct drive signal to the oscillator thereafter.

  13. RESONATOR PARTICLE SEPARATOR

    DOEpatents

    Blewett, J.P.; Kiesling, J.D.

    1963-06-11

    A wave-guide resonator structure is designed for use in separating particles of equal momentum but differing in mass, having energies exceeding one billion eiectron volts. The particles referred to are those of sub-atomic size and are generally produced as a result of the bombardment of a target by a beam such as protons produced in a high energy accelerator. In the resonator a travelling electric wave is produced which travels at the same rate of speed as the unwanted particle which is thus deflected continuously over the length of the resonator. The wanted particle is slightly out of phase with the travelling wave so that over the whole length of the resonator it has a net deflection of substantially zero. The travelling wave is established in a wave guide of rectangular cross section in which stubs are provided to store magnetic wave energy leaving the electric wave energy in the main structure to obtain the desired travelling wave and deflection. The stubs are of such shape and spacing to establish a critical mathemitical relationship. (AEC)

  14. Screening Resonances In Plasmas

    SciTech Connect

    Winkler, P.

    1998-12-01

    When it was suggested that a new recombination mechanism (Resonant Radiative Recombination (RRR)) which, based on very general physical arguments, should happen in dense plasmas and promises to provide useful information for the local temperature and density diagnostics of plasmas, they assumed the existence of screening resonances. For model potentials the existence of screening resonances has been demonstrated beyond reasonable doubt in a number of calculations. The key question, how well those potentials describe the dominant effects of a real plasma remains open. The relation of theoretical predictions to experimentally measurable effects is an important issue at the present stage of their research. In particular, RRR is expected to account for enhanced recombination rates of low energetic electrons with their ions, since the first stage is the resonant capture of a slow electron by an atom or ion. The mechanism that traps an electron is a combination of complicated many-body interactions of the ions and electrons. For clarity they start here, however, with a discussion in terms of local potential traps the shapes of which are determined predominantly and in an average way by two factors: the degree of screening present at the ionic site and the degree of short-range order in the immediate neighborhood of this ion.

  15. Width of nonlinear resonance

    SciTech Connect

    Ohnuma, S.

    1984-03-01

    Two approximations are made, one essential and the other not so essential but convenient to keep the analytical treatment manageable: (1) Only one nonlinear resonance is considered at a time so that the treatment is best suited when the tune is close to one resonance only. To improve this approximation, one must go to the next order which involves a canonical transformation of dynamical variables. Analytical treatment of more than one resonance is not possible for general cases. (2) In the formalism using the action-angle variables, the Hamiltonian can have terms which are independent of the angle variables. These terms are called phase-independent terms or shear terms. The tune is then a function of the oscillation amplitudes. In the lowest-order treatment, the (4N)-pole components but not the (4N + 2)-pole components contribute to this dependence. In deriving the resonance width analytically, one ignores these terms in the Hamiltonian for the sake of simplicity. If these are retained, one needs at least three extra parameters and the analytical treatment becomes rather unwieldy.

  16. Functional Magnetic Resonance Imaging

    ERIC Educational Resources Information Center

    Voos, Avery; Pelphrey, Kevin

    2013-01-01

    Functional magnetic resonance imaging (fMRI), with its excellent spatial resolution and ability to visualize networks of neuroanatomical structures involved in complex information processing, has become the dominant technique for the study of brain function and its development. The accessibility of in-vivo pediatric brain-imaging techniques…

  17. Improved ultraviolet resonance lamp

    NASA Technical Reports Server (NTRS)

    Bass, A. M.

    1970-01-01

    Removal of the seal area from the path of the lamp discharge eliminates the gradual deterioration of lithium fluoride window surfaces from condensation of products formed by interaction of a resonant rare-gas discharge with window sealing materials. The discharge is confined to the inner tube.

  18. Energy saver prototype accelerating resonator

    SciTech Connect

    Kerns, Q.; May, M.; Miller, H.W.; Reid, J.; Turkot, F.; Webber, R.; Wildman, D.

    1981-06-01

    A fixed frequency rf accelerating resonator has been built and tested for the Fermilab Energy Saver. The design parameters and prototype resonator test results are given. The resonator features a high permeability nickel alloy resistor which damps unwanted modes and corona rolls designed with the aid of the computer code SUPERFISH. In bench measurements, the prototype resonator has achieved peak accelerating voltages of 500 kV for a 1% duty cycle and cw operation at 360 kV. 4 refs.

  19. Microwave Resonators Containing Diamond Disks

    NASA Technical Reports Server (NTRS)

    Dick, G. John; Maleki, Lutfollah; Wang, Rabi T.

    1996-01-01

    Synthetic diamond dielectric bodies proposed for use in cylindrical resonators helping to stabilize frequencies of some microwave oscillators. Acting in conjunction with metal resonator cavities in which mounted, such dielectric bodies support "whispering-gallery" waveguide modes characterized by desired frequencies of resonance and by electro-magnetic-field configurations limiting dissipation of power on metal surfaces outside dielectric bodies. Performances at room temperature might exceed those of liquid-nitrogen-cooled sapphire-based resonators.

  20. Repetitive resonant railgun power supply

    DOEpatents

    Honig, E.M.; Nunnally, W.C.

    1985-06-19

    A repetitive resonant railgun power supply provides energy for repetitively propelling projectiles from a pair of parallel rails. The supply comprises an energy storage capacitor, a storage inductor to form a resonant circuit with the energy storage capacitor and a magnetic switch to transfer energy between the resonant circuit and the pair of parallel rails for the propelling of projectiles.